HomeMy WebLinkAboutSusitna Project Supplemental Report Low Watana Dam RCC Concept Cost Evaluation Final November 29, 2010Susitna Project
Supplemental Report
Low Watana Dam RCC Concept Cost Evaluation
FINAL
November 29,2010
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Low Watana Gravity Dam -RCC Concept
Prepared by:
R&M Consultants
Hatch Associates Consultants
Jack Linard Consulting
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
EXECUTIVE SUMMARY
At the time of the Susitna Project studies for the 1983 FERC License Application and 1985
amendment to the License Application,roller compacted concrete (RCC)technology was not
regarded as sufficiently developed to use in the construction of large dams.Over the past 30
years,however,roller compacted concrete has developed as a construction material for dams of
increasing size and techniques of material placement and composition of the RCC mix has been
refined with experience.
R&M Consultants study team (R&M)was engaged by the Alaska Energy Authority (AEA)to
develop a conceptual design and perform concept level cost estimates for a RCC dam at the
Watana site and Devil Canyon sites that were described in the R&M report dated November 16",
2009.This is an addendum to that report and examines the Low Watana RCC dam options by
exploring the cost differential between an expandable option and a non-expandable option,and
gravity section vs.gravity arch.Additionally,the advantages and disadvantages of underground
vs.surface powerhouse are explored as well as simplified transportation options utilizing updated
information on railroad costs in conjunction with "rail only”surface transport to the project.
We have found no fatal flaw in Low Watana RCC Gravity Arch Dam or surface powerhouse
options,and initial estimates indicate that there may be significant potential savings,particularly
with the RCC dam arrangements.RCC dams have been constructed in cold climates and at
greater heights than the 700-feet of Low Watana.
It is possible that developing the RCC concept to its final design configuration and moving
toward construction could result in development opportunities for basic industries in Alaska in
producing cement and exploitation of natural pozzolanic sources.
Access and logistical considerations including road,rail,and air transport are of concern at a
remote site such as the Susitna Project sites.Addition of unrestricted access to undeveloped areas
is often controversial.The access alternatives considered have assumed rail only access to the
project site.
The cost estimate summary,Table ES-1,presents the estimated construction costs of the options,
all of which consider surface powerhouses and "rail only”ground transportation.
Table ES-1 Summary of Cost of RCC Dams for the Susitna Project
Low Watana Low Watana Low Watana Low Watana
Embankment RCC RCC Gravity Arch
Non-Expandable Non-Expandable RCC
$1,000 (1)Expandable $1,000 Non-
$1,000 Expandable
Description $1,000
Construction Cost Total
(Millions of Dollars)$4,500 $3,900 $4,200 $3,600
(1)HDR 2009
Page i November 29,2010
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
Supplemental Report
Low Watana RCC Concept
November 29,2010
Table of Contents
EXECUTIVE SUMMARY i
Table of Contents ii
Figures iii
Appendices iii
1.0 Introduction 1
2.0 Project Layout 1
2.1 General .......cccecccccescccsscsesescesseencceceacennececeesaecsenseseeeaeseseceaeesneessaeeeeessneeeserssaeeeseesones 1
2.2 Altermative ........cccccccccscesssseseesseessecsceesncesaeceaeeeasesseesaecseeseneeeaneenaeeaeseessessessensseesaaees 2
2.3 Powerhouse Layout .........ccccccscccesscccsseccseccereseceececesseeenneeceanererseecesnesessssnsaseaeessaeeees 3
2.3.1 Surface vs.Underground Powerhouse .............ecccscceseesseeneeeessessessseseenees 4
2.3.2 Surface Powerhouse Configuration...eects eeseeessssesssecceseenseteeseeeeeee 5
2.4 Dam Design Considerations.....cec cece ccccesceseeessaesseesssseseneseseseesceeeestenseeneeenesaes 7
2.4.1 RCC Dam Design...cee eeseccesseceeececseneeeseeceaeecenceceneceeenaeseesdsesansssasersesesaes 7
2.4.2 Low Watana RCC Gravity Dam Expandable...ceeeeeeeesecsrereerenees 10
2.4.3.Low Watana RCC Gravity Dam Non-Expandable........ieeeeee 12
2.4.4 Low Watana Gravity Arch woo...eececeeseeeceeeeeerereceaeeseeesteetnaeseneeseessens 12
3.0 Project Access Issues 13
3.1 Previous Project Access Costs Comparisons ..............ccesseececesseeseeensecrneteenessensens 13
3.2 Rail ACCESS .......ccescccecscceeseceeneersceeeeeseeesanersnseensneeerseserecernaeeonedeesesasnacsdasssessasesseesas 14
3.3 AUIStIIP oo.cceccceseseececeeeeeeeceeeacesseeeeeerneenaceeeeeceeeeseesensseecseeseeesesasseessnessseessressesseeeseas 14
4.0 Cost Estimates 15
4.1 RCC Cots ....ccccccccccccsesseccsereecensccceeceseneeceesnseecescceeasnseteccesdeeesesesauesecssaeesonaeecnsaeeees 15
4.1.1 RCC Unit Cost Analysis for Watana Dam ............eeeeeeeeeeseeeeeeeneteeneeers 15
4.1.2 Sizing of RCC Batching Plant...cee eeeeeeeaeeeeereeneeeseeeeeesereeenes 17
4.2 Camp Cot...cccecceccscccnecseeeseeeseeeeseeersesesesseassssesseeesseassesssassssanessssessesssesseneeneenes 17
4.3 Project Access CoSt 0...eessesssesssesssssssssssesesnssessescseseseascessesensucsaseceeeseeraaseneseesens 17
4.4 Cost SUMMALY ........eceeeeeteeeseeesseeeeseessenneeseeseceeeesecereesesseceseeserneeeeeasenssaseseeseeeseees 17
5.0 Project Schedule 19
5.1 Dat oo..cccccesceecesseenccesseeescecessaeeesaeeessecensneesesenecseeseseneneessenersnseesasseasasnaseseuesesesaneenees 19
5.2 POWETHOUSE ........cceeeeeeeeceseeeseeeeseceseaeeeseeeeseeecesecesetesncersnesesseessnneeaseaseneaseeseesesesees 19
5.3 Combined Dam and Powerhouse Schedule...ceeeseeeceeeseeeneeeseeeeseeneneeenens 20
Page il November 29,2010
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
Figures
2.2-1 -Low Watana ICRD Expandable Plan
2.2-2 -Low Watana ICRD Expandable Section
2.2-3 -Low Watana ICRD Expandable Stage 2 Section
2.2-4 -Low Watana ICRD Power Facilities
2.4-1 -Low Watana RCC Expandable Plan
2.4-2 -Low Watana RCC Expandable Sections and Details
2.4-3 -Low Watana RCC Expandable Elevation Views
2.4-4 --Low Watana RCC Non-Expandable Plan and Detail View
2.4-5 -Low Watana RCC Non-Expandable Sections and Details
2.4-6 -Low Watana RCC Non-Expandable Elevation Views
2.4-7 -Low Watana RCC Non-Expandable Profile
2.4-8 -Low Watana RCC Non-Expandable Gravity Arch Plan
2.4-9 -Low Watana RCC Non-Expandable Gravity Arch Sections and Details
3.2-1 -Low Watana Rail Access
4.1-1--Borrow Areas
Appendices
A -Breakdown of Unit Cost Analysis for RCC
B -Detailed Cost Estimate
Page iii November 29,2010
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
1.0 Introduction
R&M Consultants,Inc.(R&M)formed a team under the R&M/AEA term agreement that
includes Hatch Associates Consultants,Inc.(HACI)and Jack Linard Consulting
(R&M/HACI/ILC)to investigate the feasibility of Roller Compacted Concrete (RCC)technology
for the Susitna Project as an alternative to impervious core rockfill dam (ICRD)concepts that
were developed during the licensing studies which concluded in 1985.Additionally
R&M/HACI/JLC performed a review of regulatory and FERC licensing activities and timelines
for precursor activities to issuance of a FERC license,and developed and a licensing phase
strategy for the project.The results of those investigations were presented in the R&M report
dated November 16th 2009 (R&M 2009).
The investigation was amended to consider additional alternatives with potentially lower costs.
This document presents the results of the further investigations.It is an extension of the previous
R&M 2009 report.In an effort to keep the comparison valid,the costs are based on December
2008 USD and are presented in the same format and structure as in the R&M 2009 report.The
focus will be on a Low Watana option with the same general project size as described in recent
studies (HDR 2009).Concepts focus on RCC dam options exploring the cost differential between
an expandable option and a non-expandable option and straight gravity section dam vs.gravity
arch dam.
The advantages and disadvantages of underground vs.surface powerhouse are also considered.
Transportation options utilizing updated information on railroad costs are developed with the
alternative of "rail only”surface transport to the project.The cost estimate uses
equipment/material prices consistent with the previous Watana cost estimate currently available
from AEA.
