ATT-BGCSA-MEMO-CSA 20 Joshua Tree - Sunburst Park - Section H - Exhibits 8 of 8.pdf

SECTION H

EXHIBITS

COUNTY SERVICE AREA 20

JOSHUA TREE

PARK IMPROVEMENTS AT

SUNBURST PARK AND

COMMUNITY PARK PROJECT

FOR

COUNTY SERVICE AREA (CSA) 20

JOSHUA TREE, CALIFORNIA

Substitution Request Form-1

SUBSTITUTION REQUEST FORM DATE: ____________________

TO: _______________________________________________________________________

ATTENTION: _______________________________________________________________________

PROJECT: _______________________________________________________________________

We hereby submit for your consideration the following product as a substitute for the specified product for the above project:

Section No. Paragraph Specified Product

Proposed Substitution: _____________________________________________

Product Data:

Attach complete technical data for proposed substitution.

Include complete information on changes to Contract Documents which proposed substitution will require for its proper installation.

Samples:

[ ] Attached [ ] Will be furnished upon request

Does the substitution affect dimensions shown on drawings?

[ ] No [ ] Yes (explain on attachment)

Adjustment to the Contract Sum or Schedule

Sum __________________________________________________________________________

Schedule __________________________________________________________________________

Estimated Cost of engineering, design, or agency fees:

Sum __________________________________________________________________________

Effects of proposed substitution on other trades:

San Bernardino County Public Works - Special District CSA 20 Joshua Tree Park Improvements at Sunburst Park and Community Park Project

Project No.: 30.30.0176

J6898 Text Box John Hernandez , Project Manager

J6898 Text Box San Bernardino County Public Works - Special District

J6853 Text Box CSA 20 Joshua Tree Park Improvements at Sunburst Park and Community Park Project

E4061 Snapshot

Differences between proposed substitution and specified product:

Other projects where the proposed substitution was successful.

Manufacturer’s warranties of the proposed and specified products are:

[ ] Same [ ] Different (explain on attachment)

Substitution Request Form-

San Bernardino County Public Works - Special District CSA 20 Joshua Tree Park Improvements at Sunburst Park and Community Park Project

Project No.: 30.30.0176

Maintenance services and spare parts are available for proposed product from:

Previous installations where proposed product may be seen:

Project: ______________________________ Project: _______________________________

Owner: ______________________________ Owner: ________________________________

Architect: ____________________________ Architect: ______________________________

Date Installed: ________________________ Date Installed: __________________________

Cost savings to be realized by Owner, if proposed substitution is accepted:

Change to Contract Time, if proposed substitution is accepted:

[ ] No Change [ ] Add ____ days [ ] Deduct ____ days

Substitution Request Form-

San Bernardino County Public Works - Special District CSA 20 Joshua Tree Park Improvements at Sunburst Park and Community Park Project

Project No.: 30.30.0176

By submitting this substitution request, Contractor represents that he has read and agrees to the provisions of Section 016000.

Submitted by Contractor:

Signature

Firm

For Use By Owner:

Based on the information supplied by the Contractor, the Owner has reviewed the proposed substitution on the basis of design concept of the Work and conformance with information given in Contract Documents.

[ ] Accepted [ ] Accepted as Noted [ ] Rejected

[ ] Submit Additional Information: ______________________________________________

By: ____________________________________________ Date: ____________________

GEOTECHNICAL INVESTIGATION

PROPOSED SUNBURST PARK AND

JOSHUA TREE PRESCHOOL IMPROVEMENTS

JOSHUA TREE, CALIFORNIA

OCTOBER 31, 2024

PROJECT NO. T3079-22-01

PREPARED FOR:

Albert A. Webb Associates, Inc Riverside, California

Exhibit B

78-075 Main Street #G-203 ■ La Quinta, California 92253 ■ Telephone 760.565.2002 ■ www.geoconinc.com

Project No. T3079-22-01 October 31, 2024

Albert A. Webb Associates, Inc.

3788 McCray Street Riverside, California 92506

Attention: Mr. Jeff Hutchins, PLA

Subject: GEOTECHNICAL INVESTIGATION REPORT

PROPOSED SUNBURST PARK AND JOSHUA TREE PRESCHOOL IMPROVEMENTS

JOSHUA TREE, SAN BERNARDINO COUNTY, CALIFORNIA

Mr. Hutchins:

In accordance with your authorization of our proposal dated May 3, 2024, we have performed a geotechnical investigation for the proposed Community Park and Joshua Tree Preschool improvements at Sunburst Park, in the unincorporated town of Joshua Tree, San Bernardino County, California. The accompanying report presents the findings of our study and our conclusions and recommendations pertaining to the geotechnical aspects of proposed design and construction. Based on the results of our investigation, it is our opinion that the site can be developed as proposed, provided the recommendations in this report are followed and implemented during design and construction.

If you have any questions regarding this report, or if we may be of further service, please contact the undersigned.

Sincerely, GEOCON WEST, INC.

