HomeMy WebLinkAboutParcel Map 30404 Parcel 2 Prelim Soils (Apr.24,2002)~
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W. C. HOBBS, CONSULTING ENGINEER
39697 CEDARWOOD DRNE
MURRIETA, CALIFORNIA 92563
(909) 696-7059
Date: P,pril 24, 2002
Project No: 02018-1
Sand Dollar Homes
41743 Enterprise Circle North, Suite 207
Temecula, Califomia 92592
Subject: Preliminary Soil Engineering Evaluation
Tentative Parcel Map 30404, Portion of Lot 6 of PM 6807,
30270 Santiago Road, City of Temecula, Califomia
Dear GenUemen,
Pursuantto an authorization from Vandenberg Civil Consulting, a limited soil engineering evaluation
was conducted on the subject lot to determine the distribution and engineering characteristics of earth
materials present. The results offield exploration, togetherwith the results ofthe laboratorytests, are
summarized in the attached appendix.
Additional information provided herein inGudespreliminaryfoundation designforproposed residential
construction.
Accompanying Maps and Appendices
Attached Appendix A, Summary of Laboratory Test Results, F~ccavation Logs
Attached Appendix B, General Earthwork and Grading Specifications
Plate 1, Trench Location Map
Scope of Work
The scope of work perFormed for this study included the following:
Observation of a graded lot with two pads present,
2. Laboratory testing, and;
3. Preparation of this report including conGusions and recommendations pertinent to the
proposed construction.
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 2
Project No: 02019-1
Site Description
The site is roughly rectangular located at the northwesterfy side ofthe intersection of Santiago Road
and Ormsby Road. It contains an existing residence and the land is proposed to be split. The
westem half of the site contains two pads, the lower (southem) of which is used as a horse riding
arena. PresenUy, the site is covered with a nominal growth of weeds and grasses that may be
recently cut. No visible signs of erosion were noted.
Field Work
Field work on the site consisted of observation three backhoe excavations for the purpose of
recoveringsamplesofrepresentativeearthmaterialsforlaboratorytesting. Theresultsofthesetests
are contained in the attached Appendix A. Additionally, a reconnaissance of the nearby area was
conducted in order to obtain information pertinentto the site. The trenches were strategically placed
to evaluate the condition and thickness of suspected existing fills on the site. Records of the
construction of the fills were not available at the time of this reports and it is possible that they do not
exist.
Observation and testing ofthe excavations indicated that the existing fill materials were of moderate
to low density in place with no visible pores, and is dry at the surface. The fill ranges in thickness
from 0 to approximately 8 feet or more, depending on location and original topography. The base
of the fill is an obscured contact with colluvial materials that are porous and containing numerous
roots and rooUets. The colluvium or topsoil was observed to range in thickness from 2 to 5 feet.
Belowthe colluvium, there is a gradational contact with the Pauba Formation, basically a sedimentary
sandstone with traces of silt being moist and dense.
Laboratory Testing
The maximum dry density and optimum moisture content of the soil was determined in accordance
with ASTM test designation D 1557-82. The expansion index testing should be conducted on a
representative sample at the completion of rough grading in order to determine the expansion
potential of the near surface soils in the vicinity of proposed foundations. The expansion index test
should be conducted in accordance with UBC 29-2.
W. C. HOBBS, CONSULTING ENGINEER
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 3
Project No: 02019-1
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
The development ofthe site for single or multi-story residential construction is both feasible and safe
from a geotechnical standpoint provided that the recommendations contained herein are
implemented during design and construction.
1. The site is a graded parcel with an e~usting residence and associated pads and driveways
2. Fiils observed on the lot are undocumented and observed to be loosed with poor Geanouts
beneath..
3.Observation, classfication, indicate that the near surface soils have a low to moderate expansion
potential.
Recommendations
The recommendations contained herein are contingent upon providing the services listed in the
Construction section in orderto confirm design assumptions and reviewthe field conditions of any
excavations for possible anisotropic properties. If observation indicates that the conditions are
differentthan those indicated in this report, additional, ormodificaUons tothe, recommendations may
become necessary.
