ATT-PFMD-20260930-11-Soils Report--Baker Family Learning Center Expansion.pdf

PROJECT NO.: 1775-01

REPORT NO.: 1

FEBRUARY 18, 2026

SUBMITTED TO:

TR DESIGN GROUP, INC.

2900 ADAMS STREET, STUDIO A-400

RIVERSIDE, CA 92504

PREPARED BY:

HILLTOP GEOTECHNICAL, INC.

786 SOUTH GIFFORD AVENUE

SAN BERNARDINO, CA 92408

REPORT OF PRELIMINARY

GEOTECHNICAL / GEOLOGIC INVESTIGATION

PROPOSED BAKER FAMILY LEARNING CENTER

EXPANSION

2818 MACY STREET

MUSCOY

CALIFORNIA

786 S. GIFFORD AVENUE • SAN BERNARDINO • CA 92408

Phone 909-890-9079 • FAX 909-890-9055 hilltopg@hgeotech.com

Project No.: 1775-01 Report No.: 1

February 18, 2026

TR Design Group, Inc.

2900 Adams Street, Studio A-400 Riverside, CA 92504 Attention: Mr. Thomas Riggle, President

Subject: Report of Preliminary Geotechnical / Geologic Investigation, Proposed Baker Family Learning Center Expansion, 2818 Macy Street, Muscoy, CA 92407.

References: 1. TR Design Group, Floor Plan, Baker Family Learning Center, 2818 Macy Street, Muscoy, CA 92407, Job# 24-033.

2. Technical References – See Appendix ‘B.’

Mr. Riggle:

According to your request, we have completed a preliminary geotechnical investigation for a proposed Baker Family Learning Center Expansion on the subject site. We are presenting, herein, our findings and recommendations.

The findings of this investigation indicate that the proposed improvement on the project site is feasible provided the recommendations presented in the attached report are incorporated into the design of the project and implemented during construction of the project.

Copies of this report should be forwarded to the other consultants for the project (i.e., Civil Engineer, Architect, Structural Engineer, etc.) as needed to implement the recommendations presented. The required number of the original signed reports should be saved for submittal, and the other required documentation to the appropriate agency having jurisdiction over the project for review and permitting purposes.

mailto:hilltopg@hgeotech.com mailto:thomas@trdesigngroup.com mailto:Rick@trdesigngroup.com

1775-01.1 February 18, 2026 Page iv

TABLE OF CONTENTS

Section Title Page No.

INTRODUCTION

AUTHORIZATION

PURPOSE AND SCOPE OF INVESTIGATION

PREVIOUS SITE STUDIES

PROJECT DESCRIPTION / PROPOSED DEVELOPMENT

FIELD EXPLORATION AND LAB TESTING

FINDINGS

SITE DESCRIPTION

ENGINEERING GEOTECHNICAL ANALYSIS

Regional Geological Setting

Local Subsurface Conditions

Earth Materials Description:

Groundwater

Surface Water

Site Variations

Faulting and Regional Seismicity

Secondary Seismic Hazards

Landslide

Liquefaction

Seiching

Tsunamis

Lurching

OTHER GEOLOGIC HAZARDS

Flooding

CONCLUSIONS AND RECOMMENDATIONS

GENERAL

GRADING

General Grading Requirements

FILL MATERIALS

Onsite Earth Materials

Imported Materials

1775-01.1 February 18, 2026 Page v

Section Title Page No.

HILLTOP GEOTECHNICAL, INC.

TEMPORARY EXCAVATIONS

SEISMIC DESIGN PARAMETERS

FOUNDATIONS

Lateral Resistance

Estimated Settlement

SLAB-ON-GRADE

Moisture Sensitive Floor Covering

SURFACE DRAINAGE

SOIL EXPANSIVITY AND COLLAPSIBILITY

SOIL CORROSIVITY

LIMITATIONS

REVIEW, OBSERVATION, AND TESTING

UNIFORMITY OF CONDITIONS

CHANGE IN SCOPE

TIME LIMITATIONS

PROFESSIONAL STANDARD

CLIENT'S RESPONSIBILITY

APPENDIX A

FIELD EXPLORATION

LABORATORY TESTING PROGRAM

CLASSIFICATION

IN-SITU MOISTURE CONTENT AND DRY DENSITY

CHEMICAL AND ELECTRICAL RESISTIVITY TESTS

DIRECT SHEAR TEST

‘Exploratory Excavation Location Plan’ ................................................. Plate No. 1 ‘Subsurface Exploration Legend’.................................................. Plate No. 2 ‘Subsurface Exploration Log’..................................... Plate Nos. 3 through 5 ‘Summary of Laboratory Test Result’ ‘Chemical / Minimum Electrical Resistivity

Test Results’ ............................................................ Plate No. 6 ‘Direct Shear Test Results’…………………………………............ Plate No. 7

1775-01.1 February 18, 2026 Page vi

Section Title Page No.

HILLTOP GEOTECHNICAL, INC.

APPENDIX B

TECHNICAL REFERENCES --------------------------------------------------------B-1

REPORT OF PRELIMINARY

GEOTECHNICAL / GEOLOGIC INVESTIGATION

PROPOSED BAKER FAMILY LEARNING CENTER EXPANSION

2818 MACY STREET

MUSCOY

CA, 92407

PROJECT NO.: 1775-01

REPORT NO.: 1

FEBRUARY 18, 2026

INTRODUCTION

AUTHORIZATION

This report presents results of the preliminary geotechnical/geologic investigation conducted on the subject site for the proposed Baker Family Learning Center expansion at 2818 Macy Street in the Muscoy area. The general location of the subject site is indicated on the ‘Site Location Map’ Figure No. 1.

