One of the Sewerage and Water Board’s pump-powering turbines was not operational for about two hours as heavy rains swamped the city, Executive Director Ghassan Korban said Wednesday afternoon.
In a statement posted to Twitter, Korban said Turbine 4 (T4) “tripped offline” around 8:52 a.m. But by then, Korban said, street flooding had already begun.
When it was all said in done, the morning storms dropped 3 to 6 inches, but “the rate is really what caused the issues,” said Robert Ricks, a forecaster with the National Weather Service in Slidell.
How hard did in rain in New Orleans this morning? On average: the 5-min rainfall rate peaked around 0.5 inches and the 1-hour rainfall rate peaked at just under 3 inches. That is very heavy rainfall rates!!! #turnarounddontdrown #lawx— NWS New Orleans (@NWSNewOrleans) June 10, 2020
At its peak the storm dropped anywhere from 3 to 4 inches per hour, Ricks said.
“In our area … probably a couple times a year we get rain rates that much.”
“The bottom line is that was more rain that [sic] our system could handle,” Korban tweeted.
The S&WB utilizes a combination of several turbines and generators to power the pumps that ultimately drain the city when it rains. It’s not clear how many pumps were rendered useless when T4 went offline. Korban said the utility was able to reconfigure the power supply “to slow the rising of the water,” and that T4 was back online within two hours.
While not technically part of Tropical Storm Cristobal, the remnants of which have almost reached Canada, Cristobal created the environment for Wednesday’s downpour. The tropical storm brought a lot of moisture into the atmosphere, and when that moisture combined with the Wednesday’s cold front, all the necessary ingredients were there.
“That’s what caused the process to kick in and get the heavy rain,” he said. “These rain rates are very typical of a tropical environment.”
Ricks said the heaviest rain fell in downtown New Orleans, Mid-City and near the lakefront.
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