HomeMy WebLinkAbout90-365; St. Patrick's Catholic Church - 3821 Adams Street; Investigation and Foundation Recommendations; 1990-07-26GEOTECHNICAL INVESTIGATION AND FOUNDATION RECO"DATI0NS FOR THE PROPOSED EXPANSION TO THE EXISTING ST. PATRICK'S CATHOLIC CHURCH, LOCATED AT 3821 AD- STREET, CARISBAD, SAN DIEGO COUNTY, CALIFORNIA.
PREPARED FOR:
St. Patrick*s Catholic Church
c/o Mike O'Gara 3821 Adam St. Carlsbad, CA 92008
July 26, 1990
Job NO. 90-365 ,
2194 CARMEL VALLEY ROAD DEL MAR. CALIFORNIA 92014
_.-
TABLBoFcONTENTs
PAGE -
Scope .................................................... 1 -
Site and Project Description ............................. 1
- Field Investigation and Subsurface Conditions............2
Geology and Seismicity ................................... 3
conclusions and Recommendations -
General.............. ............................... 4
Foundations for Structures..........................4
Concrete Slabs on Grade.............................6
Retaining Walls.....................................6
Site Grading ........................................ 7
Pavement Desi gn..................................... 7
-
Surface Drainage .................................... 8
Miscellaneous............................................E
Site Vicinity Map ............................. Figure No.
Site Location Map ............................. Figure No.
Site Plan/Location of Exploratory Test Pits ... Figure No.
Logs of Exploratory Test Pits ................. Figures
1
2
3
4-5
Grading Specifications .......................... Appendix A
.-
SCOPE
This report presents the results of a geotechnical
investigation for the proposed expansion at the north end of the
existing parking lot of St. Patrickls Catholic Church, located on
a parcel of land at 3821 Adams Street, Carlsbad, San Diego County,
California. Please see Figure No. 1, "Site Vicinity Mapn and
Figure No. 2, "Site Location Map". The purpose of our
investigation was to evaluate geotechnical conditions at the site
and to provide geotechnical parameters to aid in the design of the
planned development. The scope of our work included obtaining
data from a visual inspection of the site and neighboring sites,
the logging of soils in two exploratory test pits, and the
sampling and testing of the soils exposed.
Based on our evaluation and interpretation of the data
obtained, consultations with other professionals, and review of
published and unpublished data, the contents of this report
present classification of the soils, allowable bearing pressures,
and other pertinent geotechnical information necessary to safely,
yet economically, construct the proposed development at the
subject site.
-- SITE AND PROJECT DESCRIPTI 0y
The subject site is located immediately weet of 3821 Adam
Street, in the City of Carlsbad, California. Please refer to
Figure No. 2, "Site Location Map1'. The site is rectangular,
bounded on the north by residential property, on the east by the
existing St. Patrickls Catholic Church property, on the east by
Adams Street, and on the west by a playground. A concrete masonry
Page 1
Job NO. 90-365
!-
unit wall bounds the north and west sides of the site. A wood-
framed residence is present on the north portion of the parcel.
Septic tanks and leech lines associated with this residence may be
present.
Elevations on the site range from approximately 00 to 90 feet
(MSL), characterized by a gentle slope to the west. Vegetation
consists of thinly scattered grasses and trees. Drainage on the
site is to the west.
Based on conversations with Mike O'Gara, we understand that
the proposed development at the site includes the construction of
an asphalt parking lot, extending the existing parking area to the
west. It is further our understanding, that ultimately, a wood-
framed structure may be constructed on the site. We are therefore
providing herein, recommendations for the proposed asphalt parking
lot and the proposed structure.
FIELD INVESTIGATION SUBSURFACE CONDITIONS
Our field investigation consisted of a site reconnaissance
and an observation of the subsurface conditions. The
investigation consisted of an overview of the site and neighboring
sites, and an observation of the soils in two exploratory test
pits.
Two test pits were excavated during our site investigation on
7/11/90. The pits were located in accessible areas and excavated
with a rubber tire backhoe. The test pits exposed a variety of
materials consisting of 1/2 foot of dark brown, loose, silty,
sandy topsoil, overlying clean to silty residual sands to a depth
Job NO. 90-365
Page 2
of about 3 feet, where a hard, brown, cemented sandstone was
encountered to the maximum depth explored of 7 feet. The soils
classify as SM-SP, according to the unified classification system,
and have no expansion potential, with an Expansion Index of 0.
