HomeMy WebLinkAboutBradley Lake Final Risk Assessment 1990ALASKA ENERGY AUTHORITY
FINAL
RISK ASSESSMENT EVALUATION OF
THE BRADLEY LAKE PROJECT
JUNE 13, 1990
A
STCN E & WEBSTER
ALASKA ENERGY AUTHORITY
FINAL
RISK ASSESSMENT EVALUATION OF
THE BRADLEY LAKE PROJECT
JUNE 13, 1990
Stone & Webster Engineering Corporation
Stone & Webster Management Consultants, Inc.
5500 South Quebec Street
Englewood, co 80111-1914
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CONTENTS
Page
1.0 Executive Summary
1.1 Introduction 1-1
1.2 Objective 1-1
1.3 Methodology 1-1
1.4 Engineering Analysis 1-2
1.5 Risk Assessment 1-6
1.6 Conclusions and Recommendations 1-8
2.0 Introduction
2.1 Background 2-1
2.2 Project Description 2-1
2.2.1 Reservoir 2-2
2.2.2 Dam 2-2
2.2.3 Spillway 2-2
2.2.4 Powerhouse 2-2
2.2.5 Tailrace 2-3
2.2.6 Substation 2-4
2.2. 7 Climate, Topography and Geology 2-5
2.3 Objective 2-7
2.4 Methodology 2-7
2.4.1 Work Planning Meeting 2-9
2.4.2 Data 2-9
2.4.3 Identify Project Facilities 2-9
2.4.4 Damage Assessment 2-9
2.4.5 Document Review 2-11
2.4.6 Literature Search 2-11
2.4. 7 Other Perils 2-11
2.4.8 Design Criteria 2-11
2.4.9 Damage Losses 2-12
3.0 Engineering Analysis
3.1 Overview 3-1
3.2 Earthquake 3-2
3.2.1 Damage Assessments 3-6
3.2.1.1 Civil Structures 3-7
3.2.1.2 Powerhouse Structure 3-9
3.2.1.3 Equipment 3-11
3.2.1.4 Transmission Line 3-15
3.3 Flood 3-16
3.3.1 Inflow Flood 3-16
3.3.2 Tsunami Flood 3-17
3.3.3 Landslide Induced Wave in Bradley Lake 3-20
3.4 Wind 3-21
3.4.1 General 3-21
3.4.2 Powerhouse 3-21
3.4.3 Transmission Line 3-22
CONTENTS
(continued)
Page
3.5 Other Perils 3-27
3-28
3-28
3-30
3-31
3-32
3-32
3-32
3.5.1 Internal Failure
3.5.2 Snow/Avalanche
3.5.3 Subsidence, Landslide and Rockfall
3.5.4 Volcanic Eruption
3.5.5 Ice
3.5.6 Fire and Lightning
3.6 Cost Estimates
4.0 Risk Assessment
4.1 Fire, Lightning and All Other Perils 4-1
4.1.1 Fire and Lightning -Average Number of Occurrences 4-4
4.1.2 All Other Perils -Average Number of Occurrences 4-4
4.1 .3 Loss Severity 4-6
4.1 .4 Fire and Lightning -Losses 4-7
4.1.5 All Other Perils -Losses 4-8
4.1.6 Fire, Lightning and AOP Probability Analysis 4-9
4.2 Natural Perils 4-11
4.2.1 Natural Peril Probability Analysis 4-12
4.3 Summary of Dollar Losses 4-12
4.4 Insurance Observations 4-12
5.0 Conclusions and Recommendations
5.1 Conclusions 5-1
5.2 Recommendations 5-1
Exhibits
Appendices
A-Project Documents-Reference List
B-References
C-NERC Data
i
LIST OF TABLES
H.Q... Description Page
1-1 Summary of All Perils 1-8
2-1 Project Data 2-5
2-2 Facilities and Perils 2-10
3-1 Seismic Classifications 3-3
3-2 UBC Equivalent Loads 3-9
3-3 Predicted Earthquake Damage Levels 3-10
3-4 Equipment Seismic Requirements 3-12
3-5 Earthquake Magnitude Ranges 3-14
3-6 Potential Wind Damage 3-22
3-7 Transmission Line-Wind and Ice Loads 25-year return period 3-24
3-8 Transmission Line-Wind and Ice Loads 50-year return period 3-25
3-9 Transmission Line -Wind and Ice Loads 1 00-year return period 3-26
3-10 Estimated Internal Failure 3-28
3-11 Estimated Snow Loads 3-29
4-1 Forced Outages Due to Fire and Lightning 4-4
4-2 Listing of Selected Forced Outage Causes 4-5
4-3 Fire and Lightning -Loss Assumption Summary -Percent 4-8
4-4 All Other Perils -Loss Assumption Summary -Percent 4-9
iii
LIST OF EXHIBITS
N..Q.. Description
1 Bradley Lake Project General Plan (MAP)
2 Earthquake Damage Versus Annual Probability
3 Annual Exceedance Probabilities
4 Annual Probability of Exceedence for Water Levels Due to Tide and
Tsunami
5 Cross Section Detailing Estimated Tsunami Wave Heights
6 NERC Data
7 Earthquake Peril -Repair Costs and Out-of-Service Times
8 Flood Peril -Repair Costs and Out-of-Service Times
9 Other Natural Perils -Repair Costs and Out-of-Service Times
1 0 Fire and Lightning -Loss Multipliers and Damage Estimates
11 All Other Perils -Loss Multipliers and Damage Estimates
12 Fire, Lightning and All Other Perils-Total Expected Losses
13 Earthquake Peril-Total Expected Losses
14 Flood Perils-Total Expected Losses
1 5 Other Natural Perils -Total Expected Losses
16 Summary of All Perils-Total Expected Losses
17 Summary of Expected Losses by Year (Dollars)
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1.0 EXECUTIVE SUMMARY
1 . 1 Introduction
The insurable risks of the Alaska Energy Authority's (Energy Authority) electrical
systems are currently covered by a self insurance program supplemented by
Commercial Property and Boiler and Machinery insurance. This risk assessment
evaluation is designed to provide the basic information needed by the Energy
Authority, its financial consultants, and the State Division of Risk Management to
formulate the optimum overall risk management program for the Bradley Lake
hydroelectric project after construction completion.
The project, scheduled for completion in late 1991, will contribute to the electrical
generating capacity of Alaska's Railbelt, serving customers from the Kenai Peninsula
to Fairbanks. The project is located in the coastal area of Southern Alaska in close
proximity to seismically active features. The Uniform Building Code places the project
in Seismic Zone 4, the most severe classification.
1 . 2 Objective
The objective of this study is to estimate the value, in 1991 dollars, of the losses from
insurable risks that could be reasonably expected during the 30-year period, 1991-
2020, at the Bradley Lake hydroelectric project described in Section 2 of the report.
The assessment will include the above ground transmission lines between the
powerhouse and Bradley Junction.
1 .3 Methodology
Stone & Webster's study methodology was designed to develop the value of the
reasonably expected annual losses expressed in 1991 dollars. These potential
disbursements estimated at low, likely, and high ranges, will be based on the results of
a structural, civil, electrical and mechanical engineering, and probability analyses
directed to assess property damage foss to the dam, spillway, tunnels, penstocks,
powerhouse and equipment, transmission line, substation and equipment, barge dock,
landing strip and permanent camp, resulting from: Earthquake, Flood, Other Natural
Perils, Fire and Lightning, and All Other Perils.
1-1
The step-by-step procedure used to accomplish the study objective is outlined below :
Obtain the Energy Authority's agreement on the study
methodology, work plan and study results.
Obtain project data (descriptions, background studies,
design criteria, drawings, maps) from Stone & Webster
Engineering Corporation (SWEC) files.
Identify all major structures, facilities and equipment,
and relevant perils.
Organize evaluation team effort and assign damage
assessment responsibilities.
Review project design criteria and data.
Assign discrete ranges of peril magnitude and
corresponding probability to each structure under
consideration.
Assess low, likely and high levels of damage for each
range of peril magnitude.
Estimate dollar cost of each damage level and
corresponding plant downtime for repair or replacement.
Tabulate peril magnitudes, probabilities, loss estimates
and plant downtime estimates for each project.
Compute annual probable loss from each peril extended
over 30 years and present worth to 1991 dollars for the
low, likely and high estimated losses for the Bradley
Lake project.
1 .4 Engineering Analysis
This phase of the risk assessment study was performed by engineers experienced in
the design of hydroelectric structures and facilities. All disciplines reviewed the setting
of the project as revealed by the Final Supporting Design Report, photographs,
construction drawings, maps and background documents available at SWEC. The
study team also reviewed the design criteria documentation to ascertain the threshold
loading values for assessment of residual risk damage. Information was also
previously obtained from various sources which documented cases of damage and
failure of dams, penstocks, powerhouses and transmission lines from natural and
inherent phenomena.
1-2
There is little historical data specifically relating structural damage to hydro facilities to
the severity of natural perils; nevertheless, the magnitudes of the more devastating
events such as flood and earthquake have a statistical record and techniques are in
common use to predict their probability of future occurrence. Project structures and
other features are designed to ensure that they will be able to withstand defined
magnitudes of events during the project life.
The design magnitudes of these events all have a probability of being exceeded, so
there is still a potential risk to structures and facilities either from a single extreme
event or a combination of extreme events. The event or combination of events for
design is usually chosen by consensus based on judgment or dictated by FERC or the
building codes. There were five main categories of perils studied as discussed below.
1.4.1 Earthquake
The Bradley Lake hydroproject is located in the coastal area of Southern Alaska in
close proximity to seismically active features. The Uniform Building Code (USC)
places the project in Seismic Zone 4 for building design loading purposes.
Documented earthquake experience indicates that structures founded on sound rock
suffer least from high magnitude earthquakes. Since the main structures for all of the
facilities are founded on sound rock, the damage should be slight from all but the most
severe earthquakes. The effects of earthquakes on dams may be caused by ground
shaking, fault offset, landslide into the reservoir and seiche (wave in reservoir). The
two former effects are potentially the most damage causing. The kinds of structural
failure which may result are embankment slump (possibly leading to loss of freeboard)
resulting in consequent cracking of the concrete facing and/or cracking (possibly
leading to piping) of the rockfill dam; and cracking, overturning and/or sliding of the
concrete spillway.
1.4.2 Flood
The very nature of hydro projects which are designed to store and/or divert flowing
water, makes them susceptible to floods from high runoff. The FERC requires detailed
flood studies for each licensed project to protect the public where the potential failure
of a water retaining structure, such as a dam or spillway, may cause loss of life or
property damage downstream. Guidelines establishing the magnitude of flood for the
1-3
design of spillways and dams are normally those proposed and recommended by the
U. S. Army Corps of Engineers which are based upon criteria such as dam height,
volume of water impounded, possible extent of damage and loss of life downstream.
The loss of the impounding structure itself is not a concern of FERC, only the loss to
the public. However, in most cases the protection of the public from loss generally
ensures adequate protection of the structure and so is very beneficial from a risk
standpoint. The design criteria for the Bradley Lake dam and spillway requires that the
spillway be adequate to pass the Probable Maximum Flood (PMF) without overtopping
the dam. The PMF usually is assigned a probability of 1 :10,000 (once in 10,000
years), and is determined by a statistical approach using historical flow data for the
drainage basin under study.
Related to earthquakes and floods is the tsunami which is a long-period tidal wave
generated by several mechanisms: submarine earthquakes, submarine landslides,
and underwater volcanos.
Some of the facilities of the Bradley Lake Hydroelectric Project will be built on the
shores of Kachemak Bay. Examination of historical reports on tsunamis in Alaska, as
well as the seismicity and tectonics of the Gulf of Alaska, suggests that these project
facilities might experience tsunamis during their operating lifetime.
The greatest risk of powerhouse and switchyard flooding is considered to be from a
tsunami. Tsunamis were considered in the powerhouse design for the Bradley Lake
project. This risk assessment evaluated the structural damage that may occur from
higher than anticipated water loads due to tsunamis, and the consequent flooding
which may result.
1.4.3 Other Natural Perils
The site location generally experiences only moderate wind speeds, and events such
as hurricanes & tornados typically do not occur along the coastline of the Gulf of
Alaska. Apart from the dam and powerhouse most of the structures are of reinforced
concrete, and little damage is expected due to wind. Wind loading on the dam and
spillway is insignificant compared to other loads and may be neglected for this risk
assessment. The only structures at risk would seem to be building superstructures
consisting of metal panels, supporting girders (girts) and roof steel and transmission
1-4
line structures and equipment. Other 'natural' perils include ice, hail, subsidence,
landslide, snow (including avalanche), volcanic eruptions and internal failure (dams).
1.4.4 Fire and Lightning
Based on the National Weather Service data the isokerunic level for the Homer area is
estimated at less than one mean annual thunderstorm per year. Therefore, no
lightning protection was provided. The damage from a direct lighting strike on the
transmission line can include insulator damage and damage to the conductors. A
direct strike on the Bradley Junction switching station will likely damage insulators,
switches, operators, power voltage transformers for the SCADA RTU and radio.
1.4.5 All Other Perils
The 'all other' perils evaluated included both man-made as well as some additional
external or natural perils. This category of perils also included those man-made perils
that are not considered property perils, but are machinery and equipment related
perils. This broad category of perils includes: explosion, vibration, electrical overload,
rupture, electrical and mechanical breakdown, tearing apart, carelessness, as well as
natural or external phenomena not including flood, fire, lighting and earthquake.
1.4.6 Cost Estimates
The objective of this effort was to estimate the present day cost (per occurrence) for
repairing and/or replacing plant facilities damaged by the various perils identified in
this study. These replacement cost estimates assume replacement "in kind" rather
than the actual replacement costs associated with meeting future codes for
construction quality. These cost estimates were then used in the statistical risk
assessment. The estimated type and amount (low, likely and high) of damage for each
structure and piece of major equipment, for each peril was derived. Because
construction is still underway, cost estimates for replacement of plant facilities were
developed using actual or estimated installed costs and adjusted to reflect each
situation. Where repair of the plant facilities was required, a reasonable method of
repair was developed and the cost estimated. The plant time out of service for each
item was also estimated using engineering experience and judgment.
1-5
1 . 5 Risk Assessment
The risk assessment was completed in two parts (fire and lightning and all other perils,
and natural perils) due to the data that is available for the various peril categories. The
first part discusses the fire, lightning and all other peril categories. For these perils
loss experience averages are available to assess the risk (dollar value) associated
with a loss. The second part discusses the earthquake, flood and all other natural
perils. The data available for these categories are in the terms of probabilities that a
peril could occur in a stated number of years. These probabilities are then used to
quantify the risk of a dollar loss.
1.5.1 Fire and Lightning, and All Other Perils
Fire and Lightning damages or losses are estimated as follows: The probability of
damage is assumed to be zero for the dam, power tunnel, diversion tunnel, spillway,
and steel penstocks for all loss levels with the exception of the gate operating
equipment related to the tunnels. The Maximum Possible Loss (MPL) for the
structures with an assigned probability exceeds their replacement cost, as it is
possible (while not probable) that a fire loss could destroy a structure to an extent that
it would have to be taken down, debris would need to be removed, and a new
structure would have to be built. In risk management, this is known as the Maximum
Possible Loss (MPL). The MPLs are assumed to be 115 percent of the replacement
cost values for power plant superstructure and generating equipment within the
powerhouse. The MPL for switch yards and substations is 11 0 percent, for the
transmission line is 30 percent, and for permanent camp buildings is 50 percent,
respectfully. The Probable Maximum Loss (PML) ranges between 0 and 100 percent.
From our experience we determined 30 percent of the replacement cost value for
power plant superstructure, turbines, generators, switchyard and substations is
reasonable, while the PML for the permanent camp buildings is determined to be
25 percent. With respect to annual frequent losses, or Burning Layer Losses (BLL), it
has been assumed that the Bradley Lake Project will suffer no frequent losses due to
the peril of Fire and Lightning to the dam, spillway, diversion tunnel, power tunnel, and
steel penstocks. For power plant structures, turbines, generators, other equipment,
switchyards, substations and other property the annual BLL are assumed to be one
percent of the individual values. While a turbine or generator may suffer a fire loss,
most likely this would be an internal fire to the units, and be considered a boiler and
machinery loss, not a fire loss. Very little damage to the power plant structures and
equipment would result from an external fire.
1-6
For the category of All Other Perils (AOPs) the MPL can again exceed the value of the
individual power plant superstructure, turbines, generators, other equipment,
switchyards, substations and permanent camp buildings. For the MPL an estimated
115 percent of the replacement cost values was used as an estimate. With respect to
the dam, power tunnel, steel penstocks, diversion tunnel, spillway and other property,
the MPL was estimated as 33 percent of the aggregate values. The PMLs for the dam,
power tunnel, steel penstocks, diversion tunnel, spillway, and 'other property' are
estimated as 15 percent of the replacement cost values. The PMLs for the power plant
superstructure, turbines, generators, other equipment, switchyards, substations and
permanent camp buildings are estimated as 30 percent. With respect to BLL, an
estimated one percent of the values for all categories was used.
The average number of occurrences for the fire and lightning, and "all other perils"
were developed for these two categories based on the GADS data base. In order to
convert the average number of occurrences into probability values a statistical
approach was used via the Poisson distribution. The Poisson distribution assumes
that the probability of an occurrence is the same during each exposure. For this study,
it is assumed an exposure is one year of the study period. It is also assumed that the
occurrences are independent of one another. The average outage figures were used
in the Poisson distribution formula to derive the probabilities for one occurrence per
year. Then, using these probabilities, the expected losses were calculated by
multiplying the probabilities by the estimated damage cost. The probabilities derived
from the Poisson distribution for the turbine/generator were multiplied by 2 to account
for the two units at the site. The expected losses are reported on Table 1-1. The
results were computed for the total losses expected over the 30-year exposure period
in terms of 1991 dollars levelized and present-worthed to 1991.
1.5.2 Natural Perils
The natural perils cover earthquakes, floods, snow, wind, ice etc. The probability data
is used in this section to quantify the losses associated with these perils. The objective
of the natural peril probability analysis is to determine the potential loss expected over
the exposure period. Probability is the chance that something will happen, and is
expressed as decimals between 0 and 1. A probability of 0.001 means that an event
will occur once in 1 ,000 years and 0.1 will occur once in 1 0 years. For this study the
range of probabilities extends from 0.00001 to 1.0. Probability analysis is applied in
1-7
this study in the assessment of the risk associated with several different categories of
perils: i.e. earthquake, flood, and all other natural perils.
In order to calculate the expected losses, the probabilities are converted into
probabilities that represent a 30~year period and then multiplied by the replacement or
repair costs. The 30~year expected losses in 1991 dollars are computed using this
methodology for the project for each peril. These costs are escalated, and present
worthed, then levelized over the 30~year study period. The costs for the natural perils
are also reported in Table 1 ~1.
1.6 Conclusions and Recommendations
Based on the engineering analysis, construction data, firsthand knowledge of the
project and the statistical analyses, Stone & Webster has concluded that for the period
1991 through 2020 the total expected loss expressed in levelized 1991 dollars would
be $142,146, $2,094,272 and $6,166,654 under the low, most likely and high loss
scenarios, respectively. These costs are summarized in Table 1 ~1. To determine the
levelized loss that can be expected to occur in each year of the study period, the total
loss numbers are divided by 30 to obtain the annual figures of $4,738, $69,809, and
$205,555 for the three scenarios.
Peril
Earthquake Peril
Flood Peril
Other Natural Perils
Fire & Lightning
All Other Perils
Total Loss Estimate
Table 1·1
Bradley Lake
Summary of All Perils
Total Expected Loss
Total Expected Loss (1991 $) ( Levellzed 1991 $)
Low Likely High Low Likely High
$21,744 $93,486 $300,222 $38,361 $164,931 $529,661
$965 $128,859 $297,168 $1,702 $227,337 $524,273
$13,800 $77,790 $209,745 $24,346 $137,239 $370,038
$347 $8,818 $29,908 $613 $15,558 $52,765
$43,715 $878,121 $2,658,336 $77,124 $1,549,207 $4,689,916
$80,571 $1,187,074 $3,495,380 $142,146 $2,094,272 $6,166,654
While these are accurate averages based upon statistics, empirical evidence, and our
assumptions where necessary, it must be cautioned that the occurrence of any major
event could happen at any time. The statistics state that for the 28 hydroelectric
utilities for the years 1982-1986 inclusive, very few outages were caused by external
reasons. However, an occurrence could happen. Therefore, the insurance
underwriters justify their premiums by the possible loss rather than historical loss
experience.
The losses derived in this study are only expected losses, which may differ
significantly from actual future losses, thus the Energy Authority needs to formulate a
risk management program based on these expected loss estimates. The ability to
absorb losses is a function of the Energy Authority's liquidity, net worth, desire to
maintain electric rate stability, bonding requirements, state requirements, and
management's attitude towards risk. The Energy Authority should compare the total
amount of estimated insurance premiums for the 30-year period to the expected losses
to determine whether the economics justify a risk management program.
1-9
2.0 INTRODUCTION
2.1 Background
The insurable risks of the Energy Authority's electrical systems are currently covered by
combining a self insurance program with Commercial Property and Boiler and
Machinery insurance. This risk assessment evaluation is designed to provide the basic
information needed by the Energy Authority, its financial consultants, and the State
Division of Risk Management to formulate the optimum overall risk management
program for the Bradley Lake hydroelectric project after construction completion.
2.2 Project Description
The Bradley Lake Hydroelectric Project is located on the Kenai Peninsula, about 105
miles southwest of Anchorage, and 27 miles northeast of Homer, Alaska. Bradley Lake,
situated in a glacial valley in the Kenai Mountain Range, has a maximum observed
depth of about 270 ft. below the natural lake level of approximately project elevation
1080 feet.. Exhibit 1, General Plan, is a Project Map showing the project facilities.
The project, scheduled for completion in late 1991, will contribute to the electrical
generating capacity of Alaska's Railbelt, serving customers from the Kenai Peninsula to
Fairbanks.
Homer is the closest point of major road access to the region. There are no roads
connecting Homer with the Project Site. Transportation of material and personnel will
be accomplished via water, utilizing shallow draft barges unloaded at the barge dock, or
by air, utilizing the temporary landing strip.
The Bradley Lake level has been raised 100 ft. to a normal maximum surface elevation
of 1180 ft. by constructing a dam and a spillway across the mouth of the Bradley River
at the Lake outlet. A diversion tunnel has also been constructed at the Lake outlet to
divert water during construction of the dam and spillway and to provide a means of
drawing down the reservoir for purposes of repair or inspection of the dam and power
tunnel facilities. An approximately 19,000 ft. long, 13ft. diameter, concrete lined power
tunnel is being constructed to connect the intake works at Bradley Lake with a
powerhouse being constructed concurrently which will contain two 63-MVA turbine-
2-1
generator units. The powerhouse will be located on the northeast shore of Kachemak
Bay.
