2016 ANNUAL DAM AND DIKE INSPECTION REPORT. Bottom Ash Ponds. Rockport Plant Spencer County, Indiana. December 6 th, 2016

Transcription

1 2016 ANNUAL DAM AND DIKE INSPECTION REPORT Bottom Ash Ponds Rockport Plant Spencer County, Indiana December 6 th, 2016 Prepared for: Indiana Michigan Power Company Rockport Plant 2791 North US 231 Rockport, Indiana Prepared by: American Electric Power Service Corporation 1 Riverside Plaza Columbus, OH Document ID: GERS

2

3 Table of CONTENTS 1.0 Introduction Summary of Visual Observations Definitions of Visual Observations and deficiencies Bottom Ash Ponds Pond Complex Capacity and Depth Data Instrumentation Conclusion and Recommendations Bottom Ash Ponds... 6 Appendix A Figures Appendix B Inspection Photo ii

4 1.0 INTRODUCTION AEPSC Civil Engineering administers the Dam and Dike Inspection and Maintenance Program (DIMP) at American Electric Power (AEP) facilities. As part of the DIMP, staff from the Geotechnical Engineering Section conducts dam and dike inspections annually. This report has been prepared under the direction of Mr. Gary Zych, P.E. A summary of the inspection and assessment of the condition of the facilities is included herein. The inspection was performed on November10 th, 2016 with Mr. Mitch Montgomery at the Rockport Plant serving as the project facility contact. A dense fog was present at the beginning of the inspection that dissipated by the completion of the inspected area. Temperatures were in the upper 30s F and no significant precipitation had occurred within the previous seven days. Appendix A provides figures of the areas that were inspected and Appendix B provides the inspection photos. The Bottom Ash Pond Complex consists of East Bottom Ash Pond (EBAP) and West Bottom Ash Ponds (WBAP), (Figure 1 of Appendix A). The Bottom Ash Complex is generally a below ground facility with only the west dike of the WBAP extending above grade such that the normal pool elevation is maintained above ground level. The exterior slopes are 2.5 Horizontal to 1 Vertical (2.5H:1V) with interior slopes of 2 H:1V. No changes in the pond geometry or operations have occurred since the last annual inspection. 2.0 SUMMARY OF VISUAL OBSERVATIONS 2.1 DEFINITIONS OF VISUAL OBSERVATIONS AND DEFICIENCIES This summary of the visual observations uses terms to describe the general appearance or condition of an observed item, activity or structure. The meaning of these terms is as follows: Good: Fair Satisfactory: A condition or activity that is generally better or slightly better than what is minimally expected or anticipated from a design or maintenance point of view. A condition or activity that generally meets what is minimally expected or anticipated from a design or maintenance point of view. 1

5 Poor: Minor: Significant: Excessive: A condition or activity that is generally below what is minimally expected or anticipated from a design or maintenance point of view. A reference to an observed item (e.g., erosion, seepage, vegetation, etc.) where the current maintenance condition is below what is normal or desired, but which is not currently causing concern from a structure safety or stability point of view. A reference to an observed item (e.g. erosion, seepage, vegetation, etc.) where the current maintenance program has neglected to improve the condition. Usually, conditions that have been identified in the previous inspections, but have not been corrected. A reference to an observed item (e.g., erosion, seepage, vegetation, etc.) where the current maintenance condition is above or worse than what is normal or desired, and which may have affected the ability of the observer to properly evaluate the structure or particular area being observed or which may be a concern from a structure safety or stability point of view. This document also uses the definition of a deficiency as referenced in the CCR rule section (b)(5) Inspection Requirements for CCR Surface Impoundments. This definition has been assembled using the CCR rule preamble as well as guidance from MSHA, Qualifications for Impoundment Inspection CI-31, These guidance documents further elaborate on the definition of deficiency. Items not defined by deficiency are considered maintenance or items to be monitored. A deficiency is some evidence that a dam has developed a problem that could impact the structural integrity of the dam. There are four general categories of deficiencies. These four categories are described below: 1. Uncontrolled Seepage Uncontrolled seepage is seepage that is not behaving as the design engineer has intended. An example of uncontrolled seepage is seepage that comes through or around the embankment and is not picked up and safely carried off by a drain. Seepage that is collected by a drain can still be uncontrolled if it is not safely collected and transported. Seepage that is not clear and is turbid would also be considered as uncontrolled. Seepage that is unable to be measured and/or observe it is considered uncontrolled seepage. 2

