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Home My WebLink AboutAppendix E - Geotechnical Investigation 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 May 20, 2024 J.N. 24-147 NEWBRIDGE HOMES 500 Newport Center Drive, Suite 570 Newport Beach, California 92660 Attention: Mr. J. Rob Meserve Subject: Due Diligence Feasibility Geotechnical Assessment: 3-acre Vacant Property at 15547 Baseline Avenue, APN 1110-171-02-0000, Fontana, San Bernardino County, California References: See Attached List Dear Mr. Meserve: In accordance with your request, Petra Geosciences, Inc. (Petra) is providing this due diligence feasibility geotechnical assessment of the subject vacant property 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. 24-147P, dated February 26, 2024. This report presents our findings and professional opinions with respect to the geotechnical feasibility of the proposed development, geotechnical constraints that should be considered during design and development of the site, and potential mitigation measures to bring the site to compliance from a geotechnical engineering viewpoint. It must be emphasized that this report is intended as a feasibility-level geotechnical assessment only and is based solely on a review of the referenced geotechnical reports and background geologic literature, review of geotechnical reports for nearby sites by Petra, and a limited subsurface investigation. As such, the contents of this report are not suitable for submittal to regulatory agencies, nor should the findings or conclusions provided herein be relied upon for earthwork, quantity calculation or procedure, or structural engineering design. It should be further noted that this geotechnical evaluation does not address soil contamination or other environmental issues potentially affecting the property which was provided under separate cover. SITE GENERAL OVERVIEW According to the California Department of Conservation, Geologic Energy Management Division (CalGEM) Online Mapping System (2024), the site is located within Township 01 South, Range 06 West, Section 1, San Bernardino Base and Meridian. Based upon a topographic map by Inland Aerial Surveys, NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 2 Inc. (dated February 22, 2024), site elevations across the mostly level site from approximately 1,376± feet above mean sea level (msl) in the northeast corner of the subject site, to 1,366± feet above msl in the south- central portion of the subject property. A site location map is included as Figure 1. The relatively flat-lying site is comprised of one parcel of approximately 3 acres identified by San Bernardino County Assessor Parcel Number (APN) 1110-171-02-0000. The subject property is a generally rectangular-shaped vacant site, bounded on the north by Baseline Avenue, Orlando Drive on the west and Lime Avenue on the east, in the City of Fontana San Bernardino County, California. The site is surrounded by residential development. DUE DILIGENCE ASSESSMENT Literature Review No previous geotechnical reports pertaining to the subject property were provided to Petra. However, we reviewed readily available online aerial imagery on Google Earth and historical aerial photographs by EDR, as well as regional geologic maps and literature in the vicinity of the project site (see References). Subsurface Exploration A subsurface exploration program was performed under the direction of an engineering geologist from Petra on April 23, 2024. The exploration involved the excavation of seven exploratory test pits (TP-1 through TP-7) to a maximum depth of approximately 13 feet below existing grade (bgs). Two of the test pits (TP-3 and TP-5) were utilized as feasibility percolation test locations by excavating a 1-foot-deep hand auger boring in the bottom of the test pit. 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. All test pits were loosely backfilled to grade with native soils. 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. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 3 FINDINGS Current Site Conditions On April 8, 2024, a representative of Petra performed a site reconnaissance of the subject property. Vehicular access to the subject site was from the east and Lime Avenue. Test pit locations were also marked out for DigAlert notification. At the time of our field reconnaissance, the site was undeveloped land covered with short vegetation, consisting mostly of grasses. A few mature trees were observed in the northeast portion of the site. Scattered small piles of soil were observed locally within the subject property. Proposed Development A topographic map (Inland Aerial Surveys, Inc., dated February 22, 2024), provided by the client, depicted the limits of the subject site. The Conceptual Site Plan by the design Architect (Kevin L. Crook Architect, Inc., dated March 20, 2024), identifies a residential development, consisting of twelve multi-unit buildings totaling 51 single-family units with associated driveway, alleys and parking spaces, a tot lot and two open space areas. General Site History Based on information obtained from historical aerial photographs furnished by EDR from 1938 to 2020, the