HomeMy WebLinkAbout20162133.tiffColorado
Geoscience & Design, Inc.
P.O. Box 68 Franktown, Colorado 80116 • Phone: 303.688.2150 • Fax: 303.688.1295 • CoGeoDesign
Billy Enyart
4747 National Western Drive
Denver, CO 80216
SUBSURFACE INVESTIGATION
OF
1970 COUNTY ROAD 23
WELD COUNTY, COLORADO
REPORT NO. 15-635
September 3, 2015
NOT VALID WITHOUT
ORIGINAL SIGNATURE
GEOTECHNICAL STRUCTURAL CIVIL ENGINEERS
TABLE OF CONTENTS
General
Site Conditions
Field and Laboratory Investigation
Foundation Recommendations
Criteria for Concrete Slab on Grade Construction
Placement of Structural Fill
Placement of Foundation Fill
Subsurface Drainage
Surface Drainage
Foundation Excavation
General Information
Location Map
Log of Test Holes
Swell / Consolidation Charts
Summary of Laboratory Testing
Details of Foundation Drain System
Foundation Grading Detail
Appendix
1
1
1
2
3
5
6
7
7
8
8
Figure 1
Figure 2
Figure 3
Table 1
Detail 1
Detail 2
Information about the Report
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
GENERAL
This report presents the results of data obtained during the subsurface investigation at
1970 COUNTY ROAD 23, WELD COUNTY, COLORADO. This investigation was
made to determine the type of foundation required, allowable bearing capacity, and
groundwater conditions encountered at the time of the field investigation.
SITE CONDITIONS
At the present time the site is vacant. It is our understanding a 3800 sq. ft. steel
building is planned for this site. The proposed steel building will consist of metal framed
construction with a steel reinforced concrete foundation. We anticipate the foundation
loads for the steel building to range from 500 to 1,000 pounds per lineal foot of
foundation wall.
The topography of the site is generally flat. The vegetation at the site consists of native
grass and weeds. The weather was warm and clear at the time of the investigation.
If the type of construction changes from that specified above, please contact this office
for additional recommendations and/or requirements.
FIELD
AND
LABORATORY
INVESTIGATION
I
Two (2) exploratory test holes were drilled on August 17, 2015 at the site shown on the
Location Map, Figure 1. The test hole was drilled with a four -inch (4") diameter auger
advanced with a CME-45 soil exploration drill rig.
At specific intervals, the drilling tools were removed from the test holes and soil samples
were obtained with a two-inch (2") diameter spoon sampling tube. The depths at which
soil samples were taken and a description of the soil encountered are shown on the Log
of Test Holes, Figure 2, and the Summary of Laboratory Testing, Table 1.
All soil samples were carefully observed in the field during the drilling operation. These
samples were classified in the laboratory through visual observation and laboratory
testing to determine the pertinent properties. The natural moisture content and dry
density was obtained from relatively undisturbed drive samples of typical soils. Swell -
consolidation tests were performed on typical soil samples see Figure 3. These tests
indicate the behavior of the soil upon various loadings in a wetted condition.
Groundwater was encountered at a depth of 6 feet in both B1 and B2 at the time
of the field investigation. When checked later, groundwater was measured at a
depth of 3 feet in both B1 and B2; both boreholes caved to 4 feet. These
observations represent the groundwater conditions at the time of drilling or
measurement and may not be indicative of the conditions at other times. Groundwater
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
levels can be expected to fluctuate with varying seasonal weather conditions and if the
sites use irrigation for lawns.
Site soil conditions encountered may appear different from the test borings as
presented in this report. An excavation observation is required and must be
performed by a representative of this office to verify existing soil conditions, and
the proposed design bearing pressure. The excavation observation must be
performed only after the entire building footprint has been excavated to the bottom of
bearing elevation. In addition, it may be necessary to revise our foundation
recommendations based upon results of the excavation. The fee for this observation
and/or revised foundation recommendations is not included in the cost of the soil
report.
Failure to follow the observation requirements noted herein may jeopardize the
success of this construction project and shall absolve Colorado Geoscience and
Design Inc. from any and all responsibility for any damages arising from the
failure to obtain proper site observations.
