HomeMy WebLinkAboutObservation of Excavation 05.08.2023I (¡rt $j,ffifr'åifffi ,'r3;,**,
An Employac Oryncd Compony
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
IùlIay 8,2023
Btech Construction
Attn: Joaquin Bianco
P.O. Box 811
Silt, Colorado 81652
btechconstruction@hotmil. com
ProjectNo. 23-7-T74
Subject: Subsoil Study for Foundation Design, Proposed Residence and Shop Building,
897 County Road 231, Silt, Colorado
Gentlemen:
As requested, Kumar & Associates, Inc. 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 Btech Construction dated March 6,2023. The data obtained and our
recommendations based on the proposed construction and subsurface conditions encountered are
presented in this report.
Proposed Construction: The proposed building will be aZ-story structure with the residence
on the top floor and the shop on the ground floor and building footprint as shown on Figure 1.
Ground floor will be slab-on-grade. Cut depths are expected to range between about 2 to 5 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 building site consists of a vacant field of grass and weeds. The ground
surface is relatively flat with a gentle slope down to the south.
Subsurface Conditions: The subsurface conditions at the site were evaluated by observing one
exploratory pit at the approximate location shown on Figure I with respect to the proposed
building footprint. The log of the pit is presented on Figure 2. The subsoils encountered, below
about Vz foot of topsoil, consist of medium to stiff, sandy clayey silt to the pit depth of \Yz feet.
Results of swell-consolidation testing performed on a relatively undisturbed sample of the silt,
presented on Figure 3, indicate low compressibility under existing low moisture condition and
light loading and a low collapse potential (settlement under constant load) when wetted and
relatively high compressibility under additional loading after wetting. Results of classification
a
and laboratory Proctor compaction testing perfiormed on a sample of clayey silt imported to the
site are presented on Figures 4 and 44. No free water was observed in the pit at the time of
excavation and the soils were slightly moist. Our experience in the area (at kon Horse Mesa
development) indicates the silt soils are underlain by very stifflmedium dense, sandy clay to silty
sand with gravel to a depth of more than 25 feet.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pit and the nature of the proposed construction, spread footings placed on at least
3 feet of compacted structural fìll and sized for an allowable soil bearing pressure of 1,500 psf
can be used for support of the proposed building with a risk of settlement and distress. The soils
are compressible after wetting and there could be around I to 2 inches of post-construction
foundation settlement depending on the depth and extent of subsurface wetting. Footings should
be a minimum width of 20 inches for continuous walls and2 feet for columns. The topsoil and
loose disturbed soils should be removed and sub-excavated 3 feet below the footing bearing level
and to at least TYzfeetbeyond footing edges. Structural fill can consist of the onsite or imported
silt soils or granular material such as CDOT Class 6 base course compacted to at least 98% of
standard Proctor density atnear optimum moisture content. 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 heavily reinforced top and bottom to span local anomalies such as by assuming
an unsupported length ofat least 15 feet.
Floor Slabs: The natural onsite silt soils tend to settle when wetted which could cause slab
distress and atleast 2 feet of compacted structural fill is recommended for slab support to help
mitigate the settlement risk. To reduce the effects of some differential settlement, 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 CDOT Class 6 base course should be
placed beneath slabs for support. This material should consist of minus 2-inch aggregate with
less than 50%o passing the No. 4 sieve and less lhan |2o/o passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95o/o of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
onsite soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: It is our understanding the proposed finished floor elevation at the lowest
level is at or above the surrounding grade. Therefore, a foundation drain system is not
Kumar & Associates, lnc. o Project No. 23-7-174
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recommended. It has been our experience that local perched groundwater can develop during
times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a
perched condition. We recommend below-grade construction, such as retaining walls and
basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain
system.
If the fïnished floor elevation of the proposed structure is revised to have a floor level below the
surrounding grade, we should be contacted to provide recommendations for an underdrain
system. All earth retaining structures should be properly drained. 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 seasonal runoff. Frozen ground
during spring runoff can create a perched condition. We recommend below-grade construction,
such as retaining walls and basement areas (not crawlspace), be protected from wetting and
hydrostatic pressure buildup by an underdrain system.
Surface Drainage: Providing proper surface gradingand drainage will be critical to limiting
subsurface wetting and building distress. The following drainage precautions should be observed
during construction and maintained at all times after the building has been completed:
1) Inundation ofthe foundation excavations and underslab areas should be avoided
during construction.
