7305_DukeMayo_Update 7305-INDUS 2019-03-08

2500 Fairfax Road Greensboro, NC 27407

336-215-4576

Mayo Landfill Leachate Release Update Page 1 of 3
March 8, 2019 North Carolina Department of Environmental Quality
Division of Waste Management Solid Waste Section
1646 Mail Service Center
Raleigh, North Carolina 27699
Attn: Ms. Shawn McKee (submitted electronically)
Re: Mayo Industrial Solid Waste Landfill
Landfill Leachate Release Update Permit No. 7305-INDUS Mayo Steam Electric Plant
10660 Boston Road Roxboro, North Carolina 27574
Dear Ms. McKee: On 1/25/2019 a release of landfill leachate (release) occurred at the Duke Energy Progress (Duke Energy)
Mayo Steam Electric Plant (Mayo) Industrial Landfill (Landfill), North Carolina Division of Environmental Quality (NCDEQ) Division of Waste Management, Solid Waste Section (SWS) Permit
Number 7305-INDUS. The contents of this letter are presented to inform NCDEQ of the measures Duke
has put in place and/or working to implement at Mayo and across the Duke North Carolina fleet of Industrial Landfills.

The leachate release occurred at a location referred to as Cleanout 2 (CO-2). While not an identical occurrence, there was a release at this location on 6/29/2017. The cause of that release was determined
to be a failed gasket at a CO-2 bolted connection. Similar steps described in this letter took place after the 6/29/2017 release resulting in improvements to many components of the Leachate Collection System (LCS) including installation of a vault at CO-2 to contain bolted joints in addition to new HDPE piping of
all components leading to, and inside of, that vault. The 1/25/2019 release occurred inside of the CO-2 vault at a weld on the new piping which began operation in December of 2018. While similar in nature, the two releases were not on the same pipe nor similar structural component.
Engineering operational and administrative risk mitigation controls are in place at landfills including leachate collection systems (LCS). across the Duke fleet to mitigate the occurrence or impact of a system
malfunction. Duke has an internal process to investigate any failure of engineered controls at the local level in addition to review of similar components across the fleet to define improvements to existing, or
addition of new, risk mitigation controls where necessary.
Internal actions implemented immediately following the 1/25/2019 release include but were not limited
to:
• the portion of the leachate force main running from the leachate transfer station to the Flue Gas; Desulfurization (FGD) Pond and fly ash conditioning system was removed from service;
• field measurements implemented to capture released landfill leachate;
• immediate chloride analysis to validate the release material was indeed leachate;

Mayo Landfill Leachate Release Update Page 2 of 3
• reporting to NCDEQ SWS and Division of Water Resources;
• hauling of all leachate offsite for disposal by third party vendor;
• Press Release issued to the Person County news source;
• notification to Duke Energy Coal Combustion Product team about the event in order to have them
assess against conditions present at other Duke Energy landfills;
• entered the event into PlantView (internal, primary repository for daily observations of lessons learned, good catches, environmental events, and assignment of follow up actions);
• sampling of surface water and soil for full Water Quality Monitoring Plan constituents;
• Apparent Cause Evaluation (ACE) began the day after the release;
• Performance Improvement Oversight Committee (POIC) consisting of managers and directors,
reviewing evaluations;
• inspection of the Landfill and Leachate Collection System (LCS) by SWS;
• altered operation of the landfill LCS from the waste sump area to the leachate tank farm to
implement operation only when workers are present to inspect critical locations of the force main; and
• detailed visual inspection, evaluation, and engineering plan review of landfill LCS at Allen Steam
Station, Belews Creek Steam Station, Dan River Steam Station, Marshall Steam Station, Mayo Electric Plant, Rogers Steam Station, Roxboro Electric Steam Station, and Sutton Facility.

Mayo Landfill engineering operational and administrative risk mitigation controls implemented, or are in the process of being implemented, following the detailed inspection, evaluation, engineering plan review,
and project record documents of the Mayo Landfill LCS include but are not limited to:
• replacement or re-weld of 46 locations welded on the 2017-2018 force main improvement project;
• leak testing of LCS vaults; and
• implementation of leak detection on LCS vaults.
Following detailed inspections, evaluations, and engineering plan reviews of the eight landfills noted above, Duke Energy implemented, or is in the process of implementing, engineering operational and administrative risk mitigation controls, that include but are not limited to:
• revision of:
o Landfill Development Standard
o Operations and Maintenance (O&M) Maintenance Manual
o Environmental Containment Guidance
o Best Management Practice for vaults (leak testing and installation of drains in the lids to prevent rainwater intrusion)
• hydrostatic testing of vaults following installation/repair; potential for periodic vault testing;
• engineering barriers for leak detection on vaults with potential of release to the environment (float
switch, alarm system, leak identification, pressure gage, etc.);
• evaluation of Project Management (PM) program
o identify project scopes that can be performed by System Owners (SOs) vs Project
Manager
o require daily integration and weekly coordination meetings
o assess knowledge of PM staff
o utilize Implementation Manager with appropriate knowledge/experience or provide training
• SOs trained on HDPE butt fusion and Quality Control and Oversight (QC&O) weld procedure,
• evaluation of the method for verifying and validating supplied materials (meet ASTM
specification, extrusion weld process, potential destructive tests for shop fabricated welds);
• implementation of welding procedure for all HDPE projects (CCP-ENGSTD-NA-QA-004 Rev 1)
which includes:

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o ASTM 3101
o verify structural integrity of leachate force main welds with data logger rather than
pressure test
o require technical specifications of prefabricated material
• sampling and analysis program developed for Landfill Leachate Release (LLR) including
requirements for surface water and soil sampling including expectations for sampling material and bottle ware that should be stocked at active plants;
• defined oversight hold points throughout welding projects as a part of Construction Quality Assurance (CQA);
• QC&O Independent Audit (effectiveness of PFMA to make sure the program includes lessons
learned);
• implement consistent Visual Inspection Guidance to include:
o frequency of inspections
o expectations
o documentation
• establish Back Up Power Plans as needed based on risk of an extended power outage,
• revise programmatic Potential Failure Mode Analysis (PFMA) to include review when large retrofits or new leachate collection systems are placed in service; and
• visual inspection and overview of all landfill LCS components at the eight Duke Energy CCR
landfills with NCDEQ SWS.
If you have questions regarding the information presented in this letter, do not hesitate to contact me or
Ed Sullivan at: Kimberlee Witt
[phone]
[e-mail]
Ed Sullivan
[phone]
[e-mail].
Sincerely,

Kimberlee Witt, PE, ME Environmental Services
Cc: Ed Mussler - NCDEQ SWS Larry Frost - NCDEQ SWS
Ben Jackson - NCDEQ SWS
Ed Sullivan - Duke Energy Tom Copolo - Duke Energy
Tim Hill - Duke Energy
Leanne Wilson - Duke Energy