Rio Tinto says two concentrator incidents produced visible dust plumes; company outlines monitors and control work

Rio Tinto representatives told the Copperton Town Council that dust plumes from the company’s concentrator were visible in Copperton on Aug. 9 and Aug. 11 and described steps they are taking to reduce recurrence.

The company attributed the events to a “fall from height” at the concentrator involving soft rock that produced a large, visible dust cloud, and said water and dust-control systems were operating when the events occurred. Ryan, social performance manager for Rio Tinto Chemical, said the company will temporarily shut the concentrator next month to install automated sprinkler systems and make other changes that Rio Tinto expects will reduce dust from large material falls.

Why it matters: Neighbors raised health and nuisance concerns about those two events on social media and to council members. Rio Tinto and council members said publicly available air-monitoring data and clearer on-site controls are the immediate tools to assess public exposure and reduce the chance of repeat events.

Details from the meeting

- Cause and response: Rio Tinto representatives said the Aug. 9 and Aug. 11 plumes resulted when soft rock fell from a height at the concentrator and generated a large plume of dust. The company said water sprays and dust-control systems were operating and that the site will be shut down next month while automated sprinklers and other control upgrades are installed so staff can adjust systems remotely without manual entry into higher-risk working areas.

- Monitoring and data: Rio Tinto said it operates an air-monitoring station in Copperton; staff remove particulate filters monthly and the Department of Air Quality (DAQ) posts quarterly ambient data reports. The company said the monitoring data are publicly available and that the monitoring results will be shared with the town when those quarterly reports are released.

- Community contact: Company staff said they had regular direct contact with town liaisons—named in the meeting as Tessa and Kathleen—during the events, and they plan continued outreach, including a company presence at Town Days.

Council and community response

Council members and residents described seeing widespread dust across the valley during the same time period and said social media discussion prompted many complaints. A council member said dust was visible in other parts of the valley on Aug. 11 and that some areas experienced “dirty rain.” That council member and Rio Tinto both said the valley-wide dryness and wind amplified visible dust on those days.

What Rio Tinto will do next

Rio Tinto said it will: - Install automated sprinklers and change controls to allow remote adjustment of water/dust systems; - Improve early detection at the crusher and conveyor lines so the concentrator staff can reduce or halt operations when a high-dust event begins; - Continue to provide the DAQ quarterly reports and respond to council questions; and - Maintain a presence at community events to answer resident questions.

Community access to monitoring data

Rio Tinto and council staff said the DAQ produces quarterly ambient data reports that include readings from the Copperton monitor and a nearby monitor at High Country/Herriman; company representatives said they will provide the links to the council and make themselves available to explain results.

Ending

Rio Tinto told the council it expects the automatic-sprinkler work done during the planned shutdown to materially reduce the likelihood of large visible plumes from material falls. Council members asked that draft plans for upgrades and the DAQ monitoring links be provided before the next council meeting so the town can track progress and the next quarterly air data release.