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HomeMy WebLinkAboutCity Council Packet 01-20-2004 SpecialAgenda City of Plymouth Special City Council Meeting Tuesday, January 20, 2004 6:00 p.m. Public Safety Training Room 1. Call to Order 2. Receive Update On Flood Analysis 3. Review Bassett Creek Watershed Commission's 2nd Generation Plan 4. Set future Study Session topics 5. Adj ourn Agenda Number: DATE: January 15, 2004 for the City Council Meeting of January 20, 2004 TO: Laurie Ahrens, City Manager FROM: Daniel L. Faulkner, P.E. Director of Public Works SUBJECT: FLOOD ANALYSIS REPORT UPDATE AND PROJECT RECOMMENDATIONS CITY PROJECT NO. 3126 ACTION REQUESTED: Receive two additional flood analysis reports prepared by SEH and direct staff to proceed with the preparation of storm drainage and flood protection improvement plans for seven of the nine locations studied. BACKGROUND: At the October 28, 2003 Council meeting, a report was prepared updating the City Council on the status of the flood analysis reports being prepared by the City's engineering consultant, SEH. At that meeting, reports were received on four of the six designated study areas and two additional areas were added to the list of flood analysis study sites. In addition, the Council directed staff to meet with the affected property owners to review the alternatives as prepared in the consultant's reports. Staff along with SEH engineer, Rocky Keehn, met with nearly all of the affected property owners from Sites 1, 3, 4 and 6 on November 17 and 18th (November 7, 2003 letter attached). The storm drainage improvement options were explained to the residents, questions answered and there appeared to be a general understanding of the staff's proposed alternatives. Two additional reports are now completed after waiting over one month for topographic mapping information from a mapping company. DISCUSSION: The following is the status of the flood analysis reports: Renorts Completed Site 1 — Weston Lane west of Vicksburg Lane and north of County Road 6 Site 3 — 4785 Valley Forge Lane Site 4 East — 11235-52 nd Avenue Site 4 West —11735-52 nd Avenue Site 6 — 28th Avenue and Sycamore Lane Additional Resorts Completed since October 28, 2003 Site 5 —Plymouth Colony Apartments north of County Road 6 and west of County Road 101 Site 7 — Plymouth Ponds Apartments north of 45th Avenue and west of Nathan Lane Draft Reports (under review) Site 2 — Greentree West neighborhood south of 30th Avenue and east of Alvarado Lane Site 8 - Southwest corner of Teakwood Lane and Sunset Trail (145 Teakwood Lane) SUBJECT: FLOOD ANALYSIS REPORT UPDATE AND PROJECT RECOMMENDATIONS CITY PROJECT NO. 3126 Page 2 The two recently completed reports are attached for your information. City staff and our engineer have met with the affected property owner from Site 2 and additional alternatives are currently being investigated prior to completing the final report. A draft report has also been completed for Site 8 but some additional analysis is still necessary and a meeting with the property owner still needs to be scheduled. BUDGET IMPACTS: Attached is a cost estimate prepared by staff dated November 5, 2003 which estimates the cost for repair of the June 24/25, 2003 storm event. These estimated costs were included in the revised budget for the Water Resource Fund approved by the Council on November 25, 2003. Staff is now recommending some lower cost alternatives for some of the flood analysis sites as follows: RECOMMENDATIONS AND CONCLUSIONS: The flood analysis completed by SEH indicates that the following recommended improvements should adequately protect the affected residents from flooding during a storm event similar to that which occurred on June 24/25, 2003. It is recommended that the City Council direct staff to proceed with the following storm drainage improvement options. Site 1 - Weston Lane west of Vicksburg Lane and north of County Road 6. Water Resource Budget Current Recommendations 1. Site 1 -Weston Lane 137,100 56,000 2. Site 3 - 4785 Valley Fore Lane 100,000 61,900 3. Site 4 East - 11235 - 52° Avenue 12,100 12,100 4. Site 4 West - 11735 - 52° Avenue 50,000 53,000 5. Site 5 - Pl outh Colony Apartments 50,000 0_ 6. Site 6 - 28t Avenue and Sycamore Lane 16,000 7,800 7. Site 7 - Plymouth Ponds Apartments 0- 29,500 8. Site 2 - Greentree West 0- 9. Site 8 - Teakwood Lane/Sunset Trail (145 Teakwood Lane) V0.1-0-00 2 - Total 435,200 220,300 RECOMMENDATIONS AND CONCLUSIONS: The flood analysis completed by SEH indicates that the following recommended improvements should adequately protect the affected residents from flooding during a storm event similar to that which occurred on June 24/25, 2003. It is recommended that the City Council direct staff to proceed with the following storm drainage improvement options. Site 1 - Weston Lane west of Vicksburg Lane and north of County Road 6. Estimated Cost 1. Raise manhole west of Vicksburg Lane 4,500 2. Replace manhole overflow grate on manhole in the dry pond on the east side of Vicksburg Lane to help prevent plugging 1,000 3. Build a pump station adjacent to 1506 Weston Lane according to plans previously prepared by City consultant, URS. 50,000 Total 55,500 0'.\Engineering\PROJECTS\2000 - 2009\3126\Memos\CC_Update_I_I5_04.doc SUBJECT: FLOOD ANALYSIS REPORT UPDATE AND PROJECT RECOMMENDATIONS CITY PROJECT NO. 3126 Page 3 Site 3 — 4785 Valley Forge Lane/10815 — 47t Place Estimated Cost Estimated Cost 1. Create an emergency overflow swale from the pond across the 11235 — 52nd Avenue northerly down the property line to 52nd trail and through the east side yard of the home north of 4785 Avenue and continue this swale on the north side of 52nd Avenue Valley Forge Lane and continue northerly to near the intersection down the common property line to Pond SCP -17. In addition, at 47th Place. 30,000 2. Create a berm and walk up in the backyard of 4785 Valley Forge side of 52nd Avenue and connect to the existing storm sewer in Lane and install gravity pipe connection with backflow preventer this area. from this enclosed area to the existing 15 inch pipe installation. 31,900 Total 61,900 Site 4 East —11235 — 52"d Avenue/11220 — 52" Avenue Estimated Cost 1. Construct an emergency overflow swale from the backyard of 42,000 11235 — 52nd Avenue northerly down the property line to 52nd 11,000 Avenue and continue this swale on the north side of 52nd Avenue 53,000 down the common property line to Pond SCP -17. In addition, consulting engineer, SEH has analyzed the existing conditions install a side yard drainage intake between the homes on the south and has proposed a solution as indicated in the attached report. side of 52nd Avenue and connect to the existing storm sewer in This includes raising the bituminous area in front of the garages this area. 12,100 Site 4 West —11735 — 52" Avenue Estimated Cost 1. Connect the storm sewer systems in the backyard of 11735 — 52" Avenue. 42,000 2. Divert pipe flow from the above storm sewer system at its outlet point from the open ditch on the south side of the CP Railroad into existing City pond SCP -17B. 11,000 Total 53,000 Site 5 — Plymouth Colony Apartments, north of County Road 6 and west of County Road 101 Estimated Cost 1. The problems on this apartment complex site are due primarily to underground parking structures that were constructed too low without an adequate storm drainage system. The City's consulting engineer, SEH has analyzed the existing conditions and has proposed a solution as indicated in the attached report. This includes raising the bituminous area in front of the garages leading to the underground parking and installing sump pumps. 86,500* Total The City has provided an analysis of the existing storm drainage 86,500 problem but the solution is the responsibility of the apartment owner. Not a City cost) 0:\Engineering\PROJECTS\2000 - 2009\3126\Mems\CC_Update .1_15 04.doc SUBJECT: FLOOD ANALYSIS REPORT UPDATE AND PROJECT RECOMMENDATIONS CITY PROJECT NO. 31.26 Page 4 Site 6 — 28` Avenue and Sycamore Lane Estimated Cost 1. Construct a structure at the 28` Avenue culvert entrance from the side yard at 2740 Sycamore Lane including a six inch pipe for local backyard drainage along with a check valve to prevent backflow from the street into the yard. Also provide for safe slope from street to yard. 7 800 Total 7,800 Site 7 — Plymouth Ponds Apartments, north of 45t Avenue and west of Nathan Lane Estimated Cost 1. The City's engineer, SEH, has prepared the attached flood analysis report for this apartment complex property which has four underground parking garages that took on approximately three inches of water following the June 24, 2003 storm. It appears that the City's storm drainage system that flows overland through a wetland area along the south side of the apartment complex may have gotten clogged as it entered a City storm sewer under the intersection of 45'h Avenue and Nathan Lane. It is recommended that the City install a skimmer structure and weir for this storm sewer pipe to help prevent future plugging and do some additional excavation in the area. (The apartment owner may wish to provide additional protection for their on site garages by constructing a section of raised pavement in front of each garage entrance to prevent water from flowing into the underground structure; no cost was prepared for this alternative.) U1500 Total 29,500 x j_ Daniel L. Faulkner, P.E. Director of Public Works attachments: Nov. 5, 2003 estimate of drainage costs from June storm in excess of already spent Flood Analysis Reports for Site 5 and Site 7 Previously completed Flood Analysis Reports attached to Council Item No. 8.2, October 28, 2003 November 7, 2003 letter January 15, 2004 letter O \Engineering\PROJECTS\2000 - 2009\3126\Mems\CC_Update_I_15_04.doc Estimate of drainage costs -from June storm in excess of already spent 11/5/03 Project 2003 Cost 2004 Cost Comments Weston Lane Lift Station 137,100.00 SEH Study t Greentree skimmer - 2'000.00 Study r- - - 11thAve. H re1e. i e replacep fi $45 000.00 IIpipe - p 15th Ave. repairs 100,000.00' SEH stud y 50,000.00 Valley orge - - - - 100,000.00i SEH Study Excay. Pond and overflow Sycamore 16,000.00 SEH Study Pipe mod. and clean channel Ave.52nd 62,100.00 SEH Studer et rte. sdrainage- -_-- 01repairs___________ 50,000.00 SEH tudy Erosion p - -- -_ 4,000.00 ConoSMeadows bank repair Grade Powers' swale (Larch) - - L 5,000.00 After sed. removal in winter Black Oaks/Archer drainage excay. 15,000.00'! TimberCreekerosion re airp- -- - - 000009, . T eaTeak 70,000.00!,SEH Study Autumn Hills Berm repair 3,000.00! Lost Lake Outlet channel repair 8,000.00 Total 212,000.00 464,200.00, Agenda Number: rA DATE: October 23, 2003 for the City Council Meeting of October 28, 2003 TO: Laurie Ahrens, Assistant City Manager FROM: 'Zbaniel L. Faulkner, P.E. Director of Public Works SUBJECT: FLOOD ANALYSIS REPORT FOR FOUR OF THE SIX DESIGNATED STUDY AREAS CITY PROJECT NO. 3126 ACTION REQUESTED: Receive flood analysis report prepared by SEH for four of the six designated study areas and refer discussion of alternatives to a future study session. BACKGROUND: Following the June 24-25, 2003 storm event, there was some flooding in areas throughout the City of Plymouth. In most of these situations the causes and solutions were easily identifiable but six areas where identified as needing further analysis. At the July 22, 2003, Council meeting authorization was given to City consultant, SEH, to proceed with an analysis of six identified sites in accordance with their submitted proposal. The identified study sites are as follows: Site 1 — Weston Lane, west of Vicksburg Lane and north of Co. Rd. 6 Site 2 — Greentree West neighborhood, south of 30`h Ave. and east of Alvarado Lane Site 3 — 4785 Valley Forge Lane Site 4 — 11235 — 52"d Ave./11735 — 52"d Ave. Site 5 — Plymouth Colony Apts., north of Co. Rd. 6 and west of Co. Rd. 101 Site 6 — 28th Ave. and Sycamore Lane The study process began with on site reviews and individual resident interviews conducted by SEH engineers and City staff at all six site locations. This process began in late July and continued through mid August and the information obtained was documented on the attached site visit sheet forms which were also mailed to the residents interviewed. Subsequently, SEH collected all available City data and records and had detailed survey work done as necessary. City staff also had periodic conversations with the consultant to discuss preliminary findings and provide direction on the continued study. Through these staff discussions, it was mutually determined that additional topographic information would be necessary to properly analyze the Greentree West drainage area. A topographic mapping company, Horizons Inc., was hired to provide this contour mapping based on aerial photographs and specific ground control points. The consultant has continued with the flood analysis and has completed reports on four of the six sites which are attached for your information. The two sites not yet completed include Site 2, Greentree 0AEngineeringTROJECTS\2000 - 2009\3126\Memos\CC_AnalysisReport.doc Page 2 West neighborhood, and Site 5 the Plymouth Ponds Apartments. Due to a delay in getting the topographic information from Horizons Inc. and the need for hydrologic modeling of the Plymouth Ponds drainage area and system, further effort is still needed on these two areas. We hope to have these two additional reports ready for Council consideration at the November 25, 2003 meeting. All the affected property owners will be notified of our project status. The residents in the four areas completed will also receive a copy of this report and the consultant's report. DISCUSSION: The following is a summary of the four sites analyzed including possible alternatives for addressing future flooding concerns. Site 1 — Weston Lane: The consultant concluded that there is strong evidence that the flooding that occurred in the backyards and entered the walkouts at 1506, 1510 and 1530 Weston Lane resulted from the large volume of storm water entering the storm sewer system creating excessive water pressure in the manhole west of Vicksburg Lane near the backyard of 1506 Weston Lane. This excessive water pressure forced the lid off of the manhole structure and allowed excessive amounts of storm water to flow out of the manhole and into the three backyards to a level above the walkout elevations. There was also a home in the Parkers Lake development on the east side of Vicksburg at 15815 — 15th Place which had lower level flooding due to the June storm event. This lot is adjacent to the dry storage pond located in the northeast quadrant of Vicksburg Lane and Co. Rd. 6. While there is an emergency overflow structure at the outlet of this pond, it appeared that it became blocked with debris causing water to pond more than two feet above the 100 year level. ALTERNATIVES * ESTIMATED COST 1. Raise manhole west of Vicksburg Lane 4,100 Addresses manhole pressureproblem) 2. Reconstruct storm sewer in backyard 83,000 Addresses manhole pressure problem and flooding on east side of Vicksburg Lane.) 3. Build pump station(previously designed by City consultant, URS 50.000 Addresses localized backyard ponding and downstream system backup concerns) TOTAL 137,100 All alternatives should be completed Site 3 — 4785 Valley Forge Lane: The consultant has concluded that the 15 -inch outlet pipe from pond NBP3A) was not of sufficient size to convey the large volume of water entering this pond during the storm event of June 24/25. Consequently, water ponded to an elevation approximately 15 -inches above the walkout level for the home at 4785 Valley Forge Lane where water entered through the walkout. In addition, the resident at 10815 — 47th Place had enough water enter their walkout to dampen their carpet. The Plymouth Ponds Apartments located downstream of Valley Forge Lane near 45th Avenue and Nathan Lane also experienced minor flooding in their underground parking garages. The consultant conducted a full survey of the entire area, including existing topography, critical elevations such as first floor walkouts and roadway and storm sewer elevations. Using this information, a computer model was used to recreate existing conditions along with modeling proposed alternatives to ensure proper protection of the homes. 0:\Engineering\PROIECTS\2000 - 2009\3126\Memos\CC_AnalysisReport.doc Page 3 Based on the survey information and through discussions with the property owner, the June storm event reached an elevation of approximately 925.0. The elevation of the walkout at 4785 Valley Forge Lane is 923.5 and the existing elevation of the trail near Valley Forge Lane (existing emergency overflow) is at approximately 924.2. Some alternatives could be combined and some could be exclusive Site 4 East — 11235 — 52nd Avenue: There is a low area in the back yard of this property which is drained by a catch basin in the adjacent yard to the east. A storm sewer is located between these two homes and connects the backyard catch basin to a catch basin in the street which ultimately discharges north into a storage pond (SCP -17). During the June storm event, water onded in the backyard to a depth that had water flowing into the rear window wells at 11235 — 52" Avenue. Storm water also ponded in 52nd Avenue to a depth sufficient to connect to the backyard pond as well as pond in the front yards of the homes on the north side of 52nd Avenue. In addition, storage pond SCP -17, which is adjacent to the north side home, 11220 — 52nd Avenue, rose considerably, but was still approximately 3 - feet below the high water elevation in the street and over 3.5 feet lower than the top of the retaining wall in the backyard of 11220 — 52nd Avenue. These elevations indicate that the pond did not have any 0AEngineeringTROJECTS0000 - 2009\3126\M moslCC_AnalysisRepon.doc ESTIMATED ALTERNATIVES * COST 1. Expand "live storage" by 1.5 acre-feet adjacent to the storage pond 37,700 behind 4785 Valley Fore Lane Lowers flood elevation in pond approximately 0.1 -foot; Aesthetic benefits and possibly some water quality benefits 2. Remove and replace the existing 15 -inch pond outlet pipe with a 30- 57,700 inch pipe connected to the existing 30 -inch pipe on the east side of Valley Forge Lane This reduces the peak elevation for the June type storm event by 1.3 feet) 3. Increase the pond outlet pipe from 15 -inch to 30 -inch and expand the 95,400 live storage volume of the pond by 1.5 acre feet; This reduces peak elevation for June type form event by 1.7 -feet 4. Create an emergency overflow swale from the pond across the trail and 67,400 through the east side yard of the home north of 4785 Valley Forge and continue northerly to the intersection at 47th Place; a 20 -foot wide swale would be constructed 1.5 feet below the walkout elevation 923.5) and a June type storm event would reach a peak elevation of 923.3; This alternative would also include the expanding of the storage pond) 5. Create a berm in the backyard near the pond to a height sufficiently 31,900 above the June type storm event elevation; The berm would isolate the backyard from the pond, but create a ponding area in the backyard between the house and the pond which would need to be removed by a separate storm sewer or a sump pump) Some alternatives could be combined and some could be exclusive Site 4 East — 11235 — 52nd Avenue: There is a low area in the back yard of this property which is drained by a catch basin in the adjacent yard to the east. A storm sewer is located between these two homes and connects the backyard catch basin to a catch basin in the street which ultimately discharges north into a storage pond (SCP -17). During the June storm event, water onded in the backyard to a depth that had water flowing into the rear window wells at 11235 — 52" Avenue. Storm water also ponded in 52nd Avenue to a depth sufficient to connect to the backyard pond as well as pond in the front yards of the homes on the north side of 52nd Avenue. In addition, storage pond SCP -17, which is adjacent to the north side home, 11220 — 52nd Avenue, rose considerably, but was still approximately 3 - feet below the high water elevation in the street and over 3.5 feet lower than the top of the retaining wall in the backyard of 11220 — 52nd Avenue. These elevations indicate that the pond did not have any 0AEngineeringTROJECTS0000 - 2009\3126\M moslCC_AnalysisRepon.doc Page 4 impact on the flooding that occurred at 11235 — 52"d Avenue. After the site visit and survey were completed, the consultant determined that no modeling was required as part of the analysis for this site. It appears that the best solution would be to create a better overflow to the north into pond SCP -17. Site 4 West — 11735 — 52nd Avenue: This home is located in the low point of the subwatershed. The walkout sits much lower than the streets and surrounding homes and as a result had flooding in the basement where water entered through the walkout both in the June storm and in 1997. The home and yard receives drainage from overland flow and from an existing storm sewer system from the south and from 52nd Avenue. A storm sewer inlet under 52 n Avenue picks up the drainage from the back yard and conveys it north into a ditch system which travels in a culvert underneath the CP railroad tracks, and then in an open ditch between two homes on the south side of 53rd Avenue. No modeling was completed by the consultant as part of this analysis, although extensive survey work was completed of the storm sewer and critical elevations. ALTERNATNES * ESTIMATED ALTERNATNES COST 1. The primary alternative is to construct an emergency overflow swale 12,100 from the backyard of 11235 — 52"d Avenue down the property line to 52nd Avenue and continue this swale on the north side of 52"d down the common property line to pond SCP -17. The minimum elevation of the swale would be 1.5 feet lower than the top of the window well at 11235 52nd Avenue. To provide for proper side yard drainage, a yard drainage structure would be necessary between the homes on the south side of 52nd Avenue which would connect to the existing storm sewer pipe in this area. Continuing the shallow drainage swale on the north side of 52nd Avenue would also provide protection for the "threatened" home on the north side of 52nd Avenue as well. 2. Flood proof and raise the window wells approximately 3/10 feet at 11235-52 d Avenue this alternative may impact the deck as there may not be sufficient room for the east window well to be raised.) Site 4 West — 11735 — 52nd Avenue: This home is located in the low point of the subwatershed. The walkout sits much lower than the streets and surrounding homes and as a result had flooding in the basement where water entered through the walkout both in the June storm and in 1997. The home and yard receives drainage from overland flow and from an existing storm sewer system from the south and from 52nd Avenue. A storm sewer inlet under 52 n Avenue picks up the drainage from the back yard and conveys it north into a ditch system which travels in a culvert underneath the CP railroad tracks, and then in an open ditch between two homes on the south side of 53rd Avenue. No modeling was completed by the consultant as part of this analysis, although extensive survey work was completed of the storm sewer and critical elevations. ALTERNATNES * ESTIMATED COST 1. The primary alternative would be to connect the storm sewer systems 42,000 in the backyard of 11735 — 52nd Avenue. This would include both the storm sewer from the south and the storm sewer from 52nd Avenue which would be connected to the existing culvert under 52"d Avenue by means of a drainage structure which would also include an apron to collect the local yard drainage. The apron would also need to have a check valve installed to prevent backflow into the yard. 0:\EngineeringTROJECTS\2000 - 2009\3126\Memos\CC_AnalysisReport.doc Page 5 Before the pipes are connected in the backyard, this alternative should ESTIMATED COST be reviewed by completing a detailed survey and a hydrologic model to 7,800 determine correct pipe sizes and potential impacts to properties — not included in cost estimate. Another aspect of the above alternative would be to upgrade the downstream swale between the homes on the south side of 53`d Avenue which will receive the additional drainage.) 