2.2.1 Reservoir
The reservoir surface will be normally maintained between elevation 1080 ft. and
elevation 1180 ft., except during flood conditions. The Probable Maximum Flood (PMF)
condition (23,800 cubic feet per second passing over the spillway) would raise the
reservoir water surface to a maximum elevation of 1190.6 ft.. The normal active
reservoir storage capacity, which corresponds to a reservoir level of elevation 1180 ft., is
285,000 acre-feet.
2.2.2 Dam
The Bradley Lake reservoir has been created by construction of a 125-ft. high concrete
faced rockfill dam approximately 520 ft. downstream of the lake outlet. The dam is
founded on and the abutments are comprised of bedrock. The proposed dam has a
crest about 17ft. wide by 600ft. long, situated at elevation 1190 ft.
The upstream face of the dam consists of a concrete parapet wall and a concrete face
slab tied into bedrock. The parapet wall extends 4 ft. above the dam crest and has a
bevelled upstream surface to act as a wave deflector.
2.2.3 Spillway
The ungated concrete gravity ogee spillway is located on a saddle feature approximately
150 ft. to the right of the main dam and along the same general alignment. The spillway
crest is set at elevation 1180 ft. and the overall length of the spillway including
abutments is approximately 230 ft., of which 175 ft. is the ogee overflow crest. The
spillway is founded on and its abutments are comprised of bedrock. The spillway chute
directs the discharge onto exposed rock and into the large natural pool downstream.
2.2.4 Powerhouse
The powerhouse has been designed to house two Pelton-type turbines with 63-MVA,
A.C. generators and associated support equipment and systems.
2-2
The powerhouse is located at tidewater and consists of a reinforced concrete
substructure founded in rock and a structural steel superstructure enclosed with
insulated siding and roof. The structure is approximately 80 ft. wide by 160 ft. long. The
substructure extends from project El.-9 ft. at the discharge chamber level to El.42 ft. at
the generator floor level. The superstructure extends from El.42 ft. to approximately
El.85 ft.
The substructure consists of the generator floor at El.42 ft., the turbine floor at El.21 ft.,
and sumps, pits and chambers associated with operation of the turbine located at lower
levels. The turbine floor, in addition to providing access to the turbine/generators,
contains the lube oil processing and storage facilities, the battery room, the emergency
diesel generator and other equipment associated with the plant operation. The
generator floor consists of an open 56 ft. wide bay serving the two generators and
control equipment, and includes a lay down and service bay, and a 24-ft. wide auxiliary
bay housing the control and service needs of the powerhouse. The auxiliary bay
contains support facilities including the control room, plant office, lunch room, locker
room, toilets and the machine shop. The generator floor remains clear and
unobstructed with access for a 160-ton bridge crane with an auxiliary 25-ton hook. The
bridge crane can run the full length of the powerhouse. Hatches are provided to access
lower levels. The auxiliary bay is designed to support a secondary floor at El.60 ft.
which houses heating ventilating and air conditioning (HVAC) equipment and provides
room for storage.
The powerhouse substructure and superstructure are designed with the provision that a
third 63 MVA unit may be added to the south side in the future. Excavation of the rock
for the third unit's substructure was completed with the excavation for the first two units
to avoid future blasting near operational units. The excavated area is to be backfilled
until the third unit is installed.
2.2.5 Tailrace
The tailrace is a pool downstream of the powerhouse designed to collect water released
from the turbines and to provide a channel to transport that water away from the power
house. The tailrace further acts as a stilling basin by reducing the turbulent flow of
released water before it flows into Kachemak Bay.
2-3
The flow of water from the powerhouse will be channeled into the main flow path of the
tailrace channel by the discharge chamber walls constructed as part of the powerhouse
substructure. A concrete retaining wall is required to retain the fill material just north of
the powerhouse and west of the substation. The retaining wall connects with the north
end wall of the powerhouse.
The tailrace will be excavated out of the mudflats immediately to the west of the
powerhouse. Rock adjacent to the powerhouse will be removed to provide proper
channel alignment. The sides and bottom of the tailrace basin will be riprapped for
protection from scouring. The tailrace is presently sized for two units.
2.2.6 Substation
The substation consists of a Compact Gas Insulated Substation (CGIS), transformers
and line terminations on the powerhouse from the transmission system. The substation
is adjacent to and tied into the north wall of the powerhouse and as such may be
considered an extension to the powerhouse.
The CGIS is housed in a reinforced concrete extension of the powerhouse, consisting of
a 115-kV, 4 breaker ring bus. The substation area serves as the line terminals for two
power transmission circuits which connect the powerhouse to the local utility
transmission system.
Three main unit power transformers (115 kV) will be mounted on concrete pads, located
adjacent to the north wall of the extension housing the CGIS system. The transformers
are provided with separation walls and containment basins filled with crushed rock.
Approximately 20 miles of two, parallel, 115-kV transmission lines will connect the
Project to a transmission line to be built by the Homer Electric Association. Power from
the Project will be transmitted over these transmission lines to Soldotna and Diamond
Ridge on the Kenai Peninsula and to other areas of the Railbelt electrical grid system.
The Project further includes the construction of the Middle Fork Diversion and the Nuka
Glacier Diversion. The Middle Fork Diversion will consist of a small diversion canal and
a water flow system which will divert the flows from the upper Middle Fork of the Bradley
River into Bradley Lake. The Nuka Glacier Diversion will divert flow from the Nuka
Glacier pool into the Upper Bradley River.
2-4
Comoonent
Dam:
Spillway:
Power
Tunnel:
Diversion
Tunnel:
Power
Penstock:
Middle
Fork
Diversion
Channel:
Nuka
Diversion:
Table 2-1
Project Data
oescrlptlon
Concrete-faced rockfill, 600
ft. long, 125 ft. high,
362,000 cubic yards
rockfill, and 10,800 cubic
yards concrete.
Ungated concrete ogee
section, 175 ft. long.
13-ft. nominal diameter,
about 18,61 0 ft. in length.
The tunnel will be concrete
lined.
The tunnel will be lined with
concrete and a down-
stream steel liner.
Steel 9-ft. diameter,
manifolds into 6.5-ft.
diameter branches
10-50 ft. wide, 1,520 ft.
long
9-ft. high gravelfill dike
Component
Powerhouse:
Turbines:
Generators:
Annual Rrm
Energy:
Average
Annual
Energy:
Transmission
Une:
Barge Dock:
Landing Strip:
2.2.7 Climate, Topography and Geology
oescrlptlon
Surface, steel super-
structure, 160 ft. long, 80 ft.
wide, 92ft. high.
2 Pelton, vertical shaft, 6-
jet, designed for 63,500 HP
at 917 ft. net head and 300
rpm.
2 each, AC, vertical,
designed for 63 MV A at
0.95 pf, 13.8 kV and 60Hz.
329 gigawatt hours
376 gigawatt hours
115 kilovolt, two parallel
lines, 20 miles long
Sheet pile, granular fill
Gravel surfaced, 75 ft.
wide, 2,400 ft. long. The
landing strip is
incorporated into the
access road.
The area surrounding Bradley Lake consists of steep-sloped mountains reaching
6,000 ft. in height, and is dominated by the lake and canyon of Bradley River. The lake
is about three miles long and varies from approximately 0.2 miles to 1.2 miles in width.
2-5
The project is located in the coastal area of Southern Alaska in close proximity to
seismically active features. The Uniform Building Code places the project in Seismic
Zone 4, the most severe classification.
The Kenai Peninsula is strongly influenced by the maritime climate that prevails along
coastal regions adjacent to the Gulf of Alaska. Cool summers and moderate winter
temperatures prevail, with occasional winter intrusions of cold Arctic air masses. Fog,
rain, and clouds occur frequently and gusty, turbulent winds are common. Precipitation
is light during late winter and early spring, and typically increases to maximum amounts
from August through December, varying with geographic location and elevation.
Precipitation in the lower elevations is predominantly rain with upper elevations
receiving snow.
Winds vary due to mountainous terrain and coastal changes. Wind speeds have been
clocked at speeds as high as 95 mph in some of the mountain areas, with gusts at
greater speeds. High winds in excess of 80 mph should be expected occasionally at the
dam site, powerhouse, and other locations at the Project Site.
The Bradley River flows from the lake through a steep, narrow canyon for much of its
1 0-mile length. This canyon is between 725 and 1 ,200 ft. deep and up to 750 ft. wide.
In the canyon section, the river passes through several narrow reaches, resulting in a
series of steep rapids and waterfalls.
The lower reach of the Bradley River emerges from the canyon and crosses extensive
tidal flats which consist mostly of sedge-grass meadows and mud flats. These tidal flats
extend to the northwest across the head of Kachemak Bay where two major drainages,
the Fox River and Sheep Creek enter the bay.
The hydrology of the Bradley River is typical of the glacial streams in the Kenai
Mountains. Approximately 90 percent of the annual discharge occurs from May through
October. The highest flows generally occur during the late summer when glacial melt is
most rapid and precipitation rates are high. A late spring runoff peak may also occur as
the winter snowpack melts. Groundwater storage capacity is low in the Bradley River
drainage and subsurface flow is limited, so most streamflow volume is from direct
surface runoff.
2-6
Kachemak Bay is subject to tidal fluctuations of up to 27 ft.. Although some ice may
form during cold winters, the major portion of the bay is essentially open all year.
Ice and heavy snow may be accumulated in varying amounts from early fall to late
spring, with the heaviest snowfall typically in December and January. Depths of snow at
the Project Site may range from 60 in. at lower elevations to greater than 1 00 in. at
higher elevations.
2.3 Objective
The objective of this study is to estimate the value, in 1991 dollars, of the losses from
insurable risks that could be reasonably expected during the period 1991-2020 at the
Bradley Lake Hydroelectric Project discussed in the background portion of this section
of the report. The assessment will include the above ground transmission lines between
the powerhouse and Bradley Junction.
2.4 Methodology
Our study methodology was designed to develop the value of the reasonably expected
annual losses expressed in 1991 dollars. These potential disbursements estimated at
low, likely, and high ranges will be based on the results of the peril probability analyses
and by the structural, civil, electrical and mechanical engineering analyses directed to
assess property damage loss to the dam, spillway, tunnels, penstocks, powerhouse and
equipment, transmission line, substation and equipment, barge dock, landing strip and
permanent camp, resulting from:
1 . Earthquake
2. Flood and Tsunami
3. Wind
4. Fire and Lightning
5. Other Perils -Natural
-All others
Analysis was performed for the facilities on an individual basis as well as combined to
estimate the total risk to the Energy Authority. Losses are expressed in 1991 dollars,
escalated for each year of the study and discounted to present value utilizing capital
budgeting techniques recommended and approved by the Energy Authority. The results
are based upon probability theory and the best information available at the time of the
study. Notwithstanding the value of the losses determined by this study, there is always
the possibility that a major event will occur sometime within the 30-year study period
causing catastrophic losses to at least one project structure, far in excess of those
estimated on a probabilistic basis in this study.
The step-by-step procedure used to accomplish the study objective is outlined below
and further elaborated in the following text.
1. Obtain the Energy Authority's agreement on the study methodology, work plan
and study results.
2. Obtain project data (descriptions, background studies, design criteria, drawings,
maps) from Stone & Webster Engineering Corporation (SWEC) files.
3. Identify all major structures, facilities and equipment, and relevant perils.
4. Organize evaluation team effort and assign damage assessment
responsibilities.
5. Review project data.
6. Review and tabulate design criteria for each facility.
7. Assign discrete ranges of peril magnitude and corresponding probability to each
structure under consideration.
8. Assess low, likely and high levels of damage for each range of peril magnitude.
9. Estimate dollar cost of each damage level and corresponding project downtime
for repair or replacement.
10. Tabulate peril magnitudes, probabilities, loss estimates and project downtime
estimates for each project.
11. Compute annual probable loss from each peril extended over 30 years and
present-worth to 1991 the low, likely and high loss for the project.
2-8
The following paragraphs present greater details on the above study procedure outline.
2.4.1 Work Planning Meeting
A work planning meeting was held at the SWEC headquarters to make certain that the
study team had a clear understanding on the desired study output.
2.4.2 Data
The project data was obtained largely from SWEC's files and consisted of project
description, project specifications, drawings, geotechnical studies, design criteria and
Federal Energy Regulatory Commission (FERC) License documents as listed in
Appendix A.
2.4.3 Identify Project Facilities
The major structures, facilities and equipment for the project were listed and the perils to
which each would be susceptible were identified in tabular form in Table 2-2.
2.4.4 Damage Assessment
The assessment of the type and magnitude of damage to each structure was assigned
to experienced engineers in the geotechnical, civil, structural, electrical or mechanical
disciplines, as appropriate.
The evaluation of peril magnitudes and probabilities of occurrence for earthquake, flood
and tsunami were obtained or developed from the background studies and design
criteria for the project.
Other peril magnitude/probabilities were obtained from published meteorological data,
utility forced outage/loss records and insurance industry sources.
2-9
Table 2-2
Facilities and Perils
Structural Subsl-
Facility/ Earth-Salcha/ Snow/ dance/
Equipment gym .El2!2sl Wind .E.IJ:I Tsunami Avalanche ~ Landslide 2lb.ir
Main Dam X X X X X X X
Main Spillway X X X X X X
Power Tunnel
Intake X X X
Power Tunnel X
Power Tunnel Gates X X X
Diversion Tunnel X X
Diversion Tunnel
Intake X X X
Diversion Tunnel
Gates X X X
Diversion Tunnel
Outlet X X
Fishwater Bypass X
Penstock X
Powerhouse
Substructure X X X X
Powerhouse
Superstructure X X X X X X X X
Tailrace X X
P/H Machinery &
Equipment X X X X
Substation &
Equipment X X X X X X X X
Transmission Line X X X X X X X
Nuka Diversion Dam
and LLO X X X X
Middle Fork
Diversion Channel X X
Barge Dock X X X X X
Landing Strip X X X X X
Housing & Warehouse X X X X X X X
2-10
2.4.5 Document Review
The engineer responsible for damage assessment of each structure or peril
magnitude/probability evaluation reviewed the appropriate documents and drawings to
extract information pertinent to his portion of the work.
2.4.6 Literature Search
A literature search was previously carried out for the 1988 Risk Assessment Evaluation
of Major Electric Systems for documented incidents of damage or failure to dams,
powerhouses and associated facilities, their cause and the remedial action taken to
return them to service. The documents listed in the bibliography presented in
Appendix 8 were reviewed for applicability to the engineering assessment. We also
contacted the utilities and agencies listed in the Risk Assessment Section to obtain
forced outage and loss details.
2.4. 7 Other Perils
Fire, lightning and "all other" perils are not amenable to the kind of probability evaluation
which we applied to the natural perils, so the utilities and agencies contacted in 2.4.6
above were also requested to provide statistical loss data for these perils.
2.4.8 Design Criteria
Pertinent design criteria were readily available for the project and are summarized in the
text of Section 3. The assumption was made that all structures, facilities and equipment
have been designed and constructed to the specified criteria, and that the design criteria
were appropriately developed. Therefore, we did not prepare any detailed calculation
reviews or inspections to verify that the structures were constructed to meet the design
criteria.
Design criteria reviews were carried out for the purpose of identifying the peril
magnitudes which may be damage causing and to differentiate between these and the
threshold magnitudes actually used for design and for which it is assumed no damage
will occur.
2-11
In essence, this engineering evaluation estimated the "residual risk" to the project which
has been defined by the United States Bureau of Reclamation (USSR) as-"The risk of
adverse consequences that remains after the design loading conditions have been
selected, appropriate designs prepared to accommodate the loading conditions, and
safety precautions established."
In addition, the design criteria reviews identified those potential natural hazards, if any
tor which no design criteria were stated or found, and evaluated the need to consider
their effects in the assessment and, if so, estimated the magnitude to be included.
Design Factors of Safety were evaluated for applicability to threshold peril magnitude
values and for a range of loss values.
2.4.9 Damage Losses
This risk assessment adopts a qualitative quasi-engineering approach as distinct from
the actuarial approach preferred and most often used by insurance companies. The
actuarial approach relies on historical loss data from many events which have occurred
and the law of large numbers to evaluate the risk of future loss occurring from specific
perils.
Unfortunately, the industry does not have the benefit of extensive historical, documented
natural peril loss data for hydroelectric facilities and must utilize engineering judgment in
estimating damage loss from perils which have statistically determined probabilities of
occurrence in given magnitudes. The repair or replacement cost estimates used in this
study are based on replacement "in kind" costs rather than the actual replacement costs
associated with meeting future codes for construction quality. The annual value of
probable loss is equivalent to the total area under the curve of damage cost versus
probability of occurrence for each peril considered, as illustrated in Exhibit 2. In this
approach probable annual loss estimates were assessed by summing the incremental
damage which potentially could occur due to a series of discrete ranges of peril
magnitudes.
The total single year loss from all perils is obtained by summing the individual peril loss
totals. It is assumed that this estimated annual value of total probable loss applies each
year of the entire study period, years 1991 through 2020 adjusted for forecasted
escalation of labor and materials. The present worth of the estimated probable loss is
2-12
then computed using an appropriate discount rate to provide the cumulative 1991
present worth of losses that were levelized over the study period so that an "average"
loss number could be presented. "Average" is in terms of a cost that represents the
repair or replacement cost over the 30-year study period. A more detailed description of
this methodology is presented in the Risk Assessment section (4.0) of the report.
2-13
3.0 ENGINEERING ANALYSIS
3.1 Overview
This phase of the risk assessment study was performed by engineers experienced in
the design of hydroelectric structures and facilities. Included on the team were
geotechnical, civil, structural, electrical, and mechanical engineers who were assigned
specific structures, facilities and equipment for analysis according to the methodology
outlined in Section 2.0.
All disciplines reviewed the setting of the project as revealed by the Final Supporting
Design Report, photographs, construction drawings, maps and background
documents available at SWEC. They also reviewed the design criteria documentation
to ascertain the threshold loading values for assessment of residual risk damage.
Material was previously obtained from various sources which documented cases of
damage and failure of dams, penstocks, powerhouses and transmission lines from
natural and inherent phenomena.
In some instances these reports provided the basis for the damage estimates or were
used as guidelines indicating the types of damage that could occur. Engineering
judgment was used to estimate the extent of damage.
There is little historical data specifically relating structural damage to hydro facilities to
the severity of natural perils; nevertheless, the magnitudes of the more devastating
events such as flood and earthquake have a statistical record and techniques are in
common use to predict their probability of future occurrence. Project structures and
other features are designed to ensure that they will be able to withstand defined
magnitudes of events during the project life.
The design magnitudes of these events all have a probability of being exceeded, so
there is still a potential risk to structures and facilities either from a single extreme
event or a combination of extreme events. The event or combination of events for
design is usually chosen by consensus based on judgment or dictated by FERC or the
building codes.
3-1
The assessment of damages from the various perils and their magnitude ranges, and
the assignment of probabilities to these magnitude ranges is described in the following
sections.
3.2 Earthquake
The Bradley Lake hydroproject is located in the coastal area of Southern Alaska in
close proximity to seismically active features. The Uniform Building Code (UBC)
places the project in Seismic Zone 4 for building design loading purposes.
Various classifications of earthquake magnitude are used in the design of structures.
The most common classifications used by FERC and the industry in hydroelectric
project design typically include an Operational Basis Event (OBE), a Design Basis
Event (DBE) and the Maximum Credible Event (MCE) which is also referred to as the
Extreme Basis. Table 3-1 provides definitions of these classifications as applied to the
design of Bradley Lake structures and facilities.
The following "Basis for Seismic Loading" is extracted from the Project Design Criteria:
BASIS FOR SEISMIC LOADING
GENERAL
A number of investigations of the seismicity of the Bradley Lake project
have been completed by the Army Corps of Engineers (COE), the U.S.
Geological Survey (USGS), Woodward-Clyde Consultants (WCC) and
Stone & Webster Engineering Corporation (SWEC).
For information on seismotectonic setting, the reader is referred to
Section 7 of the Final Supporting Design Report for the General Civil
Construction Contract.
SEISMIC DESIGN
Design Condition
The design earthquake studies (Woodward Clyde Consultants, 1980,
1981) examined possible earthquake sources and associated maximum
magnitude estimates for each source zone. Probability curves and
tabulations of the relative contribution from various size earthquakes were
developed. An analysis of ground motion parameters was performed and
response spectra curves were formulated for a maximum credible
(continued on following pages)
3-2
Table3-1
Seizmic Classifications
Operational Basis Design Basis
Horizontal Ground upto.1g 0.1 gto.3Sg
Acceleration
Approximate Mean Amual 0.1-().2 0.007
Probability of Exceeding Specified (1·2 chances in 10 (7 chances in 1000 of
Acceleration (based on 50-year of exceeding 0. 1 g) exceeding 0.35g)
project life)
Antiicpated Downtime Project resumes operation Inspection and checkout 30 days.
within hou!'$ Repairs 1 to 6 months
Allowable Damage Luel
pro!tct Eaaturu
Dam
Spillway
Power Tunnel
Po-mouse (per UBC)
Operational
No significant damage
Turbine/Generator/Governor Operational
Controls No damage, requires integrity check
to restart Minor adjustments/
reset con1ToV spares replacement
Spherical Valves and Operators Operational
Power Tunnel and Diversion Operational
Tunnel Slide Gates and Operators,
Diversion Tunnel
Powerhouse Emergency Generator Operational
15-kV Switchgear and Bus Operational
Main Powerhouse T ranslormers Operational
Substation!T ransmission Line Operational
Emergency lighting Operational, minor damage
and light bulb replacements.
Fire Protection Operational
Environmental Systems Operational
Middle Fork and Nuka Diversions Operational
Permanent Camp Facilities Operational
Including Permanent Housing
Barge Dock Airstrip Access Roads Operational
Operational
Architectural damage. No
significant structural damage.
Minor damage, possible
replacement of components
with spare parts
Limited damage, replacement of
components with spares.
Operational
Operational
Operational
Operational
Operational
Potential interruption of service
Operational • minor damage
and light bulb replacement
Operational
Operational
Operational
Operational
Soil failures possible. Will be
repaired as needed.
(1) While the retum period lor the DBE is usually 1 in 100 years, a retum period for the MCE is not always given.
We have assumed a 1 in 10,000-year period.
(2) The UBC also has an intermediate category described as 'major' with an assumed return period of about 1,000 years.
In this category the s1Tuctures are required to resist earthquake without collapse, but with some structural as well as
nonstructural damage. Structural damage would be limited to repairabie damage.
