Photo: Al Diaz, Miami Herald

“Hurricane Irma was a game-changer for South Florida. Cities are preparing for hurricane season differently now. And the region’s largest utility, Florida Power & Light, is pushing for a method that could turn the lights back on faster after a storm…

Last month, FPL launched a three-year pilot program to put more power lines underground in more neighborhoods. According to FPL, 40 percent of its lines are already under the ground.

After the 2005 double-hitter of Hurricanes Katrina and Wilma, FPL invested nearly $3 billion to harden its electrical grid, to try to make it more resilient against the storms of the future.

Underground power lines are one of several hardening techniques that help make the grid more storm-resilient. Others include managing trees near electrical infrastructure; replacing wooden poles with concrete or steel ones; and reinforcing utility poles with guy wires (tensioned cables) for more stability.

FPL, which maintains a hybrid system of above-ground and underground lines, says it’s planning to harden all the power lines along major thoroughfares by 2024.

At the May PSC meeting, Olnick said underground power lines performed 80 percent better than overhead ones during Hurricane Irma – which means they were that much less likely to lose power.

‘Which was expected,’ he said.

If Irma had been a water storm, underground power lines would have faced other challenges, namely severe flooding and storm surge…

Buried power lines are kept inside PVC pipes that are made to be watertight. But if water manages to enter the pipes, then the outages can take longer to remedy because accessing buried infrastructure takes more time. (The U.S. Department of Energy estimates repairing ‘widespread below-ground failures an take several weeks.)

…South Florida’s geology compounds the water tradeoff. The pipes are sitting atop a bedrock of porous limestone – essentially a big sponge.

The ground material also varies with geography. Varela, the Miami Springs contractor, says he has hit sandy soil there while Coral Gables is known for its coral rock…

FPL says it’s trying to counter storm flooding. According to Olnick, the company is using flood monitors at substations to keep track of existing water. (During Irma, two substations in FPL’s 35-county territory were de-energized, or powered down, because of flooding.)

In Downtown Miami, the company is experimenting with sub-aqueous power lines that can be submerged in water, according to FPL’s Bryan Olnick.”

— Alexander Gonzalez & Caitie Switalski, WLRN Miami, South Florida
Read entire article including detailed requirements and geographical charts