Module 9: Intro to Bioretention Design

Module 9: Intro to Bioretention Design Frank Lopez, PE, QSD/P Rick Engineering Company

Bioretention Design What is Bioretention? (recap) Manufactured Bioretention Systems Bioretention Design Criteria Project Scenarios

What is Bioretention? Image Courtesy of Prince George County • Shallow depressions located in upland areas • Capture and temporarily store stormwater • Surface and sub-surface water filtration system • Treatment Train Incorporates: • surface ponding area • plants & mulch, • engineered soils, • filter fabric • gravel bed • potential underdrain

Bioretention Facilities Bioretention Bioretention facilities are landscaped shallow depressions that capture and filter stormwater. These facilities function as a soil and plant-based filtration devices and are used when the surrounding soils permit. Image Courtesy of City of Los Angeles

Bioretention Facilities Hybrid Bioretention/Dry Wells A bioretention facility with dry wells is useful in areas with low surface-level hydraulic conductivities that would normally deem a bioretention BMP infeasible but have higher levels of permeability in deeper strata Image Courtesy of City of Los Angeles

Bioretention Facilities Bioretentionw/Underdrain A bioretention facility with an underdrain system is useful in areas with low surface-level hydraulic conductivities. The facility can be lined with geo-textile fabric due to site constraints. Image Courtesy of City of Los Angeles

BioretentionFacilities Planter Box Planter boxes are bioretentiontreatment control measures that are completely contained within an impermeable structure with an underdrain(they do not infiltrate). They are similar to bioretention facilities with underdrainsexcept they are situated at or above ground and are bound by impermeable walls. Planter boxes may be placed adjacent to or near buildings, other structures, or sidewalks. Image Courtesy of City of Los Angeles

Bioretention Facilities Bioinfiltration Bioinfiltration facilities are designed for partial infiltration of runoff and partial biotreatment. These facilities are similar to bioretentiondevices with underdrainsbut they include a raised underdrain above a gravel sump designed to facilitate infiltration. These facilities can be used in areas where there are little to no hazards associated with infiltration, but infiltration screening does not allow for infiltration BMPs due to low infiltration rates or high depths of fill. Image Courtesy of City of Los Angeles

Manufactured Bioretention Systems www.filterra.com

Manufactured Bioretention Systems • www.modularwetlands.com

Manufactured Bioretention Systems • www.conteches.com

Bioretention Design Criteria • What are the design parameters? • Most agencies have sizing criteria specific to bioretention facility design. • Ponding depth limits (12”-18”) • Drawdown time (Surface = 24-72 hours; Subsurface = 96 hrs) • Treatment and evaporation surface area (4% - 6% DMA) • Max tributary drainage area • Engineered soil media infiltration rate (long term rate = 5 in/hr) • Water quality volume reduction (85th - 95th Percentile Storm) • Water quality flow treatment (I = 0.2 in/hr or 2x 85th Percentile)

Bioretention Design What is Bioretention? (recap) Manufactured Bioretention Systems Bioretention Design Project Scenarios

Project Scenario #1 Parking Lot Expansion Project Information: Project Area = 3.0 acres Type A Soil Setback Requirements No storm drain LID Components: Pervious Pavement Bioretention

Project Scenario #1

Project Scenario #1 See anything wrong?

Project Scenario #1 Ponded water on a sunny day. The facility was compacted during construction. See anything wrong?

Project Scenario #2 Parking Garage/Commercial Redevelopment Project Information: Project Area = 0.7 acres Subterranean Parking Cannot Infiltrate LID Components: Cistern to Bioretention

Project Scenario #2 Cistern

THE END www.centralcoastlidi.org

Module 9: Intro to Bioretention Design