3-3
Extreme Basis
.3Sgto.75g
0.0004
(4 chances in 10,000 of
exceeding 0. 75g)
Possibly greater than
6monlhs
Limited s1Tuctural damage, no
s1Tuctural collapse. Potential
lor functional damage.
Structural damage (no structural
collapse). Significant architectural
damage.
Possible major damage
Possible major damage
Operational
Operational
Operational by manual start Manual
cable reconnection may be required.
Minor damage
Minor damage
Out of service, possible major
damage.
May require reconnection to
emergency generator and light
bulb replacement
Possible damage
Possible damage
Potential for functional damage
Potenliallor architectural and
s1Tuctural damage
Major soil failures possible. Will be
repaired as needed.
earthquake (MCE), producing a 0.75g peak horizontal bedrock
acceleration. A response spectra curve was also formulated for a design
basis earthquake (DBE) producing a peak horizontal bedrock
acceleration of 0.35g.
The study concentrates on regional faulting, (the Aleutian
Megathrust/Benioff Zone), and four local faults (the Eagle River, Border
Ranges, Bradley River, and Bull Moose Faults) as the controlling sources
to be considered. Analysis indicated that a magnitude 8.5 event occurring
on the megathrust beneath the site and a magnitude 7.5 event occurring
on the Border Ranges or Eagle River Faults, dominate the total response
spectra for the project design maximum earthquake. Seismic design
parameters were developed from the horizontal response spectra at the
project area. Both maximum expected magnitude and recurrence
intervals were considered. Details of the seismic design spectra and
design accelerogram were provided in Volume 3 of the Final Supporting
Design Report for the General Civil Construction contract.
The summary of the alternative design cases from which the maximum
credible and design basis events were selected are detailed below:
Design
Earthguake
Magnitude 7.5
(Local
Fault)
Magnitude 8.5
(Regional
Fault)
Peak Horizontal
Acceleration
J.g}
0.75
0.55
Magnitude 8.5 0.35
(Regional
Fault
Attenuated by Distance)
Design Criteria
Peak
Velocity
(In/sec)
27.6
21.6
10.1
Peak
Displacement
il1l
1.6
1.3
0.61
Significant
Duration
LaW
2 (MCE)
45
45 (DBE)
Earthquakes will affect the operation of the Bradley Lake Project. Since
the project site is located in a seismically active area, it is desirable for the
plant to remain operational during and after minor earthquakes. A
horizontal ground acceleration of 0.1 g has been selected for this
operational basis earthquake (OBE).
Minor damage can be expected during a moderate earthquake
corresponding to a horizontal ground acceleration of 0.1g to 0.35g. This
would involve possible repair to such items as relays, light bulbs and non-
critical equipment. Architectural siding and windows may need repair.
3-4
Most repairs could be performed by plant personnel using spare parts or
replacement equipment.
During a major or extreme earthquake having a horizontal ground
acceleration of 0.35g to 0.75g, increased damage may be expected to
occur. An inspection of the plant structures and equipment will be
required. Since damage may have occurred to the generating equipment,
major repairs may be required.
With a ground acceleration greater than 0.75g, which is greater than the
mean maximum credible event presently predicted, increased damage
would occur, varying with the earthquake magnitude and period.
Table 3-2 is a seismic evaluation which addresses the project structures
and equipment. This evaluation provides an approximate annual
probability of exceedence, which is based on the 50-year project life, and
the anticipated plant downtime for inspection and repair.
It is not economically prudent to design all structures and equipment for
the Maximum Credible Earthquake event. The critical structures and
equipment including the main dam, spillway, low level outlet gates and
operators, power tunnel, power tunnel intake and intake gate shaft, intake
gates and operators, and spherical valves and operators are designed for
the Maximum Credible Earthquake. Some repair may be required after
the event. However, the operating integrity of these structures and
equipment will be maintained during and after the Maximum Credible
Earthquake.
The generating equipment will be designed to remain operational during
minor earthquake events up to a horizontal ground acceleration of 0.1 g.
Minor damage can be expected from an earthquake with a horizontal
ground acceleration of 0.1 g to 0.35g. Major damage may be possible to
the generating equipment from an earthquake with a horizontal ground
acceleration of 0.35g to 0.75g.
The powerhouse and substation will be founded on or in rock. The
powerhouse has been designed pseudostatically to maintain its structural
integrity for a 0.75g horizontal acceleration and for an independently
applied vertical acceleration of 0.50g. Ductility considerations have been
provided for in design to enable the structure to withstand higher
amplifications in acceleration. Additionally, the steel superstructure has
been dynamically analyzed for a horizontal ground acceleration of 0.35g
in accordance with the Project response spectra (Attachment A of the
General Structural Design Criteria).
Seismic loads were not considered in the design of the Middle Fork and
Nuka Diversion.
Unless specifically designated otherwise in design criteria or
specifications, all major project facilities will be founded on or in rock and
design acceleration values given below are for horizontal acceleration in
rock.
3-5
Project
Facility
Main Dam and Spillway
Intake Structure and Gate Shaft
Diversion and Outlet Facilities
Fish Water Bypass System
Power Tunnel and Inclined Shaft
Penstock and Steel Liner
Powerhouse
Other (Service buildings, roads
and other non·operational facilities)
Design Ground
Acceleration(g)
0.75
0.75
0.75
0.35
Fully embedded -Not applicable
0.75
0.35 (No collapse at 0.75)
U.B.C. Zone 4 standards (min.)
The potential for future fault rupture, including sympathetic rupture
initiated by Eagle River and/or Border Ranges Fault movements was
evaluated for the Bradley River, Bull Moose, and minor faults in the vicinity
of Bradley Lake. On this basis, the probability of rupture occurring at the
power tunnel over the next 100 years was estimated at approximately 1 in
250 (or one chance in 25,000 of a rupture in any given year) due to
movement either on the Bradley River or Bull Moose Faults. Along a
minor fault, the probability of rupture is estimated to be approximately one
in 5,000 for a 1 00-ear eriod.
3.2.1 Damage Assessments
The coefficients which were chosen for design were assumed to be the threshold
values where no significant loss will occur. The probability curves in Exhibit 3 were
used for establishing the ranges of peril magnitude, up to the MCE, which may be
damage causing.
Documented earthquake experience indicates that structures founded on sound rock
suffer least from high magnitude earthquakes. Since the main structures for all of the
facilities are founded on sound rock, the damage should be slight from all but the most
severe earthquakes.
Earthquake induced regional subsidence is expected to be an event in which no
differential movement would take place between the structures. Thus, no damage
would result except tidewater may be relatively higher or lower which may effect
loading on the powerhouse structure or turbine operation.
3-6
3.2.1.1 Civil Structures
Due to the nature of their design, it was necessary to treat civil structures such as the
dams and spillways differently from the powerhouse and gatehouse buildings and to
treat equipment differently from either. In general, however, damage is predicted in a
range from zero for the DBE to total destruction in some instances for the MCE.
The dam at Bradley Lake was designed for stability under both static and dynamic
(seismic) loads according to deign techniques unique to these structures that were
developed with structural integrity and public safety foremost in mind. If the seismic
design loadings are exceeded, it is possible to predict the kind of failure which may
occur, and the extent of the damages.
The effects of earthquakes on dams may be caused by ground shaking, fault offset,
landslide into the reservoir and seiche (wave in reservoir). The two former effects are
potentially the most damage causing. The kinds of structural failure which may result
are embankment slump (possibly leading to loss of freeboard) resulting in consequent
cracking of the concrete facing and/or cracking (possibly leading to piping) of the
rockfill dam; and cracking, overturning and/or sliding of the concrete spillway.
Damage to the dam may in the extreme require the reservoir to be drained for repair or
replacement of the upstream face.
Only minor damage would result from overtopping of the dam due to an earthquake
induced seiche.
There is no identified fault beneath the dam, therefore, there is no risk of a fault offset.
A dynamic stability analysis was performed during the design of Bradley Lake Dam
and suggests that for the most likely critical sliding surface a maximum of about 0.1 ft.
vertical and 0.2 ft. total movement will occur for the OBE and DBE earthquakes,
respectively. For the MCE a maximum vertical settlement of about 2 ft. and total
movement about 5 ft. was calculated.
Loss of freeboard is estimated to be about 20 percent (excluding the four ft. high
parapet wall) which is acceptable. Total movement of five ft. does not jeopardize the
12ft. wide transition zone function beneath the concrete face.
3-7
The reservoir rim consists of a fairly stable rock mass. Other than some sloughing of
talus slopes, no significant rock slides are postulated.
This is an old reservoir with a large delta, so subaqueous sliding and wave generation
is possible.
The spillway agee section will only incur varying degrees of cracking for different
magnitude events, but the training walls are expected to collapse at the "most likely"
damage level for the MCE. As these are founded on and backed by rock, no
subsequent damage of any significance can occur even if the reservoir is spilling at
the time.
The emergency outlet (diversion} in the rock abutment between dam and spillway is a
steel pipe in an open concrete culvert, and has upstream gates which are normally
closed. This pipe could fail; but if it did, there should be controlled flow in the concrete
culvert which should not erode. However, repair would be needed for the pipe. The
gate structure is situated in rock and should be quite stable; therefore, it should remain
operational. The intake, gateshaft, concrete conduit and outlet for the outlet works are
reinforced concrete structures in rock.
The power intake and outlet works structures are of reinforced concrete submerged in
rock trenches in the lake. The only threat to these structures is rock·fall into the trench.
The power intake has a rocktrap upstream which will collect moderate amounts of rock
debris.
The main power tunnel is approximately 19,000 ft. long, and is mostly in hard rock and
is fully concrete lined. A number of lineaments and two identified faults cross the main
power tunnel. Possible modes of failure from earthquakes include offset along the
faults, which in the worst case would require tunnel dewatering, mining the offset
sections, bolting and concreting. An annual probability of 0.00004 (1 in 25,000 years}
is assigned to this event.
The steel penstock is embedded in rock except inside the powerhouse. The backfill
concrete grout is provided with a drainage system. Except for the case of a large
ground disruption such as faulting or subsidence, the chances for damage to the
penstock are slight. The exposed portion of the penstock, and the emergency shut-off
3-8
valve in the powerhouse, are adequately supported and will likely experience little
damage.
3.2.1.2 Powerhouse Structure
The powerhouse was designed by the more commonly applied techniques of
structural analysis described in the Uniform Building Code (UBC) as it applies to
reinforced concrete and steel frame buildings.
Damage due to earthquakes on powerhouse structures is very difficult to predict.
Variables include the area's seismicity, expected site earthquake motion, and the
strength, ductility, damping, mass and rigidity of the structure, along with numerous
other factors. In order to forecast the expected damage due to such a complex
problem, the UBC was used as a guide when possible. The UBC defines equivalent
pseudostatic loads as in Table 3-2 which may be applied to the structure for seismic
design.
Earthquake Type
Max. Credible
Major
Moderate
Minor
Table 3-2
UBC Equivalent Loads
UBC Loads
1.50 x UBC
1.00 X UBC
Av. of Major & Minor= 0.71 x UBC
UBC/2.35 = 0.43 x UBC
The UBC loading for the various magnitude events was used to predict the damage
levels shown on Table 3-3 for the powerhouse superstructure and substructure.
A comparison was made of the UBC recommended loads versus the loads for which
the actual structure was designed. Based on this comparison, a damage factor was
determined to represent the probabilities of the expected damage occurring. This was
an expedient to simplify the damage estimating process.
3-9
UBC
Earthquake
Magnitude
Max. Cred.
Major
Moderate
Minor
Max. Cred.
Major
Moderate
Minor
Table 3-3
Predicted Earthquake Damage Levels
Estimated Superstructure Damage
Some steel members
yield, some precast
panels crack, con-
siderable architect-
tural damage.
Minor cracking of
a few precast pan-
els, minor archi-
tectural damage.
No damage.
No damage.
LIke I y .l::lla..b
Superstructure
collapses,
total archi-
tectural damage.
Some steel mem-
bers yield, some
precast panels
crack, consider-
able architect-
tural damage.
Minor cracking
of a few precast
panels, minor
architectural
damage. ·
No damage.
Superstructure
collapses, total
architectural
damage.
Superstructure
collapses, total
architectural
damage.
Some steel mem-
bers yield some
precast panels
crack, consider-
able architect-
Minor cracking
of a few precast
panels, minor
architectural
damage.
Estimated Substructure carnage
Some repairable
cracks.
Few repairable
cracks.
No damage.
No damage.
3-10
Likely
Major repairable
cracking.
Some repairable
cracks.
Few repairable
cracks.
No damage.
Concrete floors
collapse.
Major repairable
cracking.
Some repairable
cracks.
Few repairable
cracks.
3.2.1.3 Equipment
The equipment listed in Table 3-4 has been specified to be operational after the
seismic event magnitude indicated. In addition, all equipment is anchored into
concrete or rock, and the anchorage is designed to withstand DBE as a minimum, with
most anchorages designed for MCE. Manufacturers and contractors were required to
demonstrate that critical equipment designs meet the seismic criteria specified.
Hydro-turbine-generators are conservatively designed as a general rule and many
installations have been exposed to extreme events, such as earthquake and flood,
without any serious damage.
Cases have been documented of hydro plants in very close proximity to major
earthquakes, for instance, the 1964 Alaska earthquake (Eklutna hydro), the Chilean
(Rape! hydro) and Mexican (La Villata and El lnfiermillo hydro) earthquakes of 1985,
and the 1987 New Zealand earthquake (Matahina hydro) in which no damage was
sustained to the turbines and generators. We have been unable to uncover any cases
of significant earthquake damage to this equipment. The reason is undoubtedly due to
the normal practice of solidly embedding and anchoring the stationary parts into the
concrete foundation. The rotating parts, the turbine runner and generator rotor, are
connected by a slender but low stress main shaft, which is supported and guided by
babbit lined bearings with close running clearances and oil film lubricating cushion.
Exceptionally high impact loads due to ground motion may damage the bearing liners
and/or supports and we have assigned this as the damage level for MCE. An external
source of earthquake damage to this equipment would be from falling objects such as
roof and wall panels or the complete superstructure. At high enough ground
accelerations the substructure containing the turbines and generators could fail. The
overhead bridge crane and supports have been designed to remain in place during
the MCE.
3-11
Table 3·4
Equipment Seismic Requirements
The equipment listed below is specified to remain operational during and after the
event magnitude cited.
Penstock, Manifold, and Steel Liner
(Exposed Sections)
Main Dam Diversion Penstock and Supports
High Pressure Gates and Operating Systems
Spherical Valve
Compact Gas Insulated Substation
Diesel Generator
Firewater Equipment and Piping System
Fire Suppression Systems
Fuel Oil System (Supports)
Turbine
Generator
Governor
Powerhouse Bridge Crane
Miscellaneous Hoists
Bulkhead Gates and Guides for Power Tunnel
and Diversion
Tailrace Gates and Guides
SCAD A
Transmission Line
Main Power Transformers
15.0 kV Switchgear Assemblies
15.0 kV Bus
480 Volt Station Service Switchgear and Transformers
Project Facilities Stepdown Transformer
125 Volt DC Systems
Fish Water By-Pass System
Power Tunnel Intake Trashracks and Guides
Main Control Board and Relay Panels
Piping Systems -General
Instrumentation
Service Water System
Sump Drainage and Unwatering System
Service, Instrument, and Control Air System
Oil Conditioning Systems
Plumbing, Drainage, and Oil Separation systems
Heating and Ventilation System
Electric motors and Starters
Tailrace Depression Air System
Lighting Systems
Operational Seismic
Regu!rements
(1)
(1)
(1)
(1) (2)
( 1) (2)
MCE
MCE empty
DBE full
MCE
MCE
MCE
MCE
MCE
MCE
MCE
DBE/MCE
DBE/MCE
DBE/MCE
DBE/MCE
DBE/MCE
DBE
DBE
DBE
DBE
DBE
DBE
DBE
DBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
OBE
(1) After events of these magnitudes, the equipment will be shut down for routine damage inspections.
(2) Cranes and hoists shall remain in place for all events.
3-12
The gas insulated substation is designed to operate during and after the MCE. It is
expected that minor control devices (relays, etc.) will fail in the DBE and MCE. After
each event, the substation should be inspected for any failed components, gas
pressure, racked bus joints etc. Caution must be exercised due to the potential
presence of highly toxic dust in the event of a fault and subsequent rupture of the bus
containment.
Auxiliary equipment such as transformers, circuit breakers, control panels, diesel
generators, compressors and pumps are of fairly uniform design and construction
whether used for hydroelectric, steam or nuclear power plants.
An experience data base is being developed by an independent organization (EQE,
Inc.) in which selected types of auxiliary equipment, which have experienced
earthquakes of recorded intensities, are carefully checked for damage and operation,
and categorized. The developing data base shows that no damage was sustained
and operations continued for selected equipment during peak ground accelerations of
up to 0.35g, and only a few items of installed equipment sustained damage or tripped
off during peak ground accelerations of up to O.Sg. Based on this experience, we have
used 0.35g peak ground acceleration as the threshold value for all equipment, at
which no damage will be sustained. Degrees of damage will be assigned above this
value.
These conclusions are contingent upon the equipment being firmly anchored in place
which has been carefully specified, for the Bradley Lake Plant.
Three earthquake magnitude ranges were considered in Table 3-5 for equipment in
this assessment.
3-13
Acceleration
Range -g
0.10 to 0.35
0.35 to 0.50
0.50 to MCE
Table 3-5
Earthquake Magnitude Ranges
Probability
0.100
0.007
0.0004
likely Damage
None
Minor Damage ( 1 )
Major Damage (2)
(1) Damage at this level might be expected to include the DBE based equipment
listed in Table 3-4 such as main power transformers, excitation switchgear, 15.0
KV and 480-V switchgear, generator switchgear, main control board and relays,
batteries and all OBE based non-critical systems. Damage will be minor as all
equipment is anchored down and will not topple, but will have to be repaired and
equipment and relays operationally checked for function. All relays should be
recalibrated. There is potential for gas leakage in the substation. Gas density
and pressure should be checked and the integrity of seals visually examined.
(2} In addition to the equipment damage under (1 ), the turbines and generators will
probably sustain minor damage to bearings and their supports, and equipment
anchors designed for DBE will strain or fail. Substation damage might be
expected to include the following:
a. Additional damage to insulators on transformers and line terminations.
b. Transformers will have to be drained of oil and checked structurally as a
minimum, At higher levels, transformers and switchgear will have to be
rebuilt or replaced.
c. The entire gas bus in the substation will have to be inspected for damaged
seals, breaker alignment, and gas leakage.
The extent of damage which various magnitude earthquakes could potentially cause
at the project are estimated generally based upon the foregoing. Described below are
items which require special attention due to their design, location, foundation
conditions or other factors.
3-14
The power tunnel intake gate is housed inside the reinforced concrete gate shaft
founded in rock and is not expected to fail unless the gatehouse itself collapses. The
gate is operated by a hydraulic cylinder mounted directly above the gate. We assume
that the hydraulic operator may fail in an extreme earthquake above MCE. This same
assessment applies to the emergency outlet works gates also.
The design criteria indicates that the turbine inlet valve is to be designed to be
operational during and after the MCE.
However, the valve has a large counterweighted operator which may suffer damage,
and the anchors may be strained or stripped for very high magnitude events.
3.2.1.4 Transmission line
Seismic loading was not considered, however, due to the design of the towers,
seismic damage will be minimized. Up to 0.35g, no damage should occur.
At 0.35g the angle structures and dead-ends are rigid and above 0.35g will have some
damage (six towers). Tangent structures which are the majority will not incur any
damage.
At 0. 75g the angle and dead-end structures will be severely damaged, particularly
those along the bluffs near the powerhouse (Section 3). The Fox river valley will
liquify, and most (maybe all) of the tangent structures will fall down. The same for the
structures on the Bradley Junction Plateau. Insulator and conductor damage should
be minimal.
The transmission line tangent towers are designed for controlled failures in the event
of an earthquake. Above the design loads, the yoke shears, putting about three foot of
slack into the tower. This will dramatically reduce the tension in the conductor and
insulators. If that is not enough, and the tensions increase, the guy wires will break
and the tower will fall. For the towers on the plateau and in the valley, this will minimize
damage.
For towers along the bluff, there may be some tower damage due to the rugged terrain.
3-15
As a minimum the anchorage and supports for all equipment designed for OBE was
designed to meet DBE requirements, and for all equipment designed for DBE, the
anchorage was designed to meet MCE requirements. The anchorages actually
provided for most equipment has been designed for MCE.
Relays may trip during cited events.
3.3 Flood
3.3.1 Inflow Flood
The very nature of hydro projects which are designed to store and/or divert flowing
water, makes them susceptible to floods from high runoff. The FERC requires detailed
flood studies for each licensed project to protect the public where the potential failure
of a water retaining structure, such as a dam or spillway, may cause loss of life or
property damage downstream. Guidelines establishing the magnitude of flood for the
design of spillways and dams are normally those proposed and recommended by the
U. S. Army Corps of Engineers which are based upon criteria such as dam height,
volume of water impounded, possible extent of damage and loss of life downstream.
The loss of the impounding structure itself is not a concern of FERC, only the loss to
the public. However, in most cases the protection of the public from loss generally
ensures adequate protection of the structure and so is very beneficial from a risk
standpoint.
The design criteria for the Bradley Lake dam and spillway requires that the spillway be
adequate to pass the Probable Maximum Flood (PMF) without overtopping the dam.
The PMF usually is assigned a probability of 1 :10,000 (once in 10,000 years), and is
determined by a statistical approach using historical flow data for the drainage basin
under study.
The dam is of the concrete faced rockfill type with adjacent mass concrete spillway all
founded on and tied into rock. The spillway is of the simple ungated overflow type with
a crest elevation of 1180 ft. The dam crest elevation is 1190 ft. with a reinforced
concrete parapet wall on the upstreams side to elevation 1194 ft.
Normal maximum pond level is 1180 ft. The probable maximum flood (PMF) pond
elevation is 1190.6 ft. leaving 3.4 ft. freeboard on the parapet wall to prevent
overtopping from wind driven waves.
3-16
Spillway model tests were carried out to refine the design of the spillway discharge
area to prevent damage from PMF flows.
The structures have been designed to prevent overtopping of the dam and
downstream erosion so no damage is anticipated during the PMF.
The small diversion dam at Nuka has no flood criteria for design. The gabion structure
will overtop with a sufficiently high flood. Partial or complete replacement may be
needed if damage occurs.
Public safety is generally not an issue in connection with flood hazard to the other
hydro facilities such as the powerhouse, so the owner and designer must set
appropriate criteria. The powerhouse is located at tidewater and is situated so that the
main access floor elevation is 25.6 ft. above maximum high tide including waves.
Waves due to seismically induced Tsunamis are treated separately from a risk
standpoint.
