1. Stormwater Treatment and Flow Control Dan Cloak Presentation to the Citizens Advisory Committee November 13, 2006 Options for implementing new Phase II NPDES regulations

2. Outline Effects of runoff from new developments Stormwater regulations for new development in Marin Low Impact Development Possible Next Steps

3. Effects of New Development

4. Runoff Before Development Runoff After Development

5. Effects of increased runoff Increased flows and more frequent flooding leads to… Increased streambank erosion, which leads to… “Hardening” to prevent erosion, which leads to…

6. Loss of Stream Functions

7. Regulatory History 1987Congress adds Section 402(p) to Clean Water Act 1990USEPA regulations require states to issue stormwater NPDES permits to large municipalities 1993Marin County municipalities begin implementing “baseline” stormwater pollution prevention activities 1999USEPA promulgates “Phase II” stormwater regulations applicable to smaller municipalities. 2000State Water Resources Control Board “Bellflower decision” confirms municipalities must require new developments to treat runoff

8. 2001Regional Water Board begins adding “Provision C.3” requirements to permits in Santa Clara, Alameda, Contra Costa, and San Mateo Counties 2003State Water Board adopts General Permit for Small Municipal Separate Storm Sewer Systems (MS4s), including “Attachment 4” 2003MCSTOPPP files a Notice of Intent for coverage under the statewide General Permit 2008Implementation of all “minimum control measures” required Regulatory History

9. Which areas? What projects? All municipalities ●“Enforce a program to address stormwater runoff” ●Projects disturbing an acre or more San Rafael, County, Novato ●“Attachment 4”—design standards for Single-family hillside residences Subdivisions with 10 or more units Repair shops, gas stations, restaurants Commercial developments > 100,000 sq. ft. Parking lots with 5,000 sq. ft. or 25 spaces Or a “functionally equivalent program”

10. Ideas to Consider Involve the community in planning an approach for compliance Create our own “functionally equivalent program” and get Regional Water Board approval Seek countywide consistency Actively assist developers to use “Low Impact Development”

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

12. Example of an engineered Integrated Management Practice “Dry” swale detains and filters runoff

13. Fitting IMPs into landscaping Portland, OregonAlbany, California

14. Fitting IMPs into landscaping Seattle, Washington Spokane, Washington

15. Planter Box

16. 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

17. Implementing “LID” IMPs can be effective, attractive, and accepted by developers Incorporate IMPs in preliminary site, landscaping and drainage design drawings In-ground planter boxes under construction Residential subdivision Clayton, May 2006

18. Some Possible Next Steps Discuss options with public works directors Sponsor a public workshop with developers and land development engineers Convene a group of municipal attorneys to develop a model revised stormwater ordinance Develop more specific guidance for implementing new design standards