Water Quality Improvement Project
Simpson Timberlands Area:


The Green Diamond Resource Company, formerly known as the Simpson Timber Company, is a forestry company in the Pacific northwest.

Water quality issues

Several tributaries of the lower Chehalis and Skokomish rivers on Green Diamond Resource Company land, as well as several streams draining to South Puget Sound and Hood Canal, do not meet the state surface water quality standards for temperature. High summer water temperatures in some of these streams affect the rearing habitat for coho salmon as well as for steelhead and cutthroat trout.

Why this matters

Water temperature influences what types of organisms can live in a water body. Cooler water holds more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Threatened and endangered salmon need cold, clean water to survive.

Land use activities that can cause surface water temperature increases include forest management within riparian areas, timber harvest in sensitive areas outside the riparian zone, and roads. One way to cool water temperature is to shade the water body by adding or retaining streamside vegetation.

Status of the project

This TMDL was established for two pollutants: heat (incoming solar radiation) and sediment. It addresses four water quality-impaired segments listed on the 1996 303(d) list for temperature. These segments are within Green Diamond Resource Company’s 261,575 acres of Northwest Timberlands. The TMDL sets allocation limits to protect all 1,398 miles of the area streams from becoming impaired.

This TMDL is unique because it limits the physical scope of the TMDL to land ownership, rather than try to expand to cover all of the affected watersheds. Parameters were also limited the to those heavily impacted by forest management activities. A single landowner offered to coordinate their forest land management planning with development of the TMDL.

Ecology submitted the TMDL report to EPA, which approved it in July 2000. The TMDL implementation strategy was designed to support long-term monitoring and implementation activities.

TMDL Report

Simpson Northwest Timberlands Temperature Total Maximum Daily Load -- Submittal Report (Ecology publication)

Related information

Simpson Habitat Conservation Plan (HCP)

Cross-walk between HCP and Forest Practice Rules (updated)

Ecology publications pertaining to WRIA 22 (Ecology publication)

WRIA 22 Watershed Information (Water website)

WRIA 22 and WRIA 23: Chehalis Basin and Nearby Drainages: Salmon Habitat Limiting Factors (WA State Conservation Commission)

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Last updated June 2017
  Water resource inventory area (WRIA) 22 map, Washington State.


WRIA: #22 (Lower Chehalis)
Grays Harbor

Water-body Names:
Lower Chehalis River tributaries
Lower Skokomish River tributaries
Selected streams draining to South Puget Sound and Hood Canal


# of TMDLs: 28

TMDL 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