William Perry
Castle Rock at Lake Powell's Wahweap Bay.

SALT LAKE CITY — Heavy metals washed into Lake Powell over the decades by flash floods or rivers flows will be extracted by drilling rigs probing deep into the river deltas.

The sediment study will begin this month to collect historical and recent data on metal concentrations.

The Utah Department of Environmental Quality, the U.S. Geological Society, the National Park Service and the U.S. Bureau of Reclamation are all part of the collaborative effort.

According to the agencies, the monthlong project will extract cylindrical, long-core samples at multiple locations along the river deltas entering Lake Powell.

Scientists say the cores should reveal how flash floods, historic mining in the Upper Animas River, mine remediation activities, and spring runoff affects the timing, mass and concentration of metals deposited into the lake.

"This study will help us understand whether human activities such as mining in the San Juan River watershed have impacted or pose a risk to the important recreational, aquatic life, and cultural resources of the San Juan River and Lake Powell,” said Erica Gaddis, director of the Utah Division of Water Quality. “This project is a great example of applying science to inform water resources management.”

The survey will assess the concentration and distribution of metals at Lake Powell, including arsenic, cadmium, copper, mercury and lead.

Concentrations could affect water quality, human health and aquatic life, especially as drought continues to drag down the level of the lake. The lake is a critical component of a system that provides drinking water to 40 million people in the Southwest.

“This is the first study to collect and characterize sediment through the full thickness of the San Juan and Colorado river deltas,” said Scott Hynek, a scientists with the U.S. Geological Survey. “Drilling long cores of sediment will allow USGS scientists to analyze metal concentrations from before the Glen Canyon Dam was constructed through the present day.”

Comment on this story

In August 2015, the U.S. Environmental Protection Agency accidentally triggered a massive release of heavy metal sludge in a breach of Gold King Mine in Colorado.

The estimated 3 million gallons of wastewater carrying 540 tons of metals washed into rivers in Colorado, New Mexico and Utah.

Utah is seeking $1.9 billion from the EPA in a lawsuit after the waste wound up in the San Juan River and at Lake Powell.

The state continues to monitor the effects of that spill.

Preliminary findings of the study are expected in 2020.