FLAGSTAFF, Ariz. — Klee Benally, a member of the Navajo tribe, has gone to the mountains just north of here to pray, and he has gone to get arrested. He has chained himself to excavators; he has faced down bulldozers. For 10 years, the soft-spoken activist has fought a ski resort’s expansion plans in the San Francisco Peaks that include clear-cutting 74 acres of forest and piping treated sewage effluent onto a mountain to make snow.

But he appears to be losing the battle.

In February, a federal appeals court ruled in favor of the ski resort’s upgrade plans, ending a legal saga fought by a coalition of environmental groups and 13 American Indian tribes, which consider the mountain sacred and view the wastewater snow as a desecration.

This coming ski season, the resort, Arizona Snowbowl, will become the first ski resort in the world to use 100 percent sewage effluent to make artificial snow.

“It’s a disaster, culturally and environmentally,” said Taylor McKinnon of the Center for Biological Diversity, one of the plaintiffs. He worries about the impact on the delicate alpine tundra and to human health should skiers fall into the treated sewer-water snow and ingest it.