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Home My WebLink AboutPresentation - AllenCOAL COMB USTION RESID UAL IMPO UNDMENT RISK CLASSIFICATIONS March 2016 Collaboration between: Division of Water Resources Division of Waste Management Division of Energy, Mineral and Land Resources Department of Environmental Quality COAL COMB USTION RESID UAL IMPO UNDMENT RISK CLASSIFICATIONS Background: • Under the historic Coal Ash Management Act (CAMA) of 2014, all coal ash impoundments in North Carolina are required to be closed. • The deadlines for closure depend on the classification of each impoundment as low, intermediate, or high. • CAMA required the Department of Environmental Quality (DEQ) to make available to the public a summary of the initial draft proposed classifications in December 2015, and a full report in January 2016. • These draft proposed classifications are based on the information available to the department as of December 2015 and are posted on the departments website, local library, and health department. Department of Environmental Quality 2 COAL COMB USTION RESID UAL IMPO UNDMENT RISK CLASSIFICATIONS After the release of the summary of the initial draft proposed classifications, CAMA requires the following process: • DEQ must make available a written declaration that is a detailed report explaining the technical and scientific background data and analyses behind the draft proposed classifications. • Publish a summary of the detailed report in the local newspapers. • Make the report available to the local health director and accessible at the local library. • A public meeting in each county with a coal ash facility. • Consider all public comments and develop final proposed classifications. Department of Environmental Quality 3 COAL COMB USTION RESID UAL IMPO UNDMENT RISK CLASSIFICATIONS Closure Deadlines • High risk impoundments: Dec. 31, 2019 • Closure plan due by Dec.31, 2016 • Intermediate risk impoundments: Dec. 31, 2024 • Closure plan due by Dec. 31, 2017 • Low risk impoundments: Dec. 31, 2029 • Closure plan due by Dec. 31, 2018 COAL COMB USTION RESID UAL IMPO UNDMENT RISK CLASSIFICATIONS Four of Duke's 14 facilities are designated as high-risk by the coal ash law. Under CAMA, the department is required to consider the following factors, at a minimum, in proposing classifications for the remaining 10 facilities: 1. Any hazards to public health, safety, or welfare. 2. Structural condition and hazard potential. 3. Consideration of surface 4. Consideration of groundwater. 5. The location and nature of all receptors. 6. All factors influencing the movement of contaminants. 7. Consideration of coal combustion residuals in the impoundment. 8. Position in 100 -year flood plain 9. Any other factor the department deems relevant to the establishment of risk. COAL COMBUSTION RESIDUAL IMPOUNDMENT RISK CLASSIFICATIONS The department incorporated all of the preceding criteria into three primary categories that were used to evaluate each impoundment: • Structural Integrity • Impact to Surface Water • Impact to Groundwater The draft classification process was iterative and occurred over a series of months. Recommendations regarding the impoundments were amended and updated as additional scientific and technical information was received, reviewed and verified. Department ofEnvironmental Quality I ALLEN STEAM STATION RISK CLASSIFICATION a-� ALLEN STEAM STATION RISK CLASSIFICATION Department of Environmental Quality 7 m rr"`' ALLEN STEAM STATION RISK CLASSIFICATION Overall Risk Classification DEQ has proposed the risk classification of both the Active Ash Basin and the Retired Ash Basin as LOW TO INTERMEDIATE. Groundwater Key Factor: Based on the information received to date, there appears to be no downgradient receptors located 1,500 feet downgradient of the impoundment compliance boundary. The following data gaps related to groundwater uncertainty include: • Incomplete capture zone modeling in fractured bedrock for upgradient and side -gradient supply wells in the immediate vicinity of the impoundments • Incomplete geochemical modeling • Incomplete background concentration determination (Data gaps are currently being addressed by Duke Energy and their findings will be presented to the DEQ in supplemental reports.) Department of Environmental Quality I ALLEN STEAM STATION RISK CLASSIFICATION Surface Water Key Factor. The impoundments are not located within the 100 -year floodplain. Landscape Position and Floodplain: • Active Ash Basin. LOW RISK. The CCR Impoundment is sited along the Catawba River/Lake Wylie, outside of the 100 -year floodplain. • Retired Ash Basin. LOW RISK. The CCR Impoundment is sited along the Catawba River/Lake Wylie, outside of the 100 -year floodplain. Department of Environmental Quality I *This figure depicts landscape positions in regards to the 100 -year flood level for the CCR impoundment (Active Ash Basin (GASTO-061) and Retired Ash Basin (GASTO-016)) for the Allen Steam Electric Plant. ALLEN STEAM STATION RISK CLASSIFICATION Dam Safety Factor. The impoundments that received a high risk rating based on structural deficiencies will receive a low risk rating once repairs are completed. State of Structural Stability and Maintenance: Active Ash Basin (GASTO-061). HIGH RISK before repairs are made. LOW RISK after repairs are made. This impoundment received a notice of deficiency with structural deficiencies. The following modifications/repairs to the dam have been submitted and should be completed, as a minimum: tree removal, slope remediation, grout pipe, and installation of a new spillway. Retired Ash Basin (GASTO-016). HIGH RISK before repairs are made. LOW RISK after repairs are made. This impoundment received a notice of deficiency with structural deficiencies. The following modifications/repairs to the dam have been submitted and should be completed, as a minimum: slope improvement, grading, replace sluice lines, grout pipe, and installation of a new spillway. Department of Environmental Quality 10 ALLEN STEAM STATION RISK CLASSIFICATION We will now receive public comments To view additional information please visit www.deg.nc.gov The public comment period will close on April 18, 2016 You may submit comments three ways, all weighted equally: • Here orally and/or in writing • Email to allencomments@ncdenr.gov • Postal mail to: N.C. Division of Waste Management, Solid Waste Section, N.C. Department of Environmental Quality, Attn: Ed Mussler, 1646 Mail Service Center, Raleigh, NC 27699-1611 Department of Environmental Quality