Soil Mixing: 9 foot auger; 323 columns hot air mixed; 323 columns treated with chemical reagents and then remixed; 17,144 CY of treated soil; and an average mixing depth of 26.7 feet below ground surface.
Description of Work:
The former Confidential Manufacturing (CM) Facility is located in the town of Norwich, New York. The site consisted of approximately 88 acres of land, which includes developed buildings and landscaped areas. CM utilized this area as an industrial site for use in research and development. Environmental Resources Management (ERM) performed subsurface investigations between May and September 2010 to assess the source of acetone and methylene chloride in a portion of the property known as the Equalization Basin Area. As a result of the investigation, ERM prepared a Remedial Action Work Plan to address the acetone affected media. After the work plan was approved by the New York State Department of Environmental Conservation, Geo-Solutions teamed up with ERM to begin remediation treatment in the Equalization Basin Area.
Geo-Solutions mobilized to the site and began the Shallow Soil Mixing (SSM) within the Equalization Basin Area. The SSM activities that were performed involved a 3 step process: hot air mixing, chemical reagent addition, and chemical reagent mixing. The hot air mixing and the chemical reagent mixing were done using a Delmag RH-18 Drill Rig. An ABI Drill Rig was used for the chemical reagent addition and sample collection.
Each column was hot air mixed with a 9 foot auger for a minimum of 30 minutes as required by the specifications. A 375 CFM air compressor was used to supply the hot air to the drill rig. A relief valve was installed near the cab of the drill rig so the operator could adjust the air flow when needed.
After each column was hot air mixed, the remediation plan called for four chemical reagents to be mixed into the subsurface: calcium peroxide (oxidizer), ammonium sulfate (nutrient), potassium chloride (nutrient), and phosphoric acid (pH buffer). The calcium peroxide, ammonium sulfate, and potassium chloride were dry solids and the phosphoric acid was a liquid. The chemical reagent addition process involved driving two hollow steel casings, one for the dry regents and one for the acid, into the ground, charging the casings with the proper chemical reagent dosage, and removing the casings while leaving the reagent deposit in the ground. The ABI Drill Rig was equipped with a vibratory hammer to grip the casing, drive it into the ground, and retrieve it.
Once the reagents were in place, the Delmag Drill Rig was used to mix the column and distribute the chemicals throughout the affected media. Each column was mixed for a minimum of 2 strokes. After the reagents were mixed the column was completed.
Different levels of personal protective equipment (PPE) were required in different areas of the site depending on what type of activities were taking place. For example, while in chemical handling areas, employees were required to wear full face respirators and chemical resistant suites, gloves, and boots.
The Shallow Soil Mixing activities were completed in compliance to the project design and in accordance to the specification. All work was performed in a safe and timely manner with no safety incidents. The project was completed considerably ahead of the baseline schedule, and was a success for CM, ERM, and Geo-Solutions.
