Cape Fear Executive Summary

Comprehensive Site Assessment Report September 2015
Cape Fear Steam Electric Plant SynTerra
CAPE FEAR STEAM ELECTRIC PLANT
EXECUTIVE SUMMARY
North Carolina General Assembly Session Law 2014-122, the Coal Ash Management
Act (CAMA) of 2014, requires the owner of a coal combustion residuals surface
impoundment to submit a Groundwater Assessment Plan (GAP) to the North Carolina
Department of Environment and Natural Resources (NCDENR) no later than December
31, 2014 and a Groundwater Assessment Report [herein referred to as a Comprehensive
Site Assessment (CSA)] no later than 180 days after approval of the GAP. Data
generated by this CSA will be used in development of a Corrective Action Plan (CAP)
for each regulated facility. This report addresses the Cape Fear Steam Electric Plant
(Cape Fear Plant, Plant or Site) owned by Duke Energy Progress, LLC (Duke Energy).
The assessment was performed within 180 days of the approval of the GAP by
NCDENR dated March 6, 2015.
The purpose of this CSA is to characterize the extent of contamination resulting from
historical production and storage of coal ash, evaluate the chemical and physical
characteristics of detected constituents, investigate the geology and hydrogeology of the
Site including factors relating to constituent transport, and examine risk to potential
receptors and exposure pathways.
NCDENR prescribed the list of monitoring parameters to be measured at the Cape Fear
Plant. Following receipt of the data, parameters were evaluated to assess those most
relevant for the Site. These parameters were determined by examining data from
monitoring wells installed in ash and groundwater, and then by comparing these
results to the North Carolina Groundwater Quality Standards found in the North
Carolina Administrative Code (NCAC) Title 15A, Subchapter 2L.0202 (2L or 2L
Standards) and the Interim Maximum Allowable Concentrations (IMAC) established by
NCDENR pursuant to 15A NCAC 02L.0202(c). If a constituent concentration exceeded
the North Carolina Groundwater Quality Standards in ash pore water wells, as
specified in the 2L Standards or the IMACs, it has been designated as a "Constituent of
Interest" (COI). COIs are constituents that display correlation to ash basin influence.
Some COIs are also present in background monitoring wells or are anomalous and thus
require careful examination to determine whether their presence on the downgradient
side of the basins is from natural or other sources (e.g., rock and soil, off-site influence)
or the ash basins.
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The IMACs were issued in 2010, 2011, and 2012; however NCDENR has not established
a 2L for these constituents as described in 15A NCAC 02L.0202(c). For this reason,
IMACs noted in this report are for reference only.
The assessment addresses the horizontal and vertical extent of COIs in soil and
groundwater. Significant factors affecting constituent transport, and the geological and
hydrogeological features influencing the movement, as well as the chemical and
physical character of the COIs, were evaluated.
Data presented in this assessment report will be the basis for the CAP, required within
270 days of the approved Work Plan, unless an extension by NCDENR is granted, to
identify alternative strategies to address groundwater impacts at the Site.
Duke Energy has recommended the excavation of the ash from the basins. The CAP, as
required by CAMA, will include groundwater modeling results of anticipated ash
removal to assess effects on groundwater. A groundwater monitoring plan will be
provided to assess changes in groundwater conditions over time.
Based on scientific evaluation of historical and new groundwater assessment data
presented in this report, the following conclusions can be drawn:
41' No imminent hazard to human health or the environment has been identified as
a result of COI migration from the ash basins.
41' Recent groundwater assessment results are consistent with previous results from
historical and routine compliance boundary monitoring well data.
41 Upgradient, background monitoring wells contain naturally occurring metals
and other COIs at concentrations greater than 2L or IMAC. This information is
used to evaluate whether concentrations in groundwater downgradient of the
basins are naturally occurring, originate from upgradient sources, or might be
influenced by migration of constituents from the ash basins. Examples include
pH, beryllium, cobalt, iron, manganese, nickel, sulfate, thallium, TDS, and
vanadium, all present in background groundwater samples at concentrations
greater than 2L or IMAC.
Groundwater in the vicinity of the Cape Fear Plant is not used for public water
supply. The few private supply wells near the Plant are located in hydraulically
upgradient areas and the Plant's ash basins are not likely to be recharge areas for
the groundwater that serves the private supply wells.
