The Bureau of Land Management signed off Thursday on a massive pipeline project to carry billions of gallons of water to Las Vegas from rural counties along the Nevada-Utah line. The record of decision, signed by Deputy Interior Secretary David Hayes, authorizes the BLM to issue a right of way to Southern Nevada Water Authority for the 263-mile pipeline that will stretch from the rural areas to the desert gambling metropolis that is home to some 2 million people and attracts 40 million visitors annually.“This is a huge milestone for Southern Nevada,” said Patricia Mulroy, the water authority’s general manager.She said being able to “draw upon a portion of our own state’s renewable groundwater supplies reduces our dependence on the drought-prone Colorado River and provides a critical safety net.” The Colorado River flows into Lake Mead, southern Nevada’s main water source. A recent study projected moderate to severe water shortages over the next several decades. Lake Mead’s surface level has dropped about 100 feet since 2000 because of ongoing drought and increasing demand from the seven states and more than 25 million people sharing Colorado River water rights.“What the study really told us was that we must prepare for a much drier future and that we can’t count on the Colorado River to sustain our community in the way it once did,” Mulroy said. Environmentalists decried the decision, which comes two decades after the concept began to take shape and after years of litigation. More lawsuits are expected to follow.Nevada’s state engineer, Jason King, granted the water authority permission in March to pump up to 84,000 acre-feet of groundwater a year from four rural valleys in Lincoln and White Pine counties. An acre-foot is the volume of water needed to cover an acre of land with water 12 inches deep — about 326,000 gallons. King’s rulings are being challenged in state court.The pipeline approved by the BLM Thursday is needed to deliver that water to the Southern Nevada’s population center.Simeon Herskovits, an attorney in Taos, N.M., representing a coalition of ranchers, farmers, rural local governments and environmentalists, said the BLM decision was being reviewed but added that unless “serious deficiencies” in an earlier environmental study have been corrected, the decision to approve the pipeline cannot “be scientifically, economically or legally sound.”The BLM’s decision follows findings made in November by the U.S. Fish and Wildlife Service that the project would not significantly affect about a dozen threatened or endangered species. Environmentalists say otherwise.“Some of Nevada’s rarest, most unique species rely on wetlands and springs,” said Rob Mrowka with the Center for Biological Diversity. “The Las Vegas water grab could undo all that and drive them extinct in the blink of any eye.”BLM spokeswoman JoLynn Worley said the decision authorizes the “main conveyance and support facilities” to be built on federally owned land. It’s the last administrative ruling by the federal agency, and further challenges will be handled by the courts. She said environmental studies will still be required on specific aspects of the project as it is built.But Herskovits said smaller environmental studies are no consolation after the project as a whole is given a green light.“We don’t feel that offers an adequate safeguard,” he said.Critics also said the BLM relied on outdated or faulty data and that the project’s price tag, once estimated around $3 billion, would likely approach $16 billion. That expense, they said, should have been addressed in the agency’s environmental report to determine if the project was financially feasible.