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P.O. Box 724, Eagle, CO 81631 Tel (970) 390-0307 www.LKPEngineering.com
SOIL AND FOUNDATION INVESTIGATION
FOR THE
WHITAKER RESIDENCE
A PARCEL OF LAND IN SE1/4 SE1/4,
SECTION 6 T7S R87W 6TH PM
COUNTY PARCEL # 239106400146, CR 115
GARFIELD COUNTY, COLORADO
PROJECT NO. 21-3501
APRIL 13, 2021
PREPARED FOR:
WHIT WHITAKER
WRW LOGWORKS, LLC
1009 CATTLE CREEK RIDGE ROAD
CARBONDALE, CO 81623
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LKP Engineering, Inc.
TABLE OF CONTENTS
EXECUTIVE SUMMARY .............................................................................................................2 SCOPE OF STUDY .........................................................................................................................2 SITE DESCRIPTION ......................................................................................................................2 PROPOSED CONSTRUCTION .....................................................................................................3 FIELD INVESTIGATION ..............................................................................................................3 SUBSURFACE SOIL AND GROUNDWATER CONDITION .....................................................3 FOUNDATION RECOMMENDATIONS ......................................................................................4 SLAB CONSTRUCTION ...............................................................................................................4 RETAINING WALLS .....................................................................................................................5 UNDERDRAIN SYSTEM ..............................................................................................................5 SITE GRADING AND DRAINAGE ..............................................................................................6 LAWN IRRIGATION .....................................................................................................................6 LIMITATION ..................................................................................................................................7 FIGURES
LOCATION SKETCH …………………………………………………….. DRAWING NO. 1
SUBSURFACE EXPLORATION LOGS…………………………………..FIGURE NO=s 1 - 2
SWELL/CONSOLIDATION TEST RESULTS …………………………... FIGURE NO=S 3 - 5
PERIMETER DRAIN ………………………………………………………FIGURE NO. 6
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EXECUTIVE SUMMARY
The proposed residence should be supported
with conventional type spread footings, designed
for a maximum allowable soil bearing pressure
of 3000 psf and a minimum dead load of 1000
psf. They should construct the footings on the
undisturbed silty-sandy, clay. See Foundation
Recommendations.
SCOPE OF STUDY
This report presents the results of a subsurface Soil and Foundation Investigation for the
proposed Whitaker Residence to be constructed on A Parcel of Land in SE1/4 SE1/4, Section 6
T7S R87W 6th PM, County Parcel # 239106400146, CR 115, Garfield County, Colorado. The
purpose of the subsurface soil and foundation investigation was to determine the engineering
characteristics of the foundation soil and to provide recommendations for the foundation design,
grading, and drainage. Geologic hazard studies are outside of our scope of services.
SITE DESCRIPTION
The property is 40-acre parcel of land, on the south side of County Road 115, aka Red
Canyon Road, and it is about 1700 feet west from the intersection of Coulter Creek Road and
Red Canyon Road, Garfield County, Colorado. The topography of the lot within the building
site, where the test pits had been excavated is moderate. Drainage is to the east, towards Coulter
Creek. Vegetation on the lot consisted of a grass. To the north, west and south of the property is
The Ranch at Coulter Creek Subdivision. On the east side of the property is vacant land. The
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subject property is also vacant, except for a barn/garage structure near the entrance.
PROPOSED CONSTRUCTION
At the time of the soils and foundation investigation, there was no information available
about the proposed residence. We have assumed that the proposed residence will be two-stories,
wood frame constriction on a concrete foundation. The test pits had been excavated by your
excavator within your selected building site, prior to our site visit. Loads are anticipated to be
light, typical of residential construction.
If the finalized plans differ significantly from the above understanding, we should be
notified to reevaluate the recommendations of this report.
FIELD INVESTIGATION
The field investigation, conducted on April 9, 2021, consisted of logging and sampling
two test pits. Excavation of the test pits was done by you prior to our site visit. The test pits=
locations are shown on Drawing No. 1. We show the soil profile of the test pits on the
Subsurface Exploration Logs, Figure No=s 1 and 2. Soil samples for laboratory soil analysis and
observation were taken at selected intervals. Geologic hazard studies are outside of our scope of
services.
