GTS Technologies -- Geophysical

GTS investigated a former gasoline station and country store on the outskirts of Hagerstown, Maryland for a client considering the purchase of the property. We were asked to determine if any tanks remained on site. Expansion of the building footprint during its history implied that possible tanks may now be under the building. No records confirming the removal of reported underground storage tanks could be found.

Our recommendation was to use a combination of techniques: ground penetrating radar (GPR), magnetometer and terrain conductivity meter. A grid of GPR profiles was set up around the building and parking lot for full coverage. The magnetometer was also used over the entire lot. Extensive utility interference prevented the use of the terrain conductivity meter.

The magnetometer located two large anomalies next to the building with the larger anomaly extending outward into the parking lot to a former pump island. The GPR detected two and possibly three tank-sized anomalies within the boundaries of the larger magnetic anomaly located next to the building under the sidewalk.
The smaller magnetic anomaly appeared to be at the building foundation. The GPR did not clearly detect a tank-sized anomaly at the second smaller magnetometer anomaly.
Exploratory excavation found three 550-gallon USTs at the suspect locations of the magnetometer and GPR anomalies; two under the sidewalk in the front of the building; and, one under the sidewalk on the side of the building. Two of the USTs are shown in the adjacent photograph.

The value of applying multiple geophysical techniques was proven at this site where the GPR worked well in one location, but not as well at the other location. The magnetometer found both tank locations, but could not clearly detect the lower tank, because the upper tanks masked its presence. Both methods were instrumental in finding all the suspected USTs.

GTS was commended for a job well done at a very reasonable cost by the client who now feels more confident about purchasing the property with the UST liability eliminated and the environmental clearances obtained from the state.