HomeMy WebLinkAboutSoils Report 01.16.2020Kumar & Assamlato , km°
Gealechnical and Materials Engineers
and Environmental Scientists
An Employee Owned Company
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
RECEIVED
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
SUBSOIL STUDY
FOR FOUNDATION DESIGN
35 WILLOWVIEW WAY
LOT 2, BLOCK 6
MONUMENT CREEK VILLAGE
BATTLEMENT MESA
GARFIELD COUNTY, COLORADO
PROJECT NO. 19-7-734
JANUARY 16, 2020
PREPARED FOR:
RC CONSTRUCTION
ATTN: RUSSELL CARTWRIGHT
284 MEADOW CREEK DRIVE
PARACHUTE, COLORADO 81635
russecart a,gmail.com
Assadat
30.n
www.kumanw.mm
989_2O19
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 1 -
GEOLOGY -2-
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 2 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FOUNDATION AND RETAINING WALLS - 4 -
FLOOR SLABS - 5 -
UNDERDRAIN SYSTEM - 5 -
SURFACE DRAINAGE = 6 -
LIMITATIONS - 6 -
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 - GRADATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
Kumar & Associates, Inc. Project No. 19-7-734
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located at
35 Willowview Way, Lot 2, Block 6, Monument Creek Village, Battlement Mesa, Garfield
County, Colorado. The project site is shown on Figure 1. The purpose of the study was to
develop recommendations for the foundation design. The study was conducted in accordance
with our agreement for geotechnical engineering services to RC Construction dated December
20, 2019.
An exploratory boring was drilled to obtain information on the subsurface conditions. Samples
of the subsoils obtained during the field exploration were tested in the laboratory to determine
their classification and other engineering characteristics. The results of the field exploration and
laboratory testing were analyzed to develop recommendations for foundation types, depths and
allowable pressures for the proposed building foundation. This report summarizes the data
obtained during this study and presents our conclusions, design recommendations and other
geotechnical engineering considerations based on the proposed construction and the subsurface
conditions encountered.
PROPOSED CONSTRUCTION
At the time of our study, design plans for the residence were conceptual. In general, the
residence will be single -story over crawlspace with an attached slab -on -grade garage in the area
of the exploratory boring shown on Figure 1. We assume excavation for the building will have a
maximum cut depth of about 5 feet below the existing ground surface. For the purpose of our
analysis, foundation loadings for the structure were assumed to be relatively light and typical of
the proposed type of construction.
If building location, grading or loading information is different, we should be notified to re-
evaluate the recommendations presented in this report.
SITE CONDITIONS
The site was vacant at the time of our field exploration. The ground surface was nearly clear of
snow and vegetated with scattered grass and weeds. Minor cuts and fills were used to develop
Kumar & Associates, Inc. Project No. 19-7-734
2
the site, likely during overlot grading. The lot is relatively flat with a gentle slope down to the
northwest. Single-family residences are to the north, east and south, vacant land is to the west,
Willowview Way is to the south, and Ponderosa Circle is to the east.
GEOLOGY
According to the Preliminary Geologic Map of the Grand Valley Quadrangle, Garfield County,
Colorado, by Donnell, J.R. Yeend, W.E., and Smith, M.C., dated 1986, the site is underlain by
Mudflow and fan gravel deposits of the Pleistocene period. Mudflow and fan gravel deposits are
described as pebble, cobble, and boulder gravel in a gray matrix of coarse sand; poorly sorted;
clasts primarily unweathered basalt, but contains some sandstone, marlstone, siltstone, and
claystone fragments.
FIELD EXPLORATION
The field exploration for the project was conducted on December 26, 2019. One exploratory
boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The
boring was advanced with 4 inch diameter continuous flight augers powered by a truck -mounted
CME -45B drill rig. The boring was logged by a representative of Kumar & Associates, Inc.
Samples of the subsoils were taken with a 13/8 inch I.D. spoon sampler. The sampler was driven
into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This
test is similar to the standard penetration test described by ASTM Method D-1586. The
penetration resistance values are an indication of the relative density of the subsoils. Depths at
which the samples were taken and the penetration resistance values are shown on the Log of
Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the
project engineer and testing.
