HomeMy WebLinkAboutAugustine Island Interconnection Feasibility Study Report - FINAL - Dec 2024 - REF Grant 7015024 AUGUSTINE ISLAND INTERCONNECTION FEASIBILITY STUDY REPORT
December 2024
Prepared for
Alaska Electric & Energy Cooperative, Inc., a subsidiary of Homer
Electric Association
3977 Lake Street
Homer, Alaska 99603
Prepared by
3003 Minnesota Drive, Suite 302
Anchorage, Alaska 99503
With partners:
Augustine Island Interconnection Feasibility Study Report ii December 2024
TABLE OF CONTENTS EXECUTIVE SUMMARY ....................................................................................................ES-1 1. SCOPE OF WORK................................................................................................................1 1.1 Background and Assumptions ......................................................................................1 1.2 Feasibility Study Approach ..........................................................................................2 1.3 Report Structure ...........................................................................................................2 2. ROUTING OPTIONS ...........................................................................................................3 2.1 Subsea Cable Routing ..................................................................................................3
2.2 Onshore Routing ...........................................................................................................5
2.2.1 Augustine Island Routing .................................................................................6
2.2.2 Anchor Point Option 1: North of Point to Anchor Point Substation ................7
2.2.3 Anchor Point Options 2 and 3: South of Point to Anchor Point Substation ....7
2.3 Anchor Point Routing Discussion ................................................................................7
3. PRELIMINARY ENGINEERING ANALYSIS ...................................................................9
3.1 Selection of HVAC or HVDC Subsea Transmission ...................................................9
3.1.1 HVAC Subsea Design ....................................................................................10
3.1.2 HVDC Subsea Design ....................................................................................10
3.1.3 HVAC Versus HVDC Discussion ..................................................................10
3.1.4 Subsea Cable Energization/Black Start ..........................................................11
3.2 Cable Installation ........................................................................................................12
3.2.1 Subsea Cable Installation ...............................................................................12
3.2.2 Nearshore Cable Installation ..........................................................................13
3.3 Interconnection Substations .......................................................................................15
3.3.1 Augustine Island Substation (Plant 13.8kV to 115kV) ..................................15
3.3.2 Anchor Point Substation (Interconnection 115kV to 13.8kV) .......................16
3.4 Overhead Transmission ..............................................................................................18
4. PROJECT COSTS AND ECONOMICS .............................................................................20
4.1 HVAC Versus HVDC Costs ......................................................................................20
4.2 Budgetary Cost Estimate ............................................................................................21
4.3 Tax Incentives and Funding Opportunities ................................................................21
5. PERMITTING AND LICENSING EVALUATION ..........................................................24
5.1 Land Lease or Acquisition Needs ..............................................................................24
5.1.1 Augustine Island Surface ................................................................................24
5.1.2 Cook Inlet .......................................................................................................24
5.1.3 Anchor Point Cable Landing ..........................................................................25
5.1.4 Anchor Point Transmission Alignment: Option 1 ..........................................25
Augustine Island Interconnection Feasibility Study Report iii December 2024
5.1.5 Anchor Point Transmission Alignment – Options 2/3 ...................................26 5.2 Preliminary Permitting Requirements List .................................................................26 6. ENVIRONMENTAL SCREENING ...................................................................................27 6.1 Overall Scoring of Routing Options ...........................................................................27 6.2 Specific Environmental Considerations .....................................................................28 7. PROJECT SCHEDULE.......................................................................................................31 8. REFERENCES ....................................................................................................................33
LIST OF TABLES
Table 2-1: Summary of Evaluated Routes ...................................................................................... 3
Table 3-1: Major Equipment Needs for Anchor Point Substation Expansion .............................. 16
Table 3-2: Major Equipment Needs for New Anchor Point Substation ....................................... 17
Table 3-3: Quantity of Monopole Towers .................................................................................... 19
Table 4-1: HVAC and HVDC Solution Cost Comparison ........................................................... 20
Table 4-2: Budgetary Cost Summary (HVDC only) .................................................................... 21
Table 4-3: Financing Schedule ..................................................................................................... 23
Table 6-1: Initial Environmental Screening of Routing Options .................................................. 28
Table 6-2: Environmental Considerations .................................................................................... 29
Table 7-1: Conceptual Project Schedule Duration ........................................................................ 31
LIST OF GRAPHICS
Graphic 2-1: Elevation Profile Along Proposed Cable Routes ....................................................... 4
Graphic 2-2: Elevation and Slope Profiles at Proposed Landfalls .................................................. 5
Graphic 2-3: Potential Landing Area at Augustine Island Headland ............................................. 6
Graphic 3-1: Simplified Diagram of Design Components ............................................................. 9
Graphic 3-2: Example of a Subsea Service Crossing by a Power Cable ...................................... 13
Graphic 3-3: Example of Nearshore Connection using HDD ...................................................... 14
Graphic 3-4: Sea Stallion 2 Plough Burying Cable Nearshore ..................................................... 14
Graphic 3-5: Simplified Single Line Diagram for the HVDC Voltage Source Converter ........... 15
Graphic 3-6: Design of a Monopole Transmission Tower Suitable for 80 kV ............................. 19
Graphic 6-1: Overarching Topics Evaluated During Environmental Review .............................. 27
Augustine Island Interconnection Feasibility Study Report iv December 2024
LIST OF APPENDICES Appendix A: Routing Maps Figure 1-1: Proposed Routes for Augustine Interconnect Figure 1-2: Proposed Landfall and Overhead Route at Augustine Island Figure 1-3: Proposed Landfall and Overhead Route at Anchor Point – Option 1 Figure 1-4: Proposed Landfall and Overhead Route at Anchor Point – Option 2/3 Figure 2: Wetland and Waterways, Anchor Point Area
Figure 3: Land Ownership, Anchor Point Area
Appendix B: Electrical Diagrams
E-100: 115/34.5kV Existing Substation Power Line Single Diagram
E-101: 115/34.5kV Expansion Substation Power Line Single Diagram
E-102: 115/34.5kV New Substation Power Line Single Diagram
E-103: 115/34.5kV Generation Power Line Single Diagram
E-400: 115/34.5kV Substation Expansion Plan
E-401: 115/34.5kV Substation Plan
E-402: 115/34.5kV Substation Plan
Appendix C: Cost Estimate Details
Appendix D: Permitting Matrix
Appendix E: Environmental Scoring Matrix
Appendix F: Project Schedule
Appendix G: Supplemental Information
Augustine Island Interconnection Feasibility Study Report v December 2024
ACRONYMS AND ABBREVIATIONS µF/km microfarads per kilometer A amperes AAC Alaska Administrative Code AC alternating current AEEC Alaska Electric and Energy Cooperative, Inc.
CatEx categorical exclusion
DC direct current
DNR Alaska Department of Natural Resources
EA environmental assessment
EIS environmental impact study
HDD horizontal directional drilling
HEA Homer Electric Association
HVAC high voltage alternating current
HVDC high voltage direct current
IPP independent power producer
ITJP intertidal joining pit
km kilometer
KPB Kenai Peninsula Borough
kV kilovolt
m meter
MACRS modified accelerated cost recovery system
mm2 square millimeters
MVA megavolt-amps
MW megawatt
NEPA National Environmental Policy Act
ROW right of way
Augustine Island Interconnection Feasibility Study Report ES-1 December 2024
EXECUTIVE SUMMARY This Augustine Island Interconnection Feasibility Study Report was prepared by Geosyntec Consultants, Inc., in collaboration with COWI and Qualus, Inc., for the Alaska Electric and Energy Cooperative, Inc. (AEEC). The study evaluates the feasibility of delivering power from a possible future geothermal plant on Augustine Island in Cook Inlet to the western Kenai Peninsula at Anchor Point, Alaska. The study aims to evaluate the benefits and risks, identify permitting and environmental considerations, and develop high-level cost estimates and a schedule for the project. Three potential routing and interconnect options were evaluated. All three options originate
from the same location on Augustine Island at the possible future geothermal plant, where a
substation would be constructed, and include a subsea high voltage (HV) cable entering Cook
Inlet toward Anchor Point. Option 1 subsea cable lands just north of Anchor Point, where the
cable would be horizontally directionally drilled (HDD) through the bluff for landfall near the
Sterling Highway. The buried cable would transition to overhead transmission along an east-
trending path 3.2 km (2 miles) to connect to the existing grid via an expansion to the existing
substation at Anchor Point. Options 2 and 3 would land at the same location, just south of
Anchor Point on a parcel owned by the Alaska Department of Natural Resources (DNR). The
buried cable would transition to overhead transmission east, then north to the Anchor Point
substation 8.5 km (5.3 miles). For Option 2, the connection to the existing grid would be via an
expansion to the existing substation at Anchor Point. For Option 3, the connection would be via
a new substation located adjacent to the existing substation.
An analysis of whether the subsea cable should be HV direct current (DC) or HV alternating
current (AC) was completed. The basic parameters used in this conceptual design suggest that the
distance of the route across Cook Inlet, estimated at 111 km (69 miles), is too long for the
HVAC solution to be viable. However, an HVAC solution could be substantially lower cost
than an HVDC solution. The cost difference for this project is estimated at over $100M,
driven primarily by DC-AC converter stations and more complex design. In future more
detailed design efforts, it may be reasonable to further consider whether HVAC is viable for
this transmission project.
A conceptual design was prepared for an HVDC solution to transmit 70 megawatts (MW)
from Augustine Island and connect to the existing 115 kilovolt (kV) transmission system at
Anchor Point. The design consists of a new substation and converter station on Augustine Island,
an HVDC subsea cable, HVDC overhead transmission lines from cable landfall to the converter
station both on Augustine Island and at Anchor Point, and either a new substation at Anchor
Point or an expansion of the existing substation at Anchor Point.
Significant coordination between government agencies and private landowners will be needed for
leases, licenses, and permits. Leases from the Bureau of Ocean Energy Management (BOEM) and
DNR are needed for the subsea cable route. At least one existing communications cable, existing
oil and gas mineral leases in Cook Inlet, and an existing lease on Augustine Island will be crossed
by the conceptual routes that will require coordination with DNR and current lease holders.
For both potential overhead line routes in Anchor Point, sections of existing right-of-way are not
wide-enough to accommodate a new 115kV transmission line, and new right-of-way is needed
across both public and private parcels.
Augustine Island Interconnection Feasibility Study Report ES-2 December 2024
At least one permit required will trigger a National Environmental Policy Act (NEPA) review. An environmental assessment will be needed for the project. High level environmental screening of the routing and infrastructure identified the need for archeological evaluation on both the marine and onshore environments, wetland surveys in Anchor Point, seismic and geotechnical evaluations for the entire route, fisheries evaluation including in commercial areas of Cook Inlet, and consideration of bird and marine mammal impacts particularly during construction. The cost estimate for the conceptual design reveals that the subsea cable materials, subsea cable installation, and modular converter stations are the key cost drivers at 85% of total cost. The total
project cost is estimated at $225M to $485M for all three evaluated options. The variability in
costs associated with negotiating easements and right-of-way to differentiate routing is not well
defined at this level of conceptual design. Similarly, the variability in costs associated with
changes to the existing Anchor Point microgrid to differentiate substation expansion or
substation replacement is not well defined at this level of conceptual design. However, the cost
impacts are expected to be less than 5% of the overall project cost.
There is potential for a federal tax credit of 30% for qualifying geothermal projects that meet
apprenticeship requirements. Assuming that the project footprint is within a qualified energy
community, the project may be eligible for an additional 10% tax credit on the total installed cost.
A shortened depreciation schedule of 5 years for property may also be applicable for this project.
The overall project schedule is estimated at 12 to 16 years. The permitting and engineering design
studies will require lead time of approximately 2 years prior to developing a financing approach
and final design. Once the project is designed and ready for procurement, large electrical
equipment including transformers and converters have a long lead time of approximately 2 to 3
years. Cable installation is anticipated to take 2 years to complete. A financing schedule was
prepared to understand the borrowing needs over the project duration.
Augustine Island Interconnection Feasibility Study Report 1 December 2024
1. SCOPE OF WORKGeosyntec Consultants, Inc., and our project partners, COWI and Qualus, Inc., have prepared this Augustine Island Interconnection Feasibility Study Report in support of Homer Electric Association (HEA). HEA is evaluating prospective geothermal power delivery from Augustine Island in Cook Inlet to the western Kenai Peninsula at Anchor Point, Alaska. HEA has obtained approval from the Alaska Energy Authority, the Renewable Energy Grant Fund and Recommendation Program administrator, to proceed with a phased evaluation of the
renewable energy project addressed herein. In this phase, the goals are to evaluate benefits and
risks, identify permitting and environmental considerations, and develop high-level cost estimates
and a schedule.
1.1 Background and Assumptions
HEA’s strategic plan for 2024 through 2026 identifies geothermal energy as an area of focus under
its priority for energy resource diversification. As part of this priority, HEA is interested
in assessing the economics of geothermal prospects. Geothermal prospecting is underway
on Augustine Island on the west side of Lower Cook Inlet in the Kenai Peninsula Borough
(KPB), within which HEA territory encompasses a vast majority of the population and
communities. Initial geologic modeling suggests the potential for a high temperature
subsurface geothermal resource related to Augustine volcano, an active stratovolcano on
Augustine Island that is actively monitored by the Alaska Volcano Observatory.
The Alaska Department of Natural Resources (DNR) authorized a noncompetitive geothermal
prospecting permit to GeoAlaska, LLC, in 2022 and again in 2024 for an area on Augustine
Island. In the summers of 2023 and 2024, GeoAlaska, LLC, conducted preliminary
geothermal exploration on Augustine Island in the form of magnetotelluric (MT) data
collection to identify the potential for geothermal resources. Drilling of a temperature
gradient well to further characterize potential energy is proposed. Based on initial geologic
modelling, GeoAlaska, LLC, estimates production between 50 and 100 megawatts (MW) using
traditional geothermal methods. For the purposes of this study, it is assumed that a geothermal
facility would consist of two 35 MW plants for a total of 70 MW.
The ownership model of the potential geothermal project is not determined and is beyond the
scope of this study. It is assumed that the prospective geothermal power plant on Augustine Island
would be developed by an independent power producer (IPP), including siting the plant, drilling
wells, and installing the turbines and generators. As part of that effort, the IPP would
presumably construct infrastructure, including a dock or port facility on Augustine Island,
roads and access routes to the plant from the port, accommodations for workers, and
communications. For that reason, no costs or evaluation of the plant infrastructure on
Augustine Island is included in this study. This study assumes HEA would purchase 70 MW of
power from the IPP and be responsible for transmission of that power from the plant to the
western shore of the Kenai Peninsula, tying into the existing 115 kilovolt (kV) system at Anchor
Point.
Augustine Island Interconnection Feasibility Study Report 2 December 2024
1.2 Feasibility Study Approach The feasibility study was conducted at a desktop reconnaissance level using publicly available data and professional judgement to evaluate transmission of power. The study comprised overhead lines from the geothermal plant to a substation on Augustine Island, a subsea cable across Cook Inlet, and overhead lines from the subsea cable to a substation in Anchor Point for connection to the existing HEA electrical 115 kV transmission system. A conceptual design for electrical transmission was prepared, which included evaluating options for both electrical elements and routes. Single line drawings and general arrangement diagrams of the existing Anchor Point substation are provided, as well as drawings of the conceptual design of a substation expansion or
new substation. Maps of the possible routes are provided, with detail on potential environmental
and permitting due to routing. The potential benefits and risks of each option are discussed. Based
on the conceptual design and routing options, high level budgetary costs are estimated along with
project financing and tax incentives. The cost estimate is focused on the design, procurement of
materials and equipment, construction, and commissioning, but also includes consulting,
permitting, and environmental cost estimates.
1.3 Report Structure
The report is structured into six sections, as described below:
•Section 2: Routing Options evaluates proposed routing options for an undersea cable
across Lower Cook Inlet and overhead circuits from the western shore of the Kenai
Peninsula to a substation. Maps and figures are provided in Appendix A.
•Section 3: Preliminary Engineering Analysis discusses the method of transmitting
power from Augustine Island to the Kenai Peninsula, and the major new equipment to
connect to the existing transmission system. Electrical diagrams are provided in
Appendix B.
•Section 4: Project Costs and Economics provides a budgetary cost estimate for the
design, procurement of materials and equipment, construction, and commissioning.
Detailed tables and additional information is provided in Appendix C.
•Section 5: Permitting and Licensing Evaluation discusses land lease requirements and
a preliminary list of permitting requirements. A detailed permit matrix is provided in
Appendix D.
•Section 6: Environmental Screening evaluates potential environmental impacts and risk
factors for installation of the interconnection, including how they relate to the
permitting requirements. An environmental screening matrix is provided in
Appendix E.
Section 7 and Appendix F include a project schedule; Section 8 includes sources cited herein.
Appendix G provides supplementary information beyond what is included in the main report.
Augustine Island Interconnection Feasibility Study Report 3 December 2024
2.ROUTING OPTIONSThree routes for the interconnection from Augustine Island to the western shore of the Kenai Peninsula were evaluated as outlined by AEEC. The routes originate from the same point on Augustine Island, at the proposed geothermal plant. Option 1 intersects land at the north end of Anchor Point. Options 2 and 3 intersect land at the south end of Anchor Point. Between the two shorelines, a subsea cable would be laid. The routes are summarized in Table 2-1 and shown on appended Figure 1-1 in Appendix A.
Table 2-1: Summary of Evaluated Routes
Option
Origin Point:
Augustine Island
Geothermal
Plant
Overhead:
Plant to New
Substation
Subsea
Cable across
Cook Inlet
Subsea
Cable
Landing
Point
Overhead:
Landing to
Substation
Anchor Point
Substation
1
59.342333°
latitude
-153.433333°
longitude
2.7 km
(1.7 miles) of
new overhead
111 km
(69 miles)
with 1.13 km
(0.70 miles)
buried at
landfalls
Near MP
155
Sterling
Hwy
3.2 km (2.0
miles) of new
overhead Expansion of
existing Anchor
Point substation
2 111 km
(69 miles)
with 1.36 km
(0.85 miles)
buried at
landfalls
59.7448°
latitude
-151.8490°
longitude
8.5 km
(5.3 miles) of
new
overhead 3
New substation
near existing
Anchor Point
substation
km: kilometers
2.1 Subsea Cable Routing
At this point in the conceptual design, routing of the subsea cable can be approximated as a straight
line between the two shorelines. Considerations during design in subsea routing include avoidance
of protected areas (e.g., cultural resources, essential fish habitat), large seafloor elevation changes
(e.g., shoals, ledges, boulders, slopes), strong currents, areas of subsurface drilling or offshore
activities including dredging, and areas with increased seismic risk. The area of Lower Cook Inlet
where the cable would be routed does not show significant trenches or seafloor obstacles but would
require additional evaluation for refined routing. Graphic 2-1 shows the elevation profile along the
straight-line subsea cable route across Cook Inlet. During future design development, the subsea
cable routing would be further refined and finalized, including via more detailed studies such as
hydrographic surveys, geotechnical surveys, archeological surveys, seabed floor movement
tracking, and a cable burial risk assessment. Survey vessels are typically used for gathering this
information with several types of equipment like multi-beam sonar, side scan sonar, cone
penetration testing, and vibracoring. For the purposes of this study, the route for the subsea cable
is estimated at 111 kilometers (km; 69 miles).
Augustine Island Interconnection Feasibility Study Report 4 December 2024
Graphic 2-1: Elevation Profile Along Proposed Cable Routes
Near the western shore of the Kenai Peninsula, there are several parcels leased for oil and gas
mineral exploration, but there are no active drilling operations or platforms. The cable route should
avoid leased parcels as much as possible to minimize conflicts with mineral exploration. However,
it is possible to coordinate multiple leases if the uses do not conflict. At least one existing subsea
cable is present that crosses the proposed transmission route: a fiberoptic cable owned by General
Communications, Inc. that runs from Homer to Kenai. Laying of electrical transmission cable over
fiberoptic cable does not cause concern but should be considered in design. This is further
discussed in Section 3.2.1 and shown in Graphic 3-2.
Landfall at both the Augustine and Anchor Point shorelines would be completed by horizontal
directional drilling (HDD) and may affect routing. Additional geotechnical studies will be needed
to evaluate the soils to aid in design of the landfall HDD. On the Augustine side, the shoreline is
relatively rocky, but with plenty of beaches and small inlets that would allow for cable landing
without concern for existing infrastructure. On the Anchor Point side, a large bluff approximately
75 meters (m; 250 feet) is present, as is the outlet and floodplain of the Anchor River. For both
subsea cable ends, erosion rates will affect cable burial needs for landfall. The average erosion of
nearby bluffs is approximately 0.9 m (3 feet) per year (United States Army Corps of Engineers
[USACE] 2008). A more comprehensive study of erosion at the proposed landfall locations should
be completed during routing refinement. The buried cable at the landfall ends would extend a
minimum of 250 m (820 feet) and likely longer depending on the location of cable termination.
Graphic 2-2 shows the elevation and slope profiles for the landing points near Anchor Point.
Augustine Island Interconnection Feasibility Study Report 5 December 2024
Graphic 2-2: Elevation and Slope Profiles at Proposed Landfalls
Landing at Augustine Island
Option 1: Landing north of Anchor Point
Options 2/3: Landing south of Anchor Point
2.2 Onshore Routing
Where the subsea cable daylights and transitions to an overhead transmission line, a cable sealing
end compound is proposed to transition from underground to overhead, with overhead high voltage
direct current (HVDC) lines used to reach the substation. A converter station would be positioned
adjacent to the substation to convert from DC to alternating current (AC).
