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SUBSURFACE INVESTIGATION
PROPOSED RESIDENCE
LOT 5, BLOCK 4, FILING 2
RANCH EGGS SUBDIVISION
WELD COUNTY, COLORADO
PREPARED FOR:
CRAIG MULLENAX
PO BOX 747
ERIE, COLORADO
80516
DECEMBER 16, 1998
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PROJECT 98265
PREPARED BY:
WESTERN SOILS, INC.
6595 ODELL PLACE, SUITE G
BOULDER, COLORADO 80301
(303) 581-7711
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2008-0452
• TABLE OF CONTENTS
PROJECT 98265
PAGE
PURPOSE 1
INVESTIGATION DETAILS 1
PROPOSED DEVELOPMENT 1
SOIL CONDITIONS 2
GROUNDWATER CONDITIONS 2
FOUNDATION RECOMMENDATIONS 2
SLABS-ON-GRADE RECOMMENDATIONS 3
DRAINAGE RECOMMENDATIONS 4
• EARTH RETAINING STRUCTURES 5
LIMITATIONS 5
INSPECTIONS AND QUALITY CONTROL 5
FIGURES AND TABLES
FIGURE 1 BORING LOGS
FIGURE 2 PERIMETER DRAIN DETAILS
TABLE 1 LABORATORY TEST RESULTS
SUBSURFACE INVESTIGATION
• PROPOSED RESIDENCE
LOT 5, BLOCK 4, FILING 2
RANCH EGGS SUBDIVISION
WELD COUNTY, COLORADO
PURPOSE
This report presents the results of a subsurface investigation accomplished on Lot 5, Block
4, Filing 2 of Ranch Eggs Subdivision in Weld County, Colorado. This investigation was
made to provide design criteria for the foundation system and other pertinent geotechnical
recommendations. Two borings were drilled in or adjacent to the proposed building
envelope. Boring 1 was located near the staked northwest building corner, and Boring 2
was located at the staked southeast building corner.
Factual data gathered during the field and laboratory work is summarized in Figure I and
Table 1 attached. The results of this investigation and our opinions that are based on this
investigation and our experience in the general area are summarized in this report.
INVESTIGATION DETAILS
The borings were completed with 4-inch diameter, continuous flight power augers using a
• truck-mounted drill rig. The augers are utilized to bore and clean the hole to the desired
sampling depth. The augers are then removed and a 2-inch I.D. California spoon sampler
is inserted to the desired testing depth. The sampler is then driven with blows of a
standard 140-pound hammer falling a distance of 30 inches.
The sampler is driven a total of 12 inches or a maximum of 50 blows. The number of
blows required to drive the sampler 12 inches, or a fraction thereof, constitutes the
penetration test. The test is similar to the Standard Penetration Test described in ASTM
D1586-78 (Reapproved 1974). This test, when properly evaluated, is a measure of the
soil strength and density. The results of these tests are shown on the Boring Logs
(Figure 1).
Samples obtained from the borings were returned to our lab for testing. The test results
are indicated in Table I.
PROPOSED DEVELOPMENT
It is our understanding that the plan is to construct a wood frame structure supported by
poured-in-place reinforced concrete foundation walls. The residence will be constructed
over a basement. Light to moderate residential building loads are anticipated.
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If actual building plans differ from the above description, we should be notified so that our
• recommendations can be reviewed and revised, if necessary.
SOIL CONDITIONS
A layer of topsoil was encountered at the surface underlain by a stratum of silty to very
silty, sandy clay which continued down to approximately 4 to 5 feet beneath the existing
ground surface. At this depth, a stratum of silty, slightly sandy clay was encountered,
which continued down to approximately 20 feet. The overburden clay strata were
underlain by claystone bedrock. The claystone continued to the maximum depth of the
borings. A more detailed description of the soils encountered in this investigation is
presented in the Boring Logs (Figure 1).
GROUNDWATER CONDITIONS
Groundwater was not encountered in the borings at the time of the drilling. The elevation
of the groundwater level can be expected to fluctuate throughout the year depending upon
precipitation, surface runoff and the application of irrigation water.
FOUNDATION RECOMMENDATIONS
The overburden clay layer down to approximately 4 to 5 feet is of low expansive potential.
The underlying clay is of moderate expansive potential and the claystone is of moderate to
• high expansive potential. These soils can expand upon fluctuation of their moisture
content, resulting in significant cracking and heaving a spread footing foundation system.
For this reason, it is our opinion that the residence should be supported by a drilled pier
foundation system, which penetrates well into the competent bedrock. We recommend
that the piers be drilled with a minimum 10 feet penetration into competent bedrock. The
piers should be designed for an end bearing of 15,000 psf and a side shear of 1,500 psf
based on the length of bedrock embedment. The design pressures should be based on the
dead load plus 100% of maximum anticipated live load.
We recommend that the piers be reinforced for the loading conditions, but with a
minimum of 3 # 5 rebars, (grade 60) for their full length, assuming 10 inch diameter piers.
