CC - Geotech I ENVIRONMENTAL
ALLWEST MATERIALS OTESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
September 11, 2020
Jeff Harris
Sky Mesa Development, LLC
729 South Bridgeway Place
Eagle, Idaho 83616
RE: Geotechnical Evaluation
Sky Mesa Highlands Subdivision
South Eagle Road and East Lake Hazel Road
Meridian, Idaho
ALLWEST Project No. 519-505G
Mr. Harris:
ALLWEST has completed the authorized geotechnical evaluation for the proposed Sky
Mesa Highlands Subdivision to be located on the northwest corner of Eagle and Lake Hazel
Roads in Meridian, Idaho. The purpose of this evaluation was to characterize subsurface
soil conditions at the site and provide geotechnical recommendations to assist planning,
design, and construction of the proposed development. The attached report presents the
results of our field evaluation, laboratory testing, and our recommendations.
We appreciate the opportunity to be of service to Sky Mesa Development, LLC. If you have
any questions or need additional information, please contact us at(208) 895-7898.
Sincerely,
ALLWEST g�QMAL
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253
�EOF 10
Adrian Mascorro, P.E. '�N�IASC
Area Manager
255 N. Linder Rd., Suite#100, Meridian, ID 83642
Phone: 208.895.7898• Fax: 208.898.3959
Hayden, ID• Lewiston, ID•Meridian, ID.Spokane Valley,WA• Missoula, MT
www.allwesftesting.com
GEOTECHNICAL EVALUATION
SKY MESA HIGHLANDS SUBDIVISION
MERIDIAN, IDAHO
ALLWEST PROJECT NO. 519-505G
September 11 , 2020
Prepared for:
Sky Mesa Development, LLC
729 South Bridgeway Place
Eagle, Idaho
Prepared By:
ALLWEST
255 North Linder Road, Suite 100
Meridian, Idaho 83642
A LWE T
WWW.ALLWESTTESTING.COM
TABLE OF CONTENTS
ALLWEST Project No. 519-505G
Sky Mesa Highlands Subdivision
Meridian, Idaho
Page
1.0 SCOPE OF SERVICES ........................................................................................2
2.0 PROJECT UNDERSTANDING.............................................................................3
3.0 FIELD EVALUATION PROCEDURES.................................................................3
4.0 SITE CONDITIONS ..............................................................................................3
4.1 General Geologic Conditions............................................................................. 3
4.2 General Soil Conditions..................................................................................... 3
5.0 EXPLORATION AND SAMPLING .......................................................................4
5.1 Subsurface Soil Conditions ...............................................................................4
5.2 Subsurface Water.............................................................................................. 5
6.0 LABORATORY TESTING ....................................................................................5
7.0 CONCLUSIONS AND RECOMMENDATIONS ....................................................6
7.1 Grading ............................................................................................................. 6
7.2 Site Preparation.................................................................................................6
7.3 Subgrade Stabilization ...................................................................................... 7
7.4 Excavation......................................................................................................... 8
7.5 Materials............................................................................................................ 8
7.6 Fill Placement and Compaction......................................................................... 9
7.7 Utility Trenches.................................................................................................. 9
7.8 Wet Weather Construction ................................................................................ 9
7.9 Cold Weather Construction ............................................................................. 10
7.10 Stormwater Disposal ..................................................................................... 10
7.11 Asphalt Pavement ......................................................................................... 11
8.0 ADDITIONAL RECOMMENDED SERVICES..................................................... 12
9.0 EVALUATION LIMITATIONS............................................................................. 12
Appendix A— Site Vicinity Map, Exploration Location Plan
Appendix B —Test Pit Logs, Unified Soil Classification System
Appendix C— Laboratory Test Results
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation
Sky Mesa Highlands Subdivision
South Eagle Road and East Lake Hazel Road
Meridian, Idaho
ALLWEST has completed the geotechnical evaluation for the Sky Mesa Highlands
Subdivision located on the northwest corner of Eagle and Lake Hazel Roads in
Meridian, Idaho. The general location of the site is shown on Figure 1 — Site Vicinity
Map in Appendix A of this report. The purpose of this evaluation was to identify
subsurface soil conditions at the site, and provide opinions and recommendations
with respect to the proposed development, relative to earthwork, stormwater
disposal, and pavement section design. This report details the results of our field
evaluation and presents our recommendations to assist design and construction.
1.0 SCOPE OF SERVICES
Our scope of services for the project included the following:
1) Prior to subsurface exploration, we visited the site to observe site accessibility
and to pre-mark exploration locations, as required by Idaho Digline.
2) ALLWEST then notified Idaho Digline to mark underground utilities as required
by Idaho state law.
3) Subcontracted a backhoe and operator to observe the excavation of 13 test
pits to a maximum depth of 13 feet.
4) Visually described, classified, and logged the soils encountered within test pits
in general accordance with ASTM D 2487 and ASTM D 2488, which utilizes
the Unified Soil Classification System (USCS), and we logged the subsurface
profiles. We obtained select soil samples encountered within the test pits.
5) Performed seepage tests in select test pits to evaluate subsurface seepage.
6) At completion of exploration, the test pits were loosely backfilled approximately
level with the ground surface.
7) Performed laboratory tests on select soil samples to assess some of the soil
engineering properties and characteristics.
8) Reviewed the results of the field evaluation and laboratory testing, performed
engineering analyses, and provided recommendations to assist project design
and construction.
9) Prepared a draft report for your review. After your review and comment, we
provided this report with our field evaluation results, subsurface logs, and
geotechnical-related opinions and recommendations.
We provided our services for this project in general accordance with our revised
geotechnical proposal 519-505P, dated November 20, 2019.
