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Piece by piece Clues to the Erosion Channels under the Green Wet Area - How the dam was intended to work - Where does the water go?

To get to the next clue, it helps to see how the dam was designed with respect to water retention and the natural "seepage" through the core and transition zones. The internal water conditions are noted as "phreatic surface" or "phreatic line". This is essentially the water level within the inner sections of the dam.

The dam holds back water from a highly compacted "core" layer of clay-clayey mix (zone 1 - orange in illustration). It was placed in 10 inch lifts, carefully hydrated to a certain percentage ratio, and then compacted with a form of an additional consolidation. Documents state that the net core compaction/consolidation density rivaled or bettered the density of concrete. To structurally protect and to hydraulically protect the "core" layer, "transition zones" (Zone 2) were built on each side of the central core (dark brown in illustration). The transition zones had silts, sands, gravels, cobbles, and boulders (to 15" max). The silts in conjunction with sands formed a semi-block of waterflow. The cobbles, and boulders provided the structural support that the smaller silts sands gravels were confined within. The upstream Transition zone was designed to "heal" the core in case micro defects develop. The seepage into these defects would transport "silts" from the Transition zone and plug the micro defects in the core.

The outer layers are the massive gravity weight layers of the Zone 3 fill comprised of sands, gravels, cobbles, and boulders (to 24" max). The Zone 3 fill "shell layers" are intended to pass water, thus they are called non-pervious. Although waterflow was restricted to a slowed percolation through the smaller fines in the gravels and sand.

A very important Zone layer is the "Drain Zone" (light blue in illustration). The Drain Zone is intended to direct and pass any waterflow that seeps past the transition zones, and the core. As the Drain Zone is comprised of gravels, cobbles, and boulders it has no silts, sand, or clay-clayey material to impede waterflow. The vertical section is 20 feet thick for the vertical "chimney" part of the Drain Zone, and 10 feet thick for the bottom of the dam Drain Zone layer. The dark blue arrows depict the ideal operation of all of these fill zones working as designed. There should be no reservoir waterflow penetration beyond the Drain Zone Chimney in an ideal "phreatic level" or "phreatic surface" curve inside the dam.

On the back side of the dam, the Zone 3 outer shell will respond to rainfall in allowing the rain to percolate downward into the sands, gravels, cobbles, and boulders. This design of percolation is to prevent erosion channels from developing on the outer surface of the dam. Everything works fine as the flow and the construction compaction are in unison to gravity & gradual settlement. There will be minor erosion on the surface, but this is a very long and slow process that keeps the effect retained through the ability of the material to allow rain water to percolate into the consistent strata of sands and gravels.

The two combined dangers that may "upset" this internal percolation design function are (1) high rates of percolation flow (creating saturation pressures) in conjunction with (2) a non-unison vector flow (i.e. a lateral type of pressured flow from "deflection or redirection" instead of the vertical unison alignment).

At this point is where the clues of the Erosion channels start to emerge from of a new "source" of an "unexpected type" of water flow, other than the ideal phreatic level flow, is introduced.

A whole series of internal events start to develop. More later…

Piece by piece Clues to the Erosion Channels under the Green Wet Area - Did the early dam "saturate itself"? Or "dirt itself"?

The next clue comes from the early days of the dam operation. Something unusual develops. Large areas of Zone 3 fill become "saturated" on the backside of the dam. Even more unusual is that this large "saturation" occurs in two locations. The locations are near perfectly symmetrical adjacent to the center toe axis if the dam. The square surface area of the Zone 3 fill saturated hillside is equal to or larger than the square foot surface area of the "Erosion Channels" today. Where did this water come from? After all, in the perfect dam design, any water from the reservoir that seeps its way through the Core and Transition zones would/should be captured in the vertical "Drain Zone" chimney and out the "Drain Zone" in the bottom of the dam. There should not be a "saturation" of the Zone 3 fill, especially at the surface.

Could rainfall have caused these the large areas of "saturation"? If rainfall were to be the "original" cause, the Zone 3 fill in these areas would have to have been non-pervious with a high degree of silts, soils, or clayey material such that the designed percolation was ineffective or defective. Thus, a heavy rainfall would soak the surface and would not percolate beneath the surface as the silts, soils, or clayey mix would "hold" the water. The original imaging reveals that greening occurred in these large saturated areas. With a non-pervious deposition of moisture retentive silts, soils or clayey material base, and a saturated (water) source, vegetative growth has what it needs. These were the first "Green Wet Areas" on the dam.**

So the question becomes, what came first? The Dirt or the Saturation?

If the Dirt was there first, it had to have been from construction. But how could all those computers controlling the automated conveyor belt system's sand mix rate, to the Zone 3 fill, could have added silts, or soils, or clayey material? Bad programming? Bad Computer? And how did this computer know to do this in a perfectly symmetrical arrangement to form "twin" regions? Or was it from construction error? If so, did drivers of the load dumpers mistakenly take material from the giant fill "dump hopper" to Zone 3 fill instead of the Transition Zone (contains silts) or the Core (contains clays & silts, & clayey soil)? If they did, it had to be perfectly aligned errors to make these "twin regions". The odds of any of these conditions seem far remote, in fact they would say to defy probability.

The "other" wild supposition is - did rain somehow cause "dirt" to be brought to these spots from the tiny traces of soil particles within the Zone 3 surface area? This would defy the downward rain percolation characteristics of the Zone 3 fill. In addition, for all of the tiny traces of soil particles in the Zone 3 fill to be gathered up and deposited in the dirt spots, would require such a high concentration of collection (from tiny trace amounts) of a large volume of Zone 3 fill such that very "smart" rain would have to "collect", "redirect", and "go vertical upwards" to the dirt spots.

If the saturation was first, how did the dirt get there?

Could saturation result in the dirt spots? Yes. Where's a high concentration of dirt? The transition zones and the core. Then where's the original water source for this saturation? The reservoir. Why didn't the Drain Zone capture the water? It clogged in two areas above from the transport of silts, soils, clay & clayey material What caused this strong seepage flow? The core developed settlement leaks from longitudinal cracks. How did the water saturate the Zone 3 surface instead of curving down to the bottom to the horizontal drain zone? Good question - more clues on this later. What happened to these original settlement leaks? The upstream Transition zone sealed the leaks with its silts & sands flowing into the core

Could this be the same dynamic mechanism at play in the current "Green Wet Area"? Good question… what do you think?.. more clues/evidence later...

**note: a larger image & RGB coloration matching to trees, grasses, and other vegetation in the larger image reveal the clear greening of these saturated areas. The zoom version here is less distinguishable due to the low resolution & blurring.