Contra Costa Approach (I): Initial Implementation of LID

1. Contra Costa Approach (I):Initial Implementation of LID Tom Dalziel, Assistant Program Manager Contra Costa Clean Water Program Dan Cloak, P.E., Principal Dan Cloak Environmental Consulting

2. Contra Costa Approach: Afternoon Presentations • Experience So Far with LID(Tom Dalziel and Dan Cloak) • Sizing IMPs to manage hydrograph modification (Tony Dubin, Brown & Caldwell) • Stream Classification Methodology (Andy Collison, Philip Williams & Associates) • Next Steps in Implementation(Dan Cloak)

3. NPDES Permit New Development requirements • Treat runoff before discharge from site. • Match runoff peak flows and durations to pre-project conditions. • Cover or control sources of stormwater pollutants. • Maintain treatment facilities in perpetuity.

4. Cities, Towns, and County must • Incorporate requirements into their policies and processes for development review • Verify that on-site treatment devices are maintained • Prepare a Hydrograph Modification Management Plan to control future increases in runoff peaks and durations

5. Program Objectives • Comply with NPDES permit requirements. • Achieve reasonable protection of beneficial uses. • Minimize staff time required for additional project review. • Minimize costs to applicants. • Encourage “smart growth” and maintain economic competitiveness. • Adopt a flexible approach. • Encourage participation and consensus among interested parties.

6. Key Implementation Steps • Update to Model Stormwater Ordinance • Requires Stormwater Control Plan with Planning and Zoning Application • Adopted by each municipality countywide • Stormwater C.3 Guidebook • Workshops for municipal staff and land development professionals • Assistance with initial projects and preparation of examples

7. Stormwater C.3 Guidebook • Step-by-Step Approach to Compliance • How to Prepare a Stormwater Control Plan • Guidance for Selecting Treatment Facilities • Design Checklists and Standard Details for LID IMPs • Spreadsheet for Sizing BMPs and presenting calculations • Sample Outline and Examples • How to prepare an Operation and Maintenance Plan for treatment facilities • References and Hyperlinks to Design Resources

8. Stormwater Control Plan Contents • Project Setting • Measures to Limit Imperviousness • Selection & Design of Treatment BMPs • Source Control Measures • Permitting and Code Compliance Conflicts • BMP Maintenance • Construction Plan C.3 Checklist • Certification

9. Development Review Pre-Application Meeting Completed Application “Deemed Complete” Section Review Planning Commission Conditions of Approval CEQA Review Detailed Design Plan Check Permits to Build

10. Stormwater C.3 Compliance Section staff may review planning & zoning docs forC.3 Pre-Application Meeting Completed Application “Deemed Complete” Planning staff may determine if C.3 req’ts are addressed Staff identifies general C.3 requirements Section Review Planning Commission Conditions of Approval CEQA Review C.3 requirements attached to COAs Detailed Design Plan Check Permits to Build Staff reviews C.3 implementation in drawings & specs

11. Operation & Maintenance General descriptionof O&M requirements Detailed description and maintenance plan for each facility Certification of inspection &continued operation Stormwater Control Plan Stormwater Facilities Operation & Maintenance Plan Stormwater Facilities Compliance Certificate Submitted with Planning & Zoning Application Draft submitted with construction documents Renewedeachyear

12. Results so far • Development community has responded positively to: • Consistent ordinances countywide • Usability of Stormwater C.3 Guidebook • Workshops • Biggest Challenges: • LID requires a different approach to drainage design • Resolving conflicts with public works standards • IMP ownership and maintenance responsibility

13. Low Impact Development in Contra Costa County:Problems and Solutions Dan Cloak, P.E. Dan Cloak Environmental Consulting

14. Implementing LID • Showing compliance with NPDES permit criteria for treatment • Designing effective IMPs • Residential Subdivisions: • Street and drainage design • IMP operation and maintenance • Integrating with the HMP

15. Showing Compliance • NPDES Permit sizing criteria for treatment control: • “collect and convey” drainage design • conventional, “end of pipe” treatment • use of runoff factors to determine design inflow or volume

16. Accounting for Pervious Areas • Self-treating areas • “Zero discharge” or “self-retaining” areas • Reduced runoff areas LID Conventional

17. Zero discharge areas Conventional grading Zero-discharge area

18. Zero-discharge areas

19. Example LID Site Design

20. Example LID Site Design • Make landscaped areas “self-retaining”

21. Example LID Site Design • Delineate areas that drain to each IMP • Decide where roofs will drain • Divide paved areas along grade breaks

22. Example LID Site Design • Fit IMPs into landscaping at low points of each drainage area

23. Example LID Site Design • Show each IMP is sized to treat runoff from its tributary area

24. IMP Design Gallery } • Flow-through Planter • In-ground Planter • Bioretention Area • Vegetated or Grassy Swale • Infiltration Basin • Dry Well • Infiltration Trench “Indirect Infiltration” } “Direct Infiltration”

25. Indirect Infiltration Turf or planting Planting medium Gravel or drain rock Perforated pipe

26. Sizing Criterion 0.2 inches/hour BMP Area/Impervious Area = 0.2/5 = 0.04 Planting medium i = 5 inches/hour

27. Flow-through Planter

28. Vegetated (“Dry”) Swale

29. Design Checklists • Vegetated Swale • Setbacks from structures • Sizing criteria • Minimum depth • Side slopes • Specification for imported soil • Specification for underdrain • Irrigation

30. Direct Infiltration Dry Well

31. Residential Subdivision

32. Residential Subdivision • Suitably sized infiltration basin would require 3 of 80± lots • Roofs, driveways, and landscaped areas drain to front yard swales • Streets drain to same swales

33. Seattle “SEA” Streets

34. Swales in Front Yards • Some jurisdictions prefer monolithic curb & gutter • Access to parked vehicles • Avoid trip hazards • Standard location for public utilities • Still developing “standard” designs and maintenance responsibility

35. Curb and sidewalk

36. HMP Requirements • NPDES permittees must propose a plan • Manage increases in flow and volume where increases could: • Increase erosion • Generate silt pollution • Impact beneficial uses • Post-project runoff may not exceed pre-project rates and durations • Option: “Equivalent Limitation” • Account for expected stream change • Maintain or improve beneficial uses

37. Contra Costa HMP • Succinct standard, with four compliance options • Encourage Low Impact Development Integrated Management Practices (LID IMPs) • Allow proposals for stream restoration in lieu of flow control where benefits clearly outweigh potential impacts • No exemptions for: • Project size (>1 acre impervious area must comply) • Infill projects in highly developed watersheds • Project cost

38. Four Compliance Options • Demonstrate project will not increase impervious area • Implement pre-designed hydrograph modification IMPs • Use a continuous simulation model to compare post- to pre-project flows • Demonstrate increased flows will not accelerate stream erosion