HomeMy WebLinkAboutAppendix E - Geotechnical Assessment
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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 4, 2022
J.N. 22-237
CONIFER COURT LLC
500 Newport Center Drive, Suite 570
Newport Beach, California 92660
Attention: Mr. J. Rob Meserve
Subject: Feasibility/Due Diligence-Level Geotechnical Assessment: Conifer Ridge Property,
14.5 Acres of Vacant Land South of Conifer Court and Village Drive, APN 0237-411-
27-0000, City of Fontana, San Bernardino County, California 92337
References: See Attached List
Dear Mr. Meserve:
In accordance with your request, Petra Geosciences, Inc. (Petra) is providing this geotechnical due-
diligence review of the subject vacant property in the city of Fontana, San Bernardino County, California
(Figure 1). This report presents our findings and professional opinions with respect to the geotechnical
feasibility of the proposed development, geotechnical constraints that should be taken into consideration
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, background geologic
literature and our limited subsurface exploration and soil test data. 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
The subject property consists of an irregular-shaped 14.5-acre vacant site south of the intersection of
Conifer Court and Village Drive in the City of Fontana, California. The subject site is comprised of vacant
land identified by San Bernardino County Assessor Parcel Number (APN) 0237-411-27-0000.
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The subject property, situated east of Live Oak Avenue, is bounded by vacant land to the west (Southridge
property), Village Drive on the north, an improved drainage channel on the east (Declez Channel), and an
abandoned rock quarry on the south. A site location map is included as Figure 1.
The subject property was previously developed as a part of the Declez Granite Quarries near the former
community of Declezville. The north-northwest orientated face of the quarry is situated south of the subject
property boundary, with an exposed cut of approximately 225 feet in height (Google Earth, 2022). The
highly irregular surface of the subject property has been disturbed by quarry activities, which includes a
large rectangular-shaped stockpile of soil and rock on the northern portion of the site and a partially
excavated ridge on the west edge. The southwest and southeast property boundaries abut natural ascending
slopes. The eastern portion of the subject property, beyond the large stockpile, appears to consist of
undisturbed alluvium deposited at the outlet of a natural drainage extending upslope into the Jurupa
Mountains. Existing elevation provided on Google Earth (2022) are on the order of approximately 945± to
990± feet above mean sea level (msl).
DUE DILIGENCE ASSESSMENT
Literature Review
Petra was not provided any geotechnical report on the subject property. In addition, we reviewed available
online aerial imagery, historical aerials photographs by EDR, and background geologic maps and literature
in the vicinity of the project site (see References).
Site Reconnaissance and Subsurface Assessment
A representative of Petra conducted a site reconnaissance and performed photo documentation on May 27,
2022 to evaluate the conditions of the property. The surface of the subject property is covered mostly with
dense native vegetation (i.e., brush and bushes), which covers the dumped piles of rock and concrete. The
eastern portion of the subject property, beyond the stockpiles of rock and concrete, is mantled with thick
grasses. Dumped piles of trash and debris are common along the central dirt road loop.
Petra conducted field exploration to evaluate subsurface conditions within the subject property, as well as
to collect samples for laboratory testing and analysis also on May 27, 2022. The field assessment included
the excavation of eight exploratory test pits (T-1 thru T-8) with a John Deer 470 Excavator to depths ranging
from 2 to 21.5 feet below the ground surface (bgs).
Additionally, one boring was advanced on June 3 and three were advanced on June 15, 2022 utilizing a 4-
wheel drive, truck-mounted hollow-stem auger drill rig equipped with 8-inch diameter augers. The borings
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were drilled and sampled to depths ranging from approx. to approximately 3.5 to 56.5 feet below existing
grades. Relatively undisturbed ring and disturbed, representative bulk samples of soil were collected from
the borings for laboratory testing and the locations are depicted on Figure 2.
Laboratory Testing
The limited laboratory program consisted of testing select undisturbed ring specimens and/or bulk samples of
FINDINGS
Proposed Development
An aerial photographic map provided by the client (undated) and the APN parcel map depict the outline of
the subject site. It is our understanding, however, that a conceptual development plan is not available at this
time. Based upon discussions with the client, development of the subject property may be either a self-
storage facility or residential.
