NC0003425_Inspection_20200608

ENGINEERS &. CONSULTANTS
DRAFT REPORT
CCW IMPOUNDMENTS
INSPECTION REPORT
ROXBORO STEAM ELECTRIC PLANT
PERSON COUNTY,
NORTH CAROLINA
PREPARED FOR:
U.S. ENVIRONMENTAL PROTECTION
AGENCY
WASHINGTON, DC
UNDER SUBCONTRACTO TO:
LOCKHEED MARTIN
EDrsoN NJ
PAUL C. RIZZO ASSOCIATES, INC.
101 WESTPARK BOULEVARD, SUITE B
COLUMBIA, SOUTH CAROLINA USA 29210
PROJECT No. 09-4157
OCTOBER, 2009

vNicosT.T. is & coKsucrAINIS
Paul C. Rizzo Associates, Inc.
SOUTHEAST REGION
101 Westpark Boulevard - Suite B - Columbia, SC 29210
Phone [phone] . Fax [phone]
Mr. Dennis Miller
Lockheed Martin
2890 Woodbridge Ave #209
Edison, NJ 08837
www.rizzoassoc.com
TRANSMITTAL
October 16, 2009
Project No. 09-4157
DRAFT INSPECTION REPORT
ASSESSMENT OF DAM SAFETY COAL COMBUSTION SURFACE IMPOUNDMENTS
ROXBORO STEAM ELECTRIC PLANT
PERSON COUNTY, NORTH CAROLINA
Dear Mr. Miller:
Paul C. Rizzo Associates, Inc. (RIZZO) is pleased to submit the enclosed Draft Report,
CCW Impoundments Inspection Report for the Roxboro Steam Electric Plant (Site No.
29) for your review.
If you have any questions or require further clarification, please contact me at (803) 750-
9773, ext. 12 or [e-mail].
Sincerely Yours,
Paul C. Rizzo Associates, Inc
4F
H. Grady Adkins, Jr, P.E.
HGA/
Enclosure
cc: Stephen Hoffman - USEPA
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-Monrocsille PA(Carp.HQ)-Oakland CA•SI.Lnuis N10-Tarrrtmsn NY•Culumbia SC.
L5 094157/09 �%.II-11YALIONAL 01-FICL LOCAI IONS
•Bucnrn Aires Argentina -Mendoza Argentina•SantLigo Chile -Lima Peru-
-Abu Dhabi UAE-Brishane Auslralia•Plten Ctech Republic -So. Petersburg Russia-

TABLE OF CONTENTS
PAGE
LISTOF TABLES............................................................................................................
iv
LISTOF FIGURES..........................................................................................................
iv
LIST OF APPENDICES....................................................................................................
v
1.0 EXECUTIVE SUMMARY....................................................................................
1
1.1 GENERAL.....................................................................................................
1
1.2 SUMMARY OF FIELD INSPECTION FINDINGS .................................................
2
1.3 SUMMARY OF O&M STATUS.......................................................................
3
1.4 CONCLUSIONS..............................................................................................3
1.4.1 Project Description.......................................................................
3
1.4.2 Field Inspection............................................................................
4
1.5 SUMMARY OF RECOMMENDATIONS.............................................................
4
1.6 CERTIFICATION............................................................................................
5
1.6.1 List of All Field Inspection Participants .......................................
5
1.6.2 Signature of Independent Engineer ..............................................
6
1.6.3 PE Stamp......................................................................................
6
2.0 PROJECT DESCRIPTION.....................................................................................
7
2.1 EXISTING PROJECT FEATURES AND HAZARD POTENTIAL
CLASSIFICATION..........................................................................................
7
2.1.1 West Ash Pond Dam and Dikes 1, 2, and 4..................................
7
2. l .2 FGD Settling and Flush Ponds.....................................................9
2.1.2.a FGD Settling Pond.....................................................................
10
2.1.2.b FGD Flush Pond.........................................................................
10
2.2 SUMMARY OF STANDARD OPERATING PROCEDURES .................................
12
2.2.1 Purpose of the Project.................................................................
12
2.2.2 Current Inspection Schedule.......................................................
12
2.3 MODIFICATIONS CONDUCTED FOR PROJECT SAFETY .................................
13
2.4 Engineering Information...........................................................................
13
2.4.1 Geologic Conditions...................................................................
14
RI 094157/09/CHG/HGA

2.4.2 Seismicity...................................................................................
15
2.4.3 Slope Stability Analyses.............................................................
15
2.4.3.1 West Ash Pond Dam and Dikes 1,2, and 4................
15
2.4.3.2 New FGD Settling Pond and New FGD Flush
Pond............................................................................................
18
2.4.4 Hydrologic Studies.....................................................................
22
2.4.4.1 West Ash Pond..........................................................
22
2.4.4.2 FGD Settling Pond and FGD Flush Pond ..................
22
3.0 FIELD INSPECTION...........................................................................................
24
3.1 FIELD INSPECTION OBSERVATIONS............................................................
24
3.1.1 West Ash Pond Dam..................................................................
24
3.1.2 Dike 1 (Filter Dam)....................................................................
25
3.1.3 Dikes 2 and 4..............................................................................
26
3.1.4 FGD Settling Pond.....................................................................
26
3.1.5 FGD Flush Pond.........................................................................
27
3.1.6 West Ash Pond Dam Discharge Structure ..................................
27
3.2 STATUS OF RESPONSES TO RECOMMENDATIONS IN LAST ANNUAL
INSPECTION................................................................................................
27
3.2.1 West Ash Pond Dam..................................................................
28
3.2.2 Dike No. 1 (Filter Dam).............................................................
29
3.2.3 Dikes No. 2 and 4.......................................................................
29
4.0 RECOMMENDATIONS......................................................................................
30
4.1
RECOMMENDATION NO. 1..........................................................................
30
4.2
RECOMMENDATION NO.2..........................................................................
30
4.3
RECOMMENDATION NO.3..........................................................................
30
4.4
RECOMMENDATION NO.4..........................................................................
30
4.5
RECOMMENDATION NO.5..........................................................................
31
4.6
RECOMMENDATION NO.6..........................................................................
31
5.0 CONCLUSIONS...................................................................................................32
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TABLES
FIGURES
APPENDICES
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LIST OF TABLES
TABLE NO.
TITLE
PAGE
TABLE 1 -1
SUMMARY OF RECOMMENDATIONS ....................................
5
TABLE 2 -1
WEST ASH POND DAM AND DIKES 1, 2, & 4
LOCATIONDATA........................................................................
9
TABLE 2-2
FGD SETTLING AND FLUSH PONDS LOCATION
DATA............................................................................................
11
TABLE 2-3
EMBANKMENT MATERIAL PROPERTIES WEST
ASHPOND DAM........................................................................
16
TABLE 2-4
EMBANKMENT MATERIAL PROPERTIES DIKES
1, 2, & 4.........................................................................................17
TABLE 2-5
RESULTS OF STABILITY ANALYSES DIKES 1, 2,
& 4.................................................................................................
18
TABLE 2-6
SOIL PROPERTIES USED IN STABILITY
ANALYSES OF NEW SETTLING AND FLUSH
PONDS..........................................................................................
20
TABLE 2-7
FACTORS OF SAFETY FOR SLOPE STABILITY OF
NEW SETTLING AND FLUSH PONDS ....................................
21
TABLE 2 -8
CONTROLLING ELEVATIONS OF ASH AND
FLUSHPONDS............................................................................
23
LIST OF FIGURES
FIGURE NO. TITLE
FIGURE 1 USGS VICINITY MAP
FIGURE 2 SITE MAP
FIGURE 3 PLAN OF FGD SETTLING POND & FGD FLUSH
POND
FIGURE 4 PIEZOMETER LOCATIONS
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APPENDIX
APPENDIX A
APPENDIX B
APPENDIX C
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LIST OF APPENDICES
TITLE
PHOTO LOG
FIGURES
INSPECTION CHECKLISTS