The upper topsoils are not suitable for the support of settlement
sensitive improvements. Both the residual sands and the
sandstones are suitable for carrying foundation loads. The load
carrying capabilities of these soils increase with depth.
GEOLOGY SEZSKKUX
A review of published geologic maps, aerial photographs, and
the City of San Diego Seismic Safety Study suggests that no
geologic hazards such as active faults or potential landslides
exist within the project boundaries. No active faults are known
to exist at or in the immediate vicinity of the site, and none
were observed during our investigation. The nearest known active
faults are the Elsinore Fault and the San Jacinto Fault which lie
approximately 22 miles and 45 miles to the northeast respectively.
It is our opinion that the site could be subjected to
moderate to severe ground shaking in the event of a major
earthquake along either of the faults mentioned above or other
faults in the southern California region; however, the seismic
risk at this site is not significantly greater than that of the
surrounding developed area.
Job No. 90-365 Page 3
CONCLUSIONS REC0"D ATIONS
GENERAL
In general, it is our opinion that the site is suitable for
the proposed development, provided that recommendations presented
herein are carefully implemented into the design and construction
of the project. The on-site soils should provide a suitable
subgrade if moisture conditioned and adequately compacted. Due to
an excessive amount of organic materials in the top 4 inches, and
the low moisture content and low densities of the soils beneath,
the upper two feet of material should be removed, mixed, and
replaced as compacted fill.
FOUNDATIONS FOR STRUCTURES
In foundation recommendations for this site, the subsoil
conditions, as well as the proposed construction were evaluated.
Considerations were given to the possibility for failure of the
foundation soil or the build-up of. detrimental supplemental
stresses in the structural elements due to differential vertical
or lateral movement of the foundation soils. Foundation movement
should remain within tolerable limits, 3/4 inch total and 1/2 inch
differential, over a 15 feet horizontal distance, if the following
design and construction precautions are observed:
1. All footings or pad sizes should be computed
based on a maximum soils pressure of 1,500 psf.
All foundations on-site shall be designed in
accordance with the above values.
2. All bearing values may be increased by 33% when
considering wind, seismic, or other short duration loads.
3. All footings should be reinforced with one 84
bar top and bottom.
Job NO. 90-365
Page 4
4.
5.
6.
7.
8.
9.
At a minimum, the following footing widths and
depths below undisturbed natural or compacted final grade should be maintained:
Floors Supported Width Final Grades Depth Below
1 12" 12"
2 15" 18"
3 18" 24"
The loose soils disturbed during excavation
should be moistened and uniformly compacted prior to placing .forms and reinforcements. Special care should be taken to locate and remove all existing underground improvements such as leach field lines, septic tanks, etc. See "Site Grading".
All individual pads should be designed utilizing the above given bearing values, and be reinforced with #4 bars in each direction at
12 inches O.C.
All grading precautions given in the text and Appendix A of this report should be closely adhered to.
If fills are required to establish the desired
grades for footings, the fills should be compacted to 90% Modified Proctor Density. If any of the foundation footings are located on
fills, then all of the foundations should be located on a minimum of '24" of fill. The maximum fill depth shall not exceed the minimum
fill depth by a factor of 2.5:l. Overexcavation should be increased at the shallow fills or footings extended at the deep
fill if necessary to not exceed this ratio.
Special care and attention should be given to
the transition lot fill guidelines given in the grading section of this report and the attached Appendix A, "Grading Specif icationsV1.
Our estimates of tolerable limits of settlement should be confirmed by an engineer experienced in structural design, architect, or the designer of the residence.
None of the above is meant to preclude more stringent
engineering requirements that are felt necessary by the designer
or the engineer reviewing the structural composition of the
building.
Job No. 90-365
Page 5
CON- SmS ON GRADE
Concrete slabs may be required at this site. Slabs will be
suitable if the following guidelines are closely adhered to:
1.
2.
3.
4.
5.
Concrete slabs on grade should have a nominal thickness of 4 inches and should be reinforced
with 6 x 6 - 10/10 welded wire fabric placed
at the midpoint of the slab. The proper placement of the reinforcement is vital for satisfactory performance.
