Underground surprises and neighboring, above-ground construction projects have combined to complicate construction of an entry vestibule and the transformation of a city street into a pedestrian plaza for the Federal Reserve Bank in St. Louis.

The $80 million project, which will also encompass an offsite screening facility for security, the purchase of an existing parking garage and a five-story addition to the bank building in future phases, began in April 2004. Work in and around the bank building will continue through 2009.

The project downtown was prompted by security concerns. Built in the 1920s in a busy neighborhood, the Federal Reserve building no longer meets security requirements.

"Perimeter and distance are the easiest ways to become a lot safer," said Rob Forney, project manager for St. Louis-based The Lawrence Group, design architect for the plaza, vestibule and parking garage portions of the project.

In order to create a safety perimeter in an urban location, the bank bought one block of a city street to create a public plaza in front of the building. It also bought the land for one lane of traffic on the streets around the remainder of the bank.

advertisement

Excavating Old St. Louis

Digging into old, urban thoroughfares is not a simple task.

Eric Zimmerman, project manager for St. Louis-based Volk Construction, the general contractor on the vestibule and plaza, said there were, "a tremendous amount of unknown conditions" involved with turning the one-block length of city street into a pedestrian plaza.

"There were abandoned trolley tracks discovered, which had to be removed," he said.

"Then we found abandoned ammonia vaults that were used in early 1900s for cooling buildings."

The vaults, which had been emptied of ammonia, were essentially large concrete boxes buried outside the buildings they had once cooled. The vaults also had to be removed-a complicated process because they had backfilled with rocks and gravel.

"There were a tremendous amount of undiscovered and abandoned utilities in the ground, as well as some asbestos that had to be abated," Zimmerman added.

Relocating Utilities

The biggest headache lay in the active utilities that were relocated.

"We had to relocate pretty much every utility in St. Louis," Zimmerman said. Beneath the street lay high-pressure steam mains, sewer and water mains, electrical duct banks, high-pressure gas lines and fiber-optic telephone and cable lines.

The utilities served several nearby multistory buildings, the St. Louis Arch and a nearby entertainment district. Utility relocations had to be accomplished without any interruption of service to the customers of the various utilities.

The exact location of some of the utilities was unknown.

"Because the site had been a city street since the 1800s, the documentation from utility companies left a little to be desired," Zimmerman said.

Volk worked out an arrangement with the subcontractors through which every firm that needed excavation services would use the same excavation company.

"If the electrical people would have had to have a trench dug for a duct bank at the same time as the sewer guys would have been having their trench dig, it would have impossible," Zimmerman said.

Each subcontractor's contract was negotiated to share excavation services by Midwest Excavation of St. Louis.

Shutdowns for utility switchovers were done during off-hours, although that presented some issues as well.

"The St. Louis Cardinals were in the World Series, and we are three blocks from the stadium, so we couldn't do any shutdowns during games," Zimmerman added.

Some utilities required special care. Before the high-pressure steam lines could be brought on line, for instance, the final welds had to be completed and then X-rayed.

Then, the X-rays were inspected and OKed so the switchover could begin. Some switchovers required crews onsite for 24 hours in a row.

The underground surprises added time to the schedule, extending the completion date to the end of September.

"We were fully expecting worse delays," said Zimmerman, who added that the team effectively completed nine months of additional work in about five months.

The plaza project was further complicated by the two other large construction projects-a parking garage and security building-under way on buildings on the street/plaza, both requiring site access and equipment.

"The Federal Reserve Bank owned the street, but it was in our best interest to play nice with everyone else on the other jobs," Zimmerman said.

Schedules were integrated, space was shared for cranes and other equipment and site access was watched.

"We made quite a few concessions in how our job was staffed, in terms of working times, to get out of their way, and they also got out of ours," Zimmerman said.

Accommodating Aesthetics

The construction of a new, high-security entry vestibule to the 1920s bank building was an aesthetic issue.

"We had to use modern construction methods to make the stone exterior of the new vestibule read as a traditional, exterior bearing wall," project manager Forney said.

Although security concerns prevented Forney from discussing many of the structural details of the vestibule, he said that the exterior of the three-story, 1,500-sq.-ft. structure was designed to look as original to the building as possible, in both materials and massing.

Zimmerman added, "We had to get the vestibule to integrate seamlessly with the 1920s, hand-carved limestone and make it look like a natural extension of the building."

The quarry that produced the limestone nearly a century ago is no longer in operation, and so an extensive, international search was conducted for matching limestone, which was obtained from Indiana. Italian marble was obtained that matched what was found in the building.

"We came extremely close in our match and we also cleaned the existing building, which helped," Zimmerman said.

The interior of the vestibule also mimics the stately, original lobby of the bank building.

"The concept was to include the security requirements they needed but blend it with the traditional look of the original bank interior," Forney said. "It's not often that we get to use that kind of design palette."