LOCATION: Country Club and US60

CLIENT: Empire Southwest

CIVIL ENGINEER:

YEAR(S): 2003

DESCRIPTION: Assessment, Characterization, and Risk Assessment - Petroleum Hydrocarbons

SCOPE OF SERVICES:

GEC conducted an evaluation of a release of 3000 gallons of diesel fuel at an equipment sales and service facility in Mesa, Arizona.  The site was heavily developed with numerous buildings, above and below-grade utilities, and thick heavily reinforced concrete slabs which significantly complicated the site characterization.  Due to the extensive site development, it was not possible to remediate the petroleum hydrocarbons by conventional methods.  Therefore, GEC recommended a site-specific risk assessment to obtain closure of the site.  GEC conducted soil and soil-gas sampling and testing to characterize the site and determine the concentrations of the chemicals of concern which included extractable fuel hydrocarbons (EFH - C10 to C32 hydrocarbon range), volatile organic compounds (VOCs), and polynuclear aromatic hydrocarbons (PAHs).  GEC identified primary and secondary sources, transport mechanisms, and exposure pathways.  GEC compared site conditions with our selected Tier 1 risk-based screening levels (RBSLs).  The results of our evaluation indicated that the highest concentrations of the chemicals of concern did not exceed the Tier 1 RBSLs, demonstrating that the existing contamination did not pose a risk to human health or groundwater.  GEC prepared a report presenting the results of this work and requesting closure of the site from ADEQ.  ADEQ is currently reviewing this information.