HomeMy WebLinkAbout1ST STOP PLAZA - MINOR SUBDIVISION - 53-95 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTField density tests shall be made by the
Engineer on each layer of fill according to ASTM
D1556, D2167, or D2922. Tests shall be taken in
the compacted layer, below the disturbed surface.
If the tests show inadequate density, that layer or
portion of the layer shall be reworked until the
required density is obtained.
Fill material shall not be placed on frozen or
thawing ground, or during unfavorable weather
conditions. Fill operations shall not begin or
resume until the base, or previous fill, is
certified at the required density and moisture
content.
I I. I',i 11- `Ii IV
B. Description of Work
After the site to be filled has been properly
prepared, it shall be bladed until it is uniform
and free of large clods. The foundation for the
fill shall be brought to the proper moisture
content and compacted to not less than 95% of
maximum dry density, in accordance with current
ASTM D15571 or to such other density as may be
determined appropriate for the materials and
conditions and acceptable to the Engineer.
Materials for fill shall consist of materials
selected or approved by the Engineer. The
materials shall be borrowed from sites selected or
approved by the Engineer, and shall be free of
vegetation or other deleterious materials, and
shall not contain rocks or lumps larger than six
inches (611) in diameter.
The fill material shall be placed in uniform
layers and compacted to meet the requirements as
directed by the Engineer. Each layer shall be
thoroughly mixed to insure uniformity in each
layer. Compacted layer thickness shall be no
greater than six inches (611) unless approved
otherwise by the Engineer.
If the selected or approved fill material
contains rock, the maximum rock size shall be six
inches (611) in diameter. Care should be taken to
insure all voids are filled. No large rocks shall
be placed within twelve inches (1211) of the
finished surface.
Each layer shall be thoroughly compacted to
the specified density. The required density shall
normally be 95% of maximum dry density, as provided
in accordance with ASTM D1557. The compacted
density may vary according to the type of material
used, and will be specified by the Engineer.
Compaction of the fill shall be such that a
uniform density is obtained. Compaction shall be
accomplished with 2% of the optimum moisture.
content.
All slopes shall be compacted until the slopes
are stable, but not too dense to prohibit slope
control planting. Slope compaction may be done in
increments as the fill progresses or when the fill
is brought to its total height.
APPENDIX II
SPECIFICATIONS
FOR
PLACEMENT OF FILL MATERIAL
I. Site Preparation
A. Scope
This item shall consist of clearing and
grubbing, removal of existing structures, and
preparation of land to be filled, preparation of
the site from which the fill material is to be
borrowed, and all subsidiary work necessary to
prepare the site to be. filled according to the
plans and specifications -specifications.
B. Description of Work
All timber, logs, trees, brush and rubbish
shall be removed and disposed of in a manner
approved by the Engineer.
All vegetation and substantial amount of
topsoil shall be removed from the surface upon
which the fill is to be placed. The surface shall
then be scarified to a depth of at least ten inches
(10"), and until it is free from such defects that
would hinder the uniform compaction by the
equipment used.
When fills are made upon hillsides or slopes,
the original ground shall be scarified deeply, or
benched, if slopes are in excess of five (5)
horizontal to one (1) vertical are encountered, or
as directed by the Engineer.
II. Placement of Fills
A. Scope
This item shall consist of compaction of the
area to be filled, backfilled, filling of the land,
compaction and control of the fill, and all
subsidiary work necessary to complete the grading
according to the plans and specification.
should be hand watered only. Landscaping with a plastic
covering around the foundation area is not recommended. Check
with your local landscaper for fabrics which allow evaporation
while inhibiting plant growth when a plastic landscape
covering is desired.
Experience shows that the majority of problems with
foundations due to water conditions are generally due to the
owner's negligence of maintaining proper drainage of water
from the foundation area. The future owners should be
directed to pertinent information in this report.
REV 06/17/85
APPENDIX I
POST -CONSTRUCTION SITE PREPARATION AND MAINTENANCE
Backfi11
When encountering potentially expansive or consolidating
soils, measures should be taken to prevent the soil from being
wetted'dth'ing and after construction. Generally, this can be
accomplished by ensuring that the backfill placed around the
foundation walls will not settle after completion of
construction, and that this backfill material is relatively
impervious. Expansive claystone bedrock should not be used as
backfill against foundation walls. Water may need to be added
to backfill material to allow proper compaction -- do not
puddle or saturate. Backfil_l should be mechanically compacted
to at least 95% of Standard Proctor around all structures, and
90% of Standard Proctor elsewhere. Compaction requirements
should be verified with field tests by the Engineer.
