HomeMy WebLinkAboutTract Map 31053-1 As Graded Rough GradingRECEIV~D
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CITY OF TEMECULA
GINEERING DEPARTMENT
AS-GRADED REPORT OF ROUGH GRADING
FOR HARVESTON TRACT 31053-1, LOTS (HOME SITES) 1-38
CITY OF TEMECULA, CALIFORNIA
Prepared For:
Lennar Communities
391 N. Main Street, Suite 301
Corona, California 92880
May 25, 2004
Project No. 110231-024
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Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
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' Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
1 May 25, 2004
Project No. 1 1 023 1-024
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To: Lennar Communities
' 391 North Main Street, Suite 301
Comna, California 92880
' Attention: Mr. Kevin Lynch
Subject: As-Graded Report of Rough Grading for Harveston, Tract 31053-1, Lots (Home
' Sites) 1-38, CityofTemecula, California
In accordance with your request and authorization, I,eighton and Associates, Inc. (Leighton) has
-~ provided. geotechnical observation and testing services during rough grading operations of Tract
31053-1, located in the City of Temecula, California (See Figure 1). The accompanying as-graded
report stunmarizes our observations, field and laboratory test results and the geotechnical conditions
~' encountered during the rough grading of Lots 1 through 38 (also referred to herein as Home Sites) of
Tract 31053-1 within the Harveston Community.
' If you have any quesrions regarding this report, please do not hesitate to contact this o~ce, we
appreciate this opportunity to be of service.
, Respectfully submitted,
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LEIGH'TON AND ASSOCIATES,
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Robert F. Riha, CEG 1921 (Exp. 0:
Vice President/Principal Geologist
RFR/AXT/mm/dlm
110231-024/finaVaz-Ad tpt trac[ 31053-I
Adam erro e
Senior Project
Distribution: (4) Addressee (2 Unbound)
(1) Harveston Jobsite; Attention: Mr. Andy Hendrickson
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41715 Enterprise Circle N., Suite 103 ^ Temecula, CA 92590-5661
909.296.0530 . Fax 909.296.0534 ^ www.leightongeo.com
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11023 1-024
May 25, 2004
, TABLE OF CONTENTS
Section
Paae
~ 1.0 INTRODUCTION .......................
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2.0 SUMMARY OF ROUGH-GRADING OPERATIONS .....
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' 2.1 Site Preparation and Removals
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2 Fl
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2.3 Laboratory Testing 2
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2.4 FII Placement
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3.0 GEOTECHNICAL SUMMARY ,,,,.,,,,,,
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3.1 As-Graded Geologic Conditions
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3.2.2 Artifidal FlII Leighton (Afl) ....
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3.2.3 Allwium ~Qa~) 4
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3.2.4 Pauba frormation ~Qp) 4
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3.3 Geologic Structure and Faultin9 ...................... 4
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3.4 Landslides and Surficial Failures,,,,,,,,,,,,,,,,,,,,,,,,,,,
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5 Groundwater
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3.6 Expansion Testing of Fnish Grade Soils
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4.0 CONCLUSIONS 6
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' 4.1 General .........................................................................................
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4.2 Summary of Conclusions ...
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' S.0 RECOMMENDATIONS ..............................................
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5.1 Earthwork ........................................ $
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1 5.1.1 Excavadons 8
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5.1.2 Utility Backfill, Fill Placement and Compaction
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5.2 Foundation and Structure Design Considerations ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, g
53 Foundation Setback from Slopes,,,,,,,,,,,,,,,,,,,,,,,,
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5.4 Structure Seismic Design Parameters ,,,,,,,,,,,,, 10
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5.5 Corrosion ......................
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5.6 Lateral Earth Pressures and Retaining Wall Design Considerations ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,11
5.7 Concrete Flatwork,,,
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5.8 Control of SurFace Water and Drainage Control,,,,,,,,,,,,,,,,,; 13
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5.9 Graded Slopes ................. ....... .................................................................................
5.10 Irrigation, Landscaping and Lot Maintenance,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 13
5.11 Post-Grading Geotechnical Review ,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, , 14
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' Table of Contents (cont.)
5.11.1 Construction Review .......................................................................................14
' S.11.2 Plans and Specifications ............................................. ........14
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6.0 LIMITATIONS ..................................................................................................................15
, Accompanying Fgures, Tables, Plates and Appendices
' . Fgures
' Fgure 1- Site Location Map Rear of Text
Fgure 2- Retaining Wall Drainage Detail for Low Expansive Soils Rear of Text
Tables
Table 1- Lot (Home Site) Summary of As-graded Geotechnical
, Conditions and Recommendations Rear of Text
Table 2- Minimum Conventionai Foundation Design Recommendations Rear of Text
' Table 3-
Table 4- Minimum Post-Tensioned Foundation Design Recommendations
Lateral Earth Pressures Rear of Text
Rear of Text
' Plates
Plate 1- As-Graded Geotechnical Map In Pocket
Plate 2- Fieid Density Test Location Map In Pocket
' Appendices
' Appendix A - References
Appendix B- Summary of Feld Density Tests
Appendix C- Laboratory Testing Procedures and Test Results
' Appendix D- Lot (Home Site) Maintenance Guidelines for Owners
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1.0 INTRODUCTION
' In accordance with your request and authorization, Leighton and Associates, Ina (Leighton) has
performed geotechnical observation and testing services during the most recent phase of rough-
, grading operations of I.ots 1 through 38 (also referred to herein as Home Sites) of Tract 31053-1
within the Harveston Community. Portions of the subject Tract had been previously "sheeY' graded
under the observation and testing of Leighton (I,eighton, 2003b).
