Project Description

CASE STUDY: Chemically Oxygenated Granular Activated Carbon {COGAC™) Injection

This case study presents site information, remedial injection material, injection method and post injection results at a pipeline release site in Weld County, Colorado. Prior to the COGAC™ injection in March 2014, another carbon based injectate (CBI), BOS 200, was injected at the site in November 2011.

After the initial injection, results were generally unfavorable with some free product appearing in several of the site wells. Since the subsequent COGAC™ injection, results have remained below regulatory levels and free product has not been observed.

Site Information

The pipeline release site is located in an agricultural field in which corn is typically grown. A limited excavation and surface product recovery were initiated after the release. Free product and high levels of dissolved phase hydrocarbons were observed in the monitoring wells constructed after the initial response.

In the treatment area (as shown on the attached map), the groundwater occurs in the top of a siltstone, overlain by silty clay. This is a generally unfavorable geometry for injection. In this situation, it is difficult to achieve an effective radius of influence (ROI) as the injectate tends to “short circuit” to the more permeable soils immediately above the indurated material. Remington countered this difficulty with the injection protocol described below.

Remedial Material

During the COG AC™ injection event, 24,765 gallons of a 12% mixture was injected into 245 points across the impacted area. Down-hole pressures ranged from 350 to 20 psi and flow rates ranged from 2 to 20 gpm. The injection event was completed in 15 days for an average daily injection rate of 1,650 gallons per day.

Remedial Injection Method

As described above, the target interval was at the top of an indurated (not weathered) siltstone which was immediately overlain by soils consisting of silt and clay. It is difficult to achieve an effective ROI in the indurated material as any injected fluid will tend to migrate upward into the more permeable overlying material.

Therefore, Remington utilized our packer/auger system combined with high pressure injection at an injection interval below the top of the water table for the initial injection phase. The high downhole pressure created in this indurated material precipitated the development of fractures in the siltstone. Subsequent injections at the top of the water table were able to utilize these fractures to achieve much better distribution of the remedial fluid in the impacted interval.

COGAC™ Remedial Injection Results

As shown on the following graphs and table, dissolved petroleum hydrocarbon (represented by benzene) concentrations decreased rapidly to below regulatory standards after the COGAC™ injection event. Based on these results, the COGAC™ injection was successful in remediating contaminant mass remaining at the site, therefore achieving regulatory remedial goals for the site and eliminating potential environmental risk to the responsible party.