From the Storm LEDs Emerge

From the Storm LEDs Emerge

An epic flood, damaged infrastructure and a new lighting system. The story of the Brooklyn Battery Tunnel

By Paul Tarricone

Not all the damage from Superstorm Sandy was immediately visible to the naked eye or the news cameras. Some of the destruction from the 2012 storm was literally buried, as was the case in the Hugh L. Carey (aka Brooklyn Battery) Tunnel. The tunnel, which connects motorists to and from Manhattan and Brooklyn, flooded with 86 million gallons of seawater after the storm struck. A six-year infrastructure upgrade followed to improve the tunnel’s critical structures and facilities.

The rehab of the longest continuous underwater vehicular tunnel in North America called for structural and waterproofing repairs, as well as complete replacement/improvement of all critical electrical and ventilation systems. New lighting was also a key component, as the project ushered in the use of LED luminaires (from Kenall) in place of the existing high-pressure sodium system. All told, 3,386 new fixtures were installed, including 2,374 tunnel luminaires; more than 650 low-output beacon lights mounted to the tunnel walls to delineate tunnel geometry and emergency egress for motorists and pedestrians; and 362 luminaires in the tunnel air ducts to assist Metropolitan Transportation Authority (MTA) maintenance personnel when servicing tunnel ventilation systems. The high-efficiency, corrosion-resistant LED lighting system is projected to save more than 1.5 million kilowatt-hours and $200,000 per year in energy use and cost.

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While solid-state lighting has penetrated much of the built environment, the technology has been something of a latecomer to the tunnel market. However, the Brooklyn Battery Tunnel’s transition to LEDs is indicative of a steady move away from legacy sources. “Every tunnel lighting project currently in design that I’m aware of is being designed with LED sources,” says Michael Maltezos, Kenall’s national transportation sales manager. “The notable turning point seemed to be 2015; major tunnel lighting projects that were bid during or after 2015—including the Brooklyn Battery Tunnel, the Fort McHenry Tunnel in Baltimore and the Lytle Tunnel in Cincinnati—were all built with LED lighting systems. Simply put, LED technology has, by now, improved to a point where whole life-cycle cost analyses of LED tunnel lighting (vs. old HID/fluorescent tunnel lighting) favor LED.”

MTA Bridges and Tunnels’ project goals included improved light levels and uniformity for public safety; better visibility with glare reduction; substantive energy savings; top notch quality; and little to no maintenance. “As the owner said: ‘Let’s turn on the new lights, and fuhget-about-it for at least 30 years,’ ” recalls Maltezos.

But before flipping the switch, the project team had to overcome a number of site-specific hurdles. “First, due to conditions within the tunnel, the lighting was designed as a one-for-one replacement of the existing HPS luminaires,” says Maltezos. “More specifically, all existing HPS luminaires were ceiling recess-mounted in 30-in. long by 24-in. wide by 10-in. deep ‘box-outs,’ recessed into the concrete ceiling where existing conduit holes would be reused to feed the replacement tunnel luminaires. As a result, all LED luminaires would have to physically fit within these ceiling recessed box-outs…not a small feat at the time of design.”

Further, the LED replacement luminaires would have to provide the required light output in all the various tunnel zones, without overheating in the ceiling recesses. “This was no small feat either, particularly in the Threshold Zone where the LED fixtures would have to replace 400-W HPS luminaires,” Maltezos explains. “High-output LED fixtures inherently produce a fair amount of heat, particularly in a ceiling-mounted application. Add to that, for this project, the fact that the LED replacement fixtures would have to be tucked into the existing ceiling recesses. Suffice to say, this was a huge concern. In fact, at the time of design, no luminaire manufacturer (including Kenall) was capable of making a high-output LED tunnel fixture that would pass a heat test in the ceiling recess.”

Finally, the LED replacement luminaires would have to be mounted using the existing anchor mounting bolts that were cast into the tunnel’s concrete ceiling deck. This meant that all new luminaires needed to have a custom mounting bracket design to fit the existing fixtures’ anchor bolt mounting pattern.

The solution: invent a new luminaire with a smaller footprint to fit the existing box-out spaces in the ceiling. In fact, Kenall was able to implement the same physical design/footprint for all fixtures in the project’s various tunnel zones, which minimized the types and quantities of replacement fixtures/parts to be stocked by MTABT Maintenance Personnel.

More obstacles arose, however. One example—field surveys conducted by the contractor revealed that not all conduit feed holes were in the same location in the ceiling recessed box-outs. The design team worked with the contractor to manufacture/coordinate “A” and “B” versions of the fixtures, denoting which side of the ceiling recess box-out the conduit hole was on, and how the fixture housing and optics needed to be oriented, accordingly, for mounting.

The biggest challenge, however, was to ensure the new fixture would provide the required light output in the Threshold Zone without overheating in the ceiling recesses. Custom heat sinks were designed for the LED boards to mitigate the heat; this, combined with the new fixture housing’s shallow profile and large space behind the heat sinks for air flow, allowed the fixture to operate at a relatively low temperature despite its location in the ceiling recess. To increase the odds for success, “we also built a simulated ceiling recess at our test lab of the same size and scale as the recesses in the tunnel, and performed exhaustive heat testing on the fixtures to verify passing thermals in simulated field conditions—and not just in typical ambient lab conditions,” notes Maltezos.

The custom fixtures use CREE LED chips and meet the project specifications of 4000K, 70 CRI tunnel lighting. All elements of the Brooklyn Battery Tunnel restoration were completed last July—under budget and ahead of schedule. “The fixtures are performing as promised,” says Maltezos. “The tunnel lighting is much more uniform than before, and the 4000K/70 CRI system provides far better visibility for drivers in the tunnel than the previous HPS luminaires.”

After the storm, a clear view of new tunnel technology.

Contributor(s)

Paul Tarricone

Paul Tarricone