Belmont City Council
February 10, 2026

May 28, 2025
Colin I. Busby
Basin Research Associates
Via Email to: [email protected]
Re: Charles Armstrong School Improvements, Belmont Project, San Mateo County To Whom It May Concern:

A record search of the Native American Heritage Commission (NAHC) Sacred Lands File (SLF) was completed for the information you have submitted for the above referenced project. The results were negative. However, the absence of specific site information in the SLF does not indicate the absence of cultural resources in any project area. Other sources of cultural resources should also be contacted for information regarding known and recorded sites.

Attached is a list of Native American tribes who may also have knowledge of cultural resources in the project area. This list should provide a starting place in locating areas of potential adverse impact within the proposed project area. I suggest you contact all of those indicated; if they cannot supply information, they might recommend others with specific knowledge. By contacting all those listed, your organization will be better able to respond to claims of failure to consult with the appropriate tribe. If a response has not been received within two weeks of notification, the Commission requests that you follow-up with a telephone call or email to ensure that the project information has been received.

If you receive notification of change of addresses and phone numbers from tribes, please notify me. With your assistance, we can assure that our lists contain current information.

If you have any questions or need additional information, please contact me at [email protected].

Sincerely,
Mathew Lin, MPP
Cultural Resources Analyst
Attachment

CHAIRPERSON
Reginald Pagaling
Chumash

VICE-CHAIRPERSON
Buffy McQuillen
Yokayo Pomo, Yuki,
Nomlaki

SECRETARY
Sara Dutschke
Miwok

PARLIAMENTARIAN
Wayne Nelson
Luiseño

COMMISSIONER
Isaac Bojorquez
Ohlone-Costanoan

COMMISSIONER
Stanley Rodriguez
Kumeyaay

COMMISSIONER
Reid Milanovich
Cahuilla

COMMISSIONER
Bennae Calac
Pauma-Yuima Band of
Luiseño Indians

COMMISSIONER
Vacant

ACTING EXECUTIVE

SECRETARY
Steven Quinn

NAHC HEADQUARTERS
1550 Harbor Boulevard
Suite 100
West Sacramento,
California 95691
(916) 373-3710
[email protected]
415
05/28/2025 12:49 PM
1 of 2
Tribe Name Contact Person Contact Address Phone # Email Address Amah Mutsun Tribal Band Ed Ketchum, Vice-Chairperson (530) 578-3864 [email protected] Amah Mutsun Tribal Band Valentin Lopez, Chairperson P.O. Box 5272 Galt, CA, 95632
(916) 743-5833 [email protected]
Amah Mutsun Tribal Band of Mission San
Juan Bautista
Christopher Zimmer, Senior
Cultural Monitor & Consultant,
Councilman
PO Box 214211, 2929 Fulton Ave
Unit 19
Sacramento, CA, 95821
(650) 520-8418 [email protected]
Amah Mutsun Tribal Band of Mission San
Juan Bautista
Irenne Zwierlein, Chairperson 3030 Soda Bay Road
Lakeport, CA, 95453
(916) 730-9468 amahmutsuntribalcommunication
[email protected]
Amah Mutsun Tribal Band of Mission San
Juan Bautista
Garry Zimmer, Senior Cultural
Monitor & Consultant
PO Box 214211, 2929 Fulton Ave
Unit 19
Sacramento, CA, 95821
(408) 771-8901 [email protected]
Amah Mutsun Tribal Band of Mission San
Juan Bautista
Shelby Brown, Senior Cultural
Monitor & Consultant,
Councilwoman
2451 Tyrolean Way
Sacramento, CA, 95821
(916) 276-8380 [email protected]
Amah Mutsun Tribal Band of Mission San
Juan Bautista
Michelle Zimmer, Senior Cultural
Monitor & Consultant
PO Box 214211, 2929 Fulton Ave
Unit 19
Sacramento, CA, 95821
(916) 730-9468 [email protected]
Costanoan Rumsen Carmel Tribe Samuel Rodriguez, Cultural Resource Officer
29539 Oakbridge Dr
Menifee, CA, 92586
(760) 681-6860 [email protected]
Costanoan Rumsen Carmel Tribe Henry Muñoz, Cultural Resource Officer
108 South Acacia
Rialto, CA, 92376
(909) 254-1610 [email protected]
Costanoan Rumsen Carmel Tribe Carla Munoz, Tribal Council (415) 690-3110 [email protected] Indian Canyon Mutsun Band of Costanoan Kanyon Sayers-Roods, Tribal ChairWoman
971 S 7th Street
San Jose, CA, 95122
(408) 673-0626 [email protected]
Indian Canyon Mutsun Band of Costanoan Ann Marie Sayers, Retired Honorable Elder
P.O. Box 28
Hollister, CA, 95024
(831) 637-4238 [email protected]
Muwekma Ohlone Tribe of the SF Bay
Area
Charlene Nijmeh, Chairperson 1169 S. Main Street, Ste. 336 Manteca, CA, 95337
(408) 464-2892 [email protected]
Muwekma Ohlone Tribe of the SF Bay
Area
Richard Massiatt,
Councilmember/MLD Tribal Rep.
1169 S. Main Street, Ste. 336
Manteca, CA, 95337
(209) 321-0372 [email protected]
The Ohlone Indian Tribe Andrew Galvan, Chairperson P.O. Box 3388 Fremont, CA, 94539
Phone: (510) 882-0527 [email protected]
Native American Heritage Commission
Native American Contact List
San Mateo County
5/28/2025
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05/28/2025 12:49 PM
2 of 2
Native American Heritage Commission
Native American Contact List
San Mateo County
5/28/2025
The Ohlone Indian Tribe Desiree Vigil, THPO 259 Winwood Avenue Pacifica, CA, 94044
(650) 290-0245 [email protected]
The Ohlone Indian Tribe Vincent Medina, Cultural Leader 17365 Via Del Rey San Lorenzo, CA, 94580
(510) 610-7587 [email protected]
Wuksachi Indian Tribe/Eshom Valley Band Kenneth Woodrow, Chairperson 1179 Rock Haven Ct.

Salinas, CA, 93906
(831) 443-9702 [email protected]
This list is current only as of the date of this document. Distribution of this list does not relieve any person of statutory responsibility as defined in Section 7050.5 of the Health and Safety Code, Section 5097.94 of the Public Resources Code and Section 5097.98 of the Public Resources Code.

This list is only applicable for contacting local Native Americans with regard to cultural resources assessment for the proposed Charles Armstrong School Improvements, Belmont Project, San Mateo County.
417
6/16/2025 NWIC File No.: 24-1878
Donna M. Garaventa
Basin Research Associates
1933 Davis Street, Suite 214
San Leandro, CA 94577
Re: Armstrong Belmont
The Northwest Information Center received your record search request for the project area referenced above, located on the San Mateo USGS 7.5’ quad(s). The following reflects the results of the records search for the project area and a ¼ mile radius:

Resources within project area: None
Resources within ¼ mile radius: None
Informal Res. w/in ¼ mile radius C-331
Reports within project area: None
Reports within ¼ mile radius: S-025256
*Informal Resources are those resources not recorded on DPR 523A primary record forms and not submitted in CHRIS standard format to an IC by OHP.

Resource Database Printout (list): ☐ enclosed ☐ not requested ☒ nothing listed Resource Database Printout (details): ☐ enclosed ☐ not requested ☒ nothing listed Resource Digital Database Records: ☐ enclosed ☒ not requested ☐ nothing listed Report Database Printout (list): ☒ enclosed ☐ not requested ☐ nothing listed Report Database Printout (details): ☒ enclosed ☐ not requested ☐ nothing listed Report Digital Database Records: ☐ enclosed ☒ not requested ☐ nothing listed Resource Record Copies: ☐ enclosed ☐ not requested ☒ nothing listed Report Copies: (Client to check before ordering) ☐ enclosed ☒ not requested ☐ nothing listed OHP Built Environment Resources Directory: ☐ enclosed ☐ not requested ☒ nothing listed OHP Archaeological Resources Directory: ☐ enclosed ☐ not requested ☒ nothing listed CA Inventory of Historic Resources (1976): ☐ enclosed ☒ not requested ☐ nothing listed Caltrans Bridge Survey: ☐ enclosed ☒ not requested ☐ nothing listed Ethnographic Information: ☐ enclosed ☒ not requested ☐ nothing listed 418
Historical Literature: ☐ enclosed ☒ not requested ☐ nothing listed Historical Maps: ☐ enclosed ☒ not requested ☐ nothing listed Local Inventories: ☐ enclosed ☒ not requested ☐ nothing listed GLO and/or Rancho Plat Maps: ☐ enclosed ☒ not requested ☐ nothing listed Shipwreck Inventory: ☐ enclosed ☒ not requested ☐ nothing listed Soil Survey Maps: ☐ enclosed ☒ not requested ☐ nothing listed Please forward a copy of any resulting reports from this project to the office as soon as possible. Due to the sensitive nature of archaeological site location data, we ask that you do not include resource location maps and resource location descriptions in your report if the report is for public distribution.

If you have any questions regarding the results presented herein, please contact the office at the phone number listed above.

The provision of CHRIS Data via this records search response does not in any way constitute public disclosure of records otherwise exempt from disclosure under the California Public Records Act or any other law, including, but not limited to, records related to archeological site information maintained by or on behalf of, or in the possession of, the State of California, Department of Parks and Recreation, State Historic Preservation Officer, Office of Historic Preservation, or the State Historical Resources Commission.

Due to processing delays and other factors, not all of the historical resource reports and resource records that have been submitted to the Office of Historic Preservation are available via this records search. Additional information may be available through the federal, state, and local agencies that produced or paid for historical resource management work in the search area. Additionally, Native American tribes have historical resource information not in the CHRIS Inventory, and you should contact the California Native American Heritage Commission for information on local/regional tribal contacts.

Should you require any additional information for the above referenced project, reference the record search number listed above when making inquiries. Requests made after initial invoicing will result in the preparation of a separate invoice.

Thank you for using the California Historical Resources Information System (CHRIS).

Sincerely,
Justin Murazzo
Justin Murazzo, Researcher
419
Report List
Report No. Other IDs Year Author(s) Title Affiliation Resources 24-1878 :: Armstrong Belmont
S-025256 2000 Archaeological Field Inspection of the Ralston Village Project, Belmont, San Mateo County,
California (letter report)
Miley Holman

420
Prepared for Charles Armstrong School
1350 Ocean Avenue • Emeryville, CA 94608 • (510) 420-5738 www.rockridgegeo.com

GEOTECHNICAL INVESTIGATION

PROPOSED IMPROVEMENTS

CHARLES ARMSTRONG SCHOOL
1405 SOLANA DRIVE

BELMONT, CALIFORNIA

UNAUTHORIZED USE OR COPYING OF THIS DOCUMENT IS STRICTLY

PROHIBITED BY ANYONE OTHER THAN THE CLIENT FOR THE SPECIFIC

PROJECT
August 2, 2024
Project No. 24-2627
421
1350 Ocean Avenue • Emeryville, CA 94608 • (510) 420-5738 www.rockridgegeo.com
August 2, 2024
Project No. 24-2627
Charles Armstrong School
c/o Bob Olson, Cumming Group
1405 Solana Drive
Belmont, California 94002
Subject: Geotechnical Investigation
Proposed Improvements
Charles Armstrong School
1405 Solana Drive
Belmont, California
Dear Bob Olson:

We are pleased to present the results of our geotechnical investigation for the proposed improvements to be constructed at the Charles Armstrong School in Belmont, California. Our investigation was performed in accordance with our proposal dated April 24, 2024.

The Charles Armstrong School campus (site) encompasses an area of about 4.9 acres and slopes down to the south, with about 40 feet of elevation change between the northeastern and southeastern corners of the site. It is bordered by McDougal Park to the west, Solana Drive to the north, and single-family residences to the east and south. The site is currently occupied by single-story school buildings in the middle of the site surrounded by drive aisles, a parking lot, basketball court, and other outdoor activity areas.

Plans are to construct three new structures, including two buildings to the east of the classroom buildings and a gymnasium in the playground south of the school buildings. Cuts up to about 10 feet will be required to construct the new buildings on the eastern side of the site.

Based on the results of our geotechnical investigation, we conclude there are no major geotechnical issues that would preclude development of the site as proposed. We conclude the proposed structures can be supported on spread footings bearing in residual soil and/or bedrock or alternatively, on mat foundations.

The recommendations contained in our report are based on limited subsurface exploration.

Consequently, variations between expected and actual subsurface conditions may be encountered during construction. Therefore, we should be engaged to observe site preparation, shoring installation (if needed), fill placement, and foundation installation, during which time we may make changes to our recommendations if deemed necessary. 422
Charles Armstrong School
c/o Cumming Group
August 2, 2024

We appreciate the opportunity to provide our services to you on this project. Should you have any questions, please call.

Sincerely,
ROCKRIDGE GEOTECHNICAL, INC.

Craig S. Shields, P.E., G.E. Alex D. Limpert, P.E.

Principal Engineer Project Engineer
Enclosure
QUALITY CONTROL REVIEWER:

Linda H. J. Liang, P.E., G.E.

Principal Engineer
8/2/2024 8/2/2024
423

TABLE OF CONTENTS

1.0 INTRODUCTION ...............................................................................................................1

2.0 SCOPE OF SERVICES .......................................................................................................1

3.0 FIELD INVESTIGATION AND LABORATORY TESTING...........................................2

3.1 Dynamic Penetrometer Tests...................................................................................2

3.2 Test Borings.............................................................................................................3

3.3 Laboratory Testing...................................................................................................4

4.0 SUBSURFACE CONDITIONS ..........................................................................................4

4.1 Groundwater ............................................................................................................4

5.0 SEISMIC CONSIDERATIONS ..........................................................................................5

5.1 Regional Seismicity .................................................................................................5

5.2 Geologic Hazards.....................................................................................................7

5.2.1 Ground Shaking ...........................................................................................7

5.2.2 Ground Surface Rupture ..............................................................................7

5.2.3 Liquefaction and Liquefaction-Induced Settlement.....................................8

5.2.4 Cyclic Densification.....................................................................................8

5.2.5 Earthquake-Induced Slope Instability..........................................................9

6.0 DISCUSSION AND CONCLUSIONS ...............................................................................9

6.1 Foundations and Support .........................................................................................9

6.2 Excavation in Rock................................................................................................10

6.3 Soil Corrosivity......................................................................................................10

7.0 RECOMMENDATIONS...................................................................................................11

7.1 Site Preparation, Grading and Fill Placement........................................................11

7.1.1 Utility Trench Backfill...............................................................................12

7.1.2 Exterior Concrete Flatwork........................................................................13

7.2 Temporary and Permanent Slopes.........................................................................13

7.2.1 Temporary Slopes......................................................................................13

7.2.2 Permanent Cut and Fill Slopes...................................................................13

7.3 Surface and Subsurface Drainage ..........................................................................14

7.3.1 Surface Drainage........................................................................................14

7.3.2 Subsurface Drainage ..................................................................................15

7.4 Foundations............................................................................................................16

7.4.1 Spread Footings .........................................................................................16

7.4.2 Mat Foundation..........................................................................................17

7.5 Concrete Slabs-on-Grade and Vapor Barrier.........................................................19

7.6 Retaining Walls......................................................................................................19

7.7 Excavations and Temporary Shoring.....................................................................21

7.7.1 Cantilevered Soldier Pile and Lagging Shoring System............................27 424

7.7.2 Soil Nails....................................................................................................28

7.8 Seismic Design.......................................................................................................29

8.0 ADDITIONAL GEOTECHNICAL SERVICES...............................................................30

9.0 LIMITATIONS..................................................................................................................30

REFERENCES

FIGURES
APPENDIX A – Dynamic Penetrometer Test Results and Logs of Borings APPENDIX B – Laboratory Test Results

LIST OF FIGURES
Figure 1 Site Location Map
Figure 2 Site Plan
Figure 3 Regional Geologic Map
Figure 4 Regional Fault and Historic Seismicity Map
Figure 5 Earthquake Zones of Required Investigation
Figure 6 Generalized ICPI Permeable Paver Detail for Partial Exfiltration

APPENDIX A
Figures A-1 Dynamic Penetrometer Test Results, DPT-1 through through A-4 DPT-4
Figures A-5 Logs of Borings, B-1 through B-3
through A-7
Figure A-8 Classification Chart
Figure A-9 Physical Properties Criteria for Rock Descriptions

APPENDIX B
Figure B-1 Plasticity Chart
Figure B-2 Soil Corrosivity Test Results
425
24-2627 1 August 2, 2024

GEOTECHNICAL INVESTIGATION

PROPOSED IMPROVEMENTS

CHARLES ARMSTRONG SCHOOL
1405 SOLANA DRIVE

BELMONT, CALIFORNIA

1.0 INTRODUCTION
This report presents the results of the geotechnical investigation performed by Rockridge Geotechnical, Inc. for the proposed improvements to be constructed at the Charles Armstrong School in Belmont, California. The subject property is on the southern side of Solana Drive just west of its intersection with Altura Way, as shown in the Site Location Map (Figure 1).

The Charles Armstrong School campus (site) encompasses an area of about 4.9 acres and slopes down to the south, with about 40 feet of elevation change between the northeastern and southeastern corners of the site. It is bordered by McDougal Park to the west, Solana Drive to the north, and single-family residences to the east and south. The site is currently occupied by singlestory school buildings in the middle of the site surrounded by drive aisles, a parking lot, basketball court, and other outdoor activity areas.

Plans are to construct three new structures, including two buildings to the east of the classroom buildings and a gymnasium in the playground south of the school buildings. Cuts up to about 10 feet will be required to construct the new buildings on the eastern side of the site.

2.0 SCOPE OF SERVICES
Our investigation was performed in accordance with our proposal dated April 24, 2024. Our scope of services consisted of exploring subsurface conditions at the site, performing laboratory testing on selected soil samples, and performing engineering analyses to develop conclusions and recommendations regarding:
• soil and groundwater conditions at the site
• site seismicity and seismic hazards
• the most appropriate foundation type(s) for the proposed improvements 426
24-2627 2 August 2, 2024
• design criteria for the recommended foundation type(s), including vertical and lateral capacities
• estimates of foundation settlement
• design parameters for design of new retaining walls
• site grading and excavation, including criteria for fill quality and compaction • subgrade preparation for pavements and new concrete slab-on-grade floors • design for temporary shoring
• 2022 California Building Code (CBC) site class and design spectral response acceleration parameters
• soil corrosivity
• construction considerations.

3.0 FIELD INVESTIGATION AND LABORATORY TESTING
We explored the subsurface conditions at the site by performing four dynamic penetrometer tests (DPTs), drilling three test borings, and performing laboratory testing on selected soil samples.

Before performing the field investigation, we filed a drilling notification form in accordance with our annual permit with San Mateo County Environmental Health Services Division (SMCEHSD). We also contacted Underground Services Alert (USA) to notify them of our work, as required by law, and retained C. Cruz Sub-Surface Locators of Milpitas, California, a private utility locator, to check the DPT and boring locations to reduce the potential for encountering buried utilities during our field investigation. Details of our field investigation and laboratory testing are presented in this section.

3.1 Dynamic Penetrometer Tests
On June 12, 2024, we performed four DPTs, designated as DPT-1 through DPT-4, at the approximate locations shown in Figure 2. The DPTs consist of manually driving a 1.4-inchdiameter cone-tipped probe with a 35-pound hammer falling 15 inches. The blow counts required to drive the probe are recorded at 10-centimeter intervals. The DPTs were advanced to practical refusal, defined as more than 50 blows per 10-centimeter (4-inch) interval, at depths of about 1 to 3 feet below the ground surface (bgs). The DPT results are presented in Figures A-1 through A-4. 427
24-2627 3 August 2, 2024

3.2 Test Borings
Three test borings, designated as B-1 through B-3, were drilled on June 17, 2024 by Stapleton Engineering and Exploration of Santa Rosa, California at the approximate locations shown in Figure 2. The borings were drilled using hydraulic drilling equipment mounted on a skid steer equipped with 4-inch-diameter solid-stem flight augers. The borings were drilled to practical refusal in bedrock at depths of about 4.75 to 7.25 feet bgs.

During drilling, our field engineer logged the soil and bedrock encountered and obtained representative samples for visual classification and laboratory testing. The boring logs are presented in Figures A-5 through A-7 in Appendix A. The soil and rock encountered in the borings were classified in accordance with the classification systems presented in Figures A-8 and A-9, respectively.

Soil samples were obtained using:
• Modified California (MC) split-barrel sampler with a 3.0-inch outside diameter and 2.5- inch inside diameter, lined with 2.43-inch inside diameter stainless steel tubes. • Standard Penetration Test (SPT) split-barrel sampler with a 2.0-inch outside and 1.5-inch inside diameter; the sampler was designed to accommodate liners, but liners were not used.

The samplers were driven with a 140-pound rope-and-cathead safety hammer falling about 30 inches per drop. The samplers were driven up to 18 inches, and the hammer blows required to drive the samplers were recorded every 6 inches and are presented in the boring logs. A “blow count” is defined as the number of hammer blows per 6 inches of penetration or 50 blows for 6 inches or less of penetration. The blow counts required to drive the MC and SPT samplers were converted to approximate SPT N-values using factors of 0.7 and 1.2, respectively, to account for sampler type, approximate hammer energy, and the fact that the SPT sampler was designed to accommodate liners, but liners were not used. The blow counts used for this conversion were the last two blow counts if the sampler was advanced more than 12 inches or the last one blow count if the sampler was advanced 12 inches or less. The converted SPT N-values are presented in the boring logs.
428
24-2627 4 August 2, 2024
Upon completion of drilling, the boreholes were backfilled with neat cement grout in accordance with SMCEHSD requirements. The soil cuttings were left on-site near the boreholes.

3.3 Laboratory Testing
We re-examined the soil samples in the office to confirm the field classifications and selected representative samples for laboratory testing. Soil samples were tested by Inspection Services, Inc. of Berkeley, California to measure moisture content, dry density, and plasticity (Atterberg limits). Soil corrosivity testing was performed by Project X Corrosion Engineering, Inc. of Murrieta, California on two samples from the borings. The results of the laboratory tests are presented in the boring logs and Appendix B.

4.0 SUBSURFACE CONDITIONS
Regional geologic information (Figure 3) indicates the site is underlain by early Cretaceous and/or late Jurassic-age Franciscan complex sedimentary rock (KJfs). The results of our field investigation indicate the site is underlain by between 1 to 3 feet of soil overlying residual soil and/or bedrock. The soil encountered in our borings consists of stiff to very stiff sandy clay with occasional gravel, extending to depths of about 1.5 to 3.25 feet bgs. The surficial soil is underlain by residual soil, consisting of medium dense to very dense clayey sand and clayey gravel.

Atterberg limits tests performed on two near-surface samples indicate the near-surface soil has low to moderate expansion potential with plasticity indices (PIs) of 8 and 16.

Bedrock was encountered between 4.25 and 5 feet bgs in the three borings. Based on the shallow refusal depths in the DPTs, we estimate the depth to bedrock at the four DPT locations ranged from about 0.5 to 3 feet bgs. The bedrock encountered in the borings consisted of friable to weak, soft to low hardness, deeply to completely weathered sandstone and shale.

4.1 Groundwater
Groundwater was not encountered during our investigation. We did not observe any evidence of groundwater seepage at the site during our investigation. Groundwater levels may vary seasonally and depend on a variety of factors, such as landscape irrigation in the site vicinity and 429
24-2627 5 August 2, 2024
seasonal rainfall. Considering the site topography and potential shallow depth to bedrock, we anticipate there may be seasonal perched groundwater on or near the surface of the bedrock. This erratic and unpredictable groundwater may be controlled by installing backdrains behind new retaining walls and new basement walls (see Section 7.3.2).

5.0 SEISMIC CONSIDERATIONS

5.1 Regional Seismicity
The site is located within the Coast Ranges Geomorphic Province of California, which is characterized by northwest-trending valleys and ridges. These topographic features are controlled by folds and faults that resulted from the collision of the Farallon and North American plates and subsequent strike-slip faulting along the San Andreas Fault system. The San Andreas Fault is more than 600 miles long and extends from Point Arena in the north to the Gulf of California in the south. The Coast Ranges Geomorphic Province is bounded on the east by the Great Valley and on the west by the Pacific Ocean.

The major active faults in the area are the San Andreas, San Gregorio, and Hayward faults. These and other faults in the region are shown in Figure 4. For these and other active faults within a 50- kilometer radius of the site, the distance from the site and estimated characteristic moment magnitude1[Petersen et al. (2014) & Thompson et al. (2016)] are summarized in Table 1. These references are based on the Third Uniform California Earthquake Rupture Forecast (UCERF3), prepared by Field et al. (2013).
1 Moment magnitude (Mw) is an energy-based scale and provides a physically meaningful measure of the size of a faulting event. Moment magnitude is directly related to average slip and fault rupture area. 430
24-2627 6 August 2, 2024
TABLE 1
Regional Faults and Seismicity
Fault Segment
Approximate
Distance from Site
(km)
Direction
from Site
Characteristic
Moment
Magnitude
Monte Vista - Shannon 4.7 Southwest 7.14
Total North San Andreas
(SAO+SAN+SAP+SAS) 4.8 Southwest 8.04
North San Andreas (Peninsula,
SAP) 4.8 Southwest 7.38
San Gregorio (North) 17 West 7.44
Butano 24 Southwest 6.93
Total Hayward + Rodgers Creek
(RC+HN+HS+HE) 25 Northeast 7.58
Hayward (South, HS) 25 Northeast 7.00
Hayward (North, HN) 32 Northeast 6.90
Zayante-Vergeles (2011 CFM) 36 South 7.48
Total Calaveras (CN+CC+CS+CE) 37 East 7.43
Calaveras (North, CN) 37 East 6.86
Calaveras (Central, CC) 42 East 6.85
Mount Diablo Thrust North CFM 43 Northeast 6.72
Las Positas 43 East 6.50
Mount Diablo Thrust South 44 Northeast 6.50
Hayward (Extension, HE) 44 East 6.18
North San Andreas (Santa Cruz Mts,
SAS) 45 Southeast 7.15
Mount Diablo Thrust 45 Northeast 6.67
Damaging earthquakes have occurred along many of these faults in recorded history, as depicted in Figure 4 (USGS, 2021). Notable historic earthquakes which have impacted the Bay Area in recorded history include:
• 1838 San Andreas Earthquake, Mw = 7.4 (estimated)
• 1865 San Andreas Earthquake, Mw = 6.5 (estimated)
• 1868 Hayward Earthquake, Mw = 7.0 (estimated)
• 1906 Great San Francisco Earthquake (San Andreas Fault), Mw = 7.9 (estimated) • 1989 Loma Prieta Earthquake (San Andreas Fault), Mw = 6.9 431
24-2627 7 August 2, 2024
• 2014 West Napa Earthquake, Mw = 6.0
As a part of the UCERF3 project, researchers estimated that the probability of at least one Mw ≥ 6.7 earthquake occurring in the greater San Francisco Bay Area during a 30-year period (starting in 2014) is 72 percent. The highest probabilities are assigned to sections of the Hayward (South), Calaveras (Central), and San Andreas (Santa Cruz Mountains) faults. The respective probabilities are approximately 25, 21, and 17 percent.

5.2 Geologic Hazards
Because the site is in a seismically active region, we evaluated the potential for earthquakeinduced geologic hazards including ground shaking, ground surface rupture, liquefaction,2 lateral
spreading,3and cyclic densification.
4 We used the results of our investigation to evaluate the potential of these phenomena occurring at the site.

5.2.1 Ground Shaking
The seismicity of the site is governed by the activity of the San Andreas Fault, although ground shaking from future earthquakes on other faults, including the Hayward and San Gregorio faults, will also be felt at the site. The intensity of earthquake ground motion at the site will depend upon the characteristics of the generating fault, distance to the earthquake epicenter, and magnitude and duration of the earthquake. We judge strong to very strong ground shaking could occur at the site during a large earthquake on one of the nearby faults.

