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

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

Swale

Planter Box

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

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

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

LID Design

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

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

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

15 areas; 15 swales

Residential Development

Large hillside project

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

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

Empowering the reviewer Mandate Ordinanc e Design Guidanc e Support from peers Support from superiors

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