How the Moffat Tunnel conquered the Great Divide

The Moffat Tunnel changed the way Denver Water provided a reliable water supply to its earliest customers.

February 26, 2015 | By: Steve Snyder
The water tunnel is the pilot bore next to the famous railroad tunnel, pictured here in 1956.
The water tunnel runs parallel to the famous railroad tunnel, pictured here in 1956.

This week, 9News and History Colorado provided a historical perspective on the Moffat Tunnel. Eighty-seven years ago, that tunnel changed the way railroad travelers traversed the Continental Divide. But the Moffat Tunnel would provide groundbreaking implications when it came to water delivery as well.

In the early 1920s, the Denver Water Board (as Denver Water was called then) was a fledgling utility searching for additional water to serve a growing city. The water provider had already secured additional water rights from Colorado’s West Slope, but getting that water over the Continental Divide and into existing infrastructure was problematic. Necessity would soon meet innovation.

As David Moffat’s railroad company started construction of a tunnel to provide fast train service through the Rocky Mountains, it also bored a parallel tunnel to be used by their workers to access the main tunnel each day. Denver Water Board members saw potential in that access tunnel, envisioning that it could be reconfigured to bring water from the Fraser River on the West Slope to Denver Water’s South Platte River system on the Front Range.

Workers pose for a photo in the Moffat water tunnel in this 1930 photo.
Workers pose for a photo in the Moffat water tunnel in this 1930 photo.

In 1922, that dream became reality when the Colorado Legislature created the Moffat Tunnel Improvement District and Commission to oversee the project. Workers completed the parallel tunnel and partially lined it by June of 1936, and the first waves of water flowed through. Following the severe drought of 1950, the tunnel was enlarged again, and lining was completed in 1958. Initially, the federal government owned the tunnel and leased it back to Denver Water. After 30 years, the tunnel became Denver Water’s property.

Denver Water still relies on the Moffat water tunnel today. The 6.2-mile tunnel can deliver up to 100,000 acre-feet of water a year, providing an important source of water for Denver Water customers. The Moffat Tunnel and its parallel bore are engineering marvels — a credit to the foresight of Denver Water’s founding fathers.*


*Information for this article came from Patricia Nelson Limerick’s book A Ditch in Time – The City the West and Water.

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