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2g Riley/Rice Marsh Lake ImprovCITYOF CHANI]ASSEN PO Box 147 Chan,'~, MN 55317 Administration Phone: 952.227.1100 Fax: 952227.1110 Building InspecUons Phmm: 95222227.1180 Fax: 952.227.11O0 Engineering ~me: 952.227.1160 Fax: 952.227.1170 Finance Phone: 95222227.1140 Fax: 95222227.1110 Park & Recreation Phone: 952.227.1120 Fax:. 95,?..227.1110 ~on ~r, Ler 2310 Coulter, Boule',,a,q:l Phone: 952_227.1400 Fax:. 952227.1,40.4 Planning & Natural Resources P,'~: 95222.27.1130 Fax: 952.227.1110 Public Works 1591 Pa'k Road Phone: 952227.1300 Fax: 952.227.1310 Senior Center Phooe: 952227.1125 Fax: 952.227.1110 Web Site v,','~,;'.cJ.ctml'msen.mn.us To: From: Date: Re: Todd Gerhardt, City Manager Lori Haak, Water Resources Coordinator December 20, 2002 Resolution to Petition Riley-Purgatory-Bluff Creek Watershed District for Riley and Rice Marsh Lake Water Quality Improvement Projects Move to: REQUESTED ACTION Adopt Resolution to Petition the Riley-Purgatory-Bluff Creek Watershed District to Commit to Funding the-Riley and Rice Marsh Lake Water Quality Improvement Projects. SUMMARY Two Use Attainability Analyses CLIAA ) were completed by the Riley-Purgatory- Bluff Creek Watershed District (RPBCWD) and submitted to the Cities of Chanhassen and Eden Prairie for review. This included: · Rice Marsh Lake / Lake Susan UAA (December 1999) - The intended use for Rice Marsh lake is to provide fish and wildlife habitat. The water quality improvements in these two lakes are part of a larger project to improve Lake Riley as they both drain towards Lake Riley. · Lake Riley UAA (April 2002) - Lake Riley is a key recreafi~ resource for both Chanhassen and Eden Prairie. The intended uses'are swimming and fishing. Staff recommends petitioning the RPBCWD to undertake the water quality improvements outlined in the UAAs for Rice Marsh Lake and Lake Riley. The District will design and manage all projects and will pay 75 to 100% of the costs associated with the improvements. The City of Eden Prairie will also be submitting a petition to RPB~ to participate in this projecC Mr. Dave Florenzano, President of the Lake Riley Improvement Association, has requested that the Cities of Eden Prairie and Chanhassen forward this project to the District for completion in 2003 (attached). BACKGROUND The purpose of the Lake Use Attainability Analyses (UAA) was to provide an The City of Cf~anbassen · A gr~','/ng commonly, with clean fakes, quafiiy schools, a ctm'ning dm',,nt~'n, thriving businesses, v,qnding tmJIs, and beauUful parks. A grot place to live, work, and play. Riley and Rice Marsh Lake Water Quality Improvement Projects January 2003 assessment of the water quality of Riley and Rice Marsh Lakes, analyze the problems and provide alternative remedial measures that would result in the attainment of water quality sufficient to fully support the intended uses of the lakes. Since Lake Riley receives water from Rice Marsh Lake via Riley Creek, water quality improvements in Rice Marsh Lake will benefit the water quality of Lake Riley. Watershed Conditions The direct watershed for Riley Lake consists primarily of residential (508 acres) and park/open space (706 acres). Remaining uses include agriculture (231 acres), highway (18 acres) and open water (300 acres). Future land use is anticipated to include a switch from agriculture and open space to more residential and highway as well as some commercial. The current storm water pond.rig system for the lake's current and future watershed is inadequate. Historical Water Quality The UAA included water quality analysis from 1971 through 1998 and indicated that Lake Riley's water quality has remained relatively stable, but generally poor, during that time. The water transparency declined from 2.2 meters in 1978 to 0.9 meters in 1998. Summer algae blooms during the UAA analysis were found to have impaired recreational usage of the lake and the lake was rated as eutrophic (poor). Current Water Quality The 1997 to 1998 Secchi disc and total phosphorous concentration data indicated that the lake was eutrophic (poor water quality) during the summer and hypereutrophic (very poor water quality) during the spring and fall. The data indicated that moderate to severe recreational use impairment (primarily swimming) occurs during the summer months. RECOMMENDED ACTIONS All indications are that significant improvement to the water quality in Riley Lake will take many years. The water quality in Riley Lake now is marginal for swimming. Staff recommends that the following items be budgeted from the storm water management fund for 2003 to assist in the proposed water quality improvements. Petitioning the RPBCWD to assist in completing