HomeMy WebLinkAbout20040049 Soils and 5604 KENDALL COURT
MMaterials ARVADA,COLORADO 80002
Phone(303)431-2335
Consultants, Inc. Fax(303)431-2594
SUBSURFACE INVESTIGATION
PROPOSED RESIDENCE
LOT 9
VISION RIDGE SUBDIVISION
WELD COUNTY, COLORADO
Project No. 1-3149-01
June 23, 2003
W. LPN
Prepared for �d� ,•''.s?E us F
His Kingdom Builders, Inc. ck.,sc'G Ro �
Mr. Bing Sellers
* sf13936W' *
to
OF:C0'0
Richard W. Weber, P.E.
Principal Engineer
2004-0049
TABLE OF CONTENTS
GENERAL Page 1
PROPOSED CONSTRUCTION AND SITE CONDITIONS 1
SUBSURFACE CONDITIONS AND FIELD INVESTIGATION 1
FOUNDATION-NARROW SPREAD FOOTINGS 2
ADDITIONAL FOUNDATION DESIGN CRITERIA 3
INTERIOR FLOOR CONSTRUCTION 4
Habitable Space Area 4
Garage Floor Slab Construction 6
Slab Void Monitoring 7
DRAIN SYSTEM 7
BACKFILL & SURFACE DRAINAGE 8
LAWN IRRIGATION 8
PERCOLATION TESTING 9
GEOTECHNICAL RISK 9
DESIGN CONSULTATION & CONSTRUCTION OBSERVATIONS 10
VICINITY MAP AND TEST HOLE LOCATION PLAN Figure 1
LOGS OF TEST HOLES 2
LEGEND AND NOTES 3
SWELL - CONSOLIDATION TESTS 4-6
DRAIN SYSTEM DETAIL 7
LANDSCAPING DETAIL 8
SUMMARY OF LABORATORY TESTING Table 1
PERCOLATION TEST RESULTS 2
EXPANSION POTENTIAL AND INTERIOR
FLOOR RISK ASSESSMENT Appendix
GENERAL
This report presents the results of a subsurface investigation conducted
at the site of a proposed residence to be constructed at Lot 9, Vision Ridge
Subdivision, Weld County, Colorado. The investigation was performed to
determine the recommended types and depths of foundations, allowable soil
bearing pressures, and other precautions that should be taken in the design or
construction of the structure due to the soil and ground water conditions. The
conclusions and recommendations presented are based on the data gathered
during the site investigation, the results of the laboratory testing and our
experience with similar soil and ground water conditions.
PROPOSED CONSTRUCTION AND SITE CONDITIONS
It is our understanding that the proposed residence will be one or two
stories with an attached garage, and a partial below grade basement (shallow)
may be constructed. Construction will be of reinforced concrete foundations
with a wood frame superstructure covered by brick veneer, stucco and/or wood
siding. The site is presently vacant and is covered with native grasses. The
ground surface is relatively flat with only a very gentle slope to the north.
SUBSURFACE CONDITIONS AND FIELD INVESTIGATION
Two test holes, one profile hole and four percolation holes were originally
drilled at the approximate locations shown on Figure 1 , Test Hole Location Plan.
Two additional test holes were then drilled approximately 300 feet north of the
original two test holes because the proposed residence location may be adjusted.
The logs of the soils encountered in the test holes are shown on Figure 2, Logs
of Test Holes, and described on Figure 3, Legend and Notes. Samples of the
soils encountered were taken at the depths shown on Figure 2. The results of
the laboratory tests performed on selected samples are shown on Figures 4-6
and Table 1 .
1
The soils encountered in the test holes are somewhat uniform but vary
with depth. Generally, 2.5 to 4 feet of medium stiff to stiff, moist to very moist
clay was encountered over silty, very stiff, slightly moist, medium plasticity clay
in Test Holes 1 and 2 and very silty, some low density, medium stiff to stiff,
slightly moist clay in Test Holes 3 and 4. Bedrock was found below depths 5.5
to 8 feet in all the test holes. The bedrock consisted of medium to high
plasticity claystones that varied from firm to hard; silty to clayey sandstone that
was hard to very hard and medium moist to wet; and interbedded claystones and
sandstones.
