HomeMy WebLinkAboutSubsoil StudylGrti;,ffi fi#ix:Ëtrr'ri3;**'"
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa. colrl
www.kurnarusa. comAn Employcc Owncd Compony
Offrce Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
June 16,2021 RECEIVED
Kaegebein Fine Homebuilding
Attn: Nate Kaegebein
P.O. Box 1570
Carbondale, Colorado 81623
natekae gebein@kfhomebuildins. com
GARFIELD GO['Í{TY
t@iltftI,t iltifinr [DEviËlrCIPMEmflr
Project No. 21-7-413
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 1, Roaring Fork
Preserve, l9 Silver Spruce, Garfield County, Colorado
Dear Nate:
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 Kaegebein Fine Homebuilding dated May 6, 2021. 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 indicate it will be a one- and two-
story structure with attached garage located in the area of the pits shown on Figure 1. Ground
floors will be slab-on-grade. Cut depths are expected to range between about 1 to 3 feet.
Foundation loadings for this type of construction are assuÍred 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 recomlnendations presented in this report.
Site Conditions: The subject site was vacant at the time of our field exploration. The ground
surface is relatively flat. An irrigation ditch is south of the building envelope. Vegetation
consists of grass and weeds with small trees in the building aÍea. The Roaring Fork River
borders the north side of the site.
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 I% to 2 feet of topsoil, consist of
dense, sandy gravel down to the maximum explored depth of 6% feet. Results of a gradation
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analysis perfonned on a sample of sandy gravel (minus S-inch fraction) obtained from the site
are presented on Figure 3. Free water was observed in Pit I at 4% feet deep at the time of
excavation and the soils were slightly moist to wet.
Two profile pits were excavated for septic field exploration at the approximate locations shown
on Figure 1. The profile pits were logged by Carla Ostberg for septic design.
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 gravel soil designed for an allowable soil bearing pressure of
2,500 psf for support of the proposed residence. The soils should have relatively low
compressibility and post-construction foundation settlement should be relatively minor.
Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns.
Topsoil and loose disturbed soils encountered atthe foundation bearing level within the
excavation should be removed and the footing bearing level extended down to the undisturbed
natural gravel 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
l0 feet. Foundation walls acting as retaining structures (if any) should be designed to resist a
lateral earth pressure based on an equivalent fluid unit weight of at least 45 pcf for the on-site
soil as backfill.
Floor Slabs: The natural on-site soils, exclusivc of topsoil, arc suitablc to support lightly loadcd
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 50o/o passing the No. 4
sieve and less than 2% passing the No. 200 sieve.
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fill materials for support of floor slabs should be cornpacted to at least 950,4 of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site gravel soils devoid of vegetation, topsoil and oversized rock.
Kumar & Associrtes, lnc, 6 Project No, 21-7-413
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Underdrain System: It is our understanding the finished floor elevation at the lowest level of
the buildings will be at or above the surrounding grade. Therefore, a foundation drain system is
not required.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
l) 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 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 6 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the hrst 10 feet in pavement and walkway areas.
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.
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 veri$r that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
Kumar & Associates, lnc, @ Project No, 21-7-413
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or modificatians to the recommendations presented herein. Tfe recommend on-site observation
of excavaticns a*d faundatian 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 & Associatesr ln
James H. Parsons, P
Reviewed by:
b
Daniel E. Hardin, P.E.
JHPlkac
attachments Figure I * tc¡cation of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
Figure 3 - Gradation Test Results
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Kumar & Associates, lnc.6 Project No. 21-7-413
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21 -7 -41 3 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
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LEGEND
TOPSOIL; SAND, CLAYEY, SILTY, ORGANICS, SCATTERED GRAVEL, LOOSE T0 MEDIUM DENSE,
SLIGHTLY MOIST, BROWN.
GRAVEL (GM); SANDY TO VERY SANDY, SLIGHTLY SILTY, COBBLES, SMALL BOULDERS, DENSE,
SLIGHTLY MOIST TO WET, MIXED BROWN.
DISTURBED BULK SAMPLE.
I orprH To wATER LEVEL ENcouNTERED AT THE TIME oF DTGGTNG.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A EXCAVATOR ON JUNE 10, 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 LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER
CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME.
7. LABORATORY TEST RESULTS:
wc = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140).
21 -7 -413 Kumar & Associates LOGS OF EXPLORATORY PITS Fis. 2
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DIAMETER OF PARTICLES IN MI
CLAY TO SILT COBBLES
GRAVTL 65 X SAND
LIQUID LIMIT
SAMPLE OF: Sondy Grovel wllh Cobblos
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PLASTICITY INDEX
SILT AND CLAY 3 X
FROM:Plt1O5'-5.5'
Thclr t6rl rolull! opply only lo lh!
sqmpllt whlch r!r! lr!|.d, Th.icrllng roporl 3holl nol b. roprcducld,
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opprcvol ot Kumor & Alloclohr, lnc,
Sl.y! qnqlyrlt tlrllng l! p.rlorm.d ln
occordonc! wlth ASTM D6915, ASTM 07928,
ASÍM C136 ond/or ASTM Dl1,l0.
SIEVE ANALYSISHYDROMETER ANALYSIS
ÎlME READINOS
7 HRS
U.S. STANDARD SERIES CgR SQUARE OPENIXGS
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21 -7 -413 Kumar & Associates GRADATION TEST RESULTS Fig.5