Site Grading
In order to provide proper support for building foundations, remedial grading will be required. It is
anticipated that grading will consist of cutting areas for pads and driveway construction with the
balance placement of fills to create new pads augmenting the existing pads. All grading and/or
retaining wall backfills should be placed in accordance with minimum standards presented a the back
of this report, Appendix B, Standard Specifications for Earthwork Construction. It should be noted
that remedial grading should consist of the complete removal of all existing filis on proposed pad
areas, and the removal of porous colluvial materials beneath existing fills. All newly placed
subsequent fiil shall be placed on observed competent earth materials. It is further recommended
that fills be placed onto the observed competent bedrock materials of the Pauba Formation.
Building pads should be over excavated such that a minimum of 4 feet of fill exists beneath the
bottom of proposed footings. That is to say if a footing is 18 inches deep, then the over excavation
should consist of the removal of 4.5 feet below finished pad grade, the processing in place of an
additional 12 inches of ground and the replacement of excavated materials with observed, tested
compacted fill materials. The horizontal geometry should extend a minimum of 5 feet outside the
proposed building area.
W. C. HOBBS, CONSULTING ENGINEER
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 4
Project No: 02019-1
Recommendations, continued
Bearing Value and Footing Geometry
A safe allowable bearing value for foundations embedded into native bedrock materials or ro eri
compacted fill is 1800 psf. This value may be increased at the rate of 100 psf per foot of depth and
100 psf per foot of width over the minimums, but should not exceed 2000 psf. Continuous footings
should have a minimum width of 12 inches and depth of 18 inches and conform to the minimum
criteria of the UBC for single and or multistory construction for moderately expansive soils. The use
of isolated column footings is not discouraged, however, where utilized, should have a minimum
embedment of 18 inches below lowest soil grade. The minimum distance of the bottom of footings
on the outside edge and the native slope face on the south is 8 feet.
Settlement
The bearing value recommended above reflects a total settlement of 0.5" and a differential
settlement of 0.5". Most of this settlement is expected to occur during construction and as the loads
are being applied.
Concrete Slabs
All concrete slabs on grade should be 4 inches thick. They should be underiain by 2 inches ofsand
or gravel. Areas that are to be carpeted or tiled, or where the intrusion of moisture is objectionable,
should be underlain by 6 mil visqueen properiy protected from puncture with an additional 1 inch of
sand over it. This arrangement of materials would result in a profile downward of concrete, 1 inch
ofsand,6milvisqueen,2inchesofsandandsubgradesoil. Contractorsshouldbeadvisethatwhen
pouring during hot orwindy weatherconditions, they should provide large slabs with sufficienUy deep
weakened plane joints to inhibit the development of irregular or unsightly cracks. Also, 4 inch thick
slabs should be jointed in panels not exceeding 12 feet in both directions to augment proper crack
direction and development.
Reinforcement
Continuous footings should be reinforced with a minimum of one number 4 steel bar placed at the
top and one at the bottom. Slabs should be reinforced with a minimum of number 3 steel bars
placed at the center of thickness at 18-inch centers both ways or welded wire fabric equivalent to
10x10 10/10 may be used. It is understood that the sectional values for the two schedules are
different, and is of no design concem. The steel bars have been proven to have a better
performance history and selection is up to the builder. Additional requirements may be imposed by
the structural engineering design.
W. C. HOBBS, CONSULTING ENGINEER
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 5
Project No: 02019-1
Recommendations, continued
Retaining Walls
Retaining walis should be designed to resist the active pressures summarized in the following table.
The active pressure is normally calculated from the lowermost portion of the footing to the highest
groundsurfaceatthebackofthewall. Theactivepressuresindicatedinthetableareequivalentfluid
densities. Walls that are not free to rotate or that are braced at the top should use active pressures
that are 50% greater than those indicated in the table.
