Company lists · Data refreshed September 2026

Top 25 Environmental consulting firms based in the United States

RevenueBase identified 7,084 environmental consulting firms headquartered in the United States as of September 2026 and tracks 226,716 professional contacts across them, including 105,429 with verified work emails and 98,188 with mobile numbers. Houston is the largest hub.

This list covers environmental 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. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 2, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list RevenueBase Smart Search rating on every row Refreshed Sep 2, 2026 86% judged on-target in blind review
7,084Companies
226,716Contacts tracked
105,429Verified emails
98,188Mobile numbers
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The 25 largest environmental consulting firms based in the United States

Ranked by team size
Top 25 of 7,084 environmental consulting firms based in the United States, ranked by team size, largest first. Data refreshed Sep 2, 2026. RevenueBase Smart Search rates how each company's information relates to environmental consulting firms: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#CompanyRevenueBase Smart SearchHeadquartersEmployeesContacts
1Partial evidenceTustin, CA, United States5,001-10,0006,024 contacts →

Partial evidence

“Terracon is a 100 percent employee-owned consulting engineering firm providing quality services to clients.”

Source: RevenueBase Database · checked Sep 2, 2026
2Indirect evidenceHouston, TX, United States5,001-10,0003,183 contacts →

Indirect evidence

“Golder was acquired by WSP.”

Source: RevenueBase Database · checked Sep 2, 2026
3Partial evidenceWichita, KS, United States1,001-5,0002,644 contacts →

Partial evidence

“APTIM enhances the quality of the environment, wellbeing of people, resilience of communities, and opportunity for employees to make a difference, not just a living.”

Source: RevenueBase Database · checked Sep 2, 2026
4Indirect evidenceWalnut Creek, CA, United States1,001-5,0002,455 contacts →

Indirect evidence

“Headquartered in Walnut Creek, Calif, Brown and Caldwell is an employee-owned firm with 2,100+ professionals serving clients locally and globally from 52 locations.”

Source: RevenueBase Database · checked Sep 2, 2026
5Strong evidenceBoca Raton, FL, United States1,001-5,0002,392 contacts →

Strong evidence

“Geosyntec is a consulting and engineering firm that works with private and public sector clients to address new ventures and complex problems involving our environment, natural…”

Source: RevenueBase Database · checked Sep 2, 2026
6Partial evidenceFredericksburg, VA, United States1,001-5,0002,201 contacts →

Partial evidence

“ECS Group of Companies is a Chantilly, VA-based consulting engineering firm.”

Source: RevenueBase Database · checked Sep 2, 2026
7Strong evidenceMartinsburg, WV, United States1,001-5,0002,152 contacts →

Strong evidence

“Civil & Environmental Consultants, Inc.(CEC) provides comprehensive market-oriented consulting services that advance the strategic business objectives of its clients.”

Source: RevenueBase Database · checked Sep 2, 2026
8Partial evidenceEl Segundo, CA, United States1,001-5,0002,136 contacts →

Partial evidence

“Langan's client-focused, highly entrepreneurial culture cultivates an environment of opportunities in which career growth and teamwork flourish.”

Source: RevenueBase Database · checked Sep 2, 2026
9Strong evidenceCalifornia, MD, United States1,001-5,0002,111 contacts →

Strong evidence

“Ricardo, a member of @WSP, is a global strategic, environmental, and engineering consulting company.”

Source: RevenueBase Database · checked Sep 2, 2026
10Indirect evidenceRaleigh, NC, United States1,001-5,0002,105 contacts →

Indirect evidence

“As Hazen marks 75 years, we celebrate a legacy of absolute commitment to our clients while delivering the best technical work available anywhere.”

Source: RevenueBase Database · checked Sep 2, 2026
11Indirect evidenceSarasota, FL, United States1,001-5,0002,073 contacts →

Indirect evidence

“Employee-Owned.”

Source: RevenueBase Database · checked Sep 2, 2026
12Indirect evidenceRock Island, IL, United States1,001-5,0001,954 contacts →

Indirect evidence

“Leaders in Engineering and Innovation.”

Source: RevenueBase Database · checked Sep 2, 2026
13Indirect evidenceOklahoma City, OK, United States1,001-5,0001,709 contacts →

Indirect evidence

“For more than 90 years, Carollo Engineers has been dedicated exclusively to water and wastewater solutions.”

