HomeMy WebLinkAboutCT 15-07; OCEAN VIEW POINT; UPDATED GEOTECHNICAL EVALUATION; 2021-11-02UPDATED GEOTECHNICAL Evaluation
Oceanview Project
South End of Twain Avenue
CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
PREPARED FOR
Rincon Homes
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE, SUITE A
VISTA, CALIFORNIA 92081
PROJECT No. 3738-SD NOVEMBER 2, 2021
RECE WED
NOV 05 2021
LAND DEVELOPMENT 'r~
C EOTEK ENGINEERING
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Office (760) 599-0593 Fax www.geotekusa.com
November 2, 2021
Project No. 3738-SD
Rincon Homes
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
Attention: Mr. Cameron St. Clair
Subject: Updated Geotechnical Evaluation
Proposed Oceanview Project
Twain Avenue
Carlsbad, San Diego County, California
Dear Mr. St. Clair:
GeoTek, Inc. (GeoTek) is pleased to provide the results of this updated geotechnical
evaluation for the subject project. This report presents the results of GeoTek's recent
site visit and review of the project geotechnical documents and provides updated
preliminary geotechnical recommendations for earthwork, foundation design, and
construction. Based upon review, site development appears feasible from a geotechnical
viewpoint provided that the recommendations included herein are incorporated into the
design and construction phases of site development. The opportunity to be of service is
sincerely appreciated. If you should have any questions, please do not hesitate to call GeoTek.
Respectfully submitted,
GeoTek, Inc. lot ruc
2733
Christopher D. Livesey
CEG 2733, Exp. 05/31/23
Associate Vice President
Distribution: (I) Addressee
A.
No. GE228427-
Exp. 1V31/J
"V
Bruce A. hick
GE 2284, Exp. 12/31/22
Geotechnical Engineer
GEOTECHNICAL I ENVIRONMENTAL I MATERIALS
RINcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Ocearview Project, Carlsbad, California Page i
TABLE OF CONTENTS
I. PURPOSE AND SCOPE OF SERVICES.................................................................................................I
SITE DESCRIPTION AND PROPOSED DEVELOPMENT ...............................................................1
2.1 Site Description ................................................................................................................................ I
2.2 Proposed Development.....................................................................................................................I
FIELD EXPLORATION AND LABORATORY TESTING .................................................................2
3.1 Review of Prior Geotechnical Documents ...........................................................................................2
3.2 Field Exploration...............................................................................................................................2
3.3 Laboratory Testing............................................................................................................................3
GEOLOGIC AND SOILS CONDITIONS...............................................................................................3
4.1 Regional Setting................................................................................................................................3
4.2 EARTH MATERIALS .........................................................................................................................3
,CZ 1 Quaternary Old Paralic Deposits (Map Symbol Qop)..........................................................................4
4.2.2 Tertiary Santiago Formation (Map Symbol Tsa) .................................................................................4
4.3 SURFACE WATER AND GROUNDWATER........................................................................................4
4.3.1 Surface Water .................................................................................................................................. 4
4.3.2 Groundwater....................................................................................................................................4
4.4 EARTHQUAKE HAZARDS ................................................................................................................ 5
4.4.1 Surface Fault Rupture.......................................................................................................................5
4.4.2 Liquefaction/Seismic Settlement ......................................................................................................... 5
4,4.3 Other Seismic Hazards.....................................................................................................................5
S. CONCLUSIONS AND RECOMMENDATIONS ..................................................................................6
5.1 General............................................................................................................................................6
5.2 EARTHWORK CONSIDERATIONS ...................................................................................................6
£2.1 General............................................................................................................................................6
5.. 22 Site Clearing and Preparation............................................................................................................6
5.23 Remedial Grading.............................................................................................................................6
£2.4 Engineered Fill..................................................................................................................................7
5.23 Excavation Characteristics.................................................................................................................7
5.2.6 Shrinkage and Bulking......................................................................................................................8
5.2.7 Trench Excavations and Backfill ................................................ ........................................................ 8
5.3 DESIGN RECOMMENDATIONS ............................................... ........................................................ 9
5.3.1 Storm water Infiltration ...................................................................................................................... 9
5.12 Foundation Design Criteria...............................................................................................................11
5.3.3 Under Slab Moisture Membrane.....................................................................................................12
5.3.4 Miscellaneous Foundation Recommendations...................................................................................13
£33 Foundation Setbacks.......................................................................................................................14
5.3.6 Seismic Design Parameters .............................................................................................................14
5.3.7 Soil Sulfate Content........................................................................................................................15
5i.8 General Concrete Flatwork .............................................................................................................. 15
5.3.9 Preliminary Pavement Design ..........................................................................................................15
5.4 RETAINING WALL DESIGN AND CONSTRUCTION........................................................................16
£4.1 General Design Criteria...................................................................................................................16
5.42 Restrained Retaining Walls .............................................................................................................17
5.4.3 Wall Backfill and Drainage .............................................................................................................17
5.5 POST CONSTRUCTION CONSIDERATIONS...................................................................................18
C EOTEK
RuNcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page ii
TABLE OF CONTENTS
5.5.1 Landscape Maintenance and Planting..............................................................................................18
5.5.2 Drainage........................................................................................................................................19
5.6 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS.................................................................19
LIMITATIONS............................................................................................................................................20
SELECTED REFERENCES.......................................................................................................................21
ENCLOSURES
Figure I - Site Location Map
Figure 2 - Geotechnical Map
Appendix A - Exploratory Boring Logs (GeoTek, Inc.)
Appendix B - Exploratory Boring Logs (CWE)
Appendix C - Results of Laboratory Testing (CWE)
Appendix D - Hydrological Classification
Appendix E - General Earthwork Grading Guidelines
G EOTEK
RINcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
I. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to evaluate the geotechnical conditions of the proposed site
improvements. Services provided for this study included the following:
Research and review of available geologic and geotechnical data, and general information
pertinent to the site.
Performing a site visit and the excavation of six (6) exploratory borings onsite.
Review and evaluation of site seismicity, and
Compilation of this geotechnical report which presents GeoTek's findings of pertinent
site geotechnical conditions and geotechnical recommendations for site development.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 Site Description
The property is located south of the southern cul-de-sac of Twain Avenue, in the City of
Carlsbad. California. The property is currently unimproved land and consists of an irregularly
shaped parcel that comprises approximately I 6.5 acres. However, of that area, approximately 5
acres is proposed to be improved and referenced herein as the "site." Topography of the site
generally consists of a hillside setting with slopes descending to the east, south and west. An
existing residential development to the north ascends westerly to the site with the knoll of the
hill located in the northern portion of the site. Topographic elevations range from approximately
325 feet in the north to 272 feet in the south-southwest. Estimated gradients of the slopes range
from 2:1 (horizontal:vertical) to 3: I, however flatter and more steep gradients probably exist. A
Site Location Map is presented as Figure I.
2.2 Proposed Development
In 2018, the site was previously evaluated by Christian Wheeler Engineering (CWE) based on a
proposed five lot subdivision. Basedon updated design plans prepared by Pasco, Laret, and
Suiter (PLSA), a thirteen lot subdivision is now proposed. The project is proposed to be
developed with one to two story, wood framed and stucco finished, slab-on-grade, single-family
C EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
style residential homes. For the purposes of this report, it is assumed maximum column and wall
loads of about 50 kips and 2.5 kips per foot, respectively. If actual loads are known to exceed
these assumptions, Geolek should be notified to determine if modifications to the
recommendations presented in this report are warranted. Additional improvements include but
are not limited to a stormwater quality basin, an interior street (extension of Twain Avenue),
backbone underground utilities, concrete flatwork, and landscaping.
As site planning progresses and additional or revised plans become available, they should be
provided to Geolek for review and comment. If plans vary significantly, additional geotechnical
field exploration, laboratory testing, and engineering analyses may be necessary to provide specific
earthwork recommendations and geotechnical design parameters for actual site development
plans.
3. FIELD EXPLORATION AND LABORATORY TESTING
3.1 Review of Prior Geotechnical Documents
To aid in the preparation of this report, Geolek was provided with a previous geotechnical
report prepared by Christian Wheeler Engineering (CWE, 2018). Select data from this report
are referenced throughout this update report.
3.2 Field Exploration
Geotek performed a site visit to evaluate the current site conditions and compare the conditions
of those presented by CWE. This site visit was performed on September 28, 2021 and included
traversing the site improvement area and recording surficial observations. Outcroppings of Old
Paralic deposits were observed in the northern portion of the site and weathered claystone of
the Santiago formation was observed in the southern (lower topographic elevations) portion of
the site.
Six (6) exploratory manual augers were performed to evaluate the thickness of soil profiles
presented by CWE. The approximate locations are presented on Figure 2. The manual augers
were chosen, as the tool is operated directly by manual labor (not powered by a motor which
would provide a force multiplier). The intent was to review the soil profile thickness, as the
manual augur does not have the ability to readily advance into bedrock.
A geologist from GeoTek visually logged the boring excavations. Approximate locations of
exploration locations are presented on the Geotechnical Map, Figure 2. A description of
materials encountered in the borings are presented on test pit logs in Appendix A.
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C EOTEK
RuNcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
3.3 Laboratory Testing
Laboratory testing was performed by CWE on bulk soil samples collected during their field
explorations. A summary of results of the laboratory testing program are included in
Appendix C.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 Regional Setting
The subject property is located in the Peninsular Ranges geomorphic province. The Peninsular
Ranges province is one of the largest geomorphic units in western North America. Basically, it
extends roughly 975 miles from the north and northeasterly adjacent the Transverse Ranges
geomorphic province to the peninsula of Baja California. This province varies in width from about
30 to 100 miles. It is bounded on the west by the Pacific Ocean, on the south by the Gulf of
California and on the east by the Colorado Desert Province.
The Peninsular Ranges are essentially a series of northwest-southeast oriented fault blocks.
Several major fault zones are found in this province. The Elsinore Fault zone and the San Jacinto
Fault zones trend northwest-southeast and are found in the near the middle of the province. The
San Andreas Fault zone borders the northeasterly margin of the province. The Newport-
Inglewood-Rose Canyon Fault zone meanders the southwest margin of the province. No faults
are shown in the immediate site vicinity on the map reviewed for the area.
4.2 EARTH MATERIALS
A brief description of the earth materials encountered during the current subsurface exploration
is presented in the following sections.
CWE noted that the site was mantled by Topsoil in the upper 12 inches overlying a subsoil
between 12 and 24 inches. There was also noted to be localized slopewash deposits on the site.
All near surface soils and slopewash was underlain by Terrace Deposits (Old Paralic Deposits)
and at depth, Santiago Formation. However, based on the site visit and evaluation, the site
exposes weathered Old Paralic Deposits and Santiago Formation at the surface. The slopewash
noted by CWE was not observed, however, the slopewash noted is in actuality a weathered
claystone bed, which was observed to be dark brown and consistent with weathered claystone
that is typically found in the Santiago Formation. This lithographic interpretation is also based on
CWE's test pit logs that note Santiago Formation underlying the slopewash.
G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
Based on review of published geologic maps, GeoTek's site visit and interpretation of CWE's
geotechnical logs, the subject site is locally underlain by Old Paralic Deposits (Qop) and Santiago
Formation (Tsa).
4.2.1 Quaternary Old Paralic Deposits (Map Symbol Qop)
Old Paralic Deposits were observed on site in all borings with exception to HA-3. CWE also
noted Old Paralic Deposits in explorations TP- I, TP-3, TP-4 and TP-8 and TP-9. GeoTek's
explorations consisted of weathered silty sands, light brown, damp and loose. Deeper
explorations by CWE noted clayey sand(stone) that was medium brown, fine to coarse grained,
and medium dense to dense. Old Paralic Deposits were found and interpreted to be at the
surface and to depths explored of 8 feet. In test pit TP-9, the Old Paralic Deposits were found
to be 3.5 feet and overlying the Santiago Formation.
4.2.2 Tertiary Santiago Formation (Map Symbol Tsa)
The Santiago Formation was observed on site and in boring HA-3. CWE also noted Santiago
Formation in explorations TP-2, TP-5, TP-6 and TP-7. As encountered in GeoTek's exploration,
HA-3, the weathered Santiago Formation consisted of dark brown, firm, clayey sand. Deeper
exploration by CWE noted the Santiago Formation was dense, light brown to light olive brown,
sandy clay(stone). It should be noted that the upper weathered zone of the Santiago Formation
was noted to be dark brown sandy clay(stone). The Santiago Formation were found and
interpreted to be at the surface and to depths explored of 15 feet.
4.3 SURFACE WATER AND GROUNDWATER
4.3.1 Surface Water
Surface water was not observed during the recent site exploration. If encountered during
earthwork construction, surface water on this site is likely the result of precipitation. Overall
site area drainage crowns away from the topographic knoll in the north. Provisions for surface
drainage will need to be accounted for by the project civil engineer.
4.3.2 Groundwater
A static groundwater table was not encountered during exploration of the subject site. Based
on the anticipated depth of removals, groundwater is not anticipated to be a factor in site
development. Localized perched groundwater may be present but is also not anticipated to be a
factor in site development.
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G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
4.4 EARTHQUAKE HAZARDS
4.4.1 Surface Fault Rupture
The geologic structure of the entire southern California area is dominated mainly by northwest-
trending faults associated with the San Andreas system. The site is in a seismically active region.
No active or potentially active fault is known to exist at this site nor is the site situated within an
"Aiquist-Priolo" Earthquake Fault Zone or a Special Studies Zone (Bryant and Hart, 2007). No
faults transecting the site were identified on the readily available geologic maps reviewed. The
nearest known active fault is the Newport Inglewood-Rose Canyon fault located about 17 miles
to the southwest of the site.
