| Washington River Protection Solutions LLC | Richland | WA | $3.05B |
| Research Triangle Institute | Durham | NC | $2.87B |
| CH2M Hill, Inc. | Denver | CO | $979M |
| Eastern Research Group Inc. | Concord | MA | $653M |
| WSP USA Environment & Infrastructure Inc. | Blue Bell | PA | $580M |
| The Cadmus Group LLC | Arlington | VA | $333M |
| Brice Solutions, LLC | Anchorage | AK | $169M |
| Tetra Tech, Inc.Pittsburgh, PA · UEI FL1UPMZCC5S8 | Pittsburgh | PA | $167M |
| Tetra Tech, Inc.Chicago, IL · UEI E3QKBMJ7H9K7 | Chicago | IL | $159M |
| Chenega Reliable Services LLC | San Antonio | TX | $155M |
| Tetra Tech Inc.San Diego, CA · UEI HW1GWDNW1F21 | San Diego | CA | $150M |
| S C & A Inc. | Arlington | VA | $148M |
| Tetra Tech Inc.Virginia Beach, VA · UEI HVDMNK1MYQN3 | Virginia Beach | VA | $140M |
| National Rural Water Association | Duncan | OK | $134M |
| CDM International Inc. | Boston | MA | $120M |
| Vernadero Group Inc. | Phoenix | AZ | $116M |
| Tech2 Solutions | Richland | WA | $97.7M |
| Tetra Tech, Inc.Oakland, CA · UEI J8CNBANBZ6U8 | Oakland | CA | $92.8M |
| Gsi North America Inc.Flemington, NJ · UEI EHM2NWLJHSJ7 | Flemington | NJ | $89.8M |
| Weston - Er Federal Services, LLC | West Chester | PA | $86.4M |
| Sol Solutions, LLC | Chandler | AZ | $85.6M |
| Gulf South Research Corp. | Baton Rouge | LA | $85.4M |
| A.i.s., Inc. | North Dartmouth | MA | $80.6M |
| Specpro Sustainment And Environmental, LLC | San Antonio | TX | $76.9M |
| Cherokee Nation Environmental Solutions, L.L.C. | Tulsa | OK | $76.8M |
| Gryphon Environmental, LLC | Colorado Springs | CO | $76.4M |
| Baker-aecom Environmental Compliance JV | Moon Township | PA | $75.5M |
| Leisnoi Diversified-kemron 8a JV, LLC | Anchorage | AK | $75.3M |
| The Blackledge Group, Inc. | Jacksonville Beach | FL | $73M |
| Environmental Compliance Consultants, Inc. | Anchorage | AK | $68.9M |
| Mabbett & Associates, Inc. | Stoneham | MA | $65.6M |
| Oneida Environmental, LLC | Milwaukee | WI | $64.3M |
| Ahtna Solutions, LLC | Anchorage | AK | $64M |
| The Solution Foundry, LLC | Woodstock | GA | $61.7M |
| Stantec Gs Inc. | Charlottesville | VA | $60.5M |
| Marstel-day, LLC | Fredericksburg | VA | $59.6M |
| Leisnoi Diversified Services, LLC | Saint Ignatius | MT | $59.4M |
| Tehama Ecs LLC | Kansas City | MO | $59.4M |
| Weston-techlaw JV LLC | Chantilly | VA | $56.3M |
| Eco & Associates, Inc. | Santa Ana | CA | $55.3M |
| Environmental Research Group, L.L.C. | Baltimore | MD | $54.8M |
| Tetra Tech, Inc.Duluth, GA · UEI W4NLBJHRP7H3 | Duluth | GA | $54.4M |
| Skeo Solutions, Inc. | Charlottesville | VA | $54.3M |
| Delta Land Services LLC | Baton Rouge | LA | $52.7M |
| HGS Engineering Inc. | Anniston | AL | $51.2M |
| Toeroek Associates, Inc. | Lakewood | CO | $49.2M |
| Great Lakes Environmental Center, Inc. | Traverse City | MI | $48.8M |
| Solv LLC | Mc Lean | VA | $48M |
| Tetra Tech, Inc.Kansas City, MO · UEI HHDHBZL5PLM5 | Kansas City | MO | $48M |
