NC0003425_EPA Comments_20160916

Comments from EPA on Roxboro:
September 16, 2016 email:
1. The permit should clearly state the sampling locations for all internal and external
outfalls. For instance, there is no sampling location mentioned for outfall
001. Also, for outfall 003, the permit refers to a map, but you cannot tell from the
map the exact sample location.
Response: The map has the latitude and longitude for sampling locations for
outfalls 003, 006 and 001 which are the discharges to surface waters. The
internal outfalls are not shown on the map, All the internal outfalls include a
footnote requiring that the effluent sampling must be conducted prior to mixing
with other waste streams.
2. 1 recommend the permit list all the wastewaters that contribute to the outfall 006.
Because one of the waste streams is truck wheel wash, I recommend an oil and
grease limit or monitoring requirements for this outfall.
Response: The permit was modified to include descriptions of all wastewaters.
Oil & grease limits of 15 mg/I monthly average and 20 mg/I daily maximum were
added to outfall 006.
3. Please clarify where the emergency overflow for the FGD treatment system
goes; the fact sheet lists FGD emergency overflow as a waste stream. Is the
emergency flow all collected and eventually treated in the bioreactor, or
does some of it end up in the ash pond? If any FGD wastewater bypasses
treatment and is sent directly to the ash pond, the outfall for the ash pond should
include the EG for FGD wastewaters.
Response: No discharge of emergency overflow from untreated FGD blowdown
will be allowed.
4. The permit allows Duke until November 1, 2018, to meet the new effluent
guidelines for fly ash and bottom ash sluice wastewaters (i.e., no discharge). Can
you clarify if they are already doing dry ash handling for fly ash? The fact sheet
suggests that they are. If so, then why is the extension to 2018?
Response: A. (2) and A.(3) were modified to include the following footnote: There
shall be no discharge of pollutants in fly ash transport waters to the ash basin.
5. The permit is not specific regarding identification of new seeps. Other Duke
permits referenced a Seep Identification Plan, which EPA has commented should
be attached to the permit.
Response: Final permit copy will include a copy of the plan.

6. Internal outfall 008 only requires annual reporting for both the existing flowrate
and the expansion to 0.025 MGD. I recommend at least monitoring quarterly for
one year after the expansion then reducing the monitoring to annually.
Response: Condition A.(8) was modified to require quarterly sampling for a year,
then annual samples thereafter.
7. The is a typo in the table for outfall 010. For arsenic, the sample type is
misspelled
Response: Typo corrected
October 12, 2016 email:
The permit application dated September 27, 2001, identified and included Form
2C data for two external outfalls to Hyco Reservoir. An updated 2C data was
submitted from Duke to NC DNR via a letter dated August 12, 2016. Page 2 of
the permit implies that 001 also has a direct discharge to Hyco Reservoir. We
recommend page 2 be modified to correctly identify outfall 001 has an internal
outfall that discharge via Outfall 003 hence to Hyco Reservoir.
Response: Outfall 001 is an external outfall. This outfall used to be the discharge
of the retired ash pond in previous permits, Various seeps were identified that
discharge through this outfall, stormwater runoff also is captured at this outfall.
The outfall consists of a culvert at the intake canal near the gypsum pile. The
location is identified with latitude/longitude in the permit map.
2. The description of the wastewater contributing to internal outfall 001 should be
correctly identified on page 4. The updated flow schematic indicates that internal
Outfall 001 receives storm water from the east ash basin, discharges from "areas
of wetness" (AOW), discharges from seepages, and incidental gypsum and rail
runoff. Duke's letter to NC dated August 15, 2016, stated that the discharges
from the AOW are from the following seeps: S1, S2, S3, S4, S5, S6, S7, S8, S14,
S18 and S19. Most, not all, of these seeps were previously identified and
sampled by Duke and are included in Duke's Topographic Map and Discharge
Assessment Plan dated April 29, 2014.
Response: duke updated the seeps map on October 2014 to include seeps S8,
S9, S10 and S11 which discharge through outfall 001.
3. Please provide an explanation of how the AOW (i.e., seeps) are captured and
conveyed to internal Outfall 001.
Response: Outfall 001 used to be a permitted outfall for the discharge of the
closed ash basin. Seeps flow into a channel that flows into the intake canal.
4. The permit application dated September 27, 2011, includes a Form 2C for storm

