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Home My Public Portal About1991-84i EXECUTIVE SUMMARY This report presents the results, implementation plan, and cost estimates for the Diagnostic -Feasibility Study on Long Lake in Hennepin County. The project was funded by the Minnehaha Creek Watershed District (MCWD) and the Minnesota Pollution Control Agency (MPCA). The diagnostic study included a 12-month water quality monitoring program and subsequent data and land use assessments which characterized the sources of the water quality problems on the lake. The feasibility study evaluates the various alternatives for water quality improvement and finally, develops the implementation plan for the project. Long Lake was found to be borderline eutrophic-hypereutrophic with chronic occurrences of blue-green algae blooms and low dissolved oxygen (DO) concentrations. Historical and current monitoring data suggest that the lake is phosphorus limited. The lake has a relatively short hydrologic residence time of 0.9 years; thus, a reduction of the external phosphorus load to the lake was determined to be the necessary action to reduce the blue- green algal bloom. Currently, the lake's phosphorus concentration is 106 micrograms per liter WA); however, a goal of 67 µel was established. This goal is to be reached after all watershed improvements are implemented. An additional goal for the lake is the improvement of the sport fishery. In order to meet this goal and prevent excessive fish kills, DO levels must be maintained at 5 milligrams per liter (mg/1) or greater in the hypolimnion. It may not be necessary to have complete aeration of the hypolimnion. However, a refuge of well oxygenated water would be required to improve the fishery. In the feasibility study, a number of alternatives were evaluated to reach the phosphorus concentration goals and increase the oxygen levels in the hypolimnion. These alternatives ranged from administrative alternatives such as fertilizer management education programs, to structural alternatives such as the construction of a nutrient reducing wetland. Each of the options were evaluated for their benefit in improving water quality, their estimated initial and long-term (operation and maintenance) costs, and their technical feasibility. -1- The most technically sound and cost-effective options were incorporated into the implementation plan for improving Long Lake. The final plan elements include the following: • A local public information/education committee which will focus on informing, enlisting cooperation, and improving fertilization practices of local landowners. • Aeration systems to maintain areas of well oxygenated water in the hypolimnion and improve the sport fishery. • Removal of inlet deltas from an existing basin to reduce the pool of phosphorus in sediments and to improve the phosphorus removal efficiency. • Transformation of an existing "wet -dry" pond to a standing water pond allowing for improved sediment and phosphorus removal. • Street cleaning to capture potential pollutants before they are mixed with stormwater runoff and transported to the lake. • Construction of two first -flush stormwater detention basins to reduce the load of pollutants delivered to the lake via stormwater runoff. • Construction of a wetland area (detention basin) to reduce the load of pollutants delivered to the lake via runoff from northern subwatersheds. • Deepening and enlarging of an existing stormwater basin to increase the sediment and nutrient removal efficiency. • Development of a fisheries management plan to improve the recreational fishery in the lake. The last element of the plan is post -implementation monitoring to determine the effectiveness of the plan. The overall result of the project is an estimated 36 percent reduction in external phosphorus loading to the lake. -2- The project is to be implemented over a five-year schedule. The total project cost is estimated at $1,588,355. Grant funding will be requested for 50 percent of the project cost from MPCA Clean Water Partnership Program. The remaining local funding will be in - kind contributions from the DNR, as well as the Cities of Long Lake, Medina, and Orono. -3- Public Information Program Public information and education will be an important element of this project. The major emphasis of this element is the education of the public to different fertilizer management techniques, yard waste management techniques, and agricultural Best Management Practices (BMPs). To encourage public support and involvement, an effective public information program is needed. This type of program is specifically identified in the District's Water Management Plan. The public information program will be implemented by a Public Information Committee (PIC) which will use the MPCA document, "Community Information and Outreach for the Clean Water Partnership" (June 30, 1989) for guidance in the program. The Committee should consist of at least nine members from the community. The MCWD will provide two representatives from its Board of Managers in addition to the District Engineer. A request will be made by the MCWD to each of the following entities to provide one representative each: City of Long Lake City of Orono City of Medina DNR Hennepin Conservation District MPCA The Committee, through meetings every two months, will set goals, develop a Iong-term plan, and finally implement this plan in order to inform and educate the public of this project and what they can do to help improve the water quality of Long Lake. Some methods which might be considered in helping inform and educate the public may be sending out project newsletters, supply news releases to the local newspapers, possible cable television programs, or presentations to local groups/organizations. 5-2 Based on the results of the diagnostic study, it would appear that: some of the most important topics to be covered in the Public Information Program are: • Residential Fertilizer Management • Residential Yard Waste Management • Individual septic systems Maintenance • Agricultural BMPs In addition to the Public Information Program, the Committee should conduct public meetings. The number and appropriate timing of these meetings will be determined by the Committee. The emphasis of these meetings should be to educate the public of different fertilizer management techniques to reduce nutrient loading to area lakes from runoff, as well as improving the lake and watershed's general aesthetics. 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