Annual Inspection Report North CCR Surface Impoundment. MidAmerican Energy Company, Walter Scott Energy Center

Transcription

1 Annual Inspection Report North CCR Surface Impoundment MidAmerican Energy Company, Walter Scott Energy Center Rev 0 July 2018

2 Annual Inspection Report North CCR Surface Impoundment Prepared for MidAmerican Energy Company, Walter Scott Energy Center Council Bluffs, Iowa July 2018 Prepared by Burns & McDonnell Engineering Company, Inc. Kansas City, Missouri COPYRIGHT 2018 BURNS & McDONNELL ENGINEERING COMPANY, INC.

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4 Annual Inspection Report North CCR Surface Impoundment Table of Contents TABLE OF CONTENTS Page No. 1.0 SUMMARY OF OBJECTIVES RESULTS OF INSPECTION Description of Impoundment Review of Existing Information Approximate Volumes in Impoundment Instrumentation Changes in Impoundment RECOMMENDED REMEDIAL ACTION LIMITATIONS OF REPORT IMPOUNDMENT INSPECTION CHECKLIST PHOTOS FROM INSPECTION MidAmerican Energy Company TOC-1 Burns & McDonnell

5 Annual Inspection Report North CCR Surface Impoundment List of Abbreviations LIST OF ABBREVIATIONS Abbreviation CCR EPA MEC WSEC RCRA U.S.C. Term/Phrase/Name Coal Combustion Residual Environmental Protection Agency MidAmerican Energy Company Walter Scott Energy Center Resource Conservation and Recovery Act United States Code MidAmerican Energy Company i Burns & McDonnell

6 Annual Inspection Report North CCR Surface Impoundment Summary of Objectives 1.0 SUMMARY OF OBJECTIVES On April 17, 2015, the Environmental Protection Agency (EPA) issued the final version of the Federal Coal Combustion Residual (CCR) Rule to regulate the disposal of coal combustion residual materials generated at coal-fired units. The rule is administered as part of the Resource Conservation and Recovery Act [RCRA, 42 United States Code (U.S.C.) 6901 et seq.], using the Subtitle D approach. MidAmerican Energy Company (MEC) is subject to the CCR Rule and therefore must have a Professional Engineer conduct an annual inspection on all CCR impoundments in accordance with 40 CFR Section Burns & McDonnell conducted the 2018 annual inspection of the Walter Scott Energy Center (WSEC) North CCR Surface Impoundment (Impoundment) on June 14, 2018, on behalf of MEC. This report contains the results and observations of the inspection, as well as any recommended remedial actions. MidAmerican Energy Company 1-1 Burns & McDonnell

7 Annual Inspection Report North CCR Surface Impoundment Results of Inspection 2.0 RESULTS OF INSPECTION The main objective of the annual inspection was to examine the Impoundment to determine any possible distress or malfunction of the design, construction, operation or maintenance of the Impoundment. A visual inspection of the Impoundment was conducted and included examining the toe, crest, slopes, and other features for any signs of distress or deficient operation of the Impoundment. The observations made from the visual inspections are provided below. 2.1 Description of Impoundment The WSEC Impoundment is located on the east side of the plant site, between the plant on the west and Interstate 29 on the east. The Impoundment is located on the north side of Pony Creek and the east side of Mosquito Creek. The Impoundment encompasses approximately 156 acres. The original outlet structure is no longer in service as the site was not actively receiving flow, however a new stormwater outfall to Pony Creek has been constructed as part of the closure operations. The Impoundment consists of embankments on all sides, with the west and south sides of the Impoundment being flood control levees. The Impoundment is currently undergoing closure. 2.2 Review of Existing Information As part of the annual inspection, previous inspections were reviewed, as required in Section (b)(1)(i). The 2017 annual inspection was reviewed prior to this effort. Previous weekly inspections, performed by MEC personnel, were reviewed as well. As required in Section (b)(1)(ii) and (iii), a visual inspection was performed by Burns & McDonnell on June 14, The visual inspection involved walking the perimeter of the toe of the Impoundment, across the face of the slopes in a diagonal pattern, along the upper working area and along the crest. The stormwater outfall structure was inspected and at the time of inspection; there was no stormwater discharge leaving the site. Specific conditions that were investigated as part of a typical inspection were the following: Surface cracking; Misalignment; Displacements (slides, slumps, slips and sloughs); Animal burrows; Slope erosion; Seepage; Inadequate slope protection; MidAmerican Energy Company 2-1 Burns & McDonnell