Augustine Island Interconnection Feasibility Study Report 6 December 2024
The estimated footprint of the cable end sealing compound is 15 m by 20 m (50 feet by 65 feet). An additional consideration in the location of subsea cable landfall is access for heavy equipment to directional drill for conduit and to pull the cable ashore where Cook Inlet is too shallow for the cable laying vessel to traverse. As described in Section 3.2, a footprint of approximately 50 m by 50 m (165 feet by 165 feet) would be necessary near shore of the subsea cable landing for heavy equipment. For both the HDD buried cable and the overhead lines, the typical easement requirement for 115 kV transmission is 100 feet to mitigate effects from electromagnetic fields, and 25 feet setback
from any structure (e.g., residential building). At this point in the conceptual design, overhead lines
are proposed because of the prevalence of wetland and leased mineral rights as well as lower cost
and ease of construction. However, during refinement in the design, sections of underground lines
may be recommended due to easements or other environmental or cultural considerations.
2.2.1 Augustine Island Routing
The geothermal facility is estimated to be located on the south side of Augustine Island within the
permitted prospecting area. AEEC estimated the location at approximately 59.342333° latitude
and -153.433333° longitude, as shown on Figure 1-2. This places the plant in a drainage
approximately 1.6 km (1 mile) due north of the southern shore, mid-way in elevation between
Cook Inlet and the volcano crater summit, at an estimated elevation of 450 m (1,500 feet). This
may not be a reasonable location for the final plant; plant siting would be determined further in
the development of the geothermal resource. A new substation and converter station would be sited
adjacent to the plant.
For this study, it was assumed that the dock infrastructure to be developed by the IPP would be
located near a small cove and headland, as shown in Figure 1-2. The proposed subsea cable landfall
on Augustine would be located at approximately 59.3262° latitude and -153.4161° longitude. This
headland area is generally flat, relatively undisturbed by pyroclastic flows, without dense
vegetation, and large enough (50 acres) to accommodate construction equipment and material
staging for subsea cable landfall. The landfall is shown in Graphic 2-3.
Graphic 2-3: Potential Landing Area at Augustine Island Headland
Source: https://www.youtube.com/watch?v=JCLJokMhaPg
Augustine Island Interconnection Feasibility Study Report 7 December 2024
Two options were considered for electrical transmission routing from the plant/substation/converter station to the cable landing. Option A would follow the drainage due south from the facility to the near-shore bluff, then parallel the shoreline to the substation. The total length of Option A is 2.5 km (1.6 miles). Option B would avoid the drainage by routing east over a ridge, then follow the eastern slope of the ridge south to the substation, attempting to avoid a primary path of historical pyroclastic flows. The total length of the Option B is 3 km (1.9 miles). For both options, overhead transmission lines would be used, the terrain would be challenging for design and construction, design would require seismic evaluation and consideration of pyroclastic flows, and some clearing of vegetation would be necessary. Given the similarities in these options,
and the significant uncertainty in the location of the geothermal plant, only one route (Option A)
from the substation to cable landfall on Augustine was evaluated for design, costing,
environmental, and permitting.
2.2.2 Anchor Point Option 1: North of Point to Anchor Point Substation
For Option 1, landfall is estimated north of the point at approximately MP155 of the Sterling
Highway, as shown on Figure 1-3 (151.85103 W, 59.79686 N). The cable sealing end compound
would be located on undeveloped privately-owned land (that would be acquired) adjacent to
Sterling Highway and the existing powerline right of way (ROW). The overhead line would run
parallel to the Sterling Highway for 0.5 km (0.3 miles) where a 100-foot ROW is present, then cut
east to the existing Anchor Point substation (2.3 km; 1.4 miles). Additional easement width along
the highway may be needed to accommodate the HVDC line adjacent to existing conductor. A
new 100-foot corridor easement would be needed between the highway and substation. The
Anchor Point substation would be expanded and a DC to AC modular converter station added.
2.2.3 Anchor Point Options 2 and 3: South of Point to Anchor Point Substation
For Options 2 and 3, landfall is estimated south of the point as shown on Figure 1-4 (151.85206
W, 59.74464 N). The cable sealing end compound would be located on an undeveloped parcel
owned by DNR (Parcel 16911002). The overhead line would traverse east through a parcel owned
by KPB (Parcel 16913125) for 1.6 km (1 mile) then cut north for 5.8 km (3.6 miles) to cross the
Sterling Highway and connect to the existing 100-foot ROW to the Anchor Point substation.
Additional easement width may be needed to accommodate the HVDC line adjacent to existing
conductor. A new 100-foot corridor easement would be needed between the cable landfall and
Sterling Highway. For Option 2, the Anchor Point substation would be expanded and a DC to AC
modular converter station added. For Option 3, a new substation would be constructed on the same
parcel as the existing substation and a DC to AC modular converter station added.
2.3 Anchor Point Routing Discussion
The three options are constructable, close to developed infrastructure, but with different
advantages or disadvantages. Option 1 landfall is closer to private homes and a bluff area that may
exhibit more erosion but is only 3.2 km (2 miles) long. Options 2 and 3 landfall is on public land
further from developed areas, along a bluff that suggests more deposition than erosion, but is more
than double the transmission length at 8.5 km (5.3 miles) long. Both will require crossing large
sections of wetlands (Figure 2) and obtaining new easements and expanding existing ROW along
both public and private land (Figure 3). Options 2 and 3 require crossing the Sterling Highway,
which is a historic highway, and comes closer to known cultural sites than Option 1. A simple
Augustine Island Interconnection Feasibility Study Report 8 December 2024
weighted score matrix (Section 6) was developed to look at routing Options 1, 2 and 3 in terms of permitting and environmental screening. Option 1 scores significantly better than Options 2 and 3, primarily due to the shorter distance, including fewer wetlands and mature forest to cross. Costs for this project are primarily driven by the subsea cable; changes in onshore routing and substation do not have a major effect on the overall project cost. Substation equipment is less than 10% of the cost of the subsea transmission. Costs are discussed in Section 4 and Appendix C.
Augustine Island Interconnection Feasibility Study Report 9 December 2024
3. PRELIMINARY ENGINEERING ANALYSISThe engineering analysis for bringing geothermal power from the planned geothermal plant on Augustine Island to the existing transmission station on the Kenai Peninsula at Anchor Point includes four major components: 1.Type of subsea cable, whether an HVDC or high voltage alternating current (HVAC)solution2.Location and method of installation of subsea cable, cable landfall, and power
conversion
3.Interconnection substations, whether to expand existing or build new, including new
major equipment needed to connect to the existing transmission system
4. Location and types of overhead lines
A simplified diagram showing these major design components is provided as Graphic 3-1.
Graphic 3-1: Simplified Diagram of Design Components
Each of these components is described in detail in the following sections. The analysis uses the
metric/SI system as part of the calculation. Where appropriate, conversion into imperial
measurements has been carried out.
3.1 Selection of HVAC or HVDC Subsea Transmission
A key component of the engineering design is whether to use HVAC or HVDC undersea cabling.
Overall advantages of an HVAC solution are a lower initial cost, easier integration into the Anchor
Point AC grid, proven technology, and flexibility on distance of transmission. HVAC is typically
more suitable for shorter distances and grid integration. Overall advantages of an HVDC solution
are lower transmission losses and higher capacity than HVAC and as an asynchronous link
between AC systems of different frequencies. HVDC is typically more suitable for longer
distances and high-capacity transmission.
Augustine Island Interconnection Feasibility Study Report 10 December 2024
The decision between HVAC and HVDC is dependent on the distance of transmission, the amount of power to be transmitted, and the existing infrastructure at Anchor Point. The approximate cable length across Lower Cook Inlet from the takeoff point is 111 km (69 miles), to be refined during the front-end engineering design stage for the project. This assessment assumes a 111-km length of cable route, as shown in Figure 1-1. The minimum connection capacity is 70 MW. The existing system at Anchor Point is a 115 kV AC grid. The economic breakeven transmission distance for HVAC and HVDC depends on many changing factors and varies case by case. The general knowledge available today is that for subsurface
cables, HVDC transmission becomes more economical than the HVAC alternative at a breakeven
distance of 100 to 140 km (62 to 87 miles) for medium power transfer (i.e., below 750 MW). The
distance between Augustine and Anchor Point puts this project within the breakeven point where
neither has a clear economic advantage solely based on cable technology.
3.1.1 HVAC Subsea Design
A detailed evaluation of HVAC is provided in Appendix G. Commercially available HVAC cables
(bundled three-phase) are rated to just meet the distance needed to cross Cook Inlet from Augustine
to Anchor Point (111 km) at a size of 185 square millimeters (mm2), current carrying capacity of
420A, cable capacitance of 0.14 microfarads per kilometer (µF/km), and voltage of 115 kV.
However, to overcome a de-rating associated with HDD burial needs at both ends of the subsea
cable due to the insulative properties of soil, the conductor size must increase. A subsea joint to
change cable sizing to 300 mm2 would be completed at each end, changing the effective cable
capacitance to 0.15 µF/km. At this change in capacitance, the cable is no longer rated to meet the
distance to cross Cook Inlet (only 104 km). It is still prudent to consider this option further given
how close the generic parameters are in this high-level conceptual design.
In addition, the approximate charging current for the cable will be on the order of 310A. The design
positions a 40-megavolt-amperes (MVA) reactive shunt reactor at each end of the cable to
compensate against the charging effect associated with the cable, requiring additional network
generation capacity to be available on the transmission network to enable the HVAC cable to be
energized. This would be a short-term inrush current for which the transmission network must be
capable of withstanding and is likely not feasible with the HEA network.
3.1.2 HVDC Subsea Design
A detailed evaluation of HVDC is provided in Appendix G. An HVDC solution is viable for this
project. It would use a commercially available 300mm2 HVDC cable, terminating at the cable end
with cable end sealing compound and HVDC transmission lines to a modular voltage source
converter (VSC) technology DC to AC conversion station.
3.1.3 HVAC Versus HVDC Discussion
Both HVAC and HVDC may be viable for this project, but during this conceptual level review,
the HVAC solution is more complicated from a design perspective and the HVDC solution
provides some clear advantages. Some of the advantages for the HVDC solution include the
following:
• Power flow on the link is controllable.
Augustine Island Interconnection Feasibility Study Report 11 December 2024
• The AC frequency and voltage level at both ends can be controlled independently of each other. • The HVDC link will not contribute to short circuit levels at the connected transmission network. • Faults and oscillations at the generator end will not transfer to the main transmission network. • No requirement for reactive compensation, so no need for shunt reactors across the cable length and only a small current inrush associated with energization of the cable.
• Fewer losses across the transmission distance, estimated at 5 to 6% versus 7 to 10% for
the HVAC solution.
In addition, where the cable is proposed to be connected to the HEA transmission network is
considered to be a “weak” connection in that any major changes to the network (e.g., switching
large loads/generators/cable sections) can have a major influence on the stability of the
transmission network. An HVDC solution will help with this situation due to its ability to help
support the voltage and frequency at its point of connection.
The key advantages of the HVAC solution are connectivity to the existing Anchor Point network
at 115 kV and cost (which is discussed in Section 4). HVDC has a significantly higher capital cost
than an HVAC solution. Although the cable costs for the HVDC solution will be less than those
for the HVAC solution because of the assumptions made (i.e., a single type of cable along the
whole of the route length, three HVAC cables within a single bundle, two HVDC cables) the
system as a whole will be more costly due to the conversion stations and equipment.
Depending on the ultimate goals of the project, it may be prudent to only consider HVDC. There
have been numerous HVDC projects installed worldwide within the capacity range required for
this project. However, it is recommended that the HVAC solution should be developed further to
identify whether the existing transmission network can support the energization of a long length
cable. This can be done by undertaking power system studies utilizing the background
transmission network parameters and topology. Final selection of HVAC or HVDC is critical to
prepare the design.
3.1.4 Subsea Cable Energization/Black Start
Consideration will need to be made for the energization of the cable and black start capability. For
the HVAC solution, it will be important to ensure that the new geothermal plant will be capable
of energizing the cable. It will need to be able to provide the charging current associated with the
cable as a minimum. This will cause the steam generators an issue, in that they do not like to ramp
up very quickly (a high level of steam energy will need to be behind the turbine to enable this to
happen). Therefore, energizing the cable from the geothermal plant at Augustine Island is unlikely
to be possible. In terms of black start capability for the power plant only, this can be done at the
geothermal generator end in which the backup generator(s) can start the geothermal power plant.
With the HVDC link, this can be used to help with energizing the local transmission grid with the
help from the geothermal generating plant. In this case, the HVDC link will control the ramp up
rate when energizing parts of the transmission grid. Energizing the HVDC link takes a relatively
Augustine Island Interconnection Feasibility Study Report 12 December 2024
small amount of power (a study would need to be undertaken to confirm the value) to which the geothermal power plant turbines should be able to deliver. 3.2 Cable Installation Different installation methods are needed for the subsea environment and the nearshore environment. 3.2.1 Subsea Cable Installation The installation of the subsea cable will very much depend on the seafloor type and conditions.
For all types of subsea cable installation, specialized vessels are needed with gear to lay the cable.
Cable-laying vessels are in high demand and have limited availability. Advanced planning is
needed to secure a vessel on the project timeline. The specific vessel needed may originate in a
distant part of the world but will access Cook Inlet through routine shipping lanes. Consideration
should be made for locations in which the vessels can shelter in the event of extreme weather
events and/or poor sea conditions. Appendix G includes further details on cable laying vessels.
The area where the cable would be laid is relatively shallow, with a maximum depth of
approximately 70 m (230 feet). As shown in Graphic 2-1, the shallow zone near Augustine Island
is short (less than 5 km [3 miles]) whereas the shallow zone near Anchor Point is longer at 15 to
20 km (9 to 12 miles). Based on a typical draught of a cable-laying vessel, the remainder of the
route is adequate for vessel operations.
Cable laying can occur at any time of the year that the water is ice-free but is generally planned
when adverse weather is minimized and marine life is not present. Lower Cook Inlet in the area of
the proposed cable route may form ice in the coldest months of winter but may also remain ice-
free depending on the winter conditions. During spring and summer is the ideal timing for cable
laying partly because beluga whales are primarily found in Upper Cook Inlet and not traversing
into Lower Cook Inlet.
Once a full subsea cable routing plan is developed, including conducting several surveys and a
cable burial risk assessment as mentioned in Section 2.2, it will be determined whether burial is
recommended for the entire length or specific sections. In general, burial is used for protection
from damage that would be caused by fishing, anchors, or seabed movement. The cable will cross
both the Kamishak Bay and southern subdistricts of the Lower Cook Inlet Salmon Management
Area where commercial fishing can occur.
Appendix G provides detail on the different installation methods for subsea cable burial. Specific
devices like jetting sleds, ploughs, trenchers, and remotely operated vehicles would be used to
bury the cable in the seabed. Burial depths of 1 to 2 m (3 to 6 feet) are typically sufficient for
protection against fishing, while greater depths are needed for protection against anchoring. The
sediment conditions and maneuverability will determine the equipment needed. In general, jetting
is effective in sandy sediments but less effective in stiff clays and uses a self-propelled tracked
vehicle behind the main vessel. Ploughs are towed behind the main vessel and are less
maneuverable but are effective in most sediment types. Given the glacial origin of the sediments
in Cook Inlet, jetting or ploughing would be likely effective methods of burial.
Augustine Island Interconnection Feasibility Study Report 13 December 2024
If cable protection is recommended and burial is not viable due to rocky areas or crossing other cables, armoring can be provided with rock placement, articulated pipe, or a concrete mattress. As part of the project, there will be a need to cross at least one existing subsea service (i.e., communication cable). The method to cross the service will be determined through negotiation with the lease holders who own and operate the subsea service as described in Section 5.1. Normal practice for crossing existing subsea cables is to cross them at 90° and for the power cable not to run parallel with them for any length, although short lengths can be permitted. Graphic 3-2 shows an example of a typical service crossing.
Graphic 3-2: Example of a Subsea Service Crossing by a Power Cable
3.2.2 Nearshore Cable Installation
Specialized cable-laying vessels are not able to lay the cables in very shallow water nearshore. The
vessel approaches the beach to the closest practical point then anchors. For this project, the shallow
zone near Augustine Island is anticipated to be less than 5 km (3 miles) and near Anchor Point is
anticipated to be 15 to 20 km (9 to 12 miles).
The cable can be floated and pulled to the beach to an intertidal joining pit (ITJP) and temporarily
terminated. The ITJP is typically located between mean sea level and the seasonal high-water
mark. At the ITJP, the cable is buried to a depth of approximately 2 to 3 m (6.5 to 10 feet) below
lowest water levels to avoid daylighting at the shore. Pulling to the beach may involve a section
of HDD or could be from heavy equipment located on the beach.
Augustine Island Interconnection Feasibility Study Report 14 December 2024
Graphic 3-3: Example of Nearshore Connection using HDD
A plough is used to bury the pre-laid cable by winching/pulling from onshore. The onshore pulling
force is estimated at 50 to 80 tons. Graphic 3-4 shows a typical cable burial to the nearshore.
Graphic 3-4: Sea Stallion 2 Plough Burying Cable Nearshore
For this study, it is estimated that the leg of the cable from the beach/IJTP to the landfall location
will be installed by HDD at both the Augustine Island end and the Anchor Point end. However, it
is possible that on the Augustine Island end, the cable will not require burial when the design is
refined.
For both HVAC and HVDC solutions for subsea cabling, polyethylene pipe conduit would be used
during HDD within which to pull the cables. For HVAC, 200mm (8 inch) diameter is proposed in
three separate conduits for the three cables. For HVDC, 150mm (6 inch) diameter is proposed as
a single conduit for the two cables.
The HDD equipment would incline at a shallow angle (e.g., 12°), advancing a drill bit horizontally
down through the bluff and then be deflected upwards to exit at the intended IJTP. Drilling fluid
is pumped into the hole and returns back carrying the soil and rock cuttings. The hole is then
Augustine Island Interconnection Feasibility Study Report 15 December 2024
widened out by replacing the drill bit with a reamer and reaming out the hole. Conduit can be pulled in from the beach side or can be fed through from the land side. The conduit is typically staged in lengths that are welded together with heat fusion as they are strung through the hole. The distances estimated for HDD at Anchor Point are near the maximum range of heavy drilling rigs. However, shorter distances are likely possible when refining the design. 3.3 Interconnection Substations Two substations are needed for the interconnection between the geothermal plant and the existing Anchor Point transmission system: one on the Augustine side and one on the Anchor Point side.
For Augustine, the only option is to build a new substation. For Anchor Point, either the existing
substation could be expanded (Options 1 and 2) or a new substation could be built (Option 3).
Both HVAC and HVDC systems require a substation, but their infrastructure needs differ. For
HVAC, the onshore cable would need to be extended via an overhead 115 kV line to the substation
location, or the distribution network would need to be rebuilt and reconfigured for a substation
near the onshore landing of the undersea cable. In contrast, HVDC requires a converter station to
convert the 80 kV DC to 115 kV AC for distribution to the grid. The DC converter station could
be located at the existing Anchor Point substation, or the DC converter station could be located at
a new location where a new substation would be built. In either case, the costs for routing the 115
kV lines to either location are comparable. However, placing the DC converter station and
substation at a new location introduces additional considerations for the distribution grid. For that
reason, in this conceptual design, the DC converter station is located at the existing Anchor Point
substation. A simplified single line diagram of the converter station is provided as Graphic 3-5.
During further design development, when complete details on the HEA Anchor Point grid are
available, a microgrid analysis would be conducted to evaluate effects to the distribution.
Graphic 3-5: Simplified Single Line Diagram for the HVDC Voltage Source Converter
3.3.1 Augustine Island Substation (Plant 13.8kV to 115kV)
A new substation at the geothermal plant would need to be built to transform the assumed 13.8-kV
generated power for each 35-MW turbine. A single line diagram is attached in Appendix B. The
estimated footprint would be 76.2 m by 53.3 m (250 feet by 175 feet). Two 40/50/60-MVA
Augustine Island Interconnection Feasibility Study Report 16 December 2024
13.8/138-kV transformers would be installed in a parallel configuration, allowing operation at a lower output rating, independently. Metal clad switchgear would be used on the 13.8-kV side, which would allow each turbine unit to run independently or in parallel. A control building to house the relaying, metal clad switchgear, and battery systems could be built on-site or a prefabricated building, in sections, could be moved to the site. 3.3.2 Anchor Point Substation (Interconnection 115kV to 13.8kV) 3.3.2.1 Options 1 and 2: Expansion of Existing Anchor Point Substation Options 1 and 2 consider the addition of a 115 kV line to the existing Anchor Point substation,
requiring a reconfiguration of the current switching scheme into a ring bus configuration. A
single-line diagram and general arrangement is attached as Appendix B. This expansion involves
significant modifications, as the existing 115 kV scheme will need to be demolished or
restructured, necessitating a complete substation outage during construction. Additionally, to
accommodate the increased loads, the existing 9.375 MVA transformer must be replaced with a
70 MVA unit, adding considerable complexity. The higher capacity transformer would require
comprehensive upgrades to the existing 25 kV equipment, which is unlikely to support the
increased continuous and fault current demands.
