NCS000554_Buck Stormwater Inquiry Comments and Duke Responses_20160126

Station
NCDEQ Request
Duke Response
NCDEQ Comment
Duke Response to Comment
During our discussions at Buck I think we agreed to separately
Permit the facilities separately
No response necessary.
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process both in-house applications, one for the Steam Station, and
one for the CTCC station. Please confirm that at this time it is still
OK
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Duke's intent to permit both facilities separately for stormwater
discharges.
Immediately northeast of SW002 there appeared to be one or two
There are two additional outfalls that drain the parking lot area in the
No response necessary.
additional outfalls, apparently previously unidentified.
northwestern portion of the property (see Google Earth Image). Outfall SW078 is
a 12 -inch concrete pipe that discharges stormwater from one drain located in a
small concrete -lined ditch between the parking lot in the northwestern corner of
OK, these outfalls will be
the property and the switchyard. Outfall SW079 is a 4 -inch PVC pipe that
considered in the stormwater
discharges stormwater from one drain in the parking lot of the northwestern
permit draft.
corner of the property. Both of these lines appear to have some degree of
clogging. I have requested HDR add these outfalls to our map.
Along the river bank in the vicinity of outfall SW056, and continuing
Just west of the yard sump, outside of the station fence, there is a cluster of four
The HDPE pipe and steel pipe will
east to SW073 it was not clear that all outfalls have been positively
pipes along the bank within about ten feet of each other. Two of these pipes are
be included as outfalls as SW080
identified
SW056 and SW077; the other two were unknown at the time of NCDEQs visit.
and SW081, respectively. An
Moving from west to east, we would encounter SW077, SW056, -12-inch HDPE
Response indicates these may be
updated stormwater map will be
pipe, and then -12-inch steel pipe. In discussions with former plant personnel, it
abandoned, but no confirmation
provided once it is available. We
is believed that both the HDPE and steel pipes have been abandoned; however,
of this. If this is the case, please
intend to abandon these two
their origins could not be ascertained. During installation of the secondary
state it for us so we can remove
outfalls but do not know the
containment system (manholes) west of the yard sump, the steel pipe was
them from consideration for
timeline for abandonment.
severed and was not repaired. During my visit to the plant on 17 December 2015,
permitting. Otherwise, please
SW077 had water flowing through it, but neither the HDPE nor the steel pipe had
provide outfalls numbers for
any flow during the storm event. This leads me to believe that the two pipes are
inclusion in the permit.
indeed abandoned.
Please provide information on the size of the storm that would
I could not find a definitive answer to this question. It is thought that an overflow
Any overflow of the sump would
cause an overflow or bypass from the Yard Sump
of the yard sump would not occur during any storm event unless there is some
This one is a little confusing so we
discharge from NPDES wastewater
kind of failure in the pumping system. It is believed that the diversion structure
need some clarification on our
outfall 002A. Overflow of the
(installed in 2010 as a secondary containment measure) was designed to allow
understanding. Looking back at
diversion would discharge from
runoff in excess of a 2 -year storm event. This water would bypass the yard sump
the application information it
SW056; otherwise the flow goes to
and discharge through SW056.
appears that any overflow of the
the sump. The drainage area for
sump would actually discharge
the diversion is area 56. Duke
from NPDES Wastewater outfall
personnel have estimated that a 2-
002A. So the storm event for
year storm would allow overflow of
discharge is not an issue. For the
the diversion, however, no
Ediversion
discussed here for the 2-
specifications were found to
m
N
year storm, that only appears to
confirm this size storm.
3
be from drainage area 56.
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Anything smaller would actually
go to the sump and the ash basin
and larger events would discharge
from the stromwater outfall. Is
this correct?
You may want to assure that this
process is spelled out accurately in
the wastewater permit also for the
flows from area 56 going to the
ash pond.