' This as-graded report su~tunarizes our geotechnical observations, field and laboratory test results
and the geotechnical conditions encountered during the recent rough grading of the subject Lots
' (Home Sites) within Tract 31053-i. In addition, this report provides conclusions and
recommendations for the proposed residential development of the subject Lots (Home Sites).
' The referenced 40-scale grading plans for Tract 31053-1 (RBF, 2003) were annotated and utilized
as a base map (Plates 1. & 2) to plot geotechnical conditions and the approximate locations of the
' field density tests taken during mugh-grading operations.
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2.0 SUMMARY OF ROUGH-GRADING OPERATIONS
Portions of Tract 31053-1 were initially sheet graded as Tract 29639-1 under the observation and
testing of I,eighton (Leighton, 2003b). Rough grading to the approved design configuration
(RBF, 2003) was conducted by ACI, Inc. in June through December of 2003, under the
geotechnical observation and testing services of Leighton. L,eighton field technician(s) and
geologist were onsite on a full-time and as-needed basis, as requested, during grading operations.
Rough grading involved the removals of desiccated fill, alluvium, and weathered bedrock to
competent previously-placed compacted fill or competent Pauba Formation and the placement of
additional compacted artificial fill (I,eighton, 2003b) to depths of approximately 3 to 22 feet to
create the design residential Lots (Home Sites) and associated roadways. The total fill thicl~ess
is reported on Table 1(reaz of text).
2.1 Site Preparation and Removals
, Prior to grading, deleterious materials were removed from the areas of proposed development
and disposed of offsite. Grading of the subject site was initiated by removal of unsuitable
surficial material. The removals were completed when dense, damp to moist (near optimum
moisture content), relatively non-porous, Pauba Formation or competent previously-placed
compacted fill (I.eighton, 2003b) was encountered in accordance with the recommendations of
the project geotechnical reports (Appendix A) and the geotechnical recommendations made
during gading operations. Approximate removal bottom elevations are depicted on the
enclosed As-Graded Geotechnical Map (Plate 1).
2.2 Field Densitv Testing
Field density testing was performed using the nuclear gauge method (ASTM Test Methods
D2922 and D3017). Tested azeas appear to .meet the mivimum required 90 percent relative
compaction with optimum moisture content or above. Areas that tested less than the required 90
pe~ent relative compaction, were reworked, moisture conditioned as necessary and compacteci
until the uiiuimum 90 percent was obtained. The results and approximate locations of the field
density tests are summarized in Appendix B. The approximate locations of the fie]d density tests
aze depicted on the enclosed Field Density Test Location Map (Plate 2).
2.3 Laboratorv Testing
Laboratory compaction chazacteristics (maacimum dry density and optunum moisture),
expansion index, Atterberg limits, and soluble sulfate tests of representative onsite soils were
performed during the course of rough-grading and aze presented in Appendix C. A description
of the laboratory test procedures aze also presented in Appendix C. The interpretation of the
laboratory data for each Lot (Home Site) is presented in Table 1 at the rear of text.
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2.4 Fill Placement
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Fill materials consisting of the soil types Gsted in Appendix C was placed in thin li8s
processed and moisture conditioned to neaz optimum moisture content, and compacted in
place to a minimum of 90 percent of the laboratory derived maximum density. Fill
placement and compaction was accomplished with the use of heary earthwork equipment.
For a description of the removal criteria refer to the Supplemental Geotechnical
Investigation Report (Leighton, 2003a).
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3.0 GEOTECHNICAL SUMMARY
t 3.1 As-Graded Geoloqic Conditions
' The as-graded conditions encountered during grading of the subject Lots (Home Sites) was
, essentially as anricipated. A summary of the geologic conditions, including geologic units,
' geologic skuchue and faulting is presented below.
3.2 Geologic Units
' The geologic units observed during grading of the subject Lots (Home Sites) consisted of
artificial fill (A~, previously-placed compacted fill (Afl), alluvium (Qal), and the Pauba
' Formation (Qp) which are discussed below:
3.2.1 Artificial Fill fAfl - Locally derived aztificial fill soils generally consisted of olive gray to
' olive brown silty sand to locally slightly clayey silt}t sand. Artificial fill soils were placed
under the observation and field density testing by I.eighton representatives during this
phase of grading. After moisture conditioning and thorough mixing, the artificial fill soils
' were placed in relatively thin lifts and compacted utilizing heavy-duty constmction
equipment.
' 3.2.2 Artifiaal Fill Leighton (~fll - The artificial fill encountered from the previous phase of
grading 2002/2003 geneially consisted of brown to dazk brown, moist, medium dense to
' dense silty sand. As encountered during grading, the artificial fill was generally moderately
dense near the surface, becoming more dense with depth. The weathered artificial fill .
materials were scarified to a depth of 6 inches, moishue conditioned, thoroughly mixed
' and re-used as compacted fill. .
3.2.3 Alluvium (Oall - The alluvium generally consists of porous medium brown to dazk red-
, brown, medium dense, fine sand to silty sand. The alluvium was removed, moisture
conditioned, and re-used as compacted fill.
, 3.2.4 Pauba Formadon (Oo) - The late Pleistocene-Aged Pauba Formation generally
consists of light brown to olive-brown to medium brown, damp to moist, medium dense
to dense, siltstone, sandstone and silty claystone. Fractures aze locally lined with calcium
' carbonate. The Pleistocene-Aged formation was moishue conditioned and re-used as
compacted fill.
, 3.3 Geologic Structure and Faulting
~ Based on our geologic observations during site gading, the Pauba Formation is massive with
localized bedding, which is generally flat lying. No faulting or indications of faulting were
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anricipated or observed wiUvn or immediately adjacent to the subject tract during this phase of
' grading. The neazest "zoned" active fault is the Temecula Segment of the Elsinore Fault Zone
located approximately 0.6 miles (1.O lan) to the southwest.