DAM SAFETY INSPECTION REPORT
ROXBORO STEAM ELECTRIC PLANT
PERSON COUNTY, NORTH CAROLINA
PROJECT NO.09-4157
1.0 EXECUTIVE SUMMARY
1.1 GENERAL
This Section is a summary of the Independent Engineer's Review of Management Units for
the Roxboro Steam Electric Plant (Roxboro). The Report was prepared by Paul C. Rizzo
Associates Inc. (RIZZO) for the United States Environmental Protection Agency (USEPA)
under subcontract to Lockheed Martin. This Section summarizes the finding, assessments,
conclusions, and recommendations of the Independent Engineer.
The Roxboro Plant is a coal fired power plant located on the South side of Hyco Lake, an
impoundment of the Hyco River, near Semora, Person County, North Carolina. The
facility is located approximately 9 miles northwest of Roxboro, North Carolina and is
owned and operated by Progress Energy Carolinas, Inc. (PGN). Under normal operating
conditions, byproducts of coal combustion including fly ash, bottom ash, boiler slag, flue
gas emission control residuals, and other general wastewater products are sluiced into
either the West Ash Pond storage basin south of the plant or into a wastewater treatment
system. The waste water treatment system consists of a FGD Settling Pond and FGD
Flush Pond constructed within the West Ash Pond for the treatment of the blow down
steam from the FGD absorber units at the power plant. The three impoundments assessed
in this Report are the West Ash Pond, the FGD Settling Pond, and the FGD Flush Pond.
The ash pond dam, called the West Ash Pond Dam, was originally constructed as an earth
fill embankment with a central earth core and chimney drain in 1973 - 1974. The original
structure was raised 13 feet in 1986 to provide additional storage capacity. Along with
raising the West Ash Pond Dam in 1986, a system of dikes, Dikes 1, 2, 3, and 4, were
constructed to help increase the capacity and modify the circulation pattern of the ash
pond. Dike 3 does not normally impound water; therefore it is not included in this Dam
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Safety Inspection Report. In 2007, two ponds were constructed inside of the West Ash
Pond Dam, the Flue Gas Desulfurization (FGD) Settling Pond and the FGD Flush Pond.
For the purpose of this assessment, the West Ash Pond Dam, FGD Settling Pond, and FGD
Flush Pond have been classified as significant hazard potential structures by the USEPA.
Significant hazard potential structures are classified as structures where failure is not likely
to result in loss of life, but may cause significant economic loss, environmental damage,
disruption of lifeline facilities, or can impact other concerns. The predominant risks of
failure for the West Ash Pond Dam, FGD Settling Pond, and FGD Flush Pond are
disruption of power generation and environmental damage.
1.2 SUMMARY OF FIELD INSPECTION FINDINGS
The site inspection was conducted on September 1, 2009. The Inspection Team consisted
of representatives from PGN, North Carolina Department of Environment and Natural
Resources — Division of Land Resources (NCDENR-DLR), North Carolina Department of
Environment and Natural Resources — Department of Waste Management (NCDENR-
DWM), North Carolina Department of Environment and Natural Resources — Department
of Water Quality (NCDENR-DWQ), and RIZZO. The Team stopped at each of the Project
features to inspect the structures and the surrounding area. Particular attention was paid to
site features that may contribute to typical failure modes of embankment structures such as
settlement, seepage, and slope stability. A copy of the USEPA Inspection Checklists for
each impoundment is included in Appendix C.
The earthfill embankment on the North end of the Ash Pond (West Ash Pond Dam), the
rockfill embankment (Filter Dam or Dike No. 1) on the South end of the Ash Pond, and
Dikes 2 and 4 were found to be in good condition and well maintained at the time of
inspection. The West Ash Pond Dam had tall, thick vegetative cover that prevented full
observation of all slopes. Minor seepage was observed only at the designed discharge
points from the internal drain. The Filter Dam slopes were clear of vegetation and are
designed to filter seepage through the slopes. Decant pipes were clear of obstructions and
free flowing. Dikes 2 and 4 had tall thick vegetation on the slopes below the road and
above the riprap. Damp spots were noted in isolated areas along the toe of dike slopes.
Flowing water was not noted in these areas.
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The Settling Pond was constructed in 2007 as part of a wastewater treatment system that
also includes the Flush Pond and a Bioreactor. The Settling Pond experienced variable
amounts of seepage at spots along the northern and western sides of the pond that resulted
in localized shallow slope failures not long after it was put into service. The Settling Pond
is currently operating at a reduced water level. A repair plan has been approved by the
Owner. The sloughed areas on the outer slopes have been repaired and vegetated.
Seepage was noted in the ditch along the toe of the embankment. This seepage is collected
in sumps and pumped back into the Settling Pond. Repairs to this structure will be
initiated following completion of repairs to the Flush Pond. A second settling pond will be
constructed as part of the work.
The Flush Pond is currently under construction. It was taken out of service in February
2008 when a piping failure occurred that resulted in the development of a slough in both
the inside and outside slopes.
1.3 SUMMARY OF O&M STATUS
The Project is attended full time by plant operators and dedicated safety personnel. The
current inspection schedule for the structures consists of daily observations summarized
weekly and a monthly inspection and monitoring of piezometers by trained PGN
personnel; and an annual and a 5-year inspection by a third party Consultant.
At the time of inspection, the structures and the Plant appeared to be generally well
maintained and in good working order. The only exception to the well maintained
condition is the presence of heavy vegetation on some slopes. This work is scheduled for
the near future according to plant personnel.
1.4 CONCLUSIONS
1.4.1 Project Description
The Roxboro Steam Electric Plant is a four unit coal fired power plant that began
operations in 1966 with additions in 1973 and 1980. Coal Combustion Waste (CCW)
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El
byproducts are sluiced to on site storage or treatment ponds which appear to be well
maintained and operated.
The last major revisions to the CCW storage structures include a raise of the West Ash
Pond Dam and construction of the Filter Dam (Dike 1) and Dikes 2,3, and 4 in 1986 to
provide more storage and the construction of the gypsum Settling Pond, a bioreactor, and
the Flush Pond in 2007 for wastewater treatment. Construction is currently underway to
remediate the Flush Pond with repairs to the Settling Pond to follow. The structures are
currently regulated by the North Carolina Utilities Commission. On January 1, 2010,
regulation of the impoundments will pass to the North Carolina Department of
Environment and Natural Resources, Division of Land Resources, Dam Safety Program.
1.4.2 Field Inspection
The field inspection was performed in accordance with EPA guidelines considering typical
embankment failure modes. The embankments for the Ash Pond dam and dikes are in
good condition but have vegetative maintenance issues to be addressed. The Settling Pond
is currently operating at a reduced level awaiting repairs due to a seepage problem. With
the exception of the seepage area, the embankments for this structure are in good
condition. Reconstruction of the Flush Pond were underway at the time of the field
inspection. Recommendations were developed based on field observations and technical
review of Project documentation provided by PGN.
1.5 SUMMARY OF RECOMMENDATIONS
There were a total of six recommendations resulting from the document review and field
inspection. The recommendations are summarized below in Table 1-1 and discussed in
detail in Section 4.0.
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TABLE 1-1: SUMMARY OF RECOMMENDATIONS
NO.
RECOMMENDATION
TIMEFRAME
1
Inspect the Slopes of the West
Following Maintenance Mowing
Ash Pond Dam at the
of Vegetation
Interface of the Earth Slope
and Top of Riprap for Surface
Erosions and Scarps.
2
Check Drain Outlets of the
During Monthly Inspections
West Ash Storage Pond
During Monthly Inspections
to Determine if Soil Material
is Being Transported
3
Develop Method to Quantify
Prior to Next Annual Inspection
Amount of Seepage from
West Ash Pond Drains
4
Continue to Monitor Seepage
According to Existing Plan.
at Toe of Settling Pond
5
Follow -Up on Developing and
Prior to Next Inspection
Implementing Repair Plan for
Seepage at Discharge Weir
6
Review the 1987 Ash Pond
Prior to Next 5-year Inspection
Hydrology Study to
Determine if Results are Still
Valid
1.6 CERTIFICATION
1.6.1 List of All Field Inspection Participants
The field inspection was conducted on September 1, 2009. The individuals participating in
the inspection were:
H. Grady Adkins, PE
David W. Ray, EIT
Harry Sideris
Robert Howard
Billy Milam
Jodirah Green
Tom Copolo
Bill Forester
RIZZO — Independent Engineer
RIZZO
PGN
PGN
PGN
PGN
PGN
PGN
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0
John Edelen
E. Shannon Langley
John Holley
Gabi Jones
Elizabeth Werner
Geof Little
Autumn Hoban Romanski
PGN
PGN
NCDENR-DLR
NCDENR-DLR
NCDENR-DWM
NCDENR-DWM
NCDENR-DMQ
1.6.2 Signature of Independent Engineer
I acknowledge that the management units referenced herein were personally inspected by
me on September 1, 2009, and were found to be in the following condition:
West Ash Pond: SATISFACTORY
No existing or potential management unit safety deficiencies are recognized. Acceptable
performance is expected under all applicable loading conditions (static, hydrologic,
seismic) in accordance with the applicable criteria. Minor maintenance items may be
required.
FGD Settling Pond and FGD Flush Pond: FAIR
Acceptable performance is expected under all applicable loading conditions (static,
hydrologic, seismic) in accordance with the applicable criteria. Deficiencies may exist
that require remedial action and/or secondary studies or investigations.
When the remedial work currently underway on these two units is completed as planned,
the condition rating should be SATISFACTORY.
Signature:
H. Grady Adkins, Jr. PE,
NC Registration No. 035584
Independent Engineer
Paul C. Rizzo Associates, Inc.
1.6.3 PE Stamp
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2.0 PROJECT DESCRIPTION
2.1 EXISTING PROJECT FEATURES AND HAZARD POTENTIAL CLASSIFICATION
2.1.1 West Ash Pond Dam and Dikes 1, 2, and 4
The West Ash Pond Dam and Dikes 1, 2, and 4 are identified as Significant Hazard
Structures with the ID "NC 0003425" in the National Inventory of Dams.
The West Ash Pond Dam was constructed in 1973 across the mouth of Sargents Creek, a
tributary of the Hyco River, which was then a part of the Hyco Lake Reservoir,. Hyco
Lake is operated by PGN to provide water to the Roxboro Plant. The Dam is an earth fill
embankment with a central earth core. The Dam was constructed between two cofferdams
over a prepared foundation stripped to sound rock with a central core keyway excavated 10
feet into rock. The original structural height of the dam was 70 feet with a crest elevation
457 feet (MSL). The original pool elevation was 445 feet (MSL). In 1986, the Dam was
raised 13 feet to elevation 470 feet (MSL) to provide greater storage capacity. The normal
water level was raised to elevation 463 feet (MSL) and the maximum water level to
elevation 465 feet (MSL).
The present West Ash Pond Dam has a random earth fill shell with an impervious core and
a vertical chimney drain with a horizontal filter blanket connected to the original drain
system. The upstream slope is 2.5(H) to 1(V) and is blanketed with riprap. The
downstream slope is 2(H) to 1(V) and is blanketed with riprap on the lower portion of the
slope. The circulation pattern of the ash pond was modified in 1986 by constructing a rock