Site Reconnaissance and Aerial Photo Review
Petra conducted a site reconnaissance of the subject property on May 27, 2022. The surface of the subject
property is covered mostly with dumped piles of boulders, boulders mixed with sandy soil, concrete, and
to a lesser extent asphalt. A large rectangular-shaped stockpile within the northern portion of the subject
site, consists of a soil and rock mixture that are likely remnants of the abandoned quarry operations. One
centrally located, oblong-shaped dirt road provides entry to the site from an open chain-link gate. Most of
the dumped trash and debris are found along this road.
A second dirt road branches off the southwesterly edge of the main dirt road, traversing up and over the
ridge in the southwestern corner of the subject property. A dirt road also exists along the southerly edge of
Declez Channel, located on the east-northeast site boundary. Additionally, one trail was noted along the
southerly edge of the large stockpile and another along the northwest corner of the property. Natural
vegetation is well established within the subject property commonly covering dumped fill materials and
boulders.
Generally, that portion of the subject property disturbed by the former quarry activity slopes in a northerly
direction. The eastern subject property, beyond the large rectangular stockpile, slopes to the north-northeast.
The southern boundary, which locally appears to be a depression, encroaches slightly into the edges of the
onsite soil materials collected from the borings for in-situ dry density and moisture content, expansion
index, and general corrosion potential (sulfate and chloride content, pH, and resistivity).
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abandoned quarry slopes, which ascend at a steep gradient above the subject property. Rockfall debris
(talus) exists along the southern portion of the subject property. Rockfall hazards associated with the offsite
bedrock slopes should be assessed by an experienced rockfall hazard engineer.
Based upon historical aerial photographic and USGS topographic map assessment (EDR, 2022a, 2022b),
the quarry operation appeared to be active from at least 1938. Topographic maps from 1896, 1898, and
1901 shown no development or use of the subject property at that time. A 1938 aerial photograph depicted
an existing quarry face directly south of the subject property and what appeared to be small railroad spur
lines within the west and southwest portions of the site. The large stockpile was visible covered with native
vegetation in 1938. A main line, possibly extending east to the east end of the large rectangular stockpile
on the north portion of the subject property, was not readily detectable until after 1948 and before 1953;
however, clearing for the alignment was noted in 1938. It is reported that the quarry operation was active
from before 1900 to the early part of 1950 (MacKevkett, 1951). Subsequently, it appears that boulder and
concrete piles were placed onsite at various times after quarry operations ceased.
Field Assessment
Petra conducted limited field exploration with a John Deer 470 Excavator on May 27, 2022 to assess rock
hardness and thickness and quality of stockpiled fill within the subject property. F ield work included the
excavation of eight test pits (T-1 through T-8) to a maximum depth of 21.5 feet below the existing ground
surface (bgs). Test pits were excavated to practical refusal on either extremely hard granitic bedrock,
clustered boulders in fill, or caving sidewall conditions. Foll owing the logging of each test pit, the
excavation was backfilled with spoils. Two representative bulk samples of soil materials were collected from
the borings for laboratory testing.
Additionally, Petra conducted field exploration with a truck-mounted hollow-stem drill rig on June 3 and
15, 2022 to evaluate the natural subsurface soils. Four borings were drilled and sampled (B-1 through B-4)
to a maximum depth of 56.5 feet bgs. Three borings encountered granitic bedrock at depths of 3 feet bgs
(B-1), 55 feet bgs (B-2), and 7 feet bgs (B-4). Relatively undisturbed ring and disturbed, representative bulk
samples of soil were collected from the borings for laboratory testing. Following sampling, the borings were
backfilled with spoils.
The soil and weathered bedrock materials encountered in the exploratory trenches and borings were logged
and field classified in accordance with the visual-manual procedures outlined in the Unified Soil
Classification System and the American Society for Testing and Materials (ASTM) Procedure D 2488 and
ASTM D 2487. All field activities were performed and/or overseen by a State of California -licensed
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Certified Engineering Geologist. The approximate locations of our exploratory trenches and borings are
shown on the Exploration Location Map, Figure 2, and descriptive “Exploration Logs” for each of the
trenches and borings are presented in Appendix A.
