Fix the pumps

Thursday, October 15, 2009

Pennywise Part 2

[Updated section on channel transitions - 11-10-09]

Previously: Part 1

[Sorry for the repeat of the two introductory paragraphs from Part 1, but I never know exactly how people are coming to the blog, and if they hit this post frst, they might miss this content]

The largest refrain from those in support of Option 2, which is everyone but the Corps, is that effective flood protection is better than cheap flood protection. Supporters of Option 2 say it is just plain better than Option 1, a position even the Corps agrees with in a technical evaluation report mandated by Congress. The problem New Orleans and the surrounding area faces is that the Corps is cheaping out and going for Option 1 over Option 2, which is exactly what the Corps chose to do just months after Katrina, even though they believed it would only take another $190 million to do Option 2. Admittedly, it may have cost a little more to do Option 2, but based on the facts at the time - and what was passed up the chain to the White House and Congress - the Corps CHOSE to do Option 1 to save $190 million, and drafted the authorization and appropriation language to match it. The cheaping out began a long time ago.

However, I would go further and say that the Corps is cheaping out even on how they are planning to build Option 1. I believe they are deliberately lowballing the Option 1 estimate in order to make it look like the only way to go. They are doing this through a combination of shifting some features to future Option 2 and simply not building other features. If they didn't, it would be revealed that even Option 1 - if it was truly to be built correctly and be adaptable to Option 2 - cannot be built for the $804 million the Corps told Congress to give it.

In part 1 of this series, I introduced the various flavors and features of the Option 1 pump stations as they are laid out in three primary sources:

a) The 2009 Black and Veatch report
b) The 2009 Congressional Cost Report
c) A presentation given by the Corps to the SLFPA-E (east bank levee authority) on October 1, 2009.

See that earlier post for an explanation of the three flavors of Option 1 from the 2009 B&V report.

For reference, here's the description from the Cost Report:
"Pumping Plant - The pumping stations include the pumping station building and equipment, intake wet well, discharge section, canal transitions, generators with enclosures, a tank farm, and all the ancillary systems required for a fully functional facility. A cofferdam is required for the contruction of the pumping station. A temporary bypass may also be required to route canal flows around the cofferdam during construction."

And here are the renderings from the October 1, 2009 presentation. First, the plan for Option 1:

and the plan for Option 2:

The list of pump station features from the 2009 B&V report is:

1) Includes Floodwall/Levee Upgrades
2) Includes Gated Bypass
3) Canal Transitions
4) Deepened Sill
5) Formed Suction Intake
6) All Electric Pumps
7) Pump Station Sized for Future Pump Capacity
8) Pump Capacity Sized for Future Pump Capacity
9) Fuel Storage and Generator Sized for Future Capacity
10) Includes Siphon Recovery
11) Includes Breakwater
12) Stilling Basin at Discharge
13) Removal of ICS Facilities

As I've noted above, we've already covered the first two features. In this post we'll move on to the next few...

3) Canal transitions

The current canals have a depth of about -17 or -18 feet (at 17th) or as little as -9 feet at London or Orleans. That elevation would remain under Option 1. The future Option 2 canals would have a depth of about -29 feet. The Corps has said they will build the Option 1 pump stations with foundation depths to match the future Option 2 canals. The water needs to get from the higher Option 1 canal bottoms to the lower depths of the pump station foundations at the pump inlets.

There's two ways to do that. They could just put in an 11- to 20-foot tall "step," where water would flow rather roughly toward the pump inlets, or they could put in an extended transition section which would allow water to enter the pump inlets smoothly. The step is shown in the 2009 report like this:

The extended transition is shown here:

Obviously, the step would be cheaper. It requires less excavation and less construction. The extended transition could be over 100 feet long, while the step takes up hardly any room at all.

Here's a detail from the Corps' October 1 presentation to the SLFPA-E (entire image in part 1), showing which option they are going with for the Option 1 stations:

Remarkably, it appears they are choosing the extended transition, based on the text in the box on the left: "EXTENDED TRANSITION, SLOPE (SLOPES TO CANAL ELEVATION (~ EL -29 FT)" This, along with the deepened sill (see next entry) appears to be one of the places the Corps has decided not to cheap out.

Update - 11-10-09
Upon further review of this graphic and other information from the Corps' City Council presentation on November 5, 2009, it actually appears they are taking the cheaper route and putting in the "step." They are putting in a little slope from the top of the step to the pump station sill, but it is still the same thing.