FOUNDATION RECOMMENDATIONS
Based on our evaluation of the subsurface conditions, we recommend the proposed
steel building be founded on drilled piers and grade beams or continuous concrete
footing and pads or continuous concrete footings and pads. A professional engineer
should use the following design criteria to design the foundations.
1. Piers shall be a minimum 12 -inch diameter.
2. Piers shall be a minimum of 22 feet deep embedded 5 feet into the claystone
bedrock.
3. Piers shall be designed for a maximum end bearing capacity of 20,000 pounds
per square foot.
4. Side shear resistance of 2,000 pounds per square foot for the 5 foot portion of in
claystone bedrock.
5. Piers shall be designed to resist uplift per design requirements The pier length
should be increased to offset any deficiency as required.
6. All piers shall be reinforced their full length with steel rebar. The pier reinforcing
shall be designed to resist the tension resulting from the maximum uplift
pressures. No less than 1% of steel based on the pier end area shall be used.
The pier reinforcing steel shall extend into the foundation wall a sufficient
distance to fully develop the bars in tension.
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
7. The recommended diameter must be maintained at the top of each pier hole.
We recommend forming the top portion of the pier with cylindrical cardboard
forms to prevent mushrooming
8. The drilled pier holes shall be cleaned of all loose material and filled immediately
with concrete to prevent sloughing of loose soil or infiltration of water.
9. The foundation walls shall be designed for an active horizontal pressure based
on an equivalent fluid density of 35 pounds per cubic foot plus any applicable
surcharge or hydrostatic loads and shall be designed to distribute the applied
loads between piers.
10.A void form of a minimum of four inches (4") shall be placed under the foundation
grade beam walls between the drilled piers.
11.If water is present in the drilled pier hole, the concrete shall be pumped or
tremmied to the bottom of the pier to displace the water.
ALTERNATE FOUNDATION RECOMMENDATION;
An alternate and satisfactory foundation recommendation for the proposed steel
building would be continuous concrete footings and pads. A professional engineer
should use the following design criteria to design the foundations.
1 The footings and pads shall be designed for a maximum soil bearing pressure of
800 pounds per square foot (DL+LL). The entire foundation shall bear on the
coarse -grained sand and gravel or structural fill material at least 4 feet above the
ground water (See "Placement of Structural Fill").
2. No footing or pad shall bear upon topsoil or soils that contain organic material.
All loose and disturbed soil shall be removed before pouring the concrete for the
footings or bearing pads.
3 All continuous footings supporting perimeter concrete foundation walls shall be at
least 16 inches wide. We recommend footings be reinforced to bridge isolated
soft areas up to 10 feet. Exterior footings should be provided with at least 3 feet
of soil cover for frost protection, or per county codes.
4 The foundation walls shall be designed for an active horizontal pressure based
on an equivalent fluid density of 35 pounds per cubic foot plus any applicable
surcharge or hydrostatic loads.
5 In place structural settlements are very difficult to predict with any reasonable
accuracy, due to the large number of variable geotechnical parameters involved.
However, based upon the currently available methods of settlement prediction, it
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
is estimated that total structural settlement will be on the order of 1" and
differential structural settlement will be on the order of W.
•-� __'- -a--. -_ - _� - ---�_-.: r,..-_� rr-. -, _ -,_ _ _.._ _ _ _ _
CRITERIA
FOR SLAB
-ON
-GRADE
CONSTRUCTION
Virtually all concrete slabs undergo some type of movement. Concrete slabs placed on
soils comprised of medium dense or dense granular material, or comprised of soft or
stiff clays with swell potential less than 1% under a 1,000 lb. surcharge is considered
unlikely to sustain intolerable movement by standard engineering practice.
Cracking of slabs -on -grade is difficult to control and should be expected to occur with
time. Cracking may be the result of many factors such as concrete shrinkage and daily
and seasonal variability in temperature and humidity and not necessarily the result of
soil movement.
Further, cracks and movement of slabs -on -grade can be transmitted through rigid floor
coverings such as ceramic tile. Performance expectations should be taken into
consideration in the selection of floor slab coverings.
If floor coverings or coatings less permeable than the concrete slab are used, or if
moisture is a concern, we recommend a vapor retarder be placed beneath the slab.
