WQ0003396_Compliance Report_20221212

arauco
December 12,2022
VIA EMAIL ([e-mail]) AND U.S. MAIL
Mr. Scott Vinson
Division of Water Resources
Water Quality Regional Operations Section
3800 Barrett Drive
Raleigh, NC 27609
Subject: Notification of Wastewater Storage Lagoon Liner Disturbance (WQ0003396)
Dear Mr. Vinson:
On December 8th, 2022, Arauco North America, Inc. ("Arauco") was notified by the onsite contractor
completing work on process wastewater storage lagoon "5D" that the contractor, in the process of dredging,
encountered a section of the impoundment clay liner which had been compromised. The contractor
observed an area roughly 11,000 square feet in size that is softer than the surrounding area, indicative of
disturbance of the integrity of the clay liner in the bottom of the impoundment. Process wastewater lagoon
5D is currently being modified as detailed in the Non -Discharge permit (WQ0003396) that was approved by
the Department on August 6, 2021. This construction modification began in May 2022 with the purpose of
increasing the height of the existing surrounding berm to remove the storage pond from the 100-year
floodplain and reinforcing the existing berm in accordance with state requirements and to enhance
floodplain protection.
This area of the lagoon does not currently contain any wastewater, as the area has been drained to complete
the necessary berm modification construction. As such, Arauco believes the current risk of release of
wastewater to groundwater at this time is negligible, as the area is dredged and no wastewater is stored in
this area currently. Arauco has not yet been able to determine the root cause of the potential disturbance of
the clay liner. While it is possible that this disturbance is a result of the construction activities involved in
berm modification, Arauco has not been able to rule out the possibility that this section of the clay was
compromised during maintenance activities or as a result of the velocity and volume of a prior influent
discharge pipe which may have scoured the liner over time.
A. Corrective Actions - Liner repair and berm footing foundation: The affected area has been
evaluated by the contractor and will be repaired as part of the berm modification project. Since the
disturbed area lies completely within the berm modification project parameter, this area will no
longer be part of the retention pond wastewater holding area. The area is being repaired to provide
a solid foundation for the footing of the modified berm. The contractor is prepared to began the
process of repairing the area whenever we notify them that the sampling conducted as part of
Arauco's investigation as discussed below is completed. A layer of 2" stone will form the base of the
foundation, followed by a layer of filtration geotextile, and capped with a 2'-3' compact lift of clay
material consistent with the requirements of 15A NCAC 2T .0505. This process has been r viewed
and approved by both the project design engineer and a third party geotechnical firm has
provided geotechnical support throughout the project. The contractor, design en Ile \ nd
geotechnical support all believe this corrective action to be sufficient in repairing li m ge

arauco
providing an acceptable foundation for the impoundment berm modification in this area. The
repaired area will not be in contact with process wastewater once completed, and is not currently in
contact with wastewater, as the area was drained and dredged in preparation for this project.
B. Actions to Ensure the Problem Does Not Recur: As noted above, Arauco has not yet been able to
determine the cause of the disturbance to the clay liner as necessary to implement measures to
prevent a recurrence of this issue. As part of its investigation, Arauco has contacted Falcon
Engineering, a third party geotechnical firm that the site has been using to periodically consult on
phases of the berm modification project, to collect soil boring samples in the disturbed area. Arauco
is having this sampling completed in an effort to establish what, if any, potential impacts to soil there
were from the compromise of the integrity of the clay liner. The sampling may also provide
information needed to determine the cause of the disturbance. The samples will be collected prior to
construction of the berm modification which would limit the access of this area of the liner . To the
extent that the investigation indicates that the former influent discharge caused the disturbance, a
recurrence of this issue is unlikely since the remaining influent pipes do not discharge at the velocity
or volume of the former influent pipe in the area of the disturbance to the liner. If another cause is
identified, Arauco will implement appropriate measure to mitigate the likelihood of a recurrence.
Once the investigation is concluded, Arauco will supplement this notification with additional
information regarding any actions taken to ensure the problem does not recur.
Arauco remains committed to completion of the project in efforts to increase floodplain protection and
maintain the organization's commitment to environmental stewardship. If you have any questions, please
contact Savannah Carroll, Corporate Environmental Manager, at (843-544-3025).
Savannah Carroll
Corporate Environmental Manager for Jeff McMillian (Plant Manager)
CC'd: Ms. Lauren Raup-Plummer (via email: [e-mail])
Matt Swinnie, Bernardita Sanchez Munoz, and Jeff McMillian, Arauco North America, Inc.