HomeMy WebLinkAboutCDP 00-50; Quirck Residence; Geotechnical Preliminary Investigation; 2000-09-21American Geotechnical
Protecting Your Future
PRELIMINARY INVESTIGATION
Quirk Residence
3075 Ocean Street
Carlsbad, Califomia
File No. 22366.01R September 21, 2000
22725 Old Canal Road, Yorba Linda, CA 92887 (714) 685-3900 (800) 275-4436 FAX (714) 685-3909
5764 Pacific Center Boulevard, Suite 112, San Diego, CA 92121 (858) 450-4040 FAX (858) 457-0814
American Geotechnical
Protecting Your Future
September 21, 2000 File No. 22366.01R
Mr. Luis Quintanar
THORYK ARCHITECTURE
1235 Shafter Street
San Diego, Califomia 92106
Subject: PRELIMINARY INVESTIGATION
Quirk Residence
3075 Ocean Street
Carlsbad, Califomia
Dear Mr. Quintanar:
As requested, American Geotechnical has prepared the following report presenting the fmdings of our
geotechnical investigation at the subject project. The purpose of the investigation was to evaluate the
geotechnical conditions at the site and provide recommendations for the proposed constmction. Results of the
investigation indicate that the proposed constmction is feasible from a geotechnical standpoint provided the
recommendations contained herein are incorporated into the project plans and specifications. Specific
recommendations for foundation design for the proposed improvements are presented in the following text.
The geotechnical report should be reviewed in detail prior to proceeding further with the planned constmction.
When plans become available, they should be forwarded to this office for review and comment.
We appreciate the opportunity to be of service. If you should have any questions or require additional services,
please contact this office.
Sincerely,
AMERICAN GEOTECHNICAL
Richard K. Walsh /
Senior Engineer
G.E. 2498
Reviewed by:
'odd M. Page (/
lenior Geologist
C.E.G. 2083
idred T. Marsh
Chief Geotechnical Engineer
G.E. 2387
RKW/TMP/ETM:kr
Distribution: Mr. Luis Quintanar - (2) Via Fax & Mail
22725 Old Canal Road, Yorba Linda, CA 92887 (714) 685-3900 (800) 275-4436 FAX (714) 685-3909
5764 Pacific Center Boulevard, Suite 112, San Diego, CA 92121 (858) 450-4040 FAX (858) 457-0814
File No 22366 01 H American Geoteclmical
September 21, 2000
Page 1
1.0 INTRODUCTION
1.1 PURPOSE
The following text presents the results of our investigation for the proposed residence at 3075 Ocean Street in
Carlsbad, Califomia. The purpose of the investigation was to obtain engineering and geologic information to
estimate subsurface conditions and provide soil design parameters and foundation recommendations for
constmction of the proposed improvements.
1.2 PROPOSED CONSTRUCTION
Based on conversations with the project architect, it is our understanding that the proposed constmction at the
site will include demolishing the existing residence and constmcting a new residence in its place. The new
residence will encompass the existing footprint as well as extending approximately 11 to 14 feet further out to the
rear.
Based upon our understanding ofthe proposed constmction and our investigation it appears that minimal grading
will be needed to constmct the proposed improvements. In areas where loose near-surface material is present,
some remedial grading may be needed depending on the type of foundation system selected. Any grading
conducted will likely be limited to removing any loose near-surface soil in the area of constmction and replacing
it as properly compacted fill. Additionally, grading may be necessary to remove and recompact material
disturbed during the demolition process. Recommendations for any site grading to be conducted are included in
later sections of this report. When additional plans become available, they should be forwarded to this office for
review and comment.
1.3 SCOPE OF SERVICES
The scope of services performed during our investigation primarily included the following:
• Review of available literature and maps pertaining to geotechnical conditions at the site and surrounding
area. References utilized are presented in Appendix A.
• Excavation of two test pits including logging and soil sampling. The locations of the test excavations are
presented on Figure 1 and the logs of the test excavations are presented in Appendix B.
• Laboratory testing of collected soil samples collected from the test excavations to estimate engineering
properties of the site soil. Results of the laboratory testing are presented in Appendix C.
• Engineering and geologic analysis to develop geotechnical recommendations and design parameters.
• Preparation of this report including conclusions and recommendations for the proposed constmction.
Legend L
I i
AGTP-2 B9 Approximate location of test pit
0 5 10
Approx.l" = 10'
American
Geotechnical
Subsurface Location Plan
Quirk Residence
F.N. 22366.01 Septennber 2000
FIGURE 1
File No 22366 01 H American Geotechnical
September 21, 2000
Page 2
2.0 SITE DESCRIPTION
The subject site consists of a rectangular shaped lot. The lot lies along the coastline of the Pacific Ocean. The
property is located to the southwest of the southem end of Ocean Street in Carlsbad, Califomia. The lot is
bordered by Ocean Street to the northeast, by similar residential properties to the northwest and southeast and by
the Pacific Ocean to the southwest. Existing improvements on the lot include a single family home with attached
garages which has been sub-divided and is currently being utilized as numerous vacation rental properties. Other
improvements on the lot primarily include concrete patios and walkways. The foundation for the exiting
residence appears to primarily include a slab-on-grade with continuous footings in the front with a small portion
ofthe residence possibly being a raised wood floor foundation with a subfloor crawlspace. The residence
appears to be of typical wood-frame constmction. It was not determined as part of this investigation when the
residence was originally constmcted.
