Chemical analysis

Aquifer Biogeochemistry Analysis to Justify a Remedial Action Plan

CHALLENGE

An inactive gasoline service station in the northeastern part of the United States was discovered to have leaking underground storage tanks. A 2011 excavation to remove the tanks resulted in groundwater impact both on and offsite in a residential neighborhood. Following an extensive evaluation process, Antea Group selected injection of an in situ carbon product as the site remedy.

The in situ carbon product selected was formulated with a combination of granular activated carbon and gypsum (calcium sulfate dihydrate) to stimulate anaerobic biodegradation of petroleum hydrocarbons within the carbon matrix.

The state’s environmental department was amenable to an in situ contaminant “trap and treat” approach to remediation. However, the department wanted to ensure that aquifer conditions were suitable for anaerobic biodegradation stimulated through the addition of sulfate as an electron acceptor.  

SOLUTION

 Antea Group collected a suite of biogeochemical groundwater data across the site to evaluate the reductive potential of the aquifer. Spatial analysis of both field and laboratory analytical data helped determine the aquifer biogeochemical “zonation” downgradient of the source area, providing insight into which microbiological activities were prevalent.

RESULT

Based on the biogeochemical analyses performed, Antea Group was able to determine that sulfate reduction was the predominant microbiological activity throughout most of the extended plume footprint. With this understanding, the state’s environmental department approved the Remedial Action Plan for the site. Carbon injections took place in November 2016. Post-injection monitoring of the site following the carbon application is ongoing.