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Published byAllen Rice Modified over 9 years ago
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Dan Cloak, P.E. 18 September 2007 to achieve water quality benefits in Contra Costa County Implementing Low Impact Development
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Low Impact Development Design the site to mimic natural drainage. Disperse runoff to landscape where possible. Use Integrated Management Practices distributed around the site.
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Swale
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Planter Box
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Integrated Management Practices 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 AdvantagesChallenges
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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
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LID concept for urban areas Planting medium Gravel or drain rock Turf or planting Perforated pipe 4% of tributary impervious area
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LID Design
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9-acre, mixed use Multi-family Residential Retail nursery Retail Restaurant Clay soils Flat grades Max. use Storm drains Setbacks
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Swale “C-2” 6' to 10' width fits into setback Underdrain/ overflow to storm drain below
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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
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15 areas; 15 swales
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Residential Development
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Large hillside project
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Difficulties Implementing LID Developers plan buildings, streets, parking, and drainage before considering treatment requirements Proprietary devices = quick fix Integration with landscaping Deficiencies in construction
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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
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Empowering the reviewer Mandate Ordinanc e Design Guidanc e Support from peers Support from superiors
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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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