4.4.2 Liquefaction/Seismic Settlement
Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake-induced
ground motion, create excess pore pressures in relatively cohesionless soils. These soils may
thereby acquire a high degree of mobility, which can lead to lateral movement, sliding,
consolidation and settlement of loose sediments, sand boils and other damaging deformations.
This phenomenon occurs only below the water table, but, after liquefaction has developed, the
effects can propagate upward into overlying non-saturated soil as excess pore water dissipates.
The factors known to influence liquefaction potential include soil type and grain size, relative
density, groundwater level, confining pressures, and both intensity and duration of ground
shaking. In general, materials that are susceptible to liquefaction are loose, saturated granular
soils having low fines content under low confining pressures.
The liquefaction potential and seismic settlement potential on this site is considered negligible
due to the presence of shallow sedimentary bedrock (Qop and Tsa) and lack of groundwater.
4.4.3 Other Seismic Hazards
Landslides were not mapped to underly the site. In addition, no adverse geologic structure was
observed during the site visit or the test pit logs presented by CWE. The potential for landslide
instability is considered to be low. The potential for secondary seismic hazards such as seiche
and tsunami is remote due to site elevation and distance from an open body of water.
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G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
S. CONCLUSIONSAND RECOMMENDATIONS
5.1 General
Development of the site appears feasible from a geotechnical viewpoint provided that the
following recommendations are incorporated in the design and construction phases of the
development. The following sections present general recommendations for currently anticipated
site development.
5.2 EARTHWORK CONSIDERATIONS
52.1 General
Earthwork and grading should be performed in accordance with the applicable grading ordinances
of the City of Carlsbad, the 2019 (or current) California Building Code (CBC), and
recommendations contained in this report. The Grading Guidelines included in Appendix E
outline general procedures and do not anticipate all site-specific situations. In the event of
conflict, the recommendations presented in the text of this report should supersede those
contained in Appendix E.
5.2.2 Site Clearing and Preparation
Site preparation should start with removal of deleterious vegetation. These materials should be
disposed of properly off site.
5.2.3 Remedial Grading
Prior to placement of fill materials and in all structural areas the upper variable, potentially
compressible materials should be removed and replaced with engineered fill. Removals include
weathered Old Paralic Deposits (Qop) and Santiago Formation (also noted in the CWE report
as topsoil, subsoil, slopewash, and Terrace Deposits). Based on the weathering profile of CWE's
logs, the upper three feet of earth material will need to be reprocessed. Locally deeper areas
not explicitly explored may exist. The lateral extent of removals should extend to the limits of
grading. Competent materials will be determined upon remedial grading and shall consist of Old
Paralic Deposits or Santiago Formational material that is visually non-porous, firm to a soil probe,
and firm (non-pumping) to a CAT 924 Wheel Loader (fully loaded bucket) or equivalent. The
bottom of the removals should be observed by a GeoTek representative prior to processing the
bottom for receiving placement of compacted fills.
Based on evaluation, site grading is anticipated to result in a cut/fill transition underlying proposed
building pads. Whenever a cut/fill slope transition occurs, the cut portion of the pad should be
overexcavated a minimum of three feet and replaced with engineered fill. For Lots 7 through 10,
G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
the cut portion should be overexcavated a minimum of 5 feet, due to deeper fills required to be
placed in these lots to bring existing grades up to proposed grades.
In pavement areas, removals should extend at least two feet below finish grade, or one foot
below finished subgrade, whichever is lower.
Prior to fill placement, the bottom of all removals should be scarified to a minimum depth of six
(6) inches, brought to slightly above optimum moisture content, and then compacted to at least
90% of the soil's maximum dry density as determined by ASTM Dl 557 test procedures. The
resultant voids from remedial grading/over-excavation should be filled with materials placed in
general accordance with Section 5.2.4 Engineered Fill of this report.
5.2.4 Engineered Fill
Onsite materials are generally considered suitable for reuse as engineered fill provided they are
free from vegetation, roots, debris, and rock/concrete or hard lumps greater than six (6) inches
in maximum dimension. The earthwork contractor should have the proposed excavated
materials to be used as engineered fill at this project approved by the soils engineer prior to
placement.
Engineered fill materials should be moisture conditioned to at or above optimum moisture
content and compacted in horizontal lifts not exceeding 8 inch in loose thickness to a minimum
relative compaction of 90% as determined by ASTM D 1557 test procedures. If fill is being placed
on slopes steeper than 5:1 (horizontal : vertical), the fill should be properly benched into the
existing slopes and a sufficient size keyway shall be constructed in accordance with grading
guidelines presented in Appendix C.
5.25 Slope Construction
An engineering geologist should observe all cut slopes. Cut slopes should expose competent
bedrock. If adverse structure or incompetent materials are exposed and identified in the cut
slopes, stabilization fills may be recommended.
Where fill is to be placed against sloping ground with gradients of 5:1 (h:v) or steeper, the sloping
ground surface should be benched to remove loose and disturbed surface soil and bedrock and
to assure that the new fill is placed in direct contact with competent bedrock, and to provide
horizontal surfaces for fill placement. A keyway should be constructed at the toe of the fill slope
areas into dense natural material and in accordance with Plate G-3, Appendix D.
The base of the keyways and benches should be sloped back into the hillside at a gradient of at
least two percent. The base of the benches should be evaluated by a representative of GeoTek
prior to processing. Upon approval, the exposed materials should be moistened to at least the
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C EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
optimum moisture content and densified to a relative compaction of at least 90 percent (ASTM
D 1557). Details showing slope construction are presented in Appendix D.
Fill slopes should be overfilled during construction and then cut back to expose fully compacted
soil. A suitable alternative would be to compact the slopes during construction and then roll the
final slope to provide a dense, erosion resistant surface.
Backdrains should be installed in the keyways in accordance with the recommendations outlined
in Appendix F.
51.6 Excavation Characteristics
Excavations in the onsite materials can generally be accomplished with heavy-duty earthmoving
or excavating equipment in good operating condition.
5.2.7 Shrinkage and Bulking
Several factors will impact earthwork balancing on the site, including bedrock bulking,
undocumented fill and colluvium shrinkage, trench spoil from utilities and footing excavations, as
well as the accuracy of topography.
Shrinkage and bulking are largely dependent upon the degree of compactive effort achieved during
construction. Shrinkage of 5 percent may be applied to the upper I to 2 feet of the existing
surface. A bulking of 5 percent may be applied to material excavated in the upper 2 to 7 feet and
10 percent for material deeper than 7 feet below existing grades. Subsidence should not be a
factor on the subject site if removals are completed as recommended.
5.2.8 Trench Excavations and Backfill
Temporary excavations within the onsite materials should be stable at 1: I inclinations for short
durations during construction, and where cuts do not exceed 10 feet in height. Temporary cuts
to a maximum height of 4 feet can be excavated vertically.
Trench excavations should conform to Cal-OSHA regulations. The contractor should have a
competent person, per OSHA requirements, on site during construction to observe conditions
and to make the appropriate recommendations.
Utility trench backfill should be compacted to at least 90% relative compaction of the maximum
dry density as determined by ASTM D 1557 test procedures. Under-slab trenches should also be
compacted to project specifications.
G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
Onsite materials may not be suitable for use as bedding material but should be suitable as backfill
provided particles larger than 6± inches are removed.
Compaction should be achieved with a mechanical compaction device. Ponding or jetting of
trench backfill is not recommended. If backfill soils have dried out, they should be thoroughly
moisture conditioned prior to placement in trenches.
5.3 DESIGN RECOMMENDATIONS
5.3.1 Stormwater Infiltration
Many factors control infiltration of surface waters into the subsurface, such as consistency of
native soils and bedrock, geologic structure, fill consistency, material density differences, and
existing groundwater conditions. Current site plans indicate one, centrally located, proposed
stormwater quality basin which is shown on Figure 2.
A review of the site conditions and proposed development was performed in general accordance
to the City of Carlsbad BMP design manual. The scope of stormwater evaluation was performed
to identify infiltration characteristics. A review of the site based on the USDA NRCS indicated
the site was classified as a hydrological Group B. Based on the site specific evaluation, a
professional opinion was concluded that the site is a hydrological Group D. A copy of this letter
is provided in Appendix D. As required by the City of Carlsbad BMP design manual, the following
bullet points describe required considerations and some optional considerations.
5.3. Ia. Based on a review of www.geotracker.com, environmental impacted sites are not
reported within 100 feet of the site.
5.3.1 b. Based on a review of Geotracker.com and a reconnaissance of the properties
surrounding the site, which were found to be residential, there was not an industrial
active building that may pose a lack of source control within 100 feet of the site.
5.3.1c. Based on the surrounding existing development and the understanding that the
proposed project will be supported by a municipal sanitation system, the BMP is not
located within 50 feet of septic tanks or leach fields.
5.3.1 d. Based on a review of the proposed improvements, the BMP is designed within 10
feet of structural retaining walls.
5.3.1 e. Based on a review of the proposed improvements, the BMP is designed within 10
feet of sewer utilities.
5.3. If. Based on a review of the geologic information for the site and the site specific
evaluation that identified shallow dense bedrock within two feet of the surface.
Aa,
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Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
Also, the proposed BMP is designed within a cut portion of the project that will
expose dense bedrock. Infiltration of surface waters will develop a shallow perched
groundwater condition within 10 feet of the BMP.
5.3. 1g. Based on a review of the topography of the site, hydric soils are not prone to exist.
However, based on the shallow bedrock of the site and in low gradient proposed
areas, hydric soils have the potential to develop due to infiltration of surface waters.
5.3. I h. Based on the shallow bedrock, hazards due to liquefiable soils is considered to be
low.
5.3. Ii. Based on the proposed design, the BMP is located within 1.5 times the height of an
adjacent steep slope.
5.3.1j. Based on the site specific study and conclusion, the site is within a predominantly
type D soil.
In addition to the above considerations, concentrated infiltration of surface waters in a hillside
development is prone to destabilize earthen improvements. Therefore, based on outline
numbers 5.3. I d, e, f, I and j, the DMA's for the site are classified as restricted for infiltration. As
the DMAs are considered to be restricted design infiltration rates are not considered necessary.
Tabk D.I-1: Considerations for GcotcchnicJ Analysis of Infiltration Restrictions
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G EOTEK
RINCoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
Based on the restricted category of the DMA, the proposed basin should be designed for filtration
and all sides, including the bottom, should be designed with an impermeable liner to mitigate the
potential for groundwater to develop and impact the proposed design improvements.
5.3.2 Foundation Design Criteria
Preliminary foundation design criteria, in general conformance with the 2019 CBC, are presented
herein. These are typical design criteria and are not intended to supersede the design by the
structural engineer.
Based on visual classification of materials encountered the overall consistency of the material
anticipated to be placed near finish grades are anticipated to exhibit a "low" (21 :5 El 15 49)
expansion index potential per ASTM D4829. It should be noted that expansion index testing
results by CWE indicated "medium" expansion index material is present on site and is consistent
with claystone of the Santiago Formation, however, material having a "very low" to "low"
expansion index potential is anticipated to be excavated from the northern portion of the site
and placed as fills in the areas where Santiago Formational material is mapped. Additional
laboratory testing should be performed upon completion of site grading to verify the expansion
poter tial and plasticity index ot the subgrade soils.
DESIGN PARAMETERS FOR CONVENTIONAL REINFORCED SHALLOW
FOUNDATIONS
"Low" Expansion "Medium" Expansion
Design Parameter Potential Potential
(21 :5El:550) (50:50589)
Foundation Embedment Depth or
Minimum Perimeter Beam Depth (inches 18 inches 24 inches
below _lowest _adjacent _finished _grade)
Minimum Foundation Width for
continuous _I_ perimeter _footings* IS Inches IS Inches
Minimum Foundation Width for isolated 24 -Inches
/ column footings* (Square) 24 - Inches (Square)
Minimum Slab Thickness (actual) 4 Inches 5 Inches
No. 3 rebar at 18" No. 4 rebar at 18" on-center,
Minimum Slab Reinforcing
on-center, each
way, placed in the each way, placed in the
middle one-third of middle one-third of the slab
the thickness _slab _thickness
Two (2) No. 4 Four (4) No. 4 reinforcing
Minimum Footing Reinforcement reinforcing bars, bars, One (I) top and Two (2) top and two (2)
one (I) bottom bottom
Effective Plasticity Index** <18 I 9<Pl<25
Presaturation of Subgrade Soil (percent Minimum IIO%to Minimum 120% to a depth of
of optimum moisture content) a depth of 12 18 inchesinches
"Lode minimums per table 1809.7 of the 2019 CBC should be complied with.
**Effective Plasticity Index should be verified at the completion of the rough grading.
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RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
It should be noted that the above recommendations are based on soil support characteristics
only. The structural engineer should design the slab and beam reinforcement based on actual
loading conditions.
The following recommendations should be implemented into the design:
An allowable bearing capacity of 2,500 pounds per square foot (psf) may be
considered for design of continuous and perimeter footings that meet the depth and
width requirements in the table above. This value may be increased by 250 psf for
each additional 12 inches in depth and 250 psf for each additional 12 inches in width
to a maximum value of 4,000 psf. Additionally, an increase of one-third may be applied
when considering short-term live loads (e.g., seismic and wind loads).
Based on experience in the area, structural foundations may be designed in
accordance with 2019 CBC, and to withstand a total settlement of I inch and
maximum differential settlement of one-half of the total settlement over a horizontal
distance of 40 feet. Due to site geologic conditions, seismically induced settlement is
considered to be minimal.
The passive earth pressure may preliminarily be computed as an equivalent fluid having
a density of 250 psf per foot of depth, to a maximum earth pressure of 2,500 psf for
footings founded on engineered fill. A coefficient of friction between soil and
concrete of 0.30 may be used with dead load forces. passive pressure and frictional
resistance can be combined without reduction.
