HomeMy WebLinkAboutPUD 02-11A; LA COSTA GREENS; FINAL REPORT OF TESTING AND OBSERVATION; 2004-07-12FINAL REPORT OF
TESTING AND OBSERVATION
SERVICES PERFORMED
DURING SITE GRADING
VILLAGES OF LA COSTA
THE GREENS
LOT 47- RECREATION CENTER AND
LOT 34- POND AREA
CARLSBAD, CALIFORNIA
PREPARED FOR
REAL ESTATE COLLATERAL
MANAGEMENT COMPANY
% MORROW DEVELOPMENT INCORPORATED
CARLSBAD, CALIFORNIA
JULY 125 2004
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
Project No. 06403-52-09
August 18, 2004
Real Estate Collateral Management Company
C10 Morrow Development Incorporated
1903 Wright Place, Suite 108
Carlsbad, California 92008
Attention: Mr. Tim O'Grady
Subject: VILLAGES OF LA COSTA - THE GREENS
LOT 47— RECREATION CENTER AND LOT 34— POND AREA
CARLSBAD, CALIFORNIA
ADDENDUM TO FINAL REPORT
References: 1. Final Report of Testing and Observations Services Performed During Site
Grading, Villages of La Costa - The Greens, Lot 47 - Recreation Center and
Lot 34 - Pond Area, Carlsbad, California , prepared by Geocon Incorporated,
dated July 12, 2004 (Project No. 061403-52-09).
Precise Grading and Erosion Control Plans for: Villages of La Costa, The Greens,
Recreation Center, prepared by Hunsaker & Associates, print dated August 13,
2004 (Project Nos. PUD 02-1 I A, CT 99-03) (Drawing No. 397-2X).
The Greens Community Center - Entry Water Feature Plan, prepared by Pacific
Aquascape, Incorporated, dated May 6, 2004 (Job No. 7969-E).
Gentlemen:
This addendum letter has been prepared to provide information pertaining to Lot 47 - Recreation
Center and Lot 34 - Pond Area within the Villages of La Costa - The Greens development. Based on
our conversations with you, it is our understanding that the City of Carlsbad has issued plan check
comments that require the referenced precise grading plans to be addressed within the referenced
final report. As such, we have reviewed the precise grading plans and it is our opinion that the plans
have been prepared in substantial conformance with recommendations provided in our final report.
It should be noted that the precise grading plans indicate that a 2-foot high slope with an approximate
inclination of 0.5:1.0 (horizontal: vertical) will be constructed along the shoreline of the proposed
pond at Lot 34. The precise grading plans indicate that 4:1 slopes will be present both upslope and
downslope of the 0.5:1.0 slope at the shoreline of the pond. According to the referenced Entry Water
6960 Flanders Drive 0 San Diego, California 92121-2974 D Telephone (858) 558-6900 D Fax (858) 558-6159
PWD oUCk)
Feature Plan, this slope will be faced with sculptured concrete, a minimum of 4 inches thick and
reinforced with 1"xl'x20-gauge wire mesh. Additionally, an 8-inch wide by 8-inch deep keyway will
be constructed at the toe of the 0.5:1.0 slope and filled with concrete during the construction of the
pond. The plans indicate that the water level of the pond will be approximately six inches below the
top of the 0.5:1.0 slope. It is our opinion that the 0.5:1.0 slope faced with reinforced concrete will
possess an adequate post-construction factor of safety in terms of surficial stability. However, if the
reinforced concrete slope facing and keyway are not constructed in a timely manner after the
excavation of this slope, surficial sloughing could occur, particularly during the rainy season.
It is our opinion that the recreation center and pond area pads have been properly graded and are
ready to receive the planned improvements. All conclusions and recommendations presented in the
referenced final report remain applicable.
Should you have any questions regarding this letter, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
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(2) Addressee
(3/del) Hunsaker & Associates, Inc.
Attention: Mr. David Blalock
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Project No. 06403-52-09 - 2 - August 18, 2004
GEOCON
IN CORPORATE D
GEOTECHNICAL CONSULTANTS
Project No. 06403-52-09
July 12, 2004
Real Estate Collateral Management Company
110 Morrow Development Incorporated
1903 Wright Place, Suite 108
Carlsbad, California 92008
Attention: Mr. Tim O'Grady
Subject: VILLAGES OF LA COSTA - THE GREENS
LOT 47- RECREATION CENTER AND LOT 34— POND AREA
CARLSBAD, CALIFORNIA
FINAL REPORT OF TESTING AND OBSERVATION
SERVICES PERFORMED DURING SITE GRADING
Gentlemen:
In accordance with your request and our proposal dated May 6, 2003, we have prepared this final
report of compaction testing and observation services provided during the grading of the subject site.
