HomeMy WebLinkAboutNCP 2022-0002; DE FREITAS RESIDENCE; ADDENDUM AND RESPONSE TO CITY COMMENTS; 2023-02-01ADDENDUM AND RESPONSE TO
CITY OF CARLSBAD COMMENTS
PROPOSED SINGLE-FAMILY RESIDENCE
4339 PARK DRIVE, CARLSBAD, CALIFORNIA 92008
FOR
MS. PATIANE FREITAS
4339 PARK DRIVE
CARLSBAD, CALIFORNIA 92008
W.O. 8286-A1-SC FEBRUARY 1, 2023
Geotechnical C Geologic C Coastal C Environmental
5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com
February 1, 2023
W.O. 8286-A1-SC
Ms. Patiane Freitas
4339 Park Drive
Carlsbad, California 92008
Subject: Addendum and Response to City of Carlsbad Comments, Proposed
Single-Family Residence, 4339 Park Drive, Carlsbad, California 92008
References: 1. “Limited Geotechnical Evaluation For A Planned Single-Family Residence Including
Retaining Walls, 4339 Park Drive, Carlsbad, California,” W.O. 8286-A, dated March 8, 2022,
Revised October 10, 2022, by GeoSoils, Inc.
2. “Geotechnical Report Review, De Frietas Residence, 4339 Park Drive, Project ID NCP
2022-0002, Grading Permit No. GR2022-0048,” dated November 29, 2022, by City of
Carlsbad.
3. “Geologic Map of the Oceanside 30' x 60' quadrangle, California, California Geological
Survey, Regional Geologic Map RGM-2, 1:100,000,” dated 2007, by Kennedy, M.P., Tan,
S.S., et al.
4. “ Landslide hazards in the northern part of the San Diego metropolitan area, San Diego
County, California, DMG Open File Report 95-04, Landslide Hazard Identification Map No.
35, Relative Landslide Susceptibility and Landslide Distribution Map, Plate G, 1:24,000 scale,
dated 1995, by Tan, S.S. and Giffen, D.G.
Dear Ms. Frietas:
In accordance with your request, GeoSoils, Inc. (GSI) is providing this response to City of
Carlsbad comments. The scope of our services has included a review of the referenced
report (Reference 1), analysis of data, and preparation of this response.
Unless specifically superceded herein, the conclusions and recommendations contained
in the referenced report by GSI (see Reference No. 1) remain pertinent and applicable, and
should be appropriately implemented during planning, design, and construction.
GSI REVIEW RESPONSE
For convenience, the reviewer’s comments are repeated below in italics, followed by GSI’s
response.
GeoSoils, Inc.
Comment No. 1:
Please review the most current precise grading and building plans for the project and
provide any additional geotechnical recommendations or modifications to the geotechnical
report as necessary.
Response to Comment No. 1:
Acknowledged. No additional geotechnical recommendations or modifications are
deemed necessary by the latest grading plan by Gama Design Studio (9-19-2022).
Seismic data within Structural Design Criteria section should be incorporated into the
Structural Notes (page S1) for re-submittal.
Comment No. 2:
Please provide a statement addressing the feasibility of the proposed project from a
geotechnical standpoint.
Response to Comment No. 2:
In GSI’s opinion, the proposed project is feasible from a geotechnical standpoint.
Comment No. 3:
Please provide a statement addressing the potential impact of the proposed project on
adjacent off-site properties from a geotechnical standpoint
Response to Comment No. 3:
In GSI’s opinion, the proposed project will have no significant impact on adjacent off-site
properties, provided the recommendations presented in the referenced report are
incorporated into the design and construction of the proposed project.
Comment No. 4:
Please provide a description of the subject property and area of the proposed construction
(existing topography and structures/improvements, existing natural and/or fill slopes, etc.)
Response to Comment No. 4:
The property has an area of 3.26 acres. The site is a south-facing slope extending from
elevation 124 feet to elevation 50 feet along a swale paralleling Park Drive. Most of the site
is vegetated with trees and shrubs. A drainage swale is located along the southern
property line, parallel to Park Drive. The site appears to drain to the swale (east).
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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GeoSoils, Inc.
Comment No. 5:
Please expand on the description of the proposed project and discuss the proposed
grading (depths and limits of cut/fill necessary to establish proposed grades), type of
foundation and floor for the proposed structures, types of proposed improvements, and
heights of the proposed retaining walls.
Response to Comment No. 5:
The existing residence at the southwestern corner of the property will be remodeled with
an addition of 2,050 square feet and a new attached garage of 1,304 square feet. Three
new bedrooms and two new bathrooms will be added. The existing and new bathrooms
and bedrooms will be located on the upper level of the residence, with a floor level of
85.18 feet. The new garage will be on the lower level of the residence with a floor level of
The garage will have a concrete slab on grade. Part of the existing upper level will be
supported on a raised wood foundation system with individual footings; most of the upper
level will be supported on a slab on grade.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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Existing slopes on the hillside above the residences range from about 6:1
horizontal:vertical (h:v) to as steep as 1:1 (h:v) locally. The natural slope heights above
the residences are about 25 feet near the southwestern corner of the site to almost
40 feet at the northwestern corner of the property. The site is currently developed
with two single-family residences, and a garage/storage building. A concrete play
area is located adjacent to the garage/storage building. A driveway extends from
Park Drive to the residences and garage/storage building. The structures are
founded on level building pads. The pads for the residences appear to have been
cut into the hillside.
A septic tank, abandoned in 2021, is located within the footprint of the proposed addition
area (see Plate 1 - Boring Location Map). According to the homeowner, the septic tank
bottom was broken out, and the septic tank was backfilled with 2-sack cement/sand
slurry.
75.18 feet. Two new retaining walls will be constructed under the residence. The upper
wall will have a height of about 3 feet and will retain about 3 feet of fill to support the
expanded upper level. The basement wall for the garage will be about 4½ feet tall and
retain about 4 feet of cut.
GeoSoils, Inc.
Comment No. 6:
Please provide an updated “Boring Location Map” utilizing the most current revision of the
grading plan for the project as the base map and at a sufficiently large scale to clearly show
(at a minimum): a) existing site topography, b) proposed structures and improvements, c)
proposed finished grades, d) geologic units, e) limits of proposed remedial grading, and
f) the limits of subsurface exploration. Please note that the “Boring Location Map”
presented in the submitted report consists of a significantly reduced (approximate 1"=78')
copy of the topographic survey on an 8.5 x 11" sheet and does not show some of the
requested information above. Please produce the map at a scale that is sufficiently large
to clearly distinguish all topography, text, proposed finish grades, areas of proposed
construction, etc., and show all information requested above (a sheet larger than 8.5 x 11"
will likely be necessary to increase legibility and show all information).
Response to Comment No. 6:
The requested updated Boring Location Map (from Gama Design Studio), is attached as
Plate 1, following the text of this response.
Comment No. 7:
Please provide detailed geologic cross-sections based on the updated “Boring Location
Map” and scale/legibility comments requested above in comment #6. Please assure the
requested cross-section shows and labels, at a minimum, a) existing site topography and
adjacent slopes, b) proposed finish grades, c) the limits of the existing and proposed
structures and improvements, d) the contacts between the various soil/geologic units
underlying the site, e) limits and depths of proposed remedial grading, f) temporary slopes
necessary for the remedial grading and/or for site retaining wall construction, and g) the
locations of subsurface exploration.
Response to Comment No. 7:
GSI has provided a detailed cross-section A-A’ (see Plate 2), with the requested
information, as described in comment No. 7, a through g. Boring Log B-2 has been
corrected and is included at the end of the text.
Comment No. 8:
Please provide a detailed discussion addressing the relationship between the structural
geology of the Santiago Formation bedrock unit underlying the site direction/dip of bedding,
fracturing, shears, etc.) and gross stability of the area of proposed construction. Please
provide the basis and justification for the geologic structure of the bedrock provided.
Please discuss both surficial and gross stability of existing slopes with respect to the
proposed development as they relate to the geotechnical performance of the proposed
residential structures and associated improvements.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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GeoSoils, Inc.
Response to Comment No. 8:
During our investigation, four (4) hand-auger borings were excavated in the vicinity of the
planned improvements. Santiago Formation was encountered in Borings 1, 3, and 4.
From Kennedy and Tan ([2007] Reference No. 3), bedding attitudes of the Santiago
Formation are mapped as slightly inclined to the southwest. The subject slope faces to the
east and regional bedding favorably dips into the slope. A shear in bedding was mapped
across the street to the east, and dips 70 degrees to the northwest, which is also favorable
and into the slope.
We observed no indications of slope instability at the subject site, nor discovered any
during our review of geologic literature.
Comment No. 9:
Please provide a discussion addressing the local and regional faulting associated with the
subject site and region. Please include the names, distances, and potential magnitudes of
faults potentially impacting the subject property and region.
Response to Comment No. 9:
Regional Faults
Our review indicates that there are no known active faults crossing the project and
the site is not within an Alquist-Priolo Earthquake Fault Zone (California Geological
Survey, 2018). However, the site is situated in an area of active faulting. The Rose
Canyon fault, part of the Newport-Inglewood - Rose Canyon fault zone, is the
closest known active fault to the site (located at a distance of approximately
5.5 miles [8.9 kilometers]) and should have the greatest effect on the site in the form
of strong ground shaking, should the design earthquake occur. A list and the
location of the Rose Canyon fault and other major faults relative to the site is
provided in Appendix A. The possibility of ground acceleration, or shaking at the
site, may be considered as approximately similar to the southern California region
as a whole.
Local Faulting
Although active faults lie within miles of the site, no local active faulting was noted
in our review, nor observed to specifically transect the site during the field
investigation. Additionally, a review of available regional geologic maps does not
indicate the presence of local active faults crossing the specific project site.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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GeoSoils, Inc.
Seismicity
It is our understanding that site-specific seismic design criteria from the 2019
California Building Code ([2019 CBC], California Building Standards Commission
[CBSC], 2019), are to be used for foundation design. Much of the 2019 CBC relies
on the American Society of Civil Engineers (ASCE) Minimum Design Loads for
Buildings and Other Structures (ASCE Standard 7-16). The seismic design
parameters provided herein are based on the 2019 CBC.
The acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999) has
been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program
developed by Thomas F. Blake (2000a), which performs deterministic seismic
hazard analyses using digitized California faults as earthquake sources. The
program estimates the closest distance between each fault and a given site. If a
fault is found to be within a user-selected radius, the program estimates peak
horizontal ground acceleration that may occur at the site from an upper bound
(formerly “maximum credible earthquake”) on that fault. Upper bound refers to the
maximum expected ground acceleration produced from a given fault. Site
acceleration (g) was computed by one user-selected acceleration-attenuation
relation that is contained in EQFAULT. Based on the EQFAULT program, a peak
horizontal ground acceleration from an upper bound event on the Rose Canyon
fault may be on the order of 0.60 g. The computer printout of pertinent portions of
the EQFAULT program are included within Appendix C.
