HF Lee SOIL BTV MEMO FINAL_20171006

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synTerra
TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.19
To: Ryan Czop (Duke Energy)
Cc Kathy Webb (SynTerra)
From: Judd Mahan (SynTerra)
Subject: Background Threshold Values for Soil
H.F. Lee Energy Complex - Goldsboro, NC
An updated background soil dataset was provided to the North Carolina Department of
Environmental Quality (NCDEQ) for H.F. Lee Energy Complex (H.F. Lee) 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 groundwater are provided under
separate cover.
The updated background soil datasets provided to NCDEQ on May 26, 2017 incorporated
comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ
requested that Duke Energy collect a minimum of 10, rather than the previously planned eight,
valid background samples prior to the determination of BTVs for each constituent. For soil
datasets with less than 10 valid samples available for BTV determination, no formal upper
tolerance limit (UTL) statistics will be run and the provisional BTV (PBTVs) for a constituent
will be computed to be either:
t0 The highest value, or
h 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.
Soil samples meeting the following criteria are considered valid for use in statistical
determinations of BTVs:
t' Sample was collected from a location that is not impacted by coal combustion
residuals or coal associated materials;
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Background Threshold Values- Soil September 5, 2017
H.F. Lee Energy Complex Page 2 of 3
y Sample was collected from a depth not less than 0.5 feet below ground surface;
y Sample was collected from a location that is not impacted by other potential
anthropogenic sources of constituents; and
`7 Sample is collected from the unsaturated zone, greater than one foot (ft) above the
seasonal high water table elevation.
Additional site -specific requirements related to the H.F. Lee background soil dataset as outlined
in the July 7, 2017 NCDEQ letter have been incorporated into the soil background dataset.
This technical memorandum summarizes the revised background soil 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).
SOIL BACKGROUND DATA
Soil samples were collected from soil borings conducted at H.F. Lee during the 2015
Comprehensive Site Assessment (CSA). Background soil sample locations are presented in
Figure 1. The background dataset provided to NCDEQ on May 26, 2017 included pooled soil
samples collected from multiple depth intervals. Only samples collected from background
locations at depth intervals greater than one foot above the seasonal high water table were
included in the dataset. The background soil dataset has been further revised from the May 26,
2017 submittal based on input from NCDEQ in the July 7, 2017 letter. NCDEQ determined the
following samples are not appropriate for use in determining BTVs:
y AMW-12 SB (5-6) —collected within 1 foot of the seasonal high water table;
y IMW-05 SB (0-2.5) and IMW-05 SB (4-6) — collected in close proximity to the southeast
corner of the Inactive Basin 3 and possibly influence by the presence of the ash basin.
IMW-05 SB (0-2.5) sample was collected too shallow;
0 AMW-18 SB (0-2.5) and AMW-18 SB (3-5) — collected from the core of the plume
migrating from the Active Basin;
y AMW-04 SB (1-2) and AMW-04 SB (4-5) — collected from the western end of the Active
Basin, adjacent to the Neuse River;
E7 AMW-16 BC (19-21) — request for re-evaluation of this sample for use in BTV
determinations (see below);
AMW-11 (0-2) and AMW-12 SB (0-2), AMW-13 SB (0-2) and AMW -16 BC (0-2) —
collected too shallow.
The soil sample, AMW-16BC (19-21), appears to meet the criteria of a background soil sample
for the following reasons:
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Background Threshold Values- Soil September 5, 2017
H.F. Lee Energy Complex
Page 3 of 3
ty The highest water level recorded is 23.56 feet below ground surface on November 16,
2016;
0 The sample was collected greater than 2.5 feet above the seasonal high water table; and,
=7 The sample was collected from the location of of pair of wells (AMW-16BC and CCR-
100S) approved by NCDEQ as appropriate for use as background wells for
determination of groundwater BTVs.
For these reasons, it is requested that NCDEQ consider use of the soil sample AMW-16BC (19 -
21) in determination of soil BTVs.
Prior to statistical determinations, the background soil dataset was re -screened for outliers to
adjust for the removal of samples from the dataset. Updating the background soil dataset to
exclude samples identified by NCDEQ resulted in zero valid background soil samples.
NCDEQ requires that laboratory practical quantitation limits (PQL) for soil analytical data be
less than the NCDEQ IHSB Preliminary Soil Remediation Goals (PSRG) Protection of
Groundwater standards (dated October 2016) for the data to be valid for calculating BTVs.
Additional soil samples will be collected to satisfy the minimum number of soil samples for all
constituents. Antimony, selenium, and thallium will be analyzed by a method whereby the
PQL will be below the PSRG Protection of Groundwater values. Once data for the planned
additional samples are included in the dataset, the dataset will be screened for outliers and
BTVs will be computed. The proposed background soil sample locations are presented in
Figure 1. Boring logs and analytical results for subsequent background soil sample collection
will be submitted to the NCDEQ Regional Office if received and processed in sufficient time for
review prior to the preparation of the updated CSA report.
LIST OF FIGURES:
Figure 1 Background Soil Sample Location Map
LIST OF TABLES
Table 1 Proposed Background Soil Data Summary
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MEMO \ HF Lee \ Soil \ HF Lee SOIL BTV MEMO_FINAL.docx

