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Plans are under way to fill a honeycomb of holes, some the size of small caves, under the huge concrete walls and floor of the 650-foot-long Black Rock Lock.

John E. Derbyshire, spokesman for the Buffalo District of the U.S. Army Corps of Engineers, said today a contract will be sought next year to fill the holes.

"There is no immediate danger, but it's not something you let go," he said.

The voids -- some 3 feet long, 2 feet wide and 1 foot high -- were discovered in 1988 when the corps tested the lock and found it wasn't watertight. After exploratory drilling, the corps has not pinpointed the exact number of holes, but Derbyshire said, "There are a number of them."

The holes were created as ground water gradually dissolved limestone that forms the bedrock under the lock.

"When you empty or fill the lock it exerts tremendous pressure, and the pressure was transferred to the ground water that gradually has eaten away the limestone," Derbyshire said.

Bids will be taken in the spring for the multimillion-dollar project. Work on the job will mean reduced operating hours for the lock, which has already gone from around-the-clock operation to limited daylight hours.

The holes were first discovered in the area under the concrete blocks that form the lock walls, which are 6 to 12 feet thick and 38 feet high. The corps quickly let a $150,000 contract to drill more holes to determine the extent of the undermining of the lock. An engineering firm drilled nine holes on either side of the lock and began its detective work.

The successful bidder next spring will be called in to drill a series of holes alongside the lock walls and diagonally in from the sides of the lock. Then a concrete grouting compound will be forced through the openings and into the holes under the lock.

Derbyshire said the first step will be to drill a series of holes on either side and parallel to the locks, pump in concrete and thus form a "wall" along the sides that will prevent the concrete from moving out from the locks instead of inward to fill the voids.

"There's no way of telling if every crevice will be filled, but we think this will be effective in controlling the problem," he said.

The honeycomb of holes has apparently developed over the years since the lock was first installed. New York State built the first lock in 1833, providing a link between the downtown Buffalo terminal and the Erie Canal. Then the corps built the present-day lock between 1908 and 1913.

Filling the voids is one in a series of improvements included a major rebuilding of the 480-ton gates and improvements to its electrical and hydraulic systems.

Federal officials had proposed closing the lock, but a public outcry led them to quickly retreat. Over the years the lock has shifted from serving commercial vessels carrying coal, oil and other commodities to one used by recreational boats seeking safe passage around the swift currents of the Niagara River near the Peace Bridge.

Then the corps proposed privatizing the lock operation, but union employees protested the move and won.

The lock will take ships up to 625 feet long with a draft of 21 feet. It connects the Black Rock Channel with the Tonawanda Channel upstream. The corps announced today that winter hours are in effect, limiting operations from 8 a.m. to 4 p.m., with the overall operation due for a winter shutdown in January. Commercial vessels can radio or call if they want to use the lock at other hours.

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