NAUGHTON FGD POND 4 STRUCTURAL STABILITY ASSESSMENT

Transcription

1 NAUGHTON FGD POND 4 STRUCTURAL STABILITY ASSESSMENT Prepared for: PacifiCorp, Naughton Power Plant Project Manager: Chad Tomlinson Date: 01 September 2016 Document No.: NP-TR-014 Quality Assurance Statement Office Address Prepared by Reviewed by Approved for Issue by MWH 2890 Cottonwood Parkway, Suite 300 Salt Lake City, UT Jacob Traucht James Dixon Chad Tomlinson Revision Schedule Rev No. Date Description Prepared By Reviewed By Approved By 0 09/01/16 Issued for Use J. Traucht J. Dixon C. Tomlinson Comments: This document has been prepared for the benefit of PacifiCorp in accordance with the generally accepted practices and standards in use at the time it was prepared. No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person. This disclaimer shall apply notwithstanding that this document may be made available to other persons for an application for permission or approval to fulfill a legal requirement. Status: Rev. 0 i 01 September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

2 CERTIFICATION I hereby certify that this Structural Stability Assessment for the FGD Pond 4 located at PacifiCorp s Naughton Power Plant has been prepared in accordance with (d) Structural Integrity Criteria for Existing Surface Impoundments of the Coal Combustion Residuals (CCR) Rule - 40 CFR Parts 257 and 261, Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities; Final Rule published in the Code of Federal Regulations (CFR) on April 17, 2015 with an effective of October 19, By: Date: 09/01/2016 Chad Tomlinson, P.E. Wyoming P.E.# 15375

3 REPORT OF (D)(1) INITIAL STRUCTURAL STABILITY ASSESSMENT The (d) rule states that the owner or operator of the CCR unit must conduct initial and periodic structural stability assessments and document whether the design, construction, operation, and maintenance of the CCR unit is consistent with recognized engineering best practices. This assessment documents the design, construction, operations, and maintenance practices in accordance with the requirements of (d) as it pertains to FGD Pond 4 (the Pond). The layout of the Pond is presented in Figure 1. FGD Pond (d)(1)i. Figure 1 FGD Pond 4 Layout Foundation and Abutment Stability demonstrate that the unit, including any vertical or lateral expansions, is constructed with stable foundations and abutments Design & Construction The construction specifications for the foundation (subgrade) of the embankments called for the top 6- inches of topsoil to be stripped in all fill areas. Prior to placing embankment fill on the subgrade, the subgrade was scarified to a depth of 12 inches and compacted to 95% of maximum dry density and within Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

4 2% of optimum moisture content. In fill areas where the existing grades are steeper than 10%, the existing grade was prepared by cutting horizontal benches with bench heights of 12 inches prior to placement of embankment fill. Due to shallow groundwater underlying FGD Pond 4, a groundwater drain system was constructed on the foundation of FGD Pond 4 consisting of a geonet, perforated drain pipe, and non-perforated drain pipe. The purpose of the groundwater drain system (special foundation preparation) was to aid in construction dewatering, eliminate hydrostatic pressure below the geomembrane, and to enhance the stability of the embankments (Tetra Tech, 2009). Special foundation preparations were constructed prior to constructing the embankments. The soft material (topsoil) was left in place and was overlain by a rigid geogrid material and topped with pit run gravel (gradation allows for relative ease of compaction to acquire the required density). The embankment fill was then placed over the top (Tetra Tech, 2009). These specifications are consistent with recognized and generally accepted good engineering practices for embankment foundation preparation and general fill and embankment fill. A cross-section through the main dike of the Pond is shown in Figure 2. Figure 2 Cross-Section through Main Dike of FGD Pond 4 Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

