An inspector with the Pima County Department of Environmental Quality will spend the next few hours at the Sierrita Mine to see if Thursday's wind gusts of up to 20 mph are causing mine dust to leave the property.
Several Green Valley residents called the Green Valley News around noon questioning whether Freeport McMoran was again in violation of its permit after seeing a large amount of dust coming from near the mine. Several sent photos.
Beth Gorman, a spokeswoman with the Pima County Department of Environmental Quality, said a DEQ inspector who happened to be in the area also saw the dust and headed to the Sierrita Mine.
"He's going to stay there for the next several hours to get opacity readings," Gorman said. "He's gathering evidence, he's speaking with staff and collecting other information. He'll be writing a report."
In July, mine owner Freeport McMoran agreed to contribute $200,000 to build a two-mile walking path at Green Valley's new county park as part of a settlement reached over several mine dust violations in 2018.
In addition to creating the walking path at Canoa Hills Trails – An Open Space Park, the mining company also paid a $30,000 civil penalty because of the 2018 violations.
Hundreds of Green Valley residents reported being inundated by dust from the in early October 2018. Some compared the thick dust clouds to snowstorms; layers of dust were found inside homes and medical issues were reported. In November, dust swept past the mine's boundaries again.
The PDEQ sent two Notice of Violation letters to Freeport about the incidents. In each, officials said the company allowed mine dust to escape the boundaries on eight days in September, October and November. They also alleged the company allowed its visible emissions to exceed the 20 percent limit. At one point, it reached 63 percent opacity, according to the county.
The county informed the company it was evaluating a civil penalty for the violations that resulted in both notices. In February, Freeport spokeswoman Linda Hayes said the company had assisted about 800 residents in getting their homes cleaned at a cost of more than $200,000.
David Rhoades, general manager of Freeport's Sierrita operation, responded to the Notices of Violation with nearly identical letters Dec. 14 and Jan. 30. In each, he explained that wetting the tailings dam with water and magnesium chloride have “largely proven effective,” but because of the size of the dam, weather conditions and high wind events can overwhelm those measures.
Rob Howlett, a meteorologist with the National Weather Service in Tucson, said a weather system is responsible for today's high winds, but they should subside to 10-15 mph by Friday.
Green Valley and Sahuarita residents can expect overcast skies in the morning with a low temperature of about 36 degrees. It will eventually clear up and reach 55 degrees, he said. It will remain clear Saturday and Sunday, but the lows will range from 29 to 32 degrees. The high temperature on Saturday and Sunday will be about 62 degrees.