RETAINING WALL DESIGN PRESSURES
Slope of Active Pressure Passive Pressure
adjacent qround
LEVEL 30 pcF 350 pcF
2:1 40 pcF 200 pcf
These pressures are for retaining walis backfilled with noncohesive, granular materials and provided
with drainage devices such as weep holes or subdrains to prevent the build-up of hydrostatic
pressures beyond the design values. It is imperative that all retaining wall backfills be compacted to
a minimum of 90 percent relative compaction in order to achieve their design strength. Failure to
provide proper drainage and minimum compaction may result in pressures against the wall that will
exceed the design values indicated above. Surface waters should be directed away from retaining
wall backfill areas so as not to intrude into the backfill materials.
Lateral Loads
The bearing value of the soil may be increased by one third for short duration loading (wind,
seismic). Lateral loads may be resisted by passive forces developed along the sides of concrete
foo6ngs or by iriction along the bottom of concrete footings. The value of the passive resistance for
Ievelgroundmaybecomputedusinganequivalentfluiddensityof300pcFforlevelground. Thetotal
force should not exceed 3000 psf. A coeffiaent of friction of .40 may be used for the horizontal
soiVconcrete interface for resistance of lateral forces. If friction and passive forces are combined,
then the passive values should be reduced by one third.
W. C. HOBBS, CONSULTING ENGINEER
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 6
Project No: 02019-1
Recommendations,continued
Fine Grading
Fine grading of areas outside of the residence should be accomplished such that positive drainage
exists awayfrom all footings. Run-off should be conducted offthe property in a non erosive manner
toward approved drainage devices at the street or the rear of the property per approved plans.
Construction
A soil engineer should be present during the excavation of the foundations, as well as earthwork
construction, to test and or confirm the conditions encountered during this study. It is recommended
to have the foundation excavations observed by a soil engineer prior the placement of construction
materials in them as consequential changes and differences may exist throughout the earth
materials on the site. It may be possible that certain excavations may have to be deepened slightly
if earth materials are found to be loose or weak.
W. C. HOBBS, CONSULTING ENGINEER
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Sand Dollar Homes, TPM 30404, 30270 Santiago Rd., City of Temecula Page: 7
Project No: 02019-1
CLOSURE
This evaluation was performed in accordance with generally accepted engineering practices. The
conclusions and recommendations contained in this report were based on the data available and the
interpretation of such data as dictated by our experience and background. Hence, our conclusions
and recommendations are professional opinions; therefore, no other warranty is offered or implied.
The opportunity to be of service is appreciated. Should questions or comments arise pertaining to
this document, or if we may be of fuRher service, please do not hesitate to call our office.
Respectfuily Submitted,
W. C. HOBBS, CONSULTING ENGINEER
Bill Hobbs, RCE 42265
Civil Engineer
WILLIAM
HOBBS
No.422~
E~.931RIX
Distribution: Addressee (4)
Attachments: Appendix A- Summary of Laboratory and Field Test Results, Logs
Appendix B- General Earthworic and Grading Specifications
Plate 1, Trench Location Map
W. C. HOBBS, CONSULTING ENGINEER
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APPENDIX A
SUMMARY OF TEST RESULTS
W. C. HOBBS, CONSULTING ENGINEER
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APPENDIX A
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SUMMARY OF MAXIMUM DENSITY TEST RESULTS
Curve Soil Maximum Optimum
Letter Descriotion Densi cf Moisture %
A Silty SAND, fine to med. 126.5 10.5
tan to brown (SM)
Maximum density and optimum moisture determined in acxordance with
test method ASTM D 1557-78.
W. C. HOBBS, CONSULTING ENGINEER
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APPENDIX B
GENERAL EAR'IT~WORK AND GRADING SPECIFICATTONS
W. C. HOBBS, CONSULTING ENGINEER
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GENERAL EARTHWORK AND GRADING SPECIFICATIONS
I.0 GENERAL INTENT
These specifica6ons present general procedures and requiremenfs for grading and earthwork as shown on the approved grading plans,
including preparation of areas to be filled, placementoffill, installation ofsubdrains, and excavations. The recommendations confained in the
geotechnical report are a part ofthe earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case
ofconflict. Evaluations performed bythe consultantduring ihe course ofgrading may resuttin new recommendations ofthe geotechnical report.