5.2.2 Ground Surface Rupture
Historically, ground surface displacements closely follow the trace of geologically young faults.

The site is not within an Earthquake Fault Zone, as defined by the Alquist-Priolo Earthquake 2 Liquefaction is a phenomenon where loose, saturated, cohesionless soil experiences temporary reduction in strength during cyclic loading such as that produced by earthquakes. 3 Lateral spreading is a phenomenon in which surficial soil displaces along a shear zone that has formed within an underlying liquefied layer. Upon reaching mobilization, the surficial blocks are transported downslope or in the direction of a free face by earthquake and gravitational forces. 4 Cyclic densification is a phenomenon in which non-saturated, cohesionless soil is compacted by earthquake vibrations, causing ground-surface settlement. 432
24-2627 8 August 2, 2024
Fault Zoning Act, and no known active or potentially active faults exist on the site. Therefore, we conclude the probability of fault offset at the site from a known active fault to be very low. In a seismically active area, the remote possibility exists for future faulting in areas where no faults previously existed; however, we conclude that the probability of surface faulting, and consequently secondary ground failure from previously unknown faults, is very low.

5.2.3 Liquefaction and Liquefaction-Induced Settlement
When saturated, cohesionless soil liquefies, it experiences a temporary loss of shear strength created by a transient rise in excess pore pressure generated by a strong ground motion. Soil susceptible to liquefaction includes loose to medium dense sand and gravel, low-plasticity silt, and some low-plasticity clay deposits. Flow failure, lateral spreading, differential settlement, loss of bearing strength, ground fissures, and sand boils are evidence of excess pore pressure generation and liquefaction.

The site has not been mapped within a zone of liquefaction hazard zone as shown on the map titled Earthquake Zones of Required Investigation, San Mateo Quadrangle, prepared by the California Geological Survey and dated January 11, 2018. In our borings, bedrock was encountered at depths of 1 to 5 feet bgs, with primarily cohesive soil above the bedrock. Bedrock is not susceptible to liquefaction. Furthermore, the soil present above the bedrock is not susceptible to liquefaction due to its cohesion. Therefore, we conclude that the potential for liquefaction and liquefaction-induced ground failures, such as lateral spreading, to occur at the site during a major earthquake is nil.

5.2.4 Cyclic Densification
Cyclic densification (also referred to as differential compaction) of non-saturated sand (sand above the groundwater table) can occur during an earthquake, resulting in settlement of the ground surface and overlying improvements. The results of our field investigation indicate the soil above the groundwater at the site is not susceptible to cyclic densification due to its cohesion and/or relative density. Therefore, we conclude that the potential for ground surface settlement resulting from cyclic densification at the site is nil. 433
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5.2.5 Earthquake-Induced Slope Instability
The west-facing, moderately steep slope along the eastern edge of the property is mapped as an earthquake-induced landslide hazard zone, as shown on the map titled Earthquake Zones of Required Investigation, San Mateo Quadrangle, prepared by the California Geological Survey and dated January 11, 2018 (see Figure 5). This zone is defined as “Areas where previous occurrence of landslide movement, or local topographic, geological, geotechnical and subsurface water conditions indicate a potential for permanent ground displacements...” Areas most susceptible to earthquake-induced landslides are steep slopes in poorly cemented or highly fractured rock, areas underlain by loose, weak soils, and areas on or adjacent to existing landslide deposits. The methodology used to make the State Seismic Hazard Map is based on earthquake ground-shaking estimates, geologic material strength characteristics, and slope gradient.

Considering the shallow depth to bedrock underlying the site and the lack of evidence of past landsliding, we judge the potential for earthquake-induced landsliding adversely impacting the proposed improvements is low. In addition, we conclude the proposed structures will not negatively impact the slope stability at the site or in the surrounding area if designed and constructed following the recommendations presented in this report.

6.0 DISCUSSION AND CONCLUSIONS
From a geotechnical standpoint, we conclude the site can be developed as planned, provided the recommendations presented in this report are incorporated into the project plans and specifications and implemented during construction. The primary geotechnical concerns for the improvements are providing adequate foundation and excavation support.

6.1 Foundations and Support
Based on our field investigation, the locations for proposed improvements encountered firm native soil overlying residual soil/bedrock. We conclude new foundations for the proposed improvements may consist of spread footings bearing on residual soil and/or bedrock. Where the depth to suitable bearing soil/bedrock is more than about 3 feet deep, the lower portion of the footing excavation can be filled with controlled low-strength material (CLSM). The CLSM 434
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would serve to transfer footing loads to the bedrock and prevent the need for extending reinforced structural concrete down to rock. Alternatively, the buildings can be supported on mat foundations bearing on native soil, residual soil and/or bedrock. We estimate total and differential settlements of properly constructed shallow foundations bearing on residual soil or bedrock will be less than 1/2 inch and 1/4 over a horizontal distance of 30 feet, respectively.

6.2 Excavation in Rock
Excavations and drilling in rock will be required to construct the proposed improvements, including cuts of up to about 10 feet. Where encountered in our borings, the bedrock is generally friable to weak, soft to low hardness, deeply to completely weathered sandstone and shale, and becomes moderately hard with depth. The rock varies substantially in hardness and degree of weathering. We anticipate weathered rock can be excavated with a backhoe; however, excavation of harder rock that will require the use of hydraulic breaking equipment (i.e., a hoe ram) may be encountered. Therefore, the contractors involved in shoring and foundation installation should be prepared to excavate hard rock, including the possibility of hydraulic breaking equipment, and should bid the project accordingly. The material descriptions and SPT N-values presented in our borings should be evaluated by the contractor when bidding the project and selecting appropriate equipment.

6.3 Soil Corrosivity
Corrosivity tests were performed by Project X Corrosion Engineering of Murrieta, California on soil samples obtained from borings B-1 and B-3 at depths of 1.25 and 3.5 feet bgs, respectively.

The corrosivity test results are presented in Appendix B.

Many factors can affect the corrosion potential of soil including, but not limited to, resistivity, pH, and chloride and sulfate concentrations. Based on the minimum soil resistivity measurements of 4,020 and 3,149 ohm-cm, we conclude the soil is “corrosive” to buried metal (Roberge, 2018). Accordingly, all buried iron, steel, cast iron, galvanized steel, and dielectriccoated steel or iron should be protected against corrosion depending upon the critical nature of 435
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the structure. If it is necessary to have metal in contact with soil, a corrosion engineer should be consulted to provide recommendations for corrosion protection.

The results of the pH tests (6.5 and 6.8) indicate the near-surface soil is “mildly corrosive” to buried metallic and concrete structures. The chloride ion concentrations (24.6 and 20.7 mg/kg) indicate the chlorides in the near-surface soil are “negligibly corrosive” to buried metallic structures and reinforcing steel in concrete structures below ground. The results also indicate the sulfate ion concentrations (78.5 and 39.2 mg/kg) are sufficiently low such that sulfates do not pose a threat to buried concrete and mortars.

7.0 RECOMMENDATIONS
Our recommendations for site preparation and grading, foundation design, shoring, and other geotechnical aspects of the project are presented in this section.

7.1 Site Preparation, Grading and Fill Placement
In areas that will receive fill or improvements (i.e., new floor slabs, building pads, concrete flatwork), the soil subgrade exposed should be scarified to a depth of at least 8 inches, moistureconditioned to above optimum moisture content, and compacted to at least 90 percent relative compaction.5 The soil subgrade should be kept moist until it is covered by fill. Scarification and re-compaction will not be required where residual soil and/or bedrock is exposed at finished subgrade elevation. If zones of poorly compacted undocumented fill or weak/unstable soil are encountered during site preparation and grading within future building pads, the fill should be overexcavated under the observation of our field engineer and replaced as properly compacted fill.

Fill should consist of on-site soil or imported (select) fill that is free of organic matter, contains no rocks or lumps larger than 3 inches in greatest dimension, and be approved by the Geotechnical Engineer. Imported select fill should also have a liquid limit less than 40 and 5 Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same material, as determined by the ASTM D1557 laboratory compaction procedure.
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plasticity index less than 12 and be approved by the Geotechnical Engineer. Samples of proposed imported fill material should be submitted to the Geotechnical Engineer at least three business days prior to use at the site. The grading contractor should provide analytical test results or other suitable environmental documentation indicating the imported fill is free of hazardous materials at least three days before use at the site. If this data is not provided, a minimum of two weeks will be required to perform any necessary analytical testing.

Fill should be placed in horizontal lifts not exceeding 8 inches in uncompacted thickness, moisture-conditioned to above optimum moisture content, and compacted to at least 90 percent relative compaction. Fill consisting of clean sand or gravel (defined as poorly graded soil with less than 5 percent fines by weight) or greater than 5 feet in thickness should be compacted to at least 95 percent relative compaction. Fill placement within the upper 12 inches of vehicular pavement soil subgrade should also be compacted to at least 95 percent relative compaction and be non-yielding.

7.1.1 Utility Trench Backfill
Excavations for utility trenches can be readily made with a backhoe. All trenches should conform to the current CAL-OSHA requirements. To provide uniform support, pipes or conduits should be bedded on a minimum of 4 inches of clean sand or fine gravel. After the pipes and conduits are tested, inspected (if required), and approved, they should be covered to a depth of 6 inches with sand or fine gravel, which should be mechanically tamped.

Footings/mat foundations should be bottomed below an imaginary line extending up at a 1.5:1 (horizontal to vertical) inclination from the base of existing or new utility trenches. Alternatively, the portion of the utility trench (excluding bedding) that is below the 1.5:1 line can be backfilled with controlled low-strength material (CLSM) with a 28-day unconfined compressive strength of at least 100 pounds per square inch (psi) or Class 2 aggregate base compacted to at least 95 percent relative compaction.

Backfill for utility trenches and other excavations is also considered fill and should be placed and compacted in accordance with the recommendations previously presented. If imported clean sand 437
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or imported clean gravel (defined as soil with less than 5 percent fines) is used as backfill, it should be compacted to at least 95 percent relative compaction. Jetting of trench backfill should not be permitted. Special care should be taken when backfilling utility trenches in pavement areas. Poor compaction may cause excessive settlements, resulting in damage to the pavement section.

7.1.2 Exterior Concrete Flatwork
We recommend a minimum of 4 inches of Class 2 aggregate base be placed beneath proposed exterior concrete flatwork, including sidewalks; the aggregate base should extend at least 6 inches beyond the slab edges where the flatwork is adjacent to landscaping. Class 2 aggregate base placed beneath exterior slabs-on-grade not subject to vehicular loading, such as patios and sidewalks, should be moisture-conditioned to near optimum moisture content, and compacted to at least 90 percent relative compaction. Prior to placement of the aggregate base, the subgrade should be scarified to a depth of at least 8 inches, moisture-conditioned to above optimum moisture content, and re-compacted to at least 90 percent relative compaction.

7.2 Temporary and Permanent Slopes

7.2.1 Temporary Slopes
Where space permits, the sides of the proposed cuts may be sloped. Temporary slopes in the native soil or residual soil should be sloped no steeper than 1:1 (horizontal to vertical).

Allowable inclinations for temporary slopes in bedrock will depend on bedrock quality and the orientation of joints and fractures. For planning purposes, an allowable slope inclination of ½:1 in bedrock may be assumed; however, a geologist should examine the bedrock to confirm there is no adverse orientation of joints and fractures that may result in instability of the cuts. During construction, we should observe cut slopes to verify the inclinations are appropriate for the conditions encountered.

7.2.2 Permanent Cut and Fill Slopes
Permanent fill slopes comprised of engineered fill and cut slopes in stiff native soil should be inclined no steeper than 2:1 (horizontal to vertical). For planning purposes, an inclination of 438
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1.5:1 should be assumed for permanent cut slopes in bedrock. All permanent cut slopes in bedrock should be observed during grading by a geologist for signs of adverse orientation of joints and fractures. Should such adverse slope conditions be detected by the geologist during grading, remedial alternatives will be provided at that time based on the exposed conditions.

7.3 Surface and Subsurface Drainage

7.3.1 Surface Drainage
Positive surface drainage should be provided around the buildings to direct surface water away from the foundations. Grades around the building should be designed by the Civil Engineer and conform to the requirements of the 2022 CBC, which will help minimize stormwater accumulation adjacent to foundations. In addition, roof downspouts should be discharged into controlled drainage facilities to keep water away from the foundations. The use of waterintensive landscaping around the perimeter of the buildings should be avoided.

Care should be taken to minimize the potential for subsurface water to collect beneath pavements and pedestrian walkways. Where landscape beds and tree wells are immediately adjacent to pavements and flatwork, we recommend vertical cutoff barriers be incorporated into the design to prevent irrigation water from saturating the subgrade and aggregate base. These barriers may consist of either flexible impermeable membranes or deepened concrete curbs.

7.3.2 Bioswales
The primary concerns with providing bio-retention areas for this site are: 1) providing suitable support for foundations and curbs constructed near the bio-retention areas and 2) the potential for subsurface water from the bio-retention areas to migrate (and possibly build up) beneath pavements and the proposed building. Consequently, we recommended that bioswales constructed at the site be provided with underdrains and/or drain inlets; moreover, bioswales should be constructed at least 5 feet from buildings. The subdrain pipes should be installed 8 inches above the bottom of the infiltration area for treatment areas at least 5 feet away from the buildings and pavements. The intent of this recommendation is to allow infiltration into the 439
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underlying soil but reduce the potential for bio-retention areas to flood during periods of heavy rainfall.

Where bio-retention areas are constructed within 5 feet of buildings, the sides and bottom of the treatment area within 5 feet of buildings should be lined with an impermeable liner. Where bioretention areas are constructed within 5 feet of pavements, a 4-inch-diameter perforated subdrain pipe should be placed 4 inches above the base of the treatment area, or the bottom of the treatment area should be lined with an impermeable liner. Where a foundation is constructed near a bio-retention area, the edge of the foundation should be founded below an imaginary line extending up at an inclination of 1.5:1 (horizontal to vertical) from the base of the bio-retention area.

Where bio-retention areas are planned within parking lots or along streets adjacent to vehicular loading, the walls of the bio-retention areas should be designed as retaining walls that can withstand vehicular loading.

7.3.3 Subsurface Drainage
Because some of the proposed buildings will be constructed by cutting into a hillside, there is potential for perched water to be present in the cut. Furthermore, because residual soil and bedrock will be exposed near the ground surface in the cuts to construct the building pads, infiltration of rainwater into the ground will likely be slow. To mitigate the potential for perched water to adversely impact the proposed improvements, we recommend a foundation subdrain be installed adjacent to the entire perimeter of each building. The subdrain trench should be at least 12 inches wide and extend at least 18 inches below grade but should not extend below the bottom of spread footings/mat foundations. The bottom of the subdrain trench should slope at a minimum inclination of one percent to a suitable outlet. A perforated 4-inch-diameter Schedule 40 PVC pipe should be placed (with perforations facing down) at the bottom of the trench with a gradient of at least one percent and underlain by 2 inches of Class 2 permeable material. The trench should then be backfilled with Class 2 permeable material to within 6 inches of the ground surface. As an alternative to Class 2 permeable, 3/4-inch drain rock completely wrapped in filter 440
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fabric may be used. Regardless of the type of gravel used, a filter sock should not be placed around the perforated pipe. The trench should be capped with at least 6 inches of lowpermeability soil or a concrete slab. A cleanout should be installed at the high end of the pipe to allow for flushing of the subdrain if necessary.

If significant seepage is observed during construction, subdrains beneath the building slab-ongrade floors may also be warranted.

7.4 Foundations

7.4.1 Spread Footings
Spread footings should bottom at least 18 inches below the ground surface and bottom on residual soil (medium dense to very dense clayey sand) or bedrock. In locations where suitable bearing material is not encountered at the design bottom-of-footing elevation, the footing should be overexcavated down to residual soil or bedrock and the overexcavation should be filled with CLSM up to the design bottom-of-footing elevation. The CLSM should have a 28-day compressive strength of at least 100 psi. Spread footings situated near a slope should be setback at least 5 feet horizontally from the top of the slope. Alternatively, the footings may be deepened such that there is at least 7 feet of horizontal distance between the bottom edge of the footing and the face of the slope.

Spread footings may be designed using allowable bearing pressures of 4,000 pounds per square foot (psf) for dead-plus-live loads; this allowable bearing pressure may be increased by one-third for total design loads, which include wind and seismic forces. The allowable bearing pressures for dead-plus-live and total loads include factors of safety of at least 2.0 and 1.5, respectively.

Lateral loads may be resisted by a combination of passive pressures on the vertical faces of the footings and friction between the bottoms of the footings and the supporting bedrock. To compute lateral resistance from passive pressure, we recommend using equivalent fluid weights of 270 pounds per cubic foot (pcf) and 400 pcf in soil and bedrock, respectively. The upper foot of soil or bedrock should be ignored for lateral resistance unless confined by a slab. Lateral resistance should also be ignored where there is less than 7 feet of horizontal distance between 441
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the footing and the face of the slope. Frictional resistance should be computed using base friction coefficient of 0.35 and 0.50 in soil and bedrock, respectively. The passive pressure and frictional resistance values include a factor of safety of at least 1.5 and may be used in combination without further reduction.

We recommend spread footings be founded below an imaginary plane extending up at an inclination of 1.5:1 (horizontal to vertical) from the base of any vault, utility trench, bioswale/stormwater treatment area, etc. If the design bottom-of-footing elevation is above this plane, the edge of mat can either be deepened, or it can be overexcavated below the zone-ofinfluence line and replaced with CLSM with a 28-day unconfined compressive strength of at least 100 psi.

Footing excavations should be free of standing water, debris, and weak and disturbed materials prior to placing concrete. The bottoms and sides of the footing excavations should be maintained in a moist condition until concrete is placed. We should check footing excavations prior to placement of reinforcing steel.

7.4.2 Mat Foundation
The proposed buildings may be supported on mat foundations bearing on firm clay, residual soil and/or bedrock. The edge of the mat should be thickened, where needed, to bottom at least 9 inches below adjacent exterior grade. For preliminary structural design of the mat foundation, we recommend using a coefficient of vertical subgrade reaction of 50 pounds per cubic inch (pci) for dead-plus-live loads; this value has already been scaled to take into account the plan dimensions of the mat foundation (therefore, this is not kv1 for 1-foot-square plate) and may be increased by one-third for total load conditions. Once the Structural Engineer estimates the distribution of bearing stress on the bottom of the mat, we should review the distribution and revise the modulus of subgrade reaction, if appropriate.

Mat foundations situated near a slope should be set back at least 5 feet horizontally from the top of the slope. Alternatively, the edge of the mat may be deepened such that there is at least 7 feet of horizontal distance between the bottom edge of the footing and the face of the slope. 442
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Considering the relatively large area of the mat, we expect the average bearing stress under the mat to be relatively low; however, concentrated stresses will occur at column locations and at the edges of the mat. We recommend the mat be designed to limit bearing pressures to 4,000 psf for dead-plus-live loads; this pressure may be increased by one-third for total load conditions. The allowable bearing pressures for dead-plus-live and total loads include factors of safety of at least

2.0 and 1.5, respectively.

Lateral forces can be resisted by friction along the base of the mat and by passive pressure against the sides of the mat foundation. To compute lateral resistance, we recommend using an equivalent fluid weight (triangular distribution) of 270 pcf and 400 pcf in soil and bedrock, respectively. The upper foot of soil or bedrock should be ignored for lateral resistance unless confined by a slab. Lateral resistance should also be ignored where there is less than 7 feet of horizontal distance between the footing and the face of the slope. Frictional resistance should be computed using base friction coefficient of 0.35 and 0.50 where the bottom of the mat is in direct contact with in soil and bedrock, respectively. Where a vapor retarder is placed beneath the mat, a base friction coefficient of 0.20 should be used. The passive pressure and frictional resistance values include a factor of safety of at least 1.5 and may be used in combination without reduction.

We recommend edge of the mat bottom below an imaginary plane extending up at an inclination of 1.5:1 (horizontal to vertical) from the base of any vault, utility trench, bioswale/stormwater treatment area, etc. If the design bottom-of-mat elevation is above this plane, the edge of mat can either be deepened, or it can be overexcavated below the zone-of-influence line and replaced with CLSM with a 28-day unconfined compressive strength of at least 100 psi.

We should check the mat subgrade prior to placing the vapor retarder or rebar to confirm it is free of standing water, debris, and disturbed materials. If the mat subgrade will be potentially exposed to rain, we recommend 2 to 3 inches of mud slab be placed to protect the subgrade from rain-induced softening prior to concrete/vapor retarder placement. 443
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7.5 Concrete Slabs-on-Grade and Vapor Barrier
The subgrade for slab-on-grade floors and mats should be prepared in accordance with our recommendations in Section 7.1. Where water vapor transmission through the floor slab/mat is not desirable, we recommend installing a capillary moisture break and water vapor retarder beneath the floor slab/mat. A capillary moisture break consists of at least 4 inches of clean, freedraining, angular, crushed rock. The crushed rock should be graded so that 100 percent passes the 1-inch sieve and less than 5 percent passes the No. 4 sieve. The crushed rock should be compacted using vibratory equipment.

The vapor retarder should meet the requirements for Class A vapor retarders stated in ASTM E1745 and be placed directly below the concrete slab. Where the building will be supported on a mat, the capillary moisture break may be omitted. The vapor retarder should be placed in accordance with the requirements of ASTM E1643. These requirements include overlapping seams by 6 inches, taping seams, and sealing penetrations in the vapor retarder.

Concrete mixes with high water/cement (w/c) ratios result in excess water in the concrete, which increases the cure time and can result in excessive vapor transmission through the slab. Where the concrete is poured directly over the vapor retarder, we recommend the w/c ratio of the concrete not exceed 0.45. Water should not be added to the concrete mix in the field. If necessary, workability should be increased by adding plasticizers. In addition, the slab should be properly cured. Before the floor covering is placed, the contractor should check that the concrete surface and the moisture emission levels (if emission testing is required) meet the manufacturer’s requirements.

7.6 Retaining Walls
Permanent retaining walls should be designed to resist lateral earth pressures imposed by the retained soil, as well as a surcharge pressure from nearby foundations and vehicles where appropriate. In addition, because the site is in a seismically active area, retaining walls that retain more than 6 feet of soil should be designed for the more critical of static or seismic conditions.

Static and seismic lateral earth pressures for walls that retain soil are presented in Table 2. 444
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TABLE 2
Lateral Earth Pressures for Design of Retaining Walls with Sloping Backfill Wall Type Backslope
(horizontal to vertical)
Static Conditions
(pcf; at-rest for
restrained and active
for unrestrained)
Seismic Conditions
(pcf; active plus
seismic increment)
Restrained
Level 59 38 + 42
3:1 75 48 + 53
2:1 92 59 + 65
Unrestrained
Level 38 38 + 17
3:1 48 48 + 21
2:1 59 59 + 26
Where walls retain bedrock, the lateral earth pressures for static conditions in Table 2 can be reduced by 50 percent. A seismic increment is not needed where walls retain bedrock.

Where there will be vehicular loading behind the top of a permanent wall within a horizontal distance equal to 1.5 times the height of the wall, the wall should be designed for vehicular surcharge of 50 psf over the upper 10 feet of the wall. Where existing foundations are supported above a “zone-of-influence” line extending up from a permanent wall at an inclination of 1.5:1 (horizontal to vertical), the wall should be designed for surcharge pressure. The magnitude of the surcharge pressure will need to be evaluated on a case-by-case basis.

The recommended lateral earth pressures for “drained” conditions assume the walls are backdrained above the water table to prevent the buildup of hydrostatic pressure. Although site retaining walls will be above the groundwater level, water can accumulate behind the walls from other sources, such as rainfall, irrigation, and broken water lines. One acceptable method for backdraining a site retaining wall is to place a prefabricated drainage panel against the back of the wall. The drainage panel should extend down to a perforated PVC collector pipe at the base of the wall foundation. The drainage pipe should be surrounded by at least 4 inches of Caltrans Class 2 permeable material or 3/4-inch drain rock wrapped in filter fabric (Mirafi 140NC or equivalent). Where shoring is installed and there is insufficient room to install a perforated pipe between the shoring and the back of the basement wall, the drainage panel should extend down to a proprietary, prefabricated collector drain system, such as Tremdrain Total Drain or 445
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Hydroduct Coil (or equivalent), designed to work in conjunction with the drainage panel and may be used in lieu of the perforated pipe surrounded by gravel described above. The pipe should be connected to a suitable discharge point; a sump and pump system may be required to drain the collector pipes.

If backfill is required behind below-grade walls, the walls should be braced, or hand compaction equipment used, to prevent unacceptable surcharges on walls (as determined by the Structural Engineer).

7.7 Pavement Design
Design recommendations for asphalt and Portland cement concrete pavements are presented in the following sections.

7.7.1 Flexible (Asphalt Concrete) Pavement Design
The State of California flexible pavement design method was used to develop the recommended asphalt concrete pavement sections. Based on our experience, we selected a resistance value (RValue) of 20, which is appropriate for the clayey sand and sandy clay soils encountered in our borings. Recommended pavement sections for traffic indices (TIs) ranging from 4.5 to 7.0 are presented in Table 3. The Civil Engineer for the project should check that the TIs presented in this report are appropriate for the intended use. We can provide additional pavement sections for different TIs upon request.
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TABLE 3
Asphalt Concrete Pavement Sections
TI Asphalt Concrete
(inches)
Class 2 Aggregate Base
(inches)

4.5 2.5 7.0

5.0 3.0 7.5

5.5 3.0 9.0

6.0 3.5 9.5

6.5 4.0 10.5

7.0 4.0 12.0
The upper 8 inches of the soil subgrade should be moisture-conditioned and compacted in accordance with our recommendations presented in Section 7.1 and should be non-yielding. If residual soil or bedrock is exposed at the subgrade elevation, scarification and re-compaction is not necessary; however, the roadway subgrade should be free of loose or soft material, ponded water, and should be non-yielding. The Class 2 aggregate base should be moisture-conditioned to near optimum, compacted to at least 95 percent relative compaction, and be non-yielding.

If pavements are adjacent to irrigated landscaped areas (including infiltration basins), curbs adjacent to those areas should extend through the aggregate base and at least 3 inches into the underlying soil to reduce the potential for irrigation water to infiltrate into the pavement section.

If drip irrigation is used in the landscaping adjacent to the pavement, deepening the curbs is not required.

7.7.2 Rigid (Portland-Cement Concrete) Pavement Design
The minimum thickness for concrete pavements should be based on the anticipated traffic loading, the modulus of rupture of the concrete used, and the supporting characteristics of the subgrade below the pavement section. Pavements should be designed and constructed in accordance with the American Concrete Institute (ACI) Commercial Concrete Parking Lots and Site Paving Design and Construction Guide (ACI PRC-330-21). The compressive strength of the concrete should be at least 3,750 psi with a modulus of rupture of the concrete of 550 psi at 28 447
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days. Reinforcing steel may be used for shrinkage crack control. The recommended minimum rigid pavement section and maximum spacing between joints are presented in Table 4 below.

TABLE 4
Rigid Concrete Pavement Design
Traffic Categories Maximum
ADTT6
Concrete
Thickness
(inches)
Class 2
Aggregate Base
Thickness
(inches)
Maximum
Spacing
Between Joints
(feet)
Car parking areas
and Access Lanes
(Category A)
10 5.0 6 10
Entrance and Truck
Service Lanes
(Category B)
25 5.5 6 12.5
Garbage or Fire
Truck lane
(Category E)
1 7.0 6 15
Recommendations for subgrade preparation and aggregate base compaction for concrete pavement are the same as those described above for asphalt concrete pavement.

Recommendations for pavements adjacent to irrigated landscaped areas, bio-swales, or other storm water treatment areas are also the same as those presented above for asphalt concrete pavement.

7.8 Permeable Pavers
We recommend permeable interlocking concrete pavements (ICP) be designed in accordance with the guidelines presented by the Interlocking Concrete Pavement Institute (Smith, 2017).