Surface Drainage
The final grade should have a positive slope away from the
foundation walls on all sides. A minimum of twelve inches
(1211) in the :First ten feet (101) is recommended. Downspouts
and sill cocks should discharge into splash blocks that extend
beyond the limits of the backfill. Splash blocks should slope
away from the foundation walls. The use of long downspout
extensions in lieu of splash blocks is advisable. Surface
drainage away from the foundation should be maintained
throughout the lifetime of the structure.
Lawn Irrigation
Do not install sprinkler systems next to foundation walls,
porches, or patio slabs. If sprinkler systems are installed,
the sprinkler heads should be placed so that the spray from
the heads under full pressure does not fall within five feet
(51) of foundation walls, porches, or patio slabs. Lawn
irrigation must be carefully controlled.
If the future owners desire to plant next to foundation walls,
porches,, or patio slabs, and are willing to assume the risk of
structural damage, etc., then it is advisable to plant only
flowers and shrubbery (no lawn) of varieties that require very
little moisture. These flowers and shrubs
TABLE I
SUMMARY OF TEST RESULTS
SHEET ► OF I
DATE S-IS- 95
TEST HOLE NON
-r-H I
TH 2
NTH 3
TH T
RI - R3
TH $
DEPTH (FT.)
3
4
a
3
I- 4
)- 3
SOIL OR ROCK
Sulky
Clay
S��y
Clay
5u�ly
Cl ay
SaMay
Clay
Sail.,
Clay
sandy
Clay
NATURAL MOISTURE ('b)
23.01
24.74
Ia•82
AO.2(,
Is•52
DRY DENSITY (PCF)
16 3. 6 7
3 7. 9 7
96.13
8 8. 30
102.7 8
95., 60
104.65
94.74 t
PENETRATION
(BLOWS/IN,)
V (v
10/6
416
I12/6
5/ 6
7/6
3/ 6
4 /6
% SWELL @ 600 PSF
0.5
0.0
- 0. 1
- 0..I
SWELL PRESSURE (PSF)
1000
600
1-70 0 F
UNCONFINED
COMPRESSIVE
STRENGTH (PSF)
A770
-155
3o72.
% STRAIN
-
SOO (PPM )
LIQUID LIMIT
PLASTICITY INDEX
% PASSING #200
. Usc
CL
CL
CL
CL
GL
CL
AASHTO GROUP INDEX
MAXIMUM DRY
DENSITY (PCF)
OPTIMUM
MOISTURE CONTENT (N.)
CBR
R-VALUE
Ia
CDS ENGINEERING CORPORATION LOVELAND
COLORADO
PROJECT
NO. 813 3
-* UCON 6TRUCTED SAMPLE.
NOMOGRAPH SOLVES:
1091010KESAL - ZR So -I. 9.36'loglo(SN+1) - 0.20 +- -
99.9
T
0
�T
ee
99
v!�
a
.
