10 .SU250026 PZ Staff Report
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SU250026
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Report to the Planning and Zoning Commission
Prepared by the Maricopa County Planning and Development Department
Case:
SU250026 – Redhawk Power Plant
Hearing Date:
November 6, 2025
Supervisor District:
4
Applicant:
Kimberly Ashcroft, Arizona Public Service
Owner:
Arizona Public Service
Request:
Special Use Permit (SUP) Major Amendment in the Rural-190 zoning
district
Site Location:
Generally located 1½ miles southwest of the SWC of Elliot Rd. and 355th
Ave. in the Arlington Area
Site Size:
Approx. 460 acres
Density:
N/A
County Island:
No
County Plan:
Old US 80 Area Plan – Industrial
Municipal Plan:
N/A
Municipal Comments:
None received to date
Support/Opposition:
None known
Recommendation:
Approve with conditions
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Project Summary:
1.
The applicant is requesting a major amendment of the Z99-111 Special Use Permit (SUP) for an
electric generation facility on a 460 acre portion of an 1,848 acre parcel in the Rural-190 zoning
district. The facility is located 1½ miles southwest of the southwest corner of Elliot Rd. and 355th
Ave. in the Arlington area. The purpose of this request is for the expansion of the existing facility
onto a vacant 40 acres of the site for the addition of eight combustion turbine generator units and
associated equipment/infrastructure. This addition will be south of the developed powerplant
consisting of a ten acre laydown yard and a 20 acre electric switchyard expansion area. The
Redhawk Power Plant is currently a 1,600 megawatt (MW) combined cycle power plant that
generates electricity from the burning of fossil fuels. The expansion of this facility was recently
approved via the Certificate of Environmental Compatibility (CEC) process with the Arizona
Corporation Commission on October 8, 2024 (CEC234).
2.
The eight new turbine generation units that will be added to this facility are air-cooled containing
oil lubrication systems that use air-type fin-fan coolers. Demineralized water will be used for inlet
fogging and water spray power augmentation to reduce the turbine inlet air temperature to
improve turbine performance. To minimize nitrogen oxide emissions from the facility the turbine
units include water injections.
3.
Groundwater and natural gas for the proposed facility expansion will be provided using the
existing water rights and infrastructure that currently serves the facility which minimizes the need
for improvements. According to the applicant, the expansion site will use approximately 300 acre-
feet of pumped groundwater. This use will utilize the existing groundwater rights but will remain
under the annual allotment of 3,350 acre feet. Also, according to the applicant, most of the water
used by the existing turbine units utilize effluent water and as a result most of the groundwater
being used in a single year is limited to 872 acre feet. According to the applicant, the additional
eight turbine units being proposed is expected to be less than 1,172 acre-feet per year. Attached
with this staff report is a groundwater well impact study for this facility, which according to the
report there are no significant impacts to neighboring wells.
4.
In this SUP amendment the applicant is proposing to modify three of the Z99-111 SUP conditions.
The first modification is to condition ‘g’ which required not only the monitoring of the groundwater
levels below the site but of the water levels of neighboring wells if the applicant pumped more
than 1,172 acre-feet in the previous year. The reason for this request, according to the applicant,
is because its current and projected groundwater use are approximately one third of the allocated
3,350 acre-feet of groundwater, even with the facility expansion. According to the applicant, they
currently must enter neighboring private properties to access and monitor neighboring wells to
remain in compliance with the groundwater monitoring requirements and in some cases had to
bear the cost modifying neighboring wells for monitoring. Also according to the applicant, there
is no proposed elimination of the permit conditions or reduction of the allotted 3,350 acre-feet of
groundwater per year, which if there is ever a disruption to the effluent supply, the amount of
groundwater allotted would be a necessity. The second portion of this modification is to replace
“Pinnacle West,” a former property owner, with “the applicant” in the last part of the condition,
(See the entire condition below.)
g.
The applicant shall mitigate area well problems within the area of influence by taking
prompt corrective action. The area of influence shall be defined as that area within which
the water table drawdown may exceed ten feet over any five-year period from and after the
date of approval of this Special Use Permit (SUP) by the Maricopa County Board of
Supervisors, solely as a direct result of pumping of 3,350 acre-feet/year at the Redhawk Site,
SU250026
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based upon a study approved by the Department of Water Resource. If the results of the
integrated water study show a larger Area of Influence for Redhawk (3,350 acre-feet per
year) than Pinnacle West the applicant specified, then Pinnacle West the applicant shall
increase the Area of Influence to reflect the integrated water study results. There shall be a
trigger threshold of 1,172 acre-feet of annual ground water use before additional
groundwater monitoring is required. The applicant will bear the cost of corrective action to
restore any domestic wells to production with meet each of the following criteria:
i.
The well used solely as a domestic week from and after the date of approval of this
SUP;
ii.
The well was an active well as of the date of approval of this SUP;
iii.
The well is within the applicant’s area of influence ;
iv.
The well cannot sustain the production necessary to meet the domestic uses
established as of the date of approval of the SUP;
v.
The loss of production is not caused by the domestic well owner or the owner’s
equipment.
In the event all of the above listed criteria are met, the owner(s) of such well shall notify the
Applicant at the phone number or address which shall be kept actively on file with the
Maricopa County Planning and Development Department. It shall be the responsibility of
the well owner to notify APS if there is an issue with their well that meets the above
criteria of this condition. The applicant shall initiate corrective action within 72 hours of
receipt of such notice, even if the corrective action is temporary (the “Response Period”). In
the event the applicant has direct knowledge that all of the criteria have been met the well
owner is not required to supply any notice and the Response Period set forth above shall
run from the time the applicant acquired such knowledge.
5.
Another request is to eliminate condition ‘h’ which required the applicant to submit an annual
status report used to determine compliance with the conditions of this SUP. Status reports are
no longer necessary. The applicant has proven over the years in these annual status reports that
this facility abides by all the Z99-111 conditions of approval, see proposed modification below:
h.
The applicant shall submit an annual written report outlining the status of the development
until such time as the Special Use Permit expires. The first report shall be submitted on
April 30, 2001. The status report shall be reviewed by staff to determine compliance with
stipulations and whether the report needs to be reviewed by the Planning and Zoning
Commission. The status report shall also contain groundwater monitoring reports with
annual withdrawals as well as all other annual water use itemized by type and quantity. In
addition, the status report shall address the impact on wells in the defined Area of Influence
(drawdown). Implementation of the re-vegetation plan shall also be presented in this report
and shall include a detailed report on the progress of the re-vegetation plan.
6.
The final request is to eliminate condition ‘p’, which placed an SUP expiration of 40 years or by
May 17, 2040. According to the applicant, this facility is a vital component in APS’s electric
generation and with the proposed expansion of the site will increase the operational life for an
additional 40 years, see below:
p.
This Special Use Permit shall expire in 40 years from the date of approval by the Board of
Supervisors.
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7.
On May 17, 2000, the Board of Supervisors approved an SUP for an energy generation facility
(Z99-111) on 460 acres of the property. On December 10, 2014, the owner of this facility, APS,
entered a Memorandum of Understanding with the Planning & Development Department
exempting the requirements for applying for building permits for this facility. On May 18, 2022,
staff approved a minor SUP amendment to add two surge ponds for additional effluent capacity
on the site (Z2022071). On June 11, 2025, staff approved another minor SUP amendment, for new
chiller equipment modules and new tank on the site (SU250017). On August 19, 2025, the
Technical Advisory Committee met with the applicant to discuss the first review comments with
the applicant.
8.
The applicant is requesting to develop on a vacant 40 acre portion of the 460 acre SUP site south
of the existing electric power station to expand this facility. The central portion of this expansion
area will contain electrical generation equipment. To the east of the power generation area will
be a 10 acre temporary laydown yard to store construction equipment during the development of
the expanded electric generation area and the area to the west of the expansion area will be a 20
acre electric switchyard. Adjacent to the laydown yard will be temporary paved parking area for
construction workers with 44 spaces. The final modification will be to move the existing helipad
700 feet to the northeast of the expansion site. The facility operates daily 24 hours per day and
has 47 permanent employees with additional contract workers when needed. The applicant
believes that up to 10 personnel may be required for the expansion area. This facility is screened
by chain link fences and is gated with no access to the public. Currently the site has 59 paved
parking spaces and three of the spaces are ADA accessible.
Aerial photo of subject site
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Aerial image & surrounding environs
Eagle view of subject site looking south into subject parcel (aerial image dated 10/24).
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Portion of the Site Plan
Elevations of the new infrastructure
Elevations of the existing infrastructure
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Existing On-Site and Adjacent Zoning / Land Use:
9.
On-site:
Rural-190 SUP / Electrical generation facility
North:
Rural-190 SUP / Solar electric generation facility
South:
IND-2 IUPD / Solar electric generation facility
East:
IND-2 IUPD & Rural-190/ Solar generation facility & vacant
West:
IND-2 IUPD / Solar electric generation facility
Zoning Map
Utilities and Services:
10.
Water:
Private well
Wastewater:
Private septic system
School District:
Arlington School District
Fire:
On-Site and Tonopah Valley Fire District
Police:
MCSO
Right-of-Way:
11.
The following table includes existing and proposed half-width right-of-way and the future
classification based upon the Maricopa County Department of Transportation (MCDOT) Major
Streets and Routes Plan.
Street Name
Half-width Existing R/W
Half-width Proposed R/W
Future Classification
363rd Ave.
0’
0’
Arterial Roadway
Narramore Rd.
0’
0’
Arterial Roadway
SU250026
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Adopted Plan:
12.
Old US 80 Area Plan (adopted May 2007): This plan designates the SUP site as Industrial. The
Industrial category identifies locations for major employment centers. Appropriate uses in this
category include general warehousing, storage, distribution activities, electric generation, and
general manufacturing. Compatibility with adjacent current and future land use is an important
consideration, and developments within this category are subject to plan review and approval.
Public Participation Summary:
13.
The applicant complied with the requirements of the citizen review process with the required
posting of the site and notification by first class mail to interested parties and adjacent property
owners within 300’ of the subject parcel. Signs were posted on the site, in accordance with
applicable regulations. As to the writing of this report, neither applicant nor staff have received
any support or opposition from the public.
Outstanding Concerns from Reviewing Agencies:
14.
N/A
Staff Analysis:
15.
Redhawk Power Plant has been in operation providing power to APS customers for over 20 years.
Since 2001, the property owners have provided annual status reports that have proven that the
owner and operator of this facility have abided by every stipulation of approval of the Z99-111
SUP. Even with the allotted 3,350 acre-feet of groundwater, the existing site has been using
substantially less groundwater than allocated with the most used being 872.3 acre-feet in 2022,
according to the applicant’s water reports. Therefore, the additional groundwater usage required
for the expansion of the existing electric generation facility will not result in an exceedance of the
annual allocated groundwater amount, making the modification of Z99-111’s Stipulation ‘g’
sensible. The modification to condition ‘h’ is to eliminate the need for status reports and alteration
of condition ‘p’ to eliminate the SUP expiration is sensible. Staff supports this change since
although these were common features for entitlement during the turn of the century, these types
of instruments are rarely conditioned for entitlement for electric generation facilities. This facility
is in an isolated part of the County with the nearest residence over a mile away from this site. The
proposed expansion of the existing facility in a vacant portion of the SUP site is minimal and will
be able to provide electricity to more customers in the APS coverage area of the state. The land
use remains appropriate for this site. It is in concert with the surrounding regional land use and
development patterns. There is no known opposition to this expansion.
Recommendation:
16.
Staff recommends the Commission adopt a motion recommending that the Board of Supervisors
approve SU250026 subject to the following conditions ‘a’- ‘j’ carried forward from Z99-111 but
with modifications to condition ‘g’ and elimination of conditions ‘h’ and ‘p’ with corresponding
relabeling of conditions:
a.
Development of the site shall be in substantial conformance with the Site Plan entitled
“Redhawk Power Plant“, consisting of five full-size sheets, dated September 10, 2025, and
stamped received September 12, 2025, except as modified by the following conditions.
SU250026
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Staff may determine slight refinements to remain in substantial conformance with the
approved site plan. Minor and major amendments to the site plan will be determined in
accordance with Chapter 3 of the Maricopa County Zoning Ordinance.
b.
Development of the site shall be in substantial conformance with the Narrative Report
entitled “Redhawk Power Plant Expansion Project”, consisting of 12 pages, dated August
28, 2025, and stamped received September 12, 2025, except as modified by the following
conditions.
c.
The following Planning Engineering conditions shall apply:
1.
The requirement for the retention basin to drain within 36 hours must be
maintained.
2.
Engineering review of planning and/or zoning cases is for conceptual design only.
All development and engineering design shall be in conformance with Section
1205 of the Maricopa County Zoning Ordinance; Drainage Policies and Standards;
Floodplain Regulations for Maricopa County; MCDOT Roadway Design Manual;
and current engineering policies, standards and best practices at the time of
application for construction.
3.
Based on the conceptual design nature of the information submitted, changes to
the site layout may be necessitated by the final engineering design of the drainage
infrastructure.
d.
Maximum height for non-building appurtenant structures, such as smokestacks, water
towers, or electrical line distribution support structures, shall be 175’.
e.
This special use permit is a permanent entitlement with no expiration.
f.
Annual status reports with groundwater monitoring reports and revegetation plans for the
Z99-111 Special Use Permit are no longer required.
g.
The applicant shall mitigate area well problems within the area of influence by taking
prompt corrective action. The area of influence shall be defined as the area within which
the water table drawdown may exceed 10’ over any five-year period from and after the
date of approval of this Special Use Permit by the Maricopa County Board of Supervisors,
solely as a direct result of pumping of 3,350 acre-feet per year at the Redhawk Site, based
upon a study approved by the Department of Water Resources. If the results of the
integrated water study show a larger Area of Influence for Redhawk (3,350 acre-feet per
year) than the applicant specified, then the applicant shall increase the Area of Influence
to reflect the integrated water study results. There shall be a trigger threshold of 1,172
acre-feet of annual ground water use before additional groundwater monitoring is
required. The applicant will bear the cost of corrective action to restore any domestic wells
to production which meet each of the following criteria:
i.
The well is used solely as a domestic well from and after the date of approval of
this Special Use Permit;
ii.
The well was an active well as of the date of approval of this Special Use Permit;
iii.
The well is within the applicant’s area of influence ;
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iv.
The well cannot sustain the production necessary to meet the domestic uses
established as of the date of approval of the Special Use Permit;
v.
The loss of production is not caused by the domestic well owner or the owner’s
equipment.
It shall be the responsibility of the well owner to notify APS if there is an issue with their
well that meets the above criteria of this condition. The applicant shall initiate corrective
action within 72 hours of receipt of such notice, even if the corrective action is temporary
(the “Response Period”). In the event the applicant has direct knowledge that all the
criteria have been met the well owner is not required to supply any notice and the
Response Period set forth above shall run from the time the applicant acquired such
knowledge.
h.
All the stipulations and conditions of Z99-111 and subsequent minor amendments shall
be complied with, except for the modification to Z99-111 condition ‘g’, elimination of Z99-
111 condition ‘h’ concerning status report, and elimination to Z99-111 condition ‘p’
concerning SUP expiration.
i.
Noncompliance with any of the conditions assigned to the approval of this Special Use
Permit by the Maricopa County Board of Supervisors may be grounds for revocation in
accordance with the requirements and procedures as set forth in the Maricopa County
Zoning Ordinance.
j.