A considerable number of hydro powerhouses throughout the world have been
flooded by various natural or accidental events. Flooding to various levels have
occurred, including complete submergence of generator and auxiliaries. In most
instances the equipment only required cleaning, dry out, and testing, while in others
some electrical equipment needed replacing or rebuilding. Oil spill from governor and
bearing sumps during a flood may present the greatest difficulty during clean-up.
3.3.2 Tsunami Flood
The southcentral Alaska coastal region, where the Bradley Lake hydro project is
situated, is subject to seismic activity as detailed in the earthquake portion of this
section of the report. A phenomenon associated with seismic activity is the tsunami
which is a long-period tidal wave generated by several mechanisms: submarine
earthquakes, submarine landslides, and underwater volcanos. These waves may
travel distances of over 5,000 miles across an ocean with speeds at times exceeding
500 mph. In open oceans, the heights of these waves are generally unknown but
small, while their run-up height in coastal regions have been greater than 100 ft. The
wave may also be greatly amplified in shallow water by detraction, convergence, and
3-17
resonance when it reaches land. The Bradley Lake 'Tsunami Hazard' report dated
September 1987 summarized and concluded that:
[Some of the facilities of the Bradley Lake Hydroelectric Project will be
built on the shores of Kachemak Bay. Examination of historical reports
on tsunamis in Alaska, as well as the seismicity and tectonics of the Gulf
of Alaska, suggests that these project facilities might experience
tsunamis during their operating lifetime. Some of the communities at the
mouth of Kachemak Bay experienced a tsunami of about 20 ft in 1964.
Port Graham on the lower Kenai Peninsula also reported a 25 to 30 ft
tsunami associated with the eruption of the Augustine volcano in 1983.
Therefore, in the future, the project facilities could also experience a
tsunami of this magnitude from a similar eruption of Augustine. It can be
concluded that the tsunami hazard to project facilities located on
Kachemak Bay is real and that the tsunami may be generated by either
the occurrence of large earthquakes in the Gulf of Alaska or by a severe
eruption of Augustine volcano.
Based upon the probability curve, Exhibit 4 which was developed for the
exceedence of water levels from tide plus tsunami (including both
seismic and volcanic sources), the impact levels on the powerhouse for
two cases are shown on Exhibit 5. The two cases are: 1) total water
height of 25 feet corresponding to an annual probability of 0.007, and 2)
total water height of 44.2 feet corresponding to the maximum credible
tsunami plus the calculated maximum historic high tide. The second
case is given not to suggest that it should be used for design, but to
provide the reader with a comparison of a reasonable design case (Case
1) to the upper possible limit, having a probability of essentially zero.
A regional tsunami warning center for Alaska is located in Palmer,
Alaska. This center is responsible for seismic and tidal gauge data
collection, analysis of data, and issuance of tsunami warnings to the civil
defense authorities of various coastal communities in Alaska
(Sokolowski, 1985). It is recommended that a communication plan be
established to ensure project personnel operating the power plant are
evacuated to high ground in the case of tsunami generation in the Gulf of
Alaska from (earthquake occurrence) or in Lower Cook Inlet (from the
eruption of Augustine volcano).
Empirical estimates of tsunamis generated by large earthquakes in the
Gulf of Alaska were modified to take into account the presence of the
Barren Islands and the constriction of Lower Cook Inlet. This
modification was carried with the assumption of a diffraction coefficient
0.4 suggested by Wilson & Torum (1968). It would clearly be necessary
to carry out detailed numerical modeling of the ocean floor in the area of
Lower Cook Inlet in order to obtain a more precise diffraction factor.
Therefore, it is recommended that such studies be carried out if the
predicted recurrence of a major tsunami is felt to have significant effect
on project capital or insurance costs.
The effect of Homer Spit on tsunami propagation has not been
considered in this study. Homer Spit reduces the width of Kachemak Bay
and therefore will act as a topographic barrier to the propagation of a
tsunami towards project facilities. Homer Spit will affect tsunamis
generated by the eruption of Augustine volcano as well as by
earthquakes in the Gulf of Alaska. It is recommended that the effect of
Homer Spit be determined quantitatively by numerical modeling if further
studies are conducted.]
The greatest risk of powerhouse and switchyard flooding is considered to be from a
tsunami. Tsunamis were considered in the powerhouse design for the Bradley Lake
project. This risk assessment evaluated the structural damage that may occur from
higher than anticipated water loads due to tsunamis, and the consequent flooding
which may result.
Simple flooding of equipment in the substation at Bradley Lake is unlikely to cause
major damage. Oil samples should be taken and tested for both transformers and
circuit breakers. The rest of the switchyard equipment should be washed to remove
salt deposits before re-energizing. It is assumed that with sufficient warning, the on-
site operations personnel will deenergize the equipment before the flood can cause
electrical fault problems.
We have assigned powerhouse damage levels from three wave heights as follows:
a. Wave heights which are less than elevation 22 ft. are assumed not to
collapse the access doors. Damage is zero.
b. Wave heights to elevation 25 ft may fail the outer roll-up access door to the
substation area and NE powerhouse access double doors at elevation 21 '.
Damage is assumed to be limited to clean up, dry out and testing and
replacement of 50% of the auxiliary motors, in addition to replacing the
access doors.
c. Wave heights to elevation 44.2 ft will result in failure of all elevation 21 ft
doors, substation walls and transformer firewalls. Damage is assumed to be
the same as in (b) above plus the need to rebuild some switchgear and
motor control centers (MCC's). No damage to the powerhouse structure is
anticipated, but some wall panels will need to be replaced. Serious damage
to the substation due to falling walls will result. The effect on transformers is
3-19
likely to include the breaking of bushings and possible salt water infiltration
into the oil. High buswork is likely to be mechanically deformed or broken,
requiring replacement.
3.3.3 Landslide Induced Wave in Bradley Lake
An investigation of landslide-induced waves in Bradley Lake Reservoir was carried out
in 1987 as part of project engineering. The Executive Summary from the ensuing
report is as follows:
[By examination of the Bradley Lake reservoir rim and shoreline most
likely to experience a landslide during a major earthquake, investigating
the subsurface geology, and using both analytical and comparative
techniques; an estimate was made of the volume of material in the
Kachemak Creek Delta at the head of the lake which might liquefy during
an earthquake, causing a subaqueous landslide, and thereby inducing a
wave in the Bradley Lake reservoir. The estimated volume so obtained
was 4,000,000 cubic yards. The mass mobilized during this postulated
subaqueous landslide would be a 200 feet wide band along two-thirds of
the 5500 feet width of Kachemak Creek Delta to the head of the lake.
The extreme basis seismic event (normalized peak horizontal ground
acceleration 0. 75g) was used to generate the landslide.
The magnitude of the wave which would be generated by this landslide
and the propagation of the wave approximately three miles along the
lake to the dam were calculated. The use of three wave propagation
methods yielded close results, the largest of which indicated 9. 7 feet
wave height at the dam. The analysis was conservatively performed with
the lake water surface at elevation 1180, the maximum normal operating
level. No reduction in wave magnitude was made for the attenuating
effect that the southwest portion of the lake shoreline, which juts out in
front of the dam blocking the path of the wave, would have.
The analysis showed that the dam parapet would not be overtopped and
that the wave force would be less than that for which the top of the rock fill
dam is presently designed.)
The likely consequence of such an event would be zero damage. However, there is a
possibility that Bradley Lake will be at flood level when the event occurs resulting in a
wave elevation of up to 1190.6 ft. + 9. 7 ft. = 1200.3 ft. which would overtop the parapet
wall on top of the dam (el 1194 ft.).
The probability of these two independent events occurring simultaneously may be
estimated by the product of their individual probabilities.
3-20
Overtopping the parapet wall by 6 feet may cause one or all of the following damage to
occur:
1. Failure of the parapet wall
2. Erosion of the downstream face
3. Movement of the dam
Industry practice does not normally consider extreme events as occurring
simultaneously for design purposes, but a risk assessment should take this into
account to ascertain if catastrophic damage can occur which may be statistically
significant.
3.4 Wind
3.4.1 General
The site location generally experiences only moderate wind speeds, and events such
as hurricanes & tornados typically do not occur along the coastline of the Gulf of
Alaska. Apart from the dam and powerhouse most of the structures are of reinforced
concrete, and little damage is expected due to wind. Wind loading on the dam and
spillway is insignificant compared to other loads and may be neglected for this risk
assessment. The only structures at risk would seem to be building superstructures
consisting of metal panels, supporting girders (girts) and roof steel and transmission
line structures and equipment.
3.4.2 Powerhouse
The wind speeds used in the design criteria for determining wind loads on the
powerhouse are based on a basic wind speed at 30 feet above ground of 100 mph,
with Unified Building Code (UBC) factors applied for heights other than this. This
design wind speed has a 50 year recurrence interval. Wind gusts of 96 mph have
been recorded during a short record period (1980-1982).
The Climatic Atlas for the Gulf of Alaska (BLM) provides probability data for annual
maximum sustained wind for Homer. Wind speeds are averaged over 1 minute and
tabulated values are 60 mph, 67.5 mph and 88 mph for 50, 100 and 500 year return
periods respectively. The 68 percent confidence limits for each of these return periods
3-21
show wind speeds ranging 49.7-74.6 mph, 50.7-90.1 mph, and 45.0-150.0 mph
respectively. There is thus some probability that winds far in excess of the design
criteria will occur. These will be damage causing especially as the relationship
between wind load and wind speed is non-linear. According to UBC loads increase
incrementally at a greater rate than the wind velocity. Damage from extreme winds is
expected to strip wall and roof coverings off the powerhouse, substation and
permanent camp buildings, but no structural damage is anticipated.
Wind borne missiles may constitute a small hazard along with direct wind loads. The
only damage to equipment inside structures would be from roof and wall panels off the
building itself.
Potential wind damage has generally only been assessed for these types of structures
and typically will be as shown on Table 3-6.
Wind
Speed
(mph)
100
150
probability
0.020
0.002
Table 3·6
Potential Wind Damage
None
Minor damage to
metal wall
panels & girts.
Likely
None
Considerable damage
to metal wall & roof
panels & girts; some
damage to outside
windows & doors
on powerhouse
and permanent
camp. Damage to
transmission line
structures and
broken insulators.
3.4.3 Transmission Line
Some damage to
metal wall panels
& grits.
Wall and roof
panels & girts
destroyed; heavy
architectural
damage. Loss of
permanent camp.
Extensive damage
to transmission
line structures
and broken insula-
tors.
Transmission line loss and insulator loss at high wind speeds are possible even
though the line was designed to withstand 5 second wind gusts of up to 154 mph in
high wind areas, based on a 50-year return period. Damage to equipment such as
line terminals, disconnects, and transformers should be restricted to insulators broken
due to overstress caused by buswork deformation or blowing debris. Ice combined
3-22
with wind can put extreme loads on the transmission conductor, insulators, and
structures. Expected wind and ice loads are shown on Tables 3-7, 3-8 and 3-9.
The conductor used has a tensile strength of 42,000 pounds. The line was designed
for the 50-year wind and ice loading shown on page 3-25 with a 40-percent margin of
safety.
The Meteorological Evaluation of Bradley Lake Hydroelectric Project 115-kV
transmission line route, prepared by M. C. Richmond, dated December 19, 1985, was
used to obtain values for wind speeds and loads, and return periods. Damage
estimates are assessed using the meteorological report and the Transmission Line
Construction Contract, and some engineering judgment.
The meteorological study performed by M. C. Richmond under contract to Dryden &
LaRue Consulting Engineers prior to transmission line construction, consisted of three
parts.
Field Survey
Climatology Survey
Analysis of data and application to the proposed route.
Data was obtained from files formerly belonging to Meteorology Research, Inc.,
National Climatic Center, Arctic Environmental Information Center, and National
Weather Service in Anchorage and Homer. Due to varying climatic conditions along
the route, the line was divided into eight segments. Tables 3-7, 3-8 and 3-9 are the
conclusions from the report for the eight segments of the transmission line. These
conclusions are incorporated into the Basic Design Manual for the 115-kV
Transmission Line.
The Design Manual shows that the transmission line is designed for:
I. NESC H -1984 NESC Heavy Loading
1/2" radical ice with 4PSF wind & 0.30 constant at 0°F, initial loading.
II. NESC L-1984 NESC Light Loading
No ice with 9PSF wind & 0.05 constant at 30°F, initial loading.
3-23
SEGMENT
NUMBER
1
2
VJ
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~
4
5
6
7
'
8
TRANSMISSION LINE-WIND AND ICE LOADS-25-YEAR RETURN
EXTREME WIND ON BARE WIRE WET SNOW ICING 0.5 g cm-3
APPRO X-1-MINUTE ASSOCIATED MAXIMUM MAXIMUM MAXIMUM MAXIMUM
IMATE AVERAGE 5-SECOND ASSOCIATED WET SNOW VERTICAL TRANSVERSE TRANSVERSE
LENGTH WIND SPEED GUST SPEED WINO THICKNESS ICE LOAD WIND SPEED WIND LOAD
(miles) (mph) (mph) DIRECTION (Radial ln.) (!bilinear ft) (mph) (lbllinear ft)
2.1 80 109 NNE 1.5 2.5 35 1.0
2.2 110 145 SE 1.5 2.5 70 4.1
2.0 80 109 NNE 1.5 2.5 35 1.0
2.5 95 128 NNE 1.0 1.3 50 1.5
0.5 80 109 NNE 1.0 1.3 35 0.7
3.4 90 122 NE 1.5 2.5 40 1.3
2.8 60 83 ESE 2.0 4.0 30 0.9
4.7 92 125 NNW 2.5 5.8 45 2.5
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5
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TRANSMISSION LINE-WIND AND ICE LOADS-50-YEAR RETURN
EXTREME WIND ON BARE WIRE WET SNOW ICING 0.5 g cm-3
1-MINUTE ASSOCIATED MAXIMUM MAXIMUM MAXIMUM MAXIMUM
AVERAGE 5-SECOND ASSOCIATED WET SNOW VERTICAL TRANSVERSE TRANSVERSE
LENGTH WIND SPEED GUST SPEED WIND THICKNESS ICE LOAD WIND SPEED WIND LOAD
(miles) (mph) (mph) DIRECTION (Radial ln.) (lb/linear ft) (mph) (lbllinear ft)
2.1 85 115 NNE 1.7 3.0 39 1.4
2.2 115 154 SE 1.7 3.0 75 5.1
2.0 85 115 NNE 1.7 3.0 39 1.4
2.5 100 135 NNE 1.2 1.7 54 2.0
0.5 85 115 NNE 1.2 1.7 39 1.1
3.4 95 128 NE 1.7 3.0 44 1.8
2.8 64 90 ESE 2.2 4.6 34 1.3
4.7 97 131 NNW 2.7 6.6 49 3.2
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3
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5
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TRANSMISSION LINE· WIND AND ICE LOADS -100-VEAR RETURN
EXTREME WIND ON BARE WIRE WET SNOW ICING 0.5 g cm-3
1-MINUTE ASSOCIATED MAXIMUM MAXIMUM MAXIMUM MAXIMUM
AVERAGE 5-SECOND ASSOCIATEO WET SNOW VERTICAL TRANSVERSE TRANSVERSE
LENGTH WIND SPEED GUST SPEED WIND THICKNESS ICE LOAD WIND SPEED WIND LOAD
(miles) (mph) (mph) DIRECTION (Radial ln.) (lbllinear ft) (mph) (lbllinear ft)
2.1 90 122 NNE 1.9 3.6 43 1.8
2.2 120 160 SE 1.9 3.6 79 6.2
2.0 90 122 NNE 1.9 3.6 43 1.8
2.5 105 141 NNE 1.4 2.2 58 2.6
0.5 90 122 NNE 1.4 2.2 43 1.4
3.4 100 135 NE 1.9 3.6 48 2.3
2.8 66 91 ESE 2.4 5.4 38 1.8
4.7 102 137 NNW 2.9 7.5 53 4.0
M0390033
-I
$l) cr
CD
VJ
I
<.0
Ill. NESC W-1984 NESC Extreme Wind
Loading of 26 PSF wind on bare conductor with gust factors for wire loading
and structure loading.
IV. MCR H-MCR 50-Year Return Period
Combined wet snow and wind loading for eight (8) segments.
V. MCR W-MCR 50-Year Return Period
1-minute wind loadings and 5 sec wind loadings for eight (8) segments.
VI. CONST-Construction Loadings
Structure erection and hauling. Maintenance and repair. Stringing
VII. LONG -Longitudinal Loadings
Extreme wind, combined snow and wind, unbalanced ice and/or snow, broken
conductor, ice drop
VIII. MISC -Miscellaneous Loadings
Seismic, vibration, galloping conductors.
The following overload factors were used.
Ov~riQsU;I Csu~a~illl Factor
Load Case Wind Tension Vertical
II
Ill
IV
v
VI
NESC H
NESC L
NESCW
MCRH
MCRW
CONST
3.5 Other Perils
2.5
2.5
1.1
1.1
1.1
2.0
1.65 1.5
1.65 1.5
1 .1 1.1
1 .1 1 .1
1 .1 1 .1
2.0 2.0
The 'other perils' category to be evaluated in this risk assessment will be segregated
into 'natural' and 'all other' perils. The 'natural' perils will include ice, hail, lightning
subsidence, landslide, snow (including avalanche), volcanic eruptions and internal
failure (dams). The 'all other' perils to be evaluated will include both man-made as
3-27
well as some additional external or natural perils. This category of perils will also
include those man-made perils that are not considered property perils, but are
machinery and equipment related perils. This broad category of perils is discussed in
Section 4 and includes: explosion, vibration, electrical overload, rupture, electrical
and mechanical breakdown, tearing apart, carelessness. Natural or external
phenomena not including flood, wind, fire, lighting and earthquake are discussed
below.
3.5.1 Internal Failure
Perils such as earthquake and flood are considered to be random events. There is
also a category of perils considered to be normal events which include failure of a dam
due to deterioration or defects and is generally called internal failure. Internal failure
of dams can occur typically due to piping, slope instability, foundation failure or failure
of integral facilities. The methodology used to evaluate this risk was as developed in
the publication "Preliminary Safety Evaluation of Existing Dams" Vols. 1 and 2,
McCann, M. W. et al., which uses a Bayesian model.
The methodology when applied to the rockfill dam yielded the probability of failure
indicated in Table 3-10.
Piping
Slope Stability
Foundation
Total
Table 3-10
Estimated Internal Failure
Scale
2
2
1
Frequency of
Dam Failure
0.0000110
0.0000028
0.0000039
0.0000177
The annual probability of failure is thus 0.00002 and the estimated damage would be
complete dam failure.
3.5.2 Snow/Avalanche
Apart from the dam, most of the structures considered are of reinforced concrete and
the damage due to snow load will probably be minimal. However, the roofs of some
3-28
structures, such as the powerhouse and substations with metal deck roofs, are at risk.
However, there is no threat of avalanche reaching any of the structures, including the
transmission line.
The project design criteria utilized Corps of Engineers ETL 1110-3.37 to determine the
snow loads which are based on a 1 00 yr return period. Due to the scarcity of
probabilistic data for snow loads, the ETL 111 0-3.37 data has been extrapolated to
extreme probabilities.
The Design Criteria for the powerhouse requires the roof to be designed for the 1 00-yr.
storm and 85 pounds per square foot (psf) snow load. In addition the roof is sloped to
reduce snow loads. The tailrace deck is designed for 11 0 psf snow load.
Typically the damages shown on Table 3-11 were assessed for the powerhouse roof.
Snow
Loading
U1.S.1l
85
120
probability
0.010
0.002
Table 3-11
Estimated Snow Loads
None
None
Likely
None
Minor defor-
mation of
some roof
panels
Minor defor-
mation of some
roof panels
Replace roof
topping panels
The intake and emergency outlet gatehouses are substantial reinforced concrete
structures with a sloping concrete slab roof designed for 110 psf snow loads. Thus, no
damage is anticipated.
Tables 3-7, 3-8 and 3-9 show the expected wet snow, ice, and wind loads on the
transmission line for the 25, 50 and 1 00-year return periods. The maximum expected
loads are from a combination of snow and wind. The conductor is designed for the
50-year return snow and wind load with a 40-percent margin of safety. Insulator
strengths were selected to match the maximum conductor tension. Towers were
3-29
designed for the combined wet snow and wind loading for the 50-year return. It is
expected that the 1 00-year return storm would exceed the design strengths in some
portions of the line causing some tower, insulator, and conductor damage.
3.5.3 Subsidence, Landslide and Rockfall
All important structures are founded on good rock with the exception of the barge dock,
access roads, landing strip, and some transmission towers. Only earthquake related
subsidence could affect structures founded on rock and this would be regional so no
differential displacement would take place between structures, and no damage is
anticipated.
Regional tectonic movements could lower the powerhouse and substation structures
closer to tidewater and increase their risk of flooding, or raise these structures further
above tidewater which should have no detrimental effect.
Some of the facilities have potential for damage from subsidence and landslides most
likely triggered by earthquakes. Significant damage would be expected to the barge
dock, landing strip and transmission line towers across the Fox River valley due to
liquification of the sediments on which they are founded. This is covered under
earthquake. Normal tidal actions may result in slope instability of the barge dock
beam causing sliding damage. The probability of this occurring is estimated as
0.0001.
A few transmission line towers are founded on an old landslide and even though they
did not move during the 1964 earthquake there is still a possibility of future movement
and is accounted for with a probability of 0.0001.
There is a potential risk to high, steep, rock cuts that rockfalls will occur under "normal"
conditions. The risk would be greater for earthquakes; however, the combined risk of
failure and recurrence interval of the earthquake are considered smaller than the
"normal" condition. Conversations with a number of "experts" on tunnels and rock cuts
suggest that an annual probability of 0.0001 would be appropriate for these
occurrences. No published statistical information was located to support this
assumption.
3-30
There is a possibility of a rockfall in the rock cuts at the power tunnel and emergency
outlet intakes, although the rock cuts are bolted "as required".
The worst case would be a rock slide that would clog the intake, requiring the lake to
be drained and the intake cleared. The probability of such a landslide is estimated at
0.0001.
There is some potential for a subaqueous landslide at the upstream end of Bradley
Lake, and this is covered under Flood, but landslides into the lake from the steeper
sideslopes are unlikely due to the thin ground cover, probably the result of glacial
scouring.
3.5.4 Volcanic Eruption
Active volcanoes are situated to the north of Kodiak Island in the mainland Aleutian
Range. There is a threat of falling ash over the Bradley Lake project which may
require some cleanup of the gatehouses for the power tunnel and emergency outlet,
powerhouse, and switchyard. It may cause some turbine erosion after the ash has
settled in the Lake and passed through the power tunnel and penstock.
The powerhouse HVAC system maintains the building under positive pressure thus
tending to exclude ash from entering, and the air intakes are equipped with filters.
