Cellhouse Utility Vault & North Terrace

CPI Objectives: Military-to-civilian career training, national park stewardship

Team: Active duty military service members and CPI’s professional staff

Owner: National Park Service

Location: Alcatraz Island, Golden Gate National Recreation Area, San Francisco, California

Completed: 2025

Outcomes: Stabilization of the cellhouse utility vault and north terrace demonstrates CPI’s capacity to complete large, technically complex infrastructure repair projects.

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The concrete vault system features a 25’ high retaining wall that encloses an underground 6’ wide vault containing modern electrical, plumbing, and fiber optic cable systems along with decommissioned historic utilities. The terrace concrete slab and bond beam, that had differentially settled over time presenting tripping hazards, was demolished. Fill material behind the retaining wall was removed followed by structural repair of the wall’s full-height vertical crack. Deteriorated concrete within the vault along its structural crossbeams had presented danger to utilities within as well as a serious safety hazard to NPS staff on the terrace above and visitors below should catastrophic failure occur; the internal vault structural bracing was removed and replaced with a new engineered bracing system.

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Internal vault grouted shoring posts were installed, and concrete placed for plate and anchor blocks with tie rods through-bolted horizontally to the retaining wall. The fill behind the retaining wall was placed back in the space to provide lateral stability, followed by placement of a new concrete terrace slab and bond beam. Safety was a serious concern throughout the project, with barricades for pedestrian and jobsite protection and a worker fall protection system installed, along with an underground worker safety ventilation system within the vault.

Project & Technical Capabilities

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- Expert CPI staff engage hands-on and manage projects with teams of highly qualified and vetted members of our active duty armed forces preparing for transition to civilian careers.

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- Projects across the construction and infrastructure spectrum including strengthening & stabilization, repair & preservation, safety & access, and new construction. CPI addresses America’s national park deferred maintenance backlog, completing projects that would otherwise likely remain undone due to limited park resources.

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- Self-perform concrete, wood, steel, & composite construction as design-build projects coordinated with owners. Larger projects include self-performed work in addition to managing design, specialty consultants, and sub-contractors if needed.

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- Leader in advancing innovative technological solutions to construction and infrastructure challenges that respect historic and cultural significance, promote durability, increase accessibility and safety, reduce cost, and meet relevant regulations.

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