The granting of this change in use of the property has been at the request of the applicant,
with the consent of the landowner. The granting of this approval allows the property to
enjoy uses in excess of those permitted by the zoning existing on the date of application,
subject to conditions. In the event of the failure to comply with any condition, and at the
time of expiration of the Special Use Permit, the property may be considered for revocation
to the zoning that existed on the date of application. It is, therefore, stipulated and agreed
that either revocation due to the failure to comply with any conditions, or the expiration of
the Special Use Permit, does not reduce any rights that existed on the date of application
to use, divide, sell or possess the property and that there would be no diminution in value
of the property from the value it held on the date of application due to such revocation or
expiration of the Special Use Permit. The Special Use Permit enhances the value of the
property above its value as of the date the Special Use Permit is granted and reverting to
the prior zoning results in the same value of the property as if the Special Use Permit had
never been granted.
Presented by:
Martin Martell, Planner
Reviewed by:
Rachel Applegate, Planning Supervisor
Attachments:
Case Map (1 page)
Site Plan (reduced 8.5”x11”, 5 pages)
Narrative Report (12 pages)
MCESD comments (1 page)
DPR comments (1 page)
Memorandum of Understanding (3 pages)
Well Inventory Report (3 pages)
Groundwater Monitoring Report (2 pages)
Certificate of Environmental Compatibility (23 pages)
Water Assessment for Proposed Expansion Report (21 pages)
/
Maricopa County Planning & Development - Phoenix, AZ
4
Gross Acres: 468 approx.
Generated October 27, 2025 2:34 PM
SU250026
Application Name:
Legal Description
Redhawk Power Plant Expansion Project
Applicant
Case Address
1S 6W 23
Kimberly Ashcraft
11600 S 363RD AVE
Applicant Phone/Email
Parcel Primary:401-44-007C
(602) 309-7096
Kimberly.Ashcraft@aps.com
ARLINGTON, AZ 85322
Map scale 1:14,319
Supervisor District No.
Major Special Use Permit Amendment for an addition of eight combustion turbine generator units and
associated equipment and infrastructure to Redhawk Power Plant.
REDHAWK POWER PLANT
SPECIAL USE PERMIT MAJOR AMENDMENT
ARIZONA PUBLIC SERVICE COMPANY
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FOR PERMITTING
PURPOSES ONLY
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RECEIVED 12. SEP 25
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WORK SAFELY TODAY
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REDHAWK
WORK SAFELY TODAY
FOR PERMITTING
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Title Page
Redhawk Power Plant Expansion Project
11600 S. 363 Ave
Arlington, Arizona
Parcel: 401-44-007C
SUP Z99-111 Major Amendment
Case #: SU250026
Narrative Report
Revision 1
August 28, 2025
RECEIVED 12. SEP 25
SU250026 - 2. SUB
Redhawk SUP Z99-111 Major Amendment
CONTENTS
Title Page ......................................................................................................................... 0
Purpose of Request ...................................................................................................... 2
Description of Proposal .............................................................................................. 2
Relationship to Surrounding Properties ............................................................... 3
Location and Accessibility ......................................................................................... 4
Circulation System ....................................................................................................... 4
Grading and Drainage Plan....................................................................................... 4
Flood Control District and Stormwater Quality ................................................. 4
Development Schedule .............................................................................................. 4
Community Facilities and Services ...................................................................... 11
Public Utilities and Services ................................................................................... 11
Other Information ...................................................................................................... 11
Redhawk SUP Z99-111 Major Amendment
Purpose of Request
The purpose of this Amendment is to include the addition of eight (8) combustion turbine (CT)
generator simple cycle units (Units 3 through 10) and associated equipment and infrastructure at
the Redhawk Power Plant located in Arlington, unincorporated Maricopa County, Arizona (Figure 1).
The Expansion Project area covers approximately 40 acres (including 10 acres for the generation
expansion, 10 acres for a laydown yard, and 20 acres for a switchyard expansion area) and is
located south of the existing Power Block 2 area. The new natural gas units will be within the area
that was originally sited to have two additional combined cycle units for the Redhawk Power Plant.
Additionally, this Amendment requests to modify Special Use Permit Stipulation G relating to well
impact monitoring and Conditions H and P related to annual status reports and facility timeline,
respectively. This modification request is based on past and anticipated Plant groundwater use.
Description of Proposal
The Redhawk Power Plant is a 1,060 megawatt (MW) combined cycle power plant developed on
460 acres of land owned by Arizona Public Service (APS). The site has been developed as governed
by Special Use Permit (SUP) Z99-111, Comprehensive Plan Amendment (CPA) 99-03, and CPA
2019005. This SUP Major Amendment request is for the proposed Expansion Project, an
approximately 10-acre area of development located near the center of the 460 acres previously
approved with SUP Z99-111, to include the addition of eight (8) new natural gas units, adding up
to 397 MW to the energy grid by 2028. The Project also includes a 10-acre laydown area and a 20-
acre area for expansion of the Redhawk Switchyard (Figure 2). The expansion was approved
through the Certificate of Environmental Compatibility (CEC) process with the Arizona Corporation
Commission on October 8, 2024 (CEC234). This application also requests a modification to the
existing SUP Stipulation G (see requested revision to the stipulation as described below).
As approved in the CEC, APS will build eight (8) LM6000 combustion turbine generator units with
emission control systems, including selective catalytic reduction and carbon monoxide catalysts.
The supporting infrastructure includes balance-of-plant equipment including a plant air system, an
ammonia system, a continuous emission monitoring system, a raw water tank, a water treatment
system, and a demineralized water tank. Other systems include plant control systems, power
distribution centers, low-voltage switchgear, low-voltage motor control centers, 230 kilovolt (kV)
collector bus system, four 13.8/230kV generator step-up transformers, and a 230/500kV step-up
transformer. The new generators will be arranged in pairs, with two (2) generators connected to a
generator step-up transformer.
The eight (8) new generator units are air-cooled and contain oil lubrication systems that also are
air cooled using air-type fin-fan coolers. Demineralized water will be used for inlet fogging and
water spray power augmentation to reduce the turbine inlet air temperature to improve turbine
performance. Each generator unit is also equipped with water injection in the combustor to reduce
nitrogen oxide (NOx) emissions.
Groundwater and natural gas for the Expansion Project will be provided using the existing water
rights and infrastructure that currently serves Redhawk with minimal improvements required. The
Expansion Project will pump approximately 300 acre-feet of groundwater per year using Redhawk's
existing groundwater rights. This additional amount of groundwater usage will still remain under
the maximum annual allocated amount of 3,350 acre-feet. Redhawk’s existing units utilize effluent
for the majority of its water use, and as a result the most groundwater the facility has used in a
single year was 872 acre-feet in 2022, which was higher than typical because of a construction
project at the site (See Attachment 3, Redhawk Groundwater Monitoring Report, Annual Water Use
Table). Even with the addition of the Expansion Project, the anticipated water use at Redhawk is
expected to be less than 1,172 acre-feet per year. The applicant commissioned a groundwater and
Redhawk SUP Z99-111 Major Amendment
well impact study for Redhawk, including the Expansion Project to model the impacts of pumping
up to 1,172 acre-feet per year at the facility. The study report shows that there are no significant
impacts to neighboring wells. (See P&Z staff report’s attachments).
In this application, the applicant is seeking to modify its reporting requirements relating to
groundwater because its current and projected uses are roughly one third of the allocated 3,350
acre-feet of groundwater that Redhawk is allotted. Currently, the applicant must enter neighboring
private properties to access and monitor the neighboring wells. In some cases, the applicant has
had to bear the cost of modifications to the neighboring wells in order to gain access to remain in
compliance with the groundwater monitoring requirements. In this Application, the applicant
requests that it only be required to test and report the water levels of the neighboring wells if the
applicant pumped more than 1,172 acre-feet in the prior year.
The applicant does not propose removing any of the permit conditions or reducing the water
allotted to the facility. If there was a disruption to the effluent supply, the applicant needs to
maintain the ability to access up to the 3,350 acre-feet per year to support reliability.
To accommodate the interconnection of the Expansion Project to the grid, APS intends to construct
an addition to the Redhawk Switchyard within the Redhawk plant site owned by APS. The existing
Redhawk Switchyard occupies approximately 11 acres within the 460-acre SUP Redhawk Plant
boundary. The switchyard addition would require approximately 20 acres located within the 460-
acre SUP Redhawk Plant boundary. Currently, APS plans to construct an overhead high-voltage
transmission line from the Expansion project area to the existing Redhawk Switchyard. The
interconnection facilities required to connect the new units to the grid include an approximately
500-foot-long generator tie transmission line from the Expansion area Point Of Connection Outside
(POCO) pole to the point of interconnect in the existing Redhawk switchyard.
Per the CEC conclusions, the addition of eight (8) natural gas turbines and associated infrastructure
to the Redhawk Plant will have minimal environmental impacts on the factors identified in A.R.S.
§40-40-360.06(A). In addition, the new turbines are subject to and will comply with all applicable
air pollution standards and regulations as detailed in the Air Permit Application attached as in the
P&Z Staff report. Finally, as outlined in the "Water Assessment for the Proposed Expansion Project"
in the P&Z Staff Report, the addition of these turbines will not result in unreasonable impacts to the
groundwater aquifer beneath Redhawk and will produce minimal impact to the management area.
The Redhawk Power Plant operates 24 hours a day, 7 days a week, year-round.
The Redhawk Power Plant currently has 47 permanent APS employees. Additional contract
personnel are on site, as required. Up to 10 additional personnel may be required for the expansion
project. The addition of these employees would be covered by the existing public water system
associated with the Redhawk Power Plant.
Relationship to Surrounding Properties
The Expansion Project, including the new facility equipment, generation interconnections, natural
gas source, well water supply, and wastewater discharge, will be contained entirely within the
Existing Plant site (current land use is designated as Industrial Use) and will not affect surrounding
properties. There are two combined cycle power plants located to the west of the Redhawk Power
Plant, solar facilities immediately adjacent to the north and south property boundaries, along with a
nuclear plant located farther to the north of the property. The Expansion Project will provide
additional power to the energy grid and is a consistent and compatible land use with neighboring
and nearby properties. The immediate surrounding area has grown to become an energy
Redhawk SUP Z99-111 Major Amendment
production center, and expansion of the existing generating station is consistent and compatible
with surrounding land uses.
Location and Accessibility
The Expansion Project will be located entirely within the existing Redhawk Power Plant property
boundary, subject to the original SUP (Z99-111). Facility use is only accessible to APS personnel
and properly trained contractors. The site entrance is located on the NE corner on the eastern
boundary of the expansion area. There is additional access to the site via a manual gate on the
southern boundary.
Circulation System
No improvements have been made to the off-site access road. Onsite improvements include
additions of asphalt paved areas and access roads to prevent fugitive dust.
Grading and Drainage Plan
The Applicant will comply with the Maricopa County Drainage Regulations and adopted County
design methods and standards. A grading and drainage analysis will be prepared and submitted for
county review and approval. The Project site will be graded to accommodate all Project
components and use the existing drainage system for the site. The grading and drainage
associated with the expansion area was already considered during the original site development
and detention basin sizing and construction. New drainage facilities are not anticipated to be
required as part of the expansion project.
Flood Control District and Stormwater Quality
The proposed expansion area is not located in a Special Flood Hazard Area. The subject site is not
presently located within the County’s Urbanized Area and is not subject to the County’s Stormwater
Pollution Prevention Permit (SWPPP). The expansion area will be incorporated into the Project’s
existing stormwater management plans for operation of the facility.
Development Schedule
Construction of the CT generator simple cycle units (Units 3 through 10) and associated equipment
and infrastructure at the Redhawk Power Plant is planned to begin on or about March 2026. The
facility is anticipated to be constructed over a 24 to 26 month period.
The following section addresses the status of the Redhawk Power Plant project by CPA and SUP
stipulations:
CPA 99-03: Change land use designation for the Tonopah Area plan from Rural to
Industrial on a portion of the property (460 ac.), and Rural to Open Space on the
remainder of the property (1,388 ac.) to allow for a natural gas-powered, combined
cycle, electrical generating plant.
Redhawk SUP Z99-111 Major Amendment
a. Development shall comply with the Area Plan Amendment entitled Redhawk Combined Cycle
Power Plant stamped received April 25, 2000, except as modified by the following
stipulations.
The site has been developed in accordance with the approved site plan with five
administrative amendments to date. See Case History under Z99-111.
CPA2019005 was approved as a Major Comprehensive Plan Amendment to change
the land use designation from “open space” to “utilities” for future solar
development on the property outside of the “Industrial” use boundary. Any
development in this area will follow all conditions as outlined in the approval
letter.
b. Any request to change the land use designation from Industrial or Open Space as approved
herein shall require an Area Plan Amendment with approval by the Board of Supervisors
upon recommendation of the Planning and Zoning Commission.
Complied with. CPA 2019005 was approved to change “Open Space” to Utilities for
solar development.
c. The applicant shall participate in the Centennial Wash Groundwater Model Technical Group
to study the impacts of groundwater withdrawal on the Lower Hassayampa aquifer. The
applicant shall cooperate by providing funds in proportion with the applicant’s groundwater
requirements to the total required groundwater requirements (the sum of all applicants
needs). The applicant shall also provide all pertinent background information and materials
concerning their property to the study.
Complied with.
d. A representative of the Arizona Department of Water Resources shall review and verify the
results of the comprehensive water study on the groundwater use impacts for the Lower
Hassayampa aquifer in Arlington Valley and report their findings to Planning and
Development staff.
Complied with.
e. A re-vegetation plan shall be applied to the remainder of the site (1,388 acres). The re-
vegetation plan may be phased and submitted to staff in two phases. The first phase for the
southern portion of the site (south of the railroad tracks – 1,088 acres) shall be provided for
staff review with the first annual report as required within the Special Use Permit
stipulations (Z99-111). The second phase for the western portion of the site (300 acres)
shall be provided for staff review with the second annual report as required within the
Special Use Permit stipulations (Z99-111).
Complied with.
The revegetated areas were re-zoned under Z2021160 for the construction of the
APS Agave Solar Plant.
f.
The Industrial land use designation shall revert to the rural land use designation after 7
years unless a minimum of one unit is operational and generating electricity. An Open Space
designation shall be placed on the remainder of the property (1,388 acres). At the
expiration of the Special Use Permit (40 years from Board of Supervisors approval), the
Industrial and Open Space designations shall remain on the properties.
Redhawk SUP Z99-111 Major Amendment
Plant began commercial operation July 31, 2002 (Units 1 & 2).
Z99-111: Special Use Permit for a power generating plant (460 acres)
a. Original Z99-111 Stipulation: Development and use of the site shall comply with the site
plan entitles “Special Use Permit for Pinnacle West Energy Redhawk Power Plant”, consisting
of 10 sheets, dated (revised) April 19, 2000, and stamped received April 25, 2000, except
as modified by the following stipulations.
Minor Amendment Z2000149: Construction shall comply with the site plan entitled “Special
Use Permit for Pinnacle West Energy {revised for administrative amendment Z2000149”
consisting of 10 sheets, dated October 26, 2000 and stamped received October 27, 2000.
Minor Amendment Z2003087: Development of the site shall be in compliance with the site
plan entitled “Administrative Amendment to Special Use Permit for Pinnacle West Energy
Redhawk Power Plant”, consisting of ten (10) sheets (E-C001 – E-C010), dated October 23,
2003 (top sheet) and stamped received November 6, 2003 except as modified by the
following stipulations.
