WQ0001492_Correspondence_20200623

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
S. DANI£L SMITH
Director
MIKE ANDERSON — VICE PRESIDENT
OCCIDENTAL CHEMICAL CORPORATION
5 GREENWAY PLAZA — SUITE 110
HOUSTON, TEXAS 77046-0521
Dear Mr. Anderson:
NORTH CAROLINA
Environmental Quality
June 23, 2020
Subject: Permit No. WQ0001492
Elementis Chromium Castle
Hayne Manufacturing Facility
Surface Disposal of Residuals
New Hanover County
This letter is in response to a meeting between representatives of Elementis Chromium, LLC and
the Division of Water Resources on February 28, 2020, and a memorandum from Smith Gardner, Inc. dated
April 1, 2020.
During the February 28t" meeting and in the subsequent April 1, 2020 memorandum, Elementis
Chromium, LLC proposed to extend the life of the existing residual surface disposal unit (i.e., Quarry
Section 2) by placing the residuals in geotextile tubes and vertically expanding the surface disposal unit
above the 2-foot freeboard elevation. The long-term plan would be to utilize the residual -filled geotextile
tubes as graded fill to eventually close out the surface disposal unit in 15 to 20 years.
As noted during the February 28t" meeting, addition of residuals above the 2-foot freeboard
elevation would be considered an expansion of the existing surface disposal unit, thus requiring that the
surface disposal unit meet the requirements in 15A NCAC 02T, which was readopted September 1, 2018.
Pursuant to 15A NCAC 02T .1109(d)(1), expanding surface disposal units shall meet the following
requirements:
A. Surface disposal units shall not be located in a seismic impact zone unless designed to
withstand the maximum recorded horizontal ground level acceleration.
B. Surface disposal units shall not be located less than 60 meters from a fault that has displacement
in Holocene time.
C. Surface disposal units shall not be located within a geologically unstable area.
D. Surface disposal units shall not be located within the 100-year floodplain.
E. Surface disposal units shall not restrict base flood flow.
F. The vertical separation of the seasonal high water table and the bottom of surface disposal units
shall not be less than three feet.
N11H fH (:A�i(1!.INA �
D E Q North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
0­O'torenwm­talQ"I 919,707.9000

Mr. Mike Anderson
June 23, 2020
Page 2 of 2
G. Surface disposal units shall be provided with a liner system with a maximum hydraulic
conductivity of 10-7 centimeters per second. Units into which cake residuals are to be placed
shall be equipped with a leachate collection system. Units into which liquid residuals are to be
placed shall be equipped with a decanting system and freeboard marker.
If expanded, the existing surface disposal unit will not meet the requirements in 15A NCAC 02T
.1109(d)(1)(D), (E), (F), and (G). Accordingly, the proposal to vertically expand the surface disposal unit
above the 2-foot freeboard elevation would not be permitted under the current administrative code in 15A
NCAC 02T. I 100, and there is no mechanism within this administrative code to provide alternative criteria
to the rules in 15A NCAC 02T .1109. Furthermore, the Division is concerned about the presence of
constituents within the groundwater that appear to be associated with the disposal unit and residuals
disposed of to date. The appearance of Chromium in observation wells near the disposal unit is of particular
concern. Please note that additional assessment of the impacts may be needed and will be communicated
in a separate letter.
If you need additional information concerning this letter or require assistance, please contact me at
[phone] or nathaniel.thornburgkncdenr.gov.
Sincerely,
Nathaniel D. Thornburg, Branch Chi
Division of Water Resources
cc: Wilmington Regional Office, Water Quality Regional Operations Section (Electronic Copy)
Jeff Poupart — Water Quality Permitting Section (Electronic Copy)
Jay Zimmerman — Water Quality Regional Operations Section (Electronic Copy)
Ed Mussler — Division of Waste Management (Electronic Copy)
William M. Brinchek, PE — Smith Gardner, Inc. (Electronic Copy)
Stacey A. Smith, PE — Smith Gardner, Inc. (Electronic Copy)
Scott Drury, PE — Hart & Hickman, PC (Electronic Copy)
Sean T. Coury, PE — Coury Science and Engineering (Electronic Copy)
Kent Adamson — Elementis Chromium Inc. (Electronic Copy)
Laserfiche File (Electronic Copy)