The shallow, moist to very moist clay encountered in the test holes is
assessed as having a very low to non-swelling potential. The medium plasticity
clay exhibited a low swelling potential when wetted under a 1 ,000 psf surcharge
load. The lower density, slightly moist clay exhibited a no to very low swell
potential. The claystones exhibited only moderate swell potentials but are
assessed as having high to very high swelling potentials. The sandstone is
assessed as having a very low swell potential.
Free water was found in Test Hole 1 at depth 11 .5 feet at the time of the
drilling and in Test Holes 1 and 2 at depths 20 and 11 .5 feet, one day after
drilling. No free water was encountered in Test Holes 3 and 4 at the time of
drilling or one day later.
FOUNDATION-NARROW SPREAD FOOTINGS
It is our understanding that the use of a straight shaft, drilled pier
foundation system is not desired. To enable the use of spread footings, the
structure excavation must extend no deeper than two feet in the vicinity of the
Test Holes 1 and 2 and three feet in the vicinity of Test Holes 3 and 4. In
addition, some of the soils are somewhat low density and some in place
densification may be required prior to placing footings. This may be
accomplished by wheel-rolling the excavation bottom with a rubber tire
excavator with a loaded bucket until a deflection of less than 1/8 inch is attained
2
under the wheel loads. We should be called to observe the open excavations in
any areas where loose soils are encountered and to verify the supporting
capacities of the soils.
Following verification of the depths of excavation and supporting
capacities of the soils, the residence may be supported on narrow spread
footings or footing pads that are designed for a maximum allowable soil bearing
pressure of 2,500 pounds per square foot and a minimum dead load pressure of
800 psf in the vicinity of Test Holes 1 and 2 or 2,000 psf maximum with no
minimum dead-load pressure in the vicinity of Test Holes 3 and 4.
Minimum 14 inch wide continuous footings and 18 inch isolated pads
should be specified in the vicinity of Test Holes 1 and 2. The dead load on
footings should be proportioned as much as practicable to reduce the effects of
potential differential movement. Interior loads should be supported on beams
and columns, placed on isolated pads, designed as above. Exterior footings
should extend to a depth of at least 30 inches below final surface grade to
provide protection against frost action.
To accommodate bearing capacity, dead load and minimum footing width
requirements, it may be necessary to construct interrupted spread footings. A
minimum 4-inch void is recommended below the grade beams between footings.
Care should be taken to remove all loose, soft, or disturbed soil before placing
footings. The void should be protected during backfilling to prevent backfill
materials from filling the void.
ADDITIONAL FOUNDATION DESIGN CRITERIA
Lateral earth pressures on walls depend on such factors as the type of
wall, hydrostatic pressure behind the wall, type and slope of backfill material,
degree of backfill compaction, allowable wall movements, and surcharge loading.
Any hydrostatic pressures may be reduced by placing a drain system around the
perimeter of the foundation walls.
3
Foundation walls should be designed for lateral equivalent fluid pressure
of 40 pcf. The backfill should be compacted following the recommendations
outlined below (see Backfill and Surface Drainage). No consideration was given
to backfill sloping toward the residence, surcharge loading, or hydrostatic
pressures in the computation of the lateral equivalent fluid pressure. If any of
these conditions are anticipated, we are available to assist you in revising this
criterion.
Foundation walls should be reinforced to support the structural loads
imposed. Refer to the foundation design for actual reinforcing details.
Sulfate crystals were noted in samples taken from this site and experience
in the area indicates that relatively high sulfate levels can be anticipated.
Therefore, the site concrete should be designed for severe levels of sulfate
concentration, according to the current ACI Design Manual guidelines.
INTERIOR FLOOR CONSTRUCTION
Habitable Space Area
The soils encountered at foundation levels are stable at their natural
moisture contents. However, the builder and owner must realize that there is
always a potential for movement or cracking of concrete slabs on grade. The
site has been assessed as possessing a low expansion potential based on the
anticipated shallow excavation. Based upon this assessed expansion potential,
it is believed that there will be a low to moderate risk (vicinity Test Holes 1 and
2) or low risk (Test Holes 3 and 4) of interior slabs not performing within a
reasonable amount of movement for the anticipated use of the slab, due to soil
expansion. A reasonable amount of movement is described as floor heave of
between 1 to 3 inches with associated cracking of less than 1 /4 inch in width
and/or differential. See the Appendix to this report for a discussion of expansion
potential and interior floor risk assessment.
