1999-6142 G
~C Southland Geotechnical Consultants
GEOTECHNICAL INVESTIGATION FOR
PROPOSED RESIDENTIAL DEVELOPMENT
2070 SHERIDAN ROAD
LEUCADIA AREA OF
ENCINITAS, CALIFORNIA
Project No. 147A12
April 1, 1 999
Prepared for:
MR. DARREN CARIS
2070 Sheridan Avenue
Encinitas, California 92024
. 1238 GREENFIELD DRIVE, SUITE A EL CAJON, CAUFORNIA 92021 .
(619)442-8022 . FAX (619)442-7859
Sß.C Southland Geotechnical Consultants
April 1, 1 999
Project No. 147A12
To:
Mr. Darren Caris
2070 Sheridan Avenue
Encinitas, California 92024
Subject:
Geotechnical Investigation for Proposed Residential Development,
2070 Sheridan Road, leucadia Area of Encinitas, California
Introduction
In accordance with your request, Southland Geotechnical Consultants has performed
a geotechnical investigation for a proposed residential development at the subject
property. This report presents a summary of our field and research studies and
provides our conclusions and recommendations, from a geotechnical standpoint,
relative to the proposed development.
Scoce of Services
This report presents the results of our geotechnical investigation for the proposed
residential develòpment on the property located at 2070 Sheridan Road in the leucadia
area of Encinitas, California. The scope of our geotechnical investigation included the
following:
Review of aerial photographs, topographic maps, geologic literature and
preliminary project plans pertaining to the site and vicinity. A list of the itèms
reviewed is presented in Appendix A.
Geologic reconnaissance to observe the existing site conditions including the
bluff and general vicinity.
Preparation of a generalized profile of the bluff face (Figure 3).
Investigation of the subsurface soil conditions at the site by excavating, logging
and sampling four exploratory trenches with a backhoe.
Geotechnical analysis of the data obtained including an analysis of the stability
of the onsite bluff.
Preparation of this report summarizing the results of our geotechnical
investigation.
. 1238 GREENFIELD DRIVE, SUITE A EL CAJON, CAUFORNIA 92021 .
(6191442-8022 . FAX (619J442-7859
Project No. 147A12
Site Descriotion
The roughly rectangular subject property is located at 2070 Sheridan Road in the
Leucadia area of the City of Encinitas, California (see Figure 1). The eastern property
boundary lies along the westerly side of Sheridan Road. The westerly property
boundary is delineated by an approximately 65-foot high bluff that slopes
northwesterly to Batiquitos Lagoon at an overall gradient of about 1.6 to 1 (horizontal
to vertical). Residences exist on the adjacent properties to the north and south of the
subject property.
The bluff-top area is relatively level. A one-story, single family residence and detached
garage occupy the eastern portion of the site. Another single-family residence exists
on the northwestern portion of the property (see Figure 2). The remaining bluff-top
area consists of a yard with ornamental shrubs and trees. The bluff face is well
vegetated with grasses, weeds, iceplant, ornamental shrubs and cactuses.
The northwestern portion of the bluff edge at the property appears to have been
modified by retaining structures. The elevation of the bluff edge at .the subject
property is approximately 65 feet above sea level based on the topographic survey by
La Costa Engineering dated March 30, 1999 (Appendix A).
Prooosed Develooment
Based on our conversations with you, it is our understanding that the existing
structures will be razed and a one-story, single-family residence with a swimming pool
will be constructed. We understand that the proposed residence will be set back a
minimum of 25 feet from the bluff edge. We also understand that some site grading
may be performed to attain design finished grades for construction of the new
residence.
Subsurface Exoloration
On March 17, 1999, a geologist from our firm logged and sampled four exploratory
trenches excavated at the site with a Bobcat backhoe at the approximate locations
shown on Figure 2. The trenches were excavated to a maximum depth of 4 feet.
Logs of the exploratory trenches are included as Figure 4. Subsequent to logging and
sampling, the exploratory trenches were backfilled.
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Project No. 147A12
Soil/Geolooic Units
Based on our review of a geologic map and our onsite observations, the subject
property appears to be underlain by topsoil, Quaternary-aged terrace deposits and
Eocene-aged Scripps Formation. Minor amounts of poorly compacted fill soils,
associated with the existing improvements, may also exist at the site. Descriptions
of these units follow:
Topsoil - The topsoil mantles the natural ground surface and is developed on
and gradational with the underlying terrace deposits. As encountered, the
topsoil generally consisted of brown, loose to medium dense, silty fine sand
with roots. In its present state, the topsoil is considered potentially
compressible and should not be relied upon for the support of structural loads.
Terrace Deposits -As encountered, the terrace deposits generally consisted of
orange-brown to light brown, dense, slightly silty, fine to coarse sand with
scattered gravel/cobble. These soils are expected to be the geologic unit
encountered during excavation of foundations at the site and typically exhibit
adequate bearing characteristics.
