FINAL DRAINAGE REPORT FOR SAN BERNARDINO COUNTY

FIRE STATION NO.227

Project Location: 180 W. 38th Street, San Bernardino California.

APN-0154-281-01

Record: DRNSTY-2025-00006

March 2025

Project Number: ERSC#09003097

Prepared for:

County of San Bernadino Project and

Facilities Management Division

385 North Arrowhead Ave, 3rd Floor

San Bernardino, CA 92415

(909) 387-5000

Prepared by:

Engineering Resources of Southern California, Inc.

1861 Redlands Blvd. Bldg. 7B

Redlands, CA 92373

(909) 890-1255

K2825 Stamp

K2825

PLAN CHECKED BY

K2825 Text Box 07/29/2025

K2825 Text Box 07/29/2025

Fire Station No.227 Design Drainage Report – 100% Submittal A-i

TABLE OF CONTENTS

Acronyms and abbreviations ..................................................................................................................................................... A-iii

A. Project description

1. Location

2. Proposed Development

2.1 Site description

2.2 topography and soils

B. Historic Drainage

1. Overall drainage area Description

1.1 FEMA Flood Insurance Study

2. hystorical Drainage Patterns Through Property

C. Design Criteria

1. List References

2. Hydrologic Criteria

a. Rainfall data

b. Calculation method

c. Design frequency

3. Hydraulic Criteria

d. Infiltration Chambers System

D. Drainage Plan

1. General Concept

a. Detention ponding/water quality BMP plan, identify ownership/maintenance responsibilities. 10

2. specific Details

a. Drainage area Descriptions

E. Conclusion

F. List of References

APPENDIX 1. GEOTECHNIAL REPORT & NRCS SOILS report

APPENDIX 2. FEMA FLOOD INSURANCE STUDY

APPENDIX 3. NOAA ATLAS 14

APPENDIX 4. existing RATIONAL METHOD and HYDROGRAPH CALCULATIONS

Appendix 5. proposed RATIONAL METHOD, HYDROGRAPH, BASIN ROUTING and HYDRAULIC

CALULATIONS

APPENDIX 6. existing Hydrology MAPs

APPENDIX 7. proposed Hydrology MAPs

APPENDIX 8. grading plan REFERENCE only

APPENDIX 9. INFILTRATION CHAMBER REFERENCE only

Fire Station No.227 Design Drainage Report – 100% Submittal A-ii

LIST OF TABLES

Table 1: NRCS Web soil survey soil types

Table 2: NOAA Atlas 14, Precipitation Data

Table 3: EXISTING Drainage areas

Table 4: Proposed Condition

LIST OF FIGURES

Figure 1: PROJECT VICINITY MAP

Figure 2: EXISTING PROJECT AREA MAP

Fire Station No.227 Design Drainage Report – 100% Submittal A-iii

ACRONYMS AND ABBREVIATIONS

BMP best management practice

FEMA Federal Emergency Management Agency

NOAA National Oceanic and Atmospheric Administration

NS None specified

SFHAs Special Flood Hazard Areas

SWMP Storm Water Management Plan

Fire Station NO.227 Design Drainage Report – 100% Submittal 4

A. PROJECT DESCRIPTION

This drainage report has been prepared to address the stormwater management, hydrology, and drainage impacts of the proposed Fire Station No. 227. The project involves the construction of a 10,764 square-foot fire station on a 1.18-acre portion of the Arrowhead Elementary School play fields. The proposed facility includes a 3-bay apparatus garage, administrative offices, sleeping quarters, and site improvements such as parking areas, access roads, landscaping, and utilities.

This report evaluates the pre- and post-development hydrologic conditions and provides the necessary drainage improvements to mitigate 1-hour and 100-year storm event in accordance with local, state, and federal regulations.

1. LOCATION

The project area is located at the northwest corner of West 38th Street and Genevieve Street North in the

San Bernardino, California. The proposed fire station No.227 will be located on the southern portion of the

Arrowhead Elementary School property.

Figure 1: PROJECT VICINITY MAP

Fire Station NO.227 Design Drainage Report – 100% Submittal

2. PROPOSED DEVELOPMENT

2.1 SITE DESCRIPTION

The existing site occupies 1.18 acres and is currently covered with a grass field and large trees on the east, west and south sides. The elevations at the site range from 1,294 to 1,284 feet above mean sea level (msl). The site slopes generally to the southeast with approximately 2 percent.

2.2 TOPOGRAPHY AND SOILS

The project site is located in San Bernardino County, California, within the southwestern region of the county. The ground elevation across the site is relatively flat, with a gentle slope toward the southeast.

The predominant soil type on the project site is Hanford coarse sandy loam (HaC), which is classified as Type A soil. This soil type covers 100% of the project site and is characterized by high infiltration rates and low runoff potential. Type A soils are well-drained and highly permeable, allowing water to easily percolate into the ground. These characteristics are ideal for infiltration-based stormwater management systems, which are effective in managing and treating runoff at the source.

The high infiltration capacity of Type A soils makes them suitable for implementing infiltration trenches, bioretention areas, and pervious pavement systems, which are designed to manage stormwater by allowing it to infiltrate into the subsurface. This will help minimize surface runoff, reduce the risk of flooding, and improve groundwater recharge.

Soil data for this site was obtained from the NRCS Web Soil Survey, which can be found in Appendix

1 of this report. These soil characteristics will play a critical role in the design and placement of stormwater management facilities, ensuring that the system effectively handles both stormwater quantity and quality in compliance with local regulations.

Figure 2: existing Project Area Map

Table 1: NRSC Web Soil Survey Soil Types

Map

Symbol

Description Hydrologic

Soil Group

HaC Honford coarse Sandy loam, 2 to 9 percent slopes A

B. HISTORIC DRAINAGE

1. OVERALL DRAINAGE AREA DESCRIPTION

The project site, located in a heavily urbanized area, historically manages stormwater runoff from adjacent streets via a system of street gutters and underground storm drains. The proposed development will increase impermeable surfaces, which will, in turn, increase runoff velocity. A method to capture or slow down and divert this flow across newly paved areas is needed to prevent issues. Due to the limited construction area of the proposed fire station, an underground infiltration chambers system has been proposed.

