HomeMy WebLinkAboutGeotechnical Rpt Lots 1-5 Pse 11, Lots 6-15 4/22/20031
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N PETRA
OFFICES IN THE COUNTIES OF
ORANGE • SAN DIEGO • RIVERSIDE • LOS ANGELES • SAN BERNARDINO
April 22, 2003
J.N. 188-01
BGR No. 010340
RICHMOND AMERICAN HOMES
100 East San Marcos Boulevard, Suite 100
San Marcos, California 92069
Attention: Mr. Gary McCoy
Subject: Geotechnical Report of Rough Grading, Lots 1 through 5 (Phase 11)
and Lots 6 through 15 (Phase 12), Tract 23066-3, Temecula Area,
Riverside County, California
This report presents a summary of the observation and testing services provided by
Petra Geotechnical, Inc. (Petra) during rough -grading of Lots I through 5 (Phase 11)
and Lots 6 through 15 (Phase 12) within Tract 23066-3 located in the Temecula area
of Riverside County, California. Conclusions and recommendations pertaining to the
suitability of the grading for the proposed residential construction are provided herein,
as well as foundation -design recommendations based on the as -graded soil conditions.
REGULATORY COMPLIANCE
Cuts, overexcavation of unsuitable low-density surface soils, transition -lot
overexcavations and capping and placement of compacted fill under the purview of
this report have been completed under the observation and with selective testing by
Petra. The earthwork was performed in accordance with the recommendations
presented in previous geotechnical reports by Petra (see References) and the grading
code of the County of Riverside. Previous grading associated with the adjacent golf
course was addressed in our December 2001 report (see References).
PETRA GEOTECHNICAL, INC.
41640 Corning Place . Suite 107 . Murrieta . CA 92562 • Tel: (909) 600-9271 . Fax: (909) 600-9215
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 2
The completed earthwork has been reviewed and is considered adequate for the
construction now planned. On the basis of our observations, as well as field and
laboratory testing, the recommendations presented in this report were prepared in
conformance with generally accepted professional engineering practices in the area and
no further warranty is implied nor made.
SUMMARY OF AS -GRADED SOIL AND GEOLOGIC CONDITIONS
As -Graded Conditions and Remedial Grading
Remedial grading included overexcavations of low-density/surficial soils on the order
of 3 to 8 feet deep, compacted -fill placement to bring the subject lots to design grade
and the overexcavation and fill placement within the cut and shallow fill portions of
cut/fill transition lots. The compacted fills ranged in thickness from approximately 3
to 15 feet. A lot -by -lot summary of the compacted -fill depths and a summary of soil
or bedrock conditions is presented in the attached Table I. Lots 4, 8 and 12 through 15
were left as cut lots exposing competent bedrock. A general description of the as -
graded soil and bedrock materials underlying the subject lots is provided below and
are shown on the attached Geotechnical Map with Density Test Locations (Plate 1).
• Artificial Fill - Compacted (mapss)mbol afc) —Compacted -fill soils placed during
grading were comprised of onsite -derived and imported soil and bedrock materials
and consisted generally of fine to coarse sand, silty sand and clayey sand. Imported
materials were generated from adjacent properties.
• Pauba Formation Bedrock (Oosl — In general, the Pauba Formation consisted of
dense, fine-grained and well -graded sandstones, clayey sandstone and clay beds
with occasional gravel and cobble beds. A cross -bedded, well -graded, &fable sand
unit was also observed within the bedrock.
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RICHMOND AMERICAN HOMES
TR 23066-3 Lots 1-4 & 6-15/Temecula Area
Groundwater
No groundwater or seepage was encountered during site grading.
SUMMARY OF EARTHWORK
OBSERVATIONS AND DENSITY TESTING
Clearing and Grubbing
April 22, 2003
J.N. 188-01
Page 3
Vegetation that existed in localized areas, as well as miscellaneous debris, were
removed from the site.
Ground Preparation
Prior to placing structural fills, existing low-density surficial soils, consisting of non -
engineered fill topsoil, alluvium, colluvium and weathered bedrock, were first
overexcavated to competent undisturbed bedrock. Overexcavations varied from
approximately 3 to 8 feet.
Prior to placing fill, exposed bottom surfaces in overexcavated areas were observed
by a Petra representative. Following this observation, the exposed bottom surfaces
were scarified to depths of approximately 6 to 8 inches, watered or air-dried as
necessary to achieve a moisture content slightly above optimum moisture content and
then compacted by rolling with loaded scrapers.
Subdrain
A subdrain system consisting of 6- and 8 -inch diameter perforated pipe and gravel
enclosed with filter fabric was installed within the canyon bottom, commencing below
a portion of Yucca Street and extending easterly to its terminus at the slope face of
Lot 130. The approximate location of the subdrain is shown on the enclosed Plate 1.
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
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Cut/Fill Transition Lots
To reduce the potential for distress to residential structures related to the differential
settlement, the cut portions of cut/fill transition Lots I through 3, 5 through 7 and 9
through 11 were overexcavated to depths of approximately 3 to 10 feet below finish
grade and capped with compacted fill derived from onsite materials.
Fill Slopes
Fill slopes were constructed at a ratio of approximately 2:1 (horizontal:vertical [h:v[)
and to heights of up to approximately 10 feet. The graded -fill slopes were overfilled
during construction and then track -walked and cut-back to expose the compacted -slope
face. Fill slopes were constructed on level keys which were approximately 15 feet
wide and excavated into Pauba Formation bedrock. The fill slopes are considered
grossly and surficially stable to the heights and inclinations at which they were
constructed.
Cut Slopes
Cut slopes were constructed at a ratio of approximately 2:1 (h:v) to heights of
approximately 5 feet. The cuts extended into competent Pauba Formation bedrock and
are considered grossly and surficially stable at the heights and inclinations at which
they were constructed.
