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
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
- 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.