2. Diversion of piped flow into open ditch on the south side of the CP 11,000 railroad into existing city pond SCP -17B To reduce the flow rate going under the CP railroad and through the open swale between the homes on the south side of 53`d Avenue) 3. Flood proof the home at 11735 — 52nd Avenue by removing the walkout 40,000 to the basement and constructing a walkup which includes a concrete wall and cover over the walkup to create a 10' x 12' enclosure. Alternatives 1 and 3 are exclusive Site 6 West — 28th Avenue and Sycamore: This home is located in the low point of the subwatershed. The yard receives drainage via overland flow and from a concrete swale which drains a series of backyards upstream from the neighbors to the east. A storm sewer culvert is located in the side yard that conveys drainage to the north under 28th Avenue and eventually into Plymouth Creek via an open ditch. There are four catch basins in the street that are connected into the street culvert. Storm water appears to backflow from the street into the resident's side yard. The home had flooding in the basement during the June storm event which entered through the walkout. No survey or modeling was completed as part of the analysis for this site. The resident believes that the flooding was due to the backflow from a storm sewer in the street rather than the local drainage area. With this in mind, City staff provided a temporary solution for the flooding after the June storm which included restriction to the outlet culvert to reduce the amount of backflow that would be possible. The consultant analyzed the City's temporary solution through the use of hydraulic computations and determined that the system would work well for all storm events except when the runoff exceeds the capacity of the downstream storm sewer to a point where it would begin to pond in the street. During these events, the water would be detained in the street at the catch basins or backflow through the pipe into the yard. To prevent this backflow into the side yard, a check valve should be constructed. ALTERNATIVES * ESTIMATED COST 1. Construct a small structure at the 28t Avenue culvert entrance from the 7,800 side yard which would connect to the existing 28th Avenue culvert and include a 6 -inch pipe to pick up the drainage from the back yard. A check valve would be placed in the pipe to prevent backflow from the street into the yard. 2. Flood proof the house by removing the walkout to the basement and 40,000 construct a walkup and small berm around a portion of the yard directly in the back of the house. Alternatives are-clusive e' 0:\Engineering\PROJECTS\2000 - 2009\3126\Memos\CC_AnalysisReport.doc Page 6 Site 7 — Plymouth Pond Apartments: It is recommended that we add a site 7 to the original six for analysis as it was discovered subsequent to the identification of the original six sites that the Plymouth Pond Apartments also received flood damage. The flood damage occurred in the underground parking garages during the June storm event which resulted in the need to remove cars and damage to the stairs leading from the garage to the apartments. In addition, depending on which option is chosen for the upstream Site 3, there may be additional impacts to Site 7 which should be more fully investigated. RECOMMENDATIONS AND CONCLUSIONS: It is recommended that the City Council receive the consultant's report on four of the 6 sites authorized for flood analysis and direct staff to meet with the affected property owners to review alternatives. It is also recommended that Site 7, Plymouth Ponds Apartments, be added to the consultant's flood analysis list and included in the final report along with Sites 2 and 5. After these final three reports are completed, it is further recommended that staff meet with these affected property owners to explain the alternatives. A City Council study session could then be set to consider which options to pursue for all 7 sites and discuss funding which is not part of this report. Daniel L. Faulkner, P.E. Director of Public Works Attachment: Flood Analysis Report 0:\EngineeringTROJECTS\2000 - 200"126\Memos\CC_AnalysisReport.doc 5 November 7, 2003 CITY O PLYMOUTR FirstName)) «LastName» Address 1» City», <<State» <<PostalCode» SUBJECT: JUNE 24/25,2003 FLOOD ANALYSIS Dear ((Title)) «LastName»: This is to inform you that the City's consultant, Short, Elliott, Hendrickson, Inc. (SEH), has completed a flood analysis and report pertaining to your property which the City Council received at their October 28, 2003 meeting. A copy of that report was mailed to you prior to the City Council meeting for your information. As directed by the City Council, staff, along with our consulting engineer, would like to meet with you to explain the analysis and go over the potential options to minimize future flooding. We would like to meet with you for approximately 30 minutes on Monday, November 17, 2003, anytime between the hours of 4:30 pm to 7:00 pm in the City Council chambers. I would appreciate a call from you to set up a specific time between 4:30 pm and 7:00 pm on November 17, since we hope to talk to approximately ten residents. If this date and time does not fit into your schedule, Tuesday, November 18, could also be made available or any time during our regular working hours. Also, please let me know if you need a copy of the flood analysis report and we would gladly mail this to you before our meeting. Please call Office Support Specialist, Karen Holm at (763) 509-5503, to schedule an appointment, or me at (763) 509-5520 if you have any questions. Sincerely, Daniel L. Faulkner, P.E. Director of Public Works cc: Laurie Ahrens, Acting City Manager Ronald S. Quanbeck, P.E., City Engineer PLYMOUTH A Beau pingfft\reEff Jt%l tS\DANF.2003`FloodAnalysis_I I_7_FORM.doc 3400 PLYMOUTH BOULEVARD • PLYMOUTH, MINNESOTA 55447-1482 • TELEPHONE (763) 509-5000 www.d.plymouth.mmus Thomas Larson Ellen Feuling Resident 1944 Orchard Dr. 1506 Weston Lane 1510 Weston Lane Woodbury, MN 55125 Plymouth, MN 55447 Plymouth, MN 55447 Jacqueline Okoh 1530 Weston Lane Pliymouth, MN 55447 James Tuchtenhagen 10815 - 47th Place Plymouth, MN 55442 Stephen Koshiol 11220 - 52nd Avenue Plymouth, MN 55442 Julie Huang 4785 Valley Forge Ln. Plymouth, MN 55442 Brad & Mary Coomes 11235 - 52nd Avenue Plymouth, MN 55442 Jerry & Sue Jackson 11735 - 52nd Avenue Plymouth, MN 55442 woli/-CA14 4r Mark NAt9fisclager 4785 Valley Forge Ln. Plymouth, MN 55442 Philip Glanzer 11230 - 52nd Avenue Plymouth, MN 55442 iCu er Mark & Pitman 2740 Sycamore Lane Plymouth, MN 55441 January 15, 2004 CITY OF PLYMOUTR aFirstName» « LastName» aAddressl» City» , «State» «PostalCode» SUBJECT: FLOOD ANALYSIS REPORT AND RECOMMENDATIONS CITY PROJECT NO. 3126 Dear «Title» «LastName»: There is a special City Council meeting scheduled for Tuesday, January 20, 2004, at 6:00 pm in the Public Safety Training Room which is located on the second floor of the Public Safety building adjacent to City Hall. The purpose of this meeting is to receive your input, address any questions, and request direction from the City Council on those storm drainage improvement options that we should proceed with developing plans for constructing. At this meeting the City Council will be discussing seven of the nine flood analysis locations. The staff report for this meeting will be mailed to you on Friday, or if you prefer, it could be picked up at the Engineering Division office on Friday afternoon. If you prefer to pick the report up, please call me at 763-509-5520 and we will have the report available for you. Sincerely, JD 14a-aA ,, Daniel L. Faulkner, P.E. Director of Public Works cc: Laurie Ahrens, City Manager Ronald S. Quanbeck, P.E., City Engineer PLYMOUTH°" IPBFftffftrp Y j499'4r "' Fl«ou ys+s_0.«oma FO0.N a« 3400 PLYMOUTH BOULEVARD • PLYMOUTH, MINNESOTA 55447-1482 • TELEPHONE (763) 509-5000 www.ci.plymouth.mn.us Mr. Thomas Larson Ms. Ellen Feuling 1944 Orchard Dr. 1506 Weston Lane Woodbury, MN 55125 Plymouth, MN 55447 Ms. Jacqueline Okoh Ms. Julie Huang 1530 Weston Lane 4785 Valley Forge Ln. Pliymouth, MN 55447 Plymouth, MN 55442 Mr. James Tuchtenhagen Mr. & Mrs. Brad & Mary Coomes 10815 - 47th Place 11235 -52nd Avenue Plymouth, MN 55442 Plymouth, MN 55442 Mr. Stephen Koshiol Mr. & Mrs. Jerry & Sue Jackson 11220 - 52nd Avenue 11735 - 52nd Avenue Plymouth, MN 55442 Plymouth, MN 55442 Mr. & Mrs. Duane and Anita Bryant Mr. Ralph Netzman 11225 - 52nd Avenue 8815 A 90th St. South Plymouth, MN 55442 Cottage Grove, MN 55016 Mr. Thomas Larson 1510 Weston Lane Plymouth, MN 55447 Mr. Mark Wollschlager 4785 Valley Forge Ln. Plymouth, MN 55442 Mr. Philip Glanzer 11230 - 52nd Avenue Plymouth, MN 55442 Mr. & Mrs. Mark & Katherine Pitman 2740 Sycamore Lane Plymouth, MN 55441 Ms. Ronna Woolery 1805 County Road 101 Plymouth, MN 55447 Document" ttitt 3535 Vadnais Center Drive, St. Paul, MN 55110-5196 TO: Dan Faulkner, City of Plymouth FROM: Beth Peterson DATE: October 21, 2003 RE: Site 1- Weston Lane SEH No. A-PLYM00304.00 14.00 MEMORANDUM 651.490.2000 800.325.2055 651.490.2150 FAX SEH is submitting this technical memo to address the flooding that occurred on the east side of Weston Lane from the storm event on the evening of June 24, 2003, which produced over 6 - inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 -year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 -year storm is 6 -inches of rainfall in a 24-hour period. For the same duration as the June storm event, the 100 -year storm produces 5.3 inches of rainfall in a 12 -hour period. This memo provides a summary of the study and alternatives considered. The basis for this study included discussion with city staff and interviews with the residents. Information gathered from these interviews is attached. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. Three homes and backyards on the east side of Weston Lane had significant water go into the basements through walkouts (1506, 1510 and 1530). It was also observed that the manhole casting and the manhole in the backyard of 1506 Weston Lane (MH 22 from City storm sewer plan and profile sheet L-55), located just west of Vicksburg Lane had "blown off", and resulted in water surcharging out of the opening which caused extreme erosion around the manhole structure. It was surmised that this excessive water could have caused much of the flooding that occurred in the backyards. These backyards and the home at 1506 have experienced flooding in the past, but not to the degree experienced in June 2003. In addition, during this event, the immediate upstream pond east of Vicksburg Lane (GLP19A) reached a water surface elevation that caused water to enter the home through the walkout at 15815 15«` Place. This pond is in the upstream portion of the drainage system, which discharges into the storm sewer system that is located in the backyard of 1506 Weston Lane. The goal of this study was to evaluate the cause of the flooding and determine if previously constructed projects and the proposed pump station would still be valid solutions to the flooding Short Elliott Hendrickson Inc. Your 7rusled Resource • Equal Opportunily Employer Site 1- Weston Lane October 21, 2003 Page 2 that occurred in June. The study included reviewing the previously completed studies, as-builts of the storm sewer system and completing a survey of the critical elevations. Method of Analysis A survey of the storm sewer and critical elevations (i.e. first floor walkouts) was completed. It included the storm sewer on Vicksburg Lane, the storm sewer and pond elevations on the east side of Vicksburg Lane (off of 15t1, Place), the storm sewer through the backyards of Weston Lane, and the downstream control system. The purpose of the survey was to investigate what happened to the storm sewer manhole in the backyard of 1506 Weston Lane. The first step was to examine the existing data such as the storm sewer system and hydrologic model and drainage study prepared by Bonestroo Rosene Anderlik and Associates in 1992. Bonestroo's modeling effort included the backyard of the flooded homes on Weston Lane. After reviewing the information it was determined that it still accurately represented the area in question. The study recommended increasing two downstream outlets to 36 -inch reinforced concrete pipe (RCP). These improvements were completed in the same year in an effort to reduce the potential for flooding in the area. Since the recommended improvements in the 1992 Study have been completed and flooding still occurred, the next step was to examine the surveyed elevations of the storm sewer system and critical elevations. This was done to determine if the information collected could explain the surcharging of the storm sewer and thus allowing excessive amounts of storm water to enter the backyards once the casting on MH 22 was displaced. This condition was not modeled in any previous studies. In order- for surcharging of a storm sewer system to occur, there needs to be a downstream system unable to handle the upstream flows. This can be a result of larger upstream pipes leading to a smaller capacity system, blockage of the downstream system or an extreme flow event that exceeds the design capacity of the system. A review of the existing data showed that an 18 -inch RCP and 24 -inch RCP (from Vicksburg Lane) connect into the manhole located in the backyards of Weston Lane (MH 22). The pipe exiting the manhole is a 15 -inch RCP, which has much less capacity then the two upstream pipe systems. This limited downstream capacity supports the possibility of a surcharge condition at the manhole, due to the restricted downstream pipe allowing water to build up in the manhole. In order for there to be significant flooding of the backyards as a result of the flow out of MH 22 there needs to be a significant amount of water being stored upstream. This could occur in pond GLP19A or at the low point on Vicksburg Lane. Based on the information from the residents and the survey, the high water elevation in the pond east of Vicksburg Lane (GLP19A) was 970.6 for the June storm event. The high water elevation is based on the walkout elevation of the home at 15815 15`h PIace, east of Vicksburg Lane, which also experienced lower level flooding during this event. An additional critical elevation is the top of the outlet control structure for the pond, which is at 968.3 and acts as an emergency overflow. The purpose of the emergency overflow is to discharge flow at a greater rate downstream to prevent flooding of the pond for flow above the 100 -year event. Although it reduces flooding upstream, it can in some cases move the problem downstream, which may have occurred, in this location. The outlet from the pond is connected to a pipe which contributes directly to the flow into MH 22. Site 1- Weston Lane October 21, 2003 Page 3 The top of casting elevations for the catch basins on Vicksburg Lane were also checked. The elevations of the castings are 968.5 and are directly connected to MH 22. It was observed that this low point was full of water, and thus the potential water elevation was also near the pond high water of 970.6. The estimated high water elevation of 970.6 is about 5 feet higher than the top of casting elevation of 965.4 for the manhole (MH 22) in the backyard. Hydraulically this would be enough backwater or head to cause a casting to be displaced if it is not sealed or bolted down. Therefore there is strong evidence that the casting was displaced from MH 22 and much of the water that was ponded in GLP19A and in the street flowed into the backyards of Weston Lane from the manhole instead of into the storm sewer system, and was the source of the additional water. Alternatives The primary alternative analyzed as part of this study focused on elimination of the surcharging of water from upstream areas flowing directly into the backyards via MH 22. The first project would be to raise the manhole in the backyard to ensure surcharging would not occur in the future. Adding a new section to the existing manhole so the casting is at an elevation of approximately 971.0 will accomplish this goal. Upon review of the existing elevation of Vicksburg Lane in this location, the manhole elevation is such that it is still below the elevation of the street in this location. Once the manhole is raised, the construction of a lift station on Weston Lane will complete the City's existing plan for the area. The lift station will serve to pump the runoff from the backyards downstream into pond GLP19. The purpose of the lift station is to separate the backyard surface water from the storm sewer system, and to pump out the local water collected in the backyard that can not be served by the storm sewer. The final design of the lift station has been designed by others and is ready for bid. After our analysis we have some additional comments to consider including in the plan and specifications, primarily recommendations for redundant protection of the lift station and system. These comments have been attached. The last phase for this alternative would be to reconstruct the 15 -inch storm sewer line through the backyard to a 30 -inch RCP to increase the capacity and to alleviate the pressure on the manhole. This would also reduce the risk of flooding at 15815 15`x` Place. The reconstruction of the backyard storm sewer system is consistent with the assumptions and recommendations from the Bonestroo study, and should not cause downstream impacts. The storm sewer reconstruction could be completed as part of a street improvement project for Weston Lane. A cost estimate was completed for the manhole raising and new storm sewer. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct this project is 83,000. In addition, the estimated cost/budget for the lift station is $50,000 according to the information provided by the City. Another potential alternative considered for this site would be that the homes could be flood - proofed, by removing the first floor walkouts by filling around the back of the house and making Site 1- Weston Lane October 21, 2003 Page Q the homes walkups or totally removing the walkout. In the event the elevations are altered in the backyard due to flood proofing the home, the lift station design should be revisited to ensure that the elevation of the sump for the pump is low enough to provide additional storage in the backyards if needed. bcp Attachment x:4pi4ply=\030400\v TdVepon immnsWte I. mim tevised.dm Plymouth- Neighborhood Flood Analysis Site 1 - Weston Lane Alternative 1 Item Unit Quantity Cost Total Cost Remove storm sewer pipe LF 420 9.00 3,780 Remove drainage structure Each 1 500.00 500 Remove FES Each 1 500.00 500 Remove Bituminous Pavement SY 60 8.00 480 30" RCP LF 420 80.00 33,600 54 -inch Manhole LF 9.5 350.00 3,325 60 -inch Manhole LF 5 500.00 2,500 Connect to existing storm sewer structure Each 1 150.00 150 Bituminous Ton 10 100.00 1,000 Restoration Ac 0.4 2,500.00 1,000 Subtotal 46,835 35% Contingency 16,392 Subtotal 63,227 Mobilization (5%) 3,161 Subtotal 66,389 25% Engineering, Administration and Legal Costs 16,597 TOTAL 82,986 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Name: Site I- Weston Lane Flooding Location: Backyard and basement Visit Information: Date Time Name or Resident Address Phone No. 7130103 3:00 Jackie Okoh 1530 Weston Lane 763.476.6360 City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Dir. of Public Affiliation Works SEH SEH Phone No. 763.509.5520 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: Water came in from Vicksburg from the "culvert" that burst (according to neighbor) Water line in shed was approximately 1.5 feet high Water was approximately 1.5 feet high at basement door, water came in through the door, not the window The downstream pond overflowed. Questioned if there is a plug downstream that wasn't letting water through_ Damage tlua occurred Approximately 4 inches of standing water in basement Had to replace approximately 2 feet of sheetrock in basement Frequency of Problem There is standing water every spring in backyard Resident's proposed solutions: FEMA Assistance Financial assistance to rebuild The proposed pump station be built Doesn't want flooding to occur again Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. weston 1. a- N Data Sheet To Determine Action Pian Site Identification Problem Area Name: Slte 1 —Weston Lane Flooding Location: Backyard and basement Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8/1.9103 General Continents: The storm sewer in the backyard appears to be undersized. It appears that the rrtanhole in the backyard of 1506 Weston Lane surcharged. Check the hydraulics. Available Data: Bonestroo report, some survey information, storm sewer maps Additional Data that needs to be collected: A survey of the storm sewer in the backyard, on Vicksburg Lane and the outlet control structure for the pond east of Vicksburg lane; along with the walkout elevations of the homes that had flooding Recommended Future Action(s) based on Available Information: 1, Look at capacity of storm sewer system through backyard (Is there relief Upstream? Can we raise the casting? Can we make the pond directly upstream surge? ) 2. Should there be a flapgate on the backyard system? Do we want a positive drainage system or rely on pump station? 3. Pump station may be able to prevent flooding, will the pump station surge and back-up water? The design should be reviewed. 4. Ensure that water can't go in backyards from Weston Lane, force the water downstream. City Review on Baer Page City Review of the Problem Problem Area Name: Site 1 — Weston Lane Date: Flooding Location: Backyard and basement Date: 6/24/03 Contact: I City Contact Person: I Dan Faulkner I Phone xo. 763.509.5520 1 General Comments: Was the storm sewer system in backyard already surcharging? Survey the elevations of the walkouts and storm sewer Check the downstream control structure that Bonestroo built, Could some regrading in the backyards be helpful? Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Survey the storm sewer and walkouts 1450 GF 9103 9103 Have an additional meeting to discuss solutions 1100 GF 9103 9103 Construct pump station 50,000 Raise manhole and reconstruct storm sewer in backyard 83,000 1) GF — General Funds SU — Storm Water Utility AS — Assessment GR - Grant Total Solution Cost 335,550 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Dame: Site 1- Weston Lane Flooding Location: Backyard, basement and garage Visit Information: Date Time Name of Resident Address Phone No. 7130103 3:40 Ellen Feuling 1506 Weston Lane 763.475.9027 City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Affiliation Director of SEH SEH Public Works Pbonc,No. 763.509.5520 651.490.2026 651.765.2901 Sammary of Visit with Resident: Description of Problem based on site meeting: Typically during rain events the backyard will flood, which occurred during this storm. Water came out of manhole in backyard. Casting was pushed to the side. This brought in more water into the yard than the resident has seen in the past. Erosion occurred around the manhole, a portion of the bank slid into the backyard. Front yard was flooded too coming from the backyard, which has not happened in the past. Water in the downstream pond was almost up to the road in the morning after the rain. Are there downstream problems or impacts? Did the upstream development impact the system.? Damage that occurred Standing water in basement, up to second step (approximately 1.5 feet) Approximately 2 feet of water in garage I Backyard and front yard flooded i Frequency of Problem 2-3 tinges a year that yard would fill up with water, almost to the house. The resident would then call the City to collie pump. Even with smaller events there is usually standing water in the yard. No water has been in the house before, but there has been water in the garage. i rltesident's proposed solutions: Cite buy the house Reimbursement for damage — Is it possible to redesign the system? Back page is for site sketch Sketch of Problem Area: Include: Flooded area, Iocation of catch basins, size of catch basins, emergency overflow area, and critical structures. WA Data Sheet To Determine Action Plan Site Identification Problem Area Name: site I _ Weston Lane Flooding Location: Backyard and basement Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8114103 General Comments: The storm sewer in the backyard appears to be undersized. It appears that the manhole in the backyard of 1.506 Weston Lane surcharged. Check the hydraulics. Available Data: Bonestroo report, some survey information, storm sewer maps Additional Data that needs to be collected: A survey of the storm sewer in the backyard, on Vicksburg Lane and the outlet control structure for the pond east of Vicksburg Iane; along with the walkout elevations of the homes that had flooding Recommended Future Action(s) based on Available Information: 1. Look at capacity of storm sewer system through backyard (Is there relief upstream? Can we raise the casting? Can we make the pond directly upstream surge? ) 2. Should there be a flapgate on the backyard system? Do we want a positive drainage system or rely on pump station? 3. Pump station may be able to prevent flooding, will the pump station surge and back-up water? The design should be reviewed. 4. Ensure that water can't go in backyards from Weston Lane, force the water downstream. City Review on Back Page City Review of the Problem Problem Area Name: Site 1 - Weston Lane Date: Flooding Location: Backyards and basements Date: 6124103 City Contact' City Contact Person: I Dan Faulkner Phone No. 763.509.5520 General Comments: Was the storm sewer system in backyard already surcharging? Survey the elevations of the walkouts and storm sewer Check the downstream control structure that Bonestroo built. Could some regrading in the backyards be helpful? Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Survey the storm sewer and walkouts 1450 OF 9103 9103 Have an additional meeting to discuss solutions 1100 OF 9103 9103 Construct pump station 50,000 Raise manhole and reconstruct storm sewer in backyard 83,000 i I I i J) GF - General Funds SU --- Storm Water Utility AS - Assessment GR - Grant Total Solution Cost 1 $135,550 IM>r1} f ' i Ow" R. MOOW 5-1-4. Adi 5 MEMORANDUM 3535 Vadnais Center Drive, St. Paul, NIN 55110-5196 651.490.2000 800.325.2055 651.490.2150 FAX TO: Dan Faulkner, City of Plymouth FROM: Beth Peterson, Project Manager DATE: October 21, 2003 RE: Site 3- 4785 Valley Forge Lane N SEH No. A-PLYMO0304.00 14.00 SEH is submitting this technical memo to address the flooding that occurred at the pond NBP3A) and the property located at 4785 Valley Forge Lane N from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 -year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 - year storm is 6 -inches of rainfall in a 24-hour period. The June storm event statistical chance of occurring any one year is less than 1%. This memo provides a summary of the study and alternatives considered. