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8-1 September 24, 2010

SECTION 8. WATERSHED IMPLEMENTATION PLAN 

EVALUATION AND DRAFT BACKSTOP 

ALLOCATIONS

This section describes the process by which EPA applied the basinwide and jurisdiction-wide 

allocations described in Section 6 and developed draft segment-specific or sector-specific 

allocations. This section specifically describes the methodology that EPA used to evaluate the 

draft Phase I WIPs, the process EPA used to develop the backstop allocations, the results of 

EPA’s evaluation of the draft Phase I WIPs, and the resultant jurisdiction-specific allocations. 

Links to each jurisdiction’s draft Phase I WIP can be found at www.epa.gov/chesapeakebaytmdl.

The overall process of developing the Chesapeake Bay TMDL had four steps:

1. EPA defined 19 major river basin and jurisdictional loading allocations—July 1, 2010 for 

nitrogen and phosphorus; August 13, 2010 for sediment. The methodology that EPA used 

in defining these allocations is described in detail in Section 6.

2. Each jurisdiction developed a draft Phase I WIP that described how it would achieve the 

target allocations for nitrogen, phosphorus, and sediment assigned to the jurisdictions and 

basins in step 1.

a. Using data submitted by the jurisdictions either as input decks or spreadsheets that 

EPA processed through Scenario Builder and the Chesapeake Bay Watershed 

Model, each jurisdiction developed suballocations to assign to individual, 

significant wastewater treatment plant (WWTP) point sources; aggregate 

nonsignificant WWTPs, stormwater, and CAFO point sources; and nonpoint 

source sectors draining to each of the 92 segments of the Chesapeake Bay and its 

tidal tributaries.

b. Within their WIPs, jurisdictions also proposed strategies and permit conditions to 

achieve the suballocations, consistent with the expectations that EPA 

communicated in its letters of September 11, 2008, November 4, 2009, and 

December 29, 2009, as well as the Guide for EPA’s Evaluation of Phase I 

Watershed Implementation Plans issued April 2, 2010. Those expectations are 

further described in Section 7.

c. The jurisdiction’s proposed allocations and strategies formed the basis of its draft 

Phase I WIP delivered to EPA on September 1, 2010 (September 3 for Virginia).

3. EPA evaluated the jurisdictions’ suballocations and draft Phase I WIPs to determine 

whether they met the jurisdiction-wide and major river basin allocations, included 

adequate detail to ensure that NPDES permits are consistent with the assumptions of the 

WLAs, and provided sufficient reasonable assurance that nonpoint source reductions 

could be achieved and maintained through credible and “enforceable or otherwise 

binding” strategies. That evaluation and its results are described in detail here in Section 

8.
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4. EPA considered the results of the evaluation in its decision to establish an allocation 

scenario to complete a draft Chesapeake Bay TMDL for public review, including 

allocations for each of the 92 Bay segments, using suballocations provided in the draft 

Phase I WIPs, alternative EPA backstop allocations, or a combination of the two. Tables 

showing the 92 Bay segment-specific and sector-specific allocations of the Chesapeake 

Bay TMDL are in Section 9.

Because of significant deficiencies in the draft Phase I WIPs to identify and resolve gaps in 

authority, staff, funding, and accountability systems, EPA determined that none of the 

jurisdictions’ draft Phase I WIPs provided sufficient reasonable assurance that programs would 

be implemented to achieve the necessary pollutant load reductions. Six of the seven jurisdictions 

did not reach their jurisdiction-wide allocation targets for nitrogen, phosphorus, and sediment 

(only Maryland met the jurisdiction-wide target allocations for all three pollutants); no 

jurisdiction met its target allocations for each pollutant for each major basin within its 

jurisdiction.

Therefore, consistent with its December 29, 2009, letter to the jurisdictions, EPA is establishing 

draft backstop allocations that incorporate those parts of the jurisdictions’ draft Phase I WIP 

allocation proposals determined to be acceptable and replace some allocations proposed by 

jurisdictions; EPA is also providing a finer level of detail for allocations in headwater 

jurisdictions; and finally, EPA is making additional point source reductions and, in some cases, 

nonpoint source reductions, as necessary to achieve Bay TMDL nitrogen, phosphorus, and 

sediment allocations.

This section describes the methodology by which EPA evaluated the jurisdictions’ draft Phase I 

WIPs, the process for developing the backstop allocations, the WIP evaluation findings and the 

resulting backstop allocations EPA established for each jurisdiction.

8.1 WIP Evaluation Methodology

A team of EPA source sector experts, together with the EPA staff assigned to each of the seven 

watershed jurisdictions, conducted a rigorous, systematic evaluation of each jurisdiction’s draft 

Phase I WIP. EPA evaluated each draft Phase I WIP on the basis of how well the jurisdiction met 

the expectations articulated in EPA’s November 4, 2009, WIP expectations letter and how well 

the jurisdiction addressed each of the eight elements set out in the April 2, 2010, Guide for 

Evaluation of Phase I Watershed Implementation Plans.

In conducting the evaluations, EPA addressed two primary questions: (1) did the jurisdiction 

meet its target allocations for nitrogen, phosphorus, and sediment both jurisdiction-wide and in 

each of the major river basins to ensure attainment of each of the Chesapeake Bay WQS in all 92 

segments of the Bay and its tidal tributaries; and (2) did the jurisdiction provide sufficient 

reasonable assurance that it would implement a comprehensive approach to achieve necessary 

nutrient and sediment reductions, including documentation that nonpoint source controls will be 

achieved and maintained and permitting programs will result in point source reductions, with 

emphasis on achieving a 60 percent reduction in loadings by 2017.
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To evaluate the first question and determine whether a jurisdiction met its nitrogen, phosphorus, 

and sediment target allocations, EPA evaluated whether a jurisdiction met all three allocation 

targets in all basin-jurisdictions in the jurisdiction, and, if the jurisdiction missed them, EPA 

considered the degree to which it missed them. Table 8-1 summarizes the thresholds of the four 

evaluation tiers.

