Best by a Dam Site
Sunday, August 30, 2009
Alcova, WY
The North Platte River has run through this mountainous and geologically active area for eons -- millions of years. Over that time it cut deep canyons into the surrounding rock as incredible forces uplifted, raised, the earth's crust. In the early 20th Century some of those canyons were used as dam sites, where a substantial dam could be built utilizing the canyon walls as part of the dam. That's just what happened here at Alcova Reservoir and just to the south, upriver on the North Platte, at Pathfinder Reservoir. We explored both today.
As I've written before, we're in high country. The surface of Alcova Reservoir is about 5,500 feet and the surface of Pathfinder is about 5,800 feet. And all around are exposed rock outcroppings of various colors and composition... red, tan, white, green... granite, an iron-rich shale, limestone and sandstone. Right here at Alcova Reservoir, there's a thick layer of deep red material... obviously an iron-rich shale that's stark against the more common browns, tans, and whites of limestone, sandstone, and granite. And these layers, which must have been flat, horizontal, during their forming, are now dramatically slanted and sometimes almost vertical -- caused by a powerful uplifting. From some vantage points high on the hills around here, it looks like the entire area is tilted. It's really quite a site to see.
We drove down to Pathfinder Dam first. After parking we followed a couple other people to a fenced walkway that led to the dam. In our post-9/11 world, I've come to expect that dams are off limits. Any large dam we've been to in the past couple years has high security, serious fencing, and it's hard to get anywhere near the thing without an act of congress. But little old Pathfinder Dam, which really isn't all that little, was open for explorers today. There were a few doors here and there that were locked, but for the most part, we could wander around, open gates, walk across the dam itself to the other side, walk along the edges of the canyon below the dam... and there wasn't anyone around at all. We had the run of the place. Hmmm.
This dam was built in 1905 and is made of granite. I don't think I've seen a granite dam before -- at least one built like this. The core is random chunks of granite mortared together into a single mass. The outer walls both on both the upstream and downstream faces are large uniform blocks of granite put together like a brick wall. It still looked good after more than a hundred years.
These dams, like most, were built for fresh water supply, flood control, and recreation. In this case, the main use for the fresh water is farm irrigation.
The canyons that were cut by the river and are still visible between the two reservoirs are simply incredible. I'm always in awe at the power of water to cut through solid rock... leaving narrow canyons hundreds of feet deep. We got some good photos of what I'm talking about.
After Pathfinder Dam, we took another route back to Alcova Dam... the back road. During the exploration today, we ranged from a low of 5,400 feet of elevation below the dam at Alcova, to a high of more than 6,300 feet at the high point above Pathfinder. That's nearly 1,000 feet in just a few miles.
The Alcova Dam was not open to the public... at least not today. There's a power plant here and it was making power judging by the turbine hum and the steady flow of discharge water. Maybe that's why they keep the public at a distance. In any case, the intense sun and our hiking and climbing around at various spots along the way cause a thirst that we quenched at the General Store in Alcova. Maybe an ice cream cone too.
Well, it's time to pick up the pace a bit on our westward trek. Tomorrow, Monday, we're pulling up the jacks and heading down to Rawlins, right on I-80, then west on the super-slab to Western Wyoming where we'll try to find someplace to overnight before hitting the Oregon Trail on Tuesday.
T
Alcova, WY
The North Platte River has run through this mountainous and geologically active area for eons -- millions of years. Over that time it cut deep canyons into the surrounding rock as incredible forces uplifted, raised, the earth's crust. In the early 20th Century some of those canyons were used as dam sites, where a substantial dam could be built utilizing the canyon walls as part of the dam. That's just what happened here at Alcova Reservoir and just to the south, upriver on the North Platte, at Pathfinder Reservoir. We explored both today.
As I've written before, we're in high country. The surface of Alcova Reservoir is about 5,500 feet and the surface of Pathfinder is about 5,800 feet. And all around are exposed rock outcroppings of various colors and composition... red, tan, white, green... granite, an iron-rich shale, limestone and sandstone. Right here at Alcova Reservoir, there's a thick layer of deep red material... obviously an iron-rich shale that's stark against the more common browns, tans, and whites of limestone, sandstone, and granite. And these layers, which must have been flat, horizontal, during their forming, are now dramatically slanted and sometimes almost vertical -- caused by a powerful uplifting. From some vantage points high on the hills around here, it looks like the entire area is tilted. It's really quite a site to see.
We drove down to Pathfinder Dam first. After parking we followed a couple other people to a fenced walkway that led to the dam. In our post-9/11 world, I've come to expect that dams are off limits. Any large dam we've been to in the past couple years has high security, serious fencing, and it's hard to get anywhere near the thing without an act of congress. But little old Pathfinder Dam, which really isn't all that little, was open for explorers today. There were a few doors here and there that were locked, but for the most part, we could wander around, open gates, walk across the dam itself to the other side, walk along the edges of the canyon below the dam... and there wasn't anyone around at all. We had the run of the place. Hmmm.
This dam was built in 1905 and is made of granite. I don't think I've seen a granite dam before -- at least one built like this. The core is random chunks of granite mortared together into a single mass. The outer walls both on both the upstream and downstream faces are large uniform blocks of granite put together like a brick wall. It still looked good after more than a hundred years.
These dams, like most, were built for fresh water supply, flood control, and recreation. In this case, the main use for the fresh water is farm irrigation.
The canyons that were cut by the river and are still visible between the two reservoirs are simply incredible. I'm always in awe at the power of water to cut through solid rock... leaving narrow canyons hundreds of feet deep. We got some good photos of what I'm talking about.
After Pathfinder Dam, we took another route back to Alcova Dam... the back road. During the exploration today, we ranged from a low of 5,400 feet of elevation below the dam at Alcova, to a high of more than 6,300 feet at the high point above Pathfinder. That's nearly 1,000 feet in just a few miles.
The Alcova Dam was not open to the public... at least not today. There's a power plant here and it was making power judging by the turbine hum and the steady flow of discharge water. Maybe that's why they keep the public at a distance. In any case, the intense sun and our hiking and climbing around at various spots along the way cause a thirst that we quenched at the General Store in Alcova. Maybe an ice cream cone too.
Well, it's time to pick up the pace a bit on our westward trek. Tomorrow, Monday, we're pulling up the jacks and heading down to Rawlins, right on I-80, then west on the super-slab to Western Wyoming where we'll try to find someplace to overnight before hitting the Oregon Trail on Tuesday.
T
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