2016-05-13 Parette Expert Report - Allen Site

MATSON
ASSOCIATES
Opinions on the Appropriateness of Monitored Natural Attenuation
in_Conjunction with Cap -in -Place at the Allen Steam Station,
Belmont, NC
Prepared for:
Southern Environmental Law Center
22 South Pack Square, Suite 700
Asheville, NC 28801
Prepared by:
Robert Parette, Ph.D., P.E.
May 13, 2016

I. Qualifications...................................................................................................................................3
11. Scope of Work................................................................................................................................. 3
Ill. Basis of Opinion...........................................................................................................................3
IV. Methodology............................................................................................................................... 3
V. Background.....................................................................................................................................5
A. Coal Ash and the Allen Site...........................................................................................................5
B. Monitored Natural Attenuation (MNA)........................................................................................ 6
VI. Opinion: Monitored Natural Attenuation is not an appropriate remedy for constituents of
interest (COls) at the Allen site..............................................................................................................10
A. When MNA is based upon adsorption of COls onto precipitated iron and manganese oxides, the
utilization of MNA in combination with capping is problematic as conditions for MNA are less
favorable following capping...............................................................................................................10
B. Kd values determined in the laboratory cannot be reliably utilized as a means to demonstrate
site -specific attenuation at the Allen site...........................................................................................11
C. MNA should have not been selected as a potential site remedy for antimony, boron, chromium,
hexavalent chromium and cobalt.......................................................................................................12
D. Despite the Monitored Natural Attenuation Technical Memorandum (Appendix H of the
Corrective Action Ian art 2) stating that arsenic "could be carried through to Tier II" analysis, MNA is
not an appropriate remedy for arsenic at the Allen site.....................................................................14
E. MNA is not appropriate at the Allen site for vanadium...............................................................15
VII. References.................................................................................................................................17
K

Qual f cat ons
I am an Environmental Engineer ( .E.) at Matson & Associates, Inc. (M&A). My academic
background includes a B.S. in Chemical Engineering from Worcester olytechnic Institute and a
M.S. and a h.D. in Environmental Engineering from The ennsylvania State University. I have
over 10 years of experience in the removal of various contaminants from environmental media.
I have co-authored several peer -reviewed papers pertaining to the removal of arsenic from
groundwater utilizing iron or iron -tailored adsorbents. I have also previously evaluated
remedies for arsenic contaminated groundwater (including MNA) at coal ash disposal sites, as
well as the use of various technologies to treat effluent impacted by metals and other
constituents at a coal mining site. My CV is attached in Appendix A.
II. Scope of Work
I was retained by the Southern Environmental Law Center (SELC) to evaluate whether
Monitored Natural Attenuation (MNA), in conjunction with Cap -in- lace, is an appropriate
remedy for Duke's Allen Steam Station (Allen site) in Belmont, NC.
III. Bas s of Op n on
My opinion is based on site specific documents, as well as scientific literature, and my education
and experience. My opinion is based on a reasonable degree of engineering and scientific
certainty. I reserve the right to supplement my opinions should additional information become
available.
IV. Methodology
My role in this matter was to evaluate whether MNA, in conjunction with Cap -in- lace, is an
appropriate remedy for the Allen site. An evaluation of the appropriateness of MNA at a site
requires an in-depth understanding of the processes that constitute natural attenuation at the
site and how the site specific environmental conditions impact these processes. For the Allen
site, knowing the constituents of interest (COls) and that the remedial strategy proposed by
Duke Energy was based on co -precipitation and adsorption, I evaluated whether these processes
were occurring under the specific conditions found at the Allen site. My evaluation utilized the
criteria established by the U.S. E A for MNA of inorganic contaminants in groundwater; the
same criteria identified by Duke's consultants in their analyses.
My opinions are based on consideration of data and information provided in the Comprehensive
Site Assessment Report, the Corrective Action Ian art 1, and the Corrective Action Ian art 2
for the Allen site; and on methods that I have used in other scientific or engineering inquiries
concerning environmental processes, which are based upon methods and analysis widely
accepted in the published, peer -reviewed literature in the fields of environmental science and
engineering. First, I examine the data available to determine whether a process is working, and

if not I then conduct research to determine why. This research generally involves a review of
the relevant peer -reviewed literature followed by an analysis of the applicability of the literature
to the process being evaluated.
In this matter I examined all of the available data for the coal ash, the groundwater, and the
solid -water pair analyses to gain an understanding as to whether COls were naturally
attenuating and to gain an understanding of the site conditions influencing natural attenuation.
I then conducted a literature search for studies on similar MNA applications. Since the
application of MNA as a treatment for COls in groundwater at coal ash sites is new, published
literature on sites where it has been implemented for such purpose is not yet available for
assessment of MNA's performance in this capacity. Therefore, I reviewed a number of studies in
the peer -reviewed literature that had examined the effectiveness of treating coal ash leachate
or individual COls in other systems with iron or manganese oxides in active or engineered
treatment systems. These studies included my own publications investigating how iron and
arsenic behave in groundwater treatment operations in order to design effective treatment
systems for arsenic removal. Based on my knowledge, training, education, and years of
experience researching removal by adsorption onto iron oxides, I knew that a number of factors
can influence the adsorption of COls to metal oxides so I conducted an investigation to
determine whether the Allen site conditions were impacting MNA.
My role also involved evaluating the effectiveness of MNA under Duke's proposed plan of
capping the Allen site. Therefore, I conducted a similar analysis of MNA under altered site
conditions based on this proposed scenario.
My analysis focused on a number of COls as identified in my opinion below in Section VI. For the
COls not discussed, I am not making a determination on whether MNA is an appropriate
remedy.
4