The only positive method of preventing movement of interior floors is to
provide structural floor systems - the floors would be supported on the found-
4
ation. The builder and/or owner must realize that there is a risk of floor
movement with any other construction alternative. Floors should be supported
structurally if the owner cannot tolerate any floor movement or cracking.
If the builder and/or owner desire to use slab on grade construction
techniques and are willing to assume the risk of concrete slab movement, the
details outlined below should be followed during construction of the slab.
Experience with similar soil conditions indicates that these construction details
will help to reduce wetting of soils supporting the slab and may reduce damage
should some wetting take place:
1 . The slab should be placed directly on the undisturbed, natural soils
or well compacted fill.
2. The slab should be separated from all bearing members and utility
lines to allow its independent movement; i.e., construct a floating
slab. Provide positive control joints at the junction of the slab with
foundation walls. However, the use of a monolithic slab system
may be possible in the vicinity of Test Holes 3 and 4 - we must
observe the open excavation.
3. Joints should be scored in the slab at maximum 200 square foot
areas. A control joint should also be scored 2 feet in from, and
parallel to, all foundation walls. The joints should be scored 1/4 of
the slab thickness.
4. Construct minimum 2 inch void spaces above, or below, partitions
on the slab. In finished areas, all furring strips, drywall and
paneling should stop 2 inches from the top of the slab. The 2 inch
void spaces can be covered with molding strips.
5. If hot water heat is used, the piping should not be placed beneath
the concrete slab. If a forced air furnace is used, a 2 inch
collapsible connection should be provided between the furnace and
the heat ducts.
6. Backfill in the interior and exterior utility trenches should be care-
fully compacted (see Backfill and Surface Drainage below).
5
7. The soils that will support the slab should be kept moist during con-
struction by occasional sprinkling and especially a day or so prior
to pouring the slab.
In addition, good backfill and surface drainage should be provided, and
lawn irrigation minimized, as discussed below.
Garage Floor Slab Construction
The soils that will support the garage slab have been assessed as
possessing a low risk of a concrete slab not performing within a reasonable
amount of movement for the usage of the slab due to soil expansion. The
builder and/or owner must be willing to assume this risk of garage slab
movement if the on-site soils are used to support the slab. If it is desired to
reduce this risk, then the garage floor should be supported on a non-expansive
imported material or as a structural member.
It is recommended that the procedures outlined below be followed during
construction of garage floor slabs. Our experience with similar conditions has
shown that these details help to reduce wetting of soils supporting garage slabs
and may help to reduce damage should some wetting of the slab supporting
materials occur.
1 . The slab should be placed directly on well compacted fill.
2. Separate the slab from all bearing members to allow its independent
movement; i.e., construct a floating slab. Provide positive control
joints at the junctions of the slab with foundation walls. Again, the
use of a monolithic floor may be possible in the vicinity of Test
Holes 3 and 4.
3. Joints should be scored at maximum 200 square foot areas. Joints
should be scored to a depth of 1 /4 the thickness of the slab.
4. Construct minimum 1 '/: inch void spaces above, or below,
partitions on the slab. In finished areas, all furring strips, drywall
and paneling should stop 1 '/ inches from the top of the slab. The
11/2 inch void spaces can be covered with molding strips.
6
5. Garage door jambs and trim should be constructed with expansion
material beneath them so the slab will not interfere with the jamb
if the slab moves.
6. Garage door tracks should be constructed with a minimum one inch
void space between the bottom of the track and the floor slab.
Slab Void Monitoring
The property owner must be aware that the potential movement of slabs
supported directly on these expansive soils could exceed the partition void
spaces recommended above. These void spaces are not intended to anticipate
total potential slab movement, but are intended to prevent immediate damage to
the superstructure and serve as indicators to slab movement. These void spaces
must be maintained by the homeowner for the life of the structure.
DRAIN SYSTEM
Ground water conditions are satisfactory for lower level construction.
However, the foundation will extend into clayey soils. These materials are
relatively impervious and tend to trap water. The source of the water could be
from excessive irrigation and precipitation accumulating in backfill areas due to
poor surface drainage with resultant seepage to foundation depth. A drain
system should therefore be provided around the structure unless a non-
basement, monolithically poured floor/foundation system is used. A typical drain
system detail is as shown on Figure 7. The type drain to be used depends on
the decisions of the builder and/or owner concerning floor support methods and
associated risk. The drain system should be graded to a positive gravity outfall
or a sump. A pump would not be required until actual water accumulation
occurs, and the amount of water could not be bailed from the sump. We should
be called to observe the soils exposed in the excavations to verify the details of
the drain system.
