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Home My WebLink AboutNCS000572 Minor Modification Request_20200731,,& DUKE r. ENERGY. July 30, 2020 Annette Lucas NCDEMLR Stormwater Program 1612 Mail Service Center Raleigh, NC 27699-1612 Subject: Duke Energy Carolinas, LLC Dan River Combined Cycle Station NPDES Stormwater Permit NCS000572 Permit Minor Modification Request Dear Ms. Lucas: Dan River Combined Cycle Duke Energy Carolinas 864 South Edgewood Road Eden, NC 27288 Duke Energy Carolinas, LLC (Duke Energy) hereby requests modification of the subject NPDES permit to make the following changes: With the completion of the final site grading and landfill closure, stormwater flow from the north eastern corner of the combined cycle station will be returned to the Dan River via stormwater outfall SW002. This drainage area is 33.3 acres and includes the northern 213 of the cooling tower, the two chiller buildings, the chiller PDC, and the 1000 gallon diesel and 500 gallon kerosene storage tanks and their associated tanker unloading area. A portion of SW009's drainage which includes an oil storage building will be captured in this drainage area. The oil storage building is an enclosed building with built in containment. The Stormwater will discharge through a 48-inch RCP culvert under Edgewood Road into a riprap channel which discharges to the Dan River. Duke Energy requests the sampling location for outfall SWO02 be identified as the discharge from the culvert on the river side of Edgewood Road. It is Duke Energy's understanding the sampling requirements for this outfall will be Table 5 - Analytical Monitoring Parameters SWO09 and that the PCB monitoring requirement ha-� been met with the historical sampling of SWO09 The drainage area for SWO09 will decrease to 12.6 acres. This area does not have associated industrial activity. Duke Energy requested removal of this outfall in the permit renewal. It is Duke Energy's understanding that SWO09 will remain in the permit with the minor modification and .sampled per Table 5 — Analytical Monitoring Parameters SWO09 until the current permit is renewed. The PCB monitoring requirement has been met with the historical sampling of SW009. The drainage area SW010 is approximately 72.4 acres. The berm that separates the wetlands from the stormwater collection pond will be removed and flow will be allowed to gravity flow to the Dan River. The stormwater will discharge through a 36- inch RCP culvert under the landfill access road into a wetland prior to discharge to a riprap channel which discharges to the Dan River. Duke Energy requests the sampling location for outfall SWO10 be identified as the discharge from the culvert on the wetland side of the landfill access road. It is Duke Energy's understanding the sampling requirements for this outfall will be Table 6 - Analytical Monitoring Parameters SWO10. The PCB monitoring requirement has been met with the historical sampling of SW010. 4. The modification for this stormwater permit will be issued during the middle of a semi- annual sampling period. Current stormwater outfalls SW001, SW009, and SWO10 maybe sampled prior to the issuance of this modification. If sampling occurs prior to the issuance of the modification, the site requests that only resampling of outfalls SWO02 and SWO10 be required due to the changes in the drainage areas of these two outfalls. �. A link to The Duke Energy Dan River Coal Combustion Residuals (CCR) Visual Removal Verification Report was sent to your attention via email on 7/27/2020. 6. An updated drainage area map is attached that identifies the new drainage areas and outfall locations post final grading — Figure 1 — Stormwater Drainage Map — Final Site Grading. 7. The closure of the landfill and final grading is projected to be complete October I". There may be a transition period for each outfall requiring opening of outfalls in sequence. The original stormwater permit outlined future outfalls that were constructed as the project progressed. Duke Energy requests that the permit, if possible, be worded to allow opening of outfalls as they are completed. Should you have any questions or need additional information please feel free to contact Joyce Dishmon at 336-623-0238. Sincerely, Terry Tuck GM II - Regulated Stations Dan River Combined Cycle Power Generating Carolinas East Attachments Stormwater Drainage Map — Final Site Grading. 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