HomeMy WebLinkAboutKawerak Pilgrim Hot Springs REF App_2Appendix of Attachments
Kawerak REF Proposal
“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Table of Contents
Detailed Scope of Work for Kawerak REF……………………………………………………….1
Scope of Work & Quote from ACEP……………………………………………………………..6
Scope of Work & Quote from CRW Engineering…………………….…………………………14
Scope of Work from Deerstone Consulting for TEDC Grant Project (pending match)…………23
Map of Kawerak Region; List of Kawerak Tribes……………………………………………….24
Kawerak Organizational Chart……………………………………………..……………………25
Map of Unaatuq-MINC-BSNC property boundaries………………………………………….…26
Pages from Final Report, Pilgrim Hot Springs Geothermal Exploration (ACEP, 2010-2014)….27
“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Kawerak, Inc.
Detailed Scope of Work
1
Kawerak, Inc. requests $372,233 from Alaska Energy Authority’s Renewable Energy Fund in
order to complete the conceptual design of a geothermal power plant for Pilgrim Hot Springs,
including both energy and heat production. Kawerak plans to use grant funds for project
management personnel, materials and supplies, and contractual services.
Alaska Center for Energy and Power (ACEP) will be the main contractor for this project, based
on their experience with geothermal systems and their history working at Pilgrim Hot Springs.
Between 2010 and 2014, ACEP led an extensive geothermal exploration effort at Pilgrim Hot
Springs, located centrally on the Seward Peninsula. During this time period, a variety of
geophysical surveys were conducted in conjunction with drilling efforts that took place during the
summers of 2011, 2012, and 2013. The efforts culminated in the drilling of a large diameter well
(PS 13-1) capable of high flow rates in the fall of 2013. PS 13-1 is a production well completed
to a depth of 314 m with a diameter of 6 in. Natural artesian flow rates from this well are 60
gpm, while airlift-assisted flow testing of this well conducted by ACEP in September 2014
demonstrated that the well was capable of producing 300 gpm at temperatures ranging from
78.25 °C (172.85 °F) to 79.3 °C (174.74 °F).
The minimal pressure changes that were measured at that time, combined with an estimated
natural state heat flow from the geothermal system to be approximately 20 MWth based on
thermal data collected from ground based and aerial investigations of the site, led researchers
to conclude that the well has the ability to sustainably provide thermal fluid for on-site power
generation and district heating applications. This well could be used as a production well to
support on-site geothermal power generation using an Organic Rankine System, similar to the
system installed at Chena Hot Springs.
As part of this project, ACEP will work with Kawerak, Inc to hire a full-service engineering and
design firm based in Alaska to support this project. This firm will be responsible for identifying
project permitting requirements, reviewing geotechnical site considerations, civil design, all
engineering drawings related to the conceptual design, particularly the site layout, and working
with ACEP to design a cooling system and injection or discharge strategy for spend fluids
consistent with state and federal regulations for wetlands areas. ACEP will support Kawerak in
developing language for a Request for Proposals (RFP) for a permitting, geotechnical, and civil
design subcontractor. A quote and scope description from CRW Engineering of Anchorage,
Alaska is provided with this proposal for reference.
As part of this effort, matching funds will be provided by Kawerak in the form of salary and
materials match for project staff, as well as other match from a current Department of Energy-
Office of Indian Energy Technical Assistance Grant that retains ACEP as a contractor of
Kawerak.
Kawerak has partnered with the Native Village of Mary’s Igloo to apply for the Bureau of Indian
Affairs Division of Energy and Mineral Development – Indian Energy and Economic
Development division’s Tribal Energy Development Capacity (TEDC) grant program. If the
TEDC grant is awarded to Mary’s Igloo, with Kawerak as a sub-grantee, the work to be
performed by Kawerak and sub-contractor Deerstone Consulting will contribute as match to the
overall effort of this project and fit seamlessly into tasks related to the economic feasibility of
producing geothermal power on the site.
1 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Kawerak, Inc.
Detailed Scope of Work
2
The scope of work for this project will consist of:
Task 1: Project Scoping and Contractor Selection
Kawerak is planning to hire a full-service engineering and design firm based in Alaska to
support this project. This firm will be responsible for identifying project permitting requirements,
reviewing geotechnical site considerations, civil design, all engineering drawings related to the
conceptual design, particularly the site layout, and working with ACEP to design a cooling
system and injection or discharge strategy for spend fluids consistent with state and federal
regulations for wetlands areas. ACEP will support Kawerak in developing language for an RFP
for a permitting, geotechnical, and civil design subcontractor.
Task 2: Design Specifications for Geothermal Power Plant and Review of Potential Equipment
Vendors
ACEP will develop specifications for a geothermal power plant for the Pilgrim Hot Springs site
based on known characteristics of the resource combined with expected current and future site
loads. Based on the data from the flow test conducted in 2014, the resource should be capable
of producing 300 kW from the existing production well PS 13-1, or up to 5 MW based on the
overall natural state heat flow from the system to the surrounding environment. Developing a
smaller plant as a phase 1 project is an excellent way to stress test the resource over time,
collecting data to both better quantify the precise upflow zone of the geothermal fluids and
better assessing the maximum sustainable generation that the resource could be capable of
supporting.
In addition to the capacity of the resource to support power generation, it will be important to
design a power plant that can operate independently of an existing grid. Many ORC systems are
designed as synchronous machines and cannot operate in the absence of an existing grid. This
has been a significant challenge for Chena Hot Springs, which has not been able to operate
independently from a diesel system forming the backbone of the electric grid and providing
necessary parameters (voltage and frequency) for the ORC to follow. This can be avoided
through careful selection of the generator, or by pairing the geothermal plant with a
battery/inverter system which could also help balance load and allow other energy resources to
support site demand. ACEP will explore both pathways, with the goal of developing
specifications for a Request for Information (RFI) soliciting vendor information for prospective
equipment manufacturers.
Sub-tasks in this section include load forecasting, design parameters for power plant, and
equipment vendor assessment.
Task 3: Support Site Infrastructure Design
ACEP will work closely with engineering subcontractors retained by Kawerak, on site design to
support power generation from the geothermal resource while providing for long-term
sustainability of the resource. ACEP will be responsible for sharing data related to the resource
on behalf of Kawerak, and communicating specifications related to the power plant design.
ACEP will also support Kawerak in the review of draft plans, drawings, and infrastructure design
recommendations and provide feedback as appropriate.
Other tasks in this section will include identifying needed permits for future construction of the
power plant, including well water withdrawal and disposal, and site development.
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“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Kawerak, Inc.
Detailed Scope of Work
3
The engineering firm retained will provide a conceptual design of auxiliary power plant
components, including well pump sizing and selection, piping layout from the well to the power
plant and from the power plant to the discharge location, and a cooling system for the generator.
They will also develop engineering design drawings, including site design and facilities layout,
concept system process schematic, and provide system alternatives to consider.
Task 4: Distribution System Design
The Pilgrim Hot Springs geothermal site is currently considered a greenfield site, without any
sort of existing permanent generation or distribution infrastructure. Site power, when needed, is
currently provided by imported and portable generators. In addition to power plant design, it will
be important to carefully think through the layout of the electrical distribution system.
This also provides a unique opportunity to consider some non-traditional approaches that could
enable Kawerak and Unaatuq, LLC to seek DOE funds. Chief among these alternatives could
be an entirely DC-based microgrid. While it is understood that the REF is not intended to fund
nonconforming technologies, there may be value in conducting at least a preliminary
assessment of alternative grid architectures as it is expected that there could be future federal
funds available for innovative design in this space.
As part of the distribution design, the engineering firm will develop a plan for well water disposal,
including discharge to the surface through a pool/pond, and/or discharge to groundwater
through an underground injection well. The engineering firm will also identify additional data or
other information that will be required for permitting efforts.
Task 5: Assessment of Alternatives
ACEP will conduct a due diligence analysis of alternative energy sources at the site. In addition
to traditional diesel generation, ACEP will consider solar as an alternative. This aligns well with
an initial summer-only operation as proposed by Kawerak. Surveys of Alaska installations show
costs ranging from $2.20 to $5.00/Watt for remote installations larger than ~45 kW. Capacity
factors range from 8%-16%. For the Nome area, according to NREL's PVWatts tool, solar
irradiance levels are on the order of 5-6 kWh/m2/day in the summer months, and a ~300 kW
array is predicted to yield a little over 300,000 kWh total annual energy production.
Alaska’s cold temperatures increase system voltage, reduce electrical resistance, and yield
higher-than-rated outputs associated with reflected light and albedo effects. These factors,
combined with declining module prices, are making solar PV technology more economical.
Solar PV arrays have been installed in all areas of the state from the southwest to the Arctic,
and low sun angles and long daylight hours represent opportunities to mount panels vertically
on walls as well as on the east and west sides of buildings.
Task 6: Economic Feasibility Analysis
Based on the information derived from Tasks 2-4 and on information from geothermal power
plants of a similar size developed in other locations, ACEP will generate budget estimates and
complete a robust economic analysis for the project as well as alternatives identified through
Task 5 work. ACEP will work closely with Kawerak and the engineering firm to develop design
and construction cost estimates. The engineering firm will provide estimates for one preferred
system design.
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“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Kawerak, Inc.
Detailed Scope of Work
4
The TEDC Grant, if awarded, will contribute significantly to the economic analysis portion of this
project. As economic factors are determined and the conceptual design is developed,
Deerstone Consulting, as part of their TEDC project scope, will work with all project participants
and stakeholders, led by the Native Village of Mary’s Igloo (applicant for the TEDC grant) and
Kawerak to assist in the following tasks and deliverables:
• Facilitate a Strategic Planning Session with Unaatuq Board members with advisory
support from the Native Village of Mary’s Igloo and the Bering Strait Regional Energy
Leadership Committee to define scenarios and energy development options for Pilgrim
Hot Springs and more broadly for the Kawerak/Norton Sound region.
• Perform an Economic Analysis of the income potential and requirements for an energy
provider as well as a load analysis for various prospective businesses and enterprises
based on development scenarios identified by project participants and stakeholders.
• Conduct a Feasibility Study to determine an appropriate business structure and define
development options for Unaatuq, LLC to optimize and manage the locally available
energy resources—including possibly geothermal, solar, biomass, hydropower, and
wind—for a sustainable economy and business foundation for Pilgrim Hot Springs.
The objectives for the study are broken down as follows:
• Determine what type of business structure is best suited to the energy development
goals of the region (profit vs. nonprofit)
• Develop options for a conceptual model for selling geothermal power at Pilgrim Hot
Springs to outside entities
• Outline the economic benefits of developing a tribally-led business utility structure
including expected income, cash flow, and regional economic benefits
• Determine how the business structure could also develop regulations, best practices,
and resources to other regional utilities and standalone power plants
• Engage Unaatuq with the Bering Strait Regional Energy Leadership Committee as an
advisory group regarding energy development strategies
Task 7: Stakeholder Education
As part of this project, the project team and members of the Unaatuq Board Advisory Committee
will travel to Chena Hot Springs in Fairbanks, Alaska to view the current geothermal power plant
system at their hot springs resort. The team will meet with Chena management and staff to
discuss strategies, challenges, benefits and risks associated with the system and business.
The project team and Unaatuq Board Advisory Committee members will also visit the University
of Alaska Fairbanks’ Campus and the Alaska Center for Energy and Power to meet with ACEP
staff in person to discuss project progress, geothermal technologies, and other appropriate
microgrid technologies that may be applicable to providing energy at Pilgrim Hot Springs.
Task 8: Stakeholder Engagement
As part of this project, two meetings will be held on site at Pilgrim Hot Springs for all project staff
members, contractors, and the Unaatuq Board of Directors.
During these stakeholder engagement meetings, which will take place in conjunction with
ACEP’s visits to the site, Unaatuq Board Members as well as Kawerak Project Staff will come
4 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
“Pilgrim Hot Springs Geothermal Power Plant Conceptual Design”
Kawerak, Inc.
Detailed Scope of Work
5
together to view possible locations of the power plant components, water piping and distribution
ideas, examine the monitoring wells and production well, and discuss options for waste water
disposal.
By keeping the Unaatuq Board of Directors, as well as other stakeholders, in consistent contact
with Kawerak Project Staff and project contractors, there will be transparency in the project
details as well as valuable opportunities for feedback, suggestions, and innovative ideas suited
to the goals of the board; to help them achieve their mission and vision.
Unaatuq Mission: To promote the wellbeing of our people through sharing, protecting, and
responsibly developing the resources of Pilgrim Hot Springs.
Unaatuq Vision: A protected arctic oasis that provides for our people.
Task 9: Ongoing Grant Project Management and Financial Reporting
Kawerak will work with closely with project staff and contractors to keep on task with project
milestones and deliverables. Reports will be provided to Alaska Energy Authority in a timely
manner and as described in the grant agreement. Financials will be recorded, documented and
reported on a consistent basis throughout the life of the grant.
All project activities will be shared with appropriate stakeholders, such as the Kawerak Board of
Directors and the Unaatuq Board of Directors, on a consistent basis in the form of email reports,
verbal updates, presentations at board meetings, and through department newsletters.
5 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
Office of Grants and Contracts Administration
P.O. Box 757880, Fairbanks, Alaska 99775-7880
Tapiana Wray
Principal Grant & Contract Management Officer
(907) 474-1989 phone
(907) 474-5506 fax
uaf-ogca-preaward@alaska.edu
tewray@alaska.edu
www.uaf.edu/ogca/
UA is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual:
www.alaska.edu/titleIXcompliance/nondiscrimination.
September 23, 2020
Kawerak, Inc.
P.O. Box 948
Nome, Alaska 99762
Re: Letter of Commitment for proposal to Alaska Energy Authority 2020 Renewable Energy
Fund
The University of Alaska Fairbanks is pleased to collaborate with Kawerak, Inc., on the proposal
entitled “Pilgrim Hot Springs Geothermal Power Plant Conceptual Design,” which is being
submitted to the Alaska Energy Authority 2020 Renewable Energy Fund. The Principal
Investigator from UAF is Gwen Holdmann, Director of the Alaska Center for Energy and Power.
The appropriate administrative and programmatic personnel at UAF are aware of the pertinent
state and federal regulations and policies, and we are prepared to enter into a subcontract with
Kawerak, Inc., that ensures compliance with all such policies, should this proposal be funded.
A statement of work, budget, and budget justification for this subaward are attached.
If you have questions or need additional information, please feel free to contact me at uaf-ogca-
preaward@alaska.edu.
Sincerely,
Tapiana Wray
Principal Grant & Contract Management Officer
6 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
ACEP SCOPE OF WORK
PILGRIM HOT SPRINGS GEOTHERMAL POWER PLANT
CONCEPTUAL DESIGN
September 22, 2020
ACEP Principal Investigator
Gwen Holdmann
Director, Alaska Center for Energy and Power
Gwen.holdmann@alaska.edu
Contracting POC
Rosemary Madnick
Executive Director, Office of Grants and Contracts
University of Alaska Fairbanks
rmadnick@alaska.edu
7 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
OBJECTIVE AND INTRODUCTION
The Alaska Center for Energy and Power (ACEP) led an extensive geothermal exploration effort at Pilgrim
Hot Springs between 2010 and 2014. During this time period, a variety of geophysical surveys were
conducted in conjunction with three major drilling efforts. The drilling program culminated in the fall of
2013 with the drilling of a 6-in diameter production well (PS 13-1) capable of high flow rates. PS 13-1
was completed to a depth of 314 m. Natural artesian flow rates from this well are 60 gpm, while airlift-
assisted flow testing of this well conducted by ACEP in September 2014 demonstrated that the well is
capable of producing 300 gpm at temperatures ranging from 78.25 °C (172.85 °F) to 79.3 °C (174.74 °F).
The minimal pressure changes that were measured at that time, combined with an estimated natural
state heat flow from the geothermal system of approximately 20 MWth based on thermal data collected
from ground-based and aerial investigations of the site, led researchers to conclude that the well has the
ability to sustainably provide thermal fluid for on-site power generation and district heating
applications. This well could be used as a production well to support on-site geothermal power
generation using an Organic Rankine Cycle (ORC) system, similar to the system installed at Chena Hot
Springs. Chena Hot Springs has been operating a small geothermal power plant ranging in output from
approximately 200 to 400 kWe (net), using produced fluid at 74°C (165 °F).
The Principal Investigator of this project, Gwen Holdmann, was the lead for both the prior geothermal
exploration at Pilgrim Hot Springs and the development of the geothermal power plant at Chena Hot
Springs, and is thus well suited to lead this proposed effort. This scope of work represents a natural
extension of previous work, and focuses on supporting Kawerak in developing a geothermal power plant
at the site to benefit the people of the region.
SCOPE OF WORK
Timelines provided below are in quarters from receipt of award.
TASK 1: PROJECT SCOPING AND CONTRACTOR SELECTION
Kawerak is planning to hire a full-service engineering and design firm based in Alaska to support this
project. This firm will be responsible for identifying project permitting requirements; reviewing
geotechnical site considerations, civil design, and all engineering drawings related to the conceptual
design, particularly the site layout; and working with ACEP to design a cooling system and injection or
discharge strategy for spent fluids, consistent with state and federal regulations for wetland areas. ACEP
will support Kawerak in developing language for an RFP for a permitting, geotechnical, and civil design
subcontractor.
Deliverables: Draft language for RFP, outlining suggested responsibilities
Effort: 10% of total man-hours estimated
Timeline: TBD
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TASK 2: DESIGN SPECIFICATIONS FOR GEOTHERMAL POWER PLANT AND REVIEW OF POTENTIAL
EQUIPMENT VENDORS
ACEP will develop specifications for a geothermal power plant for the Pilgrim Hot Springs site, based on
known characteristics of the resource and expected current and future site loads. Based on data from
the flow test conducted in 2014, the resource should be capable of producing 300 kW from existing
production well PS 13-1, or up to 5 MW based on the overall natural state heat flow from the system to
the surrounding environment. Developing a smaller plant as a Phase 1 project is an excellent way to
stress test the resource over time, collecting data to both better quantify the precise upflow zone of the
geothermal fluids and better assess the maximum sustainable generation capacity of the resource.
It will also be important to design a power plant that can operate independently of an existing grid.
Many ORC systems are designed as synchronous machines and cannot operate in the absence of an
existing grid. This has been a significant challenge for Chena Hot Springs, which has not been able to
operate independently from a diesel system forming the backbone of the electric grid and providing
necessary parameters (voltage and frequency) for the ORC to follow. This issue can be avoided through
careful selection of the generator, or by pairing the geothermal plant with a battery/inverter system
that could also help balance load and allow other energy resources to support site demand. ACEP will
explore both options, with the goal of developing specifications for a Request for Information (RFI) to
solicit vendor information for prospective equipment manufacturers.
Task 2.1 – Load Forecasting. Develop a range of long-term load projections based on expected future
infrastructure needs and use patterns.
Task 2.2 – Establish optimal design parameters for power plant (input/output). Based on the known
characteristics of the resource and the load forecast developed in Task 2.1, ACEP will publish design
specifications for the system.
Task 2.2 – Equipment Vendor Assessment. ACEP will conduct a market evaluation of equipment
manufacturers, and complete due diligence research into existing products and projects on behalf of
Kawerak. ACEP will also release an RFI to solicit specific vendor input that will be used for more
advanced project design and cost modeling.
Deliverables: Design specifications and vendor report (including results of RFI) for Kawerak.
Effort: 45% of total man-hours estimated
Timeline: TBD
TASK 3: SUPPORT SITE INFRASTRUCTURE DESIGN
ACEP will work closely with engineering subcontractors retained by Kawerak for on-site design to
support power generation from the geothermal resource while providing for long-term sustainability of
the resource. ACEP will be responsible for sharing data related to the resource on behalf of Kawerak,
and communicating specifications related to the power plant design. ACEP will also support Kawerak in
reviewing draft plans, drawings, and infrastructure design recommendations and providing feedback as
appropriate.
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Deliverables: Data package for engineering subcontractor, written feedback on preliminary design.
Effort: 10% of total man-hours estimated
Timeline: TBD
TASK 4: DISTRIBUTION SYSTEM DESIGN
The Pilgrim Hot Springs geothermal site is currently considered a greenfield site, without any sort of
existing permanent generation or distribution infrastructure. Site power, when needed, is currently
provided by imported and portable generators. In addition to power plant design, it will be important to
carefully think through the layout of the electrical distribution system. This provides a unique
opportunity to consider non-traditional approaches that could enable Kawarak and Unaatuq, LLC to seek
DOE funds. Chief among these alternatives could be an entirely DC-based microgrid. While it is
understood that the Renewable Energy Fund is not intended for nonconforming technologies, there may
be value in conducting at least a preliminary assessment of alternative grid architectures since future
federal funds could be available for innovative design in this space.
Deliverables: Distribution grid layout options, provided to engineering subcontractor to incorporate into
conceptual design for site layout.
Effort: 10% of total man-hours estimated
Timeline: TBD
TASK 5: ASSESSMENT OF ALTERNATIVES
ACEP will conduct a due diligence analysis of alternative energy sources at the site. In addition to
traditional diesel generation, ACEP will consider solar power as an alternative. This aligns well with an
initial summer-only operation as proposed by Kawerak. Surveys of Alaska installations show costs
ranging from $2.20 to $5.00/Watt for remote installations larger than ~45 kW. Capacity factors range
from 8%-16%. For the Nome area, according to NREL's PVWatts tool, solar irradiance levels are on the
order of 5-6 kWh/m2/day in the summer months, and an ~300 kW array is predicted to yield a little over
300,000 kWh total annual energy production.
Alaska’s cold temperatures increase system voltage, reduce electrical resistance, and yield higher-than-
rated outputs associated with reflected light and albedo effects. These factors, combined with declining
module prices, are making solar photovoltaic (PV) technology more economical. Solar PV arrays have
been installed in all areas of the state, from the southwest to the Arctic, and low sun angles and long
daylight hours represent opportunities to mount panels vertically on walls as well as on the east and
west sides of buildings.
Deliverables: Analysis of solar and diesel as alternatives.
Effort: 10% of total man-hours estimated
Timeline: TBD
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TASK 6: ECONOMIC FEASIBILITY ANALYSIS
Based on the information derived from Tasks 2-4 and on information from geothermal power plants of a
similar size developed in other locations, ACEP will generate budget estimates and complete a robust
economic analysis for the project, as well as alternatives identified though Task 5 work.
Deliverables: Report on economic feasibility and alternatives.
Effort: 15% of total man-hours estimated
Timeline: TBD
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BUDGET JUSTIFICATION
Budget Category Total
Salaries
Gwen Holdmann (executive staff, $79.25), 160 hours $15,674
Christopher Pike (exempt staff, $37.16), 160 hours $7,563
Robert Bensin (exempt staff, $37.95), 80 hours $3,862
Jeremy Vandermeer (exempt staff, $33.00), 500 hours $20,988
Stephen Colt (adjunct faculty, $370.37), 40 hours $14,844
M.S. graduate student ($23), 640 summer hours $14,735
Total salaries $77,666
Fringe benefits
Executive staff, 27.6% $4,326
Exempt staff, 42.5% $13,775
Adjunct faculty, 11.1% $1,648
Graduate student, 9.7% during summer months $1,429
Graduate student health insurance $734
Total fringe benefits $21,912
Travel
Fairbanks, AK-Nome, AK, 2 trips, 2 people, 3 days/nights per trip $5,436
Other Costs
Poster printing, etc. $500
Truck rental $900
Total Direct Costs $106,414
Modified Total Direct Costs (MTDC) $105,514
Indirect Costs, 25% of MTDC $26,379
Total Project $132,793
Salaries
• Gwen Holdmann, Director of Alaska Center for Energy and Power (UAF executive staff): 0.92
month (160 hours). Holdmann will serve as the PI and project manager, and will be responsible for
communicating with Kawerak, the engineering contractor, and leading the development of
specifications, RFI, and design for the geothermal power plant. She has led prior resource
evaluation efforts at Pilgrim Hot Springs, and was the lead engineer for the Chena Hot Springs
geothermal power plant development which is similar in size and scope to the one proposed here.