V. Background
A. Coal Ash and the Allen Site
• Coal ash is the waste material produced from the burning of coal in coal-fired power
plants. It is comprised of a number of byproducts. For example, fly ash is "a very fine
powdery material comprised mostly of silica made from the burning of finely ground
coal in a boiler." (U.S. E A 2016). Bottom ash, is aptly named for the ash particles
that are too large to be carried into the smoke stacks and thus collect in the bottom
of the boiler (U.S. E A 2016). Both products are commonly referred to as coal ash.
• Coal ash in general is comprised mainly of oxides of silica, aluminum, iron and
calcium, and also contains numerous other elements such as antimony, beryllium,
boron, chromium, thallium, and vanadium. Exposure of coal ash to water is known
to cause the leaching and release of coal ash constituents to groundwater and
surface water (Electric ower Research Institute 2009, Liu et al. 2004, Lokeshappa et
al. 2014, Abernethy et al. 1969).
• The Allen Steam Station occupies an area of 1,009 acres along the western bank of
the Catawba River on Lake Wylie in Belmont, North Carolina. Beginning in 1957,
coal was burned at the site to produce electricity. (Corrective Action Ian art 1).
• At the Allen site, coal ash has historically been disposed of in the Allen ash basin
system, which is comprised of the inactive ash basin and the active ash basin
occupying approximately 132 acres and approximately 169 acres, respectively. The
total ash inventory is 11.9 million tons according to Duke's Corrective Acton Ian
(Corrective Action Ian art 1). Duke's website states the "total volume of ash" at
the Allen site is 19.22 million tons (Duke Energy Ash Metrics).
• Coal ash disposal at the Allen site has led to a number of constituents in site
groundwater to exceed applicable standards. Duke indicated that an examination of
the site data reveals that "groundwater concentrations of constituents of interest
(COls) attributable to source areas were identified beneath the ash throughout the
ash basins and downgradient and east of the ash basins." (Corrective Action Ian
art 1, Corrective Action Ian art 2).
• Duke has indicated that the "COls in groundwater at the Allen site are antimony,
arsenic, barium, boron, chromium, hexavalent chromium, cobalt, iron, manganese,
pH, sulfate, total dissolved solids (TDS), and vanadium." (Corrective Action Ian art
2)
• These groundwater contaminants will travel with the groundwater unless they are
removed (adsorbed, precipitated, etc.) along the groundwater flow path. According
to the Corrective Action Ian art 2 for the Allen site, "COIs in ash basin water and
L

sediment could potentially continue to migrate into groundwater through
infiltration and contribute to the flux toward the Catawba River."
• Duke has proposed to utilize an engineered cap system as a source control measure
at the Allen site "thereby reducing or eliminating infiltration through the ash and
into the groundwater" (Corrective Action Ian art 2). Duke understands that
reducing infiltration will reduce the recharge of oxygen into site groundwater and
likely create more anoxic (less oxygen) conditions, which can thus impact the
mobility of constituents in the groundwater (Corrective Action Ian art 2, Appendix
Q.
• Even with the placement of a cap over the coal ash areas, modeling performed on
behalf of Duke predicted that concentrations of antimony, arsenic, boron,
chromium, cobalt, hexavalent chromium, and vanadium in the groundwater would
exceed applicable standards at the compliance boundary 100 years (or more) into
the future (Corrective Action Ian art 2). The Cols that are projected to exceed
applicable standards at the compliance boundary 100 years (or more) into the
future based Duke's modeling are the focus of my analysis below.
• According to the Corrective Action Ian art 2 for the Allen site, "the groundwater
model did not allow for removal of COI via co -precipitation with iron oxides, which
likely resulted in an over prediction of COI transport". In response to this limitation
of the model, Duke submitted Appendix E and Appendix H of the Corrective Action
Ian art 2 to support the use of MNA as a remedy in conjunction with cap -in -place
to reduce the concentrations of the COls at the Allen site.
• Although the cap is intended to reduce or eliminate "infiltration through the ash and
into the groundwater", the model projects that ash will remain in contact with
groundwater after the Allen site is capped (Corrective Action Ian art 2).
B. Monitored Natural Attenuation (MNA
• MNA relies solely on natural environmental geochemical processes to mitigate
concentrations of contaminants (no active remediation) with regularly scheduled
monitoring to assess whether MNA is working. According to the USE A (2012):
"Monitoring typically involves collecting soil and groundwater samples to
analyze them" for the contaminants of concern and other site parameters. The
"right conditions must exist underground to clean sites properly and quickly
enough."
• COls at the Allen site are elements (inorganics), and therefore cannot be destroyed.
Natural processes to immobilize inorganics include adsorption, precipitation/co-
precipitation, and/or oxidation-reduction reactions (U.S. E A 2007a). Duke proposes
11

to rely on these natural processes in its selection of MNA as a remedy for the Allen
site (Corrective Action Ian art 2, Miller 2011).
• Specifically, Duke is relying upon adsorption/co-precipitation of COls onto hydrous
metal oxides, such as iron and manganese in its selection of MNA as a remedy
(Corrective Action Ian art 2, Appendix E, and Appendix H). In reduced forms (iron
and manganese in the +2 oxidation state), iron and manganese (also components of
coal ash) have higher solubility and mobility. As these species migrate from their
source and encounter more oxidized conditions, precipitation (particularly for iron)
as insoluble species (iron in the +3 oxidation state and manganese in the +4
oxidation state) occurs creating surfaces onto which Cols can be adsorbed. MNA
based on these processes is successful only under the right conditions, which will be
discussed in more detail below.
• In general, many groundwater constituents are known to adsorb onto iron oxide
surfaces. In general, adsorption of groundwater constituents onto manganese oxide
surfaces is not as well studied, though it is known that manganese oxide is not an
effective adsorbent for arsenic, but has been reported to have high affinity for
cobalt under the right conditions (Hoffman et al. 2006, Salminen 2005).
• In general, there are a number of factors that influence the effectiveness of natural
attenuation for inorganics at a site. These factors include (but are not limited to)
the oxidation-reduction potential of the groundwater, the pH, competition for
adsorption sites, complexation, the relative rates of oxidation between a COI and a
potential adsorbent such as iron, the amount of COI(s) in the coal ash source, and
ratios of COls to adsorbents.
o The speciation of a COI is dependent upon pH and the oxidation-reduction
potential of the groundwater. otential removal mechanisms for a COI can
change depending upon the speciation of the COI.
o In addition to COls having to compete against each other for adsorption sites,
other constituents present in the groundwater can also significantly impact the
adsorption of COls onto hydrous metal oxide surfaces. For example, silica,
phosphate, bicarbonate, and dissolved organic carbon can present competition
problems (Meng et al. 2002, Meng et al. 2000, Holm et al. 2008, Su and uls
2003, Holm 2002, Miller 2001, Swedlund and Webster 1999, Chen et al. 2007,
Sarkar et al. 2014, Mariussen et al. 2015, U.S. E A 2007b). Based on my review
of site data, to my knowledge, concentrations of silica and phosphate in Allen
site ground groundwater have not been monitored.
■ Groundwater typically contains silica in the range of 3.3 to 21 mg/L (as Si)
(Holm et al. 2008, Davis et al. 2001). Silica is known to limit the adsorption
of COls onto iron oxides (Meng et al. 2000, Davis et al. 2001, Swedlund and
7