GEOTECHNICAL I ENVIRONMENTAL
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Geotechnical Evaluation ALLWEST Project No. 519-505G
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2.0 PROJECT UNDERSTANDING
Based on review of the project's Grading Plan by J-U-B Engineers (dated August 31,
2020), we understand plans for the approximate 31-acre subdivision will consist of 75
single-family residential lots. No basements or below-ground portions of the
residences will exist. The development will include associated infrastructure, asphalt-
paved roadways, and stormwater disposal facilities. An existing residence and
outbuildings exist on the site; the residence and adjacent outbuildings will remain as
part of the development, but the outbuildings adjacent to the southern slope/hillside
will be demolished prior to development. Based on review of the grading plan, cuts
and fills of up to approximately 15 to 20 feet will be required for final grading.
3.0 FIELD EVALUATION PROCEDURES
To complete this evaluation, we subcontracted a backhoe and operator to observe
the excavation of 13 test pits using Case 580C backhoe with a 3-foot-wide bucket.
We obtained soil samples for laboratory testing. The approximate locations of the test
pits are shown on Figure A-2 — Exploration Location Plan in Appendix A.
4.0 SITE CONDITIONS
At the time of exploration, the site was undeveloped, and the ground surface was
covered with native weeds and vegetation. A residence with associated outbuildings
existed in the south and east portions of the site. The site is bordered by Eagle Road
to the east, residential development and Lake Hazel Road to the south, and new
residential developments to the west and north.
4.1 General Geologic Conditions
The geologic conditions at the site are mapped as Sandy Alluvium of Side-Stream
Valleys and Gulches (north of terrace) and Gravel of Amity Terrace (terrace) on
Geologic Map of the Boise Valley and Adjoining Area, Western Snake River Plain,
Idaho", by Othberg and Stanford (1992). North of the terrace these soils consist of
sand interbedded with silty sand and silt with minor clay and calcium carbonate, and
the terrace soils consist of gravels and sands mantled with loess. The soils
encountered within test pits are generally consistent with geologic mapping.
4.2 General Soil Conditions
The USDA Natural Resources Conservation Service (NRCS), which represents the
upper 5 feet of the soil profile, has mapped the soil on the site as Purdam silt loam
(north of terrace) and Pipeline silt loam (terrace). The parent materials of the Purdam
silt loam are mixed alluvium, lacustrine deposits, and/or loess consisting of silt loam,
silty clay loam, cemented material, and stratified sand to loam. The parent materials
of the Pipeline silt loam are silty alluvium and/or loess over sandy alluvium consisting
of silt loam, silty clay loam, cemented material, and gravelly sand. The soils
encountered within test pits are generally consistent with NRCS mapping.
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5.0 EXPLORATION AND SAMPLING
We observed the excavation of 13 test pits using Case 580C backhoe with a 3-foot-
wide bucket at the approximate locations shown on Figure A-2 — Exploration Location
Plan. We obtained Google Earth latitude and longitude coordinates of test pit
locations with a hand-held cellular device. These coordinates can be found on
individual test pit logs in Appendix B and should be considered accurate to the
degree implied by the method use.
We visually described, classified and logged soil conditions observed within test pits
in general accordance with ASTM D 2487 and D 2488. We obtained select disturbed
soil samples from exploration locations. At completion of exploration, test pits were
loosely backfilled with excavated soils approximately level with existing ground
surfaces.
5.1 Subsurface Soil Conditions
The site mainly contained 3 inches of surficial roots and vegetation at the surface.
Generally, the site consists of surficial sandy clays and sandy silts, overlying silts and
sands with variable amounts of gravels and calcium carbonate cementation, which
overly sands and gravels (with varying amounts of silt and calcium carbonate) with
depth. We also observed an area (near the southeast corner of the site) with
uncontrolled and unsuitable fill soils with debris. Specific soil descriptions of the on-
site soils observed are provided below.
Unsuitable fill soils — At the ground surface within test pit TP-13, we observed
unsuitable fill soil down to greater than 13 feet below existing ground surface. Fill soil
consisted of lean clayey sand with gravel and lean clay with sand and gravel, and
appeared brown, medium dense/stiff, and moist. The fill soil from 4 to 13 feet
contained variable chunks of hard pan/caliche throughout, asphalt debris at 9 feet,
and trash/wood debris at 12'/2 feet. It appears the area within/adjacent to TP-13 may
be an old farmer trash/backfill pit.
Sandy lean clay, lean clay with sand, or clayey sand (CL or SC) (native) — At the
ground surface within test pits TP-1 to TP-5, and underlying surficial sandy silt/silt
with sand within test pits TP-6 to TP-8, we observed native sandy lean clay, lean clay
with sand, or clayey sand to depths of 1'/2 to 3'/2 feet. The clayey soils appeared
brown to light brown/orange, firm to stiff or medium dense, and moist.
Sandy silt or silt with sand (with or without gravel) (native) — At the ground surface
within test pits TP-6 to TP-12, and underlying sandy lean clay within test pits TP-1,
TP-2, TP-3, and TP-6, we observed sandy silt and/or silt with sand (with or without
gravel) to depths varying between 1 to 12 feet. The silty soil appeared brown to tan,
medium dense to dense, moist, and contained variable weak to moderate calcium
carbonate cementation throughout.
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Silty sand (with or without gravel) (native) — Underlying clayey sand/sandy clay within
test pits TP-5, TP-7, and TP-8, and underlying silt with sand within test pit TP-10, we
observed silty sand (with or without gravel) to depths of 6 to 13 feet (maximum test
pit termination depth). The silty sand appeared tan or orange to brown, medium
dense, moist, and contained weak to moderate calcium carbonate cementation.
Gravel with silt and sand, silty gravel with sand, sand with silt and gravel f"dirty"
gravels/sands (greater than 5% silt)] — Underlying clayey and silty soils within test pits
TP-4, TP-8, TP-9, TP-11, and TP-12, we observed "dirty" gravels and sands with
varying amounts of silt (greater than 5%) to test pit termination depths of up to 13
feet. The "dirty" gravel/sand soils appeared tan to orange, medium dense to dense,
and moist. Within test pit TP-4, the gravel soils contained moderate to strong calcium
carbonate cementation where excavation refusal was observed at 6 feet.
