Chemical Grouting and Compaction Grouting for Leak Repair, Sinkhole Remediation, and Sand Filter Repair at Brazeau Dam in Alberta, Canada

At Brazeau Dam in Alberta, Canada water leaking through a crack in a structure joint between the water intake and wingwall had washed away sand in the sand filter behind the sheetpile wall on the downstream side of the dam, forming a two-foot diameter sinkhole. The geotechnical contractor proposed a chemical grouting program to stop the leak by sealing the joint, and a compaction grouting program to remediate the sinkhole and repair the sand filter by densifying the sands without restricting the flow through the filter. The work was performed in the middle of winter and in restricted access, with several safety issues. Two vertical 72-foot deep core holes were drilled along the structure joint, followed by the injection of a relatively flexible polymer grout seal. The geotechnical contractor then drilled compaction grouting probe holes to inject a mixture of sand and guar gum in and around the sinkhole and adjacent areas to densify the sand and to help locate other areas requiring densification. The guar gum additive served to suspend the sand during the densification process and, being biodegradable, disintegrate after densification to allow the sand filter to function as intended. This paper focuses on the innovative approaches to the problems presented to Geotechnical Contractor by the Geotechnical Engineer, as well as the design, monitoring, quality controls, safety procedures, and drilling and injection procedures used to repair the leak, sinkhole, and sand filter, with supporting figures. 7 pp., 10 figures.