These guidelines include specific recommendations for permeable aggregate subbase, base, and bedding courses to be placed beneath ICP pavements. We recommend permeable pavements for vehicular and pedestrian traffic be designed for partial exfiltration of water into the subgrade soil.

This requires installing a subdrain system at the base of the pervious aggregate materials, which 6 ADDT is the Average Daily Truck Traffic in both directions (excludes panel trucks, pickup trucks, and other four-wheel vehicles).
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are underlain by a filter fabric. ICPI’s generalized paver section for partial infiltration is presented in Figure 6.

The soil subgrade beneath ICP pavements should be prepared and compacted in accordance with the recommendations presented in Section 7.1. In addition, the subgrade should be a firm and non-yielding surface. The subgrade should be proof-rolled under the observation of our field engineer to confirm it is non-yielding prior to placing the filter fabric and aggregate base materials. The native soil subgrade at the bottom of the permeable section should slope down toward the drain pipe trench at a gradient of at least 2 percent. The perforated pipe should slope down to a suitable outlet at a minimum gradient of 1 percent. The pipe should be placed with the perforations down on a minimum of 2 inches of permeable subbase.

ICPI’s guidelines call for 1.5 to 2 inches of bedding material consisting of ASTM No. 8 crushed aggregate directly below the pavers. This material is also recommended for fill material between the pavers. As shown in Table 5 below, this material consists of fine gravel with 10 to 30 percent sand.

TABLE 5
Gradation Requirements for ASTM No. 8 Aggregate
Sieve Size Percentage Passing Sieve
1/2 inch 100
3/8 inch 85 – 100
No. 4 10 – 30
No. 8 0 – 10
No. 16 0 – 5
The ASTM No. 8 bedding should be underlain by a permeable base course of ASTM No. 57 crushed aggregate. As shown in Table 6, ASTM No. 57 aggregate consists of open-graded gravel with a gradation between that of the 3/4-inch drain rock and the ASTM No. 8 aggregate. 449
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TABLE 6
Gradation Requirements for ASTM No. 57 Aggregate
Sieve Size Percentage Passing Sieve
1-1/2 inch 100
1 inch 95 – 100
1/2 inch 25 – 60
No. 4 0 – 10
No. 8 0 – 5
The ASTM No. 57 permeable base course should be underlain by a permeable subbase course of ASTM No. 2 crushed aggregate. The gradation requirements for ASTM No. 2 crushed aggregate subbase are presented in Table 7.

TABLE 7
Gradation Requirements for ASTM No. 2 Aggregate
Sieve Size Percentage Passing Sieve
3 inch 100
2-1/2 inch 90-100
2 inch 35-70
1-1/2 inch 0-15
3/4 inch 0-5
The No. 2 aggregate subbase course should be placed in lifts not exceeding 6 inches in loose thickness and compacted using a smooth-drum roller, operated in static (non-vibratory) mode.

The subsequent course of No. 57 aggregate may be placed in one lift and should be compacted with a smooth-drum roller in vibratory mode with sufficient passes to create a non-yielding surface. Placement and compaction of the permeable aggregate base and subbase should be performed under the observation of our field engineer. Following compaction of the No. 57 aggregate, the No. 8 bedding, not exceeding 2 inches in loose thickness, should be placed and screeded to a level, undisturbed surface immediately prior to the paver installation. 450
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The recommended thicknesses of the permeable aggregate base and subbase courses depend on the infiltration and water storage design requirements, as well as the traffic loading demand. Our recommendations for the minimum permeable ICP pavement sections subject to vehicular traffic (including fire and garbage trucks) are presented in Table 8. Also included in Table 8 is a recommended section for permeable ICPs subject to pedestrian traffic only.

TABLE 8
Recommended Pavement Sections for
Permeable Interlocking Concrete Pavers
Pavement
Type
ASTM No. 8
Crushed Bedding
Aggregate
(inches)
ASTM No. 57
Crushed Base
(inches)
ASTM No. 2
Crushed
Subbase
(inches)
Pedestrian 1.5-2.0 4.0 6.0
Vehicular 1.5-2.0 4.0 10.0
The above-recommended ICP pavement sections are based on the ICPI technical guidelines (Smith, 2017). From a geotechnical standpoint, it is acceptable to design the pedestrian ICP section to exclude the No. 2 subbase course, in which case the No. 57 base course should be increased to 10 inches. If this approach is used, the perforated pipe should include a filter fabric sleeve to prevent the finer aggregate from entering the perforations.

7.9 Excavations and Temporary Shoring
Excavations that will be entered by workers should be shored or sloped in accordance with the Occupational Safety and Health Administration (OSHA) standards (29 CFR Part 1926). The shoring designer should be responsible for the shoring design. The contractor should be responsible for the construction and safety of temporary slopes and shoring. Recommendations for temporary cut slopes are presented in Section 7.2.1. Where temporary cut slopes are not feasible due to space constraints, temporary shoring will be required.

We judge that a soldier pile and lagging shoring system is appropriate for support of excavations.

A soldier pile and lagging shoring system usually consists of steel H-beams and concrete placed 451
24-2627 27 August 2, 2024
in predrilled holes extending below the bottom of the excavation. Wood lagging is placed between the piles as the excavation proceeds from the top down. Where the required cut is less than about 12 feet, a soldier pile and lagging system can typically provide economical shoring without tiebacks. Where cuts exceed about 12 feet in height, soldier pile and lagging systems are typically more economical if they include tieback anchors. We can provide recommendations for tieback anchors upon request.

A soil-nail wall may also be evaluated by the shoring engineer as an alternative to a soldier pile and lagging system. The construction of a soil-nail wall involves: 1) excavation, 2) installation of nails, and 3) construction of a shotcrete facing. The excavation proceeds in lifts that are generally 4 to 6 feet deep depending upon the ability of the soil/bedrock to stand temporarily unsupported.

In each excavation step, a row of nails, usually 0.75- to 1.5-inch-diameter steel bars, are placed in predrilled holes and grouted. After the installation of a row of nails and placement of drainage panels, the face of the cut is covered by a facing, which is typically 4 inches of shotcrete reinforced with wire mesh. On the following day, the nails are bolted to square plates, which are typically 8 inches square. The above steps are repeated to the bottom of the excavation.

A Structural/Civil Engineer knowledgeable in this type of construction should be retained to design the shoring. The shoring designer should design the shoring system for lateral deformation of less than an inch at any location on the shoring. We should review the final shoring plans and calculations to check that they are consistent with the recommendations presented in this report.

7.9.1 Cantilevered Soldier Pile and Lagging Shoring System We recommend a cantilevered soldier pile and lagging shoring system be designed using active equivalent fluid weights of 38 pcf for level backslope, 48 pcf for a 3:1 (horizontal to vertical) backslope; and 58 pcf for a 2:1 backslope. Where traffic loads are expected within 10 feet of the shoring walls, a vehicle surcharge pressure of 50 psf should be applied to the upper 10 feet of the wall. Where construction equipment will be working behind the walls within a horizontal distance equal to 1.5 times the shoring height, the design should include a surcharge pressure of 452
24-2627 28 August 2, 2024
250 psf. The above pressures should be assumed to act over the entire width of the lagging installed above the excavation.

Passive resistance at the toe of the soldier piles embedded in bedrock should be computed using equivalent fluid weights of 270 and 400 pcf in soil and bedrock, respectively, with a maximum pressure of 4,000 psf. The upper foot of soil or bedrock should be ignored for lateral resistance unless confined by a slab; soil above the bedrock should also be ignored for lateral resistance.

Passive pressure can be assumed to act over an area of three soldier pile widths assuming the toe of the soldier pile is filled with structural concrete. If lean concrete is placed in the soldier pile shaft, the passive pressure can be assumed to act over two pile diameters. These passive pressure values include a factor of safety of at least 1.5.

Soldier piles should be placed in pre-drilled holes backfilled with concrete. Drilling the holes for soldier piles will require equipment capable of penetration into bedrock.

7.9.2 Soil Nails
Several computer programs, such as SNAIL (California Department of Transportation, updated August 21, 2018) and SNAP_2 (FHWA 2016), are available for designing a soil-nail wall.

SNAIL uses a force limit equilibrium for the stability analyses of soil nails; the failure planes are assumed bi-linear if they pass through the toe of the wall and tri-linear if they pass beyond the toe of the wall. SNAP also uses a limit equilibrium design method (Bishop’s) and allows soil-nail wall design using allowable stress design (ASD). Internal failure modes include nail pullout and nail tensile failure analysis, along with nail head and facing element analysis for temporary and permanent conditions. External failure modes include global stability, sliding, and bearing capacity analyses.

Soil-nail systems are typically installed under a design-build contract by specialty contractors; therefore, we are not providing a specific design; however, we are providing estimated input parameters for preliminary design. The actual capacities and lengths should be determined by the design-build contractor with experience designing, building, and testing soil-nail walls in similar 453
24-2627 29 August 2, 2024
soil conditions. We should review the design prior to installation. For preliminary design, we recommend the input parameters presented in Table 9.

TABLE 9
Recommended Input Parameters for Design of Soil-Nail Walls Soil Type
Total
Density
(pcf)
Ultimate Bond
Strength (psf)
(Factor of Safety = 1.0)
Shear Strength
Parameters
c
1 
2 (psf) (deg)
Bedrock 145 5,000 4,000 0
Notes:
1 Cohesion intercept or undrained shear strength, without a factor of safety 2 Angle of internal friction, without a factor of safety We should review the design plans and design calculations prior to their issuance for construction to check for conformance with our recommendations. The design of the walls should also include appropriate testing of soil nails.

7.10 Seismic Design
The latitude and longitude of the site are 37.5107° and -122.2832°, respectively. For design per the 2022 CBC, we recommend the following:
• Site Class C (very dense soil and soft rock)
• SS = 1.97g, S1 = 0.81g
• Fa = 1.2, Fv = 1.4
• SMS = 2.36g, SM1 = 1.13g
• SDS = 1.57g, SD1 = 0.76g
• Seismic Design Category E for Risk Factors I, II, and III 454
24-2627 30 August 2, 2024

8.0 ADDITIONAL GEOTECHNICAL SERVICES
Prior to construction, we should review the project plans and specifications to check that they conform to the intent of our recommendations. During construction, our field engineer should observe shoring installation as needed, foundation excavations prior to placement of reinforcing steel, and perform field density testing to check subgrade preparation and fill compaction. These observations will allow us to compare actual with anticipated soil conditions and to check that the contractor's work conforms to the geotechnical aspects of the plans and specifications.

9.0 LIMITATIONS
This geotechnical investigation has been conducted in accordance with the standard of care commonly used as state-of-practice in the profession. No other warranties are either expressed or implied. The recommendations made in this report are based on the assumption that the subsurface conditions do not deviate appreciably from those disclosed in our field investigation.

If any variations or undesirable conditions are encountered during construction, we should be notified so that additional recommendations can be made. The foundation recommendations presented in this report are developed exclusively for the proposed development described in this report and are not valid for other locations and construction in the site vicinity. 455
24-2627 31 August 2, 2024

REFERENCES
ACI Committee 330. (2021). ACI PRC-330-21: Commercial Concrete Parking Lots and Site Paving Design and Construction. American Concrete Institute (ACI). https://www.concrete.org/store/productdetail.aspx?ItemID=33021&Language=English&Units=U S_Units
American Society of Civil Engineers (ASCE). (2017). ASCE/SEI 7-16: Minimum Design Loads and Associated Criteria for Buildings and Other Structures. ASCE Publications. http://doi.org/10.1061/9780784414248
California Department of General Services. (2022). California Building Code. State Government of California. https://www.dgs.ca.gov/BSC/Codes
California Department of Transportation (Caltrans). (2020). Caltrans Highway Design Manual.

State Government of California. https://dot.ca.gov/programs/design/manual-highway-designmanual-hdm California Department of Transportation (Caltrans). (2022). Caltrans Standard Specifications.

State Government of California. https://dot.ca.gov/-/media/dotmedia/programs/design/documents/2022_stdspecs-a11y.pdf California Geological Survey. (2018, January 11). Earthquake Zones of Required Investigation, San Mateo Quadrangle, Official Map. California Department of Conservation.

California Geological Survey. (2018). Seismic Hazard Zone Report for the San Mateo 7.5-Minute Quadrangle, San Mateo County, California. California Department of Conservation.

Field, E.H., Biasi, G.P., Bird, P., Dawson, T.E., Felzer, K.R., Jackson, D.D., Johnson, K.M., Jordan, T.H., Madden, C., Michael, A.J., Milner, K.R., Page, M.T., Parsons, T., Powers, P.M., Shaw, B.E., Thatcher, W.R., Weldon, R.J., & Zeng, Y. (2013). Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)—The Time-Independent Model (Open-File Report 2013- 1165). United States Geological Survey. http://doi.org/10.3133/ofr20131165 Graymer, R.W., Moring, B.C., Saucedo, G.J., Wentworth, C.M., Brabb, E.E., & Knudsen, K.L. (2006, March 6). Geologic Map of the San Francisco Bay Region (Scientific Investigations Map 2918). United States Geological Survey. https://pubs.usgs.gov/sim/2006/2918/ Petersen, M.D., Moschetti, M.P., Powers, P.M., Mueller, C.S., Haller, K.M., Frankel, A.D., Zeng, Y., Rezaeian, S., Harmsen, S.C., Boyd, O.S., Field, N., Chen, R., Rukstales, K.S., Luco, N., Wheeler, R.L., Williams, R.A., & Olsen, A.H. (2014). Documentation for the 2014 Update of the United States National Seismic Hazard Maps (Open-File Report 2014-1091). United States Geological Survey. https://pubs.usgs.gov/of/2014/1091/
Roberge, P. R. (2018). Corrosion Basics: An Introduction: Third Edition. NACE International. 456
24-2627 32 August 2, 2024
Smith, D.R. (2017). Permeable Interlocking Concrete Pavements, Selection, Design, Construction, Maintenance: Fifth Edition. Interlocking Concrete Pavement Institute.

Sitar, N., Mikola, R.G., & Candia, G. (2012). Seismically Induced Lateral Earth Pressures on Retaining Structures and Basement Walls. Proceedings of the ASCE GeoCongress 2012 (pp. 1- 24). Geotechnical Special Publication. https://doi.org/10.1061/9780784412138.0013 Thompson, E.M., Wald, D.J., Worden, B., Field, E.H., Luco, N., Petersen, M.D., Powers, P.M., Badie, R. (2016). Shakemap earthquake scenario: Building Seismic Safety Council 2014 Event Set (BSSC2014). United States Geological Survey. https://doi.org/10.5066/F7V122XD Triggs, J.R. & Simpson, P.D. (1990). A Portable Dynamic Penetrometer for Geotechnical Investigations. Triggs Technologies.

United States Geological Survey. (2021). Earthquake Hazards Program: Advanced National Seismic System (ANSS) Comprehensive Catalog of Earthquake Events and Products. United States Department of the Interior. https://earthquake.usgs.gov/earthquakes/search/ 457

FIGURES
458
Date 1 Project No. Figure

SITE LOCATION MAP
SITE
Base map: The Thomas Guide
San Mateo County 0 1/2 Mile
Approximate scale
1/4

ROCKRIDGE
GEOTECHNICAL 06/21/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
459
0Approximate scale60 Feet 07/22/24 24-2627 2 Belmont, California SITE PLAN Date Project No. Figure CHARLES ARMSTRONG SCHOOL Base map: Google Earth, 2024 ROCKRIDGE GEOTECHNICAL EXPLANATION Approximate location of dynamic penetrometer test by Rockridge Geotechnical, Inc., June 17, 2024 Approximate location of boring by Rockridge Geotechnical, Inc., June 17, 2024 DPT-1 B-1 DPT-1 DPT-2 DPT-3 DPT-4 B-1 B-2 B-3 SOLANA DRIVE ALTURA WAY 460
Date Project No. Figure 3
SITE

REGIONAL GEOLOGIC MAP

EXPLANATION
dashed where approximate and dotted
where concealed, queried where uncertain
0 2000 Feet
Approximate scale
1000
Base map: Google Earth with U.S. Geological Survey (USGS), San Mateo County, 2024.

Geologic contact:

Artificial Fill
Mud deposits (late Holocene)
Alluvium (Holocene)
Franciscan Complex sedimentary rocks (Cretaceous)
Franciscan Complex sedimentary rocks
(Early Cretaceous and (or) Late Jurassic)
Franciscan Complex chert
(Early Cretaceous and (or) Late Jurassic)
Franciscan Complex volcanic rocks
(Early Cretaceous and (or) Late Jurassic)
af
Qhym
Qha
Kfs
KJfs
KJfv
KJfc

ROCKRIDGE

GEOTECHNICAL
Qhym
KJfc
07/03/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
Qha
KJfs
KJfs
KJfs
KJfs
KJfs
Qsl Hillslope Deposits (Quaternary)
Qhym
Franciscan Complex melange (Eocene, Paleocene,
and (or) Late Cretaceous) fsr
461
1906, M7.9
1838, M7.4
1868, M7.0
1989, M6.9
2014, M6.0
San Andreas (SAN)
San Andreas (SAP)
Hayward (HN) Hayward (HS)
San Andreas (SAS)
Monte Vista-Shannon
Calaveras (CN)
Calaveras (CC)
Calaveras (CS)
San Gregorio (North)
San Gregorio (South)
Greenville
Green Valley
Rodgers Creek
Maacama
West Napa Concord
Great Valley (Midland)
Reliz
Great Valley (Orestimba)
1865, M6.5
Symbol Magnitude (Mw)

7.5+

7.0 - 7.4

6.5 - 6.9

6.0 - 6.4

5.0 - 5.9
Historic Earthquake Epicenters
Pre-1900 1900-1970 1971-2021
Date Project No. Figure

REGIONAL FAULT AND HISTORIC

SEISMICITY MAP
20 Miles
Approximate scale
0 10
0 16 32 Kilometers

EXPLANATION
Faults (National Seismic Hazard Model)

ROCKRIDGE
GEOTECHNICAL 4
SITE
06/21/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
462
0 4,000 Feet
Approximate scale
2,000

ROCKRIDGE
GEOTECHNICAL Date 5 Project No. Figure
Reference:

Earthquake Zones of Required Investigation
San Mateo Quadrangle
California Geological Survey
Released January 11, 2018
Earthquake-Induced Landslide Zones
Areas where previous occurrence of landslide movement, or local topographic, geological, geotechnical and subsurface water conditions indicate a potential for permanent ground displacements such that mitigation as defined in Public Resources Code Section 2693(c) would be required.

Liquefaction Zones
Areas where historical occurrence of liquefaction, or local geological, geotechnical and ground water conditions indicate a potential for permanent ground displacements such that mitigation as defined in Public Resources Code Section 2693(c) would be required.

EARTHQUAKE ZONES OF REQUIRED

INVESTIGATION MAP
06/21/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
SITE
463
Date Project No. Figure 6 Reference: "Permeable Interlocking Concrete Pavements", Third Edition, prepared by Interlocking Concrete Pavement Institute, dated 2005. 4 IN (100 MM) THICK NO. 57 STONE OPEN-GRADED BASE TYP. NO. 8, 89, OR 9 AGGREGATE IN OPENINGS CURB/EDGE RESTRAINT WITH CUT-OUTS FOR OVERFLOW DRAINAGE (CURB SHOWN) CONCRETE PAVERS MIN. 3 18 IN. (80 MM) THICK FOR VEHICULAR TRAFFIC (ASPECT RATIO< 3) BEDDING COURSE 1 12 TO 2 IN. (40 TO 50 MM) THICK (TYP. NO. 8 AGGREGATE) PERFORATED PIPES SPACED AND SLOPED TO DRAIN ALL STORED WATER SOIL SUBGRADE SLOPED TO DRAIN MIN. 6 IN. (150 MM) THICK NO. 2 STONE SUBBASE GEOTEXTILE ON TOP AND SIDES OF SUBBASE UNDER/BEYOND CURB GEOTEXTILE ON SUBGRADE NON-PERFORATED OUTFALL PIPE(S) SLOPED TO STORM SEWER OR STREAM 07/31/24 NOTES: 1. 2 38 IN. (60 MM) THICK PAVERS MAY BE USED IN RESIDENTIAL APPLICATIONS. 2. NO. 2 STONE SUBBASE THICKNESS VARIES WITH DESIGN. CONSULT ICPI PERMEABLE INTERLOCKING CONCRETE PAVEMENT MANUAL.. 3. PERFORATED PIPES MAY BE RAISED FOR WATER STORAGE FROM LARGE RAIN EVENTS WITH OUTLET(S) AT LINER BOTTOM TO DRAIN SMALL RAIN EVENTS. GENERALIZED ICPI PERMEABLE PAVER DETAIL FOR PARTIAL EXFILTRATION ROCKRIDGE GEOTECHNICAL 24-2627 Belmont, California CHARLES ARMSTRONG SCHOOL 464

APPENDIX A
Dynamic Penetrometer Test Results and Logs of Borings
465

DYNAMIC PENETROMETER

TEST RESULTS
DPT-1
Belmont, California

CHARLES ARMSTRONG SCHOOL
Date: 6/13/2024 Project No. 24-2627 Figure A-1

0.0 1.0

2.0 3.0

4.0 5.0

6.0 7.0

8.0 9.0

10.0 11.0

12.0 13.0

14.0 15.0

16.0 17.0
0 10 20 30 40 50
DEPTH BELOW GROUND SURFACE (feet)
BLOWS PER 4 INCHES (10 centimeters)
466

CHARLES ARMSTRONG SCHOOL DYNAMIC PENETROMETER

TEST RESULTS
DPT-2
Belmont, California
Date: 6/13/2024 Project No. 24-2627 Figure A-2

0.0 1.0

2.0 3.0

4.0 5.0

6.0 7.0

8.0 9.0

10.0 11.0

12.0 13.0

14.0 15.0

16.0 17.0
0 10 20 30 40 50
DEPTH BELOW GROUND SURFACE (feet)
BLOWS PER 4 INCHES (10 centimeters)
467

CHARLES ARMSTRONG SCHOOL DYNAMIC PENETROMETER

TEST RESULTS
DPT-3
Belmont, California
Date: 6/13/2024 Project No. 24-2627 Figure A-3

0.0 1.0

2.0 3.0

4.0 5.0

6.0 7.0

8.0 9.0

10.0 11.0

12.0 13.0

14.0 15.0

16.0 17.0
0 10 20 30 40 50
DEPTH BELOW GROUND SURFACE (feet)
BLOWS PER 4 INCHES (10 centimeters)
468

CHARLES ARMSTRONG SCHOOL DYNAMIC PENETROMETER

TEST RESULTS
DPT-4
Belmont, California
Date: 6/13/2024 Project No. 24-2627 Figure A-4

0.0 1.0

2.0 3.0

4.0 5.0

6.0 7.0

8.0 9.0

10.0 11.0

12.0 13.0

14.0 15.0

16.0 17.0
0 10 20 30 40 50
DEPTH BELOW GROUND SURFACE (feet)
BLOWS PER 4 INCHES (10 centimeters)
469
Sampler
Type
Sample
Blows/ 6"
SPT
N-Value1

LITHOLOGY
DEPTH
(feet)
Dry Density
Lbs/Cu Ft
Type of
Strength
Test
Shear Strength
Lbs/Sq Ft
Fines
%
Confining
Pressure
Lbs/Sq Ft
Natural
Moisture
Content, %
See Site Plan, Figure 2
06/17/2024
Hammer type:

Date finished: 06/17/2024
Hammer weight/drop: 140 lbs./30 inches
Sampler:

Boring location:

Date started:

Drilling method:
1 2
3 4
5 6
7 8
9 10
11 12

MATERIAL DESCRIPTION

LABORATORY TEST DATA

SAMPLES
PROJECT:

PAGE 1 OF 1
Log of Boring B-1 CHARLES ARMSTRONG SCHOOL
Belmont, California
J. Lei
Stapleton Engineering
& Exploration
Portable Bobcat Rig
Logged by:

Drilled by:

Rig:

Rope & cathead safety hammer
Modified California (MC)
1 MC and SPT blow counts for the last two increments
were converted to SPT N-Values using factors of 0.70
and 1.2, respectively to account for sampler type and
hammer energy.

CL
SC
4-inch-diameter solid-stem auger

4.5 inches portland cement

SANDY CLAY (CL)
red-yellow and yellow-brown, stiff, moist, fine to coarse sand, trace fine subangular gravel, rootlets
Project No.: Figure:

Boring terminated at a depth of 5.25 feet below
ground surface.

Boring backfilled with cement grout.

Groundwater not encountered during drilling.
24-2627 A-5
CLAYEY SAND with GRAVEL (SC)
yellow-brown and yellow, very dense, moist, fine to
medium sand, fine to coarse subangular gravel

10.6 114

RESIDUAL SOIL

ROCKRIDGE

GEOTECHNICAL
10 10
10 MC 14
12 13
50/3”
MC 44/9”
MC 50/3” 35/3”

2.5 inches of aggregate base
SHALE
gray and brown, low hardness, friable to weak, deeply
to completely weathered
LL = 31, PI = 16; see Appendix B
Soil Corrosivity Test; see Appendix B
470
Sampler
Type
Sample
Blows/ 6"
SPT
N-Value1

LITHOLOGY
DEPTH
(feet)
Dry Density
Lbs/Cu Ft
Type of
Strength
Test
Shear Strength
Lbs/Sq Ft
Fines
%
Confining
Pressure
Lbs/Sq Ft
Natural
Moisture
Content, %
See Site Plan, Figure 2
06/17/2024
Hammer type:

Date finished: 06/17/2024
Hammer weight/drop: 140 lbs./30 inches
Sampler:

Boring location:

Date started:

Drilling method:
1 2
3 4
5 6
7 8
9 10
11 12

MATERIAL DESCRIPTION

LABORATORY TEST DATA

SAMPLES
PROJECT:

PAGE 1 OF 1
Log of Boring B-2 CHARLES ARMSTRONG SCHOOL
Belmont, California
J. Lei
Stapleton Engineering
& Exploration
Portable Bobcat Rig
Logged by:

Drilled by:

Rig:

Rope & cathead safety hammer
Modified California (MC), Standard Penetration Test (SPT) CL
GPGC
4-inch-diameter solid-stem auger
1 MC and SPT blow counts for the last two increments
were converted to SPT N-Values using factors of 0.70
and 1.2, respectively to account for sampler type and
hammer energy.

SANDY CLAY (CL)
yellow-brown, very stiff, moist, fine to medium sand,
trace fine subangular gravel
Project No.: Figure:

Boring terminated at a depth of 4.8 feet below
ground surface.

Boring backfilled with cement grout.

Groundwater not encountered during drilling.
24-2627 A-6
SHALE
brown and dark gray, low to moderately hard,
moderately strong

ROCKRIDGE

GEOTECHNICAL
13 31
22 MC 37
SPT 50/6” 60/6”
29 50/4”
60/4”
GRAVEL with SAND and CLAY (GP-GC)
gray, dense, dry, fine to coarse sand, fine to coarse
subangular gravel
SPT
471
Sampler
Type
Sample
Blows/ 6"
SPT
N-Value1

LITHOLOGY
DEPTH
(feet)
Dry Density
Lbs/Cu Ft
Type of
Strength
Test
Shear Strength
Lbs/Sq Ft
Fines
%
Confining
Pressure
Lbs/Sq Ft
Natural
Moisture
Content, %
See Site Plan, Figure 2
06/17/2024
Hammer type:

Date finished: 06/17/2024
Hammer weight/drop: 140 lbs./30 inches
Sampler:

Boring location:

Date started:

Drilling method:
1 2
3 4
5 6
7 8
9 10
11 12

MATERIAL DESCRIPTION

LABORATORY TEST DATA

SAMPLES
PROJECT:

PAGE 1 OF 1
Log of Boring B-3 CHARLES ARMSTRONG SCHOOL
Belmont, California
J. Lei
Stapleton Engineering
& Exploration
Portable Bobcat Rig
Logged by:

Drilled by:

Rig:

Rope & cathead safety hammer
Modified California (MC), Standard Penetration Test (SPT) CL
SC
1 MC and SPT blow counts for the last two increments
were converted to SPT N-Values using factors of 0.70
and 1.2, respectively to account for sampler type and
hammer energy.
4-inch-diameter solid-stem auger

SANDY CLAY (CL)
brown and red-brown, very stiff, moist, fine sand, trace fine subangular gravel, trace debris
Project No.: Figure:

Boring terminated at a depth of 7.3 feet below
ground surface.

