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Drilling begins to stabilize Mt. Oliver homes

| Saturday, July 27, 2013, 12:58 a.m.
Justin Merriman | Tribune-Review
A drilling crew works on site Friday morning on the 100 block of Frederick Street in Mt. Oliver to begin stabilizing the ground beneath 20 damaged homes there. They hope to drill some 57 holes and pour a flowable grout underground to stabilize the homes against mine subsidence in the area.
Justin Merriman | Tribune-Review
A drilling crew works on site Friday morning on the 100 block of Frederick Street in Mt. Oliver to begin stabilizing the ground beneath 20 damaged homes there. They hope to drill some 57 holes and pour a flowable grout underground to stabilize the homes against mine subsidence in the area.

Testing for mine subsidence in Mt. Oliver Borough could expand when the state Department of Environmental Protection finishes filling sinkholes that damaged homes on Frederick Street, officials said.

Coastal Drilling East of Morgantown on Friday began tapping into the mine more than 200 feet below the street and will shoot cement in it to stabilize shaky ground. Ten homes sustained damage, and subsidence threatens 10 others. The $1.35 million project is expected to take six to eight weeks.

“In the last 10 years, we've been in Mt. Oliver four times (for emergency mine subsidence),” said Gene Trio, a DEP mining engineer. “Based on that, it warrants an exploratory drilling project to determine the extent of damage.”

What DEP finds on Frederick Street will determine whether more testing and stabilization are necessary, said agency spokesman John Poister.

Problems on Frederick Street date to long-defunct Ivill Mining Co., which worked the area from the 1860s until 1922, Trio said. This is Mt. Oliver's worst case of subsidence, according to borough engineer Ruthann Omer.

“It's not unusual in these types of situations for DEP to check if they got it all and if there are any possibilities for more of that to happen,” she said, adding that all residents should buy subsidence insurance. “We'd appreciate if they would do that, because we don't want to see that happening to another street in the borough.”

South Hills neighborhoods sit atop the Pittsburgh Seam, a coal deposit that stretches from Western Pennsylvania into Ohio and West Virginia. Much of the region is extensively undermined, according to DEP officials.

Maps of these old mines do not exist, and DEP is trying to pinpoint the Ivill mine based on surface damage. Coastal drilled down 210 feet without hitting it on Friday. Crews will resume work at 7 a.m. Monday.

Residents are happy to see workers there.

“You guys are angels, do you know that?” Janet Wolf told DEP representatives gathered on Frederick Street.

Her basement walls cracked, but insurance will cover the damage.

Trio said Ivill used room-and-pillar mining, a method in which miners leave pillars of coal for support. Those pillars deteriorate after 50 to 70 years, causing subsidence. Coastal will drill 57 holes on properties impacted by subsidence and shoot cement down the holes until voids below are full. The cement hardens and supports the ground, said Dean B. Baker, DEP environmental program manager.

“We've been doing this for 30 years, and of all the houses we've done, which is about 2,500, we've only had four instances of more subsidence once this is done,” Trio said.

Bob Bauder is a Trib Total Media staff writer. He can be reached at 412-765-2312 or bbauder@tribweb.com.

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