Flooring installation should be consistent with the flooring manufacturer's
recommendations for subsoil and slab construction and moisture testing prior to
installation.
A change in water content in soils is a major contributor to slab movement.
Colorado Geoscience and Design recommends that steps be taken to reduce the
possibility of intolerable concrete slab movement due to changes in water content.
Properly landscaped yards, drainage from the foundation walls, and the installation of
perimeter and/or under slab drainage systems are ways to mitigate changes in the
water content of the indigenous soils (See "Surface Drainage").
A slab performance risk evaluation was conducted in general compliance with industry
guidelines for the local area. The risk assessment of a site for potential movement is
not absolute; rather, it represents a judgment based upon the data available and our
experience in the area. Movement of foundations and concrete flat work will occur over
time in low to very high risk areas as the soil moisture content increases. On low and
moderate rated sites, slab movements of up to 3 inches across the slab with cracking of
up to '/� inch in width and/or differential movement are not unusual. The damage
generally increases as the risk assessment increases and as the depth of wetting
increases. It must be understood, however, that assessing risk is an opinion, and the
prediction of heave is not an exact science. Therefore, it may be possible that heave
less than or in excess of what is described herein may be experienced. This risk should
be communicated to the subsequent homebuyer. We recommend the owner or
prospective buyer review "A Guide to Swelling Soils for Colorado Homebuyers and
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
Homeowners", which is a special publication produced (SP43) by the Colorado
Geological Survey to assist homeowners in reducing damage caused by swelling soils.
Swell Potential Chart
Slab
Performance
Risk
Category
Representative
(1,000
psf
Surcharge)
Percent Swell
Low
0 to <2
Moderate
2 to <4
High
4 to <6
Very High
≥6
Note: the representative percent swell values presented are not necessarily measured values; rather,
they are a judgment of the swell of the soil and bedrock profile likely to influence slab performance.
The swell potential of the indigenous soils for the residence at this site meet the criteria
for low risk of slab -on -grade movement. Concrete slabs may be used for the building
slabs and exterior surface (sidewalks, patios and aprons) placed on the native soil.
Furthermore, intolerable movement of any slab on grade may occur at the site as a
result of future factors beyond the control of Colorado Geoscience and Design, Inc.
If differential slab -on -grade movement is not acceptable to the owner/builder and,
if the owner/builder is unwilling to accept the risk of differential slab -on -grade
movement structural floors above crawl spaces are required.
The owner/builder shall be cautioned that problems with mold may arise when floors are
built over a crawl space or with a structural floor. In order to prevent such problems, it
may be necessary to take specific actions to mitigate the potential for molds, such as
installing actively controlled humidistat systems and devices, providing adequate
ventilation of enclosed spaces below the floor, and/or treatment of the soils with anti -
mold, anti -fungal chemical agents. Colorado Geoscience and Design, Inc. will not be
responsible for any and all claims arising from issues of mold or fungal contamination.
It is the builder's responsibility to adequately address these issues during construction.
If the owner/builder accepts the risk of slab -on -grade movement and chooses a slab -on -
grade floor, the following steps shall be part of the concrete slab design:
• Any soil disturbed during construction shall be compacted by use of a vibratory
plate in the case of loose granular soils or wheel rolled by heavy equipment in
the case of soft clay or silt soils prior to placement of the concrete slab.
• The soil should be kept moist but not wet during the compaction process as well
as immediately prior to the placement of the concrete slab directly onto the soil.
Steps shall be taken to ensure that subsurface moisture beneath the concrete
slab remains constant during the construction process.
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
• The concrete slab shall be structurally isolated from all foundations and shall be
isolated from penetrations by suitable expansion material not less than 1/2" thick.
The floating concrete slab shall be completely isolated from all utility lines.
• Control joints shall be provided in the concrete slab. These control joints must be
saw cut or tooled to a minimum of one third of the thickness of the slab. No
portion of the concrete slab will have an area greater than neither 100 square
feet nor a maximum dimension of 12'-0" in any direction without a control joint.
• All non-bearing partition walls shall be constructed with a minimum of 3 inches of
float to allow for slab -on -grade movement.
PLACEMENT
OF STRUCTURAL
FILL
Where structural fill placement is required, the following requirements shall be followed.