' 3.4 Landsiides and Surficial Failures
, Based on our review of the project geotechnical reports (Appendix A) and our geologic
observations during the course of grading operations, there were no indications of landslides or
other significant surficial failures within the subject tract. It should be noted that unplanted or
' unprotected slopes aze subject to erosion and subsequent surficial instability.
3.5 Groundwater
' Groundwater was not encountered during recent or previous rough grading. Canyon
subdrains were consttucted during mass grading in general accordance with : the project
, geotechnical reports (Appendix A). However, unforeseen conditions may occur aftet the
completion of grading and establishment of site irrigation and landscaping. Perched
groundwater may accumulate at layers of differing permeability or at bedrock/fill contacts. If
' these condirions should occur, methods should be taken to mitigate any resulting seepage.
PresenUy the majority of the subject site drains towards the east and any surface runoff will tend
to collect at low points until such time that the proposed design drainage facilities are
' constructed. If water is allowed to pond in these azeas for any length of time the subgrade in
these areas may become saturated and additional grading may be required to mitigate this
condition. We recommend that the project erosion control program be designed and
' implemented as soon as possible to lunit the potential of erosion damage or adverse effects to
compacted fill.
' 3.6 Expansion Testing of Finish Grade Soils
' Expansion index testing was performed on representative near finish gade soils of the subject
Lots (Home Sites). The test results indicate the near-finish grade soils have a very low to medium
expansion potential in accordance with Table 18-I-B of the 1997 UBC. Test results of samples
' taken during the course of grading indicate that very low to very high expansive soils exist on site
at various depths and locations on the Harveston project site. Test procedures and results are
presented in Appendix C. An individual L.ot (each Home Site) interpretation of the as-graded
~ condifions and recommended expansion potential for the design on each Lot (Home Site) is
presented in Table 1.
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4.1 General
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The grading of the subject Lots (Home Sites) was performed in general accordance with the
pmject geotechnical reports and geotechnical recommendarions made during the course of mugh
grading. It is our pmfessional opinion that the subject Lots (Home Sites) are suitable far their
intended residenrial use provided the recommendations included herein and in the project
geotechnicai reports aze incorporated into the design and conshuction of the residential structures
and associated improvements.
4.2 Summary of Conclusions
. Geotechnical conditions encountered during rough grading of the subject site were generally
as anticipated.
. Excavations were made to dense previously-placed compacted fill (Afl) or Panba Formation
bedrock (Qp) material during the grading for the subject Lots (Home Sites).
. Cut and fill slopes within the subject tract range up to approximately 8 feet in height. It is
our opinion that the slopes on the subject tract are surficially and grossly stable (under
normal irrigation/precipitation pattems) provided the recommendations in the project
geotechnical repotts are incorporated into the post-grading, conshuction and post-
conshuction phases of site development. Slopes aze inherently subject to erosion. As such,
measures should be taken as soon as possible to reduce erosion for both short term and long
terrn slope integrity.
• Laboratory testing of soils encountered during the course of previous and cturent grading
for Harveston indicates site soils to possess a very low to very high expansion potential.
Some expansive soil related distress to flatwork should be anticipated.
. Laboratory testing of neaz finish grade soils within the subject Lots (Home Sites) for this
tract indicates earth materials possess a very low to medium expansion potential and have a
negligible concentration of soluble sulfate. It is our opinion tha[ the expansion potenfial of
neaz surface soils influencing the design of foundation and slabs of the subject tract should
minnnally be designed for low expansion potential (per UBC). Laboratory test results are
contained herein Table 1 and Appendix C.
. Testing for minimum resistivity, chloade concentrates, and pH was not conducted dwing
the course of rough grading. A licensed corrosion engineer should be contacted in regard to
detennining the potential for corrosion if corrosion sensitive buried improvements are to be
installed.
. The potential for ground-surface mpture on the site due to a seismic event is considered to
be low; however, as in most of southem California, strong ground shaking should be
anticipated during the life of the structures. The standazd design of structures to meet the
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seismic design requireinents of the Unifoim Building Code (LTBC), Seismic Zone 4 will be
, required.
. Where tested, fill material placed during grading of the subject tract was placed at a
, minimum of 90 percent relative compaction and near the optimum moisture content. Field
testing of compaction was performed by the nucleaz gauge method (ASTM Test Methods
D2922 and D3017).
' . Foundations should be designed by the structural engineer for the development and
constructed in accordance with Leighton's minnnum recommendations herein, the
requirements of the City of Temecula and the applicable sections of the 1997 UBC.
' . Due to the relatively dense nature of the bedtock materials that underlie the subject site, the
competency of compacted fills, as well as the lack of permanent shallow groundwater, the
, potential for liquefaction on the site is considered very low.
• The front yard and driveway azeas were intentionally left below desigi elevations
' (approximately 2 to 3.5 feet below pad grade) to accommodate future foundation excavation
spoils. Filling of these areas should be performed in accordance with the recommendations
herein for earthwork (section 5.1.2).
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5.0 RECOMMENDATIONS
~ 5.1 Earthwork
' We anticipate that future earthwork at the site will consist of precise grading of the building
pads, foundation installation, trench excavation and backfill, retaining wall backfill,
' preparation of street subgrade, and placement of aggegate base and asphalt concrete
pavement. We recommend that any additional eatthwork on the site be performed in
accordance with the following recommendations and the City of Temecula grading
' requirements.
