HomeMy WebLinkAboutGeotechnical Investigation 05.03.2023Huddleston-Berry
Engineering & Testing, LLC
Monico Murillo
250 County Road 127 #2
Glenwood Springs, Colorado 81601 -
2789 Riverside Parkway
Grand Junction, Colorado 81501
Phone: 970-255-8005
Info@huddlestonberry. com
May 2,2023
Project#0263 1-0001
Subject: Geotechnical Investigation
Parcel 212728100386
Garfield County, Colorado
Dear Mr. Mwillo,
This letter presents the results of a geotechnical investigation conducted by Huddleston-Berry
Engineering & Testing, LLC (HBET) at Parcel 212728100386 in Garfield County, Colorado.
The site location is shown on Figure 1. The proposed construction is anticipated to consist of a
new single family residence. The seope of our investigation included evaluating the subsurface
conditions at the site to aid in developing foundation recommendations for the proposed
construction and to evaluate the site soils for onsite wastewater treatment.
Site Conditions
At the time of the investigation, an existing barn occupied the eastern portion of the investigated
area. The remainder of the site was open and sloping down towards the west. Vegetation
consisted of weeds, grasses, brush, bushes, and trees. The site was bordered to the north, south,
west, and east by large vacant parcels.
Subsurface Investisation
The subsurface investigation included three test pits as shown on Figure 2. The test pits were
excavated to depths of between 8.0 and 10.0 feet below the existing ground swface. Typed test
pit logs are included in Appendix A.
As indicated on the logs, the subsurface conditions at the site were fairly consistent. The test pits
encountered 1.0 to 1.5 feet of topsoil above tan to brown, moist, loose to dense clayey sand soils
to the bottoms of the excavations. A large boulder was encountered at a depth of 6.0 feet in TP-3.
Groundwater was not encountered at the time of the investigation.
Laboratorv Testine
Laboratory testing was conducted on samples of the native soils encountered in the test pits. The
testing included grain size analysis, Atterberg limits determination, natural moisture content and
density determinationo swell/consolidation testing, and maximum dry density and optimum
moisture content (Proctor) determination. The laboratory testing results are included in
Appendix B.
Pucet212728100386
#0263 1-0001
05/02/23
Huddleston-Berry
Ln8ln.ering.t 1.$1r8. l,l.C
The laboratory testing results indicate that the native sand soils are slightly plastic. In addition,
the native soils were shown to be slightly collapsible, with up to approximately 1.5% collapse
measured in the laboratory.
Foundallon Recommendations
Based upon the results of the subsurface investigation and nature of the proposed construction,
shallow foundations are recommended. Spread footings and monolithic (turndown) structural
slabs are both appropriate foundation alternatives. However, the native soils are anticipated to be
slightly collapsible. Therefore, in order to provide a stable bearing stratum and limit the
potential for excessive differential movements, it is recommended that the foundations be
constructed above a minimum of Z4-inches of structural fill.
The native soils, exclusive of topsoil, are suitable for reuse as structural fill, Imported structural
fill should consist of a granular, non-expansive, non-free drainins material approved by HBET.
For spread footing foundations, the footing areas may be trenched. However, for monolithic slab
foundations, the structural fill should extend across the entire building pad area to a depth of 24-
inches below the lowest portion of the foundation. Structwal filI should extend laterally beyond
the edges of the foundation a distance equal to the thickness of structural fill for both foundation
types.
Prior to placement of structural fiIl, it is recommended that the bottoms of the foundation
excavations be scarified to a depth of 6 to 8-inches, moisture conditioned, and re-compacted to a
minimum of 95% of the standard Proctor maximum dry densify, within +ZYo of the optimum
moisture content as determined in accordance with ASTM D698. Structural filI should be
moisture conditioned, placed in maximum 8-inch loose lifts, and compacted to a minimum of
95Yo of the standard Proctor maximum dry density for fine grained soils or modified Proctor
maximum dry density for coarse grained soils, within x2%o of the optimum moisture content as
determined in accordance with ASTM D698 or Dl557C, respectively.
Structural fiIl should be extended to within O.l-feet of the bottom of the foundation. No more
than 0.l-feet of gravel should be placed below the footings or turndown edge as a leveling
course.