the following actions is the recommended first step. . Upgrade Storm Water Management System - Five existing storm water ponds within Chanhassen do not meet NURP standards and need to be upgraded. Two pond upgrades will also take place within Eden Prairie. Four subwatersheds do not have adequate storm water ponding in place, so ponds need to be constructed. It is estimated that these improvements would result in a reduction in annual phosphorus loading to the lake by 50 to 95 pounds for future land uses. The estimated cost is $392,000 for the improvements in Chanhassen. Cost share of 75% by the City would be required for the acquisition of additional easements or property. The City has included in the petition a cost limit of $100,000 for acquisition unless the Riley and Rice Marsh lake Water Quality Improvement Projects January 2003 , District receives prior written approval from the City. Alum-Lime Slurry Treatment of Rice Marsh I. ake - Phosphorus from Rice Marsh Lake increases the amount of phosphorus in Riley Creek by a factor of three as it moves through the lake. Alum will be applied to the lake to precipitate phosphorus onto the lake bottom, thus removing in lake phosphorus and forming a layer over the sediments to prevent the release of phosphorus. The estimated cost of this would be a one time expenditure of $200,000 for 2003~ The RPBCWD would cover 100% of this cost. 3. Alum-Lime Slurry Treaunent of Lake Riley - Alum would be applied to remove excess phosphorus currently in the lake waters and sediments. This would reduce the amount of phosphorus within the lake immediately, allowing time for the other proposed measures to work on reducing phosphorus loading to maintain the higher water quality over time. The estimated c6st of this would be a one time expenditure of $200,000 for 2003. The RPBCWD would cover 100% of this cost. If the RPBCWD approves the petition, an agreement with specific cost provisions will be developed for final approval by City Council at a later date. RECOMMENDATION Staff recommends the City Council adopt the following resolution: RESOL~ION RELATING TO THE RII.EY AND RICE MARSH LAKE WATER QUALITY IMPROVEMENT PRO~ -. WHEREAS, Riley Lake and its tributary lake, Rice Marsh Lake, 'are important features within the City of Chanhassen; and WHEREAS, the City Council is committed to water quality improvement within Riley Lake; and WHEREAS, there is a docmnented relationship between deteriorating wa. ret quality within Riley Lake and ~e current storm water ponding system; and .. WHEREAS, the City of Chanhassen has determined that i .mprovements to the storm water treatment system and fishery habitat are required to fully realize the recreational potential of the lake. NOW, THEREFORE, BE IT RKSOLVED, the City Council desires to complete'those items recommended within the Riley and Rice Marsh Lake Use Attainability Analyses to i ~mprove the quality of storm water runoff entering Riley Lake and hereby approves the attached petition to the Riley-Purgatory-Bluff Creek Watershed District to: · Upgrade of five (5) existing storm water ponds that do not meet NURP standards; · Construction of four (4) storm water ponds in areas where storm water is not treated prior to discharge; and Riley and Rice Marsh Lake Water Quality Improvement Projects January 2003 · Treatment of each lake with an alum product to remove phosphorus from the water column. BE IT FURTHER RESOLVED, the City Council does request that the Riley-Purgatory- Bluff Creek Watershed District participate in funding these activities with a cost share as defined in the attached petition. ATTAC~TS 1. Resolution 2. Petition 3. Letter from Lake Riley Improvement Association CITY OF CHANHASS~ CARVER AND ttENNF_,PIN COUNTIES, MINNESOTA RF.~OLUTION NO. 2003- RF~OLUTION RELATING TO THE RII.~ AND RICE MARSH LAKi~. WATER QUALITY IMPRO~ PROJECTS WHEREAS, Riley Lake and its tributary lake, Rice Marsh Lake, are i .mportant features within the City of Chanhassen; and WHEREAS, the City Council is committeA to water quality i .mFrovement within Riley Lake; and WHEREAS, there is a documented relationship between deteriorating water quality within Riley Lake and the current storm water ponding system; and ]NItEREAS, the City of Chanhazsen has determined that i .mFrovements to the storm water treatment system and fishery habitat are required to fully ~ the recreational potential of the lake. NOW, THEREFORE, BE IT RF~OL~, the City Council desires to complete those items recommended within the Riley and Rice Marsh Lake Use Attainability Analyses to i .reprove the quality of storm water runoff entering Riley Lake and hereby approves the attached petition to the Riley-Purgatory-Bluff Creek Watershed District to: · Upgrade of five (5) existing storm water ponds that do not meet NURP standards; · Construction of four (4) storm water ponds in areas where storm water is not treated prior to discharge; and · Treatment of each lake with an alum product to remove phosphorus from the water column. BE IT FURTHER RESOLVED, the City Council does request that the Riley-Purgatory- Bluff Creek Watershed District participate in funding these activities with a cost shore as defined in the attached petition. ADOPTED by the Chanhassen City Council January ,2003. ATFF_~T: Tom Furlong, Mayor SEAL Todd Gerhardt, City Clerk PETITION OF THE CITY OF CHANHASSEN TO RILEY PURGATORY BLUFF CREEK WATERSHED DISTRICT FOR THE LAKE IHLEY AND RICE MARSH LAKE BASIC WATER MANAGEMENT PROJECTS I. AUTHORrI~ The City of Chanhassen petitions the Riley Purgatory Bluff Creek Watershed District, pursuant to the provisions of the Minnesota Statutes Sections 103D.201, 103D.605, 103D.705, and 103D.905, to undertake a basic water management project to protect and improve the water quality in Lake Riley and Rice Marsh Lake. IL PURPOSE The purpose of the project is to improve the water quality of Lake Riley by reducing internal and external sources of phosphorus in and to the lake that contribute to alga growth, resulting in decreased water quality, clarity and transparency. The Minnesota Board of Water and Soil Resources approved and the Riley Purgatory Bluff Creek Watershed District Board of Managers adopted a watershed management plan that assessed the condition of the lake through determination of its physical, chemical and biological qualities. The approved and adopted watershed management plan dated May 1996 is incorporated by reference. This project in the cities of Chanhassen and Eden Prairie will help remedy water quality impacts from: 1) municipal sewage treatment discharges that were made to Rice Marsh Lake through the early 1970s; 2) future construction of T.H. 312 between Lake Riley and Rice Marsh Lake; and 3) increased urbanization within the watershed. The Lake Riley and Rice Marsh Lake Use Attainability Analyses dated April 2002 and November 1999 respectively are incorporated by reference. III. GENERAL DESCRIPTION OF WORK PROPOSED AND PURPOSES The project proposes application of alum-pius-lime treatments and storm water management improvements to improve the water quality of the Lake Riley and Rice Marsh Lake. Application of the alum-plus-lime treatments will remediate prior municipal sewage treatment discharges, while the storm water management improvements will limit impacts from the highway construction and increased urbanization within the lake watershed. Through 1972, the City of Chanhassen discharged treated sewage wastewater into Rice Marsh Lake, resulting in high phosphorus levels within the sediments on the bottom of the lake. Although wastewater discharges were discontinued, the excess phosphorus from years of discharge continues to degrade the water quality of Lake Riley via flows from Riley Creek. Approximately 54% of the phosphorus entering Lake Riley flows from Rice Marsh Lake through Riley Creek. Phosphorus recycled from Rice Marsh Lake sediments into Riley Creek waters is a major contributor the phosphorus draining into Lake Riley. Proposed water quality improvements are expected to reduce the phosphorus recycled from lake sediments to the overlying lake water that would otherwise support alga growth or blooms. Within the City of Chanhassen, the project includes a proposal to treat Lake Riley and Rice Marsh Lake with an alum-plus-lime slurry. The proposal also calls for upgrading five (5) existing storm water management basins and the construction of four (4) new storm water basins. The new and upgraded basins will conform to the standards for the National Urban Runoff Ponding Basins and the requirements of the Minnesota Pollution Control Agency. Petition of the City of Chanhassen of Riley-Purgatory-Bluff Creek Watershed District Riley and Rice Marsh ~ Basic Water Management Projects January 2003 Page 2 of 3 Overall the project will increase the recreational use of swimming in Lake Riley by reducing the phosphorous loads to the lake thereby limiting the number of days the actual water quality ex--.ds the standard for recreational swimming. This is a Trophic State Index (TSI) of 53 (<40 mg/l), which is the guidance published by the Minnesota Pollution Control Agency to assess full support for primary contact recreation and aesthetics. The project intends continued monitoring and m-evaluation of the effect of conslxucting the proposed improvements for the purpose of determining whether additional controls are required. The proposed work is consistent with additional controls, if required to maintain