Minor Amendment Z2012087: Development of the site shall be in compliance with the site
plan entitled “Administrative Amendment to Special Use Permit for Arizona Public Service
Redhawk Power Plant”, consisting of ten (10) sheets, dated January 21, 2013 and stamped
approved February 16, 2017, except as modified by the following stipulations.
Minor Amendment Z2022071: Development of the site shall be in compliance with the site
plan titles “Z2022071 Special Use Permit Minor Amendment for Arizona Public Service
Redhawk Power Plant”, consisting of ten (10) sheets, dated May 12, 2022 and stamped
approved May 18, 2022.
Minor Amendment SU250017: Development of the site shall be in compliance with the site
plan titled “SU250017 Special Use Permit Minor Amendment for Arizona Public Service
Redhawk Power Plant”, consisting of ten (10) sheets (Dwg 163361 sh 1-10), dated May 13,
2025 and stamped approved June 11, 2025.
Complied with.
b. Original Z99-111 Stipulation: Development and use of the site shall comply with the
narrative report entitled ‘Special Use Permit Application Narrative”, consisting of 25 pages
plus exhibits, dated April 25, 2000, and stamped received April 25, 2000, except as
modified by the following stipulations.
Minor Amendment Z2000149: Construction shall comply with the narrative report entitled
“Narrative Report Describing Zoning Permit SUP Drawing Changes Redhawk Power Plant
Project” consisting of 2 pages dated October 5, 2000 and stamped received October 25,
2000.
Minor Amendment Z2003087: Development of the site shall be in compliance with the
Narrative Report entitled “Narrative Report Describing Zoning Permit Administrative
Amendment SUP Drawings Redhawk Power Plant Project 7-22-2003 (rev. 10/24/2003)”
consisting of one page, stamped received November 6, 2003, except as modified by the
following stipulations.
Redhawk SUP Z99-111 Major Amendment
Minor Amendment Z2012087: Development of the site shall be in compliance with the
Narrative Report entitled “Special Use Permit Z99-111 Minor Amendment Case No.
Z2012087 Redhawk Combined Cycle Power Plant Narrative Report Rev 1”, dated September
28, 2016, consisting of 27 pages, including attachments, and stamped Approved on
February 16, 2017, except as modified by the following stipulations.
Minor Amendment Z2022071: Development of the site shall be in compliance with the
Narrative Report entitled “Special use Permit Z99-111 Redhawk Combined Cycle Power
Plant SUP Minor Amendment 2021196”, dated March 31, 2022, consisting of 23 pages,
including attachments, and stamped Approved on May 18, 2022.
Minor Amendment SU250017: Development of the site shall be in compliance with the
Narrative Report entitled “Special Use Permit SU250017 Redhawk Combined Cycle Power
Plant SUP Minor Amendment Narrative Report”, dated May 13, 2025, consisting of 24 pages,
including attachments, and stamped Approved on June 11, 2025.
Complied with.
c. Development of the site shall be in compliance with all applicable Maricopa County Air
Quality rules and regulations.
Complied with.
d. The applicant shall survey the subject property for cultural resources and submit the survey
to the State Historic Preservation Office for review and comment prior to zoning clearance.
Complied with.
e. The applicant shall provide documentation for legal access to site.
Complied with. Recorded easements are 01-0477699 and 01-1065838.
f.
The access easement and parking spaces (both permanent and temporary) shall be surfaced
with a form of dust-proofing deemed acceptable by the Maricopa County Department of
Environmental Services at the time of zoning clearance.
Complied with.
g. The applicant shall mitigate area well problems within the area of influence by taking
prompt corrective action. The area of influence shall be defined as that area within which
the water table drawdown may exceed ten feet over any five-year period from and after the
date of approval of this Special Use Permit (SUP) by the Maricopa County Board of
Supervisors, solely as a direct result of pumping of 3,350 acre-feet/year at the Redhawk
Site, based upon a study approved by the Department of Water Resources (See map in
application narrative entitles “Area of 10 feet Drawdown; Pumping 5 years at 3,350 AF/Yr).”
If the results of the integrated water study show a larger Area of Influence for Redhawk
(3,350 acre feet per year) than Pinnacle West specified, then Pinnacle West shall increase
the Area of Influence to reflect the integrated water study results. The applicant will bear
the cost of corrective action to restore any domestic wells to production which meet each of
the following criteria:
i. the well is used solely as a domestic well from and after the date of approval of this
Special Use Permit by the Maricopa County Board of Supervisors;
ii. the well was an active well as of the date of the approval of this Special Use Permit
by the Maricopa County Board of Supervisors;
iii. the well is within the applicant’s area of influence;
Redhawk SUP Z99-111 Major Amendment
iv. the well cannot sustain the production necessary to meet the domestic uses
established as of the date of approval of the Special Use Permit by the Maricopa
County Board of Supervisors; and
v. the loss of production is not caused by the domestic well owner or by the owner’s
equipment.
In the event all of the above-listed criteria are met, the owner(s) of such well shall notify
the Applicant at the phone number or address which shall be kept actively on file with the
Maricopa County Planning and Development Department. The applicant shall initiate
corrective action within 72 hours of receipt of such notice, even if the corrective action is
temporary (the “Response Period”). In the event the applicant has direct knowledge that all
of the criteria have been met the well owner is not required to supply any notice and the
Response Period set forth above shall run from the time the applicant acquired such
knowledge.
Proposed Modification: Replace reference to “Pinnacle West” with “the applicant.”
Well inventory was provided with the 2024 Minor Amendment.
The Redhawk Plant has been using substantially less water than allocated with the
maximum annual usage to date occurring in 2022 at 872.3 ac-ft. The applicant is
requesting a modification to SUP Stipulation G to add a trigger threshold of 1,172
ac-ft of annual water use before additional groundwater monitoring and reporting
is required.
h. The applicant shall submit an annual written report outlining the status of the development
until such time as the Special Use Permit expires. The first report shall be submitted on
April 30, 2001. The status report shall be reviewed by staff to determine compliance with
stipulations and whether the report needs to be reviewed by the Planning and Zoning
Commission. The status report shall also contain groundwater monitoring reports with
annual withdrawals as well as all other annual water use itemized by type and quantity. In
addition, the status report shall address the impact on wells in the defined Area of Influence
(drawdown). Implementation of the re-vegetation plan shall also be presented in this report
and shall include a detailed report in the progress of the re-vegetation plan.
Proposed Modification: Since the County does not require status reports any
longer, the Applicant is requesting removal of Stipulation h.
i.
Annual use of groundwater in excess of 3,350 acre-feet shall require additional groundwater
study and a major amendment to the Special Use Permit. The amendment shall be subject
to public hearings and Board of Supervisor approval. The groundwater study shall model
additional groundwater use to determine the expanded area of influence.
Groundwater use was not in excess of 3,350 acre-feet during the 2024 calendar
year interval. The additional required groundwater usage required for the
expansion project would not result in an exceedance of the annual allocated
amount.
j.
The initial construction and operation of the Redhawk Power Plant shall be limited to two
units. Prior to issuance of building permits and construction of the additional two units,
proof of contractual rights to treated effluent or other renewable water supply shall be
required and submitted to staff.
Redhawk SUP Z99-111 Major Amendment
Complied with.
k. Prior to zoning clearance the applicant shall provide a “will serve” letter from a fire service
provider that has obtained certification from the State Fire Marshall. The applicant shall also
provide a “will serve” letter from an ambulance service provider that has obtained
certification from the Arizona Department of Health Services.
Complied with. Documentation was submitted to MCP&D as part of prior
amendments. If required, additional documentation will be provided as part of the
application.
l.
Prior to the zoning clearance, the applicant shall provide a “will serve” letter from a qualified
service provider for natural gas.
Complied with. Documentation was submitted to MCP&D as a part of prior
amendments. If required, additional documentation will be provided as part of the
application.
m. Appropriate permitting shall be obtained from the Arizona Department of Environmental
Quality prior to construction of an onsite waste disposal system.
Complied with. Septic Permit issued May 29, 2002 by MCESD (File Number
011469). The increase in employees would still result in a total staff number
below the maximum employees used for the septic sizing calculations for the
existing system and associated permit (the facility was sized for up to 62
employees). No revisions to the system or associated permit would be required for
the expansion project.
n. All outdoor lighting shall be designed as recommended by the International Dark-
Sky Association and shall be in compliance with the Maricopa County Building Code, Section
2318, Outdoor Light Control Provisions.
Complied with.
o. All makeup water surge and brine concentrator ponds shall be lined and inspected by
representatives of the Maricopa County Planning and Development Department, Building
and Safety Division prior to use.
Existing ponds complied with required inspections. All new ponds associated with
the 2024 SUP amendment will be lined and will comply with inspection
requirements. No ponds are proposed as part of this amendment.
p. This Special Use Permit shall expire 40 years from the date of approval by the Board of
Supervisors.
The addition of additional units extends the operational life of the Project by a
minimum of an additional 40 years; therefore, the applicant is requesting removal
of Stipulation p, or if not feasible, an extension for an additional 40 years, expiring
in 2070.
q. Major changes to this Special Use Permit shall be processed as a revised application in the
same manner as the original application, with final determination made by the Board of
Supervisors following recommendation by staff and the Planning and Zoning Commission.
Minor changes may be administratively approved by staff of the Planning and Development
Department. Reduction in use and intensity, (i.e. decreased building footprint, increased
setback, decreased building height, etc.), regardless of percent change, shall be considered
a minor change.
Redhawk SUP Z99-111 Major Amendment
Applicant is aware of this requirement. Five minor amendments have been
approved to date.
Case History for Z99-111:
Case No.
Description
Status
Date
Notes
Z99-111
Original SUP
Approved
5/17/2000
CPA99-03
Major Comprehensive
Plan Amendment
Approved
Change Tonopah Area plan land use
designation from Rural to Industrial
on 460 acres of the property, and
Rural to Open Space on the remainder
of the property (1,388 acres)
Z2000149
Minor Amendment
Approved
11/6/2000
Update equipment and structure
layout, road alignments, storm water
channels and basins, pond sizing
Z2003071
Minor Amendment
Approved
12/10/2003
Addition of guard shack and updated
fencing for both north and south
properties
Z2006161
Minor Amendment
Closed
12/16/2011
Due to inactivity
Z2008033
Status Report
Approved
1/8/2009
Subject to resolution of Z2006161
Z2009025
Status Report
Closed
4/23/2010
Deferring to Z2010027
Z2010027
Status Report
Closed
7/27/2011
Subject to resolution of Z2006161
B201206711 to 6714
As-Built Permits
Submitted
11/2/2012
Memorandum of
Understanding
Approved
12/10/2014
Date received by APS Legal
B201206711 to 6714
As-Built Permits
Cancelled
4/23/2015
Per Memorandum
B201002806
Grading Permit
Approved
1/25/2016
Z2012087
Minor Amendment
Approved
2/16/2017
Updated Site Development and
compliance with V201101816/7.
Encompassed all site changes since
2003.
Z2017040
Status Report
Approved
7/7/2017
Z2018040
Status Report
Approved
5/18/2018
CPA2019005
Major Comprehensive
Plan Amendment
Approved
12/11/2019
Change land use designation on 1,423
acres to Utilities from Open Space
Z2019032
Status Report
Approved
3/17/2020
Z2020028
Status Report
Approved
5/18/2020
Z2021046
2020 Status Report
Approved
5/28/2021
Z2022071
2021 Minor Amendment
Approved
05/18/2022
Added planned construction of East
Makeup Water
Surge Pond and East Brine
Concentrator Surge Pond
Z2021160
Agave Floodplain Use
Permit FCP2021575
Approved
03/22/2022
Grading a new solar field, Installation
of the Solar panels,
and 8’ Chain Link Fence
Z2023044
2022 Status Report
Approved
7/3/2023
Z2024054
2023 Status Report
Approved
SU250017
2024 Minor Amendment
Approved
6/11/2025
Chiller Equipment Modules and TES
Tank
r. Non-compliance with the site plan and narrative report or the conditions of approval will be
treated as a violation in accordance with provisions of the Maricopa County Zoning
Ordinance.
Applicant is aware of this requirement.
Redhawk SUP Z99-111 Major Amendment
Community Facilities and Services
The Redhawk Power Plant is encircled by a chain link security fence with locked gates and 24 hour
security. The Redhawk industrial facility areas will not be accessible to the public. Retention basins
will not pose a safety hazard to the general public. Plant personnel are trained and qualified to
work safely in all areas of the plant; therefore, specific fencing is not required around retention
areas.
The Redhawk Power Plant is located in the Arlington School District Number 47.
Public Utilities and Services
Service
Provider
Electric
APS
Gas
El Paso Natural Gas Co. and TransWestern
Telephone
CenturyLink
Police
Maricopa County Sheriff’s Office
Water
Private Well; Plant Owner / Operator (APS)
Fire
Plant Owner / Operator (APS); Responding agency - Tonopah Valley Fire
District
Security
Plant Owner / Operator (APS)
Refuse
Plant Owner / Operator (APS)
Sewer
Septic System; Plant Owner / Operator (APS)
Other Information
The Expansion Project was subject to review through the ACC CEC process and approved as noted
in the proposal narrative above. APS conducted extensive stakeholder coordination as part of the
CEC process.
Page | 1
Subdivision
Infrastructure
& Planning Program
301 W. Jefferson St.
Phoenix, AZ 85003
S u b d i vi s io n @ m a ri co p a .go v
e s d .m a r i c o pa .g o v
The Maricopa County Environmental Services Department (MCESD) has completed review
for the Redhawk Power Plant planning case(s). Please note the following MCESD
requirements for site development:
Subdivision Infrastructure and Planning –
An Approval to Construct application is required and must be submitted to MCESD’s
Subdivision & Infrastructure Program for water, reclaimed water and/or wastewater system
infrastructure.
For subdivision related questions, please contact the Subdivision and Infrastructure
Program at (602) 506-1058 or email subdivision@maricopa.gov.
Water/Wastewater Treatment –
For treatment related questions, please contact the Water/Wastewater Treatment Program
at (602) 372-2861 or email treatmentplantprogram@maricopa.gov.
Additional Notes –
*It should be noted that this document does not approve the referenced project. Comments are provided
for the benefit of the applicant for MCESD permit requirements and as an advisory to Maricopa County
Planning and Development Department. Other Maricopa County agencies may have additional
requirements. Final review and approval will be made through Planning and Development Department
procedures. Applicant may need to submit separate applications to the Maricopa County Environmental
Services Department for approval of proposed facilities regulated by the Department. Review of any such
application will be based on current regulations at the time of application.
Project Name: Redhawk Power Plant
Primary Contact Name: Kimberly
Ashcraft
Planning Application Type: Special Use
Permit - Major Amendment
APN(s): 401-44-007C
Reviewer: Joseph Churby, P.E.
Email: Joseph.Churby@maricopa.gov
Phone: 602-372-2754
Planner Name: Martin Martell
Planning Case #: SU250026
Date: August 14, 2025
Water and Waste Management Division
Zachary Kobza, P.E.