2.0 Project Layout
2.1 General
The following assumptions and technical considerations were included in developing our
conceptual project layouts.Replacement of one dam design for another affects more than
just the dam.Many features of the project general arrangement may be affected by the
selection of dam type.In keeping with our understanding of the dam design and costing
task we have included the following considerations:
e Hydrology and hydraulics;
°Assumed the same reservoir water levels as described for the Low Watana
ICRD option;
fe)Diversion scheme and tunnel capacities are different as the diversion scheme
employs a shorter tunnel due to the smaller footprint of an RCC dam and the
consequences of overtopping of RCC dams is lower than with ICRD;
fe)The spillway configuration is different than for the ICRD alternative
(eliminating the side channel spillway)and incorporating an overflow section
into the RCC dam.The spillway configuration requirement included initial
examination of energy dissipation and potential for scour and to reduce the
potential for total dissolved gas (TDG)production at the project.The hydraulic
capacity was taken to be the same as for the current ICRD configuration.The
RCC dam Spillway design is conceptual only at this phase without detailed
analysis,modeling and in depth review of energy dissipation of potential for
rock scour.
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R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
2.2
The intake structure and water conveyance use similar invert elevations and
diameters as for the ICRD dam option;
The powerhouse layout uses the same equipment sizes at the same setting as for the
ICRD option;
Foundation Conditions and Excavation Depth:Foundation conditions and foundation
treatment,including the single line grout curtain,will be similar to those for the Full
Watana RCC dam concept,which were similar to treatment of the foundation below
the impervious core for the ICRD dam scheme;
Dam cross section design --RCC dams are designed to the same principles and
standards as concrete gravity dams.Design loadings and factors of safety are per
FERC guidelines,including;waves and freeboard,earthquake,ice and silt loads.The
principles used to develop the Full Watana RCC dam concept are the same as used
for the Low Watana RCC dam concept.
Alternatives
Several RCC alternatives were examined for comparison with previous ICRD expandable
and non-expandable Low Watana alternatives.To achieve this,we have focused on the
elements of the RCC dam alternative that differ from the existing ICRD alternative.
Elements that are similar will remain identical for both alternatives in order to achieve an
"apples to apples”comparison to the extent possible.The alternatives being compared to
the RCC schemes are the ICRD Low Watana Expandable (see Figure 2.2-1 through 2.2-
4)and the ICRD Low Watana Non-expandable.
The following alternatives are addressed in this report:
Low Watana RCC Gravity Dam Expandable;
Low Watana RCC Gravity Dam Non-Expandable;
Low Watana RCC Gravity Arch;
Additionally,there is a discussion of above ground vs.underground powerhouses for
these alternatives.
Major considerations are:
Dam layout (axis,gravity arch vs.gravity);
Intake (integral to the dam or separate,expansion to full height Watana);
Spillway sections that could be modified for the expanded option;
Powerhouse (location,surface vs.underground,expansion options).
Advantages of the RCC dam concept compared to ICRD include:a smaller footprint,
lower dam volume,integral spillway,considerably shorter diversion tunnels and no
vulnerability to overtopping.Table 2.2 shows a comparison summary of significant
features of each alternative.
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R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
Table 2.2:Low Watana ICRD and RCC Alternatives Summary
Low Watana Low Low Low Wana
Feat Description Non-Watana Watana Watana RCCeaturebescripilExpandable|Expandable |RCC-Non-|RCC-CravitICRDICRDExpandable|Expandable Achy
Total Dam Fill Volume (cy)22,000,000 32,000,000 7,600,000 7,600,000 6,000,000
oO Tunnel Diameter 36 36 7 27 7
Average Diversion Tunnel
Length (ft)3,700 3,700 2,000 2,200 2,000
Intake Area Excavation (cy)1,970,000 1,970,000 270,000 760,000 270,000
Average Power Tunnel
Length (ft)200 200 260 300 330
Average Pressure Tunnel
Length (ft)400 400 550 1500 170
Tailrace Tunnel Length 1,500 1,500 N/A N/A N/A
ine Concrete Volume |49 400 60,600 62,500 83,000 62,500
Powerplant Excavation 242,000 363,000 1,500,000 |2,200,000 |1,500,000Volume(cy)(3)-64'Tall x |(3)-64'Tall
Spillway Gates 44'Wide x 44'Wide N/A N/A N/A
Radial Gates |Radial Gates
(oy Chute Excavation 2,960,000 |2,960,000 N/A N/A N/A
Spillway Chute Conventional 130,300 130,300 99,000 99,000 99,000Concrete(cy)
This study does not have the scope for an exhaustive exploration of layout options,so
some engineering judgment has been used to develop the configurations used for
comparison.We have selected a layout based on general comparisons to existing
projects.The Shasta project in California in particular is similar in size and layout to our
selected configuration for the RCC Gravity and Gravity Arch dam arrangements
(Kollgaard and Chadwick,1988).
2.3
The powerhouse layout was examined to explore potential cost savings associated with
the smaller footprint of gravity or gravity arch dams and robust concrete construction
which allows configurations that would not be available with an ICRD dam.
Powerhouse Layout
A common reason for selecting an underground powerhouse is to take advantage of a
steep gradient of the river between the dam and the tailrace;however this is not the case
at the Watana Dam site.Another important consideration is to minimize the length of the
water passage.The smaller footprint of the RCC dam allows shorter water conveyances
as well as the option of intakes and water conveyance either through the dam,or in the
rock abutments.The geological conditions must be suitable for an underground
powerhouse,which they are at Watana.A surface powerhouse requires enough room to
place the powerhouse along the river without excessive excavation,which is also the
case.Our conclusion is that both an underground and surface powerhouse configuration
is feasible at the Watana site and the choice should be based on economics,
constructability and serviceability issues.
November 29,2010 Page 3 Final
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
2.3.1 Surface vs.Underground Powerhouses
The choice of a surface or underground powerhouse is largely dependent on the
project setting and site conditions.The following list compares the two options:
e Typical surface powerhouse advantages are:
o Elimination of tailrace tunnel;
No requirement for tailrace surge chamber;
Less expensive excavation;
Ventilation is easier;
Less geotechnical exploration required (as less geotechnical risk to
cost and schedule).0000*Typical underground powerhouse advantages
o Location is more flexible;
o Shorter headrace tunnels with considerable reduction in length of
steel-lined high pressure conduits;
o Work area can be more easily separated from dam construction (two
separate construction areas and schedules);
Powerhouse is not located in or near river bed materials;
Exterior shell not needed (rock forms support);
Protection against the elements (longer construction season);
Turbine setting can be lower;
Less concrete needed to control hydraulic uplift;
Less maintenance required.000000The 1982 Acres Feasibility report discusses the choice of an underground
powerhouse based on general assumptions of less costly installation for
underground installations,additional operational flexibility and climatic
considerations.
The 1985 Harza Ebasco FERC license application (Harza Ebasco 1885)includes
a comparison of an underground to a surface powerhouse by major civil
mechanical and electrical cost items where the surface powerhouse was shown to
be more expensive due to the far greater cost of the power tunnel/penstock (see
Table 2.3-1).The comparison in Table 2.3-1 is a simplified comparison and does
not include the costs associated with the powerhouse superstructure or the
considerable substructure required to insure that the powerhouse is stable against
hydraulic uplift.
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R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
Table 2.3-1 Comparison of Surface to Underground Powerhouse (Harza Ebasco
Study 1985)
TABLE B.2.2.6:SUMMARY COMPARISON OF POWERHOUSES AT WATANA
SURFACE ONDERGROUNOD
($006)($000)¢$000)
Item 4 x 210 MW 4 x 210 MW 6 x 140 MW
Civil Works:
Intakes 54,000 54,000 70,400
Penstocks 72,000 22,700 28,600
Powerhouse/Draft Tube 29,600 26,300 28,100
Surge Chamber NA 4,300 4,800
Transformer Gallery NA 2,700 3,400
Tailrace Tunnel NA 11,000 11,0006
Tailrace Portal .NA 1,600 -1,600
Main Access Tuanels NA 8,100 8,100
Secondary Access Tunnels NA 300 300
Main Access Shaft NA 4,200 4,200
Access Tunnel Portal NA 100 100
Cable Shafe NA 1,500 1,500
Bus Tunnel/Shafts :NA 1,000 1,200
Fire Protection Head Tank NA 400 400
Mechanical For Above Items 54,600 55,500 :57,200
Electrical -For Above Items 37,400 37,600 41,200
Switchyard All Work 14,900 14,900 14,900
TOTAL .262,500 246,200 277,000
We have developed a potential project arrangement with a surface powerhouse (loosely
based on the Shasta Hydroelectric Plant layout,Development of Dam Engineering in the
United States,1988)with an intake on the left abutment,transitioning to a tunnel.The
length of the water passage is similar to that of the Low Watana underground option
(Harza Ebasco 1985).The tailrace discharges directly into the Susitna River.
2.3.2 Surface Powerhouse Configuration
Considerations for the surface powerhouse include:setting of the units,elevation
of high tailwater to prevent powerhouse flooding,rock cover over the tunnels and
the need for steel lining,stability against hydraulic uplift,construction access,
cofferdamming and diversion requirements to accommodate dam,powerhouse
foundation,and tailrace channel.Costs of waterways (tunnels,shafts and
intakes)are not included in the cost account for powerhouse cost comparisons
but are in a separate cost account.
The conceptual layout of a surface powerhouse for the Low Watana RCC dam
alternative was selected for favorable hydraulic characteristics as well as for cost
effective excavation downstream of the proposed dam.The concrete volume for
the surface powerhouse is a volume sufficient to ensure that there would be
enough mass to prevent powerhouse floatation without installation of anchors.
