HomeMy WebLinkAboutCT 2018-0003; MAGNOLIA BRADY; FINAL SOILS REPORT; 2019-10-07FINAL REPORT OF TESTING
AND OBSERVATION SERVICES
PERFORMED DURING SITE GRADING
MAGNOLIA-BRADY
NORTHEAST CORNER
OF MAGNOLIA AVENUE
AND BRADY CIRCLE
CARLSBAD, CALIFORNIA
PREPARED FOR
ASHTON 3, LLC
RANCHO MISSION VIEJO, CALIFORNIA
OCTOBER 7, 2019
PROJECT NO. G2192-52-01
Project No. G2192-52-01
October 7, 2019
Ashton 3, LLC
5 Hoya Street
Rancho Mission Viejo, California 92694
Attention: Mr. Taylor Ashton
Subject: FINAL REPORT OF TESTING AND OBSERVATION SERVICES
PERFORMED DURING SITE GRADING
MAGNOLIA-BRADY
NORTHEAST CORNER OF MAGNOLIA AVENUE AND BRADY CIRCLE
CARLSBAD, CALIFORNIA
Dear Mr. Ashton:
In accordance with the request of Mr. David Lother with Milestone Development Advisors and our
Change-Order No. 3 dated May 1, 2019, we provided testing and observation services during the
grading operations for the subject development. We performed our services from September 10, 2019
through September 20, 2019. The scope of our services summarized in this report includes:
Observing grading operations including the removal and recompaction of existing fill soil.
Performing in-place dry density and moisture content tests on fill placed and compacted
during the grading operations.
Performing laboratory tests on samples of soil at finish grade to evaluate expansion
characteristics and water-soluble sulfate.
Preparing a Final As-Graded Geologic Map.
Preparing this final report of grading.
GENERAL
The Magnolia-Brady site is located at the northeast corner of Magnolia Avenue and Brady Circle in
the City of Carlsbad, California (see Vicinity Map, Figure 1). Access to the site during grading was
provided by an entrance from Magnolia Avenue. TNT Blanchard General Engineering, Inc. performed
the grading for the subject development.
GEOCON
INCORPORATED
GEOTECHNICAL ■ ENVIRONMENTAL ■
6960 Flanders Drive ■ San Diego, California 92121-2974 ■ Telephone 858.558.6900 ■ Fax 858.558.6159
Geocon Project No. G2192-52-01 - 2 - October 7, 2019
To aid in preparing this report, we reviewed the following reports and plans associated with the
project:
1. Geotechnical Investigation, 1534 Magnolia Avenue, Carlsbad, California, prepared by Geocon
Incorporated, dated January 17, 2018 (Project No. G2192-52-01).
2. Rough Grading Plans for: Magnolia-Brady, Carlsbad, California, prepared by Civil
Landworks, dated June 27, 2019 (Grading Plan No. GR2018-0047; Project No. CT2018-
0003).
References to elevations and locations presented herein were based on the surveyor’s or grade
checker’s stakes in the field, surveyed bottom elevations, and/or interpolation from the referenced
grading plan. Geocon Incorporated does not provide surveying services and, therefore, has no opinion
regarding the accuracy of the as-graded elevations or surface geometry with respect to the approved
plans or proper surface drainage.
GRADING
This report pertains to the rough grading operations for the 7 residential building pads for the
Magnolia-Brady development. Grading for the building pads included removal of approximately 3 to 6
feet of existing fill across the site to expose the Old Paralic Deposits. Following removal of existing
fill, the pads were either scarified and recompacted to a depth of 12-inches or undercut 3 feet prior to
placement of compacted fill to achieve building pad elevations.
During the grading operations, we observed compaction procedures and performed in-place density
tests to evaluate the dry density and moisture content of the fill materials. We performed in-place
density tests in general conformance with ASTM Test Method D 6938 (nuclear). Table I presents the
results of the in-place dry density and moisture content tests. In general, the in-place density test
results indicate the compacted fill possesses a dry density of at least 90 percent of the laboratory
maximum dry density near to slightly above optimum moisture content at the locations tested. The
Final As-Graded Geologic Map, Figure 2, presents the approximate locations of the in-place density
tests for the subject lots.
We tested laboratory samples of material used for fill to evaluate moisture-density relationships,
optimum moisture content and maximum dry density (ASTM D 1557). We tested samples material
within the upper approximately 3 feet of finish grade to evaluate the expansion index (ASTM D 4829)
and water-soluble sulfate content (California Test No. 417) characteristics.