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. During the event the water ponded to a depth of approximately 15 -inches at the house and on the door of the walkout from the basement. This water depth was significant enough to cause water to seep and flow through the walkout and cause severe flooding of the basement. During an interview with the resident, they also indicated that the water depth was approximately four feet at the shed, located on the outlot, and was deep enough to overflow east from the pond along the trail between the houses and onto Valley Forge Lane N. The resident at 10815 47th Place N also reported that street flooding occurred on 47t4 Place N and had experienced water damage in the basement where water entered through the walkout. This low point in the street is directly connected to the pond. The Plymouth Pond Apartments are located downstream of Valley Forge Lane, near 45th Avenue N and Nathan Lane. The parking garages of the apartment complex experienced minor flooding where water entered through the garage doors. Method of Analysis A full survey of the entire site was conducted since there were no existing contours of the pond. It included existing topography and critical elevation shots, such as first floor walkout, roadway and storm sewer elevations. The purpose of the survey was to provide the basis of the detention storage in the model and if needed be used to develop construction plans for any proposed improvements. A computer model was used to recreate existing conditions, along with modeling proposed alternatives to ensure proper protection of the home. Short Elliatt Hendrickson Inc. . Your Trusted Resource . Equal Opportunity Employer Site 3- 4785 Valley Forge Lane N October 21, 2003 Page 2 HydroCAD® (hydrologic model) was developed to simulate the storm event based on field surveys, the City's Water Resource Management Plan and the information received from the residents. Two different events were modeling. The first was a Type 111-24 hour, AMC -2 runoff condition for a 6 -inch rainfall in 12 hours to simulate the June storm event, and will be referred to as the June storm event. The second storm event modeled was the Type 11, AMC -2, 100 -year, 24-hour storm event, referred to as the 100 -year event. Once the existing condition model was created, the model was revised to depict the alternatives proposed to alleviate the flooding. Based on the survey, the elevation at the shed varies from 920.4 to 921.5, the first floor walkout elevation of the house is 923.5 and the emergency overflow is at approximately 924.2, which is the elevation of the bituminous path at Valley Forge Lane N directly north of the house. If the water depths described by the resident are added to these elevations, under existing conditions the high water level for the June storm event was around 925.0. Alternatives The intent of the alternative analysis is to protect the house from flooding occurring from a storm of similar intensity as the June storm event. Because of favorable site conditions, SEH discussed with City Staff during the site visit several possible alternatives that should be considered to help prevent future flooding. These alternatives are discussed in the following text. The first alternative considered expanding the storage in the pond. During the site visit it appeared that there was sufficient upland area available that could be excavated to increase the storage in the pond. Although there were several large trees in the upland area, the residents indicated that since the trees were for the most part cottonwoods, they would not be opposed to them being removed. The survey information gathered was then used to investigate creating additional storage within the pond. After the survey of the area was completed, the existing contours were revised to provide more storage. The north side of the pond was redesigned and expanded to provide approximately 1.5 ac -ft of additional Iive storage. The rest of the pond already has fairly steep slopes, so regrading the entire pond will not provide much additional storage. By increasing the storage, the peak elevation in the pond for the storm event modeled would be 924.9, a 0.1 foot reduction from existing conditions. Increasing the storage is not enough to protect the house at the 923.5 walkout elevation. It appears that this alternative would have little impact on the overall flood storage performance of the pond. However, excavation below the water elevation line would provide some water quality and aesthetic value to the pond. However, more investigation would be needed to be evaluated to determine the cost and benefits. Since there was some benefit, a cost estimate was completed for this alternative. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to complete the excavation is $37,700. Since ponding does not appear to be the solution, another method to decrease flood elevations is to increase the discharge from the pond. The next alternative investigated increased the existing Site 3- 4785 Valley Forge Lane N October 21, 2003 Page 3 outlet. Upon review of the plans, the outlet of the pond goes east from the pond, north of 4785 Valley Forge Lane N, between the houses and under an existing bituminous trail. The system then connects into the storm sewer system on Valley Forge Lane N and continues east to Pond NBP3. The existing pond outlet is a 15 -inch RCP which connects into a 30 -inch RCP on the east side of Valley Forge Lane N, which daylights in the open ditch approximately 150 feet east of Valley Forge Lane N. By replacing the existing 15 -inch outlet to match the existing downstream 30 -inch RCP at a 0.4% grade the peak elevation for the June storm event decreased to 923.7, a 1.3 foot reduction from existing conditions and is higher than the first floor walkout elevation of 923.5. The 100 - year HWL would be 922.7. By increasing the outlet and increasing the storage the peak elevation for the June storm event decreased to 923.3, a 1.7 foot reduction from existing conditions and less than the first floor walkout elevation of 923.5. The 100 -year high water level would be 922.7. The alternative of increasing the outlet and the storage of the pond appears to meet the criteria for protection of the home, but has the potential for downstream impacts due to the changes in discharge rates from the pond. With this alternative, the runoff from the pond will discharge at a higher rate and thus quicker into the downstream system. The downstream system includes the pond/wetland (ID) adjacent to the Plymouth Pond Apartments (Pond NBP3) which did have minor flooding in their parking garages during this event. Because of the flooding a site visit was arranged with the maintenance manager of the apartments. One of the significant things he indicated was that the pond/wetland appeared to continue to rise after the rain had stopped. This indicated that there is a lag or delay caused by upstream ponding and storage within the watershed. Based on this information, and knowledge of drainage systems and hydrologic response of watersheds, discharging the Valley Forge Lane N pond at a quicker rate should not have significant impacts to the downstream system. This is a result of peak discharges from the upstream system being better distributed during the storm. If this alternative is pursued further detailed modeling of the entire drainage system would be required. In addition, during one of the site visits, the outlet to the Plymouth Pond Apartment's pond/wetland was full of trash and debris and may have been partially blocked. The blockage would contribute to higher than expected high water elevations and thus contribute to the flooding that occurred in the garages of the Plymouth Pond Apartments. The blocked outlet should receive continued maintenance. A cost estimate was completed for this alternative. This project would require removal and replacement of pipe, along with associated pavement removal and replacement for Valley Forge Lane and the trail. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct this project is $95,400. The third alternative investigated creating a new emergency overflow along with expanding the storage of the pond. Based on the site visit with the City Staff and how the current overflow functioned during the flood event, the creation of an overflow at an elevation lower than the walkout appears to be feasible. The emergency overflow would need a control elevation constructed at 922.0 based on the City's guideline that an emergency overflow should be Site 3- 4785 Valley Forge Lane N October 21, 2003 Page 4 constructed 1.5 feet lower than the walkout elevation (923.5), along with downstream street elevation and survey information. Creating a the new emergency overflow would require regrading between the homes and along Valley Forge Lane N, north to the intersection at 471h Place and replacement of the trail. A twenty -foot wide section was thought to be a constructable width based on the site conditions and would minimize impacts to the resident to the north. The peak elevation for the June storm event with this overflow would be 923.3. The 100 -year HWL would be 923.1, which does not meet the one -foot minimum freeboard criteria. Since creating the overflow requires regrading private property this option would require additional discussions with the affected property owners, both 4785 Valley Forge Lane N and the neighbor to the north, if pursued further. A cost estimate was completed for this alternative. This project would require removal and replacement of curb and bituminous, along with excavation, restoration and a rough estimate for purchase of easement. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct this project is $44,000. Another altemative investigated creating a berm adjacent to the pond, but outside of the current easement, to protect the home from stormwater entering into the yard from the pond. No modeling was required for this alternative since it is a flood proofing solution. This site is suitable for the creation of a berm because the critical elevations can be tied back to the existing higher ground on the south side of the pond and the north side of the house. The berm would isolate the backyard from the pond and create a ponding area in the backyard between the house and pond, which would receive only runoff from the area within the bermed area. As part of the regrading of the backyard, additional storage in the backyard could be created to provide further flood protection. It is assumed that soil excavated from the pond would be used to construct the berm. This would need to be verified with soil borings before the project would proceed. Because of the landlocked nature of constructing a berm surrounding the house, an inlet would need to be constructed within the area of the berm to drain the backyard. There are two ways to drain the water from the inside area of the bean: one is to construct a drainage structure and connect it to the storm sewer, or to pump the water out. If a drainage structure was constructed the inlet would need to be connected downstream of the current pond outlet to assure that water would not surcharge back into the yard as the water elevation in the pond rises. The storm sewer on Valley Forge Lane N is fairly deep, at 10 feet, and should not cause any tailwater effects to the yard drainage system. The bermed alternative provides the necessary protection to the home to prevent flooding for both the June storm event and also the 100 -year event. A cost estimate was completed for this altemative. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct this project is $31,900 ($7800 for the outlet and $4800 for the excavation and placement of the berm). This cost assumes the excavation in the pond is strictly for the building of the berm. Site 3- 4785 Valley Forge Lane N October 21, 2003 Page 5 A combination of two or more of these alternatives (increase the live storage, increase the outlet size, constructing an emergency overflow or constructing a berm) can be considered to provide the level of protection desired. Dependent on the design and use of the alternatives, the cost could vary widely. bcp Attachment x:%pIVIyrw*30400%.ordVeport memoskile 3- memo nvised.doc Plymouth- Neighborhood Flood Analysis Site 3- 4785 Valley Forge Lane N Alternative 1 - Pond excavation Item Unit Quantity Cost Total Cost Pond Excavation CY 2501 $8.00 20,008 Restoration Ac 0.5 $2,500.00 1,250 Subtotal 21,258 35% Contingency 7,440 Subtotal 28,698 Mobilization (5%) 1,435 Subtotal 30,133 25% Engineering, Administration and Legal Costs 7,533 TOTAL 37,667 Plymouth- Neighborhood Flood Analysis Site 3- 4785 Valley Forge Lane N Alternative 2 - Increased outlet with pond expansion Item Unit Quantity Cost Total Cost Remove storm sewer pipe LF 312 9.00 2,808 Remove Bituminous Pavement (trail and road) SY 209 8.00 1,672 Pond Excavation CY 2501 8.00 20,008 30" RCP LF 312 80.00 24,960 Connect to existing storm sewer structure Each 3 150.00 450 Bituminous (trail and road) Ton 27 100.00 2,700 Restoration Ac 0.5 2,500.00 1,250 Subtotal 53,848 35% Contingency 18,847 Subtotal 72,695 Mobilization (5%) 3,635 Subtotal 76,330 25% Engineering, Administration and Legal Costs 19,082 TOTAL $95,412 Plymouth- Neighborhood Flood Analysis Site 3 - 11-3a52-nd-Avd Alternative 3 - Emergency Overflow Swale Item Unit Quantity Cost Total Cost Easement purchase SF 6000 2.00 12,000 Excavation CY 400 7.00 2,800 Remove Curb LF 60 5.00 300 Remove Bituminus SY 150 8.00 1,200 Install Bituminus Trail Ton 16.5 100.00 1,650 Install Curb LF 60 20.00 1,200 Restoration - Sod SY 1850 2.50 4,625 Topsoil CY 210 5.00 1,050 Subtotal 24,825 35% Contingency 8,689 Subtotal 33,514 Mobilization (5%) 1,676 Subtotal 35,189 25% Engineering, Administration and Legal Costs 8,797 TOTAL 43,987 Plymouth- Neighborhood Flood Analysis Site 3- 4785 Valley Forge Lane N Alternative 4 - Construction of berm Item Unit Quantity Cost Total Cost Remove Bituminous Trail SY 222 8.00 1,776 Pond Excavation CY 600 8.00 4,800 Manhole (w/casting) LF 3 270.00 810 15" RCP LF 136 50.00 6,800 Connect to existing storm sewer structure Each 1 150.00 150 Bituminous (trail and road) Ton 24 100.00 2,400 Restoration Ac 0.5 2,500.00 1,250 Subtotal 35% Contingency Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs 17,986 6,295 24,281 1,214 25,495 6,374 TOTAL $31,869 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymoutli Site Identification Problem Area Name: Site 3- 4785 Valley Forge Lane N Flooding Location: Pond in backyard- basement Visit Information: Date Time Name of Resident Address Phone No. 816103 3:00 Julie Huang and Mark Wollschlager 4785 Valley Forge Lane N 763.744.1486 City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Dir. of PublicAffiliation Works SEH SEH Phone No. 763.509.5520 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of 1'roblem based on site meeting: There was 15 -inches of water up at house. There was 4 -feet of water up at shed. Water eventually rose high enough to flow down path and overflow onto Valley Forge Lane_ Pumps were running continuously. Owners believe that the crest was at approximately 2-3 am. The water in the yard went down after about one full day. Damage that occurred Water came in through frame of house, not just through the walkout door. There was 2-3 inches of water in basement. Frequency of Problem With heavy rains the pond will fi 11 up into yard, usually past shed and garden. In the last 2 112 years the yard has flooded more than a dozen times. Resident's proposed solutions.- Emergency olutions: Emergency overflow is too high. Need more relief/additional outlet capacity. Pond maintenacnce- a lot of the pond has either filled in with sediment or overgrown with Vegetation Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. City Review of the Problem Problem Area dame: site 3 - 4785 Valley Forge Lane N Date: Flooding Location: Pond in backyard and basement Date: 6/24/03 City Contact: City Contact Person: I Dan Faulkner IPhone No. 763.509.5520 General Comments: Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion . Date Survey site 2200 GF 9/03 9103 Create hydrologic model 1600 GF 9103 9/03 Alt. 1: Pond expansion 37,700 Alt. 2: Pond expansion and reconstructing outlet 95,400 Alt. 3: Constructing emergency overflow 44,000 Alt. 4: Constructing berm 31,900 1) GF — GeneraI Funds SU — Storm Water Utility AS — Assessment GR - Grant Total solution Cost 1 $35,700-99,200 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identi%cation Problem Area Name: Site 3-4785 Valley Forge Lane N Flooding Location: Backyard, into basement Visit Information: Date Time Name or Resident Address Phone No. 816103 4:00 Jim Tuchtenhagen 10815 47"' Place N 763.557.2994 City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Dir. of Public Affiliation Works SEH SEH Phone No. 763.509.5520 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: Sump pump was running Backyard was under water. At 9 am the day morning after the storm, the street was flooded and water was up to the door of a minivan and up to the neighbor's driveway Damage that occurred Water in basement (unsure of the depth), but the carpet was wet at 5:30 am Water was up to door, and debris line was up about 2-3 inches on outside of house No damage to drywall Frequency of Problent Trail will often flood- more due to localized flooding Water will get into yard Resident's proposed solutions: Prevent water from coming into the house Is this property in a hole, low spot of the area? If trees need to be removed to excavate additional storage, that resident 'Ajould find that acceptable Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. Data Sheet To Determine Action Plan Site Identification Problem Area Name: Site 3 - 4785 Valley Forge Lane N Flooding Location: Pond in backyard and basement Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8119103 General Continents: There is no emergency overflow. From Plan, the NWL of the pond is 915.5 and the HWL is 920.0 Available Data: Storm sewer Additional Data that needs to be collected: Contour map of pond area Recommended Future Action(s) based on Available Information: 1. Survey site- backyards, pond, Valley Forge Lane gutter and road, and 47th Place 2. Create hydrologic model and look at a. Pond expansion b. Regrading backyards with new outlet c. Creating emergency overflow City Review on Bach Mage Data Sheet To Determine Action Plan Site Identification Problem Area Name: Site 3 Flooding Location: Backyard, into basement Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8119103 General Comments: There is no emergency overflow. From Plan, the NWL of the pond is 915.5 and the HWL is 920.0 Available Data: Storm sewer Additional Data that needs to be collected: Contour map of pond area Recommended Future Action(s) based on Available Information: 1. Survey site- backyards, pond, Valley Forge Lane gutter and road, and 47th Place 2. Create hydrologic model and look at a. Pond expansion b. Regrading backyards with new outlet c. Creating emergency overflow City Review on Back Page Cit Review of the Problem Problem Area Dame: Site 3 Date. MoodingLocation: Backyard, into basement Date: 6124103 Contact: I City Contact Person: I Dan Faulkner I Phone No. 763.509.5520 1 General Comments: Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Survey site 2200 GF 9103 9103 Create hydrologic model 1600 GF 9103 9103 AIt. 1: Pond expansion 37,700 Alt. 2: Pond expansion and reconstructing outlet 95,400 Alt. 3: Constructing emergency overflow 44,000 Alt. 4: Constructing berm 31,900 I 1) Gr — General Funds SU — Storm Water Utility AS — Assessment GR - Grant Total Solution Cost 35,700-94,200 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Name: Site 3 - 4785 Valley Forge Lane N Flooding Location: Plymouth Ponds Apartments- Parking Garages Visit Information: Date Time Name of Resident Address Phone No. 9110103 11:00 Ralph Netzlnan 4545 Nathan Lane 612.961.3818 City Representatives at site visit Name: Scott Newberger Rocky Keehn Beth Peterson Affiliation Public Works SEH S11H Phone No. 612.490.4870 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: Pond overflowed onto trail and into all 5 parking garages Water continued to rise the next morning after the rain stopped Damage that occurred 2-3 inches of water in all of the 5 parking garages Frequency of Problem There has never been a problem before Resident's proposed solutions: Have things changed within the watershed ? (i.e. new development) Study drainage system Back page is for site sketch 3 r_ "- jam r Data Sheet To Determine Action Plan Site Identification Problem Area, Name: Site 3 — 4785 Valley Forge Lane N HwdingLocation: Plymouth Pond Apartments — Parking Garage Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8119103 General Comments: There is no emergency overflow. From Plan, [lie N WL of the pond is 915.5 and the HWL is 920.0 Available Data: Storm sewer Additional Data that needs to be collected: Contour map of pond area Recommended Future Action(s) based on Available Information: 1. Survey site- backyards, pond, Valley Forge Lane gutter and road, and 47Eh Place 2. Create hydrologic model and look at a. Pond expansion b. Regrading backyards with new outlet c. Creating emergency overflow City Review on Back Page City Review of the Problem Problem Area Name: Site 3 -- 4785 Valley Forge Lane N Date: Flooding Location: Plymouth Pond Apartments — Parking Garage Date: 6124103 Contact: City Contact Person: I Dan Faulkner I Phone No. 763.509.5520 General Comments: Future Actions: Action Cost of Action Basis of Payment Proposed Completion Final Completion 1) Date Date Survey site 2200 GF 9103 9103 Create hydrologic model 1600 GF 9103 9103 Alt. 1: Pond expansion 37,700 Alt. 2: Pond expansion and reconstructing 95,400 outlet Alt. 3: Constructing emergency overflow 44,000 Alt. 4: Constructing Germ 31,900 1) GF -- General Funds SU -- Storm Water Utility AS — Assessment GR - Grant Total Solution Cost 35,700-99,200 I.A. AW IAEW5% MEMORANDUM 3535 Vadnais Center Drive, St. Paul, MN 55110-5196 651.490.2000 800.325.2055 651.490.2150 FAX TO: Dan Faulkner, City of Plymouth FROM: Beth Peterson, Project Manager DATE: October 21, 2003 RE: Site 4 East - 11235 52nd Avenue SEH No. A-PLYM00304.00 14.00 SEH is submitting this technical memo to address the flooding that occurred at 11235 52nd Avenue from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 - year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 -year storm is 6 -inches of rainfall in a 24-hour period. For the same duration as the June storm event, the 100 -year storm produces 5.3 inches of rainfall in a 12 - hour period. This memo provides a summary of the study and alternatives considered. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. The home at 11235 52nd Avenue has a backyard low area, which is drained by a catch basin in the back of the yard of the home immediately to the east. A storm sewer is located between the homes and connects the catch basin to a catch basin on the street. It ultimately discharges north across the street into pond SCP17. During the June storm event the water ponded in the backyard to a depth that had water flowing into the rear window wells at 11235 52nd Avenue, and built up enough water to break the windows which allowed water to flow into the basement. This ponded area was large enough that it connected to the low area in the street in front of the house, thus creating a flooded area that extended from the backyard of 11235 52nd Avenue, into the street and between the neighbors yards on the north side (11220 52nd Avenue). The two neighbors on the north side across the street had high water near their homes as a result of water ponding in the street, but no water damage since it overflowed to pond SCP17 before any damage occurred. The residents adjacent to pond SCP17 are also concerned with the amount that the pond bounces during storm events and the potential for future flooding problems. However, to date there has been no flooding of the homes due to the pond in their backyard. SEH was also asked to review the storage/ponding in pond SCP17 since it may be a potential solution to the flooding in the backyard at 11235 52°d Avenue. Method of Analysis The first step was to complete a site visit of the watershed and downstream controls to see if expansion of Pond SCP17 was feasible. This was followed up with a survey of the storm sewer Short Rioll Hendrickson Inc. • Your Trusled Resource • Equal Opportunity Employer Site 4 East - 11235 52nd Avenue October 21, 2003 Page 2 and critical elevations in the backyards and between the houses. Also, an estimate of the high water elevation during the storm event was determined based on information provided by the residents. After the site visit and survey were completed it was determined that no modeling was required as part of the analysis for the site since the best solution appeared to be to create a better overflow to the north into pond SCP17. A survey of the storm sewer and critical elevations (i.e. walkouts) was completed. It included the storm sewer on 52nd Avenue and the backyard structure, the high water marks at the pond, in the street and at the house according to the information provided by the residents, and the elevation of the window wells and windows. Based on this survey the high water elevation in the backyard was about 921.8 based on debris left on the fence. The window well elevation at the ground before water would overtop is 921.5 and the elevation at the bottom of the window is 920.0. Based on the survey there was enough water surface elevation in the backyard to overflow the window wells and break the windows. A second high water mark was obtained in the street based on a recorded elevation of a resident. This elevation was 921.1. The resident to the west of 11220 52nd Avenue indicated the water was just ready to go into his garage at elevation 921.2 before it overflowed north into the pond. Based on the survey, the high water elevation was within 0.1 feet of his garage. The second purpose of the survey was to help to determine if an emergency overflow from the backyard at 11235 52nd Avenue could be constructed between the houses, across the street, and between the neighbors' homes to the north to allow water to discharge into Pond SCP17. Cross- sections were taken the entire length of the location of the proposed overflow swale to determine if the construction of a swale is possible. Alternatives The primary alternative investigated the construction of an emergency overflow from the backyard to pond SCP17. This was based on discussions with City Staff and site visits. After reviewing the survey information it was determined that a shallow Swale between the house at 11235 52nd Avenue and the neighbor to the east could be graded. The proposed minimum elevation of the swale would be the same as the crown in the street which is at elevation 920.0. Because the elevation of the swale is approximately the same as the elevation of the street, it was not possible to provide adequate slope for drainage in the swale to the street. To solve this problem, adding an additional yard drainage structure between the homes near the street would increase the swale slope to provide proper drainage. This structure would be at an elevation lower than the street and would allow for adequate drainage between the houses. The drainage structure would be connected into the existing storm sewer line that runs between the houses and discharges north into pond SCP17. The minimum elevation of the swale should be 1.5 feet lower than the top of the window well. The emergency overflow swale construction should continue from the street north into the pond between the house at 11220 52nd Avenue and its neighbor to the west. Besides protecting the home at 11235 52nd Avenue, the swale will also provide additional protection from the street flooding the houses on the north side of the street. Preliminary discussion with all affected property owners indicates they would be supportive of a Swale being constructed. Site 4 East - 11235 52nd Avenue October 21, 2003 Page 3 Besides the backyard and street flooding, there was speculation that Pond SCP17 contributed to the high water elevations. Based on the survey and input from the residents next to the pond, the peak elevation of the pond was at elevation 918.7, which is approximately 3 feet below the high water elevation in the backyard and street, and over 3.5 feet lower than the top of the retaining wall at 11220 5fd Avenue (922.3). These elevations also indicate that the elevation of the pond did not have any impact on the flooding that occurred at 11235 52" Avenue. A cost estimate was completed for this alternative which includes fence removal, regrading and restoration, as well as adding the additional drainage structure. