Around Moretrench: Environmentally Sound

July 20, 2015

Redevelopment of former industrial manufacturing facilities or landfills is often complicated by the presence of contaminants in the soil and groundwater.  Moretrench is experienced in a range of environmental remediation services to address this issue, including groundwater recovery and treatment, barrier techniques (cut-off and exclusion), landfill gas and leachate systems, and contaminated soil excavation and disposal. Every project we undertake is tailored to the contaminant(s) present and the project objective.

For a site that had been contaminated with LNAPLs (light non-aqueous phase liquids), located within a residential area in Garfield, New Jersey, development for commercial occupancy was contingent on containing the impacted soil and groundwater within the property boundaries to prevent permanently impacting the surrounding groundwater regime.  The solution was a perimeter soil-bentonite barrier wall, submitted as part of the Remedial Action Work Plan for the site.  The design parameters for the trench were developed by Moretrench.

The subsurface soils consisted of surficial fill over layers of very hard cemented fine to medium silty sands and gravel, beneath which was a layer of dense glacial till and sandstone. The 750-ft long, 3-ft thick trench was designed to key a minimum of 3 ft into the sandstone.

To reach the design depth of 75 ft, Moretrench utilized a specialized excavator stick and boom assembly coupled with a Komatsu 1250 hydraulic excavator.  A centrally located slurry mixing plant and storage tanks provided an adequate supply of bentonite slurry to maintain trench stability during excavation.  Soil-bentonite backfill was mixed alongside the trench.

During the work, an experienced superintendent and quality control field engineer were on site at all times to manage trench construction. Independent laboratory  testing of soil-bentonite backfill samples  achieved results of less than 1 x 10-7, exceeding project specifications of 1 x 10-6. A structural cap composed of geo-fabric and quarry process stone was then installed to minimize settlement over the barrier wall.

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