Summit County Citizens Voice

The Roberts Tunnel, a key link in Denver Water's supply system, took about 16 years to build. PHOTO COURTESY DENVER WATER. Click on the photo to visit Denver Water's online gallery of historic water project photos.

Major maintenance of valves at east end, near Grants, will take several months to complete

By Bob Berwyn

SUMMIT COUNTY — The trans-mountain Roberts Tunnel, which transports water from Dillon Reservoir to the South Platte drainage, will remain shut off until April while Denver Water does major maintenance on the valves at the east end of the underground aqueduct.

The 23-mile tunnel under the Continental Divide was completed in 1962. It’s often shut down in the fall for shorter periods of time for regular maintenance, but this year’s project required a longer closure, said Bob Steger, Denver Water’s manager of raw water resources.

“We’re in the process of draining it right now,” Steger said. The original plan was to shut off the tunnel in early November, but after talks with Keystone Ski Area, which uses some of the water from the tunnel for snowmaking, Denver Water decided to hold off on the project until mid-December, toward the end of the snowmaking season.

Here’s how Keystone uses the water: The resort has a diversion directly on the Snake River, but in some years, flows in the stream drop to low levels in late autumn, just as the ski area really needs to ramp up snowmaking. Sometimes the flows are so low that the snowmaking diversions cause the level to drop near a state-set minimum of six cubic feet per second, established to protect aquatic life.

Several years ago, Keystone worked out a deal with Denver Water to take some water out of the Roberts Tunnel at the Montezuma Shaft, a maintenance access point located along Montezuma Road at the Blight Placer. In that area, the underground tunnel runs very near the Snake, so it’s easy to pump the water out of the tunnel and into the river to help maintain the stream flow.

This year, because of the scheduled maintenance work, Keystone activated a special provision in its snowmaking agreements which enables the resort to cut the flows well below the minimum instream flow, down to 2 cfs, in an emergency situation, under extraordinary circumstances.

Click here to visit Denver Water’s online gallery of historic photos.

Construction of the tunnel began in 1946 and was completed in 1962.

Filed under: Dillon Reservoir, Environment, rivers, Summit County Colorado Tagged: | Denver Water, Dillon Reservoir, Keystone Ski Area, Roberts Tunnel, Snake River minimum stream flows, Summit County Colorado, Summit County News