1990-344 G/H
Street Address
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Serial #
Category
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Name
Description
Year
Plan ck. #
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CALIFO RNIA
EN G INEERIN G,
CORP CIVIL ENGINEERS
. & LAND SURVEYORS
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{Y'1ADJ-L¿i /~Jdr .('¿¿Cúr
CEC#89-282
2/16/90
REV. 6/13/90
R Ilv. 7/[1/90
1 OF 12
DRAINAGE STUDY FOR PARCEL 1 OF PARCEL MAP 11513; GRADING PLAN FOR
NOBLE RESIDENCE.
THE SITE BEFORE DEVELOPMENT DRAINS TO THE NORTHEAST CORNER OF THE
SITE IN A NATURAL DRAINAGE SWALE NORTH TO HUMMINGBIRD HILL DRIVE.
AFTER DEVELOPMENT THE SITE WILL DRAIN NORTHERLY TO HUMMINGBIRD
HILL DRIVE TO THE SAME LOCATION AS THE NATURAL SWALES.
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VICTOR RODRIGUEZ-FERNANDEZ R.C.E. 35373
EXP.9/30/91
7-(0- rl°
DATE
4440 RAINIER AVENUE SUITE 210, SAN DIEGO, CALIF, 92120
TELEPHONE (619) 281-3122
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COUllTY OF SAN DIEGO
DEPARTMENT OF SANITATION &
FLOOD COllTROL
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COUNTY OF SAN DIEGO
DEPARTMENT OF SANITATION &,
FLOOD CONTROL,
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These maps are printed in the County Hydro1c
Manual (10, GO nnd 100 yr. maps included in
Design and Procedure ~Iilnual).
2) ^djust 6 hr. precipitation (if necessary) so
that it. is ,.¡ithil' the rar.!)e of 45% to 65'; of
the 24 hr. precipitation. ("ot nrr1icab1\
to' Desert) . '. )
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of the cha rt.
Ora", a line through the point parallel to th
plotted lines.
*Not Applicable to Desert Region
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APPENDIX XI ~
IV-A-14 --I
Hevised 1/B5 r-J1
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'URBAN C AREAS
TIME OF FLOW
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DEPARTMË:m:-,OF' SPECIAL DISTRICT SERVICES
-- -, 'DE SIGN MANUAL
APPROVED ,j, II. ,~~~ ~
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10
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NOMOGRAPH FOR DETERM I NArrON
. OF' TIME OF CONCENTRATION (Tc)
F'oo NATURAL WATERSHEDS
DATE /2 /II~ 7 APPENDIX X-A
V-A-IO Rev- ~/~1
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TABLE 2
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'. .' RUNOFF COEFFICIENTS (RATIOW\l METHOD)
, DEVElOPED AREAS {URBß.N~
Coefficient. C
---
Soi I Grpup (~)
land Use
A B C D
ResidentiaJ:
Single Family .l¡o .45 .50 .55
Multi-Units .45.. .50 .60 .70
Mob i J e homes .45 .50 .55 .65
RuraJ (Jots greatp-r than J /2 acre) .30 .35 .40 .45
Corrrnerci at (2) .70 .75 .Bo .85
Bo% Impervious
IndustriaJ (2) .80 .85 .90 .95
9OCk Impervi ous
NOTES:
(I) Soil Group ma~s are available at the offices of the Department of Public Norks.
(2)Where actual conditions deviate significantly from the tabulated impervious-
ness values óf 80% or 90%. 'the values given for coefficient C. may be revised
by multiplying 80% or 90% by the ratio of actual imperviousness to the
tabulated imperviousness. However, in no case shall the final coefficient
. be less than' 0.50. For example: Consider convnercial property on D soi I..group.
Actual imperviousness
.. 50%
Tabulated imperviousness Q 8~~
.\
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Revised C ~ 50 x 0.85 .0.53
80
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IV-A-9
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APPENDI X I x-a
Rev. 5/81
~
4. ~
LEIGHTON AND ASSOCIATEs, INc.
