Stormwater Quality Design Manual (May 2007) - City of Sacramento ...

These tables refer to runoff reduction credit worksheets/forms which can be found in Appendix D-1 and D-2 of thisDesign Manual.Runoff Reduction Credits for Alternative DrivewaysVariationPervious DrivewayHollywoodDrivewayDisconnectedDrivewayShared DrivewayApplications and Runoff Reduction CreditsResidential — credits can be applied for the entire driveway surface when approvedmaterials and specifications are used in accordance with the Design Requirements.Use Appendix D-1.Residential — an efficiency multiplier of 75% of the driveway area when approvedmaterials and specifications are used in accordance with the Design Requirements.Use Appendix D-1.Residential — credits can be for the entire driveway surface when designedaccording to this fact sheet. Use Appendix D-1.Residential — credits vary according to design. Consult municipal engineerRunoff Reduction Credits for Disconnected Roof DrainsVariationSplash Block/Pop-up Drainage EmitterResidentialApplications and Runoff Reduction CreditsCredit may be given for each disconnected roof drain with the amount of creditdependent upon building set back. This calculation is simplified in Appendix D-1.CommercialCredit may be given for each disconnected roof drain meeting the designrequirements. The credit calculation is simplified in Appendix D-2.Dispersal Trench and Dry WellResidentialCommercialCredit may be given for each disconnected roof drain meeting the designrequirements. The credit calculation is simplified in Appendix D-1.Credit may be given for each disconnected roof drain meeting the designrequirements. The credit calculation is simplified in Appendix D-2.Runoff Reduction Credits for Interceptor TreesVariationAll Planted TreesApplications and Runoff Reduction CreditsResidential - Credit may be given for each new tree planted in the municipal rightof-way.Consult municipality about the possibility of credits for trees outside of themunicipal right-of-way. This calculation is simplified in Appendix D-1.Commercial - Credit may be given for each new tree planted within 25 feet ofground level impervious surfaces. 25% of trees already required by zoning can beused for Interceptor Tree credits. This calculation is simplified in Appendix D-2.New Evergreen Trees 200 square feet of creditNew Deciduous Trees 100 square feet of creditExisting Trees The Runoff Reduction Credit, as applied to existing trees, is calculated by identifyingthe square-footage equal to one-half of the existing tree canopy, measured within thedrip line. The resulting square footage divided by the total site square footage isequal to the IRP. This calculation is simplified in Appendix D-1 and D-2.*Trees required by the municipality as mitigation for other trees lost on the project will not count toward Runoff Reduction CreditStormwater Quality Design Manual for the Sacramento and South Placer RegionsMay 2007 Appendix D-3 Page 3