Day 8 — Dam!
The biggest American dam project in decades—literally…
We drove an hour north of Denver first thing. After cruising past every farm animal on the roster, we arrived at a security checkpoint. The guards waved us through, and we met our hosts from Barnard Construction within America's biggest job trailer.
Did the size of the trailer correlate with the size of the project? Oh yes.
But before the visit, allow me to explain the project.
Millions call Denver and the surrounding areas east of the Rockies home. The problem? Most of Colorado's water is west of the Rockies, over the Continental Divide.
Massive pumps push the water over the mountains and into reservoirs for storage, eventually providing clean drinking water for Coloradans.
You've likely heard about the wild growth Colorado's experienced over the past decade. And with a booming population comes a need for more water. Enter Barnard and the Chimney Hollow Reservoir Project.
Once complete, the estimated $690MM dam will stand 392' tall and span 3,700' across the valley. Northern Water will then pump up to 90,000 acre-feet of water from existing standpipes through a new tunnel to fill the valley, creating the new Chimney Hollow Reservoir.
The dam itself is rock with an asphalt core. The last time I visited the project, in June of last year, Barnard crews had nearly prepared the dam's foundation, which required meticulous cleaning of the existing rock to create a blank canvas for material placement.
Onto the visit! Our first stop was the emergency outflow, a roughly 11' X 11' cast-in-place concrete culvert starting at the top of the new structure and terminating around 2,300' later at the bottom. The concrete crews had already poured and stripped some sections using forms they could slide up or down.
Next was the headline event—the dam itself. We started with the crews placing another lift of the asphalt core. Imagine a wall of asphalt, only a few feet wide, in the middle of the rock structure. If water penetrates the upstream rock, it will run into the impermeable asphalt, travel to sand chimney drains, and flow out in a controlled manner. Since it's such an essential component of the structure, Walo from Switzerland, one of the only companies in the world capable of meeting the specifications, is doing the work.
From the core, we walked over to the placement operation. Haul trucks, ranging from 45 to 100 tons, hauled material from the on-site quarry over the asphalt core using temporary bridges, dumping it in front of an awaiting D9 dozer with Trimble GPS. Every lift is around 3', and they have over ten million yards of rock in total to haul and place.
Our second to final stop was the quarry. And when I say quarry, I mean QUARRY. It's potentially the most productive quarry in Colorado, and it's temporary! We watched an arsenal of 95-150 ton excavators and mining-size loaders attack the blasted rock, filling trucks every minute.
The trucks roared off to the fill or hauled material to the monster crushing spread. To eliminate truck traffic and reduce costs, crews make all rock needed for the concrete, asphalt, and inner portion of the dam on site.
The best part? No one will ever see the quarry again—engineers designed the entire area to lie beneath the water level of the future reservoir.
For the finale, we asked to see the tunnel. Our hosts made a phone call, then gave us a nod. They were as excited as we were… They'd never seen it either!
We signed out metal tags indicating those working inside and began walking into the enormous cavern, soon leaving the daylight behind.
Barnard crews had worked for over a year to blast, excavate, and shotcrete the nearly 30' in diameter tunnel. The final step was to pour the 2' thick concrete walls using a circular form they'd assembled at the end. We watched the crews preparing for the first pour, asked a million questions, then navigated through the puddles to return to society.
Water on demand is hard work… Thank goodness we have people like the folks at Barnard to make it happen.
Where to for day 9? Here's a hint:
"I'm talkin' about a place where the beer flows like wine."
