Innovative Port of Miami Tunnel Reaches Completion
Envisioned for more than 30 years, the Port of Miami Tunnel project involves the construction of twin tunnels, 4,200 ft in length and 39 ft ID, connecting Watson Island and Dodge Island in Biscayne Bay. After a ceremonial opening on May 19, the tunnel opened to traffic on Sunday, Aug. 3, 2014.
The tunnels allow port traffic on Dodge Island direct access to the existing highway system, bypassing busy surface streets in downtown Miami, which are typically congested with more than 16,000 cargo trucks and cruise traffic each day. In addition to improving access and enhancing traffic flow to and from the port, the project improves quality of life for Downtown Miami, and promotes economic development for the entire area.
Challenges associated with the project included keeping the port operations open at all times while constructing tunnels under the Government Cut channel in complex geology that required extensive ground improvement to allow tunnel boring operations, as well as constructing in very close proximity to busy MacArthur Causeway, which also had to remain open without disruption. Additionally, the Port of Miami Tunnel project is unique in the United States in that it is among the first to use a public-private partnership approach with the private partner – MAT Concessionaire LLC – providing a portion of the financing as part of the project.
The Port of Miami Tunnel was needed to provide a direct access between the seaport, I-395 and I-95, and to create another access to PortMiami besides the Port Bridge, which is currently the only connection to the mainland. These improvements are intended to keep PortMiami – the county’s second largest economic generator and one of the busiest ports in the county – competitive. Completion of the tunnel goes hand-in-hand with port improvement projects to dredge the channel and enhance rail cargo capacity to accommodate Post-Panamax ships.
Several alternatives were developed and considered in the 1980s, including reconfiguring roadways, building a high-level bridge over the channel and a no-build option. In 1990, the Federal Highway Administration (FHWA) declared tunneling to be the most effective option. Based on engineering and environmental criteria, a tunnel was deemed best for improving safety and reducing traffic congestion. Tunneling also creates no significant long- or short-term environmental impacts and has no long-term effects on marine navigation.
To construct the project, the owner, the Florida Department of Transportation (FDOT), developed a public-private partnership (PPP or P3) project delivery approach. PPPs are uncommon in public-sector tunnel construction in the United States, but are fairly common in other markets and internationally. In using a PPP, the owner and contractor/service provider can tailor the contract to meet unique requirements of the parties involved. In this case, the owner wanted to share risks with contractors who were experienced in managing tunnel construction projects, tap in to the private-sector innovation, and have an infusion of private cash to help fund the project.
FDOT selected a full P3 contracting scheme, design-build-finance-operate-maintain (DBFOM) in which the private partner finances, designs and constructs the tunnel, and operates and maintains the finished facility. At the end of 2044, the private partner will return the tunnel to FDOT in first-class condition. According to FDOT, this type of contracting mechanism is ideal when the public agency does not have the full funding in place to construct the project. The private financing allows the construction to proceed and deliver the project earlier. Meanwhile, the stipulation that the tunnel be returned in first-class condition provides incentive for the private partner to keep the tunnel up-to-date.
FDOT graded the proposals with a technical and price component. In addition, the proposers were required to be able to finance portions of the project with the expectation of payment upon achievement of specific milestones and performance annual payments during operation and maintenance.
In 2006, FDOT issued a request for qualifications and short-listed proposers later that year. The project was awarded to MAT Concessionaire LLC, with Bouygues Civil Works Florida (BCWF) Design-Build contractor and 10% equity partner. The contract was signed on Oct. 15, 2009 (Notice to Proceed), and construction began in May 2010. The 43-ft diameter Herrenknecht EPB TBM arrived in pieces on June 23, 2011; began the eastbound tunnel on November 11, 2011 and completed it July 31, 2012. The westbound tube mining commenced on October 29, 2012 and was completed on May 6, 2013.
Building the POMT
The geology for the Port of Miami Tunnel is complex and challenging. The soils consist of weak rock and soft ground conditions – including silts and manmade fills – along with porous limestone. BCWF performed a complementary geotechnical investigation report wherein it identified zones in need of ground improvements by the means of conditioning and formation grouting. Additionally, BCWF used ground-freezing techniques for the construction of two out of the five cross-passages. The ground freezing was performed by Moretrench based on a design by Bouygues. It is a first in Florida and the first time freezing has been used in the United States for cross passages.
The highly dissolved coralline limestone layer required an extensive grouting program to be performed ahead of the TBM drive in order to reduce the porosity and permeability of the ground a to mine safely without confinement pressure. Nicholson Construction performed this formation grouting program using a unique thyxotropic grout that was also developed by Bouygues for the specific conditions. Time-restricted by the port’s busy cruise ship schedule, the program was executed both on-shore, over-water and inside buildings, consisted of over 1,000 holes – more than 18 miles of drilling and 65,000 cubic yards of grout – and at that time was the largest formation grouting program ever performed in the United States.
The highly porous and permeable ground conditions throughout the tunnel alignment did not permit the traditional routine TBM cutterhead inspections and maintenance. To meet this challenge, Malcolm Drilling constructed several refuge chambers at pre-determined locations on the alignment using cutter soil mixing (CSM) panels in order for BCWF’s TBM team divers to safely access the cutterhead.
Additionally, Malcolm performed Shallow Soil Mixing to a depth of 23 ft along the first 510 ft on Watson Island and 575 ft on Dodge Island due to the lack of ground cover for the initial sections of the tunnels and the geology. Because of limited project right-of-way along the alignment and to improve future traffic flow, the tunnels were brought together at both ends into one single shaft, which resulted in a separation between the tunnels of only 14 ft at break in/out. To ensure that the tunnels remained stable during construction, Cutter Soil Mixing columns were implemented, by Malcolm, between the tunnels over a distance of 820 ft on Watson and 740 ft on Dodge.
About a third of the overall tunnel alignment of both tubes’ geology was extremely porous rock. Safe mining through this challenging geology was accomplished using an innovative water pressure balance/control mode on the TBM – Water Control Process (WCP); making this the first-ever hybrid TBM.
With the completion of the eastbound drive on July 31, 2012, the 410’ TBM had to be turned in a very constricted space; its 1,500 ton shield was pivoted using a specially designed turn-table system in the shaft on Dodge Island and re-launched heading back toward Watson Island. This eliminated the disruption to port and general public associated with the original concept of returning the TBM to the initial launching shaft at Watson.
Installation of the internal structures, fire proofing, architectural panels, Mechanical-Electrical-Plumbing-Fire (MEPF) elements, ITS, MEP and other internal components began during the second bore, and was full speed after the TBM completed mining in May 2013. After only a few weeks’ delay due to jet fan and drainage pipe issues, the tunnel was successfully opened to traffic on Sunday, Aug. 3, 2014.
For global conglomerate, Bouygues Construction, the design-build contractor and 10 percent equity partner of the P3, this was an important and inaugural project. Project Executive Louis Brais on behalf of Bouygues and the project’s thousands of workers stated, “Bouygues put together the best team of engineers and labor to find and implement efficient solutions to this project’s many challenges, all of which proved to be successful. We stopped at nothing and delivered everything, as promised. We are very proud to leave this legacy in Florida and the U.S.”
The Tunnel Achievement Award is presented in conjunction with the Colorado School of Mines’ Tunneling Short Course Sept. 15-17 in Golden, Colo. The presentation will take place during the dinner banquet on Sept. 16 at the Golden Hotel. For more information on the Course or to register, click here.