6 Note: Wet or soft areas are not considered as uncontrolled seepage, but can lead to this type of deficiency. These areas should be monitored more frequently. 2. Displacement of the Embankment Displacement of the embankment is large scale movement of part of the dam. Common signs of displacement are cracks, scraps, bulges, depressions, sinkholes and slides. 3. Blockage of Control Features Blockage of Control Features is the restriction of flow at spillways, decant or pipe spillways, or drains. 4. Erosion Erosion is the gradual movement of surface material by water, wind or ice. Erosion is considered a deficiency when it is more than a minor routine maintenance item. 2.2 BOTTOM ASH PONDS Results of the visual inspection of the east and west bottom ash ponds are summarized below (Photographs are in Appendix B). 1. The diverter structure controlling the flow of bottom ash into the pond complex was observed to be functioning properly and in good condition (Photograph No. 1). 2. The west bottom ash pond discharge structures exposed above the pool stage show significant deterioration of the wing walls. (Photograph No. 2). 3. The channel between the diverter valve / energy dissipater and the discharge chute appeared to be in good condition. 4. The crest and interior slopes of the west east and bottom ash ponds were observed to be in good condition with no evidence of significant settlement, misalignment or erosion. Typical conditions of the crest and interior slopes are shown in Photograph Nos. 3, 4 and The southwest pond s storm water discharge pipe into the bottom ash pond shows good conditions with no erosion of the embankment or scouring of the bottom of the pond (Photograph No. 6). 3

7 6. The exterior dike for the west bottom ash pond appeared to be in good and stable condition with vegetative growth established and controlled. Minor areas of bare ground were observed to be present from previous construction activities where the storm water discharge pipe has been trenched into the embankment (Photograph No. 7). 7. The low water discharge structure # 13 appeared to be fully functional and in good condition (Photograph No. 8). 8. The skimmer structure # 5 appeared to be in good condition (Photograph No. 9). 9. The east bottom ash pond was operational and appeared to be in good condition. No visible embankment erosion, sloughing or other indications of instability were observed. (Photograph No. 10). 10. The east bottom ash pond low water discharge structure # 3 appeared to be in good condition and the skimmer structure # 4 appeared to be fully functional (Photograph Nos. 11 and 12). 11. The splitter dike between the east bottom ash pond and the metal cleaning waste tank basin appeared to be in good condition. No seepage through the embankment was observed, nor any erosion, slumping or misalignment of the dike (Photograph Nos. 13 and 14). 4

8 2.3 POND COMPLEX CAPACITY AND DEPTH DATA Based on the previous measurements and estimates and operational variation in the pond system, the capacity and volume estimates for the East & West bottom ash ponds are provided below: IMPOUNDMENT CHARACTERISTICS Bottom Ash Ponds West Bottom Ash Pond East Bottom Ash Pond Approximate Minimum depth (elevation) of 0 ft (NA)** impounded water since last 14 ft.(391 ft msl)*** annual inspection Approximate Maximum depth (elevation) of 8 ft. (394 ft msl) impounded water since last 14 ft. (391 ft msl) annual inspection Approximate Present depth of impounded water at the 8 ft. (394 ft msl) 14 ft. (391 ft msl) time of the inspection Approximate Minimum depth (elevation) of CCR 0 ft. (NA.)** 1 ft. (378 ft msl) since last annual inspection Approximate Maximum depth (elevation) of CCR 6 ft.(392 ft msl) 8 ft.(385 ft msl) since last annual inspection Approximate Present depth (elevation) of CCR at the 1 ft. (387 ft msl) 2 ft. time of the inspection Storage Capacity of impounding structure at the 352 ac-ft. 557 ac-ft. time of the inspection Approximate volume of impounded water at the time of the inspection 211 ac-ft. 337 ac-ft. Approximate volume of CCR at the time of the inspection 25 ac-ft. 197 ac-ft. * NA Not Available ** West Pond out of service and was drained at the time of the previous annual inspection. *** Depth and storage capacity are based on design information. 5

