C A S E S T U D Y

P O R T O F M I A M I T U N N E L :RES IL IE NCY THROUGH FLOOD GATES

ACHIEVEMENT: TUNNEL FUTURE-PROOFED AGAINST SEA LEVEL RISE AND CLIMATE CHANGE

CAPITAL COST OF TUNNEL FLOOD GATES: $4.8M

POTENTIAL COST OF A MAJOR STORM WITHOUT THE GATES: $1BN+

The Port of Miami Tunnel,

connecting the city with

its port on Dodge Island,

is protected against

flooding by a pair of heavy

flood gates at each end.

Activated through hurricane

preparation procedures,

the gates help to make this

modern infrastructure asset

highly resilient to the risk of

flooding.

Each year during hurricane season, between the beginning of June and the end of November, Florida will be hit by anything from 10 to 20 hurricanes. On occasion, it suffers the brunt of a powerful category four or five storm, like Hurricane Irma which struck the peninsula in September 2017 with wind speeds exceeding 150mph (241kph).

Greater Miami is particularly vulnerable to damaging floods as well as high winds during hurricane season. Florida is mostly a low-lying state and Miami is one of its most heavily built-up areas,

on the state’s eastern coast. Severe storm surges, like that experienced from Hurricane Irma, can cause water levels to rise several metres, breaching the city’s existing defences; and scientific analysis shows the risk of flooding is likely to get worse.

In this context, a road tunnel beneath Miami’s port waterway is susceptible to extreme risk of flooding. However, the Miami Tunnel has distinctively iconic yet practical features at each end: concrete portal structures which house a pair of solid steel flood gates.

Each gate – there are two at both portals, one for each tunnel bore – is a steel box section just over 31 ft. (10m) wide by 36 ft. (9m) high and weighing around 55 tonnes. They are housed in commanding structures, which rise up from the bottom of the tunnel’s approach ramps, providing essential protection against flood risk.

The organisation responsible for overseeing operation of the tunnel is Miami Access Tunnel (MAT) Concessionaire LLC, which is owned by Meridiam and its co-investors, which developed the POMT project in partnership with the Florida Department of Transportation (FDOT).MAT and FDOT signed a 35-year concession agreement for the design,

construction, financing and operation of the tunnel in 2009. Before then, as the scheme was being developed, there was a clear need for protection against flooding.

“The idea for the gates came from Meridiam CEO, Thierry Déau. He was in the room when our proposals for the tunnel were being discussed at the conceptual design stage,” says MAT Concessionaire CEO, Chris Hodgkins.

Flood gates on the tunnel portals were a necessary solution to a serious predicament for the project. The proposal was for a twin-bore road tunnel to connect the Port of Miami on Dodge Island with the MacArthur Causeway on Watson Island. For road freight and other port traffic, this would provide a highly valuable direct link with the mainland Interstate highway network, bypassing downtown Miami. But risk of flooding was high at the tunnel portals on the two low-lying islands.

“The flooding risk made the project infeasible to begin with. We would not have been able to obtain insurance for the tunnel. But with the addition of the flood gates, insurance became not only possible, but it has subsequently become considerably less expensive than policies for other comparable

B U I L D I N G R E S I L I E N C E T O C L I M A T I C R I S KS

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infrastructure assets, which have experienced increases in insurance costs,” Chris says.

Construction of the POMT project was carried out between 2010 and 2014 (the new road link opened on the 3rd of August that year), complete with one-mile-long tunnels, portal structures and flood gates, new road layouts on both islands and a widened MacArthur Bridge connecting with the mainland.

Aesthetically, the portal structures were designed with local heritage in mind, to enhance their visual impact. Conjugations of the word ‘Navigate’ have been imprinted in Latin on the concrete towers which house the gates.

Looking at the POMT from a broader perspective, this modern addition to Miami’s infrastructure has become part of a wider discussion on the need for greater resilience to flooding

and extreme weather events in general.

Hurricane Irma hit in 2017, then came Hurricane Florence a year later. Florence made landfall further north, missing Florida, but becoming the largest and most devastating storm on record to hit the States of South and North Carolina.

“Improving resilience is the hot topic that everyone is talking

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100 Resilient Cities is an initiative of the Rockefeller Foundation, with the stated aim of “helping cities around the world to become more resilient to the physical, social and economic challenges that are a growing part of the 21st century”. Meridiam is working with 100 Resilient Cities to provide support through case studies on and analysis of contractual and funding structures to procure essential infrastructure projects in cities.

Launched in 2013, with an initial group of 32 cities, including Greater Miami and the Beaches, two further rounds of bidding for places in the 100RC Network have been carried out. The list now totals 100 cities which are drawing up strategies and can apply for financial support. 100RC is financially supported by the Rockefeller

Foundation and managed as a sponsored project by Rockefeller Philanthropy Advisors – an independent non-profit organisation. Cities in the 100RC network are provided with resources necessary to develop a roadmap to resilience along four main ‘pathways’:• Financial and logistical guidance for appointing

a Chief Resilience Officer, who will lead the city’s resilience efforts

• Expert support for development of a robust Resilience Strategy

• Access to solutions, service providers and delivery partners from public, private and NGO sectors for developing and implementing resilience strategies

• Membership of a global network of member cities for learning and helping each other.

