HomeMy WebLinkAbout; Calavera Hills Park Geotechnical Reconnaissance; Calavera Hills Park Geotechnical Reconnaissance; 1986-10-21LEIGHTON antj ASSOCIATES
SOIL ENGINEERING GEOLOGY
TO:
ATTENTION:
SUBJECT:
GEOPHYSICS
October 21, 1986
GROUND WATER HAZARDOUS WASTES
Project No. 8850373-06
City of Carlsbad
Parks and Recreation Department
1166 Elm Avenue
Carlsbad, California 92008-1989
Mr. Mark Steyaert, Park Planner
Supplemental Geotechnical Reconnaissance and Grading Plan Review,
Caiavera Hills Park Site, Carlsbad, California .
References: (1)
(2)
(3)
"Geotechnical Investigation, Caiavera Hills Park Site, Carlsbad,
California," Project No. 4850373-02, dated July 24, 1985, by
Leighton and Associates, Inc.
"Supplemental Seismic Refraction Survey, Caiavera Hills Park
Site, Carlsbad, California," Project No. 4850373-05, dated
May 16, 1986, by Leighton and Associates, Inc.
"Grading Plans For: Caiavera Park Site {CUP-266)," Project
No. PE 2.86.16, Drawing No. 269-6, prepared at a scale of
1"=40', dated September 25, 1986, by Rick Engineering Company
Introduction
In accordance with your request and authorization, we have performed a supplemen-
tal geotechnical reconnaissance of the subject site and a geotechnical review of
the referenced revised 40-scale grading plans of the site. The purpose of this
study was to evaluate the changes in the geotechnical conditions at the site
since the time of our preliminary investigation (Reference 1), and relate these
conditions to the proposed grading and development as depicted on the revised
grading plans. In addition, we have compared the excavatability characteristics
of the metavolcanic bedrock underlying the site, as outlined in Reference 2, with
the grading plans. Since this is a supplemental investigation, this report
incorporates and supplements findings, conclusions, and recommendations presented
in the referenced geotechnical reports (References 1 and 2, above).
Accompanying Maps, Table, and Appendix
Table 1 - Seismic Refraction Survey Summary of Results
Plates 1 and 2 - Revised Geotechnical Maps - In Pocket
Appendix A - General Grading and Earthwork Specifications
5421 AVENIDA ENCINAS, SUITE 0, CARLSBAD, CALIFORNIA 92008
IRVINE < WESTLAKE/VENTURA o. DIAMOND BAR/WALNUT o SAN BERNARDINO/RIVERSIDE o
PALM DESERT o SANTA CLARITA/VALENCIA o CARLSBAD o TEMECULA/RANCHO CALIFORNIA
(619) 931-9953
SAN DIEGO
8850373-06
Scope of Investigation
fl Review the previous reports issued for the subject site (References 1 and 2).
• Geotechnical reconnaissance mapping of the site.
• Compilation and analysis of the geotechnical data acquired during our prelimi-
nary and supplemental investigations.
• Evaluation of the excavatability characteristics of the bedrock underlying the
subject site as they pertain to the revised grading plans (Reference 3).
fl Preparation of this report, including a revised geotechnical map, summarizing
our findings, conclusions, and recommendations of the geotechnical review of
the referenced grading plans.
Summary of Planned Rough Grading
Based on our review of the current project grading plans (Reference 3), we
understand the proposed rough grading will consist of cuts and fills to produce
building pads, roadways, parking areas, and recreational areas for a proposed
park site/community center. Comparison of the interim grading plans, approved
April 30, 1986, with the revised grading plans (Reference 3) indicates that the
overall design grades, as shown on the referenced grading plans, have been raised
approximately 3 to 4 feet.
During rough grading, we understand that areas of the site which are to be
excavated (excluding cut slopes) will be undercut a minimum of 2.5 feet, with
building pad areas to be undercut a minimum of 3.0 feet. These undercut areas
are to be brought to proposed finish grades with properly compacted fill. The
revised grading plans indicate that grading of the site will require fills up to
approximately 36 feet above existing grades. Proposed excavations range from
approximately 2.5 feet in the vicinity of the proposed cut/fill transition line
to approximately 12.5 feet (including undercut) near the toe of the proposed 2:1
(horizontal to vertical) cut slope located west of the existing Glasgow Drive,
corresponding approximately to Station 43+35 (Reference 3).
