HomeMy WebLinkAboutSubsoils Report for Foundation DesignPreha. dat%nrb!
GRAI\D JUNCTION
LINCOLN DeVORE, Inc.
GEOTECHNICAL ENGINEERS . GEOLOGISTS
219l Canyon Ct. W.
Grand Junction, CO 81507
Cell: (970) 260-3332
E-Mail: si ldem@eafthlink.net
I
March 27,2024
Mr. Tyler DiDonato
Shining Light Services
P.O. Box 759\
Fruita, Colorado 81521
Re: Subsurface Soils Exploration, 236 Limberpine Circle, Battlement Mesa, Colorado
Mr. DiDonato:
As requested, Edward M. Morris, P.E. of Grand Junction Lincoln DeVore completed a geotechnical exploratory
program at the above-refErenced site. One shallow exploration pit was excavated by the client in the vicinity
of the proposed building pad as shown on the attached sketch. This exploration pit was located north of the
assumed building envelope. This exploration pit was excavated to a total depth of 8 feet. This exploration pit
was logged and sampled by personnel of Grand Junction Lincoln DeVore on 3-6-2024. The purpose of this
exploration pit was to determine the types and character of the underlying soils and to relate these characteristics
to the proposed foundation system.
This letter contains general recommendations for construction of a residential foundation, but it is not a
foundation design and cannot be used as such. Our conclusions and recommendations for this site are presented
below.
Excavation Observation: Grand Junction Lincoln DeVore personnel should be contacted to
observe the foundation soils after the excavation has been completed and priorto placing forms or concrete. The
purpose ofthis is to observe the type and condition ofthe foundation soils throughout the excavation. Ifthe soils
are found to differ from those encountered in our exploration borings, or ifthey appear to be unstable, additional
recommendations may be required prior to construction of the foundations.
Soil Classification: This soil was classified as a Silty Clay, with Sands, Gravels and small
Boulders (CL-ML) underthe Unified Classification System. The soil is slightly stiffto soft and of low density.
The following laboratory tests were performed on representative soil samples to determine their relative
engineering properties.
ASTM D-2487 Soil Classification
ASTM D-2435 One Dimensional Consolidation
ASTM D-2g37 In-Place Soil Density ln
ASTM D-2216 Moisture Content of Soil .:
Tests were performed in accordance with test methods of the American Society for Testing and Materiat, o. ]f
other accepted standards. The results of our laboratory tests are included in this report. The in-place soil f,
density, tnoi.tut" content, and the field observations are presented on the attached exploration pit logs. S
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Mr. Tyler DiDonato, Shining Light Services
Subsurface Soils Exploration, 236Limberpine Circle, Battlement Mesa, Colorado
March 27,2024 Page2
The moisture content varied ftom 6.20/o to 7 .60/o, indicating a relatively dry to slightly moist soil. This soil is
slightly plastic and some strata are sensitive to changes in moisture content. If this soil is found in a relatively
dry, slightly compact condition, it may undergo slight expansion with the entry of small amounts of moisture,
but it will undergo collapse/long-term consolidation upon the addition of larger amounts of moisture. This
material will consolidate/collapse upon saturation or excessive loading. One dimensional consolidation tests
using the consolidation apparatus ASTM D-2435 were performed on relatively undisturbed samples of the soil.
Upon test saturation, a slight collapse of 0.94% was measured, with 0.14% consolidation occurring at an applied
load of 1025 psf. Upon further test loading, 2.28Yo consolidation occurred at an applied load of 2050 psf. If
these soils are overexcavated, water soaked, and reworked according to recommendations contained in this
report, this collapse potential should be mitigated . The maximum allowable bearing forthis reworked
soil was to be 00 psf, with 350 mrnlmum portion
soil ln
Man-made Fill: The building excavation is within an area ofthin, uncontrolled, man-made fill
placed as overlot grading during the subdivision's development phase. The man-made fills are thin and it is
believed the fills will be penetrated by the foundation subgrade soil reworking process.
