HomeMy WebLinkAboutGeotechnical Rpt Lots 16-17, 99-101 8/25/2003L'
115 THROUGH 121, TRACT 2.3066-.3.
TEMCCULA ARfARI MSME COUNTY
CALWORMA.
PETRA
OFFICES IN THE COUNTIES OF
ORANGE • SAN DIEGO • RIVERSIDE • LOS ANGELES • SAN BERNARDINO
August 25, 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 16, 17, 99 through 101
and 115 through 121, 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 16, 17, 99 through 101
' and 115 through 121 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, removals and compaction of unsuitable low-density surface soils, lot
' overexcavations 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.
' 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
' PETRA GEOTECHNICAL, INC.
41640 Corning Place . Suite 107 . Murrieta . CA 92562 . Tel: (909) 600-9271 . Fax: (909) 600-9215
1
L
1
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 2
conformance with generally accepted professional engineering practices 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 surficial overexcavations on the order of 2 to 8 feet deep
and the overexcavation of the cut portions of cut/fill transition lots. Imported fill
material was temporarily stockpiled on Lots 115 through 121. Following removal of
the stockpile, the upper 1 to 2 feet of the exposed sandstone on these lots, as well as
Lots 16 and 17, were processed and density tested during the recent finish -grading
operations. The compacted fills ranged in thickness from approximately 3 to 33 feet.
A lot -by -lot summary of the compacted -fill depths and a summary of soil conditions
is presented in the attached Table I. A general description of the soil and bedrock
materials underlying the subject lots is provided below.
• Artificial Fill (map symbol afc) — The compacted -fill soils are comprised of
onsite -derived and imported soil and bedrock materials and consisted generally of
fine to coarse sand, silty sand and clayey sand. The imported materials were
generated during post -grading operations within nearby Tract 23065.
• Pauba Formation Bedrock (Oos) — 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, friable sand
unit was observed within the Pauba Formation.
T
t
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16,17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 3
SUMMARY OF EARTHWORK
OBSERVATIONS AND DENSITY TESTING
Clearing and Grubbing
Heavy vegetation that existed in local areas, as well as some construction debris, were
removed from the site.
Ground Preparation
Prior to placing structural fill, existing low-density surficial soils or weathered bedrock
were first removed to competent undisturbed, unweathered bedrock or competent
previously placed compacted fill materials. Removals varied from approximately 2
to 8 feet.
Prior to placing fill, exposed bottom surfaces in removal areas were observed by our
project geologist or senior soil technician. 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 equal to or slightly above
optimum moisture content and then compacted in-place to a relative compaction of 90
percent or more.
Lot Overexcavations
To reduce the likelihood of distress to residential structures related to the potential
adverse effects of differential settlement, the cut portions of cut/fill transition Lots 99,
100, 101, 115 and 116 were overexcavated to a depth of 3 feet or more below finish
grade and replaced compacted fill derived from on-site materials.
Fill Placement and Testing
Fill soils were placed in loose lifts approximately 6 to 8 inches in thickness, watered
or air-dried as necessary to achieve near -optimum moisture conditions and then
[1
I
1
1
11
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16,17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 4
compacted in-place until density tests indicated relative compaction of 90 percent or
more based on ASTM D1557. Compaction was achieved by wheel -rolling with an
824 rubber -tired loader and loaded scrapers. The deepest fill placed within the subject
lots was approximately 33 feet on Lot 101.
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 II and approximate test
locations are shown on the enclosed Geotechnical Map with Density Test Locations
(Figure 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 of 90 percent or more 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 recommended relative compaction of 90
percent or if the soils were found to be above or below specified optimum 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. Single -point checks were
performed to supplement visual classification.
S
1 RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
' Page 5
Cut Slopes
Cut slopes exposed competent Pauba Formation bedrock and were constructed at a
' ratio of approximately 2:1 (h:v) and to a height of approximately 4 feet or less. The
cut slopes were considered grossly and surficially stable to the heights and slope ratios
at which they were constructed.
Construction -Material Storage
' Portions of Lots 99 and 101 have been used for construction -material storage and
' staging. We suggest that the condition of these lots be observed prior to trenching to
document that conditions are still suitable for their intended use. Any surficial
' processing that may be required can be done at that time.
LABORATORY TESTING
' Maximum Dry Density
Maximum dry density and optimum moisture content for changes in soil types
' observed during grading were determined in our laboratory in accordance with
ASTM D1557. Pertinent test values are summarized in Appendix A.
' 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
taccordance with ASTM D4829. Test results indicated that surficial soils had VERY
' LOW expansion potential.