Boring backfilled with cement grout.

Groundwater not encountered during drilling.
24-2627 A-7

13.6 119

RESIDUAL SOIL

ROCKRIDGE

GEOTECHNICAL
13 13
21 MC 24
32 50/6”
SPT 60/6”
SPT 50/4” 60/4”
10 14
27 MC 29

CLAYEY SAND (SC)
brown and red-brown, medium dense, moist, fine
sand, trace fine subangular gravel

SANDSTONE
yellow, soft to low hardness, friable, completely
weathered

2.5 inches of asphalt concrete

2.5 inches of aggregate base
LL = 27, PI = 8; see Appendix B
Soil Corrosivity Test; see Appendix B
472

CLASSIFICATION CHART
Date Project No. Figure A-8

ROCKRIDGE
GEOTECHNICAL 06/21/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
Major Divisions Symbols Typical Names
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
Highly Organic Soils PT

UNIFIED SOIL CLASSIFICATION SYSTEM
Well-graded gravels or gravel-sand mixtures, little or no fines Poorly-graded gravels or gravel-sand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures
Clayey gravels, gravel-sand-clay mixtures
Well-graded sands or gravelly sands, little or no fines Poorly-graded sands or gravelly sands, little or no fines Silty sands, sand-silt mixtures
Inorganic silts and clayey silts of low plasticity, sandy silts, gravelly silts Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, lean clays Organic silts and organic silt-clays of low plasticity
Inorganic silts of high plasticity
Inorganic clays of high plasticity, fat clays
Organic silts and clays of high plasticity
Peat and other highly organic soils
Clayey sands, sand-clay mixtures
Range of Grain Sizes
Grain Size
in Millimeters
U.S. Standard
Sieve Size
Above 12"
12" to 3"
Classification
Boulders
Cobbles
Above 305
305 to 76.2
Silt and Clay Below No. 200 Below 0.075

GRAIN SIZE CHART

SAMPLER TYPE
Coarse-Grained Soils
(more than half of soil > no. 200
sieve size)
Fine -Grained Soils
(more than half of soil
< no. 200 sieve size)
Gravels
(More than half of
coarse fraction >
no. 4 sieve size)
Sands
(More than half of
coarse fraction <
no. 4 sieve size)
Silts and Clays
LL = < 50
Silts and Clays
LL = > 50
Gravel
coarse
fine
3" to No. 4
3" to 3/4"
3/4" to No. 4
No. 4 to No. 200
No. 4 to No. 10
No. 10 to No. 40
No. 40 to No. 200

76.2 to 4.76

76.2 to 19.1

19.1 to 4.76

4.76 to 0.075

4.76 to 2.00

2.00 to 0.420

0.420 to 0.075
Sand
coarse
medium
fine
C Core barrel
CA California split-barrel sampler with 2.5-inch outside diameter and a 1.93-inch inside diameter
D&M Dames & Moore piston sampler using 2.5-inch outside diameter, thin-walled tube
O Osterberg piston sampler using 3.0-inch outside diameter, thin-walled Shelby tube
PT Pitcher tube sampler using 3.0-inch outside diameter, thin-walled Shelby tube
MC Modified California sampler with a 3.0-inch outside
diameter and a 2.43-inch inside diameter
SPT Standard Penetration Test (SPT) split-barrel sampler with a 2.0-inch outside diameter and a 1.38- or 1.5-inch inside diameter (refer to text)
ST Shelby Tube (3.0-inch outside diameter, thin-walled tube) advanced with hydraulic pressure

SAMPLE DESIGNATIONS/SYMBOLS
Sample taken with California or Modified California split-barrel sampler. Darkened area indicates soil recovered
Classification sample taken with Standard Penetration Test sampler Undisturbed sample taken with thin-walled tube
Disturbed sample
Sampling attempted with no recovery
Core sample
Analytical laboratory sample
Sample taken with Direct Push sampler
Sonic
Unstabilized groundwater level
Stabilized groundwater level
473

I FRACTURING
Intensity Size of Pieces in Feet
Very little fractured Greater than 4.0
Occasionally fractured 1.0 to 4.0
Moderately fractured 0.5 to 1.0
Closely fractured 0.1 to 0.5
Intensely fractured 0.05 to 0.1
Crushed Less than 0.05

II HARDNESS

1. Soft - reserved for plastic material alone.

2. Low hardness - can be gouged deeply or carved easily with a knife blade.

3. Moderately hard - can be readily scratched by a knife blade; scratch leaves a heavy trace of dust and is readily visible after the powder has been blown away.

4. Hard - can be scratched with difficulty; scratch produced a little powder and is often faintly visible.

5. Very hard - cannot be scratched with knife blade; leaves a metallic streak.

III STRENGTH

1. Plastic or very low strength.

2. Friable - crumbles easily by rubbing with fingers.

3. Weak - an unfractured specimen of such material will crumble under light hammer blows.

4. Moderately strong - specimen will withstand a few heavy hammer blows before breaking.

5. Strong - specimen will withstand a few heavy ringing hammer blows and will yield with difficulty only dust and small flying fragments.

6. Very strong - specimen will resist heavy ringing hammer blows and will yield with difficulty only dust and small flying fragments.

IV WEATHERING - The physical and chemical disintegration and decomposition of rocks and minerals by natural processes such as oxidation, reduction, hydration, solution, carbonation, and freezing and thawing.

D. Deep - moderate to complete mineral decomposition; extensive disintegration; deep and thorough discoloration; many fractures, all extensively coated or filled with oxides, carbonates and/or clay or silt.

M. Moderate - slight change or partial decomposition of minerals; little disintegration; cementation little to unaffected.

Moderate to occasionally intense discoloration. Moderately coated fractures.

L. Little - no megascopic decomposition of minerals; little of no effect on normal cementation. Slight and intermittent, or localized discoloration. Few stains on fracture surfaces.

F. Fresh - unaffected by weathering agents. No disintegration of discoloration. Fractures usually less numerous than joints.

ADDITIONAL COMMENTS:

V CONSOLIDATION OF SEDIMENTARY ROCKS: usually determined from unweathered samples. Largely dependent on cementation.

U = unconsolidated
P = poorly consolidated
M = moderately consolidated
W = well consolidated

VI BEDDING OF SEDIMENTARY ROCKS
Splitting Property Thickness Stratification
Massive Greater than 4.0 ft. very thick-bedded
Blocky 2.0 to 4.0 ft. thick bedded
Slabby 0.2 to 2.0 ft. thin bedded
Flaggy 0.05 to 0.2 ft. very thin-bedded
Shaly or platy 0.01 to 0.05 ft. laminated
Papery less than 0.01 thinly laminated
Date Project No. Figure A-9

PHYSICAL PROPERTIES CRITERIA

FOR ROCK DESCRIPTIONS

ROCKRIDGE
GEOTECHNICAL 07/22/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
474

APPENDIX B
Laboratory Test Results
475
ML or OL
MH or OH
Symbol Source
Natural
M.C. (%)
Liquid
Limit (%)

CL - ML
0 10
20 30
40 50
60 70
0 10 20 30 40 50 60 70 80 90 100 110 120

LIQUID LIMIT (LL)
Description and Classification
% Passing
#200 Sieve
Plasticity
Index (%)

PLASTICITY CHART
Date B-1 Project No. Figure

ROCKRIDGE
GEOTECHNICAL 07/03/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California

PLASTICITY INDEX (PI)
Ref erence:

ASTM D2487-00
B-1 at 1.8 feet
B-3 at 4.0 feet
SANDY CLAY (CL), red-yellow and
yellow-brown
CLAYEY SAND (SC), brown and redbrown

10.6 13.6
--
--
31 27
16 8
476
S240619E
Method ASTM
G51
ASTM
G200
SM
4500-D
ASTM
D4327
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D4327
ASTM
D4327
Bore# /
Description
Depth pH Redox Sulfide
S2-
Nitrate
NO3-
Ammonium
NH4+
Lithium
Li+
Sodium
Na+
Potassium
K+
Magnesium
Mg2+
Calcium
Ca2+
Fluoride
F22-
Phosphate
PO43-
(ft) (mg/kg) (wt%) (mg/kg) (wt%) (Ω-cm) (Ω-cm) (mV) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)

1.3 78.5 0.0078 24.6 0.0025 26,800 4,020 6.5 141 0.7 3.2 15.9 ND 63.0 4.6 26.2 97.6 8.3 0.63.5 39.2 0.0039 20.7 0.0021 80,400 3,149 6.8 107 0.9 8.4 1.2 ND 50.2 2.9 63.5 110.1 11.2 2.4 ASTM
G187
ASTM
D4327
ASTM
D4327
Resistivity
As Rec'd | Minimum
Sulfates
SO42-
Chlorides
ClCations and Anions, except Sulfide and Bicarbonate, tested with Ion Chromatography mg/kg = milligrams per kilogram (parts per million) of dry soil weight ND = 0 = Not Detected | NT = Not Tested | Unk = Unknown Chemical Analysis performed on 1:3 Soil-To-Water extract PPM = mg/kg (soil) = mg/L (Liquid)
Note: Sometimes a bad sulfate hit is a contaminated spot. Typical fertilizers are Potassium chloride, ammonium sulfate or ammonium sulfate nitrate (ASN). So this is another reason why testing full corrosion series is good because we then have the data to see if those other ingredients are present meaning the soil sample is just fertilizercontaminated soil. This can happen often when the soil samples collected are simply surface scoops. This is why it's best to dig in a foot, throw away the top and test the deeper stuff. Dairy farms are also notorious for these items.

If one sample pops up much more corrosive than all others, we would recommend collecting more samples surrounding the problem sample location to determine if the peak is isolated to it. This allows us to conclude it was a contaminated sample and able to declare it an outlier.

Date Project No. Figure B-2
B-1: SANDY CLAY (CL), red-yellow and yellow-brown
Project X REPORT
Corrosion Engineering
Corrosion Control – Soil, Water, Metallurgy Testing Lab 29990 Technology Dr., Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720 www.projectxcorrosion.com
ROCKRIDGEGEOTECHNICAL 07/03/24 24-2627

CHARLES ARMSTRONG SCHOOL
Belmont, California
B-3: CLAYEYSAND (SC), brown and red-brown

SOIL CORROSIVITY

TEST RESULTS
477
717 Market Street, Suite 400 San Francisco, CA 94103 650-373-1200 www.panoramaenv.com

FINAL NOISE AND VIBRATION STUDY
Date: December 19, 2025
To: Carlos De Melo, City of Belmont Community Development Director Jeremy Ruiz, Assistant Planner, City of Belmont Community Development Department From: Geoff Hornek, Senior Noise Analyst, Panorama Environmental, Inc.

Peter Mye, Senior Environmental Planner/Project Manager, Panorama Environmental, Inc.

Brent Rosenwald, Environmental Planner/Deputy Project Manager, Panorama Environmental, Inc.

Subject: Charles Armstrong School Expansion Project
Final Noise and Vibration Study

INTRODUCTION
This report evaluates potential noise and vibration impacts associated with the Charles Armstong School Expansion Project (proposed project). The analysis provided in this report evaluates the potential for short- and long-term noise and vibration impacts on noise-sensitive land uses in the immediate vicinity of the proposed project associated with construction and operation of the proposed expansion of Charles Armstrong School. The report describes the environmental setting for the proposed project, including existing noise conditions and applicable laws and regulations, and documents the assumptions, methodologies, and findings used to evaluate noise and vibration impacts. The project is subject to environmental review pursuant to the California Environmental Quality Act (CEQA) and the City’s standard conditions of approval. It is anticipated that the City of Belmont, the lead agency for the project, will use this technical report to inform the project’s analysis pursuant to the California Environmental Quality Act (CEQA).

Project Description
The project site is at 1405 Solana Drive (Assessor’s Parcel Number 045-122-190) in Belmont, in San Mateo County, California, as shown on Figure 1 and Figure 2. The 4.9-acre school campus currently is occupied by three single-story school buildings near the center of the site and an auditorium building, surrounded by drive aisles, a parking lot, a basketball court, and outdoor activity areas. The site is bordered by Solana Drive and single-family residences to the north; existing single-family residential buildings to the east; existing single-family residences within the jurisdiction of the City of San Carlos to the south; and, to the west, the existing single-family residences along Chula Vista Drive, the City of Belmont’s McDougal Park, and the San Carlos Charter Learning Center. The site topography slopes downward from the northeast to the southeast, with an elevation difference of approximately 40 feet. The northeast portion of the project site is steeply sloped and densely populated by oak trees and other trees. 478

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Figure 1 Project Vicinity
479

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Figure 2 Charles Armstrong School Expansion Project - Site Overview 480

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Charles Armstrong School Expansion Project Final Noise and Vibration Study December 19, 2025 Page F-4
The nearest cross street is Chula Vista Drive. The school is accessed via two curb cuts along Solana Drive with the westernmost driveway used for student pick-up and drop-off and the easternmost driveway used to access faculty and visitor parking. San Mateo County Transit Route 60 runs along Chula Vista Drive with bus stops within 0.2 mile of the school at Solana Drive and at Fernwood Way.

The proposed project would involve the demolition of existing outdoor hardscapes associated with school recreational spaces along its eastern and southern perimeter and the construction of four new buildings in two phases. Phase 1 would include an approximately 11,900-square-foot Academic Wing (two buildings with a connecting roof [the Area A and Area B buildings] and a small stand-alone building [Area C Building]). Phase 2 would include an approximately 11,100- square-foot Athletics Building. Should the project entitlements (new Conceptual Development Plan, Detailed Development Plan, Conditional Use Permit and other Discretionary Permits) be approved, the construction component of Phase 1 of the project would commence in late Spring 2026 and be completed approximately 15 months thereafter (Summer 2027). The Phase 2 component would be tentatively scheduled to commence in Spring 2031 and be completed approximately 15 months thereafter (Summer 2032).

The expansion is intended to support the school’s educational mission and long-term operational needs by providing modern classroom space, creative learning environments, and improved athletic / multi-purpose facilities. Additional site improvements would include a new landscaped outdoor plaza connecting the proposed buildings, stormwater management systems, utility infrastructure, and slope stabilization. The new buildings would be fully electric and powered by an upgraded campus-wide electrical service. The expansion would increase the enrollment cap to 290 students (an increase of 30 students), with minimal faculty or staff increase to support the new student enrollment (approximately 11 Armstrong staff) and introduce new sources of stationary noise, i.e., heating, ventilation, and air-conditioning (HVAC) system.

Certain aspects of campus operation would be updated as part of the new CDP-DDP-CUP for the expanded use of the Armstong buildings and grounds:
• Extend access for staff and small-group activities in the existing and proposed buildings until 10:00 p.m. on weekdays, and allow weekend access to the existing and proposed buildings from 9:00 a.m. to 6:00 p.m.
• Allow up to 12 weekend events annually involving 25 or more attendees (e.g., schoolwide gatherings, accreditation visits, graduation). • Permit three special Saturday evening events each year such as a musical or alumni gathering or benefit event with activities ending by 10:00 p.m. • Authorize dismissals on nearby neighborhood streets for up to four special events per year to ease traffic congestion associated with large on-campus gatherings. • Coordinate shared use of McDougal Park for limited weekend or additional weekday access including during the school’s four-week summer session. 481

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The Academic Wing (Phase 1) would consist of three defined buildings (as shown on Figure 3) – Area A (6,364 GSF), Area B (4,237 GSF), and Area C (1,292 GSF). The buildings would range from 20 to 35 feet in height and would be integrated with the site’s sloped topography through multiple finished floor elevations. The mechanical systems for the Academic Wing’s buildings would be all-electric variable refrigerant flow systems. The outdoor condensing units would be ground-mounted at the foot of the slope on the east side of the Area A Building (three units), Area B Building (three units), and Area C Building (one unit) and screened from both campus and residential views. These systems would include mechanical ventilation to ensure fresh air circulation under closed-window conditions. No additional enclosures for the condensing units are proposed, because of their ground-level location and lack of visibility. No emergency diesel generators are proposed for the Academic Wing.

The 11,100 sq. ft. Athletics Building (Phase 2) would be a one-story, 35-foot-tall building as shown on Figure 3. The Athletics Building would house a 7,973-square-foot gymnasium with a regulation-size indoor court for physical education and athletics and bleacher seating for approximately 188 people. This building would contain a 1,400 square-foot commercial kitchen to support daily food service, faculty offices, restrooms, laundry facilities, and dedicated electrical and janitorial closets. The Athletics Building’s HVAC system would include rooftopmounted electric heat pumps and a make-up air unit for the kitchen. The HVAC equipment would be screened from view by a 9-foot-tall parapet wall, shielding views of the equipment from the south. The Athletics Building would also have a mechanical ventilation system to control the indoor air quality. No emergency diesel generators are proposed for this building.

Sound, Noise and Vibration: Definitions, Representations and Measurement Sound is created when vibrating objects produce pressure variations that move rapidly outward into the surrounding air – the more energetic the pressure variations, the louder the sound perceived by a listener. Sound pressures are directly measured in standard units of pounds/square inch (in the English system). But because of the extremely wide range of pressures common in real world sounds, mathematical adjustments were introduced to make common operations (e.g., addition, averaging, etc.) with sound pressure levels (which are often represented by very large numbers) easier to do. This was an important consideration in the era prior to the universal availability of electronic calculators and computers.

That mathematical adjustment (i.e., the use of logarithms) defined the decibel (dB) as the standard measure of acoustical energy relative to the energy of sound at the human threshold of perception. Acoustical energy content of sound expressed in decibels is not uniform across this range, but varies exponentially with changing pressure level. For example, a one-decibel increase in sound level starting from 70 decibels has 100 times the acoustical energy of a onedecibel increase starting from 50 decibels. Table 1, p. 7, shows the range of real-world sound pressure and their representation in standard units and in decibels (the latter being relative to the human threshold of hearing). Table 2, p. 7, shows how the sound pressures from two equivalent sources combine using standard pressure units and decibels. 482

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Figure 3 Charles Armstrong School Expansion Project – Site Plan for New Academic Wing and Athletics Building 483

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Table 1: The Common Range of Sound Pressures and Their Representation in Standard Units and Decibels
Threshold of Hearing Threshold of Pain
In Standard units – L0 (lbs./sq.in.) In Standard units – 1013 L0 = 10,000,000,000,000 L0 In Decibels – 0 In Decibels – 130
The decibel value (divided by 10) tells the number of zeros behind the lead number in the ratio of measured sound pressure to the pressure at the threshold of hearing. The sound pressure at the threshold of pain is 10 trillion times (1013) larger than at the threshold of hearing.

The example below shows the addition of sound levels from two equal sources in both standard units and in decibels.

Table 2: How Sound Pressures are Combined Using Standard Units and Decibels Addition of Equal Sound Pressure Levels
(in Standard Units)
Addition of Equal Sound Pressure Levels
(in Decibels)
L1 = 106 L0 L1 = 60 decibels
L2 = 106 L0 L2 = 60 decibels
L1 + L2 = 2 x 106 L0 L1 + L2 = 63 decibels
Sound pressure levels given in standard pressure units add by the rules of standard arithmetic.

The rule for decibel addition is more complicated.
60 decibels + 60 decibels = 10log(10(60/10) + 10(60/10)) = 10log(2x106) = 63 decibels Where “log” is the inverse operation to exponentiation (e.g., log(106) = 6) A sound-level meter (SLM) is an instrument used to measure the average pressure level of realworld sounds at any moment or over extended time periods. Since most sounds are a complex mixture of time-varying frequency components and human hearing is less sensitive at low frequencies and high frequencies than in the mid-frequency range, the SLM applies human hearing sensitivity factors (as determined by laboratory measurements) to each frequency component of the sound being measured before averaging them. This is called “A” weighting, and the average pressure level measured by an SLM in this mode is called the A-weighted sound level (dBA). Table 3 presents representative noise sources and their corresponding noise levels in dBA at varying distances from the noise sources.

For environmental acoustical measurements, the following metrics of time-average sound level are commonly used:
• Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time-varying sound over the measurement period. • Day–Night Average Sound Level (Ldn) is a 24–hour average Leq with a 10–decibel penalty added to sound levels occurring at night between 10:00 p.m. and 7:00 a.m.

Community Noise Equivalent Level (CNEL) is a 24–hour average Leq very similar to Ldn, but with an additional 5–decibel penalty added to sound levels occurring in the evening between 7:00 p.m. and 10:00 p.m.
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Table 3 Typical Noise Levels in the Environment
Common Outdoor Activities Noise Level (dBA) Common Indoor Activities 110 Rock band
Jet fly-over at 1,000 feet
100
Gas lawn mower at 3 feet
90 Diesel truck at 50 feet at 50 mph Food blender at 3 feet 80 Garbage disposal at 3 feet
Noisy urban area, daytime
Gas lawn mower, 100 feet 70 Vacuum cleaner at 10 feet
Commercial area Normal speech at 3 feet
Heavy traffic at 300 feet 60
Large business office
Quiet urban daytime 50 Dishwasher in next room
Quiet urban nighttime 40 Theater, large conference room Quiet suburban nighttime
30 Library
Quiet rural nighttime Bedroom at night, concert hall
(background)
20 Broadcast/recording studio
10 0
Source: California Department of Transportation, Technical Noise Supplement to the Traffic Noise Analysis Protocol, September 2013, p. 2−20.

Noise is a sound or series of sounds that are intrusive, objectionable, or disruptive to daily life.

Many factors influence how a sound is perceived and whether it is considered disturbing to a listener; these include the physical characteristics of sound (i.e., loudness, frequency composition, etc.) and other factors relating to the situation of the listener and the following:
• Ambient (background) sound level
• Magnitude of the event sound level relative to the background • Frequency composition
• Duration of the sound event
• Number of event occurrences, repetitiveness, and intermittency • Time of day the event occurs
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The effects of noise on people fall into three general categories:
• Subjective effects of annoyance and nuisance
• Interference with activities such as speech, sleep and learning • Physiological effects such as hearing loss
In most cases, the levels associated with environmental noise produce effects only in the first two categories. However, workers in industrial plants may experience noise effects in the last category.

Just as vibrating objects radiate sound through the air, if they are in contact with the ground they also radiate mechanical energy through the ground. If such an object is massive enough and/or close enough to an observer, the ground vibrations can be perceptible and, if the vibrations are strong enough, they can cause annoyance to the observer and, if still stronger, damage to buildings. Some vibration effects can be caused by noise (e.g., the rattling of windows from truck pass-byes). Groundborne vibration attenuates rapidly as distance from the source of the vibration increases. Vibration amplitude can be measured as peak particle velocity (PPV) defined as the maximum instantaneous peak amplitude in inches per second, or as vibration decibels (VdB) referenced to 1 micro-inch per second as the vibration threshold of perception.

Sound Attenuation
As sound (noise) propagates from the source to the receptor, the attenuation, or manner of noise reduction in relation to distance, is dependent on surface characteristics, atmospheric conditions, and the presence of physical barriers. The inverse-square law describes the attenuation caused by the pattern in which sound travels from the source to the receptor. Sound travels uniformly outward from a point source in a spherical pattern with an attenuation rate of 6 dBA per doubling of distance (dBA/DD). However, from a line source (e.g., a road), sound travels uniformly outward in a cylindrical pattern with an attenuation rate of 3 dBA/DD. The characteristics of the surface between the source and the receptor may result in additional sound absorption and/or reflection. Atmospheric conditions such as wind speed, temperature, and humidity may affect noise levels. The presence of a barrier between the source and the receptor may also attenuate noise levels. The actual amount of attenuation depends on the size of the barrier and the frequency of the noise. A noise barrier may be any natural or humanmade feature such as a hill, tree, building, wall, or berm. 486

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REGULATORY FRAMEWORK
Federal
The federal Noise Control Act (1972) addressed the issue of noise as a threat to human health and welfare, particularly in urban areas. In response to the Noise Control Act, the U.S.

Environmental Protection Agency (EPA) published Information of Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety (Levels).1 Table 4 summarizes EPA recommendations for residential and other noise-sensitive land uses.

The EPA identifies an incremental increase of 5 dBA as an “adequate margin of safety” relative to a baseline outdoor noise exposure level of 55 dBA Ldn/Leq before a noticeable increase in adverse community reaction would be expected. If baseline noise levels are higher, a smaller increase can be tolerated before there is an adverse reaction.

Table 4 Noise Levels Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety Adverse Health/Welfare Effect
to be Avoided Protective Level Applicable Areas
Hearing Loss
Less than or equal to
70 dBA Leq
(24-hour average)
All areas
Outdoor activity interference
and annoyance
Less than or equal to
55 dBA Ldn
Outdoors in residential areas, on farms, and in
other outdoor areas where people spend widely
varying amounts of time and in which quiet is a
basis for use.

Less than or equal to
55 dBA Leq
(24-hour average)
Outdoor areas where people spend limited
amounts of time, such as school yards,
playgrounds, etc.

Indoor activity interference
and annoyance
Less than or equal to
45 dBA Ldn
Indoor residential areas
Less than or equal to
45 dBA Leq
(24-hour average)
Other indoor areas with human activities such as
schools, etc.

Source: US EPA. 1974. Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety.

The Federal Transit Administration (FTA) has vibration assessment methodology and impact criteria that apply directly to projects under its jurisdiction. While the proposed project would not be subject to FTA oversight, this agency’s guidance provides groundborne vibration criteria that are useful in establishing thresholds for project impact determinations. The FTA’s Transit Noise and Vibration Impact Assessment Manual provides guidance for two types of potential 1 US EPA. 1974. Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. Available at: https://www.nonoise.org/library/levels74/levels74.htm.

Accessed September 2025.
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impact: (1) damage to structures, and (2) annoyance to people, as summarized in Table 5 and Table 6.2
Table 5: Federal Transit Administration Construction Vibration Damage Criteria Building/ Structural Category PPV (in/sec) Lv (VdB)a
Reinforced-concrete, steel or timber
(no plaster) 0.5 102
Engineered concrete and masonry (no
plaster 0.3 98
Non-engineered timber and masonry
buildings 0.2 94
Buildings extremely susceptible to
vibration damage 0.12 90
Notes:
a Velocity in decibels, VdB re 1 micro-in/sec
Source: Federal Transit Administration (FTA), Transit Noise and Vibration Impact Assessment (2018).

Table 6: Indoor Groundborne Vibration (GBV) Annoyance Impact Criteria for General Vibration Assessment
Land Use Category
GBV Impact Levels
(VdB re 1 micro-inch /sec)
Frequent Events
( >70/day)
Occasional Events
(30-70/day)
Infrequent Events
(<30/day)
Category 1: Buildings where vibration would
interfere with interior operations. 65 65 65
Category 2: Residences and buildings where
people normally sleep 72 75 80
Category 3: Institutional land uses with
primarily daytime use. 75 78 83
Source: Federal Transit Administration (FTA), Transit Noise and Vibration Impact Assessment (2018).

State
California Governor’s Office of Planning and Research
The State of California has adopted noise compatibility guidelines for general land use planning. The types of land uses addressed by the State standards and the acceptable noise 2 Federal Transit Administration, 2018. Transit Noise and Vibration Impact Assessment. Available at:
https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/118131/transit-noise-andvibration-impact-assessment-manual-fta-report-no-0123_0.pdf. Accessed September 2025. 488

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categories for each land use are included in the State of California General Plan Guidelines, which is published and updated by the Governor’s Office of Planning and Research.