Further, the larger transformer would necessitate compliance with Spill Prevention Control and
Countermeasure requirements, potentially requiring a new oil containment pit. Space limitations
due to the configuration at the site may challenge the feasibility of these upgrades and raise
questions about the practicality of integrating additional loads. The current footprint is
approximately 45.7 m by 45.7 m (150 by 150 feet) and the expansion would require an additional
36.5 m (120 feet) on one side, which may also require a redesign of the ground grid to ensure
safety and operational reliability.
To support the new configuration, extensive updates to relay wiring, relay settings, and supervisory
control and data acquisition (SCADA) systems will be essential. Enhancements to the AC and DC
systems, including resizing the battery system, will be needed to meet increased operational
demands. Station service infrastructure upgrades are also likely, while the control building may
need expansion or replacement to accommodate the additional relay panels and associated
equipment. A carefully coordinated phased outage management plan will be critical to minimize
disruptions during construction. Additionally, comprehensive load flow and fault current analyses
must be performed to ensure the upgraded substation operates efficiently and meets reliability
standards post-expansion.
The major equipment needs for expanding the Anchor Point Substation are provided in Table 3-1.
Table 3-1: Major Equipment Needs for Anchor Point Substation Expansion
Equipment Specification Quantity
Main Power Transformer (MPT) 70 MVA at 65 degrees Celsius, 115-24.94Y/14.4
kV, ONAN/ONAF/ONAF with Arresters 1
Gas Circuit Breaker (GCB) 115 kV, 1200 amperes (A), 40k A 4
Gang Operated Air Break (GOAB) Switches Motor Operated, 115 kV, 1200 A 4
GOAB Switches 115 kV, 1200 A 8
Augustine Island Interconnection Feasibility Study Report 17 December 2024
Equipment Specification Quantity Arresters 98 kV maximum continuous operating voltage (MCOV) 9 Coupling Capacitor Voltage Transformer 800/1000:1:1 12 Package Control Building Includes all relay panels 1 3.3.2.2 Option 3: New Anchor Point Substation Option 3 proposes replacing the existing Anchor Point substation with a brand-new facility
designed to relocate the two current 115-kV line positions (Kasilof and Diamond Ridge) while
adding a new 115-kV line position (Augustine Island), all within a three-position ring bus
configuration. A one-line diagram and general arrangement is attached as Appendix B. This
approach offers significant advantages by allowing the new substation to be constructed while
keeping the existing Anchor Point substation online, minimizing disruptions to current loads and
limiting the need for extensive modifications to the existing infrastructure. The new substation can
incorporate future growth considerations, modern design standards, and enhanced switching
capabilities, providing greater operational flexibility. Additionally, relocating to a new site, even
if the new site is on the same parcel owned by HEA (Parcel 16516261) reduces the space and
layout constraints typically associated with expansions to exiting configurations.
However, this option comes with higher initial costs due to the construction of a separate facility.
Additional land acquisition is not anticipated because there is sufficient undeveloped area within
the existing HEA parcel. During the transition phase, maintaining two facilities may temporarily
increase operational and maintenance responsibilities. Despite these challenges, constructing a
new substation presents a strategic, long-term solution capable of meeting increased demand,
improving reliability, and supporting future system expansions effectively and efficiently.
The ideal location for the new substation would be near the existing distribution network to
minimize construction efforts and reduce outage time when transferring existing circuits to the
new substation. Conversely, if the substation is positioned closer to the subsea cable landing,
additional considerations regarding the distribution network would need to be evaluated. These
include maintaining the existing reliability of the system, accounting for changes in load
distribution, and addressing the increased distance between the new load point and end-users.
The major equipment needs for a new substation are provided in Table 3-2.
Table 3-2: Major Equipment Needs for New Anchor Point Substation
Equipment Specification Quantity
Main Power Transformer 70 MVA at 65 degrees
Celsius, 115-24.94Y/ 14.4kV,
ONAN/ONAF/ ONAF with
Arresters
1
Gas Circuit Breaker (GCB) 115 kV, 1200 A, 40
kiloamperes (kA) 4
Gang Operated Air Break (GOAB) Switches Motor Operated, 115 kV,
1200 A 4
GOAB Switches 115 kV, 1200 A 8
Augustine Island Interconnection Feasibility Study Report 18 December 2024
Equipment Specification Quantity Arresters 98 kV maximum continuous operating voltage (MCOV) 9 Coupling Capacitor Voltage Transformer 800/1000:1:1 12 Package Control Building Includes all relay panels 1 Vacuum Circuit Breaker 24kV, 1200A 2 GOAB Switches 24kV, 1200A 5 Voltage Regulators, TBD (if required) 3 Potential Transformers TBD (as needed) 6
Station Service Transformer with fused disconnect 1
Two Way Automatic Communication System Maximum
Transmission Unit (TWACS MTU)
TBD (if required) 1
3.4 Overhead Transmission
Electrical transmission between the cable termination point and the substation will primarily be
accomplished by overhead lines. Because the DC to AC converter station and substation have been
assumed to be located near each other, HVDC lines have been assumed for transmission between
the subsea cable and the substation.
Overhead lines worldwide are the preferred and the proven solution for bulk transmission of
electricity. They are highly available, have a low number of faults compared to other technologies,
and restoration can generally be completed in days in the case of interruption. Major overhead
faults like tower failures are rare. Construction of overhead lines can be completed in virtually all
types of terrain and soil conditions. Actual land use is limited to tower locations, and spans can
range in distance by increasing tower height. Maintenance includes vegetation clearing.
HVDC overhead lines consist of two conductors per circuit at a minimum, which equates to less
loading on towers than an HVAC overhead line which consists of three conductors at a minimum
voltage of 80 kV is selected as typical to transmit 100 MW on HVDC. For 80 kV HVDC overhead
transmission, either monopole or bipole towers can be used, constructed of either wood, steel, or
concrete. Wood monopoles are assumed for cost estimating purposes to match existing structures
in Anchor Point and provide an economical option for purchase and sourcing. The estimated height
is 80 to 100 feet depending on the terrain and any crossings. Further design refinement would
determine whether alternative materials would be recommended. A typical arrangement for an
HVDC monopole would be used for the design, as shown in Graphic 3-6. Lightening shield wires
are shown at the top of the tower and can be used with integrated fiber optics for communication
purposes.
Augustine Island Interconnection Feasibility Study Report 19 December 2024
Graphic 3-6: Design of a Monopole Transmission Tower Suitable for 80 kV
For this project, a current of approximately 625 A is required. A 477 kilo circular mils (kcmil)
Hawk Aluminum Conductor Steel Reinforced (ACSR) conductor rated at 660 A is recommended
due to its mechanical properties. Careful selection of the conductor size will be required during
the refined design to ensure that any future capacity increases are accommodated. This will be a
trade-off between higher voltage and a thicker conductor. A rule of thumb is to keep the conductor
resistance lower than 10 ohm per 1,000 km (620 miles). Table 3-3 proposes a rough estimate of
the number of tower structures needed for the routing options on Augustine and Anchor Point.
These would be refined during design and selection of routing.
Table 3-3: Quantity of Monopole Towers
Augustine
Option A
Augustine
Option B Anchor Point
Option 1
Anchor Point
Options 2/3
Tangents 10 11 16 53
Light Angles 3 5 3 4
Running Angles 6 4 5 7
Dead-end 2 2 2 2
Total 21 22 26 66
Augustine Island Interconnection Feasibility Study Report 20 December 2024
4. PROJECT COSTS AND ECONOMICS The electrical interconnection project costs include the design of the overall project, plus the materials, equipment, construction, and commissioning costs for the substations on both ends, the subsea cable including landfall and cable end sealing compound at both ends, the DC to AC conversion facilities at both ends, and the overhead transmission lines between subsea cable and the substation at both ends. In addition to the design, materials, equipment, construction, and commissioning costs, there are
several other owner costs that would be incurred for the project. These include items such as
permitting, land leasing, and environmental studies, geotechnical studies, project oversight by the
owner including travel, and financing costs, including legal and insurance fees. Although these
additional costs were not listed in the scope of work, a discussion and rough order of magnitude
estimates are included to provide a holistic picture of project costs. In addition to costs, a high-
level summary of available federal and state grants, tax incentives, and loans was prepared.
The lack of a developed plan for the geothermal plant will result in changes to the design over
time, including scaling up or scaling down the power and transmission needs. While the conceptual
design is flexible to the changes, the cost estimate is based on concrete assumptions that are less
flexible. In addition, costs of items continue to change significantly with various economic
pressures. The cost estimate is provided with a range of -30% to +50% to accommodate some of
the variables. Assumptions and cost ranges are provided in Appendix C.
4.1 HVAC Versus HVDC Costs
As described in Section 3.1, the cost difference between HVAC and HVDC solutions for the
subsea cable can be substantial. The costs for HVDC are used in the budgetary cost estimate in
Section 4.2.
Although HVAC was not considered viable given the estimated distance in the conceptual design,
it may still be worth pursuing for front-end engineering design. For this reason, a rough cost
comparison is provided in Table 4-1 to highlight the differences. The cost differences between
HVAC and HVDC overhead lines and substations are minimal. In both solutions, the transformers
and tower construction drive costs.
Table 4-1: HVAC and HVDC Solution Cost Comparison
Component HVAC
($M)
HVDC
($M)
Shunt reactors (40 MVA) 1.2 Not Applicable
DC to AC converter stations Not Applicable 145
Cable sealing end compound 0.22 0.2
Overhead lines (materials and installation) 0.72 0.66
Subsea cable (materials and installation) including HDD sections 169.8 132.8
Engineering 0.50 1.85
Construction 0.84 5.12
Commissioning 0.13 0.44
TOTAL 173.4 286.1
Augustine Island Interconnection Feasibility Study Report 21 December 2024
4.2 Budgetary Cost Estimate The budgetary cost estimate is provided as a bill of materials for capital expenditures of equipment, plus a table detailing the rough order of magnitude costs for 100% design, construction, and commissioning. Anticipated permitting, licensing, leasing, environmental, and engineering fees are also estimated. Escalation, inflation, and accuracy factors are provided. The complete cost table and assumptions are provided in Appendix C. Table 4-2 summarizes the overall costs. Table 4-2: Budgetary Cost Summary (HVDC only)
Option 1
($M)
Option 2
($M)
Option 3
($M)
Environmental, permitting,
consulting, and studies 5.8 5.8 5.8
Engineering design 3.0 3.0 3.0
Mobilization/Transport 3.1 3.1 3.1
Materials and Equipment 254 256 256
Construction 54 54 55
Commissioning 0.9 0.9 0.85
TOTAL 320.8 322.8 323.8
Estimate -30% 224.5 226.0 226.7
Estimate +50% 481.2 484.2 485.7
4.3 Tax Incentives and Funding Opportunities
Homer Electric’s certificated territory encompasses a vast majority of the population and
communities on the Kenai Peninsula and essentially all the populated portions of the central and
western Kenai Peninsula. Several of the communities are off the road system, including Halibut
Cove, Seldovia, Port Graham, and Nanwalek. The population served by HEA is approximately
33,000 customers and is considered rural. The villages of Port Graham and Nanwalek are Alutiiq
communities. The Port Graham Tribal Council and the Native Village of Nanwalek are federally
recognized tribes. It may be beneficial for HEA to develop a cooperative agreement to represent a
group of stakeholders that include tribal entities to pursue funding opportunities.
Financing can be coordinated using a mix of public and private funding sources for a project of
this size. Based on publicly available financial statements for HEA in the years 2022 and 2023,
long term debt was serviced by loans through the National Rural Utilities Cooperative Finance
Cooperative, National Cooperative Services Corporation, Farmer Mac, and Rural Utility Service
Guaranteed Federal Financing Bank. The overall average interest rate is estimated at 6%. Through
these services, approximately $30M is available through unadvanced loan facilities.
Through directives of the Bipartisan Infrastructure Law and Inflation Reduction Act, the United
States Department of Energy issues federal tax credits for geothermal energy production and costs
for transmission infrastructure development from qualified new geothermal production facilities.
Geothermal electricity production tax credits may be issued for up to 30% of the total installed
cost for eligible assets. Eligibility requirements include compliance with prevailing wage (Davis
Bacon Act) and workforce training and apprenticeship metrics. It is important to note that all
Augustine Island Interconnection Feasibility Study Report 22 December 2024
project participants including contractors, subcontractors, and specialty trades are subject to compliance with these conditions. The Energy Community Tax Credit Bonus Sections of the Internal Revenue Code may apply to the HEA energy project and investment under Sections 45, 48, 45Y, and 48E. The onshore substation that conditions the project’s generated electricity received from the subsea interconnect for transmission, distribution, and use is located within a qualified energy community. It is likely that the entire project footprint falls within a qualified energy community. Because this energy project would be placed in service within the community after December 31, 2024, it may qualify
for an additional 10% of the total installed cost, to be applied in bonus credit amounts or rates.
In addition to federal tax credits, the Department of Energy’s Office of State and Community
Energy Programs was established to extend the capacity and capability of states, tribes, local
governments, and community serving organizations to implement high-impact, self-sustaining
clean energy projects that center the needs of low-income and disadvantaged communities. The
office does this through the management and oversight of formula grants, competitive grant
awards, and consumer rebate grants. These grant funding announcements are released
intermittently and should be considered part of the project fund stacking strategy with active
monitoring for availability and applicability.
Qualified clean energy facilities which are placed in service after 2024 may be classified as a 5-
year property via the modified accelerated cost recovery system (MACRS) (IRA Provision 13703).
Owners of qualified facilities, property and energy storage technology placed into service after
December 31, 2024, may be eligible for the 5-year MACRS depreciation deduction. Deduction for
cost recovery for qualified clean energy facilities includes properties and technology. Under
Internal Revenue Code Section 168(e)(3)(B), qualified facilities, qualified property and energy
storage technology are considered 5-year property. These types of property are recoverable under
the MACRS.
Other IRS deductions and business credits may apply such as the Clean Energy Production Credit.
This is a newly established, technology-neutral production tax credit that replaced the Energy
Production Tax Credit once it phases out at the end of 2024. This is an emissions-based incentive
that is neutral and flexible between clean energy technologies. This credit starts for the latter of
2032 or when U.S. greenhouse gas emissions from electricity are 25% of 2022 emissions or lower.
There are several other incentives and deductions which may apply. In the next phase of due
diligence for this project, it is recommended that front end engineering design phase project
information be evaluated against the options in the potential funding stack. With the evaluation of
design and project specific data against the burden of funding compliance, it may be that the cost
outweighs the benefit of the funding. As these are unknown during this early phase of design, it is
recommended that this evaluation is revisited upon initiation of the next phase of HEA’s work.
A schedule of potential funding needs is provided in Table 4-3 along with a total accumulated
financing cost. This is based on the lead times needed for procurement, and assuming for
procurement of large equipment, such as the DC to AC converter station, transformers, and subsea
cable, a 30% deposit will be needed upon order and the remaining 70% will be needed at
completion. Based on the cost of existing debt held by HEA, the interest rate is estimated at 6%
for 30 years.
Augustine Island Interconnection Feasibility Study Report 23 December 2024
Table 4-3: Financing Schedule Year Expenditure ($M) Financing Cost ($M) Design, Engineering, Studies 1 8.9 1 Long Lead Procurement Order: Converter Station, Transformers, Subsea Cable 2 73.6 14.5 Long Lead Procurement Completion: Converter Station, Transformers,
Subsea Cable
5 171.7 15
Mobilization of Equipment and
Subsea Construction Vessel, Subsea
Construction
6 54.5 18
Onshore Construction 7 15.3 18.7
Remainder of Term 23 - 308
Approximated Total 324 375.2
Augustine Island Interconnection Feasibility Study Report 24 December 2024
5. PERMITTING AND LICENSING EVALUATION 5.1 Land Lease or Acquisition Needs 5.1.1 Augustine Island Surface Augustine Island is owned by the State of Alaska. DNR administers uses of state lands for beneficial use via permits and leases. Before approving a permit or lease, the director must determine whether the disposal is in the best interest of the state. Geothermal resource development is authorized under Alaska Statute 38.05.181 with regulatory guidance outlined in the Alaska
Administrative Code (AAC) (Title 11, Chapter 84, Sections 700-950).
The entire island is under an Interagency Land Management Agreement with the Alaska Volcano
Observatory (DNR file ADL 225681). The agreement has been in place since 1992 and grants
access but does not restrict other state or public access (DNR 2024).
The area of the proposed geothermal plant, the assumed dock infrastructure, and the proposed
transmission and substation route on Augustine Island is leased by GeoAlaska, LLC, for
geothermal prospecting (DNR file ADL 394080). Adjacent parcels to the east and west are also
leased by GeoAlaska, LLC (DNR file ADL 394174) for geothermal prospecting.
For both development of the geothermal plant and transmission, a DNR lease will be needed,
coordinated through the Division of Oil and Gas. The lease could be considered either competitive
or noncompetitive as designated by the commissioner (11 AAC 84.720). During exploration, a
primary term lease is 10 years with potential for a 5-year extension, which would be extended for
the duration of commercial production once production has begun (11 AAC 84.745).
5.1.2 Cook Inlet
The area of Lower Cook Inlet where a subsea cable would be routed from Augustine Island to
Anchor Point would include leases from the State of Alaska DNR Division of Mining, Land, and
Water and the Bureau of Ocean Energy Management.
DNR Division of Mining, Land, and Water manages state-owned tide and submerged lands, which
are seaward of mean low tide to 3 miles offshore. The DNR submerged lands leases would be
needed for both the nearshore area near Augustine Island and near Anchor Point. DNR has
discretion on the duration of the lease, which usually ranges from 10 to 25 years. Although the
Division of Mining, Land, and Water manages submerged lands leases, at DNR’s discretion, this
lease could be managed through the Division of Oil and Gas as part of a larger negotiated lease for
a transmission project associated with geothermal energy development.
The Bureau of Ocean Energy Management manages leases in the outer continental shelf, which
are generally between the DNR-managed State of Alaska submerged lands along the Cook Inlet
route. A lease for electrical transmission would be needed. The process is typically competitive,
and the term of the lease may be up to 25 years with options for renewal.
Because the subsea cable would intersect an existing cable, a fiberoptic cable owned by General
Communications Inc. that runs from Homer to Kenai, coordination between the leases may be
necessary.
Augustine Island Interconnection Feasibility Study Report 25 December 2024
5.1.3 Anchor Point Cable Landing For the Option 1 route, the subsea cable landfall would intersect two leases for oil and gas by Hilcorp Alaska, LLC (DNR files ADL 393959 and ADL 392666). Coordination between these leases will be necessary to manage combined best uses. The cable would be placed under private-owned parcels, daylighting adjacent to the Sterling Highway where the cable end sealing compound would be placed to transition from underground to overhead lines. Land would likely require subdivision and acquisition. For the Options 2 and 3 route, the subsea cable landfall intersects one lease for oil and gas by
Hilcorp Alaska, LLC (DNR file ADL392667). For Option 1, coordination between the leases will
be necessary to manage combined best uses. The cable would be placed under a parcel owned by
DNR (parcel 16911002). The Division of Mining, Land, and Water can develop a commercial or
industrial lease for their parcels for beneficial use. These leases can be long-term, sometimes up
to 50 years. The cable would daylight on this same parcel and a cable end sealing compound would
be placed relatively close to shore. Access to this parcel would require addition of a road, possibly
an expansion of an existing all-terrain vehicle trail that extends from the end of Van Seventer
Avenue, through a parcel owned by KPB (parcel 16913125).
At DNR’s discretion, these leases could be managed through the Division of Oil and Gas as part
of a larger negotiated lease for a transmission project associated with geothermal energy
development.
5.1.4 Anchor Point Transmission Alignment: Option 1
For Option 1, electrical transmission is proposed (Figure 1-3) along an existing HEA 30-m
(100-foot) ROW corridor along the west side of the Sterling Highway for 0.5 km (0.3 miles). A
portion of this ROW is currently used by HEA for electrical distribution lines. Given the 2.4-m
(8-foot) span of the tower design for 80 kV HVDC transmission, additional ROW width
(approximately 10 m [33 feet]) will be needed to accommodate setback for both sets of towers, or
re-routing of the smaller existing distribution line to the opposite side of the road may be needed.
The line would continue due east to Greenfield Road and then south to the existing Anchor Point
substation. A new easement of 30.4-m (100-foot) width would be needed for the 2.4 km (1.5 miles)
east alignment. Eight parcels are located along the north side of this route, and 16 parcels are
located along the south side. As shown on Figure 1-3, all but one of the parcels is privately owned.
Two small parcels have an existing 10-m (33-foot) property line easement that is not sufficient
width for the proposed transmission.
From Greenfield Road, the line would continue due south to the existing Anchor Point substation
along an existing HEA 30.4-m (100-foot) ROW corridor and along the northbound 115 kV HVAC
line toward Diamond Ridge. Similar to the Sterling Highway ROW, additional ROW width
(approximately 10 m [33 feet]) will be needed to accommodate setback for both sets of towers.
The additional width would be along one privately-owned parcel.
Augustine Island Interconnection Feasibility Study Report 26 December 2024
5.1.5 Anchor Point Transmission Alignment – Options 2 and 3 For Options 2 and 3, overhead line would traverse east through a parcel owned by DNR (parcel 46911002; 1 km [0.65 miles]) and then a parcel owned by KPB (Parcel 16913125; 1.6 km [1 mile]). In both instances, a 30.4-m (100-foot) easement would be needed. The line would transition north for 1 km (0.67 miles) to cross the Sterling Highway and connect to an existing 30.4-m (100-foot) ROW that leads to the Anchor Point substation. Where the line heads north, an additional DNR parcel is located to the east, and four additional private parcels are located along the sides. Where the line connects to the exiting easement, two parcels owned by the
Kenai Trust are on the west, and another KPB-owned parcel is on the right (parcel 16910215). The
Kenai Trust refers to the Kachemak Heritage Land Trust that focuses on preserving wildlife habitat
and recreation lands.
