Prospecting for seeping, buried oil wells.

What do you do when you can see the effects of crude oil spilling from buried wells but haven't a clue as to their locations? That's the dilemma Charles K. Eger faced last year, when he was named coordinator for the cleanup of unmapped, abandoned wells in the Boyd's Creek region of south central Kentucky.

A geologist in the Environmental Protection Agency's Atlanta office, Eger tackled the problem with geophysical tools he had previously reserved for hunting buried toxic wastes, such as drums of pesticides. The approach paid off with the discovery of four long-forgotten wells, he reported in Tampa, Fla., last week at the 1993 International Oil Spill Conference. Surface accumulations of leaking oil - such as a 100-yard-long, 10-yard-wide crude-oil pool atop Houchins' Spring - helped pinpoint four more wells. Eger's team has since plugged them all.

The group surveyed a 6-acre meadow at regular intervals, scouting for spots that responded "anomalously" to three types of geophysical probes. They fed data from each assay into a computer program that mapped the contours of areas responding similarly to measures of soil conductivity, magnetic-field values, or the ground's ability to transmit low-frequency radio waves. The soil-conductivity and magnetic-field maps both proved useful in identifying "odd" areas warranting additional analysis - and sometimes excavation.

Drilling at Boyd's Creek, the birthplace of Kentucky's oil industry, commenced in the early 1860s. Within a few years, wild-catters began abandoning the less-productive wells without plugging their still-flowing streams of crude. Unscrupulous drillers are still abandoning unplugged wells, Eger notes.

Eger tapped the new Oil Pollution Act (OPA) for money to plug 27 abandoned wells last year in Kentucky. Because OPA was written in the wake of the Exxon Valdez spill - and with marine contamination in mind - securing this money for terrestrial leaks initially proved challenging, he says.

According to Eger, however, the potential threat to humans is "infinitely higher" from inland oil spills than from offshore ones. He notes, for instance, that "oil contains some of the worst carcinogens known. And in groundwater wells adjacent to oil wells, levels found are typically two to three times the drinking-water standard for those chemicals."

Not only do an estimated 150,000 unmapped and abandoned oil wells exist within Kentucky, he reports, but it's likely a large number of similar sites also litter states drilled during the oil industry's initial boom - especially Pennsylvania, West Virginia, Tennessee, parts of southern Illinois and Indiana, and probably Michigan.

Eger's cleanup efforts highlight a largely unrecognized problem, the prevalence and importance of terrestrial spills, says James H. Parker, president of Industrial Marine Service, Inc., in Norfolk, Va. Parker, whose firm primarily cleans oil spills in water environments, notes that inland spills are becoming a fast-growing part of his business.

Increasingly, such pollution managers are turning to geophysical soil probes, notes Jay Rodstein, formerly with EPA and now with the National Oceanic and Atmospheric Administration in East Lansing, Mich. He recalls using such probes in 1985 to hunt buried and abandoned coal-tar pits.