HomeMy WebLinkAboutLot 1-5 Geotechnical Repots Rough Grading 3/12/97S
REDHAWK HOMEBUILDING PARTNERSHIP LTD.
AA1':'L.'flev.il Avunue:.Coi}n 9nn, .
1 PETRA
COSTA MESA • NEWPORT BEACH • SAN DIEGO • TEMECULA
' March 12, 1997
- J.N. 569-96
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' 4141 Jutland Avenue, Suite 200
San Diego, California 92117
Attention: Mr. Barry Galgut
Subject: Geotechnical Report of Rough Grading, Model Site, Lots 1
' Through 5, Tract 23064-2, Redhawk Development, County of
Riverside, California
1
PETRA GEOTECHNICAL, INC
27620 Commerce Centre Drive,
Suite 103
Temecula, CA 92590
Submitted herewith is a summary of observation and testing services provided by Petra
Geotechnical, Inc. (Petra) during recent grading operations within the subject model
site. Conclusions relative to the suitability of the grading for the proposed construction
and foundation design recommendations for the proposed residential structures are
included herein.
All fills, cuts, overexcavation, removals and processing of existing ground under the
purview of this report have been completed under the observation and with selective
testing by Petra. The earthwork was performed in general conformance with our
geotechnical recommendations and the grading requirements of the County of
Riverside.
Grading of the site commenced on December 27, 1996, with the model lots completed
on February 28, 1997. The purpose of this portion of the grading operation was to
rough -grade level pads for construction of a model site consisting of three single-family
residences. Recommendations for grading of the site were presented in the referenced
report. Limits of grading for this report are shown on the attached Xeroxed portion
of the grading plans (Figure 1). The completed earthwork has been reviewed and is
considered adequate for the construction now planned. On the basis of our findings,
' Tel: (909) 6996193
Fax (909) 699-6197 n
n
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots I through 5/TR 23064-2
1
�l
11
1
March 12, 1997
J.N. 569-96
Page 2
the following recommendations were prepared in conformance with generally accepted
professional engineering practices and no further warranty is implied nor made.
SUMMARY OF OBSERVATIONS AND TESTING
Geology
Geologic conditions observed onsite at the model site are generally as anticipated and
described in the referenced preliminary geotechnical reports. The site is underlain at
depth by the Quaternary Pauba Formation. The Pauba Formation, as observed onsite,
is a massive to thick -bedded, coarse to fine silty sandstone. Bedding orientation in the
area of the model site is generally horizontal, with minor dips, 0° to 5°, in random
orientations.
The active Wildomar fault zone is present along the western margin of the property.
Fault trenching has not identified traces of the fault within the development area, but
bedding along the western side of the property has been apparently affected by the
faulting with bedding tipped to the southwest.
Site Clearing
Vegetation was stripped and removed from the site. Clearing operations also included
the removal of existing trash and debris. Roots missed during the initial clearing
operations were collected and stockpiled by hand labor and then removed from the site.
Loose stockpiles of soil were removed to the underlying original surface of the rough -
grade pad.
Ground Preparation - Fill Areas
Prior to placing fill, existing low-density surface soils were removed to underlying
competent bedrock of the Pauba Formation. The exposed bottom surfaces were
3
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots I through 5/TR 23064-2
March 12, 1997
J.N. 569-96
Page 3
scarified to a depth of 6 inches, watered as necessary to achieve near -optimum moisture
t conditions, and then recompacted in-place to a minimum relative compaction of 90
percent. Removal depths varied from 6 to 10 feet.
Cut -to -Fill Transitions
The cut -fill transition line indicated on the attached Figure 1 is the transition resulting
from this episode of grading. The area shown as cut is actually certified fill placed
' previously as an earlier portion of the Redhawk development. The cut -fill transition
actually represents a new fill -old fill transition line. The old fill surface was scarified,
' moisture -conditioned and then recompacted to create a uniform building pad condition.
' To achieve adequate compaction to the finish surfaces, all fill slopes were overfilled and
backrolled during construction at vertical intervals not exceeding approximately 4 to
' 5 feet and then trimmed back to the compacted inner cores.
' Fill Placement
Maximum depth of fill placed during this phase of grading is approximately 35 feet. Fill
materials consisting of blended onsite soils were placed in lifts restricted to
approximately 6 inches in thickness, watered as necessary to achieve near -optimum
moisture conditions and then compacted with an 824 rubber -tired dozer and by wheel -
rolling with a loaded scraper.
