Significant Project Features:
- Auger mixing using Delmag RH-28 Drill Rig equipped with 10 foot diameter mixing auger
- Injection of Portland Cement and Sodium Persulfate into impacted soils
- Treatment of approximately 3,031 CY of impacted soils to a depth of 20 feet below ground surface.
Background:
Geo-Solutions was sub-contracted to perform in-situ soil mixing at the Coca-Cola Refreshments site located in Needham, Massachusetts. The site was an active bottling and distribution facility for Coca-Cola. Contaminants of concern were PCE. Mix design for the treatment of the contaminant plume was developed by GHD.
Description of Work:
Geo-Solutions completed the in-situ soil mixing using a Delmag RH-28 Drill Rig equipped with a 10 foot diameter mixing auger. The soil mixing was completed from the work platform to approximately 20 feet below grade. Soil mixing was performed with a blend of Portland cement and Sodium Persulfate mixed in water. The mix design consisted of a specified amount of 150 lbs. of Portland cement, 30 lbs. of sodium persulfate, and 360 lbs. of water per cubic yard of soil. Geo-Solutions used and automated mix plant capable of managing multiple reagents to mix the grout to proper proportions.
In total, 51 columns were installed for a total treatment volume of approximately 3,031 CY. Geo-Solutions performed quality control sampling and testing on the grout mix and treated soils. Grout samples were collected from the batch plant and tested for viscosity and density. Wet grab samples were collected from the freshly mixed columns using a mechanical retrieval attachment mounted on the auger stem.
Prior to commencing soil mixing, Geo-Solutions was responsible for the demolition of all concrete and asphalt covering the treatment area, and the excavation and demolition of a subgrade concrete sump. Following the soil mixing, Geo-Solutions graded the site, installed approved sub grade materials and installed asphalt pavement across the disturbed zone.
Project Challenges:
Large obstructions, mostly boulders, proved to be the biggest challenge at this site. The available boring logs provided to Geo-Solutions gave little to no indication of subsurface obstructions. Drilling was quickly halted after several different attempts to achieve full depth failed to advance past obstructions. Geo-Solutions was required to pre-excavate the entire mix area to remove the obstructions before the drill rig could continue soil mixing operations.
Other challenges revolved around the fact that the treatment area was located in the middle of the plant’s loading docks and parking areas. An aggressive schedule was to be maintained in order to reduce the impact on the plant’s ongoing operations. Geo-Solutions was provided with a narrow window in which the docks could be closed. Heavy truck traffic pathways also limited Geo-Solutions’ available space onsite.
