S.F. construction site discovery: 2 old ships ARCHAEOLOGY

Lilly Henry Robert, an archaeologist with Far Western, holds a grouping of artifacts salvaged from a ship found in a construction area just south of Candlestick Park on Thursday Feb. 10, 2011 in San Francisco, Calif. The San Francisco Public Utilities Commission has stumbled upon two old ships excavating a tunnel site for a new project near the football stadium. Both are believed to be from the late 1800s or early 1900s and ferried cargo around the Bay. less Lilly Henry Robert, an archaeologist with Far Western, holds a grouping of artifacts salvaged from a ship found in a construction area just south of Candlestick Park on Thursday Feb. 10, 2011 in San Francisco, ... more Photo: Mike Kepka, The Chronicle Photo: Mike Kepka, The Chronicle Image 1 of / 7 Caption Close S.F. construction site discovery: 2 old ships 1 / 7 Back to Gallery

When engineers working near Candlestick Park last March drilled deep into the ground for soil samples, they pulled up chunks of wood and figured it was an old pier.

They had no idea it was a century-old ship, let alone two.

But that became clear this week when the San Francisco Public Utilities Commission uncovered what maritime experts believe are a pair of scow schooners, 90-foot-long workhorse vessels that plied the bay shallows in the late 1800s to deliver hay, salt, bricks, pork, coal, lumber and other cargo. Buried under more than 14 feet of sand and fill dirt, the 45-foot-long hull sections came to light at the mouth of an enormous trench that will house a new overflow sewage pipe for the Visitacion Valley neighborhood.

"These were the flatbed trucks of San Francisco Bay from the late 19th and early 20th century," said Jim Delgado, director of maritime heritage at the National Oceanic and Atmospheric Administration in Washington, D.C. "They're largely forgotten now, but these scow schooners moved the goods that built the city and the Bay Area economy."

A single survivor

Of the 400 or so flat-bottomed scow schooners built around the bay after the Gold Rush, only the 120-year-old Alma survives as part of the collection at the San Francisco Maritime National Historic Park. Many scow schooners were abandoned after they were made obsolete by bridges, trains and trucks.

That is the most likely fate of the two ships discovered underneath a piece of unused industrial land wedged between Highway 101 and a large business park. Before it was piled with fill dirt and paved over for development, the site held a small lagoon and spit that appeared and receded with the bay tides. Archaeologists theorize the bayfront spot became a popular ship graveyard around the turn of the century. Hundreds of vessels were run ashore, stripped of rope, sails and valuable metals, broken apart, burned and left to sink, Delgado said.

Still, the discovery surprised the water utility's project team, which expected to find Native American artifacts on the site, not ships.

Digging by hand

Last Friday, as excavators clawed at the bottom of the trench, archaeologist Nick Longo noticed an abrupt change in soil color - red fill dirt giving way to shells and dark beach sand. Then a wooden beam and a hunk of metal emerged.

"It's not every day that you find a ship like this," Longo said. "It's the kind of thing you hope to come across in this kind of work."

The heavy digging machines halted and workers switched to hand shoveling the briny black dirt away from the ship's bones. A few days later they found a second hull, positioned at roughly the same angle, just 27 feet away. Both are about 25 feet wide and held together by iron spikes; at least one appears to be made of red fir and is partially charred. The soil and condition of the schooners led Scott Baxter to believe the square-nosed ships were discarded prior to the earthquake and fire of 1906.

Baxter, who is consulting the construction company on the site's historic artifacts, said the boats' frames will be photographed, measured and drawn. The team will collect the few relics - including shoes, bottles and bits of ceramic - and take samples of the wooden beams.

While the relatively intact Alma was rescued from a mudflat near San Jose in 1959 and restored, however, these vessels' remains won't be salvaged. The cost of removing and preserving a 100-foot-long ship would run into the millions of dollars.

"It would have to be a Viking ship to save it," Baxter said.