HF Lee - Soil TM_05-26-2017_20171006

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Date: May 26, 2017
To: Ryan Czop (Duke Energy)
TECHNICAL MEMORANDUM
File: 1026.104
Cc: Kathy We b (Syn, erra)
From: Judd Mahan
Subject: Up-to-date Background Soil Data—H.F. Lee Energy Complex
The North Carolina Department of Environmental Quality (NCDEQ) provided a response letter
(Zimmerman to Draovitch, April 28, 2017) to the technical memorandum titled Statistical
Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash
Facilities (HDR Engineering, Inc. and Synterra Corporation, January 2017) requesting the following
technical issues be addressed in support of site assessment and corrective action activities:
0 Collect a minimum of ten valid background soil samples, opposed to eight, prior to the
determination of background threshold values (BTVs) for constituents in soil; and
,01 Provide updated spreadsheets of background data data for each facility.
Soil samples were collected from soil borings at the HF Lee Energy Complex (Site) for
voluntary assessment in 2013, the Comprehensive Site Assessment (CSA) in 2015, and
additional assessment in 2016. Table 1 provides a summary of the samples (locations and depth
intervals) which are considered for use in statistical calculations to determine concentrations of
naturally occurring (background) inorganic constituents in Site soil. Statistical outliers omitted
from the dataset are identified within Table 1.
Soil samples that meet the following criteria are considered valid for use in the statistic
calculations for background concentrations:
,01 Soil sample is collected from a location that is not impacted by coal combustion
residuals or coal associated materials;
,�11 Soil sample is collected from a location that is not impacted by other potential
anthropogenic sources of constituents; and
,01 Soil sample is collected from the unsaturated zone, > 1 ft. above the seasonal high water
table elevation.
Based on the minimum ten sample dataset requirement established by NCDEQ, three
additional soil samples will be necessary for statistics evaluation.
P: \ Duke Energy Progress.1026 \ Statistics _CAMA \ May 26 2017 - Updated Background Data Spreadsheets for
NCDEQ \ Tech Memo - Response to NCDEQ 04282017 Letter \ Final \ HF Lee - Soil TM_05-26-2017.docx

Up-to-date Background Soil Data
May 26, 2017
H.F. Lee Energy Complex
Page 2 of 2
The analytical results presented in Table 1 for antimony and thallium present reporting limits
that are greater than the PSRG for Protection of Groundwater (POG).
ATTACHMENTS: Table 1: Background Soil Data Summary
P: \ Duke Energy Progress.1026 \ Statistics _CAMA \ May 26 2017 - Updated Background Data Spreadsheets for
NCDEQ \ Tech Memo - Response to NCDEQ 04282017 Letter \ Final \ HF Lee - Soil TM_05-26-2017.docx