HomeMy WebLinkAboutSoils Report 10.13.2020Engineering, Inc.
CIVIL/GEOTECHNICAL
SOIL AND FOUNDATION INVESTIGATION
FOR A
PROPOSED KATHA & RON RESIDENCE
LOT 11, THE RANCH AT COULTER CREEK PUD
CATTLE CREEK RIDGE ROAD
GARFIELD COUNTY, COLORADO
PROJECT NO. 20-3454
OCTOBER 13, 2020
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PREPARED FOR:
WHIT WHITAKER
WRW LOGWORKS, LLC
1009 CATTLE CREEK RIDGE ROAD
CARBONDALE, CO 81623
P.O. Box 724, Eagle, CO 81631 Tel. (970) 390-0307 www.LKPEngineering.com
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 5
RETAINING WALLS 5
UNDERDRAIN SYSTEM 6
SITE GRADING AND DRAINAGE 6
LAWN IRRIGATION 7
LIMITATION 7
FIGURES
LOCATION SKETCH DRAWING NO. 1
SUBSURFACE EXPLORATION LOGS FIGURE NO's 1-2
SWELL -CONSOLIDATION FIGURE NO. 3
PERIMETER DRAIN DETAIL FIGURE NO. 4
LKP Engineering, Inc.
EXECUTIVE SUMMARY
The proposed residence should be supported with
conventional type spread footings, designed for an allowable soil
bearing pressure of 2000 psf. They should construct the footings
on the undisturbed sandy clay with sparse cobbles and/or silty -
clayey to sandy gravel. See Foundation Recommendations.
SCOPE OF STUDY
This report presents the results of a subsurface Soil and Foundation Investigation for a
proposed residence to be constructed on Lot 11, The Ranch at Coulter Creek PUD, on Cattle
Creek Ridge Road (address not assigned yet), Garfield County, Carbondale, 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
Lot 11, The Ranch at Coulter Creek PUD is 6.396 acres (according to the survey by
Rodney P. Kiser, PLS, emailed by Whit) and it is located at the west side of Cattle Creek Ridge
Road and about 1500 feet south from the west gate of the subdivision off of Red Canyon Road,
Carbondale, Garfield County, Colorado. Vegetation within the proposed building site consisted
of grass. The topography within the selected building area (where the two test pits had been dug
prior to our site visit) was moderate with average slopes from about 6 percent. Drainage is to the
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southwest. Cattle Creek Ridge Road runs along the eastern property line. Lot 10 is to the north
and Lot 12 is to the south. To the west is BLM land. On lot 12 there was existing residence,
while Lot 10 to the north and the subject lot were vacant.
PROPOSED CONSTRUCTION
We understand that the proposed residence will be two story, wood frame construction
without a basement, on a concrete foundation, with an attached garage. We anticipate loads to be
light, typical of residential construction.
If the finalized plans differ significantly from the above understanding, they should
notify us to reevaluate the recommendations of this report.
FIELD INVESTIGATION
The field investigation, conducted on October 2, 2020, consisted of logging and sampling
two test pits. Approximate locations of the test pits 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. We understand that
your excavator dug the test pits prior to our site visit.
SUBSURFACE SOIL AND GROUNDWATER CONDITION
The soil profiles encountered in the two test pits were fairly uniform. Test Pit No. 1 had
about two feet of topsoil over blocky clay over whitish -tan, calcareous, gypsiferous, sandy clay
with sparse cobbles to about 4.5 feet over calcareous clay to about eight feet. At the bottom of
the hole was clayey, sandy gravel. Test Pit No. 2 also had about 2 feet of topsoil over
interbedded layers of calcareous, clay and silty -clayey, sandy gravel to the maximum depth
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explored of 9 feet. Ground water or bedrock were not encountered in the test pits. We sampled
the soil in the test pits at random intervals. The samples were tested for natural moisture content,
swell -consolidation potential, and natural dry density. The test results are shown on Figure 3.
The moisture content increased with depth, with about 10 percent at 4 feet and 15 percent at 8
feet. High moisture content can mask possible swelling potential of the clay soils. Swelling soils
with low expansion potential were encountered in the sample at 4 feet and not in the sample at 8
feet. Swelling soils were also encountered on the surrounding lots in previous studies.
FOUNDATION RECOMMENDATIONS
The proposed residence should be supported with conventional type spread footings,
designed for an allowable soil bearing pressure of 2000 psf. They should construct the footings
on the undisturbed sandy clay with sparse cobbles and/or silty -clayey to sandy gravel, below the
topsoil and blocky clay.
