Company lists · Data refreshed September 2026

Top 25 Hydrogeological consulting firms based in the United States

Name: Hydrogeological consulting firms based in the United States
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 3, 2026 2,065 companies tracked

RevenueBase identified 2,065 hydrogeological consulting firms headquartered in the United States as of September 2026 and tracks 86,659 professional contacts across them, including 40,836 with verified work emails and 35,764 with mobile numbers. Houston is the largest hub.

This list covers hydrogeological 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 3, 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 3, 2026 86% judged on-target in blind review

2,065Companies

86,659Contacts tracked

40,836Verified emails

35,764Mobile numbers

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The 25 largest hydrogeological consulting firms based in the United States

Ranked by team size

Top 25 of 2,065 hydrogeological consulting firms based in the United States, ranked by team size, largest first. Data refreshed Sep 3, 2026. RevenueBase Smart Search rates how each company's information relates to hydrogeological 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.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	Terracon	Partial evidence	Olathe, CA, United StatesHQ checked Sep 3, 2026	5,001-10,000	6,024 contacts →
	Partial evidence “Terracon is a 100 percent employee-owned consulting engineering firm providing quality services to clients.” Source: RevenueBase Database · checked Sep 3, 2026
2	Golder	Indirect evidence	Houston, TX, United States	5,001-10,000	3,183 contacts →
	Indirect evidence “Golder was acquired by WSP.” Source: RevenueBase Database · checked Sep 3, 2026
3	Brown And Caldwell	Indirect evidence	Walnut Creek, CA, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,455 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 3, 2026
4	Geosyntec Consultants	Partial evidence	Boca Raton, FL, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,392 contacts →
	Partial 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 3, 2026
5	ECS Group Of Companies	Partial evidence	Chantilly, VA, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,201 contacts →
	Partial evidence “ECS Group of Companies is a Chantilly, VA-based consulting engineering firm.” Source: RevenueBase Database · checked Sep 3, 2026
6	Civil & Environmental Consultants, INC	Partial evidence	Moon Township, WV, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,152 contacts →
	Partial 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 3, 2026
7	Hazen And Sawyer	Indirect evidence	New York, NC, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,105 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 3, 2026
8	GEI Consultants, INC	Indirect evidence	Woburn, MA, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,577 contacts →
	Indirect evidence Source: RevenueBase Database · checked Sep 3, 2026
9	Freese And Nichols	Partial evidence	Fort Worth, NC, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,461 contacts →
	Partial evidence “Freese and Nichols is a professional planning, consulting and engineering firm serving clients across the United States.” Source: RevenueBase Database · checked Sep 3, 2026
10	Apex Companies	Indirect evidence	Rockville, MD, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,146 contacts →
	Indirect evidence “Who is Apex?” Source: RevenueBase Database · checked Sep 3, 2026
11	Verdantas	Indirect evidence	Tampa, OH, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,127 contacts →
	Indirect 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 3, 2026
12	Barr Engineering CO	Partial evidence	Minneapolis, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,098 contacts →
	Partial evidence “Barr provides engineering and environmental consulting services to clients across the Midwest, throughout the Americas, and around the world.” Source: RevenueBase Database · checked Sep 3, 2026
13	Trinity Consultants	Indirect evidence	Dallas, TX, United StatesHQ checked Sep 3, 2026	1,001-5,000	949 contacts →
	Indirect evidence “Trinity Consultants is a global team of experts helping organizations solve complex challenges in environmental compliance, ecological protection, infrastructure performance, and…” Source: RevenueBase Database · checked Sep 3, 2026
14	GZA Geoenvironmental, INC	Indirect evidence	Norwood, MA, United StatesHQ checked Sep 3, 2026	501-1,000	872 contacts →
	Indirect evidence “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…” Source: RevenueBase Database · checked Sep 3, 2026
15	ATC Group Services LLC	Indirect evidence	Lafayette, OH, United StatesHQ checked Sep 3, 2026	1,001-5,000	868 contacts →
	Indirect evidence “ATC Group Services LLC is now Atlas.” Source: RevenueBase Database · checked Sep 3, 2026
16	DUDEK	Partial evidence	Encinitas, CA, United StatesHQ checked Sep 3, 2026	501-1,000	792 contacts →
	Partial evidence “Dudek is an environmental, planning, and engineering consulting firm.” Source: RevenueBase Database · checked Sep 3, 2026
17	Schnabel Engineering	Indirect evidence	Glen Allen, VA, United StatesHQ checked Sep 3, 2026	501-1,000	696 contacts →
	Indirect evidence “Schnabel is a trusted partner in building the foundation for project success.” Source: RevenueBase Database · checked Sep 3, 2026
18	Raba Kistner, INC	Indirect evidence	San Antonio, UT, United StatesHQ checked Sep 3, 2026	501-1,000	581 contacts →
	Indirect evidence “Founded in 1968, Raba Kistner Inc.” Source: RevenueBase Database · checked Sep 3, 2026
19	Kennedy Jenks	Indirect evidence	San Francisco, OR, United StatesHQ checked Sep 3, 2026	201-500	575 contacts →
	Indirect evidence “For over 100 years, Kennedy Jenks has provided engineering and scientific solutions for innovative water and environmental projects.” Source: RevenueBase Database · checked Sep 3, 2026
20	Trihydro Corporation	Partial evidence	Laramie, WY, United StatesHQ checked Sep 3, 2026	501-1,000	571 contacts →
	Partial evidence “Headquartered in Laramie, Wyoming, Trihydro provides environmental consulting, engineering and surveying, air quality and process management, information technology, and water and…” Source: RevenueBase Database · checked Sep 3, 2026
21	Nova Engineering And Environmental, LLC	Partial evidence	Kennesaw, FL, United StatesHQ checked Sep 3, 2026	501-1,000	510 contacts →
	Partial evidence “Established in 1996, NOVA was originally founded to provide Environmental Consulting, Geotechnical Engineering, and Construction Materials Testing and Inspection services to the…” Source: RevenueBase Database · checked Sep 3, 2026
22	Rincon Consultants	Partial evidence	Ventura, CA, United StatesHQ checked Sep 3, 2026	501-1,000	483 contacts →
	Partial evidence “Rincon Consultants is a multi-disciplinary environmental sciences, planning, and engineering consulting firm that provides quality professional services to government and industry.” Source: RevenueBase Database · checked Sep 3, 2026
23	Geoengineers INC	Indirect evidence	Redmond, WA, United StatesHQ checked Sep 3, 2026	201-500	479 contacts →
	Indirect evidence Source: RevenueBase Database · checked Sep 3, 2026
24	Anchor QEA	Partial evidence	Seattle, MD, United StatesHQ checked Sep 3, 2026	501-1,000	478 contacts →
	Partial evidence “Headquartered in Seattle, Washington, Anchor QEA is a nationally recognized environmental science and engineering consulting firm specializing in aquatic, shoreline, and water…” Source: RevenueBase Database · checked Sep 3, 2026
25	Geo-Technology Associates, Inc. GTA	Indirect evidence	Abingdon, MD, United StatesHQ checked Sep 3, 2026	501-1,000	457 contacts →
	Indirect evidence “Geo-Technology Associates, Inc.(GTA) proudly celebrates more than 40 years of service, backed by a team of 600+ professionals-including geotechnical engineers, environmental…” Source: RevenueBase Database · checked Sep 3, 2026

