Morning Call: April 23, 2004

A new sinkhole opened at the site of the dismantled Route 33 bridge Wednesday night, halting construction on the replacement span and swallowing a small Dumpster.

No one was injured when the 15-foot wide, 60-foot deep sinkhole opened suddenly about 6 p.m. on the north bank of Bushkill Creek in Northampton County, said Ron Young, spokesman for the Pennsylvania Department of Transportation.

The sinkhole didn't appear to have damaged the new bridge's concrete abutment pilings that were drilled into bedrock 250 feet below the surface, he said, so PennDOT is still confident it can finish the new bridge by mid-August.

"Luckily no one was hurt," Young said. "No equipment was really damaged, [but] there was a Dumpster of trash that was sucked up by the sinkhole."

The state Department of Environmental Protection said that after its initial investigation, Hercules Cement Co.'s nearby quarry doesn't appear to be a factor in causing the sinkhole, which opened next to the abutment pilings.

DEP spokesman Karl Lasher said staff from the department's Pottsville Mining Bureau has not been able to link the sinkhole to Hercules, which is about 25 yards west of Route 33.

"At this point we don't have anything conclusive that would say they are responsible," he said. "Despite that, the quarry has been very gracious in going out to the site. They are providing material to backfill it and they've been there since this morning and they've agreed to cooperate."

Joe Pospisil, Hercules' vice president of manufacturing, did not return phone calls.

The northbound Route 33 bridge over the Bushkill was closed Jan. 24 and was later dismantled when a sinkhole opened on the south bank of the creek, forcing the state to construct a new span. PennDOT built a crossover across Route 33's grass median so northbound motorists can use the southbound lane's passing lane to get over the southbound bridge.

Some residents who live near Route 33 have questioned whether Hercules and two other Nazareth area quarries, Eastern Industries and Essroc Italcementi Group, are partially responsible for the bridge's demise and for triggering about 90 sinkholes in and around the creek since 1999.

When a quarry or mine goes deep enough, it eventually will hit the groundwater table, causing water to flow into the pit. To keep the operation dry, a quarry must pump out the groundwater and discharge it into a stream. The pumping creates a funnel effect underground that is called the "cone of depression" or "zone of influence."

Studies have shown that depending on its size, a quarry's cone can cause sinkholes by sucking groundwater for miles, undermining the limestone, clay filling and soil until the surface buckles and eventually collapses, creating a hole.

Lasher said DEP inspectors on Thursday couldn't find traces of mud or silt in the groundwater flowing into Hercules' pit. If they had, he said, it would show that Hercules' dewatering pumps had a direct effect on the sinkhole because water would be traveling undergroundfrom the sinkhole to the pit.

Lasher said sinkholes that open as a result of the groundwater table being lowered typically open in a creek bed and not on a higher plain such as the creek bank. So the new sinkhole's location could also prove that Hercules may not be responsible, he said.

"At this point I'm not sure what else could be done to establish that guilt or innocence," Lasher said.

Young said bridge construction is continuing on the creek's south bank, but work has been halted on the north side so the sinkhole's throat can be located and the hole can be filled. He said PennDOT wants to make sure the sinkhole is filled properly so the ground willsupport the new bridge's weight.

Young said the sinkhole wasn't related to a 3-foot wide depression that formed in the northbound lanes overnight Wednesday, forcing a partial closure of the highway Wednesday morning so the road could be repaired.

Steve Esack