All required fills should be placed in accordance with the attached Appendix A and compacted to 90% Modified Proctor Density
(ASTM D-1557), at a moisture above optimum.
A uniform layer (2 to 3 inches) of clean sand should be placed under the slab in order to more uniformly support the slab, help distribute loads to the soils beneath the slab, and act as a capillary break.
Additional reinforcement of #4 bars at 12
inches on center shall extend across all transitional fills a minimum distance of 4 feet and shall also be installed in concrete driveways.
Special care should be taken to locate and remove all existing underground improvements
such as leach field lines, septic tanks, etc.
See "Site Grading".
The above precautions will not prevent some floor slab
movement if the soils beneath the floor slabs become wetted;
however, they will minimize the damage if such movement occurs.
RETAINING lllALTs
No retaining walls will be required at this site; therefore,
no recommendations have been provided. If retaining walls are
proposed, the project Geotechnical Engineer should be contacted
for appropriate recommendations.
Job NO. 90-365 Page 6
SITE GRADING
Under normal circumstances, only minor grading would be
proposed at this site; however, due to the subsoils exposed in the
test pits, and the discovery of an underground leech field and
suspicions of a buried septic tank of unknown location, we believe
that grading will be required to properly prepare the site for
parking area subgrade and building foundations. We recommend
that, at a minimum, all grading requirements given in Appendix A,
"Grading Specif icationsll be followed. In addition to those
general guidelines, the following recommendations are intended
specifically for this site.
1.
2.
3.
The upper 2 feet of material in all areas to be developed should be excavated, all roots, debris, and other unsuitable material removed and wasted, and replaced with suitable materials as compacted fill. In areas of
proposed asphalt paving, the upper 1 foot of fill shall be compacted to a minimum relative
compaction of 92%, as evaluated by ASTM D1557-
78. Fill should be placed in uniform lifts not exceeding 6 inches in loose thickness.
The extent of the leech field shall be investigated and well-defined. All soils in the area of the leech field shall be removed, and if found suitable, re-compacted uniformly under any area to receive a structural improvements. If not suitable, a granular
material shall be imported as required, to
establish the desired grades.
The septic tank shall be located and removed, and the created excavation should be filled
with compacted uniform granular material in 6
inch lifts to 92% Modified Proctor Density, ASTM D-1557-78.
PAVEHENT DEIGN
Parking area pavement section recommendations are based on an
R-value of 81, per our laboratory testing, for the subgrade,soils,
Job No. 90-365 Page 7
an R-value of 78 for Class 2 aggregate base material, per Cal
Trans standard specifications, a traffic index of 4.5, and our
engineering judgement of anticipated traffic loads. In areas of
light automobile traffic and parking, we recommend that the
asphalt pavement section consist of 3 inches of asphaltic concrete
overlaying 4 inches of Class 2 aggregate base, compacted to at
least 95% relative compaction, as evaluated by ASTM D1557-78. For
areas where heavy loads are anticipated, reinforced concrete pads
should be utilized. All drainage swales and crosspans should be
constructed with concrete.
SURFACE DRAINAGE
The ground surface surrounding the proposed building should
be sloped to drain in all directions for a minimum of 10 feet away
from the improvements. Roof downspouts and drains should be
discharged a minimum of 10 feet from the existing foundation, and
well beyond the limits of all backfill. Surface area drains
should be provided as necessary to keep water away from ponding,
and maintain adequate surface flow. If gutters are not used,
erosion protection should be provided the drip line under all
roof overhangs. Parking areas should be designed to drain
adequately. Curbs, gutters, and cross-gutters should be utilized
to facilitate drainage.
1
at
MSCELLANE OUS
It should be noted that no structure or slab should be
expected to remain totally free of cracks and minor signs of
cosmetic distress. The flexible nature of wood and and steel I
Job NO. 90-365
Page 8
structures allows them to respond to movements resulting from
minor unavoidable settlement of fill or natural soils or the
swelling of clay soils or the motions induced from seismic
activity. All of the above can induce movement that frequently
results in cosmetic cracking of brittle wall surfaces such as
stucco or interior plaster or interior brittle slab finishes.