Comment No. 10
Please justify the use of Site Class C (in accordance with Section 1613 of the 2019 California
Building Code and Chapter 20 of ASCE 7-16) to determine the seismic design parameters
provided in the report. Please provide shear wave velocity and/or blow count data from
site-specific investigation/testing that supports Site Class C. In the absence of investigative
support for Site Class C, seismic design parameters associated with Site Class D-default
(per the SEAOC/OSHPD online tool) should be provided.
Response to Comment No. 10:
The site has been re-evaluated as Class D-default, per the reviewer’s direction. In the
event of an upper bound (maximum probable) or credible earthquake occurring on any of
the nearby major faults, strong ground shaking would occur in the subject site's general
area. Potential damage to any structure(s) would likely be greatest from the vibrations and
impelling force caused by the inertia of a structure's mass. This seismic potential would
be no greater than that for other existing structures and improvements in the immediate
vicinity.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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GeoSoils, Inc.
Seismic Shaking Parameters
The following table summarizes the simplified method site-specific design criteria
derived from the 2019 CBC, Chapter 16 Structural Design, Section 1613,
Earthquake Loads for the centroid of the site, 33.1487 latitude, -117.3267 longitude.
The computer program Seismic Design Maps, provided by the California Office of
Statewide Health Planning and Development (OSHPD, 2022) has now been used
to aid in design (https://seismicmaps.org). The short spectral response uses a
period of 0.2 seconds.
2019 CBC SEISMIC DESIGN PARAMETERS
PARAMETER
VALUE
per ASCE 7-16
SIMPLIFIED METHOD
2019 CBC
or REFERENCE
Risk Category I, II, or III Table 1604.5
Site Class D- Default (See Section 11.4.3)Section 1613.2.2/ASCE 7-10
Chap. 20
Spectral Response - (0.2 sec), Ss 1.047 g Section 1613.2.1
Figure 1613.2.1(1)
Spectral Response - (1 sec), S1 0.38 g Section 1613.2.1
Figure 1613.2.1(2)
Site Coefficient, Fa 1.4 ASCE 7-10 (Table 11.4-1)
5% Damped Design Spectral Response
Acceleration (0.2 sec), SDS
0.977 g ASCE 7-16 (Eqn 11.4-3)
PGAM 0.525 g ASCE 7-16 (Eqn 11.8-1)
Seismic Design Category D Section 1613.2.5/ASCE 7-16
(p. 85: Table 11.6-1)
1. Sds=2/3 FaSs=0.66(1.4)(1.047)=0.967
2. 0.50 # Sds = 0.50 # 0.967, per Table 11.6-1 site is in Risk Category D
3. PGA=0.461 (OSHPD), From Table 11.8-1, Fpga=) (0.5-0.461)=0.039=>(1.1) + ()=0.039)= 1.139 (Fpga),
PGAM=(0.461)(1.139)=0.525 g
These parameters may only be used in structures without seismic isolation or seismic damping systems, less than
3 stories in height.
GENERAL SEISMIC PARAMETERS
PARAMETER VALUE
Distance to Seismic Source (Rose Canyon Fault)(1)±5.5 mi (8.9 km)
Upper Bound Earthquake (Rose Canyon Fault)MW = 7.2(2)
(1) - From Blake (2000a)
(2) - Cao, et al. (2003)
Ms. Patiane Freitas W.O. 8286-A1-SC
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I I I I
I
I I I
GeoSoils, Inc.
Conformance to the criteria above for seismic design does not constitute any kind
of guarantee or assurance that significant structural damage or ground failure will
not occur in the event of a large earthquake. The primary goal of seismic design is
to protect life, not to eliminate all damage, since such design may be economically
prohibitive. Cumulative effects of seismic events are not addressed in the
2019 CBC (CBSC, 2019) and regular maintenance and repair following locally
significant seismic events (i.e., Mw5.5) will likely be necessary, as is the case in all
of Southern California.
Comment No. 11
Please provide discussion addressing a) landsliding, b) groundwater, c) liquefaction with
respect to the subject site and proposed development.
Response to Comment No. 11:
Groundwater was not encountered in any of our exploratory borings, B-1 through B-4,
during our geotechnical investigation. Groundwater is anticipated to be coincident with
the Aqua Hedionda Lagoon, which is approximately 0.3 miles southwest of the subject site.
The subject site is at elevation 86 feet MSL and the lagoon is at approximately 1 foot MSL,
therefore, regional groundwater is not anticipated to significantly affect the proposed site
development, provided that the recommendations contained in the soils report are
properly incorporated into final design and construction. These observations reflect site
conditions at the time of our investigation and do not preclude future changes in local
groundwater conditions from excessive irrigation, precipitation, or that were not obvious,
at the time of our investigation.
Significant seeps, springs, or other indications of subsurface water were not noted on the
subject property during the time of our field investigation. However, localized minor
seepage cannot be precluded along zones of contrasting permeability/density
(fill/formation contact). Additional seeps and perched water conditions may occur along
geologic discontinuities. This observation and potential should be anticipated and
disclosed to all interested/affected parties. Dependant upon the time of year site grading
occurs, perched groundwater may adversely effect site development. Effects may include,
but are not limited to special handling of wet natural or fill soils (drying, spreading, mixing,
etc.), and/or specialized excavation equipment. These observations reflect site conditions
at the time of this geotechnical study and do not preclude changes in local groundwater
conditions in the future. Subdrains behind retaining walls would likely mitigate this
potential.
Mass wasting refers to the various processes by which earth materials are moved down
slope in response to the force of gravity. Examples of these processes include slope
creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass
wasting and generally involves the outer 5 to 10 feet of a slope surface. During heavy
rains, such as those in El Niño years, creep-affected materials may become saturated,
Ms. Patiane Freitas W.O. 8286-A1-SC
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resulting in a more rapid form of downslope movement (i.e., landslides and/or surficial
failures).
According to regional landslide susceptibility mapping by Tan and Giffen (1995) (Reference
no. 4), the site is located within landslide susceptibility Subarea 3-1, which are
characterized as being “generally susceptible” to landsliding. Slopes within this area are
at or near their stability limits due to weak materials and driving forces. Although landslides
are not currently present onsite, landslide potentials may be anticipated when the ground
is adversely modified. No geomorphic expressions indicative of past mass wasting events
(i.e., scarps and hummocky terrain) were observed on the site during our field studies nor
our review of regional geologic mapping. Further, no adverse geologic structures were
encountered during our subsurface exploration. Regional geologic maps do not indicate
the presence of landslides on the property. Some landslides are mapped to the south of
the site on north facing slopes. Indications of adverse onsite surficial and gross stability
were not noted during our investigation or are anticipated during construction of the
planned improvements.
The onsite soils are considered erosive. The slopes observed, being composed of these
materials, may develop significant rilling, gullying, sloughing, or surficial slope failures
depending on rainfall severity and surface drainage practices. Such risks can be
minimized through properly designed, and regularly and periodically
maintained surface drainage.
It is the opinion of GSI that the susceptibility of the site to experience damaging
deformations from seismically-induced liquefaction is relatively low owing to the dense
nature of the Santiago Formation that underlies the site in the near-surface and the depth
to groundwater. In addition, the recommendations for remedial earthwork and foundations
would further reduce any significant liquefaction potential.
The following list includes other geologic/seismic related hazards that have been
considered during our evaluation of the site. The hazards listed are considered negligible
or mitigated as a result of site location, soil characteristics, and typical site development
procedures:
• Lateral Spreading
• Subsidence
• Ground Lurching or Shallow Ground Rupture
• Tsunami
• Seiche
Comment No. 12
Strength (direct shear) testing of the on-site soils is not provided in the reviewed report.
Please provide the appropriate laboratory testing to substantiate the values for bearing
capacity, passive pressure, and coefficient of friction that are presented in the report. If
Ms. Patiane Freitas W.O. 8286-A1-SC
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presumptive values are being recommended by the consultant, please indicate the Class
and use values consistent with the appropriate soil type (Class) in Table 1806.2 of the 2019
California Building Code. The reviewer notes that the geotechnical values presented for use
in the report appear to be based on soils class 4 per Table 1806.2 are provided, please
justify the soil type by laboratory testing (see comment #13 below).
Response to Comment No. 12:
A particle-size evaluation was performed on representative sample of surficial, weathered
bedrock soils (B-1/B-3 @ 0-2.5') in general accordance with ASTM D 422-63. The testing
was used to evaluate the soil classification in accordance with the Unified Soil
Classification System (USCS). The results of the particle-size evaluation indicate that the
sample consisted of 0.1 percent gravel, 76.6 percent sand, and 23.3 percent fines,
respectively. Per the USCS, site soil tested is classified as a silty sand (USCS symbol SM).
Applying these results to Table 1806.2 yields a bearing value of 2,000 psf, a lateral
resistance of 150 psf and a friction coefficient of 0.25.
Comment No. 13
The report indicates that laboratory testing for expansion index and particle-size analysis
was performed, however, no laboratory test results for these tests are included in the report.
Please provide the results of the particle-size analysis and expansion index tests.
Response to Comment No. 13:
The soils report summarizes the laboratory testing results for expansion index and
particle-size analysis on page 2 of the soils report. The laboratory test results of the
particle-size analysis and expansion index tests are included in Appendix B.
Comment No. 14
Please provide the amount of total settlement that should be anticipated for structural design
(only the amount of differential settlement appears to be provided in the report).
Response to Comment No. 14:
As stated on page 4 of the report, “differential settlement may be assumed as 1 inch in a
40-foot span.” The differential settlement is estimated at ½ inch over 40-foot span, so total
settlement is anticipated to be 1.5 inches.
Comment No. 15
Please clarify the recommendations for remedial grading (depths and limits of removals,
etc.) for hardscape improvements.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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GeoSoils, Inc.
Response to Comment No. 15:
Limits of remedial grading should extend to 12 inches deep and compacted to 90% relative
compaction for sidewalks/patios with very low expansive soils; or 18 inches deep and
compacted to 95% relative compaction for traffic pavements with higher expansive soils.
Comment No. 16
Based on the current proposed construction, please clarify the foundation
recommendations with respect to approved embedment materials for new footings for the
case where remedial grading is performed and the proposed building area is underlain by
compacted fill (as the recommendations under “Bearing Value” (pages 4 and 5) indicate
new footings should extend to bedrock). Please clarify the approved bearing material for
new footings based on current building concept.
Response to Comment No. 16:
The new footings should be embedded into either unweathered Santiago Formation
(Sandstone) a minimum of 12 inches for the perimeter footings/grade beams and
18 inches for isolated piers, or entirely into compacted structural fill. Removals depths
should include all artificial fill and weathered bedrock and a minimum of 2 feet below the
bottom of the proposed footings (2 foot removal plus 12 to 18 inch footing embedment =
3 to 3½ feet deep).
The area of 6 to 7 feet of loose fill on the slope, described on page 7 of Referenced no. 1
was observed on the slope above the upper building pad and outside of the proposed
development area.
