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Home My WebLink About20120615 Ver 2_More Info Received_20181128(� DUKE ENERGY Nov. 21, 2018 Ms. Karen Higgins Supervisor, 401 & Buffer Permitting Branch North Carolina Division of Water Resources 1617 Mail Service Center Raleigh, North Carolina 27699-1617 RE: Response to Request for Additional Information Duke Energy Mayo Coal Combustion Product Monofill Roxboro, NC Lined Retention Basin Project DWR # 12-0615v2 Dear Ms. Higgins: 410 S Wilmington St. Raleigh NC 27601 D P.()V 2 2018 ATE RE§0_U_RZTS 1 101 & BUFFER PERMITTING Duke Energy in consultation with AMEC Environment & Infrastructure, Inc. (AMEC) recently submitted an Individual Permit application (IP) to your office for modification of U.S. Army Corps of Engineers (USACE) Mayo Coal Combustion Monofill Site Individual Permit SAW - 2011 -00181 for the above -referenced project. Mr. Paul Wcjoski responded on October 23, 2018 with an email to Duke Energy, stating that DWR had reviewed the information in the permit application and attached plans, but needed additional information/revision before the application would be considered complete. DWR provided five bulleted comments/queries in the email correspondence. These comments are repeated below and are accompanied by a response. Comment No. 1 Please copy the Division on your response to the Corps regarding the issues raised in the comment period. Response The Division of Water Resources will be copied on the response to the US Army Corps of Engineers request for additional information. The request for additional information from the US Army Corps of Engineers is required to be submitted by November 30, 2018. Comment No. 2 The original 401 Water Quality Certificate issued by the Division on July 27, 2012 (2012- 0615v1) required a Division of Waste Management (DWM) approved Surface Water Monitoring Plan to be submitted. Please clarify whether this monitoring plan been modified since being published in October 2011 and whether the plan is currently in compliance with DWM. Also clarify whether the plan will be updated and submitted to DWM for approval as part of the permitting of the Lined Retention Basin construction. Response The lined retention basin project is not part not part of the Mayo Coal Combustion Product Monofill Site permitted by DWM. The lined retention basin is a wastewater treatment facility located across US 151501 in the vicinity of the Mayo Station. The purpose of the lined retention basin is to receive wastewater from the plant processes that are currently sent to the ash basin for treatment. The lined retention basin is needed in order to facilitate closure of the ash basin. The permitting avenue chosen by the Corps to move forward with permits for impacts from the lined retention basin project, was the active Mayo Coal Combustion Monofill Individual Permit. The plans for the Monofill will not be modified or updated and sent to DWM as part of this project. Comment No. 3 The 401 Water Quality Certification (WQC) issued by the Division on July 27, 2012 (2012- 0615v1) approved the construction of the Coal Combustion Product (CCP) Monofill area (impacting 2,074 LF of stream features) and conceptually approved the construction of "future phases" of the Monofill area (impacting 2,659 LF of stream features). It's the Division's understanding that these future phases have not been constructed and currently the CCP Monofill area is still within the bounds of the area authorized in Phase I; please confirm this is correct. Also provide a narrative explaining the intention of the future phases of this Monofill area, including whether the proposed future phases to expand the current active area are still needed. Finally, explain why a different location was selected for the Lined Retention Basin (LRB) rather than the area conceptually authorized that is adjacent to the active CCP Monofill area. Response The Mayo Monofill Coal Combustion Landfill is currently within the bounds of Phase I. At this time, the total 104 acres at the Mayo Steam Electric Plant approved by NCDEQ as Site Suitable for Industrial Landfill development remains reserved for future plant production coal combustion residual disposal. Additional future acreage around the waste unit is also required for ancillary operating facilities such as storm water ponds, maintenance buildings, and leachate management. The lined retention basin is not part of solid waste disposal at the monofill, it is part of the site's wastewater treatment system, and as such is located near the operating plant's wastewater discharges. Continent No. 4 Clarify when the construction of the LRB commenced and that this application is seeking after- the -fact approval for some impacts. Amend Table 5 under Section 6.1 EXTENT OF IMPACTS to clarify which proposed impacts are after -the -fact. Response Please see the amended