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� Q
J Q"
Fr—
0q .4
:a
m
cf.90
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a
-
70
-60
50
5o -
to
USE'
70
C
10_
W O
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1.0
&4
=
T
J
-
0 <
0
a-�
ILI
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.05-
an 0
wr
DTN = 10
=iP .073-A106
ReliabiliLy (R) = 70
[10a
PSI
1o9A 1.5
1094
0.40 +
(SN+ 1) 5.19
rJ
01
� a
w 40
°4 20
A
O a 10
cc 0 -
Lu r
Q:
MR = 3525
+ 2.32'"IOMR - 8.07
■Mod
on
on
oil
ONE
9 U. 7 6 5 4 s 2 1
DESIGN STRUCTURAL NUMBER. SN
SLandard Deviation (So) =
0.4-1
SOLUTION: SN = 2.45
Estimal.cd Total 18K ESAL
= .0'13 x 106 2.45 c
G.25"M4) +
6" (0.4) +
0' (o•12)
0.8' (o•i))
= 4.5o
_ 2•46
EffecLive I.esilinnL Modules
(Mid = 3525 Psi
5.5" (0.4) +
2,250(o•1))
: 2.47
5" (0.4) +
vm7 (0•I))
2.45
Design ServicenbliliLy boss
= 2.0
45" (0.4) +
s.s-(o•12)
= 2.4(0
3.3" (0.4) +
8.7s" (0.1)i
_ 2• 45
3" (0• +
NOMOGRAPH - 171_EXIBLE
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NWO.'PROJECT 95 8�F33
SYMBOLS AND SOIL PROPERTIES
DIAGRAM NO. 1
SOIL AND ROCK
SAMPLERS
CLAY (CL,OL,MH,CH,OH) CALIFORNIA
SILT (ML,OL) THIN -WALLED
SAND (SW,SP,SM,SC) SPLIT BARREL
GRAVEL (GA,GP,GM,GC) 1 BAG SAMPLE
WEATHERED ROCK
SHALE & CLAYSTONE
SANDSTONE
PITCHER
JAR SAMPLE
PENETRATION RESISTANCE FOR COHESIONLESS SOILS ON STRENGTH CLASSIFICATIONS FOR COHESIVE SOI
BASIS OF THE STANDARD PENETRATION TEST
NUMBER OF BLOWS
PER FT., N .. RELATIVE DENSITY
CONSISTENCY
COHESION, 16 F
0 - 4 VERY LOOSE
SOFT
LESS THAN 0.5
4 - 10 LOOSE
FIRM
0.5 - 1.0
10 - 30 MEDIUM
STIFF
1.0 - 2.0
30 - 50 DENSE
VERY STIFF
2.0 - 4,0
OVER 50 VERY DENSE
HARD
GREATER THAN 4.0
°t BLOWS'1PL''R'V0bT'w- BLOW OF 140 LB,.
t` EQUIVALENT
TO PP/2 AND 6U/2
HAMMER DROPPED 30 IN. TO DRIVE
2-INC. SPLIT -BARREL SAMPLER -ONE
FOOT (ASTM DLS86-67).
Y I. ll' 1 +' +Inr
U
J
44
Soo ;
w
0
Qa��o�o
N-I
ua�
y�
`II Ip
(D
Lo
LOCATION OF TEST BORINGS
DRAWN BY* A0 NO.
tN8 LOCATION OF TEST NU LE
!GALE i M C ^ 0
- OV
DATE:
9-18-9.5'
CAS EN(31N FRIN� CORP: . ' N0Jtr.T oar-_ s.4 33
16
future owners should be directed to those items under "Post -
Construction Site Preparation and Maintenance" in Appendix
I,ijnq�4jgd in this report. Our experience has shown that
damage to foundations usually results from saturation of the
foundation soils caused by improper drainage, excessive
irrigation, poorly compacted backfills, and leaky water and
sewer lines. The elimination of the potential sources of
excessive water will greatly minimize the risks of
construction at this site.
The findings and recommendations of this report have been
obtained in accordance with accepted professional
engineering practices in the field of Geotechnical
Engineering. There is no other warranty, either expressed
or implied. This report applies only to the type of
construction anticipated in the area tested. The current
technology for dealing with expansive soils is not at a
stage where a guarantee of "absolutely no damage" can be
assured by design and construction practices.
15
8. It is recommended that CDS Engineering Corporation
or other registered professional structural
engineer design the substructure and that he take
into account the findings of 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 structure or its location are planned,
the conclusions and recommendations contained in this report
will not be considered valid unless said changes are
reviewed and conclusions of this report modified or approved
in writing by CDS Engineering Corporation, the geotechnical
engineer of record.
Every effort was made to provide comprehensive site
coverage through careful locations of the test borings,
while keeping .the site investigation economically viable.
Variations in soil and/or groundwater conditions between
test borings may be encountered during construction. In
order to permit correlation between the reported subsurface
conditions and the actual conditions encountered during
construction and to aid in carrying out the plans an
specifications as originally contemplated, it is recommended
that CDS Engineering Corporation be retained to, perform
continuous construction review during the excavation and
foundation phases of the work. CDS Engineering Corporation
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.
"The' §6ils at the site show a slight swell and
consolidation potential; therefore, future owners should be
cautioned that there is a risk of future damage caused by
introduction of excess water to the soils and/or rock. All
14
GENERAL RECOMMENDATIONS
1. Laboratory test results indicate that water
soluble sulfates in the soil are negligible, and a
Type II cement may be used in concrete exposed to
subsoils. Slabs -on -grade subjected to de-icing
chemicals should be composed of a more durable
concrete with low water -cement ratios and higher
air contents.
