One of AKT Peerless’ major petroleum retailer clients operated a convenience store and fueling station located south of Interstate 20 in Thomson, Georgia. The existing store was to be demolished and rebuilt, and the UST system removed and modernized. The facility had a single tank pit located on its southern portion that contained three (3) active and one (1) inactive double-walled composite steel underground storage tanks (USTs). All four tanks had a storage capacity of 12,000 gallons and were installed in 1982. Two of the active tanks were used for the storage of gasoline (87 and 93 octane grades) while the other active tank stored ultra-low sulfur diesel fuel. The fourth UST was a former 12,000-gallon gasoline tank that was abandoned in-place. The associated UST piping consisted of double-walled fiberglass construction.
AKT Peerless was retained by the client to perform UST system closure activities. Given that shallow groundwater was expected during closure, AKT Peerless also assisted in securing a dewatering/discharge permit from the local authority. Additionally, the environmental contractor installed metal shoring around the perimeter of the tank pit to prevent any potential collapses/cave-ins to the tank pit itself due to groundwater erosion of the soil and to minimize any potential erosional damage that could affect the adjacent roadways. During the UST closure activities, groundwater was encountered approximately 12 feet deep. Soil testing beneath the tanks, pump dispensers and system piping were performed following the removal of these components. Since groundwater was encountered, groundwater samples within the tank pit were also collected and tested. To determine if the soil data met or exceeded the appropriate soil threshold levels, AKT Peerless performed a sensitive receptor survey as part of the UST closure. Analytical testing indicated that the soil conditions met the applicable soil threshold levels; however, given that the new tanks were much larger and had to be installed within the former tank pit, the tank pit had to be over-excavated an additional 10 feet horizontally and vertically to allow room for three new 20,000-gallon tanks. Consequently, although the soil met the applicable soil threshold levels, the soil was still contaminated and could not be reused on-site or sold. As such, AKT Peerless identified several landfill options for the client. AKT Peerless completed the required waste profile form and waste characterization process in order to get the selected landfill to approve the impacted soil and pea gravel for disposal. A total of 2,114 tons of impacted soil and pea gravel were disposed at the approved landfill.
Although groundwater samples collected from the tank pit prior to the over-excavation activities exceeded the applicable standards, AKT Peerless was able to demonstrate that groundwater sampled downgradient to the tank pit and pump dispensers/system piping did not detect petroleum hydrocarbon contamination above the laboratory reporting limits based on a previous Phase II Environmental Site Assessment (Phase II ESA) we conducted before the UST closure work. Therefore, it was concluded that the groundwater contamination was limited to the tank pit.
By performing a modified Underground Storage Tank Closure Assessment, a sensitive receptor survey, the over-excavation of the tank pit that included the removal and landfilling of residually impacted soil, and achieving a very low calculated site ranking score for the facility, AKT Peerless: 1) saved the Client costs by not preparing Corrective Action Plans – Part A and B and not installing permanent wells; 2) significantly reduced the amount of project and construction time; 3) avoided direct public notice of the release; and 4) achieved a NFA status within 60 days.