A grade beam should be utilized across large entrances. The bottom of the grade
beam should be at the same elevation as the bottom of the adjoining footings.
5.3.3 Under Slab Moisture Membrane
A moisture and vapor retarding system should be placed below slabs-on-grade where moisture
migration through the slab is undesirable. Guidelines for these are provided in the 2019 California
Green Building Standards Code (CALGreen) Section 4.505.2 and the 2019 CBC Section 1907.1
It should be realized that the effectiveness of the vapor retarding membrane can be adversely
impacted as a result of construction related punctures (e.g., stake penetrations, tears, punctures
from walking on the vapor retarder placed atop the underlying aggregate layer, etc.). These
occurrences should be limited as much as possible during construction. Thicker membranes are
generally more resistant to accidental puncture that thinner ones. Products specifically designed
for use as moisture/vapor retarders may also be more puncture resistant. Although the CBC
G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
specifies a 6-mil vapor retarder membrane, it is Geolek's opinion that a minimum 10 mu
membrane with joints properly overlapped and sealed should be considered, unless otherwise
specified by the slab design professional.
Moisture and vapor retarding systems are intended to provide a certain level of resistance to
vapor and moisture transmission through the concrete, but do not eliminate it. The acceptable
level of moisture transmission through the slab is to a large extent based on the type of flooring
used and environmental conditions. Ultimately, the vapor retarding system should be comprised
of suitable elements to limit migration of water and reduce transmission of water vapor through
the slab to acceptable levels. The selected elements should have suitable properties (i.e.,
thickness, composition, strength and permeability) to achieve the desired performance level.
Moisture retarders can reduce, but not eliminate, moisture vapor rise from the underlying soils
up through the slab. Moisture retarder systems should be designed and constructed in
accordance with applicable American Concrete Institute, Portland Cement Association, Post-
Tensioning Concrete Institute, ASTM and California Building Code requirements and guidelines.
GeoTek does not practice in the field of moisture vapor transmission evaluation/migration since
that practice is not a geotechnical discipline. Therefore, it is recommended that a qualified
person, such as the flooring contractor, structural engineer, architect, and/or other experts
specializing in moisture control within the building be consulted to evaluate the general and
specific moisture and vapor transmission paths and associated potential impact on the proposed
construction. That person (or persons) should provide recommendations relative to the slab
moisture and vapor retarder systems and for migration of potential adverse impact of moisture
vapor transmission on various components of the structures, as deemed appropriate. In addition,
the recommendations in this report and GeoTek's services in general are not intended to address
mold prevention; since Geolek, along with geotechnical consultants in general, do not practice
in the area of mold prevention. If specific recommendations addressing potential mold issues are
desired, then a professional mold prevention consultant should be contacted.
5.3.4 Miscellaneous Foundation Recommendations
To reduce moisture penetration beneath the slab on grade areas, utility trenches
should be backfIlled with engineered fill, lean concrete or concrete slurry where they
intercept the perimeter footing or thickened slab edge.
Spoils from the footing excavations should not be placed in the slab-on-grade areas
unless properly moisture-conditioned, compacted and tested. The excavations should
G EOT E K
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
1 Oceanview Project, Carlsbad, California Page B- I
be free of loose/sloughed materials and be neatly trimmed at the time of concrete I placement.
' 53.5 Foundation Setbacks
Where applicable, the following setbacks should apply to all foundations. Any improvements not
I conforming to these setbacks may be subject to lateral movements and/or differential
settlements:
I . The outside bottom edge of all footings should be set back a minimum of 1-1/3 (where
H is the slope height) from the face of any descending slope. The setback should be
I at least 7 feet and need not exceed 40 feet (C BC, 2019).
The bottom of all footings for structures near retaining walls should be deepened so I as to extend below a 1: I projection upward from the bottom inside edge of the wall
stem. This applies to the existing retaining walls along the perimeter if they are to
i remain.
The bottom of any existing foundations for structures should be deepened so as to I extend below a 1: I projection upward from the bottom of the nearest excavation.
I 5.3.6 Seismic Design Parameters
The site is located at approximately 33.1385 degrees Latitude and - 117.2985 degrees Longitude. ' Site spectral accelerations (Sa and Si) for 0.2 and 1.0 second periods, for a Class "C" site, were
determined from the SEAOC/OSHPD web interface that utilizes the USGS web services and
retrieves the seismic design data and presents that information in a report format. The results, I based on the 2019 CBC, are presented in the following table.
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RuNCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 0.994g
Mapped 1.0 sec Period Spectral Acceleration, Si 0.363g
Site Coefficient for Site Class "C", Fa 1.2
Site Coefficient for Site Class "C", Fv 1.5
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 0.2 Second, SMS 1193 g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 1.0 Second, SM 0.544
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SIDS g 0.796g
5% Damped Design Spectral Response
Acceleration Parameter at I second, SDI 0.363
Site Modified Peak Ground Acceleration (PGAM) 0.522g
Seismic Design Category D
5.3.7 Soil Sulfate Content
Water soluble sulfate content tests should be performed upon reaching finish pad grades.
Preliminarily, based on experience in the project area, special recommendations for concrete are
not anticipated to be required for this project due to soil sulfate exposure. Upon reaching design
grades, soil sampling of the near surface materials should be performed and samples tested to
confirm this assumption.
5.3.8 General Concrete Flatwork
It is recommended that control joints be placed in two directions spaced the numeric equivalent
roughly 24 times the thickness of the slab in inches (e.g., a 4-inch slab would have control joints
at 96 inch [8 feet] centers). These joints are a widely accepted means to control cracks and
should be reviewed by the project structural engineer.
Presaturation of flatwork subgrade should be verified to be a minimum of 110% of the soils
optimum moisture to a depth of 12 inches for soils having a "low" expansive index potential.
Subgrade having a "medium" expansion index potential should be verified to be moisture
conditioned to a minimum of 120% of the soils optimum moisture at a depth of 18 inches below
subgrade.
5.3.9 Preliminary Pavement Design
Traffic indices have not been provided during this stage of site planning. In addition, site
conditions have not been graded to a final design to evaluate specific pavement subgrade
conditions. Therefore, the minimum structural sections provided below are based on a
preliminary assumption of an R-Value of 25 and the assumed traffic indices.
G EOTEK
RINcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
PRELIMINARY ASPHALT PAVEMENT STRUCTURAL
SECTION
Design Criteria Asphaltic Concrete (AC) Aggregate Base (AB)
Thickness (inches) Thickness (inches)
Twain Avenue
Extension 4.0
1
6.0 11
Actual structural pavement design is to be determined by the geotechnical engineer's testing (R-
Value) of the exposed subgrade. Thus, the actual R-Value of the subgrade soils can only be
determined at the completion of grading for street subgrades and the above values are subject
to change based laboratory testing of the as-graded soils near subgrade elevations.
Asphalt concrete and aggregate base should conform to current Caltrans Standard Specifications
Section 39 and 26-1.02, respectively. As an alternative, asphalt concrete can conform to Section
203-6 of the current Standard Specifications for Public Work (Green Book). Crushed aggregate
base or crushed miscellaneous base can conform to Section 200-2.2 and 200-2.4 of the Green
Book, respectively. Pavement base should be compacted to at least 95 percent of the ASTM
D 1557 laboratory maximum dry density as determined by ASTM D 1557 test procedures
All pavement installation, including preparation and compaction of subgrade, compaction of base
material, placement and rolling of asphaltic concrete, should be done in accordance with the City
of Carlsoad specifications, and under the observation and testing of GeoTek and a City Inspector
where required. Jurisdictional minimum compaction requirements in excess of the
aforementioned minimums may govern.
5.4 RETAINING WALL DESIGN AND CONSTRUCTION
54. I General Design Criteria
I Preliminary plans are not yet available. If retaining walls are added at a later date, the
recommendations presented herein may apply to typical masonry or concrete vertical retaining
I walls to a maximum height of 6 feet. The 2019 CBC only requires the additional earthquake
induced lateral force be considered on retaining walls in excess of six (6) feet in height.
I
Therefore, additional review and recommendations should be requested for higher walls.
Retaining wall foundations embedded a minimum of 18 inches into engineered fill materials should
I be designed using an allowable bearing capacity of 2,500 psf. This value may be increased by 250
psf for each additional 12 inches in depth and 250 psf for each additional 12 inches in width to a
maximum value of 4,000 psf. An increase of one-third may be applied when considering short-
term live loads (e.g., seismic and wind loads). The passive earth pressure may be computed as
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Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
an equivalent fluid having a density of 250 psf per foot of depth, to a maximum earth pressure of
2,000 psf. A coefficient of friction between soil and concrete of 0.30 may be used with dead load
forces. Passive pressure and frictional resistance can be combined without reduction.
An equivalent fluid pressure approach may be used to compute the horizontal active pressure
against the wall. The appropriate fluid unit weights are given in the table below for specific slope
gradients of retained materials utilizing imported select materials.
Surface Slope of Equivalent Fluid Pressure
Retained Materials (PCF)
(H:V) Select Backfill*
Level 35
2:1 50
*Select backfill should consist of imported sand other approved
materials with an SE>30 and an El20 and should be provided
throughout the active zone.
The above equivalent fluid weights do not include other superimposed loading conditions such
as expansive soil, vehicular traffic, structures, seismic conditions or adverse geologic conditions.
5.4.2 Restrained Retaining Walls
Any retaining wall that will be restrained prior to placing backfill or walls that have male or
reentrant corners should be designed for at-rest soil conditions using an equivalent fluid pressure
of 60 pcf (select backfill), plus any applicable surcharge loading. For areas having male or reentrant
corners, the restrained wall design should extend a minimum distance equal to twice the height
of the wall laterally from the corner, or as otherwise determined by the structural engineer.
5.4.3 Wall Backfill and Drainage
Wall backfill should include a minimum one (I) foot wide section of 3/4 to I-inch clean crushed
rock (or approved equivalent). The rock should be placed immediately adjacent to the back of
wall and extend up from the backdrain to within approximately 12 inches of finish grade. The
upper 12 inches should consist of compacted onsite materials. If the walls are designed using the
"select" backfill design parameters, then the "select" materials shall be placed within the active
zone as defined by a 1:1 (H:V) projection from the back of the retaining wall footing up to the
retained surface behind the wall. Presence of other materials might necessitate revision to the
parameters provided and modification of wall designs.
The backfill materials should be placed in lifts no greater than 8-inches in thickness and compacted
to a minimum of 90% of the maximum dry density as determined in accordance with ASTM Test
Method D 1557. Proper surface drainage needs to be provided and maintained. Water should
G EOTEK
RINCoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
not be allowed to pond behind retaining walls. Waterproofing of site walls should be performed
where moisture migration through the wall is undesirable.
Retaining walls should be provided with an adequate pipe and gravel back drain system to reduce
the potential for hydrostatic pressures to develop. A 4-inch diameter perforated collector pipe
(Schedule 40 PVC, or approved equivalent) in a minimum of one (I) cubic foot per lineal foot of
3/8 to one (I) inch clean crushed rock or equivalent, wrapped in filter fabric should be placed
near the bottom of the backfill and be directed (via a solid outlet pipe) to an appropriate disposal
area.
As an alternative to the drain, rock and fabric, a pre-manufactured wall drainage product
(example: Mira Drain 6000 or approved equivalent) may be used behind the retaining wall. The
wall drainage product should extend from the base of the wall to within two (2) feet of the
ground surface. The subdrain should be placed in direct contact with the wall drainage product.
Drain outlets should be maintained over the life of the project and should not be obstructed or
plugged by adjacent improvements.
5.5 POST CONSTRUCTION CONSIDERATIONS
5.5.1 Landscape Maintenance and Planting
Water has been shown to weaken the inherent strength of soil, and slope stability is significantly
reduced by overly wet conditions. Positive surface drainage away from graded slopes should be
maintained and only the amount of irrigation necessary to sustain plant life should be provided
for planted slopes. Controlling surface drainage and runoff and maintaining a suitable vegetation
cover can minimize erosion. Plants selected for landscaping should be lightweight, deep-rooted
types that require little water and are capable of surviving the prevailing climate.
Overwatering should be avoided. The soils should be maintained in a solid to semi-solid state as
defined by the materials Atterberg Limits. Care should be taken when adding soil amendments
to avoid excessive watering. Leaching as a method of soil preparation prior to planting is not
recommended. An abatement program to control ground-burrowing rodents should be
implemented and maintained. This is critical as burrowing rodents can decrease the long-term
performance of slopes.
It is common for planting to be placed adjacent to structures in planter or lawn areas. This will
result in the introduction of water into the ground adjacent to the foundation. This type of
landscaping should be avoided. If used, then extreme care should be exercised with regard to
G EOTEK
RINCoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
the irrigation and drainage in these areas. Waterproofing of the foundation and/or subdrains may
be warranted and advisable. GeoTek could discuss these issues, if desired, when plans are made
available.
5.5.2 Drainage
The need to maintain proper surface drainage and subsurface systems cannot be overly emphasized.
Positive site drainage should be maintained at all times. Drainage should not flow uncontrolled down
any descending slope. Water should be directed away from foundations and not allowed to pond
or seep into the ground adjacent to the footings. Site drainage should conform to Section 1804.4
of the 2019 CBC. Roof gutters and downspouts should discharge onto paved surfaces sloping away
from the structure or into a closed pipe system which outfalls to the street gutter pan or directly
to the storm drain system. Pad drainage should be directed toward approved areas and not be
blocked by other improvements..