subject property appeared to have been developed for agricultural purposes, specifically a vineyard, from at least 1938 to sometime after 1959 and before 1966 when the site appeared to be fallow land. No buildings or roads were readily detected within the subject property during this period. From 1966 to the present day, the subject parcel remained vacant undeveloped land, although in 2002 the southern edge of the site appears to be have been disturbed during development of the offsite residential tract. A few dirt roads and/or trails were noted crossing the site from 2006 to sometime before 2009. Field Assessment Based on our observations and sampling conducted from the seven exploratory test pits the subject property is underlain by a thin layer of fill. Where encountered in our test pits, the fill consisted of light brown, fine- to coarse-grained silty sand with gravel and cobbles to a depth of 1 to 3 feet bgs. Underlying the fill are young alluvial soils consisting of fine- to coarse-grain sand with silt and silty sand with increasing percentages (30 to 40 percent) of gravel and cobbles (up to 12 inches in maximum dimension) with depth. Published geologic maps of the area indicate that the site and surrounding alluvial areas are underlain by Holocene- and late Pleistocene-age Young alluvial-fan deposits of Lytle Creek (Morton, D.M., 2003). This soil is described as unconsolidated cobbly to bouldery alluvium of the Lytle Creek alluvial fan. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 4 Laboratory Testing Limited laboratory testing was completed on various representative samples collected from the backhoe locations for classification and engineering analysis purposes. Testing includes in situ density and moisture content, maximum density and optimum moisture content, expansion potential, and soil corrosivity. Expansion Potential Based upon our laboratory testing, the expansion index (EI) of the soils is considered to be in the Very Low EI range, i.e., non-expansive. Corrosivity Soluble sulfate results are in Exposure Class S1 (Moderate). For Class S0, Table 19.3.2.1 of ACI 318-14 indicates that Type II cement (in accordance with ASTM C150) would be suitable for this condition. In addition, there are no water/cement ratio restrictions and the concrete minimum unconfined compressive strength, f’c, should not be less than 2,500 psi. The results of limited in-house testing of representative samples indicate that the onsite soils tested are neutral with respect to pH. Based on this finding and according to Table 8.22.2 of Caltrans’ 2003 Bridge Design Specifications (2003 BDS) requirements (which consider the combined effects of soluble sulfates and soil pH), a commercially available Type II Modified cement may be used. The laboratory tests also indicate that the onsite soils tested contain a water-soluble chloride concentration in the Exposure Class C1 - Moderate. No special recommendations are provided for the Exposure Class C1 condition per Table 19.3.2.1 of ACI 318-14, and the concrete minimum unconfined compressive strength, f’c, should not be less than 2,500 psi. Minimum resistivity test results indicates that the on-site soils tested are Moderately Corrosive to ferrous metals and copper. As such, any ferrous metal or copper components of the subject buildings (such as cast iron or ductile iron piping, brass, copper tubing, etc.) that are expected to be placed in direct contact with site soils should be protected against the detrimental effects of corrosive soils. Such protection could include the use of protective wrapping/coating of buried pipes or the use of corrosion resistant materials. It should be noted that at this time Petra is not aware of any plans to incorporate such items for the proposed buildings. Should such elements be considered for these buildings, we recommend that a corrosion engineer be consulted to provide appropriate recommendations for long term protection of metallic elements in contact with site soils. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 5 Surface Water No indication of surface water was observed on the property or in close proximity at the time of our site field exploration. Groundwater No groundwater was encountered in any of our test pits, excavated to a maximum depth of 13 feet below the ground surface. No public groundwater wells are mapped within the subject site or in proximity to the property on the CDWR water data library (CDWR, 2024). Based on our review, one of the closest mapped wells to the subject property (Well 01S05W05A002S) is approximately 2.5 miles to the east. In February 1932 depth to groundwater was reported at approximately 201 feet (bgs). In October 1957, groundwater was reported at a depth of approximately 372 feet bgs. In April 1997, groundwater was reported at a depth of approximately 296 feet bgs. This well has been destroyed. In general, groundwater depth varies within the area and though flow direction specifically beneath the subject property is unknown, it is reasonable to estimate flow to follow regional topography to the south - southwest. 