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

Technical RequirementsVegetated SwaleStep 6 – Select VegetationA full, dense cover of sod-forming vegetation is typically recommended for vegetated swales, since mostpollutant removal performance studies are based on use of grass. Alternative vegetation such as shrubsand groundcovers may also be allowed; check with the local permitting agency.Select vegetation that:• Will be dense and strong enough to stay upright, even in flowing water and steep slopes;• Has minimum need for fertilizers;• Is not prone to pests and will not require a lot of pesticide/herbicide application, consistent withany integrated pest management (IPM) practices or policies of the local permitting agency;• Will withstand being inundated for periods of time; and• Needs little supplemental water, consistent with local water conservation ordinances. Bunch-typegrasses or grass mixes are preferred.Check with the permitting agency for approved plant and tree lists. Do not use bark or similar buoyantmaterial in the swale or around drain inlets or outlets.Construction Considerations• Divert runoff (other than necessary irrigation) during the period of vegetation establishment.Where runoff diversion is not possible, cover graded and seeded areas with suitable erosioncontrol materials.• Install sediment controls (e.g., staked straw wattles) around the swale to prevent high sedimentloads from entering the swale during ongoing upstream construction activities.• Repair, seed, or re-plant damaged areas immediately.• Apply erosion control measures as needed to stabilize side slopes and inlet areas.Long-Term MaintenanceThe local permitting agencies in the Sacramento and SouthPlacer areas will require execution of a maintenanceagreement or permit with the property owner for projectsincluding a vegetated swale. Check with the localpermitting agency about the timing for execution of theagreement. Such agreements will typically includerequirements such as those outlined in Table VS-2. Theproperty owner or his/her designee will be responsible forcompliance. See Appendix B for additional informationabout maintenance requirements and sample agreementlanguage.Swales with rock in the flowline are discouraged dueto high maintenance needs (including use of weedkillers) and potential for mosquito breeding.Stormwater Quality Design Manual for the Sacramento and South Placer RegionsMay 2007VS-5