Abstract |
The Chester Creek watershed is located in the Municipality of Anchorage (MOA), the urban center of the Anchorage Bowl in south-central Alaska. Chester Creek flows through University Lake and Westchester Lagoon. The state of Alaska included the entire length of Chester Creek, University Lake and Westchester Lagoon on its 1990 303(d) list as water quality-limited due to fecal coliform, identifying urban runoff as the expected pollutant source. These waters have been included on all subsequent state 303(d) listings. A Total Maximum Daily Load (TMDL) is established in this document for these waters to meet requirements of Section 303(d)(1)(C) of the Clean Water Act and the U.S. Environmental Protection Agencys (EPA) implementing regulations (40 CFR Part 130), which require the establishment of a TMDL for the achievement of water quality standards when a waterbody is water quality-limited. A TMDL is composed of the sum of individual waste load allocations (WLAs) for point sources and load allocations (LAs) for nonpoint sources and natural background loads. In addition, the TMDL must include a margin of safety (MOS), either implicitly or explicitly, that accounts for the uncertainty in the relationship between pollutant loads and the quality of the receiving waterbody. A TMDL represents the amount of a pollutant the waterbody can assimilate while maintaining compliance with applicable water quality standards. Although separate TMDLs could have been prepared for each of the three waters, DEC integrated them into one TMDL as University Lake and Westchester Lagoon are part of the mainstem flow of Chester Creek and have no other natural inlets or outlets. |