Relatively undisturbed ring and disturbed bulk samples of representative earth materials were collected
from the exploratory borings for classification, laboratory testing and engineering analyses. Undisturbed
samples were obtained using a 3-inch outside diameter modified California split-spoon soil sampler lined
with brass rings. The soil sampler was driven with successive 30-inch drops of a free-fall, 140-pound
automatic trip hammer. The central portions of the driven-core samples were placed in sealed containers
and transported to our laboratory for testing. The number of blows required to drive the split-spoon sampler
18 inches into the soil were recorded for each 6-inch driving increment; however, the number of blows
required to drive the sampler for the final 12 inches was noted in the boring logs as Blows per Foot.
Groundwater
The subject site is located within the Chino Sub-basin (8-002.01) of the Upper Santa Ana Valley
Groundwater Basin (Department of Water Resources, [DWR], 2022). 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 in a southwesterly direction toward the Santa
Ana River. Boring B-2, located in the eastern portion of the subject property, did not encountered
groundwater to the maximum depth of 56.5 feet.
Groundwater depths in wells located in the vicinity of the subject property were reviewed on the California
Department of Water Resources website (DWR, 2022). One active observation well, identified as local well
number Chino-1207068, is mapped near the northwest corner of Jurupa Avenue and Live Oak Avenue,
approximately 1,600 feet north-northwest of the subject property. Between January 2000 and October 2021
groundwater depths were reported to vary from approximately 225 to 250 feet below the ground surface
(bgs).
Subsurface Conditions
Boring Data
Four exploratory borings were drilled within the subject property (designated B-1 through B-4) to a
maximum depth of 56.5 feet bgs. Independent of the surface stockpiles and dumped fill materials on site,
near-surface fills were encountered in all of our recent borings at thicknesses of: 3 feet in B -1; 7 feet in B-
2; 5 feet in B-3; and 7 feet in B-4. Based on our observations and sampling conducted from the exploratory
hollow-stem auger borings, undocumented fill materials are underlain by granitic bedrock in B-1 and B-4,
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and alluvium in B-2 and B-3. Bedrock was not encountered at a depth of 26.5 feet in B-3. The locations of
our borings are shown on Figure 2. Logs of the borings are provided in Appendix A.
Test Pits
To assess the general characteristics of undocumented fill materials and bedrock depths onsite, eight
exploratory test pits (designated T-1 through T-8) were excavated within the subject property to a maximum
depth of 21.5 feet bgs. Where excavated, limited buried debris was encountered, including metal cable and
an iron rail fragment in T-7 and sandbags in T-4. Heavy sidewall caving hindered continuing excavation in
the thickest fill areas. Granitic bedrock was encountered at a depth of 2 feet in T-1; 3.5 feet in T-2; 11 feet
in T-4; 19.5 feet in T-5; and 2.5 feet in T-6. Where encountered, the underlying granitic bedrock was dense
and extremely hard, hindering continued excavation after 0.5 to 1 foot. Fill thicknesses ranged from 2.5 feet
to over 21.5 feet bgs. Locations of our test pits are shown on Figure 2. Logs of the test pits are provided in
Appendix A.
Undocumented Fill
Much of the subject property is either mantled by stockpiled fill or underlain by undocumented fill. Fills
were more than likely placed during historic quarry operations within to the subject property to create a
level working area for equipment and rail spurs. Where encountered onsite, the thickness of this material
was found to be greater than 10.5 feet in T-3; 11 feet in T-4; 14 feet in T-5; 2.5 feet in T-6; greater than
21.5 feet in T-7; and greater than 11.5 feet in T-8. Alluvial soils were found between the fill and the
underlying bedrock in T-5. Test pits not encountering bedrock encountered practical refusal on what
appeared to be clustered boulders and/or sloughing trench sidewalls, thereby preventing the determination
of total fill thickness.
Where encountered, fill materials consisted of a dry, loose, silty sand matrix with angular gravels, cobbles,
and boulders up to 5 feet in one dimension. Concentrations of coarse gravels, cobbles and boulders ranged
from 10 to 60 percent. Most of the surface piles of boulders, concrete rubble, and to a lesser extent asphalt,
appear to have been dumped well after quarry activity.
Two test pits, T-5 and T-6, we excavated in the large stockpile along the northerly portion of the subject
property. T-5 encountered 14 feet of undocumented fill overlying alluvium. T-6 encountered 2.5 feet of
undocumented fill overlying granitic bedrock.
