Denver Water is cutting down too many trees on federal land at the major expansion of Gross Dam and Reservoir in Boulder County, and must conduct more environmental impact work if it wants to expand a quarry used for the project onto U.S. Forest Service property, according to a notice from the agency. The Forest Service letter dated Tuesday faults Denver Water for “unauthorized timber removal,” and said the utility’s proposed onsite quarry expansion “would require a new and separate National Environmental Policy Act analysis.”  Denver Water hasn’t been giving the Forest Service, whose land surrounds Gross Reservoir in western Boulder County, enough lead time to evaluate change requests on cooperative agreements, the letter said.