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attainment of the 7- and 1-day means as well as the instantaneous minimum criteria 
components. If a segment was first listed in 2006 based on the 30-day mean open- 
water and/or deep-water criteria and subsequent 30-day mean open-water and/or 
deep-water criteria data now shows the segment to be in attainment, then the segment 
may be delisted for these criteria. 
WATER CLARITY CRITERIA ATTAINMENT ASSESSMENT 
The shallow-water bay grass designated use is in attainment if a sufficient number of 
acres of SAV occur within the segment or if enough acres of shallow-water habitat 
exist that meet the applicable water clarity criteria to support restoration of the 
desired acreage of SAV for that segment (U.S. EPA 2003a, 2003b). Assessment of 
either measure, or a combination of both, can serve as the basis for determining 
attainment or impairment of the shallow-water bay grass designated use. 
Since SAV is the ultimate biological measure of attainment of the designated use, in 
the absence of sufficient shallow-water monitoring data necessary to determine the 
available water clarity acres or assess water clarity criteria attainment using the 
CFD-based criteria assessment procedure, EPA recommends the States assess 
shallow-water bay grass designated use attainment/impairment based on the acres of 
mapped SAV. 
If a shallow-water bay grass designated-use segment meets its SAV restoration 
acreage, that designated use-segment is in attainment of the designated use and 
should be listed on part 2. 
If such a segment does not meet its restoration acreage, the jurisdiction can then 
assess attainment using water clarity acres or water clarity criteria as described in 
Chapter 5. If the water clarity acres or water clarity criteria are attained based on 
shallow-water monitoring data, then that segment is in attainment of the shallow- 
water bay grasses designated use and should be listed on part 2. 
Finally, if the water clarity restoration acres or water clarity criteria are not attained 
using the same data, or if there are insufficient data to make a determination using 
water clarity acres or water clarity criteria, then that segment is not in attainment of 
the shallow-water bay grasses designated use and should be listed on part 5. 
Any attainment/non-attainment determination of water clarity criteria based on mid¬ 
channel-based monitoring is strictly diagnostic. These mid-channel data should not 
directly form the basis for any listing decision based on attainment/non-attainment 
of a segment’s shallow-water bay grass designated use. 
CHLOROPHYLL A CRITERIA ATTAINMENT ASSESSMENT 
As described in Chapter 6, numerical chlorophyll a criteria attainment is assessed by 
applying the appropriate numerical criteria over the applicable season for three years 
using the CFD-based criteria assessment methodology. 
chapter viii 
Framework for Chesapeake Bay Tidal Waters 303(d) List Decision-Making 
