HomeMy WebLinkAboutSoils Report 03.06.2018H-PvKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
RECEIVED
AUG 2 2 2018
GARFIELD COUNTY 5020 County Road 154
COMMUNITY DEVELOPMENT 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
March 6, 20 ] 8
Walters Company
Attn: Ed Walters
1175 County Road 154
Glenwood Springs, Colorado 81601
info@walterscompanv.net
Subject:
Dear Ed:
Project No.18-7-168
Subsoil Study for Foundation Design, Proposed Residence, TBD County Road
132 (Mitchell Creek), Garfield County, Colorado
As requested, FI-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 February 19, 2018. The data obtained and our recommendations based on
the proposed construction and subsurface conditions encountered are presented in this report.
Proposed Construction: Plans for the proposed residence were conceptual at the time of our
study. We assume the residence will be a one to two story wood frame structure over a
crawlspace or basement level located in the area of Pit 1 as shown on Figure 1. Basement and
attached garage floors will be slab -on -grade. Cut depths are expected to range between about 3
to 8 feet. Foundation loadings for this type of construction are assumed to be relatively Iight 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 building area was vacant and accessed from Mitchell Creek Road by a
gravel driveway.
The site is located well above Mitchell Creek on a relatively steep, west facing
hillside. Site grading appears to be natural except for the driveway cut and a relatively flat
-2-
cut/fill area south of the existing well head. Vegetation consists of oak brush with an understory
of 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''Y2 to 1 foot of topsoil and about 1
foot of clayey sandy gravel (possible fill) in Pit 1, consist of 4 to 21/2 feet of sandy silty clay with
gravel. Cemented silty sandy gravel (travertine) was encountered in Pit 1 below the clay at
depths of 6 to 8 feet. Clayey sandy gravel was encountered in Pit 2 below the clay from 3 feet
down to refusal to digging at 61/2 feet. Results of swell -consolidation testing performed on a
relatively undisturbed sample of sandy clay, presented on Figure 3, indicate low compressibility
under existing moisture conditions and light loading and a minor collapse potential (settlement
under constant load) when wetted. The sample was moderately compressible under increased
loading after wetting. Results of gradation analyses performed on samples of the sandy clay and
silt with gravel (minus 11/2 inch fraction) obtained from Pit 2 are presented on Figure 4. 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 soil designed for an allowable soil bearing pressure of 2,000
psf for support of the proposed residence. The 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. The topsoil, existing fill and loose
disturbed soils 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
H-P--14KUMAR
Project No. 18-7-168
Underdrain System:
-3 -
equivalent fluid unit weight of at least 50 pcf for the on-site predominantly granular 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 basement level slabs to facilitate drainage.
This material should consist of minus 2 inch aggregate with less than 50% passing the No. 4
sieve and less than 2% 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 soils devoid of vegetation, topsoil and oversized rock.
Although free water was not encountered during our exploration, it has
been our experience in mountainous areas that local perched groundwater can develop during
times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can also
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 1'/2 feet deep.
H-P%'KUMAR
Project No. 18-7-168
-4 -
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.
Free -draining wall backfill should be capped with about 2 feet of the on-site, finer
graded soils to reduce surface water infiltration.
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 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. Consideration should be given to the use of xeriscape to
limit potential wetting of soils below the foundation caused by irrigation.
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
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.
H-PMKUMAR
Project No. 18-7-168
-5_
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,
KUMAR
Apr.
0:
4 ••
j r.,.wc
Daniel E. Hardin, P.E. •� ��
r
Rev. by: SLP 5 U�f�
DEH 1kac
attachments Figure 1 — Location of Exploratory Pits
Figure 2 — Logs of Exploratory Pits
Figure 3 — Legend and Notes
Figure 4 — Swell -Consolidation Test Results
Figure 5 — Gradation Test Results
Table 1 — Summary of Laboratory Test Results
cc: Abbey Walters Ehlers abbevwalters@hotmail.com
H-Pk'KUMAR Project No. 18-7-168
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LOCATION OF EXPLORATORY PITS Fig. 1
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PIT 1
WC=5.0
DD=97
-200=50
WC=18.9
-J -200=38
LL=44
PI=NP
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' WC=8.7
+4=28
-200=60
WC=8.9
+4=20
-200=62
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18-7-168
1
H-P%-KIJMAR
LOGS OF EXPLORATORY PITS
Fig. 2
NOTES
ETOPSOIL; ORGANIC SANDY SILTY CLAY, FIRM, MOIST, DARK BROWN.
o �
.•o
,
GRAVEL (GC); SANDY, CLAYEY, MEDIUM DENSE, SLIGHTLY MOIST, BROWN. POSSIBLE FILL (PIT 1).