The authorization to perform this investigation was in the form of a signed proposal from Hilltop Geotechnical, Inc. (HGI) (Geotechnical / Geologic

Consultant) to TR Design Group, Inc. (Client), dated January 13, 2026, Proposal Number: TRD#24-033.

PURPOSE AND SCOPE OF INVESTIGATION

The scope of work performed for this investigation was designed to determine and evaluate the surface and subsurface conditions in the vicinity of the proposed residential development on the subject site with respect to geotechnical characteristics, including potential geologic hazards that may affect the development of the site, and to provide geotechnical recommendations and criteria for use in the design and construction of the proposed carport. The scope of work included the following:

SITE

Source: Copied from USGS Topo Map- San Bernardino North Quadrangle 2012

By: MC Date: 2/2026

Project No.: 1775-01.1 Figure 1

SITE LOCATION MAP

2818 N. Macy Street, Muscoy, CA 92407

1775-01.1 February 18, 2026 P a g e | 2

HILLTOP GEOTECHNICAL, INC.

• Review of locally and easily available published and unpublished soil, geologic, and seismologic reports, and data for the area (see References in Appendix ‘B’), available photographs via Google Earth Pro, flood hazard maps, well data, etc. to ascertain earth material, geologic, and hydrologic conditions of the area.

• Telephone conversations with the client.

• Site reconnaissance.

• Subsurface exploration by hand auger borings to characterize the earth materials, geologic, and groundwater conditions that could influence the proposed development.

• Sampling of on-site earth materials from the exploratory excavations.

• Laboratory testing of selected earth material samples considered representative of the subsurface conditions to determine the engineering properties and characteristics.

• Define the general geology of the subject site and evaluate potential geologic hazards which would have an effect on the proposed site development.

• Determine seismic classification of the site to meet the requirements of the 2025 California Building Code (CBC), effective on January 1, 2026.

• Engineering and geologic analysis of field and laboratory data to provide a basis for geotechnical conclusions and recommendations regarding site grading and foundation, floor slab, etc. design parameters.

• Preparation of this report to present the geotechnical conclusions and recommendations for the proposed development.

This report presents our conclusions and/or recommendations regarding:

• The geologic setting of the site.

• Potential geologic hazards (including landslides, seismicity, faulting, liquefaction potential, etc.)

• General subsurface earth conditions.

• The presence and effect of expansive, collapsible, and compressible earth materials.

1775-01.1 February 18, 2026 P a g e | 3

• Groundwater conditions within the depth of our subsurface exploration.

• Excavation characteristics of the on-site earth materials.

• Characteristics and compaction requirements of proposed fill and backfill materials.

• Recommendations and guide specifications for earthwork.

• Seismic design parameters for structural design purposes.

• Types and depths of foundations.

• Allowable bearing pressure and lateral resistance for foundations.

• Preliminary corrosion potential evaluation for concrete and buried metal in direct contact with the on-site earth materials.

The scope of work performed for this report did not include any testing of earth materials or groundwater for environmental purposes, an environmental assessment of the property, or opinions relating to the possibility of surface or subsurface contamination by hazardous or toxic substances. In addition, an evaluation of on-site private sewage disposal systems for the proposed development was not conducted as part of this investigation.

This investigation was prepared for the exclusive use of TR Design Group, Inc.

and its consultants for specific application to the development of the proposed additions in accordance with generally accepted standards of the geotechnical and geologic professions and generally accepted geotechnical (soil and foundation) engineering and geologic principles and practices at the time this report was prepared. Other warranties, implied or expressed, are not made. Although reasonable effort has been made to obtain information regarding geotechnical / geologic and subsurface conditions of the site, limitations exist with respect to knowledge of unknown regional or localized off-site conditions which may have an impact on the site. The conclusions and recommendations presented in this report are valid as of the date of this report. However, changes in conditions of a

1775-01.1 February 18, 2026 P a g e | 4 property can occur with passage of time, whether they are due to natural processes or to works of man on this and/or adjacent properties.

If conditions are observed or information becomes available during the design and construction process which are not reflected in this report, HGI, as Geotechnical

Consultant of record for the project, should be notified so that supplemental evaluations can be performed and conclusions and recommendations presented in this report can be verified or modified in writing, as necessary. Changes in applicable or appropriate standards of care in the geotechnical professions occur, whether they result from legislation or the broadening of knowledge and experience. Accordingly, the conclusions and recommendations presented in this report may be invalidated, wholly or in part, by changes outside the influence of the project Geotechnical Consultant who occurs in the future.

PREVIOUS SITE STUDIES

A geotechnical/geologic study for a proposed Baker Family Learning Center was conducted by Hilltop Geotechnical, Inc. on the subject site in 2010. The proposed Baker Family Learning Center was built circa 2013.

PROJECT DESCRIPTION / PROPOSED DEVELOPMENT

As part of our investigation, we have discussed the project with the client. We also have been provided with the conceptual site plan noted on the first page of the cover letter for this report.

Based upon information presented to this firm by the client, it is our understanding that the proposed project will consist of proposed building additions and attached to the Baker Family Learning Center building.