1.1 FEMA FLOOD INSURANCE STUDY

The Federal Emergency Management Agency’s (FEMA) Flood Map Service Center was used to identify flood hazard areas near the project site. The project site location is dominated by native grass and large trees, and it is located in Zone X (06071C7945H, effective 08/28/2008), an area of minimal flood hazard as defined by FEMA. Map number 06071C7945H display the site lies outside of the 100-year flood plain and is designated as Zone X (Appendix 2), which is designed as an area within the 500-year flood plain; therefore, development of the site will not be impacted by a FEMA designated 100-year flood plain.

2. HYSTORICAL DRAINAGE PATTERNS THROUGH PROPERTY

The current drainage patterns indicate that stormwater runoff from the site flows over the grassed cover in a southerly direction towards West 38th Street, where it is ultimately captured by the existing curb and gutter system. The runoff is then directed into the city's storm drain system.

Currently, the amount of runoff is minimal due to the permeability of the natural ground cover.

However, the proposed development will change these patterns by increasing the impervious surface area, which will require the implementation of stormwater management practices.

C. DESIGN CRITERIA

The proposed drainage improvements will consist of constructing a concrete V-ditch to redirect offsite runoff away from the proposed improvements. Additionally, multiple drainage structures such as curb and gutter, drainage ditches, catch basins, and infiltration chambers will be built to effectively capture and manage the runoff generated by the proposed improvements.

1. LIST REFERENCES

• San Bernardino County Hydrology Manual (June 1989)

• NOAA ATLAS 14

• FEMA

• The County of San Bernadino Technical Guidance Document for Water Quality

Management Plans (June 2013)

2. HYDROLOGIC CRITERIA

a. Rainfall data

The precipitation data has been provided in Table 2: NOAA Atlas 14, Precipitation Data and a copy of the source is provided in Appendix 3.

Table 2: NOAA Atlas 14, Precipitation Data

PDS-based precipitation frequency estimates with 90% confidence intervals (in inches)

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

60-min 0.498 0.660 0.890 1.09 1.39 1.63 1.90 2.19 2.62 2.99

b. Calculation method

Hydrological analyses for the Project are performed using the Rational Method and Unit Hydrograph

Method to estimate the peak runoff rates for the pre- and post-development conditions for 100-year storm event. Parameters for Rational Method include rainfall intensity in inches per hour, a runoff coefficient representing the ratio of runoff depth to rainfall depth (dimensionless), and drainage area

(A) in acres. The values of the runoff coefficient (C) and the rainfall intensity (I) are based on a study of drainage area characteristics such as type and condition of the runoff surfaces and the time of concentration. The Unit Hydrograph Method assumes that watershed storm rainfall-runoff relationships are characterized by watershed area, slope, and that watershed discharge is related to the total volume of runoff. See Appendix 4 & 5 for Rational Method and Unit Hydrograph calculations and pipe and under sidewalk drain sizing.

A detailed description and in-depth discussion of the Rational Method and the Unit Hydrograph

Method can be found in the San Bernadino County Hydrology Manual (June 1989).

c. Design frequency

Design frequencies for stormwater infrastructure are based on the San Bernadino County, which require a 100-year return period for major storm events.

3. HYDRAULIC CRITERIA

This project has been designed to meet the standards which reference the following:

» The County of San Bernadino Technical Guidance Document for Water Quality Management

Plans

» Santa Ana Regional Water Quality Control Board for construction activities and post-construction site management

» Weir Equation for Catch Basin Sizing: Q=3.33*L*(H1.55)

d. Infiltration Chambers System

Infiltration chamber system will be developed for the project in compliance with the San Bernadino

County to accommodate the 100-year storm event. See Appendix 9 for proposed WQMP Infiltrations chamber volume calculations.

The infiltration system is designed to capture the incremental increase of stormwater between existing and proposed conditions under the 100-year 24-hour storm event. The incremental increase was determined to be 216.5 cubic feet and the provided storage of the basin is 4,917 cubic feet. The max WSEL of the basin is 1283.85’, and the system will drain in approximately 44 hours after the 100-year 24-hour storm event. When the capacity of the infiltration system is exceeded, stormwater will flow through a 12-inch emergency overflow pipe and then a 4’ wide under sidewalk drain and flow

North to 38th Street. Calculations can be found in Appendix 5.

Table 3: Hydrograph Results

Table 4: Basin Routing Results

Existing Condition Proposed Condition

Storm Event Volume

(Ac-ft)

Peak

Flow (cfs)

Volume

(Ac-ft)

Peak

Flow (cfs)

100-Year, 24-

Hour

0.3338 3.31 0.3835 3.65

Storm Event Incremental

Increase

Storage

Provided

Mitigated

Flow (cfs)

Drawdown

Time (hrs)

100-Year, 24-

Hour

0.0497 .113 3.011 44

D. DRAINAGE PLAN

1. GENERAL CONCEPT

a. Detention ponding/water quality BMP plan, identify ownership/maintenance responsibilities.

The project is subject to the requirements of various water quality permits issued by the Santa Ana

Regional Water Quality Control Board for construction activities and post-construction site management. These requirements include preparation of a Stormwater Pollution Prevention Plan

(SWPPP) for construction activities and a Project Specific Water Quality Management Plan for post construction site management.

2. SPECIFIC DETAILS

a. Drainage area Descriptions

Existing hydrology calculations are included in Appendix 4.

Table 5: Existing Drainage Areas

Proposed hydrology calculations are included in Appendix 5.

