The Colorado-based federal appeals court on Friday permitted construction to continue temporarily on Denver Water’s massive infrastructure project in Boulder County while a trial judge forges ahead with a hearing on the matter.

Earlier this 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.

Days later, Arguello allowed for necessary construction to temporarily resume, and the U.S. Court of Appeals for the 10th Circuit extended that window while it reviewed Denver Water’s request to continue work.

In an April 25 order, a two-judge panel of the 10th Circuit declined to address Denver Water’s request that it suspend, or stay, Arguello’s moratorium on construction entirely pending appeal. Instead, Judges Scott M. Matheson Jr. and Richard E.N. Federico believed it best for Arguello to proceed with the hearing she has scheduled for May 6, with construction permitted through then.

“The pending proceedings are expected to develop factual information that may result in a more precisely tailored limitation on construction of the dam and will assist us in our resolution of the stay motion,” they wrote. The judges also observed Arguello may “modify the total ban on continued construction” based on what she hears.

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 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 and told the 10th Circuit it had an obligation to its customers to proceed with reservoir expansion even in the face of litigation.

The environmental groups that successfully challenged the project, meanwhile, argued it would be more harmful to continue construction.

“Petitioners alleged catastrophic harms that will result without an injunction,” lawyers for the groups wrote. “Denver Water will kill 500,000 trees, destroy recreation areas and hiking trails, displace wildlife, degrade air and water quality, divert water from the Colorado River’s headwaters, and threaten the safety of nearby residents. These irreversible harms, especially of this immense magnitude, are irreparable.”

The 10th Circuit’s order advised that it is allowing construction to continue until Arguello issues her post-hearing order. After that, the circuit will evaluate how to proceed.

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