Water Quality Improvement Projects
Chehalis River Area:



The Chehalis River and its tributaries cover more than 3300 surface miles and span two watershed resource inventory areas (WRIAs 22 and 23). The upper watershed (from Porter to the Chehalis River headwaters) has been the subject of several water quality studies and total maximum daily load (TMDL) plans since 1990. The TMDL plans cover all of the upper watershed in WRIA 23 and address 303(d) listings for dissolved oxygen (DO), fecal coliform bacteria, and temperature (T) impairments. These TMDL plans are described together here since these pollutants are inter-related, as are the implementation activities needed to achieve water quality standards. The Grays Harbor Bacteria TMDL covers the Chehalis River watershed from Porter to the harbor at Aberdeen.

Chehalis River upstream of Pe Ell, Washington.  Photo courtesy of Dustin Bilhimer, WA Department of Ecology.

Water quality issues

The Chehalis River and many of its largest tributaries have a history of not meeting water quality standards for instream temperature, dissolved oxygen, and fecal coliform, while many waterbodies in the upper watershed also have difficulties meeting pH, total phosphorus, and turbidity criteria on occasion. A fish kill on the Black River in 1989 (see report) and other problems with dissolved oxygen on the Chehalis River spurred the water quality studies that led to the Upper Chehalis Dissolved Oxygen TMDL, which incorporated the Black River water quality studies.

Sufficient levels of dissolved oxygen (DO) in healthy water is vital for fish and aquatic life to survive. If DO levels are too low, then fish and other aquatic life will suffocate. Oxygen is also necessary to help decompose organic matter in the water and bottom sediments, as well as for other biological and chemical processes. Pollutants that affect DO include nitrogen in several forms (ammonia, nitrate, and nitrite) and phosphorus. Both nutrients are needed to fuel primary productivity, which is the process whereby energy is converted to organic substances through photosynthesis. Primary productivity can increase DO during the day as the plants photosynthesize, but DO decreases at night as a result of respiration. High concentrations of decomposing organic matter can lower DO, and high stream temperatures can lower the DO saturation point which also results in lower DO.

The Dissolved Oxygen TMDL report (2000) identified the section of the Chehalis River, called the Twin Cities Reach (which is from the confluence with the Newaukum River to the confluence with Skookumchuck River), as very sensitive to nutrient inputs due in large part to the very slow streamflow within this reach. This prompted a significant investment of money for improvements and operational changes to the city of Chehalis’ and the city of Centralia’s wastewater treatment plants in the mid-2000s. The TMDL set limits on point and nonpoint sources of ammonia and biological oxygen demand (BOD) as surrogates for improving DO in the Chehalis River watershed.

A plan to reduce instream temperatures was developed with the stream temperature TMDL (1999), which established targets for riparian restoration and improvements along the mainstem Chehalis River and several of its significant tributaries like the Newaukum River. Both juvenile and adult salmonids need cool temperatures to survive. Cooler temperatures can be achieved by restoring and protecting riparian shade which blocks solar radiation from directly warming a waterbody, and also by increasing channel complexity and restroing hydrologic functions that increase the amount of inter-gravel and hyporheic flow of cooler groundwater into the surface water to provide cold-water refugia for salmonids. Properly functioning riparian areas have the added benefit of reducing streambank erosion, and can filter stormwater runoff to remove bacteria and nutrients before they get into rivers and streams. Cooler streams also results in a higher DO saturation point which means the stream can hold higher concentrations of DO.

Fecal coliform is a group of bacteria common in human and animal waste and includes pathogens that can make people sick and cause the closure of shellfish harvesting beds when concentrations are higher than limits established by the National Sanitation and Shellfish Program (NSSP) and regulated through the Washing Department of Health (WDOH). Bacteria can get into our waters from untreated or partially treated wastewater treatment plant discharges, improperly functioning septic systems, improperly managed, manure, direct access from livestock, pets and wildlife. The fecal coliform bacteria TMDL (2004) set multiple targets for the reduction of fecal coliform bacteria in areas all throughout the upper Chehalis Watershed.

A study conducted during 2006-2009, in partnership with the Grays Harbor Community College, the Chehalis Tribes, and the Chehalis Basin Partnership, found that bacteria levels in many places around the upper watershed had decreased to levels that did not exceed water quality criteria for bacteria. The Category 4a impaired bacteria listings from those improved areas are on the proposed 2014 Water Quality Assessment list for re-categorization to Category 1 (meets criteria).