The surface powerhouse is set on the south river bank (left bank)such that the
tailrace apron end sill is adjacent to the end sill of the spillway stilling basin,as
these two features are at the same elevation of 1450 ft.The tailrace end sill
apron creates a downstream control weir for the powerhouse,thus maintaining
minimum tailwater conditions.Several design considerations including;
November 29,2010 Page 5 Final
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
excavation volumes,effects of discharge on downstream hydraulics,and the
effect of spillway discharge on powerhouse operation,must be evaluated to
determine the optimum physical setting of the powerhouse.The surface
powerhouse for the low Watana RCC alternatives was set to be offset 27 degrees
from the stilling basin,which is generally the expansion ratio of 2 longitudinal to
1 horizontal as defined by the USACE (HEC RAS v4.1 Reference Manual).This
alignment directs the Low Watana RCC dam surface powerhouse discharge
efficiently into the downstream river channel,noting that further downstream of
the dam the river bends to the north.
For this study,the dimensions of the surface powerhouse were set to
accommodate the same equipment layout proposed for the ICRD dam designs.
The transformers will be located within the surface powerhouse rather than in a
separate cavern as with the underground design.The surface alternative has the
transformer deck set above the draft tube outlets and their overall dimensions are
similar to those of the underground alternative.The entrance angle of penstocks
with respect to the surface powerhouse remains the same 62 degrees as with the
underground design.
The power intake (for the non-expandable and gravity arch RCC dam
alternatives)is integrated into the dam body and transitions into two concrete
lined tunnels that lead to vertical shafts and high pressure tunnels that bifurcate
and transition into steel lined penstocks that lead into the four Francis units in the
powerhouse.The intake invert and size for the RCC dam alternatives are
approximately the same as in the ICRD dam alternatives and the overall penstock
lengths are similar for the surface and underground alternatives.Although the
penstocks are somewhat longer in the surface alternative than in the underground
alternative,having sections of the power tunnels integral to the RCC dam may
reduce tunnel excavation/support,and concrete lining costs.
The significant cost advantage between the conceptual RCC surface powerhouse
and previously designed ICRD underground powerhouses is the elimination of
surge chambers,tailrace tunnels and access tunnels for the surface powerhouse
which are considered in the waterways cost account.Given the limited scope of
this study,the surface powerhouse was investigated to determine its feasibility
and provide an estimate of comparative costs.With this criteria,the surface
powerhouse does show to be a feasible alternative.However,the scope did not
include optimization of an underground design for the RCC designs.An
underground powerhouse with the RCC dam may have shorter pressure tunnels a
hydraulic transient analyses may demonstrate that surge chambers are not
required.
Further analyses should be performed to evaluate both surface and underground
layouts that will improve the configuration of the powerhouse,including;
optimizing unit settings considering concrete requirements and excavation costs,
optimizing high pressure and low pressure penstock lengths,as well as
optimizing the tailrace configuration.Additional study will be required to better
define hydraulic effects of the spillway discharge on powerhouse performance,
including physical model testing.Indications are that both surface and
underground powerhouse configurations are feasible for the Low Watana with an
RCC dam,and future analyses will need to be performed in order to determine
the optimum configuration.
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2.4 Dam Design Considerations
2.4.1.RCC Dam Design
The geotechnical information is typically the most influential element for
developing a dam design and the Watana site has well developed site
information.The RCC dam alternatives were developed on axes similar to that
of the ICRD dam axis.This is considered a conservative assumption,adopted to
provide a dam axis in the location with the maximum amount of existing
information on the foundation subsurface conditions,but not necessarily at the
most efficient location.It is possible or even likely that a more efficient dam axis
location could be found with further investigation.
The site has a foundation and abutments that are well suited to a concrete gravity
dam.Concrete gravity dams are relatively straight forward to design,and many
computer programs are available to improve the process of initial and final
design.The dam design can be initially developed using assumptions for
concrete strength based on similar mixes used on other projects.The final
configuration of the dam requires accurate material properties for the RCC
material that can only be determined by trial mix design using the actual selected
cement and pozzolan and the aggregate material available from the site.
Foundation treatment for all RCC dam options includes consolidation grouting
under the dam footprint and curtain grouting similar to that assumed in the
previous RCC dam study.
There is a buried channel north of the dam site which has been called the "Relict
Channel”.For the RCC alternatives,the treatment for the Relict Channel has
been taken to be identical as developed for the Low Watana non-expandable
ICRD.
It is important to note,particularly with regard to the comparison with the gravity
arch alternative that the Low Watana cross-section retains the 1H:1V
downstream slope established for the High Watana option (R&M 2009).This
face slope was considered to be on the conservative side for the high dam and is
even more so for the low dam option.
At this stage of proceedings,it is not appropriate to try to refine or optimize the
various elements of the different schemes,but it is important to bear in mind that
more detailed analyses may well change the relative ranking of project
alternatives.By the same token,more detailed analyses can only serve to ensure
that the eventually selected alternative will be more attractive than the
alternatives indicated herein because of the conservative approach adopted
throughout in these comparative studies.
A more conventional spillway option for a dam of this configuration and height
would be a smooth surfaced chute with forced air entrainment discharging back
into the river via a flip bucket into a plunge pool.Such an arrangement would
require the dam axis to be relocated to ensure that the jet from the flip bucket
impacts in the river with an alignment such that back scour is minimized.The
use of flip bucket and plunge pool may also result in hydraulic conditions that
could lead to high total dissolved gas (TDG).TDG occurs when air mixes with
water and goes into solution at depth,creating water supersaturated with air.If
November 29,2010 Page 7 Final
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
fish breathe supersaturated water,air can come out of solution in their blood
stream causing gas bubble disease,which can be fatal.The stepped spillway may
allow spill without a plunge to depth that could lead to excessive levels of TDG.
The design would look to dissipate as much energy as possible and create a
spillway that creates skimming flow downstream of the spillway.The present
work scope does not cover spillway and dam axis optimization and for that
reason,the stilling basin concept,which is compatible with the ICRD axis,has
been adopted for present reporting purposes.
The conceptual spillway for the RCC alternatives is incorporated in the dam
structure.The flood outflows are discharged through an ungated spillway into a
stepped,converging chute and terminating in a downstream stilling basin.As
discussed in the R&M 2009 Report,the stepped spillway is expected to provide
significant energy dissipation and to be compatible with the stilling basin
arrangement shown on the drawings.However,a stepped spillway of this size
exceeds precedent and details will have to be verified by comprehensive
hydraulic model studies.
An extensive study,including large scale physical models (not less than 1:40
scale)will be required prior to finalizing the details of spillway configuration.
The preliminary hydraulic calculations performed for a stepped spillway indicate
that it is a potentially cost effective configuration and should warrant further
consideration and analyses during future design studies.Modeling may well
show that the optimum stepped spillway and stilling basin is different to the
conceptual configuration,or that a different type of spillway may be required.
Any modifications may influence not only the spillway costs but also the
powerhouse costs as the layout may have to be reconfigured.
2.4.1.1 Steps for RCC Design
Development of the RCC dam design will require several steps,
comprised of:
e Confirming design criteria,including loads and _load
combinations,materials and foundation properties,minimum
factors of safety and allowable stresses;
e Evaluation of site climatic conditions which have a major impact
on both construction programming and RCC mix design;
e Performing preliminary design --determine required
performance,development of basic geometry,preliminary mix
design and strength requirements;
e Performing three-dimensional finite element analysis (using
initial assumed material properties),including dynamic and
thermal stress analyses;
e Locating and testing aggregate,cement and pozzolan sources
that will be used for construction;
e Establish RCC placement temperature,maximum allowable
interna!temperature and required temperature control measures;
and
e Developing trial mixes for the full scale trial embankments
(FSTE)to fine tune the mix design.
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R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
The trial mix program would be initially oriented towards:
e Aggregate gradation optimization;
e Selection of two preferred cement types and content;
e Selection of two preferred pozzolan types and content;and
e Selection of two preferred retarder types and content.
The minimum time from beginning the study of the prospective RCC to
confirmation of mix details is 16 months.Conservatively,it would be
appropriate to allow 18 months.At least 18 months is required to
investigate,select,procure,ship and set up the necessary equipment
(crushing plant,batching plant,conveyors).Most of this work is done
during the trial mix/FSTE phase and the end result is that the RCC
production facilities can be ready within 2 years of starting trial mixes.
An upper limit would be 2.5 years.
2.4.1.2 Seismic Design Consideration
The most important safety concern of concrete dams subjected to
earthquakes is excessive cracking,which can lead to potential instability
from sliding or overturning.Sliding could occur on an existing plane of
weakness in the dam foundation,at the foundation-dam interface or
within the dam.Although some major concrete dams have experienced
strong ground motion with some damage,it is of note that there has been
only one major concrete dam failure in recent times as a result of
earthquake induced ground motions.This failure was in Taiwan where
the dam was constructed literally over the top of an active fault.In
general,instability of gravity dams caused by excessive cracking of the
concrete is most likely to occur in the upper half of the dam.
The application of defensive design measures when designing a dam is
the most dependable approach to alleviate safety concerns.Defensive
measures for concrete dams include the following:
e Adequate drainage is the first line of defense against
foundation instability,in part because it is the most
economical;
e Designing RCC mixes and construction procedures to ensure
that direct tensile and shear strength parameters are always
achieved without excessive cement content in the mix.