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Boron is the primary constituent that can be identified at concentrations greater
than background concentrations and 2L Standards in a three dimensional area
beneath and downgradient of the ash basins. Sulfate, to a lesser extent, is
detected beyond the ash basins. The approximate extent of horizontal migration
of boron and sulfate in the surficial zone and generalized groundwater flow
direction is shown on Figure ES -1.
Ash pore water levels are nearly equivalent to standing water levels within
basins that typically contain ponded water (1970, 1978, and 1985 ash basins). Ash
pore water elevations in these basins and the 1963 ash basin are higher than
groundwater elevations surrounding and beneath the basins. Thus, the ash pore
water influences groundwater surrounding the basins, creating a pseudo -radial
flow pattern away from the basins. Further away from these basins,
groundwater flow returns to the normal flow pattern, which is toward a surface
water feature such as the Cape Fear River, Shaddox Creek, Branch A, and the
cooling water channel. Ash pore water is not present within the 1956 ash basin.
Groundwater flow in the surficial and bedrock zones is in the direction of the
Haw and Cape Fear Rivers, Shaddox Creek, an unnamed tributary east of the
1985 ash basin (Branch A), and the former cooling water channel. These
groundwater discharge areas control and limit impacts on groundwater quality
in areas beyond the Site.
0 Downward flow of ash pore water is retarded by a clay layer present beneath the
ash basins. This retardation is reduced beneath the 1956 and 1985 ash basins as
clay content in soils beneath these basins was observed to be less than observed
in borings elsewhere on the Site.
Surface water quality data for samples collected upstream and downstream of
the ash basins within the Cape Fear River do not indicate that the ash basins have
resulted in increased constituent concentrations above the North Carolina
Surface Water Quality Standards (2B Standards) downstream of the Site for select
constituents.
161' The CSA serves to characterize the horizontal and vertical extent of COIs, and
the groundwater gradients which facilitate development of the Site Conceptual
Model (SCM), i.e. the groundwater flow and contaminant migration model. This
then facilitates identification of corrective actions due in 90 days under the CAP.
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Groundwater modeling to be provided with the CAP will allow an evaluation of
potential ash removal to assess the impact to groundwater.
Brief summaries of the essential portions of the CSA are presented in the following
sections.
ES1. Source Information
Duke Energy owns and operates the Cape Fear Plant, located in Chatham County, near
Moncure, North Carolina. The Cape Fear Plant began operations in 1923 and ceased
power production in 2012. CCR was produced from the combustion of coal used to
generate power and placed in five ash basins until the Plant was retired in 2012. The
ash basins were developed near original ground surface with excavation of Site soils
and possibly ash for construction of the perimeter dikes. Mineralogical, physical, and
chemical properties of the five ash basins at the Cape Fear Plant have been
characterized for use in the hydrogeological SCM. The CSA focused on evaluation of
constituents associated with CCR, such as metals and other inorganics.
The CSA found that CCR accumulated in the ash basins, through leaching of CCRs into
underlying groundwater, is a source of impact detected in the vicinity of the ash basin
as shown on Figure ES -1. When water is present below the ash surface and above the
base of the basin, it is referred to as ash pore water. Ash pore water, where present, in
the basins is hydraulically upgradient of surrounding areas resulting in pseudo -radial
migration of ash pore water toward groundwater. Further away from these basins,
groundwater flow returns to the normal flow pattern, which is toward a surface water
feature including the Haw and Cape Fear Rivers, Shaddox Creek, an unnamed tributary
east of the 1985 ash basin (Branch A), and the former cooling water channel.
Groundwater and seeps are the primary mechanisms for migration of COI's to the
environment.
ES2. Initial Abatement and Emergency Response
The Cape Fear Plant is a retired power generating facility, the coal-fired units have been
decommissioned, and sluicing of ash to the ash basins has ceased. The CSA found no
imminent hazard to public health and safety; therefore, an emergency response to
mitigate or abate imminent hazards is not required. Duke Energy has recommended the
excavation of the ash from the basins.