The lot's topography is gently sloping down from the front to back (northeastem to southwestem) direction. It is
estimated that the total relief across the lot is on the order of 20 to 25 feet. It appears that little grading took
place during constmction of the existing improvements. The general configuration of the site is presented on
Figure 1.
File No 22366 01 ^ American Geotechnical
September 21, 2000
Page 3
3.0 GEOLOGY
3.1 GEOLOGIC SETTING
The property is located geomorphically within the Peninsular Range Province. The Peninsular Ranges extend
north to the Los Angeles Basin and south to the tip of the Baja Peninsula. The Peninsular Ranges consist of a
series of northwest to the southeast trending blocks separated by paralleling fauhs. Topographic relief reaches a
maximum of 10,000 feet at San Jacinto Peak. Rock units ranging from Paleozoic to Quatemary in age can be
found in the province. Extensive Cretaceous rocks give way to post-cretaceous marine, and non-marine, and
volcanic deposits near the coastline. Within the province, drainage is provided by the San Diego, San Luis Rey,
Santa Margarita, and San Diequito Rivers.
Local topography is characterized by the gently west sloping terrain consisting of shoreline deposits giving way
to more elevated and more resistant Quatemary terrace deposits and Tertiary near shore and lagoonal deposits to
the east.
3.2 SITE SPECIFIC GEOLOGY
The site is situated at the coastal section of northem San Diego County, just south of Buena Vista Lagoon. The
site is specifically located on the beach and adjacent shoreline bluff in Carlsbad at the west terminus of Carlsbad
Village Drive. The west portion of the lot consists of a relatively flat sandy beach and the east portion ofthe lot,
containing the four (4) unit rental property, is an elevated bluff consisting of young terrace deposits. The local '
area supports lithologies ranging from Tertiary, near shore to lagoonal, transgressive and regressive sequences to
Recent Artificial Fill and Holocene Beach deposits. According to F. Harold Weber (1982), the site is underlain
by Quatemary shoreline deposits. Holocene Beach deposits are found on the west portion ofthe property and
Pleistocene Terrace Deposits are found to the east of the bluff. The Pleistocene Terrace Deposits are
characterized as a light brown to orange, medium to coarse grained, massive to thinly laminated, pooriy cemented
sandstone deposit with occasional beach sand interbeds. The Quatemary terrace deposits transgress rapidly into
Holocene Beach Deposits approximately at the east edge of the rear (lower) patio. The Beach Deposits consist
primarily of sand, with minor amounts of silt and clay and occasional shell fragments. Shallow fill soils were
found to consist primarily of silty sand and ranged from loose to moderately dense.
Stmcturally, the site is resting on a generally stable, gendy southwest dipping shoreline platform. A secondary
terrace deposit of slightly older age creates a ridge just east of 1-5. No mapped landslides exist within the
immediate area of the site.
The site is mapped by Tan and Giffen(1995) as being within Zone 4.1, which is defined as an area "most
susceptible" to landsliding. Coastal bluff erosion and urban mnoff can create unstable slopes in an active
shoreline environment. The stmcture has been in-place for many years, providing an indication of relatively
stable slope conditions, however, periods of high tides and strong winter storms can rapidly change coastal
geography. During our investigation, no signs of slope instability were observed at the site.
File No. 22366.01
September 21, 2000
Page 4
American Geotechnical
3.3 GROUNDWATER
Groundwater was encountered at a depth of approximately 12 feet in the westem most of our excavations. This
groundwater should not be a factor in the development proposed. However, groundwater may be a factor in the
constmction of any deep foundation system and should be considered by the contractor when selecting the
method of constraction. It should also be noted that suri^ace or shallow perched groundwater conditions can and
may develop where no such conditions existed previously. This can occur due to changes made to the natural
drainage pattems during development, increased irrigation, heavy rainfall and/or other reasons. Because the
introduction of water is usually the triggering mechanism for most common types of soil problems, it is important
to provide adequate surface drainage for proposed improvement such as retaining walls, foundations and slab
areas and other improvements that could be adversely affected by water. Recommendations for drainage are
provided in section 7.6.
3.4 GEOLOGIC HAZARDS
Several geologic hazards have been known to exist along the Southem Califomia coasdine. These hazards
generally consist of landsliding, the possibility of tsunamis immediately along the coastline and ground shaking
due to earthquakes. Landsliding is not considered to be a factor in the proposed development and the possibility
for occurrence after constmction is considered negligible because ofthe relatively competent materials
underiying the site. Given the close proximity of this site to the coastline a tsunami could impact the site if one
were to occur. Finally, the presence of beach sand and groundwater in the westem portion of the lot indicates this
area would likely be susceptible to liquefaction should an earthquake occur.