Geocon Project No. G2192-52-01 - 3 - October 7, 2019
SOIL AND GEOLOGIC CONDITIONS
The soil and geologic conditions encountered during grading are similar to those described in the
project geotechnical report dated January 17, 2018. The placement of compacted fill was performed in
accordance with recommendations provided in the project geotechnical report. The Final As-Graded
Geologic Map, Figure 2, depicts the general geologic conditions observed during grading. The site is
underlain by recently compacted fill ranging in thickness between approximately 3 to 5 feet overlying
Old Paralic Deposits. In general, the compacted fill consists of silty and clayey sand.
CONCLUSIONS AND RECOMMENDATIONS
1.0 General
1.1 Based on our observations and test results, we opine that the grading to which this report
pertains has been performed in conformance with the recommendations of the previously
referenced project geotechnical report prepared by Geocon Incorporated, dated January 17,
2018, and the geotechnical requirements of the referenced grading plans.
1.2 We did not observe soil or geologic conditions during grading that would preclude the
continued development of the property as planned. Based on laboratory test results and field
observations, it is the opinion of Geocon Incorporated the fill observed and tested as part of
the grading for this project was generally compacted to a dry density of at least 90 percent
of the laboratory maximum dry density near to slightly above optimum moisture content.
1.3 The site is underlain by compacted fill and Old Paralic Deposits. We observed the
placement of compacted fill during the grading operations and performed in-place density
tests to evaluate the dry density and moisture content of the fill material.
1.4 Laboratory testing of near-grade soil conditions indicates the upper approximately 3 feet of
soil underlying the pads possess a “very low” expansion potential (expansion index of 20 or
less). In addition, the samples indicate the soil possesses “S0” water-soluble sulfate
exposure class. The results of the laboratory expansion index and water-soluble sulfate tests
are presented herein.
1.5 We understand the proposed buildings will be supported on post-tensioned foundation
systems as recommended in the project geotechnical report.
1.6 Excavations within the fill should generally be possible with moderate to heavy effort using
conventional heavy-duty equipment. In excavations for utility trenches within formational
Geocon Project No. G2192-52-01 - 4 - October 7, 2019
materials, if encountered, localized cemented zones may be encountered that will require
very heavy effort to excavate, and oversize blocks may be generated.
2.0 Finish Grade Soil Conditions
2.1 The soil encountered during grading operations is considered to be “non-expansive”
(expansion index [EI] of 20 or less) as defined by the 2016 California Building Code (CBC)
Section 1803.5.3. Table 2 presents soil classifications based on the expansion index. We
expect the existing soil possesses a “very low” to “low” expansion potential (EI of 50 or
less) in accordance with ASTM D 4829. Table III presents the results of the laboratory
expansion index tests.
TABLE 2
EXPANSIVE SOIL CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) ASTM D 4829
Expansive Soil Classification
2016 CBC
Expansion Classification
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive 51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
2.2 We performed laboratory tests on samples of the finish-grade materials to evaluate the
percentage of water-soluble sulfate content. Table IV presents results of the laboratory
water-soluble sulfate content tests. The test results indicate the on-site materials at the
locations tested possess “S0” sulfate exposure to concrete structures as defined by 2016
CBC Section 1904 and ACI 318-14 Chapter 19. The presence of water-soluble sulfates is
not a visually discernible characteristic; therefore, other soil samples from the site could
yield different concentrations. Additionally, over time landscaping activities (i.e., addition
of fertilizers and other soil nutrients) may affect the concentration.
2.3 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore,
further evaluation by a corrosion engineer may be performed if improvements susceptible to
corrosion are planned.
3.0 Seismic Design Criteria
3.1 We used the computer program U.S. Seismic Design Maps, provided by the USGS to
evaluate the seismic design criteria. Table 3.1 summarizes the seismic design criteria
Geocon Project No. G2192-52-01 - 5 - October 7, 2019
obtained from the 2016 California Building Code (CBC; Based on the 2015 International
Building Code [IBC] and ASCE 7-10), Chapter 16 Structural Design, Section 1613
Earthquake Loads. The short spectral response uses a period of 0.2 second. The building
should be designed using a Site Class C. We evaluated the Site Class based on the
discussion in Section 1613.3.2 of the 2016 CBC and Table 20.3-1 of ASCE 7-10. The
values presented in Table 3.1 are for the risk-targeted maximum considered earthquake
(MCER).
