2016-04-26_PWETC_AgendaPacket - Laserfiche WebLink

Home

1) For sites within CRWD jurisdiction, the Volume Control Worksheet (available online at www.capitolregionwd.org). 2) For sites within RCWD jurisdiction, (a) Redevelopments: The Redevelopment Guidance Worksheet available at www.ricecreek.o . (b) New Development: Provide calculations considering the same factors as RWCD Rule C(5)(b). (c) Provide alternative computation method if approved by the City Engineer prior to the information being submitted to the City for review. 3) For all other sites,provide volume calculations based on the following formula: V=Area x 1 inch x 0.08333 Where V=Required Volume Reduction in cubic feet(cf) A =New or Reconstructed Impervious Area in square feet(sf) f) Storm Sewer Conveyance Design: Local storm sewer systems shall be designed for the 10-year storm event within the crown of pipe. The Rational Method shall be the preferred methodology for the design of local systems. Culvert crossings or storm systems in County or State right-of- way may have a design frequency which differs from the City's 10-year design storm. The designer shall contact each agency/unit of government to determine the appropriate design frequency for hydrologically-connected systems. g) Outfall Energy Dissipation: For culvert outlet velocities less than or equal to four (4) feet per second (fps), check shear stress to determine if vegetation or riprap will be adequate. If vegetation is used, temporary erosion control during and immediately following construction shall be used until vegetation becomes established. For velocities greater than four (4) fps, energy dissipaters shall be designed in accordance with Mn/DOT Design Criteria. h) Landlocked Basin HWL Determination: High water elevations for landlocked areas (basins where no outlet exists) shall be established by first estimating the normal or initial water surface elevation at the beginning of a rainfall or runoff event using a documented water budget, evidence of mottled soil, and/or an established ordinary high water level. The high water level analysis shall be based on runoff volume resulting from a 100-year/10-day runoff(8.6 inches and saturated or frozen soil conditions [CN=100]) or the runoff resulting from a 100-year back-to- back event (7.4 inches followed by 7.4 inches). The high water elevation shall be the higher of these two conditions. i) Building Low Opening: The lowest floor openings of all buildings shall be set: 1) At least two (2) feet above the 100-year high water elevation and at least one (1) foot above a designated emergency overflow. 2) For landlocked basins, at least two (2) feet above the higher of the elevations determined in Part 4h. Page 4 of 8 12/11/14