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct this project is $12,100. Another alternative to consider would be to protect the home from future flooding problems by flood proofing the window wells to prevent water from getting over or through them in the future. The window well would need to be water proofed so that they did not leak and raised to an elevation that is greater than 921.8 or about 0.3 feet above were they currently are set at. This option would work well on the west window well, however the east window well is under the deck and there may be not enough room to raise it without impacting the deck. A good practice in general for this home would be to seal the window wells. Review of Ponding in SPC17 The following is a response to the concern raised by some of the residents regarding the bounce of pond SPC17. There are two ways to help alleviate dramatic changes in elevations of the pond. One is to increase live storage, and the second way is to increase the capacity of the outlet. There is a significant amount of storage upstream of pond SCP17, in SCP16 east of Zachary Lane, and hydraulically the systems are tied together. Because the ponds are connected it would take a significant amount of additional live storage to decrease the peak elevation of the pond. The City owns a 50 -foot piece of land directly north of the pond but the area is not large enough to have a significant impact. In addition, the elevations are such that the amount of excavation would be cost prohibitive and not provide a significant amount of relief to the peak elevation of the pond. Also complicating the pond expansion is a sanitary sewer line that travels through that property. The second option to help alleviate the bounce of the pond is to construct an emergency overflow pipe running west from the pond within the existing right-of-way. From the site visit, it appears the downstream system would be able to handle the flow at a quicker rate than existing flows. The overflow would have to be an additional pipe, rather than a swale, due to the elevation constraints of the site. If the option of expanding the pond and/or creating a piped emergency overflow is to be truly explored, a detailed model of the entire system would need to be created to determine if it would provide any benefit and the impacts of the work. Attachment x.,VAplynm10304001wonitrepon nvnnsNshe 4 -11235 uxun wvjs d.dnc Plymouth- Neighborhood Flood Analysis Site 4 -11235 52nd Ave. Alternative 1 Item Unit Quantity Cost Total Cost Remove chain link fence LF 120 5.00 600 Excavation CY 150 7.00 1,050 48 -inch Manhole LF 6 275.00 1,650 Connect to existing storm sewer system Each 1 150.00 150 Install chain link fence LF 120 20.00 2,400 Restoration Ac 0.2 2,500.00 500 Topsoil CY 100 5.00 500 Subtotal 6,850 35% Contingency 2,398 Subtotal 9,248 Mobilization (5%) 462 Subtotal 9,710 25% Engineering, Administration and Legal Costs 2,427 TOTAL $12,137 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Name: Site 4 East - 11235 52nd Avenue Flooding Location: Backyard, into window wells and into basement Visit Information: Date Time Name of Resident Address Phone No. 817103 3:00 Mary and Brad Coomes 11235 52nd Avenue N 763.553.0939 Citv Representatives at site visit Name. Dan Faulkner Rocky Keehn Beth Peterson Dir. of Public Affiliation Works SEH SEH Phone No. 763.509.5520 651.490.2026 651.765.2901 O Ullllll"I UL Y lblL WLLLI 1\CSILLCLLL: Description or Problem based on site meeting: Water filled in yard up to house, and at 1:30 am the water was not into the house Power went out, but it sump system did not appear to be overwhelmed The street was also flooded in the morning- approximately thigh high Water had started to recede in the yard by morning Damage that occurred 10 inches of water in basement Appears water entered through windows- water filled the window wells and broke the windows Frequency of Problem Water has never been past the garden in the back yard that the residents have ever seen Resident's proposed solutions. Concerned with value of property Would like to see physical evidence of action Inlet improvement -- adding an inlet or improving capacity Possible overflow swale Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. SMS a, Eve, Data Sheet To Determine Action Plan Site Identification Problem Area Name: Site 4 East - 11235 52°d Ave. N Flooding Location: Backyard, into window wells and basement Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn, Beth Peterson Date: $119103 General Conunents: Appears to have Iarge upstream drainage area. From original grading plan from development: HWL is 919.0, the backyard corner is 921.0 and front yard is 920.0. Original plan shows the backyard draining to front yard, but the site was not built that way and a low point was created in the backyard Available Data: Preliminary plat (1978) Additional Data that needs to be collected: Storm sewer and contours Recommended Future Action(s) based on Available information: 1. Create emergency overflow 2. Study downstream system - look at pond outlet, sediment delta and verify outlet system i i City Review on Bach Page City Review of the Problem Problem Area Name: Site 4 East - 11235 52nd Me. N Date: Flooding Location- Backyard, into window wells and basement Date. 6/24/03 Contact: City Contact Person: Dan Faulkner 763.509.552YftoneNo. !d General Comments: A house upstream of the pond (on the east side of Zachary Lane) also flooded Future Actions: Action Cost of Action Basis of Payment I) Proposed Completion Date Final Completion Date Site visit 2100 GF 9/03 9103 Survey site 2100 GF 9103 9/03 Create emergency overflow 12,100 I) GF — General Funds SU — Storm Water Utilitv AS — Assessment GR - Grant Total Solution Cost 16,300 MEMORANDUM 3535 Vadnais Center Drive, St. Paul, MN 55110.5196 651.490.2000 600.325.2055 651.490.2150 FAX TO: Dan Faulkner, City of Plymouth FROM: Beth Peterson, Project Manager DATE: October 21, 2003 RE: Site 4 West - 11735 52nd Avenue SEH No. A-PLYM00304.00 14.00 SEH is submitting this technical memo to address the flooding that occurred at 11735 521" Avenue from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 - year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 -year storm is 6 inches of rainfall in a 24-hour period. For the same duration as the June storm event, the 100 -year storm produces 5.3 inches of rainfall in a 12 - hour period. This memo provides a summary of the study and alternatives considered. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. The home is located in the low point of the subwatershed. The walkout sits much lower than the streets and surrounding homes and as a result had flooding in the basement, where water entered through the walkout. There is a drainage easement over a large portion of the yard at 11735 52nd Avenue and a small portion of the yard of the neighbor to the east. No other homes in the area received any flooding damage. The home and yard receive drainage via overland flow, and from an existing storm sewer system from the south and from 52nd Avenue N. A storm sewer inlet picks up the drainage from the backyard and conveys it to the north into a ditch system which travels underneath the Canadian Pacific Railroad tracks via culverts and then between two houses on 53rd Avenue N. The ditch then discharges water into the street, and is carried to the west to catch basins next to Bass Lake. Method of Analysis No modeling was completed as part of the analysis for the site. The first step was to complete a site visit of the watershed and downstream controls. The second step was to complete a field survey of the storm sewer and critical elevations. The survey included the storm sewer on 52nd Avenue N, the backyard storm sewer system, and the high water marks at the house according to the information provided by the resident. In addition to the critical flood elevation, survey points were taken in the backyard to determine the elevation of the yard in relationship to the storm sewer inlets and outlets to determine if there Short Elliott Hendrickson Inc. Your Trusted Resource Equal Opportunity Employer Site 4 West - 11735 52nd Avenue October 21, 2003 Page 2 was a possibility of increasing the storage in the yard. The purpose of the survey was to determine the critical elevations and to provide actual field information to determine potential solutions that could be developed without any detailed modeling. Alternatives The primary alternative analyzed was to review connecting the storm sewer systems in the backyard of 11735 52°d Avenue. We looked at connecting the culvert in the southern portion of the yard to the culvert that discharges from 52nd Avenue in the northern portion of the yard, directly into the existing storm sewer outlet which picks up the drainage for the area and takes it to the north. This would remove a significant portion of the drainage, which travels through the yard and ponds. After the storm sewer systems are connected an apron would need to be installed to pick up the remaining runoff that would still be conveyed via overland flow in the yard. The apron should have a check valve to prevent water from backflowing into the yard. Because the lot is larger than is typically seen in that neighborhood, there would be room to create some additional storage and thus protection in the backyard without significantly impacting the function and use of the yard. Any program to create additional storage will require a detailed survey of the yard and further discussions with the affected property owners. If the storm sewer systems are connected in the backyard, the water will be conveyed more rapidly downstream, which could cause impacts to the downstream ditch system. The primary concern is the ditch that discharges onto 53rd Avenue N after the flow travels under the railroad tracks. Since the ditch is currently maintained by the resident on 53`d Avenue N additional flow could create additional burden on the property owner; and until the City's street reconstruction program is completed in 2006 the ditch will need to continue to be maintained by the residents. To reduce flow into this ditch the current storm sewer discharge could be altered on the south side of the railroad tracks. Currently the discharge does not enter pond SCP17B, which is just east of the ditch, before traveling underneath the railroad tracks. The outlet from this pond also drains into the same system that comes from the backyards, and then both systems discharge into the ditch that goes under the railroad tracks. Before the pipes are connected in the backyard, this alternative should be reviewed by completing a detailed survey and a hydrologic model to determine the correct revised outlet size to dampen the peak of the runoff and to determine the impact to the adjacent properties around the pond. The final aspect of this alternative would be to upgrade the downstream swale through the backyard and the storm sewer system on 53rd Avenue N to collect the drainage. New storm sewer would be needed as part of the street reconstruction program whether the swale upgrade is completed or not, and would be constructed as part of this project which if the pond revisions are made, this part of the project could wait until proposed street reconstruction occurs in 2006 as programmed in the City's Pavement Management Update. A cost estimate was completed for the first and second parts of the alternative. This estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct the primary project is $42,100 which does not include excavation of the yard, but includes the cost of the Site 4 West - 11735 52nd Avenue October 21, 2003 Page 3 pipe, storm sewer work, and associated restoration. The estimate to construct the storm sewer diversion is $11,000 which includes the associated storm sewer work, and is subject to access to the site with construction equipment and materials. The final cost estimate for the 53rd Avenue N ditch regrading should be done as part of the cost estimate that would be required of the street reconstruction project. Another alternative considered was to flood proof the house by removing the walkout to the basement and constructing a walkup and small berm around a portion of the yard directly in the back of their house. Since this option impacts the function of the house it would have to be agreed to by the property owner. bcp Attachment x_1p[1plyrro1030400\w rdpepnn r msWie 4 -11735 52nd am. nriw mvia d.dnc Plymouth- Neighborhood Flood Analysis Site 4 - 11735 52nd Ave. Alternative 1 Item Unit Quantity Cost Remove Apron Each 1 500.00 12" DIP LF 20 35.00 18" RCP LF 270 58.00 48 -inch Manhole LF 6 275.00 End treatment for 12" DIP LS 1 1,000.00 14" O.Q. Series TF -1 Tideflex Check Valve Each 1 3,200.00 Connoct to existing storm sewer system Each 2 150.00 Restoration Ac 0.3 2,500.00 Subtotal 35% Contingency Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs TOTAL Alternative 2 Total Cost 500 700 15,660 1,650 1,000 3,200 300 750 23,760 8,316 32,076 1,604 33,680 8,420 42,100 Item Unit Quantity Cost Total Cost Salvage and reinstall apron Each 1 500.00 500 18" RCP LF 60 58.00 3,480 48 -inch Manhole LF 8 275.00 2,200 Subtotal 35% Contingency Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs 6,180 2,163 8,343 417 8,760 2,190 TOTAL $10,950 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Name: Site 4 West - 11735 52nd Ave. FloodingUcation: Backyard and basement Visit Information: Date Time Name of Resident Address Phone No. 817103 2;00 Jerry and Sue Jackson 1173552 d Ave. N 763.557.5825 City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Dir. of Public Afriliation Works SEH SEH Phone No. 763.509.5520 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: They tried vacuuming and the sump was working. Damage that occurred 18 inches of water at the back door 5-6 inches of water in basement 2 feet of water up sheetrock (which had to be removed) Shed was flooded- approximately 24 inches of water Frequency of Problem Water has been in the house before- about 3 years ago. The culvert had collapsed. With significant rains, it will pond in front of the culvert Resident's proposed solutions- l Reroute water Water isn't leaving fast enough (there are jogs in the storm sewer); increase outlet capacity?? i Back page is for site sketch Sketch of Problem Area: Include. Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. 52 Ar., r. Data Sheet To Determine Action Plan Site Identification Problem Area Name; Site 4 West - 11735 52nd Ave. N Flooding Location: Backyard and basement Preliminary discussion of the problem based on site visit: Discussion by. Rocky Keehn, Beth Peterson Date: 8119103 General Continents: The side yard is the low spot in the subwatershed. There is no emergency overflow. Why does the street discharge to the ditch in the yard and then back out again via the yard culvert? Available Data: Preliminary plan (1978) Additional Data that needs to be collected: Storm sewer information - both upstream and downstream Plan for Schmidt Lake Woods addition Reronmended Future Action(s) based on Available Information: 1. Verify drainage boundaries 2. Connect system in the yard - rather than daylighting 3. Provide storage in yard - survey site 4. Study downstream in more detail City Review on Back. Page City Review of the Problem Problem Area Name. Site 4 Vest - 11735 52od Ave. Date: Flooding Location: Backyard and basement Date: 6124103 City Contact: City Contact Person: I Dan Faulkner Phone No. 763.509.5520 General Comments: Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Complete site visit 2100 GF 9103 9103 Survey site 2100 GF 9103 9103 Connecting of storm sewer systems 42,100 Constructing storm sewer diversion 11,000 1) GF — General Funds SU — Storm Water Utility AS — Assessment GR - Grant Total Solution Cost 57,300 3535 Vadnais Center Drive, St. Paul, MN 55110-5196 TO: Dan Faulkner, City of Plymouth FROM: Beth Peterson, Project Manager DATE: October 21, 2003 RE: Site 6 - 28th and Sycamore SEH No. A-PLYM00304.00 14.00 MEMORANDUM 651.490.2000 800.325.2055 651.490.2150 FAX SEH is submitting this technical memo to address the flooding that occurred at 2740 Sycamore Lane N from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 - year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 -year storm is 6 -inches of rainfall in a 24-hour period. For the same duration as the June storm event, the 100 -year storm produces 5.3 inches of rainfall in a 12 - hour period. This memo provides a summary of the study and alternatives considered. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. The home is located in the low point of the subwatershed. The yard receives drainage via overland flow and a concrete swale which drains a series of backyards from the neighbors to the east. A corrugated metal (CMP) culvert is located in the side yard that conveys the drainage to the north, under 28th Avenue N, and eventually into Plymouth Creek. There are four catch basins in the street that are connected into the culvert that runs underneath. There is a concern that during these large events flow from the street backflows into the resident's yard. The home had flooding in their basement during this event from water entering through the walkout. No other homes in the area received any flooding damage. Method of Analysis No survey or modeling was completed as part of the analysis for the site. The first step of the analysis was to complete a site visit of the site and downstream controls, and then to review the temporary solution that was provided by the City after the June storm event. Alternatives The resident believes that the flooding was due to the backflow from the storm sewer in the street rather than the local drainage area. With this in mind the City provided a temporary solution for the flooding shortly after the storm. It included a small restriction to the outlet to reduce the amount of backflow that was possible. Shod Elliott Hendrickson loc. Your Trusted Resource Equal Opportunity Employer Site 6 -- 28th and Sycamore October 21, 2003 Page 2 The temporary solution was checked using hydraulic computations to see if the solution could be backed up with engineering computations. The drainage system from 28th Avenue N has no as - built information. The size and type of pipes were therefore determined by visual inspection and it appears that the pipe leaving the catch basins is corrugated metal and at the discharge the pipe is cast iron. Flow in this system is limited by the corrugated metal pipe which would have less capacity then the cast iron due to the roughness of the pipe, and thus was used in the hydraulic review of the system. During investigation of the operation of the system, the downstream storm sewer system was analyzed for various flows. Based on this analysis, the downstream capacity of the ditch, in which the system discharges into, is adequate because the flow in the pipe is the limiting factor in the system, not the ditch. This analysis also indicated that the proposed system would work well for all storm events, except when the runoff exceeds the capacity of the downstream storm sewer to a point were it would begin to pond in the street. During these events the water would be detained in the street at the catch basins or backflow through the pipe into the yard. To assure that during all conditions it will work a check valve should be constructed to prevent the backflow into the yards. To provide better access and a more engineered outlet a small structure should be constructed which connects into the existing CMP. This structure would include a six-inch pipe that would pick up the drainage from the backyard. A check valve would be placed on the pipe to prevent backflow from the street into the yard. Since the diameter of the proposed 6 -inch pipe is less than the current 12 -inch pipe the impact is reduced even if a check valve is not installed or fails. This reduced pipe size provides a greater level of protection than currently existed before the June storm event. A cost estimate was completed for this proposed solution. The estimate is attached and includes the major items to be completed during construction; engineering, administrative and legal costs; along with contingencies. The estimate to construct the project is $7800. Another alternative considered was to flood proof the house by removing the walkout to the basement and constructing a walkup and small berm around a portion of the yard directly in the back of their house. Since this option impacts the function of the house it would have to be agreed to by the property owner. bcp Attachment x;VtVlymo10304W1worilIV"rtnE=Asire6-r momvised.doc Plymouth- Neighborhood Flood Analysis Site 6 - 2740 Sycamore Lane N Alternative 1 Item Unit Quantity Cost Total Cost 6" DIP LF 10 25.00 250 48 -inch Manhole LF 6 275.00 1,650 End treatment for 6" DIP LS 1 1,000.00 1,000 8" O.D. Series TF -1 Tideflex Check Valve Each 1 1,100.00 1,100 Connect to existing storm sewer system Each 1 150.00 150 Restoration Ac 0.1 2,500.00 250 Subtotal 35% Contingency Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs 4,400 1,540 5,940 297 6,237 1,559 TOTAL $7,796 6 Site Visit Sheet Collect Information of identified problem related to storm water runoff in Plymouth Site Identification Problem Area Name: Site 6- 28`11 and Sycamore Flooding Location: Side yard and basement Visit Information: Date Time Name of Resident 8112103 4:00 Mark Pitman City Re resentatives at site visit Name: Ron Quanbeck Affiliation City Engineer Phone No. 763.509.5500 Address Phone Iho. 2740 Sycamore Lane N 763.553.0444 Rocky Keehn SEH 651.490.2026 Beth Peterson SEH 651.765.2901 Summary of Visit with Resident: Description or Problem based on site meeting: Water came out of culvert underneath the road and backed up into yard and filled side yard up to the house Water gets into storm sewer and typically does not flood streets or jump over the curve Resident has sump pumps Is discharge end of culvert a problem? Darnage that occurred Side yard flooded t Water was up 2-3 inches on back corner (SE) of house Carpet in the basement was wet, there was no measurable depth of water Frequency of Problem Measurable rains will usually cause water to back up from culvert into side yard, approximately . 8 -inches deep Resident's proposed solutions: Currently, the resident and the City have placed a restricter pipe within the existing culvert and surrounded the entrance with sand bags. This limits the amount of backflow from the street into the yard. The resident believes that this has been helpful and would like to do a more permanent outlet configuration similar to this concept. The resident intends to raise grade next to house and build a retaining wall. Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. Data Sheet To Determine Action Plan qitP irlentifiention Problem Area Name: Site ( _ 28th and Sycamore Flooding Location: Side yard and basement Preliminary r keussion of the n'Mblem based on site 'visit: Discussion by: Rocky Keehn, Beth Peterson Date: 8/19/03 General Comments: Is the temporary solution the City did working? (No surcharge occuring in backyard?) The backyard drainage is separate from the concrete swale Available Data: Road profiles Plymouth Creek Dike information Additional Data that needs to be collected: Storni sewer system Downstream ditch survey Recommended Future Action(s) based on Available Information: 1. Verify outlet restriction - replace with flap gate? 2. Build separate outlet system- separate yard and street drainage City Review on Back Page City Review of the Problem Problem Area Name: Site 6 - 28`h and Sycamore Date: Flooding Location: Side yard and basement Date: 6124103 City Contact: L.0Contact Person: I Dan Faulkner Phone No. 763.509.5520 General Comments: Future Actions: Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Hydraulic model 1000 GF 9103 9/03 Construct check valve system 7800 Replace drainage system (completed with street reconstruction program) t) GF — General Funds SU — Storm Water Utility AS — Assessment GR - Grant Total Solution Cost ssoo 3535 Vadnais Center Drive, St, Paul, MN 55110-5196 TO: Dan Faullaier, City of Plymouth FROM: Rocky Keelun, SEH DATE: January 16, 2004 RE: Site 5 - Plymouth Colony Apartments SEH No. A-PLYM00304.00 14.00 MEMORANDUM 651.490.2000 800.325.2055 651.490.2150 FAX SEH is submitting this technical memo to address the flooding that occurred at Plymouth Colony Apartments from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 -year storm, which is a ston'n with a statistical chance of happening in any one year of I%. For the Twin Cities metro area the 100 -year storm is 6 inches of rainfall in a 24-hour period. For the same duration as the June stone event, the 100 -year stone produces 5.3 inches of rainfall in a 12 -hour period. When the storm sewer for the apartments was plaimed in 1972 and/or 1974, a 12 -inch pipe restriction was created at Merrimac Lane to limit the flow from the 36 -inch storm sewer system from the apartments due to downstream concerns. The invert of the larger 36 -inch pipe is 3.1 feet below the elevation of the restriction. This creates permanent standing water in the stone sewer system upstreain of Merrimac Lane. Also, the outlet from Pond HLP2, according to the plans, was blocked when the storm sewer was built in the 70's. Based on the historical data, it appears that there was every intention of removing these restrictions in the future. During our field visit, it was observed that the outlet restriction from the Pond HLP2 had been removed; however, the smaller pipe restriction at Merrimac Lane remains in place. Critical elevations from the as -built plans include the top -of -casting elevations from drainage systems located at the entrance of each of the lower garage floors. The top of castings near the entrances at the garages are at 9825 feet (south garage), 981.5 feet (west garage), and 983.4 feet north garage) based on plans dated 6/27/1972. All elevations are above the 12 -inch restricted downstream outlet elevation of 979.8 which indicates that at least during small storm events the system should drain water away from the garage entrances. This memo provides a summary of the study and alternatives considered. Cost estimates provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. Method of Analysis After a site visit and review of existing information it was determined that a detailed hydrologic model would be needed to complete the analysis of this site to determine the potential impacts of Short Elicit Hendrickson Inc. Your Trusted Resource • Equal Opporlunily Employer Site 5 - January 16, 2004 Page 2 removing the restriction at Merrimac Lane. Since detailed contour information did not exist for the apartment site and area surrounding pond HLP2, and it was determined that accurate infoinnation would be critical in reviewing the impacts of changing the restrictions, an aerial contour map for the site was produced for this project. With the contour information and record drawing infonnation available, we developed a HydroCAD© (hydrologic) model to simulate the storm events. SEH modeled two flood events for each alternative; the first was a Huff -3"d Quartile distribution for a 6 -inch rainfall in 12 hours, and the second was the SCS Type II -24 hour distribution for a 6 - inch rainfall in 24 hours. The first event was used to simulate the June stone event and will be referred to as the June stone event. The second event simulates the 100-year/24 hour event and will be referred to as the 100 -year event. Once the existing condition model was created and calibrated, the model was revised to depict the alternatives proposed to alleviate the flooding. Also modeled was the 10 -year event to determine impacts related to the storm sewer design changes. Since the ponding in the apartment parking lot was not planned as a storage area for large events, the model was initially run assuming direct runoff to Pond HLP2 from both the surrounding area and apartments. This assumption would be consistent with other hydrologic models that would have been done to determine water surface elevation in ponds. Based on this assumption, the 100 -year flood elevation for Pond HLP2 would be 979.7. The City's Water Resources Management Plan reports the 100 -year event High Water Elevation (HWL) for the pond at 979.0 which is based on the 1973 and 1980 Storm Drainage Plan. Since the elevation difference was significant, an additional computer run was made to try and determine if the 979.0 elevation was still valid or different as a result in changes in modeling methods. The model was revised and it was assumed that all the area draining to the pond would be residential area (which is consistent with what was already in place in watershed around the pond in the early 1970's). Since the area where the apartments and shopping area are now located was undeveloped at this time, assuming residential area for the entire watershed would have been valid in 1973. With this change in the model, the water elevation in Pond HLP2 is just over 979 and thus validates the original flood elevation of 979.0. It thus was assumed that the changes in water surface elevation in Pond HLP2 from the previous studies are a result of a higher density development in a portion of the watershed. Backwater impacts from the restricted pipe size at Merrimac Lane were determined by assuming ponding would occur in the parking lots of the apartments and shopping area and running the model with the restriction in place. The highwater elevation for the 100 -year event in the parking lot area is 987.5 feet for the 100 -year event and for the June 24 event it was calculated to be 986.4 feet. Both elevations are well above the invert elevations of castings located at the entrance of the garages (982.5 feet , 981.5 feet, and 983.4 feet). Based on highwater elevation in Pond HLP2 (979.0), the pond would not flood the garage floors, so flooding reported by the apartment manager were more than likely a result of direct flow into the garages from the surface or as indicated in the backwater model, from the restricted storm sewer system via the catch basins at the entrances of the garages. Site 5 - Jamuary 16, 2004 Page 3 To remove the backwater impact, the restriction would need to be removed and a larger pipe installed which matches the existing 36 -inch storm sewer system from the apartments. Computer nuns were made without the restriction in place. For the 100 -year event, the parking lot flooding elevation is reduced from 987.6 to 985.2 (2.4 feet) and for the June event 2.9 feet (986.4 to 983.5). However, there is an increased impact to pond HLP2 for the 100 -year event (0.5 feet) and for the June event (0.1 feet). One goal of the project should be to remove the standing water in the existing stone sewer system, and since there was an impact to HLP2 with the restriction removed, an additional computer run was made assuming the 12 -inch outlet size would remain but be installed at a lower elevation to allow for the upstream system to drain. For this scenario, there is no impact for the 100 -year and a 0.1 foot increase for the June event. However, the flooding would remain in the apartment and shopping area parking lots. Alternatives To protect the lower elevation of the garage from flooding alternatives for solutions were evaluated and are discussed in the following text. Based on review of the hydrologic analysis and collected data, it appears that even with the elimination of the flow restriction there is still backwater impacts to the garages during large events due to the limited elevation differences between the catch basins in the garage entrances and the adjacent storm sewer system. If flooding in the parking lot cannot be eliminated by changes in the outlet, a project which eliminates the water from flowing into the garages from the surface, eliminates the connection to the catch basin to remove the threat of surcharging and adds pumps to remove the limited flow that can get to the lower garages should be considered. Upon review of the contour maps, this solution can be accomplished by raising the upper entrance to the ramps of the garages by 1 to 1.5 feet. This would force the water during extreme storm events to flow away frons the garages entrances to other drainage systems (i.e. streets) via natural or in some cases created overflow locations. With the raised area, there is still a potential for rainfall to enter the garage via the entrance ramps (about 1200 square feet). Sump pumps would need to be installed to remove the limited amount of water that would collect in the garage. To further reduce the potential of runoff into the garages, a cover could be installed over the entrance to divert the water away from the entrance ramp. The raising of the entrance to the parking garages and some additional regrading was estimated to be $86,500 (attached). Since detailed surveys of each of the garage entrances was not completed, it was assumed that about 100 feet of the drive area (which includes curb and gutter) in front of the each garage would need to be removed. It is anticipated that once a more detailed survey is completed, the project costs would be reduced when the project is designed to fit the site conditions. A cost estimate for covering the area was not completed at this tnme since it would involve a more detailed design to make sure the cover would match architectural aspects of the surrounding buildings We also considered removal of the restriction to allow flow to proceed to pond HLP2 as was originally planned when the apartments were built. This option was not pursued in any detail at Site 5 January 16, 2004 Page 4 this time due for two reasons. First, as was explained previously, there still exist a possibility of flooding in the apartment garages even if the restriction is removed. Thus a project which increases the pipe sizes would not totally solve the flooding problems. Second, the construction of a 36 -inch outlet did show an increase in water surface elevation in the Pond HPL2. Additional information would need to be collected on the history of the ponding area (for example the impact of the originally plugged outlet from the pond), easements requirements for ponding area and potential impacts to private and public structures around the pond. These issues should be discussed with he property owners prior to or part of the street reconstruction of Merrimac Lane when the new outlet should be installed. As a minimum, in the future, the outlet pipe under Merrimac Lane should be replaced and lowered to allow for water to drain from the apartment storm sewer system. The modeling showed the lowering of the restriction creates minimal downstream impacts which could be discussed as part of the street reconstruction project. pdh Attachment x:4pi1plymo50304001wordlreporl 5-plymoulh colony memo.doc Plymouth- Neighborhood Flood Analysis Site 5- Plymouth Colony Apartment Alternative - Raise area in front of garages Item Unit Quantity Cost Total Cost Sawcut Bituminous LF 180 1.50 270 Remove Bituminous SY 1000 1.60 1,600 Remove Curb & Gutter CY 300 10.00 3,000 Install Sump Pump Each 3 5,000.00 15,000 Remove Structures Each 3 200.00 600 Excavation CY 200 10.00 2,000 Bituminous Ton 165 40.00 6,600 Aggregate Base CY 200 30.00 6,000 Concrete Curb & Gutter (B618) CY 300 10.50 3,150 Speed Bump/water protection Each 3 1,000.00 3,000 Topsoil Borrow CY 180 10.00 1,800 Sod CY 600 2.00 1,200 Subtotal 43,950 50% Contingency Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs 21,975 65,925 3,296 69,221 17,305 TOTAL $86,500 Site Visit Sheet Collect Information of identified problem related to storm `eater runoff in Plymouth Site Identification Problem Area name: Site 5-Plyiriouth Colony Apartments Flooding Location: Parking garages Visit Information: Date Time Name of Resident Address Phone No. 8112103 3:00 John Amundson- Plymouth Colony Apartments 612.490.3403 Works Maintenance Manger, 1805 Co. Road 101 763.475.1679 Phone No. 763.509.5520. Wanda Moen - 651.765.2901 Apartment Manager City Representatives at site visit Name: Dan Faulkner Rocky Keehn Beth Peterson Affiliation Dir. of Public SEH SEH Works Phone No. 763.509.5520. 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: Appears that water comes out of the catch basins's at the bottom of the driveway into the parking garage Pumps were ruffling full speed (1 112" discharge, maybe 500-600 gpm) The pumps couldn't keep up with the water Damage that occurred Approximately 1-1.5 feet of water in garage, enough to where water came up to the doors of cars and entered into the cars It took a few days for the water to recede in the garages Frequency of Problem For the last few years large rains will fill the garage with water Approximately 20 cars were damaged and 2 cars were totaled In the last 5 years, this is the second stone that has totalled cars Proposed solutions. - Limit water in garages The Apartment Complex has considered valves or placing balls in the line Back page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures, NO SKETCH DEVELOPED Data Sheet To Determine Action Plan Site Identification Problem Area Name: Site 5 -Plymouth Colony Apartments Flooding Location: Parking garages Preliminary discussion of the problem based on site visit: Discussion by: Rocky Keehn hate: General Comments: Observation was that the garage are well below the natural ground line which would support the frequency of the flooding. The site drains into a pond west of the apartments. Staff discussions indicate that the pipe size is restricted. During the site visit it was observed that water was standing in the storin sewer system. Available Data: Grading plan for the apartments, stone sewer as-builts for the part of the downstream storm sewer. Additional Data that needs to be collected: There is not current contour map for the west pond HLP2 or for the apartment area so a detailed contour neap should be developed. Detailed computer model. Recommended Future Action(s) based on Available Information: Develop a detailed contour map of the area to complete a detailed hydrologic model of the area. City Review on Back Page Citv Review of the Problem Problem Area Name. Site 5 -Plymouth Colony Apartments Date: Flooding Location: Parking garages Date: City Contact: City Contact Person: I Dan Faulkner Plaoue No. 763.509,5520 General Comments: After completion of the modeling it appears the garages elevation are too low and this is the critical factor to be addressed. The removal of the restriction would aid in during the more frequent flooding but does not totally eliminate the problem without other protection measures. Also, the removal of the restriction has the potential to increase the water surface elevations in Pond HLP2 and thus any project to remove the restriction would require additional meetings with residents around the pond. The primary solution is to try and prevent water from going in the garages at the surface. Since these solutions would be on private property and would totally benefit the property owner by increasing the ability to rent out the garages, the project may be the responsibility of the owners to implement the improvements since they will benefit form it. The City would pursue removal of the pipe and restriction and complete the downstream storm sewer project as part of the street maintenance for Merrimac Lane. Future Actions: 1) GF --General Funds GR - Grant Total Solution Cost X91,000 AS— Assessment/Private NIA — Part of future project costs SU — Storm Nater Utility Basis of Proposed Final Action Cost of Action Payment Completion Completion 1) Date Date Complete more detailed review of available 5000 5104 information on historical water elevations on HLP2 by meeting with residents around the pond. This may include marking the anticipated HW elevation in the backyards. Improvements to the entrances to the parking 86,000 AS garages and changes to the storm sewer system at the entrance to the garages and minor grading. Reconstruction of storm sewer outlet at NIA Merrimac Lane as part of street reconstruction. 1) GF --General Funds GR - Grant Total Solution Cost X91,000 AS— Assessment/Private NIA — Part of future project costs SU — Storm Nater Utility O W uJ 00 0 w a a Lu a S SITE V SUMMARY - PLYMOUTH COLONY APARTMENTS HWL HWL Alternative Rainfalluration Distribution hr) Rainfall inches) Pondnow HLP2 (ft) cfs) u ow cfs) o ume ac -ft) partments now ft) (cfs) u ow cfs) Volume ac -ft) Match 1973 Study Runoff Huff 3rd Qrt 12 6.0 Assumed to be part of total drainage area Existing -restricted flow Huff 3rd Qrt 12 6.01 979.2 32.1 23.1 12.08 986.4 18.3 11.7 6.1 Remove restriction and Increase outlet to 36 -inch Huff 3rd Qrt 12 6.0 979.3 37.5 24.8 12.08 979.0 18.3 18.3 6.1 Remove existing restriction and replace with lower 15 -inch restriction Huff 3rd Qrt 12 6.0 979.3 37.6 24.8 18.34 983.5 18.3 18.3 6.1 Match 1973 Study Runoff SCS Type II 24 5.9 979.1 88.6 21.6 4.00 Assumed to be part of total drainage area Existing -restricted flow SCS Type II 24 5.9 979.2 69.1 22.5 11.80 987.5 100.5 12.7 6.0 Remove restriction and Increase outlet to 36 inch SCS Type 11 24 5.9 979.7 130,5 30.41 11.80 985.2 100.5 90.7 6.0 Remove existing restriction and replace with lower 12 -inch restriction SCS Type 11 24 5.9 979.2 71.3 23.9 11.801 987.4 100.5 14.9 6.0 Match 1973 Study Runoff SCS T pe ll 24 4.1 978.2 45.4 9.2 4.84 Assumed to be art of total drainage area Existing -restricted flow SCS Type II 24 4-11 978.6 41.4 14.2 7.02 986.8 67.1 12.0 3.9 Remove restriction and Increase outlet to 36 -inch SCS Type II 24 4.1 978.7 79.1 16.0 7.02 982.7 67.1 67.0 3.9 Remove existing restriction and replace with lower 12 -inch restriction SCS Type II 24 4.1 978.4 37,8 11.8 7.02 986.9 67.11 8.41 3.9 ASE+1 3535 Vadnais Center Drive, 5t. Paul, MN 55110-5196 TO: Dan Faulkner, City of Plymouth FROM: Rocky Keehn, Project Engineer DATE: January 16, 2003 RE: Site 7 — Plymouth Pond Apartments SEH No. A-PLYM00304.00 14.00 MEMORANDUM 651.490.2000 800.325.2055 651.490.2150 FAX SEH is submitting this technical memo to address the flooding that occurred in the garage of the Plymouth Apartments from the storm event on the evening of June 24, 2003, which produced over 6 -inches of rainfall in less than a twelve hour period. The City's design storm for ponding areas is the 100 -year storm, which is a storm with a statistical chance of happening in any one year of 1%. For the Twin Cities metro area the 100 -year stone is 6 -inches of rainfall in a 24-hour period. For the same duration as the June stornl event, the 100 -year stop -n produces 5.3 inches of rainfall in a 12 -hour period. This memo provides a summary of the study and alternatives considered. The basis for this study included discussion with city staff and interviews with apartment staff. Information gathered from these interviews is attached. The cost estimate provided should be considered very conceptual, intended to provide a basis for comparison of options. A more detailed design and estimate should be completed prior to implementation. The Plymouth Pond Apartments are located downstrearn of Valley Forge Lane, near 45t" Avenue N and Nathan Lane adjacent to Pond NBP3C. The parking garages of the apartment complex experienced about 3 inches of flooding when water entered through the garage doors. Because of the flooding, a site visit was arranged with the maintenance manager of the apartments. One of the significant things he indicated was that the pond/wetland appeared to continue to rise after the rain had stopped. This indicated that there is a lag or delay caused by upstream ponding and storage within the watershed. In addition, during the site visits, the outlet from Pond NBP3C (located in the northwest corner of 45t" Avenue N and Nathan Lane) was full of trash and debris and thus may have been partially blocked during the stonn event. The blockage could contribute to higher than expected high water elevations and thus contribute to the flooding that occurred in the garages of the Plymouth Pond Apartments. Follow-up site visits also noticed that the pipe tinder Nathan Lane and 45th Avenue N was fully submerged. The pond outlet was tracked through the downstream ponds and it appeared no blockage was occurring in the system and thus the pipes under Nathan Lane appear to be at an elevation lower than the downstream system outlets. Also, there was a ditch cut in the wetland several hundred feet upstream of the NBP3C outlet. This ditch appeared to be Shad Elliott Hendrickson Inc. Your Trusted Resource Equal opportunity Employer Error! Reference source not found.Plymouth Pond Apartments January 16, 2003 Page 2 about 1 foot lower than the surrounding ground of the wetland. To check the field observations a survey was completed. Table 1 summarized the results of the survey. Table 1. Summary of Survey Description Elevation Comments Storm sewer invert 894.94 Outlet for pond downstream of Nathan Lane and 45th Avenue N Pond NBP4) Ice on Pond NBP4 895.4 Water elevation on Pond NBP4 11125103) 27" Storm sewer invert 892.58 Stonn sewer under Nathan Lane and 45th Avenue which discharges water fiom Pond NBP3C into Pond NBP4. Pipe is submerged about 2.8 feet and has an attached a trash guard. 27" Storni sewer invert 893.13 Inlet stonn sewer under Nathan Lane and 45th Avenue N which is the outlet frons pond NBP3C. A weir is located at entrance of pipe which is 2 feet above the invert. Pipe is submerged about 2.3 feet with no trash guard Weir in front of inlet 895.11 Physical elevation control for pond NBP3C. Ditch elevation 895.6 Ditch through Pond NBP3C which conveys flow from stone sewer outlets from 45th Avenue North. This ditch is about 1 foot lower than the surrounding wetland ground elevations Peat elevation next to 896.9 Elevation of the top of peat or ditch wetland area next to the ditch describe above. West storm sewer 898.91 Due to the lower downstream ditch invert along 45th the flared end is about 1 to 2 feet Avenue N above the ground and could fall off. East storm sewer invert 895.66 Matches ditch elevations very along 45th Avenue N closely, Iee on Pond NBP3C 897.15 Water elevation of pond NBP3C. Pond elevation appears to be established by the peat blocking flow from the area not the elan -made structure at Nathan Lane and 45th Avenue N. Error? Reference source not found.Plymouth Pond Apartments January 16, 2003 Page 3 Southeast garage 901.89 Should have been built at 902.00 based on 100 -year flood elevation of 900.0 CB near garage 901.63 Lower than garage so water will flow from garage door to CB. Southwest garage 901.92 Should have been built at 902.00 based on 100 -year flood elevation of 900.0 Northwest garage 901.94 Should have been built at 902.00 based on 100 -year flood elevation of 900.0 Additional Elevation information Benchmark 908.78 Hydrant southeast corner of Nathan Lane and 45th Avenue N. Highwater NBP3C 900 From Water Resources Management Plan Highwater NBP4 900 From Water Resources Management Plan OHW of NBP3C 898 From DNR area Hydrologist Tom DNR Wetland 27- Hovey. 583W) Outlet NBP3C 895 From Water Resources Management Plan. ponding area next to apartments. Surveyed outlet at 895.11 Outlet NBP4 895 From Water Resources Management Plan. Downstream ponding area. Surveyed outlet at 894.94 Based on the survey information and water resources management plan it appears that pond NBP3C next to the apartments has an existing elevation that is higher than the outlet elevation. This appears to be a result of blockage created by moving bogs or build-up of material on the southeast end of the pond. Since the open water area needs to go through a much narrow and restricted area to drain, it would be logical for floating bogs to migrate to this outlet area and thus create a small dam effect. These assumptions are based on current site conditions and since we have not obtained records of whether or not the existing open water area was ever connected to the outlet ditch, caution should be used in assuming the pond should be lowered. Since this is a DNR protected wetland, the City contacted the area hydrologist. From this contact the following correspondence was received (via e-mail) "I (Tom Hovey, Area Hydrologist DNR Waters) have an OHW of 898.0 feet on 27-583W (NBP3C). The outlet is a mystery. There are notes in the file that a riser was planned for the outlet at elevation 897.0'. We have no indication that it was ever built, and I don't find any permits for constructing or changing the outlet". It thus appears that the elevation of the wetland (ice shot of 897.15) is close to plaimed elevation. Error! Reference source not found.Plyinouth Pond Apartments January 16, 2003 Page 4 Also, based on the survey information, the downstream outlet for Pond NBP4 is nearly the same as that for the pond next to the Plymouth Apartments (NBP3C). Therefore, the control elevation during extreme flood events for the both NBP3C and NB4 is the outlet for NB4, Since both ponds have the same highwater and normal elevations in the water resources plan, it appears that they were modeled as one large system. There is no record of the water surface elevation of the downstream pond (NBP4) during the June storm event, which makes it difficult to determine if blockage did occur at the NBP3C outlet or if the entire system was at an elevation which would flood the apartment garages. If blockage would have caused the problem, then the downstream pond elevation (NBP4) would have been lower then the upstream one (NBP3C), Alternatives The first alterative is installation of a skimmer structure and minor maintenance around the storm sewer outlet from NBP3C at Nathan Lane and 45th Avenue N. As part of the maintenance and installation of the skimmer, there will be excavation required on both the downstream and upstream ends of this storm sewer. Also, the trash guard on the downstream end should be removed to make sure debris passes through and does not get lodged inside of the storm sewer system. This alternative should greatly reduce the possibility of blockage of the NBP3C outlet and assure the two systems (NBPC3 and NBP4) are acting as one. The cost for installation of a skimmer structure and excavation is estimated to be $29,500 (see attached sheet). Since the amount of water in the garages was 2 to 3 inches deep, in conjunction with the improvements of the outlet, the apartments should prevent future water from going into the garages by having residents ramp up and down into the garage at the entrances. The ramps would raise the freeboard between the pond and the garages. Beside reconstruction of the garage entrances, this option would require installation of a small pump in each garage to discharge limited amount of water that may fall between the ramp and the door. The pump could also be eliminated by construction of a roof over the area between the ramp and the garage door. With this option a back-up power supply may be needed in case of power outage. The cost was estimated to be $2000 for each garage based on the cost to install a speed bump which requires manual concrete work. Because of an elevation difference of about 2 feet between the outlet of NBP3C and the upstream wetland, the City may want to create a permanent elevation control of the water surface elevation in the wetland. This could be done by construction of a sheet pile weir across the wetland where the blockage appears to be occurring now. If the blockage continues as an act of nature, there may be the possibility of the normal water elevation continuing to rise and thus further decreasing the available storage. Based on the survey and infonnation from the DNR, it appears that the water surface elevation is currently about 0.15 higher than what could be considered the normal water elevation. A weir would establish a permanent water surface elevation independent of the downstream pipes under Nathan Lane and provide a control elevation consistent with what the DNR has assumed. The cost of a controlled outlet is estimated to be $217,000 (see attached sheet). However, based on the information collected and the other potential variables (plugged outlet, extreme storm event, etc.), there is no evidence that had the weir been in place it would have reduced the flooding that occurred. This normal water elevation should be monitored to make sure it is not continuing to rise over time. Error! Reference source not found.Plymouth Pond Apartments January 16, 2003 Page 5 A related project would