Southwest Geophysics Inc.

During our recent survey for an environmental subcontractor for the FBI, DTSC, DOT, and the USEPA, we were tasked to locate improperly disposed buried 55 gallon drums. The subject facility recycles used drums by emptying the contents and then cleaning the drums over wash racks. A number of cleaning operations were performed on the drums, with the ultimate goal of removing the former contents. The FBI acquired information indicating that 40 to 60 drums potentially containing hazardous waste were buried at the northern portion of the facility. Evidence suggested that the drums were buried and then paved over with reinforced concrete.

Electromagnetic (EM61), Magnetics, and Ground Penetrating Radar (GPR) surveys were conducted over the suspected location of the drum burial.
In addition to the large reinforced concrete sump in the center of the search area, two large EM responses were detected.
Radar data indicated two different types of reinforcing in the concrete (mesh on the west and bars on the east).
Radar data indicated consistent bar spacing for the anomalous area in northeast corner.
Radar data indicated a slight variation in reinforcing bar depth (this was possibly due to the rebar chairs sitting lower where compaction caused the backfilled excavation to subside.
Based on results of geophysical data, the FBI decided to excavate the area of anomalous EM data.
Buried drums were found at a depth of approximately 4 feet.

EM61 DATA FROM OUR SURVEY

AREAL EXTENT OF EM ANOMALY ON NORTHEAST CORNER OF SURVEY GRID

RADAR DATA INDICATES CHANGE IN REINFORCED CONCRETE ON WEST SIDE OF GRID,

AS WELL AS SLIGHT DEPRESSION (CHANGE IN DEPTH OF REBAR) CAUSED BY THE

REINFORCING CHAIRS SITTING IN A SLIGHT DEPRESSION CAUSED BY THE EXCAVATION