Hill Air Force Base officials say work has stopped on an airplane maintenance hangar utility trench pending further study of soil feared contaminated by chromium salt.

Preliminary examination showed chromium levels below what the Environmental Protection Agency considers harmful, base spokesman Len Barry said.However, as a precaution, airplanes and the hangar floor were wiped to remove any chromium dust. Workers were advised to wash their hands before eating or smoking, Barry said.

Barry said rumors circulated among employees about a health hazard after the soil spots were discovered Thursday.

"But basically, they were erroneous," he said. "We are cautious and we certainly don't want any harm to come to our workers."

No Air Force personnel had complained of ill effects, Barry said.

Chromium and its compounds can be toxic. In sufficient quantities they can irritate skin and, when inhaled as dust, the respiratory tract. Long over-exposure can cause skin ulcers and lung cancer, research has shown.

Although work on the utility trench has stopped until more detailed analysis is completed this week, Barry said Air Force workers are continuing their overhauling of F-16 and F-4 jet fighters and C-130 cargo planes in the hangar.

The trench is in Building 225, the base's huge maintenance facility for the airplanes.

Barry said a contractor was digging the trench in the building's concrete floor to improve utility lines.

The trench is 173 feet long, 11 feet wide and 8 feet deep, he said. About 25 feet of the trench length had yellowish spots thought to be caused by chromium salts.

Barry said a possible source of the deposits was a chrome-plating process that is believed to have been performed in the building until the early 1970s. Barry said he did not know when the plating began or how chromium could have gotten into the soil.