Scripps Formation - The Quaternary terrace deposits are underlain at depth by
the Eocene-aged Scripps Formation. The Scripps Formation was not
encountered on site during our investigation, however, is exposed locally at the
base of the bluff along the lagoon. The Scripps Formation is generally
characterized by light brown and gray, very dense silty sandstone.
The soil exposed in our exploratory trenches consisted of silty fine sand to fine sand
and is similar to soils in the general site vicinity found to have a very low expansion
potential when tested in accordance with UBC Standard No. 29-2.
Geolooic Structure
Bedding in the Quaternary terrace deposits on site is obscured by surficial soils.
However, the presence of apparently horizontal-lying gravel interbeds, as well as
exposures in the general site vicinity, indicate that the Quaternary terrace deposits are
horizontally bedded with localized cross bedding. A geologic cross section of the bluff
is presented on Figure 3.
No indications of faulting or jointing were observed on site. In addition, no indications
of deep-seated landslide features were observed.
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Faults
Our review of geologic literature (Appendix A) pertaining to the general site area
indicates that there are no known major or active faults on or in the immediate vicinity
of the site. Indications of active faulting or adversely-oriented joints were not
observed at the site. The nearest known active faults are the Rose Canyon fault
located offshore approximately 4 miles west of the site, the Coronado Bank fault
located offshore approximately 20 miles west, and the Elsinore fault located
approximately 25 miles northeast of the site. The San Andreas fault is located
approximately 80 miles northeast of the site.
Tsunami
Tsunami are sea waves generated by submarine earthquakes, landslides, or volcanic
action. Submarine earthquakes are common along the edge of the Pacific Ocean and
coastal areas are subject to potential inundation by tsunami. Most of the 1 9 tsunami
recorded on the San Diego Bay tidal gauge (between 1854 to 1872 and 1906 to
1977) have only been a few tenths of a meter in height (Appendix A, Reference 1).
The largest San Diego area tidal gauge excursion (1 meter) was associated with the
tsunami of May 22, 1960 and was recorded at La Jolla (Scripps Pier) (Appendix A,
Reference 13). The tsunami was generated by a Richter magnitude 8.5 earthquake
in Chile. For comparison, the diurnal range of tides at San Diego Bay is 1.7 meters.
The possibility of a destructive tsunami along the San Diego coastline is considered
low (Appendix A, Reference 5). Tsunami or storm waves (associated with winter
storms), even in conjunction with high tides, do not have the potential for inundation
of the bluff-top building site.
Historic Research Summarv
We have reviewed the maps and aerial photographs of the site and general vicinity
listed in Appendix A. Our review of the bluff in the area of the subject property
indicates that the bluff is generally similar in configuration in the 1928, 1979, 'and
1989 aerial photographs. The bluff edge also appears to be generally similar in
configuration. No indications of slope instability, severe erosion or retreat of the bluff
top were observed in the aerial photographs reviewed.
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Bluff Retreat
The site is located atop a northwesterly-facing bluff that is not generally subjected to
marine erosion processes. However, other mechanisms can contribute to bluff retreat.
The slope is exposed to precipitation, wind, pedestrian/animal erosion, variations in
landscape, landscape maintenance, and other activities by humans. During our
studies, we did not observe indications of deep-seated instability, such as ancient or
active landslides, on or in the immediate vicinity of the site.
The rate and magnitude of bluff retreat at a specific site are dependent on a variety of
factors, both natural and manmade. Many of these factors are ongoing processes and
historic documentation can be helpful in estimating general retreat rates along similarly-
affected coastal bluff areas. However, there are other factors affecting coastal bluff
retreat that cannot be estimated from historic documentation. Such factors include
future human activities or possible extreme variations in regional weather patterns.
Detrimental changes in factors affecting bluff-edge retreat, such as misdirected
drainage, water line breaks, and/or heavy precipitation, could increase the rate of
erosion. However, favorable changes in the factors affecting bluff-edge retreat could
also decrease the rate of erosion. Some of these include proper maintenance of a
bluff-stabilizing vegetative cover and enhanced site drainage provisions.
Our historic photograph review (Appendix A) indicates that the bluff at the subject
property is generally similar in configuration in the 1953 and subsequent photos. The
location of the onsite bluff edae is also generally similar on the photographs.
It is very difficult to predict the future and the magnitude of bluff-edge retreat that may
occur in one year, during one storm event or over the 75-year assumed economic
lifetime of the new construction. Severe erosion is generally episodic in nature and is
dependent on the intensity of storms and/or man's detrimental actions. It is probable
that several feet of bluff-edge retreat could occur at one time. However, as evidenced
by the historic documentation (Appendix A), it is likely that bluff-edge retreat will
remain rather insignificant.