Planning & Development
301 W. Jefferson St., Suite 170
Phoenix, Arizona 85003
Phone: (602) 723-5248
Fax: (602) 506-8762
www.maricopa.gov/planning
Email address:
Zachary.Kobza@maricopa.gov
Planning & Development
Engineering Plan Review
Date:
October 9, 2025
Memo To: Darren Gerard, AICP, Planning Manager, Department of Planning &
Development
Attn:
Martin Martell, Planner, Planning & Development Services
cc:
Bob Fedorka, PE, Engineering Manager, Planning & Development
From:
Zachary Kobza, PE, Senior Plans Examiner Engineer, Planning &
Development
Subject:
SU250026 – Major SUP Amendment for an addition of eight
combustion turbine generator units and associated equipment and
infrastructure to Redhawk Power Plant.
APN(s):
401-44-007C
Engineering Review has reviewed the first plan and report routed for review on
09/12/2025, for the subject application and has no further objections:
The following stipulations will apply:
1. The requirement for the retention basin to drain within 36 hours must be
maintained.
2. Engineering review of planning and/or zoning cases is for conceptual design
only. All development and engineering design shall be in conformance with
Section 1205 of the Maricopa County Zoning Ordinance; Drainage Policies and
Standards; Floodplain Regulations for Maricopa County; MCDOT Roadway
Design Manual; and current engineering policies, standards and best practices
at the time of application for construction.
3. Based on the conceptual design nature of the information submitted, changes
to the site layout may be necessitated by the final engineering design of the
drainage infrastructure
Please contact me with any questions.
Redhawk SUP Z99-111 Major Amendment
ATTACHMENT 1 – Memorandum of Understanding
Redhawk SUP Z99-111 Major Amendment
ATTACHMENT 2 – Well Inventory Report
Redhawk SUP Z99-111
Attachment 2
Attachment 2
Redhawk Well Inventory Report
The inventory consists of 3 wells. Data collected on March, 3rd 2025 is as follows:
Well Owner
Name
ADWR Well
No.
Production
(GPM)
Water Table
Level (Ft)
Hixon
55-581485
Not Measured
104.54 (below
surface)
Merrill - well A
55-542813
Not Measured
87.37 (below
surface)
Merrill - well B
55-558798
Not Measured
83.37 (below
surface)
Measurements to date:
WATER LEVEL (Ft below surface)
DISCHARGE
DATE
Hixon
Merrill -
well A
(west well)
Merrill -
well B
(east well)
Hixon
Merrill -
well A
(west well)
Merrill -
well B
(east well)
3/19/2001
95.17
NA
76.95
100
21
20
6/13/2001
95.6
81.8
78.21
NR
NR
NR
12/11/2001
95.25
80.97
77.78
NR
NR
NR
1/24/2002
95.32
81
77.87
NR
NR
NR
4/25/2002
95.29
82.05
78.04
NR
NR
NR
10/15/2002*
95.52
81.46
78.4
NR
NR
NR
3/12/2003
95.18
80.9
77.95
NR
NR
NR
1/7/2004
95.44
81.18
78.6
NR
NR
NR
1/6/2005
95.35
81.25
78.18
NR
NR
NR
2/17/2006
95.81
81.4
78.59
NR
NR
NR
1/7/2007
95.7
81.45
78.7
NR
NR
NR
1/22/2008
96.2
81.46
78.79
NR
NR
NR
1/26/2009
96.22
81.56
78.95
NR
NR
NR
1/6/2010
96.4
82.2
79.66
NR
NR
NR
1/26/2011
96.42
82.02
79.27
NR
NR
NR
1/20/2012
96.4
82.2
79.48
NR
NR
NR
1/29/2013
96.5
82.08
79.25
NR
NR
NR
2/10/2014
96.47
82.05
79.77
NR
NR
NR
1/23/2015
96.75
--
79.88
NR
NR
NR
Redhawk SUP Z99-111
Attachment 2
1/26/2015
--
82.41
--
NR
NR
NR
4/14/2016
96.67
--
80.51
NR
NR
NR
4/15/2016
--
82.98
--
NR
NR
NR
2/3/2017
96.99
--
80.63
NR
NR
NR
4/11/2017
--
80.63
--
NR
NR
NR
4/16/2018
97.3
86.85
84.71
NR
NR
NR
3/28/2019
97.8
87.9
84.75
NR
NR
NR
2/4/2020
98.79
81.17
81.95
NR
NR
NR
11/5/2021
106.371
89.021
87.011
NR
NR
NR
3/1/2022
102.45
86.44
84.96
NR
NR
NR
1/18/2023
102.17
86.29
83.37
NR
NR
NR
3/28/2024
104.54
87.37
83.37
NR
NR
NR
3/7/2025
106.08
88.68
86.23
NR
NR
NR
*Due to consistency of readings over the past 24 months ending 2002, future
measurements will be taken on an annual basis.
1 Residential well measurements for 2021 were taken 11/3/21 – 11/5/21.
The Planning and Zoning stipulation also requires APS to supply a contact number and
address for the residents to contact in the event a well problem should arise. This
information is to be kept on file with Maricopa County Planning and Zoning.
As of this report, the contact phone number and address are:
Andre Bodrog
Redhawk Power Plant Manager
Arizona Public Service
400 N 5th Street, MS 5100
Phoenix, AZ 85004
Phone: 602-407-7801
Fax: 602-407-7813
Redhawk SUP Z99-111 Major Amendment
ATTACHMENT 3 – Groundwater Monitoring Report
Redhawk SUP Z99-111
Attachment 3
Attachment 3
Redhawk Groundwater Monitoring Report
In the calendar year 2024, 593.20 acre-feet of water were withdrawn from the Redhawk
property. This withdrawal quantity was reported to ADWR on or before March 31, 2025 on
form WQ2004 (Water Right #58-107804.0002).
Groundwater use was not in excess of 3,350 acre-feet during the 2024 calendar year
interval.
Annual Water Use
Year
Ground
(acre-ft)
Surface
(acre-ft)
Effluent
(acre-ft)
2000
NA
NA
NA
2001
NA
NA
NA
2002
83
0
2,358
2003
438
0
3,049
2004
17
0
2,390
2005
18
0
3,520
2006
15
0
4,304
2007
33
0
3,787
2008
51
0
3,737
2009
210
0
3,551
2010
426
0
2,843
2011
347
0
3,051
2012
521
0
3,713
2013
273
0
3,077
2014
239
0
3,333
2015
346
0
3,470
2016
579
0
4,159
2017
494
0
3634
2018
446.38
0
3,433
2019
366
0
3,817
2020
390
0
4,380
2021
625
0
4,236
2022
872.30
0
4,717.02
2023
487.06
0
4,043.32
2024
593.20
0
3,440.90
Redhawk SUP Z99-111 Major Amendment
ATTACHMENT 7 – Certificate of Environmental Compatibility
llllllllllllllllllllllll
II Il0lll0lll0ll0ll w W I
1
BEFORE THE ARIZONA CORPORATION (,u1vl1vllD»3l\)l\
2
COMMISSIONERS
3
4
5
JIM O`CONNOR - CHAIRMAN
LEA MARQUEZ PETERSON
ANNA TOVAR
KEVIN THOMPSON
NICK MYERS
6
7
DOCKET no. L-00000D-24-0156-00234
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79586
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DEcilslon no.
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Arizona Corporation Commission
DOCKETED
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OUT 2 1 2024
DOCKETED BY
.__Lam....
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IN TI IE MATTER OF THE APPUCArl0N OF
ARIZONA PUBLIC SFRVICE COMPANY. IN
CONFORMANCE WITH TIIE REQUlRIMENTS
OF ARIZONA RFVISED STATUFS 40-360. IT
SEQ.. FOR A CERTIFICATE OF
ENVIR()NMENTAL COMPATII3II.IIY
AUTHORIZING TIIF REDIIAWK POWIR
PLANT EXPANSION PROJECT. WIIICII
INCLUDES TIIF CONSTRUCII()N OI"
NATURAL GAS TURBINFS. A 500KV
SWITCI IYARI) ANI) Rl=l,A11=1> FACILlllIS.
ALL L()CAIl[) TW() Mlufs S()U1IIEASI OF
TIIII INTERSECTION or l=LLIOT ROAD AND
WINTERSBURG R()AI) IN MARIC()PA
COUNTY, ARIZONA.
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October 8. 2024
Open Meeting
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BY THE COMMISSION:
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Pursuant to A.R.S. § 40-360 et seq.. alter due consideration of all relevant matters, the
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Arizona Corporation Commission ("Commission") finds and concludes that the Certificate of
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Environmental Compatibility ("CEC") issued by the Arizona Power Plant and Transmission Line
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Siting Committee ("Siting Committee") is hereby approved as granted by this ()rder.
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The Commission. in reaching its decision. has balanced all relevant matters in the broad
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public interest. including the need for an adequate. economical. and reliable supply of electric power
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Decision No.
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L-00000D-24-0 l 56-00234
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the environment and
this
and kinds
on
effect thereof
with the desire to minimize the
state.
ecology of
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that granting the Project a CEC is in the public interest.
The Commission further finds and concludes that in balancing the broad public interest in this
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matter:
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I. The Project is in the public interest because it aids the state in meeting the need for an
adequate. economical. and reliable supply of electric power.
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2. In balancing the need br the Project with its effect on the environment and ecology of the
state. the conditions placed on the CEC effectively minimize its impact on the
environment and ecology of the state.
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3.
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The conditions placed on the CEC resolve matters concerning the need for the Project and
its impact on the environment and ecology of the state raised during the course of
proceedings and. as such. serve as the findings on the matters raised.
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4. In light of these conditions. the balancing in the broad public interest results in favor of
granting the CEC.
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Decision No.
79586
L-00000D-24-0156-00234
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THE CEC ISSUED BY THE SITING COMMITTEE IS INCORPORATED
HEREIN AND IS APPROVED BY ORDER OF THE
ARIZONA CORPORATION COMMISSION
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AIRMAN O'CONNOR
CO
s
M
E
Q EZ PETERSON
»
DISSENT
COMMISSIONER TOVAR
COMMI
COMMI
IONER
HOMPSON
ER MYERS
Qut~P/;»
xed at the Capitol, in the City of Phoenix,
, 2024.
IN
WITNESS
WHEREOF,
1,
DOUGLAS
R.
CLARK.
Executive Director of the Arizona Corporation Commission.
have hereunto, set my hand and caused the official seal of this
Commission to be a
this
6* day ofllmbe.
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Executive Director
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79586
3
Decision No.
L-000000-24-0156-00234
endm
Anna Tovar
COMMISSIONER
(602)542-3935 OFFICE
To va r We b @a zc c .g o v
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COMMISSIONERS
JimO'C o n n o r C h a i r m a n
lea Ma rq u e z Pe te rs o n
Anna Tovar
Kevin Th o m p s o n
Nick Myers
ARIZONA CORPORATION COMMISSION
OFFICE oF CoM mlsslonER ANNA TOVAR
October 2 l , 2024
Docket Control
Arizona Corporation Commission
1200 W. Washington St.
Phoenix, AZ 85007
Re: In the matter of the application of Arizona Public Service Company, in conformance with
the requirements of Arizona revised statues 40-360, ET SEQ.. for a Certificate of Environmental
Compatibility authorizing the Red hawk Power Plant Expansion Project, which includes the
construction of Natural Gas Turbines. a 500kV switchyard and related facilities, all located two
miles Southeast of the intersection of EIliot Road and Wintersburg Road in Maricopa County,
Arizona. (L-00000D-24-0] 56-00234)
Dear Commissioners and Parties:
l am confused by the advice our Legal Division's provided in this matter. This last June there
was a UNS Electric ("UNSE") line siting matter that came before the Commission for
consideration where, just as in this case. the natural gas generating units were below the 100-
megawatt threshold set forth in Arizona Revise Statute §40-360. In that matter, UNSE sought a
disclaimer ofjurisdiction instead of seeking a Certificate of Environmental Compatibility
("CEC"). It is my view that the Commission had jurisdiction over that project and should have
decided whether or not it was appropriate to issue a CEC. The majority decided otherwise.
What is battling is that in this case, even though the facts are very similar, in that the natural gas
generating units are also well under the l00-megawatt threshold set forth in the statute, the
majority determined it did have jurisdiction over the Arizona Public Service's ("APS") request.
The rationale? The Legal Division indicated that the Commission had jurisdiction because APS
submitted to the Commission'sjurisdiction of the Commission. This defies logic and the law.
Under that theory it would seem the Commission could issue driver's licenses as long as those
seeking one submitted to the Commission'sjurisdiction. In short, the Commission either has
jurisdiction or it doesn't.
While l truly believe the Commission had jurisdiction over the UNS Electric project and the
project at issue in this matter, what is more troubling is that the current majority does not show
any concern that the investment in generating assets today will have a 50-year impact that
ratepayers will shoulder when technologies are rapidly changing. l don't think APS truly
explored alternatives that could have provided the same reliability. There should be careful
consideration regarding generation, and it should not involve political catchphrases such as a
1200 WEST WASHINGTON STREET;PHOENIX, AR IZON A 850072927
www.azcc.gov
Decision No.
79586
L-00000D-24-015600234
"green new deal" or "deep state issues" when in the end I think we all want safe and reliable
service at just and reasonable rates, and clean air. We all know the sun doesnt always shine and
that the wind doesn't always blow, but we do need to very carefully consider where the utilities
we regulate invest money in generation. It is tor these reasons that l must dissent.
Sincerely,
0m4
Java/L
Anna Tovar
Commissioner
.~
in
.
VA
.
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: ,
1200 W. Washington Street, Phoenix, AZ 85007 I 6025423931 I azcc.gov
79586
Decision No.
L-000000-24~015600234
B E F O R E THE ARIZONA POWER PLANT
AND TRANSMISSION LINE SITING COMMITTEE
DOCKET NO. L-00000D-24-0156-
00234
Case No. 234
CERTIFICATE OF
ENVIRONMENTAL
COMPATIBILITY
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ex?
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=*P
IN THIS MATTER OF THE APPLICATION
OF ARIZONA PIIRIIC SFRVICI3
C O M P A NY . IN CONFORM A NCE WITII
TIIH RFOI IIRIQMENTS OF ARIZONA
RFVISFD STATIITFS 8 40-360,ET SEQ.,
I()R A CIQRTIFICATIQ OF
I€NVIR()NMI{NTAI, COMPATIRII .ITY
AI ITHORIZING TIIP RFUHAWK POWRR
PI ,ANT FXPANSION PROJFCT. WHICH
INCI I}I)I:q IIIF FONSTRIICTIGN OF
NAIIIRAI GAS TIIRBINFS. A sookv
SWI l(IHYARD AND RH ATFD
FA(lll IIIFS.
S()III IIFAS l OF
J
EI,I.lor RUAD ANI) WINTRRSBURG
ROAD IN MARICOPA COUNTY,
AR I Z O NA.
v
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an-
INTRODUCTION
Adam Stafford
Chairman, Designee for Arizona Attorney
General Kris Mayes
Leonard Drago
Designee for Director, Arizona Department of
Environmental Quality
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ALl, I,ocA1*F,o Two Mll.l€s
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am lNTERSF(l,Tl()N OF
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A.
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Pursuant to notice given as provided by law, the Arizona Power Plant and
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Transmission Line Siting Committee ("Committee") held public hearings on August 19 -
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22, 2024, in Goodyear, Arizona, in conformance with the requirements of Arizona
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Revised Statutes ("A.R.S.") § 40-360, or seq., for the purpose of receiving evidence and
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deliberating on the Application of Arizona Public Service Company ("APS" or
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"Applicant") for a Certificate of Environmental Compatibility ("Certificate") in the
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above-captioned case.