7
M
BACKFILL & SURFACE DRAINAGE C
The amount of moisture infiltration into the backfill soils from surface
drainage should be reduced. This can generally be accomplished by placing a
relatively impervious backfill around the foundation walls and providing a sloping
grade away from the foundation.
The backfill material should be free of debris and should be throughly
moistened and properly compacted to reduce settlement. Compaction of the
backfill should include the soils used to fill the construction ramp into the
excavation and utility trenches approaching the residence. Foundation walls
should be properly braced during backfilling operations.
The final grade of the backfill should have a good slope away from the
foundation walls on all sides. A fall of 12 inches in the first 10 feet away from
the structure is recommended. Downspouts and sill cocks should discharge into
splash blocks or long downspout extensions which extend past the backfill zone
when the ground surface is not protected by concrete slabs or asphalt paving.
LAWN IRRIGATION
A sprinkler system should not be installed next to foundation walls. If a
sprinkler system is installed, the sprinkler heads should be placed so the spray
from the heads, under full pressure, does not fall within 5 feet of the foundation
walls. Zone control boxes and drains should be constructed at least 10 feet
away from any foundations. It is strongly recommended that the owner install
automatic shut off valves as an integral part of the sprinkler system to help
prevent leakage. Lawn irrigation should be controlled as much as practicable.
• Particular care should be taken during final landscaping of the site. If the
owner desires to plant next to foundation walls or exterior slabs it should be
understood that there is a risk of future damage if wetting of the foundation soils
occurs.
As an alternative to planting next to foundations and exterior slabs, it is
advisable to install decorative landscaped areas such as gravel and/or bark. If
8
decorative areas are installed, the gravel or bark should be placed directly on the C
soils or on a non-woven, geotextile fabric, which will allow natural evaporation
to occur and will still inhibit weed growth - the use of polyethylene is not
recommended. The edges of decorative areas should be constructed to allow
surface drainage to be quickly discharged away from foundation walls or exterior
slabs. This can be accomplished by constructing the edges of decorative areas
• above the adjacent lawn or ground surface, and not impeding drainage with
grass stops. All grass stops should be perforated or constructed to allow
discharge out of the decorative areas. Refer to Figure 8 for a typical decorative
installation detail.
PERCOLATION TESTING
Four percolation test holes and one soil profile hole were drilled at the
approximate locations shown on Figure 1 . The soils encountered in the profile
hole are shown and described on Figures 2 and 3. The results of laboratory
testing performed on samples from the profile hole and Percolation Hole 1 are
shown on Table 1 . The test holes were 6 inch diameter, 36 inches deep and
charged with approximately two feet of water on the drilling date. On the
following day, water was still present in all 4 percolation holes and no movement
of the water levels was noted following cleaning and re-charging of the holes.
Based on this data, it is believed that a specially designed septic system will be
required for this site.
GEOTECHNICAL RISK
The concept of risk as it applies to structure construction is the single
most significant aspect of any geotechnical evaluation. The primary reason for
this is that the methods used by geotechnical engineers to develop recommenda-
tions for construction are not an exact science. The methods used are typically
empirical and, therefore, engineering judgement and experience must also be
applied. The solutions presented in any geotechnical evaluation therefore cannot
9
M
be considered risk free, and are therefore not a guarantee that the interaction
between the soils and the proposed structure will act as desired or intended.
The engineering recommendations presented in the preceding sections are our
best estimates of the measures that will be necessary to help the proposed
structure perform in a satisfactory manner. These recommendations are based
on the information generated during this and previous evaluations and our exper-
ience in working with these types of conditions. The builder and owner must
understand this concept of risk, as it is they who must decide what is an
acceptable level of risk for the type of structure to be constructed on the site.
DESIGN CONSULTATION & CONSTRUCTION OBSERVATIONS
This report has been prepared for the exclusive use of His Kingdom
Builders, Inc., and Mr. Bing Sellers for the purpose of providing geotechnical data
for the proposed project. The data gathered and the conclusions and
recommendations presented are based upon the consideration of many factors
including, but not limited to, the type of proposed construction, the configuration
of surrounding structures, the materials encountered, and our understanding of
the level of risk acceptable to the client. Therefore, the conclusions and
recommendations contained in this report shall not be considered valid for use
by others unless accompanied by written authorization from Soils and Materials
Consultants, Inc. (SMC).
