Company lists · Data refreshed October 2026

Top 25 Environmental treatment engineering firms based in the United States

Name: Environmental treatment engineering firms based in the United States
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Oct 12, 2026 3,682 companies tracked

RevenueBase identified 3,682 company matches for environmental treatment engineering firms associated with the United States as of October 2026 and tracks 130,815 professional contacts across them, including 55,401 with verified work emails. Houston is the largest hub.

This list covers company matches for environmental treatment engineering firms associated with the United States, found by RevenueBase SmartSearch using the meaning of business descriptions in its company graph at Exact. Ranked by professionals tracked, largest first. Rows show recorded descriptions where available, Exact search membership and the snapshot date. Data refreshed October 12, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase SmartSearch, 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 SmartSearch · Exact Recorded Oct 12, 2026 How this list was built

3,682Companies

130,815Contacts tracked

55,401Verified emails

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The 25 largest environmental treatment engineering firms based in the United States

Ranked by team size

Top 25 of 3,682 company matches for environmental treatment engineering firms based in the United States, ordered by professional contacts tracked in RevenueBase, largest first. Recorded Oct 12, 2026. The RevenueBase SmartSearch column shows Exact match membership in this saved search. Click a contact count to view that company's people. Totals use company locations recorded by RevenueBase; the displayed preview is a smaller selection.
#	Company	RevenueBase SmartSearch	Headquarters	Employees	Contacts
1	Tetra Tech	Exact match	Pasadena, CA, United StatesHQ recorded Oct 12, 2026	10001+	13,725 contacts →
	Exact match “Tetra Tech is the leader in water, environment and sustainable infrastructure, providing high-end technical and engineering services for projects worldwide.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
2	Terracon	Exact match	Olathe, KS, United StatesHQ recorded Oct 12, 2026	5,001-10,000	6,380 contacts →
	Exact match “Terracon is a 100 percent employee-owned consulting engineering firm providing quality services to clients.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
3	Geosyntec Consultants	Exact match	Boca Raton, FL, United StatesHQ recorded Oct 12, 2026	1,001-5,000	2,521 contacts →
	Exact match “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…” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
4	Brown And Caldwell	Exact match	Walnut Creek, CA, United StatesHQ recorded Oct 12, 2026	1,001-5,000	2,510 contacts →
	Exact match “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.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
5	Langan Engineering & Environmental Services	Exact match	Parsippany, NJ, United StatesHQ recorded Oct 12, 2026	1,001-5,000	2,402 contacts →
	Exact match “Langan's client-focused, highly entrepreneurial culture cultivates an environment of opportunities in which career growth and teamwork flourish.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
6	Providence	Exact match	Baton Rouge, LA, United StatesHQ recorded Oct 12, 2026	n/a	2,256 contacts →
	Exact match “Providence is an employee-owned engineering and environmental consulting firm.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
7	Hazen And Sawyer	Exact match	New York, NY, United StatesHQ recorded Oct 12, 2026	1,001-5,000	2,251 contacts →
	Exact match “As Hazen marks 75 years, we celebrate a legacy of absolute commitment to our clients while delivering the best technical work available anywhere.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
8	Civil & Environmental Consultants, INC	Exact match	Moon Township, PA, United StatesHQ recorded Oct 12, 2026	1,001-5,000	2,204 contacts →
	Exact match “Civil & Environmental Consultants, Inc.(CEC) provides comprehensive market-oriented consulting services that advance the strategic business objectives of its clients.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
9	Carollo Engineers	Exact match	Walnut Creek, CA, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,811 contacts →
	Exact match “For more than 90 years, Carollo Engineers has been dedicated exclusively to water and wastewater solutions.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
10	Weston Solutions, INC	Exact match	West Chester, PA, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,525 contacts →
	Exact match “Weston Solutions, Inc.(Weston) is a 100% employee-owned environmental and infrastructure services firm committed to safety and providing measurable client value.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
11	Apex Companies	Exact match	Rockville, MD, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,266 contacts →
	Exact match “Who is Apex?” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
12	Verdantas	Exact match	Tampa, FL, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,252 contacts →
	Exact match “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.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
13	Barr Engineering CO	Exact match	Minneapolis, MN, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,108 contacts →
	Exact match “Barr provides engineering and environmental consulting services to clients across the Midwest, throughout the Americas, and around the world.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
14	Trinity Consultants	Exact match	Dallas, TX, United StatesHQ recorded Oct 12, 2026	1,001-5,000	1,077 contacts →
	Exact match “Trinity Consultants is a global team of experts helping organizations solve complex challenges in environmental compliance, ecological protection, infrastructure performance, and…” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
15	GZA Geoenvironmental, INC	Exact match	Norwood, MA, United StatesHQ recorded Oct 12, 2026	501-1,000	903 contacts →
	Exact match “Founded in 1964 as a soils and foundations specialty consultant, GZA GeoEnvironmental, Inc.(GZA) has grown into a full-service company providing its clients with highly…” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
16	ATC Group Services LLC	Exact match	Lafayette, LA, United StatesHQ recorded Oct 12, 2026	1,001-5,000	872 contacts →
	Exact match “ATC Group Services LLC is now Atlas.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
17	Montrose Environmental Group	Exact match	Little Rock, AR, United StatesHQ recorded Oct 12, 2026	1,001-5,000	843 contacts →
	Exact match “Onterris (formerly Montrose Environmental Group) was one of the first to see environmental responsibility as not just an imperative but as a strategic asset.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
18	The Foth Companies	Exact match	De Pere, WI, United StatesHQ recorded Oct 12, 2026	501-1,000	812 contacts →
	Exact match “By combining science, engineering, and technology with a true collaborative spirit, Foth has delivered innovative solutions to our clients since 1938.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
19	DUDEK	Exact match	Encinitas, CA, United StatesHQ recorded Oct 12, 2026	501-1,000	807 contacts →
	Exact match “Dudek is an environmental, planning, and engineering consulting firm.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
20	Environmental Science Associates	Exact match	San Francisco, CA, United StatesHQ recorded Oct 12, 2026	501-1,000	730 contacts →
	Exact match “ESA is a 100% employee-owned environmental consulting firm.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
21	Antea Group USA	Exact match	St. Paul, MN, United StatesHQ recorded Oct 12, 2026	1,001-5,000	658 contacts →
	Exact match “Antea Group is an international engineering and environmental consulting firm specializing in full-service solutions in the fields of environment, health and safety, and…” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
22	Raba Kistner, INC	Exact match	San Antonio, TX, United StatesHQ recorded Oct 12, 2026	501-1,000	602 contacts →
	Exact match “Founded in 1968, Raba Kistner Inc.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
23	Kennedy Jenks	Exact match	San Francisco, CA, United StatesHQ recorded Oct 12, 2026	201-500	580 contacts →
	Exact match “For over 100 years, Kennedy Jenks has provided engineering and scientific solutions for innovative water and environmental projects.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
24	Westech Engineering	Exact match	Salt Lake City, UT, United StatesHQ recorded Oct 12, 2026	501-1,000	577 contacts →
	Exact match “WesTech Engineering, LLC designs, engineers, and manufactures water and wastewater treatment process equipment for mineral, industrial, and municipal applications worldwide.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase
25	DOWL	Exact match	Bellevue, WA, United StatesHQ recorded Oct 12, 2026	501-1,000	571 contacts →
	Exact match “For more than 60 years, it has been the quality of our people that defines the DOWL difference.” Recorded in the RevenueBase company graph · Oct 12, 2026 · View company records in RevenueBase