Gravel with sand f"clean" gravels (less than 5% silt)] — Underlying sandy silt, silty
sand, or silt with sand soils within test pits TP-1 to TP-3, TP-6, and TP-7, we
observed "clean" gravels with sand (less than 5% silt) to test pit termination depths of
up to 13 feet. Where encountered, "clean" gravels were first observed varying
between 6 to 9 feet below ground. The "clean" gravel soils appeared tan to orange,
medium dense, and moist.
Detailed soil descriptions, depths and notes are presented on individual test pit logs
in Appendix B. The descriptive soil terms used on the test pit logs in this report, can
be referenced by the USCS. A copy of the USCS is included in Appendix B.
Subsurface conditions may vary between exploration locations. Such changes in
subsurface conditions may not be apparent until construction, and if they change
significantly from those observed, then accordingly, construction timing, plans and
costs may change.
5.2 Subsurface Water
At the time of exploration, we did not observe groundwater to the maximum test pit
excavation depths of up to 13 feet. However, based on groundwater monitoring
throughout the 2020 snow melt and irrigation seasons, we observed groundwater
within three of the installed piezometers, test pits TP-1, TP-2, and TP-3, at shallowest
depths of 5.3, 8.6, and 11.2 feet, respectively, below existing ground surfaces.
Groundwater in the area is typically influenced by local irrigation and nearby surface
water sources (creeks and laterals), and may be influenced by precipitation,
construction, and development of adjacent sites. Groundwater will fluctuate
throughout snow melt and irrigation seasons.
6.0 LABORATORY TESTING
We performed laboratory testing to supplement field classifications and to assess
some of the soil engineering properties and parameters. The laboratory tests
GEOTECHNICAL I ENVIRONMENTAL
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Sky Mesa Highlands Subdivision Page 6
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conducted included moisture content (ASTM D 2216), gradation (ASTM D 1140),
Atterberg limits (ASTM D 4318), and California bearing ratio (CBR) (ASTM D 1883).
Laboratory test results are summarized in Appendix C, and are also presented on
test pit logs in Appendix B.
7.0 CONCLUSIONS AND RECOMMENDATIONS
Based on our observations, testing and evaluation, in our opinion, the site may be
considered suitable for the planned development. The following recommendations
are presented to assist with design and construction of the proposed development,
relative to earthwork, infrastructure, stormwater disposal, and asphalt pavements.
These recommendations are based on our understanding of the proposed
construction, the conditions observed within exploration locations, laboratory test
results, and engineering analysis. If the scope of construction changes, or if
conditions are encountered during construction that differ from those described
herein, we should be notified so we can review our recommendations and provide
revisions, if necessary.
7.1 Grading
Final grading plans for this development will consist of cuts and fills of up to
approximately 15 to 20 feet. Final site grading should adhere to civil design, ensuring
that surface flow is directed away from development areas.
7.2 Site Preparation
Prior to conducting site grading, surficial soil containing vegetation, roots and
organics should be removed below proposed site grading fill areas, pavements, and
any other development areas. We anticipate approximately 3 inches of site stripping
will be required for majority of the site to remove vegetation and roots. However, this
depth may vary and will not be fully known until construction.
Existing asphalt pavements, pavement subsections, infrastructure, unsuitable fill
soils, and any large tree root areas must be over-excavated their entire depth below
development areas. We observed unsuitable fill soils within test pit TP-13 to
excavation termination depth of 13 feet. Test pit TP-13 may be associated with an old
farmer trash/backfill area that is not suitable for development. All unsuitable fill soils
containing asphalt, concrete, and variable trash debris must be over-excavated its
entire depth below any proposed development areas, prior to fill placement.
Any over-excavated materials may only be reused within non-structural landscape
areas or must be disposed of off-site. Over-excavations within proposed pavement or
flatwork areas (such as roadways, parking areas, sidewalks, concrete curb and
gutter, or any other concrete lanes) should extend a minimum of 1 foot beyond
asphalt/concrete perimeters.
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After site stripping, any unsuitable fill over-excavations, and prior to placing site
grading fills or pavement subsections, the exposed subgrades should be proof-rolled
with a minimum of 5-ton vibratory roller or with a vibratory hoe-pack, to confirm
subgrade stability. This will also assist in identifying any soft or loose soil zones
associated with loose test pit backfill, potential groundwater, or wet/soft soils due to
precipitation. If native subgrade soil is observed to significantly deflect or pump, it
should be over-excavated and replaced with properly compacted fills, or stabilized as
recommended in section 7.3 Subgrade Stabilization.
7.3 Subgrade Stabilization
If the subgrade soils are observed to pump or deflect significantly during grading, the
subgrades should be stabilized prior to fill placement. Subgrades may be stabilized
using geosynthetic reinforcement in conjunction with imported granular structural fill.
The required thicknesses of granular structural fill (used in conjunction with
geosynthetic reinforcement) will be dependent on the construction traffic loading,
which is unknown at this time. Therefore, a certain degree of trial and error may be
required during construction to verify recommended stabilization section thicknesses.
Geosynthetic reinforcement should consist of Tensar TX-160 or equivalent.
Alternatives to Tensar TX-160 must be approved by the geotechnical engineer prior
to use on site. The following recommendations are provided for subgrade
stabilization using geosynthetic reinforcement.
• Geosynthetic reinforcement materials should be placed on a non-disturbed
subgrade with smooth surface. Loose and disturbed soil should be removed
prior to placement of geosynthetic reinforcement materials.
• A minimum weight 4-ounce, non-woven filter fabric should be placed on the
undisturbed subgrade. The geosynthetic reinforcement should be placed
directly on top of the filter fabric. The filter fabric and geosynthetic
reinforcement should be unrolled in the primary direction of fill placement and
should be over-lapped at least 3 feet.
• The geosynthetic materials should be pulled taut to remove slack.