be to redo the entire wetland area between the Plymouth Pond Apartments and 45th Avenue N. This area could be excavated to create a new lower wetland system which would be more maintainable and provide additional water quality benefits to downstream drainage systems. It would also provide some additional storage if excavation is allowed. The current ditch which cuts through this area could be detrimental to the wetland area since it is located about 1 foot below the exiting ground elevation and thus may drain the adjacent wetlands areas. Because of the impacts to the wetland, a project for this area may qualify for grant money to help offset some of the costs. rjk Attachment xap[Ipkymp1030d001 sordVrcpoit memaskim 7 memo.doc Plymouth- Neighborhood Flood Analysis Site 7 - Plymouth Pond Apartment Alternative of Sheet pipe weir Item Unit Quantity Cost Total Cost Sheetpile Weir SF 6000 18.00 108,000 Control Section of weir Each 1 2,000.00 2,000 Restoration Ac 0.1 2,500.00 250 Subtotal 110,250 50% Contingency 55,125 Subtotal 165,375 Mobilization (5%) 8,269 Subtotal 173,644 25% Engineering, Administration and Legal Costs 43,411 TOTAL 217,000 Assumed Weir is in 20 feet of peat, 10 foot penetration thus a total depth of 30 feet Width is based on areal photographs is 200 feet Plymouth- Neighborhood Flood Analysis Site 7 - Plymouth Pond Apartments Alternative of Skimmer Manhole Item Unit Quantity Cost Total Cost 24" Submerged RCP LF 20 35.00 700 48 -inch Manhole LF 6 400.00 2,400 Special overflow grate LS 1 1,000.00 1,000 Excavation CY 500 10.00 5,000 Connect to existing storm sewer system Each 1 150.00 150 Remove Existing Structure Each 1 200.00 200 Riprap CY 40 40.00 1,600 Weir for additional protection Each 1 5,000.00 5,000 Clear and Grubb Ac 0.2 2,000.00 400 Restoration Ac 0.1 2,500.00 250 Subtotal 16,700 35% Contingency 5,845 Subtotal Mobilization (5%) Subtotal 25% Engineering, Administration and Legal Costs 22,545 1,127 23,672 5,918 TOTAL $29,500 Site Visit Sheet Collect Information of identified problem related to storin water runoff in Plymouth fiitP Trlentifie.ation Probiem Area Name: Site 7 - Plymouth Ponds Apartments Flooding Location: Plymouth Ponds Apartments- Parking Garages Visit Tnfnrmation: Date Time name of Resident Address Phone No. 9/10/03 11:00 Ralph Netzman 4545 Nathan Lane 612.961.3818 City RPnrecenWives at .cite visit Name: Scott Newberger Rocky Keelnl Beth Peterson Affiliation Public Works SEH SEH Plione,No. 612.490.4870 651.490.2026 651.765.2901 Summary of Visit with Resident: Description of Problem based on site meeting: Pond overflowed onto trail and into all 5 parking garages Water continued to rise the next morning after the rain stopped Damage that occurred 2-3 inches of water in all of the 5 parking garages Frequency of Problem There has never been a problem before ResideM'SP1'01)osed solutions: Have things changed within the watershed ? (i.e. new development) Study drainage system Bach page is for site sketch Sketch of Problem Area: Include: Flooded area, location of catch basins, size of catch basins, emergency overflow area, and critical structures. No sketch was prepared for this site. city Review of the Problem Problem Area Namc: Site — et-d6 h l _ nate: 1/16/04 Flooding Location: Plymouth Pond Apartments Parking Garage nate: 6124/03 City Contact: City Contact Person: I Dan Faulkner Pbonc No. 763.509.5520 fTeneral Comments_ After review of the available data it appears that the course of action would be to make the outlet more efficient. Due to the fact the wetland is DNR protected there arc limited opportunities for additional storage and changes to the water surface elevations in Pond NBP3C. The City focus to reduce the potential for flooding would be maintenance of the outlet structure. This may require construction of a new outlet which is easier to maintain. The property owner should consider additional on-site protection measures at the entrances of the garages to provide further protection. A proposed future project is a sheet pile weir which would help water elevation control, but does not have an impact on reduction of flooding so was not considered a project which should be completed at this time. Future Aetions- Action Cost of Action Basis of Payment 1) Proposed Completion Date Final Completion Date Construction new outlet to Pond 29,500 Construction of sheet pile control weir for existing wetland open water area 217,000 Future Modification to the wetland area. N/A GR Future 1) GF — General Funds SU —Storm Water Utility A5 —Assess m ent GR — Grant NA -- Not assessed at this time Total Solution Cost 29,500-$246,500 CITY.OF PLYMOUTH CITY.COUNCIL AGENDA REPORT DATE: January 15, 2004 for the City Council Meeting of January 27, 2004 TO: ,,.-Laurie Ahrens, City Manager through aniel L. Faulkner, P.E., Director of Public Works rROM: Ronald S. Quanbeck, P.E., City Engineer SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN ACTION REQUESTED: Provide comments to the Bassett Creek Water Management Commission BCWMC) on the Second Generation Watershed Management Plan. BACKGROUND: The BCWMC has been going through the process of updating their Watershed Management Plan. The update is required by State law and State rules and commonly referred to as a Second Generation Plan. The process of developing the plan was begun in late 1999. At that time, a Steering Committee was appointed by the Commission. In addition, three advisory groups were formed. A Citizen Advisory Group (CAG), Technical Advisory Group (TAG), and Policy Advisory Group (PAG) each held several meetings. Attached is a letter from the BCWMC Consulting Engineer working on this project describing many of tlic activities through the process. The cost to support those activities identified would not include legal and incidental costs. The result of the process and lengthy discussions regarding the Capital Improvements Program (C1P) is the 60 day review draft of the BCWMC Second Generation Plan dated November 2003. The draft plan has been provided to the cities State agencies, regional authorities and the public for review. The current 60 day review period is the first of several review periods for the plan and will end on January 20, 2004. At the request of Plymouth and Golden Valley, the BCWMC voted to accept comments from member cities until February 6, 2004. In addition, on February 19, 2004, a public hearing will be held by BCWMC to present an overview of the draft plan and the comments received and to hear any additional comments. After the public bearing, the BCWMC will submit for final review the draft plan, any amendments to the plan, all written comments received on the plan, the record of the public hearing, and a summary of changes incorporated as a result of the review process to the Board of Water and Soil Resources (BWSR), Met Council and State review agencies for a 45 day review period. After completion of this second review, the BCWMC will submit the final plan to the BWSR which must complete its review, Bold the hearing and approve or disapprove the plan within 90 days. After cornpletion of the BCWMC Second Generation Plan the City will be required to update its own Water- Management Plan to conform with it. 0- 5Engineering4WTRRESPnWMC 2nd gen plans%CC_Conwicnts'_ndGenPlan.doc SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN Page 2 SUMMARY OF THE PLAN: The BCWMC Second Generation Plan includes background information, goals and policies, and an implementation program which specifies specific projects to be constructed over a ten year period. Major sections of the plan include: 1.0 EXECUTIVE SUMMARY 2.0 HISTORY AND BACKGROUND INFORMATION 3.0 LAND AND WATER RESOURCE INVENTORY 4.0 WATER QUALITY 5.0 FLOODING AND RATE CONTROL 6.0 EROSION AND SEDIMENT CONTROL 7.0 STREAM RESTORATION 8.0 WETLAND MANAGEMENT 9.0 GROUNDWATER 10.0 PUBLIC DITCHES 11.0 PUBLIC INVOLVEMENT AND PUBLIC INFORMATION 12.0 ADMINISTRATION AND IMPLEMENTATION PROGRAM Sections 4.0 tlnough 11.0 contain specific goals and policies addressing the topics. The majority of these goals and policies are consistent with the practices of the City and will require only minor changes to City procedures. The draft plan does not propose any changes to the Joint Powers Agreement governing the BCWMC to which the City is a signator. The main impact on the City is changes in the responsibilities or positions of the BCWMC and the capital projects proposed. One such issue that has been clarified is the responsibility for maintenance of the facilities constructed by the BCWMC Flood Control project which vas constructed from 1987 to 1996, at a cost of $40,000,000. The project consists of seven major features, including the 1.7 mile tunnel through downtown Minneapolis to the Mississippi River and was a cooperative effort of the Corps of Engineers, Minnesota Department of Transportation, Minnesota Department of Natural Resources, BCWMC, and cities in the watershed. The BCWMC Second Generation Plan clarifies that the BCWMC is responsible for repair and structural maintenance of the structures and cities are responsible for routine maintenance of the facilities. Funds remaining from the original flood control project have been set aside for emergency repair and long terra maintenance of the system. There may also be some annual assessment for these purchases. Another issue identified is the Public Ditch System which was developed when the majority of Hennepin County was rural and is governed by drainage laws that encouraged draining wet areas. The drainage laws make maintenance of the system extremely burdensome. The plan suggests that the public ditch system be abandoned in nonagricultural areas and managed by the BCWMC according to BCWMC policies rather than the ditch law. This would require specific legislation by the State. Many of the old ditches have been incorporated into municipal stone drainage systems. It may be easier for the municipalities to maintain these drainageways if relieved of the burden of the 0,\rngineeringMTRRESR0WMC 2nd gen plans\CC Coouncnts2nd6cnPlau.doc SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN Page 3 ditch law than the BCWMC. An exception may be those ditches that are part of what BCWMC has defined as the trunk system. Table 12-2 contains the proposed ten-year CIP. Projects for this CIP would be funded by a watershed -wide ad valorem levy as was done for the Medicine Lake Ponds. The majority of the projects identified were contained in watershed management plans developed by BCWMC for each waterbody. In addition, the Medicine Lake and Parkers Lake Projects were somewhat coordinated with the City's plans for those lakes with the exception of timing of the project. Additional potential projects were listed in Table 12-3 and include alum treatment options which are not in the City's plans. The BCWMC Second Generation Plan states "the projects listed in Table 12-3 are not likely to be ready for implementation in the ten years following adoption of the plan. The BCWMC will move ahead with the alum treatment projects listed in Table 12-3 only after sufficient time has passed to evaluate the effectiveness of the less costly water quality Best Management Practices (BMP) and other improvement projects.....The BCWMC will move ahead with the alum treatment projects listed in Table 12-3 only after it has been shown that the structural and nonstructural BMPS listed in Table 12-2 have been implemented and it is apparent that the BMPS have heen unable to achieve BCWMC water quality goals." Table 12-2 was cut off in the copies of plan provided by the BCWMC. Attached is a copy of the complete Table 12-2. The primary issue 1n the CIP is the funding source, an ad valorem tax. The Second Generation Plan must identify the fielding source or each project will require amendment to the plan. One option would be to identify ad valorem as the funding source, but include a statement that the BCWMC will work with the cities and Hennepin County to investigate flexibility for individual cities to pay their share with a different source of funds. The administration and implementation section delineates the responsibilities of various parties, including the BCWMC and cities. BCWMC responsibility includes the defined trunk system, review of improvements and developments, inter -community planning assistance, and assistance with watershed management dispute resolution. The section also includes information on project funding, updating local watershed plans, and the process for amending the BCWMC Second Generation Plan. PREVIOUS REVIEW AND COMMENTS: Prior to release of the 60 day review draft of the BCWMC Second Generation Plan, an earlier draft was provided to corn miss loilers for review. Comments on that draft were provided jointly by the City's BCWMC Commissioner, Elizahctll Thornton, Couricilmernber, Gunny Black, and myself. A copy of these continents is attached. Several of the comments have been addressed by the BCWMC and changes have been made prior to release of the 60 day review draft of the plan. The major issue not addressed is how Medicine Lake and Parkers Lake are discussed in Section 4.3.3. The BCWMC Second Generation Plan reports on the structural improvements recommended in the Watershed and Lake Management Plans in great detail, but provides little detail on events and activities since the preparation of those plans, including the development of management plans by the City of Plymouth for both lakes. The BCWMC CIP seems to have shifted the emphasis on projects to be more consistent with the City's plans, however, the text in Section 4.3 does not appear to reflect this. This section is especially prominent since it is the only section where the waterbodies arc discussed in detail. It appears that a more balanced 0.1Gngincei ing%WTRRLSRC1WN1C 2nd gen plansTC_Cammenls2ndGcnPlnn-doe SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN Page 4 impression could be accomplished by eliminating the discussion of projects in the BCWMC Lake Management Plans sticking to a more general summary of the plans. One drawback this approached may be that if removed from this location, the projects listed in the CIP would not have sufficient detail in the BCWMC Second Generation Plan. This could be overcome by putting additional detail on the projects which are selected for the ten-year CIP in Section 12 with the CIP. In addition, the update sections for the lakes could be expanded notably, including discussion of the Aquatic Vegetation Management Plan for Medicine Lake. Another option would be to create a significantly larger, more detailed section for each waterbody where the plans could be more accurately put in perspective. Councilmember Black has proposed a third option which rewrites this section of the plan. A draft prepared by Councilmember Black is attached. While considerably more information was put in the plan regarding plan amendments and administrative procedures, it is still unclear what the form of the annual CIP update will be. It Should, at a minimum, provide an opportunity for city review of the plan and any proposed modifications. In addition, provision in the plan should be made for cities to accelerate projects as was done with the Medicine Lake Ponds. The City could construct improvements in years prior to that specified in the CIP and be reimbursed for the cost in the year specified if all other procedures, including public hearings and Commission review, are done before construction of the project. Benefits of the project would begin to accrue earlier without disrupting the BCWMC funding scenario. The previous comments suggested adding to both the Turtle Lake and Lost Lake sections that the BCWMC will work with the City to develop a plan that includes structural and nonstructural remedies to address sedimentation in the waterbody. This modification was not made for the 60 day review plan and should again be emphasized. Policy 8.2.21) ori Page 8-2 is redundant and unnecessary since 8.2.2C adopts a specific wetland classification system. Section 5 of the Medicine Lake Watershed Management Plan prepared by the BCWMC contains a good description of Best Management Practices (BMP's). It would be helpful to have the information included in the BCWMC Second Generation Plan perhaps in an appendix. Lastly, a larger more detailed snap would be helpful for those unfamiliar with all areas of the watershed. Another issue that was not raised in the earlier comments is that the BCWMC is growing and will have significant capital projects for years to come as well as the current administration activities. A staff person hired by the Commission could help coordinate these activities as well as enhance communication with the cities, potentially at a lower cost and greater accountability then the current arrangement of using consultants. Consultants would still be required, but in a reduced role. The BCWMC Second Generation Plan should include a statement that other arrangements for administrative services, including hiring an executive director, will be investigated. RECOMMENDED COMMENTS: The following comments regarding the BCWMC Second Generation Plan are recommended to be forwarded to the watershed. 1 Revise the sections on Watershed Management Plans, including 4.3.2.3 and those included in 4.3.3 to remove discussion of the specific projects and provide greater WEnginceringSIYIRRGSR0WNtC 2nd gen planslCC—CommenFs2ndGenPlan.doc SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN Page 5 emphasis on both the nonstructural measures and the update sections to put the Watershed Management Plans into better perspective and specifically include information on the City's Aquatic Vegetation Management Plan for Medicine Lake. 2 Delete Policy 8.2.21) since it is redundant and unnecessary. 3 Include statements in 4.3.3.11 Turtle Lake and 4.3..3.12 Lost Lake that the BCWMC will work with the City to develop a plan that includes structural and nonstructural remedies to address the sedimentation issues in the waterbody. 4 Modify the policies in 10.2.2 Public Ditch Policies to specify that the cities will be responsible for abandoned ditches that are not on the BCWMC trunk system. 5 Revise Section 12 to include the process for annually updating the CIP including, at a minimum, review of the plan and any proposed changes by the cities. In addition, a mechanism should be provided to allow cities to construct projects in years prior to that specified in the CIP and be reimbursed for the cost in the year specified if all other procedures, including public hearings and Commission review are done before construction of the project. 6 Clarify in the plan whether moving a project from Table 12-3 into the Ten Year CIP shown in Table 12-2 can be done with the Minor Plan amendment. 7 A large map of the watershed should be provided with the plan. 8 The funding discussion in 12.2.3 on page 12---14 which specifies that capital projects listed in Table 12-2 will be funded by an ad valorem tax should include a statement that the BCWMC will work with the cities and Hennepin County to investigate flexibility for individual cities to pay their share with a different source of funds. 9 The funding discussion in 12.2.3 on page 12-14 which specifies that capital projects listed in Table 12-2 will be funded by an ad valorem tax should include a statement that the BCWMC will work with the cities and Hennepin County to investigate flexibility for individual cities to pay their share with a different source of funds. 10 Section 5 of the Medicine Lake Plan contains a good description of BMP's available. This section should be included in an appendix of the Second Generation Plan and be referenced in the body of the plan. 11 The BCWMC Second Generation Plan should include a statement that the BCWMC will investigate the feasibility and advisability of hiring an executive 0 \EngiueeringllYPR RES WMIC 2nd gen plansVCC—Canunents'_nJGrnP]an.doc SUBJECT: BASSETT CREEK WATER MANAGEMENT COMMISSION (BCWMC) SECOND GENERATION WATERSHED MANAGEMENT PLAN Page 6 director or using other arrangements for administrative services to oversee activities of the BCWMC. r 3 Ronald S. Quanbeck, P.E. VIIII City Engineer attachments: Letter describing Barr's involvement in the Second Generation planning process Comments on Commissioners draft of Second Generation Watershed Management Table 12-2 Councilnnember Black's draft 01Engincerh1p%%VTRRESRC1WMC 2nd gen plans%CC_Comments]ndGenPlan.doc JAN -14-2004 12:29 CITY OF GOLDEN VALLEY 5938109 p.02/03 4700 West 77th Street Minneapolis. MN 55435-4803 Phone: 952-832-2800 Fax; 952-832.2601 • vmm.barr,corn BAF R Minneapolis, MN • Hibbing, MN • Duluth, Mtn • Ann Arbor. MI - Jefferson City, MO January 9, 2004 Mr. John O'Toole Chair, Bassett Creek Water Management Commission c/o Bair Engineering Company 4700 'West 77`' Street Minneapolis, NW 55435 Dear Mr. O'Toole: As we discussed, the purpose of this letter is to shmmarie. Barr's involvement in the second generation planning process. A general discussion of the process that the Conunission followed is: 1999 Beginning tri late 1999, the Commission started the planning process by directing Barr to prepare letters to the'regulatory agencies that would be involved in the plan review. The letters requested that the regulatory agencies outline the issues that they perceived needed to be addressed. 2000 The Commission estnblisbed a Steering Comrr7iuee and with the assistance of Barr, they formulated the plan for the process that included the development of a planning handbook and a public information workshop. Tbcy also organized three sub -committees to obtain stakeholder input; namely: Technical Advisory Group Citizen Advisory Group Policy Advisory Group The Steering Committee assigned each of the groups with issues that needed to be addressed. These groups and the Steering Committee met individually and collectively, a total of 56 times throughout the process (2000-2003) to provide input, identify and discuss issues, and develop proposed policies and position papers. JAN -14-2004 12:29 CITY OF GOLDEN VALLEY 5938109 P.03iO3 Mr. John O'Toole January 9, 2004 pale 2 2001 Based on direction from the Commission. Barr prepared the first draft of the Water Quality Capital Improvements PIan (CIP). The plan covered a 20 -year planning period. There was extensive input from the cities to insure that the CIP was consistent with the CIPS of the individual cities. The Commission also started discussions regarding possible CIP financing options. With Barr's assistance, the Commission beld two special meetings each to discuss the proposed improvements and options for their financing. The Citizen's Advisory Group developed a Public Information Plan and presented it to the Commission and the Technical Advisory Group prepared a summary of major issues and recommendations and presented them to the Commission. 2002 The Commission conducted a public hearing and approved a plan to complete the flood control project by flood proofing homes in Golden Valley and established a long-term maintenancc plan for the flood control project. The evaluation of financing options for the C11' also continued. Many Rcrations of the CIP with various funding options were reviewed. Several communications and meeting were required with many of the cities to arrive at the CTP that is currently proposed. 2003 Four drafts of the second generation draft plan's text and maps were prepared and informally issued for preliminary review. The Commission also adopted an amendment of the 1990 plan, conducted a public hearing and ordered the construction of two water quality improvement ponds in the watershed of Medicine Lakc, and worked with the County to obtain funds for the project. Barr's charges to the Commission, as part of this process for the period 1999 through November 2003 were $424,009 for these plan. -related activities. The task of developing a second generation plan agreeable to all tmrnber cities has proven more difficult than initially anticipated. Indeed, even at this late date, and in spite of these extensive efforts, some participants do not support elements of the draft plan. The effort needed to resolve many difficult policy issues and develop a consensus CIP and a funding mechanism that could be supported by the member cities was obviously underestimated. A regrettable consequence of this difficulty in reaching consensus is that the total charges for the developrnuDt of the second generation plan are higher than initially anticipated. Sincerely, Leonard 1. Kremer, P,E, Engineer, Bassett Creek Water Management Commission c: Bassett Creek Water Management Comn-fission Charlie LeFevere P:\23\27\0511pJanlResponsc to Questions re costs_doc TOTAL P.03 MEMORANDUM To: John O'Toole, Chair, BCWMC BCWMC Commissioners From: Ginny Black, Ron Q,uanbeck, Elizabeth Thornton Re: Bassett Creek WMO Plan Review Comments August 5, 2003 General comments: The comments and reactions presented here are offered to help clarify, propose for discussion, and reflect current information. There are many sections, especially in Chapter 4, that mention the update as an afterthought where it should be the leading piece of the picture. We should be proud of what has been accomplished and put those things right up front? The document has been in production over a period of time (3? or 4? years) but the end product should be current. There is a place for history here but more emphasis should be put on the present state of the Bassett Creek Watershed so that it can be used as a plan for the future (the next 10 + years). This 2nd Generation plan is very comprehensive and covers a lot of territory (figuratively as well as literally). The documents represents a lot of time and effort on the part of the writers. it is important that it be studied so that what is adopted by the commission will reflect the thinking of the commissioners and the cities they represent and be the "state of the watershed" as it is today. Chapter 4.0 Water Quality General Comments : The sections are structured repeating the bake Management Plans then providing a brief update on what has transpired since its development. The section should be restructured to discuss important aspects of the plan in light of present circumstances that would provide current information at the beginning and throughout rather than at the end, if detailed information about a water body is desired the information can be consulted. It does not need to be reiterated here. Alum treatment is offered here as universal answer to solve a phosphate problem in almost all cases. A comprehensive listing of SMP altematives includes both structural and nonstructural techniques should be provided in the document. Specific Comments: Page 4.2. Policy„4.Z.2,1.D: First, this policy states "The BCWMC will update its 10 -year CIP annually." Plymouth believes that this is a good idea, but wonders if this will require a plan amendment on an annual basis or if the CIP will be update on an informal basis. The process for the annual updates should be detailed including the opportunity for input from the public. The discussion on Table 12-3 does not appear to match the resolution adopted by the commission. Didn't the commission make the project on Table 12-3 possible projects pending the results of structural and non- structural BMF°s. The following language should be struck and rewritten to better reflect the Commission°s resolution ". Projects listed in Table 12-3 are not likely to be ready for implementation in the 10 years following the adoption of the Plan. The BCWMC will moue ahead with the alum treatment projects listed in Table 12-3 only after sufficient time has passed to evaluate the effectiveness of the less -costly water quality best management practices and other improvement projects. " Suggested replacement language: 21L BCWMC may imolgMent thg proiect listed in Table 12-3 only after it has been shown that-thestructural and non-structural QMP's listed in Table 12-2 have been imple entgd b2v been unable to achieve management category assigned to the water body. Page 4-2. Policy 4.?,, J .E: This policy would focus the Commissions efforts on structural improvements and may detract from the non-structural improvements such as buffer strips and education. Is this the intent of the Commission? It should be reworded to ensure that non -structured projects are not excluded. Page 4-3, olicy 4.2.2.1 F: Third sentence, "This statute allows BCWMC to "direct" Hennepin County, should direct be changed to reauest? Page43, Policy 4.2,2.1 .H: What will the SCWMC do with data collected by cities? There are other cities besides Minneapolis (Mpls Park Board) who monitor in the watershed? Page 4-3, Policy 4,2.2.Z Storm water Runoff Management, Policy A: If a lake is classified as a level 11 lake, why does the storm water need to be level I quality? How does this relate to the level set for each lake? What is the rational behind this policy? This explanation should be in the Plan. Policies in section 4.2.2.1, 4.2.22, and 4.2.2.4, are all labeled A., B., C.,..., Policies under 4.2.2.3, are labeled 1- 7. Need to be consistent. Page 4-4. Policy 4.2.2.3.