The above project description and assumptions were used as the basis for the field exploration, laboratory testing program, the engineering analysis, and the conclusions and recommendations presented in this report. HGI should be

1775-01.1 February 18, 2026 P a g e | 5 notified if structures, foundation loads, grading, and/or details other than those represented herein are proposed for final development of the site so a review can be performed, a supplemental evaluation made, and revised recommendations submitted, if required.

FIELD EXPLORATION AND LAB TESTING

The field exploration performed for this report included a visual and geologic reconnaissance of existing surface conditions of the subject site. An exploration of the property's subsurface condition was performed to evaluate underlying earth strata and the presence of groundwater. Surface and subsurface conditions were explored on February 9, 2026.

The subsurface exploration consisted of using a hand auger and hand tools to conduct three (3) exploratory borings on the subject property. The approximate locations of the exploratory excavations are shown on the ‘Exploratory Excavation Location Plan,’ Plate No. 1, presented in Appendix ‘A’ of this report. The exploratory excavations were excavated, observed, and logged by a representative of HGI. Earth materials encountered in the exploratory excavations were visually described in the field in general accordance with the current Unified Soils Classification System (USCS), ASTM D2488, visual-manual procedures, as illustrated on the attached, simplified ‘Subsurface Exploration Legend,’ Plate No.

2, presented in Appendix ‘A’ of this report. The results of the borings are presented on the ‘Subsurface Exploration Log,’ Plate Nos. 3 through 5, presented in Appendix ‘A’ of this report.

A more detailed explanation of the field exploration which was performed for this report is presented in Appendix ‘A’ of this report.

1775-01.1 February 18, 2026 P a g e | 6

In-tact ring and a representative bulk sample of on-site earth materials were collected during the field exploration and returned to the laboratory for testing.

Laboratory tests were conducted to evaluate the engineering properties of on-site earth materials and included moisture density test, direct shear test, and corrosivity tests. A more detailed explanation of laboratory tests performed for this investigation and test results are presented in Appendix ‘A’ of this report, Plate Nos. 3 through 7.

FINDINGS

SITE DESCRIPTION

The subject property comprises approximately 1.67 acres, is rectangular in shape, and approximately 238 feet by 305 feet in plan dimension. The subject property is located in the northwest quadrant of the intersection of Darby Street and Macy Street in the Muscoy area of San Bernardino County, California.

The subject property is bounded by Darby Street to the south, Macy Street to the east, a Fire Station to the north, and a single-family residential property to the west. The project area of the subject site was relatively flat. At the time of field exploration, Baker Family Learning Center building, a retention basin and associated parking lots were present on the site. The sites’ southern and western boundaries were enclosed by fencing while the northern and western boundaries were enclosed by cinder block walls. Vegetation consisted of trees, shrubbery and hedges throughout the site.

Utilities consisting of electric telephone lines were observed overhead and, in the streets, right-of-way. Gas, sewer, water, as well as other unknown underground and overhead lines, were observed on the subject site.

1775-01.1 February 18, 2026 P a g e | 7

ENGINEERING GEOTECHNICAL ANALYSIS

Regional Geological Setting

San Bernardino and its namesake valley lie very near the northern margin of the Peninsular Ranges Physiographic Province, one (1) of 11 provinces recognized in California. The physiographic provinces are topographic-geologic groupings of convenience based primarily on landforms, characteristic lithologies, and late Cenozoic structural and geomorphic history. The Peninsular Ranges encompass southwestern California west of the Imperial-Coachella Valley trough and south of the elevated terraces of the San Gabriel, San Bernardino, and Santa Monica Mountains. Most of the province lies outside of California, continuing south to include much of the Baja California Peninsula. The province is characterized by youthful, steeply sloped, northwest-trending, elongated ranges and intervening valleys. In gross aspect, average elevations across the province rise slowly to the east, usually culminating in abrupt escarpments near the eastern margin.

Approaching the northern edge of the province, however, several anomalously flat and low basins stretch from the San Bernardino region to western Los Angeles as a result of fault junctures and tectonic interaction with the adjacent Transverse Ranges. Structurally, the bulk of the Peninsular Ranges are composed of a number of relatively stable crustal blocks bounded by active strike-slip faults of the San Andreas transform system. Although some folding and minor faulting have occurred within the blocks, intense structural deformation and earthquake activity are mostly limited to block margins. The anomalous east-west trending San Bernardino Valley itself defines a small, irregularly-shaped block bounded by the San Andreas fault to the northeast, the San Jacinto fault to the southwest, and an arcuate set of sometimes obscure faults trending southwest through the Yucaipa, Redlands, and Loma Linda areas. The valley is not an erosional feature, but a deep structural basin that apparently continues to slowly subside in response to the transference of slip from the San Jacinto fault to the San Andreas fault.

1775-01.1 February 18, 2026 P a g e | 8

The province contains a diverse array of metamorphic, sedimentary, volcanic, and intrusive igneous rocks. In general, the metamorphic rocks represent the highly altered host rocks for the emplacement of very large masses of granitic rock of varying composition. Closer to the coastline, younger rocks include thick sequences of marine and non-marine clastic sedimentary rocks of Mesozoic and

Tertiary age, ranging from claystones to conglomerate. Inland, the province is dominated by crystalline basement rock, but the San Bernardino region also contains thick sequences of pre-Quaternary, continental, sedimentary rocks.