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The following members and designees of members of the Committee were
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present at one or more of the hearing days for the evidentiary presentations, public
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comment, and/or for the deliberations:
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Decision No.
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L-00000D-24-0156-00234
David French
Dcsignee for Director, Arizona Department of
Water Resources
Nicole Hill
Designee for Director, Governor's Fncrgy
Office
Gabby Saucedo Mercer
I)esignee
of
the
Chairman,
Arizona
Corporation Commission ("Commission")
Jon Gold
Appointed Member, representing the General
Public
Margaret "Toby" Little
Appointed Member, representing the General
Publie
David Kryder
Appointed Member, representing Agricultural
Interests
Roman l'ontes
Appointed Member. representing Counties
Applicant was represented by Linda J. Benally of Pinnacle West Capital
Corporation and J. Matthew Derstine of Snell & Wilmer. LLP. The following parties
were granted intervention pursuant to A.R.S. § 40-360.05: Western Resource Advocates,
represented by Emily Doerfler. No person made a limited appearance pursuant to A.R.S.
§ 40-360.05(B).
At the conclusion of the hearing, the Committee, after considering the (i)
Application, (ii) appearances of the Applicant and intervenor, (iii) evidence, testimony,
and exhibits presented by the Applicant, and (iv) comments of the public, and being
advised of the legal requirements of A.R.S. §§ 40-360 through 40-360.13, upon notion
duly made and seconded, voted 8 to 0 to grant the Applicant, its successors and assigns,
this Certificate for construction of the Redhawk Power Plant Expansion Project
("Project") as described below.
B.
PROJECT DESCRIPTION
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The Project is an approximately 397 megawatt ("MW") natural gas-fired electric
generation facility consisting of eight (8) General Electric LM6000 simple-cycle
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Decision No.
79586
L-000000-24-015600234
combustion turbines, each with a nameplate capacity of49.6 MW, along with supporting
infrastructure.
The Project will be constructed within the existing Redhawk Power Plant site
located at 11600 South 363"' Avenue in Maricopa County, approximately five miles
northwest of Arlington, Arizona. The Redhawk Power Plant received a Certificate from
the Committee with respect to the site in Line Siting Case No. 95, approved by the
Commission in Decision No. 62324 ("CEC No. 95"). A copy olCEC No. 95 is attached
hereto as Exhibit A. The Project will be located entirely on land owned by APS within
the existing plant site, and for this reason APS does not require a right-of-way to access
the site. Maps showing the general location of the Project within the existing Redhawk
Power Plant site and a depiction of the proposed Project facilities are shown in Exhibit
B.
CONDITIONS
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The Conditions imposed in Cl
No. 95 remain in full force and effect for the
entire Redhawk Power Plant site. This Ccrtiticatc is granted upon the following
Conditions, applicable to the site of the Project:
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This authorization to construct the Projcct shall expire ten (10) years from
the date this Certificate is approved by the Commission, with or without modification.
Construction of the Project shall be complete, such that the Project is in service within
this ten-ycar timeframe. llowever, prior to the expiration of the time period, the
Applicant may request that the Commission extend the time limitation.
In the event the Projcct requires an extension of the term(s) of this
Certificate prior to completion of construction, the Applicant shall file such time
extension request at least one hundred and eighty (180) days prior to the expiration of
the Certificate. The Applicant shall use reasonable means to promptly notify Maricopa
County and all landowners and residents within a three (3) mile radius from the center of
the Project, all persons who made public comment at this proceeding who provided a
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Decision No.
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3.
a.
All applicable land USC regulations,
b.
All applicable zoning stipulations and conditions including, but not limited
to, landscaping and dust control requirements,
c.
All applicable air permitting, water use, discharge and/or disposal
requirements of the Arizona Department of Water Resources, the
Maricopa County Air Quality Department, and the Arizona I)cpartment of
Fnvironmental Quality,
d.
All applicable noise and lighting control standards, and
e.
All applicable regulations governing storage and handling of hazardous
chemicals and petroleum products.
4.
construct, operate, and maintain the Project required by any governmental entity having
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mailing or email address, and all parties to this proceeding. The notification provided
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will include the request and the date, time, and place of the hearing or open meetings
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during which the Commission will consider the request for the extension. Notification
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shall be no more than three (3) business days after the Applicant is made aware of the
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hearing date or the open meeting date.
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During the development, construction, operation, maintenance, and
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reclamation of the Project, the Applicant shall comply with all existing applicable air
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and water pollution control standards and regulations, and with all existing applicable
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statutes, ordinances, master plans, and regulations of any governmental entity having
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jurisdiction including, but not limited to, the United States of America, the State of
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Arizona,
Maricopa County. and their agencies and subdivisions including, but not
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limited to, the lollowing:
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The Applicant shall obtain all approvals and permits necessary to
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jurisdiction including, but not limited to, the United States of America, the Statc of
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Arizona, Maricopa County, and their agencies and subdivisions.
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5.
The Applicant shall comply with the Arizona Game and Fish Department
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("AGFD") guidelines for handling protected animal species, should any be encountered
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Decision No.
79586
L-000000-24-0156-00234
during construction and operation of the Project, and shall consult with AGFD or U.S.
Fish and Wildlife Service, as appropriate, on other issues concerning wildlife.
6.
The Applicant shall design the Project's interconnection facilities to
incorporate reasonable measures to minimize electrocution of and impacts to avian
species in accordance with the Applicant's avian protection program. Such measures
will be accomplished through incorporation of Avian Power Line Interaction Committee
guidelines set forth in the current versions of Suggested Practices for Avian Protection
on Power Lines and Reducing Avian Collisions with Power Lines manuals.
7.
The Applicant shall consult the State Historic Preservation Office
("SIIPO") pursuant to A.R.S. §§ 41-861 through 41-864, the State Historic Preservation
Act. Construction for the Project shall not occur without SHPO concurrence. Any
project involving federal land is a federal undertaking and requires SIIP() concurrence
on the adequacy of the survey and area of potential effects. The Applicant shall
coordinate with SHPO regarding the status of Section 106 consultation.
8.
If any archaeological, paleontological, or historical site or a significant
cultural object is discovered on private, state, county, or municipal land during the
construction or operation of the Project, the Applicant or its representative in charge
shall promptly report the discovery to the Director of the Arizona State Museum
("ASM"), and in consultation with the Director, shall immediately take all reasonable
steps to secure and maintain the preservation of the discovery as required by A.R.S. §
41-844 or A.R.S. §41-865, as appropriate.
9.
The Applicant shall comply with the notice and salvage requirements of
the Arizona Native Plant Law (A.R.S. § 3-901 et seq.) and shall, to the extent feasible,
minimize the destruction of native plants during the construction and operation of the
Project.
10.
The Applicant shall make every reasonable effort to promptly investigate,
identify, and correct, on a case-specific basis, all complaints of interference with radio or
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Decision No. 7
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L-00000024-0156-00234
television signals from operation of the Project addressed in this Certificate and where
such interference is caused by the Project, take reasonable measures to mitigate such
interference. The Applicant shall maintain written records for a period of five (5) years
of all complaints of radio or television interference attributable to operations, together
with the corrective action taken in response to each complaint. All complaints shall be
recorded to include notation on the corrective action taken. Complaints not leading to
specific action or for which there was no resolution shall be noted and explained. Upon
request, the written records shall be provided to the Staff of the Commission. The
Applicant shall respond to complaints and implement appropriate mitigation measures.
In addition, the Project shall be evaluated on a regular basis so that damaged insulators
or other linc materials that could cause interference are repaired or replaced in a timely
manner.
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If human remains and/or funerary objects are encountered during the
course of any ground-disturbing activities related to the construction or maintenance of
the Project, the Applicant shall cease work on the affected area of the Project and notify
the l)irector of the ASM as required by A.R.S. § 41-865 for private land, or as required
by A.R.S. § 41-844 for state, county, or municipal lands.
12.
Within one hundred twenty (120) days of the Commission's decision
approving this Certificate, the Applicant shall post signs in or near public rights-of-way,
to the extent authorized by law, reasonably adjacent to the Project giving notice of the
Project. Such Signage shall be no smaller than a roadway sign. The sign shall advise:
a. The future site of the Project,
b. A phone number and website for public information regarding the Project,
and
c. Refer the public to the Docket,
Such signs shall be inspected at least once annually and, if necessary, be repaired or
replaced, and removed at the completion of construction.
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Decision No.
79586
L-000000-24-0156-00234
The Applicant shall use non-specular conductor and non-rellcctive
The Applicant shall participate in good faith in state and regional
The Applicant shall make every reasonable effort to communicate the decision
either approving or disapproving the Certificate in digital media.
13.
At least ninety (90) days before construction commences on the Project,
the Applicant shall provide Maricopa County and known builders and developers who
arc building upon or developing land within three (3) miles from the center of the
Project with a written description, including the approximate height and width
measurements of all structure types of the Project. The written description shall identity
the location of the Project and contain a pictorial depiction of the facilities being
constructed. The Applicant shall also encourage the developers and builders to include
this information in their disclosure statements. Upon approval of this Certificate by the
Commission. the Applicant may commence construction of the Project.
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surfaces for the transmission Linc structures on the Project.
IS.
The Applicant shall be responsible for arranging that all field personnel
involved in the Project receive training as to proper ingress, egress, and on-sitc working
protocols for environmentally sensitive areas and activities. Contractors employing such
field personnel shall maintain records documenting that the personnel have received
such training.
16.
Thc Applicant shall follow the most current Westcm Electricity
Coordinating Council ("WECC") and North Amcrican Electric Reliability Corporation
("NERC") planning standards, as approved by the Federal Energy Regulatory
Commission ("FERC"), National Flectrieal Safety Code ("NlSC") standards, and
Federal Aviation Administration ("FAA") regulations.
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transmission study forums to coordinate transmission expansion plans related to the
Project and to resolve transmission constraints in a timely manner.
18.
When Project facilities are located parallel to and within one hundred
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Decision No. 79586
L~000000-24-0158-00234
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(100) feet of any existing natural gas or hazardous pipeline, the Applicant shall:
a. Ensure grounding and cathodic protection studies are performed to show
that the Project's location parallel to and within one hundred (100) feet of
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such pipeline results in no material adverse impacts to the pipeline or to
public safety when both the pipeline and the Project are in operation. The
Applicant shall take appropriate steps to ensure that any material adverse
impacts are mitigated. The Applicant shall provide to Staff of the
Commission, and file with I)ockct Control, a copy of the studies
performed and additional mitigation, if any, that was implemented as part
ofits annual compliance-certification letter, and
b. lnsure that studies are performed simulating an outage of the Project that
may be caused by the collocation of the Project parallel to and within one
hundred (l00) feet of the existing natural gas or hazardous liquid pipeline.
The studies should either: (i) show that such simulated outage does not
result in customer outages, or (ii) include operating plans to minimize any
resulting customer outages. The Applicant shall provide a copy of the
study results to Staff of the Commission and file them with Docket Control
as part of the Applicant's annual compliance certification letter.
19.
The Applicant shall submit a compliance certification letter annually,
identifying progress made with respect to each condition contained in this Certificate,
including which conditions have been met. The letter shall be submitted to the
Commission's Docket Control commencing on I)ecember l, 2025. Attached to each
certification letter shall be documentation explaining how compliance with each
condition was achieved. Copies of each letter, along with the corresponding
documentation, shall be submitted to the Arizona Attorney General's Office. With
respect to the Project, the requirement for the compliance letter shall expire on the date
the Project is placed into operation. Notification of such filing with Docket Control shall
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Decision No. _2958&_
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(a)
Prepare a report assessing whether use of hydrogen at the Project is
economical, feasible, and safe,
(b)
Include in the report an assessment and quantification of any
changes in air emissions or any other change the Project's impact to the
be made to Maricopa County, all parties to this Docket, and all parties who made a
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limited appearance in this docket.
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20.
The Applicant shall provide a copy of this Certificate to Maricopa County.
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Any transfer or assignment of this Certificate shall require the assignee or
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successor to assume, in writing, all responsibilities of the Applicant listed in this
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Certificate and its conditions as required by A.R.S. § 40-360.08(A) and Rule Rl4-3-
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213(F) of the Arizona Administrative Code.
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In the event the Applicant, its assignee, or successor seeks to modify the
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Certificate's terms at the Commission, it shall provide copies of such request to
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Maricopa County, all parties to this Docket, and all parties who made a limited
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appearance.
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The Certificate Conditions shall be binding on Applicant, its successors,
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assignee(s) and transferees, and any affiliates, agents. or lessees of the Applicant who
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have a contractual relationship with the Applicant concerning the construction,
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operation, maintenance, or reclamation of the Project. The Applicant shall provide in
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any agreement(s) or lease(s) pertaining to the Project that the contracting parties and/or
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Iessee(s) shall be responsible for compliance with the Conditions set forth herein, and
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the Applicant's responsibilities with respect to compliance with such Conditions shall
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not cease or be abated by reason of the fact that the Applicant is not in control of or
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responsible for the operation and maintenance of the Project facilities.
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At least 120 days before operating the Project with hydrogen blended fuel
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for normal operations of the Project (not including any pilot projects), the Applicant
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must first:
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Decision No.
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L-00000D-24-0156-00234
environment of the area that will occur as a result of the use of hydrogen fuel,
(c)
File the report in this proceeding, and
(d)
Serve a copy of the report on the parties.
25.
Before utilizing a hydrogen blend of greater than 35% or making any
substantial modifications to the Projcct's generating units for the purpose of enabling use
of hydrogen fuel, the Applicant must first obtain an amended Certificate for the
proposed project to convert its facility into a hydrogen compatible plant.
FINDINGS OF FACT ANI) CONCLUSIONS OF LAW
This Certificate incorporates the following Findings of Fact and Conclusions of
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Law:
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The Project aids the Stale and the Southwest Region of the llnited States
in meeting the need Tor an adequate. economical, and reliable supply ofelcctric power.
2.
When constructed in compliance with the conditions imposed in this
Ccrtilicatc, the Project aids the State, preserving a sale and reliable electric transmission
system.
3.
During the course of the hearing, the Committee considered evidence on
the environmental compatibility of the Project as required by A.R.S. § 40-360 et seq.
4.
The Project and the conditions placed on the Project in this Certificate
effectively minimize the impact of the Project on the environment and ecology of the
State.
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5.
lhc Conditions placed on the Project in this Certificate resolve matters
concerning balancing the need for the Project with its impact on the environment and
ecology of the Statc arising during the course of the proceedings and, as such, serve as
findings and conclusions on such matters.
6.
The Project is in the public interest because the Projcct's contribution to
meeting the need for an adequate, economical, and reliable supply of electric power
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Decision No. 19586
L000000-24-0156-00234
DATED this Z A day of August, 2024.
TI IE ARIZONA POWER PLANT AND
TRANSMISSION LINE SITING COMMITTEE
l
By:
Adam StaffOrd, Chairman
CERTIFICATE OF MAILING
Pursuant to A.A.C. R 14-3-204, the ORIGINAL of the foregoing and 25 copies were
Iilcd this 24'
day of August, 2024, with:
Utilities Division-Docket Control
ARIZONA CORPORATION COMMISSION
1200 West Washington St.
Phoenix, AZ 85007
COPY of the foregoing mailed
this -9
day of August, 2024, to:
Tom Van Flein, General Counsel
ARIZONA CORPORATION COMMISSION
1200 W. Washington Strcet
Phocnix, Arizona 85007
je aldiv
azcc. ov
Britton Baxter and Ranelle Paladino, Directors
Utilities Division
ARIZONA CORPORATION COMMISSION
1200 West Washington Street
Phoenix, Arizona 85007
utildivservicebyemail@azcc.gov
///
1
outweighs the minimized impact of the Project on the environment and ecology of the
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State.