It is our opinion that the new residential construction, proposed to be set back a
minimum of 25 feet from the bluff edge, will not be endangered by bluff-edge retreat
over the next 75 years. However, improvements that are nearer to the bluff edge
within this setback zone, may in the future become undermined by bluff-edge retreat
and may need to be removed from the site.
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Groundwater and Surface Water
Indications of a static, near-surface groundwater table were not observed or
encountered during our investigation. Groundwater is not anticipated to be a
constraint to the proposed development. However, our experience indicates that near-
surface groundwater conditions can develop in areas where no such groundwater
conditions previously existed, especially in areas where a substantial increase in
surface water infiltration results from landscape irrigation or unusually heavy
precipitation. It is anticipated that site development will include appropriate drainage
provisions for control and discharge of surface runoff.
CONCLUSIONS AND RECOMMENDATIONS
Based on our geotechnical investigation at the site, it is our opinion that the proposed
residential development is feasible from a geotechnical standpoint. It is our opinion
that the proposed construction (and the additional loading from this relatively light
bluff-top construction) will not adversely impact the existing bluff. If the development
is set back a minimum of 25 feet from the bluff edge as planned, it is our opinion that
the proposed construction should not be affected by the maximum anticipated bluff
retreat during its economic lifetime (assumed to be 75 years).
Slope Stabilitv and Erosion
Our geotechnical investigation of the site indicates that the bluff is grossly stable with
regard to slope stability. In its present state, the slope has a low to moderate potential
for erosional rilling and future surficial instability. We provide the following
recommendations to help reduce erosion of the bluff and to reduce potential for future
instability of the bluff face.
Irrigation of the landscape areas on the property should be curtailed and limited
to the minimum amount required to establish vegetation and maintain plant
vigor. The bluff and the bluff edge are currently well vegetated. At this time,
it is our opinion that modifications to the vegetation in these areas should not
be considered. Landscape planting and/or plant removal on the westerly bluff-
top area should be performed without significantly disturbing the bluff-top soils.
The surficial stability of those portions of the bluff that are not well vegetated
may be increased by planting in accordance with the recommendations of a
professional landscape company experienced with coastal bluffs. Terracing or
major excavation of the bluff face should be avoided.
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Project No. 147A12
Drainage at the site should be maintained such that surface waters discharge
toward Sheridan Avenue. Runoff at the site should not be directed over the
bluff edge. Eave gutters should be considered for the proposed residence and
should be properly maintained.
Pedestrian and animal traffic on the bluff face and bluff edge should not be
allowed since pedestrian/animal traffic increases erosion.
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Bluff-Too Setback
Based on our preliminary review of project plans, the proposed residential development
will be set back a minimum of 25 feet from the bluff edge. It is our opinion the
proposed set back will safeguard the proposed construction from bluff-edge retreat
during the economic lifetime of the proposed development.
Earthwork
Based on our understanding of the project, it appears that some site earthwork is
proposed to construct for the new residential construction. Site earthwork should be
performed in accordance with the following recommendations and the Recommended
Earthwork Specifications contained in Appendix B.
Site Preoaration - Prior to grading and construction activities, the site should be
cleared of vegetation, debris and loose soils. Vegetation and loose debris
should be properly disposed of off site. Holes resulting from removal of buried
obstructions which extend below finished site grades should bè filled with
properly compacted fill soils.
Removal of Unsuitable Soils - The existing fill soils and topsoil are considered
compressible and unsuitable for the support of fill and structural loads in their
present condition. We recommend that these soils be removed in areas planned
for structures, surface improvements or fill placement. As encountered in our
exploratory trenches, these soils apparently underlie the majority of the site.
The thickness and extent of these soils may vary and should be evaluated by
the geotechnical consultant during removal of these unsuitable soils. These
soils are considered suitable for re-use as compacted, structural fill provided
they are free of organic material, deleterious debris and oversized materials
(rocks with a maximum dimension greater than 6 inches).
Structural Fill Placement - Areas to receive fill and/or other surface
improvements should be scarified to a minimum depth of 6 inches, brought to
near-optimum moisture conditions, and recompacted to at least 90 percent
relative compaction, based on laboratory standard ASTM 01557. Fill soils
should be brought to near-optimum moisture conditions and compacted in
uniform lifts to at least 90 percent relative compaction (ASTM 01557). The
optimum lift thickness to produce a uniformly compacted fill will depend on the
size and type of construction equipment used. In general, fill should be placed
in loose lift thicknesses not exceeding 8 inches. Placement and compaction of
fill should be observed and tested by the geotechnical consultant. In general,
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Project No. 147A12
placement and compaction should be performed in accordance with local
grading ordinances, sound construction practices, and the Recommended
Earthwork Specifications included in Appendix B.
Transition (Cut/Fill) Condition - If site grading results in a transition (cut-fill)
condition underlying the proposed structure, we recommend that, to reduce the
potential for damage to the structure due to differential settlement across the
transition, a uniform fill thickness should be provided under the building. The
cut portion of the building area should be overexcavated to a minimum depth
of 3 feet and replaced with moisture-conditioned fill soils compacted to at least
90 percent relative compaction (ASTM 01557). The limits of overexcavation
and recompaction should extend for a distance of at least 5 feet beyond the
perimeter of the proposed building.