filter dike (Dike No. 1) at the southern end of the existing pond to create a secondary
settling basin and also to isolate the major portion of the ash pond from the remaining
watershed. A channel/dike system, which runs along the west side of the existing pond,
ultimately connects with the original spillway constructed in 1973 and discharges into
Hyco Lake.
Dike No. 1 is constructed of rock excavated from channel No. 2 (Figure 4). The crest
elevation is 473 feet (MSL). The design slopes are 1.3(H) to 1(V) on both upstream and
downstream slopes. The dam has a 20- foot wide berm on the downstream slope below
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elevation 448 feet (MSL). The normal design for the ash pond water elevation is 463 feet
(MSL) and maximum design water elevation is 465 feet (MSL) providing 8 feet of
freeboard. A sand blanket is located on the northern side of the dike to prevent pond ash
from discharging to the south side of the pond and into the channel/dike system.
Dike Nos. 2, 3, and 4 are random earth dikes constructed by end -dumping fill material
excavated from channel Nos. 1 and 2. Both upstream and downstream slopes are 2(H) to
1(V) and are protected by riprap underlain by filter fabric. A 20-foot wide berm was added
on the downstream side of Dike No. 4 during construction. The crest elevation of the dikes
is 470 feet (MSL) and normal design for the water elevation is 463 feet (MSL). The
normal design for maximum water level is 465 feet (MSL) providing 5 feet of freeboard.
Dike No. 3 is low height dike across a topographic saddle that is mainly above the normal
pond level. As it does not normally impound water, it is not included in the dam
inspection.
According to information provided by PGN, the West Ash Pond Dam and Dikes 1, 2, and
4 enclose an approximate area of 2400 acres.
Based on height and storage capacity, the West Ash Pond Dam and Dikes 1, 2, and 4 are
classified as "intermediate" in size under the Corps of Engineers Guidelines. Under North
Carolina Regulations, the West Ash Pond and Dike 1 (Filter Dam) are classified as "large"
and the remaining dikes are classified as "medium".
Based on field reconnaissance and a review of USGS maps and aerial photographs, West
Ash Pond Dam and Dikes 1, 2, and 4 have been classified by the Independent Engineer as
a significant hazard potential structure due to the possibility of disruption of power
generation or environmental damage that would be caused by misoperation or failure of the
structure.
Table 2-1 below summarizes the location information for the West Ash Pond Dam and
Dikes 1, 2, and 4.
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0
TABLE 2-1: WEST ASH POND DAM & DIKES 1, 2, & 4 LOCATION DATA
DEGREES
MINUTES
SECONDS
Longitude
36
31
16
Latitude
78
59
55
State:
North Carolina
County:
Person
2.1.2 FGD Settling Pond and FGD Flush Pond
The Settling and Flush Ponds were constructed in 2007 as part of a wastewater treatment
plant. Both ponds are diked on all sides. The wastewater treatment plant consists of a
gypsum settling pond, a bioreactor, and a bioreactor flush pond constructed for the
treatment of the blowdown steam from the FGD absorber units at the power plant. In
February 2008, variable size seeps were observed along the outer northern and western
embankments of the Settling Pond. PGN notified the state regulatory agency of the
situation and lowered the water level within the pond by controlled discharge into the Ash
Pond. Also in February 2008, a sinkhole developed in the embankment of the adjacent
Flush Pond resulting in an uncontrolled discharge of water into the Ash Pond. PGN
notified the state regulatory agency of the incident and took the Flush Pond out of service.
PGN retained the firm of Worley Parsons to design the repairs to the wastewater ponds.
The repair scheme includes:
• Construction of a permanent east settling pond to hold water removed from the
West Settling Pond and from plant discharge while the west pond is being
repaired;
• Reconstruction of the embankment of the Flush Pond to include both a clay and
synthetic liner; and
• Reconstruction of the embankment of the Settling Pond to include both a clay and
synthetic liner.
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The Flush Pond is currently under construction and the Settling Pond is scheduled for
construction following completion of the Flush Pond. The Settling and Flush Ponds were
constructed within the perimeter of the ash pond. The embankment subgrades of both
ponds consist of variable bottom ash, fly ash, and rock fill materials.
2.1.2.a FGD Settling Pond
The Settling Pond is a diked structure that is located within the West Ash Pond Dam and
constructed of variable bottom ash, fly ash, and rock fill materials with an earth fill cap.
The embankment is 38 feet high with a crest elevation 506 feet (MSL). The inside slope of
the pond is constructed at 31-1:1V and the outside slope is constructed at 2.75H:1V. The
maximum operating level for the pond is elevation 497.7 feet (MSL). At the time of the
inspection, the pond has been operating at a lower level awaiting repairs. Once the repairs
are complete the new maximum operating level of the pond will at elevation 498.2 feet
(MSL). The decant structure for the pond is a floating skimmer that operates at the pool
elevation. The spillway for the pond is located at elevation 502.5 feet. The spillway is a
trapezoidal channel spillway that has a top width of 186 feet, a bottom width of 16.5 feet,
and has a depth of 3.5 feet. Once the repairs on the pond are completed the spillway will
be raised to a new elevation of 503 feet. The Settling Pond has an approximate area of
16.6 acres. The repairs for the Settling Pond are scheduled to begin as soon as the
construction on the Flush Pond is completed.
The Settling Pond is to be relined with a 12-inch to 18-inch thick layer of riprap choked
with bottom ash. The choked bottom ash will then be covered with a 12-inch layer of
compacted clay on the bottom and an 18-inch layer up the interior slopes of the pond.
Then an additional 60-mil, conductive, white LLDPE liner will be placed over the
compacted clay and anchored to the top of the embankments.
2.1.2.b FGD Flush Pond
The Flush Pond was under construction at the time the inspection was conducted. All of
the information presented and discussed herein is for the new Flush Pond. The Flush Pond
is a diked structure that is located within the West Ash Pond Dam and constructed of
variable bottom ash, fly ash, and rock fill materials with an earth fill cap. The
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embankment will be 38 feet high with a crest elevation 506 feet. The inside slope of the
pond is constructed at 3H:1 V and the outside slope is constructed at 2.75H:1 V. The
maximum operating level for the pond is elevation 502.4 feet. The spillway for the new
pond will be located at elevation 503.5 feet. The spillway will be a trapezoidal channel
spillway that has a top width of 83 feet, a bottom width of 35 feet, and a depth of 3 feet.
The Flush Pond has an approximate area of 3.1 acres.
Based on height and storage capacity, the FGD Settling Pond Dam and the FGD Flush
Pond Dam are classified as "small" in size under the Corps of Engineers Guidelines.
Under North Carolina Regulations, they are classified as "medium" in size.
Based on field reconnaissance and a review of USGS maps and aerial photographs, the
FGD Settling and Flush Ponds have been classified by the Independent Engineer as
significant hazard potential structures due to the fact that the bottom of the two ponds are
at approximately the same elevation as the top of dam and dikes for the West Ash Pond
within which they are located. Failure of the two structures could release directly into the
channels to the Cooling Reservoir. A release could disrupt power generation and cause
environmental damage. Table 2-2 below summarizes the location information for the
FGD Settling and Flush Ponds.
TABLE 2-2: FGD SETTLING AND FLUSH PONDS LOCATION DATA
DEGREES
MINUTES
SECONDS
Longitude
36
31
16
Latitude
33
59
55
State:
North Carolina
County:
Person
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2.2 SUMMARY OF STANDARD OPERATING PROCEDURES
2.2.1 Purpose of the Project
The Roxboro Plant is a coal fired power plant. The West Ash Pond Dam and Dikes 1, 2,
and 4 were constructed to provide storage for waste coal combustion products and to
provide necessary decantation capacity for the discharge water from the plant to comply
with NPDES permit requirements. The FGD Settling Pond was constructed to store and
thicken the FGD gypsum sludge. The FGD Flush Pond was constructed as part of the
bioreactor system to remove and store metals from the settling pond discharge.
To date there has been only one failure recorded at the Roxboro Plant. In February 2008, a
failure occurred at the Flush Pond in the form of a limited slope failure on both the inner
and outer slopes. The Flush Pond was dewatered and the operating level of the Settling
Pond was lowered after variable size seeps were observed on the northern and western
outer slopes. Repairs to both ponds have been designed and approved. Construction is
currently underway at the Flush Pond with repairs to the Settling Pond scheduled to begin
after the completion of the work on the Flush Pond.
2.2.2 Current Inspection Schedule
The current inspection schedule for the structures at Roxboro is as follows:
■ Visual Inspection by Site Staff: Daily observations are made by trained PGN
personnel following an inspection checklist. The checklist contains the daily
observations for a one week period;
■ Monthly Monitoring and Inspection by Site Staff. An inspection checklist is
used by trained PGN personnel to record the West Ash Pond piezometer readings
and assessments of conditions of the main dam and each dike;
■ Annual Limited Field inspection by Independent Consultant; and
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■ Five -Year Independent Consultant Inspection: This is a more in-depth
inspection required by the North Carolina Utilities Commission.
2.3 MODIFICATIONS CONDUCTED FOR PROJECT SAFETY
To date construction is currently being conducted due to a limited slope failure of the inner
and outer slopes of the FGD Flush Pond. The FGD Settling Pond experienced sizeable
seeps on the northern and western outer slopes and is scheduled to start construction
immediately following the completion of the new FGD Flush Pond.
2.4 ENGINEERING INFORMATION
The following documents provided by PGN were reviewed in the preparation of this
Report:
• Independent Consultant Inspection Report — Main Cooling Lake dam, West Ash
Pond Dam, and Afterbay Dam, Roxboro Steam Electric Plant, Person County,
North Carolina -Historical Volume by Law Engineering and Environmental
Services, Inc., December 18, 1998;
• Five Year Independent Consultant Inspection Report Volume I by Law
Engineering, Raleigh, NC, September 1998;
• Report of Limited Field Inspection, Main Dam, West Ash Pond Dam and Dikes,
and Afterbay Dam, Roxboro Plant, Person County, North Carolina, by MACTEC
Engineering and Construction May 2007;
• Independent Consultant Inspection Report, Main Cooling Lake Dam, West Ash
Pond and Afterbay Dam, Roxboro Electric Plant, Person County, North Carolina
by MACTEC Engineering and Construction, December 29, 2008;
• Calculations for Design of Repairs to the Existing Flush and West Settling Ponds
and Construction of a New East Settling Pond by Worley Parsons;
• Progress Energy Weekly Waste Water Settling Pond Inspection Forms covering
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period 22 June 2009 through 16 August 2009; and
• Progress Energy Monthly Piezometer Monitoring Forms for West Ash Pond and
Hyco Lake Main Dam and Monthly West Ash Pond Monitoring Inspection
Worksheet. Completed forms cover the period January through August 2009.
2.4.1 Geologic Conditions (Source: "Historical Volume 1998")
The Roxboro Plant is within the Piedmont Physiographic Province, a northeast trending
maturely dissected plateau between the Blue Ridge and Coastal Plain Provinces. The