Our services were performed during the period of December 5, 2003 through June 24, 2004. The
scope of our services summarized in this report included the following:
Observing the grading operation, including the removal and/or processing of topsoil,
colluvium, and alluvium.
Performing in-place dry density and moisture content tests in fill placed and compacted at
the site.
Performing laboratory tests to aid in evaluating maximum dry density and optimum moisture
content of the compacted fill soils. Additionally, laboratory tests were performed on samples
of soil present at finish grade to evaluate expansion characteristics and water-soluble sulfate
content.
Preparing an "As-Graded" Geologic Map.
Preparing this final report of grading.
The purpose of this report is to document that the grading for Lot. 47
- Recreation Center, and
Lot 34— Pond, have been performed in substaiitial cóhf&inance with the recommendations of the.
project geotechnical report, and that the fill materials have been properly placed and compacted.
6960 Flanders Drive • San Diego, California 92121-2974 0 Telephone (858) 558-6900 0 Fax (858) 558-6159 I
It is our understanding that three separate buildings, a swimming pool, and a wading pool will be
constructed at the Lot 47 Recreation Center, and a single lined-gunite pond will be constructed for
Lot 34. The grading operations for the recreation center building pad and pond were performed
concurrently with the balance of The Greens project.
GENERAL
The grading contractor for the project was Signs and Pinnick Incorporated of El Cajon, California.
Grading plans for the project were prepared by Hunsaker and Associates and are entitled Grading
and Erosion Control Plans for Villages of La Costa, with City of Carlsbad approval date of May 27,
2003. A digital version of the grading plans was used as the base map for our As-Graded Geologic
Map (Figure 1). The project geotechnical report is entitled Update Soil and Geologic Investigation,
Villages of La Costa - The Greens, Carlsbad, California, dated June 25, 2001 (Project No. 06403-
12-03).
References to elevations and locations herein are based on surveyor's or grade-checker's stakes in the
field and/or interpolation from the referenced grading plans. 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 grading plans or proper surface drainage.
GRADING
The Recreation Center - Lot 47 and pond - Lot 34 is located within of the Villages of La Costa - The
Greens Phase I, southwest of the intersection of Amber Lane and Lapis Road. Prior to grading, this
area generally consisted of a west-trending canyon drainage that ultimately intersected San Marcos
Creek. Grading for the site consisted of daylight cuts and fills on the order of 10 and 40 feet,
respectively, to achieve the finish-grade elevations.
Grading began with the removal of brush and vegetation from the area to be graded. The brush was
then exported. Topsoil, colluvial, and alluvial soils were removed to expose formational material.
Within these areas, and prior to placing fill, the exposed (overexcavated) ground surface was scarified
(where possible), moisture conditioned, and compacted. Fill materials derived from on-site
excavations were then placed and compacted in layers until design elevations were attained.
Fill Materials and Placement Procedures
The composition of the fill materials generally varied from gravels and boulders produced by on-site
blasting of hard metavolcanic rock to clayey fine sands, sandy to silty clay, and sandy to clayey
gravels from within other portions of The Greefl 15r5ect. Excavations within the sedimentary
Santiago Formation and surficial deposits predominately produced sandy clays and silty sands and
Project No. 06403-52-09 - 2- July 12, 2004
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were suitable for capping material. Structural fill placed and compacted at the site consisted of
material that can be classified into three zones:
Zone A - Material placed within 3 feet from pad grade, consisted of "soil" fill with a
maximum particle dimension of 6 inches.
I . Zone B - Material placed within 10 feet from pad grade and below Zone A consisted of
"soil-rock" fill with a maximum particle dimension of 12 inches. In addition, material placed
on the outer 6 feet of fill slopes and 2 feet below Zone A "soil-rock" fill with a maximum
I particle dimension of 12 inches.
Zone C - Material placed below Zone B consisted of "soil-rock" fill with a maximum particle
I dimension of 48 inches. It should also be noted that larger rocks with a maximum dimension
of approximately 8 feet were buried individually during grading operations.
Placement procedures for "soil-rock" fill consisted of spreading and compacting the material with a
D9 or larger Caterpillar bulldozer with a maximum lift size of 3 feet. Materials placed as "soil-rock"
were watered heavily during spreading to help properly fill voids with finer material and "seat" the
larger rocks. During the placement of each lift, compactive effort was applied to the fill by wheel-
rolling with loaded rock trucks such that the entire lift was compacted.
"Soil fills" were placed in lifts no thicker than would allow for adequate bonding and compaction.
The soil was moisture conditioned as necessary and mixed during placement and then compacted
utilizing conventional heavy-duty compaction equipment. "Soil-rock" fills were predominately
placed within the central portion of the canyon cleanout at lower elevations.
During grading operations, compaction procedures were observed and in-place density tests were
performed to evaluate the dry density and moisture content of the "soil" and "soil-rock" fill material.