Fill Placement and Testing
Fill soils were placed in thin lifts, watered or air-dried as necessary to achieve near -
optimum moisture conditions and then compacted in-place. Compaction was achieved
by wheel -rolling with a compactor or loaded scrapers. The deepest fill placed within
the subject lots was approximately 15 feet on Lot 6.
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 5
Field density and moisture content tests were performed in accordance with nuclear -
gauge test methods (ASTM D2922 and D3017). Occasional field density tests were
also performed in accordance with the sand -cone method (ASTM D1556). Field
density test results are presented in the attached Table 11 and approximate test locations
are shown on Plate 1.
Field density tests were taken at vertical intervals of approximately 1 to 2 feet. The
compacted fills were tested at the time of placement to document that the specified
moisture content and relative compaction had been achieved. One in-place density test
was taken for approximately each 1,000 cubic yards of fill placed and/or for each
approximately 2 feet in vertical height of compacted fill. The actual number of tests
taken per day varied with the project conditions, such as the number of earthmovers
(scrapers) and availability of support equipment. When field density tests produced
results less than the specified relative compaction of 90 percent or if the soils were
found to be above or below a recommended moisture content, the approximate limits
of the substandard fill were established. The substandard area was then either removed
or reworked in-place. Visual classification of earth materials in the field was the basis
for determining which dry density value was applicable for a given density test.
LABORATORY TESTING
Laboratory Maximum Dry Density
Maximum dry density and optimum moisture content of representative samples of fill
soils were determined in our laboratory in accordance with ASTM D1557. Pertinent
test values are summarized in Appendix A.
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 6
Expansion Index Tests
Expansion index tests were performed on representative samples of soil existing at or
near finish -pad grade within the subject lots. These tests were performed in
accordance with ASTM D4829. Test results indicated soils near pad grade have a
VERY LOW expansion potential and are summarized in Appendix A.
Soluble Sulfate Analyses
Soluble sulfate contents were determined for representative samples of soil existing
at or near finish grade within the subject lots. These tests were performed in
accordance with California Test Method (CTM) No. 417. Test results are provided in
Appendix A.
Chloride, Resistivity and pH Analyses
Water-soluble chloride concentration, resistivity and pH values were determined for
selected samples in accordance with CTM Nos. 422 (chloride) and 643 (resistivity and
pH). The results of these analyses are provided in Appendix A.
CONCLUSIONS AND RECOMMENDATIONS
Foundation -Design Recommendations
Foundation Types
Based on as -graded soil and geologic conditions, the use of conventional spread
footings with slab -on -grade foundations is considered feasible for the subject lots.
Allowable Soil -Bearing Capacities
An allowable soil -bearing capacity of 1,500 pounds per square foot (psf) may be used
for 24 -inch square pad footings and 12 -inch wide continuous footings founded at a
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 7
depth of 12 inches or more below the lowest adjacent final grade or top -of -slab. This
value may be increased by 20 percent for each additional foot of depth, to a value of
2,500 psf. Recommended allowable soil -bearing values include both dead and live
loads and maybe increased by one-third when designing for short -duration wind and
seismic forces.
Anticipated Settlement
Based on the general settlement characteristics of the compacted fill soils, as well as
the anticipated loading, it has been estimated that the total settlement of building
footings is anticipated to be less than approximately 3/4 inch. Differential settlement
over a horizontal distance of 30 feet is expected to be about one-half the total
settlement. The anticipated differential settlement may be expressed as an angular
distortion of 1:960.
Lateral Resistance
A passive earth pressure of 250 psf per foot of depth to a value of up to 2,500 psf may
be used to determine lateral -bearing resistance for building footings. Where structures
such as masonry block walls and retaining walls are planned on or near descending
slopes, the passive earth pressure should be reduced to 150 psf per foot of depth to a
value of up to 1,500 psf. An increase of one-third of the above values may also be
used when designing for short -duration wind and seismic forces. hi addition, a
coefficient of friction of 0.40 times the dead -load forces may also be used between
concrete and the supporting soils to determine lateral -sliding resistance.
The above values are based on footings placed directly against compacted fill or Pauba
Formation sandstone. In the case where footing sides are formed, backfill against the
footings should be compacted to 90 percent or more of the maximum dry density.
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 8
Footing Observations
Footing trenches should be observed by a representative of Petra to document that they
have been excavated into competent -bearing soils and to the recommended
embedments. The foundation excavations should be observed prior to the placement
of forms, reinforcement or concrete. The excavations should be trimmed neat, level
and square. Loose, sloughed or moisture -softened soil and construction debris should
be removed prior to placing concrete. Excavated soils derived from footing
excavations should not be placed within slab -on -grade areas.
Expansive Soil Considerations
Laboratory testing of soils within the site indicate soils exhibit VERY LOW
expansion potential as classified in accordance with 1997 UBC Table 18 -I -B.
Very Low Expansion Potential (Expansion Index of 20 or less)
The results of our laboratory tests indicate that onsite soils of the subject lots exhibit
VERY LOW expansion potential as classified in accordance with 1997 UBC
Table 18 -I -B. For this condition, it is recommended that footings and floors be
constructed and reinforced in accordance with the following criteria. However,
additional slab thickness, footing sizes and/or reinforcement may be required by the
project architect or structural engineer.
• Footines
- Standard depth footings may be used with respect to building code requirements
for the planned construction (i.e., 12 inches deep for one-story construction and
18 inches deep for two stories). Interior continuous footings for one- or two-
story construction may be founded at a depth of 12 inches or greater below the
top -of -slab. Continuous footings should have a width of 12 and 15 inches or
more for one- and two-story buildings, respectively, and should be reinforced
with two No. 4 bars, one top and one bottom.
' RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
' Page 9
Isolated interior pad footings should be 24 inches or more square and founded
' at a depth of 12 inches.or more below the top -of -slab and reinforced in
accordance with the recommendations of the structural engineer.
' Isolated exterior pad footings should be 24 inches or more square and founded
at a depth of 18 inches or more below the lowest adjacent grade and reinforced
in accordance with recommendations of the structural engineer.