The most likely geologic hazard to affect the site would be ground shaking in the event of an earthquake. The
nearest active fault to the site is the Rose Canyon Fault Zone. The fault is found to extend from Downtown San
Diego in a north direction, roughly paralleling 1-5, until the fault bends westward through La Jolla before heading
offshore and continuing north up the coastline. The offshore segment ofthe Rose Canyon is approximately 2.5
miles west of the site. The maximum probable magnitude earthquake estimated for the Rose Canyon fault is a
(M) 6.0. Additionally, the site Ues approximately 1.75 miles northwest of a small unnamed fault segment
exposed on the north side of Agua Hedionda Lagoon. If a significant earthquake were to occur near the site,
considerable ground shaking could occur. Comparatively, any residence within Southem Califomia, in close
proximity to a significant earthquake event, could be expected to experience seismic induced damage. The
following table illustrates the characteristics of ground shaking estimated for the site from various nearby faults
using an attenuation relationship provided by Campbell generated by EQFAULT 2.0 (Blake 1988-1993):
Table 1: Selected Faults
Fault Name Approximate
Distance
(miles)
Maximum
Probaliie
Magnitude
Pe^kSite
Acceleiration
Rose Canyon 2.5 6.00 0.31
Newport-Inglewood-Offshore 7 5.75 0.15
Palos Verdes-Coronado Banks 20 6.75 0.10
Elsinore 25 6.75 0.08
La Nacion 25 4.25 0.02
San Diego Trgh-Bahia Sol 30 6.25 0.04
Catalina Escarpment 35 6.25 0.03
Whittier-North Elsinore 44 6.00 0.02
Chino 46 5.50 0.02
Caca Loma Clark (San Jacinto) 48 6.75 0.03
Glen Helen-Lytle 50 6.50 0.02
File No 22366 01 ^ American Geotechnical
September 21, 2000
Page 5
3.5 SEISMICITY AND SEISMIC RTSK
Our historical search indicates that approximately 114 events have occurred within a 50 mile radius of the site
with magnitudes (M) between 4.0 and 9.0, within the last 100 years. The largest event recorded within that time
frame was a (M) 6.8 earthquake, approximately 46 miles from the site, which produced a site acceleration of
about 0.03g.
Even if the stmctural engineer provides designs in accordance with applicable codes for seismic design, the
possibility of damage occurring cannot be mled out in the event of a large earthquake near the site. This is the
case for essentially all homes in Southem Califomia. The stmctures should be designed in accordance with the
latest UBC criteria for seismic design. The site area should be categorized as a Seismic Zone 4.
File No 22366 01 _ American Geotechnical
September 21, 2000
Page 6
4.0 SUBSURFACE EXPLORATION
The subsurface exploration consisted of two hand-excavated test pits. The approximate locations of the
excavations are depicted on Figure 1. The purpose of the excavations was to delineate the subsurface conditions
in the area of the proposed improvements. All excavations were logged by a geologist from our firm who also
obtained soil samples for laboratory testing. Additionally, each excavation was backfilled upon completion.
The test excavations revealed variable subsurface conditions. AGTP-1 revealed fine to coarse grained beach
sands. Variable moisture was also encountered with depth and the sands were found to become dense with depth.
Water was encountered in this excavation at a depth of approximately 12 feet. In AGTP-2 approximately 2.4 feet
of fill was encountered. This fill was described as fine to medium grained sands, being slightly moist and loose
to medium dense. Terrace sands were encountered below the fill. These were described as fine to medium
grained sands, being slighdy moist and medium dense to dense. Groundwater was encountered in AGTP-1 at a
depth of approximately 12 feet and was not encountered in AGTP-2. Detailed logs of these excavations are
presented in Appendix B of this report.
File No. 22366.01 H American Geotechnical
September 21, 2000
Page 7
5.0 LABORATORY TESTING
A laboratory testing program was developed for the soil samples recovered during the subsurface exploration.
The program was designed to estimate soil properties for use in engineering evaluations. The laboratory testing
included field moisture and density, maximum density, hydro-response and direct shear testing. A summary of
the laboratory test results is presented in Appendix C.
In general, the results of the laboratory testing indicated the soil at the site above the water table possessed fairiy
low moisture contents and correspondingly low levels of saturation. Additionally, the site soil was found to
possess a moderate potential for collapse with the addition of water. Given the relatively cohesionless nature of
the soil and the sampling process, a portion of the collapse potential determined through testing could be due to
sample disturbance.
File No 22366 01 American Geotechnical
September 21, 2000
Pages
6.0 CONCLUSIONS
Based upon the results of our geotechnical investigation at the subject site, np geotechnical conditions were
encountered which would preclude the proposed improvements, provided the following conclusions and
recommendations are incorporated into the project plans and specifications. Foundation recommendations have
been provided to help reduce the potential for problems associated with the soil conditions encountered. The
actual recommendations are discussed in detail in the following sections.
Based on the results of our subsurface exploration it appears as if the rear portion of the lot is comprised
primarily of beach sands overiying more competent material at depth. In it's present state this beach sand
material is not considered suitable for support of the proposed stmcture. This unsuitable material extends to
depths exceeding 12 feet near the outer edge of the proposed residence. Near the rear of the existing residence
competent terrace deposits were encountered at a relatively shallow depth. As such, it anticipated that a majority
of the existing residence is founded in competent terrace deposits. Considering this, it should be anticipated that
proposed constmction extending out past the rear of the existing residence will need to have a foundation system
deepened to competent formational soil.
Ifthe recommendations herein are followed, it is anticipated that tolerable levels of soil related movement can be
expected for the proposed stmctures.
File No 22366 01 H American Geotechnical
September 21, 2000
Page 9
7.0 RECOMMENDATIONS
7.1 GENERAL
Conclusions and recommendations contained in this report are based on information provided, information
gathered, laboratory testing, engineering and geologic evaluations, experience and professional judgment.
Recommendations contained herein are consistent with current industry practices. Other altematives exist and
can be discussed on request. Regardless of the approach taken, some risk will remain, as is always the case. The
recommendations and design parameters presented below should be utilized by the design civil/stmctural
engineer for the design of foundations. Once plans have been developed, they should be forwarded to this office
for review and comment.