These would need to be changed repeatedly during ash fall. The control room air
handling system is also equipped with an electrostatic filter to further minimize
infiltration of ash deposits should they occur inside the powerhouse. Ash particles are
not expected to affect the functioning of equipment.
The turbines would be inspected periodically and shutdown if significant erosion is
noted. Ash fall depends on the magnitude of the eruption, meteorological conditions
(particularly wind direction), type of ash particle, and the probability of damage outside
of the maintenance budget is considered to be nil.
Some flashover and tracking of insulators on Kenai transmission lines using polymer
insulators has been observed by Homer Electric Authority (HEA). The transmission
line uses some polymer insulators. Thus, there is the possibility of tracking and
flashover due to ash buildup, but no damage is expected that would not be covered by
maintenance.
3-31
3.5.5 Ice
Ice loading on the dams due to the winter ice sheet on the reservoirs is factored into
the structure design and accounts for only a small portion of the total loading. A
significant increase in the ice sheet thickness beyond design will also have an
insignificant effect on the total loads.
Ice storms may coat the structures and exterior equipment with ice. Structures and the
transmission line have ice loading in their design criteria. For buildings the ice loading
is assumed to result from a large ice block overhanging the roof.
Snow loading on the transmission line is expected to be far more severe than ice
loading according to the design criteria and is addressed in Section 3.5.2.
3.5.6 Fire and Lightning
Based on the NWS data the isokerunic level for the Homer area is estimated at less
than one mean annual thunderstorm per year. Therefore, no lightning protection was
provided. The damage from a direct lighting strike on the transmission line can
include insulator damage and damage to the conductors. A direct strike on the
Bradley Junction switching station will likely damage insulators, switches, operators,
power for the SCADA RTU and radio.
3.6 Cost Estimates
The objective of this effort was to estimate the present day cost (per occurrence} for
repairing and/or replacing plant facilities damaged by the various perils identified in
this study. These replacement cost estimates assume replacement "in kind" rather
than the actual replacement costs associated with meeting future codes for
construction quality. These cost estimates were then used in the statistical risk
assessment.
To accomplish this objective, our engineers estimated the type and amount (low, likely
and high} of damage for each structure and piece of major equipment, for each peril.
Because construction is still underway, cost estimates for replacement of plant facilities
were developed using actual or estimated installed costs and adjusted to reflect each
3-32
situation. Where repair of the plant facilities was required, a reasonable method of
repair was developed and the cost estimated. The plant time out of service for each
item was also estimated using engineering experience and judgment.
The cost estimates were based on the following sources of information as applicable:
Actual installed costs -Bid Abstracts and Contract Progress Estimates were used as
the starting point in addressing the installed costs. After breaking out the costs, and
putting them into a usable format. the applicable indirect costs were applied to develop
the total costs. The bulk of the construction work was performed in 1989 and cost
increases over the last six months have been minimal, so no escalation was applied.
Estimated installed costs -Current material and equipment costs with appropriate
installation and indirect costs were developed. Most of the electrical cost estimates
were developed this way because of limited detailed cost information available from
the above sources.
Estimated repair costs -Based on the anticipated damage, a method for repair was
developed and the required material, labor and indirect costs were estimated. These
cost estimates were based on current material/equipment costs, labor requirements,
construction labor rates. benefits and burdens. Allowances for construction equipment,
contractor's indirects, mobilization/demobilization, engineering, construction
management and owner's costs were then added as appropriate.
On Exhibits 7, 8 and 9 we have detailed the cost estimates and the outage time
associated with the perils and particular pieces of plant and equipment.
3-33
4.0 RISK ASSESSMENT
The risk assessment is completed in two parts (man-made perils and natural perils)
due to the data that is available for the various peril categories. The first part
discusses the fire, lightning and all other man-made peril categories. For these perils
loss experience averages are available to assess the risk (dollar value) associated
with a loss. The second part discusses the earthquake, flood and all other natural
perils. The data available for these categories are in the terms of probabilities that a
peril could occur in a stated number of years. These probabilities are then used to
quantify the risk of a dollar loss.
4.1 Fire, Lightning and All Other Perils
Probabilities for the peril categories, Fire, Lightning and All Other Perils (AOPs) were
developed based upon loss experience from the North American Electric Reliability
Council's (NERC) Generating Availability Data System (GADS). The data used for this
study is the same as used in the Risk Assessment study completed in March, 1988 for
the Alaska Energy Authority.
GADS was established to provide the electric utility industry with a comprehensive
generation unit and equipment availability data base which includes over 91 percent
of the installed generation capacity in North America. The GADS data base is to the
electric utility industry as the Insurance Service Offices (ISO) is to the property casualty
insurance industry. ISO collects loss data on numerous types of exposures and
approximately 90 percent of the property and casualty insurance industry belongs to
ISO. Unfortunately, ISO has not collected loss data from the insurance industry with
respect to electric utilities since 197 4, and even these rates are judgmental rather than
actuarially correct. The rates consequently are a function of the general insurance
market, and not founded upon historical loss experience. Stone & Webster found that
the insurance industry frequently utilizes loss experience, but only when it is poor
experience. Empirical evidence suggests good loss experience does not receive the
favorable rate treatment that is justified, while poor loss experience is usually reflected
in higher rates.
NERC has collected data from 28 hydroelectric utilities which represented 595
generating units for the five-year period 1982-1986 inclusive. This represents 2,396
unit years of experience. While the "Generating Availability Report" presents a variety
4-1
of performance indexes, outage and other information for various types of electric
generating units, a computer sorting was prepared by NERC at our request to isolate
full forced (unplanned) outages, the average number of occurrences per unit year, and
the average duration hours per outage with respect to hydroelectric utilities. (See
Exhibit 6.) A full forced (unplanned) outage is defined as: "The occurrence of an
unplanned component failure (immediate, delayed, postponed) or other condition
which requires that the unit be removed from service, immediately or before the next
weekend."
In reviewing the cause codes for full forced outages for hydroelectric utilities, it was
apparent that the significant causes of forced outages are related to machinery and
equipment problems, but not due to external phenomena such as fire or other
catastrophes. In insurance terminology we observed that most losses with respect to
frequency and severity are boiler and machinery insurance losses, rather than
property losses.
During the 1987-1988 study many risk managers, insurance underwriters, loss control
engineers and other individuals knowledgeable of hydroelectric operations were
contacted to verify the low probabilities of loss developed by the statistical data for All
Other Perils, and the Fire and Lightning Perils. Criteria used to estimate the losses
was also discussed. The empirical evidence also confirmed that most losses were
boiler and machinery. The literature search, which included many utility trade
journals, insurance journals, and reinsurance industry publications also confirmed the
fact that most hydroelectric losses are equipment losses (boiler and machinery type of
losses), and not property losses.
While the risk management process is often more of an art than it is a science, Stone &
Webster incorporated as much science as possible in developing the probabilities for
Fire, Lightning and AOP.
NERC is the sole entity that provides a database service or information on both
internal and external causes of loss which force a hydroelectric facility to stop
producing power. However, a cause of loss that does not effect generation would not
be reflected in these statistics. For instance, there could be a fire in the power station
that may not force the operator to shut down the generators. Thus, in this case a
forced outage would not be reported. Similarly, external causes of loss such as a
catastrophe or other event may cause damage to the dam, but not effect generation.
4-2
For the five-year period, 1982 through 1986, the 28 utilities that participated in the
GADS data base of forced outages were:
Alabama Power Co.
Appalachian Power Co.
B.C. Hydro
Central Power & Light Co.
Georgia Power Co.
Idaho Power Co.
Louisville Gas and Electric Co.
Los Angeles Dept. of Water & Power
Montana Power Co.
New Brunswick Electric Comm.
Northeast Utilities
Ontario Hydro
Otter Tail Power Co.
Pacific Gas and Electric Co.
Pennsylvania Electric Co.
Pennsylvania Power & Light Company
Portland Gas and Electric Co.
Portland General Electric Co.
Public Utility District of Chelan County
Washington
Public Utility District of Douglas County,
Washington
SMUD
Salt River Project
South Carolina Public Service Authority
Southwestern Power Administration
Tapoco, Inc.
Virginia Electric & Power Co.
Western Area Power Administration
Wisconsin Public Power Inc.
During this period, most, but not all, hydroelectric utilities presented NERC with data
on forced outages. For instance, Ontario Hydro joined the GADS system in 1985 and
only 1985 and 1986 data were collected from this utility.
Total period hours of 8713.54 were recorded based upon the five-year period. Refer
to Appendix C for details on the formulas and definitions such as period hours and unit
years. While it appeared that total available hours would be more appropriate to use
in the calculations, many utility statistics utilize period hours as suggested by Institute
of Electrical and Electronics Engineers (IEEE) Standard Number 762. To conform with
the standard, the GADS statistics utilize period hours as a base.
Of the total period hours of 8713.54, 240.87 hours or 2. 76 percent were recorded as
unplanned or forced outage hours. Based on the total available hours of 7,967.3, the
240.87 forced outage hours represent 3 percent.
While 2.76 percent may appear as a very low rate of failure, Stone & Webster's risk
management and engineering experience confirmed that forced outages to
hydroelectric utilities have the lowest incidence rate of all electric generating units.
4-3
The probability of an outage due to Fire, Lightning and AOPs represent only a portion
of the 2. 76 percent rate.
4.1.1 Fire and Lightning • Average Number of Occurrences
Utilizing this same methodology the average number of outages caused by Fire and
Lightning is calculated as shown in the following table.
Fire
Lightning
TOTAL
Table 4·1
Forced Outages Due to Fire and Lightning
Cause
Code
9010
9020
Average Number of
Occurrences Per Unit Year
0.0025 (1)
0.0200
Number of
Occurrences
6
~ (2)
54
(1) The GADS data base assigns a 0.000 to any value which is less than 0.005. Thus, we have assumed
that the average number of fires could be 6 (0.0025 x 2,396 unit years).
(2) Assumed to be 0 for Bradley Lake.
Table 4-1 indicates that 54 occurrences over a five-year period have resulted from fire
and lightning. However, in the Homer, Alaska region only 8 lightning strikes in the
past 30 years occurred. For this reason we have assumed that there would not be any
lightning strikes at this site in the category fire and lightning. Lightning is covered as a
natural peril in Section 3.5. Thus there are only 6 occurrences per year. Based on
2,396 unit years of experience, this represents 0.0025 occurrences per unit per year (6
+ 2,396), or for a two-unit power plant 0.005 Fire and Lightning occurrences per year.
4.1.2 All Other Perils .. Average Number of Occurrences
Over 150 cause codes of failure are available for a hydroelectric utility to cite as a
reason for a forced outage. For the group of perils AOPs, we selected cause codes
that had average duration hours per outage that exceeded 200 hours, as well as all
external causes of loss as shown on Table 4-2.
4-4
Table 4-2
Listing of Selected Forced Outage Causes
Cause
~ Description
9040 Any Catastrophe, not including
Average Duration
Hours per Outage
4.77
flood, fire, lightning, earthquake
9320 Other external problems
9696 Miscellaneous operational
environmental limits
9720 Other safety problems
9900 Other error
991 0 Maintenance error
9920 Contractor error
3670 Other voltage systems-
volt transformers
3671 Other voltage systems-
volt circuit breakers
4500 Rotor windings (including
damper windings and fan
blades on hydro units)
4520 Stator windings, bushings,
and terrrinals
4530 Stator core iron
7002 Bearings
7011 Other Runner Problems
7020 Nozzle assembly
7030 Vibration
7101 Lower reservoir dams and dikes
7124 Penstock
7220 Unit out due to common penstock
with unit under repair
TOTAL
12.68
.91
.23
1.82
.40
3.00
287.21
284.55
456.46
1291.13
1343.77
341.24
527.06
865.08
530.08
232.48
2,467.04
717.64
9,367.55
Average No. of
Occurrences Per
Unit Year
0.0025
0.0300
0.0025
0.0025
0.0300
0.0300
0.0100
0.0025
0.0025
0.6025
0.0300
0.0025
0.0200
0.0025
0.0025
0.0025
0.0025
0.0025
No. of
Occurrences(1)
6
72
6
6
72
72
24
6
6
6
72
6
48
6
6
6
6
6
(1) In all instances where 6 occurrences are shown this is an assumed figure because the data base showed a
0.00, while the true value could be between 0.000 and 0.0049. We have assumed six occurrences (0.0025 x
2,396 unit years).
4-5
Table 4-2 indicates that 438 occurrences have been experienced that may produce
measurable losses. During the 1982-1986 period there were a total of 4,816
occurrences. Thus, 9.09 percent of the occurrences (438 + 4816 x 1 00) during the five
years were due to the causes selected above. However, on an annual basis the
average number of forced outage occurrences from these causes is 0.18 occurrences
per unit per year (438 + 2,396 unit years). Since Bradley Lake has two generating
units, 0.36 total occurrences (2 x 0.18) can be expected each year due to AOPs.
These are non-insurance occurrences or at most, boiler and machinery types of
causes. External or property types of losses make up very few outage hours.
Based on Stone & Webster's experience, an average occurrence of an outage is 0.36
per year per hydroelectric plant for AOPs appears to be reasonable. Also, this
average assumes losses arising out of other perils such as explosion, vandalism and
sabotage.
4.1.3 Loss Severity
The expected losses from Fire, Lightning and AOPs are developed based upon the
probability of an event times the projected loss, and these products are summed.
To develop the dollar amount of losses, historical loss data was not sufficient to justify
our calculations. Once again, judgment was needed in this task of risk management.
The Maximum Possible Loss (MPL), the Probable Maximum Loss (PML), and annual
Burning Layer Loss (BLL) are developed based upon risk management experience
and communications with reinsurers, insurers, and various utility risk managers.
In risk management, Burning Layer Losses are the frequent small losses as compared
with the severity losses (MPL and PML). The use of the term "burning layer" does not
indicate that this risk management technique is applicable only to the fire peril.
With respect to loss severity, Stone & Webster developed the MPL and PML and
estimate these to be high and likely losses, respectively. While the PML developed is
called a "most likely loss", in practice, the PML is usually greater than the most likely
losses. However, since judgment in estimating dollar amounts of losses was a
4-6
significant factor, these estimates were conservative to utilize the PML as the most
likely losses.
4.1.4 Fire and Lightning -Losses
Throughout the remainder of the report we will refer to Fire and Lightning losses
because this is a common insurance industry term, although there are no lightning
losses, considered in this subsection, as this is a natural peril addressed in
Section 3.5.
Fire and Lightning damages or losses are estimated as follows: The probability of
damage is assumed to be zero for the dam, power tunnels, diversion tunnels,
spillways, steel penstocks and all other property for all loss levels, with the exception
of the gate operating equipment related to the tunnels. The MPL for the structures with
an assigned probability exceeds their replacement cost values derived by Stone &
Webster, as it is possible (while not probable) that a fire loss could destroy a structure
to an extent that it would have to be taken down, debris would need to be removed,
and a new structure would have to be built. In risk management, this is known as the
Maximum Possible Loss (MPL). The MPLs are assumed to be 115 percent of their
replacement cost values for power plant super structure, generating equipment within
the powerhouse, and tunnel gate operating equipment. The MPL for switchyards and
substations are 110 percent of their replacement cost values, while the MPL for the
permanent camp is 50 percent because these buildings are generally isolated from
each other. The transmission line is assigned an MPL of 30 percent as fire could only
destroy the line in one area.
The Probable Maximum Loss (PML) ranges between 0 and 1 00 percent. From our
experience we determined 30 percent of their replacement cost values as a
reasonable PML for power plant structures, turbines, generators, switchyard and
substations, and 15 percent for the transmission line. The PML for permanent camp
buildings is determined to be 25 percent.
With respect to annual frequent losses, or Burning Layer Losses (BLL), it has been
assumed that the Bradley Lake project will suffer no frequent losses due to the peril of
Fire and Lightning to the dams, power tunnels, and steel penstocks. For power plant
structures, turbines, generators, other equipment, switchyards, substations,
transmission line and other property the annual BLL are assumed to be one percent of
4-7
the individual values, while a turbine or generator may suffer a fire loss, most likely this
would be an internal fire to the units, and be considered a boiler and machinery loss,
not a fire loss. Very little damage to the power plant structures and equipment would
result from an external fire. Table 4-3 summarizes the losses assumed for Fire and
Lightning.
Table 4-3
Fire and Lightning
Loss Assumption Summary • Percent
Items Low BLL
Dams 0
Power tunnel (Gate Operation Only) 1
Diversion Tunnel (Gate Operation Only) 1
Spillway 0
Powerhouse (Except substructure) 1
Switchyard and substations 1
Transmission Lines 1
Permanent Camps 1
All other property 0
4.1.5 All Other Perils -Losses
Likely PML
0
30
30
0
30
30
15
25
0
High MPL
0
115
115
0
115
110
30
50
0
For the category of All Other Perils (AOPs) the MPL can again exceed the value of the
power plant super structure, turbines, generators, other equipment, switchyards,
substations and permanent camp. For the MPL an estimated 115 percent of the
replacement cost values would be a reasonable estimate. With respect to the dams,
power tunnels, steel penstocks, diversion tunnels, spillways, and other property, the
MPL was calculated as 33 percent of the aggregate values, since the major cause of a
total loss to these components is an earthquake, and earthquake damage is analyzed
in the Engineering Analysis Section of the report.
The PMLs for the dams, power tunnels, steel penstocks, diversion tunnels, spillways,
and other property are calculated as 15 percent of the replacement cost values. The
PMLs for the power plant super structure, turbines, generators, other equipment,
switchyards, substations and permanent camps are calculated as 30 percent of the
replacement cost values. Once again the estimates are conservative and predict the
most likely losses to be PML losses.
4-8
With respect to BLL, an estimated one percent of the values for all categories was
used. As previously stated, and as indicated in the exhibits of losses, most
hydroelectric losses are boiler and machinery types of losses, and not property losses.
These losses for all other perils are shown on Table 4-4.
Table 4-4
All Other Perils
Loss Assumption Summary -Percent
Items Low BLL Likely PML
Dam 1 15
Power Tunnel 1 15
Diversion Tunnel 1 15
Spillway 1 15
Powerhouse (Except Substructure) 1 30
Switchyard and substations 1 30
Transmission Line 1 30
Permanent Camp 1 30
All other property 1 15
High MPL
33
33
33
33
115
115
115
115
33
Exhibits 1 0 and 11 summarize the cost of the Fire and Lightning, and AOP losses for
the Bradley Lake project. Using the average number of occurrences, probabilities will
be developed. These probabilities which will be applied to the cost figures are
described in the following paragraphs.
4.1.6 Fire, Lightning and AOP Probability Analysis
The other perils discussed include two categories: Fire and Lightning, and All Other
Perils (AOP). As discussed earlier in this section, the average number of occurrences
were developed for these two categories based on the GADS data base. However, it
was assumed that there would be no lightning strikes on the Bradley Lake hydro
project. In order to convert the average number of occurrences into probability values,
a statistical approach was used via the Poisson distribution.
4-9
The Poisson distribution is useful in analyzing certain occurrences that have a small
chance of happening. The Poisson distribution has the form:
Poisson Probability =
N = Number of occurrences per year
M = Mean or average numbers of outages per unit year
e = a constant 2. 71828 .. .
! = Factorial (1 x2x3x4 ... xN)
The Poisson distribution assumes that the probability of an occurrence is the same
during each exposure. For this study, it is assumed an exposure is one year of the
study period. It is also assumed that the occurrences are independent of one another.
The average outage figures were used in the Poisson distribution formula to derive the
probabilities for one occurrence per year. Then, using these probabilities, the
expected losses were calculated by multiplying the probabilities by the estimated
damage cost. The probabilities derived from the Poisson distribution were multiplied
by 2 to account for the two units at the site. The probability of a single unit at Bradley
Lake being forced out of service due to fire and lightning is .0025, and for both units
the probability of an outage is twice the previous value or .005. The associated
probabilities for All Other Perils would be developed using the same process with one
exception: AOP includes different probabilities for each of the 19 events. Therefore,
the total probability of a single event occurring in the 30-year study is the sum of the 19
individual probabilities, which is 0.18.
The damage costs were not differentiated among perils, thus, damage costs for fire
were divided by 6 to represent the average for each portion of the project and then
divided by 2 to separate the fire and lightning risks. Thus, the damage costs were
divided by 12 to derive the repair/replacement costs taken from Exhibit 1 0. For AOP
the costs were divided by the number of perils (19) to develop an average damage
cost per peril.
The expected losses are reported on Exhibit 12. The expected loss results were
combined into the two categories: Fire and lightning, and AOP. The results were
computed for the total losses expected over the 30-year exposure period in terms of
1991 dollars and levelized dollars present worthed to 1991.
4-10
The levelized amounts were calculated by applying a constant to the total expected
loss in 1991 dollars. The constant was obtained by assuming that all of the losses that
would occur on a probabilistic basis over the 30-year period will occur in 1991. The
constant reflects the annual process of escalating the loss by 5.5 percent, cumulative
present worthing that escalated value at 8.5 percent and levelizing by multiplying by
the capital recovery factor. This calculation was performed in two steps. First, we
calculated the 1991 cumulative present worth of an annual stream of year-end
payments escalating at 5.5 percent. Second, we levelized that cumulative present
worth by multiplying by the capital recovery factor. These two calculations are as
follows:
1991 Cumulative Present Worth =
Capital Recover Factor =
where: E = 0.055, i = 0.085 and n = 30.
i(1 +i)n
(1+i)n -1
1990 CPW X CRF = 18.9599 X .09305 = 1.76422
= 18.9599
= .09305
A summary (Exhibit 12) lists the 1991 and levelized (in 1991 $) expected losses for
these fire, lightning, and all other perils. The total expected levelized loss based on
the probability analysis ranges from $78,000 to $4.74 million. This dollar figure
represents the expected loss due to the fire, lightning and all other perils over the
30-year exposure period.
4.2 Natural Perils
The natural perils cover earthquakes, floods, snow, wind, ice etc. The probabilities
developed for these perils are explained in Chapter 3 of this report. This probability
data is used in this section to quantify the losses associated with these perils.
4-11
4.2.1 Natural Peril Probability Analysis
The objective of the natural peril probability analysis is to determine the potential loss
expected over the exposure period. Probability is the chance that something will
happen, and is expressed as decimals between 0 and 1. A probability of 0 means that
an incident will not happen, while a probability of 1 means that the incident will
happen. A probability of 0.001 means that an event will occur once in 1 ,000 years and
0.1 will occur once in 10 years. For this study the range of probabilities extends from
0.00001 to 1.0. Probability analysis is applied in this study in the assessment of the
risk associated with several different categories of perils: earthquake, flood, and all
other natural perils. The replacement or repair costs previously presented in Exhibits
7, 8 and 9 are used for this analysis.