TABLE 3.1
2016 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2016 CBC Reference
Site Class C Section 1613.3.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS 1.127g Figure 1613.3.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1 0.433g Figure 1613.3.1(2)
Site Coefficient, FA 1.000 Table 1613.3.3(1)
Site Coefficient, FV 1.367 Table 1613.3.3(2)
Site Class Modified MCER
Spectral Response Acceleration (short), SMS 1.127g Section 1613.3.3 (Eqn 16-37)
Site Class Modified MCER
Spectral Response Acceleration (1 sec), SM1 0.592g Section 1613.3.3 (Eqn 16-38)
5% Damped Design
Spectral Response Acceleration (short), SDS 0.751g Section 1613.3.4 (Eqn 16-39)
5% Damped Design
Spectral Response Acceleration (1 sec), SD1 0.395g Section 1613.3.4 (Eqn 16-40)
3.2 Table 3.2 presents additional seismic design parameters for projects located in Seismic
Design Categories of D through F in accordance with ASCE 7-10 for the mapped maximum
considered geometric mean (MCEG).
TABLE 3.2
2016 CBC SITE ACCELERATION DESIGN PARAMETERS
Parameter Value ASCE 7-10 Reference
Mapped MCEG Peak Ground Acceleration, PGA 0.443g Figure 22-7
Site Coefficient, FPGA 1.000 Table 11.8-1
Site Class Modified MCEGPeak Ground Acceleration, PGAM 0.443g Section 11.8.3 (Eqn 11.8-1)
Geocon Project No. G2192-52-01 - 6 - October 7, 2019
3.3 Conformance to the criteria in Tables 3.1 and 3.2 for seismic design does not constitute any
kind of guarantee or assurance that significant structural damage or ground failure will not
occur if a large earthquake occurs. The primary goal of seismic design is to protect life, not
to avoid all damage, since such design may be economically prohibitive.
3.4 The project structural engineer and architect should evaluate the appropriate Risk Category
and Seismic Design Category for the planned structures. The values presented herein
assume a Rick Category of I, II or III and resulting in a Seismic Design Category D.
4.0 Shallow Foundations
4.1 The foundation recommendations herein are for the proposed residential structures founded
in compacted fill. Foundations for the structure should consist of continuous strip footings
and/or isolated spread footings. Continuous footings should be at least 18 inches wide and
extend at least 18 inches below lowest adjacent pad grade. Isolated spread footings should
have a minimum width of 24 inches and should extend at least 18 inches below lowest
adjacent pad grade. Figure 3 presents a footing dimension detail depicting the depth to
lowest adjacent grade.
4.2 Steel reinforcement for continuous footings should consist of at least four No. 4 steel
reinforcing bars placed horizontally in the footings, two near the top and two near the
bottom. Steel reinforcement for the spread footings should be designed by the project
structural engineer. The minimum reinforcement recommended herein is based on soil
characteristics only (expansion index of 50 or less) and is not intended to replace
reinforcement required for structural considerations.
4.3 The recommended allowable bearing capacity for foundations with minimum dimensions
described herein and bearing in properly compacted fill is 2,000 pounds per square foot
(psf). The values presented herein are for dead plus live loads and may be increased by one-
third when considering transient loads due to wind or seismic forces.
4.4 Total and differential settlement of the building founded on compacted fill materials is
expected to be less than ½-inch for 6-foot footings.
4.5 Where buildings or other improvements are planned near the top of a slope 3:1 (horizontal
to vertical) or steeper, special foundation and/or design considerations are recommended
due to the tendency for lateral soil movement to occur.
Footings should be deepened such that the bottom outside edge of the footing is at
least 7 feet horizontally from the face of the slope.
Geocon Project No. G2192-52-01 - 7 - October 7, 2019
Although other improvements, which are relatively rigid or brittle, such as concrete
flatwork or masonry walls, may experience some distress if located near the top of a
slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures which would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
4.6 We should observe the foundation excavations prior to the placement of reinforcing steel
and concrete to check that the exposed soil conditions are similar to those expected and that
they have been extended to the appropriate bearing strata. Foundation modifications may be
required if unexpected soil conditions are encountered.
4.7 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
5.0 Concrete Slabs-on-Grade
5.1 Concrete slabs-on-grade for the structures should be at least 4 inches thick and reinforced
with No. 3 steel reinforcing bars at 24 inches on center in both horizontal directions.
5.2 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder. The vapor retarder design should
be consistent with the guidelines presented in the American Concrete Institute’s (ACI)
Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-
06). In addition, the membrane should be installed in accordance with manufacturer’s
recommendations and ASTM requirements and installed in a manner that prevents puncture.
The vapor retarder used should be specified by the project architect or developer based on
the type of floor covering that will be installed and if the structure will possess a humidity
controlled environment.
5.3 The bedding sand thickness should be determined by the project foundation engineer,
architect, and/or developer. However, we should be contacted to provide recommendations
if the bedding sand is thicker than 6 inches. It is common to see 3 to 4 inches of sand below
the concrete slab-on-grade for 5-inch thick slabs in the southern California area. The
foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
recommendations presented on the foundation plans.