Communications with Mr. Mark Steyaert, Park Planner (City of Carlsbad), indicate,
at present, two alternate grading plans are proposed once the site is excavated
to undercut subgrades. Alternate Plan I would bring the entire site to proposed
finish grade with properly compacted fill. Alternate Plan II would bring the
southern portion of the site to finish grade, leaving the northern portion of the
site for completion at a future date.
LEIGHTON and ASSOCIATES
INCORPORATED
8850373-06
Summary of Existing Geotechnical Conditions
The subsurface geologic conditions are described in detail within the preliminary
and supplemental geotechnical reports (References 1 and 2). In summary, the site
is predominantly underlain by dense, metavolcanic bedrock locally mantled by
potentially compressible fill soils, debris, alluvium, and residual soils of
various thickness. Please refer to the attached Plates 1 and 2 (Revised
Geotechnical Map) for the distribution of the various units encountered during
our reconnaissance mapping performed on October 8, 1986. Based on the results of
our reconnaissance, mapping, two predominant changes pertinent to the proposed
development were noted at the site since our preliminary and supplemental
investigations. These consist of additional end-dumped debris fill, and fill
placed along the existing Glasgow Drive and Elm Avenue. These two items are
discussed below.
« Debris Fill -^^
In addition to previously mapped end-dumped and debris fill areas, several new
areas of end-dumped fill and debris fill were noted. These materials are not
considered reusable as fill material and should be completely removed from the
site and disposed of properly prior to the commencement of grading.
• Roadway Fill ^
In addition to previously mapped fill, fill sojls were mapped in the north and
northeastern portions of the subject site. This^fill appears to be associated
with the relatively recent construction of Glasgdw-D.riye and Elm Avenue along
the eastern and northern portions of the subject property boundary,
respectively. Comparison of the geotechnical map presented in the referenced
report with the referenced grading indicates that fills up to approximately
17 feet and 31 feet deep were placed along the southern edge of the existing
Elm Avenue, corresponding to the approximate Stations 71+46 and 70+00
(Reference 3), respectively. Please refer to the recommendations contained
herewith should structural improvements be planned for these areas underlain
by fill soils. These fills were not placed under the observation and testing
performed by a representative of Leighton and Associates, Inc. as outlined in
Section 7.10 of the preliminary geotechnical report. Therefore, these fill
areas are not considered in conformance with recommendations presented in the
report. Subsequently, the revised grading pians^.(Reference 3), from a
geotechnical standpoint, are not considered in conformance with the geotechni-
cal recommendations of our report dated July 24, 1986.
fl Rock Excavatability
Based on our review of the referenced grading plans and interpretation of the
seismic refraction data acquired during our preliminary and supplemental
investigations (References 1 and 2), it is our opinion that the majority of
the site may be generally rippable by heavy conventional construction
equipment, except for the proposed cut slope and adjacent proposed cut areas
along the western edge of Glasgow Drive (located approximately between
Station 43+00 north and Station 44+45). The interpreted seismic velocities of
seismic traverse Line 8, performed during our supplemental investigation,
indicate blasting will likely be required to reach proposed design subgrade
near the vicinity of the proposed cut slope.
- 3 -
LEIGHTON and ASSOCIATES
INCORPORATED
8850373-06
The approximate locations of the seismic traverses performed during the
preliminary and supplemental investigations (L-1 through L-8) are illustrated
on the Revised Geotechnical Map, Plate 1. A summary of the seismic refraction
survey data and interpretation for seismic traverse Lines 1 through 8 is
presented in Table 1. Table 1 includes the anticipated rippability charac-
teristics of the metavolcanic bedrock. These rippability i:haracteristics are
based on the seismic velocity charts developed by the Caterpillar Tractor
Company as referenced on Table 1. Because of the variable depths of the
weathered bedrock encountered during our previous investigations, local
anomalies of hard, nonrippable bedrock may be encountered at or near ground
surface which may require blasting within the generally rippable area. In
addition, seismic refraction surveys do not allow for predicting a percentage
of expectable oversize or hardrock floaters. Subsurface variations in the
degree of weathered rock to fractured rock are not accurately predictable.-
Conclusions and Recommendations
Based on the results of our preliminary and supplemental investigations of the
site, it is our opinion that the proposed development is feasible from a geotech-
nical standpoint, provided the recommendations of this report are implemented
during the grading and subsequent construction phases of the project.