2.0 EARTHWORK OBSERVATION AND TESTING
Prior to the commencement of grading, a qualfied geotechnical consultant (soils engineer and engineering geologist, and their
represenfatives) shall be employed for the purpose of observing earfhwork and testing ihe fills for confortnance with the recommendations
of the geotechnical report and these specfications.
It will be necessary that the consultant provide adequate testing and observation so ihat he may determine that the work was accomplished
as specified. It shall be the responsibilityof the contractorto assistthe consuftant and keep him apprised ofwork schedules and changes so
that he may schedule his personnel accordingly.
It shall be the sole responsibility of ihe contractor to provide adequate equipment and methods to accomplish the work in accordance with
applicable grading codes or agency ordinances, ihese specfications and the approved grading plans. If in ttie opinion of the consultant,
unsatisfactory conditions, such as questionable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resulting in
a qualily of woric less than required in these specfiptions, the consulTant will be empowered to reject the woric and recommend that
construction be topped un51 me conditions are rectified.
Maximum dry density tests used to determine the degree of compaction will be performed in accordance wim the American Sociery of Testing
and Materials tests method ASTM D 1557-78.
3.0 PREPARATION OF AREAS TO BE FILLED
3.1 Clearing and Grubbing: All brush, vegefation and debris shall be removed or piled and othenvise disposed of.
3.2 Processing: The existing ground which is determined to be sa6sfadoryforsupport offill shall be scarified to a minimum depth of 6 inches.
Existing ground which is not satisfactory shall be over excavated as specfied in the following section.
Scanfication shall continue until ihe soils are broken down and free of large clay lumps or clods and until the working surface is reasonably
unifortn and free of uneven features which would inhibit un'rform compaction.
3.3 Overexcavation: Soft, dry, spongy, highlyfractured orotherwise unsuifableground, e~Aending to such a depth thatthe surface processing
cannot adequately improve the condition, shall be over excavated down to firm ground, approved by lhe consultant.
3.4 Moisture Conditioning: Overexcavated and processed soils shall be watered, dried-back, blended, and/or mixed, as required to attain
a uniform moisWre content near optimum.
3.5 Recompaction: Overexcavated and processed soils which have been properly mixed and moisture-conditioned shall be recompaded
to a minimum relative compaction of 90 percent.
3.6 Benching: Where fills are to be placed on ground witli slopes steeperthan 5:1 (horizontal to vertical units), the ground shall be stepped
or benched. The lowest bench shall be a minimum of 15 feet wide, shall be at least 2 feet deep, shall expose firtn material, and shall be
approved by ttie consultant. Ofher benches shall be excavated in firm material for a minimum width of4 feet. Ground sloping flatterthan 5:
1 shall be benched or othervvise over excavated when considered necessary by the consultant.
3.7 Approval: All areas to receive fill, including processed areas, removal areas and toe-of-fill benches shall be approved by the consuliant
prior to fill placement.
W. C. HOBBS, CONSULTING ENGINEER
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4.0 FILL MATERIAL
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4.1 General: Material to be placed as fill shall be free of organic matter and other deleterious substances, and shall be approved by the
consultant. Soils of poorgradafion, expansion, orstrength charaderisfics shall be piaced in areas designated by consulfantorshall be mixed
with other soils to serve as satisfactory fill material.
4.2 Wersize: Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 12 inches, shall not
be buried or placed in fills, unless tlie location, materials, and disposal methods are specifically approved by the consultant Oversize disposal
operations shall be such that nesting of oversize material dces not occur, and such that ttie oversize material is completely surrounded by
compacted ordensfied fill. Oversize material shall not be placed wifhin 10 feet vertically offinish grade orwithin the range offuture utilities or
underground construction, unless specifically approved by the consultant.
