NC0004961_2018 FINAL Riverbend Excavation Soil Sampling Plan_20181107

EXCAVATION SOIL SAMPLING PLAN
RIVERBEND STEAM STATION
ASH BASIN SYSTEM
FOR ASH BASIN EXCAVATION
NORTH CAROLINA ASH BASIN CLOSURE
DUKE ENERGY CAROLINAS, LLC.
526 SOUTH CHURCH STREET/ECI3K
CHARLOTTE, NORTH CAROLINA 28202
DUKE
ENERGY.
Waste & Groundwater Programs
Revision 2
December 2018

Excavation Soil Sampling Plan December 2018
Riverbend Steam Station Ash Basin System Revision 2
TABLE OF CONTENTS
SECTION PAGE
1.0 PURPOSE..........................................................................................................................1
2.0 DOCUMENTATION SUMMARY...............................................................................1
3.0 SOIL SAMPLING METHODOLOGY.........................................................................1
3.1 Method Summary........................................................................................................ 1
3.1.1 Equipment...............................................................................................................2
3.1.2 Sample Locations................................................................................................... 3
3.1.3 Collection of Representative Samples................................................................. 3
3.1.4 Sample Preservation, Containers, Handling and Storage ................................ 4
3.1.5 Decontamination.................................................................................................... 4
4.0 VISUAL CONFIRMATION OF ASH REMOVAL .................................................... 4
4.1 Pre -Excavation Documentation................................................................................. 4
4.2 Ash Removal Verification Protocol........................................................................... 5
4.2.1 Field Documentation............................................................................................. 5
4.2.2 Fill Evaluation Criteria.......................................................................................... 6
4.3 Visual Removal Not Applicable................................................................................ 6
5.0 SOIL SAMPLING AND ANALYSIS........................................................................... 7
5.1 Soil Sampling................................................................................................................ 7
5.1.1 Scenario 1................................................................................................................ 7
5.1.2 Scenario 2................................................................................................................ 7
5.2 Fate and Transport Modeling..................................................................................... 8
TABLE 2 - Soil Parameters and Analytical Methods Totals and SPLP Analysis
North Carolina Ash Basins to Be Closed Via Excavation .......................................... 9
FIGURE 1 - Riverbend Steam Station Sample Grid..................................................10
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Excavation Soil Sampling Plan December 2018
Riverbend Steam Station Ash Basin System
1.0 PURPOSE
Revision 2
The purpose of this Excavation Soil Sampling Plan is to provide a standardized method for collecting soil
samples at Duke Energy North Carolina ash basins that are to be closed via excavation. Soil samples are
being collected following all visible ash removal from certain ash basins to support closure activities.
This Excavation Soil Sampling Plan is applicable to the collection of representative soil samples. Analysis
of soil samples may be chemical or physical in nature and may be used to determine the following:
• Extent and magnitude of constituent occurrence
• Input concentrations for groundwater fate and transport model
The methodologies discussed in this Excavation Soil Sampling Plan are applicable to the sampling of soil
in ash basin excavation areas. For the purposes of this plan, soils are those mineral and organic
materials remaining after all visible ash has been excavated.
2.0 DOCUMENTATION SUMMARY
TABLE 1 - Post Ash Basin Excavation Soil Data Collection
Task
Description
Test
Depth
Visual Inspection on 100' X 100'
Visually confirm primary source
grid node
removal at nodes (Figure 1) and
N/A
N/A
document with photographs.
Soil sample analysis on 100'X
Collect representative samples at
0 - 6 inches '
100' grid node
nodes (Figure 1) the appropriate
PLM
2 2.5'
depths.
0 - 6 inches'
Soil Sample Analysis on an acre
Collect representative samples at the
Total Metals
2 2.5
7 7.5
grid systeM2
appropriate depths.
SPLP
12'- 12.5'
IT- 17.5'
Notes:
' If a certain six-inch sample interval does not yield sufficient soil volume to fill five 8 -ounce sample bottles, the
sample interval may be expanded two twelve inches to allow for sufficient soil sample volume. The revised sample
interval should be appropriately documented.
2Excavation is complete once confirmed by visual inspection and PLM analysis per Section 4.0.
