HomeMy WebLinkAboutCT 02-14-04; BRESSI RANCH PA 9 UNIT 4; INTERIM AS-GRADED REPORT OF ROUGH; 2004-04-27INTERIM AS-GRADED REPORT OF ROUGH AND FINE GRADING,
MODEL LOT COMPLEXES AND PHASE 1 LOTS,
LOTS 1 THROUGH 13, 30 THROUGH 34, 55 THROUGH 63, 112,
127 THROUGH 143, 156 THROUGH 159, 169 THROUGH 172,
180 THROUGH 193, 263 THROUGH 272, 281 THROUGH 284,
374 THROUGH 377, 380 THROUGH 383, 404 THROUGH 411,
427 THROUGH 443, AND 448 THROUGH 452,
PLANNING AREAS PA-6 THROUGH PA-10 AND PA-12,
BRESSI RANCH, CARLSBAD TRACT NO. 00-06, CARLSBAD, CALIFORNIA
Prepared for:
LENNAR COMMUNITIES
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Project No. 971009-014
April 27, 2004
Leighton and Associates, Inc.
M-9
A LEIGHTON GROU P C O W P A N Y
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Leighton an(d Associates, Inc.
A LEIGHTON GROUP COMPANY April 27, 2004
ProjectNo. 971009-014
To: Lennar Communities
1525 Faraday Avenue, Suite 300
Carlsbad, Califomia 92008
Attention: Ms. Kristine Zortman
Subject: Interim As-Graded Report of Rough and Fine Grading, Model Lot Complexes and
Phase 1 Lots, Lots 1 Through 13, 30 Through 34, 55 through 63, 112, 127 Through
143, 156 Through 159, 169 Through 172, 180 Through 193, 263 Through 272, 281
Through 284, 374 Through 377, 380 Through 383, 404 Through 411, 427 Through
443, and 448 Through 452, Planning Areas PA-6 through PA-10 and PA-12, Bressi
Ranch, Carlsbad Tract No. 00-06, Carlsbad, Califomia
In accordance with the request and authorization of representatives of Lennar Communities, we
have performed geotechnical services during the rough and fme grading operations for the
residential model lot complexes and Phase 1 production lots at the Bressi Ranch project (Carlsbad
TractNo. 00-06), located in Carlsbad, Califomia. The model lot complexes and Phase 1 production
lots include Lots 1 through 13, 30 through 34, 55 through 63, 112, 127 through 143, 156 through
159, 169 through 172, 180 through 193, 263 through 272, 281 through 284, 374 through 377, 380
through 383, 404 through 411, 427 through 443, and 448 through 452 of Planning Areas PA-6
through PA-10 and PA-12.
The accompanying interim as-graded report summarizes our geotechnical observations, field and
laboratory test results, and the geotechnical conditions encountered during the rough and fme
grading operations for the subject lots. In addition, the accompanying report presents our
geotechnical conclusions and recommendations conceming the post grading and constmction
phases for the model lot complexes and Phase 1 production lots. The geotechnical information
presented herein, along with a field density test summary and geotechnical map will be presented in
the fmal as-grade reports that are currently being prepared for each of the residential planning areas.
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongeo.com
971009-014
TABLE OF CONTENTS
Section £age
1.0 INTRODUCnON 1
1.1 PROJECT DESCRIPTION 1
2.0 SUMMARY OF ROUGH AND FINE GRADING OPERATIONS 2
2.1 SITE PREPARATION AND REMOVALS 2
2.2 SUBDRAINS 2
2.3 BUTTRESS AND STABililY FILL i<EYS 3
2.4 FILL SLOPE KEYS 4
2.5 CUT/FILL TRANsmoNCONDmoNS 4
2.6 OVEREXCAVATION OF BLOCKY WELL-CEMENTED SANTIAGO FORMATION 4
2.7 OVEREXCAVATION OF HIGH TO VERY HIGH EXPANSIVE FORMATIONAL MATERIAL 5
2.8 PLACEMENT OF OVERSIZED MATERIAL 5
2.9 FILL PLACEMENT AND COMPACTION 5
2.10 FIELD DENSITY TESTING 6
2.11 LABORATORY TESTING 6
2.12 SETTLEMENT MONUMENT MONirORING OF DEEP FILLS 7
2.13 GRADED SLOPES 7
3.0 ENGINEERING GEOLOGIC SUMMARY 8
3.1 AS-GRADED GEOLOGIC CONDmONS 8
3.2 GEOLOGIC UNITS 8
3.2.1 Undocumented Fill Soils (Map Symbol - Afu) 8
3.2.2 Topsoil 8
3.2.3 Alluvium/Coiluvium, Undifferentiated 9
3.2.4 Landslide Deposits 9
3.2.5 Santiago Formation 10
3.3 GEOLOGIC STRUCTURE 10
3.4 FAULTING AND SEISMIOTY 10
3.5 GROUNDWATER 11
3.6 EXPANSION AND SULFATE CONTENT TESTING OF REPRESENTATIVE FINISH GRADE SOILS 12
4.0 CONCLUSIONS 13
4.1 GENERAL 13
4.2 SUMMARY OF "CONCLUSIONS 13
5.0 RECOMMENDATIONS 16
5.1 EARTHWORK 16
5.1.1 Site Preparation 16
5.1.2 Excavations 16
5.1.3 Fill Placement and Compaction 17
5.2 RESIDENTIAL FOUNDATION DESIGN CONSIDERATIONS 17
5.2.1 Moisture Conditioning 20
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TABLE OF CONTENTS (Continued)
5.2.2 Seismic Design Parameters 20
5.2.3 Foundation Setback 21
5.2.4 Anticipated Settlement 22
5.3 LATERAL EARTH PRESSURES 22
5.3 LATERAL EARTH PRESSURES 22
5.4 FENCES AND FREESTANDING WALLS 24
5.5 CONCRETE 25
5.6 SLOPE MAINTENANCE GUIDELINES 26
5.7 CONTROL OF SURFACE WATER AND DRAINAGE 26
5.8 LANDSCAPING AND POST-CONSTRUCTION 27
5.9 CONSTRUCTION OBSERVATION AND TESTING 28
6.0 LIMITATIONS 29
TABLES
TABLE 1 - LOT-BY-LOT SUMMARY OF AS-GRADED GEOTECHNICAL CONDmONS - REAR OF TEXT
TABLE 2 - POST-TENSIONED FOUNDATION DESIGN RECOMMENDATIONS - PAGE 18
TABLE 3 - PRESOAKING RECOMMENDATIONS BASED ON FINISH GRADE SOIL EXPANSION POTENTIAL •
PAGE 20
TABLE 4 - MINIMUM FOUNDATION SETBACK FROM SLOPE FACES - PAGE 22
TABLE 5 - LATERAL EARTH PRESSURES - PAGE 23
APPENDICES
APPENDIX A - REFERENCES
APPENDIX B - LABORATORY TESTING PROCEDURES AND TEST RESULTS
APPENDIX C - GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING
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1.0 INTRODUCnON
In accordance with the request and authorization of representatives of Lennar Communities, we
have performed geotechnical services during the rough and fine grading operations for the
residential model lot complexes and Phase 1 production lots at the Bressi Ranch project
(Carlsbad Tract No. 00-06), located in Carlsbad, Califomia. The model lot complexes and Phase
1 production lots include Lots 1 through 13, 30 through 34, 55 through 63, 112, 127 through 143,
156 through 159, 169 through 172, 180 through 193, 263 through 272, 281 through 284, 374
through 377, 380 through 383, 404 through 411, 427 through 443, and 448 through 452 of
Planning Areas PA-6 through PA-10 and PA-12.
This interim as-graded report summarizes our geotechnical observations, field and laboratory test
results, and the geotechnical conditions encountered during the rough and fine grading operations
for the subject lots. In addition, this interim report presents our geotechnical conclusions and
recommendations conceming the post grading and constmction phases for the model lot
complexes and Phase 1 production lots. As of this date, the rough and fme grading operations are
essentially complete. The geotechnical information presented herein, along with a field density
test summary and geotechnical map will be presented in the final as-grade reports, which are
currently being prepared for each of the residential plarming areas.
1.1 Project Description
The Bressi Ranch development is located southeast of the intersection of El Camino Real
and Palomar Airport Road in the central portion of the City of Carlsbad, Califomia. The site
consists of an irregular-shaped piece of property bordered on the north by Palomar Airport
Road, on the west by El Camino Real, on the southwest and south by the La Costa - The
Greens property, and by the Rancho Carrillo development and Melrose Drive to the east.
The proposed development of the model lot complexes and Phase 1 production lots is
anticipated to consist of the constmction of residential stmctures, driveways, underground
utility services, small retaining walls, concrete flatwork, landscaping, etc. We understand
the residential stmctures will be up to two-stories in height and have slab-on-grade with
wood-frame and stucco constmction.
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2.0 SUMMARY OF ROUGH AND FINE GRADING OPERATIONS
The rough and fine grading operations for the model lot complexes and Phase 1 production lots
were performed between June 2003 and April 2004. The grading operations were performed by
Nelson and Belding while Leighton and Associates performed the geotechnical observation and
testing services. Our field technicians were on site fijll-time during the grading operations while our
field and project geologists were on site on a periodic basis.
Grading of the site included: 1) the removal of potentially compressible undocumented fill,
topsoil, colluvium, alluvium, landslide deposits, and weathered formational material; 2) the
excavation of buttress keys; 3) the excavation of fill slope keys; 4) preparation of areas to receive
fill; 5) the placement of subdrains in the canyon bottoms and buttress keys; 6) excavation of
formational material; and 7) the placement of compacted fill soils. Up to approximately 40 feet
of cut was excavated and a maximum of approximately 100 feet of fill was placed within the
limits ofthe model lot complexes and Phase 1 production lots.
Table 1 (presented at the rear of text) summarizes the type of lot (cut, fill, cut/fill transition, dense
rock or expansive material overexcavation, etc.), expansion index, approximate maximum fill
thickness, and differential fill thickness on the lots graded during the rough and fine grading
operations.
2.1 Site Preparation and Removals
Prior to grading, the areas of the proposed development were stripped of surface vegetation
and debris and these materials were disposed of away from the site. Removals of unsuitable
and potentially compressible soils (including undocumented fill, topsoil, colluvium,
alluvium, landslide deposits, and weathered formational material) were made to competent
material. The removals of potentially compressible material were performed in accordance
with the reconmiendations of the project geotechnical reports (Appendix A) and
geotechnical recommendations made during the course of grading.
After the removals were made, the removal areas flatter than 5:1 (horizontal to vertical)
were scarified a minimum of 12 inches, moisture-conditioned as needed to obtain a near-
optimum moisture content and compacted to a minimum 90 percent relative compaction, as
determined by American Society for Testing and Materials (ASTM) Test Method D1557.
The steeper natural hillsides were benched into competent material as fill was placed.
2.2 Subdrains
Canyon subdrains were placed under the observation of a representative of Leighton and
Associates during the rough grading operations for the Bressi Ranch project. After the
potentially compressible material in the canyons were removed to competent material or
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when compacted fill was placed over competent material to obtain flow to a suitable outlet
location, a subdrain was installed along the canyon bottom. The canyon subdrains consist of
a 6-inch diameter perforated pipe surrounded by a minimum of 9-cubic feet (per linear foot)
of cmshed 3/4-inch gravel wrapped in Mirafi HON geofabric.
In addition to the canyon subdrains, subdrains were also installed along the bottom of the
buttress key and stability fill keys. The buttress and stability fill subdrains consisted of a 4-
inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of
clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. Where applicable, an additional
subdrain was also installed along the buttress backcut at an approximate 30-foot vertical
interval above the key bottom. The subdrains were placed with a minimum 1 -percent fall
(2-percent or greater where possible) to a suitable outlet location.
The location of the canyon subdrains placed during the rough grading operations for the
project were surveyed by the project civil engineer. The subdrain locations will be presented
on the as-graded geotechnical map for each of the planning areas.
2.3 Buttress and Stability Fill Keys
Based on geotechnical analysis performed during the preliminary and supplemental
geotechnical investigations of the site (Appendix A), buttress and stability fills were
recommended to improve the gross stability of the existing hillsides and proposed graded
areas in areas of existing landslides and/or other adverse geologic conditions.
Based on our geotechnical analysis, a buttress was excavated on Lots 427 through 433, 442,
and 443 on the north side ofPlanning Area PA-12. The other landslides encountered within
the proposed grading limits of Plarming Areas PA-6 through PA-10 and PA-12 were
removed to competent landslide material or competent formational material during the
rough and fine grading operations.