Karina Dorawala Lisa Battiato, CEG Staff Geologist CEG 2316

Ashleigh Love Harry Derkalousdian

PE 79019 PE 79694

(email) Addressee

Proposed Pickleball Courts, Yucca Valley

Geotechnical Investigation

TABLE OF CONTENTS

1. PURPOSE AND SCOPE

2. SITE AND PROJECT DESCRIPTION

3. GEOLOGIC SETTING

4. SOIL AND GEOLOGIC CONDITIONS

4.1 Undocumented Artificial Fill (afu)

4.2 Alluvium (Qa)

5. GROUNDWATER

6. GEOLOGIC HAZARDS

6.1 Surface Fault Rupture

6.2 Seismicity

6.3 Seismic Design Criteria

6.4 Liquefaction Potential

6.5 Slope Stability

6.6 Earthquake-Induced Flooding

6.7 Tsunamis, Seiches, and Flooding

6.8 Oil Fields & Methane Potential

6.9 Subsidence

7. SITE INFILTRATION

8. CONCLUSIONS AND RECOMMENDATIONS

8.1 General

8.2 Soil and Excavation Characteristics

8.3 Minimum Resistivity, pH, and Water-Soluble Chloride and Sulfate

8.4 Grading

8.5 Earthwork Grading Factors

8.6 Conventional Foundation Design

8.7 Deepened Foundations

8.8 Pile Foundation Installation

8.9 Miscellaneous Foundations

8.10 Lateral Design

8.11 Exterior Concrete Slabs-on-Grade

8.12 Preliminary Pavement Recommendations

8.13 Temporary Excavations

8.14 Surface Drainage

8.15 Plan Review

LIMITATIONS AND UNIFORMITY OF CONDITIONS

LIST OF REFERENCES

Sunburst Park Improvements, Joshua Tree

Proposed Pickleball Courts, Yucca Valley

TABLE OF CONTENTS (CONTINUED)

MAPS AND ILLUSTRATIONS

Figure 1, Vicinity Map Figure 2, Geologic Map and Site Plan

APPENDIX A

FIELD INVESTIGATION

Figures A-1 and A-6, Boring Logs Figures A-7 and A-8, Percolation Data Sheets

APPENDIX B

LABORATORY TESTING

Figures B-1 and B-2, Compaction Characteristics

Figure B-3, Corrosivity Test Results

Figures B-4 and B-5, Grain Size Distribution

Figures B-6 and B-7, Direct Shear Test Results

Project No. T3079-22-01 - 1 - October 31, 2024

GEOTECHNICAL INVESTIGATION

1. PURPOSE AND SCOPE

This report presents the results of our geotechnical investigation for the proposed improvements at the Community Center and Joshua Tree Preschool located at Sunburst Park in the unincorporated area of Joshua Tree, San Bernardino County, California (see Vicinity Map, Figure 1). The purpose of the investigation was to evaluate subsurface soil and geologic conditions underlying the site and, based on conditions encountered, to provide conclusions and recommendations pertaining to the geotechnical aspects of design and construction.

The scope of this investigation included a site reconnaissance, field exploration, percolation testing, laboratory testing, engineering analysis, and the preparation of this report. The site was explored on

September 24, 2024, by excavating six geotechnical borings to a maximum depth of 5 feet utilizing a hand auger. Percolation tests within two of these borings were performed on September 24, 2024. The approximate locations of the borings are depicted on the Geologic Map and Site Plan (see Figure 2).

A detailed discussion of the field investigation, including the boring logs and percolation test results, is presented in Appendix A. Laboratory tests were performed on selected soil samples obtained during the investigation to determine pertinent physical and chemical soil properties. Appendix B presents a summary of the laboratory test results.

The recommendations presented herein are based on analysis of the data obtained during the investigation and our experience with similar soil and geologic conditions. References reviewed to prepare this report are provided in the List of References section.

If project details vary significantly from those described herein, Geocon should be contacted to determine the necessity for review and possible revision of this report.

2. SITE AND PROJECT DESCRIPTION

The subject site is located within Sunburst Park at 6171 Sunburst Street, in the unincorporated area of

Joshua Tree, San Bernardino County, California. Sunburst Park is part of San Bernardino County’s

County Service Area 20 Parks and is home to the Joshua Tree Community Center and Joshua Tree

Preschool. The site is a 15.6-acre community park with a Community Center including basketball courts, tennis courts, picnic facilities, playgrounds, a restroom building, and Joshua Tree Preschool.

Project No. T3079-22-01 - 2 - October 31, 2024

The park is l-shaped and is bound by Joshua Tree RV & Campground to the southwest, Sunburst Street to the west, vacant land containing a natural stream channel to the north, a Joshua Basin Water District property containing water basins to the east, and Quail Springs Village apartment complex to the south.

The site is relatively flat with elevations ranging between 2,700 feet above mean seal level (MSL) at the south and west ends of the site and slopes gently to the northeast to about 2,685 feet MSL.

Based on a Landscape Concept dated August 2024, prepared by the Client, the improvements include three new playground sets, a new Ninja Warrior Course, a pump track, resurfacing of two existing tennis courts, new sidewalks, picnic tables, and associated park improvements.

Due to the preliminary nature of the design at this time, loads were not made available. It is estimated that column loads may be up to 50 kips.

Once the design phase proceeds to a more finalized plan, the recommendations within this report should be reviewed and revised, if necessary. Any changes in the design, location or elevation of the improvements, as outlined in this report, should be reviewed by this office. Geocon should be contacted to determine the necessity for review and possible revision of this report.

3. GEOLOGIC SETTING

Joshua Tree is located within the Mojave Desert Geomorphic Province (MDP). The MDP is bounded on the north by the east-west, left lateral, Garlock fault and Basin and Range and Sierra Nevada Provinces, and the south by the northwest trending, right lateral, San Andreas fault and the Colorado Desert and

Transverse Range Provinces. It is a broad interior region of isolated mountain ranges separated by expanses of desert plains. Joshua Tree is located within a broad desert valley between the Little San

Bernardino Mountains to the south and the eastern end of the San Bernardino Mountains to the north.

The Pinto Mountain and Morongo Valley faults trend generally east-west just north of the site.

