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Implementing Low Impact Development

Implementing Low Impact Development . to achieve water quality benefits in Contra Costa County. Dan Cloak, P.E. 18 September 2007. Low Impact Development. Design the site to mimic natural drainage. Disperse runoff to landscape where possible.

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Implementing Low Impact Development

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  1. Implementing Low Impact Development to achieve water quality benefitsin Contra Costa County Dan Cloak, P.E.18 September 2007

  2. Low Impact Development • Design the site to mimic natural drainage. • Disperse runoff to landscape where possible. • Use Integrated Management Practices distributed around the site.

  3. Swale

  4. Planter Box

  5. Planter Box

  6. Detain and treat runoff Typically fit into setbacks and landscaped areas Accommodate diverse plant palettes Low-maintenance Don’t breed mosquitoes Can be attractive Soil surface must be 6-12" lower than surrounding pavement Require 3-4 feet of vertical “head” Can affect decisions about placement of buildings, roadways, and parking Integrated Management Practices Advantages Challenges

  7. Contra Costa’s Path to Low Impact Development • Stormwater NPDES permit • Early outreach to land development community • Staff work groups developed LID approach to compliance • Model ordinance • Guidebook • Training for designers & reviewers • Collaborative problem-solving

  8. LID concept for urban areas 4% of tributary impervious area Turf or planting Planting medium Gravel or drain rock Perforated pipe

  9. LID Design

  10. 9-acre, mixed use • Clay soils • Flat grades • Max. use • Storm drains • Setbacks Multi-family Residential Retail Restaurant Retail nursery

  11. Swale “C-2” • 6' to 10' width fits into setback • Underdrain/ overflow to storm drain below

  12. Area “C-2” • Follow roof peaks and grade breaks • Area size determined by site layout • Use valley gutters instead of catch basins 25,825 x 0.04 = 1,033 square feet 1,033 ÷ 8 = 129 feet of swale

  13. 15 areas; 15 swales

  14. Residential Development

  15. Large hillside project

  16. Difficulties Implementing LID • Developers plan buildings, streets, parking, and drainage before considering treatment requirements • Proprietary devices = quick fix • Integration with landscaping • Deficiencies in construction

  17. What’s worked for Contra Costa • State mandate • Local compliance strategy • Collaboration and consensus • Expertise and ownership • Municipal Staff Work Groups • Mutual support at staff level • Continuous improvement of design guidance

  18. Empowering the reviewer Support fromsuperiors Support from peers Mandate Ordinance DesignGuidance

  19. More info • Google “Contra Costa Stormwater” • Other places implementing LID • San Diego County municipalities • Riverside County municipalities • San Bernardino County • Monterey County • Sacramento County

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