These rocks are widely exposed in the hills bounding the south side of the San Bernardino Valley, and underlie the valley floor at depth. The general geology in the area of the subject site is shown on the ‘Regional Geologic Map,’ Figure No. 2.

Coarse-grained Quaternary alluvium forms several massive fans extending from the mouths of Lytle Creek and Cajon Creek. The subject site has likely received material from both of the former sources. The inferred depth of Quaternary alluvium at the subject site is several hundred feet, based on water well records in the area.

Local Subsurface Conditions Earth Materials Description:

Presented as follows are brief descriptions of the earth materials encountered in the exploratory excavations. More detailed descriptions of encountered earth materials are presented on the ‘Subsurface Exploration Logs,’ Plate Nos. 3 through 5, presented in Appendix ‘A’ of this report. The earth material strata, as shown on the logs, represent conditions at the actual exploratory excavation locations. Other variations may occur beyond and/or between the excavations.

Lines of demarcation between earth materials on the logs represented the approximate boundary between the material types; however, the transition may be gradual.

SITE

Legend

Source: Copied from Geologic Map of the San Bernardino North 7.5’ Quadrangle by F. K. Miller, J. C. Matti, and S. E. Carson

By: MC Date: 2/2026

Project No.: 1775-01.1 Figure 2

REGIONAL GEOLOGIC MAP

2818 N. Macy Street, Muscoy, CA 92407

1775-01.1 February 18, 2026 P a g e | 9

The earth materials encountered on the subject site during the field exploration were identified as artificial fill (af) and alluvial deposits (Qw1).

Artificial fill was encountered at all three exploratory borings, which extended to depths of approximately 2.0 feet at the exploratory locations. The artificial fill generally consists of yellowish-brown silty sand in moist to slightly moist and loose to medium dense conditions. The alluvial deposits were encountered at all exploratory borings beneath the artificial fill to depths of 5.5 feet bgs. The alluvial deposits generally consist of brown to grayish brown gravelly and silty fine to medium-grained sand that was medium dense in relatively consistency and slightly moist to dry conditions.

Groundwater Groundwater was not encountered in the exploratory excavations to 5.5 feet bgs.

Groundwater was not encountered to 51.0 feet bgs during our May 12, 2010 exploration either.

Based upon the above-provided information, groundwater should not be considered a factor in the proposed development of the site.

Surface Water Surface water was not observed on the subject site at the time the field exploration was performed for this report.

Site Variations

Based on results of our subsurface exploration and experience, variations in the continuity and nature of surface and subsurface conditions should be anticipated.

Due to uncertainty involved in the nature and depositional characteristics of earth materials at the site, care should be exercised in extrapolating or interpolating subsurface conditions between and beyond the exploratory excavation locations.

1775-01.1 February 18, 2026 P a g e | 10

Groundwater was not encountered during our exploration. However, it should be noted that fluctuations in levels of groundwater, springs, and/or perched water may occur due to variations in precipitation, temperature, and other factors.

Faulting and Regional Seismicity The site is situated in an area of active and potentially active faults, as is most of metropolitan southern California. Active faults present a variety of potential risks to structures, the most common of which are strong ground shaking, dynamic densification, liquefaction, mass wasting, and surface rupture at the fault plane. Generally speaking, the following four (4) factors are the principal determinants of seismic risk at a given location:

• Distance to seismogenically capable faults.

• The maximum or "characteristic" magnitude earthquake for a capable fault.

• Seismic recurrence interval, in turn related to tectonic slip rates.

• Nature of earth materials underlying the site.

Surface rupture represents the primary potential hazard to structures built in an active fault zone. A review of official maps delineating State of California earthquake fault zones found that no Alquist-Priolo fault study zones passed through or by the subject site. In addition, the site is not located within a zone of mandatory study for active faulting per the San Bernardino County Planning Department, San Bernardino County Land Use Plan, GENERAL PLAN, Geologic Hazard Overlays, Sheet FH22 C San Bernardino N, Plot Date:

03/09/2010, Scale: 1:14,400 (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://lus.sbcounty.gov/wp-content/uploads/sites/48/GeoHazMaps/FH22C-20100309.pdf).

Ground shaking is judged to be the primary hazard most likely to affect the site, based upon proximity to regionally significant active faults. Per the San

1775-01.1 February 18, 2026 P a g e | 11

Bernardino County Geologic Hazard Overlays, Sheet FH22 C San Bernardino N, the nearest regionally significant active fault is the San Jacinto Fault Zone located approximately 2,000 feet west to southwest of the site.

Secondary Seismic Hazards Secondary hazards include induced land sliding, liquefaction, surface oscillations in larger lakes, or seismic sea waves, ground cracks due to ground shaking, and flooding (from ruptured tanks and reservoirs).

Landslide The subject site is located within a designated low to moderate potential landslide area per San Bernardino County Planning Department, San Bernardino

County Land Use Plan, GENERAL PLAN, Geologic Hazard Overlays, Sheet FH22 C San Bernardino N, Plot Date: 03/09/2010, Scale: 1:14,400 (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://lus.sbcounty.gov/wp-content/uploads/sites/48/GeoHazMaps/FH22C-20100309.pdf).

Field reconnaissance did not disclose the presence of older, existing landslides within or near the subject property. Since the site is on flat ground, the potential for land sliding and/or seismic induced land sliding is considered nil.