The structural fill material shall consist of non -expansive soil free of deleterious material
(organic, frozen of other unsuitable material) and rocks greater than 3" in diameter and
must be approved by Colorado Geoscience & Design, Inc.
The fill material should be compacted in lifts not to exceed 8 inches after compaction,
while maintaining a minimum of 95% of its maximum standard Proctor dry density
(ASTM D-698). Non -cohesive soils (sand) shall be placed at ±2% of the optimum
moisture content and cohesive soils (clay) shall be placed at +3% to —1% of optimum
moisture content.
A Standard or Modified Proctor Curve (whichever is applicable) by Colorado
Geoscience and Design, Inc. or an approved testing firm is required. An excavation
observation and soil density test is required and shall be performed by a
representative of Colorado Geoscience and Design, Inc. to verify soil conditions,
the depth of excavation, and quality of the compacted soil prior to the placement
of the footings and pads.
The fees for these tests are not included in the cost of the subsurface
investigation.
PLACEMENT OF FOUNDATION FILL
Expansive soil is not suitable for backfill material adjacent to the foundation
backfill or for retaining walls. Any soil disturbed or imported material adjacent to the
foundation walls shall be re -compacted to a minimum of 85% of Standard Proctor
Density, ASTM D-698. Compaction of each lift adjacent to walls should be
accomplished with hand -operated tampers or other lightweight compactors. Over
compaction may cause excessive lateral earth pressure, which could result in wall
movement. No water flooding techniques should be used in the compaction of backfill.
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
II SUBSURFACE DRAINAGE
The installation of an exterior foundation perimeter drainage system is required for any
habitable space below grade level. See Perimeter Drain Detail 1, for a suggested
method of installing this system. The perimeter drain shall discharge at a daylight
location a minimum of 15 -feet away from the home. The daylight end shall have a
screened end section to prevent rodents from entering the drain. Alternatively, the
perimeter drain may discharge into a sump pit with a sump pump. If a sump pit is used,
homeowners should perform routine observations of the sump pump system to make
sure it remains in good working order. Failure to install and failure of a sump pump
system can cause serious foundation problems. Water accumulation around
foundation elements is the major cause of foundation stress, therefore proper
installation of the perimeter drain is very important.
SURFACE DRAINAGE
I
The backfill soil around the foundations should be moistened and well -compacted in 12 -
inch maximum lifts with hand operated mechanical compaction equipment to prevent
future settling. Controlled puddling of the backfill soils is not allowed.
Site grading is critical. A simple means of reducing moisture change to prevent water
infiltration into the soil is to slope the ground away from the foundation. For proper
drainage, a slope of 10% (1' in 10') away from the foundations in all directions is
required. This slope must be maintained for a minimum distance of 10'-0".
The property owner should inspect the area around the foundation regularly particularly
after rainstorms to determine if proper drainage away from the structure has been
maintained. The owners are advised to immediately fill in any settled area near the
foundations to eliminate containment of water.
Roof drainage should include gutters, downspouts, extensions, and splash blocks.
Down spouts must discharge onto concrete splash blocks or into metal gutter
extensions at least 6 foot away from the foundation walls and beyond any backfill zones
directing water away from the foundation.
The owners should be cautioned regarding the installation of a lawn adjacent to the
foundation walls. Lawn irrigation must be more than five feet (5') from the foundation
walls to prevent wetting of the subsurface soils. Lawn and/or plants should not be
planted within five feet (5') of the foundation walls. We recommend providing decorative
gravel or bark around the foundations, as shown in Foundation Grading Detail 2. This
method will prevent ponding of water and provide for proper drainage from the
foundations. Non -woven geo textile fabric can be placed under the mulch to reduce
weed growth and still allow some evaporation of soil moisture.
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
Sprinkler heads and emitters should not be located or spray within 5 feet of the
foundation or patio slabs and beyond backfill zones. Plantings near the foundations
should not trap surface runoff. Furthermore, sidewalks or low-water consumption
groundcover are recommended to further reduce the risk of water infiltration near the
foundation walls. All pressurized irrigation lines and valve boxes should be located at
least 10 feet from the foundation or patio slabs.
