NAUGHTON NORTH ASH POND STRUCTURAL STABILITY …€¦ · The §257.73(d) rule states that the owner...

Status: Rev. 0 i 01 September 2016 Document No: NP-TR-013 Naughton North Ash Pond Structural Stability Assessment

NAUGHTON NORTH ASH POND STRUCTURAL STABILITY ASSESSMENT

Prepared for: PacifiCorp, Naughton Power Plant Project Manager: Chad Tomlinson Date: 01 September 2016

Document No.: NP-TR-013

Quality Assurance Statement

Office Address MWH 2890 Cottonwood Parkway, Suite 300 Salt Lake City, UT 84121

Prepared by Jacob Traucht Reviewed by James Dixon Approved for Issue by Chad Tomlinson

Revision Schedule

Rev No. Date Description

Prepared

By

Reviewed By

Approved

By

0 09/01/16 Issued for Use J. Trauscht 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.

CERTIFICATION

I hereby certify that this Structural Stability Assessment for the North Ash Pond located at PacifiCorp’s Naughton Power Plant has been prepared in accordance with §257.73(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, 2015.

By:

Date: 09/01/2016

Chad Tomlinson, P.E.

Wyoming P.E.# 15375

Status: Rev. 0 2 01 September 2016 Document No: NP-TR-013 Naughton North Ash Pond Structural Stability Assessment

REPORT OF §257.73 (D)(1) – INITIAL STRUCTURAL STABILITY ASSESSMENT

The §257.73(d) rule states that the owner or operator of the Coal Combustible Residual (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 §257.73(d) as it pertains to the North Ash Pond (NAP).

The NAP at PacifiCorp’s Naughton Power Plant manages CCR material, specifically bottom ash and fly ash, produced from the combustion of coal for energy production from Unit 3. The ash is sluiced to the NAP through high-density polyethylene (HDPE) pipes. This facility also accepts water from flash tank blow down from Unit 3, the domestic water and sewage system, equipment spills, equipment wash down, and process water from the Unit 3 boiler. The NAP was originally constructed in 1974, and expanded in 1976, 1981, 1987, and most recently in 1994.

The Pond contains three dikes, the Intermediate Dike, separating the NAP from the North Clear Water Pond (NCWP), the Main Dike, which is located on the south side of the NCWP, and the East Saddle Dike which confines the east side of the NCWP (Figure 1). These embankments were constructed as homogeneous compacted clay fill. The maximum embankment heights at the NAP are 56 feet and 52 feet for the intermediate dike and the main dike, respectively. The ash pond has a surface area of 107 acres and a storage capacity of 2,181 acre-feet. The clear water pond side has a surface area of 64 acres and a storage capacity of 1,360 acre-feet.

Once ash is removed in the decant basin, clear water travels through one of two discharge structures. The first structure consists of an open pipe intake on the upstream side with a gated outlet control structure on the downstream side of the main embankment and a decant structure that discharges water from the NAP decant basin to the NCWP. Water levels in the NCWP are controlled through these structures and through reuse of the clear water for sluicing bottom ash and fly ash from Unit 3. The NCWP is fed by a 24 inch diameter concrete lined cylinder pipe from the open pipe intake and maintains the normal pool elevation of the NAP at 6,885 feet above mean sea level (amsl).


Figure 1 - NAP and NCWP Layout

Additional information pertaining to the design and construction and stability of the NAP can be found in the following documents:

• Naughton North Ash Pond History of Construction (MWH, 2016a)

• Naughton North Ash Pond Safety Factor Assessment (MWH, 2016b)

§257.73(d)(1)i. Foundation and Abutment Stability “…document whether the CCR Unit has been designed, constructed, operated and maintained with stable foundations and abutments”


Design & Construction

Clearing and grubbing of the NAP site was extended to 12 inches below the ground surface to remove all stumps and roots greater than 2-inches within the limits of work. In addition, all subgrades for permanent construction, including subgrades for embankment fill were stripped of surface vegetation, sod, debris, and organic topsoil. Following clearing and grubbing and topsoil stripping, the construction specifications for the foundation (subgrade) of the constructed embankments required the top 12-inches of the subgrade be scarified and compacted to at least 95-percent of maximum dry density in order to provide a well compacted foundation. The subgrade surface was then scarified to allow bonding with the first layer of embankment fill (Black and Veatch, 1993).

Based on a review of the design drawings, there are no abutments that were constructed associated with NAP. The NAP was constructed in a broad sloping area and not against a valley sidewall.

General fill, mainly consisting of silty clays, was placed in loose lifts not to exceed 12 inches and compacted to a density of 95-percent of maximum dry density with a moisture content ranging from -4 to +2 percent of optimum moisture content. The general fill originated from several borrow pits around the Naughton site that have been previously designated as being suitable for embankment construction, through subsurface exploratory investigations. A soft soil area was encountered when the site was being prepared. The soft soils were excavated and replaced with compacted soil (general fill). These specifications are consistent with recognized and generally accepted good engineering practices for preparation of foundations to receive embankment fill.