' Fill placed against temporary backcuts and on natural slope surfaces having a slope
' gradient steeper than 5:1 (horizontal to vertical [h:v]) were keyed and benched into
competent bedrock or compacted fill materials.
t
I
1
[1
1
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
Model Site/Lots I through 5/TR 23064-2 J.N. 569-96
Page 4
Field Testing
Field density tests were performed using nuclear gauge test methods (ASTM D2922
and D3017) and the sand cone method (ASTM D1556). Test results are shown on
Table I and approximate locations of the field density tests are shown on the attached
Xeroxed portion of the grading plan (Figure 1).
The compacted fills were tested at the time of placement to ascertain that the specified
moisture content and relative compaction had been achieved. Field density tests were
taken at vertical intervals of approximately I to 2 feet.
When field density tests indicated a relative compaction of less than 90 percent, the
approximate limits of the substandard fill were established, the substandard area was
reworked, moisture -conditioned and recompacted as necessary under the observations
of our engineering technician or, the substandard materials were removed, moisture -
conditioned and replaced as properly compacted fill.
Visual classification of earth materials in the field was the basis for determining which
maximum density value summarized in the following Laboratory Testing Section was
applicable for a given density test. One -point checks were performed to supplement
visual classification.
' Laboratory Testing
• The laboratory maximum dry density and optimum moisture content for each major
' soil type encountered during grading were determined in accordance with Test
Method ASTM D1557-91, Table 2 below presents the pertinent test values.
S
REDHAWK HOMEBUILDING PARTNERSHIP LTD
Model Site/Lots I through 5/TR 23064-2
Table 2
March 12, 1997
J.N. 569-96
Page 5
Sample.
.....
'mu
Descripfton
Moisture Content
Density
I
Brown, Silty CLAY
8.0
128.0
2
Brown, Silty SAND
9.0
129.0
Tan to light brown Silty SAND
9.5
126.5
4
Reddish brown Silty SAND
8.5
131.0
5
Dark brown to black Silty CLAY
10.5
126.0
6
Reddish brown to brown Silty
10.5
127.0
SAND
7
Brown Silty SAND
11.0
125.0
8
Tan, fine to coarse SAND
10.0
126.0
9
Light tan, grey, fine to medium
10.0
124.0
SAND
10
Tan, fine to Sandy Silty mix
10.0
127.0
11
Tan, fine to coarse SILT, trace
10.0
130.0
of Grave.
12
Reddish brown SAND to Light
8.0
129.0
L ------
LSAND
• Expansion index tests were performed on representative samples of soil existing
within the building areas in accordance with Uniform Building Code (UBC)
Standard Test No. 18-2. Table ' ) below presents the results.
*W
FA
LA
REDHAWK HOMEBUILDING PARTNERSHIP LTD
Model Site/Lots 1 through 5/TR 23064-2
Table 3
March 12, 1997
J.N. 569-96
Page 6
I acation
E anion Index
Ex ancon Potential
Lots 1, 2 and 3
18
Very low
Lots 4 and 5
1
Ve low
• Soluble sulfate contents were also determined for typical samples of soil existing
at grade. Table 4 below presents the results.
Table 4
FOUNDATION DESIGN PARAMETERS
Allowable Soil Bearing Capacities
For design of building and retaining wall footings, an allowable soil bearing capacity of
1,500 pounds per square foot may be used for a 12 -inch -wide continuous footing
founded at a minimum depth of 12 inches below the lowest adjacent final grade. This
value may be increased by 20 percent for each additional foot of width of depth to a
maximum value of 2,500 pounds per square foot. Recommended allowable soil bearing
capacities include both dead and live loads and may be increased by one-third for short -
duration wind and seismic forces.
1
7
I
1
1
I
1
1
I
11
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 7
Settlement
Under the above recommended maximum soil bearing capacity, total maximum footing
settlements are expected to be less than 3/4 inch and differential settlements between
adjacent footings are expected to be less than 1/4 inch over a span of approximately 30
feet. The majority of the anticipated settlements are expected to take place during
construction as footing loads are applied.