SMC has endeavored to perform geotechnical services for this project in
accordance with the outlined scope of services and the generally accepted
geotechnical engineering practices in the area at this time. No other warranty,
expressed or implied, is made. In the event that any changes in the nature or
design of the project are planned, the conclusions and recommendations
contained in this report shall not be considered valid unless the changes are
reviewed and the conclusions of this report are modified or verified in writing.
Because of the constantly changing state of the practice in geotechnical
engineering, and the potential of site changes after our site exploration, this
10
M
report should not be relied upon after a period of three years, without this firm
being given the opportunity to review and, if necessary, revise the findings.
It is recommended that we be provided the opportunity for a general
review of the final design and specifications to evaluate whether the earthwork
and foundation recommendations have been properly interpreted and implement-
ed in the design and specifications.
The owner must be aware of those items covered under the headings
Interior Floor Construction, Backfill and Surface Drainage, Lawn Irrigation and the
Appendix. The owner must also be aware of the necessity of maintaining good
surface drainage on the site and the importance of keeping excessive water from
the foundation backfill soils.
In any geotechnical investigation it is necessary to assume that the
subsurface conditions do not vary from those encountered in the test holes. Our
experience has shown that these variations exist and that they become apparent
in the foundation excavations. It is therefore recommended that we be called to
observe the foundation excavations prior to construction.
Please contact us when further consultation or construction observation
services are necessary. The costs of these further services are not included in
the fee for this report.
RWW/tk
Copies: 3
11
VICINITY MAP
.- "M h25
DACONO
N rn
2
cc 0
0
SITE
WCR 10
6
N 3
NOT TO SCALE
VISION .RIDGE SUBDIVISION
LOT 9
3
•
4
• O
2
}
I-
2
APPROX. LOCATION OF p
U
PROPOSED HOUSE
a ' r
• 2 �� 3
3 •
• • 2
PERCOLATION HI Q E 1 • PROPOSED
PROFILE HOLE EST HOLE 1
DRIVE/ROAD TT
ELD COUNTY RD
I
SCALE 1^=200' Bench Mark: Top of gravel at
property corner. Assumed
elevation 100'.
�` a Soils a11d Project No. 1-3149-01
MaterialsVICINITY MAP AND
C� ConsultantS, Inc. TEST HOLE LOCATION PLAN Figure 1
TEST HOLE- PROFILE TEST HOLE-'-
-100 1 2 HOLE 3 4 100—
gred -
6/6,18/6 / -
95 \ 9/12 11/12 r
95
8/12 10/12
E 25/12
.: ii 7/12 _
90 = 42/12 90
50/12 10/6,23/6
V ::::: 40/12 50/10 _
w
L
85 — 85 O
k- = 31/12 —
_ 50/12
I— 80 •
80
50/6
—
50/11 _
75 \ 75
— 50/12
— 50/10 _
70 70
Refer to Figure 3 for Legend and Notes
Soils and Project No. 1-3149-01
Materials LOGS OF TEST HOLES
Consultants, Inc. Figure 2
LEGEND:
CLAY, sandy (fine grained), medium stiff to stiff, moist to very moist, brown (CL)
bb\\K\ CLAY, sandy (fine grained), silty, very stiff, slightly moist to medium moist, medium
plasticity, light brown (CL-CH)
;z CLAY, very silty and sandy (fine grained), some plasticity, medium stiff to stiff, some
low density, slightly moist to medium moist, slightly calcareous, brown (CL)
CLAYSTONE & SANDSTONE BEDROCK, interbedded, firm to hard, slightly moist,
yellow brown to gray, (CL-CH-SC-SM)
SANDSTONE BEDROCK, fine to medium grained, fair to well cemented, silty, some
clayey, hard to very hard, medium moist to wet, yellow brown (SM-SC)
CLAYSTONE BEDROCK, medium to high plasticity, soluble sulfates noted, medium
hard to hard, medium moist to moist, iron staining noted in fractures, yellow brown
(CL-CH)
CLAYSTONE BEDROCK, medium to high plasticity, soluble sulfates noted, firm to
medium hard, moist, iron staining noted in fractures, yellow brown to gray (CL-CH)
NOTES
1 . The test holes, profile hole and percolation holes were drilled on May 22 and June 11 , 2003, using
4 and 6 inch diameter, continuous flight, solid stem augers.