Comment No. 17
Please provide recommendations (slab thickness, reinforcing, subgrade preparation, etc.)
for hardscape improvements.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
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At the upper building pad area, one of our borings encountered 2 to 3.5 feet of
weathered Santiago Formation (sandstone). In order to achieve consistent support
across the structure, remediation of the upper building pad soil should be performed, to
produce a 3 feet thick pad of structural fill to support footings and the floor slab. The
scarified bottom area should be evaluated by probing prior to placement of fill. Any
areas of deeper loose material indicated by the probing can be remediated prior to
placement of fill. Footings founded on structural fill may be designed for an allowable
bearing capacity of 2,000 pounds per square foot. Recommendations for grading are
presented in Appendix D.
GeoSoils, Inc.
Response to Comment No. 17:
GSI recommendations for driveway/parking, flatwork, and other improvements are
included below:
The effects of expansive soils are cumulative, and typically occur over the lifetime of any
improvements. On relatively level areas, when the soils are allowed to dry, the dessication
and swelling process tends to cause heaving and distress to flatwork and other
improvements. The resulting potential for distress to improvements may be reduced, but
not totally eliminated. To that end, it is important that the homeowner be aware of this
long-term potential for distress. To reduce the likelihood of distress, the following
recommendations are presented for all exterior flatwork:
1. The subgrade area for concrete slabs should be compacted to achieve a
minimum 90 percent relative compaction (sidewalks, patios), and 95 percent relative
compaction (traffic pavements), and then be presoaked to 120 percent of the soils’
optimum moisture content, to a depth of 18 inches below subgrade elevation. If
very low expansive soils are present, only optimum moisture content, or greater, is
required and specific presoaking is not warranted. The moisture content of the
subgrade should be proof tested within 72 hours prior to pouring concrete.
2. Concrete slabs should be cast over a non-yielding surface, consisting of a 4-inch
layer of crushed rock, gravel, or clean sand, that should be compacted and level
prior to pouring concrete. If very low expansive soils are present, the rock or gravel
or sand may be deleted. The layer or subgrade should be wet-down completely
prior to pouring concrete, to minimize loss of concrete moisture to the surrounding
earth materials.
3. Exterior slabs (sidewalks, patios, etc.) should be a minimum of 4 inches thick.
4. Driveway and parking area slabs and approaches should be at least 6 inches thick.
Pavement slabs at trash enclosures should be at least 8 inches in thickness. A
thickened edge (12 inches) should also be considered adjacent to all landscape
areas, to help impede infiltration of landscape water under the slab(s). All pavement
construction should minimally be performed in general accordance with industry
standards and properly transitioned. Concrete flat work/pavement may consist of
plain concrete. However, the use of reinforcing steel may be considered, if desired.
5. The use of transverse and longitudinal control joints may be considered to help
control slab cracking due to concrete shrinkage or expansion. Two ways to
mitigate such cracking are: a) add a sufficient amount of reinforcing steel,
increasing tensile strength of the slab; and, b) provide an adequate amount of
control and/or expansion joints to accommodate anticipated concrete shrinkage
and expansion.
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6. In order to reduce the potential for unsightly cracks, slabs should be reinforced at
mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each
direction. If subgrade soils within the top 7 feet from finish grade are very low
expansive soils (i.e., E.I. #20), then 6 x 6 - W1.4 x W1.4 welded-wire mesh may be
substituted for the rebar, provided the reinforcement is placed on chairs, at slab
mid-height. The exterior slabs should be scored or saw cut, ½ to d inches deep,
often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or
narrow slabs, control joints should be provided at intervals of every 6 feet. The
slabs should be separated from the foundations and sidewalks with expansion joint
filler material.
7. No traffic should be allowed upon the newly poured concrete slabs until they have
been properly cured to within 75 percent of design strength. Concrete compression
strength should be a minimum of 2,500 psi for sidewalks and patios, and a
minimum 3,250 psi for traffic pavements.
8. Driveways, sidewalks, and patio slabs adjacent to the structure should be separated
from the structure with thick expansion joint filler material. In areas directly adjacent
to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should
be additionally sealed with flexible mastic.
9. Planters and walls should not be tied to the structure.
10. Overhang structures should be supported on the slabs, or structurally designed
with continuous footings tied in at least two directions. If very low expansion soils
are present, footings need only be tied in one direction.
11. Any masonry landscape walls that are to be constructed throughout the property
should be grouted and articulated in segments no more than 20 feet long. These
segments should be keyed or doweled together.
12. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible
connections to accommodate differential settlement and expansive soil conditions.
13. Positive site drainage should be maintained at all times. Finish grade on the lot
should provide a minimum of 1 to 2 percent fall to the street, as indicated herein.
It should be kept in mind that drainage reversals could occur, including
post-construction settlement, if relatively flat yard drainage gradients are not
periodically maintained by the homeowner.
14. Air conditioning (A/C) units should be supported by slabs that are incorporated into
the building foundation or constructed on a rigid slab with flexible couplings for
plumbing and electrical lines. A/C waste water lines should be drained to a suitable
non-erosive outlet.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
File: e:\wp21\8200\8286a1.raar Page 13
GeoSoils, Inc.
15. Shrinkage cracks could become excessive if proper finishing and curing practices
are not followed. Finishing and curing practices should be performed per the
Portland Cement Association Guidelines. Mix design should incorporate rate of
curing for climate and time of year, sulfate content of soils, corrosion potential of
soils, and fertilizers used on site.
Comment No. 18
Please provide recommendations for retaining wall backdrains from a geotechnical
standpoint.
Response to Comment No. 18:
Retaining Wall Backfill and Drainage:
Positive drainage must be provided behind all retaining walls in the form of gravel wrapped
in geofabric and outlets. A backdrain system is considered necessary for retaining walls
that are 2 feet or greater in height. Details 1, 2, and 3, present the back drainage options
discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS
pipe encased in either Class 2 permeable filter material or ¾-inch to 1½-inch gravel
wrapped in approved filter fabric (Mirafi 140 or equivalent). For low expansive backfill, the
filter material should extend a minimum of 1 horizontal foot behind the base of the walls
and upward at least 1 foot. For native backfill that has up to medium expansion potential,
continuous Class 2 permeable drain materials should be used behind the wall. This
material should be continuous (i.e., full height) behind the wall, and it should be
constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and
Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall
may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain
Detail Geotextile Drain). Materials with an E.I. potential of greater than 50 should not be
used as backfill for retaining walls. For more onerous expansive situations, backfill and
drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And
Subdrain Detail Clean Sand Backfill). Drain outlets should consist of a 4-inch diameter
solid PVC or ABS pipe spaced no greater than ±100 feet apart, with a minimum of two
outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not
recommended. The surface of the backfill should be sealed by pavement or the
top 18 inches compacted with native soil (E.I. < 50). Proper surface drainage should also
be provided. For additional mitigation, consideration should be given to applying a
water-proof membrane to the back of all retaining structures. The use of a waterstop
should be considered for all concrete and masonry joints.
Comment No. 19
Please evaluate and discuss the potential for storm water infiltration at the subject site as
part of the proposed development.
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
File: e:\wp21\8200\8286a1.raar Page 14
12 inches
(1) Waterproofing
membrane
Provide surface drainage via an
engineered V-ditch (see civil plans
for details)
(5) Weep hole
Proposed grade
sloped to drain
per precise civil
drawings
(4) Pipe
(3) Filter fabric
(2) Gravel
2:1 (h:v) slope
1:1 (h:v) or flatter
backcut to be properly
benched
Slope or level
Native backfill
Very Low to Low
Expansive soils,
E.I. <50, P.I. <15
(1) Waterproofing membrane.
(2) Gravel: Clean, crushed, 3 4 to 11 2 inch.
(3) Filter fabric: Mirafi 140N or approved equivalent.
(4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent
gradient sloped to suitable, approved outlet point (perforations down).
(5) Weep holes: For CMU walls, Omit grout every other block, at or slightly above finished surface. For
reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the
wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of
wall. No weep holes for below-grade walls.
(6) Footing: If bench is created behind the footing greater than the footing width using level fill or cut
natural earth materials, an additional "heel " drain will likely be required by geotechnical consultant.
Footing and wall
design by others
(6) Footing
Structural footing or
settlement-sensitive improvement
H
H/3
CMU or
reinforced-concrete
wall . .
.-·-··._ ... . .. -
I I
RETAINING WALL DETAIL -ALTERNATIVE A Detail 1
6 inches
(1) Waterproofing
membrane (optional)Provide surface drainage via engineered
V-ditch (see civil plan details)
(5) Weep hole
Proposed grade
sloped to drain per
precise civil
drawings (4) Pipe
(3) Filter fabric
(2) Composite
drain
CMU or
reinforced-concrete
wall
2:1 (h:v) slope
1:1 (h:v) or flatter
backcut to be properly
benched
Slope or level
Native backfill
Very Low to Low
Expansive soils
E.I. <50, P.I. <15
(1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent.
(2) Drain: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls; Miradrain 6200 or
J-drain 200 or equivalent for waterproofed walls (all perforations down).
(3) Filter fabric: Mirafi 140N or approved equivalent; place fabric flap behind core.
(4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent
gradient to proper outlet point (perforations down).
(5) Weep holes: For CMU walls, Omit grout every other block, at or slightly above finished surface. For
reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the
wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of
wall. No weep holes for below-grade walls.
(6) Gravel: Clean, crushed, 3 4 to 11 2 inch.
(7) Footing: If bench is created behind the footing greater than the footing width using level fill or cut
natural earth materials, an additional "heel" drain will likely be required by geotechnical consultant.
(6) 1 cubic foot of
3 4-inch crushed rock
(7) Footing
Footing and wall
design by others
Structural footing or
settlement-sensitive improvement
l_
1-
I I
.-·-·._ ...
I
RETAINING WALL DETAIL -ALTERNATIVE B Detail 2
(1) Waterproofing
membrane
Provide surface drainage
(5) Weep hole
Proposed grade
sloped to drain
per precise civil
drawings
(4) Pipe
(3) Filter fabric
(2) Gravel
CMU or
reinforced-concrete
wall
2:1 (h:v) slope
1:1 (h:v) or flatter
backcut to be
properly benched
Slope or level
(8) Native backfill
(1) Waterproofing membrane: Liquid boot or approved masticequivalent.
(2) Gravel: Clean, crushed, 3 4 to 11 2 inch.
(3) Filter fabric: Mirafi 140N or approved equivalent.
(4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent
gradient to proper outlet point (perforations down).
(5) Weep hole: For CMU walls, Omit grout every other block, at or slightly above finished surface. For
reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the
wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of
wall. No weep holes for below-grade walls.
(6) Clean sand backfill: Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water
jetting upon approval by geotechnical engineer.
(7) Footing: If bench is created behind the footing greater than the footing width using level fill or cut
natural earth materials, an additional "heel" drain will likely be required by geotechnical consultant.
(8) Native backfill: If E.I. <21 and S.E. >35 then all sand requirements also may not be required and will
be reviewed by the geotechnical consultant.