In order for HBET to isque a suberade approval letter for the Garlield Corlgtv Buildine
Department. an ooen-hole inlpection will be require!: includine proofrolline and comouction
tgstiry{. depending ulpon the suberade material. In addition. it will be necessarv for HBET to
test compaction of the stractural fill st everv L2-inch vertical intemal.
For structural fill consisting of the native soils or imported granular materials and foundation
building pad preparation as recommended, a maximum allowable bearing capacity of 1,500 psf
may be used. In addition, a modulus of subgrade reaction of 150 pci may be used for structural
fill consisting of the native soils and a modulus of 200 pci may be used for approved imported
structural fill. Foundations subject to frost should be at least 24-inches below the finished grade.
2212008 ALL PROJECTS\02631 - Monico Murillo\02631-0001 Parcel21772810O386\200 - Geo\02631-0001 LR050223-doc
Parcel 212728100386
#02631-0001
0s/02123
Huddleston-Berry
lingin..rint& llrrinn. t-l-c
Any stemwalls or retaining walls should be designed to resist lateral earth pressures. For backfill
consisting of the native soils or imported granular, non-free draining, non-expansive material, we
recommend that the walls be designed for an active equivalent fluid unit weight of 45 pcf in
areas where no surcharge loads are present. An at-rest equivalent fluid unit weight of 65 pcf is
recornmended for braced walls. Lateral earth pressures should be increased as necessary to
reflect any surcharge loading behind the walls.
Water soluble sulfates are common to the soils in Western Colorado. Therefore, at a minimum,
Type I-II sulfate resistant cement is recommended for construction at this site.
Npn-Structural F,'loor Slab and Exterior Flatwork Recommendations
In order to reduce the potential for excessive differential movements, it is recoflrmended that
non-structural floating floor slabs be constructed above a minimum of l8-inches of structuralfill
with subgrade preparation, structural fill materials, and fill placement be in accordance with the
Foundation Recommendations section of this report. It is recommended that exterior flatwork be
constructed above a minimum of 12-inches of structural fill.
Drainaqe Recommendations
Grading and drainage ary critical for the lone-term pefformance of the structure and grading
around the structure should be designed to carry precipitation and runoff away from the
structure. It is recommended that the finished ground surface drop at least twelve inches within
the first ten feet away from the structures. It is also recofirmended that landscaping within five
feet of the structures include primarily desert plants with low water requirements. In addition, it
is recommended that inigation, including drip lines, within ten feet of foundations be minimized.
HBET recommends that swface downspout extensions be used which discharge a minimum of
15 feet from the structures or beyond the backfill zoneso whichever is greater. However, if
subsurface downspout drains are utilized, they should be carefully constructed of solid-wall PVC
and should daylight a minimum of 15 feet from the structures. In addition, an impermeable
membrane is recornmended below subsurface downspout drain lines. Dry wells should not be
used.
Onpite Wastewater Treatment Svstem Feflsibility
In order to evaluate the site soils for onsite wastewater treatment, percolation testing was
conducted at the site in accordance with Garfield County regulations. The percolation rate in the
native soils ranged from 9 to 30 minutes-per-inch. The percolation testing data are included in
Appendix C.
In accordance with Garfield County regulations, a percolation rate of between 5 to 60 minutes-
per-inch is required for soils to be deemed suitable for onsite wastewater treatment. Therefore,
based upon the results of the percolation testing, HBET believes that the native soils are suitable
for onsite wastewater treatment.
JZ:V008 ALL PROJECT5\02631 - Monico Murillo\02631-0001 Parcet212728100386U00 - Geo\02631-0001 LRO50223.doc
Pwcel 212728100386
#0263 1-0001
05102/23
Huddleston-Berry
linginc.rh!.t L1lhg. l.l.C
In addition to the percolation rate of the subsurface materials, the seasonal high groundwater
elevation is an important factor in determining the suitability of the site for Onsite Wastewater
Treatment Systems. For OWTS suitability, the seasonal high groundwater elevation should be at
least four feet below the bottom of the proposed absorption bed. As disoussed previously,
groundwater was not encountered at the time of the investigation. In general, based upon the
results of the subsurface investigations, HBET believes that the seasonal high groundwater level
is deeper than 10.0 feet below the existing grade at this site.
General Notes
The recommendations included above are based upon the results of the subsurface investigation
and on our local experience. These conclusions and recommendations are valid only for the
proposed construction.