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Over-Size Rock
Large boulders are commonly buried, nested, and/or scattered throughout the subject property, typically
exceeding 3 feet in one dimension. Boulders up to 5 feet in one dimension were encountered in test pits
excavated within the subject site. Boulders exceeding 3 feet in one dimension will require special handling,
consisting of breaking, isolated burial in fills, or offsite disposal.
Compressible Soils
Young alluvial soils were encountered locally at depth in borings B-2 and B-3, and test pit T-5. Where
excavated, the upper 5 to 6 feet of the alluvial soils were loose and dry to damp. These soils, underlying
undocumented fills within the subject property, are deemed to be compressible due to low sample low
counts. In addition to all undocumented fill materials, buried compressible native soils will require removal
and recompaction.
Laboratory Testing
Limited laboratory testing of various representative samples collected from the drill rig locations for
classification and engineering analysis purposes. Testing included in-situ density and moisture content,
maximum density and optimum moisture content, expansion potential, and soil corrosivity. Results of in
situ density and moisture content are provided on the boring logs, Appendix A. Results of limited in-house
testing of a representative sample indicates that the expansion index (EI) of the soils is in the Very Low EI
range (0-20).
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
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 below in Table 1.
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
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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 chloride 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 1, 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, walkways,
ramps, steps, curbs, etc.
[Remainder of Page Intentionally Left Blank]
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TABLE 1
Soil Corrosivity Screening Results
Sample ID Test
(Test Method) Test Results Classification General Recommendations
B-1` @ 0-3’ Soluble Sulfate
(Cal 417)
SO42- > 2.00 %
by weight
S3(1) - Very
Severe
Type V cement plus pozzolan or slag
cement; maximum water/cement ratio
of the fresh concrete should not exceed
0.45; fc’(2) should not be less than
4,500 psi.
B-1 @ 0-3’ pH
(Cal 643) 7.9 – 8.4 Moderately
Alkaline(3) No special recommendations
B-1` @ 0-3’ Soluble Chloride
(Cal 422) < 500 ppm C1(1) -
Moderate
Residence: No special
recommendations; fc’(2) should not be
less than 2,500 psi.
< 500 ppm C2(4) - Severe
Pools/Decking: Increase concrete
cover thickness; maximum
water/cement ratio of the fresh
concrete should not exceed 0.40; fc’(2)
should not be less than 5,000 psi.
B-1` @ 0-3’ Resistivity
(Cal 643) 1,000 – 3,000 Highly
Corrosive(5) Consult a corrosion engineer
Notes:
1. ACI 318-14, Section 19.3
2. fc,’ 28-day unconfined compressive strength of concrete
3. The United States Department of Agriculture Natural Resources Conservation Service, formerly Soil Conservation Service
4. Exposure classification C2 applies specifically to swimming pools and appurtenant concrete elements
5. Pierre R. Roberge, “Handbook of Corrosion Engineering”
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 2019 California Building Code (2019 CBC).
Liquefaction and Dynamic Settlement Potential
Based on San Bernadino County hazard maps, the site is located in an area not susceptible to liquefaction
potential (San Bernardino County, 2007). Further, based on groundwater being deeper than 100 feet below
the site and most of the subject property is underlain by very dense granitic, liquefaction or dynamic
settlement should not be considered as a major geotechnical concern for site development.
CONCLUSIONS AND RECOMMENDATIONS
Based on our site reconnaissance, limited subsurface exploration/laboratory testing, and literature review of
readily available data, development of the proposed project within this subject site is feasible from a
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geotechnical standpoint, provided rockfall hazards associated with the offsite rock quarry can be mitigated,
and 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
condition and/or proposed development is presented herein. The following presents the salient points of our
due diligence assessment that we recommend be considered for future site development.
• Grading Plan Review: The City will require a review of the latest grading plans and any updated
report needed at that time should include recommendations for rough grading, post-grading
improvements, and preliminary building foundation design.
• Rockfall Hazard: The exposed quarry face is comprised of large, angular granitic bedrock outcrops
that are naturally and/or mechanically fractured. Open fractures are visible in some locations related
to near-vertical overhangs. One of the prominent fracture orientations is out-of-slope toward the
proposed development. Below the large angular outcrops are fan-shaped slopewash/talus deposits
that are covered with vegetation. These deposits consist of variable mixtures of sand, gravel,
cobble, and boulders. It is difficult to distinguish boulders at the toe of slope from rockfall versus
stockpiled boulders; however, the blocky nature of exposed outcrops suggest that dislodged rocks
are not likely to bounce as compared to rounded boulders. Rockfall hazards should be evaluated by
an experienced rockfall hazard professional.
