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10-1 September 24, 2010

SECTION 10. TMDL IMPLEMENTATION AND 

ADAPTIVE MANAGEMENT

10.1 Future Growth

As an assumption of the Chesapeake Bay TMDL, EPA expects Chesapeake Bay jurisdictions to 

account for and manage new or increased loadings of nitrogen, phosphorus, and sediment. Such 

loadings might be introduced by point and nonpoint sources as a result of future growth and 

development and land use changes.

10.1.1 Designating Target Loads for New or Increased Sources

Where the TMDL does not provide a specific allocation to accommodate new or increased 

loadings of nitrogen, phosphorus, or sediment, a jurisdiction may only accommodate such new or 

increased loadings through a mechanism allowing for quantifiable and accountable offsets of the 

new or increased load in an amount necessary to implement the TMDL and applicable WQS in 

the Chesapeake Bay and its tidal tributaries. Therefore, the Chesapeake Bay TMDL assumes and 

EPA expects the jurisdictions to accommodate any new or increased loadings of nitrogen, 

phosphorus, or sediment that do not have a specific allocation in the TMDL with appropriate 

offsets supported by credible and transparent offset programs subject to EPA and independent 

oversight. If a jurisdiction requests a specific allocation for future growth in its final Phase I 

WIP, EPA will evaluate whether to include such an allocation in the final TMDL.

10.1.2 Offset Programs

EPA expects that new or increased loadings of nitrogen, phosphorus, and sediment in the 

Chesapeake Bay watershed that are not specifically accounted for in the TMDL’s WLA or LA 

will be offset by loading reductions from other sources where such offset credits are generated 

under programs that are consistent with the definitions and common elements described in 

Appendix S. These definitions and common elements are important to ensure that offsets are 

achieved through reliable pollution controls and that the goals of the Chesapeake Bay TMDL are 

met. 

EPA expects such the jurisdictions to develop offset programs that are credible, transparent, 

consistent with the definitions and common elements set out in Appendix S, and subject to EPA 

and public oversight. Any such offsets are expected to account for the entire delivered nitrogen, 

phosphorus, or sediment load after accounting for location of the sources, delivery factors 

affecting pollutant fate and transport, equivalency of pollutants, and the certainty of any such 

reductions. In addition, such offsets may not cause an exceedance of local WQS or local 

TMDLs. The offsets are to be in addition to reductions already needed to meet the allocations in 

the TMDL and must be consistent with applicable federal and state laws and regulations. 

For nonpoint sources, this assumption and expectation is based on the fact that any new or 

increased nonpoint source loadings not accounted for in the TMDL’s LA will have to be offset 

by appropriate reductions from other sources if the TMDL’s pollutant loading cap and applicable 

WQS are to be met. For permitted point sources, the assumption and expectation also is based on 

the statutory and regulatory requirements that effluent limits for any such discharges are derived 

from and comply with all applicable WQS and are consistent with the assumptions and 
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10-2 September 24, 2010

requirements of any available WLAs [CWA sections 301(b)(1)(C), 303(d); 40 CFR 

122.44(d)(1)(vii)(A) & (B)].

In addition, CWA section 117(g) authorizes EPA to ensure that management plans are developed 

and implementation is begun to achieve and maintain the Bay’s nutrient goals. If jurisdictions 

authorize new or increased loadings without a specific TMDL allocation, an offset is necessary 

component of any such management plan. Accordingly, the Bay TMDL assumes that new point 

source dischargers, without an allocation in the TMDL (or in other words, with a zero 

allocation), will find offsets large enough to compensate for their entire loading. The TMDL 

similarly assumes that point source dischargers that increase pollution loading will find offsets 

large enough to compensate for the entire increase in their loading and to meet their Water 

Quality Based Effluent Limit (WQBEL) consistent with the WLA in the TMDL. In the case of 

new or increased loading from sources other than permitted point source dischargers, 

jurisdictions are to estimate loadings and ensure offsets that fully compensate for this estimated 

increase in pollutant load.

Although EPA assumes some flexibility in the design and content of Bay jurisdiction offset 

programs, EPA expects that the jurisdictions will develop and implement programs for offsetting 

new and increased loadings consistent with the definitions and common elements described in 

detail in Appendix S. Jurisdictions with existing trading programs that address new or increased 

loadings (such as several jurisdictions have), should ensure that their programs address new or 

increased loads consistent with the definitions and common elements in Appendix S. 

EPA is interested in comment on the extent to which definitions, common elements and program 

features described here and in Appendix S for new or increased loadings of nitrogen, phosphorus 

and sediment should also be applicable to trading among existing sources of those pollutants for 

purposes of achieving their WLAs or LAs under the Bay TMDL.

10.1.3 Additional Offset Program Features

EPA expects that the jurisdictions also may use the following features to build their offset 

programs for new or increased loadings of nitrogen, phosphorus, and sediment:

Net Improvement Offsets: For purposes of the Bay TMDL, this means an offset at a ratio greater 

than merely accounting for the entire new or increased load. The jurisdiction’s offset program 

needs to provide the authority and procedures for invoking such a provision. This tool may be 

used as a means to accelerate load reductions where a jurisdiction is not on a schedule to ensure 

that nitrogen, phosphorus, and sediment controls are in place by 2017 and 2025 to meet interim 

and final target loads, respectively. This may be determined to be needed based on an EPA 

evaluation of a jurisdiction’s progress on its WIP and 2-year milestones, as discussed in EPA’s 

December 29, 2009 letter (USEPA 2009d). Net improvement offsets also may be used by a 

jurisdiction in the case of permitted point sources to offset new or increased loads from nonpoint 

sources or from point sources not expected to be permitted.

Aggregated Programmatic Credits: For purposes of the Bay TMDL, this means defining a 

programmatic solution for over-control of nutrients or sediment beyond the basic WIP strategies 

to achieve the TMDL allocation. In essence, it is an aggregation of credits from reductions by a 

class or subclass of sources where such reductions have been achieved by the jurisdiction or 

another duly authorized body. Such credits may be made available by the jurisdiction to offset 
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10-3 September 24, 2010

new or increased loadings. In some circumstances, such class reductions also could be applied as 

a reallocation of loadings under the TMDL. Such reallocation may require modification of the 

TMDL.

Reserve-Offset Hybrid: For purposes of the Bay TMDL, this applies where a jurisdiction 

reserves a portion of its allocations for future growth and, once that allocation is depleted, uses 

an offset program as described herein.

10.1.4 EPA’s Oversight Role of State Offset Program

EPA expects the jurisdictions to describe their offset programs in their final Phase I and Phase II 

WIPs. EPA encourages jurisdictions to consult with EPA throughout the development of their 

offset programs to facilitate alignment with the CWA and the Bay TMDL. EPA has various 

oversight responsibilities under the CWA, MOUs for authorization of jurisdictions’ NPDES 

programs, and the TMDL/Executive Order 13508, including approval of revisions to WQS, 

review of NPDES permits, and provisions for reviewing and making recommendations regarding 

revisions to a jurisdiction’s water quality management plans through the continuing planning 

process.

