The Moffat Collection System Project, or the Gross Dam Expansion Project is a proposed water development project that would divert additional water from the Colorado River headwaters to Colorado’s Front Range. Proposed by Denver Water, the purpose of the Moffat Collection System Project is to divert 18,000 acre-feet per year of new water to the Moffat Treatment Plant through the expansion of Gross Reservoir and additional diversions from the Fraser and Williams Fork rivers (using the Moffat Tunnel) and South Boulder Creek. Gross Dam would need to be raised 131 feet in order to create an additional storage capacity of 77,000 AF, which would flood natural areas and impact nearby communities.
Average annual diversions through the Moffat Tunnel to the Front Range would increase about 10,300 AF or 15 percent. The Project would mean increased diversions by Denver Water from both the Colorado and South Platte river basins. Additional diversions would be greatest from tributaries to the Fraser and Williams Fork river basins, then from the Blue River Basin, and least from the South Platte River and South Boulder Creek.
Environmental groups file intent to sue over expansion of Boulder County’s Gross Reservoir — a Denver Water source by Charlie Brennan, Boulder Daily Camera (August 24, 2018).