The following summarizes our specific recommendations pertinent to grading of the
site. The General Earthwork and Grading Specifications included in Appendix A
should also be utilized where applicable. In addition, all other recommendations
stated in the above-referenced geotechnical reports are.still applicable.
• Erosion Control
In general, the erosion potential at the site is considered low to moderate.
Provisions for site drainage, sediment retention structures, brow ditches,
slope plantings, and other measures in accordance with the City of Carlsbad
. Gratiing Ordinance and Section 7.7 and 7.8 of the referenced geotechnical
report (Reference 1) should provide adequate erosion protection. Local areas
may require additional measures at the purview of the Civil Engineer.
fl Subdrainage
In order to reduce the potential of ground water accumulation, we recommend
that a subdrain be installed at the bottom of the existing temporary access
road, in accordance with the subdrain details presented in Appendix A. The
approximate location of the proposed subdrain is depicted on Plate 1.
fl Existing Roadway Fill
As previously mentioned, fill apparently placed during the construction of Elm
Avenue and Glasgow Drive is present on the site (see Plate 1). The compaction
and moisture content of these fill soils, or presence of a subdrain system,
were not known at the time of the preparation of this report. In addition,
the nature of removals or ground preparation beneath the fill was also not
known. Therefore, the following two alternative recommendations are provided
as possible measures to mitigate the presence of these fill soils on the site.
LEIGHTON and ASSOCIATES
INCORPORATED
8850373-06
- Designation of Nonstructural Fill Areas
Areas underlain by roadside fill may be designated as nonstructural areas.
Should this option be chosen, we recommend that no structural improvements,
including buildings, utilities, and/or structural fill,,be placed atop the
existing roadside fill.
- Geotechnical Evaluation of Roadside Fill
If the designation of areas of the site underlain by the previously
mentioned roadside fill as nonstructural areas is considered impractical,
we recommend that these fill areas be fully evaluated by an appropriate
geotechnical investigation. This should include a review of project plans
and an as-graded report associated with the placement of the roadside fill,
an appropriate subsurface exploration program, pertinent laboratory
testing, and geotechnical data analysis to access the engineering charac-
teristics of the roadside fill as it pertains to the proposed development
of the site. A proposal outlining the anticipated scope of services and
estimated costs required for this investigation can be provided upon your
request.
fl Construction Observation
The recommendations provided herein are based on surface and subsurface
conditions encountered in our investigations and their effects on the proposed
development. All removals, fill placements, trench excavations, and backfill
should be observed by a representative of this firm so that construction is in
accordance with our recommendations.
If you have any questions regarding our report, please do not hesitate to contact,
this office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
Ahmad Ghazinoor, RCE 34692
Project Geotechnical Engineer
Rodney J.'We'ick, CEG 1094
Chief Engineering Geologist
RLW/AG/RW/lj
Distribution: (4) Addressee
(2) Rick Engineering Company
Attention: Mr. Barry Bender
(2) Recreation Systems, Inc.
Attention: Mr. Rod Barrette
LEIGHTON and ASSOCIATES
INCORPORATED
8850373-06
TABLE 1
SEISMIC REFRACTION SURVEY SUMMARY OF RESULTS
Velocity of
Line . Layers (ft./sec.)
1 2,500 - 3,750
12,500
Inferred Geologic
Materials
Weathered metavolcanic
bedrock
Fresh metavolcanic
bedrock
Estimated
Thickness
(ft.)
Estimated Depth
To Top of
Layers (ft.)
Rippability Potentials*/
Comments
D-8L; Local hard anomalies
and/or an irregular surface
between weathered and fresh
bedrock should be antici-
pated. Blasting may be re-
quired locally.