Liquefaction Liquefaction describes a phenomenon in which cyclic stresses produced by ground shaking induced excess pore water pressures in the cohesionless soils which may thereby acquire a high degree of mobility leading to damage or deformations. In general, this phenomenon only occurs below the water table, but after liquefaction has developed, it can propagate upward into overlying non-saturated soil as excess pore water pressure. Liquefaction susceptibility under a given earthquake is related to the gradation and relative density characteristics of the soil, the in-situ stresses prior to ground motion, and the depth to the water table, as well as other factors.

1775-01.1 February 18, 2026 P a g e | 12

The subject site is not located within a designated zone of liquefaction susceptibility per San Bernardino County Planning Department, San

Bernardino County Land Use Plan, GENERAL PLAN, Geologic Hazard Overlays, Sheet FH22 C San Bernardino N, Plot Date: 03/09/2010, Scale: 1:14,400 (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://lus.sbcounty.gov/wp-content/uploads/sites/48/GeoHazMaps/FH22C-20100309.pdf).

Seiching Seiching involves an enclosed body of water oscillating due to ground shaking, usually following an earthquake. Lakes and water towers are typical bodies of water affected by seiching. It appears that the site is not located within a seiching impact area. Therefore, the potential of seiching to impact the site is considered low.

Tsunamis Because of the inland geographic location of the site, tsunamis are not considered a geologic hazard for the development of the subject site.

Lurching Lurching is a phenomenon in which ground cracking and/or secondary faulting occurs as a result of ground shaking. Generally, lurching primarily occurs in the immediate vicinity of faulting or steep slope areas. No known active or potential active faults pass through or by the subject site or its immediate vicinity, and no steep slope exists at the site; therefore, the likelihood for lurching to impact the site is considered low.

OTHER GEOLOGIC HAZARDS

Flooding The subject site is not located within any designated flood plain area as having a flooding potential per San Bernardino County Planning Department, San

1775-01.1 February 18, 2026 P a g e | 13

Bernardino County Land Use Plan, GENERAL PLAN, Hazard Overlays, Sheet FH22 B San Bernardino N, Plot Date: 03/09/2010, Scale: 1:14,400 (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://lus.sbcounty.gov/wp-content/uploads/sites/48/HazMaps/FH22B-20100309.pdf).

CONCLUSIONS AND RECOMMENDATIONS

GENERAL

In our opinion, the proposed building expansion on the subject site is feasible from a geotechnical engineering viewpoint provided the geotechnical recommendations presented in this report are incorporated into design of the project and implemented during construction of the project.

The following sections contain geotechnical recommendations for design and construction of the proposed development and include our recommendations and discussions about bearing capacity, settlement, flatworks, slab-on-grade, temporary excavations, site drainage, and pavement.

GRADING

In general, the subgrade preparations including fill and backfill can be conducted as follows:

General Grading Requirements

1. All existing foundations and debris, deleterious materials, vegetation, and other organic matter should be excavated and cleared out from the site.

2. Based on our field exploration and laboratory test results, areas of the proposed additions should be over-excavated to a minimum of 4 feet bgs or a minimum of 2 feet below the proposed footing bottom, whichever is deeper. The over-excavation areas should be laterally extended to a minimum of 4 feet from outlines of the footprints except for those areas

1775-01.1 February 18, 2026 P a g e | 14 joining to the existing building. The over-excavation area should be backfilled with engineered fill.

3. Those areas for slab-on-grade and other flatworks should be over-excavated to a minimum of 2 feet bgs and replaced with engineered fill.

4. The excavated bottom should be observed and inspected by the geotechnical consultant or his representative. The excavated bottom should be scarified to 6 to 8 inches and compacted to a minimum of 90 percent of the maximum dry density in accordance with the latest version of the ASTM D1557 Method. The dry density of native soil bottom should be no less than 85 percent of the maximum dry density.

5. All filling, unless otherwise specifically stated in the report, should be compacted to a minimum of 90 percent of the maximum dry density as determined by the latest version of the ASTM D1557 Method.

6. No fill should be placed until the area to receive the fill has been adequately prepared, cleared of fill soil and/or loose alluvial deposits, and approved by the Geotechnical Consultant or his representative.

7. Fill materials should be kept free of debris and organic materials.

8. Rocks or hard fragments larger than 3 inches should not be placed in the fill without the approval of the Geotechnical Consultant or his representative, and in a manner specified for each occurrence. There should not be any concentrations of gravel sizes of 2 inches or greater;

proper mixing should be performed.

9. The filling materials should be placed in lifts which, when loose, should not exceed 8 inches per lift. Each lift should be spread evenly and should be

1775-01.1 February 18, 2026 P a g e | 15 thoroughly mixed during the spreading to obtain uniformity of material and moisture.

10. When the moisture content of the fill material is lower than the specified value or is too low to obtain adequate compaction, water should be added and thoroughly dispersed until the soil has a moisture content within 2½ percent of optimum unless determined by the Geotechnical Consultant at the time of construction.

11. When the moisture content of the filling material is too high or low to obtain adequate compaction, the filling material should be aerated by blading or other satisfactory methods until the soil has a moisture content as specified herein.

FILL MATERIALS

Onsite Earth Materials The onsite sandy soils encountered in the borings are considered to have a low expansion potential. The on-site soils are considered suitable for backfilling purposes, following proper processing, provided they are free of deleterious materials, construction debris, and oversized rocks. Imported materials may also be used for backfilling purposes.

