Sinkholes discovered near Turner Tract

Published 10:19 am Saturday, March 28, 2015

On March 19, several small sinkholes were observed in the asphalt on General Thomas Highway (Route 671) by passing vehicles. The craters, as well as a larger void below the pavement, were the result of temporary equipment failure during the ongoing installation of wastewater pipes that serve the Turner Tract Industrial Park and the surrounding area.

MEB General Contractors Inc. — the company to which the construction contract was awarded — and the Virginia Department of Transportation collaborated to excavate the area that evening. After peeling the pavement back, the workers detected the root of the problem. That void was subsequently filled with a combination of stone and sand, and then covered with a temporary asphalt patch.

The patch needed reapplication as the mixture settled over the weekend, but has stabilized since.

Installation of 17,240 linear feet of these underground pipes began in November. The pipes travel under several roadways throughout the county, including General Thomas Highway, Delaware Road, New Market Road and Enviva Way, as well as a CSX railroad. They connect to an interceptor pump station located on Southampton Parkway (Route 58) between New Market Road and Shady Book Trail.

The county uses a boring process in instances such as this or other cases when installing subsurface utilities under roadways without disrupting traffic. The undertaking begins by digging a receiving hole on one side of the road and an entrance pit on the other. A horizontal drilling device drills a hole through the designed path, and then a reaming tool enlarges the opening. This continues until the diameter of the hole is large enough to fit the wastewater pipe.

For this location, specifically, 180 linear feet of parallel 24-inch steel castings were bored beneath the roadway — one for the 8-inch sewer line and one for a future waterline. During the boring, however, a void was created between the soil and pipe by the aforementioned equipment failure, causing the pavement above to collapse.

Moving forward, MEB and its subcontractor insurer will continue to evaluate the area daily for additional signs of settlement and develop an appropriate course of action. Depending on their assessment, the crossing may have to be completely excavated to assure that there are no additional voids between the pipe and the soil. An alternate option is to use ground-penetrating radar.

VDOT’s role, meanwhile, is to work with MEB to make sure the road is repaired to the department’s standards.