Asheville - Tech Memo 081117

TECHNICAL MEMORANDUM
Date: August 11, 2017 File: 1026.102
To: John Toepfer (Duke Energy)
Cc: Kathy Webb (S erra)
From: Todd Plating✓�" U
Subject: Up-to-date Bi�=/�ound Groundwater Data including GW -1 Cluster—Asheville
Steam Electric Plant
The North Carolina Department of Environmental Quality (NCDEQ) provided a response letter
(Zimmerman to Draovitch, July 7, 2017) to the technical memorandum titled Background Soil and
Groundwater Statistical Methodology for 14 Duke Energy Facilities - emails submitted May 26, 2017.
Review of the Asheville dataset identified data that are appropriate for inclusion in the
statisitical analysis to determine background threshold values following the methodology
outlined in th TM. Specific comments included:
"All identified background wells are appropriate for use.
o MW -10, CB -01, CB -09, CB-09SL, MW -24S, CB -0 1D, AMW-03B, and CB-09BR
o Duke Energy recommended adding wells GW -1, GW -1D, and GW -IBR to the
background dataset. Based on a review of the information provided, these wells
may be added to the background dataset. If these wells are added, the new raw
background dataset should be re -submitted to DWR.
The datasets for each flow layer meets the minimum requirement of at least 10 samples.
All identified sample event dates are appropriate for use.
All identified outliers are acceptable and should be removed from the background dataset.
o If GW -1, GW -1D, and GW-lBR are added to the background dataset, then re -test the
new dataset for outliers and re -submit to the DWR, including strikethroughs of outliers
and other unusable data (e.g. high pH, high turbidity, autocorrelated data)."
The attached Table 1 provides the updated data set that has been tested for outliers following
the inclusion of the GW -1 cluster. Samples with pH greater than or equal to 8.5 standard units
(S.U.) and sample turbidity greater than or equal to 10 Nephelometric Turbidity Units (NTUs)
have been removed from the data set.
ATTACHMENTS: Table 1: Background Groundwater Results through April 2017
P: \ Duke Energy Progress.1026 \ Statistics _CAMA \ May 26 2017 - Updated Background Data Spreadsheets for
NCDEQ\ GROUNDWATER\ Asheville\ Interim Submittal—with GW-1_August17\Asheville - Tech Memo
081117.docx