EPA intends to maintain regular oversight of jurisdictions’ offset programs through periodic 

audits and evaluations. EPA will report its findings to the respective jurisdiction. Such oversight 

generally will be conducted on a programmatic basis, not an individual offset basis. EPA 

reserves its authority, however, to review any individual offset (including an NPDES permit 

containing an offset) and to comment on, object to, or issue the permit as needed if EPA 

determines that the offset is not consistent with a jurisdiction’s offset program determined to be 

consistent with Appendix S. Where questions or concerns arise, EPA will use its oversight 

authorities to ensure that offset programs are fully consistent with the CWA and its 

implementing regulations. EPA recognizes the value of implementing a strategy for offsets that, 

wherever possible, is consistent among the jurisdictions to increase credibility, scalability, and 

broader regional implementation such as interstate trading.

10.2 Water Quality Trading

EPA recognizes that a number of Bay jurisdictions already are implementing water quality 

trading programs. EPA supports implementation of the Bay TMDL through such programs, as 

long as they are established and implemented in a manner consistent with the CWA, its 

implementing regulations, and EPA’s 2003 Water Quality Trading Policy1and 2007 Water 

Quality Trading Toolkit for NPDES Permit Writers.

2 An assumption of this TMDL is that trades 

may occur between sources contributing pollutant loadings to the same or different Bay 

segments, provided such trades do not cause or contribute to an exceedance of WQS in either 

receiving segment or anywhere else in the Bay watershed. EPA does not support any trading 

activity that would delay or weaken implementation of the Bay TMDL, that is inconsistent with 

the assumptions and requirements of the TMDL, or that would cause the combined point source 

and nonpoint source loadings covered by a trade to exceed the applicable loading cap established 

by the TMDL.

 

1

http://www.epa.gov/owow/watershed/trading/finalpolicy2003.pdf

2

http://www.epa.gov/owow/watershed/trading/WQTToolkit.html)
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10-4 September 24, 2010

In Section 10.1, EPA explains how Bay jurisdictions may accommodate new or increased 

loadings of nitrogen, phosphorus, and sediment either through a specific TMDL allocation or by 

offsetting those loadings with quantifiable and accountable reductions necessary to implement 

applicable WQS in the Bay and its tidal tributaries. In Appendix S, EPA discusses a number of 

definitions and common elements that EPA expects the jurisdictions to include and implement in 

their offset programs. EPA requests comment on the extent to which the policies and elements 

discussed in those sections should apply to water quality trades in Bay jurisdictions generally and 

not only to offsets for new or increased nutrient and sediment loadings.

10.3 Future Modifications to the Chesapeake Bay TMDL

Critical implementation issues for the Chesapeake Bay TMDL have been addressed in several 

ways. Through the establishment of the accountability framework, reasonable assurance has been 

built into the Chesapeake Bay TMDL development process. As part of this framework, the 

jurisdictions are expected to adhere to a phased schedule of development for their WIPs. EPA 

has provided clear expectations to the jurisdictions as they set forth and develop their WLAs and 

LAs for the Chesapeake Bay TMDL. EPA and its partners also have committed to taking an 

adaptive management approach to the Chesapeake Bay TMDL implementation. Among other 

things, jurisdictions can consider exchanges of the target loads within tributary basins and 

between nitrogen and phosphorus as long as WLAs and LAs, applied collectively across the 

entire watershed, will still result in model simulated achievement of the jurisdictions’ 

Chesapeake Bay WQS across all 92 tidal Bay segments. Such exchanges could require 

modification of the Chesapeake Bay TMDL.

EPA has agreed to consider revisions to the Phase 5.3 Chesapeake Bay Watershed Model to 

address nutrient management effectiveness and suburban land characteristics and, if appropriate, 

modify the nutrient and sediment allocations. EPA also will consider whether any other 

modifications to the model are necessary as a result of public comment or otherwise and will 

make any changes as appropriate.

EPA has documented a three-phase process to ensure that it and its watershed partners continue 

to take steps to have all practices in place to restore local waters and the Chesapeake Bay by 

2025, with 60 percent achieved by the 2017 mid-point mark (USEPA 2010e). If necessary, EPA 

will consider modifying the Chesapeake Bay TMDL in 2011 or 2017 should it appear that these 

interim marks will not be achieved, or upon a request for modification by one of the 

jurisdictions. The three-phase process is as follows:

In 2010

o On July 1, EPA assigned draft nitrogen and phosphorus allocations to the 

jurisdictions by major river basin and included a temporary reserve for any shift in 

loads that may occur from two specific Bay watershed model refinements (nutrient 

management effectiveness and suburban land characteristics).

o On August 13, EPA assigned draft sediment allocations to the jurisdictions by 

major river basin.

o The jurisdictions submitted their draft Phase I WIPs on September 1 (Virginia on 

September 3).

o On September 24, EPA issued a draft Chesapeake Bay TMDL for a 45-day formal 

public comment period.
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10-5 September 24, 2010

o The jurisdictions are expected to submit their final Phase I WIPs by November 29.

o By December 31, EPA will establish the Chesapeake Bay TMDL.

In 2011

o EPA has agreed to make revisions to the partnership’s Phase 5.3 Chesapeake Bay 

Watershed Model to address nutrient management effectiveness and suburban land 

characteristics and, if appropriate, modify the nutrient and sediment allocations.

o The jurisdictions are expected to submit their draft Phase II WIPs by June 1 and 

their final Phase II WIPs by November 1, 2011. The Phase II WIPs are expected to 

include finer-scale load distributions as described in EPA’s November 4, 2009 letter 

and any updates resulting from the Bay watershed model revisions.

o Along with their final Phase II WIPs, the jurisdictions would submit for public 

comment any intention to modify the Chesapeake Bay TMDL allocations.

o EPA will modify the Chesapeake Bay TMDL, if necessary, by December 31, 2011.

In 2017

o Before 2017, EPA will review the full suite of Bay models on the basis of the best 

available science and decision-support tools and consider whether updated models 

should be developed to support Phase III WIPs and potential modifications to 

Chesapeake Bay TMDL allocations.

o In 2017, jurisdictions are expected to submit draft Phase III WIPs by June 1, 2017 

and final WIPs by November 1, 2017 with a focus on ensuring that all practices are 

in place by 2025 as needed to fully restore the Bay and its tidal waters.

o EPA will modify the Chesapeake Bay TMDL, if necessary, by December 31, 2017.