' Floor Slabs
' Living -area concrete -floor slabs should be 4 inches or more thick and reinforced
with either 6x6-W1.4xW1.4 welded -wire mesh or with No. 3 bars spaced 24
' inches on -centers, both ways. Slab reinforcement should be properly supported
so that placement is mid -depth.
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- Living -area concrete floors should be underlain with a moisture -vapor retardant
consisting of 6 -mil thick polyethylene membrane or equivalent. Laps within the
membrane should be sealed and 2 inches or more of clean sand be placed over
the membrane to promote uniform curing of the concrete.
- Garage -floor slabs should be 4 inches or more thick and placed separately from
adjacent wall footings with a positive separation maintained with 3/8 inch felt
expansion joint materials and quartered with weakened plane joints. A 12 -inch
wide grade beam founded at the same depth as adjacent footings should be
provided across garage entrances. The grade beam should be reinforced with
two No. 4 bars, one top and one bottom and in accordance with the
recommendations of the structural engineer.
Prior to placing concrete, subgrade soils should be thoroughly moistened to
promote uniform curing of the concrete and reduce the development of
shrinkage cracks.
SEISMIC -DESIGN CONSIDERATIONS
Ground Motions
Structures within the site should be designed and constructed to resist the effects of
seismic ground motions as provided in 1997 UBC Sections 1626 through 1633. The
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
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method of design is dependent on the seismic zoning, site characteristics, occupancy
category, building configuration, type of structural system and on the building height.
For structural design in accordance with the 1997 UBC, a computer program
developed by Thomas F. Blake (UBCSEIS, 1998/1999) was utilized which compiles
fault information for a particular site using a modified version of a data file of
approximately 150 California faults that were digitized by the California Division of
Mines and Geology and the U.S. Geological Survey. This program computes various
information for a particular site including the distance of the site from each of the
faults in the data file, the estimated slip -rate for each fault and the "maximum moment
magnitude" of each fault. The program then selects the closest Type A, Type B and
Type C faults from the site and computes the seismic design coefficients for each of
the fault types. The program then selects the largest of the computed seismic design
coefficients and designates these as the design coefficients for the subject site.
Based on the computer generated data using UBCSEIS, the Elsinore -Julian (Type A)
segment of the Elsinore fault zone, located approximately 12.1 kilometers west of the
site, could generate severe site ground motions with an anticipated maximum moment
magnitude of 7.1 and anticipated slip rate of 5.0 nun/year. However, the closest
Type B fault, which is the Elsinore -Temecula located approximately 1.3 kilometers to
the southwest of Tract 23066-3, would probably generate the most severe site ground
motions with an anticipated maximum moment magnitude of 6.8 and anticipated slip
rate of 5.0 mm/year. Based on our evaluation using UBCSEIS, the following 1997
UBC seismic design coefficients are recommended for the proposed residential
structures. These criteria are based on the soil profile type as determined by existing
subsurface geologic conditions, on the proximity of the Elsinore -Temecula fault and
on the maximum moment magnitude and slip rate.
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RICHMOND AMERICAN HOMES
TR 23066-3 Lots 1-4 & 6-15/Temecula Area
SOIL CORROSIVITY
April 22, 2003
J.N. 188-01
Page 11
The corrosion potential of the on-site materials was evaluated for its effect on steel and
concrete. The corrosion potential was evaluated using the results of laboratory tests on
representative samples of the near -surface soils. Laboratory testing was performed to
evaluate pH, minimum electrical resistivity, and chloride and soluble sulfate content.
The test results indicate that the pH of the samples of soil tested was 7.3 and 7.4.
Measured electrical resistivity of 4,000 and 4,900 ohm -cm indicated that the site soils
may be considered moderately corrosive to ferrous metals. Metal piping should be
corrosion protected or consideration should be given to using plastic piping instead of
metal.
Testing further indicates soluble sulfate contents of at 0.0122 and 0.0081 percent and
chloride contents of 130 and 150 ppm. We recommend that Type I1 modified cement
be used. We further recommend that a 3 -inch thick concrete cover be maintained over
the reinforcing steel for concrete in contact with the soil. If desired, a corrosion
engineer may be consulted to provide additional recommendations.
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1997 UBC TABLE
FACTOR
Figme 16-2 Seismic Zone
4
16-1
Seismic Zone Factor Z
0.4
16-U
Seismic Source Type
B
16-J
Soil Profile Type
Sp
16-S
Near -Source Factor N,
13
16-T
Near -Source Factor N,
1.6
16-Q
Seismic Coefficient C.
0.44 N, = 0.57
16-R
Seismic Coefficient C.
0.64 N, = 1.02
SOIL CORROSIVITY
April 22, 2003
J.N. 188-01
Page 11
The corrosion potential of the on-site materials was evaluated for its effect on steel and
concrete. The corrosion potential was evaluated using the results of laboratory tests on
representative samples of the near -surface soils. Laboratory testing was performed to
evaluate pH, minimum electrical resistivity, and chloride and soluble sulfate content.
The test results indicate that the pH of the samples of soil tested was 7.3 and 7.4.
Measured electrical resistivity of 4,000 and 4,900 ohm -cm indicated that the site soils
may be considered moderately corrosive to ferrous metals. Metal piping should be
corrosion protected or consideration should be given to using plastic piping instead of
metal.
Testing further indicates soluble sulfate contents of at 0.0122 and 0.0081 percent and
chloride contents of 130 and 150 ppm. We recommend that Type I1 modified cement
be used. We further recommend that a 3 -inch thick concrete cover be maintained over
the reinforcing steel for concrete in contact with the soil. If desired, a corrosion
engineer may be consulted to provide additional recommendations.
