Signal - CODAworx


Submitted by Tom Loughlin

Client: Treasure Island Development Authority

Location: San Francisco, CA, United States

Completion date: 2019

Artwork budget: $250,000

Project Team


Tom Loughlin

metal fabricator

Kevin Manning


arts commissioner

Jill Manton

San Francisco Arts Commission

municipal lead

Peter Summerville

Treasure Island Development Authority

agency lead

Karin Betts

Bay Area Toll Authority

selection committe

Leslie Pritchett

Oakland Museum of California


Nick Guerts



Signal is a 22-ton steel ring made of material reclaimed from the original east span of San Francisco’s Bay Bridge. The ring was created from the top chords which formed the bridge’s backbone and were the largest, strongest, and heaviest pieces of the bridge. Signal also comprises a warning light salvaged from the bridge, concrete piers, and rubber elastomers which are used in bridges to dampen roadway vibration.

The final element in Signal is sound: the steel vibrates like a tuning fork at its natural resonant frequency of 35 Hz, emitting a low, recurring sound like a foghorn. The ring is nearly 25 feet in diameter, and sits low on three concrete piers, permitting visitors to climb on top of the sculpture and feel it vibrate beneath them.

Signal is located on Treasure Island, a low-lying man-made island in San Francisco Bay that hosted the 1939 World’s Fair and was to become an airport for sea planes and regional flights but World War II intervened and the island became a Navy base. The base was decommissioned, and the island is now undergoing a massive redevelopment project that aims to bring tens of thousands of dwelling units and hotels, shops, etc. to the island. Treasure Island currently hosts 1500 residents, many of whom receive Section 8 housing assistance.


The goal was to invoke the past and the future of infrastructure development in the Bay Area, and to raise questions about how they relate to the human experience.

Signal sits on the former location of the 1939 ferry terminal which brought visitors to the World’s Fair. It is a few hundred meters from a planned ferry terminal which will serve inhabitants of the high-rise apartment buildings which are being constructed.

Signal’s ring is a bridge that circles back on itself, supported by concrete piers resting on mud – the same design that resulted in catastrophic damage during the 1989 earthquake. Signal’s piers hold it 16”off the ground – the amount that the island’s ground level is being raised in the areas under development to account for coming sea level rise. The top of Signal’s ring is at the height to which the nearby seawall will be raised to prevent future flooding.

Signal’s warning light pulses like a slow heartbeat, and the foghorn tone repeats like slow breathing. Signal is oriented so that its light points to the north star.

Signal’s location offers a panoramic view of the Bay Area, and Signal’s light is visible throughout the area. Signal invites visitors to climb on top and feel its vibrations as they consider the city and the landscape around them.


Unlike most public art projects, Signal was not spearheaded by a single organization. Rather, it resulted from the ad hoc collaboration of multiple groups with a shared vision.

The project began when the Oakland Museum of California reached out to the CA Department of Transportation, the Bay Area Toll Authority, and the California Transportation Commission suggesting that salvaged Bay Bridge steel could be used to make public art. The group formed a selection committee which chose artist Tom Loughlin’s design, and the San Francisco Arts Commission reached out to the Treasure Island Development Authority (TIDA) to find a venue.

The artist, TIDA and the Arts Commission worked together to assemble the necessary permits, a multi-year process involving the S.F. Department of Building Inspection, the S.F. Bay Conservation and Development Commission, and the United States Navy. While every public art project involves some complexity, they probably don’t all involve a nuclear technician with a Geiger counter monitoring excavation as Signal did. The incredible weight of the steel and its unusual composition presented additional challenges, so the construction process involved extensive coordination between Junoworks, CalTrans, Yetiweurks Engineering, and the installation team.