HomeMy WebLinkAboutCT 13-06; LA COSTA VILLAS; GEOTECHNICAL REPORT; 2015-02-27El
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SMS GEOTEHNK2AL SOLUTIONS. INC.
Consulting Geotechnical Engineers & Geologists
1465 S. Rancho Santa Fe Road, Suite 208
San Marcos, California 92078
Office: 760-761-0799
Cell: 760-331-8738
smsgeosol.inc@gmail.com
I Project No. FC-12-14733
February 27, 2015
I NOM Development, Inc.
I Mr. Majid Mortazavi
1608 Lake Drive
Cardiff, California 92007
Report of Geotechnical Engineering Observations and Compaction Testing, Remedial,
Building Pad Grading, La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad,
California (Drawing No 483-2A)
Submitted herewith please find the following summary of geotechmcal engineering observations
and compaction testing recently completed by our firm in connection with remedial grading and
ground preparation for the graded building pad at the above-referenced property. The building pad
at the property is delineated on the enclosed Limits of Compacted Fill and Field Test Location Map
reproduced from the project Grading Plan prepared by ACE Civil Engineering.
The project consisted of an export grading operation. Overall grading designs for the project
I development chiefly consisted of cut excavations into pre-existing graded slopes on the south and
east perimeters for enlarging the pad surfaces, and the creation of level stepped surfaces for the
support of an 8-Unit condominium type residential construction Terraced site and building
basement type retaining walls are incorporated into the designs to achieve ground transitions from
upper on & off site grades to lower building pad grades near the adjacent Gibraltar Street.
I. REFERENCES
The following pertinent plans and documents were used a basis of our engineering observations and I Compaction testing services.
I i Grading Plans for La Costa Villas, Drawing No 483-2A, prepared by ACE Civil
Engineering.
I 2. "Addendum Geotechnical Plan Review Update, Proposed La Costa Villas Development,
Gibraltar Street at Jerez Court, Carlsbad, California," prepared by SMS Geotechnical
Solutions, Inc., Project No. GI-9-14-18, dated September 9, 2014.
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Report of Geotechnical Engineering Observations and Compaction Testing Page 2
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
"Second Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi-
Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by
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Allied Earth Technology, Project No. 13-1147H I, dated June 5, 2014.
"Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit
Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by
Allied Earth Technology, Project No. 13-1147H1, dated October 10, 2013.
I 5. "Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached
Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad," Prepared by Vinje &
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Middleton Engineering, Inc., Job #04-287-P, dated July 7, 2004 This report was completed
under the engineering supervision of the undersigned while employed at the Vinje &
Middleton Engineering, Inc.
.6. "Preliminary Soil and Geotechnical Investigation, Graded Hillside Property, Gibraltar Street
Near Jerez Court, La Costa Area of Carlsbad, San Diego County, California," prepared by
MV Engineering, Inc., Job #1017-91, dated February 20, 1991.
II. GEOTECIINICAL CONDITIONS
Surface conditions at the project Lot 401 substantially remained unchanged from those described
in the referenced reports However, exposures developed in the pad over-excavations and wall
backcut excavations indicated that property was mostly a graded fill pad with perimeter fill slopes
Formational bedrock units were exposed below the site fills ranging from approximately 3 to 8 feet
in the building pad areas to roughly 10 to 12 feet in the eastern (upper) wall area Site pre-existing
fills consisted of light to dark brown silty to sandy clay soils grading medium stiff to very stiff with
depth Underlying formational units consisted of dense to stiff light to tan brown clayey sandstone-
:siltstone designated as the Santaigo Formation (Tsa).
Formational rocks (Td) were exposed in the foundation trench excavation for the eastern (upper)
retaining wall with the wall foundations and shear key embedded into the undisturbed natural
formational materials The upper portion of the formational material was marked by a dark colored
stiff clayey residual soil that graded to a lighter colored mottled clayey sandstone-siltstone More
prominent natural clayey residual soils exposed directly at the bottom of the foundation trench in
the southern and northern ends were over-excavated to a minimum depth of 12 inches and
reconstructed to the bottom of the foundation elevation with compacted fills similar to the remaining
trench areas to create a uniform bearing conditions through (see enclosed Plat).
No indication of adverse geologic structure or instability was in evidence in the temporary wall
backcut exposures However, pre-existing shallow slump type failures impacted the slope face
above the temporary wall backcut, as mapped on the enclosed Limits of Compacted Fills and Test
Location Map The slump failure debris was removed and irregular slope face surfaces in the
impacted areas laid back and benched in order to enhance stability of the temporary wall backcut
Slope, face slump failure areas should he repaired by proper benching into unaffected hillsides as
Report of Geotechnical Engineering Observations and Compaction Testing Page 3
La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
approved in the field, and backflhling with compacted fills during the wall backfill operations to
achieve original or flatter slope gradients. The reconstructed slope face should be blended into
surrounding terrain to provided a smooth transition. More detail recommendations are provided in
the following sections.
