7906_Duke_DanRiver_Area1CleanupLevels_DIN26815_20161011

PAT MCCRORY Governor DONALD R. VAN DER VAART
Secretary
MICHAEL SCOTT Director
State of North Carolina | Environmental Quality | Waste Management
1646 Mail Service Center | 217 West Jones Street | Raleigh, North Carolina 27699-1646
919 707 8200 T
October 11, 2016

Sent via email to [e-mail]

Ms. Melonie Martin, Environmental Services
Duke Energy Corporation
3195 Pine Hall Road
Belews Creek, North Carolina 27009

Subject: Attachment 1, Guidance for Area 1 Dry Stack
Duke Energy Dan River Steam Station
Permit No. 7906-INDUS-2016
Rockingham County, DIN 26815

Dear Ms. Martin;
On October 5, 2016 Duke Energy (Duke) requested information from the Division of Waste
Management, Solid Waste Section (Section) regarding the applicability of the guidance entitled
Attachment 1, Coal Combustion Residuals Surface Impoundment Closure, Guidelines for
Protection of Groundwater. Prepared by NCDEQ. September 2016. DIN 26814.
(attached).
With regards to the excavation of coal combustion residuals (CCR) from Area 1 dry stack, of the
proposed Dan River Steam Station industrial landfill, the Section recognizes Attachment 1, Coal
Combustion Residuals Surface Impoundment Closure, Guidelines for Protection of Groundwater
(Guidelines) was developed to determine cleanup levels for the closure of surface
impoundments. However, the Section has been tasked to utilize the Guidelines for determination
of cleanup levels for the Area 1 dry stack in preparation for landfill construction at the Dan River
Steam Station. The Area 1 dry stack, which will be the footprint of the proposed industrial
landfill, historically stored coal ash from periodic dredging of the ash basins above the water
table and consists of soil and CCR.
The following guidance is given for preparation of an Excavation Soil Sampling Plan for Area 1
of the landfill:
1. An Excavation Soil Sampling Plan (Plan) should be prepared and submitted for review
by the Section within ten (10) business days of receipt of this letter.
2. Include in the Plan Duke’s intent to submit all sampling results to the Section for
review.
3. Regarding the portion of the Guidelines titled CCR Excavation Determination, the Plan
should include the description of the process as described in the Guidelines.
Dan River Steam Station October 7, 2016 DIN 26815
Page 2 of 2
4. Regarding the portion of the Guidelines titled Soil Sampling and Analysis, the Section
recognizes that there is no CCR encountered in the groundwater of Area 1. Once
constructed, the landfill liner system is an engineered control. Therefore, the plan
should include the description of Scenario 1: Conformation Sampling as described in
the Guidelines.
5. Regarding the portion of the Guidelines titled Characterization and Management of
Non-Ash Materials, this portion should be included in the Plan but will only be
implemented should non-ash materials be encountered during excavation.
6. Regarding the portion of the Guidelines titled Determination of Site-Specific Soil
Remediation Goals and Cleanup Levels, the Section expects Duke to address this item
at the time of submission of the prescribed sampling results.
7. Regarding the portion of the Guidelines titled Groundwater Modeling, the Section
expects Duke to address this item at the time of submission of the prescribed sampling
results.

Should you have any questions regarding this matter contact Elizabeth Werner via phone (919)
707-8253 or email [e-mail].

Sincerely,

Edward F. Mussler, III, P.E., Supervisor
Permitting Branch, Solid Waste Section
Division of Waste Management, NCDEQ

Attachment: Attachment 1, Coal Combustion Residuals Surface Impoundment Closure,
Guidelines for Protection of Groundwater
Cc: Elizabeth Werner – SWS/RCO
Larry Frost – SWS/ARO
Shannon Aufman – SWS/RCO
Shawn McKee – SWS/RCO
Ellen Lorscheider – SWS/RCO
_____________________________________________________________________________________
1 The steps or methodology for calculating SSLs for contaminant migration to groundwater were developed to identify
chemical concentrations in soil with the potential to migrate and contaminate groundwater. SSLs protective of
groundwater are calculated with a soil leachate model using default values from the 2L groundwater standard or the 2L groundwater interim maximum allowable concentration (IMAC) as target groundwater concentrations and take into consideration fate and transport parameters. Page 1 of 5
Attachment 1
Coal Combustion Residuals Surface Impoundment Closure
Guidelines for Protection of Groundwater

The overall objective of these guidelines is to address remediation of discharges or releases of
contaminants into soil and groundwater resulting from Coal Combustion Residuals (CCR) disposal to cleanup levels that meet Title 15A of the North Carolina Administrative Code Subchapter 02L standards (2L Standards):

• For groundwater, the cleanup level is the site-specific background concentration or the 2L
Standards.
• For soil, the cleanup level is either the site-specific background concentration or the lowest
soil screening level (SSL) protective of groundwater.

