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, the greatest 19th century water engineer, becomes a member of the Institution of Civil 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 a reason the country’s health and prosperity accelerated ahead of others in the following decades.
1866
WESTMINSTER, ENGLAND, UK - T&C Hawksley, an international engineering partnership between Thomas Hawksley and his son, Charles Hawksley is established.
1884
ARBROATH, SCOTLAND, UK - John Duncan Watson began his career in water and wastewater treatment. His notable achievements included the construction of the first large percolating filter plant. 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.
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.
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.
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.
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 1960s Methuen began serving private utility companies throughout the Merrimack Valley of Massachusetts and New Hampshire.
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.
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.
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.
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.
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.
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.