Montrose Environmental Group�s ECT2 Subsidiary Announces Five-Year Contract Renewal with Australian Department of Defence

IRVINE, Calif. & CANBERRA, Australia–(BUSINESS WIRE)–Montrose Environmental Group, Inc. (NYSE: MEG) today announced that its subsidiary, Emerging Compounds Treatment Technologies, Inc. (�ECT2”), has renewed its contract for five years with the Australian Department of Defence [“Defence”] to operate and maintain water treatment systems at three of the country’s military bases. The $US43 million (AU$59 million GST inclusive) contract carries an initial term of five years and provides for an additional five extensions each for one year in duration, to be determined at Defence’s discretion and subject to ongoing needs at each military location.

In 2016, Defence engaged ECT2 for the removal of per- and polyfluoroalkyl substances [“PFAS”] from water at RAAF Base Williamtown in New South Wales, and Army Aviation Centre, Oakey in Queensland. The following year the company was awarded new contracts for an additional water treatment system for Williamtown and two treatment systems at RAAF Base Tindal in the Northern Territory. The five-year contract renewal comprises these three primary military bases, as well as the interim water treatment system at the Katherine Power and Water Corporation site in Katherine, Northern Territory.

ECT2’s specialized regeneration technology sees PFAS-laden resin regenerated for continuous use, minimizing waste generation that would otherwise be sent to licensed thermal destruction facilities for further management, or to landfill for future generations to contend with. To date, ECT2 has successfully treated over 5 billion liters of surface and ground water across Australia, ensuring that PFAS concentrations in treated water consistently remain below the recommended Australian health-based guidance.

The new contract began on July 13, 2021 with ECT2 confirming that it will continue to support remote and regional employment with its workforce of operators, administrative, technical and management personnel, drawing from the local community in each of the locations. ECT2 today employs 19 workers in the local communities in direct support of its work with Defence.

About Montrose

Montrose is a leading environmental services company focused on supporting commercial and government organizations as they deal with the challenges of today, and prepare for what is coming tomorrow. With more than 2000 employees across over 70 locations around the world, Montrose combines deep local knowledge with an integrated approach to design, engineering, and operations, enabling the Company to respond effectively and efficiently to the unique requirements of each project. From comprehensive air measurement and laboratory services to regulatory compliance, emergency response, permitting, engineering, and remediation, Montrose delivers innovative and practical solutions that keep its clients on top of their immediate needs – and well ahead of the strategic curve. For more information, visit www.montrose-env.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements may be identified by the use of words such as “intend,” “expect”, and “may”, and other similar expressions that predict or indicate future events or that are not statements of historical matters. Forward-looking statements are based on current information available at the time the statements are made and on management’s reasonable belief or expectations with respect to future events, and are subject to risks and uncertainties, many of which are beyond the Company’s control, that could cause actual performance or results to differ materially from the belief or expectations expressed in or suggested by the forward-looking statements. Further, many of these factors are, and may continue to be, amplified by the COVID-19 pandemic. Additional factors or events that could cause actual results to differ may also emerge from time to time, and it is not possible for the Company to predict all of them. Forward-looking statements speak only as of the date on which they are made, and the Company undertakes no obligation to update any forward-looking statement to reflect future events, developments or otherwise, except as may be required by applicable law. Investors are referred to the Company’s filings with the Securities and Exchange Commission for additional information regarding the risks and uncertainties that may cause actual results to differ materially from those expressed in any forward-looking statement.

Contacts

ECT2 Contact [Australia]

Vicki Pearce

+61 407 540 295

vicki.pearce@ect2.com

Montrose Contacts [U.S.]

Investor Relations:

Rodny Nacier

(949) 988-3383

ir@montrose-env.com

Media Relations:

Doug Donsky

(646) 677-1844

Montrose@icrinc.com