Accommodating CSO Flows /Loadings in the Chesapeake Bay Nutrient TMDL

WWP NACWA National Perspectives, Developments and Advanced Urban Wet Weather Solutions 22 April 2010

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

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

EPA’s Chesapeake Bay TMDLHow was EPA Model Configured before V5.3?

CSO-O CSO-C

StorageFacilities1

WWTP

DWF

WWF

Bay Model Segment

EPA Watershed Model includes CSO Area with

Urban Stormwater

AgriculturalArea

Urban/SuburbanArea

CSOArea

AirDeposition

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

EPA’s Chesapeake Bay TMDLCalibration Data Provided to EPA

CSO-O CSO-C

StorageFacilities1

WWTP

DWF

WWF

Bay Model Segment

Subtract CSO Area out of Bay

Watershed Model

Provide EPA with CSO Overflow (CSO-O)

Volume & Loads

AgriculturalArea

CSOArea

AirDeposition

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/SuburbanArea

EPA’s Chesapeake Bay TMDLEPA 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 LoadControl Dial

EPA to Provide DEQ with Allocation by

Source

AgriculturalArea

CSOArea

AirDeposition DCR& DEQ

Establishes LAs & WLAs by Locality

Urban/SuburbanArea

StorageFacilities1

Note: 1. Includes Shockoe Retention Basin, Hampton/ McCloy CSO Tunnel & In-line storageNote: 2. WLA for MS4 may be an aggregate WLA to an entire watershed segment and revised at the next two year milestone.

EPA’s Chesapeake Bay TMDLRichmond CSO LTCP – Future Controls

CSO-O CSO-C

StorageFacilities

WWTP

DWF

WWF

CSO Permitted Bypassfor Disinfection

Bay Model Segment

AgriculturalArea

Urban/SuburbanArea

CSOArea

AirDeposition

Additional CSO Control Facilities Shift WWF Load Allocation from CSO-O to WWTP

(WWF Allocations under Bubble should

be considered)

DCR& DEQEstablishes LAs & WLAs by Locality

• LTCP Designed to Control Bacteria• Bay TMDL IP Schedule should not be tied to LTCP Schedule

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.

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.

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 § 130.7 and 9 VAC 25-31-220.D.1.f.

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).

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.

Richmond WWTP Historical Annual Average Flow

An

nu

al A

vera

ge

WW

TP

Flo

w

35

40

45

50

55

60

65

70

30

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Year

2006

Dry Weather Flow about 37 mgd

An

nu

al

Av

era

ge

W

et

We

ath

er

Flo

wT

rea

ted

at

WW

TP

DWF Capacity

‘93-’95 Ave WWTP Load DischargedTN = 1.3 M lbs/yr (54.7 mgd & 8 mg/L)

1994 WWTP Load DischargedTN = 1.4 M lbs/yr (58.0 mgd & 8 mg/L)

Critical Period: Bay Model Indicates

1993 thru 1995

41.55 inchesof Rainfall

41.54 inchesof Rainfall

34.44 inchesof Rainfall

63.0 mgd

54.7 mgd

2004 WWTP Load DischargedTN = 1.5 M lbs/yr(63.0 mgd & 8 mg/L)Randomness of

Annual Rainfall makes it Infeasible to

Calculate Annual Loading Limitation

Wastewater Flows Typical Wet Weather Flow Pattern

0

10

20

30

40

50

60

70

80

90

100

Date

WW

TP

Flo

w R

ate

(m

gd

)

May 13, 2002 May 14, 2002 May 15, 2002

Future Phase III: 85 to 90 mgd

DWF

WWF

Phase II WWF: 75 mgd

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.

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.

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.