Cape Fear - GW BTV MEMO_FINAL REDUCED

Lip
synTerra
TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.03
To: Ryan Czop (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Chris Suttell (SynTerra)
Subject: Background Threshold Values for Groundwater
Cape Fear Steam Electric Plant - Moncure, NC
An updated background groundwater dataset was provided to the North Carolina Department
of Environmental Quality (NCDEQ) for Cape Fear Steam Electric Plant (Cape Fear) on May 26,
2017. Additionally, the revised Statistical Methods for Developing Reference Background
Concentrations for Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR
Engineering, Inc. and SynTerra Corporation, May 2017) was provided to NCDEQ. On July 7, 2017,
NCDEQ provided a response letter (Zimmerman to Draovitch, July 7, 2017) for each Duke
Energy coal ash facility that identified soil and groundwater data appropriate for inclusion in
the statistical analysis to determine background threshold values (BTVs) for both media. As
outlined in the NCDEQ July 7, 2017 letter, Duke Energy is required to provide BTVs for both
media within 60 days from receipt of the NCDEQ letter for facilities submitting Comprehensive
Site Assessments (CSAs) later than October 31, 2017. BTVs for soil are provided under separate
cover.
The revised background groundwater dataset provided to NCDEQ on May 26, 2017 addressed
comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ
requested Duke Energy collect at least 10, rather than the previously planned eight, valid
samples from background monitoring wells prior to determination of BTVs for constituents
within each flow system. For groundwater datasets with less than 10 valid samples available
for determination of BTVs, no formal upper tolerance limit (UTL) statistics could be run and the
provisional BTV (PBTV) for a constituent and groundwater flow system was computed to be
either:
0 The highest value, or
4? If the highest value is above an order of magnitude greater than the geometric mean
of all values, then the highest value should be considered an outlier and removed
from further use and the PBTV is computed to be the second highest value.
NCDEQ requested that the updated background groundwater dataset exclude data from the
background data set due to one or more of the following conditions:
P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination
Reports\ Groundwater \Cape Fear - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
Cape Fear Steam Electric Plant Page 2 of 3
0 Sample pH is greater than or equal to 8.5 standard units (S.U.) unless the regional
DEQ office has determined an alternate background threshold pH for the site;
0 Sample turbidity is greater than 10 Nephelometric Turbidity Units (NTUs);
0 Result is a statistical outlier identified for background sample data presented to
NCDEQ on May 26,2017;
0 Sample collection occurred less than a minimum 60 days between sampling events;
and
,41P Non -detect results are greater than 2LAMAC.
Additional site-specific requirements related to groundwater background dataset for Cape Fear,
such as exclusion of data not approved by NCDEQ, as outlined in the July 7, 2017 NCDEQ letter
have been incorporated into the groundwater background dataset.
This technical memorandum summarizes the revised background groundwater datasets and
statistically determined BTVs. Statistical determinations of BTVs were performed in accordance
with the revised Statistical Methods for Developing Reference Background Concentrations for
Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR Engineering, Inc.
and SynTerra Corporation, May 2017).
GROUNDWATER BACKGROUND DATA
The current background monitoring well network consists of wells installed within two flow
zones - surficial and bedrock. Well locations are presented on Figure 1. Background datasets
provided to NCDEQ on May 26, 2017 were revised based on input from NCDEQ in the July 7,
2017 letter. Revised background datasets for each flow system used to statistically determine
naturally occurring concentrations of inorganic constituents in groundwater are provided in
Table 1. The following sections summarize the refined background datasets along with results
of statistical evaluations for determining BTVs.
SURFICIAL
Three wells - MW-15SU, MW-15SL, and MW -16S - monitor background groundwater quality
within the surficial flow zone. In the July 7, 2017 letter, NCDEQ concurred with the
background locations and samples proposed for the surficial background dataset with the
exception of those samples collected less than 60 days between sampling events, statistical
outliers, and invalid data. Those samples were omitted prior to statistical determinations.
The resulting surficial flow zone dataset meets the minimum requirement of 10 samples. Table
1 presents the revised background dataset for the surficial flow zone. BTVs were calculated for
the surficial flow zone using formal UTL statistics and are presented in Table 2.