Table 8-1. Thresholds for four evaluation tiers for assessing whether a jurisdiction met its 

nitrogen, phosphorus, and sediment target allocations

Tier 1. Met all

target allocations

Tier 2. Met most 

target allocations

Tier 3. Met some 

target allocations

Tier 4. Met few 

target allocations

Threshold Draft Phase I WIP 

is at or below 

target allocations 

for all three 

pollutants both 

jurisdiction-wide 

and in all basins 

Draft Phase I WIP met 

jurisdiction-wide target 

allocations for all 

three pollutants but 

did not meet 

basinwide target 

allocations for at least 

one pollutant in at 

least one basin; or

Draft Phase I WIP did 

not meet the 

jurisdiction-wide target 

for one or more 

pollutants but not to 

such a degree as 

would cause a 

violation of WQS 

Draft Phase I WIP 

did not meet 

jurisdiction-wide 

target allocations 

for one or more 

pollutants but 

exceeded the 

target by less than 

10%

Draft Phase I WIP 

did not meet 

jurisdiction-wide 

target allocations 

for one or more 

pollutants and 

exceeded the 

target(s) by more 

than 10%

To evaluate the second question and determine whether a jurisdiction provided sufficient 

reasonable assurance through enforceable or otherwise binding commitments to implement 

necessary controls, EPA evaluated each major pollutant source sector on a number of criteria, 

including those factors set out in the April 2, 2010, WIP guide. Table 8-2 summarizes the 

thresholds for placing a major pollutant source sector—wastewater, stormwater, and 

agriculture—in one of four tiers.
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8-4 September 24, 2010

Table 8-2. Thresholds for the four Phase I WIP evaluation tiers for the reasonable assurance 

assessment

Tier 1. Met all 

expectations

Tier 2. Met most 

expectations

Tier 3: Met some 

expectations

Tier 4: Met few 

expectations

Threshold Addresses all the 

major reasonable 

assurance 

categories 

identified in the 

November 4, 

2009, letter and 

the April 2, 2010, 

WIP evaluation 

guide.

Identifies and 

provides reasons 

for current gap.

Spells out 

numbers/percent of 

inspections and 

results.

Schedule provided 

for potential actions.

Evidence of or 

commitment to 

clear permit 

conditions.

Contingencies in 

place for high risk/ 

highly improbable 

actions.

Proposals for 

attaining additional 

resources.

Schedule to further 

flesh out details 

over time.

If any of the following 

occur:

Does not address 

known, significant 

programmatic 

shortfalls and gaps.

No discussion of 

compliance.

No schedule for 

potential actions.

Does not inform 

permit conditions.

Proposals not 

feasible or do not 

address significant 

gaps.

No commitment/ 

schedule to develop 

details over time.

Major discrepancies 

between type and 

extent of practices in 

WIP document and 

input deck.

If many of the 

following occur:

Does not address 

known, significant 

programmatic 

shortfalls and gaps.

No discussion of 

compliance.

No schedule for 

potential actions.

Does not inform 

permit conditions.

Proposals not 

feasible or do not 

address significant 

gaps.

No commitment/ 

schedule to develop 

details over time.

Major discrepancies 

between type and 

extent of practices in 

WIP document and 

input deck.

After evaluating the two key issues, EPA applied a uniform process to determine whether, and if 

so, to what degree, to apply backstop allocations. In developing the backstop allocations, EPA 

fully considered the following:

The jurisdiction’s tier placement resulting from EPA’s evaluation of whether and to what 

extent the jurisdiction met its target allocations for nitrogen, phosphorus, and sediment.

The jurisdiction’s tier placement resulting from EPA’s evaluation of whether and to what 

extent the jurisdiction demonstrated sufficient reasonable assurance.

Whether the proposed WLAs in the jurisdiction’s draft Phase I WIP were consistent with 

EPA’s definition of point source loads and could be achieved through implementation of a 

permitting program.

EPA’s own internal reasonable assurance that the Agency could ensure achievement of the 

backstopped point source reductions through enhanced program oversight, permit objections, 

compliance assurance, and enforcement actions.

8.2 WIP Evaluation Results

Where EPA determined that a jurisdiction did not meet its allocation target, EPA applied an 

allocation-target-based backstop allocation. Where EPA determined that a jurisdiction met its 

allocation target but did not provide adequate reasonable assurance, EPA applied a reasonable 

assurance-based backstop allocation. Where EPA determined that a jurisdiction neither met its 

target allocation nor provided adequate reasonable assurance, EPA applied both forms of 
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8-5 September 24, 2010

backstop allocation. After applying all backstop allocations that EPA determined were necessary, 

EPA ran the combination of specific practices and allocations through the Scenario Builder, 

Watershed Model and WQSTM to ensure that the allocations provided in the Chesapeake Bay 

TMDL would result in the attainment of WQS.

8.2.1 Target Nutrient/Sediment Allocation Gaps

Each watershed jurisdiction with the exception of Maryland failed to meet at least one of its 

jurisdiction-wide nitrogen, phosphorus, and sediment target allocations. Maryland failed to meet 

its target allocations for some major river basins, however. Other jurisdictions also failed to meet 

their target allocations for nitrogen, phosphorus, and sediment for some river basins. Table 8-3

shows whether each jurisdiction met its jurisdiction-wide target allocations for nitrogen, 

phosphorus, and sediment. Table 8-4 shows whether each jurisdiction met its basinwide target 

allocations for nitrogen, phosphorus, and sediment.

Table 8-3. Comparison of the nitrogen, phosphorus, and sediment jurisdiction-wide allocations in 

the jurisdictions’ draft Phase I WIPs with the target allocations for each pollutant

TN

(mpy)

TP

(mpy)

TSS

(mpy)

Juris. WIP Targeta % off 

target

WIP Target % off 

target

WIP Target -

low end 

of range

Target -

high end 

of range

% off 

targetb

DC 2.20 2.32 -5% 0.12 0.12 -3% 13.99 10.14 11.16 25%

DE 3.44 2.95 17% 0.28 0.26 8% 50.92 57.82 63.61 -20%

MD 39.09 39.09 0% 2.72 2.72 0% 1,222.49 1,116.16 1,227.78 0%

NY 9.48 8.23 15% 0.60 0.52 14% 269.07 292.96 322.26 -17%

PA 76.66 76.77 0% 3.03 2.74 11% 2,117.24 1,902.51 2,092.76 1%

VA 56.58 53.40 6% 5.79 5.41 7% 2,374.61 2,446.14 2,690.75 -12%

WV 5.51 4.68 18% 0.70 0.75 -6% 366.67 240.68 264.75 38%

a. Target numbers are based on proposed amended WQS.

b. Calculated on the basis of the high end of the range

c. Any discrepancy is from rounding figures.
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Table 8-4. Comparison of the nitrogen, phosphorus, and sediment basinwide allocations in the 

jurisdictions’ draft Phase I WIPs with the basinwide target nutrient (in millions of pounds per year

[mpy]) and sediment allocations (mpy) for 2025

TN

(mpy)

TP

(mpy)

TSS

(mpy)