• Christopher Pike (exempt staff): 0.92 month (160 hours). Pike will be responsible for data
management related to site layout and PS 13-1 characteristics as well as assessment of alternative
resources. Pike was the project manager for the Pilgrim Hot Springs confirmation well drilling
program and is knowledgeable about each of the drill holes on site.
• Robert Bensin (exempt staff): 0.46 month (80 hours). Bensin will support planning for the
electrical distribution system. He is intimately familiar with the site through prior employment
with Bering Straits Native Corporation and previously led the development of a small seasonal
organic farm at the site. Rob is a licensed electrician and electrical administrator in the State of
Alaska.
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• Jeremy Vandermeer (exempt staff): 2.89 months (500 hours). Vandemeer will support the
conceptual design for the electric layout for the site, as well as specifications related to the power
plant and/or ancillary support equipment (energy storage, etc). Vandermeer is an electric
engineer who has previously modeled integration of a geothermal power plant at Pilgrim Hot
Springs into the Nome grid.
• Stephen Colt (adjunct faculty): 0.46 month (80 hours) to support economic analysis.
• M.S. graduate student research assistant: 640 summer hours (16 weeks at 40 hours per week).
The graduate student will participate in the economic analysis of various design alternatives to
support engineering and site planning decisions.
Per UA policy, salaries include a leave reserve, calculated on salary at a rate of 20.6% for executive staff,
24.1% for exempt staff, 0.2% for adjunct faculty, and 0.1% for students. Salaries also include a 2.5%
annual escalation for executive and exempt staff).
Fringe Benefits
Staff benefits are negotiated annually with the Office of Naval Research. FY21 provisional fringe benefits
rates include 27.6% for executive staff, 42.5% for exempt staff, 11.1% for adjunct faculty, and 9.7% for
students during the summer months. A copy of the current rate agreement is available at:
http://www.alaska.edu/cost-analysis/negotiation-agreements/ Health insurance is included for the
graduate student research assistant during the summer, based on academic year 2020-21 rates ($734
for summer).
Travel
Costs are included for two trips to Nome, Alaska, for two project personnel. Per person costs for each 3-
day/3-night trip include $400 for airfare, $185/night for lodging, $118 per day for meals and incidental
expenses, and $50 for ground transportation and airport parking. Costs are based on current pricing
using Google flights, Department of Defense per diem rates, and previous travel to similar destinations
for other research programs.
Other Costs
Funds are budgeted for printing posters and reports for project dissemination ($500) and for truck rental
in Nome, Alaska, during fieldwork (2 trips, 3 days/trip, $150/day). Costs are based on similar costs for
other research programs. Rental vehicle costs do not incur indirect costs.
Indirect Costs
Facilities and administrative (F&A) costs are calculated at 25% of the Modified Total Direct Costs
(MTDC), based on the current MOA between UAF and the Alaska Department of Transportation and
Public Facilities. MTDC exclude equipment, capital expenditures, charges for patient care, rental costs,
tuition remission, scholarships and fellowships, participant support costs and the portion of each
subaward in excess of $25,000. A copy of the agreement is available at: http://www.alaska.edu/cost-
analysis/negotiation-agreements/.
Total Direct Costs: $106,414
MTDC: $105,514
Total Indirect Costs: $26,379
Total Project: $132,793
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Anchorage Office: 3940 Arctic Blvd. Suite 300, Anchorage, AK 99503 | (907) 562-3252 fax (907) 561-2273
Palmer Office: 808 S. Bailey St. Suite 104, Palmer, AK 99645 | (907) 707-1352
Seattle Office: 100 S. King Street, #100-749, Seattle, WA 98104 (206) 350-2791
www.crweng.com
September 24, 2020
Ms. Amanda Toerdal
Pilgrim Hot Springs General Manager
Pilgrim Hot Springs / Unaatuq, LLC
c/o Kawerak, Inc
500 Seppala Drive
Nome, AK 99762
Re: Pilgrim Hot Springs Engineering Services
Dear Amanda,
CRW Engineering Group (CRW) is pleased to provide this proposal for engineering services to assist
Unaatuq, LLC and the Alaska Center for Energy and Power (ACEP) in developing the conceptual design
for a new geothermal power plant at Pilgrim Hot Springs, Alaska. We understand that the scope and fee
developed for this effort are for budgetary purposes and may be refined before the work begins.
An existing 6-inch diameter geothermal production well has been drilled to 314 meters. Testing on the
well has been completed with a sustained flow rate of 300 gpm and a water temperature of 175° F. The
well will produce approximately 60 gpm in artesian conditions. The proposed power production for the
new plant is between 100 and 250 kW, at an anticipated flow rate of 200 gpm. Specific scope of work
items for CRW are outlined below:
SCOPE OF WORK
CRW will provide the following services:
1. Coordination with ACEP and Unaatuq LLC as needed to develop the project.
2. Identify Needed Permits
a. Identify the permits needed for construction of the power plant, including:
i. Well water withdrawal and disposal
ii. Site development
iii. Power plant construction
b. Identify additional data or other information that will be required for permitting efforts.
3. Develop a plan for well water disposal, including:
a. Discharge to the surface through a pool/pond.
b. Discharge to groundwater through an underground injection well.
4. Provide conceptual design of auxiliary power plant components, including:
a. Well pump sizing and selection
b. Piping layout from the well to the power plant and from the power plant to the discharge
location.
c. Cooling system for the generator.
d. Develop engineering design drawings, including:
i. Site design and facilities layout
ii. Concept system process schematic
iii. One alternative only
5. Develop design and construction cost estimates.
a. One estimate for preferred design.
14 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
Pilgrim Hot Springs Conceptual Power Plant Design
9/24/20
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DELIVERABLES
The scope items above will be presented in an engineering technical memorandum. Conceptual design
drawings, engineering calculations, design and construction cost estimates, and meeting summaries will
be provided as appendices to the technical memo.
ASSUMPTIONS
The following assumptions have been made:
· No site visits or field investigations will be required.
· Existing mapping and survey data for the site and surrounding area will be sufficient to complete
the conceptual design
WORK BY OTHERS –
It is assumed that ACEP will provide the following:
· Coordination with property owners and the general public.
· Mechanical and electrical design of the power plant.
FEE
The proposed Scope of Work will be performed on a time and materials, not to exceed, basis in
accordance with the attached CRW terms and conditions for an amount of $90,960.
Thank you for asking CRW to provide this proposal. We appreciate the opportunity to serve Unaatuq
LLC and ask that you contact us at (907)562-3252 if you have any questions or comments.
Sincerely,
CRW Engineering Group, LLC.
Matt Edge, P.E., Principal
Direct: (907) 646-5623 / email: medge@crweng.com
Attachment: 1) Engineering Services Fee Estimate Breakdown
2) CRW Engineering Group, LLC Terms and Conditions, 2020
15 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
Pilgrim Hot Springs Conceptual Power Plant Design
9/24/20
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________________________________________________________________________
ACCEPTANCE OF THE PROPOSAL AND AUTHORIZATION TO PROCEED
The proposed scope of services, fee, and contract conditions are acceptable to Unaatuq LLC, and CRW
Engineering Group, LLC is authorized to proceed with the work.
By ______________________________ Signature _____________________________*
Title ____________________________ Date _________________________________
* Person with authority to commit the resources of Unaatuq LLC.
16 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
Pilgrim Hot Springs Geothermal Power Plant Concept DesignFee Proposal CRW Engineering Group, LLCTask & Subtask DescriptionSenior Principal / CMJeff Stanley, PEPrincipal / PM (Civil/Environmental)Matt Edge, PESenior Engineer (Mechanical)Tracy McKeon, PERegistered Eng/SurveyorStaff Engineer IISenior Designer Admin SupportTotal LaborExpensesSubconsultantTotal Subtask$210$200$190$160$145$145$90$$$$Concept DesignTask 1 -Technical MemorandumProject Management & Coordination216444$5,380$100$5,480Identify Needed Permits11224$6,090$6,090Well Water Disposal Plan184328$8,370$50$8,420Conceptual DesignPump Sizing and Selection22416$3,740$25$3,765Piping Layout284824$7,300$25$7,325Cooling System1163224$11,850$25$11,875Engineering DrawingsSite Design1161640$11,530$100$11,630System Process Schematic1441624$7,810$50$7,860Cost Estimates28424484$13,940$25$13,965Technical Memo Preparation and Printing42484044$14,500$50$14,550Total Task 1:15984212414412412$90,510$450$0$90,960TOTAL ALL SERVICES:15984212414412412$90,510$450$0$90,960Assumptions1No site visits are required.2No electrical design included.3Unaatuq LLC will provide topographic information to form basis of site design.4Drawings will be in AutoCAD. No specifications will be provided. CRW Engineering Group, LLCPage 1 of 1Date: 9/24/202017 of 101Kawerak-Pilgrim Hot Springs-REF Proposal
CRW Engineering Group, LLC Page 1 of 5 Standard Terms and Conditions (11/6/16)
2020 SCHEDULE OF CHARGES AND STANDARD TERMS and CONDITIONS
Compensation to CRW Engineering Group, LLC for our professional services is based upon
the conditions set forth below:
SCHEDULE OF CHARGES
Charges for employees are determined by the hourly rates listed below. A new schedule is
issued at the beginning of each year. Unless other arrangements have been made, charges for
all work will be based on the latest Schedule of Charges and General Conditions.
EMPLOYEE CATEGORY
Senior Principal..................................................................................$210.00
Principal .............................................................................................$200.00
Senior Engineer/Land Surveyor.........................................................$190.00
Project Engineer/Land Surveyor ........................................................$175.00
Registered Staff Engineer/Land Surveyor .........................................$160.00
Staff Engineer/Land Surveyor II (EIT/LSIT) ....................................$145.00
Staff Engineer/Land Surveyor I .........................................................$130.00
Senior Designer..................................................................................$145.00
Engineering/Surveying Technician III...............................................$130.00
Engineering/Surveying Technician II ................................................$115.00
Engineering/Surveying Technician I .................................................$ 95.00
Clerical/Administrative Support ........................................................$ 90.00
SUPPLIES AND SERVICES
Direct Expenses and Supplies ............................................................Invoice + 10%
Subconsultants ...................................................................................Invoice + 10%
Meals (Per Diem) ...............................................................................$60.00/day
In-house Expenses
Xerox (8-1/2 x 11) ....................................................................$0.10/copy
Xerox (11 x 17) .........................................................................$0.20/copy
Color Copies (8-1/2 x 11) .........................................................$1.00/copy
Mileage (Federal Rate) .............................................................$0.58/mile
Bond Plots .................................................................................$1.00/square foot
Mylar Plots ................................................................................$2.00/square foot
18 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
CRW Engineering Group, LLC Page 2 of 5 Standard Terms and Conditions (11/6/16)
CRW ENGINEERING GROUP, LLC
STANDARD TERMS AND CONDITIONS
1. INVOICES AND PAYMENT TERMS
CRW Engineering Group, LLC (CRW) will
submit invoices to CLIENT not more than
every thirty (30) days and a final bill upon
completion of Services. CLIENT shall
notify CRW within ten (10) days of receipt
of invoice of any dispute with the invoice.
CLIENT and CRW will promptly resolve
any disputed items. Payment on undisputed
invoice amounts is due upon receipt of
invoice by CLIENT and is past due thirty
(30) days from the date of the invoice.
CLIENT agrees to pay a finance charge of
one and one-half percent (1-1/2%) per
month, or the maximum rate allowed by
law, on past due accounts. If payment
remains past due sixty (60) days from the
date of the invoice, then CRW shall have the
right to suspend all work under this
Agreement, without prejudice. CLIENT
shall pay all reasonable demobilization and
other suspension costs. CLIENT agrees to
pay attorneys’ fees, legal costs and all other
collection costs incurred by CRW in pursuit
of past due payments. Our hourly rates do
not include a sales tax and these will be
added if they become applicable in any
jurisdiction.
2. CHANGES
CLIENT and CRW recognize that it may be
necessary to modify the scope of Services,
the schedule, and/or the cost estimate
proposed in this Agreement. CRW shall
notify CLIENT in a timely manner when it
has reason to believe a change to the
Agreement is warranted. CRW shall
prepare a Change Order request outlining
the changes to the scope, schedule, and/or
cost of the project. CLIENT has a duty to
promptly consider the Change Order request
and advise CRW in a timely manner in
writing on how to proceed. If after a good
faith effort by CRW an agreement has not
been reached with the CLIENT, then CRW
shall have the right to terminate this
Agreement upon written notice to the
CLIENT.
3. DELAYS AND FORCE MAJEURE
CLIENT shall not hold CRW responsible for
damages or delays in performance caused by
acts of God, acts and/or omissions of
Federal, State, and local governmental
authorities and regulatory agencies or other
events which are beyond the reasonable
control of CRW.
4. TERMINATION
This Agreement may be terminated by either
party upon written notice in the event of
substantial failure by the other party to
perform in accordance with terms hereof.
Such termination shall not be effective if
that substantial failure has been remedied
before expiration of the period specified in
the written notice, such period shall not be
less than seven (7) calendar days. In the
event of termination, CRW shall be paid for
services performed to the termination notice
date including reasonable termination
expenses. CRW may complete such
analyses and records as are necessary to
complete their files and may also complete a
report on the Services performed to the date
of notice of termination or suspension. The
expenses of termination or suspension shall
include all direct costs of CRW in
completing such analyses, records, and
reports.
5. DATA AND INFORMATION
CLIENT shall provide to CRW all the
reports, data, studies, plans, specifications,
documents, and other information which are
relevant to the Services. CRW shall be
entitled to rely upon the reports, data,
studies, plans, specifications, documents,
and other information provided by CLIENT
or others in performing the Services, and
CRW assumes no responsibility or liability
for the accuracy or completeness of such.
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CRW Engineering Group, LLC Page 3 of 5 Standard Terms and Conditions (11/6/16)
6. RIGHT OF ENTRY
The CLIENT will furnish CRW with the
right-of-entry on the land to conduct
surveys, observations, and other
explorations as required. If the CLIENT
does not own the site, CLIENT must
obtain permission for CRW to enter the
site and perform the services.
CRW will take reasonable precautions to
minimize damage from use of equipment,
however, it is understood that in the
normal course of work some surface
damage may occur, the restoration of
which is not part of this Agreement.
The CLIENT is responsible to provide, by
map or drawing, a description of the
property, its location, and the location of
any buried utilities or structures. CRW
shall not be liable for damage or injury
arising from damage to subterranean
structures (pipes, tanks, telephone lines,
etc.) which are not called to CRW’s
attention and correctly shown on the plans
furnished by the CLIENT in connection
with work performed under this
Agreement.
7. CONTROL OF WORK AND JOB-SITE
SAFETY
CRW shall be responsible only for its
activities and that of its employees and
subcontractors. CRW’s Services under
this Agreement are performed for the sole
benefit of the CLIENT and no other entity
shall have any claim against CRW
because of this Agreement or the
performance or nonperformance of
Services hereunder. CRW will not direct,
supervise, or control the work of other
consultants and contractors or their
subcontractors.
8. PROFESSIONAL WORK PRODUCT
The Service provided by CRW is intended
for one time use only. All documents,
including but not limited to, reports, plans,
designs, field data, field notes, laboratory
test data, calculations, and estimates (the
“Documents”), and all electronic media
prepared by CRW are considered its
professional work product. CRW retains all
rights to its professional work product.
Copies of Documents shall be provided to
CLIENT upon written request and at
CLIENT’s expense. CRW shall retain these
Documents for a period of two (2) years
following submission of its report, during
which period they will be made available to
CLIENT at all reasonable times.
CLIENT acknowledges that electronic
media is susceptible to unauthorized
modification, deterioration, and
incompatibility, and therefore CLIENT shall
not rely on the accuracy of the electronic
media version of CRW’s professional work
product.
CLIENT understands that the professional
work product is not intended or represented
by CRW to be suitable for reuse by any
party, including, but not limited to, the
CLIENT, its employees, agents,
subcontractors or subsequent owners on any
extension of a specific project not covered
by this Agreement or on any other project,
whether CLIENT’s or otherwise, without
CRW’s prior written permission. CLIENT
agrees that any reuse unauthorized by CRW
will be at CLIENT’s sole risk and that
CLIENT will defend, indemnify, and hold
CRW harmless from any loss or liability
resulting from the reuse, misuse, or
negligent use of the professional work
product.
9. STANDARD OF CARE
Services performed by CRW will be
conducted in a manner consistent with that
level of care and skill ordinarily exercised
by other members of the engineering and
science professions currently practicing
under similar conditions subject to the time
limits and financial, physical, or any other
constraints applicable to the Services. No
warranty, express or implied, is made.
20 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
CRW Engineering Group, LLC Page 4 of 5 Standard Terms and Conditions (11/6/16)
10. INSURANCE AND INDEMNITY
CRW maintains General Liability Insurance
for bodily injury and property damage with
an aggregate limit of $1,000,000 per
occurrence and we will furnish certificates
of such insurance upon request. Our
liability to the CLIENT for bodily injury or
property damage arising out of work
performed for the CLIENT for which legal
liability may be found to rest upon us, other
than the professional errors and omissions,
will be limited to our General Liability
insurance coverage.
CLIENT shall, at all times, defend,
indemnify, and save harmless CRW and its
subcontractors, consultants, agents, officers,
directors, members and employees from and
against all claims, damages, losses, and
expenses, including but not limited to
reasonable attorneys’ fees, court and
arbitration costs, arising out of or resulting
from the Services of CRW, inclusive of
claims made by third parties, or any claims
against CRW arising from the acts, errors, or
omissions of CLIENT, its employees,
agents, contractors, and subcontractors.
Such indemnification shall not apply to the
extent such claims, damages, losses, or
expenses are finally determined to result
from CRW’s negligence.
CRW shall, at all times, indemnify and save
harmless CLIENT and its officers, directors,
agents, and employees from and against all
claims, damages, losses, and expenses
arising from personal injury, death, or
damage to third-party property to the extent
directly attributable to the negligent acts,
errors, or omissions of CRW.
11. LIMITATION OF LIABILITY
Our findings, recommendations, speci-
fications, or professional opinions will be
presented, within the limits prescribed by
the CLIENT, after being prepared in
accordance with generally accepted
professional engineering practice. We
make no other warranty, either express or
implied. For any injury or loss on account
of any error, omission, or other
professional negligence, the CLIENT
agrees to limit CRW and/or its
professional employees' liability to the
CLIENT and to all agents, contractors,
and subcontractors arising out of the
performance of our professional services,
such that the total aggregate liability to all
those named shall not exceed $50,000 or
our fee, whichever is greater. In the event
the CLIENT does not wish to limit our
professional liability to this sum, we will
waive this limitation upon the CLIENT's
written request made at the time of the
initial authorization, on a given project,
provided that the CLIENT agrees to pay
an additional 5% of our total fee or $500,
whichever is greater. However, the
CLIENT agrees that our maximum
liability will be limited to our Professional
Liability Insurance coverage. In the event
the CLIENT makes a claim against CRW
and/or its professional employees, at law
or otherwise, for any alleged error,
omission, or other act arising out of the
performance of our professional services,
and the CLIENT fails to prove such claim
or prevail in and adversary proceeding, the
CLIENT shall pay all costs incurred by
CRW and/or its professional staff in
defending itself against the claim.
Neither party shall be responsible to the
other for lost revenues, lost profits, cost of
capital, claims of customers, or other
special, indirect, consequential, or punitive
damages.
12. DISPUTES
All disputes, claims, and causes one party
makes against the other, at law or otherwise,
including third party or “pass-through”
claims for indemnification and/or
contribution, shall be initiated, determined,
and resolved by arbitration in accordance
with the Construction Industry Arbitration
Rules of the American Arbitration
Association, and judgment upon the award
rendered by the Arbitrator(s) may be entered
in any court having jurisdiction thereof.
21 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
CRW Engineering Group, LLC Page 5 of 5 Standard Terms and Conditions (11/6/16)
In the event that one party makes a claim
against the other, at law or otherwise, and
then fails to prove such claim, then the
prevailing party shall be entitled to all costs,
including attorneys’ fees incurred in
defending against the claim.
13. CLIENT LITIGATION
If CRW is requested to produce documents,
witnesses, or general assistance pursuant to
a litigation, arbitration, or mediation in
support of CLIENT litigation to which CRW
is not an adverse party, CLIENT shall
reimburse CRW for all direct expenses and
time in accordance with CRW’s current rate
schedule.
14. MISCELLANEOUS
a) This Agreement supersedes all other
agreements, oral or written, and contains
the entire agreement of the parties. No
cancellation, modification, amendment,
deletion, addition, waiver, or other
change in this Agreement shall have
effect unless specifically set forth in
writing signed by the party to be bound
thereby. Titles in this Agreement are for
convenience only.
b) This Agreement shall be binding upon
and inure to the benefit of the parties
hereto and their respective successors
and assigns provided that it may not be
assigned by either party without consent
of the other. It is expressly intended and
agreed that no third party beneficiaries
are created by this Agreement, and that
the rights and remedies provided herein
shall inure only to the benefit of the
parties to this Agreement.
c) No waiver of any right or remedy in
respect of any occurrence on one
occasion shall be deemed a waiver of
such right or remedy in respect of such
occurrence on any other occasion.
d) All representations and obligations
(including without limitation the
obligation of CLIENT to indemnify
CRW in Article 10 and the Limitation of
Liability in Article 11) shall survive
indefinitely the termination of the
Agreement.
e) Any provision, to the extent it is found
to be unlawful or unenforceable, shall be
stricken without affecting any other
provision of the Agreement, so that the
Agreement will be deemed to be a valid
and binding agreement enforceable in
accordance with its terms.
15. NOTICES
All notices required or permitted to be given
hereunder, shall be deemed to be properly
given if delivered in writing by hand,
facsimile machine, e-mail, or express
courier addressed to CLIENT or CRW, as
the case may be, at the addresses set forth
below, with postage thereon fully prepaid if
sent by mail or express courier.
All notices, correspondence, deliverables,
and invoices shall be submitted to CLIENT
as indicated in the signed letter agreement
unless otherwise indicated below:
___________________________________
___________________________________
___________________________________
Attn: _______________________________
All Notices and correspondence shall be
submitted to CRW as indicated below:
CRW Engineering Group, LLC
3940 Arctic Boulevard, Suite 300
Anchorage, Alaska 99503
Attn: D. Michael Rabe, PE, Member Manager
22 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
Scope of Work for DeerStone Consulting Contribution to
Mary’s Igloo and Kawerak Proposal to BIA TEDC Grant Program
DeerStone Consulting will work with all project participants and stakeholders, led by Mary’s
Igloo Traditional Council (MITC) and Kawerak, Inc., to assist in the following tasks and
deliverables:
• Conduct a Feasibility Study to determine an appropriate business structure and define
development options for Unaatuq, LLC. to optimize and manage the locally available
energy resources—including possibly geothermal, solar, biomass, hydropower, and
wind—for a sustainable economy and business foundation for Pilgrim Hot Springs.
• Perform an Economic Analysis of the income potential and requirements for an energy
provider as well as a load analysis for various prospective businesses and enterprises
based on development scenarios identified by project participants and stakeholders.
• Facilitate a Strategic Planning Session with Unaatuq Board members to define scenarios
and energy development options for Pilgrim Hot Springs and more broadly for the
Kawerak/Norton Sound region.
Assumptions
1. DeerStone Consulting team includes Brian Hirsch, Devany Plentovich, Tashina Duttle,
Alan Mitchell, and Peter Crimp.