7.2 EARTHWORK AND SITE PREPARATION
Given the improvements proposed and the configuration of the lot, it is anticipated that little grading will be
necessary as part of improvements at the site. If any grading is necessary, it would be anticipated that it would be
pnmanly for access, to remove and recompact any loose near surface material, or to remove and recompact any
material disturbed during the demolition process.
Prior to any grading, the site should be cleared of all surface and subsurface obstmctions including things such as
debris, buried utilities, existing improvements and should be stripped of vegetation. Vegetation, debris and
demolition material should be disposed of offsite. Any holes or excavations made which extend below the
finished grade should be filled with compacted soil.
7.2.1 CUTS AND EXCAVATIONS
It is not anticipated that extensive cuts or excavations will be conducted during the constmction of site
improvements. However, if any removals or excavations are required they should not be conducted at angles of
inclination of steeper than 2:1 (horizontaLvertical) without additional analysis and input by the geotechnical
consultant. Additionally, no excavation or cut should be deeper than five (5) feet without additional analysis and
recommendations by the geotechnical consultant.
7.2.2 FILLS
Our investigation did not indicate the presence of expansive soils within the subject lot. If expansive soils are
encountered during constmction, it is recommended that they not be placed within five (5) feet of finish grade in
the building pad area(s) or beneath appurtenant stmctures and should be kept a minimum of five (5) feet away
from proposed stmctures, unless special design considerations are implemented. With this exception, the on-site
soils are generally suitable for use as compacted fill provided they are free of organic material and debris. All
areas planned to receive fills and/or improvements will require removal and recompaction of the loose near
surface soil and/or unsuitable materials. If grading is to be conducted, additional input will be needed from the
geotechnical consultant.
All fill to be placed should be moisture conditioned and compacted to a minimum of 90 percent of the maximum
dry density per ASTM D-1557. Fill should be placed in thin, unifonn lifts (6 to 8 inches loose thickness). Fills
placed on natural slopes should be keyed and benched into firm, competent material and inspected prior to the
placement of fill. Any pennanently graded site slopes should be constmcted at inclinations no steeper that 2:1
(horizontaLvertical). The geotechnical consultant should be on-site to test and observe all fills/removals during
grading operations, and also to review footing excavations, cuts, etc.
File No 22366 01 H American Geotechnical
September 21, 2000
Page 10
7.2.3 CUT/FILL TRANSITIONS AND LOT CAPPING
Stmctures planned should not straddle cut/fill transitions. In order to prevent this, footings for the planned new
residence should be deepened to competent fonnational soil. This can likely be accomplished with continuous
footings where the existing residence now sits and by a deepened foundation system where the proposed
residence will extend further to the rear than the existing residence.
7.3 FOUNDATION DESIGN PARAMETERS
Based on our subsurface exploration it should be anticipated that the proposed expansion of the building footprint
to the rear ofthe home be constmcted on a deepened foundation system extending to competent formational
materials at depth. Due to the varying depth of competent formational material it may be possible to provide a
combination of continuous footings and piers. The stmctural engineer may want to consider this possibility in
the design process.
The near surface soil in the area of the proposed addition consisted of a relatively loose, cohesionless beach sand.
As such, this material is not considered suitable for the support of stmctures without deepened foundations. The
deepened foundations would also provide added protection against possible future erosion ofthe beach area
which could possibly encroach on the subject property. Additionally, the beach sand below a depth of
approximately 12 feet is considered saturated and could be subject to liquefaction should an earthquake occur.
The portion ofthe residence to be constmcted within the footprint ofthe existing residence is anticipated to be
sitting on competent tenace deposits and these soil deposits are considered to have a negligible to very low
potential for liquefaction.
Continuous Footings
Minimum Embedment depth into competent formational soil 2.0 feet
Minimum width
18 inches
Allowable Bearing Pressure for Continuous Footings Founded
in Competent Formational Material 2 500
psf
Total Loads (including wind or seismic) 3 500 psf
Increases Capacity for Each Additional Foot of Depth
Deeper Than Minimum 5O0 psf
Maximum Value . . . . '. '.'.6,000 psf
Resistance to Lateral Loads
Passive Soil Pressure (equivalent fluid pressure) 300 pcf
Coefficient of Sliding Friction for Cast Concrete on Compacted Fill 0.35
Any footing near slopes should satisfy a minimum horizontal setback as indicated in the Uniform Building Code,
Chapter 18, Figure 18-1-1. This distance should be measured from the lower leading edge of the footing to the
slope face.
Deepened Foundation
Minimum pier dimension (either diameter or side of rectangular of square shaft) 2.0 feet
Minimum pier embedment into competent formational soil 5.O feet*
File No 22366 01 H American Geotechnical
September 21, 2000
Page 11
Bearing Capacity for piers in competent formational soil (End Bearing) 6,000 psf
* the depth of competent fonnational soil adjacent the residence is presented, on the logs in Appendix B and the
depth of competent fonnational soil at the rear of the proposed addition was not determined during our
subsurface exploration but is estimated to be approximately 15 to 20 feet based on experience and observations in
other areas.
Lateral Loading
Lateral loads should be included in the design of piers. The following lateral loading criteria should be
incorporated into the project design:
Active Pressure 30pcf*
At-Rest Pressure 45 ^^^^
Passive Pressure 3QQ p^,^*
*To be applied over three (3) pier diameters. This would account for a loss of support on the beach side of the
piers. Additionally, this assumes clean, non-expansive backfill. Other design parameters may need to be
provided at the time of constmction if conditions differing from those anticipated are encountered.