The in-place density tests were performed in general conformance with ASTM Test Method
D 2922-01, Standard Test Method for Density of Soil and Soil-Aggregate in Place by Nuclear
Methods.
The results of the in-place dry density and moisture content tests are summarized on Table I. Grading
for Lot 34 and Lot 47 were performed concurrently with the balance of the, Villages of La Costa -
The Greens development. The results presented on Table I apply to Lot 34 and Lot 47 only. As such,
the test numbers are not in consecutive order. Any tests taken outside of the subject site have been
addressed in reports for other neighborhoods within the Greens.
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Project No. 06403-52-09 - 3 - July 12, 2004
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Using methods suggested by AASHTO T224-86, corrections were made to the laboratory maximum
dry density and optimum moisture content on fill soils being tested containing rocks larger than
3/4 inch. The values of maximum dry density and optimum moisture content presented on Table I
reflect these corrections.
In general, the in-place dry density test results indicate that the fill soil has a dry density of least 90
percent of the laboratory maximum dry density near to slightly above optimum moisture content at
the locations tested. In addition, moisture tests performed in "soil-rock" fills generally indicate
moisture contents at or above optimum. The approximate locations of the in-place dry density and
moisture content tests are shown on the As-Graded Geologic Map (Figure 1).
Laboratory tests were performed on samples of material used for fill to evaluate moisture-density
relationships, optimum moisture content and maximum dry density (ASTM D 1557-02), shear
strength (ASTM D 3080-03) expansion potential (ASTM D 4829-03), and water-soluble sulfate
content (California Test No. 417). The results of the laboratory tests are summarized on Tables II
through V.
Slopes
The project slopes consisted of fill slopes constructed at inclinations of 2:1 (horizontal: vertical) or
flatter, with maximum heights of approximately 20 feet. All slopes should be planted, drained, and
maintained to reduce erosion. Slope irrigation should be kept to a minimum to just support the
vegetative cover. Surface drainage should not be allowed to flow over the top of the slope.
Subdrai ns
Subdrains were installed at the general locations shown on the As-Graded Geologic Map (Figure 1).
In addition, the subdrains were "as-built" for location and elevation by the project civil engineer. The
subdrains consisted of a 6-inch and 8-inch-diameter, Schedule 40, PVC perforated pipe placed in
crushed aggregate surrounded by Mirafi 140N (or equivalent) filter fabric. The drain was placed at
least 15 feet below grade and constructed at a gradient of at least 1 percent. The canyon subdrain
outlets on the western margins of The Greens project and should be maintained regularly to prevent
sediment and debris from obstructing the free flow of water out of the subdrain system.
Finish Grade Soil Conditions
Observations and laboratory test results indicate that the prevailing soil conditions within the upper
approximately 4 feet of finish grade have an expansion potential of "medium" (Expansion Index of
90 or less) as defined by Uniform Building Code(UBC) Table 18-I-B.
Project No. 06403-52-09 - 4 - July 12, 2004
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It should be noted that although rocks larger than 6-inch-diameter were not intentionally placed
within Zone A, some larger rocks may exist at random locations.
Laboratory tests were performed on the sample from Lot 47 building pad to determine the percentage
of water-soluble sulfate. The test results indicate sulfate content that correspond to "severe" sulfate
exposure ratings as defined by UBC Table 19-A-4. The results of the soluble-sulfate test are
presented in Table V. Table 1 presents a summary of concrete requirements set forth by UBC
Table 19-A-4. It is recommended that the concrete used within Lot 47 meet the requirements for
"severe" sulfate exposure rating, as provided in Table 1.
TABLE 1
REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
Sulfate
Exposure
Water-Soluble Sulfate
Percent by Weight
Cement
Type
Maximum Water to
Cement Ratio by Weight
Minimum Compressive
Strength (psi)
Negligible 0.00-0.10 -- -- --
Moderate 0.10-0.20 II 0.50 4000
Severe 0.20-2.00 V 0.45 4500
Very Severe > 2.00 V 0.45 4500
Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
improvements that could be susceptible to corrosion are planned, it is recommended that further
evaluation by a corrosion engineer be performed.
SOIL AND GEOLOGIC CONDITIONS
The soil and geologic conditions encountered during grading were found to be similar to those
described in the project geotechnical report. The Santiago Formation (Ts) and Santiago Peak
Volcanics (Jsp) were exposed within the canyon cleanout, and compacted soils were placed in fill
areas and are designated as Qcf on Figure 1. In addition, compacted fill soils placed in undercut areas
is designated as Quc.
The enclosed "As-Graded" Geologic Map (Figure 1) depicts the general geologic conditions
observed. No soil or geologic conditions were observed during grading that would preclude the
continued development of the property as planned.
