Muni's 17-Mi. Extension

Third Street Light Rail Heading to Hunters Point

By Thomas York

It's nearly "all aboard" time on San Francisco Municipal Railway's $500 million Third Street light rail project, which will run for 17 mi. though the heart of Mission Bay all the way out to Hunters Point and Visitacion Valley.

The Fourth Street Bridge required a $17 million retrofit (photo courtesy of city of San Francisco).

San Francisco-based Mitchell Engineering/Kobyashi Corp. Joint Venture served as general contractor for three of six bid packages awarded for the new track and stations. The firm also won contracts to overhaul two bridges and install electrical transformers.

Trains should start carrying the first paying passengers on Jan. 1 after most of the construction work is completed by early summer, and the state's oldest drawbridge is overhauled and testing is completed. The new line will link underserved, out-of-the-way Southeast area neighborhoods with the bustling Financial District and South of Market neighborhood, as well as the new 43-acre Mission Bay commercial development.

Curtis Mitchell, president of Mitchell Engineering, said finding and relocating utility lines proved particularly vexing, and caused numerous delays on the first two of six segments under construction.

He said workers encountered numerous abandoned conduits that were not included in inaccurate city maps. Most 19th century city underground utility maps were destroyed in the fire that followed the 1906 earthquake.

Mitchell said 75 percent of the work effort required relocating the various utility lines to the sides of the new roadway, which will have three traffic lanes in each direction and tracks and stations in the center median. Many utility lines were removed because they are no longer used. "The flat work goes pretty fast after that," he added.

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That "flat work" includes track laying and building new pavement, curbs and gutters.

Mitchell said one highlight of the overall project was the seismic retrofit of the 87-year-old Fourth Street Bridge, which is a bascule bridge, or drawbridge, that spans the China Basin estuary. This work was performed under a contract awarded by the city's public works department.

Joseph Strauss, who designed the Golden Gate Bridge, designed and built the historic drawbridge in 1917. Strauss' firm, the Bascule Bridge Co., specialized in such bridges.

Bascule bridges are counterbalanced, so that when one end is raised, the other end is lowered to allow marine traffic to pass. The 240-ft.-long Fourth Street Bridge, which Mitchell said is the state's oldest operating drawbridge, features a 700-ton concrete counterweight.

Mitchell said the bridge was dismantled, then transported by barge to a maintenance yard for the overhaul.

This work was also delayed after officials found more rust and corrosion than originally thought. The overhaul included adding tracks to the deck.

The state contributed a portion of the $17 million cost to refurbish the bridge.

The joint venture team also dismantled and overhauled another steel-frame bridge over Islas Creek in the city's Dog Patch neighborhood, so named due to the packs of dogs that used to roam there in the 19th century when the area was more industrial.

Muni's construction division served as engineers for several segments of the project, while the San Francisco office of PGH Wong/Parsons/Korve, Joint Venture, served as the engineers on one of the six segments of the new line.

The city's department of public works designed the project.

Hayward-based Shimmick Olsen Joint Venture was the general contractor for the contract to widen the existing Hester Avenue/Bayshore Bridge spanning Highway 101 near Candlestick Park. The San Francisco office of Wong/Parsons/Korve served as engineers. The new bridge carries the Third Street line across the freeway.

Shimmick Olsen project manager Ron Llewellyn said the widening, was completed in March, but there were obstacles.

He said that, for example, the bridge had to be widened and strengthened to Caltrans specs, which "made the project a lot more difficult."

Caltrans would not allow lane closures on Highway 101 from 7 a.m. to 8 p.m. on weekdays to avoid traffic tie-ups.

As a result, Llewellyn said most of the new structural steel was put in place and reinforced concrete poured during off hours.

"We had a lot of night work, and a lot of weekend work," Llewellyn added. "During football season, we had to coordinate our work with 49er games. There also were special events at the Cow Palace."

Shimmick Olsen also took over the contract to perform architectural finishing for the 28 new stations. The work includes the installation of platform lighting, plus closed-circuit television systems, ticket vending machines and some plumbing.