4. SOIL AND GEOLOGIC CONDITIONS

Based on published geologic maps of the area, the site is underlain by undocumented artificial fill and

Pleistocene age alluvial deposits (Dibblee, 1967; California Geological Survey, 2012). Younger

(Holocene) and Older (Pleistocene) alluvial deposits are geologically mapped in the vicinity of the site.

We encountered younger alluvium in our borings and expect that older alluvium underlies the site at depth. Detailed stratigraphic profiles of the materials encountered at the site are provided on the boring log in Appendix A.

Project No. T3079-22-01 - 3 - October 31, 2024

4.1 Undocumented Artificial Fill (afu)

Undocumented artificial fill was encountered in our field explorations to depths of 1 foot in Borings

HA-1, HA-2, and HA-4. The fill consists of light yellowish brown, poorly graded and well graded sand with silt. The fill is dry to damp and loose to medium dense.

4.2 Alluvium (Qa)

Holocene-age alluvial deposits were encountered in our field explorations to depths of 3 to 5 feet in

Borings HA-1 through HA-6. The alluvium consists of light yellow brown to light brown, poorly graded sand with lesser amounts of well graded sand. The alluvium is dry to moist, and very loose to medium dense.

5. GROUNDWATER

The California Department of Water Resources indicates the closest groundwater monitoring well to the site is 01N06E25K001S. The highest groundwater level in the area is approximately 392 feet beneath the existing ground surface. Groundwater information presented in this document is generated from data collected in the late 1969 to early 1971.

Static groundwater was not encountered in our borings to the maximum explored depth of 5 feet.

Considering the lack of static groundwater encountered in our boring and the depth of the proposed construction, it is not anticipated that static groundwater will be encountered during construction nor have an adverse impact on the proposed project. However, it is not uncommon for groundwater levels to vary seasonally or for groundwater seepage conditions to develop where none previously existed, especially in impermeable fine-grained soils which are heavily irrigated or after seasonal rainfall.

In addition, recent requirements for storm water infiltration could result in shallower seepage conditions in the immediate site vicinity. Proper surface drainage of irrigation and precipitation will be critical for future performance of the project. Recommendations for drainage are provided in the

Surface Drainage section of this report.

Project No. T3079-22-01 - 4 - October 31, 2024

6. GEOLOGIC HAZARDS

6.1 Surface Fault Rupture

The numerous faults in Southern California include Holocene-active, pre-Holocene, and inactive faults.

The criteria for these major groups are based on criteria developed by the California Geological Survey

(CGS, formerly known as CDMG) for the Alquist-Priolo Earthquake Fault Zone Program (CGS, 2018).

By definition, a Holocene-active fault is one that has had surface displacement within Holocene time

(about the last 11,700 years). A pre-Holocene fault has demonstrated surface displacement during

Quaternary time (approximately the last 1.6 million years) but has had no known Holocene movement.

Faults that have not moved in the last 1.6 million years are considered inactive.

The site is not within a currently established State of California or San Bernardino County Earthquake

Fault Zone for surface fault rupture hazards. No active or potentially active faults with the potential for surface fault rupture are known to pass directly beneath the site. Therefore, the potential for surface rupture due to faulting occurring beneath the site during the design life of the proposed development is considered low. However, the site is located in the seismically active Southern California region and could be subjected to moderate to strong ground shaking in the event of an earthquake on one of the many active Southern California faults. The faults within a 50-mile radius of the site are shown on the following Regional Fault Map.

REGIONAL FAULT MAP

Reference Map: Jennings & Bryant, 2010

Project No. T3079-22-01 - 5 - October 31, 2024

The closest surface trace of a Holocene-active fault to the site is the Pinto Mountain Fault located approximately 528 feet to the northwest (Bryant, 2010). Other nearby active faults are the Copper

Mountain fault located approximately 5.87 miles northeast, and the Johnson Valley fault located approximately 7 miles to the northwest, Morongo Valley fault approximately 10 miles southwest of the site (Dibblee, 1967). The Northern Branch of the San Andreas Fault Zone is located approximately

17 miles southwest of the site.

6.2 Seismicity

As with all of Southern California, the site has experienced historic earthquakes from various regional faults. The seismicity of the region surrounding the site was formulated based on research of an electronic database of earthquake data. A partial list of moderate to major magnitude earthquakes that have occurred in the Southern California area within the last 100 years is included in the following table.

LIST OF HISTORIC EARTHQUAKES

Earthquake Date of Earthquake Magnitude

Distance to Epicenter

(Miles)

Direction to Epicenter (Oldest to Youngest)

Long Beach March 10, 1933 6.4 102 WSW

Tehachapi July 21, 1952 7.5 165 WNW

San Fernando February 9, 1971 6.6 121 W

Whittier Narrows October 1, 1987 5.9 101 W

Sierra Madre June 28, 1991 5.8 97 W

Landers June 28, 1992 7.3 9 WNW

Big Bear June 28, 1992 6.4 30 W

Northridge January 17, 1994 6.7 127 W

Hector Mine October 16, 1999 7.1 32 N

Ridgecrest July 5, 2019 7.1 134 NW

Long Beach March 10, 1933 6.4 102 WSW

The site could be subjected to strong ground shaking in the event of an earthquake. However, this hazard is common in Southern California and the effects of ground shaking can be mitigated if the proposed structures are designed and constructed in conformance with current building codes and engineering practices.

