Rockland road sinkhole is expanding

Posted Feb. 24, 2010, at 8:19 p.m.

ROCKLAND, Maine — A 65-foot-deep sinkhole on Old County Road is growing, and that might not be such a bad thing, according to state Department of Transportation officials who are working on ways to repair the road.

“We stand there and listen — you can hear gravel falling down into the hole,” said Mike Burns, acting director of maintenance and operations for DOT. “The gravel is not stable at the angle it is at. The hole will keep getting bigger, but that’s all right because it will allow us to get in and address the problem more efficiently.”

The earth below the road has been falling into the tunnel that runs below the road, perpendicular to the hole. As the soil holding the road erodes, less work remains for crews removing the unstable soils. The crews also will be able to work more easily with the extra space as the hole continues to expand, according to Burns.

Burns said one possibility for taking care of the hole is to fill it, which could pose problems.

The tunnel routes groundwater to an old quarry, so if the hole were filled with dirt, the fill might be swept away by the groundwater. So Burns is considering filling the hole with large stones to support the road, allowing water to trickle through the tunnel.

A plan will be developed in the next two weeks, Burns said. He expects the road to be fixed within weeks.

DOT has learned a little more about the hole through radar scans, which took place Monday and Tuesday.

“The tunnel is longer [than previously thought],” Burns said. “It goes under the full road and the top keeps falling in. So the sinkhole diameter at the surface is getting bigger,” Burns said.

“The tunnel is not getting bigger, but the sinkhole is,” he added.

The radar showed that the bedrock at the base of the tunnel is 90 feet down. Because of debris that fell in from the hole and from quarry rubble, the base of the tunnel is 65 feet from the top of the road.

According to Rockland Public Works Director Greg Blackwell, the state has control over the repairs now.

The hole opened in the road on Feb. 15, when a motorist called police saying his car had been damaged when it struck a pothole. Fire Department crews closed off the road to traffic.

Town officials have asked people to stay away from the sinkhole, which is on Old County Road in the vicinity of the Rockland Golf Course.

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