annual inspection report ccr surface impoundment...energy center final january 15, 2016. annual...

Annual Inspection Report CCR Surface Impoundment

MidAmerican Energy Company, Neal North

Energy Center

Final January 15, 2016

Annual Inspection Report CCR Surface Impoundment

Prepared for

MidAmerican Energy Company, Neal North Energy Center

Sergeant Bluff, Iowa

Final January 15, 2016

Prepared by

Burns & McDonnell Engineering Company, Inc. Kansas City, Missouri

COPYRIGHT © 2016 BURNS & McDONNELL ENGINEERING COMPANY, INC.

Annual Inspection Report – CCR Surface Impoundment Table of Contents

MidAmerican Energy Company TOC-1 Burns & McDonnell

TABLE OF CONTENTS

Page No.

1.0 SUMMARY OF OBJECTIVES .......................................................................... 1-1

2.0 RESULTS OF INSPECTION ............................................................................. 2-1 2.1 Description of Impoundment 3B ......................................................................... 2-1 2.2 Review of Existing Information ........................................................................... 2-1 2.3 Approximate Volumes in Impoundment 3B ........................................................ 2-4 2.4 Instrumentation .................................................................................................... 2-5 2.5 Changes in Impoundment 3B............................................................................... 2-5

3.0 RECOMMENDED REMEDIAL ACTION ........................................................... 3-1

4.0 LIMITATIONS OF REPORT .............................................................................. 4-1

APPENDIX A – IMPOUNDMENT INSPECTION CHECKLIST APPENDIX B – PHOTOS FROM INSPECTION

Annual Inspection Report – CCR Surface Impoundment List of Abbreviations

MidAmerican Energy Company i Burns & McDonnell

LIST OF ABBREVIATIONS

Abbreviation Term/Phrase/Name

CCR Coal Combustion Residual

EPA Environmental Protection Agency

MEC MidAmerican Energy Company

NNEC Neal North Energy Center

RCRA Resource Conservation and Recovery Act

U.S.C. United States Code

Annual Inspection Report – CCR Surface Impoundment Summary of Objectives

MidAmerican Energy Company 1-1 Burns & McDonnell

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 257.83. Burns & McDonnell conducted the 2015 annual inspection of the Neal North

Energy Center (NNEC) CCR Surface Impoundment 3B (Impoundment 3B) on October 21, 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.

Annual Inspection Report – CCR Surface Impoundment Results of Inspection


2.0 RESULTS OF INSPECTION

The main objective of the annual inspection was to examine Impoundment 3B to determine any possible

distress or malfunction of the design, construction, operation or maintenance of the CCR Impoundment.

A visual inspection of Impoundment 3B was conducted and included examining the toe, crest, slopes,

hydraulic structures 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 3B

The NNEC Impoundment 3B is located on the southeast side of the plant site, south of the coal pile and

railroad tracks. Impoundment 3B is located between Impoundment 3A on the west and oxbow lake on

the east. Impoundment 3B encompasses approximately 35 acres and includes four cells divided by berms

constructed of CCR. The outlet structure is located at the southwest corner and discharges through a

permitted outfall to a culvert under the existing road, conveying water to the west and eventually

daylighting 1,400 feet west of the surface impoundment. The site was actively receiving flow during the

inspection. The impoundment consists of embankments on all sides, however the north side had CCR

placed higher than the surrounding levee; this area is not active.

2.2 Review of Existing Information

As part of the annual inspection, previous inspections were reviewed, as required in Section

257.83(b)(1)(i). However, since this is the first annual inspection as required by the CCR rule, no

previous annual inspections have been performed and thus none were reviewed. Construction drawings

from the EPA CCR Impoundment, dated May 2011, did not include details of surface impoundment 3B.

Previous impoundment inspections performed by MEC personnel were reviewed. Construction drawings

of the outlet structure included in the EPA report were also reviewed.

As required in Section 257.83(b)(1)(ii) and (iii), a visual inspection was performed by Burns &

McDonnell on October 21, 2015. 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 hydraulic structure, or outfall structure, was visually inspected for signs of distress or

malfunction and none was observed 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:

Approximately 50 feet east of the building on the southwest corner of the impoundment, presented with minor erosion rills.

Vegetation categorized as being greater than 6 inches, along with additional spotty patches of bare ground were found throughout on the interior slope and along the waterline. Vegetation was dead on the exterior slope on the south and east berms.

Minor rutting was present on south exterior slope approximately 150 feet west of the north bend.

Excessive vegetation on the southeast corner of the embankment (at the location the embankment turns to the north.

Minor erosion was identified at the toe of the slope on the interior embankment at the waterline on the interior east side of the impoundment.

Minor puddles and ponding were noted on the road along the east side of the impoundment.

Minor animal burrows, approximately 1.5 inches in diameter, were identified on the east exterior berm.

Interior erosion rills on the east side of the impoundment were identified by the transmission line

pole.



Trees were noted growing on the eastern exterior slope approximately 1 inch or less in diameter. Animal burrows roughly 6-8 inches in diameter were found on the northern embankment between cells, approximately 150 feet west of the east embankment.

The west side was recently graded, but presented with minor to moderate erosion rills, and no vegetation present. There was rutting and standing water on the road of the east berm, with more severe rutting noted approximately three fourths of the way north along the road on the east side. Erosion rills were identified at the point of intersection of the curve on the north end of the east embankment and vegetation was noted to be greater than 6 inches throughout.

The west berm slope is steeper than three horizontal to one vertical (3:1), with erosion at the toe from wave action. The corrugated metal pipe through the west berm showed signs of corrosion on the exterior, and severe erosion was noted on the south side of the berm at the culvert. The north side of the west berm (approximately three quarters of the way east from the divider berm) has minor sloughing and beaching.

