NC0005088_Comments on Draft Permit_20161110

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(� DUKE
ENERGY
November 10, 2016
North Carolina Department of
Environmental Quality
Wastewater Permitting
Attn: Rogers Energy Complex
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
Duke Energy
526 South Church Street
Charlotte, NC 28202
Mailing Address:
Mail Code EC13K / P.O. Box 1006
Charlotte, NC 28201-1006
NOV 15 2016
Subject: Rogers Energy Complex (Cliffside Steam Station) Water Quality
Duke Energy Carolinas, LLC Permitting Section
NPDES Permit No. NC0005088
Comments on Draft NPDES Permit
Wastewater Permitting ,Staff:
Duke Energy Carolinas (DEC), LLC submits the following comments on the draft
National Pollutant Discharge Elimination System (NPDES) permit for Rogers Energy
Complex (REC), issued for public comment by the North Carolina Department of
Environmental Quality (NCDEQ) on September 23, 2016.
Limitations on Chromium and Zinc:
On pages 3 and 6 the draft permit proposes limits on Chromium and Zinc. On page 5 of
the fact sheet it references the basis for the limitations for Chromium and Zinc as 40
CFR 423.13 (d) (1). This regulation notes that the requirement for these limitations
applies if cooling tower maintenance chemicals are being used that contain these
parameters. The regulations also allow the permit writer the discretion to require the
permittee to submit calculations based on maintenance chemicals that are being used
in the cooling towers. At REC, the chemicals used within the cooling towers do not
contain any of the 126 priority pollutants including zinc or chromium. Therefore, it is
requested that these two parameters be removed from pages 3 and 6 and replaced with
the option to calculate the priority pollutants from maintenance chemicals.
Limitations on Copper and Iron:
On pages 3, 8, 9 and 11, the draft permit proposes limits on copper and iron during a
chemical metals cleaning. For chemical metal cleaning the Steam Electric Effluent
Limitation Guidelines (ELG) states the limitation for copper is to be 1.0 mg/I. The
proposed limitation is much more restrictive. Thus it is requested that the limitation be
in alignment with the ELG limit of 1.0 mg/I.

November 10, 2016
Rogers Energy Complex
NPDES Permit NC0005088
Page 2
Limitations on Thallium:
Thallium limitations are identified on pages 3, 11, 20, 21, 22, 24 and 25. DEC requests
that the limits for Thallium be removed from the permit for the following reasons:
1. There is no adopted numeric water quality criterion for Thallium in North
Carolina. With no adopted criteria, the State has not provided any
opportunity for public involvement or comment on recommended constituent
levels used in determining permit requirements. Unlike the defined
opportunity to comment on proposed criteria during the triennial review, the
only means for public involvement in this case is through commenting on
specific permitting actions. The NCDEQ has previously indicated no limits for
metals would be included in permits for constituents without numeric criteria.
NCDEQ recently acknowledged this in issuance of the company's Sutton
permit in which NCDEQ proposed to include an effluent limit for Aluminum but
withdrew that limit in the final permit "because ...North Carolina does not
have [an] Al standard...". North Carolina just completed an update to its
standards through the triennial review process but did not propose any
standards for Thallium.
2. The conclusion reached in the IRIS Toxicological Review (USEPA, 2009),
which DEQ seeks to base the limit on, was the available toxicity
database for Thallium which contains studies that are generally of poor
quality. Please see the attached evaluation of toxicological information of
Thallium prepared by Haley and Aldrich for DEC. This information is included
in the attachment to these comments and should be considered part of our
comments on the DRAFT permit. In the USEPA Integrated Risk Information
System (IRIS) Chemical Assessment Summary for Thallium, it was stated
"The available toxicity database for thallium contains studies that are
generally of poor quality" (USEPA, 2012a). In addition, there is not currently
an oral chronic reference dose (RfD) toxicity value for Thallium established by
the USEPA IRIS or from an USEPA Provisional Peer -Reviewed Toxicity
Value (PPRTV) assessment, which would be used to establish water quality,
criteria. Due to the significant uncertainty surrounding the study selection
used to establish the values for the 2002 water quality criteria and uncertainty
to the relevance of adverse effects of Thallium, the values used for the
derivation of the 2002 Federal Water Quality Criteria for Thallium are
questionable and greatly overestimates potential risks associated with
Thallium exposure. This is supported by other regulatory and authoritative
agencies concluding that the dataset is currently insufficient for derivation of a
non -cancer value for Thallium. In addition, human consumption of Thallium
for a substantial part of the population exceed the provision screening value
with no reported adverse effects reported, which also suggests that the
current value is unrealistic for purposes of regulatory decision making.

November 10, 2016
Rogers Energy Complex
NPDES Permit NC0005088
Page 3
3. There is no record of a determination that any limit on Thallium is
necessary to protect narrative criteria. To the contrary, the record indicates
that the receiving water currently meets narrative criteria, despite a long
history of similar discharges, indicating that effluent limits are not necessary
to protect narrative criteria or designated uses. The NCDEQ has not provided
any documentation that the factors required for consideration in developing a
BPJ limit for Thallium have been considered.