(Increased cement will increase thermal stress problems,
which may be more of a concern than the seismic risks);
e Use the best geometric design and structural detailing.The
dam should have minimum geometric irregularities and
gradual variations in structural stiffness.Examples of good
geometric design are curved transitions and minimal mass at
the crest;
e Effective quality control during construction to ensure
foundation preparation,strength of the concrete and
appropriate cleaning and preparation of lift joints and
placement of reinforcement when used;and
e Design contraction joints to accommodate displacement.
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2.4.2.Low Watana RCC Gravity Dam Expandable
The Low Watana RCC Expandable dam alternative consists of the Watana dam
constructed to a lower height of 700 feet and a four-unit powerhouse with a total
installed capacity of 600 MW (see Figures 2.4-1 to 2.4-3).The expandable
option allows for a dam raise to the height of the original Watana concept with a
dam height of 885 feet and installation of a new intake structure,an additional
power tunnel and two additional generating units with a capacity of 1,200 MW.
In order to provide for future raising of the dam and expansion of the
powerhouse,the location of the powerhouse and power intakes were adjustedfromthenon-expandable alternative.The powerhouse was translated 185 feet
downstream compared to the non-expandable RCC gravity dam alternative to
allow room for RCC material to be placed downstream of the dam as part of the
dam raise.
The power intake structure was located on the left abutment as opposed to being
integral with the dam for the non-expandable alternative to provide _more
flexibility for the dam raise.If the power intake were integral to the dam,a new
power intake would be more constrainedandcomplicated by-existing structures.
During expansion,a new intake channel could be excavated above the existing
structure at the appropriate invert elevation.Intakes for the expanded option
could be developed at a higher invert elevation than the first stage intakes.The
intakes for the expansion,second stage would be connected to the first stage
water conveyances at the vertical shaft,to tap into the lower,high pressure
portion tunnels leading to the powerhouse.
The powerhouse includes empty bays that can accommodate additional
generating units in the future.The gravity section will be raised by placing
additional RCC on the dam crest and downstream face of the dam.High strength
steel anchors will be installed_on the first stage.dam faces and will tie into the
second stage RCC placement.Prior to placement of the second stage RCC the
surface of the first stage will be cleaned and scarified using high pressure
washers.The spillway for the second stage will be constructed using the same
placement procedures and similar design as in the first stage.
The gravity dam section was checked using the CADAM program for static and
pseudo dynamic stability and found to have adequate safety factors (see R&M
2009 for a description of the analysis,loading and material properties).
The process of raising a dam at a later date is not a simple matter.We have
included some general considerations,procedures and a potential sequence to
provide some indication as to the process involved.
GENERAL
1.Planning and design prior to start of Stage 1 are critical.It may be
necessary to place some Stage 2 base RCC (up to stilling basin level)
during Stage 1 to minimize overall Stage 2 duration.
2.Stage 1 RCC mix will be designed for Stage 2 loads and loading
conditions.
3.Foundation excavation for most or all Stage 2 should be performed
during Stage 1 works to avoid blasting close to in-service dam and
powerhouse.
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4.Note that same 5.5 months per year is max time available for RCC
placement (5 months for conventional concrete).
5.Draw reservoir level down to the minimum operating level at end of
winter.Generate during summer to keep reservoir level as close as
possible to the minimum level,Note that a critical problem is handling of
flood inflows during Stage 2.
6.RCC production rates will be slower for Stage 2 than for Stage 1 due to
greater constraints on placement.
7.Dam/spillway expansion construction expected to take approximately 5
years.
PROCEDURE
1.Clean existing RCC surface to exposed coarse aggregate.
2.Make sure exposed surfaces are saturated and surface dry and that outer
18 inches is above freezing point.
3.Place bedding mix on horizontal surfaces immediately prior to placing
RCC.
4.Use grout enrichment to bond new RCC to sloping surfaces in existing
RCC.
5.Otherwise standard RCC procedures will apply (anchors between Stage 1
and Stage 2 RCC are not required).
SEQUENCE
Year 1:
Clean-up and prepare foundation and abutments.
Remove concrete from Stage 1 chute and stilling basin.
Commence aggregate production and stockpiling.
Year 2:
Place RCC in base (up to stilling basin level)and on abutments up to
approx El.1650.
Year 3:
Continue RCC placement up to El.1900 approx.
Place conventional concrete stilling basin.
Remove spillway conventional concrete including bridge and piers
(winter).
Year 4:
Place RCC to underside of stage 2 spillway.
Place conventional concrete in chute.
Complete RCC to crest El.on right abutment.
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Year 5:
Complete RCC to crest El.on left abutment.
Construct Stage 2 spillway crest works.
2.4.3 Low Watana RCC Gravity Dam Non-Expandable
The Low Watana Non-expandable RCC Gravity dam alternative has the same
dam profile and the general configuration is similar to the expandable alternative
above with a dam height of 700 feet and a four-unit powerhouse with a total
installed capacity of 600 MW (see Figures 2.4-4 to 2.4-7).
The major differences that lead to reduced installation costs are the shorter
diversion tunnel length and shorter power tunnel length for the surface
powerhouse as well as the size of power tunnel and tailrace.The intake structure
is shown as being incorporated into the dam on the left abutment.The
assumption is that conventional concrete would be used for the intake structure
with RCC placed against the conventional concrete.
The Powerhouse is shown as close to the dam and spillway as possible in order to
minimize the water conveyance length.The powerhouse layout does not
consider future expansion options.
2.4.4 Low Watana Gravity Arch
A Low Watana gravity arch RCC dam option was also considered (see Figures
2.4-8 to 2.4-10).The axis adopted for these preliminary gravity arch studies was
effectively that adopted for the conventional gravity dam option.In turn,this
was the axis chosen for the ICRD in the studies carried out in the 1980's.From
this background,it can clearly be seen that the axis used for the G-A layout is by
no means optimum.
This preliminary gravity arch dam configuration was based on several factors.
First,the crown cantilever section was selected to be similar to the Hungry Horse
(gravity arch)Dam in Montana which is sited in a geometrically similar canyon.
The Hungry Horse Dam (Development of Dam Engineering in the United States,
1988)crown cantilever was configured with a vertical upstream face and a 0.6
Horizontal to 1.0 Vertical sloped downstream face.The Low Watana gravity
arch crown cantilever section was configured with a vertical upstream face and a
0.7 Horizontal to 1.0 Vertical sloped downstream face.The larger ratio was
selected based on the larger expected seismic hazard for the Susitna site and
preliminary analysis for a gravity arch RCC dam at the High Devil Canyon site.
The stream channel physical dam location,arch (constant)radius and center point
was selected based on the qualitative topographical features at the site.In
studying the topography of the site,it appears that this site is not as well suited
for arch action foundation support over the full 700-foot height of the dam.From
about elevation 1850 to the crest elevation of 2025,the cross-valley slope is
relatively small compared to the slope below elevation 1850.Therefore,in
locating the arch,the topographic contours between elevations 1550 and 1850 on
each side of the canyon were collectively examined for orientations that would
best provide for arch thrust into the foundation.After the "best"thrust
foundation profiles were located on each side of the canyon,the approximate
tangent lines to the profiles on each side were laid out on the site plan.Their
November 29,2010 Page 12 Final
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intersection established the radius and center of the upstream arch.Having
established the arch radius and center,the remaining geometry of the dam is
integrated into the canyon using the basic section geometry of the crown
cantilever and the topography of the site.
The seismic loading will have a large component of load in the
upstream/downstream direction,and a thrust block structure may be required to
accommodate this loading.We have assumed for this preliminary estimate
(which will need to be confirmed by three-dimensional finite element analysis,
when abutment and dam properties are better known)that an additional 25%of
the base concrete costs would be sufficient to account for this component of the
dam.
With the configuration described above,the structural support behavior of the
dam is conceived to be primarily arch-gravity action in the lower two-thirds of
the dam and gravity only in the upper third.It is to be noted that the preliminary
configuration is only the starting point of the comprehensive structural and
stability analyses that would include both seismic and PMF loading.Although
the configuration is likely to be modified based on such analyses,the preliminary
configuration serves to provide a reasonable estimate of dam volumes and
construction costs.
The gravity arch has a smaller footprint than the gravity section,however the
area will remain large enough for equipment to move efficiently.The
assumption for this preliminary study has been that placement rates and RCC unit
costs would be the same for all alternatives.There will be some difference with
the grout treatment at the upstream face that will have a small increased effect on
the overall unit cost,but this should be developed in more detail if this alternative
is addressed in detail.
3.0 Project Access Issues
Access to the construction site for the alternatives considered in this report are by rail link alone
to limit access to the site and reduce costs.The Alaska Railroad provided some input on recent
costs to develop the rail link along the south side access corridor alignment.An airstrip would be
provided near the Watana project to allow use of aircraft up to a C-130 Hercules or equivalent.
3.1 Previous Project Access Costs Comparisons
Previous cost estimates for project access infrastructure for the Full Watana RCC dam
and High Devil Canyon RCC dam (R&M 2009)assumed both rail and road
transportation to the site on alignments in the south side corridor.This alternative was
compared to a Watana ICRD concept with only road access from the Denali Highway
through a northeasterly corridor (HDR 2009).While it is true that the RCC concept
would benefit greatly from the ease of transporting bulk cement and pozzolans and major
equipment and logistical access to the site by rail,road transport of these materials
equipment and supplies would also be feasible.The different project access and
logistical support transportation assumptions between the RCC and ICRD concept studies
led to a significant distortion of the comparison of the project costs.For an "apples to
apples”comparison of the options,the same basic transportation configuration (road
only,road and rail,or rail only)should be assumed for both schemes with logistics costs
included to account for transport of imported materials.
