HomeMy WebLinkAboutCT 82-23; Mass Grading for CT 82-23; Final Testing; 1984-09-19.. ..
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FINAL REPORT OF TESTING AND OBSERVATION
SERVICES DURING MASS GRADING OPERATIONS
FOR
SDP 82-4 AND CT 82-23
CARLSBAD, CALIFORNIA I
For
MOM DEVELOPMENT CORPORATION
Huntington Beach, California
I
BY
GEOCON, INCORPORATED
San Diego, California
September, 1984
I
INCORPORATED ENGINEERS AND GEOLOGISTS CONSULTANTS IN THE APPLIED EARTH SCIENCES
File No. D-2904-502
September 19, 1984
Mola Development Corporation
Huntington Beach, California 92648
808 Adams Avenue
Attention: Mr. Chris Christie
Subject: SDP 82-4 AND CT 82-23
CARLSBAD, CALIFORNIA
FINAL REPORT OF TESTING AND OBSERVATION
SERVICES DURING MASS GRADING OPERATIONS
Gentlemen:
In accordance with your request, we have provided testing and observation
services during the mass grading of the subject projects. Our services
were performed during the period of April September 26, 1983 through June
22, 1984. The scope of our services included the following:
0 Observing the grading operation.
0 Performing in-place density tests in the placed and compacted
fill.
0 Performing laboratory tests on samples of the prevailing soil
conditions used for fill.
0 Preparing an As-Graded Geologic Map.
0 Providing professional opinions as to the grading contrac-
tor's general adherence to the geotechnical aspects of the
plans and specifications.
0 Preparing this final report of grading.
General
The project plans were prepared by Sowards Engineering, Incorporated and
are entitled "Grading Plans for S.D.P. 82-4 and C.T. 82-23" dated August 1,
1983 and "Improvement Plans for Private Driveways," dated May 24, 1984.
n 9530 DOWDY DRIVE . SAN DIEGO. CALIFORNIA 92126 . PHONE (619) 695-2880
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File No. D-2904-502
September 19, 1984
The project soils report is. entitled "Geotechnical Investigation for
Tentative Planned Development, Map 82-23" prepared by Geocon, Incorporated
dated May 25, 1983.
An earlier "Report of Testing and Observation Services During Mass Grading
Operations for Carlsbad Tract 82-23" has been previously prepared by our
office and is dated May 21, 1984.
References to elevations and locations herein were based on surveyor's or
grade checker's stakes in the field and/or interpolation from the
referenced Grading Plans.
Grading
Subsequent to our earlier report, grading operations contained in the
central canyon area and in the eastern portion of the site.
During the grading operation, compaction procedures were observed and in-
compaction of the placed fill. Field observations and the results of the
place density tests (ASTM D1556) were performed to evaluate the relative
in-place density tests indicate that the fill has_generally been compacted_
to at least 90 percent relative com action T%e G&ts of the in-place
density tests are summarized in Table I1 T e approximate locations of the
for reference.
in-place density tests have been recorded on a copy of the Grading Plans
Laboratory tests were performed on samples of material used for fill to
evaluate maximum dry density (ASRI Dl557-70, Method C), optimum moisture
content, and expansion characteristics. The results of the laboratory
tests are summarized in Tables I and 111.
Slopes
Both cut and fill slopes have inclinations of 2 to 1 (horizontal to
vertical) with maximum heights on the order of 26 feet and 24 feet,
respectively. The fill slopes were periodically backrolled with a sheeps-
upon completion. All slopes should be planted, drained andmaintained to % foot compactor during construction and were track-walked with a bulldozer
reduce erosion. Slope planting should consist of a drought-tolerant ~67
mixture of native plants and trees having a variable root depth. Iceplant *,;
should not be used on slopes. Slope watering should be kept to a minimum
to just support the vegetative cover.