2) Exterior bac,kfill should be adjusted to near optimum moisture and compacted to
at least 95Yo of the maximum standard Proctor density in pavement and slab areas
and to at least 90o/o 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 pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irigation should be located at least
10 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 pit excavated at the loeation indicated on Figure I
and to the depth shown on Figure 2,the proposed type of construction, and our experience in the
Kumar & Associates, lnc. ô Project No. 23.7.174
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.arba. 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
pit 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 pulposes. 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 veriff 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.
Respectfu lly Submitted,
Kumar & Associates, lnc.
Steven L. Pawlak, P.E.
Reviewed by:
,,4\.:.
Daniel E. Hardin,
SLP/kac
Attachments: Figure 1 Pir
Figure 2 -Logof Exploratory Pit
Figure 3 - Swell-Consolidation Test Results
Figure 4 - Laboratory Proctor Compaction Test Report
Figure 4A - Particle Size Distribution Report
Table 1 - Summary of Laboratory Test Results
Kumar & A$sociates, lnc. úr Project No. 23-7-174
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23-7 -17 4 Kumar & Associates LOCATION OF EXPLORATORY PIT Fig. 1
PIT 1
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WC=10.6
DD=80
-2AO=79
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DD=85
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TOPSOIb ORGANIC SANDY CLAYEY SILT, FIRM, MOIST, DARK BROWN.
SILT (ML); CLAYEY, SANDY, MEDIUM STIFF, SLIGHTLY MOIST, BROWN.
F
HAND DRIVEN z-INCH DIAMETER LINER SAMPLE.
NOTES
f . TI{E EXPLORATORY PIT WAS EXCAVATED WITH A BACKHOE ON MARCH 29, 2023.
2. THE EXPLORATORY PIT WAS DUG AT THE CLIENT'S DESIGNATED LOCATION.
5. THE ELEVATION OF THE EXPLORATORY PIT WAS NOT MEASURED AND THE LOGS OF THE
EXPLORATORY PIT IS PLOTTED TO DEPTH.
4. THE EXPLORATORY PIT LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE
IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOG REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PIT AT THE TIME OF EXCAVATION. PIT WAS
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULÏS:
TVC = WATER CONTENT (X) (ASTM T 2216)I
DD = DRY DENSITY (PCT) (ESTU D 2216),;
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1I4O).
23-7-174 Kumar & Associates LOG OF EXPLORATORY PIT Fis. 2
SAMPLE OF: Sondy Cloyey Sill
FROM:Pitle6'
WC = 6.5 %, DD = 85 pcf
-2AO = 74 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WEÏTING
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SWELL-CONSOLIDATION TEST RESULTS Fig. 3Kumar & Associates23-7 -17 4
Laboratory Proctor Gompaction Test Report
115.5
114
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112.5
111
ZAV lor
SP.G. =
2.50
109.5
108
7.5 I 10.5 12
Water content, %
13.5 15 16.5
Test specification: ASTM D 698-12 Method B Standard
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Elevl
Depth
Classification Nat.
Moist.$p.G.LL PI
o/o )
3/8 in.
o/o 1
No.200uscsAASHTO
ML A-4(0)2t J 1.0 54.0
TEST RESULTS MATERIAL DESCRIPTION
Maximum dry density = 113.6 pcf
Optimum moisture :12.9 o/o
Sandy Silt
Proiect No. 23-7-174 Client: Btech Construction
Proiect: 897 County Road 231, Silt, Colorado
o Location: Import Sample Number: 067-23
Remarks:
See Figure lA for classification results.
Figure 4
Kumar & Associates, lnc.
Glenwood Sorinos. Colorado
Tested By: KO Checked By:SLP
Particle Size Distribution Report
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80
70
60
50
40
30
20
10
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100
GRAIN SIZE - mm.
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% +3"%Grawl % Sand % Finos
ClayGoar¡e Flne Coarso tedium Fine
0.0 0.0 2.4 2.0 3.0 39.0 54.0
(no spocifi cation provided)
Location: Import
Sampte Number: 067-23 Date: 41212023
SIEVE
stzE
PERCENT
FINER
sPEC.*
PERCENT
PASS?
(X=NOl
.75
.375
#4
#8
#16
#30
#50
#100
#200
100.0
99.0
98.0
96.0
96.A
95.0
91.0
7t.0
s4.0
Soil Description
Sandy Silt
PL= 19
Atterberg Limits
LL= 2l
GseffiE¡enls
D85= 0'2437
Pgq=\rU-
Pl= 2
D6o= o.ogsg
IJ,r ç=a tiJwC-
A-4(0)
D90= 0.2898
Diö=
USCS= ML
Glassificatiqn
AASHTO=
Remarks
See Figure I for standard Proctor compaction results.