SUBSURFACE SOIL AND GROUNDWATER CONDITION
The soil profiles encountered in the two test pits were fairly uniform. Test Pit No. 1 had
about 2 feet of topsoil over another foot of blocky clay over brown calcareous clay over, sandy
clay with fine layers of silt, fine sand, and clay to the maximum depth explored of 9.5 feet. Test
Pit No. 2 also had about 2 feet of topsoil over another two feet of blocky clay over fine layers of
silt, fine sand, and clay to the maximum depth explored of 10 feet. Ground water was not
encountered in either test pit. We sampled the soil in the test pit at random intervals. The soil
samples were observed, logged, and tested for natural moisture content, natural dry density, and
swell-consolidation. The test results are shown on figures 3 through 5.
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FOUNDATION RECOMMENDATIONS
The on-site clayey soils showed low potential for expansion. The proposed residence
should be supported with conventional type spread footings or pads and grade beams, designed
for a maximum allowable soil bearing pressure of 3000 psf and a minimum dead load of 1000
psf. They should construct the footings on the undisturbed sandy, clayey to clayey-gravelly soils.
The undersigned engineer must observe the foundation excavation to verify that the soil
conditions are as anticipated from the two test pits. For a deep foundation system alternatives,
like straight shaft piers or micro piles, an additional soils and foundation with a drill rig will be
necessary.
Continuous foundation walls should be well reinforced, top and bottom, to span an
unsupported length of at least 10 feet. A minimum backfill cover as required by the local
building department should be provided for frost protection of the footing subsoils.
The foundation excavation should be free from excavation spoils, frost, organics and
standing water. Any overexcavation within the proposed foundation should be backfilled, in 8
inches loose, level lifts and compacted to 98% of the maximum dry density and within 2 percent
of the optimum moisture content as determined in a laboratory from a Standard Proctor test
(ASTM D-698). Structural fill, placed under footings, should be tested by a qualified
professional.
SLAB CONSTRUCTION
With lightly loaded concrete slabs, the swelling soils might cause structural damage. In
areas, such as a garage, where the possible movement of the slab can be tolerated and is
acceptable by the homeowner, concrete slab on grade can be constructed.
The concrete slab should be constructed over a 4-inch layer of clean gravel consisting of -
3/4 inch gravel with at least 50% retained on the No. 4 sieve and less than 3 percent passing the
No. 200 sieve. The concrete slab-on-grade should be reinforced and control joints scored
according to the American Concrete Institute requirements and per the recommendations of the
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designer to reduce damage due to shrinkage. The concrete slab should be separated from the
foundation walls and columns with expansion joints to allow for independent movement.
As a preferred alternative, to reduce the risk of heaving of the slab-on-grade, a minimum
of three feet of the underlaying swelling soils can be replaced with a non-swelling, structural fill
improved with Tensar, triaxial geogrid. The fill should be placed in thin lifts and compacted to
95 percent of the maximum Standard Proctor (ASTM D698) dry density and within 2 percent of
the optimum moisture content as tested.
In areas, other than the garage a structural floor over crawl space is recommended. The
crawl space must be vented according to the local building code requirements.
RETAINING WALLS
Foundation walls retaining earth and retaining structures that are laterally supported
should be designed to resist an equivalent fluid density of 60 pcf for an Aat-rest@ condition.
Laterally unrestrained structures retaining the on-site earth should be designed to resist an
equivalent fluid density of 40 pcf for the Aactive@ case.
Passive earth pressure of 360 psf can be used for the lateral pressure against the sides of
the footings. Resistance to sliding at the bottom of the footings can be calculated based on a
coefficient of friction of 0.45. Undisturbed soil or a structural, non-swelling fill compacted to
100 percent of the maximum dry density and within 2 percent of the optimum moisture content
shall be used to resist lateral loads at the sides of the footings.
The above design recommendations assume drained backfill conditions and a horizontal
backfill surface. Surcharge loading due to adjacent structures, weight of temporary stored
construction materials and equipment, inclined backfill and hydrostatic pressure due to undrained
backfill should be incorporated in the design. Every attempt should be made to prevent the
buildup of hydrostatic pressure behind the retaining wall.