Over excavation and re-compaction will induce fill shrinkage. Many factors such as mixing, relative compaction of the fill, and topographic approximations will affect shrinkage. We cannot estimate the exact amount of shrinkage; however, in our opinion, the shrinkage may be on the order of 6 to 14 percent for fill when earth materials are excavated and recompacted. This estimate does not include those materials that will be required to fill in the excavations after the removal of any subsurface structures left in-place prior to use of the site and removal of topsoil.

1775-01.1 February 18, 2026 P a g e | 16

Imported Materials Any imported soil, if any, should be observed and tested by HGI prior to use in fill or backfill areas.

Imported materials should be like the on-site soil with an expansion index less than 20. Imported materials should be free from corrosive chemicals or organic substances. The water-soluble sulfate content of the import materials should be less than 0.1% by weight.

TEMPORARY EXCAVATIONS

Prior to the commencement of excavation, all utilities in the project area should be located and either rerouted or protected. Any vegetation, deleterious materials, utility lines, and other structures that conflicted with the proposed development should be cleared out from the site.

The temporary excavation in soils without any surcharge may be cut up to 4 feet vertically and 1:1 (Horizontal to Vertical) lay back over 4 feet. Where the over-excavation is adjacent to the existing footing A-B-C slot cuts should be conducted in no more than 5 feet in width and depth.

The construction equipment, vehicle, and stockpile soil should be placed in those active soil zones which are a ground surface above 1:1 plane projected from the excavation bottom. A greater setback may be necessary when considering heavy vehicles, such as concrete trucks and cranes; we should be advised of such heavy vehicle loadings so that specific setback requirements can be established. All regulations of State and Federal OSHA should be followed.

Temporary excavations are assumed to be those that will remain un-shored for a period not exceeding one week. In dry weather, the excavation slopes should be kept moist but not soaked. If excavations are made during the rainy season (normally

1775-01.1 February 18, 2026 P a g e | 17 from November through April), particular care should be taken to protect slopes against erosion. Mitigative measures, such as installation of berms, plastic sheeting, or other devices, may be warranted to prevent surface water from flowing over or ponding at the top of excavations.

SEISMIC DESIGN PARAMETERS

Based on the field investigation, the 2025 California Building Code (2025 CBC), and ASCE/SEI 7-22 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-22), the site could be designated as

Site Class D per Table 20.2-1 of ASCE 7-22. The occupancy risk category can be designated as II. Other required seismic design parameters can be obtained from Section 1613 of the 2025 CBC or could be obtained from the California Structural

Engineers Association website: https://seismicmaps.org/ below by entering address of the project site (34.1474471, -117.340569), the computer outputs are summarized in the following table:

Spectral Response Accelerations SMS and SM1

Ss = 2.71g S1 = 1.1g

Period (Sec.) Sa (g)

0.2 2.62 (SMS, Site Class D)

1.0 3.01 (SM1, Site Class D)

Design Spectral Response Accelerations SDS and SD1

SDS = 2/3 x SMS SD1 = 2/3 x SM1

Period (Sec.) Sa(g)

0.2 1.74 (SDS, Site Class D)

1.0 2.01 (SD1, Site Class D)

Seismic Design Category: E PGAM=0.9g, TS=1.15, T0=0.23, TL=12 https://seismicmaps.org/

1775-01.1 February 18, 2026 P a g e | 18

FOUNDATIONS

Conventional shallow foundations can be designed to support the proposed additions. Our field exploration dismantled that the embedment depth of existing footing was 18 inches bgs. The embedment depth of any new footing adjoining to the existing footing should be no less than 18 inches. The proposed additions should be completely supported on new footings. Any surcharge on the existing footings should not be allowed.

Pad footings should have a minimum of 18 inches in width and continuous footings should have a minimum of 12 inches in width. The bottom of footings should be located at a minimum of 12 inches below the lowest adjacent finish grade. A net vertical bearing value of 2,000 pounds per square feet (psf) can be used to design the footings. A one-third increase in the bearing value can be used when considering wind or seismic loads.

The footings should be reinforced with at least two # 4 re-bars near top and two # 4 re-bars near bottom or other reinforcement as determined by the Structural Engineer. To increase anti-earthquake capability of the proposed development, we recommend that any isolated footings be tied with the continuous footings and/or grade beams. The grade beams may be designed as bearing elements, like the footings.

Lateral Resistance Lateral load resistance can be derived from passive resistance along the vertical sides of the foundations, friction acting at the base of the foundations, or a combination of the two. A coefficient of friction of 0.35 can be used between the footings and engineered fill. The passive resistance of level properly engineered fill in direct contact with the footings can be assumed to be equal to the pressure developed by a fluid with a density of 250 pounds per cubic foot (pcf), to a maximum pressure of 2,500 pcf. A one-third increase in the passive value can be used for wind or seismic loads. The frictional resistance and the passive

1775-01.1 February 18, 2026 P a g e | 19 resistance of the engineered fill can be combined provided that the passive resistance is reduced by one-third.

Estimated Settlement Based on the results of our analyses and our recommendations which will be incorporated into design and implemented during construction, we estimate that the total static settlement of isolated and/or strip footings under sustained loads will be on the order of ¾ inch for the anticipated maximum structural loads. The maximum static differential settlement, over a horizontal distance of thirty feet, should be on the order of ½ inch for similarly loaded footings. The seismic differential settlement is expected to be on the order of ¾ inch over a horizontal distance of thirty feet.

