A drilling contractor for the Sunoco pipeline project has received permission from North Middleton Township to operate two 85-decibel drilling rigs 24 hours a day for weeks on end in a horse pasture near Creek and Spring roads.

The township board of supervisors granted Sunoco a variance Thursday from the nuisance ordinance that normally prohibits such activity from 8 p.m. to 6:30 a.m.

The supervisors attached a condition to the variance that would require the contractor to install sound barriers around each rig in the event the township receives significant noise complaints from residents about the operation of the horizontal directional drills.

Eighty-five decibels is equivalent to the sound of a propeller plane flying overhead, a diesel train going by at a half-mile distance, a food blender or garbage disposal, township solicitor Mark Allshouse said.

Brad Bonner, a construction manager for the project, said a sound barrier would reduce the noise level to about 60 decibels, which is the equivalent to a normal conversation, according to Allshouse.

The solicitor recommended the supervisors attach a condition where any complaints are brought directly to all five supervisors so that each could have their stamp on how to address a potential noise problem.

“We’re going to let you give it a try,” Allshouse told project representatives Bonner and Steve Kratz. “If there are too many problems or too many complaints, you will go right back to where you are now.”

Sunoco made the request for a variance because drilling for segments of the Mariner East 2 pipeline is behind schedule.

“We are in the process of starting the horizontal directional drill across Conodoguinet Creek,” Kratz told the supervisors. “We are under a tight timetable to finish.”

There is a rig at one end of the pasture that is drilling a pilot hole for a segment of pipeline that would run under Spring Road and the Conodoguinet Creek to near the municipal sewer plant, Bonner said. He said that rig could begin around-the-clock operations six days a week as early as next Thursday.

A pilot hole is used to designate the path in which the pipeline travels through the subsurface, Bonner said. Reamers will be used to gradually increase the width of the hole to a 30-inch diameter to enable a 20-inch product pipe to be pulled through.

The crew on that rig works six 10-hour days, Bonner said. With the variance granted, the 10-hour shift will be expanded to 12-hours and a second 12-hour shift would be added.

A second rig will be set up on the other end of the horse pasture to drill a segment of pipeline that would go under Creek Road, up a nearby hill to behind the Pine Creek development, Bonner said. He said that because of the subsurface rock formations “we are anticipating a slow crawl over for that second drill.”

With around-the-clock drilling, the crews on the rigs could get the work done within two months, Bonner said. He added without the variance it would take about three and a half months.

The current rig has been sitting idle in the pasture for about two months while Sunoco worked out an agreement with the state Department of Environmental Protection to pay a $12.6 million fine over problems with its Mariner East 2 pipeline project.

“There is no concussion or percussion,” Bonner said about the rigs. “It is just a drill. It does not bang or hammer or anything like that.”

The sound barriers, if needed, are about 15 feet tall and would be positioned between the rig and the nearest homes, Bonner said. When asked by a resident why Sunoco has opted not to set up barriers now, Bonner said the rigs will be located in a low-lying area that could create a mess if the creek rises above its bank.