Geocon Project No. G2192-52-01 - 8 - October 7, 2019
5.4 Concrete slabs should be provided with adequate crack-control joints, construction joints
and/or expansion joints to reduce unsightly shrinkage cracking. The design of joints should
consider criteria of the American Concrete Institute (ACI) when establishing crack-control
spacing. Crack-control joints should be spaced at intervals no greater than 12 feet.
Additional steel reinforcing, concrete admixtures and/or closer crack control joint spacing
should be considered where concrete-exposed finished floors are planned.
5.5 The concrete slab-on-grade recommendations are based on soil support characteristics only.
The project structural engineer should evaluate the structural requirements of the concrete
slabs for supporting vehicle, equipment and storage loads.
5.6 The recommendations presented herein are intended to reduce the potential for cracking of
slabs and foundations as a result of differential movement. However, even with the
incorporation of the recommendations presented herein, foundations and slabs-on-grade will
still exhibit some cracking. The occurrence of concrete shrinkage cracks is independent of
the soil supporting characteristics. Their occurrence may be reduced and/or controlled by
limiting the slump of the concrete, the use of crack-control joints and proper concrete
placement and curing. Literature provided by the Portland Cement Association (PCA) and
American Concrete Institute (ACI) present recommendations for proper concrete mix,
construction, and curing practices, and should be incorporated into project construction.
6.0 Post-Tensioned Foundation System Recommendations
6.1 As an alternative to the conventional foundation recommendations, consideration should be
given to the use of post-tensioned concrete slab and foundation systems for the support of
the proposed structures. The post-tensioned systems should be designed by a structural
engineer experienced in post-tensioned slab design and design criteria of the Post-
Tensioning Institute (PTI) DC 10.5-12 Standard Requirements for Design and Analysis of
Shallow Post-Tensioned Concrete Foundations on Expansive Soils or WRI/CRSI Design of
Slab-on-Ground Foundations, as required by the 2016 California Building Code (CBC
Section 1808.6.2). Although this procedure was developed for expansive soil conditions, it
can also be used to reduce the potential for foundation distress due to differential fill
settlement. The post-tensioned design should incorporate the geotechnical parameters
presented in Table 6. The parameters presented in Table 6 are based on the guidelines
presented in the PTI DC 10.5 design manual.
Geocon Project No. G2192-52-01 - 9 - October 7, 2019
TABLE 6
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)
DC10.5 Design Parameters Value
Thornthwaite Index -20
Equilibrium Suction 3.9
Edge Lift Moisture Variation Distance, eM (feet) 5.3
Edge Lift, yM (inches) 0.61
Center Lift Moisture Variation Distance, eM (feet) 9.0
Center Lift, yM (inches) 0.30
6.2 Post-tensioned foundations may be designed for an allowable soil bearing pressure of 2,000
pounds per square foot (psf) (dead plus live load). This bearing pressure may be increased
by one-third for transient loads due to wind or seismic forces. The estimated maximum total
and differential settlement for the planned structures due to foundation loads is ½ inch.
6.3 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
6.4 Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations. The use of isolated footings, which are located
beyond the perimeter of the building and support structural elements connected to the
building, are not recommended. Where this condition cannot be avoided, the isolated
footings should be connected to the building foundation system with grade beams.
6.5 Consideration should be given to using interior stiffening beams and connecting isolated
footings and/or increasing the slab thickness. In addition, consideration should be given to
connecting patio slabs, which exceed 5 feet in width, to the building foundation to reduce
the potential for future separation to occur.
6.6 If the structural engineer proposes a post-tensioned foundation design method other than
PTI, DC 10.5:
The deflection criteria presented in Table 6.1 are still applicable.
The width of the perimeter foundations should be at least 12 inches.
The perimeter footing embedment depths should be at least 18 inches. The
embedment depths should be measured from the lowest adjacent pad grade.
Geocon Project No. G2192-52-01 - 10 - October 7, 2019
6.7 Our experience indicates post-tensioned slabs may be susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. The
structural engineer should design the foundation system to reduce the potential of edge lift
occurring for the proposed structures.
6.8 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system unless designed by the structural engineer.
6.9 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisturized to maintain a moist
condition as would be expected in any such concrete placement. The slab underlayment
should be the same as previously discussed.
7.0 Concrete Flatwork
7.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations herein. Slab panels should be a minimum of 4 inches
thick and, when in excess of 8 feet square, should be reinforced with 6 x 6 - W2.9/W2.9
(6 x 6 - 6/6) welded wire mesh or No. 3 reinforcing bars spaced at least 18 inches center-to-
center in both directions to reduce the potential for cracking. In addition, concrete flatwork
should be provided with crack control joints to reduce and/or control shrinkage cracking.
