Annual Inspection Report CCR Surface Impoundment. MidAmerican Energy Company, Louisa Generating Station

Transcription

1 Annual Inspection Report CCR Surface Impoundment MidAmerican Energy Company, Louisa Generating Station Final January 15, 2016

2 Annual Inspection Report CCR Surface Impoundment Prepared for MidAmerican Energy Company, Louisa Generating Station Muscatine, Iowa Final January 15, 2016 Prepared by Burns & McDonnell Engineering Company, Inc. Kansas City, Missouri COPYRIGHT 2016 BURNS & McDONNELL ENGINEERING COMPANY, INC.

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4 Annual Inspection Report 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 Visual Inspection Approximate Volumes in the Surface Impoundment Instrumentation Changes in the Surface Impoundment RECOMMENDED REMEDIAL ACTION LIMITATIONS OF REPORT APPENDIX A IMPOUNDMENT INSPECTION CHECKLIST APPENDIX B PHOTOS FROM INSPECTION MidAmerican Energy Company TOC-1 Burns & McDonnell

5 Annual Inspection Report CCR Surface Impoundment List of Abbreviations LIST OF ABBREVIATIONS Abbreviation CCR EPA LGS MEC RCRA U.S.C. MSL Term/Phrase/Name Coal Combustion Residual Environmental Protection Agency Louisa Generating Station MidAmerican Energy Company Resource Conservation and Recovery Act United States Code Mean Sea Level MidAmerican Energy Company i Burns & McDonnell

6 Annual Inspection Report 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 CCR 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 2015 annual inspection of the Louisa Generating Station (LGS) surface impoundment on October 22, 2015, on behalf of MEC. This report contains the results and observations of the inspection, as well as any recommended remedial actions. This annual inspection is the first annual inspection required under the CCR Rule. MidAmerican Energy Company 1-1 Burns & McDonnell

7 Annual Inspection Report CCR Surface Impoundment Results of Inspection 2.0 RESULTS OF INSPECTION The main objective of the annual inspection is to examine the CCR surface impoundment (Surface Impoundment) to determine any possible distress or malfunction of the design, construction, operation or maintenance of the Surface Impoundment. Design data for the Surface Impoundment as well as previous inspections were reviewed as part of the 2015 annual inspection. A visual inspection of the Surface Impoundment was also conducted, and included examining the toe, crest, slopes, hydraulic structures and other features for any signs of distress or deficient operation of the Surface Impoundment. The observations made from the review of existing information and the visual inspections are provided below. 2.1 Description of Impoundment The LGS Surface Impoundment is located on the east side of the plant site adjacent to the Mississippi River. The impoundment is comprised of two cells, a large primary storage basin located on the western side, with a secondary eastern section, known as the Reclaim Water Pond that accepts flow from the western, primary surface impoundment. Water from the Reclaim Water Pond is either discharged to the Mississippi River through a permitted outfall or recirculated to the plant for reuse as bottom ash transport water. There is an outfall structure from the primary surface impoundment, which conveys water to the reclaim water pond. There is a lift station located on the northwest corner of the reclaim water pond, which pumps the water back to the plant for reuse. The primary surface impoundment facilitates settlement of CCR in the primary, west, basin, allowing sediment free water to enter the reclaim water pond. Both impoundments are lined with rip rap slope protection on the interiors of the embankments, with vegetated exterior embankments. The total surface area of the west impoundment is approximately 26.4 acres, while the eastern, reclaim water pond, has a surface area of approximately 2.8 acres. The eastern two thirds of the impoundment are contained within an embankment, while the western one third of the site is excavated from in situ material. The soils in the embankment appear to be highly sandy and are easily disturbed with pedestrian traffic. 2.2 Review of Existing Information As part of the annual inspection, previous inspections were reviewed as required in Section (b)(1)(i). Since this is the first annual inspection required under the CCR rule, no previous annual inspections have been performed and thus none were reviewed. Previous inspections performed by plant personnel were reviewed Burns & McDonnell. The EPA inspection dated March 2011 was also reviewed. Burns & McDonnell personnel reviewed the original construction drawing prepared by Black and Veatch and dated MidAmerican Energy Company 2-1 Burns & McDonnell

8 Annual Inspection Report CCR Surface Impoundment Results of Inspection 2.3 Visual Inspection As required in Section (b)(1)(ii) and (iii), Burns & McDonnell personnel performed a visual inspection on October 22, 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. Hydraulic structures were visually inspected for signs of distress or malfunction as appropriate and where accessible, the equalization structure, metal and concrete condition, and exterior features were reviewed. Specific conditions that were investigated as part of a typical impoundment inspection were the following: Surface cracking; Misalignment; Displacements (slides, slumps, slips and sloughs); Animal burrows; Slope erosion; Seepage; Inadequate slope protection; Patchy or inadequate vegetation; Excessive and/or woody vegetation; Debris; Settlement (or depressions); Outlet/overflow structure condition; Signs of vandalism. Based on observations at the time of the visual inspection, the following conditions were observed and should be addressed: The surface impoundment was actively receiving flow from the plant during the inspection period. North Side The northeast corner of the north interior side presented with minor vegetation in the rip rap slope protection along the interior slope. MidAmerican Energy Company 2-2 Burns & McDonnell