To be applied over two (2) pier diameters. Should be calculated from the ground surface but neglected above
the depth of water which was approximately 12 feet.
Seismic Design Parameters
The following site seismic parameters were detennined in accordance with Section 16, Division IV-Earthquake
Design of the Uniform Building Code (1997):
Seismic Zone 4
Seismic Zone Factor (Z) 0 40
Soil Profile Type
Seismic Source Type g
Seismic Coefficient (Ca) 0 44N
Seismic Coefficient (Cv) 0 64Nv
Near Source Factor (Na) ^ 25
Near Source Factor (Nv) 2 4
It should be noted that these values are considered "minimum design values" as dictated in the Uniform Building
Code. ^
7.4 STANDARD FOUNDATION RECOMMENDATIONS
Actual foundation details should be detennined by the designer using the criteria in Section 7.3, however, the
followmg are presented as a guideline to supplement the design process. These recommendations should'not
preclude stmctural requirements.
File No 22366 01 _ American Geotechnical
September 21, 2000
Page 12
7.4.1 SLABS AND FOOTINGS
New footings should be designed utilizing the criteria presented above. The new interior floor surface for the
addition will hkely either be raised wood flooring or a slab-on-grade. New interior and exterior slabs should be
at least five (5) mches thick, and reinforced with a minimum of No. 4 rebar at 16 inches on center each way.
Experience and research have shown that concrete with a high water/cement ratio can experience problems such
as excessive shnnkage cracking, moisture intmsion, and high vapor emissions, among other things Generally
speakmg, the higher the water/cement ratio, the higher the porosity and pemieability ofthe concrete, and the
lower the strength. Concrete designed for compressive strengths on the order of 2000 to 2500 psi can oftentimes
have excessive levels of mixing water and conespondingly a high water/cement ratio.
Consideration should be given to using the lowest possible water/cement ratio while still maintaining
workability. It is recommended that concrete used for footings and slab areas have a minimum compressive
strength of 3,000 psi with a maximum water/cement ratio of 0.45. All steel and concrete materials details
placement procedures, and curing should be perf-ormed strictly in accordance with ACI specifications and '
guidelines. The slab design by the stmctural engineer and/or architect should consider shrinkage ofthe concrete
to limit cracking to the slab and overiying floor coverings.
Any new interior floor slabs should be underiain by a minimum of two (2) inches of clean sand, underiain by a
moisture membrane such as visqueen. The visqueen should be a minimum of 10 mil thick and should provide a
continuous vapor banier sealed at all splices and around pipes or other protmsions. A four inch thick open
graded gravel base should be placed below the visqueen to provide a capillary break. To help protect the
visqueen from punctures during placement, it is recommended that a filter fabric such as Mirafi MON be placed
between the rock and visqueen. Finally, prior to installing any flooring in the residence moisture vapor emissions
should generally be 3.0 lbs./l,000 sq. ft./day or less. Ifthe contractor wishes to install flooring on slab with
moisture vapor emissions in excess of this value additional input may be needed from the geotechnical consultant
regarding steps to take prior to flooring installation.
7.4.2 APPURTENANT STRUCTURE FOUNDATIONS
The same guidelines for slab and footings would also pertain to design and constmction of appurtenant
stmctures, with the exception of exterior flatwork which do not usually necessitate the use of a visqueen moisture
bamer. However, the recommendations for slab thickness-and reinforcement for exterior flatwork still pertain to
help reduce the potential for cracking and separations. In addition, proper jointing should be used to control
cracking. As with mtenor concrete, all steel and concrete materials, details, placement procedures and curing
should be performed stnctly in accordance with ACI specifications and guidelines.
Special detailing may be necessary to limit unsightly cracking at stmctural interfaces, such as between
foundations and adjacent slabs. Appurtenant stmctures placed near slope tops could creep over time in response
to slope movement. Appurtenant stmctures should be kept as far away from stop tops as possible. For slopes ten
(10) feet in height or less, a minimum setback of ten (10) feet is recommended unless special detailing is
implemented. This might include stmcturally tying exterior slabs to the foundation or providing a thicker
heavily reinforced section. If needed, actual details should be developed by the project architect and/or stmctural
engineer.
File No 22366 01 ^ American Geotechnical
September 21, 2000
Page 13
7.4.3 REINFORCEMENT PLACEMENT
Care should be taken when placing foundation and slab reinforcement. Placement details should be in
confonnance with ACI specifications. Unless otherwise specified by the stmctural engineer, continuous footing
reinforcement should be placed in the upper and lower 1/3 portions of the foundation's sections. The bottom
foundation steel should not be closer than three inches to the underiying excavation. Slab reinforcement should
be placed in a positive fashion between the midpoint and upper 1/3 portion of the slab section.
"Lifting" slab steel into place following concrete placement is not recommended. Ifthe contractor elects to "lift"
the reinforcement into position following concrete placement, the owner should consider verifying steel
placement by coring of the slab.
7.5 RETAINING WALL DESIGN CRITERIA
It was not determined if retaining walls are planned at the site. Where planned they should be designed utilizing
the following design criteria:
Restrained Walls (level backfill):
At-Rest Soil Pressure 45 pcf e.f.p.
Passive Soil Resistance 300 pcf e f p
Cantilever Walls (level backfill):
Active Soil Pressure 30 pcf e.f p.
Passive Soil Resistance 300 pcf e.f.p.