Kumar & Associates, lnc.
Glenwood Springs, Colorado
Client: BtechConstruction
Projecft 897 County Road 231, Silr, Colorado
No: 23-7-174 4A
Tested By: KQ Checked By: SLP
I(+'T lfumar & Associatæ, lnc,@
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
No.23-7-174
SOILTYPE
Sandy Silt
Sandy Clayey Silt
UNCONFINED
COMPRESSME
STRENGT}I
ATTERBERG LMITS
LIQUID LIMff PtÂsTtc
INDEX
PERCENT
PASSING NO
200 SIEVE
7980
74
IATION
l"/"1
SAND
GRAI
{%}
GRAVEL
85
locfl
NATURAL
DRY
DENSTTY
10.6
6.5
lo/"1
NATURAL
MOISTURE
CONTENT
fftt
DEPTH
2
6
SAMPLE LOCATION
PIT
1
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Glenwoód SprlngÐ
Soil Compaction Report crienr;
Test Method: ASTM D 6938 Btech Construction
P.O. Box 811
silr, co 81652
23-7-174.4
Silt Shop & Residence
897 County Road 23'l
silr, co 816525020 county Boad 154
Glênwoad Springs, CO 81 601
Phonê: 970-945-79É8
/ Moisture Pass are *Direct Transmission"is noted as
calibration data on with the
Rernarks Commente
4
3
Test #
Test lnformation
4
3
Teôt #
Test Results
Fill: Bui Pad
Structural Fill: Buildinq Pad: ShoP
Test Locat¡on
Rete6t
ot
a6Í29123
o6P.9r23
Te6t Date
163-23
163-23
Proctor ¡D
B (D698)
B (D6e8)
Method
CL-ML
CL.ML
Soil
Classification
14.9
14.9
Optimum
Moisture
{%)
109.0
109.0
Maximum
Dry Dens¡ty
(pcfì
Elevat¡on
14.2
17.3
ln Place
Mo¡sture
(%)
Subqrade
Subqrade
Refercnce
108.9
107.3
ln Place
Dry
Density
(pcfì
124.4
125.9
ln Place
Wet
Density
(pc0
Troxler / 3440 I 23818 I OSl21 f2A2O
Troxler 13440 I 23818 I OSl21 Þa2A
Gauge
Make ^/ Model / SN / Calibrated
6
6
Probe
Depth
{inl
100
98
Percent
Compact¡on
98
98
Min Comp.
(%)
Sam Ernerson
Sâm Ernèrsôn
Field Technician
-3 /3
-3 /3
Opt¡mum
Mo¡sturê
folerance
(%)
DP/f\¡P
DP/[¡P
Remark
This report presents opinions formed as a result of our observations of soil compaction. We have relied on the contractor to continue applying the recommended
compaätive'etfort and moisture to the fill during times when our observer is not observing operations. Tests are made of the soils only as believed necessary to
calibrate our observer's judgement. Test data are nol sole basis for opinions on whether the soils meets specifications. These test resulls only apply to the
samples which were tesied. The testing report shall not only be reproduced, except in full, without the wrilten approval of Kumar and Associates, lnc. Nuclear
gauge density testing performed in accordance wilh ASTM D6938.
Page 1 of 1
l(+rtffiffik*'*"
-
w'tumrus-m
Glenwood Springs
5020 County Road 154
Glenwood Springs, CO 81601
Phone: 970-945-7988
Construction
Observation
Glient:
Btech Construction
P.O. Box 8'1 1
sitt, co 81æ2
Project:
z3-7-174.4
Silt Shop & Residence
897 County Road 231
s¡tt, co 81652
General lnformation
Ac'tivity Number: 1 Activity D ate: 06 I 29 DA23
Contractors Equipment: Wal k-behi nd vi bratory sheepsfoot roll er
Construction Observation and Gommunication:
We visited the site today to perform compaction testing on the building pad for the shop. The material we tested was compacted using a walk-behind vibratory s
Our test results are provided in our soil compaction report dated ı129123.
heepsfoot roller
Slte Observations
Technician: Sam Emerson Rwievtæd By: James H. Parsons, P.E.
The testing report shall not be reproduced, except in full, without the written approval of Kumar and Associates, lnc.Page 1 of 1