A four foot thick sand blanket drain was placed on the downstream side of the NCWP Main Dike to mitigate against an elevated phreatic surface within the embankment. The grain size distribution for the blanket drain was developed to meet filter compatibility with the adjacent embankment fill.

The NAP is judged to have been designed and constructed with stable foundations and abutments.

Operation & Maintenance

The NAP is judged to have been operated and maintained sufficiently to provide stable foundations and abutments.

§257.73(d)(1)ii. Slope Protection “Adequate slope protection to protect against surface erosion, wave action, and adverse effects of sudden drawdown”


The upstream dikes of the NAP are lined with a layer of riprap bedding and rip rap that is roughly 12 inches thick. The use of riprap for slope protection is consistent with recognized and generally accepted engineering design practices to provide protection against erosive forces due to wind and wave action along the embankment slope faces. The rip rap on the interior, or upstream embankment face, extends from the crest to 20 vertical feet downslope from the crest to provide erosion protection of the embankment faces for the anticipated fluid surface levels during operation (Black and Veatch, 1993).


Appropriate riprap bedding gradations were specified and constructed on each of the dikes to prevent rock loss into the embankment fill over time.

The rip rap protection extends above and below the anticipated fluid surface levels sufficiently to protect against wave action. The gradations of the riprap bedding and riprap specified in the design documentation are provided in Tables 1 and 2, respectively (Black and Veatch, 1993).

Table 1 – Riprap Bedding Gradation

U.S. Standard Sieve Size Percent Passing

3-inch 100

1-inch 40-65

No. 4 15-30

No. 40 5-10

No. 100 0-5

Table 2 – Riprap Gradation

Stone Size (in pounds) Percent of Total Weight Smaller Than Given Size

500 100

150 50

80 25

15 not to exceed 10

Based on a review of the rip rap gradation provided in Table 2 and using the United States Department of Agricultural (USDA) Technical Release No. 69 – Riprap for Slope Protection (USDA, 1983), the W50 size of the rip rap specified and placed on the interior embankment slopes are sufficient to protect against a significant wave height of approximately two feet. Although a calculation for anticipated wave height for the NAP could not be found in the design documentation, MWH performed a preliminary evaluation and determined that the size of rip rap specified was sufficient for the anticipated wave height of 1.6 feet based on a wind speed of 50 mph and fetch distance of 3000 ft.

The NAP is judged to have been designed and constructed with adequate slope protection to protect against surface erosion, wave action, and the adverse effects of sudden drawdown.


The NAP is operated with a minimum 5-foot freeboard as required by the permit with the State of Wyoming, to provide sufficient freeboard to protect against any change in water level that might occur. The operating level of the NAP is maintained below the five feet by a decant structure with a pipe invert


elevation of 6893 feet above mean sea level (AMSL). Slopes are visually inspected weekly by Naughton operations personnel as well as annually by third party personnel. Minor erosion repairs are completed as necessary as part of the NAP’s routine maintenance. Table 3 summarizes the normal pool elevation and design freeboard.

Table 3 – Operational Data for NAP

Operational Data Design Value

Normal Pool Elevation 6,900 feet AMSL

Embankment Crest Max Elevation 6,905 feet AMSL

Design Freeboard 5 feet

The NAP is judged to have been operated and maintained sufficiently to provide adequate slope protection, to protect against surface erosion, wave action, and the adverse effects of sudden drawdown.

§257.73(d)(1)iii. Dike Compaction “Dikes mechanically compacted to a density sufficient to withstand the range of loading conditions in the CCR unit”


Material testing and quality reports during construction were not available for review and therefore, this review relies on design documentation. The construction specifications for the NAP embankment required that the embankment fill be placed in horizontal layers not to exceed 9 inch lose lifts and compacted to a density of 97 percent of maximum dry density and a moisture content of -2 to +3 percent of optimum moisture content (Black and Veatch, 1993). The upstream slopes were constructed at 3H:1V and downstream slopes were constructed at slopes varying between 3H:1V and 4H:1V. It is MWH’s opinion that embankments constructed with similar compaction and moisture conditioning specification, as well as similar upstream and downstream slope geometry, are consistent with generally recognized and accepted good engineering practices for homogenous clay fill embankments and have performed as designed. A cross-section through the main dike of the NAP is shown in Figures 2. A safety factor assessment was performed for the SAP and the results indicated that the SAP meets all factor of safety requirements stipulated in the CCR rule.

The NAP is judged to have been designed and constructed with dikes mechanically compacted to a density sufficient to withstand the range of loading conditions in the CCR unit.


Figure 2 – Cross-Section through Main Dike of NAP


The NAP and NCWP embankments are visually inspected weekly by Naughton Plant personnel as well as annually by a third party. The purpose of these inspections is to observe the performance of the embankment as well as identify signs of potential instability, seepage, inappropriate or lacking vegetative cover, or other signs of deterioration that could be an indicator of, or develop into, a mode of failure. The “Assessment of Dam Safety, Coal Combustion Surface Impoundments (Task 3) Final Report” (CHA, 2009) identified differential movement, possibly related to frost heave in the main dike, seepage and sloughing in the east groin of the main dike, and a wet area beyond the toe of the east embankment near the abutment. The source of water at the toe of the east embankment near the abutment was determined to be either from seepage from FGD Pond #2 or the NAP itself. These identified deficiencies are deemed to not pose an imminent dam safety concern and are being monitored as part of the weekly and annual inspections.

