Initial Sound Study

200 Charles Ewing Blvd T +1 281-600-1000
Suite 160
Ewing, New Jersey 08628 erm.com
MEMO
TO Chelsea Solano, NextEra Energy Resources
FROM Tony Agresti, ERM
DATE February 4, 2026
REFERENCE ERM Project Number 0802264
SUBJECT Ellsworth II Ambient Noise Measurement Programs
Dear Chelsea:
Environmental Resources Management, Inc. (ERM) conducted ambient noise level
measurement programs near NextEra Energy Resources’ (NEER’s) proposed Ellsworth II
Battery Energy Storage System (BESS) project (Project) in Mesa, Arizona. The measurement
programs included the following:
• A continuous 24-hour measurement program at one location adjacent to South Ellsworth
Road to represent the existing noise environment of the residential area located
immediately east of South Ellsworth Road (Location LT1 on Figure 1).
• Short-term measurements at eight locations that included the nearest identified residential
area, school, church, park and four locations on the proposed Ellsworth II project property
line (Locations 1 through 8 on Figure 1).
The continuous 24-hour program was conducted on December 18, 2025, and the short-term
program was conducted on January 20, 2026. The measurement programs were conducted to
quantify the existing ambient conditions in the vicinity of the proposed site and at nearby noise
sensitive areas.
These measurements are being provided to the City of Mesa as the Initial Sound Study, as
required by Section 11-31-37-E-4 of the recently adopted BESS Ordinance.
Equipment
Equipment used to conduct both noise measurement programs included:
• One Casella CEL-633C Type 1 precision sound level meter for each program
• One outdoor enclosure protection system for the 24-hour program
• Weatherproof microphone windscreen
• Tripod
• Casella CEL 120 sound level meter calibrator
• Camera
• Noise Survey Data Sheets (see Attachment A)
© Copyright 2026 by The ERM International Group Limited and/or its affiliates (‘ERM’). All Rights Reserved.
No part of this work may be reproduced or transmitted in any form or by any means, without prior written permission of ERM. Page 1

¯
6 - Ellsworth II North 0 50 100 200
Miles
4 - Residential
Legend
7 - Ellsworth II East Long-Term Measurements
5 - Ellsworth II West Short-Term Measurements
Property Line
8 - Ellsworth II South
LT1
8.5x11
at
printed
when 3 - Park
1:8,400
2 - Church 1 - School
SCALE:
,
02/02/2026
REVISED:
¯
0 350 700
Feet
Figure 1
M:\US\Projects\M-O\NextEra\Ellsworth\ArcGIS\Ellsworth_NoiseStudy\Ellsworth_NoiseStudy.aprx, Ellsworth II Ambient
Noise Measurement
Locations
Ellsworth Battery Energy
Storage System Project
NextEra Energy
City of Mesa, Arizona
FILE:
Source: Esri - World Imagery; NAD 1983 UTM Zone 12N DRAWN BY: J.FERRENZ

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
Measurement Program Methodology
A Casella CEL-633 sound level meter was used for the measurement programs. The meter
microphone was fitted with a windscreen to reduce wind generated noise and was mounted on
a tripod approximately 5 feet above grade. Care was taken to avoid large reflecting surfaces.
The meter was set to measure the A-weighted ambient Leq sound levels on “slow” response
and was programmed to measure and store the sound levels in 1-minute intervals. The Leq is
the energy average of all the sounds present.
The sound level meter was placed inside a locked and secured weather-proof outdoor
enclosure for the 24-hour program. A technician was present during the measurement periods
for the short-term program. The contributing audible noise sources were observed and
documented by the technician during set-up and retrieval for the 24-hour program. The
technician observed and documented the contributing noise sources during the full short-term
measurement periods.
Meteorological data were obtained from a nearby National Weather Service station. The
recorded observations and photos of the noise measurement locations are presented on the
Noise Survey Data Sheets in Attachment A.
The sound level meter was calibrated by a calibration laboratory traceable to National Institute
of Standards and Technology (NIST) standards within 1 year of the testing programs. Field
calibrations were also conducted. The certificates of calibration for the sound level meter are
provided in Attachment B.
Continuous 24-Hour Ambient Noise Measurement Program
Meteorological conditions during the measurement program were obtained from the Falcon
Field Weather Station, approximately 10 miles northwest of the Project site, and included
hourly wind speeds that ranged from 0 to 9 miles per hour (mph). Temperatures ranged from
46 degrees Fahrenheit (°F) to 72°F. The contributing sources of sound observed included
vehicular traffic on the AZ-202 freeway, natural sounds from birds and wind, and overhead
aircraft noise.
The measured hourly Leq data results of the 24-hour ambient noise measurement program are
presented in Figure 2. Tables of the results are provided as Table C-1 in Attachment C.
Hourly noise levels at Measurement Location LT1 ranged from 54.8 to 64.4 A-weighted
decibels (dBA) with the lowest occurring at 1:00 am and the highest occurring at 14:00 pm.
The average measured noise level for the full 24-hour period was 61.8 dBA. Average nighttime
noise levels (10:00 pm to 7:00 am) were 1.5 dBA lower than average daytime noise levels.
Page 3