Soil Moisture Conditions: No free water was encountered during excavation on this site. In our
opinion, the true free water surface is fairly deep in this area and hence should not affect construction. Seepage
moisture may affect construction if surface drainage is not properly controlled.
Foundation Type Recommended: Assuming that some amount of differential movement can be
tolerated, then a conventional shallow foundation system, underlain by structural fill and placed in accordance
with the recommendations contained in this report, may be utilized. The foundation would consist ofcontinuous
spread footings beneath all bearing walls and isolated spread footings beneath all columns and other points of
concentrated load. Such a shallow foundation system,structural fill,may
be of psf maximum and 350 mlnlmum.
Recommendations pertaining to balancing, reinforcing, drainage, and inspection are considered extremely
important and must be followed. Contact stresses beneath all continuous walls should be balanced to within
+ 350 psf at all points. Isolated interior column footings should be designed for contact stresses of about 150
psf less than the average used to balance the continuous walls. The criteria for balancing will depend somewhat
on the nature of the structure. Single story slab-on-grade structures may be balanced on the basis of dead load
only. Multi-story structures may be balanced on the basis of dead load plus one-half live load for up to three
stories.
A properly designed shallow foundation system of the type, based upon the recommendations provided in this
report, has been prepared by Grand Junction Lincoln DeVore. A copy of that design has been provided to the
contractor/client. The foundation system must be constructed in sffict compliance with our plans and
specifications, with no alterations or deviations allowed unless prior approval is first obtained from this office.
Structural FilVSoil Improvement: For use in conjunction with a shallow foundation
system, a structural fill is recommended to replace the Upper Variable Density Soils. This structural fill may
Mr. Tyler DiDonato, Shining Light Services
Subsurface Soils Exploration, 236 Limberpine Circle, Battlement Mesa" Colorado
March 27,2024 Page 3
be placed in conjunction with structural fill beneath concrete slabs on grade. The existing soils should be
removed to a depth of I to l-1/2 feet below the proposed boffom footing elevation, at the direction of the
Geotechnical Engineer. The excavationffill width is to extend at least 20 inches from the interior and exterior
of the proposedfoundationwsll or bearingpad in contactwiththefill. Once it is feltthatadequate soil removal
has been achieved, it is recommended that the excavation be closely examined by a representative of Grand
Junction Lincoln-DeVore to ensure that an adequate over excavation depth has indeed occurred and that the
exposed soils are suitable to support the proposed structural man-made fill.
At the specific direction of the geotechnical engineer, it may be appropriate to extensively water soak the
overexcavated portion of the site for a minimum of I day prior to the installation of any required perimeter drain
and structural fill. The purpose ofthis wetting or soaking is to allow some immediate relief from minor swelling
pressures in any slightly expansive soil strata and to aid in compaction and stabilization of metastable (slightly
collapsible) strata in theses soils. The water soaking must penetrate to a minimum depth of 2 feet below the
overexcavated subgrade elevation and will probably require multiple water applications. For preliminary
estimates, Grand Junction Lincoln DeVore, Inc. assumes 1000 gallons/(000sq.ft. Of excavotion to be soaked
/foot of required water penetration This wetting or soaking must be controlled and must not be allowed to
adversely affect nearby strucfures.
After any required soaking has been accomplished, the subgrade soils are to be mechanically compacted to a
minimum of 86% of the soils maximum Modified Proctor dry density (ASTM D-1557) for a depth of at least
6 inches.
Once this examination has been completed, it is recommended that a coarse-grained, non-expansive, non-free
draining man-made structural fill be imported to the site and placed on the properly prepared subgrade soils.
Non-Expansive, Native soils may be utilized as structural fill, if specifically approved by the Geotechnical
Engineer. The Structural Fill should be placed as structural fill in lifts not to exceed 6 inches after compaction.
The upper 6u to l2"(minimum) of the fill is to be a sandy gravel (minus 3/4" & GI\{/GW) or a gravelly sand
(minus 3/4" &, SM/SW). The structural fill should be placed in the overexcavated portion ofthis site in lifts not
to exceed 6 inches after compaction. A minimum of 90Yo of the soils maximum Modified Proctor dry density
(ASTM D-I557) must be maintained during the soil placement. These soils should be placed at a moisture
content conducive to the required compaction (usually Proctor optimum moisture content + 2%).