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For this immediate report,we are assuming rail access only,during construction.Future
considerations regarding access may result in removal of the rails and converting the
railroad to use of trucks and other over-the-road vehicles.
3.2 Rail Access
The alignment for the rail link only option along the southern alignment (see Figure 3.2-
1)is based on the project access and logistical studies done by R&M.A report on the
Access Planning Study by R&M for Acres was issued in January 1982 and a Supplement
to the Access Planning Study was issued in September 1982.
For the R&M 2009 report on RCC concepts the rail link alignment was assumed to be as
shown on Figure 3.2-1 which was drawn from the alignment details presented in the
R&M 1982 report.The rail access would connect to the existing Anchorage-Fairbanks
alignment of the Alaska Railroad near Gold Creek on the south east side of the Susitna
River then would proceed east up the south side of the Susitna River to the Watana site
via the north end of Stephan Lake and the west end of Fog Lakes.This alignment
requires no new bridge across the Susitna River and only requires a railhead be
constructed near Gold Creek from which to stage rail transport of goods and materials to
the Watana dam site.
A railroad is considered desirable for access to the project for construction of the RCC
dam because of the large quantities of bulk materials to be moved to the construction site
and weights anticipated for large components such as gates,penstocks,turbines,
generators and transformers and structural steel.Also a railroad would lessen the impact
of project traffic and heavy haulage on the Alaska highway system.In addition,these
material and equipment items will likely be brought to Alaska by barge,rail barge and/or
ship from the source either via Seattle or other foreign or domestic port to Anchorage or
Whittier for trans-loading onto railcars for movement to the Project site.Shipping
possibilities include rail barge for most of the materials which would allow the loaded rail
cars to pass through Whittier or Anchorage directly to the project site without trans-
loading.Materials shipped in sea containers (CONEX's)could be offloaded from a
container ship in Anchorage and loaded onto rail cars for hauling to the project site.
Vehicles associated with the project can be moved via rail car to the Watana Project.
3.3 Airstrip
A permanent airstrip would be constructed at a suitable location near the main
construction camp.The runway is assumed to be 6,000 feet in length based on the
project final report and should be capable of accommodating the C-130 Hercules aircraft
as well as small jet passenger aircraft.If construction personnel transport were to be done
by using jet aircraft,such as the Boeing 737-400 or similar,the runway would require
greater length and should be constructed to generally higher standards than that serving
the C-130 aircraft.Roads will connect the airstrip to the camp,village,and dam site.A
small building will be constructed to serve as a terminal and tower and a fuel
truck/maintenance facility will be constructed.A helicopter pad will also be provided.
A temporary airstrip will be constructed to support the early phases of mobilization and
construction.This temporary runway will be 2,500 feet in length and will be located in
the vicinity of the main construction camp.The airstrip will be capable of supporting
smaller aircraft.
The temporary airstrip would eventually be incorporated into one of the main haul roads
after the permanent airstrip is in service.
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4.0 Cost Estimates
Cost estimates were developed for the alternatives examined.The cost estimates are intended to
extend the information provided previously (HDR 2009 and R&M 2009),and to be as
comparable as possible to the previous options.
4.1 RCC Costs
Due to the significant influence of the dam costs in the total project costs,the RCC unit
cost was developed further.
4.1.1 RCC Unit Cost Analysis for Watana Dam
The Watana dam RCC unit cost was analyzed utilizing the contractor estimating
approach of itemizing labor,equipment and materials (L,E &M)costs.
Furthermore the unit cost was analyzed with the L,E &M approach in respect to
three phases;the aggregate production and pozzolan materials delivery;RCC
placement;and RCC production.A detailed breakdown of RCC Unit Costs may
be viewed in Appendix A.
In the 1985 Harza Ebasco study,Borrow Pit E was designated as the
conventional concrete aggregate source (see Figure 4.1-1).Borrow Pit E is
located approximately 2 miles west of the dam axis on the north bank of the
river.
Since the proposed site access for the Low Watana Development is from the
south and aggregate production is scheduled to commence 12 months prior to
RCC production,other borrow pits were reviewed for possible RCC aggregate
sources.In review of the Acres,"Susitna Hydroelectric Project -1980-81
Geotechnical Report”,Quarry Site A was of primary interest due to its close
proximity to the dam and location on the south bank.The previous geotechnical
reports indicate that Quarry Site A contains good quality rock.It has an estimated
23 million cubic yards (mcy)of weathered rock and 71 mcy of good quality rock
above elevation 2300 ft.The geotechnical report described the rock as "very
resistant to abrasion and mechanical breakdown,seldom losing strength or
durability in the presence of water and demonstrating high resistance to
breakdown by freeze-thaw.”The requirements for RCC aggregates are different
than for conventional concrete and effectively any moderately to slightly
weathered,non-reactive rock can be assumed to be worthy of consideration until
proven otherwise.
The Borrow Pit E source was considered the primary source for aggregate in the
1985 Harza Ebasco study,however there would likely be significant excavation
below the Susitna River water line.Due to its close proximity to the dam on the
south bank,good rock qualities and abundance of material,Quarry Site A
appears to be a very attractive RCC aggregate source.Since Quarry Site A is
well above the river level,permitting would likely be less complicated than with
Borrow Pit E.Preliminary volume estimates for the Low Watana Gravity Dam
indicate that approximately 7.6 mcy of roller compacted concrete would be
required.The preliminary RCC mix design requires approximately 80%
aggregate by volume,which results in a total required aggregate volume of 6.1
mcy.
Due to the limited scope of this study,a detailed cost estimate of an aggregate
production facility at Quarry Site A was not done on an itemized basis,rather,the
November 29,2010 Page 15 Final
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costs developed in the 1982 Acres study were utilized and escalated to 2008
dollars.The 1982 unit cost for aggregate production and hauling were escalated
using the USBR Construction Cost Index under the category "Concrete Dams”.
The 1982 study utilized Borrow Pit E as the aggregate source,and it was
assumed that the crushing and screening facilities would be similar for Quarry
Site A.The estimated production from Borrow Pit E was 6.2 mcy,while the
required production at Quarry Site A is approximately 6.1 mcy or less depending
on the selected alternative.The aggregate haul costs were similarly escalated to
2008 dollars,which may be conservative since the round trip distance for Borrow
Pit E was 4 miles compared to an estimated 1 mile for Quarry Site A.Another
source of conservatism is that Quarry Site A has a much deeper groundwater
table and less overburden as compared to Borrow Pit E,which will decrease the
dewatering and clearing costs.
The cementitous material costs $180/ton ($48.86/cy)as determined in the R&M
2009 study were used in this cost analysis!.Also it was assumed that 4 ARAN
Modumix III (MM III)batch plants would be installed to produce an average of
1,000 cy/hr of RCC.The total installation cost of the batch plants was estimated
to be $20 million.Each of these assumptions is consistent with the Full Watana
RCC Analysis.Other important assumptions used in the Full Watana RCC
analysis that were utilized for determining labor and equipment costs are;RCC is
mixed in 8 cy batches;each work day consists of two 10 hour shifts;the
construction season is 5.5 months;and the total number of working days per
season is 165.
As previously mentioned,RCC will be delivered to the dam via conveyors and
chutes,Standard 10 cy (or larger)rear dump trucks will be used to transport the
mixes to various placement locations.The estimated cycle times for dump trucks
was calculated in order to determine the total number of trucks required for
placement.In order to determine the total amount of placement crews required,
the RS Means (RS Means 2010)estimation of cy of RCC placed per day per
crew was adjusted to an hourly placement rate.In this manner the total number of
haul trucks and placement crews was determined by the average RCC production
rate of 1,000 cy/hr.Additional workers including laborers,foreman,operators,
and mechanics,etc.,were estimated based on total number of crews and trucks.
Hourly labor rates for each trade were taken from the RS Means data.This
hourly rate was then prorated to include the overtime for a 10 hr work day and
multiplied by the city cost index for Fairbanks.
The total pieces of equipment was based on the number of placement crews and
batch plant operations.The RS Means (RS Means 2010)Hourly Operational
Costs and Monthly Rental Rates were utilized for the analysis.Each was
multiplied by the Fairbanks City Cost Index.Using the average production rate,a
total number of required work days for placement was determined,which
resulted in 3 construction seasons.The overall rental rates were then calculated
for operational time and idle time.Based on previous experience,it was assumed
that the total equipment operational cost of the batch plant was equal to the total
cost of supply of the batch plant,which has been estimated to be approximately
$20 million.
'Note that this cost is based on the assumption that all supplementary cementitious materials (pozzolan,fly
ash,etc)used in the mix are imported.If suitable sources of pozzolanic materials are identified within
Alaska,substantial reductions in this unit price may well be possible.
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The detailed breakdown of the RCC unit cost resulted in a total per cubic yard
cost of $97.21,which compares very well to the previous RCC unit cost of
$100/cy used in for the Full Watana alternative (R&M 2009).Further analysis of
the aggregate production plant and RCC batch plants may show additional
reductions in costs,but for the scope of this analysis an RCC unit cost of $100/cy
appears valid.