Webster 1999). Dissolved silica at concentrations even below the typical
range found in groundwater has been shown to limit adsorption of the COls
(Miller 2001). Silica comprises a major fraction of coal ash by weight
(Electric ower Research Institute 2009), and has been found in the
groundwater between 180 and 650 mg/L as Si at a coal ash site in the mid -
Atlantic region.
■ Concentrations of phosphate below 1 mg/L have been shown to limit
adsorption of COls. The presence of silica is known to magnify the impact of
phosphate. hosphorus pentaoxide (which forms phosphate in water) is a
known constituent of coal ash (Meng et al. 2002, Meng et al. 2000, Holm et
al. 2008, Su and uls 2003, Holm 2002, Blackmore et al. 1996, Liu et al.
2004).
■ With regard to cobalt adsorption onto manganese oxide, other metals such
as copper, nickel, and zinc may outcompete it for adsorption sites
(Mukherjee et al. 2013). The presence of borate (boron is a site COI) can
also significantly reduce the adsorption of cobalt onto manganese oxides
(Hasany and Qureshi 1981).
o Other constituents in groundwater can form complexes with metals which can
decrease COI adsorption/co-precipitation. For example, vanadium, a site COI
can form complexes with sulfate (Salminen 2005, U.S. E A 2007a).
o When utilizing iron to remove COls, such as arsenic and vanadium, oxidation of
these inorganics should occur simultaneously with the oxidation of iron to
achieve optimal removal (Hoffman et al. 2006, Roccaro and Vagliasindi 2015).
• Due to the number of variables that can impact MNA of inorganics, the feasibility of
utilizing natural attenuation for inorganics must be assessed on a site -by -site basis
because the effectiveness is highly site specific (Reisinger et al. 2005, Miller 2011).
• According to the U.S. E A, determining the feasibility of using MNA at a site for an
inorganic constituent at a site is a four -tiered evaluation. These tiers, summarized
from U.S. E A (2007a) are as follows (Corrective Action Ian art 2, Appendix H):
Tier I Source Control Is the contaminant mass in the plume decreasing?
Tier II Attenuation Mechanism Is the chemical mechanism well understood?
Tier III Attenuation Capacity Is the capacity and permanence of the mechanism
sufficient?
Tier IV Monitoring & Contingency How will monitoring be conducted? What actions will be
taken if monitoring indicates attenuation is lacking?
N

• The environmental geochemical processes that constitute natural attenuation for
COls at the Allen site are ongoing, and have been ongoing since coal ash disposal
began; these processes do not begin at the time MNA is approved as a remedy for a
site. Therefore, a Tier I evaluation establishes whether natural attenuation is
currently occurring at the site, and if so is the first step in demonstrating the long
term appropriateness of MNA as a site remedy. Appendix H of the Corrective Action
Ian art 2, titled "Monitored Natural Attenuation Technical Memorandum"
included a Tier I and Tier II evaluation for the Allen site and is Duke's actual
evaluation of MNA at the Allen site. The results of this appendix are then
summarized in the body of the Corrective Action Ian art 2 report. As discussed
further below, there are contradictions between the findings in Appendix H and
what is reported in the body of the Corrective Action Ian art 2.
• In the Tier I evaluation process, concentrations of COls were measured in Allen site
water and soil (solid) from the same location and depth. If attenuation is occurring
via adsorption onto aquifer solids, the concentration of the COI on the solid material
should increase with the concentration of the COI in the groundwater. An example
of this type of analysis is shown below in Table 1(U.S. E A 2007a). According to the
Monitored Natural Attenuation Memorandum for the Allen site, "[a] strong positive
correlation between COI concentration in water and solid pairs indicates
attenuation and is the first step (Tier 1) in evaluation of MNA as a remedial
technology" (Corrective Action Ian art 2, Appendix H). Conversely, according to
the U.S. E A, sites where COI attenuation is not observed "would be eliminated
from further consideration of MNA as part of the cleanup remedy" (U.S. E A 2007a).
F gure 1. Example of a sol d-water pa r analys s to
demonstrate attenuat on (adapted from U.S. EPA 2007a)
Site -Specific
Sorption Trend
(A)
Attenuation
c
0
v
(B)
s
H No Attenuation
0
0
Aquea js Coneentaation (MMI
9