III. GROUND PREPARATION AND REMEDIAL GRADING
Prior to the remedial grading operations, surface vegetation was removed and cleared for the site
as appropriate Upper soft and compressible soils were then stripped and removed from the areas
receiving new fills to expose the underlying undisturbed natural dense to stiff formational units, or
firm ground, but not less than 3 feet below rough finish pad grades throughout. The exposed bottom
surfaces were then visually examined, probed and tested to assure stable ground or competent
formational units suitable for receiving new fills. Earth deposits generated from the site remedial
grading operations predominantly consisted of silty to sandy clay (CL) soils ranging high expansion
potential The removed soils were moisture conditioned to above (approximately 2%-3%) optimum
moisture levels, processed into a uniform mixture placed in thin 6 to 8 inches thick horizontal lifts
and mechanically compacted with heavy construction equipments consisting of D-4 Bulldozer, 938
Loader and 321 Excavator, to at least 90% of the corresponding laboratory maximum density per
ASTM .D- 15.57. Approximate bottom of over-excavation elevations are shown on the enclosed
Approximate Limits of Compacted Fills and Test Location Plat and Compaction Test Results Table
Periodic engineering observations of the remedial grading operations and compaction testing of the
fills placed within the graded areas were provided by this office from January 9 through February
18, 2015 Limits of remedial grading works, approximate test locations and pertinent elevations as
established in the field based on information provided by others, are shown on the enclosed
Approximate Limits of Compacted Fills and Test Location Plat Approximate elevations and
locations of field density tests were determined by hand level and pacing/ tape measure relative to
identifiable features located at the site and noted on the grading plan. Pertaining maximum dry
density and optimum moisture content tests (ASTM D1557) were Obtained from prior site
geotechnical investigations reports (see references) and are summarized in the enclosed Compaction
Test Results Table
Site preparation and remedial grading were conducted in substantial conformance with Chapter 18
(Soils and Foundations) and Appendix "J" (Grading) of the 2013 California Building Code (CBC),
the Grading Ordinance for the City of Carlsbad, the requirements of the project soil report(s)
referenced herein and our field recommendations, where applicable and as appropriate. All
observations and testing were conducted by a representative from this office under direct supervision
of the project geotechnical engineering/engineering geologist.
Field density tests establishing both the in-place dry densities and moisture contents were performed
in accordance with the ASTM D-1556 sand cone test method as the fill was placed Test locations
were placed to provide the best possible coverage. Areas of low compaction, as indicated by the
field density tests, were brought to the attention of the contractor. These areas were reworked by
the contractor and retested. Engineering observations and compaction test results indicated that the
Report of Geotechnical Engineering Observations and Compaction Testing Page 4
La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
fills within the approved areas were properly placed and compacted to at least 90% of the
corresponding maximum dry density at the tested locations and are suitable for their intended use.
ADDITIONAL LABORATORY TESTING
One expansion index (El) test was performed during this phase of the project on a representative
50%-50% mixture of onsite soils with sandy import soils in accordance with the ASTM D-4829 to
determine suitability of the mixtures for use as wall back material. The test results are presented in
the following table..
Sample
Description
Molded Degree Of
Saturation
(%)
Final
o
(%) El
Initial Dry
Density
(PCF)
Measured
El
EL
50%
Saturation
Onsitelimport 50/50 mixture ii 50 23 105.1 44 44
() = moisture content in percent.
£150 = E1neas - (50 - Smeas) ((65 + Elmeas) — (220 - Smeas))
Expansion Index (El) Expansion Potential
0-20 Very Low
121-50 Low
51 -90 Medium
91 -130 High
)130 Very High
CONCLUSIONS AND RECOMMENDATIONS
In our opinion, site excavations and remedial grading operations were completed in substantial
conformance with the project approved grading plan, pertinent geotechrncal reports and applicable
codes, and are acceptable for their intended use Site subsurface geotechmcal conditions were found
to vary from those described in the referenced reports, as presented herein. However, earth materials
and engineering properties of the compacted fills remain the same.
Permeable Interlocking Concrete Payers (PICP) type pavements are proposed for the interior
driveway improvement surfaces as shown on the project grading plans (see Limits of Compacted
Fill and Field TestLocation Map). The proposed PJCP pavement sections as shown on the project
plans are acceptable from a georechnical standpoint provided our recommendations presented in
the following are also considered and incorporated into the project designs and constructions
Onsite clayey (CL) deposits are not suitable for wall and trench backfills and good quality sandy
granular import soils should be considered for this purpose, or used to improve the quality of the
onsite soils to an acceptable (El less than 50) mixture.
Report of Geotechnical Engineering Observations and compaction Testing Page 5
La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
A small load of sandy soils was imported to the site and was mixed "50-50" with the onsite soils and
tested in accordance with ASTM D-4829. Test results indicated a low expansion potential with an
expansion index (El) of 44 The mixture is considered suitable for use as wall backfihls Additional
sandy import soils necessary to improve the quality of the onsite soils, or where used for wall and
trench backfihls should be good quality clean, granular, non-corrosive deposits (SMISW) with very
low expansion potential (100% passing 1-inch sieve, more than 50% passing #4 sieve and less than
18% passing 4200 sieve with expansion index less than 20). Import soils should be inspected, tested
as necessary, and approved by the project geotechmcal engineer prior to delivery to the site Import
soils should also meet or exceed engineering characteristic and soil design parameters as specified
in the following sections.