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iRICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
iPage 12
RETAINING WALLS
iFooting Embedments
iThe
base of retaining -wall footings constructed on level ground may be founded at a
depth of 12 or more inches below the lowest adjacent final grade. Where retaining
iwalls
are constructed on or within 15 feet from the top of adjacent descending fill
slope, the footings should be deepened such that a horizontal setback of H/3 (one-third
ithe
slope height) is maintained between the outside bottom edges of the footings and
the slope face; however, the footing setback should be 5 feet or more. The above -
recommended footing setbacks are preliminary and may require revision based on site-
specific soil and/or bedrock conditions. Footing excavations should be observed by
ithe
project geotechnical consultant to document that they have been excavated into
competent -bearing soils and/or bedrock and to the embedments recommended above.
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These observations should be performed prior to placing forms or reinforcing steel.
iActive Earth Pressures
i An active lateral -earth pressure equivalent to a fluid having a density of 40 pounds per
cubic foot (pc0 may be used for design of cantilevered walls retaining a drained, level
i granular backfill. Where the wall backfill slopes upward at 2:1 (h:v), the above value
should be increased to 63 pcf. Retaining walls should be designed to resist surcharge
' loads imposed by other nearby walls or structures in addition to the above active earth
pressures.
iDrainage
iA perforated pipe -and -gravel subdrain should be installed behind retaining walls up
to 6 feet in height to reduce the likelihood of entrapment of water in the backfill.
iPerforated pipe should consist of 4 -inch diameter or larger PVC Schedule 40 or ABS
SDR -35, with the perforations laid down. The pipe should be embedded in 1.5 cubic
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 13
feet per foot of 0.75- to 1.5 -inch open -graded gravel wrapped in filter fabric. Filter
fabric may consist of Mirafi 140N or equivalent.
In lieu of a pipe and gravel subdrain, weepholes or open vertical masonry joints may
be considered for retaining walls not exceeding a height of approximately 3 feet.
Weepholes, if used, should be 3 inches or more in diameter and provided at intervals
of 6 feet or less along the wall. Open vertical masonry joints, if used, should be
provided at no more than 32 -inch intervals. A continuous gravel fill, 12 inches by 12
inches, should be placed behind the weepholes or open masonry joints. The gravel
should be wrapped in filter fabric to reduce the likelihood of infiltration of fines and
subsequent clogging of the gravel. Filter fabric may consist of Mirafi 140N or
equivalent.
Retaining walls greater than 6 feet high should be provided with a continuous
backdrain for the full height of the wall. This drain could consist of a geosynthetic
drainage composite, such as Miradrain 6000 or equivalent or a permeable drain
material, placed against the entire backside of the wall. If a permeable drain material
is used, the backdrain should be 1 or more feet thick. Caltrans Class II permeable
material or open -graded gravel or crushed stone (described above) may be used as
permeable drain material. If gravel or crushed stone is used, it should have less than
5 percent material passing the No. 200 sieve. The drain should be separated from the
backfill with a geofabric. The upper 1 foot of the backdrain should be covered with
compacted fill. A drainage pipe consisting of 4 -inch diameter perforated pipe
(described above) should be provided along the back of the wall. The pipe should be
placed with perforations down. The drain and pipe should be sloped at 2 percent or
more and discharge to an appropriate outlet through a solid pipe. If a geosynthetic
drainage composite is used, the perforated pipe should be surrounded by 1 cubic foot
per foot of gravel or crushed rock wrapped in a fitter fabric. The pipe should outlet
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 14
away from structures and slopes and the wall should be appropriately waterproofed.
The backfilled portions of retaining walls should be coated with an approved
waterproofing compound to inhibit migration of moisture through the walls.
Temporary Excavations
To facilitate retaining -wall construction, temporary excavations greater than 5 feet
should be cut back at a gradient of 1:1 (h:v) or flatter for the duration of construction.
However, temporary slopes should be observed by the project geotechnical consultant
for evidence of potential instability. Depending on the results of these observations,
flatter temporary slopes may be recommended. The potential effects of various
parameters, such as weather, heavy equipment travel, storage near the tops of the
temporary excavations and construction scheduling should also be considered in the
stability of temporary slopes.
Wall Backfill
Retaining -wall backfill should be placed in 6- to 8 -inch loose lifts, watered or air-dried
as necessary to achieve near -optimum -moisture conditions and compacted in place to
a relative compaction of 90 percent or more as evaluated by ASTM D 1557.
MASONRY BLOCK WALLS
Construction on or Near the Tops of Descending Slopes
Continuous footings for masonry block walls proposed on or within 7 feet from the top
of descending slopes should be deepened such that a horizontal clearance of 5 or more
feet is maintained between the outside bottom edge of the footing and the slope face.
The footings should be reinforced with two No. 4 bars, one top and one bottom for
Very Low expansion soils and in accordance with the recommendations provided by
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 15
structural engineer. Plans for top -of -slope block walls proposing pier and grade -beam
footings should be reviewed by Petra prior to construction.
Construction on Level Ground
Where masonry block walls are proposed on level ground and 5 feet or more from the
tops of descending slopes, the footings for these walls may be founded at depth of 12
or more inches below the lowest adjacent final grade. These footings should also be
reinforced with two No. 4 bars, one top and one bottom for Very Low expansion soils
and in accordance with the recommendations of the structural engineer.
Construction Joints
In order to mitigate the potential for unsightly cracking related to the effects of
differential settlement, positive separations (construction joints) should be provided
in the walls at horizontal intervals of approximately 25 feet and at each comer. The
separations should be provided in the blocks only and not extend through the footings.
The footings should be placed monolithically with continuous rebars to serve as
effective "grade beams" along the full lengths of the walls.
CONCRETE FLATWORK
Thickness and Joint Spacing
Concrete sidewalks and patio -type slabs should be 4 inches or more thick and provided
with construction joints every 6 feet or less. Concrete -driveway slabs should be 4
inches or more thick and provided with construction joints quartering the slab, but no
more than 10 feet apart.