Excavations and Trench Backfill - It is anticipated that excavation of the onsite
materials can be accomplished by conventional grading equipment in good
operating condition. The onsite soils are generally suitable as trench backfill
provided they are screened of organic matter and clasts over 6 inches in
diameter. Trench backfill should be compacted by mechanical means to at least
90 percent relative compaction (ASTM 01557).
Foundation and Slab Recommendations
We understand that the proposed development will consist of a one-story, single-family
residence with garage supported on conventional continuous perimeter and/or isolated
footings with slab-on-grade floors. Foundations and slabs should be designed in
accordance with structural considerations and the following recommendations. These
recommendations assume that the soils encountered during foundation excavation will
have a low expansion potential. If the expansion potential of the finished building pad
soils differs from that assumed herein, appropriate corresponding modifications to the
foundation and slab recommendations may be necessary.
The proposed residence may be supported on continuous or spread footings bearing
entirely in firm, formational soils QI entirely in properly compacted fill soils at a
minimum depth of 12 inches for one-story structures (18 inches for two-story
structures) beneath the lowest adjacent grade. At this depth, footings may be
designed for an allowable soil-bearing value of 2,000 pounds per square foot. This
value may be increased by one-third for loads of short duration, such as wind or
seismic forces. Footings should have a minimum width of 12 inches (15 inches for
two-story) and reinforcement consisting of two No.4 rebars (one near the top and
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bottom of each footing). Spread footings should be designed in accordance with
structural considerations and have a minimum width of 24 inches.
Concrete slabs-on-grade underlain by competent natural materials or properly
compacted fill soils should have a minimum thickness of 4 inches and be reinforced
at midheight in the slab with No.3 rebars at 18 inches on center each way (or No.4
rebars at 24 inches on center each way). Care should be taken by the contractor to
insure that the reinforcement is placed at slab midheight. Slabs should be designed
with crack control joints at appropriate spacings for the anticipated loading. Slabs
should be underlain by a 2-inch layer of sand which is underlain by a 1 O-mil moisture
barrier. The potential for slab cracking may be lessened by careful control of
water/cement ratios. The use of low slump concrete is recommended. Appropriate
curing precautions should be taken during placement of concrete during hot weather.
We recommend that the upper approximately one foot of soil beneath concrete slabs-
on-grade be presoaked to near-optimum moisture conditions prior to placing concrete.
We recommend that a slipsheet or equivalent be used if crack-sensitive flooring is
planned directly on concrete slabs.
lateral Resistance and Retainina Wall Desian Pressures
Footings and slabs founded in firm, natural soils or properly compacted fill soils may
be designed for a passive lateral bearing pressure of 350 pounds per square foot per
foot of depth. A coefficient of friction against sliding between concrete and soil of 0.4
may be assumed. These values may be increased by one-third when considering loads
of short duration, such as wind or seismic forces.
Cantilever (yielding) retaining walls may be designed for an "active" equivalent fluid
pressure of 35 pcf. Rigid (non-yielding) walls may be designed for an equivalent fluid
pressure of 60 pcf. These values assume horizontal, nonexpansive, granular backfill
and free-draining conditions. For 2 to 1 (horizontal to vertical) sloping backfill,
cantilever retaining walls may be designed for an active equivalent fluid pressure of
50 pcf and rigid retaining walls may be designed for an equivalent fluid pressure of
90 pet. A surcharge load for a restrained or unrestrained wall resulting from vehicle
traffic may be assumed to be equivalent to a uniform pressure of 75 psf which is
addition to the equivalent fluid pressures provided above. Wall footings should be
designed in accordance with structural considerations and the foundation
recommendations provided in the preceding section of this report.
We recommend that retaining walls be provided with appropriate drainage provisions.
Appendix B contains a typical detail for drainage of retaining walls. The walls should
be appropriately waterproofed. Appropriate waterproofing treatments and alternative,
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Project No. 147A12
suitable wall drainage products are available commercially. Details for the design of
waterproofing and its protection during construction should be provided by the project
architect. Wall backfill should be compacted by mechanical means to at least 90
percent relative compaction (ASTM D1557). Care should be taken when using
compaction equipment in close proximity to retaining walls so that the walls are not
damaged by excessive loading.
Surface Drainaae
Drainage at the site should be directed away from foundations and collected and
tightlined to an appropriate discharge point. Consideration may be given to collecting
roof drainage by eave gutters and directing it away from foundations via non-erosive
devices. Water, either natural or from irrigation, should not be permitted to pond,
saturate the surface soils or flow over the tops of slopes. Landscaping requiring a
heavy irrigation schedule should not be planted adjacent to foundations or paved areas.