2. Finished grade should be sloped away from the
structure on all sides to give positive drainage.
Five percent (5%) for the first ten feet (101)
away from the structure is the suggested slope.
3. Gutters and downspouts should be designed to carry
roof runoff water well beyond the backfill area.
4. Underground sprinkling systems should be designed
such that piping is placed a minimum of five feet
(51) outside the backfill of the structure. Heads
should be designed so that irrigation water is not
sprayed onto the foundation walls. These
recommendations should be taken into account in
the landscape planning.
5. Plumbing under slabs should be eliminated wherever
possible since plumbing failures are quite
frequently the source of free water which may
cause slab heave.
6. Footing and/or grade beam sizes should be
proportioned to equalize the unit loads applied to
the soil and thus minimize differential
settlements.
7. It is recommended that compaction requirements in
the project specifications be verified in the
_ field with density test performed under the
direction of the geotechnical engineer.
f
13
18-kip Equivalent Daily Load 10
Application (EDLA)
Serviceability Index 2.0
Pavement Design Life 20 years
Strength Coefficients
Asphalt 0.40'
Aggregate Base Course 0,12
Based upon this information, the R-value (Figure No. 2),
and using the Colorado Department of Transportation
design nomograph (Figure No. 3), the following minimum
pavement sections are recommended:
R-value = 12 Effective Resilient Modulus (MR) = 3929
Traffic Area Alternate Pavement Section - Total
ACS ABC Thickness
Driveways A 6.25" - 6.25"
B 3.50" 8.75" 12.25"
Parking Areas -A 5.5" - 5.5"
B 3.0" 8.0" 11.0"
ACS = Asphaltic Concrete Surface
ABC = Aggregate Base Course
The crushed aggregate basecourse should meet State of
Colorado Department of Highways Class 5 or 6
specifications (Page 742, Section 703.03). The subgrade
below the proposed asphalt pavement should be prepared in
accordance with the recommendations discussed in the
"Site Grading, Excavation and Utilities" section of this
report. Upon proper preparation of the subgrade, the
basecourse should be placed and compacted at optimum
moisture to at least ninety-five percent (95%) of
Standard Proctor Density ASTM D698.
12
Foundation Drain System
A peripheral or perimeter drain system is recommended
where slabs are to be placed below finished grade. The
dpa}n should flow by daylighting. If this is not
possible, the drain should be connected to the storm
sewer, or provisions for a sump pump for future
installation.
Drive and Parking Lot Areas
Flexible Pavement
It is our opinion that flexible pavement is suitable for
the proposed parking and drive areas and for the existing
street improvements. A flexible pavement should consist
of asphalt concrete underlain by crushed aggregate base
course.
R-values were determined from HVEEM Stabilometer tests
from samples taken from the parking and drive areas. R-
value obtained is 12 (See Figure No. 2).
The structural pavement design follows the Colorado
Department of Highways Roadway Design Manual, Section
600, entitled "Design of Pavement Structures". The
following criteria (which was determined for the
particular site) was used with the CDOH method for
determining the pavement sections listed on the following
pages.
' H !, nu i' III If
� � 1
11
It is recommended that all light standards be drilled
pier type foundations. The intensity of the ultimate
passive pressure of the upper silty soils encountered at
the site at depth Z may he expressed by the equation Pp
= 250Z pounds per square foot. Imported granular
materials may be expected to have an ultimate passive
pressure expressed by the equation Pp = 40OZ pounds per
square foot. The above passive pressures may be used in
the design criteria for resisting lateral loads and
overturning moments developed on the pier. It is
suggested that a factor of safety of 1.5 be used in
conjunction with the above equations. All piers should
extend a minimum of thirty inches (3011) below finished
grade for frost protection. Piers should be founded on
the original, undisturbed soil or properly placed fill
that has been compacted to a minimum of ninety-five
percent (95%) of Standard Proctor Density.ASTM D698 in
accordance with the recommendations discussed in the
"Site Grading, Excavation land Utilities" section of this
report.