Data for this report was derived from surface observations at
the site, knowledge of local conditions, and observation of the
soils exposed in two exploratory test pits. The recommendations
presented in this report are based on the limited soils exposed at
this site and the behavior of structures at neighboring similar
sites. We believe that this information gives a high degree of
reliability for anticipating the behavior of the proposed
improvements and structure: however, our recommendations are
professional opinions and cannot control nature, nor can they
assure the soils profiles beneath 'those or adjacent to those
observed. Therefore, no warranties of the accuracy of these
recommendations beyond the limits of the obtained data is herein
implied or expressed. This report is based on the investigation
at the described site and on the specific anticipated construction
as stated herein. If either of these conditions are changed, the
results would also most likely change.
Man made or natural changes in the conditions of a property
can also occur over a period of time. In addition, changes in
requirements due to state of the art knowledge and/or legislation,
do from time to time occur. As a result, the findings of this
report may become invalid due to these changes. Therefore this
Page 9
Job NO. 90-365
report for the, specific site is subject to review and not
considered valid after a period of two years or if conditions as
stated above are altered.
It is the responsibility of the owner or his representative
to insure that the information in this report be incorporated into
the plans and/or specifications and construction of the project.
It is advisable that a contractor familiar with construction
details generally utilized due to the local geotechnical and
seismic conditions be retained to build the structure.
If you have any questions regarding this report, or if we can
be of further service, please do not hesitate to contact us. We
hope this report provides you with the necessary information to
continue with the development of the project.
Very truly yours,
ACCUTECH ENGINEERING SYSTEMS, INC.
Robert ‘5. Randall President California RGEb000707
RJR/dh
,
. ._ .. :. ,. . *C... ... . - . .-
Job NO. 90-365
Page 10
W
SAND, silty, slightly clayey, loose, organic roots, tan to brown, dry TOPS011
SAND, silty, brown, slightly moist, medium dense, some
root hairs and roots to 3/8"
at 18" to 2'
RESIDUA1
SAND, silty, brown to orange brown, slightly moist, firm, weakly cemented
FORMATIONAI
5
7
-
7
0
-
uc=1 . 0
uc4.5
(Jatum: M.S.L. I Groundwater depth:
hlevation: r. 84.5 feet (Site Plan)
Logged by:
-----------------+--------------+----------- +-
location: S. side of lot behind) Field existing house
--f-----------------------------
JS Field description
:S I and classification: --+-----------------------------
:M SAND, silty, brown to dark iP brown, root hairs, organic
)L TOPSOIL
iM SAND, silty, brown, slightly iP moist, medium dense, some root hairs and roots to 3/88' at 18" to 2f
RESIDUAL
iM SAND, silty, brown to orange SP brown, slightly moist, firm, weakly cemented
FORMTLTIONAL
----
rid
.---
Mise. .------
.------
rc=o .5
JC=l .5
1 Value 81
JC=4.0
-------
iolic Church
QRADINQ SPECIFICATIONS
Suggested Specifications for Placement of Compacted
Earth Fill and/or Backfill
APe€t&u&
QRADINQ BPECIFICATION8
Suggested Sp ciflcations for Placement of Compa Earth Fill and/or Backfills
QENERAL
ted
It is advisable that a soils engineer be on site to provide observation during filling and grading operations and shall be the owner’s representative to inspect placement of all compacted fill and/or backfill on the project. The soils engineer shall inspect all earth materials prior to their use, plus the methods of placing, and the degree of compaction obtained.
WTERIAL(I
Soils used for all compacted fill and backfill shall be approved by the soils engineer prior to their use. No material, including rock, having a maximum dimension greater than 6 inches shall be placed In any structural fill. Any fill containing rock should be carefully mixed to avoid nesting and creation of voids. In no case shall organic material be used as a fill and/or backfill material.