• Similar to the relationship analysis shown in Figure 1, a proportionality constant (Kd)
can be determined in the laboratory by allowing site soil samples to equilibrate with
water in the laboratory. Kd is defined as the concentration of the COI in the solid
divided by the concentration of the COI dissolved in the water. Kd values can give an
indication the potential for dissolved COls in groundwater to adsorb onto soil, which
can then be related to the rate at which a COI moves in relation to the rate of
groundwater movement.
• As stated above, capping the ash basins is intended to reduce infiltration through
the coal ash and into the groundwater. According to Duke's consultants, cap -in -
place would reduce the oxygen in the subsurface, "presumably creating a more
anoxic environment" (Corrective Action Ian art 2, Appendix Q. Schwartz et al.
(2016) have also stated that capping a site will lead to more anoxic conditions in the
site groundwater. The speciation of constituents in the groundwater varies with pH
and the redox state. Appendix E of the Correction Action Ian art 2 contained the
results of geochemical modeling conducted to evaluate "the adsorption of Cols
under a wide range of dissolved oxygen, as well as pH, oxidation-reduction
potential, and TDS." The U.S. E A recommended that modeling results be "used as
secondary lines of evidence in support of site -specific measurements that
demonstrate active sorption of the contaminant onto aquifer solids" and cannot be
relied upon independently (U.S. E A 2007a).
VI. Op n on: Mon tored Natural Attenuat on s not an appropr ate remedy for
const tuents of nterestl (COls) at the Allen s te.
A. When MNA is based upon adsorption of Cols onto precipitated iron and manganese oxides, the
utilization of MNA in combination with capping is problematic as conditions for MNA are less
favorable following capping.
• The placement of a cap over the ash basins at the Allen site will lead to more anoxic
(lower oxidation-reduction potential) in site groundwater. The solubility of iron and
manganese is strongly influenced by oxidation-reduction potential conditions, with
solubility increasing as the oxidation-reduction potential is decreased. Both are
readily mobilized or resolubilized under anoxic conditions. COls that had previously
adsorbed to iron or manganese will be remobilized and potentially lead to a slug of
COls entering the groundwater. When iron and manganese are in the dissolved
phase, COls cannot adsorb to them. (Salminen 2005, Masscheleyn et al. 1991, Harte
et al. 2012, Schwartz et al. 2016, U.S. E A 2007b, Tarutis and Unz 1995).
1 Constituents of interest, as used here, refer to the constituents that are projected by Duke via modeling to
exceed applicable standards 100 years (or more) in the future. These constituents are antimony, arsenic, boron,
chromium, cobalt, hexavalent chromium, and vanadium.
10

• Though iron is readily oxidized when it comes into contact with oxygen, aeration
(oxygen) is not effective for oxidizing dissolved manganese (manganese in the +2
oxidation state) to the relatively insoluble +4 oxidation state. Therefore drinking
water treatment plants utilize a strong oxidant such as ozone, chlorine dioxide, or
potassium permanganate when manganese removal is required. Additionally, the
presence of dissolved iron in the groundwater inhibits the formation of manganese
oxides. Only 14% manganese removal was observed in a settling basin following
aeration used to treat coal ash leachate at a site in ennsylvania (Hoffman et al.
2006, Tarutis and Unz 1995, Robinson -Lora and Brennan 2011, Rightnour and
Hoover 1998). This is important because the formation of manganese oxides has
been identified as a component of the MNA site remedy in addition to iron oxides.
• Infiltration (and thus oxygen recharge) would be reduced over the area of the Allen
site under the cap, and thus iron and manganese mobility will be enhanced (less
iron and manganese oxide precipitation/COI adsorption occurring within the area
that is capped). This inherently shortens the distance to the compliance boundary
over which these MNA processes can potentially occur.
B. Kd values determined in the laboratory cannot be reliably utilized as a means to demonstrate
site -specific attenuation at the Allen site.
• As stated above, Kd is a parameter to estimate the potential for the adsorption of
the COls in the groundwater onto soil. For the Allen site, Kd values were determined
experimentally in the laboratory using "synthetic groundwater", which was very
limited in terms of the number of constituents and in many cases the concentration
of these constituents, and therefore was not representative of groundwater
impacted by coal ash at the Allen site. For example, the "synthetic groundwater" did
not include a number of competing constituents that are known to impact COI
sorption. These include silica and phosphate, which can significantly impact COI
adsorption. Silica, in particular, can be present at very high concentrations at coal
ash disposal sites.
• Therefore, the Kd values determined in the laboratory were likely biased high
because the "synthetic groundwater" did not have other constituents competing for
the same adsorption sites.
• Duke stated that "typically Kd experiments are also conducted under oxic [high
oxygen] conditions, which may not reflect actual site conditions. Consequently, Kd
values from laboratory experiments should be interpreted and used with caution
because they may not account for the full range of sorption conditions that occur in
heterogeneous, natural soils." (Corrective Action Ian art 2 Appendix E)
11

C. MNA should have not been selected as a potential site remedy for antimony, boron, chromium,
hexavalent chromium and cobalt.
Based on the Tier I evaluation for a number of Allen site COls, Duke's consultants stated that
attenuation either "was not observed" or was only "weakly observed" and that the respective
COls "should not be carried through to Tier II" analysis (Corrective Action Ian art 2, Appendix
H). Instead of eliminating MNA as a potential site remedy as U.S. E A directs (U.S. E A 2007a),
MNA was selected by Duke to supplement capping -in -place (Corrective Action Ian art 2). The
COls to which this applies are discussed below:
1. Antimony
• In the Tier I analysis, "antimony attenuation using solid- water pairs was not
observed" and a "Kd was not determined from antimony" leading Duke to conclude
that "antimony should not be carried through to Tier II" (Corrective Action Ian art
2, Appendix H). In addition, results of geochemical modeling "indicate very low
adsorption" for antimony (Corrective Action Ian art 2, Appendix E).
• The Corrective Action Ian art 2 states that the Tier I analysis indicated that
antimony is "amenable to attenuation and should be advanced to Tier II". This is
contradictory to the Monitored Natural Attenuation Technical Memorandum
(Appendix H of the Corrective Action Ian art 2) which stated that "antimony
should not be carried through to Tier II" of the four -tiered MNA feasibility
evaluation.
2. Boron
• Results of geochemical modeling "indicate very low adsorption" for boron and "COIs
with sorption coefficients similar to or less than boron are not readily attenuated by
sorption to solids site materials and are more readily transported by groundwater
moving through impacted media." (Corrective Action Ian art 2, Appendix E).
• "In general, soil sorptive capacity for Cols such as boron is typically small and even a
small addition of boron to groundwater is expected to result in increased aqueous
concentrations of boron." (Corrective Action Ian art 2, Appendix E).
• With regard to coal combustion product leachate, MNA pathways do not exist for
boron (Miller 2011).
• Boron was not effectively removed from coal ash leachate by adsorption/co-
precipitation with iron in a settling basin at a site in ennsylvania (Rightnour and
Hoover 1998).
• The Corrective Action Ian art 2 states that the Tier I analysis indicated that boron
is "amenable to attenuation and should be advanced to Tier II" and Appendix G of
12

