There is story behind this cache and its name. Very near to the cache location you’ll see the McKays Point dam and reservoir on the North Fork of the Stanislaus River. A bridge crosses the river below the dam and above it are some nice swimming and/or fishing holes. From the far side of the bridge you can make your way down to the river and take in the height of the dam and the outflow that usually creates a huge cloud of water vapor.
So what’s the “mystery?” McKay’s is a fairly large dam, but as you look at it from below and above (continue on across the bridge and up the hill for views from above) you may be surprised that there are no high voltage electrical distribution lines or towers nearby. The first time I visited it, I was surprised to see that there is no hydroelectric generating station at the dam.
I was curious and after some research, the mystery was solved. It turns out there is a hydroelectric power plant … but it is almost 9 miles away from the dam. In a feat of engineering, the engineers that designed the dam and hydroelectric system constructed an underground tunnel that carries the water to the Collierville Powerhouse that is located outside of Murphys, CA. Here’s a description:
From McKays Point, the water enters an 18-foot diameter, 8.5 mile long underground tunnel. The water picks up gravitational energy as it falls the distance of 2,270 feet from McKays Point to the Collierville Powerhouse. The energy is sufficient to rotate two large turbines and generators weighing a total of 422 tons at a speed of 450 revolutions per minute. The Collierville Powerhouse was designed to produce 253 Megawatts of hydroelectric power.
The tunnel is far underground and bored through rock and granite. It was quite a project, and was likely more cost effective to build the powerhouse in a more accessible area than the steep and rocky Stanislaus River canyon.
If you want to see the Collierville Powerhouse, take Parrot’s Ferry Road off of Hwy 4 and head towards Sonora. Camp 9 Road will be on your left not long after you turn off of Hwy 4. You follow Camp 9 Road for about 7 miles where it ends in a parking area just below the powerhouse. What you’ll notice here is that the powerhouse is built on the side of a hill (you can see the large concrete abutment behind the plant where the tunnel comes out of the hillside and into the powerplant). The outfall from the plant flows into the Stanislaus River below the plant.
The cache is accessible by car, biking, street legal motorcycles and hiking. Although there are several ways to get there, I recommend the following route if you have never explored this area before. Take Moran Road from Avery and follow Moran Road until you come to Love Creek Road. Turn on Love Creek Road and follow it until you come to Doud’s Landing Road. Turn up Doud’s Landing Road and follow it until it ends in a “T” at Forest Road 5N38. This is a wide, gravel road that eventually turns into McKay’s Dam Road (you’ll see this on a google map). You have to turn left as there is a gate across the road to the right. Follow the gravel road for about 4 miles (the last part that goes down into the canyon below the dam is paved). There is parking on the shoulder on either side of the bridge.