4.3 Import: If imporfing of fill material is required for grading, ihe import material shall meet fhe requirements of Section 4. 1.
5.0 FILL PLACEMENT AND COMPACTION
5.1 Fill Lifts: Approved fill material shall be placed in areas prepared to receivefill in near-horizontal layers not exceeding 6 inches in compacted
thickness. The consultant may approve thidcer I'rfts'rf testing indicates the grading procedures are such that adequate compaction is being
achieved with lifls of greaterthickness. Each layershall be spread evenlyand shall be thoroughly mixed during spreading to attain uniformity
of material and moisture in each layer.
5.2 Fill Moisture: Fill layers at a moisture content less than optimum shall be watered and mixed, and wet fill layers shall be aerated by
scarificafion or shall be blended with drier material. Moisture-conditioning and mixing of fill layers shall confinue until the fill material is at a
unifortn moisture content or near optimum.
5.3 Compaction of Fill: After each layer has been evenly spread, moisWre conditioned, and mixed, it shall be uniformly compacted to not
less ihan 90 percent of maximum dry density. Compaction equipment shall be adequately s¢ed and shall be eitherspecifically designed for
soil compaction or of proven reliability, to efficien8y achieve ttie specified degree of compaction.
5.4 Fill Slopes: Compaction of slopes shall be accomplished, in addition to nortnal compacting procedures, by backfilling of slopes with
sheepsfoot rollers atfrequent increments of 2 to 3feet in fill elevation gain, or byothermethods producing satisfadory results. Atthe complefion
of grading, the relative compaction of fhe slope out to the slope face shall be at least 90 percznt.
5.5 Compaction Testing: Field tests to check the ill moisture and degree of compaction will be perfortned bythe consultant. The location and
frequency of tests shall be at the consultanPs discretion. In general, the tests will be taken at an interval not exceeding 2 feet in vertical rise
and/or 1,000 cubic yards of embankment.
6.0 SUBDRAIN INSTALLATION
Subdrain systems,'rfrequired, shall be installed in approved ground to conform tothe approximate alignment and deTails shown on U~e plans
or herein. The subdrain location or materials shall not be changed ormodfied withoutthe approval of the consultant. The consultant, however,
may recommend and upon approval, direct changes in subdrain line, grade or material. All subdrains should be surveyed for line and grade
after installation, and sufficient time shall be allowed for the suroeys, prior to commencement of filling over Uie subdrains.
W. C. HOBBS, CONSULTING ENGINEER
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7.0 EXCAVATION
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Excavation and cut slopes will be examined during grading. If directed by the consultant, further excavafion or over excavation and refilling
of cut areas shall be performed, and/or remedial grading of cut slopes shall be performed. Where fillovercut slopes are to be graded, unless
otherwise approved, the cut portion of the slope shall made and approved by ihe consultant prior to placement of materials for construction
of the fill portion of the slope.
8.0 TRENCH BACKFILL
8.1 Supervision: Trench excavations for the utility pipes shall be backfilled under engineering supervision
8.2 Pipe Zone: After the utiliry pipe has been laid, ihe space under and around the pipe shall be backfilled with dean sand or approved
granular soil to a depih of at least one foot over ihe top of the pipe. The sand backfill shall be uniformlyjetted into place before the controlled
backfill is placed over the sand.
8.3 Fill Placement: The onsite materials, orothersoils approved bythe engineer, shall be watered and mixed as necessary priorto placement
in liffs over the sand backfill.
8.4 Compaction: The controlled backfill shall be compac[ed to at least 90 percent of the maximum laboratory density as determined by the
ASTM compaction method described above.
8.50bservation and Testing: Field densirytests and inspection ofthe backfill procedures shall be made bythe soil engineerduring backfilling
too see that ihe proper moisture content and uniFortn compaction is being maintained. The contractor shall provide test holes and exploratory
pits as required by the soil engineer to enable sampling and testing.
W. C. HOBBS, CONSULTING ENGINEER
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