20080868 Ver 2_R -12 Additional Information_20170804

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Helping Nature Provide
Certified Mail
August 4, 2017
Mr. David May, Regional Supervisor
NC Division of Water Resources
North Carolina Dept. of Environmental Quality
943 Washington Square Mall
Washington, North Carolina 27889
Re: Response to Additional Information Request
R-12 Groundwater Monitoring Plan
Dear Mr. May:
PotashCorp -Aurora
RECEIVED/NCDENR/DWR
AUG 7 2017
Water Quality Aoo,unai
Cperadons section
Washington Regional Office
This submittal is in response to your November 28, 2016 letter requesting additional
information regarding the R-12 groundwater monitoring plan that PCS submitted to the NC
Division of Water Resources (DWR) on June 13, 2016.
1. In response to the DWR question about Yorktown Formation groundwater
monitoring from -30 to -90 MSL:
• Six cores were taken to aid in understanding stratigraphic trends and inconsistencies
surrounding the R12 perimeter at the locations initially proposed to serve as sentinel
wells for groundwater monitoring that were located substantially inside the normal
boundary of compliance.
• Sentinel wells were developed in these core holes in accordance with sampling needs
for the Castle Hayne Formation.
• Upon geological evaluation within the R12 area, the Yorktown Formation was
encountered ranging from -38 to -90 MSL.
• The top of the formation varied due to being washed out in some places by
channelizing geologic units
• Overall, the Yorktown Formation was consistently present between -70 and -90 MSL.
• We are proposing to monitor this 20-foot interval for the surficial aquifer in the same
location as the originally contemplated Castle Hayne aquifer monitoring wells.
2. In response to DWR Issue 2, DWR's recommendation that well R12MW6 be
relocated to the west and adding a well (R12MW7) to the southwest of well
R12MW1:
1530 NC Hwy 306 South, Aurora, NC USA 22806 T [phone]
PotashCorp. I www.potashcorp.com

• Regarding R12MW6: PCS recommends leaving R12MW6 in the current location
(Figure 1). This core hole was placed in the present location due to preferred
accessibility. The sentinel well was installed in the core hole and is located in
between the two headwater prongs of Tooley Creek, which we believe provides a
more complete monitoring of groundwater impacts in this area. DWR's suggested
alternate is at the top of one prong.
• Regarding R12MW7: The proposed well location does not have suitable access and
places it too close to the gypsum -clay blend currently in R-I I to the northwest. If
installation of this well is required, PCS proposes to move the location of R12MW7
(Figure 2) to the northeast 500 ft in an effort to install this sentinel well inside our
permit line between two prongs of Huddles Cut.
3. In response to DWR Issue 3, PCS agrees to the metals parameters as listed in the
letter.
Additionally, PCS understands that any future action level regarding parameters analyzed
within the scope of this monitoring program would be based on the NC 2L Groundwater
Standards.
Your approval of this plan is requested so that PCS can install the surficial aquifer wells and
begin sampling to establish baseline data. Please call me at [phone] or e-mail me at
[e-mail] if you have questions concerning this information.
Sincerely,
AAA
J frey//UVy lFurness
Senior Scientist
PC: Anthony Scarbraugh, DWR - WaRO
Tom Steffens, USACE - Washington Regulatory Field Office
J. DeMonte, PCS - Northbrook
File 23-01-004-29

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