Sundance Environmental Consultants performed a pilot test to verify a proposed technology for the clean up of a former gas station site. The test was designed for the injection of BOS-200®, which is an activated carbon/sulfate bioremediation compound. The activated carbon draws in the volatile contamination, and the sulfate salts create a sulfate-reducing environment to biodegrade the petroleum hydrocarbons, particularly benzene. We proposed this approach because of its potential for rapid remediation with limited surface disturbance. Additionally, the technology takes advantage of the generally anaerobic environment near a petroleum hydrocarbon plume, as an alternative to fighting the geochemistry by adding oxygen.
Detail – A total of 700 pounds of BOS-200® along with a microbe inoculant were injected at 9 locations within the pilot test area around well MW-12 in June 2007. An EPA Underground Injection Control Rule Authorization was required for these injections. Borings/temporary wells DP-19 and DP-20 were installed prior to the injections to define the lithology and baseline hydrocarbon concentrations. Following the injections, borings DP-23, DP-24, and DP-25 were installed, and wells DP-24, DP-25 and MW-12 have been sampled regularly.
The pilot test design loading rate was calculated to reduce the benzene concentration by 93 percent from 0.75 milligrams per liter (mg/l) to 0.05 mg/l. The reason the loading rate was not designed to effect 100% cleanup was so that the “partial” cleanup results could be used to validate the BOS-200® vendor’s loading rate estimation calculations.
Photo 1 – Direct-push drill rig drives injection pipe string to target depth of 12 ft, for the injection of the BOS-200® activated carbon/sulfate compound. The purpose is to enhance the bio-degradation of petroleum hydrocarbons.
Photo 2 – This equipment mixes the BOS-200® materials into an aqueous solution, for pumping into the subsurface under high pressure. Alpine Remediation, Inc. is an approved installer of BOS-200®, per the product distributor Remediation Products, Inc. of Golden, Colorado.
Graph – This graph presents the benzene-in-groundwater concentrations in the BOS-200® pilot test area. Benzene is no longer detected at well MW-12, which is partially due to short-circuiting of injectant to this well. Wells DP-24 and DP-25 show a reduction of benzene concentrations of up to 99% and 81%, respectively. The results generally validate the loading rate estimation calculations, and reductions in benzene concentration persist two years later. As with any injection program, there can be variations in how the injectant is distributed in the subsurface, which is observed as the difference in the results between these test wells.
Based on the success of this pilot test, Sundance has proposed the use of this technology to remediate portions of the source area, especially where surface disruption must be limited. Greater quantities of the BOS-200® compound will be injected in each shot hole, following the vendor’s loading rate calculations, in order to achieve a remediation that meets State cleanup standards.