750 acres of shallow-water habitat (2.5 multiplier times 300 acres) is needed to attain 
the water clarity criteria to determine this segment is attaining its shallow-water bay 
grass designated use. 
The second methodology directly accounts for mapped acres of SAV within the 
calculation of water clarity acres. As part of the month-by-month accounting of 
water clarity acres, over the three-year SAV growing season assessment period, 
interpolator cells containing any mapped SAV beds are counted towards the total 
water clarity acres. 
Here’s a hypothetical example of this second methodology for determining attain¬ 
ment of the shallow-water bay grass use using both mapped SAV acreage and 
shallow-water habitat acreage meeting the water clarity criteria. Segment Y has an 
SAV restoration goal acreage of 1,400 acres. Applying the 2.5 multiplier, this 
segment also has a water clarity restoration acreage of 3,500 acres. Over the past 
three years, SAV beds totaling 1,100 acres have been mapped within the segment 
each year. During each growing season’s accounting of water clarity acres, these 
1,100 acres of mapped SAV beds are directly counted towards the growing season 
arithmetic mean water clarity acreage. Therefore, accounting directly for 1,100 acres 
of mapped SAV beds as water clarity acres, an additional 2,400 acres (3,500 water 
clarity restoration acres minus 1,100 acres of mapped SAV) of shallow-water habitat 
is needed to attain the water clarity criteria to determine this segment is attaining its 
shallow-water bay grass designated use. 
ASSESSMENT BASED ON CFD-BASED WATER CLARITY 
CRITERIA ATTAINMENT 
A jurisdiction may choose to apply the CFD-based assessment of water clarity 
criteria to evaluate attainment of the segment’s shallow-water bay grass designated 
use (U.S. EPA 2003a, 2004a). To attain the designated use, the segment must meet 
the applicable water clarity criteria throughout the applicable shallow-water habitat 
(from the shoreline out to the segment-specific water clarity criteria application 
depth contour) (see Table IV-13 on pages 115-117 in U.S. EPA 2003b) over three 
SAV growing seasons, factoring in allowable exceedances using the appropriate 
salinity-regime-based biological reference curve (see Figures V-l, V-2). Chapter 2 
and Appendix B document the application of the CFD-based criteria attainment 
assessment in detail. Chapter 7 deals with the specific elements of the shallow-water 
criteria attainment assessment procedures using a CFD-based evaluation. 
SHALLOW-WATER DESIGNATED USES 
AND SAV NO-GROW ZONES 
Shoreline habitats of 2 meters or less (where SAV is never expected to grow due to 
extreme wave energy, permanent physical alterations, natural discoloration of the 
water, and no functional shallow-water habitat from river channeling) were 
Refinements to the Shallow Water Designated Use Assessment Procedures 
