NC0084620_Response_NOVNOI2024LV0312_20240416

S I B E LCO
Sibelco North America, Inc.
P.O. Box 588 • Spruce Pine, NC 28777
(PHONE) 828/765-1114
April 16, 2024
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
Mr. Daniel Boss
ARO Assistant Regional Supervisor
Division of Water Resources, NCDEQ
2090 U. S. Highway 70
Swannanoa, North Carolina 28778
Subject: Response to Notice of Violations
Sibelco North America, Inc. — Red Hill Facility
Red Hill, North Carolina, Mitchell County
Whole Effluent Toxicity (WET) Testing
Dear Mr. Boss:
In response to the Notice of Violation & Intent to Assess Civil Penalty issued April 8, 2024 for
exceedance of TSS limitations in November 2023.
Sample
Location Parameter
Limit Reported
Date Value Value Type of Violation
001 Effluent Solids, Total Suspended - 11/1/2023 266 407.8 Daily Maximum Exceeded
Quantity Daily (QD530)
001 Effluent Solids, Total Suspended - 11/30/2023 133
Quantity Daily (QD530)
154.62 Monthly Average Exceeded
On November 1, 2023, we collected a composite sample that was sent to Environmental Testing Solutions
for TSS analysis. The result of 68 mg/L was extremely high. Upon investigation into the events of that
day, it was evident that the sample was contaminated by a flow restriction. The automated sample
collected for analysis was primarily effluent that was sent to the emergency pond and was not
representative of the water that was actually discharged to the river.
In addition to the contaminated sample, the flow restriction caused our discharge flow readings to be
elevate above actual discharge rates. We have made multiple improvements since that date to correct our
flow restriction and to have more accurate flow measurements.
Prior to November 14, 2023, we had a single flow measurement at our flume that recorded all flow from
our clarifier regardless of the flow destination. We recorded and reported water flow to our emergency

Mr. Daniel Boss
Page 2
ponds as if it was discharged to the river. Likewise, our ISCO water sampler obtains composite samples
regardless of flow destination.
On October 31, 2023, we began having difficulty pumping from our discharge tank to the river due to
pumps failing to handle the required flow needed. This continued to worsen on Nov 1, 2023. This
difficulty in pumping to the river caused our flume chamber to back up to the point that our flume
elevation was increased. Before clarifier overflow, we stopped production to decrease water usage and
diverted remaining discharge to the emergency pond. Though our water consumption and discharge was
considerably decreased, the ISCO flow meter continued to record elevated readings while the flume was
flooded. During the time that the flume chamber was backed up, the water came in contact with wall
surfaces that had not been rinsed recently so our ISCO sampled from contaminated water that was
actually diverted to the emergency pond at this time. In hindsight, a sample from that day should not have
been sent for TSS analysis because it was mostly water diverted to the emergency pond.
We performed multiple improvements to our discharge flow as a result of this. We have fully inspected
our piping for possible collapses and have replaced our discharge pumps. We have also increased piping
size from the flume chamber to the discharge tank where pumping occurs. We added additional now
meters to record clarifier flow when diverted to our emergency ponds separately from river discharge. We
are also developing a cleaning schedule for our weir walls and flume chamber so that potential backups
do not release solids to our discharge. Site personnel are currently ensuring that composite samples are
only taken during discharge to the river based on automatic diverter valve position that is visible on the
operator interface (Wonderware). We are working on programming control that prevents composite
samples from being collected during discharge to the emergency pond.
Sibelco strives to exceed environmental regulations and is proactive in maintaining compliance at our
facilities. This is the first exceedance of this type at this facility in well over two decades, if not for the
life of the site. We respectfully regret this occurred. We hope that these flow and sampling improvements
will help eliminate these oversights and incorrect sampling in the future.
If you have any questions regarding this matter or require further information, please do not hesitate to
contact me directly.
Regards,
Blake Griffith
Production Manager
Spruce Pine, NC
blake.gnttit- :.
828-765-1114
eryS. son, P.E.
Sustainability Manager North America
Spruce Pine, NC
1 e4747 r 21.±-- j__sibelco.com
828-592-2764