29 
The Chesapeake Bay Program partners continue to fund and conduct an extensive 
baywide, coordinated water quality monitoring program, much of which supports 
water quality criteria assessment. Water quality monitoring takes place at more than 
150 sites throughout the mainstem Chesapeake Bay and its tidal tributary waters 
(Figure III-2). Samples are collected at each of the fixed stations on a monthly or semi¬ 
monthly basis with data gathered since the mid-1980s (Chesapeake Bay Program 
1989). The fixed-station network provides consistent data over the entire mainstem 
Bay, major tidal tributaries, and larger embayments. The data are useful in assessing 
the published Bay water quality criteria in the open-water, deep-water, deep-channel, 
and migratory and spawning designated uses. 
Use of the fixed-station network is limited for criteria assessments in the shallow- 
water designated use habitats because the data scale is not appropriate. This network 
also proves limited in many smaller tidal tribu¬ 
taries and embayments, which have no or very few 
stations. To address these limitations, the Chesa¬ 
peake Bay Program partners developed a 
Shallow-water Monitoring Program to provide 
data collected intensively in space and time in the 
Bay’s shallow-water habitats. Chapter 7 describes 
this program and the details of data application for 
criteria assessment. 
The 2003 EPA Chesapeake Bay water quality 
criteria document describes the extent of data 
collection needed to assess the state’s Chesapeake 
Bay water quality standards (U.S. EPA 2003a). 
Three levels of effort are described for each crite¬ 
rion: marginal, adequate, and recommended (see 
pages 178-196 in U.S. EPA 2003a). The “mar¬ 
ginal” level of monitoring is the minimum data 
collection needed to support criteria assessment. 
At this level, data may not be of the right type or 
in sufficient quantity to assess all of the applicable 
criteria components. In general, this level of 
monitoring assumes that only the fixed-station 
data are available for criteria assessment. The 
“adequate” level of monitoring assumes that the 
fixed-station monitoring program will be 
combined with limited intensive data collection 
(e.g., temporally continuous monitoring for 
dissolved oxygen) to ensure that data are collected 
to support the assessment of all the applicable 
criteria components (e.g., 30-day, 7-day, and 1- 
day means, instantaneous minimum) in some 
spatial assessment units. The “recommended” 
level of monitoring assumes that the fixed-station 
chapter iii • Application of Chesapeake Bay Water Quality Criteria Assessment Procedures 
Figure 111-2. Locations of the sites that make up the 
fixed station network of the Chesapeake Bay Water 
Quality Monitoring Program. 
Source: Chesapeake Bay Program 1989. 