the existing beneficial uses of Riley and Rice Marsh Lakes. IV. DESCRIFFION OF THE LANDS OVER WHICH THE PROPOSED IMPRO~ ARE LOCATED The project will be located on property that is directly or indirectly tributary to Lake Riley, Rice Marsh Lake and Riley Creek that is locamd on the eastern and western boundaries of Chanhassen and Eden Prairie respectively..Within L-~lal~hassen, the project will be located in the general area west of Dell Road and east of Trunk Highway 101 between Pioneer Trail and Trunk Highway 5 in the City of Chanhassen. The i .mpmvements are described in detail in the Riley and Rice Marsh Lake Use Attainability Analyses, which are incorporated by reference. V. GENERAL DESCRIFFION OF THE PART OF' THE DISTRICT AFFECTED The affected lands are located in the cities of Chanhassen and Eden Prairie and include the riparian and tributary drainage areas to Lake Riley, Rice Marsh Lake and Riley Creek. Generally, the affected areas are south of Trunk Highway 5, east of Trunk Highway 101, and north of Pioneer Trail. The approximate centerline of the affected property is located along the municipal boundary between Chanlmssen and Eden Prairie. Rice Marsh Lake is located in the cities of Chanhassen and Eden Prairie and has a 821-acre watershed containing woodlands, marsh, residences, parks and open spaces. The lake's direct watershed consists of 378 acres of low and moderate density housing, 348 acres of parks and open space, 50 acres of industrial and 26 acres of commercial land use. Riley Creek is 'the outlet from Rice Marsh Lake to Lake Riley. Riley Creek has a 10 square mile watershed, with mild topography in the upper and middle portions of the watershed and a steep, north-valley wall of the Minnesota River on the downstream end of the watershed. Riley Creek originates from lakes Lucy and Ann, and flows through Lake Susan, Rice Marsh Lake and Lake Riley before it begins its descent to the Minnesota River. This project will focus on the stretch of the creek between Rice Marsh Lake and Lake Riley. Finally, Lake Riley has a direct drainage area of 818 acres consisting of 449 acres of low- density residential, 286 acres of parks and open, 1 acre of commercial, and 82 acres of agricultural property. The lake has a maximum depth of approximately 50 feet, and a mean depth of approximately 23 feet. Water flows from Rice Marsh Lake to Lake Riley through Riley Creek. Lake Riley's total drainage area, including both direct and indirect drainage, is over 4,500 acres. VI. NEED AND NECESSITY FOR THE PROPOSED IMPROVEMENT Prior years of municipal wastewater discharges to Rice Marsh Lake has deposited excessive Petition of the City of Chanhassen of Riley-Purgatory-Bluff Creek Watershed District Riley and Rice Marsh Lake Basic Water Management Projects January 2003 Page 3 of 3 mounts of phosphorus that untreated will impact Lake Riley for decades. The continued development in tributary areas and the scheduled construction of T.H. 312 between lake Riley and Rice Marsh Lake necessitates water quantity management and treatment of water quality to protect and improve the scenic, recreational and wildlife of those specific lakes and the overall water quality of the District. VII. THE PROPOSED IMPROVEMENT WILL BE CONDUCIVE TO THE PUBLIC HEALTH, CONVENIENCE AND WELFARE The City of Chanhassen petitions for the project because it will be conducive to the public health, convenience and welfare of the District and the City. Completion of the project, and associated recreational improvements, will preserve and. enhance the public use and enjoyment of Riley and Rice Marsh Lakes and their adjacent parks, all of which are significant natural resources of the District and region. VIII. FINANCING OF THE PROPOSED IMPROVEMENT The project is identified in the Riley Purgatory Bluff Creek Watershed District Water Management Plan and is a priority project of common benefit to the entire District. Minnesota Statutes Section 103D.905, Subdivision 3 provides for the project financing of the basic water management features of the project. The District will fund.100% of the costs of the project with the exception of any easement or property acquisition. The City will share (75%) in the cost of the cost of any such acquisitions. The cost to the City may not exceed $100,000 unless prior written approval is obtained from the City. IX. PROJECT ABANDONMENT The City of Chanhassen hereby states and acknowledges that it will pay all costs and expenses that may be incurred by the activities described in this petition in the event the project is dismissed, no construction contract is let, or the City withdraws its project petition. CITY OF CHANHASSEN Mayor of City Of Chanhassen CITY OF CHANHASSEN City Manager