5.1.1 F~ccavations --. Temporary excavations with vertical sides, such as utility. trenches,
, should remain stable to depths of 4 feet or less for the period required to construct the
utility. However, in accordance with OSHA requirements, excavations greater than 4
feet in depth should be shored, or laid-back to inclinations of l:l (horizontal to
' vertical), if workers aze to enter such excauations. Leighton does not consult in the
area of safety. engineering. The contractor is responsible far the safety of all
excavations.
' S.1.2 Utilitv Backfill. Fill Plaoemen and mpa ion -- Atl backfill or fill soils
should be brought to optimum moisture conditions and compacted in uniform lifts to
~ at least 90 percent relative compac6on based on the laboratory maximum dry density
(ASTM Test Method D1557). The optimum lift thickness required to produce
uniform compaction will depend on the type, size and condition of compaction
' equipment used. In general, the onsite soils should be placed in lifts not exceeding 8
inches in compacted thiclmess and placed on dense existing compacted fill or other
' earth material approved by the geotechnical consultant. The backfill that coincides
with pavement subgrade should be reworked and compacted in accordance with
pavement design requirements.
~ 5.2 Foundation and Structure Design Considerations
' It is L.eighton's understanding that single-family slructures founded on post-tensioned or
conventional foundarion systems are proposed. The proposed foundations and slabs should
be designed in accordance with the structural consultants' design, the minimum geotechnical
' recommendations presented herein (text, Tables 1 through 3), the City of Temecula
requirements and the 1997 UBC. In utilizing the minimum geotechnical foundation
recommendations, the structural consultant should design the foundarion system to acceptable
' deflection criteria as determined by the structural engineer and architect.
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Foundation footings may be designed with the following parameters:
' Allowable Bearine Canacitv: 2000 psf at a minimum depth of embedment of 12
inches, plus an additional 250 psf per 6 inches of
' addirional embedment to a m~imum of 2500 psf.
(per 1997 UBC, capacities may be increased by 1/3 for
short-term loading conditions, i.e., wind, seismic)
' Slidine Coefficient: 035
' Total: 1 inch
Stafic Settlement Potential: Differenfial: 1 inch in 40 feet
' The footing width, depth, reinforcement, slab reinforcement, and the slab-on-grade tluclrness
should be designed by the struchual consultant based on recommendations and soil
characterisrics indicated herein (Tables 1 through 3), and the most recently adopted edition of
' the UBC. The effects of seismic shaldng on foundation soils may increase the static
dif~'erential settlement noted above to approximately 1.25 inch in 40 feet.
' An under-slab moisture retarder should consist of 2 inches of sand (S.E. > 30) over 10 mil
visqueen over an additional2 inches of sand (a total of 4 inches of sand). The recommended
' vapor retarder should be sealed at all penetrations and laps. Moisture vapor transmission may
be additionally reduced by use of concrete additives. Moisture vapor retarder may reduce but
not eliminate moisture vapor movement from the underlying soils up through the slabs. A
, slipsheet or equivalent should be utilized above the concrete slab if crack-sensitive floor
coverings (such as ceramic tiles, etc.) aze 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 sluinkage cracking. However, some cracking should be
' expected as the concrete cures. Minor cracldng is considered normal; however, it is often
aggravated by a high water/cement ratio, high concrete temperatures at the time of placement,
small nominal aggregate size and rapid moishue 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.
' Future homeowners and the homeowners' association should be made awaze of the
importance of maintaining a constant level of soil moisture. Homeowners should be made
, awaze of the potential negative consequences of both excessive watering, as well as allowing
soils to become too dry. Improperly designed, constructed, or maintained planters often pond
water and cause deep moisture penetration and soil moisture change. Since deep and repeated
' soil moisture change can damage the adjacent structure, placement of planters adjacent to
foundations or other sensitive hazdscape, such as pools and spas, should be discouraged if
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adequate and proper maintenance can not be assured. Our recommendarions assume a
reasonable degree of homeowner responsibility, if the homeowners do not adequately
maintain conect irrigation and drainage, some degree of foundation movement should be
expected. However, this movement typically does not cause structural damage, but will cause
such things as stucco cracking and dry wall sepazation.
The slab subgrade soils should be presoaked in accordance with the recommendations
presented in Table 1 priar to placement of the moisture retarder and foundarion concrete.
5.3 Foundation Setback from Slopes
We recommend a minimum horizontal setback distance from the face of slopes for all
structural footings (retaining and decorative walls, building footings, pools, etc.). This
distance is measured from the outside bottom edge of the footing horizontally to the slope
face (or to the face of a retaining wall) and should be a u~iniinum of H/2, where H is the slope
height (in feet). The setback should not be less than 5 feet and need not be greater than 10
feet. Please note that the soiis within the struchual setback area possess poor lateral stability
and improvements (such as retaining walls, sidewalks, fences, pools, patios, etc.) constructed
within this setback azea may be subject to lateral movement and/or differential settlement.
The potential for distress 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. Modifications of slope
inclinations neaz foundations may reduce the setback and should be reviewed by the design
team prior to completion of design or implementation.
5.4 Structure Seismic Design Parameters
Structures should be designed as required by provisions of the Uniform Building Code (IJBC)
for Seismic Zone 4 and state-of-the-art seismic design pazameters of the Structural Engineers
Association of California. This site is located within UBC Seismic Zone 4. Seismic design
parameters in accordance with the 1997 UBC are presented below. Please refer to the
Supplemental Geotechnical Investigation (Leighton, 2003a) for additional information.
