A Colorado company is promoting an ambitious clean‑energy rail concept that would hinge on one of the most significant new mountain tunnels proposed in the state in decades — a 3.6‑mile bore beneath Berthoud Pass designed to link the I‑70 corridor directly with Grand County.
STE‑Holdings, a Denver‑based energy and transit firm, outlined its “I‑70 Mountain Express” plan to Grand County officials this month. While the project includes a 100‑mile hydrogen‑powered rail network and a solar‑financed funding model, the centrepiece is the tunnel that would carry trains under the Continental Divide and reshape access to Winter Park and the Fraser Valley.
A new era of tunnelling in Colorado
Colorado’s last transformative mountain tunnel — the Eisenhower–Johnson Memorial Tunnel — opened more than 50 years ago and permanently altered travel patterns across the state. STE‑Holdings argues that a Berthoud Pass tunnel could have a similar effect, relieving pressure on the steep, avalanche‑prone highway and providing a year‑round, weather‑resilient connection between the Front Range and Grand County.
The proposed tunnel would form the final phase of a six‑stage rail build‑out beginning in Golden and extending through Black Hawk, Idaho Springs, Georgetown and the Loveland area before reaching Breckenridge. Only after those segments are complete would the line push north, boring beneath Berthoud Pass and emerging near Winter Park, where it would tie into existing rail infrastructure.
Tunnel-driven ridership and regional impact
STE‑Holdings estimates that the Berthoud Pass tunnel alone could attract nearly 2.7 million riders annually. The company based its projections on Colorado Department of Transportation traffic counts showing roughly 8,000 vehicles per day travelling between Empire and Winter Park — a corridor frequently slowed by winter storms, closures and heavy tourist traffic.
Grand County officials noted that the ridership assumptions are aggressive, but acknowledged that a tunnel eliminating the steep climb and hazardous conditions of Berthoud Pass could dramatically change travel behaviour, much as the Eisenhower Tunnel did for Summit County.
Engineering a hydrogen rail tunnel at altitude
The company envisions hydrogen‑powered trains running through the new bore, with electricity generated by a statewide network of rooftop solar panels. Hydrogen rail technology is already in service in Germany, Japan and China, and STE‑Holdings says the tunnel would be designed to meet international safety standards for ventilation, emergency access and fire protection.
The tunnel would also require extensive geotechnical investigation, right‑of‑way coordination and environmental review — all major hurdles for a privately financed project. STE‑Holdings has not yet engaged with the Colorado Department of Transportation, which controls the Berthoud Pass corridor and would need to approve any tunnelling activity.
Housing and development tied to tunnel access
The company’s proposal includes up to 5,000 new housing units near future Grand County stations, with half reserved for low‑income and senior residents. STE‑Holdings argues that the tunnel would unlock new development potential by providing reliable, high‑capacity access to a region long constrained by limited transportation options.
Sustainability advocates say the tunnel could become the backbone of a broader hydrogen‑based economy, supporting clean mobility, renewable energy production and workforce housing in mountain communities.
A bold tunnelling vision with steep challenges
Despite the excitement surrounding the idea of a new trans‑mountain tunnel, the project faces significant obstacles: securing right‑of‑way, gaining regulatory approval for hydrogen rail, financing hundreds of thousands of solar installations and navigating political resistance from entrenched energy interests.
Grand County commissioners described the concept as imaginative but uncertain. Still, STE‑Holdings cofounder Dave Ruble said the tunnel is central to the company’s long‑term vision.
“Our goal is to make Colorado more connected, more sustainable and more resilient,” he told officials. “The tunnel is what makes that possible.”
