Operational Plan

Ellsworth II Battery Energy Storage System (BESS) Facility
+/- 20.32 acres
Mesa, Arizona
Preliminary Operational Plan
Submitted by:
Pew & Lake, PLC
1744 South Val Vista Drive, Suite 217
Mesa, AZ 85204
480-461-4670
On behalf of:
Submitted to:
The City of Mesa
Planning & Zoning Division
Revised May 18, 2026

1. Introduction
NextEra Energy Resources (NextEra) is committed to ensuring the safety of its Battery Energy
Storage System (BESS) facilities, through compliance with a comprehensive framework of local,
state, and national codes and standards. These regulations are designed to provide uniformity in the
industry, and mitigate any risks associated with a BESS facility. NextEra understands that as BESS
technologies evolve, existing codes are being adapted to address the emerging technologies that
are making BESS facilities safer, thereby safeguarding public health and safety.
2. Purpose
As required by Section 11-31-37.E.1.2, the purpose of this Operational Plan is to provide the City of
Mesa staff with information regarding the operational details of the Battery Energy Storage System
(BESS) that will be developed upon the approval of the following request:
• A Rezone of approximately 20.32 acres of property located on the north
side of Starfire Avenue, west of Ellsworth Road, to change the zoning
district from Light Industrial with a PAD Overlay (LI/PAD), to Light
Industrial (LI).
3. Property Location
The Project is proposed to be developed on approximately 20.32 acres of property located on the
north side of Starfire Avenue, east of Ellsworth Road (the “Property”). The Property is shown below
and is a portion of Maricopa County Assessor parcel number 304-31-0149A. The approximate
boundary of the entire parcel is shown outlined in red.

4. Project Overview
Ellsworth II is anticipated to provide 190MW of nameplate energy storage capacity. The Site
Plan provided in the rezoning application materials depicts the various elements that are
required for the storage and transmission of energy. These elements include:
• Battery Energy Storage units,
• An electrical collection system that includes switchgears, power conversion stations,
inverters, transformers and collection lines,
• A gen-tie transmission line, and
• Infrastructure required by the City of Mesa including perimeter landscaping, walls and
gates, and internal access driveways.
The gen-tie line that is specific to this Project is located west of the project boundary and will
connecting the Project to the Scott substation, just west of the Project. The energy stored in this
BESS facility will be transmitted back into the grid at times established by SRP, the contracted
utility for this Project.
5. Code and Regulatory Compliance
The Ellsworth II project has been designed to meet all of the requirements of applicable local
zoning, building and fire safety regulations, in addition to federal, state and industry regulations
applicable to BESS facilities including, but not limited to the following:
Mesa Code of Ordinances
• Title 4- Building Regulations
• Title 7-Fire Regulations
• Title 11- Zoning Ordinance
• Section 11-8-3: Light Industrial (LI) Zoning District
• Section 11-31-7: Battery Energy Storage System (BESS) and BESS Facilities
Maricopa County
• Dust Control Permit (during construction)
2024 International Fire Code
• Section 1207: Electrical Energy Storage Systems

National Fire Protection Association (NFPA)
• Standard 855: Standard for the Installation of Stationary Energy Storage Systems
Underwriters Laboratories (UL)
• UL 9540 (Standard): Defines requirements for the complete system, focusing on electrical
safety, fire safety, and performance, ensuring listed components (batteries, inverters)
work safely together.
• UL 9540A (Test Method): A specific test to understand how lithium-ion batteries behave
during thermal runaway (a chain reaction fire), assessing cell-to-cell propagation and fire
spread
6. Preliminary Emergency Response Plan
At NextEra Energy Resources, safety is our highest priority. All of our battery energy storage
sites go through rigorous testing and certification processes to ensure their safe operations.
Responsible energy production begins with preparation from day one.
NextEra maintains a prevention-focused fire safety and emergency response framework for
battery energy storage system (BESS) facilities. Systems are designed, tested, and certified in
accordance with applicable codes and standards, including NFPA 855, and incorporate multiple
layers of fire protection to reduce the risk of fire, electric shock, and personal injury.
NextEra Energy Resources upholds high standards of safety and reliability safeguarding
community interests through collaboration with local officials and investing in advanced safety
training. Every site has a detailed emergency action plan developed with local fire departments
and NextEra provides comprehensive training and resources to local first responders to ensure
everyone’s safety in the unlikely event of an emergency.
In the unlikely event of a BESS facility emergency, NextEra Energy Resources personnel and
systems are trained and prepared to take all necessary actions.
• Monitoring and Emergency Notification: The BESS facility onsite control center
continuously monitors key operating parameters including:
o Battery temperature
o Battery cell voltages
o Smoke alarms
o Gas alarm levels
o Status of doors and ventilation
BESS facilities are further monitored through NextEra’s Renewable Operations
Control Center (ROCC), staffed 24 hours a day, 365 days a year.