Requires blasting
2,300 - 4,300
7,000 - 8,500
Residual soil and
weathered metavolcanic
bedrock
Fresh metavolcanic
bedrock
D-8L
Very marginally rippable
with a D-10, depending on
jointing pattern and extent
of jointing or fracturing.
Blasting is likely.
1,250 - 1,500
3,000 - 4,500
8,000
Residual soil
Weathered metavolcanic
bedrock
Fresh metavolcanic
bedrock
0-5
11-20 0-5
20-25
D-7G
D-8L; Nonrippable, local
anomalies may exist near
transition to fresh meta-
volcanic bedrock.
Very marginally rippable
with a D-10. Blasting is
likely.
Caterpillar Tractor Company, 1985, Caterpillar Performance?'Handbook, Edition 16, dated October, pp. 71-74.
8850373-06
TABLE 1 (continued)
Velocity of
Line Layers (ft./sec.)
4 1,800
6,300
Inferred Geologic
Mater ial s
Residual soil
Sligthly weathered
metavolcanic bedrock
Estimated
Thickness
(ft.)
3-8
Estimated Depth
To Top of
Layers (ft.)
0
3-8
Rippability PotentiaTs*/
' Comments
D-7G
D-8L; Local anomoliesof
nonrippable metavolcanics
may be encountered.
1,600
3,400
8,200
Residual soil
Moderately weathered
metavolcanic bedrock
Relatively unweathered
metavolcanic bedrock
5
11
0
5
16
D-7G
D-7G
Very marginally rippable
with a D-IOL. Blasting isr
likely; see Line 2.
1,500
2,500
6,600
Residual soil
Weathered metavolcanic
bedrock
Relatively unweathered
metavolcanic bedrock
5-7
10
0
5-7
15-17
D-7G
D-7G
D-8L/D-9L; see Line 4.
2,100
4,500
2.800
9,300
Weathered metavolcanic
bedrock
Moderate to slightly
weathered metavolcanic
bedrock
Weathered metavolcanic
bedrock
Relatively unweathered
metavolcanic bedrock
10
0
7
0
10
D-7G
D-8L
D-7G
Requires blasting
APPENDIX A
LEIGHTON and ASSOCIATES
INCORPORATED
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
1.0 General Intent
These specifications present general procedures and requirements for
grading and earthwork as shown on the approved grading plans, including
preparation of areas to be filled, placement of fill, installation of
subdrains, and excavations. The recommendations contained in the
geotechnical report are a part of the earthwork and grading specifica-
tions and shall supersede the provisions contained hereinafter in the
case of conflict. Evaluations performed by the consultant during the
course of grading may result in new recommendations which could
supersede these specifications or the recommendations of the geotechni-
cal report.
2.0 Earthwork Observation and Testing
Prior to the commencement of grading, a qualified geotechnical consult-
ant (soils engineer and engineering geologist, and their
representatives) shall be employed for the purpose of observing
earthwork procedures and testing the fills for conformance with the
recommendations of the geotechnical report and these specifications.
It will be necessary that the consultant provide adequate testing and
observation so that he may determine that the work was accomplished as
specified. Tt shall be the responsibility of the contractor to assist
the consultant and keep him apprised of work schedules and changes so
that he may schedule his personnel accordingly.
It shall be the sole responsibility of the contractor to provide
adequate equipment and methods to accomplish the work in accordance
with applicable grading codes or agency ordinances, these specifica-
tions, and the approved grading plans. If, in the opinion of the
consultant, unsatisfactory conditions, such as questionable soil, poor
moisture condition, inadequate compaction, adverse weather, etc., are
resulting in a quality of work less than required in these specifica-
tions, the consultant will be empowered to reject the work and
recommend that construction be stopped until the conditions are
rectified.
Maximum dry density tests used to determine the degree of compaction
will be performed in accordance with the American Society for Testing
and Materials test method ASTM D1557-78.
3.0 Preparation of Areas to be Filled
3.1 Clearing and Grubbing: All brush, vegetation and debris shall be
removed or piled and otherwise disposed of.
3.2 Processin^j_ The existing ground which is determined to be
iaffsTactory for support of fill shall be scarified to a minimum
depth of 6 inches. Existing ground which is not satisfactory
shall be overexcavated as specified in the following section.
