92 
Text on page 123 in the Technical Support Document states: 
As described previously, the restoration of underwater bay grasses within a 
segment requires that shallow-water habitat meet the Chesapeake Bay water 
clarity criteria over a greater acreage than the underwater bay grasses will 
actually cover. The ratio of underwater bay grass acreage to the required 
shallow-water habitat acreage varies based on the different species of under¬ 
water bay grasses that inhabit the Bay’s four salinity regimes. Shallow-water 
habitat acreage ratios have been derived scientifically through evaluation of 
extensive underwater bay grasses distribution data within tidal fresh, low, 
medium and high salinity regimes (reflecting different levels of coverage by 
different underwater bay grass communities). 
The Chesapeake Bay Program segment-specific restoration goal acreage and 
corresponding shallow-water designated use acreage (to the previously 
determined maximum depth of abundant and persistent underwater plant 
growth) listed in Table IV-15 were summed by major salinity regimeBtidal 
fresh (0-0.5 ppt), oligohaline (> 0.5-5 ppt), mesohaline (> 5ppt— 18 ppt) and 
polyhaline (>18 ppt). The underwater bay grasses acreage to shallow-water 
habitat acreage ratios were then expressed as a percentage of the total 
shallow-water designated use habitat. Compared with a baywide value of 38 
percent, the tidal-fresh (37 percent), mesohaline (39 percent) and polyhaline 
(41 percent) values were all very close to the baywide value as well as the 
other salinity regime-specific values (Table IV-16). These values are consis¬ 
tent with findings published in the scientific literature and the 35 to 48 
percent range derived from evaluation of the 1930s through early 1970s 
historical data record by Naylor (2002) and Moore (1999, 2001). Influenced 
by the natural presence of the estuarine turbidity maximum, the value was 
21 percent in oligohaline habitats. 
The scientific literature along with analysis of the multi-decadal SAV aerial survey 
data record confirm that healthy SAV beds cover only a portion of the available suit¬ 
able habitat due to a variety of natural reasons. Given that the information 
summarized above and further documented in the Technical Support Document-2004 
Addendum indicates ratios from 1:2 to 1:3 in terms of the area covered by SAV beds 
compared to available shallow-water habitat area, a 1:2.5 ratio is recommended for 
determining the segment-specific acreage of shallow-water habitat that needs to 
achieve the applicable water clarity criteria required to support restoration of the 
segment specific SAV goal acreage. 
SAV RESTORATION GOAL ACREAGES 
The adopted Chesapeake Bay Program SAV restoration goal acreages were based on 
single best year coverages artificially clipped for shoreline and segment-specific 
water clarity criteria application depths, undercounting the actual mapped SAV 
acreages. In some segments, this resulted in the existing use acreages being higher 
than the restoration goal acreage. The chosen solution, described in more detail in 
chapter vii 
Updated Guidance for Application of Water Clarity Criteria and SAV Restoration Goal Acreages 