3.0 SOIL SAMPLING METHODOLOGY
3.1 Method Summary
This Excavation Soil Sampling Plan has been adapted from Environmental Protection Agency (EPA)
Standard Operating Procedures (SOPs) #2012 and #2006 and North Carolina Department of
Environmental Quality (NC DEQ) Attachment 1 Coal Combustion Residuals Surface Impoundment
Closure Guidelines for Protection of Groundwater, November 4, 2016.
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
Revision 2
Soil samples are collected directly using stainless steel or plastic trowel, spade, shovel, or scoops.
Following collection, soil is transferred from the sampling device to a stainless steel or plastic bowl to be
homogenized. Once homogenized, the soil is transferred into Duke Energy Laboratory supplied sample
bottles.
Soil samples will be submitted under chain of custody for the following analyses: total metals and
Synthetic Precipitation Leaching Procedure (SPLP) metals. Analytical methods for total metals and SPLP
metals are described in Table 2. Ash presence is quantitatively determined by polarized light
microscopy (PLM) by RJ Lee Laboratory (or other approved vendor). PLM analysis passes visible light
through a pair of polarizing filters to create optical effects used in identifying unknown materials. This
method is commonly used in asbestos and coal ash identification.
3.1.1 Equipment
• Stainless steel or plastic trowel, scoop, spade or shovel — Used for collecting soil samples
from surface locations.
• Sample containers — To be supplied by Duke Energy Laboratory with appropriate
cooler(s). Estimated that five 8 -ounce sample bottles with Teflon -lined lids will be
required for each sample location and sample depth. For return of cooler to the lab, ice
will be required.
• Gloves — Used for personal protection and to prevent cross -contamination of samples —
nitrile, disposable, powderless.
• Field clothing and Personal Protective Equipment — Used as specified in the site Health
and Safety Plan.
• Sampling flags — Used for identifying soil sampling locations.
• Field notebook — A bound book used to record progress of sampling effort and record
any problems and field observations during sampling.
• Three-ring binder book — Used to store necessary forms and record and track samples
collected at the site.
• Permanent marking pen — Used to label sample containers, document field logbooks,
data sheets and chain of custody.
• Stainless steel or plastic spoon — Used for homogenizing soil samples within a stainless
steel or plastic bowl.
• Stainless steel or plastic bowl — Used for homogenizing soil samples, when applicable.
• Camera — Used for photo -documentation of sample locations and samples.
• GPS — Device used to obtain elevation, latitude and longitude of sample location.
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
Revision 2
Trash bag — Used to dispose of gloves and any other non -hazardous waste generated
during sampling.
• Decontamination supplies and equipment.
3.1.2 Sample Locations
General locations for soil sampling are determined by the soil scientist in the field at a rate of
one soil sample for every 1 acre of ash basin area excavated. Actual sampling locations on site
may vary to account for site conditions and to allow collection of representative samples.
Representative samples reflect areas where all ash has been visually excavated and natural soil
is observed.
3.1.3 Collection of Representative Samples
For the purpose of this plan, surface soil is considered to range from 0 to 6 inches in depth,
while deeper samples will be collected at a range of 2 to 2.5 feet below ground surface (bgs), 7
to 7.5 feet bgs, 12 to 12.5 feet bgs, and 17 to 17.5 feet bgs (Table 1) unless bedrock, refusal, or
the water table are encountered. A surface soil sample and deeper samples will be collected at
each location for every 1 acre of ash basin excavated. A new pair of nitrile gloves is worn at
each sampling location and each depth. Each sampling location is recorded on the site map
prior to collecting the sample if location is not already noted on the map. The GPS location of
each sampling location (i.e. elevation, latitude and longitude), sample descriptions, and area
photographs are also recorded. All sampling equipment is decontaminated prior to use
irrespective of depth. The following procedure will be used to collect representative soil
samples with a scoop, shovel, trowel, geoprobe, or excavator:
• Locate general sampling locations.
• Determine suitability of sampling location for a representative sample.
• If sampling location appears to reflect representative conditions that would allow
collection of a representative sample, proceed with sampling procedure. If
location is not indicative of conditions that would allow collection of a
representative sample, notify the project manager so an alternate location can
be identified.
• Using a decontaminated sampling instrument, remove the desired thickness and
volume of soil from the sampling area. The sampler must obtain enough soil to
fill five 8 -ounce sample bottles. If a certain six-inch sample interval does not
yield sufficient soil volume to fill five 8 -ounce sample bottles, the sample interval
may be expanded to allow for sufficient soil sample volume. The revised sample
interval should be appropriately documented.