4.1.2 Sizing of RCC Batching Plant
The abutments at the Watana Site are ideal for the transportation of the RCC to
the dam surface using a 'vacuum chute'.The RCC can be lowered 250 to 350
feet for placement without difficulty.Therefore,based on potential quarry
location and using any of the above-mentioned transportation methods,the most
appropriate location for the RCC batching plant for Low Watana would appear to
be at the intake approach channel.This area is already planned to be excavated
for the intake,therefore a separate excavation for a batch plant would not be
required.It would also be approximately two-thirds the height of the dam and
allow for transport of material to the placement elevations above and below the
intake.For the bottom half of the dam,a fixed conveyor could run downwards
from the plant to a hopper at about half height near the axis of the dam.This
hopper could feed a chute that would load the trucks on the dam surface.As the
dam increased in height,sections of the chutes/pipes would be removed.For the
placement of RCC in the upper half of the dam,the fixed conveyor could run
from the concrete batching plant upwards to a hopper just above the crest of the
dam that would then feed a chute for final conveyance to the trucks on the dam
surface.This RCC transportation scheme would provide a very simple and
reliable (and inexpensive)method that has the potential for reducing the unit
costs estimated.
4.2 Camp Cost
The 1982 Acres Feasibility Study cost estimate had assumed for the Watana embankment
dam a camp for 3,600 workers,a project village,and support facilities.The 2009 HRD
report indicated a much smaller camp than anticipated in 1982.
When comparing the ICRD to the RCC dam alone,the smaller volume of the RCC dam
would logically reduce the workforce required.However is anticipated to be 24/7 for 5.5
months.Embankment fill placement for the ICRD is presumably daylight hours for 8-9
months.For RCC,crews are smaller (more highly mechanized operation)but there are
more of them.We have assumed the camp for the RCC dam construction costing about
20 percent less than that for the embankment dam concept (factor of 18.75%was used in
calculations).
4.3 Project Access Cost
It has been assumed that the rail line can be installed at the average rate of $4.7 million
per mile based on Alaska Railroad estimating guidelines.
4.4 Cost Summary
A comparison table of the Low Watana options is presented as Table 4.4-1.Detailed cost
estimates are presented in Appendix B.
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Table 4.4-1:Cost Comparison of Selected Low Watana ICRD and RCC Alternatives
Low Watana
Non-Expandable Low Watana Low Watana RCC -Low Watana RCC -Low Watana RCC
Line Item Name ICRD (1)Expandable ICRD (1)Non-Expandable Expandable Gravity Arch
Total Estimated Const.Costs
(Billions $)4.50 5.00 3.90 4.20 3.60
Low Watana
Non-Ex pandable Low Watana Low Watana RCC -Low Watana RCC -Low Watana RCC
FERC Line #Line Item Name ICRD (1)Expandable ICRD (1)Non-Expandable Expandable Gravity Arch
771A Engineering,Env,and Regulatory (7%)$236,000,000 |$259,000,000 |$203,200,000 |$217,900,000 |$186,600,000
330 Land and Land Rights $121,000,000 |$121,000,000 |$120,900,000 |$120,900,000 |$120,900,000
331 Power Plant Structure Improvements $115,000,000 |$159,000,000 |$121,219,000 |$161,389,000 |]$121,219,000
332.1-.4 Resenoir,Dams and tunnels $1,537,690,000 |$1,718,000,000 |$1,425,110,000 |$1,472,944,000 |$1,220,892,000
332.5-.9 Waterways $590,000,000 |$677,000,000 |$276,342,000 |$387,367,000 |$242,655,000
333 Waterwheels,Turbines and Generators $297,000,000 |$297,000,000 |$297,000,000 |$297,000,000 ]$297,000,000
334 Accessory Electrical Equipment $41,000,000 |$41,000,000 |$40,000,000 |$40,000,000 |$40,000,000
335 Misc Power Plant Equipment $21,000,000 ]$32,000,000 |$21,000,000 |$32,000,000 |$32,000,000
336 Roads,Rails and Air Facilities $232,000,000 |$232,000,000 |$254,700,000 |$254,700,000 |$254,700,000
350-390 Transmission Features $224,000,000 |$224,000,000 |$207,362,000 |$207,362,000 |$207 362,000
63 Main Construction Camp $180,000,000 |$180,000,000 |$123,800,000 |$123,800,000 |$123,800,000
399 Other Tangible Property $16,000,000 |$16,000,000 |$15,800,000 ]$15,800,000 |$15,800,000
71B Construction Management (4%)$135,000,000 |$148,000,000 |$116,100,000 |$124,500,000 |$106,600,000
Total Subtotal Subtotal $3,745,690,000 |$4,104,000,000 |$3,222,533,000 |$3,455,662,000 |$2,969,528,000
Total Contingency [Contingency (20%)$749,138,000 |$821,005,200 |$644,506,600 |$691,132,400 |$593,905,600
Total Total Estimated Const.Costs (Million $)$4,500 $5,000 $3,900 $4,200 $3,600
November 29,2010 Page 18 Final
(1)From
HDR 2009
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
5.0 Project Schedule
The ICRD configuration has two basic construction fronts;dam and powerhouse,which are relatively
independent of each other.With a surface powerhouse near an RCC gravity or gravity arch,the construction
area is less independent and a higher level of coordination would be required during construction operations.
5.1 Dam
The anticipated construction season for RCC or conventional concrete construction is 5.5 months,with a
maximum of 165 working days.Certain activities such as aggregate production and underground work
may be continuous,year-round operations.The ICRD dam configuration has two basic construction
fronts;dam and powerhouse,which are relatively independent of each other.With a surface
powerhouse near an RCC gravity or gravity arch,the construction area is less independent and a higher
level of coordination would be required during construction.
Previous studies (R&M 2009)for the Full Watana RCC option have assumed an average daily
placement rate of 20,000 cy/day,which equates to an average monthly placement rate of 600,000
cy/mn.Currently the maximum peak placement observed rate of RCC placement is 525,000 cy/mn
(MD&A figures for a single production plant).The significantly higher monthly placement rate for the
Watana Dam is due to the plan of installing two separate large RCC production facilities.In order to
optimize the RCC construction during the short construction season at the site,significant production
facilities will be needed.The nominal production capacity of each of the two RCC plants will be
similar to existing recent projects.The Watana site is expected to benefit from aggregate production for
more than the 5.5 months assumed for dam placement as well as advantageous location of the Site A
quarry.Aggregate production will commence at least 12 months prior to the start of RCC placement.
Production are estimated to be double shifts,6 days per week for 8 to 9 months per year and must be
planned to ensure that aggregate production does not impact critical path.The ratio of nominal daily
production capacity to average production rates will be approximately 2.By factoring the volume of the
dam and using average production rates ranging between 20,000-15,000 cy/day,the approximate dam
construction time is shown below in Table 5.1
Table 5.1-1 Time Required for RCC Dam Placement
Alternative Volume (million)Time to place material
Full Watana 15.0 4.5 to 6 years
Low Watana Gravity 8 2.4 to 3.2 years
Low Watana Gravity Arch 6.5 2 to 2.6 years
5.2 Powerhouse
A surface powerhouse would be more subject to climatic constraints than an underground powerhouse
and therefore the construction season for exterior work involving concrete placement would have
similar limitations to dam placement.Once the powerhouse shell is completed,equipment installation
could continue through the winter season.
The underground powerhouse is subject to greater geotechnical uncertainty which could result in
modifications to design plans and potential project delays.
The powerhouse excavation for the surface powerhouse may begin prior to diversion tunnel and
cofferdam completion (potentially providing material for the pre-cofferdam and cofferdam).Similarly
the south abutment excavation and grouting may be performed concurrently with the diversion
construction.Through careful scheduling,it may be possible for the excavation above river level on the
south abutment and excavation for the surface powerhouse to be completed at approximately the same
time as the diversion completion.After diversion,the dam and surface powerhouse foundation
excavation and treatment may continue.The diversion cofferdams may also function for river crossing
such that the north abutment excavation and treatment may begin.
November 29,2010 Page 19 Final
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
Once the powerhouse shell is completed,equipment installation could continue through the winter
season.Therefore the completion of the surface powerhouse shell is a significant project milestone,such
that it should have a target completion date that will not cause it to be a critical path item.
5.3 Combined Dam and Powerhouse Schedule
The schedule for the ICRD Low Watana dam (HDR 2009)shows similar time for dam construction and
powerhouse/transmission lines.More detailed review is required to determine which element is on the
critical path.The RCC dam is expected to be constructed in less time than the ICRD dam,which will
place the powerhouse onto the critical path for construction.
At this point,given the current level of design and schedule we are not able to demonstrate significant
schedule advantage for the overall!project with the RCC scheme.However it should be noted that other
projects using RCC dams that allowed early completion of the dam construction and impoundment of
the reservoir,found the benefit of early generation revenue and availability of additional construction
and management resources combined to allow powerhouse construction and equipment installation to be
significantly accelerated to significant economic advantage.
November 29,2010 Page 20 Final
R&M/Hatch/Linard Supplemental Report -Low Watana RCC Concept
References
1.
10.
11.
12.
13
Actes,1982.Susitna Hydroelectric Project,Feasibility Report.Volumes 1-7.Prepared for the Alaska
Power Authority
Harza-Ebasco Susitna Joint Venture,September 1983,"Winter 1983 Geotechnical Exploration
Program,Volume 1,Main Report”
Harza-Ebasco Susitna Joint Venture,November 1985,"Susitna Hydroelectric Project,Draft License
Application,Volume 1,Exhibit A,Project Description.