2. (24/12) Indicates location of penetration test as performed in this area. (24/12) means that 24 blows
with a 140 pound hammer, falling 30 inches, were required to drive a two inch inside diameter
sampler 12 inches.
3. The stratification lines represent the approximate boundary between soil types; the transition may be
gradual.
4. The locations of the test holes are approximate and were determined by pacing from known property
corners and using site plans made available to this firm. The elevations of the test holes are
approximate and were determined using a hand level. The locations and elevations of the holes should
be considered accurate only to the degree implied by the methods used.
5. Water level readings were made in the test holes at times and under conditions stated. This data has
been reviewed and interpretations made in the text of this report. It must be noted, however, that
fluctuations of the ground water depth may occur because of seasonal variations in rainfall, tempera-
ture, and other factors which may differ from those at the time the measurements were made.
Indicates free water level at time of drilling.
Indicates free water level one day after drilling.
Soils and
M Materials Project No. 1-3149-01
C Consultants, Inc. LEGEND AND NOTES
Figure 3
Swell under constant
pressure, due to wetting
2
rR i
O
cg 1 e/ '
Water added
to sample
100 500 1,000 Load - PSF 10,000 100,000
Sample of silty Clay from Test Hole 1 at depth 2 feet.
Natural Moisture Content 16.2% Natural Dry Density 111 pcf
Swell under constant
pressure, due to wetting
3
2
O
0 • — -
O
0
1
Water added
to sample
100 500 1,000 Load- PSF 10,000 100,000
r` T Soils and Sample of Claystone Bedrock from Test Hole 2 at depth 9 feet.
Materials Natural Moisture Content 1 6.8% Natural Dry Density 1 13 pcf
�* Consultants, Inc.
SWELL - CONSOLIDATION Project No. 1-3149-01
TESTS
Figure No. 4
No change under constant
pressure, due to wetting
F-
m
3
— 1 - _ _ .
aR
0
rl
7 0 - - . _ _
oR ��-
N
o
0
U 1 -
Water added
to sample
2 _ .
3 __, .
100 500 1.000 Load - PSF 10,000 100,000
Sample of silty Clay from Test Hole 3 at depth 2 feet.
Natural Moisture Content 1 8.4% Natural Dry Density 109 pcf
4 — - - --
'
Swell under constant
pressure, due to wetting
3 . 7------------ . , .
/
z ,
T,
3
cn 1 _ _ . . _ ,
c
2
ca 0 �, _
a
Zr \
Water added //
to sample
100 500 1,000 Load - PSF 10,000 100,000
cC
----,----, Soils and Sample of Claystone Bedrock from Test Hole 3 at depth 8 feet.
Materials Natural Moisture Content 1 4.1% Natural Dry Density 1 20 pcf
Consultants, Inc.
SWELL - CONSOLIDATION Project No. 1-3149-01
TESTS
Figure No. 5
Swell under constant
pressure, due to wetting
2
O 2
Water added
to sample
4 -
6
100 500 1,000 Load - PSF 10,000 100,000
Sample of silty Clay from Test Hole 4 at depth 3 feet.
Natural Moisture Content 10.0% Natural Dry Density 98 pcf
O
O
qC
water added
to sample
100 500 1,000 Load - PSF 10,000 100,000
Soils and
Materials
Consultants, Inc. SWELL CONSOLIDATION Project No. 1-3149-01
TESTS
Figure No. 6
•
•
Q FLOOR JOIST
-BACKFILL et--FOUNDATION WALL
PER Floor system to be determined by
REPORT) owner based on risk assessment.
SLOPE PER OSHA
COVER
SLAB
.;•;QQPtio FOOTING _ IIII p O.�'O•e.O
atr u0�
BARRIER , The drain excavation must not encroach
/ t 1:1 line from bottom edge of footing.
ITOP WIDTH I/
APPROX.t7' 1. At high point, drain trench should be at
least 4 inches below bottom of footing.