table 5 attached to the this response. Comment No. 5 Plans provided in the application discuss the future need to construct a Flue Gas Desulfurization settling basin and a Holding Basin, but specifics of construction aren't included. Do you anticipate a future modification of this authorization to include these components? Please include a cumulative impacts narrative about anticipated water resources impacts so DWR ca evaluate the project as a whole. Response These Flue Gas Desulfurization setting basin and the holding basin will contain coal combustion residuals (CCR's), the Division of Waste Management is aware of their construction and has required groundwater monitoring wells to be installed in the area of construction to collect background groundwater data. No 404/401 impacts are expected with the construction of these basins. Please do not hesitate to contact me if you have any questions regarding the above responses to your request for additional information. Respectfully, Steve Cahoon Lead Environmental Specialist Duke Energy CCP Permitting and Compliance Enclosure Duke Energy Mayo CCP Monofill Site Lined Retention Basin & Ash Basin Closure Section 404/401 Individual Permit Modification Project No. 7812180019 wood. 6.0 PROPOSED IMPACTS TO WATERS OF THE UNITED STATES 6.1 EXTENT OF IMPACTS Wetlands D, E and MMM, and Streams 5 and 6 occurred within the LRB Project area and have been impacted by the LRB construction. Wetlands B, C, F, G, H, UU, ZZ, JJJ, and LLL, and Streams 1, 2, 3, 9, and 10, occur within the Ash Basin Closure Project area. Wetlands UU and ZZ will be affected by the implementation of the ash basin closure operations. Impacts to waters of the US from the implementation of the LRB construction and ash basin closure operations are classified herein as permanent. The impacts to Wetlands D, E, MMM, Streams 5 and 6 were due to filling these features during the LRB construction. The impacts to Wetlands UU and ZZ may be due to excavating and fillings these features during ash removal as part of the ash basin closure. Table 5 presents acreage and linear foot values of the proposed impacts to jurisdictional wetlands and streams within the Project areas. The Plan View and Cross-section drawings of the LRB and Ash Basin Closure, including the work areas where the impacts to waters of the US will occur, are provided in Appendix A. Table 5. Proposed impacts to jurisdictional wetlands and streams for the LRB and Ash Basin Closure Projects, Mayo Plant, Person County, North Carolina. Resource Type Impacts Wetlands (acres) NCWAM Overall Rating Streams (linear feet) NCSAM Overall Rating LRB After -the -Fact Permit Project Impacts Wetland D 0.11* Medium - - Wetland E 0.6* Low - - Wetland MMM 0.16* Medium - - Stream 5 - - 132* Medium Stream 6 - - 95* Medium Proposed Ash Basin Closure Project Impacts Wetland UU 0.02 Low - - Wetland ZZ 0.26 Medium - - Total 1.15 227 *impacts have occurred due to the LRB construction and being proposed as after -the -fact impacts in this permit modification. 6.2 CUMULATIVE IMPACTS The USACE is required to determine both potential short-term and long-term effects of a proposed discharge of dredge and fill material on the physical, chemical, and biological components of an aquatic environment, including the effects of cumulative impacts. A review of potential cumulative impacts to waters of the US because of the construction of the LRB and the 6-1 Duke Energy Mayo CCP Monofill Site Lined Retention Basin & Ash Basin Closure Section 404/401 Individual Permit Modification wood. Project No. 7812180019 implementation of the Ash Basin Closure operations indicates that the proposed discharge would have no significant adverse effects on the aquatic ecosystem. The rationale for this presumption is based on the following considerations: No contact water (i.e., water containing CCR materials) will be discharged into waters of the US (wetlands and streams); therefore, the water quality of downstream receiving waters, specifically Mayo Lake, will not be impaired. The proposed impacts to the waters of the US from the LRB construction and implementation of ash basin closure activities should have no cumulative effect on the quality of other jurisdictional waters occurring within the Mayo Plant or beyond the station property. This presumption is based on the review of environmental documentation regarding known current and past federal and non-federal actions at the steam station. Projects in the planning phase were also considered, including reasonably foreseeable (rather than speculative) actions that have the potential to interact with the proposed action. To have reasonable assurances that there would be cumulative effects to projects when considered together or incrementally, the projects need to occur within similar time frames and within a geographic area coinciding with the proposed action. 6-2