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 16
Subgrade Preparation
As a further measure to reduce cracking of concrete flatwork, the subgrade soils below
concrete- flatwork areas should first be compacted to a relative density of 90 percent
or more, as evaluated by ASTM D1557. Water should be added then to achieve a
moisture content that is equal to or slightly greater than optimum moisture content.
This moisture should extend to a depth of 12 inches below subgrade and maintained
in the soils during placement of concrete. Pre -watering of the soils will promote
uniform curing of the concrete and reduce the development of shrinkage cracks. A
representative of the project soils engineer should observe and document the density
and moisture content of the soils and the depth of moisture penetration prior to placing
concrete.
PLANTERS
Area drains should be extended into planters that are located within 5 feet of building
walls, foundations, retaining walls and masonry block garden walls to reduce
infiltration of water into the adjacent foundation soils. The surface of the ground in
these areas should also be sloped at a gradient of 2 percent or more away from the
walls and foundations. Drip -irrigation systems are also recommended to reduce the
likelihood of overwatering and subsequent saturation of the adjacent foundation soils.
UTILITY TRENCHES
Utility -trench backfill within street right-of-ways, utility easements, under sidewalks,
driveways and building -floor slabs, as well as within or in proximity to slopes should
be compacted to a relative density of 90 percent or more as evaluated by ASTM
D1557. Soils utilized as backfill should be mechanically compacted. Density testing,
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area. J.N. 188-01
Page 17
along with probing, should be performed by the project soils engineer or his
representative, to document proper compaction.
For trenches with vertical walls, backfill should be placed in approximately 1- to 2 -
foot thick loose lifts and then mechanically compacted with a hydra -hammer,
pneumatic tampers or similar equipment. For trenches with sloped -walls, backfill
materials should be placed in approximately 8- to 12 -inch thick loose lifts and then
compacted by rolling with a sheepsfoot tamper or similar equipment.
To avoid point -loads and subsequent distress to clay, cement or plastic pipe, imported
sand bedding should be placed l foot or more above pipe in areas where excavated
trench materials contain significant cobbles. Bedding materials should be
mechanically compacted to 90 percent or more relative compaction as evaluated by
ASTM D1557 and tested. Flooding of sand bedding should not be allowed.
Where utility trenches are proposed parallel to building footings (interior and/or
exterior trenches), the bottom of the trench should not be located within a l: l (h:v)
plane projected downward from the outside bottom edge of the adjacent footing.
SLOPE LANDSCAPING AND MAINTENANCE
The engineered slopes within the subject tract are considered grossly and surficially
stable and are expected to remain so under normal conditions provided the slopes are
landscaped and maintained thereafter in accordance with the following
recommendations.
• Compacted -earth berms should be constructed along the tops of the engineered fill
slopes, as well as natural slopes, to reduce the likelihood of water from flowing
directly onto the slope surfaces.
U
I
' During construction of terrace drains, downdrains or earth benns, care should be
taken to avoid placement of loose soil on the slope surfaces.
RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
'
Page 18
• The engineered cut and fill slopes should be landscaped as soon as practical when
'
irrigation water is available. The landscaping should consist of deep-rooted,
'
drought -tolerant and maintenance -free plant species. A landscape architect should
be consulted to determine suitable groundcover. If landscaping cannot be provided
'
within a reasonable period of time, jute matting (or equivalent) or a spray -on
product designed to seal slope surfaces should be considered as a temporary
'
measure to reduce surface erosion until such a time that permanent landscape plants
'
have become well-established.
• Irrigation systems should be installed on the engineered slopes and a watering
'
program then implemented which maintains a uniform, near -optimum moisture
condition in the soils. Overwatering and subsequent saturation of the slope soils
'
should be avoided. On the other hand, allowing the soils to dry -out is also
detrimental to slope
performance.
• Irrigation systems should be constructed at the surface only. Construction of
'
sprinkler lines in trenches is not recommended.
' During construction of terrace drains, downdrains or earth benns, care should be
taken to avoid placement of loose soil on the slope surfaces.
F
I
• A permanent slope -maintenance program should be initiated for major slopes not
maintained by individual homeowners. Proper slope maintenance should include
the care of drainage and erosion -control provisions, rodent control and repair of
leaking or damaged irrigation systems.
• Provided the above recommendations are followed with respect to slope drainage,
'
maintenance and landscaping, the potential for deep saturation of slope soils is
considered low.
'
• Property owners should be advised of the potential problems that can develop when
drainage on the building pads and adjacent slopes are altered. Drainage can be
'
altered due to the placement of fill and construction of garden walls, retaining
and
walls, walkways, patios, swimming pools, spas planters.
F
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1
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1
1
1
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RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 19
POST -GRADING OBSERVATIONS AND TESTING
Petra should be notified at the appropriate times in order that we may provide the
following observation and testing services during the various phases of post grading
construction.
• Building Construction
- Observe footing trenches when first excavated to document specified depth and
competent soil -bearing conditions.
- Observe moisture conditioning of subgrade soils below living -area and garage
floor slabs to document moisture content and penetration.
• Retaining -Wall Construction
- Observe footing trenches when first excavated to document specified depth and
competent soil -bearing conditions.
- Observe and document proper installation of backdrain systems prior to placing
wall backfill.
- Observe and test placement of wall backfill to document specified compaction.
• Masonry Block -Wall Construction
Observe footing trenches when first excavated to document depth and presence
of competent soil -bearing conditions.
• Exterior Concrete-Flatwork Construction
- Observe and test subgrade soils below concrete-flatwork areas to document
compaction and moisture content.
• Utility -Trench Backfill
- Observe and test placement of utility -trench backfill to document specified
compaction.
0�0
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[]
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I
RICHMOND AMERICAN HOMES April 22, 2003
TR 23066-3 Lots 1-4 & 6-15/Temecula Area J.N. 188-01
Page 20
• Re -Gradin -
Observe and test placement of fill to be placed above or beyond the grades
shown on the approved grading plans.
This opportunity to be of service is sincerely appreciated. If you have questions, please
contact this office.
