5.5. SR 08-06-2007 - Laserfiche WebLink

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f We propose no analysis of City land that has not changed since 1988, unless it lies within the Cities currently defined 2020 growth area. discharges across municipal boundaries. Evaluation point selection will be based upon discussion with, and guidance from, the MPCA. We propose no analysis of City land that has not changed since 1988, unless it lies within the City's currently defined 2020 growth area. Our preliminary conversations with the MPCA indicate that this approach will be accepted. The areas that have developed since 1988 are indicated in the City's RFP and include no more than 5,000 acres. The growth area will be defined by City staff. Within the growth area, we assume treatment levels consistent with current City policy. It is conceivable that analysis of Elk River's growth area will show that current City policies lead to increased loadings. If this is the case, we will determine load limits for the two pollutants and water volume that bring the City into compliance with nondegradation requirements. These load limits might become the basis of future City policy for the growth area. Whatever the City's decision regarding loadings from future growth areas, these will be discussed in the Nondegradation Report prepared under this project. One critical aspect to our approach emphasizes that rural residential land use of a certain minimum lot size reduces loadings of the two pollutants and water volume. Consequently, these rural residential areas of the growth plan do not need to be analyzed in this project. Based on our work with previous loading assessments, we have compiled volumetric runoff coefficients and phosphorus concentration values that, when combined with precipitation data, generate anticipated loading rates for specific land uses. Using this previous experience, we will establish loading rates associated with individual land use conditions, and use these to complete a GIS-based loading assessment for Elk River. We will define hydrologic and pollutant loading parameters similar to those we are using in our other Loading Assessments. These assumptions will be modified as needed to match the unique soils, topography, and climate of the Elk River area. Elk River's hydrologic and pollutant loading parameters will be supported by the same literature citations used for our ongoing Loading Assessments. This means a consistent approach is pursued among the various MS4 Cities. We have reviewed our hydrologic and pollutant loading parameters with the MPCA, and though the MPCA is reluctant to endorse a particular approach, they indicate there is acceptance for our assumptions regarding these parameters. The analysis required for the Loading Assessment is based entirely on changes in land use and the estimated resulting changes in pollutant loading. The reduction in pollutant loading from BMPs, typically ponds, will be reflected in coefficient changes for pollutant loading from the appropriate land areas. In most cases, modeling water quality in the receiving waters will not be necessary or appropriate for the Loading Assessment. -# Bonestroo 6