Seismic Source Type =. B
Neaz Source Factor, Na = 1.3
Near Source Factor, N~ =1.6
Soii Profile Type = Sp
Horizontal Peak Ground Acceleration = 0.68g
(10% probability of exceedance in 50 years)
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5.5 Corrosion
For sulfate exposure and cement type refer to Table 1 and the conesponding sections of the
UBC. Other than buried concrete improvements, a licensed corrosion engineer should be
contacted in order to determine. the potential for corrosion if conosion sensitive buried
improvements are planned.
~ 5.6 Lateral Earth Pressures and Retaining Wall Design Considerations
, The recommended lateral pressures for very low to low expansive soil (expansion index less
than 51) and level or sloping backfill aze presented on Table 4(rear of text). The onsite wall
excavation materials should be reviewed by the geotechnical consultant priar to use as wall
' backfill.
Embedded structural 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 sheaz strength of the soil, it can be
designed far "active". pressure. If the wall cannot yield under the applied load, the shear
' shrength of the soil cannot be mobilized and the earth pressure will be highec Such walls
should be designed for "at rest" conditions. If a struchu-e moves towazd the soils, the resulting
resistance developed by the soil is the "passive" resistance.
~ The equivalent fluid weights of Table 4 assume very low to low expansive, free-draining
conditions. If conditions other than those assumed above ue anticipated, equivalent fluid
' weights should be provided on a case by case basis by the geotechnical engineer. Surchazge
loading effects from adjacent structures should be evaluated by the shucturai engineer. All
retanung wall structures should be provided with appropriate drainage and waterproofing. The
~ outlet pipe should be sloped to drain to a suitable outlet. Typical wall drainage design is
illustrated in Figure 2.
' Lateral passive pressures may be deternuned using the values provided in Table 4. 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 s[ructural
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 behveen
' foundation elements providing passive resistance should be a minimum of three times the
depth of the elements to allow full development of these passive pressures. The total depth of
retained earth for 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.
' Foundations for retaining walls in competent formational soils or properly compacted fill
should be embedded at least 18 inches below the lowest adjacent finish grade. At this depth,
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an allowable bearing capacity of 2,250 psf may be utilized. The bearing capacity may be
' increased by 250 psf for each additional six inches of embedment to a maz~imum of 4000 psf.
Wall backcut excavations less than 4 feet in height can be made neaz verticaL For backcuts
' greater than 5 feet in height, the backcut should be flattened to a gradient not steeper than 1:1
(horizontal to vertical). Backfill soils should be compacted to at least 90 percent relative
' compaction (based on ASTM Test Method D 1557). Backfill should extend horizontally to a
minimum distance equal to one-half the wall height behind the walls. The walls should be
constructed and backfilled as soon as possible after backcut excavation. Prolonged exposure
, of backcut slopes may result in some localized slope instability.
Fot unresfrained retaining walis within this tract that are greater than 5 feet (exposed; retained
' earth) or that may present a life/safety. hazazd during strong ground shaldng, the lateral earth
pressures should be increased by a seismic surcharge (seismic increment) in general
accordance with chapter 16 of the 1997 UBC. The location, distribu6on and magnitude of this
' surcharge will be provided if such walls aze proposed. The design of walls with such seismic
increment should achieve a factor of safety between 1.1 and 1.2 when evaluating stability
(sliding and overtuming) of the wall (NAVFAC DM7.02).
' SJ Concrete Flatwork
' Expansive soils are known to exist onsite and therefore concrete flatwork should be designed
and constructed with the anticipation of expansive soil related distress. Closer spacing of
control joints, reinforcement and keeping the flatwork subgrade at or. above optimum
' moisture prior to the placement of concrete may minimize cracking and differential
movement.
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City of Temecula Standard No. 401 "Sidewallc and Curb" specifies aggregate base or
approved select material under sidewalks and curbs when expansive soil is present. In lieu of
the aggregate base or select material under sidewalks and curbs, and with the approval of the
City. of Temecula, the sidewallc and curb subgrade may be presoaked such that 120% of
optimum moisture content to a minimum depth of 8 inches is achieved prior to the placement
of concrete. Moisture testing must be perfotmed by the geotechnical consultant prior to
concrete placement.
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5.8 Control of Surface Water and Drainage Control
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Positive drainage of surface water away &om structures must be incorporated into the design
of the proposed improvements. No water should be allowed to pond adjacent to buildings.
Positive drainage may be accomplished by providing drainage away from buildings at a
gradient of at least 2 percent for a distance of at least 5 feet, and fiuther maintained by a swale
on drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yuds,
drainage should be directed away from £oundations for a minimum of 3 feet and into a
collector swale or pipe system. Where necessary, drainage paths may be shortened by use of
area drains and collector pipes and/or paved swales. Eave gutters also help reduce water
infiltration mto the subgrade soils if the downspouts are properly connected to appropriate
outlets.
Planters with open bottoms adjacent to buildings should be avoided, if possible. Planters
should not be designed adjacent to buildings unless provisions for drainage, such as catch
basins and pipe drains, aze made. No ponding of water from any source (including
irrigation) should be permitted onsite as moisture infiltration may increase the potential for
moisture-related distress. Experience has shown that even with these controls for surface
drainage, a shallow perched ground water or subsurface water condition can and may
develop in areas where no such condition previously existed. This is particularly true where
a substantial increase in surface water infiltration resulting from site irrigation occurs.
Mitigation of these conditions should be performed under the recommendations of the
geotechnical consultant on a case-by-case basis.
~ 5.9 Graded Slopes
It is recommended that all slopes be planted with drought-tolerant, ground cover vegetation
, as soon as practical to protect against erosion by reducing runoff velocity. Deep-rooted
vegetation should also be established to provide resistance to surficial slumping.
' Oversteepening of existing slopes should be avoided during fine grading and construction.