region is underlain primarily by metamorphic and igneous rocks, most of which have been
complexly folded and faulted. The Piedmont in the southeast has been divided into several
northeast trending lithographic structural belts. The site is near the eastern edge of the
Charlotte Belt, near the boundary with the Carolina Slate Belt. The Charlotte Belt is
characterized by a high degree of anatexis and metamorphism to higher levels of the
amphibolite facies and the rocks are mostly coarse grained gneisses, schists, and
amphibolites.
The bedrock at the site was grouped into three main classes:
(a) Hornblende Gneiss A metamorphic rock consisting of quartz, orthoclase
feldspar, mica, and hornblende;
(b) Chlorite Schist — A crystalline rock having foliated structure in which chlorite is
a predominant mineral. Other minerals are mainly silicate with little or no
feldspar;
(c) Diabase — An ancient basalt which has undergone metamorphic alteration. The
rock is composed mainly of minute crystals of plagioclase and pyroxene with
some other ferrous minerals.
The overburden in the area generally consists of a layer of loose silty fine sand resulting
from the weathering of the parent gneiss and chlorite schist formations. In some cases, a
thin cap of reddish brown sandy clay overlies the silty fine sand. Thickness of overburden
varies from one to as much as 15 feet.
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2.4.2 Seismicity
The site is located in a relatively inactive seismic area of the Southeastern United States
that has experienced only occasional earthquakes of moderate intensities in historic times.
Notable exceptions are the earthquakes near Charleston, South Carolina, New Madrid,
Missouri, and Giles County, Virginia. Under the Guidelines of the U.S. Army Corps of
Engineers Recommended Guidelines for Safety Inspection of Dams (ER 1110-2-106, 26
Sep 1979), the site is located in Seismic Zone 2. A seismic coefficient of 0.05g is
recommended for pseudo static seismic analyses. The U.S. Geological Survey Open File
Report 2008-1128 "Update of the USNational Seismic Hazard Maps" Figure 30 shows a
Peak Ground Acceleration of 0.07g for 2 per cent probability of exceedance in 50 years.
This equates to a return period of about 2500 years. The USACE guidelines do not require
seismic stability assessment of dams in Seismic Zones 0, 1, and 2 provided static stability
analyses are satisfactory and conventional safety margins exist.
2.4.3 Slope Stability Analyses
2.4.3.1 West Ash Pond Dam and Dikes 1, 2, and 4
Summaries of the results of slope stability analyses for the West Ash Pond and Dikes 1, 2,
and 4 are summarized in the reference material. Copies of the actual calculations and
laboratory tests were not provided at the time of inspection. Since Dike 2 does not
impound water, no stability analyses have been performed. The strength properties used in
the analyses are reported to be based on laboratory tests on remolded, saturated samples or
on reasonable assumed values.
The soil properties used in the analysis of the West Ash Pond Dam are shown in Table 2-3.
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TABLE 2-3 EMBANKMENT MATERIAL PROPERTIES WEST ASH POND DAM
MATERIAL
C, ksf
� DEGREES
UNIT WEIGHT
MOIST, pcf
I SATURATED, pcf
ORIGINAL MAIN DAM
Soil "A"
0
35
125
135
Soil `B"
0
32
120
130
NEW PORTIONS OF MAIN DAM
Random Fill
0.120
28
125
135
Core
0.050
25
120
130
Sand Drains, Shot Rock Fill
0
35
125
135
The analysis of the downstream slope used the following conditions:
• Crest Elevation 470 feet (MSL);
• Pool Elevation 463 feet (MSL);
• Tailwater Elevation 410 feet (MSL); and
• Phreatic Surface Elevation 414 feet (MSL) to 410 feet (MSL)
The calculated factors of safety were 1.58 for a deep circular failure that did not intercept
the core and 1.46 for a shallow circular failure.
The soil properties used in the analysis of Dikes 1, 2, and 4 are shown in Table 2-4.
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TABLE 2-4
EMBANKMENT MATERIAL PROPERTIES DIKES 1, 2, & 4
LOCATION
DIKE No. 1
DIKE NO.2
DIKE NO.4
UNIT WT,
C
STRENGTH
Unit Wt,
C
STRENGTH
PARAMETERS
UNIT WT,
C
STRENGTH
Soil Type
Moist
Sat.
C,
ksf
�,
Deg
Moist
Sat.
C, ksf
+,
Deg
Moist
Sat.
C,
ksf
De
1
125
130
1 0.150
28
1 125
130
1 0.150
28
125
130
0.150
28
2
110
115
0.050
20
110
115
0.050
20
110
115
0.050
20
3
105
110
0.025
15
105
110
0.025
15
--
--
--
--
4
125
130
0.500
20
125
130
0.500
20
125
130
0.500
20
5
130
140
0
45
--
--
--
--
130
140
1 0
45
6
*
*
0
37
--
--
--
--
--
--
I --
SOIL TYPE
DESCRIPTION
1
Random fill above water
2
Random fill below water
3
Uncompacted end -dumped material
4
Ash
5
Rockfill berm
6
End -dumped random fill mixture of soil and ripped rock
*
Unit weight used in analysis not available from reference
The reported factors of safety for stability of the exterior slopes of Dikes 1, 2, and 4 are
shown in Table 2-5. Dike 2 was analyzed for two different pool elevations.
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TABLE 2-5
RESULTS OF STABILITY ANALYSES DIKES 1, 2, & 4
Dike
1
2
2
4
Crest Elev (Ft
473
470
470
470
MSL
Pool Elev (Ft
463
463
457
463
MSL
Tailwater Elev
445
445
445
445
Ft MSL
Phreatic Surface
453 to 445
449 to 445
449 to 445
455 to 450
Ft MSL)
Slope Analyzed
Downstream w/ 20
Downstream
Downstream
Downstream w/ 20
Ft Berm
Ft Berm
Factor of Safety
1.45
1.38
1.48
1.46
2.4.3.2 New FGD Settling Pond and New FGD Flush Pond
The Design Report prepared by Worley Parsons contained the results of stability analyses
made for the construction of the new East Settling Pond and the reconstruction of the West
Settling Pond and the Flush Pond. Laboratory tests were run on samples taken from the
new borrow area for the random fill. Properties for the existing ash and soil materials were
the same as used for the stability analyses of the existing embankments and are
summarized in Table 2-6.
The following Sections were considered the critical sections for slope stability evaluation:
• Section 1-1: Full West Settling Pond seeping to the existing ash pond canal (in
area of largest observed seepage);
• Section 2-2: Full West Settling Pond seeping into the lower existing dam;
• Section 3-3: Full West Settling Pond seeping into the empty East Settling Pond;
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• Section 4-4: Full East Settling Pond seeping into adjacent ash pond;
• Section 5-5: Full Flush Pond seeping into adjacent ash pond;
• Section 6-6: Full East Pond seeping into empty Flush Pond; and
• Section 7-7: Full Flush Pond seeping into empty East Settling Pond
Sections 1-1 and 1-2 were analyzed in the initial design and were not reevaluated during
the design of the repairs. Section 1-1 was reported to exhibit a factor of safety of 1.70 in
its existing condition and Section 2-2 was reported to have a safety factor of 1.63. Both
factors of safety are expected to increase when the new clay liner is installed.
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TABLE 2-6
SOIL PROPERTIES USED IN STABILITY ANALYSES OF NEW SETTLING
AND FLUSH PONDS
STRATUM
TOTAL
UNIT
WEIGHT
(PCF)
SATURATED
UNIT
WEIGHT
(PCF)
STRENGTH
PARAMETERS
COHESION
(PSF)
FRICTION
ANGLE
DEG
Random Fill(New Embankment
115
120
500
28
Soil Cover Exterior Slopes)
110
115
100
28
ABC Stone Cover
130
130
0
32
Clay Liner
115
122.4
3000
0
Choked Riprap
130
130
0
32
Consolidated Pond Ash (Top 5 ft.
95
100
220
25
Ash Pond
92.4
92.4
220
23
Partially Weathered Rock
130.4
130.4
18,000
0
Existing Embankment
85
97
0
30
Lower Embankment lower 3 — 4 ft
85
96
0
28
Compact Bottom of Pond
90
92.4
0
30
Existing Gypsum Sludge
65
65
0
0
Concrete Revetment
150
150
0
36
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Table 2-7 summarizes the results of the stability analyses performed for Sections 3-3
through 7-7
TABLE 2-7
FACTORS OF SAFETY FOR SLOPE STABILITY OF NEW SETTLING AND
FLUSH PONDS
WATER OPERATING LEVELS
WATER SPILLWAY ELEVATION
SECTION &
CONDITION
LONG-TERM
STATIC
CONDITION
TRANSIENT
CONDITION
EQ (1)
TEMPORARY
CONDITION
TRANSIENT
CONDITION
EQ (1) (2)
Section 3-3
1.75
1.44
1.42
1.15
Section 4-4
2.11
1.79
1.57
1.23
Section 5-5
1.49
1.18
1.48
1.17
Section 6-6
2.13
1.83
1.43
1.18
Section 7-7
1.43
1.17
1.38
1.13
NOTES:
(1) Earthquake (EQ) condition assumes a maximum horizontal ground acceleration of 0.1
9-
(2) The earthquake loading combined with the maximum water elevation and a surcharge
load of 500 psf for truck traffic include extreme events that likely will not occur at the
same time.
Safety factors were computed by the Modified Bishop Method using the computer
program STABL6 by Purdue University. The recommended minimum factors of safety
contained in the USACE ER 1110-2-106 Recommended Guidelines for Safety Inspection of
Dams are:
• Steady Seepage: FS = 1.5; and
• Steady Seepage with Earthquake: FS = 1.0
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The computed safety factors for several loading conditions are less than 1.5. The
conditions analyzed assume a breach in the LLDPE liner overlaying the clay liner from
either the operating level or the spillway level. The target safety factors selected by the
designers for the temporary condition were 1.25 and 1.5 for the long term condition. We
concur that with the conservative selection of parameters used; the computed safety factors
are adequate.
2.4.4 Hydrologic Studies
2.4.4.1 West Ash Pond
When the West Ash Pond Dam was constructed, the drainage area was 3.67 square miles.
Construction of the dike and channel system in 1986 redirects the runoff from 3.49 square
miles of watershed around the main body of the ash pond. The drainage area for the ash
pond as presently configured is reported as 1.4 square miles, including 0.5 square miles
within the pond and 0.9 square miles of drainage from the East Ash Pond Landfill.
A design flood study for the modified dam and dike system was performed in 1987 by
Carolina Power and Light. The design rainfall event was the 0.5 PMP 6-hour duration
storm. Rainfall data was taken from Hydrometerological Report No. 51, "Probable
Maximum Preeipitation Estimates, United States East of the 105th Meridian" by the U.S.
National Oceanic and Atmospheric Administration. Reports reviewed state that the study
showed that the design rainfall event would result in 5 feet of freeboard. The calculations
were not available for review for this Report.
We recommend that PGN review this study in light of the changes that have occurred
within the ash pond since 1987 to confirm that the West Ash Pond remains capable of
safely passing the design storm.
2.4.4.2 FGD Settling Ponds and FGD Flush Pond
These ponds have no external drainage area; therefore the only uncontrolled liquid into the
pond is direct rainfall. Worley Parsons, the pond designers has taken a very conservative
approach to sizing the spillway systems for these embankments. Between the maximum
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operating level and the crest of the spillway, the ponds are sized to contain a surge flow in
the Settling Ponds and a "live storage" in the Flush Pond plus the 100-year rainfall. The
spillways are sized to pass the peak discharge, computed using the Rational Formula, from
the 100-year storm with 0.5 feet maximum depth of flow over the spillway crest. The
spillways have 2 to 3 feet of freeboard from the design depth of flow to the top of dam.
The design elevations for the new or reconstructed ponds are shown in Table 2-8.
TABLE 2-8.
CONTROLLING ELEVATIONS OF ASH AND FLUSH PONDS
`VEST ASH
POND
FLUSH POND
NEW EAST ASH
POND
Maximum Operating Level Ft, MSL
498.4
502.4
489.5
100 Year + Storage Ft, MSL
502.4
502.9
501.9
Spillway Crest Ft, MSL
503.0
1 503.5
1 502.5
Top of Dam Ft, MSL
506.0
506.0
1 506.0
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3.0 FIELD INSPECTION
3.1 FIELD INSPECTION OBSERVATIONS
The site inspection was conducted on September 1, 2009. The Inspection Team consisted
of representatives from (PGN), North Carolina Department of Environment and Natural
Resources — Division of Land Resources (NCDENR-DLR), North Carolina Department of
Environment and Natural Resources — Department of Waste Management (NCDENR-
