Monday, May 07, 2007

Should We Be Worried?

Last Friday’s storm was non-tropical, but the Sewerage and Water Board still had to switch over to back up power for the pumps in New Orleans:

And on Friday, the loss of 60-cycle commercial electricity also knocked out a compressor that increases the pressure of natural gas to operate the water board's 25-cycle power plant, causing it to shut down, too.

Water board officials scrambled to switch to diesel fuel to operate the power plant, but the failure led to most individual pump stations west of the Industrial Canal being knocked out for periods lasting from a few minutes to 45 minutes, St. Martin said.
The 60-cycle/25-cycle problem is explained in the article and is blamed for the loss of power to the pumps. While the explanation for why the pumps lost power is important, whatever the reason, we still had to switch to back up power (diesel generators) in a storm outside of hurricane season and non-tropical in nature.

Also, the London Avenue Canal exceeded its safe water level:
At the London Avenue Canal in New Orleans, U.S. Army Corps of Engineers requested the Sewerage & Water Board shut down Pump Station No. 3 at 1:30 p.m. because the water level in the canal reached 4.3 feet. While that would not seem particularly high in a canal where the floodwalls extend 14 feet above sea level, the Army Corps has set conservative limits for those drainage canals that suffered catastrophic floodwall failure during Katrina and allowed a swollen Lake Pontchartain to empty into the city.

The safe water level for the London Avenue Canal is 4 feet.
Once again, this was a storm outside of hurricane season and non-tropical in nature. Yet, we had to shut down one pumping station because an outfall canal reached the highest level of water the U.S. Army Corps of Engineers is confident that the floodwalls they built can handle. And most of the other pumps were running on backup power.

Look, I don’t expect the city’s pumps to do the impossible. I don’t expect the city to stay completely dry when the rain is coming down hard.

But, I do expect an honest assessment of where we’re at heading into this hurricane season.

Sewerage & Water Board Executive Director Marcia St. Martin provides an assessment:
"But the real key to this afternoon is, irrespective to our problems, the rainfall event was greater than our capabilities with everything working perfect," she said.
Everything working perfect. Sounds like we should be worried.

[UPDATE] prytaniawaterline provides another assessment:
This tells me that the levees and the pumping system are not to pre-katrina levels. In the event of a large hurricane we would be in deep poo-poo at the very least deep water with poo-poo in it.

5 comments:

Leigh C. said...

Should we be worried? Hell, yes!

Schroeder said...

I'm wondering what the safe water level in the London Avenue Canal (and the others) was pre-Katrina.

I don't recall canal problems pre-Katrina. It was always pump failures, clogged drain basins, or more rain than the pumps could handle, which explained pre-Katrina flooding.

Is the Corps being overly cautious post-Katrina, or was it being overly careless pre-Katrina?

Ray said...

So I don't know whether to be worried about distatrous flooding here. In a case where we have a tropical system with potential surge, the canal gates will be closed. So lets say gates are closed and gate pumps fail; then we shut off the SWB pumps in order to keep the water below the safe water level. We then end up with rainfall-induced flooding, which is ungood but not catastrophic on the level of Katrina.

The disaster scenario is if the gates fail to close due to sediment or debris (see http://ngmag.com/levees), and then there is no way to keep the storm surge out of the canals and water levels in the canals below the safe-water level. Then levees pop like before, and we're partying like it's 2005.

Anonymous said...

By "compressor" do they mean "frequency changer"?

TravelingMermaid said...

I think we're f***ed.