#1_: Vegetative buffer strips are not just a fish and wildlife habitat management strategy. It is also a nutrient and sediment management tool. Page 4-4. Policy 4.2.2,3,#2: should read: When them' i n deems agoropriaJ2M 1 react tp r r agencies regardin2f'an_)yildlife issues. Page 4-4: Policy 4.2.2.3. #7,_The cities are (delete "will be") required to maintain control.......,. (the first sentence could also just be deleted). P2ggs 4- 4-11- Section 4.3.1 51grmrRunoff; This long discussion primarily talks about the USEPA°s Phase 11 storm water program that will be administered in this state by the MPGA. This level of detail is not needed in the 2nd Generation Plan. The section states " Managing storm water runoff is a basic responsibility of local governments. The BCWMC looks to its member cities for primary management of storm water runoff issues." Portions of sections 4.2.2 and 6.2.2.1) seem to indicate that the BCWMC is taking on this role.. This section needs to be tied more directly into the Plan. Page 4-16. There is no map showing the drainage districts clearly, At least nothing cited in the text. Figure 12 was very difficult to read. BC -10-3, BC -91-5, HH -1 1, and HH 1 1-0 could not be located. Paae 4-17. detention basin 11111-1, should the be HH1 1-1 ? Page 4-23, BMP #2, delete first sentence (state law), rewrite "Each City shall n r M State Law limiting the use of lawn fertilizers shall v i wi n 2ducation Urgaram thal educates -Egsidents about the importance of sail testing_to determine their lawns nutrient needs, Education programs should include— factuatiaLgrmation regardloa Jbg affecJ5 gf gbg§2b2rUs and nitroaen on Jbg water gUalily and streams,"_ Note: State Law does NOT ban phosphorus, rather limits the use to lawns that have soil test indicating a need for phosphorus. Page 4-2 3. BMP -#5., reword "]:.be BCWMC and cities shall implement an education program Wat educates watershed ....." Strike "Implement a program to". P MP #6, reword " will encgurage citiesi vecletated- buffer strias between maintained lawns.andwater bodkL. Strike "Required/encourage vegetated buffer strips....." Page 4-24. BMP #(addition). There should be an inclusion of rain gardens as a best practice to improve water quality. 4.3.3.1 Medicine Lake (pages 4-24 IR 4-299, General Comments: This sections should start with the positive things that have been accomplished in Medicine Lake. The first 3.5 pages of section focuses on the Commission's activities and recommendations related to improving the water quality of Medicine Lake. It begins with a brief background of the Commissions activities but does not include the activities of City of Plymouth. The City of Plymouth's activities are given one paragraph near the end of the section. This seems rather strange since the Commission has adopted the CIP from the Plymouth Medicine Lake Plan. This raises two interesting questions that the BCWMC need to consider. "How does the Commission better coordinate its activities with the cities in the watershed?" When Cities try to implement their Surface Water Management Plan how does the Commission incorporate that work into the Commissions priorities and work plan? The activities that have raised these issues are the creation of the two plans for improving the water quality of Medicine Lake, i.e. the Commission's Plan and the Plymouth Plan, that have two very different approaches. The Commissions Plan focuses on structural remedies while the Plymouth Plan focuses on pollution prevention remedies. The Commissions plan for Medicine Lake had little or no input from citizens while the Plymouth Plan focused on pollution prevention and changing habits of residents and businesses within the watershed. In addition the plan was developed by residents and businesses within the Medicine Lake and Plymouth Creek Drainage Districts and from Three Rivers Park's staff and reflects their wishes for how the water quality in Medicine Lake should be improved. Finally, Plymouth wanted the plan to include the concerns of all interested parties and invited broad participation in the development of its plan - the BCWMC, DNR, and the City of Medicine Lake, all of whom choose not to actively participate in the process. Specific Comments Pape 4-24: The first sentence refers to the BCWMC Plan for Medicine Lake prepared by Barr Engineering . There is no reference to the City of Plymouth's Medicine Lake Plan until the second to last paragraphs in the Medicine Lake Section. Plymouth believes that the information about the City's Medicine Lake Plan should be incorporated at the beginning of the and there should be a discussion of the similarities and differences of the two plans. The 2nd generation plan should indicate that the Commission adopted the City of Plymouth's Medicine Lake CIP at the beginning of the Plan and the discussion of the alum treatment recommendations of the BCWMC Medicine Lake Plan were put on a list of optional BMPs, pending the implementation of pollution prevention strategies and the evaluation of the success of those strategies. Pages 4-25. -26. 4-27,E-28 and 4-29: Plymouth believes that the information related to the alum treatment should be struck or reworded to reflect the changes the Commission made to the CIP. Discussion of alum treatment recommended for Medicine Lake, the Plymouth Creek Drainage District and the Ridgedale Creek Drainage should reflect that these recommendations have been moved to a lower priority and may not be needed, pending the results of the implementation of pollution strategies recommended in the Plymouth Plan. Parties interested in the alum treatment strategies, recommended in the Commission Medicine Lake Plan should be referred to the plan itself. Page 4-24. Reword to "Medicine Lake, in the cities of Medicine Lake and Plymouth, is the secgr,d.lar_ggs lake ....... Page4-24: Change Hennepin Parks to Three River5Parks. A search/replace should be preformed on the entire plan to replace Hennepin Parks with Three Rivers Parks._ Pages 4-25 & 426. Aquatic Plant MAngo-e_m rpt.' Plymouth believes this section should be rewritten to reflect the Plymouth Aquatic Vegetation Plan (PAVMP) which was developed by the Plymouth Vegetation Management Committee and approved by the DNR. The PAVMP was developed by the citizens of Plymouth, a council member from the City of Medicine Lake, and experts from Three Rivers Park and the DNR. Other entities invited to participate in that process were the BCWMC and the MPCA, who elected to take a less active role in the development of the plan. The PAVMP is a comprehensive approach to management of vegetation in Medicine Lake and is the first of its kind. It is highly endorsed by the DNR who actively participated in its development. Page 4-25, Plymouth Creek Drijt@gei The Commission plan called for an alum treatment facility near the outlet of the Plymouth Creek to Medicine Lake. The Plymouth Medicine Lake Plan delays all alum treatment pending the evaluation of the data collected from monitoring Plymouth Creek and the effectiveness of the pollution prevention strategies identified in its Medicine Lake Plan. The Plymouth Plan does not identify any structural strategies for removal of phosphorus and sediment from Plymouth Creek. Rather, the City has been engaged in a monitoring program to more accurately identify the sources of phosphorus/sediment that effect the water quality of Medicine Lake. The intent of the City was to use the data collected in the monitoring program to craft a specific plan for Plymouth Creek that reducing the P- loading/sediment to Medicine Lake. The development of a Plymouth Creek plan would have a public input process with significant citizen and agency participation. The Commission's second generation plan should reflect the data gathering and public process. Recommendations_ The second generation plan should more fully recognize the Plymouth Plan The Second Generation Plan should include the PAVMP as approved by the DNR. The Commission's second generation plan should reflect the data gathering and public process. The Plan should state that alum treatments should be a last resort and only implemented after other methods are tried and failed. General Comments This section discusses first the BCWMC recommendations and then what the City of Plymouth has done. It leaves the information that Parkers Lake, as a result of I mplementing the BCWMC/City Surface Water Management Plan, has meet and exceeded the water quality goals until the middle of the section. This is a huge accomplishment and a wonderful success and it should be the opening of the section. 4.3.3.17 Turtle Lake This lake seems like a perfect place to implement non-structural BMP's. The recommendation for this lake is for the BCWMC to do nothing in this 10 -year plan. It is proposed to replace that language with "_Over the VQ-Vear ul velop_a Ulan that includes ngn-struct ral remedies to addre5$ the sedimentation issues of Turtle Lake.". 4.3.3.12 Lost Lake_ This is another lake that could possibly benefit From non-structural BMP's. The city is already harvesting geese, providing education in its city newsletter the "Environmental Extra",and offering classes on lakescaping and native gardens. The recommendation ,for this lake is for the'BCWMC to do nothing in this 10 -year plan. It is proposed to replace that language language that says something to the effect of "Over 1- nin i!lvQ[k w' h Plymouth to develor)I n Ihat includes strucluraL and non-structural remedi s to address the sedimentation issuesLf Lg5t Lae"_ Point of Clarification: What does this mean? ["upon adoption of the second generation plan, the BCWMC will require that all regulated storm water (e.g., developments and redevelopments) be treated to BCWMC Level l standards. This means the water quality goal of Lost Lake could be changed to Level lll.] This same statement is included at the end of the section on Turtle -Lake, page 4-53. Chapter 8.0 Wetland Management Page 8-1. 8.2.2.0:_ How will these standards/methodologies/guidelines impact cities that have already done inventories? Wetland inventories are very expensive and unless significantly greater benefit is gained cities should not be requested to replace an existing one. Page 8=2. ,8:2;2.Q:_ Why is,the -Commission developing a wetland classification system when -there are already many out there? What is wrong with what is already in place? The Commission should serve as a resource -for the- cities to use- in deciding their own system. Page 8-2. 8.2.2.E:_ this is a very politically volatile issue and usually resolved by each city. This policy should be changed to say that the Commission would supply member cities with copies of ordinances from other cities and the. most current research on the subject. Decisions on what.the buffers should be are. up to the cities. Chapter 11.0 Public Involvement and public Information Care must be taken to coordinate activities with the cities to avoid duplication of effort, Page 11-9, 11.2.2.4K: The award-winning Plymouth educational materials for the Medicine Lake Watershed and the Parkers Lake Watershed which are in the Bassett Creek watershed should be mentioned instead of the Chain of Lakes Water Partnership. 12.0 Administration and Implementation Program Plymouth still opposes using the ad valorem tax levy to fund the BCWMC CIP and recommends that the plan be written to provide flexibility in funding source rather than relying on the ad valorem tax. 4.3.3.1 Medicine Lake Watershed Introduction The BCWMC, the City of Plymouth, Three Rivers Parks and the City of Medicine Lake have been partners in working to improve the water quality of Medicine Lake for many years. The BCWMC adopted a plan for Medicine Lake in 2000. The City of Plymouth adopted a Medicine Lake Plan in 2001. The City's plan was the result of a committee process that involved citizens, businesses, and professionals in the water quality field. Three Rivers Park district (formerly Hennepin Parks District) has been monitoring Medicine Lake for many years. The monitoring data indicates...... John and Brian what should we say about the health of die Lake? The following information briefly reviews the contents of the two Medicine Lake plans and recent actions taken by the BCWMC and the City to improve the water duality of Medicine Lake. In addition, a strategy to improve the water quality and meet the BCWMC's goal 30 ug/l is described. History Commission Work Medicine Lake, located in the City of Plymouth, is the second largest lake iii Hennepin County and is considered the most important recreational water body in the watershed. Regional and local parks and trails are located on or near the lake. These amenities provide access to the lake and contribute to the intense uses of the lake during both summer and whiter months. Fishing, boating, swimming, water-skiing and aesthetic viewing are some of the major recreational uses made of the lake. As part of the BCWMC's work, classifications were set for each lake in the watershed. The classification for Medicine Lake is Level 1. This classification establishes a water quality for Medicine Lake that supports all recreational activities - boating, fishing and swimming - and reflects the current and expected future uses of the Iake. BCWMC's Medicine Lake Plan As a result of setting that classification, the BCWMC, in the mid to late 1990's, under took a study of Medicine Lake and in 2000 issued the Medicine Lake PIan (BC -MLP). The BD -MLP established priorities and provided guidelines for the water quality of the lake. The BC -MLP divided the Medicine lake watershed into five drainage districts: Plymouth Creek, Ridgedale Creek, Medicine Lake North, Boat Landing, and Medicine Lake Direct. Each drainage district was evaluated for nutrient removal efficiency under existing conditions defined as full -development land use conditions. That evaluation assigned a percentage for which each district was responsible for contributing phosphorous load to the Lake. It also found that the lake typically falls below the water quality goals. Trend analyses of historical water quality data for Medicine Lake indicates that, while brief periods of poor water quality occur annually during late summer, overall conditions remain steady. The leveling off of the decline in water quality is likely, in part due to the City of Plymouth implementing, in 1993, the requirement that all new developments over 5 acres include a National Urban Runoff Pond (NURP). Since the Medicine Lake watershed is nearly fully developed, the impacts of new development are expected to be minimal as NURP will be required. By state law, cities of a certain size are required to develop a water resources management plan that includes the requirement of the watersheds) within their political boundaries. Medicine Lake falls within the boundaries of the City of Plymouth which updated its water resource management plan in the mid 2000. That Placa is described below. The City of Medicine was not required to adopt a water resources management plan and is generally guided by the BCWMC's management plan. Three Rivers Parks District Three Rivers Parks District (TRPD) has been a driving force for improving water quality on Medicine. The TRPD Headquarters is within the Plymouth Creek sub -watershed and French Regional Park lies on the north end of Medicine Lake. French Regional Park offers Lake amenities to the area that include a boat landing and beach. The TRP has monitored the water quality conditions in the lake for XX ),ears and has been instrumental in monitoring the water quality of the creeks coming in to the Lake. The data collected has been used by the BCWMC and the City of Plymouth to develop their Medicine Lake Plans. John and Brian: What should `ve say about RUST monitoring? What should «re say tice monitoring is showing? What else should we add here? City of Medicine Lake's Activities The City of Medicine Lake has been an active participant in Plymouth's Medicine Lake sub -committee and Aquatic Vegetation Management (AVM) Group. In addition, the City of Medicine Lake has dedicated a portion of the revenues raised from property tax to the activities identified by the AVM Group. The City of Medicine Lake also engages in street sweeping and educating its residents about activities they can engage in to improve the water quality of the Lake. (What else?) City of Plymouth's Water Resources Management Planning The City of Plymouth's Water Resources Management Plan (PWRMP), adopted in February 2000, was developed with active participation of its Environmental Quality Committee (EQC). The plan established ten citywide goals and one specific goal for Medicine Lake. The citywide goals include general goals for flooding, water quality, erosion control, wetlands, public participation and education, monitoring, maintenance and inspection of 2 water structures, recreation, ground water, and finance. The specific goal for Medicine Lake that states, "Increase clarity and reduce total phosphorus and chlorophyll a concentrations, working toward the goal for total phosphorus established by the Bassett Creek Watershed Management Commission." Citizen's and staff identified the need to extend the 1995 Plymouth ordinance restricting the use of lawn fertilizers containing phosphorus by commercial applicators. The EQC recommend that restriction be extended to residents applying fertilizers and in 1999, prior to the adoption of the PWRMP, the city council enacted the recommendation. In August 2000, the city council adopted the PWRMP and it has been the guiding force in the City's activities since its adoption. The first activity undertaken was the evaluation of a funding mechanism (goal 10) for the capital projects and activities. The city council began the evaluation of the use of property taxes or Surface Water Management utility fee in July of 1999. It was determined that a fee best suited the City's needs and adopted a fee in XXXX. This allowed the city to begin implementing the PWRMP. The PWRMP recommended strengthening City's ongoing education efforts. The adoption of the PWRMP and a funding mechanism allowed the city to expand an existing part-time position to a full-time position and incorporate water quality educations into that position. This allowed the City to expand its educational efforts. Publication of the Envirownental Extra insert to the City newsletter was expanded from two to three times a year, with the July issue dedicated to water quality information. Lake -specific newsletters, "landscaping for water quality" workshops, and shoreline and upland native plant gardens are among the many activities added to the City's water quality education program. The Plymouth Water Resource Management Plan placed a high priority on citizen involvement in water resource planning and implementation. As a result, the Plymouth City Council directed its EQC to establish a sub -committee of residents and businesses whose purpose would be to develop management plan for Medicine Lake. City of Plymouth's Medicine Lake Plan The Medicine Lake sub -committee first met on October 19, 2000 and met once a mouth until June 5, 2001. The sub -committee used the BC -MLP as well as published research and information provided to the committee by Three Rivers Parks and outside lake consultants. The sub -committee's Medicine Lake Plan was presented to the EQC on June 13, 2001. The EQC recommended the plan to the City Council. The Council and EQC held a joint meeting on July 17, 2001 to receive comments from the public on the Plymouth Medicine Lake Plan (P -MLP). The City Council adopted the plan in August, 2001. The primary focus of the current P -MLP was external and internal BMP for the Medicine Lake Direct Drainage District. However, recommendations were made regarding in -lake alum treatment and the construction of alum treatment facilities. These recommendations are discussed in the appropriate sections below. Recommendations for the Plymouth Creek subwatershed were not included in the P - MLP, as a monitoring plan had been developed for Plymouth Creek which was to be implemented in the summer of 2001. Although monitoring is continues, enough data has been collected to warrant reconvening the City's Medicine Lake Sub -committee. On September 23, 2003, the Plymouth City council directed staff to bring the Medicine Lake Committee back together to develop a plan for Plymouth Creek. in November 2003, the City Council expanded the scope of the committee to all remaining areas not addressed in the initial P -MLP. It is expected that the committee will meet for 6 — 9 months before forwarding recommendations to the EQC and City Council. Medicine Lake Drainage Districts The BC -MLP divides the Medicine Lake Watershed into five major drainage districts: Medicine Lake Direct, Plymouth Creek, Ridgedale Creek, Medicine Lake North, and the Boat Landing. The BC -MLP evaluated each district for nutrient removal efficiency under existing conditions, i.e. frill development. The specific BMP's recommend by the BC - MLP are discussed for each drainage district in the following paragraphs. Irl addition, the P -MLP recommendations have been incorporated into the discussion since the most recent efforts to improve the water quality of Medicine Lake have been undertaken by the City of Plymouth. 1. Medicine Lake Direct District Since the BC -MLP was completed in 2000, and recommended in -Lake alum treatment to reduce the impact of in -lake phosphorus and the management of aquatic plants. The BC - MLP recommended management of purple loosestrife through the introduction of two beetle species that effectively prey on purple loosestrife. The P -MLP, completed in 2001, relied heavily on the BC -MLP and expertise from TRPD staff and the Blue Water Science consulting firm. The recommendations from the sub- committee reordered the BMP's recommended in the BC -MLP. The sub -committee emphasized the prevention of pollutants from getting to the lake throiigll the use of structural and non-structural BMP's. Further, the sub -committee recommended that the alum treatment recommended by the BC -MLP be delayed. The committee was not certain it would be needed if the other structural and non-structural BMP's were effective in reaching the Lake's goals. In addition, even if the alum treatment were still needed, the implenlentation of the other BMP's prior to treatment would likely enhance the effectiveness of the alum treatment. The P -MLP recommends an evaluation of the effectiveness of the BMP's in 2006. The P -MLP focuses on two primary areas: 1) External nutrient management, and 2) Internal nutrient management. Details of the plan are given below. 