The Road to TMDL is Paved with Good Intentions--Total Maximum Daily Loads for a Wild and Scenic River in the Southern Appalachians

We monitored water quality in the Chattooga River Watershed (NE Georgia, NW South Carolina,and SW North Carolina) to compare sediment TMDLs with observed water quality. A judicialconsent decree required the EPA to establish TMDLs in one year. The EPA was unable to fullycharacterize the sediment budgets of these streams and consequently issued phased sedimentTMDLs which can be revised because information on the actual contributions of sediment tothe Chattooga River Watershed from both point and nonpoint sources will be much bettercharacterized in the future. The EPA listed streams as sediment impaired based upon aquaticindicator species data and relied upon total suspended solids (TSS) data and modeling toestablish the sediment TMDLs. We found that TSS concentrations do not reflect mineralsediment concentrations because the organic and mineral components of TSS were highlyvariable between streams. TSS in forested streams could get quite high and were largely organicwhereas TSS in streams more heavily impacted by land use change and roads were mostlymineral sediment. TSS and mineral sediment in a stream listed as being sediment impaired weresignificantly lower than streams listed as being only threatened. We also monitored bed materialtransport and sampled sediment mineralogy on one of our study streams. The sand and finegravel in this stream were very dynamic. In-stream scour and deposition occurred frequently.No in-stream deposition occurred during small events; when road runoff was negligible. Duringlarger events, road runoff and in-stream sediment deposition occurred. This suggests that theexisting sediment TMDLs may not address the causes of sediment impairment of the aquaticecosystems. The EPAs issuance of phased sediment TMDLs was insightful because itacknowledged our lack of understanding of the impacts of land usage and sediment dynamics onstreams in the Chattooga River watershed.