All conclusions and recommendations including soil design parameters, geotehnical
foundation/slab designs and improvement sections provided in the referenced reports and subsequent
letters and addendums will stay unchanged, as specified therein and should be considered in the final
designs and implemented during the construction phase, except where specifically superceded
below:
A. Footings and Slab-on-Grade Foundations
The proposed residential units may be supported on shallow stiff concrete footings and slab-
on-grade floor foundations designed based upon the as-graded engineering properties of
foundation bearing and subgrade: soils. Other foundation system alternatives such as post-
tensioned or structural slab-on-ground foundations consistent with the onsite high expansive
soils are also available The choice of appropriate option will depend on acceptable levels
of future building and improvement performance, economic feasibility and ease of
construction.
Site earth bearing and subgrade soils predominantly consist of silty to sandy clay (CL)
deposits ranging to high in expansion potential (expansion index of 98 based on ASTM
D-4829 classification) Expansive soils will require adequate moisture conditioning, deeper
foundations and thicker slabs with heavier reinforcement in order to alleviate their potential
adverse impacts The following minimum foundation and slab recommendations are
consistent with the site clayey bearing and subgrade soils:
1. Perimeter and interior continuous strip foundations should be sized at least 18 inches
wide and 24 inches deep Spread pad footings, if any, should be at least 30 inches square
and 18 inches deep and structurally interconnected with the continuous strip footings
with grade beams Interconnecting grade beams should be a minimum of 12 inches wide
by 18 inches deep Footing depths are measured from the lowest adjacent ground
surface, not including the sand/gravel layer beneath floor slabs.
Exterior continuous footings should enclose the entire building perimeter. Flagpole
footings also need to be tied together if the footing depth is less than 4 feet below rough
finish grade.
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Report of Geotéchnical Engineering Observations and Compaction Testing Page 6
La Costa Villas Project, Lot 401,7570 Gibraltar Street, Carlsbad February 27,2015
Continuous interior and exterior foundations should be reinforced, with a minimum of
four #5 reinforcing bars. Place 245 bars 3 inches above the bottom of the footing and
245 bars 3 inches below the top of the footmg Interconnecting grade beams should also
be reinforced with a minimum of 244 bars top and bottom and #3 ties at 30 inches on
center maximum Reinforcement details for spread pad footings should be provided by
the project architect/structural engineer.
2. Deepenedfoundations shall be required for all building walls adjacent to the internal
driveway with Permeable Interlocking Concrete Paver (PICP) type pavementsurfaces
Deepened foundations adjacent to the internal driveway shall be a minimum of 30
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inches deep or extend a minimum of 12 inches below the bottom of the paver section,
whichever, is more. Unit 1 western building foundations adjacent to the detention
basin retaining walls should also be adequately deepened to avoid surcharging of the
lower walls (a 1:1 projected line from the bottom outside edge of the building
foundations shall be below the bottom of lower wall)
I 3. The slab subgrade andfoundation bearing soils should not be allowed to dry prior to
pouring the concrete or additional groundpreparations, moisture reconditioning and
.pre saturation will be necessary as directed in thefiehL The required moisture content
I ,of the bearing soils is approximately 3% Over the optimum moisture content to the depth
of 24 inches below slab subgrade Attempts should be made to maintain as-graded
moisture contents in order to preclude the need for pre saturation of the subgrade and
I bearing soils.
4. Dowel the slab to the footings using #4 reinforcing bars spaced 18 inches on center
I maximum extending at least 20 inches into the footing and 20 inches into the slab. The
dowels should be placed mid-height in the slab Alternate the dowels each way for all
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interior footings.
5 After the footings are dug and cleaned, place the reinforcing steel and dowels and pour
the footings. This office should be notified to inspect the foundation trenches and
I reinforcing prior to pouring concrete.
Once the concrete for the footings has cured and underground utilities tested, place 4
I inches of 3/a-inch rock over the slab subgrade Flood with water to the top of the -3/8-inch
rock, and allow the slab subgrade to soak until moisture testing indicates that the
required moisture content is present. After the slab subgrade soils have soaked, notify
I this office and schedule for appropriate moisture testing.
When the required moisture content has been achieved, place .a well-performing moisture
I barrier/vapor retardant (minimum 15-mil Stego) over the %-inch rock, and place 2
inches of clean sand (SE 30 or greater) on top of the plastic.
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La Costa Villas Project, Lot 401,7570 Gibraltar Street, Carlsbad February 27, 2015
If sufficient moisture is present, flooding/pre saturation will not be required and slab
underlayment may consist of 2 inches of clean sand (SE 30 or greater) over a well
performing moisture barrier/vapor retardant (minimum 15-mil Stego) over 2 inches
of clean sand, and thefootings and slab may be poured monolithically. Alternatively,
a 4-inch thick base of compacted '/2-inch clean aggregate provided with the vapor
barrier (minimum 15-md Stego) in direct contact with (beneath) the concrete may also
be considered provided a concrete mix which can address bleeding, shrinkage and
curling is used
This office should be notified to inspect the sand, slab thickness, and reinforcing prior
to concrete pour.
Adequate setback or deepened foundations shall be required for all foundations
constructed on or near the top of descending slopes to maintain minimum horizontal
distances to daylight or adjacent slope face. There should be a minimum of 7 feet or ½
of the slope height, whichever is more, horizontal setback from the bottom outside edge
of the footing to daylight for foundations, unless otherwise specified or approved.