The buttress key on the north side of Plarming Area PA-12 ranged from approximately 50 to
60 feet wide at an approximate depth of 5 feet below the clayseam/potential failure surface
(i.e. at an approximate elevation of 179 to 181 feet mean sea level [msl]). The buttress key
bottom was also excavated with a minimum 2 percent inclination into the slope. The
buttresses front cut and backcuts were excavated at overall slope inclinations of 1:1
(horizontal to vertical) or flatter. The approximate location of the buttress will be presented
on the as-graded geotechnical map of the fmal as-grade report for Planning Area PA-12.
Based on our geotechnical analysis, two stability keys were excavated adjacent to the
model lot complexes and Phase 1 production lots. One of the stability fill keys was
constmcted on the north side of Lots 443 and 518 in Planning Area PA-12 while the other
stability fill was constmcted on the northeast side of Lots 276 through 280 in Planning
Area PA-9.
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The stability fills were constmcted to stabilize the exposed claystone/siltstone and/or
adverse geologic conditions within the Santiago Formation. The stability fill keys were
excavated a minimum of 5 feet below the toe-of-slope, a minimum of 15 feet to 20 feet
wide, with the key bottom angled at least 2 percent into-the-slope. The stability fill front
cuts were excavated near vertical while the backcuts were excavated at an approximate 1:1
or less (horizontal to vertical) inclination. The approximate location of the stability fills will
be presented on the as-graded geotechnical maps of the final as-grade reports for Planning
Areas PA-9 and PA-12.
2.4 Fill Slope Kevs
Prior to the placement of fill slopes that were placed above natural and/or cut areas on the
site, a fill slope key was constmcted. The fill slope keys were excavated at least 2 feet into
competent soil along the toe-of-slope and constmcted approximately 15 feet wide with the
key bottom angled a minimum of 2 percent into-the-slope.
2.5 Cut/Fill Transition Conditions
The cut portion of lots that exposed the cut/fill transition within the relatively level
building pad was overexcavated a minimum of 3 feet below finish pad grade.
Overexcavation of the building pad was performed to mitigate the transitional condition
and related adverse effects of differential settlement that can result due to this underlying
condition. The limits of the overexcavations were made at least 5 feet outside the
anticipated building limits (or building footprint). To reduce the potential of a perched
ground water condition within the transition lots, the pads were overexcavated with a 1-
foot fall in the overexcavation bottom toward the fill. Lots that were overexcavated due to
a cut/fill transition condition included Lots 7, 8, 136, 156, 171, 187, 375 through 377,
381, and 382.
2.6 Overexcavation of Blocky Well-Cemented Santiaao Formation
During the rough and fine grading of the Bressi Ranch project, geologic mapping indicated
that a number of lots contained well-cemented sandstone beds (or concretion layers) and
very dense or hard Santiago Formation at or near finish grade. Due to the potential
difficulties in excavating the well-cemented layers and very dense or hard Santiago
Formation, recommendations were made during the coarse of the grading operations to
overexcavate and replace the material with compacted fill. The lots exposing the well-
cemented sandstone and very dense or hard Santiago Formation were overexcavated to a
minimum depth of 3 feet at the rear ofthe lot and a minimum depth of 4 feet at the fi-ont of
the lot (i.e. with a 1-foot fall in the overexcavation bottom toward the street) in order to
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reduce the potential of a perched groundwater condition on the lots. Lots where
overexcavation was performed due to the well-cemented sandstone and very dense or hard
Santiago Formation included Lots 9 through 13, 127 through 135, 137 through 143, 169,
170, 180 through 186, 188 through 193, 263, 264, 268 through 272, 380, 383, and 407
through 411.
2.7 Overexcavation of Hiqh to Ven/ High Expansive Formational Material
Due to the expansive nature of some of the siltstones and claystones present on the site,
geologic observation and mapping was performed during the grading operations to
determine if high to very highly expansive formational materials were located at finish grade
on the lots. Cut lots where expansive formational material was identified at finish grade
were undercut until the expansive material was removed or to a minimimi depth of
approximately 4 feet. The lots exposing the expansive formational materials were also
overexcavated with a 1-foot fall in the undercut bottom towards to the street (in order to
reduce the potential of perched groimd water on the lots). Upon completion of the rough and
fme grading, expansion potential testing was performed on the lots to determine the
expansion potential of the finish grade soils on the lots. Lots that were undercut due to
expansive formational materials include Lots 281 through 284.
2.8 Placement of Oversized Material
During the rough and fine grading operations of the Bressi Ranch project, the well cemented
or concretionary beds that where encountered within the Santiago Formation typically
resulted in the generation of rock fi-agments ranging from less than 6 inches to greater than 4
feet in maximum dimension. In order to minimize difficult excavation of future utility
trenches or foundations excavations, recommendations were made during the rough grading
operations to place the oversized rock (generally defined as greater than 8 inches in
diameter) below a depth of 5 to 10 feet below the finish grade elevation of the fill areas.
While the contractor made their best effort to minimize the rock within the upper 5 to 10
feet of the finish grade surface, some oversized rock should be anticipated. In addition,
cemented or concretionary beds may be encountered below shallow fills on the site during
future grading and utility trench excavation that may result in the generation of additional
oversized rock.
2.9 Fill Placement and Compaction
After the completion of the remedial grading removals, processing of the excavated areas,
and/or installation of the subdrains, on-site soil was placed as compacted fill. The on-site
soil was generally spread in 4- to 8-inch loose lifts; moisture conditioned as needed to attain
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a near-optimum moisture content, and compacted. Field density test results performed
during the grading operations indicated the fill soils were compacted to at least 90 percent of
the maximum dry density in accordance with ASTM Test Method D1557.
To mitigate post-constmction settlement, the lower portions of the deep fill areas (i.e. areas
where the fill soils are generally deeper than approximately 40 feet below the proposed
finish grade elevations of the site) were placed in accordance with the geotechnical
recommendations relative to deep fills (Leighton, 2003d). In general, the fill soils below a
depth of approximately 40 from the sheet-graded pad elevations were placed and compacted
to a minimum relative compaction of 95 percent relative compaction. Deep fill areas are
present beneath Lots 1 through 4, 55 through 59, 427 through 434, 440 through 443 and
448 through 452.
Compaction of the fill soils was achieved by use of heavy-duty constmction equipment
(including mbber-tire compactors and 637, 651, and 657 scrapers). Areas of fill in which
field density tests indicated compactions less than the recommended relative compaction or
where the soils exhibited nonuniformity or had field moisture contents less than
approximately 1 to 2 percent below the laboratory optimum moisture content, were
reworked. The reworked areas were recompacted, and re-tested until the reconimended
minimum 90 or 95 percent relative compaction and near-optimum moisture content was
achieved.
Table 1 (presented at the rear of text) summarizes the type of lot (cut, fill, cut/fill transition,
rock or expansive material overexcavation, etc.), expansion index, approximate maximum
fill thickness, and differential fill thickness on the lots graded during the rough and fine
grading operations. The differential fill thickness values presented on Table 1 and utilized in
the design recommendations of this report are the difference between the minimum and
maximum fill thicknesses across the relatively level building pad on each of the lots as
shown on the grading plans.
2.10 Field Density Testinq
Field density testing and observations were performed using the Nuclear-Gauge Method
(ASTM Test Methods D2922 and D3017). The field density testing was performed in
general accordance with the applicable ASTM Standards, the current standard of care in the
industiy, and the precision of tiie testing method itself Variations in relative compaction
should be expected from the documented results. The approximate test locations and test
results will be provided in the final as-grade report for each of the planning areas.
2.11 Laboratory Testinq
Laboratory maximum dry density tests of representative on-site soils were performed in
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general accordance with ASTM Test Method D1557. Expansion potential and soluble
sulfate content tests of representative finish grade soils were also performed in accordance
with UBC 18-2 and standeird geochemical methods, respectively. The test results are
presented in Appendix B, on Table 1, and discussed in Section 3.6.
2.12 Settlement Monument Monitorinq of Deep Fills
Upon completion of the rough and fine grading operations in deep fill areas (i.e. fill areas
generally greater than approximately 40 feet in depth) within the Bressi Ranch project,
settlement monuments were placed. The settlement monuments were initially surveyed
following the installation and on a periodic basis (generally on a weekly basis). Preliminary
review of the settlement readings indicates that most of the anticipated primary settlement
has occurred. However, we recommend that the settlement monuments continue to be
surveyed and the results reviewed by Leighton. With the exception of Lots 448 through 452
in Planning Area PA-12, the stmctures on the lots within the deep fill areas (i.e. Lots 1
through 4 and 55 tiirough 59 in Planning Area PA-6 and Lots 427 through 434 and 440
through 443 in Planning Area PA-12) should not be started until our settlement analysis
indicates the primary settlement is essentially completed. The residential stmctures of the
model lots and Phase 1 production lots in the deep fill areas should be designed in
accordance with the recommendations presented in Section 5.2.
2.13 Graded Slopes
Graded and natural slopes wdthin the developed portion of the tract are considered grossly
and surficially stable from a geotechnical standpoint. Manufactured cut and fill slopes
within the tract were surveyed by the civil engineer are understood to have been constmcted
with slope inclinations of 2:1 (horizontal to vertical) or flatter.
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3.0 ENGINEERING GEOLOGIC SUMMARY
3.1 As-Graded Geologic Conditions
The geologic or geotechnical conditions encountered during the rough and fine grading of
the site were essentially as anticipated. A comprehensive summary of the geologic
conditions (including geologic units, geologic stmcture, and faulting) is presented below.
3.2 Geologic Units
The geologic units encountered during the rough and fine grading operations consisted of
undocumented fill, topsoil, colluvium, alluvium, landslide deposits, and the Santiago
Formation. Due to the potentially compressible nature of the undocumented fill, topsoil,
colluvium, alluvium, landslide deposits, and weathered formational material, these soils
were removed to competent material during the rough and fine grading operations. The as-
graded geologic units encountered during the grading operations are discussed (youngest to
oldest) below.
3.2.1 Undocumented Fill Soils
Undocumented fill soils were observed in a number of places on the site. The
undocumented fills were generally associated with the grading of the onsite dirt
roads, retention basins, and prior fanning activities. These fill soils ranged from 1 to
10 feet in depth, and generally consist of dry to damp, loose or soft sand and clay.
All existing undocumented fill located within the limits of grading were removed to
competent formational material.
3.2.2 Topsoil
A relatively thin veneer of topsoil was removed from the majority of the site. The
topsoil, as encountered, consisted predominantly of a brown, damp to moist, loose,
sandy clay and minor clayey to silty sand. The topsoil was generally massive,
porous, and contained scattered roots and organics. Topsoil removal thicknesses
were on the order of 1 to 4 feet thick. During the grading operations, the topsoil was
observed to have been removed within the limits of grading.
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3.2.3 Alluvium/Colluvium, Undifferentiated
Alluvium and colluvium was encountered during the rough grading operations in
the tributary canyons and on the lower portion of the hillsides on the site. As
encountered, the alluvium and colluvium consisted of dark brown, moist, loose to
stiff, clayey sand, sandy clay, and silty sand. Where encountered, the alluvium and
colluvium was removed to competent material. Up to approximately 20 feet of
alluvium and colluvium was removed during the rough and fine grading
operations.
3.2.4 Landslide Deposits
Several ancient landslides were encountered in Planning Areas PA-6, PA-10, and
PA-12. The landslide deposits generally consisted of moderately loose to dense
materials derived from the Santiago Formation. The landslide deposits included
graben in-fill material, relatively undisturbed blocks of formational material (within
the central portion of the landslide mass), and disturbed/weathered material and
buried topsoil, colluvium and/or alluvium (around the side flanks and the toe of the
landslides). The landslide deposits generally consisted of moderately to heavily
fractured silty sand and sandy clay. The landslide basal mpture surfaces generally
consisted of a remolded clay seam. Geologic mapping during the buttress
excavation and landslide removals indicated the landslides failed on slightly
undulatory, very shallow dipping (2 to 5 degrees out-of-slope inclinations) planner
and polished surfaces. Up to approximately 20 feet of the compressible landslide
deposits were removed during the rough and fine grading operations.