Lateral Resistance
A passive earth pressure of 250 pounds per square foot per foot of depth to a maximum
value of 2,500 pounds per square foot may be used to determine lateral bearing for
building and retaining wall footings located at least 7 feet from the top of any adjacent
descending slope. Where retaining wall footings are to be constructed on or within 7
feet from the top of a descending slope, a passive earth pressure of 150 pounds per
square foot per foot of depth to a maximum value of 1,500 pounds per square foot
should be used to determine the lateral bearing resistance. A coefficient of friction of
0.35 times the dead load forces may also be sued between concrete and the supporting
soils to determine lateral sliding resistance for all building and retaining wall footings.
An increase of one-third of the above values may be used when designing for short -
duration wind and seismic forces.
Footing Observations
All footing trenches should be observed by the project geotechnical consultant to
ascertain that they have been excavated into competent bearing soils. These
observations should be performed prior to placement of forms or reinforcement. The
excavations should be trimmed neat, level and square. All loose, sloughed or moisture -
softened materials and any debris should be removed prior to placing concrete.
1 d*
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots 1 through 5/TR 23064-2
[1
n
C
1
I
I
March 12, 1997
J.N. 569-96
Page 8
Excavated soils derived from footing and utility trenches should not be placed in slab -
on -grade areas unless they are compacted to at least 90 percent of maximum dry
density.
Expansive Soil and Bedrock Considerations
The results of our laboratory tests indicate that the onsite soils and bedrock materials
exhibit a very low expansion potential as classified in accordance with UBC
Table 18 -I -B. For this condition, it is recommended that footings and floors be
constructed and reinforced in accordance with the following minimum criteria.
However, additional slab thickness, footing sizes and reinforcement should be provided
as required by the project architect or structural engineer.
• 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-story construction). Interior continuous footings for two-
story construction may be founded at a minimum depth of 12 inches below the
lowest adjacent final grade.
• All continuous footings should be reinforced with two No. 4 bars, one top and one
bottom.
• Interior isolated pad footings supporting raised floors should be a minimum of 24
inches square and founded at a minimum depths of 12 and 18 inches below the
lowest adjacent final grade for one- and two-story construction, respectively. The
pad footings should be reinforced with No. 4 bars spaced 18 inches on center, both
ways, near the bottom of the footings.
• Exterior isolated pad footings intended for support of roof overhangs, such as
patio covers, should be a minimum of 24 inches square and founded at a minimum
depth of 18 inches below the lowest adjacent final grade. The pad footings should
be reinforced with No. 4 bars spaced 18 inches on center, both ways, near the
bottom of the footings.
• Living area concrete floor stabs should be 4 inches thick and reinforced with 6 -inch
by 6 -inch, No. 10 by No. 10 welded -wire mesh, or with No. 3 bars spaced 24
VA
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots I through 5/TR 23064-2
11
I
1
I
1
March 12, 1997
J.N. 569-96
Page 9
inches on center, both ways. All slab reinforcement should be supported on
concrete chairs or brick to ensure the desired placement near mid -depth.
• Living area concrete floors should be underlain with a moisture vapor barrier
consisting of a polyvinyl chloride membrane such as 6 -mil visqueen or equivalent.
At least 2 inches of clean sand should be placed over the membrane to promote
uniform curing of the concrete.
• Garage floor slabs should be 4 inches thick and reinforced in a similar manner as
living area floor slabs. Garage floor slabs should also be poured separately rom
adjacent wall footings with a positive separation maintained with 3/8 -inch -
minimum 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.
• Presaturation of the subgrade below slab areas will not be required. However,
prior to placing concrete the subgrade should be thoroughly moistened to promote
uniform curing of the concrete and mitigate the development of shrinkage cracks.
RETAINING WALL DESIGN RECOMMENDATIONS
Minimum Footing Embedment
To mitigate the potential adverse effects of creep that will develop on the cut -and -fill
slopes with a passage of time, footings for retaining walls proposed at the tops of
descending slopes should be founded at a depth that will provide a minimum horizontal
setback of 7 feet between the outside bottom edges of the footings and the slope face.
This minimum embedment is expected to place the footings below any further creep -
affected slope soils, as well as provide adequate vertical and lateral support without
subjecting the footings to detrimental settlement. Where retaining walls are proposed
at distances of 7 feet and greater from the tops of descending slopes, the footings may
be founded at minimum depth of 12 inches below the lowest adjacent final grade;
/D
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots 1 through 5/TR 23064-2
11
1
1
I
I
I
1
1
11
H
March 12, 1997
J.N. 569-96
Page 10
however, a minimum embedment if 18 inches may be preferable to provide t least 6
inches of cover over the footings.
