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Home My WebLink AboutAppendix E - Residential Development Site Geotechnical InvestigationEN G I N E E R S + GE O L O G I S T S + EN V I R O N M E N T A L S C I E N T I S T S PRELIMINARY GEOTECHNICAL EVALUATION DISTRICT PROPERTY 1, 28.7 ACRES ON KNOX AVENUE NORTH OF WALNUT STREET AND SOUTH OF S. HIGHLAND AVENUE CITY OF FONTANA, SAN BERNARDINO COUNTY, CALIFORNIA FONTANA INVESTMENT 2023, LLC August 16, 2023 J.N. 23-202 ENGINEERS + GEOLOGISTS + ENVIRONMENTAL SCIENTISTS Offices Strategically Positioned Throughout Southern California RIVERSIDE COUNTY OFFICE 40880 County Center Drive, Suite M, Temecula, CA 92591 T: 951.600.9271 F: 951.719.1499 For more information visit us online at www.petra-inc.com August 16, 2023 J.N. 23-202 FONTANA INVESTMENT 2023, LLC 10621 Civic Center Drive Rancho Cucamonga, California 91730 Attention: Mr. Nolan Leggio Subject: Preliminary Geotechnical Evaluation: District Property 1, 28.7 Acres on Knox Avenue North of Walnut Street and South of S. Highland Avenue, City of Fontana, San Bernardino County, California Dear Mr. Leggio: Petra Geosciences, Inc. (Petra) is submitting herewith our preliminary geotechnical evaluation report for the proposed development of mostly undeveloped land on Knox Avenue, between S. Highland Avenue and Walnut Street, in the city of Fontana, San Bernardino County, California. This work was performed in general accordance with the scope of work outlined in our Proposal No. 23-202P, dated May 11, 2023. This report presents the results of our field exploration, infiltration evaluation, the requirements of the 2022 California Building Code (CBC) and our engineering judgment, opinions, conclusions, and recommendations pertaining to geotechnical design aspects for the proposed development. It has been a pleasure to be of service to you on this project. Should you have questions regarding the contents of this report or should you require additional information, please contact this office. Respectfully submitted, PETRA GEOSCIENCES, INC. Edward Lump, CEG Grayson R. Walker, GE Associate Geologist Principal Engineer FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 TABLE OF CONTENTS Page INTRODUCTION ......................................................................................................................................................... 1 PURPOSE AND SCOPE OF SERVICES ..................................................................................................................... 1 SITE LOCATION AND DESCRIPTION ..................................................................................................................... 2 Historic Land Use .............................................................................................................................................. 2 PROPOSED DEVELOPMENT .................................................................................................................................... 3 Literature Review ............................................................................................................................................... 3 Subsurface Exploration ...................................................................................................................................... 3 Laboratory Testing ............................................................................................................................................. 4 FINDINGS .................................................................................................................................................................... 4 Regional Geologic Setting ................................................................................................................................. 4 Local Geology and Subsurface Soil Conditions ................................................................................................. 4 Surface Water ..................................................................................................................................................... 5 Groundwater ....................................................................................................................................................... 6 Faulting .............................................................................................................................................................. 7 Seismic Design Parameters ................................................................................................................................ 7 Discussion ........................................................................................................................................................ 10 CONCLUSIONS ......................................................................................................................................................... 11 Site Suitability .................................................................................................................................................. 11 Primary Geologic/Geotechnical Considerations .................................................................................................... 11 Groundwater ..................................................................................................................................................... 11 Fault Rupture .................................................................................................................................................... 11 Strong Ground Motions .................................................................................................................................... 11 Liquefaction, Landslides and Secondary Seismic Effects ................................................................................ 11 Compressible Soils ........................................................................................................................................... 12 Flooding ........................................................................................................................................................... 12 EARTHWORK RECOMMENDATIONS .................................................................................................................. 12 Earthwork Criteria ............................................................................................................................................ 12 Geotechnical Observations and Testing ........................................................................................................... 12 Clearing and Grubbing ..................................................................................................................................... 13 Excavation Characteristics ............................................................................................................................... 13 Ground Preparation - General ................................................................................................................................ 14 Unsuitable Soil Removals ................................................................................................................................ 14 Ground Preparation - Roadways ...................................................................................................................... 15 Cut Lots ............................................................................................................................................................ 15 Cut-Fill Transition Lots/Building Pads ............................................................................................................ 16 Suitability of Site Soils as Fill .......................................................................................................................... 16 Fill Placement .................................................................................................................................................. 16 Import Soils for Grading .................................................................................................................................. 16 Shrinkage and Subsidence ................................................................................................................................ 16 Temporary Excavations.................................................................................................................................... 17 FOUNDATION DESIGN RECOMMENDATIONS .................................................................................................. 17 Allowable Soil Bearing Capacities................................................................................................................... 17 Estimated Footing Settlement .......................................................................................................................... 18 Lateral Resistance ............................................................................................................................................ 18 Guidelines for Footings and Slabs on-Grade Design and Construction ................................................................. 18 Conventional Slab-on-Ground Foundation System .......................................................................................... 19 Footing Observations ....................................................................................................................................... 21 PRELIMINARY PAVEMENT DESIGN RECOMMENDATIONS .......................................................................... 22 General Corrosivity Screening ............................................................................................................................... 22 FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 TABLE OF CONTENTS Page Exterior Concrete Flatwork .................................................................................................................................... 24 General ............................................................................................................................................................. 24 Subgrade Preparation ....................................................................................................................................... 24 Thickness and Joint Spacing ............................................................................................................................ 25 Reinforcement .................................................................................................................................................. 26 Edge Beams (Optional) .................................................................................................................................... 26 Drainage ........................................................................................................................................................... 26 Tree Wells ........................................................................................................................................................ 27 INFILTRATION TEST RESULTS ............................................................................................................................. 27 POST-GRADING RECOMMENDATIONS .............................................................................................................. 27 Site Drainage .................................................................................................................................................... 27 Slope Landscaping and Maintenance ............................................................................................................... 28 Utility Trenches ................................................................................................................................................ 29 Retaining Walls ...................................................................................................................................................... 29 Footing Embedment ......................................................................................................................................... 29 Allowable Bearing Values and Lateral Resistance .......................................................................................... 30 Active Earth Pressures ..................................................................................................................................... 30 Earthquake Loads ............................................................................................................................................. 31 Geotechnical Observation and Testing ............................................................................................................. 31 Backdrains ........................................................................................................................................................ 31 Waterproofing .................................................................................................................................................. 32 Temporary Excavations.................................................................................................................................... 32 Wall Backfill .................................................................................................................................................... 32 Masonry Block Screen Walls ................................................................................................................................. 32 Construction On or Near the Tops of Descending Slopes ................................................................................ 32 Construction on Level Ground ......................................................................................................................... 33 Construction Joints ........................................................................................................................................... 33 CONSTRUCTION SERVICES ................................................................................................................................... 33 LIMITATIONS ........................................................................................................................................................... 33 REFERENCES ............................................................................................................................................................ 35 ATTACHMENTS FIGURES RW-1 – RW-3 – RETAINING WALL DETAILS FIGURE 1 – SITE LOCATION MAP FIGURE 2 – EXPLORATION LOCATION MAP APPENDICES APPENDIX A – FIELD EXPLORATION LOGS (TEST PITS) APPENDIX B – LABORATORY TEST PROCEDURES / LABORATORY DATA SUMMARY APPENDIX C – SEISMIC DESIGN PARAMETERS APPENDIX D – INFILTRATION TEST RESULTS APPENDIX E – STANDARD GRADING SPECIFICATIONS PRELIMINARY GEOTECHNICAL EVALUATION DISTRICT PROPERTY 1, 28.7 ACRES ON KNOX AVENUE NORTH OF WALNUT STREET AND SOUTH OF W. HIGHLAND AVENUE CITY OF FONTANA, SAN BERNARDINO COUNTY, CALIFORNIA INTRODUCTION Petra Geosciences, Inc. (Petra) is presenting herein the results of our updated geotechnical evaluation for the subject 28.7-acre site, which is mostly undeveloped property. Our geotechnical evaluation included a review of regional geological maps published by the California Geological Survey (CGS) and other sources that encompass the site, including review of limited historic aerial photos and online imagery (Google Earth Imagery, 1994-2022) in the vicinity of the project site. The scope of work included the excavation of 11 exploratory test pits and 1 infiltration test pit within the subject property. PURPOSE AND SCOPE OF SERVICES The purposes of this phase of evaluation were to obtain information on the subsurface geologic and soil conditions within the project area, assess a preliminary infiltration rate in anticipated basin location, evaluate the field and laboratory data, and provide conclusions and recommendations for design and construction of the proposed building and other site improvements, as influenced by the subsurface conditions. The scope of our evaluation consisted of the following: • Reconnaissance of the site to evaluate existing conditions. • Review of available published and unpublished data and maps concerning geologic and soil conditions within and adjacent to the site which could have an impact on the proposed improvements. • Excavation of 11 exploratory test pits, utilizing a rubber tire backhoe, to evaluate the stratigraphy of the subsurface soils and collect representative bulk samples for laboratory testing. • Excavate 1 percolation test pit, utilizing a rubber-tired backhoe, to measure infiltration rates. • Log and visually classify soil materials encountered in the borings in accordance with the Unified Soil Classification System. • Conduct laboratory testing of representative samples (bulk) obtained from the test pits to determine their engineering properties. • Perform engineering and geologic analysis of the data with respect to the proposed improvements. • Preparation of this report, including pertinent figures and appendices, presenting the results of our evaluation and recommendations for the proposed improvements in general conformance with the requirements of the 2022 California Building Code (CBC), as well as in accordance with applicable local jurisdictional requirements. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 2 SITE LOCATION AND DESCRIPTION The subject property is a mostly vacant site located on both sides of Knox Avenue, between S. Highland Avenue on the north and Walnut Street on the south, in the city of Fontana, San Bernardino County, California. The site is bounded by vacant and residential land to the north with S. Highland Avenue beyond; residential tract development to the east; Walnut Street to the south; and residential tract development to the west. At this time, Knox Avenue is asphalt paved south of S. Highland Avenue for a distance of approximately 650 feet to provide access to three occupied residences, which are not a part of the subject property. Wooden poles and overhead lines are located along the east side of Knox Avenue. The poles and lines step over to the east portion of the property near the pavement end of Knox Avenue and continue south to Walnut Street. Concrete slabs, concrete rubble, and a fenced mobile classroom trailer were observed in the northern portion of the subject property. A site location map is included as Figure 1. The subject site is comprised of 32 contiguous parcels encompassing approximately 28.7 acres. Vegetation consists predominantly of uniform native grasses and weeds. Trees are scattered in the northeast portion of the subject site. Dirt roads exist along the northeast and east edges of the subject property. An earthen berm has been placed at the south end of pavement to Knox Avenue; however, remnants of a dirt road continue south to Walnut Street. Chain-link fencing bounds the subject site on the south, with a sidewalk beyond along Walnut Street. A concrete block wall bounds the property on the west. Assorted fences/walls bound the subject site on the east. No fencing exists along S. Highland Avenue. A plan showing recent surface conditions of the subject site is included as Figure 2. Historic Land Use Information obtained during the concurrent Phase I Environmental Site Assessment indicated that the subject property appeared to have been mostly undeveloped land with native vegetation from at least 1938 to the present. One or two buildings were noted in an aerial photograph within the northeastern portion of the subject site from at least 1949. The number increased to four by 1953. Two runways associated with Gilfillan Airport were observed directly west of the subject property also in 1953. The land surrounding the subject property was either undeveloped, residential or (to a lesser extent) agricultural. Five (or possibly 6) buildings were observed in the northeast corner of the subject site by 1959. One residence was also noted onsite in 1959, on the west side of Knox Avenue near the north central property boundary. The north runway of the adjacent airport was marked an “X” and “CLOSED” in 1959. In 1966, there appeared to be three buildings in the northeast area of the subject site, and one along Knox Avenue. In 1985, the south portion of the subject property was cleared of vegetation and contained what appeared to be stockpiled material (soils or vegetation). The area may have also been mass graded. The onsite residence on Knox Avenue FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 3 appears to have had a swimming pool in 1985. Also in 1985, both runways west of the subject site were labeled with an “X” (i.e., closed). Sometime between 1994 and 2002, the airport was replaced by a residential housing tract west of the subject site. By 2002 or 2005, the swimming pool appeared to be backfilled with soil. In 2002, only one building was observed in the northwest corner of the subject site and one building onsite along Knox Avenue. By 2009, buildings were removed from the subject property and only concrete slabs were visible. From 2012 through 2023, no significant changes were observed within the subject property limits. PROPOSED DEVELOPMENT As of the date of this report, we are not aware of a conceptual plan for the subject property; however, we anticipate residential development. Overall, the subject property is level, gently sloping to the south. Based upon information provided on Google Earth, existing elevations ranged from approximately 1,430 feet above mean sea level (msl) near the southwest corner of the subject site to 1,470 feet above msl near the north boundary of the subject property. Proposed elevations are not know at this time. It is expected that the residential buildings will be of wood-frame construction supported on conventional slab-on-ground foundations. Appurtenant structures will likely include paved access streets and driveways, concrete patio-type slabs and walkways, masonry block walls, surface and subsurface drainage control devices, landscaped areas, and above- and below-ground utilities Given the relatively level topography within the proposed development, earthwork within the site is generally expected to entail m inor cuts and fills up to approximately 5 feet, except for water quality basins. It should be noted, however, that the ultimate amount of new fill required throughout the project will be greater due to the required remedial grading (i.e., removal and re-compaction of existing unsuitable surficial soils). Literature Review It is our understanding that geotechnical reports pertaining to the subject property do not exist. Petra researched and reviewed available published and unpublished geologic data pertaining to regional geology, faulting, and geologic hazards that may affect the site. The results of this review are discussed under the Findings and Conclusions sections presented in this report. Subsurface Exploration A subsurface exploration program was performed under the direction of an engineering geologist from Petra on July 28, 2023. The exploration involved the excavation of 11 exploratory test pits (TP-1 through FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 4 TP-11) to a maximum depth of approximately 10 feet below existing grade (bgs). Earth materials encountered within the exploratory test pits were classified and logged by a geologist in accordance with the visual-manual procedures of the Unified Soil Classification System. Disturbed bulk samples of soil materials were collected for classification, laboratory testing and engineering analyses. The approximate locations of the exploratory borings are shown on Figure 2 (Field Exploration Map). The test pit logs are presented in Appendix A. Laboratory Testing Maximum dry density and optimum moisture content, expansion index, and corrosion suite (sulfate content, chloride content, pH/resistivity) for selected samples of onsite soils materials was conducted. A description of laboratory test methods and summaries of the laboratory test data are presented in Appendix B. FINDINGS Regional Geologic Setting Geologically, the site lies within the northern portion of the Peninsular Ranges Geomorphic Province (CGS, 2002). The Peninsular Range Province extends from the tip of Baja California north to the Transverse Ranges Geomorphic Province and is characterized by northwest trending mountain ranges separated by subparallel fault zones. The San Bernardino Mountains, located on the north side of the valley, provides the boundary between the Peninsula Range Province and the Transverse Ranges Province . In general, the province is underlain primarily of plutonic rock of the Southern California Batholith . These rocks formed from the cooling of molten magma deep within the earth's crust. Intense heat associated with the plutonic magma metamorphosed the ancient sedimentary rocks into which the plutons intruded. The Peninsular Range Geomorphic Province is generally characterized by alluviated basins and elevated erosion surfaces. More specifically, the subject site is mapped as Holocene-age Young alluvial fan deposits consisting unconsolidated to moderately consolidated, coarse-grained sand and bouldery fan deposits (Morton and Matti, 2001). A portion of this regional geologic map exhibiting the subject property location is provided below as Figure A. The site does not lie within an Alquist-Priolo Earthquake Fault Zone (Bryant and Hart, 2007; CGS, 2023). Local Geology and Subsurface Soil Conditions Earth units encountered onsite consisted of topsoil and alluvial deposits. The site is covered by a ½- to 2- foot layer of topsoil overlying young alluvium, which generally consists of loose, dry, silty sands with minor gravel in the upper ½ to 3 feet. Below this depth native alluvial soils were found to consist FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 5 predominately of brown-yellow, brown-gray and brown, dry to moist, loose to medium dense, fine- to coarse-grained gravelly sands with 10 to 55 percent gravel and cobbles on the order of 8 to 12 inches in size. Minor small boulders were locally encountered. Within the southern portion of the subject site, concentrations of cobbles and boulders decreased substantially. While the deeper alluvium was generally observed to be medium to very dense, zones of low density and/or porous soils were observed within the upper 4 to 5 feet in test pits. Logs of exploratory test pits are presented in Appendix A. Test pit locations are presented on the Test Pit Location Map (Figure 2). Figure A – Regional Geologic Map (Morton and Matti, 2001). Surface Water No indication of surface water was observed on the property or in close proximity at the time of our site field exploration. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 6 The west parcel of subject property is situated within Flood Insurance Rate Map (FIRMette) 06071C7915H, and the east parcel is located in FIRMette 06071C7920H. Both parcels are mapped within Zone X, defined as an area defined as areas of 0.2 percent annual chance flood; areas of 1 percent annual chance flood with average depths of less than 1 foot or within drainage areas less than 1 square mile; and areas protected by levees from 1 percent annual chance flood. Figure B below depicts the Flood Insurance Rate Map (FIRM) for the subject site and vicinity. The FIRMette map (Map Revised August 28, 2008) is provided in Appendix B. Figure B – General Flood Insurance Map (FEMA, 2023) Groundwater No groundwater was encountered in any of our test pits to a maximum depth of 10 feet below the ground surface. The site is located within the Upper Santa Ana Valley – Chino Groundwater Basin, 8-002.01 (California Department of Water Resources [CDWR, 2023], Water Data Library). Groundwater depth varies within the subject property area and, though flow direction beneath the subject site is unknown, it is believed to be toward the south. No groundwater wells were listed on the property (CDWR, 2023). FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 7 One well (local ID: CHINO-1200219) is mapped approximately 1.5 miles east-southeast of the subject property. Groundwater depths reported from 641 feet below the ground surface (bgs) in April 1993 to 653 feet bgs in March 2012 to 711 feet bgs in September 2022. Groundwater is not expected to affect development of the subject property. Faulting Based on our review of the referenced geologic maps and literature, no active faults are known to project through the property. Furthermore, the site does not lie within the boundaries of an “Earthquake Fault Zone” as defined by the State of California in the Alquist-Priolo Earthquake Fault Zoning Act (CGS, 2018). The Alquist-Priolo Earthquake Fault Zoning Act (AP Act) defines an active fault as one that “has had surface displacement within Holocene time (about the last 11,000 years).” The main objective of the AP Act is to prevent the construction of dwellings on top of active faults that could displace the ground surface resulting in loss of life and property. However, it should be noted that according to the USGS Unified Hazard Tool website, the 2010 CGS Fault Activity Map of California, and the CGS Earthquake Hazard Zones (EQZapp) interactive map (CGS, 2023), the Lytle Creek Connector of the San Jacinto Fault zone, located approximately 3.5 miles (5.59 kilometers) east of the site, would probably generate the most severe site ground motions and, therefore, is the majority contributor to the deterministic minimum component of the ground motion models. The subject site is located at less than 5 miles (8 km) from the surface projection of this fault system, which is capable of producing a magnitude 7 or larger events with a slip rate along the fault greater than 0.04 inch per year. As such, the site should be considered as a Near-Fault Site in accordance with ASCE 7-16, Section 11.4.1. Seismic Design Parameters Earthquake loads on earthen structures and buildings are a function of ground acceleration which may be determined from the site-specific ground motion analysis. Alternatively, a design response spectrum can be developed for certain sites based on the code guidelines. To provide the design team with the parameters necessary to construct the design acceleration response spectrum for this project, we used two computer applications. Specifically, the first computer application, which was jointly developed by the Structural Engineering Association of California (SEAOC) and California’s Office of Statewide Health Planning and Development (OSHPD), the SEAOC/OSHPD Seismic Design Maps Tool website, https://seismicmaps.org, is used to calculate the ground motion parameters. The second computer application, the United Stated Geological Survey (USGS) Unified Hazard Tool website, https://earthquake.usgs.gov/hazards/interactive/, is used to estimate the earthquake magnitude and the distance to surface projection of the fault. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 8 To run the above computer applications, site latitude and longitude, seismic risk category and knowledge of site class are required. The site class definition depends on the direct measurement and the ASCE 7-16 recommended procedure for calculating average small-strain shear wave velocity, Vs30, within the upper 30 meters (approximately 100 feet) of site soils. A seismic risk category of II was assigned to the proposed buildings in accordance with 2022 CBC, Table 1604.5. No shear wave velocity measurement was performed at the site, however, the subsurface materials at the site appear to exhibit the characteristics of stiff soils condition for Site Class D designation. Therefore, an average shear wave velocity of 850 feet per second (259 meters per second) for the upper 100 feet was assigned to the site based on engineering judgment and geophysical experience. As such, in accordance with ASCE 7-16, Table 20.3-1, Site Class D (D- Default as per SEAOC/OSHPD software) has been assigned to the subject site. The following table, Table 1, provides parameters required to construct the Seismic Response Coefficient – Natural Period, Cs – T, curve based on ASCE 7-16, Article 12.8 guidelines. A printout of the computer output is attached in Appendix C. ~Remainder of Page Intentionally Left Blank~ FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 9 TABLE 1 Seismic Design Parameters Ground Motion Parameters Specific Reference Parameter Value Unit Site Latitude (North) - 34.1317 ° Site Longitude (West) - -117. 