Reducing Conduit Water Flow into a Quarry in North-Central Alabama: A Case Study

Water began to flow into a quarry through a karst conduit connecting the quarry to a large nearby creek. Flow into the quarry was about 4,000 gallons per minute (gpm) [15,150 liters per minute]. The site, a dolomite quarry in north-central Alabama, is in an area underlain by structurally deformed Cambrian carbonates with documented karst development. Field mapping identified a dominant fracture orientation that controlled ground-water flow and permitted development and implementation of a grouting program to inhibit water flow in the conduits. The quarry and inflow point are about 400 feet (122 meters) southwest of a large creek. Bedrock exposed in the bed of the creek is fractured and cavernous openings were observed, as was a sinkhole on the left bank (the southwest bank) of the creek. The quarry operators had attempted to repair the sinkhole with gravel and other materials prior to the investigation. However, water continued to flow from the creek into the sinkhole. The flow in the creek was about 5,000 gpm (18,900 liters per minute) less (about 40 percent) downstream of the sinkhole than at the upstream measuring location. Dye was introduced into the stream near the sinkhole and appeared in the inflow of the quarry within about 4 minutes. Based on the dye study, a grouting program was designed. Ten boreholes were drilled to depths as great as 120 feet (37 meters) below land surface in a line nearly perpendicular to the line between the sinkhole and the inflow. During drilling of some of these boreholes, water-filled cavities were penetrated and the water flowing into the quarry became muddy. A secondary line of two boreholes was drilled and grouted about 10 feet (3 meters) toward the creek from the first line. A third line of three boreholes was drilled along the highwall near the inflow point. All boreholes, and the sinkhole on the left bank of the creek, were grouted using high viscosity grout. As a result of the grouting program, inflow into the quarry was reduced to less than 1,000 gpm (3,790 liters per minute).