For the section of line (4.7 km [3 miles]) that continues north along the existing 30.4-m (100-foot)
easement, the existing Kasilof 115 kV transmission line is present. Similar to Option 1, additional
ROW width (approximately 10 m [33 feet]) will be needed to accommodate setback for both sets
of towers following the same easement. This ROW has been coordinated along 14 privately-owned
parcels, 3 KPB parcels, 1 DNR parcel, 1 Kenai Trust parcel, and 1 Cook Inlet Region, Inc. parcel.
5.2 Preliminary Permitting Requirements List
Several agencies will require permits for the interconnect project through the investigation and
design phases, construction phases, and operational phase. In all phases, permits will focus on
preserving cultural and ecological resources and obtaining access and use of land and water. This
will include easements, heavy equipment use, vegetation clearing and wetland/stream crossings.
As part of planning, the prevalence of wetlands within the proposed alignment will include a
Section 404 Permit that involves a National Environmental Policy Act (NEPA) review. NEPA is
discussed in Section 6.
In the construction phase, permits will also be needed to manage waste generation, such as
stormwater, land clearing, air emissions, oil releases, or incidental take of marine mammals. A
cable landing license through the Federal Communications Commission (FCC) is specific to the
subsea transmission. In the operational phase, ongoing monitoring or ROW requirements may
apply.
A permitting matrix is provided in Appendix D to provide an overview of the permits and
regulatory requirements that may apply to the interconnect project. The matrix is not intended to
be comprehensive at this conceptual phase of the design; additional notifications and approvals
may be required as determined during refinement of the design.
Augustine Island Interconnection Feasibility Study Report 27 December 2024
6. ENVIRONMENTAL SCREENING Based on the general interconnect project footprint, the presence of wetlands, marine mammals, the subsea cable crossing zones, and the understanding that AEEC will be pursuing federal grant or loan funding, the project will trigger NEPA requirements. NEPA review will be a key component for the project and in obtaining federal funding. There are three categories of NEPA review: categorical exclusions (CatEx), environmental assessments (EAs), and environmental impact statements (EISs). Based on the current options being evaluated, an EA will likely be required.
• CatEx: Allowed for actions that do not have a significant impact on the environment
and can be excluded from detailed environmental review. CatEx is not reasonable to
assume for this interconnect project.
• EA: A concise review that determines whether an action has potential to cause
significant environmental effects. If no significant environmental impacts are
identified, a Findings of No Significant Impacts (FONSI) is issued. But if significant
environmental impacts are identified, an EIS is required.
• EIS: A detailed review that provides a comprehensive analysis of significant
environmental impacts of a proposed action, including alternatives. A minimum of 45
days for public comments is required.
The environmental review generally evaluates the topics shown in Graphic 6-1.
Graphic 6-1: Overarching Topics Evaluated During Environmental Review
6.1 Overall Scoring of Routing Options
An initial analysis was completed for the primary environmental topics based on the conceptual
design. The two Anchor Point routes were reviewed for the land status (public/private), roadway
crossings, stream crossings, wetlands, areas of critical environmental concern, critical habitat,
forested areas, existing electrical utility crossings, wilderness areas, cultural resources (as available
Augustine Island Interconnection Feasibility Study Report 28 December 2024
in the National and Historic Preservation Act [NHRA] database), and proximity to residences and community gathering areas. The categories were weighted, and final scoring was calculated. The detailed scoring summary is provided in Appendix D and is summarized in Table 6-1 as combined into the two routing options. The initial review shows that Option 2 and 3 will have the least overall environmental impact. Table 6-1: Initial Environmental Screening of Routing Options Weighting Factor Option 1 Score Option 2 and 3 Score
Land Status/Ownership-Public 1 1320 5204
Land Status/Ownership-Private 2 6230 27596
Road Crossings 2 8 18
Stream Crossings 2 2 4
Existing Electrical Utility Crossings 3 3 15
Wetlands (combined types)
PEM: 3
PSS: 4
PFO: 5
14003 37773
Critical Environmental Areas 5 0 0
Mature Forested Areas 2 1984 6934
Wilderness Areas 4 0 0
Cultural Resources 5 0 5
Proximity to Residences Less than 250 feet: 5
Less than 500 feet: 3 190 515
Near Places of Community Gathering 5 0 0
Note: Score represents a distance or count multiplied by a weighting factor. Details are provided in Appendix E.
PEM: Palustrine Emergent Wetland
PFO: Palustrine Forested Wetland
PSS: Palustrine Scrub-Shrub Wetland
6.2 Specific Environmental Considerations
A high-level environmental screening review was conducted to evaluate potential environmental
impacts and risk factors for the electrical interconnection. A summary of critical items is included
in Table 6-2. Additional detail is provided in Appendix G.
A similar evaluation was conducted for the Augustine Island area as part of the geothermal
prospecting permit written finding of the director (DNR 2022). Much of the information as it
pertains to the Augustine Island side and Cook Inlet are from the prior evaluation. Additional
information is included as it pertains to the Anchor Point side.
Key considerations include critical habitat for fish in Cook Inlet, which may be affected during
subsea cable construction activities, wetlands present on the parcels to be developed on the Anchor
Point side, which may need to be avoided or effects mitigated, and land ownership effects on the
Anchor Point side depending on the final route selected, which may be mitigated by beneficial use
of state-owned lands.
Augustine Island Interconnection Feasibility Study Report 29 December 2024
Table 6-2: Environmental Considerations Augustine Island Cook Inlet Anchor Point
Biological
Resources
Bald eagles (and other MBTA-protected birds) breed on island and may require nest monitoring during construction. Plan vegetation clearing activities early or late in the season to limit potential impacts to ground nesting birds. Streams have not
yet been surveyed for
anadromous fish. Boat access
and traffic will need to consider
avoidance of harbor seal
rookeries and haul-outs.
Biosecurity protocols will need
to be followed to prevent
introduction of species that may
affect birds (e.g., rats).
Essential fish habitat is present in Lower Cook Inlet and may require quantification of potential impacts to commercial and recreational groundfish and salmon fisheries. Subsea cabling will cross
critical habitat for the
northern sea otter. Sound
impacts to beluga whale
habitat will need
consideration. Actions will
be taken to prevent
entanglement during
construction of the subsea
cable.
Bald eagles and MBTA-protected birds breed or have potential breeding habitats along proposed transmission line alignments. These species
may require nest
monitoring during
construction. Plan
vegetation clearing
activities early or late in
the season to limit
potential impacts to
ground nesting birds.
Water Resources No wetlands are identified.
Appropriate permits are
needed to cross the water
body.
Wetlands and
jurisdictional waterways
are present across several
of the parcels proposed for
routing. Mitigation
measures may be needed
if wetlands cannot be
avoided and tree clearing
is required.
Cultural
Resources
Outreach should be conducted
with State Historic Preservation
Office and Alaska Native
Communities in Lower Cook
Inlet to confirm to historic or
prehistoric sites.
One potential cultural site
may be within the buffer
distance for the cable
crossing and additional
studies will be needed to
confirm whether
additional sites are
present.
One potential cultural site
may be within the buffer
distance for one of the line
options, but additional
studies and monitoring
will be needed during final
routing.
Geology, Soils,
and Mineral
Resources
The area is seismically active
and may have induced seismicity
from the geothermal plant.
Augustine Island is an active
volcano with regular eruptions
and pyroclastic flows.
Geotechnical evaluations are
needed for siting considerations
as well as risk evaluation of
volcanic eruption impacts.
Leases are in place for
mineral exploration near
shore at Anchor Point and
will be coordinated with
landfall for the cable. The
area is seismically active
and will require
accommodation in design.
The area is seismically
active and will require
accommodation in design.
Air Quality Consideration for short-term emissions, dust, and equipment during construction. No long-
term impacts to air quality are anticipated from the electrical interconnection.
Socioeconomics /
Environmental
Justice
The island is uninhabited and
rarely used for recreational
tourism. No long-term impacts
are anticipated.
No long-term impacts are
anticipated for the fishing
economy.
Local short-term
construction jobs may be
created and some potential
for additional jobs for
electrical system
maintenance. No long-
term impacts are
Augustine Island Interconnection Feasibility Study Report 30 December 2024
Augustine Island Cook Inlet Anchor Point anticipated for the tourism fishing economy. Public Safety Augustine volcano is active and monitored for eruptions and will requiring planning for coordination with worker safety. During construction of the subsea cable, public notification and coordination of Cook Inlet use will be needed. Electromagnetic fields are generated from transmission lines that will require setback and avoidance. Noise Consideration for short-term construction noise, including mitigation for marine mammals during subsea cable laying. Long term noise is low at 75 dBA from electrical generators.
Airspace
Overhead lines are 80 feet and
not within 25 miles of
commercial airports.
No anticipated effects on
airspace from subsea
cable.
Overhead lines are 80 feet
and not within 25 miles of
commercial airports.
Visual
Resources/
Aesthetics
Addition of electrical lines and
infrastructure will not be visible
by most of the population due to
the remote nature of the island.
No anticipated effects on
visual resources from
subsea cable.
Addition of a new
substation, expansion of
an existing substation, and
towers will alter the
landscape.
Land
Ownership,
Land Use, and
Recreation
Recreation may be inhibited in
the small section of the island
developed for electrical
transmission, but it accounts for
only a small segment of the total
island and recreation is rare.
No anticipated effects on
recreation from subsea
cable.
Private parcels may be
acquired or state-owned
parcels may be leased.
Recreation will not be
significantly impacted.
dBA: decibel A
MBTA: Migratory Bird Treaty Act
Augustine Island Interconnection Feasibility Study Report 31 December 2024
7. PROJECT SCHEDULE A project of this magnitude will take several years to complete from the initial studies and design through construction and commissioning. A rough estimate of 15 years is appropriate for the interconnection. Depending on the sequencing of activities, the project may take much longer to complete, but it is unlikely to be significantly shorter given that some activities cannot be conducted in parallel. The NEPA environmental review process is on the critical path for project lead times and can take
an additional 2 to 3 years for an EIS instead of an EA. A key component in the environmental
review process is to coordinate early with agencies, define the decision-making process, and set
clear schedules for preparing the documents and studies. This approach will streamline the NEPA
and permitting processes.
Lead times for procurement of switchgears, transformers, and breakers is on the critical path,
presently taking up to 4 years. Reserving a cable laying vessel must be coordinated in advance but
can be completed during equipment procurement.
Table 7-1 provides a conceptual schedule for the project in ranges of months and in typical order
of sequencing. Neither one of the routing options will require significantly more or less time than
another. Using an HVAC solution would not significantly alter the schedule duration either.
Table 7-1: Conceptual Project Schedule Duration
Item Duration Notes
Pre-design and pre-application studies
(geotechnical, wetland, hydrographic,
cultural, land ownership)
12 to 24 months
Accommodates potential issues with
availability of vessel for hydrographic
studies
NEPA review EA: 12 to 24 months
EIS: 36 to 60 months
Includes time for public review and
comment
Negotiation and approval of land leases
and ROW 24 to 36 months
Permitting (excluding NEPA) 12 to 24 months
Engineering design 12 months
Procurement: converter plant 44 months
Procurement: subsea cable 44 months
Procurement: substation equipment 12 to 48 months Procured through Korea, Japan, or
Vietnam
Procurement: overhead materials
equipment 12 to 18 months Procured in North America; will depend
on the amount needing to be purchased
Mobilization of equipment to site 6 to 8 months
Must be conducted when Cook Inlet is
ice-free; assumed by barge from Port of
Alaska (Anchorage) to Augustine and
Homer, then truck from Homer to Anchor
Point
Construction: subsea cable 26 months
If Cook Inlet remains ice-free, this could
be conducted continuously, contingent on
other weather issues with wind and storms
Construction: substations and converter
stations build 18 to 24 months
Augustine Island Interconnection Feasibility Study Report 32 December 2024
Item Duration Notes Construction: overhead lines 12 to 18 months Depends on the method of installation (e.g., land access or via helicopter for construction materials) Commissioning and takeover 3 to 6 months Overall duration 12 to 16 years Assumes that some permitting and design activities happen concurrently, and some construction activities happen concurrently EA: environmental assessment
EIS: environmental impact statement
NEPA: National Environmental Policy Act
ROW: right-of-way
Augustine Island Interconnection Feasibility Study Report 33 December 2024
8. REFERENCES DNR. 2022. South Augustine Island Noncompetitive Geothermal Prospecting Permit Preliminary Written Finding of the Director. Alaska Department of Natural Resources. April 28. DNR. 2024. 2024 Augustine Island Noncompetitive Geothermal Prospecting Permit Final Written Finding of the Director. Division of Oil and Gas. January 10. USACE. 2008. Erosion Information Paper—Anchor Point, Alaska. Alaska Baseline Erosion Assessment. United States Army Corps of Engineers. April 29.
https://www.poa.usace.army.mil/Portals/34/docs/civilworks/BEA/Anchor%20Point_Final%
20Report.pdf
Augustine Island Interconnection Feasibility Study
APPENDIX A
Routing Maps
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig01-1_FullCable 12/11/2024 4:23 PM (Eric.Petersen)
0 10
Kilometers
³Figure
PNA0023 December 2024
Cook Inlet, Alaska
Proposed Routes for Augustine Interconnect
1-1
Legend
Augustine Proposed Locations
Proposed Cables
Cook Inlet Bathymetry (depth in m)
0
211
Notes:
ArcticDEM hillshades are shown for Augustine and Anchor Point area. Bathymetry is shown in
depth below mean high water (MHW).
Proposed
Geothermal
Plant
Landfall Option 1
Landfall Option 2
Anchor Point Substation
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig01-2_Augustine_Cable_Detail 12/11/2024 4:23 PM (Eric.Petersen)
0 0.6
Kilometers
³Figure
PNA0023 December 2024
Mt Augustine
Cook Inlet, Alaska
Proposed Landfall and Overhead Route
at Augustine Island
1-2
Legend
Proposed Cables
Overhead
Subsea
Landfall/Underground
Augustine Proposed Locations
Cable End Sealing Compound
Geothermal Leases
Elevation Contours 100 m Interval
Notes:
Basemap is ArcticDEM hillshade overlaid on imagery. Elevation contours with 100 m intervals are derived from ArcticDEM.
1
0
6
.
1
7
km
0
.
6
4
km2.72
km2.78
km
Proposed
Geothermal
Plant
Option A
Option B
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig01-3_AnchorPoint_Option1_Detail 12/11/2024 4:59 PM (Eric.Petersen)
0 300
Meters
³Figure
PNA0023 December 2024
Anchor Point
Cook Inlet, Alaska
Proposed Landfall and Overhead Route
at Anchor Point - Option 1
1-3
Legend
Proposed Cables
Overhead
Subsea
Landfall/Underground
Cable End Sealing Compound
Substation Expansion and Converter
Station SterlingHwyAgustaLnSterl
i
ngHwyWhisk e y G u lchStNorthForkAnchorRiverSarah Ave
Chil ly wind D r
N o rth F o rk A n c h o r R iv e r
NForkRdGill h a m C t
SarahLn
M a r k Ln
0.49 km
106.17 km3.21 km
Anchor Point
Substation
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig01-4_AnchorPoint_Option2_Detail_Portrait 12/11/2024 4:59 PM (Eric.Petersen)0 940
Meters
³Figure
PNA0023 December 2024
Anchor Point
Cook Inlet, Alaska
Proposed Landfall and Overhead Route
at Anchor Point - Option 2/3
1-4
Legend
Proposed Cables
Overhead
Subsea
Landfall/Underground
Substation Expansion and
Converter Station
Cable End Sealing Compound
Est e r AveGranrossStAgustaLn SterlingHwyA n c h o r P o i n t
DanverStS c hool S t
Mof
f
i
tPl
Fi r e weed
M e adow s Golf
Cou r se
A n c ho r Riv er
S tate
R ec r ea tion A r ea NForkRdGr i ne r Ave
Sterl
i
n
g
Hwy
Old
Sterl
i
n
gHwy
1
Ol
d
S
te
r
li
ngHwyLukeRd0.72 km
102.04 km
2.66 km 5.84 kmAnchor PointSubstation
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig02_Wetlands 12/11/2024 4:59 PM (Eric.Petersen)0 1,040
Meters
³Figure
PNA0023 December 2024
Anchor Point
Cook Inlet, Alaska
Wetlands and Waterways, Anchor Point Area
2
Legend
Proposed Cables
Overhead
Subsea
Landfall/Underground
Cable End Sealing Compound
Substation Expansion and
Converter Station
Existing Anchor Point Area
Conductor
Wetland, Class PEM
Wetland, Class PFO
Wetland, Class PSS
Wetland, Class PUB
Riverine
InterconnectOption 1
Interconnect
Options
2 and 3
Anchor PointSubstation
Note: Wetlands from NWI Database
P:\Clients\Alaska Energy and Electric Cooperative\PNA0023_Augustine FS\06_DataManagement_Visualization\GIS\Projects\Augustine_Explore\Augustine_Explore.aprx\Fig03_LandOwnership 12/11/2024 4:59 PM (Eric.Petersen)³Figure
PNA0023 December 2024
Anchor Point
Cook Inlet, Alaska
Land Ownership, Anchor Point Area
3
Legend
Mineral Permit/Lease
State of Alaska DNR Property
Kenai Peninsula Borough Property
Kenai Trust Property
University of Alaska Property
Property Parcels: Other Owners
Proposed Cables
Overhead
Subsea
Landfall/Underground
Substation Expansion and
Converter Station
Cable End Sealing Compound
InterconnectOption 1
Interconnect
Options
2 and 3
Anchor PointSubstation
0 1,000
Meters
Augustine Island Interconnection Feasibility Study
APPENDIX B
Electrical Diagrams
Augustine Island Interconnection Feasibility Study
APPENDIX C
Cost Estimate
OPTION 1 - AUGUSTINE TO NORTH OF ANCHOR POINT TO EXISTING SUBSTATION
ROUGH ORDER OF MAGNITUDE COST ESTIMATE ON CONCEPTUAL DESIGN
AUGUSTINE ISLAND INTERCONNECT FEASIBILITY STUDY
Activity Unit Amount Unit Cost Extended Cost
Extended Cost
(-30%)
Extended Cost
(+50%)Assumptions
Project Management and Administration ls 1 $805,066 $805,066 $402,540 $1,207,600 % of total project labor and studies (no materials and equipment)
NEPA Permitting ls 1 $100,000 $100,000 $50,000 $150,000 Assumes an EA or less. EIS would be 5-10X an EA
Environmental Planning ls 1 $200,000 $200,000 $100,000 $300,000
Routing Studies - Cook Inlet ls 1 $1,250,000
$1,250,000 $625,000 $1,875,000 Vessel-based work, includes geotechnical, hydrographic plus reporting
Archeology Studies - Cook Inlet ls 1 $2,000,000 $2,000,000 $1,000,000 $3,000,000 Vessel-based work, includes archeological plus reporting
Geotechnical - Onshore and Nearshore ls 1 $1,000,000
$1,000,000 $500,000 $1,500,000 Mobilization of rig, investigation for HDD, facilities, towers, lab testing, reporting
Leasing, ROW, Land ls 1 $500,000 $500,000 $350,000 $750,000 Highly variable based on negotiations with private property owners
Engineering Design - Transmission ls 1 $1,850,660 $1,850,660
$1,295,462 $2,775,990
Engineering Design - Substation ls 1 $1,150,000 $1,150,000 $805,000 $1,725,000
Subtotal $8,855,726 $6,199,010 $13,283,590
Mobilization of Equipment from Mfg to Anchorage ls 1 $1,740,000 $1,740,000
$1,218,000 $2,610,000 Assumes vessel transport from Asia to Anchorage for transformers and from Europe to Anchorage for converters
Railbelt Mobilization to Anchor Point ls 1 $90,000 $90,000 $63,000 $135,000 Assumes four heavy-haul loads from Homer to Anchor Point
Barging Mobilization Anchorage to Augustine/Homer ls 1 $1,160,109 $1,160,109
$812,076 $1,740,164 Pricing for a 6-day barge charter at current fuel pricing
Charter Aircraft Transport Homer to Augustine RTs 56 $3,015 $168,840 $118,188 $253,260 Assumes weekly helicopter RT from Homer for 13 month duration
Subtotal $3,158,949 $2,211,270 $4,738,430
Generator Step Up Transformer Unit 2 $3,465,000 $6,930,000
$4,851,000 $10,395,000
HV Breakers Unit 2 $235,000 $470,000 $329,000 $705,000
115kV GOAB Switch Unit 6 $14,167 $85,000
$59,500 $127,500 2000A
CCVT Unit 6 $12,000 $72,000 $50,400 $108,000
Arresters Unit 6 $1,750 $10,500
$7,350 $15,750
34.5kV GOAB Switch Unit 2 $7,250 $14,500 $10,150 $21,750 2000A
MV Switchgear and Relay Building Unit 1 $990,000 $990,000
$693,000 $1,485,000 inlcudes all relays
Package Substation ls 1 $639,500 $639,500 $447,650 $959,250 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction ls 1 $2,762,500 $2,762,500 $1,933,750 $4,143,750 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...)