The Structural Fill must be brought to the required density by mechanical means. No soaking, jetting or puddling
techniques of any type should be used in placement of fill on this site. To confirm the quality of the compacted
fill product, it is recommended that surface density tests be taken at maximum 2 foot vertical intervals.
It is recommended that any required perimeter drain be placed in the exterior portion of the structural fill, at the
base of the more perrneable portion of the fill, in order to prevent or at least minimize the collection of water
in the soils and fill beneath the structure.
Voids Beneath Foundation Walls:Voids are not required for this foundation design.
Reinforcing: All foundation stemwalls should be designed as "grade beams" capable of spanning
at least 12 feet. Where the foundation stemwalls are relatively shallow in height, vertical reinforcing will not
be necessary. However, in walls retaining soil in excess of 4 feet in height, vertical reinforcing may be
Mr. Tyler DiDonato, Shining Light Services
Subsurface Soils Explorationo 236Limberpine Circle, Battlement Mesa, Colorado
March 27,2024 Page 4
necessary to resist the lateral pressures (resffained case) of the soils along the wall exterior. To aid in designing
such vertical reinforcing, an equivalent fluid pressure (EFP) on the order of 55 pcf would be appropriate for the
native soils.
The foundation shall be reinforced as shown on the foundation design. No changes shall be made to this
placement of reinforcing without written approval of the design engineer or architect.
Floor Slabs: Non-structural floor slabs on grade, if any, should be positively separated from all
structural portions of this building and allowed to float freely. Frequent scoring (control joints) of the slabs
should be provided to allow for possible shrinkage cracking of the slab. These control joints should be placed
to provide maximum slab areas of approximately 200 to 360 square feet. Any man-made fill placed below floor
slabs on grade should be compacted to aminimum of9Oolo of its maximum modified proctor dry density(ASTM
D-1557). These soils should be placed at a moisture content conducive to the required compaction (usually
proctor optimum moisture content + 2%).
Drainage and Grading: Adequate site drainage should be provided in the foundation area both
during and after construction to prevent the ponding of water and the wetting or saturation of the subsurface
soils. We recommend that the ground surface around the structure be graded so that surface water will be carried
quickly away from the building. The minimum gradient within 10 feet of the building will depend on surface
landscaping. We recommend that paved areas maintain a minimum gradient of 2% and that landscaped areas
maintain a minimum gradient of 8To. It is further recommended that roof drain downspouts be carried at least
5 feet beyond all backfilled areas and discharge a minimum of 10 feet away from the structure. Proper
discharge of roof drain downspouts may require the use of subsurface piping in some areas. Under no
circumstances should a "dry well discharge" be used on this site unless specifically sited by a geotechnical
engineer. Planters, if any, should be constructed so that moisture is not allowed to seep into foundation areas
or beneath slabs or pavements.
The existing drainage on the site must either be maintained carefully or improved. We recommend that water
be drained away from structures as rapidly as possible and not be allowed to stand or pond within 15 feet of the
building or foundation. We recommend that water removed from one building not be directed onto the backfill
areas of adjacent buildings.
Should an automatic lawn irrigation system be used on this site, we recommend that the sprinkler heads,
irrigation piping, and valves be installed no less than 5 feet from the building. In addition, these heads should
be adjusted so that spray from the system does not fall onto the walls of the building, and that such water does
not excessively wet the backfill soils.
It is recommended that lawn and landscaping irrigation be reasonably limited so as to prevent undesirable
saturation of subsurface soils or backfilled areas. Several methods of irrigation water control are possible, to
include, but not be limited to:
. Metering the irrigation water.
. Sizing the irrigation distribution service piping to limit onsite water usage.
. Encourage efficient landscaping practices.
. Enforcing reasonable limits on the size of high water usage landscaping within 5 feet of the building
Mr. Tyler DiDonato, Shining Light Services
Subsurface Soils Exploration, 236Limberpine Circle, Battlement Mesa, Colorado
March 27,2024 Page 5
or foundation.
