Level Sensors Keep The Miami Tunnel Dry


the port of miami tunnel during controls testingSome sumps are small, like the one in your grandma’s basement. Others are large, like the ones in the basement of a high-rise building. Still, others are gargantuan, like the ones in the underwater Port of Miami Tunnel, where our float switches and submersible pressure transducers were chosen for redundant pump control.

The pumps at the bottom of the tunnel are large. Their task, along with our sensors, is to keep the underwater tunnel dry. Naturally, the equipment needs to be reliable.

The Tunnel

The tunnel allows heavy trucks and port traffic to bypass the congested downtown Miami area and access the port directly from I-395. This is especially crucial with the large increase in trade traffic expected from the Deep Dredge Project (expansion of the Miami Port) and the enlargement of the Panama Canal. The tunnel opened August 3rd, 2014.

With cargo and passenger traffic expanding at the port, it is important that the tunnel be protected from the potential of rising water levels from severe storms or hurricanes, which could close the tunnel and interrupt the functionality of the port. In fact, the operators of the tunnel, MAT Concessionaire LLC, will owe $115,000 for every day the tunnel is closed! That’s reason enough to keep the tunnel open at all times.

It’s no easy task. The tunnel runs under the Biscayne Bay, connecting the MacArthur Causeway on Watson Island with Port of Miami on Dodge Island. That’s 4,200 feet of undersea tunnel, two of them, at 43 ft. wide each and up to 120 feet below sea level. It is, however, incredibly important, as the tunnel is expected to host 26,000 vehicles a day – and cost $668 million to build.

Level Control

SICE, the Control and Communication Systems contractor, was charged with designing a SCADA system with enough redundancies to keep the tunnel open, even during severe hurricanes. That means continuous and precise monitoring of the water levels in the drainage and ballast areas of the tunnel.

Redundancy is important because it prevents a single erroneous sensor from creating a system failure. If one sensor goes down the other triggers the pumps and the tunnel is saved. The concept of redundancy is commonly used in critical applications where lives or large investments are on the line. In the case of the Port of Miami Tunnel, both situations apply.

With this in mind, SICE turned to APG for instruments. SICE requested multiple-float sensors for a multi-stage level alarm sequence, and submersible pressure sensors for continuous level monitoring. Our FL series float sensors and PT-500 submersible pressure sensors fit the job description perfectly.

port of miami tunnel sump and pumps

Along the length of each tunnel, in the ballast area below the roadway, are pump rooms. In each of these pump rooms are several of our float switches with multiple switch points and submersible pressure transducers with 4-20mA outputs. They are connected to Programmable Logic Controllers (PLC) and the tunnel SCADA system. If the water level climbs too high, the sensors activate the pumps that remove the rising water.

The operators, in the mean time, avoid a hefty $115,000 daily fine for closure. Phew!

The application of the sensors is simple. Combining the continuous level output of the submersible pressure sensors with the multi-float-switch sensors for multi-stage level alarms provides efficient and easily managed redundancy. The result is an elegant and reliable solution for water-level management in a key facility with no tolerance for failure.

Simple sensors, straightforward application, and a high-leverage situation. If APG’s sensors can be counted on to keep important infrastructure in operation at all times, they can work for you, too. Let us know if you have any questions about pump control, level measurement, or redundancy by visiting our contact us page or by starting a live chat on our website.

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