Piece by piece Clues to the Erosion Channels under the Green Wet Area - DWR/DSOD recognizes dense Erosion channels in "determining what...needs to be done …re: slope stability
DSOD documents reveal that there is a "slope stability" issue worthy of noting in their 2015 inspection report regarding the "Green Wet Area". The context of their "slope stability" notation is in reference to the Green Wet spot. For beneath the Green Wet spot is a dense series of mysterious "erosion channels" that DSOD has investigated in 2011 (documented in their inspection report) of noting that they didn't see any waterflow in the erosion channel but the Greening area was "wet and damp". They too thought that there might be a clue to water flowing in the channels when the wet area was saturated. After all, something has to be forming these channels…
Piece by piece Clues to the Erosion Channels under the Green Wet Area - Clean Surface of dam with no erosion channels vs Dense Erosion channels - Linked?
DSOD had good reason to note of a "slope stability" issue in their 2105 report. Here are side-by-side images of a Clean surface of the dam and the dense erosion channels forming on the dam's surface. Same elevations, same left side of the dam. (side note - note the revealed construction layering strata lines in the Clean image).
Both of these areas of the dam have been exposed to the same weather since 1967, same heat/cold, same rains. The "normal" time weathering of the intended Zone 3 fill design is revealed in the minor weathering of finer materials, revealing minor areas of cobble rock, in the "Clean surface". The slope remains stable and resists even the strongest of rains endured over 48 years. At the Dense Erosion channel section, it too has been exposed to the same weather & rains. Yet, over 48 years, these dense erosion channels have been forming slowly, gradually.
Both of these areas were constructed in compacted layer fill at the same time in 1965 as these images are at the same elevation section. The same sands, gravels, cobbles, and boulders comprising the Zone 3 fill "shell layer" were laid in 2 ft "lifts" and compacted. So there is no evidence that a difference in construction & materials composition would be a likely mechanism tied to the "erosion channels". The "differential" key, between these two areas, is that the "erosion channels" originate at a "long established wet area" (as named/stated in DSOD inspection reports).
Yet there is a "clue" that helps answer the differences between these areas in the light of evidence to an underlying mechanism to the formation of the "erosion channels".
