ACP Permeable Reactive Barrier Wall Installation

Trichloroethylene (TCE), once widely used in the electroplating industry as a degreasing agent, has caused significant environmental concerns. TCE was employed as a pretreatment step to clean and remove grease from metal surfaces before plating to ensure a high-quality finish. However, due to its considerable health and environmental risks, the use of TCE has been heavily regulated. Over time, its application has declined in favor of safer alternatives.

At a former plating facility in Kansas, a substantial quantity of TCE leached into the soil, leading to contamination of the groundwater. Now in need of remediation, the site presented additional challenges due to the presence of sensitive live utilities. These include a 200-pair AT&T copper communications line, water lines, fire hydrants, a natural gas line, and two abandoned AT&T communication lines.

Additionally, overhead power lines posed a potential electrocution risk. The complexity of the site’s infrastructure necessitated careful planning and execution of remediation efforts to ensure the safety of workers and the surrounding community while addressing the environmental contamination caused by TCE.

Leveraging our significant experience in handling contaminated materials, our team stepped in to install a Permeable Reactive Barrier (PRB) wall. We designed the PRB to intersect and treat the groundwater contaminated with TCE and constructed it with blended mixtures of sand and zero valent iron (ZVI), which we placed in a 2 foot wide trench to depths between 30 and 52 feet below ground surface. The wall measured 440 linear feet in length with a maximum depth of 52 feet and average depths of 40 feet. The final construction covered 12,358 square feet. We constructed the wall using a PC 800 with a specialized boom and stick attachment capable of reaching maximum depth. We used Bio-polymer slurry to support excavation and backfill operations and created two different zones of treatment media by installing a series of sheet pile bulkheads along the trench alignment. Contaminated trench spoils were hauled to and disposed of in an approved landfill, totaling 2,400 tons.

To manage the live underground utility lines, our team utilized hydro vacuuming for utility potholing, helping to avoid damaging these critical infrastructures. Additionally, utility monitoring points were established on existing utilities, and daily surveying of these points was conducted during and after construction to ensure their integrity. We also implemented traffic control measures to maintain safety and minimize disruption to the local community. After the completion of the PRB, we carried out site restoration. The project team in a partner relationship with the engineer worked though project challenges and other delays completing the project within an agreed upon revised schedule. The PRB wall was completed without any OSHA recordable injuries and no major incidents during construction of the wall despite proximity to overhead electric and public utilities. The project was recognized as a success by the engineer, client, and Kansas Department of Health who express interest in using the project in future state conferences.

The completed remediation project at the former plating facility addressed the critical issue of TCE contamination in groundwater using a PRB constructed with sand and ZVI designed to react with the TCE and turn it into less harmful compounds. The project’s success was marked by its adherence to safety protocols, effective handling of contaminated materials, and careful management of utilities. The recognition by the Kansas Department of Health underscores the project’s importance and its potential as a model for future remediation efforts. This project not only improved the environmental health of the area but also demonstrated the effectiveness of modern remediation techniques in addressing complex contamination issues.