5 Operation & Maintenance FGD Pond 4 is visually inspected weekly for signs of instability. No signs of instability have been reported as part of these weekly inspections. Additionally, an annual inspection was completed by URS in 2015 and reported no signs of instability (URS, 2015) (d)(1)ii. Slope Protection Adequate slope protection to protect against surface erosion, wave action, and adverse effects of sudden drawdown Design & Construction The upstream dikes of FGD Pond 4 is lined with a 60-mil HDPE liner. Although the main purpose of the liner is to prevent leakage through the pond, it also serves as slope protection for wave action on the embankment structure. There is a soil layer overlying the liner on the internal slopes of the pond. However, the purpose of this soil layer is to protect the liner from long-term ultraviolet (UV) radiation and not for slope protection. The utilization of liner for slope protection of embankments is consistent with recognized and generally accepted good engineering practices. Operation & Maintenance The liner lining the interior slopes of FGD Pond 4 is inspected as part of the weekly inspections. No signs of wind erosion or damage to the liner have been documented. The protective layer of soil overlying the liner has been observed to have minor rilling and erosion associated with stormwater runoff and wave action. However, this does not constitute a dam safety concern given that the soil is sacrificial and does not serve as the main erosion protection for wind action (d)(1)iii. Dike Compaction Dikes mechanically compacted to a density sufficient to withstand the range of loading conditions in the CCR unit Design & Construction The construction specifications required the embankment fill to be placed in maximum loose lifts not to exceed 9-inches in thickness and compacted to 95% of maximum dry density and within 2% of optimum moisture content (Tetra Tech, 2009). The Tetra Tech geotechnical design report did not specify a maximum lift thickness for the embankment construction. The upstream and downstream slopes were constructed at 3H:1V. The construction specifications were developed consistent with recognized and generally accepted good engineering practices. Operation & Maintenance No operation or maintenance activities have taken place along the embankments or embankment crests that would decrease the compaction specifications of the embankment fill materials. No major repairs Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

6 have been performed FGD Pond 4, any repairs that have taken place in the past are superficial and were not required to be mechanically compacted (d)(1)iv. Vegetated Slopes Vegetated slopes of dikes and surrounding areas not to exceed a height of six inches above the slope of the dike, except for slopes which have an alternate form or forms of slope protection Design & Construction The exterior slopes of the Pond were covered with topsoil and amended with fertilizer prior to drill seeding following construction to provide erosion protection. Seeding was applied at a rate of 23 pounds per acre of 90-percent live seed. Based on field observations, vegetation on FGD Pond 4 has been successfully established with the majority of the downstream face having sufficient vegetation coverage to mitigate the potential for erosion. Operation & Maintenance The vegetated slopes of FGD Pond 4 are inspected as part of the weekly inspections. No major maintenance or repairs have been made along the embankment surfaces. Due to the use of native grasses, which would die if routinely mowed and the safety concerns associated with operating a mower on the embankment slopes, trimming of the vegetation is not being performed. Currently, plant personnel is documenting the grass over 6-inches tall as well as the large brush and weeds over 6-inches during the weekly inspections Large brush and weeds over 6-inches tall are being sprayed with an herbicide to kill the undesirable vegetation (d)(1)v. Spillways A single spillway or a combination of spillways configured as specified in paragraph A. The combined capacity of all spillways must be designed, constructed, operated, and maintained to adequately manage flow during and following the peak discharge from the event specified in paragraph B. A. All spillways must be either a. Earth or grass lined and designed to carry short-term, infrequent flows at non-erosive velocities where sustained flows are not expected. B. Combined capacity of all spillways must manage flow during and following peak discharge from a: a. PMP for a high hazard impoundment b. 1,000-yr flood for a significant hazard impoundment No spillway is installed on the Pond. The spillway section of Rule can be addressed through a probable maximum precipitation (PMP) analysis. Since this pond does not receive inflows from the surrounding topography, an off-channel basin analysis was deemed sufficient. MWH completed a PMP study at Naughton in 2012, indicating that a 72 hour PMP event would raise the water level by 10.6 inches, which is contained by the designed freeboard of the pond of 5-feet. Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

7 257.73(d)(1)vi. Hydraulic Structures Hydraulic structures underlying the base of the CCR unit or passing through the dike of the CCR unit that maintain structural integrity and are free of significant deterioration, deformation, distortion, bedding deficiencies, sedimentation, and debris which may negatively affect the operation of the hydraulic structure Design & Construction There are no hydraulic structures associated with the Pond. Operation & Maintenance There are no hydraulic structures associated with the Pond (d)(1)vii. Downstream Inundated Slope Stability For CCR units with downstream slopes which can be inundated by the pool of an adjacent water body such as a river, stream, or lake, downstream slopes that maintain structural stability during low pool of the adjacent water body or sudden drawdown of the adjacent water body Design & Construction There are no downstream slopes which may be inundated by the pool of an adjacent water body. Operation & Maintenance There are no downstream slopes which may be inundated by the pool of an adjacent water body (d)(2) Structural Stability Deficiencies No observations have been made during the weekly inspections that would be interpreted as an indicator of a structural deficiency or developing failure mode. An initial annual inspection of the Pond was completed in 2015 by URS in accordance with (2)(ii)(b) and the results of the inspection indicated that there was nothing observed suggesting an active or impending dam safety issue. The 2015 annual inspection report for the Pond is provided in Appendix A. Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

