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Countywide Model SUSMP

Countywide Model SUSMP. July 17, 2008. Topics. SUSMP Timeline Goals Approach to Compliance NPDES Permit Requirements Model SUSMP Features. Model SUSMP Timeline. Goals for SUSMP. Make it easier for applicants to prepare submittals

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Countywide Model SUSMP

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  1. Countywide Model SUSMP July 17, 2008

  2. Topics • SUSMP Timeline • Goals • Approach to Compliance • NPDES Permit Requirements • Model SUSMP Features

  3. Model SUSMP Timeline

  4. Goals for SUSMP • Make it easier for applicants to prepare submittals • Make it easier for municipal staff to review submittals for compliance • Promote consistent and fair implementation countywide • Integrate LID, treatment, and hydrograph modification management requirements

  5. SUSMP Compliance Approach • Comply with new requirements: • Low Impact Development • Treatment • Hydromodification management • Provide options and flexibility • Municipalities • Developers • Create option to use integrated design approach • Promote consistent and complete presentation of design information and calculations

  6. Low Impact Development D.1.d.(4) • NPDES Permit: • Use LID site design principles • Drain a portion of impervious areas to pervious areas • Use permeable surfaces • Model SUSMP—LID Design Guide • Guidance for applying site design principles and using pervious pavements • Divide the site into Drainage Management Areas • Identify surface cover for each DMA • Account for drainage from each DMA • Design criteria for LID features and facilities • Design recommendations learned from experience

  7. Treatment Controls D.1.d.(6) • NPDES Permit • Infiltrate, filter, or treat flow from all developed portions of the project • Select more effective controls including bioretention • Correctly size and design to achieve MEP • Model SUSMP • LID Design Guide ensures integrated LID design meets treatment criteria • SUSMP specifies selection and design criteria if applicant chooses not to use the integrated approach

  8. Hydromodification (D.1.d.10) • NPDES Permit: • Apply criteria so runoff rates, durations, and velocities are controlled (all projects) • Interim criteria for projects 50 acres and up • To be superseded by HMP (D.1.g.) • Model SUSMP • Integrated LID design controls runoff rates • Facility designs will be updated for HMP • Option to perform continuous simulation

  9. Source Controls (D.1.d.(5)) • NPDES Permit: • Implement source control BMPs to minimize pollutants of concern • Model SUSMP: • Appendix lists sources to be controlled and specifies the control measures to be used

  10. Implementation Process (D.1.d.(9)) • NPDES Permit: • Each Copermittee shall implement a process • Identify measures necessary for implementation • Model SUSMP: • Acknowledges each municipality will apply their own requirements • Provides a general model for preparing project submittals • Facilitates countywide consistency and streamlined reviews

  11. Pollutants of Concern (D.1.d.(3)) • NPDES Permit • Local SUSMPs shall include a procedure to identify Pollutants of Concern • Model SUSMP • Pragmatic approach • Identify Pollutants of Concern countywide • Specify practicable and effective source controls and treatment controls • Allow for rare circumstances when controls should be tailored to land use or watershed

  12. Summary • Pro-active approach to compliance with new NPDES Permit requirements • Flexibility for municipalities and developers • Detailed support for an integrated design option applicable to most developments • Promotes consistency and streamlined preparation and review of submittals • Incorporates design knowledge and lessons learned from LID implementation

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