HomeMy WebLinkAboutSubsoil Studylcrt
An Employee Owned Compony
5020 County Road 154
Glenwood Springs, CO 8160 I
phone: (970) 945-7988
fax: (970) 945-8454
ernail: kaglenwood@knmarusa.com
lvtl'rv. ktt t.n aLusa. cotn
Oflìce Locations: Denver (l-lQ), Parker, Colorado Springs, Fort Collins, Glenrvoocl Springs, and Sumrnit County, Coloraclo
october 18,202t RËcElvËa
Jorge Guillerïno Lopez i;i¡'iìi ,i Ì .ríj;'l
175 West 93'd Street, Apt. 12H GARFTËLþ (:OUNT'
New York, New York 10025 comutiurry nevrltjpur¡lr
lneuìolnx lopez(Ôgnla i l.conl
Project No.2I-7-725
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot22, Panorama
Ranches, Panorama Drive, Garfield County, Colorado
Dear Mr. Lopez:
As requested, Kumar & Associates, Inc. performed a subsoil study for foundation design and
septic disposal feasibility at the subject site. The study was conducted in accordance with our
proposal for geotechnical engineering services to you dated August30,202I. 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 one to two story structure over a
crawlspace or slab-on-grade, located on the site as shown on Figure 1. Cut depths are expected
to range between about 4 to 8 feet. Foundation loadings for this type of construction are
assumed to be relatively light and typical of the proposed type of construction. The septic
disposal system is proposed to be located in one of the two areas indicated on the site plan.
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 reporl.
Site Conditions: The site was vacant of structures and vegetated with sage brush, scrub oak,
grass and weeds. The ground surface appears natural and slopes gently to moderately down to
the west-northwest. There has been some minor grading for Panorama Drive on the north, west
and south sides of the site.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits in the building area and one profile pit in each of the designatecl septic disposal
areas, A and B, at the approximate locations shown on Figure l. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about 1 foot of topsoil, consist of stiff,
sandy silty clay to clayey sand with gravel (Pit l) or medium clense, silty sand and gravel down
to the bottom of the pits at 8 feet (Pit 2). Results of gradation analyses perfonned on samples of
the deeper soils (minus 3-inch fraction) obtained frorn the pits are presented on Figure 3. The
Kumar & Associates, lnc.'
Geo[echnical and Materials Engineers
and Envìronmental Scientists
1
laboratory test results are summarized in Table 1. No free water was observed in the pits at the
time of excavation and the soils were slightly rnoist 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 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
16 inches for continuous walls and2 feet for columns. Loose and 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. We should observe the completed
foundation excavation to confirm suitable bearing conditions. 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 feef . 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, excluding organics and rock larger fhan 6
inches.
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 ntovement, floor slabs
should be separated frorn all bearing walls and columns with expansion joints which allow
unrestrained vertical rnovement. 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 50Yo passing the No. 4
sieve and less than 2%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 on-
site soils devoid of vegetation, topsoil ancl 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 tirnes 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, crawlspace and
Kumar & Associates, lnc. @ Project No. 21-7-725
-J-
basement areas, be protected frorn wetting and hydrostatic pressure buildup by an underdrain
system.
The drains should consist of drainpipe placed in the bottom of the wall backfill sunounded 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 l%o to
a suitable gravity outlet. Free-draining granular material used in the underdrain system should
contain less than 2o/o 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 lYz 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 ofthe 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 95o/o 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 feetof 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 frrst 10 feet in pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the lirnits 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 building caused by irrigation.
Septic System: One profile pit was dug at each of the two septic fielcl locations shown on
Figure 1. The soils exposed in the Profile Pits are shown on Figure 2 and consist of loam.
USDA gradations were performed on soils frorn each pit as shown on Figures 4 and 5. Based on
the subsurface conditions encountered, either septic area should be suitable for a conventional
infiltration septic disposal system. A civil engineer should design the infiltration septic disposal
system.
Limitations: This study has been conductecl in accordance with generally accepted geotechnical
engineering principles and practices in this arca af this time. We make no warranty either
Kumar & Associates, lnc. @ Project No. 21-7-725
4
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 l,
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.
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 fietd services during construction to review and
monitor the implementation of our recommendations, and to verifi, 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 obseruation
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,
i-.1 i U; t t r ¡' ï!. 1 A =t.::,,,J
t:i tZ 1 t: f,, l. Z: t:,
Daniel E. Hardin, P.
Rev. by: SLP
DEHlkac
attachments Figure 1 - Location of Expioratory Pits
Figure 2 - Logs of Exploratory Pits
Figure 3 - Gradation Test Results
Figures 4 8.5 - USDA Gradation Test Results
Table 1 - Summary of Laboratory Test Results
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PIT 1 PII 2 PP_A PP-B
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WC= I 0.1
DD= l 07
-¡ \,tC=7.7- 44=18
-200= 60
WC=8.7
DD=86
-l wc=+. t
'+4=37
-200= 1 9
I wc=7.s
'GRAVEL=9
SAND=30
SILT=37
CLAY=24
I wc= t s.+- GRAVEL=2
SAND=55
SILT=38
CLAY=27
10
LEGEND
F|LL; ORGANIC SANDY SILTY CLAY WITH ROOTS, GRAVELLY, SOFT, Mo|ST, DARK BROWN
CLAY (CL); SILTY, SANDY, WITH GRAVEL AND COBBLES, STIFF, SLIGHTLY MOIST' BROWN.
sAND AND GRAVEL (CV-SU); SILTY, MEDIUM DENSE, SLIGHTLY MOIST, BROWN
HAND DRIVE SAMPLE.