2. DeerStone will work closely with designated staff from MITC and Kawerak. Amanda
Toerdal or her delegate will be primary Point of Contact for MITC and Kawerak and Brian
Hirsch or his delegate will be primary Point of Contact for DeerStone.
3. The Economic Analysis will be a stand-alone activity but will be included as a major
component of the broader Feasibility Study. The Economic Analysis will primarily be a
techno-economic optimization of various energy options designed to meet different
load profiles based on expected business activity at Pilgrim Hot Springs. The Feasibility
Study will incorporate the Economic Analysis and Strategic Planning outputs into a much
broader review of development pathways, approaches, institutional considerations, and
overall strategies to support goal- and value-driven development of Pilgrim Hot Springs
to serve as a role model for the region.
4. All Unaatuq partners will strive to have at least one representative available for the
Strategic Planning Session, which will take place in Nome, Alaska, as travel restrictions
allow, including a site tour of Pilgrim Hot Springs.
5. The Strategic Planning Session will be for 2 days in-person (if possible, or 1 day if virtual),
and will require 1-2 person-days of preparation and 1-2 person-days of follow-up from
DeerStone (depending on if in-person or virtual), including a write-up of the event,
follow up next steps, and outreach support to participants before and after.
23 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
List of Bering Strait Tribes
Chinik Eskimo Community (aka Golovin)
King Island Native Community
Native Village of Brevig Mission
Native Village of Council
Native Village of Diomede (aka Inalik)
Native Village of Elim
Native Village of Gambell
Native Village of Koyuk
Native Village of Mary’s Igloo
Native Village of Saint Michael
Native Village of Savoonga
Native Village of Shaktoolik
Native Village of Shishmaref
Native Village of Teller
Native Village of Unalakleet
Native Village of Wales
Native Village of White Mountain
Nome Eskimo Community
Stebbins Community Association
Village of Solomon
24 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
2020 KAWERAK, INC.
Organizational Chart
NATURAL RESOURCES DIVISION
Kawerak President
Kawerak Natural Resources Committee
Executive Vice President
Vice President Natural Resources
Administrative Assistant
Land Management Services Program Director
Eskimo Walrus Commission Director
Eskimo Walrus Commission
Reindeer Herders Association
Subsistence Resources Director
Special Projects Assistant
Land Management Specialist I
Land Management Specialist II (2)
Revised: 8/2020
Natural Resources Specialist
Social Science Program Director
Ice Seal Committee, Northern Norton Sound Advisory Committee, SPSRAC
Local Assistant II (Nome)
Social Science Research Assistant
Natural Resources Advocate
Probate Specialist II
AYKSSI Steering Committee, NPFMC Ecosystem Committee, WASC Representative, WALCC Steering Committee
Marine Mammal Commission, ICC Alaska Board and Executive Committee, AK Seagrant Advisory Member, Arctic Marine Mammal Commission, Arctic Waterway Safety Committee, IPCOMM Member
FSB Tribal Consultation Committee
* Kawerak Board Committee
* NR programs serve as support staff
* NR staff serve on these boards or committees
Color Key:
Society for the Anthropology of Consciousness
Environmental Program Director
Environmental Assistant
Brownfields Coordinator
Village IGAP Programs
Probate Specialist I
Local Assistants I (Villages)
Bering Strait/Norton Sound Migratory Bird Council, Alaska Migratory Bird Co-management Council
Emergency Preparedness Specialist
Energy Development Specialist
Marine Advocate
Pilgrim Hot
Springs General
Manager &
Caretaker25 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
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Geothermal Exploration at Pilgrim Hot Springs 2010 to 2014:
Final Report
Prepared by the Alaska Center for Energy and Power at the University of Alaska
Fairbanks
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Acknowledgments
Activities described in this report were made possible with funding from a variety of federal,
state, local, private and tribal sources including the U.S. Department of Energy under DE-
EE0002846, “Validation of Innovative Exploration Techniques, Pilgrim Hot Springs, Alaska”
and DE-EE0000263, “Southwest Alaska Regional Geothermal Energy Project, Pilgrim Hot
Springs, Alaska,” The Alaska Energy Authority through RSA R1108 and R1215, the City of
Nome, Bering Straits Native Corporation, White Mountain Native Corporation, Sitnasuak Native
Corporation, Potelco, Inc., and the Norton Sound Economic Development Corporation.
The geothermal exploration described in this report required a significant amount of planning
and organization, and would not have been possible without the generous support from numerous
individuals and organizations. The importance of local people and groups on the Seward
Peninsula to this project’s success cannot be overstated. The employees of Bering Straits Native
Corporation were generous with never-ending useful snippets of local knowledge as well as
logistical support, in addition to the monetary support already described. Assistance from Robert
Bensin, Kevin Bahnke, Larry Pederson, Matt Ganley, and Jerald Brown was indispensable and
deserves special mention. The support of staff from the Norton Sound Economic Development
Corporation and the City of Nome, especially John Handeland of the Nome Joint Utility Service
and Mayor Denise Michels, were instrumental in overcoming logistical and funding challenges.
Unaatuq, LLC and its board of directors have continued to have the vision required to keep the
project moving forward. Unaatuq board member Roy Ashenfelter provided logistical support and
boat transport up and down the Pilgrim River.
Mary’s Igloo Native Corporation, whose land abuts the hot spring property was an important
project partner and allowed land access for project activities. Mary’s Igloo Native Corporation
tribal member Dora Mae Hughes and her family members provided important cultural
background and shared stories about the regional history. Louis Green Sr. willingly shared his
knowledge of the Pilgrim Hot Springs site and its history and provided logistical support. Chuck
Fagerstrom freely shared his knowledge and was always willing to share site history and stories.
Bryant Hammond and Amy Russell from Kawerak provided additional local support. University
of Alaska faculty member Dr. Catherine Hanks assisted with technical editing and offered her
expertise on the geology of the Seward Peninsula. Joe Batir and others from Southern Methodist
University assisted with well logging and allowed ACEP to use high quality geothermal logging
equipment. Jo Price and Graphite One Resources willingly shared data that they acquired to
assist with the development of a regional geothermal understanding. In addition, former
University of Alaska faculty members Dr. Ronald Daanen and Jo Mongraine were heavily
involved and instrumental in project planning and data collection.
The staff of the U.S. Geologic Survey (USGS) assisted in a variety of ways. Art Clark and the
USGS drilling team made the initial stages of the project possible. John Glen and his crew
accomplished an extensive set of geophysical surveys and interpretations and provided technical
assistance at various stages of the project.
The University of Alaska Fairbanks Geophysical Institute including Anupma Prakash, Christian
Haselwimmer and Jeff Benowitz and graduate students Josh Miller and Arvind Chittambakkam
28 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
ii
worked tirelessly to complete the remote sensing and conceptual modeling, adding an important
piece to the body of knowledge about Pilgrim Hot Springs.
Ryan Purcella of Baker Hughes and Mark Kumataka provided valuable engineering guidance
related to well pumping and flow testing. Additional technical assistance was provided by Bill
Cummings, and Dr. Dave Blackwell. Cheryl Thompson, collections assistant at the Carrie M.
McLain Memorial Museum in Nome, was extremely helpful, providing assistance with historical
research and obtaining historic photos. Ethan Berkowitz assisted with organizing and
maintaining positive momentum during the final round of drilling and Howard Trott contributed
his time and supplied equipment used in the flow testing.
Joel Renner and Fran Pedersen spent long hours on a technical review of this report for which we
are very grateful. A special thank you goes out to Dick Benoit who provided endless advice and
technical assistance and who was always willing to answer his phone when we called.
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Table of Contents
Acknowledgments ....................................................................................................................... i
List of Figures ............................................................................................................................. v
List of Tables ............................................................................................................................. vi
Terms and Acronyms ................................................................................................................ vii
1. EXECUTIVE SUMMARY .................................................................................................... 1
2. BACKGROUND – KRUZGAMEPA HOT SPRINGS .......................................................... 2
2.1 Geothermal Exploration History ....................................................................................... 4
3. GEOLOGIC SETTING .......................................................................................................... 6
3.1 Regional Geologic Setting ................................................................................................ 6
3.2 Local Geology ................................................................................................................... 8
4. SUBSURFACE TEMPERATURES ...................................................................................... 8
4.1 Updated Temperature Logging ....................................................................................... 11
5. REMOTE SENSING ............................................................................................................ 14
5.1 Satellite-based Geothermal Anomaly Mapping .............................................................. 15
5.2 Airborne Forward Looking Infrared Surveys ................................................................. 17
6. GEOPHYSICAL SURVEYS ............................................................................................... 27
6.1 Gravity Surveys .............................................................................................................. 28
6.2 Airborne Magnetic and Electromagnetic Surveys .......................................................... 29
6.3 Magnetotellurics Survey ................................................................................................. 31
7. DRILLING ACTIVITIES ..................................................................................................... 35
7.1 Permitting ........................................................................................................................ 36
7.2 Legacy Wellhead Repairs ............................................................................................... 36
7.3 Shallow Temperature Survey .......................................................................................... 37
7.4 Deep Drilling .................................................................................................................. 40
8. WATER CHEMISTRY ........................................................................................................ 42
9. FLOW AND INTERFERENCE TESTING ......................................................................... 44
9.1 Interference Testing of Wells PS-3, PS-4, and MI-1 ...................................................... 45
9.2 Interference Testing of PS-3, PS-13-1, and PS-13-3 ...................................................... 46
9.3 Flow Testing of PS-13-1 ................................................................................................. 46
9.4 Temperature and Pressure Monitoring in PS-13-2 ......................................................... 52
9.5 Temperature and Pressure Monitoring in PS-13-3 ......................................................... 52
9.6 Historic Hot Springs Temperature Monitoring ............................................................... 54
9.7 Flow Testing Conclusions .............................................................................................. 55
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10. PILGRIM GEOTHERMAL SYSTEM CONCEPTUAL MODEL .................................... 56
10.1 Conceptual Model History ............................................................................................ 56
10.2 Current Pilgrim Geothermal System Understanding .................................................... 61
11. EXPORTING GEOTHERMAL ENERGY TO NOME ..................................................... 64
11.1 Geothermal Power Economics ...................................................................................... 64
11.2 Wind-Diesel-Geothermal Microgrid Modeling ............................................................ 64
11.3 Transmission from Pilgrim Hot Springs to Nome ........................................................ 65
12. LESSONS LEARNED ....................................................................................................... 65
13. CONCLUSIONS ................................................................................................................ 66
14. REFERENCES ................................................................................................................... 68
APPENDICES
APPENDIX A Well Schematics
APPENDIX B Well Temperature Profiles
APPENDIX C Well Locations and Descriptions
APPENDIX D Wellhead Repair Description
APPENDIX E Geophysical Survey Report
APPENDIX F 2012 Mud Logging Records
APPENDIX G Geophysical Well Logs for 2011 and 2012 Drilling
APPENDIX H September 2013 Interference Testing
APPENDIX I February 2014 Interference Testing
APPENDIX J 2012 Drilling Logs
APPENDIX K 2013 Geophysical Logs
APPENDIX L Fugro MT Report
APPENDIX M A Conceptual Model of Pilgrim Hot Springs: Joshua Miller Master Thesis
APPENDIX N Reservoir Simulation Modeling: Arvind Chittambakkam Thesis
APPENDIX O Tectono-thermal History of Pilgrim Hot Springs, Alaska
APPENDIX P Wind-Geothermal-Diesel Microgrid Development: Jeremy VanderMeer
Thesis
APPENDIX Q Fuel Oil Volatility – Complications for Evaluating a Proposed Power
Purchase Agreement for Renewable Energy in Nome, Alaska
APPENDIX R High Voltage Direct Current Transmission Assessment at Pilgrim Hot
Springs
APPENDIX S Wind-Geothermal-Diesel Microgrid Development
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List of Figures
Figure 1. The location of Pilgrim Hot Springs on the Seward Peninsula. ...................................... 2
Figure 2. Index maps showing the topography and regional geology. ........................................... 6
Figure 3. Topographic map of the area surrounding Pilgrim Hot Springs, .................................... 7
Figure 4. Map of all drill holes and well locations ....................................................................... 10
Figure 5. The1982 temperature logs from the original wells ........................................................ 11
Figure 6. Temperature profiles of all holes and wells .................................................................. 12
Figure 7. Map showing the approximate margin of the very shallow thermal aquifer ................. 13
Figure 8. Plan view temperature maps of Pilgrim Hot Springs .................................................... 14
Figure 9. A time series of ASTER visible to near-infrared imagery ............................................ 16
Figure 10. A subset of an ASTER wintertime false color composite image ................................ 16
Figure 11. Landsat 7 satellite images of the Pilgrim Hot Springs ................................................ 17
Figure 12. Low-emissivity thermal blankets ................................................................................ 18
Figure 13. Field calibration and validation data sites for the primary target area ........................ 19
Figure 14. Comparison of a FLIR-derived temperatures profile .................................................. 19
Figure 15. Mosaicked FLIR surface temperature data.................................................................. 20
Figure 16. FLIR (left) and optical data (right) from the fall 2010 survey .................................... 21
Figure 17. Processed airborne images for parts of the study area ................................................ 22
Figure 18. A simplified conceptual model of the Pilgrim geothermal system ............................. 23
Figure 19. A total surface energy budget model for the Pilgrim geothermal system ................... 24
Figure 20. The effect of wind speed on heat flux ......................................................................... 27
Figure 21. Gravity stations are labeled on a topographic map ..................................................... 28
Figure 22. Isostatic residual gravity map ...................................................................................... 29
Figure 23. Magnetic field maps from Glen et al. (2014) .............................................................. 30
Figure 24. Magnetic lineations interpreted from maximum horizontal gradients ........................ 30
Figure 25. Airborne EM resistivity slices ..................................................................................... 31
Figure 26. Magnetotellurics site locations. ................................................................................... 32
Figure 27. Resistivity at Profile D from a 1D MT inversion. ....................................................... 32
Figure 28. Resistivity maps at 25 m and 50 m from the blind 3D MT inversion. ........................ 33
Figure 29. Resistivity maps at 100 m, 150 m, 200 m, and 300 m ................................................ 34
Figure 30. Resistivity maps at 400 m, 500 m, 750 m, and 1000 m .............................................. 35
Figure 31. Areas of leaking, scale, and corrosion are shown on PS-4. ......................................... 37
Figure 32. The PS-4 completed replacement valve installation. .................................................. 37
Figure 33. Installing Geoprobe holes at Pilgrim Hot Springs. ...................................................... 38
Figure 34. Location of Geoprobe holes and their temperatures in Fahrenheit at 60 feet. ............ 39
Figure 35. The temperature logs from all Geoprobe holes ........................................................... 40
Figure 36. The mixing trend between sodium and chloride is shown for all samples .................. 43
Figure 37. Chloride content is shown along with well temperature ............................................. 44
Figure 38. PS-3 downhole pressure during interference testing. .................................................. 45
Figure 39. PS-3 temperature response during 2013 interference testing. ..................................... 46
Figure 40. Surface equipment used for the airlift of PS-13-1 ....................................................... 47
Figure 41. Downhole pressure and temperature record of PS-13-1 .............................................. 49
Figure 42. PS-13-1 downhole pressure and temperature .............................................................. 49
Figure 43. Downhole pressure and temperature at the end of the second airlift .......................... 50
Figure 44. Detailed flowing and static logs from PS-13-1 ........................................................... 51
Figure 45. PS-13-2 pressure and temperature response during PS-13-1 flow testing. ................. 53
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Figure 46. PS-13-3 pressure and temperature response during PS-13-1 flow testing. ................. 53
Figure 47. The historic hot spring pool ......................................................................................... 54
Figure 48. Hot spring pool temperatures during the September 2014 flow testing ...................... 55
Figure 49. Conceptual model from Miller et al. (2013a). ............................................................. 58
Figure 50. Regional conceptual model cartoon from Glen et al. (2014). ..................................... 59
Figure 51. The current conceptual model of Pilgrim Hot Springs ................................................ 63
List of Tables
Table 1. FLIR heat flux estimates. ................................................................................................ 26
Table 2. Permits and approvals ..................................................................................................... 36
Table 3. Pilgrim Hot Springs well chemistry in PPM .................................................................. 42
Table 4. Well productivity data .................................................................................................... 52
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Terms and Acronyms
ACEP Alaska Center for Energy and Power
ASTER Advanced Spaceborne Thermal Emission and Reflection
Radiometer
DOE U.S. Department of Energy
NETL National Energy Technology Lab
EM Electromagnetic
ETM+ Enhanced Thematic Mapper
FLIR Forward looking infrared radiometry
gpm Gallons per minute
IGRF International Geomagnetic Reference Field
Kauweraq The region of the central Seward Peninsula (also spelled Kawerak)
MHG Maximum horizontal gradient
MT Magnetotellurics
MWe Megawatt electric
MWth Megawatt thermal
PGS Pilgrim Geothermal System
PHS Pilgrim Hot Springs
SMU Southern Methodist University
TG Temperature gradient
UAF University of Alaska Fairbanks
Unaatuq Inupiaq word (also spelled Oonuktuak) meaning hot water/ hot
spring. Also refers to the group of Native Alaskan and non-profit
organizations that own Pilgrim Hot Springs.
USGS United States Geological Survey
VNIR Visible and near-infrared
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1. EXECUTIVE SUMMARY
This document is the final report for the Pilgrim Hot Springs (PHS) geothermal exploration
project, funded by the U.S. Department of Energy (DOE), The Alaska Energy Authority, the
City of Nome, Bering Straits Native Corporation, White Mountain Native Corporation, Sitnasuak
Native Corporation, Potelco, Inc., and the Norton Sound Economic Development Corparation.
The first round of funding in 2009 was awarded under Alaska Energy Authority RSA R1108 and
R1215 and DOE award DE-EE0002846. In 2013, DOE award DE-EE0000263 along with match
money from the six other organizations listed above was awarded. This report details the
activities that occurred as part of the first and second rounds of funding for geothermal
exploration at PHS in 2010 and 2013. The project objectives were to test innovative geothermal
exploration techniques for low-to-moderate-temperature geothermal resources and conduct
resource evaluations of PHS.
A variety of methods including geophysical surveys, remote sensing techniques, and heat budget
modeling estimated that the geothermal resource might support electrical power generation of
approximately 2 MWe using a binary power plant. Further flow testing of the deep geothermal
aquifer is needed to verify this estimate.
Eight new wells were drilled around the PHS site to a maximum depth of 1294 feet. Five of these
wells use sealed casing and can be used only to collect temperature logs. The other three wells
have perforated casing and are capable of measuring temperature as well as artesian flow. A
maximum temperature of 91°C (196°F) was measured in two different wells: in the shallow
thermal aquifer at approximately 120 feet in depth and in the deep aquifer at approximately 1100
feet in depth. These wells were drilled in what is believed to be the vicinity of the upwelling
zone, but both wells show a temperature reversal between the shallow and deep thermal aquifers,
suggesting they are not directly over the main area of upwelling. Based on data collected to date,
the main upwelling zone is likely northwest of well PS-13-1 in a swampy area that has been
inaccessible for drilling.
As in past surveys, geothermometry from water samples collected suggests maximum system
temperatures could be as high as 145°C (293°F), based on Na-K-Ca geothermometry. The most
concentrated geothermal fluid with 3500 ppm (parts per million) chloride continues to be
collected from the traditional thermal hot spring located directly south of the church.
Thermochronology data analyzed by University of Alaska Fairbanks (UAF) researchers suggest
that the Pilgrim geothermal system (PGS) is relatively young, and core samples collected from
the drilling indicate that temperatures have likely reached approximately 150°C (302°F) in the
past 1000 years.
In 2014, a power purchase agreement was signed between the City of Nome and Pilgrim
Geothermal LLC, who has sent a letter of intent to the landowners to develop the resource.
Modeling by the UAF power integration program, examined the effect of adding a geothermal
generation source to the existing wind-diesel islanded grid in Nome. Adding 2 MW of
geothermal power to the Nome grid displaces approximately 1 million gallons of diesel fuel per
year (VanderMeer and Mueller-Stoffels, 2014).
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Flow testing of the shallow thermal aquifer reached maximum flow rates of 350 gpm (gallons
per minute), and sustained flow rates of 300 gpm for 7.5 hours. Based on the observed flow rates
and minimum pressure decline, it appears likely that the shallow thermal aquifer could sustain
this flow long term, opening up the potential for on-site direct geothermal heating or electrical
power generation.
2. BACKGROUND – KRUZGAMEPA HOT SPRINGS
Pilgrim Hot Springs, formerly known as Kruzgamepa Hot Springs, is located on Alaska’s
Seward Peninsula about 60 miles north of Nome and 75 miles south of the Arctic Circle (Figure
1). The site has a long, colorful human history, which has included use as a traditional Native
Alaskan gathering place, a farm, a dancehall and roadhouse, a Catholic orphanage and mission,
and most recently as a recreational bathing and hunting site. The lush and tall local vegetation,
dominated by cottonwood trees, contrasts with the otherwise treeless tundra of the western
Seward Peninsula and is visible from miles away. Since the late 1970s, the area has seen two
extensive geothermal exploration efforts that have extended road access to the site from the
Nome-Taylor Highway.
Before outsiders came to the region, the people of Kauweraq (the region of the central Seward
Peninsula) used the area known as Oonuktuak (also spelled Unaatuq), also known as
Kruzgamepa and later as Pilgrim Hot Springs. Traditionally, the hunting camp served as a
Figure 1. The location of Pilgrim Hot Springs on the Seward Peninsula.
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tropical oasis for the Kauweramuit (the people of Kauweraq) (D. Hughes, personal
communication, February 17, 2015). During the winter months, Oonuktuak was an ideal living
area with fresh water, plenty of wood for heat, and bountiful hunting and fishing. After
successful ceremonial caribou hunts, other native groups such as the King Islanders would visit
the area (Ray, 1992).
Pressure from commercial whaling and hunting significantly reduced the marine mammal
population in the region, and local government officials became concerned about the well-being
of the region’s native inhabitants. In 1892, reindeer from northeastern Siberia were first
introduced, after Dr. Sheldon Jackson, the Commissioner of Education in Alaska, received
congressional approval. A reindeer station was established at Teller, about 40 miles west of the
hot springs (Bucki, 2004). Later reindeer fairs were held, the first of which took place in 1915 at
Pilgrim Hot Springs (Van Stone et al., 2000).
Modern development at the hot springs began around the year 1900, during the Nome Gold
Rush, when a family homesteaded 160 acres and worked the land, raising cows, chickens, pigs,
and horses (Bland, 1972). After several years, the land was leased or sold to a series of people
who developed a roadhouse. During the gold rush period, a bathhouse, greenhouse, roadhouse
(hotel), and stables were built on the site. The facilities were frequented by the miners, their
“fancy ladies,” and gamblers who reached the area by dog team. A railroad once passed within 8
miles of the site. In 1908, the roadhouse and saloon-dancehall burned to the ground. By this time,
the gold rush was ebbing and a second roadhouse was constructed to serve travelers (National
Register of Historic Places, 1977). By the late 1910s, mining on the Seward Peninsula had
greatly diminished, and eventually, after another series of transactions, the land was deeded to
the Catholic Church by two brothers with no heirs.
In 1917 and 1918, an influenza epidemic decimated the area’s Native Alaskan adult population.
On April 22, 1918, a Canadian priest and pastor of a Nome church, Father Bellarmine Lafortune,
S.J, moved out to the hot springs to build an orphanage (The Alaskan Shepherd, 2009). Many
buildings were moved from a mission that existed in the village of Mary’s Igloo, several miles
north of the hot springs, to the present-day site. Additional buildings were constructed using
lumber from a nearby mining site as well as the on-site timber (National Register of Historic
Places, 1977). During this time, the site became known as Pilgrim Hot Springs (PHS).