ES3. Receptor Information
The requirement contained in the NORR and the CAMA concerning receptors was
completed with the results provided in Section 4.0. A Screening Level Human Health
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Risk Assessment and Screening Level Ecological Risk Assessment were conducted with
the results provided in Section 12.0.
Land use surrounding the Cape Fear Plant includes industrial, rural residential,
agricultural, and forest land. The Haw and Cape Fear Rivers border the Site to the
west. Shaddox Creek flows along the northern portion of the Site. An unnamed
tributary to the Cape Fear River (Branch A) flows along the eastern portion of the Site.
A former cooling water channel flows from central portions of the Site toward an
unnamed tributary to the Cape Fear River.
A surface water intake within the Cape Fear River is located three miles downstream of
the Plant where Highway 42 crosses the river. The river provides water to the City of
Sanford and Lee County.
ES.3-1 Public Water Supply Wells
Surveys of public and private water supply wells within a 1/2 mile radius of the ash
basin compliance boundaries have been conducted. Available information is
provided in Section 4.0. Groundwater in the vicinity of the Cape Fear Plant's ash
basins is not used for public water supply.
ES.3-2 Private Water Supply Wells
Inventories of public and private water supply wells have been compiled. NCDENR
contacted nearby residents regarding private wells and managed the sampling of
the wells in accordance with CAMA. The few private supply wells near the Plant
are located in hydraulically upgradient areas and the Plant's ash basins are not
recharge areas for the aquifers that serve the private supply wells. NCDENR
sampled one private well at a residence across the Haw River from the Site. As of
the writing of this report, analytical results from this sample were not available.
ES.3-3 Human and Ecological Receptors
The exposure medium for human receptors includes potentially impacted
groundwater, soil, surface water, seeps, and sediments. Potential routes for human
exposure to be considered for the Site include ingestion, inhalation and dermal
contact of environmental media. Potential human receptors, current or future,
include recreational swimmers, recreational fisherman, recreational hunters,
industrial workers, construction workers, and future residents.
Potential exposure medium for ecological receptors includes soil, surface water and
sediments. Direct contact with groundwater does not present a complete exposure
pathway to ecological receptors. Exposure routes to constituents of potential concern
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(COPCs) associated with potentially completed exposure pathways include dermal
contact, ingestion (incidental and purposeful) and ingestion of prey or plants.
Wildlife expected to be near the Site would potentially include those listed in Table
12-16, and also other game and non -game wildlife endemic to the Piedmont and
Southeastern Floodplains and Low Terraces ecoregions.
COPCs for human and ecological receptors were identified using screening level
risk assessment methodology for receiving areas as listed in Section 12.5. The list of
COPCs is longer than the list of Site-specific COIs due to the conservative approach
of comparing analytical results to published reference criterion in the risk
assessment screening process.
ES4. Sampling / Investigation Results
The Cape Fear CSA was generally implemented as planned with a few modifications in
well placement due to access. Figure ES -1 shows the horizontal extent of groundwater
impact to the surficial zone that can be attributed to migration of constituents from the
ash basins.
ES.4-1 Nature and Extent of Contamination
Based on detections in ash pore water samples at concentrations greater than the 2L
or IMAC at the Cape Fear Plant, COIs were identified, including antimony, arsenic,
beryllium, boron, chromium, cobalt, iron, manganese, nickel, selenium, sulfate,
thallium, TDS, vanadium and zinc. Selenium was slightly below the 2L in an ash
pore water sample and was detected above the 2L in two groundwater samples.
Therefore, it is retained as a COI.
Beryllium, cobalt, iron, manganese, nickel, pH, sulfate, thallium, vanadium, and
TDS were detected at concentrations greater than the 2L or IMAC in one or more of
the background locations. Calculation of proposed site-specific background
concentrations will occur when a sufficient number of samples to perform statistical
analysis have been collected.
The distribution of boron and sulfate in groundwater best represents the extent of
impact and the horizontal extent of groundwater impact to the surficial zone,
attributed to migration of constituents from the ash basins. This extent is shown on
Figure ES -1. Analytical results indicate that COIs or other constituents detected at
concentrations above the 2L or IMAC and are attributable to the ash basins have not
migrated beyond the boundary of the Site. The horizontal extent of migration is
controlled by the Haw and Cape Fear Rivers to the west, Shaddox Creek to the
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north, an unnamed tributary (Branch A) to the east, and the former cooling water
channel to the south (with respect to the 1985 ash basin). These surface water
features act as major groundwater to surface water discharge zones. See Figure 6-10
for a cross-section showing the migration pathways for the COIs and the
groundwater discharge area that limit the amount of impacted groundwater.