" . ,
Geotechnical and Environmental Engineering Consultants
March 21, 1991
Project No. 8901198-02
I,'
To:
Noble Design
5963 La Place Court, Suite 207
Carlsbad, California 92008
Attention:
Mr. Robert Noble
Subject:
As-Graded Report of Rough Grading Operations, Noble Residence, Parcel 1,
Lot 74, Hummingbird Hill Drive, Encinitas, California
References:
California Engineering Corporation, 1990, Grading Plan for Noble Residence,
Sheet 3 of 3, dated October 11, 1990
Leighton and Associates, Inc., 1990, Preliminary Geotechnical Investigation,
Noble Residence, Parcel 1, Lot 74, Hummingbird Hill Drive, Encinitas, California,
Project No, 8901198-01, dated August 31, 1990
Introduction
In accordance with your request, we have performed field density testing, laboratory testing, and
geotechnical observation during rough grading operations for the subject development. This as-
graded report summarizes our observations and field and laboratory test results taken during
rough grading operations of the subject lot.
Project Description and Location
The subject property consists of an approximately 1/2-acre, triangular-shaped parcel located on
the south side of Hummingbird Hill Drive in the city of Encinitas (Figure 1). Proposed
development consists of one two-story, single-family residence, The proposed structure will be
slab on grade with masonry block retaining walls at the lower floor with wood frame construction
for the second floor, Future improvements include a swimming pool and deck area on an upper
level at the rear of house (Figure 2),
5421 AVENIDA ENCINAS, SUITE C, CARLSBAD, CALIFORNIA 92008
(619) 931-9953
FAX (619) 931-9326
8901198-02
Gradinq Operations
Rough grading of the site consisted of excavating the building pad area and filling a small area
at the rear of house to support a portion of the proposed pool and associated decking. Grading
of the site was performed by Mike Scott Grading during the period of March 6 through March 13,
1990, Observation of grading operations and field density testing of compacted fills were
performed by our field technicians under the supervision of the project engineering geologist and
geotechnical engineer. The referenced 10-scale plans were utilized during grading operations
and as the base map for this project.
Prior to grading, the areas to receive fill material were stripped of surface vegetation and debris,
Loose, native soils were removed to competent formational material and recompacted in
accordance with the recommendations of our project geotechnical report (Leighton 1990) and
our field recommendations. Prior to filling, the natural ground was scarified, brought to near-
optimum moisture content, and compacted to at least 90 percent of the laboratory maximum
dry density as determined by ASTM Test Method 01557-78.
Geologic mapping of the excavated pad area and removals was performed by our field
representatives. A summary of our geologic observations is presented in this report.
The results of our field density tests taken in fill placed and compacted during grading are
presented in Appendix A, Summary of Field Density Tests. Laboratory determinations of the
maximum dry density and the optimum moisture content of representative samples of the fill soils
are presented in Appendix B, Laboratory Test Results. The approximate locations of the field
density tests and limits of the compacted fill soils are presented on the As-Graded Geotechnical
Map, Figure 2,
Engineerinq Geology
The geologic units encountered during site grading are generally the same as those described
in the project geotechnical investigation report (Leighton 1990), The limits of the geologic units
mapped within the subject lots are indicated on the As-Graded Geotechnical Map (Figure 2) and
are described as follows:
. Documented, Compacted Fill Soils (At)
, I
Fill soils placed and compacted under the observation and testing of Leighton and
Associates.
. Del Mar Formation (Td)
The Tertiary-aged Del Mar Formation encountered during grading consisted of light gray to
tan, slightly damp, dense, fine- to medium-grained sandstone.
- 2 -
8901198-02
Ground Water
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(-
II
I
I ,.
j
Ground water was not encountered during grading of the site. It is our opinion that ground water
will not be a potential geologic hazard to the site as graded provided the recommendations in
this report are followed.
Fill Compaction
Our observations and test results indicate that structural fills placed during rough grading have
been compacted to at least 90 percent of the laboratory maximum dry density as determined by
ASTM Test Method 01557-78 and in accordance with our recommendations. Field density tests
were taken in accordance with ASTM Test Method 02922-81.
