A federal judge on Tuesday heard expert testimony about a massive Denver Water project in Boulder County as she decides how much construction is needed to shore up the unlawfully permitted reservoir expansion.

Last month, U.S. District Court Senior Judge Christine M. Arguello found that, as a result of federal law violations, the expansion of Gross Reservoir and Dam should cease permanently and any further construction on the ongoing project would stop temporarily. The pause on construction, Arguello wrote, would give her time to hear from engineers and determine what work would need to occur to make the dam safe.

However, Arguello and the Denver-based federal appeals court both allowed construction to resume until she could hold a hearing to determine the scope of essential work.

At a May 6 hearing, Arguello heard about the technical aspects of the project, including from Indianapolis-based civil engineer Michael Rogers, who was the project manager and engineer of record for Gross Reservoir until he moved away in 2022.

“I’m still very interested in the project. It’s kind of my baby,” testified Rogers, who said he continues to field questions from the project team. He added that the effort to raise Gross Reservoir by 131 feet was “the first of its kind” in the world.

Arguello previously found the U.S. Army Corps of Engineers wrongfully approved a discharge permit for the project after it improperly eliminated alternatives that avoided disturbing wetlands. Further, the Corps improperly combined two distinct goals that had the effect of steering the project toward reservoir expansion. The actions violated both the Clean Water Act and the National Environmental Policy Act.

Denver Water said it has already incurred $314 million in construction costs on the 60%-completed project, with an additional $4 million per week in construction delays. The utility warned of safety risks if the deconstructed-and-reconstructed dam is left in its current state.

Much of Rogers’ testimony occurred behind closed doors, so as not to publicly divulge information Denver Water deemed confidential.

In his public testimony, Rogers described the structure as a concrete gravity dam held in place by its weight. However, it also had a slight arch to it. The new dam, as designed, would not only be raised, but would have upgraded seismic standards and could absorb greater strain.

“This dam is a high-hazard type, which means a failure could lead to loss of life and extreme property damage,” Rogers said. “Changing it midstream would be very complicated. It would need to go through a whole rigorous design process.”

The U.S. Court of Appeals for the 10th Circuit previously declined to entirely set aside Arguello’s original moratorium on construction while Denver Water appeals her findings of unlawful permitting. Rather, it allowed construction to continue while it awaits Arguello’s post-hearing decision on the scope of additional dam work.

It acknowledged Arguello will issue a “tailored permanent injunction” on dam construction based on what she heard from Rogers and other experts.

The case is Save the Colorado et al. v. Graham et al.