Transcript for Challenge at Glen Canyon, segment 04 of 11

{{{Background noise of rushing water}}}

Although engineers had no way to see into operating spillways, they could tell what was happening by the action of the water emerging from the lower portal flip bucket. On June nineteenth, the left spillway stopped sweeping, indicating that erosion by cavitation was damaging the concrete tunnel lining. The flow was raised from twelve thousand to seventeen thousand cubic feet per second and the sweep resumed. But on June twenty-eighth, the sweeping again ceased. When the flow was raised, this time to thirty-two thousand cubic feet per second, the increased flow brought forth sandstone colored water. Pieces of concrete and rock were hurled from the spillway. Obviously the spillway was being heavily damaged. The flow was immediately reduced and the water cleared. By this time, however, the peak of the spring runoff, over one hundred twenty thousand cubic feet per second, was flowing into Lake Powell. Much of this inflow would have to be sent through the spillways.

It was a tense situation for the engineers in charge. No one could enter the left spillway, yet no one knew the extent of the damage.

Hopefully we'll be able to keep them online.

Yeah, that's really large flows, and they've been that way for a long time and will have to stay that way, again for a long time, so you can see that it will be very critical in the decision that we make. The only way we can get additional storage is to add flashboards on top of the gates, tie them back down into the gate struts, and that will add additional storage in the reservoir.

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