Limitations on Turbidity:
On pages 3, 4, 6 and 7 the draft permit proposes limits on turbidity. These pages also
incorporate limits on Total Suspended Solids (TSS). TSS is a parameter that is
sufficient to show that the wastewater treatment system is properly operating. The
potential exists for significant interferences in the analysis for turbidity. For example, air
bubbles and/or light absorbing materials can significantly interfere with the readings.
Turbidity is also not a direct measurement of the total suspended materials in water.
Turbidity is instead a measure of relative clarity, and is often used to indicate changes in
the total suspended solids concentration in water without providing an exact
measurement of solids. DEC requests that since these outfalls are limited by TSS that
the limitations and monitoring of turbidity be removed.
Monitoring and Limitations on Seeps:
On pages 13 through 30 of the draft permit there are many parameters and limitations
proposed for 18 seeps. These seeps are relatively very low flow and will not cause an
adverse impact to main water body of Suck Creek and/or the Broad River. With so
many parameters and monthly monitoring proposed, it is a large burden on the station.
Prior to 2016 many of the seeps samples were collected in such a way that outside
contamination could influence the sample results. Beginning in April 2016 an improved
sampling process was implemented. The April 2016 sampling results for these seeps
determined that no Water Quality Standards are exceeded from seeps that had
sufficient flow for sample collection. Additionally, seeps 128, 129, 130, 131 and 132 are
located in a very rough terrain that presents a safety hazard for sample collection. In
addition, in recent sampling events there was not enough flow at these locations to
collect a sample. Thus DEC requests the following for pages 13 through 30:
1. Eliminate all monitoring requirements for 128, 129, 130, 131 and 132. DEC will
escort DEQ to evaluate the safety concerns associated with these outfalls.
2. 'Eliminate all monitoring for parameters other than low volume wastewater
parameters (e.g. pH, TSS and Oil and Grease). Allow for the upstream and
downstream semi-annual monitoring in addition to future form 2C sampling during the
NPDES permit renewal to identify whether any water quality based parameters are
needed to be monitored and/or limited.

November 10, 2016
Rogers Energy Complex
NPDES Permit NC0005088
Page 4
3. Allow one seep to be sampled as a representation of the other seeps (114, 115, 116,
121, 127) at Suck Creek.
4. Change the monitoring frequency for low volume wastewater parameters to
quarterly.
Chronic Toxicity:
REC has a long term compliance history on chronic toxicity monitoring, which shows the
effluent passes the chronic toxicity limits. It is requested that on page 3 and 6 that the
monitoring frequency be changed from monthly to quarterly.
Continuous pH and TSS Monitoring:
On pages 4 and 7 continuous pH and TSS monitoring is included for decanting and
dewatering activities. It is requested that this requirement be restricted to in -process
monitoring and allow for these parameters to be limited by the routine monitoring.
Change to Flow Diagram:
It was determined that the flue gas desulfurization (FGD) wastewater treatment system
(WWTS) should not discharge into beginning of the future WWTS. For the initial
requirements for Outfall 004, the WWTS for the FGD system is sufficient and no
additional treatment is needed by the future WWTS. Thus it is planned that the
discharge of the FGD WWTS (Outfall 004) will combine with the discharge from the
future WWTS discharge at the proposed Outfall 005. See attachment for the updated
flow diagram.
Reasonable Potential Analysis Determinations:
On page 3 and 4 of the fact sheet it is DEC understanding that the monthly maximum
flow was used in the RPA calculation. It is requested that this be revisited. In review of
the EPA Technical Support Document for Water Quality Based Toxic Control, the Long
Term Average (LTA) flow should be used in conducting the RPA and determining water
quality based effluent limits. It is, therefore, requested that the LTA flow be used for the
RPA and to determine water quality based limits.
On page 10 of the fact sheet it identifies the methodology used to calculate the RPA for
the seeps. It is requested that the summation of the seeps be verified. Plus DEC
objects to the methodology of using a safety factor of 10 in multiplying to the total flow.
The majority of the seeps have very low flows and at times non-measureable.
Multiplying the summation of the seeps by 10 is a misrepresentation of the actual flow
and is overly conservative in the RPA analysis. It is requested that no safety factor be
added and the RPA be conducted based on the reported flows.

November 10, 2016
Rogers Energy Complex
NPDES Permit NC0005088
Page 5
No Discharge of Bottom Ash Transport Water:
On page 3 of the fact sheet within the Outfall 002 — Ash Basin — Decanting/Normal
Operations section, DEC requests the addition of the following statement to the bottom
ash compliance date:
"An underneath the boiler mechanical drag system will be installed and
operational for REC Unit 5 by December 31, 2020 and is already installed
for REC Unit 6. This technology will not generate bottom ash transport
water per 80 Fed. Reg. at 67,892 col. 3."
Additional comments are included on the last attachment for your consideration.
DEC welcomes any further discussion on these comments. If you have any questions
or need additional information, please contact Robert Wylie at [phone].