8 Annual Inspection Report North CCR Surface Impoundment Results of Inspection Patchy or inadequate vegetation; Excessive and/or woody vegetation; Debris; Settlement (or depressions); Signs of vandalism. Based on observations at the time of the visual inspection, the following conditions were observed and should be addressed: The Impoundment appeared to be in good condition. There was minor rutting at the tops of the berms on the southeast corner of the Impoundment due to construction traffic associated with the ongoing construction operations. Minor erosion was observed in areas disturbed by construction activities, due to recent rain. The north face of the south berm had bare soil due to recent re-grading activities and seed not germinating; MEC personnel indicated that they were working on a solution to this issue. One animal burrow was observed on the south face of the south impoundment embankment. MEC personnel marked the burrow for correction. In discussions with MEC personnel, the issues will be addressed under ongoing maintenance activities. No other issues were observed at the site. 2.3 Approximate Volumes in Impoundment Section (b)(2)(v) requires the approximate volume of CCR and water in the Impoundment to be estimated as part of the annual report. Approximate volumes of CCR in the Impoundment were estimated using a topographic survey conducted by HGM on September 23, The survey was compared to the bottom elevations of CCR material in the Impoundment, to estimate a total volume of CCR material being stored in the Impoundment. The total volume of CCR in the Impoundment as of the survey date was approximately 2,462,300 cubic yards. The total volume of CCR material in the Impoundment has not changed since At the time of the inspection, stormwater was ponded in areas amounting to an estimated 1-acre of the 156-acre Impoundment. The ponded areas held a foot or two of water, thereby resulting up to 650,000 gallons of impounded water at the time of the inspection. Section (b)(2)(iv) requires the total storage capacity of the impounding structure at the time of the inspection to be included in the annual report. There is no storage available within the Impoundment as the Impoundment is inactive and currently undergoing closure operations. MidAmerican Energy Company 2-2 Burns & McDonnell

9 Annual Inspection Report North CCR Surface Impoundment Results of Inspection 2.4 Instrumentation Instrumentation has been removed from the Impoundment because the Impoundment is inactive and is currently undergoing closure. 2.5 Changes in Impoundment Section (b)(2)(i) of the CCR rule requires that any changes in geometry be noted since the previous annual inspection and Section (b)(2)(vii) of the CCR Rule requires discussion of any changes affecting the stability or operation of the impounding structure since the previous inspection. There do not appear to be changes since 2017 in the berms or geometry that would affect the stability. Previous weekly inspections do not indicate a change to the Impoundment or cross-sectional area. MidAmerican Energy Company 2-3 Burns & McDonnell

10 Annual Inspection Report North CCR Surface Impoundment Recommended Remedial Action 3.0 RECOMMENDED REMEDIAL ACTION Based on observations made at the site, remediation measures are currently being implemented as part of the ongoing maintenance activities by filling and regrading rutting associated with hauling operations and runoff erosion. The animal burrow on the south berm, as discussed with MEC personnel, should be filled per MEC s ongoing animal burrow maintenance. No additional remedial action is required, at this time. MidAmerican Energy Company 3-1 Burns & McDonnell

11 Annual Inspection Report North CCR Surface Impoundment Limitations of Report 4.0 LIMITATIONS OF REPORT This report is based on observations made of features that could be visually inspected at the time of the inspection. Drawings and survey information were provided by MEC. Features not visible at the surface could not be observed or assessed. No assessment or confirmation of the design was performed as part of this inspection. No subsurface information, construction quality assurance documents or operational placement records were reviewed as part of this inspection. Any recommended remedial action or further monitoring noted in this report is assumed to be performed by MEC in a timely fashion and monitored by MEC on the required 7-day inspection schedule currently being performed. MidAmerican Energy Company 4-1 Burns & McDonnell

12 IMPOUNDMENT INSPECTION

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17 CHECKLIST PHOTOS FROM INSPECTION

18 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Facility Name CCR Unit Name Date of Inspection Date of Last Prior Inspection Name of Qualified Inspector (performing inspection) Weather Conditions Walter Scott Energy Center North Impoundment June 14, 2018 May 5, 2017 Richard E. Besancon, PE Overcast, 70 degrees Photograph Number: 7435 Description of Photograph: East side of north berm looking north minor rutting due to construction activities

19 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7436 Description of Photograph: North impoundment north berm looking northwest Photograph Number:7437 Description of Photograph: West levee interior looking south

20 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7439 Description of Photograph: West levee looking north Photograph Number: 7440 Description of Photograph: Exterior toe of west levee looking south

21 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7441 Description of Photograph: West levee looking north Photograph Number: 7442 Description of Photograph: West levee looking south

22 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7444 Description of Photograph: Exterior toe of slope on the west levee of the north impoundment Photograph Number: 7446 Description of Photograph: Southwest corner of north impoundment looking east note fill operations along the south levee

23 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7447 Description of Photograph: Southwest corner of the north impoundment note filling operations in the lower right corner Photograph Number: 7448 Description of Photograph: Interior of the west levee of north impoundment looking north

24 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7449 Description of Photograph: South levee of north impoundment looking west Photograph Number: 7450 Description of Photograph: Driving surface and crown of the south levee looking east

25 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7451 Description of Photograph: From the south levee looking north northeast into the north impoundment bare ground with minor rills in the foreground Photograph Number: 7453 Description of Photograph: From the south levee looking north northwest rip rap overlay in the foreground, ongoing stormwater maintenance in the mid-ground

26 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7454 Description of Photograph: Animal burrow on the exterior of the south levee marked for correction Photograph Number: 7455 Description of Photograph: Riverward stormwater outfall structure with flap gate and rip rap

27 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7456 Description of Photograph: Stormwater outfall river side with flap gate Photograph Number: 7457 Description of Photograph: Looking into the stormwater outfall structure at the gate

28 EPA - Disposal of Coal Combustion Residuals (CCR) from Electric Utilities Final Rule Regulatory Compliance Inspection 40 CFR and CCR Surface Impoundments and Landfills Photographic Log Photograph Number: 7458 Description of Photograph: Southeast corner of impoundment looking northeast rip rap overlay and access road Photograph Number: 7459 Description of Photograph: Southeast corner of impoundment looking northeast rip rap at storm outlet

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