| Ahtna-arcadis 8(a) JV, LLC | Anchorage | AK | $47.7M |
| Haztrain Inc. | Waldorf | MD | $47.6M |
| Specpro-bb&e JV, LLC | Anchorage | AK | $45M |
| Mse Group LLC | North Little Rock | AR | $44.8M |
| Independent Strategic Management Solutions Inc. | Richland | WA | $43.2M |
| HSG, LLC | Merritt Island | FL | $42.6M |
| Pacific States Marine Fisheries Commission | Portland | OR | $41.6M |
| North Wind Resource Consulting LLC | Idaho Falls | ID | $40.2M |
| Tetra Tech Inc.Denver, CO · UEI WL4VMSDRCLR5 | Denver | CO | $38.3M |
| Ardl Inc. | Mount Vernon | IL | $37.7M |
| Kearns & West Inc. | San Francisco | CA | $37.4M |
| Genwest Systems Inc. | Edmonds | WA | $37.1M |
| HDR And Tehama Joint Venture | Kansas City | MO | $36.7M |
| Osage Nation Energy Services LLC | Tulsa | OK | $36M |
| Verina Consulting Group LLC | Bridgewater | NJ | $35.7M |
| Tetra Tech, Inc.Fairfax, VA · UEI X38LAAB5HB64 | Fairfax | VA | $33.4M |
| Environmental Management Support, Inc. | Silver Spring | MD | $33M |
| Stell Environmental Enterprises Inc. | Redmond | WA | $32.6M |
| Paleowest LLC | Phoenix | AZ | $31.6M |
| CDM Federal Programs Corporation | Jacksonville | FL | $31.3M |
| Rpi-css, LLC | Columbia | SC | $30M |
| Tetra Tech, Inc.Germantown, MD · UEI J8CVJQCB1PJ3 | Germantown | MD | $29.8M |
| Gsi Environmental Inc. | Houston | TX | $28.8M |
| Credere Associates, LLC | Westbrook | ME | $28.4M |
| Applied Environmental, Inc. | Herndon | VA | $28.1M |
| Kian International Inc. | Clearwater | FL | $27.9M |
| Association Of Consultants And Engineers | Leonardtown | MD | $27.8M |
| Straughan Environmental, Inc. | Columbia | MD | $27.7M |
| Bluestone Interspec JV, LLC | Malvern | PA | $27.2M |
| Rsi Services LLC | Oak Ridge | TN | $26.7M |
| The NDN Companies | Jacksonville | FL | $26.2M |
| Gsina-gilbane II JV LLC | Flemington | NJ | $26M |
| Statistical Research Inc. | Tucson | AZ | $25.9M |
| Auxilio Management Services | Denver | CO | $25.8M |
| Umyuaq Consulting Group, LLC | Anchorage | AK | $25.7M |
| Research Planning, Inc. | Columbia | SC | $25M |
| G & Rk Consulting Associates LLC | Englewood | CO | $24.8M |
| Tierra Right Of Way Services Ltd. | Tucson | AZ | $24.3M |
| S.p. Cramer & Associates, Inc. | Portland | OR | $23.6M |
| Neptune And Company, Incorporated | Lakewood | CO | $23.6M |
| Gsi North America Inc.Honolulu, HI · UEI K7ZHNF6YJMB3 | Honolulu | HI | $23.2M |
| Pb&a/css JV, LLC. | Austin | TX | $23M |
| Cardno Tec-leidos, LLC | Charlottesville | VA | $22.1M |
| Water, Civil And Environmental Incorporated | Boise | ID | $21.8M |
| Sustainable Design Consortium, (SDC) Inc. | Baltimore | MD | $21.7M |
| Swca, Incorporated | Phoenix | AZ | $21.6M |
| First Environment Inc. | Butler | NJ | $21.5M |
| Al-mustashar Lil-handasah | Amman | | $21.4M |
| Horsley Witten Group, Inc. | Sandwich | MA | $21.4M |
| Stantec Gs - Aecom Atlantic Joint Venture | Charlottesville | VA | $21.3M |
| Egc, Inc. | San Antonio | TX | $20.7M |