(6) Clean
sand backfill
H
±12 inches
H/2
minimum
Heel
width
(7) Footing
Footing and wall
design by others
Structural footing or
settlement-sensitive improvement
4 .
-· -·-··. -· ---
<I
4
7-
I I
RETAINING WALL DETAIL -ALTERNATIVE C Detail 3
GeoSoils, Inc.
Response to Comment No. 19:
A review of the United States Department of Agriculture database ([USDA]; 1973, 2023)
indicates that four (4) types of site soils located within the site is classified as Carlsbad
gravelly loamy sand (9 to 15 percent slopes) at the NE corner of the lot; Corralitos loamy
sand (5 to 9 percent slopes) at the NE portion of the lot; Las Flores-urban complex, 2 to
9 percent slopes, to the east side of the lot ; and Loamy alluvial land - Huerhuero complex,
9 to 50 percent, which is primarily within the improvement area (west side). The USDA
study further indicates that the Loamy alluvial land - Huerhuero complex is classified as
belonging to Hydrologic Soil Group “B.” A review of USDA (1973 and 2023) indicates that
the capacity of the most limiting layer to transmit water (Ksat) within the Loamy alluvial land
- Huerhuero complex is very low to low (0.00 to 0.06 inches per hour [in/hr]). Only the
Carlsbad gravelly loamy sand shows any appreciable water transmission rate at high (1.98
to 5.95 inches per hour [in/hr]), however this unit only occupies a small area at the
northeast corner of the lot.
Based on our review and engineering analysis, the site improvement area is more correctly
characterized as belonging to HSG “D,” and we recommend “no-infiltration” BMP design
due to the fact that high groundwater conditions will be within 10 feet of planned or existing
structures and they would likely be affected. Due to the potential for associated settlement,
distress, and perched groundwater for any BMP structure within close proximity
(i.e., potentially within 10 feet) of any foundations, retaining walls, slopes, and other
settlement-sensitive improvements, a “no infiltration” BMP design is warranted. An
“analysis of infiltration restrictions” was completed according to Section D.1-1 of
Appendix C of the 2020 City of Carlsbad Storm Water manual and is included in
Appendix C. Furthermore, any basin constructed entirely of compacted fill is considered
as belonging to HSG D, and a “no infiltration” BMP design is also warranted
(Clar, et al., 2004).
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
File: e:\wp21\8200\8286a1.raar Page 18
GeoSoils, Inc.
The opportunity to be of service is sincerely appreciated. If you should have any
questions, please do not hesitate to contact our office.
Respectfully submitted,
GeoSoils, Inc.
Todd M. Page Stephen J. Coover
Engineering Geologist, CEG 2083 Geotechnical Engineer, GE 2057
TMP/JPF/SJC/sh/jh
Attachments:Revised Plate B-2 - Boring Log B-2 (Corrected)
Plate 1 - Boring Location Map
Plate 2 - Cross Section A-A’
Appendix A - Seismic Data (EQ Fault)
Appendix B - Laboratory Testing
Appendix C - Infiltration Data (Form I-8)
Appendix D - General Earthwork, Grading Guidelines, and Preliminary
Criteria
Distribution:(1) Addressee (PDF via email)
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad February 1, 2023
File: e:\wp21\8200\8286a1.raar Page 19
0
5
10
15
20
25
30
SM
SP-SM
SP-SM
WEATHERED SANTIAGO FORMATION:@ 0', SILTY SAND, light yellowish brown, dry, loose to medium dense;fine to medium grain sand.@ 1', SILTY SAND with trace CLAY, dark brown to dark yellowish brown,slightly moist, medium dense; fine to medium sand.@ 3', SAND with trace SILT, light brown to light yellow brown, dry, looseto medium dense.
SANTIAGO FORMATION:@ 3.5', SAND with trace SILT, light brown to light yellow brown, dry,medium dense to dense; less weathered.
Total Depth = 5'No Groundwater or Caving Encountered.Backfilled 2-10-22.
GeoSoils, Inc.BORING LOG
PROJECT:4339 PARK DRIVE, CARLSBAD W.O.8286-A-SC BORING B-2 SHEET 1 OF
DATE EXCAVATED 2-10-22 LOGGED BY:MJS APPROX. ELEV.:84'NAVD88
SAMPLE METHOD:Hand-auger
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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TD=5'
B-3
B-4
TD=5'
TD=5'
B-2
TD=5'
W.O.DATE:SCALE:8286-A1-SC 1" = 50'
Plate 1
BORING LOCATION
MAP
02/23
ALL LOCATIONS ARE APPROXIMATE
This document or efile is not a part of the Construction
Documents and should not be relied upon as being an
accurate depiction of design.
APPROXIMATE LOCATION OF EXPLORATORY BORING
WITH TOTAL DEPTH IN FEET
B-4
TD=5'
GSI LEGEND
BASE MAP FROM:
N
S
E
W
0
GRAPHIC SCALE
50 25 50 100
1" = 50'
APPROXIMATE LOCATION OF GEOLOGIC CROSS
SECTION
A A'
A A'
APPROXIMATE LIMITS OF PROPOSED REMEDIAL
GRADING
AREA OF
OVEREXCAVATION
ABANDONED
SEPTIC TANK
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4339 PARK DR
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W.O.DATE:SCALE:8286-A1-SC 02/23 1" = 40'
Plate 2
GEOLOGIC CROSS SECTION
A-A'
ALL LOCATIONS ARE APPROXIMATE
This document or efile is not a part of the Construction
Documents and should not be relied upon as being an
accurate depiction of design.
GSI LEGEND
Tsa
A
11°
S31°W
A'
7°
Tsa
Tsa Tsa
140 140
I · PROPOSED · I ADDITION
120 8-3 120
EXISTING
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GRADE 40 40 -·--·-· ---· -· -·-20 20 -·-· -· ---·
0 0
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 JOO J20 J40 J60 J80 400 420 440 460
DISTANCE (FEET)
'
GRAPHIC SCALE
40 0 20 40 80
1" = 40'
TERTIARY SANTAGO FORMATION
---·-BEDDING AmTUDE, WITH APPARENT DIP IN DEGREES
V/'//1 -APPROX/MA TE LIMITS OF PROPOSED REMEDIAL GRADING
GeoSoils, Inc.
APPENDIX A
SEISMICITY DATA (EQ FAULT)
***********************
* *
* E Q F A U L T *
* *
* Version 3.00 *
* *
***********************
DETERMINISTIC ESTIMATION OF
PEAK ACCELERATION FROM DIGITIZED FAULTS
JOB NUMBER: 8286
DATE: 02-21-2022
JOB NAME: Freitas
CALCULATION NAME: Test Run Analysis
FAULT-DATA-FILE NAME: C:\Users\Matt\Documents\EQFAULT1\CGSFLTE.DAT
SITE COORDINATES:
SITE LATITUDE: 33.1487
SITE LONGITUDE: 117.3267
SEARCH RADIUS: 62.4 mi
ATTENUATION RELATION: 12) Bozorgnia Campbell Niazi (1999) Hor.-Soft Rock-Cor.
UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0
DISTANCE MEASURE: cdist
SCOND: 0
Basement Depth: .10 km Campbell SSR: 1 Campbell SHR: 0
COMPUTE PEAK HORIZONTAL ACCELERATION
FAULT-DATA FILE USED: C:\Users\Matt\Documents\EQFAULT1\CGSFLTE.DAT
MINIMUM DEPTH VALUE (km): 3.0
W.O. 8286-A1-SC Plate A-1
---------------
EQFAULT SUMMARY
---------------
-----------------------------
DETERMINISTIC SITE PARAMETERS
-----------------------------
Page 1
-------------------------------------------------------------------------------
| |ESTIMATED MAX. EARTHQUAKE EVENT
| APPROXIMATE |-------------------------------
ABBREVIATED | DISTANCE | MAXIMUM | PEAK |EST. SITE
FAULT NAME | mi (km) |EARTHQUAKE| SITE |INTENSITY
| | MAG.(Mw) | ACCEL. g |MOD.MERC.
================================|==============|==========|==========|=========
ROSE CANYON | 5.5( 8.9)| 7.2 | 0.595 | X
NEWPORT-INGLEWOOD (Offshore) | 6.2( 10.0)| 7.1 | 0.538 | X
CORONADO BANK | 21.3( 34.3)| 7.6 | 0.266 | IX
ELSINORE (TEMECULA) | 24.0( 38.6)| 6.8 | 0.139 | VIII
ELSINORE (JULIAN) | 24.1( 38.8)| 7.1 | 0.169 | VIII
ELSINORE (GLEN IVY) | 34.2( 55.1)| 6.8 | 0.096 | VII
SAN JOAQUIN HILLS | 36.2( 58.3)| 6.6 | 0.112 | VII
PALOS VERDES | 36.7( 59.1)| 7.3 | 0.126 | VIII
EARTHQUAKE VALLEY | 43.2( 69.5)| 6.5 | 0.062 | VI
SAN JACINTO-ANZA | 46.7( 75.1)| 7.2 | 0.092 | VII
NEWPORT-INGLEWOOD (L.A.Basin) | 46.9( 75.5)| 7.1 | 0.085 | VII
SAN JACINTO-SAN JACINTO VALLEY | 47.3( 76.1)| 6.9 | 0.073 | VII
CHINO-CENTRAL AVE. (Elsinore) | 48.5( 78.0)| 6.7 | 0.088 | VII
SAN JACINTO-COYOTE CREEK | 51.9( 83.6)| 6.6 | 0.054 | VI
WHITTIER | 52.3( 84.2)| 6.8 | 0.062 | VI
ELSINORE (COYOTE MOUNTAIN) | 57.3( 92.2)| 6.8 | 0.056 | VI
W.O. 8286-A1-SC Plate A-2
SAN JACINTO-SAN BERNARDINO | 60.3( 97.0)| 6.7 | 0.050 | VI
PUENTE HILLS BLIND THRUST | 62.3( 100.2)| 7.1 | 0.090 | VII
*******************************************************************************
-END OF SEARCH- 18 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS.
THE ROSE CANYON FAULT IS CLOSEST TO THE SITE.
IT IS ABOUT 5.5 MILES (8.9 km) AWAY.
LARGEST MAXIMUM-EARTHQUAKE SITE ACCELERATION: 0.5945 g
W.O. 8286-A1-SC Plate A-3
GeoSoils, Inc.
APPENDIX B
LABORATORY TESTING
General Accordance with ASTM 4829
Sample Data
Freitas Date Started:2/22/22
8286-A-SC Date Completed:2/23/22
2/23/2022 Tested By:TR
4.01 in.Layers:2 Date Received:2/10/22
1 in Blows:15 By:MS
5.5 lbs.Drop:12"Ring Volume:0.0073 cf
Test Data
B-1/B-3
Lot Number
Depth 0-2.5ft
Phase/Tract Number
Sample Description SM
% Retained on #4 0.1%
Wet Weight, Mw (g)601.3
Ring #
Ring Weight, Mr (g)201
Wet Weight, Mw-Mr (g)400.3
Wet Density, Dw (pcf)120.9
% Moisture (W)9.4%
Dry Density (pcf) DD 110.5
% Saturation*48.4%
Test Results
Start Dial Reading (in)0.2000
Initial Time 10:00
Final Dial Reading (in)0.203
Final Time 7:00
Expansion (in)-0.0030
Expansion Index 0
EXPANSION INDEX VERY LOW #VALUE!