Due to their compressible nature and potential instability, remedial measures were
performed on the landslides encountered during the rough grading operations within
the graded limits of the site. The remedial grading measures included the removal of
the loose and compressible landslide material of the larger landslides; complete
removal of minor landslides; and the constmction of buttress fills to stabilize the
landslides. In general, the buttress keys were excavated a minimum of 5 feet below
the landslide mpture surface.
The approximate limits of the landslide deposits encountered during the grading
operations will be presented on the as-graded geotechnical map in the final as-
graded report for each of the planning areas.
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3.2.5 Santiago Formation
The Tertiary-aged Santiago Formation, as encountered during the rough and fine
grading operations, consisted primarily of massively bedded sandstones and
claystones/siltstones. The sandstones generally consisted of orange-brown (iron-
oxide staining) to light brown, damp to moist, dense to very dense, silty very fine to
medium grained sandstone. The siltstones and claystones were generally olive-green
to gray (unweathered), damp to moist, stiff to hard, moderately weathered, and
occasionally fractured and moderately sheared. Several well-cemented fossiliferous
sandstone beds were encountered during the rough and fine grading operations.
3.3 Geoloqic Structure
The general stmcture of the formational material appears to be near horizontal. Based on
our geologic mapping during the rough and fine grading operations, bedding within the
Santiago Formation generally exhibited somewhat variable bedding with strikes ranging
from northwest to northeast and dips typically 2 to 9 degrees to the southeast and northwest.
Locally, cross bedding was observed with dips steeper than 15 degrees.
Jointing on-site was observed to be very variable, but predominantiy trended subparallel to
the existing slopes. Jointing dips were found to be generally moderately to steeply dipping.
Jointing was mainly encountered in the upper portion of the bedrock becoming less
pronounced wdth depth.
Randomly oriented shears were encountered in the Santiago Formation claystone and
siltstone units. Numerous wide, diffuse zones of shearing, as well as more well-defined
zones, were encountered in the bedrock, and are thought to be the result of regional tectonic
shearing of the relatively stiff and unyielding siltstone and claystone.
3.4 Faultinq and Seismicity
Our discussion of faults on the site is prefaced with a discussion of Califomia legislation
and state policies conceming the classification and land-use criteria associated with faults.
By definition of the Califomia Mining and Geology Board, an active fault is a fault that has
had surface displacement wdthin Holocene time (about the last 11,000 years). The State
Geologist has defined a potentiallv active fault as any fault considered to have been active
during Quatemary time (last 1,600,000 years) but that has not been proven to be active or
inactive. This definition is used in delineating Fault-Rupture Hazard Zones as mandated by
the Alquist-Priolo Earthquake Fault Zoning Act of 1972 and as most recentiy revised in
1997. The intent of this act is to assure that unwise urban development does not occur
across the traces of active faults. Based on our review of the Fault-Rupture Hazard Zones,
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the site is not located within any Fault-Rupture Hazard Zone as created by the Alquist-
Priolo Act (Hart, 1997).
San Diego, like the rest of southem Califomia, is seismically active as a result of being
located near the active margin between the North American and Pacific tectonic plates. The
principal source of seismic activity is movement along the northwest-trending regional fault
zones such as the San Andreas, San Jacinto and Elsinore Faults Zones, as well as along less
active faults such as the Rose Canyon Fault Zone.
As indicated in the Supplemental Geotechnical Report for the Bressi Ranch project
(Leighton, 2001), there are no known major or active faults on or in the immediate vicinity
of the site. Evidence of active faulting was not encountered during the rough and fine
grading operations. However, several minor inactive faults were encountered but are not
considered a constraint to development. The nearest knovm active fault is the Rose Canyon
Fault Zone, which is considered a Type B Seismic Source based on the 1997 Uniform
Building Code (UBC), is located approximately 7.0 miles (11.2 kilometers) west of the site.
Because ofthe lack of knovm active faults on the site, the potential for surface mpture at the
site is considered low. Shallow ground mpture due to shaking from distant seismic events
is not considered a significant hazard, although it is a possibility at any site.
Liquefaction and dynamic settlement of soils can be caused by strong vibratory motion
due to earthquakes. Both research and historical data indicate that loose, saturated,
granular soils are susceptible to liquefaction and dynamic settlement. Liquefaction is
typified by a loss of shear strength in the affected soil layer, thereby causing the soil to act
as a viscous liquid. This effect may be manifested by excessive settlements and sand boils
at the ground surface. The fill and formational materials underlying the site are not
considered liquefiable due to their fine-grained nature, dense physical characteristics
and/or unsaturated condition.
3.5 Ground Water
Perched ground water was encountered during the rough grading operations in the alluvial
soils within the main drainages on the site. Since the alluvial soils were completely removed
during the rough grading operations and subdrains installed in the canyon bottoms,
groundwater conditions should not be a constiaint to development. Based on the site-
specific as-graded geotechnical conditions and our geotechnical analysis during site grading,
the geotechnical consultant has analyzed conditions that may result in ground water seepage
and appropriate recommendations, if necessary, have been made. However, unanticipated
seepage or ground water conditions may occur after the completion of grading and
establishment of site irrigation and landscaping. If these conditions should occur, steps to
mitigate the seepage should be made on a case-by-case basis.
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3.6 Expansion and Sulfate Content Testinq of Representative Finish Grade Soils
Expansion potential and soluble sulfate content tests were performed on representative
finish grade soils of the residential model lots and Phase 1 production lots. The test results
indicate the representative finish grade soils have a very low to high expansion potential and
have a negligible to severe soluble sulfate content per the UBC criteria (ICBO, 1997). The
laboratory test resuhs and procedures are presented in Appendix B and on Table 1.
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4.0 CONCLUSIONS
4.1 General
The rough and fine grading operations for the residential model lot complexes and Phase 1
production lots ofthe Bressi Ranch project were performed in general accordance with the
project geotechnical reports (Appendix A), geotechnical recommendations made during
grading, and the City of Carlsbad requirements, ft is our professional opinion that tiie
subject lots are suitable for the intended residential use provided the recommendations
included herein and in the project geotechnical report are incorporated into the design and
constmction of the residential stmctures and associated improvements. The following is a
summary of our conclusions conceming the rough and fine grading of the site.
4.2 Summan/ of Conclusions
• Geotechnical conditions encountered during rough and fine grading were generally as
anticipated.
• Site preparation and removals were geotechnically observed.
• The geologic units encountered during the rough and fine grading of the site consisted
of undocumented fill soils, topsoil, colluvium, alluvium, landslide deposits, and the
Santiago Formation.
• Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, landslide deposits,
and weathered formational material were removed to competent material within the
limits of grading.
• Subdrains were placed in the canyon bottoms and along the heel of tiie buttress and
stability fill keys during the rough and fine grading operations.
• Buttress and stability fills were constmcted to improve the gross stability of the
landslides and cut slopes exposing fractured and blocky formational material and/or
adverse geologic conditions on the site. The buttress and stability fill keys were
excavated in accordance with the project geotechnical recommendations.
• Fill slopes located above natural ground or cut areas were constmcted with a fill slope
key. All keys were excavated to a minimum 15 feet wide, at least 2 feet into competent
material along the toe-of-slope with the key inclined 2 percent into the slope.
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The cut/fill transition conditions on Lots 7, 8, 136, 156, 171, 187, 375 tiirough 377, 381,
and 382 were geotechnically mitigated by the overexcavation and recompaction of
approximately the upper 3 to 4 feet of the lot.
The well-cemented sandstone beds and very dense or hard Santiago Formation on
Lots 9 through 13, 127 through 135, 137 through 143, 169, 170, 180 through 186, 188
through 193, 263, 264, 268 through 272, 380, 383, and 407 through 411 was
overexcavated to a minimum depth of 3 feet and replaced with compacted fill.
Cut lots where expansive formational material was identified at finish grade were
undercut until the expansive material was removed or to a minimum depth of
approximately 4 feet. Lots that were undercut due to expansive formational materials
include Lots 281 through 284.
Oversized rock generated during the grading operations was placed at least 5 feet below
finish grade elevations.
Fill soils were derived from onsite soils. The maximum fill depth within the limits of
the model lots and Phase 1 production lots ranged from 4 to approximately 100 feet in
depth. Field density testing indicated that the fill soils were placed and compacted to at
least 90 percent relative compaction (based on ASTM Test Method D1557) and near-
optimum moisture content in accordance with the recommendations of Leighton and
Associates and the requirements of the City of Carlsbad.
To mitigate post-constmction settlement, deep fills (i.e. areas where the fill soils are
generally deeper than approximately 40 feet below the finish grade elevations of the
site) were placed at a minimum 95 percent relative compaction. Deep fill areas are
present beneath Lots 1 through 4, 55 through 59, 427 through 434, 440 through 443,
and 448 through 452.
Ground water seepage conditions were encountered during the mass grading operations
of the Bressi Ranch project.
No evidence of active faulting was encountered during the grading operations within the
limits of model lot complexes or the Phase 1 production lots. However, minor inactive
faulting was encountered but should not be a constraint to development.
Due to the dense nature of the onsite soils, it is our professional opinion that the
liquefaction hazard at the site is considered low.
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Settlement monitoring of tiie deep fills indicates that most of tiie primary settlement of
tiie deep fills has already occurred. With the exception of Lots 448 through 452 in
Planning Area PA-12, the stmctures on the lots within the deep fill areas (i.e. Lots 1
through 4 and 55 through 59 in Planning Area PA-6 and Lots 427 through 434 and
440 through 443 in Planning Area PA-12) should not be started until our settlement
analysis indicates the primary settlement is essentially completed.
The expansion potential of representative finish grade soils of the lots was tested and
found to have a very low to high expansion potential. The laboratory test results are
presented in Appendix B and on Table 1.
The potential for soluble sulfate attack (on Type I/II cement) of the finish grade soils
was tested and possess negligible to severe soluble sulfate contents. The laboratory test
results are presented in Appendix B.
It is our opinion that the slopes of the development possess a static factor of safety ofat
least 1.5 to resist deep-seated failure (under normal irrigation/precipitation pattems),
provided the recommendations in the project geotechnical reports are incorporated into
the post-grading, constmction and post-constmction phases of site development.
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5.0 RECOMMENDATIONS
5.1 Earthwork
We anticipate that future earthwork at the site will consist of site preparation, fine grading,
utility trench excavation and backfill, and retaining wall backflll and compaction. We
recommend that the earthwork on site be performed in accordance with the following
recommendations, the General Earthwork and Grading Specifications for Rough Grading
included in Appendix C, and the City of Carlsbad grading requirements. In case of conflict,
the following recommendations shall supersede those in Appendix C. The contract between
the developer and earthwork contractor should be worded such that it is the responsibility of
the contractor to place the fill properly and in accordance with the recommendations of this
report and the specifications in Appendix C, notwithstanding the testing and observation of
the geotechnical consultant.
5.1.1 Site Preparation
During future grading, the areas to receive stmctural fill or engineered stmctures
should be cleared of surface obstmctions, potentially compressible material (such as
desiccated fill soils or weathered formational material), and stripped of vegetation.
Vegetation and debris should be removed and properly disposed of off site. Holes
resulting from removal of buried obstmctions that extend below finish site grades
should be replaced with suitable compacted fill material. Areas to receive fill and/or
other surface improvements should be scarified to a minimum depth of 12 inches,
brought to moisture contents of at least 2-percent over the optimum moisture
content, and recompacted to at least 90 percent relative compaction (based on
ASTM Test Method D1557).
If the length of time between the completion of grading and the constmction of the
lots is longer than six months, we recommend that the building pads be evaluated by
the geotechnical consultant and, if needed, the finish grade soils on the building
pads should be scarified a minimum of 12 inches, moisture-conditioned to 2-percent
above the optimum moisture-content and recompacted to a minimum 90 percent
relative compaction (based on ASTM Test Method D1557).
5.1.2 Excavations
Excavations of the on-site materials may generally be accomplished with
conventional heavy-duty earthwork equipment. It is not anticipated that blasting will
be required or that significant quantities of oversized rock (i.e. rock with maximum
dimensions greater than 8 inches) will be generated during future grading. However,
localized cemented zones within the shallow fill and cut areas and oversized rock
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placed within the compacted fill may be encountered that may require heavy ripping
or special grading measures. If oversized rock is encountered, it should be placed in
accordance with the recommendations presented in Appendix C, hauled offsite, or
placed in non-stmctural or landscape areas.
Due to the relatively dense characteristics of the on-site soils, temporary excavations
such as utility trenches in the on-site soils should remain stable for the period
required to constmct the utility, provided they are constmcted and monitored in
accordance with OSHA requirements.
