HomeMy WebLinkAboutSubsoil Study for Foundation Design 06.09.2022I Grt iitiå*ifßtrn'liå*' "
An Employeg Owned Compony
5020 CountyRoad 154
Glenwood Springs, CO 81601
phone; (970)945-7988
fax: (970) 945-8454
email: kaglenwood@kuman¡sa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker', Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
June 9,2022
Lyndsay and Garret Jammaron RECEIVED
4909 Highway 82
Glenwood Springs, Colorado 81601
ljammaron3l6@gmail.com GAF¡FIË.¡-"Ð ütrrþJ1y
Proj ecÊ'0$öÂt W- 7 sÐffiûPll Ë # T
Subject: Subsoil Study for Foundation Design, Proposed Residence, 35 Acre Parcel East of
Sunlight View, Accessed Off Deer Park Court, Garfield County, Colorado
Dear Lyndsay and Garret:
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 you dated March 31,2022. 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-story structure over a walk-out
basement level with an attached garage located in the area of the exploratory pits shown on
Figure l. Ground floor 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 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 project site is currently vacant. There is a rough graded driveway that
accesses the proposed building area from Deer Park Court. Topography at the site is hillside to
hilltop with moderate sloping to moderately steep terrain down to the west. Vegetation at the
site consists of native grass and weeds, and pinyon and juniper trees.
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 %to I foot of topsoil, consist of
llz to 2 feel of Silty Sand underlain by siltstone/sandstone bedrock down to the maximum depth
explored of 6 feet. The upper I to 2 feet of the bedrock was highly weathered and moderately
fractured. Laboratory test results are presented on Figure 4 and summarized in Table l. No free
water was observed in the pits at the time of excavation and the soils were slightly moist.
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Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread footings
placed entirely on the undisturbed natural bedrock and sized for an allowable bearing pressure
of 3,000 psf for support of the proposed residence. Footings should be a minimum width of
li.j¡Êb€ålar continuous walls ut{€!$E$tts. The upper fine-grained soils and loose
disturbed soils and rock encountered at the foundation bearing level within the excavation should
be removed and the footing bearing level extended down to the undisturbed natural bedrock.
Exterior footings should be provided with adequate cover above their bearing elevations for frost
protection. Placement of footings at leas![$helSlow 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 alaleral earth pressure based on an
equivalent fluid unit weight of at least 50 pcf for the on-site 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 50Yo passing the No. 4
sieve and less than 2'Yo 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 and oversized rock.
Underdrain System: Although free water was not encountered during our exploration, it has
been our experience in the area and in areas of shallow bedrock 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, crawlspace and basement areas, be protected from wetting and hydrostatic
pressure buildup by an underdrain system.
The drains should consist of 4-inch diameter PVC drainpipe placed in the bottom of the wall
backfill surrountletl above l"he inverl. level with free-tlraining grarrular rnaterial. The tlrairr slulultl
Kumar & Associates, lnc. 6 Project No. 22-7-266
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be placed at each level of excavation and at least I foot below lowest adjacent finish grade and
sloped at a minimum/zYo to a suitable gravity outlet. Free-draining granular material used in the
underdrain system should contain less than 2Yo 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 I Vz leet deep and covered with filter fabric such as Mirafi 140N.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
l) 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 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 covered with filter fabric and 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. Vy'e recommend a minimum
slope of 6 inches in the first l0 feet in unpaved areas and a minimum slope of
3 inches in the first l0 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
10 feet from the building.
Septic Disposal System: One 4-foot deep profile pit was observed at the location shown on
Figure l. The pit had been dug prior to our arrival at the site. The soils exposed in the Profile
Pit shown on Figure 2 consist of 3% feet of blocky loam beneath about lzfoot of topsoil.
Gradation and hydrometer analysis of the loam soil is presented on Figure 4. Based on the
subsurface conditions encountered, the area should be suitable for a conventional infiltration
septic disposal system provided there is adequate depth of loam soil above top of bedrock.. A
civil engineer should design the infiltration septic disposal system.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. V/e 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 I
and to the depths shown on Figure 2,the proposed type of construction, and our experience in
Kumar & Associates, lnc. o Project No. 22-7-266
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the arca. 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 concemed
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 implanentation of our recommendations, and to veriry 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 fillby 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 & Associates, Inc.
