A routine camera download from the two time-lapse stations was accomplished last Saturday (17Sep11). Progress observed at the deconstruction site was significant, with tunneling approaching the 40 foot mark (almost half way toward the upstream target at the dam’s face). The photo above shows a first view of the tunnel site. This tunnel will be used to breach the dam in late October, and allow flushing the entire reservoir volume (and the majority of the accumulated sediments) from the upstream reservoir (soon to be canyon), in six hours, at a rate of 10,000 cubic feet per second. This will be the first time that this method of dam removal has been employed… and historic in many respects.
Note the steel mesh blanket above the tunnel, which is draped over the opening during blasts to prevent fly-rock. This is a very important consideration, since one of the two deaths occurring during original construction in 1912-13 was consequent to a worker being struck in the head by a flying rock. The tunnel is being excavated on the far eastern edge of “Cameron Canyon”, and the native basalt contact is readily visible on the right of the tunnel bore.
As previously mentioned, all equipment is being delivered to the canyon using a cable yarding system. This same system is being used to “fly-out” all resulting concrete and steel debris in a large aerial bucket. The photo above shows the cable anchors and blocks used to affix the yarding cable on the west wall of the canyon. This attachment point is along the “goat trail” being used by the authors to access time-lapse Station 1.
Finally, another major activity occurring Saturday was mobilization of the floating crane near the upstream face of the dam. Soon, the crane will be used to dredge sediment and logs from the base of the reservoir to allow free and rapid draining of the reservoir in October.