Active and At -Rest Earth Pressures
An active lateral earth pressure equivalent fluid having a density of 45 pounds per cubic
foot is tentatively recommended for design of cantilevered walls retaining a drained
level backfill. Where the wall backfill slopes upward at 2:1 (h:v) the above value
should be increased to 75 pounds per cubic foot. All retaining walls should be designed
to resist any surcharge loads imposed by other nearby walls or structures in addition to
the above active earth pressures.
For design of retaining walls that are restrained at the top, an at -rest earth pressure
equivalent to a fluid having density of 68 pounds per cubic foot should tentatively be
used for walls supporting a an ascending 2:1 (h:v) backfill.
Drainage
Perforated pipe and gravel subdrains should be installed behind all retaining wall to
prevent entrapment of water in the backfill. Perforated pipe should consist of 4 -inch -
minimum -diameter PVC Schedule 40, or ABS SDR -35, with the perforations laid
down. The pipe should be encased in a 1 -foot -wide column of 3/4 inch to 1.5 -inch
open -graded gravel extending above the wall footing to a height equal to two-thirds of
the wall height, or to a minimum height of 1.5 feet above the footing, whichever is
greater. The gravel should be completely wrapped in filter fabric consisting ofMirafi
140N, or equivalent. Solid outlet pipes should be connected to the subdrains and
routed to areas suitable for discharge of accumulated water.
For low -height walls retaining less than approximately 2.5 feet of backfill, an alternative
drainage system consisting of weepholes or open masonry joints may be used in -lieu of
Z
I/
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots 1 through 5/TR 23064-2
1
C
1
1
[l
1
March 12, 1997
J.N. 569-96
Page 11
a pipe and gravel subdrain. Weepholes, if used, should be 3 inches minimum diameter
and provided at maximum intervals of 6 feet along the walls. Open vertical masonry
joints should be provided at 32 -inch -minimum intervals. One cubic foot of gravel
should be placed behind the weepholes or open masonry joints. The gravel should be
wrapped in filter fabric to prevent infiltration of fines and subsequent clogging of the
gravel. Filter fabric should consist of Mirafi 140N, or equivalent. _
Waterproofing
Consideration should be given to coating the outside portions of retaining walls
supporting backfill with an approved waterproofing compound or covered with a
similar material to inhibit infiltration of moisture through the walls.
Retaining Wall Backfill
All retaining wall backfill should be placed in 6- to 8 -inch -thick maximum horizontal
lifts, watered or air-dried as necessary to achieve near -optimum moisture conditions
and then mechanically compacted in-place to a minimum relative compaction of 90
percent. Flooding or jetting of backfill materials should be avoided. A representative
of this firm should probe and test the backfills to ascertain adequate compaction.
EXTERIOR CONCRETE FLATWORK
Thickness and Expansion Joint Spacing
To reduce the potential for excessive and unsightly cracking related to the effects of
expansive soils, walkways and patio -type slabs should be at least 4 inches thick and
provided with weakened plane joints or expansion joints every 6 feet or less. L Subslabs
to be covered with decorative pavers should also be at least 4 inches thick and provided
with weakened plane joints or expansion joints every 6 feet or less. Concrete driveway
I 4t
lO,Z-
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD
' Model Site/Lots 1 through 5/TR 23064-2
1
1
1
1
1
1
March 12, 1997
J.N. 569-96
Page 12
slabs should also be at least 5 inches thick and provided with weakened plane joints or
expansion joints every 10 feet or less.
Reinforcement
Consideration should be given to reinforcing all concrete patio -type slabs, driveways
and sidewalks greater than 5 feet in width with 6 -inch by 6 -inch, No. 10 by No. 10
welded -wire fabric, or with No. 3 bars spaced 24 inches on centers, both ways. The
reinforcement should be positioned near the middle of the slabs by means of concrete
chairs or brick.
