HomeMy WebLinkAboutJETTY PUD AT THE LANDINGS - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -REPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
CORNELL CONSULTING COMPANY
FORT COLLINS, COLORADO
PROJECT NO. 3890-79
RE: THE RIDGE SUBDIVISION
FORT COLLINS, COLORADO
THE E'T'r'Y C,ndor u h.i u,snS
BY
EMPIRE LABORATORIES, INC.
214 NORTH HOWES STREET
FORT COLLINS, COLORADO
80521
A.
TABLE OF CONTENTS
Table of Contents ................................................ i
Letter of. Transmittal ..........:...............................
Report................................,.......................... 1
AppendixA ................................................. A-1
Test Boring Location Plan .... ................................. A-2
Key to Borings ................................................ A-3
Log of Borings • .......'- ....... .. .................... , . . .. ... . .. A- 4
Appendix B ...................... B-1
Consolidation Test Data ......... ............................... B-2
Summary of Test Results ......... .............................. B-5
Appendix C...................................................... C-1
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Empire &boratories, Inc.
MATERIALS AND FOUNDATION ENGINEERS
214 No. Howes Fort Collins, Colorado 80522
P.O. Box 429 (303) 484.0359
January 21, 1980
Cornell Consulting Company
155 North College.Avenue
Fort Collins, Colorado 80521
Attention: Mr. Wil'liam.Blackwell
Gentlemen,
Branch Offices
1242 Bramwood Place
Longmont, Colorado 80501
P.O. Box 1135
303) 776 3921
31.51 Nation way
Cheyenne, Wyoming 82001
P.O. Box 10076
307) 632-9224
We are pleased to submit our Report of a Geotechnical Investigation
prepared for the proposed subdivision to be located in south Fort
Collins, Colorado.
The subsurface conditions revealed.by this investigation are suitable
for the intended construction, provided construction is in accordance.
with the recommendations contained in this report. The attached report
presentsthesubsurface conditions at the site and our recommendations for
foundation design and. construction.. We
appreciate this opportunity of consulting with you on this project. If
you have any questions or if we can be of further assistance, please contact
us. Very
truly yours, EMPI
E LABORATORIES, INC. , L
James E. Veith, P.E. Geotechnical.
Engineer Reviewed
by: Chester
C. Smith, P..E. President
cic
sm4808
MEMBER
OF CONSULTINGENGINEERS COUNCIL
i ,
REPORT
OF, A
GEOTECHNICAL INVESTIGATION
SCOPE
This report presents the results of a geotechnical investigation
prepared for. The Ridge Subdivision in south Fort Collins, Colorado. The
investigation included test borings, laboratory testing, engineering
evaluation, and preparation of this report.
The purposes of the investigation were to determine subsurface
conditions at the site and to provide recommendations for development of
the site as influenced by the subsurface conditions.
SITE INVESTIGATION
Thirteen (13) test borings were drilled at the site on January 8,
1980. Locations of the test borings are shown on the Test Boring Lo-
cation Plan included in Appendix A.. Borings l through 10 were drilled
within the area of the proposed subdivision. Borings 11, 12, and 13
were drilled for proposed single-family residences on the east side of
the site.
The borings were advanced with continuous -flight augers to depths
approximately fifteen (15) feet below present grades. Samples were
recovered with two and one-half (235) inch Shelby tubes and the standard
penetration sample ;technique. During drilling, a geotechnical engineer
of Empire Laboratories, Inc. was present and made a continuous visual
inspection of soils encountered. Logs prepared. from the.field logs are
included i`n Appendix A of this report. Indicated on the logs are the
primary strata encountered, locations of samples, and groundwater con-
ditions.
SITE LOCATION AND DESCRIPTION
The project site is located east of College Avenue, south of The.
Landings, Second Filing in south Fort Collins, Colorado. More speci-
fically, the site can be described as a tract of land situate in the
west ;-p of Section 36., Township 7 North, Range 69 West of the Sixth Prime
Meridian, Larimer County, Colorado.