• Construction equipment should not be operated directly on the geosynthetic
materials. Fill should be placed from outside the excavation to create a pad to
operate equipment on. We recommend a minimum of 12 to 18 inches of
granular structural fill be placed over the geosynthetic reinforcement before
operating construction equipment on the fill. Low pressure, track-mounted
equipment should be used to place fill over the geosynthetic reinforcement.
• Granular structural fill placed over geosynthetic reinforcement should be
properly moisture-conditioned prior to placement, and once placed, statically
rolled. This section is considered the "bridge" section over soft subgrades.
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• After the first "bridge" lift has been placed, the remaining fill material above the
"bridge" section should be compacted to structural fill criteria in section 7.6 Fill
Placement and Compaction, utilizing vibratory compaction methods.
• Vibration should be discontinued if it reduces the subgrade stability. If
compaction criterion is not met within the fill lift above the "bridge" section, the
"bridge" section thickness is not enough, and subgrade stabilization must be
attempted again with a greater "bridge" section.
The geotechnical engineer or a representative of the geotechnical engineer must be
on-site during subgrade stabilization to verify our recommendations are followed, and
to provide additional recommendations, as needed.
7.4 Excavation
Excavation of on-site soil can be accomplished with typical excavation equipment.
We recommend excavations greater than 4 feet deep be sloped no steeper than
1.5H:1 V (horizontal to vertical). Alternatively, deeper excavations may be shored or
braced in accordance with Occupational Safety and Health Administration (OSHA)
specifications and local codes. Regarding trench wall support, the site soil is
considered Type C soil according to OSHA guidelines. Ultimately, the contractor is
responsible for site safety, excavation configurations and following OSHA guidelines.
7.5 Materials
Stripped soils and/or soils containing vegetation or debris are only suitable for use in
non-structural landscape areas. Existing on-site soils may be reused as site grading
fill, provided they are stockpiled separately, they meet the criteria below, and they are
compacted as required in this report. Imported granular soils should be free of
organics, debris, and other deleterious material, and meet the following criteria.
Import materials should be approved by ALLWEST prior to delivery to the site.
Fill Type Criteria
Site Grading, Maximum size <_ 6 inches;
Structural Fill Retained on %-inch sieve < 30%; Liquid limit < 50%
Maximum size <_ 6 inches;
Granular Structural Fill, Retained on 3/4-inch sieve < 30%;
Granular Subbase Passing No. 200 sieve <_ 15%; Non-plastic
Alternatively, meet ISPWC section 801 6 inches
Maximum size <_ 1 inch;
Crushed Base Course Retained on 3/4-inch sieve < 10%;
Passing No. 200 sieve < 10%; Non-plastic
Alternatively, meet ISPWC section 802 (Type 1)
Maximum size <_ 2 inches;
Utility Trench Backfill Retained on %-inch sieve <030%;
Passing No. 200 sieve <_ 10/o; Non-plastic
Alternatively, meet ISPWC section 305 (Type I
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7.6 Fill Placement and Compaction
Fill should be placed in lift thicknesses which are appropriate for the compaction
equipment used. Typically, 8- to 12-inch-thick loose-lifts are appropriate for typical
rubber-tire and steel-drum compaction equipment. Lift thicknesses should be reduced
to 4 inches for hand-operated compaction equipment. Fill should be moisture
conditioned to within 2% of the optimum moisture content prior to placement to
facilitate compaction. Fill should be compacted to the following percentages of the
maximum dry density as determined by ASTM D 1557 (modified Proctor).
Fill Area Compaction
M'-��
Sub grade Proof-roll*
Site Grading / Granular Structural Fill / Pavements 95
Base Course/ Subbase 95
Utility Trench Backfill 92
* Proof-roll should be observed and approved by a representative of the geotechnical engineer.
7.7 Utility Trenches
Support soils for underground utilities will likely consist of sandy lean clay, clayey
sand, silt with sand, sandy silt, sandy silt with gravel, or poorly-graded gravel with
sand. These soils should provide adequate support for utilities, provided utility
subgrades are compacted utilizing vibratory methods, such as with a large vibratory
hoe-pack. If utility pipe subgrades are soft, yielding, and/or saturated at the time of
construction, subgrade over-excavation and replacement with competent structural fill
may be required below utilities. If support soils yield and/or are saturated at the time
of construction, we should be notified to observe these soils and provide additional
recommendations, as necessary.
We recommend backfilling trench excavations with fill soils which meet criteria in
section 7.5 Materials, as on-site fine-grained soils (clays and silts) with variable
amounts of calcium carbonate cementation may be difficult to moisture-condition and
compact in utility trenches.
7.8 Wet Weather Construction
We recommend earthwork for this site be scheduled for the drier seasons of the year.
If construction is undertaken in wet periods of the year, it will be important to slope
the ground surface to provide drainage away from construction. If construction occurs
during or immediately after excessive precipitation, it may be necessary to over-
excavate and replace saturated subgrade soil, which might otherwise be suitable.
The on-site soils are sensitive to disturbance when wet. If these soils become wet
and unstable, we recommend construction traffic is minimized where these soils are
exposed. Low ground-pressure (tracked) equipment should be used to minimize
disturbance. Soft and disturbed subgrade areas should be over-excavated to
undisturbed soil and backfilled with structural fill.
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In addition, it should be noted the on-site soils tend to have notable adhesion when
wet and may be easily transported off-site by construction traffic.
7.9 Cold Weather Construction
The on-site soils are frost susceptible. If site grading and construction are anticipated
during cold weather, we recommend good winter construction practices be observed.
Snow and ice should be removed from excavated and fill areas prior to additional
earthwork or construction. Pavement and flatwork portions of the construction should
not be placed on frozen ground; nor should the supporting soils be permitted to
freeze during or after construction. Frozen soils must not be used as fill.
If native subgrades, or suitably moisture-conditioned and compacted fill lifts, will be
left exposed to freezing temperatures overnight, those areas should be protected
with a minimum of 12 inches of loose soil, or covered with heated construction
blankets, so construction subgrades do not freeze. Any frozen soils should be
removed prior to additional fill placement or construction of any kind.
