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Evaluation of CSO Control Alternatives

Evaluation of CSO Control Alternatives. Adrienne Nemura, P.E. Limno-Tech, Inc. Items to Be Covered. Evaluation of CSO controls Public participation Selection of controls. Evaluation of CSO Controls. The evaluation should:

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Evaluation of CSO Control Alternatives

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  1. Evaluation of CSO Control Alternatives Adrienne Nemura, P.E.Limno-Tech, Inc.

  2. Items to Be Covered • Evaluation of CSO controls • Public participation • Selection of controls Evaluation of CSO Control Alternatives

  3. Evaluation of CSO Controls The evaluation should: • Build upon existing infrastructure (POTW, interceptors, pumping stations, etc.) • Consider maximization of treatment at the existing POTW (primary clarification, solids and floatables control, disinfection) Evaluation of CSO Control Alternatives

  4. Build on Existing Infrastructure: Pump Station Expansion 4 Evaluation of CSO Control Alternatives

  5. Maximize Treatment at the Existing POTW 5 Evaluation of CSO Control Alternatives

  6. Expectations for Maximization of Treatment at the POTW • Discussion of what has been done and what will be done to ensure that CSOs will be minimized by maximizing the conveyance of flow to the POTW Evaluation of CSO Control Alternatives

  7. Screening/Evaluation • Detailed evaluation of CSO controls is often preceded by screening level analysis • Two step process: • Screen 10 to 20 different CSO control technologies. • Conduct detailed evaluation of 3 or 4 CSO control technologies that meet local needs. Evaluation of CSO Control Alternatives

  8. Screening and Evaluation of CSO Controls The screening and evaluation of controls should: • Include WQ considerations • Site specific control needs • Performance of control technologies • Implementation issues • Explain reasons for selecting CSO control alternatives • Explain reasons for rejecting other controls Note: Looking for logical decision-making process Evaluation of CSO Control Alternatives

  9. Screening – WQ Considerations • Principal considerations in prioritizing individual CSO discharges for control: • Sensitive areas • Dry weather overflows (prohibited) • Risk to public health • Contribution to non-attainment of use • Frequency and volume of discharge Evaluation of CSO Control Alternatives

  10. Sensitive Areas • Have sensitive areas been identified during system characterization as present and impacted by CSO discharges? Evaluation of CSO Control Alternatives

  11. Sensitive Areas • If sensitive areas are present and impacted, the LTCP should address plans for: • Prohibition of new or significantly increased overflows • Elimination or relocation of overflows where possible • Treatment of overflows where necessary • Reassessment of impacts each permit cycle where elimination or treatment are not achievable Evaluation of CSO Control Alternatives

  12. Screening:Identify Appropriate Controls • Review full range of controls with respect to site-specific conditions: • Widespread use of control (e.g., catch basin modifications) • Localized use (e.g., retention basin) • Interim use • Eliminated from further consideration Evaluation of CSO Control Alternatives

  13. Screening:Control Performance • Evaluate performance and capability of CSO control alternatives to: • Reduce CSO volume, frequency • Control bacteria • Capture floatables • Remove solids • Eliminate basement or street flooding • Etc. Evaluation of CSO Control Alternatives

  14. Screening: Implementation Issues • Assess implementation, environmental and technical issues: • Reliability of control • Land requirements • Siting issues • Operating issues • Aesthetics (noise, traffic, etc.) • Capital costs • O&M costs Evaluation of CSO Control Alternatives

  15. Evaluation of CSO Control Alternatives • ID conditions under which controls are evaluated • Typically involves reference to baseline condition • Presumption approach (e.g., 4-6 overflow event per year or capture for treatment of 85% volume) requires analysis to be on a system-wide, annual average basis • Analysis of rainfall and identification of annual average conditions should be documented Note: permittee should describe how CSO control alternatives have been evaluated Evaluation of CSO Control Alternatives

  16. What about rainfall in Springfield? 16 Evaluation of CSO Control Alternatives

  17. Rainfall Analysis • Permittees are expected to describe how “annual average” conditions were determined. May include: • Ranking of annual rainfall • Assessment of month-to month variations • Assessment of rainfall intensity • Assessment of return frequency Evaluation of CSO Control Alternatives