The main issue that should be given priority, aside from general maintenance, is located on the exterior

east berm at the waterline. There appears to be erosion at the waterline and a vertical drop that begins

above the waterline, however the extent below water could not be determined. This should be addressed

immediately to prevent additional erosion and embankment sloughing. The area of concern is shown in

Figure 2-1, below:



Figure 2-1: Area of Erosion

The surface impoundment was actively receiving flow during the time of the inspection. Construction

equipment was onsite working on the west side of Impoundment 3B.

2.3 Approximate Volumes in Impoundment 3B

Section 257.83(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 October 5, 2015. Because as-built information for the

impoundment construction does not exist, Burns & McDonnell used geotechnical information gathered in

November 2015 by Terracon to estimate the base of CCR in the impoundment at an elevation of 1068.43



feet above mean sea level. The survey was compared to the bottom elevations of CCR material in the

surface impoundment, to estimate a total volume of CCR material being stored in the impoundment.

The bottom of CCR elevations varied greatly throughout the impoundment area, therefore the elevations

were averaged and the averages were used to calculate approximate volumes of CCR in the

impoundment. The total volume of CCR in the CCR Impoundment is approximately 602,000 cubic

yards.

There are approximately 28 acre-feet of water in the impoundment at the time of survey. The

impoundment is divided by a berm with active discharge into the north cell and a culvert through the

dividing berm into the south cell, see Figure 2-1. The water surface in the north portion was 1081.0

above mean sea level at an approximate depth of six feet. The CCR depth in the north cell is

approximately 1075.0 with a depth of approximately 6.5 feet. The water surface in the southern portion

was at elevation 1077.00 above mean sea level with an approximate depth of four feet. The CCR

elevation in the south cell is approximately 1073 for a depth of approximately 4.5 feet.

Section 257.83(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. The total available storage volume with two feet of

freeboard is approximately 16.7 acre-feet.

2.4 Instrumentation

The staff gauge located at the outlet structure, which is located at the southwest corner of impoundment

3B, was in good condition and read a water surface measurement of 6.5. Based on previous inspection

reports the water surface had been reported to be 7.2. Measurement 6.5 is 6.5 feet below the top of the

outlet structure and coincides with water surface elevation 1077.0 above mean sea level. The graduations

are in feet and tenths of feet.

2.5 Changes in Impoundment 3B

Section 257.83(b)(2)(i) of the CCR rule requires that any changes in geometry be noted since the previous

annual inspection and Section 257.863(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. Previous weekly inspections do not



indicate a change to the surface impoundment of cross sectional area based on written descriptions and

photo logs.

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 areas of dead or patchy vegetation will need to be performed. For areas with dead

vegetation, reseeding with appropriate grass that will grow in this area 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.

Minor erosion should be re-graded and seeded during the spring to repair and re-vegetate the eroded

areas.

The corroded pipe should be monitored. It does not appear that the pipe should be replaced immediately,

and a monitoring program should be adequate.

The area along the exterior of the eastern berm, at the waterline of the oxbow lake should be addressed.

The toe appears to have been eroded by the adjacent water and minor surficial sloughing was observed on

the embankment above the erosion. To prevent additional future surface failures, the toe of slope should

be stabilized with rip rap to not only provide ballast at the toe of slope, but also to counteract future wave

action.

Areas of severe erosion, serious erosion rills, along the west embankment should be filled and re-graded

and either stabilized with vegetation or the surface re-graded to direct flow downslope at desired

locations. The areas to direct flow downslope should be armored with stone to prevent future erosion.

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.

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.

Burns & McDonnell World Headquarters9400 Ward Parkway

Kansas City, MO 64114 O 816-333-9400 F 816-333-3690

www.burnsmcd.com

APPENDIX A – IMPOUNDMENT INSPECTION CHECKLIST


Kansas City, MO 64114 O 816-333-9400 F 816-333-3690

www.burnsmcd.com

APPENDIX B – PHOTOS FROM INSPECTION

MidAmerican Energy Impoundment Inspection

Photographs October 21, 2015

Neal North Energy Center

Photograph B-1: Looking east along the south embankment.

Photograph B-2: Looking east along south embankment.




Photograph B-3: Minor surficial sloughing on south interior embankment.

Photograph B-4: Interior south embankment, bare earth and signs of rutting.




Photograph B-5: South embankment, exterior, dead vegetation.

Photograph B-6: South embankment access road, showing depressions.




Photograph B-7: Dead vegetation along south side of exterior embankment.

Photograph B-8: Dead vegetation along exterior berm.




Photograph B-9: Access road along east embankment.

Photograph B-10: Interior eastern embankment.




Photograph B-11: Minor erosion rills on interior of east embankment.

Photograph B-12: Small trees on the exterior of the east embankment.




Photograph B-13: Access road along east embankment, north of the central divider berm.




Photograph B-14: Severe erosion rills and gullies – interior of west embankment.




Photograph B-15: Sloughing along interior road.

Photograph B-16: Erosion rills on interior slope.




Photograph B-17: Erosion rills.

Photograph B-18: Erosion rills on interior slope of west embankment.




Photograph B-19: CMP between cells.

Photograph B-20: Erosion rill.




Photograph B-21: Animal burrow.

Photograph B-22: Animal burrow approximately 6-8inches.




Photograph B-23: Severe erosion on the interior of the west embankment.

Photograph B-24: Moderate erosion rills on the interior of the west embankment.




Photograph B-25: Gage on interior of outlet structure.

Photograph B-26: Outlet structure.




Photograph B-27: Looking east along south embankment.




Photograph B-28: Looking northwest from the outfall structure – minor beaching along the west interior embankment.


Kansas City, MO 64114 O 816-333-9400 F 816-333-3690

www.burnsmcd.com

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