Water Quality Improvement Project
Sumas River Area:


The Sumas River is a Class A waterbody located in Whatcom County. Water in the Sumas River watershed is used mainly for agriculture, specifically dairy farming. There are a number of dairy pastures along the banks of the Sumas River. Johnson Creek, a major tributary to the Sumas River, meanders through the city of Sumas before joining the Sumas River one mile above the Sumas wastewater treatment plant (WWTP) outfall. It drains much of the agricultural lands.

Water Quality Issues

At one time the Sumas River received water discharged from the town of Sumas WWTP. Studies found the following issues:

  • There were specific concerns with BOD, ammonia-nitrogen, chlorine, and fecal coliform.
  • Dissolved oxygen (DO) violations from WWTP discharges sometimes occurred under summer design conditions.
  • Total residual Chlorine exceeded proposed daily permit limits under both annual and seasonal discharge conditions.
  • Nonpoint sources upstream of the WWTP may have contributed to fecal coliform and nutrient loads to the Sumas River, mainly from agricultural discharges to the Johnson Creek drainage.

Why this matters

Ammonia-N is a form of nitrogen, a nutrient. It is comes from fertilizer applied to land, and can be carried into rivers, lakes and streams through stormwater runoff, for example. Too many nutrients in the water encourages the growth of algae, especially in lakes. As the algae die and decompose in the water, the dissolved oxygen is used up, leaving less available to fish and other aquatic life.

Biological oxygen demand (BOD) is a measure of the amount of oxygen used by microorganisms to decompose organic matter in water. The amount of nutrients in the water, e.g. nitrogen, can lead to high BOD levels as algae grow, die, and are decomposed by bacteria which uses the oxygen in the water.

Chlorine is widely used to disinfect municipal wastewater. Chlorine can irritate the skin and mucous membranes of fish, even at low levels. If it combines with ammonia in the water, the resultant product can pass through fish gills and enter the bloodstream, preventing oxygen from entering the blood and causing suffocation.

What was done

On April 29, 1996 EPA approved the water quality-based National Primary Discharge Elimination Systems Permit (NPDES) for the city of Sumas as a TMDL for the Sumas River Biochemical Oxygen Deman, ammonia-nitrogen, and chlorine parameters. The TMDL established seasonal loading capacities for BOD, total residual chlorine, and ammonia-nitrogen. The city of Sumas WWTP was given a wasteload allocation for all three parameters. The TMDL also included a load allocation for the nonpoint sources, and an allowable mixing zone for ammonia-nitrogen and chlorine.

The wasteload allocations were implemented through effluent limitation conditions in the city of Sumas NPDES permit. The load allocations represented the watershed conditions at that time. They were to be maintained through Ecology's voluntary compliance program for nonpoint source pollution control. Pollution sources not under NPDES authority could be controlled through administrative order if voluntary compliance failed.

Status of the project

The city of Sumas no longer discharges treated sewage to the Sumas River. They send their sewage to Canada for treatment by the Greater Vancouver Regional District. Washington State's 2008 Water Quality Assessment lists the Sumas River as category 1 - available data shows that the waterbody segment meets the state's water quality standard for Ammonia-N. There are no listings for BOD or chlorine in the 2008 assessment.

If the city resumes discharging to the river again, a new TMDL would be necessary to establish appropriate wasteload allocations (WLAs), because the oxygen criteria has been revised since the establishment of the TMDL, and conditions are expected to be different than they were in 1992.

Technical information

Sumas River Receiving Water Study (Ecology publication)

Approval of the Water Quality-Based National Primary Discharge Elimination Systems Permit (NPDES) for the city of Sumas as a Total Maximum Daily Load (TMDL) for Sumas River-Biochemical Oxygen Demand, Ammonia-Nitrogen, Chlorine (TMDL Submittal)

Related information

Washington State's Water Quality Assessment - Simple Query Tool

WRIA 1: Nooksack Watershed Information (Water web site)


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Last updated July 2015
  Water resource inventory area (WRIA) 1 map, Washington State.


WRIA: #1 (Nooksack)
County: Whatcom

Water-body Name:
Sumas River

Biochemical Oxygen Demand (BOD)

# of TMDLs: 3

TMDL project is complete for the above-listed parameters

Contact Info:
Steve Hood
Phone: 360-715-5211
Email: Steve.Hood@ecy.wa.gov

Bellingham Field Office
Department of Ecology
1440 - 10th St., Suite 102
Bellingham, WA 98225-7028