Here’s a report from Chris Woodka writing for The Pueblo Chieftain. Click through for the before and after construction photos. Here’s a excerpt:
A 75-foot hole is being dug down to bedrock in the narrow shale arroyo below where the North Outlet Works will be installed later this year. Much of the work is within the federal security boundary that protects the dam, so workers are under 24-hour surveillance by armed guards. To the south, water is gushing mightily out of all three outlets on the face of the dam. The workers are protected by a coffer dam made from more than 300 giant bags, each filled with 2 tons of sand. It seems safe enough, although work already is about 35 feet below the water level and getting deeper. Soon, a ramp will be built to get equipment in and out. For now, if the coffer dam should fail, a 220-ton crane is standing by to pluck out the track hoe and loader in the hole. For the workers, it would mean a mad dash for a ladder that leads to safety…
“We found a buffalo skull,” said MWH engineer Greg Minnick, when asked whether anything unusual has been encountered. “Other than that, just a lot of wet dirt.”[…]
The digging at the base of the dam should be complete by early July. About 6,000 cubic yards of material will have been removed. About 350 to 400 truckloads of concrete will be placed in the hole to form an apron about 30 feet from the dam. The rest of the area will be back-filled. Minnick said about 15 to 16 trucks a day will come to the site, pouring in the early morning hours to take advantage of lower temperatures. That work should be finished in August. After that, a stainless steel sleeve will be placed inside the dam outlet. It will connect to a Y-shaped pipe that will supply both the river — at the same rate as the old outlet did — and the Juniper Pump Station to be built about one-quarter mile to the northeast. The first section of pipe from the North Outlet Works will taper out to a maximum of 90 inches in diameter, separating into a 48-inch line that will supply Pueblo West with up to 18 million gallons of water daily, and a 66-inch line that will deliver up to 78 million gallons daily to El Paso County. Part of that pipe will have to be installed through the rocky formations at the base of the dam, and engineers are now working on a design and work plan to do that without causing vibrations that could disturb the dam, Tunnah said.