COIs detected in bedrock wells at concentrations above 2L or IMAC are limited to
an area beneath a portion of the 1985 ash basin. Constituents including iron and
manganese were detected at concentrations above 2L in bedrock wells; however,
these constituents likely occur naturally at these concentrations in bedrock
groundwater and may not be attributable to the ash basins.
Field observations indicate fine grained sediments (silt and clay to clayey silty sand)
in the upper surficial zone limit downward migration of constituents from the ash
basins to underlying groundwater. This effect is limited beneath the 1956 and 1985
ash basins where clay content in shallow alluvial deposits was observed to be less
than elsewhere across the Site.
ES.4-2 Maximum Contaminant Concentrations
For the COIs identified in groundwater, the highest concentrations were detected in
surficial groundwater with the exception of hexavalent chromium which was
detected at the highest concentration in a bedrock well (refer to Figures 8-1, 8-2, 8-3,
10-1 through 10-57,11-1 through 11-14 and also Tables 7-7 and 10-1 for extent of
concentrations in excess of 2L or IMAC). Cobalt, iron, manganese, and vanadium
were detected at concentrations greater than the 2L or IMAC in groundwater
samples collected from most locations across the Site, including background wells.
Their presence in background wells indicates these constituents are naturally
occurring in groundwater. Spatial distribution of these constituents at
concentrations above the 2L or IMAC is variable, although generally higher
concentrations were detected north of the 1985 ash basin.
Sulfate and boron are the most prevalent COIs identified in groundwater other than
cobalt, iron, manganese, and vanadium. The highest concentration of sulfate in
groundwater was detected at the proposed background location north of Shaddox
Creek. This well (MW-15SU) is installed in shallow (upper) surficial sediments in an
area where several wetlands are present. These wetlands may influence sulfate
concentrations in groundwater in this area at this depth and therefore, sulfate may
also be naturally occurring at this and other locations across the Site. Sulfate
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concentrations at this location in the lower surficial zone (MW-15SL) are less than
the 2L.
The highest boron concentration in groundwater was detected in the surficial zone
in a piezometer near the toe of the dike on west side of the 1985 ash basin. Boron
was also detected in excess of the 2L in wells adjacent to the northern and southern
portion of the 1985 ash basin, north of the 1956 ash basin, and west of the 1963 and
1970 ash basins. While boron is prevalent at the site, it is limited in area and depth
and in each area it is bound by surface water features including Shaddox Creek, the
Cape Fear River and Branch A. Refer to Figure ES -1 for extent of boron
concentrations in excess of the 2L concentration of 700 µg/L.
The highest groundwater concentrations of antimony and arsenic were detected in a
well (ABMW-01S) installed in the surficial zone beneath the 1985 ash basin. This is
the only location where these COIs were detected above the 2L or IMAC.
The highest concentration of hexavalent chromium in groundwater detected greater
than the USEPA Tapwater value was detected in a bedrock well installed beneath
the 1985 ash basin. Hexavalent chromium was also detected in bedrock wells above
the USEPA Tapwater value north of the 1985 ash basin, southwest of the 1985 ash
basin and between the 1963 ash basin and the Cape Fear River. In the surficial zone,
the highest hexavalent chromium concentration was detected beneath the 1970 ash
basin but was not detected in adjacent surficial wells at concentrations above the
USEPA Tapwater value. Hexavalent was detected at concentrations greater than the
USEPA Tapwater value in wells installed in two other isolated areas: 1) west of the
northern portion of the 1963 ash basin along the Cape Fear River; and 2) between
Shaddox Creek and northwest portion of the 1985 ash basin.
The highest concentrations of selenium and thallium in groundwater were detected
in a well installed beneath the 1978 ash basin. Selenium was detected at a
concentration above the 2L in only one other location: north of the 1956 ash basin.
Thallium was detected at concentrations above the IMAC in various locations across
the Site including at the proposed background well (MW-15SU) north of Shaddox
Creek.
