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stormwater through stormwater pretreatment systems. Improvement of the water quality in Lake Owasso was discussed as being of primary concern for the neighborhood committee as well as City staff and Grass Lake WMO. Between Rice Street and Western Avenue: Approximately 160 acres of single family residential property drain into Ladyslipper Park through a drainage ditch that cuts through the park in a north south direction conveying storm water runoff northerly to Lake Owasso. This ditch was constructed in 1971, as a canoe access to Lake Owasso. In the 1991 Lake Owasso Survey report, it was determined that the removal efficiency of this system is very limited. Only 30 to 50% of suspended solids and 9% of the total phosphorus were removed before being discharged into Lake Owasso. Phosphorus removal is important because of the role it plays as a nutrient for algal growth in the receiving water bodies. This subwatershed is the largest remaining untreated direct discharge of stormwater into Lake Owasso. GL WMO as well as the City of Roseville, have included the reduction of sediment and phosphorus loading in Lake Owasso as a primary goal in their comprehensive storm water management plans. We have been working with SEH, to design storm water treatment ponds for this The proposal is to excavate out a portion of Ladyslipper Park to provide this treatment. We are proposing to have the section of the road adjacent to Ladyslipper Park be constructed with a rural cross-section. Part of the reason for this is to provide water quality treatment for the street runoff by directing the storm water into rain gardens on the south side of the road. A rain garden is a shallow depression that collects stormwater from impervious surfaces and infiltrates, filters and evaporates the runoff. Rain gardens are typically planted with a diverse mix of native wildflowers, grasses, shrubs and trees, and are an attractive, low maintenance addition to the right- of- way. The other part of the reason is for flexibility. This is the section of road that is being constructed on top of less than suitable soils. It may not be possible to rely on concrete curb to convey runoff to the storm sewer and then on to a pond for treatment. The grades in this area are also very flat. It would be difficult if not impossible to have adequate cover over a storm sewer pipe under the road. The westerly 1700 feet of this project, between the Railroad tracks and Dale Street, is already served by storm sewer. The reconstructed road will tie into this storm sewer and be treated in the pond off of Heinel Drive. For the remainder of the roadway runoff we will need to provide in-line treatment. There is no additional right- of- way to accommodate ponds or rain gardens. This solution D. Property Considerations . Ladyslipper Park: between Marion and Matilda, S. Owasso Boulevard goes Project P-ST-SW-05-06 S. Owasso Boulevard Reconstruction Feasibility Report 23