Edge Beams (Optional)
Where the outer edges of concrete patios and driveways are to be bordered by
landscaping, consideration should be given to the use of edge beams (thickened edges)
to prevent excessive infiltration and accumulation of water under the slabs. Edge
beams, if used, should be 6 to 8 inches wide, extend 8 inches below the tops of the
finish slab surfaces and be reinforced with a minimum of two No. 4 bars, one top and
one bottom. Edge beams are not mandatory; however, their inclusion in flatwork
construction adjacent to landscaped areas will significantly reduce the potential for
vertical and horizontal movements and subsequent cracking of the flatwork related to
the effects of high uplift forces that can develop in expansive soils.
Subgrade Preparation
As a further measure to minimize cracking and/or shifting of concrete flatwork, the
subgrade soils below concrete flatwork areas should be compacted to a minimum
relative compaction of 90 percent and then thoroughly moistened prior to placing
concrete. The moisture content of the soils should be 5 percent or greater above
optimum moisture content and penetrate to a depth of approximately 12 inches into the
1 V
�3
I
' REDHAWK HOMEBUILDING PARTNERSHIP LTD
Model Site/Lots 1 through 5/TR 23064-2
[1
[l
1
1
t
March 12, 1997
J.N. 569-96
Page 13
subgrade. Flooding or ponding of the subgrade is not considered feasible to achieve
the above moisture conditions since this method would likely require construction of
numerous earth berms to contain the water. Therefore, moisture conditioning should
be achieved with sprinklers or a light spray applied to the subgrade over a period of
several days just prior to pouring concrete. A Petra representative should observe and
verify the density and moisture content of the soils and the depth of moisture
penetration prior to pouring concrete.
MASONRY BLOCK GARDEN WALLS AND SOUND WALL
Footing Embedment
Footings for masonry block walls should be constructed in a similar manner as
recommended for retaining wall footings. That is, to mitigate the potential adverse
effects of creep that will develop on the cut -and -fill slopes with the passage of time,
footings for the sound attenuation walls, as well other masonry block walls proposed
near the tops of descending slopes, should be founded at a depth that will provide a
minimum horizontal setback of 7 feet between the outside bottom edges of the footings
and the slope face. Where masonry block walls are proposed at distances of 7 feet and
greater from the tops of descending slopes, the footings may be founded at a minimum
depth of 12 inches below the lowest adjacent final grade; however, a minimum
embedment of 18 inches may be preferable to provide at least 6 inches of cover over
the footings.
Reinforcement and Positive Separations
All masonry block wall footings should be reinforced with a minimum of two No. 4
bars, one top and one bottom. In order to mitigate the potential for unsightly cracking,
positive separations should also be provided in the garden walls at horizontal spacings
of approximately 20 to 25 feet and at each corner. These separations should be
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
' Model Site/Lots I through 5/TR 23064-2 J.N. 569-96
Page 14
' provided in the blocks only and not extend through the footing. The footing should be
' pored monolithically with continuous rebars to serve as an effective "grade beam"
below the wall.
PLANTERS AND PLANTER WALLS
' Area drains should be extended into all planter areas that are located within 5 feet of
building walls and foundations, retaining walls and garden walls to minimize excessive
' infiltration of water into the adjacent foundation soils. The surface of the ground in
these areas should be loped at a minimum gradient of 2 percent away from the walls
' and foundations. Drip -irrigation systems are also recommended to prevent over
watering and subsequent saturation of the adjacent foundation soils.
' Low -height planter walls should be supported by continuous concrete footings founded
' at a minimum depth of 12 inches below the lowest adjacent final grade; however, a
minimum embedment of 18 inches may be preferable to allow for 6 inches of cover over
the footings. The footings should be reinforced with two No. 4 bars, one top and one
bottom. Positive separations should also be provided in the planter walls in a similar
' manner as recommended for masonry block walls.
' SOLUBLE SULFATE ANALYSES
' Laboratory test data indicate that onsite soils contain water-soluble sulfate contents less
than 0.1 percent. Therefore, negligible to low exposure to sulfate can be expected for
concrete placed in contact with onsite soil. As such, no special mitigation measures are
necessitated or required. Careful control of maximum water-cementatious ratio and
' minimum concrete compressive strength can also improve resistance to deterioration
' due to sulfates. We also recommend that the procedures provided in Section 1904.3.1
and Table 19-A-3 of the 1994 UBC be followed.
