| Solutio Environmental Inc. | San Antonio | TX | Subcontractor |
| Spangler Environmental, Inc. | Raleigh | NC | $0 |
| Specialty Technical Consultants, Inc. | Bridgewater | NJ | Subcontractor |
| Spillman, Bud | Cheyenne | WY | $0 |
| Spring Environmental Inc. | Spokane | WA | $0 |
| Spring Rivers Ecological Sciences LLC | Cassel | CA | $0 |
| S&R Environmental Consulting, Inc. | Denver | CO | $0 |
| Steven Lohrenz | Marion | MA | $0 |
| Stirling Dale A | Coupeville | WA | $0 |
| Stohl Environmental LLC | Orchard Park | NY | $0 |
| Stokes Environmental Associates, Ltd. | Norfolk | VA | $0 |
| Stonefly Consulting LLC | Clarkston | WA | $0 |
| Strata-geo LLC | Arlington | VA | $0 |
| Stratus Corp. | Pelham | NY | $0 |
| Stream Dynamics Inc. | Silver City | NM | $0 |
| Street Sounds Ecology LLC | Seattle | WA | $0 |
| Sunzi Consulting LLC | Folsom | CA | Subcontractor |
| Swaim Biological Inc. | Livermore | CA | Subcontractor |
| Taconic Ridge Environmental Inc. | Worcester | MA | Subcontractor |
| Tallgrass Restoration, LLC | Milton | WI | $0 |
| Tallpines Environmental Consulting Co. | Flagstaff | AZ | $0 |
| Task Environmental, Inc. | Mount Dora | FL | $0 |
| Td Environmental Services LLC | Petaluma | CA | Subcontractor |
| Teamag, Inc. | Ephrata | PA | $0 |
| Technical Environmental Services Inc. | Marrero | LA | Subcontractor |
| Technical Monitoring Services Inc. | Clinton | LA | $0 |
| Technical Specialists LLP | Carlsbad | NM | Subcontractor |
| Tem Environmental Inc. | Glendale Heights | IL | $0 |
| Tenera Environmental, Inc. | San Luis Obispo | CA | Subcontractor |
| Terra Global Capital, LLC | Oakland | CA | Subcontractor |
| Tetra Tech Bas, Inc. | Diamond Bar | CA | Subcontractor |
| Tetra Tech Inc.Missoula, MT · UEI HLUNH9Y9HTM7 | Missoula | MT | Subcontractor |
| Tetra Tech Inc.Salem, NH · UEI KTCGYH51RCY4 | Salem | NH | Subcontractor |
| Tetra Tech Inc.Cincinnati, OH · UEI NBQGMM91DZF7 | Cincinnati | OH | $0 |
| Tetra Tech, Inc.Superior, CO · UEI S9H2EJL7HHD4 | Superior | CO | $0 |
| Tetra Tech, Inc.Salt Lake City, UT · UEI HN2SQA3ZDJ56 | Salt Lake City | UT | $0 |
| Tetra Tech, Inc.Houston, TX · UEI MXCEW32187N4 | Houston | TX | $0 |
| Tetra Tech, Inc.Helena, MT · UEI P1LUDN2PZ3Y9 | Helena | MT | $0 |
| Tetra Tech, Inc.Oak Ridge, TN · UEI P69YVKGUBDM9 | Oak Ridge | TN | Subcontractor |
| Tetra Tech, Inc.Portland, ME · UEI TMLKTPR57BL3 | Portland | ME | $0 |
| Tetra Tech, Inc.Parsippany, NJ · UEI ZJEUNJGBXU64 | Parsippany | NJ | Subcontractor |
| The Adopt-a-stream Foundation | Everett | WA | $0 |
| The Arrowrock Group Inc. | Boise | ID | $0 |
| The Biodiversity Consultancy Limited | London | | Subcontractor |
| The California Land Stewardship Institute | Napa | CA | $0 |
| The Climate Registry | Los Angeles | CA | $0 |
| The Data Validation Group Inc. | Mission Viejo | CA | Subcontractor |
| The Dredging Professor LLC | Meridian | MS | Subcontractor |
