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HomeMy WebLinkAboutNCS000554_Buck Stormwater Inquiry Comments and Duke Responses_20160126Station 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. m 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 t� 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. m 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 o 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.