HomeMy WebLinkAboutSoils Report 12.04.2018H p�KUMAR
Geotechnical Engineering I Engineering Geology
Materials Testing I Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa,com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
December 4, 2018
Darren Gallegos
394 Silver King Court
Glenwood Springs, Colorado 81601
Project No. 18-7-690
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 12, Ranch Creek
PUD, Surrey Street, Ranch at Roaring Fork, Garfield County, Colorado
Dear Mr. Gallegos:
As requested, H-P/Kumar performed a subsoil study for design of foundations at the subject site.
The study was conducted in accordance with our agreement for geotechnical engineering
services to you dated November 12, 2018. The data obtained and our recommendations based on
the proposed construction and subsurface conditions encountered are presented in this report.
Proposed Construction: The proposed residence will be a two-story wood -frame structure with
an attached garage, located on the site in the area of the pits as shown on Figure 1. Ground floor
will be slab -on -grade. Cut depths are expected to range between about 1 to 2 feet. Foundation
loadings for this type of construction are assumed to be relatively light and typical of the
proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The subject site is currently vacant. There is a minor amount of previously
placed fill in the proposed building area. Topography at the site is valley bottom with slopes less
than 5 percent grade down to the southwest. There is approximately 2 feet of elevation
difference across the lot. Vegetation consists of native grass and weeds.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about one foot of previously placed
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gravel fill, consist of around 2 feel of stiff, sandy clay and silt with scattered gravel overlying
relatively dense silty sand and gravel with cobbles down to the maximum depth explored of 4
feet. Digging in the relatively dense granular soils was difficult and digging refusal was
encountered in the deposit. Results of a gradation analysis performed on a sample of silty sand
and gravel (minus 5 -inch fraction) obtained from the site are presented on Figure 3. No free
water was observed in the pits at the time of excavation and the soils were slightly moist to
moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread footings
placed on the undisturbed natural soils designed for an allowable soil bearing pressure of 1,500
psf for support of the proposed residence. Groundwater in the area is generally known to be
shallow and cut -depths should be limited to avoid excavation below water level. The upper,
fine-grained soils tend to compress after wetting and there could be some post -construction
foundation settlement. Footings should be a minimum width of 18 inches for continuous walls
and 2 feet for columns. Loose and disturbed soils and existing fill encountered at the foundation
bearing level within the excavation should be removed and the footing bearing level extended
down to the undisturbed natural soils. Exterior footings should be provided with adequate cover
above their bearing elevations for frost protection. Placement of footings at least 36 inches
below the exterior grade is typically used in this area. Continuous foundation walls should be
reinforced top and bottom to span local anomalies such as by assuming an unsupported length of
at least 12 feet. Foundation walls acting as retaining structures should be designed to resist a
lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site
soil as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab -on -grade construction.
To reduce the effects of some differential movement, floor slabs
should be separated from all bearing walls and columns with expansion joints which allow
unrestrained vertical movement. Floor slab control joints should be used to reduce damage due
to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be
established by the designer based on experience and the intended slab use. A minimum 4 inch
layer of free -draining gravel should be placed beneath slabs -on -grade for support. This material
should consist of minus 2 inch aggregate with less than 50% passing the No. 4 sieve and less
than 12% passing the No. 200 sieve.
H-P�KUMAR
Project No. 18.7-690
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All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: A foundation underdrain should not be required in shallow crawlspace
areas of less than 3 feet or where slabs -on -grade are near the exterior ground surface, provided
that foundation wall backfill is adequately compacted and surface drainage precautions (below)
are taken.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least
5 feet from the building.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. Our services do not include determining the presence, prevention or possibility of mold
or other biological contaminants (MOBC) developing in the future. If the client is concerned
about MOBC, then a professional in this special field of practice should be consulted. Our
findings include interpolation and extrapolation of the subsurface conditions identified at the
Project No 18 7-690
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exploratory pits and variations in the subsurface conditions may not become evident until
excavation is performed. If conditions encountered during construction appear different from
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
H -P KU MAR
Robert L. Duran, E. I.