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79586
Decision No.
L.00000D-24-015600234
1
Glennie Reporting Services, LLC
1555 East Orangewood
Phoenix, Arizona 85020
admin@2lennie-reportin2.com
2
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Linda J. Benally
Pinnacle West Capital Corporation
400 North 5th Street, MS 8695
Phoenix, Arizona 85004
Linda.Benallv@pinnaclewest.com
Counsel for Applicant Arizona Public Service Company
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J. Matthew Derstine
Sncll & Wilmer, L.L.P.
One East Washington Street
Suite 2700
Phoenix, Arizona 85004
mderstine@swlaw.com
Counsel fOr Applicant Arizona Public Service Company
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O
Emily Doerller
Western Resource Advocatcs
1429 North IS Street, Suite 100
Phoenix, Arizona 85004
emilv.doertler (I westernresources.or2
Attorney for Western Resource Advocates
..,,,,/_,_4
'_,.,__
By:
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79586
Decision No.
P
ExhibitA
I
L0wwuu0wwwm4
I
lx
....w um nm ala ll\Il II IIII
BEFORE THEAMMMMQMM cw3Mlsslon
DOCKETED
F55 2 3 2000
696142750 BY
CARL J. KUNASEK
Chairman
JIM IRVIN
Commissioner
WILLIAM A. MUNDELL
Commissioner
• 4
1
2
3
4
5
6
7
8
9
10
CASE no. 95
Docket No. L-000001-99-0095
DECISION no._ 7 3
I I
12
ORDER
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14
15
16
IN THE MATTER OF THE APPLICATION
OF PINNACLE VVEST ENERGY
CORPORATION OR THEIR
ASSIGNEE(S), IN CONFORMANCE WITH
THE REQUIREMENTS OF ARIZONA
REVISED STATUTES 40-360.03 AND 40-
360-06, FOR A CERTIFICATE OF
ENVIRONMENTAL COMPATIBILITY
AUTHORIZING THE CONSTRUCTION OF
NATURAL GAS-FIRED, COMBINED
CYCLE GENERATING FACILITIES AND
ASSOCIATED INTRA-PLANT
TRANSMISSION LINES, SWITCHYARD,
AND RELATED FACILITIES IN
MARICOPA COUNTY, ARIZONA
LOCATED TWO MILES SOUTHEAST OF
THE INTERSECTION OF ELLIOT ROAD
AND WINTERSBURG ROAD IN
SECTIONS 14, 22, AND 23, TOWNSHIP 1
SOUTH, RANGE 6 WEST, GILA AND SALT
RIVER BASE AND MERIDIAN.
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17
CER TIFICA TE OF ENVIRONMENTAL COMPA TIBILITY
18
19
Pursuant to notice given as provided by law, the Arizona Power Plant and Transmission
20
21
Line Siting Committee, (the "Committee") held a public hearing at the Arizona Corporation
22
Commission, 1200 W. Washington, Phoenix, Arizona, on December 9, 1999, in conformance
23
24
with the requirements of Arizona Revised Statutes § 40-360 ez seq., for the purpose of receiving
evidence and deliberating on the Application of Pinnacle West Energy Corporation ("PWE") for
a Certificate of Environmental Compatibility ("Certificate") in the above-captioned case.
25
26
27
6:1394
DecisionNo.:
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79586
Decision No.
u
Exhibit A
I
Docket No.: L-0000t>
L-00000D-24-0156-00234
.
z,
1
The following members and designees of members of the Committee were present to.
deliberations and vote on the Application at the December 9, 1999 hearing:
2
Charles S. Pierson
3
l
Chairman, Designee for Arizona Attorney General
Janet Napolitano
4
5
6
7
8
9
10
Arizona Corporation Commission
Arizona Department of Environmental Quality
Department of Commerce
Appointed Member
Appointed Member
Appointed Member
Appointed Member
Steve Olea
Charles "Matt" Mathewson
Mark McWhirter
Wayne Smith
Robert C. Berger
Arlo B. Lee
Jeff Maguire
15
11
12
The Applicant was represented by Steven M. Wheeler and Jeffrey B. Guldner of Snell &
13
Wilmer L.L.P., Attorneys for PWE. Staff of the Arizona Corporation Commission ("StafF')
14
noticed their intervention as a party, and were represented by Teena I. Wolfe. Staff presented
evidence regarding the necessity of evaluating transmission system adequacy and reliability in
16
consideration of plant-siting Certificate requests generally, and in particular, transmission system
reliability issues related to the PWE application.
There
other
ll
Certificate of Environmental Compatibility (Case No. 95), and on January 12, 2000, issued the
17
adequacy and
were no
18
interventions or limited appearances.
19
At the conclusion of the hearing, the Committee, having received the Application, the
20
appearance of PWE, the evidence, testimony and exhibits presented by PWE, and having
21
received the appearance of intervenor Staff and the evidence and exhibit presented by Staff, and
22
being advised of the legal requirements of Arizona Revised Statutes §§ 40-360 to 40-360.13,
23
upon motion duly made and seconded, voted 6-0 (with two abstentions) to grant PWE a
24
Certificate as follows:
25
26
"Pinnacle West Energy Corporation and its assigr1ee(s), hereby are granted a Certificate
27
of Environmental Compatibility authorizing construction of four 530 megawatt (nominal) natural
28
2
Decision No.:
.
, .
. ..,
. .. ay
,. ...
62324
Decision No. 79586
Docket No.: L-000001-99-0095
Exhibit A
I
v
L-00000D-240156-00234
1
2
3
gas-fired,
combined
cycle
generating
units,
together
with
related
infrastructure
and
appurtenances including intra-plant transmission and a switchyard, which generating units shall
be located in Maricopa County, Arizona, approximately two miles southeast of the intersection
of Elliot Road and Wintersburg Road, in Sections 14, 22, and 23, Township l South, Range 6
4
West, Gila and Salt River Base and Meridian."
5
The Certificate was granted upon the following conditions:
6
7
1.
8
9
The Applicant and its assignees will comply with all existing applicable air and
water pollution control standards and regulations, and with all existing applicable
ordinances, master plans and regulations of the State of Arizona, the County of
Maricopa, the United States, and any other governmental entities having
jurisdiction.
10
2.
I I
12
This authorization to construct the Project will expire ten (10) years from the date
the Certificate is approved by the Arizona Corporation Commission unless
construction is completed to the point that the plant is capable of operating at its
rated capacity by that time, provided, however, that prior to such expiration the
Project owner may request that the Arizona Corporation Commission extend this
time limitation."
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17
On January 27, 2000, pursuant to A.R.S. § 40-360.07.A and A.A.C. R14~2~214.B, Staff
filed its Notice of Request for Review and Request for Procedural Order ("Request for Review").
In the Request for Review, Staff requested that the Commission review the Committee's
Decision and make a determination, based upon the entire record of the proceeding, of whether
18
the Certificate granted by the Cormnittee should be modified or denied pursuant to A.R.S. § 40-
19
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360.07.B.
The Request for Review included Staff's recommendation that after Commission
review of the record, the Commission should either (1) modify the Certificate as reflected in
Staff' s testimony at the proceeding before the Committee, or (2) deny the application without
prejudice for applicant's refiling in order to have Staffs concerns fully addressed by the
Committee.
Pursuant to the Commission's Procedural Order of February 2, 2000, PWE filed its
Response to StarT's Notice of Request tor Review on February 4, 2000 ("Response"). In its
Response, PWE alleged that Staffs Request for Review seeks relief that is beyond the
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3
Decision No.:__62 32 '/
..a...
».-
Decision No.
79588
I
Docket No.: L-00000/-99-0095
Exhibit A
. I
a.,
L-00000D-240158-00234
1
Commission's authority to grant.
PWE requested that this matter be recommended for
immediate Commission consideration, and that any further briefing be ordered on an accelerated
2
schedule.
3
Pursuant to the Commission's Procedural Order of February 2, 2000, a procedural
4
conference was convened on February 7, 2000. Following that procedural conference, PWE and
5
Staff entered into an agreement to jointly file a proposed form of order for the Commission to
6
consider in its decision to approve, modify, or deny the Certificate. In that proposed form of
7
order, PWE and Staff proposed that the Certificate be granted based upon the following
8
conditions in place of those included in the Certificate as granted by the Committee:
9
10
11
1. The Applicant and its assignees will comply with all existing applicable air and water
pollution control standards and regulations, and with all existing applicable ordinances,
master plans and regulations of the State of Arizona, the County of Maricopa, the United
States, and any other governmental entities having jurisdiction.
12
13
14
2. This authorization to construct the Project will expire seven (7) years from the date the
Certificate is approved by the Arizona Corporation Commission unless construction is
completed to the point that the plant is capable of operating at its rated capacity by that time;
provided, however, that prior to such expiration the Project owner may request that the
Arizona Corporation Commission extend this time limitation.
15
3. To ensure reliability, the Certificate of Environmental Compatibility will be conditioned
upon the following:
a.
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PWE providing evidence to the Commission that two or more transmission lines will
emanate from the power plant switchyard and interconnect with the existing transmission
system. This plant interconnection must satisfy the single contingency outage criteria (N-
1) without reliance on remedial action such as generator unit tripping or load shedding. If
achieving this objective involves the construction of any new transmission line or lines,
approval of a Certificate of Environmental Compatibility application (if otherwise
required by law) will be required for the constnxction of any such new transmission line
or lines.
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b. PWE providing to the Commission, not more than 12 months prior to the commercial
operation of each unit of the plant, a technical study regarding the sufficiency of
transmission capacity to accommodate that unit of the plant and that shows that such
additional unit will not compromise the reliable operation of the state's interconnected
transmission system. PWE has satisfied this condition for Unit 1 of the plant.
24
c.
25
PWE submitting to the Commission an interconnection agreement with the transmission
provider with whom they are interconnecting.
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27
d. PWE becoming a member of WSCC, or its successor, and Filing a copy of its WSCC
Reliability Criteria Agreement or Reliability Management System (RMS) Generator
Agreement with the Commission.
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4
Decision No.: 6 2 3-24
Decision No. 79586
Docket No.: L-000001-99-0095
Exhibit A
Q
L-000000-24-0156-00234
e.
1
2
PWE using its best efforts to become a member of the Southwest Reserve Sharing Group,
or its successor, thereby making its units available for reserve sharing purposes, subject
to reasonable pricing.
3
4
4. Condition 3 above shall automatically terminate if it or substantially similar conditions not
included in future generating facility Certificates of Environmental Compatibility as
approved by the Commission or upon any subsequent amendment or invalidation by the
Commission or a reviewing court.
IT IS THEREFORE ORDERED that the Certificate of Environmental Compatibility
granted to Pinnacle West Energy Corporation by the Arizona Power Plant and Line Siting
Committee on January 12, 2000 is hereby approved as modified hereinabove.
IT IS FURTHER ORDERED that this Decision shall become effective immediately.
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BY ORDER OF THE ARIZONA C0RP0RATI0N COMMISSION
/
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C
-4¢'
44-4.4,
Commissioner
Commissioner
n
Char
I/ . 4
9 '
43
In Witness Hereof, I, Brian C. McNeil,
Executive
Secretary
of
the
Arizona
Corporation Commission, set my hand and
cause the official seal of thls
ommission to
be
affixed,
this
day
of
2000.
7
/
/
By:
,
.
B anC. Mc ell
ecutive ecret
/
I..I
/
1-/'v
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Dissent.
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Decision No.:_6 .1 82 'f
Decision No.
79586
www.haleyaldrich.com
WATER ASSESSMENT FOR PROPOSED EXPANSION
REDHAWK POWER PLANT
ARLINGTON, ARIZONA
Prepared by
Haley & Aldrich, Inc.
Phoenix, Arizona
for
Arizona Public Service Company
Phoenix, Arizona
File No. 0210763-000
July 2025
Table of Contents
Page
i
List of Figures
ii
1.
Introduction
3
2.
Regional Physiographic Setting
4
2.1
REGIONAL GEOLOGY
4
2.2
REGIONAL HYDROGEOLOGY
5
2.3
SITE GROUNDWATER LEVEL CONDITIONS
5
3.
Project Area Setting
6
3.1
GROUNDWATER AVAILABILITY
6
3.1.1
Groundwater Withdrawal Authority
6
3.1.2
Groundwater Quality
6
4.
Effect of Expansion on the Phoenix AMA Fourth Management Plan
7
5.
Groundwater Assessment
8
5.1
METHODOLOGY
8
5.2
MODEL RESULTS
9
5.2.1
Scenario 1 (Current Conditions, 500 AFY)
9
5.2.2
Scenario 2 (Proposed Expansion, 800 AFY)
10
5.2.3
Scenario 3 (Worst Case Scenario, 1,172 AFY)
10
5.2.4
Scenario 4 (Differential Water Level Change Between 500 AFY and 800 AFY,
After 40 Years)
10
6.
Findings
12
References
13
ii
List of Figures
Figure No.
Title
1
Redhawk Power Plant Project Location
2
Registered Wells Located Within One-Half Mile of Project Site
3
Redhawk Power Plant Generation Water Supply Well Locations
4
APS Pumping Modeled Drawdown Contours (500 ACRE FT/YEAR)
5
APS Pumping Modeled Drawdown Contours (800 ACRE FT/YEAR)
6
APS Pumping Modeled Drawdown Contours (1,172 ACRE FT/YEAR)
1.
Introduction
Arizona Public Service Company (APS) proposes to expand its Redhawk Power Plant with the addition of
eight new GE LM6000 simple cycle natural gas generating units with water augmentation.1 The
proposed expansion will add up to 397 megawatts (MW) to the energy grid by 2028, and will require
additional groundwater to support power generation. The anticipated water demand for the proposed
new generating units will be up to 300 acre-feet per year (AFY) of groundwater sourced from two
existing on-site wells for a period of approximately 40 years. The total planned groundwater use to
support existing and proposed new plant operations is within the total withdrawal authority presently
held by APS in the form of a Type 1 Non-Irrigation Grandfathered Water Right (Type 1 Right).2 This
report describes analyses conducted to evaluate the effects of the proposed additional groundwater
pumping, and summarizes the results of the water use analyses.
Haley & Aldrich, Inc. (Haley & Aldrich) used an existing groundwater model developed by the Arizona
Department of Water Resources (ADWR) to evaluate water availability and both immediate and future
effects of the proposed increased groundwater pumping at the Redhawk Power Plant. The groundwater
model used for these analyses is the most recent version of the Phoenix Active Management Area
(AMA) groundwater model, which was published in June 2023 (ADWR, 2023). The Phoenix AMA
groundwater model was developed to support decision making and regulatory initiatives that protect
groundwater resources in the Phoenix AMA. The recently published model was used for this evaluation
without modification of the model grid, boundaries, or other parameters to ensure consistency with
current ADWR analyses.
The availability of groundwater was evaluated based on the effects of the proposed increased
groundwater pumping on aquifer water levels and the continued availability of groundwater for use by
the plant and others. The criteria used to quantify effects of the proposed groundwater use included:
1. The horizontal and vertical extent of the cone of depression resulting from the increased
groundwater pumping associated with the proposed Redhawk Power Plant expansion; and
2. The contribution to regional groundwater elevation change during the planned operational
period of the generating unit’s expansion.