Major river 

basin

Juris. WIP Targeta % off 

target

WIP Target % off 

target

WIP Target % off 

targetb

Potomac DC 2.20 2.32 -5% 0.12 0.12 -3%c

13.99 11.16 25%

Eastern Shore DE 3.44 2.95 17% 0.28 0.26 8% 50.92 63.61 -20%

Eastern Shore MD 10.26 9.71 6% 1.02 1.09 -7% 169.70 182.47 -7%

Patuxent MD 2.81 2.85 -1% 0.24 0.21 13% 106.69 90.12 18%

Potomac MD 15.67 15.70 0% 0.90 0.90 0% 682.33 718.97 -5%

Susquehanna MD 1.18 1.08 10% 0.05 0.05 1% 62.94 65.83 -4%

Western Shore MD 9.16 9.74 -6% 0.51 0.46 10% 200.83 170.38 18%

Susquehanna NY 9.48 8.23 15% 0.60 0.52 14% 269.07 322.26 -17%

Eastern Shore PA 0.27 0.28 -3% 0.01 0.01 -48% 23.62 23.25 2%

Potomac PA 4.51 4.72 -4% 0.39 0.42 -8% 254.71 243.22 5%

Susquehanna PA 71.86 71.74 0% 2.63 2.31 14% 1,838.50 1,825.88 1%

Western Shore PA 0.02 0.02 0% 0.00 0.00 0% 0.41 0.41 0%

Eastern Shore VA 1.29 1.21 7% 0.14 0.16 -14% 10.54 12.00 -12%

James VA 27.20 23.48 16% 2.85 2.34 22% 840.93 920.23 -9%

Potomac VA 17.09 17.46 -2% 1.31 1.47 -11% 741.21 891.08 -17%

Rappahannock VA 5.88 5.84 1% 0.91 0.90 2% 683.58 749.64 -9%

York VA 5.13 5.41 -5% 0.57 0.54 6% 98.33 117.80 -17%

James WV 0.02 0.02 19% 0.01 0.01 38% 28.00 16.65 68%

Potomac WV 5.48 4.67 18% 0.69 0.74 -7% 338.68 248.11 37%

TOTAL 192.97 187.45 13.23 12.52 6,415 6,673

a. Target numbers are based on proposed amended WQS.

b. Calculated on the basis of the high end of the range

c. Any discrepancy is from rounding figures.

8.2.2 Insufficient Reasonable Assurance

Because of significant deficiencies in plans presented to resolve gaps in authority, staff, funding 

and accountability systems, and on the basis of the criteria discussed below and EPA’s best 

professional judgment, EPA determined that none of the seven watershed jurisdictions’ draft 

Phase I WIPs provided adequate reasonable assurance that programs would be implemented to 

achieve reduction targets, including where significant reductions are projected in the regulated 

source sectors. The top reasons for insufficient reasonable assurance are the following:

No strategy for filling recognized staff, funding, legislative, or regulatory gaps.

Very few enforceable or otherwise binding commitments to achieve reductions from 

agricultural and stormwater pollutant source sectors. Specific examples include

No changes to state technical standards

No specific and enforceable commitments to building into MS4 permits and stormwater 

programs

No mention of requiring retrofits despite committing to reduce stormwater loads
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8-7 September 24, 2010

Discrepancies between programs and strategies described in the draft Phase I WIP and the 

specific level of practices committed to in the detailed WIP input deck (used for running the 

WIP practices through Scenario Builder and the Chesapeake Bay Watershed Model to 

determine the resultant nutrient and sediment loads delivered to the Bay).

Heavy reliance on trading to finance reductions and offset growth, but no commitment to 

adopt critical trading components such as clear baselines, liability, enforceability, tracking, 

and regulatory drivers.

No dates for key actions and program-building milestones.

8.2.3 Summary of Results of EPA Evaluation of Draft Phase I WIPs

The results of EPA’s evaluation of the jurisdictions’ draft Phase I WIPs can be summarized as 

follows:

Delaware:

Target Allocations: Tier 4—nitrogen 17 percent over target; phosphorus 8 percent over

target; sediment 20 percent under target

Reasonable Assurance: Tier 3—Met Some Expectations

District of Columbia

Target Allocations: Tier 2—nitrogen 5 percent under target; phosphorus 3 percent under 

target; sediment 25 percent over target

Reasonable Assurance: Tier 2—Met Most Expectations

Maryland

Target Allocations: Tier 2—nitrogen and phosphorus 0 percent under target statewide, 

though over and under in particular major river basins; sediment 0 percent under target

Reasonable Assurance: Tier 2—Met Most Expectations

New York

Target Allocations: Tier 4—nitrogen 15 percent over target; phosphorus 14 percent over

target; sediment 17 percent under target

Reasonable Assurance: Tier 3—Met Some Expectations

Pennsylvania

Target Allocations: Tier 3—after adjusting for Bay Watershed Model and draft Phase I 

WIP discrepancies in the onsite wastewater treatment systems and forest lands source 

sectors—nitrogen 40 percent under target; phosphorus 11 percent over target; sediment 1

percent over target

Reasonable Assurance: Tier 3—Met Some Expectations

Virginia

Target Allocations: Tier 3—nitrogen 6 percent over target; phosphorus 7 percent over target; 

sediment 12 percent under target

Reasonable Assurance: Tier 3—Met Some Expectations
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8-8 September 24, 2010

West Virginia

Target Allocations: Tier 4—nitrogen 18 percent over target; phosphorus 6 percent under

target; sediment 38 percent over target

Reasonable Assurance: Tier 3—Met Some Expectations

Table 8-5 shows the results of EPA’s evaluation of both key aspects of the jurisdictions’ draft 

Phase I WIPs in table format.

Table 8-5. Draft Phase I WIP evaluation ratings by jurisdiction by the three major pollutant loading 

source sectors

Jurisdiction

Reasonable assurance for gap-filling strategies

2025 WIP

allocation

numbers

Tier 1: Met all 

expectations

Tier 2: Met 

most 

expectations

Tier 3: Met 

some 

expectations

Tier 4: Met 

few 

expectations

DC SW Tier 2

WW Tier 2 Tier 2

Overall Tier 2

DE Ag Tier 3

SW Tier 3 Tier 4

WW Tier 2

Overall Tier 3

MD Ag Tier 2

SW Tier 2 Tier 2

WW Tier 2

Overall Tier 2

NY Ag Tier 3

SW Tier 3 Tier 4

WW Tier 3

Overall Tier 3

PA Ag Tier 3

SW Tier 4 Tier 4

WW Tier 3

Overall Tier 3

VA Ag Tier 3

SW Tier 3 Tier 3

WW Tier 2

Overall Tier 3

WV Ag Tier 3

SW Tier 2 Tier 4

WW Tier 3

Overall Tier 3

8.3 Draft Backstop Allocations

EPA established backstop allocations in which EPA determines that the draft Phase I WIP did

not achieve the jurisdiction basin target allocation or where the draft Phase I WIP did not provide 

adequate reasonable assurance that the LA reductions can be achieved by the nonpoint sources. 
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8-9 September 24, 2010

Backstop allocations are established to fill a loading shortfall in the jurisdiction’s draft Phase I

WIP or to increase the level of reasonable assurance that the overall TMDL pollutant cap will be 

achieved.

8.3.1 Methodology for Backstop Allocations

Where EPA determined that a jurisdiction did not meet its target allocations or did not provide 

adequate reasonable assurance, EPA calculated that jurisdiction’s draft backstop allocations by 

relying on the adequate portion(s) of the jurisdiction’s draft Phase I WIP, where possible, and 

supplementing any remaining shortfall or insufficient amount of reasonable assurance with its 

allocation adjustments and determinations of reasonable assurance to achieve the necessary 

reductions.

