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. EPA’s Chesapeake Bay TMDL How was EPA Model Configured before V5.3?
EPA Watershed Model includes CSO Area with Urban Stormwater
Bay Model Segment
Agricultural
Area
Urban/Suburban
Area
CSO
Area
Air
Deposition
EPA Water Quality Model includes Loads based on WWTP DMRs,
which includes WWF Volume & Loads
Storage
Facilities1
CSO-C
CSO-O
DWF
EPA Watershed Model currently does not recognize CSO controls or storage facilities
WWF
WWTP
CSO Captured (CSO-C) portion of Stormwater may be double counted
as part of WWF at WWTP
Note: 1. Includes Shockoe Retention Basin, Hampton/ McCloy CSO Tunnel & In-line storage

5. EPA’s Chesapeake Bay TMDL Calibration Data Provided to EPA
Subtract CSO Area out of Bay Watershed Model
Bay Model Segment
Agricultural
Area
Urban/Suburban
Area
CSO
Area
Air
Deposition
Storage
Facilities1
CSO-C
CSO-O
DWF
Provide EPA with
CSO Overflow (CSO-O) Volume & Loads
WWF
WWTP
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

6. EPA’s Chesapeake Bay TMDL EPA develops Preliminary Load Allocation
EPA Modelers to Adjust Loads by Source to meet WQS
Bay Model Segment
Model Load
Control Dial
Agricultural
Area
Urban/Suburban
Area
CSO
Area
Air
Deposition
DCR& DEQ
Establishes LAs & WLAs by Locality
Storage
Facilities1
CSO-C
CSO-O
DWF
EPA to Provide DEQ with Allocation by Source
WWF
WWTP
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. EPA’s Chesapeake Bay TMDL Richmond CSO LTCP – Future Controls
LTCP Designed to Control Bacteria
Bay TMDL IP Schedule should not be tied to LTCP Schedule
Bay Model Segment
Agricultural
Area
Urban/Suburban
Area
CSO
Area
Air
Deposition
DCR& DEQ
Establishes LAs & WLAs by Locality
Storage
Facilities
CSO-C
CSO-O
DWF
Additional CSO Control Facilities Shift WWF Load Allocation from CSO-O to WWTP
(WWF Allocations under Bubble should be considered)
WWF
WWTP
CSO Permitted Bypass
for Disinfection

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 Richmond’s and Lynchburg’s CSO outfalls and the WLAs for CSS flows discharged from their treatment plants should be aggregated; and
The WLAs for Alexandria’s CSO outfalls and the WLAs for CSS flows discharged from ASA’s 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 city’s treatment plant and an aggregated WLA for each city’s CSO outfalls and CSS flows discharged from each city’s plant);
Two WLAs for ASA (an individual WLA for the treatment plant’s 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 City’s 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
‘93-’95 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 1995
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 70 65 60 55
41.55 inches
of Rainfall
41.54 inches
34.44 inches
Annual Average WWTP Flow 50
Wet Weather Flow
Annual Average
Treated at WWTP 45
DWF Capacity 40 35
Dry Weather Flow about 37 mgd 30
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year

14. Wastewater Flows Typical Wet Weather Flow Pattern
Phase II
WWF: 75 mgd
Future Phase III: 85 to 90 mgd 10 20 30 40 50 60 70 80 90
100
Date
WWTP Flow Rate (mgd)
May 13, 2002
May 14, 2002
May 15, 2002
WWF
DWF

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 doesn’t actually end up impeding progress toward achieving WQS.