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, how directly it supports the match, 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 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 Match evidence 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

Unlock all 2,065 companies Free signup · no credit card · 500 free credits

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. Evidence rates how directly each company's own description names hydrogeological consulting firms: strong (names it), partial (names part of it), indirect (matched on its full profile rather than the summary shown). Click a count to unlock that company's people.
#	Company	Headquarters	Employees	Contacts
1	TerraconPartial evidence	Olathe, CA, United StatesHQ checked Sep 3, 2026	5,001-10,000	6,024
	“Terracon is a 100 percent employee-owned consulting engineering firm providing quality services to clients.” Source: company website · checked Sep 3, 2026
2	GolderIndirect evidence	Houston, TX, United States	5,001-10,000	3,183
	“Golder was acquired by WSP.” Source: company website · checked Sep 3, 2026
3	Brown And CaldwellIndirect evidence	Walnut Creek, CA, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,455
	“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: company website · checked Sep 3, 2026
4	Geosyntec ConsultantsPartial evidence	Boca Raton, FL, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,392
	“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: company website · checked Sep 3, 2026
5	ECS Group Of CompaniesPartial evidence	Chantilly, VA, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,201
	“ECS Group of Companies is a Chantilly, VA-based consulting engineering firm.” Source: company website · checked Sep 3, 2026
6	Civil & Environmental Consultants, INCPartial evidence	Moon Township, WV, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,152
	“Civil & Environmental Consultants, Inc.(CEC) provides comprehensive market-oriented consulting services that advance the strategic business objectives of its clients.” Source: company website · checked Sep 3, 2026
7	Hazen And SawyerIndirect evidence	New York, NC, United StatesHQ checked Sep 3, 2026	1,001-5,000	2,105
	“As Hazen marks 75 years, we celebrate a legacy of absolute commitment to our clients while delivering the best technical work available anywhere.” Source: company website · checked Sep 3, 2026
8	GEI Consultants, INCIndirect evidence	Woburn, MA, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,577
	Source: company website · checked Sep 3, 2026
9	Freese And NicholsPartial evidence	Fort Worth, NC, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,461
	“Freese and Nichols is a professional planning, consulting and engineering firm serving clients across the United States.” Source: company website · checked Sep 3, 2026
10	Apex CompaniesIndirect evidence	Rockville, MD, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,146
	“Who is Apex?” Source: company website · checked Sep 3, 2026
11	VerdantasIndirect evidence	Tampa, OH, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,127
	“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: company website · checked Sep 3, 2026
12	Barr Engineering COPartial evidence	Minneapolis, United StatesHQ checked Sep 3, 2026	1,001-5,000	1,098
	“Barr provides engineering and environmental consulting services to clients across the Midwest, throughout the Americas, and around the world.” Source: company website · checked Sep 3, 2026
13	Trinity ConsultantsIndirect evidence	Dallas, TX, United StatesHQ checked Sep 3, 2026	1,001-5,000	949
	“Trinity Consultants is a global team of experts helping organizations solve complex challenges in environmental compliance, ecological protection, infrastructure performance, and…” Source: company website · checked Sep 3, 2026
14	GZA Geoenvironmental, INCIndirect evidence	Norwood, MA, United StatesHQ checked Sep 3, 2026	501-1,000	872
	“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: company website · checked Sep 3, 2026
15	ATC Group Services LLCIndirect evidence	Lafayette, OH, United StatesHQ checked Sep 3, 2026	1,001-5,000	868
	“ATC Group Services LLC is now Atlas.” Source: company website · checked Sep 3, 2026
16	DUDEKPartial evidence	Encinitas, CA, United StatesHQ checked Sep 3, 2026	501-1,000	792
	“Dudek is an environmental, planning, and engineering consulting firm.” Source: company website · checked Sep 3, 2026
17	Schnabel EngineeringIndirect evidence	Glen Allen, VA, United StatesHQ checked Sep 3, 2026	501-1,000	696
	“Schnabel is a trusted partner in building the foundation for project success.” Source: company website · checked Sep 3, 2026
18	Raba Kistner, INCIndirect evidence	San Antonio, UT, United StatesHQ checked Sep 3, 2026	501-1,000	581
	“Founded in 1968, Raba Kistner Inc.” Source: company website · checked Sep 3, 2026
19	Kennedy JenksIndirect evidence	San Francisco, OR, United StatesHQ checked Sep 3, 2026	201-500	575
	“For over 100 years, Kennedy Jenks has provided engineering and scientific solutions for innovative water and environmental projects.” Source: company website · checked Sep 3, 2026
20	Trihydro CorporationPartial evidence	Laramie, WY, United StatesHQ checked Sep 3, 2026	501-1,000	571
	“Headquartered in Laramie, Wyoming, Trihydro provides environmental consulting, engineering and surveying, air quality and process management, information technology, and water and…” Source: company website · checked Sep 3, 2026
21	Nova Engineering And Environmental, LLCPartial evidence	Kennesaw, FL, United StatesHQ checked Sep 3, 2026	501-1,000	510
	“Established in 1996, NOVA was originally founded to provide Environmental Consulting, Geotechnical Engineering, and Construction Materials Testing and Inspection services to the…” Source: company website · checked Sep 3, 2026
22	Rincon ConsultantsPartial evidence	Ventura, CA, United StatesHQ checked Sep 3, 2026	501-1,000	483
	“Rincon Consultants is a multi-disciplinary environmental sciences, planning, and engineering consulting firm that provides quality professional services to government and industry.” Source: company website · checked Sep 3, 2026
23	Geoengineers INCIndirect evidence	Redmond, WA, United StatesHQ checked Sep 3, 2026	201-500	479
	Source: company website · checked Sep 3, 2026
24	Anchor QEAPartial evidence	Seattle, MD, United StatesHQ checked Sep 3, 2026	501-1,000	478
	“Headquartered in Seattle, Washington, Anchor QEA is a nationally recognized environmental science and engineering consulting firm specializing in aquatic, shoreline, and water…” Source: company website · checked Sep 3, 2026
25	Geo-Technology Associates, Inc. GTAIndirect evidence	Abingdon, MD, United StatesHQ checked Sep 3, 2026	501-1,000	457
	“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: company website · checked Sep 3, 2026

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

See the full list, filter by size, metro and specialty, and get verified emails and direct dials for all 40,836 reachable decision-makers.

Free signup · no credit card

See all 2,065 companies

Hydrogeological consulting firms based in the United States at a glance

As of Sep 3, 2026

11-50Median size (employees)

HoustonLargest hub · 69 HQs

35,764Contacts with mobile numbers

Sep 3, 2026Data 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

Verified emails by last verification

0–30

31–60

3,513

61–90

23,571

90–180

13,471

180+

281

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 evidence 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 SmartSearch, 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.
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 an evidence 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

Hydrogeological consulting firms in Houston69
Hydrogeological consulting firms in Denver28
Hydrogeological consulting firms in Portland25

Frequently asked

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.

Ready to reach these companies? Verified emails and direct dials for all 2,065 hydrogeological consulting firms based in the United States. Start with a free account, no credit card.

Get the full list

Related lists

Hydrogeological consulting firms by geography

Browse the directory

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

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.