Based on URS’s annual inspection performed during 2015, there are no observations that indicate imminent weakness in the embankment (no tension cracks or movement). Seepage at the toe near the right and left abutments are observations that there is potential seepage from the embankment, which is being monitored as part of the NAP weekly inspections.

The NAP is judged to have been operated and maintained to preserve the compaction density of the dike to withstand the range of loading conditions in the CCR unit.

§257.73(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”


The exterior slopes of the NAP 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 (Black and Veatch, 1993).

The NAP was designed and constructed with vegetated slopes of dikes. However, no specification was provided to identify maintenance procedures after construction.



The EPA (CHA, 2009) site assessment stated that PacifiCorp was not maintaining the vegetation along the embankments down to within six inches of ground surface to deter animal burrowing and allow in better inspection of the embankments. However, it has been determined that due to the presence 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. Based on field observations made by URS during the 2015 annual inspection, minor woody vegetation and minor erosion was observed on the south embankment. There were no recommendations associated with these minor erosion and vegetation issues (URS, 2015b).

Despite non-conformance with the current regulations associated with maintaining vegetation on slopes to less than six inches, this does not impede the ability to perform routine inspections of the NAP embankment. Therefore, it is MWH’s opinion that the current maintenance methods are appropriate for the type of vegetation found on the NAP. The NAP is judged to have been operated and maintained with vegetated slopes of dikes and surrounding areas not exceeding a height of six inches above the slope of the dike, except for slopes which have an alternate form or forms of slope protection.

§257.73(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”


The NAP does not have a spillway. Discharges from the NAP to the NCWP is controlled via a decant tower. The NCWP discharges to surface water via a weir discharge structure. Overtopping of embankment caused by stormwater events is managed via a 5-foot freeboard measured from normal pool elevation to top of crest.

MWH performed a Probable Maximum Precipitation (PMP) analysis for the NAP. MWH’s evaluation considered that the NAP is an off-channel basin, meaning that it does not receive inflows from sources outside of direct rainfall. The collection area of the NAP is 24 acres with an available freeboard of 5-feet.


Using rainfall isohyetal contour maps provided by the National Weather Service, a PMP for the area in question during a 72 hour period resulted in 10.6 inches of rainfall. This only consumes a small amount of the available freeboard. A summary of the PMP evaluation is provided in Table 4.

Table 4 – NAP PMP Analysis

On Channel Basin

Impoundment EPA PMP Requirement

Collection Area Water Level Increase

Freeboard

NAP Full 24 acres 10.6-inch 5-feet


Given that the NAP does not include a spillway, there are no active maintenance or operation associated with this requirement. However, the operating level and available free-board are monitored as part of the weekly inspections to confirm that the minimum freeboard is being maintained.

§257.73(d)(1)v. Hydraulic Structures “Hydraulic structures underlying the base of the CCR unit or passing through the dike of the CCR unit 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”


The NAP shares a dividing embankment with the NCWP. Water is discharged from the NAP to the NCWP through a concrete and steel decanting tower structure located within the NAP. The discharge is conveyed to the NCWP through a 24-inch concrete cylinder pipe. According to the design drawings, seepage collars were placed at the mid-span of each 20-foot pipe section. Information pertinent to the discharge structure is provided in Table 5.

Table 5 – Pertinent Information Pertaining to the NAP and NCWP Discharge Structure

Top of Concrete Structure Elevation 6,903 feet amsl

Crest Length (trench width) 3-ft (stoplog)

Gate Invert 6,892 feet amsl

Conveyance 24-inch concrete lined cylinder

Materials of Construction Concrete walls, with concrete footer and metal gates

Base Elevation of Structure (footer) 6888.46 feet AMSL


This requirement deals only with operation and maintenance. An evaluation of the design and construction of the hydraulic structures would not apply to this rule.


The decant tower structure is visually inspected as part of the weekly and annual pond inspection. No issues have been identified with respect to the current state of the decant structure (no increased seepage or subsidence above the pipe). Additionally, no major repairs associated with the decant tower structure have been conducted. As such, the decant tower structure continues to operate as designed.

The NAP is judged to have operated and maintained all hydraulic structures sufficiently to preserve structural integrity and prevent significant deterioration, deformation, distortion, bedding deficiencies, sedimentation, and debris which may negatively affect the operation of the hydraulic structure.

§257.73(d)(1)vi. 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”


The main embankment of the NAP serves as a dividing embankment to separate the NAP from NCWP as shown in Figure 2. The normal pool elevations for the NAP and NCWP are 6900 feet AMSL and 6885 feet AMSL respectively. The safety factor assessment of the NAP, conducted by MWH concluded that the SAP is stable against all anticipated loading conditions (MWH, 2016b).

The NAP is judged to have been designed and constructed adequately to maintain structural stability with downstream inundated slopes, during low pool of the NCWP or sudden drawdown of the NCWP.