8 REFERENCES MWH, Naughton Power Plant Phase II Geotechnical Investigation, Tetra Tech, Geotechnical Engineering Study: FGD Effluent Disposal Pond 4. September 11, URS Corporation, 2015 Coal combustion Residuals Annual Inspection, Naughton Power Plant, FGD Pond #4. January Status: Rev September 2016 Document No: NP-TR-014 Naughton FGD Pond 4 Structural Stability Assessment

9 Appendix A Annual Inspection Report

10 2015 Coal Combustion Residuals Annual Inspection Naughton Power Plant FGD Pond #4 Prepared for PacifiCorp Energy North Temple Office 1407 West North Temple Salt Lake City, Utah Final December 29, 2015 URS Corporation 756 East Winchester, Suite 400 Salt Lake City, Utah 84107

11 Contents 1 Findings Description and History of FGD Pond # General Overview Location FGD Pond #4 Description Performance History Construction History Review of Operating Record Files Design and Construction Information Previous Periodic Structural Analyses Results of Inspection by a Qualified Person Results of Previous Annual Inspections Field Inspection of FGD Pond # General FGD Pond #4 Geometry Instrumentation Impounded Water Depth and Volume Storage Capacity Observed or Potential Structural Weaknesses Observed Changes Limitations and Consultant Qualifications Limitations Professional Engineer Qualifications References... 7 Appendices Appendix A Appendix B Appendix C Photograph Log Annual Inspection Report Form Example PacifiCorp Inspection Form 2015 Naughton FGD Pond #4 Inspection i

12 1 Findings This annual inspection and report are being completed for the purpose of providing due diligence by PacifiCorp to ensure the safety of its coal combustion residual facilities. The inspection was performed according to the requirements for annual inspections under Section (CCR surface impoundments) of 40 CFR Parts 257 and 261, Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals from Electric Utilities, Final Rule, dated April 17, 2015[19]. The field inspection was performed on August 24, 2015 and found the principal project features of Flue Gas Desulfurization (FGD) Pond #4 to be in satisfactory condition. Nothing was observed that would suggest an active or impending dam safety issue. None of the inspection findings indicate the need for immediate action to address a dam safety concern. Figure 1 1 is an aerial image of the pond taken in Observations from the 2015 inspection include: Figure 1 1. FGD Pond #4 1. Animal burrows (Photo 2) 2. Erosion along the interior embankment (Photo 1) A CCR requirement for signage requires the 1) name of owner; 2) name of unit; and 3) state ID number. The following photo (Figure 1 2) demonstrates that the signage requirement has been met. It is advised to add the National Inventory of Dams (NID) number, WYO Naughton FGD Pond #4 Inspection 1

13 Figure Description and History of FGD Pond #4 2.1 General Overview The Naughton Plant is operated and fully owned by PacifiCorp. FGD Pond #4 was constructed in Location The Naughton Power Plant is located in western Wyoming approximately four miles southwest of the community of Kemmerer in Lincoln County. The plant is immediately west of Wyoming State Highway 189 at the Elkol turnoff [5] and immediately east of the Westmoreland Coal Kemmerer Mine, which supplies coal to the plant. 2.3 FGD Pond #4 Description FGD Pond #4 is located approximately 0.8 miles southeast of the plant generation facility and immediately east of the South Ash Pond. The pond was originally constructed in 2010 to dispose of FGD waste materials from Units 1 and 2 [10]. The pond did not exist when the previous independent consultant inspection was conducted in FGD Pond #4 actively receives FGD waste slurry from the plant through an inlet at the northwest corner of the pond. The membrane lined FGD Pond #4 was completed in It receives waste materials that are removed from treating the flue gases discharged from all three units of the plant. The pond is contained entirely by an earthen embankment and is located immediately adjacent to the east embankment of the South Ash Pond. The maximum embankment height is approximately 60 feet and it has a storage capacity of 1,407 acre feet. If the FGD Pond #4 embankment were to breach, it would impact property downstream 2015 Naughton FGD Pond #4 Inspection 2

14 of PacifiCorp property. However, downstream impacts resulting from a failure of the FGD Pond #4 embankment are not known because a dam breach analysis and downstream inundation mapping have not been completed. Refer to Table 2 1 for a summary of pertinent data for the FGD Pond #4. Table 2 1. FGD Pond #4 Pertinent Data Description Design Value Pond: Total Pond Capacity (acre feet) 1,407 [8] Maximum Pond Elevation (feet) 6,865 [8] Surface Area (acres) 36.9 [8] Pond Perimeter (feet) 5,200 1 Drainage Area (square miles) None Design Freeboard (feet) 5 [8] Embankment: Type Maximum Design Height (feet) Unknown 60 Downstream [8] Design Crest Width (feet) 25 [8] Design Crest Length (feet) Unknown Design Crest Elevation (feet) 6,870 [8] Design Upstream Slope (feet) 3:1 [8] Design Downstream Slope (feet) 3:1 [8] Pond Outlet Structure: Type Gates Crest Elevation (feet) Crest Length (feet) Gate Invert Elevations (feet) Conveyance None 2015 Naughton FGD Pond #4 Inspection 3

