HomeMy WebLinkAboutSoils Report 07.13.2020Engineering, Inc.
CIVIL/GEOTECHNICAL
SOIL AND FOUNDATION INVESTIGATION
FOR THE
PROPOSED LLOYD GARAGE
PARCEL 6, WESTHOFF-BAKER RANCH
1108 COUNTY ROAD 110
GARFIELD COUNTY, COLORADO
PROJECT NO. 20-3416
JULY 13, 2020
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PREPARED FOR:
WHIT WHITAKER
WRW LOGWORKS, LLC
1009 CATTLE CREEK RANCH 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 4
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's 3-4
PERIMETER DRAIN DETAIL FIGURE NO. 5
P.O. Box 724, Eagle, CO 81631 Tel (970) 390-0307 www.LKPEnginecring.com
EXECUTIVE SUMMARY
The proposed garage 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 the
proposed Lloyd's Garage on Parcel 6, Westhoff -Baker Ranch, 1108 County Road 110, 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
Parcel 6, Westhoff -Baker Ranch is 35.597 acres (according to the Garfield County GIS),
at 1108 County Road 110, Garfield County, Colorado and it is located east of Colorado Highway
82 and about 9 miles south of Glenwood Springs, Garfield County, Colorado. The driveway
starts at Spring Valley Road (CR 110) goes south and splits into the driveway for the project and
to North Meadow View Lane. The building site for the proposed garage was located just north of
the existing residence and across from the driveway loop. The vegetation within the proposed
building site consisted of juniper trees and not much of ground cover. The topography within the
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selected building area (where the two test pits had been dug) was flat to moderate.
Topographical survey for the garage building site was not available. The surrounding properties
are large parcels, according to the Garfield County GIS Maps.
PROPOSED CONSTRUCTION
We understand that the proposed garage will be detached, single story structure, about 48
feet long and about 30 feet wide, wood frame construction without a basement, on a concrete
foundation. 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 July 9, 2020, consisted of logging and sampling
two test pits. The test pits were dug by Whit Whitaker's excavators. 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.
SUBSURFACE SOIL AND GROUNDWATER CONDITION
The soil profiles encountered in the two test pits were fairly uniform. Test Pit No. 1 had
blocky clay with subround cobbles over brown, calcareous, silty -sandy clay to about 4.5 feet
over silty -clayey, calcareous matrix, gravelly with basalt cobbles and boulders, to the maximum
depth explored of 8 feet. Test Pit No. 2 had a thin layer of man-made fill over blocky clay with
roots, over tan, silty -sandy, calcareous, clay over a layer of sandy gravelly clay over tan to
brown, silty -sandy, calcareous clay.to the maximum depth explored of 8.5 feet. Ground water or
bedrock were not encountered in the test pits. We sampled the soil in the test pits at random
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intervals. The samples were tested for natural moisture content, swell -consolidation, and natural
dry density. The test results are shown on Figure numbers 3 and 4. Geologic hazard studies are
outside of our scope of services.
FOUNDATION RECOMMENDATIONS
The proposed garage should be supported with conventional type spread footings,
designed for an allowable soil bearing pressure of 1500 psf. They should construct the footings
on the undisturbed clay with gravel, below the blocky clay and root layer.
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.
We recommend a minimum of 48 inches of backfill cover for frost protection of the
footing subsoils. The foundation excavation should be observed by the undersigned engineer to
verify that the soil conditions encountered during construction are as anticipated in this report.
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 on regular basis.
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
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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 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.
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UNDERDRAIN SYSTEM
To reduce the risk of surface water infiltrating the foundation subsoil, we recommend
installation of a foundation perimeter drain (see Figure No. 5). 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. Grading plan was not available at the time
of writing of this report. 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.
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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 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 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 Whit Whitaker, WRW Logworks,
LLC, for the specific application to the proposed Lloyd's Garage on Parcel 6, Westhoff -Baker
Ranch, 1108 County Road 110, Garfield County, Colorado.
Sincerely, �'' ..p REGj ,,,
LKP ENGINEERING, INC. :' ��y p�TRO ;fib
7110026
h'1211Ya-Cfe
Luiza Petrovska, PE
J:\ WP X4-LKP\ 2020\20-3416CLAY-SND-BASALT-PITS.DOCX
LKP Engineering, Inc.