The area of the proposed subdivision is bordered on the north,
south, and east sides by irrigation ditches. A fence exists along the
west property line. The property slopes to the northeast, southeast and
east from :a high point in the area of Boring 8. The site is presently
open with weed- and grass -cover. The area of the proposed estate lots
represented by Borings 11, 12, and 13 is surrounded on all sides by
irrigation ditches. This area of the property is generally level with
weed and grass cover. Some large trees exist along the irrigation ditch
on the north side of the property. The Landings, Second Filing, a
residential subdivision, is located north of the property. Areas to ..the
west:, south, and east are presently undeveloped.
LABORATORY TESTS AND EXAMINATION
Representative samples recovered in the test borings were selected
for tests in the laboratory to determine their physical characteristics
and engineering properties. Included in the test program were natural
moisture content, water soluble sulfates, Atterberg limits, dry density,
unconfined compressive strength, swell potential,.and swell -consolidation
potential. Laboratory test results are summarized in Appendix B.
SOIL AND GROUNDWATER CONDITIONS
The following are the characteristics of the primary soil strata
encountered at the site.
c
1) Topsoil: Thickness of topsoil at test boring locations
varies from approximately six (6) to twelve (12) inches. The.
upper six (6) inches of the topsoil have been penetrated by
root growth and organic matter and should not be used for
foundation bearing or as backfill material.
2) Sandy. S1_ty Clay: The topsoil is underlain by brown sandy
silty clay extending to the bedrock surface. The sandy silty
clay is dry and stiff i.n situ. In its natural, undisturbed
state, this material has moderate shear strength and bearing
qualities. Upon wetting, the sandy silty clay exhibits.
moderate to high swell potential.
3) Claystone-Siltstone Bedrock: The surface of interbedded
claystone and si.ltstone bedrock was encountered at depths one
and one-half (12) to nine (9) feet below present grades. The
bedrock. surface slopes to the east with the greatest depths
being encountered. in Borings 11, 12, and 13. The upper one
1) to two and one-half (22) feet of the bedrock formation,is
weathered. The underlying siltstone-claystone is firm and has
very good shear strength and bearing characteristics. Upon
wetting, the bedrock exhibits moderate to high swell poten
tial.
4) Groundwater: No water was encountered in, the test borings at
the time of this investigation. Groundwater levels at the
site will fluctuate with seasonal variations and conditions.
Due to the low permeability of the siltstone and claystone
bedrock, formation of a perched water table on the bedrock
surface is probable.
ANALYSES AND.RECOMMENDATIONS
We understand that the:western portion of the property represented.
by Borings 1 through 10 will be developed for condominimum units. The
units will be three. (3) story with garden -level .construction. A swim.-
ming pool and tennis courts are proposed in the area of Boring 8. The
east section of the site represented by Borings 11, 12, and 13 will be
divided into five (5) estate lots.
The following are our recommendations for development of the.
property as influenced by the subsurface conditions encountered in the
test borings.
Site Grading
Some cutting and filling will probably be required on the property
to achieve desired finished .grades. As building foundations and/or
slabs on grade may be supported on fill, we recommend that fill place-
ment be in accordance with FHA "Data Sheet 79G." The following are our
recommendations for site grading and placement of compacted fill.
The upper six (6) inches of all topsoil should be stripped in
proposed cut and fill areas and in building and pavement areas which
will remain at.present grades. The topsoil can be stockpiled on the
site and used for final grading outside of building and pavement areas.
At cut subIgrade elevation and in areas to receive fill, the.upper six
6) inches of the subgrade should be scarified and.recompacted at two
percent (2q) wet of optimum moisture content to a minimum oU ninety
percent (90%) of Standard Proctor Density ASTM D 698-70. (See Appendix
C. )
The.on-site overburden materials are suitable: for fill in proposed
building and pavement areas. We recommend that excavated bedrock not be
used as fill in nr_gposed bu,i1di.n.g areas or withU the.- "fir two (2) feet
at pavement sub -grade elevation. Any additional off -site fill requ fired
should be a material approved by the geotechnical engineer. We recom-
mend that all fill be placed in horizontal six (6) to eight (8) inch
lifts at two percent (.2%),wet of optimum moisture content and compacted
to a minimum of ninety -.five percent (95%) of Standard Proctor.Density
ASTM D 698- 70.