  18. “Annual Average” Conditions 18

  19. Evaluation of CSO Control Alternatives • Individual control alternatives may include a mix of different technologies (e.g., partial sewer separation, floatables control, expansion of primary treatment capacity, etc.) • Evaluation should include cost-performance information for a range of overflow frequencies • 0 overflow events per year, 1–3 per year, 4–7 per year, 8–12 per year • Percent capture for treatment (e.g., 100%, 85%, 80%, 75%) Evaluation of CSO Control Alternatives

  20. Interpretation of Results- Springfield, USA CSO #1 CSO #2 CSO #3 Control Technologies 1-12 or more Control Alt. A CSO #1 – Storage CSO #2 – Storage CSO #3 – Swirl Pump Station Upgrade Control Alt. B CSO #1 – Separation CSO #2 – Storage CSO #3 – Swirl Pump Station Upgrade Control Alt. C Full separation 20 Evaluation of CSO Control Alternatives

  21. Range of CSO ControlComparison of Overflow Frequency 40 35 30 25 OverflowEventsPer Year 20 15 10 5 0 Baseline Alt A Alt B Alt C Evaluation of CSO Control Alternatives

  22. $7 $6 $5 $4 $3 $2 $1 $0 1 3 5 7 9 11 13 15 Knee of Curve ExampleCost in Millions vs. CSO Frequency Cost inMillions Number of Overflows Evaluation of CSO Control Alternatives

  23. Non-Monetary Evaluation Factors Evaluation of CSO Control Alternatives

  24. Selecting the Best CSO Control Alternative • Will water quality and designated uses be protected? • Have sensitive areas been considered? • Has a reasonable range of CSO control alternatives been considered? • Has public input been obtained and used? • Has financial capability been assessed? Evaluation of CSO Control Alternatives

  25. Will WQ Standards and Designated Uses Be Protected? • Evaluation is very site specific • Bacteria—monthly geomean vs. single sample maximum—what governs ??? • Where do standards apply (end-of-pipe or beach)? • How do CSO impact these areas? • How do other sources impact these areas? Note: Protection of designated uses is probably the most important consideration in review of LTCPs Evaluation of CSO Control Alternatives

  26. What Are the Designated Uses? 26 Evaluation of CSO Control Alternatives

  27. bridge bridge bridge Park Beach Back in Springfield Public Boat Launch 27

  28. Example Monitoring Locations Station 1 Station 3 Station 2 Station 4 Station 5 Station 6 Station 7 Evaluation of CSO Control Alternatives

  29. Bacteria: Monthly GeomeanBabbling Brook July Evaluation of CSO Control Alternatives

  30. Bacteria: Babbling Brookat the Beach Evaluation of CSO Control Alternatives

  31. Annual BOD Load(Thousands of Pounds) Evaluation of CSO Control Alternatives

  32. Key Questions That Are Often Raised • Can water quality standards and designated use protection be attained through CSO control? • Are uses attainable? • Is a use attainability analysis (UAA) needed? • Should a water quality standards review be undertaken? Evaluation of CSO Control Alternatives

  33. Public Participation • Includes interaction between the municipality and the general public and stakeholders – This is best led by the CSO community. • Includes interaction between the municipality and regulatory agencies including WQ standards authority – This is best led by the permit writer. Evaluation of CSO Control Alternatives

  34. Expectations: Public Participation • Did the public participation process involve rate payers and users of receiving waters? • Was the public briefed on characterization, CSO impacts, control alternatives and costs? • Did the public participate in the decision process to select CSO controls? Evaluation of CSO Control Alternatives

  35. In reality it can be difficult to get the public involved, but the CSO community must show effort. 35 Evaluation of CSO Control Alternatives

  36. Final Selection of CSO Control Alternatives • Should be based on: • Control priorities • Site specific conditions • Protection of WQS and designated uses • Public input • Cost-effectiveness of controls • Financial capability • Other considerations Evaluation of CSO Control Alternatives

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