Total Maximum Daily Load (TMDL) is the maximum amount of pollution that a water body can receive without violating state water quality standards.
Establishing TMDLs for water bodies that do not meet water quality standards has been required for several years. It was mandated by Section 303(d) of the Clean Water Act (passed in 1972).
Pollution can come from many sources and activities dispersed throughout the watershed. We call this pollution non-point source pollution. In addition to setting a TMDL, the responsibility for reducing pollution from both point sources (pipes) and non-point sources is assigned to the offenders. Non-point sources include, but are not limited to, stormwater run-off, leaking underground storage tanks and septic systems, and soil erosion.
The TMDL process consists of the following steps:
Concentrations of pollutants that exceed state standards, including fecal coliform, temperature, phosphorus and dissolved oxygen (DO) have been measured in many city streams and in Lake Whatcom. Lake Whatcom and Whatcom Creek have been assigned the highest priority for clean up.
The City of Bellingham has partnered with Ecology to conduct two separate TMDL studies for Whatcom Creek. Whatcom Creek has been placed on the state's 303(d) list of impaired waterbodies since 1998 for both temperature and fecal coliform. Technical studies began in the winter of 2002. The temperature study is still underway, while the fecal coliform technical study is complete. The Department of Ecology provides more information on TMDLs for local water resources.