Incorporating "xeriscaping" landscaping and irrigation techniques.
A plastic membrane placed on any crawlspace ground surfaces may retain/trap excessive amounts of water
beneath the membrane. If future moisture problems develop or are anticipated, the foundation design engineer
or the geotechnical engineer may require that the membrane be partially or completely removed from the
crawlspace area.
Provided that all recommendations found herein pertaining to site surface drainage, grading, and soil compaction
are closely followed, a perimeter foundation drain would not be required. For fully finished basements, however,
the use of a perimeter foundation drain would significantly reduce potential moisture related problems which
can arise from subsequent area development.
Backfill: To reduce settlement and aid in keeping water from reaching beneath this building, all
backfill aroundthis building should be mechanically compactedto aminimum of90o/o of its maximum modified
proctor dry density (ASTM D-1557). The only exception to this would be the components of the perimeter
foundation draino if any. All backfill should be composed of the native soils and should not be placed by
soaking, jetting or puddling. All backfill placed in utility trenches around this structure or below foundation
walls should be mechanically compacted to a minimum of 90% of its maximum modified proctor dry density
(ASTM D-1557). These soils should be placed at a moisture content conducive to the required compaction
(usually proctor optimum content + 2%).
Cement Tvpe: Type II, Type I-II, or Type II-V cement is recommended for all concrete in contact
with the soils on this site. Calcium chloride should not be added to a Type II, Type I-II, or Type II-V cement
under any circumstances.
Remarks: We recommend that the bottoms of all foundation components rest a minimum of
l-Il2 feetbelow finished grade or as required by the local building codes. Foundation components must not
be placed on frozen soils.
Senate Bill l3 (CRS 6-6.5-101) Discussion: This particular residence is being constructed on
foundation soils which overlie or are in near proximity to soils that may possess a slight potential for
expansion." Therefore, in compliance with Senate Bill 13 (CRS 6-6.5-101), we recommend that you provide
the owner with the following:
l) A copy of this summary report of our soil analysis and recommendations.
2) A copy of Special Publication 43,"A Guide to Swelling Soils for Colorado Homebuyers and
Homeowners." This publication is available through the Colorado Geological Survey, 1313 Sherman
St., Room 715, Denver, CO, 80203, or phone (303) 866-3340.
Limitations: This report is issued with the understanding that it is the responsibility of the owner
or his representative to ensure that the information and recommendations contained herein are brought to the
attention of the architect and engineer for the project and are incorporated into the plans. In addition, it is his
Mr. Tyler DiDonato, Shining Light Services
Subsurface Soils Exploration, 236 Limberpine Circle, Battlement Mesa, Colorado
March 27,2024 Page 6
responsibility that the necessary steps are taken to see that the contractor and his subcontractors carry out these
recommendations during construction. The findings of this report are valid as of the present date. However,
changes in the conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in acceptable or appropriate
standards may occur or may result from legislation or the broadening of engineering knowledge. Accordingly,
the findings of this report may be invalid, wholly or partially, by changes outside our control. Therefore, this
report is subject to review and should not be relied upon after a period of3 years.
The recommendations of this report pertain only to the site investigated and are based on the assumption that
the soil conditions do not deviate from those described in this report. If any variations or undesirable conditions
are encountered during construction or the proposed construction will differ from that planned on the day of this
report, Grand Junction Lincoln DeVore should be notified so that supplemental recommendations can be
provided, if appropriate.
Grand Junction Lincoln DeVore makes no warranty, either expressed or implied, as to the findings,
recommendations, specifications or professional advice, except that they were prepared in accordance with
generally accepted professional engineering practices in the field ofgeotechnical engineering.
Respectfu lly submitted,
GRAND JUNCTION .)',
LINCOLN DeVORE, INC. '
''.3 :.1'l :
by: Edward M. Morris, P.E.
Principal Engineer
GJLD Job No. 95824-GJ
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LINCOLN-DeV0RE, Inc.
CEOTECHI{TCAI. ENGINEERS*GEOIOGSITS