The National Park Service’s new plan for the Grand Canyon river corridor may torpedo wilderness advocates, who are already swimming against a tide of motorboats and helicopters.

Ten years ago, the Grand Canyon Management Plan required park managers to devise a new recreation strategy for the Colorado River that would address motorized usage, tourism’s impacts on tribes, and protecting the canyon’s "wild and primitive condition."

The plan, released in November, divides the 227-mile-long river corridor into two stretches: a long stretch from Lee’s Ferry to Diamond Creek, and the Lower Gorge, a shorter but far more heavily trafficked stretch dominated by day trips to Lake Mead. Although jet-boat tours were ruled out, the Hualapai Tribe can take up to 600 motorized pontoon passengers and three commercial overnight trips on the Lower Gorge each day — three times more than they are now allowed, but far fewer than the 1,800 passengers per day they originally requested, says Mary Killeen, chief management analyst for the park.

Other provisions include transforming a decades-long waiting list for noncommercial river permits into an annual lottery system, and revamping concessionaire contracts for 16 commercial operators. In addition, on the upper river, maximum group sizes and the number of daily launches will drop, and the months restricted to oar-powered access will more than double, to six months.

But wilderness proponents say that continued motorized access ensures the 1.1 million acres proposed for wilderness in the Grand Canyon won’t be designated as such any time soon — and they think it may take a lengthy lawsuit to override the entrenched motorized use on the river. "The river is managed by politics," says Tom Martin, co-director of River Runners for Wilderness. "They’re managing the resource for the benefit of the concessionaires."