“C.3” Implementation

Assistance to the Contra Costa Clean Water Program

The Contra Costa Clean Water Program (CCCWP) comprises Contra Costa County, nineteen cities and towns and the Contra Costa Flood Control & Water Conservation District. These agencies are named as Co-permittees in a stormwater NPDES permit issued by the San Francisco Bay Regional Water Qualiity Control Board (Water Board). CCCWP assists its member agencies to plan and implement compliance with the permit.

In February 2003, the Water Board added new “C.3” provisions requiring CCCWP member agencies to revise their development review procedures so that future development and redevelopment projects are designed to prevent pollutant discharges, minimize the impact of increased runoff on streams, and protect beneficial uses of receiving waters—to the maximum extent practicable.

Since November 2003, Dan Cloak Environmental Consulting has been assisting CCCWP to comply with the new “C.3” provisions.

Planning for C.3 compliance was accomplished through CCCWP work groups:

C.3 Oversight Committee
Planning/Permitting Work Group
Technical Work Group
Legal Work Group
C.3 Capital Improvement Project Work Group

Dan assisted these groups and CCCWP management to develop a uniquely successful approach to implementing stormwater new development controls.

Key Decisions

The key decisions were:

Municipalities will review Planning and Zoning applications for stormwater compliance, rather than waiting until construction drawings are submitted for review.
Applicants must submit, with the application for Planning and Zoning approval, a Stormwater Control Plan showing how the project will be designed to achieve compliance with all provisions in the stormwater permit.
The Program prepared a Stormwater C.3 Guidebook with step-by-step instructions for preparing a Stormwater Control Plan. All municipalities adopted ordinances referencing the Guidebook, ensuring consistent implementation countywide.
The Guidebook encourages use of Low Impact Development Integrated Management Practices, including swales, planter boxes, and bioretention areas. The Guidebook includes a recommended design procedure, sizing factors, and a spreadsheet-based tool for performing and presenting sizing calculations.l

In addition to writing and producing the Stormwater C.3 Guidebook, Dan also produced fact sheets, guidance memos to municipal staff, and required submittals to the Water Board.

Hydrograph Modification Management Plan

Dan wrote the workplan for CCCWP's Hydrograph Modification Management Plan (HMP), which was submitted to the Water Board in February 2005. Dan has guided the regulatory compliance strategy for the HMP, guided the technical contributions by Philip Williams and Associates (PWA) and Brown and Caldwell (BC), and compiled and prepared the HMP submittals to the Water Board. The final HMP was submitted in May 2005.

For the HMP Dan provided the following key insights regarding hydrograph modification in the Bay Area:

Most Bay Area streams have an incised cross-section; they are geomorphically unstable and undergoing relatively rapid channel evolution. Theories and practices developed to preserve geomorphically stable streams in geologically older, humid areas have limited applicability here.
Although it is generally not possible to demonstrate that a future watershed condition will guarantee stream stability, it is possible to ensure individual development projects will not increase runoff peaks and durations.
The Bay Area's clay soils and sparse vegetation provide limited infiltration capacity; therefore it is easier for hydrograph modification management facilities to meet the "pre-project condition" baseline.
Soil-filtration IMPs, such as swales, planter boxes and bioretention areas, provide substantial retention capacity in the "spongy" imported soils used to filter stormwater.

Subsequent modeling by the PWA/BC team confirmed these insights. The resulting strategy—detailed in the final HMP—allows applicants to fully comply with the Water Board's hydrograph modification management requirements at only incremental cost beyond that required to meet stormwater treatment requirements using IMPs.

Current Work and Recent Products

The CCCWP extended Dan's contract through 2005-2006. Current work includes assisting developers and municipalities with preparation and review of Stormwater Control Plans, and continuing to assist municipal staff work groups to develop and refine implementation policies.

Recent products include a policy on the use of hydrodynamic separators for stormater NPDES compliance and a response to Water Board staff comments on the Final HMP.

With CCCWP Assistant Program Manager Tom Dalziel, Dan prepared and presented a paper at the October 2005 conference of the California Stormwater Quality Association (CASQA). The paper, “Simplified Low Impact Development Design for Compliance with Stormwater Treatment Requirements,” summarizes key aspects of Contra Costa's experience implementing the C.3 provisions. A companion paper describes the adaptation of IMPs for hydrograph modification management.

(Updated 8 January 2006)

Special Link for the Guidebook Project Team and CCCWP Reviewers: click here (4.5 MB).

Text, images, design, CSS all by Dan Cloak. Comments? email me!