A Project Team Works Long Hours to Accomodate Historic Retrofit

The Sacramento Valley Depot in Sacramento, Calif., is undergoing an $11 million seismic retrofit to bring the historic structure into compliance with today’s Seismic Life Safety and Americans with Disabilities standards. The architecturally and historically significant depot is named on the National Registry of Historic Places as the Southern Pacific Railroad Sacramento Depot.

The depot is the country’s seventh largest Amtrak station with 1.2 million riders every year and is the ground transportation hub for Sacramento; therefore, closing for renovations was not an option for the project team. The depot also serves the Sacramento Regional Transit Light Rail and bus service along with Amtrak’s thruway motor coaches.

The depot project is part of the revitalization of the old Southern Pacific rail yard, which includes relocation of tracks and platforms, and construction of a light rail station on the site of the old platforms. The rail yard site will eventually be an extension of downtown Sacramento with housing, retail, and other multi-use purposes.

History Lesson

Located at the foot of the Sierra Mountains, Sacramento, once the hub of the California gold rush and the largest inland port, became the state’s capital in 1854. Close by was the Overland Trail—a route for stagecoaches, mail routes, the famous Pony Express, and later the Transcontinental Railroad through the Sierras; today, the trail is Highways 50 and 80.

The first railroad in California was the Sacramento Valley Railroad (SVRR), which eventually ran 22 miles from Sacramento to Folsom by 1852. The chief engineer of the SVRR was Theodore Judah, who later would be the chief engineer on the Central Pacific Railroad and championed having the Transcontinental Railway pass through the Sierras.

Sacramento was the logical choice to be the western termi- nal of the Transcontinental Railroad. Tracks for the Central Pacific Railroad began being laid in 1883, heading east over the Sierras to meet up with the Union Pacific. Seven years later on May 10, 1869, in Promontory Point, Utah, the trans- continental route to Council Bluffs, Iowa, was completed. In 1885 the Southern Pacific, located in Sacramento, absorbed the Central Pacific.

After World War I, Sacramento pressured Southern Pacific to build a new, grander station to welcome people to the city. Construction was completed on the Southern Pacific Railroad Sacramento Depot, now the Sacramento Valley Depot, in 1926.

The building was designed and constructed in renaissance revival style with a red tile roof and terracotta trim throughout. The main waiting room has soaring 40-ft. arched ceilings and a mural depicting the groundbreaking of the Transcontinental Railroad in 1883 by western mural artist John MacQuarrie.

The Retrofit

When the time came to retrofit the historic structure, Skyline Scaffold provided shoring, scaffold towers, overhead protection, and a full deck inside the hung ceiling of the building.

The first pieces of scaffold erected were shoring towers to help suspend the lath and plaster ceilings while the retrofit was going on above them. These towers stabilized the ceilings while carpenters added joists and blocking. Opening the floors above these ceilings highlighted the beauty of the full-dimension redwood that was used in the building’s construction.

Next was the full overhead protection of the waiting room and ticketing areas. The majority of the work was completed at night as the station’s hours of operation are 4:00 a.m. to 12:00 a.m., seven days a week; and its waiting room hosts 3,000-plus passengers a day along with Amtrak employees, vendors, light rail and bus passengers, and the general public.

The overhead protection needed to be as unobtrusive as possible and allow for the maximum public use of the space, so Skyline designed an overhead canopy using system scaffold to allow for the greatest use of space while providing the maximum protection. The overhead protection was built at a height of 14 ft. to allow the ticketing sign boards to be viewable to the public.

Preserving Historic Integrity

One of the greatest challenges to the interior overhead protection was the waiting area benches. The mahogany benches are part of the historic fixtures of the building and connect to the building’s heating system. Since they could not be moved the scaffold was designed to go around them, keeping them in use.

To combat a trip hazard created by a forest of columns with standard mudsills inside a public space, minimal plywood pads cut to the size of the base plate were used to protect the marble flooring.

Another hazard to combat with the columns was the rosettes sticking out from the standards. To protect the public, 4-in. plastic corrugated drainpipe tubing was cut down one side and wrapped around the columns providing padding so that the standard would be softened.

Once the overhead protection was complete, work on the deck in the ceiling began.The team began with a solid site survey, and then set necessary fall protection measures, warning lines, and calculations of the imposed roof load; a crane at midnight picked and placed all of the necessary gear onto the roof.

To reduce the roof load all plank and trusses were moved inside the adjacent roof space leaving just the horizontals and verticals on the roof. Skyline started building the deck moving the scaffold parts and pieces through the 3’x3’ roof vents into the ceiling void. The grand ceiling in the waiting area was constructed from wire grid lathe and plaster, suspended from the main roof trusses. The curve meant that the supports had to come down 3 ft. in the center from the bottom cord of the trusses, and then curve down to 16 ft. from the bottom of the truss at the edges of the building.

The deck was built to engineered drawings using suspending lattice girders over the buildings trusses and then building a deck down from them—stair-stepping to match the contour of the ceiling.

The deck had to be built with metal plank because wood was not allowed in the ceiling void because of fire hazard concerns. In order to keep the weight down, aluminum hook plank was used with steel plank filling in the remaining spaces.

The historic nature of the ceiling meant using tool lanyards to control all tools in the ceiling and working around all of the centenary wires, cables, and suspension points with minimum disturbance of the system. The contractor also had to reroute roof drain lines and some mechanical fixtures around the deck space. Once in place, the deck allowed the contractor to have full access to the trusses above and the ceiling below to complete the seismic retrofit and install fire sprinklers in the ceiling.

Another challenge on the project concerned the long cantilevered decks on each side of the platform that could not be supported from the lattice girders. The solution involved using roof beams and beam clamps to suspend the free ends of the decks that were then cantilevered back to the main deck with double diagonal braces. This allowed for the end decks to be installed without drilling into the end wall that were part of the seismic retrofit.

Overall historic restoration projects are always approached differently than other construction projects. The Skyline team worked day and night to accomodate the City of Sacramento and the general contractor, ensuring not only the end-product, but the path to it was safe, met the needs of the team, upheld the depot’s historic integrity, and didn’t impact its demanding schedule.