Scarification shall continue until the soils are broken down and
free of large clay lumps or clods and until, the working surface is
reasonably uniform and free of uneven features which would inhibit
uniform compaction.
3.3 Overexcavation: Soft, dry, spongy, highly fractured or otherwise
unsuitable ground, extending to such a depth that surface process-
ing cannot adequately improve the condition, shal1 be
overexcavated down to firm ground, approved by the consultant.
3.4 Moisture Conditioning: Overexcavated and processed soils shall be
watered, dried-back, blended, and/or mixed, as required to attain
a uniform moisture content near optimum.
3.5 Recompaction: Overexcavated and processed soils which have been
properly mixed and moisture-conditioned shall be recompacted to a
minimum relative compaction of 90 percent.
3.6 Benching: Where fills are to be placed on ground slopes steeper
than 5:1 (horizontal to vertical units), the ground shall be
stepped or benched. The lowest bench shall be a minimum of
15 feet wide, shall be at least 2 feet deep, shall expose firm
material, and shall be approved by the consultant.. Other benches
shall be excavated in firm material for a minimum width of 4 feet..
Ground sloping flatter than 5:1 shall be benched or otherwise
overexcavated when considered necessary by the consultant.
3.7 Approval: All areas to receive fill, including processed areas,,
removal areas and toe-of-fill benches shall be approved by the
consultant prior to fill placement.
4.0 Fill Material
4.1 General: Material to be placed as fill shall be free of organic
matter and other deleterious substances, and shall be approved by
the consultant. Soils of poor gradation, expansion, or strength
characteristics shall be placed in areas designated by the
consultant or shall be mixed with other soils to serve as satis-
factory fill material.
I
I 4.2 Oversize: Oversize material defined as rock, or other irreducible
material with a maximum dimension greater than 12 inches, shall
not be buried or placed in fills, unless the location, materials,
and disposal methods are.specifically approved by the consultant.
Oversize disposal operations shall be such that nesting of
oversize material does not occur, and such that the oversize
material is completely surrounded by compacted or densified fill.
Oversize material shall not be placed within 10 feet vertically of
finish grade or within the range of future utilities or under-
ground construction, unless specifically approved by the
consultant.
4.3 Import: If importing of fill material is required for grading,
the import material shall meet the requirements of Section 4.1,
5.0 Fill Placement and Compaction
5.1 fill Lifts: Approved fill material shal1 . be placed in areas
prepared to receive fill in near-horizontal layers not exceeding
6 inches in compacted thickness. The consultant may approve
thicker lifts if testing indicates the grading procedures are such
that adequate compaction is being achieved with lifts of greater
thickness. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to attain uniformity of material
and moisture in each layer.
5.2 Fi 1 l_Mo2sture: Fill layers at a moisture content less than
opfmium shall be watered and mixed, and wet fill layers shall be
aerated by scarification or shall be blended with drier material.
Moisture-conditioning and mixing of fill layers shall be blended
with drier material. Moisture-conditioning and mixing of fill
layers shall continue until the fill material is at a uniform
moisture content at or near optimum.
5.3 Compaction of Fill: After each layer has been evenly spread,
moisture-conditioned, and mixed, it shall be uniformly compacted
to not less than 90 percent of maximum dry density. Compaction
equipment shall be adequately sized and shall be either specifi-
cally designed for soil compaction or of proven reliability, to
efficiently achieve the specified degree of compaction.
5.4 Fill Slopes: Compacting of slopes shall be accomplished, in
addition to normal compacting, procedures, by backrolling of slopes
with sheepsfoot rollers at frequent increments of 2 to 3 feet in
fill elevation gain, or by other methods producing satisfactory
results. At the completion of grading, the relative compaction of
the slope out to the slope face shall be at least 90 percent.
5.5 Compaction Testing: Field tests to check the fill moisture and
degree of compaction will be performed by the consultant. The
location and frequency of tests shall be at the consultant's
discretion. In general, the tests will be taken at an interval
not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of
embankment. In addition, on slope faces, at least one test shall
be taken for each 5,000 square feet of slope face and/or each
10 feet of vertical height of slope.
