Oakland Design Review Manual for the Central ... - City of Oakland

3.11Bio-RetentionBio-retention facilities slow and treat stormwater by temporarily retainingit using soil, vegetation, hardscape elements and other materialsto support and enhance the infiltration and bioremediation processes.Bio-retention facilities include artificial wetlands, swales, raingardens, and flow-through planters. See Figure 3.11.f and 3.11.g.XX Figure 3.11.f: This stormwater channelserves a dual purpose of containingrunoff and providing visual interest atthe street level.3.11.4 Incorporate bio-retention facilities in projects and particularlyin communal open spaces where they can provide habitat andaesthetic value.3.11.5 To prevent clogging by construction debris, these facilitiesshould be built last or runoff should be diverted around themuntil two months after construction is completed.Bio-FiltrationBio-filtration facilities filter runoff through soils and plant material toremove suspended sediments. The design solutions in this categorydiffer from bio-retention facilities in that their primary purpose isusually to convey stormwater rather than to retain or store it. Often,bio-filtration facilities can be used to pre-treat runoff before it entersbio-retention facilities or infiltration basins/trenches, which requirelow sediment loads to prevent clogging. Bio-filtration facilities includegrass filter strips and vegetated swales. See Figure 3.11.h.XX Figure 3.11.g: The flow-through planterprovides seating along the sidewalk anda planting buffer next to the building.3.11.6 Incorporate bio-filtration facilities into surface parking lots andother large, paved circulation, service and storage areas.InfiltrationInfiltration facilities slow and filter runoff, improving the water qualityand reducing the volume of runoff leaving the site. Infiltration trenchesand basins can be designed with larger reservoirs and some degreeof exfiltration to compensate for compacted soils. Infiltration facilitiesinclude infiltration basins, trenches, sand filters, and French drains.3.11.7 Review the potential to incorporate infiltration capacity intothe design of street tree trenches.XX 3.11.h: This vegetated swalecollects runoff from the adjacentparking lot and sidewalk andslows and treats the stormwaterprior to release into the stormdrain system.30OAKLAND DESIGN REVIEW MANUAL FOR CENTRAL ESTUARY