Table 6: Proposed Condition

E. CONCLUSION

The undeveloped current flow rate is approximately 13.65 cubic feet per second per existing hydrology map in Appendix 6. The current drainage area in question has produced a lower runoff compared to the combined flow of 9.5 cubic feet per second (cfs) from offsite sources and the runoff generated by onsite development (FS227). When the reduced offsite drainage area is combined with the developed onsite area, a total runoff of 17.28 cfs is generated. The reduced offsite area specifically

Drainage area ID Area

(acres)

% IMP

Q100

(cfs)

TOTAL 3.46 40 13.65

Drainage area ID Area

(acres)

% IMP

Q100

(cfs)

A 2.22 40 9.77

B & C 1.18

77 7.51

3.4 17.28 generates a flow of 9.77 cfs, which will be directed and channeled through a concrete V-ditch. This flow will move from east to west, ultimately reaching the lowest point on the southwest corner of the

Arrowhead Elementary School property. This runoff will then be directed through a wall opening at the southwest corner of Arrowhead Elementary School. A catch basin, along with two 8-inch concrete pipe outlets, will be utilized to manage the 10-year storm events. The 10-year storm event runoff from

Existing Site A will be diverted via catch basin, 8-inch pipes and under sidewalk drain. Existing site A generates 4.975 cubic feet per second, and calculations demonstrating that the catch basin, 8-inch pipes and under sidewalk drain have been adequately sized can be found in Appendix 5. For major storm events, the proposed wall opening will handle the runoff effectively. The wall opening is designed to handle the flow of a 100-year storm event, ultimately releasing the tributary runoff flows at Genevieve Street per exiting proposed hydrology map in Appendix 7.

For more information on the wall opening and concrete V-ditch and catch basin, please refer to the attached grading plan in Appendix 8.

Hydrograph and Basin routing calculations have been provided in this report showing that the proposed chamber system can capture the incremental difference between existing and proposed conditions, as well as mitigating the peak flow below existing peak flow, calculations have been provided in Appendix 5.

The runoff from onsite (FS227) will flow as sheet flow through a concrete gutter and be directed into the catch basin system. The catch basin system will then route its flows into infiltration chambers as detailed in the Water Quality Management Plan (WQMP) report, with infiltration chambers calculations provided in Appendix 9. Any excess runoff that overflows the chambers will flow through a 12” pipe and then the 4’ wide under sidewalk drain to finally discharge to 38th Street. By utilizing a combination of infiltration, detention, and water quality Best Management Practices (BMPs), we will effectively manage both the quantity and quality of stormwater, thereby minimizing any adverse effects on the surrounding area.

F . LIST OF REFERENCES

Maps

FEMA, FIRM Panels 06065C0829G, and 06065C0837G

Criteria

San Bernadino Storm Drainage Criteria

National Oceanic and Atmospheric Administration (NOAA), Atlas 14

Natural Resources Conservation Service (NRCS) Web Soil Survey

NOAA National Centers for Environmental Information, Climate Normal

San Bernadino County Flood Control and Water Conservation District

Santa Ana Regional Water Quality Control Board for construction activities and post-construction site management

APPENDIX 1. GEOTECHNIAL REPORT &

NRCS SOILS REPORT

IFE Inland Foundation Engineering, Inc.

inlandfoundation.com

1310 South Santa Fe Ave. PO Box 937 San Jacinto, CA 92581 ꓲ (951) 654-1555

77622 Country Club Dr. Suite Q, Palm Desert, CA 92211 ꓲ (760) 200-2400

September 6, 2024

Project No. S168-193

STK ARCHITECTURE, INC.

42095 Zeno Drive, Suite A15

Temecula, California 92590

Attention: Tony Finaldi

Subject: Geotechnical Investigation

Proposed Fire Station 227

NWC Genevieve Street N. and W. 38th Street

San Bernardino, California

Dear Mr. Finaldi:

This report presents the results of the geotechnical investigation for the proposed Fire

Station 227. The investigation was conducted in general conformance with our proposal dated March 6, 2024.

This report includes project design and construction recommendations along with the field and laboratory data. The primary geotechnical issues are the potential for strong ground shaking and the presence of variable soil conditions within the building areas that will require removal and recompaction.

We appreciate the opportunity to work with you on this project. Please call if you have any questions or need any other information.

Sincerely, INLAND FOUNDATION ENGINEERING, INC.

Allen D. Evans, P.E., G.E.

Principal

Christopher Hogan Rangel, PG

Project Geologist

ADE:CHR:sd i

TABLE OF CONTENTS

INTRODUCTION

SCOPE OF SERVICE

PROJECT DESCRIPTION

SITE DESCRIPTION

GEOLOGIC HAZARD EVALUATION

SUBSURFACE CONDITIONS

INFILTRATION TESTING

CONCLUSIONS AND RECOMMENDATIONS

Foundation Design Lateral Resistance Lateral Earth Pressure Concrete Slabs-on-Grade Portland Cement Concrete (PCC) Pavement Asphalt Concrete Pavement General Site Grading

LIMITATIONS

REFERENCES

APPENDICES

APPENDIX A - Site Exploration ..................................................................................... A-1 - A-7 Explanation of Logs ............................................................................................................ A-2 Exploratory Borings and Trenches ............................................................................ A-3 - A-6 Site Plan ............................................................................................................................ A-7

APPENDIX B - Laboratory Testing ................................................................................B-1 - B-10 Maximum Density - Optimum Moisture. .............................................................................. B-3 Sieve Analysis ........................................................................................................... B-4 - B-5 Plastic Index .............................................................................................................. B-4 - B-5 Consolidation ..................................................................................................................... B-6 Direct Shear Strength ................................................................................................ B-7 - B-8 Corrosion ........................................................................................................................... B-9 R-value ............................................................................................................................ B-10

APPENDIX C - Infiltration Testing .............................................................................................. C

APPENDIX D - Liquefaction and Seismic Settlement Analysis ................................................... D

APPENDIX E - Geologic Hazard Report .................................................................................... E ii

LIST OF FIGURES

• Figure 1 – USGS Topographical Map

LIST OF TABLES

• Table 1 – Seismic Design Parameters

• Table 2 – Infiltration Rates

• Table 3 – Portland Cement Concrete Pavement

• Table 4 – Asphalt Concrete Pavement

• Table 5 – Recommended Import Soil Criteria

Fire Station No. 227 – Geotechnical Report

Project No. S168-193, September 2024 1 of 11 Inland Foundation Engineering, Inc.