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils consist of about 6 inches silty sand and gravel fill overlying dense, silty to very silty,
clayey to very clayey, sand and gravel with cobbles and possible boulders. Drilling in the dense
Kumar & Associates, Inc. Project No. 19-7-734
3
granular soils with auger equipment was difficult due to the cobbles and possible boulders and
drilling refusal was encountered in the deposit at approximately 14'/2 feet.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and gradation analyses. Results of gradation analyses performed on a small diameter
drive samples (minus 11/2 -inch fraction) of the coarse granular subsoils are shown on Figure 3.
The laboratory testing is summarized in Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist to moist.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, we recommend the building be founded with spread footings bearing
on the natural granular soils.
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undis . s .+ granular soils should be designed for
an allowable bearing pre ure of 2,54 t psf. :.. ed on experience, we expect
settlement of footings des' _ :.- ..• cted as discussed in this section will
be about 1 inch or less.
2) The footings should have a minimum width of 16 inches for continuous walls and
2 feet for isolated pads.
3) Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement
of foundations at least 36 inches below exterior grade is typically used in this
area.
4) Continuous foundation walls should be reinforced top and bottom to span local
anomalies such as by assuming an unsupported length of at least 10 feet.
Kumar & Associates, Inc. ® Project No. 19-7-734
4
Foundation walls acting as retaining structures should also be designed to resist
lateral earth pressures as discussed in the "Foundation and Retaining Walls"
section of this report.
5) All existing fill, topsoil and any loose or disturbed soils should be removed and
the footing bearing level extended down to the relatively dense natural granular
soils. The exposed soils in footing area should then be moistened and compacted.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FOUNDATION AND RETAINING WALLS
Foundation walls and retaining structures which are laterally supported and can be expected to
undergo only a slight amount of deflection should be designed for a lateral earth pressure
computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting
of the on-site granular soils. Cantilevered retaining structures which are separate from the
residence and can be expected to deflect sufficiently to mobilize the full active earth pressure
condition should be designed for a lateral earth pressure computed on the basis of an equivalent
fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. Backfill
should not contain organics, debris or rock larger than about 6 inches.
All foundation and retaining structures should be designed for appropriate hydrostatic and
surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The
pressures recommended above assume drained conditions behind the walls and a horizontal
backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will
increase the lateral pressure imposed on a foundation wall or retaining. structure. An underdrain
should be provided to prevent hydrostatic pressure buildup behind walls.
Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum
standard Proctor density at a moisture content near optimum. Backfill placed in pavement and
walkway areas should be compacted to at least 95% of the maximum standard Proctor density.
Care should be taken not to overcompact the backfill or use large equipment near the wall, since
this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall
Kumar & Associates, Inc. Project No. 19-7.734
5
backfill should be expected, even if the material is placed correctly, and could result in distress to
facilities constructed on the backfill.
The lateral resistance of foundation or retaining wall footings will be a combination of the
sliding resistance of the footing on the foundation materials and passive earth pressure against
the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated
based on a coefficient of friction of 0.45. Passive pressure of compacted backfill against the
sides of the footings can be calculated using an equivalent fluid unit weight of 400 pcf. The
coefficient of friction and passive pressure values recommended above assume ultimate soil
strength. Suitable factors of safety should be included in the design to limit the strain which will
occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against
the sides of the footings to resist lateral loads should be a granular material compacted to at least
95% of the maximum standard Proctor density at a moisture content near optimum.
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 relatively
well graded sand and gravel such as road base should be placed beneath slabs for support. This
material should consist of minus 2 -inch aggregate with at least 50% retained on the No. 4 sieve
and less than 12% passing the No. 200 sieve.
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 granular soils devoid of vegetation, topsoil and oversized rock.
UNDERDRAIN SYSTEM
Although free water was not encountered during our exploration, it has been our experience in
the area that local perched groundwater can develop during times of heavy precipitation or
Kumar & Associates, Inc. ® Project No. 19-7-734
6
seasonal runoff. Frozen ground during spring runoff can create a perched condition. We
recommend below -grade construction, such as retaining walls, crawlspace and basement areas,
be protected from wetting and hydrostatic pressure buildup by an underdrain system.
The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above
the invert level with free -draining granular material. The drain should be placed at each level of
excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to
a suitable gravity outlet. Free -draining granular material used in the underdrain system should
contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a
maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep.
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 12 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in paved 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 foundation walls.
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.
Kumar & Associates, Inc. Project No. 19-7-734
7
The conclusions and recommendations submitted in this report are based upon the data obtained
from the exploratory boring drilled at the location indicated on Figure 1, 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 exploratory boring 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 so
that 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.