I N C R E A S I N G R E S I L I E N C Y G L O B A L L Y

During a storm event, full closure of the POMT to traffic, including lowering of the flood gates, is initiated at ‘Action Level 3’, when notification of ‘Hurricane Condition Yankee’ is made by the Miami Coastguard. At this stage, the port and wider Miami area have already made preparations required at Hurricane Conditions Whiskey and X-Ray.At Yankee, tropical storm force winds are expected within 24 hours. All staff and employees are notified of the change of condition and procedures set in place for a ‘Severe Weather Closure procedure’. This is

communicated to motorists via dynamic signs and radio

of the city’s traffic management system.

“We inform all of our employees and stakeholders of the imminent closure of the tunnel, but we let but we let the Captain of the Port take the lead on communications as we ultimately are its tenant or customer,” says MAT Concessionaire Operations Manager, Wendy Conforme. “Well trained staff that knows how to flawlessly execute

our hurricane procedures is paramount in critical events

like this.

Additionally, throughout the year we ensure proper maintenance of the gates and all drainage and safety systems in order to avoid last minute incidents. Advanced preparation is key.”

about, because of the increasing number of ever more extreme events,” Chris says. “The POMT is central to the discussions, in Florida at least, because it was the first and so far only project of its kind to have flood resilience built-in from the start. We’ve proved the economics of providing resilience, showing that it’s good business.”

Besides making the POMT project feasible, from a basic cost benefit analysis, the flood gates account for around $4.8m – less than 1% – of the project’s total $600m construction cost. “The flood gates do not just protect the tunnel’s roadway from flooding. They also guard against damage to mechanical, electrical and safety systems. Without the gates, the effects of a category four storm could cost as much as $1bn,” Chris says.

The actuary work of insurance companies has “undoubtedly stepped-up” in the wake of recent

flooding and storm events in the US, says Chris. For MAT, however, a recent flood risk assessment has resulted in a $120,000 reduction in property insurance premium.

Storm surges combined with rising sea levels present an increasing threat to Miami and its surrounding communities, many of whom reside at less than one metre above mean high tide levels. Forecasts vary for how much sea levels will change in future. Regardless of whether climate change is due to human activity or not, which is a separate argument, sea level predictions for the year 2100 vary from a rise of 31 inches (787mm), according to the UN’s Intergovernmental Panel on Climate Change (IPCC), to the 81-inch (2m) rise calculated by the US National Oceanic and Atmospheric Administration.

“Even at the IPCC’s lower predicted rate of sea level rise, virtually all of Miami will be under water within

100 years unless something is done about it, but the city appears to have recognised this and is now acting to reduce the risks,” says Chris.

The cities of Miami, Miami Beach and Miami-Dade County have teamed up to form the ‘Resilient Greater Miami and the Beaches’ (GM&B) partnership, which has successfully applied to join the International 100 Resilient Cities Network (see box 1). With support from 100 Resilient Cities, GM&B is expected to launch a comprehensive new resilience strategy in 2019.

Meanwhile, Miami has POMT as an example of an infrastructure asset that can endure the twin-threat of extreme weather and sea level rise.

Since the tunnel opened in August 2014, the gates have been lowered three times in anticipation of significant flooding events, in

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accordance with the operation’s hurricane response plans (see box 2).

MAT Concessionaire’s Operations Manager, Wendy Conforme, says: “We also close the gates yearly to test them prior to hurricane season, to ensure everything is working properly. It then becomes a matter of observing storm warnings and acting accordingly. We start planning meetings five days before any major storm is due to make landfall. Ultimately, the gates are closed when the warnings reach a certain critical level, by order of the Coastguard’s Captain of the Port.”

Demonstration of what might happen without the protection of the tunnel flood gates came in 2012, when MAT was part way

through construction. Hurricane Sandy caused a reported $70bn of damage across the State of New York that year. Many of the City of New York’s road tunnels were flooded and have since had heavy flood gates fitted (see box 3).

“F i t t ing f l o o d g a t e s r e t r o s p e c t i v e l y c o s t s considerably more than it does to build them into projects from the start,” says Chris. “As the evidence of rising sea levels and climate change mounts, it really does make economic sense to ensure infrastructure is designed to be resilient. This is what Miami now has: so far the only transformational project across the Eastern United States built to endure projected rises in sea level.”

New York’s Metropolitan Transportation Authority (MTA) has completed a $64m project for fitting flood gates to critical road and metro subway tunnels. Steel doors, each weighing 25 tonnes, are now protecting both ends of road tunnels connecting Manhattan Island with the boroughs of Queens and Brooklyn, as well as the Holland and Lincoln Tunnels between New York and New Jersey.

The additional flood protection has been carried out after Hurricane Sandy caused over $60bn of damage across New York State in 2012. Many of New York City’s metro subways and road tunnels were flooded due to hurricane storm surges, putting large parts of the city’s transport network out of action for several weeks while a recovery operation was set in action.

Street-level subway entrances now have retractable heavy-duty fabric flood covers (see picture) and hinged steel doors have been fitted to pedestrian subway tunnels. Other openings in the subway metro system vulnerable to flooding, including train tunnels and lift shafts, have systems of steel ‘logs’, which operatives will build-up to form barriers for guarding against flooding when hurricane warnings reach critical levels.

A GLOBAL VIEW ON THE END-USER’S EXPERIENCE