Sincerely,
I W � �
Richard Baker
Director Environmental Programs
EHS CCP
cc: Teresa Rodriquez - NCDEQ Raleigh Office (Electronic Copy)
Attachments: 1. Evaluation of Toxicological Information for Thallium Report
2. Updated Flow Diagram
3. Additional Comments
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Thallium Toxicity Value Review
EVALUATION OF THE TOXICITY VALUE FOR THALLIUM
1. Current Screening Provisional Toxicity Value
There is not currently an oral chronic reference dose (RfD) toxicity value for thallium established by the
United States Environmental Protection Agency (USEPA) Integrated Risk Information System (IRIS) or
from an USEPA Provisional Peer -Reviewed Toxicity Value (PPRTV) assessment. The USEPA PPRTV
document for thallium (TI) concluded that it is inappropriate to derive a provisional subchronic or
chronic provisional RfD (p-RfD) for thallium; however, USEPA states that information is available which,
although insufficient to support derivation of a provisional toxicity value under current guidelines, may
be of limited use to risk assessors (USEPA, 2012). The PPRTV document contains a separate Appendix A
that provides rationale for the derivation of a subchronic and chronic "screening provisional oral
reference dose" for thallium compounds of 0.00004 mg TI/kg-day and 0.00001 mg TI/kg-day,
respectively. Appendix A of the PPRTV document also notes that, "Users of screening toxicity values in
an appendix to a PPRTV assessment should understand that there is considerably more uncertainty
associated with the derivation of a supplemental screening toxicity value than for a value presented in
the body of the assessment (USEPA, 2012a)." The screening p-RfD is expressed in units of milligrams of
thallium per kilogram of body weight per day (mg TI/kg-day).
Due to limitations in the toxicology database and general poor quality of available studies, the USEPA
IRIS Toxicological Review of Thallium and Compounds (USEPA, 2009) also concluded that reference
doses or reference concentrations could not be derived for human health following thallium exposures.
2. Information on Human Exposure to Thallium
The conservative nature of the p-RfD can be illustrated by considering the amount of thallium ingested
daily by Americans in their diet. It is estimated by the World Health Organization (WHO) and the U.S.
Agency for Toxic Substances for and Disease Registry (ATSDR) that a 70 kilogram adult ingests
approximately 0.005 mg thallium per day in the diet, especially from consumption of home-grown fruits
and green vegetables (WHO, 1996; ATSDR, 1992). This is equivalent to a daily dose of 0.00007 mg TI/kg-
day. The USEPA supplemental p-RfD for thallium is 1E-05 mg/kg -day (0.00001 mg/kg -day). This is seven
times lower than the estimated dietary intake. In other words, use of this dose -response value to
evaluate natural dietary exposure to thallium would indicate a hazard that is unlikely to exist.
Stated another way, assuming that an average adult weighs 70 kg, and using the screening level p-RfD of
0.00001 mg/kg bw-day, it could be concluded that an adult should not consume more than 0.0007 mg
TI/day, which is well below the estimated dietary intake of 0.005 mg thallium per day in the diet.
Currently, there have not been substantial reports of toxicological effects associated with typical dietary
ingestion of TI in the general population, suggesting that the use of the "screening provisional oral
reference dose" greatly overestimates the potential risks associated with oral exposure to TI
compounds.
The 90th percentile adult urinary thallium elimination from the National Health and Nutrition
Examination Survey (NHANES) (CDC, 2016) is 0.380-0.390 micrograms per liter (ug/L) which is about
0.760-0.780 ug/day in the urine alone. This suggests that greater than 10% of Americans, and probably
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Thallium Toxicity Value Review
closer to 50% of Americans, ingest more than the screening level p-RfD. From the IRIS assessment
conducted in 2009, a reviewer stated that there is no evidence that thallium in the current U.S. diet
poses any threat, and the adoption of this screening level p-RfD would produce unnecessary concern if
the above calculation is correct. This indicates the poor quality of the existing data, and brings into
question the validity of the analysis using the available data on thallium used by USEPA (USEPA, 2009).
3. Derivation of the Current Screening Provisional Toxicity Value
Below is a summary of the data and assessment that was used by USEPA in the derivation of the oral
chronic screening level p-RfD for thallium.
3.1 HAZARD EVALUATION/STUDY SELECTION
Note: Human or animal studies examining the carcinogenicity of thallium following oral exposure are
not available. The cancer weight -of -evidence (WOE) provided in the IRIS review (USEPA, 2009) is listed
as "Inadequate Information to Assess Carcinogenic Potential (both oral and inhalation)."
3.1.1 Human Studies
Most information on thallium toxicity in humans comes from poisonings, suicide attempts, or accidental
exposures. Symptoms observed after acute exposures to high doses of thallium in humans include
alopecia (hair loss), gastrointestinal disturbances, and neurological symptoms such as paresthesia and
neuropathy. Epidemiologic studies of either the general population or occupationally exposed groups
are limited by inadequate study design, undefined exposure parameters, and inconclusive associations
between thallium exposure and specific health effects. Therefore, USEPA (2012a) concluded in the
PPRTV document that "available human studies do not support oral RfD derivation."
