Without those measures in place, Isaac's surge almost certainly would have caused serious flooding in Orleans Parish. Just knowing the new floodgates and surge barriers were there contributed to most locals' decisions to hunker rather than bolt as the storm drew nearer. Had it not been for our subsequent dissatisfaction with one of America's "Top Utilities" I'm sure we'd be patting ourselves on the back for that decision even more conspicuously than we have been.
But then there were the signs that maybe things were a little more tenuous than we thought. There was this bit about the 17th Street Canal pumps needing to be manually started. There was the matter of a pump on the Orleans canal catching on fire. And now it turns out that the gauges which measure safe water levels along the outfall canals were barely functional themselves.
Once the corps closes the floodgates at the Lake Pontchartrain end of the 17th Street, Orleans Avenue and London Avenue canals, it has to pump rainwater out of the canals as fast as the New Orleans Sewerage & Water Board pumps it in. Corps employees monitor eight gauges in each canal to make sure the water doesn’t rise so high that it overwhelms the canal walls.
Of the 25 gauges in the outfall canals and at the entrance of Bayou St. John, 16 went out or registered false readings at some point on Aug. 29, according to Rivergages.com, which records hourly readings.
When the city was feeling the brunt of the storm, six of the eight gauges on the 17th Street Canal malfunctioned for some period of time. One of them registered 8.12 feet before it went out — well over the 6½-foot limit for that canal.
Gauges in other canals worked intermittently, too, including four in a row near the interior end of the London canal and one on the lake-side of that floodgate.
Remember also, operation and maintenance of these systems is slated to be tied to local funding sources in the future.
It's estimated the local cost burden will be ~$5 mil./yr. Maybe less, if they're not run much. Maybe more if the Corps doesn't learn what galvanic corrosion is (like the debacle of the MWI pumps).
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