Adjusted to 50% Sat -1 #VALUE!
Moisture Content After Test
Final Weight (gms), Mf 627.2
Wet Weight, Mf-Mr (g)426.2
Dry Weight, D (g)365.9
% Moisture Sat.16.5%#DIV/0!
Oversize Sample Data
Weight of Soils (g)1562.6
Weight of + #4 (g)2.1
* Saturation = W/((62.4/DD)-(1/2.7))Dry Density = C22/(1+C23)Amended:Rev 8/08
Expansion (in) = Final Dial Reading - Start Dial Reading Uncor. Exp.Undex = Expansion (in) * 1000
Adjusted to 50% Sat = Expansion-((65+Expansion)/(220-% Saturation*100))*(50-% Saturation*100)
% Moisture Sat. = (Mf-Mr)/D Specific Gravity Assumed 2.70
Remarks:
Sample ID
EXPANSION INDEX TEST
Ring Height:
Hammer Wt:
Project Name:
Project Number:
Report Date:
Ring Diameter:
GeoSoils Inc., 5741 Palmer Way, Carlsbad CA 92010, (760) 438-3155 W.O. 8286-A1-SC Plate B-1
□
Tested By: TR Checked By: TR
2-22-22
(no specification provided)
PL=LL=PI=
D90=D85=D60=D50=D30=D15=D10=Cu=Cc=
USCS=AASHTO=
*
Brown Silty Sand
.375
#4
#10
#20
#40
#60
#100
#200
100.0
99.9
99.6
97.3
78.2
47.8
30.6
23.3
0.5765 0.4960 0.3098
0.2606 0.1454
SM
Freitas
4339 Park Drive
8286-A-SC
Soil Description
Atterberg Limits
Coefficients
Classification
Remarks
Source of Sample: B-1/B-3 Depth: 0-2.5
Sample Number: B-1/B-3 Date:
Client:
Project:
Project No:Plate
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
PE
R
C
E
N
T
F
I
N
E
R
0
10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 0.0 0.1 0.3 21.4 54.9 23.3
6
i
n
.
3
i
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.
2
i
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#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
Particle Size Distribution Report
W.O. 8286-A1-SC Plate B-2
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APPENDIX C
INFILTRATION DATA (FORM I-8)
Appendix I: Forms and Checklists
Categorization of Infiltration Condition Form I-8
Part 1 - Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences
that cannot be reasonably mitigated?
Note that it is not necessary to investigate each and every criterion in the worksheet if infiltration is precluded.
Instead a letter of justification from a geotechnical professional familiar with the local conditions substantiating
any geotechnical issues will be required.
Criteria Screening Question Yes No
1
Is the estimated reliable infiltration rate below proposed facility locations greater
than 0.5 inches per hour? The response to this Screening Question shall be based on
a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.
X
Provide basis:
No. Initial USDA Testing demonstrates that the estimated reliable infiltration rate is less than 0.5 in/hr
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
2
Can infiltration greater than 0.5 inches per hour be allowed without increasing
risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or
other factors) that cannot be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.2.
X
Provide basis:
No, High groundwater mounding potentials, and location to retaining walls will likely be affected.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
Storm Water Standards
Part 1: BMP Design Manual
January 2016 Edition C-11
Page 2 of 4
Criteria Screening Question Yes No
3
Can infiltration greater than 0.5 inches per hour be allowed without increasing
risk of groundwater contamination (shallow water table, storm water pollutants
or other factors) that cannot be mitigated to an acceptable level? The response to
this Screening Question shall be based on a comprehensible evaluation of the factors
presented in Appendix C.3.
Provide basis:
No response required. See Criteria No. 1.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
4
Can infiltration greater than 0.5 inches per hour be allowed without causing
potential water balance issues such as a change of seasonality of ephemeral streams
or increased discharge of contaminated groundwater to surface waters? The
response to this Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
No, All factors considered within Appendix C, Section C.3, will have a significant impact on ephemeral
streams or increase discharge of contaminated groundwater.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
Part 1
Result*
In the answers to rows 1-4 are “Yes” a full infiltration design is potentially feasible. The feasibility
screening category is Full Infiltration
If any answer from row 1-4 is “No”, infiltration may be possible to some extent but would not generally
be feasible or desirable to achieve a “full infiltration” design.
Proceed to Part 2
Proceed
to Part 2
* To be completed using gathered site information and best professional judgement considering the definition of MEP in the MS4
Permit. Additional testing and/or studies may be required by [City Engineer] to substantiate findings.
Storm Water Standards
Part 1: BMP Design Manual
January 2016 Edition C-12
x
x
Page 3 of 4
Part 2 - Partial Infiltration vs. No Infiltration Feasibility Screening Criteria
Would infiltration of water in an appreciable amount be physically feasible without any negative consequences
that cannot be reasonably mitigated?
Criteria Screening Question Yes No
5
Do soil and geologic conditions allow for infiltration in any appreciable
rate or volume? The response to this Screening Question shall be based on
a comprehensive evaluation of the factors presented in Appendix C.2 and
Appendix D.
x
Provide basis:
KSAT = 0.00 + 0.06 in/hr per USDA
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
6
Can infiltration in any appreciable quantity be allowed without
increasing risk of geotechnical hazards (slope stability, groundwater
mounding, utilities, or other factors) that cannot be mitigated to an
acceptable level? The response to this Screening Question shall be based on
a comprehensive evaluation of the factors presented in Appendix C.2.
Provide basis:
If storm water infiltration into the onsite soils were to occur, there would be an increased potential for
shallow perched groundwater conditions (i.e., groundwater mounding) to develop, owing to the
collection of water upon the indurated and less permeable unweathered formation, which occur at
depths ranging between approximately 3 feet and 5 feet below the existing grades, within the project area.
Perched groundwater conditions which would adversely affect the performance of the onsite
improvements and the existing offsite improvements on adjacent private properties and the public right-
of-way.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Storm Water Standards
Part 1: BMP Design Manual
January 2016 Edition C-13
x
Page 4 of 4
Criteria Screening Question Yes No
7
Can Infiltration in any appreciable quantity be allowed without posing
significant risk for groundwater related concerns (shallow water table,
storm water pollutants or other factors)? The response to this Screening
Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.3.
Provide basis:
No, the groundwater table is within 9 feet in depth and will likely be impacted due to lower permeabilities
at depth. See Criteria 6
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
8
Can infiltration be allowed without violating downstream water rights?
The response to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis:
Downstream water rights are a legal matter that do not fall under the purview of geotechnical engineering.
However, the site drains directly into the Agua Hedionda Lagoon, at the site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Part 2
Result*
If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. The
feasibility screening category is Partial Infiltration.
If any answer from row 5-8 is no, then infiltration of any volume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
No
Infiltration
* To be completed using gathered site information and best professional judgement considering the definition of MEP in the MS4
Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings.
Storm Water Standards
Part 1: BMP Design Manual
January 2016 Edition C-14
X
GeoSoils, Inc.
APPENDIX D
GENERAL EARTHWORK, GRADING GUIDELINES
AND PRELIMINARY CRITERIA
GeoSoils, Inc.
GENERAL EARTHWORK, GRADING GUIDELINES, AND PRELIMINARY CRITERIA
General
These guidelines present general procedures and requirements for earthwork and grading
as shown on the approved grading plans, including preparation of areas to be filled,
placement of fill, installation of subdrains, excavations, and appurtenant structures or
flatwork. The recommendations contained in the geotechnical report are part of these
earthwork and grading guidelines and would supercede the provisions contained hereafter
in the case of conflict. Evaluations performed by the consultant during the course of
grading may result in new or revised recommendations which could supercede these
guidelines or the recommendations contained in the geotechnical report. Generalized
details follow this text.
The contractor is responsible for the satisfactory completion of all earthwork in accordance
with provisions of the project plans and specifications and latest adopted Code. In the
case of conflict, the most onerous provisions shall prevail. The project geotechnical
engineer and engineering geologist (geotechnical consultant), and/or their representatives,
should provide observation and testing services, and geotechnical consultation during the
duration of the project.
EARTHWORK OBSERVATIONS AND TESTING
Geotechnical Consultant
Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer
and engineering geologist) should be employed for the purpose of observing earthwork
procedures and testing the fills for general conformance with the recommendations of the
geotechnical report(s), the approved grading plans, and applicable grading codes and
ordinances.
The geotechnical consultant should provide testing and observation so that an evaluation
may be made that the work is being accomplished as specified. It is the responsibility of
the contractor to assist the consultants and keep them apprised of anticipated work
schedules and changes, so that they may schedule their personnel accordingly.
All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and
subdrain installation should be observed and documented by the geotechnical consultant
prior to placing any fill. It is the contractor’s responsibility to notify the geotechnical
consultant when such areas are ready for observation.
Laboratory and Field Tests
Maximum dry density tests to determine the degree of compaction should be performed
in accordance with American Standard Testing Materials test method ASTM designation
D-1557. Random or representative field compaction tests should be performed in
GeoSoils, Inc.
accordance with test methods ASTM designation D-1556, D-2937 or D-2922, and D-3017,
at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards
placed. These criteria would vary depending on the soil conditions and the size of the
project. The location and frequency of testing would be at the discretion of the
geotechnical consultant.
Contractor's Responsibility
All clearing, site preparation, and earthwork performed on the project should be conducted
by the contractor, with observation by a geotechnical consultant, and staged approval by
the governing agencies, as applicable. It is the contractor's responsibility to prepare the
ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to
place, spread, moisture condition, mix, and compact the fill in accordance with the
recommendations of the geotechnical consultant. The contractor should also remove all
non-earth material considered unsatisfactory by the geotechnical consultant.
Notwithstanding the services provided by the geotechnical consultant, it is the sole
responsibility of the contractor to provide adequate equipment and methods to accomplish
the earthwork in strict accordance with applicable grading guidelines, latest adopted Code
or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient
watering apparatus and compaction equipment should be provided by the contractor with
due consideration for the fill material, rate of placement, and climatic conditions. If, in the
opinion of the geotechnical consultant, unsatisfactory conditions such as questionable
weather, excessive oversized rock or deleterious material, insufficient support equipment,
etc., are resulting in a quality of work that is not acceptable, the consultant will inform the
contractor, and the contractor is expected to rectify the conditions, and if necessary, stop
work until conditions are satisfactory.
During construction, the contractor shall properly grade all surfaces to maintain good
drainage and prevent ponding of water. The contractor shall take remedial measures to
control surface water and to prevent erosion of graded areas until such time as permanent
drainage and erosion control measures have been installed.
