Just over a year ago, a major rockslide on Easter closed Dillon Dam Road for around two and a half weeks in what officials considered to be the largest rockslide in the last 30 years on the road. Now having more clarity around why the rockslide happened, officials are contemplating significant preventative efforts to avoid the situation repeating itself on the well traveled road known for its views. 

Experts told the Summit Board of County Commissioners at an April 29 meeting that the 2024 Easter rockslide resulted in an estimated $155,000 in direct costs to get the road back up and running. Indirect costs of the road being closed came out to an estimated $800,000. RockSol Consulting Group representative Ty Ortiz told commissioners the indirect cost estimate stems from commuters losing access to a heavily used road and the detour that had to be set up because of it. 

What Ortiz described as a “slope failure” caused the Easter 2024 rockslide. 

“What occurred on Eastern 2024 is the failure of a massive rock. … I think (it was around) 60-foot-by-60-foot, probably about 10-feet thick,” he said. 

His consulting group determined the area where that slide occurred is still “susceptible to additional rockslides” given its slope and other factors, like the type and density of rocks there. 

Ortiz presented officials with three different project options, all with very tentative price tags. The first involves aggressive rock scaling, reinforcement and netting with a potential price tag of $2.7 million, and the second option is a more intensified version of the first in that it would include rock bonding, or essentially gluing rocks to the slope. The second option’s presented price tag was around $3.3 million. The third option entails some of the same reinforcement elements, but is much more significant in that it would include rock excavation and the creation of a ditch. The consulting team said the results of Option 3 would have more of a lasting impact. 

“Having a ditch is by far the safest thing you can do so the rockfall has a place to land, as opposed to (landing on) the roadway,” Ortiz said. 

The presented price tag for Option 3 comes out to around $8.9 million. Commissioner Tamara Pogue wanted to know if these price tags were “pre or post tariffs,” referencing the potential impact they could have of increasing the costs of construction. The consulting team said they came up with these price tags in January, before any serious conversations around tariffs began. They said they based their estimates off the rock-related project costs for the Floyd Hill project on Interstate 70 near Idaho Springs. 

Officials showed interest in Option 3, but were wary of the high price tag. They saw value in Option 2 as well, but numerous factors dissuaded them from making a concrete decision. One of those was the sentiment that the county isn’t the only player at the table. 

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“There are some partners that we ought to talk to about this project, Denver Water (because of the Lake Dillon Reservoir they control just below the dam) certainly, and Dillon and Silverthorne … even Frisco benefits from the road as well,” Pogue said. 

“We should start by having some conversations with partners about what they might contribute,” she later added. 

Another partner, one that officials indicated likely wouldn’t be asked to contribute financially, is the U.S. Forest Service, a landowner along the Dillon Dam Road.

County staff members and the consulting team said the options presented could all take around three months to complete. This would warrant a road closure, but staff and officials said they would like to see work staggered to avoid a three-month closure. 

Out of all the entities with a stake in Dillon Dam Road, Denver Water is among those yielding the most influence. Commissioner Eric Mamula wondered if there was a way to shift the bike path and the road to create room for the ditch versus having to excavate the rock wall to create it, asking staff members if it could help cut costs. Staff members responded that Denver Water would have to move one of their facilities along the reservoir in order to do that. 

“I guess we need to have a talk with Denver Water also about what their 20-year future looks like,” said Mamula, highlighting the need to be aware of any major changes the district plans to make for the sake of the planning process. 

Thinking of the nearby reservoir that provides drinking water, commissioner Nina Water questioned the consulting team if any environmental impact analysis was done to determine if any materials or substances used in the project could be harmful if they made their way into the water. 

The team said they would look into that once a project is chosen, and they know what materials will need to be used. 

Officials also discussed what funding was available to them for these projects, with Mamula noting he doesn’t feel like the county has $8.9 million for it given work that needs to be done on numerous other key roads. 

County staff members said there’s grant funding opportunities out there, and laid out an approaching deadline of May 19 for one and June and August deadlines for others. If the county were to go for the one with a May 19 deadline, a decision would need to be made before then. 

Commissioner Mamula said he would broach the topic at an upcoming mayors and managers meeting involving the county and local governments to gauge what other local officials are thinking.