Earthwork construction during cold inclement weather will require a higher level of
attention and detail to achieve required earthwork construction and compaction
criteria, and may lead to additional earthwork requirements and extended
construction schedules.
7.10 Stormwater Disposal
During our field investigation, we performed field seepage tests within test pits TP-2
and TP-6 at depths of 9 to 9'/2 feet within "clean" poorly-graded gravel with sand,
where we measured field seepage rates of greater than 15 inches per hour (in/hr).
Based on our field seepage testing and observations, and consistent soil properties
of the "clean" poorly-graded gravel with sand soil, we recommend stormwater
disposal occur within poorly-graded gravel with sand, encountered at depths between
6 to 12 feet below existing ground surfaces, within the north, northeast, and east
portions of the site (test pits TP-1 to TP-3, TP-6 and TP-7). Stormwater disposal
should not be disposed of within or above soils containing calcium carbonate
cementation; refer to individual test pit logs in Appendix A for detailed descriptions of
subsurface soils that contain calcium carbonate cementation.
The following allowable design seepage rate may be utilized for stormwater disposal:
Poorly-graded gravel with sand ("clean") ................................ 8 in/hr
Stormwater disposal facilities should be constructed a minimum of 1 foot into poorly-
graded gravel with sand. Seepage beds should be "burrito wrapped" or otherwise
maintain a separation/filter fabric between native fine-grained soils and drain
rock/filter sand to help prevent fine-soil migration into drainable/filtering media.
ALLWEST should observe stormwater disposal facility subgrades, to establish if
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suitable receiving soil is encountered, to confirm the recommended seepage rate,
and to ensure the separation/filter fabric has been properly installed. Refer to test pit
logs in Appendix A for soil contact depths.
The proper separation from bottom of stormwater disposal facilities and seasonal
high groundwater should be maintained. We installed slotted piezometer pipes within
select test pits on-site for future groundwater monitoring.
ALLWEST started monitoring these on-site piezometer pipes in February of 2020,
where we observed groundwater (to the maximum piezometer pipe depths) within
test pits TP-11, TP-2, and TP-3. Based on the measurements obtained to-date, the
shallowest groundwater depths measured were 5.3, 8.6, and 11.2 feet, below
existing ground surfaces, within TP-1, TP-2, and TP-3, respectively. Groundwater
should be monitored as required by governing jurisdictions in the area, to confirm
seasonal high groundwater elevations at the site.
7.11 Asphalt Pavement
Prior to pavement section construction, the subgrade should be prepared as
recommended in section 7.2 Site Preparation. Local and collector roadways should
be designed for a 20-year Equivalent Single Axle Load (ESAL) of 33,000 and
370,000, respectively, which is equivalent to a traffic index (TI) of 6 and 8,
respectively. If actual traffic conditions are different than what is stated, we should be
notified so that we may modify our pavement section design. Based on laboratory
testing, we obtained a CBR value of 6.3 for surficial sandy lean clay soils on-site,
which relates to an R-value of 15.
The following flexible asphalt pavement section design is provided based on the Idaho
Transportation Department (ITD) design methodology, utilizing Ada County Highway
District (ACHD) substitution ratios. Based on our observations, laboratory testing, and
assumptions, we recommend the following pavement sections be utilized for
subdivision roadway construction for local and collector roadways. The following table
presents these pavement sections.
Asphalt Aggregate Granular
Pavement Application Concrete Base Course Subbase
inches inches inches
Local Roadway 2.5 4 11
Collector Roadway 3 6 14
Base course and subbase should conform to the material recommendations as noted
in this report and should be placed over a properly prepared subgrade. The
subgrade, subbase, and base course surfaces should slope at no less than 2% away
from the crown of the roadway to help reduce the potential for surface water
infiltration into the underlying pavement subgrade.
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation ALLWEST Project No. 519-505G
Sky Mesa Highlands Subdivision Page 12
Meridian, Idaho
Asphalt concrete pavement should be compacted to minimum of 92% of the Rice
density. Crack maintenance on pavements should be performed at a minimum of
every 3 years, or when cracking is evident. Crack sealing will help reduce surface
water infiltration into the supporting soils.
8.0 ADDITIONAL RECOMMENDED SERVICES
To maintain continuity and efficiency, we recommend ALLWEST be retained to
provide observations and testing throughout construction. As an independent testing
laboratory, ALLWEST can document the recommendations included in this report are
properly implemented, provide quality control testing, and observe earthwork for
conformance to project specifications. As a minimum, we recommend the following
testing and observations be provided by ALLWEST:
• Observe site stripping and unsuitable fill over-excavation, and removal of any
other unsuitable debris and soils.
• Observe subgrade proof-rolling and approve subgrades prior to fill
construction materials placement and roadway section construction.
• Observe removal of disturbed soil and subgrade stabilization, if required.
• Conduct compaction testing of fill for general site grading, utilities, and
pavement areas.
• Observe placement of/test asphalt for compaction, oil content and gradation.
• Observe concrete placement, and test for slump, air entrainment, and
compressive strength.
• Provide special inspections as required by the IBC and the structural engineer.
If we are not retained to provide the recommended construction observation and
testing services, we shall not be responsible for soil engineering-related construction
errors or omissions.
9.0 EVALUATION LIMITATIONS
This report has been prepared to assist design and construction of the proposed Sky
Mesa Highlands Subdivision in Meridian, Idaho. Our services consist of professional
opinions and conclusions made in accordance with generally accepted geotechnical
engineering principles and practices in our local area at the time this report was
prepared. This acknowledgement is in lieu of all warranties either expressed or
implied.
The following plates complete this report:
Appendix A— Site Vicinity Map, Exploration Location Plan
Appendix B — Test Pit Logs, Unified Soil Classification System
Appendix C — Laboratory Test Results
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Appendix A
A-1 — Site Vicinity Map
A-2 — Exploration Location Plan
ALLWEST
• t L • t
■,..
v a46
At
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184
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a
ar �
LakeL,Haz I Rd
v
r
r r - - • i
.. tuna
Figure A-1 Site Vicinity . .
