Significant Project Features:
- Technical Assist
- Excavator-based ISS of 22,700 CY up to 11-feet in depth
- Target Unconfined Compressive Strength of 50-180 psi at 28-days of cure
Background:
The 35-acre parcel at 1 Horizon Way (formerly Chemical Lane) in Boston, Massachusetts, on the banks of the Mystic River, was home to chemical manufacturing companies including Merrimack Chemical and Monsanto Chemical from the late 1800’s through 1980. During the mid-1990’s the land was used to store rock and sediments from the construction for the Deer Island Treatment Facility. Subsequent studies identified 3 primary areas of contamination:
- Area A-5 – High Arsenic and Lead (Soil)
- Area 2 – High Arsenic and Lead (Groundwater)
- Area 3 – Low pH/Elevated Arsenic and Lead
The property was recently purchased by Wynn Resorts. Following remediation, the site is slated to be the home of a $1.7 billion-dollar water-front casino complex to include a five-star resort, 600+ hotel rooms, as well as retail and dining amenities.
Geo-Solutions was contracted to provide key equipment and personnel for the In-Situ Solidification of the sediments and soils in the low pH area to reduce groundwater contaminant concentrations and immobilize arsenic and lead in the soils, ultimately preventing the continued leaching of low pH/arsenic/lead-contaminated groundwater into the mystic river.
Description of Work:
Numerous buildings and other structures formerly existed on the site, and specifically, in the low pH treatment area. While the structures themselves were razed years ago, their foundations, footings, shoring, abandoned utilities and other subsurface features remained. Due to the high probability of encountering subsurface obstructions, an excavator-based ISS approach was selected. The site was divided up into discreet mixing “ISS Cells” providing 100% coverage of the treatment area. The selected reagent, a mixture of water and Portland cement, was manufactured in Geo-Solutions’ batch plant and pumped to the ISS Cell location. 22,700 Cubic Yards (CY) were completed using this method. Samples of the soil mix were collected and tested for pH and Unconfined Compressive Strength to ensure the contaminants are immobilized within the solidified soil-mixed monolith.
