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The federal government has taken a step toward approving the reopening of an oil-shale mine in Utah, one of four experimental works on Western lands that are intended to boost domestic oil production.

In Colorado, three oil companies won environmental clearance in August for their plans to start producing shale oil by heating layers of rock using electric oven-like elements, steam injection or hot natural gas.

Utah's is the only mining project where oil shale will be brought to the surface, crushed into gravel and fed into a furnace-like retort. The White River Mine was abandoned by three major oil companies in 1985 when falling crude prices made shale oil - long an elusive bonanza in the West - uneconomical.

The White River Mine reaches a relatively thin layer of oil shale 1,000 feet underground. The richest layer is only 58 feet thick, compared with zones 1,000 feet thick in Colorado that are closer to the surface, where heating the ground is thought to be more practical.

The U.S. Bureau of Land Management posted a report early this week on an agency Web site that suggested the White River Mine could be reopened without any environmental problems.

''We are committed to being in the oil shale business for years and years to come. We know we can open the mine,'' said Dan Elcan, managing partner for Oil Shale Exploration Co., backed by Twin Pines Coal Co. of Alabama.

The 241-page assessment, however, stops short of clearing the mining project for approval. That decision will come after a 30-day public comment period, said James F. Kohler, solid minerals chief for the BLM in Utah.

By year's end, BLM officials expect to award research and development leases on 160-acre tracts of land in Colorado and Utah. That will give the players preferential leasing rights to a contiguous 4,960 acres of federal land for commercial production.

Oil shale is said to be ''rich'' when it contains 30 gallons of petroleum for each ton of rock, but pound for pound that amounts to only 1/10th of the energy of liquid crude oil. Those tough economics have defied efforts at oil shale development for more than a century, most recently in 1982, when Exxon shut down its $5 billion Colony project in western Colorado and laid off 2,200 workers.