10.4 Federal Facilities and Lands

Federal lands account for approximately 5.5 percent of the Chesapeake Bay watershed. The 

federal sector is like other sectors in that EPA expects federal land owners to be responsible for 

achieving LA and WLA through actions, programs, and policies that will reduce the release of 

nitrogen, phosphorous, and sediment (CWA section 313, 33 U.S.C. 1323).

Federal agencies with property in the watershed will provide leadership and will work with the 

seven Bay watershed jurisdictions in developing and implementing their WIPs. Federal agencies 

have provided information on the spatial boundaries and land use types for facilities in the 

watershed. EPA used that information to model pollutant loads from federal facilities and has 

provided the estimated loads to the jurisdictions.

In their final Phase I WIPs, the jurisdictions are expected to propose final LAs and WLAs that 

include federal lands. In the Phase II WIPs, the jurisdictions are expected to further distribute LA 

and WLA allocations at the local level (counties, subwatersheds, and such) including federal 

facilities. The Phase II WIPs are expected to identify federal agency actions, programs, policies, 

and resources necessary to achieve federal facility-specific allocations. Federal agencies are 

expected to create 2-year milestones related to planned actions for inclusion in jurisdictions’ 

Phase II WIPs. The milestones will be the basis for tracking progress and providing transparency 

on federal sector performance related to agency TMDL responsibilities in the watershed.
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10-6 September 24, 2010

Federal facility-specific allocations and load reduction plans are expected to be developed as part 

of the jurisdictions’ Phase II WIPs in 2011 via one of two approaches: (a) jurisdictions could 

establish explicit load reduction expectations for federal facilities as part of the Phase II WIP 

process; or (b) on the basis of broad load reduction goals established by the jurisdiction,

individual federal facilities/installations could develop Federal Facility Implementation Plans 

(FFIPs), which would explain to the jurisdiction how the facility would achieve needed load 

reductions in nitrogen, phosphorus, and sediment. The FFIPs would address, at a minimum, the 

following in targeting and achieving load reductions:

Assess properties to determine the feasibility of installing urban retrofit practices and 

implementing nonstructural control measures that reduce volume and improve quality of 

stormwater runoff.

Align cost-effective, urban stormwater retrofits and erosion repairs with the Bay TMDL 

allocations and jurisdictions’ 2-year milestones.

Assess and implement appropriate nonstructural practices to control stormwater discharges 

from developed areas and to reduce, prevent, or control erosion from unpaved roads, trails, 

and ditches.

Consider the full spectrum of nutrient and sediment sources at a facility or installation to 

assess the ideal approach to achieve the needed nutrient and sediment reduction.

In addition, section 501 of Executive Order 13508 and the subsequent Executive Order Federal 

Strategy (FLCCB 2010) direct each federal agency with land, facilities or installation 

management responsibilities affecting 10 or more acres in the Bay watershed to implement 

section 502 guidance on federal land management. Pursuant to section 502 of the Executive 

Order, EPA issued on May 12, 2010, the Guidance for Federal Land Management in the 

Chesapeake Bay Watershed (EPA May 12, 2010), EPA 841-R-10-002 (―section 502 guidance‖).

EPA’s objective in developing the section 502 guidance was to provide information and data on 

appropriate, proven, and cost-effective tools and practices for implementation on federal lands 

and at federal facilities.

The section 502 guidance includes chapters addressing agriculture, urban and suburban areas 

(including turf), forestry, riparian area management, decentralized wastewater treatment systems, 

and hydromodification. Each chapter contains one or more implementation measures that 

provide the framework for the chapter. They are intended to convey the actions that will help 

ensure that the broad goals of the Chesapeake Bay Executive Order are achieved. Each chapter 

also includes information on practices that can be used to achieve the goals; information on the 

effectiveness and costs of the practices; where relevant, cost savings or other economic/societal 

benefits (in addition to the pollutant reduction benefits) that derive from the implementation 

goals or practices; and copious references to other documents that provide additional 

information. Federal agencies are to incorporate section 502 guidance as part of their overall 

strategy to meet the loading reductions that the jurisdictions in their Phase II WIPs assign to 

them.

In addition, the Executive Order strategy calls for federal agencies to adopt an agency-specific 

policy by December 2010 to ensure implementation of the stormwater requirements in section 

438 of the Energy Independence and Security Act (EISA) for new development and 

redevelopment activities consistent with guidance developed by EPA. Section 438 of EISA 
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10-7 September 24, 2010

requires federal agencies to maintain or restore the predevelopment hydrology (the runoff 

volume, rate, temperature, and duration of flow that typically existed on the site before humaninduced land disturbance occurred) of any project with a footprint that exceeds 5,000 square feet. 

The agency-specific policy should include mechanisms for producing an annual internal agency 

action plan and progress report. Implementation of the agency-specific policy is to begin in 2011. 

The results of each federal agency’s actions to comply with section 438 of EISA will be 

published as part of the annual progress report issued under the direction of the Executive Order 

discussed above.

10.5 Factoring in Effects from Continued Climate Change

The Chesapeake Executive Order 13508 specifies that the 2017 assessment of implementation 

progress will include an explicit assessment of climate change influences. Water managers in the 

Chesapeake watershed face significant challenges associated with climate change and the 

impacts of land use, increases in water demand, ecosystem degradation, and other stressors. 

Some stressors interact in ways that reinforce detrimental effects. For example increased 

population increases impervious area, which results in warmer, flashier runoff which reinforces 

similar climate change impacts.

To support the 2017 assessment requirement, climate change will be examined to explicitly 

determine the scope, magnitude, and timing of potential effects. An improved understanding of 

climate change impacts through an extension of the CBP partnership’s model capabilities will 

enable water managers to better evaluate risk and make informed decisions about meeting supply 

needs, complying with water quality regulations, and protecting aquatic ecosystems over a range 

of time scales. Future assessments will include the tidal Bay response in DO, chlorophyll a, 

SAV, and water clarity, which can be estimated by linking the climate change scenarios with the 

Chesapeake Water Quality and Sediment Transport Model as well as assessment of the effect of 

water column temperature changes on the Bay water quality and biological communities.

10.6 Sediments behind the Susquehanna River Dams

The dams along the lower Susquehanna River are a significant factor influencing nitrogen, 

phosphorus, and sediment loads to the Bay because they retain large quantities of sediment and 

phosphorus, and some nitrogen, in their reservoirs (Appendix T). The three major dams along the 

lower Susquehanna River are the Safe Harbor Dam, Holtwood Dam, and Conowingo Dam. In 

developing the TMDL, EPA considered the impact of these dams on the pollutant loads to the 

Bay and how those loads will change when the dams no longer function to trap nitrogen, 

phosphorus, and sediment.