SITE PREPARATION
All major vegetation, including brush, trees, thick grasses, organic debris, and other
deleterious material, should be removed and disposed of off-site. These removals must
be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock
materials, as evaluated by the geotechnical consultant as being unsuitable, should be
removed prior to any fill placement. Depending upon the soil conditions, these materials
may be reused as compacted fills. Any materials incorporated as part of the compacted
fills should be approved by the geotechnical consultant.
Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic
tanks, wells, pipelines, or other structures not located prior to grading, are to be removed
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or treated in a manner recommended by the geotechnical consultant. Soft, dry, 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
firm ground and approved by the geotechnical consultant before compaction and filling
operations continue. Overexcavated and processed soils, which have been properly
mixed and moisture conditioned, should be re-compacted to the minimum relative
compaction as specified in these guidelines.
Existing ground, which is determined to be satisfactory for support of the fills, should be
scarified (ripped) to a minimum depth of 6 to 8 inches, or as directed by the geotechnical
consultant. After the scarified ground is brought to optimum moisture content, or greater
and mixed, the materials should be compacted as specified herein. If the scarified zone
is greater than 6 to 8 inches in depth, it may be necessary to remove the excess and place
the material in lifts restricted to about 6 to 8 inches in compacted thickness.
Existing ground which is not satisfactory to support compacted fill should be
overexcavated as required in the geotechnical report, or by the on-site geotechnical
consultant. Scarification, disc harrowing, or other acceptable forms of mixing should
continue until the soils are broken down and free of large lumps or clods, until the working
surface is reasonably uniform and free from ruts, hollows, hummocks, mounds, or other
uneven features, which would inhibit compaction as described previously.
Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical
[h:v]), the ground should be stepped or benched. The lowest bench, which will act as a
key, should be a minimum of 15 feet wide and should be at least 2 feet deep into firm
material, and approved by the geotechnical consultant. In fill-over-cut slope conditions,
the recommended minimum width of the lowest bench or key is also 15 feet, with the key
founded on firm material, as designated by the geotechnical consultant. As a general rule,
unless specifically recommended otherwise by the geotechnical consultant, the minimum
width of fill keys should be equal to ½ the height of the slope.
Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable
material. Benching may be used to remove unsuitable materials, although it is understood
that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered
for unsuitable materials in excess of 4 feet in thickness.
All areas to receive fill, including processed areas, removal areas, and the toes of fill
benches, should be observed and approved by the geotechnical consultant prior to
placement of fill. Fills may then be properly placed and compacted until design grades
(elevations) are attained.
COMPACTED FILLS
Any earth materials imported or excavated on the property may be utilized in the fill
provided that each material has been evaluated to be suitable by the geotechnical
consultant. These materials should be free of roots, tree branches, other organic matter,
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or other deleterious materials. All unsuitable materials should be removed from the fill as
directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion
potential, or substandard strength characteristics may be designated by the consultant as
unsuitable and may require blending with other soils to serve as a satisfactory fill material.
Fill materials derived from benching operations should be dispersed throughout the fill
area and blended with other approved material. Benching operations should not result in
the benched material being placed only within a single equipment width away from the
fill/bedrock contact.
Oversized materials defined as rock, or other irreducible materials, with a maximum
dimension greater than 12 inches, should not be buried or placed in fills unless the
location of materials and disposal methods are specifically approved by the geotechnical
consultant. Oversized material should be taken offsite, or placed in accordance with
recommendations of the geotechnical consultant in areas designated as suitable for rock
disposal. GSI anticipates that soils to be utilized as fill material for the subject project may
contain some rock. Appropriately, the need for rock disposal may be necessary during
grading operations on the site. From a geotechnical standpoint, the depth of any rocks,
rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is
generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and
generally facilitates the excavation of structural footings and substructures. Should deeper
excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas,
etc.), the developer may consider increasing the hold-down depth of any rocky fills to be
placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific
hold-down depth for oversize materials placed in fills. The hold-down depth, and potential
to encounter oversize rock, both within fills, and occurring in cut or natural areas, would
need to be disclosed to all interested/affected parties. Once approved by the governing
agency, the hold-down depth for oversized rock (i.e., greater than 12 inches) in fills on this
project is provided as 10 feet, unless specified differently in the text of this report. The
governing agency may require that these materials need to be deeper, crushed, or
reduced to less than 12 inches in maximum dimension, at their discretion.
To facilitate future trenching, rock (or oversized material), should not be placed within the
hold-down depth feet from finish grade, the range of foundation excavations, future utilities,
or underground construction unless specifically approved by the governing agency, the
geotechnical consultant, and/or the developer’s representative.
If import material is required for grading, representative samples of the materials to be
utilized as compacted fill should be analyzed in the laboratory by the geotechnical
consultant to evaluate it’s physical properties and suitability for use onsite. Such testing
should be performed three (3) days prior to importation. If any material other than that
previously tested is encountered during grading, an appropriate analysis of this material
should be conducted by the geotechnical consultant as soon as possible.
Approved fill material should be placed in areas prepared to receive fill in near horizontal
layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The
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geotechnical consultant may approve thick lifts if testing indicates the grading procedures
are such that adequate compaction is being achieved with lifts of greater thickness. Each
layer should be spread evenly and blended to attain uniformity of material and moisture
suitable for compaction.
Fill layers at a moisture content less than optimum should be watered and mixed, and wet
fill layers should be aerated by scarification, or should be blended with drier material.
Moisture conditioning, blending, and mixing of the fill layer should continue until the fill
materials have a uniform moisture content at, or above, optimum moisture.
After each layer has been evenly spread, moisture conditioned, and mixed, it should be
uniformly compacted to a minimum of 90 percent of the maximum density as evaluated by
ASTM test designation D 1557, or as otherwise recommended by the geotechnical
consultant. Compaction equipment should be adequately sized and should be specifically
designed for soil compaction, or of proven reliability to efficiently achieve the specified
degree of compaction.
Where tests indicate that the density of any layer of fill, or portion thereof, is below the
required relative compaction, or improper moisture is in evidence, the particular layer or
portion shall be re-worked until the required density and/or moisture content has been
attained. No additional fill shall be placed in an area until the last placed lift of fill has been
tested and found to meet the density and moisture requirements, and is approved by the
geotechnical consultant.
In general, per the latest adopted Code, fill slopes should be designed and constructed
at a gradient of 2:1 (h:v), or flatter. Compaction of slopes should be accomplished by over-
building a minimum of 3 feet horizontally, and subsequently trimming back to the design
slope configuration. Testing shall be performed as the fill is elevated to evaluate
compaction as the fill core is being developed. Special efforts may be necessary to attain
the specified compaction in the fill slope zone. Final slope shaping should be performed
by trimming and removing loose materials with appropriate equipment. A final evaluation
of fill slope compaction should be based on observation and/or testing of the finished
slope face. Where compacted fill slopes are designed steeper than 2:1 (h:v), prior
approval from the governing agency, specific material types, a higher minimum relative
compaction, special reinforcement, and special grading procedures will be recommended.
If an alternative to over-building and cutting back the compacted fill slopes is selected,
then special effort should be made to achieve the required compaction in the outer 10 feet
of each lift of fill by undertaking the following:
1. An extra piece of equipment consisting of a heavy, short-shanked sheepsfoot
should be used to roll (horizontal) parallel to the slopes continuously as fill is
placed. The sheepsfoot roller should also be used to roll perpendicular to the
slopes, and extend out over the slope to provide adequate compaction to the face
of the slope.
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2. Loose fill should not be spilled out over the face of the slope as each lift is
compacted. Any loose fill spilled over a previously completed slope face should be
trimmed off or be subject to re-rolling.
3. Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the
slope at appropriate vertical intervals, subsequent to compaction operations.
4. After completion of the slope, the slope face should be shaped with a small tractor
and then re-rolled with a sheepsfoot to achieve compaction to near the slope face.
Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to
achieve compaction to the slope face. Final testing should be used to evaluate
compaction after grid rolling.
5. Where testing indicates less than adequate compaction, the contractor will be
responsible to rip, water, mix, and recompact the slope material as necessary to
achieve compaction. Additional testing should be performed to evaluate
compaction.
SUBDRAIN INSTALLATION
Subdrains should be installed in approved ground in accordance with the approximate
alignment and details indicated by the geotechnical consultant. Subdrain locations or
materials should not be changed or modified without approval of the geotechnical
consultant. The geotechnical consultant may recommend and direct changes in subdrain
line, grade, and drain material in the field, pending exposed conditions. The location of
constructed subdrains, especially the outlets, should be recorded/surveyed by the project
civil engineer. Drainage at the subdrain outlets should be provided by the project civil
engineer.
EXCAVATIONS
Excavations and cut slopes should be examined during grading by the geotechnical
consultant. If directed by the geotechnical consultant, further excavations or
overexcavation and refilling of cut areas should be performed, and/or remedial grading of
cut slopes should be performed. When fill-over-cut slopes are to be graded, unless
otherwise approved, the cut portion of the slope should be observed by the geotechnical
consultant prior to placement of materials for construction of the fill portion of the slope.
The geotechnical consultant should observe all cut slopes, and should be notified by the
contractor when excavation of cut slopes commence.
If, during the course of grading, unforeseen adverse or potentially adverse geologic
conditions are encountered, the geotechnical consultant should investigate, evaluate, and
make appropriate recommendations for mitigation of these conditions. The need for cut
slope buttressing or stabilizing should be based on in-grading evaluation by the
geotechnical consultant, whether anticipated or not.
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Unless otherwise specified in geotechnical and geological report(s), no cut slopes should
be excavated higher or steeper than that allowed by the ordinances of controlling
governmental agencies. Additionally, short-term stability of temporary cut slopes is the
contractor’s responsibility.
Erosion control and drainage devices should be designed by the project civil engineer and
should be constructed in compliance with the ordinances of the controlling governmental
agencies, and/or in accordance with the recommendations of the geotechnical consultant.
COMPLETION
Observation, testing, and consultation by the geotechnical consultant should be
conducted during the grading operations in order to state an opinion that all cut and fill
areas are graded in accordance with the approved project specifications. After completion
of grading, and after the geotechnical consultant has finished observations of the work,
final reports should be submitted, and may be subject to review by the controlling
governmental agencies. No further excavation or filling should be undertaken without prior
notification of the geotechnical consultant or approved plans.
All finished cut and fill slopes should be protected from erosion and/or be planted in
accordance with the project specifications and/or as recommended by a landscape
architect. Such protection and/or planning should be undertaken as soon as practical after
completion of grading.
PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS
The following preliminary recommendations are provided for consideration in pool/spa
design and planning. Actual recommendations should be provided by a qualified
geotechnical consultant, based on site specific geotechnical conditions, including a
subsurface investigation, differential settlement potential, expansive and corrosive soil
potential, proximity of the proposed pool/spa to any slopes with regard to slope creep and
lateral fill extension, as well as slope setbacks per Code, and geometry of the proposed
improvements. Recommendations for pools/spas and/or deck flatwork underlain by
expansive soils, or for areas with differential settlement greater than ¼-inch over 40 feet
horizontally, will be more onerous than the preliminary recommendations presented below.
