48 
depth contour (segment-specific water clarity criteria application depth) based on the 
cumulative frequency diagram (CFD) assessment methodology, then the segment is 
also considered in attainment of this designated use. Like the water clarity acres 
approach, the CFD-based assessment would be performed using data from the 
shallow-water monitoring program (see Chapter 7 for details). 
For the 2006 Impaired Water 303(d) listing cycle, insufficient data existed to assess 
water clarity criteria attainment in nearly all of the Chesapeake Bay segments’ 
shallow-water bay grass designated-use habitats. The SAV acreages have been quan¬ 
tified for many years (annually since 1984), however, and this data collection is 
expected to continue. Thus, the 2006 assessments used SAV acreages over the three- 
year assessment period from 2001 through 2004. If the single best year of SAV 
coverage from that period exceeded the established, state-adopted SAV restoration 
goal, then the segment’s shallow-water designated use was deemed in attainment. If 
the SAV restoration goal was not attained, then the segment’s shallow-water desig¬ 
nated use was listed either as impaired (category 5) or as insufficient data (category 
3) since shallow-water monitoring data were unavailable for the segment. 
The procedures for assessing attainment of the Chesapeake Bay shallow-water 
designated use using the water clarity criteria and SAV restoration acreages, first 
published by EPA in 2003, were broadly defined and had not been extensively 
applied in the Chesapeake Bay prior to the 2006 303(d) listing cycle (U.S. EPA 
2003a, 2003b). The jurisdictions and the EPA identified and resolved many issues 
during the first baywide application. This chapter provides detailed and refined guid¬ 
ance on the assessment of the water clarity criteria and the SAV restoration goals. 
Ultimately, the chapter evaluates attainment of the shallow-water bay grass desig¬ 
nated use. This guidance replaces the applicable criteria assessment methodologies 
previously published by the U.S. EPA (2003a, 2003b, 2004a, 2004c). 
SHALLOW-WATER DESIGNATED-USE 
ATTAINMENT ASSESSMENT 
The shallow-water bay grass designated use is considered in attainment if sufficient 
acres of SAV are observed within the segment or enough acres of shallow-water 
habitat meet the applicable water clarity criteria to support restoration of the desired 
SAV acreage for that segment (U.S. EPA 2003a, 2003b). Assessment of either 
measure, or a combination of both, serves as the basis for determining attainment or 
impairment of the shallow-water bay grass designated use. 
Given 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, the EPA recommends the States assess 
shallow-water bay grass designated use attainment/impairment based on the acres of 
aerial mapped SAV. 
chapter v 
Refinements to the Shallow-Water Designated-Use Assessment Procedures 