Retaining structures to support graded slopes should be designed with structural
considerations and appropriate soil pazameters provided in Section 5.6.
' S.10 Irriaation, landscaaing and Lot Maintenance
' Site irrigation should be conholled at all times. We recommend that only the minimum
amount of imgation necessary to maintain plant vigor be utilized. For irrigation of trees and
shrubs, a drip irrigation system should be considered. We recommend that where possible,
landscaping consist primarily of drought-tolerant vegetation. A landscape consultant should
be contacted for proper plant selection. For large graded slopes adjacent to open space
areas, we recommend native plant species be utilized and that irrigation be utilized only
, until plants aze well established. At that time, irrigation could be significantly reduced.
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May 25, 2004
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Upon sale of Home Sites, maintenance of Home Sites and common areas by the homeowners
' and homeowner's association, respectively, is recommended. Recommendations for the
maintenance of slopes and property aze included in Appendix D for your review and
dishibution to future homeowners and/or homeowner's associations.
' S.11 Post-Grading Geotechnical Review
t 5.11.1 C~ncrr ~c+ion Revi w- Construcrion observation and testing should be performed
by the geotechnical consultant during future excavations, utility trench backfilling
and foundation or retaining wall wnstruction at the site.. Additionally, footing
' excavations should be observed and moisture detemunarion tests of subgrade soils
should be performed by the geotechnical consultant prior to the pouring of concrete.
' 5.11.2 Plans and Specifications - The geotechnical engineer should review foundation
plans to evaluate if the recommendations herein have been incorporated. Foundation
' design plans and specifications should be reviewed by the geotechnical consultant
prior to excavation or installarion of residential development.
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110231-024
May 25, 2004
6.0 LIMITAIIONS
The presence of our field representative at the site was intended to provide the owner with
professional advice, opinions, and recommendations based on obseroations of the contractor's
work. Although the obseroations did not reveal obvious deficiencies or deviations from project
specifications, we do not guatantee the contractor's work, nor do ouc services relieve the contractor
or his subcontractors of their responsibility if defects are subsequently discovered in their work. Our
responsibilities did not include any supervision or d'uection of the actual work procedures of the
contractor, tus personnel, or subcontractors. . The conclusions in this report aze based on test results
and observations of the gading and earthwork procedures used and represent oar engineering
opinion as to the compliance ofthe results with the project specifications.
This report was prepared for Lennar Communities, based on their needs, directions, and requirements
at the tune: This report is not authorized for use by, and is not to be relied upon..by any party
except, Lennaz Communiries, with whom Leighton contracted for the work. Use of or reliance on
tYus report by any other pariy is at that party's risk. Unauthorized use of or reliance on this
Report constitutes an agreement to defend and indemnify I,eighton and Associates from and
against any liability which may arise as a result of such use or reliance, regardless of any fault,
negligence, or strict liability of Leighton and Associates.
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Base Map: The Thomas Guide Digitai Edition Inland Empire 2004, Not To Scale
Harveston
Tract 31053-1,
Temecula, California
Riverside County, California
SITE LOCATION
MAP
Project No. ~
110231-024
Date
May 2004 Figure No.1
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SUBDRAIN OPTIONS AND BACKFILL WHEN NATIVE MATERIAL HAS EXPANSION INDIX OF 550
OPftON 1: P~E SURRIX/NDm. WiT}1
CUSS 2 PERMEABLE M47ERIAL OPT[ON 2: GRAVEL WRAPPED
[N FILTERFABRIC
WITH PRWER WITH P{tOPER
SURFA~ DRAQJNGE SURFACE DRAIIJAGE
SIAPE SIDPE
OR LEVEL OR LEVEI.
12" 12"
NATNE NATIVE
WATERPROOFIN6
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(SEEGENERALNO'fE5) WATERPI200FING 'r.
(SEE GENERAL NOTES) Fll7ER FABRIC
12" MINIMUM (SEE NO7E 4)
CLASS 2 PERFEABIE 12" MINIMUM
WEEP HIXE FILTER MATERIAL WEEP HOIE
(SEE GRADATIINJ) ~Yi ro 1'h INp7 5¢E
(SEE NOTE ~
(5EE NOTE ~ GRAYEL WrtnPPED II! Fa7ER
- 4lNCTIDIAMETER F~ewc . -
LEVELOR PERFORATEDPIPE ~~pR ~
SIDPE (SEE NOTE 3) SIAPE
~ Clas 2 Fil~r Pem~eable hiaMrial Gradation
Per Caltrans Specifications
I ~Sieve Size Per~nt Pa$ino
' 1" 100
3/4" 90-100
3/8" 40-100
I No.4 25-40
No. 8 18-33
' No.30 5-15
No. SO o-~
~ No.200 0-3
ENERAL NOTES
I~ Waterpraofing should be provided where rtaisture nuisance problem thivugh the wall is undesirable. .
Water proofing of the walls is not under purview ~ the geotechnical engineer
All drains should. have a gradient of 1 percent minimum
I*Outlet portion af the subdrein should have a 4-inch diarneter sdid pipe disrharged into a suitable disposal area d~igned by the projed
~ngineer. The subdrain pipe sFauld be aaessible for maintenance (rodding)
Other subdrain bacl6ill options are wbject to the review by the geotechnical engineer and modification of design parameters.
I Notes:
~) Sand should have a sand equivalent of 30 or greater and may be densified by water jetting.