• Undocumented Fill: Much of the subject property is either mantled by stockpiled boulders and
concrete rubble or underlain by undocumented rock fill likely placed during historic quarry
operations or after abandonment of the quarry. Where encountered in borings onsite, the thickness
of this material was found as 3 feet (B-1), 7 feet (B-2), 5 feet (B-3), and 7 feet (B-4) within the
northern portion of the subject property. The absence of residual soil and/or young alluvial soils
found between the fill and the underlying bedrock suggests the southern portion of the site may
have been lowered to create a level working surface.
Where encountered in test pits, undocumented fill materials consisted of dry, loose silty sand with
angular rock fragments up to 5 feet in one dimension. Where encountered onsite, the thickness of
this material was found to be greater than 10.5 feet in T-3; 11 feet in T-4; 14 feet in T-5; 2.5 feet in
T-6; greater than 21.5 feet in T-7; and greater than 11.5 feet in T-8. Test pits not encountering
bedrock found practical refusal on what appeared to be clustered boulders and/or sloughing trench
sidewalls, thereby preventing the determination of total fill thickness.
Based upon the dry and loose nature of the undocumented fill materials (and the upper portion of
alluvial soils) encountered onsite, these materials are considered unsuitable to support settlement
sensitive improvements in their present condition and should be completely removed. Based upon
the limited existing data, undocumented and dumped fill thicknesses appear to be irregular but is
anticipated to the thickest within the north central portion of the subject property (T-7 and T-8).
Additional subsurface exploration is recommended to further characterize remedial earthwork
limits once conceptual development plans are available.
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• Over-Size Rock: Large boulders are commonly scattered throughout the subject property, typically
consisting of clusters and piles. Boulders up to 5 feet in one dimension were encountered in test
pits excavated within the subject site. Boulders exceeding 3 feet in one dimension will require
special handling, consisting of breaking, isolated burial in fills, or offsite disposal. 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. Additional recommendations can be provided upon request.
• Settlement: Based upon the dry and loose nature of the undocumented fill materials encountered
onsite, as well as the likely presence of voids in buried rock clusters, these materials are susceptible
to piping and seismically induced settlement in their present condition and should be completely
removed and replaced as compacted (engineered) fill. Additional subsurface exploration is
recommended to further characterize remedial earthwork limits once conceptual development plans
are available.
• Clearing and Grubbing: The subject site has a moderate to heavy amount of vegetation growth
throughout, and scattered trash and debris along the dirt road loop. All vegetation, debris, trash etc.
should be cleared and hauled offsite. Voids created by removal of large bushes and trees shall be
cleaned of loose soil and the backfill compacted to at least 90 percent relative compaction with
reference to ASTM D 1557.
• Suitability of Onsite Soils for Fill: All onsite soils consisting of “clean” fill are considered suitable
for use in engineering fill provided they are free of all organics, deleterious construction materials
or debris, as well as any oversize rocks.
• Importing of Fill: Preliminary grading plans and quantities are currently unknown at this time. It is
our understanding that excess rock fill and oversize rock generated from the adjacent Southridge
Village project may be imported to the subject property to raise grades. The geotechnical consultant
should evaluate these materials relative to placement prior to import. As with any grading job,
contingences should be made to account for variations in both shrinkage and compaction percent
during future grading and calculating grading quantities.
• Expansion Potential of Soils / Foundations: Limited testing by this office found soils within the
subject tract indicated a Very Low expansion potential. It is expected that graded building pads
finished with native soil will likely exhibit Very Low expansion potential. Such expansion
conditions typically are accommodated by conventional slab-on-ground foundation systems.
Additional laboratory testing would be required at the completion of rough grading to confirm the
as-built expansion conditions prior to finalizing foundation recommendations.
• Corrosion Potential: Our limited corrosion testing indicates site soils have a very severe exposure
to soluble sulfates, moderate exposure to soluble chlorides and are extremely corrosive to metallic
elements such as copper, iron, and brass. We recommend enlisting a corrosion engineer to provide
corrosion protection recommendations, in addition to sampling and testing of pad grade soils during
future precise grading.