Project No. T3079-22-01 - 6 - October 31, 2024

6.3 Seismic Design Criteria

The following table summarizes site-specific design criteria obtained from the 2022 California Building

Code (CBC; Based on the 2021 International Building Code [IBC] and ASCE 7-16), Chapter 16 Structural

Design, Section 1613 Earthquake Loads. The data was calculated using the online application Seismic

Design Maps, provided by Structural Engineers Association of California (SEAOC). The short spectral response uses a period of 0.2 second. We evaluated the Site Class based on the discussion in Section

1613.2.2 of the 2022 CBC and Table 20.3-1 of ASCE 7-16. The values presented on the following page are for the risk-targeted maximum considered earthquake (MCER).

2022 CBC SEISMIC DESIGN PARAMETERS

Parameter Value 2022 CBC Reference

Site Class D Section 1613.2.2

MCER Ground Motion Spectral Response

Acceleration – Class B (short), SS 2.045g Figure 1613.2.1(1)

MCER Ground Motion Spectral Response

Acceleration – Class B (1 sec), S1 0.738g Figure 1613.2.1(2)

Site Coefficient, FA 1 Table 1613.2.3(1)

Site Coefficient, FV 1.7* Table 1613.2.3(2)

Site Class Modified MCER Spectral

Response Acceleration (short), SMS 2.045g Section 1613.2.3 (Eqn 16-36)

Site Class Modified MCER Spectral

Response Acceleration – (1 sec), SM1 1.255g* Section 1613.2.3 (Eqn 16-37)

5% Damped Design

Spectral Response Acceleration (short), SDS

1.363g Section 1613.2.4 (Eqn 16-38)

5% Damped Design

Spectral Response Acceleration (1 sec), SD1

0.837g* Section 1613.2.4 (Eqn 16-39)

*Per Supplement 3 of ASCE 7-16, a ground motion hazard analysis (GMHA) shall be performed for projects on Site

Class “D” sites with 1-second spectral acceleration (S1) greater than or equal to 0.2g, which is true for this site.

However, Supplement 3 of ASCE 7-16 provides an exception stating that that the GMHA may be waived provided that the parameter SM1 is increased by 50% for all applications of SM1. The values for parameters SM1 and SD1 presented above have not been increased in accordance with Supplement 3 of ASCE 7-16.

Project No. T3079-22-01 - 7 - October 31, 2024

The table below presents the mapped maximum considered geometric mean (MCEG) seismic design parameters for projects located in Seismic Design Categories of D through F in accordance with

ASCE 7-16.

ASCE 7-16 PEAK GROUND ACCELERATION

Parameter Value ASCE 7-16 Reference

Mapped MCEG Peak Ground Acceleration, PGA 0.874g Figure 22-9

Site Coefficient, FPGA 1.1 Table 11.8-1

Site Class Modified MCEG Peak Ground

Acceleration, PGAM 0.961g Section 11.8.3 (Eqn 11.8-1)

The Maximum Considered Earthquake Ground Motion (MCE) is the level of ground motion that has a

2 percent chance of exceedance in 50 years, with a statistical return period of 2,475 years. According to the 2022 California Building Code and ASCE 7-16, the MCE is to be utilized for the evaluation of liquefaction, lateral spreading, seismic settlements, and it is our understanding that the intent of the

Building code is to maintain “Life Safety” during an MCE event. The Design Earthquake Ground Motion

(DE) is the level of ground motion that has a 10 percent chance of exceedance in 50 years, with a statistical return period of 475 years.

Deaggregation of the MCE peak ground acceleration was performed using the USGS online Unified

Hazard Tool, 2014 Conterminous U.S. Dynamic edition (v4.2.0). The result of the deaggregation analysis indicates that the predominant earthquake contributing to the MCE peak ground acceleration is characterized as a 6.51 magnitude event occurring at a hypocentral distance of 6.2 kilometers from the site.

Conformance to the criteria in the above tables for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur if a large earthquake occurs. The primary goal of seismic design is to protect life, not to avoid all damage, since such design may be economically prohibitive.

6.4 Liquefaction Potential

A review of the San Bernadino County Land Use Service (SBCLUS, 2009) indicates that the site is located in an area identified as having a low potential for liquefaction. Additionally, liquefaction is not a design consideration for the development of the proposed improvements.

Project No. T3079-22-01 - 8 - October 31, 2024

6.5 Slope Stability

The topography at the site is relatively level and the topography in the vicinity of the site slopes gently to the northeast. The site is not located within an area identified as having a potential for seismic slope instability (SBCP 2024; CGS, 2014). There are no known landslides near the site, nor is the site in the path of any known or potential landslides. Therefore, the potential for slope stability hazards to adversely affect the proposed development is considered low.

6.6 Earthquake-Induced Flooding

Earthquake-induced flooding is inundation caused by failure of dams or other water-retaining structures due to earthquakes. The San Bernadino Countywide Plan (SBCP, 2024) indicates that the site is not located within a potential inundation area. Therefore, the potential for inundation at the site as a result of an earthquake-induced dam failure is considered low.

6.7 Tsunamis, Seiches, and Flooding

The site is not located within a coastal area. Therefore, tsunamis are not considered a significant hazard at the site.

Seiches are large waves generated in enclosed bodies of water in response to ground shaking. No major water-retaining structures are located immediately up gradient from the project site. Therefore, flooding resulting from a seismic-induced seiche is considered unlikely.

The site is within a FEMA 100-year flood zone as defined by the Federal Emergency Management

Agency (SBCP, 2024; FEMA, 2022). FEMA 100-year flood zone has a 1% annual minimal potential for flooding (FEMA, 2024).