The Bay TMDL incorporates the current sediment-trapping capacity of the Conowingo Dam at 

55 percent, with nitrogen and phosphorus trapping capacity at 2 percent and 40 percent, 

respectively. That allows the sediment, nitrogen, and phosphorus allocations to the jurisdictions 

to reflect the actual input to the Bay. If future monitoring shows an increase or a reduction in 

trapping capacity in the Conowingo Dam, the 2-year milestone delivered load reductions could 

be adjusted accordingly. The adjusted loads may be compared to the 2-year milestone 

commitments to ensure that each jurisdiction is meeting its obligations. For example, if there 

were a reduction in the sediment-trapping capacity in the reservoir, an upland jurisdiction might 

need to increase its sediment-reduction efforts to meet the allocations it has been assigned in the 

Bay TMDL. The jurisdictions’ sediment allocation would not necessarily change, but the 
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10-8 September 24, 2010

jurisdictions might need to increase the level of effort in reducing sediment to account for the 

loss of trapping capacity in the reservoir. Changes in the sediment-trapping capacity are not 

expected to alter the amount of sediment that the Bay is able to assimilate and, therefore, are not 

expected to change the allocations in this Bay TMDL.

For the purposes of the Chesapeake Bay TMDL, EPA and the partners assumed the current 

trapping efficiencies will continue. If future monitoring shows that trapping efficiencies are 

reduced, Pennsylvania, New York, and Maryland’s respective 2-year milestone delivered loads 

could be adjusted accordingly. Therefore it is imperative that those jurisdictions work together to 

develop an implementation strategy for addressing the sediment, nitrogen, and phosphorus 

behind the Conowingo Dam through their respective WIPs, so that they are prepared if the 

trapping efficiencies decrease.

10.7 Filter Feeders

Filter feeders play an important role in the uptake of nitrogen and phosphorus from the 

Chesapeake Bay and have the potential significantly improve water quality if present in large 

numbers (Appendix U). The organisms of interest for their ability to improve water quality are 

the native Eastern oyster, Crassostrea virginica, and menhaden fish, Brevoortia tyrannus. Each 

market-sized oyster contains about 0.5 gram of nitrogen and 0.16 gram of phosphorus. 

Menhaden fish are another filter feeding organism in the Chesapeake Bay. The Chesapeake Bay 

TMDL incorporates the effects of filter feeders.

EPA is basing the TMDL on the current assimilative capacity of filter feeders at existing 

populations built into the calibration of the oyster filter feeding submodel of the Chesapeake Bay 

Water Quality/Sediment Transport Model. Potential future population changes would not be 

accounted for in the Bay TMDL. If future monitoring data indicate an increase in the filter feeder 

population, the appropriate jurisdiction’s 2-year milestone delivered load reductions can be 

adjusted accordingly. Similarly if reductions in future filter feeder populations are observed that 

result in reduced nutrient assimilation, the 2-year milestone delivered load reductions can be 

adjusted to account for the change. The adjusted loads will be compared to the 2-year milestone 

commitments to ensure that each jurisdiction is meeting its obligations.
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SECTION 11. PUBLIC PARTICIPATION

EPA and the Bay jurisdictions have benefitted from a comprehensive effort to exchange 

information with key stakeholders and the broader public on the Chesapeake Bay TMDL.

By the end of 2010, a 2-year outreach effort will have included hundreds of meetings with 

interested groups; two rounds of public meetings, stakeholder sessions and media interviews 

throughout the watershed; a dedicated EPA website; monthly interactive webinars; three notices 

published in the Federal Register; and a close working relationship with Chesapeake Bay 

Program committees representing citizens, local governments, and the scientific community.

The outreach will continue in 2011 and beyond as the Bay TMDL is implemented.

11.1 Stakeholder and Local Government Outreach and Involvement

EPA has made a concerted effort over the past years to involve stakeholders and local 

governments in the development of the Chesapeake Bay TMDL. This section describes some of 

the more significant aspects of that effort.

11.1.1 Open Collaboration with Stakeholders

EPA has taken extra efforts to reach out to groups and sectors that will be particularly affected 

by the Bay TMDL. EPA principals involved in developing the Bay TMDL have attended dozens 

of meetings with a wide variety of groups throughout the watershed to give and receive 

information about the TMDL. A full list of those meetings held since January 2008 is provided 

in Appendix C.

During the course of a 7-week outreach campaign in the fall of 2009, EPA teams conducted 

nearly 50 separate meetings and briefings with key stakeholder groups to share sector-specific 

information and address questions in a productive setting. Those groups included farmers and 

producers, homebuilders and developers, municipal authorities, local elected officials, 

conservation groups, and environmental advocacy organizations. The outreach generated key 

insights and perspectives.

11.1.2 Outreach to Local Governments and Elected Officials

EPA and the jurisdictions have made a special effort to involve local governments in the Bay 

TMDL process to better understand how the TMDL can best be tailored to local scales for 

implementation. EPA has the scientific ability in the TMDL to identify pollution sources and 

impacts on a relatively local level.
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11-2 September 24, 2010

11.1.3 Local Pilots

EPA provided $300,000 in technical assistance for a series of pilot projects to help the 

jurisdictions engage local partners as part of their watershed implementation plan process. Local 

governments, conservation districts, watershed groups and others were eligible for a share of the 

assistance. The projects were to demonstrate how local needs, priorities, and existing restoration 

efforts could be incorporated in the implementation plans. EPA awarded funds to the following 

communities and watersheds:

District of Columbia

Maryland: Anne Arundel and Caroline counties

New York: Chemung River Watershed

Pennsylvania: Conewago Creek Watershed

Virginia: Prince William County and Rivanna River Basin

West Virginia: Berkeley, Jefferson, and Morgan counties

Information on the pilot projects are at 

http://www.epa.gov/reg3wapd/pdf/pdf_chesbay/WIPPilotProjectSummary_4222010.pdf.

11.2 Public Outreach

EPA’s extensive outreach efforts included public meetings, webinars, and a dedicated website 

that facilitated the continuing dialogue between EPA, the seven watershed jurisdictions, and key 

stakeholders on the Chesapeake Bay TMDL for nutrients and sediment.

11.2.1 Public Meetings

Two rounds of public meetings in each of the watershed jurisdictions are a centerpiece of EPA’s 

outreach efforts.

November–December 2009 Public Meetings

EPA and its jurisdiction partners sponsored 16 public meetings in the fall of 2009 to share 

information on the forthcoming Bay TMDL. A number of the public meetings were broadcast to 

a live, online audience via webinar. More than 2,000 people participated in the meetings, 

including 1,815 in the live audiences and 263 online via webinar at six of the locations. There 

was also a kickoff public meeting in Richmond, Virginia, in October 2009 that drew a combined 

live and online audience of more than 400 people.