Note: 1. Sump should not be within 5 feet of 2. Slope drain trench at least 1 % to gravity
footing corner or within 2 feet of outfall and/or to sump.
footing edge. 3. Attach minimum 10 mil. polyethylene barrier
to foundation wall. Extend barrier to bottom
2. If crawl space is constructed, the edge of foundation excavation.
ground surface in the crawl space 4. 3 or 4 inch diameter perforated drain pipe
must be covered with a vapor barrier. (ASTM D2729) PVC rigid.
The barrier should be sealed against 5. 3/4 inch clean drain gravel to top of void
the interior foundation wall with a elevation.
mastic compound. Joints should also 6. Cover with non-woven geotextile (Mirafi 140
be sealed. NSL or approved equivalent) or 15# building
felt paper.
NOT TO SCALE
Soils and DRAIN SYSTEM DETAIL
Materials Figure No.
Consultants, Inc. •
SO-COM 3/22/02
J,
- . Brick or
Siding
Frame
5' Minimum Wall
Wood or metal edging above top
or sod with weep hales in Rock or bark area with
bottom to allow water flow out downspout extended
onto fawn. beyond edging,
Sod ✓4V ‘..�
'o0 oEW6:.. O i CJ:Y:•
minrnftlnnnninl rnuunrrnunlnruuinrllflllifl- • ' ��
•
•
• •
Non woven geotextife fabric. Sloped
away from foundation, under edging
and above sod elevation.
Maintain designed slope away from
foundation. Minimum fall of 12" in the
first 10 feat away from the foundation
is recommended.
Foundation Wall
Soils and
Materials NOT TO SCALE
C Consultants, inc. LANDSCAPING DETAIL
Figure No. 8
M-0 G.eax 7/98
) )
Soil Description Test Hole Sample Dry Moisture Swell/ Gradation Atterberg AASHTO See
Depth Density Content Consol* Analysis Limits Classification Fig.
(ft.) (pcf) (%) (%) (Group Index) No.
• Gravel Sand Silt/Clay LL PI
1%1 1%) (%)
silty Clay 1 2 111 16.2 +2.1 4
Claystone Bedrock 2 9 113 16.8 +3.2 4
Clay Profile Hole 3 0 9 91 38 21 A-6(19)
Clay Percolation 0-3 0 10 90 42 23 A-7-6(21)
Hole 1
silty Clay 3 2 109 18.4 0 5
Claystone Bedrock 3 8 120 14.1 +3.4 5
silty Clay 4 3 98 10.0 +0.2 6
- -
* Percent Swell (+) or Consolidation (-) of a sample when wetted under a 1,000 psf surcharge load.
Soils and
0)
Materials SUMMARY OF LABORATORY Project No. 1-3149-01
Consultants, inc. TESTING
Table No. 1
PERCOLATION TEST RESULTS
Percolation Diameter Depth Soil in Lower Foot of Percolation Rate
Hole (in.) in. Percolation Hole (min./in.)
P-1 6 36 Clay No Movement*
P-2 6 36 Clay No Movement*
P-3 6 36 Clay No Movement*
P-4 6 36 Clay No Movement*
* Water was present in the percolation hole approximately 24 hours after
the holes were charged, and no movement was noted for one hour after
the holes were cleaned and re-charged.
Soils and
Materials Project No. 1-3149-01
_ (1) Consultants, Inc. PERCOLATION TEST RESULTS
Table 2
APPENDIX
EXPANSION POTENTIAL AND
INTERIOR FLOOR RISK ASSESSMENT
The decision as to the type of floor to place in residences constructed in expansive soil and
bedrock environments is one of the most complicated and subjective tasks in current home building
and geotechnical engineering practice. The reason for this is that there are a number of factors
which must be addressed, understood, and evaluated in making this decision. Among these factors
are the following:
1. The material types that comprise the foundation supporting subgrade (i.e. clay,
sand, sandstone, claystone, etc.) and their variability in the surrounding area
2. The soil profile, soil density and moisture content, and soil plasticity
3. The swell characteristics for the material directly beneath the foundation and at
least 3 to 5 feet beneath the foundation
4. The depth to ground water and anticipated depth fluctuation
5. Whether the lot is situated in a cut or fill area
6. The surface topography and general site drainage, both pre- and post development.
7. The presence and location of surface water features
8. The type of space to be constructed (e.g., unfinished full depth basement, finished
full walkout, etc.)
