Shotcrete Repairs and Stabilizes Failing Slope on Alcatraz Island

The Challenge:

Apply and sculpt shotcrete on a failing slope on Alcatraz Island within a six-week time frame

The Players:

The Quikrete Companies

The Process:

The Quikrete Companies, a leading manufacturer of packaged cement mixes for the construction and home improvement markets recently supplied shotcrete in 3,000-pound bulk bags for a restoration project on Alcatraz Island, also known as “The Rock.” Boulderscape, a premier design architect that specializes in shotcrete application used Quikrete Shotcrete MS – Fiber Reinforced and Quikrete Shotcrete MS to successfully repair and stabilize a failing slope on the 22-acre island.

In addition to facing dangerous application conditions, a condensed six-week shotcrete schedule was required to avoid disruptions to regular tour operations while also considering the habitat and migration patterns of local sea birds.

In one weekend, 131 bulk bags of Quikrete Shotcrete MS – Fiber Reinforced and 126 bulk bags of Quikrete Shotcrete MS were delivered to Alcatraz Island for the project. Quikrete delivered 16 truckloads of material to Pier 50 in San Francisco before being shipped on two barges to Pier 33 on Alcatraz Island where it was offloaded at night, by crane, one-by-one before finally being transported to the jobsite on trailers pulled by four-wheel all-terrain vehicles.

“Navigating a variety of unique factors made this a very fulfilling project for everyone,” said Steve Jimenez, senior vice president commercial sales for Boulderscape. “We couldn't start until the indigenous birds migrated from the island in November and we had to complete our portion of the work before the birds returned in February, which meant everything had to be expedited starting with the delivery of material. Beyond the challenging schedule, the application process was full of danger. The nozzlemen had to be hoisted more than 60 feet in lifts to spray apply the shotcrete before sculptors repelled down the cliff to shape the material. The end result was a structurally sound slope that matched the surrounding environment.”