1
I
I
I
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 6
Atterberg Limits
Atterberg limits were determined for selected soil samples per ASTM D4318. Test
results are presented 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. Test results indicated that soluble -sulfate contents were negligible.
Therefore, according to 1997 Uniform Building Code (UBC) Table 19-A-4, no special
cement is specified for concrete to be placed in contact with onsite soils. However,
we recommend that Type 11 cement be used for concrete. For concrete in contact with
the soil, we recommend that 3 inches or more of concrete be placed over reinforcing
steel.
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. Test results indicated
that soils were moderately corrosive to ferrous metal. Ferrous metal pipe, if used,
should be corrosion -protected or an alternative piping that is not subject to corrosion,
such as plastic pipe, should be used.
W
I
1
I
1
1
I
1
I
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 7
CONCLUSIONS AND RECOMMENDATIONS
Foundation -Design Recommendations
Foundation Types
Based on as -graded soil and geologic conditions, the use of conventional slab -on -
ground 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
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 may be 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 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
W
J
I
I
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 8
slopes, the passive earth pressure should be reduced to 150 psf per foot of depth to a
value of 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. In addition, a coefficient
of friction of 0.35 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 maximum dry density.
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 -ground 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-13. For this condition, it is recommended that footings and floors be constructed
and reinforced in accordance with the following criteria. However, additional slab
U
1
1
1
1
I
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16,17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 9
thickness, footing sizes and/or reinforcement may be required by the project architect
or structural engineer.
• Footings
- 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 be reinforced with two No. 4 bars, one top and one
bottom.
Isolated pad footings should be 24 inches or more square and founded at a depth
of 12 inches or more below the lowest adjacent final grade or top -of -slab.
• Floor Slabs
- Living -area concrete -floor slabs should be 4 inches or more thick and reinforced
with either 6x6 -W 1.4xW 1.4 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.
- Living -area concrete floors should be underlain with a moisture -vapor retardant
consisting of 6 -mil thick polyethylene membrane or equivalent. Two inches or
more of clean sand should 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.
- Prior to placing concrete, subgrade soils should be thoroughly moistened to
promote uniform curing of the concrete and reduce the development of
shrinkage cracks.
Ito
LO
I
I
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 10
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
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 mm/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
T
C
1
RICHMOND AMERICAN HOMES
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area
August 25 , 2003
J.N. 188-01
Page 11
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.
.,,;1997 UBGaTABLE
Figure 16-2 Seismic Zone
4
16-I
Seismic Zone Factor Z
0.4
16-U
Seismic Source Type
B
16-J
Soil Profile Type
So
16-S
Near -Source Factor N.
1.3
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
RETAINING WALLS
Retaining walls are not currently proposed within the subject site. The following
retaining and masonry wall information is being provided to assist the future
homeowners in the event they construct retaining walls within their lots.
Footing Embedments
The base of retaining -wall footings constructed on level ground may be founded at a
depth of 12 inches below the lowest adjacent final grade. Where retaining walls 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 the 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 the project
l�_
I
1
1
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 12
geotechnical consultant to document that they have been excavated into competent -
bearing soils and/or bedrock and to the embedments recommended above. These
observations should be performed prior to placing forms or reinforcing steel.
Active Earth Pressures
An active lateral -earth pressure equivalent to a fluid having a density of 40 pounds per
cubic foot (pcl) may be used for design of cantilevered walls retaining a drained, level
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.
Drainage
A 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.
Perforated 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
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.
/3
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 13
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 11 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 filter fabric. The pipe should outlet
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 slopes may be cut back at a
gradient of 1:1 (h:v) or gentler 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.
WAI
I
RICHMOND AMERICAN HOMES August 25 , 2003
t TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 14
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.
' 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 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
' 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
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.
' 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 corner. The
separations should be provided in the blocks only and not extend through the footings.
15
I
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16,17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 15
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.
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 and then wetted 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.
I to
I
I
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 16
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. Soils utilized as backfill
should be mechanically compacted. Density testing, 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 1 foot or more above pipe in areas where excavated
trench materials contain significant cobbles.
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 1:1 (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.
11
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 17
' • Compacted -earth berms should be constructed along the tops of the engineered fill
slopes to reduce the likelihood of water from flowing directly onto the slope
surfaces.
' • The 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.
• 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
' walls, walkways, patios, swimming pools, spas and planters.
IT
I
1
1
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 18
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 pre-soaking 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- fl atwork areas to document
compaction and moisture content.
• Utility -Trench Backfill
- Observe and test placement of utility -trench backfill to document specified
compaction.
