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Bay Water Quality Responses to Simulated Nutrient and

Sediment Load Reductions: Findings and Recommendations

Presentation VIII-A CBP Principals’ Staff Committee Meeting

Lancaster, Pa.April 30, 2010

Bob Koroncai Lewis Linker

USEPA

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Presentation Preview

• Nutrients: Dissolved Oxygen and Chlorophyll ‘a’ Criteria Attainment– Past decisions– Current model results– Next steps toward full attainment: decision

• Sediment: Clarity and SAV Attainment– Current model results– Next steps towards full attainment: decision

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Remember, in October 2009 the PSC agreed to a basin-wide target loads of…

200 mpyNitrogen

15 mpyPhosphorus

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PSC Told in October The Recommended Basinwide Loads Will Change Due to…

Updated critical period Upgraded watershed model (Phase 5.2 to 5.3) Filter feeder inclusion in the WQ model Atmospheric deposition allocation and impact

on ocean load Modified assessment procedures for Bay

criteria• SAV/clarity target load analysis • Trade-offs between N and P • Loading reductions needed to meet local Bay

segments

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0

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Base Target E3

Calibration Load Scenario

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Open Water DO Violations Phase 5.3

Deep Water VO Violations Phase 5.3

Deep Channel DO Violations Phase 5.3

Open Water DO Violations Phase 5.2

Deep Water DO Violations Phase 5.2

Deep Channel DO Violations Phase 5.2

DO Stoplight Plot Summary Information Violation Count >1% for the ’93-’95 Critical Period

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DO Non-attainment – All Scenarios

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1985 Base 2007 Target Loading Loading E3

Scenario Calibration Scenario Load Scenario Scenario Scenario

342 TN, 309 TN, 254 TN, 200 TN, 195 TN, 186 TN, 141 TN,

24.1 TP 19.5 TP 17.1 TP 15.0 TP 14.3 TP 10.9 TP 8.5 TP

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Open Water DO Violations

Deep Water VO Violations

Deep Channel DO Violations

Violation counts based on >1% for the ’93-’95 critical period

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Deep-Channel Use Dissolved Oxygen at Current Target Loads

(200 TN, 15 TP+ 15.7 air allocation)

• Non-attainment in 3 segments (>1%)– CB4 (2%)– Lower Chester (14%)– Eastern Bay (4%)

• 1 segment at <1%• Reaching attainment will

require further reductions in nutrient loads from larger Bay watershed

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Deep-Water Use Dissolved Oxygen at Current Target Loads

(200 TN, 15 TP+ 15.7 air allocation)

• Non-attainment in 2 segments (>1%)– Lower Chester River

(3%)– Magothy (16%)

• 4 segments at <1%• Reaching attainment will

require further reductions in nutrient loads from basinwide and local watershed scales

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Open-Water Use Dissolved Oxygen at Current Target Loads

(200 TN, 15 TP+ 15.7 air allocation)

• Non-attainment in 15 segments (>1%), ex:– Pocomoke (25%)– Anacostia (16%)– Wicomico (15%)– Severn (6%)– Lower York (3%)

• 8 segments at <1%• Reaching attainment will

require further reductions in nutrient loads from local watershed scales

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Dissolved oxygen/chlorophyll:where do we go from here?

• Identify loads to achieve full attainment– Identify non-attaining segments– For each non-attaining segment:

• Identify watershed(s) having the most influence on tidal water quality

• Identify loadings needed to fully attain• Understand any other factors contributing to

sustained non-attainment (beyond E3)

• PSC agreement with this approach?

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What about sediment?

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Clarity/SAV Non-attainment

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1985 Base 2007 Target Loading Loading E3

Scenario Calibration Scenario Load Scenario Scenario Scenario

342 TN, 309 TN, 254 TN, 200 TN, 195 TN, 186 TN, 141 TN,

24.1 TP 19.5 TP 17.1 TP 15.0 TP 14.3 TP 10.9 TP 8.5 TP

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Clarity Assessment Only Violations

Clarity + SAV Assessment Violations

Violation counts based on >1% for the ’93-’95 critical period

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Clarity/SAV:where do we go from here?

• Confirm assessment procedures fully consistent with states’ WQ standards regulations

• Identify loads to achieve full attainment– Identify non-attaining segments– For each non-attaining segment:

• Diagnosis major contributor(s) to reduce water clarity: nutrient, sediments

• Identify watershed(s) having the most influence on tidal water quality

• Identify loadings needed to fully attain• Understand any other factors contributing to sustained non-

attainment (beyond E3)

• PSC agreement with this approach?

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When?

• State/basin nutrient allocations by July 1

• State/basin sediment allocations by August 15

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Nutrient and Sediment Summary

• Need to refine state/basin nutrient allocations by meeting WQS in ‘local’ segments

• Much sediment attainment achieved with P controls planned

• Need to commit to extensive review in June (N/P) and July/August (S)

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Questions?