Concrete Reinforcement
gait 'a°d footings which are sixteen inches (16" ) in width
or less and are not subjected to overturning loads should
be reinforced with a minimum of two (2) Grade 40 No. 4
rebar. For footings greater than sixteen inches (1611) in
width, the footing should be designed and reinforced per
ACI 318 for all applied vertical and lateral loads. Stem
walls should be reinforced with a minimum of two (2)
Grade 40 No. 4 rebar for each eighteen inches (1811) of
height to resist temperature stresses. The stem walls
should, however, be designed and reinforced to resist all
lateral and vertical loads per ACI 318. Caissons and
grade beams should be reinforced per ACI 318.
IT 1
10
approved, free -draining granular material to within one
and one-half to two feet (1 z' - 2' ) of the top of the
structure. The granular backfill should be compacted to
at least seventy percent (70%) of Relative Density ASTM
D4253-830 D4254-83. The granular backfill should be
overlain by an untreated building paper or filter fabric
to prevent the overlying backfill from clogging the
filter material. The upper one and one-half to two feet
(1k' to 21)of backfill behind retaining walls over three
feet (31) in height should consist of the on -site
impervious clay material compacted to the above -required
density. Retaining walls backfilled with the on -site
Li, pily
ays may be designed using a hydrostatic pressure
distribution and equivalent fluid pressure of fifty (50)
pounds per cubic foot per foot depth of backfill.
Retaining walls backfilled with imported granular
material may be designed using a hydrostatic pressure
distribution and equivalent fluid pressure of forty (40)
pounds per cubic foot per foot depth of granular
backfill. The maximum toe pressure should not exceed
three thousand pounds per square foot (3000 PSF), and the
bottom of the footing should be placed a minimum of
thirty inches (3011) below the low side finished grade for
frost protection. Footings should be founded on the
original, undisturbed soils or on properly compacted
structural fill constructed in accordance with the
recommendations discussed in the "Site Grading,
Excavation and Utilities" section of this report. Weep
holes should be provided in the retaining wall so that
hydrostatic pressures which may develop behind the walls
will be minimized. Positive drainage should be provided
away from the top of the wall to prevent ponding of water
in the area behind the wall.
I: •
To minimize and control shrinkage cracks which may
develop in slabs -on -grade, we suggest that control joints
be placed every twelve (12) to fifteen (15) feet and that
the total area contained within these joints be no
greater than two hundred -twenty-five (225) square feet.
When slab construction will be undertaken in the winter
months, it is recommended that slabs -on -grade not be
poured until the building has been enclosed and heat is
available within the building area so that slab -on -grade
concrete is not placed on frozen ground. This will also
aid in proper curing of slab concrete.
We further recommend that nonbearing partitions placed on
+ floor slabs be provided with a slip joint (either top or
bottom). Slip joints reduce pressure applied by heaving
floor slabs and thus minimize damage to the portion of
the structure above. It is emphasized that if the
subsoils are kept dry, movement of slabs -on -grade should
be minimal. However,_if moisture is permitted to reach
the subsoils below the slabs, heaving may occur. Maximum
slab movement due to heaving of the subsoils is
anticipated to be approximately one inch (±111). If the
excavation is dug to the sand and gravel depth, the slip
joint may be eliminated as the expansive material has
been removed.
Retaining Walls and Light Standards
Retaining walls three feet (31) or less in height
constructed at the site should be backfilled with the on -
site clay soils. The clay backfill should be compacted
in uniform lifts from zero (0%) to plus two percent _(+2%)
wet of optimum moisture to a minimum of ninety-five
percent (95%) of Standard Proctor Density ASTM D698.
Retaining wall structures over three feet (31) in height
constructed a the site should be backfilled with
a
walls and the lower portion of the exterior foundation
YFIhl,, of the structure. The upper one (1) to two ( 2 ) feet
of backfill adjacent to exterior walls in open and
planted areas should consist of the on -site clay soils
compacted to the above required density.
Slabs -on -Grade
The sandy clay soils and bedrock encountered in our test
boring exhibited a slight swelling condition when
saturated from in -situ moisture conditions.
Subgrade below slabs -on -grade should be prepared in
accordance with the recommendations discussed in the
"Site grading, Excavation, and Utilities" section of this
report. If imported granular materials are utilized as
fill below slabs -on -grade, the potential for slab
movement will be minimal. It is recommended that
imported granular material used at the site be placed
below the proposed building slab. If the subgrade below
slabs -on -grade is allowed to dry below. the required
moisture,.the subgrade should be prewetted from zero to
plus two percent (0 to +2%) of optimum moisture prior to
placement of underslab gravel and concrete. The moisture
content of the subgrade soil should be evaluated by the
geotechnical engineer prior to placement of slab
concrete. Slabs -on -grade should be designed and
6'ditg'tructed structurally independent of bearing members.