The 2009 public meetings were held in

Martinsburg, West Virginia, November 4*

Moorefield, West Virginia, November 5

Washington, D.C., November 16*

Ashley, Pennsylvania, November 17

Williamsport, Pennsylvania, November 18

State College, Pennsylvania, November 19

Lancaster, Pennsylvania, November 23*
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Binghamton, New York, December 1*

Baltimore, Maryland, December 8*

Laurel, Delaware, December 10*

Wye Mills, Maryland, December 11

Falls Church, Virginia, December 14

Chesapeake, Virginia, December 15

Williamsburg, Virginia, December 15

Penn Laird, Virginia, December 16

Fredericksburg, Virginia, December 17

* Meeting also was broadcast online via webinar. The largest live audiences were in Penn Laird, 

Virginia (205), and Lancaster, Pennsylvania (196).

September-November 2010 Public Meetings

A total of 18 public meetings are scheduled to be held in the fall of 2010 in all seven watershed 

jurisdictions. One of the 18 is strictly a webinar, and, as in 2009, in the other jurisdictions, one of 

the public meetings in each jurisdiction will also be broadcast online via webinar to a broader 

audience. Times, specific locations, directions, and parking information are on the Bay TMDL 

website: http://www.epa.gov/chesapeakebaytmdl.

The meetings are scheduled for

Washington, D.C., September 29*

Harrisonburg, Virginia, October 4

Annandale, Virginia, October 5

Richmond, Virginia, October 6

Webinar, October 7

Hampton, Virginia, October 7

Georgetown, Delaware, October 11*

Easton, Maryland, October 12

Annapolis, Maryland, October 13

Hagerstown, Maryland, October 14*

Lancaster, Pennsylvania, October 18

State College, Pennsylvania, October 19

Williamsport, Pennsylvania, October 20*

Ashley, Pennsylvania, October 21

Elmira, New York, October 26

Binghamton, New York, October 27*

Martinsburg, West Virginia, November 3
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11-4 September 24, 2010

Romney, West Virginia, November 4*

* Meeting will also be broadcast online via webinar. Webinar registration links are available on 

the Bay TMDL website listed above.

11.2.2 Webinars to Expand Audiences

EPA Region 3 was one of the first regional offices to acquire capacity to host large webinars. 

The system was obtained specifically to broadcast a representative number of the 2009 fall 

public meetings to online audiences, thus expanding the ability for the public to hear and 

participate in the meetings. The webinars have since been broadcast about monthly and will be 

incorporated in a number of the fall 2010 public meetings—one in each jurisdiction.

Monthly Webinars

EPA sponsored monthly webinars in 2010 to keep the public up to date on Bay TMDL 

developments. The regularly scheduled webinars, each attracting hundreds of participants, 

represent one of EPA’s Open Government flagship initiatives for public outreach. A substantial 

portion of each webinar is reserved for informal questions and answers.

The monthly webinars have been advertised widely using stakeholder and jurisdiction lists of 

hundreds of people and organizations that have expressed an interest in the Bay TMDL. The 

registration links for the webinars have been published prominently on the Bay TMDL website.

The monthly webinars were held on

February 25, 2010 TMDL Update 1 529 participants

March 25, 2010 TMDL Update 2 379 participants

May 17, 2010 TMDL Update 3 294 participants

June 7, 2010 TMDL Update 4 288 participants

July 8, 2010 TMDL Update 5 383 participants

August 9, 2010 TMDL Update 6 385 participants

A monthly webinar is scheduled for September 28, 2010, at 10 a.m., on the eve of the first fall 

2010 public meeting.

Webinars Tailored to Specific Stakeholder Communities

In addition to the monthly webinars, EPA sponsored two webinars to review detailed modeling 

and other technical information with representatives of the agriculture and development 

communities.

The webinars were held on

March 22, 2010 Webinar for the Agriculture Community 218 participants

May 6, 2010 Webinar for the Development Community 84 participants

11.2.3 Chesapeake Bay TMDL Web Site

EPA established a website for the Chesapeake Bay TMDL in August 2009. The address is 

http://www.epa.gov/chesapeakebaytmdl.
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11-5 September 24, 2010

The site continues to include the latest news and information on the Bay TMDL, along with fact 

sheets, questions and answers, presentations, and other features. The site has consistently been 

one of the most popular in EPA Region 3 according to access numbers.

11.2.4 Public Notices

Federal Register Notices

EPA has issued notices in the Federal Register regarding the Chesapeake Bay TMDL to ensure 

that the public has full advance notification of major events. The two notices issued to-date 

include a September 17, 2009, announcement (USEPA 2009a) of the public meetings and a 

September 22, 2010 announcement (USEPA 2010c) of the public review and comment period. 

EPA will publish a Federal Register notice in December 2010 for the final Bay TMDL 

publication.

Newspaper Notices

EPA has issued notices in regional and local newspapers regarding the Chesapeake Bay TMDL 

to ensure that the public throughout the watershed has full advance notification of major events.

11.3 Responses to Public Comments

The Draft Chesapeake Bay TMDL will be available for public comment from September 24, 

2010, to November 8, 2010. EPA invites anyone wishing to comment on the information in the 

TMDL to do so by November 8, 2010. All comments must be postmarked no later than 

November 8, 2010. All comments must be written (or electronically received), include the name, 

address and telephone number of the commenter, and should be as concise and as specific as 

possible for EPA to develop meaningful responses. EPA encourages electronic submission of 

comments as described below. EPA will review all written comments submitted during the 

public comment period and will consider them in establishing the final TMDL as appropriate.

Responses to comments will be included in Appendix V in the final Chesapeake Bay TMDL 

document.

Comments may be submitted, identified by Docket ID No. EPA-R03-OW-2010-0736, by the 

following methods:

1. http://www.regulations.gov: After entering the docket for this action, click the Draft Bay 

TMDL to make a comment. Click the Submit a Comment button at the top right of the 

Web page, and then follow the online instructions.

2. Mail: Water Docket, Environmental Protection Agency, Mailcode: 28221T, 1200 

Pennsylvania Ave., N.W., Washington, DC 20460.

3. Hand Delivery: EPA Docket Center Public Reading Room, EPA Headquarters West, 

Room 3334, 1301 Constitution Avenue, NW., Washington, DC. Such deliveries are 

accepted only during the Docket Center’s normal hours of operation (8:30 a.m. to 4:30 

p.m.), and special arrangements should be made for deliveries of boxed information by 

contacting the Docket Center at 202-566-174
DRAFT Chesapeake Bay TMDL

12-1 September 24, 2010

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dissolved oxygen criteria assessment. STAC Review and Recommendations for the 

Chesapeake Bay Program. STAC Publication 09-005. Chesapeake Bay Program Scientific 

and Technical Advisory Committee. Chesapeake Research Consortium, Edgewater, MD.

Stevenson, J. C., R. Brinsfield, and K. Staver. 1987. Surface runoff and groundwater impacts 

from agricultural activities in the Chesapeake region. Ed. Stevens, Larry Proceedings of the 

U.S. Committee on Irrigation and Drainage, Regional Meeting, Washington, DC.