In order for these soil design parameters to be valid, all planned retaining walls should be designed with
appropriate detailing including an adequate backdrain system and a clean, non-expansive backfill for a width of
at least the height of the retaining wall for level backfill conditions.
All retaining walls should be waterproofed from above the highest point of earth retained to the heel ofthe
foundation. The architect should provide details for waterproofing including termination details and provisions
for protecting the waterproofing. Each retaining wall should be provided with an appropriate backdrain system
designed by the project architect or civil engineer. It is recommended that the backdrain system extend to the
heel ofthe foundation, and at least one foot below interior slab elevation (where applicable). Water collected in
the backdrain system should ideally be recovered in a peri^orated PVC plastic pipe (perforations down) and
directed to a suitable disposal area at two percent gradient unless otherwise specified by the project civil
engineer.
Retaining wall backfill should be placed in thin lifts (6-8 inches) and compacted by mechanical means. Care
should be taken not to utilize heavy compaction equipment in close proximity to the walls to help reduce the
possibility of damage to the wall and an increase in the above recommended earth pressures.
File No 22366 01 _ American Geotechnical
September 21, 2000
Page 14
7.6 SITE DRAINAGE
Proper surface drainage should be incorporated into the design for the proposed project. Because of potential
problems associated with poor drainage conditions, proper surface drainage should be maintained at all times. As
a minimum, the following standard drainage guidelines are recommended and should be considered by the civil
engineer during final plan preparation:
A. Roof drains should be installed on all stmctures and tied via a "tight line" to a drain system that empties to a
storm drain or tenace drain.
B. Surface water should flow away from stractures and slopes and be directed to suitable (maintained) disposal
systems such as yard drains, drainage swales, street gutters, etc. Five percent drainage directed away from
stractures is recommended, and two percent minimum is recommended over soil areas. Planter areas adjacent the
foundation are not recommended, unless the plants are self-contained with appropriate drainage outlets (i.e.,
drainage outlets tied via a "tight line" to a yard drain system).
C. No drains should be allowed to empty adjacent foundations or over slopes.
D. PVC Schedule 40 or equivalent is prefened for yard drains. A cormgated plastic yard drain is not
recommended.
7.7 UTILITIES
It is not recommended that utilities be planned below a 1:1 projection extending down from the outer edge of
foundations. Footings should be deepened to satisfy the foregoing recommendation. Backfill for all utilities
should be placed by mechanical compaction methods. Flooding and/or jetting of utility or other trench backfill
should not be undertaken.
7.8 CORROSIVITY
With respect to buried piping, it is considered good constmction practice to provide conosion protection by
means of a suitable coating. Placing pressure plumbing overhead instead of under slabs is desirable. It is
recommended that slab and footing concrete be at least Type II with a maximum water-cement ratio of 0.45 by
weight.
7.9 GEOTECHNICAL SERVICES DURING CONSTRUCTION
A representative ofthis office should be on hand during constmction to provide observation and testing services.
Our representatives should be on site whenever compacted fill is being placed. We recommend providing
observation of all foundation excavations prior to the placement of forms, reinforcement or concrete.
Furthemiore, it is recommended that our office be requested to review the slab subgrade areas prior to the
placement of concrete.
7.10 PLAN REVIEW
When final plans are available, they should be forwarded to our office for review and comment and/or signature
indicating compliance with the intentions of the recommendations contained in this report. If any of the other
design professionals or constmction members have any questions regarding the site geotechnical conditions or
the recommendations of this report, our office should be contacted.
File No 22366 01 H American Geotechnical
September 21, 2000
Page 15
8.0 OTHER CONSIDERATIONS
8.1 GRADING CONSIDERATIONS
Recommended grading included removing and recompacting loose near surface material. Other than possible
limited removal and recompaction no other grading is anticipated at the site. If additional grading is planned, the
geotechnical consultant should be contacted for additional input and recommendations.
8.2 SUPPLEMENTAL CONSULTING
This office should be contacted for review of plans for improvements, and should be involved during
constmction in order to monitor the geotechnical aspects of the development (i.e., grading, foundation
excavations, etc.). Unless other anangements are made, supplemental consulting will be on a time-and-expense
basis.
8.3 FIELD CONSTRUCTION REVIEW
During constraction, it is recommended that this office verify site geotechnical conditions and conformance with
the intentions of the recommendations for constmction. Although not all possible geotechnical observation and
testing services are required by the goveming agencies, the more site reviews performed, the lower the risk of
future problems.
8.4 PRO.IECT SAFETY
The contractor is the party responsible for providing a safe site. American Geotechnical will not direct the
contractor's operations and cannot be responsible for the safety of personnel other than our own representatives
on-site. The contractor should notify the owner if he is aware of, and/or anticipates, unsafe conditions. At the
time of constmction, if the geotechnical consultant considers conditions unsafe, the contractor, as well as the
owner's representative, will be notified.
8.5 GROUNDWATER CONSIDERATIONS
As discussed groundwater should be anticipated to be a factor in the excavation of any deep foundation system.
Excavations in the cohesionless beach sands under water should be considered to likely slough into any open
excavations. Excavating below the water table may require temporary shoring and should be considered by the
contractor in planning the method of constraction.
File No 22366 01 IH American Geotechnical
September 21, 2000
Page 16
9.0 REMARKS
The design parameters and foundation guidelines presented above should be considered minimums. The
stractural requirements may dictate more rigorous design and as such should govem. Once final plans have been
prepared, they should be submitted to American Geotechnical for review. In addition, all footing excavations,
removal and compaction operations should be verified by a representative of this office.