5.6 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS
GeoTek recommends that site grading, specifications, retaining wall/shoring plans and foundation
plans be reviewed by this office prior to construction to check for conformance with the
recommendations of this report. Additional recommendations may be necessary based on these
reviews. It is also recommended that GeoTek representatives be present during site grading and
foundation construction to check for proper implementation of the geotechnical
recommendations. The owner/developer should have GeoTek's representative perform at least
the following duties:
Observe site clearing and grubbing operations for proper removal of unsuitable materials.
Observe and test bottom of removals prior to fill placement.
Evaluate the suitability of on-site and import materials for fill placement and collect soil
samples for laboratory testing when necessary.
Observe the fill for uniformity during placement including utility trenches.
Observe and test the fill for field density and relative compaction.
Observe and probe foundation excavations to confirm suitability of bearing materials.
If requested, a construction observation and compaction report can be provided by GeoTek,
which can comply with the requirements of the governmental agencies having jurisdiction over
the project. GeoTek recommends that these agencies be notified prior to commencement of
construction so that necessary grading permits can be obtained.
C EOTEK
RINcoN HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
6. LIMITATIONS
The scope of this evaluation is limited to the area explored that is shown on the Geotechnical
Map (Figure 2). This evaluation does not and should in no way be construed to encompass any
areas beyond the specific area of proposed construction as indicated to us by the client. The
scope is based on GeoTek's understanding of the project and the client's needs, GeoTek's
proposal (Proposal No. P-0800221 -SD) dated September 20, 2021, and geotechnical engineering
standards normally used on similar projects in this region.
The materials observed on the project site appear to be representative of the area; however, soil
and bedrock materials vary in character between excavations and natural outcrops, or conditions
exposed during site construction. Site conditions may vary due to seasonal changes or other
factors. GeoTek, Inc. assumes no responsibility or liability for work, testing or recommendations
performed or provided by others.
Since GeoTek's recommendations are based on the site conditions observed and encountered,
and laboratory testing, GeoTek's conclusions and recommendations are professional opinions
that are limited to the extent of the available data. Observations during construction are
important to allow for any change in recommendations found to be warranted. These opinions
have been derived in accordance with current standards of practice and no warranty is expressed
or implied. Standards of practice are subject to change with time.
G EOTEK
RINCON HOMES Project No. 3738-SD
Updated Geotechnical Evaluation November 2, 2021
Oceanview Project, Carlsbad, California Page B- I
7. SELECTED REFERENCES
American Society of Civil Engineers (ASCE), 2016, "Minimum Design Loads for Buildings and
Other Structures," ASCE/SEI 7-16.
ASTM International (ASTM), "ASTM Volumes 4.08 and 4.09 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 Code of Regulations, Title 24, 2019 "California Building Code," 2 volumes.
California Geological Survey (CGS, formerly referred to as the California Division of Mines and
Geology), 1977, "Geologic Map of California."
1998, "Maps of Known Active Fault Near-Source Zones in California and Adjacent
Portions of Nevada," International Conference of Building Officials.
Christion Wheeler Engineering (CWE), 2018, Updated geotechnical investigation report,
Carlsbad Tract 02-06, Twain Avenue, Carlsbad, California, Project Number CWE
2180124.01, dated February 16, 2018.
GeoTek, Inc., In-house proprietary information.
_____ 2021, Hydrologic Classification, Proposed Oceanview Project, Twain Avenue, Carlsbad,
California, PN 3738-SD, dated October 26, 2021.
Structural Engineers Association of California/California Office of Statewide Health Planning and
Development (SEOC/OSHPD), 2019, Seismic Design Maps web interface,
https://seismicmaps.org
Terzaghi, K. and Peck, R., 1967, "Soil Mechanics in Engineering Practice", second edition.
C EOTEK
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Carlsbad
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Approximate Site
Location
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1384 Poinsettia Avenue, Suite A
Vista, California 92081
CIO
Not toScale
Imagery from US Forestry Service, 2021
Rincon Homes
Ocean View
Carlsbad, California
PN: 3738-SD I DATE: November 2021
Figure I
Site Location Map
Tsa
Tsa
Figure 2 ,G:~
G EOTE K
Geotechnical Map 1384 Poinsettia Avenue, Suite A
Vista, California 92081
LEGEND
HA-6
Approximate Location of Hand Auger Boring This Study
T-9
- - - - ______ Approximate Location and Orientation of
Tsa Test Pit, CME. 2018
— — Approximate Limits of Study \ Approximate Limits of Geological Contact
r Qop Quaternary Old Paralic Deposits
( irfl.A'4
Tsa Tertiary Santiago Formation, Circled where Buried
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PLAN VIEW - GRADING PLAN
Rinron Homes
Ocean View
Carlsbad, California
PN: 3738-SD I DATE November 20? 1
APPENDIX A
EXPLORATORY BORING LOGS
(GeoTek, Inc.)
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Page A- I
A - FIELD TESTING AND SAMPLING PROCEDURES
Bulk Samples (Large)
These samples are normally large bags of earth materials over 20 pounds in weight collected from the
field by means of hand digging or exploratory cuttings.
Bulk Samples (Small)
These are plastic bag samples which are normally airtight and contain less than 5 pounds in weight of
earth materials collected from the field by means of hand digging or exploratory cuttings. These samples
are primarily used for determining natural moisture content and classification indices.
B - EXPLORATORY LOG LEGEND
The following abbreviations and symbols often appear in the classification and description of soil and rock
on the logs of borings:
SOILS
USCS Unified Soil Classification System
f-c Fine to coarse
f-m Fine to medium
GEOLOGIC
Attitudes Bedding: strike/dip
J: Attitudes Joint: strike/dip
Contact line
Dashed line denotes USCS material change
Solid Line denotes unit I formational change
Thick solid line denotes end of the boring
(Additional denotations and symbols are provided on the log of Explorations)
'G.,
C EOTEK
GeoTek, Inc.
LOG OF EXPLORATORY BORING
CLIENT: Rincon DRILLER: GeoTek LOGGED BY: MSB
PROJECT NAME Oceanview DRILL METHOD: Boring OPERATOR: MSB
PROJECT NO.: 3738-SD HAMMER: - RIG TYPE: Manual Auger
LOCATION: Carlsbad, CA ELEVATION: -_- -- DATE: 9/28/2021
SAMPLES Laboratory Testing -
S BORING NO.: HA-I 0-
0- 8 0 E 0.0 aj S 7E
0- E 2 (0 coz (1) ____________________________ 5 0 0
MATERIAL DESCRIPTION AND COMMENTS
- Weathered Old Paralic Deposits (Qop)
SM Silty SAND, light brown, damp, loose
Practical refusal of auger - -
- 2.5• HOLE TERMINATED AT 18 INCHES
No groundwater encountered
- Backfilled with soil cuttings
5-
7.5-
10-
12.5-
15—
z Sample type: E--Ring ---SPT Z---Small Bulk ---Large Bulk ---No Recovery ---Water Table
C,' AL = Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test Lab testirg. SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
GeoTek, Inc.
LOG OF EXPLORATORY BORING
CLIENT: Rincon DRILLER: GeoTek LOGGED BY: MSB
PROJECT NAME: Oceanvew DRILL METHOD: Boring OPERATOR:MSB
PROJECT NO.: 3738-SD HAMMER: - RIG TYPE: Manual Auger
LOCATION: Carlsbad, CA ELEVATION: - DATE: 9/28/2021
SAMPLES Laboratory Testing - aI E > BORING NO.: HA-2
S ES ta 0 a'
2 M
oz (1)
0 0
MATERIAL DESCRIPTION AND COMMENTS
- Weathered Old Paralic Deposits (Qop)
SM Silty SAND, light brown, damp, loose
Practical refusal of auger - -
HOLE TERMINATED AT 15 INCHES - 2.5-
= No groundwater encountered
- Backfilled with soil cuttings
5-
7.5-
10-
12.5-
15-
I Sample type: [---Ring ---SPT Z---Small Bulk ---Large Bulk ---No Recovery - --Water Table wi
AL = Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test Lab testing: SR = Sulfate/Resisitivity Test SN = Shear Test CO -= Consolidation test MD = Maximum Density
GeoTek, Inc.
LOG OF EXPLORATORY BORING
CLIENT: Rincon DRILLER: GeoTek LOGGED BY: MSB
PROJECT NAME: Oceanview DRILL METHOD: Bong OPERATOR: MSB
PROJECT NO.: 3738-SD HAMMER: - RIG TYPE: Manual Auger
LOCATION: Carlsbad, CA ELEVATION: - DATE: 9/28/2021
SAMPLES . Laboratory Testing -
>I (0 .t?i E > BORING NO.: HA-3
I EE U'
(UI
2 COz U)
0 MATERIAL DESCRIPTION AND COMMENTS
- Weathered Santiago Formation (Tsa)
SM Clayey SAND, dark brown, damp, firm
Practical refusal of auger - -
- 2.5• HOLE TERMINATED AT 18 INCHES
- No groundwater encountered
Backfilled with soil cuttings
5-
7.5-
10-
12.5-
15-
z
Sample type: ---Ring ---SPT Z---Small Bulk ---Large Bulk ---No Recovery 50 --Water Table
AL = Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test Lab testing. SR = Sulfate/Resistivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
GeoTek, Inc.
LOG OF EXPLORATORY BORING
CLIENT:
PROJECT NAME:
PROJECT NO.:
LOCATION:
Rincon
Oceanview
3738-SD
Carlsbad, CA
DRILLER: GeoTek LOGGED BY:
DRILL METHOD: Boring OPERATOR:
HAMMER: - RIG TYPE:
ELEVATION: - DATE:
MSB
MSB
Manual Auger
9/28/2021
SAMPLES Laboratory Testing -
CO .SW CL M g
(I) BORING NO.: HA-4 5
°
I-i
a l
EE CV =
Co 0 Co
(SI °
2 Co coz (1)
0 MATERIAL DESCRIPTION AND COMMENTS
- Weathered Old Paralic Deposits (Clop)
SM Silty SAND, light brown, damp, loose
Practical refusal of auger
- -
- 2.5• HOLE TERMINATED AT 18 INCHES
- No groundwater encountered
Backfilled with soil cuttings
5-
7.5-
10-
12.5-
15—
z
Sample type: ---Ring ---SPT Z---Small Bulk ---Large Bulk --No Recovey - ---Water Table
Lab testing: AL = Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
GeoTek, Inc.
LOG OF EXPLORATORY BORING
CLIENT: Rincon DRILLER: GeoTek LOGGED BY: MSB
PROJECT NAME: Oceanview DRILL METHOD: Boring OPERATOR: MSB
PROJECT NO.: 3738-SD HAMMER: - RIG TYPE: Manual Auger
LOCATION: Carlsbad, CA ELEVATION: - DATE: 9128/2021
SAMPLES Laboratory Testing -
>I (0 a) .! E BORING NO.: HA-5 5 FTh
S EE cc U , a
E2 Fn coz co D ______________________________ 0 MATERIAL DESCRIPTION AND COMMENTS
- Weathered Old Paralic Deposits (Qop)
SM Silty SAND, light brown, damp, loose
Practical refusal of auger -
- 2.5. HOLE TERMINATED AT 19 INCHES
- No groundwater encountered
Backirlied with soil cuttings
5-
7.5-
10-
12.5-
15—
z Sample type: El --Ring --SPT Z--Small Bulk _NJ---Large Bulk El ---No Recovery - —Water Table
0I
Lab testing: AL" Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
CLIENT:
PROJECT NAME
PROJECT NO.:
LOCATION:
Rincon
Oceanview
3738-SD
Carlsbad" CA
DRILLER: GeoTek LOGGED BY:
DRILL METHOD: Boring OPERATOR:
HAMMER: - RIG TYPE:
ELEVATION: - DATE:
MSB
MSB
Manual Auger
9/28/2021
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SAMPLES Laboratory Testing
-I E E
(0 BORING NO.: HA-6
S EE cv = 0
5)
E
5, 2 5) oz (I)
0 0
0
MATERIAL DESCRIPTION AND COMMENTS
- Weathered Old Paralic Deposits (Qop)
= SM Silty SAND, light brown, damp, loose
Practical refusal of auger
- -
- 2.5• HOLE TERMINATED AT 18 INCHES
No groundwater encountered
- Backfilled with soil cuttings
5-
7.5-
10-
12.5-
15-
z Sample type: El --Ring _-SPT Z---Small Bulk s--Large Bulk El --No Recovery - —Water Table
I I AL = Atterberg Limits El = Expansion Index SA = Sieve Analysis RV = R-Value Test Lab SR = Sulfate/Resisitivity Test SN = Shear Test CO = Consolidation test MD = Maximum Density
APPENDIX B
EXPLORATORY BORING LOGS
(CWE, 2018)
G EOTEK
LOG OF TEST TRENCH NUMBER T-1
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 313 feet Depth to Water: N/A
Proposed Elevation: 328 feet Bucket Size: 24 inches
- -
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS
OH
(Ti
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
grained.
- - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
L 2 / dense, fine- to medium-grained.
- - -
- Terrace Deposits (Qt): Orangish-brown, CLAYEY SAND (SC), moist,
- 3 dense, fine- to coarse-grained. CK 7.3 111.1
SA
- 4
El
MD
-5 .,
DS
-6",.
CK 6.4 115.5
-7
-
- 9 Terminated at 8 feet.
- 10 -
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHR-ISTIAN WHEELER BY: SCC DATE: February 27, 2001
E N C I N L E R I N C JOB NO.: 201.116 1PLATE NO.: 2
LOG OF TEST TRENCH NUMBER T-2
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 325 feet Depth to Water: N/A
Proposed Elevation: 328 feet Bucket Size: 24 inches
- -
SAMI'LES
SUMMARY OF SUBSURFACE CONDITIONS H
Z OH z
&)
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained.
- - - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 2 dense, fine- to medium-grained.
