91 
SHALLOW-WATER HABITAT ACREAGES 
New information on shallow-water habitat acreages has been published in the Tech¬ 
nical Support Document for Identification of Chesapeake Bay Designated Uses and 
Attainabilit)'-2004 Addendum (U.S. EPA 2004). These updated shallow-water 
habitat acreages factor in the full extent of the 0 to 2 meter depth contour area of 
shallow water habitat, minus the delineated SAV no-grow zones. Through compar¬ 
ison with the expanded restoration acreages, described below, new segment-specific 
expanded restoration acreages as a percentage of the shallow-water habitat acreages 
have also been published in the Technical Support Document 2004 Addendum. 
SAV RESTORATION ACREAGE TO SHALLOW-WATER HABITAT 
ACREAGE RATIO 
There is scientific documentation originally published in both the Ambient Water 
Quality- Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the 
Chesapeake Bay and its Tidal Tributaries (U.S. EPA 2003a) and the Technical 
Support Document for Identification of Chesapeake Bay Designated Uses and 
Attainability (U.S. EPA 2003b) supporting the findings that suitable shallow-water 
habitat must be at acreages greater than the corresponding SAV restoration goal to 
support restoration of SAV to those acreages. 
Text on page 198 in the Regional Criteria Guidance states: 
Restoring underwater water grasses within a segment requires that the 
particular shallow-water habitat meet the Chesapeake Bay water clarity 
criteria across acreages much greater than those actually covered by bay 
grasses. The ratio of underwater bay grass acreage to the required shallow- 
water habitat acreage achieving the necessary level of water clarity to 
support return of those underwater bay grasses varies based upon the 
different species of bay grasses inhabiting the Chesapeake Bay’s four 
salinity regimes. The baywide average ratio of underwater bay grass acreage 
to suitable shallow-water habitat acreage is approximately one acre of 
underwater bay grasses for every three acres of shallow-water habitat 
achieving the Chesapeake Bay water clarity criteria. 
The salinity regime and, therefore, bay grass community-specific under¬ 
water bay grass acreage to shallow-water habitat acreage ratios have been 
derived through an evaluation of extensive underwater bay grass distribution 
data within tidal-fresh, low (oligohaline), medium (mesohaline) and high 
(polyhaline) salinity regimes (reflecting different levels of coverage by 
different bay grass communities). The Technical Support Document for the 
Identification of Chesapeake Bay Designated Uses and Attainability docu¬ 
ments the methodology followed and the resulting bay grasses acreage to 
shallow water habitat acreage ratios derived for each of the four salinity 
regimes (U.S. EPA 2003). 
chapter vii 
Updated Guidance for Application of Water Clarity Criteria and SAV Restoration Goal Acreages 