Station
NCDEQ Request
Duke Response
NCDEQ Comment
Duke Response to Comment
Please refresh us on the status of the paired oil traps (north of the
The trap tanks originally drained straight to the river, but this was changed by the
The diversion mentioned in the
boat house) wrt any potential for discharges from them. Although
2010 secondary containment installation, which sends drainage to the yard sump
comment above is part of the 2010
we discussed them while visiting; I can't recall the comments made
and then to the ash basin. The structures inside the CT island perimeter road
secondary containment
about them
have been demolished except for a few buried utilities. We have preserved the
installation. So, flow from the oil
drainage loop around the outside of this perimeter road, and it continues to drain
traps flows past encounters this
to these trap tanks. We are working to begin remediation of oil -impacted soil
So no flow to stormwater, all to
diversion on its way to the sump.
over the entire old CT site, fuel unloading pad, and fuel oil storage tank area in
sump. OK
early 2016. With the fuel oil tank demolished, the CT equipment and structures
removed, the fuel oil lines removed already, and the surrounding soil remediated
in 2016, we believe that there will be little if any need for the trap tanks beyond
2016.
Please refresh me on the flow in SW002. My meeting notes seem to
From discussions with former plant personnel, I discovered that SW002 in the
Duke agrees.
indicate that Duke reports a dry weather flow in that outfall
past had dry weather flow. This was believed to be caused by a service water leak
The stormwater permit is written
that infiltrated the 5 and 6 switchyard. I visited the plant on 16 December 2015
for stormwater discharges only.
during a dry weather day and observed no water flowing from SW002. Since the
Duke will be required to certify
plant is no longer operational and dry weather flow was not observed at SW002,
outfalls as not having stormwater
the service water leak hypothesis may have been plausible.
flow.
It appeared that there may have been some recent changes to the
I believe the discrepancy involves two manholes located to the south of the
drainage features not reflected in the site maps we currently have in
cooling towers and at the base of the additional primary ash pond dam.
hand. The drainage features and contributing areas east of the
Investigative work was performed in this area in 2014 to assess the condition and
Admin/Control Building around the entrance gate and CB40 are
status of some unknown terracotta pipes that attached to both manholes. Stantec
unclear to us. In the same general vicinity there appeared to be an
noted that seepage was encountered but that the water was not coming from the
additional manhole south of the cooling towers not shown on our
direction of the dam. Plant personnel noted that during construction of the
drawings. Please provide expanded and updated drainage maps
cooling towers springs were encountered in the area. Only Manhole#1 can receive
that show the full extent of all site stormwater drainage
water since the receiving pipes of Manhole#2 have been sealed. Manhole#1 does
connect to the plant's stormwater system (see figure). According to CCP
Engineering the riprap ditch that runs in between Manhole#1 and Manhole#2 is
Pipes to Manhole #2 sealed, can
connected to the toe drain system and can therefore receive toe drain seepage
pipes to #1 be sealed also? This
(water still exists in the additional primary ash basin though it is about 10 feet
information indicates that there
below the surface of the ash). The riprap ditch moves water to the southwest until
may be toe drain flows in the ditch
it reaches a headwall at the plant's gate. Water then is directed underneath the
that goes to the stormwater
We need additional information on the pipe and drainage system
road to "CB40", which is part of the plant's stormwater drainage system. Both
pond? This is not stormwater and
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that carries drainage from around the ash basin into the catch basin
manholes were included in Buck's 2014 NPDES wastewater permit modification;
can't be permitted in this permit.
that then flows to the stormwater pond. Hs this been submitted in
we are currently compiling materials for Buck's NPDES wastewater permit
Should consider alternatives
the wastewater application? Can this flow be removed from the
renewal. Designs are being developed to collect and reroute any seepage if it is
noted in your response such as
stormwater drainage at the CT site?
determined to contain coal combustion residuals. For stormwaterjust outside of
collection and pump back to ash
the maingate and on the ash basin side of the road, water flows along the eastern
pond. We still need some
m
part of the entrance road and eventually through a culvert and past AOW 5-9. For
additional resolution on this issue.
stormwaterjust outside the maingate and on the plant side of the road, water
flows in the plant's perimeter ditch and eventually makes its way to the sediment
basin.
While on site there was some confusion as to the ultimate
Plant personnel have confirmed that the water discharge from the oil/water
No response necessary.
destination of the water discharge from the o/w separator
separator immediately south of the steam turbine building does not go to the
immediately south of the steam turbine building. Please confirm
stormwater drainage system.
OK
that that flow does/does not go to the stormwater drainage system.