Where fill is placed on slopes greater than 4:1, horizontal benches
should be cut in the slopes to insure integrity of the new fill on the
existing slopes. For stability, we recommend that all cut and fill
slopes be no steeper than 2 1, Flatter slopes are suggested for ease.of
maintenance. Finished slopes should be seeded with native grasses to
minimize erosion.
Qualified geotechnical personnel should be presentduring all phases
of earthwork to observe stripping of the topsoil:, scarification of
the subgrade, and placement and compaction of fill. In -place density tests
should be taken daily to determine the degree. of compaction being attained
and compliance with project specifications. For
installation of utilities, we anticipate that the overburden materials
will be stable -on temporary 1:1 cut.slopes. The bedrock will. stand
on near -vertical temporary slopes. We anticipate that the bedrock can
be excavated with conventional heavy-duty excavation equipment. All
backfill placed in utility trenches in open and planted areas should
be compacted to uniform lifts at optimum moisture to at least ninety
percent (90%) of Standard Proctor Density ASTM.D 698-.70 the full depth
of the trench. The upper four (4) feet of backfill placed in utility
trenches under roadways and paved areas.should be compacted. at or
near optimum moisture to at least ninety-five percent.(95%) of Stand- ard
Proctor Density ASTM D 698-70, and the lower portion of these trenches should
be compacted to at least ni.nety percent (90%) of.Standard Proctor Density
ASTM D 698-70. Addition of moisture to the subsoils may be required
to assure proper compaction.. It, is recommended that all com- paction
requirements for utility trenches be verified in the field with density
tests performed .under the direction of the geotechnical engineer. r
Foundations
Based upon the anticipated structural loads and the high swell
potential of the overburden and bedrock materials, we recommend that the
proposed condominium units and the single-family residences to be
constructed on the east side *of the property be supported by a drilled
pier foundation system. It is recommended that all piers be straight -
shaft and they they be drilled a minimum of three (3) feet into the firm
bedrock stratum. Piers bearing in the bedrock as recommended above may
be designed for a maximum allowable end bearing pressure of twenty
thousand. (,20.0.00) pounds per square foot. For that portion of the pier
embedded into the firm bedrock stratum, a skin friction of two thousand
2000) pounds per square foot may be used in determining allowable pier
capacity. To counteract swelling pressures which will develop if the,
subsoils become wetted, all piers should be designed for a minimum dead
load of ten thousand (10,000). pounds per square foot. Where this
minimum dead load requirement cannot be satisfied, it.is recommended
that skin friction from additional embedment into the firm bedrock be
used to resist uplift.. All piers should.be reinforced their full length
to resist tensile stresses created by swelling pressures acting on the
pier. It is essential that all grade beams have a minimum four (4) inch
void between the bottom of the beam and the soil below. The anticipated
settlement under the above maximum loading should be negligible.
It is strongly recommended that the geotechnical engineer be pre-
sent during the drilling operations to identify the.firm bedrock stratum,
confirm that proper penetration into the firm bedrock stratum is ob-
tained, ascertain that all drill holes are thoroughly cleaned and
dewatered prior to placement of any foundation.concrete, check all drill.
holes to assure that they are plumb and of the proper diameter, and
11insure proper placement of concrete and reinforcement.
Garden -Levels, Basements and Slabs on Grade
Due to the swelling pressures exerted by the materials at subgrade,
it is our opinion that the only positive solution for construction of
the slabs is a structural floor with a void beneath it. However, the
cost of this type of system is prohibitive. It is our opinion that,
with certain precautions and knowing that some risk is involved, floating
floor slabs are feasible. If the owner is. willing to assume the risk of
future slab movement and related structural damage, the following recom-
mendations may reduce slab movement and its adverse effects.
