naughton south ash pond structural stability …...integrity criteria for existing surface...

Status: Rev. 0 i 01 September 2016 Document No: NP-TR-008 Naughton South Ash Pond Structural Stability Assessment

NAUGHTON SOUTH ASH POND STRUCTURAL STABILITY ASSESSMENT

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

Document No.: NP-TR-008 Quality Assurance Statement

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

Prepared by Jacob Trauscht 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 South 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 1 01 September 2016 Document No: NP-TR-008 Naughton South 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 Combustion 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 report documents the design, construction, operations, and maintenance practices for the Naughton South Ash Pond (SAP) in accordance with the requirements of §257.73(d).

The SAP 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 Units 1 and 2. The ash is sluiced to the SAP through high-density polyethylene (HDPE) pipes. This facility also accepts water from the fire water system, seal water, waste water from the process filtration system, and process water from boilers 1 and 2. The SAP was originally constructed in 1974, and expanded in 1976, 1981, 1987 and most recently in 1994.

The Pond contains two dikes, the Intermediate Dike, separating the SAP from the South Clear Water Pond (SCWP) and the Main Dike, which is located on the south and east sides of the SAP and the east side of the SCWP (Figure 1). These embankments were constructed as homogeneous compacted clay fill. The highest embankment of the SAP is 68 feet high. The SAP has a surface area of 82 acres and a storage capacity of 1,855 acre-feet at a freeboard of 5 feet. The perimeter of the pond is 10,800 feet and has a total drainage area of one square mile.

Once ash is removed in the SAP, clear water is then discharged to the SCWP. Flow is control from the SAP to the SCWP by a drop decant tower, located along the southern portion of the intermediate dike. Clear water is transferred via a 24 inch concrete conveyance pipe that runs below the crest of the dike and discharges to the SCWP. The SCWP has a surface area of 22 acres and a storage capacity of 464 acre-feet at 5 feet of freeboard, with a total perimeter of 4,750 feet. The clear water that is collected here is then allowed to drain off site through a nearby creek.


Figure 1 – SAP and SCWP Layout

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

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

• Naughton South Ash Pond initial 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

The SAP was designed by Black and Veatch in 1993 as a homogeneous clay fill embankment dam (Black and Veatch, 1993). Further design details are provided in the Naughton South Ash Pond Initial Safety Factor Assessment (MWH, 2016b).

Clearing and grubbing of the SAP site was extended to 12 inches below the ground surface. All overburden and ground cover within the embankment footprint was removed and stockpiled outside the limits of work. The construction specifications for the embankment foundations (subgrade) required the top 12 inches of the subgrade to be scarified and re-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). In areas where ash was present, the construction specifications required that the ash be excavated to a depth of 20-feet, extending 10-feet beyond the toe of the embankments and replaced with general fill.

Based on a review of the design drawings, there are no abutments that were constructed associated with SAP. The SAP 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 exceeding 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 had been previously designated as being suitable for embankment construction based on subsurface exploratory investigation and geotechnical testing results.

A review of the moisture-compaction curves for the general fill indicated that the placement specifications used during the embankment construction were appropriate for the type of soil (silty clays) used for the general embankment fill. These specifications are consistent with recognized and generally accepted good engineering practices for placement of homogenous clay embankment fill. A cross-section through the main dike of the SAP, showing the interior embankment fill geometry, is shown in Figure 2.

Additionally, a four foot thick blanket sand drain was placed on the downstream side of the main embankments. The grain size distribution for the blanket drain was developed to meet filter compatibility with the adjacent embankment fill.

Figure 2 – Cross-Section through Main Dike of SAP

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

Operation & Maintenance

There has been no issues reported associated with the foundation of the SAP during weekly and annual inspections. Minor seepage at the toe of the SAP is due to the presence of the toe drains and does not constitute a concern associated with the foundations. Additional detail associated with the seepage is provided in the dike §257.73(d)(1)iii. Dike Compaction.