DWM), North Carolina Department of Environment and Natural Resources — Department
of Water Quality (NCDENR-DWQ), and RIZZO. The Team stopped at each of the Project
features to inspect the structures and the surrounding area. Particular attention was paid to
site features that may contribute to typical failure modes of embankment structures such as
settlement, seepage, and slope stability. Photographs taken during the site inspection can
be reviewed in Appendix A.
The individuals participating in the inspection were:
H. Grady Adkins, PE
David W. Ray, EIT
Harry Sideris
Robert Howard
Billy Milam
Jodirah Green
Tom Copolo
Bill Forester
John Edelen
E. Shannon Langley
John Holley
Gabi Jones
Elizabeth Werner
Geof Little
Autumn Hoban Romanski
RIZZO — Independent Engineer
RIZZO
PGN
PGN
PGN
PGN
PGN
PGN
PGN
PGN
NCDENR-DLR
NCDENR-DLR
NCDENR-DWM
NCDENR-DWM
NCDENR-DWQ
3.1.1 West Ash Pond Dam
At the time of inspection, the West Ash Pond Dam appeared to be well maintained and in
good condition. The crest of the structure has a hard surface that was well maintained and
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showed no signs of settlement or rutting. The upstream slope is covered by the
embankment of the FGD Settling Pond. Where observed, the downstream slope appeared
to be uniformly graded, without signs of significant sloughing or sliding. The downstream
slope is covered with brushy vegetation making a close inspection of the slope difficult.
According to PGN personnel the dam is scheduled for mowing in the near future. The
slope should be inspected following mowing for surface erosion at the top of the riprap
blanket. One small scarp (Photo 5, Appendix A) was observed about three feet above the
top of the riprap between the second and third drain outlets from the right (East) end of the
dam. This could be either the top of a shallow slide or a tractor rut. The abutment contacts
appeared to be in good condition both downstream and upstream.
The area between the toe of the dam and the cooling pond had been mowed prior to the
inspection. There are seven concrete lined swales that convey seepage from the internal
drainage system of the dam to Hyco Lake. These swales had been recently cleaned and all
were capable of safely conveying the seepage water from the toe of the dam to the lake.
Seepage water was clear with orange stain typical of flow from dam drainage systems in
the Piedmont region. Two drains that were seeping had developed deltas of sand size
materials possibly indicative of transport of fine filter material. The deltas could also be
from local erosion due to the clean -out operation. The drains should be observed during
the weekly inspections to determine if material is being transported from within the dam.
A method to quantify the amount of seepage from each outlet is recommended.
The discharge ends of the concrete swales are undermined. This is not considered a dam
safety concern due to the distance from the toe of the dam.
3.1.2 Dike 1 (Filter Dam)
Dike 1 is a rockfill structure designed to allow flow through the dam. In addition two
discharge structures consisting of vertical risers connected to horizontal conduits through
the dam are located in Dike 1. The intake risers have metal trash racks and the conduits
outlet through flap gates which appear to be in good condition and functioning normally.
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The crest of the dike has a hard surface that is relatively flat with no visible signs of
rutting, cracking or settlement. Both interior and exterior slopes are uniform and appear to
be in good condition. The berm at the toe of the exterior slope is covered with vegetation
except at the outlet channels for the conduits. The outlet channels are free flowing and the
seepage through the rockfill appears to be uniform along the toe. Neither cloudy water nor
any other indicator of soil transport through the dike was observed.
3.1.3 Dikes 2 and 4
The crest of both dikes has a hard surface that is relatively flat with no visible signs of
rutting, cracking or settlement. Both dikes have riprap over filter fabric on both the
interior and exterior slopes; however the interior slope of Dike 2 is covered by the exterior
slope of the Settling Pond and no longer impounds water.
The exterior slopes terminate at a berm of varying width along the discharge channel. No
indications of instability were observed at the time of inspection. No seepage was
observed. The downstream slopes and the riprap have small trees, briars, and bushes
growing along with the grasses on the earth slopes. Maintenance of the area is needed to
control the vegetative growth.
3.1.4 FGD Settling Pond
At the time of inspection, the Settling Pond was operating at a significantly reduced water
level due to seepage problems that occurred in February, 2008. The Settling Pond is a
completely diked configuration approximately two years old that is scheduled for remedial
construction once the new East Settling Pond and repairs to the Flush Pond are completed.
The crest of the structure has a hard surface that is relatively new and showed no signs of
cracking, settlement or rutting. The interior slope is covered by riprap and appeared to be
uniform with no sloughing, bulging, or scarps. The exterior slope is generally uniform and
well grassed with the exception of isolated sloughs that had been patched following the
seepage event. See Photo 13, Appendix A.
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Seepage is present along the toe of the exterior slope. See Photo 12, Appendix A. This
seepage is carried in a toe ditch to a sump where it is pumped back into the pond. Seepage
is generally clear; however small boils and deposits of fines indicate that piping of
materials is occurring. (Photo 14, Appendix A). Monitoring of the seepage should be
continued until the repairs are initiated.
3.1.5 FGD Flush Pond
The Flush Pond is currently under reconstruction and was not inspected.
3.1.6 West Ash Pond Discharge Structure
The discharge weir structure is the NPDES Permit NC-0003425 discharge point. (See
Photo 27, Appendix A). At the time of inspection clear water was freely flowing from the
canal to Hyco Lake. Significant seepage was noted flowing from beneath the concrete
abutment on the right (East) side of the structure. The flow appears to be coming through
the rock foundation. The 2007 Report of Limited Field Inspection by MACTEC noted this
concern and offered assistance in developing and implementing a repair plan for the
condition. RIZZO recommends that this action be taken along with monitoring the flow on
a monthly basis concurrent with existing scheduled inspections.
3.2 STATUS OF RESPONSES TO RECOMMENDATIONS IN LAST ANNUAL INSPECTION
The following Recommendations were made in the 2008 Independent Consultant
Inspection Report prepared for PGN by MACTEC Engineering and Consulting, Inc. In
general, the inspection found no indications of concern for dam safety and as such the
recommendations are minor in nature.
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3.2.1 West Ash Pond Dam
Recommendation 1:
Drain outlet channels at the toe of the dam will require regular maintenance to clear
vegetation and sediment. The cleaning should be done at least every two years.
Status•
At the time of inspection, outlet channels had been recently cleaned.
Recommendation 2:
Continue maintenance work (cutting and spraying) to control vegetation growth on the
downstream slope with particular attention to the lower third of the downstream slope.
Status•
At the time of the inspection, the area between the toe and Lake Hyco had been mowed,
the downstream slope had not.
Recommendation 3:
The wet area at the east end of the dam where seepage has occasionally been seen should
be observed during each regular inspection for signs of flow or movement of soil in the
flow.
Status•
Seepage was not observed at this location at the time of inspection.
Recommendation 4:
Increase frequency of reading West Ash Pond Dam piezometers to monthly until the
planned revisions to the 2006 wastewater treatment pond dike within the ash pond area
have been completed.
Status:
Underway -Piezometers are being read and recorded on a monthly basis.
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3.2.2 Dike No. 1 (Filter Dam)
Recommendation 1:
Complete placement of additional riprap in small slide areas on the interior slope within
the next year.
Status:
Complete
Recommendation 2:
Continue to observe the erosion ditch on the east end of the dike to check that the riprap
placed is retarding erosion.
Status:
No erosion problem was noted.
Recommendation 3:
Vegetation and silt accumulations at the flap gates and in the outlet channels leading from
them to the channels should continue to be removed during normal maintenance.
Status:
Outlet channels appeared to be free flowing at the time of the inspection.
3.2.3 Dikes No. 2 and 4
Recommendation 1:
Continue maintenance of trees and vegetation on the interior and exterior slopes of Dike
No. 4 and on the exterior slope of Dike No. 2 (the interior slope is now covered by the new
wastewater treatment and flush pond dikes).
Status:
Maintenance cutting is still needed.
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4.0 RECOMMENDATIONS
A total of six recommendations were generated during the preparation of this Inspection
Report. All of the Recommendations are considered items that will enhance the existing
dam safety program. Each recommendation is presented below along with a proposed
schedule to address the recommendation.
4.1 RECOMMENDATION NO. I
Inspect the slopes of the West Ash Pond Dam at the interface of the earth slope and the top
of the riprap blanket for surface erosion or scarps.
Schedule: Following vegetative maintenance mowing.
4.2 RECOMMENDATION NO.2
Check the drain outlets of the West Ash Storage Dam during monthly inspections to
determine if soil material is being transported.
Schedule: During Monthly Inspections.
4.3 RECOMMENDATION NO.3
A method to quantify the amount of seepage from the West Ash Pond Dam internal drain
outlets is recommended
Schedule: Prior to Next Inspection.
4.4 RECOMMENDATION NO.4
Continue to monitor the seepage at the toe of the Settling Pond Dike until the pond is taken
out of service for repairs.
Schedule: According to existing plans.
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4.5 RECOMMENDATION NO. 5
Follow-up to developing and implementing a repair plan for the seepage at the NPDES
Discharge Point.
Schedule: Prior to Next Inspection.
4.6 RECOMMENDATION NO. C
Since the 1987 Ash Pond Hydrology Study was completed, portions of the pond have filled
with ash and three diked structures have been or will be constructed within the ash pond.
The details of the study were not available to determine if these changes were predicted in
the 1987 study. We recommend that PGN review this study to determine if the results are
still valid.
Schedule: Prior to Next 5-yeat Inspection
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5.0 CONCLUSIONS
Based on our review of the engineering documentation, inspection forms, and the results of
our field inspection, we conclude that the West Ash Pond Complex impoundment is
structurally sound and all components are in Satisfactory condition as defined by the
USEPA, i.e.,"No existing or potential management unit safety deficiencies are recognized.
Acceptable performance is expected under all applicable loading conditions (static,
hydrologic, seismic) in accordance with the applicable criteria. Minor maintenance items
may be required. "
We have concluded that the FGD Settling Pond and the FGD Flush Pond are in Fair
condition as defined by the USEPA, i.e., "Acceptable performance is expected under all
applicable loading conditions (static, hydrologic, seismic) in accordance with the
applicable criteria. Deficiencies may exist that require remedial action and/or secondary
studies or investigations. "
When the remedial work currently underway on these two units is completed as planned,
the condition rating should be SATISFACTORY.
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APPENDIX A
ROXBORO STEAM PLANT PHOTO LOG

