Section 8. 
Implementation Plan for Diagnostics Research 
Problem 
States list surface waters as impaired on 305(b) reports or 303(d) listings based on one or more of 
three types of criteria: biological criteria (narrative or numeric), chemical criteria, or physical 
attributes (e.g., habitat quality assessments). When impairment is determined based on 
biological criteria (26% of impairment decisions). States are faced with the problem of 
diagnosing the cause of impairment before plans can be made to reduce the loading of pollutants 
through the TMDL process (40 CFR Ch.l, Part 130; U.S. EPA 1991; 
httD://www.epa.gov/owow/tiTidl/l . The nation-wide scope of this problem is enormous; 
approximately 21,000 water bodies have been designated as impaired; or 44% of stream or river 
miles, 49% of lakes, reservoirs, and ponds; 98% of Great Lakes shoreline waters; and 42% of 
estuaries (EPA 2000a). 
To improve overall efficiency of the TMDL process and to coordinate remediation activities, 
diagnosis of the cause of impairment is needed not only at the scale of individual water bodies, 
but also at the watershed scale. Unified Watershed Assessments, as specified in the Clean Water 
Action Plan (EPA 1998a) are needed at the watershed scale to identify aquatic systems for 
restoration actions (EPA 1999, Federal Register 2000, http://www.epa.gov/owow/uwaL 
Overall vision 
This plan for diagnostics research provides a comprehensive and integrated approach for problem 
solving. It is primarily responsive to EPA’s regulatory and management needs, in particular the 
need for research related to the TMDL program, but also supports needs defined under 
Superfund, National Pollution Discharge Elimination System (NPDES), site remediations, and 
other relevant activities (e.g., FWS Natural Resource Damage Assessments). It provides a 
conceptual framework to determine current and future research priorities coordinated across 
NHEERL, and also discusses implementation in the context of research and expertise provided 
by other ORD Laboratories and the broader scientific community. Outputs from diagnostics 
research will be incorporated into a series of decision-support systems or modules for use by 
clients (EPA Regions, States, Tribes, and Program Offices). 
NHEERL’s diagnostic research focuses on the need to diagnose causes of biological impairment 
within an integrated framework linking watersheds with receiving water bodies to support the 
TMDL process and other regulatory programs. All stressors (habitat alteration, nutrients, 
suspended and bedded sediments, and toxic chemicals) will be considered under diagnostics 
research; however, greater emphasis may be placed on an individual stressor, combinations of 
stressors, and/or modes of action according to the prevailing problems or issues of a habitat, 
water body, ecosystem, region, or the nation as a whole. The starting point for diagnostic 
research is the need to respond to reports of biological impairment, nonattainment of aquatic life 
use, and other indications of adverse effects (e.g., toxicity). Initial assessments also can record 
evidence of multiple potential causes of impairment and conflicting lines of evidence that might 
138 
