WQ0002708_GW Monitoring Review_20220121

1
Robson, Dorothy M
From:Robson, Dorothy M
Sent:Friday, January 21, 2022 12:47 PM
To:Black, Samantha
Cc:Vinson, Scott
Subject:Wrenn Road Facility. WQ 0002708
Hi Samantha,

The staff of NC Division of Water Resources (DWR), Water Quality Regional Operations Section (WQROS), Raleigh Regional Office
(RRO) conducted a review of the Groundwater Monitoring Results Memorandum dated September 13, 2021 for Wrenn Road
Facility Wastewater Irrigation System, permit no. WQ0002708. The purpose of the submitted groundwater monitoring memo
report was to evaluate conditions at the site to recommend groundwater background concentrations for arsenic, iron, and
manganese.
The report discusses the installation and suitability of proposed background monitoring wells, PMW-1, PMW-2, PMW-3, PMW-4
and previously installed well MW-B3. The Division agrees that the locations of PMW-1, PMW-2 and MW-B3 are suitable for
utilization as background groundwater monitoring wells. Monitoring well PMW -4 was not considered appropriate for a
background well given its apparent location cross gradient from the application field and observed field parameters (conductivity)
for PMW-4 appears to differ from other approved background locations. Additionally, the well construction in PMW-4 consisted
of 74 feet of total depth with 10 feet of screen as compared to PMW-1, PMW-2 and MW-B3 in the range of 20 to 43 feet total depth
in topographically up gradient locations. PMW-4 may be considered as a boundary/compliance monitoring well. The location of
PMW-3 was observed to be down gradient and in or near the hyporheic zone of a streambed and so is not consistent in the
groundwater regime of the approved background well set (PMW-1, PMW-2, MW-B3). PMW-3 is not suitable as a background well
but may be considered for a boundary/ compliance well.
Given the Division has approved background well locations PMW-1, PMW-2 and MW-B3, the well data collected from these
approved wells can be utilized to compile a dataset to calculate background values for arsenic, iron and manganese. If you have
any questions, please feel free to contact the DWR.
Respectfully,

Dorothy M Robson
Environmental Program Consultant
North Carolina Department of Environmental Quality
Division of Water Resources
Raleigh Regional Office
_______________________________________________
Physical: 3800 Barrett Drive, Raleigh, NC 27609
Mailing: 1628 Mail Service Center, Raleigh, NC 27699-1628
_______________________________________________
Office: 919-791-4241; Mobile: [phone]

_______________________________________________
E-mail correspondence to and from this address may be subject
to the North Carolina Public Records Law and may be disclosed
to third parties.