EPA determined each jurisdiction’s backstop allocation for sediment on the basis of whether and 

to what extent the jurisdiction met the target allocation range for sediment provided on August 

13, 2010. EPA ran the BMPs assumed within the backstop allocations through Scenario Builder 

and the Chesapeake Bay Program Watershed Model. EPA then compared the sediment outputs 

from that scenario run to the target allocation range for sediment that it communicated to the 

jurisdictions on August 13, 2010. Where a jurisdiction more than met the target allocation (i.e., 

came in under the low end of the target range), EPA assigned that jurisdiction the low end of the 

target allocation range. Where a jurisdiction did not meet its target allocation (i.e., came in above 

the high end of the target range), EPA assigned that jurisdiction the high end of the target 

allocation range. Where a jurisdiction met its target allocation (i.e., fell within the low and high 

ends of the target range), EPA assigned that jurisdiction the amount that resulted from its draft 

Phase I WIP.

Although a number of backstop options existed, EPA primarily relied on decreasing the WLAs 

to the point sources. EPA did that because point sources are the pollutant discharging source 

sector for which the CWA gives EPA the clearest authority to ensure implementation of needed 

controls. Because EPA has determined that the jurisdictions’ draft Phase I WIPs do not achieve 

the target allocations or do not provide adequate reasonable assurance, EPA is establishing draft

backstop allocations that reduce the point source loadings as necessary to compensate for the 

deficiencies EPA identified in the reasonable assurance components of the jurisdictions’ draft 

Phase I WIPs addressing nonpoint source reductions.

Another aspect of the backstop allocations that EPA established for the nontidal jurisdictions of 

Pennsylvania, New York, and West Virginia is to make finer-scale allocations than those 

included in the draft Phase I WIPs provided by the nontidal jurisdictions. EPA stated in its 

November 4 and December 29, 2009, letters to the jurisdictions that it would do so by 

establishing draft individual and aggregate, rather than gross, WLAs and LAs for the nontidal 

jurisdictions if their draft Phase I WIPs did not provide adequate reasonable assurance. That

finer-scale allocation sets individual WLAs for the significant municipal and industrial 

wastewater discharging facilities and sector-specific aggregate WLAs for stormwater, CAFOs, 

and nonsignificant municipal and industrial wastewater discharging facilities. EPA is 

establishing the finer-scale draft allocations to provide permit writers with enough information to 

issue and renew NPDES permits consistent with the Chesapeake Bay TMDL WLAs. Those 
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8-10 September 24, 2010

allocations are at the same scale as those made to the tidal jurisdictions of Delaware, Maryland, 

Virginia, and the District of Columbia.

In part on the basis of the assumptions described in Section 8.3.2 below, EPA developed four 

levels of backstop allocations (Table 8-6). The allocations are based on assumed future EPA 

actions regarding regulated point source discharges over which EPA has current CWA legal 

authority (e.g., permitting and enforcement) certain assumptions regarding certain unregulated 

stormwater and animal feeding operations, and additional appropriate adjustments to nonpoint 

source loads necessary to meet the jurisdictions’ target nitrogen, phosphorus, and sediment 

allocations. In some cases, the backstop allocations increase the LAs for nonpoint source sectors 

for which the jurisdictions provided insufficient demonstrations of reasonable assurance.

For purposes of making allocations to stormwater and AFO/CAFO sources not regulated by the 

NDPES permit program but that could become NPDES regulated facilities (either through 

residual designation authority or other mechanisms), EPA has included those categories of 

sources in the draft WLA portion of the TMDL consistent with EPA guidance, Establishing 

Total Maximum Daily Loads (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources 

and NPDES Permit Requirements Based on Those WLAs, dated November 22, 2002 (EPA 

11/22/2002). EPA has authority to designate such nonregulated stormwater sources as regulated 

by NPDES authorities. See section 402(p)(2)(E) and (6) and 40 CFR 122.26(a)(9)(i)(C)(D). EPA 

also has authority to designate AFOs as CAFOs as set forth in 40 CFR 122.23(c).

For stormwater, EPA has decided to include in its draft WLA allocation the unregulated 

stormwater point sources along with NPDES regulated sources. For point sources already 

covered by NPDES permits, reasonable assurance is provided through EPA’s authority to issue 

or oversee NPDES permitting that adequately assures implementation of the additional waterquality-based controls on those sources necessary to achieve the levels of pollutant reduction 

specified in Table 8-6. For those sources not currently regulated by NPDES permits, EPA 

establishes this backstop allocation on the basis of two assumptions: (1) currently unregulated 

sources will become regulated under the NPDES permit program through appropriate 

designation/rulemaking/ permits; and (2) the aggregate projected load reductions (based on 

NPDES effluent controls consistent with the WLA) will result in those needed reductions. 

Additional controls for currently unregulated sources could be imposed only after the source is 

designated and after a final NPDES permit is issued to cover the source with the added controls. 

The inclusion of currently unregulated sources in the WLA by itself does not constitute a 

designation or regulatory action to include such sources in the NPDES program. The TMDL is a 

plan, not a regulatory determination to change a source’s legal status. As with any NPDES 

permitting or rulemaking decision, applying new controls or designations must be consistent 

with applicable procedural and substantive requirements.

For the Bay TMDL, EPA believes that the assumptions underlying its backstop allocations are 

reasonable according to EPA’s existing authority under the CWA and EPA’s commitment to 

ensure and track implementation of actions necessary to restore the Bay by 2025 consistent with 

Executive Order 13508 (FLCCB 2010). EPA has described in the Federal Strategy and 

elsewhere, including in its May 2010 settlement agreement resolving the Chesapeake Bay 

Foundation’s lawsuit, its plans for rulemaking addressing nutrient and sediment pollution in the 
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8-11 September 24, 2010

Bay from both the stormwater and CAFO sectors and for tracking and ensuring progress in 

meeting the TMDL’s nutrient and sediment targets.

The same rationale described above also applies to making backstop allocations to the 

AFO/CAFO sector. For those CAFO facilities already under NPDES permit coverage, EPA has 

broad authority to ensure that the necessary controls are included to implement the Bay TMDL. 

As with stormwater point sources, in its backstop allocations EPA has included currently 

unregulated AFOs in the WLA portion of the TMDL. For such sources, EPA’s draft backstop 

allocation is based on two assumptions: (1) currently unregulated sources will become regulated 

under the NPDES permit program some day through appropriate 

designation/rulemaking/permits; and (2) the projected sector wasteload reductions (based on 

NPDES effluent controls consistent with the WLA) will result in those needed reductions. 

Additional controls would be imposed only after the source is designated and after it is given a 

permit with the added controls. The inclusion of currently unregulated sources in the WLA by 

itself does not constitute a designation or regulatory action to include such sources in the NPDES 

program. The TMDL is a plan, not a regulatory determination to change a source’s legal status. 