CLAY (CL); SANDY, SILTY, SCATTERED GRAVEL, CHARCOAL FRAGMENTS, VERY STIFF, SLIGHTLY
MOIST, BROWN.
GRAVEL (GC—GM); SANDY, CLAYEY, SILTY TO VERY SILTY, DENSE, SLIGHTLY MOIST, LIGHT
BROWN (PIT 2).
GRAVEL (GM); SANDY, SILTY, MEDIUM DENSE, SLIGHTLY MOIST, MIXED YELLOW BROWN.
TRAVERTINE (PIT 1).
Sl HAND DRIVEN LINER SAMPLE.
DISTURBED BULK SAMPLE.
t PRACTICAL DIGGING REFUSAL.
LEGEND
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON FEBRUARY 19, 2018.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE PROVIDED BY THE CLIENT.
3. THE tLEVATIONS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE
EXPLORATORY PITS ARE PLOTTED TO DEPTH.
4. THE EXPLORATORY PIT LOCATIONS 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 EXCAVATION. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
-1-4 = 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);
NP = NON—PLASTIC (ASTM D 4318).
18-7-168
FH-P%KU AR
LEGEND AND NOTES
Fig. 3
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SWELL -CONSOLIDATION TEST RESULTS
CONSOLIDATION - SWELL (%)
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SAMPLE OF: Sandy Silty Clay
FROM: Pit 1 0 3'
WC = 5.0 %, DD = 97 pcf
IONAL
CONS
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HYDROMETER ANALYSIS
SIEVE ANALYSIS —
100
24 HRS 7 HIS
46 MIN 16—LIC, SWIM
TIME REAOIN05
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OF PARTICI.ES IN MILLIMETERS
5 L6 11 pc 31J1 •i
152
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CLAY TO SILT
SAND
GRAVEL.
GRAVEL 28 X
LIOUID LIMIT
SAMPLE OF: Sandy Clay with Gravel
SAND
FINE MEDIUM COARSE
12 X SILT
PLASTICITY INDEX
FROM:
FINE I COARSE
AND CLAY 60 X
Pit 2 0 2.5' to 3'
COBBLES
HYDROMETER ANALYSIS
SIEVE ANALYSIS
'14 HRS 7 HRS
..
TME READINGS
..
5]00
U.S. STANDARD
I= 570
SERIES
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CLEAR SQUARE OPENINGS
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DIAMETER
1..11 r—
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OF PARTICLES
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1 .600 1.
IN
--�TT— r -r r"r'711
a 12.56 1.75 6 5 14
MILLIMETERS
t -I 1 1 1 ] 1 1 1
56.1 7e,2 122
1
000
100
CLAY TO SILT
SAND -
FINE J MEDIUM ,COARSE
GRAVEL
FINE I COARSE
CODDLES
GRAVEL 20 X SAND 18 X SILT AND CLAY 62 X
UOUID LIMIT PLASTICITY INDEX
SAMPLE OF: Sandy Clayey SIR with Grovel FROM: Pit 2 0 5.5' to 6'
Thew test results apply
samples which were fasted.
M111ny report shall not ba
eo *pl In full, without the
approval of Kumar & Associotes,
Stere 00011.ta leelfnp 1■
acc5rdance wlth ASTO 0422,
and/or A5111 0111D.
only to the
The
reproduced,
r pen.
Inc.
performed In
ASTM C136
18-7-168
FI -P KUTAR
GRADATION TEST RESULTS
Fig. 5
SAMPLE
H-PKUMAp
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 18-7-168
OCATION
PIT
1
DEPTH
(ft)
3
7 to 8
NATURAL
MOISTURE
CONTENT
(%)
5.0
NATURAL
DRY
DENSITY
(pcf)
97
GRADATION
GRAVEL
(%)
SAND
(%)
PERCENT
PASSING
NO. 200
SIEVE
50
18.9
38
2
2Y2to3
5% to 6
8.7
8.9
28
20
12
18
60
62
AT'rERBERG LIMITS
SOIL TYPE
i
LIQUID
LIMIT
(%)
—
PLASTIC
INDEX
(%)
UNCONFINED
COMPRESSIVE
STRENGTH
(psf)
____
Sandy Silty Clay
44
NP
Silty Sand with Gravel
Sandy Clay with Gravel
Sandy Clayey Silt with
Gravel
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