4618 ° Site Class Definition Section 1613.2.2 (1), Chapter 20 (2) D-Default (4) - Assumed Seismic Risk Category Table 1604.5 (1) II - Mw - Earthquake Magnitude USGS Unified Hazard Tool (3) 7.98 (3) - R – Distance to Surface Projection of Fault USGS Unified Hazard Tool (3) 5.59 (3) km Ss - Mapped Spectral Response Acceleration Short Period (0.2 second) Figure 1613.2.1(1) (1) 2.149 (4) g S1 - Mapped Spectral Response Acceleration Long Period (1.0 second) Figure 1613.2.1(3) (1) 0.717 (4) g Fa – Short Period (0.2 second) Site Coefficient Table 1613.2.3(1) (1) 1.2 (4) - Fv – Long Period (1.0 second) Site Coefficient Table 1613.2.3(2) (1) Null (4) - SMS – MCER Spectral Response Acceleration Parameter Adjusted for Site Class Effect (0.2 second) Equation 16-20 (1) 2.579 (4) g SM1 - MCER Spectral Response Acceleration Parameter Adjusted for Site Class Effect (1.0 second) Equation 16-21 (1) Null (4) g SDS - Design Spectral Response Acceleration at 0.2-s Equation 16-22 (1) 1.719 (4) g SD1 - Design Spectral Response Acceleration at 1-s Equation 16-23 (1) Null (4) g Domain of Constant Acceleration Ts = SD1/ SDS Section 11.4.6 (2) Null s To = 0.2 SD1/ SDS Section 11.4.6 (2) Null s TL - Long Period Transition Period Figure 22-14 (2) 12 (4) s PGA - Peak Ground Acceleration Maximum Considered Earthquake Geometric Mean, MCEG (*) Figure 22-9 (2) 0.898 g FPGA - Site Coefficient Adjusted for Site Class Effect (2) Table 11.8-1 (2) 1.2 (4) - PGAM –Peak Ground Acceleration (2) Adjusted for Site Class Effect Equation 11.8-1 (2) 1.077 (4) g Design PGA ≈ (⅔ PGAM) - Slope Stability (†) Similar to Eqs. 16-22 & 16-23 (2) 0.718 g Design PGA ≈ (0.4 SDS) – Short Retaining Walls (‡) Equation 11.4-5 (2) 0.688 g CRS - Short Period Risk Coefficient Figure 22-18A (2) 0.918 (4) - CR1 - Long Period Risk Coefficient Figure 22-19A (2) 0.895 (4) - SDC - Seismic Design Category (§) Section 1613.2.5 (1) Null (4) - References: (1) California Building Code (CBC), 2022, California Code of Regulations, Title 24, Part 2, Volume I and II. (2) American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI), 2016, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, Standards 7-16. (3) USGS Unified Hazard Tool - https://earthquake.usgs.gov/hazards/interactive/ [Dynamic: Conterminous U.S. 2014 (update) (v4.2.0)] (4) SEAOC/OSHPD Seismic Design Map Application – https://seismicmaps.org [Reference: ASCE 7-16] Related References: Federal Emergency Management Agency (FEMA), 2015, NEHRP (National Earthquake Hazards Reduction Program) Recommended Seismic Provision for New Building and Other Structures (FEMA P-1050). Notes: * PGA Calculated at the MCE return period of 2475 years (2 percent chance of exceedance in 50 years). † PGA Calculated at the Design Level of ⅔ of MCE; approximately equivalent to a return period of 475 years (10 percent chance o f exceedance in 50 years). ‡ PGA Calculated for short, stubby retaining walls with an infinitesimal (zero) fundamental period. § The designation provided herein may be superseded by the structural engineer in accordance with Section 1613.2.5.1, if applic able. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 10 Discussion General Owing to the characteristics of the subsurface soils, as defined by Site Class D-Default designation, and proximity of the site to the sources of major ground shaking, the site is expected to experience strong ground shaking during its anticipated life span. Under these circumstances, where the code-specified design response spectrum may not adequately characterize site response, the 2022 CBC typically requires a site- specific seismic response analysis to be performed. This requirement is signified/identified by the “null” values that are output using SEAOC/OSHPD software in determination of short period, but mostly, in determination of long period seismic parameters, see Table 1. For conditions where a “null” value is reported for the site, a variety of analytical design approaches are permitted by 2022 CBC and ASCE 7-16 (see Table 12.6-1)in lieu of a site-specific seismic hazard analysis. For any specific site, these alternative design approaches, which include Equivalent Lateral Force (ELF) procedure, Modal Response Spectrum Analysis (MRSA) procedure, Linear Response History Analysis (LRHA) procedure and Simplified Design procedure, among other methods, are expected to provide results that may or may not be more economical than those that are obtai ned if a site-specific seismic hazards analysis is performed. These design approaches and their limitations should be evaluated by the project structural engineer. Seismic Design Category Please note that the Seismic Design Category, SDC, is also designated as “null” in Table 1. For condition where the mapped spectral response acceleration parameter at 1 – second period, S1, is less than 0.75, the 2022 CBC, Section 1613.2.5.1 allows that seismic design category to be determined from Table 1613.2.5(1) alone provided that all 4 requirements concerning fundamental period of structure, story drift, seismic response coefficient, and relative rigidity of the diaphragms are met. For this condition, Site Coefficient Fv, should be taken from Table 1613.2.3(2) for Site Class D, only for calculation of Ts. Our interpretation of ASCE 7-16 is that for conditions where one or more of these 4 conditions are not met, seismic design category should be assigned based on: 1) 2022 CBC, Table 1613.2.5(1), 2) structure’s risk category and 3) the value of SDS, at the discretion of the project structural engineer. Equivalent Lateral Force Method As stated herein, the subject site is considered to be within a Site Class D-Stiff Soil. Per ASCE 7-16 Supplement 3, a site-specific ground motion hazard analysis is not required for structures on Site Class D- Stiff Soil with S1 > 0.2 provided that the value of the parameter SM1 determined by Eq. (11.4-2) is increased FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 11 by 50 percent for all applications of SM1 and structural design is performed in accordance with Equivalent Lateral Force (ELF) procedure. CONCLUSIONS Site Suitability From a geotechnical engineering and engineering geologic point of view, the subject property is considered suitable for the proposed development provided the following conclusions and recommendations are incorporated into the design criteria and project specifications. Primary Geologic/Geotechnical Considerations Groundwater Groundwater was not encountered in any of our exploratory test pits, excavated to a maximum depth of 10 feet below the ground surface. Data provided in a nearby well indicates groundwater is at depths exceeding 500 feet bgs. Regional groundwater is not anticipated to affect the subject development. Fault Rupture The site is not located within a currently designated State of California Alquist-Priolo Earthquake Fault Zone (CGS, 2023), nor is it within a San Bernardino County Fault Zone (County of San Bernardino, 2010). In addition, no known active faults have been identified on the site. While fault rupture would most likely occur along previously established fault traces, fault rupture could occur at other locations. However, the potential for active fault rupture at the site is considered to be very low. Strong Ground Motions The site is located in a seismically active area of southern California and will likely be subjected to very strong seismically related ground shaking during the anticipated life span of the project. Structures within the site should therefore be designed and constructed to resist the effects of strong ground motion in accordance with the 2022 California Building Code (CBC) and the seismic parameters included in the recommendations section herein. Liquefaction, Landslides and Secondary Seismic Effects The proposed residential development is not mapped within a zone with an expected liquefaction susceptibility (County of San Bernardino, 2010). The site and immediate area exhibit level topography that is not prone to landsliding. Secondary effects of seismic activity normally considered as possible hazards FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 12 to a site include several types of ground failure. Such ground failures, which might occur as a consequence of severe ground shaking at the site, include ground subsidence, ground lurching and lateral spreading. The probability of occurrence of each type of ground failure depends on the severity of the earthquake, distance from faults, topography, subsoils, and groundwater conditions, in addition to other factors. Based on the site conditions, proposed grading, depth to groundwater exceeding 500 feet, and gentle topography across the site, landsliding, liquefaction, ground subsidence, ground lurching and lateral spreading are considered unlikely at the site. The potential for seismic flooding due to a tsunami or seiche is considered negligible. Compressible Soils The most significant geotechnical factor affecting the project site is the presence of near -surface compressible soils. Such native soils consist of surficial topsoil/colluvium/alluvium and are not considered suitable for support of fill or structural loads. Based on our subsurface assessment and laboratory test results, remedial removal depths on the order of 3 to 5 feet below existing grades are expected. Accordingly, these materials will require removal to competent alluvial deposit soils and replacement with properly compacted fill. Flooding The subject property is situated within Flood Insurance Rate Map (FIRMette) 06071C7915H. The subject property and vicinity are mapped within Zone X, defined as an area defined as areas of 0.2 percent annual chance flood; areas of 1 percent annual chance flood with average depths of less than 1 foot or within drainage areas less than 1 square mile; and areas protected by levees from 1 percent annual chance flood. Figure B above depicts the Flood Insurance Rate Map (FIRM) for the subject site and vicinity. EARTHWORK RECOMMENDATIONS Earthwork Criteria Earthwork should be performed in accordance with the Grading Code of the County of San Bernardino, in addition to the applicable provisions of the 2022 CBC. Grading should also be performed in accordance with the following site-specific recommendations prepared by Petra based on the proposed construction. Geotechnical Observations and Testing Prior to the start of earthwork, a meeting should be held at the site with the owner, contractor, and geotechnical consultant to discuss the work schedule and geotechnical aspects of the grading. Earthwork, FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 13 which in this instance will generally entail removal and re-compaction of the near surface soils, should be accomplished under full-time observation and testing of the geotechnical consultant. A representative of the project geotechnical consultant should be present onsite during all earthwork operations to document proper placement and compaction of fills, as well as to document compliance with the other recommendations presented herein. Clearing and Grubbing All existing weeds, grasses, brush, shrubs, trees, tree stumps and root balls, and similar vegetation existing within areas to be graded should be stripped and removed from the site . Clearing operations should also include the demolition and removal of all existing improvements (concrete slabs, concrete and asphalt rubble piles, scattered soil, concrete and rock piles, etc.), any remaining trash, debris, vegetation, and similar deleterious materials. A backfilled swimming pool was noted in aerial photographs in the vicinity of TP- 11. Additional effort to locate the former pool is recommended to verify the shell was removed in its entirety. Any cavities or excavations created upon removal of structures or existing trees (i.e., root ball) or any unknown subsurface structures (included buried pool, septic tanks and systems, storm drain pipes, and foundations), should be cleared of loose soil, shaped to provide access for backfilling and compaction equipment and then backfilled with properly compacted fill. Septic systems may be present in the concrete slabs area near TP-11 and TP-12, and the former residence near TP-7. A concrete headwall inlet and dual pipes were observed in the north central portion of the subject property (see Figure 2). Note that deleterious materials may be encountered within the site and may need to be removed by hand, i.e., root pickers, during the grading operations. The project geotechnical consultant should provide periodic observation and testing services during clearing and grubbing operations to document compliance with the above recommendations. In addition, should unusual or adverse soil conditions or buried structures be encountered during grading that are not described herein, these conditions should be brought to the immediate attention of the project geotechnical consultant for corrective recommendations. Excavation Characteristics The existing site soil is expected to be excavated with conventional earthmoving equipment. Although a limited number of oversize rocks (i.e., 12-inches in one dimension or greater) were encountered in our test pits, they are commonly associated with the native alluvial fan materials underlying the subject property and were observed in piles within the property. Overside rocks should be disposed of either offsite or FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 14 properly buried within the planned deeper fills in an approved engineered fashion, a minimum of 10 feet below finish pad grades. Ground Preparation - General Our field evaluation revealed that near-surface soils within the areas of proposed construction generally exhibit low to moderate in-place densities, contain some rootlets and other isolated organic material, and have been locally disturbed from previous onsite activities. This soil is subject to compression and settlement under the proposed fill surcharge and foundation loadings. As such, if these materials are left unmitigated and the condition may result in excessive differential settlement beneath the proposed structures, associated foundations, and/or associated appurtenant improvements. To create a uniform compacted fill mat below the proposed improvements and reduce the potential for distress due to excessive differential settlement, it is recommended that all near surface low-density native materials be removed to underlying competent alluvial materials and replaced as properly compacted fill materials. Based on our subsurface exploration and laboratory test results, remedial removal depths on the order of 3 to 5 feet below existing grades are expected, except where septic systems may be encountered. The horizontal limits of removal and re-compaction should extend to a minimum distance of 5 feet beyond the proposed improvements. It must be noted that the depths of remedial grading provided herein are estimates only and are based on conditions observed at the boring locations. Subsurface conditions can and usually do vary between points of exploration. For this reason, the actual removal depths will have to be determined on the basis of in- grading observations and testing performed by a representative of the project geotechnical consultant. The Client, civil engineer, and project grading contractor should allow contingencies for additional earthwork quantities should adverse conditions and deeper removals be required. Unsuitable Soil Removals Existing surficial soils including disturbed topsoil/alluvium and upper weather alluvium deposits that are considered unsuitable for support of proposed fills, structures, flatwork, pavement, or other improvements and should be removed to underlying competent native valley deposit materials. All existing low-density, compressible surficial soils in areas to receive compacted fill or to support the residential building pads should be removed to underlying competent soils as approved by the project geotechnical consultant. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 15 Based on our subsurface assessment and laboratory test results, remedial removal depths on the order of 3 to 5 feet below existing grades are expected. Unsuitable soil removals may also need to be locally deeper, depending on the exposed conditions encountered during grading. The actual depths and horizontal limits of removals and over-excavations should be evaluated during grading on the basis of observations and testing performed by the project geotechnical consultant. Prior to placing engineered fill, all exposed bottom surfaces in the removal areas should be approved by a representative of project geotechnical consultant and then scarified to a minimum depth of 12 inches, flooded with water and compacted with heavy vibratory equipment to achieve near-optimum moisture conditions and then compacted in-place to no less than 90 percent relative compaction. Ground Preparation - Roadways For proposed roadways, the existing ground surfaces should be over-excavated to a minimum depth of 1 foot below the existing ground surface or 2 feet below the proposed subgrade elevations, whichever is deeper. After completion of over-excavation, the areas should be scarified to a minimum depth of 6 inches, moisture-conditioned, and re-compacted to no less than 90 percent relative compaction. The excavated materials may be replaced as properly compacted fill. The horizontal limits of over-excavation should extend to a minimum horizontal distance of 12 inches beyond the perimeter of the proposed improvements. All fills should be placed in 6- to 8-inch-thick maximum lifts, watered or air dried as necessary to achieve slightly above-optimum moisture conditions, and then compacted to a minimum relative compaction of 90 percent per ASTM D 1557. The laboratory maximum dry density and optimum moisture content for each change in soil type should be determined in accordance with Test Method ASTM D 1557. It should be noted that the upper 12 inches of the pavement subgrade shall be compacted to no less than 95 percent relative compaction prior to placement of aggregate base. Cut Lots Lots located entirely in cut exceeding 1 foot should be over-excavated a minimum of 3 feet below the bottom of the proposed foundations and replaced as properly compacted fill. Cut lots with less than 1 foot of cut should be over-excavated to a depth of 4 feet below existing grade. Prior to placing engineered fill, all exposed over-excavation bottom surfaces in the building pad areas should be first scarified to a depth of 12 inches, flooded with water and compacted with heavy vibratory equipment to achieve near-optimum moisture conditions and then compacted in-place to no less than 90 percent relative compaction. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 16 Cut-Fill Transition Lots/Building Pads Cut/fill transitions should be eliminated from building-pad areas to reduce the detrimental effects of differential settlement. This should be accomplished by over-excavating the "cut" or shallow-fill portions to a depth of 3 feet below the bottom of the proposed foundations and replacing the excavated materials as properly compacted fill. Horizontal limits of over-excavation should extend across the entire level portion of the lot. Prior to placing engineered fill, all exposed over-excavation bottom surfaces in the removal areas should be first scarified to a depth of 12 inches, moisture-conditioned to achieve near-optimum moisture and then compacted in- place with heavy vibratory equipment to no less than 90 percent relative compaction. Suitability of Site Soils as Fill Site soils are suitable for use in engineered fills provided they are clean from organics and/or debris . Oversize rock, that exceeding 12 inches, should be excluded from placement in the upper 4 feet of the building pads. Fill Placement Fill materials should be placed in approximately 6- to 8-inch-thick loose lifts, moisture-conditioned as necessary to achieve a moisture content approximately 2 percent above optimum moisture condition, and then compacted in-place to no less than 90 percent relative compaction. The laboratory maximum dry density and optimum moisture content for each major soil type should be determined in accordance with ASTM D 1557. Import Soils for Grading If import soils are needed to achieve final design grades, import soils should be free of deleterious materials, oversize rock, and any hazardous materials. The soils should also be non-expansive and essentially non- corrosive and approved by the project geotechnical consultant prior to being brought onsite. The geotechnical consultant should inspect the potential borrow site and conduct testing of the soil at least three days before the commencement of import operations. Shrinkage and Subsidence Volumetric changes in earth quantities will occur when excavated onsite soils are replaced as properly compacted fill. Following is an estimate of shrinkage factors for the alluvial soil present onsite. These FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 17 estimates are based on in-place densities of the various materials and on the estimated average degree of relative compaction achieved during grading. • Disturbed Surface Soils (0-2± feet).……………………………… Shrinkage of 15 to 20%± • Alluvium (Upper 2-7± ft.) ……………………….…..................... Shrinkage of 10 to 15%± Subsidence from scarification and re-compaction of exposed bottom surfaces in removal areas to receive fill is expected to vary from negligible to approximately 0.1 foot. The above estimates of shrinkage and subsidence are intended as an aid for project engineers in determining earthwork quantities. However, these estimates should not be considered as absolute values and should be used with some caution. Contingencies should be made for balancing earthwork quantities based on actual shrinkage and subsidence that occurs during the grading operations. Temporary Excavations Temporary excavations to a depth possibly as much as 5± feet below existing grades may be required to accommodate the recommended over-excavation of unsuitable materials. Based on the physical properties of the onsite cohesionless soils, temporary excavations exceeding 4 feet in depth should be cut back to an inclination of 1:1 (h:v) or flatter. However, the temporary excavations should be observed by a representative of the project geotechnical consultant for evidence of potential instability. Depending on the results of these observations, revised slope configurations may be necessary. Other factors which should be considered with respect to the stability of the temporary slopes include construction traffic an d/or storage of materials on or near the tops of the slopes, construction scheduling, presence of nearby walls or structures on adjacent properties and weather conditions at the time of construction. Applicable requirements of the California Construction and General Industry Safety Orders, the Occupational Safety and Health act of 1970 and the Construction Safety Act should also be followed. FOUNDATION DESIGN RECOMMENDATIONS Allowable Soil Bearing Capacities Pad Footings An allowable soil bearing capacity of 1,500 pounds per square foot may be utilized for design of isolated 24-inch-square footings founded at a minimum depth of 12 inches below the lowest adjacent final grade for pad footings that are not a part of the slab system and are used for support of such features as roof overhang, second-story decks, patio covers, etc. This value may be increased by 20 percent for each additional foot of depth and by 10 percent for each additional foot of width, to a maximum value of 2,500 FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 18 pounds per square foot. The recommended allowable bearing value includes both dead and live loads and may be increased by one-third for short duration wind and seismic forces. Continuous Footings An allowable soil bearing capacity of 1,500 pounds per square foot may be utilized for design of continuous footings founded at a minimum depth of 12 inches below the lowest adjacent final grade . This value may be increased by 20 percent for each additional foot of depth and by 10 percent for each additional foot of width, to a maximum value of 2,500 pounds per square foot. The recommended allowable bearing value includes both dead and live loads and may be increased by one-third for short duration wind and seismic forces. Estimated Footing Settlement Based on the allowable bearing values provided above, total static settlement of the footings under the anticipated loads is expected to be on the order of 3/4 inch. Differential settlement is expected to be less than 1/2 inch over a horizontal span of 20 feet. The majority of settlement is likely to take place as footing loads are applied or shortly thereafter. Lateral Resistance A passive earth pressure of 250 pounds per square foot per foot of depth, to a maximum valu e of 2,500 pounds per square foot, may be used to determine lateral bearing resistance for footings. The above values may be increased by one-third when designing for transient wind or seismic forces. In addition, a coefficient of friction of 0.35 times the dead load forces may be used between concrete and the supporting soils to determine lateral sliding resistance. It should be noted that the above values are based on the condition where footings are cast in direct contact with compacted fill or competent native soils. In cases where the footing sides are formed, all backfill placed against the footings upon removal of forms should be compacted to at least 90 percent of the applicable maximum dry density. Guidelines for Footings and Slabs on-Grade Design and Construction The results of our laboratory tests performed on representative samples of near-surface soils within the site during our evaluation indicate that these materials predominantly exhibit expansion indices that are less than 20. As indicated in Section 1803.5.3 of 2022 California Building Code (2022 CBC), these soils are considered non-expansive and, as such, the design of slabs on-grade is considered to be exempt from the procedures outlined in Sections 1808.6.2 of the 2022 CBC and may be performed using any method deemed rational and appropriate by the project structural engineer. However, the following minimum FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 19 recommendations are presented herein for conditions where the project design team may require geotechnical engineering guidelines for design and construction of footings and slabs on-grade at the project site. The design and construction guidelines that follow are based on the above soil conditions and may be considered for reducing the effects of variability in fabric, composition and, therefore, the detrimental behavior of the site soils such as excessive short- and long-term total and differential heave or settlement. These guidelines have been developed on the basis of the previous experience of this firm on projects with similar soil conditions. Although construction performed in accordance with these guidelines has been found to reduce post-construction movement and/or distress, they generally do not positively eliminate all potential effects of variability in soils characteristics and future heave or settlement. It should also be noted that the suggestions for dimension and reinforcement provided herein are performance-based and intended only as preliminary guidelines to achieve adequate performance under the anticipated soil conditions. However, they should not be construed as replacement for structural engineering analyses, experience, and judgment. The project structural engineer, architect and/or civil engineer should make appropriate adjustments to slab and footing dimensions, and reinforcement type, size and spacing to account for internal concrete forces (e.g., thermal, shrinkage and expansion), as well as external forces (e.g., applied loads) as deemed necessary. Consideration should also be given to minimum design criteria as dictated by local building code requirements. Conventional Slab-on-Ground Foundation System Given the expansion index of less than 20, as generally exhibited by onsite soils, we recommend that footings and floor slabs be designed and constructed in accordance with the following minimum criteria. Footings 1. Exterior continuous footings supporting one- and two-story structures should be founded at a minimum depth of 12 inches below the lowest adjacent final grade. Interior continuous footings may be founded at a minimum depth of 10 inches below the top of the adjacent finish floor slabs. The width and spacing of interior continuous footings should be designed by the project structural engineer. 2. In accordance with Table 1809.7 of 2022 CBC for light-frame construction, all continuous footings should have minimum widths of 12 inches for one- and two-story construction. We recommend all continuous footings should be reinforced with a minimum of two No. 4 bars, one top and one bottom. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 20 3. A minimum 12-inch-wide grade beam founded at the same depth as adjacent footings should be provided across the garage entrances or similar openings (such as large doors or bay windows). The grade beam should be reinforced with a similar manner as provided above. 4. Interior isolated pad footings, if required, should be a minimum of 24 inches square and founded at a minimum depth of 12 inches below the bottoms of the adjacent floor slabs. Pad footings should be reinforced with No. 4 bars spaced a maximum of 18 inches on centers, both ways, placed near the bottoms of the footings. 5. Exterior isolated pad footings intended for support of colonnades, roof overhangs, upper -story decks, patio covers, and similar construction should be a minimum of 24 inches square and founded at a minimum depth of 18 inches below the lowest adjacent final grade. The pad footings should be reinforced with No. 4 bars spaced a maximum of 18 inches on centers, both ways, placed near the bottoms of the footings. 6. Exterior isolated pad footings may need to be connected to adjacent pad and/or continuous footings via tie beams at the discretion of the project structural engineer. Further, where excessive soils settlement issues have been identified for this site elsewhere in the report, it is strongly recommended to tie all footings both interior and exterior with a network of grade beams to reduce the potential differential settlement or isolated bearing distress issues below any independent footings. 7. The spacing and layout of the interior concrete grade beam system, if required below floor slabs, should be determined by the project structural engineer in accordance with the WRI publication. 8. The minimum footing dimensions and reinforcement recommended herein may be modified (increased or decreased subject to the constraints of Chapter 18 of the 2022 CBC) by the structural engineer responsible for foundation design based on his/her calculations, engineering experience, and judgment. Building Floor Slabs 1. Concrete floor slabs should be a minimum of 4 inches thick and reinforced with a minimum of No. 3 bars spaced a maximum of 24 inches on center, both ways. Alternatively, the structural engineer may recommend the use of prefabricated welded wire mesh for slab reinforcement. For this condition, the welded wire mesh should be of sheet type (not rolled) and should consist of 6x6/W2.9xW2.9 (per the Wire Reinforcement Institute, WRI, designation) or stronger. All slab reinforcement should be properly supported to ensure the desired placement near mid-depth. Care should be exercised to prevent warping of the welded wire mesh between the chairs in order to ensure its placement at the desired mid -slab position. Slab dimension, reinforcement type, size and spacing need to account for internal concrete forces (e.g., thermal, shrinkage and expansion) as well as external forces (e.g., applied loads), as deemed necessary. It should be noted that some of the non-climatic site parameters, which may impact slabs on- grade performance, are not known at this time, as it is the case for many projects at the design stage. Some of these site parameters include unsaturated soils diffusion conditions pre- and post-construction (e.g., casting the slabs at the end of long, dry or wet periods, maint enance during long, dry and wet periods, etc.), landscaping, alterations in site surface gradient, irrigation, trees, etc. While the effects of any or a combination of these parameters on slab performance cannot be accurately predicted, maintaining moisture content equilibrium within the soils mass and planting trees at a distance greater than half of their mature height away FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 21 from the edge of foundation may reduce the potential for the adverse impact of these site parameters on slabs on-grade performance. 