INTRODUCTION

This report presents the results of the geotechnical investigation conducted for the proposed San Bernardino County Fire Station 227. Fire Station 227 will be located on the northwest corner of Genevieve Street N. and W. 38th Street in San Bernardino, California. Our project understanding was based on the discussions with STK

Architecture and review of the following plan.

• FS 227 – Conceptual Site Plan, W. 38th Street, San Bernardino, CA, prepared by

STK Architecture Inc, dated June 12, 2024

SCOPE OF SERVICE

The purpose of this geotechnical investigation was to provide geotechnical parameters for design and construction of the proposed project. The scope of the geotechnical services included:

• Evaluation of existing geologic conditions at the site and review of potential geologic and seismic hazards.

• Evaluation of the local and regional tectonic setting and historical seismic activity, including a site-specific ground motion analysis.

• Reconnaissance of the site and surrounding area to ascertain the presence of unstable or adverse geologic conditions.

• Subsurface sampling and laboratory testing.

• Analysis of the data collected and the preparation of this report with geotechnical engineering conclusions and recommendations for design and construction.

Evaluation of hazardous waste was not within the scope of services provided.

PROJECT DESCRIPTION

The Fire Station No. 227 project will consist of the construction of a new single-story structure comprising approximately 9,870 square feet. The station will be constructed on the southerly portion of the existing Arrowhead Elementary School property.

The fire station will include 3 truck bays, sleeping quarters for 8 crew members and will provide storage for 2 Type 1 Engines and a future ladder truck. A storage building and generator / fuel tank pad will be constructed in the northwest site area. Foundations for

Project No. S168-193, September 2024 2 of 11 Inland Foundation Engineering, Inc.

the proposed structures are expected to consist of shallow continuous and isolated concrete spread footings with slab-on-grade floors. Off-site improvements on

Genevieve Street and 38th Street will be necessary. Site grading is expected to consist of minor cuts and fills of 2 to 3 feet, exclusive of remedial removals as recommended in this report.

Stormwater infiltration basins are planned in the southern and northwestern portions of the site. The basin depths are expected to be no deeper than five feet below existing surface grades.

SITE DESCRIPTION

The subject site is located on the northwest corner of Genevieve Street N. and W. 38th

Street in San Bernardino, California (34.160118˚, -117.286677˚). The site occupies

1.21 acres and is currently covered with a grass field and large trees on the east, west and south sides. Figure 1 below shows the site location.

Figure 1: USGS San Bernardino North 7.5’ Quadrangle (2021)

According to Google Earth, elevations at the site range from 1,279 to 1,283 feet above mean sea level (msl). The site slopes generally to the south at an overall rate of approximately 2 percent.

Subject Site Approximate Location

Project No. S168-193, September 2024 3 of 11 Inland Foundation Engineering, Inc.

GEOLOGIC HAZARDS EVALUATION

A geologic hazards report for this project was prepared by our subconsultant, Terra

Geosciences, and is appended. The engineering geology and seismicity review was performed using the suggested “Checklist for the Review of Geologic/Seismic Reports for California Public Schools, Hospitals and Essential Services Buildings” (California

Geologic Survey, Note 48, 2022).

The geologic hazards study indicates that the proposed fire station and associated structures are considered feasible from a geologic standpoint, providing that the conclusions and recommendations presented in the report are considered during planning and construction. No adverse geologic conditions were found within the proposed construction area, with the exception of the potential for strong ground shaking from nearby seismogenic fault sources.

The geologic hazards study included a site-specific ground motion analysis. The mapped spectral acceleration parameters, coefficients, and other related seismic parameters were evaluated using the OSHPD Seismic Design Maps web application

(OSHPD, 2020) and the California Building Code criteria (CBC, 2022), with the site-specific ground motion analysis being performed following Section 21 of the ASCE 7-16

Standard (2017). The results of the site-specific analysis are summarized and tabulated in Table 1 below:

Table 1: Seismic Design Parameters

Factor or Coefficient Value

SS 2.506g

S1 1.002g

Fa 1.2g

FV 1.7g

SDS 1.670g

SD1 1.620g

SMS 2.506g

SM1 2.429g

TL 8 Seconds

MCEG PGA 0.95g

Site Class D

Project No. S168-193, September 2024 4 of 11 Inland Foundation Engineering, Inc.

SUBSURFACE CONDITIONS

Subsurface exploration at the site consisted of four (4) exploratory borings to depths ranging from approximately 16.5 to 50.5 feet below existing site grades. The site exploration is described in Appendix A. Boring locations are shown on Figure A-7.

The soil encountered in the borings consisted of quaternary alluvial materials comprised of interlayered silty sand (SM), sand with silt and gravel (SP/SW-SM), and silty clayey sand (SC-SM). Cobbles and boulders were encountered in boring B-01 at a depth of

30.5 feet. The soil encountered was generally fine to very coarse grained, loose to very dense and in a slightly moist to moist state.

Corrosion Potential: Analytical testing indicates the concentration of sulfates is 52 ppm. In accordance with ACI 318, Table 4.2.1, the soil is classified as having a negligible sulfate exposure. The chloride concentration in the tested sample was 30 ppm and indicates that the soil is generally not corrosive with respect to ferrous metal.

The soil is alkaline with a pH value of 8.5. The saturated minimum resistivity value of

7,790 ohm-cm indicates the soil may be moderately corrosive to buried ferrous metal.

Alternative material such as PVC piping should be considered in the project design.

Inland Foundation Engineering, Inc. does not practice corrosion engineering. A qualified corrosion engineer should be consulted for additional guidance.

Hydrocollapse Potential: Consolidation testing indicates that the soil is compressible and normally consolidated. The results show a slight to moderate potential for hydrocollapse when saturated under anticipated foundation and soil overburden loads.

Provided that the building pad area is prepared as recommended herein, and appropriate surface drainage is provided in accordance with contemporary design practice, the potential for adverse building settlement due to hydrocollapse is not significant.

Expansive Soil: The site soil is granular, non-plastic, and non-expansive. Design measures to mitigate soil expansion are not necessary.

