HomeMy WebLinkAboutSoils Report 07.22.2020Engineering, Inc.
CIVIL/GEOTECHNICAL
SOIL AND FOUNDATION INVESTIGATION
FOR A
PROPOSED OUTDOOR SWIMMING POOL
PARCEL #1 COX EXEMPTION PLAT
2932 COUNTY ROAD 115
(COUNTY PARCEL 2187-193-001-32)
GARFIELD COUNTY, COLORADO
PROJECT NO. 20-3418
JULY 22. 2020
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PREPARED FOR:
BRETT LEABLE
HAMMERHEAD OPERATIONS
727 COUNTY ROAD 120
GLENWOOD SPRINGS, CO 81601
P.O. Box 724, Eagle, CO 81631 Tel. (970) 390-0307 ‘vww.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
POOL FOUNDATION RECOMMENDATIONS 1
CONCRETE PATIO 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. 1
SWELL -CONSOLIDATION FIGURE NO. 2
PERIMETER DRAIN DETAIL FIGURE NO. 3
STRUCTURAL FILL WITH GEOGRID FIGURE NO. 4
LKP Engineering, Inc.
EXECUTIVE SUMMARY
The proposed outdoor swimming pool foundation should be
constructed on a geogrid reinforced structural fill and designed for
an allowable soil bearing pressure of 2000 psf. See Foundation
Recommendations.
SCOPE OF STUDY
This report presents the results of a subsurface Soil and Foundation Investigation for a
proposed outdoor swimming pool to be constructed on Parcel #1 Cox Exemption Plat, 2932
County Road 115, (County Parcel 2187-193-001-32), 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 #1, Cox Exemption Plat contains 35 acres (according to the Garfield County GIS)
and it is located between Kindall Road (AKA CR 119) on the south and Red Canyon Road
(AKA CR 115) on the north, in Garfield County, Colorado. The building site for the proposed
outdoor swimming pool is the area just south of the existing concrete patio on the south side of
the existing residence. The vegetation within the proposed building site was lawn irrigated with
a sprinkler system. Based on visual observation, the topography within the selected building area
was relatively flat with a gentle slope to the south (topographical survey was not available).
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South from the lawn area the slope was moderate and with vegetation consisting of sage brush
and grass.
PROPOSED CONSTRUCTION
We understand (based on the emailed sketch) that the proposed swimming pool will be
30 feet long and 8 feet wide with 4 to 5 feet depth and it will be surrounded with 5 feet wide,
concrete patio. The area between the semi -circular edge of the existing patio and the new
swimming pool will be a sun tan ledge. We anticipate loads to be light to moderate, 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 16, 2020, consisted of logging and sampling
one test pits. The excavation of the test pit was trench like, extending over the entire width of the
lawn area. The test pit was dug by an excavator brought by Brett Leable with Hammerhead
Operations. Approximate location of the test pit is shown on Drawing No. 1. We show the soil
profile of the test pit on the Subsurface Exploration Log, Figure No. 1. Soil samples for
laboratory soil analysis and observation were taken at selected intervals.
SUBSURFACE SOIL AND GROUNDWATER CONDITION
The soil profile encountered in the test pit was fairly uniform. The portion of the test pit
close to the existing concrete patio had some topsoil and man-made fill down to about 18 inches
below the surface. Below the topsoil and the fill layer the soil consisted of reddish -brown to tan,
calcareous clay with sparse gravel and some cobbles to the maximum depth explored of 10 feet.
Free ground water was or bedrock were not observed in the test pit. We sampled the soil in the
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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 number 2.
The clay soil samples had high moisture content of 18.4% at 5 feet and 18.5% at 9.5 feet.
Changes in the moisture content can cause movement and possible cracking of the proposed
swimming pool structure.
POOL FOUNDATION RECOMMENDATIONS
Due to the high moisture content of the soil, (the soil samples had high moisture content
of 18.4% at 5 feet and 18.5% at 9.5 feet) we recommend that the proposed swimming pool
subgrade is improved with layers of structural fill and geogrid, according to the attached detail
shown on Figure No. 4. The proposed pool foundation can then be designed for an allowable soil
bearing pressure of 2000psf, supported on the improved subgrade with layers of structural fill
and geogrid.
The completed foundation excavation must be observed by the undersigned engineer to
verify that the soil conditions encountered during construction are as anticipated in this report.
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.
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CONCRETE PATIO 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 patio around the pool should be separated from
the pool foundation walls with expansion joints to allow for independent movement without
causing damage. Caulking the expansion joint around the pool (between the pool coping and
pool deck) is important to keep out water, which can freeze and expand in the joint during
changing temperatures.
RETAINING WALLS
The pool 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.
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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 pool foundation subsoil, we
recommend installation of a foundation perimeter drain (see Figure No. 3). 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
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density under landscaped areas. They should use mechanical methods of compaction. Do not
puddle the foundation excavation.
The site surrounding the pool structure should slope away from the pool 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 pool 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 structure. 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
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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 Brett Leable, Hammerhead
Operations, for the specific application to the proposed Mayer -Wood outdoor swimming pool on
Parcel #1 Cox Exemption Plat, 2932 County Road 115, (County Parcel 2187-193-001-32),
Garfield County, Colorado.
Sincerely,
LKP ENGINEERING, INC. .ti � • 1)004%?..3)
- 7122/2026'17
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Luiza Petrovska, PE'",„,PON•
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LKP Engineering, Inc.