Temporary Construction Camp mo 13 $186,000 $2,418,000 $1,692,600 $3,627,000 Assumes camp durations of 9 months (Yr 8-9) and 4 months (Yr 10) for 24-person camp, 2x setup/tear down
Testing and Commissioning ls 1 $200,000 $200,000 $140,000 $300,000
Subtotal $14,592,000 $10,214,410 $21,888,010
HVDC Converter Station unit 2 $72,500,000 $145,000,000 $101,500,000 $217,500,000 Modular system from manufacturer
OH Lines - Augustine km 2 $101,800 $203,600
$142,520 $305,400 HVDC
Cable sealing end compound - Augustine unit 1 $102,500 $102,500 $71,750 $153,750
Subsea cable - HDD sections - Augustine km 0.5 $1,394,000 $697,000 $487,900 $1,045,500
OH Lines - Anchor Point km 2.8 $101,800 $285,040 $199,528 $427,560
Cable sealing end compound - Anchor Point unit 1 $102,500 $102,500 $71,750 $153,750
Subsea cable - HDD sections - Anchor Point km 1.23 $1,394,000 $1,714,620 $1,200,234 $2,571,930
Subsea cable km 111 $810,000 $89,910,000 $62,937,000 $134,865,000 Estimated based on copper pricing
OH lines installation - Anchor Point km 2.8 $34,800 $97,440 $68,208 $146,160
OH lines installation - Augustine km 2 $34,800 $69,600 $48,720 $104,400
Cable installation HDD - Augustine Island km 0.5 $170,000 $85,000 $59,500 $127,500
Cable installation HDD - Anchor Point km 1.23 $170,000 $209,100 $146,370 $313,650
Subsea cable installation km 111 $362,500 $40,237,500 $28,166,250 $60,356,250
Construction ls 1 $5,122,100 $5,122,100 $3,585,470 $7,683,150 Civil works
Comissioning ls 1 $442,065 $442,065 $309,446 $663,098
Subtotal $283,836,000 $198,685,200 $425,754,000
Main Power Transformer Unit 1 $3,450,000 $3,450,000 $2,415,000 $5,175,000 Due to loading need to replace existing with new 70/93.1/116.3 MVA 115/29.94 Delta/Wye Transformer
HV Breakers Unit 4 $295,000 $1,180,000 $826,000 $1,770,000 1200A, lead time 110-114 weeks
115kV GOAB Switches Unit 8 $14,250 $114,000 $79,800 $171,000 1200A
115kV GOAB Switches w/ MO Unit 4 $21,750 $87,000 $60,900 $130,500 1200A
115kV CCVTs Unit 12 $12,000 $144,000 $100,800 $216,000
Arresters Unit 9 $1,750 $15,750 $11,025 $23,625 98kV MCOV
Packaged Control Building Unit 1 $740,000 $740,000 $518,000 $1,110,000 Includes all relay panels
Packaged Substation Materials ls 1 $1,103,890 $1,103,890 $772,723 $1,655,835 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction ls 1 $3,158,300 $3,158,300
$2,210,810 $4,737,450 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...)
Testing and Commissioning ls 1 $250,000 $250,000 $175,000 $375,000
Subtotal $10,242,940 $7,170,060 $15,364,410
Grand Total $320,685,615 $224,479,940 $481,028,430
Design, Engineering, Environmental, Permitting, and Project Management
Mobilization/Demobilization (Fixed Costs)
Materials and Construction Operations - Augustine Island Substation to Anchor Point Substation Transmission
Materials and Construction Operations - Anchor Point Substation
Materials and Construction Operations - Augustine Island Substation
OPTION 2 - AUGUSTINE TO SOUTH OF ANCHOR POINT TO EXISTING SUBSTATION
ROUGH ORDER OF MAGNITUDE COST ESTIMATE
AUGUSTINE ISLAND INTERCONNECT FEASIBILITY STUDY
Activity Unit Amount Unit Cost Extended Cost
Extended Cost
(-30%)
Extended Cost
(+50%)Assumptions
Project Management and Administration ls 1 $805,066 $805,066 $402,540 $1,207,600 % of total project labor and studies (no materials and equipment)
NEPA Permitting ls 1 $100,000 $100,000 $50,000 $150,000 Assumes an EA or less. EIS would be 5-10X an EA
Environmental Planning ls 1 $200,000
$200,000 $100,000 $300,000
Routing Studies - Cook Inlet ls 1 $1,250,000 $1,250,000 $625,000 $1,875,000 Vessel-based work, includes geotechnical, hydrographic plus reporting
Archeology Studies - Cook Inlet ls 1 $2,000,000
$2,000,000 $1,000,000 $3,000,000 Vessel-based work, includes archeological plus reporting
Geotechnical - Onshore and Nearshore ls 1 $1,000,000 $1,000,000 $500,000 $1,500,000 Mobilization of rig, investigation for HDD, facilities, towers, lab testing, reporting
Leasing, ROW, Land ls 1 $500,000
$500,000 $350,000 $750,000 Highly variable based on negotiations with private property owners
Engineering Design - Transmission ls 1 $1,850,660 $1,850,660 $1,295,462 $2,775,990
Engineering Design - Substation ls 1 $1,150,000 $1,150,000
$805,000 $1,725,000
Subtotal $8,855,726 $6,199,010 $13,283,590
Mobilization of Equipment from Mfg to Anchorage ls 1 $1,740,000 $1,740,000 $1,218,000 $2,610,000 Assumes vessel transport from Asia to Anchorage on a charter day rate, different vessel for transformer and converter
Railbelt Mobilization to Anchor Point ls 1 $90,000 $90,000
$63,000 $135,000 Assumes four heavy-haul loads from Homer to Anchor Point
Barging Mobilization Anchorage to Augustine/Homer ls 1 $1,160,109 $1,160,109 $812,076 $1,740,164 Pricing for a 6-day barge charter at current fuel pricing
Charter Aircraft Transport Homer to Augustine RTs 56 $3,015 $168,840
$118,188 $253,260 Assumes weekly helicopter RT from Homer for 13 month duration
Subtotal $3,158,949 $2,211,270 $4,738,430
Generator Step Up Transformer Unit 2 $3,465,000 $6,930,000 $4,851,000 $10,395,000
HV Breakers Unit 2 $235,000 $470,000
$329,000 $705,000
115kV GOAB Switch Unit 6 $14,167 $85,000 $59,500 $127,500 2000A
CCVT Unit 6 $12,000 $72,000 $50,400 $108,000
Arresters Unit 6 $1,750 $10,500 $7,350 $15,750
34.5kV GOAB Switch Unit 2 $7,250 $14,500
$10,150 $21,750 2000A
MV Switchgear and Relay Building Unit 1 $990,000 $990,000 $693,000 $1,485,000 inlcudes all relays
Package Substation ls 1 $639,500 $639,500 $447,650 $959,250 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction Cost ls 1 $2,762,500 $2,762,500 $1,933,750 $4,143,750 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...)
Temporary Construction Camp mo 13 $186,000 $2,418,000
$1,692,600 $3,627,000 Assumes camp durations of 9 months (Yr 8-9) and 4 months (Yr 10) for 24-person camp, 2x setup/tear down
Testing and Commissioning ls 1 $200,000 $200,000 $140,000 $300,000
Subtotal $14,592,000 $10,214,410 $21,888,010
HVDC Converter Station unit 2 $72,500,000 $145,000,000
$101,500,000 $217,500,000 Modular system from manufacturer
OH Lines - Augustine km 2 $101,800 $203,600 $142,520 $305,400 HVDC
Cable sealing end compound - Augustine unit 1 $102,500 $102,500
$71,750 $153,750
Subsea cable - HDD sections - Augustine km 0.5 $1,394,000 $697,000 $487,900 $1,045,500
OH lines - Anchor Point km 8.3 $101,800 $844,940 $591,458 $1,267,410
Cable sealing end compound - Anchor Point unit 1 $102,500 $102,500 $71,750 $153,750
Subsea cable - HDD sections - Anchor Point km 2.05 $1,394,000 $2,857,700 $2,000,390 $4,286,550
Subsea cable km 111 $810,000 $89,910,000 $62,937,000 $134,865,000 Estimated based on copper pricing
OH lines installation - Anchor Point km 8.3 $34,800 $288,840 $202,188 $433,260
OH lines installation - Augustine km 2 $34,800 $69,600 $48,720 $104,400
Cable installation HDD - Augustine Island km 0.5 $170,000 $85,000 $59,500 $127,500
Cable installation HDD - Anchor Point km 2.05 $170,000 $348,500 $243,950 $522,750
Subsea cable installation km 111 $362,500 $40,237,500
$28,166,250 $60,356,250
Construction ls 1 $5,122,100 $5,122,100 $3,585,470 $7,683,150 Civil works
Comissioning ls 1 $442,065 $442,065
$309,446 $663,098
Subtotal $286,311,845 $200,418,292 $429,467,768
Main Power Transformer Unit 1 $3,450,000 $3,450,000 $2,415,000 $5,175,000 Due to loading need to replace existing with new 70/93.1/116.3 MVA 115/29.94 Delta/Wye Transformer
HV Breakers Unit 4 $295,000 $1,180,000
$826,000 $1,770,000 1200A, lead time 110-114 weeks
115kV GOAB Switches Unit 8 $14,250 $114,000 $79,800 $171,000 1200A
115kV GOAB Switches w/ MO Unit 4 $21,750 $87,000
$60,900 $130,500 1200A
115kV CCVTs Unit 12 $12,000 $144,000 $100,800 $216,000
Arresters Unit 9 $1,750 $15,750 $11,025 $23,625 98kV MCOV
Packaged Control Building Unit 1 $740,000 $740,000 $518,000 $1,110,000 Includes all relay panels
Packaged Substation Materials Unit 1 $1,103,890 $1,103,890
$772,723 $1,655,835 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction Cost Unit 1 $3,158,300 $3,158,300 $2,210,810 $4,737,450 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...) and Site Management
Commissioning and Testing Unit 1 $250,000 $250,000
$175,000 $375,000
Construction Costs $10,242,940 $7,170,060 $15,364,410
Grand Total $323,161,460 $226,213,042 $484,742,208
Design, Engineering, Environmental, Permitting, and Project Management
Mobilization/Demobilization (Fixed Costs)
Materials and Construction Operations - Augustine Substation to Anchor Point Substation
Materials and Construction Operations - Anchor Point Substation
Materials and Construction Operations - Augustine Island Substation
OPTION 3 - AUGUSTINE TO SOUTH OF ANCHOR POINT TO NEW SUBSTATION
ROUGH ORDER OF MAGNITUDE COST ESTIMATE
AUGUSTINE ISLAND INTERCONNECT FEASIBILITY STUDY
Activity Unit Amount Unit Cost Extended Cost
Extended Cost
(-30%)
Extended Cost
(+50%)Assumptions
Project Management and Administration ls 1 $805,066 $805,066 $402,540 $1,207,600 % of total project labor and studies (no materials and equipment)
NEPA Permitting ls 1 $100,000 $100,000 $50,000 $150,000 Assumes an EA or less. EIS would be 5-10X an EA
Environmental Planning ls 1 $200,000
$200,000 $100,000 $300,000
Routing Studies - Cook Inlet ls 1 $1,250,000 $1,250,000 $625,000 $1,875,000 Vessel-based work, includes geotechnical, hydrographic plus reporting
Archeology Studies - Cook Inlet ls 1 $2,000,000
$2,000,000 $1,000,000 $3,000,000 Vessel-based work, includes archeological plus reporting
Geotechnical - Onshore and Nearshore ls 1 $1,000,000 $1,000,000 $500,000 $1,500,000 Mobilization of rig, investigation for HDD, facilities, towers, lab testing, reporting
Leasing, ROW, Land ls 1 $500,000
$500,000 $350,000 $750,000 Highly variable based on negotiations with private property owners
Engineering Design - Transmission ls 1 $1,850,660 $1,850,660 $1,295,462 $2,775,990
Engineering Design - Substation ls 1 $1,150,000 $1,150,000
$805,000 $1,725,000
Total Planning $8,855,726 $6,199,010 $13,283,590
Mobilization of Equipment from Mfg to Anchorage ls 1 $1,740,000 $1,740,000 $1,218,000 $2,610,000 Assumes vessel transport from Asia to Anchorage on a charter day rate, different vessel for transformer and converter
Railbelt Mobilization to Anchor Point ls 1 $90,000 $90,000
$63,000 $135,000 Assumes four heavy-haul loads from Homer to Anchor Point
Barging Mobilization Anchorage to Augustine/Homer ls 1 $1,160,109 $1,160,109 $812,076 $1,740,164 Pricing for a 6-day barge charter at current fuel pricing
Charter Aircraft Transport Homer to Augustine RTs 56 $3,015 $168,840
$118,188 $253,260 Assumes weekly helicopter RT from Homer for 13 month duration
Total Mobilization/Demobilization $3,158,949 $2,211,270 $4,738,430
Generator Step Up Transformer Unit 2 $3,465,000 $6,930,000 $4,851,000 $10,395,000
HV Breakers Unit 2 $235,000 $470,000
$329,000 $705,000
115kV GOAB Switch Unit 6 $14,167 $85,000 $59,500 $127,500 2000A
CCVT Unit 6 $12,000 $72,000 $50,400 $108,000
Arresters Unit 6 $1,750 $10,500 $7,350 $15,750
34.5kV GOAB Switch Unit 2 $7,250 $14,500
$10,150 $21,750 2000A
MV Switchgear and Relay Building Unit 1 $990,000 $990,000 $693,000 $1,485,000 inlcudes all relays
Package Substation ls 1 $639,500 $639,500 $447,650 $959,250 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction Cost ls 1 $2,762,500 $2,762,500 $1,933,750 $4,143,750 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...)
Temporary Construction Camp mo 13 $186,000 $2,418,000
$1,692,600 $3,627,000 Assumes camp durations of 9 months (Yr 8-9) and 4 months (Yr 10) for 24-person camp, 2x setup/tear down
Testing and Commissioning ls 1 $200,000 $200,000 $140,000 $300,000
Construction Costs $14,592,000 $10,214,410 $21,888,010
HVDC Converter Station unit 2 $72,500,000 $145,000,000
$101,500,000 $217,500,000 Modular system from manufacturer
OH Lines - Augustine km 2 $101,800 $203,600 $142,520 $305,400 HVDC
Cable sealing end compound - Augustine unit 1 $102,500 $102,500
$71,750 $153,750
Subsea cable - HDD sections - Augustine km 0.5 $1,394,000 $697,000 $487,900 $1,045,500
Overhead lines - Anchor Point km 8.3 $101,800 $844,940 $591,458 $1,267,410
Cable sealing end compound - Anchor Point unit 1 $102,500 $102,500 $71,750 $153,750
Subsea cable - HDD sections - Anchor Point km 2.05 $1,394,000 $2,857,700 $2,000,390 $4,286,550
Subsea cable km 111 $810,000 $89,910,000 $62,937,000 $134,865,000 Estimated based on copper pricing
OH lines installation - Anchor Point km 8.3 $34,800 $288,840 $202,188 $433,260
OH lines installation - Augustine km 2 $34,800 $69,600 $48,720 $104,400
Cable installation HDD - Augustine Island km 0.5 $170,000 $85,000 $59,500 $127,500
Cable installation HDD - Anchor Point km 2.05 $170,000 $348,500 $243,950 $522,750
Subsea cable installation km 111 $362,500 $40,237,500
$28,166,250 $60,356,250
Construction ls 1 $5,087,330 $5,087,330 $3,561,131 $7,630,995 Civil works
Comissioning ls 1 $436,845 $436,845
$305,792 $655,268
Construction Costs $286,271,855 $200,390,299 $429,407,783
Main Power Transformer Unit 1 $3,450,000 $3,450,000 $2,415,000 $5,175,000 due to loading need to replace existing with new 70/93.1/116.3 MVA 115/29.94 Delta/Wye Transformer
HV Breakers Unit 4 $295,000 $1,180,000
$826,000 $1,770,000 1200A, lead time 110-114 weeks
115kV GOAB Switches Unit 8 $14,250 $114,000 $79,800 $171,000 1200A
115kV GOAB Switches w/ MO Unit 4 $21,750 $87,000
$60,900 $130,500 1200A
115kV CCVTs Unit 12 $12,000 $144,000 $100,800 $216,000
Arresters Unit 9 $1,750 $15,750 $11,025 $23,625 98kV MCOV
Packaged Control Building Unit 1 $740,000 $740,000 $518,000 $1,110,000 Includes all relay panels
Packaged Substation Materials Unit 1 $1,251,408 $1,251,408
$875,986 $1,877,112 All other material, MV/LV materials, steel structures, grounding, metering, etc...
Construction Cost Unit 1 $3,833,319 $3,833,319 $2,683,323 $5,749,979 Civil and Electrical, inlcudes consumables (concrete, gravel, fencing, etc...)
Commissioning and Testing Unit 1 $250,000 $250,000
$175,000 $375,000
Construction Costs $10,815,477 $7,570,840 $16,223,220
Grand Total $323,694,007 $226,585,829 $485,541,033
Design, Engineering, Environmental, Permitting, and Project Management
Mobilization/Demobilization (Fixed Costs)
Materials and Construction Operations - Augustine Substation to Anchor Point New Substation
Materials and Construction Operations - Anchor Point New Substation
Materials and Construction Operations - Augustine Island Substation
Cost Estimate 1 December 2024
1. COST ESTIMATE AND ASSUMPTIONS 1.1 Engineering Design The engineering design consists of the two substations, the overhead circuits on both ends, the subsea cable and AC to DC conversion, and integration across the entire interconnect. Engineering design is estimated as the following:
• The conversion facility is modular and will be undertaken by the manufacturer, so is
included in equipment costs. However, the design costs associated with technical
parameters and civil works design and included.
• Design is assumed to be straightforward for HDD at Augustine, using a cofferdam at
the point of entry into Cook Inlet.
• Design for the HDD at Anchor Point is assumed to have the cable sealing end
compound very close to the entry point for HDD to avoid the need for an onshore
transitional joint pit.
• Routing hydrographic and geotechnical studies will be conducted using a specialized
vessel and equipment, virbacores or gravity cores, and 700 miles of multibeam
bathymetry, side-scan sonar, and magnetometer.
• Routing archeological studies will be conducted using a specialized vessel and
equipment.
• Overhead transmission lines design assumes a simple T-type arrangement for a single
DC circuit on Augustine and on Anchor Point.
• Overhead cable routing geotechnical studies on both Augustine Island and within
Anchor Point includes marine jack-up and conventional drill rigs, nearshore borings
for HDD, onshore facilites, and transmission towers.
• Reporting and data analysis costs are included for the studies.
1.2 Materials
Materials consist primarily of conductor, but also overhead mounting poles, conduit for HDD
burial, insulators, grounding, and mounting hardware.
• Subsea HVDC copper conductored cable is estimated using the London Metal
Exchange average price for copper in 2024 of $9,740 per ton of copper.
• Subsea cables and cable sealing ends have been assumed to be manufactured in either
Europe or Southeast Asia (e.g., South Korea).
1.3 Equipment
Equipment consists of HVAC switchgear, metering current and voltage transformers, busbars etc.
It also includes all the equipment associated with the HVDC converter station e.g., converter
Cost Estimate 2 December 2024
transformer, DC switchgear, AC and DC filters, voltage dividers, insulated-gate bipolar transistor valves, control systems, etc. • The HVDC converters are modular and assumed to be manufactured in Europe. However, some components such as the AC and DC filters and converter transformers could be manufactured in North America which could reduce the cost of the converter station. • Transformers are assumed to be manufactured in Asia.
1.4 Construction
Construction includes the earthworks to prepare the substation site, converter site, erect towers and
overhead lines, and also earthworks to prepare staging sites. No costs are included for building
infrastructure.
• Subsea cable length has been allowed for to cover the fluctuations in elevation along
the seabed.
• Average daily hire rate for a cable laying vessel is approximately $80,000 to $120,000.
A typical transit time would be 35 to 45 days. The vessel would collect the cables from
the manufacturer and bring them to the site for laying.
• HDD is assumed to be needed at both ends, staging area needed for pulling the cable
through conduit
• Assumes local Alaska labor with specialist site supervision provided by the
manufacturer
• Assumes overhead lines can be constructed using ground mounted plant and
equipment. It excludes the costs associated with temporary roads to access the overhead
line route or the use of helicopters in the transportation of materials and personnel. If
helicopters and temporary roads are needed for construction, assume additional costs.
Approximately $3k per trip for use of helicopter for transport of personnel and
materials should the ground conditions dictate that this is the best method.
Approximately $27k per mile for the construction of temporary access roads along
the overhead line routes on Augustine Island and Anchor Point.
• Civil works assumes construction labor will be local and not require housing on Anchor
Point. Costs for a temporary construction camp are included in the estimate for
Augustin.
• Civil works assumes heavy equipment will be sourced locally on the Kenai.
1.5 Commissioning
Commissioning is needed for each component of the design as well as the system as a whole.
• Converter stations will be commissioned by specialists from the manufacturer.
• Commissioning engineers will be sourced locally from Alaska
Augustine Island Interconnection Feasibility Study
APPENDIX D
Permitting Matrix
APPENDIX D - PERMITTING MATRIX
Agency Permit Description Applicable Estimate Agency
Review Time
Alaska DEC 401 WQC
Alaska Department of Environmental Conservation (DEC) conducts Section 401 certification reviews of projects in
Alaska in regards to federal permits from USACE.