- 3 Santiago Formation (Tsa): Light brown, CLAYEY SAND (SC), moist,
dense, fine- to medium-grained. CK 7.6 116.5
ri Light brown to olive brown, SANDY CLAY (CL), moist, very hard.
CK 19.1 101.1 SA
-6!
- 7
..................................................................................................................................................................
Terminated at 6 feet.
-8
-9
10
PROPOSED 5-LOT RESIDENTIAL PROJECT
IN West of Faraday Road, Carlsbad, California
CHR1S11AN WHEELER, BY: SCC DATE: February 27, 2001
E N C.1 N E E ft I N C
_JOB NO.: 201.116 IPLATE NO.: 3
LOG OF TEST TRENCH NUMBER T-3
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 317 feet Depth to Water: N/A
Proposed Elevation: 314 feet Bucket Size: 24 inches
- -
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS F
zo
. 0 Pq
U)
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained.
- - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 2 dense, fine- to medium-grained.
- 3 ..• Terrace Deposits Qt): Orangish-brown, CLAYEY SAND (SC), moist,
dense to very dense, fine- to coarse-grained with occasional 3 inch cobble.
4••• CK
-5••
- 6 Santiago Formation (Tsa): Light brown to white, SILTY SAND (SM),
moist, dense to very dense, fine- to medium-grained.
- 7
CK 11.0 111.9
-8
-9
1 1 .10-
Terminated at 10 feet.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHPJS11AN WHEELER BY: SCC DATE: February 27, 2001
E N G I N E E K I N G OBNO.: 201.116 1 PLATE NO.: 4
LOG OF TEST TRENCH NUMBER T-4
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 317 feet Depth to Water: N/A
Proposed Elevation: 314 feet Bucket Size: 24 inches
- -
SAMPLES
4
SUMMARY OF SUBSURFACE CONDITIONS
PQ
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained.
- - - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 2 dense, fine- to medium-grained.
- 3 ../ Terrace Deposits Qt): Orangish-brown, CLAYEY SAND/SILTY SAND
(SC/SM), moist, dense to very dense, occasional gravel and cobble.
-4 .....,
1
CK
- 6 Xil
-7 --
- 8 Terminated at 7 feet.
-9
L 10
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRISTIAN WHEELER BY: SCC DATE: February 27, 2001
1: N G I N I: I: ft I N C JOB NO.: 201.116 IPLATE NO.: 5
LOG OF TEST TRENCH NUMBER T-5
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 290 feet Depth to Water: N/A
Proposed Elevation: 306 feet Bucket Size: 24 inches
- -
SAM1LES
Z (J
SUMMARY OF SUBSURFACE CONDITIONS H
z z
Cl)
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained.
- - - -
Slopewash (Osw: Dark brown, SANDY CLAY (CL), wet, soft,
- 2 slight amount of gravel and cobble.
- 3 .." Santiago Formation (Tsa): Light brown to light orangish-brown,
CLAYEY SAND (SC), moist, medium dense to dense. CK
- 4
- 5 Becomes very dense.
CK 11.2 114.3 -6
- 7
-8 •.
-9 ,..,..
L 10
Trench log continued on Plate 7.
lop& it
CHPJS11AN WHEELER BY:
E N G I N E E P. I N C JOB NO.:
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
SCC DATE:
201.116 PLATE NO.:
27.2001
LOG OF TEST TRENCH NUMBER T-5 (Continued)
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 290 feet Depth to Water: N/A
Proposed Elevation: 306 feet Bucket Size: 24 inches
-
SAMPLES
U 75
SUMMARY OF SUBSURFACE CONDITIONS H Cn
/ Santiago Formation (Tsa): Light brown to light orangish-brown,
- 11 CLAYEY SAND (SC), moist, very dense.
- 12
- 13
- 14
-15— CK
-- --
15.5 113.2
--
- 16 Terminated at 15 feet.
- 17
- 18
- 19
- 20
PROPOSED 5-LOT RESIDENTIAL PROJECT
AN West of Faraday Road, Carlsbad, California
CHPJS11AN WHEELER BY: SCC DATE: February 27, 2001
!:NGINEEftNG )OBNO.: 201.116 PLATE NO.: 7
LOG OF TEST TRENCH NUMBER T-6
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 313 feet Depth to Water: N/A
Proposed Elevation: 300/306 feet Bucket Size: 24 inches
- -
SAMPLES
zi
SUMMARY OF SUBSURFACE CONDITIONS H
. -
Cl)
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
grained.
- - - - -
Slopewash (Qsw): Dark brown, SANDY CLAY (CL), wet, soft,
- 2 slight amount of gravel and cobble.
- 3 Santiago Formation (Tsa): Light brown to light orangish-brown,
SANDY CLAY (CL), moist, very stiff. SA
El
-4
Becomes hard. NO
DS
-5
-6
-7/ /
-8
CK 15.4 110.4
-9
.10 - - - -
Trench log continued on Plate 9.
PROPOSED 5-LOT RESIDENTIAL PROJECT
of California West Faraday Road, Carlsbad,
BY: SCC DATE: February 27, 2001 CHRiSliAN WHEELER.
E N C I N E E ft I N C JOB NO.: 201.116 IPLATE NO.: 8
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
BY: SCC
JOB NO.: 201.116
IN
CHPJS11AN WHEELEK
E N C I N S S ft I N C
TE: February 27, 2001
TE NO.:
LOG OF TEST TRENCH NUMBER T-6 (Continued)
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 313 feet Depth to Water: N/A
Proposed Elevation: 300/306 feet Bucket Size: 24 inches
- -
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS F
., v O
Santiago Formation (Tsa): Light brown to light orangish-brown,
- 11 SANDY CLAY (CL), moist, hard.
- 12
-13
14 ______________________________________________________________________________________ CK 1 1 18.0 108.6
- 15 Terminated at 14 feet.
-16
- 17
- 18
- 19
20
LOG OF TEST TRENCH NUMBER T-7
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 275 feet Depth to Water: N/A
Proposed Elevation: 315 feet Bucket Size: 24 inches
-
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS H
Topsoil: Dark brown, SILTY SAND/CLAYEY SAND (SM/SC), moist,
1, I loose, fine- to medium-grained.
4 Slopewash (Osw: Dark brown, SANDY CLAY (CL), wet, soft
- 2 -I, to medium sflff, slight amount of gravel and cobble.
Santiago Formation (Tsa): Light olive brown to light orangish-brown,
- 4 CLAYEY SAND (SC), moist, dense to very dense, fine- to medium-grained. CK 16.3 109.3
-5 ..
- 6
-7
CK 16.8 110.0 -8 •.
9•
- 10 -
Practical refusal at 9 feet.
Pr
PROPOSED 5-LOT RESIDENTIAL PROJECT
led West of Faraday Road, Carlsbad, California
CHRISTIAN WHEELER, BY: SCC DATE: February 27, 2001
E N G I N E E ft I N G
,JOB NO.: 201.116 IPLATE NO.: 10
LOG OF TEST TRENCH NUMBER T-8
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 314 feet Depth to Water: N/A
Proposed Elevation: 315 feet Bucket Size: 24 inches
- -
SAMPLES
SUMMARY
CIO
OF SUBSURFACE CONDITIONS H
z Z OH
-
C,)
'-.
Topsoil: Dark bron, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained.
- - - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 2 dense, fine- to medium-grained.
- 3 .." Terrace Deposits (Ot): Orangish-brown, CLAYEY SAND (SC), moist,
dense to very dense, fine- to coarse-grained, occasional 2½ inch gravel.
- 4 / CK 6.0 113.0
-5',:
-6',.
CK
- ----
- 8 Terminated at 7 feet.
-9
.10 - ---- ___ -
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRISTIAN WHEELER BY: SCC DATE: February 27, 2001
E 1' C I N E E ft I N C JOBNO.: 201.116 IPLATE NO.: 11
LOG OF TEST TRENCH NUMBER T-9
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 314 feet Depth to Water: N/A
Proposed Elevation: -- Bucket Size: 24 inches
- -
SAMPLES
4
SUMMARY OF SUBSURFACE CONDITIONS
z Z OH
Cl) -'
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 1 dense, fine- to medium-grained.
- 2 .
Terrace Deposits (Qt): Orangish-brown, CLAYEY SAND (SC), moist,
-
very dense, fine- to coarse-grained, abundant gravel and cobble. CK 5.7 122.8
-3 .
- 4 / Santiago Formation (Tsa): Light olive brown, CLAYEY SAND (SC),
moist, dense to very dense, fine- to medium-grained.
CK 15.8 111.0
-6
7
CK
9•.
L CK 10
Terminated at 10 feet.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West Faraday Road, of Carlsbad, California
BY: SCC DATE: February 27, 2001 CHRISTIAN WHEELER
E ' G I N E F R I N G JOB NO.: 201.116 PLATE NO.: 12
APPENDIX C
RESULTS OF LABORATORY TESTING
(CWE, 2018)
G EOTEK
LABORATORY TEST RESULTS
PROPOSED FIVE-LOT RESIDENTIAL PROJECT
WEST OF FARADAY ROAD
POWAY, CALIFORNIA
MAXIMUM DENSITY! OPTIMUM MOISTURE CONTENT
Sample Number Trench T-1 @ 2'-8' Trench T-6 @ 3'-12'
Description Orangish-brown, clayey sand (SC) Brown, sandy clay (CL)
Maximum Density 127.1 pcf 106.0 pcf
Optimum Moisture Content 8.5 percent 18.5 pcf
DIRECT SHEAR TEST
Sample Number
Description
Angle of Internal Friction
Apparent Cohesion
Trench T-1 @ 2'-8'
Remolded To 90 Percent
33 degrees
100 psf
Trench T-6 @ 3'-12'
Remolded to 90 Percent
21 degrees
300 psf
GRAIN SIZE DISTRIBUTION
Sample Number T-1 @ 2'-8' T-2 @ 4'-6' T-6 @ 3'-12'
Sieve Size Percent Passing Percent Passing Percent Passing
#4 100
#8 93 100 100
#15 78 99 699
#30 59 98 98
#50 37 97 96
#100 22 87 84
#200 19 70 69
0.05 mm 18 60 55
0.005 mm 11 27 21
0.001 min 8 18 7
Classification SC CL CL
EXPANSION INDEX TESTS
Sample Number:
Initial Moisture:
Initial Dry Density:
Final Moisture:
Expansion Index:
Trench T-8 @ 2'-8'
8.0 percent
108.3 pcf
17.7 percent
6 (very low)
Trench T-6 @ 3'-12'
13.7 percent
101.4 pcf
29.5 percent
85 (medium)
CWE 201116.1 March 14, 2001 Plate No. 13
APPENDIX D
HYDROLOGICAL CALSSIFICATION
G EOTEK
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Office (760) 599-0593 Fax www.geotekusa.com
October 26, 2021
Project No. 3738-SD
Rincon Homes
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
Attention: Mr. Cameron St. Clair
Subject: Hydrologic Classification
Proposed Oceanview Project
Twain Avenue
Carlsbad, California
Dear Mr. St. Clair:
This letter offers an opinion of the hydrological classification for the subject project based
on data from a site study performed by GeoTek, Inc. (GeoTek).
Project Site Description
The property is located south of the southern Cul-De-Sac of Twain Avenue, in the City of
Carlsbad, California. The property is currently unimproved land and consists of an irregularly
shaped parcel that comprises approximately I 6.5 acres. However, of that area, approximately 5
acres is proposed to be improved and referenced herein as the "site." A site location map is
presented as Figure I.
Proposed Improvements
Proposed improvements include a subdivision of thirteen (13), single-family, wood framed
structures and the extension of Twain Avenue. The Preliminary Grading Plan, by Pasco, Laret,
Suiter & Assoc, (PLSA), 2021, indicates site grades will be lowered approximately 20 feet in the
north portion of the site and raised in the southern portion of the site and around the periphery
of the proposed building pads. Associated improvements are anticipated consist of a stormwater
management system to include a collection basin, utilities, asphalt concrete and Portland cement
concrete flatwork for the building pads and extension of Twain Avenue.
GEOTECHNICAL I ENVIRONMENTAL I MATERIALS
Rincon Homes Project No. 3738-SD
Hydroogic Classification October 26, 2021
Twain Avenue, Carlsbad, CA Page 2
Summary of Mapped Soil Conditions
The United States Department of Agriculture, Natural Resource Conservation Service, Web Soil
Survey (WSS), an internet based map service, classifies the majority of the site (approximately
90% based on area) as MIC Marina loamy coarse sand, 2-9% slopes. A minor portion of the site
(approximately 10% by area) is classified as LvF3 loamy alluvial land-Huerhuero complex, 9-50%
slopes. Both interpretative units (MlC and LvF3) have been classified as a hydrological Group B.
Figure 2 presents a summary output of the WSS plot based on the proposed area of disturbance
(outlined by a red line) of the proposed project and the mapped soil units.
The WSS classifies map units based on topography, weather, typical soil section in the upper 40
inches, hydrological properties (slope gradient, drainage class, infiltration rates, runoff potential,
flood potential) and interpretative groups (land capability classification, hydrologic soil group,
hydric soil rating).
The WSS uses the National Soil Survey Handbook (NSSH) and its eDirectives to provide national
continuity of soil classifications related to the agricultural industry. Classification is based on
laboratory testing of field samples, direct testing in the field, and interpretations from aerial and
satellite photography. Samplings and laboratory analyses are performed on select sites and
extrapolated beyond the sampled locations.
The NSSH states that "increased mapping has been performed by remote spatial interpretations
in lieu of updating surveys based on new or supplemental laboratory data."