15
I
11
I
11
I
1
Ll
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 15
UTILITY TRENCH BACKFILL
All utility trench backfill should be compacted to a minimum relative compaction of 90
percent. Where onsite soils are utilized as backfill, mechanical compaction will be
required. Therefore, trench backfill materials should be placed in approximately 12- to
18 -inch -maximum lifts, watered or air-dried as necessary to achieve near -optimum
moisture conditions and then mechanically compacted in-place with a hydra -hammer,
pneumatic tamper or similar equipment to a minimum relative compaction of 90
percent. A Petra representative should be notified at the appropriate times to ascertain
the relative compaction of the backfill.
For shallow trenches where pipe or utilities might be damaged by mechanical
compaction equipment, imported sand having a sand equivalent value of 30 or greater
may be used for backfill. Sand backfill materials should be watered to achieve near -
optimum moisture conditions and then tamped with hand -operated pneumatic tampers
to ensure proper consolidation of the backfill. No specific relative compaction will be
required. However, observation, probing and, if deemed necessary, testing should be
performed to ascertain that the backfill is adequately compacted.
Where exterior and interior utility trenches are proposed parallel to building footings,
the bottom of the trench should not extend below a 1:1 (h:v) plane projected downward
from the bottom edge of the adjacent footing. Where this condition occurs, the
adjacent footing should be deepened or backfilled with sand -cement slurry.
POST -CONSTRUCTION AND LONG-TERM
EFFECTS OF EXPANSIVE SOILS
The preceding recommendations for design of foundations and floor slabs for the
residence and other site improvements are provided to mitigate distress related to
%/0
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 16
' effects of moderately expansive soils. However, our experience has shown that over
' long time periods, expansive soils can and do result in some differential movement of
structures built on them. Consequently, a certain amount of cracking and/or horizontal
' and vertical displacement can generally be anticipated
' SLOPE LANDSCAPING AND MAINTENANCE
All cut -and -fill slopes should be provided with the proposed drainage facilities and
' landscaping as soon as practical upon completion of rough grading to minimize the
potential for erosion, raveling or slumping. Additional recommendations with respect
to slope landscaping and maintenance are presented below to mitigate surficial
instability.
'0 The landscaping for all cut -and -fill slopes should consist of a deep-rooted,
' drought -resistant and maintenance -free plan species. A landscape architect should
be consulted to determine the most suitable ground cover for both cut -and -fill
slopes. 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 inhibit surface erosion.
• Irrigation systems should be installed on slopes exceeding a height of 10 feet and
a watering program then implemented which maintains a uniform near -optimum
' moisture condition int he soils. Over watering 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 should not be allowed without prior approval from this
' firm.
• During construction of the proposed drainage facilities, care must be taken to
' avoid placement of loose soil on the slope surfaces.
• A permanent slope maintenance program should be initiated. Proper slope
maintenance must include the care of drainage and erosion control provisions,
rodent control and timely repair of leaking irrigation systems.
/I
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
' Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 17
' REPORT LIMITATIONS
This report has been prepared consistent with that level of care being provided by other
professionals providing similar services at the same locale and in the same time period.
' The contents of this report are professional opinions and as such are not to be
considered a guaranty or warranty.
' This report has not bee prepared for use by parties or projects other than those named
or described herein. This report may not contain sufficient information for other parties
' or other purposes.
' 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
1
/V
Provided the above recommendations are followed with respect to slope drainage,
'
maintenance and landscaping, the cut -and -fill slopes are expected to be surficially
stable and to remain so under normal conditions.
FUTURE IMPROVEMENTS
'
Should any new structures or improvements be proposed at any time in the future,
other than those shown on the enclosed grading plan, Petra should be notified so that
'
we may provide design recommendations to mitigate movement and/or tilting of the
tstructures
related to the effects of expansive earth materials.
' REPORT LIMITATIONS
This report has been prepared consistent with that level of care being provided by other
professionals providing similar services at the same locale and in the same time period.
' The contents of this report are professional opinions and as such are not to be
considered a guaranty or warranty.
' This report has not bee prepared for use by parties or projects other than those named
or described herein. This report may not contain sufficient information for other parties
' or other purposes.
' 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
1
/V
I
REDHAWK HOMEBUILDING PARTNERSHIP LTD March 12, 1997
' Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 18
- Observe footing trenches when first excavated to ascertain depth and competent
' soil bearing conditions.
' - Reobserve all footing trenches, if necessary, if trenches are found to be
excavated to inadequate depth and/or are found to contain significant slough,
saturated or compressible soils.
