A precast concrete utility tunnel was the solution for one of the world’s largest drug manufacturers.
By Fernando Pagés Ruiz
Eli Lilly and Co. grew from a tiny laboratory in Indianapolis in 1876 to become one of the world’s largest pharmaceutical companies with more than 31,000 employees in 170 countries. Despite this international profile, Lilly keeps its headquarters near the company’s spawning grounds at the “Crossroads of America,” where the company recently completed a $55 million expansion to accommodate more than 300,000 square feet of new laboratories and manufacturing facilities.
The freshly remodeled Lilly Technology Center sits at the historic hub of Indianapolis where four national highways once converged. Kentucky Avenue, which runs through the heart of the center, used to carry most of the city’s east-west traffic. As a tribute to this highway, Lilly decided to preserve portions of the old road as a park-like, pedestrian thoroughfare. If you take a stroll across the Lilly grounds, you won’t feel like you’re walking through a bustling industrial plant. The ambiance resembles a college campus with its broad, green lawns and curvilinear paths paved in cobblestone mined from old Kentucky Avenue.
Lilly had to find a way to bury new utility lines for its expansion buildings while providing a means for repairs and upgrades that did not require digging up the grounds. The company decided to build a tunnel that could house plumbing and telecommunications lines while providing ready access for maintenance and future additions. David Broekers, P.E., the project manager for Ter Horst, Lamson & Fisk Inc., consulting site and civil engineers, had the task of selecting the best materials to construct a 1,000-foot-long tunnel for utilities, personnel and material transfer between buildings. Broekers’ selection criteria included three critical requirements: lowest cost, speed of construction and durability.
Broekers contemplated cast-in-place concrete construction, Utilidor (a hot-dipped galvanized corrugated steel pipe made for utility tunnels) and precast concrete. He quickly dismissed the galvanized corrugated pipe option because, despite a coating of bituminous mastic on the exterior of the pipe, even galvanized metal will eventually corrode. Cast-in-place concrete offered design flexibility and durability, but Broekers was surprised to discover that Hartford Concrete Products Inc., Hartford City, Ind., could supply high-quality precast concrete tunnel sections with factory-installed steel pipe racks at a lower cost – even before factoring in time saved and quality assurance. This, plus the reliability of precast concrete as a product manufactured off-site and Hartford’s willingness to deliver tunnel sections on schedule for installation, made Broekers’ decision easy.
The best of both worlds
One concern raised over the use of a manufactured product, whether it be corrugated steel pipe or precast concrete, was fit. Since the tunnel connected existing and new facilities in five discrete locations, every component had to match exact specifications. To ensure a perfect fit, engineers designed the tunnels with precast concrete sections and cast-in-place concrete at the connecting points. Precast concrete worked well in combination with cast-in-place concrete, whereas a corrugated steel tunnel would have required a more challenging connection. Despite the concern for critical connection points, Hartford came within one-eighth of an inch in 1,000 feet, says Greg Stutz, vice president of business development at Hartford.
It turns out that precast concrete also had an advantage only the Farmer’s Almanac could have predicted: During spring 2003, while Shiel Sexton, general contractor in Indianapolis, installed Hartford’s precast concrete tunnel sections, Mother Nature hit Indianapolis with two unprecedented floods in as many months. “It was one of the rainiest years on record; the White River overflowed its banks twice,” says Phil Hall, field representative for Hartford. The tunnel excavation filled with surging water and the ground under the tunnel washed away. As a self-supporting structure, the precast concrete sections suffered only minor damage. “A little backfill and construction continued,” says Hall.
The off-site manufacturing of tunnel sections offered by precast concrete allowed work to proceed in crowded conditions without extra storage and staging requirements. Workers could install about 40 feet of tunnel each day, and Hartford delivered sections as needed.
Space, safety and convenience
Each precast concrete tunnel section consisted of two parts: a U-shaped base and a lid. The sections measured 10 feet in length, 7 feet in width and 9 feet from floor to ceiling. The U shape provided more floor space and headroom than a round, galvanized corrugated pipe tunnel could offer. A flat concrete base coated with non-slip paint allowed plenty of room for pipe racks, spaced every 10 feet, which served to suspend cables and utility lines, as well as a 3-foot corridor in which to walk and transport materials.
Safety concerns for toxic fumes and the high volatility of welding gases forced pipe fitters to weld their connections outside the tunnel, says Charan Ahluwalia, coordinating project manager for applied engineering services, which designed and oversaw the mechanical and electrical installations. The factory-installed utility racks, a ladder-like structure of concave rollers designed to hold various diameter pipes, ranging from telecommunications conduit to 12-inch diameter steam ducts, allowed the pipe fitters to weld sections together outside and feed the pipeline through the underground tunnel as if fishing electrical wires through conduit. Since Hartford installed the pipe racks at its plant, the mechanical contractors did not have to wait for workers to bolt the racks in place on site, “which avoided errors and saved time on the job,” says Ahluwalia.
Because the tunnels might have to resist the weight of fire trucks in an emergency and, in one location, a bus line’s turnaround point, engineers required all the precast concrete sections to meet HS-20 live load and impact standards as specified by the American Association of State Highway Transportation Officials (AASHTO). In other words, “Anything that can travel on a superhighway can go over this tunnel,” says David Broekers, structural project manager.
Although the density and strength of factory-cured precast concrete assures a virtually watertight structure, Hartford treated each section of tunnel with a factory-applied coating of concrete sealant. To fit the sections without leaks, Hartford designed connections with “bell and spigot ends” that slide together somewhat like a carpenter’s tongue-and-groove joint. Mastic and rope sealant supplied by Concrete Sealants Inc., New Carlisle, Ohio, with an impermeable wrap over each joint finished the seal. “And it sure was nice to have the comfort that, when these pieces came on site, they were ready to go,” says Broekers.
If any project had good excuses to come in late and over budget, this one did. But in the end – despite two floods – the precast concrete tunnel sections saved Eli Lilly about one-third the price of cast-in-place concrete and helped complete the job. Precast will provide the company with a durable underground corridor to access its utility infrastructure for repairs and upgrades without having to disturb the tranquility of its sprawling campus.