A collapsing 72-inch corrugated metal pipe jeopardized operations at a stone quarry in Stafford, Va. The 800-foot pipe was the main dewatering system for the pit, and the quarry dewatered every other day. Beginning in a 20-foot-deep swale, the pipe also collected stormwater and carried a continuous flow of groundwater.
Large rocks and 3- to 5-foot-diameter boulders rolling into the sinkhole compressed the downstream pipe, backing up runoff. Workers who discovered the situation cut back 50 feet into an 85-foot-high sand hill to expose and remove the bad section, but the attempt failed.