Crack control spacing should be determined by the project structural engineer based upon
the slab thickness and intended usage. Criteria of the American Concrete Institute (ACI)
should be taken into consideration when establishing crack control spacing. Subgrade soil
for exterior slabs not subjected to vehicle loads should be compacted in accordance with
criteria presented in the grading section prior to concrete placement. Subgrade soil should be
properly compacted and the moisture content of subgrade soil should be checked prior to
placing concrete.
7.2 Even with the incorporation of the recommendations within this report, the exterior concrete
flatwork has a likelihood of experiencing some uplift due to expansive soil beneath grade;
therefore, the steel reinforcement should overlap continuously in flatwork to reduce the
potential for vertical offsets within flatwork. Additionally, flatwork should be structurally
connected to the curbs, where possible, to reduce the potential for offsets between the curbs
and the flatwork.
Geocon Project No. G2192-52-01 - 11 - October 7, 2019
7.3 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should
be dowelled into the structure’s foundation stemwall. This recommendation is intended to
reduce the potential for differential elevations that could result from differential settlement
or minor heave of the flatwork. Dowelling details should be designed by the project
structural engineer.
8.0 Retaining Walls
8.1 Retaining walls not restrained at the top and having a level backfill surface should be
designed for an active soil pressure equivalent to the pressure exerted by a fluid with a
density of 35 pounds per cubic foot (pcf). Where the backfill will be inclined at no steeper
than 2H:1V, an active soil pressure of 50 pcf is recommended. These soil pressures assume
that the backfill materials within an area bounded by the wall and a 1:1 plane extending
upward from the base of the wall possess an expansion index of 50 or less.
8.2 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top (at-rest condition), an additional uniform pressure of
7H psf should be added to the active soil pressure for walls 8 feet or less. For retaining walls
subject to vehicular loads within a horizontal distance equal to two-thirds the wall height, a
surcharge equivalent to 2 feet of fill soil should be added.
8.3 The structural engineer should determine the seismic design category for the project. If the
project possesses a seismic design category of D, E, or F, the proposed retaining walls
should be designed with seismic lateral pressure. A seismic load of 16H psf should be used
for design of walls that support more than 6 feet of backfill in accordance with
Section 1803.5.12 of the 2016 CBC. The seismic load is dependent on the retained height
where H is the height of the wall, in feet, and the calculated loads result in pounds per
square foot (psf) exerted at the base of the wall and zero at the top of the wall. We used the
peak site acceleration, PGAM, of 0.443g calculated from ASCE 7-10 Section 11.8.3.
8.4 The retaining walls may be designed using either the active and restrained (at-rest) loading
condition or the active and seismic loading condition as suggested by the structural
engineer. Typically, it appears the design of the restrained condition for retaining wall
loading may be adequate for the seismic design of the retaining walls. However, the active
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
8.5 Retaining walls should be provided with a drainage system adequate to prevent the buildup
of hydrostatic forces and should be waterproofed as required by the project architect. The
Geocon Project No. G2192-52-01 - 12 - October 7, 2019
use of drainage openings through the base of the wall (weep holes) is not recommended
where the seepage could be a nuisance or otherwise adversely affect the property adjacent to
the base of the wall. The recommendations herein assume a properly compacted free-
draining backfill material (EI of 50 or less) with no hydrostatic forces or imposed surcharge
load. Figure 4 presents a typical retaining wall drain detail. If conditions different than those
described are expected, or if specific drainage details are desired, Geocon Incorporated
should be contacted for additional recommendations.
8.6 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active lateral
earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may
or may not meet the values for standard wall designs. Geocon Incorporated should be
consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall
designs will be used.
8.7 In general, wall foundations having a minimum depth and width of 1 foot may be designed
for an allowable soil bearing pressure of 2,000 psf. The proximity of the foundation to the
top of a slope steeper than 3:1 could impact the allowable soil bearing pressure. Therefore,
retaining wall foundations should be deepened such that the bottom outside edge of the
footing is at least 7 feet horizontally from the face of the slope.
8.8 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
8.9 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls having a maximum height of 8 feet. In the event that
walls higher than 8 feet or other types of walls (such as mechanically stabilized earth [MSE]
walls, soil nail walls, or soldier pile walls) are planned, Geocon Incorporated should be
consulted for additional recommendations.
9.0 Lateral Loading
9.1 To resist lateral loads, a passive pressure exerted by an equivalent fluid weight of
350 pounds per cubic foot (pcf) should be used for the design of footings or shear keys
Geocon Project No. G2192-52-01 - 13 - October 7, 2019
poured neat in compacted fill. The passive pressure assumes a horizontal surface extending
at least 5 feet, or three times the surface generating the passive pressure, whichever is
greater. The upper 12 inches of material in areas not protected by floor slabs or pavement
should not be included in design for passive resistance.