Reviewed by:
=V1= 11,9 `�1"Ce`
: 4443 z,, • •;1
Daniel E. Hardin, P. � ', -z/G7 ,' � cie
RLD/kac G ,11'q,: • /4.`-'41
attachments Figure 1 l'f1; ` ,wi. ploratory Pits
Figure 2 — Lo 't+xploratory Pits
Figure 3 — Gradation Test Results
Table 1 — Summary of Laboratory Test Results
H-PKUNWR
Project No, 18-7-090
18-7-690
GeoteohnlcW Enpinearinp I Enpineennp Geolo y
Materials Testlno 1 Environmental
LOCATION OF EXPLORATORY PITS
0
O
N
O
O
O
LFigure 1
0
LEGEND
PIT 1
EL. 101'
WC=5.4
-200=54
LL=23
P1=7
PIT 2
EL. 100.5'
+4=65
_i -200=8
0
5
Ic
FILL: ORGANIC SAND AND GRAVEL, CLAYEY, LOOSE TO MEDIUM DENSE, MOIST, MIXED BROWN,
FROZEN AT TIME OF EXCAVATION.
CLAY AND SILT (CL -ML); SANDY, SCATTERED GRAVEL, STIFF, MOIST, BROWN.
GRAVEL AND SAND (GM -SM); SILTY, WITH COBBLES AND SMALL BOULDERS WITH DEPTH,
DENSE, SLIGHTLY MOIST, MIXED BROWN.
DISTURBED BULK SAMPLE.
t PRACTICAL DIGGING REFUSAL.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON NOVEMBER 19, 2018.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL BASED ON THE
MANHOLE RIM NEAR THE SOUTHEAST PROPERTY CORNER ELEVATION = 100.0'.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY
TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF DRILLING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140);
LL = LIQUID LIMIT (ASTM D 4318);
PI = PLASTICITY INDEX (ASTM D 4318).
18-7-690
H-PWUMAR
LOGS OF EXPLORATORY PITS
Fig. 2
HYDROMETER ANALYSIS
SIEVE ANALYSIS
71ME READINGS
24 NRS 7 MRS
47 .444. 10.AIR E0424 14Mft
41.1H
DOH.. hRR•f00
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STAND=
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CLEAN SQUARE OPENINGS
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a m•ma»� amINIreewr sOl MIIMlaae�immmmaa
.001 .1102 .005 .000 .011 037 .073 .160 .300 1 .600
,425
DIAMETER OF PARTICLES
1.
IN MILLIMETERS
1
0 1 2.3S
2.0
rrrr
4.75 0
I --'I
5 w
i- h—t r 4 n 1- r—
50.1 761 127
102
100
200
SAND GRAVEL
CLAY TO SILT .COBBLES
FINE MEDIUM (COARSE FINE COARSE
GRAVEL 65 X SAND 27 X SILT AND CLAY 8 X
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Silty Sand and Gravel with Cobbles FROM: Pit 2 0 3'-4'
These test results apply only to the
samples which were tested. The
testing report shall not Cr roproduced,
excep! In full. without the w:llIoo
approval of Humor d Aveoclvlre. Inc.
Slave analysis testing la performed In
accordonc. with ASTM D422, ASTM C136
and/or ASTM D1140.
18-7-690
H -P KUIVIAR
GRADATION TEST RESULTS
Fig. 3
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 18-7-690
SAMPLE LOCATION
NATURAL NATURAL
MOISTURE i DRY '
CONTENT DENSITY
(%) (PO
GRADATION
-"
PERCENT
PASSING
NO. 200
SIEVE
ATTERBERG LIMITS
1
UNCONFINED
COMPRESSIVE
STRENGTH
(psf)
SOIL TYPE
-
PIT
i _
DEPTH
(ft)
GRAVEL
SAND
(%)
,
LIQUID
LIMIT
(%)
PLASTIC
INDEX
(%)
1
2 - 2%
5.4
54
23
7
Sandy Silt and Clay with
Scattered Gravel
2
3 - 4
65
27
8
Silty Sand and Gravel with
Cobbles
1
1