15 2.4 Performance History Naughton Power Plant personnel confirmed that leak testing was conducted on the lining. The lining was determined to be damaged on the west interior slope and repairs were made in 2010[2]. There is no other history of performance for this facility. 2.5 Construction History FGD Pond #4 was constructed in Figure 3 1 is a cross section from the design drawings for FGD Pond #4 [8]. FGD waste delivery to FGD Pond #4 is by pipe discharging to a concrete structure in the inside slope near the crest of the pond. The slope is lined with 100 mil HDPE. Refer to Photo 9. Since embankments for the structure were completed to their final heights, there are no pipe penetrations. 2.6 Review of Operating Record Files The list of operating records to be reviewed during the annual inspection as contained in 40 CFR 257, Disposal of Coal Combustion Residuals for Electric Utilities is CCR unit design and construction information required by (c)(1) and (c)(1), previous periodic structural stability assessments required under (d) and (d), the results of inspections by a qualified person, and results of previous annual inspections [19]. The following subsection describes the review of operating record files Design and Construction Information FGD Pond #4 was designed by Tetra Tech in 2009 [8]. URS reviewed the design drawings. The drawings show a robust lining and leak detection system comprised of a layer each of 60 mil and 40 mil HDPE. 100 mil textured HDPE was used at the discharge inlet Previous Periodic Structural Analyses Structural analysis for design of FGD Pond #4 was performed by Tetra Tech but this analysis is not part of the record files. There have been no structural analyses subsequent to the design Results of Inspection by a Qualified Person The FGD Pond #4 is subject to periodic inspections by the Naughton Power Plant staff. URS reviewed the inspection reports; however, this is the beginning of the first cycle of inspections under CCR regulations and the record using the new forms is limited to a few weeks of inspections. Field monitoring forms were used prior to the current forms [9]. These inspections are documented and retained by PacifiCorp. A sample of the current PacifiCorp s Inspection Form can be found in Appendix C. Review of the results of these inspections did not identify any previously unidentified issues Naughton FGD Pond #4 Inspection 4

16 2.6.4 Results of Previous Annual Inspections This is the initial and only annual inspection conducted under CCR rules [19] for the Naughton FGD Pond #4. PacifiCorp has completed one other independent inspection in 2014 by URS [1]. None of the observations from this or previous inspections indicated imminent dam safety concerns. This report and other pertinent reports and data are accessible at the following website: Section 5 of this report is a complete list of references for the Naughton FGD Pond #4. 3 Field Inspection of FGD Pond #4 A field inspection was conducted on August 24, 2015 by URS staff, Rick J. Cox, P.E. and Matthew Zion. Personnel from the Naughton Power Plant participated in an interview prior to the field inspection to answer questions. A photo log documenting features and their condition at the time of the inspection is presented in Appendix A. These photos are referenced in the report. The completed Annual Field Inspection Report is presented in Appendix B. This checklist should be considered an integral part of the report and remain attached whenever the report is forwarded or otherwise reproduced. 3.1 General The field inspection was performed by the URS team by walking along the FGD Pond #4 embankments and driving along the embankments crest. Features and conditions were documented on the inspection report form and were photographed and marked with GPS coordinates. The approximate locations of the photos are detailed in the inspection photo log overview map on the first page of Appendix A. In addition to documenting current features, the photograph log of existing conditions is intended to provide a baseline for future inspections. 3.2 FGD Pond #4 Geometry FGD Pond #4 is a homogeneous earthen embankment with no internal drainage system. The reservoir is lined and the lining includes a leak detection system. It has a 25 foot crest width and both upstream and downstream slopes of 3 vertical to 1 horizontal (3:1). Figure 3 1 is a cross section of the embankment Naughton FGD Pond #4 Inspection 5

17 Figure 3 1. FGD Pond #4 Maximum Section [8] 3.3 Instrumentation The only instrumentation associated with FGD Pond #4 is the leak detection system for the lining [8]. It is shown as a detail on Sheet 6 of the design drawings [8]. There is no instrumentation, such as piezometers, in the embankment. 3.4 Impounded Water Depth and Volume On the day of the field inspection, the URS inspectors estimate there was over 30 feet of freeboard in the reservoir. Based on this estimate and using the Stage Capacity Table from the design drawings [8], approximately 600 acre feet of storage was occupied (FGD and water) at an approximate depth of 27 feet. 3.5 Storage Capacity The pond s capacity is reported at 1,407 acres feet [8]. 3.6 Observed or Potential Structural Weaknesses There were no observations that would indicate imminent weaknesses in the embankments Naughton FGD Pond #4 Inspection 6