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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
2932 COUNTY ROAD 115
PARCEL #1, COX EXEMPTION PLAT
COUNTY PARCEL #218719300132
GARFIELD COUNTY, COLORADO
PROJECT NO.:
20-3418
SCALE:
—1"=50'
IJRAWING NO.:
1
DATE OBSERVED: JULY 16, 2020
ELEVATION:
Test Pit # 1
DEPTH
FEET
S
Y
M
B
0
L
S
A
M
P
L
E
DESCRIP71ON OF MATER/AL
AND SAMPLE LOCA770N
LABORATORY
TEST RESULTS
REMARKS
- 5
- 10
- 15
- 20
Topsoil, over man—mode fill
Reddish—brown to tan, calcareous, clay
❑ with sparse gravel and few cobbles DD= 106.6 pcf
MC= 18.4 X
O
DD= 104.6 pcf
MC= 18.5 X
Bottom Of Test Pit at 10 feet
No Ground Water
Encountered
LEGEND:
o - 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
PRO.ECT Na:
20-3418
FIGURE NO.:
1
1
0
° —1
k
—2
— 3
y —4
v —5
— 6
0
° —1
0,
— 2
Compression
— 3
— 4
— 5
— 6
LKP Engineering, Inc.
Swell — Consolidation Test Results
PRO.ECT Na:
20-3418
FIGURE NO.:
2
COMPRESSION
CONSTANT
1
PRESSURE
WHEN
WETTED UNDER
OF 1000
PSF
Ns
I
1
Reddish—brown,
Unit
Weight
Con
ten
0.1
of:
Dry
Moisture
t
1 0 10 100
APPLIED PRESSURE — ksf
Sample
Natural
Natural
calcareous clay From: Test Pit 1 at 5 feet
= 106.6 pcf
= 18.4 percent
LKP Engineering, Inc.
Swell — Consolidation Test Results
PRO.ECT Na:
20-3418
FIGURE NO.:
2
COMPRESSION
CONSTANT
1
PRESSURE
WHEN
WETTED UNDER
OF 1000
PSF
I
1
0.1 1 0 10 100
APPLIED PRESSURE — ksf
Sample of: Tan, calcareous clay From: Test Pit 1 at 9.5 feet
Natural Dry Unit Weight = 104.6 pcf
Natural Moisture Content = 18.5 percent
LKP Engineering, Inc.
Swell — Consolidation Test Results
PRO.ECT Na:
20-3418
FIGURE NO.:
2
*9
•
D J
•
e
e �
•
e
•5 D
LOPE AWAY FROM BUILDING
COVER BACKFILL WITH A MINIMUM
OF ONE FOOT OF RELATIVELY
IMPERVIOUS SOIL
FOOTING
■
a
•
•
:tip//, �/X/x</z //.W
30 MIL MINIMUM THICKNESS,
PLASTIC LINER, GLUED TO TH
FOUNDATION WALL
GRANULAR FILL
•
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
2932 COUNTY ROAD 115
PARCEL #1, COX EXEMPTION PLAT
COUNTY PARCEL #218719300132
GARFIELD COUNTY, COLORADO
PROJECT NO.: 20-3418
SCALE:
N.T.S.
FIGURE NO.:
3
OVEREXCAVATION-STRUCTURAL FILL
AND GEOGRID
N.T.S.
MINUS 3/4 -INCH CLEAN
CRUSH ROCK
r-- 5' min outside—I-1 SWIMMING POOL FOUNDATION 5' min outs[de--� }
j� t4 "C,6"..
l '"... p. - ax.1
!i 10' :��;� r � T" r'i di'� AlP r X4,1* r �'
aPPApilvitiooK-4442,004.witlitikleggvtattweittt. 0;,7.0
.\ \ .:.'.. ,.ti ,, .N..-<, -
18" 1
NOTE:
TENSAR TriAx
TX5
MINUS 3 -INCH ROAD BASE OR OTHER
SUITABLE STRUCTURAL FILL
APPROVED BY THE ENGINEER
UNDISTURBED SUBGRADE
18"
1. EXCAVATE THE THE SOIL DOWN TO THE REQUIRED DEPTH OF THE BOTTOM OF THE POOL
2. EXCAVATE ADDITIONAL 4 FEET OF THE POOL SUBGRADE
3. BACKFILL WITH 6 INCHES OF STRUCTURAL FILL
4. CONSTRUCT THE FIRST LAYER OF TENSAR TriAx GEOGRID OVER THE STRUCTURAL FILL
5. CONTINUE WITH THE STRUCTURAL FILL AND TENSAR GEOGRID TO WITHIN 6 -INCHES OF THE BOTTOM OF
POOL FOUNDATION.
6. BACKFILL OVER THE LAST LAYER OF GEOGRID WITH 8 -INCHES OF MINUS 3/4 -INCH CLEAN CRUSH ROCK.
7. ANY SUBSTITUTIONS MUST BE VERIFIED WITH THE ENGINEER.
THE GEOGRID AND GEOTEXTILE PLACEMENT WILL BE ACCORDING TO THE MANUFACTURERS
RECOMMENDATIONS.
CIVIL/GEOTECHNICAL
Engineering, Inc.
P.O. Box 724, Eagle, CO 81631
Tel (970) 390-0307 www.LKPEngineering.com
STRUCTURAL FILL WITH GEOGRID
2932 COUNTY ROAD 115
PARCEL #1, COX EXEMPTION PLAT
COUNTY PARCEL #218719300132
GARFIELD COUNTY, COLORADO
PROJECT NO.:
20-3418
SCALE: N.T.S.
nouRE NO.:
4