To assess potential impacts to the AMA’s current management plan and groundwater levels, Haley &
Aldrich modeled the effects of the proposed water use on groundwater levels, evaluated whether
effects of the proposed use would unduly burden neighboring groundwater users, and whether the
proposed expansion complies with the AMA’s current management plan requirements for combustion
turbine power plants.
The methodology and results of these analyses are described in the following sections.
1 Water augmentation is a process whereby water is used to cool the air drawn into the turbine to increase power
generation efficiency.
2 APS has 3,356 AFY of Type 1 water rights, and up to 7,644 AFY of Type 2 water rights which may be applied at the
Redhawk Power Plant property.
2.
Regional Physiographic Setting
The Redhawk Power Plant is located in the southern portion of the Hassayampa groundwater sub-basin,
near the western edge of the Phoenix AMA boundary (project site, Figure 1). The Hassayampa sub-basin
is drained by the ephemeral Hassayampa River that enters the sub-basin in the northeast and flows to
the south to its confluence with the Gila River near the town of Arlington in the southern part of the
sub-basin. The Gila River is a perennial river that flows southeast until turning south near the town of
Arlington before exiting the Hassayampa sub-basin at its southern boundary. Two major ephemeral
tributaries are found in the Hassayampa sub-basin; Jackrabbit Wash, a tributary to the ephemeral
Hassayampa River, and Centennial Wash, a tributary to the perennial Gila River.
Groundwater enters the Hassayampa sub-basin from the northeast and flows south toward the Gila
River (ADWR, 2010). Some groundwater from the Hassayampa sub-basin historically flowed towards the
West Salt River Valley sub-basin but has subsequently been redirected due to a change in the
groundwater gradient in response to groundwater withdrawal in the sub-basin. Groundwater is the
main source of water supply for irrigation in the Hassayampa sub-basin and is pumped from aquifers
comprised of the basin-fill deposits.
The Hassayampa sub-basin includes the Hassayampa Plain, north of the Belmont Mountains, and the
Lower Hassayampa Area, generally south of the Belmont Mountains. The Hassayampa sub-basin consists
largely of undeveloped desert and agricultural land. The Hassayampa sub-basin lies within the Basin and
Range physiographic province, which is characterized by northwest trending fault-block mountains
separated by wide alluvial plains. The ground surface of the Hassayampa sub-basin is a gently sloping
alluvial plain bounded on the north by the Vulture and Wickenburg mountains, on the east by the White
Tank Mountains, on the south by the Buckeye Hills and the Gila Bend Mountains, and on the west by the
Big Horn and Belmont mountains and the Palo Verde Hills (ADWR, 1994).
2.1
REGIONAL GEOLOGY
The Lower Hassayampa Area is separated from the Hassayampa Plain by the Belmont Mountains and a
shallow subsurface bedrock ridge extending to the southeast (ADWR, 1994). Depth to bedrock in the
Hassayampa sub-basin is a few tens of feet near the basin margins to over 1,200 feet near the center of
the basin (ADWR, 1994). Precambrian granite, gneiss, and schist, Cretaceous andesite, and Quaternary
basalt make up most of the mountain ranges surrounding the basin, with the Quaternary basalt of the
Palo Verde Hills being the closest outcrop to the site (Wilson et al., 1957).
The Hassayampa sub-basin is filled with alluvial material derived from weathering and transportation of
rock material from adjacent highlands. The basin fill in the Lower Hassayampa Area, and beneath the
Redhawk Power Plant, consists of three hydrogeologic units designated as the Upper, Middle, and Lower
Alluvial Units. The Upper Alluvial Unit is generally 30 to 60 feet thick, consisting of unconsolidated silty
sands, gravelly sands with clay, and clay lenses. The Middle Alluvial Unit is approximately 230 to 300 feet
thick and is primarily clay, consisting of silty clay, clayey silt, clayey sand, and silty sand lenses. The
Lower Alluvial Unit ranges in thickness from 100 feet to more than 1,000 feet thick and consists of
unconsolidated silty sand, sand, and gravelly sand, as well as moderately- to well-consolidated alluvial
fan deposits.
2.2
REGIONAL HYDROGEOLOGY
Groundwater in the Hassayampa sub-basin generally occurs under unconfined conditions; however,
there are local areas of confined (artesian) or perched aquifer conditions in the Lower Hassayampa Area
(ADWR, 2010). Groundwater recharge sources include infiltration from the Hassayampa and Gila rivers,
infiltration from mountain front recharge, and incidental recharge from irrigation and canal seepage
(ADWR, 1994). Predevelopment groundwater generally flowed towards the Gila River but has been
artificially modified by historic groundwater withdrawal (ADWR, 2010). Groundwater in the Lower
Hassayampa Area flows toward the pumping centers in the Tonopah Desert and Centennial Wash areas
(ADWR, 2010).
2.3
SITE GROUNDWATER LEVEL CONDITIONS
Groundwater occurs naturally beneath the Redhawk Power Plant site in the Lower Alluvial Unit at
depths that are attainable for conventional pumping equipment. APS currently has two water supply
wells that are consistently3 pumped to support power generation at the project site. The static water
level at the two active production wells was 233.7 feet below land surface (bls)4 and 235.6 feet bls5 in
August 2019 and July 2020, respectively. Available water level data indicate that groundwater elevation
has declined by approximately 3 feet per year6 at an ADWR Groundwater Site Inventory well located
approximately 1 mile northeast of the project site. Regional measured groundwater levels and water
level changes over time were incorporated in the 2023 ADWR Phoenix AMA groundwater model. The
measured groundwater levels were used to calibrate the groundwater model, ensuring that the model
reasonably reflects observed groundwater conditions.
3 APS has five active wells at the Redhawk Power Plant: two wells support power generation, one well for domestic
water supply at the plant, and two wells are used for construction water supply and dust control.
4 Well 55-230361.
5 Well 55-231818.
6 Groundwater Site Inventory Well 332054112494901, Registry No. 55-608004.
3.
Project Area Setting
The Redhawk Power Plant is situated on basin fill and the closest surface bedrock exposure is
Quaternary basalt of the Palo Verde Hills, northwest of the project site. The total thickness of alluvial fill
is greater than 1,050 feet bls7 at the project site, based on wells installed in 2019 and 2020. A depth to
bedrock map developed by the Arizona Geological Survey (Richard, et al., 2007) based on gravity, well
log data, and well depth data shows a depth to bedrock at the project site of approximately 1,200 feet
bls. Several wells located on or near the project site have depths ranging from 950 to 1,150 feet bls and
are constructed to produce from the Lower Alluvial Unit. Groundwater flow in the vicinity of the site is
to the south-southwest, toward the Centennial Wash (ADWR, 2010).
3.1
GROUNDWATER AVAILABILITY
The availability of groundwater to meet the planned water requirements of the proposed expansion and
known existing uses was evaluated as part of this analysis using the Phoenix AMA groundwater model
(ADWR, 2023). Although not the primary water source, groundwater is currently used at the Redhawk
Power Plant for power generation and other site water needs. Groundwater has previously been
demonstrated to be available to support the current Redhawk Power Plant generation configuration.
The Phoenix AMA groundwater model was used to evaluate groundwater availability for the proposed
expansion and known existing groundwater uses by both APS and other groundwater users. This analysis
assumes that current groundwater uses will continue for the planned operational life of the Redhawk
Power Plant expansion. The results of the model analyses are described in Section 5.2, Model Results.
3.1.1
Groundwater Withdrawal Authority
Within the Phoenix AMA (and other AMAs), each groundwater user must have authority to withdraw
groundwater, in the form of either established water rights or a permit from ADWR. Existing
groundwater withdrawals at the Redhawk Power Plant project site are made pursuant to a Type 1
Non-Irrigation Groundwater Right of 3,356 AFY that are appurtenant to the 1,749 acres of APS land on
which the Redhawk Power Plant was built. This Type 1 Right was obtained by APS by retiring 1,749 acres
of designated agricultural land and converting the former irrigation rights to industrial use. By doing so,
APS converted 5,604 acre-feet of Grandfathered Irrigation Groundwater Rights to 3,356 acre-feet of
Type 1 Non-Irrigation Groundwater Rights for industrial purposes. The remaining 2,248 AFY (40 percent)
of the agricultural water right was extinguished, meaning that this water would now remain in the
aquifer to benefit all groundwater users.
The Redhawk Power Plant currently uses only approximately 500 AFY (approximately 15 percent) of
groundwater under the remaining Type 1 Right. The proposed expansion would increase groundwater
pumping at the Redhawk Power Plant to approximately 24 percent of the current Type 1 Right.
3.1.2
Groundwater Quality
Groundwater from the Lower Alluvial Unit beneath the Redhawk Power Plant is currently used for
power generation, construction, dust control, and domestic water uses. The quality of groundwater
obtained from the existing on-site water wells is suitable for each of these uses. Production of an
additional 300 AFY from the existing on-site water wells is not anticipated to change groundwater
quality.
7 Well completion reports for APS water supply wells 55-230316 and 55-231818.
4.
Effect of Expansion on the Phoenix AMA Fourth Management Plan
The proposed Redhawk Power Plant expansion consists of the addition of eight new GE LM6000 simple
cycle natural gas generating units to the existing plant. Water use restrictions at new combustion
turbine power plants are set forth in Sections 6.3.4.2, and 6-908 of the Phoenix AMA fourth
management plan.8 The water use restrictions set forth in the management plan include water quality
criteria specific to operation and blow down of cooling towers at combustion turbine power plants. The
proposed expansion generation units to be installed at the Redhawk Power Plant will be air cooled. No
cooling towers are proposed in conjunction with the proposed expansion; consequently, the proposed
expansion complies with the Phoenix AMA fourth management plan.
8 The Phoenix AMA fourth management plan remains in effect until December 31, 2024. The fifth management
plan will become effective on January 1, 2025. The water use restrictions for combustion turbine power plants set
forth in Section 6.3.4.2 of the Pheonix AMA fourth management plan pertaining to cooling towers have been
carried forward to the fifth management plan. Conservation requirements for cooling towers at combustion
turbine power plants were updated in the fourth and fifth management plans. Water use restrictions for
combustion turbine power plants included in both the fourth and fifth management plans pertain only to plants
that use cooling towers.
5.
Groundwater Assessment
5.1
METHODOLOGY
The ADWR developed and published a regional groundwater flow model of the Phoenix AMA (ADWR,
2023). The Phoenix AMA model replaced the older Salt River Valley model and the Lower Hassayampa
sub-basin groundwater model. The Phoenix AMA model is a three-layer transient MODFLOW-NWT flow
model with uniform horizontal grid cells of dimensions 0.5-mile by 0.5-mile.
From the ground surface, vertically downward, the three model layers represent the Upper Alluvial Unit,
the Middle Alluvial Unit, and the Lower Alluvial Unit, respectively. The model simulates the timeframe
1900 through 2021 using transient stress periods of varying length. For the period 1921 to 2021, annual
stress periods are used. Within each stress period, model boundary conditions representing stream
stage, recharge, evapotranspiration, groundwater pumping, and specified head boundaries are held
constant. Groundwater production wells are assigned total annual pumping based on reported
groundwater production. Comprehensive model documentation is provided in the Phoenix AMA model
report (ADWR, 2023).
Haley & Aldrich used the Phoenix AMA groundwater model to simulate groundwater withdrawal at the
APS Redhawk Power Plant wells and calculated the associated drawdown. No changes were made to the
model grid or layering discretization, and no changes were made to the published model
parameterization. The simulated groundwater pumping was held constant for each model scenario
(except APS Redhawk Power Plant) at 2021 levels for each groundwater user represented in the 2023
Phoenix AMA model. Groundwater pumping at the APS Redhawk Power Plant was adjusted for each
model scenario to reflect different conditions as described below. Groundwater pumping trends,
groundwater management practices, and groundwater elevation changes resulting from those practices
outside of the Redhawk Power Plant property, as reflected in the 2023 Phoenix AMA model (ADWR,
2023), are assumed to continue for the simulation periods. The only change made to the published
ADWR model was adjustment of the locations of the two on-site production wells at the Redhawk
Power Plant to reflect actual well locations.
In the vicinity of the APS Redhawk facility, the published Phoenix AMA model includes eight APS wells.
Figure 2 shows the six active APS wells and other registered wells located within 0.5 mile of the project
site. Data from the model show that only the two APS production wells on the Redhawk Power Plant site
were used for power production in year 2021.9 The remaining six production wells were either turned
off during 2021 or had production totals of less than 20 acre-feet in 2021.
To calculate drawdown associated with the planned plant expansion, a “baseline” scenario was set up to
simulate groundwater levels through year 2060 by “turning off” production at the APS Redhawk facility
wells. The boundary conditions and parameters were held constant at the 2021 specified values.
9 Wells 55-623232 and 55-230361 were used to supply water to plant operations in 2021. Well 55-623232 has
since been replaced for operations purposes by well 55-231818. Well 55-230361 remains active but is used only for
small incidental water supply needs.
Three forecast scenarios representing the period 2021 through 2060 were used to simulate total
production at the APS Redhawk facility, and calculate the respective drawdown values:
Scenario 1 – current conditions, total production of 500 AFY;
Scenario 2 – proposed expansion, total production of 800 AFY;
Scenario 3 – worst-case total production of 1,172 AFY; and
Scenario 4 – groundwater elevation change contribution after 40 years of groundwater use with
proposed expansion, total production of 800 AFY.
For each of the forecast scenarios, groundwater withdrawal was simulated at the two APS wells shown
on Figure 3 (55-231818 and 55-23036110). The total specified production for the respective scenarios is
divided evenly between the two wells. The horizontal and vertical extent of the cone of depression is
quantified in terms of potential drawdown impacts to wells owned by parties other than APS.
Drawdown due to production at these two APS wells for each scenario is calculated as the difference of
simulated water levels in the baseline scenario and the respective scenario at the end of a five-year
pumping period. The five-year pumping period was used because it is consistent with the standard
applied by ADWR11 to determine if unreasonable increasing damage will occur at wells not owned by the
applicant. Unreasonable increasing damage is defined as 10 feet or more of additional drawdown at
wells not owned by the applicant at the end of a five-year pumping period. Calculated drawdown due to
production at the APS Redhawk facility under each scenario at the end of the five-year pumping period
is presented in Figures 4, 5, and 6, respectively.
5.2
MODEL RESULTS
Key observations regarding each model scenario are described below.
5.2.1
Scenario 1 (Current Conditions, 500 AFY)
This model scenario represents groundwater pumping under current plant operating conditions. The
Redhawk Power Plant currently uses approximately 500 AFY for power generation water supply. This
scenario was run so that it can be used to compare additional off-site groundwater drawdown that will
occur if the proposed expansion is authorized to the existing simulated drawdown conditions. Under this
scenario, a maximum drawdown of 2.2 feet occurs at the two APS production wells at the end of the
five-year pumping period (Figure 4). No off-site wells experience 10 feet or greater drawdown at the end
of the five-year pumping period and therefore do not experience unreasonable impact as a result of the
current groundwater use.
10 Wells 55-623232 and 55-230361 were used to supply water to plant operations in 2021. Well 55-623232 has
since been replaced for operations purposes by well 55-231818. Well 55-230361 remains active but is used only for
small incidental water supply needs.
