AST Background
During an aboveground storage tank (AST) closure, soils affected with petroleum hydrocarbons were encountered. The affected soils were excavated and confirmation soil sampling was performed. Benzene was detected at concentrations exceeding the soil to groundwater standard for the state of Kentucky in the soil samples. Additional investigation of local groundwater was required to determine if groundwater had been affected. The site was high profile due to the close proximity of residential property.
Tank Closure and Groundwater Sampling
To better define the area of impact, AGES conducted a 1-day groundwater survey of the former AST area with a Geoprobe. Shallow groundwater samples were collected and screened in the field for the presence of VOCs. Based on the survey, the extent of potentially affected groundwater was defined.
To evaluate groundwater quality, AGES installed five (5) temporary piezometers in the area: 1 upgradient, 2 within the former excavation and 2 downgradient. Benzene was detected in groundwater samples collected from all of the piezometers at extremely low concentrations. The results were first compared to the Primary Drinking Water Standard (Maximum Contaminant Level [MCL]) developed by U.S.EPA. All results for Benzene in groundwater were less than the U.S.EPA drinking water standard of 5 ug/l. The results were then compared to the most conservative Preliminary Remediation Goal (PRG) used by the Kentucky Department of Environmental Protection for Benzene (0.34 ug/l) in their state-lead Voluntary Clean-up Program (VCP). Benzene results for two (2) groundwater samples exceeded the PRG for residential tap water.
Following field work, AGES oversaw the restoration of the property to pre-investigation conditions. AGES staff also communicated with the local landowner to ensure their satisfaction with the program.
To evaluate potential risks to nearby groundwater users, AGES conducted an on-line review of Water Well and Spring Location Maps maintained by the Kentucky Geological Survey. The objective of the review was to determine if any private and public supply wells (potential receptors) were present within a 0.5-mile radius of the site. Based on this review, there were no potential receptors within 0.5 mile downgradient of the site.
Because there were no local groundwater users, AGES proposed to the KYDEP that no further action was required to address groundwater at the site. The KYDEP approved AGES’ proposal and issued a letter stating that no further action was required at the site.
Special Project Features
1.) By determining there were no private or public supply wells in a 0.5-mile radius of the site, AGES was able to convince the KYDEP that no further action was required at the site.
2.) By working with the local landowner and ensuring their satisfaction, AGES was able to limit our client’s exposure to future litigation and public relations issues.
