Post-Construction Requirements Design Challenges Dan Cloak, P.E.

Topics Low Impact Development Site Design –Design philosophy (what and why) –Benefits and some drawbacks Challenges to Achieving LID Site Design –Space constraints –Geotechnical and foundation design –Soil permeability –Groundwater

LID: What Preserve and replicate natural site hydrology Detain and retain runoff throughout the site

LID: Why? Why? Resilience. –Community engagement and acceptance –Education and awareness –Habitat –Temperature moderation –Air quality –Most robust and effective treatment –Hydrologic control

LID: Challenges More facilities to build, maintain, and inspect Higher costs More structural elements (sidewalls, overflows) More design effort –Integration with buildings, parking, and circulation

Design Challenges and Solutions Space constraints –Integrate LID at earliest stages of design Geotechnical and foundation design –Modify and enhance structures Low permeability of soils Groundwater

Space Constraints Solution: Incorporate site drainage and Stormwater Control Measures in preliminary site plan

Require Stormwater Plan Early Pre-Application Meeting Completed Application “Deemed Complete” Section Review CEQA Review Conditions of Approval Planning Commission Detailed Design Plan Set and Permit Application Construction

4% Sizing Factor (Tier 2) ½ Acre 4% 30 ft

Strategies to Minimize Facility Size Minimize impervious area Make landscaped areas self-treating or self-retaining Disperse runoff to landscape

Example Commercial Site

Example Residential Subdivision

Non-LID Treatment

Steep Site, Remediated Slide

Next to Building Foundations

Bioretention & High Groundwater 6" 18"

Summary: LID Design Challenges Design for resilience Disperse runoff where possible Use the sizing calculator to iterate design Get the geotech working with you