BOSTON (AP) – The engineer hired by the state to investigate the leak in one of the Big Dig’s tunnels has called for an extensive review of tunnel maintenance records to determine whether there is evidence of additional water leaks.

Jack Lemley, a consultant on tunnel projects worldwide, said it is too early to tell whether the 8-inch leak that sprung in the northbound lanes of the Interstate 93 tunnel on Wednesday and caused 10-mile backups on the highway, is a one-time event or a sign of more serious problems in the future.

Lemley said he has called in engineer George Tamaro to aid in the investigation. Tamaro designed the foundation walls of the World Trade Center in New York, which held even after the Sept. 11 terrorist attacks.

Tamaro was scheduled to arrive in Boston on Saturday, said Edward M. Ginsburg, a retired judge appointed by the state last year to lead the team reviewing the $14.6 billion project for overcharges by contractors.

“The leak is not necessarily unexpected in a project as large as this,” Lemley said. “But by the same token, you want to be absolutely sure there isn’t a systematic problem, and that is what the project team is trying to establish, that it’s not an extensive problem.”

Workers filled the hole with grout and covered the opening with a 6-foot-by-4-foot steel plate on Friday, said a spokesman for the Massachusetts Turnpike Authority, the agency that oversees the project.

The wall will not be permanently retiled until officials are sure the patch is secure, he said.

Bechtel/Parsons Brinckerhoff, the private consortium that headed construction of the project, released a statement in which it said “Our preliminary assessment is that soil composition unique to that particular location was a major factor,” in the leak.

Lemley agreed that the leak was probably caused by a sand pocket in the tunnel wall. Finding out how that pocket became a part of the wall will be part of the investigation, he said.

“More investigative work needs to be done,” he said. “I don’t think anyone has reached any conclusions yet.”

The leak was the latest in a series of embarrassing episodes in the two-decade construction of the Big Dig.

In January, ice formed in the tunnels, forcing officials to close lanes and jamming up traffic. And in 2001, a leak spouted from under one of six concrete tubes being put in place to carry Interstate 90 through the Fort Point Channel.

The Big Dig replaced the elevated Central Artery of Interstate 93 with underground tunnels through downtown Boston. It also connected Interstate 90 – the Massachusetts Turnpike – to Logan International Airport, and added the Ted Williams Tunnel beneath Boston Harbor.

AP-ES-09-18-04 0237EDT