The former HoltraChem manufacturing facility was constructed in 1967 to manufacture chlorine and sodium hydroxide for use in the pulp and paper industry in Maine. Other products were also produced at the plant over the years before it ceased operation in 2000.

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The Plant Area at the Site, which is approximately 12 acres in size, is the area where the former manufacturing processes took place. This area included numerous buildings and related infrastructure such as storage tanks and associated piping. The former “Cell Building” was where most of the manufacturing operations occurred, although there were other buildings for various ancillary production processes, maintenance, and materials storage. (All of the former HoltraChem tanks and piping have since been demolished and the current groundwater treatment plant, constructed in 2012, was not part of the former HoltraChem facility.) 
 
The soils in and around the Plant Area have been investigated and some soils were identified as impacted by historical facility operations.  The original Corrective Measures Implementation Plan (CMIP) (remedial design) for the Plant Area was submitted in early 2017. Based on subsequent discussions between Maine DEP and Mallinckrodt, the remediation of the Plant Area was separated into distinct areas and phases. The Phase 1 design was submitted to Maine DEP in December 2017 and involved excavating impacted soils above the Soil Media Protection Standard in the least impacted areas and transporting those soils offsite to a secure landfill. Maine DEP approved Phase 1 in January 2018 and the removal of 65,321 cubic yards of impacted soils was completed in early 2019. Final backfill was completed in early summer 2019 and final restoration was completed in 2019.

Technical discussions were held with Maine DEP in December 2018 and design plans for the next phases of work were developed. The Phase 1A scope of work included excavation and restoration of the former Retort Area and pre-trenching in preparation for installation of a temporary sheet pile wall around the former Cell Building. Maine DEP issued a conditional approval for this CMIP in July 2019 and the Phase 1A work remediation was completed in late 2020. Concurrent with the Phase 1A work, the design for the Cell Building, including installation of a temporary sheet pile wall around the former cell building followed by excavation of soils, was submitted in August 2019 and conditionally approved in September 2019.

Separate from the soil remediation, work in the Plant Area also included  Concrete and Utility Removal. This CMIP was submitted and approved by Maine DEP in July 2020. The objective of this work was to identify and remove obstructions (e.g. foundations and utilities) and prepare portions of the Plant Area for site clearance and future activities. Because foundations and utilities were located across the entire site, defining this scope of work was an iterative process. Work began in fall 2020, with frequent discussions and multiple CMIP addendums taking place through 2023.

Another discrete area of remediation activity is the removal of a paved sump and catch basin, both of which are part of the former drainage system at the Site. The Catch Basin #6/Paved Sump CMIP was approved by Maine DEP in August 2022. This work focuses on an area downgradient of the Cell Building and adjacent to the former Landfill 1 area. Activities began in late 2022 and continued through the fall of 2023.