The 1:1 (h:v) influence zone of any nearby retaining wall site structures should be
delineated on the project civil drawings with the pool/spa. This 1:1 (h:v) zone is defined
as a plane up from the lower-most heel of the retaining structure, to the daylight grade of
the nearby building pad or slope. If pools/spas or associated pool/spa improvements are
constructed within this zone, they should be re-positioned (horizontally or vertically) so that
they are supported by earth materials that are outside or below this 1:1 plane. If this is not
possible given the area of the building pad, the owner should consider eliminating these
improvements or allow for increased potential for lateral/vertical deformations and
associated distress that may render these improvements unusable in the future, unless
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they are periodically repaired and maintained. The conditions and recommendations
presented herein should be disclosed to all homeowners and any interested/affected
parties.
General
1. The equivalent fluid pressure to be used for the pool/spa design should be
60 pounds per cubic foot (pcf) for pool/spa walls with level backfill, and 75 pcf for
a 2:1 sloped backfill condition. In addition, backdrains should be provided behind
pool/spa walls subjacent to slopes.
2. Passive earth pressure may be computed as an equivalent fluid having a density of
150 pcf, to a maximum lateral earth pressure of 1,000 pounds per square foot (psf).
3. An allowable coefficient of friction between soil and concrete of 0.30 may be used
with the dead load forces.
4. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
5. Where pools/spas are planned near structures, appropriate surcharge loads need
to be incorporated into design and construction by the pool/spa designer. This
includes, but is not limited to landscape berms, decorative walls, footings, built-in
barbeques, utility poles, etc.
6. All pool/spa walls should be designed as “free standing” and be capable of
supporting the water in the pool/spa without soil support. The shape of pool/spa
in cross section and plan view may affect the performance of the pool, from a
geotechnical standpoint. Pools and spas should also be designed in accordance
with the latest adopted Code. Minimally, the bottoms of the pools/spas, should
maintain a distance H/3, where H is the height of the slope (in feet), from the slope
face. This distance should not be less than 7 feet, nor need not be greater than
40 feet.
7. The soil beneath the pool/spa bottom should be uniformly moist with the same
stiffness throughout. If a fill/cut transition occurs beneath the pool/spa bottom, the
cut portion should be overexcavated to a minimum depth of 48 inches, and
replaced with compacted fill, such that there is a uniform blanket that is a minimum
of 48 inches below the pool/spa shell. If very low expansive soil is used for fill, the
fill should be placed at a minimum of 95 percent relative compaction, at optimum
moisture conditions. This requirement should be 90 percent relative compaction
at over optimum moisture if the pool/spa is constructed within or near expansive
soils. The potential for grading and/or re-grading of the pool/spa bottom, and
attendant potential for shoring and/or slot excavation, needs to be considered
during all aspects of pool/spa planning, design, and construction.
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8. If the pool/spa is founded entirely in compacted fill placed during rough grading, the
deepest portion of the pool/spa should correspond with the thickest fill on the lot.
9. Hydrostatic pressure relief valves should be incorporated into the pool and spa
designs. A pool/spa under-drain system is also recommended, with an appropriate
outlet for discharge.
10. All fittings and pipe joints, particularly fittings in the side of the pool or spa, should
be properly sealed to prevent water from leaking into the adjacent soils materials,
and be fitted with slip or expandible joints between connections transecting varying
soil conditions.
11. An elastic expansion joint (flexible waterproof sealant) should be installed to prevent
water from seeping into the soil at all deck joints.
12. A reinforced grade beam should be placed around skimmer inlets to provide
support and mitigate cracking around the skimmer face.
13. In order to reduce unsightly cracking, deck slabs should minimally be 4 inches
thick, and reinforced with No. 3 reinforcing bars at 18 inches on-center. All slab
reinforcement should be supported to ensure proper mid-slab positioning during
the placement of concrete. Wire mesh reinforcing is specifically not recommended.
Deck slabs should not be tied to the pool/spa structure. Pre-moistening and/or
pre-soaking of the slab subgrade is recommended, to a depth of 12 inches
(optimum moisture content), or 18 inches (120 percent of the soil’s optimum
moisture content, or 3 percent over optimum moisture content, whichever is
greater), for very low to low, and medium expansive soils, respectively. This
moisture content should be maintained in the subgrade soils during concrete
placement to promote uniform curing of the concrete and minimize the
development of unsightly shrinkage cracks. Slab underlayment should consist of
a 1- to 2-inch leveling course of sand (S.E.>30) and a minimum of 4 to 6 inches of
Class 2 base compacted to 90 percent. Deck slabs within the H/3 zone, where H
is the height of the slope (in feet), will have an increased potential for distress
relative to other areas outside of the H/3 zone. If distress is undesirable,
improvements, deck slabs or flatwork should not be constructed closer than H/3 or
7 feet (whichever is greater) from the slope face, in order to reduce, but not
eliminate, this potential.
14. Pool/spa bottom or deck slabs should be founded entirely on competent bedrock,
or properly compacted fill. Fill should be compacted to achieve a minimum
90 percent relative compaction, as discussed above. Prior to pouring concrete,
subgrade soils below the pool/spa decking should be throughly watered to achieve
a moisture content that is at least 2 percent above optimum moisture content, to a
depth of at least 18 inches below the bottom of slabs. This moisture content should
be maintained in the subgrade soils during concrete placement to promote uniform
curing of the concrete and minimize the development of unsightly shrinkage cracks.
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15. In order to reduce unsightly cracking, the outer edges of pool/spa decking to be
bordered by landscaping, and the edges immediately adjacent to the pool/spa,
should be underlain by an 8-inch wide concrete cutoff shoulder (thickened edge)
extending to a depth of at least 12 inches below the bottoms of the slabs to mitigate
excessive infiltration of water under the pool/spa deck. These thickened edges
should be reinforced with two No. 4 bars, one at the top and one at the bottom.
Deck slabs may be minimally reinforced with No. 3 reinforcing bars placed at
18 inches on-center, in both directions. All slab reinforcement should be supported
on chairs to ensure proper mid-slab positioning during the placement of concrete.
16. Surface and shrinkage cracking of the finish slab may be reduced if a low slump
and water-cement ratio are maintained during concrete placement. Concrete
utilized should have a minimum compressive strength of 4,000 psi. Excessive water
added to concrete prior to placement is likely to cause shrinkage cracking, and
should be avoided. Some concrete shrinkage cracking, however, is unavoidable.
17. Joint and sawcut locations for the pool/spa deck should be determined by the
design engineer and/or contractor. However, spacings should not exceed 6 feet on
center.
18. Considering the nature of the onsite earth materials, it should be anticipated that
caving or sloughing could be a factor in subsurface excavations and trenching.
Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25
to 45 degrees), should be anticipated. All excavations should be observed by a
representative of the geotechnical consultant, including the project geologist and/or
geotechnical engineer, prior to workers entering the excavation or trench, and
minimally conform to Cal/OSHA (“Type C” soils may be assumed), state, and local
safety codes. Should adverse conditions exist, appropriate recommendations
should be offered at that time by the geotechnical consultant. GSI does not consult
in the area of safety engineering and the safety of the construction crew is the
responsibility of the pool/spa builder.
19. It is imperative that adequate provisions for surface drainage are incorporated by
the homeowners into their overall improvement scheme. Ponding water, ground
saturation and flow over slope faces, are all situations which must be avoided to
enhance long term performance of the pool/spa and associated improvements, and
reduce the likelihood of distress.
20. Regardless of the methods employed, once the pool/spa is filled with water, should
it be emptied, there exists some potential that if emptied, significant distress may
occur. Accordingly, once filled, the pool/spa should not be emptied unless
evaluated by the geotechnical consultant and the pool/spa builder.
21. For pools/spas built within (all or part) of the Code setback and/or geotechnical
setback, as indicated in the site geotechnical documents, special foundations are
recommended to mitigate the affects of creep, lateral fill extension, expansive soils
and settlement on the proposed pool/spa. Most municipalities or County reviewers
Ms. Patiane Freitas Appendix D
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do not consider these effects in pool/spa plan approvals. As such, where
pools/spas are proposed on 20 feet or more of fill, medium or highly expansive
soils, or rock fill with limited “cap soils” and built within Code setbacks, or within the
influence of the creep zone, or lateral fill extension, the following should be
considered during design and construction:
OPTION A: Shallow foundations with or without overexcavation of the
pool/spa “shell,” such that the pool/spa is surrounded by 5 feet of very low
to low expansive soils (without irreducible particles greater that 6 inches),
and the pool/spa walls closer to the slope(s) are designed to be free
standing. GSI recommends a pool/spa under-drain or blanket system (see
attached Typical Pool/Spa Detail). The pool/spa builders and owner in this
optional construction technique should be generally satisfied with pool/spa
performance under this scenario; however, some settlement, tilting, cracking,
and leakage of the pool/spa is likely over the life of the project.
OPTION B: Pier supported pool/spa foundations with or without
overexcavation of the pool/spa shell such that the pool/spa is surrounded by
5 feet of very low to low expansive soils (without irreducible particles greater
than 6 inches), and the pool/spa walls closer to the slope(s) are designed to
be free standing. The need for a pool/spa under-drain system may be
installed for leak detection purposes. Piers that support the pool/spa should
be a minimum of 12 inches in diameter and at a spacing to provide vertical
and lateral support of the pool/spa, in accordance with the pool/spa
designers recommendations current applicable Codes. The pool/spa builder
and owner in this second scenario construction technique should be more
satisfied with pool/spa performance. This construction will reduce settlement
and creep effects on the pool/spa; however, it will not eliminate these
potentials, nor make the pool/spa “leak-free.”
22. The temperature of the water lines for spas and pools may affect the corrosion
properties of site soils, thus, a corrosion specialist should be retained to review all
spa and pool plans, and provide mitigative recommendations, as warranted.
Concrete mix design should be reviewed by a qualified corrosion consultant and
materials engineer.
23. All pool/spa utility trenches should be compacted to 90 percent of the laboratory
standard, under the full-time observation and testing of a qualified geotechnical
consultant. Utility trench bottoms should be sloped away from the primary structure
on the property (typically the residence).
24. Pool and spa utility lines should not cross the primary structure’s utility lines (i.e.,
not stacked, or sharing of trenches, etc.).
25. The pool/spa or associated utilities should not intercept, interrupt, or otherwise
adversely impact any area drain, roof drain, or other drainage conveyances. If it is
necessary to modify, move, or disrupt existing area drains, subdrains, or tightlines,
Ms. Patiane Freitas Appendix D
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GeoSoils, Inc.
then the design civil engineer should be consulted, and mitigative measures
provided. Such measures should be further reviewed and approved by the
geotechnical consultant, prior to proceeding with any further construction.
26. The geotechnical consultant should review and approve all aspects of pool/spa and
flatwork design prior to construction. A design civil engineer should review all
aspects of such design, including drainage and setback conditions. Prior to
acceptance of the pool/spa construction, the project builder, geotechnical
consultant and civil designer should evaluate the performance of the area drains
and other site drainage pipes, following pool/spa construction.