Buried rain gutter discharge pipes are not recommended because of often undetected
seepage problems caused by clogging, crushing and adverse grading of the pipes.
Similarly, infiltration basins are not recommended adjacent to or upgrade of adjacent
structures. If detention is required by statute, infiltration basins should be located down
gradient and at least 30 feet from foundations.
Changes in site grading by landscapers or property owners can have damaging effects
on foundations and concrete basement and garage slabs -on -grade. It is the property
owner's responsibility to control water and maintain the site to prevent infiltration near
foundations. Additionally, it is the property owner's responsibility to maintain
downspouts and buried sprinkler system conduits.
FOUNDATION EXCAVATION
Precautions should be taken in deep excavations for safety of workers and to protect
nearby structures. The sides of the temporary excavations should be sloped or
benched at a '/zH to 1V maximum rate. Spoils for the excavation should not be placed
within 2 feet of the excavation sidewalls and the excavation should not be subject to
excess vibration wetting or drying. The owner contractor should be familiar with the
OSHA Safety and Health Standards for the Construction Industry, 29 CFR, Part 1926,
or the appropriate foundation chapters of the International Building Code prior to
construction.
GENERAL INFORMATION
Based on this subsurface investigation, the proposed foundations appear to be
technically feasible to be constructed at the proposed site. The structures should be
designed for construction in the direct vicinity of the boring location. If the proposed
locations change, additional borings will be required to assess the soil conditions at the
new location.
Permitting work will be required to obtain any local and state approval, and design work
will need to be performed by a qualified professional engineer to bring this project into
final design, and subsequent construction.
A qualified contractor experienced with similar projects should carry out the construction
of this project. The construction process should be carefully observed and documented
Subsurface Investigation
Billy Eynart
Colorado Geoscience and Design, Inc. Report No. 15-635
to ensure the construction is performed in accordance with the design drawings and
technical specifications.
In any soil investigation it is necessary to assume that the subsurface soil conditions do
not vary greatly from the conditions encountered in our field and laboratory testing. Our
experience has been that at times soil conditions do change and variations do occur
and may become apparent at the time of excavation for the foundation system.
The work contained herein was performed by, or under the direct supervision of a
licensed Professional Engineer in the State of Colorado. Professional judgments and
evaluations are presented based on information gathered during the drilling operations,
conversations with the owner and/or contractor, and on experience with similar projects.
The performance of the project is not guaranteed in any manner, only that the
engineering work and judgments rendered meet the standard of care of the engineering
profession. The engineering services performed are within the limits set by the Client,
with the usual thoroughness and competence of the engineering profession. No other
representation, expressed or implied, is included or intended.
The parties specifically agree that Colorado Geoscience and Design, Inc. has not been
retained nor will they render an opinion concerning any environmental issues,
hazardous waste or any other known or unknown conditions that may be present on this
site, since this is not in the scope of this report.
COUNTY ROAD 23
AFOUNDATION SOIL TEST BORINGS
OPERCOLATION TEST HOLES
SOIL PROFILE HOLE
UNSUITABLE SOIL PROFILE HOLE
PROPERTY LINE
GARAGE
PROPERTY LINE
100°
45?
B?
b
72
P3
N
P2
SJ
P1
165°
17
ID
GPS LOCATOR
ELEV
B1
N 40°01.631'
W 104°50.850'
4957
SPH
N 40°01.628'
W 104°50.824'
4956
1144
Colorado
Geosclence & Design,Inc.
P.O. BOX 66, FRAMCT°WN, CO. 6011e,
�PFICHE / (303) MS -2150
SITE MAP
ALL LOCATIONS SHOWN ARE BASED ON SPECIFIC INFORMATION FURNISHED BY OTHERS OR
ESTIMATES MADE IN THE FIELD BY COLORADO GEOSCIENCE PERSONNEL THE LOCATIONS,
DISTANCES, DIRECTIONS, ETC. ARE NOT THE RESULT OF A PROPERTY SURVEY BUT ARE
APPROXIMATIONS AND ARE NOT WARRANTED TO BE EXACT. IT 1S THE OWNER/BUILDER'S
RESPONSIBILITY TO DEFINE PROPERTY BOUNDARIES AND ENSURE ALL ON -SITE IMPROVEMENTS
ARE LOCATED WITHIN THE PLATTED SITE AND OUT OF INAPPROPRIATE EASEMENTS.
