CASE STUDY: Chemically Oxygenated Granular Activated Carbon (COGAC™) Injection
This case study presents site information, remedial injection remedial material, injection method and post injection results at a petroleum hydrocarbon underground storage tank release site in the state of Washington. This was the first site in which Remington combined oxidizers with powdered activated carbon and, therefore, the longest period of post injection monitoring.
In the treatment area, the groundwater occurred within a sandy silt to a silty sand. The depth to groundwater was approximately 4 to 6 feet below ground surface (bgs) overlain by roadbase associated with the site development. Impacted soil in the saturated zone and unsaturated zone appeared to be limited to the source area. As shown on the map, groundwater impacts, above regulatory standards, extended over 500 feet downgradient and impacted three other properties. Prior to the remedial activities, the owners of these properties were considering litigation. After the injections, the threat of litigation was removed as a result of the decline in dissolved phase contamination.
The two injection events predated the final formulation of COGAC™ and the patent application. However, the injectate used at the site consisted of the same materials (oxidizers and powdered activated carbon) eventually incorporated in the patented remedial material developed by Remington Technologies. Therefore, the post injection data from this site covers a period of sufficient length to demonstrate the longevity of the remedial effect.
Each of the two events lasted approximately one week and over 200 injection points were advanced across the dissolved phase plume. The Valley Plaza building and extensive underground utilities limited injections into portions of the dissolved phase plume. However, most of the plume was overlain by a grocery store parking lot that was accessible during offpeak hours.
Remedial Injection Method
The remedial injection method used at the injection site utilized Direct Push Technology (DPT) and Remington’s auger/packer system. Approximately 70% of the injection points utilized the auger/packer system with the remaining 30% utilizing the DPT approach.
During the two events, approximately 9,000 gallons of the remedial material was injected at a 12% concentration by weight. On average, each injection point received 45 gallons of the material. There was some surfacing around the DPT points due to the shallow injection interval, so the decision was made to switch to the auger/packer system. There was no surfacing around the injection points using this technique.
COGAC™ Remedial Injection Results
As shown on the following graphs and table, dissolved petroleum hydrocarbon concentrations decreased rapidly to below laboratory detection limits after the injection events. Based on these results, the COGAC™ like injection was successful in remediating the contaminant mass remaining at the site, therefore achieving regulatory remedial goals for the site and eliminating the threat of litigation.