4 External Lake Recommendations Both MLP's set a goal of reducing the inflow of phosphorus and sediment into the lake. Recommendations for management include the construction of N URP ponds where feasible, street sweeping, lakescaping, rain gardens, education and management of geese. As a result of the recommendations in both the BCWMC and the Plymouth Medicine Lake Plans, the City of Plymouth began the process of planning and constructing storm water ponds, BC98 and BC107. At its November 12, 2002 meeting, the City Council approved a staff recommendation that the City hire an engineering firm to design and construct these two ponds. Public meetings were held on January G and February 10, 2003, to present the conceptual designs to interested parties and gather their comments. Comments focused on expanding the ponds and moving BC107 to minimize impact on East Medicine Lake Park. The City presented the project to the BCWMC commission April 2003 (?) and requested financial assistance. The Commission agreed to assist the City and began the process of amending the previous plan to accommodate that request. The City has had ongoing discussions with Ryerson Steel to see if an agreement call be reached to use a portion of the Ryerson property for the pond. This would reduce the impact on the Park and allow for the construction of the largest pond possible. At this time, the outcome of those discussions is unknown. In addition, the City has begun a small grant program that assists residents in planting1.11 rain gardens and lakescaping within the Medicine Lake watershed. In 2003, city staff notif ed residents Iiving on the lake of a grant program available to the to do lakescaping on their shoreline. Twenty-seven residents indicated an interest and city staff was able to combine some of the residential lots into one site. As a result, city will begin working with 9 sites in the spring of 2004 and 9 sites in the fall. To supplement the Environmental Extra, the City has established a newsletter for Medicine Lake that is mailed at least twice yearly to each resident within the watershed. The newsletter contains infon-nation on the condition of the lake and what residents can do in their homes to help the water quality of the lake. Finally, the city has included additional funding in its annual budget for extra street sweeping and continues its goose round -up program. In -lake Improvement Recommendations The BCWMC and Plymouth Lake Management plans recommended internal management strategies that included management of aquatic vegetation. The P -MLP recommended the establislunent of an aquatic vegetation management group to develop a management plan for both exotic and native plant species. Lakescaping, aquascaping, and management of rough fish is also recommended 5 Aquatic Vegetation Management Group As a result of the recommendations from the P -MLP an Aquatic Vegetation Management Group (AVM) was establish. Members of the AVM included the MN DNR, TRPD, Plymouth Parks and Engineering Departments, City of Medicine Lake, Bassett Creek WMO, Association of Medicine Lake Area citizens, an the Plymouth EQC. Resources used to develop the AVM plan included a TRPD survey of the locations, type and extend of aquatic plant beds within the Lake, citizen surveys of the Medicine Lake Skiing Group and Sailing club, as well as the Marina owner. Lake usage patterns were supplied by TRPD and the City of Plymouth's Parks Department. Once the final plan was approved by the Plymouth City Council it was submitted to the DNR for approval. The Commissioner of the DNR approved the plan and DNR staff has been very active in the AVM committee. They are assisting the City in implementing a lake -wide treatment for curly leaf pondweed in the spring of 2004. Aquatic Vegetation Management Plan Content The AVM developed a management plan that establishes three types of management areas: 1) Protection, 2) Shoreline Restoration, and 3) Control. Protection Areas have significant populations of desirable native aquatic plants that the AVM plan seeks to protect and expand. Examples of these plants include: Flatstenl, Sago, and Richard's pondweed, Northern milfoil, Coontail and many others. The Shoreland Restorations Areas were identified as areas that have significant numbers of undesirable plants, shoreline erosion, and lack of turf or other vegetative cover on upland areas. The AVM plan targets these areas for shoreline restoration program and the City established the grant program described above to assist residents interested in lakescaping and rain gardens. In addition, City and TRP staff provide assistance to residents in developing plans for lakescaping and rain gardens. Control areas are those areas with excessive aquatic plant growth that has significantly diminished the lakes use and or health. The purpose of controlling excessive plant growth would be to reestablish Iake uses and promote the health of the lake. The plant survey showed that, in 2003, Medicine Lake was infested with 300 acres of Curly Leaf Pondweed (CLP), virtually the entire littoral zone of the lake. The Army Corp of Engineers and another scientist have identified CLP as a major contributor to increased phosphorus and blue green algae blooms. The AVM is working with the DNR to implement an aggressive lake -wide treatment for curly leaf pondweed. Public information meetings are scheduled for January 2004. It is projected that this BMP could reduce the amount of in -lake phosphorus loading by 15%. Implementation of the control plan is scheduled for May 2004. The recommendations of the Medicine Lake and AVM plan have been incorporated into the City's 5 -year Capital Improvement Plan and into the work plan for City and Parks staff. 2. Plymouth Creek Drainage District The Plymouth Creek sub -watershed contributes more than 30 percent of the annual phosphorus Ioad and 60 percent of the total phosphorus load to Medicine Lake. This makes Plymouth Creek the largest single contributor of phosphorus to Medicine Lake. The BCWMC and the PIymouth's Medicine Lake Plans outline significantly different approaches to the issue of phosphorus entering Medicine Lake from Plymouth Creek. The BC -MLP analyzed several different options involving the construction of NURP ponds and two options for an alum treatment facility at the confluence of Medicine Lake and Plymouth Creek. The BCWMC's final recommendation was for the construction of an alum treatment facility with the implementation of other BMP's as a secondary focus. In contrast, while the City's Medicine Lake sub -committee made no specific recommendations for Plymouth Creek, there was a consensus that any type of alum treatment be delayed. There were two reasons for this recommendation: 1) a monitoring program for Plymouth Creek and been developed and would be implemented in the summer of 2001, and 2) BMP's that prevented pollution from reaching the lake should be implemented and monitored to determine their impact on the Lake before alum is used. P] south Creek Monitoring Plan At the time the P -MLP was developed, the city and the TRPD had developed a monitoring program for the sub -watershed that would be implemented in the sunmler of 2001. Since the focus of the monitoring plan was to collect data that would identify the origins of the phosphorus from this sub -watershed the sub -committee determined that it would be appropriate to wait for the data, then reconvene the sub -committee to develop a plan for Plymouth Creek. The BC -MLP treats Plymouth Creek as a single sub -watershed. In contrast, the Plymouth WRMP breaks Plymouth Creek sub -watershed into 4 components, Upper, Middle and Lower PIymouth Creek and Turtle Lake. The monitoring program that the City and TRPD designed placed monitoring stations at the junction of Middle (receiving stonri water from Upper, Middle and Turtle Lake Districts) and Lower Plymouth Creek and at the confluence of Plymouth Creek with Medicine Lake, In 2001, monitoring was conducted at these two sites. As a result of the initial monitoring, three sites (the two original and additional site) were monitored in 2002, and three more sites (six total) were monitored in 2003. The results of that monitoring are currently being evaluated and the sub-corrinittee will make recommendations to the EQC and Plymouth City Council in mid -2004. The approved recommendations will be formally presented to the BCWMC. 7 As previously mentioned, the Plymouth City Council authorized the re -convening of the City's Medicine Lake sub -committee. At this time the committee has met three times and reaffirmed its approach of focusing on BMP's that promote pollution prevention strategies with the use of mechanical or structural BMP's as indicated by the monitoring data. The sub -committee has requested that P -S models be run using the current data with a variety of external and internal non-structural BMP's. The goal is to determine what the most effective combinations of BMP's may be to achieve the water quality goal of 30µg11. Experts attending the sub -committee meetings believe that some combination of these BMP's has a real chance of achieving the Goal without the use of alum treatments. The sub -committee is discussing the use of a combination of structural and non-structural BMP' s. Structural BMP's include the construction of a large NURP pond in a wetland area upstream of the confluence of Plymouth Creek and Medicine Lake and west of West Medicine Lake Drive. The added benefit to this particular BMP is that it will also treat water coining into Plymouth Creek via the Parkers Lake Drainage. As discussions progress, other structural BMP's may be identified by the sub -committee. Non- structural BMP's being discussed by the sub -committee include, street sweeping, programs to better manage yard waste (Ieaves and grass), rain gardens, lakescaping, and public education. These are all critical elements of the original Medicine Lake Plan and the committee's recommendations may expand these programs. Metropolitan Council Grant The city applied for and received a Metropolitan Council grant that is focusing on reducing runoff from impervious surfaces. The grant includes industrial and residential areas located in the Middle and Lower Plymouth Creek and West Medicine Lake sub watershed. The project is divided into four parts: data acquisition, identification of high priority areas, contacting possible participants in the sub -watershed, and implementation of BMP's. Seventy percent of the total budget is allocated as financial incentives to implement BMP' s that can include, but are not limited to rain gardens, native plantings or enviromnentally friendly materials applied to lawns. It is hoped that this project as a model for other areas within the City. At the present time activities undertaken in the grant include the use of GFS to determine storm water drainage, and impervious area. That information has been digitized using a year 2000 aerial map to identify high priority areas. Next, the ratio of impervious area to the total district within the 17 districts were identified and second, known persistent problems identified by City staff. Letters were sent to the identified owners and/or occupants on July 22, 2003. Contact with an engineering firm to design the plan is the next step. 3. Ridgedale Creek Drainage District E Medicine Lake receives about 6 percent of its annual phosphorus load from Ridgedale Creek. The Ridgedale Creek Drainage district represents about 12 percent of the total phosphorus load from the Medicine Lake Watershed. Also, Ridgedale Creek represents nearly 70 percent of the total phosphorus load to the eastern half of the Medicine Lake west bay. The BC -MLP originally recommended constructing an alum treatment plant within the Medicine Lake Park Area, west of the Medicine Lake west bay. However, this plan does not recommend that BMP, as it is not needed to meet the BCWMC's water quality goals for Medicine Lake. Long term goals for this sub -watershed may be to work with Ridgedale Center to replace impermeable pavement with permeable pavement, install rain gardens in the parking lot, and street sweeping. Focused public education may also be an option for this sub - watershed. Since this sub -watershed lies within the cities of Minnetonka and Plymouth, coordination on many of these non-structural options would be beneficial to both cities and the Lake. 4. Medicine Lake North Drainage District Medicine Lake receives more than 2 percent of its annual phosphorus Ioad from this drainage district. This represents about 5 percent of the total phosphorus load from the Medicine Lake Watershed. Since the completion of the BC -MLP significant development has occurred in this sub -watershed, including a large commercial complex, residential housing with the accompanying roads. h1 addition, significant upgrades to Rockford Road (CR 9) and Northwest Blvd. (CR 61) that crisscross this drainage district have been made. The Commission's plan does not recommend implementation of additional structural BMP's in this district. However, Three Rivers Parks District has brought a severe erosion problem to the attention of the City of Plymouth and Hennepin County which will likely result in a project during the time period that this plan is in effect. At the time that CR 9 was reconstructed, the TRPD constructed a pair of box culverts under CR 9 to provide a trail -friendly crossing. The box culvert is now virtually impassable as a result of being filled with sediment and standing water. The loss of the use of the box culverts has resulted in trail users crossing CR 9 at grade, cast of the controlled intersection of CR 9 and CR 61. This creates a significant safety hazard. The sediment and water are diverted into the box culvert for two reasons: I) The development in this drainage district in the Iate-eighty's and early ninety's has increased the volume of water in the small creek by approximately XX percent, and 2) the pipe constructed to convey the water under County Road 9 and into Medicine Lake was 0 undersized for the volume of water it now receives. These two factors have resulted in the water being diverted into the box culverts, rendering them unusable to trail users. Erosion has become a significant factor in this small watershed. This small creek, which once meandered on the surface, has eroded a valley that is now over 10 feet deep along much of its length. To address these issues and return the trail to a useable condition, Hennepin County began constructing a NURP pond on the south side of CR 9 in the fall of 2003. In addition, a berm will be constructed on the north side of CR 9 to divert the water and sediment through the western box culvert. This NURP pond is considered a temporary fix to the problem as a solution needs to be found that will prevent the erosion upstream. Two possible solutions to this erosion issue have been discussed: 1) the construction of a series of NURP ponds that will step the storm water down the slope without erosion, and 2) a pipe that will convey the water to the NURP pond constructed by Hennepin County or the wetland at the end of the north aril of Medicine Lake. Construction of the NURP ponds is estimated to be in the range of 400,000 to $600,000. The pipe options is estimated at approximately half that. At this time the Medicine Lake sub -committee will be examining this situation and making recommendations for solutions. 5. Boat Landing District This drainage district is identified as the NE Medicine Lake Drainage District in the city's WRIvMP. This district contributes less than 2 percent of the annual phosphorous load to Medicine Lake and represents about 3 percent of the total phosphorus load from the Medicine Lake Watershed. Both the Commission and City's WR -.\4P include no s}UructuraI BMP's for this drainage district. The BC -MLP makes general recommendations that non-structural BMP's be implemented. The sub -committee will be reviewing these recommendations and may make specific recommendations for the implementation of non-structural BMP's. 6. Summary Similarities of the two plans Difference on alum treatment. 10 Table 12-2. Draft Water Quality Management and Flood Control 10 -Year Capital Improvements Program Map ID # Water Quality Improvement Option 1 ML -1 s Construct wet detention pond for subwatershed BC94131 (Option 8 in Medicine Lake Plan) ML -2 Reduce Goose Loadings by 75% (Option 17 in Medicine Lake Plan) ML -3 4 Reroute flows from subwatershed BC94 to a larger wet detention pond for BC92 (Option 9a in Medicine Lake Plan) & dredging of accumulated sediment ML -4 4 Medicine Lake East Beach wet detention pond for subwatershed BC 107 (Option 11 in Medicine Lake Pian) & dredging of accumulated sediment ML -5 4' 5 Construct wet detention pond for subwatersheds BC98, BC98A and BC98B (Option 10a in Medicine Lake Plan) & dredging of accumulated sediment MLS Construct wet detention pond for subwatershed BC94152 (Option 6 in Medicine Lake ML -7 lin-Lake Herbicide Treatment (Option 18 in Medicine Lake Plan) PL -6 Ilmprovements to stormwater basin in PL -A13 near Circle Park (from the City of Plymouth's Parkers Lake Implementation Plan) WTH-1 0, ' Dredging subwatershed FR -5 detention pond (Option 2 in Wirth Lake Plan) WTH-2 7 Highway 55 detention pond (Option 3 in Wirth Lake Plan) WTH-3 7.8 In -lake alum treatment (Option 1 in Wirth Lake Plan) I None - see Table 2. Potential Future Water Quality Capital Improvement Projects TWA IPond Expansion (Option 1 in Twin Lake Plan) WST-1 n IFlag Avenue detentionlskimmIng facility (Option 1 in Westwood Lake Plan) I None - see Table 2. Potential Future Water Quality Capital Improvement Projects Capital Cost 2 20051 2006 0 Year 20081 20091 20101 20111 20121 2013 102,500 $34,170 $34,1701 $34,160 104,100 $90,200 13,900 0 0 10,800 195,000 r err r r— r ME_....`.x 141,100 90,0001$105,000 215, 10,800 231,9001$231,900 0 241,9001$241,9001$241, 201 74, 45, GR -2" Grimes Pond wet detention pond (Option 4 in Rice and Grimes Ponds Plan) 1 $80,000 1 1 1 1 $80,0001 4 ! ! E 1 1 CL -1 IRamada Inn detention/skimming facility (Option 1 in Crane Lake Plan) 1 $89,100 1 1 1 1 1 1 1 1 1 1 $89,100 CL -2 JJoy Lane Wet Detention Pond (Alt. #2) 1 $85,100 1 1 1 1 1 1 1 1 1 1 $85,100 I -- !None - see Table 2. Potential Future Water Quality Capital Improvement Projects I I { I I I I j { None - see Table 2. Potential Future Water Quality Capital Improvement Projects I I I I I I I Year Map ID # Flood Control Improvement Option Capital Cost 20051 20061 2007 20081 2009 20101 20111 20121 20131 2014 Flood proofing of homes along trunk system 14 $400,000 1 $0 $0 $0 $0 Bassett Creek Water Management Commission Watershed Management Plan P:12312710511plan1CIP Table 12-2.doc MM4 t - Other potential projects that the cities may implement will be evaluated at the time the projects become more definite 2 - Capital Cost does not include land acquisition costs, but does include legal, administration, and 25% additional for contingencies. All costs are in 2003 dollars. 3 - Already constructed. 4 - This project includes dredging of accumulated sediment, as recommended by the City of Plymouth's Medicine Lake Watershed Implementation and Management Plan and will be constructed in 2004. The total project cost is estimated to be $880,100. MnDOT sound wall construction In New Hope will require relocation & resizing of storm sewer in this watershed, which could lead to City of New Hope participation in this project. 6 - The Commission will consider including repair of the existing control structure as part of the feasibility study for this project. Project is in City of Golden Valley's CIP. a - Project costs may be offset by $160,000 LCMR grant. e - Project is in City of Golden Valley's CIP. s - The Cityof 5t. Louis Park supportspports a scaled-down, less costly project that includes park and playground improvements. The city staff agrees with the Commission's proposed schedule, but suggests re-evaluation of the Commission's water quality goal for Westwood Lake. io The City of New Hope has constructed N13 -35A, B, C, but not to the same degree as proposed in the lake and watershed management plan. NB -29A & B have not been constructed. These improvements will need to be re-evaluated as part of the feasibility study. Costs shown are for NB -29A S B only. 11 - The City of New Hope has already constructed NB- 28A & B. The city will be constructing ponds NB -37A & NB -38A in the next year. Pond NB -36A may be constructed in conjunction with a church expansion project. These improvements will need to be re- evaluated as part of the feasibility study. Costs shown are for N13 -36A, NB -37A & NB -38A only. 12 - This project to be completed as part of the Boone Avenue and Brookview Golf Course improvement projects in 2004. 13 - This project should be feasible as part of the City of Robbinsdale's street reconstruction project taking place in the near future. 14 - Funding is from remaining flood control project construction funds ($700,000). The floodproofing funds are proposed to be allocated as follows: 2003 - $100,000, 2004 - 200,000, 2005 - $300,000 and 2006 - $100,000. These amounts are the BCWMC costs, assuming the BCWMC funds 72.5% of the floodproofing costs. See Table 5-2. November 2003 Draft Page 12-27 Agenda Number: (-- TO: Mayor and City Council FROM: Laurie Ahrens, City Manager SUBJECT: Set Future Study Sessions DATE: January 16, 2004, for City Council study session of January 20, 2004 1. ACTION REQUESTED: Review the pending study session topics list and, if desired, establish future special meetings or amend the topics list. 2. BACKGROUND: Attached is the list of pending study session topics, as well as calendars to assist in scheduling. Pending Study Session Topics at least 3 Council members have approved the following study items on the list) Pond and Drainage Issues and Creek Cleaning (Council) Flood Claims (Hewitt, Slavik, Black) Discuss redevelopment options in City Center area (Hewitt) Other requests for study session topics: Request of Trigve Svard to give presentation on public helistops Meeting with Hennepin County Commissioners (Hewitt) Review Transportation Studies for Vicksburg Lane and Medina Road Review Lighting Regulations OFFICIAL CITY MEETINGS January 2004 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 1 2 3 Dec 2003 S M T W T F S Feb 2004 S M T W T F S City Offices closed 1 2 3 4 5 6 1 2 3 4 5 6 7 7 8 9 10 11 12 13 14 15 16 17 18 19 20 8 9 10 11 12 13 14 15 16 17 18 19 20 21 NEW YEAR'S DAY 21 22 23 24 25 26 27 22 23 24 25 26 27 28 28 29 30 31 29 4 5 6 7 8 9 10 7:00 PM PLANNING COMMISSION, Council Chambers 6:30 PM MEDICINE LAKE WATER QUALITY PONDS PUBLIC MEETING, Plymouth Creek Center 7:00 PM PARK & REC ADVISORY COMMISSION (PRAC), Council Chambers 11 12 13 14 15 16 17 6:45 PM YOUTH ADVISORY COUNCIL, Council Chambers 7 30 AM MLC REGIONAL LEGISLATIVE MEETING, Plymouth Radisson, 3131 Campus Drive 5 00 PM SPECIAL COUNCIL MEETING: SURFACE WATER FEE, Coundl Chamlxra 7:00 PM ENVIRONMENTAL QUALITY COMMITTEE EQC), Plymouth Creek Center 7:00 PM HUMAN RIGHTS COMMISSION - Medicine Lake Room 7'.0o PM REGULAR COUNCIL MEETING, Council Chambers 18 19 20 21 22 23 24 MARTIN LUTHER KING JR. BIRTHDAY Observed)- City Offices Closed 6:00 PM BASSETT I CREEK WATERSHED I COMMISSION'S 2NDGENERATIONPLANd UPDATE ON FLOOD ANALYSIS - Public Safety Training Room 5:30 PM SPECIAL CITY COUNCIL MEETING WITH PLYMOUTH AREA LEGISLATORS; Plymouth Creek Center 7:00 PM JOINT MEETING w/ HRA SALE OF CITY -OWNED PROPERTY (NW BLVD & SCHMIDT LAKE RD) TO 7:00 PM PLANNING COMMISSION, Council Chambers HRA, Public Safety Training Room 25 26 6:45 PM YOUTH ADVISORY COUNCIL, Council Chambers 17 11:45 AM PLYMOUTH-MTKA BUSINESS COUNCIL, 0 BORN Conference Room, 301 Carlson Parkway, 4th floor 28 4.00 PM MEDICINE LAKE WATERSHED MANAGEMENTANDSUBCOMMITTEE, Bass Lake Room 7:00 PM PLYMOUTH ADVISORY COMMITTEE ON TRANSIT (PACT) - Medicine Lake Room 29 30 31 10:00 AM COUNCIL GOALS PRIORITIES - Fireside Room, Plymouth Creek Center 0NCIL MEETING, 7,: O00 PM REGULAR ouncil Chambers modified on 1/16/2004 OFFICIAL CITY MEETINGS February 2004 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 1 2 3 4 7:00 PM PLANNING COMMISSION, Council Chambers 5 7:00 PM HUMAN RIGHTS co - akRMedicinmeeLLakeRoom 6 7 2:00 PM -7:00 PM FIRE & ICE FESTIVAL, Parkers Lake 7:00 PM PARK 8 REC ADVISORY COMMISSION PRAC), Council Chambers 8 9 10 11 12 13 14 6:45 PM YOUTH ADVISORY COUNCIL, Council Chambers 7:00 PM REGULAR COUNCIL MEETING, Council Chambers 11:30 AM TWIN WEST STATE OF THE CITY - Plymouth Creek Center 7:00 PM ENVIRONMENTAL QUALITY COMMITTEE EQC), Plymouth Creek Center 15 16 17 18 19 20 21 PRESIDENTS DAY - City Offices Closed 7:00 PM PLANNING COMMISSION, Council Chambers 7:00 PM HOUSING & REDEVELOPMENT AUTHORITY (HRA), Medicine Lake Room 22 23 24 25 26 27 28 6:00 PM BOARD & 7:00 PM 4:00 PM MEDICINE LAKE WATERSHED COMMISSION RECOGNITION EVENT - Plymouth REGULAR COUNCIL MEETING, Council MANAGEMENTSUBCOMMITTEE, Bass Lake Room Creek Center Chambers 7 00 PM PLYMOUTH ADVISORY COMMITTEE ON TRANSIT (PACT) - McEicine Lake Room Ash Wednesday (First Day of Lent) 29 afar 2004Jan2004 S M T W T F S S M T 11' T F S 1 2 3 4 5 6123 4 5 6 7 8 9 10 7 8 9 10 11 12 13 11 12 13 14 15 16 17 14 15 16 17 18 19 20 18 19 20 21 22 23 24 21 22 23 24 25 26 27 25 26 27 28 29 30 31 28 29 30 31 modified on 1/16/2004 OFFICIAL CITY MEETINGS March 2004 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 1 2 3 4 5 6 5:00 PM Caucus Night 7:00 PM 7:00 PM HUMAN YOUTH TOWN PLANNING RIGHTS UM, COMMISSION, COMMISSION - FOR Creek Council Chambers Medicine Lake Plymouth Room Center 7 8 9 10 11 12 13 7:00 PM REGULAR COUNCIL MEETING, Council Chambers 7:00 PM ENVIRONMENTAL QUALITY COMMITTEE EQC), Plymouth Creek Center 7:00 PM PARK & REC ADVISORY COMMISSION PRAC), Council Chambers 14 15 16 17 18 19 20 6:45 PM YOUTH ADVISORY COUNCIL, Council Chambers 7:00 PM PLANNING COMMISSION, Council Chambers 1:00 PM HOUSING & REDEVELOPMENT AUTHORITY (HRA), Medicine Lake Room 21 22 23 24 25 26 27 11:45 AM PLYMOUTH-MTKA BUSINESS COUNCIL, BORN Conference Room, 301 Carlson Parkway, 4th Iloor 7:00 PM PLYMOUTH ADVISORY COMMITTEE ON TRANSIT (PACT) - Medicine Lake Room 7:00 PM REGULAR COUNCIL MEETING, Council Chambers 28 29 30 31 Feb 2004 Apr 2004 6:45 PM YOUTH ADVISORY COUNCIL, Council Chambers S M T W T F S S M T NV T F S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6 7 8 9 10 15 16 17 18 19 20 21 11 12 13 14 15 16 17 22 23 24 25 26 27 28 18 19 20 21 22 23 24 29 25 26 27 28 29 30 modified on 1/16/2004 OFFICIAL CITY MEETINGS April 2004 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 1 2 3 Mar 2004 S M T W T F S May 2004 S M T W T F S 7:00 PM HUMAN RIGHTS 1 2 3 4 5 6 1 COMMISSION - 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Medicine Lake Room 21 22 23 24 25 26 27 16 17 18 19 20 21 22 28 29 30 31 23 24 25 26 27 28 29 30 31 4 S 6 7 8 9 10 DAYLIGHT SAVINGS COMMENCES- set clocks ahead 1 hour Passover begins at sunset 7:00 PM PLANNING COMMISSION, Council Chambers 7:00 PM PARK & REC ADVISORY COMMISSION PRAC), Council Chambers Good Friday Palm Sunday 11 12 13 14 15 16 17 Easter 6:45 PM YOUTH ADVISORY COUNCIL, PublicQUALITY Safety Training Room 7:00 PM REGULAR COUNCIL MEETING, Council 7:00 PM ENVIRONMENTAL COMMITTEE EQC). Plymouth Creek 7:00 PM HOUSING & REDEVELOPMENT AUTHORITY (HRA), Medicine Lake Room Chambers 7:00 PM BOARD OF EQUALIZATION, Council Chambers 18 19 20 21 22 23 24 7:00 PM8:00 AM -1:00 PM HUMAN RIGHTS PLANNING COMMISSION COMMISSION, STUDENT Council Chambers WORKSHOP, Plymouth Ice Center 25 26 27 28 29 30 6:45 PM YOUTH ADVISORY COUNCIL, Public Safety Training Room 7:00 PM REGULAR COUNCIL MEETING, Council 7:00 PM PLYMOUTH ADVISORY COMMITTEE ON Chambers TRANSIT (PACT) - 7:00 PM BOARD OF EQUALIZATION Medicine Lake Room RECONVENED), Council Chambers modified on 1/16/2004