Geophysical Surveys to Locate Underground Storage Tanks
Location
Statewide, North Carolina
Client
Various
Services Provided
Review of Aerial Photos and Sanborn Fire Maps
EM-61 Surveys
GPR Surveys
Located Unknown USTs
Air Evacuation and Backhoe Confirmation
Data Analysis and Report
Project Overview
Schnabel surveyed a number of sites for the presence of abandoned underground storage tanks (USTs). Some sites have also been surveyed for buried drums. Many of these sites were former or active gasoline service stations, while other sites included former or active residences that contained abandoned heating oil tanks. In most cases, the sites had been regraded and paved, and there was no visible evidence of USTs.
For a typical site, Schnabel established a site grid on the ground using pin flags or marking paint. The grid locations of relevant site features were noted for later correlation with the geophysical data. Aerial photographs and Sanborn fire maps showing historical use were reviewed for indication of possible USTs.
Most surveys were conducted using an EM-61 metal detector, an electromagnetic induction tool that has a high spatial resolution. The EM-61 data was contoured as above, showing possible USTs. Confirmatory surveys using a ground-penetrating radar (GPR) were conducted to obtain images and approximate depth of the USTs. To verify the presence of USTs, intrusive investigations were performed. On some sites, Schnabel provided backhoe and air evacuation subcontractors to expose the USTs.
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