The WSS provides the location of data points on their interpretive maps. Data sets are
predominately concentrated in agricultural areas and are sparsely available in urban and suburban
areas (if at all). A review of the WSS data set was performed. The closest data sample identified
is located at the approximate location of El Mirlo Drive, Oceanside, California. That data point
is approximately 8 miles north of the subject site, in a different geologic unit (Kt-
Tonalite/granitics) and presumably obtained prior to the existing development of the residential
tract homes at the stated location. The survey methodology on the WSS for the site is noted to
be based on aerial photography dated January 24 to February 12, 2020.
Site Specific C3eotechnical Report
A Preliminary Geotechnical Investigation of the site was performed by Christian Wheeler
Engineering (CWE, 2016). CWE's investigation included the excavation and logging of nine (9)
exploratory test pits excavated with a backhoe that ranged in depth between six and fifteen feet
below the existing ground surface. In general, CWE stated the upper 12 inches of the surface
G EOTEK
Rincon Homes Project No. 3738-SD
Hydrologic Classification October 26, 2021
Twain Avenue, Carlsbad, CA Page 3
consisted of a silty sand (SM soil typed based upon the Unified Soil Classification System) overlying
a subsoil from 12 to 24 inches consisting of a clayey sand (SC soil type). Localized slope wash
material was present that consisted of clay soil (CL soil type), however, since the unit is localized,
this material has been excluded from consideration. The materials below the topsoil, subsoil, and
slope wash are sedimentary bedrock consisting of gravelly clayey sandstones of Old Paralic
deposits overlying clayey sandstones and claystones of the Santiago formation.
Clays and silts, as well as, cementitious properties of bedrock significantly impact infiltration
qualities. A site specific infiltration was not performed by CWE.
Geotek performed a site visit to evaluate the current site conditions and compare the conditions
of those presented by CWE. This site visit was performed on September 28, 2021 and included
traversing the site improvement area and recording surficial observations. Outcroppings of Old
Paralic deposits were observed in the northern portion of the site and weathered claystone of
the Santiago formation was observed in the southern (lower topographic elevations) portion of
the site.
Six (6) exploratory manual augers were performed to evaluate the thickness of soil profiles
presented by CWE. The approximate locations are presented on Figure 2. The manual augers
were chosen, as the tool is operated directly by manual labor (not powered by a motor which
would provide a force multiplier). The intent was to review the soil profile thickness, as the
manual augur does not have the ability to readily advance into bedrock.
The results of the supplemental borings indicated the soil profile ranged in thickness between
fifteen and nineteen inches below the ground surface. A copy of the exploratory logs are
presented in the rear of this letter.
Discussion of WSS Interpretive Groups and The Site Specific Findings
The WSS has classified the site improvement area as a hydrological Group B. It should be noted
that the soil classification in the WSS are based on taxonomy principally for agricultural purposes.
Classification of soils presented on the logs utilize the Unified Soil Classification Standard, as per
industry standards. GeoTek's findings result in inconsistencies between the site and information
provided on the WSS. These inconsistencies include:
The WSS classifies the site as a hydrological Group B, which is defined by eDirective 630, Chapter
7 as:
'r~
G EOTEK
Rincon Homes Project No. 3738-SD
Hydrologic Classification October 26, 2021
Twain Avenue, Carlsbad, CA Page 4
Group B—Soils in this group have moderately low runoff potential when thoroughly wet.
Group B soils typically have less than 10 to 20 percent clay and 50 to 90 percent sand.
The limits on the diagnostic physical characteristics of group B are as follows.....Soils that
are deeper than 40 inches to a water impermeable layer and a water table are in group B
if the saturated hydraulic conductivity of all soil layers within 40 inches of the surface is
between 0.57 and 1.42 inches per hour.
Based on GeoTek's site specific study, the site has less than 20 inches of soil development, not
20 to 40 inches.
Group D—Soils in this group have a high runoff potential when thoroughly wet. Group
D soils typically have greater than 40 percent clay and less than 50 percent sand. All soils
with a depth to a water impermeable layer less than 20 inches and all soils with a water
table within 24 inches of the surface are in this group....
An impermeable layer is identified as having a component restriction of. . . .densic material;
bedrock, paralithic; bedrock, lithic; bedrock, densic... [lithic is defining sedimentary
bedrock]
The WSS National Engineering Handbook provides a table summarizing the criteria for
assignment of hydrological soil groups in Table 7-I. This table has been presented herein and
highlights the criteria that identifies the site, specific to our findings (noted in yellow high lighter):
"C~
C EOTEK
Rincon Homes Project No. 3738-SD
Hydra ogic Classification October 26, 2021
Twain Avenue, Carlsbad, CA Page 5
Table 7-I (NEH, 2009)
Depth to water Depth to high JL of lean trans1s&ve X depth HSG iv
tmeieei&yer water table F 1*yà in depth muge ruge
<50 en) - - (<20 in)
400 pnVs 0 to 60 cm
(>5.67 In/h) 10 to 24 In)
>10.0to40.0iim/s 0to60cm
<60 CM (>1.42L0-<-5.6711't/h) 10 tO 24 in]
>L0to5.10A)pniis 0to60cm UD .c24in]
(>0.14 to L'-1,42 In/h) [01024 in]
f1.0llrn/s Oto 60 cm D 50to100cm (50,141n/h) [0to24in]
[20 to 40 ml >400 SUB/S 0 to. 60 cm A (>5.67 in/h) 10 to 20 in)
>10.0 to 4(U) pnVs 0 to 50 cm
~60 CM (>1.42 to :!~5.67 ia/h) 10 to 20 inj
>1.0 to 10.O I1uVs - 0 to 50 em 14 m]
(>0.14 to :5142 ia/h) 10 to 20 in)
1.0 Irn/s 0 to 50 cm
(A.14 in/h) 10to20in]
>10.0 lrn/s 0 to 100 cm
(>L42in/h) loto4oini
>4.0 to !~10,0 I.inVs 0 to 100 cm WD <60 cm (>0.57 to :!1,42 in/h) 10 to 40 in]
[<24 In] >0.40 to 54.0 1nn/s 0 to 100 cm
(>0.06 to 0.57 in/h) 10 to 40 in]
<0.40 3.Int/s (Ito 100 cm
>100 cm (~0.06 in/h) 10 to 40 in]
>400jimi/s 0to50vni A 1>40 in
(>5.67 in/h) 10to20inl
>10.0 to 40.() tmi/s 0 to
60 ell, B 60 to 100 ciii (>1,42 to -<5A37d in/h) 10 to 20 in]
1241040 ] >LO to :S 10.0 pni/s C) to i0 cm
(>0.l4to51.42h.vh) 1010201nJ
1.0jim/s 0to50cm
(0. .14 In/h) 10 to 20 In]
>10.0nn/s 0 t 100 cm
(>L42 in/h) 10 to 40 in]
A
>4.0 to !~ 10.0 pm/s 0 to 1(10 cm B
> (>0.57 to ::51.42 in/h) [0 to 40 in]
>(k40 to 0.0 trnfs (Ito 100 cm [>40 in]
(>0.06 to -<0.57 in/h) 10 to 40 in]
0.40 pn/s C) to 100 cm D (nA06 in/h) 10 to 40 in! if An lmpemwable leSS Lhan 0.01 im1s 10.0014 infli] or a comp ntrstict1on of fragipin;
dwipm I rocalcic orstin4 pefro&vT)siq cemented horizon; deiisic miei1ai; piack bedrock, pamlithic;
bedrock, 11thk bedrock, densic: or VtTunafmi.
2/ High water titik during any month during the year.
3/ riud H cJase are applied only for wet soiEs (water table less than 00 cm 124 ml), If these soils can be
dmhed, a leas rtrkt1ve HSG can be assigned, deeriding on Lite iç1.
G EOTEK
Rincon Homes Project No. 3738-SD
Hydrologic Classification October 26, 2021
Twain Avenue, Carlsbad, CA Page 6
Conclusions
The WSS survey was based on a photographic interpretation. GeoTek's evaluation consisted of
performing six manual auger borings to physically assess the soil profile throughout the site. The
test borings reached practical refusal on bedrock between a depth of fifteen and nineteen inches.
Thus, based on the WSS NEH Table 7-I, the site should be classified as a hydrologic soil Group
D.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to contact GeoTek.
Respectfully submitted,
GeoTek, Inc.
0/
Christopher D. Livesey
CEG 2733, Exp. 05/31/23
Attachments: Figure I - Site Location Map
Figure 2 - Geotechnical map
Typical Boring Log Legend
Logs of Exploratory Borings
Distribution: (I) Addressee
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G LOT E K
Rincon Homes Project No. 3738-SD
Hydrologic Classification October 26, 2021
Twain Avenue, Carlsbad. CA
.
Page 7
SELECTED REFERENCES
Christian Wheeler Engineering (CWE), 2018Updated Geotechnical Investigation Report, Project
number CWE 2180124.0 1, dated February 16, 2018.
Pasco, Laret, Suiter & Assoc, (PLSA), 2021, Grading Plan for Twain Homes, Twain Avenue,
received September 21, 2021.
Soil Web Survey.com
U.S. Department of Agriculture, Natural Resources Conservation Service, National Soil Survey
Handbook, Title 210, Part 630, Chapter 7, Hydrologic Soil Groups.
G EOTEK
Carlsbad "
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\ \\ I• I Approximate Site
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Imagery from US Forestry Service, 2021
- Crud
Rincon Homes Figure I 2090 Twain Avenue g
Carlsbad, California Site Location Map G E 0 T E K
____ 1384 Poinsettia Avenue, Suite A
PN: 3738-SD DATE: October 2021 Vista, California 92081
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Approximate Location of Hand Rincon Homes
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- Approximate Limits of Study Carlsbad, California
Plan adapted from "Web Soil Survey" by Natural ________________________
Resources Conservation Service PN: 3738-SD DATE: October 2021
Figure 2
G EOT E K
Geotechnical Map 1384 Poinsettia Avenue, Suite A
Vista, California 92081
APPENDIX E
GENERAL EARTHWORK GRADING GUIDELINES
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G EOTEK
GENERAL GRADING GUIDELINES APPENDIX E
GENERAL GRADING GUIDELINES
Guidelines presented herein are intended to address general construction procedures for earthwork
construction. Specific situations and conditions often arise which cannot reasonably be discussed in
general guidelines, when anticipated these are discussed in the text of the report. Often
unanticipated conditions are encountered which may necessitate modification or changes to these
guidelines. It is our hope that these will assist the contractor to more efficiently complete the
project by providing a reasonable understanding of the procedures that would be expected during
earthwork and the testing and observation used to evaluate those procedures.
General
Grading should be performed to at least the minimum requirements of governing agencies, the
California Building Code, CBC (2019) and the guidelines presented below.
Preconstruction Meeting
A preconstruction meeting should be held prior to site earthwork. Any questions the contractor has
regarding our recommendations, general site conditions, apparent discrepancies between reported
and actual conditions and/or differences in procedures the contractor intends to use should be
brought up at that meeting. The contractor (including the main onsite representative) should review
our report and these guidelines in advance of the meeting. Any comments the contractor may have
regarding these guidelines should be brought up at that meeting.
Grading Observation and Testing
Observation of the fill placement should be provided by our representative during grading.
Verbal communication during the course of each day will be used to inform the contractor of
test results. The contractor should receive a copy of the "Daily Field Report" indicating
results of field density tests that day. If our representative does not provide the contractor
with these reports, our office should be notified.
Testing and observation procedures are, by their nature, specific to the work or area
observed and location of the tests taken, variability may occur in other locations. The
contractor is responsible for the uniformity of the grading operations; our observations and
test results are intended to evaluate the contractor's overall level of efforts during grading.
The contractor's personnel are the only individuals participating in all aspect of site work.
Compaction testing and observation should not be considered as relieving the contractor's
responsibility to properly compact the fill.
Cleanouts, processed ground to receive fill, key excavations, and subdrains should be
observed by our representative prior to placing any fill. It will be the contractor's
responsibility to notify our representative or office when such areas are ready for
observation.
Density tests may be made on the surface material to receive fill, as considered warranted by
this firm.
In general, density tests would be made at maximum intervals of two feet of fill height or
every 1,000 cubic yards of fill placed. Criteria will vary depending on soil conditions and size
of the fill. More frequent testing may be performed. In any case, an adequate number of
field density tests should be made to evaluate the required compaction and moisture content
is generally being obtained.
G EOTE K
GENERAL GRADING GUIDELINES APPENDIX E
6. Laboratory testing to support field test procedures will be performed, as considered
warranted, based on conditions encountered (e.g. change of material sources, types, etc.)
Every effort will be made to process samples in the laboratory as quickly as possible and in
progress construction projects are our first priority. However, laboratory workloads may
cause in delays and some soils may require a minimum of 48 to 72 hours to complete
test procedures. Whenever possible, our representative(s) should be informed in advance
of operational changes that might result in different source areas for materials.
7. Procedures for testing of fill slopes are as follows:
Density tests should be taken periodically during grading on the flat surface of the fill,
three to five feet horizontally from the face of the slope.
If a method other than over building and cutting back to the compacted core is to be
employed, slope compaction testing during construction should include testing the
outer six inches to three feet in the slope face to determine if the required
compaction is being achieved.
8. Finish grade testing of slopes and pad surfaces should be performed after construction is
complete.
Site Clearing
All vegetation, and other deleterious materials, should be removed from the site. If material
is not immediately removed from the site it should be stockpiled in a designated area(s) well
outside of all current work areas and delineated with flagging or other means. Site clearing
should be performed in advance of any grading in a specific area.
Efforts should be made by the contractor to remove all organic or other deleterious material
from the fill, as even the most diligent efforts may result in the incorporation of some
materials. This is especially important when grading is occurring near the natural grade. All
equipment operators should be aware of these efforts. Laborers may be required as root
pickers.
