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About

Our History

Vintage photo of Matthew Mills, the founder of Engineering Works
1820
Heywood, England, UK

Moss Foundry and Engineering Works is founded by Matthew Mills and later taken over by James Mills.

1840
London, England, UK

Thomas Hawksley becomes a member of the Institution of Civil Engineers.

Hawksley was one of the greatest 19th century water engineers. In his lifetime, he achieved international recognition for developing the first pressurized clean water supply available at the turn of a tap. This system saved countless lives when cholera struck Great Britain in 1848 and is one of the reasons the country’s health and prosperity accelerated ahead of many others in the following decades.

Vintage portrait of Thomas Hawksley
1866
Westminster, England, UK

The T&C Hawksley international engineering partnership between Thomas Hawksley and his son, Charles Hawksley is established.

1884
Arbroath, Scotland, UK

John Duncan Watson began his revolutionary career in water and wastewater treatment with an appointment as Borough Surveyor. His notable achievements included the construction of the first large percolating filter plant, abandoning traditional methods for more innovative techniques. Other radical changes that he led were the recovery and utilization of methane for energy in gas engines, separate sludge digestion, and two-stage purification of tank effluents by primary flocculation prior to percolating filter treatment.

Vintage portrait of John Watson
Vintage advertisement of a water pump
1892
Heywood, England, UK

The son of James Mills, Matthew William Mills, who later became a leading authority in sewage machinery, revives Moss Foundry and Engineering Works under the name of James Mills and Company, Ltd.

1918
Heywood, England, UK

Matthew William Mills, son of James Mills, of James Mills and Company, Ltd. files a patent for a new type of machinery for the activated sludge process, used in the mechanical aeration of sewage. The process was afterwards very widely adopted.

Vintage portrait of Matthew Mills
Vintage portrait of Leroy F. Harza
1920
Chicago, Illinois, USA

Harza Engineering Company, which offered energy and environmental engineering services is founded by Leroy F. Harza

1926
Nottingham, England, UK

Ames Crosta Mills and Company, Ltd. is formed for developing the sales of sewage purification machinery patented by James Mills and Company, Ltd. Matthew Mills is one of the original directors.

Map of the sewage purification in Scotland
Vintage portrait of John Duncan Watson
1934
London, England, UK

The JD & DM Watson partnership between the retired John Duncan Watson and his son David M. Watson is formed for municipal wastewater treatment.

1937
Nottingham, England, UK

Ames Crosta Mills and Company, Ltd. manufactures the simplex sewage purification plant that drives the modernization of environmental standards for wastewater treatment and for mechanical aeration products used in the activated sludge process, still in use today.

Vintage advertisement for a variable capacity pump
Men in suits meeting around a table with blueprints and contracts
1945
Pasadena, California, USA

James M. Montgomery (JMM), an environmental engineering consultancy firm specializing in water and wastewater, is established by James McKee Montgomery and begins to offer construction management services. JMM is later incorporated in 1954.

1960
Methuen, Massachusetts, USA

Methuen Construction Company was founded in 1960 by Leon and Elizabeth Asadoorian. The Company had its origins in residential and commercial site construction. In the mid 1960's Methuen began serving private utility companies throughout the Merrimack Valley of Massachusetts and New Hampshire. This is the original office at 90 North Lowell Street in Methuen, MA.

Eagle-eye view of a town intersection in Massachusetts
Men in suits posing for the camera
1968
Kent, England, UK

Biwater Treatment Company, Ltd. is formed by Sir Adrian White, establishing themselves as pioneers in the field of water, wastewater and sludge treatment.

1975
Heywood, England, UK

Ames Crosta Mills and Company, Ltd. is briefly absorbed by Babcock and Wilcox, Ltd. (est. 1867) and renamed as Ames Crosta Babcock, Ltd.

Vintage advertisement for Babcock Constructors
Vintage aerial view of a town in England
1978
High wycombe, England, UK

JD & DM Watson and T&C Hawksley merge to form Watson Hawksley, Ltd.

1984
Stayton, Oregon, USA

Slayden Construction Group, Inc. is established, focusing on water and wastewater construction projects in the Pacific Northwest.

Company sign for Slayden Construction Group
Vintage advertisement for Biwater Treatment Company
1988
Kent, England, UK

Biwater Treatment Company, Ltd. acquires Ames Crosta Babcock, Ltd.

1992
Pasadena, California, USA

JMM merges with English firm, Watson Hawksley, Ltd. to become the global environmental engineering firm of Montgomery Watson, Inc.

Six men in suits posing for the camera
Vintage image of construction equipment moving barrels
1993
Boulder, Colorado, USA

Montgomery Watson Constructors, Inc. is established as the construction company with Montgomery Watson, Inc. for construction management-at-risk and alternative delivery contracts for municipal and federal clients.

2001
Broomfield, Colorado, USA

Montgomery Watson, Inc. merges with Harza Engineering Company to create global energy, utility, and environmental engineering company known as MWH Global, Inc.

Montgomery Watson Constructors Inc. becomes MWH Constructors, Inc.

Aerial view of MWH company employees standing in the shape of "MWH"
Construction workers observing the installation of equipment
2010
Heywood, England, UK

MWH Constructors, Inc. acquires leading UK water construction and engineering firm Biwater Services Ltd., to form MWH Treatment, Ltd.

2015
Stayton, Oregon, USA

MWH Constructors, Inc. acquires Slayden Constructors, Inc.

Aerial view of a water facility building
Methuen Construction workers posing in front of the company headquarters
2021
Plaistow, New Hampshire, USA

MWH acquires Methuen Construction Company, a self-performing general contractor with more than 60 years of experience in the Northeast.

2023
Minato City, Tokyo, Japan

MWH enters an agreement to join forces with Obayashi Corporation, a global leader in construction with a rich history dating back to 1892 based in Tokyo, Japan.

MWH CEO Blair Lavoie signs agreement at Obayashi Corporation headquarters.

Company News

Welcome to the New Phoenix Office

After a year of meticulous planning and excited anticipation, MWH’s Phoenix Team moved into their new office on June 1, 2023. Let’s take a look around!

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Pioneering Water Reclamation at James M. Montgomery Consulting Engineers

In 1945, James McKee Montgomery laid the foundation for an environmental engineering consultancy firm named James M. Montgomery Consulting Engineers, Inc. (JMM) in Pasadena, CA, focusing on water and wastewater solutions. You may recognize “Montgomery” as the “M” in MWH. The company was officially incorporated in 1954 and offered a range of engineering and construction management services.

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