Groundwater: Groundwater was not encountered within the exploratory borings, which extended to a maximum depth of 50.5 feet below existing ground surface. Based on a review of pertinent groundwater data (referenced in appended geologic hazards report), the depth to the high groundwater mark in the general region is greater than 120 feet.

Liquefaction and Seismically-Induced Settlement: In general, liquefaction is a phenomenon that occurs where there is a loss of strength or stiffness in the soil that can result in the settlement of buildings, ground failure, or other hazards. The main factors contributing to this phenomenon are: 1) cohesionless, granular soil with relatively low density (usually of Holocene age); 2) shallow ground water (generally less than 50 feet);

shernandez Highlight The site soil is granular, non-plastic, and non-expansive. Design measures to mitigate soil expansion are not necessary.

shernandez Highlight silty sand (SM), sand with silt and gravel (SP/SW-SM), and silty clayey sand (SC-SM) shernandez Highlight fine to very coarse grained, loose to very dense and in a slightly moist to moist state

Project No. S168-193, September 2024 5 of 11 Inland Foundation Engineering, Inc.

and 3) moderate to high seismic ground shaking. Based on current and historical groundwater levels of more than 120 feet below ground surface, the potential for soil liquefaction is not significant.

“Dry sand” settlement occurs in loose granular soil as a result of seismic ground shaking. The potential for “dry sand” settlement was evaluated using GeoSuite® software and Pradel’s method (1998). The results indicate a potential for seismically-induced “dry sand” settlement of less than 1 inch. The estimated differential seismic settlement is less than ½ inch over 30 feet. A discussion of the seismic settlement analysis, with graphic results, is included in Appendix D.

INFILTRATION TESTING

Infiltration testing was conducted in general accordance with Appendix D of the

Technical Guidance Document for Water Quality Management Plans, prepared by CDM

Smith for the County of San Bernardino Areawide Stormwater Program (2013). The shallow percolation test method was used per the Riverside County Department of

Environmental Health guidelines. Four percolation tests were performed at the locations shown on Figure A-7. The testing procedures are described, and the test data is included in Appendix C of this report.

The test results are shown in Table 2. The corresponding calculated infiltration rate (Ic) ranges from 2.0 inches per hour to 5.7 inches per hour. These values exclude a factor of safety. The appropriate factor of safety should be determined by the design engineer.

Table 2: Infiltration Rate

Percolation

Test No.

Percolation

Rate (min/in)

Depth Below

Ground Surface (in)

Infiltration Rate

(Ic) (in/hr)

P-01 1.0 60 5.7

P-02 1.0 48 5.7

P-03 2.5 60 2.0

P-04

1.0 48 5.7

CONCLUSIONS AND RECOMMENDATIONS

The primary geotechnical issue that will require mitigation is the presence of loose compressible near surface soil conditions within the proposed structure areas. The near surface soil is not suitable for supporting foundations in its existing condition and should be over-excavated and recompacted. This and other geotechnical engineering recommendations for project design and construction are presented below.

Project No. S168-193, September 2024 6 of 11 Inland Foundation Engineering, Inc.

Foundation Design: The proposed fire station and associated structures can be supported by shallow continuous and isolated spread footings designed with an allowable bearing pressure of 2,000 pounds per square foot (psf). Footings should have a minimum width of 12 inches and bottoms a minimum depth of 12 inches below the lowest adjacent grade. The allowable bearing pressure can be increased by 400 psf for each additional foot of width and by 800 psf for each additional foot of depth, to a maximum allowable bearing pressure of 4,000 psf. The allowable bearing pressure can be further increased by ⅓ for short-term transient wind and seismic loads.

Static settlement of footings designed and constructed as recommended herein is expected to be less than one inch. Differential settlement between footings of similar size and load is expected to be less than one-half inch.

Lateral Resistance: Resistance to lateral loads will be provided by a combination of friction acting at the base of the slab or foundation and passive earth pressure. A coefficient of friction of 0.45 between soil and concrete may be used with dead load forces only. A passive earth pressure of 250 psf/ft may be used for the sides of footings poured against recompacted or dense native material. These values may be increased by ⅓ for short-term transient wind and seismic loads. Passive earth pressure should be ignored within the upper one foot, except where confined as beneath a floor slab, for example.

Lateral Earth Pressure: Retaining walls should be designed for an active earth pressure equivalent to that exerted by a fluid weighing not less than 40 pcf. Any applicable construction or seismic surcharges should be added to this pressure.

Retaining wall backfill should have an expansion index of less than 20.

Concrete Slabs-on-Grade: Concrete slabs-on-grade should have a minimum thickness of four inches. During final grading and prior to the placement of concrete, all surfaces to receive concrete slabs-on-grade should be compacted to maintain a minimum compacted fill thickness of 12 inches.

Load bearing slabs should be designed using a modulus of subgrade reaction (k) not exceeding 200 pounds per square inch per inch. This value is based on an applied foundation load area of 1.0 square foot. The k value should be reduced for larger foundation areas according to the following formula:

kR = k * ((B+1) / 2B))2 where kR = reduced modulus of subgrade reaction

B = foundation width (feet)

Project No. S168-193, September 2024 7 of 11 Inland Foundation Engineering, Inc.

Slabs should be designed and constructed in accordance with the provisions of the

American Concrete Institute (ACI). Shrinkage of concrete should be anticipated and will result in cracks in all concrete slabs-on-grade. Shrinkage cracks may be directed to saw-cut "control joints" spaced on the basis of slab thickness and reinforcement.

Control joint spacing in unreinforced concrete at maximum intervals equal to the slab thickness times 24 is recommended.

Slabs to receive moisture-sensitive coverings should be provided with a moisture vapor retarder/barrier designed and constructed according to the American Concrete Institute

302.1 R, Concrete Floor and Slab Construction, which addresses moisture vapor retarder/barrier construction. At a minimum, the vapor retarder/barrier should comply with ASTM El745 and have a nominal thickness of at least 10 mils. The vapor retarder/barrier should be properly sealed, per the manufacturer’s recommendations, and protected from punctures and other damage.

