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Mr. Michael Grochala April 8, 2020 Page 2 • Protect life, public and private property, and the natural resources from damage resulting from runoff and the dangers associated with flooding. Existing Conditions The study area currently consists of agricultural area, rural residential, and park and open space areas. The impervious surface is primarily made up of the existing roadways. The major roads include 2Ot" Avenue, 8Ot" Street, County Road 14, and Interstates 35E and 35W. There are four major watersheds within the study area. The west and central portion of the study area is part of the Peltier subwatershed. The north part of the study area is within the Hardwood Creek subwatershed and Upper Rice Creek subwatershed, and the southeast part is within the Clearwater Creek subwatershed. All of these subwatersheds drain to Peltier Lake through tile drain or county ditch systems. Future development will need to address any requirements that are established due to current regulatory standards adopted by the RCWD, City of Lino Lakes, and Minnesota Pollution Control Agency (MPCA). The MPCA has listed three water resources within the study area as impaired: Peltier Lake, Hardwood Creek, and Clearwater Creek. Peltier Lake and Hardwood Creek have approved Total Maximum Daily Load (TMDL) that provides additional guidance and requirements for pollutant loads. Approximately 68% of the study area consists of Group D soils, and the remaining area consists of Group A and B soils. These soil ratings are based on hydrologic soil classifications with A soils having high infiltration rates even when thoroughly wetted. The infiltration rates for A soils range from 0.8 to 1.63 inches per hour (Minnesota Stormwater Manual). These soils consist chiefly of deep, well drained to excessively drained sands and gravel. Group A soils have a high rate of water transmission, therefore resulting in a low runoff potential. Group B soils have moderate infiltration rates ranging from 0.3 to 0.6 inches per hour when thoroughly wetted. Group B soils consist of deep moderately well to well drained soils with moderately fine to moderately coarse textures. Infiltration is very low in areas with Group D soils, and the design of infiltration basins is not recommended in areas with Group D soils (per the MPCA National Pollution Discharge Elimination System Construction General Permit). Proposed Conditions The three revised scenarios were considered in this analysis in the proposed conditions. Due to the conceptual nature of the development scenarios, the Land Use type classifications for each scenario were evaluated using curve numbers from the NRCS. The existing conditions and three proposed revised land use scenarios were evaluated. Stormwater management for any scenario can be provided through a combination of wet detention ponds and infiltration and filtration features. Achieving volume reduction and pollutant reduction through the use of infiltration may be challenging for a majority of the study area due to a majority D soils with low infiltration rates, and a high groundwater table. Stormwater management via green infrastructure such as stormwater reuse will be encouraged by the City of Lino Lakes and RCWD to achieve volume reduction and pollutant removal requirements. KA015144-000\Admin\DOCSWUAR -Update 2020\Stormwater\MEMO - 040920 - Stormwater AP.docx