9.2 If friction is to be used to resist lateral loads, an allowable coefficient of friction between
soil and concrete of 0.35 should be used for design. The friction coefficient may be reduced
to 0.2 to 0.25 depending on the vapor barrier or waterproofing material used for construction
in accordance with the manufacturer’s recommendations
9.3 The passive and frictional resistant loads can be combined for design purposes. The lateral
passive pressures may be increased by one-third when considering transient loads due to
wind or seismic forces.
10.0 Site Drainage and Moisture Protection
10.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2016 CBC 1804.3 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be directed
into conduits that carry runoff away from the proposed structure. Appendix C presents the
results of the storm water management investigation.
10.2 The performance of pavements is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. If planter islands are proposed, the
perimeter curb should extend at least 12 inches below proposed subgrade elevations. In
addition, the surface drainage within the planter should be such that ponding will not occur.
10.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
10.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. Area drains
to collect excess irrigation water and transmit it to drainage structures or impervious above-
grade planter boxes can be used. In addition, where landscaping is planned adjacent to the
Geocon Project No. G2192-52-01 - 14 - October 7, 2019
pavement, construction of a cutoff wall along the edge of the pavement that extends at least
6 inches below the bottom of the base material should be considered.
LIMITATIONS
The conclusions and recommendations contained herein apply only to our work with respect to
development, and represent conditions on the date of our final observation. Any subsequent
improvement should be done in conjunction with our observation and testing services. As used herein,
the term “observation” implies only that we observed the progress of the work with which we agreed
to be involved. Our services did not include the evaluation or identification of the potential presence of
hazardous materials. Our conclusions and opinions as to whether the work essentially complies with
the job specifications are based on our observations, experience and test results. Subsurface
conditions, and the accuracy of tests used to measure such conditions, can vary greatly at any time. We
make no warranty, express or implied, except that our services were performed in accordance with
engineering principles generally accepted at this time and location.
We will accept no responsibility for any subsequent changes made to the site by others, by the
uncontrolled action of water, or by the failure of others to properly repair damages caused by the
uncontrolled action of water. The findings and recommendations of this report may be invalidated
wholly or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
Should you have any questions regarding this report, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Matt R. Love
RCE 84154
Shawn Foy Weedon
GE 2714
MRL:SFW:kcd
(e-mail) Addressee
)lOL
SITESITE
NO SCALE
FIG. 1
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT IS
NOT INTENDED FOR CLIENT'S USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO.G2192 - 52 - 01ML / CW
MAGNOLIA-BRADY
NORTHEAST CORNER OF MAGNOLIA
AVENUE AND BRADY CIRCLE
CARLSBAD, CALIFORNIA
GEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:10/07/2019 2:10PM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2192-52-01 1534 Magnolia Ave\DETAILS\G2192-52-01_Vicinity Map.dwg
DATE 10 - 07 - 2019
t
N
GEOCON
INCORPORATED
■ ■
I I