As with any NPDES permitting or rulemaking decision, applying new controls or designations 

must be consistent with applicable procedural and substantive requirements.

Table 8-6. Definitions of the backstop allocation options that EPA considered to replace 

jurisdictions’ WIP point source allocations

Option Source category

Backstop WWTP Stormwater AFO Production Area

None As proposed in jurisdiction’s draft Phase I WIP

Minor No changes to point source WLAs that would change assumed NPDES permit 

conditions. Adjustments to allocations, primarily nonpoint source LAs, to meet July 1 

and August 13 nutrient and sediment allocations. 

Moderate -

Similar to 

most 

aggressive 

jurisdiction’s 

WIP 

proposal for 

a sector

Effluent concentrations 

of 4 mg/L TN, 0.3 mg/L 

TP at design flow.

Construction: 100% Erosion & 

Sediment Control

MS4: 50% of urban MS4 

lands meet aggressive 

performance standard 

through retrofit/ 

redevelopment; 50% of 

unregulated land treated as 

regulated, so that 25% of 

unregulated land meets 

aggressive performance 

standard; designation as 

necessary.

Waste management, 

barnyard runoff control, 

mortality composting.

Precision feed 

management for all 

animals.

Same standards apply to 

currently unregulated 

AFOs not subject to 

CAFO permits EXCEPT 

no feed management on 

dairies; designation as 

necessary.

High Limit of Technology 

concentrations of 3 mg/L 

N and 0.1 mg/L P at 

design flow.

Same as Moderate. Same as Moderate.

Full Limit of Technology

concentrations of 3 mg/L 

N and 0.1 mg/L P at 

current flow.

Same as Moderate. Same as Moderate.
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8.3.2 Assumptions Supporting the Draft Bay TMDL Backstop 

Allocations

EPA has established draft WLAs for point sources and draft LAs for nonpoint sources based in 

part upon the assumption that certain nutrient and sediment controls are implemented on a 

certain percentage of available land. Over time, implementing nutrient and sediment controls 

could involve a combination of (a) different practices; (b) implementation in different locations; 

or (c) implementation at different implementation rates so long as an equivalent or greater 

nutrient and sediment reduction occurs within the portion of the watershed draining to a 

particular tidal segment of the Chesapeake Bay.

This section summarizes the assumptions that are incorporated into the Chesapeake Bay TMDL 

allocations, and the allocations proposed by the seven watershed jurisdictions in their draft Phase 

I WIPs and the full backstop allocations that EPA might apply in the final Chesapeake Bay 

TMDL. EPA regulations require that NPDES permits be consistent with requirements and 

assumptions of WLAs. 40 CFR 122.44(d)(1)(vii)(B). The jurisdictions’ draft Phase I WIPs and 

EPA’s full backstop allocations bookend EPA proposed draft backstop allocations featured in the

Bay TMDL.

Nonpoint Sources

The draft Phase I WIPs provided the starting point for EPA’s consideration and development of 

allocation scenarios. EPA assumed for purposes of the evaluation that jurisdictions will

implement the practices that will result in the same or greater nutrient and sediment controls as 

provided in their draft Phase I WIP scenario input decks and as evaluated by the Bay model 

outputs. EPA also evaluated whether the controls provided an adequate demonstration of 

reasonable assurance that the load reductions would be achieved. As necessary, such as where 

necessary to satisfy the requirements of reasonable assurance, EPA has adjusted the nonpoint 

source allocations to ensure attainment of the nitrogen, phosphorus, and sediment allocations 

within the 19 basin-jurisdictions in the Chesapeake Bay watershed. EPA will assess 

jurisdictions’ progress toward meeting those LAs through the final Phase I WIPs, the Phase II 

and Phase III WIPs, and the 2-year milestones. EPA also will consider whether to take 

appropriate federal backstop actions, as detailed in its letter of December 29, 2009, to the 

Chesapeake Bay watershed jurisdictions, to ensure that adequate progress is made toward 

achieving and maintaining the nonpoint source load reductions.

Point Sources—Minor Backstop Allocations (Maryland, District of Columbia)

EPA is establishing minor backstop allocations for certain Maryland point sources in the

wastewater, stormwater, and CAFO sectors, and it established minor backstop allocations for the 

District of Columbia in the wastewater and urban stormwater sectors. This means that EPA is 

making smaller WLAs to those sectors and will require some adjustment to NPDES permit 

effluent controls.

Maryland

Maryland’s draft Phase I WIP had only minor deficiencies for demonstrating reasonable 

assurance that it could meet its nutrient and sediment allocations. Therefore, EPA determined 

that point source allocations in Maryland’s draft Phase I WIP were adequate and appropriate as 
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8-13 September 24, 2010

described below. EPA’s backstop allocation for Maryland follows the draft Phase I WIP 

allocation scheme for point sources.

Wastewater

Maryland’s WLAs for WWTPs are based on

Significant Municipal WWTPs: implementation of Enhanced Nutrient Removal standards 

that treat wastewater to 4 mg/L TN and 0.3 mg/L TP

Significant Industrial WWTPs: continued retrofits and optimization to meet Maryland’s 

Tributary Load cap for such facilities

Nonsignificant Municipal WWTPs: implementation of Maryland’s Tributary Strategy 

nutrient reduction goals

Nonsignificant Industrial WWTPs: reduce nutrient loads by 26 percent by 2017

Stormwater

Maryland’s draft Phase I WIP provides that 50 percent of the state’s urban acres developed 

before 1985 in Phase I MS4 jurisdictions will be redeveloped or retrofit by 2020 to a 25 percent 

stormwater efficiency. Forty percent of the state’s urban acres developed before 1985 in Phase II 

MS4 jurisdictions and smaller, non-MS4 areas will be redeveloped or retrofit by 2020 to a 25 

percent stormwater efficiency. If those retrofit and redevelopment requirements are not sufficient 

to have practices in place by 2020 to meet Maryland’s stormwater WLAs, EPA assumes that 

Maryland will increase these retrofit and redevelopment requirements accordingly.

CAFOs

Maryland’s draft Phase I WIP provides that permitted CAFOs will fully implement 

comprehensive nutrient management plans that include both nutrient management and soil and 

water conservation plans. Maryland’s draft Phase I WIP also indicates that state and federal costshare dollars will be used to implement heavy-use poultry area concrete pads, livestock and 

poultry waste structures, manure transport, runoff control systems, phytase additions to diet to 

manage nutrient levels in manure, and mortality composters at rates specified in the draft Phase I 

WIP. If cost-share programs do not achieve those implementation rates, EPA assumes that 

Maryland will revise its technical standards and CAFO comprehensive nutrient management 

plan requirements to require those controls. Depending on EPA’s review of Maryland’s CAFO 

technical standards that is underway, EPA may require additional changes to the standards to 

ensure that they are protective of water quality in the tidal waters of Chesapeake Bay and its 

tributaries and nontidal local waters.