PHOTO 3: CHIMNEY DRAIN AT TOE OF WEST ASH POND DAM
PHOTO 4: END OF CHIMNEY DRAIN AT WEST ASH POND DAM

PHOTO 5: SMALL SCARP LOCATED BETWEEN SECOND AND THIRD
DRAIN OUTLETS OF WEST ASH POND DAM
PHOTO 6: ON TOP OF WEST ASH POND DAM LOOKING AT FGD

PH(
PHOTO 9: TOP OF FGD SETTLING POND
G N)
5 M-~I-q1-

PHOTO 12: TOE OF FGD SETTLING POND (LOOKING S)

PHOTO 13: DOWNSTREAM EMBANKMENT OF FGD SETTLING POND
PHOTO 14: TOE OF FGD SETTLING POND

PHOTO 15: AT BIOREACTOR LOOKING AT FGD FLUSH POND
PHOTO 16: DOWNSTREAM TOE OF FGD FLUSH POND
71
KING NE)
8 M-~I-q1-

PHOTO 17: DOWNSTREAM EMBANKMENT OF DIKE 1 (FILTER DIKE,
LOOKING SW)
PHOTO 18: DISCHARGE RISER PIPES AT DIKE 1 (FILTER DIKE, LOOKING
9 M21-1cl-

Pl
PHOTO 19: UPSTREAM EMBANKMENT OF DIKE 1 (FILTER DIKE,
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a
10

PHOTO 21: DIKE I DOWNSTREAM EMBANKMENT AND DISCHARGE
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11
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PHOTO 23: WEST ASH POND DAM DOWNSTREAM ALONG DISCHARGE
CHANNEL (LOOKING SE)
PHOTO 24: WEST ASH POND DAM DOWNSTREAM SLOPE
12 poQ

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PHOTO 27: CLOSE UP OF WEST ASH POND DAM DISHARGE WEIR
STRUCTURE
14

APPENDIX B
FIGURES

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APPENDIX C
FIELD INSPECTION CHECKLISTS

US Environmental Ck
Coal Combustion Dam Inspection Checklist Form Protection Agency
ry .we
Site Name: Roxboro Power Plant Date: 09/01/2009
Unit Name: West Ash Pond Dam & Dikes 1, 2„& 4 Operator's Name: Progress Energy
Unit I.D.: Hazard Potential Classification: High❑significant❑X Low❑
Inspector's Name: Grady Adkins, David Ray
Check the appropriate box below. Provide comments when appropriate. If not applicable or not available, record "N/A". Any unusual conditions or
construction practices that should be noted in the comments section. For large diked embankments, separate checklists may be used for different
embankment areas. If separate forms are used, identify approximate area that the form applies to in comments.
Yes No Yes No
1. Frequency of Company's Dam Inspections?
Regular
18. Sloughing or bulging on slopes?
X
2. Pool elevation (operator records)?
463 *
19. Major erosion or slope deterioration?
X
3. Decant inlet elevation (operator records)?
463 *
20. Decant Pipes:
4. Open channel spillway elevation (operator records)?
N/A
Is water entering inlet, but not exiting outlet?
X
5. Lowest dam crest elevation (operator records)?
470 *
Is water exiting outlet, but not entering inlet?
X
6. If instrumentation is present, are readings
recorded (operator records)?
X
Is water exiting outlet flowing clear?
X
7. Is the embankment currently under construction?
X
21. Seepage (specify location, if seepage carries fines,
and approximate seepage rate below):
8. Foundation preparation (remove vegetation,stumps,
topsoil in area where embankment fill will be placed)?
X
From underdrain?
X
9. Trees growing on embankment? (If so, indicate
largest diameter below)
X
At isolated points on embankment slopes?
X
10. Cracks or scarps on crest?
X
At natural hillside in the embankment area?
X
11. Is there significant settlement along the crest?
X
Over widespread areas?
X
12. Are decant trashracks clear and in place?
X
From downstream foundation area?
X
13. Depressions or sinkholes in tailings surface or
whirlpool in the pool area?
X
"Boils" beneath stream or ponded water?
X
14. Clogged spillways, groin or diversion ditches?
X
Around the outside of the decant pipe?
X
15. Are spillway or ditch linings deteriorated?
X
22. Surface movements in valley bottom or on hillside?
X
16. Are outlets of decant or underdrains blocked?
X
23. Water against downstream toe?
X
17. Cracks or scarps on slopes?
X
24. Were Photos taken during the dam inspection?
X
Major adverse changes in these items could cause instability and should be reported for
further evaluation. Adverse conditions noted in these items should normally be described (extent, location,
volume, etc.) in the space below and on the back of this sheet.
Inspection Issue # Comments
* See attached Comment Sheet
EPA FORM -XXXX

Coal Combustion Waste Dam Inspection Checklist Form - Continuation
Roxboro Power Plant NC
West Ash Pond and Dikes 1, 2, & 4
Comment Sheet
Inspection Issue No. and Comments
1. Operating Personnel ride the perimeter daily or weekly. Monthly report of
piezometer readings and visual assessment. Limited field inspections by
Independent Consultant annually since at least 2004. 5-Yr. Independent
Consultant Inspection — latest in 2008.
2. Maximum operating level for pool is Elevation 465 to maintain minimum
freeboard of 5 feet.
5. Crest of West Ash Pond Dam and Dikes 2 and 4 is Elevation 470. Crest of
Filter Dam (Dike 1) is Elevation 473.
8. Record drawings show that West Dam was founded on competent bedrock.
9. Small trees and brush on West Dam are 2 inches or less max diameter.
17. Tall, thick vegetative cover prevents full observation of all slopes. One small
scarp approximately 6 inches high was noted and photographed near upper limit
of riprap on West Pond Dam — may be indicative of shallow surface slide.
21. Minor seepage at designated discharge points (concrete flumes) at West
Ash Pond Dam. Deposit of fines was observed at upstream end of two discharge
flumes.
The Filter Dam is designed to filter seepage through it. Seepage water is clear.
Seepage outcrops (wet spots rather than running water) were noted at isolated
spots along toe of dike slopes.
23. There is a berm between the toe of the West dam and standing water from
the cooling pond. The Filter Dam (Dike 1) has water at the toe. These are both
design features.

U. S. Environmental Protection Agency
0 Srq�s
$R1 YJ
o=
Coal Combustion Waste (CCW)
Impoundment Inspection
Impoundment NPDES Permit # NC-0003425
Date 09/01/2009
Impoundment Name West Ash Pond
Impoundment Company Progress Energy
EPA Region 4
State Agency (Field Office) Addresss
INSPECTOR Grady Adkins/David Ray
NC Department of Environment and Natural Resources (NCDENR)
Division of Water Quality, Raleigh, NC
Name of Impoundment West Ash Pond
(Report each impoundment on a separate form under the same Impoundment NPDES
Permit number)
New Update
Yes No
Is impoundment currently under construction? X
Is water or ccw currently being pumped into
the impoundment? X
IMPOUNDMENT FUNCTION: CCW Impoundment
Nearest Downstream Town : Name Homes on Hyco Lake
Distance from the impoundment Adjacent to Roxboro Power Plant
Impoundment
Location: Longitude 36 Degrees 31 Minutes 16
Latitude 78
State NC
Degrees 59 Minutes 55
County Person County
Does a state agency regulate this impoundment? YES X NO
Seconds
Seconds
If So Which State Agency? NC Utilities Commission. In Jan 2010,NCDENR Dam Safety will regulate.
EPA Form XXXX-XXX, Jan 09

HAZARD POTENTIAL (In the event the impoundment should fail, the
following would occur):
LESS THAN LOW HAZARD POTENTIAL: Failure or misoperation of
the dam results in no probable loss of human life or economic or environmental
losses.
LOW HAZARD POTENTIAL: Dams assigned the low hazard potential
classification are those where failure or misoperation results in no probable loss of
human life and low economic and/or environmental losses. Losses are principally
limited to the owner's property.
X SIGNIFICANT HAZARD POTENTIAL: Dams assigned the significant
hazard potential classification are those dams where failure or misoperation results
in no probable loss of human life but can cause economic loss, environmental
damage, disruption of lifeline facilities, or can impact other concerns. Significant
hazard potential classification dams are often located in predominantly rural or
agricultural areas but could be located in areas with population and significant
infrastructure.
HIGH HAZARD POTENTIAL: Dams assigned the high hazard
potential classification are those where failure or misoperation will probably cause
loss of human life.
DESCRIBE REASONING FOR HAZARD RATING CHOSEN:
Failure of the West Ash Pond Dam or Dikes would release directly or indirectly into
the cooling lake reservoir (Lake Hyco). A release could disrupt power generation
and cause environmental damage. A release would be contained in the lake.
EPA Form XXXX-XXX, Jan 09

CONFIGURATION:
i
Water or ccw
original
iMPDUNDMENT
$t nd Height
� /
V
CROSS -VALLEY
UiP0U10YENT y
Water or ccw
+ar
f
�
z;z
gror—md Q Height
SIDE-H ILL
'
DIKED
IN ?:ir?
Water or ccw
original ground Height
INCISED
\
Water or ccw
NNNNNNNNNNN
�MHNNNNN�
�
i\\
original
\ x �� \
ground
X Cross -Valley A-1 0:ke 1)
Side -Hill
X Diked C o,
Incised (form completion optional)
Combination Incised/Diked
Embankment Height _ 93 feet
Pool Area 2400
Current Freeboard
5
acres
feet
Embankment Material earth fill
Liner NIA
Liner Permeability N/A
EPA Form XXXX-XXX, Jan 09

