The Capitol's big dig is turning into a long slog.

A fresh round of problems has slowed progress of the three-story subterranean visitor center under construction on the east side of the Capitol. According to the latest oversight report by the Government Accountability Office, released July 14, the $500 million-plus facility may not be ready to receive tourists until March 2007, as opposed to September 2006, the current target date.

The GAO found that the Architect of the Capitol's office and its construction contractors are missing deadlines because of their own mistakes as well as circumstances beyond their control. "We've got some issues that have come up," architect Alan M. Hantman told a Senate appropriations subcommittee last week.

One is the utility tunnel being built along the first block of East Capitol Street. Construction of the tunnel is running five months behind schedule, the GAO found, in part because of problems with antiquated water line valves. Further delays could have "significant adverse effects on other project elements," the report found. But the steps needed to accelerate the tunnel's completion -- extra labor, for instance -- could add to the project's cost, already far higher than Congress had intended to spend.

Inadequate coordination with fire inspectors has led to more than $3.5 million in safety-related contract modifications, the GAO found. The architect's office recently spent $90,000 to redesign the mechanical system in the tunnel to the Library of Congress in order to meet fire safety requirements. To prevent further problems, a fire safety official is now present in the project office twice a week.

"Hopefully we can work more closely together," Hantman told senators.

Another thorny area is the extensive stonework inside the facility and on the East Front plaza -- essentially the roof of the 580,000-square-foot center, which also functions as the Capitol's main entrance. Paving stones were laid on the plaza so it could be used for President Bush's second inauguration, but the report found that many of stones must be replaced because of quality problems and damage after installation.

More seriously, an ongoing legal dispute between project subcontractors has delayed deliveries of sandstone, a primary construction material. That disruption alone has pushed back the opening date by 24 days, the report found. Visitor center project executive Bob Hixon assured senators in last week's hearing that the judge involved in the case was aware of the problem and was taking action to put Capitol deliveries back on track.

But GAO assistant director Terrell Dorn told the Senate there was no indication that stone deliveries would resume at an adequate pace anytime soon. It is possible that a second supplier could be sought, "but what cost is that going to be?" Dorn said. "Someone can't start up immediately and produce the stone that you need. And second, it would be a non-competitive procurement, so you've got an additional cost risk there."

Initially, the center was supposed to cost about $265 million and open in time for last January's inauguration. But those targets slipped after the Sept. 11, 2001, terrorist attacks, when Congress signed off on extensive security improvements along with additional House and Senate office space.

Members of Congress raised few concerns about the project in the early days, when its main intent was to enhance the experience of the 3 million tourists that the Capitol attracts yearly. But as the years rolled by and the dump trucks and bulldozers continued to roll across the once peaceful and park-like East Front, the regular requests for additional funding began to rankle lawmakers. They began to complain about the ever-shifting completion date and the center's many amenities, including two orientation theaters, radio and television facilities, a 600-person dining facility and an exhibition gallery.

The center was supposed to be partially funded with private donations, but that effort fell flat. Meanwhile, the scope expanded with the addition of the House and Senate office space and a tunnel to the Library of Congress, widely criticized as unnecessary. As the cost ticked up and the delays mounted, members became incensed. Citizens Against Government Waste declared it a "five-acre money pit."

"The construction of the Capitol Visitor Center has been a story of serious mismanagement and colossal government waste," grumbled Rep. David R. Obey (Wis.), senior Democrat on the House Appropriations Committee. Obey is especially annoyed that the facility will provide little new meeting space for members. "This is because the real work of Congress was not a primary consideration in its construction."

The GAO now predicts the visitor center will cost as much as $559 million, depending on what snags lie ahead. As of July 11, 2005, Congress had provided about $483.7 million for visitor center construction. The architect has sought an additional $36.9 million for fiscal 2006, which begins Oct. 1.

That request includes $4.2 million to add congressional seals, an orientation film -- presumably for the orientation theaters, and storage space for backpacks, the report found. But the GAO warned that given the current pace of change orders, the architect's office is likely to need an additional $5 million to $15 million for fiscal 2006.

Progress on the Capitol Visitor Center has been slowed by a rash of problems, including inadequate coordination with fire inspectors, delays in delivery of materials and complications arising in the construction of a utility tunnel.