RevenueBase Smart Search

RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: hydrogeological consulting firms. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.

Strong evidence: The company's own public description of its business names hydrogeological consulting firms.
Partial evidence: Its own public description names part of hydrogeological consulting firms, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name hydrogeological consulting firms. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.

RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.

Showing 25 of 2,065 hydrogeological consulting firms based in the United States

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Hydrogeological consulting firms based in the United States at a glance

As of Sep 3, 2026

47.1%Verified-email coverage

41.3%Mobile-number coverage

42.0Average contacts per company

11-50Median size (employees)

3.3%Largest-city concentration · Houston

Sep 3, 2026Page data refreshed

Companies by employee count

1-10

999

11-50

737

51-200

239

201-500

501-1,000

1,001-5,000

5,001-10,000

Freshness & accuracy

How recently the business emails on this list were verified

Email last verified

00–30

3,51331–60

23,57161–90

13,47190–180

281180+

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 hydrogeological 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 “hydrogeological 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 hydrogeological 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 hydrogeological 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, 40,836 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 3, 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.

Hydrogeological consulting firms by metro

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 hydrogeological 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 hydrogeological consulting firms are there based in the United States?

RevenueBase identified 2,065 hydrogeological 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 hydrogeological consulting firms?

Houston leads with 69 headquartered companies, followed by Denver (28) and Portland (25).

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 40,836 verified decision-maker contacts tracked across these 2,065 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 3, 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.