Background Threshold Values- Soil
September 5, 2017
H.F. Lee Energy Complex
FIGURE
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MEMO \ HF Lee \ Soil \ HF Lee SOIL BTV MEMO_FINAL.docx

* Z"
+—
LEGEND
O
PROPOSED BACKGROUND SOIL
SAMPLE LOCATION
EXISTING MONITORING WELL
®
LOCATIONS
WASTE BOUNDARY
COMPLIANCE BOUNDARY
DUKE POWER H.F. LEE PLANT
BOUNDARY
NOTES:
2014 AERIAL ORTHOPHOTOGRAPHY OBTAINED FROM
USDA NRCS GEOSPATIAL DATA GATEWAY
(https://gdg.sc.egov.usda.gov/GDGOrder.aspx).
DRAWING HAS BEEN SET WITH A PROJECTION OF
NORTH CAROLINA STATE PLANE COORDINATE
SYSTEM FIPS 3200 (NAD83/2011).
C
K
-
PZ-10
PZ-I
13S PW-01
V-13BC -
11�
P
r �
1 7 !
I�
J�lo
"SI
• r-
... r,
`BGSB 12", ��--
AMW-21 S
AMW-21 BC r-
,ez
GRAPHIC SCALE
250 125 0 250 500
IN FEET
10
148 RIVER STREET, SUITE 220
GREENVILLE, SOUTH CAROLINA 29601
PHONE [phone]
n or QM
synTerra
DRAWN BY: A. ROBINSON DATE: 08/03/2017
PROD
PROJECT MAA NAGER: J. MAHAN
J.
CHECKED BY: C. PONCE
BGMW-10
1
FIGURE 1
BACKGROUND SOIL
SAMPLE LOCATION
H.F. LEE ENERGY COMPLEX
GOLDSBORO, NORTH CAROLINA

Background Threshold Values- Soil
September 5, 2017
H.F. Lee Energy Complex
TABLE
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MEMO \ HF Lee \ Soil \ HF Lee SOIL BTV MEMO_FINAL.docx

TABLE 1
UNSATURATED BACKGROUND SOIL DATA SUMMARY
H.F. LEE ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, GOLDSBORO, NC
Analytical Parameter
pH
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
it N)
Potassium
Selenium
Sodium
Strontium
Sulfate
Thallium
Vanadium
Zinc
Reporting Units
S.U.
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
PSRG Protection of Groundwater
NE
NE
0.9
5.8
580
63
45
3
NE
NE
360000
0.9
700
150
270
NE
65
1
NE
130
NE
NE
2.1
NE
NE
NE
0.28
6
1200
Sample ID
Sample
Analytical Results
Collection Date
AMW-16BC (19-21)
05/24/2016
NA
6220
---
<IA
14.6
<0.057
<2.8
<0.14
62.5
NA
4.2
---
2
3440
NA
177
12.3
<0.0094
<0.57
2
NA
123
<1.1
<56.8
1.4
NA
---
7.7
4.7
Prepared by: JHG Checked by: JDM
Notes:
54 - Indicates values omitted from dataset.
Indicates data removed /identified as an outlier
--- - Non -detect value removed from dataset; concentration greater than PSRG Protection of Groundwater
< - concentration not detected at or above the adjusted reporting limit.
mg/kg - milligrams per kilogram
NA - Not applicable; sample not collected or analyzed
NE - Not established
PSRG Protection of Groundwater - NCDEQ IHSB Preliminary Soil Remediation Soil Remediation Goals Table - October 2016
S.U. - Standard Units
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