All interior slabs should be a minimum of 5 inches in thickness reinforced with #3
reinforcing bars spaced 12 inches on center maximum each way placed near the slab
mid-height.
Interior slabs should be provided with "sôficut" contraction/control joints consisting of
sawcuts spaced 10 feet on center maximum each way. Cut as soon as the slab will
support the weight of the saw, and operate without disturbing the final finish which is
normally within 2 hours after final finish at each control joint location or 150 psi to 800
psi The softcuts should be a minimum of 1-mch in depth, but should not exceed 11/4-
inch deep maximum. Anti-ravel skid plates should be used and replaced with each blade
to avoid spalling and raveling. Avoid wheeled equipment across cuts for at least 24
hours.
.. Provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners will
depend on slab geometry and/or interior column locations. The enclosed Isolation Joint
and Re-Entrant Corner Reinforcement (Plate 1) may bed as a general guideline.
Foundation trenches and slab subgrade soils should be inspected and tested for proper
moisture and specified compaction levels and approved by the project geotechmcal
consultant prior to the placement of concrete.
All soil design parameters will remain the same as specified in the referenced reports.
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
B. Eastern Slope Face Repairs and Restorations
Shallow slump type failures impacted the slope face above the temporary wall baekcut at the
southeast corner, as, mapped on the enclosed Limits of Compacted Fills and Test Location
Map. The slump failure debris was removed and irregular slope face surfaces in the
impacted areas laid back and benched in Order to enhance stability of the temporary wall
backcut No indication of adverse geologic structure or instability was in evidence in the
temporary wall backcut exposures.
The local slope face erosional slump failures are thought to have chiefly resulted from
previous uncontrolled drainage run-off above that concentrated over the slope surfaces.
Lack of periodic maintenance and clearing of slope face drainage terraces and failure of
concrete ditches are also thought to have caused slope face saturations, and may be the
initiating factor of the slope face slumping Slope face soils are also in a soft condition
Slope face slump failure areas should be repaired by proper benching into unaffected
hillsides as approved in the field, and backfilling with compacted fills during the wall
backfill operations to achieve original or flatter slope gradients The reconstructed slope
face should be blended into surrounding terrain to provided a smooth transition. The
following are appropriate:
Remove and clear all vegetation from the repair areas, where they occur and as
necessary.
Clean out existing level benches/steps developed during grading operations to lay back
impacted portions of the slope face, and further remove additional all slump debris and
failed soils, where they occur, as necessary. Levels benches should at least 2 feet wide,
expose firm unaffected soils and slightly heeled back into the hillside
Backfill soils should consist of the 5050u onsite-import soil mixture generated for wall
backfills, pre-manufactured into a well processed and moisture-conditioned mixture
prior to the actual placement. The backfill soils should be moisture conditioned to
approximately 2% above the optimum moisture levels, throughly mixed and processed
into a uniform and homogeneous blend as approved in the field by the project
geotechmcal engineer or his designated representative
Mechanically compact pre-manufactured backfill soils upon level benches approved by
the project geotechmcal consultant in thin (4 to 6 inches) horizontal lifts to minimum
190% of the laboratory maximum dry density (per ASTM D-1557) using hand held
equipments (whacker or similar). The reconstructed embankment should be compacted
to minimum 90% compaction levels out to the finish slope face and neatly blended into
the surrounding areas.
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
Slope face restorations and recompaction operations should be inspected and tested by
project soils engineer to verify minimum 90% compaction levels within the slope face
materials in the repair areas Testing of fill will also assist the contractor to achieve
proper moisture and compaction levels. Slopeface repair and restoration geotechnical
inspection and compaction testing should be completed as part of the wall backfill
testing work and presented in a separate Wall Backfill and Slope Repair and
Restoration Compaction Report.
Controlling slope face surface drainage is an important factor in the overall stability and
future performance of the project hillside This can be achieved by improving the slope
face drainage and disallowing concentrated run-off from above Surface runoff over the
slope surfaces should also not be allowed to saturate the soils within the outer
embankment face or percolate into the hillside, and should be collected and directed in
a controlled manner. Overflow of the upper (off site) pad surface water from the top of
the slope should be avoided. Slope face drainage terraces and concrete lined drainage
swales behind the retaining walls should collect and divert Surface water to suitable
discharge locations. Period maintenance and upkeep of site drainage facility shall be
required to assure continued popper and unobstructed functioning of all surface and
subsurface drainage facilities.
The completed slope face should be provided with a suitable plant cover. Natural brush
is best but difficult to quickly establish Initially, only broad-leafed deep rooted
vegetation which requires a minimum of irrigation should be used Over watering of site
vegetation should be avoided Only the amount of water to sustain vegetation life should
be provided. A well-qualified landscape architect should be consulted for this purpose.