Harza-Ebasco Susitna Joint Venture,November 1985,"Susitna Hydroelectric Project,Draft License
Application,Volume 12,Chapter 6 -Geological and Soil Resources”
HDR 2009,Susitna Hydroelectric Project,Conceptual Alternatives Design Report,Final Draft,
November 23,2009
R&M 2009 Susitna Project,Watana and High Devil Canyon RCC Dam Cost Evaluation
Kollgaard,Eric B.and Chadwick,Wallace L."Development of Dam Engineering in the United
States,Prepared in Commemoration of the Sixteenth Congress of the International Commission
on Large Dams by the United States Committee on Large Dams”1988
USACE,Dec 31,1985."Engineering and Design Hydropower,Engineering Manual 1110-2-
1701”
USBR,1958."Hydro-electric Power Plant Costs,Drawing 104-D-701,Series 150 Estimating,
United States Bureau of Reclamation,dated:Nov 7,1958”
American Society of Civil Engineers (ASCE),1989."Civil Engineering Guidelines for
Planning and Designing Hydroelectric Developments.Volume 3 -Powerhouses and Related
Topics”
USACE,2010."HEC-RAS River Analysis System Hydraulic Reference Manual.Version 4.1.
January 2010”
USBR,1986,"Engineering Monograph No.3 -Welded Steel Penstocks
.USBR,2010."Bureau of Reclamation Construction Cost Trends,Jan 2008 -Jul 2010”
14.
15.
16.
USBR,1983."Bureau of Reclamation Construction Cost Trends,Jan 1980 -Oct 1983”
Acres,1982.Susitna Hydroelectric Project,1980-81 Geotechnical Report.Volume 1
Acres,1982.Book B -Watana Dam Development of Unit Costs
November 29,2010 Page 21 Final
Figures
NOTICE TO READER-Some of the Figures have been taken from previous Susitna Project
reports and the conventions for cardinal direction are inconsistent from report to report in many
cases,i.e.North is the top of the page on some figures and the bottom of the page on others.The
Figures were not re-drawn for this report.New figures use the convention of North at the top of
the sheet.Many old figures use the convention of stream flow from left to right;the Susitna River
in the area of the Susitna project flows from east to west.
List ofFigures
Figure 2.2-1 Low Watana ICRD Expandable Plan
Figure 2.2-2 Low Watana ICRD Expandable Section
Figure 2.2-3 Low Watana ICRD Expandable Stage 2 Section
Figure 2.2-4 Low Watana ICRD Power Facilities
Figure 2.4-1 Low Watana RCC Expandable Plan
Figure 2.4-2 Low Watana RCC Expandable Sections and Details
Figure 2.4-3 Low Watana RCC Expandable Elevation Views
Figure 2.4-4 Low Watana RCC Non-Expandable Plan and Detail View
Figure 2.4-5 Low Watana RCC Non-Expandable Sections and Details
Figure 2.4-6 Low Watana RCC Non-Expandable Elevation Views
Figure 2.4-7 Low Watana RCC Non-Expandable Profile
Figure 2.4-8 Low Watana RCC Non-Expandable Gravity Arch Plan
Figure 2.4-9 Low Watana RCC Non-Expandable Gravity Arch Sections and Details
Figure 3.2-1 Low Watana Rail Access
Figure 4.1-1 Borrow Areas
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LOCATION MAP ceace GomerMEYfts
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Figure 4.1-1 Borrow Areas
Appendix A
Breakdown of Unit Cost Analysis for RCC
11/29/2010
Low Watana RCC Dam
RCC Unit Cost Analysis
November 3,2010
Low Watana RCC Assumptions/Totals USBR Construction Cost Index
Total RCC Volume (cyd)7,600,000 USBR Category Concrete Dams
Percent of Aggregate by Volume 80.3%Jan 1982 Factor 128
Total Required Aggregate Volume (cyd)6,102,800 Oct 2008 Factor 334
Est.Round Trip Haul Dist.From Borrow Pit A to Processing (mi.)1 Jul 2010 Factor 325
Low Watana Embankment 1982 Assumptions/Totals (Book B -Development of Unit Costs)
Total Volume (cyd)6,200,000
Total Production Hours (hr)13,000
Avg Production Rate (cyd/hr)(Not in Book B)476.92
Est.Round Trip Haul Dist.From Borrow Pit E to Processing (mi.)4
*Costs used for 1982 Aggregate Production will be escalated to 2010 costs.Total aggregate
volumes are very similar.Also the haul costs will be conservative since haul distance to
Borrow Pit A is less than Borrow Pit E.
Low Watana Embankment 1982 Aggregate Production Costs (Book B -Development of Unit Costs)
Description Labor Materials Equipment Total
Aggregate Processing $16,584,230.00 |}$2,930,400.00 |$36,322,000.00 |$55,836,630.00
Install &Removal of Plant $1,650,000.00 |$-$-$1,650,000.00
Total Aggregate Processing Cost ($/cyd)$18,234,230.00 |$2,930,400.00 |$36,322,000.00 |$57,486,630.00
Aggregate Processing Unit Cost ($/cyd)2.941 0.473 5.858 9.272
Aggregate Hauling Unit Cost ($/cyd)1.104 0.01 3.583 4.697
Total Aggregate Production Cost ($/cyd)$4.05 |$0.48 |$9.44 |$13.97
USBR Ratio Jul 2010:Jan 1982 2.54 2.54 2.54 2.54
Jul 2010 Total Agg Production Cost ($/cyd)$10.27 |$1.23 |$23.97 |$35.47
Total Cost of 4 ARAN Modumix {I}Batch Plants incl Installation $20,000,000.00
Total Batch Plant Unit Cost ($/cyd)$2.63 |$2.63
Cement &Fly Ash Cost ($/cyd)$-$48.86 |$:$48.86
RCC Placement Cost ($/cyd)$1.22 |$-$3.22 |$4.44
RCC production Cost ($/cyd)$0.75 |$-$5.05 |$5.81
Final RCC Unit Cost ($/cyd)$12.24 $50.09 $34.88 $97.21
RCC Labor Costs
City Cost Index for Fairbanks,AK
Division Installation Index
0241,31-34 Site &Infrastructure,Demolition 131.5
03 Concrete 115.3
Adjustment Factor for Overtime
RS Means Work Day (hr)8
Low Watana RCC Work Day (hr)10
Pay Rate Increase for Overtime 1.5
Ajustment Factor 1.375
RS Means 2010 -:Total Hourly ;Total HourlyWervorsTradeTotalHourlyRateAdjustmentRateincladreRateatWatana
.incl.O &P ($/hr)Overtime ($/hr)
7|Equipment Operator (med.)-Dozer $64.30 1.375]$88.41 131.5|$116.26
5 7|Equipment Operator (light.)-Roller $61.85 1.375!$85.04 131.5]$111.83
a 7|Laborers -RCC Placement $48.45 1.375!$66.62 131.5]$87.60
5 7|Foreman Average,Outside $68.55 1.375]$94.26 131.5|$123.95
5 5|Laborers -Flagman (Directing Truck Traffic)$48.45 1.3751 $66.62 131.5]$87.60
Ee 4|Mechanic -Trucks,Dozers &Rollers $66.75 1.375]$91.78 131.51 $120.69
8 1|Electrician -Converyors &Equipment $72.85 1.375]$100.17 131.5]$131.72
a 25|Truck Drivers (Light)-8 cyd Rear Dump $49.20 1.375{$67.65 131.5]$88.96
2 2|Truck Drivers (Light)-Fuel Trucks $49.20 1.375]$67.65 131.5]$88.96
a4 2|Equipment Operator (light.)-Skid Steer Loader $61.85 1.375]$85.04 131.5|$111.83
1|Site Supervisor $82.26 1.3751 $113.11 131.51 $148.74
68/Total Hourly Wages $1,218.15
Average RCC Production Rate (cyd/hr)1000
Total Labor Costs per Unit ($/cyd)$1.22
S 4|Batch Plant Operator $82.26 1.375]$113.11 131.5}$148.74
8 8|Equipment Operator (med.)-Front End Loader $64.30 1.375]$88.41 131.5]$116.26
8 2|Mechanic-Batch Plant $66.75 1.375]$91.78 131.5}$120.69
Oo 1}Electrician -Batch Plants $72.85 1.375]$100.17 131.5}$131.72
8 7|Laborers -Flagman (At Dishcarge Chutes)$48.45 1.375]$66.62 131.51 $87.60
a 1|Site Supervisor $82.26 1.375|$113.11 131.51 $148.74
23}Total Hourly Wages $753.75
Average RCC Production Rate (cyd/hr)1000
Total Labor Costs per Unit ($/cyd)$0.75
91
Total #of Workers,assumes (2)-10hr Shifts 182
RCC Equipment Costs
City Cost Index for Fairbanks,AK
Division Installation Index
0241,31-34 Site &Infrastructure,Demolition 131.5
