Mayo BTV GW Response to comments_20170816

TECHNICAL MEMORANDUM
Date: August 16, 2017 File: 1026.105
To: Kimberlee Witt
Cc: Kathy Webb
From: Jerry Wylie
Subject: Response to Comments — Mayo Background Groundwater Datasets
(Comments provided via electronic mail by NCDEQ (Eric Rice) on August
10, 2017)
Mayo Steam Electric Plant (Roxboro, NCS
Sample BG -01 for the bedrock dataset has turbidity measured at 10 NTUs on 7/7/2015.
Because the turbidity was measured at 10 NTUs for this sampling event (per guidance
document 10 NTUs or greater was to be excluded from the dataset) it is necessary to remove
the sampling event from the dataset.
RESPONSE. The 7/7/2015 value for BG -01 has been removed and the statistical
evaluation has been updated. A revised and updated technical memorandum has been
prepared and is included as a separate document.
2. Two values appear to be erroneous in the transition zone dataset. BG -02 collected on
9/11/2015 has a -58 ug/L recorded for the chromium +6 analyte. MW -12D collected on
3/28/2017 has a 96 ug/L thallium concentration recorded. This measured concentration is not
consistent with previous measured thallium concentrations. Please verify that the recorded
values are valid and whether they should be included in the datasets.
RESPONSE: The concentration for Cr(VI)reported in Table 1 was erroneous and has
been removed. This value was not included in statistical determinations. Results from
MW -12D on 3/28/2017 for thallium incorrectly reported a concentration of 96 ug/L and a
TDS concentration of <0.2 ug/L. These values were switched during formatting. Table 1
has been revised to indicate the correct values for thallium (<0.2 ug/L) and TDS (96
ug/L). Statistical determinations were originally computed using the correct values;
therefore, no revision is necessary.
3. For radionuclides the dataset list analytical results for the requested analytes by Totals for
Radium and Uranium and likewise reported as BTVs in Table 2. Previous analytical results
consisted of individual species for Radium (226, 228) and Uranium (233, 234, 236, 238) per
P:\Duke Energy Progress. 1026\Statistics—LAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO\ Mayo\ Groundwater\ Mayo Tech Memo Response to DEQ RRO Comments BG GW Datasets 15Aug2017.docx

Response to Comments — Roxboro and Mayo Background Groundwater Datasets August 14, 2017
Mayo Steam Electric Plant and Roxboro Steam Electric Plant Page 2 of 2
the guidance document. Please explain why radionuclides were reported as totals and the
method/s used to calculate the values (BTUs).
RESPONSE: NCDEQ, including representatives from the Central Office and Raleigh
Regional Office, met with Duke Energy and SynTerra on October 7, 2015 in Raleigh, NC
to discuss NCDEQ comments pertaining to the CSA report (SynTerra, September 2015).
Review comments were presented in three categories: general comments applicable to
CSA reports regardless of site; site-specific comments applicable to a specific site (in
this case, Mayo Plant); and editorial or fact errors. From that meeting:
"NCDEQ General Comment No. 13 - Include analysis for total uranium, radium -226, and
radium -228 in background, below ash basin, immediate downgradient, and other
downgradient locations. Use Federal MCL for standard for Ra 226, Ra 228, and U."
Therefore, although analytical results are reported by the analytical laboratory as
individual species, for comparison with the Federal MCLS and for comparison to
background concentrations, total Uranium and combined Ra226 + Ra228 values are used.
4. If your actions to address item #'s 1-3 above result in the removal or addition of sampling
events or data from a particular dataset/s, it will be necessary to recalculate the background
threshold values and submit updated BTVs to the Department.
RESPONSE: BTVs have been recalculated, as necessary, in response to comments #1
and #2 and the new values are included as revised and updated Technical Memorandum
- Background Threshold Values for Groundwater (Mayo Steam Electric Plant) which is
attached as a separate document.
P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH
MEMO\ Mayo\ Groundwater\ Mayo Tech Memo Response to DEQ RRO Comments BG GW Datasets 15Aug2017.docx