In our opinion, a vapor barrier may not be required below
slabs -on -grade. The vapor barrier will collect free
water and moisture penetrating the slab prior to building .
enclosure. This collected moisture may be detrimental to
proper placement of certain floor coverings.
7
for a maximum allowable bearing capacity of 1500 psf and
a minimum dead load of 500 psf. The foundation is to
bear on natural sandy clays and not on uncompacted fill,
topsoil, or frozen ground. An alternate would be to over
excavate to the gravel depths and bear the foundation
directly on the gravel or compacted granular fill back to
the needed footing depth at 95% of ASTM D698 at proper
moisture. If this is done, the foundation could be
designed for a maximum allowable bearing capacity of 3000
psf. The bottom of all foundation components should be
kept at least thirty inches (3011) below finished grade
for frost protection. The open excavation should not be
left open for an extended period of time or exposed to
adverse weather conditions. The completed open
excavation should be inspected by a representative of CDS
Engineering Corporation in order to verify the subsurface
conditions from test hole data.
Backf ill .
Backfill placed adjacent to the building should consist
of the on -site sandy clays or imported granular material
approved by the geotechnical engineer. The backfill
"8hdUld be mechanically compacted in uniform six inch (611)
to eight inch (811) lifts to a minimum of ninety-five
percent (95%) of Standard Proctor Density ASTM D698.
Foundation walls backfilled with on -site clays may be
designed with a hydrostatic pressure distribution of 50
pounds per square foot per foot of depth of backfill.
Free-standing foundation walls backfilled with imported -
granular material may be designed using a hydrostatic
pressure -distribution and equivalent fluid pressure of
backfill of forty (40) pounds per square foot per foot
depth of backfill. Where possible, granular soils should
be used as backfill adjacent to the inside foundation
6
be needed for proper compaction. Expansive claystone
bedrock should not be used as backfill in areas to
receive buildings or paving.
Stripping, grubbing, subgrade preparation, and fill and
ii I II �'
back�ill placement should be accomplished under
continuous observation of the geotechnical engineer.
Field density tests should be taken daily in the
compacted subgrade, fill, and backfill under the
direction of the geotechnical engineer.
Continuous Spread Footing and/or Grade Beam Foundations
Because of the depth of the bedrock and the type of upper
soils encountered, a continuous spread footing and grade
beam foundation can be used.
The upper soils at the site exhibit swell pressures as
high as 1700 pounds per square foot and a volume change
as high as +1.8% when wetted. The lower sands and
gravels could not be adequately sampled without
disturbance.
Where dense sandy clays are encountered in the excavation
the foundation may be a continuous spread footing and/or
grade beam foundation designed for a maximum allowable
bearing capacity of 3000 pounds per square foot
(psf)(dead load plus full live load) and a minimum dead
load of 1000 pounds per square foot to help counteract
, p,,,Swelling should the subsoils become wetted. Total
differential movement is estimated to be 3/4 inch or_
less. Four -inch (411) high void forms may be needed in
strategic areas under the grade beams in order to achieve
the recommended minimal dead load. Where loose sandy
clays are encountered the foundation should be designed
5
In computing earthwork quantities, an estimated shrinkage
factor of eighteen percent (18%) to twenty-three percent
(23%) may be used for the on -site clays compacted to the
above recommended density.
All excavations should be dug on safe and stable slopes.
It is suggested that excavated slopes be on minimum
grades of 1 1/2:1 or flatter. The slope of the sides of
the excavations should comply with local codes and OSHA
regulations. Where this is not practical, sheeting,
shoring, and/or bracing of the excavation will be
rgq�}red. The sheeting, shoring, and bracing of the
excavation should be done to prevent sliding or caving of
the excavation walls and to protect construction workers.
The side slopes of the excavation or sheeting, shoring,
or bracing should be maintained under safe conditions
until completion of backfilling. In addition, heavy
construction equipment should be kept a safe distance
from"the edge of the excavation.
All utility piping should be adequately bedded for proper
load distribution. Backfill placed in utility trenches
in open and planted areas should be compacted in uniform
lifts at optimum moisture to at least ninety percent
(90%) of the Standard Proctor Density ASTM D698 the full
depth of the trench. The upper four feet (41) 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
Standard Proctor Density ASTM D698, and the lower portion .
of these trenches should be compacted to at least ninety
percent (90%) of Standard Proctor Density ASTM D698.
