PennDOT Subsurface Utility Engineering Investigations

Rhea has supported Skelly & Loy to undertake specialty Subsurface Utility Engineering (SUE) investigations at approximately 20 PennDOT project locations to identify the presence of potential obstructions that are not typically identified on the basis of conventional SUE investigations using the PA One-Call process. In particular, many town intersections were the location of small services stations that have long since disappeared and there are no records of whether or not the underground storage tanks (USTs) have been removed.

For this project, four locations were surveyed designated as the Russell’s Auto Sales, Luigetta’s of Hollidaysburg, Blair County Oil and Supply, and CK Plaza sites. Two geophysical techniques were applied: deep metal detection with a Geonics EM61 time domain metal detector; and ground penetrating radar (GPR) using a MALÅ Geoscience system with a shielded 250 megahertz antenna.

Interpretation of the EM61 data is based on the pattern of response to metal. Linear anomalies are interpreted to be buried pipes or cables. Isolated anomalies are more difficult to interpret, unless the size of the anomaly in association with smaller linear anomalies suggests the presence of a UST. The GPR data were processed such that interpretation could be made on the basis of visualizing the data both in terms of individual GPR profiles, as well as three-dimensional blocks.

The presence of USTs was found to be likely at the location of Luigetta’s Restaurant on the basis of deep metal detection. Luigetta’s was known to have been a small gas station in the 1950s.

Services: Geophysics

Industries: Transportation