Project No. 06403-52-09 - 5 - July 12, 2004
CONCLUSIONS AND RECOMMENDATIONS
1.0 General
1 1.1 Based on observations and test results, it is the opinion of Geocon Incorporated that the
grading to which this report pertains has been performed in substantial conformance with
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the recommendations of the previously referenced project soils report and the geotechnical
requirements of the grading plans. Soil and geologic conditions encountered during grading
that differ from those anticipated in the project soils report are not uncommon. Where such
5 conditions required a significant modification to the recommendations of the project soils
report, they have been described herein.
1.2 No soil or geologic conditions were observed 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 that the fill soils observed and
tested as part of the grading for this area were 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 pond should be properly waterproofed to reduce the potential for moisture migration
into the underlying soils.
2.0 Future Grading
2.1 Any additional grading performed at the site should be accomplished in conjunction with
our observation and compaction testing services. Grading plans for any future grading
should be reviewed by Geocon Incorporated prior to finalizing. All trench and wall backfill
should be compacted to a dry density of at least 90 percent of the laboratory maximum dry
density near or above optimum moisture content. This office should be notified at least 48
hours prior to commencing additional grading or backfill operations.
3.0 Seismic Design Criteria
3.1 The site is located within Seismic Zone 4 according to UBC Figure 16-J. Compacted fill
soils underlie the proposed buildings. For seismic design, the site is characterized as soil
type SD. Table 3 summarizes site design criteria. The values listed on Table 4.1 are for the
Rose Canyon Fault, which is identified as a Type B fault. The Rose Canyon Fault is located
approximately 10 miles west of site. The corresponding values from Table 3 should be
— used for seismic design. -
Project No. 06403-52-09 - 6 - July 12, 2004 I
TABLE 3
SITE DESIGN CRITERIA
Parameter Value UBC Reference
Seismic Zone Factor 0.40 Table 16-I
Soil Profile SD Table 16-J
Seismic Coefficient, Ca 0.44 Table 16-Q
Seismic Coefficient, C 0.64 Table 16-R
Near-Source Factor, Na 1.0 Table 16-S
Near-Source Factor, N 1.0 Table 16-T
Seismic Source B Table 16-U
4.0 Foundations
4.1 Due to the presence of significant differential fill thickness within Lot 47, Foundation
Category III is recommended for the proposed recreation buildings. We understand that a
post-tensioned foundation system will be used for the buildings.
4.2 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 (UBC
Section 1816). Although this procedure was developed for expansive soils, 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 on Table 4
for the particular foundation category designated.
TABLE 4
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI) Design Parameters Foundation Category III
Thornthwaite Index -20
Clay Type - Montmorillonite Yes
Clay Portion (Maximum) 70%
Depth to Constant Soil Suction 7.0 ft.
Soil Suction 3.6 ft.
Moisture Velocity 0.7 in./mo.
Edge Lift Moisture Variation Distance 2.6 ft.
Edge Lift 1.15 in.
Center Lift Moisture Variation Distance 5.3 ft.
Center Lift 4.74 in.
Project No. 06403-52-09 -7- July 12, 2004
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4. 33 UBC Section 1816 uses interior stiffener beams in its structural design procedures. If the
structural engineer proposes a post-tensioned foundation design method other than UBC
Section 1816, it is recommended that interior stiffener beams be used. The depth of the
1 perimeter foundation should be at least 18 inches. Geocon Incorporated should be
consulted to provide additional design parameters as required by the structural engineer.
4.4 Foundations may be designed for an allowable soil bearing pressure of 2,000 pounds per
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square foot (psf) (dead plus live load). This bearing pressure may be increased by one-third
for transient loads such as wind or seismic forces.
4.5 The use of isolated footings that are located beyond the perimeter of the building
and support structural elements connected to the building is not recommended. Where this
condition cannot be avoided, the isolated footings should be connected to the building
foundation system with grade beams.
4.6 No special subgrade presaturation is deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soils should be sprinkled, as necessary, to
maintain a moist condition as would be expected in any such concrete placement.
4.7 Our experience indicates post-tensioned slabs may be susceptible to excessive edge lift,
regardless of the underlying soil conditions, unless reinforcing steel is placed at the bottom
of the perimeter footings and the interior stiffener beams. Current PTI design procedures
primarily address the potential center lift of slabs but, because of the placement of the
reinforcing tendons in the top of the slab, the resulting eccentricity after tensioning may
reduce the ability of the system to mitigate edge lift. The foundation system should be
designed to reduce the potential for edge lift to occur.
4.8 Consideration should be given to connecting exterior slabs that exceed 5 feet in width to
the building foundation to reduce the potential for future separation to occur.
4.9 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal: vertical), special foundations and/or design considerations are recommended
due to the tendency for lateral soil movement to occur.