6.8 Oil Fields & Methane Potential

Based on a review of the California Geologic Energy Management Division (CalGEM) Well Finder

Website, the site is not located within an oil field and oil or gas wells are not documented in the immediate site vicinity (CalGEM, 2024). However, due to the voluntary nature of record reporting by the oil well drilling companies, wells may be improperly located or not documented on the location map and undocumented wells could be encountered during construction. Any wells encountered during construction will need to be properly abandoned in accordance with the current requirements of the CalGEM.

Project No. T3079-22-01 - 9 - October 31, 2024

The site is not located within the boundaries of a designated Methane Zone or Methane Buffer Zone

(CalGEM, 2024). Since the site is not located within the boundaries of a known oil field, the potential for the presence of methane or other volatile gases at the site is considered low. However, should it be determined that a methane study is required for the proposed development it is recommended that a qualified methane consultant be retained to perform the study and provide mitigation measures as necessary.

6.9 Subsidence

Subsidence occurs when a large portion of land is displaced vertically, usually due to the withdrawal of groundwater, oil, or natural gas. Soils that are particularly subject to subsidence include those with high silt or clay content. The site is not located within an area of known ground subsidence. No large-scale extraction of groundwater, gas, oil, or geothermal energy is occurring or planned at the site or in the general site vicinity. There appears to be little or no potential for ground subsidence due to withdrawal of fluids or gases at the site.

7. SITE INFILTRATION

Percolation testing was performed in general accordance with the San Bernardino County Stormwater

Program, Technical Guidance Document for Water Quality Management Plans (WQMP), for percolation testing and calculating infiltration rates. The percolation test locations are depicted on the Geologic

Map and Site Plan, Figure 2.

Percolation test borings, HA-1 and HA-2, were excavated to depths of 5 feet. The borings were excavated using a hand auger. A perforated pipe with a filter sock was placed within the borings.

The boring logs and percolation data are presented in Appendix A. A summary of the calculated infiltration rates are provided in the following table.

CALCULATED INFILTRATION RATES FROM PERCOLATION TEST RESULTS

Parameter HA-1 HA-2

Depth (feet) 5 5

Test Type Sandy Sandy

Change in head over time: ∆H (inches) 9.6 16.8

Average head: Havg (inches) 9.6 18.2

Time Interval: ∆t (minutes) 10 10

Radius of test hole: r (inches) 4.0 4.0

Calculated Infiltration Rate: It (inches/hour) 11.08 16.19

Project No. T3079-22-01 - 10 - October 31, 2024

The results of the percolation testing indicate that the calculated infiltration rates at the locations tested are 11.08 (HA-1) and 16.19 (HA-2) inches per hour. The WQMP requires a safety factor be applied to the calculated infiltration rates shown in the previous table.

The in-situ field percolation tests performed provide short-term infiltration rates. Where appropriate, the short-term infiltration rates shall be converted to long-term infiltration rates using reduction factors depending on the degree of infiltration quality, maintenance access and frequency, site variability, subsurface stratigraphy variation, and other factors. The small-scale percolation testing cannot model the complexity of the effect of interbedded layers of different soil composition, and our test results should be considered only as index values of infiltration rates.

Although not evaluated during this investigation, due to the potential presence of hydrocompressive soils, the proposed infiltration system should be located a minimum distance of 15 feet from site improvements to reduce the potential for induced settlements to adversely impact the proposed improvements. Provided these offsets are maintained, there is a very low potential for infiltration-related soil settlement to adversely affect existing structures; some settlement may occur locally within the area of the infiltration system.

The civil engineer should also evaluate the impact on surface drainage should some soil settlement occur locally within the area of the infiltration system. It is suggested that flexible connections be utilized between the storm drainpipes and infiltration chambers.

Project No. T3079-22-01 - 11 - October 31, 2024

8. CONCLUSIONS AND RECOMMENDATIONS

8.1 General

8.1.1 It is our opinion that neither soil nor geologic conditions were encountered during the investigation that would preclude the construction of the proposed improvements provided the recommendations presented herein are followed and implemented during design and construction.

8.1.2 The upper 5 feet of artificial fill and alluvium encountered at the site is dry to damp, and very loose to medium dense. As a minimum, it is recommended that the upper 4 feet of existing site soils within proposed improvement footprint areas be excavated and properly compacted for miscellaneous foundations and slab support. Excavations should be conducted as necessary to remove all existing fill at the direction of the Geotechnical

Engineer (a representative of Geocon). The excavation for proposed improvement footprint areas should extend laterally a minimum distance of 2 feet beyond the footprint area or for a distance equal to the depth of fill below the foundation, whichever is greater.

Recommendations for earthwork are provided in the Grading section of this report.

8.1.3 Subsequent to the recommended grading, a conventional foundation system may be utilized for support of the proposed improvements, provided foundations derive support in the newly placed engineered fill.

8.1.4 A deepened foundation system consisting of drilled cast-in-place concrete friction piles or end bearing piers deriving support in undisturbed alluvial soils may be utilized for support of proposed light poles and shade structures. Recommendations for design and installation of deepened foundations are provided in the Deepened Foundations section of this report.

8.1.5 Foundations for small outlying structures, such as block walls up to 6 feet in height, planter walls or trash enclosures, may be supported on conventional foundations bearing on a minimum of 12 inches of newly placed engineered fill which extends laterally at least

12 inches beyond the foundation area. Where excavation and proper compaction cannot be performed, foundations may derive support directly in the undisturbed alluvial soils and should be deepened as necessary to maintain a minimum 18-inch embedment into the recommended bearing materials. If the soils exposed in the excavation bottom are soft or loose, compaction of the soils will be required prior to placing steel or concrete. Compaction of the foundation excavation bottom is typically accomplished with a compaction wheel or mechanical whacker and must be observed and approved by a Geocon representative.

