WATERTOWN — The second phase to remove contamination will soon start at a 1.9-acre site of a former Niagara Mohawk manufactured gas plant on Engine Street.
To be finished over three phases, the comprehensive cleanup to rid the site of contamination left by a coal-gas plant that ended operation in the 1950s will cost $18 million.
The next phase of the project will consist of cleaning up a small piece of property that the city’s Department of Public Works owns, with the final phase in 2021.
The second phase addresses impacts in an area east of the CSX-owned railroad right-of-way and north of the city of Watertown’s sanitary sewer utility easement.
The work will take approximately six months to complete. The state Department of Environmental Conservation is overseeing the remediation project.
The cleanup includes removing contaminated soil down to the bedrock and disposing it off-site; cleaning the bedrock surface; bringing in clean soil to the site; and installing a cover system that consists of a delineation layer and one foot of crushed stone.
The work also includes cleaning the bedrock surface and fractures for visual inspection of tar to inform the location of potential coal tar extraction wells.
National Grid, formerly known as NiMo, will pay for the cleanup at a vacant, fenced-in site that it owns.
In 1992, NiMo was directed by DEC to look for and clean up hazardous materials at the Engine Street site and 20 other former coal-gas plants statewide it once owned.
The Watertown Gas and Light Company, the site’s original owner, constructed the coal-gas plant in 1905 and it was operated by various companies until the 1950s. Those companies were then consolidated into NiMo.
The plant produced manufactured gas using coal gasification and carbureted water gas processes, which led to the site being contaminated by its by-product, coal tar, an oily tar-like material commonly found at former MGP sites.
A series of related volatile organic compounds, including benzene, toluene, cyanide and ethylbenzene, also were found. They are considered carcinogens.
A health and safety plan for the site and a community air monitoring plan will be implemented during the remediation project.