9 Annual Inspection Report CCR Surface Impoundment Results of Inspection There was patchy vegetation ranging in height between 12 inches to greater than six feet along the north exterior slope. Large stumps (3) were identified at ground level that measured approximately inches, 9 inches, and 10 inches in diameter. Minor erosion rills were identified, near the Y in the access road that minor grading and seeding should correct. There was evidence of gopher or mole holes on the north side of the impoundment, as well as evidence of stumps greater than 7 inches in diameter along the exterior slope. East Side There was minor weathering of the riprap on the interior slope protection on the east side. South Side Along the interior south side embankment, there was vegetation adjacent to the waterline and minor degradation of the rip rap slope protection. A 4-inch tree stump was noted on the exterior slope approximately 25 feet east-south-east of monitoring well 102. The vegetation along the exterior slope was measured to be greater than 6 inches in height, ranging in height up to approximately four feet. Some bald patches in vegetation were noted sporadically along the slope. Erosion rills were identified approximately 200 feet east of the west end on the exterior of the southern embankment. A circular slough was noted mid-berm to the bottom of the slope 150 feet west of the east monitoring well (MW 105). Reclaim Water Pond An erosion rill was present immediately west of the west berm exterior on the north side of the exterior berm. The gauge at the pump station read approximately elevation 562 feet the lower portion of the gauge is corroded and difficult to read. The gauge should have the corrosion repaired to improve the readability of the staff gauge. Overall, the Surface Impoundment appeared to be well maintained and in good working order. Vegetation should be maintained to no taller than 6 inches to facilitate inspections. MidAmerican Energy Company 2-3 Burns & McDonnell

10 Annual Inspection Report CCR Surface Impoundment Results of Inspection 2.4 Approximate Volumes in the Surface 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 determined using a topographic survey conducted by HGM on July 17, Burns & McDonnell used existing drawings showing the bottom of impoundment elevation at feet (above mean sea level). This base elevation was compared to the topographic survey to estimate a CCR volume. The total volume of CCR in the Surface Impoundment is approximately 842,000 cubic yards. The water surface on the date of survey, elevation MSL, was used to approximate the volume of water in the impoundment. Based on the survey information the depth of water is 13 feet at time of topographic survey, while 14 feet at the time of the inspection. The water volume in the impoundment was approximately 71 acre-feet. 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. Using the water surface on the date of the July 2015 survey, the total storage volume available with two feet of freeboard is 562 acre-feet. 2.5 Instrumentation The staff gauge located on the lift station located at the northwest corner of the reclaim water pond was observed during the inspection. The staff gauge read approximately elevation 562 feet mean sea level. The maximum recorded value documented by MEC personnel or the inspector is feet. 2.6 Changes in the Surface 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. Since this is the first annual inspection, there is no basis for a discussion of any changes in geometry or changes that may affect the stability or operation of the Surface Impoundment. The surface impoundment appeared to closely mimic the design drawings without major deviation regarding embankment alignment, slopes, or grades. MidAmerican Energy Company 2-4 Burns & McDonnell

11 Annual Inspection Report CCR Surface Impoundment Recommended Remedial Action 3.0 RECOMMENDED REMEDIAL ACTION Based on observations made at the site, remediation measures to backfill minor depressions and animal burrows and correct limited areas of dead or patchy vegetation will need to be performed. For areas with dead vegetation, reseeding with appropriate grass that will grow in these areas should occur. If environmental factors are causing the vegetation to die, determination and remediation of these factors or utilization of other erosion control measures should be made. At this time, the rip rap degradation does not appear to be significant enough to require rip rap replacement. The rip rap should be monitored for further degradation. Minor erosion rills should be fixed by re-grading and seeding the impacted sites. The stumps in the embankment do not appear to be causing any detrimental effects on the embankment and may be left in place for the time being. They should continue to be monitored for seepage and/or rot. Vegetation should be maintained at or less than 6-inches. This should be achieved by regular mowing of the slopes. A low-growth deep-rooted native grass, such as buffalo grass, would help stabilize the soil and minimize erosion. Vegetation adjacent to the waterline can be sprayed with an herbicide, which is safe to use in, or in close proximity to water, and applied according to manufacturer s recommendations by qualified personnel. MidAmerican Energy Company 3-1 Burns & McDonnell

12 Annual Inspection Report 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, permit drawings and survey information provided by MEC. Features not visible at the surface could not be observed or assessed. Drawings prepared by Black and Veatch dated June 10, 1981, were reviewed to gain an understanding of the impoundment geometry and cover. 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

13 APPENDIX A IMPOUNDMENT INSPECTION CHECKLIST Burns & McDonnell World Headquarters 9400 Ward Parkway Kansas City, MO O F

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17 APPENDIX B PHOTOS FROM INSPECTION Burns & McDonnell World Headquarters 9400 Ward Parkway Kansas City, MO O F

18 Photograph B-1: Interior north embankment looking west. Photograph B-2: Degrading rip rap, typical interior protection. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

19 Photograph B-3: South embankment looking east. Photograph B-4: South embankment looking east, note vegetation along water line on the interior. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

20 Photograph B-5: Animal burrow on south embankment. Photograph B-6: Minor surficial slope failure along south embankment. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

21 Photograph B-1: Minor slope failure on south embankment. Photograph B-1: East embankment looking north along access road. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

22 Photograph B-2: Rock dumped on north embankment note proximity to the lift station. Minor erosion rills are located at the same location. Photograph B-1: Stumps in north embankment typical. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

23 Photograph B-2: Staff gauge at lift station. Photograph B-1: Berm between impoundments looking south. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

24 Photograph B-2: Access road along north embankment, looking west. Photograph B-1: Access road along north embankment looking east. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

25 Photograph B-2: North embankment looking east Photograph B-1: Minor vegetation in rip rap. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

26 Photograph B-2: Vegetation in rip rap typical. MidAmerican Energy Impoundment Inspection Photographs October 30, 2015 Louisa Generating Station

27 Burns & McDonnell World Headquarters 9400 Ward Parkway Kansas City, MO O F