Seismic Considerations
The principal seismic considerations for most structures in southern California are
surface rupturing of fault traces and damage caused by ground shaking or seismically-
induced ground settlement or liquefaction. The possibility of damage due to ground
rupture is considered minimal since no active faults are known to cross the site.
It is our opinion that the potential for liquefaction or seismically-induced ground
settlement at the site due to an earthquake is very low because of the dense nature
of the underlying terrace deposits and anticipated absence of a static, near-surface
ground water table in the area of proposed development.
The seismic hazard most likely to impact the site is ground shaking resulting from an
earthquake on one of the major active regional faults. The effects of seismic shaking
can be reduced by adhering to the most recent edition of the Uniform Building Code
and current design parameters of the Structural Engineers Association of California.
In general, the role seismic shaking plays in bluff retreat is dependent on bluff
conditions at the moment of shaking. Oversteepened portions of the terrace deposits
may undergo shallow failure and some ravelling of the poorly indurated bluff-face
terrace deposits may also occur during ground shaking, especially on the unvegetated
portions of the bluff face. However, it is our opinion that the potential for deep-seated
or severe, catastrophic failure of the bluff due to expected seismic ground shaking is
low at the site.
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Construction Observation and Testina
The recommendations provided in this report are based on our understanding of the
project and subsurface soil conditions exposed during our investigation. The
interpolated subsurface conditions should be checked in the field during grading and
construction. Field density testing of compacted fill and foundation excavation
observation should also be performed by the geotechnical consultant to check that
construction is in accordance with the recommendations of this report.
If you have any questions regarding our report, please call.
opportunity to be of service.
We appreciate this
Sincerely,
SOUTHLAND GEOTECHNICAL CONSULTANTS
Attachments:
Figure 1 - Site Location Map
Figure 2 - Site Plan
Figure 3 - Coastal Bluff Profile
Figure 4 - Logs of Exploratory Trenches
Appendix A - References
Appendix B - Recommended Earthwork Specifications
Distribution:
(3) Addressee
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1
N
SITE LOCATION MAP
Project No. 147A12
2070 Sheridan Road, Encinitas
Scale (approximate!: 1 inch = 2,200 feet
8ase Map:
Pleistocene and Eocene geology of the
Encinitas and Rancho Santa Fe quadrangles
San Diego County, California
by L. Eisenberg, 1983.
FIGURE 1
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SITE PLAN
LEGEND
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- Approximate location ot
T-4 exploratory trench
20.00'
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Project No. 147A12
2070 Sheridan Road, Encinitas
Approximate Scale; 1 inch ~ 20 feet
Base map from Topographic Map
prepared by La Costa Engineering, dated 3-31-99
FIGURE 2
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~
Project No. 147A12
Approximate location~
of bluff edge :
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TERRACE DEPOSITS
-----_?
SCRIPPS FORMATION
GENERALIZED BLUFF PROFILE
Project No. 147A12
2070 Sheridan Road, Encinitas
Approximate Scale: 1 inch = 20 feet
See Figure 2 for location of
Generalized Bluff Profile
Based on our approximate measurement and the
Topographic Map prepared by La Costa Engineering, dated 3-31-99
FIGURE 3
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TRENCH NO.
T-1
T.2
Project No. 147A12
LOGS OF EXPLORATORY TRENCHES
DEPTH
0-12"
12-22"
22-38"
38-42"
0-6"
6-24"
24-42"
42-48"
DESCRIPTION
Toosoil - Brown, moist, loose, silty fine to coarse sand ISM);
with roots
Terrace DeDosits - Brown, moist, medium dense, slightly silty
fine to coarse sand (SM); with scattered roots. gravel/cobble
Terrace Deoosits - Brown, moist, dense, slightly silty fine to
coarse sand ISM); with shell fragments
Terrace Deoosits - Light brown. damp. dense. fine to coarse
sand ISM); with scattered gravel/cobble
Total depth = 42 inches
No groundwater encountered
Sample 1 at 0-22"
Excavated and backfilled 03-17-99
----------------------
Toosoil - Dark brown, damp~ loose, silty fine sand ISM); with
roots
Toosoil - Dark brown, moist, loose to medium dense, silty fine
to coarse sand ISM); with scattered roots and gravel/cobble
Terrace DeDas its - Brown, moist, dense, slightly siity fine to
coarse sand (SM)
Terrace DeDosits - Light brown, moist, dense, slightly silty fine
to coarse sand ISM); with gravel/cobble
Total depth = 48 inches
No groundwater encountered
Sample 1 at 0-18"
Sample 2 at 18-30"
Sample 3 at 36-48"
Excavated and backfilled 03-17-99
----------------------
FIGURE 4
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LOGS OF EXPLORATORY TRENCHES
(Continued)
TRENCH NO.