District of Columbia

Almost all sources of nutrients and sediment in the District of Columbia are covered by NPDES 

permits issued by EPA. Because the jurisdiction’s draft Phase I WIP does not meet the District of

Columbia’s target sediment allocation, EPA is making a smaller sediment allocation that will 

ensure protection of WQS. EPA’s NPDES permit authority and the requirement that NPDES 

effluent limits be consistent with the WLAs provide reasonable assurance that the smaller 

allocations will be met. The following section describes the nutrient and sediment controls that 
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8-14 September 24, 2010

are assumed within the District of Columbia’s WLAs. Compliance with effective NPDES permit 

effluent limits is assumed.

Wastewater

WLAs for wastewater in the District of Columbia are based on the assumption that limits in 

NPDES permits issued by EPA for Blue Plains WWTP and nonsignificant industrial wastewater 

dischargers are consistent with the WLAs in the TMDL and that DC WASA’s Long Term 

Control Plan for the CSS in the District of Columbia is fully implemented.

Urban Stormwater

WLAs for urban stormwater are based on the assumption that limits, controls and conditions in 

NPDES permits for municipal stormwater (the DC MS4 permit), industrial stormwater, and 

construction activities are consistent with the TMDL WLA and are implemented. 

Point Sources—Moderate Backstop Allocations (Virginia)

Wastewater

The WLAs for WWTPs receiving a moderate backstop allocation are based on the assumption 

that significant municipal WWTPs discharge loads equal to [(design flow) × (concentration)], 

where concentration is the lesser of Tributary Strategy concentrations, or 4 mg/L TN and 0.3 

mg/L TP. The maximum allowable concentration of 4 mg/L TN and 0.3 mg/L TP is equal to the 

most aggressive statewide WWTP commitment included in any of the jurisdictions’ draft Phase I 

WIPs. The WLAs for industrial WWTPs and nonsignificant WWTPs are assumed at the same 

level as the Virginia draft Phase I WIP allocations. Facilities may achieve these WLAs through 

appropriate upgrades or by purchasing credits from an offset or trading program established and 

operated consistent with the CWA, the Bay TMDL, and EPA guidance.

Urban Stormwater

In the urban lands covered by MS4 permits, the TMDL WLAs for jurisdictions receiving a 

moderate backstop (Virginia) make an assumption that the MS4 permit has controls sufficient to 

implement a performance standard equal to the nutrient and sediment reductions that would 

result from the following practices:

Regions with karst topography (low permeability); Coastal Plain Lowlands (groundwater).

o 50 percent of area—impervious cover reduction, e.g., cisterns and collections systems to 

capture rainwater for reuse 

o 30 percent of area—filtering practices e.g., sand filters, bioretention, dry wells, designed 

to reduce nitrogen by 40 percent, phosphorus by 60 percent, and sediment by 80 percent 

from a pre-BMP condition.

o 20 percent of area—infiltration practices e.g., infiltration trenches and basins, designed to

reduce nitrogen by 85 percent, phosphorus by 85 percent, and sediment by 95 percent 

from a pre-BMP condition.

Ultra-urban regions—defined as high- and medium-intensity land cover

o 50 percent of area—impervious cover reductions, e.g., cisterns and collections systems to 

capture rainwater for reuse.

o 30 percent of area—filtering practices, e.g., sand filters, bioretention, dry wells, designed 

to reduce nitrogen by 40 percent, phosphorus by 60 percent, and sediment by 80 

percent from a pre-BMP condition.
DRAFT Chesapeake Bay TMDL

8-15 September 24, 2010

o 20 percent of area—infiltration practices, e.g., infiltration trenches and basins, designed 

to reduce nitrogen by 85 percent, phosphorus by 85 percent, and sediment by 95

percent from a pre-BMP condition.

Other urban/suburban regions

o 10 percent of area—impervious cover reduction.

o 30 percent of area—filtering practices, e.g., sand filters, bioretention, designed to reduce 

nitrogen by 40 percent, phosphorus by 60 percent, and sediment by 80 percent from a 

pre-BMP condition.

o 60 percent of area—infiltration practices designed to reduce nitrogen by 85 percent, 

phosphorus by 85 percent, and sediment by 95 percent from a pre-BMP condition.

EPA assumes that the applicable MS4 performance standard applies to 50 percent of urban lands

through a combination of retrofit and redevelopment requirements. Jurisdictions may meet the 

WLA assumptions by: (a) applying a different set of practices that would result in equivalent 

nutrient and sediment reductions, (b) applying a more aggressive performance standard on a 

smaller percentage of urban lands included within the WLA, or (c) apply a less aggressive 

performance standard on a larger percentage of urban lands as long as the total nutrient and 

sediment reduction from the urban lands assumed to be within the WLA are equal to or greater 

than the reductions that are assumed within the WLA compared to a pre-BMP condition.

The stormwater WLA also assumes that 50 percent of urban lands that are not covered by MS4 

permits are treated like MS4 areas, meaning that 25 percent of unregulated stormwater (i.e., 50 

percent of 50 percent) is assumed to meet the performance standard for nutrient and sediment 

reductions described above. Before imposing such controls, it is assumed that (1) unregulated 

sources will someday be regulated under the NPDES permit program through appropriate 

designation/rulemaking/permits; and (2) the categories’ projected load reductions (based on 

NPDES effluent controls consistent with the WLA) will result in those needed reductions. As 

explained above in Section 8.3.1, additional controls would be imposed only after the source is 

designated or otherwise regulated by an NPDES permit, and after an effective NPDES permit 

coverage is established.

Finally, the stormwater WLA assumes that all areas subject to a construction general NPDES 

permit will implement erosion and sediment control practices that would result in a 25 percent 

reduction in nitrogen, a 40 percent reduction in phosphorus and sediment compared to a preBMP condition on bare, construction land.

If a jurisdiction’s draft Phase I WIP identifies that urban nutrient management or street sweeping 

will be implemented on urban lands, EPA assumes that these practices will also be applied to 

urban lands that contribute stormwater loads to the TMDL WLA, and these practices will be 

incorporated into MS4 permits, stormwater management plans, and ordinances as appropriate.

CAFOs

The CAFO WLA assumes that all AFO production areas are regulated with an NPDES permit 

with controls sufficient for a full treatment train of waste management, barnyard runoff control, 

and mortality composting. These practices are assumed to result in approximately 80 percent 

decrease in nutrient loads from production areas compared to a pre-BMP condition. Further, the 
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8-16 September 24, 2010

CAFO permitted facilities are assumed to have a control that all animals subject to CAFO permit 

conditions must receive feed management. EPA also assumes that all animals except dairies 

(e.g., poultry and swine) on AFOs that are not subject to CAFO permit conditions are assumed to

receive feed management. Poultry phytase is assumed to result in a 32 percent reduction in 

phosphorus content in manure compared to a pre-feed management condition; swine phytase is 

assumed to result in a 17 percent reduction in phosphorus content in manure compared to a prefeed management condition. Dairy feed management is assumed to result in a 24 percent 

reduction in nitrogen content and a 28 percent reduction in phosphorus content in manure 

compared to a pre-feed management condition.

