Betcha y’all didn’t know 9

[EB-80/8inPA 1,947]

54 minutes ago, Handy Don said:

The ground wasn’t as impermeable as the original builders surmised!

What, no hydrogeology study?  Not even a perc test?  Yikes.  I guess that’s what you get for surmising in lieu of testing.

[Handy Don 15,606]

23 minutes ago, EB-80/8inPA said:

What, no hydrogeology study?  Not even a perc test?  Yikes.  I guess that’s what you get for surmising in lieu of testing.

They had done both of those, but it was as much as 30’ deep over 1,900 flat acres and the original bottom seal needed work. Not feasible to test every square yard. 

The upgraded bottom used an additional layer of clay trucked in and carefully compacted.

[Ed Kennell 44,085]

2 hours ago, Handy Don said:

The reservoir, as you probably know, was built on flat ground surrounded by a high levee. The ground wasn’t as impermeable as the original builders surmised!

I only modeled the hydraulic surfaces from the intake to the discharge.   So I never got involved with the size or shape of the upper and lower reservoirs.

I only needed the max and min water levels and the flow rates to conduct the model tests.   There was one TVA project where the prototype index test showed 4.5% less HP output than the model test.  After extensive testing and inspection of the new runners we supplied and of the modifications we made to the draft tube shapes, we determined the turbine was not seeing the correct flow.   Divers were sent down upstream of the intake and discovered a silt build up that was blocking a lower corner of the intake.  Using a Garmin depth/fish finder with GPS I made a map of the silt and installed the same scaled down obstruction on the model. The model test now matched the lower output of the prototype.   There is a lot of reluctance to disturb these silt deposits.  I do not know if TVA ever removed the silt or just lived with the reduced output.

[Handy Don 15,606]

11 hours ago, Ed Kennell said:

There is a lot of reluctance to disturb these silt deposits. 

.No point touching it until the “Why?” and “If removed, then what?” questions had sensible answers, right?

Like the Aswan--either the planning never really fully grasped the silting situation or addressing it wasn’t sufficiently remunerative to the decision makers economically or politically.