DEPTH
T-3
0-6"
6-24"
24-42"
42-48"
T-4
0-6"
6-24"
24-42"
42-48"
DESCRIPTION
Topsoil - Dark brown, damp, loose, silty fine sand (SM); with
roots
Topsoil - Dark brown, damp, loose to medium dense, slightly
silty fine to coarse sand (SM); with scattered roots
Terrace Deposits - Brown, moist, dense. silty fine to coarse
sand (SM); with scattered roots
Terrace Deposits - Light brown. damp, dense, silty fine to
coarse sand ISM)
Total depth = 48 inches
No groundwater encountered
Sample 1 at 6-24"
Sample 2 at 30-36"
Excavated and backfilled 03-17-99
----------___o-_m---
Topsoil - Dark brown. damp to moist, loose, silty fine sand
ISM); with roots
Topsoil - Dark brown, damp, loose to medium dense, slightly
silty fine to coarse sand ISM); with scattered roots
Terrace Deposits - Brown, moist, dense, silty fine to coarse
sand (SM); with scattered roots
Terrace Deposits - Light brown. damp. dense. silty fine to
coarse sand (SM)
Total depth = 48 inches
No groundwater encountered
Sample 1 at 6-24"
Sample 2 at 30-36"
Excavated and backfilled 03-17-99
FIGURE 4
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APPENDIX A
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Project No. 147A12
APPENDIX A
REFERENCES
1.
Agnew, D.C., 1979, Tsunami history of San Diego, ill Abbott, P.L., and Elliott,
W.J., eds., Earthquakes and Other Perils: Geological Society of America field
trip guidebook.
2.
California Division of Mines and Geology, 1994, Fault activity map of California
and adjacent areas: CDMG Geologic Data Map No.6.
3.
Flick, R.E., ed., 1994, Shoreline erosion assessment and atlas of the San Diego
region: California Department of Boating and Waterways and the San Diego
Association of Governments publication, dated December.
4.
Kennedy, M.P., and Peterson, G.L., 1975, Geology of the San Diego
Metropolitan Area, California: California Division of Mines and Geology,
Bulletin 200.
5.
Lee, L.J., 1977, Potential foundation problems associated with earthquakes in
San Diego, ill Abbott, P.L., and Victoria, J.K., eds., Geologic Hazards in San
Diego, Earthquakes, Landslides, and Floods: San Diego Society of Natural
History John Porter Dexter Memorial Publication.
6.
Lee, L., Pinckney, C., and Bemis, C., 1976, Sea bluff erosion: American Society
of Civil Engineers, National Water Resources and Ocean Engineering Convention
Preprint No. 2708.
7.
Legg, M.R., Agnew, D.C., and Simons, R.S., 1978, Earthquake history and
seismicity of coastal San Diego County, California, 1800-1976 (unpublished).
8.
Southland Geotechnical Consultants, in-house geologic information.
9.
Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the
San Diego metropolitan area: California Division of Mines and Geology, Open-
file Report 95-04.
11.
U.S. Army Corps of Engineers, 1985, Coast of California Storm and Tidal
Waves Study, Shoreline Movement Data Report, Portuguese Point to Mexican
Border (1852-1982) (CCSTWS 85-10), dated December.
12.
U.S. Army Corps of Engineers, 1985, Coast of California Storm and Tidal
Waves Study, Coastal Cliff Sediments, San Diego Region (CCSTWS 87-2),
dated June.
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Project No. 147A12
APPENDIX A
REFERENCES
(continued)
13.
Van Dorn, W.G., 1979, Theoretical aspects of tsunamis along the San Diego
coastline, ill Abbott, P.L., and Elliott, W.J., eds., Earthquakes and Other Perils:
Geological Society of America field trip guidebook.
AERIAL PHOTOGRAPHS
County of San Diego, 1928, Aerial Photograph 30 A 1-8, set flown between
November 1928 and March 1929.
County of San Diego, 1978, Flight SDCO 210, Flight Line 15, Photos 34 and 35,
dated December 13.
County of San Diego, 1989, Flight WAC-89CA, Photo 3-3, dated April 7.
PROJECT PLANS
La Costa Engineering, 1999, Topographic Map, 2070-72 Sheridan Road, Leucadia,
California, dated March 30.
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APPENDIX B
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1.0
2.0
3.0
RECOMMENDED EARTHWORK SPECIFICATIONS
General Intent
These specifications are presented as general procedures and recommendations
for grading and earthwork to be used in conjunction with the approved grading
plans. These general earthwork specifications are considered a part of the
recommendations contained in the geotechnical report and are superseded by
recommendations in the geotechnical report in the case of conflict. Evaluations
performed by the consultant during the course of grading may result in new
recommendations which could supersede these specifications or the
recommendations of the geotechnical report. It shall be the responsibility of the
contractor to read and understand these specifications, as well as the
geotechnical report and approved grading plans.