water outfalls SW -A and SW-B, which discharge to Hyco Reservoir. How are
these two outfall addressed in the permit?
Response: The stormwater outfalls will be covered by stormwater permit
NCS000581. The SW permit is in draft at the moment.
5. The sampling location for internal Outfall 001 should be more specific. We
recommend the permit state that sampling for internal outfall 001 be performed at
the nearest accessible point after treatment and prior to discharging into Outfall
003.
Response: Location latitude and longitude are shown in the permit map. Outfall
001 is not tributary to outfall 003, it discharges to Hyco Lake at the intake canal.
6. The updated flow schematic shows that all emergency overflows from the FGD
unit will be collected and routed back to either the lined ash pond (once it is
operational) or back to the bioreactor for treatment prior to being discharged to
Outfall 002. For clarity, we recommend the permit be revised to prohibit the
discharge of emergency overflows from the FGD unit.
Response: No discharge of emergency overflow from untreated FGD blowdown
will be allowed.
7. There was no RPA submitted for outfall 006, which is comprised of coal pile
runoff, limestone pile runoff, emergency gypsum stack, truck wheel wash, storm
water, and raw water tank drainage from maintenance operations. Due to the
nature of some of these discharges, we recommend NC submitted an RPA
based on more recent data than that in the September 2011 permit application.
Response: Copies of all the RPA were attached tot eh fact sheet. The Division
does not have more data for this outfall. A special condition was added to
request that the permittee submits Form 2C analysis within 180 days of the
permit effective date.
8. Based on information in Duke's August 15, 2016, letter to NC, the plant is already
uses a dry fly ash handling system; therefore, there is no need to allow them until
November 18, 2018, to come in compliance with the new steam electric effluent
guidelines for fly ash transport.
Response: A. (2) and A.(3) were modified to include the following footnote: There
shall be no discharge of pollutants in fly ash transport waters to the ash basin.
9. In its August 15, 2016, letter to NC, Duke stated that it plans to install a vapor
suppression system in 2016 at the anhydrous ammonia tank. In the event of an
emergency, this unit may release anhydrous ammonia to the retention

pond. This waste stream should be included in the description of outfall 003.
Response: The description of the wastewaters in the supplement to cover sheet
was clarified. Anhydrous ammonia emergency flows are discharged to the
discharge canal under the current configuration and will be discharged to the low
volume waste treatment system when the system is constructed.
10. EPA recognizes that NC followed its mixing zone policy to establish a thermal
mixing zone in the Hyco Reservoir. Typically, waterbodies with a 7Q10 of zero
cubic feet per second have no assimilative capacity. We recommend the permit
include a reopener in part A.17 that specifically states that NC will automatically
reopen the permit to include a temperature in the permit in the event that
instream monitoring indicates the water quality standard for temperature is not
being met at the point of discharge.
Response: The following footnote was added in in Condition A.(4): This permit
may be reopened to implement a temperature limit if the permittee is not in
compliance with Special Condition A. (18).
11. The RPA for Outfall 003 indicates that one sample was taken for instream
hardness and that the average background hardness is 99 mg/L. When and
where was this sample taken?
Response: Hardness data came from the biological monitoring report. All
reported values were above 100 mg/I.
12. The RPA for Outfall 003 indicates that data between 2010-2011 was used to
determine the appropriateness of limits for chlorides, copper, nickel, selenium,
thallium and strontium. Why wasn't more recent data used by NC? By contrast,
data from 2011-2016 was used in the RPA for arsenic.
Response: Data for chlorides, copper, nickel, selenium, thallium and strontium
was collected for a special study during 2010-2011. Data for the remaining
parameters was collected as per permit requirements.
13. How does the RPA addresses changes in the ash pond effluent during both
planned decanting and dewatering operations?
Response: Data was evaluated for the water above the ash and for the interstitial
water. This is an internal outfall so monitoring was implemented for parameters
of concern. An RPA is not applicable for this outfall.
14. For consistency with other permit conditions for decanting operations at other NC
Duke facilities, we recommend the following additional pollutants be added to
outfall 002 during decanting and dewatering operations: total iron, total cadmium,
total chromium, total dissolved solids, and total hardness.

Response: Since the ash basin is an internal outfall monitoring for most of the
parameters related to ash coal were applied at the final outfall to Hyco Lake.
Cadmium and iron were not detected in the samples for the ash basin water or
the interstitial water. Hardness and total dissolved solids will be monitored at the
discharge to the lake.