Building 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.
Swimming pools located wifliiri Tfeèi of the t01 of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, it is recommended that
the portion of the swimming pool wall within 7 feet of the slope face be designed
Project No. 06403-52-09 - 8 - July 12, 2004 I
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with the assumption that the adjacent soil provides no lateral support. This
recommendation applies to fill slopes up to 30 feet in height, and cut slopes
regardless of height.
I • Although other improvements that 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,
I however, to incorporate design measures that would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
4.10 Exterior slabs should be at least 4 inches thick and reinforced with 6 x 6-W2.9 x W2.9
(6 x 6-6/6) welded wire mesh. The mesh should be placed within the upper one-third of the
slab. Proper mesh positioning is critical to future performance of the slabs. It has been our
experience that the mesh must be physically pulled up into the slab after concrete
placement. The contractor should take extra measures to provide proper mesh placement.
Prior to construction of slabs, the subgrade should be moisture conditioned to at least
optimum moisture content and compacted to a dry density of at least 90 percent of the
laboratory maximum dry density.
4.11 All concrete slabs should be provided with adequate construction joints and/or expansion
joints to control unsightly shrinkage cracking. The design of joints should consider criteria
of the American Concrete Institute when establishing crack-control spacing patterns.
4.12 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.
4.13 The recommendations of this report are intended to reduce the potential for cracking of
slabs due to expansive soils (if present), differential settlement of deep fills, or fills of
varying thicknesses. However, even with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper
concrete placement and curing, and by the placement of crack control joints at periodic
intervals, particularly where re-entrant slab corners occur.
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5.0 Retaining Walls
5.1 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 density
of 35 pounds per cubic foot (pcf). Where the backfill will be inclined at no steeper than 2:1,
an active soil pressure of 45 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 less than 90. For those lots with
finish-grade soils having an Expansion Index greater than 90 and/or where backfill
materials do not conform to the above criteria, Geocon Incorporated should be consulted
for additional recommendations.
5.2 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining wall portion of the wall in feet) at the top of the wall. Where
walls are restrained from movement at the top, an additional uniform pressure of 7H psf
should be added to the above active soil pressure. For retaining walls subjected to vehicular
loads within a horizontal distance equal to two-thirds of the wall height, a surcharge
equivalent to 2 feet soil should be added.
5.3 All 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 use of drainage openings through the base of the wall (weep holes, etc.) is
not recommended where the seepage could be a nuisance or otherwise adversely impact the
property adjacent to the base of the wall. A typical retaining wall drainage system is
presented as Figure 2. The above recommendations assume a properly compacted granular
(Expansion Index less than 90) backfill material with no hydrostatic forces or imposed
surcharge load. If conditions different than those described are anticipated, or if specific
drainage details are desired, Geocon Incorporated should be contacted for additional
recommendations.
5.4 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, provided the soil within 3 feet below
the base of the wall has an Expansion Index of less than 90. The proximity of the
foundation to the top of a slope steeper than 3:1 could impact the allowable soil bearing
pressure. Therefore, Geocon Incorporated should be consulted where such a condition is
anticipated. The location of the retaining wall footings, however, should comply with the
recommendations presented in Section 4.8.
Project No. 06403-52-09 _10 - July 12, 2004
6.0 Lateral Loads
6.1 For resistance to lateral loads, an allowable passive earth pressure equivalent to a fluid
density of 300 pcf is recommended for footings or shear keys poured neat against properly
compacted granular fill soils or undisturbed natural soils. The allowable 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 not protected by
floor slabs or pavement should not be included in the design for lateral resistance. An
allowable friction coefficient of 0.4 may be used for resistance to sliding between soil and
concrete. This friction coefficient may be combined with the allowable passive earth
pressure when determining resistance to lateral loads.
6.2 The recommendations presented above 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 crib-type walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
7.0 Pool/Spa Recommendations
7.1 The proposed swimming pool/spa should be reinforced and designed by a structural
engineer. The soils have an expansion index category of medium. The corresponding
lateral pressures used for the design should be equivalent to a fluid pressure of at least
40 pcf. The swimming pool/spa also should be designed for any possible surcharge loading
if such nearby loading is a lateral distance from the top of the pool equal to the depth of
the pool.
7.2 The bottom of the swimming pool/spa should not be supported by different types of earth
materials. A uniform layer of common bearing material is needed to provide uniform
support for the pool/spa. If a formational cut/fill condition is present on the bottom of the
pool/spa, the bottom of the excavation should be overexcavated at least 3 feet and
recompacted up to rough grade. The bottom of the excavation should be scarified, moisture
conditioned, and compacted prior to the placement of fill soils. The grading should be
performed in accordance with Section 2.0 of this report. Geocon Incorporated should
observe the bottom of the excavation to verify the geologic conditions.