The subsurface conditions encountered at the site will permit
excavation of garden -levels and basements. However, due to the shallow
depth to bedrock and probable formation of a perched water table on the
bedrock surface, dewaterinq systems are. recommended around all basements
and garden-IeYel areas. The dewaterino systems should include perimeter
foundation, drains and.granu;lar material beneath the lower level slabs 'on
grade.
We recommend that four (4) inch. diameter open -jointed or perforated
tile be placed around all garden -level and basement areas. The tile
should be surrounded by clean, graded gravel from three -fourths ('3/4). to
one and one-half (1 1/2.) inch in size extending from at least six (,6)
inches below the bottom of the tile to at least three (3) feet above the
tile the full width of the trench. It is recommended that the drainage
tile be placed at least eighteen (18) inches below the lower level
finished floor on a minimum grade of one -eighth (1/8) inch per foot.
The top of the gravel media should be covered with an untreated building
paper to.prevent the. media from becoming clogged by earth backfill. 'To
prevent surface, water from entering the system, it is recommended that a
clay backfill be placed over the system and compacted at or near optimum
moisture; to at least,ninety percent (90%) of Standard Proctor Density
ASTM D 698-10. (See Appendix C.) 'We suggest that the perimeter foun-
dation drai'n connect to underdrains placed beneath sanitary sewers.
As a part of the dewatering system, all basement and garden -level
slabs on grade. should be underlain by at least twelve (12.).inches of
clean, graded gravel from three -fourths (3/4) to one and one-half (1
1/2) inch in size. Prior to placement of the gravel, the subgrade
should be prewet.
All slabs on grade at the upper level should be placed directly on
the undisturbed soil which has been slightly wetted prior to concrete
placement. Slabs on.grade at the basement, garden -level, and upper
level should be designed and constructed structurally independent of all
bearing members.
All nonbearing partitions placed on the.slabs on grade should be
provided with slip joints (top or bottom) so that pressure from heaving.
slabs will not damage the partition or the structure above. It.should
be emphasized that if the subgrade soils are kept dry, movement of the
slabs will be minimized. If moisture is permitted to reach the subgrade
soils, heaving of the slabs is anticipated..
To minimize and control shrinkage cracks which will develop in the
slabs, control joints should be spacedevery fifteen (15) to -twenty (20) feet.
The total area within control joints should be no greater than four
hundred (400) square feet. It
should be re-emphasized that even with these precautions, the potential
for slab movement exists. Slab -on -grade construction should be
undertaken only if the owner is willing to assume the risk of po- tential
slab heave and possible structural damage. Pool
and Tennis Courts As
discussed above, the overburden and bedrock materials on the site
exhibit moderate to high swell potential.upon wetting. The pro- posed
swimming pool should be designed and constructed to.resist an anticipated
two thousand (2000_) pounds per square foot swell pressure. We
recommend that the pool be underlain by at least six (6) inches of clean,
well -graded free -draining gravel. Prior to placement of the gravel,
the subgrade beneath the pool should be prew.et. To drain water collecting
in the gravel beneath the pool, a four (4') inch diameter solid
pipe should connect from the low point of the pool excavation to the
underdrain recommended beneath the sanitary sewers.
Stripping of topsoil, preparation of the subgrade, and placement of
fill in the proposed tennis court area should be accomplished as recom-
mended in the "Site Grading" portion of this report. Beneath the tennis:
court surface material, we recommend that a minimum of six (6) inches of
select base course material be placed. The base course should be
placed at optimum moisture content and compacted to a minimum of ninety-
five percent (95%) of Standard Proctor Density ASTM D 698-70. (See
Appendix C. )
Pavements
Preparation to proposed pavement subgrade elevations should be
accomplished as recommended in the "Site Grading" portion of this report.