If the use of a nationwide permit (NWP) or individual permit (IP) is required, it would trigger Alaska Department of
Environmental Conservation (DEC) 401 WQC. This requirement includes compliance with erosion control, post-
construction total suspended solids (TSS) control, and sedimentation control best management practices (BMPs).
Yes 90-days
Alaska DEC Air Quality Construction Permit
This permit ensures that the construction activities comply with air quality standards and regulations to protect
the environment and public health. The use of vessels and heavy equipment may require air permitting and
dispersion modeling.
Maybe 6-9 months
Alaska DEC APDES Construction General Permit
APDES Construction General Permit is required if stormwater discharge occurs from a construction site disturbing
1 acre or more of land. Activities associated with unrefined oil, including pipelines, are exempt from this
requirement.
For construction projects disturbing greater than 1 acre, a SWPPP is required. For projects disturbing greater than
5 acres and located outside the area of a permitted MS4, a Notice of Intent (NOI) and SWPPP must be submitted
to Alaska Department of Environmental Conservation (DEC). For projects disturbing greater than 5 acres and
located inside the area of a permitted MS4, the SWPPP must be submitted to the MS4 prior to the NOI being
submitted to the DEC. For projects less than 1 acre, the plan would be retained on-site and not submitted to
agency. A generally applicable construction SWPPP template is available from the Alaska Department of
Environmental Conservation (DEC) or EPA's website.
Yes 30 days
Alaska DEC APDES Excavation Dewatering General Permit
Dewatering discharges eligible for coverage under this general permit consist of water pumped from excavation
areas through the use of temporary dewatering wells or submersible pumps to lower the water table to support a
construction activity. The dewatering of accumulated groundwater and stormwater that accumulates within an
excavation area is an authorized discharge under the permit. The permit provides discharge authorization for
dewatering conducted within 1,500 feet of a permit defined “DEC-identified contaminated site” although special
permit conditions apply, and additional requirements may be added in the discharge authorization.
Maybe 30 days
Alaska DF&G Alaska Threatened and
Endangered Species Regulations
These laws and regulations protect T&E species in Alaska by prohibiting the taking, possession, transportation, or
sale of protected species without the issuance of a permit. Several species are listed as occurring in Kenai
Peninsula Borough.
Recommend initiation of coordination with Alaska Department of Fish & Game (ADF&G) to confirm no impacts
with selected route.
Yes 60 days
Alaska DF&G Fish Habitat Permit A permit is required for projects that involve water withdrawal or an activity that may have an impact on fish
passage and the waterbody supports resident or anadromous fish.Maybe 4-6 weeks
Alaska DF&G Special Area Permit A project/activity located within a legislatively designated Special Area (state game refuge, critical habitat area, or
wildlife sanctuary) will require a permit.Maybe 4-6 weeks
Alaska DOT & PF Oversize/Overweight Permit For construction equipment to use or cross state roads exceeding the size and weight limits.Maybe
1 day
5 working days if
superload
Alaska DNR Land Use Permit Land use permits are used for used for use of any state-owned lands (including tidelands, shorelands, submerged
lands). These permits will be needed for easements, development, transmission, and vehicle access. Yes 30 days
Page 1 of 4
APPENDIX D - PERMITTING MATRIX
Agency Permit Description Applicable Estimate Agency
Review Time
Alaska DNR Temporary Water Use Authorization
Per 11 AAC 93.035 (a) (b) and 11 AAC 93.220, a temporary water use authorization must be received from DNR
prior to:
(1) the consumptive use of more than 5,000 gallons of water from a single source in a single day; or (2) the regular
daily or recurring consumptive use of more than 500 gallons per day (gpd) from a single source for more than 10
days per calendar year; or (3) the non-consumptive use of more than 30,000 gpd (0.05 cubic feet per second) from
a single source; or (4) any water use that may adversely affect the water rights of other appropriators or the public
interest. This permit is recommended if water will be withdrawn from
waters of the State.The process is initiated with submittal of an application to DNR.
Maybe 60 days
Alaska SHPO (OHA)Section 106 Consultation Process, National Historic Preservation Act (NHPA)
Consultation with State Historic Preservation Office and tribes is required if a federal nexus (e.g. ESA, Section 404
Permit) is identified.
This is triggered by impacts to WOTUS. This will require a Phase 1A desktop review and then a Phase 1B to do a
site assessment, including shovel tests and trenching in deeper areas.
Coordinate with State Historic Preservation Office and the USACE to determine the appropriate site assessment
protocols.
Yes 90 days
Bureau of Ocean Energy Management
(BOEM)Outer Continental Shelf Planning and Coordination
Prior to initiating environmental surveys for the offshore portion of the project, a Development Plan has to
beprepared and submitted to BOEM that includes a narrative summary and maps to show proximity to the
following features:
• Air Quality
• Archeological Assessments
• Oil Spill Modeling
• Deepwater Information (Chemical)
• Artificial Reefs
• Biological
• Economic impact analysis
• Military
• Ordnance dumping
Any study or survey has to be approved by BOEM before being completed. The cost includes coordination and
review of existing data to determine what surveys and monitoring would be required. In addition, the route of the
offshore transmissionline would be required to compare the proximity to the above referenced features.
Yes 3 months
EPA Construction Spill Prevention, Control, and Countermeasure (SPCC) Plan
Construction SPCC required if total aggregate capacity of aboveground oil storage containers is greater than
1,320 gallons of oil or underground storage of oil is greater than 42,000 gallons.
The need for a SPCC will depend on the total capacity of all oil stored at the Project Area during construction. ASTs
and equipment that stores > or = 55 gallons of oil would be included in the stored amount.
Maybe Automatic
Multiple public and private land owners Individual landowner easement agreements Case-by-case consultation will be needed for several land owners in the routing options. Yes 6-12 months
NOAA Incidental Take Permit for Marine Mammals Requires projects with a potential to affect marine mammals to consult with the NMFS/ USFWS. A marine
mammal Protection Plan and monitoring will be required during construction. Maybe 5 to 15 months
NOAA, National marine Fisheries Service
(NMFS)Section 7, Endangered Species Acta
Requires projects with a federal nexus to ensure that the action is not likely to jeopardize the continued existence
of any threatened and endangered (T&E) species or result in the destruction or adverse modification of critical
habitat of such species. The act requires projects affecting WOTUS to consult with the USFWS and the state
agency responsible for fish and wildlife resources. Consultation with USFWS is required for potential impacts to
T&E species. An evaluation of the selected site will need to be performed. The NMFS database can identify
species with the potential to be impacted by the proposed project.
Yes 90 - 165 days
US Coast Guard (USCG) Navigation Concurrence via Bridge Permit USCG coordinates construction across navigable waterways. Coordination with USCG should be considered to
coordinate vessel navigation during subsea cable laying.Maybe 6-12 months
Page 2 of 4
APPENDIX D - PERMITTING MATRIX
Agency Permit Description Applicable Estimate Agency
Review Time
USACE Alaska District / Alaska DEC Clean Water Act (CWA) Section 10 and Section 404 Nationwide Permit or Individual
Permit
Section 404, Permits for Dredged or Fill Material, regulates the discharge of dredged or fill material in
jurisdictional wetlands and waters of the United States (WOTUS). Alaska is seeking to assume the dredge and fill
program under Section 404 of the Clean Water Act (CWA). If approved, applications will go through the Alaska
DEC instead of the USACE.
Section 10 Navigable Waters include those waters subject to the ebb and flow of the tide shoreward to the mean
high water mark and/or those waters that are presently used, or have been used in the past, or may be susceptible
for use to transport interstate or foreign commerce. Section 10 Navigable Waters are regulated under the Rivers
and Harbors Act of 1899.
If impacts exceed those allowed under the Nationwide Permit Program (0.5 acre of impact), an Individual Permit
(IP) may be required which entails additional coordination for clearance under NEPA and has an extended review
period with no administratively designated review clock.
Yes Individual Permit -
12-18 months
USACE Alaska District / Alaska DEC CWA Section 408
Section 408 authorization is required for any alteration of a USACE Civil Works/USACE levee project to ensure the
alteration does not cause adverse impacts. Section 408 is a threshold review, and, if required, must be obtained
before the USACE can issue a Section 404 permit. The 408 approval process requires four steps: completeness
determination, review and decision, final decision notification, and construction oversight.
Yes 6-9 months
USACE Alaska District / Alaska DEC Environmental Assessment Concurrent with a Section 404 Permit for review of the project for compliance with the National Environmental
Policy Act (NEPA)Yes 12-24 months
USFWS Section 7, Endangered Species Acta
Requires projects with a federal nexus to ensure that the action is not likely to jeopardize the continued existence
of any threatened and endangered (T&E) species or result in the destruction or adverse modification of critical
habitat of such species. The act requires projects affecting WOTUS to consult with the USFWS and the state
agency responsible for fish and wildlife resources. Consultation with USFWS is required for potential impacts to
T&E species. An evaluation of the selected site will need to be performed. The Information for Planning and
Consultation (IPaC) tool can identify species with the potential to be impacted by the proposed project.
Yes 60 days
USFWS Migratory Bird Treaty Act Compliance (MBTA)
The MBTA regulates the take and harvest of migratory birds, their nests, and eggs. Regulated under UFSWS.
Requires a pre-construction nesting survey within ~14 days of clearing activities if construction happens during
nesting season (March 15 to September 15).
Given that the facility will be located in Kenai Peninsula Borough, birds protected by MBTA may pass through or
overwinter in this area and could occur in the Project Area. It is recommended to initiate construction outside of
the nesting season (March 15 to September 15) to avoid impacts to nesting birds and their offspring. Nests should
be avoided if observed during construction. No risk unless species intentionally killed.
Yes N/A
USFWS Bald and Golden Eagle Protection Act
This law prohibits the take, possession, and commerce of golden eagles and bald eagles, their nests, and eggs
except under certain specified conditions. An evaluation will need to occur to determine if suitable roosts exist
within the project footprint boundaries.
Yes N/A
Kenai Peninsula Borough Special Waste Disposal Request Required for the disposal of special waste generated within Kenai Peninsula Borough. Wastes generated outside
of the KPB and hazardous wastes are not accepted with this approval.Maybe 14 days
Kenai Peninsula Borough Individual Utility Construction Project Required for utility construction projects within the Borough's right-of-way (ROW).Yes 90 days
Kenai Peninsula Borough Floodplain Permitting
The borough has floodplain regulations requiring permitting for development within floodplains. - Elevation
certificate is required for development in a flood plain. The proposed route will need to be evaluated for being
within floodplains. If the route is within a floodplain, permitting with the borough to allow for development within
the floodplain will be required. Recommend contacting borough floodplain administrator to determine
appropriate permit path. This may be applied for as part of the Multi-Agency Permit Application.
Maybe 30 - 60 days
Kenai Peninsula Borough Conditional Use Permit Conditional Use Permits are permits issued for projects that fall outside the normal permitting guidelines. They
may be subject to special requirements, and must be approved by the KPB Planning Commission.Maybe 30 - 60 days
Local Development
Page 3 of 4
APPENDIX D - PERMITTING MATRIX
Agency Permit Description Applicable Estimate Agency
Review Time
Kenai Peninsula Borough Minor Vegetation Permit
A Minor Vegetation (MV) permit is required for all pruning, trimming, or removal of shrubs and/or hazard trees
within the KPB 50-foot Habitat Protection District, including dead or diseased trees. These over-the-counter tree
removal permits are completely free, and can be completed online, via email, or in person. This may be applied
for as part of the Multi-Agency Permit Application.
Maybe 30 - 60 days
Kenai Peninsula Borough Preliminary and Final Plat Preliminary and final plats must be approved and recorded with the Borough.Yes 6 - 12 months
Kenai Peninsula Borough Easement Application To obtain an easement from KPB land, an easement application must be approved. Platting process will need to
be completed prior to the easement being granted.Yes 6 - 12 months
Kenai Peninsula Borough Weight Restriction Waiver For construction equipment to use or cross borough roads exceeding the 50% weight restrictions on gravel roads
and 75% weight restrictions on paved roads.Maybe 1 Week
Page 4 of 4
Augustine Island Interconnection Feasibility Study
APPENDIX E
Environmental Scoring Matrix
APPENDIX E
ENVIRONMENTAL SCORING MATRIX
Feature Measurement
Ranking Weight
(1-5)Features Score Features Score
Topography: Total Climb Over Path Rise 2 160 320 409 818
Land Status / Ownership (Public) Number 1 1320 1320 5204 5204
Land Status / Ownership (Private) Number 2 3115 6230 13798 27596
Roadways and Roadway Crossings Number 2 4 8 9 18
Stream Crossings Number 2 1 2 2 4
Railroad Crossings Number 1 0 0 0 0
Existing Electrical Utilities Crossings Number 3 1 3 5 15
Wetlands (PEM: Palustrine Emergent) Distance 3 1749 5247 0 0
Wetlands (PSS: Palustrine Scrub-Shrub) Distance 4 2189 8756 9152 36608
Wetlands (PFO: Palustrine Forested) Distance 5 0 0 233 1165
Areas of Critical Environmental Concern Distance 5 0 0 0 0
US Fish and Wildlife Service Critical Habitat Distance 5 0 0 0 0
National Marine Fisheries Service Essential Fish Habitat Distance 4 0 0 0 0
Herd Management Areas Distance 2 0 0 0 0
Mature Forested Areas Distance 2 992 1984 3467 6934
Wilderness Areas and Wilderness Study Areas Distance 4 0 0 0 0
Cultural Resources Sites 5 0 0 1 5
Proximity to residential Houses (<250 ft) Number 5 14 70 49 245
Proximity to residential Houses (<500 ft) Number 3 40 120 90 270
Places of community gathering (churches, recreation centers, etc) Number 5 0 0 0 0
Option 1 Options 2/3
Augustine Island Interconnection Feasibility Study
APPENDIX F
Project Schedule
AUGUSTINE INTERCONNECT SCHEDULE (PLANNING AND CONSTRUCTION)
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
Concept Design
Project start u
Basis of Design
Cable routing detailed design
Sea Bed surveys
Environmental surveys u
Geotechnical surveys
Survey reporting
NEPA u
ROW
Land Use
Technical parameters and specifications u
Principal drawings
Power system studies
Scoping documentation
RFP Release and Bids u
Negotiation
Finacial Investment Decision
Contract Award u u
Detailed design - switchgear and P&C systems
Detailed design - transformers
Detailed design - overhead lines
Procurement - switchgear u
Procurement - transformers u
Procurement - overhead lines
Shipping to site from manufacturers
RFP Release and Bids u
Negotiation
Finacial Investment Decision
Contract Award u
Detailed Design - HVDC Subsea Cable u u u u
Procurement - HVDC Subsea Cable u u u u u u u u
Procurement - HVDC Converter transformer u
Shipping to site from manufacturers
Site Mobilization (both ends)u
Enabling works
Earthworks and Civils
Erection
Cold Commissioning
Hot Commissioning
Vessel mobilization with cable
Onshore HDD
Pre-install seabed survey
Cable installation
Post-install seabed survey
Cold Commissioning
Hot Commissioning
Connection Date (Backfeed Available)u u u
Synchronisation
Take Over
Construction - Subsea Cables
Construction - Plant and Equipment
Year 4Year 1
Procurement - Subsea Cables
Year 2
Permitting and Leases
Year 5
Procurement - Plant and Equipment
Year 3
Detailed Design
Page 1 of 2
AUGUSTINE INTERCONNECT SCHEDULE (PLANNING AND CONSTRUCTION)
Concept Design
Project start
Basis of Design
Cable routing detailed design
Sea Bed surveys
Environmental surveys
Geotechnical surveys
Survey reporting
NEPA
ROW
Land Use
Technical parameters and specifications
Principal drawings
Power system studies
Scoping documentation
RFP Release and Bids
Negotiation
Finacial Investment Decision
Contract Award
Detailed design - switchgear and P&C systems
Detailed design - transformers
Detailed design - overhead lines
Procurement - switchgear
Procurement - transformers
Procurement - overhead lines
Shipping to site from manufacturers
RFP Release and Bids
Negotiation
Finacial Investment Decision
Contract Award
Detailed Design - HVDC Subsea Cable
Procurement - HVDC Subsea Cable
Procurement - HVDC Converter transformer
Shipping to site from manufacturers
Site Mobilization (both ends)
Enabling works
Earthworks and Civils
Erection
Cold Commissioning
Hot Commissioning
Vessel mobilization with cable
Onshore HDD
Pre-install seabed survey
Cable installation
Post-install seabed survey
Cold Commissioning
Hot Commissioning
Connection Date (Backfeed Available)
Synchronisation
Take Over
Construction - Subsea Cables
Construction - Plant and Equipment
Procurement - Subsea Cables
Permitting and Leases
Procurement - Plant and Equipment
Detailed Design
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
u u
u u
u u
u
u
u u
u u u
u u
u
Year 10Year 7 Year 9Year 6 Year 8
Page 2 of 2
Augustine Island Interconnection Feasibility Study
APPENDIX G
Supplemental Information
Supplementary Information ii December 2024
TABLE OF CONTENTS 1. DETAILED EVALUATION OF HVAC AND HVDC ........................................................1 1.1 Evaluation of HVAC ....................................................................................................1 1.1.1 Critical Length ..................................................................................................1 1.1.2 Reactor Compensation .....................................................................................2 1.1.3 Cable Landfall ..................................................................................................4 1.1.4 Cable Sealing End Compound .........................................................................5 1.2 Evaluation of HVDC ....................................................................................................6
1.2.1 Technical Parameters .......................................................................................6
1.2.2 Current Source or Voltage Source Conversion ................................................7
1.2.3 DC to AC Conversion Station ..........................................................................8
2. CABLE INSTALLATION METHODS ..............................................................................11
2.1 Cable Laying Vessels .................................................................................................11
2.2 Method ........................................................................................................................12
2.2.1 Trench Jetting .................................................................................................13
2.2.2 Trench Ploughing ...........................................................................................14
2.2.3 Trench Cutting ................................................................................................15
2.3 Armoring ....................................................................................................................16
3. ENVIRONMENTAL REVIEW DETAILS ........................................................................18
3.1 Ecological Resources and Wildlife ............................................................................18
3.2 Fisheries ......................................................................................................................19
3.3 Protected Species ........................................................................................................20
3.4 Water Resources .........................................................................................................22
3.5 Air Quality ..................................................................................................................23
3.6 Cultural Resources .....................................................................................................23
3.7 Geology and Soil Resources .......................................................................................24
3.8 Environmental Justice ................................................................................................25
3.9 Human Health and Safety ...........................................................................................25
3.10 Noise ...........................................................................................................................26
3.11 Airspace ......................................................................................................................26
3.12 Visual Resources ........................................................................................................27
4. REFERENCES ....................................................................................................................28
Supplementary Information iii December 2024
LIST OF TABLES Table 1: HVAC Cable Critical Length Parameters at 115 kV Table 2: HVAC Cable Technical Parameters Table 3: HVDC Cable Technical Parameters Table 4: Similar Relevant HVDC VSC Projects Table 5: Hitachi Light Technology VSC Converter Station Sizing
LIST OF GRAPHICS
Graphic 1: Typical HVAC Three-Phase Cable Arrangement
Graphic 2: Typical Shunt Reactor
Graphic 3: Typical HVAC Cable Sealing End Arrangement
Graphic 4: Typical HVDC Monopole Cable Arrangement
Graphic 5: Siemens HVDC Plus VSC Converter Station Layout
Graphic 6: Valhall Project VSC Converter Station Layout (Norway)
Graphic 7: Cable Laying Vessel
Graphic 8: ROV Jet Trencher Diagram
Graphic 9: Typical Tracked ROV Jetting Machine
Graphic 10: Trench Ploughing Diagram
Graphic 11: Typical Subsea Cable Plough
Graphic 12: Trench Cutting Diagram
Graphic 13: OTTER Subsea Tracked Cable Trencher
Supplementary Information 1 December 2024
1. DETAILED EVALUATION OF HVAC AND HVDC 1.1 Evaluation of HVAC To evaluate whether a high voltage alternating current (HVAC) cable would be viable, the following high level technical parameters were considered: • 70 megawatt (MW) energy transfer capacity
• 390 ampere (A) amperage requirement
• 115 kilovolt (kV) voltage level
• 3 cables
• 107 kilometers (km) (66 miles) subsea, 4 km (2.5 miles) landfall connection via
horizontal directional drilling (HDD)
Graphic 1 shows a typical arrangement of a three-phase HVAC cable.
Graphic 1: Typical HVAC Three-Phase Cable Arrangement
Source: European Subsea Cable Association
1.1.1 Critical Length
In an alternating current (AC) solution, as the cable length increases, the current delivered to the
load decreases because of an increasing charging current. The length at which the charging current
becomes equal to the supply current is defined as the critical length and it is at this point the
charging current accounts for all heat losses in the cable. Using a commercially available cable—
a cross-linked polyethylene (XLPE), copper-conductored submarine cable by ABB Group—the
critical length was calculated as shown in Table 1, assuming that the same cable type would be
used along the entire route.
Supplementary Information 2 December 2024
Table 1: HVAC Cable Critical Length Parameters at 115 kV Maximum Length (km) Size (mm2) Cable Capacitance (µF/km) Maximum Current Carrying Capacity (A) 111.3 185 0.14 420 91.65 300 0.17 530 77.9 400 0.2 590 55.6 1,000 0.28 825
Note: No de-rating applied based on method of installation. The installation method will have an impact on the
current carrying capability of the cable, but not on the cable parameters.