Transfer the sample into an appropriate sample or homogenization bowl. Non-
dedicated containers should be adequately decontaminated. Stir for
approximately one minute until there appears to be a uniform color and
consistency.
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
Revision 2
Transfer homogenized sample to a labeled container(s) of appropriate size and
construction for the analyses requested.
• Secure sample container tightly.
3.1.4 Sample Preservation, Containers, Handling and Storage
Chemical preservation of soils is generally not recommended. Cooling to 4°C on wet ice is
usually the best approach, supplemented by the appropriate holding time for the analyses
requested.
The Duke Energy Laboratory will supply the appropriate sample bottles for the collected soil
samples. The sample volume is a function of the analytical requirements and the Duke Energy
Laboratory will ensure the appropriate number of bottles are supplied. Ensure chain of custody
is completed for sample bottle return to the Duke Energy Laboratory.
Table 2 contains a list of parameters to be analyzed with corresponding reporting units and
analytical methods. If a parameter or group of parameters is not included in Table 2, the
laboratory performing the analysis should be contacted to determine the appropriate sample
bottles, volumes, and preservatives.
All non -dedicated sampling devices should be decontaminated and wrapped in plastic. The
sampling device should remain in this wrapping until it is needed. Each sampling device should
be used for only one sample and then decontaminated or disposed of. Non -dedicated sampling
devices should be cleaned in the field using the decontamination procedure described below.
3.1.5 Decontamination
Decontamination procedures can be time consuming; having a sufficient quantity of sampling
tools available is recommended. All non -dedicated sampling equipment must be
decontaminated prior to reuse. Equipment decontamination consists of:
1. Detergent wash and brush cleaning
2. Tap water rinse
3. De -ionized water rinse
4. Air dry
5. Wrap sampling tools with plastic
4.1 Pre -Excavation Documentation
Closure by removal is defined herein as removing the primary source (primary source of potential
constituents of interest) to the point that ash is not visible to the unaided eye at the ground surface.
Primary source ash is the main body of ash that was deposited in the basin. This method is intended
solely to verify and document primary source ash removal and is not intended to validate environmental
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Excavation Soil Sampling Plan
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quality standards of the subsurface (considered the secondary source of potential constituents of
interest). Pre -excavation documentation would consist of:
• Review topographic mapping, aerial photography, construction drawings, and boring logs to
estimate the pre -ash placement topography and/or ash/soil interface
• Preparation of an ash basin figure illustrating a grid spacing of 100 feet (Figure 1). Each grid
point (node) will be assigned a unique identifier. Each node of the grid spacing (grid point) will
represent a visual verification location.
4.2 Ash Removal Verification Protocol
Ash excavation will be considered complete based on visual confirmation that all ash has been removed.
Ash removal will be based on sampling of the ash/soil interface and analysis by PLM. Soil samples will
be examined utilizing methods outlined in American Society for Testing and Materials (ASTM) D2488,
Standard Practice for Description and Identification of Soils (Visual -Manual Procedure). Vertical and
horizontal excavation of ash can terminate when the remaining material can be documented using PLM
to contain less than 50% ash.
Project will excavate ash until a visible change in color or texture confirms removal. This location shall
be referred to as the ash/soil interface. If visual evaluation is inconclusive, then request additional
evaluation to confirm ash removal.
4.2.1 Field Documentation
Evaluate the excavated surface elevation relative to the pre -ash placement topography.
Periodically check bottom elevation to evaluate if fill is present above historic bottom elevation.
Visual confirmation will be performed on a 100 -foot grid system (Figure 1), unless conditions
prevent such confirmation, as described in Section 4.3. Soil sampling will be performed on a
100 -foot grid system and will be analyzed using PLM.
• Personnel will locate each node by GPS or survey control, determine elevation, and
evaluate whether that point is above or below the historic bottom elevation.
Personnel will then observe the surface area represented by the node, to note if visible
ash is present at the surface. If present, the location should be documented and
excavation will need to continue. If the evaluation indicates the surface soils are
residuum or bedrock, then hand auger to two feet below surface (or refusal) and
perform visual -manual classification of the soils at the surface and depth according to
ASTM method D2488. Submit sample from surface and depth (or shallower if refusal)
for PLM analysis. The conditions shall be documented by taking photographs.
