Decision Rationale Total Maximum Daily Loads Rock Creek Tributaries for Organics and Metals

摘要

The Clean Water Act requires that Total Maximum Daily Loads (TMDLs) be developed for those water bodies that will not attain water quality standards after application of technologybased and other required controls. A TMDL sets the quantity of a pollutant that may be introduced into a waterbody without exceeding the applicable water quality standard. EPA regulations define a TMDL as the sum of the wasteload allocations (WLAs) assigned to point sources, the load allocations (LAs) assigned to nonpoint sources and natural background, and a margin of safety (MOS). The TMDL is commonly expressed as: TMDL = WLAs + LAs + MOS This document sets forth EPAs rationale for approving the District of Columbia Final Total Maximum Daily Loads for Organics and Metals in Broad Branch, Dumbarton Oaks, Fenwick Branch, Klingle Valley Creek, Luzon Branch, Melvin Hazen, Valley Branch, Normanstone Creek, Pinehurst Branch, Piney Branch, Portal Branch and Soapstone Creek. The following TMDL Summary table is discussed in Section V.2. of the decision rationale.