Nevada state engineer Jason King cleared the Southern Nevada Water Authority to draw 83,988 acre-ft of water annually from four valleys in rural White Pine and Lincoln counties in northeast Nevada, advancing toward the adoption of a proposed groundwater pipeline network that is designed to slake Las Vegas' growing thirst.

"This is another step in a permitting process that will help provide a greater degree of certainty for our long-term water supply," says John Entsminger, SNWA's senior deputy general manager, in a statement.

The water would be carried to the Las Vegas valley via a proposed 300-mile buried pipeline. The bond-backed project is estimated to cost at least $3 billion; the debt would be retired through water-use and connection fees.

The 150-mgd pipeline and accompanying infrastructure still face hurdles, including a possible court challenge from the Great Basin Water Network, a Reno-based watchdog group that fears underground pumping would result in long-term, irreversible ecosystem damage. Network coordinator Susan Lynn calls the plan "unsustainable, environmentally destructive and illegal," vowing that the ruling "will not go without challenge."

SNWA's water supply in recent years has dwindled to critical levels, drained by lingering drought conditions and decades of boom growth. The surface level of Lake Mead—the region's main water supply—dipped to 1,133 ft in February, or 96 ft below its maximum. "Southern Nevada needs a water resource that is independent of the Colorado River," King wrote in his ruling. "That resource is over-appropriated, highly susceptible to drought and shortage, and almost certain to provide significantly less water to Southern Nevada in the future."

The decision doesn't allow the full amount of water to be drawn all at once. The authority can proceed only after hydrologic and biological studies, and it must conduct aquifer and biological monitoring. If the effects remain minimal after eight years, more water can be pumped.

The undertaking will consist of five pumping stations, six regulating tanks, three pressure-reducing stations, a 40-million-gallon buried-storage reservoir and a 165-mgd water treatment facility. Construction also would entail 323 miles of overhead power lines ranging from 230 kV to 25 kV, plus two primary and five secondary electrical substations.

HDR Inc., Omaha, Neb., conducted the pipeline's preliminary engineering and design under a 2007 contract worth $4 million. ENSER International, Westford, Mass., performed the environmental impact statement for the Bureau of Land Management, which must first grant permission for right-of-way access. A decision is due by mid-September. Meanwhile, the authority insists the pipeline project is a safeguard precaution that would be developed only in stages, if needed, says Entsminger.