) 1 Cu. ft. pec ft. of 1/4- to 1 1/2-inch size gravel wrapped in filter fabric
I ) Pipe type should be 0.5TM D1527 Acrylonitrile Butadiene Sryrene (ABS) SDR35 or ASiM DI785 Polyvinyl Chloride plastlc (PVC), Schedule
40, Armco A2000 PVC, or approved equivalent. Pipe should be installed with perforadons down. Perforations sFrould be 3/8 inch in
iameter placed at the ends of a 120-degree arc in two ravs at 3tinch on center (slaggered)
) Fiter fabric should be Mirafi 140NC or approved equivalent
I 5) Weephole should be 3-inch minimum diameter and provided at SO-foot ma~dmum inteivals. If e~ire is permitted, weephdes should
e laated 12 inches above finished grade. If eacposure is not pertnitted such as fw a wall adjacent to a sdewalk/curb, a pipe under the
idewalk to be discharged through the curb face or equivalent should be provided. For a basement-type wall, a proper wbdrain outl~
tem should be provided.
I 6) Retaining wall pians should be reviewed and approved by the geotechnical engineer.
`) Walis over six feet in height are subject to a special review by the geotechnical engineer and modificadons M the above requiremen~.
I, RETAINING WALL BACKFILL AND SUBDRAIN DETAIL
FOR WALLS 6 FEET OR LESS IN HEIGHT
WHEN NATIVE MATERIAL HAS IXPANSION INDEX OF <50
7A
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110231-024
May 25, 2004
TABLE 2
Minimum Conventionai Foundation Design Recommendations
UBC Expansion Potential
Very Low to Low Medium
1-Story Footing Depth ofEmbedment 12"
18
(Exterior and
Interior ~xterior and Tnterior)
2-Story Footing Depth of Embedment 18" Exterior 18"
12" Interior Exterior and Interior
Isolated Column Footings Exterior of „
Mnumum Foundation 18 24"
Presoaking See Table 1
No. 3 rebar placed at
mid-slab height No. 3 rebaz placed at
Minimum Slab Reinforcement spaced 18 inches on ~d-slab height spaced
Thiclrness
center, each way; 15 inches on center,
minimum slab each way; minimum
Uuckness 4 inches slab thickness 5 inches
Two inches of sand over a 10-mil vapor retazder
Underslab Treahnent (Visqueen or equivalent) over an additional two
inches of sand.
Notes:
(1) Depth of interior or exterior footing to be measured from lowest adjacent soil grade. If
drainage swale jlowline elevation is less than 5 feet laterally from footing, footing bottom
to be minimum 6 inches below swale flowline
(2) Living azea slabs should be tied to the footings as directed by the structural engineer.
(3) Garage slabs should be isolated from stem wall footings with a minimum 3/8° felt expansion
joint.
(4) Underslab treatment sand should have a Sand Equivalent of 30 or greater.
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110231-024
May 25, 2004
TABLE 3
Minimum Post-Tensioned Foundation Design Recommendations
Expansion Potential (UBC 18-2)
Desi
n Crite
ia
g
r Very Low Low Medium
EI= 0-20 EI= 21-50 EI= 51-90
Edge Moisture Center Lift: 5.5 feet
Variation, e,,, Edge Lift: 3.0 feet
Differential Center Lift: 1.25 inches 2.0 inches 2.4 inches
Swell, ym Edge Lift: 0.4 inches 0.4 inches 0.8 inches
Modulus of Subgrade Reaction (k) 150 psi/in 125 psi/in 125 psilin
Plasticity Index 5 12 30
Minimum Perimeter Footing
Embedment Depth 12 inches 12 inches 18 inches
Underslab Trearinent Two inches of sand over a 10-mil vapor retazder (Vis4ueen
or uivalerit over an additional two inches of sand.
Presoaking See Table 1
(1) llepth oY extenor Yoohng to be measured from lowest adjacent soil grade or drainage swale flowline
elevation (less than 5 feet laterally from footing, per code).
(2) Living azea slabs should be tied to the footings as directed by the structural engineer.
(3) Detailing of expansion crack control joints for PT slabs per structural engineer.
(4) Underslab treatment sand should have a Sand Equivalent of 30 or greater.
(5) Potential total and differential settlement should be iacluded cumu(atively with differential swell
parameters.
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TABLE 4
Lateral Earth Pressures'~a
For Ve Low to Low. Ex ansive Soil Backfiil
di
C
i Equivalent Fluid Weight (pc~
on
t
ons
Level Backfi112 2:1 Slope Bac~ll
Acrive 45 67
At-Rest 65 95
Passive3 300 125 (Sloping Down)
~Assumes drained condition (See Figure 2)
ZAssumes a level condition behind and in front of wall fo~mdarion of project.
'Maximum passive pressure = 4000 psf, level conditions.
°Assumes use of very low to low expansive soil (EI= 0-50).
110231-024
May 25, 2004
/~'
' 110231-024
May 25, 2004
'
' APPENDD(A
'' ~? f - n oc
' Leighton and Associates, 2003a, Supplemental Geotechnical Investigation and Geotechnical
Review of 100-Scale Mass Grading Plan, Tentative Tract No. 29639 - Phase
2, Harveston, Temecula, California, Project No. 110231-017, dated January
' 17, 2003.
Leighton and Associafes, 2003b, As-Graded Report of Mass Grading Hacveston, Tract 29639-1,
' City of Temecula, California, Project No. 1 1 023 1-006, dated February 5,
2003.
' Naval Facilities Engineering Command, 1986a, Soil mechanics design manual 7.01, Change 1:
U.S. Navy, September.
' Naval Facilities Engineeiaug Command, 1986b, Foundations and earth structures, design manual
7.02, Changes 1: U.S. Navy, September.
' RBF Consulting, 2003, Harveston Tract 31053, -1, -2, and -3. Rough Grading Plan And Erosion
Control Plan, October 2003, LD03-024GR, Sheet 6 of 7, dated October 28,
2003.