The ROCC monitors real-time operating conditions, including temperature and
electrical parameters, to identify abnormal conditions. If necessary, the ROCC notify
local operating personnel and appropriate emergency responders and, if necessary,
can initiate a safe remote shutdown of the facility.
• Emergency Shutdown, De-Energization, and Isolation: Under emergency
conditions, or prior to maintenance activities, BESS facilities may be placed in a safe
state through shutdown, de-energization, or isolation, as appropriate to the
circumstances and in accordance with manufacturer procedures. Emergency
response actions may include:
o Isolation by the Battery Management System to limit energy transfer and
support isolation of the affected system components from the grid
o Electrical isolation to prevent unintended re-energization
o Controlled shutdown of applicable auxiliary systems
o Verification that residual electrical energy has been isolated prior to personnel
access
These actions are coordinated with trained operations personnel and documented to
support safe response and recovery.
• Coordination With Local Responders: Coordination includes technology-specific
training, site familiarization, and briefings with local officials conducted prior to
construction and as requested by the Authority Having Jurisdiction (AHJ), to align
emergency procedures with local response protocols.
• Safe Start-Up Following Emergency Conditions: If emergency conditions occur,
return to service will follow a controlled, safety-focused process consistent with
applicable requirements and manufacturer procedures. As needed, this process may
include system inspections, functional checks, staged energization, performance
verification, and coordination with the electric grid, with notification to and coordination
with the Authority Having Jurisdiction (AHJ), as appropriate.
7. Preliminary Decommissioning Plan
The purpose of this preliminary decommissioning plan is to provide procedures for closure of the
BESS facility. This decommissioning plan details provisions for facility deconstruction and site
restoration. This decommissioning plan shall take effect upon facility abandonment,
discontinuation of operation, or expiration of the use permit as defined by Mesa City Code.
Decommissioning a BESS facility takes place after a facility discontinues operations. NextEra,
or its successor, will manage the decommissioning of this facility. The facility is expected to be
decommissioned using the steps outlined in this Preliminary Decommissioning Plan.

It is anticipated that the BESS will have an expected useful lifetime of thirty (30) to thirty-five (35)
years and is expected to be operational for the entire useful life. At the end of its useful life, the
facility would be decommissioned with the goal of restoring the site, as closely as practicable, to
its pre-developed condition.
The final Decommissioning Plan will include the following:
o Reasons for commencement of decommissioning
o The manner in which the battery energy storage system (BESS) will be
decommissioned
o Procedures for removal of above- and below-ground equipment, structures, and
foundations
o Procedures for restoration of the surface grade and soil after removal of equipment
o Procedure for revegetation of restored soil areas with native seed mixes, excluding
any invasive species
o The timeframe for the completion of site restoration work
To decommission the facility, the following steps will be undertaken:
o Disconnection from the utility power grid.
o Removal of all BESS facility components: any perimeter fences, any concrete or
steel foundations, pipelines, alternators, generators, aboveground and
underground cables, transformers, inverters, fans, switch boxes, fixtures, site
substation, etc.
o Removal of all non-utility owned equipment (at point of interconnection), conduits,
structures, fencing, and foundations to a depth of at least four feet (48 inches)
below grade.
o Restoration of property to a condition reasonably similar to its condition prior to
Facility installation, or as agreed upon with the City of Mesa. This restoration may
consist of de-compaction of the topsoil by disking or tilling and re-vegetation of the
property where impervious surfaces were used, i.e. access roads, inverter pads,
BESS pads, substation area, etc. Mass grading is not anticipated since the initial
project will not alter topography significantly.
o Plant vegetation suitable for the location, native to the region, and which matches
surrounding vegetation.
o The appropriate management and disposition of materials and waste. The
decommissioning process will prioritize the recycling, reuse and salvage of
applicable facility components. Decommissioning activities will not begin prior to
issuance of approved permits by local regulatory agencies with appropriate
jurisdiction.
This decommissioning plan is based on current best management practices and procedures.
This Plan may be subject to revision based on new standards and emergent best management

practices at the time of decommissioning. Permits will be obtained as required and notification
will be given to stakeholders prior to decommissioning.
NextEra will coordinate with the City to monitor vegetation and drainage following restoration.
Erosion and sediment control, soil stabilization, weed control and fertilization will be provided by
NextEra as needed until the site is stabilized and approved by the City of Mesa.
NextEra will have twelve (12) months from the date decommissioning commences to complete
the decommissioning process. Provided, however, NextEra may request an extension of an
additional six (6) months if it is in good faith diligently implementing the decommissioning process
or is delayed due to weather conditions or other items outside its control.
NextEra is responsible for this decommissioning, provided however that it may contract with a
third party to perform the decommissioning on its behalf.
8. Conclusion
NextEra looks forward to working with the City of Mesa during the development and construction
of the Ellsworth II BESS facility, and is eager to start a dialogue with building and fire officials
so that the Emergency Response and Decommissioning Plans may be further developed to
address NextEra’s operating needs while addressing the interests of the City’s planning, building
and fire safety departments. Ultimately, this Operational Plan will comply with 2023 NFPA 855.