the Corrective Action Ian art 2 (Evaluation of otential Groundwater Remedial
Alternatives" states that "attenuation is taking place" for boron. This is
contradictory to both published research (Rightnour and Hoover 1998) and the
Monitored Natural Attenuation Technical Memorandum (Appendix H of the
Corrective Action Ian art 2) which stated that a "Kd value for boron was not
determinable from the laboratory data" and "the attenuation of boron has not been
observed and it should not be carried through to a Tier II evaluation."
3. Chromium and hexavalent chromium
• The Monitored Natural Attenuation Technical Memorandum (Appendix H of the
Corrective Action Ian art 2) did not distinguish between hexavalent chromium
(chromium in the more toxic +6 oxidation state) or chromium (total chromium). As
stated above, attenuation of chromium was not observed at the Allen site.
• Capping of the site will lead to more anoxic conditions in the site groundwater
(Schwartz et al. 2016, Corrective Action Ian art 2, Appendix E), which could lead to
hexavalent chromium (if present) converting to a less oxidized chromium species.
• At pH values above 2 and in the presence of oxygen, chromium in the +3 oxidation
state is subject to oxidation to chromium in the +6 oxidation state (U.S. E A 2007b).
If hexavalent chromium still remained following capping, or formed from Cr+3
migrating to areas of higher oxygen, MNA would not be an appropriate remedy as
hexavalent chromium "is highly mobile as an aqueous complexed species and, in
situations where oxygen bearing recharge have been identified, has been known to
persist above acceptable limits in widespread areas from point sources in numerous
studies." (Corrective Action Ian art 2, Appendix Q. Chromium in the +6 oxidation
state [Cr(VI)] is typically not sorbed as well as many other groundwater constituents
and is often outcompeted for adsorption sites. The presence of sulfate, a weakly
adsorbing species, can also cause significant reductions in the amount of Cr(VI)
adsorbed onto hydrous metal oxides, and sulfate was measured at concentrations
as high as 2,900 mg/L in Allen site groundwater in 2015 (U.S. E A 2007b, Corrective
Action Ian art 2).
• The Corrective Action Ian art 2 states that the Tier I analysis indicated that
chromium is "amenable to attenuation and should be advanced to Tier II". This is
contradictory to the Monitored Natural Attenuation Technical Memorandum
(Appendix H of the Corrective Action Ian art 2) which stated that "attenuation is
not observed" for chromium and that "chromium should not be carried through to a
Tier II analysis".
13

4. Cobalt
• It was claimed that "cobalt attenuation using solid -water pairs was weakly observed
on the basis of one data point" (Corrective Action Ian art 2, Appendix H).
• "A determination of Kd for cobalt was not made" by Duke (Corrective Action Ian
art 2 Appendix H)
• The Monitored Natural Attenuation Technical Memorandum (Appendix H of the
Corrective Action Ian art 2) concluded that "cobalt should not be carried through
to Tier II analysis" of the four -tiered MNA feasibility evaluation.
D. Despite the Monitored Natural Attenuation Technical Memorandum (Appendix H of the
Corrective Action Ian art 2) stating that arsenic "could be carried through to Tier II"
analvsis. MNA is not an appropriate remedv for arsenic at the Allen site.
• The Monitored Natural Attenuation Technical Memorandum stated that "arsenic
attenuation using solid -water pairs was not observed" and "there is limited
evidence for attenuation of arsenic."
• Arsenic in water is typically present in the +3 oxidation state [As(III)] or the +5
oxidation state depending the oxidation-reduction potential (oxygen concentration)
of the groundwater. As(III) is favored under reduced (low oxygen) conditions and
As(V) is favored under oxidized conditions. Compared to As(V), As(III) is more toxic,
more soluble, and more difficult to adsorb (e.g. more mobile). Therefore the
leaching and mobility of arsenic generally increases as redox potential decreases
(Schwartz et al. 2016, Harte et al. 2012, Masscheleyn et al. 1991).
• For arsenic in groundwater at the Allen site "approximately 50% is present as
reduced arsenic [As(III)], with a range of 9% to 93%." (Corrective Action Ian art 2)
• Capping the site will make conditions less favorable for MNA of arsenic. Capping of
the site will lead to more anoxic conditions in the site groundwater (Schwartz et al.
2016, Corrective Action Ian art 2, Appendix E), which would likely lead to an
increase in the ratio of As(III) to As(V); thus the addition of a cap would likely
increase the mobility of arsenic at the Allen site.
• Concern over a reduction in site groundwater oxidation-reduction potential and
enhancement of arsenic solubility as a result of closure plans for coal ash
impoundments that include capping, led a group of scientists to recently state that
"even if no previous groundwater contamination issues have been reported,
capping methods that might induce anaerobic conditions should be avoided in the
closure of unlined impoundments" (Schwartz et al. 2016).
14