RevenueBase SmartSearch

Describe a niche business in your own words. RevenueBase SmartSearch compares the meaning of your description with company business descriptions compiled in the RevenueBase company graph. Exact, Similar, Related and Broad control how closely companies must fit.

This list uses Exact for “environmental treatment engineering firms”. Each Exact match badge shows membership in that saved search; it is not an individual similarity score or a service-quality rating. Recorded descriptions are shown where available.

Showing 25 of 3,682 environmental treatment engineering firms based in the United States

See the full list, filter by size, metro and specialty, and access 55,401 tracked professional contacts with verified work emails. Direct dials are available where recorded.

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Environmental treatment engineering firms based in the United States at a glance

As of Oct 12, 2026

42.4%Verified-email coverage

35.5Average contacts per company

11-50Median size (employees)

2.3%Largest-city concentration · Houston

Oct 12, 2026Page data refreshed

Companies by employee count

1-10

1,578

11-50

1,435

51-200

476

201-500

109

501-1,000

1,001-5,000

5,001-10,000

10001+

Email recency for this list is measured worldwide rather than for United States, so it is reported there. Company counts and contact totals on this page are exact for United States, over 3,682 companies.

How this list was built

The recorded descriptions help you assess these company matches. Check a company’s website for its current services and locations.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase SmartSearch, the natural-language company search available to every RevenueBase user.
What qualifies: Company records associated with the United States whose business descriptions match “environmental treatment engineering firms” by meaning at the Exact setting. Descriptions are compiled in the RevenueBase company graph from public websites, profiles and company information where available; they are not guaranteed quotations from the company's website.
RevenueBase SmartSearch: Describe a niche company in your own words to find businesses by meaning. Exact, Similar, Related and Broad control the breadth of RevenueBase SmartSearch. This saved list uses Exact. Each row's Exact match badge shows inclusion in that search, not an individual score or a service-quality judgment.
Public preview: The public preview omits records without a verified work email. Where headquarters information is recorded, preview rows are also filtered to this page’s location. Dataset totals and geographic summaries describe the full matched records before these preview filters.
Match quality: RevenueBase's August 25, 2026 study assessed 4,198 description/company pairs across matching settings. The publisher reports 86% good or better at Exact. This evaluates the method across queries; it does not audit this individual list. Recorded company descriptions, where available, help you judge each match yourself. Read the full methodology: how the lists are built and what the study measures.
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 displayed company carries at least one verified work email. RevenueBase tracks 55,401 professional contacts with verified work emails across the full matched dataset. 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 October 12, 2026. Lists refresh periodically as the graph is re-checked.
Record context: Company records and descriptions can change. Check the company's website for its current services and locations.

Environmental treatment engineering firms by metro

Frequently asked

What is RevenueBase SmartSearch?

RevenueBase SmartSearch finds niche companies by the meaning of their business descriptions in the RevenueBase company graph. Exact, Similar, Related and Broad control how closely companies must fit your description. This list uses Exact for “environmental treatment engineering firms”; each Exact match badge shows search membership, not an individual similarity or quality score.

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

RevenueBase identified 3,682 company matches for environmental treatment engineering firms associated with the United States as of October 2026, using the meaning of business descriptions at Exact. This is the recorded matched set in the RevenueBase company graph.

What is the largest company on this list?

Tetra Tech tops the displayed preview by professional contacts tracked in RevenueBase. Recorded headquarters appear in the company rows.

Which city has the most environmental treatment engineering firms?

Houston leads with 85 company records, followed by Tampa (35) and Indianapolis (32).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work limited free results with 500 credits to start. Upgrading provides access to the 55,401 professional contacts with verified work emails tracked across these 3,682 companies; direct dials are available where recorded.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on October 12, 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 SmartSearch, 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.