Total Maximum Daily Load Studies

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:

Identify waters that do not meet water quality standards. In this process, the state identifies the particular pollutant(s) causing the water to exceed state standards.
Prioritize waters that do not meet standards for TMDL development based on amounts and sources of pollution. For example, waters with high naturally occurring “pollution” will fall to the bottom of the list.
Establish TMDLs by setting a target for the amount of pollution reduction, and assign responsibility for achieving those reductions to polluters to ensure that state water quality standards will be met. A separate TMDL is set for each pollutant with concentrations over the state standard.
Develop strategies for reducing pollutant inputs and assess progress made during implementation of the TMDL. This is when establishing watershed partnerships can be most effective. If a partnership has developed a strategy, it should share it with the state. In fact, several states have incorporated watershed partnership plans in their strategies for implementing specific TMDLs.

Current TMDL’s in Bellingham

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.