Respectfully Submitted,
Kumar & Associates, Inc.
Shane J. Robat, P.E.
Reviewed by:
SJR/kac
Kumar & Associates, Inc.
Project No. 19-7-734
1
PONDEROSA CIRCLE
1111111111111
O
La
c�
(OZg
N w J
Io
Zd OOZY
m O w
O M
CD 0
A
i
)4(4
A
•
•
4
4:
.
35 WILLOWVIEW WAY
APPROXIMATE SCALE -FEET
0)
L
LOCATION OF EXPLORATORY BORING
Kumar & Associates
1 9 —7-734
kaP'lNpra/MINO.IUWOV45. ..I+.GII;M SL 124-t-41. \41 V .W4\:
144.1 '91 ilaauur
DEPTH -FEET
0
5
10
15
BORING 1
0
0
49/12
WC=4.4
- 200=22
18/6,40/6
WC=7.8
+4=31
- 200=40
LEGEND
FILL; SILTY SAND AND GRAVEL, MEDIUM DENSE, MOIST, BROWN.
SAND AND GRAVEL (SM -GM, SC -GC); SILTY TO VERY SILTY,
CLAYEY TO VERY CLAYEY WITH COBBLES AND POSSIBLE
BOULDERS, DENSE, SLIGHTLY MOIST, LIGHT BROWN TO BROWN,
SLIGHTLY CALCAREOUS.
DRIVE SAMPLE, 1 3/8 -INCH I.D. SPLIT SPOON STANDARD
PENETRATION TEST.
49/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 49 BLOWS OF
A 140 -POUND HAMMER FALLING 30 INCHES WERE REQUIRED
TO DRIVE THE SAMPLER 12 INCHES.
50/6 t PRACTICAL AUGER REFUSAL.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON DECEMBER 26,
2019 WITH A 4 -INCH DIAMETER CONTINUOUS FLIGHT POWER
AUGER.
2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE
SITE PLAN PROVIDED.
3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT
MEASURED AND THE LOG OF THE EXPLORATORY BORING IS
PLOTTED TO DEPTH.
4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED
ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD
USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES
BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE
GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE
TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 6913);
-200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140).
19-7-734
Kumar & Associates
LOG OF EXPLORATORY BORING
Fig. 2
5
it
y t
100
90
a
70
60
50
40
HYDROMETER ANALYSIS
TIME READINGS
24 HOS 7 1195
43 MIN 15 MIN 901119 man
30
20 —
10
01111 t
M.S. STANDARD SUMS
SIEVE ANALYSIS
CLEAR SOSIAAL OPE10N0S
(
I'
20
30
40
50
60
70
e0
90
0 11 ....1 1 I .J L I. J. 1 1.J .1.1.1 _ [ l' 1 I III . 1 1 1 1 1 1 1 1 1 I 1 1 1 1 11 $1_1_ 100
.W1 .002 .065 .066 .019 .057 ,075 .15D .300 .425.900 1. 8 2 0 .3e 4.75 9.5 19 38.1 76.2 127. 200
52
DIAMETER OF PARTICLES IN MILLIMETERS
CLAY TO SILT
SAND
GRAVEL
FINE 1 MEDIUM (COARSE
FINE
COARSE
COBBLES
GRAVEL 31 % SAND 29 %
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Very Silty Very Clayey Sand and Gravel
SILT AND CLAY 40 %
FROM: Boring 1 0 5'
These test results apply only to the
samples which were tested. The
testing report shall not be reproduced,
except In full, without the written
appronol of Kumar & Asnoclotnn, Inc.
Sfone anolyOID fo14Ing In performed In
accordance will+ ASTM D9913, ASTM D7928,
ASTM C136 and/or ASTM 01140.
19-7-734
Kumar & Associates
GRADATION TEST RESULTS
Fig. 3
I (--A kumar & Associates,
-ect nical and Materials
E Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 19-7-734
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITY(,�o)
(Pcf)
GRADATION
PERCENT
PASSING0 S E • SIEVEQUID
ATTERSERG LIMITS
UNCONFINED
COMPRESSIVE
STRENGTH
(Qsf)
SOIL TYPE
BORING
DEPTH
(ft)
GRAVEL
SAND
(,A)
LIMIT
(%)
PLASTIC
INDEX
(%)
1
21/2
4.4
22
Silty Clayey Sandy Gravel
5
7.8
31
29
40
Very Silty Very Clayey
Sand and Gravel