AASHTO classification of the materials forming pavement subgrade are A-
4, A-6, and A-7-6. Based upon the classification test data, the following
pavement thickness is recommended,
Select. Subbase 4"
Select Base Course V
Asphaltic Concrete 2_"
Total Pavementh Thickness 10"
The base course overlying the subgrade should consist.of a hard,
durable, crushed rock or stone and filler and should have a minimum
C.B.R. value of 80. The composite base course material should be free
from vegetable matter and lumps or balls of clay and should meet the.
Colorado Department of Highways Specification .Class 6 Aggregate Base
Course which follows:
Sieve Size Passing
3/ 4" 100
4 30- 65
8 25-55
200 3-12
Liquid L.imi.t - 30 Maximum
Plasticity Index - 6 Maximum
The base course should be placed on the subgrade at or near optimum
moisture and compacted to -at least ninety-five percent (95%) of Standard
Proctor Density ASTM D 69840. -(See Appendix C.) It is important that
the base course be shaped to grade so that proper drainage of the parking
area is obtained.
If streets are paved prior to construction,we recommend that the
asphaltic concrete consist of two.(2) lifts, each one and one-half (12)
inch thick. The final lift should: be placed following completion of all
construct ion. Any failed .sections resulting from the construction
traffic should.be removed and replaced prior to placement of the final
lift.
GENERAL RECOMMENDATIONS
1) Laboratory tests indicate that water soluble sulfates in the
soil are positive, and a Type II cement should be .used in.all
concrete exposed to subsoils. All slabs on grade subjected to
de-icing chemicals should be composed of a more durable con-
crete with low water -cement ratios and higher air contents.
2) Finished grade should be sloped away from the structures on
all sides to give positive drainage. Ten percent (10%) for
the first ten (10) feet away from the structures is the sug-
gested slope.
3) Backfill around the outside perimeter of the structures
should be mechanically compacted at optimum.moisture to at
least ninety percent (90%) of.Standard Proctor Density ASTM D
698-70. (See Appendix C.) Puddling should not be permitted
as a method of compaction.
4) All plumbing and utility trenches underlying slabs and paved
areas should be backfilled with an approved material compacted
to at least ninety-fi've percent (95%) of Standard Proctor
1n
Density ASTM D 698- 70. Puddling should not be permitted as a
method of compaction.
5) Gutters and downspouts should be designed to carry roof runoff
water well beyond the backfill area.
6)' Underground sprinkling systems should not be installed within
ten (10) feet of the structures,.and this recommendation
should be taken into account in the landscape planning.
7) Plumbing under slabs should be eliminated wherever possible
since plumbing.failures are quite frequently the source of
free water which causes slab heave.
8) It is recommended that all compaction requirements. specified
herein be verified in the field with density tests performed
under the direction of the geotechnical engineer.
9) It is recommended that a registered professional engineer
design the foundations using the recommendations presented in
this report.
GENERAL COMMENTS
This report has been prepared to aid in the evaluation of the
property and to assist the architect and/or engineer in the design of
this project. In the event that any changes in the design of the
structures or their locations are planned, the conclusions :and recom-
mendations contained in this report will not be considered valid unless
said changes are reviewed and conclusions of this report mod.ified.or
approved in writing by Empire Laboratories, Inc., the soils engineer of
record.
Every effort was made to provide comprehensive site coverage
through careful locations of the test borings, while keeping the site
11-
investi'gation.economically feasible. Variations in soil and groundwater
conditions between test borings may be encountered during construction.
In order to permit correlation between the reported subsurface con-
ditions and the actual conditions encountered during construction and to
aid in carrying.out the plans and specifications as originally con-
templated, it is recommended that Empire Laboratories, Inc.. be retained
to perform continuous construction review during the excavation and
foundation phases of the work. Empire Laboratories, Inc. assumes no
responsibility for compliance with the recommendations included in this
report unless they have been retained to perform adequate on -site
construction review during the course of construction.