TYPE OF OUTLET (Mark all that apply)
Fd
Open Channel Spillway
Trapezoidal
Triangular
Rectangular
Irregular
depth
bottom (or average) width
top width
Outlet
48" inside diameter
TRAPEZOIDAL
Material
corrugated metal
X welded steel 0, -z, r P, P" s
X concrete co .A,-,'4-s +L m, 3t`
plastic (hdpe, pvc, etc.)
other (specify)
Is water flowing through the outlet?
No Outlet
TRIANGULAR
Top Width Top Width
4►
Depth Dcpth
Bottom
Width
Dcpth
Width
YES X NO
X Other Type of Outlet (specify) Filter Dam (Dike 1)
The Impoundment was Designed By Brown and Root, Inc.
IRREGULAR
Avctagc Width
Avg
Depth
EPA Form XXXX-XXX, Jan 09

Has there ever been a failure at this site? YES NO
If So When?
If So Please Describe :
EPA Form XXXX-XXX, Jan 09

Has there ever been significant seepages at this site? YES NO
If So When?
IF So Please Describe:
EPA Form XXXX-XXX, Jan 09

Has there ever been any measures undertaken to monitor/lower
Phreatic water table levels based on past seepages or breaches
at this site? YES X NO
If so, which method (e.g., piezometers, gw pumping,...)?
If so Please Describe :
Piezometers were installed in 1987 and monitored on a regular basis. Monitoring was
increased from quarterly to monthly following recommendation in the 2007
Independent Consultant's Limited Field Inspection Report.
EPA Form XXXX-XXX, Jan 09

ADDITIONAL INSPECTION QUESTIONS
ROXBORO POWER STATION — SEMORA, NC — WEST ASH POND AND
DIKES 1, 2, AND 4
Concerning the embankment foundation, was the embankment construction built over
wet ash, slag, or other unsuitable materials? If there is no information just note that.
The record drawings show that the West Ash Pond Dam and Dikes 1 and 2 were
constructed over a prepared foundation stripped to sound rock with a central core keyway
excavated 10 feet into rock.
Did the dam assessor meet with, or have documentation from, the design Engineer -of -
Record concerning the foundation preparation?
Record Drawings were provided by the owner. There was no contact with the design
Engineer of Record.
From the site visit or from photographic documentation, was there evidence of prior
releases, failures, or patchwork on the dikes?
None on this structure. Dikes constructed within the Ash Pond have experienced seepage
problems in the past and are addressed in a separate report.

US Environmental a k
Coal Combustion Dam Inspection Checklist Form Protection Agency
ry .we
Site Name: Roxboro Power Plant Date: 09/01/2009
Unit Name: FGD Settling Pond Operator's Name: Progress Energy
Unit I.D.: Hazard Potential Classification: High❑significant❑X Low❑
Inspector's Name: Grady Adkins, David Ray
Check the appropriate box below. Provide comments when appropriate. If not applicable or not available, record "N/A". Any unusual conditions or
construction practices that should be noted in the comments section. For large diked embankments, separate checklists may be used for different
embankment areas. If separate forms are used, identify approximate area that the form applies to in comments.
Yes No Yes No
1. Frequency of Company's Dam Inspections?
Regular
18. Sloughing or bulging on slopes?
X
2. Pool elevation (operator records)?
497 *
19. Major erosion or slope deterioration?
X
3. Decant inlet elevation (operator records)?
Pool Level
20. Decant Pipes:
4. Open channel spillway elevation (operator records)?
502.5
Is water entering inlet, but not exiting outlet?
X
5. Lowest dam crest elevation (operator records)?
506
Is water exiting outlet, but not entering inlet?
X
6. If instrumentation is present, are readings
recorded (operator records)?
X
Is water exiting outlet flowing clear?
X
7. Is the embankment currently under construction?
X
21. Seepage (specify location, if seepage carries fines,
and approximate seepage rate below):
8. Foundation preparation (remove vegetation,stumps,
topsoil in area where embankment fill will be placed)?
X
From underdrain?
X
9. Trees growing on embankment? (If so, indicate
largest diameter below
X
At isolated points on embankment slopes?
X
10. Cracks or scarps on crest?
X
At natural hillside in the embankment area?
X
11. Is there significant settlement along the crest?
X
Over widespread areas?
X
12. Are decant trashracks clear and in place?
X
From downstream foundation area?
X
13. Depressions or sinkholes in tailings surface or
whirlpool in the pool area?
X
"Boils" beneath stream or ponded water?
X
14. Clogged spillways, groin or diversion ditches?
X
Around the outside of the decant pipe?
X
15. Are spillway or ditch linings deteriorated?
X
22. Surface movements in valley bottom or on hillside?
X
16. Are outlets of decant or underdrains blocked?
X
23. Water against downstream toe?
X
17. Cracks or scarps on slopes?
X
24. Were Photos taken during the dam inspection?
X
Major adverse changes in these items could cause instability and should be reported for
further evaluation. Adverse conditions noted in these items should normally be described (extent, location,
volume, etc.) in the space below and on the back of this sheet.
Inspection Issue # Comments
* See attached Comment Sheet
EPA FORM -XXXX

Coal Combustion Waste Dam Inspection Checklist Form - Continuation
Roxboro Power Plant NC
Settling Pond
Comment Sheet
Inspection Issue No. and Comments
1. Operating Personnel ride the perimeter daily or weekly. Monthly report of
piezometer readings and visual assessment. Limited field inspections by
Independent Consultant annually since at least 2004. 5-Yr. Independent
Consultant Inspection — latest in 2008.
2. Maximum operating level for pond is Elevation 497.7. Pond is now operating
at a lower level awaiting repairs. Future maximum operating level is planned to
be Elevation 498.2
3. Decant is floating skimmer that operates at pool elevation.
7. Embankment is scheduled for repair after construction of repairs to the Flush
Pond are completed.
8. The Settling Pond was constructed within the perimeter of the Ash Pond. The
embankment subgrade consists of variable bottom ash, fly ash, and rock fill
materials.
17 &18. Repaired sloughs and scarps from seepage on outside face of Settling
Pond were noted.
21. Seepage is exiting into a toe ditch downstream of Settling Pond and Flush
Pond. Seepage is collected in sumps and pumped back into pond. One area
with small (1-inch or less diameter) boils was observed in the toe ditch. Seepage
outcrops (wet spots rather than running water) at isolated spots along dike slopes
were noted.
23. The only water at the toe is in the seepage collection ditch along the base of
the embankment.

U. S. Environmental Protection Agency
0 Srq�s
$R1 YJ
o=
Coal Combustion Waste (CCW)
Impoundment Inspection
Impoundment NPDES Permit # NC-0003425
Date 09/01/2009
Impoundment Name FGD Settling Pond
Impoundment Company Progress Energy
EPA Region 4
State Agency (Field Office) Addresss
INSPECTOR Grady Adkins, David Ray
NC Department of Environment and Natural Resources (NCDENR)
Division of Water Quality, Raleigh, NC
Name of Impoundment FGD Settling Pond
(Report each impoundment on a separate form under the same Impoundment NPDES
Permit number)
New Update
Yes No
Is impoundment currently under construction? X
Is water or ccw currently being pumped into
the impoundment? X
IMPOUNDMENT FUNCTION: Store and thicken the FGD gypsum sludge
Nearest Downstream Town : Name Homes on Hyco Lake
Distance from the impoundment Adjacent to Roxboro Power Plant
Impoundment
Location: Longitude 36 Degrees 31 Minutes 16
Latitude 78
State NC
Degrees 59 Minutes 55
County Person County
Does a state agency regulate this impoundment? YES X NO
Seconds
Seconds
If So Which State Agency? NC Utilities Commission. In Jan 2010, NCDENR Dam Safety will regulate.
EPA Form XXXX-XXX, Jan 09

HAZARD POTENTIAL (In the event the impoundment should fail, the
following would occur):
LESS THAN LOW HAZARD POTENTIAL: Failure or misoperation of
the dam results in no probable loss of human life or economic or environmental
losses.
LOW HAZARD POTENTIAL: Dams assigned the low hazard potential
classification are those where failure or misoperation results in no probable loss of
human life and low economic and/or environmental losses. Losses are principally
limited to the owner's property.
X SIGNIFICANT HAZARD POTENTIAL: Dams assigned the significant
hazard potential classification are those dams where failure or misoperation results
in no probable loss of human life but can cause economic loss, environmental
damage, disruption of lifeline facilities, or can impact other concerns. Significant
hazard potential classification dams are often located in predominantly rural or
agricultural areas but could be located in areas with population and significant
infrastructure.
HIGH HAZARD POTENTIAL: Dams assigned the high hazard
potential classification are those where failure or misoperation will probably cause
loss of human life.
DESCRIBE REASONING FOR HAZARD RATING CHOSEN:
The bottom of this pond is at approximately the same elevation as the top of dam
and dikes for the Ash Pond within which it is located. Failure of this structure could
release directly into the channels to the Cooling Reservoir. A release could disrupt
power generation and cause environmental damage - A release would e contained
within Lake I lyco.
EPA Form XXXX-XXX, Jan 09

CONFIGURATION:
Water or ccw
Water
IMPOUNDMENT
originalht
Hei
ground g
F
�lL
III
CROSS -VALLEY
PAPOUN DwN r
Water or ccw
gromd Height
SIDE -HILL
-DIKED
Water or ccw
Height
original ground
_j
INCISED
Water or ccw
original
ground
Cross -Valley
Side -Hill
x Diked
Incised (form completion optional)
Combination Incised/Diked
Embankment Height _
Pool Area 16.6
Current Freeboard
38 feet Embankment Material Ash with earth fill cap
8.3
acres Liner GCL
feet
Liner Permeability unknown
EPA Form XXXX-XXX, Jan 09

TYPE OF OUTLET (Marls all that apply)
Open Channel Spillway
X Trapezoidal
Triangular
Rectangular
Irregular
3.5 depth
16.5 bottom (or average) width
186 top width
Outlet
inside diameter
Material
corrugated metal
welded steel
concrete
plastic (hdpe, pvc, etc.)
other (specify)
Is water flowing through the outlet?
No Outlet
TRAPEZOIDAL
TRIANGULAR
Top Width Top Width
Depth Depth
Bottom
Width
RECTANGULAR
Other Type of Outlet (specify)
Depth
�i
Width
YES NO X
The Impoundment was Designed By Brown and Root, Inc.
IRREGULAR
Average Width
Avg
Depth
EPA Form XXXX-XXX, Jan 09 4

Has there ever been a failure at this site? YES NO
If So When?
If So Please Describe :
EPA Form XXXX-XXX, Jan 09