18 3.7 Observed Changes This is the initial and only annual inspection conducted under the CCR rules [18] for the Naughton FGD Pond #4. However, PacifiCorp historically commissioned other third party inspections that were not related to the CCR rules, the latest being completed by URS in 2014 [1]. This report of observed changes is based on the 2014 report. Observations from 2014 and 2015 are provided in the photographic log side by side. Refer to Photo 10. This comparison documents standing water found during the 2014 inspection and the same area dry in Limitations and Consultant Qualifications 4.1 Limitations This report presents observations, and conclusions drawn from a review of pertinent documents referenced in Section 5, and a field inspection of the Naughton FGD Pond #4. The purpose of the review and inspection has been to assess the safety or adequacy of the facilities against catastrophic failure of the major constructed elements during normal operations or unusual or extreme events based on visual inspection and available information. A secondary purpose is to identify any potential deficiencies related to the CCR rules [19]. The conclusions and professional opinions presented herein were developed by the independent consultant and are in accordance with generally accepted engineering principles and practices at the time and location the services were provided. URS makes no other warranty, either expressed or implied. 4.2 Professional Engineer Qualifications The professional engineer for this inspection is Rick J. Cox. He is licensed in the State of Wyoming (13825) as a civil engineer. He has over 32 years experience in civil/structural engineering and has performed inspections and safety evaluations on dams, canals and numerous other water containing structures. 5 References [1] URS, 2014 Coal Combustion Residuals Impoundment Inspection and Assessment Naughton Power Plant, January 12, [2] CHA, Assessment of Dam Safety: Coal Combustion Surface Impoundments (Task 3), Final Report, Naughton Power Station, Kemmerer, Wyoming, [3] Cornforth Consultants, Inc., Phase I Geotechnical Assessments: Coal Combustion Waste Pond Embankments, Naughton Power Plant, Kemmerer, Wyoming, [4] MWH, Naughton Power Plant: Phase II Geotechnical Investigation, Salt Lake City, Utah, Naughton FGD Pond #4 Inspection 7

19 [5] Maxim Technologies, Inc., FGD Pond 2 Project, Naughton Plant Unit 3, Kemmerer, Wyoming, [6] Maxim Technologies, Inc., Unit 3 FGD Pond 1 Modifications Design Report, Naughton Power Plant, Kemmerer, Wyoming, [7] Crank Companies, Inc., Inspection Review Summary: Waste Ponds Dikes and Dams, Kemmerer, Wyoming, [8] Tetra Tech, Inc., FGD Effluent Disposal Pond 4 Design Drawings, Kemmerer, Wyoming, [9] A. Eldridge, Naughton Power Plant Field Monitoring Forms, November 2012 through September 2014, Naughton Power Plant, Kemmerer, Wyoming, [10] Tetra Tech, Inc., Notice of Completion of Construction, FGD Effluent Disposal Pond 4 Reservoir (Permit No R), Cheyenne, Wyoming, [11] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 1). Kemmerer, Wyoming, 1993, p [12] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 2). Kemmerer, Wyoming, 1993, p [13] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 3). Kemmerer, Wyoming, 1993, p [14] MWH, Probable Maximum Precipitation Analysis, Steamboat Springs, Colorado, [15] PacifiCorp Energy, Scope of Work: Coal Combustion Residuals Impoundment Inspection and Assessment, Salt Lake City, Utah, [16] Wyoming State Engineer's Office Regulations and Instructions; Part I, Surface Water, Chapter 5. Adopted in 1913, last revised in [17] Federal Emergency Management Agency s (FEMA), Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, April [18] United States Geological Survey [USGS], 2008 Interactive Deaggregations, [Online]. Available: [Accessed: 27 Oct 2014]. [19] 40 CFS 257 Disposal of Coal Combustion Residuals from Electric Utilities, April 17, Naughton FGD Pond #4 Inspection 8

20 Appendix A Photograph Log 2015 Naughton FGD Pond #4 Inspection

21 Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-1

22 Photograph No. 1 Erosion on the interior slope of the southwestern corner of FGD Pond #4. Note exposed membrane liner. Photograph No. 2 Animal burrows on the southern embankment of the FGD Pond #4. Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-2

