On Alcatraz Island — California’s most-visited state park — Boulderscape stabilized a failing slope below the historic Warden’s House, sculpting 10,515 square feet of structural and architectural shotcrete into a Pacific Granite finish that disappears into the native rock — completed in just 8 days at 56% below traditional construction.
Record Installation Time
Savings Over Alternatives
Wall Square Footage
California State Parks needed to stabilize a failing slope below the historic Warden's House on Alcatraz Island while preserving the appearance of the island's weathered coastal rock formations. Boulderscape developed a rock bolt supported shotcrete solution and constructed full scale Pacific Granite mockups that were shipped to the island for review and approval by California State Parks before production began.
The project encompassed 10,515 square feet of wall surface consisting of a 13" thick structural shotcrete section with an average 3" thick architectural relief over a rock bolt stabilization system using a 5,500 PSI mix design. More than 380 totes of specialty shotcrete, each weighing approximately 2,800 pounds, were placed to create both the structural and architectural wall face. The mix design incorporated silica fume to enhance durability and long term performance in the harsh marine environment of San Francisco Bay. The entire scope was completed in just 8 days, resulting in a stabilized slope that blended seamlessly with the surrounding natural rock formations. See our sculpted shotcrete process or explore more shotcrete finishes.
Installation of an 8” structural shotcrete and a 1”- 4” thick Pacific Granite sculpted finish.
Pacific Granite
Medium Earth Blend
13"
Rock Bolt
5,500 PSI
Silica Fume was added to make the concrete more durable resist strong storm surges.