TMDL implementation: getting to clean water

Chehalis River upstream of Pe Ell, Washington.  Photo courtesy of Dustin Bilhimer, WA Department of Ecology.

To address the fishery resource concerns the Chehalis Salmon Recovery Lead Entity coordinates salmon recovery funding and projects sponsored by various organizations to protect and enhance the riparian corridor (see the Partners webpage). Funding opportunities are made available through Ecology, the Governor’s Salmon Recovery Office, Natural Resource Conservation Service (NRCS), the US Fish and Wildlife Service, and other public and private entities. Landowners, the local conservation districts, the Confederated Tribes of the Chehalis Indian Reservation, cities, volunteer groups including students, land trusts, and local fishery support groups provide labor and plant materials for stabilizing the stream banks and to increase riparian shade.

In addition to preserving current riparian areas, restoring riparian shade is one of the most important implementation activities to directly lower stream temperatures. Where livestock are present, landowners should install fencing to keep livestock out of rivers, streams, and away from eroding river banks, as well as fixing denuded riparian areas to increase shade. The fence and vegetative “buffers” reduce animal waste and other pollutants washed off adjacent lands from getting into the river or stream. A functioning riparian area prevents or reduces transport of nutrient and BOD materials into the river to help improve DO conditions too.

Ecology (along with WDFW, WDNR, the salmon recovery Lead Entity, and others) is engaged with the Chehalis Flood Strategy efforts to reduce flood damage and restore aquatic species habitat throughout the Chehalis River basin. Solutions to reduce flooding and restore natural functions and aquatic habitat can also have benefits for the improvement of water quality and to meet TMDL objectives.

Current Monitoring

Ecology’s Streamflow Gaging and WQ Monitoring Network for the Chehalis Flood Strategy Workgroup can be found on the web. In addition, Ecology has maintained two long-term ambient water quality monitoring stations with data going back to the ‘80s and later (available on the web).

In addition to Ecology’s monitoring, Thurston County also collects water quality data within the county’s part of the upper Chehalis Basin (parts of the Scatter Creek and Black River watersheds). The county’s data is available on the web. The Chehalis Tribe also collects surface water quality data.

Technical information

TMDL reports are submitted to the U.S. EPA for approval. These documents are also called WQ Improvement Reports (WQIRs). Sometimes the study on which these reports are based is published separately as a TMDL study, or technical report, that describes the results and analysis of the study. The precursor to a study is a Quality Assurance Project Plan (QAPP). The QAPP describes the study design, data collection and data quality objectives. Important follow-up studies to a TMDL are also included in the following table. Unless otherwise specified the following documents are Ecology publications.

Document Type Pollutant Title Publication #
TMDL Reports Temperature Upper Chehalis River Basin Temperature Total Maximum Daily Load Submittal 99-52
Dissolved Oxygen

Revised -- Upper Chehalis River Basin Dissolved Oxygen Total Maximum Daily Load Submittal Report

Fecal Coliform Bacteria Upper Chehalis River Fecal Coliform Bacteria Total Maximum Daily Load: Submittal Report 04-10-041
TMDL Implementation Plan

Fecal Coliform Bacteria


Dissolved Oxygen

The Chehalis/Grays Harbor Watershed Dissolved Oxygen, Temperature, and Fecal Coliform Bacteria TMDL: Detailed Implementation (Cleanup) Plan 04-10-065
TMDL Studies Dissolved Oxygen Black River Dissolved Oxygen and Phosphorus Total Maximum Daily Load Study 94-106
Fecal Coliform Bacteria

Black River Wet Season Nonpoint Source Total Maximum Daily Load Study

Upper Chehalis River Dry Season Total Maximum Daily Load Study

Upper Chehalis River Fecal Coliform Bacteria Total Maximum Daily Load Recommendations



Follow-up Studies Fecal Coliform Bacteria Upper Chehalis River Watershed Multi-Parameter Total Maximum Daily Load: Water Quality Data Review 10-03-057



Related information

WRIA 22 23 Watershed Information (Water web site)


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Last updated October 2016
Map of Upper Chehalis River Watershed TMDLs


#22 (Lower Chehalis)
#23 (Upper Chehalis)
County: Grays Harbor

Water-body Name:
Upper Chehalis River

Dissolved Oxygen
Fecal Coliform Bacteria

# of TMDLs:
Ammonia-N/BOD: 34
Dissolved Oxygen: 3
Temperature: 11

Approved by EPA

Contact Info:
Brett Raunig
Phone: 360-690-4660
Email: Brett.Raunig@ecy.wa.gov

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