2016-04-26_PWETC_AgendaPacket - Laserfiche WebLink

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2) Water Quality Treatment a) InfiltrationNolume Control Requirement 1) For all new or reconstructed impervious portions of a project, a runoff volume based on the requirements of the governing Capitol Region (CRWD) or Rice Creek Watershed District (RCWD) rules. Within all other Watershed jurisdictions, a runoff volume of one (1)inch must be treated through infiltration practices. 2) For all redevelopment impervious portions of a project, a runoff volume based on the requirements of the governing Capitol Region (CRWD) or Rice Creek Watershed District (RCWD) rules. Within all other Watershed jurisdictions, a runoff volume of one (1) inch must be treated through infiltration practices. 3) Filtration practices that are designed for partial recharge (e.g., bioretention basin with under drains) shall receive seventy percent (70%) credit for infiltration/volume control. Incorporation of trees and shrubs into filtration practices is encouraged. b) Pollutant Removal Requirements. For projects that have met the infiltration/volume control requirements above, the pollutant removal requirements are considered to be met. For projects where infiltration or filtration is not feasible or is prohibited (see Item 5.a.), the following pollutant removal standards (based on a standard Nationwide Urban Runoff Program, NURP, particle size distribution) apply prior to reaching a downstream receiving water: 1) For new development and redevelopment portions of a site, provide treatment to remove ninety percent (90%) total suspended solids (TSS) and sixty percent (60%) total phosphorus (TP) modeled for an annual average rainfall. 3) RateNolume Control. a) Discharge rates leaving the site must not exceed the current rates for the 1, 2, 10 and 100-year, critical duration (24-hour) storm events, using a Type 11 storm distribution and antecedent moisture conditions 2 (AMC-2). b) The City of Roseville shall apply all City standards for developments and redevelopments outside of the City limits which discharge into waterbodies or storm drainage systems within the City limits. All plan submittals shall comply with City of Roseville storm water regulations. c) For development and redevelopment projects affecting storm water problem areas identified in the City's SWMP, the City requires the developer to incorporate such practices to resolve a proportionate share of the problem through a reduction based on existing runoff volumes. 1) The "problem" as defined by the City is that excess volume of water that either causes a downstream storm sewer system to exceed a 10-year/24-hour design capacity or causes a downstream waterbody to exceed its designated 100-year flood elevation at a given point. 2) The "proportionate share" of the problem is defined as a ratio of contributing runoff volume from a given parcel to the overall subwatershed contributing runoff volume upstream of the problem area. 3) The procedure for computing the volume reduction for a development or redevelopment site is as follows: Page 2 of 8 12/11/14