On August 5, 2015, a crew of EPA workers and contractors surveying the abandoned Gold King Mine in Colorado dislodged a plug at the site, letting 3 million gallons of trapped water — containing arsenic, mercury, lead, and more — wash into a tributary of the Animas River.

The river carried the sludge southwest, and within days the Animas and San Juan rivers turned an alarming shade of yellow. After two weeks, the EPA announced an investigation into the causes of the event and the agency’s response to it.

Downstream in New Mexico, in the Navajo community of Shiprock, farmers use river water to irrigate corn and cantaloupe, and raise sheep and goats. The spill caught farmers in the middle of their growing season.

Navajo Nation community health representative Mae-Gilene Begay mobilized a crew to warn residents to steer clear of the river water. “A lot of them were concerned because they go fishing in the river either for recreation for livestock or for farming,” she told BuzzFeed News.

The community closed the irrigation canals for eight months, until April 2016. A few months later, the Navajo Nation sued the EPA and mine owners and operators, claiming that the parties' negligence caused an accident they should have foreseen and prevented.

Over the last year and a half, a group of scientists from the University of Arizona has been working to help the Navajo understand the impact of the spill, by presenting data about contaminant levels to the community so that they feel empowered to decide whether to start using river water again.

Led by Karletta Chief, a hydrologist, and Paloma Beamer, professor of environmental health, the team has collected about 1,000 environmental samples: water and soil from the river and irrigation canals, water from wells and conduits, and samples of blood, urine, and drinking water from 60 homes in three communities.

On Wednesday afternoon, the researchers returned to Shiprock Chapter in New Mexico to share their preliminary findings. And it’s good news, at least for now: lead and arsenic levels in the water are within the levels defined as drinkable by the EPA. In all but four of the water samples, the lead levels were also below the guidelines that the National Oceanographic and Atmospheric Administration has deemed fit for aquatic life.

Some Navajo are relieved by the data, though they are slow to fully trust. “There is justified apprehension by farmers on whether to plant this year considering the questionable state of the river,” Duane Chili Yazzie, Shiprock Chapter President, said at Wednesday's event, according to an email he sent to BuzzFeed News. “This apprehension is only partly relieved by all the studies that purportedly show the water to be safe for irrigation.”