5.1.3 Fill Placement and Compaction
The on-site soils are generally suitable for re-use as compacted fill provided they are
free or organic material, debris, and rock fragments larger than 8 inches in
maximum dimension. We do not recommend that high or very high expansive soils
be utilized as retaining wall backfill.
In general, all fill soils should be brought to 2-percent over the optimum moisture
content and compacted in uniform lifts to at least 90 percent relative compaction
based on the laboratory maximum dry density (ASTM Test Method D1557). The
optimum lift thickness required to produce a uniformly compacted fill will depend
on the type and size of compaction equipment used. In general, fill should be placed
in lifts not exceeding 8 inches in compacted thickness. Placement and compaction
of fill should be performed in general accordance with Appendix C, the current City
of Carlsbad grading ordinances, sound constmction practices, and the geotechnical
recommendations presented herein.
5.2 Residential Foundation Design Considerations
The proposed foundations and slabs of the proposed stmctures should be designed in
accordance with stmctural considerations and recommendations presented herein. Since
soils ranging from very low to high expansion potential are present, as well as building pads
having a significant fill differential thickness (considered to be a fill thickness differential of
20 feet or more) and/or within deep fill areas (i.e. areas underlain by approximately 40 feet
or more of fill), we recommend the use of post-tensioned slab and foundation systems.
We recommend that the post-tensioned slabs be designed in accordance with the followdng
design parameters presented on Table 2 and the criteria of the current edition of the Uniform
Building Code/Califomia Building Code. The post-tensioned foundations should be
designed in accordance with building pad specific expansion potential, significant deep fill
or fill differential and anticipated long-term differential settlement (if applicable) as
indicated in Section 5.2.4.
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Table 2
Post-Tensioned Foundation Design Recomnnendations
Lot Numbers
Design Criteria
Lots 5-9, ISO-
IS 1,263,264, 267-
272,281-2S4,
374-377, 380-383,
404-410, and 435-
439
Lots 10-13,31-
34,112, 127-131,
137-143, 156-159,
169-172, and 182-
193
Lots 132-136 and
411
Lots 1-4,30,55-
63, 265-266,427-
434, 440-443, and
448-452
Lot Numbers
Design Criteria
Minimal Fill
Thickness or Fill
Differential and
Very Low to Low
Expansion
Potential
(Expansion Index
less than 50)
Minimal Fill
Thickness or Fill
Differential and
Medium
Expansion
Potential
(Expansion Index
between 51 and
90)
Minimal Fill
Thickness or Fill
Differential and
High Expansion
Potential
(Expansion Index
between 91 and
120)
Significant Fill
Thickness and/or
Fill Differential
with Low to High
Expansion
Potential
(Expansion Index
between 21 and
120)
Edge
Moisture
Variation, Cm
Center
Lift: 5.5 feet 5.5 feet 5.5 feet 5.5 feet Edge
Moisture
Variation, Cm Edge
Lift: 2.5 feet 3.0 feet 4.5 feet 5.5 feet
Differential
Swell, ym
Center
Lift: 1.0 inches 2.0 inches 3.0 inches 4.0 inches Differential
Swell, ym Edge
Lift: 0.4 inches 0.8 inches 1.2 inches 1.5 inches
Angular Distortion
Value: 1/800 1/600 1/600 1/500
Allowable Bearing
Capacity: 2,000 psf
Perimeter Footing
Depth: 12 inches 18 inches 24 inches 30 inches
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Long-term differential settlement is anticipated to occur when the fill soils become wetted
by irrigation and/or precipitation years after the completion of constmction. Angular
distortion values, which are the ratio of the estimated differential settlement to the
horizontal distance over which the settlement is likely to occur, are provided on Table 2.
The estimated angular distortion value assumes 1) a relatively uniform fill settlement across
the stmcture; and 2) the actual settlement will not likely vary more than one-quarter of the
stated angular distortion at any one point. The angular distortion values may be further
evaluated based on a review of the precise grading plans.
The post-tensioned foundations and slabs should be designed in accordance with stmctural
considerations. Continuous footings wdth a minimimi width of 12 inches and a minimum
depth of 12, 18, 24, or 30 inches below adjacent grade (as indicated on Table 2) may be
designed for a maximum allowable bearing pressure of 2,000 pounds per square foot if
founded into competent formational soils or properly compacted fill soils. The allowable
bearing capacity may be increased by one-third for short-term loading such as wind or
seismic forces. Where the foundation is within 4 feet (horizontally) of adjacent drainage
swales, the adjacent footing should be embedded a minimum depth of 12 inches below the
swale flowline.
The post-tension slabs should be a minimum of 5 inches thick. The slabs should be
underlain by a minimum of 2 inches of clean sand (sand equivalent greater than 30) that is
in tum underlain by plastic sheeting (10-mil) and an additional 2 inches of clean sand. The
plastic sheeting should be sealed at all penefrations and laps. Moisture vapor transmission
may be additionally reduced by use of concrete additives. Moisture barriers (i.e. plastic
sheeting) can retard, but not eliminate moisture vapor movement from the underlying soils
up through the slabs. We recommend that the floor covering installer test the moisture vapor
flux rate prior to attempting applications of the flooring. "Breathable" floor coverings
should be considered if the vapor flux rates are high. A slipsheet or equivalent should be
utilized above the concrete slab if crack-sensitive floor coverings (such as ceramic tiles,
etc.) are to be placed directly on the concrete slab.
Our experience indicates that use of reinforcement in slabs and foundations will generally
reduce the potential for drying and shrinkage cracking. However, some cracking should be
expected as the concrete cures. Minor cracking is considered normal; however, it is often
aggravated by a high water/cement ratio, high concrete temperature at the time of
placement, small nominal aggregate size, and rapid moisture loss due to hot, dry and/or
windy weather conditions during placement and curing. Cracking due to temperature and
moisture fluctuations can also be expected. The use of low slump concrete (not exceeding 4
to 5 inches at the time of placement) can reduce the potential for shrinkage cracking and the
action of tensioning the tendons can close small shrinkage cracks. In addition to the careful
control of water/cement ratios and slump of concrete, application of 50 percent of the
design post-tensioning load within three to four days of slab pour is found to be an effective
method of reducing the cracking potential.
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The slab subgrade soils underlying the post-tensioned foundation systems should be
presoaked as indicated in Section 5.2.1 prior to placement of the moisture barrier and slab
concrete.
5.2.1 Moisture Conditioninq
The slab subgrade soils underlying the post-tensioned foundation systems of the
proposed stmctures should be presoaked in accordance with the recommendations
presented in Table 3 prior to placement of the moisture barrier and slab concrete.
The subgrade soil moisture content should be checked by a representative of
Leighton and Associates prior to slab constmction.
Presoaking or moisture conditioning may be achieved in a number of ways, but
based on our professional experience, we have found that minimizing the moisture
loss of pads that have been completed (by periodic wetting to keep the upper portion
of the pad from drying out) and/or berming the lot and flooding if for a short period
of time (days to a few weeks) are some of the more efficient ways to meet the
presoaking requirements. If flooding is performed, a couple of days to let the upper
portion of the pad dry out and form a cmst so equipment can be utilized should be
anticipated.
Table 3
Presaturation Recommendations Based on Finish Grade Soil Expansion Potential
Presaturation
Criteria
Expansion Potential (per UBC 18-I-B)
Presaturation
Criteria
Very Low
(0-20)
Low
(21-50)
Medium
(51-90)
High
(91-130)
Minimum
Presoaking Depth
(in inches)
6 12 18 24
Minimum
Recommended
Moisture Content
Near optimum
moisture
1.2 times
optimum
moisture
1.2 times
optimum
moisture
1.3 times
optimum
moisture
5.2.2 Seismic Desiqn Parameters
The site lies within Seismic Zone 4, as defined in the UBC, 1997 edition. The
nearest known active fault is the Rose Canyon Fault Zone, which is considered a
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Type B Seismic Source (per 1997 UBC criteria) and is located approximately 7.0
miles (or 11.2 kilometers) west of the site. The closest Type A Seismic Source is the
Julian segment of the Elsinore Fault Zone, which is located approximately 23.5
miles (or 38 kilometers) east of the site.
The following data should be considered for the seismic analysis of the proposed
stmctures:
Causative Fault: Rose Canyon Fault Zone
Maximum Magnitude: 7.2
Seismic Source Type: B
Seismic Zone Factor: 0.40
Soil Profile Tvpe: Sc
Near Source Factors: Na= 1.0/Nv = 1.0
5.2.3 Foundation Setback
We recommend a mimmum horizontal setback distance from the face of slopes or
adjacent retaining walls for all stmctural foundations, footings, and other settlement-
sensitive sti:iictures as indicated on Table 4. This distance is measured from the
outside bottom edge of the footing, horizontally to the slope face and is based on the
slope height and type of soil. However, the foundation setback distance may be
revised by the geotechnical consuhant on a case-by-case basis if the geotechnical
conditions are different than anticipated.
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Table 4
Minimum Foundation Setback from Slope Faces
Slope Height Minimum Reconimended Foundation
Setback
Less than 5 feet 5 feet
5 to 15 feet 7 feet
15 to 30 feet 10 feet
Greater than 30 feet 20 feet
Please note that the soils wdthin the stmctural setback area possess poor lateral
stability, and improvements (such as retaining walls, sidewalks, fences, pavements,
etc.) constmcted within this setback area may be subject to lateral movement and/or
differential settlement. Potential disfress to such improvements may be mitigated by
providing a deepened footing or a pier and grade beam foundation system to support
the improvement. The deepened footing should meet the setback as described
above.
5.2.4 Anticipated Settlement
Settlement is anticipated to occur at varying times over the life of the project. Short-
term settlement typically occurs upon application of the foundation loads and is
essentially completed within the constmction period. Long-term
(hydroconsolidation) settlement typically occurs in deep fills upon additional water
infiltration into the fill soils (even in properly compacted fill soils and even wdth
subdrains provided). This settlement typically occurs over many years. The total
future settlement is expected to be order of 1/2 to 2 inches and differential
settlement is estimated to be on the order of 1/2 inch to 1-1/2 inches.
5.3 Lateral Earth Pressures
The reconimended lateral pressures for the onsite very low to low expansive soil (expansion
index less than 50 per UBC Table 18-I-B) or medium expansive soil (expansion index
between 51 and 90 per UBC Table 18-I-B) and level or sloping backfill are presented on
Table 5. High to very high expansive soils (having an expansion potential greater than 91
per UBC Table 18-I-B) should not be used as backfill soils.
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Table 5
Lateral Earth Pressures
Conditions
Equivalent Fluid Weight (pcf)
Conditions Very Low to Low Expansive Soils Medium Expansive Soils Conditions
Expansion Index less than 50 Expansion Index between 51 and 90
Conditions
Level 2:1 Slope Level 2:1 Slope
Active 35 55 60 70
At-Rest 55 65 70 80
Passive 350 150 350 150
Embedded stmctural walls should be designed for lateral earth pressures exerted on them.
The magnitude of these pressures depends on the amount of deformation that the wall can
yield under load. If the wall can yield enough to mobilize the full shear strength of the soil,
it can be designed for "active" pressure. If the wall cannot yield under the applied load, the
shear strength of the soil cannot be mobilized and the earth pressure will be higher. Such
walls should be designed for "at rest" conditions. If a stmcture moves toward the soils, the
resulting resistance developed by the soil is the "passive" resistance. The above noted
passive resistance assumes an appropriate setback per Section 5.2.3.
For design purposes, the recommended equivalent fluid pressure for each case for walls
founded above the static ground water and backfilled wdth soils of very low to low
expansion potential or medium expansion potential is provided on Table 5. The equivalent
fluid pressure values assume free-draining conditions. If conditions other than those
assumed above are anticipated, the equivalent fluid pressures values should be provided on
an individual-case basis by the geotechnical engineer. The geotechnical and stmctural
engineer should evaluate surcharge-loading effects from the adjacent stmctures. All
retaining wall stmctures should be provided with appropriate drainage and appropriately
waterproofed. The outlet pipe should be sloped to drain to a suitable outlet. Typical wall
drainage design is illustrated in Appendix C.
