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Accommodating CSO Flows /Loadings in the Chesapeake Bay Nutrient TMDL WWP NACWA National Perspectives, Developments and Advanced Urban Wet Weather Solutions.

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Presentation on theme: "Accommodating CSO Flows /Loadings in the Chesapeake Bay Nutrient TMDL WWP NACWA National Perspectives, Developments and Advanced Urban Wet Weather Solutions."— Presentation transcript:

1 Accommodating CSO Flows /Loadings in the Chesapeake Bay Nutrient TMDL WWP NACWA National Perspectives, Developments and Advanced Urban Wet Weather Solutions 22 April 2010

2 Why was a working group of CSO communities formed in Virginia and DC? A Long Term Control Plan (LTCP) that is not complete separation needs an allocation. No allocation, no allowable discharge from the combined sewer system under the Total Maximum Daily Load (TMDL) calculation and no loadings for the Watershed Implementation Plan. Reasonable assurance of compliance with the TMDL

3 Characterization of Combined Sewer Overflow (CSO) Discharges to the Chesapeake Bay 9 October 2009 Limo Tech on behalf of the Combined Sewer System (CSS) Working Group Develop information to be used by the U.S. EPA Chesapeake Bay Program (CBP) and jurisdictional regulatory agencies –Characterize CSS pollutant loads for the Chesapeake Bay Nutrient and Total Suspended Solids TMDL study. Calibration of the Chesapeake Bay Water Quality Sediment Transport Model (WQSTM) Development of TMDLs

4 EPAs Chesapeake Bay TMDL How was EPA Model Configured before V5.3? CSO-O CSO-C Storage Facilities 1 WWTP DWF WWF Bay Model Segment EPA Watershed Model includes CSO Area with Urban Stormwater Agricultural Area Urban/Suburban Area CSO Area Air Deposition CSO Captured (CSO-C) portion of Stormwater may be double counted as part of WWF at WWTP EPA Water Quality Model includes Loads based on WWTP DMRs, which includes WWF Volume & Loads EPA Watershed Model currently does not recognize CSO controls or storage facilities Note: 1. Includes Shockoe Retention Basin, Hampton/ McCloy CSO Tunnel & In-line storage

5 EPAs Chesapeake Bay TMDL Calibration Data Provided to EPA CSO-O CSO-C Storage Facilities 1 WWTP DWF WWF Bay Model Segment Subtract CSO Area out of Bay Watershed Model Provide EPA with CSO Overflow (CSO-O) Volume & Loads Agricultural Area CSO Area Air Deposition Verify that EPA is using the proper Dry Weather Flow and Wet Weather Flow Loads from WWTP DMR Note: 1. Includes Shockoe Retention Basin, Hampton/ McCloy CSO Tunnel & In-line storage Urban/Suburban Area

6 EPAs Chesapeake Bay TMDL EPA develops Preliminary Load Allocation CSO-O CSO-C WWTP DWF WWF Bay Model Segment EPA Modelers to Adjust Loads by Source to meet WQS Model Load Control Dial EPA to Provide DEQ with Allocation by Source Agricultural Area CSO Area Air Deposition DCR& DEQ Establishes LAs & WLAs by Locality Urban/Suburban Area Storage Facilities 1 Note: 1. Includes Shockoe Retention Basin, Hampton/ McCloy CSO Tunnel & In-line storage Note: 2. WLA for MS4 may be an aggregate WLA to an entire watershed segment and revised at the next two year milestone.

7 EPAs Chesapeake Bay TMDL Richmond CSO LTCP – Future Controls CSO-O CSO-C Storage Facilities WWTP DWF WWF CSO Permitted Bypass for Disinfection Bay Model Segment Agricultural Area Urban/Suburban Area CSO Area Air Deposition Additional CSO Control Facilities Shift WWF Load Allocation from CSO-O to WWTP (WWF Allocations under Bubble should be considered) DCR& DEQ Establishes LAs & WLAs by Locality LTCP Designed to Control Bacteria Bay TMDL IP Schedule should not be tied to LTCP Schedule

8 Conclusion of Characterization Report CBP and jurisdictional agencies should ensure that there is consistency between the Long Term Control Plans (LTCPs) developed by the CSS Working Group members and the CSS allocations proposed under the TMDL. This consistency should be expressly acknowledged in the discussion of CSOs and CSO allocations in the final TMDL report.