Source: RevenueBase Database · checked Sep 2, 2026
14Strong evidencePhoenix, AZ, United States1,001-5,0001,618 contacts →

Strong evidence

“Founded on a commitment to sound science and creative solutions, SWCA is a leader in environmental and management consulting services.”

Source: RevenueBase Database · checked Sep 2, 2026
15Indirect evidenceWoburn, MA, United States1,001-5,0001,577 contacts →

Indirect evidence

Source: RevenueBase Database · checked Sep 2, 2026
16Partial evidenceHouston, TX, United States1,001-5,0001,571 contacts →

Partial evidence

“UES provides professional engineering, environmental, testing and inspection services to clients across the United States.”

Source: RevenueBase Database · checked Sep 2, 2026
17Partial evidenceLittle Rock, AR, United States1,001-5,0001,516 contacts →

Partial evidence

“Onterris (formerly Montrose Environmental Group) was one of the first to see environmental responsibility as not just an imperative but as a strategic asset.”

Source: RevenueBase Database · checked Sep 2, 2026
18Strong evidenceDenver, CO, United States1,001-5,0001,515 contacts →

Strong evidence

“Atlas Technical Consultants (Atlas) provides professional testing, inspection, engineering, environmental and consulting services nationwide.”

Source: RevenueBase Database · checked Sep 2, 2026
19Partial evidenceWest Chester, PA, United States1,001-5,0001,450 contacts →

Partial evidence

“Weston Solutions, Inc.(Weston) is a 100% employee-owned environmental and infrastructure services firm committed to safety and providing measurable client value.”

Source: RevenueBase Database · checked Sep 2, 2026
20Indirect evidencePasadena, CA, United States1,001-5,0001,348 contacts →

Indirect evidence

“Partner Assessment Corp.”

Source: RevenueBase Database · checked Sep 2, 2026
21Partial evidenceLong Beach, CA, United States1,001-5,0001,191 contacts →

Partial evidence

“SCS Engineers delivers environmental solutions by combining long-term experience with compliance and technological expertise.”

Source: RevenueBase Database · checked Sep 2, 2026
22Indirect evidenceOmaha, NE, United States1,001-5,0001,170 contacts →

Indirect evidence

“Consultants.”

Source: RevenueBase Database · checked Sep 2, 2026
23Indirect evidenceRockville, MD, United States1,001-5,0001,146 contacts →

Indirect evidence

“Who is Apex?”

Source: RevenueBase Database · checked Sep 2, 2026
24Indirect evidenceVero Beach, FL, United States1,001-5,0001,129 contacts →

Indirect evidence

“Ranked No.”

Source: RevenueBase Database · checked Sep 2, 2026
25Partial evidenceToledo, OH, United States1,001-5,0001,127 contacts →

Partial evidence

“At Verdantas, we blend engineering and environmental science together with advanced technology and world-renowned labs to create solutions with the big picture in mind.”

Source: RevenueBase Database · checked Sep 2, 2026

Showing 25 of 7,084 environmental consulting firms based in the United States

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Environmental consulting firms based in the United States at a glance

As of Sep 2, 2026
46.5%Verified-email coverage
43.3%Mobile-number coverage
32.0Average contacts per company
1-10Median size (employees)
1.9%Largest-city concentration · Houston
Sep 2, 2026Page data refreshed

Companies by employee count

1-10
3,795
11-50
2,274
51-200
706
201-500
156
501-1,000
54
1,001-5,000
58
5,001-10,000
9

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among environmental consulting firms, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source
The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
What qualifies
Companies headquartered in the United States whose own description of what they do matches “environmental consulting firms”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search
RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names environmental consulting firms), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude
Companies whose own description does not clearly place them among environmental consulting firms, and records with no verified work email. Companies headquartered outside United States are excluded even when they keep an office there.
Match quality
In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
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
Every listed company carries at least one verified work email, 105,429 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh
This page's figures were pulled from the company graph on September 2, 2026. Lists refresh periodically as the graph is re-checked.
Corrections
Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names environmental consulting firms, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

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

RevenueBase identified 7,084 environmental consulting firms headquartered in the United States as of September 2026, matched on each company's own description of what it does rather than its industry code.

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 environmental consulting firms?

Houston leads with 133 headquartered companies, followed by New York (117) and Seattle (80).

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 105,429 verified decision-maker contacts tracked across these 7,084 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 2, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 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 with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.