California also requires each local government entity to perform noise studies and implement a noise element as part of its general plan. The purpose of the noise element is to limit the exposure of the community to excessive noise levels; the noise element must be used to guide decisions concerning land use. A discussion of relevant noise-related policies in the City of Belmont 2035 General Plan is provided below.

California Department of Transportation
There are no federal or state agency vibration standards that directly apply to the proposed project. Thus, while the proposed project would not be subject to Caltrans oversight, this agency’s guidance provides groundborne vibration criteria that are useful in establishing thresholds for project impact determinations. Caltrans’ Transportation and Construction Vibration Guidance Manual provides guidance for two types of potential impact: (1) damage to structures, and (2) annoyance to people, as summarized in Table 7 and Table 8.

Table 7:Caltrans Guidelines for Vibration-Related Damage Structure and Condition
Maximum PPV (in/sec) a
Transient Sources b
Continuous /
Frequent Intermittent
Sources c
Extremely fragile historic buildings, ruins, ancient monuments 0.12 0.08 Fragile buildings 0.2 0.1
Historic and some old buildings 0.5 0.25
Older residential structures 0.5 0.3
New residential structures 1.0 0.5
Modern industrial/commercial buildings 2.0 0.5
Notes:
a PPV = Peak Particle Velocity (vibration level) in inches per second. b Transient sources create a single, isolated vibration event, such as blasting or drop balls. c Continuous/frequent intermittent sources include pile drivers (impact and vibratory), crack-and-seat equipment, and vibratory compaction equipment.

Source: California Department of Transportation. 2020. Transportation and Construction Vibration Guidance Manual. April.

Available at: https://dot.ca.gov/-/media/dot-media/programs/environmental-analysis/documents/env/tcvgm-apr2020- a11y.pdf. Accessed September 2025.
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Table 8:Caltrans Guidelines for Vibration-Related Annoyance Human Response
Maximum PPV (in/sec) a
Transient Sources b Continuous / Frequent Intermittent
Sources c
Barely Perceptible 0.04 0.01
Distinctly Perceptible 0.25 0.04
Strongly Perceptible 0.9 0.10
Severe 2.0 0.4
Notes:
a PPV = Peak Particle Velocity (vibration level) in inches per second. b Transient sources create a single, isolated vibration event, such as blasting or drop balls. c Continuous/frequent intermittent sources include pile drivers (impact and vibratory), crack-and-seat equipment, and vibratory compaction equipment.

Source: California Department of Transportation. 2020. Transportation and Construction Vibration Guidance Manual. April.

Available at: https://dot.ca.gov/-/media/dot-media/programs/environmental-analysis/documents/env/tcvgm-apr2020- a11y.pdf. Accessed September 2025.

Local
City of Belmont General Plan – Noise Element
The Noise Element of the General Plan, adopted in 2017, includes City land use compatibility standards that outline acceptable outdoor noise environment noise levels for various land use categories in the City. In general, the purpose behind land use compatibility standards is to help jurisdictions determine if the existing ambient noise level in a given area would be compatible with a particular developed use.

Table 7-1 of the General Plan outlines land use compatibility guidelines for all land uses in the City of Belmont.3 The following summarizes the compatibility standards for school, library, church, hospital, and nursing home land uses included in the General Plan:
• Normally Acceptable: up to 70 dBA Ldn
• Conditionally Acceptable: 60–70 dBA Ldn
• Normally Unacceptable: 70–80 dBA Ldn
• Clearly Unacceptable: 80+ dBA Ldn
3 City of Belmont. 2017 (November 14). City of Belmont 2035 General Plan. Final Adopted General Plan, Section 7 – Noise Element, Table 7-1: Community Noise Exposure Matrix, p. 7-14. Available at:
https://www.belmont.gov/departments/community-development/2035-general-plan-update/finaladopted-general-plan. Accessed September 2025. 490

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The following summarizes the General Plan compatibility standards for single-family residential land uses which is the predominant land use surrounding the project site. • Normally Acceptable: up to 60 dBA Ldn
• Conditionally Acceptable: 55–70 dBA Ldn4
• Normally Unacceptable: 70–75 dBA Ldn
• Clearly Unacceptable: 75+ dBA Ldn
The General Plan also established standards for non-aircraft transportation noise sources. • For schools, there is no noise limit for outdoor activity areas, but a 45 dBA Leq limit for interior spaces.
• For single-family residential, there is a 60 dBA CNEL noise limit for outdoor activity areas and a 45 dBA CNEL limit for interior spaces.

The General Plan standards for stationary sources of noise are as follows [underline added to text with particular applicability to the proposed project]:
• Daytime noise levels (occurring from 8:00 a.m. to sunset on weekdays, or 10:00 a.m. to sunset on Saturday, Sunday, and holidays) are limited to 50 dBA Leq and 70 dBA Lmax.
• Nighttime noise levels are limited to 45 dBA Leq and 65 dBA Lmax.

City of Belmont General Plan Policies
The General Plan includes goals, policies, and actions related to noise in the City of Belmont.

The following goals, policies and actions are relevant to the proposed project [underline added to text in measures with particular applicability to the proposed project]:
• Goal 7.1: Strive to achieve an acceptable noise environment for the environmental, health, and safety needs of present and future residents of Belmont. • Action 7.1-1.a: Continue to limit hours for certain construction and demolition work to reduce construction-related noises.
• Action 7.1-1.b: Address sources of excessive neighborhood noise that can cause nuisances for residents, such as gas leaf blowers, wireless telecommunication facilities, power sources, ventilation, and cooling facilities. • Policy 7.1-2: Use the Community Noise Level Exposure Standards, shown in [General Plan] Table 7-1, as review criteria for new land uses. Require all new development that would be exposed to noise greater than the “normally acceptable” noise level range to reduce interior noise through design, sound insulation, or other measures.
4 New construction or development should be undertaken only after a detailed analysis of the noise reduction requirements is made and needed noise insulation features included in the design.

Conventional construction, but with closed windows and fresh air supply systems or air conditioning will normally suffice.
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• Policy 7.1-3: Require noise-reducing mitigation to meet allowable outdoor and indoor noise exposure standards in [General Plan] Table 7-2. Noise mitigation measures that may be approved to achieve these noise level targets include but are not limited to the following:
‑ Construct façades with substantial weight and insulation; ‑ Use sound-rated windows for primary sleeping and activity areas; ‑ Use sound-rated doors for all exterior entries at primary sleeping and activity areas;
‑ Use minimum setbacks and exterior barriers;
‑ Use acoustic baffling of vents for chimneys, attic and gable ends; and, ‑ Install a mechanical ventilation system that provides fresh air under closed window conditions.
‑ Alternative acoustical designs that achieve the prescribed noise level reduction may be approved, provided a qualified Acoustical Consultant submits information demonstrating that the required reductions to meet the specific targets for outdoor activity areas and interior spaces can be achieved and maintained.
• Policy 7.1-8: Continue to enforce applicable Federal and State Noise Insulation Standards (CCR, Title 24) and noise requirements.
• Policy 7.1-10: Require developers of new development anticipated to generate a substantial amount of vibration during construction to implement mitigation practices to reduce vibration, which can include: operating heavy equipment as far as practical from residential uses; using smaller bulldozers (operating weight less than 20,000 pounds) when grading must occur within approximately 50 feet of residential uses or other vibration sensitive uses; and using quiet pile driving technology when feasible.

City of Belmont Municipal Code – Noise Ordinance
The City of Belmont City Code contains noise regulations to protect the community from excessive noise.5 The code specifies how noise will be measured and regulated. Specifically, the City Code addresses noise issues and protects the community from substantial noise sources such as construction activity, animals, amplified sound, and stationary equipment. 5 City of Belmont City Code, Article VIII--Noise Control, Section 15-100. Available at:
https://library.municode.com/ca/belmont/codes/code_of_ordinances?nodeId=CICO_CH15OFIS_ARTVIII NOCO. Accessed October 2025.
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Section 15-102(c) establishes daytime (i.e., 8:00 a.m. to sunset on weekdays and 10:00 a.m. to sunset on Saturdays, Sundays, and holidays) and nighttime noise limits for various uses in the City. Continuous noise sources use the average noise level (Leq) while impulse noises should use the peak noise level (Lmax). The limits by land use that may be relevant for the proposed project are included below:
• Residential. For all sources of sound measured from any residential property:
‑ Nighttime Hours - 55 dBA
‑ Daytime Hours – 65 dBA
• Non-Residential. For all sources of sound measured from any non-residential property:
‑ Nighttime Hours – 55 dBA
‑ Daytime Hours – 65 dBA
Section 15-102(c) also establishes the following nonquantitative definition of a noise disturbance to residential land uses in the City:
“Regardless of residential noise limits, sound shall be considered a disturbance if it offends reasonable peace and quiet and/or interferes with the comfortable enjoyment of life or property.”
Regarding noise from construction and demolition activities, Section 15-102(d) of the City Code states that construction activity is not limited by these aforementioned noise standards.

Pursuant to the City Code, noise-generating construction activities are restricted to the hours of 8:00 a.m. to 5:00 p.m., Monday through Friday and 10:00 a.m. to 5:00 p.m. on Saturdays. No construction activity or related activities shall be allowed outside of the aforementioned hours or on Sundays and holidays. During these allowable hours, the City Code does not include numerical thresholds that apply to construction noise. However, all gasoline-powered construction equipment must be equipped with an operating muffler or baffling system as originally provided by the manufacturer, and no modification to these systems is permitted. In addition, authorized land uses and construction activity established through the City’s discretionary land use permit process may be subject to specific noise conditions of approval that may be more restrictive. Construction occurring outside of the daytime allowable hours for construction must be approved by the Building Official.

City of San Carlos General Plan – Noise Element6
The City of San Carlos General Plan, amended in 2020, establishes policies to protect residents, workers, and visitors from excessive noise exposure and to maintain acceptable noise environments throughout the city. The Noise Element identifies transportation corridors, 6 City of San Carlos, General Plan, Chapter 9: Noise Element. Available at:
https://cms3.revize.com/revize/sancarlos/Document%20Center/Chapter%209%20Noise.pdf?t=2025072418 20000&t=202507241820000. Accessed October 2025.
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industrial activities, and construction as the primary community noise sources and provides quantitative noise-land-use compatibility standards for evaluating new development.

San Carlos General Plan Figure 9-1 (Land Use Compatibility for Community Noise Environment) defines exterior noise exposure ranges (Ldn) for sensitive land uses. This figure summarizes the compatibility standards for school, library, church, hospital, and nursing home land uses included in the General Plan:

Schools, Libraries, Museums, Hospitals, and Churches
• Normally Acceptable: up to 70 dBA Ldn
• Conditionally Acceptable: 70–80 dBA Ldn
• Normally Unacceptable: 70–75 dBA Ldn
• Clearly Unacceptable: 75+ dBA Ldn
Figure 9-1 also summarizes the General Plan compatibility standards for single-family residential land uses which is the predominant land use surrounding the project site.

Residential – Single Family
• Normally Acceptable: up to 70 dBA Ldn
• Conditionally Acceptable: 70–80 dBA Ldn
• Normally Unacceptable: 70–75 dBA Ldn
• Clearly Unacceptable: 75+ dBA Ldn
The General Plan also establishes non-transportation noise standards for stationary and operational noise sources in Table 9-1 (Non-Transportation Noise Standards):
• For schools, libraries, and museums, exterior noise levels should not exceed 55 dBA Leq during daytime hours or 45 dBA Leq at night, and interior spaces should not exceed 40 dBA Leq.
• For single-family residential uses, exterior noise levels should not exceed 55 dBA Leq during daytime hours or 45 dBA Leq at night, and interior spaces should not exceed 45 dBA Leq during the day or 40 dBA Leq at night.

City of San Carlos General Plan Policies
The General Plan includes goals and policies related to noise in the City of San Carlos. The following goals and policies are relevant to the proposed project:
• Goal NOI-1: Encourage compatible noise environments for new development and control sources of excessive noise throughout the city. • Policy NOI-1.1: Use the Noise and Land Use Compatibility Standards shown in Figure 9-1 of the General Plan, the performance standards in Table 9-1, and projected noise contours as guides in planning and development decisions. • Policy NOI-1.2: Require new development that could generate substantial noise to include measures such as setbacks, sound barriers, or building insulation to reduce exposure of sensitive receptors, including residences and schools, to noise levels exceeding applicable standards. Minimize noise impacts on noise-sensitive land 494

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uses. Noise-sensitive land uses include residential uses, retirement homes, hotel/motels, schools, libraries, community centers, places of Public assembly, daycare facilities, churches and hospitals.
• Policy NOI-1.3: Limit noise impacts on noise-sensitive uses to noise level standards as indicated in Table 9-1.
• Policy NOI-1.4: Require a detailed acoustic report in all cases where noisesensitive land uses are proposed in areas exposed to exterior noise levels of 60 CNEL Ldn or greater. If recommended in the report, mitigation measures shall be required as conditions of project approval.
• Policy NOI-1.5: Encourage the use of modern building materials and design techniques that enhance sound insulation and reduce interior noise in new and remodeled structures. New development of noise-sensitive land uses proposed in noise-impacted areas shall incorporate effective mitigation measures into the project design to reduce exterior and interior noise levels to the following acceptable levels: a. For new single-family residential development, maintain a standard of 60 Ldn (day/night average noise level) for exterior noise in private use areas.
• Policy NOI-1.6: Where noise mitigation measures are required to achieve the noise level standards, the emphasis of such measures shall be placed upon site planning and project design. The use of noise barriers shall be considered after practical design-related noise mitigation measures have been integrated into the project. • Policy NOI-1.8: All construction activities shall comply with the City’s noise ordinance. Development projects that require an acoustical study shall incorporate reasonable noise and vibration reduction measures and best management practices to minimize excessive noise levels during all phases of construction activity.

Reduction measures and best management practices may include, but are not limited to, noise control techniques for construction tools and equipment, construction site management techniques, temporary noise barriers, noise monitoring and reporting, and/or construction traffic management.

City of San Carlos Municipal Code – Noise Ordinance
The City of San Carlos Municipal Code contains noise regulations to protect the community from excessive and unnecessary noise associated with machines, persons, and devices. The code specifies how noise will be measured and regulated. Specifically, the Municipal Code addresses noise issues and protects the community from substantial sources of noise such as construction activity, amplified sound, mechanical equipment, and vehicles. The residences adjacent to the project site’s south boundary are in the City of San Carlos and it is proper to apply the noise limitations contained in the City of San Carlos Municipal Code – Noise Ordinance to evaluate potential project noise impacts on these noise-sensitive receptors. The City of San Carlos defines 495

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noise limits in Chapter 9.30 (Noise Control)7 and Chapter 18.21 (Performance Standards)8.

Sections relevant to the proposed project are summarized below:

Chapter 9.30 (Noise Control) defines unreasonable noise as that which exceeds 10 dBA above the local ambient noise level when measured at or beyond the property line of the receiving property. Noise levels are typically measured at a reference distance of 50 feet from the noise source or at the nearest property line.

Chapter 18.21.050. The median residential noise level may not exceed 55 dBA during the daytime or 45 dBA during nighttime (after 10:00 p.m.). The maximum noise level may not exceed 70 or 60 dBA, during the same time periods. If ambient noise levels are 10 dBA or more below the limit, the limit shall be decreased by 5 dB.

ENVIRONMENTAL IMPACTS AND SIGNIFICANCE
Significance Thresholds
The CEQA Appendix G Checklist defines the issues relevant to determining the significance of project noise or vibration impacts. To meet the requirements of the CEQA Guidelines potential impacts must be evaluated against the standards of the local General Plan or Noise Ordinance or State/Federal regulatory agencies. The following questions are addressed in this report to evaluate the significance of the project noise and vibration impacts:

1. Would the project result in the generation of a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies?

2. Would the project result in the generation of excessive groundborne vibration or groundborne noise levels?

3. For a project located within the vicinity of a private airstrip or an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport, would the project result in a safety hazard or expose people residing or working in the project area to excessive noise levels? Is this project located within airport noise contours?
7 City of San Carlos Municipal Code, Chapter 9.30: Noise Control. Available at:
https://www.codepublishing.com/CA/SanCarlos/html/SanCarlos09/SanCarlos0930.html.

Accessed October 2025.
8 City of San Carlos Municipal Code, Chapter 18.21.050 (Noise Limits). Available at:
https://www.codepublishing.com/CA/SanCarlos/#!/SanCarlos18/SanCarlos1821.html#18.21.050.

Accessed October 2025.
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Impact 1. Temporary or permanent increase in ambient noise levels Analysis of the existing and future noise environments presented in this section is based on noise monitoring and noise prediction modeling.

Existing Noise Sensitive Receptors
The City of Belmont and City of San Carlos generally define noise-sensitive receptors as residences, religious facilities, schools, childcare centers, hospitals, long-term health care facilities, convalescent centers, and retirement homes. Based on review of existing Google aerial and street-view imagery, the closest existing noise-sensitive receptors in the project site vicinity include residences approximately 25 feet to the east along the site’s eastern boundary and 18 feet to the south along the site’s southern boundary. The noise-sensitive receptors along the site’s southern boundary are in the City of San Carlos. Residential uses are also located farther to the north across Solana Drive and along the site’s northwest perimeter along Chula Vista Drive.

Existing Monitored Noise Levels
To establish existing ambient noise levels on the project site and in adjacent residential areas surrounding it, a field monitoring study was conducted on two days: July 15 and August 26, 2025. The student population onsite varied on these two days. The July visit occurred during the Summer session when only about half of the school’s normal population was onsite, while the August visit was during the Fall session when attendance was close to its approved capacity (i.e., about 260). The weather conditions were clear and nothing that seemed atypical of normal school activities occurred during the time onsite.

The following noise measurement locations were selected as shown in Figure 4:
• Location #1 – near the school’s main student drop-off/pick-up area during weekday morning arrival and afternoon departure periods to establish the effect of motor vehicle and student activity on local noise levels. • Location #3 – near the school’s main outdoor instruction/play/eating areas to measure noise generated by such activities, as well as background levels when these activities were not occurring (i.e., when the students were inside at class). • Locations #2, #4, #5 – near the site boundary where noise levels were expected to be highest (i.e., #5 near the site’s main access road) or lowest (i.e., #2 and #4) farthest from roads or school facilities).
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Figure 4 Charles Armstrong School Expansion Project – Short Term Noise Measurement Locations The purpose of the measurements was to identify and assess noise sources typical of school activity and their potential to adversely affect adjacent residential uses if project implementation would substantially change the on-site distribution and noise-generation potential of those sources. The noise measurements were taken with a sound level meter and the data recorded to allow its analysis and graphing. A summary of the monitoring data is shown in Table 9 and Table 10.

At all measurement locations (except #5 near the main access road), the sources consistently contributing most to ambient noise levels were the students themselves. Even near the arrival/departure location (#1), motor vehicle sound was second to human activity because most of the time the vehicles moved slowly or were stationary with engines stopped or idling (and a good percentage of the vehicles were electric). Sounds from outdoor play and social activities were always perceptible during the time spent on site and were the dominant component in the data captured by the sound level meter near outdoor activity areas. Local mid-day vehicle traffic was very light on the nearby neighborhood streets surrounding the Project site. With the exception of the site entrance onto Solana Drive, motor vehicle noise was not perceptible onsite.

Noise from private and commercial aircraft operating out of regional airports occasionally intrude on and briefly exceed the site background levels especially when student outdoor play and social activities are absent.
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Table 9: Existing Ambient Monitored Noise Levels (Summer Session – July 15, 2025) Measurement Location /
Activity
Lmin
(dBA)
L90
(dBA)
Leq
(dBA)
L10
(dBA)
Lmax
(dBA)
Observations during
Measurement
#1 Arrival
#1 Departure
Car Arrivals / Student
Loading / Departures
(1:50 p.m. – 2:05 p.m.)
Pre-Departure
----

50.0 49.7
----

54.7 50.3
----

68.2 52.6
----

69.5 54.0
----

83.0 58.9
Arrival measurements
not taken during July
survey.

Vehicles arriving before
release time “stack-up”
in the parking lot, engines
off or idling; students
gather on stairway,
gradually join cars which
then depart.
#2 Background
(mid-morning)
No apparent local activity
(10:50 a.m.– 11:00 a.m.)

39.5 40.7 43.3 44.8 47.8
Representative of lowest
daytime noise levels near
the site boundary, likely
the quietest on-site level.
#3 Recess
Full recess begins /
proceeds
(11:20 a.m. – 11:35 a.m.)
Pre-Recess

40.7 42.7

46.7 43.9

58.5 46.4

61.7 47.9

65.9 51.4
Students exit classrooms
at designated times to sit
at tables/amphitheater
area, or play on local
hard-surface areas.
#4 Garden
No instruction / recess
activity in progress
---- ---- ---- ---- ---- Measurements not taken
here during July visit.
#5 Site Access
Vehicle access to site on
Armstrong driveway
(11:55 a.m. – 12:10 p.m.)

40.7 42.6 54.7 55.8 71.9
Passing vehicles on
Solana Drive and
entering the site via the
school driveway are the
major influences.

Notes:

The decibel (dB) is the standard measure of a sound’s intensity (which correlates with perceived loudness) relative to the human threshold of perception. A decibel value, as measured by a Sound Level Meter (SLM), is said to be A– weighted (dBA) when the SLM makes adjustments to an actual sound’s frequency components to reflect the known, varying sensitivity of the human ear to each different frequency before averaging them. The Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time–varying sound over the measurement period. Statistical Sound Levels - Lmin, L90, L10 and Lmax - are the minimum sound level, the sound level exceeded 90% of the time, the sound level exceeded 10% of the time and the maximum sound level, respectively; all as recorded during the designated measurement periods.
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Table 10: Existing Ambient Monitored Noise Levels (Fall Session – August 26, 2025) Measurement Location /
Activity Measured
Lmin
(dBA)
L90
(dBA)
Leq
(dBA)
L10
(dBA)
Lmax
(dBA)
Observations during
Measurement
#1 Arrival
Car Arrivals / Student
Unloading / Enter Class
(7:45 a.m. – 8:15 p.m.)
Pre-Arrival
#1 Departure
Students Released,
Load Cars, Depart
(3:00 p.m.– 3:30 p.m.)
Pre-Loading

45.6 43.6

50.1 49.3

50.0 44.8

51.7 49.7

58.3 47.6

64.9 50.7

61.3 49.8

67.1 51.3

69.5 53.3

79.3 54.9
Vehicles are directed
along the parking lot
perimeter to drop off
students in front of
school; students gather
in outdoor areas until
first bell.

Vehicles accumulate in
parking lot with engines
idle or off; students are
released to join cars at
3:00 p.m.; all cars out by
about 3:30 p.m.
#2 Background
(mid-morning)
No apparent local
outdoor activity
(8:40 a.m. – 9:00 p.m.)

40.4 41.6 43.6 45.2 50.6
Representative of lowest
daytime noise levels near
the site boundary, likely
the quietest on-site level.
#3 Recess
Full recess
(9:45 a.m. – 10:15 a.m.)
#3 Lunch
(12:25 p.m. – 12:45 p.m.)

41.5 55.0

47.8 61.1

59.6 67.2

62.7 69.5

74.6 86.5
Students sit at tables and
in amphitheater area, or
play on local hardsurface areas.
#4 Garden

37.9 39.2 44.0 46.7 55.9
No instruction / recess
activity in progress
#5 Site Access
Vehicle access to site
on Armstrong driveway
---- ---- ---- ---- ---- Measurements not taken
here during August visit.

Notes:

The decibel (dB) is the standard measure of a sound’s intensity (which correlates with loudness) relative to the human threshold of perception. A decibel value, as measured by a Sound Level Meter (SLM), is said to be A– weighted (dBA) when the SLM makes adjustments to an actual sound’s frequency components to reflect the known, varying sensitivity of the human ear to each different frequency before averaging them. The Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time–varying sound over the measurement period. Statistical Sound Levels - Lmin, L90, L10 and Lmax - are the minimum sound level, the sound level exceeded 90% of the time, the sound level exceeded 10% of the time and the maximum sound level, respectively; all as recorded during the designated measurement periods.
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Existing Noise from Morning Student Arrivals
The photo below (Figure 5) shows the procedure (as it occurred August 26, 2025) for morning drop-off of students at the school. Cars arriving before 7:45 a.m. queue at the upper blacktop area, where they wait for admittance to the large hard-surface parking lot/athletic area south of the school buildings. When the gate opens, the cars are directed counterclockwise along the lot perimeter to drop off students in front of the school building. Then each car immediately departs the school site. The whole process of entry/drop-off/departure takes about a half hour each school day.

The temporal pattern of noise levels associated with drop-off activity is shown in the graph and table below (Table 11). The rising noise levels shown in the graph between 7:45 a.m. and 8:10 a.m. are not produced by the cars, but by the students who grow in number and linger in the outdoor spaces around the site until called to class at the end of that period.

Figure 5 Charles Armstrong School Expansion Project – Pickup and Dropoff Location (Mornings) 501

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Table 11: Existing Ambient Monitored Noise Levels for Morning Arrivals Noise Levels as Recorded during Morning Arrival (8/26/2025) Activity Type / Duration Lmin L90 Leq L10 Lmax
Observations During
Measurements
Pre-Arrival
(7:30 a.m. – 7:45 a.m.) 43.6 44.8 47.6 49.8 53.3
Vehicles arriving early wait in
the school driveway for the
gate to open.

Arrival
(7:45 a.m. – 8:10 a.m.)
Arrival Noise Incrementa

45.6 50.0 58.3
+10.7

61.3 69.5
After admission to the lot,
vehicles are directed along its
perimeter to drop off students
in front of school; students
gather in outdoor areas until
first bell.

Retire to Classes
(8:10 a.m. – 8:30 a.m.) 43.1 44.3 49.0 50.4 63.2
At a signal, students leave
outdoor gathering area and
head into classes.

Notes:

The decibel (dB) is the standard measure of a sound’s intensity (which correlates with loudness) relative to the human threshold of perception. A decibel value, as measured by a Sound Level Meter (SLM), is said to be A– weighted (dBA) when the SLM makes adjustments to an actual sound’s frequency components to reflect the known, varying sensitivity of the human ear to each different frequency before averaging them. The Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time–varying sound over the measurement period. Statistical Sound Levels - Lmin, L90, L10 and Lmax - are the minimum sound level, the sound level exceeded 90% of the time, the sound level exceeded 10% of the time and the maximum sound level, respectively; all as recorded during the designated measurement periods. a Indicates difference between pre-arrival and arrival Leq.

Existing Noise from Outdoor Student Activities
The photos below Figure 6 and Figure 7) show two different instances of on-site outdoor activity (also on August 26, 2025): the first shows students socializing in the play area along the 40 45
50 55
60 65
70 7:30 7:35 7:40 7:45 7:50 7:55 8:00 8:05 8:10 8:15 8:20 8:25 8:30 502

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site’s south boundary (next to off-site adjacent residential land use, i.e. a noise -sensitive receptor) while waiting for classes to begin after drop-off that morning; the second shows recess later that morning at the covered sitting area near the east boundary (also close to off-site adjacent residential land use). The temporal pattern of noise levels associated with recess activity is shown in the graph and table below (Table 12).

Figure 6 Charles Armstrong School Expansion Project – Outdoor Activity Area 503

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Figure 7 Charles Armstrong School Expansion Project – Shaded Outdoor Area Table 12: Existing Ambient Monitored Noise Levels for Morning Recess Noise Levels as Recorded during Morning Recess (8/26/2025) 35 40
45 50
55 60
65 70
9:20 9:25 9:30 9:35 9:40 9:45 9:50 9:55 10:00 10:05 10:10 504

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Activity Type / Duration Lmin L90 Leq L10 Lmax
Observations during
Measurements
No Local Activity
(9:20 a.m. – 9:45 a.m.) 39.1 40.9 46.8 50.0 58.2
Sounds of more distant
outdoor or indoor activity
onsite, just not in the
adjacent activity area.