Geotechnical Evaluation
Sky Mesa Highlands •• •
Meridian, •, •
Linder255 N. Road, Suite 100 Development,
Meridian, •, • 83642 Project • • 1
Block 1
Block 1
50 1 Block 2 3 9
COMMON ■'qN 2 3 4 5 6 7 1 2 3 4 5 6 7
LOT -
TP-3 N * Lq
49 •
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48 32 l ..OMMON LOT
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Block 3 TP2
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44 TP-4 28 4 Z25
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TP-5 7 `� T
42 27 26 25 e .. r Co■mr*
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41 23 9 �
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TP-10 A� �,� Block 3 TP-8 33
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N89'50'51"W �� '�s• 19
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in c0
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02 LOT •
NO'1 3'0S"E O
40.00' Z N89.56'45"w TP-13
A _ N89'56'45'W 1329.5T _ 205.28'
E. LAKE HAZEL ROAD
N
Legend w, �i/ E
0 Approximate location of test pit observed by ALLWEST.
* Slotted PVC pipe installed in test pit.
Figure A-2 - Exploration Location Plan
Geotechnical Evaluation
ALLWEST
Sky Mesa Highlands Subdivision
Meridian, Idaho
255 N. Linder Road, Suite 100 Client: Sky Mesa Development, LLC
Meridian, Idaho 83642 Project No.: 519-505G
Phone: (208) 895-7898 Fax: (208) 898-3959 Date: September 2020
Appendix B
Test Pit Logs
Unified Soil Classification System (USCS)
ALLWEST
ALLWEST DATE STARTED: 12/12/2019 TP - 1
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'58.7004"(43.549639°)
= LONGITUDE(DEGREES):W-116°21'17.3052" (-116.354807°) Lu
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Sandy lean CLAY(Native); brown to light brown,firm, moist Significant roots and vegetation observed to 3
inches.
1 BG CBR=6.3
CL
2 BG Passing No.200 sieve=66%
Moisture content=31%
Atterberg limits: LL=42,PL=24, PI =18
3 Sandy SILT;tan,medium dense to dense, moist,weak to
moderate cementation
4
ML
5
6 Poorly-graded GRAVEL with sand;tan to orange, medium dense,
moist °
0
Q
7 0�
0
Q
o�
O
Q
o�
O
9 ....wet at 9 feet
o�
GP
O
Q
1
0
Q
1
o�
O
1 O
o�
O
Q
1 Test pit terminated at 13 feet.
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 2
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'58.5672"(43.549602°)
= LONGITUDE(DEGREES):W-116°21'22.5936" (-116.356276°) W
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Sandy lean CLAY(Native); brown,stiff, moist Significant roots and vegetation observed to 3
inches.
1
CL
2
Sandy SILT;tan,medium dense to dense, moist,weak to
moderate cementation
3
4 ML
5
Sandy SILT with gravel;tan, medium dense, moist,weak to
moderate cementation
6
7
ML
8
9 Poorly-graded GRAVEL with sand;tan to orange, medium dense,
moist °
o Field seepage test performed at 9-1/2 feet.
O Field seepage rate=>15 in/hr.
1
0
O
o�
1 GP
O
O
o�
1 O
0
O
1 Test pit terminated at 13 feet.
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 3
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'59.802"(43.549945°)
= LONGITUDE(DEGREES):W-116°21'30.258" (-116.358405°) W
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Sandy lean CLAY(Native); brown to light brown,firm, moist Significant roots and vegetation observed to 3
inches.
1 cL
2 Sandy SILT;tan,medium dense to dense, moist,weak to
moderate cementation
3
4
5
ML
6
7
8
Sandy SILT with gravel;tan, medium dense, moist,weak to
moderate cementation
9
1
ML
1
1 Poorly-graded GRAVEL with sand;tan to orange, medium dense,
GP moist,with calcium carbonate °
O
Q
1 Test pit terminated at 13 feet.
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 4
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
TEST PIT LOG LOGGER:Maxwell Thomas
WEATHER:Sunny
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'56.8356"(43.549121°)
= LONGITUDE(DEGREES):W-116°21'30.51" (-116.358475°) W
F U U �
o j TOTAL DEPTH:6'
0CL
DESCRIPTION W U) NOTES
Lean CLAY with sand(Native);brown,stiff, moist Significant roots and vegetation observed to 18
inches.
CL
1 Passing No.200 sieve=73%
BG Moisture content= 10%
Poorly-graded GRAVEL with silt,sand,and cobbles;tan,medium Atterberg limits: ILL=41,PL=20, PI =21
dense to dense, moist, moderate to strong cementation °
2 0
0
O
3
° BG
GP-GM
4 0
0
0
5
0
0
O
6 Test pit terminated at 6 feet due to excavation refusal on strong
cementation.
7
8
9
1
1
1
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 5
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'55.6224"(43.548784°)
= LONGITUDE(DEGREES):W-116°21'26.442" (-116.357345°) W
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Clayey SAND(Native); brown to orange,medium dense, moist Significant roots and vegetation observed to 3
inches.
1
....cobbles observed at 1-1/2 feet
sc
2
BG
3
Silty SAND with gravel;tan, medium dense,moist,weak to
moderate cementation
4
5
6
7
8
SM
9
.... hard pan/caliche observed at 9 to 10 feet
1
1
1
1 Test pit terminated at 13 feet.
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 6
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'54.6684"(43.548519°)
= LONGITUDE(DEGREES):W-116°21'19.4832" (-116.355412°) W
F U U �
o j TOTAL DEPTH: 12.5'
0CL
DESCRIPTION W U) NOTES
Sandy SILT(Native);tan,medium dense, moist Significant roots and vegetation observed to 3
inches.
