5.5. SR 08-06-2007 - Laserfiche WebLink

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Qualifications (cont.) City Of Eden Prairie Loading Assessment And Nondegradation Plan Wenck is currently developing the City of Eden Prairie's Loading Assessment and Nondegradation Plan. The Watershed Districts that cover the City of Eden Prairie have previously completed modeling that will be used as the basis for the loading assessment. Wenck is using the available P8 models to assess changes in loading, providing a significant cost saving to the City. One of the key tasks in the City's Nondegradation Assessment will be to coordinate activities already being undertaken by the Watersheds and those that may be required as a result of the nondegradation assessment. Wenck is also conducting field surveys of the streams in Eden Prairie to identify outfalls, illicit discharges, and stream bank erosion areas. City Of Chanhassen Nondegradation Plan Wenck Associates, Inc. is currently developing a nondegradation report for the City of Chanhassen. Similar to the City of Andover, Wenck staff is working with watershed districts within the City to determine past, present and future loadings. Development within the City exploded during the 1990's, so Wenck staff will determine whether the water quality standards in place were appropriate to satisfy the nondegradation standard. Similarly, Wenck staff will evaluate where and how the City is to grow in the next 13 years and provide guidance on how to meet the nondegradation standard in 2020. MODELING APPROACH Wenck Associates, Inc. staffhas used two modeling approaches in completing loading assessments for municipalities: 1) the P8 computer model, and 2) a spreadsheet using the EP A Simple Method. Model selection depends upon the level of detail desired in the model and future plans by the municipality to use the model for additional analysis. The P8 computer model is ideal for urban areas where subwatersheds have been previously delineated and the treatment efficiency for a variety of BMPs must be evaluated. The spreadsheet model, however, is a less complex approach and requires less data and time to execute. Based on our understanding of the City's goals for this study, Wenck proposes to use a spreadsheet model as the basis for the loading assessment. The spreadsheet model will provide a clear-cut method in calculating the loading assessment and allow Wenck staff to emphasize addressing potential changes to stormwater management in the City. Although feasible, creating a P8 model does not seem to serve the City's primary needs of addressing future stormwater management and development rules. As stated above, the spreadsheet model uses the US EP A Simple Method. This method is a standard area load model that uses event mean concentrations and runoff volume to predict area-loading rates. Simple multiplication of the concentration by the volume yields the loading rate from a particular land use. T:I0598100INonDegradation ProposallQualifications.doc 2 g..L~Wenck