Project No. T3079-22-01 - 12 - October 31, 2024

8.1.6 All excavations must be observed and approved in writing by the Geotechnical Engineer

(a representative of Geocon). Prior to placing any fill, the excavation bottom must be scarified, moistened, and proof-rolled with heavy equipment in the presence of the

Geotechnical Engineer (a representative of Geocon).

8.1.7 Site soils are generally comprised of sand with little or no cohesion that are highly susceptible to caving in un-shored excavations. It is the responsibility of the contractor to ensure that excavations and trenches are properly shored and maintained in accordance with Cal-OSHA rules and regulations. The contractor should be aware that formwork will likely be required to prevent caving of shallow excavations. Recommendations are provided in the Temporary

Excavations section of this report. In addition, the soils are susceptible to rapid erosion during a wet-weather event.

8.1.8 Where new paving is to be placed, it is recommended that all existing fill (if encountered) and loose alluvial soils be excavated and properly compacted for paving support. The client should be aware that excavation and compaction of all existing fill and loose alluvial soils in the area of new paving is not required; however, paving constructed over existing uncertified fill or unsuitable alluvial soil may experience increased settlement and/or cracking, and may therefore have a shorter design life and increased maintenance costs. As a minimum, the upper 12 inches of subgrade soil should be scarified and properly compacted for paving support. Recommendations for pavement are provided in the Pavement Recommendations section of this report.

8.1.9 Once the design and foundation loading configuration proceeds to a more finalized plan, the recommendations within this report should be reviewed and revised, if necessary. If the proposed structural loads will exceed those presented herein, the potential for settlement should be reevaluated by this office.

8.1.10 Any changes in the design, location or elevation, as outlined in this report, should be reviewed by this office. Geocon should be contacted to determine the necessity for review and possible revision of this report.

Project No. T3079-22-01 - 13 - October 31, 2024

8.2 Soil and Excavation Characteristics

8.2.1 The in-situ soils can be excavated with moderate effort using conventional excavation equipment. Caving should be anticipated in unshored excavations.

8.2.2 It is the responsibility of the contractor to ensure that all excavations and trenches are properly shored and maintained in accordance with applicable OSHA rules and regulations to maintain safety and maintain the stability of existing adjacent improvements.

8.2.3 Onsite excavations must be conducted in such a manner that potential surcharges from existing structures, construction equipment, and vehicle loads are resisted. The surcharge area may be defined by a 1:1 projection down and away from the bottom of an existing foundation or vehicle load. Penetrations below this 1:1 projection will require special excavation measures such as sloping or shoring. Excavation recommendations are provided in the Temporary Excavations section of this report.

8.2.4 Due to the granular nature and lack of expansive fines contained in the site soils encountered during the investigation, existing site soils are considered to have a “very low” expansion potential and are classified as “non-expansive” (expansion index [EI] of 20 or less) in accordance with the 2022 California Building Code (CBC) Section 1803.5.3. The following table presents soil classifications based on the EI.

SOIL CLASSIFICATION BASED ON EXPANSION INDEX

Expansion Index (EI) Expansion Classification 2022 CBC Expansion Classification

0 – 20 Very Low Non-Expansive

21 – 50 Low

Expansive 51 – 90 Medium

91 – 130 High

Greater Than 130 Very High

8.2.5 The recommendations presented herein assume that foundations and slabs will derive support in these materials. Although unlikely, any medium to highly expansive soils encountered at the site should not be placed within 4 feet of the proposed foundations, flatwork, or paving improvements.

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8.3 Minimum Resistivity, pH, and Water-Soluble Chloride and Sulfate

8.3.1 We performed laboratory tests on samples of the site materials to evaluate the percentage of water-soluble sulfate content. Appendix B (Figure B-3) presents results of the laboratory water-soluble sulfate content tests. Laboratory tests performed on samples of the site materials indicate that the on-site materials possess an “S0” sulfate exposure to concrete structures as defined by 2022 CBC Section 1904 and ACI 318-19, Chapter 19. The following table presents a summary of concrete requirements set forth by 2022 CBC Section 1904.3 and ACI 318. The presence of water-soluble sulfates is not a visually discernible characteristic;

therefore, other soil samples from the site could yield different concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers and other soil nutrients) may affect the concentration.

REQUIREMENTS FOR CONCRETE EXPOSED TO SULFATE-CONTAINING SOLUTIONS

Exposure Class

Water-Soluble

Sulfate (SO4)

Percent by Weight

Cement

Type (ASTM C

150)

Maximum

Water to

Cement Ratio by Weight1

Minimum

Compressive

Strength (psi)

S0 SO4<0.10 No Type Restriction n/a 2,500

S1 0.10<SO4<0.20 II 0.50 4,000

S2 0.20<SO4<2.00 V 0.45 4,500

S3 Option 1

SO4>2.00

V+Pozzolan or Slag 0.45 4,500

Option 2 V 0.40 5,000 1 Maximum water to cement ratio limits do not apply to lightweight concrete.

8.3.2 Laboratory testing of Potential of Hydrogen (pH), minimum resistivity, and water soluble chloride content was performed on representative site soils to generally evaluate the corrosion potential to surface utilities. Laboratory test results indicate a resistivity of

10,000 ohm-cm, pH of 8.8, and a water soluble chloride content of 30 ppm. Based on the test results, the site soils would be considered “non-corrosive” to metal improvements based on resistivity in accordance with the Caltrans Corrosion Guidelines (Caltrans, 2021) as shown in the following table.