ALL DISTANCES ARE TO BE VERIFIED PRIOR TO EXCAVATION.
BILLY ENYART
SITE LOCATION
1970 COUNTY ROAD 23
WELD COUNTY,
COLORADO
SCALE
111=100'
JOB NO.
15-635
FIG. 1 J
Colorado Geoscience and Design, Inc.
PROJECT: Subsurface Investigation JOB NO: 15-635
CLIENT: Billy Enyart
Log of
Test
Holes
LOCATION:1790 County Road 23, Weld County, Colorado
DRILLING METHOD: 4" Continuous Flight Auger
1 2
El. 100 El. 100
Elevation Feet
100
- 8/12
:: :
.. • H.
•.:.:
Fine-grained sand, clayey,
loose, moist, brown
y
: ; " ::
... . ;
•• ••..•
Fine-grained sand, clayey,• 100
loose, moist, brown _
Elevation Feet
` ;
12/12
a
. •
— Hrs Coarse -grained sand and
24 -
gravel, medium dense,
96
-
_:
ia•
•
0 .
24Hrs. Coarse -grained sand and ■
gravel, medium dense,
slightly moist, brown
•��.
S;
96
slightly moist, brown
—
- 19/12
ebb.
.!•.
��•
Q .
.!.
".
92 ■
-
-
-
••`.
�!
Vii.`
.a
:i.o:
.
15/12
■
�•..
:•CIr
•.
jp:`
.!•.
e•:t
.s.
92
-
-
88
28/12
�..;,
% t .
•D •
•�"1
.!.
is
► t •.
1►i.`.
•ra.
.!.
88 -
84
•
. a •
Ic.
.0.
ID.•
► 0
j••
84•
-
Claystone, very moist,
gray
•wbrown
NR
■
-
Claystone, very moist,
gray
No Recovery
brown
80
80
50/6
=
_.
76 ■
76
72 72
Notes:
1. x/y
inches
2.
indicates that "x" number of blows of a 140 -pound hammer falling 30
are required to drive a 2 -inch diameter sampler "y" number of inches.
Indicates depth at which soil samples were taken.
Where Applicable --
z
a: Indicates ground water encountered during the drilling operation.
Q
b.
c.
Indicates ground water encountered after 24 hours.
Indicates auger refusal. d. C Indicates caving.
Figure 2
SWELL - CONSOLIDATION TESTS
+ +8
J +6
J
+4
ur
O Ce O +2
O
Z 0
`" O
_
Z -2
U O
W O -4
CL
z -6
0
U
-8
IMP
Swell/Consolidation under
pressure due to wetting
Water added
to sample
i
a
100 300 1M 3M 5M 10M 20,000
APPLIED PRESSURE (PSF)
Test Hole No. 1 Depth 3' Soil Description: Fine-grained sand, clayey, loose, moist, brown
+ +8
J
J
+4
Cl,
O +2
O 0
0
z 0
o
W Q 2
U C1
W O -4
a. co
-6
0
U
+6
-8
28,000
Swell/Consolidation under
pressure due to wetting
Water added
to sample
I
100 300 1M 3M 5M 10M 20,000
APPLIED PRESSURE (PSF)
Test Hole No. 1 Depth 8' Soil Description: Coarse -grained sand and gravel, medium dense, slightly moist
brown
28,000
JOB NO. 15-635
FIGURE 3
t))
L;
CD CD
E
z
.O
O
SUMMARY OF LABORATORY TESTING
•
Soil Description
Fine-grained sand, clayey, loose, moist, brown
Coarse -grained sand and gravel, medium dense, slightly
moist, brown
Coarse -grained sand and gravel, clayey, medium dense,
slightly moist, brown
Claystone, very moist, gray brown
Coarse -grained sand and gravel, medium dense, slightly
moist, brown
Coarse -grained sand and gravel, medium dense, slightly
moist, brown
e%AN
13
C Cl.N
CD
O
N
r
CO
N
r
I
O
N1
r
1
O
r
r
C
O
0
*,
Lc" 37) '
N =
CC 0
O
U
C'7
g
O
o
Nh
8
J
0
N
c)
i
8
J
o
o
2 19 20 38 30 32 NR* Loose
'.