• The classification indicator for fly ash will be grey to black silt -sized particles with no
plasticity. The classification indicator for bottom ash will be grey to black sand to gravel
sized particles and porous. If the material cannot be positively identified as soil, submit
a sample for PLM analysis.
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
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• If the node point elevation is near the historic bottom elevation then personnel can
conclude the primary source is removed when the following criteria are met:
1. Residuum is indicated by observation
Soil is confirmed by visual manual classification (ASTM D2488) and PLM analysis
less than 50%
4.2.2 Fill Evaluation Criteria
The following procedure provides an approach that can be used to ascertain if the fill can remain
in place. The procedure specified is based on the fill material and depth.
• If the elevation is less than eight feet above the historic bottom elevation and residuum
is not observed, then test pits may be excavated to historic bottom elevation or until
residuum or bedrock is encountered, but no more than eight feet below the surface.
o Personnel will evaluate existing information to determine if the test pits are
necessary. If necessary, personnel may recommend excavating test pits at a
frequency no tighter than 100 feet by 100 feet.
o If visible ash is not discovered based on information defined above, then the
primary source removal may be confirmed.
o If visible ash is discovered, then continue excavation.
• If the elevation is more than eight feet above historic bottom elevation and residuum is
not observed, discuss with CCP Closure Personnel.
o CCP Closure Personnel will confirm historic information and recommend a
drilling and sampling program at a frequency no tighter than 100 feet by 100
feet to evaluate the presence of ash below the fill in accordance with the
information defined above. If unusual features are revealed by the drilling, CCP
Closure Engineering may request/recommend additional borings. Exploration is
to be performed by continuous sampling during drilling.
o If visible ash is not discovered based on information defined above, then the
primary source removal may be confirmed.
o If visible ash is discovered, then continue excavation.
4.3 Visual Removal Not Applicable
If possible, excavation of ash should continue even if groundwater is encountered. Visual
documentation cannot be completed where ash is under the water table. If Duke Energy cannot
complete visual removal because of site conditions or other restricting factors, documentation shall be
presented to NC DEQ.
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Excavation Soil Sampling Plan December 2018
Riverbend Steam Station Ash Basin System Revision 2
5.0 SOIL SAMPLING AND ANALYSIS
5.1 Soil Sampling
Soil sampling of the remaining soils (less than 50% ash per PLM analysis) will be necessary to evaluate
the extent of potential secondary source impacts depending on the depth of the water table and any
proposed institutional or engineering controls that may be used in the area of excavation. Soil sampling
will not be required if refusal or the top of bedrock are encountered or the remaining soils are below the
water table. Soil samples for laboratory analysis must be collected in a manner that will ensure a
relatively uniform distribution of particles throughout the six inch sample.
The systematic approach and design for soil sampling an analysis is dependent upon two scenarios:
• Scenario 1: Remaining soil (containing less than 50% ash per PLM analysis) is located above the
seasonal high water table and final constructed institutional and/or engineering controls will
restrict infiltration from the surface reaching the water table (e.g. installation of a liner system).
Scenario 2: Remaining soil (containing less than 50% ash per PLM analysis) is located above the
seasonal high water table and infiltration from the surface would continue to reach the water
table.
5.1.1 Scenario 1
Confirmation sampling will include discrete surface samples collected from the first six inches of
the soil. Sampling will be performed on an acre grid system. This sample collection
methodology shall be sufficient to characterize the horizontal extent of any remaining potential
secondary source impacts for comparison with the NC DEQ Preliminary Soil Remediation Goals
(PSRG). The samples shall be analyzed by a North Carolina certified laboratory for total
concentrations for the following parameters: antimony, aluminum, arsenic, barium, beryllium,
boron, cadmium, calcium, chloride, chromium (total and hexavalent), cobalt, copper, iron, lead,
magnesium, manganese, mercury, molybdenum, nickel, nitrate as nitrogen, pH, potassium,
selenium, silver, sodium, strontium, sulfate, thallium, vanadium, and zinc. No SPLP testing is
required.