CALTRANS CORROSION GUIDELINES

Corrosion Exposure

Resistivity (ohm-cm)

Chloride (ppm) Sulfate (ppm) pH

Corrosive <1,500 500 or greater 1,500 or greater 5.5 or less

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8.3.3 The laboratory test results are presented in Appendix B (Figure B-3) and should be considered for design of underground structures and concrete footings.

8.3.4 Geocon does not practice in the field of corrosion engineering and mitigation.

If corrosion sensitive improvements are planned, it is recommended that a corrosion engineer be retained to evaluate corrosion test results and incorporate the necessary precautions to avoid premature corrosion of buried metal pipes and concrete structures in direct contact with the soils.

8.4 Grading

8.4.1 Grading should be performed in accordance with the following recommendations, the

Recommended Grading Specifications contained in Appendix C, and the Grading Ordinances of San Bernardino County.

8.4.2 A preconstruction conference should be held at the site prior to the beginning of grading operations with the owner, contractor, civil engineer, geotechnical engineer, and, if applicable, building official in attendance. Special soil handling requirements can be discussed at that time.

8.4.3 Earthwork should be observed, and compacted fill tested by representatives of Geocon.

The existing artificial fill and alluvium encountered during exploration is suitable for re-use as an engineered fill, provided oversize material (greater than 6 inches) and deleterious debris is removed.

8.4.4 Grading should commence with the removal of all existing vegetation and existing improvements from the area to be graded. Asphalt and concrete should not be mixed with the fill soils unless approved by the Geotechnical Engineer and Building Official. Existing underground improvements planned for removal should be completely excavated and the resulting depressions properly backfilled in accordance with the procedures described herein. Once a clean excavation bottom has been established it must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon).

8.4.5 Based on visual observations, surficial site soils may be significantly dry when compared to the optimum moisture content, as determined by ASTM D1557. Significant moisture conditioning of materials to be used as engineered fill should be expected by the contractor during grading operations in order to achieve the recommended compaction and moisture content.

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8.4.6 As a minimum, it is recommended that the upper 4 feet of existing site soils within proposed improvement footprint areas be excavated and properly compacted for foundation and slab support. Excavations should be conducted as necessary to remove all existing fill at the direction of the Geotechnical Engineer (a representative of Geocon). The excavation for proposed improvement footprint areas should extend laterally a minimum distance of 2 feet beyond the footprint area or for a distance equal to the depth of fill below the foundation, whichever is greater.

8.4.7 Once approved, the bottoms of the excavations should be scarified to a depth of at least

1 foot, moisture conditioned to within 0 to 2 percent above optimum moisture content and compacted to a minimum of 90 percent of the maximum dry density (ASTM D1557), prior to fill placement. All excavation bottoms must be observed and approved by the Geotechnical

Engineer (a representative of Geocon) prior to placing and compacting fill.

8.4.8 Foundations for small outlying structures, such as block walls up to 6 feet in height, planter walls or trash enclosures, may be supported on conventional foundations deriving support on a minimum of 24 inches of newly placed engineered fill which extends laterally at least 12 inches beyond the foundation area. Where excavation and proper compaction cannot be performed, such as adjacent to existing amenities or utilities, foundations may bear in the undisturbed alluvial soils at or below a depth of 2 feet below the existing grade, and should be deepened as necessary to maintain a minimum 18 inch embedment into the undisturbed alluvial soil. If the soils exposed in the excavation bottom are soft or loose, compaction of the soils will be required prior to placing steel or concrete. Compaction of the foundation excavation bottom is typically accomplished with a compaction wheel or mechanical whacker and must be observed and approved by a Geocon representative.

8.4.9 Fill and backfill soils should be placed in horizontal loose layers approximately 6 to 8 inches thick, moisture conditioned at 0 to 2 percent above optimum moisture content, and compacted to at least 90 percent of the maximum dry density per ASTM D1557. Fill materials placed below optimum moisture content will require additional moisture conditioning prior to placing additional fill. Earthwork should be observed, and compacted fill tested by representatives of Geocon.

8.4.10 Excavations must be observed and approved in writing by the Geotechnical Engineer

(a representative of Geocon). Prior to placing any fill, the bottom must be scarified, moisture conditioned, and proof-rolled with heavy equipment in the presence of the Geotechnical

Engineer (a representative of Geocon).

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8.4.11 Where new paving is to be placed, it is recommended that existing fill and soft alluvial soils be excavated and properly compacted for paving support. The client should be aware that excavation and compaction of existing fill and soft alluvial soils in the area of new paving is not required; however, paving constructed over existing uncertified fill or unsuitable alluvial soil may experience increased settlement and/or cracking and may therefore have a shorter design life and increased maintenance costs. As a minimum, the upper 12 inches of subgrade soil should be scarified and properly compacted to a minimum of 95 percent of the laboratory maximum dry density in accordance with ASTM D 1557 (latest edition).

8.4.12 Imported fill shall be observed, tested, and approved by Geocon prior to bringing soil to the site. Import fill should consist of the characteristics presented in the table below.

SUMMARY OF IMPORT FILL RECOMMENDATIONS

Soil Characteristic Values

Expansion Potential “Very Low” (Expansion Index of 20 or less)

Particle Size Maximum Dimension Less Than 6 Inches

Free of Debris

Corrosivity Less Detrimental Than Existing Onsite Soils

8.4.13 Utility trenches should be properly backfilled in accordance with the following requirements.

The pipe should be bedded with clean sands (Sand Equivalent greater than 30) to a depth of at least 1 foot over the pipe, and the bedding material must be inspected and approved in writing by the Geotechnical Engineer (a representative of Geocon). The use of gravel is not acceptable unless used in conjunction with filter fabric to prevent the gravel from having direct contact with soil. The remainder of the trench backfill may be derived from onsite soil or approved import soil, compacted as necessary, until the required compaction is obtained.

