HomeMy WebLinkAboutTract Map 9833-1 Lot 28 Preliminary Soil Eval
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w. C. HOBBS, CONSULTING ENGINEER
39281 VIA PAMPLONA
MURRIETA, CALIFORNIA 92563
(909) 696-7059
Date: June 7, 2001
Project No: 01036-1
I Mr. Sean Malek.
: 3772 Brannen Avenue
I Perris, California 92570
! Subject:
Preliminary Soil Engineering Evaluation
for Proposed Residence Located at Pio Pico and Margarita Road
Lot 28 of Tract 9833-1, City of Temecula, California
I Dear Mr. Malek,
I Pursuant to yourauthorization and a requirement by the City ofTemecula, a limited soil engineering
, evaluation was .conducted on the subject lot to determine the distribution and engineering
: characteristics of earth materials present. The results of field exploration, together with the results of
: the laboratory tests, are summarized in the attached appendix.
I Additional information provided herein includes preliminary foundation design for proposed
, residential construction.
I Accompanyingl Maps and Appendices
'Attached Appendix A, Summary of Laboratory and Field Test Results
I Attached Appendix S, General Earthwork and Grading Specifications
, Plate 1, Trench Location Map
! Scope of Work
. The scope of work performed for this study included the following:
, 1. Observation of a natural lot,
,2. Excavation of an exploration trench into the subject site to observe the existing soil conditions
and recover samples.
: 3. Laboratory testing, and;
:4. Preparation of this report including conclusions and recommendations pertinent to the
proposed construction.
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. Mr. Sean Malek, Lot 28, Tr. 9833-1
Project No: 01036.1
Page: 2
: Site Description
. The site is roughly rectangular in shape, fronting 783 feet along the west side of Margarita Road and
I extending an average of 175 feet to the west. The site is currently not graded with the exception of
i aminortravel way for access to the drainage easement thattransects the property, see Plate 1. The
I site is generally flat, sloping gently to the south on the south side ofthe drainage easement. The site
I contains various trees and bushes, and a prominent row of trees along Margarita Road. Presently,
I the site is covered with a nominal growth of weeds and grasses that were recently cut. No visible
! signs of erosion were noted.
lliield Work
I Field work on the site consisted of observation an excavation made by backhoe for the purpose of
I recovering samples of representative earth materials for laboratory testing. The results of these tests
i are contained in the attached Appendix A. Additionally, a reconnaissance of the nearby area was
, conducted in order to obtain information pertinent to the site.
: Observation and testing of the excavation indicated that the existing materials were of a low density
in place with visible pores, and is dry at the surface, damp at 1 foot and moist below 5 feet. Location
: of the Test Trench is indicated on Plate 1, Trench Location Map Observation of the earth materials
indicates a thin mantle of top soil with minor root materials, transitioning quickly at a depth of 1 foot
! to alluvium. The alluvium is comprised of relatively clean sand. It contains several observed fining
, upward sequences, suggesting rapid high energy deposit with waning flow. These were observed
. to approximately 4 to 5 feet below the surface. Grain sizes ranged from .01 mm to 1 mm. The
, alluvium was observed to be well bedded, with layers of different colors and grain sizes. The soils
,were observed to be damp and even moist below 5 feet or so. No standing or free water was
: observed in the trench to 18 feet below the ground surface. The sands dug easily and although
: caving was an obvious possibility, none occurred. The hole was left open approximately 30 minutes
: prior to backfilling. Mottling ofthe soil was not observed in the upper 6 feet below the ground surface.
, When the trench was backfilled, all of the excavated soil went back into the hole and there was still
, a depression in the ground to be filled, suggesting that the alluvial soils are very loose in their current
i state.
I Laboratory Testing
. The maximum dry density and optimum moisture content of the soil was determined in a=rdance
,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 a=rdance with USC 29-2.
W. C. HOBBS, CONSULTING ENGINEER
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I Mr. Sean Malek, Lot 28, Tr. 9833.1
I Project No: 01036-1
Page: 3
CONCLUSIONS AND RECOMMENDATIONS
I Conclusions
The development of the site for single or multi-story residential construction is both feasible and safe
I from a geotechnical standpoint provided that the recommendations contained herein are
I implemented during design and construction.
. 1. The site is essentially untouched, graded only at the eastem and southem edges for roadway
: construction.
; 2. The soil is observed to be loose in place.
: 3.0bservation, classification, indicate that the nearsurface soils have a very low expansion potential.
