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Sunny southern Florida is world famous for its spectacular scenery, white sand beaches and fantastic scuba diving. And scuba gear, joked local splicing crews, was just about what you needed to work in the flooded underground vaults of Florida Power & Light Co. (FP&L), Miami Beach district. The unique combination of the high-water table, salt-water corrosion, high hydraulic pressure and dangerous hydrogen-sulfide gas has made working in underground vaults a difficult job. When Miami Beach was developed in the late 1940s, the existing mangrove swamps were filled over and replaced by the Miami Beach tourist and resort area. Over time, the mangrove trees decayed and produced various gases, including the noxious and potentially dangerous hydrogen sulfide, which makes its way into the underground duct and manhole system. Coupled with the gas problem is the high-water table and strong hydraulic pressure in the area.
The situation is matched by no other utility in the country, where water pressure is so strong that it blows out the duct plugs and water hits the far wall like it's coming from a fire hose. When crews arrived for service restorations, it was commonplace for the manholes to be full to the brim with water. Even sidewalk vaults with sump pumps constantly running would have water in them. Over the years, FP&L tried various methods to seal the vaults, including duct seals and oakum, but nothing was strong enough to hold the water pressure. Any plugs put in would quickly blow out, with a torrent of water flooding the vault. The prevailing attitude among splicing crews was that when you worked the Miami Beach District, flooded manholes just came with the territory.