Water Quality Improvement Project
Lower Skokomish River Basin:
Fecal Coliform Bacteria


The Skokomish River drains a basin of about 247 square miles. It empties into Annas Bay in southern Hood Canal near Potlatch, Washington. Major sub-basins include the North Fork Skokomish River (118 square miles), South Fork Skokomish River (104 square miles), and Vance Creek (25 square miles).

The upper reaches of the Skokomish River lie within the Olympic National Park. The North Fork basin includes Lake Cushman, a reservoir maintained for hydroelectric power generation whose shores include residential development. The basin is sparsely populated and rural. The Skokomish Indian Reservation is located at the mouth of the basin and contains low-density residential development. Commercial and noncommercial agricultural activities occur in the lower river valley and include cattle and other livestock culture, hay and Christmas tree production, and some vegetable cropping. Silviculture on U.S. Forest Service and privately-owned lands dominate the upper basins. The Annas Bay estuary contains a rich shellfish resource that is used by Tribal, commercial, and recreational harvesters. Recreational shellfish beds are located within, and to the south of, Potlatch State Park. Potlatch State Park is also a center of primary contact recreation, being used by swimmers and scuba divers. The mainstem Skokomish River and lower Vance Creek are also used by swimmers and waders during the summer months. The Skokomish River valley provides important habitat to a variety of terrestrial wildlife such as elk, deer, beaver, and waterfowl. Wildlife, shellfish, and finfish are important cultural and economic resources for the Tribe. The Skokomish River system provides valuable habitat for important species of fish such as chinook, coho, and chum salmon; steelhead; and various trout.

The lower Skokomish Valley has several streams crossing it, the largest of which are Purdy Creek, Weaver Creek, and Hunter Creek. Streams and springs in the valley contribute to several large wetland areas, which drain to the mainstem of the Skokomish River mostly downstream of Highway 101. The river then discharges to the tidal estuary of Annas Bay and Hood Canal. Rainfall in the basin varies from 75 inches per year near the mouth to 230 inches per year at the crest of the Olympic Mountains near 6,000 ft. elevation. Winter precipitation in the mountains, mainly in the form of snow, provides runoff in the North and South Forks through the spring and early summer months. The dry season runs from July into September, followed by an October through March wet season in which more than 75% of the annual precipitation occurs. The courses of these streams seem to have changed over the years due to flood activity, wetland dynamics, and human management.

Innovative partnerships have been formed to preserve and protect this watershed. See video “Coming Back: Restoring the Skokomish Watershed."

Water quality issues

Human activities altered the natural hydrologic regime in the entire Skokomish basin. Sedimentation in the lower river channel due to forestry, road building, dikes, levies, and other land use practices have resulted in an increase in the frequency and intensity of flood events, higher basin groundwater levels, and subsequent septic system failures.

A study (TMDL) for fecal coliform bacteria (FC) for the Skokomish River found that FC levels were not meeting fresh water quality standards due to nonpoint source pollution. The study found that concentrations of fecal coliform bacteria in the lower river valley exceed state water quality standards.

The 2000 study area included the south and north forks of the Skokomish River, as well as Purdy Creek, Weaver Creek, Ten-Acre Creek, Vance Creek and Hunter Creek. The Department of Ecology conducted the study with the cooperation of the Skokomish Tribe, whose reservation includes part of the watershed.

Why this matters

Fecal coliform bacteria are found in the waste of warm-blooded animals. They are a major concern in the river because they indicate that people may be exposed to a variety of harmful bacteria and viruses. In downstream Annas Bay, too much bacteria may cause shellfish harvesting to be restricted or closed.

Status of the project

EPA approved the Total Maximum Daily Load (TMDL) submittal for fecal coliform bacteria in 2001. The submittal included a study of the water quality issues and recommendations based on the results of the study. The submittal also included a strategy on how to carry out the recommended actions in the study.

Following the study, responsible agencies, the Tribe, and local landowners developed a detailed implementation cleanup plan. That plan was completed in February 2003. Many actions have been taken to improve water quality. Monitoring continues to measure progress towards cleanup goals.

In January 2005, Mason Conservation District began monitoring in the Skokomish valley. The data was to be used to:

  • Evaluate progress towards water quality goals.
  • Help identify current source areas (after several years of apparent improvement, bacteria concentrations suddenly began increasing in the spring of 2004 – the data may help us to understand why).
  • Help focus cleanup actions.

We identified four main sampling locations from the 2000 water quality study. These are the places where bacteria concentrations need to be reduced – Weaver, Purdy, and Ten Acre Creeks, and at the Highway 106 Bridge. The Conservation District monitored each of these stations, plus one “background” station (called mid-Skokomish) that is located above most of the development in the lower valley. Monitoring is planned every two weeks through November 2006, totaling 46 sampling events. The Conservation District monitored according to a Quality Assurance Project Plan developed by the Department of Ecology.

Technical information

Unless otherwise specified, the following documents are Ecology publications.

Related information

Washington: Skokomish River - Watershed-scale Effort Removes Bacteria Sources (EPA web site)

Cleaning up bacteria in the Skokomish Watershed Newsletter:

Skokomish River TMDL Cleans Up Bacteria (Ecology water quality story)

EPA Section 319 - Nonpoint Source Program Success Story: Watershed-scale Effort Removes Bacteria Sources (EPA)

Weaver Creek (Mason County) Fecal Coliform Attainment Monitoring (Ecology publication)

WRIA 16: Skokomish-Dosewallips Watershed Information (Water web site)

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Last updated October 2016
  Map for water resource inventory area (WRIA) 16, Washington State.


WRIA: 16 - Skokomish-Dosewallips

Water-body Names:
Lower Skokomish River
Vance Creek

Fecal coliform bacteria

# of TMDLs: 5

Approved by EPA
Has implementation plan

Contact Info:
Andrew Kolosseus
Phone: 360-407-7543
Email: Andrew.Kolosseus@ecy.wa.gov

Southwest Region
Department of Ecology
P.O. Box 47775
Olympia, WA 98504-7775