Introduction
Parley Lake lies along a chain of lakes that compose Six Mile Creek which ultimately discharges into Lake Minnetonka. Hydrology for Parley Lake is primarily derived from three sources: the judicial ditch (Six Mile Creek), a small stream from the east and a larger stream from the southwest. Parley Lake is currently on the State list of Impaired Waters and a draft TMDL was developed for the lake in 2005. The TMDL recommended a capital project to restore wetland area on the tributary to the southwest in order to reduce the external nutrient loading to Parley Lake. Sub-basins SMC-40 and SMC-41 drain approximately 1100 acres through the southwest stream entering Parley Lake. The 2007 MCWD Comprehensive Water Resources Management Plan has identified a capital project in this area to achieve an external nutrient loading reduction to the lake. Existing land use in this area includes agricultural row cropping, large lot single family residential and a golf course.
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The annual phosphorus concentration goal identified for Parley Lake is 50 mg/L. In order to meet loading goals, MCWD will need to reduce loading to the lake by 1469 lbs. of phosphorus per year. The external load component of this reduction is 343 lbs. per year, with a goal of a 95 lb. reduction with a proposed project in SMC-41. It is worthwhile to note that paleo-limnologic testing of Parley Lake recently demonstrated historic water quality in the 90 mg/L range which will likely have implications for the future loading goal for the lake itself, however, given the need for external load reductions to Halsted Bay on Lake Minnetonka, load reductions to Parley should serve to benefit both waters.
MCWD has identified a 119-acre property (shown above) within the subwatershed where a potential project could occur to achieve this goal. Through preliminary investigations, MCWD has explored a number of opportunities on this site to reduce external loads to Parley Lake, however, the current effort of this report seeks to develop a more detailed assessment of project alternatives and cost estimates to narrow the focus for final design (the current project).
The proposed project should investigate the Feasibility of restoring wetland and/or creating stormwater features that will assist in achieving the 95 lb. load reduction, enhance existing habitat features and improve the overall ecosystem function of Parley Lake and the southwest tributary. Development of the Parley Lake Wetland Restoration Project requires investigation of the following issues:
Wetland type
Wetland Type and Classification must be integrated into the other important natural resources planning throughout the site. Considerations of vegetation species and wetland function must be evaluated in order to optimize the value of existing wetlands on site as well as the restored features. Proposed restored wetlands on site should be representative of natural or historic wetland features within the area and should complement the vegetation types of high quality upland features on the site. Wetland vegetation must be selected relative to the hydrologic considerations cited above in analysis of wetland siting.
Upland Resources
Wetland buffers adjacent to restoration areas should be free and clear of exotic and invasive species and generally consistent with other natural features on the site. Evaluation of existing and proposed site conditions must take into account the establishment and maintenance of buffer areas as well as restoration areas.
Feasibility study Report
Further questions and concerns can be addressed by contacting MCWD Planner Michael Wyatt at (952)471-0590 ext. 204 or mwyatt@minnehahacreek.org.
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