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

p22958

Comment on Text

Here, we state there are no abutments.

p22958

Comment on Text

Here, we state that the SAP is operated to maintain stable 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 interior (wetted) perimeter of the dikes of the SAP are lined with a layer of riprap bedding and rip rap that is roughly 12 inches thick. The use of rip rap for slope protection is consistent with recognized and generally accepted engineering design practices to protect the embankment face against wind and wave action erosion, which may occur along the embankment face. The rip rap on the interior faces of the SAP dikes extend from the crest to 20 vertical feet downslope from the crest providing wave action/erosion protection of the embankment faces for the anticipated fluid surface levels during operations (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 gradations of the riprap bedding and riprap specified in the design documentation (Black and Veatch, 1993) are provided in Tables 1 and 2, respectively.

Table 1 – Riprap Bedding Gradation

U.S. Standard Sieve Size Percent Passing

3-inch 100

1-inch 70-90

No. 4 40-60

No. 40 5-15

No. 100 0-5

Table 2 – Riprap Gradation

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

150 100

80 70-90

50 40-60

2-inch screen 5-15

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 slope is sufficient to protect against a significant wave height of approximately 2.5 feet. Although a calculation for anticipated wave height for


the SAP 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 based on wind speed and fetch distance.

The SAP 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 SAP 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 changes in water elevation or wave action that might occur. The operating level of the SAP is maintained below the five feet by a decant structure with a pipe invert elevation of 6877 feet above mean sea level (AMSL). Embankment slopes are visually inspected annually by a third party. Plant personnel performs visual inspections weekly and makes repairs for erosion that has taken place. Table 3 summarizes the normal pool elevation and design freeboard.

Table 3 – Operational Data for SAP Operational Data Design Value

Normal Pool Elevation 6,885 feet AMSL

Embankment Crest Max Elevation 6,890 feet AMSL

Design Freeboard 5 feet

The SAP 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 SAP embankment required that the embankment fill be placed in horizontal layers not to exceed 9 inch loose 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 for similar types of soil, 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 subsequent 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 SAP 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.


The SAP embankment is 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 instability, such as seepage, inappropriate vegetative cover, and other signs of deterioration that could be an indicator of, or develop into, a mode of failure. During the weekly inspections, only minor issues, such as small animal burrows and locations showing signs of minimal seepage through the embankment. These issues were reported in the “Assessment of Dam Safety, Coal Combustion Surface Impoundments (Task 3) Final Report for the Naughton Power Plant”, and Prepared for Lockheed Martin by CHA in 2009. The seepage detected is associated with the blanket drains discharging seepage water as designed. The rate of seepage is monitored using a v-shaped weir downstream of the discharge location of the blanket drains. The seepage is also inspected visually for clarity to help evaluate if piping of embankment material is potentially occurring. There have been no incidences of embankment failure, movement, or seepage requiring remediation of the SAP embankment in the record files (URS, 2015a).

A field inspection conducted in 2015 by URS, as part of the annual inspection, observed a damp toe ditch that is associated with the blanket drain; erosion on the downstream slope of the south embankment; minor woody vegetation on the south embankment; and one animal burrow on the downstream slope of the south embankment. None of these observed features constitute and imminent dam safety concern (URS, 2015b).

There have been no modifications or any major repairs to the SAP embankments. Any superficial repairs requiring placement of soil within the embankment have been completed in conformance with the original compaction and moisture conditioning specifications and have not diminished the performance of the embankment.

As part of URS’s (URS, 2015a) assessment of the SAP, it was recommended to continue monitoring of the toe ditch of the SAP associated with the blanket drains. This is being performed as part of the weekly inspections.

The SAP 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 initial construction specifications required that the exterior slopes of the SAP embankment be covered with topsoil, amended with fertilizer and drill seeded following the completion of construction to provide erosion protection of the downstream portions of the embankment. Seeding was applied at a


rate of 23 pounds per acre of 90-percent live seed. Based on field observations, vegetation on the SAP has been successfully established with the majority of the downstream fence having sufficient vegetation coverage to mitigate the potential for erosion.

