The Clean Water Act (CWA) section 305(b) requires that states report biennially on the water quality standards (WQS) attainment status of all waters. The United States Environmental Protection Agency (USEPA) has recognized that biological assessment data are very valuable and should serve as a core indicator in determining aquatic life use attainment status (USEPA 2002). However, great (or large-floodplain) rivers, such as the Ohio River, are one type of aquatic resource for which biological assessment data typically have been deficient, primarily due to difficulty in sampling (Emery et al. 2003). The Ohio River Valley Water Sanitation Commission (ORSANCO), a compact of eight states and the federal government is responsible for assessment of the Ohio River. Recognizing the abundance of stresses on this system and the lack of biological data for the river, ORSANCO developed a bioassessment program several years ago. In 1990, ORSANCO began a Long-Term Intensive Survey (LTIS) of the Ohio River to provide high sample density (one sample every 3.2-6.4 km) from selected reach segments of the river. Beginning with this effort, a fish-based index of biotic integrity (IBI) for the Ohio River was developed (Emery et al. 2003). Although the LTIS approach provided valuable data for the development of a fish IBI and biocriteria, this approach was very resource-intensive and time-consuming and was not feasible for routine sampling of the entire river. To support the development of a cost-effective program for routine monitoring, the minimal amount of effort required to produce an adequate assessment needed to be determined.

"September 2006." "EPA 600/R-06/089." Includes bibliographical references (p. 24-26).