NAVIGATING THE TMDL PROCESS: APPROACHES FOR LISTING AND DELISTING

The TMDL process is initiated by the listing process which involves placing a water body on the 303(d) list. A water body is placed on the 303(d) list when it is impaired (not attaining water quality standards (WQS)). This report describes the range of approaches to listing and delisting for four important elements of the lising/delisting process: Water quality standards, data collection and acquisition, comparative methodology, and list content and format. The description emerged from surveys of 9 states, reviews of approaches used by selected other states, published literature, and from project team experience.Analysis of the state survey results indicated the following conclusions:States recognize that physiography influences designated uses and criteria, but there were significant differences among states in how this variation was considered in WQS.States generally do not consider hydrologic variability in establishing water quality criteria.With the exception of UAAs, states have not explicitly determined that designated uses are attainable.All states considered existing criteria protective of designated uses but the rationale varied from site-specific determinations to adopting EPA national criteria.Narrative criteria are useful for problem identification, but listing decisions should be made based on monitoring or site-specific data.No states used a formal statistical approach to compare data with criteria.Evaluation procedures generally have been tested only through special studies or informally.All states have formal QA/QC programs for their monitoring data and all require QA reviews for extant data.None of the states use formal statistical approaches for delisting.