P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination
Reports\ Groundwater \Cape Fear - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
Cape Fear Steam Electric Plant Page 3 of 3
BEDROCK
Four wells — MW -09, MW-09BR, MW-15BR, and MW-16BR — monitor background groundwater
quality within fractured bedrock. In the July 7, 2017 letter, NCDEQ concurred with the
background locations and samples proposed for the fractured bedrock background dataset with
the exception of those samples collected less than 60 days between sampling events, statistical
outliers, and invalid data. Those samples were omitted prior to statistical determinations.
The resulting fractured bedrock dataset meets the minimum requirement of 10 samples. Table
1 presents the revised background dataset for fractured bedrock. BTVs were calculated for
fractured bedrock zone using formal UTL statistics and are presented in Table 2.
LIST OF FIGURE:
Figure 1 Well Location Map
LIST OF TABLES:
Table 1 Background Groundwater Results through February 2017
Table 2 Background Threshold Values for Groundwater
P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination
Reports\ Groundwater \Cape Fear - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
Cape Fear Steam Electric Plant
FIGURES
P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination
Reports\ Groundwater \Cape Fear - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
Cape Fear Steam Electric Plant
TABLES
P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination
Reports\ Groundwater \Cape Fear - GW BTV MEMO_FINAL.docx

TABLE 1
UPDATED BACKGROUND GROUNDWATER ANALYTICAL RESULTS THROUGH FEBRUARY 2017
CAPE FEAR STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, MONCURE, NC
Prepared by: 3 Checked by: CIS
Notes:
54 - Indicates value omitted from au[od..—
- Indl[a[escatepareme[er not measuretl or analyzetl.
lhd
® thcls data removed/Identl0u
Indas
outlier
- icates data removed due to co—rrelatlon
mg - N/L - Milligrams nI[rogen per liter pCl/L - plmcurles per Ilter
mg/L- Mllligrems per liter S.U. - Standard Unit
NE - Not established ug/L- Ml—grems per liter
NTU - Nephelometric turbidity unit ug/mL - ml—g— per milliliter
< - concentration not detected at or above the adjusted reporting limit.
- Interim Maximum Allowable Concentretipns (IM—) of the 15A NCAC 02L Standard, Appendix 1, ApNI, 1, 2013.
- Hexavalent chmmi um does not have a NC 2L/IMAC ft.—M; therefore, Me NC 2L standard for total chromium is relied upon as a surrogate.
B -Target analyte detected in method blank Ih or above the reporting I -t. Target analyte concenI'd- In sample is less than SOX the mncentretion In the method blank. Analyte Com—tratlon In sample Could be due to blank contamination.
B2 - Target analyb, was det—d in blank(s) at a mncenfation greater than 1/2 the repotting limlt but less Man Me reporting Ilmlt. Analyte concentration In sample Is valid and may be used f,,—pllance purposes.
D3 - Sample was dlluted due to the presence of high levels of non -target analytes or other mahlx interference.
j - Estimated cahmh.b.h above the adjusted method detection Iimlt and below the adjusted reporting Iimlt.
M3 - Matrix spike recovery was high: Me associated Laboratory Control Splke (LCS) was ameptable.
M4 -The spike recovery value was unusable since the analyte concentration In the sample was c1 propprtlonate M the spike Ievel. The assod-d Laboratory Control Spike recovery was acceptable.
S - Associated wllbratlon check did not meet Ip,.Fled crI[eria.
P:\Duke Energy Progress.1025\103. Cape Fear Ash Basin GW Assessment\35.eackground Detertnlnation Reports\Gmundwater\TM Tables\TABLE 1- Cape Feat_BG GW Page 1 of 1
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Prepared by: 3 Checked by: CIS
Notes:
54 - Indicates value omitted from au[od..—
- Indl[a[escatepareme[er not measuretl or analyzetl.
lhd
® thcls data removed/Identl0u
Indas
outlier
- icates data removed due to co—rrelatlon
mg - N/L - Milligrams nI[rogen per liter pCl/L - plmcurles per Ilter
mg/L- Mllligrems per liter S.U. - Standard Unit
NE - Not established ug/L- Ml—grems per liter
NTU - Nephelometric turbidity unit ug/mL - ml—g— per milliliter
< - concentration not detected at or above the adjusted reporting limit.
- Interim Maximum Allowable Concentretipns (IM—) of the 15A NCAC 02L Standard, Appendix 1, ApNI, 1, 2013.
- Hexavalent chmmi um does not have a NC 2L/IMAC ft.—M; therefore, Me NC 2L standard for total chromium is relied upon as a surrogate.