A six-inch void space should be provided under the grade beam foundation walls between
the pier locations. The grade beam spanning the piers should be designed for the
appropriate loading conditions and reinforced accordingly. Based on the groundwater
conditions encountered in the two borings, we anticipate that the piers can be drilled
without casing as long as the concrete and reinforcement are placed immediately after
drilling.
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• SLABS-ON-GRADE RECOMMENDATIONS
As previously mentioned, the onsite clay and claystone are of moderate to high expansive
potential. These soils are capable of significant heaving and cracking of lightly loaded
slabs-on-grade upon fluctuation of their moisture content. Due to the moderately to
highly expansive nature of these soils, slab-on-grade construction is not recommended for
this site. We strongly recommend the use of a structural floor system, independent
of the underlying soils. In our opinion, this is the only positive method to eliminate slab
damage due to the expansive soils on this site.
If the decision is made to use slab-on-grade construction, the owner and all concerned
parties should realize and accept the risk that at least 2 to 3 inches of slab heaving is very
likely. We recommend that the following slab-on-grade construction techniques be
utilized to help prevent secondary damage that could be caused by slab movement.
1. Separate slabs from the foundation elements with a slip joint. A slip joint should be
used around the perimeter of the slab and adjacent to any other structural elements.
2. Moderately reinforce slabs with rebar reinforcement both ways on 2 feet centers
continuous through interior slab joints. Slab joints must be provided to control the
cracking. The floor joint grid should be designed to allow no more than 100 square
feet of continuos slab. Maximum joint spacing should be limited to 10 feet.
• 3. Any load bearing partitions must be provided with their own foundation system and
the slab separated as outlined above.
4. Provide a 4 inch minimum air space below any interior non-load bearing partition to
provide for slab movement without damage to the structure.
5. Any pipes rising through the slab should be provided with flexible couplings or other
means to allow substantial movement without damage to the piping. Any ducts
connecting to equipment founded on the slab should be equipped with flexible or
crushable connections to allow for some slab movement. Equipment and other
building appurtenances constructed on the slab should be constructed so that slab
movement will not cause damage.
Following the recommendations given above will not prevent movement of the floor slabs
in the event that the moisture content of the soil beneath the slab changes. However, if
movement occurs, damage may have been reduced for a relatively small investment.
Prior to pouring any slab it is essential that all debris, topsoil and organic materials be
removed and all loose fill either removed or compacted to 95% of maximum density as
determined by the standard moisture/density relationship test ASTM D698-78. Following
• approval of the stripped surface and prior to placement of any new fill, the surface should
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be scarified and wetted or dried to bring the surface soils to a moisture content at or
• within 2% of the optimum moisture content. If any fill is required, we recommend using a
granular non- expansive structural fill compacted in 9" maximum lifts to the standard
referenced above.
DRAINAGE RECOMMENDATIONS
It is essential that proper site drainage be provided to divert all surface water runoff
and water from the roofs well away from the foundation walls. Satisfactory long-term
performance of any foundation system depends on prevention of infiltration of water into
the soils supporting the foundation. The following methods of preventing this infiltration
are recommend.
1. Mechanically compact all fill around the building, including the backfill. Compaction
by ponding or saturation must not be permitted. The backfill should be compacted to
not less than 90% of maximum density as determined by the standard moisture/density
relationship ASTM D698-78. Backfill, which is to support slabs, should be compacted
to 95% of maximum dry density. Note that some moisture may need to be added to
the soils in order to obtain the proper compaction.
2. Provide an adequate grade for rapid runoff of surface water away from the structure (a
minimum of 10 percent for the first 10 feet away from the structure is essential for
unpaved areas).
• 3. A well constructed, leak-resistant series of gutters, or other roof drainage system, is
essential.
4. Discharge roof downspouts and all other water collection systems well beyond the
limits of the backfill, a minimum of 5 feet. We recommend against landscaping which
requires watering within 5 feet of the foundation walls.
It is our opinion that the entire residence should have the protection of a perimeter
drainage system. The perimeter drainage system should consist of 4-inch perforated pipe,
surrounded by washed gravel. The pipe should be bedded on 2 inches of washed gravel
and backfilled with 6 inches of gravel over and around the pipe. The drains should be
placed at least 6 inches below the bottom of the excavation at the high point of the
drainline and should drain at a 1% slope to a positive gravity discharge if possible or to a
sump from which water can be pumped. The sump should be equipped with a pump.
We also recommend that the basement floor have the protection of an interior drainage
system. Typical details of these drains are also shown on Figure 3.
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EARTH RETAINING STRUCTURES
• Any walls that are to retain soil should be designed as retaining walls to resist the lateral
earth pressure. Due to the moderately to highly expansive nature of the clay soils below 5
feet, this material is not recommended for backfill. If the moderately to highly expansive
soils are used as backfill, the walls must be designed for a very high lateral pressure, 90
pcf. This will result in a very heavily reinforced wall. We recommend a non-expansive or
low expansive soil be used for the backfill. The overburden sandy clays down to 5 feet will
be suitable for the backfill. Using this approach, a lateral earth pressure of 45 pcf will be
appropriate. Use of this value assumes that the wall will be backfilled with the select soils
and that these soils will not be allowed to become saturated at any time during the life of
the wall. Saturation can be prevented by proper site grading and drainage and installation
of drainage systems at the base of any walls that are to retain soil.