23 Photograph No. 3 Downstream face of southwest embankment. Note wet area beyond toe. Photograph No. 4 Crest of southwest embankment. No observable depressions. Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-3

24 Photograph No. 5 Downstream face of southwest embankment. No observed anomalies. Photograph No. 6 Minor erosion from wave action at water surface on east embankment. Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-4

25 Photograph No. 7 Wave action erosion on east embankment. Photograph No. 8 Upstream face of east embankment. Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-5

26 Photograph No. 9 Inlet structure and membrane channel. No observed deficiencies. Photograph No. 10 Downstream toe of east embankment. October 2014 photo on left and August 2015 photo on right. Inspection Photographs PacifiCorp Energy FGD Pond No Naughton Power Plant August 24, 2015 Page A-6

27 Appendix B Annual Inspection Report Form 2015 Naughton FGD Pond #4 Inspection

28 Feature Name: Naughton FGD Pond #4 Annual CCR Impoundment Inspection Report Feature ID: Issue Date: Form XXXXX Revision A Page 1 of 4 Date: August 24, 2015 Station/Owner PacifiCorp County, Lincoln Inspected By Date Rick J. Cox, P.E. and Matt Zion Type of Dam Concrete Gravity Embankment Concrete Arch Stone Masonry State Wyoming Phone No Weather Wet Dry Snow Cover Concrete Buttress Other Other Type of Inspection Initial Periodic Follow up Other Hazard Description Low. No buildings immediately downstream. Remarks This was the initial inspection under CCR regulations. Pool Level (ft) Estimated by inspection team to have 30 feet freeboard Condition Assessment Satisfactory Unsatisfactory Poor Not rated Fair Actions None Maintenance Monitoring Minor Repair Engineering Recommendations Inspection letter Deficiency letter EOR notice Engineering study Inspection by EOR Hazard Class Low (A) Intermediate (B) High (C) Inspection by DSE Dam safety order Enforcement Periodic reinspection Other reinspection Total Precipitation since last inspection 10 am of inspection, large thunderstorm. Estimate ½ inch UPSTREAM SLOPE/FACE Problems COVER: 1. None 2. Vegetation >2 dia. 3. Veg. height >6 4. High bushes 5. Animal Burrows 6. Livestock damage 7. Wave Erosion 8. Slides 9. Depressions 10. Bulges 11. Cracks 12. Spalling 13. Scarps 14. Sloughing 15. Holes 16. Undermining 17. Displaced joints 18. Deteriorated joints 19. Exposed reinforcement 20. Veg. or sediment in rip rap 21. Displaced rip rap 22. Sparse rip rap 23. Other Erosion 24. Other Vegetation Rip rap Concrete Asphalt Other Membrane liner with earth cover Comments /Action Items : Minor erosion at water surface of earthen cover over lining. Minor other eroson down interior face. Actions None Maintenance Monitoring Minor Repair Engineering TOP OF DAM/CREST 1. None 2. Vegetation >2 dia. 3. Veg. height >6 4. High bushes 5. Animal Burrows 6. Livestock damage Comments /Action Items 7. Ruts 8. Depressions 9. Unlevel 10. Misalignment 11. Signs of overtopping PROBLEMS 12. Cracks 13. Deteriorated joints 14. Displaced joints 15. Exposed reinforcement 16. Settlement 17. Scarps 18. Spalling 19. Sinkholes 20. Puddles 21. Other COVER: Vegetation Rip rap Concrete Asphalt Other gravel Actions None Maintenance Monitoring Minor Repair Engineering