9 Chesapeake Bay TMDL Waste Load Allocations for Combined Sewer Systems 20 January 2010 Communication to the Virginia Department of Environmental Quality (DEQ) and follow up to a meeting of 7 December 2009 with the Communities. –The WLAs should reflect the nutrient and sediment load reductions already achieved by the Communities CSO control programs. –The combined sewer system WLA-based permit conditions and compliance demonstrations should reflect the fact that combined sewer flows consist largely of storm water and that the resulting flows and loads are highly variable. –The WLAs should accommodate load transfers resulting from –implementation of CSO controls in the future.

10 Proposed Chesapeake Bay TMDL Waste Load Allocations and Footnotes for Combined Sewer Systems 24 February 2010 Communication to the Virginia Department of Environmental Quality (DEQ) and follow up to a meeting of 27 January 2010 with the Communities. Communities proposed CSS WLAs derived using the approach outlined in a letter to DEQ and discussed during our January 27, 2010 meeting. Proposed language for the footnotes to the Communities CSS WLAs. –Designed to ensure that the basis for the WLAs is clearly stated in the TMDLs. –Provide permit writers sufficient guidance and direction to ensure that the CSS-related conditions in the Communities VPDES permits are consistent with the assumptions and requirements of the WLAs as required by 40 CFR § and 9 VAC D.1.f.

11 Establishing WLAs The WLAs for the Communities treatment plant dry weather design flow capacities should be kept separate from the WLAs for CSS flows discharged from the plants; The WLAs for Richmonds and Lynchburgs CSO outfalls and the WLAs for CSS flows discharged from their treatment plants should be aggregated; and The WLAs for Alexandrias CSO outfalls and the WLAs for CSS flows discharged from ASAs treatment plant should be kept separate because they are separate permit holders. This approach will require the following seven WLAs for each of the three pollutants (total nitrogen, total phosphorus, and sediment) for which TMDLs are being established: –Two WLAs each for Lynchburg and Richmond (an individual WLA for the dry weather design flow capacity of each citys treatment plant and an aggregated WLA for each citys CSO outfalls and CSS flows discharged from each citys plant); –Two WLAs for ASA (an individual WLA for the treatment plants dry weather design flow capacity and an individual WLA for CSS flows discharged from the plant); and –One WLA for Alexandria (an individual WLA for the Citys CSO outfalls).

12 Footnotes While this language is proposed as footnotes to the WLAs, it is not mean to suggest that it must be included in footnotes. Some or all of this language can be included in the TMDL and Watershed Implementation Plan documents as other than footnotes so long as it is clear that the language is tied to the Communities CSS WLAs.

13 Richmond WWTP Historical Annual Average Flow Annual Average WWTP Flow Year 2006 Dry Weather Flow about 37 mgd Annual Average Wet Weather Flow Treated at WWTP DWF Capacity Ave WWTP Load Discharged TN = 1.3 M lbs/yr (54.7 mgd & 8 mg/L) 1994 WWTP Load Discharged TN = 1.4 M lbs/yr (58.0 mgd & 8 mg/L) Critical Period: Bay Model Indicates 1993 thru inches of Rainfall inches of Rainfall inches of Rainfall 63.0 mgd 54.7 mgd 2004 WWTP Load Discharged TN = 1.5 M lbs/yr (63.0 mgd & 8 mg/L) Randomness of Annual Rainfall makes it Infeasible to Calculate Annual Loading Limitation

14 Wastewater Flows Typical Wet Weather Flow Pattern Future Phase III: 85 to 90 mgd DWF WWF Phase II WWF: 75 mgd

15 Chesapeake Bay TMDL Source Sector Allocation Worksheet 25 Feb 2010 EPA EXPECTATIONS FOR WIP: CSO compliance with their approved Long Term Control Plan. Approach to Develop WLA: Determine the nutrient/sediment loads from CSO discharges based upon complete implementation of the approved LTCP for the critical period. Establish WLA for nutrient and sediment loads discharged from VA CSO outfalls and combined flows conveyed to WWTP for full treatment.

16 In Summary: CSO communities have developed LTCPs in accordance with the national CSO policy as stated in the Clean Water Act. Controls are being implemented under LTCPs for pathogens, floatables, total suspended solids and biochemical oxygen demand. Now, TMDLs look at different goals, different modeling segments, different hydrologic time periods, change the target for pathogen control, and look to control additional pollutants (nitrogen, phosphorus, PCBs, sediment) and pollutant characteristics (chlorophyll A) from CSO communities. A CSO community must secure WLAs in each TMDL whether the LTCP is complete separation or not.

17 Conclusion You are the only stakeholder who cares that CSOs secure a WLA and if you pass on participating in the TMDL process the outcome and your future will be determined by others. The general idea is to let you the CSO communities have flexibility with the WLAs, so that you can get the most bang for the buck you implement your LTCP and to make sure the TMDL doesnt actually end up impeding progress toward achieving WQS.


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