Eastern Slope Face Contour Cut Grading
The existing concrete ditch near the top of the temporary wall backcut is planned for
removals and replacement with a new concrete-lined drainage ditch directly behind the wall,
as shown on the enclosed Limits of Compacted Fill and Field Test Location Map (also see
the project final gradmg plan) Upon removal of the existing concrete ditch, the disturbed
slope face areas may be contour cut graded to provide a smooth transition and blend into the
surrounding areas Finish slope face should expose firm and competent stable surfaces, as
approved in the field Unfavorable slope face exposures will require stabilization including
reconstruction with compacted fills upon level benches as discussed herein or compacting
the slope face exposures to enhance surficial stability as directed in the field Slope face
drainage improvements, maintenance, and plant cover remains the same as specified.
Permeable Interlocking Concrete Payers (PICP)
Permeable Interlocking Concrete Payers (PICP) are planned for the internal driveway
improvement surfaces as a part of the project BMP designs, as shown on the grading plans
(see Plate 1). The proposed PICP pavement sections as shown on the project plans are
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
considered substantially acceptable from a geotechnical standpoint provided the following
are also considered and incorporated into the design and construction of the proposed
permeable/previous paving surfaces:
In general, infiltrated water through the PICP pavements shall not impact the driveway
subgrade and nearby building foundation bearing soils, adjacent wall backfihls and
nearby graded embankments. For this purpose, under drains perforated pipes (Sch. 40
or greater) placed approximately 3 inches above the bottom of pavement base course
(ASTM No 57 stone) should be installed Due to the site highly moisture sensitive
plastic clayey subgrade sods and very close proximity of the budding foundations to
the permeable driveway pavements, an impervious liner (minimum 15-mil Stago)
should be provided at the bottom ofpavement base course (ASTMNo. 57stone) over
the approved compacted subgrade. Saturation of site clayey soils will result in loss of
strength and periodic heaving and shrinkage can occur in response to wetting and drying
and shall not be allowed. Outlet box structures which capture and discharge the
infiltrated runoff via the storm drain pipes to the designated locations are critical
components of the pavement system.
Planned PICP pavements should .be provided with thickened concrete curb/edge
restraints, as necessary and appropriate. Deepened building and wall. foundations shall
also be necessary where they occur near or adjacent (less than 15 feet) to the permeable
pavements or site bioretention basin. Other similar protective measures such as
minimum 3 sack concrete slurry cutoff walls may also be considered along the edges of
the proposed PICP pavements and bioretention system near the project building and wall.
foundations.
:3. PICP pavement structural section will depend to storage and infiltration capacity of the
system, as well as engineering properties of subgrade soils, and should be provided by
the project design consultant. From a geotechnical engineering standpoint, based on our
analysis and design assumptions (R-Value of 5 and TI of 4 5), as a minimum PICP
pavement section should consist of 31/8-inch PICP over a minimum of 2 inches of ASTM
No. 8 bedding course/choke stone over a minimum of 12 inches of ASTM No. 57 stone
base course over a minimum of 12 inches of 95% compacted subgrade. R-Value testing
of subgrade Soils may also be performed toconfirm structural section designs. Bedding
course/choke stone and base course stone should also be well compacted, consolidated
and interlocked (avoid crushing the under drain pipes) with heavy construction
equipment (minimum 95%) ASTM No 8, No 9 or No 89 should be used for joint
materials depending on the joint size and per manufacturer recommendations
4. Gradation requirements for ASTM No. 57, No. 8, No. 89 and No. 9 are as follows:
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
Sieve
Size
Percent Passing
No. 57 No. 8 No. 89 No. 9
100
1" 95 to 100
'/2" 25to60 100 100
85 to 100 90 to 100 100
No.4 OtolO 10to30 20to55 85to100
No. 8 0 to 5 0 to 10 5 to 30 10 to 40
No. 16 0 to 5 0 to 10 0 to 10
No. 50 0to5 0to5
Pervious concrete pavement section, if considered, should consist of a minimum of 8
inches thick pervious concrete (modulus of rapture of 600 psi) over a minimum of 6
inches of ASTM No 57 stone base course over a minimum of 12 inches of 95%
compacted subgrade, as indicated on the project pians, is considered adequate. The need
for an impervious liner at the bottom ofpavement base course (ASTMNo. 57 stone)
over the compacted subgrade will remain the same as specfled.
A concrete transition strip should be provided between the project asphalt, PICP and
pervious concrete pavements and around the perimeter of the PICP installations.
E. Exterior Concrete Slabs / Flatworks
1 1. All exterior slabs (walkways, patios) supported on highly expansive subgrade soils
should be a minimum of 4 inches in thickness reinforced with #3 bars at 12 inches on
centers in both directions placed mid-height in the slab The subgrade soils should be I compacted to minimum 90% compaction levels at the time of fine grading and before
placing the slab reinforcement.
I In order to enhance performance of exterior slabs and flatworks supported on potentially
expansive and moisture sensitive subgrade soils, a mmimum 8 inches wide by 12 inches ' deep thickened edge reinforced with a minimum of 144 continuous bar near the bottom
should be considered along the slab penmeter. Tying the slab panels to adjacent curbs,
where they occur, with #3 bars at 12 inches on centers, may also be considered.
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La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015
Reinforcements lying on subgrade will be ineffective and shortly corrode due to lack of
adequate concrete cover. Reinforcing bars should be correctly placed extending through
the construction Joints tying the slab panels In construction practices where the
reinforcements are discontinued or cut at the construction joints, slab panels should be
tied together with minimum 18 inches long #3 dowels (dowel baskets) at 12 inches on
centers placed mid-height in the slab (9 inches on either side of the joint).
Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not
to exceed 12 feet maximum) each way The larger dimension of any panel shall not
exceed 125% of the smaller dimension Tool or cut as soon as slab will support weight,
and can be operated without disturbing the final finish which is normally within 2 hours
after final finish at each control joint location or 150 psi to 800 psi Tool or softcuts
should be a minimum of 1-inch but should not exceed 1¼-inch deep maximum In case
of softcut Joints, anti-ravel skid plates should be used and replaced with each blade to
avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours.
Joints shall intersect free-edges at a 90° angle and shall extend straight for a minimum
I of 1 'A feet from the edge The minimum angle between any two intersecting Joints shall
be 800 Align joints of adjacent panels Also, align joints in attached curbs with joints
in slab panels Provide adequate curing using approved methods (curing compound
I maximum coverage rate = 200 sq. ft/gal.).
Subgrade soils should be tested for proper moisture and specified compaction levels and I approved by the project geotechnical consultant prior to the placement of concrete.
V. ADDITIONAL GEOTECHNICAL OBSERVATIONS AND TESTING
This office should be notified no later than 2 p.m. on the day before any of the following operations
begin, in order to schedule appropriate testing and/or field observations for confirmation and
approval of the completed work:
A. Wall Backfihls
Observe wall back drain installations in substantial accordance with the enclosed
Retaining wall Drain Detail, Plate 2 The crushed rock backfill zone should be well
consolidated and interlocked by mechanical/hand-operated equipments and construction
tools suitable to the site conditions.
Wall backfill soils shall be compacted by mechanical means to .a minimum of 90% of
the corresponding maximum dry density, unless otherwise specified Good quality
sandy import soils or "50-50" manufactured mix should be used.
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La Costa Villas Project, Lot 401, 1570 Gibraltar Street, Carlsbad February 27, 2015
B. Foundations and Utility Trenches
Observe the plumbing and utility trenches after the pipes are laid and prior to backfihling.
Backfill soils within trenches 12-inches or more in depth shall be compacted by
mechanical means to a minimum of 90% Of the corresponding maximum dry density,
unless otherwise specified Good quality sandy import soils or 5050u manufactured
mix should be used Jetting or flooding of the backfill is not allowed Care should be
taken not to crush the utilities or pipes during the compaction of the trench backfill.
Test the plumbing trenches beneath slabs for minimum compaction requirements prior
to sand and moisture barrier placement.
Observe the bottom of the footing trenches for proper embedment, compaction levels,
and design widths and embedment.
Confirm footing reinforcement size and placement, slab thickness and reinforcing, sand
thickness and moisture barrier placement.
C. Fine Grading, Pavement Base and Subgrade and Site Improvements
Observe placement and perform compaction testing for fills placed under any conditions
12-inches or more in depth, to include:
Building pad contour grading.
Driveways, street and yard improvements, sidewalks, curbs and gutters.
The spreading or placement of soil obtained from any excavation (spoils from
footings, underground utilities, swimming pools, etc.).
Observation and testing of base and subgrade beneath the driveway, perimeter yards,
patios, sidewalks, etc., prior to placement of pavement surface or concrete.
Moisture testing prior to concrete pour, if required and as specified.
Any operation not included herein which requires our testing, observation, or
conformation for submittal to the appropriate agencies.
I VI. DRAINAGE
I The ownerideveloper is responsible for insuring adequate measures are taken to properly
finish grade the building pad after the structures and other improvements are in-place so that
the drainage waters from the improved site and adjacent properties are directed .away from
I proposed structures in accordance with the designed drainage patterns shown on the
approved plans.
'I
Report of Geotechnical Engineering Observations and Compaction Testing Page 14
La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27,2015
A minimum of 2% gradient should be maintained away from all foundations. Roof gutters
and downspouts should be installed on the building, all discharge from downspouts should
be led away from the foundations and slab to a suitable location Install area drams in the
yards for collection and disposal of surface water.
Planter areas adjacent to foundations should be provided with damp/water proofing, using
an impermeable liner against the footings, and a subdrainage system within the.planter area.
Site and building stem type retaining walls should be provided a well-constructed back drain
as specified in the project soil reports Planting large trees behind site retaining walls should
be avoided.
It should be noted that shallow groundwater conditions may develop in areas where no such
conditions existed prior to site development This can be contributed to by substantial
increases of surface water infiltration resulting from landscape irrigation which was not
present prior to the site redevelopment. It is almost impossible to absolutely prevent the
possibility of shallow water conditions developed from excessive landscape irrigation over
the entire site Therefore, we recommend that shallow water conditions, if developed, be
immediately remedied.
The property owner should be made aware that altering drainage patterns, landscaping, the
addition of patios, planters, and other improvements, as well as over-irrigation and variations
in seasonal rainfall, all effect subsurface moisture conditions, which in turn affect structural
performance.