For sliding resistance, the friction coefficient of 0.35 may be used at the concrete and soil
interface. In combining the total lateral resistance, the passive pressure or the frictional
resistance should be reduced by 50 percent. Wall footings should be designed in accordance
with stmctural considerations. The passive resistance value may be increased by one-third
when considering loads of short duration including wind or seismic loads. The horizontal
distance between foundation elements providing passive resistance should be minimum of
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three times the depth of the elements to allow full development of these passive pressures.
The total depth of retained earth for the design of cantilever walls should be the vertical
distance below the ground surface measured at the wall face for stem design or measured at
the heel of the footing for overtuming and sliding. All wall backcuts should be made in
accordance with the current OSHA requirements.
The granular and native backfill soils should be compacted to at least 90 percent relative
compaction (based on ASTM Test Method D1557). The granular fill should extend
horizontally to a minimum distance equal to one-half the wall height behind the walls. The
walls should be constmcted and backfilled as soon as possible after backcut excavations.
Prolonged exposure of backcut slopes may result in some localized slope instability
Foundations for retaining walls in competent formational soils or properly compacted fill
should be embedded at least 18 inches below lowest adjacent grade. At this depth, an
allowable bearing capacity of 2,000 psf may be assumed.
5.4 Fences and Freestandinq Walls
Footings for freestanding walls should be founded a minimum of 18 inches below lowest
adjacent grade (or 30 inches for walls founded on high expansive soils). To reduce the
potential for unsightly cracks in freestanding walls, we recommend inclusion of
constmction joints at a maximum of 15-foot intervals. This spacing may be altered in
accordance with the recommendations of the stmctural engineer, based on wall
reinforcement details.
Our experience on similar sites in older developments indicates that walls on shallow
foundations near the top-of-slopes tend to tilt excessively over time as a result of slope
creep. Ifthe effects of slope creep on top-of-slope walls are not deemed acceptable, one or
a combination of the options provided in the following paragraphs should be utilized in
the design of such stmctures, based on the desired level of mitigation of creep-related
effects on them.
A relatively inexpensive option to address creep related problems in top-of-slope walls
and fences is to allow some degree of creep damage and design the stmctures so that
tilting or cracking will be less visually obvious, or such that they may be economically
repaired or replaced. If, however, a better degree of creep mitigation is desired, the walls
and fences may be provided with the deepened footings to met the foundation setback
criteria laid out in Figure 18-1-1 of the UBC, 1997 edition, or these stmctures may be
constmcted to accommodate potential movement.
Under certain circumstances, an effective solution to minimize the effects of creep on top-
of-slope walls and fences is to support these stmctures on a pier-and-grade-beam system.
The piers normally consist of minimum 12-inch diameter cast-in-place caissons spaced at a
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maximum of 8 feet on center, and connected together by a minimum 12-inch-thick grade
beam at a shallow depth. The piers are typically at least 10 feet deep for medium or high
expansive soil. The steel reinforcement for the system should be designed with
consideration of wall/fence type and loading. Walls or fences aligned essentially
perpendicular to the top of the slope are normally supported on the pier-and-grade-beam
system for at least that part of the wall that is within 15 feet from the top-of-slope. Caisson
support is reconimended for all top-of-slope walls where slopes are greater than 10 feet in
height. And the slopes consist of high or very high expansive soils.
5.5 Concrete
In-place concrete is subject to adverse conditions such as unsightly cracking, excessive
water vapor transmission, sulfate attack, efflorescence, and other adverse conditions.
Adherence to the following guidelines will help mitigate against the above adverse hazards.
1) Exposure to sulfate-containing solutions:
• The soluble sulfate content of the finish grade soils on the site are anticipated to
be in the negligible to severe range based on 1997 Uniform Building Code
criteria.
• Comply with 1997 UBC Table 19-A-4; and
• Maintain concrete water/cement ratio less than 0.5.
2) Drying shrinkage cracking:
• Follow recommendations of ACI 302.IF for industrial/commercial stmctures,
or follow recommendations of ACI 332.R for residential constmction, as
appropriate;
• Maintain concrete water/cement ratio less than 0.5.
• Use minimum cement required to achieve desired strength;
• Provide effective concrete curing for seven days after placing;
• Design confrol joints into slab; and
• Do not place concrete on hot, wdndy low-humidity days.
3) Reduction of vapor fransmission:
• Maintain concrete water/cement ratio less than 0.5.
• Avoid constmction punctures of vapor barriers;
• Seal vapor barrier joints;
• Extend vapor barrier into footing/grade beam excavation (not covering bottom
of excavation);
• Prevent excessive irrigation of landscaping; and
• Use floor-covering adhesives that are not water-soluble.
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5.6 Slope Maintenance Guidelines
It is the responsibility of the owner to maintain the slopes, including adequate planting,
proper irrigation and maintenance, and repair of faulty irrigation systems. To reduce the
potential for erosion and slumping of graded slopes, all slopes should be planted with
ground cover, shmbs, and plants that develop dense, deep root stmctures and require
minimal irrigation. Slope planting should be carried out as soon as practical upon
completion of grading. Surface-water mnoff and standing water at the top-of-slopes
should be avoided. Oversteepening of slopes should be avoided during constmction
activities and landscaping. Maintenance of proper lot drainage, undertaking of property
improvements in accordance with sound engineering practices, and proper maintenance
of vegetation, including regular slope irrigation, should be performed. Slope irrigation
sprinklers should be adjusted to provide maximum uniform coverage with minimal of
water usage and overlap. Overwatering and consequent runoff and ground saturation
should be avoided. If automatic sprinklers systems are installed, their use must be
adjusted to account for rainfall conditions.
Trenches excavated on a slope face for any purpose should be properly backfllled and
compacted in order to obtain a minimum of 90 percent relative compaction, in accordance
with ASTM Test Method D1557. Observation/testing and acceptance by the geotechnical
consultant during trench backfill is reconimended. A rodent-control program should be
established and maintained. Prior to planting, recently graded slopes should be
temporarily protected against erosion resulting from rainfall, by the implementing slope
protection measures such as polymer covering, jute mesh, etc.
5.7 Control of Surface Water and Drainaqe
Surface drainage should be carefully taken into consideration during precise grading,
landscaping, and building constmction. Positive drainage (e.g., roof gutters, dovmspouts,
area drain, etc.) should be provided to direct surface water away from stmctures and
towards the street or suitable drainage devices. Ponding of water adjacent to stmctures
should be avoided; roof gutters, dovmspouts, and area drains should be aligned so as to
transport surface water to a minimum distance of 5 feet away from stmctures. The
performance of stmctural foundations is dependent upon maintaining adequate surface
drainage away from stmctures.
Water should be transported off the site in approved drainage devices or unobstmcted
swales. We recommend that the minimum flow gradient for the drainage be 1-percent for
area drains and paved drainage swales; and 2-percent for unpaved drainage swales. We
recommend that where stmctures will be located within 5 feet of a proposed drainage
swale, the surface drainage adjacent to the stmctures be accomplished with a gradient of
at least 3-1/2 percent away from the stmcture for a minimum horizontal distance of 3 feet.
Drainage should be fiirther maintained by a swale or drainage path at a gradient of at least
4 -26-
Leighton
971009-014
1-percent for area drains and paved drainage swales and 2-percent for unpaved drainage
swales to a suitable collection device (i.e. area drain, street gutter, etc.). We also
recommend that stmctural footings within 4 feet of the drainage swale flowline be
deepened so that the bottom of the footing is at least 12 inches below the flow-line of the
drainage swale. In places where the prospect of maintaining the minimum recommended
gradient for the drainage swales and the constmction of additional area drains is not
feasible, provisions for specific recommendations may be necessary, outlining the
importance of maintaining positive drainage.
The impact of heavy irrigation or inadequate runoff gradient can create perched water
conditions, resuhing in seepage or shallow groundwater conditions where previously none
existed. Maintaining adequate surface drainage and confrolled irrigation will significantly
reduce the potential for nuisance-type moisture problems. To reduce differential earth
movements (such as heaving and shrinkage due to the change in moisture content of
foundation soils, which may cause distress to a stmcture or improvement), the moisture
content of the soils surrounding the stmcture should be kept as relatively constant as
possible.
All area drain inlets should be maintained and kept clear of debris in order to function
properly. In addition, yard landscaping should not cause any obstmction to the yard
drainage. Rerouting of yard drainage pattem and/or installation of area drains should be
performed, if necessary. A qualified civil engineer or a landscape architect should be
consulted prior to rerouting of drainage.
5.8 Landscapinq and Post-Construction
Landscaping and post-constmction practices carried out by the ovmer(s) and their
representative bodies exert significant influences on the integrity of stmctures founded on
expansive soils. Improper landscaping and post-constmction practices, which are beyond
the control of the geotechnical engineer, are frequently the primary cause of distress to these
stmctures. Recommendations for proper landscaping and post-constmction practices are
provided in the following paragraphs within this section. Adhering to these
recommendations will help in minimizing distress due to expansive soils, and in ensuring
that such effects are limited to cosmetic damages, without compromising the overall
integrity of stmctures. The recommendations provided herein have been developed in
general accordance with the guidelines provided within the Post-Tensioning Institute's
(1996) recommendations for the design and constmction of post-tensioned slabs-on-ground.
Initial landscaping should be done on all sides adjacent to the foundation of a stmcture, and
adequate measures should be taken to ensure drainage of water away from the foundation. If
larger, shade providing trees are desired, such frees should be planted away from stmctures
(at a minimum distance equal to half the mature height of the tree) in order to prevent
penetration of the tree roots beneath the foundation of the stmcture.
-27-
Leighton
971009-014
Locating planters adjacent to buildings or stmctures should be avoided as much as possible.
If planters are utilized in these locations, they should be properly designed so as to prevent
fluctuations in the moisture content of subgrade soils. Planting areas at grade should be
provided with appropriate positive drainage. Wherever possible, exposed soil areas should
be above paved grades. Planters should not be depressed below adjacent paved grades
unless provisions for drainage, such as catch basins and drains, are made. Adequate
drainage gradients, devices, and curbing should be provided to prevent runoff from adjacent
pavement or walks into planting areas.
Watering should be done in a unifomi, systematic manner as equally as possible on all sides
of the foundation, to keep the soil moist. Irrigation methods should promote uniformity of
moisture in planters and beneath adjacent concrete flatwork. Overwatering and
underwatering of landscape areas must be avoided. Areas of soil that do no have ground
cover may require more moisture, as they are more susceptible to evaporation. Ponding or
frapping of water in localized areas adjacent to the foundations can cause differential
moisture levels in subsurface soils and should, therefore, not be allowed. Trees located
within a distance of 20 feet of foundations would require more water in periods of extreme
drought, and in some cases, a root injection system may be required to maintain moisture
equilibrium. During exfreme hot and dry periods, close observations should be carried out
around foundations to ensure that adequate watering is being undertaken to prevent soil
from separating or pulling back from the foundations.
5.9 Construction Observation and Testinq
Constmction observation and testing should be performed by the geotechnical consultant
during future excavations and foundation or retaining wall constmction on the graded
portions of the site. Additionally, footing excavations should be observed and moisture
determination tests of subgrade soils should be performed by the geotechnical consultant
prior to the pouring of concrete. Foundation design plans should also be reviewed by the
geotechnical consultant prior to excavations.
-28-
Leighton
971009-014
6.0 LIMFFATIONS
The presence of our field representative at the site was intended to provide the ovmer wdth
professional advice, opinions, and recommendations based on observations of the contractor's
work. Although the observations did not reveal obvious deficiencies or deviations from project
specifications, we do not guarantee the contractor's work, nor do our services relieve the contractor
or his subcontractor's work, nor do our services relieve the contractor or his subconfractors of tiieir
responsibility if defects are subsequently discovered in their work. Our responsibilities did not
include any supervision or direction of the actual work procedures of the confractor, his persormel,
or subcontractors. The conclusions in this report are based on test results and observations of the
grading and earthwork procedures used and represent our engineering opinion as to the compliance
of the results with the project specifications.