Eventually the orphanage included a machine shop, student dormitories, nun and priest quarters,
a sizable church that now dominates the site, a variety of lesser buildings, a cemetery, and
reportedly an unmarked or lost burial ground where victims of the Spanish influenza outbreak
were interred. Some of the buildings were reportedly heated with the natural springs; others were
heated using wood stoves. Historic photos show huge piles of firewood stacked near the church
and a substantial treeless area around the springs, now heavily wooded. Toward the latter stages
of the orphanage, firewood became scarce in the region (The Alaskan Shepherd, 2009). The
orphanage was largely self-sustaining thanks to the gardens that flourished on the permafrost-
free soil, producing legendary crops of potatoes, cabbages, turnips, and other vegetables. The
population averaged about 100 youth and 20 adults then (National Register of Historic Places,
1977). A field of shoulder-high oats was growing in the thawed area in September 1915 (Waring,
1917). The orphanage closed in 1941; however, caretakers continued to grow produce, and up to
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7 airplane flights a day ferried this produce to Nome (Bland, 1972), as there was no road access
at the time.
During World War II, military forces used the site for rest and recreational purposes. In 1969,
Pilgrim Springs Ltd. signed a 99-year lease on the property with the Catholic Church to develop
the site as a historical resort (Bland, 1972). This plan never materialized, but the land continued
to be farmed by a number of caretakers. In 2010, Unaatuq LLC, a consortium of Alaska Native
and nonprofit entities from the Seward Peninsula, purchased the property and decaying buildings
for $1.9 million from the Fairbanks Catholic Diocese after the Diocese filed for Chapter 11
bankruptcy (Smetzer, 2010). Since acquiring the property, Unaatuq has been investigating
various options for the development and preservation of the site. Throughout the site’s history, it
has continuously been used for bathing and recreational purposes.
2.1 Geothermal Exploration History
The first recorded description and map of the hot springs dates from 1915, after the local area
had already seen significant development (Waring, 1917). Waring apparently reached the site via
light carts pulled by dog teams on the old railroad grade that passed 8 miles east of the hot
springs. Waring described a permafrost-free area 100 yards wide and a half-mile long, and
measured a maximum spring temperature of 156°F. The visible single-point discharge in 1915
was only about 8 gpm, but additional diffuse discharge increased this amount to an estimated 60
gpm. The water was reported clear with a slight hydrogen sulfide odor. Waring collected a
thermal water sample for chemical analysis. This analysis, now a century old, is remarkably
similar to modern analyses of the thermal water (Table 3).
In 1968, the Catholic Church leased the geothermal rights to C. J. Phillips of Nome (Kirkwood,
1979). However, no significant exploratory work occurred under this lease, which ultimately was
revoked. The U.S. Geological Survey (USGS) designated the hot springs as a Known
Geothermal Resource Area in the 1970s.
In the early 1970s, initial evaluation of the geothermal resource commenced. The USGS
revisited some of the thermal springs in central and western Alaska and published a new
chemical analysis of the PHS thermal water (Miller et al., 1975). The quartz and Na-K-4/3Ca
geothermometers from this analysis predicted subsurface hot springs temperatures of 137°C and
120°C. In October 1973, Harding-Lawson Associates ran two resistivity lines and concluded that
a fault crossed the area and down-dropped bedrock from a depth of 100 feet to 600 feet
(Kirkwood, 1979). In 1974, a 2250-foot-long north–south seismic refraction line and surface
magnetic profile were run (Forbes et al., 1975). Forbes et al. measured a maximum temperature
of 80°C in the thermal pool and deployed a portable seismograph for two nights to try to detect
any tremors. They found the area quiet.
The first major geothermal studies at PHS were led by the Geophysical Institute at the University
of Alaska, the Alaska Division of Geological and Geophysical Survey, and the State Division of
Energy and Power Development in 1979, using funding from the Alaska Division of Energy and
Power and the U.S. Department of Energy. During the 45-day field season, a variety of
geological, geochemical, geophysical, hydrological, and shallow drilling studies were performed
at the site (Turner and Forbes, 1980). In the fall of 1979, the first two wells at PHS were drilled
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to a maximum depth of 160 feet and initially flowed, allowing the first analysis of subsurface
thermal water (Kline et al., 1980).
During a 30-day field season in 1980, the central Seward Peninsula was evaluated on a more
regional scale for its geothermal potential (Wescott and Turner, 1981). This helicopter-supported
work included geologic, geophysical, and geochemical studies near PHS. It also incorporated a
remote sensing component (Dean et al., 1982).
In 1982, a 7-mile-long road was at last constructed from the Nome-Taylor Highway to Pilgrim
Hot Springs, allowing reasonable access for a drilling rig and associated equipment capable of
drilling larger-diameter and deeper wells (P. Eagan, personal communication, April 29, 2015).
During summer 1982, four wells were drilled to a maximum depth of 1001 feet (Kunze and
Lofgren, 1983; Lofgren, 1983). These wells were flowed, brief interference tests were
conducted, and chemical analyses were obtained (Economides, 1982; Economides et al., 1982).
This work represented the end of the first major exploration effort at PHS, as the maximum
measured well temperature of 91°C was far too low for electrical power generation with the
technology that existed at the time.
Pilgrim Hot Springs attracted very little geothermal interest between 1983 and the early 2000s,
with the exception of a comprehensive water and gas sampling program conducted in 1993 (Liss
and Motyka, 1994). In the early 2000s, interest in the PGS gradually revived with the National
Renewable Energy Laboratory sponsoring a site visit (Huttrer, 2002) and the Alaska Energy
Authority funding a preliminary development feasibility study (Dilley, 2007). In 2008, the
Nome Region Energy Assessment concluded that geothermal energy was a potentially economic
option for the region (Sheets et al., 2008).
In 2006, the first geothermal power plant in Alaska was installed at Chena Hot Springs, near
Fairbanks. The project was able to generate electricity using 165°F (73°C) fluid, effectively
making it the lowest temperature geothermal power plant in the world and demonstrating that
generating electricity from low temperature geothermal resources was technically and
economically feasible (Holdmann, 2007). Following this success, overall interest in developing
Alaska’s low-to-moderate temperature resources increased, and the Alaska Center for Energy
and Power (ACEP) secured grant funding from the U.S. Department of Energy and the Alaska
Energy Authority to resume exploration of the PGS. This work began in 2010, with repairs to the
existing wellheads so that those wells could be relogged and flow tested. Remote sensing studies
also began at this time (Haselwimmer et al., 2011), followed by numerical modeling of existing
data (Daanen et al., 2012). The USGS also collected additional geophysical data around the hot
springs (Glen et al., 2012). In 2011, two 500-foot temperature gradient holes were drilled to
evaluate the northern part of the thermal anomaly where the thermal upwelling was then
expected to be located.
In 2012, three deep holes were drilled in an attempt to precisely define the location of the
thermal upwelling beneath the shallow thermal anomaly (Miller et al., 2013a; Miller et al.,
2013b; Benoit et al., 2014a). Recent modeling efforts used data from the deep holes drilled in
2012 (Chittambakkam et al., 2013). In 2013, additional funding became available through the
U.S. Department of Energy. ACEP drilled a deep, large-diameter well and two shallower wells
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to locate and produce fluid directly from the deep thermal upwelling (Benoit et al., 2014b).
These holes failed to penetrate or precisely locate the thermal upwelling, but were completed as
possible future production wells for direct-use projects. In September 2014, these three wells
were flow tested and monitored for interference.
3. GEOLOGIC SETTING
3.1 Regional Geologic Setting
The central Seward Peninsula is underlain by a Precambrian metamorphic complex, intruded by
Cretaceous granitic rocks (Amato and Miller, 2004; Till et al., 2011). In the vicinity of Pilgrim
Hot Springs (PHS), Quaternary alluvial fill overlies this basement complex. The metamorphic
and intrusive rocks are well exposed in the Kigluaik Mountains 2.5 miles south of the PGS and
on Mary’s Mountain and Hen and Chickens Mountain 2.5 miles north of the hot springs (Figure
2). Nowhere is the alluvial fill dissected to the point that any meaningful thickness can be viewed
in any detail at the surface.
The dominant regional structural feature near PHS is the east–west trending Kigluaik-
Bendeleben system of normal faults. These normal faults are interpreted as due to regional north-
south extension (Ruppert, 2008), which led Wescott and Turner (1981) to propose that the
central part of the Seward Peninsula is a 250 km long east-west striking rift system. The Kigluaik
section of the fault system uplifts the Kigluaik Mountains in the south relative to the Imuruk
Basin in the north, where the hot springs are located.
Hudson and Plafker (1978) divided the Kigluaik section of the fault system into three segments.
The western and central section’s show clear surface traces and post Wisconsin or Holocene
vertical displacements up to 10 m. The eastern section, which passes about 2.5 miles south of
PHS, has less definable surface traces, being more obscured by glacial deposits (Hudson and
Plafker, 1978). The eastern section is more complex, with two distinct northward steps, giving
Figure 2. Index maps showing the topography and regional geology.The red box in the left
panel shows the area in the geologic map on right. The location of Pilgrim Hot Springs is
shown by the red star. Map after Till et al. (2011). The red box in the right panel outlines the
area of Figure 3.
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the range front an en echelon system of at least three mappable faults. Geomorphic features
suggest that displacement of the western en echelon section is younger than displacement of the
eastern section. The vertical displacement on the Kigluaik fault zone is at least several hundred
meters and probably exceeds 1200 m. While it is tempting to hypothesize that this major
extensional structure somehow plays a role in the geothermal system, no serious arguments for
this have yet been made.
Up to 320 m of Quaternary alluvium ranging from clay to gravel in size and consisting of
alluvial, fluvial, glaciolacustrine, and brackish lagoon sediments has been drilled in the
immediate vicinity of PHS (Miller et al., 2013a, 2013b).
The volcanic rocks closest to the PGS are the Holocene Lost Jim basaltic lava flows (Till et al.,
2011). These flows cover 88 square miles and lie about 30 miles northeast of the PGS. They are
outside of the boundary of Figure 2. This distance from the PGS makes it unlikely that the Lost
Jim lava flows represent a possible direct magmatic heat source for the PGS. The northern horn
of the Seward Peninsula also hosts the world’s largest maar craters, dated at 21,000 years
(Rozell, 2006), but these craters are much farther away. If there is a magmatic heat source for the
PGS, no author has yet tried to make a convincing case for its existence
Figure 3. Topographic map of the area surrounding Pilgrim Hot Springs, indicated by
the red star.
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3.2 Local Geology
The localized surficial geology surrounding the PGS consists of a flat, wide valley covered
mostly by thermokarst lakes, permafrost tundra, and muskeg swamps (Miller et al., 2013b). The
most striking local surface feature is a thaw in the permafrost, covering an area of about one-half
square mile (~0.58 mi2 or 1.5 km2) that allows anomalous vegetation such as cottonwood trees,
alders, grass, and various wildflowers to thrive.
The most extensive published surficial geology description of the PGS suggests that the hot
springs might be located near the western edge of an actively subsiding north-south striking
graben, apparently resulting from north–south-trending faults (Kline et al., 1980). The
publication offers eight brief lines of evidence as support, but unfortunately, contains no maps,
photos, and/or diagrams to back the evidence, nor has any been reported in more recent
publications. Swanson et al. (1980, p.11) suggest that “many of the canyons found on the north
flank of the Kigluaik Mountains are apparently controlled by north–south-trending faults.”
However, the 2011 geologic map of the Seward Peninsula (Till et al., 2011) shows no north–
south-trending faults in the Kigluaik Mountains, casting serious doubt on the earlier suggestion.
In spite of the 2011 map, inferred or buried north–south-trending faults are shown by Miller et al.
(2013a) and are included in discussion by Glen et al. (2014). Thus, at this time, north–south-
trending structures have been proposed by several researchers, but no recent geological work has
focused on the Pilgrim Valley to confirm the existence of these structures, and a more recent
geologic map did not give them any credence.
On a smaller scale, the local geology has been evaluated with several recent drill holes to a
maximum depth of 350 m (Miller et al., 2013a, 2013b). This evaluation primarily focused on the
stratigraphy of the Quaternary alluvium and showed that metamorphic bedrock is present at a
depth of about 320 m. Particle sizes in the alluvium range from clay to gravel, with sand, silt, and
clay predominating. The sand is locally indurated with silica cement near most of the deeper
wells that have been drilled. The most laterally extensive silt and clay unit is located about 164
feet (50 m) above the top of the metamorphic basement.
4. SUBSURFACE TEMPERATURES
Above the top of the metamorphic bedrock at depths of about 1050 feet (320 m) the thermal fluid
flow pattern has become much better defined by the activities described in this report. Some type
of vertical or near-vertical permeable channel allows the thermal fluid to rise to the surface
through a sequence of unconsolidated Quaternary fluvial material. If any elongation or dip
accompanies this channel, it has not yet been recognized. It is possible that the access limitations
for drill-hole locations allow some northwest–southeast elongation, which could be hypothesized
as evidence for a fault. Drilling and temperature logging completed between 1979 and 2014 have
delineated a 2 square mile permafrost-free area and a series of thermal aquifers overlying each
other within this location. All holes and wells that were drilled between 1979 and 2013 are
shown in Figure 4.
The oldest well logs are from September 1982, when flowing and static temperature logs were
obtained from the first six wells using a FENWAL model UUT-51J1 thermistor instrument, with
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an estimated absolute accuracy of about 1°C (Lofgren, 1983) (Figure 5).A few logs from this era
are questionable, especially below a depth of 200 feet in the PS-5 well log, but overall these well
logs give a valuable baseline dataset with which to measure long-term aquifer temperatures.
All existing and new holes and wells, except for PS-2, were repeatedly logged between 2011 and
2014. In general, temperature profiles matched the profiles reported in Woodward-Clyde (1983).
Recent well logs were obtained using two different instruments. Many logs were obtained using
one of three Kuster K-10 memory tools owned by the Alaska Center for Energy and Power. The
Kuster tools are extremely robust, can be used up to 150°C (302°F) and 5000 psi, and can remain
downhole for long periods. This tool measures temperature and pressure with an accuracy of
0.2°C. The Kuster tools were used with a strong reel of aircraft cable that could be operated by
hand by one person. Once retrieved from the hole, the Kuster tool is disassembled and the data
are downloaded onto a computer.
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Figure 4. Map of all drill holes and well locations at Pilgrim Hot Springs.
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The second tool was a light and simple portable wireline temperature measurement tool with
surface readout, custom built for Southern Methodist University (SMU). The tool employs a
platinum thermistor with a reported accuracy of ±.01°C depending on the depth. It is simply
referred to here as the SMU tool. Both types of equipment were compared with one another, and
the readings were virtually identical.
4.1 Updated Temperature Logging
A presentation of all available PHS temperature profiles to a depth of 160 feet (Figure 6) reveals
a confusing picture, but highlights a hot shallow aquifer of varying depths. The thermal anomaly
consists of a shallow aquifer 10 to 20 feet deep (Figure 7) above an aquifer 55 to 90 feet deep,
which is referred to here as the shallow thermal aquifer (Benoit et al., 2014a). The shallow
thermal aquifer is the primary geothermal discharge zone of the geothermal fluid within the PGS.
The shallow thermal aquifer can be subdivided into northern and southern portions based on the
shape of the static temperature profiles measured in the associated holes and wells. While these
northern and southern shallow thermal aquifers have different characteristics, they are likely not
independent aquifers and are certainly hydraulically connected. Where the holes and wells
penetrate the shallow thermal anomaly and show a temperature reversal, the temperature profiles
define the aquifer temperature, depth, and thickness. These data were used to create an aquifer
temperature map showing the flow direction and the division of the northern and southern
shallow aquifers (Figure 8).
Figure 5. The1982 temperature logs from the original wells drilled at Pilgrim Hot
Springs from 1979–81.
0
100
200
300
400
500
600
700
800
900
30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Depth (feet) Temperature (F)
Pilgrim Hot Springs Static Temperature Logs
PS-1
PS-2
PS-3
PS-4
PS-5
MI-1
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Figure 6. Temperature profiles of all holes and wells drilled to date at Pilgrim Hot Springs
are shown. The temperature profiles in the top graph define the shallow and very shallow
thermal aquifers shown in Figure 8 and Figure 7. The bottom graph shows all the deep holes
and wells drilled to date. These profiles show the temperature minimum data that were used
to create Figure 8.
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
20 40 60 80 100 120 140 160 180 200
Depth (feet) Temperature (F)
All Pilgrim Hot Springs Static Temperature Logs
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
40 60 80 100 120 140 160 180 200
Depth (feet) Temperature (F)
Pilgrim Hot Springs Deeper Static Temperature Logs
S1 S9 PS-3 1982 PS-4 1982
PS-5 1982 MINC-1 1982 PS 12-1 2013 PS 12-2 2013
PS 12-3 2013 PS 13-1 Combined PS 13-2 Combined PS 13-3 10-29-13
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The hottest measured temperatures
in the shallow aquifer occur near the
boundary of the northern and
southern thermal aquifers,
indicating that both are supplied
from the same upwelling source and
represent thermal fluid moving
through permeable intervals of
varying thicknesses and depths.
Overall, temperature distribution of
the shallow thermal aquifer appears
to show primitive waters rising in
its center and flowing out laterally
(Figure 8). The weaker thermal
aquifers penetrated by the remote
northeasterly S1 and S9 holes are
most likely a continuation of the
northern aquifer
The deep holes that have been
drilled at PHS show temperature
minimums in between depths of 220
and 400 feet (Figure 6). While only
the 12 deepest holes penetrate the
temperature minimum to a depth
where positive gradients occur, they
allow the creation of plan view map
showing temperature minimum
contours (Figure 8).
The temperature minimums
measured between the shallow and
deep thermal aquifers, and shown in
Figure 6, provide the best dataset to define the location of the upwelling zone in Figure 8. Since
91°C (196°F) fluid has been measured in the deep thermal aquifer at the top of bedrock, and
91°C fluid has been measured in the shallow thermal aquifer, there must be a zone where the
91°C fluid emerges from a fracture of some type in the metamorphic bedrock and travels
between those two aquifers. The two maps in Figure 8 suggest that the thermal fluid is rising
through bedrock in the northwest swampy area and flowing northeast and south through the
shallow thermal aquifer.
The temperature profile from well PS-12-2 shows identical temperatures of 90°C (194°F) at
depths of 126 feet and 1148 feet, indicating that the geothermal fluid loses no heat as it rises
from the top of bedrock to the shallow thermal aquifer. Therefore, we speculate that the hottest
and most saline fluid samples collected from the thermal springs and the shallow thermal aquifer
have probably not been diluted by any shallow groundwater within the unconsolidated
Figure 7. Map showing the approximate margin of the
very shallow thermal aquifer, the temperatures within
this aquifer, and the temperatures of thermal water
measured at the surface. The red boundary closely
approximates a temperature of 80°F (27°C).
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Quaternary fluvial material. This indicates that pressures are higher within the plumbing hosting
the thermal flow than in the surrounding Quaternary material.
5. REMOTE SENSING
The first calculations of heat loss and potential power output of the Pilgrim geothermal system
(PGS) were developed from 1979 data (Harrison and Hawkins, 1980; Osterkamp et al., 1980).
Harrison and Hawkins (1980) indirectly measured the surface discharge downstream from the
main area of PHS at 67 gpm and used a hot water temperature of 81°C to calculate admittedly
crude numbers of 1.5 and 2.2 MW due to thermal water surface discharge. A 10 MW total
vertical heat flow from the thawed area around the springs was also determined. Harrison and
Hawkins (1980) indicate that this total vertical heat flow is probably a serious underestimate, as
it did not include the power removed by groundwater movement. It is now known that 91°C
would be a more accurate original thermal water temperature. Osterkamp et al. (1980), using a
Figure 8. Plan view temperature maps of Pilgrim Hot Springs. The temperature contour map on
the left shows the shallow thermal aquifer at the hot springs, and is based on the shallow
temperature maximum. On the right, temperature minimum contours are shown at the hot
springs. Known temperature contours are shown as solid lines. Hypothetical higher temperature
contours are shown as the closely spaced dashed lines These minimum temperature contours,
based on deep holes and wells, in conjunction with the shallow aquifer temperature profiles,
indicate the direction of thermal water flow and help pinpoint the likely upwelling zone
northwest of the area where past drilling occurred.
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more systemwide approach to estimate the heat loss, analyzed the temperature and salinity
increases in the Pilgrim River after it had passed through the geothermal area. This approach
resulted in minimum total accessible power values of 350 to perhaps 500 MW. However,
Osterkamp et al. admit that these numbers are highly uncertain, and caution that the values
“should not result in unbridled optimism.”
The first remote sensing efforts at PHS occurred in 1980 with radar and infrared surveys (Dean
et al., 1982). The radar study identified numerous lineaments near the PGS that have received
little or no recent attention. The high altitude (60,000 ft) infrared work indicated the presence of
two large and unusually warm areas along the Pilgrim River north of the hot springs, but
provided no quantitative thermal data.
Remote sensing work since 2010 has extended the traditional use of remote sensing for
geothermal exploration by developing methods for acquiring and processing remote sensing
images (Haselwimmer et al., 2011). These methods identified various surface signatures
associated with the geothermal systems and derived first-order quantitative estimates of thermal
fluxes. Permafrost-free areas, snowmelt areas in early spring, anomalous vegetation patterns, and
heated ground and water bodies were identified as areas that warrant further study. The
temperature images derived from remote sensing provided the basis for heat budget modeling.
This helped to focus the field efforts for further investigation and helped to target drilling
activities and develop a conceptual heat flow model.
5.1 Satellite-based Geothermal Anomaly Mapping
Satellite images from Landsat, Advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER), and WorldView-2 (WV-2) were processed and used to identify areas of
persistent high temperature, areas of snowmelt in winter images, and areas of greener vegetation
in springtime images. An iterative approach to the use of satellite data followed by airborne
surveys and traditional ground-based exploration was recommended as a routine part of a
systematic geothermal exploration program.
5.1.1 Analysis of Landsat 7 Data
A search of the Landsat 7 archive for ETM+ images from the PGS region yielded 18 scenes,
which had been acquired between August 1999 and July 2010. Eleven datasets were selected for
further analysis of cloud and snow-free images.
The discrimination of thermal anomalies was undertaken using the image “stacking” approach
(Prakash et al., 2011). This included pre-processing the band 6L thermal data for each dataset
using the three-step procedure described by Chander et al. (2009). Thermal hot spot images for
each year were integrated to identify temporally persistent thermal anomalies most likely to
represent geothermal sources. A thermally anomalous pixel identified in data from three different
years was labeled persistent. The ETM+ data highlight five persistent thermal anomalies located
within the broad region of the PGS. These anomalies were later investigated in detail during the
aerial FLIR survey.
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5.1.2 Analysis of ASTER
Data
The ASTER multispectral
thermal infrared data were
acquired over the PHS site to
identify geothermal
anomalies (Figure 9). The 90
m spatial resolution of the
ASTER thermal bands is
lower than that of Landsat 7;
however, as a multispectral
instrument, ASTER is
routinely used to acquire data
during its nighttime
ascending orbit, minimizing
the effects of solar heating.
The five ASTER thermal
bands also enable the effects
of emissivity to be accounted
for within geothermal
anomaly detection. The ASTER data delineated potential surface indicators of geothermal
activity such as snowmelt anomalies, anomalous river ice melt, and areas of vegetation growth in
the PGS region.
Figure 9. A time series of ASTER visible to near-infrared
imagery (top) and thermal (bottom) data from Pilgrim Hot
Springs, showing snow-free areas and vegetation growth
anomalies associated with geothermally heated ground.
