HomeMy WebLinkAboutSoils Report 11.15.2019Engineering, Inc.
CMYJGEOTECHNICAL
SOIL AND FOUNDATION INVESTIGATION
FOR A
PROPOSED RESIDENCE
LOT 8, THE RANCH AT COULTER CREEK PUD
FISHER CREEK LANE
GARFIELD COUNTY, COLORADO
PROJECT NO. 19-3379
NOVEMBER 15, 2019
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PREPARED FOR:
HARRY & KATHRYN PEISACH
510 OREGON TRAIL
ASPEN, CO 81611
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 6
UNDERDRAIN SYSTEM 6
SITE GRADING AND DRAINAGE 7
LAWN IRRIGATION 7
LIMITATION 8
FIGURES
LOCATION SKETCH DRAWING NO. 1
SUBSURFACE EXPLORATION LOGS FIGURE NO's 1-2
SWELL -CONSOLIDATION FIGURE NO's 3-4
GRAIN -SIZE DISTRIBUTION FIGURE NO's 5
PERIMETER DRAIN DETAIL FIGURE NO. 6
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 clay with 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 8, The Ranch at Coulter Creek PUD, at Fisher
Creek Lane (address number 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 8, The Ranch at Coulter Creek PUD is 4.396 acres (according to the survey, emailed
by your builder, Whit Whitaker, WRW Logworks, LLC, and the Garfield County GIS) and it is
located in the northwest portion of the subdivision off of Fisher Creek Lane, of off Cattle Creek
Ridge Road, just south from the upper gate in the subdivision, Garfield County, Colorado. There
was a long driveway starting on the west side from the Fisher Creek Lane cul-de-sac and
continuing to the west property line of Lot 8. The building site was located near the top of a
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drainageway. The vegetation within the proposed building site consisted of tall grass for the
most part with scrub oak trees on the higher ground. The topography within the selected building
area (where the two test pits had been dug) was flat to moderate with average slopes from about
4 to 6 percent. According to the topographical survey, the site is sloping from the west and east
toward the building site with the drainage swale being between the two test pits and sloping
(draining) to the east and southeast. Along the south property line is BLM land. To the west and
northwest is Ranch at Coulter Creek PUD Private Open Space. To the northeast is Lot 9 and to
the east is Lot 10. Lot 8 and the adjoining lots were vacant.
PROPOSED CONSTRUCTION
We have assumed 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 November 11, 2019, consisted of logging and
sampling two test pits. The test pits were dug by Whit Whitaker's excavators. Approximate
locations of the test pits (as marked by Whit) 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.
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 and blocky clay over brown, calcareous, sandy clay with basalt rocks to
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about 4 feet over multi -colored, calcareous, gypsiferous silt and clay with pockets of gravel to
about 7 feet over grayish layer of silty to clayey, gravelly sand to the maximum depth explored
of 8 feet. Test Pit No. 2 had about 3 feet of topsoil and blocky clay over brown, calcareous, clay
with gravel size volcanic rocks over light to reddish brown, calcareous, sandy clay to the
maximum depth explored of 8 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, grain -size distribution, swell -consolidation potential, and natural dry density.
The test results are shown on Figure numbers 3 through 5. The clay soil samples had high
moisture content of 17.1 and 22.4 percent. The high moisture content might mask possible high
swelling potential of the clay soils. The soil sample from test pit 2 at 8 feet exhibited a low
swelling potential. Swelling soils with high expansion potential were encountered on the
surrounding lots. Also, the high moisture content of the clayey soils might be the result of
surface water penetrating the subgrade soils at a higher rate due to its location in the
drainageway. It recommended to consider moving the proposed building site away from the
middle of the drainage way so that the proposed foundation is not subjected to fluctuating
moisture levels that may cause movement and structural damage at a later date.
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 clay with gravel, below the topsoil and blocky clay.
The clay soil samples had high moisture content of 17.1 and 22.4 percent. The high
moisture content might mask possible high swelling potential of the clay soils. The soil sample
from test pit 2 at 8 feet exhibited a low swelling potential. Swelling soils with high expansion
potential were encountered on the surrounding lots. The completed foundation excavation must
be observed and tested by the undersigned engineer to verb that the soil conditions encountered
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during construction are as anticipated in this report. If swelling soils with high expansion
potential 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
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
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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 60pcf for an "at -rest" condition.
Laterally unrestrained structures, retaining the on -site earth, should be designed to resist an
equivalent fluid density of 40pcf 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 360psf 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
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installation of a foundation perimeter drain (see Figure No. 6). 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
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
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sprinkler systems next 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 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,
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 Harry & Kathryn Peisach, for the
specific application to their proposed residence on Lot 8, The Ranch at Coulter Creek PUD, at
Fisher Creek Lane, Carbondale, Garfield County, Colorado.
Sincerely,
LKP ENGINEERING, INC.
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Luiza Petrovska, PE
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RIVEWAY
FROM FISHER
CREEK LANE
NOTE: THE LOCATION OF THE TEST PITS IS
APPROXIMATE. IT IS NOT BASED ON A SURVEY.