A: amperes
µF/km: microfarads per kilometer
mm2: square millimeters
As shown in Table 1, the HVAC cable size of 185 square millimeters (mm2) (0.6 feet) meets the
distance from Augustine to Anchor Point. However, the capacitance of the cable has a major
impact on the length of cable possible at HVAC. For other manufacturers, the range for cable
capacitance at 115 kV is between 0.13 and 0.16 microfarads per kilogram (µF/km). Using a cable
rated at the edge of its range means that some manufacturers might not be able to supply the
required cable. Evaluation of another voltage level was not considered because the next standard
voltage level used in Anchor Point is 69 kV, which would not work for the HVAC solution.
1.1.2 Reactor Compensation
Given that the distance is possible with an HVAC cable, reactor compensation was evaluated to
ensure stable voltage levels and improve efficiency. The compensation requirement was calculated
to evaluate both the ability to cope with voltage dips for no-load and compensation of the charging
current for full-load conditions. Shunt reactors would be used along the route to compensate for
the cable capacitive reactance. In this preliminary power study, a simple formula was used to
provide a basic indication for cable compensation to summarize the reactive power requirements
of an underground cable. For the 185 mm2 copper-conductored cable at 110 km, the compensation
required is 76.7 megavolt-ampere reactive (MVAr).
Shunt inductive reactors could be placed at regular intervals along the cable, but that would prove
costly given the lack of available infrastructure (e.g., platforms) upon which to place the reactors.
An image of a typical shunt reactor is shown in Graphic 2. To accommodate reactive compensation
across Cook Inlet, the most economical option would be to locate a 40 MVAr shunt reactor at each
end of the cable. The recommended arrangements are shown in Graphics 3 and 4.
At the shunt reactor compound, additional equipment will be needed, including a relay/control
room, an uninterrupted power supply battery for the relays and supervisory control and data
acquisition (SCADA), an auxiliary transformer to provide power to the shunt reactor and
relay/control room, and power supply. At the Anchor Point end, the power supply would come
from the existing distribution grid. At the Augustine Island end, it would likely be best to have a
standby generator.
Supplementary Information 3 December 2024
During future design development, a power system study should consider whether additional variable reactive compensation would be required at Anchor Point for generation. Graphic 2: Typical Shunt Reactor
Graphic 3: Augustine Island End Shunt Reactor
Preferred Arrangement
Minimum Arrangement
Notes:
1. Disconnectors (isolators) and earth (grounding) switches are not shown.
2. Current and voltage transformers are not shown.
Supplementary Information 4 December 2024
Graphic 4: Anchor Point End Shunt Reactor
Preferred Arrangement
Minimum Arrangement
Notes:
1. Disconnectors (isolators) and earth (grounding) switches are not shown.
2. Current and voltage transformers are not shown.
3. Preliminary reactor size is 40 MVAr.
4. Voltage level assumed to be 115 kV.
5. There is a possible need for some variable reactive compensation required at the Anchor Point end for the
generation (to be confirmed via power system studies).
1.1.3 Cable Landfall
As the cable approaches landfall, there will be a requirement for the cable to be buried through the
seashore and daylight at a cable sealing end compound. The seashore at Anchor Point is relatively
shallow so the cable will begin HDD around 100 meters (m) to 150 m from the mean sea level on
the coast. The burial will extend at least 250 m (820 feet) from shore to ensure that the cable will
not be affected by erosion of the alluvium coast and will meet the coastal zone construction
requirements. At Augustine Island, it may be possible to install the cable without using an HDD
at landfall. However, this depends on the exact landing point, which remains uncertain. Therefore,
it is considered worst case within this study to also use HDD at the Augustine Island landfall.
For this study, the estimated depth for HDD cable installation is 5 to 10 m (16 to 33 feet). When
an HVAC cable is buried, the surrounding soil acts as an insulator, which prevents heat dissipation
and requires a de-rating factor to be applied. A typical de-rating factor applied for HDD is 0.85 to
prevent overheating. The rating of 420 A for the 185 mm2 cable will be derated to a maximum
capacity of 357 A, which is insufficient for the project. A typical practice to accommodate this
de-rating is to increase the cable diameter near landfall, requiring a subsea joint.
Based on the parameters shown in Table 1, the next conductor size is 300 mm2, with an
approximate capacitance of 0.17 µF/km. Assuming the length of the larger diameter cable at each
end is 1,000 m, the overall capacitance of the cable will change from 0.14 µF/km to approximately
0.15 µF/km. Using the modified parameters to accommodate the increase in cable size for landfall,
the critical length of the cable decreases to 104 km (65 miles), which is insufficient for the project.
Table 2 summarizes the calculations with landfall.
Supplementary Information 5 December 2024
Table 2: HVAC Cable Technical Parameters Technical Parameter Value Notes AC nominal voltage 115 kV Based on Anchor Point system Base power ~78 MVA Includes real power and reactive power AC cable current rating required ~390 A Before derating AC cable conductor size (subsea) 185 mm² copper (fully insulated) All three cores bundled together Applied installation derating (subsea) 1.0 Assumed that the cable will be buried in ideal
seabed conditions with a seabed thermal resistivity
of 1 Kelvin meters per watt (k.m/W)
AC cable conductor size (landfall) 300 mm² copper
(fully insulated)
All three cores bundled together
Applied installation derating (landfall) 0.85 Applied at the landing point for the cables with an
assumed burial depth of 10 m (33 feet)
AC cable current rating required ~459 A After derating for the landfall
Estimated electrical losses ~7% to 10% Ohmic losses in conductor.
Induced losses in conductor.
Induced losses in sheath.
Induced losses in armoring.
Charging current due to length.
1.1.4 Cable Sealing End Compound
For the transitioning of the subsea/underground cable to an overhead line, there will be a need for
a cable sealing end compound to be constructed. In a typical arrangement, the tower is located
close to the waterfront. The cable sealing ends are located on the tower along with support
insulators and also surge arresters on the line side as shown in Graphic 5.
Graphic 5: Typical HVAC Cable Sealing End Arrangement
Supplementary Information 6 December 2024
1.2 Evaluation of HVDC To evaluate whether a high voltage direct current (HVDC) cable would be viable, the following high level technical parameters were considered: • 100 MW energy transfer capacity • ±80 kV voltage level • Voltage source converter (VSC) technology
• VSC converter station using a symmetric monopole design
• 2 cables
• 105 km (65 miles) subsea, 6 km (3.7 miles) landfall connection via HDD
Graphic 6 shows a typical arrangement of a HVDC monopole cable arrangement with a metallic
return.
Graphic 6: Typical HVDC Monopole Cable Arrangement
Source: Trans Bay Cable
1.2.1 Technical Parameters
The provisional sizing of the HVDC cables is a 300 mm2 copper conductor XLPE direct current
(DC) submarine cable, assuming that both cables will be touching along the whole of the cable
route. This will provide an approximate rating of 662 A or 106 MW at 80 kV, assuming that the
same cable type is used along the entire route. With DC cabling, no reactive compensation is
needed.
Supplementary Information 7 December 2024
Table 3: HVDC Cable Technical Parameters Technical Parameter Value DC voltage (pole to ground) 80 kV Base power ~100 MVA DC current ~625 A DC main pole conductor size 300 mm² copper (fully insulated) DC return conductor size 300 mm² copper (insulated)
Estimated electrical losses (Ohmic losses in
conductor, Losses associated with the
conversion from DC to AC and vice versa)
~5% to 6%
1.2.2 Current Source or Voltage Source Conversion
For the HVDC converter station, either current source converters (CSC) or VSC technology can
be used, corresponding to two HVDC transmission technologies that are commercially available.
CSC are also known as line commutated compensation, using thyristors as the key power
electronic device. VSC uses insulated date bipolar transistor (IGBT)/injection-enhanced gate
transistor (IEGT) as the key power electronic device. There are some functions that for certain
networks are seen as a benefit but for other networks can be seen as a weakness. Therefore, the
HVDC technology should be selected to best suit the needs for the network but not cause additional
problems.
The traditional CSC technology, which is suitable for non-weak networks, has been installed for
applications up to 5 gigawatts (GW) while the newer VSC technology is available presently for 1
to 1.2 GW. VSC converter technology was first introduced to the market by ABB (now Hitachi)
using pulse width modulated (PWM) technology. This had advantages over CSC technology in
that it did not present a reactive power demand to the network and could effectively transmit real
power and reactive power in both directions. However, the converter losses of Hitachi’s VSC
technology were larger than CSC technology. Hitachi was followed into the market by Siemens,
who offered a multi-layer VSC technology that has reduced losses compared with Hitachi’s
original PWM technology. GE Vernova now has a VSC product on the market that has adopted
the lower loss multi-layer technology.
The transmission network within the Anchor Point area is considered to be “weak” (e.g., due to
the lack of interconnections with other parts of the main transmission grid). Because of the need
to control the active and reactive power, VSC technology is the only viable DC option for this
project. In addition, VSC technology will be able to provide the mainland grid with black start
capability in the event of a power failure of the Alaskan transmission network.
Several projects in both North America and Europe use HVDC VSC technology that are similar
in size. Table 4 provides a reference list of relevant projects for comparison.
Supplementary Information 8 December 2024
Table 4: Similar Relevant HVDC VSC Projects Location Name Year Built Cable Length (km) Size (MW) Voltage (kV DC) North America: USA Cross Sound Cable 2002 40 330 150 North America: USA Trans Bay Cable 2010 85 400 200 North America: Canada Maritime Link 2017 360 500 200 Europe: Norway Valhall 2011 292 78 150
Europe: Norway Troll A 2004 70 80 60
Europe: Norway Troll A 3 and 4 2015 70 100 66
Europe: Norway Johan Sverdrup Phase 2 2022 200 200 80
Europe: Finland ÅL Link 2015 80 100 80
1.2.3 DC to AC Conversion Station
Typically, an HVDC cable will extend to the converter station, which is the approach taken for
this project. In some instances where ground conditions are considered challenging, an end sealing
compound can be used to convert to overhead before the converter station, but this was not
considered necessary at Anchor Point.
HVDC VSC converter stations generally come in module form, depending on the manufacturer.
Table 5 shows the module sizing of the Hitachi HVDC Light technology as an example. For this
project, the M1 size would be needed. Graphic 7 shows a typical layout for an HVDC VSC
converter station, as provided by Siemens HVDC Plus. Graphic 8 shows the layout for the onshore
HVDC VSC converter station for the 78 MW Valhall project in Norway. A simplified diagram is
provided in Graphic 9.
Table 5: Hitachi Light Technology VSC Converter Station Sizing
Symmetric Base Modules Units Size M1 Size M2 Size M3 Size M3x
DC Voltage (pole to ground) kVDC 80 80 80 80
Base Power MVA 106 209 319 430
AC Current AC 580 1,140 1,740 2,610
Supplementary Information 9 December 2024
Graphic 7: Siemens HVDC Plus VSC Converter Station Layout
Graphic 8: Valhall Project VSC Converter Station Layout (Norway)
Plan View
Side View
Supplementary Information 10 December 2024
Graphic 9: Valhall Project VSC Converter Station Layout (Norway)
Supplementary Information 11 December 2024
2. CABLE INSTALLATION METHODS 2.1 Cable Laying Vessels For long subsea cables, more sophisticated cable lay vessels are required (Graphic 10). Required cable lengths can now be around 100 km, and larger purpose-built cable lay vessels with integrated carousels are required to carry these much longer cable lengths safely. Graphic 10: Cable Laying Vessel
The new generation CLVs are multi-purpose: they are able to lay, trench and survey the cable from
an integrated system; with a typical dead weight of 9,000 tonnes (20,000 pounds), vessel length of
120 m and 28 m beam, these vessels are able to lay heavy and long cables. Equipped with a DP2
positioning systems, they can position these cables accurately on the seabed. However, operations
with these larger vessels may be restricted by shallow water. When selecting a CLV, factors to be
considered include the following:
• Cargo capacities
• Maneuverability properties
• Deck space for cable handling equipment
• Good sea-keeping properties i.e. stability of the vessel in wind and waves
• Bollard pull for cable plough
• Common issues/costs to consider re: cable installation vessel on an offshore wind
project
• Availability
Supplementary Information 12 December 2024
• Weather window • Speed of installation • Crew quarter size (accommodation for about 60 people) • Barge management system • Anchor handlers • Anchor patterns: innovative to maneuver around foundations to keep time to a
minimum
• Transfer vessels and planning
• Insurance
• Contractor interface (foundation, j-tube design –vessel coordination)
• Communications (v-sat or like transmit large amounts of data on a daily basis)
• Overall project logistics
• Turntable
Typical characteristics of CLVs include the following:
• Draught ranges between 2 m and 10 m
• Cargo capacities range from 500 tonnes to 10,500 tonnes
• Deck space varies from 500 square meters (m2) to 3000m2
• Service speed ranges of 7.8 to 12.5 knots
• On board accommodation capacities varies between 50 and 100 beds
The overall concept and holistic view in the selection of vessels, including how vessels work
alongside one another, how they operate and dependencies and interdependencies within an
emergency situation, is essential. Alongside the vessels themselves is the wide range of project
equipment that is required.
2.2 Method
Both ploughing and trench-cutting require the trench to be pre-formed and held open ahead of the
cable, which therefore has to be fed into the machine between the cutters or ploughshare and the
cable depressor. This is more complex than for a jetting machine that simply fluidizes the soil
around the cable. Jetting is therefore seen as posing the least risk to a pre-laid cable, although it
may also be the least effective at burying in certain soil types.
With the complexities of subsea cable-handling, trench-cutting may be better suited to a
simultaneous lay-and-trench operation. While this has potential to reduce offshore timing, and
certainly minimizes the risk of cable movement between lay and burial, the combined operation
Supplementary Information 13 December 2024
will be more complex than simple cable laying, with the required weather-windows being more restrictive. 2.2.1 Trench Jetting Jetting machines operate by pumping high-pressure water to fluidize or displace the soil. For electrical cables that are more flexible than pipelines and heavier than the surrounding soil, it is sufficient to form a slot of fluidized soil into which the cable is lowered, all within the footprint of the trenching machine itself. Trench jetting may have season restrictions applied based on the
occurrence of sensitive marine life during larval and juvenile life stages.
Jetting machines are generally tracked self-propelled crawlers with a power cable required from
the mothership. Being remotely operated, they may sometimes be referred to as ROVs; they should
not be confused with neutrally buoyant ROVs that operate throughout the water-column, which
can also be used for localized jetting operations that do not justify mobilization of tracked
trenching machinery.
Jetting is particularly effective in sandy soils, less so in cohesive materials such as firm or stiff
clays. Larger soil particles require more jetting power, so the method may be less successful in
gravelly sands; indeed, in such conditions, there may be a tendency for the gravel particles to sink
during the fluidization process, displacing the sand upwards. This aspect of the potential backfill
material needs to be understood on a case-by-case basis. Graphics 11 and 12 show a typical ROV
jet trencher and the principle of the operation.
Graphic 11: ROV Jet Trencher Diagram
Source: DNV
Supplementary Information 14 December 2024
Graphic 12: Typical Tracked ROV Jetting Machine
Source: Global Marine
2.2.2 Trench Ploughing
Ploughs are passive machines towed behind the mothership, the towing distance being a function
of water depth. This makes them less maneuverable than self-propelled machines, particularly in
confined areas.
This method is generally effective in most soil types (granular and cohesive), although variable
conditions such as stiff clays with embedded cobbles can be problematic. For electrical cables, the
plough may be equipped with a cable depressor, so that the removed soil can be backfilled within
the plough’s footprint.
Graphics 13 and 14 show a typical ploughing machine and the principle of the operation.
Supplementary Information 15 December 2024
Graphic 13: Trench Ploughing Diagram
Source: DNV
Graphic 14: Typical Subsea Cable Plough
2.2.3 Trench Cutting
Trench cutting is performed using a similar self-propelled vehicle to that used for Jetting, except
that it is equipped with a cutter chain that creates a vertical slot into which the cable is lowered.
The technique is particularly suited to firm or stiff clays where jetting would be ineffective, and
where the soil can maintain a vertical-sided profile. However, the rotating cutters present the
greatest risk to the cable of the three trenching methods. Graphic 15 shows a typical chain cutter
and the principle of the operation.
Supplementary Information 16 December 2024
Graphic 15: Trench Cutting Diagram
Source: DNV
Graphic 15: OTTER Subsea Tracked Cable Trencher
2.3 Armoring
Since the majority of cable damage is caused by human activities, such activities must be kept
away from the installed cables. The cable is installed, usually 1 to several meters beneath the
seabed, to protect against fishing and anchoring activities (with a minimum buried depth of 1 m,
per industry standards). A burial depth of 1-2 m seems sufficient to protect against fishing
activities. To protect effectively against anchoring activities (a few meters burial depth is usually
Supplementary Information 17 December 2024
not enough and is related to the size of vessels crossing the cable route), additional protection may be required. Another reason for sheltering the cables is to protect against sabotage. Finally, when the cable cannot be buried in the seabed (long rocky stretches, crossing other cables or pipes, too thin a sand layer, area where large vessels are not allowed) additional protection is needed. The common methods include the following: • Rock placement • Articulated pipe
• Concrete mattress
Further cable installation protection can be provided, such as warning signs onshore, a constructive
dialog with fishermen and their organizations about the presence of the cable circuit. Another way
to protect the cable is to monitor ship movement close to the route. In case a ship has dropped an
anchor in the vicinity of the cable circuit, divers may investigate the risk of retrieving the anchor
and may occasionally even cut the anchor free to avoid cable damage. These are typical
considerations that may require to be taken into account when designing the cable system.
Supplementary Information 18 December 2024
3. ENVIRONMENTAL REVIEW DETAILS 3.1 Ecological Resources and Wildlife Biological resources include native and non-native plants and animals and the habitats in which they occur. Habitat is defined as the natural environment of an organism, the type of place in which it is natural for it to live and grow. Augustine Island is a part of the Alaska Peninsula ecoregion (Alaska Department of Fish and Game
[ADFG] 2015). Vegetation communities on lower portions of the island are predominantly shrub
(primarily alder, Alnus species [sp.]). Patches of deciduous forest (black cottonwood, Populus
balsamifera) and conifer Sitka spruce (Picea sitchensis). Dwarf shrub communities (alpine
bearberry [Arctostaphylos uva-ursi], crowberry [Empetrum nigrans], bog blueberry [Vaccinium
uliginosum], and lingonberry [Vaccinium vitis-idaea]) are also present in small portions of the
permit area. These vegetation communities are typical of the region.
The coastline within the permit area is steep bluffs and gravel or sand beach with abundant
boulders. Multiple biotic communities found in Augustine Island tidal zones (DNR 2022), but in
the permit area, biota most likely to be present include rockweed (Fucus distichus), blue mussel
(Mytilus trossulu), and barnacle (Balanus glandula or Semibalanus balanoides) that may attach to
boulder substrates. Lower intertidal communities may include soft brown kelps (Saccharina
latissimi) and others, Alaria (Alaria marginata), and red algae (Odonthalia sp.). Although eelgrass
(Zostera marina) has been identified on Augustine Island, it was not associated with subtidal
waters off of the permit area (DNR 2022).
Kittlitz’s murrelet (Brachyramphus brevirostris) is a small seabird that nests on steep slopes with
no or sparse, low vegetative cover. Nesting habitat has primarily been associated with glacial
terminal zones but habitat suitability modeling indicates potential nesting habitat may be present
within the Permit Area (Felis et al. 2016). Kittlitz’s murrelet is a candidate for listing under the
Endangered Species Act (ESA) (ADFG 2024).
At Anchor Point, habitats include a willow and alder shrub and woodland, black spruce (Picea
mariana) forest, and low scrub bog. Anchor River and several tributaries flow west into Cook Inlet
at Anchor Point, and riparian habitats are present along waterways. These habitats provide
breeding or migration stopover habitat for many species of songbirds, shorebirds, and waterfowl
(USFWS 2024a, ADFG 2015). A variety of mammals may also utilize these areas, including
moose (Alces alces), black bear (Ursus americanus), beaver (Castor canadensis), and muskrat
(Ondatra zibethicus) (ADFG 2015).
Consideration needs to be taken to minimize potential impacts to terrestrial and marine ecosystems
and wildlife that may be present:
• Many species of birds have the potential to nest within the Permit Area on Augustine
Island including species like Kittlitz’s murrelet that nest on the ground and can be
difficult to detect. Additionally, several species of birds may nest within the proposed
transmission line alignments at Anchor Point, including sensitive species such as
Aleutian tern (Onychoprion aleuticus), olive-sided flycatcher (Contopus cooperi),
Supplementary Information 19 December 2024
lesser yellowlegs (Tringa flavipes), and short-billed dowitcher (Limnodromus griseus). Actions may include performing bird nest clearance surveys prior to vegetation clearing, excavations, and other ground-disturbing activities. When possible, planning to perform vegetation clearing activities early or late in the season may limit potential impacts on nesting birds. 3.2 Fisheries The primary use of fish and wildlife populations on and around Augustine Island are commercial
and sport fisheries in marine waters around Augustine Island for salmon, halibut, and groundfish.
These commercial and sport fisheries target fishes that occur across state, federal, and international
waters that are managed for sustainable harvest ADFG, North Pacific Fisheries Management
Council, National Marine Fisheries Service, and International Pacific Halibut Commission.