9 2.4 INSTRUMENTATION The bottom ash ponds do not have any instrumentation that is used to monitor the stability of the ponds. 3.0 CONCLUSION AND RECOMMENDATIONS Based on the visual inspection, the general condition of the Bottom Ash Ponds are good. The plant is performing maintenance and inspection activities on a regular basis. An itemized summary of the inspection is presented below. 3.1 BOTTOM ASH PONDS 1. The upstream, crest and downstream slopes of the west bottom ash pond and the splitter dike between the bottom ash ponds were observed to be in good condition and well maintained. The riprap quality and in-place condition were good with no significant deterioration due to weathering or fragmentation. Grass areas were generally well controlled. No erosion gullies or significant animal holes were noted. 2. The dike crest and roads were in good condition with no evidence of rutting, settlement or misalignment. 3. There were no signs of structural weakness or disruptive conditions that were observed at the time of the inspection that would require additional investigation or remedial action. There were no deficiencies noted this inspection or during any of the periodic 7-day or 30-day inspections. A deficiency is defined as either 1) uncontrolled seepage, 2) displacement of the embankment, 3) blockage of control features, or 4) erosion, more than minor maintenance. Based on the inspection performed and our review of relevant documents for the Rockport Plant, Civil Engineering believes that the Bottom Ash Ponds should be characterized as exhibiting good and functional condition. 6

10 Appendix A Figures

11 FIGURE 1 BOTTOM ASH PONDS THIS DRAWING IS CLASSIFIED AS: AEP PUBLIC REFERENCE AEP's CORPORATE INFORMATION SECURITY POLICY AMERICAN ELECTRIC "THIS DRAWING IS THE PROPERTY OF THE POWER SERVICE CORP. AND IS LOANED UPON CONDITION THAT IT IS NOT TO BE REPRODUCED OR COPIED, IN WHOLE OR IN PART, OR USED FOR FURNISHING INFORMATION TO ANY PERSON WITHOUT THE WRITTEN CONSENT OF THE AEP SERVICE CORP.,OR FOR ANY PURPOSE DETRIMENTAL TO THEIR INTEREST, AND IS TO BE RETURNED UPON REQUEST" ROCKPORT INDIANA MICHIGAN POWER COMPANY ROCKPORT PLANT BOTTOM ASH PONDS USGS TOPO MAP 7.5-MINUTE SERIES INDIANA UNIT: 12 LOCATION MAP 1 SCALE: 1"=2000' DR: CH: SUP: ENG: DATE: 12/1/16 DRAWING NUMBER: CIVIL ENGINEERING AEP SERVICE CORP. 1 RIVERSIDE PLAZA COLUMBUS, OH REV:

12

13 Appendix B Inspection Photos Page 2 of 11

14 2016 Annual Dam and Dike Inspection Bottom Ash Ponds Rockport plant Photo # 1 View illustrating bottom ash being discharged into diverter structure. Photo # 2 Typical view of discharge chutes into the pond showing poor condition of exposed concrete. The west bottom ash pond was out of service but is allowed to fill to its operating water level. Photo # 3 View of the west bottom ash pond showing good conditions along the crest and interior slope in the vicinity of the return storm water discharge line.

15 2016 Annual Dam and Dike Inspection Bottom Ash Ponds Rockport Plant Photo # 4 View of the rip rap along the west bottom ash pond showing good conditions where the storm water discharge enters into the pond. Photo # 5 Typical view of the splitter dike between the west and east bottom ash ponds. No misalignment, of the dike was observed or rutting along the crest. Photo # 6 Typical view of the interior splitter dike between the west bottom ash pond and the west waste water pond. The CCR monitoring wells are depicted in the foreground and monitor the underlying sand and gravel aquifer at three different depths.

16 2016Annual Dam and Dike Inspection Bottom Ash Ponds Rockport Plant Photo # 7 View of the exterior slope for the west bottom ash pond showing minor area of bare ground. No bulges, slumping or other defects were observed. Vegetative growth was established and regularly controlled with periodic mowing. Photo # 8 View of west bottom ash pond showing low water discharge structure No. 13. Photo # 9 View of skimmer structure No 5 for the west bottom ash pond..

17 2016 Annual Dam and Dike Inspection Bottom Ash Ponds Rockport Plant Photo # 10 Typical view of the east bottom ash pond showing good conditions of the splitter dike and rip rap. Photo # 11 View of east bottom ash pond showing low water discharge structure No. 3. The CCR monitoring wells are depicted to the east of the structure and monitor the underlying sand and gravel aquifer at three different depths. Photo # 12 View of east bottom ash pond showing skimmer structure No. 4.

18 2016Annual Dam and Dike Inspection Bottom Ash Ponds Rockport Plant Photo # 13 Typical view of the splitter dike between the east bottom ash pond and the metal cleaning waste tank basin. Photo # 14 Close up view of the splitter dike between the east bottom ash pond and the metal cleaning waste tank basin