NOTE: THE LOCATION OF THE TEST PITS IS
APPROXIMATE. IT IS NOT BASED ON A SURVEY,
CIVIL/GEOTECHNICAL
Engineering, Inc,
P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www,LKPEngineering.com
LOCATION SKETCH
1108 COUNTY ROAD 110
GARFIELD COUNTY PARCEL
#239308300007
GARFIELD COUNTY, COLORADO
PROJECT NO.:
20-3416
SCALE:
—1"=50'
DRAWING NO
1
DATE OBSERVED: JULY 9, 2020 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
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04
No Topsoil
Blocky clay with subround cobbles
Brown, silty -sandy calcareous clay
Whitish -tan, silty -clayey, calcareous
matrix, gravelly with basalt cobbles and
boulders
-
DD= 98.5 pcf
MC=9.1Z
No Ground Water
Encountered
5
—
—ti
Bottom Of Test Pit at 8 feet
—
10
15
20
-
LEGEND:
❑ — 2-inch O.D. California Liner Sample
■ - Bulk Sample
DD - Natural Dry Density (pcf)
MC - Natural Moisture Content (9)
-200 - Percent Passing No. 200 Sieve
LL - Liquid Limit
PI - Plasticity Index
GW - Ground water
LKP ENGINEERING, INC.
SUBSURFACE EXPLORATION LOG
PRO„ECT NO.:
20-3416
MORE NO.:
1
DATE OBSERVED: JULY 9, 2020 Test Pit # 2
ELEVATION:
DEPTH
FEET
S
Y
M
B
O
L
S
A
M
P
L
E
DESCRIPTION OF MATERIAL
AND SAMPLE LOCATION
LABORATORY
TEST RESULTS
REMARKS
97'
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❑
0
No Topsoil
Mon —made fill over blocky clay with
roots
Tan, silty —sandy calcareous clay
Sandy gravelly clay
Tan to brown, silty —sandy calcareous
clay
DD= 102.0 pcf
MC— 8.6 %
DD= 108.4 pcf
MC= 11.8 Z
—
—
5
Bottom of Test Pit at 8.5 feet
No Ground Water
Encountered
10
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.:
20-3416
FIGURE NO.:
2
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y
y
E
O
0
- 3
- 4
-6
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COMPRESSION WHEN WETTED UNDER
CONSTANT PRESSURE OF 1000 PSF
a
10
APPLIED PRESSURE - ksf
Sample of.• Tan, calcareous, silty Clay
Natural Dry Unit Weight = 98.5 pcf
Natural Moisture Content = 9.1 percent
10
100
From: Test Pit 1 at 4 feet
�_
-COMPRESSION
CONSTANT
PRESSURE
WHEN
WETTED UNDER
OF 1000
PSF
0.1 1 0 10 100
APPLIED PRESSURE - ksf
Sample of.• Silty -sandy Clay From: Test Pit 2 at 4 feet
Natural Dry Unit Weight = 102.0 pcf
Natural Moisture Content = 8.6 percent
LKP Engineering, Inc.
Swell — Consolidation Test Results
PROJECT Na:
20-3416
MORE NO:
3
1
0
.o
—1
63
a
W —2
—3
0
y —4
a
E
v —5
—6
L
irk-COMPRESSCONSTANTIONPRESSURE
■
WHEN
WETTEDOF1000 UNDERPSF
0.1 1 0 10 100
APPLIED PRESSURE — ksf
Sample of:Brown, calcareous, clay From: Test Pit No. 2 at 8 feet
Natural Dry Unit Weight = 108.4 pcf
Natural Moisture Content = 11.8 percent
LKP Engineering, Inc.
Swell — Consolidation Test Results
PR0.LCrNa:
20-3416
F7CURE NO.:
4
A
Da'
4
c a.
PaD
FOOTING
LOPE AWAY FROM BUILDING
OVER BACKFILL WITH A MINIMUM
OF ONE FOOT OF RELATIVELY
IMPERVIOUS SOIL
GRANULAR FILL
A
n
30 MIL MINIMUM THICKNESS,
PLASTIC LINER, GLUED TO TH
FOUNDATION WALL
aa. .0 a
� o
X\
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
1108 COUNTY ROAD 110
GARFIELD COUNTY PARCEL
#239308300007
GARFIELD COUNTY, COLORADO
PROJECT NO.:
20-3416
SCALE:
N.T.S.
FIGURE NO.:
5