Portland Cement Concrete (PCC) Pavement: All surfaces that will support fire apparatus should be paved with Portland cement concrete (PCC). PCC pavement should consist of 9 inches of PCC over 6 inches of Class 2 aggregate base. The concrete should have a minimum 28-day modulus of rupture of 600 psi. This corresponds to a compressive strength of approximately 4,500 psi.

For all other areas that will utilize PCC pavement the below table can be utilized for design sections. The following Portland cement concrete pavement sections are based on the American Concrete Institute (ACI) Guide for Design and Construction of

Concrete Parking Lots and Site Paving (ACI 330-21). The concrete to be utilized for

Category A and B areas as well as pedestrian areas should have a minimum 28-day modulus of rupture of 500 psi. This corresponds to a compressive strength of approximately 2,500 psi. The actual pavement subgrade soil should be evaluated during construction to verify that the recommended pavement sections are appropriate.

Table 3: Portland Cement Concrete Pavement

Service Concrete Thickness (in.) Aggregate Base (in.)

Car parking and access lanes (Category A) 4.25 4.0

Entrance and truck service lanes (Category B) 5.25 4.0

Pedestrian, non-vehicular hardscape 4.0 0.0

The Class 2 aggregate base should comply with current Caltrans requirements. The aggregate base should be compacted to at least 95 percent relative compaction based on ASTM D1557. The upper 12 inches of pavement subgrade soil, below the aggregate base, should also be compacted to a minimum relative compaction of 95 percent.

shernandez Highlight aggregate base should be compacted to at least 95 percent relative compaction based on ASTM D1557. The upper 12 inches of pavement subgrade soil, below the aggregat shernandez Highlight 9 inches of PCC over 6 inches of Class 2 aggregate base shernandez Highlight 4.25 shernandez Highlight 4.

shernandez Highlight 4.0 shernandez Highlight base, should also be compacted to a minimum relative compaction of 95 percen

Project No. S168-193, September 2024 8 of 11 Inland Foundation Engineering, Inc.

The concrete pavement should be constructed with doweled joints and be restrained laterally by concrete curb/gutter or building foundations. The edges of the concrete should be protected from traffic loads by curbs or paved shoulders. If unrestrained pavement edges or non-doweled joints are desired, this firm should be contacted so that revised recommendations can be developed.

Construction joints should be sawcut in the pavement at a maximum spacing of

30 times the thickness of the slab, up to a maximum of 15 feet. Pavement sawcutting should be performed within 12 hours of concrete placement, preferably sooner. Sawcut depths should be equal to approximately ¼ of the slab thickness for conventional saws or one inch when early-entry saws are utilized on slabs nine inches thick or less.

Construction joints should not be placed near flow lines. The use of plastic strips for formation of jointing is not recommended. The use of expansion joints is not recommended, except where the pavement will adjoin structures.

Asphalt Concrete Pavement: Recommended asphalt concrete structural pavement sections are shown below in Table 4.

Table 4: Asphalt Concrete Pavement

Service Asphalt Concrete

Thickness (ft.)

Base Course

Thickness (ft.)

Light traffic (autos, parking areas, T.I. = 5.0) 0.25 0.35

Heavy traffic (trucks, driveways, T.I. =7.0) 0.30 0.45

Inland Foundation Engineering, Inc. does not practice traffic engineering. The T.I.

values used to develop the recommended pavement sections are typical for projects of this type. The project civil engineer or traffic engineer should review the T.I. values used to verify that they are appropriate for this project.

General Site Grading: All grading should be performed per the applicable provisions of the 2022 California Building Code and the following recommendations.

1. Clearing and Grubbing: All building and pavement areas and all surfaces to receive compacted fill should be cleared of vegetation, debris, and other unsuitable materials. All such material should be disposed of off-site.

All undocumented artificial fill and loose native soil within the grading limits should be completely removed. Such material is suitable for use as compacted fill as recommended herein.

2. Preparation of Surfaces to Receive Compacted Fill: All surfaces to receive compacted fill should be reviewed by a geologist or engineer from this firm prior

Project No. S168-193, September 2024 9 of 11 Inland Foundation Engineering, Inc.

to processing. If roots or other deleterious materials are encountered or if the exposed excavation bottom is loose or unstable, additional over-excavation may be required until satisfactory conditions are encountered. Upon approval, surfaces to receive fill should be scarified to a minimum depth of eight inches, brought to near optimum moisture content, and compacted to a minimum of 90 percent relative compaction.

3. Placement of Compacted Fill: Fill materials consisting of on-site soil or approved imported granular soil should be spread in shallow lifts and compacted at near optimum moisture content to a minimum of 90 percent relative compaction, based on ASTM D1557. Fill placed within 10 feet of finish grade should not contain any particles larger than 12 inches (boulders). Boulder-size particles should be disposed of off-site or in designated rock disposal fill areas.

4. Import Soil: All proposed import soil should be tested prior to placement on the site to verify that it is not corrosive or expansive. Recommended import soil criteria are shown in the following Table 5.

Table 5: Recommended Import Soil Criteria

Sieve Size Recommended Criteria

Percent Passing 3-Inch Sieve 100

Percent Passing No. 4 Sieve 85 – 100

Percent Passing No. 200 Sieve 15 – 40

Plasticity Index Less than 15

Expansion Index (ASTM D4829) 20 or less (very low)

Organic content Less than 1 percent by weight

Sulfates < 1,000 ppm

Min. Resistivity > 10,000 ohm-cm

5. Preparation of Building Areas: All proposed building areas should be over-excavated to a depth of at least 8 feet below existing grade or 24 inches below the bottom of the deepest footing, whichever is greater. Building area excavation should extend laterally for at least 5 feet outside of exterior building foundation lines. Following excavation, the exposed soil should be evaluated by this firm to verify it is suitable to receive compacted fill. The removed soil should be placed and compacted as recommended above. Soil within 5 feet of finish grade and within 2 feet of footing and slab bottoms should not contain any particles larger than 3 inches (cobbles).

shernandez Highlight depth of at least 8 feet below existing grade or 24 inches below the bottom of the deepest footing, whichever is greater. Building area excavation should extend laterally for at least 5 feet outside of exterior building foundation lines.

