UST Closure, Assessment and Remeditation

Date Completed: June 1, 2012
Category: general
Location: Beaverdam, OH

This project included the removal of underground storage tank (UST) systems, completion of BUSTR Tier 1 and Tier 2 investigation, and remediation of soil and groundwater contamination. The subject property consisted of a 14-acre abandoned truck stop/fueling station located in Beaverdam, Ohio. The client, a local commercial lending firm, acquired the property through foreclosure and inherited the liability associated with the UST systems.

Allied conducted all aspects of the excavation, removal, and disposal of eleven (11) UST systems containing gasoline, diesel fuel, kerosene, heating oil and waste oil. The fueling systems included ten (10) dispenser islands and several hundred feet of piping. Free product encountered at the time of UST removal necessitated interim response actions including the removal and disposal of 24,400 gallons of petroleum contaminated water, and excavation and disposal of 940 cubic yards of petroleum contaminated soil.

The UST Closure Assessment conducted at the time of removal determined that concentrations of benzene in groundwater within the UST cavity exceeded action levels. Due to the elevated levels of benzene found, it was determined that additional assessment (i.e. Tier 1 Assessment) was required to delineate the extent of contamination at the site.

The purpose of the Tier 1 assessment was to confirm the contaminants of concern and points of origin, evaluation of exposure pathways and transport mechanisms, development of appropriate action levels, and the determination of the vertical and lateral extent of contamination. The assessment included the advancement of 32 soil borings and the installation of four (4) monitoring wells. Results of the Tier 1 assessment indicated benzene, xylenes, toluene and ethylbenzene as contaminants of concern, and revealed two contaminant sources: the former UST cavity and the former remote fuel dispenser island. The assessment also revealed a complex geologic setting, including two water-bearing zones: a shallow sand seam, and a deeper sand aquifer. Soil at the source areas, and groundwater within the upper saturated zone were affected by petroleum contamination.

To better define the extent of contamination and provide predictions of contaminant behavior, Allied conducted a Tier 2 assessment. The assessment included installation of additional groundwater monitoring wells, and development of computer-generated flow and transport models to estimate potential contaminant migration patterns and rate of attenuation. The models predicted that groundwater contamination would not migrate onto adjoining properties and would naturally attenuate to acceptable concentrations over time. Based on this data, Allied proposed a remedial action plan consisting of the excavation of remaining contaminated soil, and natural attenuation of groundwater coupled with quarterly monitoring and implementation of an Environmental Covenant-Not-To-Sue. The covenant included groundwater use restrictions. This plan was approved by Ohio BUSTR and the site ultimately received a corrective action status of No Further Action (NFA). Petroleum contaminant concerns were successfully abated and the property is currently on the market for sale.