All topsoil, vegetation (including trees and brush), timber, debris, rubbish, and other unsuitable material shall be removed to a depth satisfactory to the soils engineer and disposed of by - suitable means before beginning preparation of the subgrade. The subgrade surface of the area to be filled shall be scarified to a minimum depth of 6 Inches, moistened or dried as necessary, and compacted in a manner specified below for the subsequent layers of fill. Fill shall not be placed on muddy ground. -
- IuGxN!3€ILll
No organic or other unsuitable material shall be placed in the fill, and no flll shall be placed during unfavorable weather conditions, which will be adverse to the fill placement. All clods shall be broken into small pieces, and distribution of material in the fill shall be such as to preclude the formation of - lenses of matertal differing from the surrounding material. The materials shall be delivered to and spread on the fill surface in a manner which will result in a uniformly compacted fi.11. Each
- layer shall be thoroughly mixed during spreading to insure
-
-1-
,-
uniformity of material and moisture in each layer. Prior to
compacting, each layer shall have a maximum thickness of 8 to 10 inches, and its upper surface shall be approximately horizontal.
Each successive 8 to 10 inch lift of fill being placed on elopes
or hillsldes should be benched Into the existing slopes, providing
good bond between the fill and existing ground.
HOfSTURECONTROL
While being compacted, the fill material in each layer shall,
as nearly as practical, contain the amount of moisture required for optimum compaction, and the moisture shall be uniform throughout the flll. If, in the opinion of the soils engineer,
the material proposed for use in the compacted fill is too wet to permit adequate compaction, it shall be dried In an acceptable manner prior to placement and compaction.
CO"
When an acceptable, uniform moisture content is obtained, each layer shall be compacted by a method acceptable to the soils
engineer and as specified in the foregoing report as determined by applicable standards. Compaction shall be performed by rolling with approved equipment, well suited to the soils being compacted.
If a sheepfoot roller le used, it shall be provided with cleaner bars attached in a manner which will prevent the accumulation of material between the tamper feet. The rollers should be designed
so that effective weight can be increased. -- -
Samples of representative fill materials to be placed shall
be furnished by the contractor to the soils englneer for deter-
mination of maximum density and optimum moisture or Relative Density for these materials. Tests for this determination will be
made using methods conformlng to requirements of ASTM D-698, ASTM
D-1557 or ASTM 0-2049. The results of these teats shall be the basis of control for all compaction effort.
DEN8ITYIEBL8
The denslty and moisture content of each layer of compacted
fill will be determined by the soils engineer in accordance with
ASTM D-1558, ASTM D-2167 or ASTM D-2922. Any material found not to comply with the minimum specified density shall be recompacted until the required density is obtained. Sufficient density tests
shall be made and submitted to support the solls engineer's
recommendations. The results of density tests will also be furnished to the owner, the project engineer, and the cqntractor
by the soils engineer.
-2-
- -
TRANSITION LOT DETAILS
EXISTING
GROUND WRFACE I
OVEREXCAVATE
AND RECOMPACT
SUITABLE MATERIAL REMOVE UNSUITABLB
MATERIAL AS D~ERMIN~ By \
THE GEOTECHNICAL
CONSULTANT,
EXISTING
GROUND SURFACE
LIMITS OF BUILDING
OVEREXCAVATE
AND RECOMPACT
1
HOT6
+--- SUITABLEMATERIAL/
AS D6TERMINED BY nlE GM)TIXHNICAL
CONSULTANT.
MORE EXTENSIVE OVEREXCAVATION AND
RECOMPACTION MAY BE RECOMENDED BY THE
GEOTECHNICAL CONSULTANT BASED ON ACTUAL FlUD CONDITIONS ENCOUNTERED. I FI#.No. A- I .
SI fi BILI~ FIU I BUTTRESS DFI.-,L
OUTLET PIPES 4.0 NONPERFORATED PIPE,
100' MAX. O.C. HORIZONTALLY, 30' MAX. O.C. VERTICALLY 1:1 OR FLATTER
SEE SUEDRAIN TRENCH
LOWEST SUBDRAIN SHOULD
BE SITUATEI) AS LOW AS POSSleLB TO AUOW SUITABLE OUW
1
KEY WIDTH
AS NOTED ON GRADING PLANS IS MIN. 6' MIN.
3f4.- l-l/2* OVERLAP
CLEANGRAVEL - &.MINm
NON PERFORATED
FILTER FABRIC
ENVELOPE (MIRAFI OWDING I4ON OR APPROVED
EQUIVALENT) OR
CALTRANS CLAM 2 PERMEABLE MATERIAL
SUBDRAIN TRENCH DETAIL
nom:
SUBDIAIN INSTALLATION SUEDRAIN PIPE SHOULD BE
INSTAUED WITH PERFORATIONS DOWN.