Figure 10. A subset of an ASTER wintertime false color composite image with 15 m spatial
resolution is shown on the left. Prominent snow-free areas are indicated with red arrows. The
left arrow points to the area near the hot springs. The right arrow points to a persistent snow-
free region. A WV-2 color infrared image acquired in May 2010 is shown on the right. Healthy
green vegetation (bright pink/reddish tones) and senescent vegetation (dark brownish red tones)
are clearly visible (left). The processed WV-2 image (right) shows vegetation vigor, the dashed
white line marking the approximate limit of vigorous nontundra vegetation. This map (right) is
a color-coded Normalized Difference Vegetation Index (NDVI) image, where NDVI = (Near-
infrared – Red) / (Near-infrared + Red).
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5.1.3 Analysis of WorldView-2 Data
Analysis of high-resolution VNIR (visible and near-infrared) data was completed using the
commercial WV-2 satellite data. Images from WV-2 are acquired in the visible and near-infrared
region of the electromagnetic spectrum at a spatial resolution of 1.2 m. The presence of the near-
infrared band and high spatial resolution makes the dataset suitable for detailed vegetation
mapping. Data were acquired during May 2010 and defined vegetation growth anomalies
associated with geothermally heated ground (Figure 10). This work was validated with shallow-
temperature survey measurements during the 2011 and 2012 field seasons that outlined the
extent of the shallow and very shallow thermal aquifers (Benoit et al., 2014a).
5.2 Airborne Forward Looking Infrared Surveys
Forward Looking Infrared Radiometer (FLIR) data collected from airborne surveys were used to
calculate the geothermal potential of the PGS using a thermal budget model. Airborne surveys
were conducted in fall 2010 and spring 2011, and data were mosaicked and processed to create
high-resolution optical and thermal images. Thermal data-processing algorithms used by the
volcanology community were adapted to compute heat flux.
Airborne surveys were planned around high- and low-priority survey areas (Figure 11) to
provide flexibility in case of poor weather conditions. The primary survey area covered a region
approximately 27 km2, centered on the main PGS site encompassing the most likely geothermal
anomalies detected from the Landsat 7 ETM+ data (red polygons in Figure 11). The secondary
survey area covered a region approximately 175 km2, including the sites of the other thermal
anomalies detected from Landsat.
Figure 11. Landsat 7 satellite images of the Pilgrim Hot Springs region. The left image
shows the extent of the primary and secondary survey areas; thermal anomalies detected
from Landsat 7 satellite data are indicated by red filled polygons. On the right are the
flight line locations for the aerial survey over the hot springs; cloud and turbulence
restricted data acquisition over the southern half of the secondary survey area.
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The first airborne survey was undertaken from September 9–15, 2010, using the Nome Airport as
the base for flight operations. Favorable weather conditions enabled acquisition of data over the
entire primary survey area and the northern portion of the secondary survey area. Flights over the
southern portion of the secondary area were not possible due to persistent cloud cover and
turbulence around the northern flanks of the Kigluaik Mountains. The FLIR images were
successfully acquired along all the flight lines shown in Figure 11. Optical imagery was acquired
for most of the flight lines; however, technical issues led to some gaps in the imagery in the
northern part of the secondary survey area.
Thermal images were acquired using a FLIR Systems A320 camera that records emitted thermal
infrared radiation in the 7.5 to 13 µm wavelength region. The FLIR has a 320 240 pixel sensor
with a 25 µm sensor pitch and 18 mm lens. Visible images were acquired using a Nikon D700
digital camera with an 85 mm f/1.8 lens fixed at infinity. The FLIR and D700 cameras were
positioned side-by-side in a fixed nadir-looking mount within the aircraft. The FLIR camera was
set to continuously record thermal images at a frame rate of 5 Hz, and Topoflight Navigator
software triggered the shutter of the D700 camera at pre-programmed intervals along the flight
lines. A Crossbow NAV440 GPS/IMU unit recorded the position, roll, pitch, and yaw of the
plane during the survey. A flying
height of about 1000 m yielded an
approximate spatial resolution of 1.4 m
for the thermal imagery and 20 cm for
the optical imagery.
The second airborne survey was flown
in April 2011 and was restricted to a
small area centered on the PGS
property. During this survey, optical
images were acquired at 20 cm
resolution and FLIR data were
acquired at 1.2 m spatial resolution. In-
flight GPS data were recorded and
time synced with the optical and FLIR
image frames.
5.2.1 Field Calibration and
Validation
Concurrent with the fall 2010 airborne
survey, a field party of three undertook
ground calibration and validation work
in support of the airborne FLIR and
optical data collection. Accurate
geographic positions of well-spaced
and notable ground features and thermal blankets (Figure 13) were recorded using portable
Garmin and Trimble GPS receivers. These ground control points enabled georegistration of the
FLIR and optical data. Thermal blankets provided geo-located “cool” targets readily delineated
from the FLIR data (Figure 12).
Figure 12. Low-emissivity thermal blankets (cold
targets) were used as ground control points for
registration of airborne FLIR and optical image data.
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Figure 13. Field calibration and validation data sites for the
primary target area of the Pilgrim Hot Springs survey; the
data are overlain on a high resolution color near-infrared
aerial photograph (AHAP) of the study area.
Wind speed, temperature, and
humidity measurements were
recorded throughout the
collection period to calibrate the
thermal data. Ground and water
temperatures were recorded
using TEGAM thermocouple
sensors. Several ground
temperature profiles were also
recorded near the main hot
spring site to compare against
the retrieved FLIR surface
temperature data, enabling
further calibration as needed
(Figure 13). Two HOBO
temperature-logging systems
provided continuous
measurements of ground
temperatures after the survey
had been completed.
The region around the main hot
springs site and an area about
3.5 km northeast along the
Pilgrim River, where field
observations provided some
evidence for a geothermal anomaly, were the priority regions (Figure 15). Initial processing of
the FLIR data required knowledge of the surface temperatures and humidity values as inputs to
the ThermaCam research software. The average flying height was also integrated to correct for
atmospheric absorption and emission.
A comparison of collected FLIR surface
temperature values with ground-based
temperature profiles shows agreement to
within about 5°C (Figure 14).
For the first airborne survey, the surface
temperature images were manually
georegistered to a high-resolution aerial
photograph of the region from the Alaska
High-Altitude Aerial Photography (AHAP)
program and then mosaicked using ArcGIS
software. There was significant overlap of the
individual FLIR frames, associated with the 5
Hz acquisition rate. A high-quality mosaic
Figure 14. Comparison of a FLIR-derived
temperatures profile (black line) with a field
temperature profile (red line) for a selected
profile line.
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image was obtained using every fifth image. Color in the visible images was adjusted to improve
the contrast, then georeferenced against the AHAP aerial photograph and mosaicked together
with a minimum of overlap.
A semi-automated methodology was used to mosaic the spring 2011 images. The in-flight time
synced GPS information was synchronized with the optical and FLIR sensor systems to
georeference each image. To mosaic the images together, 2d3 software was used. Due to
logistical challenges, the second round of field validation work was delayed until August 2011.
This fieldwork included:
Gathering in situ measurements of hot spring temperatures.
Validating the locations of springs mapped from FLIR data, and acquiring in situ thermal
images of hot springs and pools.
Measuring the outflow rate of hot springs.
Validating the extent of snowmelt anomalies and inferred geothermally heated ground using
1.20 cm shallow temperature probes.
Recording the temperature and conductivity of the Pilgrim River as well as local streams and
locating outflow of saline geothermal waters.
5.2.2 Mapping Using Airborne Images
The main surface geothermal features such as hot springs, wells, pools, and areas of hot ground
can be clearly delineated using the fall 2010 FLIR imagery with its 1.3 m resolution. The surface
water temperatures in the images are as high as 40.5°C (105°F). The FLIR imagery helped
Figure 15. Mosaicked FLIR surface temperature data for the
main Pilgrim Hot Springs site (bottom left) and possible
geothermal area to the northeast (top right).
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researchers to delineate geothermal features that would be difficult to map using visual imagery
alone. Examples of such features include:
Upwelling thermal plumes within pools of water
Temperature gradients within pools and streams indicating the flow paths and mixing of
hot and cool waters
Subtle thermal features that may represent previously unmapped small springs
Areas of hot ground away from the main spring complex.
The optical images acquired during the same period provide useful complementary information,
especially about land cover in the area (Figure 16).
The analysis of the FLIR data from the area northeast of the main PHS site (Figure 15) provided
little evidence for current geothermal activity. The range of surface temperatures is consistent
with the different surface types (vegetation, soil, water ponds), and there are no obvious thermal
anomalies. Nevertheless, the ground cover present in this region is similar to the ground cover
near the hot springs, and it is not found elsewhere in the region.
The April 2011 survey was completed in early spring when the region usually is still covered by
a thick blanket of snow. The survey timing proved useful for mapping areas of snowmelt (Figure
17), a direct indicator of surface heating from the very shallow geothermal aquifer. Snowmelt
areas also correspond to permafrost-free areas and anomalous vegetation growth not regularly
found on the Seward Peninsula. The spring FLIR data were more useful than the fall FLIR data
in identifying the limits of the very shallow thermal aquifer (Figure 17).
Figure 16. FLIR (left) and optical data (right) from the fall 2010 survey over the
main Pilgrim Hot Springs site. The FLIR data effectively delineate surface
features associated with the geothermal system, such as hot springs, pools, and
warm ground.
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Figure 17. Processed airborne images for parts of the study area. Top left: Temperature
map from September 2010 FLIR survey. Top right: Temperature map from April 2011
FLIR survey. The April 2011 image more clearly reveals the limits of the shallow hot
aquifer. Bottom left: Subset of the April 2011 image, indicated with a white box in top
right panel. Bottom right: Optical image of the area corresponding to the image in the
bottom left panel. The optical image reveals underlying soils (brown), as the snow has
melted over these areas due to geothermal heating.
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5.2.3 Heat Budget Modeling
A heat budget model was developed to quantify the radiant and convective heat flux and the flow
rate of surface geothermal waters (Figure 18).
An initial model treated all hot pixels in the same way, regardless of whether they were
associated with heated ground or hot water. Upon further examination, it became clear that hot
ground and hot water gain and lose heat differently, and the thermal flux estimations for these
features need different approaches. An improved heat flux modeling process was developed
(Haselwimmer et al., 2011; Haselwimmer and Prakash, 2011). Both approaches are discussed in
this section.
Initially, heat loss was estimated from the geothermal system by correcting for background
temperature and the natural radiative heat loss of the earth and sun. Using a modified Stefan-
Boltzmann equation (see below) with fixed values for surface emissivity and background
temperature, the radiant flux was calculated for each pixel representing a geothermal feature:
Figure 18. A simplified conceptual model of the Pilgrim geothermal system used for
numerical calculations of thermal flux from the processed FLIR data.
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Μ (Τh4 - Τb4)
where
To delineate the pixels associated with geothermal areas, a mask was created using a temperature
threshold applied to the FLIR image. The background temperature value used in the thermal flux
calculation was the average temperature value from the non-geothermal areas (not including
anthropogenic and other non-geothermal temperature anomalies). The radiant flux value for each
geothermal pixel was summed to calculate the total radiant flux, which amounted to 6.2 105
Watts. This method underestimated the thermal flux associated with the hot waters, so a
sensitivity analysis was not performed (Haselwimmer et al., 2011).
Upon further consideration, we concluded that the convective component was likely the
dominant heat transfer component. Later model development attempted to establish methods for
estimating the convective heat flux from geothermal hot springs and pools. Pixels associated
with hot waters and hot ground are easily separated on the FLIR image mosaics. These water
pixels were isolated for further analysis.
Adapting an approach applied to volcanic crater lakes (e.g., Patrick et al., 2004), an energy
budget model was developed to quantify the convective heat flux along with the flow rate of the
surface geothermal waters at PHS (Figure 19). Complete details about the thermal model used
for the quantitative analysis are presented in Haselwimmer and Prakash (2011) and are briefly
Μ = radiant flux density (W/m2)
ε = emissivity
σ = Stefan-Boltzmann constant
Τh4 = temperature of pixel in Kelvin
Τb4 =temperature of background in Kelvin
Figure 19. A total surface energy budget model for the Pilgrim geothermal system. Refer
to the main text for an explanation of each term.
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described below.
The total heat budget for a water body (in Watts) expressed as
Фtotal = Фgeo + Фppt + Фseep + Фevap + Фsens + Фrad + Фsun + Фsky where
Simplifying this model further, Фppt and Фseep were removed, as these heat fluxes are small.
The temperature of surface non-geothermal waters was used to account for Фsun and Фsky terms.
Pixels associated with geothermal surface waters were isolated, and the geothermal heat flux
density was calculated in W/m2on a pixel-by-pixel basis using the following equation:
qgeo = (qrad + qevap + qsens) - (qradAmb + qevapAmb + qsensAmb)
where
qrad, qevap, qsens and qradAmb, qevapAmb, qsensAmb are radiative, evaporative, and sensible heat fluxes
for each pixel at the ambient temperature of non-geothermal waters.
Further, qrad, the radiative heat flux, was calculated using the Stefan-Boltzmann equation:
qrad = εσT4
where
Also, qevap+sens, the evaporative and sensible heat fluxes, were calculated using the formula
presented by Ryan et al. (1974):
qevap+sens = [λ(Tsv-Tav)1/3+ boW2][es-e2+C(Ts-Ta)]
Фgeo = heat input from geothermal fluids
Фppt = heat input from precipitation
Фseep= heat flux from seepage
Фevap= heat loss from evaporation
Фsens= heat loss via sensible heat transfer
Фrad = heat loss by radiation
Фsun = heat input from solar radiation
Фsky = heat input from atmospheric radiation
σ = 5.67 x 10-8 (Stefan-Boltzmann constant in W/m2 K-4)
ε = water emissivity(0.98)
T = water temperature (°C).
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where
This model was applied to both FLIR datasets. The total heat flux is the sum of heat fluxes for
each pixel, representing the hot water at the surface.
Flow Rates
Assuming a fixed hot springs temperature of 81°C and water at the ambient air temperature, the
flow rate (V) in m3/s was calculated from the total geothermal heat flux (Фgeo) using the
following equation:
V = [Фgeo / (hs-hamb)] / ρw
where
Heat Budget Modeling Results
The computed heat flux/flow rate estimates are generally higher than the in situ observations.
This difference is likely caused by underestimating in situ measurements of the total outflow rate
of the hot springs. These calculated results are quite conservative as they assume a wind speed of
0 m/s, which is unrealistic for the PHS area. The nearest meteorological station about 50 km
northeast of PHS reports an average annual wind speed of 3.18 m/s. Therefore, the true heat flux
is likely to be higher than estimated in the following table:
Table 1. FLIR heat flux estimates.
λ = 2.7 (constant)
bo = 3.2 (constant)
W2 = wind speed at 2 m height (m/s)
es = vapor pressure of water at Ts (mbar)
e2 = vapor pressure of water at 2 m height (mbar)
C = 0.61 (constant)
Ts = water surface temperature (°C)
Ta = air temperature (°C)
Tsv = virtual water surface temperature (°C)
Tav = virtual air temperature (°C)
hs = enthalpy of hot spring water
hamb = enthalpy of water at ambient temperature
ρw = density of water (kg/m3)
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Heat flux estimates are sensitive to wind speeds, as shown in Figure 20. Using a wind speed of
1.5 m/s, the heat flux estimated using FLIR data is 6.96 MW, which corresponds to a flow rate of
0.90 ft3/s, equivalent to 404 gpm.
5.2.4 Discussion
Aerial FLIR surveys have been a useful tool in the
initial stages of geothermal exploration at PHS. For
geothermal exploration using aerial FLIR surveys at
systems similar to PHS, 1 to 2 m spatial resolution
appears to be sufficient to estimate heat flux using
the steps outlined above.
A springtime FLIR survey is likely more useful than
a fall FLIR survey for identifying blind geothermal
resources in high-latitude snow-covered regions
where the hot ground contrasts well with cooler
snow-covered areas.
Combined optical and FLIR airborne surveys offer a
relatively inexpensive addition to geothermal
resource exploration for targeting further field-based
data collection strategies. In logistically challenging areas, such as many areas of Alaska, these
surveys may be the most cost-effective method for the first phase of geothermal exploration.
While airborne surveys were limited to the use of optical and FLIR cameras, the future use of
multispectral or hyperspectral imaging sensors, consisting of several spectral bands in the near-
and shortwave-infrared regions, may better characterize the vegetation signatures and alteration
minerals associated with the geothermal activity.
Heat budget modeling performed in this study estimated that heat flux and flow rates of
geothermal waters can be transferred to the characterization of both low-temperature and high-
temperature geothermal resources.
6. GEOPHYSICAL SURVEYS
In collaboration with the USGS, ACEP conducted geophysical surveys between 2010 and 2013,
including a gravity survey in 2010, a high-resolution airborne magnetic and electromagnetic
(EM) survey in 2011, and a magnetotellurics (MT) survey in 2012. The goal of these surveys
was to provide the regional geophysical framework of the area and help delineate key local and
regional structures controlling hydrothermal fluid flow, and characterize the basin geometry and
depth to bedrock.
Figure 20. The effect of wind speed
on heat flux is estimated from fall
2010 and spring 2011 FLIR data for
the Pilgrim geothermal system area.
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6.1 Gravity Surveys
The PGS gravity data were obtained in
1979 and 1980 (Kienle and Lockhart, 1980;
Lockhart, 1981) and in 2010 by the USGS.
In 1979, 122 stations were occupied along
several traverses made on foot and by
helicopter, boat, and car. In 1980, one 43
km long north–south regional line was run
through PHS (Figure 21). Stations in 1979
were generally along lines, and most
stations were 1 to 3 km apart. In the
immediate vicinity of the thermal springs,
stations were more closely spaced. Station
spacing along the 1980 line was anywhere
from 1 to 5 km apart. These surveys lacked
precise elevation control. Two sets of
closely spaced gravity contours trending
east–northeast and north–northeast and
intersecting a short distance southwest of
the thermal area were hypothesized to result
from a down dropped basement fault block
(Kienle and Lockhart, 1980).
The 295 USGS gravity stations in 2010 were located along five north–south lines and one
northeast–southeast line, with an additional scattering of more regional points. These data have
been merged with the 1979 and 1980 data (Glen et al., 2014). The additional data generally
confirmed the earlier contour pattern, with a pronounced gravity low centered about 4 km
southwest of the thermal springs being the dominant feature in the valley (Figure 22).The second
and more dominant regional gravity feature is along the Kigluaik Mountains range front 2½
miles south of the thermal springs.
Figure 21. Gravity stations are labeled on a
topographic map of the Pilgrim Hot Springs
region. Stations shown by red dots are from the
2010 survey. The earlier stations are shown by
gray dots.
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6.2 Airborne Magnetic and Electromagnetic Surveys
In October 2011, airborne and electromagnetic surveys were flown over the hot springs area. The
USGS was primarily responsible for managing this program and interpreting the data. Survey
details can be found in Appendix E. About 556 km were flown along north–south lines with
east–west tie lines. The mean survey drape of the instrument was 38.2 m. The contractor, Fugro,
performed the basic data processing, and the USGS applied additional processing with derivative
and filtering methods (Glen et al., 2014).
Aeromagnetic data usually provide the most complex and ambiguous geophysical data normally
used in geothermal exploration, and the PHS aeromagnetic results live up to this reputation. Glen
et al. (2014) note magnetic highs in the vicinity of the PGS and further northwest, and a
pronounced magnetic low along the Kigluaik Mountains range front on a reduced-to-pole
Figure 22. Isostatic residual gravity map from Glen et al. (2014) used to map the
structural basin. Light blue (immediately below Pilgrim Hot Springs) correlates to
a basin depth to basement at 320 m (corroborated with drilling contact). Southwest
of the hot springs, the deeper basin, indicated by dark blue, is estimated at about
800 m depth. Shallow areas are represented by red.
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magnetic field map (Figure 23). A residual reduced-to-pole magnetic map shows a more
complicated pattern of shallow-sourced anomalies, with a small magnetic low in the immediate
vicinity of the thermal springs (Figure 23). Two narrow northeast–southwest-trending anomalies
northwest and north–northeast of the hot springs have magnetic signatures in good alignment
with mapped mafic dikes in the Kigluaik Mountains (Glen et al., 2014) and may represent
possible dikes that either have not yet been found on the surface or do not quite reach the
surface.
A magnetic lineation map based on maximum
horizontal gradients shows that the PGS is in a
somewhat unique position, where two trends
terminate as they intersect a third trend. A broad
east–west trend is largely terminated by a
northeast–southwest trend, and a northwest–
southeast trend is terminated by a northeasterly
trend (Figure 24). The same generalized trends
are present on the isostatic gravity map (Figure
22), giving additional credence to these regional
magnetic trends.
The depth extent of the electromagnetic survey is
in the range of 20 to 125 m (Figure 3 in Glen et
al., 2014). The most striking low resistivity in the
survey area is centered on the PGS and is
approximately co-located with the thawed area at
shallow depths near 15 m (Figure 25). A much
larger but less intense shallow resistivity
anomaly is located north and northeast of the
center of the PGS, and overlies the known, but
Figure 23. Magnetic field maps from Glen et al. (2014). Magnetic highs appear as reds and
pinks, gravity lows as blues and purples, in the reduced-to-pole magnetic anomaly map
(left). Magnetic highs appear as reds and pinks, gravity lows as blues and purples, in the
differential reduced-to-pole map (right).
Figure 24. Magnetic lineations interpreted
from maximum horizontal gradients of
pseudogravity. Colored by trend (EW,
red; NW, blue; NE, green). From Glen et
al. (2014).
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largely unexplored, northeastern thermal anomaly. At a slightly greater depth of 35 m, the
northeastern thermal anomaly area is the dominant low-resistivity area, and the core of the
known PGS is no longer particularly low in resistivity (Figure 25). The presumed upflow area is
in this region and will be discussed later in this report.
Two areas west–southwest and southwest of the PGS have interesting low-resistivity values at a
depth of 15 m, and it is speculated that they result from graphitic metamorphic rocks (Glen et al.,
2014). The higher-resistivity rocks reflect metamorphic bedrock and coarser-grained glacial
outwash sediments. Unfortunately, the electromagnetic survey was not capable of penetrating to
depths near the PGS, which would have helped locate the upwelling zone, but the survey does
offer the possibility that other and possibly even larger thermal areas are in the Pilgrim Valley.
6.3 Magnetotellurics Survey
In August 2012, Fugro obtained 59 magnetotellurics (MT) soundings at the PGS. Spacing
between sites varied from about 300 feet to about 1800 feet, with less-dense coverage away from
the center of the known thermal anomaly (Figure 26). The outer ring of MT sites was specifically
chosen to extend beyond the known limits of the shallow thermal anomaly in all directions
except toward the northeast. No sites were occupied north of the Pilgrim River, as the intent was
to locate the upwelling of the PGS, not to study the more inaccessible northeastern thermal
anomaly.
At a depth of 25 m, approximately the known depth of the shallow thermal aquifer, the MT data
show a nearly circular low-resistivity area about 900 m in diameter, with resistivities as low as 2
Ohm-m. The MT is probably responding to the high salinity of the PHS thermal fluid. The area
with resistivity less than about 5 Ohm-m is a good approximation of the 49°C (120°F)
temperature contour defining the shallow thermal aquifer. Above about 5 Ohm-m, the resistivity
contours are tight, rapidly climbing to values above 100 Ohm-m. The high resistivity values
probably reflect the low-salinity permafrost surrounding the thermal anomaly.
Figure 25. Airborne EM resistivity slices shown at 15 m (left) and at 35 m
(right). From Glen et al. (2014).
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The sharp margins of the MT anomaly are also clearly defined in cross-sectional view (Figure
27). The temperature contours at shallow depths generally behave in a sharply bounded fashion,
near the edge of the shallow thermal aquifer (Figure 28). The obvious exception to the sharp
boundaries for both datasets is toward the northeast, where the shallow thermal aquifer has its
greatest known length. The MT anomaly also extends that direction. The MT data show a short
“nose” extending southwest of the PS-5 hole that was not picked up by the temperature data. At a
depth of 50 m, a short distance below the shallow thermal aquifer the resistivity increased
slightly, but the circular anomaly core is still present (Figure 28).