29 Feature Name: Naughton FGD Pond #4 Annual CCR Impoundment Inspection Report Feature ID: Issue Date: Form XXXXX Revision A Page 2 of 4 Date: August 24, 2015 DOWNSTREAM SLOPE/FACE 1. None 2. Vegetation >2 dia.\ 3. Veg. height >6 4. High bushes 5. Poor grass cover 6. Animal Burrows 7. Livestock damage 8. Wetness 9. Seepage 10. Boils 11. Puddles 12. Erosion 13. Slope instability 14. Scarps PROBLEMS 15. Sloughs/bulges 16. Depressions 17. Undercutting 18. Rutting/rills 19. Cracks 20. Scour 21. Spalling 22. Displaced joints 23. Deteriorated joints 24. Exposed reinforcement 25. Riprap needs attention 26. Veg. or sediment in rip rap 27. Other 28. Does standing water or seepage contain sediment? Yes No NA 29. Is there natural hillside seepage in in embankment area? Yes No NA Describe seepage with regard to quantity and clarity (turbidity). Note changes: COVER: Vegetation Rip rap Concrete Asphalt Other Comments /Action Items: Fill on one animal burrow observed. TOE CONTACT Actions None Maintenance Monitoring Minor Repair Engineering PROBLEMS COVER: 1. None 8. Wetness 15. Sloughs/bulges 22. Displaced joints 2. Vegetation >2 dia. 9. Seepage 16. Depressions Vegetation 23. Deteriorated joints 3. Veg. height >6 10. Boils 17. Undercutting Rip rap 24. Exposed reinforcement 4. High bushes 11. Puddles 18. Rutting/rills Concrete 25. Riprap needs attention 5. Poor grass cover 12. Erosion 19. Cracks Asphalt 26. Veg. or sediment in rip rap 6. Animal Burrows 13. Slope instability 20. Scour Other 27. Other 7. Livestock damage 14. Scarps 21. Spalling 28. Does standing water or seepage contain sediment? Yes No NA Describe seepage with regard to quantity and clarity (turbidity). Note changes: Wet area at toe of east embankment in 2014 is now totally dry. Comments /Action Items ABUTMENT CONTACTS Actions None Maintenance Monitoring Minor Repair Engineering PROBLEMS COVER: 1. None 8. Wetness 15. Sloughs/bulges 22. Displaced joints 2. Vegetation >2 dia. 9. Seepage 16. Depressions Vegetation 23. Deteriorated joints 3. Veg. height >6 10. Boils 17. Undercutting Rip rap 24. Exposed reinforcement 4. High bushes 11. Puddles 18. Rutting/rills Concrete 25. Riprap needs attention 5. Poor grass cover 12. Erosion 19. Cracks Asphalt 26. Veg. or sediment in rip rap 6. Animal Burrows 13. Slope instability 20. Scour Other 27. Other 7. Livestock damage 14. Scarps 21. Spalling Comments /Action Items Actions None Maintenance Monitoring Minor Repair Engineering

30 Feature Name: Naughton FGD Pond #4 Annual CCR Impoundment Inspection Report Feature ID: Issue Date: Form XXXXX Revision A Page 3 of 4 Date: August 24, 2015 PRINCIPAL SPILLWAY OBSERVATIONS No Spillway Is spillway control system operating properly? Yes No PROBLEMS CHANNEL LINING 1. None 16. Undermining 23. Sloughing 9. Misalignment 2. Trashguard 17. Voids 24. Scarps 10. Joints leaking Vegetation 3. Debris 18. Cracks 25. Deteriorated lining 11. Joint deterioration Rip rap 4. Obstructed 19. Holes 26. Boils 12. Joint displacement Concrete 5. Plugged/Clogged 20. Spalling 27. Outlet erosion 13. Conduit collapsed Asphalt 6. Gates Damaged 21. Slides 28. Displaced rip rap 14. Exposed reinforcement Other 7. Gates leaking 22. Outlet 29. Sparse rip rap 15. Erosion 8. Gates Rusted undercutting 30. Other Comments /Action Items EMERGENCY SPILLWAY Actions None Maintenance Monitoring Minor Repair Engineering OBSERVATIONS No emergency spillway Same as primary spillway PROBLEMS CHANNEL LINING 9. Undermining 14. Displaced rip rap Vegetation 1. None 5. Joint deterioration 10. Voids 15. Sparse rip rap Rip rap 2. Debris in channel 6. Joint displacement 11. Cracks 16. Outlet undercutting Concrete 3. Gates 7. Exposed reinforcement 12. Holes 17. Inadequate capacity Asphalt 4. Misalignment 8. Erosion 13. Outlet erosion 18. Other Other Comments /Action Items DRAINS/OUTLET STRUCTURE Actions None Maintenance Monitoring Minor Repair Engineering Observations 1. Is discharge system operating properly? Zero discharge facility Yes No N/A 2. Valves and operators in good condition? None Yes No N/A 3. Walkway in good condition? Yes No N/A 4. Is there any turbidity observed at the outlet? Yes No N/A 5. Seepage at pipe outlet. Outlet is submerged. Yes No N/A 6. No Bottom Drain Yes No N/A 7. Bottom Drain Operable Yes No N/A 8. Subsurface Drain Dry Yes No N/A 9. Subsurface drain muddy flow Yes No N/A 10. Subsurface drain obstructed Yes No N/A 11. Animal guard Yes No N/A 12. other Yes No N/A Comments /Action Items Actions None Maintenance Monitoring Minor Repair Engineering

