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Spillway Slippage Targets on Sidewall backside - cleared foundation area of Elect Tower (straight view to targets)..

Image zoom infers that two more targets were bolted at abutting expansion joints on the left spillway sidewall. These optical targets have concise black and white aligned stripes on two panels. Each panel is bolted to one side of the expansion joint seam. Any differential movement (i.e. expansion) of the joint would cause the stripes to shift with respect to each other. Using a good zoom camera, the shift may be detected & measured from a safe distance away from the wall. The clearing of the foundation of the removed electrical tower shows the clearing extended to the sidewall. This clearing provides a good "straight on" view to the targets. Prior to clearing the hillside soil base was blocking a straight view to the uppermost target.

The green drain piping installed into the original broken section of the sidewall drain shows waterflow from the output.

Two "slippage detection" targets bolted to backside of left spillway sidewall. Cleared foundation area of removed electrical tower allows view access of the optical targets. note: Green drain pipe waterflow - working drains.

"Slippage detection" optical target bolted to inside of spillway chute sidewall. This is at a damaged section of the upper spillway where downslope movement of the left sidewall and adjacent main slab occurred before repairs.

Recent Subsurface Rock Core Drilling & sampling - Hard Amphibolite, soil, weathered rock…

Drilling rigs are taking core samples. Hard Amphibolite (blue grey color) is observed in the center of the longer core sample under inspection. If you have a good zoom on the image you can see black "line" markings placed on the rock to measure angles of the fractures (note drafting tools). The whiteboard denotes "Oroville Spillway Emergency". However, the drilling location may only be roughly inferred from electrical power lines in another image. Core sampling of the subsurface rock is data that would be important for any "next step" phases or proposed options for a new spillway replacement and/or repairs.

Core Sample Analysis - A hard Amphibolite rock seam (blue grey color) observable in the middle of the longer core sample being inspected.

Confirmed: Pre-indicator Failure detection optical targets bolted to Spillway Sidewall backside (two targets)

New DWR hi-res image confirms that two more targets were bolted at abutting expansion joints on the left spillway sidewall (this was inferred from a longer distance image from a post on 3/21 - see link below). These optical targets have concise black and white aligned stripes. Each panel is bolted to one side of the expansion joint seam. Any differential movement would indicate a potential "pre-failure" development of downslope shifting of the damaged end of the spillway. These two sections are in an area that was heavily re-inforced by the installation of drilled emplaced "rock bolts" via repair work. The repairs are designed to (1) consolidate the weathered rock substructure by injection of pressurized grout into any fractures and (2) to provide an anchoring of these deep "bolts" to the top surface of the concrete. In order to safely view these optical targets, the hillside was excavated.

The green pipe reveals the sidewall drain water flow that normally would be connected to the pipe coupling in the sidewall. The original connecting pipe to this coupling has broken away from the hillside erosion.

Not sure yet what to make of the "wet" spots in the green "hydro seeding grass"' area in the excavated bank and the lower leveled off region. The darker green indicates moisture. (other than subsurface soil waterflow from recent rains). The reason for the interest in potential "wet spots" is due to the Board Of Consultants note of extended release waterflow in the drains after the spillway gates are closed. If the "basin" of backfill was pooling the underdrain water (as the source of a back flow into the low point of the drains after the gates were closed) there is the potential that this water would work its way in saturating the surrounding hillside.

One of the upper spillway sidewall drains circled. Just a note in comparison to the other drains of a higher flow.

The four concrete blocks just above the hydro grass seeding embankment may have been the footings of the removed electrical tower as they remain in a matching footing pattern (in comparison to the other tower footing(s)).

Spillway Slippage Targets on Sidewall backside - cleared foundation area of Elect Tower (straight view to targets)..

New DWR hi-res image confirms that two more "slip" detection targets were bolted at abutting expansion joints on the left spillway sidewall. "Wet spots" in hillside. Stronger sidewall drain flow. Green repair pipe dumps broken drain line water on shotcrete repair area.