Calaveras Dam

Drill Tech was subcontracted to provide ground improvement for an earthen dam replacement project taken on by the San Francisco Public Utilities Commission, with Dragados-Flatiron-Sukut Joint Venture (DFSJV) working as the general contractor. The subcontract included deep soil mixing to stabilize the disposal site, as well as the excavation and support of a shaft and five tunnels. Drill Tech excavated the 154-foot-deep shaft with drill and blast techniques and drove the tunnels with a roadheader. For ground improvement and spillway stabilization, Drill Tech installed CSM panels, soil snails, rock bolts, and tie-back walls exceeding 100,000 linear feet.

As the dam project progressed, DFSJV asked Drill Tech to expand their scope and provide additional services. Drill Tech installed slide stabilization with tie-back and concrete walers, rock fall mitigation, compensation grouting, and waterproofing, as well as facilitated the demolition and replacement of concrete slope protection and concrete coring for quality control purposes. The added services included approximately 385 tie-back walls and more than 700 cubic yards of shotcrete. At the conclusion of the project, the value of the added scope exceeded the base contract value.