State-Of-The-Art Portmiami Tunnel Raises the Bar for Tunnel Construction in North America by Jim Rush

COVER STORY Photo by Daniel Azoulay – Courtesy of BCWF THINKINGCOVER STORY STATE-OF-THE-ART PortMiami Tunnel Raises the Bar for Tunnel Construction in North America By Jim Rush hen you think about state-of-the-art tunneling existing highway system and bypass surface streets downtown, projects, places like New York, San Francisco which can become congested with cargo trucks and cruise line and Los Angeles immediately jump to mind. buses. In addition to enhancing traffic flow to and from the port, These urban centers, after all, are home to mass the project will help improve quality of life downtown and promote Wtransit systems that weave their way near the surface through development. Envisioned for more than 30 years, the tunnel is well densely populated cities and in proximity to existing buildings under way and is on schedule to open to traffic in 2014. and utilities. And while some of the projects under way or Challenges associated with the project include keeping the in the planning stages in these areas are indeed pushing the port operations open at all times while constructing tunnels limits of tunneling technology, the PortMiami Tunnel is faced under the Government Cut channel in complex geology that with its own set of challenges in an area that has never seen required extensive ground improvement to allow tunnel boring mega-tunnel projects. operations. Additionally, the PortMiami Tunnel project is The PortMiami Tunnel project involves the construction of unique in the United States in that it is among the first to use a twin tunnels, 4,200 ft in length and 39 ft ID, connecting Watson public-private partnership approach with the private partner – Island and Dodge Island in Biscayne Bay. The tunnels allow traffic MAT Concessionaire LLC – providing a portion of the financing generated by the Port, located on Dodge Island, to flow into the as part of the project. 16 tunnelingonline.com JUNE 2013 COVER STORY ENTERING INTO A PPP PROJECT BACkgROUND sector tunnel construction in the United States, but are fairly common in other Every project delivery mechanism comes The PortMiami Tunnel was needed markets and internationally. In using a with pros and cons. When considering a to provide a direct access between the PPP, the owner and contractor/service public-private partnership, the decision- seaport, I-395 and I-95, and to create provider can tailor the contract to meet making process can become even more another access to PortMiami besides unique requirements of the parties difficult considering the myriad alterna- the Port Bridge, which is currently the involved. In this case, the owner wanted tives that can be built into the contract. only connection to the mainland. These to share risks with contractors who We asked FDOT what advice they would improvements are intended to keep were experienced in managing tunnel give to an owner considering a PPP for PortMiami – the county’s second largest construction projects, tap in to the private- the first time, and here’s what they said: economic generator and one of the sector innovation, and have an infusion of busiest ports in the county – competitive. private cash to help fund the project. Completion of the tunnel goes hand-in- FDOT selected a contracting scheme • Pick the right projects and secure hand with port improvement projects referred to as a design-build-finance- government and community to dredge the channel and enhance rail operate-maintain (DBFOM) in which stakeholders’ support cargo capacity to accommodate Post- the private partner finances, designs and • Be flexible and transparent in Panamax ships. constructs the tunnel, and operates and procurement, contracting, and finance Several alternatives have been maintains the finished facility. At the end process considered, including reconfiguring of 2044, the private partner will return the roadways, building a high-level tunnel to FDOT in first-class condition. • Secure outside experts with P3 bridge over the channel and a no- According to FDOT, this type of contracting experience build option, but tunneling emerged mechanism is ideal when the public agency as the most effective option. Based on does not have the full funding in place to • Do not assume that the initial the engineering and environmental construct the project. The private financing Concession Agreement intended criteria, the tunnel best improves safety allows the construction to proceed and result will be the final result. conditions, reduces traffic congestion, deliver the project earlier. Meanwhile, the • Do not assume local experienced creates no significant long- or short- stipulation that the tunnel be