Stoddard, J.L., ed. 1994. Long-term changes in watershed retention of nitrogen: Its causes and 

aquatic consequences: L.A. Baker (ed.), Environmental Chemistry of Lakes and Reservoirs, 

ACS Advances in Chemistry Series No. 237: Washington, D.C., American Chemical 

Society, 83 p.

Tetra Tech, Inc. 1999 (September 8). Improving Point Source Loadings Data for Reporting 

National Water Quality Indicators, Final Report. Final Report. Prepared for: U.S. 
DRAFT Chesapeake Bay TMDL

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Environmental Protection Agency, Office of Wastewater Management (OWM). Contract 

#68-C-0014, Work Assignment 1-31. Tetra Tech, Inc., Fairfax, Virginia.

Thomann, R.V., J.R. Collier, A. Butt, E. Casman, and L.C. Linker.1994. Response of the 

Chesapeake Bay Water Quality Model to Loading Scenarios. CBP/TRS 101/94. U.S. 

Environmental Protection Agency, Chesapeake Bay Program Office, Annapolis, MD.

Trimble, S.W. 1999. Decreased rates of alluvial storage in the Coon Creek Basin, Wisconsin, 

1975–1993. Science 285:1244–1246.

USEPA (U.S. Environmental Protection Agency). 1976. [Biosolids 4.7.1]

USEPA (U.S. Environmental Protection Agency). 1978. [Biosolids 4.7.1]

USEPA (U.S. Environmental Protection Agency). 1982. Chesapeake Bay Program Technical 

Studies: A Synthesis. U.S. Environmental Protection Agency, Washington, DC.

USEPA (U.S. Environmental Protection Agency). 1983a. Chesapeake Bay: A Framework for 

Action. U.S. Environmental Protection Agency, Philadelphia, PA.

USEPA (U.S. Environmental Protection Agency). 1983b. Chesapeake Bay: A Framework for 

Action—Appendices. U.S. Environmental Protection Agency, Philadelphia, PA.

USEPA (U.S. Environmental Protection Agency). 1983c. Chesapeake Bay: A Profile of 

Environmental Change. U.S. Environmental Protection Agency, Philadelphia, PA.

USEPA (U.S. Environmental Protection Agency). 1983d. Chesapeake Bay Program: Findings 

and Recommendations. U.S. Environmental Protection Agency, Philadelphia, PA.

USEPA (U.S. Environmental Protection Agency). 1991a. Guidance for Water Quality-Based 

Decisions: The TMDL Process. EPA 440/4-91-001. U.S. Environmental Protection Agency, 

Washington, DC.

USEPA (U.S. Environmental Protection Agency). 1991b. Chesapeake Bay Coordinated Split 

Sample Program Implementation Guidelines. May 1991. CBP/TRS 58/91. Region 3 

Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 1996. Recommended Guidelines for Sampling 

and Analysis in the Chesapeake Bay Monitoring Program. August 1996. EPA 903-R-96-

006. CBP/TRS 148/96. Region 3 Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 1999. Draft Guidance for Water QualityBased Decisions: The TMDL Process. (Second Edition). EPA 844-D-99-001. U.S. 

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Program Biological and Living Resources Monitoring Data. EPA 903-R 99-xx or 00-xx.

U.S. Environmental Protection Agency, Washington, DC.

USEPA (U.S. Environmental Protection Agency). 2001. Frequently Asked Questions About 

Atmospheric Deposition: A Handbook for Watershed Managers. EPA-453/R-01-009. U.S. 
DRAFT Chesapeake Bay TMDL

12-11 September 24, 2010

Environmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, 

Washington, DC.

USEPA (U.S. Environmental Protection Agency). 2002. (Section 1.4)

USEPA (U.S. Environmental Protection Agency). 2002. (Section 4.5.5)

USEPA (U.S. Environmental Protection Agency). 2003a. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries. EPA 903-R-03-002. U.S. Environmental Protection Agency, Region 3, 

Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2003b. Setting and Allocating the Chesapeake 

Bay Basin Nutrient and Sediment Loads, the Collaborative Process, Technical Tools and 

Innovative Approaches. U.S. Environmental Protection Agency, Region 3, Chesapeake Bay 

Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2003c. Technical Support Document for 

Identification of Chesapeake Bay Designated Uses and Attainability. EPA 903-R-03-004. 

U.S. Environmental Protection Agency, Region 3, Chesapeake Bay Program Office, 

Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2004a. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries. 2004 Addendum. EPA 903-R-03-002. U.S. Environmental Protection Agency, 

Region 3, Chesapeake Bay Program Office, Annapolis, MD.

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Segmentation Scheme: Revisions, Decisions and Rationales 1983–2003. EPA 903-R-04-008.

CBP/TRS 268/04. U.S. Environmental Protection Agency, Region 3, Chesapeake Bay 

Program Office, Annapolis, MD.

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Jon Capacasa, March 3, 2004. Annual Permit Limits for Nitrogen and Phosphorus for 

Permits Designed to Protect Chesapeake Bay and its tidal tributaries from Excess Nutrient 

Loading under the National Pollutant Discharge Elimination System. U.S. Environmental 

Protection Agency, Washington, DC.

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Discharges of Nutrients in the Chesapeake Bay Watershed—December 2004. U.S. 

Environmental Protection Agency, Region 3, Philadelphia, PA. 

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Identification of Chesapeake Bay Designated Uses and Attainability–2004 Addendum. EPA 

903-R-04-006. U.S. Environmental Protection Agency, Region 3 Chesapeake Bay Program 

Office, Annapolis, MD.

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EPA 903-R-05-004. CBP/TRS 278-06. U.S. Environmental Protection Agency, Region 3

Chesapeake Bay Program Office, Annapolis, MD.
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12-12 September 24, 2010

USEPA (U.S. Environmental Protection Agency). 2006. Establishing TMDL ―Daily‖ Loads in 

Light of the Decision by the U.S. Court of Appeals for the D.C. Circuit in Friends of the 

Earth, Inc. v. EPA, et al., No.05-5015, (April 25, 2006) and Implications for NPDES permits. 

Memorandum from Benjamin Grumbles, Assistant Administrator, Office of Water. U.S. 

Environmental Protection Agency, Washington, DC.

USEPA (U.S. Environmental Protection Agency). 2007a. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries—2007 Addendum. EPA 903-R-07-003. CBP/TRS 285-07. U.S. Environmental 

Protection Agency, Region 3, Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2007b. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries. 2007 Chlorophyll Criteria Addendum. EPA 903-R-07-005 CBP/TRS 288/07. 

U.S. Environmental Protection Agency, Region 3 Chesapeake Bay Program Office, 

Annapolis, MD.

