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These approaches to assessing attainment of the shallow-water bay grass designated 
use were described in more detail in Chapter 6 of the Regional Criteria Guidance 
document (U.S. EPA 2003a). Since the 2003 publication of both the Regional 
Criteria Guidance and the Technical Support Document , new information has 
become available to the watershed jurisdictions and EPA in support of state adoption 
of SAV restoration goal, shallow water habitat and shallow-water existing use 
acreages into their water quality standards regulations. This new information will 
also help the four jurisdictions with Chesapeake Bay tidal waters adopt consistent, 
specific procedures for determining attainment of the shallow-water bay grass desig¬ 
nated uses into their regulations. (Note the terms ‘underwater bay grasses’ and 
‘submerged aquatic vegetation’ or ‘SAV’ are used interchangeably in this document.) 
EPA continues to support and encourage the jurisdictions’ adoption of the Chesapeake 
Bay Program segment-specific submerged aquatic vegetation (SAV) restoration goal 
acreages and the corresponding water clarity criteria attaining shallow-water acreage 
necessary to support restoration of those acreages of SAV into each jurisdictions’ 
respective water quality standards regulations. Achievement of the SAV restoration 
goal and shallow-water acreages are two additional means, beyond numerical water 
clarity criteria applied to segment-specific application depths, for defining attainment 
of the shallow-water bay grass designated use. 
WATER CLARITY CRITERIA APPLICATION PERIODS 
The temporal application periods for the water clarity criteria were determined based 
on the growing seasons for the salinity-based SAV plant communities: April 1 
through October 31 for tidal fresh, oligohaline and mesohaline salinity regimes and 
March 1 through May 31 and September 1 through November 30 for polyhaline 
regimes (U.S. EPA 2003a; Batiuk et al. 1992, 2000). The tidal fresh, oligohaline and 
mesohaline salinity regimes application period was based on the combined growing 
seasons for tidal fresh to middle salinity SAV species communities. The polyhaline 
temporal application periods were based on the bimodal Zoster a marina or eelgrass 
growing seasons (Batiuk et al. 1992). 
Given that Ruppia maritima or widgeon grass, principally a mesohaline species, has 
been found growing along with eelgrass in a majority of the polyhaline regions of 
the Chesapeake Bay and its tidal tributaries in Virginia waters (Moore et al. 2000), 
the water clarity criteria temporal application period for polyhaline waters should be 
an inclusive combination of the mesohaline and polyhaline temporal application 
periods or March 1 through November 30. This expanded temporal application 
period should apply to polyhaline Chesapeake Bay Program segments where there is 
evidence of past or present widgeon grass growth or the potential for future growth. 
chapter vii 
Updated Guidance for Application of Water Clarity Criteria and SAV Restoration Goal Acreages 
