The specific concern with Rough River Dam is the karst features of specific geologic formations that lie beneath the dam. The seepage construction project will rehabilitate the foundation to eliminate seepage concerns. The construction involves grouting of the bedrock as an initial phase. Based on the conditions encountered, a decision will be made whether to go to Phase 2, which could involve a deep concrete cutoff wall through the embankment and into the foundation rock. (USACE)
When conducting drilling operations within earthen embankments and their underlying rock interfaces, extreme care needs to be taken to prevent damage from increasing pore pressures, hydraulic (and pneumatic) fracturing, erosion, heave, or other mechanisms as stated by the USACE ER 1110-1-1807. At Rough River Dam, the challenge imposed was to drill and install PVC Grout Pipe and associated treatment devices in and below the embankment material in a manner that satisfies the owners engineering requirements for Dam Safety.
This can be a major challenge to successfully complete efficiently with today’s conventional drills and tooling, especially in relatively deeper/taller embankments.
Through Cascade’s years of experience operating within the limits of the USACE’s ER 1110-1-1807, utilizing our TruSonic equipment and qualified personnel on site we were able to deliver a cost-effective, efficient and quality product to our client. Cascade’s sonic drills have the ability to achieve resonance throughout a wide band of frequencies, and maintain this resonance throughout the entire length of the borehole including: changes in subsurface material, engineered embankment, fill, native unconsolidated formations and bedrock. Our successes have been delivered though the use of this TruSonic technology combined with the focused techniques our experienced sonic drillers.