A study of the Dam .
Was this dam in such an advanced state of decomposition that it was on the brink of failure.
Lee Lake and Dam -
The state of the dam today.
This lake was completely filled just a few years ago in this same condition. Just how dangerous was this situation? Was the lake drained due to drought or due to fears of the dam collapsing. The water for our reservoir's comes from the Owens Valley and is not dependent on rain fall or run off. So why is the water level so low?
The spillway area and superstructure of the dam.
This part appears to have been constructed at a later time than the rest of the structure - probably in the 1970's and is of a more sophisticated design.
The spillway section.
Notice the landslides to the right of the overflow dam on the water side. There was a larger landslide into the spillway which may be viewed in the next shots.
Once again, notice the large cracks in the dam wall. Also It seems that there was a large amount of grouting used on the canyon walls. This makes one wonder - why was so much support needed. The gray material on the canyon walls is the Grouting. In dam terminology this is called "Dental Work" where all openings are sealed.
The Landslide area
This is the overflow section of the dam on the drainage side of the spillway.Once again notice the grouting in the left side of the shot. Once again these boulders are the size of a mid sized car. There appear to have been more that one landslide.
To see this, view the rubble on the left side of the spillway dam. The spillway is actually another dam in itself and much better built than the rest of the system.
The spillway section.
This area hase about a 60-70 foot drop off so care should be taken in this area of the dam. Most of the concrete structure is in this area. One must walk the lenght of the dam though to get to this part. Notice there's no grout next to the concrete area though.
The damage to the side walls of the dam and support section.
In this situation the disintegration of the concrete can cause a condition called hydraulic uplift. In this case water seepage causes the dam to be literally lifted off it's foundation.This was the case in the St. Francis failure of 1928, with the dam failing at 12 midnight and killing hundreds while they slept.
The entire Dam, except the spillway.
By observing closely, the dam appears to have been constructed in four different stages. The first part was most likely built in the 1920's.
This section is almost completely gone and is mostly rumble. You may see the second level towards the middle of the shot. This too is in terrible condition.
The third part is concrete and earthen fill comprising the upper level of the dam.
The spillway dam is of a much higher quality of construction and appears to be much newer. Also it is a much more sophisticated design than the rest of the dam. Were the dam to fail this section would most likely remain intact.
This shot is of the landslide area in the spillway. Theses boulders are the size of a Mid sized Car. Notice the landslides around the spillway dam on the water side of the concrete also. In order for this to occur there must have been considerable ground movement and shifting.
The Discharge pipe.
This is for lowering the water level. This is one of the most important sections of the system. Without this feature there would be no way of controlling the water levels and flow. Without this drainage system any dam is doomed to failure. It's not a question of how or when, but just how badly.
The side abutment of the dam.
Notice the dam is not really anchored into the canyon wall but just runs into it. The Dam should go into the mountain side for more support.
This water system is what is called a Gravity Arch Dam, meaning that the shear dead weight of the structure is enough to contain the water.The arch configuration gives the dam added strenght with this design.
By calculating the weight and strength of the concrete and the PSI of water, the structure should have the sufficient tensile strenght to contain the water...hopefully. This isn't always the case though as with the St. Francis, which was a Gravity Arch Dam,but completely different in design than this structure, being made entirely of concrete.
Severe damage to the original dam
This would be part of the original dam. Notice the almost totally disintegration of the base. This is an extremely dangerous situation. Water seepage through the opening can cause "Hydraulic Uplift" and breach the dam sending a huge wall of water down the canyon.
In conclusion -
While first visiting this site, I filmed a large amount of video footage and began viewing it. This was when I noticed all the damage to the concrete and the structure.
I realized this dam was in an extremely dangerous state of decomposition. One doesn't have time to examine the dam to this degree while there the first time, but after watching hours of footage I came to the conclusion this lake was lowered deliberately with no doubt in my mind the dam was ready to collapse in the next several years if not sooner.
By
Ken Lafler
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