Jurisdictions may meet the WLA assumptions by: (a) applying a different set of practices that 

would result in equivalent nutrient and sediment reductions, or (b) applying a more aggressive 

performance standard on a smaller percentage of AFO production areas as long as the total 

nutrient and sediment reduction from AFO production areas assumed to be within the WLA are 

equal to or greater than the reductions that are assumed within the WLA compared to a pre-BMP 

condition.

Point Sources—High Level Backstop Allocations (Delaware, New York, Pennsylvania, 

West Virginia)

Wastewater

EPA’s backstop WLAs for WWTPs receiving a high level backstop allocation are based on the 

assumptions that significant municipal WWTPs loads are equal to [(design flow) × 

(concentration)], where concentration is the current limit of technology, or 3 mg/L TN and 0.1

mg/L TP; and nonsignificant municipal WWTPs discharge loads equal to existing flows (design 

or current flows if design flow are not available) with TN at 8 mg/L and TP at 2 mg/L. The 

WLAs for industrial WWTPs make the assumption that the loads are reduced below the loads 

identified in the jurisdiction’s draft Phase I WIP at a rate equivalent to significant municipal 

WWTPs going from the WIP loading level to an E3 loading level (down to 3 mg/L TN and 0.1 

mg/L TP). The WLAs for nonsignificant industrial WWTPs make the assumption that the loads 

are reduced below those identified in the jurisdiction’s draft Phase I WIP at a rate equivalent to 

taking the significant municipal facilities from a No Action loading level to an E3 loading 

level—reducing TN from 18 to 3 mg/L and TP from 3 to 0.1 mg/L. NPDES permits for those 

types of facilities should be consistent with these assumptions. Facilities may achieve these 

WLAs through appropriate upgrades or by purchasing offsets from an offset or trading program 

established and operated consistent with the CWA, the Bay TMDL, and EPA guidance.

Urban Stormwater

The same assumptions as those described above for moderate backstop allocations for 

stormwater apply to a high level backstop WLAs for urban stormwater and the associated MS4 

permits.

CAFOs

The same assumptions as those described above for moderate backstop allocations for CAFO 

and AFO production areas are equally applicable to NPDES permits subject to a high level 

backstop WLA for CAFOs.
DRAFT Chesapeake Bay TMDL

8-17 September 24, 2010

Full Backstop Allocations

Although no jurisdiction received a full backstop allocation in the draft Chesapeake Bay TMDL, 

EPA is reserving the option to apply the full backstop allocations as described below in any of 

the seven watershed jurisdictions if EPA determines that a jurisdiction’s final Phase I WIP is

weaker than its draft Phase I WIP and requires additional backstop actions to ensure that point 

and nonpoint source reductions sufficient to meet WLAs and LAs are achieved and maintained. 

Some, but not necessarily all, of EPA’s potential full backstop actions are described below.

Wastewater

The WLAs for WWTPs under a full backstop allocation might assume that the loading for a 

significant municipal WWTPs is set equal to [(current flow) × (concentration)], where 

concentration is the limit of technology, or 3 mg/L TN and 0.1 mg/L TP. The assumption would 

be that current flow is calculated as the average current flow from 2007 to 2009. For facilities 

having no current flow data, the WLA would assume that the flows identified in the draft Phase I 

WIP flows would be adjusted by the average current flow adjustment rates by jurisdiction, which 

are calculated on the basis of facilities with current flows by jurisdiction and their total current 

flows/total WIP flows.

The WLAs for nonsignificant WWTPs could be set equal to current or adjusted flows with TN at 

8 mg/L and TP at 2 mg/L. The WLAs for industrial WWTPs could be calculated at a level where 

the reduction rates for significant industrial WWTPs by jurisdiction are equivalent to the 

significant municipal WWTP reduction from WIP to E3 (3 mg/L TN and 0.1 mg/L TP) and the 

reduction rates for nonsignificant industrial plants are equivalent to municipal reduction from No 

Action to E3 (TN from 18 to 3 mg/L and TP from 3 to 0.1 mg/L). The WLAs also could assume 

that the calculated industrial loads would then be adjusted by their current flows over WIP flows 

to get the full backstop allocations for industrial WWTPs. Facilities may achieve these WLAs 

through appropriate upgrades or by purchasing offsets from an offset or trading program 

established and operated consistent with the CWA, the Bay TMDL, and EPA guidance.

Stormwater

The same assumptions as those described above for moderate backstop allocations for 

stormwater would apply to a full backstop allocations for urban stormwater.

CAFOs

The same assumptions as those described above for moderate backstop allocations for CAFO 

and AFO production areas would apply to a full backstop allocation scenario for CAFOs.

8.3.3 Summary of Backstop Allocations

On the basis of EPA’s evaluations of the three major pollution source sectors combined with the 

nitrogen, phosphorus, and sediment allocation gaps illustrated in Tables 8-3 and 8-4, EPA 

assigned a draft backstop allocation according to the assumptions detailed above for each of the 

seven watershed jurisdictions (Table 8-7).

The draft Phase I WIP submissions contained enough of the expected information that no 

jurisdiction received a full backstop allocation; however, EPA reserves its authority to apply full 

backstop allocations if EPA determines that a jurisdiction’s final Phase I WIP is weaker than its 
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8-18 September 24, 2010

draft Phase I WIP or otherwise fails to meet expectations. By contrast, if EPA determines that the 

jurisdictions’ final Phase I WIPs meet all target allocations and demonstrate adequate reasonable 

assurance, EPA may decide to reduce or eliminate backstop allocations.

In its December 29, 2009, letter to the jurisdictions, EPA outlined additional possible federal 

actions it could take (USEPA 2009d) (see Section 7.2.4). In correspondence directed individually 

to each jurisdiction providing detailed feedback on the evaluation of the draft Phase I WIPs, EPA 

will communicate its intent to pursue additional federal actions if EPA determines that the 

respective jurisdiction’s final Phase I WIP, Phase II WIP, and 2-year milestones do not provide 

sufficient reasonable assurance that implementation will occur as described their plans.

Table 8-7. Summary of backstop allocations applied to the seven watershed jurisdictions in 

developing the draft Bay TMDL WLAs and LAs

Jurisidiction Minor Moderate High Full

Delaware

District of Columbia

Maryland

New York

Pennsylvania

Virginia

West Virginia

Delaware:

Nitrogen: 2.95 mpy; phosphorus 0.26 mpy; sediment 57.82 mpy.

It is not possible to meet Delaware’s nitrogen allocation by implementing the most 

aggressive point source controls. Therefore, EPA assumed additional nonpoint source 

reductions from the agriculture sector and will ensure that the reductions are achieved 

through additional federal backstop actions, as described in EPA’s letter of December 29, 

2009, as necessary.