E. MNA is not appropriate at the Allen site for vanadium
• Batch testing of site samples (Kd determination) indicated that the adsorption of
vanadium at the site was weaker than the adsorption of chromium at the site.
"Attenuation is not observed" at the Allen site for chromium.
• An analysis of solid -water pairs for vanadium was not performed in Appendix H, but
the data for such an analysis was found in Table 3 of this same appendix. Vanadium
concentrations on the solid phase are plotted against the dissolved vanadium
concentrations in the water phase in Figure 2 shown below.
F gure 2. Sol d-water pa r analys s for Vanad um (data from Append x H of the Correct ve Act on
Plan Part 2).
100
90
80
Y 70
" 60
E 50
F3 40
�o
c
30
20
10
0
0 5 10 15 20 25 30
Vanadium, dissolved (ug/L)
15
35

• The trend line for this solid -water pairs analysis for vanadium clearly has a
decreasing slope, thus attenuation of vanadium is not observed at the Allen site,
and therefore vanadium does not pass Tier I of the four -tiered MNA feasibility
evaluation for the Allen site. As a reminder, Duke recognizes that "a strong positive
correlation between COI concentration in water and solid pairs indicates
attenuation and is the first step (Tier 1) in evaluation of MNA as a remedial
technology." (Corrective Action Ian art 2, Appendix H)
• In general, vanadium in the +3 oxidation state [V(111)] is less soluble than vanadium
in the +5 oxidation state (Salminen 2005). Attenuation of vanadium is not observed
at the Allen site despite that under current conditions at the Allen site, vanadium "is
expected to predominantly exist as V(111)" (Corrective Action Ian art 2, Appendix
E).
16

VII. References
Abernethy, RF; MJ eterson and FH Gibson (1969). Spectrochemical analyses of coal ash for trace
elements. United States Department of the Interior, Report of Investigations 7281.
Blackmore, D T; J Ellis and J Riley (1996). Treatment of a vanadium -containing effluent by
adsorption/coprecipitation with iron oxyhydroxide. Water Research 30(10): 2512-6.
Chen, W; R arette, J Zou, FS Cannon and BA Dempsey (2007). Arsenic removal by iron modified
activated carbon. Water Research 41: 1851-8.
Corrective Action Ian art 2. Allen Steam Station Ash Basin. For Duke Energy Carolinas, prepared
by HDR Engineering Inc. February 19, 2016.
Corrective Action Ian art 1. Allen Steam Station Ash Basin. For Duke Energy Carolinas, prepared
by HDR Engineering Inc. November 20, 2015.
Davis, CC; WR Knocke and M Edwards (2001). Implications of aqueous silica sorption to iron
hydroxide: mobilization of iron colloids and interference with sorption of arsenate and humic
substances. Environmental Science & Technology 35: 3158-62.
Duke Energy (2015). Duke Energy Ash Metrics. https://www.duke-energy.com/pdfs/duke-energy-
ash-metrics.pdf
Electric ower Research Institute (2009). Coal Ash: Characteristics, Management, and Environmental
Issues. www.whitehouse.gov/sites/default/files/omb/assets/oira_2050/2050_meeting_101609-
2.pdf
Harte, T; JD Ayotte, A Hoffman, KM Revesz, S Lamb and JK Bohlke (2012). Heterogeneous redox
conditions, arsenic mobility, and groundwater flow in a fractured -rock aquifer near a waste
repository site in New Hampshire, USA. Hydrogeology Journal 20(6): 1189-1201.
Hasany, QM and MA Qureshi (1981). Adsorption studies of cobalt (II) on manganese dioxide from
aqueous solutions. International Journal of Applied Radiation and Isotopes 32: 747-52.
Hoffman, GL; DA Lytle, TJ Sorg, ASC Chen and L Wang (2006). Design Manual: Removal of Arsenic
from Drinking Water Supplies by Iron Removal rocess. April 2006. E A/600/R-06/030.
Holm, TR; WR Kelly, SD Wilson and JLTalbott (2008). Arsenic removal at Illinois iron removal plants.
Journal AWWA 100(9): 139-150.
Holm, TR (2002). Effects of C032-/bicarbonate, Si, and 043- on arsenic sorption to HFO. Journal
AWWA 94(4): 174-81.
17

Liu, G; H Zhang, L Gao, L Zheng and Z eng (2004). etrological and mineralogical characterizations
and chemical compositions of coal ashes from power plants in Yanzhou mining district, China. Fuel
rocessing Technology 85: 1635-46.
Lokeshappa, B; AK Dikshit, Y Luo, TJ Hutchinson and DE Giammar (2014). Assessing bioaccessible
fractions of arsenic, chromium, lead, selenium, and zinc in coal fly ashes. International Journal of
Environmental Science and Technology 11: 1601-10.
Mariussen, E: IV Johnsen and AE Stromseng (2015). Selective adsorption of lead, copper, and
antimony in runoff water from a small arms shooting rnage with a combination of charcoal and iron
hydroxide. Journal of Environmental Management 150: 281-7.
Masscheleyn, H; RD Delaune and WH atrick Jr. (1991). Arsenic and selenium chemistry as affected
by sediment redox potential and pH. Journal of Environmental Quality 20: 522-7.
Meng, X; G Korfiatis, S Bang and KW Bang (2002). Combined effects of anions on arsenic removal
by iron hydroxides. Toxicology Letters 133: 103-11.
Meng, X; S Bang and G Korfiatis (2000). Effects of silicate, sulfate, and carbonate on arsenic
removal by ferric chloride. Water Research 34(4): 1255-61.
Miller, G (2011). Monitored natural attenuation: a remediation strategy for groundwater impacted
by coal combustion product leachate. 2011 World of Coal Ash Conference. May 9-12, 2011. Denver,
CO.
Miller, G (2001). Surface complexation modeling of arsenic in natural water and sediment systems.
h.D. dissertation, New Mexico Institute of Mining and Technology.
Mukherjee, J; J Ramkumar, S Chandramoukeeswaran, R Shukla and AK Tyagi (2013). Sorption
characteristics of nano manganese oxide: efficient sorbent for removal of metal ions from aqueous
streams. Journal of Radioanalytical and Nuclear Chemistry 297: 49-57.
Rightnour, TA and KL Hoover (1998). The Springdale roject: Applying Constructed Wetland
Treatment to Coal Combustion By- roduct Leachate. E RI report TR-111473.
Robinson -Lora, MA and RA Brennan (2011). Anaerobic precipitation of manganese and co -existing
metals in mine impacted water treated with crab shell -associated minerals. Applied Geochemistry
26: 853-62.
Roccaro, and FGA Vagliasindi (2015). Coprecipitation of vanadium with iron(III) in drinking water: a
pilot -scale study. Desalination and Water Treatment 55: 799-809.
18