Sections 10, 11, and 17 discuss these conditions in more detail and also addresses the
following additional COIs: beryllium, nickel, pH, TDS, and zinc. For the most part
these COIs are present in isolated wells with no evidence of a "plume".
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ES.4-3 Source Characterization
COIs leached from ash into ash basin pore water at concentrations greater than 2L or
IMAC include antimony, arsenic, beryllium, boron, chromium, cobalt, iron,
manganese, nickel, sulfate, thallium, TDS, vanadium and zinc (Figure ES -1).
Selenium was slightly below the 2L in an ash pore water sample and was detected
above the 2L in two groundwater samples. Thus, selenium was included as a COI.
Ash pore water may discharge through the perimeter dikes and bottom of the ash
basins into perimeter ditches and shallow groundwater.
Ash pore water is not present within the 1956 ash basin. Ash pore water is present
within the 1963, 1970, 1978, and 1985 ash basins. A separate source area associated
with coal mill rejects is located atop the northern portion of the 1963 ash basin.
Standing water is in the 1978 and 1985 ash basins and seasonally present at the
southern end of the 1970 basin.
ES.4-4 Receptor Survey
Developed properties adjoining the Site are serviced by a municipal water line.
Groundwater in the vicinity of the Cape Fear Plant is not used for public water
supply. The few private supply wells near the Plant are located in hydraulically
upgradient areas. In 2015, NCDENR contacted residents to potentially sample
private supply wells. NCDENR collected a sample from one location and, as of the
writing of this report, results have not been received or provided to Duke Energy.
COPCs for human and ecological receptors identified using screening level risk
assessment methodology for receiving areas at the Site include aluminum, arsenic,
beryllium, boron, cadmium, chromium, cobalt, copper, lead, iron, manganese,
mercury, nickel, pH, selenium, sulfate, TDS, thallium, vanadium, and zinc. This list
is more comprehensive than the list of Site-specific COIs due to the conservative
approach of comparing analytical results to published reference criterion in the risk
assessment screening process.
ES.4-5 Regional Geology and Hydrogeology
The vicinity of the Cape Fear Plant is included within the Piedmont physiographic
province and is generally characterized by shallow water table conditions occurring
in surficial soils and saprolite underlain by sedimentary bedrock. Mudstone and
sandstone associated with the Deep River Basin, a Mesozoic sedimentary basin
included within the Newark Supergroup are present in the vicinity of the Plant.
These rocks are typically fractured, weathered, and typically covered with
unconsolidated material known as regolith.
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The groundwater system in the Piedmont Province, in the vicinity of the Site is
comprised of two interconnected layers: 1) residual soil/saprolite and weathered
fractured rock (regolith) overlying 2) fractured bedrock. Typically, the base of the
regolith layer serves as the storage reservoir and provides a medium through which
the recharge and discharge of water from the underlying fractured rock occurs.
Secondary porosity within fractured zones of the bedrock is greater than the
primary porosity in the rocks.
ES.4-6 Site Geology and Hydrogeology
Field observations indicate that much of the regolith above the bedrock has been
scoured by ancient meandering of major river systems in the area which eroded
much of the saprolite and deposited alluvium. Alluvium deposits range in thickness
at Plant; deposits are thicker closer to the Haw and Cape Fear Rivers and pinch out
farther from and topographically upgradient from the rivers. Observations indicate
the alluvium consists of fine grained material (silty clays) grading to coarse grain
sands and gravel. The alluvium sits unconformably atop weathered and competent
bedrock consisting of mudstone and sandstone.
The alluvium comprises the surficial monitoring zone above the bedrock monitoring
zone. Groundwater flow direction within each hydrostratigraphic zone generally
mimics surface topography and migrates toward surface water discharge features
such as the Cape Fear River and Shaddox Creek. Groundwater within the surficial
zone primarily migrates laterally across the top of bedrock discharging to surface
water features; relatively little surficial water mixes or migrates downward to
bedrock.
The potentiometric head created by the ash pore water within the 1963, 1970, 1978,
and 1985 ash basins on underlying saturated soils creates a mounding effect and
influences groundwater flow direction in the immediate vicinity of the ash basins.