03 Concrete 115.3
Assumptions /Variables
Shift Duration (hr)10,
Shifts per Day 2
Work Hours per Day 20
Average Production RCC Production Rate (cyd/hr)4,000
Average RCC Production Per Day (cyd/day)20,000
Total RCC Volume (cyd)}7,600,000
Required Days of Production 380
Construction Season (Months/Yr)5.5
Construction Season (Days/Yr}165
Minimum Construction Seasons.2.30
Total Number of Construction Season 3}
Rental Rate Adjustment Factor for Unit Down Time
Total Months in Operation per Year 5.5
idle Equipment Cost vs Operation 75%
Total RCC Construction Seasons 3
Total Months of Operation 16.5
Total Months Idle 13.0
Daily Operation Costs Equipment Rental Costs
RS Means 2010 -Hours of Total Equipment Total Equipment |Total Operation +
#of Units Trade Total Hourly Rate |Operation Production Operation Cost clan Monthy Rental ar pertal Rentai Cost per Rental Cost per Total Ait Units Total Inct Cost Index
incl.O &P($/nr)per Day Days per Unit Unit Unit
7|Dozer 200 hp 68.60 20 380 521,360.00 16.5 9,650.00 13.0 253,312.50 774,672.50 5,422,707,50 7,130,860.36
7{Vibratory Roller 35 hp 10.40 20 380 79,040.00 16.5 275.00 13.0 59,718.75 138,758.75 971,311.25 1,277,274.29
Ee 25|Truck,Dump,2-axle,12 ton,8 cy payload 33.35 20 380 253,460.00 16.5 2,025.00 13.0 $3,156.25 306,616.25 7,665,406.25 10,080,009.22
a 2{Fuel Truck (Used RS Means Water Truck Data}84.65 20 380 643,340.00 16.5 290,00 13.0 490,312.50 833,652.50 4,667,305,.00 2,192,506.08
c 1/Forklift,straight mast,21'lift,4WD 20.20 20 380 153,520.00 16.5 2,225.00 13.0 58,406.25 211,926.25 211,926.25 278,683.02
=2|Skid Steer Loader,1 cyd,78 hp 19.00 20 380 144 400.00 16.5 2,075.00 13.0 54,468.75 198,868.75 397,737.50 523,024.81
d 13|Pickup Truck,4WD.13.50 20 380 402,600.00 16.5 645.00 13.0 16,931.25 419,531.25 1,553,906.25 2,043,386.72
5 7|Laser Level -Grading 1.17 20 380 8,892.00 16.5 700.00 13.0 18,375.00 27,267.00 190,869.00 250,992.74
®40|Floodlights,trailer mounted w generator -(4)300 watts 4.20 10:380 15,960.00 16.5 795.00 13.0 20,868.75 36,828.75 368,287.50 484 298.06
o 3{Misc Hand Tools 5.00 20 380 38,000.00 16.5 850.00 13.0 22,312.50 60,312.50 180,937.50 237,932.81
°7 Total Placement Equipment Costs 24,498,968.11
Total RCC cyd 7,600,000
Total Placement Equipment Cost per Unit RCC ($/cyd) $3.22
&]Front End Loader,10 cyd,620 hp 129.55 20 380 984 580.00 16.5 23,500.00 13.0 616,875.00 1,601,455.00 12,811,640.00 16,847 306.60
2|Forklift,straight mast,21"lift,4WD 20.20 20 380 153,520.00 16.5 2,225.00 13.0 58,406.25 211,926.25 423,852.50 $57,366.04
&8|Pickup Truck,4WD 13.50 20 380 102,600.00 16.5 645.00 13.0 16,931.25 419,531.25 956,250.00 1,257,468.75
8 8}Floodiights,trailer mounted w generator -(4)300 watts 4.20 10 380 15,960.00 16.5 795.00 13.0 20,868.75 36,828.75 294,630.00 387,438.45
8 2{Misc Hand Tools 5.00 20 380 38,000.00 16.5 850.00 13.0 22,312.50 60,312.50 120,625.00 158.621.88
iw 28 3 19,208,201.71
8 Ls Total sum of ail Batch Piants and Conveyence Systems (Assume Equal to all other Production Equipment Costs)$19,208,201.71
va Total Equipment Costs $38,416,403.43TotalRCCcyd7,600,000|Total Production Equipment Cost per Unit RCC ($/cyd)$§.05
RCC PRODUCTION
Full Watana RCC Low Watana RCC
Parameter US Standard Metric US Standard -Metric
Quantity 45,000,000/Cy 11,468,300"7,600,000|Cy -11,468,300/2
Construction season (months/year)5.5)Mn/yr 5.5|Mn/yr 5.5iMn/Yr §.5|Mn/yr
Construction seasons 5iYr 51Yr 3.00/Yr :;51Yr
Placing days/year 165/Yr 160]Yr 4165/Yr
_
460/Yr
Total required placing days based on avg daily 825|Dy 800/Dy 380]Dy 800)Dy
placing rate :A
Total placing days 825|Dy 800]Dy 495|Dy '800)|Dy
z months 25|Mn 25{Mn 12.66666667|Mn 25)Mn
Nominal monthly capacity 600,000/Cy 458,732|)°600,000/Cy 8 458,732)"
Average daily placing rate 20,000|Cy 15,2911 Mo 20,000/Cy »15,294]
Required daily average capacity 44,920|Cy 34,3441 N48 44,920|Cy 34,344|3
Required maximum month 1,200,000/Cy 917,464]py?1,200,000/Cy 917,464)n3
Required nominal capacity 15,000,000/Cy 11,468,300}n4°7,600,000/Cy 11,468,300)
Mixer capacity,8ICy 6/2 8ICy :6ime
Total mix time -start charge to complete 2|Min 2|Min 2)Min _2|Min
discharge,min oe
batches/mixer/hour 30/Per Hr 30]Per hr 30|Per Hr 4,=30/Per hr
Vol/mixer/hour 235)/Cy 180)3 235/Cy 18013
Total #of mixers 10}Ea 10/Ea 10/Ea :10/Ea
Nominal hourly production 2,350/Cy 1,800]e 2,350|Cy co ee or 800/35
Daily hours 20}Hr 20}Hr 20/Hr 20/Hr
Nominal daily production 47 ,000/Cy 36,000/p4°47,000|Cy f 36,000}py3
Nominal monthly 1,175,000|Cy 900,000}y43 1,175,000|Cy :900,000/ye
Ratio nominal to average 1.96 1.96 1.96 :1.96
Long term average monthly 600,000;Cy 458,732|M5 600,000}Cy cee 5 468,732 15
Total RCC placed 15,000,000/Cy 11,468,300]p43 7,600,000|Cy 11,468,300)4°
Appendix B
Detailed Cost Estimate
11/29/2010
SUSITNA PROJECT -LOW WATANA DAM OPTIONS COST SUMMARY
Table 4.4-1:Cost Comparison of Selected Low Watana ICRD and RCC Alternatives
Low Watana
Non-Expandable ICRD Low Watana Low Watana RCC -Low Watana RCC -Low Watana RCC
Line Item Name (1)Expandable ICRD (1)Non-Expandable Expandable Gravity Arch
Total Estimated Const.Costs (Billions
$)4.50 5.00 3.90 4.20 3.60
Low Watana
Non-Expandable ICRD Low Watana Low Watana RCC -Low Watana RCC -Low Watana RCC
FERC Line #Line Item Name (1)Expandable ICRD (1)Non-Expandable Expandable Gravity Arch
71A Engineering,Env,and Regulatory (7%)$236,000,000 |$259,000,000 |$203,200,000 |$217,900,000 |$186,600,000
330 Land and Land Rights $121,000,000 |$121,000,000 |$120,900,000 |$120,900,000 |$120,900,000
331 Power Plant Structure Improvements $115,000,000 f $159,000,000 |$121,219,000 |$161,389,000 |$121,219,000
332.1-.4 Reservoir,Dams and tunnels $1,537,690,000 |$1,718,000,000 |$1,425,110,000 |$1,472,944,000 |$1,220,892,000
332.5-.9 Waterways $590,000,000 }$677,000,000 |$276,342,000 |$387,367,000 |$242,655,000
333 Waterwheels,Turbines and Generators $297,000,000 |$297,000,000 |$297,000,000 |$297,000,000 |$297,000,000
334 Accessory Electrical Equipment $41,000,000 |$41,000,000 |$40,000,000 |$40,000,000 |$40,000,000
335 Misc Power Plant Equipment $21,000,000 |$32,000,000 |$21,000,000 |$32,000,000 f $32,000,000
336 Roads,Rails and Air Facilities $232,000,000 |$232,000,000 |$254,700,000 |$254,700,000 |$254,700,000
350-390 Transmission Features $224,000,000 |$224,000,000 I$207,362,000 |$207,362,000 |$207,362,000
63 Main Construction Camp $180,000,000 }$180,000,000 |$123,800,000 |$123,800,000 F $123,800,000
399 Other Tangible Property $16,000,000 |$16,000,000 |$15,800,000 |$15,800,000 |$15,800,000
71B Construction Management (4%)$135,000,000 |$148,000,000 |$116,100,000 |$124,500,000 |$406,600,000
Total Subtotal Subtotal $3,745,690,000 |$4,104,000,000 |$3,222,533,000 |$3,455,662,000 |$2,969,528,000
Total Contingency |Contingency (20%)$749,138,000 |$821,005,200 |$644,506,600 }$691,132,400 |$593,905,600
Total Total Estimated Const.Costs (Million $)$4,500 $5,000 $3,900 $4,200 $3,600
Page 1 of 61
(1)From
HDR 2009
Page 1 of 61