-29-
Leighton
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feet)
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-6 Model Lot Complex
60 Fill Medium 35 20
61 Fill Medium 30 20
62 Fill Medium 30 20
63 Fill Medium 25 20
PA-7 Model Lot Complex
112 Fill Medium 15 11
156 Transition Medium 5 2
157 Fill Medium 10 6
15S Fill Medium 25 15
159 Fill Medium 35 10
PA-8 Model Lot Complex
169 Overexcavation Medium 4 1
170 Overexcavation Medium 4 1
171 Transition Medium 20 15
172 Fill Medium 30 10
PA-9 Model Lot Complex
269 Overexcavation Low 5 1
270 Overexcavation Low 5 1
271 Overexcavation Low 5 1
272 Overexcavation Low 5 1
PA-10 Model Lot Complex
374 Fill Low 30 20
T-l
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feet)
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-10 Model Lot Complex (continued)
375 Transition Low 6 2
376 Transition Low 6 2
377 Transition Low 7 1
PA-12 Model Lot Complex
448 Fill Low 75 15
449 Fill Low 75 20
450 Fill Medium 80 15
451 Fill Medium SO 15
452 Fill Medium 80 15
PA-6 Phase 1 Production Lots
30 Fill High 35 25
31 Fill Medium 25 15
32 Fill Medium 20 10
33 Fill Medium 20 10
34 Fill Medium 20 10
55 Fill Low 55 15
56 Fill Low 55 10
57 Fill Medium 55 10
58 Fill Medium 60 20
59 Fill Medium 55 30
380 Overexcavation Low 7 2
381 Transition Low 8 2
382 Transition Low 6 2
383 Overexcavation Low 6 1
T-2
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feet)
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-6 Phase 1 Production Lots (Continued)
404 Cut Very Low 0 0
405 Cut Very Low 0 0
406 Cut Very Low 0 0
407 Overexcavation Low 5 1
408 Overexcavation Low 5 1
409 Overexcavation Low 5 1
410 Overexcavation Low 5 1
411 Overexcavation High 5 1
PA-7 Phase 1 Production Lots
127 Overexcavation Medium 4 1
128 Overexcavation Medium 4 1
129 Overexcavation Medium 4 1
130 Overexcavation Medium 4 1
131 Overexcavation Medium 4 1
132 Overexcavation High 4 1
133 Overexcavation High 4 1
134 Overexcavation High 4 1
135 Overexcavation High 4 1
136 Transition High 10
137 Overexcavation Medium 4 1
138 Overexcavation Medium 4 1
139 Overexcavation Medium 4 1
140 Overexcavation Medium 4 1
141 Overexcavation Medium 4 1
T-3
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feet)
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-7 Phase 1 Production Lots (Continued)
142 Overexcavation Medium 4 1
143 Overexcavation Medium 4 1
180 Overexcavation Low 4 1
181 Overexcavation Low 4 1
182 Overexcavation Medium 4 1
183 Overexcavation Medium 4 1
184 Overexcavation Medium 4 1
185 Overexcavation Medium 4 1
186 Overexcavation Medium 4 1
187 Transition Medium 10
188 Overexcavation Medium 4 1
189 Overexcavation Medium 4 1
190 Overexcavation Medium 4 1
191 Overexcavation Medium 4 1
192 Overexcavation Medium 4 1
193 Overexcavation Medium 4 1
PA-9 Phase 1 Production Lots
263 Overexcavation Low 4 1
264 Overexcavation Low 5 2
265 Fill Low 35 25
266 Fill Low 30 20
267 Fill Low 20 10
268 Overexcavation Low 5 1
281 Overexcavation Low 4 1
T-4
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feet)
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-9 Phase 1 Production Lots (Continued)
282 Overexcavation Low 4 1
283 Overexcavation Low 4 1
284 Overexcavation Low 4 1
PA-10 Phase 1 Production Lots
1 Fill Low 100 10
2 Fill Low 100 30
3 Fill Low 70 35
4 Fill Low 55 25
5 Fill Low 20 10
6 Fill Low 15 10
7 Transition Low 10 3
8 Transition Low 5 1
9 Overexcavation Low 5 1
10 Overexcavation Medium 5 1
11 Overexcavation Medium 5 1
12 Overexcavation Medium 5 1
13 Overexcavation Medium 5 1
PA-12 Phase 1 Production Lots
427 Fill Medium 65 20
428 Fill Medium 55 20
429 Fill Medium 50 20
430 Fill Medium 50 20
431 Fill Medium 50 15
432 Fill Medium 55 20
T-5
971009-014
Table 1
Lot-By-Lot Summary of As-Graded Geotechnical Conditions
Model and Phase 1 Production Lots
Lot
Number Lot Type Finish Grade
Expansion Potential
Approximate Maximum
Fill Thickness on Lot (in
feeO
Approximate Differential
Fill Thickness Across
Proposed Building
Footprint (in feet)
PA-12 Phase 1 Production Lots (Continued)
433 Fill Medium 55 20
434 Fill Medium 70 20
435 Fill Low 35 15
436 Fill Low 25 15
437 Fill Low 15 10
438 Fill Low 12 8
439 Fill Low 20 15
440 Fill Low 55 25
441 Fill Low 55 35
442 Fill Low 55 35
443 Fill Low 55 35
T-6
971009-014
APPENDIX A
References
Califomia Building Standards Commission (CBSC), 2001, CaHfomia Building Code, Volume I -
Adminisfrative, Fire- and Life-Safety, and Field Inspection Provision, Volume II -
Stmctural Engineering Design Provision, and Volume HI - Material, Testing and
Installation Provision, ICBO.
Hart, E.W., 1997, Fault-Rupture Hazard Zones in Califomia, Alquist-Priolo Special Studies Zones
Act of 1972 with Index to Special Studies Zones Maps: Department of Conservation,
Division of Mines and Geology, Special Publication 42.
Intemational Conference of Building Officials (ICBO), 1997, Uniform Building Code, Volume I -
Adminisfrative, Fire- and Life-Safety, and Field Inspection Provisions, Volume II -
Stmctural Engineering Design Provisions, and Volume III - Material, Testing and
Installation Provision, ICBO.
Leighton and Associates, Inc., 1997, Preliminary Geotechnical Investigation, Bressi Ranch,
Carlsbad, Califomia, Project No. 4971009-002, dated July 29, 1997.
, 2001, Supplemental Geotechnical hivestigation for Mass Grading, Bressi Ranch,
Carlsbad, Califomia, ProjectNo. 971009-0015, dated March 14,2001.
—, 2003a, Geotechnical Grading Plan Review of the Mass Grading plans, Bressi Ranch,
Carlsbad, Califomia, ProjectNo. 971009-007, dated January 17, 2003.
—, 2003b, Preliminary Residential and Commercial Foundation Design
Recommendations, Bressi Rcinch, Carlsbad, Califomia, Project No. 971009-007,
dated Febmary 5, 2003.
- 2003c, Geotechnical Recommendations Conceming 95 Percent Relative Compaction
of Fills Deeper than 40 Feet, Bressi Ranch, Carlsbad, Califomia, Project No.
971009-007, dated Febmary 13, 2003.
- 2003d, Reconimended Type of Pipe for Proposed Subdrains, Bressi Ranch, Carisbad,
Califomia, ProjectNo. 971009-007, dated April 17, 2003.
-, 2003e, Advanced Preliminary Street Pavement Sections Based on Assumed Street
Subgrade Soil R-Values and Traffic Indexes, Bressi Ranch, Carisbad, Califomia,
August 8,2003, dated August 8, 2003.
- 2003f, Side-Yard Drainage Recommendation Altemative, Bressi Ranch, Carlsbad,
Califomia, Project No. 971009-014, dated August 28,2003.
A-l
971009-014
APPENDIX A (continued)
Project Design Consultants, 2003a, Mass Grading and Erosion Control Plans for: Bressi Ranch,
Carlsbad, Califomia, Carlsbad Tract No. 00-06, Drawing No. 400-8A; dated
January 7, 2003, revised November 24, 2003.
-, 2003b, Grading and Erosion Control Plans: Bressi Ranch Planning Area 7, Unit No. 2,
Carlsbad Tract No. CT 02-14(2), Carisbad, Califomia, Drawing No. 411-4A, 9
Sheets, dated December 19, 2003.
-, 2003c, Grading and Erosion Confrol Plans: Bressi Ranch Planning Area 8, Unit No. 3,
Carlsbad Tract No. CT 02-14(3), Carlsbad, Califomia, Drawing No. 411-8A, 9
Sheets, dated December 19,2003.
-, 2003d, Grading and Erosion Control Plans: Bressi Ranch Planning Area 9, Unit No. 4,
Carlsbad Tract No. CT 02-14(4), Carlsbad, Califomia, Drawing No. 41I-7A, 9
Sheets, dated December 21, 2003.
2004a, Grading and Erosion Confrol Plans: Bressi Ranch Planning Area 6, Unit No. 1,
Carlsbad Tract No. CT 02-14(1), Carisbad, Califomia, Drawing No. 4I1-3A, 7
Sheets, dated Febmary 3,2004.
-, 2004b, Grading and Erosion Control Plans: Bressi Ranch Planning Area 10, Unit No.
5, Carlsbad Tract No. CT 02-14(5), Carisbad, Califomia, Drawing No. 411-lA, 9
Sheets, dated Febmary 3, 2004.
-, 2004c, Grading and Erosion Control Plans: Bressi Ranch Planning Area 12, Unit No.
6, Carlsbad Tract No. CT 02-14, Carlsbad, Califomia, Drawing No. 411-2A, 9
Sheets, dated Febmary 3, 2004.
A-2
971009-014
APPENDIX B
1 ahnratnry Testing Proredure.«; and Test Resulte
Maximum Densitv Tests: The maximum dry density and optimum moisture content of typical soils
were determined in accordance with ASTM Test Method D1557. The results of these tests are
presented in the table below:
Sample
Number Sample Description Maximum Dry
Density (pcf)
Optimum Moisture
Content (%)
1 Light-brown clayey SAND (Alluvium) 125.0 11.0
2 Brown sandy silty CLAY (Alluvium) 122.5 11.5
3 Light-brown silty clayey SAND (Alluvium) 122.0 11.0
4 Olive-brown clayey SAND (Alluvium) 120.5 12.5
5 Olive brown sandy CLAY (Alluvium) 124.0 12.0
6 Red-brown sandy CLAY (Alluvium) 122.5 11.5
7 Olive light brown silty fine SAND 122.0 13.0
8 Gray Brown to Olive Brown clayey silty fme SAND 117.5 14.0
9 Light Olive-gray clayey silty SAND 118.0 15.0
10 Light brown Clayey very fine SAND 112.5 16.0
11 Brown clayey SAND (fill mix) 120.0 13.0
12 Brown clayey SAND (fill mix) 120.0 12.5
13 Dark brown sandy CLAY (Alluvium) 115.0 16.5
14 Light brown olive brown 124.0 12.0
15 Light gray brown silty very fine to fine SAND 112.0 15.5
16 Light gray fine sand 117.0 14.0
17 Light yellow-brown clayey silty SAND 114.0 14.5
18 Light olive brown silty clayey SAND 113.0 16.0
19 Yellow brown clayey silty SAND 118.0 15.0
20 Pale Olive light brown clayey silty SAND 116.0 14.0
21 Pale Olive light brown clayey silty SAND 118.0 13.0
B-l
APPENDIX B (Continued)
971009-014
Sample
Number Sample Description Maximum Dry
Density (pcO
Optimum
Moisture Content
(%)
22 Pale olive to gray brown silty sand 124.0 12.0
23 Pale Olive to Gray brown clayey silty SAND 119.0 13.0
24 Yellow-Brown Clayey SAND 116.0 13.5
25 Brown CLAY 104.0 19.0
26 Olive Gray CLAY 112.0 17.0
27 Yellow-Brown Clayey SAND 118.5 14.0
28 Brown Silty SAND 126.0 9.5
Expansion Index Tests: The expansion potential of selected materials was evaluated by the
Expansion Index Test, UBC Standard No. 18-2. Specimens are molded under a given compactive
energy to approximately the optimum moisture content and approximately 90 percent relative
compaction. The prepared l-inch thick by 4-inch diameter specimens are loaded to an equivalent
144 psf surcharge and are inundated with distilled water until volumetric equilibrium is reach. The
results of these tests are presented in the table below:
Sample
Number
Representative
Lots
Sample
Location Soil Type Expansion
Index
Expansion
Potential*
E12 Lots 13-15 Lot 14 Yellow-brown sandy CLAY 51 Medium
E13 Lots 10-12 Lot 11 Yellow-brown sandy CLAY 63 Medium
E14 Lots 7-9 Lots Olive-brown silty SAND 32 Low
E15 Lots 4-6 Lot 5 YeUow-brown silty SAND 39 Low
E16 Lots 60-63 Lot 62 Yellow-brown sandy CLAY 76 Medium
E17 Lots 57-59 Lot 59 Brown sandy CLAY 85 Medium
E18 Lots 55-56 Lot 56 Yellow-brown silty SAND 27 Low
E19 Lots 1-3 Lot 2 Yellow-brown silty SAND 47 Low
E26 Lots 28-30 Lot 28 Dark brown sandy CLAY 92 High
E27 Lots 31-34 Lot 31 Light brown clayey SAND 56 Medium
B-2
APPENDIX B (Continued)
971009-014
Sample
Number
Representative
Lots
Sample
Location Soil Type Expansion
Index
Expansion
Potential*
E40 Lots 380-383 Lot 381 Pale gray silty SAND 22 Low
E41 Lots 377-379 Lot 378 YeUow-brown silty clayey
SAND 23 Low
E42 Lots 374-376 Lot 374 YeUow-brown silty clayey
SAND 28 Low
E45 Lots 404-406 Lot 405 Pale gray silty SAND 6 Very Low
E46 Lots 450-452 Lot 451 YeUow-brown sandy SILT 56 Medium
E47 Lots 447-449 Lot 447 YeUow-brown silty clayey
SAND 38 Low
E50 Lots 425-429 Lot 427 Pale gray sandy SILT 66 Medium
ESl Lots 430-434 Lot 432 Pale gray sandy CLAY 77 Medium
E54 Lots 439-443 Lot 441 Pale gray silty clayey SAND 42 Low
E55 Lots 435-438 Lot 437 Pale gray silty clayey SAND 23 Low
E58 Lots 127-131 Lot 128 Olive-brown sandy CLAY 83 Medium
E59 Lots 132-136 Lot 133 YeUow-brown sandy CLAY 102 High
E60 Lots 137-140 Lot 139 Olive-brown sandy CLAY 76 Medium
E61 Lots 141-143 Lot 142 Brown clayey SAND to sandy
CLAY
67 Medium
E65 Lots 407-410 Lot 409 YeUow-brown silty clayey
SAND 27 Low
E66 Lots 411-414 Lot 413 Olive-brown sandy CLAY 111 High
E76 Lots 263-267 Lot 270 YeUow-brown silty clayey
SAND 24 Low
E77 Lots 268-272 Lot 270 YeUow-brown silty clayey
SAND 26 Low
E91 Lots 112-115 Lot 113 Olive-brown sandy SILT 56 Medium
B-3
971009-014
APPENDIX B(Continued)
Sample
Number
Representative
Lots
Sample
Location Soil Type Expansion
Index
Expansion
Potential*
E94 Lots 156-159 Lot 158 Yellow-brown sandy SILT 51 Medium
ElOO Lots 279-284 Lot 281 YeUow-brown silty SAND 38 Low
E102 Lots 168-172 Lot 169 Brown sandy SILT 55 Medium
E104 Lots 177-181 Lot 180 Yellow-Brown sandy SILT 29 Low
E105 Lots 182-186 Lot 185 YeUow-brown sandy 60 Medium
E106 Lots 187-190 Lot 188 Olive-brown sandy CLAY 83 Medium
E107 Lots 191-195 Lot 194 Olive-brown silty SAND 31 Low
* Based on the 1997 edition ofthe Uniform Building Code Table 18-I-B.
