"You have been informed of a suspected contamination site but no one knows much about it and information is sketchy at best. To make maters worse, the site is an area where it isn't possible to drill a lot of boreholes to look for the plume. What do you do now?

The 509th Civil Engineering Squadron at Whiteman Air Force Base, MO, faced that situation -- at four different sites -- and found the answer in two pieces of technology that when used in tandem make it easier to locate and analyze underground contamination.

The first technology is called a gradiometer, which is used to first locate the plume. This piece of equipment measures the contamination width and length, but not the depth. Without this information, however, the contractor would depend solely on the site owner's knowledge of the area to determine where the environmental survey should be conducted.

Once the plume is located, Electromagnetic Offset Logging, or EOL, comes into play. EOL measures resistivity below the ground's surface or subsurface. All free hydrocarbon-based contaminates (such as those found in fuels) are highly resistive while subsurface waters are less so. EOL records variations in resistivity to produce a three dimensional CAT scan-like picture that allows researchers to determine a plume's size, shape, and depth." .........................

"What are the advantages of using the EOL/gradiometer method versus traditional methods? First, the savings in employing the EOL method can be significant. Using an exact same grid as that used for boring logs and holes only, the EOL method saves money because only two or three boreholes are needed. Considering the contractors bill by the foot for borings and logging information, not to mention the numerous lab fees to determine if a site is contaminated and at what depth, the EOL readily pays for itself in the first step of the site characterization.

Whitman Air Force Base used EOL technology four times in the past and realized cost savings of $6,000 to over $30,000 in projects ranging in budgets of $25,000 to $250,000.

A second advantage is the time saved with this technology. Lab test of soil borings take a minimum of five days for testing for minimum contaminates and usually take two weeks for a thorough scan of several contaminates. Multiply this by numerous boring samples and weeks becomes months before a sketchy plot begins to take form. But by using the EOL method and getting the resistance reading in real time, the plume can be defined in less than two weeks and confirmation bore samples can be taken to determine contaminate intensity before the first lab reports arrive using the old methods." ....................................

The final, and maybe the most important advantage, is the technology's non-intrusive, non-destructive nature. Only two logging wells and confirmation boring logs are needed to provide plume verification. The EOL can work over almost any material, even over a swampy site, and can be performed on most surfaces or within structures, without having to bore holes in sensitive areas or provide a contamination conduit for a suspect plume. This aspect can be critical at certain contaminated sites where keeping a plume in check is vital or where the surface cannot be compromised or breached , such as in a wetland area." ...

"EOL technology isn't limited to the Air Force or Whiteman. It has been used by the Navy and independent business on isolated projects located around the United States with highly successful results." .........................

"The Missouri Department of Natural Resources has recognized EOL as an acceptable tool in site characterization, responsible party determination, remediation design and clean-up procedures."