Site Remediation at Former Retail Gasoline Distribution Facility
Challenge
The site operated as a retail gasoline distribution facility and at least two underground storage tanks (USTs) were closed in place circa 1973. The property sits on a corner lot and is currently a multi-tenant office building. In 2016, the Bureau of Underground Storage Tank Regulations (BUSTR) determined that soil and groundwater contamination existed at the site after a Phase II Environmental Assessment found xylenes concentrations above BUSTR action levels (ALs).
Soil borings and groundwater monitoring wells were installed in 2016, 2017, and 2018. Soil samples collected indicated that total xylenes and total petroleum hydrocarbons (TPH) were present above applicable ALs on-site. Groundwater monitoring wells were installed on-site and off-site, in the downgradient direction; laboratory analyses indicated that all monitoring wells were below applicable ALs and soil and groundwater impacts were delineated.
An excavation to address soil contamination on-site was completed in late 2018. A total of 378 tons of soil were removed from two excavation areas and transported off-site for proper disposal. Due to excavation limitations (proximity to utilities and other physical site limitations), two post excavation soil samples exceeded ALs for xylenes and TPH. BUSTR denied the “No Further Action” (NFA) request due to the remaining soil contamination present on-site.
Solution
The injection of PersulfOx® was determined to be the most effective remedial strategy to address the remaining impacted soil on-site since the excavation of the soils could not be completed safely. The remedial strategy included pre and post-injection groundwater sampling, monthly injections of PersulfOx® over a three-month period, and confirmatory soil sampling three months after the final injection event.
Antea Group retained and managed a local drilling contractor to complete the injections and confirmatory soil borings. The PersulfOx® injections were completed in 2019 and soil sampling was completed in 2020.
Per BUSTR requirements for confirmatory soil sampling, three soil borings were advanced within two feet of each excavation sample location that exceeded BUSTR ALs. Three soil samples from each boring were submitted for laboratory analysis: the interval with the highest photoionization detector reading, the interval immediately above the soil/water interface, and the interval of the original exceedance.
Result
Pre- and post-groundwater sampling was consistent with historical results, and post-injection results confirmed dissolved phase hydrocarbons did not increase due to the injections. No chemicals of concern were detected above applicable BUSTR ALs in any soil sample collected from the confirmatory soil borings. All remaining soil contamination had been effectively remediated.
A Remedial Action Completion Report (RACR) was submitted to BUSTR and a NFA regarding corrective action requirements was granted in April 2020. All site monitoring wells were properly plugged and abandoned on May 14, 2020, in accordance with the Ohio Department of Natural Resources (ODNR) Well Abandonment Rules.