However, groundwater flow returns to natural flow directions near the basins and
migrates toward surface water discharge locations including Shaddox Creek on the
north, Branch A on the east, the cooling water channel on the south, and the Cape
Fear River on the west. Downward flow of ash pore water to groundwater is
retarded by clayey alluvium present beneath the ash basins. These groundwater
discharge areas and clay alluvium beneath the basins control and limit impacts of
the ash basins on groundwater quality. This retardation is reduced beneath the 1956
and 1985 ash basins as clay content in soils beneath these basins was observed to be
less than observed in borings elsewhere on the Site.
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ES.4-7 Existing Groundwater Monitoring Data
The CSA provided source and perimeter information to support routine compliance
boundary data. National Pollution Discharge Elimination System (NPDES)
compliance groundwater monitoring data indicate that boron, cobalt, iron,
manganese, sulfate, selenium, TDS and pH have been elevated relative to 2L.
ES.4-8 Development of Site Conceptual Model
A hydrogeological Site Conceptual Model was developed from data generated
during previous assessments, existing groundwater monitoring data, and 2015
groundwater assessment activities.
Alluvium comprises the surficial monitoring zone above the bedrock monitoring
zone. Clayey shallow (upper) alluvial deposits that cover the Site limit the vertical
migration of constituents from the ash basins, and the perimeter dikes constructed
atop the clayey alluvium limit the lateral migration of constituents from ash pore
water to groundwater. Once in groundwater, constituents primarily migrate
laterally within the surficial zone atop bedrock, flowing toward surface water
discharge features including the Cape Fear River, Shaddox Creek, Branch A, and the
former cooling water channel. The potentiometric head created by the ash pore
water within the 1963, 1970, 1978, and 1985 ash basins on underlying saturated soils
creates a mounding effect and influences groundwater flow direction in the
immediate vicinity of the ash basins. However, groundwater flow returns to natural
flow directions near the basins and migrates toward surface water discharge
locations. Groundwater within bedrock migrates primarily through fractures and
joints and mimics the flow direction of the surficial zone, toward surface water
discharge features. These groundwater discharge areas control and limit impacts of
the ash basins on groundwater quality. Although groundwater within the surficial
zone recharges bedrock, groundwater within the surficial zone primarily migrates
across the bedrock surface within the coarse sand and gravel and weathered rock.
ESS. Identification of Data Gaps
The horizontal and vertical extent of COIs occurring at or above regulatory standards
have been determined for soil and groundwater. Source area and groundwater
characterization data have been used to develop hydrogeologic and geochemical SCMs
that will support preparation of fate and transport groundwater modeling for the Site.
There are no data gaps that will be limiting factors in the execution of the groundwater
model or development of the CAP.
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ES6. Conclusions
1. No imminent hazards to human health or the environment were identified
during the screening -level risk assessments.
2. The CSA evaluated the horizontal and vertical extent of COIs in soil and
groundwater at the Site and found that some of the COIs (shown on Figure ES -1)
detected in soil, surface water, and groundwater above applicable regulatory
values are the result of constituents leaching from CCR contained within the ash
basins.
3. Boron is the primary constituent in groundwater detected at concentrations
greater than background concentrations and 2L. Boron is detected at
concentrations greater than 2L beneath and downgradient of the ash basins. The
lateral extent of boron is limited to alluvium in areas in the immediate vicinity of
the basins and is bounded by surface water features including the Cape Fear
River, Shaddox Creek, Branch A, and the former cooling water channel. The
vertical extent of boron is limited to an area beneath the 1985 ash basin.
4. Background monitoring wells contained naturally -occurring metals and other
constituents at concentrations that exceeded their respective 2L or IMAC values.
These constituents included beryllium, cobalt, iron, manganese, nickel, pH,
sulfate, TDS, thallium, and vanadium.
5. Duke Energy has recommended the excavation of the ash from the basins.
Potential effects of this on groundwater quality will be evaluated through
groundwater modeling to be provided in the CAP.
6. An interim groundwater monitoring plan is presented in Section 16 of this
report. A performance monitoring plan to the support the remedy in the
proposed CAP will be submitted within 90 days of September 2, 2015.
7. The CSA and the groundwater modeling work will allow for completion of a
CAP within 90 days of submittal of this report.
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