CIVIL/GEOTECHNICAL
LKP Engineering, Inc.
rIE P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www.LKPEngineering.com
LOCATION SKETCH
LOT 8, THE RANCH AT COULTER CREEK
FISHER LANE,
Account: R041266
Parcel: 239301401008
GARFIELD COUNTY, COLORADO
PROJECT NO.:
19-3379
SCALE
--1"=80'
DRAWING NO.:
1
DATE OBSERVED: NOVEMBER 11, 2019 Test Pit # 1
ELEVATION:
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�'
/11
Topsoil, silty with fine roots over
blocky clay
r
❑
Brown,calcareous sandy clay with basalt rocks,
DD= 91.4 pcf
MC= 12.6 Z
J
j,
❑
Multi—colored, calcareous, gypsiferous silt
and clay with pockets of gravel
DD= 82.0 pcf
MC= 22.4 Z
10
■
Grayish, silty —clayey, gravelly sand
MC=12.4%
—200=10.69
Bottom Of Test Pit at 8 feet
No Ground Water
Encountered
15
20
LEGEND:
o - 2—inch O.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.:
19-3379
FIGURE NO.:
1
DATE OBSERVED: NOVEMBER 11, 2019 Test Pit # 2
ELEVATION:
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
Topsoil, silty with fine roots over
blocky clay
; f
V*
Brown, hard, clay with basalt rocks,
calcareous
10
l`•"!
/
/
///
//
❑
Light brown to reddish, sandy clay,
calcareous
DD= 108.3 pcf
MC= 17.1 Z
Bottom Of Test Pit at 8 feet
No Ground Water
Encountered
15
20
LEGEND:
❑ — 2—inch O.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.:
19-3379
FIGURE NO.:
2
0
Compression
1
0
— 1
—2
— 3
— 4
—5
— 6
1
0
o • —1
6
a
—2
Compression
— 3
— 4
— 5
— 6
0.1
Sample
Natural
Natural
1 0 10
APPLIED PRESSURE — ksf
Pit
100
of. Brown, sandy clay with basalt rocks
Dry Unit Weight = 91.4 pcf
Moisture Content = 12.6 percent
From: Test
1 at 3 feet
OMPRESSION
CONSTANT
PRESSURE
WHEN
WETTED UNDER
OF 1000
PSF
0.1 1 0 10 100
APPLIED PRESSURE — ksf
Sample of.• Multi —colored, calcareous, gypsiferous silt & clay From: Test Pit 1 at 5 feet
Natural Dry Unit Weight = 82.0 pcf
Natural Moisture Content = 22.4 percent
LKP Engineering, Inc.
PROJECT NO.:
19-3379
Swell — Consolidation Test Results
FIGURE NO.:
3
0
.63
Compression
1
0
— 1
—2
— 3
— 4
—5
— 6
EXPANSION
CONSTANT
WHEN
PRESSURE
WETTED
OF
UNDER
1000
PSF
0.1
1 0
10 100
APPLIED PRESSURE — ksf
Sample of:Reddish, calcareous, clay From: Test Pit No. 2 at 8 feet
Natural Dry Unit Weight = 108.3 pcf
Natural Moisture Content = 17.1 percent 0.3% SWELL AT 1.5 KSF
LKP Engineering, Inc.
Swell — Consolidation Test Results
PROJECT NO.:
19-3379
FIGURE NO.:
4
FROM: Test Pit 1 at 8 feet
U.S. STANDARD SIEVE OPENING IN INCHES U.S STANDARD SIEVE NUMBERS HYDROMETER
��� 6 4 3 2 1+a 1 .w va .w 3 4 6 810 1416 20 3040 50 70 100 140 200 n
Percent Coarser by Weight
o
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O
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to
O
O
d
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O
O
O
in
O
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O
O
10
0
O
0
0
to
O
Gravel: 30.6% Sand: 58.8.1% Fines: 10.6%
Moisture Content: 12.4% Description: Silty —clayey, gravelly Sand
Silt or Clay
pups
coarse medium fine
•
-
Gravel
coarse fine
-
N
-p
0
()
0o) co N 0 co in in
Percent Finer by Weight
LKP Engineering, Inc.
GRAIN —SIZE DISTRIBUTION
PROJECT NO.
19-3379
RGURE NO
5
A
D D
> A
.
Q D
AD
D D
AD
A D.
A
SLOPE AWAY FROM BUILDING
OVER BACKFILL WITH A MINIMUM
OF ONE FOOT OF RELATIVELY
IMPERVIOUS SOIL
t.. ' FOOTING
GRANULAR FILL
s
D G A
30 MIL MINIMUM THICKNESS,
PLASTIC LINER, GLUED TO TH
FOUNDATION WALL
•
ILTER FABRIC (MIRAFI
140N OR EQUIVALENT)
\\/\ %\\
INUS 3/4-INCH DIAMETER, COARSE,
CLEAN CRUSH ROCK
-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.
P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www.lkpengineering.com
PERIMETER DRAIN
LOT 8, THE RANCH AT COULTER CREEK PROJECT NO.:
19-3379
FISHER LANE,
Account: R041266 SCALE:
N.T.S.
Parcel: 239301401008 FIGURE NO.
GARFIELD COUNTY, COLORADO
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