' Retaining Wall Construction
' Observe all footing trenches when first excavated to ascertain depth and
competent soil -bearing conditions.
' Observe and test subgrade soils below all concrete flatwork areas to ascertain
relative compaction, moisture content and moisture penetration.
• Utility Trench Backfill
Observe and test placement of all utility trench backfill.
r9
- Reobserve all footings trenches, if necessary, if trenches are found to be
excavated to inadequate depth and/or are found to contain significant slough,
saturated or compressible soils.
'
- Observe and ascertain proper installation of subdrainage systems prior to
placing wall backfill.
'
- Observe and test placement of all wall backfill.
'
Masonry Garden Walls and Planter Walls
- Observe all footing trenches when first excavated to ascertain depth and
'
competent soil bearing conditions.
- Reobserve all footing trenches, if necessary, if trenches are found to be
excavated to inadequate depth and/or are found to contain significant slough,
saturated or compressible soils.
'
Concrete Flatwork Construction
' Observe and test subgrade soils below all concrete flatwork areas to ascertain
relative compaction, moisture content and moisture penetration.
• Utility Trench Backfill
Observe and test placement of all utility trench backfill.
r9
REDHAWK HOMEBUILDING PARTNERSHfP LTD March 12, 1997
Model Site/Lots 1 through 5/TR 23064-2 J.N. 569-96
Page 19
• Regrading
- Observe and test placement of any fill to be placed above or beyond the grades
shown on the grading plan.
This report is subject to review by the controlling authorities for this project.
Respectfully submitted,
PETRA GEOTECHNICAL, INC.
Gl N IE
�
Step en W. Jens Siamak Jafroudi,
Prin al Geo, gist EG. 1074 Principal Enginee
CEG 1074 Oreo z' RCE 36641
�c
SWJ/SJ/keb
OF CAN"
Attachments: Figure 1 - Density cation
Table I - Summary of Field Density Tests
Distribution: (2) Addressee
(4) County of Riverside Planning Department
Attention: Mr. Abdul Benwah
I
M
i
1
1
1
i
1
1
1
1
1
I
1
1
1
1
1
North
\ 9Q? _ `\ Scale
0 40 Feet
V
X15 ;.
1
2462
L\
9b`
� •,� � / 238 � `•
M `
16 237 9
ti 16 �g2
:i
\� o
o ^'a
,> C.
\ n\ \
As -Graded Geotechnical Report
Model Site
Lot Numbers 1-5, Tract 23064-2, (Redhawk)
County of Riverside, CA
236 0
`g5
PETRA GEOTECHNICAL, INC.
JN 569-96 3-7-97
FIGURE 1
02/
REDHAWK HOMEBUILDING PARTNERSHIP LTD. March 12, 1997
TR 23064-2 J.N. 569-96
TABLE I
Field Density Test Results
ANTE t]P
GEST.....
TEST
NO.
..C...ATIOT#
T,
ION
TY
.:
TR 23064-2 MODELS
02/07/97
58
Lot 2
1160
11.8
119.6
91
4
02/07/97
59
Lot 2
1161
13.0
117.8
91
4
02/07/97
60
Lot 1
1162
13.2
116.8
91
1
02/11/97
82
Lot 2
1158
13.6
116.0
91
1
02/11/97 1
83
Lot 2
1159
16.3
111.5
90
9
02/14/97
112
Lot 1
1176
1 11.7
116.3
90
2
02/14/97
113
Lot 1
1177
10.2
117.7
90
4
02/19/97
148
Lot 5
1187
14.1
112.6
91
9
02/19/97
149
Lot 3
1186
14.9
1 116.2
90
2
02/20/97
162
Lot 4
RT 163
14.0
109.9
87
8
02/20/97
163
Lot 4
RT 162
13.6
115.0
91
8
02/20/97
172
Lot 2
1185
14.1
116.7
90
2
03/04/97
236
Lot 5 (FG)
1195.5
10.5
121.3
93
11
03/04/97
237
Lot 4 (FG)
1192.9
11.1
1 119.3
92
11
103/04/97
1 238
Lot 3 (FG)
1189.6
12.6
119.9
92
11
103/05/97
1 246
Lot 2 (FG)
1186.2
11.9
117.0
1 91
2
F03/05197
1 247
Lot I (FG)
1182.7
13.1
117.2
91
2
Failing Tests
ff-j