Weather No Setback for CVC

Posted January 15, 2003 at 6:44pm

By Suzanne Nelson Roll Call Staff A wetter-than-anticipated winter has not slowed progress on construction of the Capitol Visitor Center, according to officials, and the second phase of the massive project is set to begin soon.

Behind the noise-resistant glass shielding East Front offices and the perimeter fence obstructing the view, work is humming right along, those overseeing the creation of the complex say. A new truck tunnel designed to bring deliveries to the Capitol underground is moving forward rapidly. Foundation walls are going in every day, and the roof slab for the new structure is expected to be in place by late summer. The “Sequence Two” contract — which includes electrical, mechanical and finishing work — will be awarded in late February or early March.

All of these elements add up to the subterranean center still being on track to become operational in time for the 2005 presidential inauguration.

“We have at times been working 24 hours a day” and seven days a week, said CVC project spokesman Tom Fontana.

One motivation for the stepped-up schedule has been the recent heavy precipitation, which has far exceeded what was forecast for the season, Fontana said. Heavy trucks hauling material to and from the worksite were getting stuck in the mud despite the use of gravel to provide traction.

“Fortunately, [the soil] is a clay material that doesn’t allow a lot of permeation,” he added, but some of the water pooled on the East Front still hasn’t dried.

Work was also stepped up during the winter recess to get as much done as possible when Members of Congress weren’t in town. Project managers target as much utility work as possible for periods when few of the Hill’s tens of thousands of workers are at their desks, in case power or water lines are accidentally cut. Fontana said such work has been particularly challenging on this project because of a lack of accurate historical records covering utility systems.

Last October, project managers forecast that trucks would soon be making 500 trips a day on and off the East Front Plaza, hauling dirt to make way for the 580,000-square-foot center. That volume of traffic has yet to materialize, but Fontana said the frequency of trucks rumbling across the plaza will increase dramatically before long.

“Two months from now, this will look quiet,” he noted, referring to the relative calm now prevailing on the East Front. “By this summer, the site will be excavated to 50 feet.”

Thus far, only about 6 to 8 feet of soil has been excavated. Because of the proximity to the Capitol, the foundation walls have to go in before Capitol Hill’s version of the “Big Dig” can begin.

The process involves the removal of soil to a depth of approximately 8 feet along the perimeter of the CVC “footprint” to allow for the construction of guide walls — two 18-inch-wide concrete slabs spaced a few feet apart. A large “clamshell” bucket is then to be lowered into the gap between the walls and used to excavate a narrow trench to a depth of 70 feet. A muddy mixture known as slurry is then to be poured into the trench as the soil is removed, maintaining the stability of the trench until a steel rebar cage is placed into the trench and concrete is poured. The concrete displaces the lighter slurry, which is removed and reused later.

The epoxy-coated rebar cages are equipped with tubing that could serve as a conduit for grout if cracks in the foundation need to be repaired in the years ahead. Some of the tubes will also have an inclinometer to detect potentially damaging shifting of the walls.

The slurry process is often used on irreplaceable historical buildings in Europe because it minimizes disruption to adjacent structures.

The walls are about 60 percent complete on the Senate side, while the process has just begun on the House side of the plaza.

In the coming months, 30 to 40 trucks will each be making six to eight trips a day to remove 600,000 cubic yards of soil, Fontana said. (Each truck is rinsed before it leaves the East Front Plaza to prevent dirt from littering the streets.)

With the near-constant beeping of trucks backing up, this will probably be the most disruptive phase of the project. But the noise-reduction windows on the East Front seem to be doing the job: Fontana said there have been no noise complaints thus far.

In some respects, work on the truck tunnel is less complicated because slurry walls aren’t necessary. The entrance to the tunnel will be along New Jersey Avenue Northwest and will attach to the CVC on the Senate side. In the next few weeks, a 50-foot silo will go up on the south side of Constitution Avenue to prepare the cement.

“We hope to be using the tunnel” for the second sequence of the project, set to begin later this year, Fontana said, describing the tunnel as a “more secure, certainly more aesthetically appropriate” way to receive deliveries.

Though the passage will be 70 feet beneath Constitution Avenue, the busy thoroughfare will never close entirely. For the next month, the street will be reduced to two lanes between 8 p.m. and 6 a.m. to allow crews to complete utility work and install beams for the tunnel. The sidewalk along Constitution Avenue has been cordoned off, but a walkway was created with Jersey barriers along the street.

The parallel parking along that portion of Constitution was also eliminated, but the spots have been made up in other areas. Approximately 80 temporary spots on the West Front lawn and 55 spaces near the Taft Tower between Louisiana and Constitution avenues were created for Senate staffers. Parallel parking spots along the north and south drives and in other areas were restriped to be diagonal, creating more spaces. Additionally, Member parking on the House and Senate sides has been reconfigured to make up for lost spaces on the Plaza. The spaces will be restriped again when the weather warms up, creating even more. (The weather needs to be warmer for the yellow paint to dry properly.)

“There has been no net loss so far in parking,” Fontana said.