Project No. S168-193, September 2024 10 of 11 Inland Foundation Engineering, Inc.

6. Preparation of Paving Areas: During final grading and immediately prior to the placement of aggregate base, all surfaces to receive asphalt concrete or Portland cement concrete paving should be processed to remove all particles larger than

3 inches within 12 inches of subgrade. The upper 12 inches of pavement subgrade should be tested to assure compaction for a depth of at least 12 inches. Compaction within proposed pavement areas should be to a minimum of

95 percent relative compaction for both the subgrade and base course.

7. Utility Trench Backfill: Utility trench backfill consisting of the on-site soil types should be placed by mechanical compaction to a minimum of 90 percent relative compaction. This is with the exception of the upper 12 inches under pavement areas where the minimum relative compaction should be 95 percent. Jetting of the native soil is not recommended.

8. Testing and Observation: During grading, tests and observations should be performed by a representative of this firm to verify that the grading is performed per the project specifications. Density testing should be performed per the current ASTM D1556 or ASTM D6938 test methods. The minimum acceptable degree of compaction should be 90 percent of the maximum dry density, based on ASTM D1557, except where superseded by more stringent requirements, such as beneath pavement. Where testing indicates insufficient density, additional compactive effort should be applied until retesting indicates satisfactory compaction.

LIMITATIONS

The findings and recommendations presented in this report are based on the soil conditions encountered at the boring locations. Should conditions be encountered during grading that appear to be different than those indicated by this report, this office should be notified.

This report was prepared for STK Architecture, Inc. for their use in the design of the proposed Fire Station No. 227. This report may only be used by STK Architecture, Inc for this purpose. The use of this report by parties or for other purposes is not authorized without written permission by Inland Foundation Engineering, Inc. Inland Foundation

Engineering, Inc. will not be liable for any projects connected with the unauthorized use of this report.

The recommendations of this report are considered to be preliminary. The final design parameters may only be determined or confirmed at the completion of site grading on the basis of observations made during the site grading operation. To this extent, this report is not considered to be complete until the completion of both the design process and the site preparation.

Project No. S168-193, September 2024 11 of 11 Inland Foundation Engineering, Inc.

The information in this report represents professional opinions that have been developed using that degree of care and skill ordinarily exercised, under similar circumstances, by reputable geotechnical consultants practicing in this or similar localities. No warranty, express or implied, is made.

REFERENCES

American Concrete Institute 318 (2019), Building Code Requirements for Structural

Concrete.

American Society of Civil Engineers (ASCE), 2017, Minimum Design Loads and

Associated Criteria for Buildings and other Structures, ASCE Standard 7-16, 889pp.

California Building Standards Commission, 2022, California Building Code (CBC), California Code of Regulations, Title 24, Part 2, Volume 2.

County of San Bernardino (2013), Areawide Stormwater Program, Technical Guidance

Document for Water Quality Management Plans

Terra Geosciences, Geologic Hazards Report, San Bernardino County Fire Station 227, NWC of 38th Street and Genevieve Avenue, City of San Bernardino, California, Project

No. 244073-1, dated July 20, 2024

United States Geologic Survey, San Bernardino North 7.5’ Quadrangle (2021)

APPENDIX A –

Site Exploration

Project No. S168-193, September 2024 A-1 Inland Foundation Engineering, Inc.

APPENDIX A

SITE EXPLORATION

Four exploratory borings were drilled at the approximate locations shown on Figure A-7.

The materials encountered during drilling were logged by a staff geologist. Boring logs are included with this report as Figures A-3 through A-6.

Representative undisturbed soil samples were obtained within the borings by driving a modified California split spoon sampler and thin-walled steel penetration sampler.

Representative bulk soil samples were also obtained from the excavation cuttings.

Samples were placed in moisture sealed containers and transported to our laboratory for further testing and evaluation. Laboratory tests results are discussed and included in Appendix B.

UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM D2487)

PRIMARY DIVISIONS GROUP SYMBOLS SECONDARY DIVISIONS

C O

A R

S E

G R

A

IN

E D

S O

IL

S

M O

R E

T H

A N

H A

L F

O F

M A

T E

R

IA

L S

I S

L A

R G

E R

T H

A N

S

IE

V

E S

IZ

G

A V

E L

R E

T H

A N

L F

O F

C O

A R

F

A C

T

IO

N I

R G

E R

T H

S

IE

V

CLEAN

GRAVELS

(LESS

THAN) 5%

FINES

GW

WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES, LITTLE OR NO FINES

GP

POORLY GRADED GRAVELS OR GRAVEL-SAND MIXTURES, LITTLE OR NO

GRAVEL

WITH

GM

SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES

GC

CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES

A

N D

R E

T H

L F

O F

C O

A R

A C

T

IO

N

A L L E

R T

H

S

IE

V

CLEAN

SANDS

(LESS

THAN) 5%

SW

WELL GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES

SP

POORLY GRADED SANDS OR GRAVELLY SANDS, LITTLE OR NO FINES

SANDS

WITH

SM

SILTY SANDS, SAND-SILT MIXTURES

SC

CLAYEY SANDS, SAND-CLAY MIXTURES

IN

E G

R A

IN

E

D S

O

R E

T H

A N

H A

L F

O F

M A

T E

R

IA

L S

A L L E

R T

H

S

IE

V

E S

IZ

T S

A

C

A

Y

IQ

U

ID

L

IM

IT

IS

A N

ML

INORGANIC SILTS, VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY

FINE SANDS

CL

INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS,

SANDY CLAYS, SILTY CLAYS, LEAN CLAYS

OL

ORGANIC SILTS AND ORGANIC SILT-CLAYS OF LOW PLASTICITY

IL

T S

A

C

A

Y

IQ

U

ID

L

IM

IT

IS

G

R E

A T

A N

MH

INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SANDS OR

SILTS, ELASTIC SILTS

CH

INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS

OH

ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS

HIGHLY ORGANIC SOILS PT

PEAT, MUCK AND OTHER HIGHLY ORGANIC SOILS

Y

P

IC

A L F

O R

M A

T

IO

N

T E

R

IA

SANDSTONES SS

SILTSTONES SH

CLAYSTONES CS

LIMESTONES LS

SHALE SL

CONSISTENCY CRITERIA BASES ON FIELD TESTS

RELATIVE DENSITY – COARSE – GRAIN SOIL

CONSISTENCY –

FINE-GRAIN SOIL

TORVANE

POCKET **

PENETROMETER

RELATIVE

DENSITY

SPT *

(# BLOWS/FT)