Protection of groundwater criteria dictates groundwater and soil remediation goals in the closure process. Either Preliminary Soil Remediation Goals (PSRGs) identified using North Carolina’s Department of Environmental Quality (DEQ)’s Inactive Hazardous Sites Branch (IHSB) SSLs,1
or site-specific background concentrations in soil will be used to identify soil remediation goals
that are protective of groundwater quality. Any wastes encountered that are not associated with
CCR will be addressed by applicable DEQ Division of Waste Management (DWM) program guidance. Excavation Soil Sampling Plan

Sampling and analyses of soil collected during excavation of a CCR Impoundment is needed in order to develop soil remediation goals and corresponding cleanup levels. The responsible party may need to prescribe additional sampling and analysis based on site-specific conditions.

A stand-alone Excavation Soil Sampling Plan (Plan) generated for closure of a CCR surface
impoundment shall be developed to ensure the proposed excavation design is comprehensive
enough in scope to meet the performance standards for closure. This Plan shall be submitted to
DEQ as part of an Excavation Plan, with details to show how the sample analytical results and
related modeling will incorporate the data collected as part of the final overall closure plan for
approval, as dictated by §130A-309.214.

CCR Excavation Determination

CCR excavation will be considered complete based on a visual confirmation that all CCR and co-mingled CCR/soil has been removed. The extent of co-mingled CCR/soil will be based on
Page 2 of 5

sampling of the material and analysis under Polarized Light Microscopy (PLM). Soil samples will
be examined utilizing methods outlined in American Standards for Testing and Measures (ASTM)
D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure).
Vertical and horizontal excavation of CCR can terminate when the remaining material can be documented using PLM to contain less than 50% CCR.
Visual confirmation sampling of CCR will be performed on a 100-foot grid system. The soil
sample will be performed on an acre grid system and should be collected by advancing a boring
using a hand-auger or from a test pit at a minimum depth of 2 feet below ground surface unless
refusal, bedrock, or the water table are encountered. The sample should be analyzed using PLM
and excavation of the CCR will be considered complete when the sample contains less than 50%
CCR.
If possible, excavation of CCR material should continue even if groundwater is encountered. If
complete excavation of the CCR and co-mingled CCR/soil (greater than 50% CCR) is not able to
be completed, documentation of site conditions or other restricting factors shall be presented to
the DEQ.
Soil Sampling and Analysis
Sampling of the remaining soils (containing less than 50% CCR) will be necessary to evaluate the
extent of contamination depending on the depth of 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 6-inch sample.

The systematic approach and design for soil sampling and analysis is dependent upon two scenarios:

• Scenario 1: Remaining soil (containing less than 50% CCR) 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% CCR) is located above the seasonal
high water table and infiltration from the surface would continue to reach the water table.
Scenario 1. Confirmation sampling will include discrete surface samples collected from the first
6 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 soil
contamination for comparison with the PSRG. The samples shall be analyzed by a North Carolina
certified lab for total concentrations of 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.

Page 3 of 5
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 6 inches of the soil and a subsurface soil sample will be collected from a 6-inch discrete
interval at a minimum depth of 2-feet below the surface soil sample depth interval unless refusal, bedrock, or the water table are encountered. This sample collection methodology shall be
sufficient to characterize both the horizontal and vertical extent of any remaining soil
contamination for comparison with the PSRG and/or input into the soil leachate model. The
samples shall be analyzed by a North Carolina certified lab for both total concentrations and by
the Synthetic Precipitation Leaching Procedure (SPLP) of 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.
Characterization and Management of Non-Ash Material
If non-ash materials are discovered during ash removal activities, work in that area will be stopped,
temporarily relocated to another area, and the Duke Energy environmental team will be contacted
to perform the appropriate assessment(s) to determine the nature and the extent of the non-ash related impacts. Depending upon the material encountered, the area will either be delineated and segregated for profiling and proper disposal, or placed directly into roll-off containers for proper
disposal.

Hazardous Waste Operations and Emergency Response (HAZWOPER) crews will be mobilized to the site to perform the excavation activities if hazardous materials are encountered. The appropriate DEQ Division of Water Resources Regional Office or the DWM will be contacted if
these areas are discovered and the plan for proper removal and disposal will be discussed. Non-
ash related areas will be documented on excavation drawings and information recorded will
include, but not be limited to, the material encountered, the dimensions with coordinates of the excavated area, the health and safety protocols used to protect human health and the environment during the execution of these activities, a summary of the sample and confirmation analytical
results, and copies of the appropriate manifests.