Essential Fish Habitat (EFH) for salmon, groundfish, and Pacific scallops exists in lower Cook
Inlet (DNR 2022). EFH is habitat necessary for spawning, breeding, feeding or growth to maturity
for fishes managed under federal fishery management plans (FMPs). EFH for one or more life
stages for most fishes covered under the Gulf of Alaska Groundfish FMP occur in nearshore
subtidal and intertidal waters, or shallow inner shelf waters 1 to less than 164 feet (1 to less than
50 m) deep around Augustine Island (DNR 2022).
Bottom trawl survey abundance estimates for commercially and recreationally important
groundfish in the Kamishak Bay area south and east of Augustine Island from 1998 to 2012
identified the presence of several species, including Pacific halibut (Hippoglossus stenolepis)
Pacific cod (Gadus macrocephalus), walleye pollock (Gadus chalcogramma), sablefish
(Anoplopoma fimbria), and rockfish (Sebastes sp.) (DNR 2022).
No freshwater stream habitats for anadromous fish have so far been identified on Augustine Island
in the ADFG anadromous waters catalog (ADFG 2024), although salmon may use stream, pond,
and tidal lagoon habitats on Augustine Island for spawning and rearing. All five Pacific salmon
occur in and are harvested from the marine waters of Kamishak Bay and lower Cook Inlet. Pacific
herring spawn along northwestern shorelines and razor clam (Siliqua patula) beds occur along the
southwestern shorelines.
ADFG lists Anchor River and its tributaries in Anchor Point as anadromous waters providing
habitat for all five Pacific salmon species, Dolly Varden (Salvelinus malma), and steelhead
(Oncorhynchus mykiss). Construction activities for the transmission line and associated
infrastructure may impact anadromous fish habitat, including spawning habitat, at Anchor Point.
Intertidal and nearshore habitats around the island support eelgrass communities that are used for
spawning by Pacific herring, but none have been identified in waters off of the permit area.
Consideration needs to be given to the following:
• Although no streams on Augustine Island are listed in the ADFG anadromous catalog,
this may be because the island has not yet been surveyed. Actions may include an
evaluation of habitat suitability of streams within the Permit Area for salmon.
Supplementary Information 20 December 2024
• Multiple species of anadromous fish have been identified in the Anchor River in the Anchor Point area. An ADFG Fish Habitat Permit may be required if transmission line construction will affect waterways at Anchor Point. • Razor clam beds have been identified in nearshore habitats of the western portion of the Permit Area. Actions may include detailed mapping of potential razor clam habitat and planning to minimize potential impacts to those areas. • Dredging and cable installation can result in destruction of organisms and habitats that can lead to long-term or permanent damage depending on the extent and type of habitat
disturbed and mitigation measures used (DNR 2022; 74 Federal Register 51988).
Planning may include quantification of potential impacts to commercial and
recreational groundfish and salmon fisheries.
3.3 Protected Species
Protected species include those that are federally listed, or proposed for listing, as threatened or
endangered under the ESA by the United States Fish and Wildlife Service (USFWS). Management
and protection of listed species is given priority in natural resource management. In cases where
threatened and endangered species management, in accordance with the appropriate guidance,
would conflict with other mission activities, consultation with the USFWS will be initiated to avoid
jeopardizing any listed species or its critical habitat.
Portions of marine waters near Augustine Island are designated as critical habitat under the ESA
for endangered Cook Inlet beluga whales (Delphinapterus leucas) (76 Federal Register 20180)
and threatened southwest distinct population segment of northern sea otters (Enhydra lutris
kenyoni) (74 Code of Federal Regulations [CFR] 51988). Although not designated as critical
habitat, some threatened Steller’s eiders (Polysticta stelleri) (62 CFR 31748) may aggregate in
lower Cook Inlet in late summer through early spring for molting and over winter (DNR 2022).
The short-tailed albatross (Phoebastria albatrus) (65 CFR 46643) is also listed as a federally
endangered and Special Status species by the ADF&G with the potential of being present at
Augustine Island (USFWS 2024a). However, adverse effects from the use of the nearshore marine
environment around the AWS FUDS is not expected. Short-tailed albatrosses presently breed on
islands in the western Pacific, Nonbreeding birds do however forage in the open ocean, consuming
food items such as squid, shrimp, and small fish such as flying fish (USFWS 2008). It is possible
that the short-tailed albatross may visit the marine waters near the Permit Area; however,
interaction would be limited and would not impact breeding.
There are hundreds of bird species protected under the Migratory Bird Treaty Act (MBTA) (16
United States Code [USC] 703-712) that are known to occur in Alaska, either seasonally or year-
round, and the scenarios must comply with the MBTA. No native terrestrial mammals are found
on Augustine Island. Additionally, there are no records of introduced brown rats or other invasive
animal or plant species.
Bald eagles (Haliaeetus leucocephalus), which are protected under the federal Bald and Golden
Eagle Protection Act (16 USC 668-668d), are widely distributed along waterways and are likely
present in the Permit Area and at Anchor Point (DNR 2022). Bald eagles are usually found near
Supplementary Information 21 December 2024
water in coastal areas and along lake and river shorelines. The breeding season in Alaska begins with courtship and nest building in February and ends when the young fledge by late August into early September. Nests are large structures constructed in mature old-growth trees or snags, and on cliffs or rock outcrops. In coastal Alaska breeding eagles may remain near their nests year-round (DNR 2022). The Marine Mammal Protection Act (MMPA) (16 USC 136-1423h) prohibits harassment of marine mammal and activities that have the potential to kill, injure, or disrupt behavioral patterns of marine mammals. The MMPA extends protections similar to those given to ESA species. At
Augustine Island, harbor seals (Phoca vitulina) are present in coastal waters off Augustine Island
and multiple haulouts for 50 or more harbor seals have been identified along the shoreline of the
southern coast of island, including the Permit Area. Undersea cable laying activities will cross
waters in lower Cook Inlet that may be seasonally inhabited by cetaceans (whales and porpoises)
including killer whale (Orcinus orca), humpback whale (Megaptera novaeangliae), fin whale
(Balaenoptera physalus), minke whale (Balaenoptera acutorostrata), and Pacific white-sided
dolphin (Lagenorhynchus obliquidens) (National Oceanic and Atmospheric Administration
[NOAA] 2024a). A Marine Mammal Protection Plan and monitoring would be required during
construction. The marine mammal monitor would have the authority to stop construction, while
marine mammals are in the vicinity of the project.
Consideration needs to be given to the following:
• Waters offshore of the Permit Area are designated critical habitat for the distinct
population segment of the northern sea otter. Routing for a subsea cable to the Kenai
Peninsula from Augustine Island would likely cross through northern sea otter critical
habitat that surrounds the island (74 Federal Register 51988).
• Undersea cable placement will cross habitat for Cook Inlet beluga whale (DNR 2022).
Determine whether this activity laying has the potential to generate sound of a
frequency and volume that may disturb marine life, particularly cetaceans such as the
endangered Cook Inlet beluga that is likely present throughout the area. Develop plans
to mitigate potential sound impacts to terrestrial and aquatic biota. The National
Oceanographic and Atmospheric Administration (NOAA) recommends maintaining a
100-yard distance from whales (NOAA 2024b).
• Potential for disturbing established harbor seal rookeries and haul-outs within or near
the permit area on Augustine Island. Evaluating alternative landing points for boat
access and controlling boat traffic as to minimize the number of trips required during
sensitive periods. NOAA recommends maintaining a 100-yard distance from harbor
seal haul-outs (NOAA 2024b).
• Records do not indicate that Norway (brown) rats or other invasive non-native species
have been identified on Augustine Island. Project planning should include biosecurity
protocols development and implementation for all phases of onsite planning,
construction, and long-term operation of the geothermal plant to prevent accidental
introduction of non-native plant and animal species.
Supplementary Information 22 December 2024
• Bald Eagles (Haliaeetus leucocephalus) have been recorded as breeding on Augustine Island and at Anchor Point. Actions may include nest monitoring before and during construction. Additionally, overhead transmission lines at Anchor Point should be designed so as to minimize the risk to bald eagles from collision, entanglement, or electrocution. • Many species of birds protected under MBTA have the potential to nest within the Permit Area on Augustine Island and at Anchor Point. Actions may include performing bird nest clearance surveys prior to vegetation clearing, excavations, and other ground-
disturbing activities. When possible, planning to perform vegetation clearing activities
early or late in the season may limit potential impacts to nesting birds.
3.4 Water Resources
The water resources described in this section include surface water features (e.g., lakes, streams,
rivers), groundwater, floodplains, and stormwater specific to the Augustine Island permit area.
Wetlands are defined, per 33 CFR Part 328.3(b) of the CWA, as “those areas that are inundated
or saturated by surface or groundwater at a frequency and duration to support, and that under
normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated
soil conditions.” Section 404 of the CWA regulates the discharge of dredge or fill material into
waters of the United States, and United States Army Corps of Engineers (USACE) holds the
primary federal authority for regulation of these discharges.
A search of the National Wetlands Inventory indicates that there are no wetlands or other
jurisdictional waters identified within the Augustine Island permit area (USFWS 2024b). It should
be noted that the National Wetland Inventory mapping is based on the interpretation of infrared
imagery collected in 1978. Given the dynamic nature of Augustine Island, the data included NWI
may not reflect current conditions within the permit area. Several streams are present with the
Permit Area. All are perennial streams with unconsolidated bottoms. Headwaters for streams are
on the middle slopes of Augustine volcano and each flow into Cook Inlet.
Several waterways, including the Anchor River and its tributaries, overlap the proposed
transmission line alignment. Additionally, freshwater forest and shrub wetlands and emergent
wetlands are found along both alignment options (USFWS 2024b).
Consideration needs to be given to the following things:
• Assessment of the wetlands and water of the United States (WOTUS) resources at the
proposed construction sites would be required
• Obtaining appropriate USACE coordination and permitting for construction
• Designing appropriate systems for the conveyance of stormwater and treatment of
wastewater generated during construction of the electrical interconnect to protect
surface water and groundwater resources that may be present.
• Studies of groundwater contamination depths may be needed to identify potential
aquifer impacts in areas where HDD will occur.
Supplementary Information 23 December 2024
3.5 Air Quality As defined by Alaska Statute, air pollution is the presence in the outdoor atmosphere of one or more contaminants (e.g., dust, fumes, gas, mist, odor, smoke, or vapor) in quantities and of characteristics and duration such as to be injurious to human, plant, or animal life or to property, or to interfere unreasonably with the comfortable enjoyment of life and property (Alaska Statutes 46.04.900(2)). Both the Environmental Protection Agency (EPA) and Alaska Department of Environmental Conservation (ADEC) regulate air quality in Alaska. Six criteria pollutants are established with National Ambient Air Quality Standards (NAAQS; 40 CFR Part 50) under EPA:
• Particulate matter (PM): smaller than 10 microns in diameter or 2.5 microns in diameter
• Sulfur dioxide (SO2)
• Carbon monoxide (CO)
• Nitrogen dioxide (NO2)
• Ozone (O3)
• Lead
ADEC accepts the EPA standards with the addition of ammonia (NH3). ADEC also implements a
program for permitting the construction and operation of new or modified stationary sources of air
emissions that emit regulated pollutants.
Construction of the electrical interconnect will generate some amount of air pollutants. Short-term
increases in air pollution in the region may be caused by diesel exhaust from construction and
drilling equipment and dust from road and staging area construction. However, over the life of the
project, the amount of air pollutants generated by the geothermal plant will be minimal compared
to fossil fuel-powered plants.
Consideration needs to be given to the following activities:
• Short-term emissions from dust and construction equipment during construction of the
facility. Minor source permits may be required.
3.6 Cultural Resources
Cultural and historical resources commonly refer to physical material items associated with past
human activities. Under the National Historic Preservation Act (NHPA) (16 USC 470), as
amended, only historic properties warrant consideration of impacts from a proposed action and
any associated proposed mitigation, and are defined by the NHPA as any districts, sites, buildings,
structures, or objects included on or eligible for inclusion on the National Register of Historic
Places (NRHP). Historic properties include traditional cultural properties and are associated with
important national events or are “exceptionally significant” in another way. To be considered
significant, archaeological or architectural resources must meet one or more specific NHPA
criteria, which include: association with events that have made a significant contribution to the
broad patterns of history; association with the lives of persons significant to our past; embody a
distinctive characteristic of a type, period, construction; or that have yielded or may be likely to
Supplementary Information 24 December 2024
yield information important to history or prehistory. In addition to consideration of impacts to historic properties in accordance with the NHPA, other cultural resource considerations are also taken into account in accordance with the National Environmental Policy Act (NEPA). Lower Cook Inlet has been inhabited for at least 3,500 years, and the region includes Alutiiq (Sugpiaq), Dena’ina Ełnena, and Dënéndeh homelands (Native Land Digital 2024). However, although historical subsistence hunting and gathering has occurred near Augustine Island, there are currently no records of settlements on the island aside from a remote, abandoned cabin likely used by miners during a brief stint of pumice mining on the island in the late 1940s (DNR 2022).
Consideration needs to be given to the following:
• Under Section 106 of the NHPA, an intensive archaeological survey of the subsea and
the terrestrial transmission line may be required. This would be at the request of the
USACE archeologist as well as the Alaska Native Communities.
• No historic or prehistoric sites have been reported on Augustine Island (DNR 2024).
Actions may include outreach to Alaska Native Communities in Lower Cook Inlet and
coordination with Alutiiq (Sugpiaq), Dena’ina Ełnena, and Dënéndeh representatives
and the State Historic Preservation Office (SHPO) prior to land disturbing activities.
3.7 Geology and Soil Resources
Geology and soil resources include the surface and subsurface materials of the earth. Within a
given physiographic province, where applicable, these resources typically are described in terms
of topography, soils, geology, minerals, and paleontology. Site-specific geological resources
typically consist of surface and subsurface materials and their inherent properties. Principal factors
influencing the ability of geological resources to support structural development are the seismic
conditions (i.e., potential for subsurface shifting, faulting, or crustal disturbance), topography, and
soil stability.
Geothermal fields are typically located in seismically active areas or along active faults.
Earthquakes may triggered by plant operations because geothermal resource extraction affects
fluid pressure in the subsurface. Geothermal operations in tectonically active regions often show
increased seismicity, but not always of large magnitude (DNR 2022).
Consideration needs to be given to the following things:
• Geotechnical evaluations will be needed for siting of the electrical interconnect
facilities and transmission routes.
• Augustine Island is a seismically active area. Seismic hazard building protocols will
need to be followed to minimize risk to workers from both natural and induced
earthquakes.
Supplementary Information 25 December 2024
3.8 Environmental Justice The definition of minority as defined by the White House Council on Environmental Quality (CEQ) guidelines is Black or African American, American Indian, and Alaska Native, Asian, Native Hawaiian and Other Pacific Islander, and multi-race that includes one of these races, and Hispanic or Latino. A minority population also exists if there is more than one minority group present and the minority percentage, as calculated by aggregating all minority persons, meets one of the above stated thresholds (CEQ 1997). Low-income populations are identified in this analysis by using the statistical poverty threshold of the United States Census Bureau (USCB), which is
based on income and family size.
For the purposes of this environmental justice analysis, children are defined as people 17 years of
age and under. Executive Order (EO) 12898 also requires that federal agencies analyze the
environmental effects, including human health, economic, and social effects, of federal actions on
tribal populations. None of the communities in the ROI are associated with federally recognized
tribes. Consultation with tribes is discussed in Section 5.4.12, Cultural Resources.
Augustine Island is an uninhabited island. The closest communities are Nanwalek and Port
Graham (2020 Census populations 247 and 162, respectively), located on the Kenai Peninsula,
approximately 55 miles northeast of the permit area. No impacts to this or other communities are
anticipated.
Consideration needs to be given to the following:
• Construction and operation of the geothermal plant may provide job opportunities for
residents of communities on the Kenai Peninsula. Community outreach may include
efforts to support hiring of local community residents to fill available positions.
• Any unanticipated impacts from the geothermal plant may be offset by reduced overall
greenhouse gas emissions will result in better air quality for communities in the Lower
Cook Inlet. Community outreach may include discussion of how geothermal energy
may support the long-term health and wellbeing of community members.
3.9 Human Health and Safety
Human health and safety consider those facets of military activities and materials that potentially
pose a risk to the health, safety, and well-being of the public, military personnel, civilian
employees, and dependents. Aspects of construction and operation activities that can present risk
to human health and safety include vehicle operation, occupational and construction safety
hazards, and handling and management of hazardous materials and hazardous waste. Geothermal
power has potential to require the handling of high-temperature water and steam that may cause
health and safety impacts.
Considerations should be given to the following:
• Mitigation measures may include development of a plan to address potential geohazard
impacts on operations to mitigate risk to facilities and personnel and coordination with
the Alaska Volcano Observatory to ensure that the permittee or operator is always
Supplementary Information 26 December 2024
aware of Augustine Volcano’s current activity status when personnel are on Augustine Island. 3.10 Noise Noise is defined as any sound that is undesirable because it interferes with communication, is intense enough to damage hearing, or is otherwise annoying. Noise can be intermittent or continuous, can be steady or impulsive, and can involve a number of sources and frequencies. Sound intensity is quantified using decibels (dBs), a measure of sound pressure level.
Noise is generated during construction, drilling, and subsequent operation of geothermal facilities.
Construction-related noise may have upper volumes ranging from 80 to 120 decibels (DNR 2022).
During normal geothermal power plant operation sound may be generated by hydraulic power
packs and electrical generators. Typical noise levels are 72 to 75 dBA at 20 m distance. Undersea
cable laying may also generate noise that may affect marine wildlife.
Consideration should be given to the following:
• Loud noise may disturb breeding birds, causing them to abandon their nests or flush
them and make them more vulnerable to predation. Likewise, laying undersea cable
may cause noise of a frequency, volume, or duration to affect the hunting, foraging,
and social behaviors of fish and cetaceans (DNR 2022, NOAA 2022). Actions may
include performing nest clearance surveys and implementing sound engineering
controls to limit effects on wildlife.
3.11 Airspace
The airspace environment is described in terms of its principal attributes, namely controlled and
uncontrolled airspace and Special Use Airspace. Controlled airspace is a generic term that
encompasses the different classifications of airspace and defines dimensions within which air
traffic control service is provided to flights under instrument meteorological conditions and visual
meteorological conditions. Obstructions to flights, which include towers and power transmission
lines, represent safety concerns for aircrews, especially those engaged in low-altitude flight
training. Airfields have areas immediately surrounding runways where development actions may
be restricted or prohibited altogether to eliminate potential obstructions that would affect safe
approach to or departure from a runway.
There are no airfields within 25 miles of Augustine Island. Access to McNeil State Game Refuge
and Sanctuary is by float plane landing at McNeil River Campground, approximately 32 miles
southwest.
From Anchor Point, there are several communities on the Kenai Peninsula with airport. The closest
commercial air facilities are in Homer (15 miles), Seldovia (25 miles) and Nanwalek (28 miles).
Several private airstrips are also present in the area.
Major air facilities (Ted Stevens Anchorage International Airport, Merrill Field Airport, and Joint
Base Elmendorf-Richardson) are located in Anchorage, approximately 170 miles north.
Supplementary Information 27 December 2024
No airspace effects are anticipated from the subsea cable, substation facilities, or electrical transmission lines. Anticipated height of the transmission lines is 80 feet, which is lower than the 200 foot minimum for Federal Aviation Administration notification. Consideration needs to be given to the following: • Actions may include determining whether there would be an effect on air traffic. 3.12 Visual Resources
Visual resources are the natural and man-made features that make up the landscape of an area.
Natural features include water surfaces, vegetation, and topography, and man-made features
include buildings, towers, roads, and airfields. These features combine to give an area its unique
characteristics and are inherent to the structure and function of that landscape. The importance of
modifications to these visual resources is influenced by the assessed value it has to the viewer,
public awareness of the area, and general community concern for visual resources in the area.
Recreational resources consist of the activities, both indoor and outdoor, that are available to a
population in a certain area, and potential impacts to this resource are evaluated by the effect of a
proposed action to the facilities or natural resources that support these activities.
Impacts on visual resources are considered minimal on Augustine Island because the area is
uninhabited and virtually no infrastructure exists for visitation. In Anchor Point transmission
infrastructure may impact visual resources for some residents and visitors, depending on final
design, particularly in more populated areas of Anchor Point.
Supplementary Information 28 December 2024
4. REFERENCES ADFG. 2015. 2015 Alaska Wildlife Action Plan. Alaska Department of Fish and Game. Juneau, Alaska. ADFG. 2024. “Kittlitz’s Murrelet (Brachyramphus brevirostris) Species Profile.” Alaska Department of Fish and Game. https://www.adfg.alaska.gov/index.cfm?adfg=kittlitzmurrelet.main.
CEQ. 1997. Environmental Justice Guidance Under the National Environmental Policy Act.
Washington, D.C. White House Council on Environmental Quality.
DNR. 2022. South Augustine Island Noncompetitive Geothermal Prospecting Permit Preliminary
Written Finding of the Director. Alaska Department of Natural Resources. April 28.
DNR. 2024. 2024 Augustine Island Noncompetitive Geothermal Prospecting Permit Final Written
Finding of the Director. Division of Oil and Gas. January 10.
Felis, J.J., M.L. Kissling, R.S.A. Kaler, L.A. Kenney, and M.J. Lawonn. 2016. “Identifying
Kittlitz’s Murrelet Nesting Habitat in North America at the Landscape Scale.” Journal of Fish
and Wildlife Management 7(2): 323–33. https://doi.org/10.3996/112015-JFWM-116.
Native Land Digital. 2024. Native Land Digital. https://native-land.ca/. September.
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