WI. EXPANSIVE SOIL AND DRAINAGE MAINTENANCE CLAUSE
Onsite bearing and subgrade soils consist of highly expansive moisture sensitive silty to
sandy clayey (CL) soils. These deposits can experience movements and undergo volume
changes upon wetting and drying which can be detrimental to the site improvements and
structures. Building foundations/ slabs and site improvement recommendations provided
herein are provided with the intent to alleviate adverse impacts of site potentially expansive
soils. However, maintaining a uniform as-graded soil moisture during the post construction
periods is essential in the future performance and stability of site structures, embankments
and improvements. Drainage improvements should be installed and well-maintain and water
intrusions into the site clayey bearing and subgrade soils prevented.
A maintenance program for continuous inspections and upkeep of the project surface and
subsurface drainage facilities, as well as the retention basin will be required to assure proper
functioning and uninterrupted continuous discharge flow of the captured runoff water as
specified. A maintenance schedule consisting of at least two times a year, before and after
the annual rainy season is recommended. In case of deficiencies , noted conditions should
be immediately repaired. Development of an unfavorable condition, if noted during the
scheduled maintenance should also be to the attention of the project consultant to provide
appropriate mitigation recommendations.
Report of Geotechnical Engineering Observations and ( Testing Page 15
La Costa Villas Project, Lot 401, 7570 Gibraltar Street, February 27,2015
VIII. LIMITATIONS
Our description of grading operations, as well as observations and testing services herein, has been
limited to those pad remedial grading operations performed periodically from January 9 to February
18, 2015. The recommendations provided herein have been based on our field observations and
testing as noted No representations are made as to the quality or extent of materials, not observed
and tested.
This report is issued with the understanding that the owner or his representative is responsible for
ensuring that the information and recommendations are provided to the project architect/structural
engineer and other design consultants so that they can be incorporated into the plans Necessary
steps shall be taken to ensure that the project general contractor and subcontractors carry out such
recommendations during construction..
This report should be considered valid for permit purposes for a period of six months and is subject
to review by our firm following that time. IFANYCHANGESAREMAJ)EIN THE FINAL PAD
SIZE, LINESAND GRADES, BUILDING LOCATION, ELEVATIONS, ETC ,PRIOR TO THE
CONSTRUCTION, THIS REPORT WILL BECOME INVALID AND FURTHER
ENGINEERING AN!) RECOMMENDATIONS WILL BECOME NECESSARY.
If you have any questions or need clarification, please contact this office at your convenience.
Reference to our Project No. FC-12-14 -33 will help to expedite our response to your inquiries.
We appreciate this opportunity to be of service to
Geotechnical Solutions, Inc.
'4vIehdi S. Shariat
G81#2885
;i 'k 711W
Steven J. Melzer 0. co CERTIRED
L* ENGINEERING CEO #2362 p' GEOLOGIST
Attachments: Plate 1, Isolation Joint and er Reinforcement
Plate 2, Retaining Wall Drain 1taffr
Compaction Test Results
Approximate Limits of Compacted Fills and .Test Location Map
Distribution: Addressee (5, e-mail)
ACE Civil Engineering (e-mail)
S!IS GEOTECHIVICAL SOLUTIONS, INC.
Consulting Geotechnical Engineers &. Geologists
ISOLATION JOINTS AND REENTRANT CORNER REINFORCEMENT
Typal - no scale
(a) (b)
ISOLATION JOINTS
L- coNTRAcilo: JOINTS
CORNER CRACK
RE-ENTRANT CORNER
::c[\
REINFORCEMENT
NO. 4 BARS PLACED 1." ;
BELOW TOP OF SLAB
NOTES:
isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (b) If no isolation joints are used around columns or if the corners of the isolation joints do not meet the contraction
joints, radial cracking as shown in (c)may occur (reference Ad).
In order to control cracking at the re-entrant corners (±270 corners), provide reinforcement as shown in (c).
Re-entrant corner reinforcement shown herein is provided as.a general guideline only and is subject to verification
and changes by the project architect and/or structural engineer based upon slab geometry, locator and other engineeririg and construction factors.
SMS GEOTECHNICAL SOLUTIONS, INC.
Consulting Ge.otechnical Engineers & Geo!ogiSts
PLATE 1
RETAINING WALL DRAIN DETAIL
Typical - no scale
drainage
Granular, non-expansive non-expansive
backfill Corrtoacied
,
//
Waterproofing
1'1 /
Filter Material Crushed rock (wrapped in
filter fabric) or Class 2 Permeable Material
erforated drain pipe / (see specifications below)
/
Competent, approved
soils or bedrock
v-
valet> 75
CONSTRUCTION SPECIFICATIONS:
Provide granular, hon-expansive backfill soil in 1:1 gradient wedge behind wall. Compact backfill to minimum 90% of laboratory
standard.
Provide back drainage for Wall to prevent build-up of hydrostatic pressures. Use drainage openings along base of wall or back drain system as outlined below:
3 Backdrain should consist of 4 diameter PVC pipe (Schedule 40 or equivalent) with perforaons down Drain to suitable outlet
at minimum 1% Provide Y4 1% crushed gravel filter wrapped in filter fabric (Mirafi 140N or equivalent) Delete fitter fabric
wrap if Caltrans Class 2 permeable material is used. Compact Class 2 material to minimum 90% of laboratory standard.
Seal back of wall with waterproofing in accordance with architects specifications.