3.1.2 Animal studies
Studies in animals show that oral exposure to thallium produces effects similar to those observed in
humans, most notably, alopecia. Other findings observed in animal studies include biochemical
changes, lipid peroxidation, liver and kidney damage, and histopathologic changes in the brain and
nerves. The doses at which these systemic effects were observed range from 0.2 —1.8 mg TI/kg-day
(ATSDR, 1992). Reproductive and developmental studies in animals show some evidence of adverse
effects upon oral exposure to thallium at doses of 0.08 mg TI/kg-day —1.6 mg TI/kg-day; however,
available studies have significant limitations and the same effects have not been observed in humans
(ATSDR, 1992).
Only four repeat -dose oral toxicity studies with more than one dose level are available in animals. Of
these four studies, three were not considered adequate for RfD derivation (USEPA, 2009).
3.1.3 Conclusion
The conclusion reached in the IRIS Toxicological Review (USEPA, 2009) was that the available toxicity
database for thallium contains studies that are generally of poor quality. One animal subchronic study
conducted by the Midwest Research Institute (MRI, 1988) was selected as a candidate principal study for
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Thallium Toxicity Value Review
RfD derivation but was found to include critical limitations such as high background incidence of
alopecia, lack of histopathological examination of skin tissue in low -and mid -dose groups, and
inadequate examination of objective measures of neurotoxicity, thus making it difficult to select
appropriate endpoints. On this basis, a RfD for thallium salts was not derived by IRIS (USEPA, 2012a).
3.2 BASIS FOR PROVISIONAL SCREENING ORAL CHRONIC P -RFD
As indicated above, the PPRTV assessment (USEPA, 2012a) does not derive a typical provisional toxicity
value for thallium but rather uses the limited toxicological information to develop a screening level
value.
3.2.1 Study Selection
A 90 -day Good Laboratory Practice (GLP) oral gavage study in male and female rats conducted with
thallium sulfate by MRI (1988) was selected as the principal study for the screening level p-RfD. Doses
were approximately 0, 0.008, 0.04, and 0.2 mg TI/kg-day.
3.2.2 Selection of Point of Departure
Several critical endpoints were considered, but ultimately USEPA (2009) considered only two endpoints
to be appropriate for a screening level p-RfD development:
• Hair follicle atrophy in female rats that also had alopecia; and
• Clinical observations related to animal coat, eyes, and behavior.
The clinical observation endpoint was discounted because the underlying basis for the observations is
unknown. Hair follicle atrophy was determined to be most consistent with the atrophic changes
observed in cases of human thallium poisoning and may be best indication for human response to
thallium exposure.
MRI (1998) concluded that the minor dose-related changes in the study did not affect the health status
of the treated animals and were not toxicologically significant. MRI considered the highest dose (0.2 mg
TI/kg-day) as the no -observed -effect level (NOEL). However, USEPA conducted its own analyses of the
raw data from the study to come up with different conclusions. Of the 12 high -dose females with
alopecia, 5 instances were not totally attributed to barbering behavior. Histopathologic examinations
revealed atrophy of the hair follicles in two high -dose female rats that also had alopecia. It was noted
that there were no discernable differences in either the severity or distribution pattern of alopecia
across control and treated groups (USEPA, 2009).
The high dose (0.2 mg TI/kg-day) was identified by USEPA as the LOAEL. Because histopathology of skin
tissue from the low -and mid -dose groups was not conducted, the NOAEL for this endpoint cannot be
determined with certainty. Given the low incidence of hair follicle atrophy in females in the high dose
group and absence of cases of hair follicle atrophy in male rats, USEPA (2012a) assumed that the mid -
dose could be used to approximate a NOAEL for skin histopathology.
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Thallium Toxicity Value Review
Therefore, the estimated NOAEL of 0.04 mg TI/kg-day was used as the point of departure (POD) for hair
follicle atrophy (USEPA, 2012a).
3.2.3 Uncertainty Factors
Using the NOAEL of 0.04 mg TI/kg-day for hair follicle atrophy and using an uncertainty factor (UF) of
3000, the screening level p-RfD was calculated to be 0.00001 mg TI/kg-day. Justification for the applied
OF is summarized in table below.
Table 1: Uncertaintv Factors Applied by USEPA in Screening Level p-RfD Derivation
Uncertainty Factor
Justification
10
Extrapolation from laboratory animals to humans since no information is
available to characterize the toxicokinetic differences between experimental
animals and humans.
10
Variation in human susceptibility in the absence of information on the
variability of response to thallium in the human population.
10
Lack of adequate developmental toxicity studies and a two -generation
reproductive study, and additional uncertainty associated with the limited
data available on neurotoxicity.
3
Extrapolation from subchronic to chronic exposure duration. Effects on the
coat/skin as well as other clinical observations occur within weeks of exposure
to thallium (does not required chronic exposure in order to manifest).
Composite OF = 3000
Note that there are considerable and critical limitations with the principal study selected by USEPA
(2009) including:
• High background of incidence of alopecia (POD selected)
• Lack of histopathological examination of skin tissue in low -and mid -dose groups
• Inadequate examination of objective measures of neurotoxicity
4. Other Available Sources for Derivation of Toxicity Values for Thallium
The following sections describe sources consulted for information on the toxicology of thallium.