Nonorganic debris or concrete may be placed in deeper fill areas provided the procedures
used are observed and found acceptable by our representative. Typical procedures are
similar to those indicated on Plate G-4.
Treatment of Existing Ground
Following site clearing, all surficial deposits of alluvium and colluvium as well as weathered or
creep effected bedrock, should be removed (see Plates G-1, G-2 and G-3) unless otherwise
specifically indicated in the text of this report.
In some cases, removal may be recommended to a specified depth (e.g. flat sites where
partial alluvial removals may be sufficient). The contractor should not exceed these depths
unless directed otherwise by our representative.
Groundwater existing in alluvial areas may make excavation difficult. Deeper removals than
indicated in the text of the report may be necessary due to saturation during winter months.
Subsequent to removals, the natural ground should be processed to a depth of six inches,
moistened to near optimum moisture conditions and compacted to fill standards.
Exploratory back hoe or dozer trenches still remaining after site removal should be
excavated and filled with compacted fill if they can be located.
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GENERAL GRADING GUIDELINES APPENDIX E
Subdrainage
I. Subdrainage systems should be provided in canyon bottoms prior to placing fill, and behind
buttress and stabilization fills and in other areas indicated in the report. Subdrains should
conform to schematic diagrams G- I and G-5, and be acceptable to our representative.
For canyon subdrains, runs less than 500 feet may use six-inch pipe. Typically, runs in excess
of 500 feet should have the lower end as eight-inch minimum.
Filter material should be clean, 1/2 to I-inch gravel wrapped in a suitable filter fabric. Class 2
permeable filter material per California Department of Transportation Standards tested by
this office to verify its suitability, may be used without filter fabric. A sample of the material
should be provided to the Soils Engineer by the contractor at least two working days before
it is delivered to the site. The filter should be clean with a wide range of sizes.
Approximate delineation of anticipated subdrain locations may be offered at 40-scale plan
review stage. During grading, this office would evaluate the necessity of placing additional
drains.
All subdrainage systems should be observed by our representative during construction and
prior to covering with compacted fill.
Subdrains should outlet into storm drains where possible. Outlets should be located and
protected. The need for backflow preventers should be assessed during construction.
Consideration should be given to having subdrains located by the project surveyors.
Fill Placement
1. Unless otherwise indicated, all site soil and bedrock may be reused for compacted fill;
however, some special processing or handling may be required (see text of report).
2. Material used in the compacting process should be evenly spread, moisture conditioned,
processed, and compacted in thin lifts six (6) to eight (8) inches in compacted thickness to
obtain a uniformly dense layer. The fill should be placed and compacted on a nearly
horizontal plane, unless otherwise found acceptable by our representative.
3. If the moisture content or relative density varies from that recommended by this firm, the
contractor should rework the fill until it is in accordance with the following:
Moisture content of the fill should be at or above optimum moisture. Moisture
should be evenly distributed without wet and dry pockets. Pre-watering of cut or
removal areas should be considered in addition to watering during fill placement,
particularly in clay or dry surficial soils. The ability of the contractor to obtain the
proper moisture content will control production rates.
Each six-inch layer should be compacted to at least 90 percent of the maximum dry
density in compliance with the testing method specified by the controlling
governmental agency. In most cases, the testing method is ASTM Test Designation
D 1557.
4. Rock fragments less than eight inches in diameter may be utilized in the fill, provided:
They are not placed in concentrated pockets;
There is a sufficient percentage of fine-grained material to surround the rocks;
C) The distribution of the rocks is observed by, and acceptable to, our representative.
5. Rocks exceeding eight (8) inches in diameter should be taken off site, broken into smaller
fragments, or placed in accordance with recommendations of this firm in areas designated
suitable for rock disposal (see Plate G-4). On projects where significant large quantities of
oversized materials are anticipated, alternate guidelines for placement may be included. If
G EOTEK
GENERAL GRADING GUIDELINES APPENDIX E
significant oversize materials are encountered during construction, these guidelines should be
requested.
6. In clay soil, dry or large chunks or blocks are common. If in excess of eight (8) inches
minimum dimension, then they are considered as oversized. Sheepsfoot compactors or
other suitable methods should be used to break up blocks. When dry, they should be
moisture conditioned to provide a uniform condition with the surrounding fill.
Slope Construction
1. The contractor should obtain a minimum relative compaction of 90 percent out to the
finished slope face of fill slopes. This may be achieved by either overbuilding the slope and
cutting back to the compacted core, or by direct compaction of the slope face with suitable
equipment.
2. Slopes trimmed to the compacted core should be overbuilt by at least three (3) feet with
compaction efforts out to the edge of the false slope. Failure to properly compact the outer
edge results in trimming not exposing the compacted core and additional compaction after
trimming may be necessary.
3. If fill slopes are built "at grade" using direct compaction methods, then the slope construction
should be performed so that a constant gradient is maintained throughout construction. Soil
should not be "spilled" over the slope face nor should slopes be "pushed out" to obtain
grades. Compaction equipment should compact each lift along the immediate top of slope.
Slopes should be back rolled or otherwise compacted at approximately every 4 feet vertically
as the slope is built.
4. Corners and bends in slopes should have special attention during construction as these are
the most difficult areas to obtain proper compaction.
5. Cut slopes should be cut to the finished surface. Excessive undercutting and smoothing of
the face with fill may necessitate stabilization.
Keyways, Buttress and Stabilization Fills
Keyways are needed to provide support for fill slope and various corrective procedures.
Side-hill fills should have an equipment-width key at their toe excavated through all surficial
soil and into competent material and tilted back into the hill (Plates G-2, G-3). As the fill is
elevated, it should be benched through surficial soil and slopewash, and into competent
bedrock or other material deemed suitable by our representatives (See Plates G- I, G-2, and
G-3).
2. Fill over cut slopes should be constructed in the following manner:
All surficial soils and weathered rock materials should be removed at the cut-fill
interface.
A key at least one and one-half (1.5) equipment width wide (or as needed for
compaction), and tipped at least one (I) foot into slope, should be excavated into
competent materials and observed by our representative.
C) The cut portion of the slope should be excavated prior to fill placement to evaluate if
stabilization is necessary. The contractor should be responsible for any additional
earthwork created by placing fill prior to cut excavation. (see Plate G-3 for
schematic details.)
3. Daylight cut lots above descending natural slopes may require removal and replacement of
the outer portion of the lot. A schematic diagram for this condition is presented on Plate G-
2.
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GENERAL GRADING GUIDELINES APPENDIX E
Page E- 5
A basal key is needed for fill slopes extending over natural slopes. A schematic diagram for
this condition is presented on Plate G-2.
All fill slopes should be provided with a key unless within the body of a larger overall fill
mass. Please refer to Plate G-3 for specific guidelines.
Anticipated buttress and stabilization fills are discussed in the text of the report. The need to
stabilize other proposed cut slopes will be evaluated during construction. Plate G-5 shows a
schematic of buttress construction.
All backcuts should be excavated at gradients of 1:1 or flatter. The backcut configuration
should be determined based on the design, exposed conditions, and need to maintain a
minimum fill width and provide working room for the equipment.
On longer slopes, backcuts and keyways should be excavated in maximum 250 feet long
segments. The specific configurations will be determined during construction.
All keys should be a minimum of two (2) feet deep at the toe and slope toward the heel at
least one foot or two (2%) percent, whichever is greater.
Subdrains are to be placed for all stabilization slopes exceeding 10 feet in height. Lower
slopes are subject to review. Drains may be required. Guidelines for subdrains are
presented on Plate G-5.
Benching of backcuts during fill placement is required.
Lot Capping
When practical, the upper three (3) feet of material placed below finish grade should be
comprised of the least expansive material available. Preferably, highly and very highly
expansive materials should not be used. We will attempt to offer advice based on visual
evaluations of the materials during grading, but it must be realized that laboratory testing is
needed to evaluate the expansive potential of soil. Minimally, this testing takes two (2) to
four (4) days to complete.
Transition lots (cut and fill) both per plan and those created by remedial grading (e.g. lots
above stabilization fills, along daylight lines, above natural slopes, etc.) should be capped with
a minimum three foot thick compacted fill blanket.
Cut pads should be observed by our representative(s) to evaluate the need for
overexcavation and replacement with fill. This may be necessary to reduce water infiltration
into highly fractured bedrock or other permeable zones, and/or due to differing expansive
potential of materials beneath a structure. The overexcavation should be at least three feet.
Deeper overexcavation may be recommended in some cases.
ROCK PLACEMENT AND ROCK FILL GUIDELINES
If large quantities of oversize material would be generated during grading, it's likely that such
materials may require special handling for burial. Although alternatives may be developed in the field,
the following methods of rock disposal are recommended on a preliminary basis.
Limited Larger Rock
When materials encountered are principally soil with limited quantities of larger rock fragments or
boulders, placement in windrows is recommended. The following procedures should be applied:
I. Oversize rock (greater than 8 inches) should be placed in windrows.
a) Windrows are rows of single file rocks placed to avoid nesting or clusters of rock.
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GENERAL GRADING GUIDELINES APPENDIX E
b) Each adjacent rock should be approximately the same size (within —one foot in
diameter).
C) The maximum rock size allowed in windrows is four feet
A minimum vertical distance of three feet between lifts should be maintained. Also, the
windrows should be offset from lift to lift. Rock windrows should not be closer than IS feet
to the face of fill slopes and sufficient space must be maintained for proper slope
construction (see Plate G-4).
Rocks greater than eight inches in diameter should not be placed within seven feet of the
finished subgrade for a roadway or pads and should be held below the depth of the lowest
utility. This will allow easier trenching for utility lines.
Rocks greater than four feet in diameter should be broken down, if possible, or they may be
placed in a dozer trench. Each trench should be, excavated into the compacted fill a
minimum of one foot deeper than the largest diameter of rock.
The rock should be placed in the trench and granular fill materials (SE>30) should be
flooded into the trench to fill voids around the rock.
The over size rock trenches should be no closer together than IS feet from any
slope face.
C) Trenches at higher elevation should be staggered and there should be a minimum of
four feet of compacted fill between the top of the one trench and the bottom of the
next higher trench.
d) It would be necessary to verify 90 percent relative compaction in these pits. A 24 to
72 hour delay to allow for water dissipation should be anticipated prior to additional
fill placement.
Structural Rock Fills
If the materials generated for placement in structural fills contains a significant percentage of material
more than six (6) inches in one dimension, then placement using conventional soil fill methods with
isolated windrows would not be feasible. In such cases the following could be considered:
I. Mixes of large rock or boulders may be placed as rock fill. They should be below the depth
of all utilities both on pads and in roadways and below any proposed swimming pools or
other excavations. If these fills are placed within seven (7) feet of finished grade, they may
affect foundation design.
2. Rock fills are required to be placed in horizontal layers that should not exceed two feet in
thickness, or the maximum rock size present, which ever is less. All rocks
exceeding two feet should be broken down to a smaller size, windrowed (see above), or
disposed of in non-structural fill areas. Localized larger rock up to 3 feet in largest dimension
may be placed in rock fill as follows:
individual rocks are placed in a given lift so as to be roughly 50% exposed above the
typical surface of the fill
loaded rock trucks or alternate compactors are worked around the rock on all sides
to the satisfaction of the soil engineer,
C) the portion of the rock above grade is covered with a second lift.
3. Material placed in each lift should be well graded. No unfilled spaces (voids) should be
permitted in the rock fill.
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GENERAL GRADING GUIDELINES APPENDIX E
Compaction Procedures
Compaction of rock fills is largely procedural
generally produce satisfactory compaction.
The following procedures have been found to
Provisions for routing of construction traffic over the fill should be implemented.
Placement should be by rock trucks crossing the lift being placed and dumping at its
edge.
The trucks should be routed so that each pass across the fill is via a different path
and that all areas are uniformly traversed.
C) The dumped piles should be knocked down and spread by a large dozer (D-8 or
larger suggested). (Water should be applied before and during spreading.)
2. Rock fill should be generously watered (sluiced)
a) Water should be applied by water trucks to the:
dump piles,
front face of the lift being placed and,
surface of the fill prior to compaction.
b) No material should be placed without adequate water.
C) The number of water trucks and water supply should be sufficient to provide
constant water.
d) Rock fill placement should be suspended when water trucks are unavailable:
for more than 5 minutes straight, or,
for more than 10 minutes/hour.
3. In addition to the truck pattern and at the discretion of the soil engineer, large, rubber tired
compactors may be required.
The need for this equipment will depend largely on the ability of the operators to
provide complete and uniform coverage by wheel rolling with the trucks.
Other large compactors will also be considered by the soil engineer provided that
required compaction is achieved.
4. Placement and compaction of the rock fill is largely procedural. Observation by trenching
should be made to check:
the general segregation of rock size,
for any unfilled spaces between the large blocks, and
C) the matrix compaction and moisture content.
5. Test fills may be required to evaluate relative compaction of finer grained zones or as
deemed appropriate by the soil engineer.
a) A lift should be constructed by the methods proposed, as proposed
6. Frequency of the test trenching is to be at the discretion of the soil engineer. Control areas
may be used to evaluate the contractor's procedures.
7. A minimum horizontal distance of 15 feet should be maintained from the face of the rock fill
and any finish slope face. At least the outer 15 feet should be built of conventional fill
materials.
Piping Potential and Filter Blankets
Where conventional fill is placed over rock fill, the potential for piping (migration) of the fine grained
material from the conventional fill into rock fills will need to be addressed.
The potential for particle migration is related to the grain size comparisons of the materials present
and in contact with each other. Provided that 15 percent of the finer soil is larger than the effective
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GENERAL GRADING GUIDELINES APPENDIX E
pore size of the coarse soil, then particle migration is substantially mitigated. This can be
accomplished with a well-graded matrix material for the rock fill and a zone of fill similar to the
matrix above it. The specific gradation of the fill materials placed during grading must be known to
evaluate the need for any type of filter that may be necessary to cap the rock fills. This,
unfortunately, can only be accurately determined during construction.