High-level backstop allocations for Delaware point sources.

District of Columbia

Nitrogen: 2.32 mpy; phosphorus 0.12 mpy; sediment 11.16 mpy.

Minor backstop allocation to meet sediment allocation. EPA can ensure that all allocations, 

including sediment, are met through the NPDES permits issued in the District.

Maryland

Nitrogen: 39.09 mpy; phosphorus 2.72 mpy; sediment 1,175.47 mpy.

Minor backstop allocations to meet and nitrogen, phosphorus, and sediment allocations in 

each of Maryland’s five major river basins.

New York

Nitrogen: 8.23 mpy; phosphorus 0.52 mpy; sediment 292.96 mpy.

High level backstop allocations for New York point sources.
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8-19 September 24, 2010

It is not possible to meet New York’s nitrogen allocation by implementing the most 

aggressive point source controls. Therefore, EPA assumed additional nonpoint source 

reductions from the agriculture sector and will ensure that the reductions are achieved 

through additional federal backstop actions, as described in EPA’s letter of December 29, 

2009, as necessary.

Finer-scale WLAs and LAs (same level of detail as the tidal jurisdictions) to help ensure that 

NPDES permits will be consistent with Chesapeake Bay TMDL WLAs.

Pennsylvania

Nitrogen: 76.77 mpy; phosphorus 2.74 mpy; sediment 2,013.62 mpy.

High-level backstop allocations for Pennsylvania point sources.

Finer-scale WLAs and LAs (same level of detail as tidal jurisdictions) to help ensure that 

NPDES permits will be consistent with Chesapeake Bay TMDL WLAs. Excess loads from 

reducing WWTP allocations distributed back to forest, onsite wastewater treatment systems 

and agriculture source sectors.

Virginia

Nitrogen: 53.40 mpy; phosphorus 5.41 mpy; sediment 2,469.35 mpy.

Moderate backstop allocations for Virginia point sources. Excess loads from reducing 

WWTP allocations distributed back to urban stormwater, onsite wastewater treatment 

systems, and agriculture source sectors.

West Virginia

Nitrogen: 4.68 mpy; phosphorus 0.75 mpy; sediment 264.76 mpy.

High-level backstop allocations for West Virginia point sources.

It is not possible to meet West Virginia’s nitrogen and sediment allocations by implementing 

the most aggressive point source controls. Therefore, EPA assumed additional nonpoint 

source reductions from the agriculture sector and will ensure that those reductions are 

achieved through additional federal backstop actions, as described in EPA’s letter of 

December 29, 2009, as necessary.

Finer-scale WLAs and LAs (same level of detail as tidal jurisdictions) to help ensure that 

NPDES permits will be consistent with Chesapeake Bay TMDL WLAs.

The draft proposed backstop allocations for nitrogen, phosphorus, and sediment listed above, 

which are based on proposed amended WQS, also are presented in Table 8-8 at both the 

jurisdiction and major river basin scales for each of the jurisdictions. These draft allocations are 

further sub-allocated to the 92 Bay segment watersheds by draft individual and aggregate WLAs 

and LAs in Section 9. 
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8-20 September 24, 2010

Table 8-8. Chesapeake Bay watershed nutrient and sediment draft backstop allocations by 

jurisdiction and by major river basin to achieve the proposed amended Chesapeake Bay WQS 

Jurisdiction Basin Nitrogen

draft allocations

(million lbs/year)

Phosphorus

draft allocations

(million lbs/year)

Sediment

draft allocations

(million lbs/year)

Pennsylvania Susquehanna 71.74 2.31 1,758.20

Potomac 4.72 0.42 233.93

Eastern Shore 0.28 0.01 21.12

Western Shore 0.02 0.001 0.37

PA Total 76.77 2.74 2,013.62

Maryland Susquehanna 1.08 0.05 62.94

Eastern Shore 9.71 1.09 169.70

Western Shore 9.74 0.46 170.38

Patuxent 2.85 0.21 90.12

Potomac 15.70 0.90 682.33

MD Total 39.09 2.72 1,175.47

Virginia Eastern Shore 1.21 0.16 10.91

Potomac 17.46 1.47 810.07

Rappahannock 5.84 0.90 688.51

York 5.41 0.54 107.09

James 23.48 2.34 852.77

VA Total 53.40 5.41 2,469.35

District of Columbia Potomac 2.32 0.12 11.16

DC Total 2.32 0.12 11.16

New York Susquehanna 8.23 0.52 292.96

NY Total 8.23 0.52 292.96

Delaware Eastern Shore 2.95 0.26 57.82

DE Total 2.95 0.26 57.82

West Virginia Potomac 4.67 0.74 248.11

James 0.02 0.01 16.65

WV Total 4.68 0.75 264.76

Although the draft Phase I WIPs were evaluated based on proposed amended WQS, it is possible 

that the proposed amendments will not be completed before December 31, 2010 and that, as a 

result, the final TMDL allocations will need to be made based on current WQS. Table 8-9 lists 

the draft proposed allocations for nitrogen, phosphorus, and sediment based on current WQS at 

both the jurisdiction and major river basin scales. Just as with the allocations based on proposed 

amended WQS, these draft allocations are further sub-allocated to the 92 Bay segment 

watersheds by draft individual and aggregate WLAs and LAs in Section 9.
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8-21 September 24, 2010

Table 8-9. Chesapeake Bay watershed nutrient and sediment draft allocations by jurisdiction and

by major river basin to achieve the current Chesapeake Bay water quality standards.

Jurisdiction Basin

Nitrogen

draft allocations

(million lbs/year)

Phosphorus 

draft allocations

(million lbs/year)

Sediment

draft allocations

(million lbs/year)

Pennsylvania Susquehanna 56.89 1.76 1,756.80

Potomac 3.50 0.33 233.93

Eastern Shore 0.20 0.01 21.12

Western Shore 0.01 0.001 0.17

PA Total 60.59* 2.10 2,012.03

Maryland Susquehanna 0.87 0.04 63.72

Eastern Shore 7.18 0.83 51.13

Western Shore 5.99 0.25 81.81

Patuxent 2.03 0.13 91.83

Potomac 11.42 0.63 659.64

MD Total 27.49 1.88 948.13

Virginia Eastern Shore 0.79 0.12 10.86

Potomac 13.31 0.98 802.13

Rappahannock 4.39 0.60 688.29

York 3.83 0.35 106.95

James 16.44 1.55 848.89

VA Total 38.77 3.60 2,457.13

District of Columbia Potomac 1.47 0.05 11.37

DC Total 1.47 0.05 11.37

New York Susquehanna 6.39 0.43 289.02

NY Total 6.39 0.43 289.02

Delaware Eastern Shore 2.22 0.19 54.50

DE Total 2.22 0.19 54.50

West Virginia Potomac 3.61 0.37 263.22

James 0.02 0.01 22.95

WV Total 3.63 0.38 286.17

* Any discrepancies in totals are due to rounding.