Yesterday was a landmark day at the Clary Lake dam for several reasons, not just because the underground storage tank was removed but also because PCS “shot gunite” to seal the upstream face of the dam! What an exciting (and loud!!) experience that was! I wasn’t familiar with gunite and had never seen the process so I didn’t know what to expect. The cement comes in a cement truck like regular concrete, but there the similarity ends; rather than a concrete slurry, the stuff that comes down the chute is actually only slightly damp concrete and sand mix. It dumps into a device with a strainer to trap large particles that “fluffs” it up and then blows it down a long rubber hose. At the nozzle end high pressure water is injected into the stream. The whole system is powered by high pressure air from a compressor.

It was very gratifying watching the high pressure stream of water and cement fill holes, cracks, and voids. Some of the larger voids took as much as 30 seconds to fill. I half expected one in a while to see water and cement come shooting out the other side of the dam, but I never did. Here are some more pictures of them “shooting” gunite:

All told it didn’t take them long once they got started. The were plagued with equipment malfunctions all morning, but once the cement truck arrived around noon, they got right to it and were done in less than 2 hours. Then they draped insulating blankets over the dam to help hold in the heat generated by the curing of the concrete.

I’ve got a couple of short videos I’ll post separately.

Day 5 of Clary Lake dam repairs: cleaning old mortar out of the seams on the upstream face of the dam in preparation to sealing them against leaking with gunite.

I’ve added another dozen or so pictures of day 4 of repairs to the Clary Lake dam. On Friday PCS finally finished demolition of the deteriorating concrete plug which was blocking the original log weir in the middle of the dam (picture at left). The crew proceeded to remove material cautiously, being careful to keep the demolition debris out of the stream. One big surprise was finding a layer of old wooden timbers laid on top of the bottom layer of rock and covered with concrete. These date back to around 1950. The wood was punky but still relatively solid, and came out in individual pieces roughly 6″ x 8″ x 36″ long. I have no idea why they were left in place. Continue reading →

Today was day 2 of repairs on the Clary Lake dam and I’ve taken more pictures (see the Fall 2018 Gallery) to show the work in progress. They’ve started demolishing the old concrete plug in preparation for pouring new concrete and installing a weir in the top. The two piers and the concrete on top is newer and still pretty hard, it looked like a lot of work busting it up with those little pneumatic hammers. I remarked that my dentist has bigger drills than those they’re using, but they like them because they’re easier to use and don’t throw debris all over the place.  They’re sure doing the job- especially lower down in the rotten concrete. The demolition of the concrete plug should be finished tomorrow or early Friday.

Here’s a picture from 1950 showing what those two concrete piers were used for: they held a mechanism for opening and closing a sluice gate. This gate was built to replace an even larger original gate that was roughly 65″ tall and 84″ wide. About 1960 Chester Chase removed this sluice gate, filled it with concrete, and installed the current gate mechanism for the existing 34″ diameter pipe which you can just see to the bottom right. That pipe was originally installed by Henry Clary when the dam was built in 1903 and connected to a penstock that ran all the way down to the wheel house located below and behind the mill. You can see the outlines of the original 65″ by 84″ weir in the photographs and the vertical seam where they partially filled in the left side to create the weir shown in this picture. There’s a lot of history here.