• Building Foundation Design: Development of the subject property is unknown at this time. Seismic
and foundation design recommendations for the future development of the subject property should
be provided once a conceptual plan is available, in accordance with the most recently approved
California Building Code (CBC), which is currently the 2019 CBC. Proposed structures should also
be designed in accordance with the most recently approved CBC.
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REPORT LIMITATIONS
This report is based on the existing conditions of the subject property and the geotechnical observations
made during our site reconnaissance, limited field exploration, and limited laboratory testing. However,
note that soil and groundwater/moisture conditions can vary in characteristics between points of
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.
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.
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.
8/4/22
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 – Field Exploration Map
Appendix A – Boring and Test Pit Logs
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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.
Anicic, John Charles, Jr., 2005, Images of America Series - Eight, Ailea, San Sevaine, Declez, Declezville,
and South Fontana, 1888 to Present, Arcadia Publishing.
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 (2019), California Code of Regulations, Title 24, Par 2, Volume 2 of 2, Based on
the 2018 International Building Code, California Building Standards Commission.
California Department of Water Resources, 2004, California Groundwater - Bulletin 118.
, 2022, Water Data Library, accessed May,
http://www.water.ca.gov/waterdatalibrary/groundwater/
County of San Bernardino, 2007, San Bernardino County Land Use Plan, General Plan, Geologic Hazards
Overlay, Sheet FH29 C, Fontana, accessed May 2021.
EDR, 2022a, The EDR Aerial Photo Decade Package, Village Property, Conifer Ct. & Village Dr., Fontana,
CA 92337, Inquiry Number 6994915.11, dated May 25.
____, 2022b, The EDR Historical Topo Map Report, Village Property, Conifer Ct. & Village Dr., Fontana,
CA 92337, Inquiry Number 6994915.4, dated May 25.
Google Earth™ 2022, by Google Earth, Inc., http://www.google.com/earth/index.html, accessed May.
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.
MacKevett, 1951, Geology of the Jurupa Mountains, San Bernardino and Riverside Counties, California,
Department of Natural Resources, Division of Mines, San Francisco Special Report, dated
February 5.
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.
Site Location Map
PETRA GEOSCIENCES, INC.
COSTA MESA MURRIETA PALM DESERT SANTA CLARITA
Figure 1J.N.:
SCALE:
August 2022 22-237
epl see map
DATE:
DWG BY:
40880 COUNTY CENTER DRIVE, SUITE M
TEMECULA, CALIFORNIA 92591
PHONE: (951) 600-9271
Village Project
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
SCALE
1 MILE0
SITE
Base Map Reference: Google Earth, 2022, Photo dated August 2019.
PETRA GEOSCIENCES, INC.
40880 County Center Drive, Suite M
Temecula, California 92591
PHONE: (714) 549-8921
COSTA MESA TEMECULA VALENCIA PALM DESERT CORONA
Field Exploration Map
Village Property, Conifer Court & Village Drive
Fontana, San Bernardino County, California
DATE: August 2022
J.N.: 22-237
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
GEOLOGIC UNITS
GEOSCIENCES
N
175 ft.0
LEGEND
- Approximate Location of Exploratory Test Pit
- Approximate Location of Exploratory Boring
T-1
T-2
T-3
T-4
T-5
T-6
T-7
T-8
T-8
B-4
B-1
B-4
B-3
B-2
- Approximate Limits of Subject Property
Live
O
a
k
A
ven
u
e
175 ft.
Scale
- Approximate Limits of Large Stockpile
APPENDIX A
BORING AND TEST PIT LOGS
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand (SM): Gray brown, dry, loose, fine to coarse grained, contains sub
angular fine to coarse grained gravel.
Granitic Bedrock
Gray, dry, hard, crystalline bedrock.
Refusal at 3.5 feet on hard bedrock.
No groundwater or seepage.
Backfilled with cuttings.
50
Project:Conifer Court Boring No.:B-1
Location:Fontana, California Elevation:
Job No.:22-237 Client:Newbridge Date:June 3, 2022
Drill Method:Truck Mounted Hollowstem Driving Weight:140 lbs Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
3.0
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand (SM): Brown, dry, loose, fine to medium grained, contains angular
and sub angular fine- to coarse-grain gravels.