2. Living area concrete floor slabs and areas to receive moisture sensitive floor covering should be underlain with a moisture vapor retarder consisting of a minimum 10-mil-thick polyethylene or polyolefin membrane that meets the minimum requirements of ASTM E96 and ASTM E1745 for vapor retarders (such as Husky Yellow Guard®, Stego® Wrap, or equivalent). All laps within the membrane should be sealed, and at least 2 inches of clean sand should be placed over the membrane to promote uniform curing of the concrete. In general, to reduce the potential for punctures, the membrane should be placed on a pad surface that has been graded smooth without any sharp protrusions. If a smooth surface cannot be achieved by grading, consideration should be given to lowering the pad finished grade an additional inch and then placing a 1-inch-thick leveling course of sand across the pad surface prior to the placement of the membrane. Foot traffic on the membrane should be reduced to a minimum. Additional steps would also need to be taken to prevent puncturing of the vapor retarder during concrete placement. At the present time, some slab designers, geotechnical professionals and concrete experts view the sand layer below the slab (blotting sand) as a place for entrapment of excess moisture that could adversely impact moisture-sensitive floor coverings. As a preventive measure, the potential for moisture intrusion into the concrete slab could be reduced if the concrete is placed directly on the vapor retarder. However, if this sand layer is omitted, appropriate curing methods must be implemented to ensure that the concrete slab cures uniformly. A qualified contractor with experience in slab construction and curing should provide recommendations for alternative methods of curing and supervise the construction process to ensure uniform slab curing. 3. Garage floor slabs should be a minimum 4 inches thick and reinforced in a similar manner as living area floor slabs. Garage slabs should also be poured separately from adjacent wall footings with a positive separation maintained using ¾-inch-minimum felt expansion joint material. To control the propagation of shrinkage cracks, garage floor slabs should be quartered with weakened plane joints . Consideration should be given to placement of a moisture vapor retarder below the garage slab, similar to that provided in Item 2 above, should the garage slab be overlain with moisture sensitive floor covering. 4. Presaturation of the subgrade below floor slabs will not be required; however, prior to placing concrete, the subgrade below all dwelling and garage floor slab areas should be thoroughly moistened to achieve a moisture content that is at least equal to or slightly greater than optimum moisture content. This moisture content should penetrate to a minimum depth of 12 inches below the bottoms of the slabs. 5. The minimum dimensions and reinforcement recommended herein for building floor slabs may be modified (increased or decreased subject to the constraints of Chapter 18 of the 2022 CBC) by the structural engineer responsible for foundation design based on his/her calculations, engineering experience, and judgment. Footing Observations Foundation footing trenches should be observed by the project geotechnical consultant to document into competent bearing-soils. The foundation excavations should be observed prior to the placement of forms, FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 22 reinforcement, or concrete. The excavations should be trimmed neat, level, and square. Prior to placing concrete, all loose, sloughed, or softened soils and/or construction debris should be removed. Excavated soils derived from footing and utility trench excavations should not be placed in slab-on-grade areas unless the soils are compacted to a relative compaction of 90 percent or more. PRELIMINARY PAVEMENT DESIGN RECOMMENDATIONS Based on experience with nearby sites, an R-value of 70 was estimated for the subject site. A traffic index (TI) of 5.5 was assumed for interior (local) streets and 6.5 for collectors in accordance with City of Fontana Standard Plan No. 402, Roadway Design Requirements. The traffic indices, along with the estimated design R-value, were utilized for preliminary pavement section design. The following pavement sections have been computed in accordance with Caltrans design procedures and presented in the following table, Table 2. TABLE 2 Preliminary Pavement Design Location Design R-value Traffic Index Pavement Section Interior (Local) Streets 70 5.5 4 in. AC1 / Compacted Subgrade Collectors 70 6.5 4.5 in. AC1 / Compacted Subgrade Notes: AC = Asphalt Concrete AB = Aggregate Base 1 = Min. AC section per City of Fontana Standard Plan 400 The upper 12 inches of subgrade soils immediately below the aggregate base (base) or full -depth asphalt concrete section should be compacted to 95 percent or more relative compaction based on ASTM D 1557 to a depth of 12 inches or more. Final subgrade compaction should be performed prior to placing base and after utility trench backfills have been compacted and tested. Subgrade shall be firm and unyielding, as exhibited by proof-rolling, prior to placement of asphalt concrete. Asphalt-concrete materials and construction should conform to Section 203 of the Greenbook. General Corrosivity Screening As a screening level study, limited chemical and electrical tests were performed on samples considered representative of the onsite soils to identify potential corrosive characteristics of these soils. The common indicators that are generally associated with soil corrosivity, among other indicators, include water-soluble sulfate (a measure of soil corrosivity on concrete), water-soluble chloride (a measure of soil corrosivity on FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 23 metals embedded in concrete), pH (a measure of soil acidity), and minimum electrical resistivity (a measure of corrosivity on metals embedded in soils). Test methodology and results are presented in Appendix B. It should be noted that Petra does not practice corrosion engineering; therefore, the test results, opinion and engineering judgment provided herein should be considered as general guidelines only. Additional analyses, and/or determination of other indicators, would be warranted, especially, for cases where buried metallic building materials (such as copper and cast or ductile iron pipes) in contact with site soils are planned for the project. In many cases, the project geotechnical engineer may not be informed of these choices. Therefore, for conditions where such elements are considered, we recommend that other, relevant project design professionals (e.g., the architect, landscape architect, civil and/or structural engineer, etc.) to be involved. We also recommend considering a qualified corrosion engineer to conduct additional sampling and testing of near-surface soils during the final stages of site grading to provide a complete assessment of soil corrosivity. Recommendations to mitigate the detrimental effects of corrosive soils on buried metallic and other building materials that may be exposed to corrosive soils should be provided by the corrosion engineer as deemed appropriate. In general, a soil’s water-soluble sulfate levels and pH relate to the potential for concrete degradation; water-soluble chlorides in soils impact ferrous metals embedded or encased in concrete, e.g., reinforcing steel; and electrical resistivity is a measure of a soil’s corrosion potential to a variety of buried metals used in the building industry, such as copper tubing and cast or ductile iron pipes. Table 3, below, presents test results with an interpretation of current code approach and guidelines that are commonly used in building construction industry. The table includes the code-related classifications of the soils as they relate to the various tests, as well as a general recommendation for possible mitigation measures in view of the potential adverse impact of corrosive soils on various components of the proposed structures in direct contact with site soils. The guidelines provided herein should be evaluated and confirmed, or modified, in their entirety by the project structural engineer, corrosion engineer and/or the contractor responsible for concrete placement for structural concrete used in exterior and interior footings, interior slabs on -ground, garage slabs, wall foundations and concrete exposed to weather such as driveways, patios, porches, wa lkways, ramps, steps, curbs, etc. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 24 TABLE 3 Soil Corrosivity Screening Results Test (Test Method Designation) Test Results Classification General Recommendations Soluble Sulfate (Cal 417) SO42- < 0.10 % by weight S0(1) - Not Applicable Type II cement; minimum fc’ = 2,500 psi; no water/cement ratio restrictions. pH (Cal 643) 5.6 – 6.0 Moderately Acid(3) No special recommendations Soluble Chloride (Cal 422) Cl1- < 500 ppm C1(2) - Moderate Residence: No special recommendations; fc’ should not be less than 2,500 psi. Resistivity (Cal 643) 1,000 – 3,000 Highly Corrosive Consult a Corrosion Engineer Notes: 1. ACI 318-14, Section 19.3 2. ACI 318-14, Section 19.3 3. Pierre R. Roberge, “Handbook of Corrosion Engineering” 4. Exposure classification C2 applies specifically to swimming pools and appurtenant concrete elements 5. fc’, 28-day unconfined compressive strength of concrete Exterior Concrete Flatwork General Near-surface compacted fill soils within the site are variable in fines content, however, they are expected to exhibit a range of expansion indices that classify them as non-expansive, i.e., Expansion Index, EI, < 20. Therefore, we recommend that all exterior concrete flatwork such as sidewalks, patio slabs, large decorative slabs, concrete subslabs that will be covered with decorative pavers, private and/or public vehicular parking, driveways and/or access roads within and adjacent to the site be designed by the project architect, civil and/or structural engineer with consideration given to mitigating the potential for cracking, curling, etc. that can potentially develop as a result of being underlain with soils that essentially exhibiting expansion index values that fall in the non-expansive category. The guidelines that follow should be considered as minimums and are subject to review and revision by the project architect, civil engineer, structural engineer and/or landscape consultant as deemed appropriate. Subgrade Preparation Compaction To reduce the potential for distress to concrete flatwork, the subgrade soils below concrete flatwork areas to a minimum depth of 12 inches (or deeper, as either prescribed elsewhere in this report or determined in FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 25 the field) should be moisture conditioned to at least equal to, or slightly greater than, the optimum moisture content and then compacted to a minimum relative compaction of 90 percent. Where concrete public roads, concrete segments of roads and/or concrete access driveways and heavy recreational vehicles parking are proposed, the upper 6 inches of subgrade soil should be compacted to a minimum 95 percent relative compaction. Pre-Moistening As a further measure to reduce the potential for concrete flatwork distress, subgrade soils should be thoroughly moistened prior to placing concrete. The moisture content of the soils should be at least 1.1 times the optimum moisture content and penetrate to a minimum depth of 12 inches into the subgrade . Flooding or ponding of the subgrade is not considered feasible to achieve the above moisture conditions since this method would likely require construction of numerous earth berms to contain the water . Therefore, moisture conditioning may be achieved with sprinklers or a light spray applied to the subgrade over a period of several hours to few days just prior to pouring concrete. Pre-watering of the soils is intended to promote uniform curing of the concrete, reduce the development of shrinkage cracks, and reduce the potential for differential expansion pressure on freshly poured flatwork. A representative of the project geotechnical consultant should observe and verify the density and moisture content of the soils, and the depth of moisture penetration prior to pouring concrete. Thickness and Joint Spacing To reduce the potential of unsightly cracking, concrete walkways, patio-type slabs, large decorative slabs and concrete subslabs to be covered with decorative pavers should be at least 4 inches thick and provided with construction joints or expansion joints every 6 feet or less. Private driveways that will be designed for the use of passenger cars for access to private garages should also be at least 4 inches thick and provided with construction joints or expansion joints every 10 feet or less. Concrete pavement that will be designed based on an unlimited number of applications of an 18-kip single-axle load in public access areas, segments of road that will be paved with concrete (such as bus stops and cross-walks) or access roads and driveways, which serve multiple residential units or garages, that will be subject to heavy truck loadings and parking of recreational vehicles should have a minimum thickness of 5 inches and be provided with control joints spaced at maximum 10-foot intervals. A modulus of subgrade reaction of 125 pounds per cubic foot may be used for design of the public and access roads. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 26 Reinforcement All concrete flatwork having their largest plan-view panel dimensions exceeding 10 feet should be reinforced with a minimum of No. 3 bars spaced 18 inches for 4-inch-thick slabs and No. 4 bars spaced 24 inches for 5-inch-thick slabs on centers, both ways. Alternatively, the slab reinforcement may consist of welded wire mesh of the sheet type (not rolled) with 6x6/W1.4xW1.4 WWF designations for 4-inch-thick slabs and 6x6/W2.9xW2.9 designations for 5-inch-thick slabs in accordance with the Wire Reinforcement Institute (WRI). The reinforcement should be properly positioned near the middle of the slabs. All foot and equipment traffic on the reinforcement should be avoided or reduced to a minimum. The reinforcement recommendations provided herein are intended as a guideline to achieve adequate performance for anticipated soil conditions. As such, this guideline may not satisfy certain acceptable approaches, e.g., the area of reinforcement to be equal to or greater that 0.2 percent of the area of concrete. The project architect, civil and/or structural engineer should make appropriate adjustments in reinforcement type, size and spacing to account for concrete internal (e.g., shrinkage and thermal) and external (e.g., applied loads) forces as deemed necessary. Edge Beams (Optional) Where the outer edges of concrete flatwork are to be bordered by land scaping, it is recommended that considerations be given to the use of edge beams (thickened edges) to prevent excessive infiltration and accumulation of water under the slabs. Edge beams, if used, should be 6 to 8 inches wide, extend 8 inches below the tops of the finish slab surfaces. Edge beams are not mandatory; however, their inclusion in flatwork construction adjacent to landscaped areas is intended to reduce the potential for vertical and horizontal movement and subsequent cracking of the flatwork related to uplift forces that can develop in expansive soils. Drainage Drainage from patios and other flatwork areas should be directed to local area drains and/or graded earth swales designed to carry runoff water to the adjacent streets or other approved drainage structures. The concrete flatwork should be sloped at a minimum gradient of one percent, or as prescribed by project civil engineer or local codes, away from building foundations, retaining walls, masonry garden walls and slope areas. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 27 Tree Wells Tree wells are not recommended in concrete flatwork areas because they typically introduce excessive water into the subgrade soils and allow root invasion, both of which can cause heaving and cracking of the flatwork. INFILTRATION TEST RESULTS Plans for development of the subject property were not available at the time of field work or this report; however, one representative infiltration test hole (P-1) was completed within the subject property at a depth of 5 feet bgs to assess infiltration rates of the near-surface onsite soils for preliminary design of detention basins to manage storm water runoff. The infiltration test hole (P-1) was excavated using a rubber-tired backhoe. A one-foot square hole was hand excavated from 4 to 5.4 feet bgs and 1 foot of perforated pipe embedded in 1 foot pea gravel was placed in the hand excavation. Solid pipe was added to the surface and the test pit was backfilled with native soils. Pre-soaking and testing was conducted at a depth of 4 to 5 feet using the Falling Head Test Method (RCFCD, 2011). Infiltration rates were then calculated using the Porchet Method (RCFCD, 2011), commonly called the “inversed auger-hole method.” The infiltration test was conducted in the lower one foot of the test pit. The hole was pre-soaked immediately after excavating. Soils encountered in test locations consisted of medium- to course-grained gravelly sand. The test location is shown on Figure 2. Test pit logs are provided in Appendix A. The un-factored infiltration rate results are summarized below in Table 4, and are provided in Appendix D. TABLE 4 Summary of Infiltration Rates Percolation Test Location And Date Depth of Test (feet below surface) Percolation Rate (gallons/day/ft2) Infiltration Rate (inches/hour) P-1 4 – 5.4 800 130 POST-GRADING RECOMMENDATIONS Site Drainage Surface drainage systems consisting of sloping concrete flatwork, graded earth swales and/or an underground area drain system are anticipated to be constructed to collect and direct all surface waters to FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 28 the adjacent streets and storm drain facilities. In addition, the ground surface around the proposed buildings should be sloped at a positive gradient away from the structures. The purpose of the precise grading is to prevent ponding of surface water within the level areas of the site and against building f oundations and associated site improvements. The drainage systems should be properly maintained throughout the life of the proposed development. It should be emphasized that the slopes away from the structures area drain inlets and storm drain structures to be properly maintained, not to be obstructed, and that future improvements not to alter established gradients unless replaced with suitable alternative drainage systems. Slope Landscaping and Maintenance Adequate slope and pad drainage facilities are essential in the design of grading for the subject site. An anticipated rainfall equivalency on the order of 60 to 100 inches per year at the site can result due to irrigation. The overall stability of the graded slopes should not be adversely affected provided drainage provisions are properly constructed and maintained thereafter and provided engineered slopes are landscaped immediately following grading with a deep-rooted, drought-tolerant, and maintenance-free plant species, as recommended by the project landscape architect. Additional comments and recommendations are presented below with respect to slope drainage, landscaping, and irrigation. A common type of slope failure in hillside areas is the surficial instability and usually involves the upper 1 to 6 feet. For a given gradient, these surficial slope failures are generally caused by a wide variety of conditions, such as overwatering, cyclic changes in moisture content and density of slope soils from both seasonal and irrigation-induced wetting and drying, soil expansiveness, time lapse between slope construction and slope planting, type and spacing of plant materials used for slope protection, rainfall intensity and/or lack of a proper maintenance program. Based on this discussion, the following recommendations are presented to mitigate potential surficial slope failures. • Proper drainage provisions for engineered slopes should consist of concrete terrace drains, downdrains and energy dissipaters (where required) constructed in accordance with the Grading Code of the City of Fontana. Provisions should also be made for construction of compacted-earth berms along the tops of engineered slopes. • Permanent engineered slopes should be landscaped as soon as practical at the completion of grading. As noted, the landscaping should consist of a deep-rooted, drought-tolerant, and maintenance-free plant species. If landscaping cannot be provided within a reasonable period of time, jute matting (or equivalent) or a spray-on product designed to seal slope surfaces should be considered as a temporary measure to inhibit surface erosion until such time permanent landscape plants have become well-established. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 29 • Irrigation systems should be installed on the engineered slopes and a watering program then implemented which maintains a uniform, near-optimum moisture condition in the soils. Overwatering and subsequent saturation of the slope soils should be avoided. On the other hand, allowing the soils to dry-out is also detrimental to slope performance. • Irrigation systems should be constructed at the surface only. Construction of sprinkler lines in trenches should not be allowed without prior approval from the geotechnical engineer and engineering geologist. • A permanent slope-maintenance program should be initiated for major slopes not maintained by individual homeowners. Proper slope maintenance should include the care of drainage- and erosion-control provisions, rodent control, and repair of leaking or damaged irrigation systems. • Homeowners should be advised of the potential problems that can develop when drainage on the pads and slopes is altered. Drainage can be altered due to the placement of fill and construction of garden walls, retaining walls, walkways, patios, swimming pools, spas, and planters. Utility Trenches Utility-trench backfill within street rights-of-way, utility easements, under sidewalks, driveways and building-floor slabs should be compacted to a relative compaction of 90 percent or more. Where onsite soils are utilized as backfill, mechanical compaction should be used. Density testing, along with probing, should be performed by the project geotechnical consultant or his representative to document adequate compaction. Utility-trench sidewalls deeper than about 4 feet should be laid back at a ratio of 1:1 (h:v) or flatter or shored. A trench box may be used in lieu of shoring. If shoring is anticipated, the project geotechnical consultant should be contacted to provide design parameters. For trenches with vertical walls, backfill should be placed i n approximately 1- to 2-foot-thick loose lifts and then mechanically compacted with a hydra-hammer, pneumatic tampers, or similar compaction equipment. For deep trenches with sloped walls, backfill materials should be placed in approximately 8- to 12-inch-thick loose lifts and then compacted by rolling with a sheepsfoot tamper or similar equipment. Where utility trenches are proposed in a direction that parallels any building footing (interior and/or exterior trenches), the bottom of the trench should not be located within a 1:1 (h:v) plane projected downward from the outside bottom edge of the adjacent footing. Retaining Walls Footing Embedment The base of retaining-wall footings constructed on level ground may be founded at a depth of 12 inches or more below the lowest adjacent final grade for low height walls. Where retaining walls are proposed on or FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 30 within 15 feet from the top of adjacent descending fill slope, the footings should be deepened such that a horizontal clearance of 7 feet or more is maintained between the outside bottom edges of the footings and the face of the slope. The above-recommended footing setback is preliminary and may be revised based on site-specific soil conditions. Footing trenches should be observed by the project geotechnical representative to document that the footing trenches have been excavated into competent bearing soils and to the embedments recommended above. These observations should be performed prior to placing forms or reinforcing steel. Allowable Bearing Values and Lateral Resistance Retaining wall footings may be designed using the allowable bearing values and lateral resistance values provided previously for building foundations; however, when calculating passive resistance, the resistance of the upper 6 inches of the soil cover in front of the wall should be ignored in areas where the front of the wall will not be covered with concrete flatwork. Active Earth Pressures As of the date of this report, it is uncertain whether the proposed retaining walls will be backfilled with on- site soils or imported granular materials. For this reason, active and at-rest earth pressures are provided below for both conditions. However, considering that the onsite earth materials have an expansion index of 0 to 20, the use of imported granular materials for backfilling behind the retaining walls as described in the following sections is optional. 1. Onsite Soils Used for Backfill Onsite soils have an expansion index of 0 to 20. Therefore, active earth pressures equivalent to fluids having a density of 35 psf/ft and 51 psf/ft should be used for design of cantilevered walls retaining a level backfill and ascending 2:1 backfill, respectively. For walls that are restrained at the top, at-rest earth pressures of 53 pounds per cubic foot (equivalent fluid pressures) should be used. The above values are for retaining walls that have been supplied with a proper subdrain system (see Figure RW-1). All walls should be designed to support any adjacent structural surcharge loads imposed by other nearby walls or footings in addition to the above recommended active and at-rest earth pressures. 2. Imported Sand, Pea Gravel or Rock Used for Wall Backfill Imported clean sand exhibiting a sand equivalent value (SE) of 30 or greater, pea gravel or crushed rock may be used for wall backfill to reduce the lateral earth pressures provided these granular backfill materials extend behind the walls to a minimum horizontal distance equal to one-half the wall height. In addition, the sand, pea gravel or rock backfill materials should extend behind the walls to a minimum horizontal distance of 2 feet at the base of the wall or to a horizontal distance equal to the heel width of the footing, whichever is greater (see Figures RW-2 and RW-3). For the above FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 31 conditions, cantilevered walls retaining a level backfill and ascending 2:1 backfill may be designed to resist active earth pressures equivalent to fluids having densities of 30 and 41 pounds per cubic f oot, respectively. For walls that are restrained at the top, at-rest earth pressures equivalent to fluids having densities of 45 and 62 pounds per cubic foot are recommended for design of restrained walls supporting a level backfill and ascending 2:1 backfill, respectively. These values are also for retaining walls supplied with a proper subdrain system. Furthermore, as with native soil backfill, the walls should be designed to support any adjacent structural surcharge loads imposed by other nearby walls or footings in addition to the recommended active and at-rest earth pressures. All structural calculations and details should be provided to the project geotechnical consultant for verification purposes prior to grading and construction phases. Earthquake Loads It is our understanding that retaining wall plans are not available at the time of this report. Section 1803.5.12 of the 2022 CBC requires the determination of lateral loads on retaining walls from earthquake forces for structures in seismic design categories D through E that are supporting more than six feet of backfill height. Recommendations for design of walls exceeding six feet in height can be provided once retaining walls plans are available for review. Geotechnical Observation and Testing All grading associated with retaining wall construction, including backcut excavations, observation of the footing trenches, installation of the subdrainage systems, and placement of backfill should be provided by a representative of the project geotechnical consultant. Backdrains To reduce the likelihood of the entrapment of water in the backfill soils, weepholes or open vertical masonry joints may be considered for retaining walls not exceeding a height of 3 feet. Weepholes, if used, should be 3-inches minimum diameter and provided at intervals of 6 feet or less along the wall. Open vertical masonry joints, if used, should be provided at 32-inch intervals. A continuous gravel fill, 3 inches by 12 inches, should be placed behind the weepholes or open masonry joints. The gravel should be wrapped in filter fabric to prevent infiltration of fines and subsequent clogging of the gravel. Filter fabric may consist of Mirafi 140N or equivalent. A perforated pipe-and-gravel backdrain should be constructed behind retaining walls exceeding a height of 3 feet (see Figure RW-1). Perforated pipe should consist of 4-inch-minimum diameter PVC Schedule 40, or ABS SDR-35, with the perforations laid down. The pipe should be encased in a 1-foot-wide column of ¾-inch to 1½-inch open-graded gravel. If on-site soils are used as backfill, the open-graded gravel should FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 32 extend above the wall footings to a minimum height equal to one-third the wall height or to a minimum height of 1.5 feet above the footing, whichever is greater. The open-graded gravel should be completely wrapped in filter fabric consisting of Mirafi 140N or equivalent. Solid outlet pipes should be connected to the subdrains and then routed to a suitable area for discharge of accumulated water. Waterproofing The backfilled sides of retaining walls should be coated with an approved waterproofing compound or covered with a similar material to inhibit migration of moisture through the walls. Temporary Excavations Temporary slopes may be cut at a gradient no steeper than 1:1 (h:v). However, the project geotechnical engineer should observe temporary slopes for evidence of potential instability. Depending on the results of these observations, flatter slopes may be necessary. The potential effects of various parameters such as weather, heavy equipment travel, storage near the tops of the temporary excavations and construction scheduling should also be considered in the stability of temporary slopes. Wall Backfill Recommended active and at-rest earth pressures for design of retaining walls are based on the physical and mechanical properties of the onsite soil materials. The backfill behind the proposed retaining walls, they should be placed in approximately 6- to 8-inch-thick maximum lifts, watered as necessary to achieve near optimum moisture conditions, and then mechanically compacted in place to a minimum relative compaction of 90 percent. Flooding or jetting of the backfill materials should be avoided. A representative of the project geotechnical consultant should observe the backfill procedures and test the wall backfill to verify adequate compaction. Masonry Block Screen Walls Construction On or Near the Tops of Descending Slopes Continuous footings for masonry walls proposed on or within 5 feet from the top of a descending cut or fill slope should be deepened such that a horizontal clearance of 5 feet is maintained between the outside bottom edge of the footing and the slope