7.3 Surface drainage around the pool/spa should be designed to prevent water from ponding
and seeping into the ground. Surface water should be collected and conducted through non-
erosive devices to the street, storm drain, or other approved water course or disposal area.
Leakage from the proposed pool/spa will create an artificial groundwater condition that
Project No. 06403-52-09 - 11 - July 12, 2004
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will likely create instability problems. Therefore, all plumbing and the pool/spa should be I absolutely leak free.
7.4 The deck for the swimming pool/spa should be cast separately of the swimming pool/spa,
and water stops should be provided between the bond beam and the deck. Jointing for
concrete flatwork should be provided in accordance with the recommendations of the
American Concrete Institute. All joints should be sealed with an approved flexible sealant
to reduce the potential for introduction of surface water into the underlying soils.
8.0 Slope Maintenance
8.1 Slopes that are steeper than 3:1 (horizontal: vertical) may, under conditions that are both
difficult to prevent and predict, be susceptible to near-surface (surficial) slope instability.
The instability is typically limited to the outer 3 feet of a portion of the slope and usually
does not directly impact the improvements on the pad areas above or below the slope. The
occurrence of surficial instability is more prevalent on fill slopes and is generally preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance and/or loosening of the surficial soils (as might result from root growth,
soil expansion, or excavation for irrigation lines and slope planting) may also be a signifi-
cant contributing factor to surficial instability. It is therefore recommended that, to the
maximum extent practical: (a) disturbed/loosened surficial soils be either removed or
properly recompacted; (b) irrigation systems be periodically inspected and maintained to
eliminate leaks and excessive irrigation; and (c) surface drains on and adjacent to slopes be
periodically maintained to preclude ponding or erosion. It should be noted that although the
incorporation of the above recommendations should reduce the potential for surficial slope
instability, it will not eliminate the possibility, and therefore it may be necessary to rebuild
or repair a portion of the project's slopes in the future.
9.0 Drainage
9.1 Adequate drainage provisions are critical to the future performance of the project. Under no
circumstances should water be allowed to pond. The building pads and sheet-graded areas
should be properly finish graded so that drainage water is directed away from foundations,
pavements, concrete slabs, and slope tops to controlled drainage devices.
9.2 All underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks for early detection of water infiltration and detected leaks should be
repaired promptly. Detrimental soil movement could occur if water is allowed to infiltrate
the soil over a prolonged period of time.
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Project No. 06403-52-09 -12 - July 12, 2004
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9.3 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. We
recommend that subdrains to collect excess irrigation water and transmit it to drainage
I
structures or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the base material.
LIMITATIONS
U The conclusions and recommendations contained herein apply only to our work with respect to
grading and represent conditions at the date of our final observation on June 24, 2004. Any
subsequent grading 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 or corrosive 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, expressed or implied, except that our services were
performed in accordance with engineering principles generally accepted at this time and location.
U
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,
Project No. 06403-52-09 - 13 - July 12, 2004
GEOCON INCORPORATED
L-TJ'E Rö
Shane odacke UJ 0. 6329