• Re -Grading
��-2 It
19
I
RICHMOND AMERICAN HOMES August 25 , 2003
TR 23066-3 Lots 16, 17, 99-101 & 115-121/Temecula Area J.N. 188-01
Page 19
- 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,
PETRA GEOT IN .
Robert L. Gregorek II
Principal Geologist
CEG 1257
RLG/GRW/keb
Gr son R. ",r,,
Principal Engineer
GE 871
Attachments: Table I - Lot -By -Lot Summary of As -Graded Soil Conditions
Table H - Field Density Test Results
References
Figure 1 - Geotechnical Map with Density Test Locations
Appendix A - Laboratory Test Criteria/Laboratory Test Data
' Distribution: (1) Addressee
(3) Richmond American Homes
' Attention: Ms. Dee Gallegos
(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
Q
No. 871 ._
Exp: �'l
TABLE I Tract 23066-3 Lots 16, 17, 99 - 101 & 115 -121
LOT -BY -LOT SUMMARY OF SOIL CONDITIONS
Lot
Number
Maximum Fill
Depth (ft)
Minimum Fill
Thickness ft)
Estimated
Differentia
I
Settlement
Soil Expansion
Index/Potential
Post -Tensioned
Slab
Soil Condition
Codes*
Remarks
16
1
1
1:960
ON Low
Not Required
Z
17
1
1
1:960
ON Low
Not Required
Z
99
16
8
1:960
8/V Low
Not Required
Z
100
6
3
1:960
4/V Low
Not Required
Z
101
33
l0
1:960
4/V Low
Not Required
Z
115
15
7.5
1:960
ON Low
Not Required
Z
116
6
3
1:960
ON Low
Not Required
Z
117
2
1
L960
ON Low
Not Required
Z
IIS
2
I
1:960
ON Low
Not Required
Z
119
2
l
1:960
ON Low
Not Required
Z
120
2
1
1:960
ON Low
Not Required
Z
121
2
l
1:960
ON Low
Not Required
Z
* per County of Riverside, Building and Safety Department Plan Check Memorandum dated April 5, 2001
Code Defini(ions (Reference: 1997 URCJ:
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 19-A-4
IT D Differential deflection in the foundation due to differential settlement exceeds value in Table 18 -III -GG (consider Prefab Roof Trusses) (noted if>1:4801
P If post -tensioned slab system is to be used
7. If none of the above is aoolicable
Plate T-11
' TABLE II
' Field Density Test Results
06/11/02
1488
Lot 101
1196.0
14.9
110.4
86
4
' 06/11/02
1489
Lot 101
1195.0
8.1
112.3
90
10
06/11/02
1497
RT No. 1488
-
8.9
117.4
91
4
06/12/02
1509
Lot 99
FG
10.3
118.9
91
9
06/12/02
1525
Lot 101
1202.0
10.1
120.5
92
9
07/22/02
1888
Lot 99
FG
10.5
117.4
90*
9
03/21/03
2052
Lot 115
1199.0
11.1
119.0
90
11
03/22/03
2056
Lot 115
1202.0
12.1
118.5
90
11
03/24/03
2061
Lot 116
1204.0
9.4
119.1
90
12
'03/25/03
2064
Lot 116
1201.0
12.2
114.8
90
3
03/25/03
2066
Lot 116
1203.0
10.5
119.6
91
11
03/26/03
2071
Lot 115
1208.0
10.4
120.3
91
11
' 03/26/03
2073
Lot 116
1206.0
10.2
120.6
91
11
03/27/03
2078
Lot 115 slope
1209.0
10.1
120.8
92
11
2086
Lot 115
1209.0
8.3
119.8
90
12
'03/31/03
08/07/03
2133
Lot 99
FG
7.9
117.7
90
G
08/07/03
2134
Lot 100
FG
8.5
118.8
92
G
08/07/03
2135
Lot 115
FG
5.7
113.9
88
G
08/07/03
2136
Lot 116
FG
3.8
116.2
90
G
08/07/03
2137
Lot 117
FG
5.6
113.4
88
G
'08/07/03
2138
Lot 118
FG
5.5
112.1
87
G
08/07/03
2139
Lot 119
FG
10.0
107.6
85
G
08/07/03
2140
Lot 120
FG
11.2
12.0
90
G
t08/07/03
2141
Lot 16
FG
13.2
104.6
90
5
08/07/03
2142
Lot 17
FG
12.9
105.5
91
5
2143
Lot 121
FG
9.1
125.4
94
G
'08/07/03
08/07/03
2144
Lot 101
FG
7.8
122.5
92
11
08/08/03
2145
RT No. 2137
-
8.6
124.3
93
G
2146
RT No. 2138
-
9.1
119.8
93
G
'08/08/03
08/08/03
2147
RT No. 2139
10.7
119.6
93
G
08/08/03
2148
RT No. 2136
-
9.6
116.6
90
G
2149
RT No. 2135
-
11.3
117.6
91
G
t08/08/03
08/08/03
2150
Lot 121
FG
9.6
117.8
91
G
TR 23066-3
' PETRA GEOTECHNICAL, INC. Lots 16, 17, 99 - 101 115 - 121 AUGUST 2002
J.N. 188-01 * Sandcone TABLE II
ao-
I
I
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.