I Recommendations
. The recommendations contained herein are contingent upon W. C. Hobbs, Consulting Engineer or
I his assigns providing the services listed in the Construction section in order to confirm design
: assumptions and review the field conditions of any excavations for possible anisotropic properties.
I If observation indicates that the conditions are different than those indicated in this report, additional,
: or modifications to the, recommendations may become necessary.
! Site Grading
Iln order to provide proper support for building foundations, remedial grading will be required.
I Proposed grading consists of creating a driveway, pad and foundation areas and or the balance
: placement of fills on the site for a pad area in the vicinity of the proposed residence and driveway.
,All grading and retaining wall backfills should be plaoed in a=rdance with minimum standards
: presented a the back of this report, Appendix 8, Standard Specifications for Earthwork Construction.
: Grading should consist of the removal of the upper 6 to 7 feet of alluvial soils in the building area and
I approximately 15 feet beyond the perimeter. Also, this removal area should extend an equal
: distance away from the lowest outside edge of the foundations as the final thickness of fill in the
: proposed area, or a minimum of 15 feet, whichever is the greater. Final determination for the depth
: of excavation shall be made in the field during grading operations. It is possible that additional
i excavations may resu~ in more or less excavation due to the density of alluvial soils.
: Oare should be taken to properly locate the proposed structure and grading area on the site. This
: area should be strictly adhered to during construction to minimize the possibility of detrimental
! settlements of the structure from being founded on materials that were not compacted.
W. C. HOBBS, CONSULTING ENGINEER
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I Mr. Sean Malek, Lot 28, Tr. 9833-1
I Project No: 01036-1
Page: 4
I Recommendations, continued
I Bearing Value and Footing Geometry
, A safe allowable bearing value for foundations embedded into native bedrock materials or properly
. compacted fill is 1500 pst. 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 12 inches and conform to the minimum
: criteria of the UBC for single and or multistory construction for very low expansive soils. The use of
isolated column footings is not discouraged, however, where utilized, should have a minimum
i embedment of 12 inches below lowest soil grade. The minimum distance of the bottom of footings
: on the outside edge and the native slope face is 10 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
I All concrete slabs on grade should be 4 inches thick. They should be underlain by 2 inches of sand
. or gravel. Areas that are to be carpeted or tiled, or where the intrusion of moisture is objectionable,
I should be underlain by 6 mil visqueen properly protected from puncture with an additional 1 inch of
i sand over it. This arrangement of materials would resu~ in a profile downward of concrete, 1 inch of
,sand, 6 mil visqueen, 2 inches of sand and subgrade soil. Contractors should be advise that when
: pouring during hot or windy weather conditions, they should provide large slabs with sufficiently deep
,weakened plane joints to inhibit the development of irregular or unsightly cracks. Also, 4 inch thick
i slabs should be jointed in panels not exceeding 12 feet in both directions to augment proper crack
: direction and development. Sands encountered on the site may qualify as slab underlayment.
: Reinforcement
: Continuous footings should be reinforced with a minimum of one number 4 steel bar plaoed at the
,top and one at the bottom. Slabs should be reinforoed with a minimum of number 3 steel bars
. plaoed at the center of thickness at 18-inch centers both ways or welded wire fabric equivalent to
110x10 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
Ithe structural engineering design.
w. C. HOBBS, CONSULTING ENGINEER
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I Mr. Sean Malek, Lot 28, Tr. 9833.1
I Project No: 01036-1
Page: 5
I Recommendations, continued
I Retaining Walls
I Retaining walls 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
: ground surface atthe back of the wall. The active pressures indicated in the table are equivalentfluid
: densities. Walls that are not free to rotate or that are braced at the top should use active pressures
I that are 50% greater than those indicated in the table.
RETAINING WALL DESIGN PRESSURES
Slooeof
adiacent around
Active Pressure
Passive Pressure
LEVEL
2:1
30 pet
40 pet
300 pet
200 pet
. These pressures are for retaining walls 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
i aminimum of 90 percent relative compaction in order to achieve their design strength. Failure to
: provide proper drainage and minimum compaction may resu~ in pressures against the wall that will
i 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.
I Lateral Loads
. The bearing value of the soil may be increased by one third for short duration loading (wind,
I seismic). Lateral.loads may be resisted by passive forces developed along the sides of concrete
footings or by friction along the bottom of concrete footings. The value of the passive resistance for
,level ground may be computed using an equivalentfluid density of 300 pet for level ground. The total
force should not exceed 3000 psf. A coefficient 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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I Mr. Sean MaJek, Lot 28, Tr. 9833-1
, Project No: 01036-1
Page: 6
I Recommendations, continued
I Fine Grading
, Fine grading of areas outside of the residence should be a=mplished such that positive drainage
: exists away from all footings. Run-off should be conducted off the property in a non erosive manner
: toward approved drainage devices at the street or the rear of the property per approved plans.