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File No. D-2304-502
September 19, 1984
Finish Grade Soil Conditions
During the grading operation, building pads which encountered clayey soils
at grade were undercut at least 2.5 feet and capped with granular soils.
were placed within at least the upper 3 feet of finish grade on fill lots.
Similarly, our observations and test results indicate that granular soils
The laboratory test results indicate that the prevailing soil conditions
within 3 feet of finished grade on each building padhave an Expansion-
Index of less than 20 and are classified as having a "very low" expansion
summary of the indicated Expansion Index of the prevailing soil conditions
potential as defined by UBC Standard Table 29-C. Table 111 presents a
on the site.
In addition to capping building pads as described above, the cut portion of
those pads which contained a cut-fill transition within the building area
was undercut at least 2.5 feet and replaced with compacted fill soil.
Subdrains
Subdrains were installed at the general locations shovn on the approved +
Grading Plans. In addition, a blanket drain was installed in the seepage r-.-
areas at the bottom of the canyon fill. The subdrains were "as-built" for a.3:
location and elevation by the project Civil Engineer. C{HC -
Soil and Geologic Conditions
The soil and geologic conditions encountered during grading were found to
be similar to those' described in the project geotechnical report. The
geologic conditions observed. The approximate locations of subdrains and
enclosed reductions of the approved Grading Plans depict the as-graded
observed during the grading which, in our opinion, would preclude thF
the blanket drain are also indicated. No soil or Reologic conditions were
continued development of the property as planned.
CONCLUSIONS AND RECOHNEMlATIONS
Based upon laboratory test results and field observations, it is our
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opinion -that the prevailing soil conditions within 2.5 feet of finish pad
grade consist . of "very low" expansive soils as classified by UBC Table 29C.
We recommend the following foundation and slab design criteria for the
proposed residential and commercial structures.
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- File No. D-2904-502
September 19, 1984
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Foundations
1. Conventional spread and/or continuous footings founded at least 12
inches beLoL12west adjacent grade in properly compacted or dense
undisturbed "low" expansive soil may be designed for an allowable soil
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bearing pressure of 2.000 psf (dead plus live loads). Footings should have
a minimum width of 12 inches. This bearing pressure may be increased by up
to one-third for transient loads such as wind or seismic forces.
2. All -s should be Ieinforced with at least two KO. 4
bottom. The above minimum reinforcement is based on soil characteristics
reinforcing bars, one placed near the top of the footing and one near the
and is not intended to be in lieu of reinforcement necessary for structural
considerations.
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- 3. Concrete slahs-on-grade should have a nominal thickness of_4&&<5 and should be reinforced with 6x6-10/10 welded wire mesh. The slabs should be
. underlain with 4 inches of clean sand and,moisture sensitive floor
coverings are planned, a vlsqueen moisture barrier protected by a 2-inch
sand cushion should be provided. Great care should be taken during the
placement and curing of concrete flatwork to reduce the potential for
shrinkage cracking.
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4- Footings should not be placed within 8 feet of the top of slopes.
Footings that must be located in this zone should be extended in depth such
that the outer bottom edge of the footing is at least 8 feet horizontally
from the face of the slope.
5. No special subgrade presaturation is deemed necessary prior to placing
concrete, however, the exposed foundation and slab subnrade soils should be
sprinkled as necessary to maintain a moist condition as would be expected
in any such concrete placement.
Lateral Loads
6. The pressure exerted by an equivalent fluid veight of 300 pcf should be
used to provide resistance to design lateral loads. This design value
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assumes that footings or shear ke;s are poured neat against properly
compacted granilar fill soils or undisturbed formational soils and that the
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Oil mass extends at least 5 feet..hJrizonfallx from the face of the footing
whichever is greater. The upper 12 inches of material not protected by
or three times the height of the surface generating passive pressure,
resistance.
floor slabs or pavement should not be included in design for passive
7- If friction is to be used to resist lateral loads, a coefficient of
friction between soil and concrete of 0.40 may be utilized.