DISTURBED BULK SAMPLE
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A CAT 307 BACKHOE ON OCTOBER 8, 2021.
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 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 (PCT) (¡STU D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
_2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140);
GRAVEL = PERCENT RETAINED ON NO. 10 SIEVE;
SAND = PERCENT PASSING N0.10 SIEVE AND RETAINED ON NO.325 SIEVE;
SILT = PERCENT PASSING NO. 325 SIEVE TO PARTICLE SIZE .002MM;
CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002MM.
10
lig. 2LOGS OF EXPLORATORY PITS21 -7 -725 Kumar & Associates
SIEVE ANALYSISHYDROMETER ANALYSIS
U.S. STANDARD SERIES CLEAR SOUARE OPENINGS
z/e. \/^n 1 r/t6
TIME REAOINGS
24 HRS 7 HRS MN
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DIAMETER OF c N MILLIMETERS
CLAY TO SILT COBBLES
GRAVEL 18 % SAND
LIQUID LIMIT
SAMPLE OF: Grovelly Sondy Silty Cloy
22%
PLASTICITY INDEX
SILT ÀND CLAY 60 %
FROM:Piil@6'-7'
=
100
s0
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60
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LLIM ETERS
9.5 l9 54.1 1
DIAMETER OF PARTICLES IN MI
CLAY TO SILT COBBLES
GRAVEL 37 % SAND
LIQUID LIMIT
SAMPLE OF: Silfy Sond ond Grovel
44%SILT AND CLAY 19%
Th6sê lêsl r€sulls opply only lo lhê
somples which wor€ l€slod. The
l€stlng roport sholl not be roproducod,
.ôxcept ln full, wllhoul lho wrlll€n
ôpprovol of Kumor & Associolos, lnc.
Si6v6 onolysis lesling ls p6rformed ln
occordoncà wlth ASTM 06913, ASTM D7928,
ASTM Cl36 ond/or ASTM D1140.
PLASTICITY INDEX
FROM:Pit2@6'-7'
GRAVELSAND
FINE MEDIUM COARSE FIN E COARSE
SIEVE ANALYS¡SHYDROMETER ANALYSIS
U.S. STANDARD SERIES CLEAR SOUARE OPENINGS
\/A" \/¿" I 1/t^24 HRS 7 HRS
TIME READINGS
60!tN lgMtN 4MtN
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1
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SAND GRAVEL
FINE COARSEFINEMEDIUMCOARSE
21 -7 -725 Kumar & Associates GRADATION TEST RTSULTS Fig.3
¡
4
4
SF
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SIEVE ANALYSISHYDROMETER ANALYSIS
TJME U.S. ST
*140 #60
CLEAR SQUARE OPENINGS
24HR 7HR ] MIN.
#325 #35 #18 +10 #4 3/B' 3/4 1 3" 5"6 8',
045 100
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30 70
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.001 .002 .005 .009 .0'19 .045 106 .025 .500 1.00 2.00 4.75 9.5 19.0 37.5 76.2 152 203
DIAI\4ETER OF PARTICLES IN [/ILLIIVETERS
CLAY COBBLES
GRAVEL 9 %SAND 30 %SILT 37 %CLAY 24 %
USDASOILWPE: Loam FROM: PP-A @ 5-6
SAND
SILT V. FINE FINE
21 -7 -725 Kumar & Associates USDA GRADATION TEST RESULTS Fig. 4
SIEVE ANALYSISHYDROMETER ANALYSIS
TIME REAEIN U.S, STANDARD
#140 #60 #35
CLEAR SQUARE OPËNINGS
24 HB, 7HR lMIN.
#325 #18 +10 3/8 314' 1 112', 3', 5',6" B
045
MIN 15MIN,100
10
20
30 70
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100 0
.001 .002 .005 .009 .019 .045 106 .025 .500 1.00 2.00
DIAIVETER OF PARTICLES IN MILLIMETERS
CLAY COBBLES
GRAVEL 2 %SAND 33 %SILT 38 %CLAY 27 %
USDA SOIL WPE: Loam FROM: PP-B @ 5'-6'
SAND
I ARGEV FINE FINE [/EDIUSlLT
21 -7 -725 Kumar & Associates USDA GRADATION TIST RESULTS Fig.5
l(lKumar & Associates, lnc.'Geotechnical and l\ilaterials Engineersand Environmental ScientistsTABLE 1SUMMARY OF LABORATORY TEST RESULTSNo.21-7-7251PITBProfileAProfile26-7JDEPTH(ft)SAMPLE LOCATIONs-65-66-7510.1NATURALMOISTURECONTENT(%)13.47.9418.7r07NATURALDRYDENSITY(pc086JI184422196092JJ3038372724Clayey SandGravelly SandySilty ClaySandy Silty Clay& CLAY(klSANDf/"1SILT(%)CLAY(%)f/"1SOIL TYPE%tGRAVEL%tGRAVELSANDGRADATIONUSDA SOIL TEXTURELoamLoamSilty Sand andGravel