Manufactured Gas Plants

In the late 1990s, one of Unitil’s predecessor companies, Northern Utilities, Inc., was one of the first utilities in Maine and New Hampshire to enroll its former manufactured gas plant (MGP) sites in the respective states’ voluntary response action programs.  Throughout their operations, MGPs provided the communities they served with gas that powered progress.  With the expansion of natural gas into New England beginning in the 1950s, these plants were eventually retired but left behind notable environmental impacts.

What's an MGP site?

An MGP was an industrial facility at which gas was produced from the heating of coal, oil and other petroleum-based products via a process called de-gasification.  The resulting gas was stored and then piped to the surrounding communities, where it was used for lighting, cooking and heating homes and businesses.  The first MGPs in New England were constructed in the early to mid-1800s with most of these facilities closing by the 1960s due to the arrival of interstate, natural gas transmission pipelines.  Limited environmental knowledge and scrutiny during the years of their operation often resulted in wastes being discarded or buried directly at the MGP sites.

Why are former MGPs sites a concern?

Most of these facilities have been closed for about 50 years now.  And in some cases, subsequent redevelopment of the MGP sites has removed or covered wastes which were once exposed at the surface.  However, these sites often contain abandoned underground structures and pipes containing wastes or other related residuals from their activities as an MGP.  Some of these wastes (especially coal tars) may have migrated from these structures and impacted the soil and groundwater beneath the MGP site.  Impacts to surface waters and their historical sediments are also common since MGP sites were typically located near a source of water.

What is being done with the former MGPs?

To date, four of the original nine sites have completed remedial activities with active remediation/monitoring occurring at the remaining five MGP sites.  The goal is to restore these sites to conditions that no longer pose an environmental or safety concern and provide added value to the communities in which they’re located. 

As an example, Gas Light Park in Lewiston, Maine was developed along the historic waters of the Androscoggin River and atop the remains of the former Lewiston Gas Works.  Although groundwater remediation continues below the surface, residents of the city and state enjoy unobstructed access to the riverfront in a setting respective of the City’s historical use of water during the Industrial Revolution.

Fact sheets have been prepared on several former MGP sites, which further describe the actions that have been taken to date to restore the properties.


Environmental Fact Sheets

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