Tr EN
2 3
ca ca
=
N
r
o0
N_
a)
N_
Co
N
O
Q
N
N
r
N_
1
1.0
r
c
O
Gravel Sand Passing
#200 sieve
eita 0/0
N
N
r
CO
Nr
co
7 --
co
-O
/co
V
Co
N-
co
LO
co
CD
o0
r
O)
to
O
Co
`
'Cr
N
N
C)
'Cr
c
L. 4,
O
O C
2 O
U
M
r
N-
r
(t)
r
o
N
r
t -
d
o 't-
t7
CO
d
N
d
o)
o
O O
2
r-
r
t--
r
N
N
*NR - No Recovery
COLORADO GEOSCIENCE AND DESIGN, INC.
APPENDIX
Important Information About the Report
The data collected by Colorado Geoscience & Design, Inc. during this
investigation was used to provide geotechnical information and recommendations
regarding subsurface conditions on the site investigated, the effect of those conditions on
the proposed construction, and the foundation type for the named client. The
stratification lines indicated on the boring log are approximate, and subsurface conditions
encountered may differ from those presented herein. This uncertainty cannot be
eliminated because of the many variabilities associated with geology. For example,
material and engineering characteristics of soil and bedrock may change more gradually
or more quickly than indicated in this report, and the actual engineering properties of
non -sampled soil or rock may differ from interpretations made based on boring logs.
Quantitative conclusions regarding the performance of geotechnical structures prior to
construction are not possible because of the complexity of subsurface conditions. Rather,
engineering judgments and experience are used to estimate likely geotechnical
performance and provide the necessary recommendations for design and construction.
Put another way, we cannot be sure about what is not visible, so the collected data and
our training and experience are used to develop predictions and recommendations. There
are no guarantees or warranties implied or expressed.
The owner and/or client must understand that uncertainties are associated with
geotechnical engineering, and they, the owner and/or client, must determine the level of
risk they are willing to accept for the proposed construction. The risks can be reduced,
but not eliminated, through more detailed investigation, which costs more money and
takes more time, and through any appropriate construction which might be recommended
as a result of that more detailed investigation. To reduce the level of uncertainty, this
report was prepared only for the referenced client and for the proposed construction
indicated in the report. Unless authorized by Colorado Geoscience & Design, Inc. in
writing, the owner will assume additional geotechnical risk if this report is used for any
construction that differs from that indicated in the report. Our firm should be consulted
well before changes in the proposed construction occur, such as the nature, size,
configuration, orientation, or location of any improvements. Additionally, the knowledge
and experience of local geotechnical practices is continually expanding and it must be
understood the presented recommendations were made according to the standard of
practice at the time of report issuance. If the construction occurs one or more years after
issuance of the report, the owner and/or client should contact our firm to determine if
additional investigation or revised recommendations would be advisable.
Geotechnical practice in the Denver Region must consider the risk associated with
expansive soils and bedrock. Geotechnical practice in the Denver area uses a relative
scale to evaluate swelling potentials. As stated in the Subsurface Investigation, when the
sample is wetted under a surcharge pressure (loading) of 1000 pounds per square foot
(PSF), the measured amount of swell is classified as low, moderate, high, or very high.
Page 1 of 3
Table 1 presents the relative classification criteria for the percentage of expansion relative
to the initial sample height, at the indicated surcharge pressure.
Swell Potential Chart
SWELL POTENTIAL AT 1,000 LBS.
CLASSIFICATION
0 to %2%
Non-expansive/Very low
1/2 to 11/2%
Low
1'/2 to 31/2%
Moderate
3'/2to6%
High
6 to 8%
Very High
Greater than
8%
Critical I
The swell potential classifications are based on the percentage of swell for samples placed on
swell/consolidation machines under a surcharge of 1000 pounds per square foot.
The relative swell classification can be correlated to potential slab damage as
follows:
Low - minor slab cracking, minor differential movement, and heave
Moderate - lab cracking and differential movement, partial framing void and
furnace plenum closure.
