Ohio suspends well operations after series of small quakes

CLEVELAND (Reuters) - Ohio has suspended operations at five deep-well hazardous fluid disposal sites after a series of 11 earthquakes in Youngstown last year including one on Saturday with a magnitude of 4.0, officials said on Sunday.

The Ohio Department of Natural Resources said it was halting operations at five Mahoning County wells owned by Northstar Disposal Services LLC as a precaution, citing concerns of a possible link between well activity and the quakes.

"We are being overly cautious in order to ensure public safety in asking the company to halt disposal injections at one site on Friday and then asking for a halt to any injections in a five-mile radius Saturday," Ohio Department of Natural Resources deputy director Andy Ware told Reuters.

"Our geologist would say there is a strong chance there is a fault line very close to the site of the well," Ware said, adding the department was concerned that pressure from the fluid disposal could be affecting a previously unknown fault line.

Earthquakes induced by human activity have been documented in a few locations in the United States, Japan and Canada, according to the U.S. Geological Survey web site. The largest and best known resulted from fluid injection at the Rocky Mountain Arsenal near Denver, Colorado, where in 1967 a 5.5 magnitude earthquake followed a series of smaller quakes.

Ware said Northstar won the right to drill in the area in March 2010 and began drilling in mid-summer. The injection disposal started in December 2010 and the first earthquake occurred in 2011. A representative for Northstar could not be reached for comment on Sunday.

Ohio Governor John Kasich felt the move was important to "quickly ensure the safety of the public," spokesman Robert Nichols said.

"We fully expect to be criticized for overreacting on this, but we are okay with that," Nichols said.

Earthquakes are not common in Youngstown, and seismic records going back to 1980 show no reports of earthquakes prior to the series of quakes last year. A 2.1 magnitude quake, the first of 11 in 2011, was reported on March 17. More were reported in August, September, October, November and December.

Ware said that after a 2.7 magnitude quake was reported on December 24, Northstar Disposal Services voluntarily lowered the pressure at one well, known as Northstar No. 1.

At 3:05 p.m. on New Year's Eve, a 4.0 earthquake was reported, "causing the Ohio Department of Resources to recommend all wells in the area stop operations," Ware said.

After the initial spate of earthquakes in the area, four more monitors were set up in the proximity of the first well to get more data on the source of the seismic activity.

There are 177 disposal wells currently in operation in Ohio. The Mahoning County well is 9,000 feet deep and is used to dispose hazardous fluids, injecting fluid that cannot be disposed of in landfills into sandstone well below groundwater level.

An internal briefing was scheduled for later on Sunday, and Ware could not say when or if the wells would resume operations. Authorities said there may be a change in how the wells operate.

"That is one of the things that would be discussed, possibly plugging the well to a certain level." Ware said. "We will continue to monitor and have our geologists monitor the data."

(Writing and reporting by Kim Palmer; Editing by Mary Wisniewski and Cynthia Johnston)