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard
geochemical methods. The test resuhs are presented in the table below:
Sample
Location Sample Description Sulfate
Content (%)
Potential Degree of
Sulfate Attack*
Lot 14 YeUow-brown sandy CLAY 0.10 Moderate
Lot 11 YeUow-brown sandy CLAY 0.125 Moderate
Lot 8 Olive-browTi silty SAND 0.05 Negligible
Lot 5 YeUow-brown silty SAND 0.07 Negligible
Lot 62 YeUow-brown sandy CLAY 0.06 Negligible
Lot 59 Brown sandy CLAY <0.015 Negligible
Lot 56 YeUow-brown silty SAND 0.021 Negligible
Lot 2 YeUow-brown silty SAND 0.15 Moderate
Lot 28 Dark brown sandy CLAY 0.021 Negligible
Lot 31 Light brown clayey SAND 0.018 Negligible
Lot 381 Pale gray silty SAND <0.015 Negligible
B-4
APPENDIX B(Continued)
971009-014
Sample
Location Sample Description Sulfate
Content (%)
Potential Degree of
Sulfate Attack*
Lot 378 Yellow-brown silty clayey SAND <0.015 Negligible
Lot 374 YeUow-brown silty clayey SAND <0.015 Negligible
Lot 405 Pale gray silty SAND <0.015 Negligible
Lot 451 YeUow-brown sandy SILT 0.10 Moderate
Lot 447 Yellow-brown silty clayey SAND 0.063 Negligible
Lot 427 Pale gray sandy SILT 0.10 Moderate
Lot 432 Pale gray sandy CLAY 0.10 Moderate
Lot 441 Pale gray silty clayey SAND 0.063 Negligible
Lot 437 Pale gray silty clayey SAND 0.075 Negligible
Lot 128 Olive-brown sandy CLAY 0.063 Negligible
Lot 133 YeUow-brown sandy CLAY 0.027 Negligible
Lot 139 Olive-brown sandy CLAY 0.06 Negligible
Lot 142 Brown clayey SAND to sandy CLAY 0.075 Negligible
Lot 409 YeUow-brown silty clayey SAND 0.15 Moderate
Lot 413 Olive-brown sandy CLAY 0.20 Severe
Lot 265 YeUow-brown silty clayey SAND 0.06 Negligible
Lot 270 YeUow-brown silty clayey SAND 0.15 Moderate
Lot 113 Olive-brown sandy SILT 0.20 Severe
Lot 158 YeUow-brown sandy SILT 0.125 Moderate
Lot 181 YeUow-brown silty SAND 0.075 Negligible
B-5
971009-014
APPENDIX B (Continued)
Sample
Location Sample Description Sulfate
Content (%)
Potential Degree of
Sulfate Attack*
Lot 169 Brown sandy SILT 0.10 Moderate
Lot 180 Yellow-Brown sandy SILT 0.03 Negligible
Lot 185 YeUow-brown sandy 0.062 Negligible
Lot 188 Olive-brown sandy CLAY 0.035 Negligible
Lot 194 Olive-brown silty SAND 0.10 Moderate
* Based on the 1997 edition of the Uniform Building Code Table 19-A-4.
B-6
Leightonand Associates,Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 1 of 6
LEIGHTON AND ASSOCIATES, INC.
GENERAL EARTHWORK AND GRADING SPECIFICATIONSFOR ROUGH GRADING
1.0 General
1.1 Intent: These General Earthwork and Grading Specifications are for the grading and
earthwork shown on the approved grading plan(s) and/or indicated in the geotechnical
report(s). These Specifications are a part of the recommendations contained in the
geotechnical report(s). In case of conflict, the specific recommendations in the
geotechnical report shall supersede these more general Specifications. Observations of the
earthwork by the project Geotechnical Consultant during the course of grading may result
in new or revised recommendations that could supersede these specifications or the
recommendations in the geotechnical report(s).
1.2 The Geotechnical Consultant of Record: Prior to commencement of work, the owner shall
employ the Geotechnical Consultant of Record (Geotechnical Consultant). The
Geotechnical Consultants shall be responsible for reviewing the approved geotechnical
report(s) and accepting the adequacy of the preliminary geotechnical findings, conclusions,
and recommendationsprior to the commencementof the grading.
Prior to commencement of grading, the Geotechnical Consuhant shall review the "work
plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel
to perform the appropriate level of observation, mapping, and compaction testing.
During the grading and earthwork operations, the Geotechnical Consultant shall observe,
map, and document the subsurface exposures to verify the geotechnical design
assumptions. If the observed conditions are found to be significantly different than the
interpreted assumptions during the design phase, the Geotechnical Consultant shall infonn
the owner, recommend appropriate changes in design to accommodate the observed
conditions, and notify the review agency where required. Subsurface areas to be
geotechnically observed, mapped, elevations recorded, and/or tested include natural ground
after it has been cleared for receiving fill but before fill is placed, bottoms of all "remedial
removal" areas, all key bottoms, and benches made on sloping ground to receive fill.
The GeotechnicalConsultantshall observe the moisture-conditioningand processing ofthe
subgrade and fill materials and perform relative compaction testing of fill to determine the
attained level of compaction. The Geotechnical Consultant shall provide the test results to
the owner and the Contractor on a routine and frequent basis.
3030.1094
Leightonand Associates,Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 2 of 6
The Earthwork Contractor: The Earthwork Contractor (Contractor) shall be qualified,
experienced, and knowledgeable in earthwork logistics, preparation and processing of
ground to receive fill, moisture-conditioningand processing of fill, and compacting fill.
The Contractor shall review and accept the plans, geotechnical report(s), and these
Specifications prior to commencement of grading. The Contractor shall be solely
responsible for performing the grading in accordance with the plans and specifications.
The Contractor shall prepare and submit to the owner and the Geotechnical Consultant a
work plan that indicates the sequence of earthwork grading, the number of "spreads" of
work and the estimated quantities of daily earthwork contemplated for the site prior to
commencement of grading. The Contractor shall inform the owner and the Geotechnical
Consultant of changes in work schedules and updates to the work plan at least 24 hours in
advance of such changes so that appropriate observations and tests can be planned and
accomplished. The Contractor shall not assume that the Geotechnical Consultant is aware
of all grading operations.
The Contractor shall have the sole responsibility to provide adequate equipment and
methods to accomplish the earthwork in accordance with the applicable grading codes and
agency ordinances, these Specifications, and the recommendations in the approved
geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical
Consultant, unsatisfactory conditions, such as unsuitable soil, improper moisture condition,
inadequate compaction, insufficient buttress key size, adverse weather, etc., are resulting in
a quality of work less than required in these specifications, the Geotechnical Consultant
shall reject the work and may recommend to the owner that construction be stopped until
the conditions are rectified.
2.0 Preparation of Areas to be Filled
2.1 Clearing and Grubbing: Vegetation, such as brush, grass, roots, and other deleterious
material shall be sufficiently removed and properly disposed of in a method acceptable to
the owner, goveming agencies, and the Geotechnical Consultant.
The Geotechnical Consultant shall evaluate the extent of these removals depending on
specific site conditions. Earth fill material shall not contain more than 1 percent of organic
materials (by volume). No fill lift shall contain more than 5 percent of organic matter.
Nesting of the organic materials shall not be allowed.
If potentially hazardous materials are encountered, the Contractor shall stop work in the
affected area, and a hazardous material specialist shall be informed immediately for proper
evaluation and handling of these materials prior to continuing to work in that area.
As presently defined by the State of Califomia, most refined petroleum products (gasoline,
diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered
to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids
onto the ground may constitute a misdemeanor, punishable by fines and/or imprisonment,
and shall not be allowed.
Leightonand Associates,Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 3 of 6
2.2 Processing: Existing ground that has been declared satisfactory for support of fill by the
Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing
ground that is not satisfactory shall be overexcavated as specified in the following section.
Scarification shall continue until soils are broken down and free of large clay lumps or
clods and the working surface is reasonably uniform, flat, and free of uneven features that
would inhibit uniform compaction.
2.3 Overexcavation: In addition to removals and overexcavations recommended in the
approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy,
organic-rich, highly fractured or otherwise unsuitable ground shall be overexcavated to
competent ground as evaluated by the Geotechnical Consultant during grading.
2.4 Benching: Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal
to vertical units), the ground shall be stepped or benched. Please see the Standard Details
for a graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and
at least 2 feet deep, into competent material as evaluated by the Geotechnical Consultant.
Other benches shall be excavated a minimum height of 4 feet into competent material or as
otherwise recommended by the Geotechnical Consultant. Fill placed on ground sloping
flatterthan 5:1 shall also be benched or otherwise overexcavated to provide a flat subgrade
forthefiU.
2.5 Evaluation/Acceptance of Fill Areas: All areas to receive fill, including removal and
processed areas, key bottoms, and benches, shall be observed, mapped, elevations
recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable
to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical
Consultant prior to fill placement. A licensed surveyor shall provide the survey control for
determ ining elevations of processed areas, keys, and benches.
3.0 Fill Material
3.1 General: Material to be used as fill shall be essentially free of organic matter and other
deleterious substances evaluated and accepted by the Geotechnical Consultant prior to
placement. Soils of poor quality, such as those with unacceptable gradation, high
expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical
Consuhant or mixed with other soils to achieve satisfactoryfill material.
