A federal judge late Thursday ordered Denver Water to halt construction on the massive expansion of Gross Reservoir’s dam in western Boulder County and sent three key environmental permits back to the Army Corps of Engineers for a rewrite. The order hands a major, if temporary, victory to environmental and neighborhood opponents fighting the half-finished, $531 million project to nearly triple the storage capacity of the reservoir on South Boulder Creek. Senior U.S. District Court Judge Christine Arguello put a halt to construction nearly four months after Denver Water and the river-defending nonprofit Save the Colorado failed to negotiate a settlement that would further mitigate damage from the project. When settlement talks stalled, Save the Colorado asked for an injunction and Denver Water argued it should go forward pending more talks.