Respectfully submitted,
V, GREG\
m�Q No. 1257 nF�
CERTIFIED
Robert L. Gregorek Il
Principal Geologist
WC/RLG/CAC/keb
Cliffo A. �ft�
Principal Engineer
gOFESS;p.V
w v N0. GE00021)'-i }r^
�1�,nfl�
Attaclunents: Table I - Lot -By -Lot Summary of As -Graded Soil Conditions
Table 11 - Field Density Test Results (1989 and 1990)
Table III - Field Density Test Results (2002 and 2003)
References
Plate 1 - Geotechnical Map with Density Test Locations (in pocket)
Appendix A - Laboratory Test Criteria/Laboratory Test Data
Distribution: (1)
Addressee
(3)
Richmond American Homes
Attention: Ms. Theresa Johnson
(1)
Richmond American Homes - Field Office
Attention: Mr. Craig Peters
(2)
Riverside County Building and Safety
Attention: Mr. Mack Hakakian
(1)
Hunsaker & Associates
Attention: Mr. Dan Hosseninvadeh
(1)
Option One Consulting
Attention: Mr. Ross Kuster
OF
IkV
TABLE I Lots 1-5 and Lots 6-15, Tract 23066-3
LOT -BY -LOT SUMMARY OF SOIL CONDITIONS
Lot
Number
Maximum Fill
Depth (f[)
Minimum Fill
Thiclmess ft)
Estimated
Differential
Settlement
Soil Expansion
Index/Potential
Post -Tensioned
Slab
.Soil Condition
Codes*
Remarks
Phase I I
1
8
4
1:960
0/V Low
Optional
Z
2
8
4
1:960
0/V Low
Optional
Z
3
3
3
1:960
0/V Low
Optional
Z
4
0
0
1:960
0/V Low
Optional
Z
5
4
3
1:960
0/V Low
Optional
Z
Phase 12
6
15
8
1:960
0/V Low
Optional
Z
7
5
5
1:960
0/V Low
Optional
Z
8
0
0
1:960
0/V Low
Optional
Z
9
6
3
1:960
0/V Low
Optional
Z
10
6
3
1:960
0/V Low
Optional
Z
11
5
3
1:960
0/V Low
Optional
Z
12
0
0
1:960
0/V Low
Optional
Z
13
0
0
1:960
0/V Low
Optional
Z
14
0
0
1:960
IS/V Low
Optional
Z
-
IS
1 0
1 0
1 1:960
1 I8/V Low
Optional
Z
* per County of Riverside, Building and Safety Department Plan Check Memorandum dated April 5, 2001
Code Definitions (Reference: 1997 UBC):
E .Foundations for structures resting on soils with an expansion index greater than 20 (Section 1803.2)
C For corrosion protection, if Table 19-A-2 is applicable
S If exposure of concrete to sulfate -containing solutions is moderate or higher per Table I9 -A-4
D Differential deflection in the foundation due to differential settlement exceeds value in Table 18 -111 -GG (consider Pi cfab Roof Trusses) [noted if>1:480]
P If post -tensioned slab system is to be used
Z If none of the above is applicable
Plate T-1 1
TABLE 11
Field Density Test Results
Test
T
Test
-_yDens
RG-
'
Date
110.:Ylp
X.- x
016)
�O .. .. ...
... 't%
'T
03/29/89
A456
Embassy Ave
1203
8.7
117.3
92
5
04/04/89
A485
Lot 10
1207
10.5
108.4
84
2
04/04/89
A486
RT No. A485
--
10.5
116.2
90
2
04/04/89
A489
Lot 10
1212
8.7
118.7
92
2
04/04/89
A490
Lot 10
1209
12.4
118.9
92
12
04/04/89
A493
Embassy Ave
1205
11.1
117.8
91
2
04/05/89
A496
Embassy Ave
1208
11.1
120.5
92
12
04/05/89
A497
Lot 10
1215
11.1
118.6
92
2
04/06/89
A498
Lot 10
1215
10.5
116.1
90
2
04/06/89
A499
Lot 1
1216
11.1
117.3
91
22
04/06/89
A500
Embassy Ave
1212
11.1
119.5
93
2
04/06/89
A502
Lot 11
1217
9.9
116.3
90
2
04/10/89
A504
Embassy Ave
1213
11.1
118.8
92
2
04/10/89
A506
Lot 9
1217
12.4
116.9
91
2
04/10/89
A511
Embassy Ave
1219
11.7
114.3
90
N
04/10/89
A514
Embassy Ave
1218
10.5
118.4
92
2
04/14/89
A539
Lot 1
1221
12.4
116.2
90
2
PETRA GEOTECHNICAL, INC.
