Manson Restores Alcatraz Wharf

Manson DB HAGAR working at the Stabilize Alcatraz Wharf Project. Photo credit: Matua Sablan-EHS Manager

Just a mile and a half offshore in the San Francisco Bay, a small skiff weaves back and forth between the derrick barge (“DB”) HAGAR and an aging wharf, which marks the only access point to Alcatraz Island–commonly known as “The Rock.” There, the Manson crew are hard at work transferring materials for a highly anticipated and historically significant restoration project: the repair and seismic reinforcement of the island’s nearly century-old marine infrastructure.

A high priority for the National Park Service, Manson’s three-year Stabilize Alcatraz Wharf project is focused on demolishing and reinforcing sections underneath the original wharf to ensure it can withstand earthquakes and the ever-changing tides. The work is vital to preserving one of the nation’s most visited national parks, which welcomes over a million visitors annually to explore the island’s unique history—the site of the first lighthouse built on the West Coast, a military fortification (Fort Alcatraz) and prison, an infamous federal penitentiary, and a brief Native American occupancy.

The Alcatraz Project Team closing out a successful day on the island. Photo credit: Alcatraz Project Team

Planning with Precision

With laydown space limited to a very small footprint by the contract, all materials and equipment had to be strategically located. Photo credit: Alvaro Leal de la Torre-Sr. Graphic Designer

From the beginning, Project Sponsor Matt Lehmann and the project team were committed to careful planning. Consistent meetings with the client helped define the unique constraints of the job: limited working hours, difficult logistics, the importance of maintaining ferry schedules, the absence of on-site power, preserving the adjacent historical structures, protecting birds and other wildlife on the island, and the direct and constant proximity of the visiting public.

“For this project, we originally estimated the majority of the work to occur during the evening and have a derrick barge present at all times” Matt explains. “During the planning phase, we presented the idea to operate from the project’s footprint, using a rough terrain crane to hoist materials instead of relying on a derrick, which had the potential to disturb ferry traffic and added a risk of performing heavy lifts near visitors.”

With limited power and other utilities on the island, the project team used generators for temporary power and received bi-weekly support from the DB HAGAR or DB EINAR to deliver fuel, fresh port-a-potties, fresh water, and supplies to keep the crews properly supported.

Another challenge the project team faced was planning the work around the location’s rough weather, which included high winds, rough waves, and strong currents. To provide a safe environment, the team regularly studied local tide charts and planned the work accordingly.

“Our number one priority on any job is to keep the craft personnel safe, but you also want to protect the surrounding areas and local wildlife,” says Project Manager Conner Long. “We installed debris booms to catch any objects that might fall into the water and netting over the construction area to prevent local birds from nesting near the project.”

DID YOU KNOW? Alcatraz Island has fascinated tourists for decades, thanks to its storied past as an impenetrable federal penitentiary. Since the 1960s, it has served as the backdrop for numerous novels and high-profile films, including: "Birdman of Alcatraz (1962), "Escape from Alcatraz" (1979), "Slaughterhouse Rock"(1988), "The Rock" (1996), "Catch Me If You Can" (2002), and "X-Men: The Last Stand" (2006).

Diving for Pile Repair at Alcatraz

Mobilization began in January 2023, when the DB HAGAR and M62 flat barge delivered a jobsite trailer, 65-ton RT crane, and established a laydown area that would serve as the projects dedicated work area on the top of the wharf for the next 3 years. First in the water was diving subcontractor Crux Diving, who tackled two types of pile repairs underneath the wharf—Type I concrete and Type II concrete and rebar. After identifying unsound piles, the divers chipped away old concrete, replaced or repaired rebar, and encased the piles in fiberglass jackets before grouting them in place.

“The Stabilize Alcatraz Wharf project is basically a big wharf repair with the majority of the work done beneath the structure,” says Field Engineer Nick Van Meter. “We are repairing the piles, beams, and deck by demolishing the concrete and putting in new rebar with new concrete.”

By the end of the first season, Crux Diving had repaired over 100 piles, clearing the way for the next phase of work: deck demolition and beam repair starting in December 2023.

The access area under the wharf was only 4.5 ft tall, making tight working quarters for the crew. Photo credit: Alvaro Leal de la Torre-Sr. Graphic Designer

Working Below Deck

To prepare for the demolition and deck repair, the piledriving crew cut an access hole in the wharf deck to allow crews to travel and easily hoist materials and equipment under the wharf using the RT Crane.

Over the next two years, piledrivers worked within tight spaces–with the access area only 4.5 ft tall–repairing damaged beams and installing formwork for shotcrete placement. The limited access space required constant kneeling, restricted movement, and lifting heavy drilling equipment above the shoulders, presenting the risk of strains, muscle pulls, and other injuries. Faced with the physically demanding work, Superintendent Mike Ramos and crew members improved ergonomic conditions by creating stools for the crew to sit on, as well as creating a pulley system to help lift the handheld equipment such as rivet busters used for demolishing concrete, easing strain and reducing fatigue.

Subcontractor Dees-Hennessy applied shotcrete, spraying wet concrete through hoses onto approximately 5,000 ft2 of area underneath the deck.

For concrete placement, the project team opted for shotcrete instead of cast-in-place application to preserve the structure’s original look, with the latter requiring drilling thousands of holes along the deck.

“In all reality, no one will ever know that we were here because all the work is invisible with the repairs taking place underneath the wharf,” Nick says. “Tourists will walk on it and think nothing of it, but the structure itself will be seismically sound.”

Concurrently, Manson coordinated with subcontractor Malcom Drilling to install multiple piles ranging from 16 to 30 inches in diameter for new seismic mooring dolphins. Due to the site’s existing geography and constant tide change, drilling through rock was required to install the piles.

Once the piles were set, piledrivers worked quickly to install falsework and formwork in preparation for the installation. The crew installed the remaining components including two caps, extending nearly 4.5 ft below the top deck.

The Final Stretch

As the project team and crew enter the final stretch of the project, work continues with deck demolition and beam repairs. Crew members who have been on the island since day one are starting to reflect on the importance of their work.

“Working on this project for a few years, it didn’t hit me right away that this is a once-in-a-generation project,” says Piledriver Marcelo Sanabria Peña. “This job is really rewarding and as I get further into my career, I can look back and say I helped restore Alcatraz Island.”