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
FIGURE 2. HOURLY NOISE LEVELS (LEQ) AT MEASUREMENT LOCATION LT1
Page 4

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
Short-Term Ambient Noise Measurement Program
Meteorological conditions during the measurement program were obtained from the
Falcon Field Weather Station, approximately 10 miles northwest of the Project site,
and included light and variable winds (less than 5 mph) and temperatures that
ranged from 66°F to 72°F. The contributing sources of sound observed included
vehicular traffic, human activity, natural sounds from birds, and overhead aircraft
noise.
Summary of Ambient Measurement Programs
The measured noise levels, measurement periods, and contributing sources of noise
from both ambient noise measurement programs are summarized in Table 1 and
Table 2.
TABLE 1: 24-HOUR AMBIENT NOISE MEASUREMENT PROGRAM SUMMARY
24-Hour Program (December 18, 2025)
Measurement Measurement Overall Average Average Contributing
Location Period Average Measured Measured Noise
Measured Daytime Nighttime Sources
Leq (dBA) Leq (dBA) Leq (dBA)
LT1 December 18, 61.8 62.3 60.8 Vehicular
2025, at 0000 traffic on the
through AZ-202
December 19, freeway,
2025, at 0000 natural sounds
from birds and
wind, aircraft
TABLE 2: SHORT-TERM AMBIENT NOISE MEASUREMENT PROGRAM SUMMARY
Short-Term Program (January 20, 2026)
Measurement Measurement Average Contributing Noise Sources
Location Period Measured
Leq (dBA)
1 – School 1344 – 1354 65.2 School buses, vehicular traffic,
human activity (tennis courts,
pedestrians), aircraft
2 – Church 1403 – 1413 61.8 Vehicular traffic, leaf blowers,
activity at skate park
Page 5

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
Short-Term Program (January 20, 2026)
Measurement Measurement Average Contributing Noise Sources
Location Period Measured
Leq (dBA)
3 – Park 1420 – 1430 57.6 Vehicular traffic, activity at park,
fire department, school bus
4 – Residential 1511 – 1521 66.8 Vehicular traffic, helicopter,
natural sounds
5 – Ellsworth II 1559 - 1609 55.9 Vehicular traffic
West
6 – Ellsworth II 1618 – 1628 53.3 Vehicular traffic, aircraft
North
7 – Ellsworth II 1635 – 1645 50.9 Vehicular traffic, aircraft
East
8 – Ellsworth II 1656 - 1706 53.7 Natural sounds, vehicular traffic
South
Conclusion
The measurement programs revealed that measured noise levels during the
continuous 24-hour program ranged from 54.8 dBA to 64.4 dBA, with an average of
61.8 dBA over the full period. The short-term measurement program revealed
measured noise levels at the noise sensitive locations (residential, school, church
and park) that ranged from 57.6 dBA to 66.8 dBA.
I trust this memo provides the summary required. Please let me know if you have
any questions or require additional information.
Sincerely,
Tony Agresti
Technical Consulting Director, ERM
Page 6

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
ATTACHMENT A NOISE SURVEY DATA SHEETS

Noise Survey Data Sheet
Project/Location Name: Ellsworth, Long-Term 1 (LT1) Location
Investigator Name: Eliza Laden Mauro
Date: 12/16/2025
Meter Manufacturer and Model Casella 63-X (633)
Number:
Serial Number: 1438704
Calibrator Manufacturer, Model, and Casella 114 dB
dB:
Calibrator Serial Number: 2651624
Initial Calibration: 12/16/2025 0714
Final Calibration: 12/20/2025 0944
Meteorological Conditions
Wind Speed: 5 mph
Direction: East
Temperature: 47⁰F
RH %: 62%
Barometric Pressure in mmHg: 763
Predominant noise source(s): Ellsworth Rd traffic, birds
Other noise source(s): AZ-202 Freeway, planes
Time start: 12/18/2025 0000
Time end: 12/19/2025 0000
Comments: N/A
Page 1