As discussed previously, the subsurface conditions encountered in the test pits were fairly
consistent. However, the precise nafure and extent of any subsurface variability may not become
evident until construction. As discussed previously, it is recommended that HBET provide
construction materials testing and engineering oversight during the entire construction process.
In addition, the builder and any subcontractors working on the project should be provided a copy
of this report and informed of the issues associated with the presence of moisture sensitive
subgrade materials at this site.
It is important to note that the recommenlations herein are intended, to redryce the risk of
structural movemcnt and/or damase. to varving degrees. associated with volumc chaqge of the
native soils, However. HBET cannot predict lone-term chanses in subsurface moistare
co4ditions qnd/or the. orec,ise masnitude or extent of volame chanse, Where sienificant
increoses in subsurface maisture occur due to poor grading. improper stormvllter
manasement. utilitv line failure, excess brieation, or other cause. either during construction
or lhe resalt of actions of lhe prooertv ?wner. several inches of movemcnt are possihle. I!
adlition. anv failure to complv with the recommendations in thit leport releases Huddlestqn-
Berrv Ensineerins & Testins, LLC of anv liabilitv with resard to the structure performflnce.
We are pleased to be of service to your project. Please contact us if you have any questions or
comments regarding the contents of this report.
Respectfully Submitted:
Huddleston-Berry Engineering and Testing' LLC
Michael A. Berry, P.E.
Vice President of Engineering
4
3 010
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2:\2008 ALL PROIECTS\02631 - Monico Murillo\02631-0001Parce|21272810Q386\200 - Geo\02631-0001 LR050223.doc
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Date created: 3/30/2023
Last Data Uploaded: 3/30/2023 2:39:58 AM
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2789 Riverside Parkway
Grand Jrmction, CO 81501
970-25s-8005
GRAIN SIZE DISTRIBUTION
PRo.'ECT NAME Parcel 212728100386
PROJECT NUMBER 02631 -0001 PROJECT LOCATION Gerfield Corrntu CO
CLIENT Monico Murillo
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ATTERBERG LIMITS' RESULTS
PROJECT i|AME Parcel 212728100386
PROJECT LOCATION Garfield Countv, COPRA'ECTNUMBER 02631-0001
CLIENT Monico Murillo
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MOISTURE.DENSIW RELATIONSHI P
CLIENT Monico Murillo PROJECT NAME Parcel 212728100386
PROJECT NUMBER 02631-OOO1 PROJECT LOCATION Garfield County, CO
$ample Date:
Sample No.:
Source of Material:
Description of Material
3t31t2023
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Test Method (manual):ASTM D698A
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PERCOLATION TESTING
srP322Huddleston-Berry
Enginccrlng.g Tcsting, LLc
Project Name Parcel 212728100386 Location: Garfield County, CO
Testing Conducted By:
$upervising Engineer:
Test Number:
Top of Hole Depth:
Diameter of Hole:
Depth of Hole:
T. Collins
M,Berrv
TEST PIT DIMENSIONS
SOIL PROFILE
Test Number: 1
Top of Hole Depth: 5 (ft)
Diameter of Hole
Depth of Hole:
Time
(min.)
Water
Depth
fin.)
Change
(in.)
0 1.625
10 2j25 0.5
20 2.375 0.25
30 2.875 0.5
40 3.375 0.5
50 3.625 025
60 4.125 0.5
70 4.375 0.25
80 4.625 0.25
90 4.875 0.25
r00 5.375 0.5
110 5.625 o.25
120 5.875 0.25
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(in)
(in)
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3 (in)
17 (in)
Test Number: _
Top of Hole Depth: (ft)
Diameter of Hole: _(in)
Depth of Hole: _(in)
Length
{ft)
width
(n)
Depth
(ft)
Water Level Depth {ft)
Depth (ft)Not Encountered
8.0 X
Depth
(ft)Description Remarks
0-1 Sandy Clavwith Oroanics fiOPSOIL)
1-8 Clavev SAND (sc), tan to brown, moist, medium dense to dense
Time
(min.)
watef
Depth
(in.)
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(in.)
0 1.875
10 6.625 4.75
20 I 125 2.5
30 11.125 2
40 12.625 1.5
50 14.125 1.5
60 15j25 1
70 16.125 1
80 17.125 1
90 17.625 0.5
100 Drv
110 1
120 3 2
9
Time
(min.)
Water
Depth
(in.)
Change
(in.)
I
Average Percolation Rate (min/in):
Rate (min/in):