Brown, damp, loose, fine to medium sand, micaceous.
Brown to dark brown, damp, loose, fine- to medium-grain.
Alluvium (Qal)
Poorly Graded Sand with Silt (SP-SM): Brown, damp, loose, fine to coarse
grained, contains sub angular fine- to coarse-grain gravel.
Brown, damp, loose, fine to medium grained, micaceous.
Poorly Graded Sand (SP): Gray brown, damp, medium dense, fine- to
medium-grain.
Gray brown, damp, medium dense, fine- to coarse-grain, broken cobble
lodged in tip of sampler. Contains sub rounded fine to coarse gravels.
Gray, damp, dense, fine- to coarse-grain, contains 20 to 30 percent sub
rounded fine to coarse gravel.
Olive brown, damp, lose, fine-grain, contains 5 percent sub rounded fine
gravel.
No recovery (SPT).
5
7
7
5
5
6
5
5
7
7
7
8
6
9
19
10
14
22
20
33
43
4
5
7
27
36
38
9
Project:Conifer Court Boring No.:B-2
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:June 15, 2022
Drill Method:Truck Mounted Hollowstem Driving Weight:140lbs Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
116.12.6
3.7 109.2
3.0 109.5
4.3 115.3
3.0 109.5
1.8 115.3
1.6
2.5 127.7
40
45
50
55
60
65
70
Silty Sand (SM): Gray to dark gray, damp, fine- to coarse-grain, very dense,
contains 10 percent sub rounded fine to coarse gravels.
Clayey Sand (SC): Brown to dark brown, damp to moist, very dense, fine- to
coarse -grain, contains 10 to 20 percent fine to coarse sub rounded gravel.
Dark gray to black, moist, very dense, fine- to coarse-grain, some visible
water. Contains 10 to 20 percent sub angular fine to coarse grained gravel.
Granitic Bedrock (Kgr)
Light Gray, dry, hard, crystalline bedrock.
Total depth 56.5 feet.
No groundwater or seepage.
Backfilled with cuttings.
14
17
50/5"
22
25
45
50/5"
32
50/4"
Project:Conifer Court Boring No.:B-2
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:June 15, 2022
Drill Method:Truck Mounted Hollowstem Driving Weight:140lbs Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
4.7 121.1
6.0 131.9
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand (SM): Brown to dark gray brown, dry, loose, fine- to medium-
grain, porous,.
Gray brown, damp, loose, micaceous.
Alluvium (Qal)
Silty Sand (SM): Light brown, dry to damp, medium dense, fine grained,
micaceous.
Poorly Graded Sand with Silt (SP-SM): Gray brown, damp, dense, fine- to
coarse-grain, contains 10 percent sub rounded fine to coarse gravels and
fine cobbles.
very dense.
Interbedded Sand and Silt (SM/ML): Olive gray, damp, medium dense to
dense, interbedded silty fine sand and poorly graded fine to coarse sand that
contains 10 percent fine to coarse sub rounded gravels.
Poorly Graded Sand (SP): Gray, damp, very dense, fine -to coarse- grain,
contains 5 to 10 percent sub rounded fine to coarse gravels.
Total depth 26.5 feet.
No groundwater or seepage.
Backfilled with cuttings.
4
5
6
4
8
12
17
25
20
29
43
46
15
18
23
13
24
50/5"
7
14
20
Project:Conifer Court Boring No.:B-3
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:June 15, 2022
Drill Method:Truck Mounted Hollowstem Driving Weight:140lbs Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
2.6 111.9
3.9 106.6
1.5
1.1
1.4
1.1
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand (SM): Gray brown, dry, fine- to medium- grain.
Brown, damp, loose, fine- to medium-grain,
Granitic Bedrock (Kgr)
Gray to light gray, dry, hard, crystalline bedrock.
Total depth 8.5 feet.
No groundwater or seepage.
Backfilled with cuttings.
10
11
14
10
14
15
14
22
30
Project:Conifer Court Boring No.:B-4
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:June 15, 2022
Drill Method:Truck Mounted Hollowstem Driving Weight:140 lbs Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
8.4 109.4
3.6 119.9
0
5
10
15
20
25
30
35
Topsoil
Silty Sand and Gravel (SM/GM): Light gray brown, dry, loose, fine to coarse
grained, contains 10 to 15 percent angular fine to coarse gravels, cobbles,
and boulders.
