Crews reached a milestone in late September, completing the grouting program on both the saddle dam and main dam. Together, more than 33 miles of grout holes were drilled at the rate of about one mile per month since the start of the grouting program in January 2021. It was key for the crews to work around the clock for the past 33 months to stay ahead of the asphalt core placement at the main dam.  

Workers use grout to fill and intersect fractures, voids and anomalies down into the bedrock. This reduces the foundation permeability, mitigates the risk of turbulent flow and erosion through the foundation, increases the length of seepage paths and further investigates geologic conditions.  

Stantec’s Principal Engineering Geologist Don Riley said being “diligent, systematic and consistent” is the key to a successful grouting program. 

The process of drilling and grouting uses rigs to drill holes 3 to 3.8 inches in diameter in 10-to-20-foot stages starting at 20 feet apart and moving closer with each stage. After a hole is drilled, a packer seals each hole so that grout can be injected to specific stages using high pressure. The grouting undergoes rigorous testing throughout the process to ensure it meets quality standards.