The San Francisco 49ers’ new Levi’s Stadium and the APM Tunnel Extension at the Hartsfield-Jackson Atlanta International Airport are just two recent projects that called for the proven expertise and experience of the Berkel & Company Contractors Inc. team of professionals. Both projects were prominent in the public eye and both had an added level of complexity that set them apart from the average contract.
Let the games begin
Construction of the new $1.2-billion home of the San Francisco 49ers – Levi’s Stadium – began in 2006. The cutting-edge stadium features 1.85 million square feet, can seat approximately 68,500 fans and offers 165 luxury suites and 8,500 club seats.
One of the more significant features of the new stadium is next-generation design, which includes a 27,000-square-foot green roof and three solar bridges (comprised of hundreds of solar panels) that connect the main parking areas to the stadium. It is expected to be the first United States professional football stadium to achieve LEED Gold certification.
Another interesting feature of the stadium is the fact that it used 3,081 Auger Pressure Grouted Displacement (APGD) piles with lengths of up to 72 feet. Over 3,000 piles were installed during a five-week period, using four displacement piling drill rigs simultaneously.
“We needed 12-yard loads of fluid grout every 10 to 15 minutes for the first 3,000 piles to be drilled into the site in order to guarantee a secure foundation for the stadium,” states Brian Zuckerman, vice-president, West Coast Regional Manager, Berkel & Company Contractors. “If laid end to end, those 3,000 piles would stretch more than 31 miles, almost the same distance between the new stadium and the old Candlestick Park.”
According to Zuckerman, the piles ranged from between 55 to 72 feet in length. Installing the piles took some extra engineering and co-ordination. The auger machines were used to displace the penetrated earth, the rebar cage was put in and the hole was then immediately filled with fluid grout. The timing had to be perfect.
Every APGD hole required approximately four cubic yards of fluid grout.
“It was a perfect execution,” says Zuckerman. “It was very well-coordinated; a real team effort. We had a real spirit of co-operation at every level – from the ownership to the general contractor to all of the design professionals and the trades. Everyone was really trying to make this happen in the quickest and most efficient way possible. It was the best type of working environment to be involved in.”
Cleared for takeoff
The Automated People Mover (APM) Tunnel Extension for the Maynard H. Jackson Terminal at Hartsfield-Jackson Atlanta International Airport was a $1.2 billion expansion project that saw the construction of the new Maynard H. Jackson International Terminal. All of the airport’s international operations have been transferred to the new terminal since its completion in 2012. But the work required to make this a reality was both extensive and complex. And for Berkel & Company Contractors, it necessitated a multi-year, multi-million dollar project that put their proven foundation and shoring support expertise to the test.
“We started the project in 2008,” explains Adam Hurley, regional manager, Berkel & Company Contractors. “It was certainly a complex project, one in which we’re proud to have been involved. It was a design/build project that involved a very team-minded approach on the part of ourselves, the structural engineer and the general contractor in order to get the job done in the most efficient and cost-effective way possible.”
The APM Tunnel Extension necessitated that the APM trains, which are used to transfer passengers from one terminal to another, be extended by approximately half a mile to reach the new International Terminal. Prior to this construction project, the APM tunnel ended at Concourse E.
The project itself involved two major components. The first of these was the construction of the APM extension that required an excavation support system for a 450-foot long and 55-foot deep excavation across Taxiway Dixie. The second required a 900-foot long, 35-foot excavation beneath the basement of the existing Concourse E.
“The biggest driver on this portion of the project was the time that Taxiway Dixie would be closed,” explains Hurley. “The customer was interested in getting it done as quickly as possible because the closure of Taxiway Dixie added about 13 minutes to every arriving and departing international flight. The closure meant that the planes had to take the long way around the terminal to get to their respective gates. As a result, speed was of the essence.”
A “cut and cover” method was chosen as the mode of construction for the APM tunnel expansion. It involved a soldier pile and lagging wall with tiebacks to support the excavation. Approximately 100 soldier piles and over 200 tiebacks were installed in the wall under Taxiway Dixie. The shoring aspect of the work involved installing shoring, where possible, with a top elevation 10 feet below the finished grade to eliminate the need for shoring cutoff – a costly procedure because of the depth of cutoff required.
The shoring system necessitated some demolition of the existing Taxiway Dixie before completion of the work. Additionally, the soldier piles were installed on a 10-degree batter to reduce earth pressures to allow for the use of smaller piles and fewer tiebacks.
“We had one shift working six days a week,” states Hurley, who estimates that the APM Tunnel Expansion took about seven weeks in total to complete. “The work required that we install the shoring right up to the active plane gates, which made it a bit more difficult. We had to keep the planes in service at all times. There were two instances, in particular, where the excavation work was within 50 feet of the plane gates. We also had to use shoring to support one of the airport’s main fuel lines and a portion of its utility bridge.”
Confines of Concourse E
The excavation work under Concourse E was made more difficult for a couple of reasons. One, it was a confined space with limited headroom. And two, it included the exposure and underpinning of much of the deep foundations below the concourse.
“We had to support the structure from underneath in order to complete the 30 foot excavation work,” explains Hurley. “The original structure support consisted of Auger Pressure Grouted (APG) piles that were installed in the early 1990s.”
Hurley goes on to explain that the excavation work took place in what was initially the baggage handling area.
“It would have been more efficient to have the entire area open for us to work in but we had to deal with only one small area at a time in order to keep the baggage handling system operational,” he says. “This greatly increased the amount of time we needed to do the work.”
The support system used a combined approach of soldier piles and lagging wall with tiebacks, with hand-dug underpinning piers around the majority of the 36 existing columns to minimize the number of exposed columns requiring support.
“We initially planned on having to deal with about seven or eight of the original columns but we were able to re-configure our work to reduce that number to four,” adds Hurley.
Shotcrete was applied to protect the existing auger-cast piles exposed during the excavation. Additionally, steel pipe piles with walers and tiebacks were installed where the bays between the columns were particularly long.
The new support system included over 100 hand-dug underpinning piers as deep as 50 feet, approximately 40 soldier piles and over 400 tiebacks.
Solidifying a reputation
With two high-profile projects under their belt, the Berkel & Company Contractors team of professionals have solidified their reputation as a capable and versatile provider of deep foundation support systems. The company’s work on the San Francisco 49ers’ Levi’s Stadium and the APM Tunnel Extension at the Hartsfield-Atlanta International Airport have brought to the fore the company’s ability to handle projects of any size and complexity. Better yet, they have managed to bring to fruition two significant projects that will be enjoyed by North Americans for many years yet to come.