27. All aspects of construction should be reviewed and approved by the geotechnical
consultant, including during excavation, prior to the placement of any additional fill,
prior to the placement of any reinforcement or pouring of any concrete.
28. Any changes in design or location of the pool/spa should be reviewed and
approved by the geotechnical and design civil engineer prior to construction. Field
adjustments should not be allowed until written approval of the proposed field
changes are obtained from the geotechnical and design civil engineer.
29. Disclosure should be made to homeowners and builders, contractors, and any
interested/affected parties, that pools/spas built within about 15 feet of the top of a
slope, and/or H/3, where H is the height of the slope (in feet), will experience some
movement or tilting. While the pool/spa shell or coping may not necessarily crack,
the levelness of the pool/spa will likely tilt toward the slope, and may not be
esthetically pleasing. The same is true with decking, flatwork and other
improvements in this zone.
30. Failure to adhere to the above recommendations will significantly increase the
potential for distress to the pool/spa, flatwork, etc.
31. Local seismicity and/or the design earthquake will cause some distress to the
pool/spa and decking or flatwork, possibly including total functional and economic
loss.
32. The information and recommendations discussed above should be provided to any
contractors and/or subcontractors, or homeowners, interested/affected parties, etc.,
that may perform or may be affected by such work.
JOB SAFETY
General
At GSI, getting the job done safely is of primary concern. The following is the company's
safety considerations for use by all employees on multi-employer construction sites.
On-ground personnel are at highest risk of injury, and possible fatality, on grading and
Ms. Patiane Freitas Appendix D
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GeoSoils, Inc.
construction projects. GSI recognizes that construction activities will vary on each site, and
that site safety is the prime responsibility of the contractor; however, everyone must be
safety conscious and responsible at all times. To achieve our goal of avoiding accidents,
cooperation between the client, the contractor, and GSI personnel must be maintained.
In an effort to minimize risks associated with geotechnical testing and observation, the
following precautions are to be implemented for the safety of field personnel on grading
and construction projects:
Safety Meetings: GSI field personnel are directed to attend contractor’s regularly
scheduled and documented safety meetings.
Safety Vests: Safety vests are provided for, and are to be worn by GSI personnel,
at all times, when they are working in the field.
Safety Flags:Two safety flags are provided to GSI field technicians; one is to be
affixed to the vehicle when on site, the other is to be placed atop the
spoil pile on all test pits.
Flashing Lights:All vehicles stationary in the grading area shall use rotating or flashing
amber beacons, or strobe lights, on the vehicle during all field testing.
While operating a vehicle in the grading area, the emergency flasher
on the vehicle shall be activated.
In the event that the contractor's representative observes any of our personnel not
following the above, we request that it be brought to the attention of our office.
Test Pits Location, Orientation, and Clearance
The technician is responsible for selecting test pit locations. A primary concern should be
the technician’s safety. Efforts will be made to coordinate locations with the grading
contractor’s authorized representative, and to select locations following or behind the
established traffic pattern, preferably outside of current traffic. The contractor’s authorized
representative (supervisor, grade checker, dump man, operator, etc.) should direct
excavation of the pit and safety during the test period. Of paramount concern should be
the soil technician’s safety, and obtaining enough tests to represent the fill.
Test pits should be excavated so that the spoil pile is placed away from oncoming traffic,
whenever possible. The technician's vehicle is to be placed next to the test pit, opposite
the spoil pile. This necessitates the fill be maintained in a driveable condition.
Alternatively, the contractor may wish to park a piece of equipment in front of the test
holes, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits. No grading equipment
should enter this zone during the testing procedure. The zone should extend
approximately 50 feet outward from the center of the test pit. This zone is established for
safety and to avoid excessive ground vibration, which typically decreases test results.
Ms. Patiane Freitas Appendix D
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GeoSoils, Inc.
When taking slope tests, the technician should park the vehicle directly above or below the
test location. If this is not possible, a prominent flag should be placed at the top of the
slope. The contractor's representative should effectively keep all equipment at a safe
operational distance (e.g., 50 feet) away from the slope during this testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible
following testing. The technician's vehicle should be parked at the perimeter of the fill in
a highly visible location, well away from the equipment traffic pattern. The contractor
should inform our personnel of all changes to haul roads, cut and fill areas or other factors
that may affect site access and site safety.
In the event that the technician’s safety is jeopardized or compromised as a result of the
contractor’s failure to comply with any of the above, the technician is required, by company
policy, to immediately withdraw and notify his/her supervisor. The grading contractor’s
representative will be contacted in an effort to affect a solution. However, in the interim,
no further testing will be performed until the situation is rectified. Any fill placed can be
considered unacceptable and subject to reprocessing, recompaction, or removal.
In the event that the soil technician does not comply with the above or other established
safety guidelines, we request that the contractor bring this to the technician’s attention and
notify this office. Effective communication and coordination between the contractor’s
representative and the soil technician is strongly encouraged in order to implement the
above safety plan.
Trench and Vertical Excavation
It is the contractor's responsibility to provide safe access into trenches where compaction
testing is needed. Our personnel are directed not to enter any excavation or vertical cut
which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of
instability, has any loose rock or other debris which could fall into the trench; or 3) displays
any other evidence of any unsafe conditions regardless of depth.
All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters,
should be shored or laid back. Trench access should be provided in accordance with
Cal/OSHA and/or state and local standards. Our personnel are directed not to enter any
trench by being lowered or “riding down” on the equipment.
If the contractor fails to provide safe access to trenches for compaction testing, our
company policy requires that the soil technician withdraw and notify his/her supervisor.
The contractor’s representative will be contacted in an effort to affect a solution. All backfill
not tested due to safety concerns or other reasons could be subject to reprocessing and/or
removal.
If GSI personnel become aware of anyone working beneath an unsafe trench wall or
vertical excavation, we have a legal obligation to put the contractor and owner/developer
on notice to immediately correct the situation. If corrective steps are not taken, GSI then
has an obligation to notify Cal/OSHA and/or the proper controlling authorities.
Ms. Patiane Freitas Appendix D
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MAP VIEW
NOTTO SCALE Concrete cut-off wall
SEE NOTE_l _s __________ J
B I Top of elope ~
2-inch-thick
sand layer
Gravity-flow,
nonperforated subdrain I=== pipe (tra.,...,,-eel
Toe of slope 4
I
1--Sleet
Pool
4-inch perforated
subdrain pipe
(longitudinal)
Coping A'
4-inch perforated
subdrain pipe
(transverse)
Pool
Direction
of drainage
B'
CROSS SECTION VIEW
Coping
NOTTO SCALE
SEE NOTES
Pool encapsulated in 5-foot
thickness of sand --~
6-inch-thick gravel layer
B
NOTES:
r
H
Gravity-flow nonperforated
subdrain pipe
4-inch perforated subdrain pipe
I I 1 1--steet
Coping B'
Vapor retarder
Perforated subdrain pipe
1. 6-inch-thick, clean gravel(¾ to 1½ inch) sub-base encapsulated in Mirafi 140N or equivalent, underlain by
a 15-mil vapor retarder, with 4-inch-diameter perforated pipe longitudinal connected to 4-inch-diameter
perforated pipe transverse. Connect transverse pipe to 4-inch-diameter nonperforated pipe at low point
and outlet or to sump pump area.
2. Pools on fills thicker than 20 feet should be constructed on deep foundations; otherwise, distress (titting,
cracking, etc.) should be expected.
3. Design does not apply to infinity-edge pools/ spas.
c. TYPICAL POOL/SPA DETAIL Plate 0-17
•
Geotechnical • Geologic • Coastal • Environmental
5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com
DATE:
TO:
FROM:
SUBJECT:
PROJECT:
REFERENCES:
MEMORANDUM
February 23, 2023
Ms. Patiane Freitas
Stephen J. Coover, G.E.
Site Visit of February 23, 2023
W.O. 8286-A1
(Jf
Proposed Single Family Residence, 4339 Park Drive, Carlsbad, CA
1. "Limited Geotechnical Evaluation For A Planned Single Family Residence,
Including Retaining Walls, 4339 Park Drive, Carlsbad, California," W.O. 8286-A-SC
dated March 8, 2022 Revised October 10, 2022 by GeoSoils, Inc.
2. "Addendum and Response to City of Carlsbad Comments, Proposed Single
Family Residence, 4339 Park Drive, Carlsbad, California, W.O. 8286-A!-SC, dated
February 1, 2023 by GeoSoils, Inc.
This memorandum summarizes GSl's (GeoSoils, lnc.'s) field visit of today. The purpose of our visit was to
probe the proposed building pad areas and evaluate whether additional subsurface investigation is
warranted.
I probed the building pads, both the upper and lower one, using a 1 /2-inch diameter pointed steel probe.
Both pads probed very dense (no more than 1 inch penetration) in all areas except the location of the
abandoned septic tank on the north side of the upper pad. The probe penetrated to its full length at that
location. Our addendum and response to comments report (Reference 2) provided recommendations for
remediating the septic tank location so it will support the new construction.
Based on our probing and our knowledge of the subject site, in our opinion no remedial grading is warranted
(except for the septic tank location) other than preparation and excavation of the building pads so that a
uniform layer of fill underlies the proposed foundations and floor slabs, as recommended in the referenced
reports.
Geotechnical C Geologic C Coastal C Environmental
5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com
April 11, 2023
W.O. 8286-A1-SC
Ms. Patiane Freitas
4339 Park Drive
Carlsbad, California 92008
Subject:Remedial Grading Limits, Proposed Single-Family Residence,
4339 Park Drive, Carlsbad, San Diego County, California 92008
Reference:“Limited Geotechnical Evaluation for a Planned Single-Family Residence,
Including Retaining Walls, 4339 Park Drive, Carlsbad, California 92028,
APN 206-192-01-00,” W.O. 8286-A-SC, dated March 8, 2022, Revised
October 10, 2022, by GeoSoils, Inc.
Dear Ms. Freitas:
As requested, this letter affirms the remedial grading limits for the proposed development.
The lateral extent of remedial grading recommended in the referenced report, five (5) feet
laterally outside of the building limits, does not include excavating laterally into the slope
between the upper and lower building pads. The slope comprises formational material;
excavating into the slope would reduce lateral support (comparing fill density to
formational material density) along the lower building pad where it abuts the slope, and
would be detrimental. Lateral extent of removals should be confined to the other three
sides of the lower building pad.
Unless specifically superceded herein, the conclusions and recommendations contained
in the referenced report by GSI remain pertinent and applicable, and should be
appropriately implemented during planning, design, and construction.
GeoSoils, Inc.
The opportunity to be of service is sincerely appreciated. If you should have any
questions, please do not hesitate to contact our office.
Respectfully submitted,
GeoSoils, Inc.
John P. Franklin Stephen J. Coover
Engineering Geologist, CEG 1340 Geotechnical Engineer, GE 2057
SJC/JPF/sh
Distribution:(1) Addressee (PDF via email)
Ms. Patiane Freitas W.O. 8286-A1-SC
4339 Park Drive, Carlsbad April 11, 2023
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