TEST BORING LOCATION PLAN
C1s
7'BM Ili 'TOP .Q RE/SR 6
GOF?IJ R OF` N.W % OF Sf_CT 36 -
ION 5036.9'
ZOO,
Ne• 9 TNf— L/NND1N4s.S FjU W zv
1.0. B
L/.SFR I M E_R GOU
KEY TO BORING LOGS
TOPSOIL GRAVEL
FILL SAND & GRAVEL
SILT=77.SILTY SAND & GRAVEL
CLAYEY SILT ep COBBLES
Di SANDY SILT o. SAND, GRAVEL & COBBLES
CLAY WEATHERED BEDROCK.
i
SILTY CLAY SILTSTONE BEDROCK
SANDY CLAY CLAYSTONE BEDROCK
SAND SANDSTONEBEDROCK
SILTY SAND. LIMESTONE
CLAYEY SAND
x x
R R R
GRANITE
SANDY SILTY CLAY El
SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 24 HOURS AFTER DRILLING
C
T
HOLECAVED
5/12 Indicates that 5 blows of a 146 pound ham ier falling 30 inches was required to penetrate 12 inches.
A-3
F..MPIRF LARORATORIF..S, INC.
5030
5025
5020
A-4
EMPIRE LABORATORIES, INC.:
5045 `---
5040
5035
5030
5025
50.20
5030
5025
5020
5015
LOG OF BORINGS
5025
5020
5015
5010
A-7
EMPIRE LABORATORIES, INC.
CONSOLIDATION —SWELL TEST
90
80
a.
1 .70
60
0
20
BORING NO. 3 DEPTH-L. _W
DRY DENSITY---89--.-I---'P-'L.F—t- 3
MOISTURE, 10.3 %
0.1 0.5 1.0 5 10
APPLIED PRESSURE-TONS/SQ, FT.
0.1 0.5 1.0 S 10
APPLIED PRESSURE-TONS/SQ. FT.
EMPIRE LABC&ORIES, INC.
CONSOLIDATION --SWELL TEST
BORING NO.— _ DEPTH 7.01
DRY DENSITY j O9.4 #, / Ft . 3
MOISTURE 1 . _ OX
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0
50
49
48
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62
61
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59
58
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54
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CON SOU.DATION--SWELL TEST
BORING NO. 8 DEPTH_LJQL
1111111101011 NONE
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APPLIED PRESSURE—TONS/SQ. FT.
0.1 0.5 1.0 5 10
APPLIED PRESSURE—TONS/SQ. FT. .
B-4
EMPIRE LABORATORIES,. INC.____ r_
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CONSOLIDATION ---SWELL TEST
68
BORING NO._IZ DEPTH M'
67
DRY DENSITir 98.6 l—.
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MOISTURE 12.8
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SUMMARY OF TEST RESULTS
Swelling Pressures
Boring Depth Moisture Dry Density Swelling
Number Ft.) Before Test PCF Pressure PSF
1 7.0-8.0 15.7 102.8 935
4 3.0-4.0 14.0 108.4 2305
6 3.0-4.0 14.8 110.5 1735
8 7.0-8.0 13.0 122.4 3920
1.0 3.0-4.0 12.0 120.1 1960
11 3.0-4.0 13.1 103.1 855
12 7.0-8.0 13.3 115.1 1080
13 8.0-4.0 11.6 111.9 1320
Atterberg Summary
Boring Number 3 5 @ 8 @ 13 @
and Depth 3'.0-4..0 3.0-4.0 3.0-4.0 3.0-4.0
Liquid Limit 40.0 48.5 23.3 37.3
Plastic. Limit 22.5 19.0 14:6 17.3
Plasticity Index 117.5 29.5 8.7 20.0
Passing #f200 Sieve 62.0 .98.2 39.2 70.8
Group Index
AASIIO 14145-49 8.3 17.6 0.8 11.1
AASI-ITO M145-73 8.9 31.6 0.2. 12.3
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Classification
Unified CL CH SC CL
AASHTO A-6(9) A-7-6(32) A-.4(0) A-6(12)
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A
APPENDIX C.
Suggested.Specificati fts for Placement of Compacted Earth Fill
and/or Backfills.