The use of a minimum of 2-sack slurry as backfill is also acceptable. Prior to placing any bedding materials or pipes, the excavation bottom must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon).

8.4.14 All excavation bottoms must be observed and approved in writing by the Geotechnical

Engineer (a representative of Geocon), prior to placing bedding materials, fill, steel, gravel, or concrete.

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8.5 Earthwork Grading Factors

8.5.1 Estimates of shrinkage factors are based on empirical judgments comparing the material in its existing or natural state as encountered in the exploratory excavations to a compacted state. Variations in natural soil density and in compacted fill density render shrinkage value estimates as rough approximations. As an example, the contractor can compact the fill to a dry density of 90 percent or higher of the laboratory maximum dry density. Thus, the contractor has an approximately 10 percent range of control over the fill volume. Due to the variations in the actual shrinkage/bulking factors, a balance area should be provided to accommodate variations.

8.6 Conventional Foundation Design

8.6.1 A conventional shallow spread foundation system may be utilized for support of proposed miscellaneous foundations, provided foundations derive support in the newly placed engineered fill. All foundation excavations must be observed and approved in writing by the

Geotechnical Engineer (a representative of Geocon), prior to placing steel or concrete.

8.6.2 Conventional shallow spread foundations for the proposed improvements should consist of isolated spread footings and should be designed using the parameters in the table on the following page.

SUMMARY OF MISCELLANEOUS FOUNDATION RECOMMENDATIONS

Parameter Value

Minimum Isolated Foundation Width 24 Inches

Minimum Foundation Depth 18 Inches Below Lowest Adjacent Grade

12 Inches into Recommended Bearing Material

Minimum Steel Reinforcement 4 No. 4 Bars, 2 Top and 2 Bottom

Allowable Bearing Capacity – Isolated Foundation

1,500 psf

Bearing Capacity Increase 200 psf per Foot of Width

300 psf per Foot of Depth

Maximum Allowable Bearing Capacity 1,800 psf

Estimated Total Settlement 1 Inch

Estimated Differential Settlement ½ Inch over 20 Feet

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8.6.3 The above foundation dimensions and minimum reinforcement recommendations are based on soil conditions and building code requirements only and are not intended to be used in lieu of those required for structural purposes.

8.6.4 The allowable bearing pressures may be increased by one-third for transient loads due to wind or seismic forces.

8.6.5 Once the design and foundation loading configurations for the proposed miscellaneous structures proceeds to a more finalized plan, the estimated settlements presented in this report should be reviewed and revised, if necessary. If the final foundation loading configurations are greater than the assumed loading conditions, the potential for settlement should be reevaluated by this office.

8.6.6 No special subgrade presaturation is required prior to placement of concrete. However, the moisture in the foundation subgrade should be sprinkled as necessary to maintain a moist condition at the time of concrete placement.

8.6.7 Foundation excavations should be observed and approved in writing by the Geotechnical

Engineer (a representative of Geocon West, Inc.), prior to the placement of reinforcing steel and concrete to verify that the excavations and exposed soil conditions are consistent with those anticipated. If unanticipated soil conditions are encountered, foundation modifications may be required.

8.6.8 This office should be provided with a copy of the final construction plans so that the excavation recommendations presented herein could be properly reviewed and revised if necessary.

8.7 Deepened Foundations

8.7.1 A deepened foundation system consisting of drilled cast-in-place concrete friction piles or end bearing piers deriving support in undisturbed alluvial soils may be utilized for support of the proposed light poles and shade structures. Piles should be a minimum of 24 inches in diameter, and should be embedded a minimum of 6 feet in depth below the ground surface and 4 feet into undisturbed alluvium. If the excavation bottom is cleaned of all loose soils the end bearing properties of the soils may be utilized and foundation may be designed for an allowable bearing capacity of 1,800 pounds per square foot.

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8.7.2 Friction piles should be a minimum of 24 inches in diameter and should be embedded a minimum of 10 feet in depth below the ground surface and 4 feet into undisturbed alluvium.

Where piles penetrate through unsuitable fill or soft alluvial soils at the surface, these materials should not be considered in the contribution of the pile capacity and the embedment depth should be extended so that 6 feet of the pile is embedded in the undisturbed alluvial soils. Additionally, where not protected by pavement, the upper two feet of soil should be ignored when calculating axial and lateral capacity.

8.7.3 Friction piles may be designed based on a skin friction capacity of 100 pounds per square foot and do not require the complete removal of all loose earth materials from the bottom of the excavation since the end-bearing capacity is not being considered for design. However, a clean out of the excavation bottom will be required. Single pile uplift capacity can be taken as ½ of the allowable downward capacity. The allowable downward capacity and allowable uplift capacity may be increased by one-third when considering transient wind or seismic loads. Piles may be assumed fixed at an embedment depth of 5 feet below the ground surface.

8.7.4 The maximum expected total settlement for proposed improvements supported on friction piles is estimated to be ½-inch. Differential settlement between adjacent caisson foundations is not expected to exceed ¼-inch. Most of the settlement of the foundation system is expected to occur on initial application of loading.

8.7.5 For design purposes, an allowable passive value for the soils may be assumed to be 200 psf per foot with a maximum earth pressure of 2,000 psf. To develop the full lateral value, provisions should be implemented to assure firm contact between the piles and the engineered fill and/or underlying alluvial soils. A one-third increase in the passive value may be used for wind or seismic loads.