TMDLs for Segments Listed for Mercury in Fish Tissue for the Ouachita River Basin, and Bayou Bartholomew, Arkansas and Louisiana to Columbia.

摘要

The Arkansas and Louisiana 1998 Section 303(d) Lists include segments and subsegments in the Ouachita River basin that are impaired due to excess concentrations of mercury in fish. Additional waterbodies in the Ouachita River basin that are not included on the 1998 Section 303(d) List are subject mercury related fish consumption advisories. While there have been no known violations of the numeric mercury water quality standard and fishable designated use for these waterbodies, these segments and subsegments are not meeting the narrative water quality standard and designated uses of fishable water bodies. A basin-wide approach is being used in this TMDL due to similar ecoregions and watershed characteristics and because of similar causative factors such as atmospheric and geologic contributions. The Ouachita River basin is in the Ouachita Mountain, South Central Plain, and Mississippi Alluvial Plain ecoregions. It has gently rolling topography, with hilly uplands, flatwood uplands, terraces, and floodplains. Land use in the basin is 71% forest with 13% in wetlands. There is one NPDES point source with permit mercury limits in the basin. There are seven air emission point sources with permit mercury limits.