RCE 63291 EJca.&oi
*
SR:AS:JH:bjl
(4/del) Addressee
1
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GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 - FAX 858 558-6159
PROJECT NO. 06403 .52-09
AS - GRADED GEOLOGIC MAP fl
DATE 07_ 12-2004
GURE1
LEGEND
cf ........ COMPACTED FILL
UC ........ COMPACTED FILL IN UNDERCUT AREA
Ts ........ SANTIAGO FORMATION (Dotted Where Buried)
VSp ........ SANTIAGO PEAK VOLCANICS (Dotted Where Buried)
APPROX. LOCATION OF GEOLOGIC CONTACT
(Dotted Where Buried)
APPROX. LOCATION OF DENSITY TEST
FG ... Finish Grade ST ... Slope Test R...Removed
.APPROX BASE OF FILL
.APPROX. LOCATION OF 8-INCH SUBDRAIN
APPROX. LOCATION OF 6-INCH SUBDRAIN
.APPROX. ELEVATION OF SUBDRAIN
GEOCON
INCORPORATED GO)
/
SCALE: 1"= 60
VILLAGES OF LA COSTA- THE GREENS
LOT 47- RECREATION CENTER AND LOT 34- POND AREA
CARLSBAD, CALIFORNIA
IUU4I I KMW(._LUI4/$4.L)WLjIn,J
TABLE I
SUMMARY OF FIELD DENSITY TEST RESULTS
Test No. Date Location
1573 12/05/03 Lot: 34; Pond
1574 12/05/03 Lot: 34; Pond
1575 12/05/03 Lot: 34;Pond
1576 12/05/03 Lot: 34; Pond
1589 12/08/03 Lot: 34; Pond
1590 12/08/03
---------------------------------------------------------------------------------------------
Lot: 34; Pond
1591 12/08/03 Lot: 34; Pond
1592 12/08/03 Lot: 34; Pond
1671 12/15/03 Lot: 34; Pond
.1672 12/15/03 ---------------------------------------------------------------------------------------------- Lot: 47; Rec Pad
1697 12/17/03 Lot: 34;Pond
1704 12/17/03 Lot: 47; Rec Pad
1739 12/18/03 Lot: 34;Pond
1739 A 12/18/03 Lot: 34; Pond
1739 Bt 12/18/03 Lot: 34; Pond
1740 12/18/03 Lot: 34; Pond
1740.A 12/19/03 Lot: 34;Pond
1740 B 12/19/03 Lot: 34; Pond
1741 12/19/03 Lot: 47; Rec Pad
1744 12/19/03 Lot: 47; Rec Pad
1745 12/19/03 Lot: 47; Rec Pad
1746 12/19/03 Lot: 47; Rec Pad
SZ 1757 12/22/03 Lot: 47; Rec Pad
SZ 1758 12/23/03 Lot: 47; Rec Pad
SZ 1759 12/23/03 Unit: 1.09; Amber 11+80
2557 04/12/04 Lot: 47; Rec Pad
2558 04/12/04 Lot: 47; Rec Pad
2559 04/12/04 Lot: 47; Rec Pad
2560 04/12/04 Lot: 47; Rec Pad
2561 04/13/04 Lot: 47; Rec Pad
2562 04/13/04 Lot: 47; Rec Pad
Elev. Plus Field Field Field Req'd.
or 3/4" Adj. Adj. Dry Moist. Rd. Rd.
Depth Curve Rock MDD OMC Dens. Cont. Comp. Comp.
(ft) No. (%) (pci) (%) (pci) (%) (%) (%)
168 14 40 133.6 7.8 120.9 7.8 91 90
171 14 20 127.9 9.8 117.8 13.6 92 90
173 14 40 133.6 7.8 121.2 8.8 91 90
175 14 40 133.6 7.8 125.7 9.6 94 90
181 14 40 . 133.6 7.8 121.2 9.8 91 90
184 14 40 133.6 7.8 120.7 9.7 90 90
188 14 20 127.9 9.8 118.6 11.5 93 90
185 14 40 133.6 7.8 120.1 10.9 90 90
192 14 20 127.9 9.8 117.2 12.8 92 90
195 14 30 130.7 8.8 119.4 10.3 91 90
194 17 0 116.5 13.3 107.6 16.6 92 90
206 14 40 133.6 7.8 125.2 8.3 94 90
187 30 0 118.4 12.5 100.9 8.5 85 90
187 30 0 118.4 12.5 101.3 12.3 86 90
187 30 0 118.4 12.5 106.0 17.3 90 90
187 30 0 118.4 12.5 98.7 8.0 83 90
187 30 0 118.4 12.5 101.1 17.0 85 90
187 30 0 118.4 12.5 106.5 15.4 90 90
195 30 0 118.4 12.5 107.5 15.7 91 90
203 30 0 118.4 12.5 108.0 16.9 91 90
210 30 0 118.4 12.5 109.4 17.5 92 90
207 30 0 118.4 12.5 108.8 15.6 92 90
210 17 0 116.5 13.3 104.9 16.6 90 90
212 17 0 116.5 13.3 107.2 13.6 92 90
214 19 0 111.8 15.8 102.8 18.1 92 90
210 24 0 117.0 14.7 105.4 16.3 90 90
214 24 0 117.0 14.7 108.4 . 15.0 93 90
210 24 0 117.0 14.7 106.2 14.9 91 90
212 24 0 117.0 14.7 106.7 17.3 91 90
210 24 0 117.0 14.7 105.6 16.7 90 90
214 24 0 117.0 14.7 106.2 15.9 91 90
Project No. 06403-12-09 . July 12, 2004
Test No. Date Location
2563 04/14/04 Lot: 34; Pond
2564 04/14/04 Lot: 34; Pond
2565 04/14/04 Lot: 34; Pond
2566 04/14/04 Lot: 34; Pond
ST 2849 06/09/04 Lot: 47; Rec Pad
ST 2850 06/09/04 Lot: 47; Rec Pad
ST 2851 06/09/04 Lot: 47; Rec Pad
2852 06/14/04 Lot: 47; Rec Pad
2853 06/14/04 Lot: 47; Rec Pad
2854 06/15/04 Lot: 47; Rec Pad
2855 06/15/04 Lot: 47; Rec Pad
ST 2856 06/16/04 Lot: 47; Rec Pad
ST 2857 . 06/16/04 Lot: 47; Rec Pad
FG 2860 06/24/04 Lot: 47; Rec Pad
ST 2861 06/24/04 Lot: 47; Rec Pad
ST 2862 06/24/04 Lot:47;Rec Pad
TABLE I
SUMMARY OF FIELD DENSITY TEST RESULTS
Elev. Plus Field Field Field Req'd.
or 3/4" Adj. Adj. Dry Moist. Rel. Rel.
