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• Review and Evaluate Available Precipitation Data Available data from precipitation gauges in the vicinity of the Lake Owasso watersheds will be evaluated for use in the P8 model. • Conduct a Field Survey of all Significant Ponds and Wetland Areas Within Each Subwatershed The storm water quality treatment provided by upstream ponds and wetland areas is important to the water quality of the downstream lake. During a storm, polluted runoff enters the ponds and displaces "clean" water until the plume of polluted-runoff reaches the pond's outlet structure. When the runoff does reach the outlet, it will have been treated by the settling of sediments and, in some cases, the biological uptake of nutrients. Therefore, the treatment effectiveness of a pond is directly correlated with the volume of its permanent pool, also known as the "dead storage volume." A survey of the ponds and wetland areas in the lake's subwatersheds will be conducted by Barr staff in order to determine the dead storage volume of each of the water bodies. The survey involves measuring the perimeter of each pond, standing water depths at various locations in the pond, the overflow point, and outlet sizes, types and relative elevations. Barr proposes to survey up to 14 ponds throughout the Lake Owasso watershed. The data collected in the survey will be processed using GIS technology to generate the dead storage volume of each pond in the lake's tributary watersheds. • Create GIS land use coverages representing current and future conditions for the Lake Owasso tributary watershed. Two different land use scenarios (current and future) will be modeled using P8. The existing conditions model will be developed for the purposes of calibrating the in-lake model. The future (i.e., ultimate development) conditions model will be used to assess the attainability of the beneficial use water quality goals and to analyze alternative remedial measures. • Create GIS soils coverage characterizing the infiltration capacity of the soils for the Lake Owasso watersheds. The GIS soils coverage will be based on information from the most recent Ramsey County NRCS soil survey. The GIS soils coverage will be used to develop hydrologic input parameters for P8 modeling and as a screening tool for identifying potential BMP locations. After all of these data are collected and analyzed, Barr will develop a detailed P8 model of the lake's watershed. Setting up the P8 models will include entering all of the pond and wetland areas and volumes, outflow devices, overflow elevations and outflow destinations for each drainage area in each lake's subwatershed, as well. as gathering land use information for each drainage area. Once the P8 model for the lake's watershed is created and calibrated to inflow monitoring data they will be used to generate water and phosphorus budgets for the lake under existing land use conditions. Barr Engineering Company :ODMA\PCDOCS\DOCS\247725\ 1