North East
South West
Page 2

Noise Survey Data Sheet
Project Name: Ellsworth II, Short-Term Locations
Investigator Name: Eliza Laden Mauro
Date: 1/20/2026
Meter Manufacturer and Model Number: Casella 63X
Serial Number: 4222234
Calibrator Manufacturer, Model, and dB: Casella CEL Class I 114 dB
Calibrator Serial Number: 5060841
Initial Calibration: 13:43
Final Calibration: 19:31
Meteorological Conditions
Wind Speed: 2 mph
Direction: 223⁰SW
Temperature: 72⁰F
RH %: 20
Barometric Pressure in mmHg: 763
Page 1

Measurement Location 1 (School)
Predominant noise source(s): School buses, road noise
Other noise source(s): People (tennis courts, pedestrians),
planes
Time start: 13:44
Time end: 13:54
Photo:
West East
North South
Page 2

Measurement Location 2 (Church)
Predominant noise source(s): Road noise (Point 22 Road)
Other noise source(s): Leaf blowers, skate park
Time start: 14:03
Time end: 14:13
Photo:
North South
East West
Page 3

Measurement Location 3 (Park)
Predominant noise source(s): Road Noise, people at park
Other noise source(s): Fire department, school bus stop
Time start: 14:20
Time end: 14:30
Photo:
North South
East West
Page 4

Measurement Location 4 (Residential)
Predominant noise source(s): Vehicle traffic
Other noise source(s): Helicopter overhead, birds
Time start: 15:11
Time end: 15:21
Photo:
North South
East West
Page 5

Measurement Location 5 (Ellsworth 2_West)
Predominant noise source(s): Cars
Other noise source(s): Freeway traffic
Time start: 15:59
Time end: 16:09
Photo:
North South
East West
Page 6

Measurement Location 6 (Ellsworth 2_North)
Predominant noise source(s): Vehicle traffic
Other noise source(s): Planes
Time start: 16:18
Time end: 16:28
Photo:
North South
East West
Page 7

Measurement Location 7 (Ellsworth 2_ East)
Predominant noise source(s): Vehicle traffic
Other noise source(s): Planes
Time start: 16:35
Time end: 16:45
Photo:
North South
East West
Page 8

Measurement Location 8 (Ellsworth 2_South)
Predominant noise source(s): Birds, vehicle traffic
Other noise source(s): None
Time start: 16:56
Time end: 17:06
Photo:
North South
East West
Page 9

DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
ATTACHMENT B SOUND LEVEL METER
CALIBRATION CERTIFICATE



DATE REFERENCE
February 4, 2026 ERM Project Number 0802264
ATTACHMENT C LOCATION LT1 HOURLY NOISE
LEVEL DATA
TABLE C-1. MEASUREMENT LOCATION LT1 AMBIENT NOISE SUMMARY
Day 3
Measured Leq
Date/Hour Beginning
12/18/2025 0:00 62.8
12/18/2025 1:00 54.8
12/18/2025 2:00 55.4
12/18/2025 3:00 56.6
12/18/2025 4:00 62.3
12/18/2025 5:00 64.2
12/18/2025 6:00 63.7
12/18/2025 7:00 63.8
12/18/2025 8:00 63.9
12/18/2025 9:00 61.5
12/18/2025 10:00 61.5
12/18/2025 11:00 62.0
12/18/2025 12:00 63.4
12/18/2025 13:00 62.0
12/18/2025 14:00 64.4
12/18/2025 15:00 60.9
12/18/2025 16:00 61.9
12/18/2025 17:00 63.4
12/18/2025 18:00 61.5
12/18/2025 19:00 61.1
12/18/2025 20:00 60.2
12/18/2025 21:00 59.7
12/18/2025 22:00 58.1
12/18/2025 23:00 57.5
Lowest Noise Level 54.8
Highest Noise Level 64.4
Daytime (7:00am-10:00pm) 62.3
Nighttime (10:00pm-7:00am) 60.8
Overall Average Leq 61.8