The NCWP is directly fed through the ash pond decant tower structure and remains filled at all times. The level is controlled by a stoplog structure in order to maintain a constant water level (URS, 2015a). The NCWP drains through a v-notch weir and into a rip rap lined channel. Rapid drawdown analyses have been completed and show that a rapid drawdown event will not affect the stability of the embankment (see Factor of Safety Assessment).

The most recent annual dam safety inspection of the NAP was completed in 2015 (URS, 2015a). There were no new recommendations that were made by URS based on this recent inspection. Previously, several recommendations were made by CHA, MWH, and URS in previous assessments, however no comments, suggestions and recommendations raised imminent dam safety concerns.

The NAP is judged to have been operated and maintained adequately to preserve structural stability with downstream inundated slopes, during low pool of the NCWP or sudden drawdown of the NCWP.


§257.73(d)(2) Structural Stability Deficiencies No structural stability deficiencies have been identified associated with the NAP during the weekly inspections. An initial annual inspection of the NAP was completed in 2015 by URS in accordance with §257.83(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 NAP is provided in Appendix A.

There are no outstanding structural stability deficiencies associated with the NAP.

§257.73(d)(3) Certification from Qualified Professional Engineer The initial assessment and each subsequent periodic assessment was conducted in accordance with the requirements of section 257.73d.


REFERENCES Black and Veatch. PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion,

Naughton Power Plant (Vol. 1), 1993.

Black and Veatch. PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 2), 1993.

Black and Veatch. PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 3), 1993.

CHA, Assessment of Dam Safety, Coal Combustion Surface Impoundments (Task 3), Final Report, 2009.

MWH, 2012. Naughton Power Plant Geotechnical Investigation. September 2012.

MWH, 2016a. Naughton South Ash Pond History of Construction, October 2016

MWH, 2016b. Naughton South Ash Pond Safety Factor Assessment, October 2016PacifiCorp Energy Memo to Environmental Protection Agency. PacifiCorp Comments Regarding the Assessment of Dam Safety Coal Combustion Surface Impoundments Final Report at the PacifiCorp Naughton Power Station. January 14, 2010.

URS Corporation, 2015a Coal Combustions Residuals Annual Inspection, Naughton Power Plant, North Ash Pond. December 2015.

URS Corporation, 2015b Coal Combustions Residuals Impoundment Inspection and Assessment, Naughton Power Plant. January 2015.

Appendix A

Annual Inspection Report

2015 Coal Combustion Residuals Annual Inspection

Naughton Power Plant North Ash Pond

Prepared for PacifiCorp Energy North Temple Office 1407 West North Temple Salt Lake City, Utah 84116

Final December 29, 2015

URS Corporation 756 East Winchester, Suite 400 Salt Lake City, Utah 84107

2015 Naughton North Ash Pond Inspection i

Contents1 Findings ................................................................................................................................................. 1

2 Description and History of North Ash Pond .......................................................................................... 2

2.1 General Overview ......................................................................................................................... 2

2.2 Location ......................................................................................................................................... 2

2.3 North Ash Pond Description ......................................................................................................... 2

2.4 Performance History ..................................................................................................................... 4

2.5 Construction History ..................................................................................................................... 5

2.6 Review of Operating Record Files ................................................................................................. 5

2.6.1 Design and Construction Information ................................................................................... 5

2.6.2 Previous Periodic Structural Analyses ................................................................................... 5

2.6.3 Results of Inspection by a Qualified Person .......................................................................... 5

2.6.4 Results of Previous Annual Inspections ................................................................................ 5

3 Field Inspection of North Ash Pond ...................................................................................................... 6

3.1 General .......................................................................................................................................... 6

3.2 North Ash Pond Geometry ............................................................................................................ 6

3.3 Instrumentation ............................................................................................................................ 8

3.4 Impounded Water Depth and Volume ......................................................................................... 8

3.5 Storage Capacity ........................................................................................................................... 8

3.6 Observed or Potential Structural Weaknesses ............................................................................. 8

3.7 Observed Changes ........................................................................................................................ 8

4 Limitations and Consultant Qualifications ............................................................................................ 8

4.1 Limitations ..................................................................................................................................... 8

4.2 Professional Engineer Qualifications ............................................................................................ 9

5 References ............................................................................................................................................ 9

Appendices

Appendix A Photograph Log

Appendix B Annual Inspection Report Form

Appendix C Example PacifiCorp Inspection Form

2015 Naughton North Ash Pond Inspection 1

1 FindingsThis 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 257.83 (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[18].

The field inspection was performed on August 24, 2015 and found the principal project features of the

North Ash Pond to be in satisfactory condition. Nothing was observed suggesting 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 July 2014.

Figure 1‐1. North Ash Pond

Observations from the 2015 inspection include:

1. Animal burrows (Photos 3,5,6 and 10)

2. An area of signification vegetation beyond the embankment toe near the pump station

(Photo 2). There is no observable change from 2014.

3. An historic erosion rill related to crest runoff that has been repaired at the crest to prevent

additional erosion (Photo 4).