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Loads in TMDLs. U.S. Environmental Protection Agency, Office of Wetlands, Oceans, and 

Watersheds. Washington, DC.

USEPA (U.S. Environmental Protection Agency). 2008a. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries–2008 Technical Support for Criteria Assessment Protocols Addendum. EPA 903-

R-08-001. CBP/TRS 290-08. U.S. Environmental Protection Agency, Region 3, Chesapeake 

Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2008b. September 11, 2008, Letter from 

Region 3 Administrator Donald Welsh to Secretary John Griffin, Maryland Department of 

the Environment. 

USEPA 2008c.

USEPA (U.S. Environmental Protection Agency). 2009a. Clean Water Act Section 303(d): 

Preliminary Notice of Total Maximum Daily Load (TMDL) Development for the 

Chesapeake Bay. U.S. Environmental Protection Agency, Region 3, Water Protection 

Division. Federal Register. September 17, 2009, 74:47794.

USEPA (U.S. Environmental Protection Agency). 2009b. Letter from Region 3, Acting 

Administrator William C. Early to Secretary L. Preston Bryant, Virginia Department of 

Natural Resources, November 3, 2009.

USEPA (U.S. Environmental Protection Agency). 2009c. Letter from Region 3, Acting 

Administrator William C. Early to Secretary L. Preston Bryant, Virginia Department of 

Natural Resources, November 4, 2009.

USEPA (U.S. Environmental Protection Agency). 2009d. Letter from Region 3 Administrator 

Shawn M. Garvin to Secretary L. Preston Bryant, Virginia Department of Natural Resources, 

December 29, 2009.
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12-13 September 24, 2010

USEPA (U.S. Environmental Protection Agency). 2010a. Ambient Water Quality Criteria for 

Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal 

Tributaries: 2010 Technical Support for Criteria Assessment Protocols Addendum. May

2010. EPA 903-R-10-002. CBP/TRS 301-10. U.S. Environmental Protection Agency, Region 

3 Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2010b. Chesapeake Bay Program Grant and 

Cooperative Guidance: Attachment 6—CBP Wastewater Facility & Nonpoint Source Data 

Submission Specifications and Requirements. U.S. Environmental Protection Agency, Region 

3, Chesapeake Bay Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2010c. Clean Water Act Section 303(d): 

Notice for the public review of the Draft Total Maximum Daily Load (TMDL) for the 

Chesapeake Bay. U.S. Environmental Protection Agency, Region 3, Water Protection 

Division. Federal Register. September 22, 2010, ##:#####.

USEPA (U.S. Environmental Protection Agency). 2010d. Estimates of County Level Nitrogen 

and Phosphorus Data for Use in Modeling Pollutant Reductions. September 2010 (Draft).

U.S. Environmental Protection Agency, Region 3 Chesapeake Bay Program Office, 

Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2010e. Guide for EPA’s Evaluation of Phase I 

Watershed Implementation Plans. U.S. Environmental Protection Agency, Region 3, 

Philadelphia, PA.

USEPA (U.S. Environmental Protection Agency). 2010f. Letter from Region 3 Administrator 

Shawn M. Garvin to the Chesapeake Bay Program Principals’ Staff Committee Members, 

June 11, 2010.

USEPA (U.S. Environmental Protection Agency). 2010g. Letter from Region 3 Administrator 

Shawn M. Garvin to the Chesapeake Bay Program Principals’ Staff Committee Members, 

July 1, 2010.

USEPA (U.S. Environmental Protection Agency). 2010h. Letter from Region 3 Administrator 

Shawn M. Garvin to the Chesapeake Bay Program Principals’ Staff Committee Members, 

August 13, 2010.

USEPA (U.S. Environmental Protection Agency). 2010i. Our Nation’s Air: Status and Trends 

Through 2008. EPA-454/R-09-002. U.S. Environmental Protection Agency, Office of Air 

Quality Planning and Standards, Research Triangle Park, North Carolina.

USEPA (U.S. Environmental Protection Agency). 2010j. Phase 5.3 Chesapeake Bay Watershed 

Model Documentation. U.S. Environmental Protection Agency, Region 3 Chesapeake Bay 

Program Office, Annapolis, MD.

USEPA (U.S. Environmental Protection Agency). 2010k. Quality Management Plan for the 

Chesapeake Bay Program Office. September 2010. Region 3 Chesapeake Bay Program 

Office, Annapolis, MD.
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VADEQ (Virginia Department of Environmental Quality). 2004. James River Alternatives 

Analysis. Addendum #4. Virginia Department of Environmental Quality, Richmond, VA.

VADEQ (Virginia Department of Environmental Quality). 2008. Integrated Report.

Walter, Robert C., and Dorothy J. Merritts, 2008. Natural Streams and the Legacy of WaterPowered Mills. Science 319(5861):299–304.

Wang, P., and L.C. Linker. 2009. Assessment of Nitrogen and Phosphorus Control Trade-Offs 

Using a Water Quality Model with a Response Surface Method. Journal of Water Resources 

Planning and Management 135:3(171–177).

Wang, P., L.C. Linker, R.A. Batiuk, and C.F. Cerco. 2006. Surface Analysis of Chesapeake Bay 

Water Quality Response to Different Nutrient and Sediment Loads. Journal of 

Environmental Engineering. 132:3(377–383).
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SECTION 13. GLOSSARY

Airshed. A geographic area delineating the relative location of air emission sources contributing 

to the atmospheric deposition to a down-wind watershed.

Bay Segment. Subunits of the Chesapeake Bay estuary that were derived on the basis of specific 

selection criteria related to factors such as jurisdictional boundaries and other water quality, 

physical, and habitat related characteristics. The Chesapeake Bay is divided into 92 segments.

Critical Condition. Critical conditions are represented by the combination of loading, 

waterbody conditions and other environmental conditions that result in impairment and violation 

of water quality standards. Critical conditions for an individual TMDL typically depend on 

applicable water quality standards, characteristics of the observed impairments, source type and 

behavior, pollutant, and waterbody type.

Critical Period. A period during which hydrologic, temperature, environmental, flow, and other 

such conditions result in a waterbody experiencing critical conditions with respect to an 

identified impairment (e.g., summer low flow, winter high flow).

Delivered Load. The amount of a pollutant delivered to the tidal waters of the Chesapeake Bay 

or its tributaries from an upstream point of discharge/runoff after accounting for permanent 

reductions in pollutant loads due to natural in-stream processes in nontidal rivers.

Edge-of-Stream Load. The amount of a pollutant reaching a simulated stream segment from a 

point in that stream’s watershed.

Existing Flow. The average flow volume discharged from a facility based on monitored data.

Facility Design Flow. The maximum flow volume for which a facility is designed and 

permitted. 

Load Allocation. The portion of the TMDL allocated to existing or future nonpoint sources and 

natural background.