ML
1
cL Sandy lean CLAY;brown,firm, moist
2 Sandy SILT;tan,medium dense, moist,weak to moderate
cementation
ML
BG Passing No.200 sieve=67%
Moisture content= 13%
3 SILT with sand;tan, medium dense,moist
BG
4
5
ML
6
7
8 Poorly-graded GRAVEL with sand;tan to orange, medium dense,
moist ° BG
0
O
g ° Field seepage test performed at 9 feet.
o Field seepage rate=>15 in/hr.
O
1 0
GP O
o�
1 O
0
O
0
Test pit terminated at 12-1/2 feet.
Slotted PVC pipe terminated at 12-1/2 feet.
1
1
—75 WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
T AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 7
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'52.152"(43.54782°)
= LONGITUDE(DEGREES):W-116°21'16.7004" (-116.354639°) W
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Sandy SILT(Native);tan,medium dense, moist Significant roots and vegetation observed to 3
ML inches.
1 Sandy lean CLAY;brown,firm, moist
CL
2 Silty SAND;orange to brown,medium dense, moist,weak to
moderate cementation
3
4 sM
5
6 Poorly-graded GRAVEL with sand;tan to orange, medium dense,
moist °
0
O
7 0�
o BG
O
8 0
O
o�
9 O
GP
O
O
1
0
O
1
O
o�
1 �
O
0
O
1 Test pit terminated at 13 feet.
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 8
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'53.07"(43.548075°)
= LONGITUDE(DEGREES):W-116°21'23.0364" (-116.356399°) W
F U U �
o j TOTAL DEPTH: 13'
0CL
DESCRIPTION W U) NOTES
Sandy SILT(Native);tan,medium dense, moist,weak Significant roots and vegetation observed to 3
cementation inches.
ML BG Passing No.200 sieve=69%
Moisture content=5%
1
Sandy lean CLAY;brown,firm, moist BG Passing No.200 sieve=53%
2 cL Moisture content= 11%
Atterberg limits: LL=41,PL=21, PI =20
Silty SAND;tan,medium dense, moist,weak to moderate
cementation
3
BG Passing No.200 sieve=39%
4 Moisture content= 16%
SM
5
6
Silty GRAVEL with sand;tan, medium dense,moist
0
7
° BG Passing No.200 sieve= 13%
Moisture content= 10%
8
0
9 0
GM
0
1
0
1
0
1 °
BG
1 Test pit terminated at 13 feet. °
Slotted PVC pipe installed to 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 9
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'53.5524"(43.548209°)
= LONGITUDE(DEGREES):W-116°21'28.89" (-116.358025°) W
F U U �
o j TOTAL DEPTH: 12.5'
0CL
DESCRIPTION W U) NOTES
SILT with sand(Native);brown to tan, medium dense,moist Significant roots and vegetation observed to 3
inches.
1 ML
2 SILT with sand and gravel;brown to tan, medium dense,moist
3-
ML
4 Poorly-graded SAND with silt and gravel;tan, medium dense,
moist
gG Passing No.200 sieve=5%
Moisture content=5%
5
6
7
8
SP-SM
9
1
1
1
Test pit terminated at 12-1/2 feet.
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 10
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'52.7208"(43.547978°)
= LONGITUDE(DEGREES):W-116°21'32.8608" (-116.359128°) OJ W
F U U Lu
o j TOTAL DEPTH:8.5' o-
0
DESCRIPTION W U) NOTES
SILT with sand(Native);brown to tan, medium dense,moist Significant roots and vegetation observed to 3
inches.
BG Passing No.200 sieve=72%
Moisture content=24%
1
.....weak to moderate cementation observed at 1-1/2 feet
2 ML
BG
3
4 Silty SAND with gravel;tan, medium dense,moist, moderate
cementation
5
6
SM
7
....cobbles observed at 7-1/2 feet
8 BG Passing No.200 sieve= 16%
Moisture content= 10%
Test pit terminated at 8-1/2 feet due to excavation refusal on
large cobbles.
9
1
1
1
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 11
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'51.2124"(43.547559°)
= LONGITUDE(DEGREES):W-116°21'24.9588" (-116.356933°) OJ W
F U U Lu
o j TOTAL DEPTH: 13' o-
0
DESCRIPTION W U) NOTES
SILT with sand(Native);brown to tan, medium dense,moist Significant roots and vegetation observed to 3
inches.
1
2
3
ML
4
5
6
Sandy SILT with gravel and cobbles;tan, medium dense,moist
7
ML
8 Poorly-graded GRAVEL with silt,sand,and cobbles;tan,medium
dense,moist
0
9 0
0
0
1 0
GP-GM
0
O
1
0
0
1 0
0
0
1 Test pit terminated at 13 feet.
1
—75 WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
T AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 12
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'50.1936"(43.547276°)
= LONGITUDE(DEGREES):W-116°21'20.5416" (-116.355706°) OJ W
F U U Lu
o j TOTAL DEPTH:7' o-
0
DESCRIPTION W U) NOTES
SILT with sand(Native);brown to tan, medium dense,moist, Significant roots and vegetation observed to 3
weak cementation inches.
1
2
ML
3
4—
Poorly-graded SAND with silt,gravel,and cobbles;tan,medium
dense to dense, moist
5
BG
SP-SM
6
7 Test pit terminated at 7 feet.
8
9
1
1
1
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 12/12/2019 TP - 13
DATE FINISHED: 12/12/2019 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Maxwell Thomas
TEST PIT LOG WEATHER:Cloudy
PROJECT:519-505G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Sky Mesa Highlands Subdivision
LATITUDE(DEGREES):N 43°32'48.3"(43.54675°)
= LONGITUDE(DEGREES):W-116°21'16.7004" (-116.354639°) OJ W
F U U Lu
o j TOTAL DEPTH: 13' o-
0
DESCRIPTION W U) NOTES
Clayey SAND with gravel(Fill); brown, medium dense, moist v1y, Significant roots and vegetation observed to 3
inches.