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 and/or the USGS Quaternary Fault and Fold Database, the San Bernardino segment of the San Jacinto Fault, located approximately 6.3 miles (10.18 kilometers) northeast 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 a distance of less than 9.5 miles (15 km) from the surface projection of this fault system, which is capable of producing 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. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 6 Strong Ground Motions The site is located in a seismically active area of southern California and will likely be subjected to very strong seismic-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 provisions of the 2022 California Building Code (CBC). Liquefaction and Dynamic Settlement Potential In view of the dense and coarse-grained nature of the alluvial fan deposits underlying the site vicinity and the lack of a shallow groundwater table, it is our professional opinion that the potential for liquefaction within the site is very low. The subject property is not mapped within a County of San Bernardino area of liquefaction susceptibility (County of San Bernardino, 2009). The relatively dense nature of the underlying alluvial fan soils, together with the anticipated remedial grading of the near -surface soils, likely preclude significant dynamic settlement within the site in the event of seismically induced strong ground motion. This should be further evaluated via field exploration once development plans are available. The site and immediate area exhibit level topography that is not prone to landsliding. Secondary effects of seismic activity normally considered as possible hazards 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 depth to groundwater exceeding 100 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. Shrinkage and Subsidence Volumetric changes in earth quantities will occur when excavated onsite soils are replaced as properly compacted fill. The following is an estimate of shrinkage factors for the alluvial soil present onsite. These estimates are based on in-place densities of the various materials and on the estimated average degree of relative compaction achieved during grading. • Disturbed Fill Soils (1-3± feet).……..…………………………… Shrinkage of 15 to 20%± • Alluvium (Upper 2-7± ft.) ……………………….…..................... Shrinkage of 10 to 15%± NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 7 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. CONCLUSIONS AND RECOMMENDATIONS Based on our knowledge of the subject site area, development of the subject property is considered feasible from a geotechnical engineering standpoint. It is recommended that the following geotechnical issues be considered by the Client during this due diligence period. Primary Geotechnical Issues Our professional opinion, from a geotechnical engineering viewpoint, regarding various aspects of site conditions and/or proposed development, is presented herein. The following items are the salient points of our due diligence assessment that we recommend be considered for future site development. • Grading Plan Review: The City of Fontana may require a review of the final rough grading plans during future grading plan approval processes. • Demolition, Clearing and Grubbing: No surface structures are known to be located within the site; however, subsurface utility lines and power poles are present along the south side of Baseline Avenue. All existing surface vegetation and/or other deleterious materials will require clearing and hauling offsite prior to grading activities. Any existing improvements such as old irrigation lines or unknown underground structures encountered during grading should be demolished and hauled offsite and contingencies should be planned. • Removal of Unsuitable Soil Materials and Ground Preparation: Following demolition and removal of all existing subsurface structures and improvements (if any) and clearing of all organic materials and debris from the site, surficial soils/topsoil and the upper portions of low-density natural alluvial soils should be removed in areas that will support structures, pavements, or other settlement sensitive improvements. Based on our experience on residential projects in proximity to the subject property, estimated remedial removal depths are on the order of 4 feet below existing grades. This should be further evaluated via field exploration once grading plans are available. Street pavement areas and non-structural areas (i.e., landscaping, greenbelts) may be cut to subgrade levels prior to processing if the cut is deeper than 2 feet below existing grades, depending largely upon the thickness of surficial fill. For street pavement areas and non-structural areas that will be at grade or will be in fill, over excavation depths should be at least 1 foot into natural medium dense alluvial soils. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 8 Prior to placing structural fill, all exposed approved competent bottom surfaces should be watered as necessary, to achieve moisture conditions at least 2 percent above optimum moisture and then compacted in-place to a relative compaction of 90 percent or more based on ASTM D 1557. Scarification of the removal-bottom surfaces to a depth of approximately 12 inches should be performed when exposing silty sands soil types. 