Recess,
then Return to Class
(9:45 a.m. – 10:15 a.m.)
Recess Noise Increment a

41.5 47.8 59.6
+12.7

62.7 74.6
Students sit at tables under
canopy or in amphitheater
area, or play on local hardsurface areas.

Notes:

The decibel (dB) is the standard measure of a sound’s intensity (which correlates with loudness) relative to the human threshold of perception. A decibel value, as measured by a Sound Level Meter (SLM), is said to be A– weighted (dBA) when the SLM makes adjustments to an actual sound’s frequency components to reflect the known, varying sensitivity of the human ear to each different frequency before averaging them. The Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time–varying sound over the measurement period. Statistical Sound Levels - Lmin, L90, L10 and Lmax - are the minimum sound level, the sound level exceeded 90% of the time, the sound level exceeded 10% of the time and the maximum sound level, respectively; all as recorded during the designated measurement periods.
a Indicates difference between no localized onsite activities and recess activities Leq.

Existing Noise from Afternoon Departures
The photo below (Figure 8) shows the procedure (as it occurred August 26, 2025) for afternoon pickup of students at the school. Here cars arriving before student release begins at about 3:00 p.m., are “stacked” in the hardcourt area under the direction of school staff. When the gate opens, the cars are directed counterclockwise along the lot perimeter to drop off students in front of the school building. Then each car immediately departs the school site. The whole process of entry/drop-off/departure takes about a half hour each school day.

The temporal pattern of noise levels associated with drop-off activity is shown in the graph and table below (Table 13). The on-site wait period for the cars before student release is about a half hour, but it is generally a quiet time because most cars wait with engines off. The two periods of higher noise levels (seen in the graph at about 3:05 p.m. and 3:20 p.m.) are produced by groups of students running to the cars after release.
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Figure 8 Charles Armstrong School Expansion Project – Pickup and Dropoff Location (Afternoons) Table 13: Existing Ambient Monitored Noise Levels for Afternoon Departures Noise Levels as Recorded during Afternoon Departures (8/26/2025) 40 45
50 55
60 65
70 75
14:36 14:40 14:44 14:48 14:52 14:56 15:00 15:04 15:08 15:12 15:16 15:20 15:24 15:28 15:32 506

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Activity Type / Duration Lmin L90 Leq L10 Lmax
Observations during
Measurements
Cars Admitted to Lot and
Wait
(2:35 p.m. – 3:00 p.m.)

49.3 49.7 50.7 51.3 54.9
Vehicles arriving before
release time “stack-up” in
the parking lot, engines off
or idling.

Students Dismissed to Join
Cars, begin Departure
(3:00 p.m. – 3:20 p.m.)
Departure Increment a

50.1 51.7 64.9
+14.2

67.1 79.3
Students are released to
join cars beginning about
3:00 p.m.; it takes about
20 minutes for all to load
and go.

Departure
(3:20 p.m. – 3:35 p.m.) 37.6 40.6 60.2 60.8 81.9
All cars out and local
human activity ceases by
about 3:30 p.m.

Notes:

The decibel (dB) is the standard measure of a sound’s intensity (a correlate of loudness) relative to the human threshold of perception. Decibels, as measured by a Sound Level Meter (SLM), are said to be A–weighted (dBA) when the SLM makes adjustments to an actual sound’s frequency components to reflect the known, varying sensitivity of the human ear to each different frequency before averaging them. The Equivalent Sound Level (Leq) is a constant sound level that carries the same sound energy as the actual time–varying sound over the measurement period. Statistical Sound Levels - Lmin, L90, L10 and Lmax - are the minimum sound level, the sound level exceeded 90% of the time, the sound level exceeded 10% of the time and the maximum sound level, respectively; all as recorded during the designated measurement periods.
a Indicates difference between pre-dismissal activities with cars waiting and student dismissal activities Leq.

Project Operational Noise Impacts from Changes to the Existing School’s Student Population and Operations, and the Addition of New Stationary Noise Sources This report’s conclusion about the significance of project operational noise impacts are based on the following observations and analysis of site conditions. The most relevant noise measurement data from the project site survey is summarized in Table 14 to facilitate references and reader understanding of the impact discussion that follows.

Table 14: Sound Level Measurement Data Summary (dBA) - Charles Armstrong School, Belmont CA (Summer [7/15/25] & Fall [8/26/25])
School Activity during Measurement L90
(dB)
Leq
(dB)
L10
(dB)
Range
L10 to L90 (dB) Notes
Arrival Summer Session
(Not measured)
Arrival Fall Session (from Table 10)
7:45 a.m. – 8:15 p.m.
---

50.0 ---

58.3 ---

61.3 ---

11.3 For all Armstrong
activities, the
measured sound
levels had a high
variability, ranging
over about 10-
15 dB.

Recess Summer Session (from Table 9)
11:20 a.m. – 11:35 a.m.

46.7 58.5 61.7 15.0
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School Activity during Measurement L90
(dB)
Leq
(dB)
L10
(dB)
Range
L10 to L90 (dB) Notes
Recess Fall Session (from Table 10)
9:45 a.m. – 10:15 a.m.

47.8 59.6 62.7 14.9 During activities
where comparisons
are possible (i.e.,
Recess &
Departure) there is
no consistent
relationship
between the
number of students
present at a
session and the
higher Leq (e.g.,
Departure Leq was
higher during the
Summer Session
when attendance
was lower)
Lunch Fall Session (from Table 10)
12:25 p.m. – 12:45 p.m. 61.1 67.2 69.5 8.4
Departure Summer Session (from Table 9)
1:50 p.m. – 2:05 p.m.

Departure Fall Session (from Table 10)
3:00 p.m.– 3:30 p.m.

54.7 51.7

68.2 64.9

69.5 67.1

14.8 15.4
Background Summer Session (from Table 9)
10:50 a.m.– 11:00 a.m.

Background Fall Session (from Table 10)
8:40 a.m. – 9:00 p.m.

Background (Garden) Fall Session
(from Table 10)
10:20 a.m. – 10:41 a.m.

40.7 41.6

39.2 43.3

43.6 44.0

44.8 45.2

46.7 4.1

3.6 7.5
For all background
measurements, the
averages (Leq) are
all mid 40s dB, each
within 1 dB of the
others.

Existing On-site and Near Site Boundary Noise Levels
Based on the noise measurements during weekday daytime with school in session, background values measured near the east and south boundary were in the 40s dBA range when students were in class. During outdoor recess/play/lunch they were mostly in the 50s dBA range.

Expected nighttime noise levels would be in the 30s dBA range. This is strong evidence that the Ldn (24-hour average noise level with penalty added for nighttime noise) onsite near the boundary with the adjacent residential uses is less than— and likely substantially less than— 60 dBA Ldn, which is the City land use compatibility standard “normally acceptable” for school and residential land uses. This conclusion is supported by the City of Belmont General Plan noise contour maps (General Plan, Figure 7-2 and Figure 7-3, Existing & Future Noise Contours) that show motor vehicle traffic noise levels (the most important local noise source) on site to be below 60 dBA Ldn.
9 9 City of Belmont. 2017 (November 14). City of Belmont 2035 General Plan. Final Adopted General Plan, Section 7 – Noise Element, pp. 7-8 and 7-9. Accessed October 2025. 508

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Increase Due to Site Population Increase
The present school enrollment cap is currently 260 students, with present enrollment at 240 students. Proposed project expansion could increase the enrollment cap to 290 students — an increase of 30 students. Approximately 11 additional Armstrong staff will support the increased student enrollment. There is no simple model to predict local noise level dependence on student number given that the students move around the project site during a typical school day, at times being indoors or outdoors, being quiet or talkative, stationary or active etc. But the simplest model equates a doubling of sound source strength to a 3 dB increase in sound level.

Applying this relationship to the above-mentioned existing and potential future enrollment would give a maximum possible daily average activity noise increment around the site of about

0.5 dB (i.e., 10 log [290/260]).

Increase Due to Project Traffic
The increase in daily drop-off/pick-up motor vehicle trips to support 30 additional students and approximately 11 additional Armstrong staff would be minimal. And as noted and observed during the on-site noise measurements, the dominant contribution to on-site and near roadway noise levels is from human activity, not motor vehicles, which move at slow speed or idle while on site and are well-muffled, late-model gasoline-powered or electric.

Movement of the Main Areas of Outdoor Activity away from the Site’s East and South Boundaries
The new Academic Wing buildings and Athletics Building would be located at sites close to the east and south boundaries of the school campus that currently support outdoor social and athletic activities (e.g., an outdoor basketball court would be removed, and the new Athletics Building would include an indoor court). Thus, noise-generating outdoor areas would be removed and a portion of the outdoor activities they now support would be moved indoors.

Changes to On-Site Activity Noise with Expanded Operations The proposed new CDP-DDP-CUP would expand the daily times and/or annual frequencies of on-site, noise-generating activities. Expanded operations would include more nighttime access for staff during weekdays and occasional nighttime and weekend special events, e.g., school musicals, alumni gatherings, back-to-school nights, accreditation visits, and graduations with their associated on-street arrival/departure activities. Some of the weekend special events may occur outdoors but most extended use activities would occur within school buildings. Event attendance typically ranges from 25 to 500 participants with graduations and community picnics as the high-attendance events.

As observed (and measured) during the site surveys, the most important noise influences on adjacent residential receptors come from outdoor activities on the Armstrong campus. Indoor activities in the existing buildings had no audible influence on outdoor noise levels (see noise data summary tables where such levels are labeled as “background”). The same would be expected from the expanded operations proposed with the new CDP-DDP-CUP, i.e., increased indoor nighttime presence of staff or from the attendees at the few permitted nighttime indoor 509

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meetings or weekend special events. Thus, expanded operations to include limited nighttime use of campus buildings would not result in substantial change to ambient conditions.

Stationary Noise
The project’s stationary noise sources (i.e., its HVAC equipment) would be located in four discrete locations along the eastern and southern edges of the Armstrong campus in the vicinity of Belmont residences located along Altura Way and San Carlos residences along Dartmouth Avenue. The HVAC systems are required to meet the City of Belmont’s and/or the City of San Carlos’ applicable General Plan or Noise Ordinance standards (depending on the city they are in; residences along the project site’s southern boundary are in the latter city). They are the same for both cities. Daytime noise levels as measured at the receiving property are limited to 50 dba Leq and 70 dba Lmax. There are nighttime limits that would be applicable to the expanded daily and weekly operations proposed by the Charles Armstrong School.10 Nighttime noise levels as measured at the receiving property are limited to 45 dba Leq and 65 dba Lmax. Daytime hours in the City of Belmont end at sunset by General Plan definition. In the City of San Carlos nighttime limits are applicable after 10:00 p.m.

As currently proposed, screened outdoor ground-level HVAC equipment would be placed at three locations on the eastern perimeter of the project site where the Academic Wing buildings are proposed. Outdoor HVAC equipment would also be located on the second floor of the Athletics Building behind a 9-foot-tall parapet wall along the site’s southern perimeter.

The project sponsor hired Smith, Fause & McDonald, Inc. (SFMcD) as their acoustic consultant to evaluate project HVAC noise impacts to adjacent residences in the cities of Belmont and San Carlos based on a preliminary list of HVAC equipment.11 Noise propagating from the ground-level HVAC equipment next to the Academic Wing buildings would be attenuated by the distances to the closest residential property line (i.e., approximately 25 feet as shown in Figure 1 of the SFMcD Study included in Appendix B) and by intervening terrain features (e.g. the steeply sloped and wooded hillside and property line fence that would block a direct line of sight/path of noise propagation from the HVAC equipment to the residences atop the hill.

Similarly, noise from the Athletics Building’s HVAC equipment (i.e., as shown in Figure 2 of the SFMcD Study included in Appendix B) would be attenuated by distance to the closest residential property (more than 18 feet) and the 9-foot-tall building parapet wall that is part of the project design, and the fact there would be no direct line of sight/path of noise propagation from the HVAC equipment to the residents to the east or the south. 10 City of Belmont. 2017 (November 14). City of Belmont 2035 General Plan. Final Adopted General Plan, Section 7 – Noise Element, Table 7-3: Stationary Noise Sources, p. 7-15. Available at:
https://www.belmont.gov/departments/community-development/2035-general-plan-update/finaladopted-general-plan. Accessed September 2025. 11 Smith, Fause & McDonald, Inc., Noise Impact Study, October 16, 2025. Included as Appendix B. 510

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SFMcD’s quantitative noise impact findings relating to modeled HVAC noise increments in the context of existing ambient conditions with comparison to City standards are summarized in Table 15.

Table 15: HVAC Sound Level Modeling Results Summary (dBA) - Charles Armstrong School, Belmont CA HVAC Noise Source
Daytime Noise Levels
(dBA @ nearest property line)
Nighttime Noise Levels
(dBA @ nearest property line)
HVAC Ambient Composite HVAC Ambient* Composite
Academic Wing (Area A
Building—All three HVAC
Units Operating)

42.4 44.0 46.3 42.4 ---- 42.4
Academic Wing (Area B
Building--All three HVAC
Units Operating)

47.9 44.0 49.4 47.9 ---- 47.9***
Academic Wing (Area B
Building--Only one HVAC
Unit Operating)

44.8 44.0 47.4 44.8 ---- 44.8
Academic Wing (Area C
Building one HVAC Unit
Operating)
< 44.8** 44.0 < 47.4 < 44.8** ---- < 44.8
Athletics Building
(Mechanical Equipment
Area) All Units Operating

43.3 44.0 46.7 43.3 ---- 43.3
Notes:
* Nighttime ambient noise levels were not measured during the project site surveys. Nighttime ambient levels are typically substantially below daytime levels (i.e., 10 dBA or more). And thus, would contribute < 0.1 dBA to the composite values as shown in the table.
** The single HVAC unit installed adjacent to the Academic Wing’s Area C Building is very similar in noise generation characteristics to any one of the three units installed adjacent to the Academic Wing’s Area B Building. But its location is farther from the residential property line than the units associated with the Academic Wing’s Area B Building. Thus, its noise impact would be less than any one of the units associated with the Academic Wing’s Area B Building. Its specific impact was not modeled because being farther from the site property line would guarantee it would have less of a noise impact than any single unit associated with the Academic Wing’s Area B Building.
*** The modeled composite values were compared with Belmont and San Carlos stationary equipment noise limits (i.e., 50 dBA daytime and 45 dBA nighttime for both cities). In only one case was the nighttime limit exceeded – at the Belmont property line closest to the Academic Wing’s Area B Building when all three HVAC units operate at full capacity at night (see the single table entry in Red Bold). When the Area B Building’s noise is modeled with only one HVAC unit in operation, modeled levels were below the nighttime limit suggesting the restriction of operating only one unit at night to avoid potential noise disturbance to residential neighbors is necessary.

Reduced nighttime operations would keep the Area B Building’s HVAC equipment noise below the nighttime limit by about 0.2 dBA. Additionally, sound-absorbent materials or barriers can be incorporated in the screened enclosure system to more substantially reduce noise propagating from the HVAC equipment.

Source: Smith, Fause & McDonald, Inc., Noise Impact Study, October 16, 2025. 511

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The SFMcD modeling was based mostly on available HVAC equipment manufacturer data (as detailed in the SFMcD study table, included in Appendix B) or using conservative assumptions when data was not available. Operation of the new HVAC mechanical units at the Charles Armstrong School at full output would be compliant with the Noise Ordinances or General Plans of the City of Belmont and the City of San Carlos, with one exception: the composite noise level from the simultaneous operation of all three HVAC units associated with the Academic Wing’s Area B Building is modeled to exceed the Belmont General Plan stationary equipment nighttime limit (i.e., 45 dBA Leq). But this exceedance can be avoided by either running only one HVAC unit at night or only running all three HVAC units during the day (note: the City of Belmont General Plan defines “nighttime” as beginning at sunset).

Incorporation of additional design recommendations as identified by SFMcD (e.g., additional screening with sound absorbent materials, and/or enclosing them in sound-rated enclosures) should be considered by the City if the model’s shortfall of 0.2 dBA from the 45 dBA nighttime standard (with only one of three HVAC units associated with the Area B Building operating) is judged to be too small a margin of safety on the potential for annoyance to residences closest to the Area B Building’s stationary noise sources.

Thus, based on the above analysis, operational noise increases associated with the introduction of new stationary noise sources are assumed; however, incorporation of the final design recommendations identified by SFMcD (e.g., additional screening with sound absorbent materials or use of sound-rate mechanical system enclosures) would ensure that exposure to noise in excess of established standards would be less than significant.

Temporary Increase in Ambient Noise due to Project Construction Project construction would temporarily increase ambient noise levels on site and in adjacent areas where there are single family residential uses close to its east and south boundaries.

Construction of the proposed Academic Wing buildings---assuming development entitlement and construction permits are secured--would take about 15 months beginning in late Spring 2026. Construction of the proposed Athletics Building would also take about 15 months, beginning in Summer 2031. The construction phases for each project component would be similar, have similar characteristic equipment mixes and durations of use (as specified in the Project Description) and their locations of work activity would vary on each building site and in relation to the noise-sensitive uses that surround them. Project construction equipment noise levels were modeled using the Federal Highway Administration’s (FHWA) Roadway Construction Noise Model (RCNM) assuming the specified equipment types per phase were operating simultaneously in close proximity to each other at the chosen distances from a receptor, as shown Figure 9 and presented in Table 16. In actuality, the operation of such equipment would not be constant throughout the workdays over the duration of the phases, so the data presented would be the highest possible workday average noise level affecting a sensitive receptor at the specified distance if all equipment operated continuously there during that day.
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Given that the City General Plan or Noise Ordinance have not set maximum quantitative standards at noise-sensitive receptors near construction sites, a reasonable choice for an evaluative standard for this CEQA analysis would be a daytime noise level that is clearly above local weekday average weekday levels and which could demonstrably interfere with normal outdoor activities on closest portions of the adjacent resident lots facing the school site.

Noise measurements at the school site near the eastern and southern boundaries with the adjacent residential areas show that noise levels most of the time (on a weekday mid-morning) were in the 40s dBA range, except during periods when proximate student outdoor activities push average noise levels up, mostly into the 50s dBA range, and occasionally as high as 65 dBA. The EPA’s Protective Noise Levels found that speech intelligibility in outdoor environments begins to decline rapidly when background noise levels begin to exceed 65 dBA.

Thus, project construction activities that take place on portions of the site 250 feet or closer to the adjacent property owners’ backyards could have disruptive impacts on outdoor recreational activity at those locations.

Figure 9 Construction Noise Levels within 250 feet
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Table 16: Modeled Construction Noise Levels
Project Phase /
Duration
Dominant
Equipment
Modeled Noise Level at x feet from work activity locus (dBA) 50 feet 100 feet 200 feet 400 feet 800 feet
Phase 1: Academic Wing (Buildings A, B and C) – May 2026 to August 2027 Phase 2: Athletics Building – May 2031 to August 2032
Site Preparation /
2 weeks
Concrete Saw
Backhoe
(Backhoe only)

83.1 (73.6)

77.1 (67.6)

71.1 (61.5)

65.0 (55.5)

59.0 (49.5)
Grading /
4 weeks
Excavator
Backhoe
Dozer

81.1 75.1 69.1 63.0 57.0
Site Utilities /
6 weeks
Concrete Saw
Backhoe
(Backhoe only)

83.1 (73.6)

77.1 (67.6)

71.1 (61.5)

65.0 (55.5)

59.0 (49.5)
Building Construction /
11 months
Forklift
Crane
Concrete Pump

76.6 70.6 64.6 58.5 52.5
Site Hardscape &
Landscape /
10 weeks
Backhoe
Excavator 78.4 72.4 66.4 60.4 54.4
Notes:

Modeled construction noise level table entries shown in red would be high enough (i.e., 65 dBA or more) to interfere with speech occurring at normal conversational levels.

Concrete saws are typically used for only the first few days of the site preparation phase, so, their effects have been separated out of the composite noise levels above to show the noise levels that would affect proximate receptors for most of the rest of the construction phases in which they are included.

Project construction would generate temporary increases in noise levels to the east and south at the facing residential owners’ property line that would be noticeable. The following measures are based on the City’s standard conditions of approval for construction noise and are required to be followed by project sponsor to reduce the potential effects of construction noise on adjacent properties (also see Appendix A).
• Limit construction activity to the hours 8:00 am to 5:00 pm on weekdays, 10:00 am to 5:00 pm on Saturdays, with no construction activity permitted on Sundays and holidays.
• Schedule highest noise-generating activity and construction activity away from noise-sensitive land uses.
• Equip internal combustion engine-driven equipment with original factory (or equivalent) intake and exhaust mufflers which are maintained in good condition. • Prohibit and post signs prohibiting unnecessary idling of internal combustion engines.
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• Locate all stationary noise-generating equipment such as air compressors and portable generators as far as practicable from noise-sensitive land uses. • Utilize “quiet” air compressors and other stationary equipment where feasible and available.
• Designate a noise disturbance coordinator who would respond to neighborhood complaints about construction noise by determining the cause of the noise complaints and require implementation of reasonable measures to correct the problem. Conspicuously post a telephone number for the disturbance coordinator at the construction site.
• When project construction work lasting more than a week is necessary on project building sites within 250 feet of the existing homes facing the site to the east and south, the Project contractor shall provide at least three-days’ notice to the residents and advise them on short-term shifts to less-affected outdoor play/recreation spaces or to other indoor rooms less exposed to the direct noise from the construction activity until the more noise-intensive project construction stages are complete.

The General Plan and Noise Ordinance exempt construction noise from the quantitative guidelines applicable to other transportation and stationary noise sources, provided the construction activities are limited to the allowable hours indicated in City General Plan and Noise Ordinance.

With limitation of project construction to these hours and days and the additional measures based on the City’s standard conditions of approval above, the project’s temporary construction noise impact would be less than significant.

Impact 2. Excessive groundborne vibration
Temporary Increase in Groundborne Vibration due to Project Construction The closest residential uses to the east and south of the proposed construction activities would be potential targets for vibration damage and occupant annoyance from heavy construction equipment movements. The existing onsite school buildings and the students/staff within them would also be potential targets for vibration damage and occupant annoyance from heavy construction equipment movements. The City requires that projects which use heavy-duty equipment implement standard conditions of approval for heavy-duty equipment during construction (e.g., bulldozing).

Project construction would not require substantial heavy equipment operating for long periods close to these onsite and offsite receptors. Dozers would be the most vibration-intensive equipment types required for the site grading. In Table 17, vibration screening methodology has been applied to the most vibration-intensive construction equipment likely to be regularly used on the project site. Vibration levels during work on site areas closest to the closest sensitive receptors (about 50-100 feet distant) would be far below the range where there would be any potential for on-going substantial annoyance (80 VdB) or structural damage (94 VdB) due to 515

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project construction activity. The onsite buildings and receptors would be much closer on average to the project construction work (e.g., the Academic Wing buildings would be right next to these existing building’s eastern walls) than the adjacent existing residents. Because of this, there may be times during construction when vibration annoyance levels in the closest parts of the school interfere with instructional activity and may also cause structural damage.

School authorities can act to temporarily move instruction to less affected parts of the buildings and instruct their contractors to repair any damage to existing school buildings they might cause.

Table 17: Modeled Construction Vibration Levels
Equipment Type
Modeled vibration level at x feet from work activity locus (VdB) 25 feet 100 feet 200 feet 300 feet
Bulldozer 87 69 60 55
Loaded Heavy Truck 86 68 59 54
Source: Federal Transit Administration (FTA), Transit Noise and Vibration Impact Assessment (2018).

Project construction would generate temporary increases in groundborne vibration levels that could affect onsite buildings and sensitive receptors (students). Due to distance from project construction activities would not affect the closest residential receptors and buildings to the east and south. The City’s standard conditions of approval for construction vibration are required to be followed by the project sponsor to reduce the potential effects of construction-related groundborne vibration on buildings and sensitive receptors (see Appendix A).

With implementation of the City’s standard conditions of approval, the project’s temporary construction vibration impacts to off-site and on-site buildings and receptors would be less than significant.

Impact 3. Airport noise exposure
The project site is located outside the noise impact contours (i.e., 65 dBA CNEL) of all the nearest public airports, including San Carlos Airport (2 miles east), San Francisco International Airport (10 miles north), and San Jose Mineta International Airport (30 miles southeast).

Because the proposed project would not locate new noise-sensitive uses (i.e., it would continue to operate an existing school) near these airports, the proposed project would not expose people residing or working on the project site to excessive noise levels. Therefore, there would be no impact.
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APPENDIX A: City of Belmont Standard Conditions of Approval -- Noise and Vibration
The potential construction noise, ground borne vibration, and operational noise impacts of the General Plan/BVSP buildout cannot be fully mitigated at the Program EIR (General Plan EIR) level, because of the uncertainty involved in evaluating the impacts on all potential future users of new development. The evaluation of noise impacts is “project/location specific” and noise impacts change over time as development occurs and traffic patterns change. Thus, in order to address potential noise impacts, the General Plan EIR: 1) identified comprehensive policies to limit the exposure of sensitive receptors to construction noise, ground borne vibration, and operational noise; and 2) required that applicants for individual development projects evaluate potential noise and vibration impacts and develop appropriate measures to avoid or reduce these impacts.

The City developed a Standard Development Requirement (SDR) to implement General Plan policies that mitigate for noise and vibration impacts. Applicants are required to submit a noise and vibration assessment that identifies potential impacts and prescribes project-specific measures to address them, including the potential use of temporary noise barriers during construction. These measures become part of the project, and are enforced through the project conditions of approval. In addition, the City requires the following standard conditions of approval for all large projects:

Construction

1. Noise Control Plan. The applicant must prepare and implement a noise control plan. Said plan must incorporate the noise reduction measures identified in the Noise and Vibration study prepared for the project, and the City standard construction noise COAs required for all projects.

2. Noise Coordinator. Prior to construction activities, the project applicant or contactor shall designate a “Construction Noise Coordinator” who would be responsible for responding to any local complaints about construction noise. The Construction Noise Coordinator shall determine the cause of the complaint and shall require that reasonable measures warranted to correct the problem be implemented. The telephone number for the Construction Noise Coordinator must be conspicuously posted at the construction site. Prior to construction activities, the project applicant or contactor shall notify adjacent residents of the construction schedule in writing and provide them with the contact information of the Construction Noise Coordinator.

3. Notice. The applicant shall notify property owners within 300 feet of the project site two weeks prior to the initiation of construction activities on site. A schedule of construction activities, contact phone number for the Noise Coordinator, and a copy of the noise control plan shall be included with this notice. 517

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4. Grading & Building Noise. The applicant must ensure that the following preventative and monitoring measures are enforced during grading and building operations:
a. Limit construction activity to the hours listed in the City Noise Ordinance. (8:00 am to 5:00 pm on weekdays, 10:00 am to 5:00 pm on Saturdays, no construction activity on Sundays and holidays).
b. Schedule highest noise-generating activity and construction activity away from noise-sensitive land uses.
c. Equip internal combustion engine-driven equipment with original factory (or equivalent) intake and exhaust mufflers which are maintained in good condition.
d. Prohibit and post signs prohibiting unnecessary idling of internal combustion engines.
e. Locate all stationary noise-generating equipment such as air compressors and portable generators as far as practicable from noise-sensitive land uses. f. Utilize “quiet” air compressors and other stationary where feasible and available.

5. Noise Barrier Standards. When noise barriers are required or proposed, their design and placement must be reviewed and approved by the project noise consultant, prior to issuance of grading or building permits. These barriers must be installed prior to grading and excavation activities, and must be inspected by the project noise consultant to ensure that it has been properly constructed/installed.

The barrier must remain in place for the duration of grading and excavation activities, unless approved for removal by the noise consultant to allow work at that location.

6. Engine Noise. Prior to issuance of grading or building permits, the applicant must demonstrate that a condition of contract of all contractors and subcontractors requires the use of internal combustion engine-driven equipment with original factory (or equivalent) intake and exhaust mufflers, which are maintained in good condition.