J.N. 188-01
1989-1990
TABLE T-11 1
TABLE III
Field Density Test Results
PETRA GEOTECHNICAL, INC. TR 23O6G-3/Lotsj^5(Phase 11\ APRIL 2003
N� J.N.88~0j �ndLot�G^15/�»h��m1�\ 7���E^���
` ' �y
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07/17/02
1857
Lot
1217.0
105
120.4
90*
ll
N�
�
07/19/02
^
1883
Lot}
1218.0
11.7
110.19l*
8
wm
07/19/02
1884
Lot
1221.0
10.5
1176
90*
9
07/26/02
1930
Lot ll
1214.0
10.5
121.0
91*
ll
N�
07/26/02
1931
Lot
1214.0
10.5
125.4
94*
ll
.~
08/05/02
1961
Lot
F(}
75
114.8
90*
3
08/05/02
1962
Lot
P(}
6.9
114.9
90*
3
N�
08/05/02
1963
Lot 3
F(}
4.7
1138
93*
10
08/05/02
1964
Lot
B(}
8.1
114.8
90*
3
08/05/02
1965
Lot 10
F{}
6.9
113.2
92*
10
08/05/02
1966
Lot ll
F{}
8.1
112.6
91*
10
03/07/03
1994
Yucca Street
1199.0
10.6
117.8
92
3
03/10/03
2010
Yucca Street
1199.0
11.2
117.1
92
3
w�
03/10/03
2012
}uodStrrrt
1198.0
10.1
1118
91
l]
03/10/03
2014
Yucca Street
1200.0
109
115.7
91
3
03/14/03
2031
Lot
1201.0
17.1
120.0
91
ll
w�
03/14/03
2032
Lot
1201.0
10.9
1202
91
|]
03/31/03
2087
Yucca St/8\u2l+0V
1206.0
9.0
119.5
90
14
0�
N�
03/31/03
2088
Lot
1203.0
8.8
1207
91
14
03{31/03
2089
Lot
1209.0
9.1
118.8
VO
14
03/31/03
2090
Yucca St/Otu2l+85
1212.0
10.3
121.6
92
14
0�
03/31/03
2091
Lot
1210.0
10.1
120.9
91
13
04/01/03
2092
Lot
1212.0
112
119J
90
13
04/01/03
2093
Lot
1214.0
10.9
1202
91
13
04/01/03
2094
Lot 6
1212.0
10.6
121.4
91
13
PETRA GEOTECHNICAL, INC. TR 23O6G-3/Lotsj^5(Phase 11\ APRIL 2003
N� J.N.88~0j �ndLot�G^15/�»h��m1�\ 7���E^���
` ' �y
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1�
REFERENCES
Blake, T.F., 1998/1999, "UBCSEIS" Version 1.03, A Computer Program for the Estimation of Uniform Building Code
Coefficients Using 3-D Fault Sources.
International Conference of Building Officials, 1997, Uniform Building Code, Volume 2, Structural Engineering
Design Provisions, dated April,
Earth Research Associates, Inc., 1987, Evaluation of Faulting and Liquefaction Potential, Portion of Wolf Valley
Project, Rancho California, County of Riverside, California, J.N. 298-87, dated November 20.
, 1988, Preliminary Soils Engineering and Engineering Geologic Investigation, Red Hawk Project, Rancho
California Area, County of Riverside, California, J.N. 298-87, dated February 2.
Kennedy, M.P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County,
California, CDMG Special Report 131.
Petra Geotechnical, Inc., 1989, Supplemental Soils Engineering and Engineering Geologic Investigation, Portion of
Redhawk Project, Vesting Tentative Tract Map Nos. 23064, 23065, 23066 and 23067, Rancho California,
County of Riverside, California, Volumes I and 11, J.N. 298-87, dated May 8.
, 2001a, Due -Diligence Geotechnical Assessment of Planned Grading and Site Development, Tracts 23066-1,
23066-2 and 23066-3, Redhawk Development, Temecula Area, Riverside County, California, J.N. 188-01,
dated March 30.
, 2001b, Supplemental Geotechnical Investigation, Tract 23066-3, Lot 129, Redhawk Development, Temecula
Area, Riverside County, California, J.N. 188-01, dated April, 18.
, 2001c, Response to Riverside County Geotechnical Report Review Sheet Dated April 24, 2001, Tracts
23066-1, 23066-2 and 23066-3, Redhawk Development, Temecula Area, Riverside County, California; for The
Garrett Group LLC, J.N. 188-01, dated December 11.
2001d, Documentation of Previous Interface Grading Adjacent to Golf Course Fairways, Tracts 23066-1,
23066-2 and 23066-3; Temecula Area of Riverside County, California, I.N. 188-01, dated December 10.
2001 e, Geotechnical Review of 40 -Scale Rough Grading Plans, Tracts 23066, 23066-1, 23066-2 and 23066-3,
Temecula Area of Riverside County, California, dated December 11.
, 2002a, Geotechnical Recommendations Regarding Expansive Soils, Tracts 23066-1, 23066-2, 23066-3 and
30246, Temecula Area, Riverside County, California, J.N. 188-01, dated March 20.
, 2002b, Response to Riverside County Building and Safety Department Geotechnical Report Review Sheet,
Dated February 21, 2002 and Grading Plan Review Report, Tract 30246, Temecula Area, Riverside County, -
California, BGR No. 020159, J.N. 188-01, dated March 21.
, 2002c, Geotechnical Design Parameters for Medium Expansive Soils, Tracts 23066-1, 23066-2, 23066-3 and
30246, Temecula Area, Riverside County, California, J.N. 188-01, dated March 26.
PETRA GEOTECHNICAL, INC. APRIL 2003
J.N. 188-01
)S
REFERENCES (Continued)
2002d, Preliminary Geotechnical Recommendations Regarding Expansive Soils, Model Lots, Tract 23066-1,
Lots 3 through 5, Temecula Area, Riverside County, California, J.N. 188-01, dated April 3.
, 2002e, Preliminary Geotechnical Recommendations Regarding Expansive Soils, Phase I, Tract 23066-2,
Lots 10 through 39, Temecula Area, Riverside County, California, J.N. 188-01, dated April 3.
2002£, Geotechnical Recommendations, Post -Tensioned Slabs, Tracts 23066-1, 23066-2, 23066-3 and 30246,
Temecula Area, Riverside County, California, J.N. 188-01, dated April 9.
2002g, Geotechnical Report of Rough Grading, Model Lots 1 through 8, Tract 23066-2, Temecula Area,
Riverside County, California, J.N. 188-01, dated April 26.
2002h, Geotechnical Report of Rough Grading, Lots 9 through 39, Tract 23066-2, City of Temecula,
Riverside County, California, J.N. 188-01, dated May 8.
, 2002i, Geotechnical Report of Rough Grading, Model Lots 92 through 95, Tract 23066-1, City of Temecula,
Riverside County, California, J.N. 188-01, dated May 30.
, 2002j, Geotechnical Report of Rough Grading, Lots 54 through 77 and 115, Tract 23066-1, City of Temecula,
Riverside County, California, J.N. 188-01, dated June 20.