I 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.
I Grading Plan Review
. The grading plan should be reviewed prior to the grading to verify that the recommendations of this
'report are implemented for remedial grading and to assist in verifying extent and depth of
i excavations based on actual building placement and elevation with respect to existing ground
i surface. This review is additional and beyond the scope of this report.
W. C. HOBBS, CONSULTING ENGINEER
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. Mr. Sean Malek, Lot 28, Tr. 9833-1
Project No: 01036-1
Page: 7
CLOSURE
, This evaluation was performed in a=rdance with generally accepted engineering practices. The
I conclusions and recommendations contained in this report were based on the data available and the
i interpretation of such data as dictated by our experience and background. Hence, our conclusions
I 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 further service, please do not hesitate to call our office.
i Respectfully Submitted,
I W. C. HOBBS, CONSULTING ENGINEER
bs, RCE 42265
: CMI Engineer
: Distribution:
: Attachments:
Addressee (4)
Appendix A - Summary of Laboratory and Field Test Results
Appendix 8 - General Earthwork and Grading Specifications
Plate 1, Trench Location Map
W. C. HOBBS, CONSULTING ENGINEER
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APPENDIX A
SUMl\1ARY OF TEST RESULTS
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w. C. HOBBS, CONSULTING ENGINEER
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APPENDIX A
SUMMARY OF MAXIMUM DENSITY TEST RESULTS
Curve
Letter
Soil
Description
Maximum Optimum
Density oct Moisture %
A
SAND, fine to med..
Tan to Gray (SM)
122.7 10.8
Maximum density and optimum moisture determined in a=rdance with
test method ASTM D 1557-78.
W. C. HOBBS, CONSULTING ENGINEER
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APPENDIX B
GENERAL EARTIIWORK AND GRADING SPECIFICATIONS
w. C. HOBBS, CONSULTING ENGINEER
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GENERAL EARTHWORK AND GRADING SPECIRCATlONS
1.0 I GENERAL INTENT
These specifications present general procedures and requirements for grading and earthwork as shown on the approved grading plans,
including preparation of areas to be filled, placement of fill, installation of subdrains, and excavations. The recommendations contained in the
geotechnical report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case
of conflict. Evaluations performed by the consultant during the course of grading mayresu~ in new recommendations of the geotechnical report.
2.0 I EARTHWORK OBSERVATION AND TESTING
Prior tol the commencement of grading, a qualified geotechnical consultant (soils engineer and engineering geologist, and their
representatives) shall be employed for the purpose of observing earthwork and testing the fills for conformance with the recommendations
of the geotechnical report and these specifications.
It will be necessary that the consultant provide adequate testing and observation so that he may determine that the work was aocomplished
as specified. It shall be the responsibility of the contractor to assist the consultant and keep him apprised of work schedules and changes so
that he may schedule his personnel accordingly.
It shall be the sole responsibility of the contractor to provide adequate equipment and methods to aooomplish the work in aocordance with
applicable grading codes or agency ordinances, these specifications and the approved grading plans. If in the opinion of the consultant,
unsatisfactory conditions, such as questionable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resu~ing in
a quality of work less than required in these specifications, the consultant will be empowered to reject the work and recommend that
construction be topped until the conditions are rectified,
Maximum dry density tests used to determine the degree of compaction will be performed in aooordance with the American SocietyofT esting
and Materials tests method ASTM D 1557-78.
3.0 ! PREPARATION OF AREAS TO BE FILLED
3.1 Clearing and Grubbing;'A11 brush, vegetation and debris shall be removed or piled and otherwise disposed of.
3.2 Processing: The existing groundwhich is determined to be satisfactoryfor support of fill shall be scarified to a minimum depth of 6 inches.
Existing;ground which is not satisfactory shall be over excavated as specified in the following section.
Scarification shall continue until the soils are broken down and free of large clay lumps or clods and until the working surface is reasonably
uniform and free of uneven features which would inhibit uniform compaction.
3.3 Overexcavation: Soft, dry, spongy, highlyfracturedorotherwise unsuitable ground, extending to such a depth that the surface processing
cannot adequately improve the condition, shall be over excavated down to firm ground, approved by the consultant.
3.4 Moisture Conditioning: Over excavated and processed soils shall be watered, dried-back, blended, and/or mixed, as required to attain
a uniform moisture content near optimum.
