Theme: 01. Remediation Technology Innovations

Topic Area: 01j. Injectable Activated Carbon Amendments: Lessons Learned and Best Practices

Formatted Title:

Carbon Injection for Treatment of Volatile Organic Compounds Close to a Pipeline and under a Roadway

Background/Objectives:

A pipeline release led to elevated concentrations of petroleum hydrocarbon-related compounds in soil and groundwater. Benzene was the key compound of concern. Excavation was performed in the primary release area, however benzene had migrated beneath a road. It was not possible to dig up the road so these impacts were not accessible. In situ treatment was required to address these impacts. ORC socks were deployed, however this remedy controlled migration but did not decrease the contaminant mass. Other in situ remedies were evaluated however remedies such as biosparge were not feasible due to the lack of electrical service to the site and most chemical injection remedies were not feasible due to the proximity of the pipeline and the requirement that anything injected not have the risk of corrosion of the pipeline.

Carbon can be injected in a single injection event and does not require any ongoing operation and maintenance that would be difficult to achieve without electricity and is a chemically inert material that would not pose a risk to the pipeline. It can be injected using direct push technology which can be accomplished within a short period of time without leaving any infrastructure that would impact traffic on the roadway. For these reasons injectable carbon was selected for this site.

Approach/Activities:

An injectable carbon program was first pilot tested and then a full-scale application consisting of 30 direct push injection locations was performed. Twenty-eight of these injection locations were within the roadway and an additional two locations were located downgradient of the road to address impacts that had already migrated across the road. Injections were performed at up to four injection locations at a time with monitoring at piezometers installed among the injection locations to ensure adequate distribution of the injectable carbon. Soil cores were collected after the injection to verify the placement of injectable carbon. Groundwater monitoring was performed 6 months after the injectable carbon application.

Results/Lessons Learned:

Injection of the injectable carbon was successfully performed. Groundwater mounding and some surfacing of the injected material was observed during the injection so the concentration of injectable carbon in the injection fluid was increased and the injection volume was decreased slightly. Carbon concentrations at up to 7,900 ppm were observed in the piezometers during the injection. Groundwater monitoring was performed 6 months after the carbon application and no benzene was detected in any of the groundwater wells in the treatment area. This means that the injectable carbon treatment reduced benzene from 38 µg/L to below 0.4 µg/L within 6 months.

Menu

Ashley Valentine