| The E-quest Corporation | Silverthorne | CO | $0 |
| The Hawaii Association For Marine Education & Research Inc. | Lahaina | HI | $0 |
| The Sonoran Institute | Tucson | AZ | $0 |
| Third Rock Consultants, LLC | Lexington | KY | $0 |
| Thomas Environmental Water Sampling LLC | Madison | FL | $0 |
| Throwe Environmental LLC | Bristol | RI | Subcontractor |
| Tiger Environmental Inc. | Lakewood | NJ | $0 |
| TKT Consulting LLC | Reno | NV | $0 |
| Tommy Rambin Enterprises, L.L.C. | Dry Prong | LA | $0 |
| T.P.M., Inc. | Bowling Green | KY | $0 |
| Training Services International | Eastlake | OH | Subcontractor |
| Tremaine & Associates, Inc. | Dixon | CA | Subcontractor |
| Trieco LLC | Louisville | KY | $0 |
| Trinity Source Group, Inc. | Santa Cruz | CA | $0 |
| Triple Hs, Inc. | Los Gatos | CA | Subcontractor |
| Triterra, LLC | Lansing | MI | Subcontractor |
| True North Consultants, Inc. | Naperville | IL | Subcontractor |
| Tse Environmental | Carrollton | GA | Subcontractor |
| Turnstone E H & S, A Texas For-profit Corporation | Houston | TX | Subcontractor |
| Understory Consulting LLC | Medford | OR | $0 |
| Upstate Freshwater Institute | Syracuse | NY | $0 |
| USA Environmental Management Inc. | Trenton | NJ | Subcontractor |
| Uxo Pro, Inc. | Laurel | MD | Subcontractor |
| Validata Chemical Services, Inc. | Duluth | GA | Subcontractor |
| Vantage Observing, LLC | Fernandina Beach | FL | Subcontractor |
| Ventrex Environmental Services LLC | Fort Worth | TX | $0 |
| Verdad Group LLC | Tucson | AZ | $0 |
| Vestra Resources, Inc. | Redding | CA | $0 |
| Vireo Advisors LLC | Jamaica Plain | MA | Subcontractor |
| Vissering Consulting Group Inc. | Rockville | MD | Subcontractor |
| Vollmar Natural Lands Consulting Inc. | Berkeley | CA | $0 |
| Wang Xiaoliang | Reno | NV | $0 |
| Wasatch Ecology LLC | Salt Lake City | UT | $0 |
| Washington J Braida LLC | Princeton Junction | NJ | Subcontractor |
| Water Balance Consulting LLC | Nederland | CO | $0 |
| Water For Life Solutions LLC | Oakton | VA | Subcontractor |
| Waterra USA Inc. | Peshastin | WA | $0 |
| Water Science Institute | Lancaster | PA | $0 |
| Watershed Artisans, Inc. | Vallecitos | NM | $0 |
| Watershed Institute Inc. | Belton | MO | $0 |
| Watershed Professionals Network, LLC | Hood River | OR | Subcontractor |
| Weecycle Environmental Consulting Inc. | Lafayette | CO | $0 |
| Werier David | Willseyville | NY | $0 |
| Westech Environmental Services Inc. | Helena | MT | $0 |
| Western Bioacoustics Inc. | Fairbanks | AK | $0 |
| Western Biological LLC | Elko | NV | Subcontractor |
| Western Plains Consulting, Inc. | Bismarck | ND | $0 |
| Western Rock Art Research | Costa Mesa | CA | $0 |
| Western States Air Resources Council | Santa Fe | NM | $0 |
| Wetlands Management Sf, LLC | Port St Lucie | FL | $0 |
| Whitson Contracting & Management, Inc. | Escondido | CA | $0 |
| Wilcox & Barton, Inc. | Concord | NH | Subcontractor |