Only a portion of subsurface conditions have been reviewed and evaluated. Conclusions and recommendations
and other infonnation contained in this report are based upon the assumptions that subsurface conditions do not
vary appreciably between and adjacent, observation points. Although no significant variation is anticipated, it
must be recognized that variations can occur.
This report has been prepared for the sole use and benefit of our client. The intent of the report is to advise our
client on geotechnical matters involving the proposed improvements. It should be understood that the
geotechnical consulting provided and the contents of this report are not perfect. Any enors or emissions, and/or
any other geotechnical aspect of the project, noted by any party reviewing this report, should be reported'to this
office in a timely fashion. The client is the only party intended by this office to directly receive this advice.
Subsequent use of this report can only be authorized by the client. Any transferring of information or other
directed use by the client should be considered "advice by the client."
File No. 22366.01 HI American Geotechnical
September 21, 2000
APPENDIX A -REFERENCES
"Landslide Hazards in the Northem Part of the San Diego Metropolitan Area, San Diego County, Califomia,"
prepared by Siang S. Tan and Desmond G. Giffen, dated 1995.
"Geologic Map of North-Central Coastal Area of San Diego County, Califomia, Showing Recent Slope Failures
and Pre-Development Landslides," prepared by F. Harold Weber, Jr., dated 1982.
"Geology^of the San Diego Metropolitan Area, Califomia, Bulletin 200," prepared by Michael P. Kennedy, dated
"Physical Geology," prepared by James S. Monroe and Reed Wiscander, dated 1992.
File No 22366 01 H American Geotechnical
September 21, 2000
APPENDIX B -
SUBSURFACE LOGS
• AGTP-1
• AGTP-2
testpit No: AGTP-1 F.N. 22366
Project NaraeLQukkResidence_ •Sheet: 1 Of 1
Location: 3075 Ocean Street, Carlsbad, CA. 17' S & 14.5' W of NW comer of building. start JZ26M-
Estimated Surface Elevations 8' Total Depth: 12' Rig Type : Haud ExCaVated/SaWCUt P.nd : 7/26/00
4-> 4-»
ad)
0) 0)
a u,
0,0)
g a
CO EH
Field Description By: TMP
Surface Conditions: Dry Concrete
Subsurface Conditions: FORMATION: Classification, color, moisture, tightness, etc
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
= 1 IIII: ~1M 1
m
tl
0-0.3' - CONCRETE SLAB-
BEACH SANDS (Oh):
0.3-4.2' - Fine SAND, light brown, slightly moist, loose to moderately dense with depth, massive,
possibly fill soils.
4.2- 5.0' - Fine SAND, light brown/black, moist, medium dense to dense, laminated bedding in upper 6".
5.0-6.3' - Coarse SAND, orange light brown; moist to very moist with depth, medium dense to dense,
clean.
@ 6.0' - Becomes dense.
6.3- 9.0' - Fine SAND, olive light brown, slightly moist, dense, occasional rounded gravel to 1/2"
diameter, occasional shell fragments.
9.0-12.0' - Coarse SANDS, olive light brown, moist, medium dense, no binder.
11.2'- Becomes dense, moist to very moist.
12.0' - Saturated SANDS, ground water, salt water wedge?. Test pit terminated. Seepage at 12.0'.
Legend: HQsheiby
[| Large Bag
American Geotechnical
Test Pit AGTP-1-
testpit No: AGTP-2 F.N. 22366
Project Name: QuirkRcsideuce Sheet: 1 of 1
Location: 3075 Ocean Street, Carlsbad, CA. 11.5' S of NW comer of building, adjacent footing. start :7/26/00
Estimated Surface Elevations 10' Total Depth: 9' Rig Type: Hand ExCaVatcd/SaWCUt End: 7/26/00
0) 0) Q li.
s a
10 >. CO EH
Field Description By: TMP
Surface Conditions: Dry Concrete
Subsurface Conditions: FORMATION: Classification, color, moisture, tightness, etc
0.0-
0.5-
1.0-
1.5-
2.0-
2.5-
3.0-
3.5-
4.0-
4.5-
5.0-
5.5-
6.0-
6.5-
7.0-
7.5-
8.0-
8.5-
9.0-
w
! IllililM
lllll
I I I , llll llllllllll
IIIIIJIJJ
TTTT
0-0.37' - CONCRETE SLAB.
FILL:
0.30-2.4' - Fine to Medium SANDS, olive brown, slightly moist, loose to medium dense, occasional
rootlets/rounded cobble to 6" diameter, undulatory lower contact variable from 1.8-2.4', lower at NW
comer of test pit.
@ 0.90'-Ash bed, 1/4" thick.
TERRACE SAND (OhvY
2.4- 3.5' - Fine to Medium SAND, orange light brown, slightly moist to moist, medium dense to dense,
slightly cemented.
3.5- 5.8' - Fine SAND, olive light brown, slightly moist, medium dense, inter-tongued beach sands.
6.5-7.5' - Medium SAND, orange light brown, slightly moist, dense, no binder, beach sands?,
inter-tongued beach sands below 3.5'.
8.5-9.0' - Fine to Medium SANDS, tan, slightly moist, medium dense to dense, no binder, beach sands.
@ 9.0' - Test pit terminated. No caving. No seepage.