The soil samples from test pit 1 at 8 feet, had moisture content of 15.2 percent. The high
moisture content might mask possible swelling potential of the clay soils. Swelling soils were
encountered on the surrounding lots. The completed foundation excavation should be observed
and tested by the undersigned engineer to verify that the soil conditions encountered during
construction are as anticipated in this report. If swelling soils with high potential for expansion
are encountered during the open hole observation, the foundation will have to be redesigned to
account for the soil conditions prevailing in the foundation excavation.
We recommend a minimum width of 16 inches for the continuous footings and 2 feet for
the isolated footing pads. Continuous foundation walls should be reinforced top and bottom to
span an unsupported length of at least 10 feet.
The proposed foundation should be set at a minimum depth of four feet below the
finished grade or at the minimum depth required by the local building code. The foundation
excavation should be free from excavation spoils, frost, organics and standing water. We
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recommend proof -rolling of the foundation excavation. Soft spots detected during the proof -
rolling, should be removed by overexcavation. Any overexcavation within the proposed
foundation should be backfilled, in 8 inches loose level lifts and compacted to 100% 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). A structural fill, placed under footings
should be tested by a qualified professional.
SLAB CONSTRUCTION
The natural on -site soils, exclusive of topsoil and organics, are suitable to support lightly
loaded slab -on -grade construction. The subgrade for the slab -on -grade construction should be
proof compacted to detect and remove soft spots. They should backfill overexcavated soft spots
and other underslab fill with the on -site soil, free from topsoil and organics, or other suitable
material, compacted to a minimum of 95 percent of the maximum standard Proctor density
(ASTM D-698). Suitable material should be free from topsoil, organics and rock fragments
greater than 3 inches.
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.
They should reinforce the concrete slab -on -grade and score control joints according to
the American Concrete Institute requirements and per the recommendations of the 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 without causing
damage.
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 "at -rest" condition.
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Laterally unrestrained structures, retaining the on -site earth, should be designed to resist an
equivalent fluid density of 40 pcf for the "active" case.
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. They should try to prevent the buildup
of hydrostatic pressure behind the retaining wall.
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 0.5. Undisturbed soil or a structural fill compacted to 100 percent of the
maximum dry density and within 2 percent of the optimum moisture content will be used to
resist lateral loads at the sides of the footings.
UNDERDRAIN SYSTEM
To reduce the risk of surface water infiltrating the foundation subsoil, we recommend
installation of a foundation perimeter drain (see Figure No. 4). The foundation perimeter drain
should consist of a 4-inch diameter, perforated pipe, sloped to a suitable gravity outlet, at a 1/4
inch per foot for flexible or at a 1/8 of an inch for rigid pipe. 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 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.
SITE GRADING AND DRAINAGE
The following recommendations are general. Exterior backfill should be compacted at or
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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. They should use mechanical methods of compaction. Do not
puddle the foundation excavation.
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 1 foot of relatively impervious fill to reduce the potential of
surface water infiltrating the foundation subsoils.
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 next to the building. The installation of the sprinkler heads should insure that
the spray from the heads will not fall within 10 feet of foundation walls, porches or patio 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 type of
soil testing was selected by the owner and general contractor as the preferred method for the soil
and foundation investigation over a soil and foundation investigation with a drill rig. There is no
other warranty either expressed or implied.
The findings and recommendations of this report are based on field exploration,
laboratory testing of samples obtained at the specific locations shown on the Location Sketch,
LKP Engineering, Inc.
Drawing No.1 and on assumptions stated in the report. Soil conditions at other locations 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.
This report has been prepared for the exclusive use of Whit Whitaker, for the specific
application to the proposed Katha and Ron Residence on Lot 11, The Ranch at Coulter Creek
PUD, Cattle Creek Ridge Road, Carbondale, Garfield County, Colorado.
Sincerely,
LKP ENGINEERING, INC.
Luiza Petrovska, PE
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CIVIL/GEOTECHNICAL
Engineering, Inc.
P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www.LKPEngineering.com
LOCATION SKETCH
LOT 11, RANCH AT COULTER CREEK
CATTLE CREEK RIDGE ROAD
GARFIELD COUNTY, COLORADO
PROJECT NO..
