HomeMy WebLinkAboutGeotechnical Investigation 09.12.2023Huddleston-Berry
Engineering & Testing, LLC
2789 Riverside Parkway
Grand Junction, Colorado 81501
Phone: 970-255-8005
Info@huddlestonberry.com
September 12,2023
Project#927 16-0001
I.Martinez & Co.
1161 Munro Avenue
Rifle, Colorado 81650
Attention: Mr. Tyler Miles
Subject Geotechnical Investigation
Parcel 217535400193
Garfield County, Colorado
Dear Mr. Miles,
This letter presents the results of a geotechnical investigation conducted by Huddleston-Berry
Engineering & Testing, LLC (HBET) at Parcel 217535400193 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 scope 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, the site was open with undulating terrain. However, the
topography in the vicinity of the investigated area was sloping down towards the north.
Vegetation consisted of weeds, grasses, bushes, and trees. The site was bordered to the north and
west by alarge agricultural/residential property, to the south and east by vacantparcels.
Subsurface Investigation
The subsurface investigation included two test pits as shown on Figure 2. The test pits were
excavated to depths of 8.0 and 9.0 feet below the existing ground surface. 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, moist, medium dense to dense sandy lean clay
with gravel, cobble, and boulder soils to the bottoms of the excavations. Groundwater was not
encountered at the time of the investigation.
Laboratorv Testing
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
determination, and maximum dry density and optimum moisture content (Proctor) determination.
The laboratory testing results are included in Appendix B.
Parce| 2175354Q0193
#027t6-0001
09/12/23
Huddlcston-Strry
6qh!!dot& T.sin! LLC
The laboratory testing results indicate that the native clay soils are slightly plastic. In general,
based upon the presence of larger particles and density of the material, the native soils are
anticipated to be fairly stable under loading.
Foundation 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 altematives. However, 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 24-inches of structural fill.
The native soils, exclusive of topsoil, are suitable for reuse as structural fill; provided particles in
excess of 3-inches in diameter are removed. Imported structural fill should consist of a granular,
non-expansive, ry:fry irsirrllg material with greater than 10% passing the #200 sieve and
Liquid Limit of less than 30. However, all proposed imported structural fiIl materials should be
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. Structural fill 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 fill, it is recommended that the bottom of the foundation
excavation be scarified to a depth of 6 to 9 inches, moisture conditioned, and compacted to a
minimum of 95%o of the standard Proctor maximum dry density, within + 2oh of the optimum
moisture content as determined in accordance with ASTM D698. Structural fill should be
moisture conditioned, placed in maximum 8-inch loose lifts, and compacted to a minimum of
95o/o of the standard Proctor maximum dry density for fine grained soils and 90o/o of the modified
Proctor maximum dry density for coarse grained soils, within + 2Yo of the optimum moisture
content as determined in accordance with ASTM D698 and DI557, respectively.
Structural fill should be extended to within 0.l-feet of the bottom of the foundation. No more
than 0.1-feet of gravel should be placed below the footings or turndown edge as a leveling
course.
For structural fill consisting of the native soils or imported granular materials and foundation
building padpreparation 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
fiIl 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 36-inches below the finished grade.
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
recommended for braced walls. Lateral earth pressures should be increased as necessary to
reflect any surcharge loading behind the walls.
2Z:V008 ALL PROJECTS\O27 I 6 - J Martinez and Co\027 16-0001 - Parcel 2 I 7535400 I 93V00 - Geo\027 I 6-0001 LR09 1223.doc
Parce| 217 535400193
#02716-0001
09/12/23
Iloddlcson-Bcrry
Enrb!.fit & Tdins LLC
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.
Non-Structural Floor Slab and Exterior Flatwork Recommendations
In order to reduce the potential for excessive differential movements, it is recommended that
non-structural floating floor slabs be constructed above a minimum of 18-inches of structural fill
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 l2-inches of structural fill.
Drainage Recommendations
Grading and drsinsge ure critical for the long-term oerformsnce 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 recommended that landscaping within five
feet of the structures include primarily desert plants with low water requirements. In addition, it
is recommended that irrigation, including drip lines, within ten feet of foundations be minimized.
HBET recommends that surface downspout sxtensions be used which discharge a minimum of
15 feet from the structures or beyond the backfill zones, 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 recommended below subsurface downspout drain lines. Dry wells should not be
used.
Onsite Wastewater enf Svsfem Feasihilitv
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 1 I to 22 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.
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 discussed 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 8.0 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.
Z:r2008 ALL PROJECTS\O2716 - J Martinez and Co\02716-0001 - Parcel 217535400193\200 - Geo\02716-0001 LR09l223.doc 3
Parcel 217535400193
#027t6-000t
09112/23
Hsddlcsto!.8Gny
Eorh..tut8 LS& [C
As discussed previously, the subsurface conditions encountered in the test pits were fairly
consistent. However, the precise nature and extent of any subsurface variability may not become
evident until construction. As a result, it is recommended that HBET provide construction
materials testing and engineering oversight during the entire construction process. In addition,
the homeowner and any subcontractors working on the project should be provided with 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 recommendations herein are intended to reduce the risk of
structural movement snd/ot damuge, to varving degrees. associated h,ith volume chsnge of the
nutive soils. However, IIBET cannot predict long-term changes in subsurface moisture
conditions and/or the precise magnitude or extent of onv volume change in the native soils.