9. Previous experience with floor construction in the immediate area
10. The amount of irrigation that will be introduced within a completed development.
In order to help characterize the risk of floor movement on expansive sites, the concept of
expansion potential has been developed. Expansion potential is a subjective assessment of all of
the factors which could contribute to the potential for soil to heave a floor under normal service
conditions. Expansion potential is differentiated from "swell potential" or "percent swell" in that
these terms refer to specific laboratory testing of an expansive material. Expansion potential is the
engineers assessment of all of these factors using experience and engineering judgment. Expansion
potential in terms of possible slab on grade damage can be described as follows:
Expansion Potential Possible Slab on Grade Damage
Low Light cracking, small differential movements, small heaves
Heavy cracking, differential movements, heave closing framing
Moderate voids, some movement of utility lines
Large slab and differential cracks and movement, framing voids
High to Very High closed, utility lines under heavy pressure
Again, these categories are not uniform and are developed by experience. Additionally, the
categories do not necessarily correlate to the extent of damages that may occur. Every engineering
firm which has long experience in the Denver area has observed significant cracking on soils
characterized with a low expansion potential and no movement on materials characterized with a
high expansion potential. Currently, there is no type of testing or correlation of factors that will
definitively define the amount of movement that any soil will experience.
Since the swell consolidation test is extensively used in the Denver area, we have
correlated percent swell to expansion potential. As a general guideline, soils that swell 0 to 2%
are considered low; 2% to 4% are considered moderate; 4% to 6% are considered high; and over
6% swells are considered very high. These swell percentages are based upon loading a sample to
a pressure of 1,000 pounds per square foot, wetting the sample, and measuring its swell.
The percent swell is tempered using all of the other factors noted above on specific and
adjacent lots in order to determine the expansion potential for a specific site. The variation in
subsurface profile comes into effect if a high expansion potential soil or bedrock was encountered
A-1 Appendix.I
in a test hole at a depth below the slab bearing zone in once location and the same material was
found at the ground surface in an adjacent test hole. The presence of ground water probably •
indicates that a low swelling soil beneath the ground water level should not be included in the
average of the same material that was high swelling in areas of the site that were dry. If the site
is significantly excavated, it may possess a higher or lower expansion potential as it is now subject
to the natural wetting and drying cycles. The presence of a new pond or the removal of an old
pond would change the soil moisture conditions and indicate a higher or lower expansion potential
for a site.
Obviously, some of these factors may conflict and any laboratory data must be tempered
by judgment and experience. Any single factor on a lot may indicate a higher or lower expansion
potential; however, all of the factors must be considered together in determining the expansion
potential for any specific lot.
It must also be noted that perhaps the largest factor and the largest variable involved in
judging expansion potential at any site is the post construction landscaping and irrigation practices
on the site and across the general area. Expansive soils do not expand until their moisture content
rises. The construction of a structure will cause soil moisture contents to rise due to the cut off
of natural evaporation. This will cause some movement and heaving. However, experience has
shown that irrigation of landscaping adds far more moisture to the soil than the cut off of
evaporation. Landscaping and irrigation practices must be tempered by the expansion potential of
the site.
Experience both within this firm and in discussion with other firms in the Denver area
indicates that the following floor types are generally appropriate for each level of expansion
potential and risk assessment.
Expansion Potential Risk Assessment Floor Type
Non Expansive
Low
Concrete Slab on Grade
Low
Low to Moderate
Moderate
Moderate to High
High Structural Floor
High to Very High
Very High
These alternatives must be fully understood by each homebuyer. The homebuyer must
understand the subjective nature of the evaluation of expansion potential and the construction
methods under consideration. The homebuyer must understand that there is a risk of heaving
and/or cracking with the construction of any concrete slab on grade on any soil type. They must
also understand that these evaluations are subjective in nature, based upon the experience and
opinion of the design engineer and, therefore, are not a guarantee that the interaction between the
soils and structure will occur as designed or intended. If the homebuyer wishes to reduce the risk
of floor movement, a structural floor must be constructed. The homebuyer must also understand
that the use of a structural floor is not without other risks [e.g., elevated humidity (moisture) in the
crawl space, possible presence of free water in the crawl space, etc. which may be associated with
improperly maintained drainage and/or site grading alterations by the homebuyer or his agents; the
growth of moisture related molds and mildews, etc.]. All of the above should be understood and
evaluated by the homebuyer(s) in making their choice of floor for their residence.
A-2 Appendix.1
Hello