00(
00( BG
1 00(
00(
00(
00<
2 FILL 00(
00(
00(
00(
00(
4 Lean CLAY with sand and gravel(Fill); brown,stiff, moist,with
calcium carbonate cementation/caliche chunk
00(
00(00(
00(
00(
00<
00(
6 00<00( BG Passing No.200 sieve=78%
00< Moisture content=27%
00<
00(
00(
8
FILL
9 Asphalt debris observed at 9 feet.
1
1
1
Trash and wood debris observed at 12-1/2 feet.
00(
1 Test pit terminated at 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
Unified Soil Classification System
MAJOR DIVISIONS SYMBOL TYPICAL NAMES
Well-Graded Gravel,
CLEAN GW Gravel-Sand Mixtures.
GRAVELS GP Poorly-Graded Gravel,
GRAVELS Gravel-Sand Mixtures.
Silty Gravel,
COARSE GRAVELS GM Gravel-Sand-Silt Mixtures.
GRAINED WITH FINES GC Clayey Gravel,
SOILS Gravel-Sand-Clay Mixtures.
Well-Graded Sand,
CLEAN SW Gravelly Sand.
SANDS SP Poorly-Graded Sand,
SANDS Gravelly Sand.
Silty Sand,
SANDS L SM Sand-Silt Mixtures.
WITH FINES Sc Clayey Sand,
Sand-Clay Mixtures.
ML Inorganic Silt,
SILTS AND CLAYS Silty or Clayey Fine Sand.
Inorganic Clay of Low to
LIQUID LIMIT CL Medium Plasticity,
LESS THAN 50% Sandy or Silty Clay.
FINE OL Organic Silt and Clay of Low
GRAINED Plasticity.
SOILS Inorganic Silt, Elastic Silt,
SILTS AND CLAYS MH Micaceous Silt,
Fine Sand or Silt.
LIQUID LIMIT CH Inorganic Clay of High Plasticity,
GREATER THAN 50% Fat Clay.
OH Organic Clay of Medium to High
Plasticity.
Highly Organic Soils PT Peat, Muck and Other Highly
Organic Soils.
ALLWEST
Appendix C
Laboratory Test Results
ALLWEST
Summary of Laboratory Test Results
Moisture Gradation Atterberg Limits
Test Pit Depth Content Liquid Plasticity CBR Sample Classification
No. (Feet) M Gravel Sand Silt/Clay Limit Index (USCS)
M M M M M
1 1 -2 6.3 Sandy Lean CLAY(CL)
1 2 -2.5 31 34 66 42 18 Sandy Lean CLAY CL
4 0.5- 1 10 27 73 41 21 Lean CLAY with sand (CL)
6 2.5- 3 13 33 67 Sandy SILT ML
8 0.5- 1 5 31 69 Sandy SILT (ML)
8 1.5- 2 11 47 53 41 20 Sandy Lean CLAY CL
8 3.5 -4 16 61 39 Silty SAND SM
8 7.5- 8 10 - - 13 Silty GRAVEL with sand GM
9 4.5 - 5 5 - - 5 Poorly-graded SAND with silt&gravel SP-SM
10 0 - 0.5 24 28 72 SILT with sand ML
10 8- 8.5 10 - - 16 Silty SAND with gravel SM
13 6 -6.5 27 - - 78 Lean CLAY with sand and gravel CL
Table C-1
255 N. Linder Road, Suite 100 • Meridian, Idaho 83642 • (208) 895-7895 • Fax (208) 898-3959
www.allwesttesting.com
This report may not be reproduced, except in full, without the permission of ALLWEST.
LIQUID AND PLASTIC LIMITS TEST REPORT
60
Dashed line indicates the approximate
upper limit boundary for natural soils
50
�0
' G
40
U
C �
X
W
N— Z_
�
v
F /
30
c
W � '
Q i
J /
C d %/ O�
O 20 4
U)
LU
J /
J
Q 10
0 ;
c
L-ML ML or OL MH or OH
0
0 10 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT
MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
• Sandy Lean Clay 42 24 18 66% CL
c■ Lean Clay with sand 41 20 21 73% CL
C♦ Sandy Lean Clay 41 21 20 53% CL
X
m
m
U
7
O
` Project No. 519-505G Client: Sky Mesa Development,LLC Remarks:
aD Project: Sky Mesa Highlands Subdivision
c *Location: TP-1 Depth:2-2.5'
■Location: TP-4 Depth: 0.5-l'
ALocation: TP-8 Depth: 1.5-2'
0
cn
ALLWEST
Figure C-1
Tested By: C. Downes Checked By:J.Varozza
California Bearing Ratio
ASTM D 1883
Project: Sky Mesa Highlands Subdivision Project No.: 519-505G
Client: Sky Mesa Development, LLC Location: TP-1 @ 1'- 2'
Date Tested: 12/20/19 Compaction Method: ASTM D1557
Tested By: C. Downes / J. Varozza Classification: Sandy Lean Clay (CL)
110
100
90
80
N 70
a
2 60
ii PSI @ 0.1 inch penetration= 63
0 50
iA
4A
a
n 40
30
20
10
0
0 0.1 0.2 0.3 0.4 0.5
Penetration(inches)
CBR @ 0.1 Inch Penetration: 6.3 Maximum Dry Unit Weight (pcf): 104.5
Swell (%): 4.1 Optimum Water Content (%): 19
Dry Unit Weight Before Soak(pcf): 94.3 Remold of Max. Dry Unt Wgt(%): 90
Water Content Before Soak (%): 18.7
Water Content After Soak, Top 1 Inch (%): 36.2
Surcharge (psf): 100
Immersion Period (hrs): 96
Reviewed By: Isaac Rede
Figure: C-2
►LLWET
255 N Linder Rd,Suite 100•Meridian,ID 83642•(208)895-7898•Fax(208)898-3959
www.allwesttesting.com
This report shall not be reproduced except in full without the permission of ALLW EST.