Vl/here significunt increases in subsurfuce moisture occur dae to Door grading, improper
stormwster management, utilitv line failure, excess irrigation, or other cause, either during
construction or the result of actions of the propertv owner, several inches of movement are
possible. In sddition. anv failure to complv with the recommendations in this report releases
Huddleston-Berrv Ensineering & Testins, LLC of anv liabilitv with regard to the structure
performance.
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
4Z:U008 ALL PROJECTS\02716 - J Martinez and Co\02716-0001 - Parcel 217535400193\200 - Geo\02716-0001 LRO91223.doc
FIGURES
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Date created: 8/10/2023
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APPENDIX A
Typed Test Pit Logs
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APPENDIX B
Laboratory Testing Results
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Huddleston-Berry Engineering & Testing, LLC
2789 fuverside Parkway
Grand Junction, CO 81501
970-255-8005
GRAIN SIZE DISTRIBUTION
CLIENT J. Martinez & Co.PROJECT MME Parcel 21753U00193
PROJECT NUMBER 02716-0001 PROJECT LOCATION Garfield Couniv. CO
U.S. SIEVE OPENING IN INCHES6 4 3 21.5 1314
U.S. SIEVE NUMBERS HYDROMETER3t834 6 810
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20
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10
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GRAIN SIZE IN MILLIMETERS
0.1 0.01 0.001
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COBBLES GRAVEL SAND SILT OR CLAY
coarse fine coarse medium fine
Specimen ldentification Classification LL PL PI Cc Cu
o TP-l, GB-l 8l'17 SANDY LEAN CLAY(CL)27 18 9
Specimen ldentification D100 D60 D30 D10 %Gravel %Sand %sitt %Clav
o TP-1, GB-1 8117 12.5 0.117 8.0 40.0 52.0
Huddleston-Berry Engineering & Testing, LLC
2789 Riverside Parkway
Grand Junction, CO 81501
970-255-8005
ATTERBERG LIMITS' RESULTS
CLIENT J. Martinez & Co.PROJECT NAME Parcel 217535400193
PROJECT NUMBER 02716-0001 PROJECT LOCATION Garfield County, CO
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Specimen ldentification LL PL PI #200 Classification
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2789 Riverside Parkway
Grand Junction, CO 81501
970-255-8005
MOISTURE.DENSITY RELATIONSHIP
PROJECT l,lAME Parcel 21753900193
PROJECT LOCATION Garfield Countv. COPROJECT NUMBER 02716-0001
CLIENT J. Martinez & Co.
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Sample Date:
Sample No.:
Source of Material:
Description of Material
8t17t2023
23-0497
145 TP.1 GB.1
SANDY LEAN CLAY(CL)
Test Method (manual):ASTM D698A
140
135 TEST RESULTS
Maximum Dry Density 113.0 PGF
Optimum Water Content 14.5 %
130
125
GRADA'|ION RESULTS (% PASSTNG)
#200 #4 314"
52 92 100
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ATTERBERG LIMITS
1 20
LL PL PI
27 18 I
115 Curves of 100o/o Saturation
for Specific Gravity Equal to
110
2.80
2.70
2.60
105
100
95
5 15
WATER CONTENT, %
90
0 10 20 25 30
APPENDIX C
Percolation Testing Results
PERCOLATION TESTING
STP322Huddleston-Berry
EnglncqiDg & fcrting, LI-C:
Project Name: Parcel217535400193 Location: Garfield County, CO
Testing Conducted By: T. Collins
Supervising Engineer: M. Berry
TEST PIT DIMENSIONS
SOIL PROFILE
02716-0001
8117t2023
TP-1
Project No
Test Pit No
Date
Length
(ft)
widrh
(ft)
Depth
(ft)
Water Level Depth (ft)
Depth (ft)Not Encountered
8.0 X
Depth
(ft)Description Rernarks
0-1 Sandv Clav with Oroanics fiOPSOIL)
1-8
Sandy Lean CLAY with Gravels, Cobbles, and Boulders (CL), tan,
moist, medium dense to dense
Test Number: 1
Top of Hole Depth: Z fl
Diameter of Hole: 3 (in)
Depth of Hole: tS (in)
Time
(min.)
Water
Depth
(in.)
Change
(in.)
0 1.5
10 2.75 1.25
20 3.5 0.75
30 4.25 0.75
40 5 0.75
50 6 I
60 6.5 0.5
70 6.75 0.25
80 7.75 1
90 8.875 1.125
100 s.25 0.375
110 9.75 0.5
120 10.25 0.5
22Rate (min/in):
Test Number: I
Top of Hole Depth: + (tt)
Diameter of Hole: 3 (in)
Depth of Hole. t O (in)
17
Test Number:
Top of Hole Depth
Diameter of Hole:
Depth of Hole:
_ (ft)
_ (in)
_ (in)
Time
(min.)
Water
Depth
(in.)
Change
(in.)
0 1.875
10 3.375 1.5
20 4.625 1.25
30 5.875 1.25
40 7.125 1.25
50 7.875 0.75
60 9.125 1.25
70 9.375 0.25
80 10.375 1
90 11.125 0.75
100 11.875 0.75
110 12.875 1
120 13.875 1
11
Time
(min.)
Water
Depth
(in.)
Change
(in. )
Average Percolation Rate (min/in)
Rate (min/in):Rate (min/in)