20-3454
SCALE:
-1"=80'
DRAWING NO.:
1
DATE OBSERVED: OCTOBER 2, 2020 Test Pit # 1
ELEVATION: ,- 7409
DEPTH
FEET
S
Y
M
B
0
L
S
A
M
P
L
E
DESCRIPTION OF MATERIAL
AND SAMPLE LOCATION
LABORATORY
TEST RESULTS
REMARKS
5
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❑
❑
Topsoil
Blocky caly
Whitish —tan, calcareous, gypsiferous,
sandy clay with sparse cobbles
Brown, calcareous, silty clay
Clayey, sandy gravel at the bottom
DD= 99.3 pcf
MC= 10.0 2;
DD= 96.0 pcf
MC= 15.2 %
10
Bottom Of Test Pit at 8.3 feet
No Ground Water
Encountered
15
20
LEGEND:
❑ — 2—inch 0.D. California Liner Sample
■ — Bulk Sample
DD — Natural Dry Density (pcf)
MC — Natural Moisture Content (Z)
—200 — Percent Passing No. 200 Sieve
LL — Liquid Limit
PI — Plasticity Index
GW — Ground water
LKP ENGINEERING, INC.
SUBSURFACE EXPLORATION LOG
PROJECT NO.:
20-3454
FIGURE NO.:
1
DATE OBSERVED: OCTOBER 2, 2020 Test Pit # 2
ELEVATION: r-7403.5'
DEPTH
FEET
S
Y
M
B
0
L
S
A
M
P
L
E
DESCRIPTION OF MATERIAL
AND SAMPLE LOCATION
LABORATORY
TEST RESULTS
REMARKS
5
Or
r
Topsoil, silty with fine roots over
blocky clay
Whitish, calcareous, silty —clayey, sandy
gravel with cobbles
calcareous clay
Sandy—silty gravel
calcareous clay
Sandy —silty gravel
,
//Brown,
//
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10
Bottom Of Test Pit at 9 feet
No Ground Water
Encountered
15
20
LEGEND:
❑ — 2—inch 0.D. California Liner Sample
■ — Bulk Sample
DD — Natural Dry Density (pcf)
MC — Natural Moisture Content (. )
—200 — Percent Passing No. 200 Sieve
LL — Liquid Limit
PI — Plasticity Index
GW — Ground water
LKP ENGINEERING, INC.
SUBSURFACE EXPLORATION LOG
PROJECT NO.:
20-3454
FIGURE NO.:
2
0
o.
Compression
Compression
3
2
1
0
— 1
—2
— 3
— 4
3
2
1
0
— 1
— 2
— 3
— 4
EXPANSION
CONSTANT
WHEN
PRESSURE
WETTED
UNDER
OF 1000
PSF
0.1 1 0 10 100
APPLIED PRESSURE — ksf
Sample of: Tan, sandy —silty, calcareous Clay From: Test Pit 1 at 4 feet
Natural Dry Unit Weight = 99.3 pcf
Natural Moisture Con ten t = 10.0 percent 0.4% SWELL AT 2.2 KSF
OMPRESSION
CONSTANT
PRESSURE
WHEN
WETTED
OF 1000
UNDER
PSF
0.1 1 0 10 100
APPLIED PRESSURE — ksf
Sample of: Tan, calcareous, silty clay From: Test Pit 1 at 8 feet
Natural Dry Unit Weight = 96.0 pcf
Natural Moisture Con ten t = 15.2 percen t
LKP Engineering, Inc.
PROJECT NO.:
20-3454
Swell — Consolidation Test Results
FIGURE NO.:
3
1/77
D j D D'
°
D D
SLOPE AWAY FROM BUILDING
OVER BACKFILL WITH A MINIMUM
OF ONE FOOT OF RELATIVELY
IMPERVIOUS SOIL
D FOOTING
°
30 MIL MINIMUM THICKNESS
PLASTIC LINER, GLUED TO TH
FOUNDATION WALL
GRANULAR FILL
\
0 0
0. .0. CI)
�\ �/\ INUS 3/4-INCH DIAMETER, COARSE,
\ CLEAN CRUSH ROCK
ILTER FABRIC (MIRAFI
140N OR EQUIVALENT)
-INCH DIAMETER PERFORATED PIPE SLOPED TO
A DAYLIGHT LOCATION AWAY FROM THE
FOUNDATION AT 1/4-INCH PER FOOT FOR
FLEXIBLE AND 1/8-INCH MINIMUM FOR RIGID PIPE
CIVIL/GEOTECHNICAL
Engineering, Inc.
PERIMETER DRAIN
PROJECT Na:
LOT 11, RANCH AT COULTER CREEK 20-3454
GARFIELD COUNTY, COLORADO
CATTLE CREEK RIDGE ROAD SCALE:
N.T.S.
P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www.lkpengineering.com
FIGURE NO.
4