Check out this slide from the City Council presentation, which was NOT shown to the public:

It clearly shows a huge step from where the current bottom of canal (shown as elevation -9) to a slightly extended transition leading into the pump inlets down at -37 feet. This is clearly a cheap-out by the Corps, and it needs to be stopped.

4) Deepened Sill

This refers to the Corps generously building the Option 1 stations with foundations deep enough to accommodate future Option 2 canals. If they didn't do this (what is referred to in the 2009 B&V report as "Non-Adaptable Option 1,"), construction of Option 2 would be impossible. Those shallower Option 1 stations would have to be completely ripped out and rebuilt from scratch if Option 2 ever came to pass, because their foundations would have to be rebuilt about 11 to 20 feet deeper. Fortunately, that's not what is going to happen, though that has only become clear within the last couple of months.

What's interesting about this particular feature is that it is not required for Option 1, only for Option 2. Yet the Corps is proceeding with it. This is in direct opposition to their claim they are not authorized to build Option 2. How can they proceed with spending dollars on a deeper foundation for an Option for which they claim they don't have authorization? It is these legalistic arguments that unfortunately have come to dominate much of the Corps' work, as their lawyers count angels, heads of pins, and ways NOT to do things, no matter how much everyone tells then they're wrong.

5) Formed suction intake

This one is linked to the deeper sill. A formed suction intake, or "FSI," is a Corps invention that they're very proud of. It's a contoured tube that goes on a pump inlet to smooth the flow into the pump guts. Without it - according to the Corps - vortices can develop between the submerged inlet and the water surface. This can break down the flow through the pump, making it run rougher. An FSI can also cut down on cost, because it allows a shallower foundation than would be needed without an FSI. That is, the "submergence" of the pump can be less with an FSI than without.

The Corps used FSI's on the 19 direct drive pumps that were installed at the 17th Street and London Avenue gate structures in 2007. They provided a snazzy graphic of those pumps with their attached FSI's in the February 21, 2007 Task Force Hope Update:

Those FSI's were steel. The ones on the pump stations would be concrete with steel reinforcement.

The choice here is whether to use an FSI on each pump inlet, or to simply have the inlets be open pits, or "wet wells" as the Corps refers to them. The 2009 B&V report does an excellent summary of the choice of FSI vs. wet wells, so I'll quote large parts of it here:
"A FSI is required for Option 1 Non-Adaptable, Option 2, and Option 2a to improve laminar inflow into the pumps and to reduce the required submergence and pump station foundation depth."

That is saying that the water depths in the Non-Adaptable Option 1 case and the Option 2 case are not great enough to avoid using an FSI.
"The Base Adaptable Option 1 pump station does not require a FSI because the foundation of the pump station is deepened to reflect the depth of an Option 2 pump station. The deeper foundation in combination with the Option 1 canal water elevations allows the pump intake to be adequately submerged in the water to eliminate the need for a FSI."

That is, since the foundation of the Base Adaptable Option 1 (which is the plan closest to what the Corps wants to do with Option 1) is deeper, but the inlet water level remains the same as current levels, the pump submergence in that scenario is great enough to avoid the need for an FSI.

But here's the kicker:
"A FSI would be required to be constructed in the wet well area of the Base Adaptable Option 1 pump station if the pump station is converted into an Option 2 pump station. The Robust Adaptable Option 1 Pump Station included a FSI as part of the adaptability of the pump station. The construction of the FSI during construction sequence 1 of the four phased construction approach reduces the future cost of converting the pump station to an Option 2 Pump Station and thus is included in the Robust Adaptable Option 1 Pump Station."

In plain English, that's saying the that if Option 2 comes about after the Corps' preferred Option 1 (basically the Base Adapatable Option 1) is built, the Corps will have to go back and install FSI's anyway. They could save future dollars by putting the FSI's in now.

So what is the Corps planning for? Remember the description of the pump stations in the Congressional Cost Report?
"Pumping Plant - The pumping stations include the pumping station building and equipment, intake wet well, ..."

The graphics in the October 1, 2009 SLFPA-E presentation back this up:

This is one if the exact spots where the Corps has CHOSEN to move costs from Option 1 to Option 2. Just as with the deepened foundation - which is needed for Option 2 but not for Option 1 - they could have chosen to install the FSI's as part of Option 1. They chose not to, likely strictly for cost reasons.

If the Corps' preliminary hydraulic analysis is correct, their elimination of FSI's from Option 1 deliberately makes Option 2 more expensive and difficult in the future. Is it an attempt to hobble Option 2, or simply nearsighted pennypinching?

Next: Part 3
Followed by: Part 4
Previously: Part 1


Post a Comment

<< Home

Go to older posts Go to newer posts