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Company lists · Data verified August 2026

Top 25 Ecological consulting firms based in the United States

Compiled by the RevenueBase Data Team Verified Aug 28, 2026 4,819 companies tracked

There are 4,819 ecological consulting firms headquartered in the United States (RevenueBase, August 2026). RevenueBase tracks 150,555 professional contacts across them, including 73,143 with verified work emails and 65,274 with mobile numbers. Houston is the largest hub.

This list covers ecological consulting firms headquartered in the United States, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Data current as of August 28, 2026.

4,819Companies
150,555Contacts tracked
73,143Verified emails
65,274Mobile numbers
Unlock all 4,819 companies Free account · no credit card · 2 minutes

The 25 largest ecological consulting firms based in the United States

Ranked by team size
Top 25 of 4,819 ecological consulting firms based in the United States, ranked by team size, largest first. Data verified Aug 28, 2026. Click a count to unlock that company's people.
#CompanyHQEmployeesContactsVerified emails
1TerraconTustin, CA5,001-10,0006,0243,163
2GolderHouston, TX5,001-10,0003,1831,044
3APTIMWichita, KS1,001-5,0002,6441,098
4Brown And CaldwellWalnut Creek, CA1,001-5,0002,4551
5Geosyntec ConsultantsBoca Raton, FL1,001-5,0002,3921,594
6Civil & Environmental Consultants, INCMartinsburg, WV1,001-5,0002,152945
7Langan Engineering & Environmental ServicesEl Segundo, CA1,001-5,0002,1361,662
8Hazen And SawyerRaleigh, NC1,001-5,0002,1051,457
9LJASarasota, FL1,001-5,0002,0731,578
10Swca Environmental ConsultantsPhoenix, AZ1,001-5,0001,6181,159
11GEI Consultants, INCWoburn, MA1,001-5,0001,5771,237
12Montrose Environmental GroupLittle Rock, AR1,001-5,0001,516846
13SCS EngineersLong Beach, CA1,001-5,0001,191675
14Apex CompaniesRockville, MD1,001-5,0001,146591
15Bge, INCVero Beach, FL1,001-5,0001,129682
16Haley & AldrichBurlington, MA501-1,0001,128789
17VerdantasToledo, OH1,001-5,0001,127795
18Barr Engineering COWashington1,001-5,0001,098828
19Braun Intertec CorporationAmarillo, TX1,001-5,0001,054691
20Trinity ConsultantsDallas, TX1,001-5,000949615
21Alliance Technical GroupPittsburgh, PA1,001-5,000946549
22ParametrixBerkeley, CA501-1,000875678
23GZA Geoenvironmental, INCBoston, MA501-1,000872627
24ATC Group Services LLCSharonville, OH1,001-5,000868278
25ENVUCary, NC1,001-5,000822443

Showing 25 of 4,819 ecological consulting firms based in the United States

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Ecological consulting firms based in the United States at a glance

As of Aug 28, 2026
1-10Median size (employees)
HoustonLargest hub · 77 HQs
65,274Contacts with mobile numbers
118Emails re-verified in last 30 days

Companies by employee count

1-10
2,796
11-50
1,471
51-200
372
201-500
85
501-1,000
34
1,001-5,000
33
5,001-10,000
6

Ecological consulting firms by metro

MetroCompanies
Ecological consulting firms in Houston77
Ecological consulting firms in New York70
Ecological consulting firms in Portland64
Ecological consulting firms in Seattle57
Ecological consulting firms in Washington52
Ecological consulting firms in Chicago48
Ecological consulting firms in San Diego47

How this list was built

Source
The RevenueBase company graph: 21.3 million companies and 398.9 million professional contacts resolved from primary sources.
Inclusion
Companies whose own business descriptions match “ecological consulting firms”, with match quality audited by blind human judging, and headquartered in the United States.
Ranking
Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification
Contact records re-verify on a rolling cadence; 118 contacts on this list were re-verified in the last 30 days.
Refresh
Lists are refreshed periodically as the underlying company graph is re-verified. Last verified Aug 28, 2026.

Frequently asked

How many ecological consulting firms are there based in the United States?

There are 4,819 ecological consulting firms headquartered in the United States as of August 2026 (RevenueBase).

What is the largest company on this list?

Terracon, headquartered in Tustin, tops this list with the largest team on record.

Which city has the most ecological consulting firms?

Houston leads with 77 headquartered companies, followed by New York (70) and Portland (64).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 73,143 verified decision-maker contacts tracked across these 4,819 companies.

How current is this list?

The list is refreshed periodically as the underlying company graph is re-verified. It was last verified on August 28, 2026.

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Related lists

Browse: Companies home · All United States lists · All Ecological consulting firms lists · New lists

About this data

RevenueBase is a B2B contact data platform. Its company graph covers 21.3 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph, the same data that powers RevenueBase's B2B data products and the free research portal.

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