In order to calculate the expected losses, the probabilities are converted into
probabilities that represent a 30-year period and are multiplied by the replacement or
repair costs.
The 30-year expected losses in 1991 dollars are computed using this methodology for
the Bradley Lake project for each peril. Exhibits 13 through 15 show the total expected
loss expressed in 1991 dollars and on a levelized 1991 dollar basis for the
earthquake, flood and other perils.
4.3 Summary of Dollar Losses
The losses for all perils are summarized in Exhibit 16. Exhibit 17 is a listing of the
expected annual losses for the Bradley Lake Project for each year of the 30-year study
period. The expected annual dollar loss was calculated by taking the single year loss
numbers from Exhibit 16, escalating by 5.5 percent and dividing by 30 so that a single
year average loss number could be derived. However, it must be noted that this
expected loss figure may not be enough to cover some of the structures if a major
catastrophe did occur.
4.4 Insurance Observations
While these are accurate averages based upon statistics, empirical evidence and our
assumptions where necessary, it must be cautioned that the occurrence of any major
event could happen at any time. These statistics state that for the 28 hydroelectric
4-12
utilities for the years 1982-1986 inclusive, very few outages were caused by external
reasons. However, an occurrence could happen. Therefore, the insurance
underwriters justify their premiums by the possible loss rather than historical loss
experience.
Once again, these are only expected losses, which may differ significantly from actual
future losses. The ability to absorb losses is a function of the Energy Authority's
liquidity, net worth, desire to maintain electric rate stability, bonding requirements,
state requirements, and management's attitude towards risk.
4-13
5.0 CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusion
Based on the engineering analysis, construction data, firsthand knowledge of the
project and the statistical analyses, Stone & Webster has concluded that for the period
1991 through 2020 the total expected loss expressed in levelized 1991 dollars would
be $142,146, $2,094,272, and $6,166,654 under the low, most likely and high loss
scenarios, respectively. To determine the levelized loss that can be expected to occur
in each year of the study period, the total loss numbers are divided by 30 to obtain the
annual figures of $4,738, $69,809, and $205,555 for the three scenarios.
While these are accurate averages based upon statistics, empirical evidence and our
assumptions where necessary, it must be cautioned that the occurrence of any major
event could happen at any time. These statistics state that for the 28 hydroelectric
utilities for the years 1982-1986 inclusive, very few outages were caused by external
reasons. However, an occurrence could happen. Therefore, the insurance
underwriters justify their premiums by the possible loss rather than historical loss
experience.
5.2 Recommendation
The losses derived in this study are only expected losses, which may differ
significantly from actual future losses, thus the Energy Authority needs to formulate a
risk management program based on these expected loss estimates. The ability to
absorb losses is a function of the Energy Authority's liquidity, net worth, desire to
maintain electric rate stability, bonding requirements, state requirements, and
management's attitude towards risk. The Energy Authority should compare the total
amount of estimated insurance premiums for the 30-year period to the expected losses
to determine whether the economics justify a risk management program.
.I
I I
I I
I
I BRADLEY JUNCTION 11-* *
I I' HOMER ELECTRIC ASSOCIATION
I FRITZ CREEK-SOLDOTNA 115 KV
TRANSMISSION LINE * * *
I
I
:
I
I
REL" TIONSHIP OF VERTIC"L DATUMS
Bear Cove
I.ILLW
Datum
HT t 25.0
"'~•u• I.IHW 17.10
ProJect
Datum 13.83
Origin
(Auumod)
I.ISL 1.11
I.ILW f 1.81
I.ILLW 0.00
LT l e.o
~
Bear Cove
MSL
Datum
II.U
1.10
7 •••
4.01
o.oo
c .....
....
Brodloy
ProJo~t
Datum
U.37
4.?1
~.17
0.00
-4.01
r· •13.13
-tt.Q
REFINED TRANSMISSION
liNE ROUTE * * *
MIDDLE FORK
DIVERSION * • *
*CONSTRUCTED UNDER SITE PREPARATION CONTRACT
**PARTIALLY CONSTRUCTED UNDER SITE PREPARATION
CONSTRUCTED UNDER SEPARATE CONTRACT
. '
NUKA RIVER
DIVERSION * * *
1, ~).\
\~
" ( "f/ "· '\ \ 'r'(," r-~~ j
~
~I ..
'. ~ v -~·----' , · ' r ,
QP..l.,(Y...,._
10 0 :10 40 _60 ___ 80________!X)MIB
~
0 1 2 3 ------SCALE IN MILES
..... ,,
........ ,
c::>""' .... ~~ '•-,,,
'<"' ' .!~_.. '•,,
'90...... \\
"' :\
I I
I I
I ' ' ' ' \ \ '.\
\ ...... 1' ........ --......... :
\
\\
'•,
'· l ~ \ ~
\ ' .. ?: ,, ,---... -.... , ! \ ~
I \ ... _.. \.. ~
' . I I I \ ' ..... _ ... , \
I o ' \ \" \, ", ................... , .....
) ' \ .. , : \
I o ' ..... ,..... ....... ,., \
'.! ----;.--::::::::::-.:.:=< :.~··' ~\_)
f ' ,' ' . '' \ '"'' \ ' \ ... . ,~'-\.<:::··._
'o
GENERAL. PLAN
ADDENDUM No. 1
March 1, 1988
PLATE 1
EXHIBIT 1
N
Q
Q ,... .. --a:l
-----------------------------------------------------------,~
w
0
::i
.0001
----DBE
...,..__ __ usc
.001 .01 .1
LOG ANNUAL PROBABILITY
TOTAL DAMAGE LOSS IS REPRESENTED BY THE AREA UNDER THE
CURVE WHICH MAY BE APPROXIMATED BY THE SUM OF THE PRODUCTS
OF AVERAGE DAMAGE COST AND THE PROBABILITY INTERVAL FOR
EACHINTERVALCHOSEN
EARTHQUAKE DAMAGE VS ANNUAL PROBABILITY
AEA RISK ASSESSMENT ....__ ______________ EXHIBIT 2
1.0
0
0 • <'I
0
<(
CIVIL DESIGN CATEGORY UBC DESIGN
.....-----..--~------r------r-OPERATIONAL BASIS __ ....., MINOR
0.1 EARTHQUAKE (OBE) (UBC)
0.01 DESIGN BASIS MODERATE
w EARTHQUAKE (DBE) (UBC)
0 z
<(
Cl w w
0
X w
_J
<( ~ :::J z ~ z
<( ~ u. ;J-
0 0.001 ~ MAJOR
~ ~ (UBC)
::::i
en
<( en
0 a: a..
Cl w
1-
<(
:::2
1-en MAXIMUM w
0.0001 CREDIBLE
MAXIMUM (UBC)
CREDIBLE
EARTHQUAKE
(MCE)
0.00001 .____....L...---'-----1--..L..---'-----L--'---....L...---'----1
0 0.2 0.4 0.6 0.8 1.0
HORIZONTAL ACCLERATION (g's)
ANNUAL EXCEEDANCE PROBABILITIES
AEA RISK ASSESSMENT ..__ ____________ EXHIBIT 3
------------------------------------------------~0
~
1-
.....J
co
~
CL
w u z
~
~
X w
...J
<3::
:) z z
<3::
0.1()
I
\
~
"" ~ 0.01 ...........
..........
..........
...........
K
" ·-
""' "' -
"\
\
0.001 1\
\
\
\
\
\
\
\
\
0.0001 \
5 10 15 20 25 30 3 5 40
WATER LEVEL (FT. ABOVE BRADLEY LAKE PROJECT DATUM)
ANNUAL PROBABILITY OF EXCEEDENCE FOR
WATER LEVELS DUE TO TIDE AND TSUNAMI
'-(R-'EF.-ER_F._IG-UR_'E_14_8_RAD __ LE_Y_LAK._'E_T._SU-'NAM-I R-'EP-0-RT)_____________ EXH I 8 IT 4
0
0 ... ...
0
o(
------------------~----------------------------~~ 0
CD MAXIMUM WAVE ELEVATION :::-25.0'
FOR AN EVENT WITH AN ANNUAL
PROBABILITY OF 0.007.
@ MAXIMUM -WAVE ELEVATION .::-44. 2'
'"' ........
FOR THE OCCURRENCE OF THE MAX CREDIBLE
TSUNAMI AND THE MAXIMUM HISTORIC
HIGH TIDE SIMULTANEOUSLY. .
CROSS SECTION DETAILING ESTIMATED
TSUNAMI WAVE HEIGHTS
._ ______________ EXHIBIT 5
0
0 .,.
~
0
4:
NORTH AMERICAN ELECTRIC RELIABILITY COUNCIL PAGE Of OF 04
----------...COMI'!.OHEIH--SUMI'IAR-'t--RER.ORT--
-~4¥~~~~4-*~one~~-Uab•t•~---~--------HydPO-~.mil:.s only,--!:.11 sizes -j 992-1 S.i:i6
-----
--·--~COMPONEIH OUTAGES -------··---
-·---------------lO.fAL---NUMBER 0~ -UI'UL---'tEAI'tS--lS---2390--------------595 TOTAL UHITS
'
E-------~-----------------~-----~---------~-----------~~~~-_-~~_~=~-_~_~~=_----_--.,-~-.. -..,.----------_----_ -_---------_ --------------FULb---FORCED--<UNPL.ANNiii).)..-OUTA~ES--------------UNPLANNED--OERAT IHGS-----!:" . .ORCEO, NAINT, PLAIINEO & EllUl V DERAT I NGS
--~~·· .. ---~· ---------------~--------... ---------------··--·----,.-~-----:-.... ~..----~~"':'-~=~~~~'!!':"!::.~-~~~!'!""-~-. ·--:::~---:~~":":-'!"'"-!":'~-::::------':""------------
-AYG--NO AYG-HRS--------A\1~-0UR-------------···· A'v'G H(l AltG-EQIII-----AIIG .. EOJV AVG .. HO.. .AVG HRS AVG DUR
HRS PER
OUTAGE
·I CAUSE-OCC --PER PER-HRS -PER -·--CAUSE--OCC PER HRS. PER HRS ---PER CAUSE OCC-PER PER
-GOQ&--liiH T----¥P -UH-H-V-R-----\IUJAGE--------COOii--UN IT --¥R -UNlT -l'R---------.OUTAGE---COO£ --UNU--~R-------UHU .. 't'R
-------·--·--------~---------------------·
f---------.3600 OdlO' G-rh2---d0..-9~---···-~60u-------tl.OO -0.01---·--------3.91--3600------.0~0.3
------·36H----------Ih01---ll.05---3.81 -3620 0.00 ----0,80 174,52--3611-fLfll
1 a6 12 o~a o.~4-----t,.;J9--------3682 -----o, oo-·----0.4 ~---1-93-.J+-------l612 o. os
--------3619-------&.ot---~As----t-4--.22------4500-o.oo---0.19 ---~26.56 ---3619 o.oJ
~620---lh92----------&r40 24-,94--630---·--0.00-·----0.-tl 1.(>,21-----3620-----0.17.
' --·--3621---~. 00----0.-01--3,04------4740 0, 00 --0711------126,00 -3621 -0.01
' 3623 O.tl-0 O-rl.l~--a.-t~4------------4-750 --O,OC. ---0,-tJO-----2.6S----·-3623----0.00
3629---0.01----o--.-13 10.40 --4950 o.oo o.oo---0.64 3629--0.03-
' 631 0.-00-----·-lhOO---2,~3------4899 0.00------~-IH----4 . .21----:363-1-------..0..01--
-3632-----o.oo o.ot---tt.t>7-. 7002 o.oo ----o.uo -t-.60-----:3632 ---O.OO-
. 63+---~1 o,-o-e-------0.6-7 -.. --705{) O. 00 --0.64 -----SU ...:l-7-----310.34---O~..OJ
:!641 o.e o.-o-6-----8.29-----7052 o.oo 0.-13----315~25 ---3641-...o.o2
.... 6-42 e.oo ~s----24.-?o------109'3------o.co ----O.oJ-------44.38-----3642------o . .o2.
.-------36H--1h-62-----o.-n----39,06---7101-o.oo --2.17--57e,o1 ---3644 o.o3
---a6+9 o.oe o.eo------lhS3-----------7HO ----o.oo-------O~O-u.. ------o.-74-------lt.H -.o.oo
, . 365it----Odl-0--·--0,I:HJ----1-....-7-t-------.......;z.Ht---thllO -----~.IH--~~ ----J:!.-24-----3650-0.00---
. 65t------O.-OO-~r&O 5.-95 7Hil9-----'l-..-li0-------ur1-3----1,5JT68 --3651 0 • .00--
.-----------3652-----0.00 9-..---&0---h·H------1299 --0,00--------O.Ou --------0,63-3652-0,00
• -----3b53 o. 01 0.-97 ?.-38-· 9~1l0---·lh00------UT!f6------+"8. 70 3653 . -o. 02
!---------3659-----e,ot----o~G 6.94 ---9320----0.ot---· o.oJ.-----6.91 --·· J6S9 o.o1
36-i'O . 0-.--&it----0.2-4-----287ri21 ****-·----0,.(}0 -------OT Oil------· 0, 00.--------3661-0, 0 0
36?-t---o.&o-------·th-59--~94.-55--·----u• -o.oo o.oo u.OO-3670 o.oo
?2 O-rlH----·-Ih51l 79,-89------••------0,00--~ --CI.410---------0 • .00---.. -.3671 -0.00...
-J6?3----~.oo---th-13--Hl5.26------•"*** o.oo o.oo o.oo 3672 o.o1
~6i'-9---'----~-0dl3----3il-.31 _, ____ ...,,.. ... .....__ --o.oo. --------0,-00--------0.-00------367~---0. 00 -
36at----lh·Oo --o.ot-------6.01 ----••••----o,.oo -o.oo --o,oo 3679 o.oo-
::6132 0 , £1 &---~.-05 ----+t--&-, 16 --·--·-* *'**--0 . 0 0-----4)., 0 0---· ---0 . 0 0.-----36 S 0 --0. 0 IL
-------3683---o,oo-----o.oo· 1..11 ......... "' o.oo--~o.ou o.oo 3681 o.oo
3699 o.-eo o.oo-----·h-9+-----~-__.... ....... ,.. ___ o. oo 0-. ou..------oToo 3682 o. 01 --
... 819-~---o,ao--~--o.oe-----·-o.;ze-----**"'* o.oo o.oo .o.oo 3683 o.oo
v92t o.&&·-------O-.--&t-------t6-.5S **** 0.00 0,00------0.00 3689 0.00
--------'3823---o-.oo·-o.o2 41.93·· -......... o.uo o.oo---------o.oo 3813 u.oo
..,869 Od)O--------(h-02--5thl&----••* 0.00-----OrOO -0.00 3819-0.00
,-,899-----------0;00 (L02 6-.91---·--->~<<~<o~u~< 0.00 u.OO 0.00 3821 -0.00
395()-------o.-oo----o,oo----o.i-4 -••>~<• o.oo ·--u.oo o.oo----3823 o.oo
-450Q---1l.OO·-·-t.91 456c46---"'*"'* 0.00 o.oo 0.00 3841 o.ou
-45tt)---.o.ot-------Q,09:_tt.le--------·••••------o.eo o.-ou --o.oo 3861 o.oo--452&~'~9.:•()3-·-~33.41_ 12~R13-----•++>~<-o,oo ---0,00---0.00 3SG9 0.00
530 &;-OO----·---t-.6&-----4343,..:j7?---·---****-.. -0,00 ----0,00----0,00 3399 0.00
-------454o---0.01 ---();fi"--·--21.69 --------••*"' ~LOO-o,oo----~-0.00 -3950 0.01
~-~·-----~-~·---·-·--
.I.. -----------------~-·-
.o. 41
1..09
0.. I 5
l • 09
5. I 1
0.02
o. 03 -
0.22
o.u2
0.01
0.00
0.25
0.28
0.99
0-.04
--0 • .00
o.ul
0. 0 I
0. 15
0.07
0.00
0.24
0.60.
0.54
0. 13
0.03
0. I 0
0.04
0.64
0.05
0. 0 I
o.ou
0. u 0
0. 01
o.u2
0.00
o.uo
0.03
0.0;2
0.00
This data is for a five-year period 1982 through 1986 for 28 hydroelectric utilities having 595
gene.r:at~~g units _and representing 2396 unit y~ars o! information.
13.20
37.29
2.92
35.18
30.89
3.53
10.40
7.98
4.39
1 I . 6 7
. 0.67
13.69
14. 12
33.20
8.51
2. ul
4.19
4.03
7. 78.
5.93
5. ?6
191 .86
238.24
61.69
1 OS .26
37.31
48. 14
12.98
109.34
16.73
3. I 0
3.92
0.76
16.5S
41.83--
4.36
5.66
I 0.63
5.85
0.55 -urn
O>X
1.0 :::T CDfr _...;::::;:
om -.(::>.
NORTH AMERICAN ELECTRIC RELIABILITY COUNCIL PAGE 02 OF 04
___ .-~ CJJI'lf>llNEtll-.SJ.Il'IM&B 't .llEei!BL _,_
::>Ritl?,;22\i for R. C.arris 9 Stcm~t li. W.ebst~~.r. •... ___ _ I:I!.Ld~Q __ OJI\ i.tL. Pnly_,. 8 I LJti;u_~
. ' --------~--
-····-·--~-----··--·· ~-·------
------------COMeuHEH Lil.UT l'iGE:7l ... -------
_I£lTI:lL -~UMBER .. OLUNIL.'l'EflRS __ .IS .219li ....
-------------::---:-·-:--::-:·-··-:c:-c-::--=-:.--·------·--~----· ----~-----·---~~~ _TOTAL_l!!!.H~
'= =-= ~ ':':".~-~-~ ~~ ~= ~ = ~=::'!"-=:.'".:"':':..=-=-'::::.!""--.==-.::=: ~_:: = =-=-=-=---=-------------------------------------------------------------------------------------------UHPLaHt~Eo. I>E-asii'"HGs_~--~-=-=--__E.QECs!L M!UHr:.PbiM!'IE!L~.i'Q.!JJY_Q::~AT~HG~----------£ULL . .fORCED ! UNPLaNNED l .OUTAGES_
----.,,_=,"'~,.~~~""~~~==--~~~~~~~--=~~~=~~~~=---=--~~--~-~~~~~~-,_-~~-l~~~~~.::~~Z"E~i~----==-~~-~=~~a~G=N-f~--~~~_.=~Ri~~~~§g-i:ij.=~~=~=-
--CAUSE -OCC EER. _. _ . PER. _ _ _ HflS .f'ER.. ____ CAUSE__O.C.C..J:>ER __ J:IRS.fEfL_.J:i.RS. PER -.C.A!.l~E'_ __ Q.C.Lf.ER PER H.R~_j!ER __
. ~ COOL.UtUT YR ___ UHIL\'IL OUIA:GL. ___ COOL UHI.L':!R ___ ilfUT YR llUJ£\GE__ .CQ.QE_ __ !J!fJLY.!L._YtH.L~{!.? ____ OUlAGE _________ -,-
;:'"';."':-:'"'-:~--"'=---""!~-!':': --·~--=--~~~===------------------------------------~-~------------
. 4550 0.03. 3.2J ___ JO:L32. ____ ....!.!1!U __________ .lL.O.IL ........ .ILOQ ____ ~.JL.Jl!l ____ 3~2.'Z ___ Q.,_!!L__ 9,H __ .'~.-'-~!> _______ _
45Ss o. oL.. .o. o6. 9.ZJ _______ ~>t"'"'-------.o~on _____ JL.QJ) ____ o, _oo_ ____ ~5oo ____ o.oa ______ ;l_c_~~ ---~_g~_!_!~_g __________ _
---4560 0. 0 0 0. 02 6.Z8 ______ Hti -----JLOO -~ --~Jl, 0.0 ________ !)_._ QQ ___ 451.0 ___ _o~ l!~ ____ j), ;J~-__ gg_! ~~---....
4SZO -0 . .0.0 _ -----0 • .00 2. O~L ___ --.i>t<!l!!l! ____ .Jl._G(l___ JL .ll4L _______ JL Q.Jl __ !152L---~-47,~tl_--~~~! 99
4590 u~ oo... ___ o • .01. ____ £..55 _____ _j<_!l!-'f'l!__ ___ .o__._.oo___ o. O.!l _ o.oo _ -----"~;:s,Q _____ Q._dH ____ 5,1~L_.H.~-~ o6
----4600 ---o.oo ____ .il • .OI ____ :I.sa ____ __!l!li<!I!!L ___ o.oo. --~ o.o.o _____ . __ o.oo _______ !l::i<I:Jl. o,_Qi ___ · ____ Q._,~s _____ ?!~L ________ _
4t.01 .0.01---O • .il:l----3-03. _______ uu ... ___ 0..00. 11..011. 0., 00 !45::JO ____ J;!<JHL _________ .@._._t t __ _!05!_QI _____ _
--461)2 o.o1 o....oa u . ....99-----'•n•'-**·--..Jl-Oo ______ .o.oo _ o.oo .4555~ __ _o_._o2 _______ o..t_s ____ 1J_,.!i~-----
-46 03 0. 00-----0.03----------Z .• .BS .. ___ ___;j<!l!.!t!l!. ___ .o__. .OIL _____ J)L!IO j), 00 .4~6i_ _____ Q_,_l)2__ ___ Q_,_n ___ 2?~.--
-~-----461)9_ -o. 06 --.. 0 • .5.5.-------.....9.-23------>~<*'~'"'-----IL..D.O. _______ a. oo o. oo ____ 4SZO _______ lldlt_____ ____ _a__,__i~---~AL _________ _
-46 l 0 0. 0 0 0. 06 ---.3-Z-90 ____ 'I<·'I'H~---. 1). 0 0 ________ 0. 00. ll. Q(L .. ___ 4580 !l_,_ 0 0 ..... ___ -~'.0!) _____ ~_,__g~
4620 -----0. 01 ~------0. 04 .. 3.64------.......!!'.~>~<>~<--~--JL.OO ___ JI .• 00 ___ .JLJi!l ·---~521) ___ O. .• JlL O _ _,_Jll. 5'-_g~-----_____ _
4630 .. .0. 01 _ 0.05 .. _ 4.40 __ >I<U!i! ... _ 0. oo _____ ~J). 00 ~---------0• ilil_~---·.4600 ______ .!L.01 _ 9, ~HL ____ _l2!_gof __________ __
----465!L .(). 00. .,{J.. 01 _ ;L_gs__ _____ ____..,to.L ___ . .0~00 11...00 0 ,(I(L ____<!61.11 _____ 0, 02.. _______ 0.05 ______ 2_,_2_~---~
_____ 47 oo o. o4 _ o. z-;; 20.:16 __ ... t>t<u o. oo.. __ o. oo o. oo ____ :~t.o2__ _ ___ Jl. oz.___ o .. H ___ -~' ~~-------------__ _
.. ----4 710----0. 0 t.. 0.23----· .17. 4~L --~~--. >I<.Ut .O~JlO ___ .fi...Ji iL 1l0 ____ 46fll ___ ~_j)_,Qt_ _____ jl,__ll~-------.i_!.~~L ...