4. Woody vegetation (Photos 7 and 8)


5. Minor undercutting of the outlet pipe (Photo9)

6. A damp area on the downstream slope of the east embankment (Photo 12). There is no

observable change from 2014.

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.

Figure 1‐2

2 DescriptionandHistoryofNorthAshPond

2.1 GeneralOverviewThe Naughton Plant is operated and fully‐owned by PacifiCorp.

The Black & Veatch Construction Permit Application for Combustion Waste Disposal Expansion Volume 2

[12] contains a full set of drawings for the North and South Ash systems. Although it is stamped “Not to

be used for construction” it is the most complete set of drawings and was likely stamped not for

construction because it was part of the application. URS relied on these drawings for this report on the

assumption that few changes likely occurred between application and construction.

2.2 LocationThe 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 NorthAshPondDescriptionThe North Ash Pond is located approximately 0.3 miles north and east of the plant generation facility,

and between FGD Pond #1 and the North Clear Pond. The pond actively receives hydraulically conveyed

bottom ash and fly ash waste material from Unit 3. The North Ash Pond has been referred to as the Unit

3 Ash Pond in previous reports [2]‐[4].


A single, homogeneous fill embankment, approximately 3,500 feet in length, forms the southeast

boundary of the pond. The embankment extends to the east where it wraps around toward the north

to the abutment. The embankment was generally constructed of native clayey soils obtained from

nearby borrow sources [3]. The specification for the embankment material required “…loose earth

having a moisture content such that the required density of the compacted soil will be obtained….” [11].

Supporting documentation reported that the compaction requirement was 95% by ASTM D698, plus or

minus 2% optimum moisture; however, the engineering properties were not identified in the supporting

documents. Both the upstream and downstream faces are armored with 24 inches of 6‐inch diameter

riprap. A cross section of the embankment is shown on Figure 3‐1.The North Ash Pond has a surface

area of approximately 151.5 acres and has a storage capacity of 2,100 acre‐feet [4]. The embankment

ranges in height from only a few feet to a maximum height of approximately 56 feet [12], [4]. The

existing embankment was constructed to a crest elevation of approximately 6,905 feet amsl. The crest

of the embankment is approximately 25‐feet wide with both upstream and downstream slopes

constructed at 3H:1V [12].

The outlet for the North Ash Pond consists of a reinforced concrete drop decant tower, which flows into

the North Clear Pond. The top of the tower is at elevation 6,903 feet amsl, which provides an

uncontrolled overflow into the tower at this elevation. The normal operating level of the pond is

controlled by a stoplog structure on the upstream face of the tower with a bottom sill elevation of

6,896 feet amsl. The conveyance pipe consists of 24‐inch diameter concrete cylinder pipe with an

upstream invert elevation of approximately 6,882 feet amsl [12]. According to the drawings, seepage

collars were placed at the mid‐span of each 20‐ft pipe section. The pond does not have any emergency

spillway and the pond is not lined; however, to reduce seepage, it has two feet of compacted, earth‐

lining in small unidentified areas where unsuitable material was encountered within the pond during

construction (page 12 Earthwork Specification) [11].


Refer to Table 2‐1 for a summary of pertinent data for the North Ash Pond.

Table 2‐1. North Ash Pond Pertinent Data

Description Design Value

Pond:

Total Pond Capacity (acre-feet) 2,100 [4]

Maximum Pond Elevation (feet) 6,900 [12]

Surface Area (acres) 151.5 [4]

Pond Perimeter (feet) 12,0001

Drainage Area (square miles) Unknown

Design Freeboard (feet) 5 [12]

Embankment:

Type Homogeneous3 [12]

Maximum Design Height (feet) 56 [12] [4]

Design Crest Width (feet) 25 [12]

Design Crest Length (feet) 3,500 [12]

Design Crest Elevation (feet) 6,905 [12]

Design Upstream Slope (feet) 3:1 [12]

Design Downstream Slope (feet) 3:1 [12]

Pond Outlet Structure:

Type Drop Decant Tower

Crest Elevation (feet) 6903.0 [12]

Crest Length (feet) 3 ft. (stoplog)

Gates Yes

Gate Invert Elevations (feet) 6882

Conveyance 24-inch CCP

2.4 PerformanceHistoryA wet area beyond the toe of the east embankment near the abutment was first documented by the

2009 Crank report[7]. The source of water may be either FGD Pond #2 or the North Ash Pond and it is

monitored. Groundwater in this area is pumped back to FGD Pond #2.

The CHA report [2] did not identify the wet area below the toe near the right abutment but the area is

shown on photographs in the report.

There have been no incidences of embankment failure, movement or seepage requiring remediation of

the North Ash Pond embankment reported in the record files.


2.5 ConstructionHistoryThe North Ash Pond was originally constructed in 1974. Several modifications to its configuration were

completed between 1974 and 1994.The North Ash Pond was constructed to its current configuration in

1994. The current embankment footprints are outside previous embankment alignments. No

significant subsequent modifications have been completed since 1994, although, the current North Ash

Pond encompasses the spatial extent of the ponds previously used for CCR disposal.

