Theme: 01. Remediation Technology Innovations

Topic Area: 01m. In Situ Technologies: Lessons Learned

Formatted Title:

In Situ Stabilization of Impacted Organic Peat during Ongoing Development

Background/Objectives:

A former chemical manufacturing facility was slated for development of a warehouse under the New Jersey Brownfields Program within a fast timeline to achieve regulatory closure so that construction could begin. The site contained variable thicknesses of meadow mat (peat) which were highly impacted with benzene, chlorobenzene and trichloroethylene, as well as LNAPL and DNAPL. After evaluating remedies including fracturing for amendment distribution, Cascade suggested in situ stabilization (ISS) for the client to achieve their schedule and reduce the mobility of the contaminants.

Approach/Activities:

An extensive treatability study was conducted to optimize reagent formulation which could be used to treat and stabilize the challenging contaminants and lithology. Since the treatment zone contained thick areas of organic peat, which are highly absorptive and challenging to effectively mix and stabilize, Cascade modified the mixing technique and amendment. Excavator bucket mixing using a specialized skeleton bucket was used to achieve homogeneous mixing within each cell through the meadow mat to a confining clay unit. A cement accelerator and water to reagents ratio adjustment were conducted when necessary to improve the rates of curing and overall performance. Cells pre-delineated with extremely high contaminant concentrations were excavated, treated and sent-off-site for disposal.

While the treatment zone compiled approximately 30,000 cubic yards (CY), a majority of the Cascade’s ISS cells were within the building footprint. Construction challenges with concurrent ISS activities and heavy construction, including pile installation, included schedule, on-site truck traffic, and water management. Cascade successfully maintained production and stayed ahead of the pile installations to meet the client’s goals. The schedule included a quality control program where samples from each cell were collected and analyzed at 7 and 14 days for unconfined compression strength, permeability and random SPLP, all managed by the oversight engineer.

Results/Lessons Learned:

After completing the treatability study in March 2022, Cascade immediately transitioned to full-scale ISS and completed all activities within four (4) months from mobilization. The general contractor completed pile installation and began pouring slabs for a 325,000 SF warehouse within two (2) months following Cascade’s demobilization. While meeting all regulatory requirements for brownfields reclamation, the combined effort of managing a tight schedule with multiple large remediation and construction companies is paramount. Daily communication and sharing resources are important between multiple contractors in order to meet client’s needs and most importantly, maintaining a safe environment.

Many contaminated sites, especially in New Jersey, are being developed as distribution centers under aggressive schedules. Cascade will present the stepwise process from the treatability study through full-scale ISS implementation will be discussed as well as the alternative ISS methods and challenges with the contaminants and lithology. The importance of multiple contractors, scheduling and projections to completion are necessary for a successfully project.

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Jonathan Simpson