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Overview of Construction General Permit and Risk-Based Approach to Storm Water Management

This document outlines the approach and overview of the Tentative Draft Construction General Permit by the State Water Resources Control Board's Division of Water Quality. It highlights the risks associated with construction activities over an acre that may impact water quality, focusing on sediment discharge and hydromodification. The permit aims to adopt a risk-based approach, improve performance measurement, and establish standards for mitigating impacts. The stakeholder process has fostered valuable input, enhancing public engagement and compliance with federal regulations concerning electronic reporting.

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Overview of Construction General Permit and Risk-Based Approach to Storm Water Management

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  1. June 4, 2008 – Public Hearing State Water Resources Control Board Division of Water Quality Storm Water Section Tentative Draft Construction General Permit:Approach and Overview

  2. Construction Activity Threats • Two-fold – construction projects over an acre have the potential to cause impacts to our beneficial uses of water both during and after the project. • During – potential for sediment and erosion discharges. • After – potential for hydromodification impacts as a result of how the new landscape functions.

  3. Construction WQ threats = + +

  4. Staff Permit Reissuance Goals(from pre draft, April 2007) • Adopt a risk-based permit approach • Improve “performance” measurement of program • Establish a standard to avoid, minimize and mitigate hydromodification impacts associated with all new and re-development projects triggering the construction activity permit.

  5. Risk Approach • Tentative permit has a detailed risk approach that separates risk into two functions - sediment discharge risk and receiving water risk • Tentative permit matches “implementation levels” to overall risk, which is based on a combination of the two functions, above.

  6. Performance-based Permit • Direct requirements (vs. ones embedded in the SWPPP) = more enforceable, easier to enforce and more transparent for public • Numeric effluent limits for turbidity set at minimum technology level = more enforceable, easier to enforce • Monitoring requirements designed to assess various levels of outcomes and outputs

  7. Runoff Reduction Measures • Aimed at parts of State without MS4 coverage • Water balance approach – match pre-construction • Represent an interim step towards more specific hydromodification standards • Credits will reduce runoff and provide multiple, community benefits

  8. Permit Support Efforts • Public process and e-Business solution • Screens are being designed and process is on track • Built in compliance with federal rule on electronic reporting (CROMERR) • CGP Training partnership • Being co-led by staff and CASQA • Includes most interests and 15+ participants from around the State

  9. Stakeholder Process • Stakeholder input beginning in April 2007 – pre-draft permit • Multiple opportunities for comments and suggestions • Provided invaluable input to the tentative permit • Staff committed to continued development and growth of partnerships and relationships w/ stakeholders

  10. Patrick Otsuji Supervisor NOI Processing E-Business Project Co-manager (916) 341-5292 potsuji@waterboards.ca.gov Leo Cosentini Industrial Permit Writer E-Business Project Co-manager (916) 341-5524 lcosentini@waterboards.ca.gov Laurel Warddrip Construction Permit Writer (916) 341-5531 lwarddrip@waterboards.ca.gov Annalisa Kihara Construction Permit Writer (916) 324-6786 akihara@waterboards.ca.gov Eric Berntsen Construction Permit Writer (916) 341-5911 eberntsen@waterboards.ca.gov Greg Gearheart Program / Project Manager (916) 341-5892 ggearheart@waterboards.ca.gov Who are we? DWQ Permit Team

  11. Hydromodification Impacts

  12. Hydrologic Cycle From Lake (2004)

  13. Pre-development Aggradation Phase • hillslope erosion is largest sediment source • width:depth may increase or stay constant • cross-sectional area increases Erosional Phase • channel erosion is largest sediment source • width:depth increase eventually • cross-sectional area increased to accommodate larger bankfull discharge

  14. After Lane (1955) as cited in Rosgen (1996)

  15. Urbanization tends to increase storm water runoff: • peak flows • volume • frequency Post-Develop. Increase in Bankfull Discharge Pre-Development Runoff Time From Haltiner (2006)

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