7. Equipment Noise. Prior to issuance of grading or building permits, the applicant must demonstrate that a condition of contract of all contractors and subcontractors requires the use of “quiet” air compressors and other stationary equipment. If the applicant demonstrates that the use of quiet air compressors and other stationary equipment is not feasible, moveable sound barriers or portable sound huts must be used for noise mitigation.

Operation

8. The Project Noise Consultant shall conduct a noise analysis of all mechanical and HVAC equipment proposed with the final building permit plans. The results of the analysis and design recommendations to ensure compliance with the City’s Noise Ordinance shall be summarized by the Consultant in a letter submitted with the 518

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Charles Armstrong School Expansion Project Final Noise and Vibration Study December 19, 2025 Page A-3
building permit plans. The consultant’s recommendations shall be incorporated into the building plans, prior to issuance of a building permit.

Construction Vibration

1. After obtaining permission from the subject property owners, the applicant must conduct preconstruction photo surveys of foundation/building wall cracks in adjacent structures, and install vibration monitors at any sensitive receptor sites identified in the project Vibration Assessment. The applicant must submit a copy of the photo survey and written confirmation from the Project Acoustic Consultant to the Planning and Building Departments that all required monitors have been installed and inspected, and that they meet the consultant’s specifications, prior to issuance of grading or building permits.

2. The applicant must designate a person responsible for registering and investigating claims of excessive vibration. The contact information of such person shall be clearly posted on the construction site.

3. Neighboring property owners within 300 feet of the project site must be noticed of the construction activities and construction schedule (including estimated dates of various construction phases) at least two weeks prior to the start of construction.

4. The applicant must ensure that the preventative and monitoring measures identified in the Vibration Assessment are enforced during grading and building operations. The applicant must demonstrate that all project construction personnel have been made aware of these measures, prior to issuance of a grading or building permits. On-site identification of any buffer distances between construction (i.e., vibratory rollers, excavators, backhoes, etc.) and adjacent structures that are specified in the Vibration Assessment must occur prior to grading operations.

5. Vibration monitors shall be placed at the sensitive receptors to monitor construction activities and make sure the project thresholds are met. Real-time alerts must be sent to the Contractor in case of near threshold vibration levels or in case of threshold exceedances. In case of exceedances, work must stop, and the source of the exceedance must be identified, and the required mitigation measure should be incorporated.

6. Building structures near the project must be periodically checked for cracks, and any cracks must be monitored. If minor cracks are reported or existing cracks propagate, vibration project action levels must be restricted.

7. Whenever possible, construction or equipment activity generating relatively high levels of vibration must not occur at the same time and shall be spaced as far apart in time as possible from one another. In general, the most severe activities must be reserved for the middle of the day (noon). If activities must occur simultaneously, they shall be performed as far away from one-another as possible within the construction zone.
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8. All deliveries of material and equipment must occur during daytime hours, including queueing of construction vehicles outside the site. Vehicles delivering materials and equipment must be operated in strict conformance with regulations established by the United States Department of Transportation and all State and Local requirements. All materials and equipment must be stored onsite and within the confines of the construction barricades.

9. Stationary and portable construction equipment must be located at positions where the noise/vibration impact to nearby noise/vibration-sensitive receptors is minimal. At times where the equipment cannot be positioned at a minimal noise/vibration impacting location, mitigation devices shall be implemented, as determined by the Project Acoustic Consultant or designated Vibration Monitor.

10. After construction activities are complete, the applicant must conduct a postconstruction photo survey of previously surveyed buildings for foundation /building wall cracks. The post construction survey, and a summary letter of any resulting actions taken (repairs or restitutions) must be provided to the Community Development Department, prior to final building permit inspection. 520

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Charles Armstrong School Expansion Project Final Noise and Vibration Study Appendix B December 19, 2025 Page B-1
APPENDIX B: Noise Impact Study for Charles Armstrong School HVAC Equipment, Smith, Fause, McDonald, Inc., October 16, 2025 521
October 16, 2025
Ratcliff Architects
5856 Doyle Street
Emeryville, California 94608
Project: Charles Armstrong School Expansion
SFMI Project No.: 2001598A
Subject: Noise Impact Study
To whom it may concern:

As requested, please find herein a summary of our findings on calculated noise levels from new equipment proposed for the Charles Armstrong School expansion project, with analysis on the existing noise environment and other aspects of relevant Municipal Codes and General Plans.

Background
The Charles Armstrong School, located in Belmont, California, is adding new academic buildings and an athletics building adjacent to existing buildings. Mechanical HVAC units are proposed to be installed next to the new buildings, in close proximity to residences within the Cities of Belmont and San Carlos.

Panorama Environmental, Inc. has provided the design team with a draft noise and vibration study with comprehensive analysis of the project’s noise impact, including noise measurements at several areas of the site. This report does not provide an explicit calculation of noise levels from new mechanical HVAC units, and it has been requested that a qualified acoustician perform such an analysis.

What follows is a summary of relevant Codes and Standards, noise measurements of the existing environment, the known or assumed noise rating of each unit, and calculated noise impact at nearby properties.

Terms
Decibel: Often abbreviated to “dB,” decibels are a logarithmic measure of the intensity of sound relative to a reference air pressure. Per the City of Belmont General Plan, a 3 dB change is barely noticeable, a 5 dB change is clearly noticeable, and a 10 dB change is perceived as twice (or half) as loud.
dBA: The A-weighted sound level, a standard intended to reflect the frequency response of the human ear of the softest sounds that it can perceive by emphasizing the mid-to-high frequency range at the expense of lower frequencies. dBA based metrics are ubiquitous throughout community noise standards.

Distance Correction: In the absence of reflective surfaces, a point source of sound attenuates at a rate of 6 dB per doubling of distance due to geometrical spreading. Mathematically expressed, a sound level L1 measured at a distance R1 may be adjusted to a sound level L2 at a different distance R2 with the formula L2 = L1 – 20*log10(R2/R1).
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Codes and Standards
The City of Belmont defines noise limits in Chapter 15 Article VIII – NOISE CONTROL. Sections relevant to this Project are listed below:
§15-102.b Sound level measurements shall be made on the receiving property nearest where the sound source generates the highest sound level. Microphones shall be placed 5 feet above the floor; this is assumed to also mean 5 feet above ground when outdoors
§15-102.c.1 Sound sources measured from any residential property shall not exceed 55 dBA during nighttime and 65 dBA during daytime
§15-102.c.4 In the event an offensive noise contains a steady, audible tone, such as a whine, screech, beating, pulsating, throbbing or hum the [noise limit] shall be reduced by five (5) dB
§15-102.c.5 Regardless of residential noise limits, sound shall be considered a disturbance if it offends peace and quiet of persons of ordinary or reasonable sensibilities and/or interferes with the comfortable enjoyment of life or property
The City of Belmont General Plan also discusses noise in Chapter 4.10 Noise of its General Plan. Table

4.10-12 restricts noise from stationary sources, as received at the nearest property line, to 50 dBA during daytime and 45 dBA during nighttime.

The City of San Carlos defines noise limits in Chapter 9.30 NOISE CONTROL and Chapter 18.21 PERFORMANCE STANDARDS. Sections relevant to this Project are summarized below:
§9.30.030 Sound as measured at a receiving property line may not exceed the noise limits outlined in Table 18.21.050-A
§18.21.050 Per Table 18.21.050-A, the median residential noise level may not exceed 55 dBA during the daytime or 45 dBA during nighttime. The maximum noise level may not exceed 70 or 60 dBA, during the same time periods. §18.21.050 If ambient noise levels are 10 dBA or more below the limit, the limit shall be decreased by 5 dB
Noise limits in the San Carlos General Plan are identical to the Municipal Code: 55 dBA during daytime and 45 dBA during nighttime at residential properties.
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Equipment
The Project proposes to install various mechanical units at different locations outside the new buildings:

Unit Tag Make & Model Noise Level
HRV-11 Ventacity VS3000 71.5 dBA at 3.28ft (1m)
Based off noise levels for a similar unit
VRF-3 Mitsubishi PRUY-EP336TSNU-A-BS 65.5 dBA at 3.28 ft (1m) Assumed to be rated at 1m similar to
other Mitsubishi products
VRF-4 Mitsubishi PUHY-EP312TSNU-A-BS 63.5 dBA at 3.28 (1m) Assumed to be rated at 1m similar to
other Mitsubishi products
KEF-1, -2, -3 Greenheck USF-13 13.5 Sones
KEF-4 Greenheck USF-16 12.3 Sones
EF-1 Greenheck G-103-VG 4.0 Sones
untagged Daikin RKF18BVJU9 54 dBA at 3.28ft (1m)
untagged Daikin REYA72AAYDA 61 dBA at 3.28ft (1m)
Assumed to be at the same distance as
the other Daikin unit
Table 1: Manufacturer noise ratings for the new units. Some noise ratings are assumed to be of a similar format to other units by the same manufacturer.

Reasonable assumptions can be made for most units, filling in specific details not yet available. Noise for Greenheck units has been provided in Sones, which are not translatable to dBA with the currently available information. 13.5 Sones is, however, comparatively as loud as the Daikin and Mitsubishi units.
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Figure 1: eastern portion of the mechanical plan, from Sheet AS-103 of the Entitlement Application. Daikin units will be placed on equipment platforms next to the new buildings. 525
Charles Armstrong School Expansion
October 16, 2025

Figure 2: southern equipment yard, from Sheet AS-103 of the Entitlement Application. KEF, VRV and HRV units are within a mechanical equipment yard behind a 9-foot tall stucco parapet. 526
Charles Armstrong School Expansion
October 16, 2025

Site Description and Existing Noise Levels
The Project Site is within a Belmont residential neighborhood, between Solana Drive and Dartmouth Avenue. The School and the residences to the east along Altura Way are within the City of Belmont, while the residences to the south along Dartmouth Avenue are within the City of San Carlos.

Figure 3: Satellite view of Charles Armstrong School. Image from Google Maps.

There is a steep hill between the School and the surrounding residences, where the property line occurs at the crest of a ridge ranging between 14 to 19 feet above the mechanical units. Additionally, the hill appears to be densely foliaged, with wood paneled fencing at the property line.

The Panorama Environmental Noise Study includes noise measurements throughout the site for various activity levels. The most relevant one to this study is a “no activity” level taken in the garden, near where some mechanical units will be located, with an hourly Leq of 44.0 dBA. This is considered the minimum noise level for the site, and using higher noise levels measured at other times would show mechanical units as having less of an impact.
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Analysis
Each cluster of mechanical units can be evaluated for its impact on the nearest property line, with respect to both the Municipal Code/General Plan and the environmental noise measurements. Based on available information, the noise character of the units is not believed to contain harsh or otherwise objectionable tones that would lower noise limits by an additional 5 dB.

The cluster of three units seen in figure 1 – consisting of two Daikin REYA72AAYDA and one Daikin RKF18BVJU9 – is at minimum 30 feet (23+ feet horizontal, 19 feet vertical) away from the nearest property line. All three units running at full capacity results in a combined noise level of 47.9 dBA at that location. For the measured 44 dBA ambient, the combined noise level is then 49.4 dBA – a 5.4 dB increase.

49.4 dBA meets the Belmont Municipal Code’s 55 and 65 dBA nighttime and daytime limits, respectively, and meets the General Plan’s 50 dBA daytime limit. It does not meet the General Plan’s 45 dBA nighttime limit. A 5.4 dB increase to the ambient level will be noticeable per earlier definitions.

With only one unit operating at a time, the noise impact drops to 44.8 dBA (meeting the nighttime limit) and causes a barely noticeable 3.4 dB increase over ambient. This also demonstrates compliance for the single unit to the north of the three-unit cluster, as that one unit is 1) singular and 2) at a farther distance than the triple cluster.

Results will likely be even lower in reality, as this calculation does not take into account partial/staggered load, the actual distance due to the elevation change, or sound blocking/absorption from the hill, vegetation, or fencing. The calculation also includes a +3 dBA reflection factor to account for the adjacent building wall, when in practice not 100% of the sound hitting the building will be redirected straight to the residences.

The other cluster in figure 1, 58 diagonal feet away from the nearest property line, calculates to a combined 42.4 dBA using the same methodology. This meets the nighttime and daytime noise limits for both Belmont’s Municipal Code and General Plan. The new cumulative noise level is calculated to be 46.3 dBA, or 2.3 dB over ambient – a barely noticeable change.

That same cluster is at least 90 feet away from the City of San Carlos property line, which has a 50 dBA (reduced from 55 dBA due to a low ambient level) daytime limit, and a 45 dBA nighttime limit.

The noise level at that distance is 38.3 dBA, well below either limit. The cumulative level is 45.0 dBA, or an imperceptible 1 dB increase over ambient.

The mechanical equipment yard shown in figure 2 contains VRFs, (K)EFs, and the HRV. Exhaust fan noise ratings are given in Sones, which are not translatable to dBA with the information available at this time. For the sake of this analysis the Greenheck units are assumed to generate the same noise levels as the loudest Daikin unit – 61 dBA at 1 meter. The Sone level of EF-1, however, is low enough that this unit will have a negligible impact compared to the other units and so is not included in this calculation.

The units are between 35 and 60 feet away from an adjacent residential property within the City of San Carlos. A 9-foot tall stucco parapet surrounding the equipment acts as a sound barrier.

With the outlined assumptions, the same methodology used for the Daikin clusters, and barrier effects from the parapet, all units operating simultaneously calculate to a combined noise level of 43.3 dBA 528
Charles Armstrong School Expansion
October 16, 2025

at the property line. This meets both the daytime and nighttime noise limits for the City of San Carlos, and results in a 46.7 dBA cumulative noise level – 2.7 dB over ambient, defined as barely noticeable.

The different clusters are sufficiently far apart that their combined noise at a shared middle distance does not exceed the noise at the location closest to a single cluster.

Conclusions
Based on available manufacturer data, and using conservative assumptions when data is not available, the new mechanical units at the Charles Armstrong School are calculated to not generate noise levels in compliance with the Noise Ordinances of the City of Belmont and the City of San Carlos, where applicable. One specific set of equipment causes noise levels in excess of nighttime limits from the Belmont General Plan, but this can be mitigated by either running only one unit at a time, or only running units during the day (defined as 8am to sunset).

Note that the buildings serviced by this equipment are intended to only operate during the daytime, making it unlikely this equipment will be operated during nighttime hours.

Based on environmental noise measurements performed by Others, the new mechanical units are not generally expected to be noticeably louder at neighboring properties than the existing ambient level.

The same set of units described above is the exception and will be more noticeable, but can be mitigated for the few required decibels with screens, sound barriers, or similar if found necessary.

Several units are missing noise data appropriate to this type of analysis, and if a more precise study is requested the first priority should be obtaining this data. Similarly, most units are rated on a simple overall dBA basis, and acquisition of frequency-specific sound data for both the new equipment and the environmental measurements would enable a comparison on the character of sound and a qualitative discussion on noticeability.

Despite these deficiencies, conservative methodology and multiple safety factors still results in overall compliance with the relevant Codes and Standards. If it is later found that a specific unit is louder than assumed, it is probable that real-world performance (absorption from the hill, scattering instead of reflection, units operating at a fraction of full capacity) will offset this increase and the Project will still be in compliance.

We thank you for the opportunity to be a part of the Charles Armstrong School Expansion, and hope these findings aid the project. Should you have any questions or wish to discuss this study further, please do not hesitate to contact us.

Sincerely,
Smith, Fause & McDonald, Inc.

Nick Peters, Acoustician
Institute of Noise Control and Engineering
Acoustical Society of America, SF Bay Area Chapter
529
RESOLUTION NO. 2026-01

RESOLUTION OF THE PLANNING COMMISSION OF THE CITY OF BELMONT

RECOMMENDING CITY COUNCIL ADOPTION OF A CONCEPTUAL DEVELOPMENT

PLAN (CDP) FOR THE PLANNED DEVELOPMENT (PD) ZONED PROPERTY LOCATED AT 1405 SOLANA DRIVE (ASSESSOR’S PARCEL NUMBER 045-122-190) FOR THE CHARLES ARMSTRONG SCHOOL PROJECT (APPL. NO. PA2024-0050) WHEREAS, Charles Armstrong School, applicant and property owner, requests a Conceptual Development Plan (CDP) for the Planned Development (PD) Zoned property located at 1405 Solana Drive (Assessor’s Parcel Number 045-122-190); and, WHEREAS, on January 6, 2026, the Planning Commission, following notification in the prescribed manner, conducted a public hearing, at which hearing the Commission considered public testimony and a staff report on the aforementioned requested entitlement; and, WHEREAS, the Planning Commission of the City of Belmont finds the project is subject to environmental review under provisions of the California Environmental Quality Act (CEQA), and a Categorical Exemption as per CEQA Guidelines Section 15314 - Minor Additions to Schools (Class 14) was prepared for the Project – see Attachment 7 to this report; and, WHEREAS, the Planning Commission considered and discussed the adequacy of CEQA Guidelines Section 15314 – Minor Additions to Schools, or Class 14, which consists of projects characterized as minor additions to existing schools within existing school grounds meeting the condition: “the addition does not increase original student capacity by more than twenty-five (25) percent or ten (10) classrooms, whichever is less.” The project scope (proposed new buildings in phases, and school operation modifications) qualifies for this exemption under CEQA. The Planning Commission applied its own independent judgment and analysis to the project, and recommends that the project environmental review was completed in compliance with CEQA; and, WHEREAS, the Planning Commission hereby adopts the staff report dated January 6, 2026, and the facts contained therein as its own findings of facts; and, WHEREAS, the Planning Commission did hear and use their independent judgment and considered all said reports, recommendations and testimony herein above set forth; and, NOW, THEREFORE, BE IT RESOLVED that the Planning Commission, recommends the City Council adopt a Conceptual Development Plan (CDP) for the Planned Development (PD) Zoned property located at 1405 Solana Drive, based on the following CDP findings, and as described in Exhibit A to this Resolution and Attachment 5 to this Report, and also subject to the Project Conditions of Approval as enumerated in Attachment 4 to this Report.

General Plan Consistency
The General Plan designates the project site as Public/Community Facilities (PCF). The proposed project does not change the intended land use for the established use of the property (Existing School). The existing and proposed uses are reasonable and in conformance with the general plan designation. The General Plan Consistency analysis for the project is described in Exhibit B to this Resolution. Based on this analysis, the Planning Commission has determined that, in balance, the Charles Armstrong School Project is consistent with the objectives of the Zoning Plan, any applicable specific plan, and the General Plan.
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Resolution: Conceptual Development Plan (CDP) – Charles Armstrong School Project No: 2024-0050; 1405 Solana Drive (Assessor’s Parcel Number 045-122-190) January 6, 2026; Page 2 of 4
WHEREAS, the Planning Commission, after consideration of all testimony and reports, hereby determines that Belmont Zoning Ordinance (BZO) Section 12.3.B (1-5) - Conceptual Development Plan (CDP) Findings for the Conceptual Development Plan (CDP) for the Planned Development (PD) Zoned property at 1405 Solana Drive for the Charles Armstrong School Project are made in the affirmative for the following reasons:

Conceptual Development Plan (CDP) Findings

1. That the total development in each individual unit therein can exist as an independent unit capable of creating an environment of sustained desirability and stability or the adequate assurance will be provided that such objective will be attained; that the uses proposed will not be detrimental to present and potential surrounding uses, but will have a beneficial effect which couldn’t be achieved under other zoning districts.

The Project can exist as an independent unit capable of creating an environment of sustained desirability and stability. The Charles Armstrong School campus will include all facilities required to function independently, including academic buildings, a multi-purpose building, an athletics building, access to McDougal Park for school use, and site circulation and parking. The school’s enrollment of up to 290 students and 87 faculty and staff members ensures that the campus will have sustained desirability and stability into the future.

The Project will not be detrimental to the present and potential surrounding uses, but will have a beneficial effect that could not be achieved under other zoning districts. For example, the Project will continue to provide the public reasonable access to their campus during non-school hours for use of Armstrong playgrounds/equipment, and parking. Additionally, the school has committed to providing the City with a community benefit monetary donation of $100,000 for McDougal Park improvements. As the City of Belmont generally is underserved with respect to park and recreational facilities, this represents a reasonable public benefit that could not be achieved under other zoning districts.

Additionally, conditions of approval requiring compliance with several operational and development controls assure that the Project will not be detrimental to the present or potential surrounding uses. These measures will include a vegetation management plan (VMP) to reduce the risk for wildfires, the use of sound barriers, carefully planned construction phasing, regular equipment management, all of which ensures that neighboring land uses are not subjected to unreasonable noise as a result of school-related construction and operational activities.

Lastly, the implementation of environmentally sensitive features and extensive tree plantings/landscaping, enables proposed buildings to blend naturally with surrounding uses and the environment. All of these features work to ensure that the Project will not adversely affect other property in the vicinity or the general welfare of the City. This Finding is affirmed.

2. That the streets and thoroughfares proposed are suitable and adequate to carry anticipated traffic and the density will not generate traffic in such amounts as to overload the street network outside the PD District.

The project would maintain and enhance internal circulation for pedestrians and vehicles, including Americans with Disabilities Act-compliant access routes, drop-off/pick-up staging, and designated parking areas. The small enrollment increase (from 260 to 290) would not generate significant new trips, and the Transportation Demand Management (TDM) practices - such as staggered dismissal and carpool coordination - would reduce potential traffic impacts. 531
Resolution: Conceptual Development Plan (CDP) – Charles Armstrong School Project No: 2024-0050; 1405 Solana Drive (Assessor’s Parcel Number 045-122-190) January 6, 2026; Page 3 of 4
The campus is near existing transit corridors, and the project design/scale would accommodate multimodal access without altering public street infrastructure.

The project would increase the existing on-site parking supply of 83 by two spaces to 85 spaces across the upper and lower lots. With a projected staffing increase of approximately 11 persons and all staff being required to park on campus, the parking demand would remain within capacity because of staggered schedules and part-time staffing. The school would also implement carpooling strategies and formalize this protocol in its TDM Plan. No on-street parking demand or oversupply is expected to occur. This Finding is affirmed.

3. That any proposed commercial development can be justified economically at the locations proposed to provide for adequate commercial facilities of the types proposed.

Thisfinding is not applicable. The project does not propose any commercial development. This Finding is affirmed.

4. That the economic impact created by the PD District can be absorbed by the City (police and fire service, water supply, sewage disposal, etc.).

The project would enhance a long-standing community-serving educational use in an established residential neighborhood. The school’s expansion would strengthen local access to specialized educational services without introducing land use conflicts or disrupting the existing neighborhood fabric. Accordingly, there is sufficient capacity to serve the Project’s water, sewer, drainage and landfill demands.

The Project will not burden park and recreational facilities. By continuing to make their campus grounds available for community use during non-school hours, the Project increases recreational facilities available for neighborhood use. The Project’s implementation of a VMP also ensures that the Project will not place an undue burden on fire safety services. In addition, the applicant would be required to pay all applicable development fees including plan check, building permit, grading permit, hauling permit, General Plan Maintenance, Affordable Housing Impact, Traffic Impact, Park Impact, Business License, sewer fees, planned drainage fees, and Public Art in-lieu fees as specified by each respective City Ordinance and/ortheCity's Master Fee Schedule, and pay for all applicable project monitoring fees (i.e., Transportation Demand Management (TDM)). This Finding is affirmed.

5. That the proposed off-street parking isin substantial conformance with the provision of Section 8 of the Belmont Zoning Ordinance; that where an applicant’s proposed off-street parking is less than that set forth by the standards of Section 8, circumstances are such that it would be a practical difficulty or create a physical hardship on the applicant for him to conform to the standards of Section 8.

The Project will be in substantial conformance with Section 8 (Parking) of the Belmont Zoning Ordinance (BZO). The parking spaces will also comply with the design requirements of BZO Section 8. The proposed project would not alter the school’s existing drop-off and pick-up circulation routes, and no changes are proposed to public park access or waste and recycling pickup. The existing parking area would be maintained and expanded slightly to provide 85 total automobile spaces, which would be an increase of two spaces. The parking area would include four Americans with Disabilities Act (ADA) accessible spaces and long-term bicycle parking, consistent with applicable City requirements. This Finding is affirmed. 532
Resolution: Conceptual Development Plan (CDP) – Charles Armstrong School Project No: 2024-0050; 1405 Solana Drive (Assessor’s Parcel Number 045-122-190) January 6, 2026; Page 4 of 4
* * * * * * * * * * * * * * *
Passed and adopted at a regular meeting of the Planning Commission of the City of Belmont held on January 6, 2026, by the following vote:

Ayes,
Commissioners: Adamkewicz, Kramer, Kulich, Majeski, Twigg, Jadallah Noes,
Commissioners: None
Absent,
Commissioners: None
Abstain,
Commissioners: None
Recuse,
Commissioners: None
_________________________________
Carlos de Melo
Planning Commission Secretary
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MINUTES OF PLANNING COMMISSION MEETING
City Council Chambers, City Hall, One Twin Pines Lane, Belmont, California TUESDAY, JANUARY 6, 2026
CALL TO ORDER: 7:00 PM

1. ROLL CALL 7:00 P.M.

Planning Commission members present: Jadallah, Adamkewicz, Kulich, Twigg, Majeski, Kramer Commission members absent: None
Staff Present: Community Development Director Carlos de Melo, Assistant Planner Jeremy Ruiz, Administrative Assistant Courtney Brown

2. PLEDGE OF ALLEGIANCE
Led by Chair Kulich.

3. COMMUNITY FORUM
Chair Kulich opened the community forum. No speakers in house or on Zoom. Chair Kulich closed the community forum.

4. COMMISSIONER ANNOUNCEMENTS AND AGENDA AMENDMENTS
Commissioner Adamkewicz reminded staff and the public of the upcoming deadline of January 9th, 2026 to submit applications to join the Commissions (Planning and Parks & Rec). Director de Melo introduced Community Development’s new Principal Planner, Adrienne Smith, to the Commission. Principal Planner Smith made a brief statement.

5. CONSENT BUSINESS
5A. ACTION: On a motion by Commissioner Adamkewicz, seconded by Commissioner Twigg for approval of meeting minutes for the December 16, 2025 Planning Commission meeting.

Motion Passes 5-0-1 (5 Ayes, 0 Noes, 1 Abstain)

6. STUDY SESSION (None)

7. PUBLIC HEARINGS
7A. The Charles Armstrong School - 1405 Solana Drive - Conceptual Development Plan (CDP), Detailed Development Plan (DDP), Conditional Use Permit (CUP), Design Review, Grading Plan, and Tree Removal Permit
Chair Kulich confirmed there were no ex-parte communications. Assistant Planner Ruiz presented the staff report to consider the proposed development project which would allow constructing buildings in two phases. Phase 1 will consist of an approximately 11,900-square-foot Academic Wing (two buildings with a connecting roof and a small stand-alone building), and Phase 2 consists of an approximate 11,100-square-foot Athletics Building. The project also includes proposed school operation modifications to: increase the maximum allowed enrollment from the current cap of 260 students to a cap of 290 students, extend hours of operation by one hour during weekdays, allow weekend campus access, and increase faculty staff by approximately 11 new members. 534
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Commissioner Questions and Comments
The applicant, Neil Tuch with Charles Armstrong School, and other members of their applicant team, provided a presentation. Commissioners asked questions regarding the school traffic/circulation/parking plan, waste collection process, rear set back of the project, proposed uses of the gymnasium on campus, impact fees for the school, elevations of the kitchen area of the building, arborist mapping and plans, current and future uses of McDougal Park in relation to Charles Armstrong School, the possibility of minor deviations to the Conditions of Approval that could be considered, as well as entitlements and how they will be applied in the future if the Building Code changes, etc. Commissioners also discussed the classification of the recreation building and associated parking, the proposed project and CEQA determination, the phasing of the project based on the construction, and the Commission review based on the totality of the project scope. City Staff, Armstrong School Applicant team, and CEQA Environmental Consultant, Panorama Environmental, provided responses to Commission questions.