Fly ash and bottom ash slurry are delivered from Unit 3 via pipe to a point near the North Ash Pond

where it is conveyed into the pond by open channel. The pipe does not penetrate any constructed

embankments.

2.6 ReviewofOperatingRecordFilesThe 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 §§2557.73(c) (1) and 257.74(c) (1), previous periodic structural stability

assessments required under §§257.73(d) and 257.74(d), the results of inspections by a qualified person,

and results of previous annual inspections” [18]. The following subsection describes the review of

operating record files.

2.6.1 DesignandConstructionInformationURS reviewed the three volumes of construction documents contained in the Black & Veatch Permit

Application [11], [12], and [13]. These documents contain design drawings, specifications and reports in

support of constructing the North Ash Pond.

2.6.2 PreviousPeriodicStructuralAnalysesThe 2014 inspection [1] identified that a stability analysis was completed by CHA[2] and that its stability

met the factor of safety criteria being used. However, the original analysis was not available for URS to

review. Seismic analysis using current loading and methodology has not been performed [1]. There

were no recommendations for embankment remediation.

2.6.3 ResultsofInspectionbyaQualifiedPersonThe North Ash Pond 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. It is the

opinion of the author of this document that the interim inspections and reporting by plant staff are

appropriate and adequate for this CCR Unit.

2.6.4 ResultsofPreviousAnnualInspectionsThis is the initial and only annual inspection conducted under CCR rules [18] for the Naughton Power

Plant North Ash Pond. PacifiCorp has completed other independent inspections by third parties. 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:

http://www.berkshirehathawayenergyco.com/ccr/ppw.html

Section 5 of this report is a complete list of references for the Naughton North Ash Pond.

3 FieldInspectionofNorthAshPondA field inspection was conducted on August 24, 2015 by URS staff, Rick J. Cox, P.E. and Matthew Zion.

Mr. Cox previously participated in the CCR impoundment inspections in 2014 for Naughton Power Plant

[1] and was the principal author of the inspection report. Personnel from the Naughton Power Plant

participated in an interview prior to the field inspection to answer questions.

A photograph log documenting features and their condition at the time of the inspection is presented in

Appendix A.

The completed Annual Inspection Report form 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 GeneralThe field inspection was performed by the URS team by walking along the North Ash Ponds southeast

and east embankments and driving along the embankments crest. Features and conditions were

documented on the inspection checklist and were photographed and marked with GPS coordinates. The

approximate locations of the photos are detailed in the inspection photograph log overview map

located at the beginning of Appendix A, Photograph Log. In addition to documenting current features,

the photograph log of existing conditions is intended on aiding future inspections.

3.2 NorthAshPondGeometryThe North Ash Pond is a homogeneous earthen embankment with no internal drainage system. The

reservoir is unlined. Its horizontal configuration is comprised of a southeast and an east embankment as

shown on Figure 1‐1. Figure 3‐1 below is a cross section of the embankment showing the previous

embankment at the upstream toe. It has a 25‐foot crest width and both upstream and downstream

slopes of 3 vertical to 1 horizontal (3:1). Approximately half of the downstream face of the embankment

is submerged by the North Clear Pond.


Figure 3‐1. North Ash Pond Section [12]


3.3 InstrumentationThere is only one piezometer in the North Ash Pond embankment. Piezometer PZ‐9 is located in the

crest near the left abutment. Data indicates a relatively constant piezometric surface with a highest

elevation of 15.3 feet below ground (November 7, 20012) and a lowest elevation of 13.6 feet below

ground (November 5, 2013)1 . MWH reports that PZ9 was installed in response to the wet area below

the toe between FGD Pond #2 and the North Ash Pond [4]. The data does not offer any explanation or

concern about seepage at that location.

3.4 ImpoundedWaterDepthandVolumeOn the day of the field inspection, Naughton staff estimated the freeboard at 6.5 feet, making the water

surface at 6898.5. There is no stage/capacity curve or table in the records for the North Ash Pond.

3.5 StorageCapacityThe pond’s capacity is reported at 2,100 acres feet [4].

3.6 ObservedorPotentialStructuralWeaknessesThere were no observations that indicated imminent weaknesses in the embankment (no tension cracks

or movement) or outlet works (no increased seepage or subsidence above the pipe). Seepage at the toe

near both the right and left abutments are observations that there is potential seepage from the

embankment that requires monitoring for changes.

3.7 ObservedChangesThis is the initial and only annual inspection conducted under the CCR rules [18] for the Naughton North

Ash Pond. 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.

In two instances, observations from 2014 and 2015 are provided side by side in the photograph log in

Appendix A. Refer to Photos 2 and 12. These are both photos of the vegetation at the toe near both

abutments. In neither case was there an observable difference in vegetation between the 2014 and the

2015 photographs.

4 LimitationsandConsultantQualifications

4.1 LimitationsThis report presents observations, and conclusions drawn from a review of pertinent documents

referenced in Section 5, and a field inspection of the Huntington CCR Landfill. The field inspection was

limited to the interior of the perimeter road. 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

1 Piezometer data provided by Naughton Plant staff.


available information. A secondary purpose is to identify any potential deficiencies related to the CCR rules [18].

