- Agra Earth & Environmental - Bellevue, Kirkland
- Alisto - Portland
- Alton Geoscience - Seattle
- Applied Geosciences - Tuston, CA
- Applied Geotechnology - Bellevue; Portland
- ARCO
- ASI - Lakewood, CO
- ATC Environmental - Seattle
- Boeing Corporation - Auburn
- Bonneville Power Administration
- Bovay Northwest - Spokane
- CDM Federal
- Century West Engineering - Portland; Spokane
- CH2M Hill - Bellevue WA; Corvallis, Portland OR
- Chevron - Seattle
- Columbia Environmental - Federal Way
- Dames & Moore - Portland; Los Angeles; Seattle
- Dowl Engineers - Redmond
- E A Engineering Science & Tech. - Bellevue
- ECOVA - Redmond
- EGE
- EMCON - Bothell WA; Eugene, Portland OR
- EMR - Redmond
- Enecotech
- ENSR Consulting & Engineering - Redmond
- Environmental Associates - Bellevue
- Environmental Partners - Bellevue
- Environmental Science & Engineering - Redmond
- ERM Northwest - Redmond
- Fluor Daniel GTI - Albuquerque NM; Kent WA; Sacramento, Torrance CA
- Foster Wheeler - Bellevue
- Geoengineers - Redmond, Tacoma WA; Portland OR
- Geotech Consultants - Bellevue
- Geraghty & Miller - Portland OR; Redmond WA
- Golder & Associates - Redmond
- Hart Crowser - Seattle
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- ICF Kaiser - Seattle
- IT Corp - Albuquerque NM
- Kennedy/Jenks Consultants - Federal Way WA; Portland OR; Sacramento CA
- Kleinfelder & Assoc. - Beaverton OR; Bellevue WA; Los Angeles, San Diego CA
- Landau Associates - Edmonds
- Maxim - Boise; Yakima
- Ninyo & Moore - San Diego
- Nowicki & Associates - Federal Way
- OHM Remediation - Kent
- Optech - San Antonio TX
- Pacific Environmental Group - Portland OR; Redmond WA
- PBS Environmental - Portland OR; Seattle WA
- Radian - Seattle, Vancouver BC
- Retec - Seattle
- Riedel Environmental Services - Portland
- SAIC - San Diego and Seattle
- SCS Engineers - Bellevue
- Secor - Bellevue WA; Tualatin OR
- Shannon & Wilson - Richland, Seattle
- SME Corporation - Tacoma
- Tacoma Public Utilities
- Tetra Tech - Redmond
- Texaco Environmental Serv. - Kirkland WA; Universal City CA
- Thomas Hill Associates - Seattle
- Time Oil - Seattle
- UNOCAL - Seattle
- URS Consultants - Seattle
- U.S. Coast Guard
- U.S. Navy
- W. W. Irwin - Long Beach
- WA State Dept of Ecology - Olympia, Yakima
- Westinghouse Remediation Services - Murray UT
- Weston (Roy F) - Portland OR; Seattle WA
- Weyerhaeuser
- Woodward Clyde - Seattle
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