Figure 26. Magnetotellurics site locations.
Figure 27. Resistivity at Profile D from a 1D MT inversion.
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The thermal minimum in the deeper PGS wells occurs near a depth of 100 m. At this depth, the
MT shows the smallest areal extent of less than 3 Ohm-m resistivity of any of the depths (Figure
29). The lowest resistivity values are now centered about 85 m southeast of well PS-12-2. At
depths between 100 and 300 m, which are within the Quaternary alluvium, the area of less than 5
Ohm-m gradually expands and moves toward the northwest (Figure 29). Between depths of 300
and 500 m, in the metamorphic bedrock, the lowest resistivity values shift noticeably about 0.5
km to the southwest; by 500 m, they are centered beneath well PS-5 (Figure 29 and Figure 30).
By a depth of 1000 m, the lowest resistivity values have radically shifted east and northwest of
the shallow thermal anomaly (Figure 30).
Since the MT survey was run to help locate the upwelling zone, the question of whether this
survey was successful must be addressed. While MT clearly succeeded in locating and outlining
the shallow thermal anomaly, there is no clear evidence that MT located the thermal upwelling.
The small volume of low-resistivity values near PS-12-2 at depths of 100 to 200 m within the
alluvium cannot directly represent thermal upwelling, given the temperature profile of PS-12-2.
The large horizontal shifts of low-resistivity areas below 300 m in metamorphic basement rocks
may represent some larger-volume conductor(s) other than hot water. The full Fugro (2012)
report, which discusses this topic in detail, is included as Appendix L.
Figure 28. Resistivity maps at 25 m and 50 m from the blind 3D MT inversion. The red
line represents the 49°C (120°F) temperature contour in the shallow thermal aquifer. The
straight black lines are the MT transects.
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Figure 29. Resistivity maps at 100 m, 150 m, 200 m, and 300 m depths from the blind
3D MT inversion. The red line represents the 49°C (120°F) temperature contour in the
shallow thermal aquifer.
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7. DRILLING ACTIVITIES
The bulk of the money and effort invested in the geothermal exploration project at PHS was used
for drilling activities, with the aim of obtaining accurate subsurface temperature data and
identifying the main upwelling zone. Drilling ranged from very shallow activities carried out
with a simple gasoline-powered backpack drill, to large-diameter drilling that required a large
rotary drill rig and mud circulation systems capable of drilling a 14-inch-diameter well to
bedrock. Additionally, the valves on the wellheads of the wells drilled in 1979 and 1982 were
replaced to cease uncontrolled artesian flows and allow the wells to be logged in a static state.
The deep holes and wells that have been drilled at the site since 1979 are shown on Figure 4.
Figure 30. Resistivity maps at 400 m, 500 m, 750 m, and 1000 m depths from the
blind 3D MT inversion. The red line represents the 49°C (120°F) temperature contour
in the shallow thermal aquifer.
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7.1 Permitting
Before any of the drilling activities described in this report could occur, a variety of permits and
land usage agreements had to be secured. Permits were obtained in several phases as drilling
plans were refined and new data were input into geothermal models of the area. Land use permits
were also obtained so that UAF and its contractors could legally perform activities associated
with geothermal exploration on the landholdings of various entities. The land use agreements,
permits, and waivers that were obtained for this project are summarized in Table 2.
Table 2. Permits and approvals
7.2 Legacy Wellhead Repairs
During 1979 and 1982, six wells penetrating the shallow thermal aquifer were drilled to depths
of 1000 feet. These wells were never plugged and were abandoned. Due to a lack of
maintenance, the wellheads were in extremely poor condition when examined by ACEP in 2009.
The wellheads had to be repaired to control artesian flows and permit new static temperature logs
and water samples.
During an initial site visit in July of 2010, an assessment of each well was made and work plans
were developed. Wellhead repairs occurred September 13–18, 2010. The team completing the
repairs was able to replace the master gate valves on wells PS-1, PS-3, PS-4, and MI-1. Wells
PS-2 and PS-5 were not found to be leaking, and the team was not able to replace the gate valves
because of swampy conditions around the wells, which restricted heavy equipment access. At
each of the four repaired wellheads, the team removed the existing gate valves while pumping
down the water and installed new stainless steel valves. Detailed repair descriptions for each well
are given in Appendix D. Images from the repair of well PS-4 are shown in Figure 31 and Figure
32.
Entity Permit or Approval
Alaska Oil and Gas Conservation Commission Permits to drill
Alaska Department of Environmental
Conservation
Storage/discharge of drilling waste solids,
Waste water discharge approval/ waiver
National Environmental Policy Act Project review
Department of Natural Resources
Temporary water use permit for drilling makeup
water and flow testing
Alaska Department of Fish and Game Project approval,
Waiver of fish habitat permit for flow test
U.S. Bureau of Land Management
Permit for road or trail improvements,
Gravel pit use
U.S .Army Corp of Engineers
Verification that project is in Nationwide Permit 6
accordance
Mary’s Igloo Native Corporation Land use permit
Unaatuq, LLC Exploration license
Bering Straits Native Corporation Exploration license
State Historic Preservation Office Finding of no historic properties effected
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Multiple static and flowing
temperature and pressure logs
were obtained for all wells
except for PS-2, where the
wellhead has sunk into the
soft ground and the master
valve is inoperable. Water
samples were collected from
these wells and from the
natural hot springs for
chemical analysis.
7.3 Shallow Temperature
Survey
At shallow depths, the PGS is
dominated by a strong lateral
flow of geothermal water,
identified three decades ago
when the first six wells were
drilled into the system. The
maximum temperature of this
shallow aquifer is slightly
below boiling, and the depth
to the most hydraulically
conductive part of the aquifer
is less than 100 feet. This
combination of factors
produces very high shallow-
temperature gradients above
the thermal aquifer and sharp
temperature declines below
the aquifer.
The smooth nature of the six early shallow temperature profiles strongly suggests that the aquifer
began transmitting hot water in the relatively recent past and that the lower temperatures beneath
the aquifer are a result of downward conduction of heat from the aquifer—not a flow of cold
water beneath the thermal aquifer. If there were a counterflow of cold water, complexity such as
isothermal segments in the temperature profile separated by short intervals of extremely high
temperature gradients would be expected. This combination of characteristics at PHS allows the
possibility of defining the shallow thermal aquifer with abnormally shallow holes compared with
most other geothermal systems. Characterizing the shallow thermal aquifer allows definition of
the directions of thermal fluid flow within the aquifer and recognition of the hottest part, which
most likely would overlie thermal upwelling beneath the aquifer.
The absence of bedrock and coarse conglomerate in the vicinity of PHS is also an important
factor that allowed consideration of low-cost and unconventional drilling techniques. The flat,
Figure 31. Areas of leaking, scale, and corrosion are shown
on PS-4.
Figure 32. The PS-4 completed replacement valve
installation.
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swampy topography at PHS is an advantage to the extent that it minimizes topographic effects at
shallow depths; however, it also inhibits access to much of the area with machinery.
The first shallow temperature holes at PHS were installed in 1979, when about 70 “pipes” were
hand driven to a maximum depth of 5 to 9.5 m (Harrison and Hawkins, 1979; Osterkamp et al.,
1980). An isothermal map at a depth of 4.5 m was prepared, outlining the central part of the
shallow thermal anomaly with temperatures between 30°C and 80°C (86°F–176°F). Effort was
focused on the heart of the shallow thermal anomaly, and none of the holes was deep enough to
penetrate into or beneath the shallow thermal aquifer.
7.3.1 Backpack Drilling Program
Two additional shallow temperature surveys were attempted in April 2011 using a small
backpack-mounted drill. Thirty-one holes were drilled to depths of 3 m while the area was still
snow-covered and could be accessed by snowmobile. However, a number of challenges arose
including holes collapsing before tubing could be installed and snow depths of 2 m. These
challenges limited the ability to install as many holes as desired to a uniform depth, which
presents difficulty with interpretation. The backpack-drilling effort did not produce results much
better than the effort made in the 1970s.
7.3.2 Geoprobe Drilling Program
Discussion with USGS project partners revealed that they had a self-contained track-mounted
direct-drive Geoprobe unit, touted as capable of driving pipes to depths of less than 30 m. The
unit is highly mobile, and at a weight of 5000 pounds, was light enough to travel on trails in the
PHS area with minimal impact. The Geoprobe unit drives small-diameter sealed pipes into the
ground without the need for circulatory fluids (Figure 33), eliminating the mud system that
traditional drill rigs require.
During the summer of 2011, sixteen Geoprobe holes with an outer pipe diameter of 2.25 inches
(5.7 cm) and a hole diameter of 1.5 inches (3.81 cm) were installed to a maximum depth of 109
Figure 33. Installing Geoprobe holes at Pilgrim Hot Springs.
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feet. Locations and temperatures are shown in Figure 34. Prior to the end of the 2011 season, all
holes were decommissioned by pulling the pipes and sealing the holes with grout as the pipes
were removed.
Figure 34. Location of Geoprobe holes and their temperatures in Fahrenheit at 60 feet.
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Nearly all of the Geoprobe holes from 2011 failed to reach beyond 80 feet deep; none penetrated
into or beneath the shallow thermal aquifer. In 2012, smaller pipe (1.25 in. outer diameter; 0.5 in.
inner diameter) was used in 54 holes, enabling deeper penetration (Figure 34). The deepest hole
reached 154 feet. The majority of these holes still have positive temperature gradients, but some
have encountered isothermal conditions indicative of having penetrated the shallow thermal
aquifer, documenting its maximum temperature (Figure 35). Phase 2 drilling produced known
depths of the aquifer, so it was possible to extrapolate some of the Geoprobe hole temperature
profiles and better define the flow pattern within the shallow thermal aquifer. All Geoprobe
locations and depths are shown in Appendix C.
7.4 Deep Drilling
Deep drilling at PHS occurred over three different field seasons: 2011, 2012, and 2013. Holes
and wells drilled more than 500 feet in total depth required permits from the Alaska Oil and Gas
Conservation Commission, while those shallower than 500 feet did not. During 2012, a blowout
preventer (BOP) was required when drilling below 1000 feet. In 2013, a waiver was obtained,
and a BOP was not required. Drilling in 2011 and 2012 was accomplished with USGS Alaska
Rural Energy Project equipment and personnel. This drilling was done with an Atlas Copco CS-
Figure 35. The temperature logs from all Geoprobe holes show a wide variety of
temperatures and profile shapes. A shallow thermal aquifer of varying depths and
characteristics is clearly visible.
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
20 40 60 80 100 120 140 160 180 200
Depth (feet) Temperature (F)
Pilgrim Hot Springs Geoprobe Temperature
Logs
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1000-P6L drill rig, while in 2013, drilling was done by MW Drilling using their Schramm Model
T555 Rotadrill rig based out of Anchorage, Alaska. Well schematics and detailed descriptions
for each well are found in Appendix A.
In June 2011, prior to drilling activities, researchers from ACEP and the USGS conducted an
aerial inspection of PHS via helicopter to locate suitable temperature gradient (TG) hole drilling
locations. Nine possible drill sites were identified. The initial drilling targets were northeast of
the historic hot springs, located on land owned by the Mary’s Igloo Native Corporation. This
decision was based on data from the 1982 drilling effort, especially the cool temperatures and
low bottom-hole gradient measured in well PS-5 (Figure 5). Drilled in 1982, PS-5 was the
deepest well that had been drilled during that effort; it also recorded the coolest temperatures.
This information clearly showed that the upwelling zone could not be located south of the
existing well field. The upwelling zone appeared to be located northeast of the existing wells,
with evidence for this supported by the appearance of a thawed zone in the northeast area.
In 2011, drilling was sited as far north as logistically possible, where the USGS drill rig could
access the area using existing primitive roads and trails. Drilling took place just southwest of the
Pilgrim River and resulted in TG holes S-1 and S-9 (Figure 4). The temperatures measured in
these holes were significantly cooler than the temperatures measured in the existing wells,
suggesting that these two holes were too far to the northeast and that the upwelling zone must be
closer to the historic hot springs.
In 2012, three TG slim holes were drilled on the PHS property owned by Unaatuq, LLC. Drilling
logs for these wells are shown in Appendix J. The 2012 drilling activities moved farther to the
south, with the first hole (PS-12-1) located slightly north of the historic orphanage buildings and
the second and third holes (PS-12-2 and PS-12-3) drilled near the existing well field. The
equilibrated temperature profiles (shown in Appendix B) collected from these three wells show
temperature reversals beneath the shallow thermal aquifer, indicating that they are not directly
over the upwelling zone.
The holes drilled in 2011 and 2012 used sealed casing cemented in place. The holes were only
permitted as TG holes and were not intended to have the ability to access fluids in the
geothermal aquifer. Once drilling was completed, the casing was filled with water so that a
temperature probe could be lowered into the hole to record accurate static aquifer temperature
profiles. Wells drilled in 2012 were at first assigned names by the Alaska Oil and Gas
Conservation Commission: TG-1, PS-12-3, and PS-12-9. In order to be consistent with the
existing nomenclature, the names of these wells were changed so that TG-1 became PS-12-1, PS-
12-3 became PS-12-2, and PS-12-9 became PS-12-3.
In 2013, an attempt was made to drill a large-diameter well into the predicted upwelling zone
and test fluid production from the aquifer above the bedrock. The drilling methods used were
similar to those used in 2011 and 2012, but makeup water was pumped from the slough on the
property in accordance with state and federal regulations. The first drill site was chosen based on
data from the wells drilled in 2012, which suggested that those wells surrounded the upwelling.
When the first well drilled in 2013—PS-13-1—encountered the usual large temperature reversal
and showed lower temperatures than hoped, it was completed in the shallow aquifer. Two more
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small-diameter wells were drilled in 2013 to 400 feet. All wells drilled in 2013 showed
temperature reversals, indicating that they were not directly over the upwelling. All three holes
drilled in 2013 used perforated casing or well screen and have artesian flows. Details about each
deep TG hole and well are described in Appendix A.
8. WATER CHEMISTRY
The geochemistry of the thermal fluid at PHS is one of the primary reasons why so much effort
over so many years has been put into exploring this geothermal system. In addition to its
relatively hot surface temperature, thermal fluid at PHS has the highest predicted quartz
geothermometer temperature (137°C) and one of the highest Na-K-Ca geothermometer
temperatures (146°C) of the thermal springs on the mainland of Alaska (Miller et al., 1975).
Chemical analyses of PHS thermal waters now cover a century (Waring, 1917; Miller et al.,
1975; Liss and Motyka, 1994; Benoit et al., 2014b), and an extensive water chemistry database
has been assembled (Table 3). The thermal water at PHS is relatively high in sodium and
chloride, but stable isotope analyses of thermal and cold waters at this location show that the
thermal water is derived from local meteoric runoff and not from seawater (Miller et al., 1975;
Liss and Motyka, 1994). Only three noncondensible gas samples from PHS thermal waters have
been analyzed, and these contain mostly methane and nitrogen and are relatively high in
hydrogen (Liss and Motyka, 1994). Gas geothermometry results indicate subsurface
temperatures from 113°C to 230°C (235°F–446°F). The surface flowing temperatures and brine
chemistry of some of the PHS wells have changed with time (Liss and Motyka, 1994), but these
changes have since been shown to result from changes in fluid entry points in those wells (Benoit
et al., 2014b).
Table 3. Pilgrim Hot Springs well chemistry in PPM
Sample Date T°C pH Na K Ca Mg Li B SiO2 HCO3 CO3 SO4 CL F
Spring 1915 70 1590 61 545 7.4 87 21 25 3450
Spring 1972 82 6.75 1450 61 530 1.4 4.0 2.4 100 30.1 24 3346 4.7
Spring 1982 55 6.8 1660 59 542 1.0 4.5 2.2 91 36 15 3360 4.3
Spring 1993 42 6.5 1580 65 569 1.5 4.0 2.7 86 19 18 3530 4.7
Spring 1993 55 6.8 1660 59 542 1.0 4.5 2.2 91 36 15 3360 4.3
Spring 2012 6.65 1480 62.8 508 0.38 3.6 2.0 86 14 22 3350 4.6
Spring 2014 73 6.63 1400 58 460 1.00 3.4 2.1 80 15 3500
PS-1 1979 90.5 6.4 1828 75 518 0.9 3.9 2.5 95 16 16 3590 4.8
PS-1 1982 92 7.5 1720 60 511 0.9 4.7 2.3 94 30 19 3420 4.4
PS-1 1993 82 7.1 1560 65 545 0.6 4.2 2.4 90 20 7 3460 5.3
PS-1 2010 79 7.1 1530 61.6 519 1.21 3.5 2.2 83 27.8 14.3 3460 4.5
PS-2 1979 90 6.4 1820 75 516 0.9 3.9 2.3 101 19 15 3540 4.8
PS-2 1982 96 7.3 1510 57 516 0.9 4.7 2.3 92 26 19 3420 4.5
PS-3 1982 75 8.0 592 25 260 0.4 2.0 1.0 60 36 15 1430 1.3
PS-3 1993 65 6.8 1100 43 441 0.6 3.2 1.5 67 27 6 2450 2.9
PS-3 2010 67 7.0 1140 40.9 412 0.85 2.8 1.7 71 23.7 10.8 2650 3.0
PS-4 1982 48 8.6 115 4.8 23 0 0.3 0.5 35 80 11 284 0.5
PS-4 1993 45 8.6 146 7.8 98 0.2 0.2 0.2 27 48 1 386 0.3
PS-4 2010 44 8.52 152 5.9 73 0.14 0.5 28 34 9.4 353 0.4
PS-4 2013 44.6 8.47 128 5.5 45 0 0.4 0.2 29 39.9 1.5 9.3 260 0.6
PS-5 1993 32 9.6 36 1.1 2 0.2 0.1 0.6 21 81 5 6 0.5
PS-5 2010 30 9.6 36 1.09 1 0 0.1 20 49.6 5.4 2 0.5
MI-1 1982 22 9.7 16 0.5 5 0 0.1 21 37 9 5 0.2
MI-1 1993 31 8.3 29 1.5 23 0.6 0.2 0.1 20 32 10 66 0.2
MI-1 2010 29 7.8 130 4.4 93 0 0.5 21 25.8 9.5 337 0.2
PS 12-3 2012 65.5 7.52 731 29.9 281 0.78 1.8 1.0 51 30.6 8.2 1640 1.9
PS 13-1 (open
to 1036 ft)
2013 70.5 7.51 537 26.1 236 0.4 1.4 0.8 54 25.1 9.3 1300 1.4
PS13-1 2013 77 7.27 1090 50.9 370 0.7 2.6 1.5 79 22.8 12.4 2500 3.3
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Sample Date T°C pH Na K Ca Mg Li B SiO2 HCO3 CO3 SO4 CL F
(shallow
Completion)
PS 13-1 300
gpm 2014 79 7.26 1000 35.0 250 2.0 1.5 59 18 2500
PS 13-1 60 gpm 2014 77 7.05 950 37.0 250 2.1 1.4 67 15 2300
PS 13-2 2013 71 8.95 124 25 49 0 0.3 0.2 62 39.4 11.1 5.8 265 0.5
PS 13-2 55 gpm 2014 69 7.52 53 3.1 9 0.2 0.1 54 62 5.5 65
PS 13-3 2013 79 7.27 1070 46.3 373 0.7 2.5 1.4 74 22.1 12.3 2424 3.0
PS 13-3 60 gpm 2014 78 6.97 920 37.0 280 2.2 1.3 66 16 2200
There is an obvious mixing trend between dilute cold groundwater, and primitive geothermal
fluid, exemplified by sodium and chloride contents (Figure 36) and temperature (Figure 37) (Liss
and Motyka, 1994). The same relationship is shown in cross plots involving all other chemical
species except sulfate, which has more scatter. Flowing temperature profiles show little or no
mixing of different fluids within the wellbores (Benoit et al., 2014b) and thin discrete aquifers
with discrete chemistries that are supplying the PHS wells.
The mixing trend shown in Figure 36 does not fall along the line of charge balance where
sodium ions equal the chloride ions. The thermal fluid at PHS is deficient in sodium, and this
deficiency is balanced by an abundance of calcium, causing the apparent mixing to diverge from
the Na-Cl line. The calcium content of the primitive geothermal fluid is greater than 525 ppm,
and exceptionally high when compared with most other low-salinity geothermal waters
throughout the world.
A major disappointment of recent exploration at PHS has been the inability to find the more
optimistic temperatures predicted by geothermometry. The exceptionally high gas
geothermometry values have always been viewed as questionable (Liss and Motyka, 1994), but
the low magnesium content and the neutral chloride nature of the thermal fluid along with the
Figure 36. The mixing trend between sodium and chloride is shown for all samples
collected from the Pilgrim Hot Springs site.
0
500
1000
1500
2000
2500
3000
3500
4000
0 500 1000 1500 2000Chloride ppm Sodium ppm
Pilgrim Springs Chemistry
Hot Springs
PS-1
PS-2
PS-3
PS-4
PS-5
MI-1
Lake
NaCl equivalent line
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quartz and the Na-K-1/3Ca geothermometry appeared to credibly predict temperatures of 130 to
145°C (266°F–293°F). To date, all drilling to depths as great as 1294 feet has resulted in a
measured maximum temperature of only 91°C (196°F). To compound the frustration of this
finding, temperature profiles in the deeper wells cannot be extrapolated to significantly greater
depths to predict reliably where these higher temperatures may be present. Of course, it is always
possible that higher temperatures are located at a much greater depth or lateral separation.
However, other geothermometers might be more appropriate for PHS. The chalcedony
geothermometer predicts subsurface temperatures of 99°C to 111°C (210°F–232°F), and the Na-
K-4/3Ca geothermometer gives values near 120°C (248°F). The 120°C value is still 29°C above
the maximum measured temperature and begs the question of whether the geothermometer is
valid for the PGS brine chemistry. The 525 ppm of calcium in the PGS water is an obvious
suspect in raising the question of whether thermal waters with exceptionally high calcium
content provide accurate geothermometry calculations.
9. FLOW AND INTERFERENCE TESTING
The first flow testing and interference testing of the PGS were performed in 1982, when well PS-
1 was flowed at 30 to 35 gpm and pressures were recorded in well PS-2. Type-curve matching of
the drawdown gave an estimated permeability of 4.5 darcys (Economides et al., 1982). In 1982,
the productivity of the wells ranged from 2.5 to 19 gpm/ft, and the transmissivity of the wells
ranged from 300 to 40,000 gpd/ft (Kunze and Lofgren, 1982).
Figure 37. Chloride content is shown along with well temperature. The PS-13-2
chloride content appears to be low, given its temperature.
0
10
20
30
40
50
60
70
80
90
100
0 1000 2000 3000 4000Sampling Temperature C Chloride ppm
Pilgrim Springs Sampling Temperature versus Chloride Content
Hot Springs
PS-1
PS-2
PS-3
PS-4
PS-5
MI-1
13-1
13-2 ?
PS 13-3
PS 12-3
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9.1 Interference Testing of Wells PS-3, PS-4, and MI-1
Three interference tests using downhole temperature and pressure monitoring were performed in
September 2013 (Benoit, 2013). The first test involved “static” pressure and temperature
monitoring of well PS-3, with wells MI-1 and PS-4 being flowed with different start and stop
times over a period of two and a quarter days. The second test involved flowing well PS-4 for 3
hours and monitoring wells PS-1 and PS-5. The third test was a mirror image of the first test,
with well PS-3 being flowed for 3.5 hours and downhole pressure and temperature monitoring in
wells PS-4 and MI-1.
The interference tests conducted on September 7, 8, 9, 11, and 22 generally confirmed the
observations made by Woodward-Clyde during their flow tests in 1982. Examples of the
temperature and pressure responses during these tests are shown as Figure 38 and Figure 39.
