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

Runoff Reduction Fact SheetDisconnected Roof DrainsDesign CriteriaDesign criteria for disconnected roof drains and discharge variations are listed in Table DRD-2.Construction ConsiderationsSplash Block and Pop-up Drainage Emitter• Site must be graded to prevent ponding of water at base of building.• Splash blocks must be secured in place over compacted soil.• Roof drainage conveyance areas must be protected from erosion during vegetation establishmentperiod. Temporary measures such as erosion control blanketing may be used, however it may benecessary to bypass the stormwater around the conveyance zone during the stabilization period.Dispersal Trench and Dry Well• Do not allow soil below trench area to be compacted during construction.• The floor of the trench/well must be level to allow for spreading of flow across the trench.• To prevent sedimentation of the structure, the inlet pipe must be plugged until soil on the site isstabilized. To protect the structure during construction, provisions for sediment control must beincluded in the design.Long-term Maintenance RecommendationsTable DRD-3 presents inspection and maintenance recommendations for disconnected roof drains ingeneral and two design variations related to disconnected roof drains (dispersal trench and dry well). Thelocal permitting agencies require that the property owner be responsible for maintaining the features toensure continued, long-term performance. The pervious features should not be removed or replaced or allwater quality benefits will be lost. In general, a maintenance agreement will not be required for this typeof installation. However, developers are responsible for educating new homeowners that such devices areinstalled on their property and should be maintained following the recommendations provided in TableDRD-3. Where possible, such recommendations should be included in Covenants, Codes and Restrictionsfor new residential subdivisions.Stormwater Quality Design Manual for the Sacramento and South Placer RegionsDRD-6 May 2007