6.0 Subdrain Installation .
Subdrain systems, if required, shall be installed in approved ground to
conform to the approximate alignment and details shown on the plans or
herein. The subdrain location or materials shall not be changed or
modified without the approval of the consultant. The consultant,
however, may recommend and upon approval, direct changes in subdrain
line, grade or material. All subdrains should be surveyed for line and
grade after installation and sufficient time shall be allowed for the
surveys, prior to commencement of filling over the subdrains.
7.0 Excavations
Excavations and cut slopes will be examined during grading. If
directed by the consultant, further excavation or overexcavation and
refilling of cut areas shall be performed, and/or remedial grading of
cut slopes shall be performed. Where fill-over-cut slopes are to be
graded, unless otherwise approved, the cut portion of the slope shall
be made and approved by the consultant prior to placement of materials
for construction of the fill portion of the slope.
TRANSITION LOT DETAILS
CUT-FILL LOT
NATURAL GROUND
' TT — ^ \ I OVEREXCAVATE AND RECOMPACT
UNWEATHERED BEDROCK OR
MATERIAL APPROVED BY
I THE GEOTECHNICAL CONSULTANT
CUT LOT
NATURAL GROUND
REMOVE.
UNSUITABLE
MATERIAL
.1.
5' L-
MIN'. Ij i
" — ^j^:^- X- ^^sv/N- —
MIN.
• COMPACTED ----J?^--.
-T-JilLL 7^ OVEREXCAVATE AND RECOMPACT
UNWEATHERED BEDROCK OR
MATERIAL APPROVED BY 1
f THE GEOTECHNICAL CONSULTANT
NOTE:
Deeper overexcavation and recompaction shall be performed,
if determined to be necessary by the geotechnical consultant.
SIDE HILL
CUT PAD DETAIL
NATURAL
GROUND >-•
FINISHED CUT PAD
OVEREXCAVATE
AND RECOMPACT
(REPLACEMENT
OVERBURDEN —i
OR UNSUITABLE
MATERIAL
Pad overexcavation and recompaction
shall be performed if determined to
be necessary by the geotechnical
consultant.
UNWEATHERED BEDROCK OR "
MATERIAL APPROVED BY —
THE GEOTECHNICAL CONSULTANT
SUBDRAIN AND KEY WIDTH REQUIREMENTS
DETERMINED BASED ON EXPOSED SUBSURFACE
CONDITIONS AND THICKNESS OF OVERBURDEN
BENCHING DETAILS
FILL SLOPE
PROJECTED PLANE
I lo I maximum from toe
of slope to approved ground
COMPACTED -".SLr-
- -FILL
REMOVE
NATURAL
GROUND
« I V Typical' UNSUITABLE
y^JTS^^jrlzq''^^'" X MATERIAL
BENCH
HEIGHT
I 5-MIN. J
OWEST BENCH H
DEPTH (KEY)
FILL-OVER-CUT SLOPE
REMOVE.
UNSUITABLE
MATERIAL
NATURAL
GROUND \^ ^^^^s^jrjrjS^x^^'^^
, ly MIN.—-J
LOWEST BENCH
/CfCOMPACTED .-_-_-.;i.-r
4' Typical
BENCH
HEIGHT |»-BENCH*j
CUT
FACE
To be consTiTjcted prior
to fill placement
CUT-OVER-FILL SLOPE
CUT FACE
To Be Constructed Prior to Fill Placement
NATURAL GROUND
OVERBUILD t TRIM BACK
PROJECT PLANE
1 to I maximuxn fram^^
toe of slope to
approved
ground
^BENCH HEIGHT
'viilH.l 15' HIN. _J
HEY ~LOWEST BENCH"
DEPTH <'^E'')
NOTES:
LOWEST BENCH : Depth and width subject to field change
based on consultant's inspection.
SUBDRAINAGE: Back drains may be required at the
discretion of the geotechnical consultant.