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


The EPA site assessment conducted by CHA (CHA, 2009) found that PacifiCorp was required to trim 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 SAP embankment. Therefore, it is MWH’s opinion that the current maintenance methods are appropriate for the type of vegetation found on the SAP.

§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. PMP for a high hazard impoundment

b. 1,000-yr flood for a significant hazard impoundment” Design & Construction

The SAP does not have a spillway. Discharge from the SAP to the SCWP is controlled via a decant tower. The SCWP discharges to surface water via a weir discharge structure which is explained further in the Hydraulic Structures section of this report.


Overtopping of embankment caused by extreme precipitation events is mitigated by maintaining a 5 ft freeboard measured from normal pool elevation to top of crest.

MWH’s evaluation considered that the SAP is an on-channel basin, meaning that it receives inflows from sources outside of direct rainfall. The collection area of the SAP is 610 acres with an available freeboard volume of 680 acre-feet. Using rainfall isohyetal contour maps provided by the National Weather Service, a probably maximum precipitation (PMP) for the area in question during a 72 hour period resulted in 10.6 inches of rainfall. This equates to a total PMP event volume of 540 acre-feet, which only occupies about 80% of the total freeboard volume. A summary of the PMP evaluation is provided in Table 4.

Table 4 – SAP PMP Analysis On Channel Basin

Impoundment EPA PMP Requirement Collection Area Volume of Water

(PMP of 10.6”) Freeboard

Volume

SAP Full 610 acres 540 acre-feet 680 acre-feet

The SAP is judged to have been designed and constructed to adequately manage flow during and following the PMF.


Given that the SAP 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)vi. 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 SAP shares a pond wall with the SCWP. Flow is controlled from the SAP to the SCWP by a drop decant tower located along the southern portion of the intermediate dike. Clear water is transferred via a 24 inch concrete conveyance pipe that between the intermediate dike and discharges to the SCWP. Information pertinent to the discharge structure is provided in Table 5.


Table 5 –SAP and SCWP Discharge Structure Description Design Value

Crest EL 6,890 feet AMSL

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

Gate Invert 6,877 feet AMSL

Conveyance Pipe 24-inch CCP

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

Base Elevation of Structure 6873.67 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 pond inspection. No issues have been identified with the current state of the decant structure. Additionally, No major repairs associated with the decant tower structure have been conducted. As such, the decant tower structure continues to operate as designed and based on visual inspection, the conduit is free of significant deterioration, deformation, distortion, bedding deficiencies, sedimentation, and debris.

The SAP 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)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”


The SAP shares an intermediate embankment with the SCWP to the northeast. Slopes of the intermediate embankment were constructed to 3H:1V on both the upstream and downstream sides. The slope angle near the toe of the embankments was brought down to 4H:1V on the taller slopes to reduce the potential for piping or erosion of the silty embankment fill soils. The normal pool elevations for the SAP and SCWP are Elevation 6885 and 6882 AMSL. The safety factor assessment of the SAP, conducted by MWH concluded that the SAP is stable against all anticipated loading conditions (MWH, 2016b). A cross-section through the intermediate dike separating the SAP and SCWP is shown in Figure 3.


Figure 3 – Cross-Section through Intermediate Dike of SAP and SCWP The SAP is judged to have been designed and constructed adequately to maintain structural stability with downstream inundated slopes, during low pool of the SCWP or sudden drawdown of the SCWP.


Inflow to the SCWP comes from the SAP decant tower structure. The SCWP level is maintained at or below the normal pool operating level at all times. Outflow from the SCWP is provided through a drop inlet structure, leading to a v-notch weir, and then to a rip rap lined channel (CHA, 2009).

The most recent annual dam safety inspection of the SAP was completed in 2015 (URS, 2015b) and did not identify any deficiencies or conditions that require maintenance actions to address.

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

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

§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 2016

PacifiCorp 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, South Ash Pond. December 2015.

URS Corporation, 2015b 2014 Coal Combustions Residuals Impoundment Inspection and Assessment, Naughton Power Plant. January 2015.

