VERTEX was retained to oversee the removal of an underground storage tank (UST) system at a gasoline station with known historical petroleum-related contamination.  In addition to overseeing remedial activities, VERTEX’s role was to separate potential petroleum impacts that may have originated from the insured’s UST system from pre-existing petroleum impacts related to the known historical release.  During remedial oversight, VERTEX identified the presence of a plastic layer beneath what appeared to be minimally impacted sand that was in direct contact with the insured’s UST.  The soil beneath the plastic layer appeared to be impacted by petroleum from a source other than the UST system.
VERTEX reviewed the UST removal analytical results and compared them to historical data from previous releases, concluding that the observed petroleum impacts were consistent with the previous sampling results and did not demonstrate consistency with the recent release from the UST system.  
To further support these conclusions, VERTEX collected soil and groundwater samples for forensic age dating analysis to evaluate if the observed petroleum impacts were consistent with the historic release.  Samples were severely weathered and decomposed, consistent with a historic release.  VERTEX was able to use the multiple lines of evidence collected to demonstrate that the observed petroleum impacts were related to the documented historic release and not from a release from the insured’s UST system, thus reducing our client’s exposure to additional remediation costs.