Has there ever been significant seepages at this site? YES X NO
If So When?
IF So Please Describe:
Pond was constructed in 2007. Variable size seeps were observed along the outer
slope of the northern and western embankments. A sinkhole developed in the
embankment of the adjacent flush pond that is currently under construction. The
settling pond will be modified to place a more impervious liner. Design has been
approve - Construction will follow reconstruction of the Flush Pond.
EPA Form XXXX-XXX, Jan 09

Has there ever been any measures undertaken to monitor/lower
Phreatic water table levels based on past seepages or breaches
at this site? YES X NO
If so, which method (e.g., piezometers, gw pumping,...)?
If so Please Describe :
Operating level has been lowered following seepage at this embankment and sinkhole
at Flush Pond.
EPA Form XXXX-XXX, Jan 09

ADDITIONAL INSPECTION QUESTIONS
ROXBORO POWER STATION — SEMORA, NC — FGD SETTLING POND
Concerning the embankment foundation, was the embankment construction built over
wet ash, slag, or other unsuitable materials? If there is no information just note that.
The embankment was constructed over a subgrade consisting of variable Bottom Ash,
Fly Ash, and Rock Fill Materials.
Did the dam assessor meet with, or have documentation from, the design Engineer -of -
Record concerning the foundation preparation?
Copies of Construction Drawings and calculations for repair were provided by the
Owner. There was no contact with the design Engineer of Record.
From the site visit or from photographic documentation, was there evidence of prior
releases, failures, or patchwork on the dikes?
The FGD Settling Pond experienced variable amounts of seepage at spots along the
northern and western sides of the ponds not long after it was put in service in 2007. In
response to the seepage problems at the Flush Pond, the water level was lowered and a
repair plan developed. Spot repairs were made at several locations. Final repair work
will follow completion of repairs to the Flush Pond.

US Environmental a k
Coal Combustion Dam Inspection Checklist Form Protection Agency
ry .we
Site Name: Roxboro Power Plant Date: 09/01/2009
Unit Name: FGD Flush Pond Operator's Name: Progress Energy
Unit I.D.: Hazard Potential Classification: High❑significant❑X Low❑
Inspector's Name: Grady Adkins, David Ray
Check the appropriate box below. Provide comments when appropriate. If not applicable or not available, record "N/A". Any unusual conditions or
construction practices that should be noted in the comments section. For large diked embankments, separate checklists may be used for different
embankment areas. If separate forms are used, identify approximate area that the form applies to in comments.
Yes No Yes No
1. Frequency of Company's Dam Inspections?
Regular
18. Sloughing or bulging on slopes?
2. Pool elevation (operator records)?
502.4
19. Major erosion or slope deterioration?
3. Decant inlet elevation (operator records)?
501
20. Decant Pipes:
4. Open channel spillway elevation (operator records)?
503.5
Is water entering inlet, but not exiting outlet?
5. Lowest dam crest elevation (operator records)?
506
Is water exiting outlet, but not entering inlet?
6. If instrumentation is present, are readings
recorded (operator records)?
X
Is water exiting outlet flowing clear?
7. Is the embankment currently under construction?
X
21. Seepage (specify location, if seepage carries fines,
and approximate seepage rate below):
8. Foundation preparation (remove vegetation,stumps,
topsoil in area where embankment fill will be placed)?
X
From underdrain?
9. Trees growing on embankment? (If so, indicate
largest diameter below
At isolated points on embankment slopes?
10. Cracks or scarps on crest?
At natural hillside in the embankment area?
11. Is there significant settlement along the crest?
Over widespread areas?
12. Are decant trashracks clear and in place?
From downstream foundation area?
13. Depressions or sinkholes in tailings surface or
whirlpool in the pool area?
"Boils" beneath stream or ponded water?
14. Clogged spillways, groin or diversion ditches?
Around the outside of the decant pipe?
15. Are spillway or ditch linings deteriorated?
22. Surface movements in valley bottom or on hillside?
16. Are outlets of decant or underdrains blocked?
23. Water against downstream toe?
17. Cracks or scarps on slopes?
24. Were Photos taken during the dam inspection?
X
Major adverse changes in these items could cause instability and should be reported for
further evaluation. Adverse conditions noted in these items should normally be described (extent, location,
volume, etc.) in the space below and on the back of this sheet.
Inspection Issue # Comments
9-24 Flush pond is under construction - being rebuilt after seepage and piping problems in February 2008. No water is impounded.
2-5 Elevations are new construction elevations.
8 - Foundation will be existing or reworked fly ash and and rock fill. The Flush Pond is inside the perimeter of the Ash Pond.
EPA FORM -XXXX

U. S. Environmental Protection Agency
0 Srq�s
$R1 YJ
o=
Coal Combustion Waste (CCW)
Impoundment Inspection
Impoundment NPDES Permit # NC-0003425
Date 09/01/2009
Impoundment Name FGD Flush Pond
Impoundment Company Progress Energy
EPA Region 4
State Agency (Field Office) Addresss
INSPECTOR Grady Adkins, David Ray
NC Department of Environment and Natural Resources
Division of Water Quality, Raleigh, NC
Name of Impoundment FGD Flush Pond
(Report each impoundment on a separate form under the same Impoundment NPDES
Permit number)
New X Update
Yes No
Is impoundment currently under construction? X
Is water or ccw currently being pumped into
the impoundment? X
IMPOUNDMENT FUNCTION• Part of the bioreactor system to remove and store the metals from settling pond discharge.
Nearest Downstream Town : Name Homes on Hyco Lake
Distance from the impoundment Adjacent to the Roxboro Power Plant
Impoundment
Location: Longitude 36 Degrees 31 Minutes 16
Latitude 78
State NC
Degrees 59 Minutes 55
County Person County
Does a state agency regulate this impoundment? YES X NO
Seconds
Seconds
If So Which State Agency? NC Utilities Commission. In Jan 2010, NCDENR Dam Safety will regulate.
EPA Form XXXX-XXX, Jan 09

HAZARD POTENTIAL (In the event the impoundment should fail, the
following would occur):
LESS THAN LOW HAZARD POTENTIAL: Failure or misoperation of
the dam results in no probable loss of human life or economic or environmental
losses.
LOW HAZARD POTENTIAL: Dams assigned the low hazard potential
classification are those where failure or misoperation results in no probable loss of
human life and low economic and/or environmental losses. Losses are principally
limited to the owner's property.
X SIGNIFICANT HAZARD POTENTIAL: Dams assigned the significant
hazard potential classification are those dams where failure or misoperation results
in no probable loss of human life but can cause economic loss, environmental
damage, disruption of lifeline facilities, or can impact other concerns. Significant
hazard potential classification dams are often located in predominantly rural or
agricultural areas but could be located in areas with population and significant
infrastructure.
HIGH HAZARD POTENTIAL: Dams assigned the high hazard
potential classification are those where failure or misoperation will probably cause
loss of human life.
DESCRIBE REASONING FOR HAZARD RATING CHOSEN:
The bottom of this pond is at approximately the same elevation as the top of dam
and dikes for the Ash Pond within which it is located. Failure of this structure could
release directly or indirectly into the channels to the Cooling Reservoir. A release
could disrupt power generation and cause environmental damage - A release would
be contained within Lake I lyco.
EPA Form XXXX-XXX, Jan 09

CONFIGURATION:
Water or ccw
Water
IMPOUNDMENT
originalht
Hei
ground g
F
�lL
III
CROSS -VALLEY
PAPOUN DwN r
Water or ccw
gromd Height
SIDE -HILL
-DIKED
Water or ccw
Height
original ground
_j
INCISED
Water or ccw
original
ground
Cross -Valley
Side -Hill
x Diked
Incised (form completion optional)
Combination Incised/Diked
Embankment Height _
Pool Area 3.1
Current Freeboard
37.5 feet Embankment Material Ash with earth fill cap
4
acres Liner 60 MIL LLDPE
feet
Liner Permeability very low
EPA Form XXXX-XXX, Jan 09

TYPE OF OUTLET (Mark all that apply)
Open Channel Spillway
X Trapezoidal
Triangular
Rectangular
Irregular
3' depth
35' bottom (or average) width
83' top width
Outlet
inside diameter
Material
corrugated metal
welded steel
concrete
plastic (hdpe, pvc, etc.)
other (specify)
TRAPEZOIDAL
TRIANGULAR
Top Width Top Width
Depth Depth
Bottom
Width
RECTANGULAR
Depth
�i
Width
Is water flowing through the outlet? YES
No Outlet
Other Type of Outlet (specify)
The Impoundment was Designed By Worley Parsons
NO X
IRREGULAR
Average Width
Avg
Depth
EPA Form XXXX-XXX, Jan 09 4

Has there ever been a failure at this site? YES X NO
If So when? February 2008
If So Please Describe :
In 2007, a wastewater treatment system, consisting of a gypsum settling pond, a
bioreactor flush pond and a bioreactor was constructed for treatment of the blowdown
steam from the FGD absorber units at the power plant. Pond water leakage was
observed at various locations along the outer slopes of the settling and flushponds.
failure on both inner and outer slopes. The Flush Pond was dewatered and the
operating level of the Settling Pond was lowered. Repairs to both ponds have been
designed and approved. Construction is currently underway at the Flush Pond with
repairs to the Settling Fond scheduled after completion of the work on the Flush Pond. -
EPA Form XXXX-XXX, Jan 09

Has there ever been significant seepages at this site? YES X NO
If So When?
IF So Please Describe:
See previous sheet
EPA Form XXXX-XXX, Jan 09

Has there ever been any measures undertaken to monitor/lower
Phreatic water table levels based on past seepages or breaches
at this site? YES NO X
If so, which method (e.g., piezometers, gw pumping,...)?
If so Please Describe :
EPA Form XXXX-XXX, Jan 09

ADDITIONAL INSPECTION QUESTIONS
ROXBORO POWER STATION — SEMORA, NC — FGD FLUSH POND
Concerning the embankment foundation, was the embankment construction built over
wet ash, slag, or other unsuitable materials? If there is no information just note that.
The embankment was constructed over a subgrade consisting of variable Bottom Ash,
Fly Ash, and Rock Fill Materials.
Did the dam assessor meet with, or have documentation from, the design Engineer -of -
Record concerning the foundation preparation?
Copies of Construction Drawings and calculations for repair were provided by the
Owner. There was no contact with the design Engineer of Record.
From the site visit or from photographic documentation, was there evidence of prior
releases, failures, or patchwork on the dikes?
The FGD Flush Pond experienced a failure in February 2008 that is described in a
previous section. Repair work is under construction at the time of this inspection.