DENVER -- Denver Water officials said Tuesday they will close Dillon Dam Road indefinitely beginning at midnight.
The public recreation trail will remain open to bicycles and pedestrians. Denver Water also will work with local officials to allow access for emergency vehicles.
"We have decided to close the road as a proactive measure to maintain public safety," said Penfield Tate, Denver Board of Water commissioner. "We are not aware of an imminent threat, but in the last several months we’ve grown far more concerned about the vulnerability of the dam and the potential for catastrophic consequences downstream if the dam were targeted."
The reservoir in Summit County serves as a primary source for Denver’s drinking water supply. Dillon is the utility’s largest and most accessible reservoir.
The one-mile public-access road crosses the top of the dam from Dillon to Frisco. Dillon Reservoir holds 254,000 acre-feet of water, is of earth-fill construction and is immediately upstream of a large retail area, a recreation facility, Interstate 70 and many homes. If the dam were compromised, thousands of lives would be affected.
"Good sense dictates closure of the road," said Tate.
Some public access roads across dams in other parts of the country -- New York and California, for example -- have also been closed due to vulnerability concerns.
"We understand that the closure will inconvenience motorists in Summit County," said Tate. "However, we have concluded that the grave danger presented by a dam failure outweighs the disruption to travelers."
In the last seven years, Denver Water has spent more than $10 million to enhance the safety and security of its facilities. At Dillon, changes include fencing, barriers of various types, camera surveillance and 24-hour security guards.
"Having exhausted other options and still being uncomfortable with the level of risk, we consider road closure the action necessary to best protect the residents of Summit County as well as the water supply," said Tate.
He added, "The best long-term solution to this issue may be an alternative road alignment that connects one side of the reservoir to the other without traversing the dam. This type of solution would require a cooperative effort among many different parties."
To help begin that cooperative effort, Denver Water has hired an engineering firm to consider potential alternative alignments, and preliminary meetings with affected jurisdictions have begun. Denver Water will include Summit County communities in further defining the dam’s vulnerability and determining whether alternate security measures should be taken.