1234567891011121314151617181920FG-21FG-22FG-23FG-24FG-25FG-26FG-27144.8143.5142.0140.8143.8146.0147.3148.3149.3150.6151.1150.3149.5148.3142.0148.3143.0147.3146.5145.4146.4146.4146.5147.0147.5147.4147.0147.4142.8144.3148.4149.5149.5149.5151.0151.0150.8151.0150.9151.0151.0149.5148.4146.5146.5142.6146.3147.148.3149.5145.6148.3APPROX. LIMITSOF GRADINGQcf/Qcf/Qcf/AS - GRADED GEOLOGIC MAP2MAGNOLIA-BRADYNORTHEAST CORNER OF MAGNOLIAAVENUE AND BRADY CIRCLECARLSBAD, CALIFORNIA6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974PHONE 858 558-6900 - FAX 858 558-6159PROJECT NO. G2192 - 52 - 01DATE 10 - 07 - 2019 FIGURE GEOTECHNICAL ENVIRONMENTAL MATERIALSPlotted:10/07/2019 2:10PM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2192-52-01 1534 Magnolia Ave\SHEETS\G2192-52-01 Geologic map.dwg........COMPACTED FILL........OLD PARALIC DEPOSITS (Dotted Where Buried)........APPROX. LOCATION OF DENSITY TEST (FG...Finish Grade)........APPROX. ELEVATION AT BOTTOM OF FILL (Feet, MSL)QcfGEOCON LEGENDQop149FG-27l• J ---/ c§r1 I ~ · 205-220-83 ---~-._·_ ·-~~ GEOCON INCORPORATED 0 • ■ ■ a· 40' 80' - - -- - -SCALE 1n= 40' {On 11x17)
CONCRETE SLAB
FOOTING*DEPTHFOOTING WIDTH*
SAND AND VAPOR
RETARDER IN
ACCORDANCE WITH ACI
FOOTING*
WIDTH
CONCRETE SLAB
PAD GRADE
FOOTING*DEPTHSAND AND VAPOR
RETARDER IN
ACCORDANCE WITH ACI
FIG. 3
WALL / COLUMN FOOTING DIMENSION DETAIL
NO SCALE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO.G2192 - 52 - 01ML / CW
MAGNOLIA-BRADY
NORTHEAST CORNER OF MAGNOLIA
AVENUE AND BRADY CIRCLE
CARLSBAD, CALIFORNIA
GEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:10/07/2019 2:10PM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2192-52-01 1534 Magnolia Ave\DETAILS\Wall-Column Footing Dimension Detail (COLFOOT2).dwg
DATE 10 - 07 - 2019
*....SEE REPORT FOR FOUNDATION WIDTH AND DEPTH RECOMMENDATION
GEOCON
INCORPORATED
■ ■
I I
PROPERLY
COMPACTED
BACKFILL
CONCRETE
BROWDITCH
2/3 H
PROPOSED
RETAINING WALL
GROUND SURFACE
1"
FOOTING 4" DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVED OUTLET
MIRAFI 140N FILTER FABRIC
(OR EQUIVALENT)
1" MAX. AGGREGATE
OPEN GRADED
GROUND SURFACE
TEMPORARY BACKCUT
PER OSHA
12"
WATER PROOFING
PER ARCHITECT
FOOTING
PROPOSED
GRADE
4" DIA. SCHEDULE 40
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
RETAINING
WALL
3/4" CRUSHED ROCK
(1 CU.FT./FT.)
NOTE :
DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET
OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING
CONCRETE
BROWDITCH
WATER PROOFING
PER ARCHITECT
GROUND SURFACE
12"
2/3 H 2/3 H
FOOTING
PROPOSED
GRADE
RETAINING
WALL
CONCRETE
BROWDITCH
WATER PROOFING
PER ARCHITECT
GROUND SURFACE
FILTER FABRIC
ENVELOPE
MIRAFI 140N OR
EQUIVALENT
4" DIA. SCHEDULE 40
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
FIG. 4
TYPICAL RETAINING WALL DRAIN DETAIL
NO SCALE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO.G2192 - 52 - 01ML / CW
MAGNOLIA-BRADY
NORTHEAST CORNER OF MAGNOLIA
AVENUE AND BRADY CIRCLE
CARLSBAD, CALIFORNIA
GEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:10/07/2019 2:11PM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2192-52-01 1534 Magnolia Ave\DETAILS\Typical Retaining Wall Drainage Detail (RWDD7A).dwg
DATE 10 - 07 - 2019
GEOCON
INCORPORATED
■ ■
I I
TABLE I
SUMMARY OF FIELD DENSITY TEST RESULTS
Project Name:Project No.:
Pre. No. Re.
1 09/10/19 Lot 7 144 1 0 132.8 8.1 119.9 7.9 90 90
2 09/10/19 Lot 6 146 1 0 132.8 8.1 122.4 8.3 92 90
3 09/11/19 Lot 5 145 1 0 132.8 8.1 119.9 7.8 90 90
4 09/11/19 Lot 5 146 1 0 132.8 8.1 120.9 8.2 91 90
5 09/12/19 Lot 4 150 1 0 132.8 8.1 124.3 10.3 94 90
6 09/12/19 Lot 5 150 1 0 132.8 8.1 122.9 9.8 93 90
7 09/12/19 Lot 5 147 1 0 132.8 8.1 120.7 8.4 91 90
8 09/13/19 Lot 1 153 1 0 132.8 8.1 126.0 7.8 95 90
9 09/13/19 Lot 2 152 1 0 132.8 8.1 125.1 8.2 94 90
10 09/13/19 Lot 3 151 1 0 132.8 8.1 128.2 8.3 97 90
11 09/16/19 Lot 2 152 1 0 132.8 8.1 120.6 8.1 91 90
12 09/16/19 Lot 1 152 1 0 132.8 8.1 119.7 8.5 90 90
13 09/16/19 Lot 5 148 2 0 130.5 9.0 113.9 12.2 87 90
13 A 09/16/19 Lot 5 148 2 0 130.5 9.0 117.8 13.2 90 90
14 09/16/19 Lot 3 151 1 0 132.8 8.1 121.0 10.1 91 90
15 09/17/19 Lot 6 149 1 0 132.8 8.1 124.8 10.4 94 90
16 09/17/19 Lot 7 148 1 0 132.8 8.1 120.8 10.1 91 90
17 09/18/19 Lot 4 148 1 0 132.8 8.1 121.9 8.4 92 90
18 09/18/19 Lot 4 150 1 0 132.8 8.1 121.4 9.3 91 90
19 09/19/19 Lot 2 152 1 0 132.8 8.1 119.9 8.3 90 90
20 09/19/19 Lot 6 149 1 0 132.8 8.1 121.4 8.5 91 90
FG 21 09/20/19 Lot 1 154 1 0 132.8 8.1 120.3 8.3 91 90
FG 22 09/20/19 Lot 2 153 1 0 132.8 8.1 122.0 8.1 92 90
FG 23 09/20/19 Lot 3 152 1 0 132.8 8.1 127.0 7.7 96 90
FG 24 09/20/19 Lot 4 151 1 0 132.8 8.1 121.5 8.8 91 90
FG 25 09/20/19 Lot 5 150 1 0 132.8 8.1 119.6 7.8 90 90
FG 26 09/20/19 Lot 6 149 1 0 132.8 8.1 127.7 7.8 96 90
FG 27 09/20/19 Lot 7 149 1 0 132.8 8.1 126.4 8.1 95 90
Curve
No.
