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Stabilizing sinkholes delay, raise cost of road

June 06, 2007|by ANDREW SCHOTZ

WASHINGTON COUNTY - To stabilize the ground under Maugans Avenue before a sinkhole strikes again, Washington County probably will spend $200,000 to $250,000, Public Works Director Joseph Kroboth III said Tuesday.

This will delay an already late road project another 30 to 60 days, he said.

After the third sinkhole opened in that area in about a year, a state geologist recommended that the county fill subsurface caverns with pressurized grout, Kroboth said.

Kroboth estimated the cost of fixing a large sinkhole on May 14 at $46,000, not including the contractor's cost of labor, which hadn't been submitted yet.

He said the sinkhole problems need to be corrected before the $7.4 million road-widening project can continue.

The project entails widening the road from two lanes to five lanes and adding turn lanes and traffic signals. It already was delayed by utility companies behind in their preparation work, county officials have said.

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Many parts of the county are susceptible to sinkholes because of the region's karst topography, which is characterized by hollow limestone pocked with ridges.

Usually, sinkholes aren't as big as the one that closed one lane of Maugans Avenue last month; it was about 20 feet at a narrow point and about 30 feet at its widest.

Kroboth told the Washington County Commissioners that was the third sinkhole to emerge in a stretch of about 200 feet.

The contractor, C. William Hetzer Inc. of Hagerstown, filled a small one, about two feet in diameter, around the beginning of May, Kroboth said in an interview later.

Kroboth told the commissioners he expects to give them, by early July, a specific plan to fix the sinkhole problem.

Before then, the county will discuss with Hetzer whether the work will be part of the current Maugans Avenue project or a separate contract with another company.

David Martin, a Maryland State Highway Administration geologist, suggested the grout procedure because it can pinpoint and fill caverns without shutting down the road for long periods, SHA spokesman Chuck Gischlar said.

Kroboth said the procedure involves drilling down at points 10 feet apart. When the drill hits several feet of solid rock, it's removed and grout is injected into the hole.

The $46,000 estimate for the May 14 sinkhole covered about 220 cubic yards of riprap, or rocks with other material, and about 140 cubic yards of "flowable fill" on top of the rocks, Kroboth said.

The labor estimate for Hetzer's employees had not been determined yet.

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