Legend: IjOsheiby
Ql Large Bag
American Geotechnical
Test Pit AGTP-2-
File No. 22366.01 H American Geotechnical
September 21, 2000
APPENDIX C -
LABORATORY PROCEDURES & RESULTS
Moisture Content Determinations
Moisture content determinations were made in accordance with ASTM method of test D2216-92.
Drv Unit Weight
Dry unit weight testing of soil samples were determined in accordance with conventional laboratory techniques.
Compaction Tests
Maximum dry density and optimum moisture content determinations were performed in accordance with ASTM
method of test D1557-91A.
Direct Shear
Direct shear tests were performed on samples remolded to in-place moisture and density. Soil samples were
allowed to soak for about 24 hours while under the confining pressure specified for testing. Consolidated drained
conditions were approximated by using a slow, strain-controlled approach, similar to that outlined in ASTM
method of test D3080-90.
Simple Collapse Tests
Simple collapse tests were performed on remolded ring samples in accordance with ASTM test method D5333-
92, except that time-rate readings were not taken.
File No. 22366.01
September 21, 2000 American Geotechnical
MOISTURE/DENSITY RELATIONSHIP TEST SUMMARY
LOCATTOV
VISUAL
DESCRIPTION
TEST.
METHOD
MAX DRY
DENSITY
(pcO
OPTIMUM^MOISTORE
AGTP-1 @ 0.4-1.9' Beach SAND ASTM D1557-91, "A" 112.5 12.0
File No. 22366.01
September 21, 2000 American Geotechnical
FIELD DENSITY TEST SUMMARY
LOCATION
FIELD DRY
DElSfSITY •fief)
FIELD
. MOISTURE
CONTENT
(%)
DEGREE OF
SATURATION
(%)
SAMPLE
TYPE
AGTP-1 @ 0.4-1.9' 94.7 4.6 16 T
AGTP-1 @ 3.3-4.9' 101.6 5.7 23 T
AGTP-1 @ 5.0-6.3' 103.0 10.8 46 T
AGTP-2 @ 2.3-3.7' 96.7 5.3 19 T
AGTP-2 @ 4.3-5.8' 96.2 3.3 12 T
AGTP-2 @ 6.7-7.5' 85.7 3.7 10 T
AGTP-2 @ 8.5-9.0' 91.2 3.2 10 T
T = Shelby Tube Sample
File No. 22366.01
September 21, 2000 American Geotechnical
SIMPLE COLLAPSE TEST DATA SUMMARY
(inlg^t) : *'
SAMPLL
TYPE
INITIAL DRY
DENSITY
(pcf)
INHIAL
-MOISTURE
(%)
LOAD WHEN
HaOis
ADBBD
(psf)
PERCENT ,
SATURATT^
/55«?ELL'.ft) after KjO
Ull P-2 (" 2 ^-V7 T 96.7 5.3 1000 19 -0.86
AGTP-2 @ 4.3-5.8' T 96.2 3.3 1000 12 -0.67
AGTP-2 @6.7-7.5' T 85.7 3.7 1000 10 -1.51
AGTP-2 @8.5-9.0' T 91.2 3.2 1000 10 -1.53
T = Shelby Tube Sample
133
131
129
127
125
123
121
119
117
115
113
111
109
107
105
103
101
99
97
95
93
91
89
87
85
83
81
79
77
75'
•
-
\ File no. 22366.01 Date 8/2/00
Project Quirk residence
Date
Project
\
• • \ • \
Sn„r...nfn..t.H.l AGTP-1 (g 0.4-1.9' Sn„r...nfn..t.H.l AGTP-1 (g 0.4-1.9' \ Sn„r...nfn..t.H.l AGTP-1 (g 0.4-1.9'
\ Description of Materia medium coarse beach sand Description of Materia
Test Method A.S.T.M.D1557-91,"A" \ Test Method A.S.T.M.D1557-91,"A"
>
-
>
/
/ I TCCTDCeillTO
/ T
\
/ Maximum Dry Density ^^•^••^ ^'-^
/ \ Optimum Water Contei It 12.0 % Optimum Water Contei %
f \
/ >
/ \
\ CURVES OF 100% SATURATION
T7r\T> CT%T^r^^T:^r^ r^-n A T/TTP^/- r?/~vT TAT T^Z-V.
CURVES OF 100% SATURATION
T7r\T> CT%T^r^^T:^r^ r^-n A T/TTP^/- r?/~vT TAT T^Z-V. \
. — 0 cn
\ 2.70 2.70
>
\
\
\
\
0 10 15 20 25
WATER CONTENT (Percent)
30 35 40 45
MOISTURE-DENSITY RELATIONSHIP
American Geotechnical F.N. 22366.01 August 2000
ID
X h-o z
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X
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>
H-o llJ U-
Li_ UJ
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SYMBOLS
o O O
^•5 -
INTACT
REMOLDED
PEAK STRESS
ULTIMATE STRESS
RESIDUAL
INITIAL DRY DENSITY PCF
INITIAL MOISTURE CONTENT
0
NORMAL PRESSURE (Ksf)
4
DIRECT SHEAR TEST PLOT
AMERICAN GEOTECHNICAL F.N. 22 36C'-Oj
PLATE
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SYMBOLS
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7.:.s,
INTACT
REMOLDED
PEAK STRESS
ULTIMATE STRESS
RESIDUAL
INITIAL DRY DENSITY
INITIAL MOISTURE CONTENT
PCF
t)
NORMAL PRESSURE (Ksf)
I
DIREqT SHEAR TEST PLOT
AMERICAN GEOTECHNICAL F.N. Z2i<^^^ o ) PLATE