B -Target analyte detected in method blank Ih or above the reporting I -t. Target analyte concenI'd- In sample is less than SOX the mncentretion In the method blank. Analyte Com—tratlon In sample Could be due to blank contamination.
B2 - Target analyb, was det—d in blank(s) at a mncenfation greater than 1/2 the repotting limlt but less Man Me reporting Ilmlt. Analyte concentration In sample Is valid and may be used f,,—pllance purposes.
D3 - Sample was dlluted due to the presence of high levels of non -target analytes or other mahlx interference.
j - Estimated cahmh.b.h above the adjusted method detection Iimlt and below the adjusted reporting Iimlt.
M3 - Matrix spike recovery was high: Me associated Laboratory Control Splke (LCS) was ameptable.
M4 -The spike recovery value was unusable since the analyte concentration In the sample was c1 propprtlonate M the spike Ievel. The assod-d Laboratory Control Spike recovery was acceptable.
S - Associated wllbratlon check did not meet Ip,.Fled crI[eria.
P:\Duke Energy Progress.1025\103. Cape Fear Ash Basin GW Assessment\35.eackground Detertnlnation Reports\Gmundwater\TM Tables\TABLE 1- Cape Feat_BG GW Page 1 of 1

TABLE 2
GROUNDWATER BACKGROUND THRESHOLD VALUES
CAPE FEAR STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, MONCURE, NC
Parameter
Reporting Unit
NCAC 02L Standard
Background Threshold Values
Surficial Bedrock
pH*
S.U.
6.5-8.5
5.8 - 6.4
5.5 -8.2
Alkalinity
mg/L
NE
206
237
Aluminum
lag/L
NE
323
118
Antimony
pg/L
1A
1
1
Arsenic
ug/L
10
3
6
Barium
pg/L
700
183
471
Beryllium
pg/L
46
1
1
Bicarbonate
mg/L
NE
206
235
Boron
lag/L
700
177
50
Cadmium
lag/L
2
1
1
Calcium
mg/L
NE
82.6
62.6
Carbonate
mg/L
NE
5
5
Chloride
mg/ L
250
250
220
Chromium (VI) 1
lag/L
10
0.12
0.03
Chromium
lag/L
10
1
1
Cobalt
lag/L
1A
89
1
Copper
lag/L
1000
4
1
Iron
lag/L
300
37500
910
Lead
lag/L
15
1
1
Magnesium
mg/L
NE
32.5
30.8
Manganese
pg/L
50
9170
901
Mercury
pg/L
1
0.05
0.05
Methane
pg/L
NE
10
25
Molybdenum
pg/L
NE
1
12
Nickel
pg/L
100
78
2
Nitrate + Nitrite
mg-N/L
NE
2
2
Potassium
mg/L
NE
1.61
2.49
Selenium
pg/L
20
1
2
Sodium
mg/L
NE
190
72.5
Strontium
pg/L
NE
994
806
Sulfate
mg/L
250
510
96
Sulfide
mg/L
NE
0.1
0.1
TDS
mg/L
500
1200
675
Thallium
pg/L
0.2°
0.2
0.2
TOC
mg/L
NE
6.3
1.3
Vanadium
pg/L
0.3°
1
2
Zinc
lag/L
1000
62
5
Radium (Total)
pCi/L
NE
3.60
3.46
Uranium (Total)
pg/mL
NE
0.0167
0.00196
Prepared by: LWD Checked by: TCP
Notes:
* - Upper and lower tolerance limits calculated for parameter
A - Interim Maximum Allowable Concentrations (IMACs) of 15A NCAC .021- Standard, Appendix 1, April 1, 2013
' - Hexavalent chromium does not have a NC 2L/IMAC standard; therefore, the NC 2L standard for total chromium is relied upon as a surrogate.
mg/L - milligrams per liter
NE - Not Established
pCi/L - picocuries per liter
Radium (Total) - Radium -226 and Radium -228 combined
S.U. - Standard Unit
TDS - Total Dissolved Solids
TOC - Total Organic Carbon
pg/L - micrograms per liter
pg/mL - micrograms per milliliter
P:\Duke Energy Progress. 1026\103. Cape Fear Ash Basin GW Assessment\35. Background Determination Reports\Groundwater\TM Tables\TABLE 2 - Cape Fear GW BG Threshold ValuesTABLE 2
- Cape Fear GW BG Threshold Values Page 1 of 1