SUBDRAIN TTPE- SUBDRAIN TYPE SHOULD BE (PVC) OR APPROVED
EQUIVALENT. .,
SUEDRAIN SHOULD BE CONSTRUCTED ONLY ON COMPETENT
MATERIAL AS EVALUTED BY THE GU)TEMINICAL CONSULTANT.
- - DE HILL STABILITY FIU D&T. .L
EXISTING GROUND FINISHED SLDPE FACE
PROJECT I TO I LINE
FROM TOP OF SLOPE TO OUTSIDE EDC6 OF KEY
SEe TRANSITION LOT
DETAIL IF APPLICABLE
OVERBURDEN OR
COMPETENT MATERIAL
AS EVALUATED BY
THB Gw~CHNlCAL
CONSULTANT
NOTE: SUBDRAIN DETAILS AND KEY WIDTH RECOMMENDATIONS TO 86 PROVIDED BASED
ON EXPOSED SUBSURFACES CONDITIONS
KEY AND BENCHINO DETAILS
MAXIMUM
RECOMENDED SLOPE PROJECT I TO 1 LINE FROM TOE OF SLOPE
TO COMPETENT MATERIAL
EXISTING GROUND SURFACE
MATERIAL
COMPACTED
GROUND SURFACE
KEY CUT SLOPE
DEPTH
101E
BACK DRAIN MAY BE RECOMMENMDED AND/OR BENCH DIMENSION RECOMMENDATIONS MAY BE ALTERED BY
GEOTECHNICAL CONSULTANT BASED ON FIGLD CONDITIONS ENCOUNTERED.
RE INING WALL DRAINAGE DI-UL
SOIL BACKFILL, COMPACTED TO
80 PERCENT PROCTOR DENSITY
(ASTM Dl5571 /-
RETAINING WAIL
WALL WATERPROOFING PER ARCHITECTS SPECIFICATIONS
WEEP HOLES 4'-W O.C. HORIZ. AND VERTICAL FOR EXTERIOR WAUS . TYP. 3/4- I -112- CLEAN GRAVEL"
4- (MIN.) DIAMETERPERFORATED PVC PIP6 (SCHEDULE 40 OR
EQUIVAtocT) WITH PERFORATIONS
ORIENTED DOWN AS DEPlCrm MINIMUM 1 PERCENT GRADIENT TO SUITABLE OUW
COMPETENTBEDROCK OR SUITABLE MATERIAL AS EVALUAtED BV TH6 GEOTECHNICAL
SPECIFICATIONS FOR CALTRANS CONSULTANT
CLASS 2 PERMEAELEMATEAIAL
U.S STANDARD SIEVE SIZE
I'
314-
3/8. No. 4 No. 8 Ne. 30 Ne. 50 No. 200
PASSING " IF CALTRANS CLASS 2 PERMEABLE MATERIAL (SEE GRADATION TO LEFT) IS UsEb IN PLACE OF
DELETED. CALTRANS CLASS 2 PERMEABLE MAl'FAIAL SHOULD BE COMPACTED TO 90
-
too 3/4. - 1-112' GRAVeL. FILTER FABRIC MAY 813
90- 100
40- 100 2s-40 PERCENT PROCTOR COMPACTION
18-33 5-15 0-7 0-3
SAND EQUIVALENT > 75
NOT TO SCALB
- -
CANYON SUBDRAIN DETAILS
UNSUITABLE
BRAIN MATERIAL -
FILTER FABRIC ENVELOPE 6’ MIN. OVERLAP
3/4- - 1-1/2- CLEAl
3/4. - l-l/2’ CLEAN * IF CALTRANS CLASS 2 PERMEABLG MAtERlAL IS USED IN PLACE OF 3/4- I I/2’ GRAVEL. FlLWl FABRl MAY BE DELETED
GRAVEL (9C.F.I It. MI
PERFORATED
PIPE -
DESIGN FINISH SUBDRAIN
INONPERFORA~ 6- e MIN.~
nom
FOR SUBDRAIN TRENUI NOTES SEE STABILITY FILL DETAIL. I Fig. NO. A-6