SLAB-ON-GRADE

Concrete slab-on-grade should consist of a nominal 4-inch thickness of concrete and contain at a minimum #3 re-bars spaced a maximum of sixteen inches on centers, both ways. Thicker slabs and additional reinforcement may be required depending on the floor loads and the structural requirements as determined by the Structural Engineer.

The subgrade preparations should follow the recommendations provided in the Grading Section above. It is recommended that the compacted subgrade be moistened prior to placement of the vapor retarder.

It is essential to minimize differential settlements, for each floor unit (room) to be found entirely on competent bedrock or structurally supported (as raised floor).

Moisture Sensitive Floor Covering Water vapor transmitted through floor slabs is a common cause of floor covering problems. In areas where moisture-sensitive floor coverings (such as tile, hardwood floors, linoleum, or carpeting) are planned, a vapor retarder should be

1775-01.1 February 18, 2026 P a g e | 20 installed below the concrete slabs to reduce excess vapor transmission through the slab.

The function of the recommended relatively impermeable membrane (vapor retarder) is to reduce the amount of soil moisture or water vapor that is transmitted through the floor slab. The membrane should be 10-mil thick, Class

A, and care should be taken to preserve the continuity and integrity of the membrane beneath the floor slab. The vapor retarder should conform to ASTM E1745. The vapor retarder should be installed in strict conformance with the manufacture recommendations.

If a capillary break is used, a 4-inch layer of ½- ¾ inch diameter gravels should be placed below the moisture barrier for capillary break to comply with the requirements of current California Green Building Code.

SURFACE DRAINAGE

Foundation, slab, flatwork, and pavement performance depend greatly on proper drainage within and along the boundary of the improvements. Perimeter grades around the shade structures should be sloped in a manner allowing water to drain away from the structures and not pond next to the foundations. Roof downdrains should be connected to underground pipes carrying water away from the foundation area or have extenders so water does not drain and pond next to foundations. Per the 2025 CBC, landscape areas within 10 feet of structures should slope away at gradients of at least 5 percent. Paved areas within 10 feet of structures should slope away at gradients of at least 2 percent unless flatter gradients are needed for parking requirements. Proper drainage is recommended for all surfaces to reduce the potential settlement due to water infiltration.

SOIL EXPANSIVITY AND COLLAPSIBILITY

The subsurface soils encountered at shallow depths consist mostly of gravelly and silty sand. These types of material generally have a low susceptibility to

1775-01.1 February 18, 2026 P a g e | 21 expansion and a medium susceptibility to collapse when facing seasonal cycles of saturation/desiccation. Consequently, the recommendations provided in this report regarding drainage, moisture content during compaction and other pertinent recommendations for site improvements should be incorporated into the design and construction.

SOIL CORROSIVITY

The corrosion potential of the onsite materials to steel and buried concrete was preliminarily evaluated. Laboratory testing was performed on a selected soil sample to evaluate pH, minimum resistivity, chloride, and soluble sulfate content. The test results are presented in Appendix A, Plate No. 6.

These tests are only an indicator of soil corrosivity for the samples tested. Other soils found on site may be more, less, or of a similar corrosive nature. Imported fill materials should be tested to confirm their corrosion potential. Based on the minimum resistivity results from the soil tested, some of the near-surface site soils are mildly corrosive towards buried ferrous metals. The soluble sulfate concentration of 0.00119 percent indicates that the potential of sulfate attack on concrete in contact with the onsite soils is within exposure category S0 based on

ACI 318-19 Tables 19.3.1.1 and 19.3.2.1. Cement Type I or II can be used in concrete. Maximum water-cement ratios are not specified for the sulfate concentrations; however, the Structural Engineer should select a type of concrete with appropriate strength. The soluble chloride concentration of 7.24 ppm can be considered negligible for concrete per ACI 318-19 Tables 19.3.2.1. The pH value measured in the soil sample is 8.37; and the resistivity value measured in the soil sample is 18,899 ohm-cm. The soil corrosion on the site is considered mild.

Further interpretation of the corrosivity test results, including the resistivity value, and providing corrosion design and construction recommendations are the purview of corrosion specialists/consultants.

1775-01.1 February 18, 2026 P a g e | 22

LIMITATIONS

REVIEW, OBSERVATION, AND TESTING

The recommendations presented in this report are contingent upon review of final plans and specifications for the project by HGI. The project Geotechnical /

Geologic Consultant should review and verify in writing the compliance of the final grading plan and the final foundation plans with the recommendations presented in this report.

It is recommended that HGI be retained to provide continuous Geotechnical / Geologic Consulting services during the earthwork operations (i.e., rough grading, utility trench backfill, subgrade preparation for slabs-on-grade and pavement areas, finish grading, etc.) and foundation installation process. This is to observe compliance with the design concepts, specifications, and recommendations and to allow for design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. If HGI is replaced as Geotechnical / Geologic Consultant of record for the project, the work on the project should be stopped until the replacement Geotechnical / Geologic

Consultant has reviewed the previous reports and work performed for the project, agreed in writing to accept the recommendations and prior work performed by HGI for the subject project, or has submitted their revised recommendations.