5.1.2 Scenario 2
Confirmation sampling will include collection of both discrete surface and subsurface soil
samples performed on an acre grid system. Discrete surface samples will be collected from the
first six inches of the soil and a subsurface soil sample will be collected at 2 to 2.5 feet below
ground surface (bgs), 7 to 7.5 feet bgs, 12 to 12.5 feet bgs, and 17 to 17.5 feet bgs unless refusal,
bedrock, or the water table are encountered. The use of a geoprobe or excavator is anticipated.
This sample collection methodology shall be sufficient to characterize both the horizontal and
vertical extent of any remaining potential secondary source impacts for comparison with the NC
DEQ PSRGs and/or input into the soil leachate model. The samples shall be analyzed by a North
Carolina certified laboratory for both total concentrations and SPLP for the following
parameters: antimony, aluminum, arsenic, barium, beryllium, boron, cadmium, calcium,
chloride, chromium (total and hexavalent), cobalt, copper, iron, lead, magnesium, manganese,
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
Revision 2
mercury, molybdenum, nickel, nitrate as nitrogen, pH, potassium, selenium, silver, sodium,
strontium, sulfate, thallium, vanadium, and zinc.
5.2 Fate and Transport Modeling
Contingency for stabilization of remaining amounts of potential secondary source impacts in a manner
that will meet the intent of North Carolina Groundwater 2L Rules and closure requirements shall be
considered as site conditions dictate. Provisions to develop groundwater flow and transport models to
evaluate protection of groundwater criteria if some secondary source impacts are left in place shall be
considered. In addition, the possibility of metals leaching from a potential change in pH and
geochemical conditions related to dewatering and excavation shall be considered along with plans for
groundwater models to assess resulting site conditions.
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
December 2018
TABLE 2 - Soil Parameters and Analytical Methods Totals and SPLP Analysis
North Carolina Ash Basins to Be Closed Via Excavation
Revision 2
INORGANIC COMPOUNDS
UNITS
METHOD'
Aluminum
mg/kg or µg/I
EPA 6010D
Antimony
mg/kg or µg/I
EPA 6020B
Arsenic
mg/kg or µg/I
EPA 6020B
Barium
mg/kg or µg/I
EPA 6010D
Beryllium
mg/kg or µg/I
EPA 6020B
Boron
mg/kg or µg/I
EPA 6010D
Cadmium
mg/kg or µg/I
EPA 6020B
Calcium
mg/kg or µg/I
EPA 6010D
Chloride
mg/kg or µg/I
EPA 9056A
Chromium
mg/kg or µg/I
EPA 6010D
Cobalt
mg/kg or µg/I
EPA 6020B
Copper
mg/kg or µg/I
EPA 6010D
Hexavalent Chromium
mg/kg or
g/ g µg/I
EPA Method
7199/218.7
Iron
mg/kg or µg/I
EPA 6010D
Lead
mg/kg or µg/I
EPA 6020B
Magnesium
mg/kg or µg/I
EPA 6010D
Manganese
mg/kg or µg/I
EPA 6010D
Mercury
mg/kg or µg/I
EPA Method
7470A/7471B
Molybdenum
mg/kg or µg/I
EPA 6010D
Nickel
mg/kg or µg/I
EPA 6010D
Nitrate as Nitrogen
mg/kg or µg/I
EPA 9056A
pH
SU
EPA 9045D
Potassium
mg/kg or µg/I
EPA 6010D
Selenium
mg/kg or µg/I
EPA 6020B
Silver
mg/kg or µg/I
EPA 6020B
Sodium
mg/kg or µg/I
EPA 6010D
Strontium
mg/kg or µg/I
EPA 6010D
Sulfate
mg/kg or µg/I
EPA 9056A
Thallium (low level) (SPLP Extract only)
mg/kg or µg/I
EPA 6020B
Vanadium
mg/kg or µg/I
EPA 6020B
Zinc
mg/kg or µg/I
EPA 6010D
Notes:
1. Soil samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH
using USEPA Method 9045, as noted above (or similar approved methods). Soil samples will
also be analyzed for leaching potential using SPLP Extraction Method 1312 in conjunction with
USEPA Methods 6010/6020 (or similar approved methods).
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Excavation Soil Sampling Plan
Riverbend Steam Station Ash Basin System
FIGURE 1- Riverbend Steam Station Sample Grid
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December 2018
Revision 2
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