Company lists · Data refreshed September 2026

Top 25 Hydrogeological consultants based in the United States

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

Compiled by the RevenueBase Data Team Data refreshed Sep 21, 2026 4,224 companies tracked

RevenueBase identified 4,224 hydrogeological consultants headquartered in the United States as of September 2026 and tracks 133,767 professional contacts across them, including 64,106 with verified work emails. Houston is the largest hub.

This list covers hydrogeological consultants 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 21, 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 HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 21, 2026 86% judged on-target in blind review

4,224Companies

133,767Contacts tracked

64,106Verified emails

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The 25 largest hydrogeological consultants based in the United States

Ranked by team size

Top 25 of 4,224 hydrogeological consultants based in the United States, ranked by team size, largest first. Data refreshed Sep 21, 2026. RevenueBase Smart Search rates how each company's information relates to hydrogeological consultants: 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	Tetra Tech	Indirect evidence	Pasadena, CA, United StatesHQ checked Sep 21, 2026	10001+	12,999 contacts →
	Indirect evidence “Tetra Tech is the leader in water, environment and sustainable infrastructure, providing high-end technical and engineering services for projects worldwide.” Source: RevenueBase Database · checked Sep 21, 2026
2	Terracon	Indirect evidence	Olathe, KS, United StatesHQ checked Sep 21, 2026	5,001-10,000	6,113 contacts →
	Indirect evidence “Terracon is a 100 percent employee-owned consulting engineering firm providing quality services to clients.” Source: RevenueBase Database · checked Sep 21, 2026
3	Brown And Caldwell	Indirect evidence	Walnut Creek, CA, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,473 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 21, 2026
4	Geosyntec Consultants	Indirect evidence	Boca Raton, FL, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,393 contacts →
	Indirect 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 21, 2026
5	Providence	Indirect evidence	Baton Rouge, LA, United StatesHQ checked Sep 21, 2026	n/a	2,232 contacts →
	Indirect evidence “Providence is an employee-owned engineering and environmental consulting firm.” Source: RevenueBase Database · checked Sep 21, 2026
6	ECS Group Of Companies	Indirect evidence	Chantilly, VA, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,210 contacts →
	Indirect evidence “ECS Group of Companies is a Chantilly, VA-based consulting engineering firm.” Source: RevenueBase Database · checked Sep 21, 2026
7	Langan Engineering & Environmental Services	Indirect evidence	Parsippany, NJ, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,177 contacts →
	Indirect 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 21, 2026
8	Civil & Environmental Consultants, INC	Partial evidence	Moon Township, PA, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,145 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 21, 2026
9	Hazen And Sawyer	Indirect evidence	New York, NY, United StatesHQ checked Sep 21, 2026	1,001-5,000	2,100 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 21, 2026
10	Carollo Engineers	Indirect evidence	Walnut Creek, CA, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,718 contacts →
	Indirect evidence “For more than 90 years, Carollo Engineers has been dedicated exclusively to water and wastewater solutions.” Source: RevenueBase Database · checked Sep 21, 2026
11	GEI Consultants, INC	Indirect evidence	Woburn, MA, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,604 contacts →
	Indirect evidence Source: RevenueBase Database · checked Sep 21, 2026
12	UES	Indirect evidence	Orlando, FL, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,595 contacts →
	Indirect evidence “UES provides professional engineering, environmental, testing and inspection services to clients across the United States.” Source: RevenueBase Database · checked Sep 21, 2026
13	Exponent	Indirect evidence	Menlo Park, CA, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,560 contacts →
	Indirect evidence “In an era of accelerating change, Exponent is the only premium engineering and scientific consulting firm with the depth and breadth of expertise to solve our clients’ most…” Source: RevenueBase Database · checked Sep 21, 2026
14	Freese And Nichols	Indirect evidence	Fort Worth, TX, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,496 contacts →
	Indirect evidence “Freese and Nichols is a professional planning, consulting and engineering firm serving clients across the United States.” Source: RevenueBase Database · checked Sep 21, 2026
15	Knight Piesold	Indirect evidence	Denver, CO, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,231 contacts →
	Indirect evidence “Knight Piésold is an employee-owned, global consulting firm providing specialist services to the mining, power, water resources, and infrastructure industries.” Source: RevenueBase Database · checked Sep 21, 2026
16	Verdantas	Indirect evidence	Tampa, FL, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,139 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 21, 2026
17	Apex Companies	Indirect evidence	Rockville, MD, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,137 contacts →
	Indirect evidence “Who is Apex?” Source: RevenueBase Database · checked Sep 21, 2026
18	Haley & Aldrich	Indirect evidence	Burlington, MA, United StatesHQ checked Sep 21, 2026	501-1,000	1,124 contacts →
	Indirect evidence “Haley & Aldrich is committed to solving our clients’ most meaningful challenges in the built and natural environments.” Source: RevenueBase Database · checked Sep 21, 2026
19	Barr Engineering CO	Indirect evidence	Minneapolis, MN, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,088 contacts →
	Indirect 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 21, 2026
20	S&me	Indirect evidence	Raleigh, NC, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,034 contacts →
	Indirect evidence “We are S & ME.” Source: RevenueBase Database · checked Sep 21, 2026
21	Trinity Consultants	Partial evidence	Dallas, TX, United StatesHQ checked Sep 21, 2026	1,001-5,000	961 contacts →
	Partial 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 21, 2026
22	GZA Geoenvironmental, INC	Partial evidence	Norwood, MA, United StatesHQ checked Sep 21, 2026	501-1,000	880 contacts →
	Partial 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 21, 2026
23	ATC Group Services LLC	Indirect evidence	Lafayette, LA, United StatesHQ checked Sep 21, 2026	1,001-5,000	865 contacts →
	Indirect evidence “ATC Group Services LLC is now Atlas.” Source: RevenueBase Database · checked Sep 21, 2026
24	DUDEK	Indirect evidence	Encinitas, CA, United StatesHQ checked Sep 21, 2026	501-1,000	795 contacts →
	Indirect evidence “Dudek is an environmental, planning, and engineering consulting firm.” Source: RevenueBase Database · checked Sep 21, 2026
25	Hatch Mott Macdonald	Indirect evidence	Iselin, NJ, United StatesHQ checked Sep 21, 2026	1,001-5,000	762 contacts →
	Indirect evidence “This page is now closed.” Source: RevenueBase Database · checked Sep 21, 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 consultants. 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 consultants.
Partial evidence: Its own public description names part of hydrogeological consultants, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name hydrogeological consultants. 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 4,224 hydrogeological consultants based in the United States

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Hydrogeological consultants based in the United States at a glance

As of Sep 21, 2026

47.9%Verified-email coverage

31.7Average contacts per company

11-50Median size (employees)

4.5%Largest-city concentration · Houston

Sep 21, 2026Page data refreshed

Companies by employee count

1-10

2,064

11-50

1,488

51-200

503

201-500

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 4,224 companies.

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 consultants, 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 consultants”. 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 consultants), 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 consultants, 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, 64,106 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 21, 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 consultants 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 consultants, 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 consultants are there based in the United States?

RevenueBase identified 4,224 hydrogeological consultants 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?

Tetra Tech, headquartered in Pasadena, tops this list with the largest team on record.

Which city has the most hydrogeological consultants?

Houston leads with 188 headquartered companies, followed by Denver (61) and Austin (38).

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 64,106 verified decision-maker contacts tracked across these 4,224 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 21, 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.