4.1 WORLD HEALTH ORGANIZATION
The World Health Organization (WHO) (1996) concluded that in the general population, environmental
exposure to thallium does not pose a health threat. The total intake has been estimated to be less than
5 ug/day with the vast majority coming from foodstuffs; drinking -water and air generally contribute very
small amounts of thallium. Concentrations of thallium in urine may be considered a relatively reliable
indicator of exposure. Exposure to thallium resulting in urine concentrations below 5 ug/liter is unlikely
to cause adverse human health effects. The estimated daily oral intake corresponding to a urinary
thallium concentration of 5 ug/liter in urine is approximately 10 ug thallium in the form of a soluble
compound. Assuming an average adult body weight of 80 kg (USEPA, 2014), this would be equivalent
to 0.000125 mg/kg -day which is a 10 -fold factor above the USEPA screening level p-RfD. The WHO
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Thallium Toxicity Value Review
Task Group thus concluded that "in view of the considerable uncertainties in the evaluation, it was not
possible to recommend a health -based exposure limit. Until better information on the dose -response
relationship becomes available, it seems prudent to keep human exposures at levels that lead to urinary
concentrations of less than 5 ug/liter." In reviewing the animal studies, the WHO Task Group also noted
that, "it appears that an intake of 0.01 mg/kg -day may be associated with adverse effects. No doses
lower than this have been tested."
ATSDR (1992) notes, "Data on effects of intermediate duration oral exposure in animals do not reliably
identify the most sensitive target organ or the threshold for adverse effects. No data on effects of
chronic -duration oral exposure to thallium were located. Therefore, intermediate -duration and chronic -
duration oral minimum risk levels (MRLs) were not derived for thallium." Note that review of the MRI
1988 study (originally Stoltz 1986) was conducted by ASTDR but not used in the derivation of the MRL.
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USEPA's Maximum Contaminant Level (MCL) (USEPA, 2012b) for drinking water is 2.0 ug/L or 0.002
mg/L. The USEPA Human Health Water Quality Criteria (HHWQC) (USEPA, 2015) for thallium is 0.24 ug/L
or 0.00024 mg/L for the consumption of water and organisms from a surface water body, and is 0.47
ug/L or 0.00047 mg/L for the consumption of organisms only. These levels were derived based on the
90 -day subchronic study in rats (MRI, 1988).
4.4 CALIFORNIA EPA
In California, the MCL and Public Health Goal (PHG) for thallium in drinking water are currently set at 2.0
and 0.1 ug/L, respectively (CaIEPA, 1999, 2004). The Office of Environmental Health Hazard Assessment
(OEHHA) prepared the PHG for thallium in drinking water also using the MRI (1988) study in which
alopecia was observed in both male and female rats and consistent with other reports of toxicity of
thallium in both experimental animals and in humans. OEHHA determined that the incidence of
alopecia in female rats at the highest dose of 0.25 mg/kg -day represented a biologically significant
effect. Therefore, the no -observed -effect -level (NOEL) was identified to be the administered mid -dose
level of 0.04 mg TI/kg-day. For the calculation of the PHG, a cumulative uncertainty factor of 3,000 was
incorporated to account for the use of a subchronic study, uncertainty in inter -and intra -species
extrapolation and the steep dose -response curve. Based on these uncertainty factors, OEHHA derived a
PHG for thallium in drinking water of 0.0001 mg/L (0.1 ug/L). OEHHA notes that USEPA chose to
consider the dose that resulted in alopecia and increased serum enzymes indicated of liver damage as a
NOAEL, which is why the federal values are higher than those estimated by OEHHA.
4.5 CANADIAN COUNCIL OF MINISTERS OF THE ENVIRONMENT
The Canadian Council of Ministers of the Environment (1999) also adopted the USEPA screening level p-
RfD based on the MRI (1988) study as a provisional tolerable daily intake (TDI) for derivation of health -
based soil quality guidelines for thallium at contaminated sites in Canada.
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Thallium Toxicity Value Review
4.6 EUROPEAN UNION
No data were available on thallium or thallium compounds on the European Chemical Agency (ECHA)
Portal where the Registration, Evaluation, Authorization and Restriction of Chemical Substances (REACH)
Registration Dossiers are posted (ECHA, 2016). Thus, no derived no effect level (DNEL) is available for
thallium from this source.
4.7 OTHER
No other relevant data were located with respect to thallium toxicity since the publication of the USEPA
PPRTV assessment that could better inform the dose -response assessment and toxicity value derivation
for thallium.
S. Critique of Toxicity Value for Thallium
The current screening level p-RfD currently being used by USEPA as a toxicity value is a highly
conservative and inappropriate value for use in evaluating human health risks from oral chronic
exposure to thallium on the basis of: 1) the lack of appropriate toxicological studies on subchronic and
chronic exposures to thallium that provide relevant data and endpoints to be used in a dose -response
assessments; 2) the fact that other regulatory authorities (ATSDR, WHO) have concluded that sufficient
data on thallium does not exist and have not generated toxicity values for thallium and have placed a
low priority on development of additional toxicology data for thallium; 3) the study and POD using
alopecia as the endpoint as selected'for the derivation of the screening level p-RfD by USEPA (2012a)
results in significant uncertainty to the applicability of the effects to human exposure to thallium; and 4)
the screening level p-RfD greatly overestimates the risk associated with human exposures as compared
to the typical ingestion of thallium in foods.