Earthwork Observation and Testina
Prior to grading, a qualified geotechnical consultant should be employed for the
purpose of observing earthwork procedures and testing fill placement for
conformance with the recommendations of the geotechnical report and these
specifications. It shall be the responsibility of the contractor to keep the
geotechnical consultant apprised of work schedules and changes, at least 24
hours in advance, so that he may schedule his personnel accordingly. No
grading operations shall be performed without the knowledge of the
geotechnical consultant. The contractor shall not assume that the geotechnical
consultant is aware of all site grading operations.
It shall be the sole responsibility of the contractor to provide adequate
equipment and methods to accomplish the work in accordance with applicable
grading codes and agency ordinances, recommendations of the geotechnical
report, and the approved grading plans. If, in the opinion of the geotechnical
consultant, unsatisfactory conditions, such as unsuitable soil, poor moisture
condition, inadequate compaction, adverse weather, etc., are resulting in a
quality of work less than recommended in the geotechnical report and the
specifications, the consultant will be empowered to reject the work and
recommend that construction be stopped until the conditions are rectified.
Preoaration of Areas to be Filled
3.1
Clearina and Grubbina: Sufficient brush, vegetation, roots, and all other
deleterious material should be removed or properly disposed of in a
method acceptable to the owner, design engineer, governing agencies
and the geotechnical consultant.
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3.2
3.3
3.4
3.5
3.6
3.7
The geotechnical consultant should evaluate the extent of these removals
depending on specific site conditions. In general, no more than one
percent (by volume) of the fill material should consist of these materials.
In addition, nesting of these materials should not be allowed.
Processina: The existing ground which has been evaluated by the
geotechnical consultant to be satisfactory for support of fill, should be
scarified to a minimum depth of 6 inches. Existing ground which is not
satisfactory should be overexcavated as specified in the following
section. Scarification should continue until the soils are broken down
and free of large clay lumps or clods and until the working surface is
reasonably uniform, flat, and free of features which would inhibit uniform
compaction.
Overexcavation: Soft, dry, organic-rich, spongy, highly fractured, or
otherwise unsuitable ground, extending to such a depth that surface
processing cannot adequately improve the condition, should be
overexcavated down to competent ground, as evaluated by the
geotechnical consultant. For purposes of determining pay quantities of
materials overexcavated, the services of a licensed land surveyor or civil
engineer should be used.
Moisture Conditionina: Overexcavated and processed soils should be
watered, dried, or blended as necessary to attain a uniform near-
optimum moisture content as determined by test method ASTM 01557.
Recomoaction: Overexcavated and processed soils which have been
properly mixed, screened of deleterious material, and moisture-
conditioned should be recompacted to a minimum relative compaction of
90 percent as determined by test method ASTM 01557.
Benchina: Where fills are placed on ground sloping steeper than 5:1
(horizontal to vertical), the ground should be stepped or benched. The
lowest bench should be a minimum of 15 feet wide, excavated at least
2 feet into competent material as evaluated by the geotechnical
consultant. Ground sloping flatter than 5: 1 should be benched or
otherwise overexcavated when recommended by the geotechnical
consultant.
Evaluation of Fill Areas: All areas to receive fill, including processed
areas, areas of removal, and fill benches should be evaluated by the
geotechnical consultant prior to fill placement.
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4.0
Fill Material
4.1
4.2
4.3
General: Material to be placed as fill should be sufficiently free of
organic matter and other deleterious substances, and should be evaluated
by the geotechnical consultant prior to placement. Soils of poor
gradation, expansion, or strength characteristics should be placed as
recommended by the geotechnical consultant.
Oversize Material: Oversize fill material, defined as material with a
maximum dimension greater than 6 inches should not be buried or placed
in fills unless the location, materials, and methods are specifically
recommended by the geotechnical consultant.
Imoort: If grading operations include importing of fill material, the import
material should meet the requirements of Section 4.1. Sufficient time
should be given to allow the geotechnical consultant to test and evaluate
proposed import as necessary, prior to importing to the site.
5.0
Fill Placement and Comoaction
5.1
5.2
5.3
5.4
Fill Lifts: Fill material should be placed in areas properly prepared and
evaluated as acceptable to receive fill. Fill should be placed in near-
horizontal layers approximately 6 inches in compacted thickness. Each
layer should be spread evenly and thoroughly mixed to attain uniformity
of material and moisture content throughout.
Moisture Conditionina: Fill soils should be watered, dried or blended as
necessary to attain a uniform near-optimum moisture content as
determined by test method ASTM 01557.
Comoaction of Fill: After each layer has been evenly spread, moisture
conditioned, and mixed, it should be uniformly compacted to not less
than 90 percent of maximum dry density as determined by test method
ASTM 01557. Compaction equipment should be adequately sized and
be either specifically designed for soil compaction or of proven reliability
to efficiently achieve the specified degree and uniformity of compaction.