2002k, Geotechnical Report of Rough Grading, Lots 40 through 82, Tract 23066-2, City of Temecula,
Riverside County, California, J.N. 188-01, dated August 13.
, 20021, Geotechnical Report of Rough Grading, Lots 39 through 95, Tract 23066-2, City of Temecula,
Riverside County, California, J.N. 188-01, dated August 27.
, 2003a, Geotechnical Report of Rough Grading, Lots 27 through 38, Tract 23066-3, Temecula Area, Riverside
County, California, J.N. 188-01, dated April 15.
, 2003b, Geotechnical Report of Rough Grading, Lots 18 through 26 and 96 through 98, Tract 23066-3,
Temecula Area, Riverside County, California, J.N. 188-01, dated June 25.
2003c, Geotechnical Report of Rough Grading, Lots 16, 17, 99 through 101 and 115 through 121,
Tract 23066-3, Temecula Area, Riverside County, California, J.N. 188-01, dated August 25.
, 2003d, Geotechnical Report of Rough Grading, Lots 122 through 129 (Phase 11), Tract 23066-3, Temecula
Area, Riverside County, California, J.N. 188-01, dated October 24.
2003e, Geotechnical Report of Rough Grading, Lots 102 through 114 (Phase 10), Tract 23066-3, Temecula
Area, Riverside County, California, J.N. 188-01, dated November 12.
PETRA GEOTECHNICAL, INC. APRIL 2003
1.N. 188-01
I
1
1
1
1 APPENDIX A
1
L
1
1
1
1
1
I
1
1
1
1
LABORATORY TEST CRITERIA
LABORATORY TEST DATA
♦ PETRA
4�7
APPENDIX A
' LABORATORY TEST CRITERIA
Laboratory Maximum Dry Density
' Maximum dry density and optimum moisture content were determined for selected samples of soil in accordance with
ASTM Test Method D1557. Pertinent test values are presented on Plate A-1.
' Expansion Index
t Expansion index tests were performed on selected samples of soil in accordance with ASTM Test Method D4829.
Expansion potential classifications were determined from 1997 UBC Table 184-13 on the basis of the expansion index
values. Test results and expansion potentials are presented on Plate A-2.
Corrosion Tests
' Chemical analyses were performed on selected samples of onsite soil to determine concentrations of soluble sulfate
and chloride, as well as pH and resistivity. These tests were performed in accordance with California Test Method
Nos. 417 (sulfate), 422 (chloride) and 643 (pH and resistivity). Test results are included on Plate A-2.
I
1
L
' PETRA GEOTECHNICAL, INC. APRIL 2003
J.N. 188-01
'
LABORATORY MAXIMUM DRY DENSITY
1989
Soil Type
Q� ue.,.. 15,E
Maxunum Dry, enstty
p '�aRM
to Soil Type wr ,
r r�,,� - -- ".
Maxunum Dry Densly
3
p$#
b...'mS.,�T!L._v �p'/zi"t'LYkt`V•'s+'�`��V�„'uLli`'tR
RQ
10.5
¢C
7uV11.,.'h
2
129.0
12
130.0
5
127.5
22
129.0
2002 and 2003'
S m le "
rvn
r s'sCp�pq&{
-?=�VO LR_.
tom' 3yi zt'S^' e
-Typ i t
Soil Tt e
't+ygii ''j�YG1P��+YituF+aGhd Yl+cY�°d 'Sf dna jiL. s3j A F
S>=�.`.�....�Im-'»k.c+v�..��a'NEv-eC°�°'�VDv.uJwu.....a:3e.J..... vui�um.�-i';r�u.+�%[.d1Y
aOptunum
a Mots[ure
Maxunum
D Densrt "i
ry y
..3.�.�C•/r..�_it�
3
Brown Clayey tine SAND
10.5
127.5
8
Yellowish light brown tine to medium SAND with trace Clay and Silt
12.5
120.5
9
Light brown Silty SAND with trace Clay
8.5
130.5
10
Medium brown Clayey SILT
11.5
124.5
11
Medium brown Clayey medium to coarse SAND with cobbles
8.0
133.5
13
Brown Silty SAND
10.0
132.0
14
Brown Silty SAND
8.0
132.0
(1) PER ASTM D1557
1
' PETRA GEOTECHNICAL, INC. APRIL 2003
tJ.N. 188-01 PlateA-1
�. 9
EXPANSION INDEX TEST DATA
a —�• a •e- ^°°
1fl.,Sample Lot No
+ „-: ,r�Re" r` ese n tivOLro c. * �.;.`
, p �, z.
`�R'.
i �
Rik ]Is
L .5'i t �i
�"3�...EIndex, 3w
r.pExpanstonx F
Potential_
4
1 through 6
0
Very Low
8
7 through 10
0
Very Low
12
11 through 13
0
Very Low
15
14 and 15
18
Ver Low
CORROSION TESTS
h1e I ,1 1 t pa
Lot Numbers
�° ge 2tit.Ts
It' _ F s
w s -0m a
'Sulfate S`
_ (%)
ie tib? sus
Cliloctde h
� iii) l
-xPHbI!M1
�„
s : ;
Resutiv fy' 1tA
rE
(ohmecm)_ r
tZ�Coerosrvttyz
x. ,
3Z Potentials.
7
0.0081
130
7.3
4,900
concrete: negligible
steel: moderate
15
0.0122
150
7.3
4,000
concrete: negligible
steel: moderate
(2) PER ASTM D4829
(3) PER 1997 UBC TABLE 18-1-B
(4) PER CALIFORNIA TEST METHOD NO. 417
(5) PER CALIFORNIA TEST METHOD NO. 422
(6) PER CALIFORNIA TEST METHOD NO. 643
(7) PER CALIFORNIA TEST METHOD NO. 643
PETRA GEOTECHNICAL, INC. APRIL 2003
1. N. 188-01 Plate A-2
T624306a,410 -It -.Il, 2 30