Gabion mattress deployment at former manufacutured gas plant site case study
Project: Island End River Sediment Cap
Location: Boston, MA
Products: Organoclay Reactive Core Mat? Triton Marine Mattresses
Background: The project is situated on a former manufactured gas plant (MGP) site located adjacent to the Boston Harbor. Previous remedial work included dredge and disposal in CAD cell and cap. Persistent sheen resulting from gas ebullition was apparent.
Challenge: Treating contaminated sediments in a subaqueous environment is always a unique challenge. In these types of applications, a mechanism is needed to aid in placement of the underlying geotextile treatment layer with minimal displacement of sediment. In this particular application, the underlying geotextile was Reactive Core Mat* (RCM), which is designed to sequester and treat contaminants within the soil.
Solution: The remediation strategy included the placement of a modular reactive capping system, including Triton Marine Mattresses used in conjunction with 135,000 lbs of Organoclay bulk capping material and 35,000 square feet of Reactive Core Mat, in order to prevent non-aqueous phase liquid (NAPL) contamination from reaching the surface waters. The modified mattress system utilizes Organoclay filled within the Reactive Core Mat to adsorb contaminants.
Result: With the help of underwater divers, the Triton Marine Mattresses and Reactive Core Mat sediment treatment layer was installed with ease and is performing as expected. The system allowed for minimal displacement of sediments and elimated the need for a thick sand cap.