3.5 Recompaction: Over excavated and processed soils which have been properly mixed and moisture- conditioned shall be recompacted
to a minimum relative compaction of 90 percent.
3.6 Benching: Where fills are to be placed on ground with slopes steeper than 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 firm material, and shall be
approved by the consultant. 0ther benches shall be excavated in firm material for a minimum width of 4 feet. Ground sloping flatter than 5
: 1 shall be benched or otherwise over excavated when considered necessary by the consultant.
3.], Approval: All areas to receive fill, including processed areas, removal areas and toe-of-fill benches shall be approved by the consultant
prior to fill placement.
W, C. HOBBS, CONSULTING ENGINEER
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4.0 I RLL MATERIAL
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 poor gradation, expansion, or strength characteristics shall be placed in areas designated by consultant or shall be mixed
with other soil~ to serve as satisfactory fill material.
4.2 Oversize: 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 the location, materials, and disposal methods are spec~ically approved by the consultant. Oversize disposal
operations shall be such that nesting of oversize material does not occur, and such that the oversize material is completely surrounded by
compacted or dens~ied fill. Oversize material shall not be placed within 10 feet vertically of finish grade or within the range of future utilities or
underground construction, unless spec~ically approved by the consultant.
4.3 Import: If importing of fill material is required for grading, the import material shall meet the requirements of Section 4. 1.
5.0 I FILL PLACEMENT AND COMPACTION
5.1 Fill Lifts: Approvedfill material shall be placed in areas prepared to receive fill in near-horizontal layers not exceeding 6 inches in compacted
thickness, The consultant may approve thicker lifts ~ testing indicates the grading procedures are such that adequate compaction is being
achieved with lifts of greater thickness. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to attain un~ormity
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
scarification or shall be blended with drier material. Moisture-conditioning and mixing of fill layers shall continue until the fill material is at a
un~orm moisture content or near optimum.
5.3 Compaction of Fill: After each layer has been evenly spread, moisture conditioned, and mixed, it shall be un~ormly compacted to not
less thar190 percent of maximum dry density. Compaction equipment shall be adequately sized and shall be either spec~ically designed for
soil compaction or of proven reliability, to efficiently achieve the spec~ied degree of compaction.
5.4 Fill Slopes: Compaction of slopes shall be aocomplished, in addition to normal compacting procedures, by backfilling of slopes with
sheepsfoot rollers at frequent increments of 2to 3 feet in fill elevation gain, or byothermethods producing satisfactory results. Atthecompletion
of gradi~g, the relative compaction of the slope out to the slope face shall be at least 90 percent.
5.5,Compaction Testing: Field tests to check the ill moisture and degree of compaction will be performed by the consultant. The location
and frequency of tests shall be at the consultanfs discretion. In general, the tests will be taken at an interval not exceeding 2 feet in vertical
rise ancVor 1,000 cubic yards of embankment.
6.0 :SUBDRAlN INSTALLATION
Subdrain systems, ~ required, shall be installed in approved ground to conform to the approximate alignment and details shown on the plans
or herein. The subdraln location or materials shall not bechanged or modITiedwithoutthe 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 surveys, prior to commencement of filling over the subdrains.
W. C. HOBBS, CONSULTING ENGINEER
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7.0
. EXCAVATION
Excavation and cut slopes will be examined during grading. ~ directed by the consultant, further excavation or over excavation and refilling of
cut areas shall be performed, and/or remedial grading of cut slopes shall be performed, Where fiil-over-cut slopes are to be graded, unless
otherwise approved, the cut portion of the slope shall made and approved by the consultant prior to placement of materials for construction
of the fiil portion of the slope.
8.0 'TRENCH BACKRLL
8.1, Supervision: Trench excavations for the utility pipes shall be backfiiled under engineering supervision.
8.2 Pipe Zone: After the utiiity pipe has been laid, the space under and around the pipe shall be backfiiled with clean sand or approved
granular soil to a depth of at least one foot over the top of the pipe. The sand backfiil shall be unfformly jetted into place before the controlled
backfill Is placed over the sand.
8.3 Fill Rlacement: The onstte materials, orother soiis approved by the engineer, shall be watered and mixed as necessarypriorto placement
in lifts over the sand backfill.
8.4 Compaction: The controlled backfiil shall be compacted to at least 90 percent of the maximum iaboratory density as determined by the
ASTM compaction method described above.
8.5 Observation and Testing: Fielddensitytests and inspection of the backfiil procedures shall be made by the soil engineer during backfilling
too see that the proper moisture content and unfform 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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