High to Very High - large slab cracking and differential movement, closed voids,
closed furnace plenum, and possible pipe rupture.
These effects are based on monitoring and observation by several firms in the Denver
metropolitan area and are not limited to the relative swell classification. More or less
damage can occur in all classifications because of the uncertainty associated with
subsurface conditions and geotechnical engineering.
It is important to note that measured swell or soil expansion is not the only geotechnical
criteria for the type of floor and foundation recommendations. Additional criteria
considered include:
• Soil and bedrock type and variability
• Stratigraphy
• Groundwater depth and anticipated post -construction moisture conditions.
• Surface water drainage and features
• Post -construction landscaping and irrigation
• Construction details and proposed use
• Local experience
Page 2 of 3
Post -construction landscaping and owner maintenance will greatly affect
structures on expansive soils and bedrock. Typically, irrigated landscaping increases the
soil moisture content above the pre -constructed water content. Slabs, pavements, and
structures significantly reduce evaporation of the soil moisture. Therefore, post -
construction heave and resulting damage to buildings and other improvements are likely
to occur on sites with expansive soils because of the high probability that subsurface
moisture content will increase as the property and surrounding area is developed. Poor
owner maintenance, such as negative slopes adjacent to foundation walls and irrigated
landscaping adjacent to the foundation, also will significantly increase the risk of damage
from expansive soil and bedrock. The property owner, and anyone he or she plans to sell
the property to, must understand the risks associated with construction in an expansive
soil area and also must assume responsibility for maintenance of the structure. The
owner and prospective purchaser also should review "A Guide to Swelling Soils for
Colorado Homebuyers and Homeowners, " which is a special publication (SP 43)
produced by the Colorado Geological Survey to assist homeowners in reducing damage
caused by swelling soils.
Page 3 of 3
BRACE WALLS, TOP & BOTTOM,
PRIOR TO BACKFILL
CONCRETE GRADE BEAM
FLOOR SLAB
EXPANSION JOI
VOID BETWEEN PI
WELL SLOPED - 1211'Ilj' PER
r10 FT. MIN. DO NOT DIKE WITH
(500 OR EDGING
z
4
TOP 12" OF WELL -COMPACTED
BACKFILL
MODERATELY COMPACTED
BACKFILL
DAMP PROOFING
POLYETHYLENE GLUED TO WALL
AND EXTENDED ALONG THE
BOTTOM OF THE EXCAVATION.
15# BUILDING FELT
4" MIN.
4" MIN.
ye -
3/4" TO 1 1/2" CLEAN GRAVEL
4I1'III' DIAMETER PERFORATED PIPE.
SLOPE DRAIN PIPE 1/8" PER FOOT TO
DAYLIGHT, OR TO A SUMP PIT. IF TO
DAYLIGHT, COVER END WITH SCREEN.
BACKFILL AROUND THE FOUNDATION SHOULD BE MOISTENED AND
COMPACTED AND THE FINAL GRADE SHOULD BE WELL SLOPED TO
PRECLUDE PONDING OF RAINFALL, IRRIGATION WATER, AND SNOW
MELT ADJACENT TO FOUNDATION WALLS.
CAUTION:
DO NOT DIKE OR IMPEDE THE FLOW OF WATER AWAY FROM
FOUNDATION WALLS WITH SOD, EDGING OR DECORATIVE GRAVEL
AND POLYETHYLENE. DOWNSPOUTS AND SILL COCKS SHOULD DISCHARGE
INTO SPLASH BLOCKS OR LONG EXTENSIONS.
DRAIN SYSTEM BELOW GLADE
AND BACKFILL DETAILS
(FOR PIER FOUNDATION)
DETAIL 1
FOUNDATION GRADING DETAIL
1
4'-0" MINIMUM
„too.
btzgiP o.�0po,00t,
o40
ry/
SOIL TO BE
SLOPED AWAY FROM
FOUNDATION.
FOUNDATION WALL
NOTE:
1. PROVIDE A MINIMUM SLOPE OF 6" IN THE
FIRST 10'--0" FROM HOUSE (10%).
2. DOWNSPOUTS AND EXTENSIONS SHOULD
EXTENDED 5'-0" BEYOND THE FOUNDATION.
GRADE
DETAIL 2
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