Just days after ordering a permanent halt to the Gross Reservoir expansion project in Boulder County, a federal judge has granted Denver Water a narrow, temporary window to continue limited construction activities. This decision allows the utility to move forward while it appeals the ruling, despite concerns about prior missteps.

On April 3, U.S. District Court Senior Judge Christine M. Arguello issued a decisive order halting further work on the controversial project, citing violations of federal environmental law. Specifically, she ruled that the U.S. Army Corps of Engineers had improperly approved the project under the Clean Water Act and National Environmental Policy Act by failing to consider less damaging alternatives to expanding the dam.

But in a follow-up order on Sunday, April 6, Judge Arguello slightly eased her previous restrictions to allow for certain safety-related construction activities, while making it clear her stance on the underlying legal issues had not changed. She wrote:

"Denver Water argues nothing new. The Court will not allow Denver Water to relitigate issues it has already lost on before this Court."

The Gross Reservoir expansion, a $464 million project intended to increase storage capacity to serve 1.5 million people—roughly 25% of Colorado’s population—was already 60% complete when the halt was ordered. Opponents of the project, including six environmental groups, argued it would irreparably damage wetlands and local ecosystems. Judge Arguello agreed, criticizing the Corps for failing to properly assess other water storage alternatives.

Denver Water immediately filed for a stay of the ruling and announced its intent to appeal to the 10th U.S. Circuit Court of Appeals. In the request, the utility warned of potential hazards resulting from an unfinished dam structure.

"Public and worker safety, Dam stability, flood control, and sufficient water supply hang in the balance. These are precisely the circumstances where courts permit projects to proceed despite concerns about potential errors in related permitting decisions," Denver Water attorneys argued.

Although Judge Arguello acknowledged these concerns, she remained skeptical of the utility’s approach, writing:

"It is not clear to the Court that the only means of addressing the safety concerns is to complete construction of the dam to the specifications originally contemplated by the Project."

She also reiterated her earlier criticism of Denver Water’s decision to move forward with construction despite a pending legal challenge.

"Denver Water [was] choosing to immediately begin construction despite repeated warnings from Petitioners that they intended to challenge the Corps’ discharge permit."

Still, recognizing the potential for structural instability if left unaddressed, Arguello agreed to grant a 14-day stay that temporarily lifts her prior prohibition on any and all construction. She emphasized that the brief window is intended only to address urgent structural concerns and will be followed by a hearing with expert engineers to determine any additional actions needed.

"The Court will not allow Denver Water to relitigate issues it has already lost... [but] the Court believed the construction that may be completed in that window would not exceed what the challengers previously felt was appropriate."

The Gross Reservoir expansion has been the subject of public controversy for years, with environmental advocates accusing Denver Water of sidestepping accountability and pushing forward a project with long-term ecological consequences. The Corps of Engineers initially greenlit the project in 2017, labeling it the “environmentally preferable alternative” — a characterization now questioned by the court.

As litigation proceeds and the appeal is filed, the temporary construction window marks a rare moment of leniency from a judge who has otherwise issued scathing rebukes of how Denver Water has handled the project.

“The Court will not allow Denver Water to relitigate issues it has already lost on before this Court,” Arguello concluded.

Originally reported by Micheal in Colorado Politics.