Chair Kulich opened the public hearing.

Members of the public spoke on the increase in footprint of the proposed project, the CEQA review, the proximity of the gymnasium building in relation to the single family homes in the abutting neighborhood, concerns of noise coming from the school, traffic in the surrounding area and related fire safety concerns. The public also spoke on the appropriateness of the current location for the growth that Charles Armstrong School is proposing, the school’s communication efforts to the surrounding neighborhood, the proposed expansion in 2005, the success of children that attend the school, the significant number of both public & private school students attending surrounding schools in comparison to Charles Armstrong School, and the possibility of satellite campuses.

Chair Kulich closed the public hearing.

COMMISSION DISCUSSION AND DELIBERATION
Commissioners discussed the staggered start times of schools in the surrounding area of Charles Armstrong School, the differences in the project brought to the Planning Commission in 2005 versus today, impacts to private views and Commission purview on the matter, the school’s community newsletter regarding the existing Conditional Use Permit (CUP) & school operations, traffic impacts to the area, as well as the comparison of residential building height that could be achieved in the same location as the gymnasium under different zoning regulations.

Commissioners also discussed, for comparison, the gym at Ralston Middle School as being twice as high and four times the square footage as the proposed gym at Charles Armstrong School, while also not being located near a property line that abuts a residential lot.

Commissioners deliberated the Conceptual Development Plan (CDP) Resolution. Commissioner Adamkewicz offered a motion to strike Phase 2 of the CDP from the Resolution. Commissioner Twigg seconded the motion. Director de Melo clarified that the Conceptual Development Plan (CDP) would approve the overarching development standards/allowances for the total project (Phase 1 & 2) for the campus, while the Detailed Development Plan (DDP) would focus on and approve the building design/massing and other specifics (architecture, landscaping, tree removal/replacement, etc.) for the project.

Given that the Commission’s main concern was with the Phase 2 gymnasium building regarding siting/details/appearance etc., and not the concept of allowing the building itself, Director de Melo recommended that the Commission take a vote on the Conceptual Development Plan (CDP) 535
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January 6, 2026
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Resolution as presented and deliberate separately on the Detailed Development Plan (DDP) Resolution for any amendments to be made. Commissioners further discussed the CDP and expressed bifurcation concerns regarding certain details already mentioned in the Conceptual Development Plan Resolution. Commissioners voted on the original proposed Conceptual Development Plan (CDP) motion offered by Commissioner Adamkewicz. The motion did not pass (0-6). Commissioners then decided to take action on the original Conceptual Development Plan (CDP) Resolution with no amendments.

ACTION: On a motion by Commissioner Kramer, seconded by Commissioner Majeski to approve The Charles Armstrong School - 1405 Solana Drive (Conceptual Development Plan (CDP) and Categorical Exemption)
Motion Passes 6-0-0 (6 Ayes, 0 Noes, 0 Recusal)
Commissioners deliberated on amending the Detailed Development Plan (DDP) Resolution in a few different ways:

1.) Separate the academic buildings (Phase 1) from the gymnasium portion of the project (Phase 2) in the Resolution for the Detailed Development Plan (DDP). The reasons behind this were: the CEQA exemption applying to the gym itself was unclear to certain Commissioners, the PG&E easement and trees for screening/coverage, and the height of the proposed gym in relation to adjacent neighbors. This approach would also facilitate building design/articulation adjustments that may be considered in the next five years before construction occurs. Commissioner Adamkewicz proposes this motion.

Commissioner Twigg seconds. Motion does not pass (3-3).

2.) Commissioner Majeski offers a motion for the Detailed Development Plan Resolution with no amendments. No second. Motion failed.

3.) Ultimately, a majority of the Commission was unable to reach a decision related to the Phase 2 component of the Detailed Development Plan (DDP). The Commission recommended to the City Council that they are supportive of the proposed overarching DDP entitlements but could not reach a majority decision related to the Phase 2 athletic building component. The Commission also recommended that should the Council approve the project, that the Phase 2 component come back for further review at a future date. The Commission unanimously agreed on approval of the Detailed Development Plan (DDP) Phase 1 (Academic Building) component. It was agreed that the totality of the Commission recommendation will be conveyed to the City Council.

Commissioners concluded their deliberation.

8. OTHER BUSINESS AND UPDATES
Director de Melo reiterated Commissioner Adamkewicz’s reminder of the upcoming deadline of January 9th, 2026 to submit applications to join the Commissions (Planning and Parks & Rec).

Director de Melo provided a reminder of the Lunar New Year Celebration on February 8th at the Twin Pines Senior Center as well as the upcoming Planning Commission Meeting on January 20th.

9. ADJOURNMENT 10:30 PM
Approved by:

Carlos de Melo, Community Development Director
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Attachment 7
Public Outreach Communications
Charles Armstrong School - 1405 Solana Drive
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Arborist OnSite®
Horticultural Consulting, Inc.

ISA Certified Arborist Report
Submitted To:

Sample Report
Redwood City, California
Project Location:

Redwood City, California
Submitted By:

Robert Booty, Registered Member # 487
ISA Qualified Tree Risk Assessor
The American Society of Consulting Arborists
ISA Certified Arborist WC-4286
March 22, 2025
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Limits of Assignment
This assignment is limited to Root mapping along a damaged concrete driveway. My investigation involves root locating to determine root loss due to excavation on a construction site. Ground penetrating radar can not identify the presence of structural defects in roots located below ground, such as cracks, girdling or roots weakened by decay that can be associated with tree failures. GPR can evaluate both depth, location and estimate root diameters. Because trees continually change, this evaluation is valid only for the date of this inspection.

Disclaimer1
Although studies have shown ground penetrating radar to have a high degree of accuracy2 for below-ground root identification, these are not photographs but images of predicted root targets. Arborist OnSite endeavors to use equipment that generates useful information to prepare reports that will reflect its best judgment in light of the facts as it knows them.

Assignment
I have been retained by Juan Carlos Rivera who is the project construction coordinator for the local design and construction department. A sample is being remodeled; part of the construction project involves the replacement of a damaged concrete driveway that is used as the entrance to the property. The driveway is located along the property boundary line next to a neighboring fence. It is suspected that roots from a neighboring Redwood tree have contributed to the damaged concrete. Prior to the replacement of the concrete driveway I have been requested to provide a root study of the area using ground penetrating radar.

This will provide some insight as to our ability to perform root pruning during the proposed excavation and concrete replacement without damaging the trees.

Observations
I visited the site March 15, 2025. I observed the driveway being cracked and raised in different places from one end to the other. In addition it appears that the driveway is not level, the entrance seems lower then raises as you travel further in. The main interest regarding this root study is the large Redwood tree #1757 (Sequoia sempervirens) located about three feet away from the existing concrete. It appears to be in good health and has a height3
of 58 feet. Other neighboring trees and shrubs just inside the fence, they include one orange tree, two lemon trees and a Glossy Privet hedge all these appear to be in good health.

1 Use of Copyrighted material. Services provided under this Agreement, including all reports, information or recommendations prepared or issued by Arborist OnSite®, are for the exclusive use of the local design and construction department for the project specified herein. No other use is authorized under this agreement. Client will not distribute or convey Consultant’s reports or recommendations to any other person or organization other than those identified in the project description without Consultant’s written authorization. Client hereby releases Consultant from liability and agrees to defend, indemnify and hold Arborist OnSite® harmless from any and all claims, liabilities, damages or expenses arising, in whole or in part, from such unauthorized distribution.

2 Nina Bassuk, Cornell University “Ground-Penetrating Radar Accurately Locates Tree Roots in Two Soil Media Under Pavement” Arboriculture & Urban Forestry, International Society of Arboricultural 2011. 3 Height measurement was obtained by using a Nikon Forestry PRO II Laser Rangefinder/Hypsometer.

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Conclusions
I was informed that excavation for the new driveway would require a depth of three feet. Tree roots can and do crack and raise concrete, I don’t know if this is the case with the whole length of the driveway being damaged to this extent or not. The root study indicated roots consistently to a depth of 40 inches. The GPR was programmed to a depth of 48 inches. The proposed excavation would sever the majority of the root systems of the trees and plants along the neighboring property line.

Root studies4 have indicated that trees have the ability to affect hard surfaces. As the diameter of a root increases in size, soil is displaced, hydraulically moved above and around the root. To illustrate, consider that the pressure exerted by roots axially and radically is substantial (Feldman). For instance, a 15-inch segment of root one inch in diameter exerts 175 psi; this force is capable of lifting a concrete sidewalk slab 10 feet long and 4 feet wide (Dunn).

All of the trees and shrubs identified in this study are on another property. Although you can root prune on your property offending roots, you have the responsibility of not harming or damaging your neighbor’s trees or plants. If the excavation for the new driveway was performed as planned it would severely affect the health of the trees and destabilize them. In addition, the county would deny a root pruning permit that close to the trees even if they were your trees.

Alternatives
#1 Can the driveway be replaced without excavation? Can the damaged concrete be removed and the road bed be built-up or elevated with maybe using a greater amount of base rock and the concrete being poured at a higher elevation? With no root pruning.
#2 Would be to move the driveway entrance further away from the trees. While I was on site I did some testing farther away from the trees just to see what kind of roots would be found. Trees send their roots out depending on soil conditions at least the height of the tree. This is what stabilizes them since most roots can be found three feet below ground. If you look at driveway entrance #2 on the site map on page 10 scan #8 is located about 41 feet from the trees this scan was performed just to see what roots were in this area. The data on scan #8 indicated much less roots and much further away from the trees.

Excavation in this area would have little to no negative impact on the neighboring trees. You would still need a root pruning permit from the county which I feel they would have no problem with. A project arborist would need to be on site overseeing any root pruning. You can list Robert Booty as your project arborist.

Recommendations
I would be in agreement with alternatives #1 or 2 to resolve these issues.

4 Arborist News June 2001 International Society of Arboriculture, Champaign, IL. “Space Wars, Can Trees Win the Battle with Infrastructure?” E. Gregory McPherson, Laurence R. Costello, David W. Burger.

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Redwood tree
#1757
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Glossy Privet
privacy hedge
Redwood tree
Orange tree
There are 2 Lemon
trees on the property
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Methodology
How does it work?
Ground-Penetrating Radar (GPR) is an established technology that has been used worldwide for over 60 years. Radar is an object-detection system that uses electromagnetic waves – specifically radio waves – to identify the range, altitude, direction, or speed of both moving and fixed objects. When an electromagnetic wave5 emitted from a small surface transmit antenna / receiver encounters a boundary between objects with different electromagnetic properties, it will reflect, refract, and or diffract from the boundary in a predictable manner. Radar waves or signals are reflected especially well by materials of considerable electrical conductivity.

The radar signals that are reflected back towards the antenna are the desirable ones that create the image and make radar work. The radar signal detects water in the root system of the tree and can distinguish this water from water in the surrounding soil matrix. An air-filled tree trunk (with a decayed hollow) or a partially airfilled incipient (early stage) decay zone inside a cell wall within a tree are excellent reflectors for detection by GPR systems. Use of GPR instrumentation for internal tree trunk decay detection and below ground root locating is one of its latest uses in the field of tree risk assessment.

Its uses today seem endless. When you look at the weather report, you are looking at a weather radar scan; it will tell you where the heaviest amounts of rain will fall in your area. It works like this, the radar signal, as it passes through the clouds is reflected back to a transmit receiver antenna that measures the density of the moisture in them and the speed they are traveling. You can then determine approximately when it will start raining and how much rain will fall in a given area. Radar is used in aviation, automobiles, law enforcement and locating objects below ground.

5 Daniels, D.J. 1996, Surface-Penetrating Radar. The Institute of Electrical Engineers, ISBN 0-85296-0.

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Root Mapping
An Introduction to Below-Ground Tree Root Mapping using Ground – Penetrating Radar (GPR)
Ground-Penetrating Radar used as a method of mapping tree roots has several of the following advantages over other methods of root locating,

1. It is capable of scanning the root systems of multiple trees under field conditions in a short time.

2. It is completely non-invasive and does not disturb the soils or damage the trees being examined, and causes no harm to the environment.

3. Being non-invasive, it allows repeated measurements that reveal long-term root system development.

4. It allows observation of root distribution beneath hard surfaces (concrete, asphalt, and bricks) roads and buildings.

It’s accuracy is sufficient to resolve structural roots with diameters from less than 1 cm (0.4 in.) to 3 cm (1.2 in.) or more. It can characterize roots at both the individual tree and stand levels, facilitating correlations with tree and stand level measurements of physiological processes in complex ecological studies.

This is how the radar looks at the existing roots, as the antenna is moved along the ground every 2/10ths of an inch a radar signal is released into the soil at a predetermined depth.

As this signal encounters a root it is reflected off its top and back to a receiver inside the antenna. This returned signal is displayed as an x in the final report indicating the presence of a root, the colored x indicates the depth of the root.

Secondly one can observe all roots within a given soil profile depth, on the following pages you will notice 3 soil profiles depicted. When looking at the virtual trench view of maps keep in mind that each x marks the presence of a root. These roots are connected to the tree or root flare as they grow into the soil and then grow out ward in all directions, some have indicated roots that have no obstructions can travel laterally twice the height of the tree; this is what gives the tree stability.

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General Conditions Disclaimer.

Arborists are tree specialists who use their education, knowledge, training and experience to examine trees, recommend measures to enhance the beauty and health of the trees and attempt to reduce the risk of living near trees. Arborists cannot detect every condition that could possibly lead to the structural failure of a tree.

Since trees are living organisms, conditions are often hidden within the tree and below ground. Arborists cannot guarantee that a tree will be healthy or safe under all circumstances, or for a specific period of time. Likewise, remedial treatments cannot be guaranteed. Trees can be managed but they cannot be controlled. To live near trees is to accept some degree of risk and the only way to eliminate all risk associated with trees is to eliminate all trees.

Although studies have shown that imaging technology and wood testing, using a Resistograph® to have a high degree of accuracy for below-ground root identification or of predicted changes in wood structure; these are not photographs but images of predicted changes in wood composition or root targets. Arborist OnSite® Inc. endeavors to use equipment that generates useful information to prepare reports that will reflect its best judgment in light of the facts as it knows them.

By your use of our services you expressly understand and agree that:

Arborist OnSite® Inc. does not guarantee the outcome of its efforts or the structural integrity of any tree.

Any report prepared by Arborist OnSite® Inc. or equipment and data analysis provided by Arborist OnSite® Inc. is used strictly at your sole risk
Your use of imaging technology services, are provided on an “as is and “as available” basis. Arborist OnSite® Inc. expressly disclaims all warranties of any kind, expressed or implied, including but not limited to implied warranties of merchantability, fitness for a particular purpose and non-infringement. Arborist OnSite® Inc. makes no warranty that the equipment will be error-free or the data results obtained from the use of this equipment will be reliable.

Arborist OnSite® Inc. shall not be liable for any direct, indirect, incidental, special, consequential or exemplary damages, including but not limited to damages for goodwill, injury to body or property, death or other losses even if Arborist OnSite® Inc. has been advised of the possibility of such damages resulting from the use or reliance on imaging equipment or Arborist OnSite® Inc. use of imaging technology.

Although imaging devices have no known harmful physical affects on trees the client agrees to indemnify, defend and hold Arborist OnSite® Inc. or employees harmless from and against any and all claims, liabilities, suite, demands, losses, costs and expenses, including, but not limited to, reasonable attorneys’ fees and all legal expenses and fees incurred through appeal, and all interest thereon, accruing or resulting to any and all persons, firms or any other legal entities on account of any damages or losses to property or persons, including injuries or death, or economic losses, arising out of the Services and/or this Agreement, except to the extent that said damages or losses are caused by Arborist OnSite® Inc. gross negligence or willful misconduct. This indemnity, shall survive any expiration or termination of this Agreement with regard to any claims arising during, or related to, facts or circumstances that occurred during the term of this Agreement or any extension thereof.

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No warranty, representation or guarantee, express or implied, is intended by this agreement. Arborist OnSite® Inc. is not responsible for the completion or quality of work that is dependant upon or performed by the Client or third parties not under the direct control of Arborist OnSite® Inc. or for their acts or omissions or for any damages resulting there from.

Client acknowledges that it has read and agrees to the General Conditions contained in this document which are incorporated herein and made a part of this Agreement and report and shall apply to all services performed by Arborist OnSite® Inc. If this document is attached to another form of agreement whose terms and conditions conflict with this Agreement the General Conditions contained in this document shall prevail.

Assumptions and Limiting Conditions

1. Any legal description provided to the consultant is assumed to be correct. No responsibility is assumed for matters legal in character nor is any opinion rendered as to the quality of any title.

2. The consultant can neither guarantee nor be responsible for accuracy of information provided by others, information not provided or disclosed.

3. The consultant shall not be required to give testimony or to attend court by reason of this consultation/reports unless subsequent written arrangements are made, including payment of an additional fee for services.

4. Loss or removal of any part of this report invalidates the entire report/evaluation.

5. Possession of this report or a copy thereof does not imply right of publication or use for any purpose by any other than the persons(s) to whom it is addressed without written consent of this consultant.

6. This report represents the opinion of consultant, and the consultant’s fee is in no way contingent upon the reporting upon any pre-determined findings.

7. Sketches, diagrams, graphs, photos, ect., in this report, being intended as visual aids, are not necessarily to scale and should not be construed as engineering reports or surveys.

8. This report has been made in conformity with acceptable evaluation/diagnostic reporting techniques and procedures, as recommended by the International Society of Arboriculture.

9. No tree described in this report was climbed, unless otherwise stated. Arborist OnSite® cannot assume responsibility for any defects which could only have been discovered by climbing. A full root collar or root crown inspection, consisting of excavating the soil around the tree to uncover hidden defects or disease involving the root collar and major buttress roots, was not performed, unless otherwise stated. Arborist OnSite® cannot accept responsibility for any root defects which could only have been discovered by such an inspection.

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Certification of Performance
I, Robert Booty, certify:
 That I have personally inspected the tree(s) and/or the property referred to in this report, and have stated my findings accurately. The extent of the evaluation and or appraisal is stated in the attached report and the terms and conditions;
 That I have no current interest in the vegetation or the property that is the subject of this report, and I have no personal interest or bias with respect to the parties involved;  That the analysis, opinions and conclusions stated herein are my own, and are based on current scientific procedures and facts;
 That my compensation is not contingent upon the reporting of a predetermined conclusion that favors the cause of the client or any other party, nor upon the results of the assessment, the attainment of stipulated results, or the occurrence of any subsequent events;  That my analysis, opinions, and conclusions were developed and this report has been prepared according to commonly accepted arboricultural practices;  That no one provided significant professional assistance to the consultant, except as indicated within the report.

I further certify that I am a Registered Member of the American Society of Consulting Arborists, and I am an International Society of Arboriculture Certified Arborist. I have been involved in the practice of arboriculture and the care and study of trees for over 50 years.

Signed:________________________

Date: March 22, 2025
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1 Courtney Brown
From: Dean Wilson
Sent: Tuesday, January 6, 2026 3:59 PM
To: x-community development
Subject: Item 7A. Charles Armstrong School
[You don't oŌen get email from . Learn why this is important at hƩps://aka.ms/LearnAboutSenderIdenƟficaƟon ]
Dear Commissioners,
This same gym was proposed 20 years ago and aŌer community input, was denied. Nothing has really changed in the neighborhood to make a middle school gym acceptable now. Once a gym is built there is no going back, why then isn”t the denial of the gym also permanent?
Love the school and greatly support its mission.

This is an Elementary school site tucked into a quiet neighborhood. It is probably the smallest footprint site of any other Belmont Elementary school and they are trying to squeeze a Middle School gym onto that Elementary school site with impacts to the residenƟal properƟes it buts up against.

There are quesƟons about the CUPs for it’s use and I think needs a City facilitated Q&A with the community prior to approval.

I would like to see the gym porƟon considered separately to so that these quesƟons can be presented.

Proceed with the academic porƟon approval, possibly including a kitchen, but remove the gym porƟon for later/further input and consideraƟon.

Thank you
Dean Wilson
Solana Court
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Sincerely,
Tiffany Lieuw
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2026-01-05
Dear Belmont City Council, Members of the Planning Commission, Planning Director, City Attorney:

Regarding the proposed Charles Armstrong School project at 1405 Solana Drive (Application No. 2024-0050), I am writing to formally object to the determination that the project qualifies for a categorical exemption under California Environmental Quality Act (CEQA) Guidelines §15314 (Class 14 – Minor Additions to Schools).

Based on the project description, its scale, its operational impacts, the documented history of this site, the proposed removal of heritage trees, and other factors: The proposed development does not meet the criteria for a Class 14 exemption. In fact, the project is expressly barred from exemption by the "unusual circumstances" exception set forth in CEQA Guidelines §15300.2(c). Under that guideline, categorical exemptions do not apply where there is a reasonable possibility that the activity will have a significant effect on the environment due to unusual circumstances. The scale of heritage tree removal proposed here -- combined with extensive grading, hillside excavation, and expansion of enrollment and staffing -- constitutes precisely such an unusual circumstance.

1. The Project Cannot Reasonably Be Characterized As "Minor" Class 14 exemptions are limited to minor additions to existing schools. The current proposal includes multiple new buildings constructed in phases, along with material operational modifications. Taken as a whole, this represents a substantial intensification of use on a constrained site.

CEQA does not permit a purely arithmetic interpretation of "minor." Courts have consistently held that context, location, and intensity matter. A project of this scale, located on a narrow residential cul-de-sac and immediately adjacent to private homes, cannot reasonably be presumed to have no significant environmental effects.

2. Prior City Findings Establish Unusual Circumstances
In June 2005, after extensive public hearings, both the Belmont Planning Commission and City Council denied a significantly smaller Charles Armstrong School expansion. The denial was based on explicit findings regarding:
- Traffic congestion and safety risks
- Inadequate parking and emergency access
- Excessive bulk and mass incompatible with surrounding residences - Intensification of use inconsistent with the General Plan - Adverse neighborhood impacts on a dead-end residential street Those findings constitute substantial evidence that this site presents unusual circumstances within the meaning of CEQA Guidelines §15300.2(c). The City’s own prior conclusions establish a reasonable possibility of significant environmental effects, which legally precludes reliance on a categorical exemption.

3. Piecemealing and Phasing Undermine the Exemption
The project description references construction "in phases" and includes both physical development and operational changes. CEQA expressly prohibits the piecemealing of a larger project into smaller components to avoid environmental review. When viewed as an integrated whole — as CEQA requires — the proposed development significantly exceeds the scope of a minor addition and must be evaluated accordingly.
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4. “Original Student Capacity” Requires Substantiation
The Class 14 exemption hinges on increases relative to "original student capacity." The notice does not identify the baseline capacity being used, nor does it explain how that baseline was established or whether prior increases have already occurred, or have been accounted for.

Without a clearly defined and defensible baseline, the exemption determination is unsupported.

5. Core Belmont Value of Tree Conservation
Belmont maintains some of the most stringent tree protection ordinances in the region.

Individual homeowners are generally prohibited from removing even a single protected tree without extensive review, justification, permitting, fees and mitigation. By contrast, this proposal contemplates the mass removal of dozens of protected trees as part of a single project, fundamentally altering a hillside ecosystem and neighborhood character.

The removal of these trees would have lasting and irreparable impacts on visual character, slope stability, stormwater runoff, habitat value, noise buffering, and neighborhood quality of life. These impacts are neither minor nor temporary, and they cannot be reconciled with a finding of insignificance under CEQA.

6. Unrestricted Monetary Contribution as Improper Mitigation The applicant has pledged a $100,000 donation of unrestricted funds to the City of Belmont, purportedly for maintenance and upgrades to McDougal Park. Because these funds are unrestricted, there is no enforceable assurance that they will be used to benefit the park, the surrounding neighborhood, or to mitigate project impacts. Under CEQA, mitigation must be specific, enforceable, and directly related to identified impacts. A discretionary monetary contribution does not constitute valid mitigation and cannot lawfully support reliance on a categorical exemption.

Moreover, the appearance of offering financial inducements contemporaneously with discretionary approvals raises serious concerns regarding procedural integrity. CEQA does not permit agencies to trade environmental review for monetary concessions, particularly where significant and unusual environmental impacts are present.

7. Proposed Shared Use of Gymnasium Intensifies Project Impacts The applicant has also proposed making the new gymnasium available for use by the City’s Parks and Recreation Department when school is not in session. This proposal fundamentally alters the nature of the project. Rather than a facility limited to school-related activities, the gym would function as a community-use facility, generating evening, weekend, and potentially year-round activity.

Such shared use would significantly increase noise, traffic, parking demand, and intensity of use within a quiet residential cul-de-sac. This directly contradicts the assertion that the project is a minor, academic-focused addition eligible for Class 14 exemption, and instead demonstrates a substantial change in operational scope requiring full environmental review.

8. Consistency with CEQA’s Core Purpose
CEQA is designed to ensure informed decision-making where there is a reasonable possibility of environmental harm. Given the documented history of this site, the residential character of the surrounding neighborhood, and the magnitude of the proposed changes, applying a categorical exemption here undermines CEQA’s fundamental purpose. At minimum, preparation of an Initial Study is required to evaluate traffic, parking, noise, safety, and neighborhood compatibility impacts before any discretionary approvals are considered. 590
Conclusion
Considering everything together -- extensive hillside excavation, removal of dozens of protected heritage trees, increased student enrollment and staffing, increased hours of operation and intensity of use, improper inducements -- the City must reject reliance on a categorical exemption and require preparation of a full Initial Study, and if warranted, an Environmental Impact Report, before considering any discretionary approvals for this project.

I respectfully request that the City rescind the Class 14 categorical exemption determination and require appropriate CEQA review consistent with the project’s true scope and context.

Accordingly, I request that the City place the CEQA exemption determination on a public agenda for deliberation prior to any further discretionary approvals.

Thank you for your careful consideration and for ensuring that the City’s actions remain consistent with both CEQA and Belmont’s own established findings and precedents.

Sincerely,
Barry Lake
P.S. For relevant case law regarding CEQA categorical exemptions and piecemealing, please see:

Berkeley Hillside Preservation v. City of Berkeley (2015) Protect Niles v. City of Fremont (2018)
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Dear Members of the Belmont Planning Commission:

My name is Liliana Davidovich, and I am writing in full support of Charles Armstrong School's proposed expansion. I am also writing as someone whose life was changed through and through by this school.

I went to Charles Armstrong School throughout the early 2000s, from third through sixth grade. I was a child with severe learning disabilities at the time, barely surviving in traditional school environments that didn't understand how my brain worked. I was overwhelmed, ashamed, and in deep fear of school. I really believed there was something wrong with me. Charles Armstrong School changed that.

I finally saw and found myself at Armstrong. I was not taught how to hide my disability, rather how to work with it. I learned how my brain works, how to advocate for myself, and how to believe that I was worthy and capable of success. Those lessons did not end when I graduated.

They became the foundation of my entire life. The things I have learned at Charles Armstrong School have made me the successful adult I am today.

There is another piece of Armstrong's impact that I did not fully appreciate until much later in my life, and that is the parent education. My parents attended the school's parent education classes where they learned about how my brain works and how to support and parent a child with dyslexia. Parenting a child with an invisible learning disability is not easy, and very little guidance or education is available to families who navigate it. Armstrong did not just support me, they supported my entire family.

So, if it means 30 more kids get to experience that same life changing education that I received, then yes it is about more than just a school. Yes is about kids finally feeling understood, families finally feeling supported, and futures finally being possible. I am the living proof of what happens when children with learning disabilities receive the proper equipment, the proper teacher, and the proper environment.

I kindly ask that the Charles Armstrong School be allowed to flourish so that the outstanding work that the school has conducted for decades to transform lives, build families, and empower kids to succeed as successful adults continues to happen.

Thank you for your time, your compassion, and for considering the long-term effects of this decision.

Thank you
Liliana Davidovich
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