Depth Curve Rock MDD OMC Dens. Cont. Comp. Comp.
(ft) No. (%) (pet) (%) (pet)
187 24 0 117.0 14.7 105.1 18.0 90 90
190 24 0 117.0 14.7 106.7 16.2 91 90
192 24 0 117.0 14.7 106.3 16.3 91 90
195 24 0 117.0 14.7 110.4 15.8 94 90
227 24 0 117.0 14.7 106.8 16.2 91 90
234 - 24 0 117.0 14.7 109.6 14.9 94 90
240 24 0 117.0 14.7 105.9 14.8 91 90
214 24 0 117.0 14.7 106.8 15.6 91 90
215 24 0 117.0 14.7 108.4 14.7 93 90
216 24 0 117.0 14.7 109.4 15.3 94 90
217 24 0 117.0 14.7 109.0 15.6 93 90
212 24 0 117.0 14.7 107.9 14.8 92 90
210 24 0 117.0 14.7 111.8 15.1 96 90
218 24 0 117.0 14.7 108.3 14.8 93 90
208 24 0 117.0 14.7 108.3 14.8 93 90
206 24 0 117.0 14.7 106.7 14.8 91 90
Project No. 06403-12-09 July 12, 2004
TABLE I
EXPLANATION OF CODED TERMS
- TEST SUFFIX
A, B, C.....Retest of previous density test failure, following moisture conditioning and/or recompaction.
- STRllcl-OUT
Fill in area of density test failure was removed and replaced with properly compacted fill soil.
- PREFIX CODE DESIGNATION FOR TEST NUMBERS
FG - FINISH GRADE ST - SLOPE TEST
SZ - SLOPE ZONE
- CURVE NO.
Corresponds to curve numbers listed in the summary of laboratory maximum dry density and optimum
moisture content test results table for selected fill soil samples encountered during testing and observation.
- ROCK CORRECTION
For denity tests with rock percentage greater than zero, laboratory maximum dry density and optimum
moisture content were adjusted for rock content. For tests with rock content equal to zero, laboratory
maximum dry density and optimum moisture content values are unadjusted.
- TYPE OF TEST
SC: Sand Cone Test (ASTM D1556)
Nil: Nuclear Density Test (ASTM D2922)
OT: Other
- ELEVATION/DEPTH
Test elevations/depths have been rounded to the nearest whole foot.
Project No. 06403-12-09 July 12,
TABLE II
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557-02
Sample Maximum Optimum
No Description Dry Density Moisture Content
(pci) (% dry weight)
14 Grayish brown, Silty, fine to coarse SAND 122.2 12.1
17 Light yellowish brown, Silty, fine to medium 116.5 13.3 SAND, with trace clay
19 Olive gray, Silty, fine SAND 111.8 15.8
24 Grayish green, fine to medium Sandy CLAY 117.0 14.7
30 Light brown, Silty, fine SAND 118.4 12.5
TABLE III
SUMMARY OF LABORATORY SHEAR TEST RESULTS
ASTM D 3080-03
Sample
No.
Dry Density
(pci)
Moisture Content
(%)
Unit Cohesion
(psi)
Angle of Shear
Resistance (degrees)
24 105.3 14.7 480 35
30 106.6 12.7 390 36
Samples were remolded to a dry density of approximately 90 percent of the laboratory maximum dry density at
near optimum moisture content.
TABLE IV
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Sample
No.
Moisture Content Dry Density
(pci)
Expansion
Index Before Test (%) I After Test (%)
El-AX 11.9 25.1 108.9 68
Project No. 06403-52-09 July 12, 2004
I TABLE V
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
VILLAGES OF LA COSTA - THE GREENS
I
LOT NO. 47— RECREATION CENTER BUILDING PAD
CALIFORNIA TEST NO. 417
Sample No. Water-Soluble Sulfate (%) Sulfate Exposure
El-AX 0.765 Severe
TABLE VI
SUMMARY OF AS-GRADED BUILDING PAD CONDITION AND FOUNDATION
CATEGORY FOR VILLAGES OF LA COSTA - THE GREENS
LOT NO. 47— RECREATION CENTER BUILDING PAD AND LOT 34— POND
Approximate Approximate
Lot Pad Maximum Maximum Expansion Foundation
No. Condition Depth of Fill Depth of Index Category
(feet) Differential
Fill (feet)
34 Fill Pad 24 12 N/A N/A
47
(Recreation Center)
Fill Pad 29 25 68 in
July 12, 2004