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Enhancing Stormwater Quality through County Green Street Task Force Collaboration

Los Angeles County's Green Street Task Force, comprising various departments, aims to identify optimal locations for constructing green streets to address stormwater quality. With a screening process and feasibility studies, the project seeks to prioritize and select top sites for implementation, focusing on sustainability and efficiency. Lessons learned and funding from measures passed enrich the Safe Clean Water Program, integrating stormwater and transportation efforts for a greener, safer community.

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Enhancing Stormwater Quality through County Green Street Task Force Collaboration

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  1. LA County’s Green Street Task Force: Stormwater & Transportation working together TJ Moon County of Los Angeles Department of Public Works

  2. Los Angeles County Stormwater Quality Nutrients Trash 33 TMDLs l Metals Bacteria Leads Nation Toxics

  3. Stormwater Quality Solutions Regional Projects Green Streets Low Impact Development

  4. How Much Green Streets Do We Need?

  5. Green Street Task Force Participants • Stormwater Quality • Road Maintenance • Transportation Planning • Traffic & Lighting • Geotechnical • Parks and Recreation Objectives • Collaboration • Sustainability • Efficiency

  6. Stormwater Green Street Master Plan Question: • Where are the most optimal locations to construct Green Streets to address stormwater quality? Master Plan Goal: • Create Prioritization Process • Identify top 100+ half-mile road segments 5336 Total Miles

  7. Screening Process Overview County Roads Phase 1 Screening Phase 2 Screening Phase 3 Screening Phase 4 Feasibility Field Recon Steep Slope Geotechnical Modeling Utilities Contamination Groundwater Table Final Site Selection Environmental Geotechnical

  8. Phase 1 Screening Phase 1 Screening Steep Slope Slope > 5% Contamination 60 feet buffer from contamination sites 40% Remain 60% Out 5,336 Total Miles

  9. Phase 2 Screening Phase 2 Screening Phase 2 Phase 1 Geotechnical • Landslides • Bedrock • Liquefaction • Seismic • Surface Soils Groundwater Table • GW depth Varies • Usually more than 10+ feet • Not Considered 40% Remain 60% Out 36% Remain 64% Out

  10. Phase 3 Screening Phase 3 Screening Phase 2 Modeling • Impervious drainage area drives water quality need 36% Remain 64% Out

  11. Phase 3 Screening Tributary Area Step 1: Identify catch basins and open channels

  12. Phase 3 Screening Tributary Area Step 2: Cluster catch basins to create downstream node

  13. Phase 3 Screening Tributary Area Step 3: Digital Elevation Model + Flow Direction

  14. Phase 3 Screening Tributary Area Step 4: Drainage Area Delineation

  15. Phase 3 Screening Impervious Area Step 5: Impervious Score

  16. Phase 3 Screening Storm Drain Step 6: Qualitative Selection • Major storm drain • Large Parkway Space • Maximize Drainage Area

  17. Phase 3 Screening Phase 2 Phase 3 Screening Phase 3 Modeling • Impervious drainage area drives water quality need Final Site Selection • Top 110 Sites Selected • 55 Miles 36% Remain 64% Out 99% Out

  18. Phase 4 Feasibility Phase 4 Feasibility Field Recon Utilities • IPad entry • GPS • Photos • Automatic reporting • Existing Substructure Map • Recording of Dig Alert for Geotech Field Recon Utilities Environmental Geotech Phase 1 Assessment • 3 CPTs per Site • 330 Total CPTS • 80’ Deep Environmental Geotechnical

  19. Phase 4 Feasibility - Geotechnical • 110 Potential Sites • 3 Cone Penetration Tests per Site • 80 Feet Deep • Full Understanding of Soils • Soils will dictate the BMP Type Sand Clay

  20. 10 Feet Deep Phase 4 Feasibility - Geotechnical Sand Clay • How do we maximize infiltration? • Take advantage of sandy soils • Depth may be deeper • Adjust BMP for sandy soil 75 Feet Deep 60 Feet Deep 50 Feet Deep 30 Feet Deep 40 Feet Deep 20 Feet Deep

  21. Lessons Learned • Lesson Learned #1 • Not enough space to capture sufficient stormwater • Solution • Go deeper – Infiltration Wells • Regional Green Streets

  22. Lessons Learned Existing Storm Drain Dry Wells • Solution • Green Alley Master Plan • Lesson Learned #2 • Alleys are a great location

  23. Measure W Tax Measure passed on November 2018 Estimated Revenue: $300 M SAFE CLEAN WATER PROGRAM

  24. Stormwater & Transportation Coming Together

  25. Stormwater & Transportation Coming Together • Project Planning can include: • Road Rehabilitation • Safety (Vision Zero) • Connectivity Corridors • Stormwater Capture • Native Landscaping • Heat Island Effect • Multiple Funding Sources!

  26. Safety: Vision Zero Street East Rancho Dominguez Street Improvement Project Stormwater Capture Feature Compton Blvd Road Improvement Limits Road Improvement Limits E. Rancho Dominguez Park Atlantic Ave E. Rancho Dominguez Library • Connect Library + Parks • Enhance Safety Ex. Storm Drain

  27. Contact Information Paul Alva palva@dpw.lacounty.gov (626) 458-4325 TJ Moon tmoon@dpw.lacounty.gov (626) 458-4380

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