t 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 II, J.N. 298-87, dated May 8.
t , 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, J.N. 188-01, dated December 10.
' , 200le, 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. AUGUST 2003
' J.N. 188-01
�3
I
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.
, 2002f, 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.
12002i, 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 S4 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.
PETRA GEOTECHNICAL, INC. AUGUST 2003
J.N. 188-01
EXPLANATION
__ \\ (LOCATIONS ARE APPROXIMATE)
afcARTIFICIAL FILL.
;j- COMPACTED
QpS QUATERNARY PAUBA
FORMATION
SANDSTONE
gYj 9
xQ� �ytia�0ol°u ��� ft� GEOLOGIC CONTACT
2150 DENSITY TEST
LOCATION
� 1190.8 INDICATES REMOVAL
DEPTH ELEVATION
76 IN FEET
A
North
Scale
0 40 Feet
GEOTECHNICAL MAP WITH
DENSITY TEST LOCATIONS
95
APPENDIX A
LABORATORY TEST CRITERIA
LABORATORY TEST DATA
1 PETRA
I
a�
I
' APPENDIX A
' LABORATORY TEST CRITERIA
' Laboratory Maximum Dry Density
Maximum dry density and optimum moisture content were determined for selected samples of soil and bedrock materials
in accordance with ASTM D1557. Pertinent test values are given on Plate A -l.
' Expansion Index
' Expansion index tests were performed on selected samples of soil in accordance with ASTM D4829. Expansion
potential classifications were determined from 1997 UBC Table 18-1-B on the basis of the expansion index values. Test
results and expansion potentials are presented on Plate A-1.
Soil Chemistry
Tests 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.
Atterberg-Limits
Atterberg limit tests (Liquid Limit and Plastic Index) were performed on selected samples to verify visual classifications.
These tests were performed in accordance with ASTM D4318. Test results are presented on Plate A-2.
PETRA GEOTECHNICAL, INC. AUGUST 2003
J.N. 188-01
I
1
1
I
1
LABORATORY MAXIMUM DRY DENSITY'
W71s
a<mentative�Loisi`x..,_
� x t+
O um
nmum
3
Brown Fine Clayey SAND
10.5
127.5
4
Light Brown Silty, Clayey Fine to Medium SAND
10.0
128.5
5
Light Brown Fine Sandy SILT
14.0
116.0
9
Light Brown Silty SAND with Trace Clay
10.0
130.5
10
Brown Clayey SILT
11.5
124.5
11
Brown Medium to Coarse SAND
8.0
133.5
12
Light Brown Fine Clayey Silty SAND
10.5
126.5
G
Silty SAND
8.5
129.5
EXPANSION INDEX TEST DATA
L"o No
i
a<mentative�Loisi`x..,_
� x t+
��ann
lr
dexa
E 3f -
0
o WE
16
16 and 17
0
Very Low
99
99
8
Very Low
100
100 and 101
4
Very Low
115
115 and 116
0
Very Low
118
117 through 121
0
Very Low
' PETRA GEOTECHNICAL, INC. AUGUST 2003
' J.N. 188-01 Plate A-1
1 -
) 8
SOIL CHEMISTRY
F:. �o w�riber �
Sulfat {�
Ghltir�ae'
�VNIM
is�fi zty�
as eyt
! ,t
- t..
32
15
17
-
o c_m :
99
ND
138
7.9
2,100
concrete: negligible
steel: moderate
17
0.006
158
7.4
3,300
concrete: negligible
steel: moderate
ATTERBERG LIMITS'
(I) PER ASTM DI557
(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
(8) PER ASTM D4318
PETRA GEOTECHNICAL, INC. AUGUST 2003
J.N. 188-01 Plate A-2
Y
o w.
SW a eun k
�1a I
-0 nu
P sde '
a to
.lasaclty"
4
Silty, Clayey SAND
32
15
17
(I) PER ASTM DI557
(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
(8) PER ASTM D4318
PETRA GEOTECHNICAL, INC. AUGUST 2003
J.N. 188-01 Plate A-2