'
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Leighton
~ 110231-024
May 25, 2004
'
APPENDDCB
' Exolanation of Summarv of Field Densitv Tests
' A: Retest of previously failing compaction test.
B: Second retest of previously failing compaction test.
' Compaction tests taken during mass grading of site unless indicated by:
FG: Compaction tests taken on rough finish grade.
SF: . Compaction tests taken on slope face.
' Test Location: Indicated by Home Site number.
, Test Method: Compaction test by Nuclear Gage (ASTM 2922) unless indicated by
S: Sand Cone Method (ASTM 1556).
' Test Elevation: Approximate elevation above mean sea level.
'
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110231-024
May 25, 2004
APPENDIX C
' Laboratory Testing Procedures and Test Results
Expansion Index Tests: The expansion potential of selected materials was evaluated by the
' Expansion Index Test, ASTM test method D4829 or U.B.C. Standazd No. 18-2. Specimens aze
molded under a given compactive energy to approximately the optimum moisture content and
approximately 50 percent saturation or approximately 90 percent relative compaction. The prepazed
' 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are
inundated with tap water until volumetric equilibritun is reached. The results of these tests aze
presented in the table below and in the soil characteristics table herewith Appendix C:
Sample Location Sample Description Expansion
Index *Expansion
Potential
Lots 1-4 Brown silty clayey SAND 27 I.ow
Lots 5-8 Brown silty SAND 0 Very Low
Lots 9-12 Brown silty clayey SAND 31 Low
I,ots 13-16 Brown silty SAND 10 Very Low
Lots 17-20 Brown silty SAND 13 Very Low
I.ots 21-23 Brown silty clayey SAND 19 Very Low
Lots 24-27 Brown siity SAND 1 Very I,ow
Lots 28-33 Brown silty clayey SAND 39 Low
Lots 34-35 Light brown lean SILT 55 Medium
L,ots 36-38 Brown sandy lean SILT 36 Low
•Refer to Table 1 for Lot specific Eacpansion Potential to be used for design and construcrion.
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APPENDIX D
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110231-024
May 25, 2004
Development azeas, in general, and hillside lots, in particulaz, need maintenance to continue to
function and retain their value. Many owners aze unawaze of this and allow deterioration of the
property. It is important to familiarize owners with some guidelines for maintenance of their
properties and make them awaze of the importance of maintenance.
' Some goveming agencies require hillside property developers to utilize specific methods of
engineering and consh-uction to protect tho§e inves6ng in improved Home Sites or constructed
homes. For example, the developer may be required to grade the property in such a manner that
' rainwater will be drained away from the Home Site and to plant slopes so that erosion will be
minimized. They may also be required to install permanent drains.
t However, once the Home Site is purchased, it is the buyer's responsibility to maintain these safety
features by observing a prudent program of Home Site caze and maintenance. Failure to make
regulaz inspection and maintenance of drainage devices and sloping areas may cause severe
' financial loss. In addition to their own property damage, they may be subject to civil liability for
damage occurring to neighboring properties as a result of his negligence.
' The following maintenance guidelines aze provided for the protection of the owner's investment.
' a) Caze should be taken that slopes, terraces, berms (ridges at crown of slopes) and proper Home
Site drainage aze not disturbed. Surface drainage should be conducted from the reaz yard to
the street through the side yazd, or alternative appmved devices.
' b) In general, roof and yard runoff should be conducted to either the sireet or storm drain by
nonerosive devices such as sidewalks, drainage pipes, ground gutters, and driveways. Drainage
' systems should not be altered without expert consultation.
• c) All drains should be kept cleaned and unclogged, including gutters and downspouts. Terrace
' drains or gunite ditches should be kept free of debris to allow proper drainage. During heavy
rain periods, performance of the drainage system should be inspected. Problems, such as
gullying and ponding, if observed, should be corrected as soon as possible.
' d) Any leakage from pools, water lines, etc. or bypassing of drains should be repaired as soon as
practical.
' e) Animal burrows should be eliminated since they may cause diversion of surface runoff,
promote accelerated erosion, and even trigger shallow soil flowage.
'
'
3'~
' D-1
' 110231-024
May 25, 2004
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~ Slopes should not be altered without expert consultation. Whenever a significant topographic
' modification of the Home Site or slope, is desired a qualified geotechnical consultant should
be contacted.
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g) If the owner plans to modify cut or natural slopes aze pmposed, an engineering geologist
should be consulted. Any oversteepening may result in a need for expensive retaining devices.
Undercutting of a toe-of-slope would reduce the safety factor of the slope and should not be
undertaken without expert consultation.
h) If unusual cracldng, settling or earth slippage occurs on the property, the owner should consult
a qualified soil engineer or an engineering geologist immediately.
i) The most common causes of slope erosion and shallow slope failures are as follows:
• Gross neglect of the caze and maintenance of the slopes and drainage devices.
• Inadequate and/or improper planting. (Barren azeas should be replanted as soon as
possible.)
• Excessive or insufficient irrigation or diversion of runoff over the slope.
j) Hillside Home Site owners should not let conditions on their property create a problem for
their neighbors. Cooperation with neighbors could prevent problems, promote slope stability,
adequate drainage, proper maintenance, and also increase the aesthetic attractiveness of the
community.
k) . Owner's should be aware of the chemical composition of imported soils, soil amendments, and
fertilizers to be utilized for landscaping purposes. Some soils, soil amendments and fertilizer
can leach soluble sulfates, increasing soluble sulfate concentrations to moderate or severe
concentrations, negatively affecting the performance of concrete improvements, including
foundations and flatwork.
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