UNIFORMITY OF CONDITIONS

The recommendations and opinions expressed in this report reflect our understanding of the project requirements based on an evaluation of subsurface earth material conditions encountered at the subsurface exploration locations and the assumption that earth material conditions do not deviate appreciably from those encountered. It should be recognized that the performance of the foundations may be influenced by undisclosed or unforeseen variations in earth material conditions that may occur in intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site

1775-01.1 February 18, 2026 P a g e | 23 development should be brought to the attention of HGI so that we may make modifications, if necessary.

CHANGE IN SCOPE

HGI should be advised of any changes in the project scope of proposed site grading so that it may be determined if recommendations contained herein are valid. This should be verified in writing or modified by a written addendum.

TIME LIMITATIONS

The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur with the passage of time, whether they be due to natural processes or the work of man on this or adjacent properties. In addition, changes in the State-of-the-Art and/or government codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control. Therefore, this report should not be relied upon after a period of two (2) years without a review by HGI verifying the validity of the conclusions and recommendations.

PROFESSIONAL STANDARD

In the performance of our professional services, we comply with the standard of care and skill ordinarily exercised under similar circumstances by members of the geologic / geotechnical professions currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the locations where our surveys and exploratory excavations were made, and that our data, interpretations, and recommendations are based solely on information obtained by us. We will be responsible for those data, interpretations, and recommendations, but should not be responsible for interpretations by others of the information presented and/or developed. Our services consist of professional consultation and observation only, and other warranties, expressed or implied, are not made or intended in

1775-01.1 February 18, 2026 P a g e | 24 connection with work performed by HGI or by the proposal for consulting or other services or by the furnishing of oral or written reports or findings.

CLIENT'S RESPONSIBILITY

It is the responsibility of the client and/or the client's representatives to ensure that information and recommendations contained herein are brought to the attention of the Engineers and Architect for the project and incorporated into project plans and specifications. It is further their responsibility to take measures so that the contractor and his subcontractors carry out such recommendations during construction.

APPENDIX A

1775-01.1 February 18, 2026 P a g e | A-1

FIELD EXPLORATION

The field study performed for this report included a visual geologic reconnaissance of existing surface conditions of the subject site. Site observations and geologic mapping were conducted by a representative of HGI on February 9th, 2026.

A study of the property's subsurface condition was performed to evaluate underlying earth strata and the presence of groundwater. Three (3) exploratory borings were performed at the area of the proposed development on the subject site on February 9th, 2026. Locations of the exploratory excavations were determined in the field by pacing, tape measuring, and sighting from the adjacent existing streets, adjacent structures, and topographic features as shown on Plate No. 1. Approximate locations of the exploratory excavations are denoted on Plate No. 1. Approximate elevations at the locations of the exploratory excavations were determined from the Google Earth Website (http://www/google.com/earth).

Locations and elevations of the exploratory excavations should be considered accurate only to the degree implied by the method used in determining them.

Three exploratory borings were excavated by a hand auger. The depths explored in the borings extended to depths ranging from 5.2 to 5.5 feet below the existing ground surface at the excavation locations. Bulk and relatively undisturbed ring samples were obtained from cuttings developed during the drilling excavation process and represent the earth materials within the depth indicated.

Groundwater observations were made during, and at the completion of the excavation process and are noted on the ‘Subsurface Exploration Log’ presented in this Appendix A, if encountered.

The exploratory excavations were logged by a representative of HGI for fill material, natural earth material, and subsurface conditions encountered. Earth materials encountered in the exploratory excavations were visually described in

1775-01.1 February 18, 2026 P a g e | A-2 the field in general accordance with the current Unified Soils Classification System (USCS), ASTM D2488, visual-manual procedures, as illustrated on the attached, simplified ‘Subsurface Exploration Legend,’ Plate No. 2, presented in this Appendix A. The visual textural description, color of the earth material at natural moisture content, apparent moisture condition of the earth materials, and apparent relative density or consistency of the earth materials, etc., were recorded on the field logs. The ‘Relative Density’ of granular soils (SP, SW, SM, SC, GP, GW, GM, GC) is given as very loose, loose, medium dense, dense, or very dense and is based on the number of blows to drive the sampler 1.0 foot or fraction thereof. The ‘Consistency’ of silts or clays (ML, CL, MH, CH) is given as very soft, soft, medium stiff, stiff, very stiff, or hard and is also based on the number of blows to drive the sampler 1.0 foot or fraction thereof. The field log for each excavation contains factual information and interpretation of earth material conditions between samples. The ‘Subsurface Exploration Log’ presented in this

Appendix A represents our interpretation of the field log contents and results of laboratory observations and tests performed on samples obtained in the field from the exploratory excavations.

LABORATORY TESTING PROGRAM

Laboratory tests were performed on selected, relatively undisturbed ring and bulk samples obtained from exploratory excavations during field study. Tests were performed in general accordance with generally accepted American Society for Testing and Materials (ASTM), State of California - Department of Transportation (CALTRANS), Environmental Protection Agency (EPA) or other suitable test methods or procedures. The remaining samples obtained during the field study will be discarded 30 days after the date of this report. This office should be notified immediately if retention of samples is needed more than 30 days. A brief description of the tests performed is presented below:

1775-01.1 February 18, 2026 P a g e | A-3

CLASSIFICATION

The field classification of earth material materials encountered in the exploratory excavations was verified in the laboratory in general accordance with the current Unified Soils Classification System, ASTM D2488, ‘Standard Practice for Determination and Identification of Soils (Visual-Manual Procedures).’ The final classification is…