Removals of Potentially Compressible Soils
-l
Potentially compressible topsoils and alluvium were removed within the area of proposed
structures In general accordance with our geotechnical report (Leighton 1989) and
recommendations made during grading prior to the placement of compacted fill.
l
Finish Grade Soils
I
A representative sample of the soils within 3 feet of finish grade were obtained for expansion
index testing after completion of rough grading. An expansion test was performed on the
representative sample in accordance with USC Test Method 29-2. The results of the expansion
test which is included in Appendix S indicate that the finish grade soils have a very low
expansion potential. Recommendations for foundations and slabs are presented in Table 1 and
are discussed in a following section of this report,
I
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¡
"
Conclusions and Recommendations
. Conclusions
l
"
The following conclusions are based on our observations and testing during site grading.
I
. Geotechnical conditions encountered during rough grading were generally as anticipated
(Leighton 1990).
ï
I
. In areas of planned grading, potentially compressible soils were excavated as part of the
planned grading or removed to dense formational material prior to fill placement.
....,
,
. Cleanouts were observed and geologically mapped.
- 3 -
l
1
,
I
8901198-02
. Fill soils were derived from on site materials. Documented fill soils were placed and
compacted to at least 90 percent relative compaction (based on ASTM Test Method
01557-78) in accordance with our specifications and the requirements of the City of
Encinitas.
~
. The subject lots are underlain by soils with expansion potentials that are very low, Refer
to Table 1 and the following section for foundation, slab, and soil presoaking
requirements.
j
J
Based on our observations and testing, rough grading of the subject lot was performed in
general accordance with our recommendations and the City of Encinitas requirements, In
our professional opinion, the geotechnical aspects of the subject area have been evaluated
and properly treated during rough grading, The subject lot is considered suitable for its
intended residential use provided the recommendations contained in this report are
incorporated into the fine-grading and construction phases.
J
"l
. Recommendations
.
Foundation and Slab Desiqn
l
Table 1 provides minimum recommendations for slab and footing design based on the
expansion potential of finish grade soils, The expansion index test results are presented
in Appendix B. Soils should be moisture conditioned as described in Table 1 prior to
the placement of concrete.
l
l
.
Foundations
l
The proposed two-story residential building may be supported on continuous footings
bearing in firm, formational soils at a minimum depth of 18 inches beneath lowest
adjacent finish grade (for low expansive soils). At this depth, footings may be designed
for an allowable soil bearing value of 2,500 pst. This value may be increased one-third
for loads of short duration, such as wind or seismic forces, Footings should have a
minimum width of 15 inches and reinforcement consisting of two No.4 rebars, one top
and one bottom, We recommend a minimum width of 24 inches for isolated spread
footings,
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Foundation Setbacks
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We recommend a minimum horizontal setback distance from the face of slopes for all
structural footings and settlement-sensitive structures. This distance is measured from
the outside edge of the footing, horizontally to the slope face (or to the face of a
retaining wall) and should be a minimum 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 soils within the structural setback area possess poor lateral stability,
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8901198-02
and improvements (such as retaining walls, pools, sidewalks, fences, pavements, etc.)
constructed within this setback area may be subject to lateral movement and/or
differential settlement.
Based on our review of the site grading plan, it appears that portions of the residence
and several retaining walls may require the use of deepened foundations where adjacent
to slopes and the rock-lined swale.
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Floor Slabs
Floor slabs should be designed based on the soil expansion potential of very low in
accordance with Table 1. If crushed rock or gravel is used adjacent to the Visqueen
moisture barrier, as indicated in Table 1, 1 O-mil Visqueen is recommended to reduce the
potential of moisture barrier perforation.
The potential for slab cracking may be reduced by careful control of water/cement ratios,
The contractor should take appropriate curing precautions during the pouring of
concrete in hot or windy weather to minimize the cracking of slabs, We recommend that
a slipsheet (or equivalent) be utilized if grouted tile, marble tile or other crack sensitive
floor covering is planned directly on concrete slabs. All slabs should be designed in
accordance with structural considerations,
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lateral Earth Pressure and lateral Resistance
The following earth pressure values for level or sloping backfill are recommended for
walls backfilled with onsite nonexpansive soils.
