The long-buried skeleton of colonial San Francisco is being brought to the surface at the site of the old Spanish fort in Yerba Buena, where California as we know it was born.

Archaeologists for the Presidio Trust are building interpretive replicas of the ruins of El Presidio de San Francisco directly above the famous garrison's original stone and adobe walls. The displays will use the exact same construction methods and, where possible, materials that were used in the historic 1815 expansion of El Presidio, the ruins of which were recently uncovered.

The idea is to allow visitors to see, feel and identify with the city's imperial Spanish roots.

"We want people to have an immediate visceral connection to the place, which is what this is an attempt to do," said Kari Jones, an archaeologist for the Presidio Trust, as she stood next to a not-yet-complete stone wall covered in a mud mortar concoction. "This is the foundation of San Francisco. We think it is one of the most important sites in the West."

Historic discovery

Jones and her supervisor, Eric Blind, have been working with architects and builders on ways to reveal to the public the treasure trove of history that was unearthed after being underground for more than 150 years.

The foundation walls of the Spanish fort were discovered by the Army as it prepared for the 1994 transfer of the Presidio to the National Park Service. Workers were attempting to remove underground heating fuel tanks from a row of houses on Funston Avenue when they found stonework running along the backyards.

The walls were outside the boundaries of the original 1776 garrison built by the Spanish, but subsequent archival work revealed that El Presidio had been rebuilt in 1815 after the original structure was severely damaged during earthquakes in 1808 and 1812.

"There had been a long-standing search for where El Presidio might be," but nobody had done any real archaeological work, Jones said. "They expected something would be here, but I don't think anyone expected El Presidio to be preserved as much as it was."

Attempted repair

The renovated adobe fort had apparently fallen into disrepair and had pretty much disintegrated by the time Mexico ceded California to the United States in 1848. What remained in the Presidio at the time were deemed "mud huts not fit for officers."

The Funston cottages, which were used as officers' quarters during the Civil War, were built parallel to the remains of the rebuilt Spanish adobe garrison in 1863. Some of the original adobe remained standing in Pershing Square until the 1906 earthquake.

The historic officers' club, which is now undergoing a $15 million renovation, is the last remnant of the original Spanish fort. The foundation stones and disintegrated adobe outlining the rest of the giant quadrangle is still underground.

There is good reason the actual ruins of the 1815 garrison will remain buried, officials said, not the least of which is how much it would cost the Presidio Trust to dig them up. Maintaining them and protecting them from vandals, the elements and the large community of gophers in the area would be costly.

Another issue is the fact that lead paint from the row of buildings adjacent to the ruins has contaminated the soil, according to Michael Lamb, the Presidio Trust's historic landscape architect. Consequently, in 2008, the remains were buried and capped in a protective coating.

Lamb said the project, which he expects to be completed in the fall, is to preserve the artifacts underground for archaeologists to study in the future and build removable structures above them that give passers-by an idea of the history buried below.

Explaining to the public

"What we're trying to do here is develop a system that will assist in explaining to the public the layout of El Presidio," said Lamb, adding that the three displays under construction, including a corner section, will likely resemble the wall as it looked nearly two centuries ago when it was a comparatively young ruin. "We don't want an architecturally clean finish. We want to reinforce the notion that the wall extends farther than we can build."

Making the displays authentic is complicated because adobe bricks from the Spanish era were large and measured in varas, which are about 3 inches shorter than yards. In an attempt to get it right, the trust enlisted the help of Egyptian archaeological intern Nabil Fahmy, who has worked extensively on Shunet El Zebib - a ruin in Abydos, Egypt, that dates from the 27th century B.C. and is the oldest known adobe building in the world.

Fahmy searched the Presidio and found the right kind of soil-and-sand mixture to make the mortar. A company in Arizona is making the adobe bricks, which require 90 consecutive hot dry days of curing before they can be used, Jones said.

The project is part of a major archaeological push in the park. Recent excavations have uncovered a wide array of artifacts - 526,000 in all.

"This settlement here was a fort, but when they came, they brought their families, so it was really a little town," Jones said. "One of the only ways we know about the Presidio during these times is through archaeology. We want people to see the mass of the site, the scale of the site," which is why "we have a plan to do long-term excavations followed by treatments like this one."