Addition of moisture to and/or drying of the subsoils may
4
etc., are not. anticipated. With proper site grading around
the proposed building and paved areas, erosional problems at
the site should be minimal.
RECOMMENDATIONS AND DISCUSSION
It is our understanding that the proposed site will include
two (2) retail buildings. Asphalt paved parking area will be
located across the site.
Site Grading, Excavation, and Utilities
It is recommended that the upper eight inches (811) of
topsoil and soils containing organics below the building,
fills, and paved areas be stripped and stockpiled for
reuse in planted areas. Th upper six inches (611) of the
subgrade below building, paved and filled areas should be
scarified and recompacted from zero percent (0%) to plus
two percent (+2%) wet of optimum moisture and to at least
ninety-five percent (95%) of Standard Proctor Density
ASTM D698. It is important that the subgrade below
slabs -on -grade be at zero percent (0%) to plus two
percent (+2%) wet of optimum moisture just prior to
placement of underslab gravel or concrete. Fill should
consist of imported granular material approved by the
geotechnical engineer. Fill should be placed in uniform
six to eight inches (6" - 811) lifts and mechanically
compacted from zero (0%) to two percent (2%) wet of
optimum moisture and to at least ninety-five percent
(95%) of Standard Proctor Density ASTM D698.
Aipossibility exists that previously excavated/backfilled
areas will be .encountered during construction. These
previously backfilled areas must be evaluated by the
Geotechnical Engineer prior to proceeding with
construction. Excavation and recompaction of these areas
is likely.
3
Groundwater was encountered in the test holes twenty-four
(24) hours after drilling at depths varying from seven to nine
feet (7'-91).
Sulfate concentrations are such that Type II cement could
-- be used for concrete exposed to the soils.
GEOLOGY
The proposed commercial building site is located within the
Colorado Piedmont section of the Great Plains physiographic
province. The Colorado Piedmont, formed during Late Tertiary
and early Quaternary time (approximately sixty-five million
year ago), is a broad, erosional trench which separates the
SqI uthern Rocky Mountains from the High Plains. Structurally,
i, icy i ��inr
the property lies along the western flank of the Denver Basin.
During the Late Mesozoic and early Cenozoic Periods
(approximately seventy million years ago), intense tectonic
activity occurred, causing the uplifting of the Front Range to
the west and the associated downwarping of the Denver Basin to
the east. Relatively flat uplands and broad valleys
characterize the present-day topography of the Colorado
Piedmont in this region. The site is underlain by the
Cretaceous Pierre Formation. The Pierre Shale is overlain by
colluvial and alluvial clays and gravels of Pleistocene and/or
Recent Age.
The regional dip of the bedrock in this area is slight and
in an easterly direction. Seismic activity in the area is
anticipated to be low; therefore, from a structural
standpoint, the property should be relatively stable. In our
opinion, construction of the site should be designed in'
accordance with the Uniform Building Code Seismic Zone 1. In
view of the relatively flat nature of the site, geologic
hazards due to mass movement, such as landslides, mudflows,
r
2
SITE LOCATION AND DESCRIPTION
The site is located in the north part of the City of Fort
Cowl Iips,jp,,Larimer County, Colorado, north of the Cache La
Poudre River just east of Highway 287. This site is
relatively flat with vegetation on the southeast part of the
site consisting of various grasses and alfalfa. The remainder
of the site is covered with asphalt and an existing
restaurant.
SUBSURFACE CONDITIONS
Refer to Log of Borings, Drawing Nos. 2-1 to 2-3. The
subsurface conditions were uniform throughout the site. A
general description of the soils and/or rock encountered are
as follows:
Topsoil - A layer of approximately six inches (611) of
topsoil overlies the site on the southeast portion of the
site. The topsoil should not be used as foundation
bearing material, structural fill, or backfill. It is
suggested. that the topsoil which has been stripped be
stockpiled and used for landscaped areas.
Pavement - 2" to 3" of asphalt, 4" to 6" of roadbase was
encountered across the majority of the site.
Sandy Clay - Dk. brown to brown, moist, soft, sandy clay
was encountered beneath the topsoil and pavement to
depths varying from four to seven feet (4'-71).
