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Poor foundation material removal - Clay from under Original Upper Spillway revealed - Rest of Upper Spillway needs 3,000 rock anchor bolts to secure slabs

Photos reveal the original foundation materials that the old spillway was built upon. All of the unacceptable foundation material has been excavated to "sound" rock (bedrock). The depth of the excavation reveals how much "unacceptable" foundation material was underneath the Spillway (Fig 2).

Deep Clay is revealed in the deepest of rock crevices (Fig 1) that are being hand excavated. Dump box reveals the clay and its consistency as dumped from a bucket. The upper right corner of the dump box shows how the clay responds to moisture (pasty). The existence of this deep layer of clay reveals that the spillway operation did not wash as deep to this level to remove or erode. But it does reveal the substructure stability risk issue(s) (clay seams and saturation potential) that the upper "unacceptable" foundation material was built upon.

This is very likely why DWR/BOC has emplaced ~3,000 rock anchor bolts in the remaining section of the upper main spillway. They likely are concerned about the "unacceptable" foundation material and the "clay layers & seams", revealed in these photos, of the Upper Spillway that is being rebuilt securely.

Fig 1. Deep seams of clay being hand excavated by workers (in Upper Main Spillway section). Reveals the existence of clay even in deep foundation areas of the original spillway. Poses numerous issues with piping potential, slump of structural support, and anchorage integrity problems if not removed to sound bedrock.

Fig 2. Clay qualities revealed in dump box. Pasty wet clay in corner of box when clay is moisturized. Depth of excavation reveals how much "unacceptable" foundation material existed under the original Upper Main Spillway. No sign of any "backfill" concrete from original construction - even from residual attachment to clean bedrock.

Upper Spillway new drain system revealed - Same basic architecture as Old spillway - Access Cleanouts (vertical) & Longitudinal collector drains

This image reveals the drain system design. Two longitudinal drain pipes are captured showing the downslope rise of the longitudinal pipes AND the outward spacing of the higher pipe. This outward spacing "jog" is important as it allows clearance for the vertical access cleanout pipes. Without this "jog" outward the overlapping downslope longitudinal pipe would block the vertical pipes that are needed for inspection and cleanout (maintenance - if needed) to each underslab drain pipe.

Each longitudinal drain pipe is connected to a given set of underslab drains (not revealed in this image). If a person was clever they could estimate the number of drains connected together based on this photo and then reverse engineer the slope of the spillway. These drains are angled downhill such that water "self flows" all of the way to the end point. Each longitudinal drain section "end" will be at a spillway sidewall opening to allow the water to trickle or flow back into the main spillway chute. Note that the pipes may not look angled properly, but the camera image has an optical effect demonstrated by the image's artificial curvature of the leveling concrete edge (see edge just above center workers' helmets).

It is likely that the first drain outlet will be connected to the original spillway section that will remain for 2017/2018. I would anticipate that the designers would want to keep these drains isolated from the new spillway drains as a problem could occur from the old spillway section "pre-charging" the new spillway drains from any potential "excessive flows". (excessive flows from the know design issues of the highly cracked slabs, clay seam underslab voiding channels [further erosion] facilitating "piping", and old style contraction joint "seams" without "waterstops" to block water penetration).

Another revelation to this design is that it evidences that they likely plan on placing back fill material behind the new sidewalls. This back fill material provides protection for the piping, insulation to cold temperatures, and would provide important structural support to the vertical sidewalls.

Underslab Upper Spillway drain pipe dumps into a longitudinal drain pipe. Longitudinal drain connects to a given number of nearby slab drains, then angles outward, downslope and then into upper spillway sidewall to dump back into the spillway chute.