Conditions
Equivalent Fluid Weight (pcf)
level
2: 1 Slope
55
Active
35
50
65
150 (Sloping Down)
At-Rest
Passive
300
Unrestrained (yielding) cantilever walls should be designed for an active equivalent fluid
weight value provided above. In the design of walls restrained from movement at the
top (nonyielding), such as basement or garage walls, the at-rest equivalent fluid weight
value should be used. The above values assume nonexpansive backfill and free-
draining conditions. Should a sloping backfill other than 2: 1 (horizontal to vertical) be
designed, or if a backfill is loaded by an adjacent surcharge load, the equivalent fluid
weight values provided above should be evaluated on an individual-case basis by the
geotechnical engineer. All retaining wall structures should be provided with appropriate
drainage. Typical drainage design is contained in Figure 3. The total depth of retained
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8901198-02
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 overturning and sliding calculation. Wall footings should be designed in accordance
with structural considerations and the recommendations above. Wall backfill should be
compacted by mechanical methods to at least 90 percent relative compaction based on
ASTM Test Method D1557-78,
Soil resistance developed against lateral structural movement can be obtained from the
passive pressure value provided above, Further, for sliding resistance, a friction
coefficient of 0.35 may be used at the concrete and soil interface. The passive value
may be increased by one-third when considering loads of short duration including wind
or seismic loads. The total lateral resistance may be taken as the sum of the frictional
and passive resistances provided that the passive portion does not exceed two-thirds
of the total resistance,
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Exterior Concrete Flatwork
In areas where cracking of exterior concrete flatwork is not considered tolerable,
potential cracking may be reduced by providing reinforcement consisting of 6x6-1 0/1 0
welded wire mesh. Reinforcement should be placed mid height in the concrete.
Subgrade soils for the concrete driveway and exterior flatwork areas should be
compacted to a minimum of 90 percent relative compaction and tested by the
geotechnical consultant prior to concrete placement. Soils should be thoroughly
moistened prior to concrete placement.
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Retaininq Wall Drainaqe
All retaining wall structures should be provided with appropriate drainage, Typical
drainage design is provided in Figure 3, Retaining Wall Drainage Detail. The invert of
the subdrain pipe adjacent to the living area or garage slab should be placed below the
elevation of moisture barriers as depicted on Figure 3. If drainage outlet pipes are
placed below the residential slab, these outlet pipes should be nonperforated, In
addition, concrete cut-off wall should be constructed between the perforated and
nonperforated pipe.
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Surface Drainaqe and Lot Maintenance
Positive drainage of surface water away from the structure is very important. No water
should be allowed to pond adjacent to the building. Positive drainage may be
accomplished by providing drainage away from the building at a gradient of at least
2 percent for a distance of at least 5 feet away from the building, and further maintained
by a swale or drainage path at a gradient of at least 1 percent. Where necessary,
drainage paths may be shortened by use of area drains and collector pipes. We
suggest the installation of eave gutters and downspouts on the building, which will help
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facilitate roof runoff away from the foundations, The discharged water from the
downspouts should be directed away from the building to an appropriate outlet.
Planters with open bottoms adjacent to the building should be avoided if possible.
Planting areas at grade should be provided with adequate positive drainage directed
away from the building. Planters should not be designed below grade unless provisions
for drainage such as catch basins and pipe drains are made.
Drainage away from the slopes should be maintained at all times such that water does
not drain over the top of the slopes. The need for and design of drainage devices on
the site is within the purview of the design civil engineer,
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Construction Observation and Testing
Construction observation and testing should be performed by the geotechnical
consultant during foundation construction and retaining wall backfill. Footing
excavations should be observed by the geotechnical consultant prior to the placement
of steel reinforcement and the pouring of concrete. Foundation design plans should be
reviewed by the geotechnical consultant prior to excavation. Retaining wall drainage
construction should be observed by the geotechnical consultant prior to placement of
backfill material.
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Please do not hesitate to contact this office if you have any questions regarding our report. We
appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
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Michael R. Stewart, CEG 1349 (Exp. 6/30/92)
Chief Geologist
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Stan Helenschmidt, GE 2064 (Exp. 6/30/92)
Chief Engineer/Manager
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Attachments:
Figure 1 - Site Location Map
Figure 2 - As-Graded Geotechnical Map
Figure 3 - Retaining Wall Drainage Detail
Table 1 - Minimum Foundation and Slab Recommendations for Expansive Soils
Appendix A - Summary of Field Density Tests
Appendix 8 - Laboratory Testing Procedures and Test Results
Appendix C - Slope Maintenance Guidelines for Homeowners
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