Sand and Gravel - Moist to wet, sand and gravel was
encountered beneath the sandy clay down to a depth of
eleven ,feet (111), where drilling refusal occurred.
1
SCOPE
This report presents the results of a geotechnical
investigation for the proposed commercial buildings to be
located on 1st Stop Plaza Minor Subdivision, City of Fort
Collins, Larimer County, Colorado. The investigation was
prepared by means of test borings and laboratory testing of
samples obtained from these borings.
This investigation was made to determine the type and
depth of foundation, allowable soil bearing pressures,
groundwater conditions, and any problems that might be
encountered during or after construction due to subsurface
conditions.
SITE INVESTIGATION
The field investigation performed on September 12, 1995,
consisted of drilling, logging, and sampling eight (8) test
hples. The Location of the Test Holes is shown on Drawing No.
i, ;?� i �' tutu
1. A Log of Borings is shown on Drawing Nos. 2-1 to 2-3. A
Summary of the Swell -Consolidation Test Results is shown on
Figure Nos. 1-1 to 1-3. A Summary of Test Results is shown on
Table No. 1.
The test borings were advanced with a four -inch (411)
diameter auger drill. A six inch (611) diameter auger drill
was used to sample for the R-Value. Laboratory samples were
obtained by driving a two and one-half inch (2h") California -
type sampler into undisturbed soils with a 140-pound hammer
falling thirty inches (3011) and by bagging samples exposed by
the six inch (611) auger.
Laboratory tests performed were - Swell -Consolidation,
Natural Moisture, Natural Dry Densities, Sulfate
Concentrations, Grain -Size Analysis, Unconfined Compressive,
Strengths, Atterberg Limits, and HVEEM Stabilometer.
TABLE OF CONTENTS
Continued
Location of Test Borings Drawing No. 1
Symbols and Soil Properties Diagram No. 1
Log of Borings Drawing Nos. 2-1 to 2-3
Swell -Consolidation Test Results
Figure Nos. 1-1 to 1-3
HVEEM (R-value) Stabilometer Test Results Figure No. 2
Nomograph - Flexible Pavements (CDOT) Figure No. 3
�guri nfair9�1 of Test Results Table No. 1
' Post -Construction Site
Preparation and Maintenance Appendix I
Specificatfbns for Placement of
Fill Material Appendix II
iii
TABLE OF CONTENTS
Pace
Letter of Transmittal
i
Table of Contents
Scope
1
Site Investigation
i
Site Location and Description
2
SuiuXace Conditions
2-3
Geology
3-4
Recommendations and Discussion
4-13
Site Grading, Excavation, and Utilities
4-6
Continuous Spread Footings and/or Grade
Beams 6,7
Backfill
8-9
Slabs -on -grade
8-9
Retaining Walls and Light Standards
9-11
Concrete Reinforcement
11
Foundation Drain System
12
Drive and Parking Lot Areas
12-13
Flexible Pavement
12-13
General Recommendations
14,15
General Comments
15,16
ii
_ October 4, 1995
„V Project No. 95-8433
Mr. Ric Hattman
Gefroh Hattman Architects & Planners
145 W. Swallow Rd.
Fort Collins, CO 80526
Dear Ric,
Enclosed is the report you requested of the geotechnical
investigation for the proposed commercial buildings to be
located on 1st Stop Plaza Minor Subdivision, City of Fort
Collins, Larimer County, Colorado.
The site is suitable for the construction of the proposed
commercial building, provided the design criteria and
recommendations given in this report are met.
If you have any further questions concerning the
information in this report, please contact this office.
Sincerely,
C:D;S�7 C REGS/.,
L--A;h 1bny/a J. Wernsman, Po 4 .",
P�/ojedt Engineer 0''1p'g s5•' _�
AJW/bjd
Enclosures
1714 Topaz Dr., Suite 215 • Loveland, CO 80537 • (970) 667-8010 0 Fax: (970) 667-8024
r-
r
GEOTECHNICAL INVESTIGATION
1ST STOP PLAZA MINOR SUBDIVISION,
CITY OF FORT COLLINS,
LARIMER COUNTY, COLORADO
FOR
GEFROH HATTMAN ARCHITECTS AND PLANNERS
CDS ENGINEERING CORPORATION
LOVELAND, COLORADO
PROJECT NUMBER
95-8433
OCTOBER 4, 1995