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 half the depth of fill. Lots located entirely in cut should be over excavated to a minimum of 3 feet below proposed finished pad grade elevations and replaced as properly compacted fill. Prior to placing engineered fill, all exposed over excavation bottom surfaces in the building pad areas should be scarified, then watered as necessary, to achieve moisture conditions at least 2 percent above optimum and then compacted in-place to a relative compaction of 90 percent or more based on ASTM D 1557. • Suitability of Onsite Soils for Fill: Onsite soils are granular in nature and considered suitable for use in engineering fill provided they are free of over-size rock, vegetation, or other deleterious materials. The shallow subsurface silty sand and sandy soils may locally be in a dry condition to a depth of several feet such that an appreciable amount of water is required to bring to the soils to near optimum conditions. Pre-watering of the site may be considered prior to site grading. • Over-Size Rock: Gravel and cobbles are scattered throughout the surface of the subject property. Cuts and over-excavation during grading are expected to produce rock fragments on the order of 12 inches± in diameter. Although not encountered during our field exploration, oversize rock is defined as rock or irreducible rock fragments greater than 12 inches in diameter. Boulders exceeding 3 feet in one dimension will require special handling, consisting of breaking, isolated burial in fills, or offsite disposal. If encountered, over-size rock buried in engineering fills within the site shall be at least 10 feet below finish pad grade and 15 feet from the face of finished slope grade. This should be further evaluated via field exploration once development plans are available. • Importing of Fill: It this time, future development of the subject property is not known. In the event imported soil martial is needed in the future, all potential import source(s) should be evaluated at least one week prior to confirm that non-expansive, low corrosive soils that are free of deleterious materials or environmental contaminants will be imported. • Expansion and Corrosion Potential of Soils to Foundations: Generally, soils within the subject property are considered to have a very low expansion potential (non-expansive) and have a moderate level of soluble sulfates, low levels of soluble chloride, and may be moderately corrosive to ferrous metals (i.e., cast iron, copper, brass, etc.) in direct contact with site soils. • Building Foundations: In view of the granular onsite materials and our experience with similar developments in the general area, the foundation system may consist of conventional slab-on- ground foundations. Post-tension foundations should not be necessary. Seismic design parameters are provided in Appendix B. • Pavement Design: Based on the observed surface soil types and our experience in the area, R-values are expected to allow for a City of Fontana minimum pavement design for the in-tract driveway. This should be further evaluated via field exploration and laboratory testing once development plans are available. Final pavement design should be performed at the completion of driveway rough grading with final R-value testing. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 9 • Feasibility Infiltration Results: A plan depicting the locations of two sites to be tested for preliminary infiltration rates associated with buried stormwater infiltration chambers was provided by the design Architect (Kevin L. Crook Architect, Inc., dated March 20, 2024). A total of two percolation tests were conducted in backhoe test pits at the proposed chamber locations. Soils encountered in test locations consisted of medium- to course-grained gravelly sand. The un- factored infiltration rate results are summarized in the table below. Further testing is recommended once the design, depth, and location of buried infiltration chambers is finalized. Summary of Feasibility Infiltration Rates Percolation Test Depth of Test (feet below surface) Percolation Rate (gallons/day/ft2) Infiltration Rate (inches/hour) P-1 4½ to 5½ 1,827 173 P-2 5 to 6 787 75 REPORT LIMITATIONS This report is based on the existing conditions of the subject property and the geotechnical observations made during our site reconnaissance and limited laboratory testing. The conclusions and opinions contained in this report are based on the results of the described geotechnical evaluations and represent our professional judgment. This report has been prepared consistent with that level of care being provided by other professionals providing similar services at the same locale and in the same time period. The contents of this report are professional opinions and as such, are not to be considered a guaranty or warranty. This report should be reviewed and updated after a period of one year or if the site ownership or project concept changes from that described herein. This report has not been prepared for use by parties or projects other than those named or described herein. This report may not contain sufficient information for other parties or other purposes. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 10 This opportunity to be of service is sincerely appreciated. If you have any additional questions or concerns, please feel free contact this office. Respectfully submitted, PETRA GEOSCIENCES, INC. 5/20/24 Edward Lump Grayson R. Walker Associate Geologist Principal Engineer CEG 1924 GE 871 EL/GRW/lv Attachments: References Figure 1 – Site Location Map Figure 2 – Test Pit Location Map Appendix A – Test Pit Logs Appendix B – Seismic Design Parameters W:\2020-2025\2024\100\24-147\Reports\24-147 100 Due Diligence Report.docx NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 Page 11 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. 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, California Geological Survey, Special Publication 42. California Building Code (2022), California Code of Regulations, Title 24, Par 2, Volume 2 of 2, Based on the 20 21 International Building Code, California Building Standards Commission. California Department of Water Resources, 2004, California Groundwater - Bulletin 118. , 2024, Water Data Library, accessed March, http://www.water.ca.gov/waterdatalibrary/groundwater/ California Geological Survey, 2024, Earthquake Zones of Required Investigation, EQZApp interactive map, https://maps.conservation.ca.gov/cgs/EQZApp/app/ County of San Bernardino, 2007, San Bernardino County Land Use Plan, General Plan, Geologic Hazards Overlay, Sheet FH29 C, Fontana, accessed April 2024. Kevin L. Crook Architect, Inc., 2024, Conceptual Site Plan, Baseline & Lime, Fontana, CA, dated March 20. EDR, 2024, The EDR Aerial Photo Decade Package, 3-Acre Vacant Fontana Site, 15547 Baseline Ave., Fontana, CA, 92336 (Inquiry No. 7606786.11), dated March 28. Google Earth™ 2024, by Google Earth, Inc., http://www.google.com/earth/index.html, accessed March. 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.T., 2003, Preliminary Geologic Map of the Fontana 7.5’ Quadrangle, San Bernardino and Riverside Counties, California, USGS Open-File Report 03-418. Office of Statewide Health Planning and Development (OSHPD), 2021, Seismic Design Maps, U.S. Seismic Design Maps (seismicmaps.org) Southern California Earthquake Data Center (SCEDC), 2014, http://www.data.scec.org/significant/index.html. Standard Specifications for Public Works Construction (Greenbook), 2009, BNI Publishers. 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. FIGURES Site Location Map PETRA GEOSCIENCES, INC. COSTA MESA MURRIETA PALM DESERT SANTA CLARITA Figure 1J.N.: SCALE: May 2024 24-147 *** see map DATE: DWG BY: 40880 COUNTY CENTER DRIVE, SUITE M TEMECULA, CALIFORNIA 92591 PHONE: (951) 600-9271 15547 Baseline 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 SCALE SITE - Reproduced from: USGS, 2024, The National Map Viewer Base Map Reference: Google Earth, 2024, Photograph dated May 2023. 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 15547 Baseline Avenue Fontana, San Bernardino County, California D ATE: May, 2024 J.N.: 24-147 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 N L E G E N D - Approximate Limits of Property Boundary 269 ft. TP-7TP-1 TP-2 TP-4 TP-6 TP-3/P-1 TP-5/P-2 - Approximate Location of Backhoe Test Pit/Percolation Test TP-7 TP-5/P-2 - Approximate Location of Backhoe Test Pit APPENDIX A TEST PIT LOGS 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown to brown, slightly moist to moist, loose, some gravel. ALLUVIUM (Qal) Sand with Silt (SP-SM): Brown to pale yellow, slightly moist, loose, fine- to coarse-grained, 30% gravels and cobbles up to 6" in diameter. Brown to pale olive, 15% gravels and cobbles up to 4" in diameter. 30% - 40% gravels and cobbles up to 12" in diameter. moist. Total Depth = 12' Some caving No groundwater encountered Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-1 Location:15548 Baseline Avenue, Fontana Elevation:1371± Job No.:24-147 Client:Newbridge Homes Date:4/23/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown, dry, loose, fine- to coarse-grained, some gravel. Brown to olive, slightly moist, 30% gravels and cobbles up to 6" in diameter. ALLUVIUM (Qal) Sand with Silt (SP-SM): Brown to pale yellow, slightly moist, loose to medium dense, fine- to coarse-grained, 20% gravels and cobbles up to 6" in diameter. 30% gravels and cobbles up to 10" in diameter. Brown to pale dark yellow, 20% gravels and cobbles up to 8" in diameter. 