Salminen, R (2005). Geochemical Atlas of Europe, art 1— Background Information, Methodology,
and Maps. weppi.gtk.fi/publ/foregsatlas/text.
Sarkar, D; DK De, R Das and B Mandal (2014). Removal of organic matter and oxides of iron and
manganese from soil influences boron adsorption in soil. Geoderma 214-5: 213-6.
Schwartz, GE; N Rivera, SW Lee, JM Harrington, JC Hower, KE Levine, A Vengosh and H Hsu -Kim
(2016). Leaching potential and redox transformations of arsenic and selenium in sediment
microcosms with fly ash. Applied Geochemistry 67: 177-85.
Swedlund, J and JG Webster (1999). Adsorption and polymerization of silicic acid on ferrihydride,
and its effect on arsenic adsorption. Water Research 33(16): 3413-22.
Tarutis, WJ and RF Unz (1995). Iron and manganese release in coal mine drainage wetland
microcosms. Water Science & Technology 32(3): 187-92.
U.S. E A (2007a). Monitored Natural Attenuation of Inorganic Contaminants in Ground Water,
Volume 1, Technical Basis of Assessment. E A/600/R-03/139.
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Volume 2, Assessment for Non -Radionuclides Including Arsenic, Cadmium, Chromium, Copper, Lead,
Nickel, Nitrate, erchlorate, and Selenium. E A/600/R-03/140.
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basics#02
19

A ENDIX A
Dr. Robert Parette CV
20

ROBERT PARETTE
Matson & Assoc ates, Inc.
331 East Foster Avenue, State College, PA 16801
Phone: [phone] Ema I: bparette@matson-assoc ates.com
EDUCATIO
Doctor of Philosophy August 2005
Env ronmental Eng neer ng
The Pennsylvan a State Un vers ty, Un vers ty Park, PA
D ssertat on: The Removal of Perchlorate from Groundwater v a Quaternary
Ammon um Cat on c Surfactant Pre -Loaded GAC
Master of Science May 2004
Env ronmental Eng neer ng
The Pennsylvan a State Un vers ty, Un vers ty Park, PA
Thes s: GAC Ta lored w th Organ c Cat ons for the Removal of Perchlorate from
Groundwater and Base/Ac d Chem cal Regenerat on of the GAC
Bachelor of Science February 1999
Chem cal Eng neer ng
Worcester Polytechn c Inst tute, Worcester, MA
WORK EXPERIE CE
Matson and Associates, Inc., State College, PA
Env ronmental Eng neer (P.E.)/Env ronmental Chem st (2009-2014)
V ce Pres dent of Eng neer ng/Project Manager for Matson B ofuels (2009-2011)
The Pennsylvania State University, Dept. of Civil and Environmental Engineering
Post -Doctoral Research Assoc ate (2005-2009)
Graduate Research Ass stant (2000-2005)
Environmental Consultant
Ass stant to Penn State professor sery ng as an expert w tness (2007)
Hercules Incorporated Research Center, Wilmington, DE
Research Ass stant (1998)
REPRESE TATIVE PROJECT EXPERIE CE
• Rev ewed closure plan alternat ves for a coal ash mpoundment located n Conway, South
Carol na. Prepared wr tten comments address ng the lack of groundwater treatment (as part of
these closure plan alternat ves) and the feas b I ty of remed at ng the arsen c contam nated
groundwater.
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• Evaluated the d sposal pract ces of waste salt conta n ng arsen c at a fac I ty along the
Menom nee R ver n W scons n n relat on to waste d sposal standards and the alternat ve
d sposal opt ons ava lable. Invest gated the spec at on of arsen c n the waste salts, the
propert es of the var ous arsen c spec es, and the transformat ons these arsen c spec es would
undergo n the env ronment.
• At Penn State, 9% years of R&D on technolog es to remed ate ground water. Th s R&D resulted
n numerous publ cat ons (I sted below) on the removal of arsen c and perchlorate from water.
Des gned and produced custom adsorbents for the removal of arsen c from groundwater.
Des gned and fabr cated a p lot plant w th a capac ty n excess of one m II on gallons per year to
study the removal of arsen c by a comb nat on of act vated carbon and ron from a var ety of
d fferent sources. Respons ble for develop ng exper mental and sampl ng plans for a number of
p lot and laboratory stud es.
• Evaluated treatment technolog es, and the feas b I ty of employ ng such technolog es, n
connect on w th remed at ng a large lake contam nated w th selen um. Prepared a report to be
ut I zed for publ c comments and negot at ons w th the power company.
• Evaluated the potent al mplementat on of var ous technolog es for a number of outfalls at a
coal m n ng operat on n western Pennsylvan a. Prepared wr tten comments address ng
shortcom ngs of a consent decree perta n ng to the s te.
• Evaluated wastewater treatment pract ces of a paper m II along the Fox R ver n W scons n n
relat on to the treatment opt ons ava lable (chronolog cally) to the pulp and paper ndustry and
the removal eff c enc es ach eved by var ous treatment technolog es across the ndustry.
• Des gned and conducted laboratory exper ments to test the mpact of MTBE on the removal of
other organ c contam nants from groundwater for a case nvolv ng MTBE n Suffolk County, NY.
Ut I zed mult ple f eld data sets to assess the ab I ty of act vated carbon to remove MTBE,
ass sted n the preparat on of expert w tness reports, and performed an extens ve I terature
rev ew pert nent to the case.
• Correlated s to act v t es at an abandoned chem cal manufactur ng plant n NJ w th
contam nants found n the near offshore areas of the s te; determ ned the or g n and chem cal
react ons beh nd the presence of 2,4,6,8-tetrachlorod benzoth ophene (2,4,6,8-TCDT), a
contam nant whose source was prev ously unknown.
• Evaluated the s ngle phase eff c ency for the str pp ng of COZ n a cool ng tower model for an
nternat onal company that spec al zes n gases. Mod f ed the model's source code to reflect the
determ ned s ngle stage eff c ency, evaluated the I qu d to gas rat o ut I zed by the model, and
compared results from the model aga nst the exper mental data.
• Invest gated groundwater qual ty and consulted w th a forester at a res dent al s to n Centre
County, PA, mpacted by a nearby hous ng development.
• D rected the R&D efforts for Matson B ofuels from 2009 through 2011. Respons ble for the
management of three b od esel projects, w th grant fund ng n excess of $250K. Developed sol d
A-2

