DAQ-2025-000040

RioTinto Rio Tlnto Kennecott
4700 Daybreak Parkway
South Jordan, Utah
84009
Tel: [phone]
October 4,2024
Mr. Bryce Bird, Director
Department of Environmental Quality
Division of Air Quality
195 N 1950 W
Salt Lake City, UT 84116
Attention: Mr. Joe Randolph
Subject: R307-107 and l.S.2.c: Smelter Main Stack
Particulate Breakdown
Kennecott Utah Copper - Smelter Facilitv
Title V operatino Permit 3500030004
Dear Mr. Bird,
Rio Tinto Kennecott Utah Copper LLC (Kennecott) is hereby submitting this
letter to report a deviation to the Smelter-Refinery Title V permit 350030004
that occurred at the Smelter facility Main Stack (SME01 1). The deviation is
related to the operation of the Main Stack continuous particulate sampler
between the dates of August 11, 2024 and September 04, 2024. This report
is intended to satisfy the requirements of Permit Condition 1.S.2.c, deviation
reporting.
Background and Summary of Event
The Main Stack (SME01 1) is the exhaust stack for gases from the acid plant,
secondary gas system, rotary dryer, powerhouse superheater, matte grinding plant,
anodes area, and hydrometallurgical plant. To monitor particulate emissions,
Kennecott operates a continuous particulate sampler (CPS) to collect a daily sample
which provides a calendar-day average for particulate emissions in pounds per hour
(lbs/hr). The sample is a filter installed in the CPS, operated for between 20-28
hours, samples are then removed from the CPS, and desiccated in the Smelter
laboratory for 24 hours or more. For this reason, Main Stack particulate emission
results are provided to Kennecott personnel between 25-30 hours after the sample
has completed.
On August 11th, a maintenance activity was performed on the CPS and the sample
box was replaced so the result for August 11th filter was invalidated due to
maintenance. The following samples from August 12 through September 3,2024, had
an average of 3.66 lbs/hr which is lower than the annual average of 28.5 lbs/hr, but
the laboratory team did not invalidate the sample as described in the procedure. On
September 3,2024, after the period of samples was additionally reviewed, it was
decided to inspect the equipment. When the inspection was performed on September
3,2024, and it was identified that the CPS sample hose was not properly connected
to the CPS particulate filter holder. Mr. Sean Daly called Mr. Joseph Randolph of the
Utah Division of Air Quality to provide initial notification.
i'la,rd jc-li U,e.reol
ocT - 4 2024
DIVISION OF AIR OUALITY
REVIEWED
Initials JBR Date 7/8/2024
Comp Status Meets
File # 10346 Blue 2
per telephone conv - this
new system was configued
from factory and changes
not made for specfific use.
no further down periods
have been noted. NFA
After the hardware issue was identified, Kennecott retroactively invalidated the
samples collected for the dates of August 1 1 to September 3, 2024.- September 3'd
as "invalid" due to the stack probe sampling hardware issues. The stack probe
sampling hardware issues were resolved on September 3,2024, and the days
following met criteria for valid samples.
Data Evaluation
Due to the hardware malfunction, Kennecott operated the CPS without meeting the
criteria for valid samples. This affects the data recovery requirements outlined in
the current UDAQ Particulate Monitoring Plan. However, during this time,
Kennecott has no indication that particulate emissions would have been above
permitted limits. Also, the CPS operation is based on an Environmental Protection
Agency Method 5 procedure and for that reason; it measures all Total Suspended
Particulate (TSP) rather than the particulate matter less than 10 microns (PM10)
fraction. For comparison with the permitted PM10 emissions limit, Kennecott also
performs an annual PM10 stack test. The 2023 stack test performed on December
21-22,2023, measured 7.38 lbs/hr of PM10 compared to the CPS result of 16
lbs/hr for the same day. ln the past five years, the comparison of the CPS data and
the stack test results have indicated that the PM10 fraction of the CPS measured
value ranges trom 24-59 percent, all of which would suggest that the PM10
emissions from the Main Stack during the deviation event were below the limit.
Corrective Action Summary
Kennecott believes the Main Stack CPS sample probe and related process
equipment are maintained and operated in a manner consistent with good practices
for minimizing emissions. All practicable steps were taken to repair the CPS when
the issue was identified and there is no indication that this deviation event is part of a
pattern. Additionally, Kennecott has communicated with teams about reporting
validation criteria in the laboratory reports and additionaldata checks have been
assigned to team members to better identify potential issues.
Prior to this event, Kennecott had also initiated a project to investigate improvements
for the CPS. The project is currently looking to implement changes that would allow
the CPS to improve isokinetic samplings rates and communicate the isokinetic data
to a manner that provides that data to the control room operators and allows for
better alarms on CPS performance.
Based on information and belief formed after reasonable inquiry, the statements and
information in this document are true, accurate, and complete (R307-415-5d).
lf you have any questions about this change, please contact Sean Daly at 801-204-
2563.
Yours since_pely,4rZ<---Z'14, llM**+fil- t,tt*,tr'cq -trA6D ? Bffpo>t<fS
Matt Tobey
General Manager - Metals