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, 2015.

[2] CHA, “Assessment of Dam Safety: Coal Combustion Surface Impoundments (Task 3), Final Report, Naughton Power Station,” Kemmerer, Wyoming, 2009.

[3] Cornforth Consultants, Inc., “Phase I Geotechnical Assessments: Coal Combustion Waste Pond Embankments, Naughton Power Plant,” Kemmerer, Wyoming, 2009.

[4] MWH, “Naughton Power Plant: Phase II Geotechnical Investigation,” Salt Lake City, Utah, 2012.

[5] Maxim Technologies, Inc., “FGD Pond 2 Project, Naughton Plant Unit 3,” Kemmerer, Wyoming, 1998.

[6] Maxim Technologies, Inc., “Unit 3 FGD Pond 1 Modifications Design Report, Naughton Power Plant,” Kemmerer, Wyoming, 2002.

[7] Crank Companies, Inc., “Inspection Review Summary: Waste Ponds - Dikes and Dams,” Kemmerer, Wyoming, 2009.

[8] Tetra Tech, Inc., “FGD Effluent Disposal Pond 4 Design Drawings,” Kemmerer, Wyoming, 2009.

[9] A. Eldridge, “Naughton Power Plant Field Monitoring Forms, November 2012 through September 2014,” Naughton Power Plant, Kemmerer, Wyoming, 2014.

[10] Tetra Tech, Inc., “Notice of Completion of Construction, FGD Effluent Disposal Pond 4 Reservoir (Permit No. 13536R),” Cheyenne, Wyoming, 2010.

[11] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal Expansion, Naughton Power Plant (Vol. 1). Kemmerer, Wyoming, 1993, p. 459.


[12] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal

Expansion, Naughton Power Plant (Vol. 2). Kemmerer, Wyoming, 1993, p. 317.

[13] Black & Veatch, PacifiCorp Construction Permit Application: Combustion Waste Disposal

Expansion, Naughton Power Plant (Vol. 3). Kemmerer, Wyoming, 1993, p. 531.

[14] MWH, “Probable Maximum Precipitation Analysis,” Steamboat Springs, Colorado, 2011.

[15] Wyoming State Engineer's Office Regulations and Instructions; Part I, Surface Water, Chapter 5.

Adopted in 1913, last revised in 1974.

[16] Federal Emergency Management Agency’s (FEMA), Federal Guidelines for Dam Safety: Hazard

Potential Classification System for Dams, April 2004.

[17] United States Geological Survey [USGS], “2008 Interactive Deaggregations,” 2014. [Online].

Available: http://geohazards.usgs.gov/deaggint/2008/. [Accessed: 27‐Oct‐2014].

[18] 40 CFS § 257 Disposal of Coal Combustion Residuals from Electric Utilities, April 17, 2015.

2015 Naughton North Ash Pond Inspection

AppendixA

PhotographLog

Inspection PhotographsPacifiCorp Energy

North Ash Pond -- Naughton Power PlantAugust 24, 2015

Page A-1



Page A-2

Photograph No. 1 View south of the North Ash Pond along the northern boundary road.

Photograph No. 2 Overflow pipe along North Ash Pond south dam. Note significant vegetation at toe of downstream embankment. The left photo is October 2014 and the right photo is August 2015. No observable difference.



Page A-3

Photograph No. 3 Animal burrow along the downstream side of the North Ash Pond southern dam.



Page A-4

Photograph No. 4 Erosion gully on the North Ash Pond southern embankment.



Page A-5

Photograph No. 5 Animal burrows on the downstream slope of the North Ash Pond south embankment.

Photograph No. 6 View of animal burrows on the south embankment of the North Ash Pond.



Page A-6

Photograph No. 7 Vegetation on the upstream side of the North Ash Pond south embankment.

Photograph No. 8 Vegetation along the downstream side of the North Ash Pond south embankment.



Page A-7

Photograph No. 9 Outlet discharge from the North Ash Pond to the North Clear Pond.

Photograph No. 10 Animal burrows on the south embankment of the North Ash Pond.



Page A-8

Photograph No. 11 Possible slump. Crest of the embankment is receded and the toe is enlarged.

Photograph No. 12 View of the drainages vegetation and proximity to the north embankment. Left photo is October 2014 and right photo is August 2015. No observable difference.



Page A-9

Photograph No. 13 Upstream face of south embankment of North Ash Pond. No undulation of the crest or fence. View to southwest.

Photograph No. 14 Upstream face of south embankment of North Ash Pond. No undulation of the crest or fence. View to northeast.


AppendixB

AnnualInspectionReportForm

Annual CCR Impoundment Inspection Report

Issue Date: 8-24-2015 Form XXXXX Revision A

Page 1 of 4

Feature Name: Naughton North Ash Pond

Feature ID: Date: August 24, 2015

Station/Owner PacifiCorp

County, Lincoln

State Wyoming

Inspected By Rick J. Cox, P.E. and Matt Zion

Date 8‐24‐15

Phone No. 801‐904‐4096

Type of Dam Concrete Gravity Embankment Concrete Arch Stone Masonry

Concrete Buttress Other

Weather Wet Dry Snow Cover

Other

Type of Inspection Initial Periodic Follow up Other

Hazard Description Low. No buildings immediately downstream.

