Challenge & Solution
In an effort to achieve groundwater protection standards (GPS) and system closeout, the federal government selected Rhea to monitor, operate, and maintain a closed federal government landfill in Virginia.
The work includes monitoring and reporting for the landfill facilities, HRC® (hydrogen release compound) injections and monitoring (i.e., reductive dechlorination of organic contamination exceeding GPS levels), evaluation of chlorinated organics and metals exceeding GPS levels, and remediation approach design for these constituents.
Project Description & Highlights
As a result of the quarterly HRC® injections, arsenic levels have increased significantly above the GPS in one of the site monitoring wells along the southern corrective action area within the radius of influence of a HRC® injection point, and arsenic concentrations close to the GPS have been measured in a downgradient well. With increased levels of HRC® injection, arsenic becomes more mobile. A HRC® injection design evaluation was completed to determine the optimum HRC® to inject to minimize arsenic mobility while continuing to provide effective treatment for the chlorinated organics.
Based on the results of the evaluation, recommendations were made to reduce the frequency of HRC® injections to minimize arsenic concentrations in the monitoring wells. The concentrations of arsenic have decreased in this area during subsequent monitoring events without a discernible increase in chlorinated organics. In 2011, Rhea led additional sampling efforts along the southern corrective action area to assist in the on-going evaluation of the corrective action approach at the site.
Additional parameters tested as part of this evaluation included CENSUS-DNA (Dehalococcoides DHC and VC reductase genes), dissolved gasses, total organic carbon, volatile organic acids, and geochemistry analyses. The results of the testing are currently being evaluated to optimize the corrective action approach at the site.
Rhea is evaluating the effectiveness of the in situ treatment systems and is developing steps to optimize their operation to achieve closure. Through our experience with treatment technologies, Rhea has optimized the remediation at this federal government landfill.