USDA, 1983. Technical Release No. 69 – Riprap for Slope Protection. 1983

Appendix A

Annual Inspection Report

2015 Coal Combustion Residuals Annual Inspection

Naughton Power Plant South 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 South Ash Pond Inspection i

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

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

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

2.2 Location ......................................................................................................................................... 3

2.3 South Ash Pond Description.......................................................................................................... 3

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 ................................................................................... 6

2.6.2 Previous Periodic Structural Analyses ................................................................................... 6

2.6.3 Results of Inspection by a Qualified Person .......................................................................... 6

2.6.4 Results of Previous Annual Inspections ................................................................................ 6

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

3.1 General .......................................................................................................................................... 7

3.2 South Ash Pond Geometry ............................................................................................................ 7

3.3 Instrumentation ............................................................................................................................ 7

3.4 Impounded Water Depth and Volume ......................................................................................... 9

3.5 Storage Capacity ........................................................................................................................... 9

3.6 Observed or Potential Structural Weaknesses ............................................................................. 9

3.7 Observed Changes ........................................................................................................................ 9

4 Limitations and Consultant Qualifications ............................................................................................ 9

4.1 Limitations ..................................................................................................................................... 9

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

5 References .......................................................................................................................................... 10

Appendices

Appendix A Photograph Log

Appendix B Annual Inspection Report Form

Appendix C Example PacifiCorp Inspection Form

2015 Naughton South 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

South Ash Pond to be in satisfactory condition. Nothing was observed suggesting an active or

impending dam safety issue.

Figure 1‐1 is an aerial image of the pond taken in July 2014.

Figure 1‐1. South Ash Pond

Since this aerial photograph was taken the plant has installed a new low dike along the north end of the

South Ash Pond containing the ash delivery channels (Figure 2‐1). It is understood that this dike is a

temporary facility to improve the ability of the delta to settle out CCR. This temporary dike is not

included in this inspection. It is shown in Photos 17 and 18 of Appendix A, Photograph Log.


Observations from the 2015 inspection include:

1. A damp area along the toe of the south embankment

2. Seepage water bypassing weir VS 1

3. Animal burrows (Photos 1 and 7)

4. Woody vegetation along the crest and toe of the south embankment (Photos 2, 8, and 12)

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 for State of Wyoming ID

number has not been met. It is suggested that the National Inventory of Dams (NID) number be added

to the sign. For this facility it is WYO1546

Figure 1‐2.

2 DescriptionandHistoryofSouthAshPond

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 SouthAshPondDescriptionThe South Ash Pond is located approximately 0.5 miles directly south of the plant generation facility and

west of and adjacent to the South Clear Pond. The two ponds are separated by the northeastern

embankment of the South Ash Pond, which in effect is a dike. FGD Pond #4 is located immediately east

of the toe of the east embankment. The South Ash Pond actively receives hydraulically conveyed ash

from Units 1 and 2.

The unlined South Ash Pond receives fly ash and bottom ash slurry from Units 1 and 2 of the Plant.The

South Ash Pond is created by an earthen embankment on the south and east sides of the pond and a

divider dike seperating it from the South Clear Pond. It has a maximum embankment height of

approximately 68 feet and a storage capacity of 3,754 acre‐feet. It decants water through a tower

structure to the South Clear Pond.

The South Ash Pond and South Clear Pond are treated by the Wyoming State Engineers Office, and in

some studies, as a single system [2]. For example, MWH [4, 14] considered the two ponds as single unit

for the purpose of hydrologic analysis. Only the South Ash Pond is a CCR unit.

A single, homogeneous fill embankment, approximately 4,000 feet in length, forms the south and east

boundary of the pond. A 2,300‐foot long dike forms the northeast boundary of the pond, separating the

South Ash Pond from the South Clear Pond. The west side of the pond is bounded to the north and west

by the ground surface. The total perimeter is approximately 10,800 feet. The embankment was

generally constructed of native clayey soils obtained from nearby borrow sources [3]. The upstream

faces of the embankment and intermediate dike are armored with riprap.