Determination of Site-Specific Soil Remediation Goals and Cleanup Levels Protection of groundwater soil remediation goals can be identified by following specific
instruction found in DWM remediation guidance (referred to below). Only requirements for
remediation goals that involve protection of groundwater criteria will be considered. Risk-based
or health-based remediation goals for unrestricted land use will not be considered for closure performance standards.
The DWM IHSB guidance documents that contain direction for establishing remediation goals
include:

Page 4 of 5
• Inactive Hazardous Sites Guidelines for Assessment and Cleanup:
http://portal.ncdenr.org/c/document_library/get_file?uuid=32af7da0-d350-4392-8a87-
201f94b2eedc&groupId=38361 and
• Registered Environmental Consultant (REC) Program Implementation Guidance:
http://portal.ncdenr.org/c/document_library/get_file?uuid=3049dcfb-b0cf-4ebf-8459-
5018415fb6a3&groupId=38361
Site-specific soil remediation goals are identified by:
• Identifying PSRGs that relate to the SSLs that meet the protection of groundwater criteria
for a specific constituent, and
• Determining site-specific background concentrations in soil.
The procedure for identifying PSRG that meets protection of groundwater criteria and the
corresponding SSL involves the following:

• Screening Values. The screening values that relate to SSLs protective of groundwater are shown in the PSRG Table located at:
http://portal.ncdenr.org/c/document_library/get_file?uuid=13ccab00-3c6a-48c5-abe4-
41b96d7ea6cb&groupId=38361.
• PSRG table. This contains a column with soil remediation goals titled “Protection of Groundwater PSRG” that should be used in evaluating soil-to-groundwater values that
meet and are protective of 2L standards. The values in this table for the respective
constituents are the SSLs, which are the contaminant-specific soil remediation goals that
are the cleanup levels for site closure. Note that the DWM updates this table during the first and third quarter of each calendar year.
• Transport Model. A transport model is included in the PSRG table for calculating other
SSLs not specifically listed in the table in order to meet protection of groundwater criteria.
15A NCAC 2L .0202 (c) does specify substances that are not permitted in groundwater and indicates that even those which are not specifically listed in the rule are not allowed above
the PQL, unless they are naturally occurring. The approved laboratory method PQL for
the substance can be used in the equation if there is no specifically listed 2L standard.
• Background Concentrations. Background concentrations of naturally occurring metals in soil at a site can be established using US Environmental Protection Agency guidance for comparing background and chemical concentrations in soil:
http://itrcweb.org/FileCabinet/GetFile?fileID=6931

Groundwater Modeling Contingency for stabilization of remaining amounts of contaminated soil in a manner that will
meet the intent of the 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 soil contamination is left in place shall be considered. In addition, the possibility of metals leaching into soils 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.
Page 5 of 5
References
American Standards for Testing and Measures Standard D D2488-09a Standard Description and
Identification of Soils (Visual-Manual Procedure), 2009.
North Carolina Department of Environment and Natural Resources Division of Waste
Management – Superfund Section – Inactive Hazardous Sites Branch, Inactive Hazardous Sites
Guidelines for Assessment and Cleanup, November 2014, https://ncdenr.s3.amazonaws.com/s3fs-
public/Waste%20Management/DWM/SF/IHS/guidance/IHSB%20GUIDANCE%20Assessment%20and%20Remediation%20saved%202-9-2016.pdf.

North Carolina Department of Environment and Natural Resources Division of Waste
Management – Superfund Section – Inactive Hazardous Sites Branch, Inactive Hazardous Sites Branch Preliminary Soil Remediation Goals (PSRG) Table, http://portal.ncdenr.org/c/document_library/get_file?uuid=13ccab00-3c6a-48c5-abe4-
41b96d7ea6cb&groupId=38361

North Carolina Department of Environment and Natural Resources Division of Waste
Management – Superfund Section – Inactive Hazardous Sites Branch, Registered Environmental Consultant Program Implementation Guidance, November 2014, http://portal.ncdenr.org/c/document_library/get_file?uuid=3049dcfb-b0cf-4ebf-8459-
5018415fb6a3&groupId=38361

North Carolina Administrative Code Title 15A Subchapter 2L Section .0100, .0200, .0300, Classifications and Water Quality Standards Applicable to the Groundwaters of North Carolina.
April 1, 2013. http://portal.ncdenr.org/c/document_library/get_file?uuid=1aa3fa13-2c0f-45b7-
ae96-5427fb1d25b4&groupId=38364

US Environmental Protection Agency. Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites, EPA 540-R-01-003OSWER 9285.7-41, September
2002. http://itrcweb.org/FileCabinet/GetFile?fileID=6931.

US Environmental Protection Agency. Final Rule for Disposal of Coal Combustion Residuals from Electric Utilities. 80 FR 21301. 40 CFR Parts 257 and 261. April 17, 2015. https://www.federalregister.gov/articles/2015/04/17/2015-00257/hazardous-and-solid-waste-
management-system-disposal-of-coal-combustion-residuals-from-electric