returned in engineers or contractors will be in- term environmental impacts and has no first-class condition provides incentive for volved with the Concessionaire. long-term effects on marine navigation. the private partner to keep the tunnel up- To construct the project, the owner, the to-date. • Both the design-builder and operator Florida Department of Transportation FDOT graded the proposals with should have equal rights (both (FDOT), developed a public-private a technical and price component. In equity) or the operator should have partnership (PPP or P3) project delivery addition, the proposers were required to an equity stake in the Concession. approach. PPPs are uncommon in public- be able to finance portions of the project Photo by Daniel Azoulay – Courtesy of BCWF JUNE 2013 TBM: Tunnel Business Magazine 17 COVER STORY with the expectation of payment upon performed by Moretrench based on a MEET “HarrIET” achievement of specific milestones and design by Bouygues. It is a first in Florida performance annual payments during and the first time freezing has been used The star performer of the PortMiami Tun- operation and maintenance. in the United States for cross passages. nel is the 43-ft diameter Herrenknecht EPB In 2006, FDOT issued a request for The highly dissolved coralline TBM nicknamed Harriet. Harriet has com- qualifications and short-listed proposers limestone layer required an extensive pleted both of its 4,200-lf drives under Bis- later that year. The project was awarded to grouting program to be performed cayne Bay, leading the way to the comple- MAT Concessionaire LLC, with Bouygues ahead of the TBM drive in order to tion of Miami’s long-awaited program to Civil Works Florida (BCWF) Design- reduce the porosity and permeability improve efficiency in and around the port. Build contractor and 10% equity partner. of the ground a to mine safely without The TBM was built in Germany and arrived The contract was signed on Oct. 15, 2009, confinement pressure. Nicholson in South Florida on June 23, 2011. Below and Notice to Proceed was issued in May Construction performed this formation are some of Harriet’s vital stats: 2010. The 43-ft diameter Herrenknecht grouting program using a unique Namesake: Harriet Tubman. The Miami- EPB TBM arrived in pieces on June 23, thyxotropic grout that was also Dade County Girl Scouts Troop named the 2011; began the eastbound tunnel on developed by Bouygues for the specific TBM Harriet, after the African-American November 11, 2011 and completed it July conditions. Time-restricted by the port’s abolitionist who escaped slavery and led 31, 2012. The westbound tube mining busy cruise ship schedule, the program several rescue missions through a net- commenced on October 29, 2012 and was was executed both on-shore, over-water, work of secret passages and safe house completed on May 6, 2013. inside buildings, and consisted of over known as The Underground Railroad. 1,000 holes – more than 18 miles of BUILDING THE POMT drilling and 65,000 cubic yards of grout. Diameter: 43 ft. At the time it was The highly porous and permeable launched, it was the largest soft-ground The geology for the PortMiami Tunnel ground conditions throughout the tunnel machine used in North America. is complex and challenging. The soils alignment did not permit the traditional Length: 457 ft including trailing gear. consist of weak rock and soft ground routine TBM cutterhead inspections and conditions – including silts and manmade maintenance. To meet this challenge, Drives: Harriet completed two drives of fills – along with porous limestone. BCWF Malcolm Drilling constructed several approximately 4,200 lf each. The east- performed a complementary geotechnical refuge chambers at pre-determined bound tunnel was driven from Watson investigation report wherein it identified locations on the alignment using cutter Island to Dodge Island from Nov. 11, zones in need of ground improvements by soil mixing (CSM) panels in order for 2011 to July 31, 2012. Upon completion, the means of conditioning and formation BCWF’s TBM team divers to safely access the TBM was turned around in the shaft grouting. Additionally, BCWF is using the cutterhead. and re-launched to mine the westbound ground-freezing techniques for the Additionally, Malcolm performed tunnel from Dodge to Watson. The west- construction of two out of the five cross- Shallow Soil Mixing to a depth of 23 bound tunnel was mined from Oct. 29, passages. The ground freezing is being ft along the first 510 ft on Watson 2012 to May 6, 2013. Photo by Daniel Azoulay – Courtesy of BCWF 18 tunnelingonline.com JUNE 2013 COVER STORY 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.

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