Test No.
Magnolia - Brady
Date
(MM/DD
/YY)
Elev.
or
Depth
(feet)
Location
G2192-52-01
>¾"
Rock
(%)
Max.
Dry
Density
(pcf)
Opt.
Moist
Content
(%)
Field
Dry
Density
(pcf)
Field
Moisture
Content
(%)
Relative
Compaction
(%)
Required
Relative
Compaction
(%)
~GEOCON
TABLE I
EXPLANATION OF CODED TERMS
AC Asphalt Concrete IT Irrigation Trench SG Subgrade
AD Area Drain JT Joint Trench SL Sewer Lateral
B Base M Moisture Test SM Sewer Main
CG Curb/Gutter MG Minor Grading SR Slope Repair
DW Driveway MSE Mechanically Stabilized Earth Wall ST Slope Test
ET Electrical Trench PT Plumbing Trench SW Sidewalk
ETB Exploratory Trench RG Regrade SZ Slope Zone
FB Footing Backfill RWL Reclaimed Water Lateral UT Utility Trench
FG Finish Grade RWM Reclaimed Water Main WB Wall Backfill
FS Fire Service SBT Subdrain Trench WL Water Lateral
GT Gas Trench SD Storm Drain WM Water Main
A, B, C, …
R
>¾" ROCK - ROCK CORRECTION
The laboratory maximum dry density and optimum moisture content can be adjusted for in-place soil that possesses rock larger than
¾ inch. The curve no. is adjusted for the percentage of ¾ inch rock in accordance with ASTM D 4718 or Woodward Clyde
guidelines.
TEST NO. PREFIX
TEST NO. RE.
Retest of previous density test failure following additional moisture conditioning or recompaction
Fill in area of density test was removed during construction operations
CURVE NO.
Corresponds to the curve numbers presented in the summary of the laboratory maximum dry density and optimum moisture content
test results. The field representative selected the curve no. based on the laboratory test results and field observations.
ELEVATION OR DEPTH
Corresponds to the elevation or the depth, in feet, of the in-place density/moisture content test. The value has been rounded to the
nearest whole foot.
~GEOCON
Geocon Project No. G2192-52-01 October 7, 2019
TABLE II
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Curve No. Description Maximum Dry
Density (pcf)
Optimum
Moisture Content
(% dry weight)
1 Reddish brown, Silty, fine to medium SAND (Qop) 132.8 8.1
2 Light reddish brown, Silty, fine to medium SAND (Qop) 130.5 9.0
TABLE III
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829
Sample No.
Moisture Content (%) Dry Density
(pcf)
Expansion
Index
ASTM Soil
Expansion
Classification
2016 CBC
Expansion
Classification Before Test After Test
EI-1 (Lot 1) 8.2 15.0 117.6 2 Very Low Non-Expansive
EI-2 (Lot 3) 8.0 14.3 118.3 2 Very Low Non-Expansive
EI-3 (Lot 5) 7.6 14.4 118.0 3 Very Low Non-Expansive
EI-4 (Lot 7) 7.6 14.5 119.8 0 Very Low Non-Expansive
TABLE IV
SUMMARY OF WATER SOLUBLE SULFATE LABORATORY TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Water Soluble Sulfate (%) ACI 318 Sulfate Exposure
EI-1 (Lot 1) 0.014 S0
EI-2 (Lot 3) 0.017 S0
EI-3 (Lot 5) 0.006 S0
EI-4 (Lot 7) 0.006 S0