Method Development for Addressing Narrative Criteria in the TMDL Process: A Water Environment Research Foundation Project Update

The project “Method Development for Addressing Narrative Criteria in the TMDL Process” is a WERF-funded research effort begun in 2001 directed toward improving the TMDL process for narrative criteria. The research will be completed in the fall of 2002. The objectives of the Narrative Criteria TMDL study are to:Characterize the current “state of the practice” of TMDL development for narrative criteria, based on a critical review of a representative sample of approved and draft narrative criteria TMDLs;Integrate the information from the individual TMDL reviews and use this information to generate guiding principles for proper consideration of narrative criteria TMDLs; andTest the real world applicability of the guiding principles identified above via application to real world TMDL case studies.A detailed review of approximately 100 narrative criteria TMDLs was conducted for a wide range of impairment types. These reviews have identified specific problems and issues associated with narrative criteria. To organize the review, the various types of TMDLs have been placed in three different classes keyed to the wording of the particular narrative criterion: 1) toxicological, 2) ecological, or 3) aesthetic. Particular problems identified include: defining the cause-effect linkages in cases of biological impairment; interpretation of toxicity test data in defining the presence and cause of impairment; and defining specific levels regarding what constitutes impairment for aesthetic criteria.Guiding principles for the proper consideration of narrative criteria in TMDL development are currently being developed in three areas: 1) determining impairment; 2) identifying cause-effect relationships; and 3) selecting TMDL endpoints. These guiding principles will subsequently be tested on a series of existing TMDLs to verify their applicability. The Water Environment Research Foundation will publish final research findings once they are produced in the fall of 2002.