01-09-2023 City Council Packet - Laserfiche WebLink

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19 runoff event during which it is assumed the ground is frozen solid and no infiltration occurs (CN set to 100 for all areas). The City Engineer may require analysis of additional precipitation durations to determine the critical duration flood event. Analysis of the ten-day snowmelt event is not required for stormwater management detention basins with a defined outlet elevation at or below the 100-year, 24-hour event elevation. (4)(5) Water quality treatment. The City Adopts by reference RCWD Rule C6. Water Quality Treatment as amended. (d) Land development activities creating impervious surface shall address the use of better site design (BSD) techniques as outlined in the better site design and low impact development sections of the Minnesota Stormwater Manual (MPCA, 2014 and subsequent revisions). (e) The water quality treatment volume standard for all projects, except public linear projects, is determined as follows (Table 2): Table 2. Required quality volume calculations for new or reconstructed developments BMP BMP Design Variation Water Treatment Volume Calculation [ft3] Infiltration Infiltration Feature Impervious surface [ft2] * 1.1 [in] /12 [in/ft] Water Reuse Irrigation Impervious surface [ft2] * 1.1 [in] / 12 [in/ft] Biofiltration Underdrain Impervious surface [ft2] * 1.1 [in] / (0.65 * 12 [in/ft]) Filtration Sand or Rock Filter Impervious surface [ft2] * 1.1 [in] / (0.50 * 12 [in/ft]) Stormwater Wetlands Shallow Wetland Impervious surface [ft2] * 1.1 [in] / (0.40 * 12 [in/ft]) Pond/Wetland Impervious surface [ft2] * 1.1 [in] / (0.55 * 12 [in/ft]) Stormwater Pond Wet Pond Impervious surface [ft2] * 1.1 [in] / (0.50 * 12 [in/ft]) Multiple Pond Impervious surface [ft2] * 1.1 [in] / (0.60 * 12 [in/ft])