5.1 TOXICOLOGY DATABASE ON THALLIUM
The toxicity database for thallium in consideration of a dose -response assessment and derivation of a
toxicity value is limited. Low confidence in the screening level p-RfD is attributed to the limited
database including the lack of studies addressing the known toxic effects of thallium including
neurotoxicity, developmental toxicity, and endocrine effects, and failure of the MRI (1988) study to
identify a NOAEL of all relevant endpoints are considered. It is questionable as to whether a screening
level p-RfD should have been derived and if such an analysis is even valid knowing the database
limitations resulting in the application of such high uncertainty factors, given USEPA's own discussion of
the limitations in the PPRTV document (USEPA, 2012a).
5.2 OTHER REGULATORY SOURCES/VALUES
Most regulatory sources acknowledge -the paucity of data for thallium and have not derived toxicity
values. USEPA IRS, WHO, and ATSDR have not generated oral chronic RfDs for thallium. For those that
have, the MRI (1988) study has been identified as the principal study despite the fact that it has not
been published in a peer-reviewed journal, did not provide statistical analyses, and the study did not
show a statistically significant dose -response effect for alopecia in male rats.
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Thallium Toxicity Value Review
On the Priority List of Hazardous Substances established by ATSDR last updated February 12, 2016,
thallium is listed as #275 out of 275 compounds indicating its low priority and concern for review
(http://www.atsdr.cdc.gov/SPL/). In addition, the National Toxicology Program (NTP) (2016a) has
reviewed petitions and proposals for conducting additional toxicology studies on thallium to decrease
the limitations and uncertainty with the current toxicology database but in a recent meeting on June 15,
2016, the NTP scientific board placed low priority on moving forward with these efforts.
One could infer that the low priority established by regulatory authorities on continued development
and review of the toxicology data for thallium indicates a low concern of the potential for human health
risk effects of oral exposures to thallium as compared to other compounds.
5.3 STUDY SELECTION AND POD
It has been questioned as to whether alopecia is considered an adverse event and should have been
used as the POD for the screening level p-RfD. USEPA has stated: "Whether alopecia is itself an adverse
effect merits consideration. In humans, alopecia is generally reversible upon cessation of thallium
exposure. Alopecia, however, appears to be a part of a continuum of dermal changes observed
following thallium exposure, as well as one of a spectrum of effects on target organs that include the
nervous and gastrointestinal systems. For these reasons, alopecia supported by two cases of hair follicle
atrophy is considered an adverse effect (USEPA, 2009)." USEPA (2009) acknowledged that other factors
such as caging and husbandry can cause alopecia in laboratory rodents; however, the incidence was
clearly elevated in both male and female rats over controls. Further, to the extent that alopecia was due
to barbering, research has shown that barbering in rodents can reflect a stress -evoked behavioral
response. For these reasons, some IRIS reviewers thought it was reasonable to use the alopecia as a
"biomarker" for adverse effects until additional studies are conducted to better identify adverse effects
of thallium exposures in animals and/or humans.
NTP (2016b) has also noted that the dose selection for the subchronic study was deemed inappropriate
for evaluation of alopecia since the 14 -day range -finding study performed prior to the 90 -day study
indicated hair follicle, alterations together with decreases in body weight at a dose of 2.5 mg/kg -day of
thallium sulfate; however, a dose of ten times lower than that which effects were noted, 0.25 mg/kg -day
thallium sulfate was chosen as the high dose in the subchronic study. Further, review of the results also
show that there were challenges in distinguishing between normal hair cycling, self -barbering, and
incidences of true alopecia.
Since hair follicle histopathology and self -barbering is not a standard assessment in subchronic studies, it
is difficult to know whether what was observed in the MRI study (1988) is within the range of normal or
truly adverse. Therefore, the use of this endpoint as the POD brings considerable uncertainty to the
screening level p-RfD derived using these data.
No other studies have been identified by reviewers that could bring more certainty and validity to the
current screening level p-RfD proposed by USEPA (2012a).
November 2016 7 "Aglaq

Thallium Toxicity Value Review
6. Final Assessment
Due to the significant uncertainty surrounding the study selection and uncertainty to the relevance of
adverse effects in the selected study and POD, the screening level p-RfD value as provided in Appendix A
of the USEPA PPRTV document for thallium (USEPA, 2012a) greatly overestimates potential risks
associated with exposure to TI. This is supported by other regulatory and authoritative agencies
concluding that the dataset is currently insufficient for derivation of a non -cancer value for TI. In
addition, current intakes of TI for a substantial part of the population exceed the provision screening
value with no reported adverse effects reported, which also suggests that the current value is unrealistic
for purposes of regulatory decision making.