Condition Assessment Satisfactory Unsatisfactory Poor Not rated Fair

Hazard Class Low (A) Intermediate (B) High (C)

Remarks This was the initial inspection under CCR regulations.

Actions None Maintenance Monitoring Minor Repair Engineering

Recommendations Inspection letter Inspection by DSE Deficiency letter Dam safety order EOR notice Enforcement Engineering study Periodic reinspection Inspection by EOR

Pool Level (ft) Reported by PacifiCorp staff at 6.5 feet below crest. Same as

South Ash Pond

Total Precipitation since last inspection 10 am of inspection, large thunderstorm. Estimate ½ inch

UPSTREA

M SLO

PE/FA

CE

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

Comments /Action Items Refer to Photo 7, Photolog showing brush on upstream slope


TOP OF DAM/CREST

PROBLEMS COVER: 1. None 2. Vegetation >2” dia. 3. Veg. height >6” 4. High bushes 5. Animal Burrows 6. Livestock damage

7. Ruts 8. Depressions 9. Unlevel 10. Misalignment 11. Signs of overtopping

12. Cracks 13. Deteriorated joints 14. Displaced joints 15. Exposed reinforcement 16. Settlement

17. Scarps 18. Spalling 19. Sinkholes 20. Puddles 21. Other


gravel

Comments /Action Items




Page 2 of 4



TOE CONTA

CT

PROBLEMS COVER:

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

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

Describe seepage with regard to quantity and clarity (turbidity). Note changes: Only damp areas near each abutment. No moving water.

No turbidity.



ABUTM

ENT CONTA

CTS

PROBLEMS COVER:

1. None 2. Vegetation >2” dia. 3. Veg. height >6” 4. High bushes 5. Poor grass cover 6. Animal Burrows 7. Livestock damage





Comments /Action Items Abutement exist, just that they taper out to nothing as natural ground.


DOWNSTREA

M SLO

PE/FA

CE

PROBLEMS COVER: 1. None 2. Vegetation >2” dia.\ 3. Veg. height >6” 4. High bushes 5. Poor grass cover 6. Animal Burrows 7. Livestock damage





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: Outlet pipe undercut.

Comments /Action Items: Fill in burrows, remove vegetation, monitor undercutting of outlet pipe. .




Page 3 of 4



PRINCIPAL SPILLW

AY

OBSERVATIONS No Spillway

Is spillway control system operating properly? Yes No

PROBLEMS CHANNEL LINING 1. None 2. Trashguard 3. Debris 4. Obstructed 5. Plugged/Clogged 6. Gates Damaged 7. Gates leaking 8. Gates Rusted

9. Misalignment 10. Joints leaking 11. Joint deterioration 12. Joint displacement 13. Conduit collapsed 14. Exposed reinforcement 15. Erosion

16. Undermining 17. Voids 18. Cracks 19. Holes 20. Spalling 21. Slides 22. Outlet

undercutting

23. Sloughing 24. Scarps 25. Deteriorated lining 26. Boils 27. Outlet erosion 28. Displaced rip rap 29. Sparse rip rap 30. Other




EMER

GEN

CY SPILLW

AY

OBSERVATIONS

No emergency spillway Same as primary spillway

PROBLEMS CHANNEL LINING

1. None 2. Debris in channel 3. Gates 4. Misalignment

5. Joint deterioration 6. Joint displacement 7. Exposed reinforcement 8. Erosion

9. Undermining 10. Voids 11. Cracks 12. Holes 13. Outlet erosion

14. Displaced rip rap 15. Sparse rip rap 16. Outlet undercutting 17. Inadequate capacity 18. Other




DRAINS/OUTLET

STR

UCTU

RE

Observations

1. Is discharge system operating properly? Yes No N/A

2. Valves and operators in good condition? Not manually operated during inspection. 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





Page 4 of 4



OTH

ER

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



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

RESER

VIOR/POOL

OBSERVATION

Has there been a sudden drop in the content level of the Impoundment Yes No

PROBLEMS

1. None 2. Inadequate freeboard

3. Skimmer 4. Depressions

5. Whirlpools 6. Sinkholes 7. Unwanted growth in pond water




AppendixC

ExamplePacifiCorpInspectionForm

1

Issue Date: Rev. 1

Naughton Impoundment Inspection Report

Impoundment Name: Naughton North Ash Pond 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 _____________________________

Up

stre

am F

ace

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#:

Dow

nst

ream

Fac

e

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:


2

Issue Date: Rev. 1

Cre

st

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:


Ru

le

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

18. Abnormal discoloration, flow, or discharge of debris or sediment from outlets or structures that pass underneath the impoundment, or through the dike?

Yes No NA

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:


Sit

e S

pec

ific

Changes to the damp area on the downstream slope of the east embankment of the North Ash Pond are apparent.

Yes No

Changes to the depression in the crest of the south embankment of the North Clear Pond are apparent. Yes No

Observations:


Inspector Signature: ________________________________________________ Date: _________________________

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