31 Feature Name: Naughton FGD Pond #4 Annual CCR Impoundment Inspection Report Feature ID: Issue Date: Form XXXXX Revision A Page 4 of 4 Date: August 24, 2015 RESERVIOR/POOL OTHER OBSERVATION Has there been a sudden drop in the content level of the Impoundment Yes No PROBLEMS 1. None 2. Inadequate freeboard Comments /Action Items 3. Skimmer 4. Depressions 5. Whirlpools 6. Sinkholes 7. Unwanted growth in pond water Actions None Maintenance Monitoring Minor Repair Engineering OBSERVATIONS 1. leachate/stormwater (RCP; CMP) drain pipes that pass through or under an ash basin intact? Yes No N/A 2. Drainage/ diversion ditches/riprap lined channels in good condition? Yes No N/A 3. Other steel structures/steel reinforcement in concrete structures in good condition? Yes No N/A 4. Other concrete structures in good condition? Yes No N/A 5. Overflow pipes and flap gates on filter dam/ drain pipe filter zone in good condition? Yes No N/A 6. Howell Bunger Valves in good condition? Yes No N/A 7. Weirs in good condition? Yes No N/A 8. Fences and Gates in good condition? Yes No N/A 9. Security devices in good condition Yes No N/A 10. Signs in good condition Yes No N/A 11. Instrumentation in good condition Yes No N/A 12. Reference monuments/survey Monuments in good condition Yes No N/A 13. other Yes No N/A Comments /Action Items Actions None Maintenance Monitoring Minor Repair Engineering Routine instrumentation monitoring (piezometers, inclinometers, etc.) are recorded separately. Have these measurements been collected, and properly recorded. Yes No N/A Are additional sheets included, if applicable to address regulatory, or third party inspection issues? Yes No N/A Are there any other abnormal conditions at the Impoundment that could pose a risk to public health, safety or welfare; the environment or natural resources Yes No Inspector Signature Date 8/24/2015

32 Appendix C Example PacifiCorp Inspection Form 2015 Naughton FGD Pond #4 Inspection

33 1 Naughton Impoundment Inspection Report Impoundment Name: Naughton FGD Pond 4 Date: Time: Inspected By: Type of Impoundment: Active Inactive Weather Conditions: Wet Dry Snow Cover Other Discharge: Yes No Water Elevation: Instrumentation Monitoring Completed: Yes No NA Inspection Frequency: Routine Weather/Seismic Event High Flow Other Upstream Face 1. Evidence of erosion from surface runoff or other effects on the face of the embankment. Yes No 2. Riprap or erosion protection damaged, needs repair. Yes No 3. Water elevation exceeds freeboard requirements for the impoundment and may overtop. Yes No 4. Animal burrows or other animal damage present on the face of the embankment. Yes No 5. Vegetation taller than 6 inches is present on the embankment. Yes No 6. Signs of settlement, low spots, depressions, sinkholes, cracks, or other instability visible on the embankment. Yes No Observations: Actions: None Maintenance Monitoring Engineering Notification/Work Order#: Downstream Face 7. Indicators of seepage or evidence of seepage are present on the face, abutments, or toe of the embankment. Yes No 8. Evidence of erosion from surface runoff or other effects on the face of the embankment. Yes No 9. Animal burrows or other animal damage present on the face of the embankment. Yes No 10. Vegetation taller than 6 inches is present on the embankment. Yes No 11. Signs of settlement, slides, low spots, depressions, sinkholes, cracks, or other instability visible on the embankment. Yes No Observations: Actions: None Maintenance Monitoring Engineering Issue Date: Rev. 1 Notification/Work Order#:

34 2 12. Signs of surface damage from vehicles (wheel ruts), drainage, or other activity are present. Yes No 13. Evidence of erosion from surface runoff on the crest. Yes No 14. Animal burrows or other animal damage present on the crest. Yes No 15. Vegetation taller than 6 inches is present on the crest. Yes No 16. Signs of settlement, low spots, depressions, sinkholes, cracks, or other instability visible on the crest. Yes No Observations: Crest Actions: None Maintenance Monitoring Engineering Notification/Work Order#: Rule 17. Any appearance of actual or potential structural weakness and other conditions which are disrupting or have the potential to disrupt the operation or safety of the CCR unit? Yes No NA Yes No NA 18. Abnormal discoloration, flow, or discharge of debris or sediment from outlets or structures that pass underneath the impoundment, or through the dike? 19. Outlets, conduits, and hydraulic gates malfunctioning, with seepage or other evidence of damage. Yes No NA 20. Instrumentation, pump-back systems, drains, and other monitoring intact. Yes No NA 21. Other non-structural or non-emergency safety issues. Yes No NA Observations: Actions: None Maintenance Monitoring Engineering Notification/Work Order#: Inspector Signature: Date: Issue Date: Rev. 1