4Z20 O.OL O.OL 2 .. 13 __________ .H'i'!l< _____ 0.00 .0..0.0 .. 0.00 ____ .4609 Q,ll _ 2.Q~ _____ I?d>:L ______________ _
4730--.o. oo. 0.30. _,_~71. 22. ________ 11!>~<'~<.'~' _______ o, oo._~ ___ .IL IlL ____ O. 00. ___ 46 I 0 0. 00 ___________ !LJHL ___ 3~_,_!H
-4740 0.11 3.S5 35.22 ... **'*"'-O. •. J)JL ___ Jl,Q(L _____ l),0{L ___ 46.20 ___ !L02 ________ .J!._,_~L ___ 1J-'-!?_ ________ _
4750 ----0.06 0.7.3 -..... 12..45 -UtL ___ j),1)0 ____ OLJliL ___ jLQ0 ____ 46JQ ____ Q,05_~ __ !l,~i_ ______ U_!55 ______________ _
------48oo --o . .ot. 0.12 -~12.62.. *H"'-. o.oo ____ oLoo _____ ~JLOO _____ !164Q _ lLOO o.o3 13.21
481 0 ---~---ll. 02------0.64 __ J3. t ;i!-*>fllt ___ Q._I).Jl _______ _j) .oo ------~.il ... llll -----· .4650 ·--~-: o. fit===-~::: o:~_q6 ------~~gi~----
4$31) o.OO-----o • .oo __ Q,96. ~--uu -~--o.oo ______ o.oo 1.LOO __________ 47.00 ________ o..oa _______ td~Q ___ ~1,
4640 .0.00 0.11 ---32.57 -----***;~~ _Ji,OO 0.00 O.Oo _____ 47to. O.QJ ............ .O....JI ______ _,~'---"
4i50 o.oo-o.oo _ o.33 u*'P 1LOO .o.oo .a.oo. !!l72o ____ o.ot o.o7 _____ ~·7fl
4899 0.02 0.33 -----.!5.40 ____ uu .. --~-0.00 .0.00 ______ 0.00 .~730 _______ Q.OL 0,36 27'.~~
7000-0.00 0.43 .171.36 UH Q,l)(l 0.00 0.00 ..... ~740 Q,_J6_ :4.~-J 26,Q!
-7001 --0.01 0.19---.t6~74 ****·-0.00 .... o.oo. 0.00-----~-4750 ___ 0.16 ....... 4.13 26,34
7.00:2 0.0:2 6.69 341.24 *'~'** 0.00 0.00 o.oo ___ _41300 .0.03 1 •. 01 J~.J!
-----7003 o.o3 o.as __ 2a.s3 .. H*'~> o.oo~ o.oo o.oo __ .4810 -~----··0.06~------l.7L. _27~::1::1
.. -~---7004 o.oo 0.04 -18.45 H'l'~ 0.00 0.00 0.00 __ .4830 Jl.04 2S.Q7 ?55,7§ --..
7005 o.oo o.oo .. o.so -**** o.oo o.oo o.oo ... 4840.. 0.27 41.31 t55 •. H ____________ _
7007 .().OJ 1. 15 37.67 **** 0. 00 0. 00 IL 00 .41350 !L 00 o. 00 --.. Q.dL .. ·--------~~
7 o oe --o. o 1 o. 26 ~ --:21.29 ___ .. ........ o. o o o .oo o. uo _____ .4sss _ IL oa -------" .2:L~ 2i ,z:z._ ____ __
70to o.oo o.oa J.os .. u'~'• o.oo o.oo o.oo 7ooo 1LOL 1.41 __ ue.c::i~ __
7011 0.00 1.10 527r06 **** 0.00 0.00 0.00. __ ---.7001. 0 .• 02. 0.22 12,2f!
7012 0.00 0.03 36.30 uu 0.00 0.00 O.QQ.. _____ 7002 0.03 7.62 270,E!3 ..
1020 o.oo o.36 865.08--.. ..,.,. o.OO--~--.o.oo o.oo ____ zooJ __ .o.o6 L82 2i.~L
-7030 0.00 1.99 530.6-J. UJII;a. ---.0.00. 0.00 0.00 ________ ]004 0.01 0.11 13.~3'
7o4o o.oo ---o.oJ --754.39 -------••••--...o . .oo o.oo ---------o. •. oo-----7oo5-----o.oo. ______ .o,o& ____ 16.53_
-em
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NORTH AMERICAN ELECTRIC RELIABILITY COUNCIL
.-COMPOUEIU-SUMMAR'l.-REMRI:-
PAGE 03 OF 04
~-~9-~~~aPri• e ,ltt;one--t.~ebSU#'--•-~-------~-------·-------Hyd,..o-unit.s -or-~ly, All si:::es 1982-19&6
!------------------------·--
-COMPONENT OUTAGES
---· -TOTAL-NUHBER 05 UHIT YE~RS IS--23~6 595 TOTAL UIH TS
~·--~-·--·----------------------------------"""'-----..., ---. ..-----------.-ro""" ~----.-1':'1'.'!!!!! -.""'! --""'~~--~--~ ~-~ --:--. ""'!------~ ----~----------~-------------
~UU.-F-()RCED~UNPLANNEO-)--~UTACES ------------UNPLANNED OERAT WCS--------FORCED, I'IAHH, PLANNED & EQU IV OERATIHGS
1-----------AVG NO---~VG HRS-AIJG--OUR---------AVG NO -SWC EQIV AVG EQIV----AVG HO AVG HRS
------------{;AUSE--oCC PER-----PER --HRG---PER --CAUSE OCC PER----HRS PE-A -HRS PER -CAUSE OCC PER PER
.r=-----~~~~~~:~:=:;:~:-~_-==::~:-~-~~-:~:~;~==-=:;~= :~~~:;~-~------~;~~;·· --~~:::;;-~~~~:;~;; ..
i'OSt---9.01 0.14----17,74---**** 0.00-------0.00 -0.00 7008 0.02 0.45
~o52----(h93----o.-7e----2-7~J--------·-****-----O.oo-----1}~-0I}...---O.--Oo--------70to o. 03 -.. --. a.33
· .. 099·---o-.o7---··-4-.-t5----6Q,32---------•*** o.oo o.oO--------o.oo 7011 o.oo 1.97
1 ,·Hl8---4}r09-----9--r-&3 ~ •-----0,00---~-0.00-----0~00 7012 --0.00 0.55 ..
: -------~1 Ot---· 9dl9----0.-t9---232-.-4S---.. ---****-· ---0, 00 ------0,00--------0.00 7020-0. 00 0. 36
-HIO lh-H---~.-67 -4-.:1-J---***------0.-00 ---OAIQ-----0.-00 7030 ---0.01-;0!.32
: -t-t-·-G*OG---9 Ot--~~--·-?l-30---------~*••-----· 0.00 ·010B--0,00 7040 0.02 7.82
129 (h-9-1 9.05 ---7.24 ·-·----0.00---th-0~------0.-00-----7050-------0.-22----__ £.,99--
;f-----~-7-tU-~--9-dH----lh-+-9--_--19.-42-----**** ---0.00 ---0.00--------0.00 7051 0~01-----0.16
-, -1?3 &-rll& o. Ot---"----a-.----t-3-------****---o.oo.-------O~.oo ~~ oo-------7-052-----0-.--06---·-t.ao
: ~H~4------0·d)9----19c30~67r04-------****-O, 00----0,0-0----·-O, 00 ----7099-----0.5~--32.80.
• 1-3-a o.-u---9.--t-o---H~-7-1----•••,..____----o, oo----0~-0~---0.00-----7-1-00-----o.oz ----o.s4
-------i"·t-40 o-.t)2·-----9,-t?-------'7-,46--------"**** --o.oo -0..00-----0.00-7101 0.11 -6.71
I ~ ,. , e .--o2 a -.-1-1"----• ~h6 o-----*** -------(). o o -----o .-0 O-----~-o.-o o ------71 02--------o . .o o --o. o a
' , ---i"H2 0.-9t------9,-0o4-··----2·r96------****-0,-00 --Or00----0.-00-7110 ---0.33.-5.45
-:r+so o.-oe o.t7 t&a-.-16-------•••-------.o.oo-----o.-oo------O.oo 7111-o.o3 t.Js __
, ·166---0-dlO 0.-91---------18,--73------->1<***-0.00 0-TOO---0,00 7120 0.03 1.12
; i't62 0.-ilO 0.9-1 -4.-S~-u••----lhiHi---------0,011-----0.00------7121 Or03 1.01
, --?t7e---Od1o o-.--&o 2.-22------~••••---o • .oo-o.oo---o.oo 7122 o.oo o.o;:
, i't--60 9,91 9-.---92----4-.-85 *'**---·Or-00--0,00------0.00------7123 0.01--0.24
l-------7tEH---e.oe------o.oo------h09---------••••----o.oo ---o.oo o.oo -7124 o.o6 24.91
· ~ ·~&----o--M~-t------o-.-oo ~o ·-----.o . .oo----4-.--00--.. o,OO----'liJO .. o.oo o.l3
rt99-----e.o&---o.sa --22.39 •••------o.oo o.oo o.oo 7140 o.o4 o.56
-1'2-&& o.ot----9.·21 25-.-99 **---~-.oo----O.oo ------o.oO-----714t ---o.o3--o.24
-2ot-----o,-oo------o.as --6L91--------.... ••• ---o.oo o.oo o.oo 7142 o.oa o.o4
' I& o,ee 9,oJ-----2M7-2--------'~~-***--·---tkOO----·---4>~-0C-----o.oo. --7150 o.oa o.23
.-----i'22o---o.oo-~-t-.-2o ?!?.64-------••u---o.oo ---o.oo o.oo 7160 o.oo o.us
· --i'£99 e.o-+--~lih-5o---£-4T3s-----.,.••----O.oo---0,00------0.oo 7161 o.oo o.ot
'-------900&-----9, 90 ------9, 02---9-rJS--· ---**** --'--0, 00 ()TOO ··--0. 00 7162 0, 00 0. 33
I 902&--e.02-------o.e-+ t.7s-----**** ------O.oo .. -o,oO-------o.oo 7170 o.o5 o.s1
·--'!1036-------o,oo o,·t4------s7-;aa------•••• o.oo --o.oo------o.oo---71Bo o.o5 1.53
·-----90-4& o.oo----o,-ot--------4.-77-----•••----~-o.oo--------o,oo-------o.oo-71~1 ---o.oa. o.04
: --9135 0.-33 -29.31 139.33 ----..,..,...,. ____ 0.00 ---OAlO----0.00 7190 0.01 3.75
, ----930& th22--·--thee----J.97------... ••• o.oo----o.oo-------0-.oo 7199 o.o5 -1.44
I --93to o.oo------o.oo-----0,45 ----__ .....,..., o.oo o.oo -----o.oo 7200 o.o6 25.85
.,J2:o----o-.-o3 tLJe-----t2.6B----·--••••,--o.oo -o.oo------o.oo 7201 -0,14 36.32
. ..6-96----o,oo -----o.oo----·o.9t---•••• o.oo o.oo o.oo 7210 ·o.oo o.o6
, ,no----a-.-oo----&.oe-----o.2J-----•••• ----o.oo------o.oo-----o.oo 1220 --o.oo. 4.81
.-9oo----e,o3-----o.-o6----t -dil2 --=---------+••• o. oo o, oo o. oo 7299 o. 20 e .40
J.. ------------------------·---·-------
A\IG OUR
HRS PER
.OUTAGE
39.49
22.84
281 . 05
430.04
330.44
865.08
.370.12
435.51
31 '89
18.32
32.69
57.62
29. a·?
61. 3B
I .23
16.64
43.27
34.35
39.50
19.66
35.91
426.30
45. 06
13.26
9. 13
2.84
31 .89
15.74
25.26
79.43
14.74
29.65
4.47
272.29
27. 13
439.33
262. II
30.57
I 047.60
41. 17
-om
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HORTH AMERICAN ELECTRIC RELIABILITY COUNCIL f'AGE 04 OF' 04
-r------·-----· -~--~ --·-----·-·-·-J:.QJ'!PJ)!H::!'!L ~JJ~tlf!R'LBEE'..QRL .... _ _ __ ____ _ __
~iz~s _1992-1986
__ ---.COHPOHEHT OUTAGES ..
----·-·--____ TQTAL __ HUMBER .OF __ JJHJI .. '!'I':A~~-~~-$~1~---~9? _TO!AL UH~ t~
w:. ::~.-::_=!':'!-'::!':...:::~=·==~~~~=.::=~=-:::::._::::-::-::-:-~=..."':" '"'::-::=--,..:-_;:=.==_:::::~-------------~-':'--:: "':"'-::.=----_-.':""-------------------------------------------
--__ £ULL_EJlRCE.IL (UHPLAHHEIH .. OUTaGES UNPLMiH!"I.) QER(HJN4~-_fyRCEO, MAIIH, PLANt-lED li. (;:QUIV DERAT IHGS
------~~.:--: "':""".::!!::.::::' ==--:.. -::.....::-=--=.':""~"':.~:::"": =:--=-= -_-:_-::.~ ::=.::::..=..=::..=-------==--= '::_:'"' ~.::-.::=.:: :"'.:-.::.::-:.:::---------"':.":.::': :-_-:::_.::~---: . .
E ----~CL.HO ___ A'l/.G .. HRS _ _ll.IJjLfWR ________________ AYG NO .... JWG. E!HIL __ IWG EQl\l____ -~----A.YG_ NO AVG HRS
; -CA1JSE._OCC. .. e.EIL. ...... PE.IL __ HR~LPE1L .. ---CAUSE ... OC_ C _ P_ER HR_ S _P_E_R .... HR.S fElL. _ ~-fiUS.E . 0(:(: _pER PER
• _ _c.QO.E.__llli.l.I......YR _ _LJ.I:UT VR OUIA.GE._ ___ __c_o_[)_E_UI:IlLYJL_ li~HLYS JJUJfjG~ GOP~ ___ UNIT YR __ l! .. !T '(R
------~=:-:===-----"~=--==:-:= -----=~-=.:::._::-.....::-=----~·-· -=~~-"':==----=-::oo.=..::.--::::. --------
t----~-~910 JL.OJ O....OJ~. o.~.IL~.--......!!'>1<!'! ___ 1),(10_ 0.00 .. ····--·Q,Q!L_ ___ 'lQOQ_ 0,00 0.(12
--------29.20-_.0.01 11~02_~_3.00 ... --··--...!t!!U ... -.-.0 ... 00 Jl.OO O,QO ......... 'HI20 Q,O;J 0.11
.:19~9___,__o_~.no .o~.o.o ____ Jl~tb__ ___ ..... .:~<>t_. __ a.. . .oo _____ o.Jl!L _____ ~_o.oo ~.203Q__ Q.Qo o.!4
' J<>l!1l<L--_..a~oo JL..no. ______ o.oo __ ~ __ _!I!_U'!' _______ o.oo ______ .o.oo ... _. ___ .. JLoo _ ---~!NO Q.Qt 9.12
' ,..,..J!!.!J!.__Q,.OIL O~DO. ll. •. oo_ **>f!>II _______ Q,QO ______ Q.,O.!L ____ Q,JHl .. _ i!P!:?. 1!,~!) _____ .. 47~11
' _JioJI<.>~<..____.o • ..ao.._ ____ o .. oo_. ___ o.Jlo _______ ,...n>~< ... o.oo........ o.oo .... JLOo. ____ :HOO o.Jo ! .~o
' ***L..-.-___j}_.._jjiL..... ____ O~OO.. ....Jl.Q. ___ . ___ '!'!! . .>!."' ____ CL OL ____ . _Q,QQ --·-·--·.0 ,_SH!. __ ···--· _ 'lJI 0 _ .9. 0-L __ .. 0. 0~
' **!liJIL__ ___ A~0.0.----0.00---Q,QQ ____ uu_ _ 0.00 ___ ._ O.OIL._. ___ JLJlO. __ 9320 !).11 --16.77
1 "'*..u__ -ll~llO _____ .n~o.o o~oo _____ .'!'~t<>t_ ____ 0. !lO _______ OJ ..OIL ____ 0 ,.OIL _____ 9!590 _o. 0 L . Q.,J9
' ·•**" ---.O.ilO o •. OO ---·-· 0-00 _ . --··--·~.!foot.t.. 0. DO _._Jl.OQ. ____ .lL. 00 ....... _ __.2l$'Z6. ~, ()0 0. 03 ~ uu a..o.o_____.a •. oD , o~oo _____ .!!<tH .. ___ .o. o!L ____ o Loo .. ·-·-·-··---o.LJHL noo ____ .J! ,J!Q.. o. oo
' ,..,..,.. ... ___ JLOD---.o~oo. __ .o.oo __________ uu o,.lHl o.oo~---o.oo ~no o.o6_~-Q.63
' ot<JU<« 0, .04--~.0. .. 0Q. ___ Il •. OtL-----_u'f"t' _____ O.Q!l _____ Q, 00 Jl.O!L_ ~90Q ___ JLO:J __ Q, 06
~ !l!!l!tUL_ ..• .il ~il o ______ Q •. .Oo. ___ Q.. o o_ _______ uu ·---o. o o _o. o o 0. 00......... 991 0 o. OJ o. o t
' *.!1!.!1!* 0~.00 O..QQ _____ lLQL __ ......3!'!f!!!!.!I! ___ LOO ......... !LfUl ______ JLOO __ ._.9920 __ lLOL_ l!t02
' ,.,....__. __ Jl~.04-----4.0Q ___ n.oo.._ _____ u.!l!*-·--.tl. OQ _______ ~O• Oll _____ J),OO. _______ 99'2'2 .. _.___ Q, 01 0. II
--~ --· +-----"' -----------
·--·--~---~--·-··--·-·---
------· ------------
+-----------------------------------·
+------------·---
AVG DIJR
HRS PER
OUTAGE
9.35
4. 14
57.BB
II. 77
125.28
4.92
0.82
152. 19
22.85
37.37
I, 47
I 9. 41
1 . 78
0' 40
3.uo
12.73
-urn ro><
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE-EARTHQUAKE PERIL
REPAIR OR TIME PLANT
ANNUAL REPLACEMENT COST (1991$l OUT OF SERVICE
STRUCTURE MAGNITUDE PROBABILITY LON LIKELY HIGH LOW LIKELY HIGH
DAM .75g 0.000400 $225,000 $2,900,000 $3,100,000 0 0 0
.35g 0.007000 $0 $0 $225,000 0 0 0
.10g 0.100000 $0 $0 $0 0 0 0
SPILLWAY .75g 0.000400 $0 $50,000 $500,000 0 0 0
NUKA DIVERSION .75g 0.000400 $10,000 $200,000 $200,000 0 0 0
MIDDLE FORK DIVERSION .75g 0.000400 $0 $50,000 $200,000 0 0 0
BARGE DOCK .75g 0.000400 $10,000 $30,000 $440,000 0 0 0
.35g 0.007000 $0 10,000 $30,000 0 0 0
PERMANENT CAMP .75g 0.000400 $20,000 $100,000 $250,000 0 0 0
.35g 0.007000 $0 $0 $20,000 0 0 0
LANDING STRIP/LOWER ROADS .75g 0.000400 $10,000 $20,000 $40,000 0 0 0
.35g 0.007000 $0 $10,000 $20,000 0 0 0
OUTLET WORKS (DIVERSION) .75g 0.000400 $0 $100,000 $580,000 0 0 0
.35g 0.007000 $0 $0 $100,000 0 0 0
POWER INTAKE .75g 0.000400 $0 $5,000 $320,000 0 0 2MO
.35g 0.007000 $0 $0 $5,000 0 0 0
POWER TUNNEL .75g 0.000400 $0 $50,000 $1,150,000 1 WK 2MO 6MO
PENSTOCK .75g 0.000400 $20,000 20,000 $330,000 1 WK 2MO 4MO
POWERHOUSE & TAILRACE .75g 0.000400 $100,000 $320,000 $640,000 0 0 0
.35g 0.007000 $0 $0 $100,000 0 0 0
MACHINERY & EQUIPMENT .75g 0.000400 $0 $75,000 $175,000 1 WK 3WK 2MO
MACHINERY .35g 0.007000 $0 $0 $25,000 0 0 1 WK
ELECTRICAL-PH .75g 0.000400 $80,000 $100,000 $200,000 1 WK 2WK 4WK
.35g 0.007000 $1,000 $3,000 $5,000 1 DY 2 DY 3DY
.10g 0.100000 $0 $0 $1,000 0 0 1 DY
SUBSTATION EQUIPMENT .75g 0.000400 $5,000 $15,000 $40,000 1 WK 2WK 4WK
.35g 0.007000 $0 $0 $0 0 0 0
SCADA REMOTES .75g 0.000400 $2,000 $3,000 $6,000 0 0 0
.35g 0.007000 $1,000 $2,000 $3,000 0 0 0
TRANSMISSION LINE .75g 0.000400 $240,000 $1,200,000 $3,000,000 4WK 6WK 8WK ttl
.35g 0.007000 $60,000 $120,000 $240,000 1 WK 3WK 4WK ~
::T
BRADLEY JUNCTION .75g 0.000400 $5,000 $15,000 $70,000 2DY 5 DY 6WK 1-'· cr
1-'·
rt
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE-FLOOD PERIL
REPAIR OR TIME PLANT
ANNUAL REPLACEMENT COST {1991$} OUT OF SERVICE
STRUCTURE MAGNITUDE PROBABILITY LOW LIKELY HIGH LOW LIKELY HIGH
POWERHOUSE EL44 0.000010 $40,000 $90,000 $100,000 0 0 0
EL 2S 0.007000 $0 $20,000 $30,000 0 0 0
MACHINERY & EQUIPMENT EL44 0.000010 $4S,OOO $70,000 $13S,OOO 3DY SOY 10DY
MACHINERY EL2S 0.007000 $0 $20,000 4SOOO 0 1 DY SOY
ELECTRICAL -PH EL44 0.000010 $240,000 360,000 S50,000 4WK 6WK 6WK
EL25 0.007000 $0 $240,000 360,000 0 4WK 6WK
SUBSTATION EQUIPMENT EL44 0.000010 $120,000 750,000 1,500,000 2WK 6WK 6MO
EL25 0.007000 $0 $120,000 $400,000 0 2WK 6WK
SCAD A EL44 0.000010 $60,000 $60,000 $60,000 0 0 0
EL25 0.007000 $2,000 $5,000 $60,000 0 0 0
BARGE DOCK EL44 0.000010 $300,000 $800,000 $2,000,000 0 0 0
EL25 0.007000 $0 $200,000 $500,000 0 0 0
PERMANENT CAMP EL44 0.000010 $300,000 $700,000 $2,500,000 0 0 0
LANDING STRIP & LOWER EL44 0.000010 $10,000 $1,800,000 $3,000,000 0 0 0
ACCESS ROAD EL 25 0.007000 $1,000 $2,000 $6,000 0 0 0
TRANSMISSION LINE EL44 0.000010 $0 $0 1S,OOO 0 0 4DY tx:l
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE-OTHER NATURAL PERILS
REPAIR OR TIME PLANT
ANNUAL REPLACEMENT COST {1991$} OUT OF SERVICE
STRUCTURE MAGNITUDE PROBABILITY TYPE OF DAMAGE LOW LIKELY HIGH LOW LIKELY HIGH
DAM-NORMAL OPERATING 0.00002 Dam Break $20,000,000 $25,000,000 $30,000,000 0 0 0
OUTLET WORKS (DIVERSION) 0.00010 Rockfall $0 $0 $70,000 0 0 0
POWER INTAKE 0.00010 Rockfall $0 $0 $175,000 0 0 2MO
TRANSMISSION LINE 0.00100 Landslide $0 $50,000 $100,000 0 1 WK 1 WK
BARGE DOCK 0.00010 Slope Instability $0 $0 $20,000
TRANSMISSION LINE 0.02500 Lightning $0 $10,000 $15,000 0 0 0
BRADLEY JUNCTION 0.02500 Lightning $0 $15,000 $30,000 0 3DY 8DY
POWERHOUSE 120#/SF 0.00200 Snow Load $0 $14,000 $150,000 0 0 0
85#/SF 0.01000 Snow Load $0 $0 $14,000 0 0 0
TRANSMISSION LINE See Table 3-9 0.01000 Snoww/Wind $0 $30,000 $60,000 0 3DY 5DY
POWERHOUSE 150 MPH 0.00200 Wind $30,000 $420,000 $1,500,000 0 0 0
100 MPH 0.02000 Wind $0 $0 $30,000 0 0 0
TRANSMISSION LINE 150 MPH 0.00200 Wind $0 $125,000 $250,000 0 5DY 8DY
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
FIRE AND LIGHTNING-BRADLEY LAKE
(1991 $)
REPLACEMENT FIRE AND LIGHTNING LOSSES
COST LOSS MULTIPLIER {%}
STRUCTURE VALUES LOW LIKELY
DAM $12,600,000 0 0
POWER TUNNEL $2,240,000 1 30
(Gate Operation Only)
DIVERSION TUNNEL $2,380,000 1 30
(Gate Operation Only)
SPILLWAY $6,510,000 0 0
POWERHOUSE $41 ,300,000 1 30
(Except Substation)
SUBSTATION/SWITCHYARD $8,540,000 1 30
TRANSMISSION LINE $24,01 0,000 1 15
PERMANENT CAMP $5,110,000 1 25
OTHER PROPERTY (1) $34,300,000 0 0
TOTAL $136,990,000
(1) Includes the following items: Barge Dock, Middle Fork!Nuka, Diversions,
Roads/Airstrips. and miscellaneous property.