RELATIVE

DENSITY

CONSISTENCY

SPT*

(# BLOWS/FT)

UNDRAINED

SHEAR

STRENGTH

(tsf)

UNCONFINED

COMPRESSIVE

STRENGTH (tsf)

VERY LOOSE <4 0-15 Very Soft <2 <0.13 <0.25

LOOSE 4-10 15-35 Soft 2-4 0.13-0.25 0.25-0.5

MEDIUM

DENSE

10-30 35-65

Medium Stiff 4-8 0.25-0.5 0.5-1.0

DENSE 30-50 65-85 Stiff 8-15 0.5-1.0 1.0-2.0

VERY DENSE >50 85-100

Very Stiff 15-30 1.0-2.0 2.0-4.0

Hard >30 >2.0 >4.0

MOISTURE CONTENT CEMENTATION

DESCRIPTION FIELD TEST

DESCRIPTION FIELD TEST

DRY Absence of moisture, dusty, dry to the touch Weakly Crumbled or breaks with handling or slight finger pressure

MOIST Damp but no visible water Moderately Crumbles or breaks with considerable finger pressure WET Visible free water, usually soil is below water table Strongly Will not crumble or break with finger pressure

EXPLANATION OF LOGS

A-2

* NUMBER OF BLOWS

OF 140 POUND

HAMMER FALLING

30 INCHES TO DRIVE A

2 INCH O.D.

(1 3/8 INCH I.D.) SPLIT

BARREL SAMPLER

(ASTM -1586 STANDARD

PENETRATION TEST)

** UNCONFINED

COMPRESSIVE

STRENGTH IN

TONS/SQ.FT. READ

FROM POCKET

PENETROMETER

SP-

SM

SM

SW-

SM

SC-

SM

SW-

SM

SM

SW-

SM

50/3"

AU

SS

AU

SS

SS

AU

SS

SS

SS

SPT

SPT

GRASS,

SILTY SAND, with trace gravel, fine to very coarse, very dark grayish-brown (10YR 3/2), moist, medium dense.

SAND with SILT and GRAVEL, fine to very coarse, gray-brown (2.5Y 5/2), slightly moist, medium dense.

SILTY SAND, with trace gravel, fine to very coarse, very dark grayish-brown (10YR 3/2), moist, medium dense.

SAND with SILT and GRAVEL, fine to coarse, grayish-brown (10YR 5/2), slightly moist, medium dense.

SILTY, CLAYEY SAND, very fine to fine, olive-brown (2.5Y 4/4), moist, medium dense.

SAND with SILT and GRAVEL, fine to very coarse, light olive-brown (2.5Y 5/4), slightly moist, medium dense.

SILTY SAND, with trace gravel, very fine to fine, grayish-brown (2.5Y 5/2), moist, dense.

SAND with SILT and GRAVEL, fine to very coarse, gray-brown (2.5Y 5/2), slightly moist, medium dense.

COBBLES and BOULDERS, End of boring at 30.8 feet. No groundwater encountered. Backfilled with native soil.

U .S

.C .S

G R

A P

H

IC

LO

G

LOG OF BORING B-01

B

LO

W C

O U

N T

S /6

S A

M P

LE

T

Y P

E

M O

IS

T

U R

E

D R

Y U

N

IT

W T

(p cf

SUMMARY OF SUBSURFACE CONDITIONS

B U

LK

S

A M

P

LE

This summary applies only at the location of the boring and at the time of drilling.

Subsurface conditions may differ at other locations and may change at this location with the passage of time. The data presented is a simplification of actual conditions encountered and is representative of interpretations made during drilling. Contrasting data derived from laboratory analysis may not be reflected in these representations.

D R

IV

E

S A

M P

LE

D E

P T

H (f t)

DRILLING RIG Mobile B-61

DRILLING METHOD Rotary Auger

LOGGED BY FWC

HAMMER TYPE Auto-Trip

HAMMER WEIGHT 140-lb.

HAMMER DROP 30-inches

BORING DIAMETER 8-inches

DATE DRILLED 7/11/24

GROUND ELEVATION +/-

Inland Foundation Engineering, Inc.

PROJECT NUMBER S168-193

. San Bernardino, CA

PROJECT LOCATION NWC Genevieve St. & W. 38th St.

PROJECT NAME Fire Station #227

CLIENT STK Architecture, Inc. FIGURE NO.

A-3

IF

E

B O

R

IN

G

G

IN

T S

T D

U S

L A

B .G

D T

/1 9/

4:

P

S

8\

S

8-

S

B F

S

\G

IN

T

.G P

J

SP-

SM

SW-

SM

GW

50/5"

50/5"

SS

SS

SS

SS

SS

SS

SPT

SPT

SPT

SPT

SPT

SPT

GRASS,

SILTY SAND, with trace gravel, fine to medium, dark grayish-brown (10YR 5/2), moist, loose.

SILTY SAND, with trace gravel, fine to medium, light olive-brown (2.5Y 5/2), slightly moist, medium dense.

SAND with SILT, fine to coarse, dark grayish-brown (10YR 4/2), moist, loose to medium dense.

SAND with SILT and GRAVEL, fine to medium, grayish-brown (10YR 5/2), slightly moist, medium dense.

GRAVEL with SAND, fine to coarse, olive-gray (5Y 4/2), moist, dense.

SAND with SILT and GRAVEL, fine to medium, olive-gray (5Y 5/2), slightly moist, dense.

End of boring at 50.5 feet.