3.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum
dimension greater than 8 inches, shall not be buried or placed in fill unless location,
materials, and placement methods are specifically accepted by the Geotechnical
Consultant. Placement operations shall be such that nesting of oversized material does not
occur and such that oversize material is completely surrounded by compacted or densified
fill. Oversize material shall not be placed within 10 vertical feet of finish grade or within
2 feet of future utilities or underground construction.
3030.1094
Leightonand Associates,Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 4 of 6
3.3 Import: If importing of fill material is required for grading, proposed import material shall
meet the requirements of Section 3.1. The potential import source shall be given to the
Geotechnical Consuhant at least 48 hours (2 working days) before importing begins so that
its suitability can be determined and appropriate tests performed.
4.0 Fill Placementand Compaction
4.1 Fill Layers: Approved fill material shall be placed in areas prepared to receive fill (per
Section 3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The
Geotechnical Consultant may accept thicker layers if testing indicates the grading
procedures can adequately compact the thicker layers. Each layer shall be spread evenly
and mixed thoroughlyto attain relative uniformity of material and moisture throughout.
4.2 Fill Moisture Conditioning: Fill soils shall be watered, dried back, blended, and/or mixed,
as necessary to attain a relatively uniform moisture content at or slightly over optimum.
Maximum density and optimum soil moisture content tests shall be performed in
accordance with the American Society of Testing and Materials (ASTM Test Method
D1557-91).
4.3 Compaction of Fill: After each layer has been moisture-conditioned, mixed, and evenly
spread, it shall be uniformly compactedto not less than 90 percentof maximum dry density
(ASTM Test Method D1557-91). Compaction equipment shall be adequately sized and be
either specifically designed for soil compaction or of proven reliability to efficiently
achieve the specified level of compaction with uniformity.
4.4 Compaction of Fill Slopes: In addition to normal compaction procedures specified above,
compaction of slopes shall be accomplished by backrolling of slopes with sheepsfoot
rollers at increments of 3 to 4 feet in fill elevation, or by other methods producing
satisfactory results acceptable to the Geotechnical Consultant. Upon completion of
grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of
maximum density per ASTM Test Method Dl 557-91.
4.5 Compaction Testing: Field tests for moisture content and relative compaction of the fill
soils shall be performed by the Geotechnical Consultant. Location and frequency of tests
shall be at the Consultant's discretion based on field conditions encountered. Compaction
test locations will not necessarily be selected on a random basis. Test locations shall be
selected to verify adequacy of compaction levels in areas that are judged to be prone to
inadequate compaction (such as close to slope faces and at the fill/bedrock benches).
3030.1094
Leighton and Associates, Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 5 of 6
4.6 Frequency of Compaction Testing: Tests shall be taken at intervals not exceeding 2 feet in
vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a
guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope
face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill
construction is such that the testing schedule can be accomplished by the Geotechnical
Consultant. The Contractor shall stop or slow down the earthwork construction if these
minimum standards are not met.
4.7 Compaction Test Locations: The Geotechnical Consultant shall document the approximate
elevation and horizontal coordinates of each test location. The Contractor shall coordinate
with the project surveyor to assure that sufficient grade stakes are established so that the
Geotechnical Consultant can determine the test locations with sufficient accuracy. At a
minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than
5 feet apart from potential test locations shall be provided.
5.0 Subdrain Installation
Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the
grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional
subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions
encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for
line and grade after installation and prior to burial. Sufficient time should be allowed by the
Contractor for these surveys.
6.0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the
Geotechnical Consuhant during grading. Remedial removal depths shown on geotechnical plans
are estimates only. The actual extent of removal shall be determined by the Geotechnical
Consultant based on the field evaluation of exposed conditions during grading. Where fill-over-cut
slopes are to be graded, the cut portion of the slope shall be made, evaluated, and accepted by the
Geotechnical Consultant prior to placement of materials for construction of the fill portion of the
slope, unless otherwise recommended by the Geotechnical Consultant.
3030.1094
Leightonand Associates,Inc.
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Page 6 of 6
7.0 Trench Backfills
7.1 The Contractor shall follow all OHSA and Cal/OSHA requirements for safety of trench
excavations.
7.2 All bedding and backflll of utility trenches shall be done in accordance with the applicable
provisions of Standard Specifications of Public Works Construction. Bedding material
shall have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1
foot over the top of the conduit and densified by jetting. Backfill shall be placed and
densified to a minimum of 90 percent of maximum from 1 foot above the top of the
conduit to the surface.
7.3 The jetting of the bedding around the conduits shall be observed by the Geotechnical
Consultant
7.4 The GeotechnicalConsultant shall test the trench backfill for relative compaction. At least
one test should be made for every 300 feet of trench and 2 feet of fill.
7.5 Lift thickness of trench backflll shall not exceed those allowed in the Standard
Specifications of Public Works Construction unless the Contractor can demonstrate to the
Geotechnical Consultant that the fill lift can be compacted to the minimum relative
compaction by his alternative equipment and method.
3030.1094
FILL SLOPE
EXISTING-
GROUND SURFACE
PROJECTED PLANE
1 TO 1 MAXIMUM FROM
TOE OF SLOPE TO
APPROVED GROUND
2' MIN.—'
KEY
DEPTH
.y^yr.-----j\pj*:T^—'—=jiiiiih
BENCH HEIGHT
(4' TYPICAL)
REMOVE
UNSUITABLE
MATERIAL
15' MIN.
LOWEST
BENCH
(KEY)
FILL-OVER-CUT SLOPE
EXISTING
GROUND SURFACE
-BENCH HEIGHT
(4' TYPICAL)
REMOVE
UNSUITABLE
MATERIAL
-CUT FACE
SHALL BE CONSTRUCTED PRIOR
TO FILL PLACEMENT TO ASSURE
ADEQUATE GEOLOGIC CONDITIONS
CUT-OVER-FILL SLOPE
OVERBUILD AND
TRIM BACK
PROJECTED PLANE
1 TO 1 MAXIMUM
FROM TOE OF SLOPE
TO APPROVED GROUND
CUT FACE SHALL BE
CONSTRUCTED PRIOR
TO FILL PLACEMENT
•REMOVE
UNSUITABLE
MATERIAL
BENCH HEIGHT
(4' TYPICAL)
FOR SUBDRAINS SEE
STANDARD DETAIL C
2' MIN.-
KEY
DEPTH
15' MIN.
LOWEST
BENCH
(KEY)
BENCHING SHALL BE DONE WHEN SLOPE'S
ANGLE IS EQUAL TO OR GREATER THAN 5:1.
MINIMUM BENCH HEIGHT SHALL BE 4 FEET
AND MINIMUM FILL WIDTH SHALL BE 9 FEET
KEYING AND BENCHING
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAILS A
LEIGHTON ANO ASSOCIATES
FINISH GRADE
SLOPE FACE
-fo''UN:C^^^^55S$$5$>^^ 5lMiE^l:-:-:-:-:->:-:-x^^^^
* OVERSIZE ROCK IS LARGER THAN
8 INCHES IN LARGEST DIMENSION.
* EXCAVATE A TRENCH IN THE COMPACTED
FILL DEEP ENOUGH TO BURY ALL THE
ROCK.
* BACKFILL WITH GRANULAR SOIL JETTED
OR FLOODED IN PLACE TO FILL ALL THE
VOIDS.
GRANULAR MATERIAL TO BE'
DENSIFIED IN PLACE BY
FLOODING OR JETTING.
DETAIL
* DO NOT BURY ROCK WITHIN 10 FEET OF
FINISH GRADE.
* WINDROW OF BURIED ROCK SHALL BE
PARALLEL TO THE FINISHED SLOPE.
-JETTED OR FLOODED
GRANULAR MATERIAL
TYPICAL PROFILE ALONG WINDROW
OVERSIZE
ROCK DISPOSAL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAILS B
LEIGHTON AND ASSOCIATES
EXISTING
GROUND SURFACE
BENCHING
j>>^::^
riiiiiE==jiiiii=
A
/
-REMOVE
UNSUITABLE
MATERIAL
SUBDRAIN
TRENCH
SEE DETAIL BELOW
CALTRANS CLASS 2 PERMEABLE-.... yy
OR #2 ROCK (9FT"3/FT) WRAPPED
IN FILTER FABRIC //
FILTER FABRIC
(MIRAFI UON OR APPROVED
EQUIVALENT)*
4" MIN. BEDDING
COLLECTOR PIPE SHALL
BE MINIMUM 6" DIAMETER
SCHEDULE 40 PVC PERFORATED
PIPE. SEE STANDARD DETAIL D
FQR PIPE SPECIFICATIONS
SMBPRAIN PETAIL
DESIGN FINISH
GRADE
NONPERFORATED 6"0 MIN 6 0MiN. PIPE
FILTER FABRIC
(MIRAFI MON OR APPROVED
EQUIVALENT)
CALTRANS CLASS 2 PERMEABLE
OR #2 ROCK (9FT''3/FT) WRAPPED
IN FILTER FABRIC
DETAIL OF CANYON SUBDRAIN OUTLET
CANYON SUBDRAINS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAILS C
LEIGHTON AND ASSOCIATES
15' MIN.
OUTLET PIPES
4" 0 NONPERFORATED PIPE,
100' MAX. O.C. HORIZONTALLY
30' MAX O.C. VERTICALLY
BACK CUT
1 OR FLATTER
•SEE SUBDRAIN TRENCH
DETAIL
LOWEST SUBDRAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
-KEY DEP
(2' MIN.)
KEY WIDTH
AS NOTED ON GRADING PLANS
TH (15' MIN.) 12 MIN. OVERLAP--
FROM THE TOP HOG
RING TIED EVERY
6 FEET
CALTRANS CLASS II
PERMEABLE OR #2
ROCK (3 FT"3/FT)
WRAPPED IN FILTER
FABRIC
• 4" 0
NON-PERFORATED
OUTLET PIPE
PROVIDE POSITIVE
SEAL AT THE
JOINT
T-CONNECTION
FOR COLLECTOR
PIPE TO OUTLET PIPE
6 MIN.
COVER
4 0
PERFORATED
PIPE
-FILTER FABRIC
ENVELOPE (MIRAFI
140 OR APPROVED
EQUIVALENT)
4" MIN.
BEDDING
SUBDRAIN TRENCH DETAIL
SUBDRAIN INSTALLATION - subdrain collector pipe sholl be installed with perforation down or,
unless otherwise designated by the geotechnical consultont. Outlet pipes shall be non-perforated
pipe. The subdrain pipe shall hove ot leost 8 perforations unifornnly spoced per foot. Perforation
shall be 1/4" to 1/2" if drill holes ore used. All subdroin pipes shall hove o grodient of at
least 2% towards the outlet.
SUBDRAIN PIPE - Subdroin pipe shall be ASTM D2751. SDR 23.5 or ASTM D1527, Schedule 40. or
ASTM D3034. SDR 23.5. Schedule 40 Polyvinyl Chloride Plostic (PVC) pipe.
All outlet pipe shall be placed in o trench no wide than twice the subdrain pipe. Pipe shall be in
soil of SE >/=30 jetted or flooded in place except for the outside 5 feet which shall be notive
soil backfill.
BUTTRESS OR
REPLACEMENT FILL
SUBDRAINS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAILS D
LEIGHTON AND ASSOCIATES
-SOIL BACKFILL, COMPACTED TO
90 PERCENT RELATIVE COMPACTION
BASED ON ASTM D1557
RETAINING WALL-
WALL WATERPROOFING
PER ARCHITECTS
SPECIFICATIONS
5" MIN. •
rOVERLAP
o •
3 2 TYP.:-
WALL FOOTING
FILTER FABRIC ENVELOPE
'(MIRAFI MON OR APPROVED
EQUIVALENT)"
-3/4" TO 1-1/2" CLEAN GRAVEL
-4" (MIN.) DIAMETER PERFORATED
PVC PIPE (SCHEDULE 40 OR
EQUIVALENT) WITH PERFORATIONS
ORIENTED DOWN AS DEPICTED
MINIMUM 1 PERCENT GRADIENT
TO SUITABLE OUTLET
-3" MIN.
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
NOTE: UPON REVIEW BY THE GEOTECHNICAL CONSULTANT,
COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR
J-DRAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR
CLASS 2 PERMEABLE MATERIAL INSTALLATION SHOULD BE
PERFORMED IN ACCORDANCE WITH MANUFACTURER'S
SPECIFICATIONS.
RETAINING WALL
DRAINAGE DETAIL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAILS E
LEIGHTON ANO ASSOCIATES