The South Ash Pond was originally constructed in 1974. Expansions or modifications were built in 1976,

1981, 1987, and again in 1994 [2], although details of the modifications to the South Ash Pond were

unavailable for review. The embankment ranges in height from only a few feet to a maximum height of

approximately 68 feet [12]. The existing embankment was constructed to a crest elevation of

approximately 6,890 feet amsl with a crest width of approximately 25 feet. The upstream slopes were

constructed at 3H:1V and downstream slopes were constructed at 3H to 4H:1V [12]. The South Ash

Pond has a surface area of approximately 183 acres and has a storage capacity of 3,754 acre‐feet [4].


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

Table 2‐1. South Ash Pond Pertinent Data

Description Design Value

South Ash Pond

Pond:

Total Pond Capacity (acre‐feet) 3754 [4]

Maximum Pond Elevation (feet) 6,885 [12]

Surface Area (acres) 183 [4]

Pond Perimeter (feet) 10,8001

Drainage Area (square miles) 1.02

Design Freeboard (feet) 5 [12]

Embankment:

Type Homogeneous with Blanket Drain [12]

Maximum Design Height (feet) 68 [12]

Design Crest Width (feet) 25 [12]

Design Crest Length (feet) 4,000 [12]

Design Crest Elevation (feet) 6,890 [12]

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

Design Downstream Slope (feet) 3 to 4:1 [12]

Pond Outlet Structure:

Type Drop Decant

Tower

Crest Elevation (feet) 6,888.0 [12]

Crest Length (feet) 3 ft (stoplog)

Gates Yes

Gate Invert Elevations (feet) 6,877

Conveyance 24‐inch CCP

2.4 PerformanceHistoryThe seepage at the toe of the south embankment was discussed in the previous inspection reports [2],

[3], [7]. However, the blanket drain in this embankment is collecting and discharging seepage at the toe

as designed. Refer to Figure 3‐1.


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

the South Ash Pond embankment reported in the record files.

2.5 ConstructionHistorySouth Pond was originally constructed in 1974. Several modifications to its configuration were

completed between 1974 and 1994. The South 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.

Fly ash and bottom ash from Units 1 and 2 are delivered as slurry by a short (approximately 50 feet)

section of pipe to an open ditch near the southeast corner of the plant. The ditch is approximately 1,000

feet long and conveys the ash slurry to the South Ash Pond. The pipe does not penetrate any

constructed embankments.

Figure 2‐1 shows the ash delivery channels for the South Ash Pond.

Figure 2‐1. Ash Delivery Channels for South Ash Pond

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 South Ash Pond.

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

Ash Pond’s embankment 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].

2.6.3 ResultsofInspectionbyaQualifiedPersonThe South 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. In the

opinion of this report author, the interim inspections by the plant staff are adequate and appropriate for

this CCR unit.

2.6.4 ResultsofPreviousAnnualInspectionsThis is the initial and only annual inspection conducted under CCR rules [18] for the Naughton South 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 South Ash Pond.

3 FieldInspectionofSouthAshPondA 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]. 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 and inspection checklist.

The detailed inspection checklist is presented in Appendix B. The 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 South Ash Ponds south and

east downstream embankments and driving along the embankments crest. The divider dike was only

inspected along the crest because of the presence of the ponds along the embankment sides. Features

and conditions were documented on the inspection checklist and were photographed and logged with

corresponding GPS coordinates. The approximate locations of the photos are detailed in the inspection

photo log overview map [Appendix A]. In addition to documenting current features, the photo log of

existing conditions is provided as a comparison for future inspections.

3.2 SouthAshPondGeometryThe South Ash Pond is a homogeneous earthen embankment with an internal blanket drainage system

along the downstream embankment. The reservoir is unlined. Its horizontal configuration is comprised

of a south and an east embankment and a divider dike between the South Ash and South Clear Ponds as

shown on Figure 1‐1. Figure 3‐1 below is a cross section of the embankment. It has a 25‐foot crest

width and both upstream and downstream slopes of 3 to 4 vertical to 1 horizontal (3:1 and 4:1) ratios

[12].

