Massachusetts Contingency Plan (MCP), Site Assessment, and Remediation
Holyoke Gas and Electric • Holyoke, MA
Holyoke Gas and Electric (HG&E)
- Widespread contamination from former manufactured gas plant (MGP) operations
- A thorough, creative, and cost-effective approach to remediate all continuing sources of contamination and prepare the site for beneficial reuse
- Reuse of over 7K tons of treated soil
- Cost savings of $1M over traditional remedial methods
Tar wastes emanating from historical operations at a former MGP facility located on the Connecticut River in Holyoke, Massachusetts had impacted local soil and groundwater and were found within the breeding grounds of an endangered fish species in the adjacent river system. Both light and dense non‑aqueous phase tars (LNAPL and DNAPL) were also detected in several on‑ and off‑property wells.
Apex Companies provided Phase II site assessment/remediation services, including site engineering, remedial evaluation and design, remedy implementation, construction oversight, and perimeter air monitoring (PAM).
Apex completed comprehensive site assessment activities that defined the extent of the MGP impact in the terrestrial environment and developed a site remediation plan to reduce potential exposures and alleviate potential risk to human and environmental receptors in accordance with the MCP. Activities included a Phase II comprehensive environmental site assessment (ESA) and addendum that included a Method 3 risk characterization and a Stage I and II ecological risk assessment. Apex also completed a Phase III remedial action plan (RAP) involving the identification, evaluation, and selection of a comprehensive remedial action alternative. The remedial measures selected via the MCP RAP process were implemented via a series of Remedy Implementation Plans (RIPs). These response actions, combined with source area removal activities, have substantially reduced the potential risk posed by the site.
Each risk reduction/remediation measure implemented at the site is highlighted as follows:
UST Removal—One 10K and two 20K gallon tanks that had contained tar waste-containing fuel oils were removed/abandoned to eliminate potential continuing sources of contamination. This included cleaning the 100-year-old tank interiors and removing the 10K gallon tank for off‑site disposal. The 20K gallon tanks were abandoned in place and filled with a sand and Portland cement slurry to not impact the structural integrity of nearby buildings.
Aboveground Storage Tank (AST) Removal—Two number six fuel oil ASTs that had been left in place with over 20K gallons of remaining oil were also cleaned and removed from the site. This oil had been released by site vandals to the secondary containment units of both tanks. Apex removed the oil, cleaned the secondary containment and tank interiors, dismantled the tanks, and collected confirmatory soil samples.
Tar Well Abandonment—When MGP operations ceased in the early 1950s, three masonry underground tar wells with a combined capacity of over 100K gallons were filled with tar waste and left in place. The tar in each of these wells was heated and removed via pumping. Once removed, the recovered tar was then recycled and reused as low British thermal unit (BTU) fuel at a cement plant. The interior of the structures was then cleaned and backfilled with soil.
DNAPL Recovery—DNAPL coal tar is present ranging from 30 to 80 feet below grade with an accumulated thickness of over 12 feet. The tars include a mobile fraction which has migrated several thousand feet away, and a less mobile, more viscous tar present beneath the facility. Apex pilot tested a multi‑point DNAPL recovery system to address the mobile coal tars and a steam‑enhanced DNAPL recovery system to recover the viscous tars. Using super‑heated, super‑saturated steam, Apex designed a steam sparge system with the capacity to raise subsurface temperatures over 200°F and influence monitoring points up to 150 feet away. This proved so effective that, after approximately three years, the area of viscous tar was successfully remediated and the steam sparge system was deactivated. Recovery activities of the mobile tars continue at off‑property locations. Since the initiation of recovery operations in early 2007, approximately 15K gallons of tar have been recovered.
Soil Stabilization (Former Relief Holders)—Two former relief holders, a tar well, and a tar separator were demolished in place in the 1950s and 1960s by collapsing them into their coal tar-containing foundations and adding soil fill to grade. Due to the volume of material and magnitude of the impact, excavation, and off‑site disposal was cost prohibitive. Working with our partners and leveraging our regulatory knowledge, we excavated and stabilized the soils on site, returning them to the excavation area as backfill. We also obtained approval for the use of cleaned building as backfill under a beneficial reuse determination.
Bulkhead Wall Installation—Site response actions were initiated at this facility in the late 1980s with the appearance of an iridescent sheen on the surface of the Connecticut River. The sheen was determined to be composed of light-end MGP residuals that had migrated from the site to the bank. Components of the previously discussed DNAPL recovery system were installed immediately inland of the sheen breakout location to cut off any continuing source material, but a permanent solution was also needed. To address this, Apex designed and installed a bulkhead wall constructed of sheet piling driven to bedrock, after which the riverbank was restored.
No. 2 Overflow Raceway Sediment Cap—During the 100+ years of MGP operation, sediments in the waterway adjacent to the site—part of Holyoke’s floodwall system—had become impacted with coal tar and MGP residuals. Excavation and removal of the impacted material had the potential to undermine the city’s flood protection system, so Apex designed and installed a subaqueous cap system to encapsulate the impacted sediments. Prior to initiating construction, permits were obtained from the Massachusetts Department of Environmental Protection (DEP), US Army Corps of Engineers (USACE), and the Federal Energy Regulatory Commission.
PAM—To ensure that the site remediation activities did not adversely impact air quality, Apex prepared and implemented a perimeter air monitoring plan (PAMP) which included establishing pre‑remediation baseline odor and contaminant data. Real-time data was collected for total volatile organic compounds (VOCs) and respirable dust. time-weighted average (TWA) data was collected on a weekly basis for VOCs, semivolatile organic compounds (SVOCs), Resource Conservation and Recovery Act eight metals (RCRA 8), and total respirable dust.
These response actions, combined with source area removal activities, have substantially reduced the potential risk posed by the site.
At the conclusion of the project, approximately 7,800 tons of soil had been stabilized and reused on site. By implementing this alternative strategy, our client was able to realize a cost savings of approximately $1M versus excavation and off‑site disposal.