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M-1 September 24, 2010

Appendix M. Chesapeake Bay Water Quality/Sediment Transport Model Management 

Scenario Criteria Attainment Assessment Results and 2008 303(d) List Assessment Results

This appendix presents the Chesapeake Bay water quality criteria attainment assessment results 

of various Bay Water Quality Model management scenarios in a stoplight format used by EPA 

its partners jurisdictions in development of the Chesapeake Bay TMDL. The stoplight 

spreadsheets summarize the percentage of space and time exceeding the Bay water quality 

criteria for each of the 92 Chesapeake Bay segments. They are produced from an assessment of 

Bay Water Quality Model outputs and Bay water quality monitoring data (described in Section 

6.2.1). These spreadsheets were used to evaluate whether a given management scenario met all 

applicable criteria across all designated use-segments. Green highlighted percentages represent 

attainment of the applicable water quality criterion. Red highlighted percentages represent a 

violation or an exceedance of current water quality standards. The assessment results here in this 

appendix in three spreadsheets:

Appendix M-1: Chesapeake Bay Dissolved Oxygen Criteria Attainment Assessment Results 

(P1_DO_Stoplight_Appendix)

Appendix M-2: Chesapeake Bay Chlorophyll a Criteria Attainment Assessment Results 

(P2_CL_Stoplight_Appendix)

Appendix M-3: Chesapeake Bay SAV/Water Clarity Criteria Attainment Assessment Results 

(P3_SAV-Clarity_Appendix)

The loading values in appendices M-1 and M-2 are derived in one of two ways. Loading values 

for the 1985 Scenario, 2009 Scenario, Tributary Strategy, and E3 2010 Scenario are derived from 

explicit management scenarios and described further in Appendix K. Loading values for the 

remaining scenarios were calculated as ratios of existing management scenarios to achieve 

particular basin-wide loading targets.

Also contained within this appendix is the Chesapeake Bay segments 2008 303(d) list 

assessment results spreadsheet.

Interpreting the Spreadsheets

Appendix M-1: Chesapeake Bay Dissolved Oxygen Criteria Attainment 

Assessment Results

The dissolved oxygen water quality criteria stoplight plots describe the degree of nonattainment 

(as percent of volume and time) of dissolved oxygen water quality criteria for each Chesapeake 

Bay segment by designated use criteria. The dissolved oxygen criteria attainment assessment 

results are based on assessing the open-water 30-day mean, deep-water 30-day mean, and deepchannel instantaneous minimum criteria during the June 1 through September 30 summer period 

(see Table 3-4 in Section 3.1.2). The green highlighted percentages represent attainment of the 

applicable dissolved oxygen criterion. The red highlighted percentages represent nonattainment 

of dissolved oxygen criterion. The rows show the percent nonattainment by Bay segment. The 

columns show the percent nonattainment by Bay Water Quality Model scenario and are listed 

from left to right in descending order of loading values for total nitrogen (TN), total phosphorous 
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M-2 September 24, 2010

(TP), and total suspended solids (TSS). The Bay Water Quality scenarios are grouped by 3-year 

water quality model assessment windows and are ordered chronologically. The Bay Water 

Quality Model scenarios marked with an asterisk (*) had loading values derived from the key 

management scenario spreadsheets (see Appendix K). All other scenarios’ loading values were 

calculated as ratios of existing management scenarios to achieve particular basin-wide loading 

targets. The critical period for the Chesapeake Bay TMDL was selected as 1993–1995 for 

assessment of the dissolved oxygen criteria (see Section 6.1.2).

Appendix M-2: Chesapeake Bay Chlorophyll a Criteria Attainment 

Assessment Results 

The chlorophyll a water quality criteria stoplight plots show the percent nonattainment of 

chlorophyll a (CL) criteria by two periods: CL Spring Seasonal (March 1 through May 31) and 

CL Summer Seasonal (July 1 through September 30). The green highlighted percentages 

represent attainment of chlorophyll a criteria. The red highlighted percentages represent 

nonattainment of chlorophyll a criteria. The rows show percent nonattainment by Bay segment. 

The columns show the percent attainment by Bay Water Quality Model scenario and are listed 

from left to right in descending order by loading values for TN and TP. The Bay Water Quality 

Model scenarios are grouped by 3-year water quality model assessment windows and are ordered 

chronologically. For allocation scenarios specific to the James River Basin, loading values were 

calculated as ratios of existing management scenarios to achieve particular loading targets. 

Analysis failed to identify a critical period for the chlorophyll water quality criteria so all 3-year 

periods had equal weight in the Bay TMDL assessment (see Section 6.1.2).

Appendix M-3: Chesapeake Bay SAV/Water Clarity Criteria Attainment 

Assessment Results 

The submerged aquatic vegetation (SAV)/water clarity stoplight spreadsheets describe the degree 

of nonattainment (as percent of SAV acreage + water clarity acres—see Section 6.2.1 and 

Appendix O) of SAV/water clarity criteria for each of the Bay segments assigned a shallowwater bay grass designated use. The green highlighted percentages represent the percent 

nonattainment of SAV/water clarity criteria. The red highlighted percentages represent the 

percent nonattainment of SAV/water clarity criteria. The rows show the percent nonattainment 

by Bay segment. The columns show the percent nonattainment by Bay Water Quality Model 

scenario and are listed from left to right in descending order of loading values for TN, TP, and 

TSS.

The Bay Water Quality scenarios are grouped by 3-year water quality model assessment 

windows and are ordered chronologically. The Bay Water Quality Model scenarios marked with 

an asterisk (*) had loading values derived from the key management scenario spreadsheets (see 

Appendix K). All other scenarios’ loading values were calculated as ratios of existing 

management scenarios to achieve particular basin-wide loading targets. The critical period for 

the Chesapeake Bay TMDL was selected as 1993–1995 for assessment of the SAV/water clarity 

criteria (see Section 6.1.2).

 
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M-3 September 24, 2010

Appendix M-4: Chesapeake Bay Segments 2008 303(d) List Assessment 

Results

The following are short descriptions of the information/data found in each column in this 

Appendix M-4 spreadsheet. Green means the criterion/designated is attained; red means the 

criterion/designated use not is attained; and yellow means insufficient data for criterion 

assessment/no published criteria assessment protocol.

A: Chesapeake Bay segment.

B: Jurisdiction.

C: Designated used: MSN-migratory spawning and nursery; SWSAV-shallow-water bay grass, 

OW- open water; DW-deep-water; DC-deep-channel.

D: Season for criteria application: Summer-June 1 through September 30; ROY-October 1 

through May 31.

E: 30-day mean dissolved oxygen criterion. Value is the applicable criterion.

F: 7-day mean dissolved oxygen criterion. Value is the applicable criterion.

G: 1-day mean dissolved oxygen criterion. Value is the applicable criterion.

H: Instantaneous minimum dissolved oxygen criterion. Value is the applicable criterion.

I: Temperature based dissolved oxygen criterion protective of shortnose sturgeon (species listed 

as endangered.

J: Numerical chlorophyll a criteria assessment results.

K: SAV restoration acreage criteria assessment results. Value is the applicable SAV restoration 

acreage.

L: Water clarity acreage assessment results.

M: Combined SAV restoration acreage + water clarity acreage assessment results.

N: Water clarity criteria assessment results.

O: Description of criteria attainment assessment results by designated use-segment.

P: 303(d) listing category

Q: Benthic community impairment status.