3.3 InstrumentationThe South Ash Pond has piezometers installed along the pond’s embankments. Piezometer PZ‐1, PZ‐4,

PZ‐2, PZ‐5 are found along the south embankment and PZ‐3 is located on the south end of the east

embankment. The South Ash Pond also has a V‐notch weir, VS‐1, installed along the south

embankment. The V‐notch weir is four inches deep at a notch angle of 22.5 degrees [4].


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


3.4 Impounded Water Depth and Volume On the day of the field inspection, Naughton staff estimated the freeboard at 6.5 feet, making the water surface at 6879.5 amsl.

3.5 Storage Capacity The pond’s capacity is reported at 3,754 acres feet [4].

3.6 Observed or Potential Structural Weaknesses There were no visual observations that indicated imminent weaknesses in the embankment or outlet works.

3.7 Observed Changes Photo 9, Appendix A shows tracks on the south embankment that were not present in during the 2014 inspection. Photos 17 and 18 show a temporary dike that was also not present in 2014. There are no other observed changes between the 2014 annual inspection and the 2015 annual inspection.

4 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 South Ash Pond. 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 [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.





[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 South Ash Pond Inspection

AppendixA

PhotographLog

Inspection PhotographsPacifiCorp Energy

South Ash Pond -- Naughton Power PlantAugust 24, 2015

Page A-1

Inspection Photographs PacifiCorp Energy

South Ash Pond -- Naughton Power Plant August 24, 2015

Page A-2

Photograph No. 1 Animal burrow on the downstream toe of the South Ash Pond south embankment.

Photograph No. 2 Vegetation on the upstream side of the South Ash Pond south embankment.



Page A-3

Photograph No. 3 View west along the south embankment

Photograph No. 4 View east along the south embankment.



Page A-4

Photograph No. 5 View east along the south embankment. Note wet area at toe.

Photograph No. 6 Wet area at toe of south embankment (same as Photo 7).



Page A-5

Photograph No. 7 Animal burrow uphill from wet area on the south embankment.

Photograph No. 8 Woody vegetation near the toe of the south embankment.



Page A-6

Photograph No. 9 Equipment tracking on the south embankment.



Page A-7

Photograph No. 10 Wet area near the toe of the south embankment.

Photograph No. 11 Submerged weir at the toe of the south embankment.



Page A-8

Photograph No. 12 View of Russian Olive tree located approximately 10' up from downstream toe on South Ash Pond South Embankment, near left abutment.

Photograph No. 13 View to north of the riprap on the upstream slope of the east embankment. No vegetation.



Page A-9

Photograph No. 14 Outlet works in South Ash Pond.

Photograph No. 15 View west of upstream face of the divider dike between South Ash Pond (left) and South Clear Pond (right).



Page A-10

Photograph No. 16 View west along the divider dike separating the South Clear Pond (right) and South Ash Pond (left).

Photograph No. 17 A newly constructed low dike along the north end of the South Ash Pond looking south.



Page A-11

Photograph No. 18 View of a newly constructed dike and ash inlet.


AppendixB

AnnualInspectionReportForm

Annual CCR Impoundment Inspection Report

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

Page 1 of 4

Feature Name: Naughton South 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.

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


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






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: On‐going monitoring of seepage. Likely associated with

blanket drain. Weir install in toe ditch. Weir is not functioning properly.



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:





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

Comments /Action Items There is a blanket drain that results in seepage at the toe. No observed muddy flow.




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? Needs maintenance. Flow cuts around weir. 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 Correct installation of weir at toe of embankment. A temporary berm in delta of fly ash to try to concentrate ash deposition before main body of water.


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 South 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 wet area below the toe of the north embankment of the clear pond are apparent. Yes No Observations:


Inspector Signature: ________________________________________________ Date: _________________________

naughton south ash pond structural stability …...integrity criteria for existing surface...

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