Granitic Bedrock (Kgr)
Dark gray, dry, crystalline bedrock, very hard.
Refusal on rock at 2.0 feet.
No caving.
No groundwater or seepage.
Backfilled with cuttings..
Project:Conifer Court Boring No.:T-1
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Topsoil
Silty Sand and Gravel (SM/GM): Gray brown, dry, loose, fine to coarse
grained, contains 30 to 40 percent gravels , cobbles, and boulders up to
approximately 3 feet in largest diameter. Porous with rootlets. Fill lifts are
inclined toward slope.
Granitic Bedrock (Kgr)
Dark gray, dry, crystalline bedrock, very hard.
Refusal on rock at 3 feet.
Caving from 0 to 3 feet.
No groundwater or seepage.
Backfilled with cuttings..
Project:Conifer Court Boring No.:T-2
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand and Gravel (SM/GM): Gray brown, dry, loose, fine to coarse
grained, contains 40 percent angular fine to coarse gravels, cobbles, and
boulders up to 4 feet in largest diameter..
Practical refusal at 10.5 feet due to caving and large nested boulders at
bottom of excavation.
No groundwater or seepage.
Caving conditions from 0 to 10.5 feet.
Backfilled with cuttings..
Project:Conifer Court Boring No.:T-3
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand and Gravel (SM/GM): Gray brown, dry, loose, fine to coarse
grained, contains 30 to 35 percent gravels cobbles and boulders up to 5 feet
in largest dimension. Porous.
layer of sandbags.
damp.
Granitic Bedrock (Kgr)
Dark gray, dry, crystalline bedrock, very hard.
Refusal on rock at 11.5 feet.
Caving from 0 to 11 feet.
No groundwater or seepage.
Backfilled with cuttings..
Project:Conifer Court Boring No.:T-4
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:Br
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand and Gravel (SM/GM): Dark gray brown to gray brown, dry to damp,
loose, fine to coarse grained, contains 25 to 35 percent angular fine to coarse
grained gravels, cobbles, and boulders..
Alluvium (Qal)
Poorly Graded Sand (SP): Dark gray, damp, fine to coarse grained, sub
angular fine to coarse grained gravel.
Granitic Bedrock (Kgr)
Dark gray, dry, crystalline bedrock, very hard.
Refusal on rock at 20.0 feet.
Caving from 0 to 14 feet.
No groundwater or seepage.
Backfilled with cuttings.
Project:Conifer Court Boring No.:T-5
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand (SM/GM): Light gray brown to brown, dry, loose, fine to coarse
grained, contains 10 to 20 percent angular fine to coarse gravels, cobbles,
and boulders up to approximately 3 feet in largest diameter..
Granitic Bedrock (Kgr)
Dark gray, dry, crystalline bedrock, very hard.
Refusal on rock at 3.5 feet.
No groundwater or seepage.
Backfilled with cuttings..
Project:Conifer Court Boring No.:T-6
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Light brown, dry, loose, fine to coarse grained, contains 15 to 20 percent
angular fine to coarse grained gravels, cobbles, and boulders up to
approximately 3 feet in largest diameter..
Gray brown.
Pieces of steel and cable.
damp.
Refusal due to caving at 21.5 feet.
Caving from 0 to 21.5 feet.
No groundwater or seepage.
Backfilled with cuttings.
Project:Conifer Court Boring No.:T-7
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE
0
5
10
15
20
25
30
35
Undocumented Fill (Afu)
Silty Sand and Gravel (SM/GM): Gray brown, dry, loose, fine to coarse
grained.
50 to 60 percent angular fine to coarse gravels, cobbles, and boulders.
40 percent angular fine to coarse gravels, cobbles, and boulders..
50 to 60 percent angular fine to coarse gravels, cobbles and boulders.
Refusal due to caving conditions and nested boulders at 11.5 feet.
Caving from 0 to 11.5 feet.
No groundwater or seepage.
Backfilled with cuttings.
Project:Conifer Court Boring No.:T-8
Location:Fontana, California Elevation:
Job No.:22-237 Client: Conifer Court LLC Date:May 26, 2022
Drill Method:John Deere 470 Excavator Driving Weight:N/A Logged By:BR
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
E X P L O R A T I O N L O G
Petra Geosciences, Inc.
PLATE