Therefore, it seems most appropriate to establish a screening level based on the level of thallium in the
diet; clearly exposure to thallium at this level are without adverse effects. Using the information from
WHO (1996) that the estimated daily oral intake corresponding to a urinary thallium concentration of
5 ug/liter in urine is approximately 10 ug thallium in the form of a soluble compound, and assuming
an average adult body weight of 80 kg (USEPA, 2014), a RfD of 0.000125 mg/kg -day can be calculated,
which is a 10 -fold factor above the USEPA screening level p-RfD. This value is still a conservative
derivation, considering that it is well below the intake of 0.01 mg/kg -day that WHO indicated was the
lowest associated with adverse effects.
7. References
ATSDR. 2004. Toxicological Profile for Cobalt. U.S. Department of Health and Human Services,
Public Health Service, Agency for Toxic Substances and Disease Registry. Available at:
http://www.atsdr.cdc.gov/toxprofiles/TP.asp?id=309&tid=49
2. CDC. 2016. National Health and Nutrition Examination Survey. U.S. Center for Disease Control and
Prevention. Available at: http://www.cdc.gov/nchs/nhanes/­
3. CaIEPA. 1999. Public Health Goal for Thallium in Drinking Water. Office of Environmental Health
Hazard Assessment (OEHHA). Available at:
http://oehha.ca.gov/media/downloads/pesticides/report/thaIf 1.pdf
4. CalEPA. 2004. Update of Public Health Goal (PHG)-Thallium. Office of Environmental Health Hazard
Assessment (OEHHA). Available at:
http://oehha.ca.gov/media/downloads/pesticides/report/thallll04.pdf
5. Canadian Council of Ministers of the Environment. 1999. Canadian soil quality guidelines for the
protection of environmental and human health: Thallium (1999). In: Canadian environmental quality
guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg. Available at:
http://cegg-rcqe.ccme.ca/download/en/215
6. ECHA. 2016. ECHA Portal for Registration, Evaluation and Authorisation of Chemicals (REACH)
Registered Substances. European Chemicals Agency (ECHA). Available from:
http://echa.europa.eu/information-on-chemicals/registered-substances
November 2016 8 �%RICH

Thallium Toxicity Value Review
7. OEHHA. 1999. Public Health Goal for thallium in drinking water. Office of Environmental Health
Hazard Assessment, Berkeley and Sacramento, CA. Accessible at
http://www.oehha.ca.gov/water/phg/index.html
8. NTP. 2016a. NTP Board of Scientific Counselors Meeting. Webinar presentation. Thallium
Compounds. June 15. See: http://ntp.niehs.nih.gov/about/org/bsc/meetings/past/index.htmi
9. NTP. 2016b. Draft NTP Board of Scientific Counselors Meeting. NTP Research Concept: Thallium
Compounds. June 15-16. Available at:
http://ntp.niehs.nih.gov/ntp/about ntp/bsc/2016/iune/meeting%20materials/thallium-
compounds 508.pdf
10. USEPA. 2009. Toxicological Review of Thallium and Compounds -In Support of Summary
Information on the Integrated Risk Information System (IRIS). September. Available at:
https://cfpub.epa.gov/ncea/iris/iris documents/documents/toxreviews/1012tr.pdf
11. USEPA. 2012a. Final Provisional Peer Reviewed Toxicity Values for Thallium and Compounds.
Superfund Health Risk Technical Support Center, National Center for Environmental Assessment,
Office of Research and Development, US Environmental Protection Agency, Cincinnati, OH.
Available at: https://hhpprtv.ornl.gov/issue papers/ThalliumSolubleSalts.pdf
12. USEPA. 2012b. USEPA 2012 Edition of the Drinking Water Standards and Health Advisories, Spring
2012. U.S. Environmental Protection Agency. Available at:
http://rais.ornl.gov/documents/2012 drinking water.pdf
13. USEPA. 2014. Human Health Evaluation Manual, Supplemental Guidance: Update of Standard
Default Exposure Factors. OSWER 9200.1-120. February 6, 2011. U.S. Environmental Protection
Agency. Available at: http://nepis.epa.gov/Exe/ZyPDF.cgi/P100NQNA.PDF?Docker=P100NQNA.PDF
14. USEPA. 2015. Human Health Ambient Water Quality Criteria. U.S. Environmental Protection
Agency. Available at: https://www.epa.gov/wgc/national-recommended-water-quality-criteria-
human-health-criteria-table
15. WHO. 1996. Thallium. Environmental Health Criteria 182. World Health Organization. Available
at: http://www.inchem.org/documents/ehc/ehc/ehcl82.htm
November 2016 9 '!kRICH

Attachment 2
Updated Flow Diagram

Emergency
Overflow
002C
Optional
Rogers, Energy Complex Simplified, .
Holding Basin
Process Flow Diagram` Post Outf_,all,005
External
Coal Pile
Temporary
Operation .
Dewatering
Runoff
1:0 MGD,
0.05 MGD
Gypsum Pile
1 10
'Overflow'
-- — -
Runoff.
. Overflows'
'002B
Broad River
Intake Screen
I
Optional
Backwash ;
Limestone
Holding Cell
Pile Runoff
0.03 MGD
Unit 5 Storm/
Unit
6 Cooling
RO Reject '
Unit 6 Sanitary
Process Water_
Tower
Auxiliary
—
Blowdown
0.2 MGD
Basin .