Fill Siooes: Compaction of slopes should be accomplished, in addition to
normal compaction procedures, by backrolling slopes with sheepsfoot
rollers at increments of 3 to 4 feet in fill elevation gain, or by other
methods producing satisfactory results. At the completion of grading,
the relative compaction of the fill, including the embankment face should
be at least 90 percent as determined by test method ASTM 01557.
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6.0
7.0
8.0
5.5
Comoaction Testina: Field tests of the moisture content and degree of
compaction of the fill soils should be performed by the geotechnical
consultant. The location and frequency of tests should be at the
consultant's discretion based on observations of the field conditions. In
general, the tests should be taken at approximate intervals of 2 feet in
elevation gain and/or each 1,000 cubic yards of fill placed. In addition,
on slope faces, as a guideline, one test should be taken for each 5,000
square feet of slope face and/or each 1O-foot interval of vertical slope
height.
Subdrain Construction
Subdrain systems, if recommended, should be constructed in areas evaluated
for suitability by the geotechnical consultant. The subdrain system should be
constructed to the approximate alignment in accordance with the details shown
on the approved plans or provided herein. The subdrain location or materials
should not be modified unless recommended by the geotechnical consultant.
The consultant may recommend modifications to the subdrain system
depending on conditions encountered. Completed subdrains should be surveyed
for line and grade by a licensed land surveyor or civil engineer.
Excavations
Excavations and cut slopes should be evaluated by the geotechnical consultant
during grading. If directed by the geotechnical consultant, further excavation,
overexcavation, and/or remedial grading of cut slopes (i.e., stability fills or slope
buttresses) may be recommended.
Quantitv Determination
The services of a licensed land surveyor or civil engineer should be retained to
determine quantities of materials excavated during grading and/or the limits of
overexcavation.
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RETAINING WALL DRAINAGE DETAIL
SOIL BACKFILL, COIolPACTED TO
80 PERCENT RELATIVE COMPACTION.
RETAINING WALL
WALL WATERPROOFING
PER ARCHITECT'S
SPECIFICATIONS
3/4"-1.1/2" CLEAN GRAVEL'"
4" CIoUN.) DIAMETëR PERFORATED
PVC PIPE CSCHEDULE 40 OR.
EQUIVALENT) WITH PERFQRATIONS
ORIENTED DOWN AS DEPICTED .
MINIMUM 1 PERCENT GRADIENT
TO SUITABLE OUTLET
WALL FOOTING
NOT TO SCALE
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
SPECIFICATIONS FOR CALTRANS
CLASS 2 PERMEABLE MATERIAL
U.S. Standard
Sieve Size
.BASED ON ASN 01551
~ Passinq
* . IF CAL TRANS CLASS 2 PERMEABLE iotA TERIA L
CSEE GRADATION TO LEFT) IS USED IN PLACE OF
3/4"-1-1/2' GRAVEL, FILTER FABRIC MAY BE
DELETED. CAL TRANS CLASS 2 PERMEABLE
MATERIAL SHOULD BE COMPACTED TO 80
PERCENT RELATIVE COMPACTION.
l' 100
3/4" 90-100
3/8" 40-100
No.4 25-40
No.8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3
Sand Equ;vaJent>75
NOTE:COMPOSITE DRAINAGE PRODUCTS SUCH AS ~RADRAIN
,OR J-DRAIN MAY BE uSED AS AN ALTERNATIVE TO GRAVEL OR
CLASS 2. INSTALLATION SHOULD BE PERFCRtÆD IN ACCORDANCE
'MTH MANUFACTURER'S SPEOACATIOIS.
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TRANSITION LOT DETAILS
CUT-FILL LOT
COMPeTENT BEDROCK. . . ¡
--- OR MATeRIAL eVALUATED --/"
.Y BY THe GEOTECHNICAL
CONSULTANT
CUT LOT
EXISTING
GROUND SURFAce
J--
---
---
OVEREXCAVATe
AND RECOMPACT
COMPETENT BEDROCK ./
~R MATERIAL EVALUATED'-----
BY THE GEOTECHNICAL
CONSULTANT
,oNOTe:
Deeper or laterally more extensive overexcavation and
recompaction may be recommended by the "eotechnical
consultant based on actual field conditions encountered
and locations of proposed improvements
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,
..
KEY AND BENCHING DETAILS
EXISTING
GROUND SURFACE
FILL SLOPE
FILL-OVER-CUT SLOPE
PROJECT 1 TO 1
UNE FROM TOE
OF SLOPE TO
COMPeTENT
MATERIAL
///
EXISTING / /'
GROUND / /
SURFACE------ / / f(
// ,"-.,7
/ ¿ ",<-
/
CUT SLOPE
(TO BE EXCAVATED
PRIOR TO FILL
PLACEMENT)
CUT-OVER-FILL SLOPE
NOTE: Back drain may be recommended by the geotechnical consultant based on
actual field conditions encountered. Bench dimension recommendations may
also be altered based on field conditions encountered.
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