BLL PML
HIGH {LOW} (LIKELY}
0 $0 $0
115 $22,400 $672,000
115 $23,800 $714,000
0 $0 $0
115 $413,000 $12,390,000
110 $85,400 $2,562,000
30 $240,100 $3,601,500
50 $51,100 $1,277,500
0 $0 $0
$835,800 $21,217,000
MPL
(HIGH) -··--····-
$0
$2,576,000
$2,737,000
$0
$47,495,000
$9,394,000
$7,203,000
$2,555,000
$0
$71,960,000
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
ALL OTHER PERILS-BRADLEY LAKE
(1991 $}
REPLACEMENT ALL OTHER PERILS 'AOP) LOSSES
COST LOSS MULTIPLIER (%}
STRUCTURE VALUES LOW LIKELY
DAM $12,600,000 1 15
POWER TUNNEL $90,510,000 1 15
DIVERSION TUNNEL $9,940,000 1 1 5
SPILLWAY $6,510,000 1 15
POWERHOUSE $41,300,000 1 30
(Except substructure)
SUBSTATION/SWITCHYARD $8,540,000 1 30
TRANSMISSION LINE $24,010,000 1 30
PERMANENT CAMP $5,110,000 1 30
OTHER PROPERTY (1) $34,300,000 1 1 5
TOTAL $232,820,000
(1) Includes the following items: Barge Dock, Middle Fork!Nuka, Diversions,
Roads/Airstrips. and miscellaneous property.
BLL PML
HIGH (LOW} (LIKELY}
33 $126,000 $1,890,000
33 $905,100 $13,576,500
33 $99.400 $1,491,000
33 $65,100 $976,500
11 5 $413,000 $12,390,000
115 $85,400 $2,562,000
11 5 $240,100 $7,203,000
115 $51,100 $1,533,000
33 $343,000 $5,145,000
$2,328,200 $46,767,000
MPL
(HIGH)
$4,158,000
$29,868,300
$3,280,200
$2,148,300
$47,495,000
$9,821,000
$27,611,500
$5,876,500
$11,319,000
$141,sn,soo
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BRADLEY LAKE
FIRE & LIGHTNING
AOP
TOTAL
Note (1)
ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
FIRE, LIGHTNING AND ALL OTHER PERILS
REPAIR OR REPLACEMENT COST (1991$)(1)
LOW LIKELY HIGH
$69,650 $1,768,083 $5,996,667
$122,537 $2,461,421 $7,451,463
TOTAL EXPECTED LOSS (1991$)
LOW LIKELY HIGH
$347
$43,715
$44,063
$8,818 $29,908
$878,121 $2,658,336
$886,939 $2,688,245
Repair or replacement costs were obtained by dividing the Fire & Lightning losses,
as shown in Exhibit 10, by 12 and the AOP total losses, as shown on Exhibit 11, by 19.
TOTAL EXPECTED LOSS (LEVELIZED 1991$)
LOW LIKELY HIGH
$613 $15,558
$77,124 $1,549,207
$77' 737 $1,564,765
$52,765
$4,689,916
$4,742,682
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ALASKA POWER AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE -EARTHQUAKE PERIL
REPAIR OR TOTAL
ANNUAL REPLACEMENT COST {1991$~ EXPECTED LOSS (1991 $)
STRUCTURE MAGNITUDE PROBABILITY LOW LIKELY HIGH LOW LIKELY HIGH
DAM .75g 0.000400 $225,000 $2,900,000 $3,100,000 $2,700 $34,600 $37,200
.35g 0.007000 $0 $0 $225,000 $0 $0 $47,250
.10g 0.100000 $0 $0 $0 $0 $0 $0
SPilLWAY .75g 0.000400 $0 $50,000 $500,000 $0 $600 $6,000
NUKA DIVERSION .75g 0.000400 $10,000 $200,000 $200,000 $120 $2,400 $2,400
MIDDLE FORK DIVERSION .75g 0.000400 $0 $50,000 $200,000 $0 $600 $2,400
BARGE DOCK .75g 0.000400 $10,000 $30,000 $440,000 $120 $360 $5,280
.35g 0.007000 $0 10,000 $30,000 $0 $2,100 $6,300
PERMANENT CAMP .75g 0.000400 $20,000 $100,000 $250,000 $240 $1,200 $3,000
.35g 0.007000 $0 $0 $20,000 $0 $0 $4,200
LANDING STRIP/LOWER ROAm .75g 0.000400 $10,000 $20,000 $40,000 $120 $240 $460
.35g 0.007000 $0 $10,000 $20,000 $0 $2,100 $4,200
OUTLET WORKS (DIVERSION) .75g 0.000400 $0 $100,000 $560,000 $0 $1,200 $6,960
.35g 0.007000 $0 $0 $100,000 $0 $0 $21,000
POWER INTAKE .75g 0.000400 $0 $5,000 $320,000 $0 $60 $3,840
.35g 0.007000 $0 $0 $5,000 $0 $0 $1,050
POWER TUNNEL .75g 0.000400 $0 $50,000 $1,150,000 $0 $600 $13,600
PENSTOCK .75g 0.000400 $20,000 20,000 $330,000 $240 $240 $3,960
POWERHOUSE&TALRACE .75g 0.000400 $100,000 $320,000 $640,000 $1,200 $3,840 $7,680
.35g 0.007000 $0 $0 $100,000 $0 $0 $21,000
MACHINERY & EQUIPMENT .75g 0.000400 $0 $75,000 $175,000 $0 $900 $2,100
MACHINERY .35g 0.007000 $0 $0 $25,000 $0 $0 $5,250
ElECTRICAL -PH .75g 0.000400 $60,000 $100,000 $200,000 $960 $1,200 $2,400
.35g 0.007000 $1,000 $3,000 $5,000 $210 $630 $1,050
.10g 0.100000 $0 $0 $1,000 $0 $0 $3,000
SUBSTATION EQUIPMENT .75g 0.000400 $5,000 $15,000 $40,000 $60 $160 $460
.35g 0.007000 $0 $0 $0 $0 $0 $0
SCADA REMOTES .75g 0.000400 $2,000 $3,000 $6,000 $24 $36 $72
.35g 0.007000 $1,000 $2,000 $3,000 $210 $420 $630
TRANSMISSION LINE .75g 0.000400 $240,000 $1,200,000 $3,000,000 $2,860 $14,400 $36,000
.35g 0.007000 $60,000 $120,000 $240,000 $12,600 $25,200 $50,400
BRADLEY JUNCTION .75g 0.000400 $5,000 $15,000 $70,000 $60 $160 $840
TOTAL EXPECTED LOSS (1991$) $21,744 $93,486 $300,222
TOTAL EXPECTED LOSS
(LEVELIZED 1991$!
LOW LIKELY -HIGH
$4,763 $61,395 $65,629
$0 $0 $83,360
$0 $0 $0
$0 $1,059 $10,585
$212 $4,234 $4,234
$0 $1,059 $4,234
$212 $635 $9,315
$0 $3,705 $11,115
$423 $2.117 $5,293
$0 $0 $7,410
$212 $423 $847
$0 $3,705 $7,410
$0 $2.117 $12,279
$0 $0 $37,049
$0 $106 $6,775
$0 $0 $1,852
$0 $1,059 $24,346
$423 $423 $6,986
$2,117 $6,775 $13,549
$0 $0 $37,049
$0 $1,588 $3,705
$0 $0 $9,262
$1,694 $2.117 $4,234
$370 $1,111 $1,852
$0 $0 $5,293
$106 $318 $847
$0 $0 $0
$42 $64 $127
$370 $741 $1,111
$5,081 $25,405 $63,512
$22,229 $44,459 $88,917
$106 $318 $1,482
$38,361 $164,931 $529,661
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE-FLOOD PERILS
REPAIR OR TOTAL
ANNUAL REPLACEMENT COST (1991$} EXPECTED LOSS (1991$}
STRUCTURE MAGNITUDE PROBABILITY LOW LIKELY HIGH LOW LIKELY HIGH
POWERHOUSE EL44 0.000010 $40,000 $90,000 $100,000 $12 $27 $30
EL25 0.007000 $0 $20,000 $30,000 $0 $4,200 $6,300
MACHINERY & EQUIPMENT EL44 0.000010 $45,000 $70,000 $135,000 $14 $21 $41
MACHINERY EL25 0.007000 $0 $20,000 $45,000 $0 $4,200 $9,450
ELECTRICAL -PH EL44 0.000010 $240,000 $360,000 $550,000 $72 $108 $165
EL25 0.007000 $0 $240,000 $360,000 $0 $50,400 $75,600
SUBSTATION EQUIPMENT EL44 0.000010 $120,000 $750,000 $1,500,000 $36 $225 $450
EL25 0.007000 $0 $120,000 $400,000 $0 $25,200 $84,000
SCAD A EL44 0.000010 $60,000 $60,000 $60,000 $18 $18 $18
EL25 0.007000 $2,000 $5,000 $60,000 $420 $1,050 $12,600
BARGE DOCK EL44 0.000010 $300,000 $800,000 $2,000,000 $90 $240 $600
EL25 0.007000 $0 $200,000 $500,000 $0 $42,000 $105,000
PERMANENT CAMP El44 0.000010 $300,000 $700,000 $2,500,000 $90 $210 $750
LANDING STRIP & LOWER EL44 0.000010 $10,000 $1,800,000 $3,000,000 $3 $540 $900
ACCESS ROAD EL25 0.007000 $1,000 $2,000 $6,000 $210 $420 $1,260
TRANSMISSION LINE EL44 0.000010 $0 $0 $15,000 $0 $0 $5
TOTAL EXPECTED LOSS (1991$) $965 $128,859 $297,168
TOTAL EXPECTED LOSS
(LEVELIZED 1991 $}
LOW LIKELY HIGH
$21 $48 $53
$0 $7,410 $11,115
$24 $37 $71
$0 $7,410 $16,672
$127 $191 $291
$0 $88,917 $133,376
$64 $397 $794
$0 $44,459 $148,195
$32 $32 $32
$741 $1,852 $22,229
$159 $423 $1,059
$0 $74,098 $185,244
$159 $370 $1,323
$5 $953 $1,588
$370 $741 $2,223
$0 $0 $8
$1,702 $227,337 $524,273
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ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE· OTHER NATURAL PERILS
REPAIR OR TOTAL
ANNUAL TYPE OF REPLACEMENT COST j1991$) EXPECTED LOSS (1991$)
STRUCTURE MAGNITUDE PROBABILITY DAMAGE LOW LIKELY HIGH LOW LIKELY HIGH
DAM (NORMAL OPERATING) 0.00002 Dam Break $20,000,000 $25,000,000 $30,000,000 $12,000 $15,000 $18,000
OUllET WORKS (DIVERSION) 0.00010 Rockfall $0 $0 $70,000 $0 $0 $210
POWER INTAKE 0.0001 o Rockfall $0 $0 $175,000 $0 $0 $525
TRANSMISSION LINE 0.00100 Landslide $0 $50,000 $100,000 $0 $1,500 $3,000
BARGE DOCK 0.0001 0 Slope Ins tablllly $0 $0 $20,000 $0 $0 $60
TRANSMISSION LINE 0.02500 Llghlnlng $0 $10,000 $15,000 $0 $7,500 $11,250
BRADLEY JUNCTION 0.02500 Llghlnlng $0 $15,000 $30,000 $0 $11,250 $22,500
POWERHOUSE 120 tt/SF 0.00200 Snow Load $0 $14,000 $150,000 $0 $840 $9,000
85tt/SF 0.01000 Snow Load $0 $0 $14,000 $0 $0 $4,200
TRANSMISSION LINE 0.01000 Ice $0 $30,000 $60,000 $0 $9,000 $18,000
POWERHOUSE 150 MPH 0.00200 Wind $30,000 $420,000 $1,500,000 $1,800 $25,200 $90,000
100MPH 0.02000 Wind $0 $0 $30,000 $0 $0 $18,000
TRANSMISSION LINE 150MPH 0.00200 Wind $0 $125,000 $250,000 $0 $7,500 $15,000
TOTAL EXPECTED LOSS (1991$) $13,800 $n,790 $209,745
TOTAL EXPECTED LOSS
(LEVELIZED 1991$)
LOW LIKELY HIGH
$21,171 $26,463 $31,756
$0 $0 $370
$0 $0 $926
$0 $2,646 $5,293
$0 $0 $106
$0 $13,232 $19,848
$0 $19,848 $39,695
$0 $1,482 $15,878
$0 $0 $7,410
$0 $15,878 $31,756
$3,176 $44,459 $158,781
$0 $0 $31,756
$0 $13,232 $26,463
$24,346 $137,239 $370,038
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PERIL
EARTHQUAKE
FLOOD
OTHER NATURAL
FIRE & LIGHTNING
All OTHER PERILS
TOTAL LOSS ESTIMATE
ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
Bradley lake
SUMMARY OF ALL PERILS
TOTAL EXPECTED LOSS
TOTAL EXPECTED LOSS (1991$) (LEVELIZED 1991$)
LOW LIKELY HIGH LOW LIKELY HIGH
$21,744 $93,486 $300,222 $38,361 $164,931 $529,661
$965 $128,859 $297,168 $1,702 $227,337 $524,273
$13,800 $77,790 $209,745 $24,346 $137,239 $370,038
$347 $8,818 $29,908 $613 $15,558 $52,765
$43,715 $878,121 $2,658,336 $77,124 $1,549,207 $4,689,916
$80,571 $1,187,074 $3,495,380 $142,146 $2,094,272 $6,166,654
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YEAR
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
ALASKA ENERGY AUTHORITY
RISK ASSESSMENT STUDY
BRADLEY LAKE
SUMMARY OF EXPECTED LOSSES
BY YEAR (Dollars)
LOW LIKELY
2,686 39,569
2,833 41,745
2,989 44,041
3,154 46,464
3,327 49,01 9
3,510 51,715
3,703 54,560
3,907 57,560
4,122 60,726
4,348 64,066
4,588 67,590
4,840 71,307
5,106 75,229
5,387 79,367
5,683 83,732
5,996 88,337
6,326 93,196
6,673 98,321
7,041 103,729
7,428 109,434
7,836 115,453
8,267 121,803
8,722 128,502
9,202 135,570
9,708 143,026
10,242 150,893
10,805 159,192
11 ,399 167,947
12,026 177,184
12,688 186,930
Exhibit 17
HIGH
116,513
122,921
129,681
136,814
144,339
152,277
160,653
169,489
178,810
188,645
199,020
209,967
221,515
233,698
246,551
260,112
274,418
289,511
305,434
322,233
339,956
358,653
378,379
399,190
421,145
444,308
468,745
494,526
521,725
550,420
APPENDIX A
Reviewed Project Documents-Reference List
Stone & Webster Documents
Application for FERC License -Bradley Lake
-Hydroelectric Project
Final Supporting Design Report -General Civil Construction
-Contract -March 1988
Final Supporting Design Report -Powerhouse Construction
-Contract -July 1988
General Civil Construction Contract Documents
Powerhouse Construction Contract
Tsunami Hazard to the Facilities of Bradley Lake
Investigation of Landslide-Induced Wave in Bradley Lake
Other Documents
Design Earthquake Study -Bradley Lake 1981
Woodward-Clyde Consultants
U.S. Corps of Engineers
Bradley 115-kV Transmission Lines -Basic Design Manual
Dryden & LaRue, Inc.
APPENDIX B
Lessons from pam !ncjdents, USA, ASCE/USCOLD 1975.
Dams and Public Safety· Robert B. Jansen, U.S. Dept. of the Interior (USSR) 1983.
Preliminary Safety Evaluation of Existing Oams Volumes 1 and 2-M. W. McCann, Jr.,
J. B. Franzini, E. Kavazanjian, Jr., H. C. Shah of Stanford University, FEMA, 1985.
The Response of Concrete Dams to Earthguakes, K. D. Hansen and L. H. Boehm,
Water Power and Dam Construction, April1979.
Safety of Existing Oams. Evaluation and Improvement, National Research Council,
1983
Safety of Qams. Flood and Earthguake Crjterja, National Research Council, 1985
Publications by EOE Incorporated
Summary of the March 3, 1985, Chile Earthquake
Summary of the September 19, 1985, Mexico Earthquake
Summary of the March 2, 1987, New Zealand Earthquake
Detail of the Effects on the Rape! Hydro Plant of the March 3, 1985 Chile
Earthquake
A Summary of the Seismic Qualifications Utilities Group (SQUG) Program 1985
The Alaska Earthguake, March 27, 1964
Eklutna Power Project
USGS Paper 545-A
Climatic Atlas Vol. 1. Gulf of Alaska
NOAA/BLM 1977
Insuring Dam Risks, J. P. Germond
Water Power and Dam Construction, June 1977
Risk in Hydroelectricity Production, Herbert lnhaber, The International Journal
Pergamon Press-Oxford, December 1978, p. 769
Schedule for Rating Electric Generating Stations Including Substations. Transformers.
Storage Battery. Swjtchjng Stations and Central Heating Plants,
Insurance Service Office, 1974 Edition
APPENDIX C
FORMULAS AND DEFINITIONS
Number of
occurrences
1) Average number of
occurrences per unit
year Number of unit years
Since the number of unit years <2396, a constant) are known, the number
of occurrences per cause code were developed by multiplying the average
number of occurrences <decimal value> per unit year by 2,396 unit year.
While the GADS data base assigns a value of·o.oo for all values less that
0.005, we took a conservative approach and utilized a 0.0025 occurence
rate when the average number of occurrences was shown as 0.00.
2) Unit years= is as a common denominator used to normalize
data from hydro units of the same type, but with
different 1 engths of service during the reporting period.
For instance four-unit years can represent four years of
data from one unit or one year of data from four units.
Example
Unit
Yrs. of data in
Period
A
5
B
3
3> Full forced <unplanned) outage-
c
4
Total
Unit Years
12
Unit Year = 12
The occurence of an unplanned component failure (immediate, delayed,
postponed> or other condition which requires that the unit be removed
from service immediately or before the next weekend.
4) Unplanned {forced derating)
The occurence of an unplanned component failure (immediate, delayed,
postponed) or other condition which requires that the load on the unit be
reduced immediately or before the next weekend.
5) "Risk" is used in risk management and insurance literature and practice
to mean:
-the possibility of loss
-the probability of loss
-a peril
-a hazard
-the property or person exposed to damage or loss
-potential losses
-variation in potential losses
-uncertainty concerning loss.
C-1
APPENDIX C
{continued)
FORMULAS AND DEFINITIONS
6) Burning Layer Losses in risk management are known as the losses that are
small, and frequent as compared to MPL and PML losses that are the
severity losses. The use of the term 11 burning layer 11 does not indicate
that this risk management technique is applicable only to the fire peril.
7> MPL =Maximum Possible Loss
The worst dollar loss that could possibly happen in the period 1988-2010
inclusive.
8) PML = Probable Maximum Loss
9)
<Also, referred to by some as the Maximum Probable Loss. However, since
the above MPL has the same acronym, we took the approach in this report
of referring to this as the PML, the probable maximum loss.)
Lightning is considered as a fire peril. This
property insurance policies for the last 100 years.
included the lighting peril.
is consistent with
Fire policies always
10) A forced outage or unplanned derating results whenever a possible loss
occurs.
For example, if there is a fire to an irrsured property, we assume the
fire will have an impact on the generation of electricity.
11) All perils are assumed to be mutually exclusive.
12) All risks <locations> are assumed to be independent exposures. That is,
the probability of an occurence at one site, does not have any impact at
another site.
13) We have only calculated direct damage losses, not indirect losses such as
extra expenses, or loss of revenue.
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