Robert L. Duran, P.E.
Reviewed by:
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Steven L. Pawlak, P.E.
RLD/kac
attachments Figure I - Location of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
Figure 3 - Legend or Notes
Figure 4 - USDA Gradation Test Results
Table I - Summary of Laboratory Test Results
Kumar & Associates, lnc. o Project No. 22-7-266
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s87056'33'E t492.57'
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SEC, 34
1,540,555 SQ. FT
35.366 ACRES *
ZONING: RURAI-Nù t
50 50 100
APPROXIMATE SCALE-FEET
PIT 1
22-7 -266 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
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PIT 1
EL. 6580'
PIT 2
EL. 6572'
PROFILE PIT
EL. 6582'
0 WC=5.1
LL=25
Pl=2
-200=21
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GRAVEL= 1 %
SAND=36%
SILT=59%
CLAY=24%
22-7-266 Kumar & Associates LOGS OF TXPLORATORY PITS Fis. 2
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LEGEND
TOPSOIL. SANDY CLAY AND SILT, FIRM, MOIST, REDDISH BROWN.
CLAY LOAM, BLOCKY, MOIST, RED, CALCAREOUS.
SAND (SM), StLTy, MEDTUM DENSE, MO|ST, RED.
WEATHERED SILTSTONE/SANDSTONE, MEDIUM HARD, SLIGHTLY MOIST, RED,
SILTSTONE/SANDSTONE, HARD, SLIGHTLY MOIST, RED.
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HAND DRIVE SAMPLE
PRACTICAL AUGER REFUSAL.
DISTURBED BULK SAMPLE.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON APRIL 18, 2022
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 OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS 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.
7. LABORATORY TEST RESULTST
WC = WATER CONTENT (%) (ASTM D 2216);
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140);
LL = LIQUID LIMIT (ASTM D 4318);
PI = PLASTICITY INDEX (ASTM D 4318);
GRAVEL = PERCENT RETAINED ON N0. 10 SIEVE;
SAND = PERCENT PASSING NO. 10 SIEVE AND RETAINED ON NO.525 SIEVE;
SILT = PERCENT PASSING NO. 525 SIEVE T0 PARTICLE SIZE .002MM;
CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002MM.
22-7 -266 Kumar & Associates LEGEND AND NOTES Fig. 3
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HYDROMETER ANALYSIS SIEVE ANALYSIS
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T¡ME SERIES CLEAR SQUARE OPENINGS
24 HB. 7 HR 1MIN.
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100 0.001 .002 .005 .009 .019 .045 .106 .025 ,500 1.00 2.00 4.75 9.5 19.0 37.5 76.2 152 203
DIAMETER OF PARTICLES IN MILLIIVETERS
CLAY COBBLES
GRAVEL 1 o/"SAND 36 %SILT 39 %CLAY 24 %
USDA SOIL TYPE: Loam FROM: Profile P¡t 1 @ 2'-3
SÀ,4ALL LABGE
GRAVEL
À,1EDIUÀISILT
22-7 -266 Kumar & Associates USDA GRADATION TEST RESULTS Fig. 4
lcrtlftmar &Associab,lnc.'Geotechnical and Materials Engineersand Environmental ScientistsTABLE ISUMMARY OF LABORATORY TEST RESULTSNo.22-7-266ProfilePit2PITSAMPLE LOCATION2-31DEPTH(ft)51(%)NATURALMOISTURECONTENT(pc0NATURALDRYDENSITY25LIQUID LIMIT("/rl2PLASTICINDEX(%)ATTERBERG LIMITS2IPERCENTPASSING NO.200 stEvE1GRAVEL("/")36(%)SAND39SILT("/"1USDA SOIL TEXTURE24CLAY(%)LoamSilty SandSOIL TYPE