LIMITATIONS
The borings in this investigation present a reasonably accurate knowledge of the existing
subsoils. However, variations of subsoils not indicated by the borings are always possible.
Therefore, we strongly recommend that all excavations be observed by an engineer from
our office to confirm that the soils actually are as indicated by the investigation and to
make recommendations if differences are noted.
It should be mentioned, that the foundation system is designed assuming that the drainage
• recommendations provided in this report are strictly adhered to. If the soil supporting the
foundation becomes inundated over a period of time due to poor surface drainage, it is
possible that there could be damage to the foundation system and the slabs-on-grade.
INSPECTIONS AND QUALITY CONTROL
Placement of any significant thickness of fill, particularly fill which is to remain in place
beneath loaded slabs and pavement should be tested to verify that proper compaction is
obtained. The pier drilling operation, should be observed by an engineer from our office
to verify that the piers are constructed in accordance with the specifications on the
foundation plans.
If you have any questions concerning the investigation, this report or when we can be of
further assistance please call.
S1ttStit:!lilyr�,
Sincerely, (yyq�.\.1asoaa® J�,+✓fi,
iat
WESTERN SOILS, C. aca:-4 en 3
9:
By.
Gary Ro son, P.E. 141baON pL ,
• "wuaaeunn0
5
Boring Logs
• T'ri :ti T'ri #2
0
\\\ ANA
\\\ I 26/12 \\\
C \\
07 „, ,
\ I I 38/12 \�
It i0 43/12
,..
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L Ni
3 \ H 41/12N, •
110 1
20 I 50/12
8
25 � II 50/8 \ .
30
35
• FIGURE 1
PROJECT 98265
• Lli131i1VL L11VL 1VV LGJ
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TOPSOIL, clayey, silty , sandy , dark brown
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\\ CLAY, silty to very silty, sandy, brown with off-white
calcareous deposits
•N‘ CLAY, silty, slightly sandy to sandy, brown
CLAYSTONE , silty , grey
Indicates change in soil type , transition may be gradual .
12. Indicates grounwater level and date which reading was taken.
( 126/12 Indicates that 26 blows of a 140 pound hammer were required
to drive a 2 inch diameter sampler 12 inches .
** The borings were drilled on 12/7/98 .
PROJECT 98265
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TYPICAL DETAILS R THE PERIMETER & SUBFLOO DRAINAGE SYSTEMS
PROJECT 98265-FIGURE 2 5
FOUNDATION
WALL
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WATER PROOFING
Fr_ FABRIC
1 3/4^ m 1 '
r w RASED GRAVEL
• L . __ -
8" WASHED l
GRAVEL • • / 6" MIN.
4" PERFORATED PIPE 1 ' FROM / 6" MIN.
THE WALL WITH LATERALS ON /
10' to 12' CENTERS
10 MIL. PVC LINER
OR EQUIVALENT
4" PERFORATED PIPE
• ( OPTION )
FODNDATION
WALL
A./ t N
.__WATER PROOFING
FILTER FABRIC 3/4" to I
nasEED GRava.
W4" m11" 1' ` •
��.— _ _
te GRAVEL ,
• • 6" MIN.\l /
6" MIN.
•
4" PERFORATED PIPE 10 MIL. PVC LINER
1, FROM ypre tau WITH OR EQUIVALENT
LATERALS ON 10' to 12' 4^ PERFORATED PIPE
• •
Laboratory Test Results
Table 1
• Project 98265
PROPER lIbS AT NATURAL CONSOLIDATION/SWELL DESCRIPTION
MOISTURE CONTENT
Natural Natural Unconfined Loading Settlement Settlement Swell
Moisture Dry Density Compression (DRY) (Saturated)
(%) (PCF) (PSF) (PSF) (%) (%) (%)
Test Boring t! 1 @ 3'
100 0.2 2.2 Clay, silty to very silty, sandy,
8.3 101.6 >9000 1000 0.1 brown with off white calcareous
3000 3.7 deposits
2.4%Swell upon the addition of water
Test Boring# 1 @ 13'
100 0.5 5.5 Clay, silty slightly sandy to
8.2 >9000 1000 2.3 sandy, brown
3500 0.5
6.0%Swell upon the addition of water 8500 2.2
Test Boring 4 2 @ 8'
100 0.1 7.4 Clay, silty, slightly sandy to
8.9 116.1 >9000 1000 4.1 sandy,brown
3500 1.0
5%Swell upon the addition of water
t Boring 4 1 @ 23'
100 0.7 9.0 Claystone, silty, grey with
19.1 112.4 >9000 1000 7.2 orange-brown
3500 3.0
8500 3.3
9.7%Swell upon the addition of water
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