Wells PS-1 and PS-2, completed in the shallow thermal aquifer, do not quickly or obviously
communicate with the deeper and cooler aquifers exposed in wells PS-3, 4, 5 and MI-1. More
precise tools available in 2013 have shown that wells MI-1, PS-3, and PS-4 have a rapid but
barely detectable pressure communication of 0.1 to 0.25 psi. This communication occurs at flow
rates of 50 to 100 gpm from individual wells.
This small pressure communication creates a much stronger and surprising temperature change
in the static well PS-3 when wells MI-1 and PS-4 are flowed. The speed with which this
temperature communication occurs indicates that the small changes in pressure create flow rate
changes that quickly change the water flow past the tool in the “static” PS-3 well. More likely,
the temperature changes are related to flow rates and mixing than to a single fluid entry changing
its temperature. No obvious temperature changes appear in well PS-4 when PS-3 is flowed. Well
MI-1 showed some small temperature changes when PS-3 was flowed, but these changes are not
Figure 38. PS-3 downhole pressure during interference testing.
84
84.5
85
85.5
86
86.5
0 5 10 15 20 25 30 35 40 45 50 55Pressure at 59.35 Meters Below Flange (psig) Time (hours)
PS-3 Downhole Pressure Record
Sept. 7-9, 2013
Downhole
Pressure
Open MI-1
Reinstall
pressure tool
Shutin MI-1
Open PS-4
Shutin PS-4
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as clearly related to starting and stopping PS-3 flow. Wells PS-3, PS-4, and MI-1 have relatively
similar depth permeable intervals, which is a first-cut explanation for their measurable short-term
communication. Some background temperature and pressure trends in the PHS wells are not
understood and will require additional and/or longer-term monitoring to understand. The full
flow-testing report for September 2013 is shown in Appendix H.
9.2 Interference Testing of PS-3, PS-13-1, and PS-13-3
Interference testing and flow testing of the 2013 wells were conducted twice about 6 months
apart. The first testing occurred in February 2014 during a winter trip to the hot springs. The
purpose of this trip was primarily for collecting equilibrated temperature logs of the 2013 wells,
and time available for flow testing was limited. The temperature and pressure were monitored in
wells PS-3, PS-13-1, and PS-13-3, while well PS-13-1 and later well PS-13-3 were allowed to
flow at natural artesian rates of 50 to 70 gpm (Appendix I). Flows were visually estimated, as no
flow metering was available. Well PS-13-3 was allowed to flow for just under 5 hours, and
immediately after the flow was cut off, well PS-13-1 was opened and allowed to flow overnight
for 12 hours. At artesian flow rates, the recorded pressure and temperature effects between the
wells were extremely minimal, on the order of 0.2 psi and 0.02°C. In each well, productivity was
approximately 20 gal/psi. Productivity will be discussed in further detail in the next section.
9.3 Flow Testing of PS-13-1
To date, the most significant flow test at the PGS was conducted between September 15 and 17,
2014, by airlifting well PS-13-1. The airlift was accomplished using thin-wall 1-inch-diameter
aluminum tubing with a dispersion head on the bottom and an Atlas Copco trailer-mounted air
compressor rated at 100 psi and 185 cfm. This hardware was supplied by Howard Trott of
Potelco and rented locally in Nome. A 6-inch Krohne magnetic flow meter (magmeter), supplied
by ACEP, was used to measure the flow rates. The surface equipment is shown in Figure 40. The
Figure 39. PS-3 temperature response during 2013 interference testing.
75
75.5
76
76.5
77
77.5
78
78.5
79
0 5 10 15 20 25 30 35 40 45 50 55Temperature C Time (hours)
PS-3 Downhole Temperature Record
Sept. 7-9, 2013
Downhole
Temperature
Open MI-1
Reinstall
pressure tool
Shutin MI-1
Open PS-4
Shutin PS-4
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5-inch-diameter dispersion head was backed up with 1/8 inch aircraft cable to prevent accidental
loss of the downhole equipment in the well.
The air-water mixture flowed with considerable turbulence into the first tank shown in Figure 40.
As the water flowed into the second tank, no turbulence occurred, and the tank provided
adequate head to push the water through the magmeter and out a 240-foot-long 6-inch PVC
pipeline to flow through a hot springs pond, where the water cooled.
The first airlift only lasted about an hour, as the flow was limited by a constriction in the flow
line downstream of the second tank. Expansion of the flow line caused a short flexible hose to
partially collapse, reducing the flow rate out of the second tank. This first test was more a test of
the equipment than a test of the
resource. The aluminum tubing was
run to a depth of 12.2 m below the
top of the standpipe (8.8 m below
ground level). The average airlift
flow rate during the first test was 172
gpm, and the magmeter readings
were confirmed by measuring that it
took 18 seconds to fill a 55-gallon
drum from the discharge of the
pipeline into the flow through a hot
springs pond. Pumping at a higher air
rate increased the flow rate to 177
gpm, but resulted in the water
overflowing the top of the wellhead
standpipe.
While the well was being airlifted
and the wellhead appeared to be
stable, a Kuster tool was run to a
depth of 30 m below the top of the
master gate, with the heavier aircraft
cable used as a backup in case the
small 1/16-inch-diameter cable
normally used on the reel was cut.
The Kuster tool hung in the well just
over a half hour before the air was
cut off. Once the air was cut off, the
well resumed its natural artesian flow
of 55 gpm, and the Kuster tool
remained hanging in the well
overnight to record pressure buildup.
There was no wing valve on the flow
line to allow the well to be shut in
Figure 40. Surface equipment used for the airlift of
PS-13-1. The magmeter is in the silver spool between
the black and white parts of the flow line. The black
large-diameter hose serving as a standpipe on top of
the wellhead was needed to prevent water from
overflowing the top of the wellhead, which could not
be sealed. The clamp holding the aluminum tubing is
visible on top of the standpipe. The blue hoses are the
air lines coming from the air compressor.
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with the aluminum tubing and Kuster tool hanging inside it.
On the morning of September 16, additional flow line parts were obtained in Nome, and the line
was modified to remove the constriction. The aluminum tubing in the well was deepened from
12.2 m to 21.9 m below the top of the standpipe on the wellhead (18.6 m below ground level).
This depth was about the maximum practical for one person on a large A-frame ladder to raise
and lower the downhole equipment; it was also the maximum depth at which the on-hand larger-
diameter aircraft cable could be used to hold and protect the Kuster tool.
In the second test, there was adequate confidence to run the Kuster tool into the well under
artesian flow conditions before starting the airlift. The air volume was quickly increased in three
steps to find the maximum airlift rate that would not flow water out the top of the wellhead. This
flow rate was about 300 gpm. The highest flow rate reported briefly by the magmeter was about
350 gpm. The 300 gpm airlifted flow rate was held for about 7.5 hours, until the air compressor
was almost out of diesel fuel at 01:00 hours on September 17. After the compressor was shut off,
the well continued artesian flow until after the Kuster tool was retrieved late in the morning on
September 17. Also on that morning, the downhole hardware was pulled out of the well.
Airlifting increased the scatter in the pressure and temperature data as compared with the
unassisted artesian flow (Figure 41 and Figure 42). During the first airlift, it is unclear if there
was any decline trend in the downhole pressure. The first 15 minutes of downhole data indicate a
decline, but perhaps this was simply the tool equilibrating to the downhole conditions (Figure
42). During the second 15 minutes, no decline is evident. At 19:00, the amount of air being
pumped was increased for 2 minutes to assess the plumbing system at higher flow rates and was
then shut off (Figure 42). The amount flowing through the meter increased by only about 5 gpm
to 177 gpm, but water occasionally geysered at the top of the wellhead. A constriction in the soft
6-inch hose between the two tanks limited the flow through the meter. The downhole flowing
temperatures were measured below the air injection depth and, therefore, were not cooled by the
air injection, as the surface-measured temperatures were. The maximum downhole temperature
measured during the first airlift was 78.28°C (Figure 42).
Immediately upon shutting off the air, the temperature took a 0.2°C decline and then quickly
climbed for the next 13 minutes to its maximum value of 78.8°C, then quickly cooled. The
temperature was down to 77°C when the tool was removed the following morning and showed a
range of 1.7°C during this logging. During the airlift, the temperature increased slightly. After
airlifting ceased, the bulk of the temperature change occurred, first with a short 0.2°C decrease,
probably related to the short increased volume airlift, and then with a 0.8°C increase followed by
a long decline until the temperature was about 1°C lower than during the airlifting. During this
decline, the well was flowing under natural artesian conditions. This variation of temperatures
with flow rates demonstrates that there is more than one feed zone for this well, with differing
temperatures. Higher temperatures coincide with higher flow rates. A similar response was seen
upon stopping the second airlift (Figure 43); however, this response lacked the sharp initial drop
in temperature as seen at the end of the first airlift (Figure 42).
The maximum temperature recorded after stopping the second airlift was 79.8°C, or 1.0°C hotter
than seen after the first airlift stopped (Figure 41). After the second airlift was finished, the
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artesian flow temperature declined to 76.9°C, about 0.25°C cooler than that seen after the end of
the first airlift.
Figure 42. PS-13-1 downhole pressure and temperature record just before and after
stopping the first airlift at 19:02 hours on September 15, 2014.
77
77.2
77.4
77.6
77.8
78
78.2
78.4
78.6
78.8
79
37
38
39
40
41
42
43
44
9/15/2014 18:009/15/2014 18:159/15/2014 18:309/15/2014 18:459/15/2014 19:009/15/2014 19:159/15/2014 19:309/15/2014 19:459/15/2014 20:00Temperature C Pressure (psi) Date and Time
PS-13-1 Monitoring at 30 m During and After First Airlift
Pressure
Temperature
Increase air
injection rate
Stop First Airlift
Figure 41. Downhole pressure and temperature record of PS-13-1 during the two airlifts.
76
76.5
77
77.5
78
78.5
79
79.5
80
36
38
40
42
44
46
48
50
9/15/2014 18:009/16/2014 0:009/16/2014 6:009/16/2014 12:009/16/2014 18:009/17/2014 0:009/17/2014 6:009/17/2014 12:00Temperature C Pressure (psi) Date and Time
PS 13-1 Monitoring at +30 m During Airlifts
September 15-17, 2014
Pressure
Temperature
stop airlift and
start 300 gpm airlift
stop 172 gpm airlift
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This temperature variability points to a fairly complex interplay between two or more feed zones
with differing temperatures. This idea led to a detailed flowing log run on the morning of
September 18, before the well was shut in and the artesian flow was stopped. This artesian
flowing log and a static log run on September 7, 2014, show some of the details of the fluid entry
points (Figure 44).
The flowing SMU log shows multiple sharp reversals in temperature gradient between depths of
56 and 67 m, which define all the possible fluid entry points. The top of the screen in the wells is
at 57.3 m, which is in good agreement with the flowing temperature log. Due to minimal
divergence between the flowing and static logs between depths of 65 and 67 m, any fluid entry
point in that interval is suspect, as the temperature readings were not stable in that and shallower
intervals. The deepest significant fluid entry is at a depth near 65 m, and the shallowest major
entry as defined by temperature is near 60 m. All of the defined fluid-entry temperatures are
between 77.02°C and 77.18°C on the flowing log. However, the static temperatures in this
interval range from 77.4°C to 77.7°C. During airlifting, temperatures as high as 78.25°C to
79.3°C were measured, which had to have come from shallower depths in the well, perhaps as
shallow as 35 or 40 m. This fluid would then have had to flow down the outside of the
uncemented 14-inch casing and enter the screened interval between 57.3 and 72.5 m (see
Appendix A for well schematic). The maximum temperature measured during the airlifting
operations was the 79.8°C spike shortly after ceasing the airlift. This temperature is only 0.18°C
hotter than the maximum measured tempeature of 79.62°C during the static log prior to flowing
the well. Thus, we now have a good idea as to the origin of the fluid producing the temperature
spike.
Figure 43. Downhole pressure and temperature at the end of the second airlift at
01:00 hours on September 17, 2014.
76.5
77
77.5
78
78.5
79
79.5
80
36
38
40
42
44
46
48
50
9/17/2014 0:009/17/2014 0:309/17/2014 1:009/17/2014 1:309/17/2014 2:00Temperature C Pressure (psi) Date and Time
PS-13-1 Monitoring at +31 m Depth at End of Second Airlift
Pressure
Temperature
stop air lift and
resumeartesian flow
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It was decided that during the airlift the internal wellbore conditions would probably be too
severe for the small SMU tool and its delicate electrical cable. The primary use of the Kuster tool
was for pressure monitoring, so it was not moved during the airlifting. However, during any
future airlift, a traversing Kuster survey should be run.
Four major flow rate changes were monitored with downhole pressure changes in PS-13-1
during September 2014. The first was done on September 15, prior to the airlifting, and involved
opening up the well so that it could artesian flow. During this flow, the rate was somewhere
between 60 and 75 gpm, as measured with a 5-gallon bucket. Three major flow rate changes
were then monitored during airlifting while the Kuster tool was downhole (Figure 41, Table 4)
and the magmeter was providing the flow rate data. The first flow rate change was the cessation
of the first airlift, the second was the start of the second airlift, and the third was the end of the
second airlift. All of these changes had natural artesian flow either before or after. None of the
changes involved the larger change of going from a static condition to the airlift.
The productivity measurement involving the lowest flow rate and the smallest downhole pressure
change was between 20.4 and 25.5 gpm/psi. The next largest flow rate change was at the end of
the first airlift, and it produced a productivity value of 22.2 gpm/psi, the same as the average
value of the cessation of artesian flow. The two largest flow rate changes at the start and stop of
the second airlift give virtually identical and higher productivity values of 27.5 and 27.2 gpm/psi.
Figure 44. Detailed flowing and static logs from PS-13-1 run in September 2014 with
precision SMU logging equipment. The flowing log was run during artesian flows, and the
depths were increased by 1.4 m to have exactly the same bottomhole depth as the static log,
as this is the most important part of the hole for this discussion.
20
25
30
35
40
45
50
55
60
65
70
76.2 76.4 76.6 76.8 77 77.2 77.4 77.6 77.8 78
Depth (meters)Temperature C
PS 13-1 Sept. 2014 Static and Flowing SMU Logs
PS 13-1 9-7-14 Static SMU
PS 13-1 9-18-14 Flowing SMUCemented CastingSolid CasingWell Screen85 of 101 Kawerak-Pilgrim Hot Springs-REF Proposal
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These values are quite encouraging, as the well did not give lower productivity values as higher
flow rate changes occurred, indicating that the well is capable of flowing at significantly higher
rates. However, the values do not indicate that the temperatures seen during testing are
sustainable over the long term.
Table 4. Well productivity data
Start Artesian
Flow
Stop First
Airlift
Start Second
Airlift
Stop Second
Airlift
Starting Flow
Rate
0 172 65 300
Ending Flow
Rate
60 – 75? 55 300 60?
Change in Flow
Rate
60 – 75? 117 235 240
Pressure Before
Change
103.40 38.27 46.45 39.4
Pressure After
Change
100.46 43.54 37.91 48.23
Change in
Pressure
2.94 5.27 8.54 8.83
Productivity
(gpm/psi)
20.4 – 25.5 22.2 27.5 27.2
The pressure record in PS-13-1 shows a 2 psi increase after 22:30 hours on September 16 (Figure
41). This increase reflects the thin cable holding the tool breaking, and the tool moving part of a
meter downhole until it was held by the thicker aircraft cable, which turned out to be useful
backup for the Kuster tool.
9.4 Temperature and Pressure Monitoring in PS-13-2
Two hours after the first airlift of well PS-13-1, a Kuster tool was hung in well PS-13-2 near a
depth of 30 m to monitor its downhole temperature and pressure for a few days during the
expected longer and more voluminous second airlift. This PS-13-2 record is exceptionally
complex for a well that was not flowing (Figure 45). The start and stop of the second airlift is
marked by sharp pressure changes of about 0.2 psi. No net longer-term pressure change occurred
between the pressure prior to the airlift and pressures near the end of the monitoring period.
During the airlift, a curious temperature increase and decline was recorded that requires a much
deeper understanding of the hydrology to explain (Figure 45). Equally large or larger
temperature changes occurred when the airlift was not in progress.
9.5 Temperature and Pressure Monitoring in PS-13-3
A Kuster tool was also hung in PS-13-3 after the first airlift of PS-13-1 to document the
downhole pressure and temperature changes (Figure 46). This record shows a sharp 0.2 psi
reaction to both the start and stop of the airlift. There is no longer-term net pressure change from
the start of monitoring to the end. A tiny 0.05°C temperature rise was associated with the higher
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flow that did not reverse after the airlift. Also, three tiny temperature spikes occurred after 20:00,
close to one day apart, that are not understood.
Figure 45. PS-13-2 pressure and temperature response during PS-13-1 flow testing.
Figure 46. PS-13-3 pressure and temperature response during PS-13-1 flow testing.
70
70.5
71
71.5
72
72.5
73
42
42.2
42.4
42.6
42.8
43
43.2
43.4
43.6
43.8
44
9/15/2014 12:009/16/2014 0:009/16/2014 12:009/17/2014 0:009/17/2014 12:009/18/2014 0:009/18/2014 12:00Temperature CPressure (psig)Date and Time
PS 13-2 Monitoring Sept. 15-18, 2014 During 300 gpm Airlift of PS 13-1
Pressure
Start 300 gpm air lift
Stop 300 gpm airlift
Temperature
Resume 60 gpm artesian flowFlowing 60 gpm artesian
78
78.1
78.2
78.3
78.4
78.5
78.6
78.7
78.8
78.9
79
51
51.1
51.2
51.3
51.4
51.5
51.6
51.7
51.8
51.9
52
9/15/2014 12:009/16/2014 0:009/16/2014 12:009/17/2014 0:009/17/2014 12:009/18/2014 0:009/18/2014 12:00Temperature CPressure (psig)Date and Time
PS 13-3 Sept 15-18, 2014 Monitoring During 300 gpm Airlift of PS 13-1
Pressure
Start 300 gpm Air lift
Stop 300 gpm Air Lift
Temperature
Resume 60 gpm artesian flowFlowing 60 gpm artesian
Flowing
300 gpm
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9.6 Historic Hot Springs Temperature Monitoring
A small Hobo brand temperature monitoring probe was placed in the discharge area in the
historic hot spring pool at PHS during testing of the wells. The pool is located 750 feet northeast
of well PS-13-1. During the testing period, the sensor was placed in the northwest corner of the
pool, about 2 feet below the water surface (Figure 47).
Researchers Chris Pike and Dick Benoit also used a presision temperature measuring probe
owned by Southern Methodist University to measure temperatures in the bottom of the pool,
inserting the probe several inches into the sandy bottom of the pool and recording the
temperatures. A maximum temperature of 73°C (163°F) was encountered in the extreme eastern
edge of the pool.
The water temperature of the pool was monitored between September 9 and 18, 2014, with a
brief interuption during the early morning hours of September 16 to download data. During the
time that the temperature was being recorded, the hot spring pool was being used by the public
for soaking and relaxation activities. Chris Pike, an ACEP staff member, monitored the
temperature probe on a nightly basis to ensure that it was still in position. During a brief period
Figure 47. The historic hot spring pool temperature was monitored during flow testing of PS-
13-1.
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on September 12, the probe was removed from the spring. The data collected show that the pool
temperature varied for unknown reasons, but mostly stayed between 38°C and 43°C (100°F–
110°F) (Figure 48).
During the 300 gpm flow testing, the pool temperature dropped and did not stabilize and begin to
rise again until after airlift pumping was stopped. During this time, the pool dropped to its
coolest recorded temperature, below 34°C (94°F) (Figure 48). Further testing is needed to draw a
difinitive correlation between the temperature of the hot spring pool and the flow of the wells.
However, pumping of water from the shallow thermal aquifer likely impacts the flow of hot
water into the pool.
9.7 Flow Testing Conclusions
Well PS-13-1 was airlifted for over 7 hours at an average flow rate of 300 gpm, which
represented about the largest flow that could have been achieved with available equipment. A
Figure 48. Hot spring pool temperatures during the September 2014 flow testing. The lowest
temperature recorded occurred when the greatest flow rates were being pumped from PS-13-1.
90
92
94
96
98
100
102
104
106
108
110
9/9/14 0:009/10/14 0:009/11/14 0:009/12/14 0:009/13/14 0:009/14/14 0:009/15/14 0:009/16/14 0:009/17/14 0:009/18/14 0:00Temperature (°F)Pilgrim Hot Springs Hot Pool Temperatures During
Well Testing
PS13-3 Flowing ~ 60 GPM Artesian PS13-1 Flowing ~60 GPM Artesian
PS13-1 Flowing 300 GPM PS13-1 Flowing 172 GPM
Erroneous Data Hourly Hot Pool Temeprature (°F)
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longer flow test would have been more desireable, and help to better define the resource
however, due to time and funding constraints it was not possible. We acknowledge this
weakness and recommend future flow testing prior to substantial investment in anything other
than small scale power generation.
Repeated productivity measurements with flow rate changes of 60 to 240 gpm gave values of
20.4 to 27.5 gpm/psi which indicate a productive well. It is encouraging that the productivity
values associated with the higher flow rates had the highest values. During the airlift, most of the
fluid must have entered the wellbore in the main shallow thermal aquifer and flowed down
through the sediments along the blank casing to enter the screened part of the well below 57.3 m.
The airlift test impacted wells PS-13-2 and PS-13-3 nearby with a 0.2 psi pressure decline.
Apparently, temperature impacts also occurred, but the indicators are not convincingly
explicable with the available data.
10. PILGRIM GEOTHERMAL SYSTEM CONCEPTUAL MODEL
10.1 Conceptual Model History
Conceptual speculation about the PGS dates to its first recorded visit by geologist G. A. Waring,
who was interested in the geothermal system (Waring, 1917). Waring noted that the sulfate-to-
chloride and the calcium-to-sodium ratios in the thermal water were much different from
seawater and that the relatively high salinity was not due to “an admixture with sea water”
(p.74). Also, Waring speculated that “beneath the river alluvium the bedrock may be gneiss,
intruded by a granitic mass … the heated water rises along the fractured contact zone between
the two kinds of rock”(p.75). Waring drew no schematic diagrams of the PGS.
In the early 1970s, the USGS embarked on a program to improve the understanding of
geothermal systems in the United States; it developed long-lasting conceptual understandings of
the PGS even if it did not draw a specific conceptual model. In Alaska, Miller et al. (1975)
assessed the geochemistry of many of the known springs and their regional geologic setting. In
terms of regional setting, the proximal relationship between thermal springs and granitic plutons
was recognized. Miller et al. (1975) presented the first stable isotope analysis of the Pilgrim
thermal water, which showed the water to be derived from local rain and snowmelt. The thermal
fluid is not a mixture of meteoric water and seawater. Miller et al. (1975) presented the first
predicted PGS subsurface temperatures—137°C (279°F) based on the quartz geothermometer
and 146°C (295°F) based on the Na-K-Ca geothermometer—and concluded that the thermal
water must be at depths of 9000 to 15,000 feet (3.3 to 5.3 km) to reach these temperatures, based
on a gradient of 30°C–50°C/km. Finally, Miller et al. (1975) observed that “most, if not all, of
the hot springs are characterized by reservoirs of limited extent and relatively low temperatures
in comparison with temperatures of geothermal systems presently being exploited for power
generation”(p.12).
The first conceptual model of the PGS was bravely put forth following the 1979 field season,
with the focus on small-scale and very shallow convection cells and a water balance model
(Osterkamp et al., 1980). The water balance model (Figure 14 from Osterkamp et al., 1980)
allows for the possibility of rising hot water being impacted by subpermafrost cold recharge and
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recirculation of thermal water. Various power estimates were made. The geothermometry from
PHS and the first two wells drilled in late 1979 indicated the presence of a deeper and hotter
145°C–150°C (293°F–302°F) reservoir (Motyka et al., 1980).
