BOULDER, Colo. (AP) – Six environmental groups have asked a federal judge to block the expansion of Gross Reservoir in the foothills southwest of Boulder. The Daily Camera reports a lawsuit filed Wednesday claims the U.S. Army Corps of Engineers violated environmental laws when it granted a permit last year to increase the height of Gross Dam by 131 feet and nearly triple the amount of water it stores.

Federal law requires many water projects to get approval from the Corps of Engineers. The agency said Wednesday it doesn’t comment on lawsuits.

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The suit was filed by Save the Colorado, The Environmental Group, WildEarth Guardians, Living Rivers, the Waterkeeper Alliance and the Sierra Club.

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Denver Water operates the dam and oversees the expansion project. The utility was not named as a defendant in the lawsuit.

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