Provide positive drainage to disallow ponding Of Water above wall. Lined drainage ditch to
minimum 2% flow away from wail is recommended.
* Use 1,7% cubic, foot per foot with granular backfill soil and 4 cubic foot per foot if expansive backfill soil is used.
SMS GEO.TECH..NiCAL SOLUTIONS. INC.
Consulting Geotechhic.al Engineers & Geologists ....
PLATE 2
.. . U
- - - - - - - - - - - - - - - - - - - COMPACTION TEST RESULTS
PROJECT NO: IFC42-14-33
PROJECT NAME: La Costa Villas, Lot 401, Building Pad Grading (CT13-.06, Drawing No. 483-2A):
PROJECT LOCATION: 7570 Gibraltar Street, Carlsbad, California
LABORATORY MAXIMUM DRY DENSITY/OPTIMUM MOISTURE CONTENT TEST.RESULTS (ASTM D1557):
Soil Type (1):. Light Brown to Tan Clayey Sand to Sandy Clay Soil Type (2): Light to Dark Brown silty sandy Clay
Maximum Dry Density: 115.7 pcf Maximum Dry Density: 114.5 pcf
Optimum Moisture: 15% Optimum Moisture: 166/o
FIELD COMPACTION TEST RESULTS (ASTM 111556):
Date
. 2015
Test
No.
.. Location
Approximate
Test
Elevation
(Ft)
Moisture
" °'
Field
Density
Dry
(PcI)
Max,
Dry
Density Density
Relative
Compaction
(PCI)
Comments
1/9 1 Keyway, NW Corner of Unit l .86.5 14 106.6 114.5 93 Bottom of Over-Excavation @86.0'
1/9 2 NW Area, B/W Detention Basin & Driveway 89 1.6 105.2 114.5 92
1/9 3 Detention Basin 90 15 106 114.5 93
1/9' 4 Unit I 91 16 103.9 114.5 91 IBottom of Over-Excavation® 89.5'
1/12 5 Unit .2 91.5 17 .1071 1115 94 . .
1/12 6 Unit 3 90 17 .105.9 114.5 92 Bottom of Over-Excavation @88.5'
1/12 7 Unit 4 .92 IS 106.1 114.5 93 Bottom of Over-Excavation @90.5'
1/12 8 Driveway, B/W Units I & 5 92 16 . 106.7 114.5 93 . Bottom of Over-Excavation, @ 91.0'
1/12 9 Unit2 93 17 104.1 114.5 1 91
1/13 JO 1 Unit 3 93 16 1,04.9. 1.14.5 92
11/13 11 Unit 1 94 17 105.7 114.5 92
1/13 ' 12 Unit 4 94 16 106.3. . 114.5 93 ' Bottom of Over-Excavation @93.5'
1/14 13 Unit 95 18 104.8 114.5 92
1/14 14 Driveway, B/W Units 4 & 8 95 18 104.9 114.5 92
- - - - - - - - - - - - - - - - - Date
2015
Test
No.
. Location
Approximate
Test
. Elevation
(Ft)
Field
. Moisture
. " °'
Field
Dry
Density
PcI
Max
Dry
. Density,
Pc1
Relative
Compaction Comments
1/14 15 Unit 96 17 105.4 114.5 92
1/14 16 Driveway, B/W Units 3 & 7 94 16 107.1 114.4 94 Bottom of Over-Excavation @93.0'
1/15 17 Unit 92 18 103.7 114.5 91 Bottom of Over-Excavation @ 91.5'
I/IS 18 Unit 6 93.0 18 104.8 114.5 92 Bottom of Over-Excavation @92.0'
1/15 19 Unit 94.5 15 107.4 11.4.5 94
1/15 20 Unit 7 . 93.5 15 106.6 114.5 93 Bottom of Over-Excavation @92.5'
1/15 21 Unit 8 94 16 105 114.5 92 Bottom of Over-Excavation @ 93.5'
1/16 22 Unit 5 94.5 16 105.6 114.5 92 Bottom of Over-Excavation @ 91.5'
1/17 . 23 Unit 7 95 18 107.1 114.5 94
1/17 24 Unit 8 96 17 106.7 11.4.5 93 Bottom of Over-Excavation @ 93.0'
1/17 25 S. End of E'ly Ret. Wall Fnd..Over-Ex. .107 16 106.8 11.5.7 92 Over-Ex. Bottom of Fnd. Trench a
mm. 12" & Reconst. W/ Comp'd Fill
2/18 26 Unit 1 F.G. 16 105.3 1 114.5 92
2/18 27 Unit 2 F.G. 16 106.6 114.5 93
2/18 28 Unit 3 F.G. 16 106.2 114.5 93
2/18 29 Unit 4 F.G. 17 109 114.5 95
2/18 30 Unit 5 F.G. 17 106.2 114.5 93
2/18 31 Unit 6 F.G. 15 106.6 114.5 93
2/18 32 Unit . . F.G. 17 106.7 114.5 93
.2/18 33 i Unit 8 F.G. 17 105.4 .114.5 92
Explanations: Over-Ex. or OX (Over-Excavate), F.G. (Finish Grade).
Approximate test elevations are measured from staking and grading controls provided by others..
See attached Approximate Limits of Compacted Fills and Test Location Plat for test locations