The second conceptual understanding of the PGS was developed in 1982 after the first six wells
had been drilled and flow tested (Figure 3 from Economides, 1982). The primary result was the
recognition of the shallow reservoir of laterally flowing thermal aquifer and the exceptionally
bold conclusion was that “the existence of a hot water zone of about 150°C (302°F) and at a
depth of around 5000 feet is now virtually certain” (Economides, 1982; Economides et al., 1982,
p.30). In fact, a more specific depth of 4875 feet was stated, based on extrapolating the positive
temperature gradients beneath the shallow thermal aquifer. The researchers also stated that
“locating the hot water source for the shallow zone is relatively unimportant, since the fluid at
depth provides a high temperature source formation extending aerially at least as far as the total
area drilled” (p.28). Regrettably, the total area drilled by 1982 amounted to only a few square
acres.
Liss and Motyka (1994) relied upon geochemical data to suggest that Tertiary–Quaternary
marine sediments might underlie PHS and that the PGS might have subsurface temperatures as
hot as 190°C–230°C (374°F–446°F) based on a Mg-Li geothermometer and admittedly suspect
noncondensible gas geothermometry. More recent drilling at PHS did not encounter Tertiary–
Quaternary marine sediments. Liss and Motyka (1994) also noted a 3He/4He value of 0.9, which
suggested a mantle component of helium. No work was performed on the PGS from 1993 until
2010.
Following this nearly two-decade hiatus, Daanen et al. (2012) utilized the COMSOL
Multiphysics finite element package to develop the first numerical model of the PGS. This
modeling assumed steady-state conditions with an ongoing flow of cold water toward the
geothermal system being required to maintain the high negative-temperature gradients beneath
the shallow thermal aquifer. The model indicated that potentially 38 MW of thermal energy
moves through the shallow groundwater system near PHS. Concurrently, Chittambakkam et al.
(2013) utilized the TOUGH2 simulator and assumed similar steady-state conditions to estimate a
total heat loss of 26 MW (Appendix N).
Unfortunately, more recent geologic studies have brought new information to light which does
not coincide with the results of these modeling efforts. In the case of Daanen et al. (2012), the
observed vertical temperature distribution given in their Figure 3 shows no shallow lateral flow
and implies that it should be possible to drill a well below PS-1 with near isothermal
temperatures of 90°C (194°F), which was disproven by the drilling of well PS-13-3. In the case
of Chittambakkam et al. (2013), their simulated temperatures in Figures 12 and 13 do not show
90°C water flowing from depth to the surface. Instead, there is an unexplained cooling and then
reheating of the thermal upwelling.
Benowitz et al. (2013) used thermochronology modeling to constrain the tectonic regime
responsible for the PGS. They conclude that the thermal anomaly is related to the youthful
extensional setting of the Kigluaik range front fault and is not thermally equilibrating, suggesting
that the hottest temperatures have not been accessed (Appendix O).
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Miller et al. (2013a) present the most complete and detailed conceptual picture of the upper 700
feet of the PGS (Figure 49). In their model, an areally restricted near-vertical thermal upwelling
transmits 90°C water almost to the surface. There is a near-cylindrical thermal anomaly with a
radius of 500 to 800 m extending outward from this upwelling that, by the distance of the
temperature decline to 20°C (68°F), is basically vertical. Also shown in the Miller et al. (2013a)
model (Figure 49) is a strong flow of cold groundwater beneath the shallow aquifer flowing
toward the thermal upwelling from both east and west and then flowing north toward the Pilgrim
River. This is the steady-state model wherein the thermal anomaly and static temperature profiles
of the various wells could remain in the described condition for an indefinite period provided the
relative flow rates of hot and cold water remain more or less constant. One other challenge for
the model developed by Miller et al. (2013a) is that three recent wells drilled to locate thermal
upwelling do not show it located where it is shown in the model (Benoit et al., 2014a).
All subsurface temperature data acquired to date were used to create the plan view maps shown
in Figure 8. These maps show temperature contours of the shallow thermal aquifer and the
temperature minimum, measured from the deep wells. These data along with modifications to the
Miller et al. (2013a) model were used to create Figure 51, which shows the current
understanding of the PHS upwelling.
The model in Figure 51 shows temperature contours across the thermal anomaly, using a
northwest to southeast cross section. The upwelling is shown in the area northwest of PS-13-1,
where no subsurface exploration has been attempted due to swampy conditions and challenging
access. Numerous Geoprobe and temperature gradient holes south and east of PS-13-1 allow a
Figure 49. Conceptual model from Miller et al. (2013a).
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high degree of confidence in the subsurface temperatures. North and west of PS-13-1, no drilling
activities have taken place, and the temperatures shown are estimates that could occur, based on
the conditions given in the model.
Glen et al. (2014) developed a more regional conceptual model of the overall geothermal system
(Figure 50). This model consists of a diffuse downward flow of meteoric water through
basement rocks, along range-bounding faults that separate the Kigluaik Mountains and Hen and
Chickens Mountain from the Imuruk Basin. Hot fluid is shown diffusely rising through bedrock
beneath the valley; it becomes focused in a narrow inferred northeast-trending structure that is
diagonal across the basin, and then rises obliquely in a northeasterly direction. The proposed
northeastward hot flow direction is largely based on a prominent gravity low southwest of PHS,
which suggests 800 m depth to bedrock (Figure 22). Fluid then flows along the shallowing and
narrowing bedrock contact toward the northeast, where close to the surface location of the hot
springs it is further concentrated into north- and northeast-trending structures that allow it to rise
steeply through approximately 300 m of clay-rich alluvium to the surface. This model is
constrained by drill-hole data only in a small area near the hot springs. No temperature or
quantitative depth distribution of the thermal fluid is shown in the Glen et al. conceptual model.
Figure 50. Regional conceptual model cartoon from Glen et al. (2014).
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The culmination of this report is to present as complete a conceptual model as possible of the
PGS. This model uses to the maximum extent the previous efforts and covers the range from
regional aspects to quite detailed local features within the thermal area.
There is no doubt that the thermal fluid at PHS comes from a local meteoric source. Whether this
fluid is recharged from the Kigluaik Mountains to the south or from the Pilgrim River Valley is
unknown, as not enough local meteoric isotopic samples have been collected from these areas.
Discriminating between these two possibilities will first require determining if there are
measurable isotopic differences between precipitation falling on the south and north sides of the
Kigluaik Mountains. Obviously, this information is of more academic than practical interest in
trying to develop the PGS, which is why it was not pursued as an integral part of the recent
exploration effort.
To date, drilling efforts at PHS have been unsuccessful in finding the estimated subsurface
temperatures of 140°C to 150°C (284°F–302°F) that have provided much of the impetus for
extensive exploration of this location over the past 40 years. Perhaps the higher temperatures are
a relatively large lateral distance away from the thermal springs or at much greater depths. If so,
the direction to go is uncertain. Even if a location lateral to the thermal springs were known, the
costs to access it by road would likely be high. Alternatively, perhaps the quartz and NA-K-
1/3Ca geothermometers may not have been appropriate for the PGS, and more conservative
predictions, such as the chalcedony and Na-K-4/3Ca geothermometer, should have been used. In
this case, the predicted subsurface temperatures would be near boiling at depth. Another
possibility is that somehow the exceptionally high calcium content in the PHS water is impacting
the accuracy of the cation geothermometers. A lower base temperature of perhaps 100°C (212°F)
for the geothermal system does not require the meteoric water to descend to depths of 9000 to
15,000 feet, as calculated by Miller et al. (1975); it still would have to go as deep as 10,000 feet.
Unfortunately, no background heat flow holes are anywhere near PHS to constrain the regional
background temperature gradient.
In west-central Alaska, Miller et al. (1975) observed that “apparently fracture systems were not
developed or are not sufficiently open in well-foliated regionally metamorphosed rocks to allow
deeply circulating hot water to gain access to the surface” (p.6). In the 40 years since this
observation was first printed, very few producing geothermal fields have been hosted by foliated
metamorphic rocks. The few examples of wells producing from foliated rocks are not highly
productive. This makes it more challenging and risky to drill into the metamorphic bedrock
beneath PHS to produce from fractured bedrock. To date, the bedrock samples recovered from
PHS drilling have been metamorphic, not granitic. Granitic rocks and other volcanic and
sedimentary rocks in west-central Alaska regularly host geothermal systems. However, no
geophysical interpretation or discussion has yet argued granitic rocks are present beneath PHS.
The structure(s) controlling the thermal fluid flow remain poorly understood, though there is
agreement that the east–west-trending Kigluaik range-front fault is the dominant structure in the
vicinity of the PGS, and is probably close to optimal orientation for the critical failure needed to
create open space for thermal fluid flow. Structures trending north–south or northeast–southwest
would be much less likely to pull apart to create the needed open space for fluid flow. Structures
oriented in these less optimal directions would need to be in more complex local settings for
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permeability. Intersections of single narrow faults present small targets and are unlikely to have
enough areal extent for development as geothermal fields. This kind of geometry would require
some second permeability, such as a connection to nearby permeable formations, to store enough
fluid to develop a viable production/injection strategy. The dip of the Kigluaik range-front fault
at depth is unknown, so it is highly speculative to draw it at a low enough angle for realistic
penetration by a well near the thermal springs. If other east–west-trending faults are present
beneath the Pilgrim Valley, they have not created a density contrast large enough to be
recognized on the gravity map.
It is interesting to speculate on the nature of the local structure or feature at PHS that is
transmitting the thermal water from the top of the metamorphic rocks at 320 m to the surface.
Nobody has yet described any surficial indication of such a structure, which must be either very
young or somehow continuously active to maintain its permeability. Miller et al. (2013a)
recognize a 1 m high north–south terrace that is near the west edge of the thermal anomaly near
the postulated north–south-trending fault, but also note that the terrace could be the result of frost
heaving. This feature must penetrate and keep open multiple layers of soft clay above the
bedrock. It is difficult to describe a feature that has proven so elusive. The drilling and
temperature results to date indicate this feature is most likely northwest of where drilling has
occurred. If the zone of upwelling is located between the already drilled wells, then it is likely so
small that whether it represents a viable target becomes a question.
10.2 Current Pilgrim Geothermal System Understanding
With the background presented thus far, the conceptual model based on our current
understanding of the PGS contains the following components:
1. Local meteoric water must travel to depths of 15,000 feet to provide a resource temperature of
150°C (302°F) if the regional temperature gradient is 30°C–50°C/km (Miller et al., 1975). If a
lower resource temperature near 100°C (212°F) is present then the water may only need to travel
as deep as 10,000 feet. Whether the cold water flows down a single fault in a concentrated
manner or through myriad small fractures in bedrock is only of academic interest, as no
developer’s activities are likely to impact this flow.
2. The area of the top hundred or so feet near the discharge point of the PGS has been quite well
characterized. Some thermal water is actually able to reach the surface and discharge through the
thermal springs. This water reaches the near surface with a temperature of 91°C (196°F). Some
thermal water is discharged into a very shallow aquifer several feet or meters below the surface
and spreads laterally over a fairly large area. Most of the thermal water is discharged through the
shallow thermal aquifer near a depth of 100 feet. Most likely, this shallow aquifer is charged not
too far to the northwest of well PS-13-1. Where the water that percolates through the shallow
aquifer eventually travels is unknown, as this has not been the primary purpose of recent
exploration. It is suspected, however that this water travels to local sloughs, natural hot springs,
and the Pilgrim River. The amount of water discharged onto the surface and into the shallow
subsurface amounts to about 20 to 40 MW thermal.
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3. The nature of the feature or features allowing the thermal water to rise through the Quaternary
alluvium is unknown. Individual faults or intersecting structures have been previously proposed,
but as noted, the proposed ideas are somewhat questionable and nobody has yet strongly argued
the case for these features.
4. The northeast thermal anomaly is real, but so little is known about it at this time that it is
unclear if it is part of the same geothermal system as the PGS. If it is part of the same system,
then the argument for a northeast-trending structure becomes stronger. If the northeast thermal
anomaly is not actually part of the PGS, then the possible northeast trend might actually be
misleading.
5. The sharply declining temperatures beneath the shallow thermal aquifer can be interpreted in
two ways. A steady-state model requires that cold water be flowing beneath the shallow thermal
aquifer to remove the heat. A transient model does not require such cold groundwater flow.
Arguments against the steady-state model are based on two facts. First, the original static
temperature profiles in the deeper wells were all very smooth and showed none of the
complexity that moving water imparts to them. Once the wellbores connected various zones of
permeability, then water movement in the static temperature profiles became obvious (Benoit et
al., 2014b). Second, the hot and cold flowing water would be competing for the same
permeability channels near the thermal upwelling, presumably in gravel and sandy layers. The
thermal water clearly has enough pressure to flow up to the surface but there are no recognized
cold springs near the thermal springs. If there were abundant cold water with artesian pressure
coming from the Kigluaik Mountains, only a perfect seal or a near-perfect pressure balance could
separate the two hydrologies. With the amount of gravel described by Miller et al. (2014a), this
seems quite unlikely. An argument might be proposed that having 100 m of permafrost
surrounding the thaw bulb offers the best available protection from invading cold water at
shallow depths.
To place the proceeding arguments into a picture, we know there must be a thermal upwelling,
and by default, the most likely place for its location is a modest distance to the northwest of well
PS-13-1 (Figure 51). The nature of the permeability in this channel is uncertain. Faults or fault
intersections have been hypothesized, but no convincing evidence has been presented for
verification. The thermal water must have circulated deeply within the metamorphic or
metamorphic/granitic bedrock. It is not known at what depth the thermal water became
concentrated into the focused flow we see near the surface. Whether it has diffusely flowed along
the top of the bedrock or has risen as concentrated flow through the upper part of the bedrock is
speculative.
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Figure 51. The current conceptual model of Pilgrim Hot Springs as shown in a cross-sectional view looking from southwest
to northeast. This model, which is based on all data acquired through September 2014, indicates that the main upwelling zone
is in the swampy area northwest of PS-13-1. Bedrock is represented by the dashed horizontal line at approximately 320 m in
depth. The dashed temperature contours represent areas where the temperatures have not been well measured.
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11. EXPORTING GEOTHERMAL ENERGY TO NOME
Like most rural areas of Alaska, Nome relies on a diesel microgrid for its electrical power. The
diesel fuel that powers this grid is shipped long distances during a short period when the sea is
ice free and is stored in bulk fuel storage tanks until it is used for home heating or electricity
generation. Rural communities in Alaska face challenging logistics, limited infrastructure, and
poor economies of scale. These factors coupled with high oil prices equate to expensive energy
prices that make economic development challenging in many of Alaska’s rural communities.
In 2008, the Nome Region Energy Assessment, funded by the U.S. Department of Energy and
the National Energy Technology Laboratory, concluded that geothermal energy was a potentially
economic option for the region, depending on the size of the power plant that the geothermal
resource could support (Sheets et al., 2008). Following the success of the Chena Hot Springs
project, a preliminary feasibility study was performed in conjunction with the Nome Regional
Energy Assessment report (Dilley, 2007).
To support landowners and the City of Nome in their decision-making process regarding
possible development options, several studies related to the integration of 2 MW of geothermally
generated electricity into the existing Nome grid and the economics of the project have been
conducted in conjunction with the geothermal exploration described in this report.
11.1 Geothermal Power Economics
In 2012, a private developer representing Potelco Power and Telecommunications expressed
interest in developing a geothermal project at PHS. Potelco believed the project could be
economically viable, and transmission infrastructure could be constructed between PHS and
Nome if the resource could provide at least 2 MWe. Potelco created Pilgrim Geothermal LLC,
under which development activities would take place. The City of Nome negotiated a power
purchase agreement with Pilgrim Geothermal LLC to purchase 2 MW of geothermally generated
electricity. To determine if this energy would be cheaper for their ratepayers than traditional
electrical power generated with diesel generators, UAF economist Antony Scott modeled the
price of Nome diesel versus the price of Arctic North Slope crude and then used this information
to project possible future Nome diesel prices based on U.S. Department of Energy crude oil price
predictions. The work provided a framework for decision makers as they weighed the pros and
cons of integrating a geothermal generation source into the Nome grid. Indeed, from a utility
point of view, the most compelling aspect of adding geothermal is the opportunity to reduce the
price volatility that results from the fluctuating price of diesel (Scott, 2015). This was the first
attempt to quantify diesel price risk in remote locations that receive only a few fuel deliveries per
year. The full report is shown in Appendix Q.
11.2 Wind-Diesel-Geothermal Microgrid Modeling
In 2013, Nome increased its nameplate wind power capacity to 2.7 MW to provide a portion of
the annual average load of 4 MW. To model the effect of 2 MW of geothermal power, which had
been negotiated as a take or pay power purchase agreement, UAF researchers created a time step
simulation model using two years of Nome grid data. As with the economic analysis explained in
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the previous section, the grid modeling was intended to serve as a guide to Nome decision
makers as they decided if the integration of geothermally generated electricity was beneficial to
the utility’s ratepayers. A non-load following 2 MWe geothermal generation scheme was
modeled in conjunction with the installed wind and diesel capacity. The Nome utility wished to
observe the effect of possible geothermal power on its ability to fully utilize the wind resource,
which would soon be owned, maintained, and controlled by them, and minimize the wind that
would need to be “dumped.” Researchers also modeled the utility’s ability to fully use the wind
if it added smaller generators to the diesel powerhouse. According to VanderMeer and Mueller-
Stoffels (2014), “adding to the diesel generator fleet to create smaller, more consistent
differences between the combined capacities of diesel generator combinations resulted in less
diverted wind energy, more displaced diesel generated energy, a higher diesel generator load
factor, and more diesel generator switching” (p.4). This modeling allowed the utility to
determine the value of adding geothermal generation, while still considering the decrease in
performance due to increased switching and decreased load factor.
11.3 Transmission from Pilgrim Hot Springs to Nome
The remote location of PHS, 60 miles north of Nome, complicates any future development of a
power generation facility. While the site is accessible via road, the transmission infrastructure
must be constructed from PHS to Nome if any power generated on-site is to be purchased and
consumed in Nome. A transmission option that has been investigated in hopes of lowering the
infrastructure cost of transmission in rural Alaska is a high-voltage direct current (HVDC)
transmission line. Conventional alternating current (AC) transmission requires three- or four-
wire transmission infrastructure, while HVDC transmission requires one or two wires. This could
reduce cost through wire savings and reduced structural loads, requiring fewer poles and saving
money in materials and construction time (Polar Consult Alaska, 2012). This research is
discussed in detail in Appendix R.
12. LESSONS LEARNED
The remote location of Pilgrim Hot Springs, short snow-free construction season, thick layer of
Quaternary alluvial fill above the bedrock which included multiple permeable layers, and limited
accessibility, necessitated careful operational planning. During the course of the research at
Pilgrim Hot Springs it has become clear that some parts of the project were highly successful,
and other elements of the project could have been done differently and more efficiently. Many
of the lessons learned are detailed below in the hopes that future geothermal exploration in the
area can benefit from this experience. These lessons learned include:
The combination of the aerial FLIR and optical remote sensing data used in conjunction
with the geoprobe exploration was an efficient and relatively cost-effective way to define
the extent and temperatures of the shallow thermal aquifer. A slightly larger geoprobe
unit might have been able to consistently penetrate through the temperature maximum of
the shallow thermal aquifer and enable data collection as deep as 200 feet without the
need for a full drill rig. If this unit had been used in the springtime when temperatures
were cool and the ground was still firm, exploration northwest of PS13-1 might have
been possible.
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FLIR surveys served the dual purpose of finding hot seeps and allowing the heat flux
associated with the PGS to be modeled. Two surveys were performed, one in the spring
and one in the fall time. The spring survey was the most useful for mapping areas of
snowmelt that correspond to permafrost-free areas and anomalous vegetation growth not
regularly found on the Seward Peninsula.
Flow testing wells at flow rates exceeding the natural artesian flows proved to be
challenging at PHS given the remoteness of the location, cost limitations, and
temperatures. Basic water well pumps were not rated for the temperatures encountered at
Pilgrim and required a rig on site to install. The lightweight air lifting apparatus that was
utilized worked very well, however it did require close monitoring and regular refueling
every couple hours. Flowing the well at rates greater than 300 gpm would have required
additional manpower and equipment. The 6-inch Krohne magnetic flow meter that was
used during this flow test was extremely reliable, effective, and accurate as well as user
friendly.
The 525 ppm of calcium in the Pilgrim water is an obvious suspect in raising the question
of whether thermal waters with exceptionally high calcium contents provide accurate
geothermometry calculations. Given the inability to encounter the temperatures predicted
by established geothermometry techniques, additional research is warranted to see if there
are other geothermal systems where high levels of calcium caused overly optimistic
geothermometry estimates.
The drilling associated costs consumed the most time and financial resources. The legacy
wellhead repairs allowed researchers to utilize the wells that were drilled in the 1970’s
and 1980’s for temperature and flow testing, and improved our understanding of the field.
In addition, we were able to characterize subtle long term changes that have occurred
over time. The temperature gradient slim holes were an economic way to measure
temperatures at the top of bedrock. Ideally one or two more additional slim holes would
have been drilled near where PS13-1 was eventually drilled and northwest of this area to
help guide the later drilling of the large diameter well capable of flowing large quantities
of geothermal fluid.
The Alaska Oil and Gas Conservation Commission regulates geothermal exploration and
drilling in the same way as oil and gas associated activities are regulated, regardless of
depth, or the temperatures and pressures that one is likely to encounter. Applying the
same standards that the oil and gas industry is bound to for low temperature geothermal
exploration creates a situation where this type of exploration becomes cost prohibitive
and disincentivizes the development of small geothermal resources. Revisiting the
regulations associated with geothermal exploration in Alaska is warranted.
13. CONCLUSIONS
Geothermal exploration at Pilgrim Hot Springs (PHS) has significantly increased the
understanding of this resource and enabled the planning of possible next steps, which are being
carried out at the time this report is being written.
Initial project planning included the consideration of helicopter supported drilling based
on the belief that the area of upwelling could be north of the Pilgrim River. Slim hole
drilling was able to define the edges of the shallow thermal aquifer and the depth of the
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deep aquifer at PHS. Bedrock was encountered on several occasions which had not
occurred during previous drilling at the site.
The possible upwelling area was constrained by drilling and the most likely upwelling
zone feeding PHS is located slightly northwest of well PS13-1 (Figure 51). This idea is
supported by the plan view temperature maps in Figure 8, which describe the flow
direction of the thermal fluids.
We continue to believe the site is capable of supporting two megawatts of electrical
power generation. The economic viability of exporting this power to Nome remains a
question that private industry is best suited to answer. Repeated productivity
measurements of well PS13-1with flow rate changes of 60 to 240 gpm gave values of
20.4 to 27.5 gpm/psi which indicate good productivity. A longer flow test would have
been more desireable, and helped to better define the resource, however, due to time and
funding constraints it was not possible. We acknowledge this weakness and recommend
future flow testing prior to substantial investment in anything other than small scale
power generation.
The landowners at PHS are investigating different on-site development options and are
currently moving forward with plans to begin producing agricultural products on the site.
This could include the construction of greenhouses to produce food for export to local
communities, tourism infrastructure, and community facilities. Traditionally, the export
of geothermal power has occurred in the form of electricity; however, using the heat
energy at PHS to grow food for the region could be a creative way to export the “energy”
and supply a much-needed commodity that otherwise is shipped into the region. The high
cost of food transported to the area is heavily impacted by the price of petroleum.
Pilgrim Geothermal, LLC has indicated that it is planning additional drilling activities to
identify the future production-well location for a large-scale geothermal electric power
plant. Future exploration could rely on angle drilling from the existing drill to access the
northwest target area.
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