Fix the pumps

Wednesday, October 27, 2010

The winches

In the previous four parts of this series on the gates, we've looked at the trench the gates sit in when lowered, the gates themselves, the guide columns, the seals, and the pins that are meant to lock the gates in place. This part covers the equipment that lifts and lowers the gates - the winches.

The Basics

When the gate structures were first built in 2006, they were not automated. The individual segments, known as needles, were lowered and raised by crane. For example, here's the Orleans Avenue gates in October, 2006:

And 17th Street in July, 2006:

This presented a number of problems. Cranes couldn't operate in winds over 30 mph - a problem if there's a tropical storm or hurricane on the way. Also, it took many hours to lower the needles into place. The gate closure process laid out in the 2006 operating manual is actually 5 days long.

In mid-2006, or perhaps earlier, the Corps recognized this problem and started designing and installing an automated winching system at all three sites. With winches, there would be no need to worry about the wind speed. The final system would allow the gates to be dropped into place in less than an hour. That would allow the Corps to keep them open for much longer, avoiding or minimizing use of the suspect pumps installed at all three sites.

By the 2007 hurricane season, the guide columns at all three sites had been extended vertically and every needle had a winch installed above it. 17th Street got them first, as seen here:

The winches are manufactured by Pullmaster division of TWG (formerly Tulsa Winch Group), which is itself part of the Dover Corporation, a multinational that focuses on commerical and indutrial equipment. Pullmaster is in Surrey, British Columbia.

The Corps went with the model R7 from Pullmaster (their general sales bulletin is here). And so that the winch is not pulling the entire weight of each needle, the design firms called for multipart lines between the needles and the winches. At 17th Street, the line travels through two pulleys before attaching to the needles, while at London/Orleans it goes through three pulleys:

17th Street:

And from the drawings attached to modification P00037 to Boh Brothers' construction contract (obtained via FOIA by Molly Peterson):

London (Orleans is similar) (via Flickr here):

Zooming in for more detail:

The Problems

The winches are powered by hydraulic power units (HPU), with two units at 17th Street, and one each at Orleans Avenue and London Avenue. Each HPU has a control cabinet adjacent to it which allows the operators to raise and lower the winches.

Not much has been written about the winches, other than the Corps pointing them out when they were installed. However, in December, 2006, the local paper in Tulsa, Oklahoma, the Tulsa World, wrote an article about the hydraulic power unit and control cabinet that was installed at the London Avenue site. It's got a good picture of the unit, and it's worth reading.

Now the problems... Despite the front line importance of the gates and the ability to lower and raise them, the winch hydraulic power units and control boxes are not located in a secure locations far away from storm surge. This is different from the controls and most of the power units for the hydraulic pumps, which are in elevated blockhouses on the perimeter of the site. In fact, the winch controls and power units are directly in the line of fire.

At London (gates shown raised) (2nd photo via Flickr here):

Orleans (gates shown raised):

and 17th Street (pics here):

That is the winch hydraulic power unit on the west side of the site (note drive unit for bridge pump placed next to it). A matching winch HPU is on the east side of the structure:

We know the current gates' tops are 16 feet above sea level. The winch power units and controls also rest on concrete or steel (depending on the site), exposed at the same 16 foot elevation. We also know that is two feet shorter than what the Corps' own design guidelines call for.

What if a wave washes over the gates and the concrete cells next to them, as is likely? At 17th Street, the Corps' 100 year storm calculations call for wavetops at 17.4 feet. And what if a 200 year storm comes rolling toward the city?

Or what about flying debris? Can we be sure that all those light poles on the structures will hold up in 100 mph winds? The controls and HPU's aren't exactly housed in hardened boxes. There's nothing around them at 17th Street, and at London and Orleans Avenues, the only thing protecting them is a canvas tarp:

Better than most, this picture (via Flickr here) shows the delicate positioning of the winch power unit and controls when the gates are lowered.

My point is that the controls and power units for the gates themselves are placed in about as vulnerable a spot as the Corps could find. At 17th Street, they're actualy in front of the gates. The only worse spot would be a barge out in the lake. It doesn't take a genius to think of bad news scenarios resulting from this vulnerability.

The nightmare situation is some kind of combined human factor/technological failure of the system during a storm which causes one of the gates to raise with surge against it, pouring water into the canals again. I can't speak to the exact controls architecture on this matter, but is it really that inconceivable?

The solution to part of this problem is simple - use electric winches. The New Orleans' District's mechanical love affair with all things hydraulic makes no sense when placing those things in a hurricane. From pumps to winches, simpler is better when one is talking about systems meant to protect hundreds of thousands of lives and the property belonging to those people. Instead, the Corps has put hydraulic pumps and hydraulic winches with tons of moving parts, pressurized oil, and which have critical pieces totally exposed to hurricane storm conditions. And because the distance from the winches' hydraulic power units to the winches themselves is limited by the fluid nature of the system, they had to place the power units close to the winches, i.e. on the deck. It's stupid.

Electric winches would have eliminated the hydraulic power units and allowed placement of the winch controls in the blockhouses, protecting both the operators and the equipment during a storm. Black & Veatch also noted this deficiency in their evaluation of the Interim Closure Structures, pointing out "Hoisting equipment is exposed to hurricane blown debris" and "Remote operation of gates is needed to protect personnel during storm events."

There is a larger problem with placing the winch controls in such a vulnerable position. If they go out during one storm, they will likely not be available for a few weeks while repairs are effected (lots of moving parts, remember). That's not a big deal when raising the gates after a storm has passed - the cranes can do that. But what happens if another storm comes in on the heels of that first one? It's not a theoretical question. Rita followed Katrina in 2005 by just 3 weeks. Ike was only 2.5 weeks after Gustav in 2008. In an active season, there can be up to four storms brewing in the Atlantic basin.

If the winches are not available to lower the gates, then the Corps is left with the system in place during the 2006 season - rental cranes. And those things can't be used in winds over 30 mph, and take much, much longer to lower the gates. Plus those cranes were "pre-owned" when the Corps first started renting them in 2006. Now they're four years older, and the Corps has already had to pay Scott Equipment over $8000 for damaging them.

In sum, the Corps could have done a lot better going with electric winches. However, since they insisted on hydraulic winches, and also insisted on placing the hydraulic power units on the gate structures in the line of fire for storm surge, the least they could have done is place them inside a hardened, vented steel box. That goes for the winches themselves as well. But not even that small bit of protection was implemented.

Karen Gadbois of The Lens and Molly Peterson of Southern California Public Radio contributed to this report.

Go to older posts Go to newer posts