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Bloom, Page 3, 1/31/05 trenches, or a settling basin prior to discharge into the wetland, will reduce the rates discharged from the site. WATER QUALITY Development and redevelopment projects must incorporate effective non point source pollution reduction BMPs. Effectiveness will be defined as meeting NURP criteria or achieving 60% annual phosphor�us reduction, 90% sediment removal and 95% heavy metal removal. Met Council's Small Site BMP Manual can be referred to for selecting and designing alternative BMPs. — Water quality treatment for 0.5 acres of the site will be provided by the infiltration in the — detention pond. As most of the drainage will be unrestricted, it is unlikely that the District's — criteria for water quality will be met. Additional volume control practices for unrestricted areas such as underground treatment structures, rain gardens and infiltration basins will aid in the removal of total phosphorus from the site. Routing more of the site to a wet pond instead of a dry pond will also aid in phosphorus removal. VOLUME CONTROL AND INFILTRATION All land developmentand redevelopmentactivitiesmust create stormwater volumes less than or equivalent to the volume of water producedfrom the site at existing level of impervious or 25% imperviouswhichever is less. This analysis is to be based on existingsoils and geology. Refer to the Met Council Small Site BMP Manual for volume control BMPs such as the use ofvegetated su�ales and redirecting impervious areas onto pervious areas. Storm Event, 24-hr Existing Conditions Proposed Conditions ac-ft ac-ft 2 2.80" 0.108 0.253 Table 2. Comparison of Peak Discharge Volumes Based on a 2-yr water quality event, the proposed conditions will produce more than double the volume of existing conditions. Therefore, the site does not meet the District's volume control criteria. The volume control practices indicated under Water Quality would aid in reducing runoff volumes from the site. Currently, the wetland on this site is landlocked and all water that drains to this wetland infiltrates or evapotranspires. This subwatershed is likely providing significant groundwater recharge. Maintaining infiltration (controlling the volume leaving the site) is a high priority for the CRWD. FLOODING A proposedpond 100 year high water level can be above adjacent existing str�ucture's lowest flaor elevation as long as the structure is at least 14(1 feet horizontally away fram the pond's 10- year flood extent. A structure's lowest exposed r�c�� elevation must be 2 feet above the 100 year high water level of adjacentponds and water bodies. "Our mission is to protect, manage, and improve the water resources of the Capitol Region Watershed District. "