UNDERDRAIN SYSTEM
To reduce the risk of surface water infiltrating the foundation subsoil, installation of a
foundation perimeter drain is recommended (see Figure No. 6). The foundation perimeter drain
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should consist of a 4-inch diameter perforated pipe sloped to a suitable gravity outlet, or to a
sump pump location. The drain should slope at 1/4 inch per foot if flexible or at 1/8 of an inch if
rigid pipe is used. The bottom of the trench adjacent to the footing should be lined with a
polyethylene moisture barrier glued to the foundation wall. The drain pipe should be placed over
the moisture barrier and covered with a minimum of 6 inches of -3/4 inch free-draining granular
material. Geotextile (Mirafi 140N or equivalent) should be used to cover the free-draining gravel
to prevent siltation and clogging of the drain. The backfill above the drain should be granular
material to within 2 feet of the ground surface to prevent a buildup of hydrostatic pressure. The
top one foot of the backfill material should consist of a relatively impervious fill. The backfill
should be sloping away from the building.
SITE GRADING AND DRAINAGE
The following recommendations are general in nature. The site surrounding the building
structure should slope away from the building in all directions. A minimum of 12 inches in the
first 10 feet is recommended in unpaved areas, and three inches in the first 10 feet in paved areas.
The top of the granular foundation backfill should be covered with a minimum of one foot of
relatively impervious fill to reduce the potential of surface water infiltrating the foundation
subsoils. Exterior backfill should be compacted at or near the optimum moisture content to at
least 95% of the maximum standard Proctor density under pavement, sidewalk and patio areas
and to at least 90% of the maximum standard Proctor density under landscaped areas.
Mechanical methods of compaction should be used. Do not puddle the foundation excavation.
Surface water naturally draining toward the proposed building site should be diverted
around and away from it by means of drainage swales or other approved methods. The roof
drains and downspouts should extend and discharge beyond the limits of the backfill.
LAWN IRRIGATION
It is not recommended to introduce excess water to the foundation soils by installing
sprinkler systems adjacent to the building. The installation of the sprinkler heads should ensure
that the spray from the heads will not fall within 10 feet of foundation walls, porches or patio
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slabs. Lawn irrigation must be controlled.
LIMITATION
This report has been prepared according to locally accepted professional Geotechnical
engineering standards for similar methods of testing and soil conditions at this time. The test pits
were dug with a backhoe by your excavator prior to our site visit. The findings and
recommendations of this report are based on field exploration, laboratory testing of samples
obtained at the specific locations and depths shown on the Location Sketch Figure No. 1 and on
assumptions stated in the report. Soil conditions at other locations and depths may vary, which
may not become evident until the foundation excavation is completed. If soil or water conditions
seem different from those described in this report, we should be contacted immediately to
reevaluate the recommendations of this report. We are not responsible for technical interpretation
by others of the data presented in this report. There is no other warranty either expressed or
implied.
This report has been prepared for the exclusive use of Whit Whitaker, for the specific
application of the Whitaker Residence to be constructed on a Parcel of Land in SE1/4 SE1/4,
Section 6 T7S R87W 6th PM, County Parcel # 239106400146, CR 115, Garfield County,
Colorado.
Sincerely,
LKP ENGINEERING, INC.
Luiza Petrovska, PE
J:\_WP X4-LKP\_2021\21-3501SWEL.DOCX
4/13/2021
TEST
PIT - 2
TEST
PIT - 1
WELL
W
CR 115
PROJECT NO.:
SCALE:
DRAWING NO.:
NOTE: AN APPROXIMATE SKETCH OF THE LOCATION OF
THE TEST PITS WAS PROVIDED BY THE CLIENT. IT IS
NOT BASED ON A SURVEY.
A PARCEL OF LAND IN SE14 SE14, SECTION 6
T7S R87W 6TH PM
COUNTY PARCEL # 239106400146, CR 115
GARFIELD COUNTY, COLORADO
21-3501
~ 1" = 300'
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