In the event that poorly graded matrix is used in the rock fills, properly graded filter blankets 2 to 3
feet thick separating rock fills and conventional fill may be needed. As an alternative, use of two
layers of filter fabric (Mirafi 700 x or equivalent) could be employed on top of the rock fill. In order
to mitigate excess puncturing, the surface of the rock fill should be well broken down and smoothed
prior to placing the filter fabric. The first layer of the fabric may then be placed and covered with
relatively permeable fill material (with respect to overlying material) I to 2 feet thick. The relative
permeable material should be compacted to fill standards. The second layer of fabric should be
placed and conventional fill placement continued.
Subdrainage
Rock fill areas should be tied to a subdrainage system. If conventional fill is placed that separates the
rock from the main canyon subdrain, then a secondary system should be installed. A system
consisting of an adequately graded base (3 to 4 percent to the lower side) with a collector system
and outlets may suffice.
Additionally, at approximately every 25 foot vertical interval, a collector system with outlets should
be placed at the interface of the rock fill and the conventional fill blanketing a fill slope.
Monitoring
Depending upon the depth of the rock fill and other factors, monitoring for settlement of the fill
areas may be needed following completion of grading. Typically, if rock fill depths exceed 40 feet,
monitoring would be recommend prior to construction of any settlement sensitive improvements.
Delays of 3 to 6 months or longer can be expected prior to the start of construction.
UTILITY TRENCH CONSTRUCTION AND BACKFILL
Utility trench excavation and backfill is the contractor's responsibility. The geotechnical consultant
typically provides periodic observation and testing of these operations. While efforts are made to
make sufficient observations and tests to verify that the contractors' methods and procedures are
adequate to achieve proper compaction, it is typically impractical to observe all backfill procedures.
As such, it is critical that the contractor use consistent backfill procedures.
Compaction methods vary for trench compaction and experience indicates many methods can be
successful. However, procedures that "worked" on previous projects may or may not prove
effective on a given site. The contractor(s) should outline the procedures proposed, so that we may
discuss them prior to construction. We will offer comments based on our knowledge of site
conditions and experience.
Utility trench backfill in slopes, structural areas, in streets and beneath flat work or
hardscape should be brought to at least optimum moisture and compacted to at least 90
percent of the laboratory standard. Soil should be moisture conditioned prior to placing in
the trench.
G EOTEK
GENERAL GRADING GUIDELINES APPENDIX E
2. Flooding and jetting are not typically recommended or acceptable for native soils. Flooding
or jetting may be used with select sand having a Sand Equivalent (SE) of 30 or higher. This is
typically limited to the following uses:
shallow (12 + inches) under slab interior trenches and,
as bedding in pipe zone.
The water should be allowed to dissipate prior to pouring slabs or completing trench
compaction.
3. Care should be taken not to place soils at high moisture content within the upper three feet
of the trench backfill in street areas, as overly wet soils may impact subgrade preparation.
Moisture may be reduced to 2% below optimum moisture in areas to be paved within the
upper three feet below sub grade.
4. Sand backfill should not be allowed in exterior trenches adjacent to and within an area
extending below a I: I projection from the outside bottom edge of a footing, unless it is
similar to the surrounding soil.
5. Trench compaction testing is generally at the discretion of the geotechnical consultant.
Testing frequency will be based on trench depth and the contractor's procedures. A probing
rod would be used to assess the consistency of compaction between tested areas and
untested areas. If zones are found that are considered less compact than other areas, this
would be brought to the contractor's attention.
JOB SAFETY
General
Personnel safety is a primary concern on all job sites. The following summaries are safety
considerations for use by all our employees on multi-employer construction sites. On ground
personnel are at highest risk of injury and possible fatality on grading construction projects. The
company recognizes that construction activities will vary on each site and that job site safety is the
contractor's responsibility. However, it is, imperative that all personnel be safety conscious to avoid
accidents and potential injury.
In an effort to minimize risks associated with geotechnical testing and observation, the following
precautions are to be implemented for the safety of our field personnel on grading and construction
projects.
I. Safety Meetings: Our field personnel are directed to attend the contractor's regularly
scheduled safety meetings.
Safety Vests: Safety vests are provided for and are to be worn by our personnel while on the
job site.
Safety Flags: Safety flags are provided to our field technicians; one is to be affixed to the
vehicle when on site, the other is to be placed atop the spoil pile on all test pits.
In the event that the contractor's representative observes any of our personnel not following the
above, we request that it be brought to the attention of our office.
Test Pits Location, Orientation and Clearance
The technician is responsible for selecting test pit locations. The primary concern is the technician's
safety. However, it is necessary to take sufficient tests at various locations to obtain a representative
sampling of the fill. As such, efforts will be made to coordinate locations 'with the grading
contractors authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.),
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GENERAL GRADING GUIDELINES APPENDIX E
and to select locations following or behind the established traffic pattern, preferably outside of
current traffic. The contractors authorized representative should direct excavation of the pit and
safety during the test period. Again, safety is the paramount concern.
Test pits should be excavated so that the spoil pile is placed away from oncoming traffic. The
technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that
the fill be maintained in a drivable condition. Alternatively, the contractor may opt to park a piece of
equipment in front of test pits, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits (see diagram below). No grading
equipment should enter this zone during the test procedure. The zone should extend outward to
the sides approximately 50 feet from the center of the test pit and 100 feet in the direction of traffic
flow. This zone is established both for safety and to avoid excessive ground vibration, which typically
decreases test results.
TEST PIT SAFETY PLAN
~SIDE VIEW
Test Pit Spoil
pile
50 ft Zone of Traffic Direction Non-Encroachment
Vehicle
parked here -Test Pit Spoil
pile
looftZoneof
Non-E 50ftZoneofncroachment
Non-Encroachment
PLAN VIEW
Slope Tests
When taking slope tests, the technician should park their vehicle directly above or below the test
location on the slope. The contractor's representative should effectively keep all equipment at a safe
operation distance (e.g. 50 feet) away from the slope during testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible following
testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible
location.
Trench Safety
It is the contractor's responsibility to provide safe access into trenches where compaction testing is
needed. Trenches for all utilities should be excavated in accordance with CAL-OSHA and any other
applicable safety standards. Safe conditions will be required to enable compaction testing of the
trench backfill.
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GENERAL GRADING GUIDELINES APPENDIX E
All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid
back. Trench access should be provided in accordance with OSHA standards. Our personnel are
directed not to enter any trench by being lowered or "riding down" on the equipment.
Our personnel are directed not to enter any excavation which;
I. is 5. feet or deeper unless shored or laid back,
exit points or ladders are not provided,
displays any evidence of instability, has any loose rock or other debris which could fall into the
trench, or
displays any other evidence of any unsafe conditions regardless of depth.
If the contractor fails to provide safe access to trenches for compaction testing, our company policy
requires that the soil technician withdraws and notifies their supervisor. The contractor's
representative will then be contacted in an effort to affect a solution. All backfill not tested due to
safety concerns or other reasons is subject to reprocessing and/or removal.
Procedures
In the event that the technician's safety is jeopardized or compromised as a result of the contractor's
failure to comply with any of the above, the technician is directed to inform both the developer's and
contractor's representatives. If the condition is not rectified, the technician is required, by company
policy, to immediately withdraw and notify their supervisor. The contractor's representative will
then be contacted in an effort to affect a solution. No further testing will be performed until the
situation is rectified. Any fill placed in the interim can be considered unacceptable and subject to
reprocessing, recompaction or removal.
In the event that the soil technician does not comply with the above or other established safety
guidelines, we request that the contractor bring this to technician's attention and notify our project
manager or office. Effective communication and coordination between the contractors'
representative and the field technician(s) is strongly encouraged in order to implement the above
safety program and safety in general.
The safety procedures outlined above should be discussed at the contractor's safety meetings. This
will serve to inform and remind equipment operators of these safety procedures particularly the
zone of non-encroachment.
The safety procedures outlined above should be discussed at the contractor's safety meetings. This
will serve to inform and remind equipment operators of these safety procedures particularly the
zone of non-encroachment.
"C~
G EOTEK
ALTERNATES
Bottom of Cleanout to Be At , t
Least 1.5 Times the Width of 6" Perforated Pipe in 9 cubic feet per Lineal
Compaction Equipment , Foot Clean Gravel Wrapped in Filter Fabric
Bottom of Cleanout to Be At
6" Perforated Pipe in 9 cubic feet Least 1.5 Times the Width of
per Lineal Foot Clean Gravel Compaction Equipment
Wrapped in Filter Fabric
TYPICAL CANYON STANDARD GRADING
1384 Poinsettia Avenue, Suite A GUIDELINES
Vista, California 92083 CLEANOUT PLATE G-1
2% FaL__2 ~eetj:::':'~_~'—_-
iVlinirnurn 15 Feet Wide
or 1.5 Equipment
Widths for Compaction
Mn in
TYPICAL FILL SLOPE OVER
NATURAL DESCENDING SLOPE
Finish Grade
Mm 3Fe
Compacted Fill Slope
Compacted Fill
Toe of Fill Slope
-------------------
OP5lluvep zone
per Plan
Project Removal
at I to I
DAYLIGHT CUT AREA OVER
NATURAL DESCENDING SLOPE
Structural Setback
ithout Corrective Work Daylight Cut
= ; -: . Line er Plan
Finish Grade f Project Removal
at I to 1
Min.3 Feet
Compacted Fill
Compacted Fill
4 Topsoil
: 2 Feet l •. Colluvium
MiiFall * Creep Zone
':::'•Bedrock. • '
• •
•. • .,
Minimum 15 Feet Wide .'.' .."'' •
orl.5Equipnient ' ' . •• .•.. .
Widths br Compaction ' . ••••• ,•' , •'• .
1384 Poinsettia Avenue, Suite A I TREATMENT ABOVE I STANDARD GRADING
Vista, California 92081-8505 I GUIDELINES NATURAL SLOPES
PLATE G-2
TYPICAL FILL SLOPE OVER
CUT SLOPE
Finish Grade
2:1 Fill Slope
Toe of Fill Slope
or 1.5 Equipment
Widths for Compaction
Cut Slope
Bedrock
TYPICAL FILL SLOPE
SLOPE
HEIGHT
MIN. KEY MIN. KEY
WIDTH DEPTH
5 7 1
10 10 1.5
15 15 2
20 15 2.5
25 15 3
>25 SEE TEXT
UON FRAU FOR TO VERIFY
WITH SOIL ENGINEER
PRIOR TO CONSTRUCTION
l384 Poinsettia Avenue, Suite A I COMMON FILL I STANDARD GRADING
Vista, California 92081-8505 GUIDELINES
SLOPE KEYS PLATE G-3
FILL SLOPE
CROSS SECTIONAL VIEW
PLAN VIEW
FILL I SLOPE
NOTES:
SOIL FILL OVER WINDROW SHOULE BE 7 FEET OR PER JURISDUICTIONAL STANDARDS AND SUFFICIENT
FOR FUTURE EXCAVATIONS TO AVOID ROCKS
MAXIMUM ROCK SIZE IN WINDROWS IS 4 FEET MINIMUM DIAMETER
SOIL AROUND WINDROWS TO BE SANDY MATERIAL SUBJECT TO SOIL ENGINEER ACCEPTANCE
SPACING AND CLEARANCES MUST BE SUFFICIENT TO ALLOW FOR PROPER COMPACTION
INDIVDUAL LARGE ROCKS MAY BE BURIED IN PITS.
1384 Poinsettia Avenue, Suite A
STANDARD GRADING
Vista, California 92081-8505 ROCK BURIAL GUIDELINES
DETAILS I PLATE G-4
TERRACE DRAIN
AS REQUIRED
/ . . . ............ 1.
I
BEDROCK / COMPACTED FILL 2
'a)
X?
EIVIBEDDIVIENT
MIN 2% FALL
MI. 15 FEET WIDE OR 1.5 EQUIPMENT
I WIDTHS FOR COMPACTION
4" or 6" Perforated Pipe in 6 cubic
feet per lineal foot clean gravel
wrapped in filter fabric outlet pipe
to gravity flow at 2% mm.
6" Perforated Pipe in 6 cubic
feet per lineal foot clean gravel
wrapped in filter fabric outlet
pipe to gravity flow
1384 Poinsettia Avenue, Suite A Typical Buttress and
Vista, California 92083 Stabilization Fill
PLATE G-5
TRANSITION LOT
I PROPOSED STRUCTURE
PROPSED FINISH GRADE L
COMPACTED FILL
.00
001! 0
COMPETENT MATERIA1 Xf
OVEREXCAVATION AND BENCHING NOT OVEREXCAVATE AND
TO EXCEED INCLINATION OF 3:1 (H:V) RECOMPACT
UNDERCUT LOT
PROPOSED STRUCTURE
PROPSED FINISH GRADE
COMPACTED FILL 4' MIN.
4
..............................
. ,. .,,- , . 4 .•.• II,I I,,..,.,I.,.,l .......... S
COMPETENT MATERIAL
i. :
. , 414 41 II ,l...,.....d. ••4_I_•_•_•_I_I•I_•_fS_•••
OVEREXCAVATION TO HAVE 1% OVEREXCAVATE AND
FALL TOWARD FRONT OF LOT RECOMPACT
Notes:
1 Removed/overexcavated soils should be recompacted in accordance with recommendations included in the text of the report.
2. Location of cut/fill transition should verified in the field during site grading.
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505 TRANSITION &
UNDERCUT LOTS
STANDARD GRADING
GUIDELINES
PLATE G-6