In a race against time and the elements, a team of historic rehab experts has mobilized to save a former machine shop from collapse at San Francisco’s Pier 70 shipyard. Their strategy calls for inserting a new structural steel frame within a 19th-century unreinforced masonry building, which had been red-tagged for years and was already crumbling by the time the project team began construction.

“There was a sense of urgency,” says James Madsen, partner with developer Orton Development Inc. “There were bricks falling down literally every day. You’d walk into this building and you’d have patches where you could see daylight through the walls.”

The project aims to stabilize and repurpose the structure into high-tech, biotech and light industrial space while leaving its historic character unmarred.

Built by Union Iron Works in 1885, the machine shop—known as Building 113/114—remains the oldest structure at Pier 70, a 69-acre site in the Dogpatch neighborhood south of Mission Bay that comprises one of the most intact 19th-century industrial complexes west of the Mississippi River, according to Port of San Francisco officials. Steel workers for Union Iron Works and later Bethlehem Steel—which took over the site in 1905—used the structure to manufacture supplies for the Transcontinental Railway and built U.S. military ships used in the Spanish American War and the two world wars.

Today, a portion of Pier 70 with the largest floating dry dock on the West Coast still functions as a shipyard.

Orton will redevelop around five acres of the pier known as the Historic Core—an area featuring multiple buildings totaling about 300,000 sq ft, including several interconnected industrial buildings built in the 1910s. The overall project will cost between $100 million and $120 million, depending on tenant improvement requirements. Tenant spaces will begin opening to the public in 2017.

Unobtrusive Rehab

Orton formulated its approach by first hunting down original construction documents. The 492-ft-long, 175.5-ft-wide structure actually encompasses three separate structures built at different times—two brick buildings that were joined together in 1914 via a reinforced concrete connector.

Next, structural engineer Nabih Youssef Associates (NYA) reviewed historic documents pertaining to the 1906 San Francisco earthquake and found that “parts of the east and west walls had actually collapsed during the quake and were subsequently repaired and bracing was added,” says Anthony Giammona, the firm’s project manager. “This kind of information and real-world seismic testing helped us understand the structure and its deficiencies.” Because part of the building was built on fill, liquefaction during seismic events had to also be mitigated.

NYA worked with design firm Marcy Wong Donn Logan Architects (MWDL) to develop a building-within-a-building concept that would preserve the historic perimeter brick walls, reduce the cost of temporary shoring and retain the large open volume in the 62-ft-tall space.

“To do this, we developed a steel-braced frame system that weaves through the existing building elements to provide bracing without being too intrusive,” Giammona says. “To seismically brace the brick walls, and to reduce the amount of construction shoring needed, we introduced a perimeter mezzanine level near the wall mid-height.” The approximately 40-ft-wide new mezzanines (and one existing one in the northwest corner) run the length of the building on the north and south sides, except for within the center 1914 connector, which will become a breezeway to allow pedestrians to cross through the building and access a courtyard.

The design configures the mezzanine-level structural steel “as ‘rectangular donuts’ in plan, [which] create shear diaphragms to resist structural forces and reduce the unbraced length of the unreinforced brick walls,” says Kent Royle, associate principal at MWDL. Buckling restrained braces provide enhanced seismic performance.

A horizontal steel truss braces the top of the existing brick walls while mimicking an existing wood truss in the same location. Several steel bridges—designed to resemble existing 20- and 30-ton overhead bridge cranes dating back to the 1890s that will remain in place—seismically join the different portions of the mezzanine and provide access for tenants.

“Essentially the [existing] walls become cladding for the building, and you have a completely code-compliant building-within-a-building that is built out of steel,” Madsen says.

Early construction work began in spring 2015, when crews with Orton and its abatement contractors began clearing the building of trash and such hazardous materials as lead paint and asbestos, repointing the brick and performing soft demolition.

In October, Nibbi Brothers General Contractors began work on its $12.2-million contract to execute the rehab by performing structural demolition to identify locations for new grade beams and placing 73 micropiles in accordance with those locales. The 8-in. to 10-in. micropiles range from 25 ft to 70 ft in depth throughout the nearly 90,000-sq-ft interior footprint. These help mitigate liquefaction and settlement issues, Giammona says.

Once crews finish reinforcing the footings and placing concrete, erection of around 400 tons of structural steel will begin. “For the next three to five months, we are going to have primarily one subcontractor in here installing steel,” says Norman Hayes, Nibbi’s senior project manager.

Around 50,000 sq ft of lightweight concrete will finish out the mezzanines, and then Nibbi will install new building systems. “Technological upgrades such as state-of-the-art electrical power and Internet distribution coupled with radiant floor heating are carefully integrated into the structure,” says Marcy Wong, partner with MWDL.

By the time the core and shell rehab of Building 113/114 wraps up in October, crews will expand the operation to tackle multiple neighboring buildings in the Historic Core. “At some point, they will all be under construction at the same time,” Hayes says.

Worker safety remains a major consideration when working in a former red-tagged structure in a seismic zone. Temporary shoring helps support the perimeter walls during construction. Nibbi holds pretask safety meetings with each subcontractor, and everyone on site is contracted to follow a health and safety plan that includes education about the building’s remaining hazardous materials, which are below harmful levels.

Each morning Nibbi takes a worker head count. In the event of a seismic event, crews are instructed to evacuate to an exterior courtyard area, where Nibbi performs a supplemental count to ensure everyone got out safely, Hayes says.

Area Master Plan

Under a separate project, developer Forest City will revitalize 28 acres of Pier 70. The massive undertaking will rehabilitate several historic structures and construct multiple new buildings, totaling between 1 million sq ft and 2 million sq ft of commercial office, with up to 2,150 residential units and approximately 450,000 sq ft of retail, light industrial and arts spaces. Forest City, which is currently ushering the project through the environmental review process, hopes to begin the first phase of construction in 2017, according to Forest City.

North of the Historic Core, the Port of San Francisco plans to develop Crane Cove Park at the site of the shipyard’s former slipway. The project, expected to break ground next year, will preserve two historic cranes and open 1,000 ft of shoreline to the public.

While full build-out will take many years, city planners expect Pier 70’s transformation to boost economic development and preserve a piece of San Francisco’s maritime history.