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- File No. D-2904-502
September 19, 1984
Retaining Walls
- 8. Unrestrained retaining walls should be designed to resist the pressure
granular onsite material will be used for backfill, that the backfill
exerted by an equivalent fluid weight of 30 pcf. This value assumes that
wall. For walls with backfill surfaces inclined at no steeper than 2.0 to
1.0, an active pressure exerted by an equivalent fluid weight of 45 pcf
should be used.
9. For walls restrained from movement at the top, such as basement walls,
an additional uniform horizontal pressure of (7H) psf (H equals the height
pressures given above.
- surface will be level, and that no surcharge loads will be acting on the
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- of the wall in feet) should be applied in addition to the active lateral
c 10. All retainiq walls should be provided with a backfill drainage system
adequate to prevent Lb,e-b.uildup of hydrostatic forces.
Drainage
11. Adequate drainage provisions are imperative. Under no circumstances
should water be allowed to pond adjacent to footings. The lots and
improvements are in place so that drainage water is directed away from
foundations, concrete slabs and slope tops to controlled drainage devices.
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- building pads should be properly finish graded after buildings and other
LIMITATIONS
Any additional grading performed at the site should be done under our
observation and testing. All trench backfill material in excess of 12
inches in depth should be compacted to at least 90 percent relative compac-
tion. This office should be notified at least 48 hours prior to commencing
additional grading or backfill testing.
The conclusions and recommendations contained herein apply only to our work
with respect to grading, and represent conditions at the date of our final
inspection, June 22, 1984. Any subsequent grading should be done under our
observation and testing. As used herein, the term "observation" implies
only that we observed the progress of the work with which we agreed to be
complies with the job specifications are based on our observations,
involved. Our conclusions and opinions as to whether the work essentially
experience and testing. Subsurface conditions, and the accuracy of tests
used to measure such Conditions, can vary greatly at any time. IJe make no
warranty, expressed or implied, except that our services were performed in
accordance with engineering principles generally accepted at this time and
location.
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File No. D-2904-302
September 19, 1984
We will accept no responsibility for any subsequent changes made to the
site by others, by the uncontrolled action of water, or by the failure of
others to properly repair damages caused by the uncontrolled action of
water.
further service, please contact the undersigned.
If there are any questions regarding our recommendations or if we may be of
Very truly yours,
GEOCM, INCORPORATED
~~
Ja s E. Likins Michael W. Hart
Rdd 17030 CEG 706
RRG: JEL: lm
(5) addressee
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&P4& Raul R. Garcia
Staff Engineer
GEOCON
File No. D-2904-502
September 19, 1984
TABLE I
Summary of Laboratory Compaction Test Results
ASRI D1557-70
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Description
Brown-tan, fine to medium
slightly Clayey SAND
Brown, Clayey, Silty, fine
SAND
Green-tan, Silty, Sandy. CLAY
Brown. fine to medium, Silty
Clayey SAND
Tan, fine to medium, Silty
SAND
Brown, very fine to fine,
Silty SAND
Tan, very fine to fine, Silty
SAND
Reddish-brown, very fine to
fine, Silty SAND
White to gray, very fine to fine, Silty SAND
Red-brown, very fine to fine
SAND
Tan, medium-grained, Clayey
SAND
Dark brown, fine SAND
Light green, Silty Sandy CLAY
Golden light brown, very fine
to fine SAND
Yellow to tan, fine to medium
SAND
Naximum Dry
Density
PC f
123.1
120.2
111.1
122.1
117.4
119.2
118.0
117.8
112.9
127.2
125.2
124.9
124.0
120.6
119.0
Optimum
Eloisture
% Dry Wt.
11.1
12.5
16.6
11.6
12.9
11.8
12.8
12.1
15.0
10.1
10.6
10.7
11.5
11.3
12.2
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File NO. D-2904-302
September 19, 1984
TABLE I11
Summary of Expansion Index Test Results
Unit Nos.
1, 2, 3
7, a, 9, 10
Commercial Site
Expansion Index
14
7
14
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