11 Arizona Administrative Code R12-15-1302 defines unreasonably increasing damage to an existing well as more
than 10 feet of additional drawdown within the first five years of operation of a new extraction well. Although the
proposed Redhawk expansion relies on two existing production wells, this criterion was applied to conservatively
evaluate the potential effects of the increased groundwater pumping associated with the expansion.
5.2.2
Scenario 2 (Proposed Expansion, 800 AFY)
This model scenario represents groundwater pumping with the proposed plant expansion. The proposed
expansion is estimated to use up to 300 AFY of additional groundwater pumped from the two existing
water supply wells. This pumping scenario assumes 800 AFY of groundwater pumping; the current
500 AFY of groundwater use plus an additional 300 AFY of groundwater for the proposed new units. This
scenario was run to examine the total simulated off-site groundwater drawdown that will occur if the
proposed expansion is authorized. Under this scenario, a maximum drawdown of 3.4 feet occurs at the
two APS production wells at the end of the five-year pumping period (Figure 5). The maximum
drawdown simulated at any off-site water wells owned by parties other than APS is 2.6 feet at
well 55-608003 at the end of the simulated five-year pumping period. No off-site wells experience
10 feet or greater drawdown at the end of the five-year pumping period and therefore do not
experience unreasonable impact as a result of increased groundwater pumping to support generation
from the proposed expansion.
5.2.3
Scenario 3 (Worst Case Scenario, 1,172 AFY)
This model scenario represents the greatest reported past groundwater use at the Redhawk Power
Plant, plus the additional 300 AFY of groundwater use associated with the proposed expansion. The
greatest reported groundwater use at the Redhawk Power Plant occurred in 2022 as the result of a large
construction project that used water in addition to that required for power generation. The 2022
groundwater use of 872 AFY plus the groundwater use associated with the proposed expansion
(300 AFY) total 1,172 AFY. This amount of groundwater use exceeds the anticipated total required for
plant operations with the proposed expansion but remains well within the total withdrawal authority
presently held by APS. This model scenario was run to examine off-site water level impacts under a
worst-case scenario. Under this worst-case scenario, a maximum drawdown of 4.9 feet occurs at the two
APS production wells at the end of the five-year pumping period (Figure 6). No off-site wells experience
10 feet or greater drawdown at the end of the five-year pumping period and therefore do not
experience unreasonable impact as a result of the worst-case groundwater use.
5.2.4
Scenario 4 (Differential Water Level Change Between 500 AFY and 800 AFY, After 40 Years)
This model scenario represents groundwater pumping under the proposed plant expansion operating
conditions for a period of 40 years. The plant expansion would include a total groundwater use of
approximately 800 AFY. This scenario was run to examine the total projected contribution to
groundwater elevation change after 40 years of plant operations. Groundwater elevation conditions
were evaluated after 40 years of pumping at rates of 500 AFY and 800 AFY to examine the change in
groundwater elevations attributable to the proposed expansion. At the end of the 40-year simulation
period, the 800 AFY of groundwater pumping associated with the proposed expansion resulted in a total
of approximately 2.0 feet of additional groundwater elevation decline at the Redhawk Power Plant site
over 40 years of pumping at the APS production wells over the current 500 AFY of groundwater pumping
over the same period of time. This amount of groundwater elevation decline equates to approximately
0.6 inches (or 0.05 feet) of additional groundwater decline per year from operation of the Redhawk
expansion. A groundwater elevation decline of 0.05 feet per year is very small in comparison to the
overall groundwater elevation decline resulting from the combined pumping of all wells incorporated in
the ADWR model.
The total groundwater elevation change over the 40-year simulation period with the proposed
expansion groundwater use and all reported groundwater production from all other well owners
registered as of 2021 is approximately 2.36 feet per year combined. This value represents the simulated
groundwater elevation change over the 40-year simulation period resulting from all combined
groundwater pumping included in the published Phoenix AMA (ADWR, 2023) groundwater model, and
groundwater pumping associated with the proposed expansion.
6.
Findings
Haley & Aldrich evaluated future additional groundwater pumping associated with the proposed
expansion of the Redhawk Power Plant located in Arlington, Arizona. The purpose of the evaluation was
to quantify potential effects of the increased groundwater pumping that would occur from the two
existing water supply wells should the proposed expansion be authorized. Current groundwater use at
the Redhawk Power Plant is approximately 500 AFY, and the proposed expansion would increase
groundwater use to a total of approximately 800 AFY. Haley & Aldrich used a recent groundwater model
published by ADWR (2023) to quantify the potential effects of increased groundwater pumping in terms
of impacts to off-site wells owned by parties other than APS, and the total contribution to groundwater
elevation change over the 40-year operational period of the proposed expansion generating units. The
key findings resulting from this evaluation are listed below.
1. Sufficient groundwater is available from the aquifers beneath the Redhawk Power Plant site to
support the proposed expansion, and to continue all known existing current off-site water uses
for the duration of the proposed 40-year operation of the expansion generating units.
2. The horizontal and vertical extent of the cone of depression resulting from the increased
groundwater use (800 AFY total groundwater use) associated with the proposed Redhawk
Power Plant expansion does not result in unreasonable impact to existing registered water wells
owned by parties other than APS based on criteria established by ADWR (10 feet or more of
additional drawdown over a period of five years of pumping).
a. The maximum groundwater drawdown resulting from the current and proposed
expansion groundwater pumping (800 AFY total groundwater use) is 3.43 feet at the APS
production wells on the Redhawk Power Plant site, at the end of the simulated five-year
pumping period.
b. All off-site water wells owned by parties other than APS experience drawdown less than
that simulated at the APS production wells on the Redhawk Power Plant site at the end
of the simulated five-year pumping period.
c. The maximum drawdown simulated at off-site water wells owned by parties other than
APS is 2.6 feet at well 55-608003 at the end of the simulated five-year pumping period.
No water wells owned by others experience drawdown of 10 feet or more during the
five-year simulated pumping period.
3. Groundwater elevation change resulting from all current APS and non-APS groundwater
pumping accounted for in the Phoenix AMA groundwater model, including the current 500 AFY
of groundwater use at the Redhawk Power Plant, was projected for the planned 40-year
operational period of the expansion generating units. This groundwater elevation change was
compared to the projection of all current groundwater pumping, Redhawk Power Plant
groundwater use, plus the 300 AFY of groundwater use associated with the proposed expansion,
to determine the relative change in groundwater elevation attributable to the expansion related
groundwater use. This comparison showed that the proposed additional 300 AFY of
groundwater pumping for the expansion will result in approximately 2 feet of additional
groundwater elevation drawdown over the planned 40-year operational period of the expansion
generating units. This small amount of groundwater elevation change equates to approximately
0.05 feet per year of additional drawdown resulting from the proposed expansion.
References
1.
Arizona Department of Water Resources (ADWR), 1994. Arizona Water Resources Assessment –
Volume II Hydrologic Summary. August.
2.
ADWR, 2010. Arizona Water Atlas, Volume 8 Active Management Area Planning Area. April.
3.
ADWR, 2023. Phoenix Active Management Area Groundwater Model.
4.
Richard, S.M., Shipman, T.C., Greene, L.C., and Harris, R.C., 2007. Estimated Depth to Bedrock in
Arizona, v 1.0. Arizona Geology Survey Document Repository.
5.
Wilson, E.D., Moore, R.T., and Peirce, W.H., 1957. Geologic Map of Maricopa County, Arizona.
Prepared by the Arizona Bureau of Mines and University of Arizona.
FIGURES
"
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REDHAWK
POWER PLANT
BELMONT
MOUNTAINS
VULTURE
MOUNTAINS
WHITE TANK MOUNTAINS
WICKENBURG
MOUNTAINS
BIG HORN
MOUNTAINS
PALO VERDE
HILLS
0
12
24
SCALE IN MILES
FIGURE 1
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
REDHAWK POWER PLANT
PROJECT LOCATION
JUNE 2024
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NOTES
1. ALL LOCATIONS AND DIMENSIONS ARE APPROXIMATE.
2. AMA = ACTIVE MANAGEMENT AREA
3. SUBBASIN DATA SOURCE: PHOENIX AMA, 2023
4. BASE MAP SOURCE: ESRI
"
LEGEND
#
MOUNTAIN
"
REDHAWK POWER PLANT SITE
HASSAYAMPA SUBBASIN
PHOENIX AMA MODEL NO-FLOW (INACTIVE) AREA
PHOENIX AMA BOUNDARY
EDGE OF PHOENIX AMA MODEL DOMAIN
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#
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!
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#
349TH AVE
355TH AVE
351ST AVE
353RD AVE
ELLIOT RD
383RD AVE
802026
229443
608003
230361
231818
589492
623229
623232
928703
LEGEND
!
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#
!
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APS WATER SUPPLY WELL
WELL, OTHER OWNER
PHOENIX AMA MODEL NO-FLOW (INACTIVE) AREAS, HILLS
OR SUBSURFACE BEDROCK
REDHAWK POWER PLANT BOUNDARY
APS PROPERTY BOUNDARY
HALF MILE BUFFER AROUND REDHAWK POWER
PLANT BOUNDARY
0
2,500
5,000
SCALE IN FEET
NOTES
1. SOME LOCATIONS WITHIN THE ARIZONA DEPARTMENT OF WATER
RESOURCES (ADWR) WELL REGISTRY ARE CADASTRAL AND MAY NOT
REPRESENT THE TRUE WELL LOCATION.
2. WELL DATA SOURCE: ADWR WELL REGISTRY
3. DEFINITIONS:
APS = ARIZONA PUBLIC SERVICE
AMA = ACTIVE MANAGEMENT AREA
4. AERIAL IMAGERY SOURCE: GOOGLE, 2024
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
REGISTERED WELLS LOCATED
WITHIN ONE HALF-MILE
OF PROJECT SITE
FIGURE 2
JUNE 2024
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!
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230361
231818
LEGEND
!
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#
APS GENERATION WATER SUPLLY WELL
REDHAWK POWER PLANT BOUNDARY
0
600
1,200
SCALE IN FEET
NOTES
1. ALL LOCATIONS AND DIMENSIONS ARE APPROXIMATE.
2. WELL DATA SOURCE: ARIZONA DEPARTMENT OF WATER
RESOURCES (ADWR) WELL REGISTRY
3. AERIAL IMAGERY SOURCE: GOOGLE, 2024
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
REDHAWK POWER PLANT
GENERATION WATER
SUPPLY WELL LOCATIONS
FIGURE 3
JUNE 2024
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!
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349TH AVE
355TH AVE
351ST AVE
353RD AVE
ELLIOT RD
383RD AVE
1.5
1.5
0.5
0.5
1
2
1
0.5
1
230361
231818
LEGEND
!
?
#
APS GENERATION WATER SUPPLY WELL
MODELED DRAWDOWN CONTOUR (IN FEET),
500 ACRE FT/YR
PHOENIX AMA MODEL NO-FLOW (INACTIVE) AREAS, HILLS
OR SUBSURFACE BEDROCK
REDHAWK POWER PLANT BOUNDARY
APS PROPERTY BOUNDARY
0
2,500
5,000
SCALE IN FEET
NOTES
1. SOME LOCATIONS WITHIN THE ARIZONA DEPARTMENT OF WATER
RESOURCES (ADWR) WELL REGISTRY ARE CADASTRAL AND MAY NOT
REPRESENT THE TRUE WELL LOCATION.
2. WELL DATA SOURCE: ADWR WELL REGISTRY
3. SIMULATED APS PUMPING WELL RATES:
230361: 250 ACRE FT/YR (154.8 GPM)
623232: 250 ACRE FT/YR (154.8 GPM)
4. DEFINITIONS:
APS = ARIZONA PUBLIC SERVICE
FT = FEET
YR = YEAR
GPM = GALLONS PER MINUTE
AMA = ACTIVE MANAGEMENT AREA
5. AERIAL IMAGERY SOURCE: GOOGLE, 2024
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
APS PUMPING
MODELED DRAWDOWN CONTOURS
(500 ACRE FT/YEAR)
FIGURE 4
JUNE 2024
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#
!
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#
349TH AVE
355TH AVE
351ST AVE
353RD AVE
ELLIOT RD
383RD AVE
1.5
2.5
0.5
2.5
2
1
3
1.5
1
1
1
2
1.5
230361
231818
LEGEND
!
?
#
APS GENERATION WATER SUPPLY WELL
MODELED DRAWDOWN CONTOUR (IN FEET),
800 ACRE FT/YR
PHOENIX AMA MODEL NO-FLOW (INACTIVE) AREAS, HILLS
OR SUBSURFACE BEDROCK
REDHAWK POWER PLANT BOUNDARY
APS PROPERTY BOUNDARY
0
2,500
5,000
SCALE IN FEET
NOTES
1. SOME LOCATIONS WITHIN THE ARIZONA DEPARTMENT OF WATER
RESOURCES (ADWR) WELL REGISTRY ARE CADASTRAL AND MAY NOT
REPRESENT THE TRUE WELL LOCATION.
2. WELL DATA SOURCE: ADWR WELL REGISTRY
3. SIMULATED APS PUMPING WELL RATES:
230361: 400 ACRE FT/YR (247.8 GPM)
623232: 400 ACRE FT/YR (247.8 GPM)
4. DEFINITIONS:
APS = ARIZONA PUBLIC SERVICE
FT = FEET
YR = YEAR
GPM = GALLONS PER MINUTE
AMA = ACTIVE MANAGEMENT AREA
5. AERIAL IMAGERY SOURCE: GOOGLE, 2024
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
APS PUMPING
MODELED DRAWDOWN CONTOURS
(800 ACRE FT/YEAR)
FIGURE 5
JUNE 2024
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!
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#
!
?
#
349TH AVE
355TH AVE
351ST AVE
353RD AVE
ELLIOT RD
383RD AVE
2
1.5
1
3.5
3
2.5
1.5
4.5
2
1
3.5
4
1.5
1.5
3
2
2.5
230361
231818
LEGEND
!
?
#
APS WATER SUPPLY WELL
MODELED DRAWDOWN CONTOUR (IN FEET),
1172 ACRE FT/YR
PHOENIX AMA MODEL NO-FLOW (INACTIVE) AREAS, HILLS
OR SUBSURFACE BEDROCK
REDHAWK POWER PLANT BOUNDARY
APS PROPERTY BOUNDARY
0
2,500
5,000
SCALE IN FEET
NOTES
1. SOME LOCATIONS WITHIN THE ARIZONA DEPARTMENT OF WATER
RESOURCES (ADWR) WELL REGISTRY ARE CADASTRAL AND MAY NOT
REPRESENT THE TRUE WELL LOCATION.
2. WELL DATA SOURCE: ADWR WELL REGISTRY
3. SIMULATED APS PUMPING WELL RATES:
230361: 586 ACRE FT/YR (363.0 GPM)
623232: 586 ACRE FT/YR (363.0 GPM)
4. DEFINITIONS:
APS = ARIZONA PUBLIC SERVICE
FT = FEET
YR = YEAR
GPM = GALLONS PER MINUTE
AMA = ACTIVE MANAGEMENT AREA
5. AERIAL IMAGERY SOURCE: GOOGLE, 2024
APS REDHAWK FACILITY
ARLINGTON, ARIZONA
APS PUMPING MODELED
DRAWDOWN CONTOURS
(1,172 ACRE FT/YEAR)
FIGURE 6
MAY 2024
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