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I . , I I I I I I II I I I I I I I {' I 9.7.01 Section 3 - Hydraulic and Water Quality Analyses Hydraulic Analyses Regional Stormwater Treatment Locations There are thirteen proposed potential regional ponds in Arden Hills that were identified in a 1999 comprehensive drainage study by BRW Inc. (Dames and Moore Group Company). TCAAP property was not considered or modeled as part of this Plan. Two ponds within TCAAP, P-l and P-] 3, will be completed as part of the reconstruction of TH 96, and will not be discussed in this Plan. Figure 11 shows the approximate locations of the proposed regional ponds. They are mostly located in natural low lands or inlets to lakes. It should be noted that the City would need to further investigate the proposed regional pond locations with respect to jurisdictional wetlands and regulatory restrictions that may affect the construction of these facilities. Even though the BRW, Inc. study and this Plan evaluate the proposed construction of regional ponds, other stormwater treatment best management practices will be addressed in the feasibility study stage. Summary Discharge Data HydroCAD@ modeling was completed for the eleven proposed regional ponds. At this stage the ponds are only concepts, and therefore the modeling consisted of the drainage districts identified in the 1999 comprehensive drainage study by BRW, Inc. and the proposed concept pond. The concept pond was assumed to be rectangular in shape, with a ten-foot shelf below the normal water level, side slopes of 3: 1 everywhere else, and a depth of six feet. The 5, 10, and 100-year, 24-hour, storms were run, using antecedent moisture conditions II. The results of these models can be seen in Appendix D. The 100- year design storm was used to calculate a peak height of the pond and to determine if any potential damage or flooding could occur at the neighboring structures. Only one pond, P-l2, has the potential for flooding the low point on North Hamline Avenue and will need more detailed analysis during the feasibility study/design stage to ensure no damage to the surrounding structures will occur. In addition to the HydroCAD modeling, stormwater quality and treatment modeling was undertaken using the P8 Urban Catchment model. City of Arden Hills, Minnesota Local Stormwater Management Plan A,ARDEN0101.00 Page 24