face. The footings should be reinforced with two No. 4 bars, one top and one bottom. Plans for top-of-slope masonry walls proposing pier and grade beam footings should be reviewed by the project geotechnical consultant prior to construction. FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 33 Construction on Level Ground Where masonry walls are proposed on level ground and 5 feet or more from the tops of descending slopes, the footings for these walls may be founded 18 inches or more below the lowest adjacent final grade. These footings should also be reinforced with two No. 4 bars, one top and one bottom. Construction Joints In order to reduce the potential for unsightly cracking related to the effects of differential settlement, positive separations (construction joints) should be provided in the walls at horizontal intervals of approximately 20 to 25 feet and at each corner. The separations should be provided in the blocks only and not extend through the footings. The footings should be placed monolithically with continuous rebars to serve as effective "grade beams" along the full lengths of the walls. CONSTRUCTION SERVICES This report has been prepared for the exclusive use of Fontana Investment 2023, LLC to assist the project engineers and architect in the design of the proposed development. It is recommended that Petra be engaged to review the final-design drawings and specifications prior to construction. This is to document that the recommendations contained in this report have been properly interpreted and are incorporated into the project specifications. If Petra is not accorded the opportunity to review these documents, we can take no responsibility for misinterpretation of our recommendations. We recommend that Petra be retained to provide soil-engineering services during construction of the excavation and foundation phases of the work. This is to observe compliance with the design, specifications, or recommendations and to allow design changes if subsurface conditions differ from those anticipated prior to start of construction. If the project plans change significantly (e.g., building loads or type of structures), we should be retained to review our original design recommendations and their applicability to the revised construction . If conditions are encountered during construction that appears to be different than those indicated in this report, this office should be notified immediately. Design and construction revisions may be required. LIMITATIONS This report is based on the project, as described and the geotechnical data obtained from the field tests performed and our laboratory test data. The materials encountered on the project site and utilized in our FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 34 laboratory evaluation are believed representative of the total area . However, soil materials can vary in characteristics between excavations, both laterally and vertically. The conclusions and opinions contained in this report are based on the results of the described geotechnical evaluations and represent our professional judgment. The findings, conclusions and opinions contained in this report are to be considered tentative only and subject to confirmation by the undersigned during the construction process. Without this confirmation, this report is to be considered incomplete and Petra or the undersigned professionals assume no responsibility for its use. In addition, this report should be reviewed and updated after a period of 1 year or if the site ownership or project concept changes from that described herein. The professional opinions contained herein have been derived in accordance with current standards of practice and no warranty is expressed or implied. Respectfully submitted, PETRA GEOSCIENCES, INC. 8/16/23 Edward Lump Grayson R. Walker Associate Geologist Principal Engineer CEG 1924 GE 871 EL/GRW/lv W:\2020-2025\2023\200\23-202\Reports\23-202 110 Preliminary Geotechnical Evaluation.docx FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 35 REFERENCES American Concrete Institute, 2008, Building Code Requirements for Structural Concrete (ACI 318 -08) and Commentary. American Society for Testing and Materials (ASTM) – Standard – Section Four – Construction, Volume 04.08 Soil and Rock American Society of Civil Engineers (ASCE) 7 -05 Minimum Design Loads for Buildings and Other Structures. Bedrossian, T.L., Hayhurst, C.A., and Roffers, P.D., 2010, Geologic Compilation o f Quaternary Surficial Deposits in Southern California, San Bernardino 30’ x 60’ Quadrangle, CGS Special Report 217, Plate 13, July. Bryant, W.A., and Hart, E.W., 2007, Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps, Californ ia Geological Survey, Special Publication 42. California Building Code (2022), California Code of Regulations, Title 24, Par 2, Volume 2 of 2, Based on the 2021 International Building Code, California Building Standards Commission. California Department of Water Resources, 2023, Water Data Library, http://www.water.ca.gov/waterdatalibrary/groundwater/. California Geological Survey (CGS), 2023, California Earthquake Hazards Zone Application (EQ Zapp), https://www.conservation.ca.gov/cgs/geohazards/eq-zapp, searched June. Cao, T., et al., 2003, Revised 2002 California Probabilistic Seismic Hazard Maps, June 2003: California Geological Survey. Environmental Data Resources, Inc. (EDR), 2023a, EDR Historical Topo Map Report, District Property 1, Knox Ave. South of S. Highland Ave, Fontana, CA, 92336 (Inquiry No. 7352995.4), dated June 1. _______, 2023b, The EDR Aerial Photo Decade Package, District Property 1, Knox Ave. South of S. Highland Ave., Fontana, CA, 92336 (Inquiry No. 7352995.11), dated June 1. Federal Emergency Management Agency (FEMA), 2008, Flood Insurance Rate Map (FIRMette), San Bernardino County, California and Incorporated Areas, Map Number 06071C7915H, revised August 28. Google Earth™ 2023, by Google Earth, Inc., http://www.google.com/earth/index.html, accessed May. Greenbook, 2012, Standard Specifications for Public Works Construction, by Public Works Standards, Inc., BNI Publishers. International Conference of Building Officials, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada”, California Division of Mines and Geology. Jennings, C.W. and Bryant, W.A., 2010, Fault Activity Map of California: California Geological Survey, Geologic Data Map No. 6. Morton, D.M. and Matt, J.C., 2001, Geologic Map of the Devore 7.5’ Quadrangle, San Bernardino County, California, USGS Open-File Report 01-173, Version 1.0. Office of Statewide Health Planning and Development (OSHPD), 2021, Seismic Design Maps, U.S. Seismic Design Maps (seismicmaps.org) FONTANA INVESTMENT 2023, LLC August 16, 2023 District Property 1, Knox Avenue / Fontana J.N. 23-202 Page 36 REFERENCES San Bernardino County, 2010, County Land Use Plan, General Plan, Geologic Hazard Overlays, Devore Sheet, FH21 C, plot date March 9. Southern California Earthquake Center (SCEC), 1999, Recommended Procedures for Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction Hazards in California: organized through the Southern California Earthquake Center, University of Southern California. Southern California Earthquake Data Center (SCEDC), 2014, http://www.data.scec.org/significant/index.html. Tokimatsu, K.; Seed, H.B.; 1987; Evaluation of settlements in sands due to earthquake shaking; Journal of Geotechnical Engineering: Vol. 113, No. 8, p. 861-879. United States Geologic Survey (U.S.G.S.), 1996a, Probabilistic Seismic Hazard Assessment for the State of California, Open-File Report 96-706. ______, 1996b, National Seismic-Hazards Maps, Open-File Report 96-532. ______, 2002, Documentations for the 2002 Update of the National Seismic Hazard Maps, Open -File Report 02-20. ______, 2007, Preliminary Documentation for the 2007 Update of the United States National Seismic Hazard Maps, Seismic Hazards Mapping Project, Open-File Report 2007-June Draft. ______, 2011, Earthquake Ground Motion Parameters, Version 5.1.0, utilizing ASCE 7 Standard Analysis Option, dated February 10. ______, 2021, Unified Hazard Tool Calculator, Unified Hazard Tool (usgs.gov) Wire Reinforcement Institute (WRI), 1996, Design of Slabs on Ground. FIGURES Site Location Map PETRA GEOSCIENCES, INC. COSTA MESA MURRIETA PALM DESERT SANTA CLARITA Figure 1J.N.: SCALE: see map DATE: DWG BY: 40880 COUNTY CENTER DRIVE, SUITE M TEMECULA, CALIFORNIA 92591 PHONE: (951) 600-9271 District Property 1, Knox Avenue Fontana, San Bernardino County, California - Approximate Site Location LEGEND N N TP-15 - Approximate location of exploratory test pit - Approximate Location of Exploratory Boring LEGEND B-7 Af Qal - Artificial Fill - Quaternary Young Alluvium - Quaternary/Tertiary Sandstone Qls - Quaternary Landslide Deposits QTsw GEOLOGIC UNITS N 1 mile - Reproduced from: USGS, 2023, The National Map August 2023 23-202 epl Base Map Reference: Google Earth, 2023, aerial dated September 2021. P E TR A G E O S C I E NC E S, I N C. 40880 County Center Drive, Suite M Temecula, California 92591 PHONE: (714) 549-8921 COSTA MESA TEMECULA VALENCIA PALM DESERT CORONA Test Pit Location Map District Property 1, Walnut Street Fontana, San Bernardino County, California DAT E: August, 2023 J.N.: 23-202 Figure 2 N N TP-15 - Approximate location of exploratory test pit - Approximate Location of Exploratory Boring LEGEND B-7 Af Qal - Artificial Fill - Quaternary Young Alluvium - Quaternary/Tertiary Sandstone Qls - Quaternary Landslide Deposits QTsw G EO L O G I C UN I T S GEOSCIENCES LE G E ND - Approximate Limits of Subject Property N 1,033 ft. - Approximate Location of Exploratory Test PitTP-11 P-1 TP-11 TP-1 TP-2 TP-3 TP-4 TP-5 TP-6 TP-7 TP-8 TP-9 TP-10 P-1 - Approximate Location of Percolation Test Pit Storm Drain Inlet Partially Buried Concrete Headwall and Two Inlet Pipes APPENDIX A EXPLORATION LOGS 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, fine grained rounded gravel - 10%. YOUNGER ALLUVIUM (Qya) Silty SAND (SM): Grayish brown, dry, 2" rounded gravel - 5%. Gravelly SAND to Sandy GRAVEL (SP/GP): Brown, dry, fine grained gravel - 50%, cobbles - 5%. SAND (SP): Dark yellowish brown, medium- to coarse-grained, some gravel. Total Depth = 9' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-1 Project:Knox Avenue and Walnut Street Boring No.: TP-1 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, fine- to medium-grained, 3" rounded gravel - 10%, rootlets. YOUNGER ALLUVIUM (Qya) Silty SAND (SM): Grayish brown, dry, fine grained to 2" gravel - 20%. Gravelly SAND (SP/GP): Yellowish brown, dry, loose, fine- to coarse-grained, gravel - 55%, cobbles up to 8" - 15%, boulders - 2%. moist. Total Depth = 9.5' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-2 Project:Knox Avenue and Walnut Street Boring No.:TP-2 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, fine grained to rounded 2" gravel - 15%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Gray to yellowish brown, dry, loose, medium- to coarse-grained, gravel - 40%, up to 8" cobbles - 5%. thick bed of course grained sand. sand -70%, gravel - 25%, cobbles - 5%. Total Depth = 10' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-3 Project:Knox Avenue and Walnut Street Boring No.:TP-3 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, fine- to medium-grained, rootlets. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Grayish brown, dry, fine- to medium-grained, rounded gravel - 15%, cobbles up to 9" - 10%. Yellowish brown, slightly moist, gravel - 45%, cobbles up to 8" - 10%. Total Depth = 10' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-4 Project:Knox Avenue and Walnut Street Boring No.:TP-4 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, fine- to medium-grained, rootlets, gravel - 10%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Gray, dry, fine- to medium-grained, gravel - 55%, cobbles up to 8" - 10%. Yellowish brown, slightly moist, gravel - 40%, cobbles up to 12". Total Depth = 8.5' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-5 Project:Knox Avenue and Walnut Street Boring No.:TP-5 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Brown, dry, loose, fine-grained, rootlets, gravel up to 2" - 5%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Gray, dry, medium-grained, rounded gravel - 35%, cobbles up to 8" - 15%. Yellowish brown, sand - 50%, gravel - 35%, cobbles 10%, boulders up to 14" - 5%. Total Depth = 10' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-6 Project:Knox Avenue and Walnut Street Boring No.:TP-6 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, fine- to medium-grained, gravel up to 2" - 15%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Yellowish brown, dry, gravel - 45%, cobbles up o 7" - 10%. Gray. Dark yellowish brown, slightly moist, trace roots, gravel - 45%, cobbles - 5%, boulders up to 12" - 5%. SAND (SP): gravel - 15%, cobbles - 5%, boulders up to 13" - 5%. Total Depth = 10' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-7 Project:Knox Avenue and Walnut Street Boring No.:TP-7 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, fine-grained, rootlets, gravel up tom .75" - 3%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Yellowish brown to gray, dry, medium-grained, Total Depth = 10' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-8 Project:Knox Avenue and Walnut Street Boring No.:TP-8 Location:Fontana Elevation: gravel - 30%, cobbles up to 6" - 2%. Dark yellowish brown, slightly moist . Gray to yellowish brown. 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, fine-grained, rootlets, gravel up to 1" - 10%. YOUNGER ALLUVIUM (Qyf) Gravelly SAND (SP/GP): Gray, dry, medium- to coarse-grained, gravel - 45%, cobbles up to 6" - 10%. Yellowish brown, rootlets, cobbles size increases up to 8". Dark yellowish brown, medium- to coarse-grained, gravel - 10%, cobbles - 5%, sand 85%. Total Depth = 9.5' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-9 Project:Knox Avenue and Walnut Street Boring No.:TP-9 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, loose, rootlets, gravel up to 1" - 10%. YOUNGER ALLUVIUM (Qya) Gravelly SAND (SP/GP): Yellowish brown to brown, dry, fine- to medium- grained, gravel - 30%, cobbles up to 6" - 20%. Gray. Dark yellowish brown, medium-grained, gravel - 25%, cobbles - 5%, boulders up to 12" - 5%. medium- to coarse-grained. Total Depth = 9' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-10 Project:Knox Avenue and Walnut Street Boring No.:TP-10 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Brown, slightly moist, fine-grained, trace garbage/plastic debris. YOUNGER ALLUVIUM (Qya) Gravvley SAND (SP/GP): Yellowish brown, slightly moist, medium-grained, gravel - 30%, cobbles - 10%, boulders up to 10" - 3%. Total Depth = 5.5' No groundwater Test pit backfilled with cuttings. Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Backhoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-11 Project:Knox Avenue and Walnut Street Boring No.:TP-11 Location:Fontana Elevation: 0 5 10 15 20 25 30 35 TOPSOIL Silty SAND (SM): Grayish brown, dry, fine- to medium-grained, rootlets, gravel up to 2" - 10%. YOUNGER ALLUVIUM (Qya) Gravelly SANd (SP/GP): Gray, dry, medium-grained, gravel - 35%, cobbles up to 8" - 10%. Yellowish brown, gravel - 35%, cobbles - 10%, boulders up to 18" - 5%. Total Depth = 5' No groundwater Percolation test installed at bottom of pit (4-5'). Project:Knox Avenue and Walnut Street Boring No.:P-1 Location:Fontana Elevation: Job No.:23-202 Client:Diversified Pacific Communities Date:7/28/23 Drill Method:Bachoe Driving Weight:N/A Logged By:KTM Depth (Feet) Lith- ology Material Description W A T E R Blows per 6 in. Samples C o r e B u l k Moisture Content (%) Laboratory Tests Dry Density (pcf) Other Lab Tests T E S T P I T L O G Petra Geosciences, Inc. PLATE A-12 APPENDIX B LABORATORY TEST PROCEDURES LABORATORY DATA SUMMARY _____________________________________________________ ______________________________________ PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882 J.N. 23-202 LABORATORY TEST PROCEDURES Soil Classification Soils encountered within the exploratory borings were initially classified in the field in general accordance with the visual-manual procedures of the Unified Soil Classification System (ASTM D 2488). The samples were re-examined in the laboratory and the classifications reviewed and then revised where appropriate . The assigned group symbols are presented in the Boring Logs (Appendix A). Maximum Dry Density and Optimum Moisture Content The maximum dry density and optimum moisture content of the on-site soils were determined for selected bulk samples in accordance with current version of ASTM D 1557. The results of these tests are presented on Plate B-1. Expansion Index The expansion index of onsite soils was determined per ASTM D 4829. The expansion index and expansion potential are presented in Plate B-1. Corrosivity Tests Chemical analyses were performed on a selected sample to determine concentrations of soluble sulfate and chloride, as well as pH and resistivity. These tests were performed in accordance with California Test Method Nos. 417 (sulfate), 422 (chloride) and 643 (pH and resistivity). Test results are presented in Plate B-1. Percent Passing No. 200 Sieve Selected samples were run through a number 200 sieve in general accordance with the latest version of Test Method ASTM D 1140. The results of these tests are included on Plate B-1. _____________________________________________________ ______________________________________ PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882 J.N. 23-202 PLATE B-1 LABORATORY DATA SUMMARY Laboratory Maximum Dry Density Sample Location Soil Type Optimum Moisture (%) Maximum Dry Density (pcf) P-1 @ 0-4’ Gravelly silty fine- to coarse-grain SAND 5.5 138.0 PER ASTM D 1557 and D4718-15 (Oversize Correction at 20.6%) Corrosivity Sample Location Sulfate1 (%) Chloride2 (ppm) pH3 Resistivity3 (ohm-cm) P-1 @ 0-4’ 0.0027 248 5.7 1,200 (1) PER CALIFORNIA TEST METHOD NO. 417 (2) PER CALIFORNIA TEST METHOD NO. 422 (3) PER CALIFORNIA TEST METHOD NO. 643 Expansion Index Sample Location Depth (feet) Soil Type Expansion1 Index Expansion Potential P-1 @ 0-4’ Gravelly silty fine- to coarse-grain SAND 0 Very Low (1) PER ASTM D 4829 Percent Passing No. 200 Sieve Sample Location Depth (feet) Soil Type Passing No. 200 Sieve (Percent) P-1 @ 0-4’ Gravelly silty fine- to coarse-grain SAND 14.6 TP-1 @ 0-5’ Gravelly silty fine- to coarse-grain SAND 20.1 (1) PER ASTM D 1140 APPENDIX C SEISMIC DESIGN PARAMETERS APPENDIX D INFILTRATION TEST RESULTS Total Depth of Boring, Dt (ft):5.4 Zone Tested: 4' -5.4' Diameter of Hole, D (in): 15 Date: 7-25-2023 Diameter of Pipe, d (in): 2 Agg. Correction (% Voids): 40 Pre-soak depth (ft): 5 1st Reading 2nd Reading 1 4.33 5.00 8.0 0.12 884 1 4.42 5.00 7.0 0.14 800 1 4.33 5.00 8.0 0.12 884 1 4.33 5.00 8.0 0.12 884 1 4.46 5.00 6.5 0.15 760 1 4.42 5.00 7.0 0.14 800 1 4.42 5.00 7.0 0.14 800 1 4.42 5.00 7.0 0.14 800 1 4.42 5.00 7.0 0.14 800 Soil Description*: medium Gravelly Sand * predominant materials within test zone Percolation Rate: 0.14 min/in 800 gal/day/ft2 Infiltration Rate:130 in/hr* (Porchet Method) r = D / 2 Ho = Dt - Do Hf = Dt - Df DH = ΔD = Ho - Hf Havg = (Ho + Hf) / 2 *Raw Number, Does Not Include a Factor of Safety Reference: RCFCWCD, Design Handbook for LIDBMP, dated September, 2011 August 2023 J.N.: 23-202 Test Number: P-1 40880 County Center Drive, Suite M Temecula, CA 92591 PHONE: (951) 600-9271 Perc. Rate (gal/day/ft^2) Shallow Percolation Test Method Time Interval (min) Depth to Water Surface Dw (ft) Change in Head (in) Perc. Rate (min/in) where Infiltration Rate, It =DH (60r) / Dt (r + 2Havg ) Figure 2 Diversified Pacific / Tennesee & Lugonia Redlands, California PERCOLATION TEST SUMMARY PETRA GEOSCIENCES, INC. COSTA MESA TEMECULA VALENCIA PALM DESERT CORONA SAN DIEGO APPENDIX E STANDARD GRADING SPECIFICATIONS STANDARD GRADING SPECIFICATIONS Page 1 These specifications present the usual and minimum requirements for projects on which Petra Geosciences, Inc. (Petra) is the geotechnical consultant. No deviation from these specifications will be allowed, except where specifically superseded in the preliminary geology and soils report, or in other written communication signed by the Soils Engineer and Engineering Geologist of record (Geotechnical Consultant). I. GENERAL A. The Geotechnical Consultant is the Owner's or Builder's representative on the project. For the purpose of these specifications, participation by the Geotechnical Consultant includes that observation performed by any person or persons employed by, and responsible to, the licensed Soils Engineer and Engineering Geologist signing the soils report. B. The contractor should prepare and submit to the Owner and Geotechnical Consultant a work plan that indicates the sequence of earthwork grading, the number of "spreads" and the estimated quantities of daily earthwork to be performed prior to the commencement of grading. This work plan should be reviewed by the Geotechnical Consultant to schedule personnel to perform the appropriate level of observation, mapping, and compaction testing as necessary. C. All clearing, site preparation, or earthwork performed on the project shall be conducted by the Contractor in accordance with the recommendations presented in the geotechnical report and under the observation of the Geotechnical Consultant. D. It is the Contractor's responsibility to prepare the ground surface to receive the fills to the satisfaction of the Geotechnical Consultant and to place, spread, mix, water, and compact the fill in accordance with the specifications of the Geotechnical Consultant. The Contractor shall also remove all material considered unsatisfactory by the Geotechnical Consultant. E. It is the Contractor's responsibility to have suitable and sufficient compaction equipment on the job site to handle the amount of fill being placed. If necessary, excavation equipment will be shut down to permit completion of compaction to project specifications. Sufficient watering apparatus will also be provided by the Contractor, with due consideration for the fill material, rate of placement, and time of year. F. After completion of grading a report will be submitted by the Geotechnical Consultant. II. SITE PREPARATION A. Clearing and Grubbing 1. All vegetation such as trees, brush, grass, roots, and deleterious material shall be disposed of offsite. This removal shall be concluded prior to placing fill. 2. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipe lines, etc., are to be removed or treated in a manner prescribed by the Geotechnical Consultant. STANDARD GRADING SPECIFICATIONS Page 2 III. FILL AREA PREPARATION A. Remedial Removals/Overexcavations 1. Remedial removals, as well as overexcavation for remedial purposes, shall be evaluated by the Geotechnical Consultant. Remedial removal depths presented in the geotechnical report and shown on the geotechnical plans are estimates only. The actual extent of removal should be determined by the Geotechnical Consultant based on the conditions exposed during grading. All soft, loose, dry, saturated, spongy, organic-rich, highly fractured or otherwise unsuitable ground shall be overexcavated to competent ground as determined by the Geotechnical Consultant. 2. Soil, alluvium, or bedrock materials determined by the Soils Engineer as being unsuitable for placement in compacted fills shall be removed from the site. Any material incorporated as a part of a compacted fill must be approved by the Geotechnical Consultant. 3. Should potentially hazardous materials be encountered, the Contractor should stop work in the affected area. An environmental consultant specializing in hazardous materials should be notified immediately for evaluation and handling of these materials prior to continuing work in the affected area. B. Evaluation/Acceptance of Fill Areas All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide sufficient survey control for determining locations and elevations of processed areas, keys, and benches. C. Processing After the ground surface to receive fill has been declared satisfactory for support of fill by the Geotechnical Consultant, it shall be scarified to a minimum depth of 6 inches and until the ground surface is uniform and free from ruts, hollows, hummocks, or other uneven features which may prevent uniform compaction. The scarified ground surface shall then be brought to optimum moisture, mixed as required, and compacted to a minimum relative compaction of 90 percent. D. Subdrains Subdrainage devices shall be constructed in compliance with the ordinances of the controlling governmental agency, and/or with the recommendations of the Geotechnical Consultant. (Typical Canyon Subdrain details are given on Plate SG-1). E. Cut/Fill & Deep Fill/Shallow Fill Transitions In order to provide uniform bearing conditions in cut/fill and deep fill/shallow fill transi tion lots, the cut and shallow fill portions of the lot should be overexcavated to the depths and the horizontal limits discussed in the approved geotechnical report and replaced with compacted fill. (Typical details are given on Plate SG-7.) STANDARD GRADING SPECIFICATIONS Page 3 IV. COMPACTED FILL MATERIAL A. General Materials excavated on the property may be utilized in the fill, provided each material has been determined to be suitable by the Geotechnical Consultant. Material to be used for fill shall be essentially free of organic material and other deleterious substances. Roots, tree branches, and other matter missed during clearing shall be removed from the fill as recommended by the Geotechnical Consultant. Material that is spongy, subject to decay, or otherwise considered unsuitable shall not be used in the compacted fill. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material. B. Oversize Materials Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 12 inches in diameter, shall be taken offsite or placed in accordance with the recommendations of the Geotechnical Consultant in areas designated as suitable for rock disposal (Typical details for Rock Disposal are given on Plate SG-4). Rock fragments less than 12 inches in diameter may be utilized in the fill provided, they are not nested or placed in concentrated pockets; they are surrounded by compacted fine grained soil material and the distribution of rocks is approved by the Geotechnical Consultant. C. Laboratory Testing Representative samples of materials to be utilized as compacted fill shall be analyzed by the laboratory of the Geotechnical Consultant to determine their physical properties. If any material other than that previously tested is encountered during grading, the appropriate analysis of this material shall be conducted by the Geotechnical Consultant as soon as possible. D. Import If importing of fill material is required for grading, proposed import material should meet the requirements of the previous section. The import source shall be given to the Geotechnical Consultant at least 2 working days prior to importing so that appropriate tests can be performed and its suitability determined. V. FILL PLACEMENT AND COMPACTION A. Fill Layers Material used in the compacting process shall be evenly spread, watered, processed, and compacted in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer . The fill shall be placed and compacted on a horizontal plane, unless otherwise approved by the Geotechnical Consultant. STANDARD GRADING SPECIFICATIONS Page 4 B. Moisture Conditioning Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively uniform moisture content at or slightly above optimum moisture content. C. Compaction Each layer shall be compacted to 90 percent of the maximum density in compliance with the testing method specified by the controlling governmental agency. (In general, ASTM D 1557- 02, will be used.) If compaction to a lesser percentage is authorized by the controlling governmental agency because of a specific land use or expansive soils condition, the area to received fill compacted to less than 90 percent shall either be delineated on the grading plan or appropriate reference made to the area in the soils report. D. Failing Areas If the moisture content or relative density varies from that required by the Geotechnical Consultant, the Contractor shall rework the fill until it is approved by the Geotechnical Consultant. E. Benching All fills shall be keyed and benched through all topsoil, colluvium, alluvium or creep material, into sound bedrock or firm material where the slope receiving fill exceeds a ratio of 5 horizontal to 1 vertical, in accordance with the recommendations of the Geotechnical Consultant. VI. SLOPES A. Fill Slopes The contractor will be required to obtain a minimum relative compaction of 90 percent out to the finish slope face of fill slopes, buttresses, and stabilization fills. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct compaction of the slope face with suitable equipment, or by any other procedure that produces the required compaction. B. Side Hill Fills The key for side hill fills shall be a minimum of 15 feet within bedrock or firm materials, unless otherwise specified in the soils report. (See detail on Plate SG-5.) C. Fill-Over-Cut Slopes Fill-over-cut slopes shall be properly keyed through topsoil, colluvium or creep material into rock or firm materials, and the transition shall be stripped of all soils prior to placing fill. (see detail on Plate SG-6). STANDARD GRADING SPECIFICATIONS Page 5 D. Landscaping All fill slopes should be planted or protected from erosion by other methods specified in the soils report. E. Cut Slopes 1. The Geotechnical Consultant should observe all cut slopes at vertical intervals not exceeding 10 feet. 2. If any conditions not anticipated in the preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions shall be evaluated by the Geotechnical Consultant, and recommendations shall be made to treat these problems (Typical details for stabilization of a portion of a cut slope are given in Plates SG-2 and SG-3.). 3. Cut slopes that face in the same direction as the prevailing drainage shall be protected from slope wash by a non-erodible interceptor swale placed at the top of the slope. 4. Unless otherwise specified in the soils and geological report, no cut slopes shall be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. 5. Drainage terraces shall be constructed in compliance with the ordinances of controlling governmental agencies, or with the recommendations of the Geotechnical Consultant. VII. GRADING OBSERVATION A. General All cleanouts, processed ground to receive fill, key excavations, subdrains, and rock disposals must be observed and approved by the Geotechnical Consultant prior to placing any fill. It shall be the Contractor's responsibility to notify the Geotechnical Consultant when such areas are ready. B. Compaction Testing Observation of the fill placement shall be provided by the Geotechnical Consultant during the progress of grading. Location and frequency of tests shall be at the Consultants discretion based on field conditions encountered. Compaction test locations will not necessarily be selected on a random basis. Test locations may be selected to verify adequacy of compaction levels in areas that are judged to be susceptible to inadequate compaction. C. Frequency of Compaction Testing In general, density tests should be made at intervals not exceeding 2 feet of fill height or every 1000 cubic yards of fill placed. This criteria will vary depending on soil conditions and the size of the job. In any event, an adequate number of field density tests shall be made to verify that the required compaction is being achieved. STANDARD GRADING SPECIFICATIONS Page 6 VIII. CONSTRUCTION CONSIDERATIONS A. Erosion control measures, when necessary, shall be provided by the Contractor during grading and prior to the completion and construction of permanent drainage controls. B. Upon completion of grading and termination of observations by the Geotechnical Consultant, no further filling or excavating, including that necessary for footings, foundations, large tree wells, retaining walls, or other features shall be performed without the approval of the Geotechnical Consultant. C. Care shall be taken by the Contractor during final grading to preserve any berms, drainage terraces, interceptor swales, or other devices of permanent nature on or adjacent to the property. S:\!BOILERS-WORK\REPORT INSERTS\STANDARD GRADING SPECS