Two white lines on Eastlake Avenue East indicate exactly where a new tunnel now runs through it. It wasn't bored by Bertha—or anything resembling the massive machine poised to dig a highway beneath downtown Seattle.
"This tunnel was essentially dug by hand," said Al Spencer, senior project manager, referring to all 79 feet of it—from the P3 garage level in the 1100 Eastlake Building to the boiler room and mechanical space in the Weintraub Building.
The tunnel is the first of several projects to provide safe access and unite 1100 Eastlake with the rest of the Fred Hutchinson Cancer Research Center campus.
"The tunnel is funded by long-term, tax-exempt bonds that were issued to purchase 1100 Eastlake, build out all labs and offices, and construct the tunnel and skybridge," said Randy Main, vice president and chief financial officer. "These remaining construction funds are held in a special trust account and can only be used for the stated purpose—to fund the tunnel and skybridge."
When the new tunnel is complete in July, it will be small and strictly utilitarian—nothing like the comparatively cavernous underground connections between some of the other campus buildings.
Excavation took approximately nine weeks, a process Spencer describes as laboriously slow, but—using laser-beam guidance—precise.
Tunneling began in late January on the 1100 Eastlake side. The initial effort focused on creating a temporary structure to enable the construction of the actual concrete tunnel. Workers built a thickened concrete wall in the garage, then, on the P2 level, drilled an arch of spiles—pipes that extended underground across the street and contained openings. Through each opening they ejected grout into voids in the soil, forming a canopy beneath which they could dig.
"There were a lot of pieces in motion," said Spencer, a civil engineer. "It was not a simple project.
"You've got this machine with a guy using a joystick controller, and he's moving a shovel. You're doing baby steps. You can't dig too far because you have to reinforce everything with steel ribs, plates and grout to prevent the soil from collapsing. The small width of the tunnel also required alternating between the equipment used to dig and the equipment used to remove the dirt," Spencer said.
An unexpected run-in with rock
The work crew anticipated running into a sandy, watery layer of earth near the Weintraub Building. What they didn't expect, 8 feet away, was to hit granite—a boulder so large it had to come out in pieces. Workers used a Bobcat loader to haul out a total 630 cubic yards of dirt along with the rock.
'Tunnels don't just happen;' this one took multiple teams
Prior to the big dig, even more pieces were in motion on the campus side. Last summer, in preparation for the tunnel to break through and become a bridge in the Weintraub boiler room, Fred Hutch engineers and contractors shut the boiler room down for the first time ever. "We had to find the warmest days and, more importantly, warmest nights of the year so we could turn everything off without compromising research," said Bob Cowan, director of Facilities Engineering.
The three-day, round-the-clock shutdown enabled Cowan's team to relocate major hot water lines, pumps, tanks and fuel lines that supply the Weintraub and Hutchinson buildings. It got even more complicated earlier this year.
"As the tunnel inched closer to Weintraub, we had to relocate virtually the entire power supply to Weintraub and Hutchinson to accommodate the bridge being built in the boiler room," Cowan said of the process, which involved major electric shutdowns at night and on weekends. "Moving the electrical feeds was kind of like untangling a kite string a little bit at a time."
"Tunnels don't just happen," Cowan said. "Thanks to a well-coordinated effort on the part of the planning team, the design team, the construction team and engineering teams, this one is going in with minimal impact to the Center's research mission."
Crowning touches for the tunnel
Today, 18 feet below Eastlake Avenue East, the tunnel is almost complete. Workers have just finished putting concrete in the arched crown of the structure. A team is also framing the elevated bridge in Weintraub—a structure capable of opening to allow the passage of large equipment.
The finished tunnel and elevated walkway will be 7 feet, 2 inches wide and just under 8 feet high. The ceiling will be lower in areas where original boiler room piping could not easily be moved.
"Yes, the tunnel is small," said Spencer. "And it's not intended to be pretty. Its purpose is strictly practical."
Facilities & Operations and Facilities Engineering would like to thank contractors involved in this project including: Turner Construction, Frank Coluccio Construction, University Mechanical Contractors and SASCO.
Structure will enhance safety and unify the campus; construction will begin in August and be complete early next year
Last fall the Seattle City Council approved the construction of a skybridge to connect the 1100 Eastlake Building with the Weintraub Building on the Hutchinson Center campus.
The skybridge will span Eastlake Avenue East and connect the third floor of 1100 Eastlake to the third interstitial floor of Weintraub. Safe movement of faculty and staff between parts of the campus divided by the busy street was a paramount concern for Center leadership, said Scott Rusch, vice president of Facilities and Operations. Work on the skybridge is scheduled to begin this August and be complete early next year, Rusch said.
The city council's approval of the project includes a crosswalk with a stoplight activated by pedestrians. The crosswalk will increase pedestrian safety at the street level while the tunnel directly below will ease the movement of materials between labs.
Seattle has an ordinance against the construction of new skybridges. In fact, cities across the country have been removing skybridges because the reduction of street- level foot traffic can negatively affect business owners.
"To gain approval, the Center had to show how our proposed skybridge would serve the greater public good. We proved that public benefit," Rusch said. "Many Center departments and individuals made critical contributions to the process, including Communications, Facilities and Operations, and the General Counsel's Office."
In addition to building the skybridge, Fred Hutch will provide other public enhancements in the area, including a hill climb to connect Eastlake Avenue East to Fairview Avenue North.
"Seattle Mayor Mike McGinn and the city council have always supported Fred Hutch and this is an extremely important example of their support," Rusch said.