GENERAL
A soils engineer shall be on -site to provide continuous observation
during filling and grading.operations and shall be the owner's repre-
sentative to inspect placement of all compacted fill and/or backfill on
the project. The soils engineer shall approve all earth materials.prior
to their use, the methods of placing, and the degree of compaction
obtained.
MATERIALS
Soils used for all compacted fill and backfill shall be approved by the
soils engineer prior to their use. The upper two (2) feet of compacted.
earth backfill.placed adjacent to exterior foundation walls shall be an
impervious, nonexpansive material. No material, including rock, having
a maximum dimension'greater than six inches shall be placed in any fill.
Any fill containing rock should be carefully mixed to avoid nesting and
creation of voids. In no case shall frozen material be used as a fill
and/or backfill material.
PREPARATION OF SUBGRADE
All topsoil, vegetation (including trees and brush), timber, debris.,
rubbish, and other unsuitable material shall.be removed to a depth
satisfactory to the soils engineer and disposed of by suitable means
before beginning preparation of the subgrade. The subgrade surface of
the area to be filled shall be scarified a minimum depth of six inches,
moistened as necessary, and compacted in a manner specified below for
the subsequent layers of fill. Fill shall not be placed on frozen or
muddy ground.
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PLACING FILL
No sod, brush, frozen or thawing material, or other unsuitable material
shall..be placed in the fill, and no fill shall be placed during unfavorable
weather conditions. All clods shall be broken into small pieces, and
distribution of material in the fill shall be such as to preclude the
formation of lenses of material differing from the surrounding -material.
The materials shall be delivered to and spread on the fill surface in a.
manner which will.result'in a uniformly compacted fill. Each layer
shall be thoroughly blade mixed during spreading to insure uniformity of
material and moisture in each layer. Prior to compacting, each layer
shall have a maximum thickness of eight inches, and its upper surface
shall be approximately horizontal. Each successive 6" to $" lift of
fill being placed on slopes or hillsides should be benched into the
existing slopes, providing good bond between the fill and existing
ground.
MOISTURE CONTROL
While being compacted, the fill material in each layer shall as nearly
as practical contain the'amount of moisture required for optimum compaction
or as specified, and the moisture shall. be uniform throughout the fill.
The contractor may be required to add necessary moisture to the fill
material :and to uniformly mix the water with the fill material if, in .
the opinion of the soils engineer, it is not possible to obtain uniform
moisture content by adding water on the fill surface. If, in the opinion
of the soils engineer, the material proposed for use in the compacted,
fill is too wet to permit adequate compaction, it shall be dried in an
acceptable manner prior to placement and compaction.
COMPACTION
When an.acceptable, uniform moisture content is obtained, each.layer
shall be compacted by a method acceptable to the soils engineer and as
specified in the foregoing report as determined by applicable standards.
Compaction shall be performed by rolling with approved tamping rollers,
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C-3
v, pneumatic -tired rollers, three -wheel power rollers, vibratory compactors,
or other approved equipment well -suited to the soil being compacted. If
a sheepfoot roller is used, it shall be provided with cleaner bars
attached in a manner which will prevent the accumulation of material
between the tamper feet. The rollers should be designed so that effective
weight can be increased.
KISTURE-DENSITY DETERMINATION
Samples of representative fill materials to be. placed shall be furnished
by the contractor to the soils engineer for determination of maximum
density and optimum moisture or percent of Relative Density for those
materials. Tests for.this determination will be made using methods
conforming to requirements of ASTM D 698, ASTM D 1557, or ASTM D 2049.
Copies of the results of these tests will be furnished to the owner,'the
project engineer, and the contractor. These test results shall be the
basis of control for all compaction effort.
DENSITY TESTS
1
The density and moisture content of each layer of compacted fill will be,
determined by the soils engineer in accordance with ASTM D 1556, ASTM D
2167, or ASTM D 2922. Any material found not to comply with the minimum
specified density shall be recompacted until the required density is
obtained. Sufficient density tests shall be made and submitted to
support the soils engi'neer's recommendations. The results of density
tests will also be furnished to .the owner, the project engineer, and the
contractor by the soils engineer.
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