catalysts capable of convert ng low qual ty o I feedstocks to b od esel w th no feedstock
pretreatment and no soap format on. Des gned a p lot plant, w th a capac ty to produce more
than 1 m II on gallons of b od esel annually.
PUBLICATIO 5
R Parette, R McCr ndle, KS McMahon, M Pena-Abaurrea, E Re ner, B Ch tt m, N R ddell, G Voss, FL
Dorman, WN Pearson and M Robson (2016). Response to the comment on "Halogenated nd go dyes
I kely source of 1,3,6,8-tetrabromocarbazole and some other halogenated carbazoles n the
env ronment". Chemosphere 150: 414-5.
N R ddell, UH J n, S Safe, Y Cheng, B Ch tt m, A Konstant nov, R Parette, M Pena-Abaurrea, EJ Re ner, D
Po r er, T Stefanac, AJ McAlees and R McCr ndle (2015). Character zat on and b olog cal potency of
mono- to tetra -halogenated carbazoles. Env ronmental Sc ence & Technology 49 (17): 10658-66.
R Parette, R McCr ndle, KS McMahon, M Pena-Abaurrea, E Re ner, B Ch tt m, N R ddell, G Voss, FL
Dorman and WN Pearson (2015). Halogenated nd go dyes: a I kely source of 1,3,6,8-
tetrabromocarbazole and some other halogenated carbazoles n the env ronment. Chemosphere 127:
18-26.
R Parette and WN Pearson (2014). 2,4,6,8-Tetrachlorod benzoth ophene n the Newark Bay Estuary: the
I kely source and react on pathways. Chemosphere 111: 157-63.
W Chen, R Parette and FS Cannon (2012). P lot -scale stud es of arsen c removal w th granular act vated
carbon and zero-valent ron. Env ronmental Eng neer ng Sc ence 29(9): 897-901.
K Gombotz, R Parette, G Aust c, D Kannan and J Matson (2012). MnO and T O sol d catalysts w th low-
grade feedstocks for b od esel product on. Fuel 92(1): 9-15.
MK Sel em, S Komarnen, R Parette, H Katsuk, FS Cannon, MG Shah en, AA Khal I and IM Abdel-Ga d
(2011). Perchlorate uptake by organos I cas, organo-clay m nerals and compos tes of r ce husk w th
MCM-48. Appl ed Clay Sc ence 53: 621-6.
JP Patterson, R Parette and FS Cannon (2011). Compet t on of an ons w th perchlorate for exchange s tes
on cat on c surfactant-ta lored GAC. Env ronmental Eng neer ng Sc ence 28(4): 249-56.
JY K m, S Komarnen , R Parette and FS Cannon (2011). Perchlorate uptake by synthet c layered double
hydrox des and organoclays. Appl ed Clay Sc ence 51(1-2): 158-64.
JP Patterson, R Parette and FS Cannon (2010). Ox dat on of ntermed ate sulfur spec es (th osulfate) by
free chlor ne to ncrease the bed I fe of to lored GAC to remove perchlorate. Env ronmental Eng neer ng
Sc ence 27(10): 835-43.
MK Sel em, S Komarnen, R Parette, H Katsuk, FS Cannon, MG Shah en, AA Khal I and IM Abdel-Ga d
(2010). Compos tes of MCM-41 s I ca w th r ce husk: Hydrothermal synthes s, character zat on and
appl cat on for perchlorate separat on. Mater als Research Innovat ons 14(5): 351-4.
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S Komarnen , J Y K m, R Parette and FS Cannon (2010). As-synthes zed MCM-41 s I ca: New adsorbent for
perchlorate. Journal of Porous Mater als 17: 651-6.
MJ Jang, FS Cannon, R Parette, S Yoon and W Chen (2009). Comb ned hydrous ferr c ox de and
quaternary ammon um surfactant to for ng of granular act vated carbon for concurrent arsen c and
perchlorate removal. Water Research 43(12): 3133-43.
W Chen, R Parette and FS Cannon FS (2008). Arsen c adsorpt on v a ron preloaded act vated carbon and
zero-valent ron. Journal of Amer can Water Works Assoc at on 100(8): 96-105.
W Chen, R Parette, J Zou, FS Cannon and BA Dempsey (2007). Arsen c removal by ron-mod f ed
act vated carbon. Water Research 41(9): 1851-8.
R Parette and FS Cannon (2006). Perchlorate removal by mod f ed act vated carbon. In Perchlorate
Env ronmental Occurrence, Chem stry, Tox cology, and Remed at on Technolog es. Spr nger Publ sh ng
Company, New York.
R Parette and FS Cannon (2005). The removal of perchlorate from groundwater by act vated carbon
to lored w th cat on c surfactants. Water Research 39(16): 4020-28.
R Parette, FS Cannon and K Weeks (2005). Remov ng low ppb level perchlorate, RDX, and HMX from
groundwater w th cetyltr methylammon um chlor de (CTAC) pre -loaded act vated carbon. Water
Research 39(19): 4683-92.
A-4