SAN FRANCISCO -- Bay Area Rapid Transit officials unveiled a new earthquake retrofit plan Sunday for the Transbay Tube -- one that will allow the popular farmers market at the Ferry Building to stay open during the project's construction.

BART spokesman Linton Johnson said the project was necessary because there is "a 62 percent chance of at least one 6.7 or greater magnitude earthquake happening within the next 30 years" and he said currently, BART is not completely prepared.

According to Johnson, because the tube runs directly beneath the Ferry Building, previous retrofitting plans were thought to have to cause the Ferry Building and Farmers Market to be closed during construction.

He said the new plans allow the building and market to remain open.

While Johnson said there is no need to retrofit BART stations, the Transbay Tube, which opened in 1974, is located beneath the bay and "if the tube moves in an earthquake, the joints connecting the tube to land can move 360 degrees of rotation."

"However, if it moves too far joints could break and cause a leak," Johnson said.

According to Johnson, there were 1300 people in the Transbay Tube when the Loma Preita earthquake occurred, but because the earthquake did not take place on a nearby fault, passengers did not experience any difficulties.

"If that same earthquake were to happen in the Bay Area, especially on the Hayward fault which is the next fault scheduled to erupt according to geologists, there would major problems that would shut down the system for years," Johnson said.

Each weekday, nearly half of BART's 325,000 riders pass through the Transbay Tube, and while Johnson said few people are likely to be in the tube during an earthquake, retrofitting should assuage passengers' fears during the approximately four-to-six-minute journey.

Johnson said retrofitting on the Oakland side of the Transbay Tube began in April, with the award of a $9.2 million contract to Condon Johnson & Associates and is part of a 10-year Earthquake Safety Program, costing $1.3 billion.

According to Johnson, retrofitting plans include compacting the soil surrounding the tube so that it will be less likely to move in the event of an earthquake.