The Adams Tunnel: A River Under the Mountains
Near Grand Lake, Colorado
On the eastern shore of Grand Lake, hidden beneath the water, is the intake for one of the most ambitious pieces of plumbing ever built in Colorado. This is where water enters the Alva B. Adams Tunnel, a channel bored more than thirteen miles straight through the solid rock of the Continental Divide.
The tunnel is the heart of the Colorado Big Thompson Project. About eighty percent of Colorado's precipitation falls on the western slope, in these mountains, but about eighty percent of the state's people live on the eastern side. So engineers decided to move the water to the people.
Grand Lake was joined to two new reservoirs, Shadow Mountain Lake and Lake Granby, and water is pumped up and funneled to the tunnel's mouth here. From this spot it flows by gravity under the mountains to the eastern slope, carrying up to five hundred fifty cubic feet per second. The tunnel is named for Alva Adams, a United States senator from Colorado who convinced Congress to pay for it.
Construction began in nineteen forty, paused during the Second World War, and the crews finally holed through in nineteen forty four, an event broadcast live across the country on national radio. The first water flowed through in nineteen forty seven.
