Abstract |
Section 303(d) of the federal Clean Water Act directs States to identify and list waters, known as water quality limited segments (WQLS), in which currently required pollution controls are inadequate to achieve water quality standards. For each WQLS, the State is to establish a Total Maximum Daily Load (TMDL) of the specified substance that the waterbody can receive without violating water quality standards. The Western Branch of the Patuxent River was identified on the States 1996 list of WQLSs because of low dissolved oxygen. Although recent data shows that the dissolved oxygen standard violations in the Western Branch are minor and infrequent, it is suspected that the violations could increase in both severity and frequency in the future. The cause of these violations was initially suspected to be nutrients. Subsequent investigation, however, determined that biochemical oxygen demand (BOD) is the dominant cause of the low dissolved oxygen concentrations. This report documents the proposed establishment of a TMDL for the Western Branch to improve dissolved oxygen concentrations. Once approved by the United States Environmental Protection Agency (EPA), the TMDL will be reflected in the States Continuing Planning Process. In the future, the established TMDL will support regulatory and voluntary measures needed to protect water quality in the Western Branch of the Patuxent River. |