Former Chemical Manufacturing Site Remediation

At this former industrial site, in situ stabilization (ISS) was selected as the remedial approach to address constituents impacting soil and groundwater and protect the public and surrounding environment from impacts of these contaminants. Contaminates of concern at the site included  ethylene dibromide (EDB), 1, 2 dichloroethane (DCA), Vinyl Chloride, and other volatile organic compounds (VOCs). The contamination had severely impacted both soil and groundwater, specifically affecting two water-bearing zones within the designated treatment area.
 
During remediation activities, a major concern was maintaining perimeter air quality, with strict monitoring action levels necessary to control VOC emissions. This was crucial to ensure that VOC concentrations did not exceed regulatory limits, which could endanger workers and nearby communities. Environmental management was also a key consideration for the project. Stringent control measures were needed to prevent the release of fugitive dust, debris, and run-off, which could negatively impact adjacent properties and cause cross-contamination. Operational constraints also complicated the remediation. Activities had to be conducted without disrupting ongoing work at adjacent properties or overhead and underground utilities which intersected the phase II treatment area.
 
The health and safety of the site workers and surrounding community were also a significant concern due to the hazardous nature of the contaminants. The remediation team needed to operate in a way that minimized exposure to harmful chemicals, ensuring the safety of both workers and the local population. The presence of EDB and DCA in soil and groundwater posed a significant threat, requiring robust safety protocols to manage the associated risks effectively.

Forgen successfully executed a comprehensive remediation plan for the legacy industrial site. This plan combined geotechnical construction techniques and meticulous safety protocols to address the complex contamination issues while meeting regulatory requirements for treatment. The project involved extensive site preparation, stormwater management, utility protection, demolition of above and below surface structures, excavation of overburden soils, soil management, disposal of impacted soils, and the installation of a final cover system to secure the site. Remediation and treatment at the site was accomplished in two phases in order to avoid impacts with overhead and underground utilities within the phase II area of the project site.

To treat the contaminated soils within the phase I area, Forgen mobilized an 888 Manitowoc crane equipped with a Hain platform and a 10-foot auger to treat 45,800 cubic yards of impacted soils. A fully automated and programmable grout batch plant along with reagent silos, and a series of pumps were used for preparation of the treatment grout mixing operations.

Given the range of VOCs and other contaminants of concern present in the ISS treatment zone, ground personnel donned Level B personal protective equipment with supplied air during work activities. To control VOC emissions, Forgen designed, fabricated and installed a 12-foot diameter vapor shroud suspended from the Hain platform, which the crane operator could raise and lower to encompass the auger, Kelly bar, and soil during treatment.  The vapor control  system included two 8-foot diameter vapor phase carbon absorbers in a lead-lag configuration and blower capable of 3,500 cfm. The absorbers were charged with 4,000 pounds of virgin coconut shell vapor phase activated carbon and consistently sampled to monitor for potential breakthrough.

The  vapor control system along with supplement odor control measures allowed Forgen to meet strict perimeter air monitoring VOC concentrations limits. Elevated air monitoring readings could occur when handling site soils and during remedial activities. To mitigate this Forgen used a combination of odor control foam, water, and a perimeter misting system to effectively mitigate VOC emissions. The project was completed while ensuring compliance with the approved air monitoring and mitigation plans for the site.

Phase II of the project required ISS treatment of impacted soils while working under 115 kV power lines. To complete the work, Forgen used a low-profile deep soil mixing rig and a custom-fabricated shroud to capture VOCs. The work also required removal of two 33-inch wastewater force mains that were abandoned by others.

In order to complete treatment beneath the powerlines to depths of 18 to 25 feet, Forgen worked with local fabricators and equipment vendors to setup the low-profile drill rig and a custom-fabricated shroud to capture VOCs. Forgen’s successful design and implementation allowed use of the vapor control system specified for the project while completing treatment below the live powerlines. As with the previous phase, workers conducted all ISS and earthwork activities in Level B PPE to ensure safety of the employees

Following completion of ISS treatment, Forgen installed a cap and cover system to encompass all of the phase I and II treatment areas. The cap and cover consisted of clean soil cover with a geotextile and geosynthetic liners and vapor collection system. The final cap was covered with soil and native vegetation.

The successful completion of this geotechnical remediation construction project paved the way for the site’s redevelopment into a vibrant community space. This demonstrated Forgen’s commitment to environmental stewardship and public health. Overall, Forgen’s remediation solutions effectively addressed the contamination at the legacy industrial site while meeting all regulatory requirements for cleanup at the site. Our geotechnical construction approach mitigated environmental risks, ensured compliance with safety standards, and prepared the site for its new role in the community.

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