ROCK DISPOSAL DETAIL
FINISH GRADE
SLOPE
FACE
GRANULAR SOIL
To fill voids,
densified by
flooding
PROFILE ALONG WINDROW
CANYON SUBDRAIN DETAIL
BENCHING
REMOVE
UNSUITABLE
MATERIAL
SUBDRAIN TRENCH
SEE ALTERNATES A&B
SUBDRAIN Perforated Pipe Surrounded With
ALTERNATE A: Filter Material
FILTER MATERIAL-
S'
FILTER MATERIAL
Filter material snail be
Class 2 permeable material
per State of Calitornia
Standard Specifications,
or approved alternate.
Class 2 grading as follows:
•PERFORATED PIPE'
6" 0 MIN.
SIEVE SIZE PERCENT PASSING
1* - 100
3/4* 90-100
3/8* . 40-100
No. 4 25-40
No. 8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3
SUBDRAIN 1 1/2" Gravel Wrapped
ALTERNATE B: in Filter Fabric
6" MIN. OVERUP
DETAIL OF CANYON SUBDRAIN TERMINAL
DESIGN FINISHED GRADE-
FILTER FABRIC (MIRAFI luo OR APPROVED EQUIVALENT)
OR APPROVED
EQUIVALENT)
I VMAX.GRAVEL OR-^»»e'-"a«« ^
APPROVED EQUIVALENT
9 ft. ^/ft.
MAX.OPEN CRAOEO
GRAVEL OR APPROVED
EQUIVALENT
• SUBDRAIN INSTALLATION - Subdrain pipe shall be installed with perforations down or,
at locations designated by the geotechnical consultant, shall be nonperforated pipe.
• SUBDRAIN TYPE - Subdrain type shall be ASTM C508 Asbestos Cement Pipe (ACP)
or ASTM D275I, SDR 23.5 or ASTM DI527, Schedule 40 Acrylonitrile Butadiene Styrene
(ABS) or ASTM D3034 SDR 23.5 or ASTM DI785, Schedule 40 Polyvinyl Chloride Plastic
(PVC) pipe or approved equivalent.
SLOPE BUTTRESS OR
REPLACEMENT FILL DETAIL
OUTLET PIPES
4" D Nonperforated Pipe,
100' Max. O.C. Horizontally,
30' Max. O.C. Vertically
FILL BLANKET
30" MIN.
BACK CUT
1:1 OR FLATTER
BENCHING
RLTER MATERIAL
Filter material, shall be
Class 2 permeable material
per State of California
Standard Specifications,
or iapprov6d alternate.
Class 2 grading as follows:
SIEVE SIZE PERCENT PASSING
DETAIL A-A'
NOTES:
• Fill blanket, back cut, key width and
key depth are subject to field change,
per report/plons.
• Key heel subdrain, blanket drain, or
vertical drain may be required at the
discretion of the geotechnical consultant
• SUBDRAIN INSTALLATION - Subdrain
pipe shall be installed with perforations
down or, at locations designated by
the geotechnical consultant, shall be
nonperforated pipe.
• SUBDRAIN TYPE - Subdroin type shall
be ASTM C508 Asbestos Cement Pipe
(ACP) or ASTM D275I, SDR 23.5 or ASTM
DI527, Schedule 40 Acrylonitrile Butadiene
Styrene (ABS) or ASTM D3034 SDR 23.5
or ASTM DI785, Schedule 40 Polyvinyl
Chloride Plostic (PVC) pipe or approved
equivalent.
1"
3/4-
3/8'
No. 4
No. 8
No. 30
No. 50
No. 200
100
90-100
40-100
25-40
18-33
5-15
0-7
0-3
DETAIL OF BUTTRESS SUBDRAIN TERMINAL
DESIGN FINISHCO CAAOC-
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SPECIFICATIONS FOR CLASS 2
PERf^EABLE MATERIAL
(CALTRANS SPECIFICATIONS)
Sieve Size % Passing
1" 100
3/4" . 90-100
3/8" 40-100
No. 4 25-40
No. 8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3 Soil Backfill, Conpacted to
90 percent relative density^
i
Class 2 Permeable Filter
aterial, Compacted to
90 percent relative density*
1' minimum
Wall Footing
6" Diameter perforated
PVC pipe (schedule 40
or equivalent). Minimum
1 percent gradient to
suitable outlet
Minimum 6" layer of
filter rock beneath
pipe
•Based on ASTM D1557- 82