Gross Reservoir facts for kids
Quick facts for kids Gross Reservoir |
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The reservoir in 2014.
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 Gross Reservoir
Location in Colorado
Gross Reservoir
Location in the United States
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| Location | Boulder County, Colorado |
| Coordinates | 39°56′31″N 105°22′22″W / 39.94194°N 105.37278°W |
| Type | reservoir |
| Etymology | Named for Denver Water former Chief Engineer Dwight D. Gross. |
| Primary outflows | South Boulder Creek |
| Basin countries | United States |
| Managing agency | Denver Water |
| Water volume | 41,811 acre⋅ft (51,573,000 m3) |
| Surface elevation | 2,222 m (7,290 ft) |
Gross Reservoir, located in Boulder County, Colorado, is owned and operated by Denver Water. Completed in 1954, the reservoir has a surface area of 440 acres, and the spillway sits at 7,225 feet elevation.
The reservoir receives water from the western side of the Continental Divide through the Moffat Tunnel. South Boulder Creek flows out of the 340 foot-high dam.
Recreation
The reservoir provides opportunities for fishing (including ice fishing), hiking, canoeing, kayaking, and some camping. No water-contact sports such as swimming or wading are allowed. Only non-motorized boats are permitted — the type that can be attached to the top of a car.
Expansion project
The proposed expansion of Gross Reservoir would allow Denver Water to store 77,000 additional acre feet of water, drawn mostly from the Fraser and Williams Fork Rivers. Construction on the project, expected to be complete around 2025, will raise the level of the dam by 131 feet (40 meters), resulting in an additional 77,000 acre-feet (95,000,000 cubic meters) of water storage capacity in the reservoir and making it the tallest dam in Colorado.
Denver Water applied to the U.S. Army Corps of Engineers for a permit under section 404 of the Clean Water Act, required to construct the expansion, and that permit was granted in 2017. In response, several environmental groups sued USACE on grounds that the agency's deliberations about granting the permit violated the Clean Water Act, Endangered Species Act, and National Environmental Policy Act. In July 2020 the Federal Energy Regulatory Commission granted a required modification to the Federal Power Act license granted to Colorado Water for Gross Dam before it was built.
A contract for design services was awarded to Stantec, an engineering consulting firm, in 2017.
Boulder County announced in spring 2019 that it would require Denver Water to obtain a land use permit under Colorado law before commencing the expansion project. Denver Water submitted its application for that permit in September 2020.
