Cave Buttes Dam Modifications

About This Project

Starting in April 2020, Midwest Mole was the tunneling subcontractor of choice for the Coffman-SSC joint venture tasked with modifying the Cave Buttes Dam in Phoenix, Arizona.

While it doesn’t hold water year-round, the dam prevents the flooding of thousands of homes during large rain events. To alleviate the water pressure build-up as stormwater accumulates behind the earthen dam, the Flood Control District of Maricopa County decided to build an additional 61” outflow structure.

Midwest Mole opted for a refurbished 66” American Augers TBM that our talented mechanics refurbished in-house to bore the tunnel.

The entire 943’ run was through rock. Even though it was all rock, the ground conditions still ranged from fractured rock to extremely hard material, making our production numbers vary greatly between 30’ a day to only 4’ a day.

From the receiving pit at the bottom of the dam, Midwest Mole crews bored the tunnel at a 0.77% grade. We daylighted near the top of the dam with the deepest point underneath the dam being 50’ below the surface.