Unit 6 Storm
Unit 6/FGD
Water
0.15 MGD
,Raw Water
Sanitary System
'Tanks
1.5 MGD
0.0015 MGD
Unit 6 Mechanical 0.35 MGD
Unit 6 Process
Drag Chain
3.15 MGD
External
Sump.
Firia_I WWT_S
Overflow
Outfall 005
.
0.3 MGD
6;0 MGD
Raw Water
Unit 6,Plant
Landfill Leachate
Treatment,
Drains
Exchangers"
::::
Cooling
Internal
Water
FGDWWTS
Outfall 004
FGD
M
Unit 5 Plant
Drains
MGDS
stemUnit
5 Mechanical
Drag ChainL#101.0021
Overflow
0.95 MGD
Unit 5 Cooling
Tower
Unit
5 Process
Blowdown . 1.5 MGD
Sump
Unit
5 Fly Ash
Silo Sump ,
Emergency
Overflow
002C
ble 2.5 MGD
Users
Optional
Holding Basin
External
Decanting and
Temporary
Outfall 002
Dewatering
WWTS
1:0 MGD,
0.05 MGD
Emergency
1 10
'Overflow'
-- — -
- -� -
. Overflows'
'002B
I
Optional
Holding Cell
0.0035 MGD
Unit 6 Sanitary
Auxiliary
Potable
System
0.2 MGD
Basin .
Water Users
Unit 6/FGD
0.15 MGD
Sanitary System
0.0015 MGD
3.15 MGD
External
Firia_I WWT_S
Outfall 005
6;0 MGD
1.0 MGD
0.8 MGD
Heat
Exchangers"
::::
Internal
FGDWWTS
Outfall 004
IN
M
0.2 MGD
ble 2.5 MGD
Users
Optional
Ash Basin
External
Decanting and
Temporary
Outfall 002
Dewatering
WWTS
1:0 MGD,
0.05 MGD
_-_'.Legend._
1 10
Process Flows ,
-- — -
- -� -
. Overflows'

Attachment 3
Additional Comments

Rogers Energy Complex
Additional Comments on Draft NPDES Permit
Page
Comment
3
The maximum Total Suspended Solids limit should be 100 mg/I since
the treatment system is designed, constructed, and operated to treat
the volume of coal pile runoff associated with a 10 year, 24 hour
rainfall. This is based on the Steam Electric Effluent Guidelines (40 CFR
§423.12(b)(10)).
3
Fecal coliform and BOD are included with limits. The ponds are open to
geese and the potential exists that fecal coliform and/or BOD could be
generated from natural outside conditions. It is requested that it be
noted that it is permitted to discharge the fecal coliform and/or BOD if
due to natural outside wildlife.
3
It is requested that Chronic toxicity testing be quarterly instead of
monthly based on the longterm compliance record of toxicity testing
showing the effluent passing the chronic toxicity standard
4
Item 10 should be revised to quarterly based on the good long term
compliance record for toxicity testing.
4
The last sentence should have the date of November 1, 2018 changed
to December 31, 2020.
5
The first and fifth sentences should include that the three feet above
ash level is measured "at the pump intake".
5
Delete the third sentence. Flexibility is needed in the pumping
operation.
5
The fourth sentence should only apply to dewatering. Treatment
during decanting should already be sufficient by the current treatment
systems. If not then treatment adjustments will be made.
6
The first listing for Chromium and Zinc are duplicated. It appears that
these should be replaced with Copper and Iron.
7
Items 4 and 7 apply only for in -process operations.
7
Eight sentence change fly to bottom and change the date to December
31, 2020.
7
Delete tenth sentence.
7
Last sentence should apply only to dewatering.
Page 1 of 2

Rogers Energy Complex
Additional Comments on Draft NPDES Permit
Continued
Page
Comment
9
The maximum Total Suspended Solids limit should be 100 mg/I since the
treatment system is designed, constructed, and operated to treat the
volume of coal pile runoff associated with a 10 year, 24 hour. This is
based on the Steam Electric Effluent Guidelines (40 CFR §423.12(b)(10)).
10
Clarification is requested on monitoring requirements prior to
December 31, 2023.
10
Since this is an internal outfall EPA guidance is that pH limits are not
required. Please delete the limits for pH.
11
It is requested that all sample types listed as composite be revised to
grab.
13
Limits on sulfates should be eliminated since sulfates do not exceed the
reasonable potential analysis.
31
In the second paragraph monthly should be changed to quarterly.
32
In the second paragraph monthly should be changed to quarterly.
34
Outfalls 002 B and C are not likely to discharge. It is requested that the
last three sentences be revised to just require an annual sample if a
discharge does occur.
36
Item A.(37) remove "and overflow from the settling basin". The settling
basin no longer exists.
37
The actual intake flow (AIF) for REC is less than 125 million gallons per
day (MGD), therefore, no biological study plans or biological study
results will be prepared. Duke plans to submit information required in
40 C.F.R 122.21 (r)(2)-(8). We request the deletion of study plans and
study results from A.(44.) CWA 316(b) Requirements.
43
Outfall 113 is not noted. Please include.
Page 2 of 2