Total Maximum Daily Loads of Polychlorinated Biphenyls in Back River Oligohaline Tidal Chesapeake Bay Segment, Maryland. Final.

摘要

This document, upon approval by the U.S. Environmental Protection Agency (EPA), establishes a Total Maximum Daily Load (TMDL) for Polychlorinated Biphenyls (PCBs) in the Back River Oligohaline Tidal Chesapeake Bay Segment. Section 303(d) of the federal Clean Water Act (CWA) and the EPAs implementing regulations direct each State to identify and list waters, known as water quality limited segments (WQLSs), in which current required controls of a specified substance are inadequate to achieve water quality standards (WQSs). For each WQLS, the State is to either establish a TMDL of the specified substance that the waterbody can receive without violating WQSs, or demonstrate that WQSs are being met (CFR 2011b). Maryland WQSs specify that all surface waters of the State shall be protected for water contact recreation, fishing, and the protection of aquatic life (COMAR 2011a). Additionally, the specific designated use of the Back River Oligohaline Tidal Chesapeake Bay Segment is Use II Support of Estuarine and Marine Aquatic Life and Shellfish Harvesting (COMAR 2011b). The Maryland Department of the Environment (MDE) has identified the waters of the Back River Oligohaline Tidal Chesapeake Bay Segment (Integrated Report Assessment Unit ID: BACOH) on the States 2010 Integrated Report as impaired by PCBs in both sediment (1998) and fish tissue (2008), sediments (1996), chlordane (1996), zinc (1998), nutrients nitrogen and phosphorus (1996), and impacts to biological communities (2002) (MDE 2011a). The Back River Oligohaline Tidal Chesapeake Bay Segment is often referred to as the Back River embayment, and therefore, for the purposes of this report, will be referred to as such for simplicity. The TMDL established herein by MDE will address the total PCB (tPCB) listing for the Back River embayment, for which a data solicitation was conducted, and all readily available data from the past five years have been considered. Chlordane and nutrients (nitrogen and phosphorus) TMDLs, and a zinc water quality analysis (WQA) were approved by the EPA in 1999, 2005, and 2004, respectively. Then, in 2010, the Chesapeake Bay nutrient and sediment TMDLs were developed by EPA, which addressed the sediment impairment listing for the embayment. The listing for impacts to biological communities will be addressed at a future date.