30% - 40% gravels and cobbles up to 12" in diameter. Total Depth = 13' Some caving No groundwater encountered Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-2 Location:15548 Baseline Avenue, Fontana Elevation:1369± Job No.:24-147 Client:Newbridge Homes Date:4/23/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown, dry to slightly moist, loose, fine- to coarse- grained, some gravel. ALLUVIUM (Qal) Silty Sand (SM): Light brown to brown, dry to slightly moist, loose, 20% gravels and cobbles up to 5" in diameter. Sand with Silt (SP-SM): Light brown to pale yellow, slightly moist, loose to medium dense, 20% gravels and cobbles up to 5" in diameter. Total depth of test pit = 5' Depth extended with hand augering to 5.5' to install percolation pipe Slight caving No groundwater encountered Percolation well P-1 installed Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-3/P-1 Location:15548 Baseline Avenue, Fontana Elevation:1371± Job No.:24-147 Client:Newbridge Homes Date:2/23/34 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown, dry to slightly moist, loose, fine- to coarse- grained, some gravel. slightly moist, 15% gravels and cobbles up to 5" in diameter. ALLUVIUM (Qal) Sand with Silt (SP-SM): Brown to pale yellow, slightly moist, loose to medium dense, 30% gravels and cobbles up to 10" in diameter. Light brown to pale olive. slightly moist to moist, 20% - 30% gravels and cobbles up to 8" in diameter. Total Depth = 12' Some caving No groundwater encountered Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-4 Location:15548 Baseline Avenue, Fontana Elevation:1369± Job No.:24-147 Client:Newbridge Homes Date:4/23/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Brown to pale olive, dry to slightly moist, loose, fine- to coarse-grained, some gravel. ALLUVIUM (Qal) Silty Sand (SM): Brown to pale olive, dry to slightly moist, loose, fine- to coarse-grained, 30% gravels and cobbles up to 8" in diameter. Sand with Silt (SP-SM): Light brown to pale yellow, slightly moist, loose to medium dense, 20% gravels and cobbles up to 6" in diameter. Total Depth = 5' Depth extended with hand augering to 6' to install percolation pipe Slight caving No groundwater encountered Percolation well P-2 installed Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-5/P-2 Location:15548 Baseline Avenue, Fontana Elevation:1369± Job No.:24-147 Client:Newbridge Homes Date:4/23/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown, dry, loose, fine- to coarse-grained, some gravel. Brown to olive, 20% gravels and cobbles up to 6" in diameter. ALLUVIUM (Qal) Sand with Silt (SP-SM): Brown to pale yellow, slightly moist, loose to medium dense, fine- to coarse-grained, 30% - 40% gravels and cobbles up to 8" in diameter. 30% - 40% gravels and cobbles up to 10" in diameter. slightly moist to moist. Total Depth = 13' Some caving No groundwater encountered Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-6 Location:15548 Baseline Avenue, Fontana Elevation:1372± Job No.:24-147 Client:Newbridge Homes Date:4/23/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 0 5 10 15 20 25 30 35 ARTIFICIAL FILL (af) Silty Sand (SM): Light brown, dry, loose, fine- to coarse-grained, some gravel, trace cobbles. Brown to olive, slightly moist, 25% gravels and cobbles up to 8" in diameter. ALLUVIUM (Qal) Sand with Silt (SP-SM): Light brown to pale yellow, slightly moist, loose to medium dense, fine- to coarse-grained, 30% gravels and cobbles up to 12" in diameter. moist, 30% - 40% gravels and cobbles up to 12" in diameter. Total Depth = 13' Some caving No groundwater encountered Test pit backilled with spoils. Project:Baseline and Lime Boring No.:TP-7 Location:15548 Baseline Avenue, Fontana Elevation:1373± Job No.:24-147 Client:Newbridge Homes Date:4/25/24 Drill Method:Backhoe Driving Weight:N/A Logged By:SS 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 APPENDIX B SEISMIC DESIGN PARAMETERS NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 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 t he 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. 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 building(s) 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 appears 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 B. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 TABLE 1 Seismic Design Parameters Ground Motion Parameters Specific Reference Parameter Value Unit Site Latitude (North) - 34.1209 ° Site Longitude (West) - -117. 4656 ° 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) 8.05 (3) - R – Distance to Surface Projection of Fault USGS Unified Hazard Tool (3) 10.18 (3) km Ss - Mapped Spectral Response Acceleration Short Period (0.2 second) Figure 1613.2.1(1) (1) 2.072 (4) g S1 - Mapped Spectral Response Acceleration Long Period (1.0 second) Figure 1613.2.1(3) (1) 0.736 (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) 2.486 (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) 1.567 (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) 0.892 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) 1.071 (4) g Design PGA ≈ (⅔ PGAM) - Slope Stability (†) Similar to Eqs. 16-22 & 16-23 (2) 0.714 g Design PGA ≈ (0.4 SDS) – Short Retaining Walls (‡) Equation 11.4-5 (2) 0.663 g CRS - Short Period Risk Coefficient Figure 22-18A (2) 0.921 (4) - CR1 - Long Period Risk Coefficient Figure 22-19A (2) 0.898 (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 Cr iteria 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 applicable. NEWBRIDGE HOMES May 20, 2024 15547 Baseline Avenue / Fontana J.N. 24-147 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 obtained 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 by 50 percent for all applications of SM1 and structural design is performed in accordance with Equivalent Lateral Force (ELF) procedure.