Loading Capacity. The greatest pollutant loading a waterbody can receive without exceeding 

water quality standards.

Margin of Safety. An accounting of uncertainty about the relationship between pollutant loads 

and receiving water quality. The margin of safety can be provided implicitly through analytical 

assumptions or explicitly by reserving a portion of loading capacity.

Nonpoint Source. Any source of water pollution that does not meet the legal definition of point 

source. Nonpoint source pollution generally results from land runoff, precipitation, atmospheric 

deposition, drainage, seepage or hydrologic modification
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Nonsignificant Discharge Facility. A municipal or industrial wastewater discharge facility that 

is not defined as a significant facility by the jurisdiction in which it is permitted. In general, 

nonsignificant municipal facilities have design flows less than 0.4 million gallons per day 

(Virginia and Maryland thresholds are slightly different). Nonsignificant industrial facilities 

discharge less than 3,800 pounds per year total phosphorus and less than 27,000 pounds per year 

total nitrogen. 

NPDES. The National Pollutant Discharge Elimination System (NPDES) permit program is 

authorized by the Clean Water Act and works to control water pollution by regulating point 

sources that discharge pollutants into waters of the United States. Industrial, municipal, and other 

facilities must obtain permits if their discharges go directly to surface waters. In most cases, the 

NPDES permit program is administered by authorized states.

Point Source. Any discernible, confined, and discrete conveyance, including but not limited to 

any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, 

concentrated animal feeding operation, vessel or other floating craft from which pollutants are or 

may be discharged.

Pollutant Source Sector. Category of related sources of nutrient and sediment loads identified 

for purposes of quantifying load allocations. Examples include agriculture, wastewater, forest, 

urban runoff.

Segment Watershed. Watershed area draining into one of the 92 Chesapeake Bay segments.

Significant Discharge Facility. A municipal or industrial wastewater facility defined as such by 

the jurisdiction in which it is permitted. Significant facilities are distinguished from 

nonsignificant facilities on the basis of flow for municipals and loads for industrials. In general, 

significant municipal facilities have flows larger than 0.4 million gallons per day, and significant 

industrial facilities discharge loads larger than 3,800 pounds per year of total phosphorus and 

27,000 pounds per year of total nitrogen. 

Simulation Period. A period used to run the simulation, selected to ensure that the simulated 

rainfall, meteorological, and environmental time series used to drive the watershed simulation 

such that it accurately simulates the critical conditions.

Total Maximum Daily Load. Specifies the maximum amount of a pollutant that a waterbody 

can receive and still meet applicable water quality standards. It is the sum of the individual 

allocations for point sources (called wasteloads) and allocations for nonpoint sources (called

loads) and natural background with a margin of safety (CWA section 303(d)(1)(c)). The TMDL 

can be described by the following equation:

TMDL = LC = ΣWLA + ΣLA + MOS

Wasteload Allocation. The portion of the TMDL allocated to existing or future point sources.
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Water Clarity Acre. An acre of shallow-water bay grass designated-use bottom habitat, located 

anywhere between the 2-meter depth contour and the adjacent shoreline inclusively, which has 

been observed to achieve the applicable salinity-regime-specific water clarity criteria.

Watershed. An area of land from which all water drains to a common point. 
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SECTION 14. ABBREVIATIONS

μg/L microgram per liter

AEU animal equivalent units

AFO animal feeding operation

ASMFC Atlantic States Marine Fisheries Commission

BART best available retrofit technology

BMP best management practice

BOD biological oxygen demand

CAA Clean Air Act

CAC Citizen’s Advisory Committee

CAFO concentrated animal feeding operation

CAMR Clean Air Mercury Rule

CBP Chesapeake Bay Program

CEC Chesapeake Executive Council

CFD cumulative frequency distribution

CFR Code of Federal Regulations

CMAQ Community Multi-scale Air Quality model

COMAR Code of Maryland

CONMON continuous monitoring

CSO combined sewer overflow

CSS combined sewer system

CWA Clean Water Act

DAITS Data and Information Tracking System

DC District of Columbia

DC WASA District of Columbia Water and Sewer Authority

DE Delaware

DE DNREC Delaware Department of Natural Resources and Environmental Control

DO dissolved oxygen

DUQAT Data Upload and Quality Assurance Tool

E3 everything by everyone everywhere

EGU electric generating unit

EISA Energy Independence and Security Act

ELG effluent limit guidelines

EO Executive Order

EPA U.S. Environmental Protection Agency

FFIP federal facility implementation plan

FR Federal Register

GIS geographic information system

ICIS Integrated Compliance Information System

Kd light attenuation coefficient

LA load allocation

lbs pounds

LC loading capacity

LGAC Local Governments Advisory Committee
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Ln natural log

LOESS locally weighted scatter plot smoother

LTCP Long-Term Control Plan

m meter

MAWP Mid-Atlantic Water Program

MD Maryland

MDE Maryland Department of the Environment

mgd million gallons per day

mg/L milligrams per liter

MOS margin of safety

MOU memorandum of understanding

MRAT Monitoring Realignment Action Team

MS4 Municipal Separate Storm Sewer System

NADP National Atmospheric Deposition Program

NAS National Agricultural Statistics

NEIEN National Environmental Information Exchange Network

NH3 ammonia

NMFS National Marine Fisheries Service

NMP nutrient management plan

NO2 nitrite

NO3 nitrate

NOI notice of intent

NOx nitrogen oxides

NPDES National Pollutant Discharge Elimination System

NRCS Natural Resources Conservation Service

NY New York

OSWTS on-site wastewater treatment system

PA Pennsylvania

PA DEP Pennsylvania Department of Environmental Protection

PAR photosynthetically active radiation

PCS Permit Compliance System

PLW percent light through water

POTW publicly owned treatment works

PSC Principals’ Staff Committee

ppt parts per thousand (salinity)

RDA Residual Designation Authority

RESAC University of Maryland’s Regional Earth Science Applications Center

SAV submerged aquatic vegetation

SIP state implementation plan

SPARROW Spatially Referenced Regressions on Watershed Attributes

SSO sanitary sewer overflow

STAC Scientific and Technical Advisory Committee

TMDL total maximum daily load

TN total nitrogen

TP total phosphorus

TSS total suspended solids
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USC Upper Susquehanna Coalition

U.S.C. United States Code

USDA U.S. Department of Agriculture

VA Virginia

VA DEQ Virginia Department of Environmental Quality

VA DCR Virginia Department of Conservation and Recreation

WIP watershed implementation plan

WLA wasteload allocation

WQBELs water quality-based effluent limits

WQGIT Water Quality Group Implementation Team

WQS water quality standards

WV West Virginia

WV DEP West Virginia Department of Environmental Protection

WWTP wastewater treatment plant

yr year

z depth