PZ - Geotech Report GEOTECHNICAL I ENVIRONMENTAL
ALLWEST MATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
March 4, 2020
Meghan Smith
Criterion Land Management, LLC
7629 E. Pinnacle Peak Rd., Suite #110
Scottsdale, Arizona 85255
ieq hann-criterion land.com
RE: Geotechnical Evaluation
Daphne Properties Development
Black Cat Road and McMillan Road
Ada County, Idaho
ALLWEST Project No. 519-522G
Ms. Smith:
ALLWEST Testing & Engineering, Inc. (ALLWEST) has completed the authorized
geotechnical evaluation for the proposed Daphne Properties Development to be located in
Ada County, 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 Criterion Land Management. If you have
any questions or need additional information, please contact us at(208)895-7898.
Sincerely,
$S�pNAL
ALLWEST Testing & Engineering, Inc. �, GE
1425 OF
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Adrian Mascorro, P.E. � MAS Bill Armaghani, P.E
Area Manager Engineering Services 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.allwesttesting.com
GEOTECHNICAL EVALUATION
DAPHNE PROPERTIES DEVELOPMENT
BLACK CAT ROAD AND MCMILLAN ROAD
ADA COUNTY, IDAHO
ALLWEST PROJECT NO. 519-522G
March 4, 2020
Prepared for:
Criterion Land Management, LLC
7629 E. Pinnacle Peak Rd., Suite #110
Scottsdale, Arizona 85255
Prepared By:
ALLWEST Testing & Engineering, Inc.
255 North Linder Road, Suite 100
Meridian, Idaho 83642
A LWE T
WWW.ALLWESTTESTING.COM
Appendix A
A-1 — Site Vicinity Map
A-2 — Exploration Location Plan
ALLWEST
TABLE OF CONTENTS
ALLWEST Project No. 519-522G
Daphne Properties Development
Ada County, 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 ....................................................5
7.1 Grading and Over-Excavation Considerations .................................................. 5
7.2 Site Preparation................................................................................................. 6
7.3 Subgrade Stabilization ...................................................................................... 6
7.4 Excavation......................................................................................................... 7
7.5 Materials............................................................................................................ 7
7.6 Fill Placement and Compaction......................................................................... 8
7.7 Utility Trenches.................................................................................................. 8
7.8 Wet Weather Construction ................................................................................ 9
7.9 Cold Weather Construction ............................................................................... 9
7.10 Stormwater Disposal ....................................................................................... 9
7.11 Asphalt Pavements ....................................................................................... 10
8.0 ADDITIONAL RECOMMENDED SERVICES..................................................... 11
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
Daphne Properties Development
Ada County, Idaho
ALLWEST Testing & Engineering, Inc. (ALLWEST) has completed the geotechnical
evaluation for the proposed Daphne Properties Development located in Ada County
just northwest of Meridian, Idaho. The general location of the site is shown on Figure
A-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 for the proposed development, relative to earthwork, stormwater
disposal, and pavement section design. This report details the results of our field
evaluation and presents recommendations to assist planning, 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 6 test pits
at the site to a maximum depth of 10 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 disturbed soil samples within select test pits.
5) Performed seepage tests within select test pits to evaluate subsurface seepage.
In addition, we installed PVC pipes within test pits for future groundwater
monitoring
6) At completion of exploration, the test pits were loosely backfilled with excavated
soil 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
planning, design, and construction.
9) Prepared this report with our field evaluation results, subsurface logs, and
geotechnical-related opinions and recommendations.
We provided our services for the project in general accordance with our geotechnical
proposal 519-522P dated November 27, 2019.
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation ALLWEST Project No. No. 519-522G
Daphne Properties Development Page 3
Ada County, Idaho
2.0 PROJECT UNDERSTANDING
Based on electronic communication with you and review of the Conceptual Site Plan
by Kimley Horn (dated January 7, 2019), we understand the project consists of an
approximate 15-acre residential development with associated infrastructure,
stormwater disposal facilities, and asphalt-paved roadways. Three existing residences
with associated outbuildings exist throughout the site; these structures and associated
infrastructure will be demolished as part of the development.
We did not review any preliminary site grading plans, as they were not available at the
time of this report, but we anticipate cut and fill for the site to be approximately 2 feet.
3.0 FIELD EVALUATION PROCEDURES
To complete this evaluation, we subcontracted a backhoe and an operator to observe
the excavation of 6 test pits using a Case 580C backhoe with a 3-foot-wide bucket.
We obtained soil samples for further identification and 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
The site is bordered by residential property/farm fields to the north, east, and south,
and by North Black Cat Road to the west. Daphne Street traverses the site from west
to east along near the center of the site. At the time of exploration, where residential
construction did not exist, the site was primarily used for farming activities. Three
residences with associated outbuildings exist throughout the site.
4.1 General Geologic Conditions
The geologic conditions at the site are mapped as Gravel of Whitney Terrace (Qwg)
on the "Geologic Map of the Boise Valley and Adjoining Area, Western Snake River
Plain, Idaho" (by Othberg and Stanford, 1992). These soils are sandy pebble and
cobble gravel mantled with 3 to 6 feet of 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 soil profile, has mapped the soils on the site as Purdam silt loam. The
parent materials are mixed alluvium, lacustrine deposits, and/or loess consisting of silt
loam, silty clay loam, stratified sand to loam with cemented material.
The soils encountered within test pits are generally consistent with NRCS mapping.
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
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Geotechnical Evaluation ALLWEST Project No. No. 519-522G
Daphne Properties Development Page 4
Ada County, Idaho
5.0 EXPLORATION AND SAMPLING
We observed the excavation of 6 test pits using a 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 the 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 typically contained surficial roots and vegetation, which varied between 6 to 8
inches in depth. In general, the subsurface soils were consistent throughout the site.
The soils mainly comprised of surficial native lean clay with sand or sandy lean clay
underlain by poorly-graded gravel with silt and sand to the end of test pit depths.
Surficial fill soils were encountered in the upper 6 inches of the soil profiles within test
pits TP-1 and TP-3, and the fill soils comprised of poorly-graded gravel with silt and
sand and lean clay with sand, respectively.
Specific descriptions of the native soil types observed throughout our field exploration
follow:
Lean clay with sand or sandy lean clay (CL)(nativeh—At the ground surface, or below
surficial fill in test pits TP-1 and TP-3, we observed native lean clay with sand or sandy
lean clay to depths of 3 to 5'/2 feet below ground. The clayey soils appeared brown,
very stiff to hard, moist, and contained weak to moderate cementation within the bottom
portions of these layers.
Poorly-graded gravel with silt and sand (GP-GM)— Underlying surficial clayey soils, we
observed poorly-graded gravel with silt and sand extending to test pit termination
depths of up to 10 feet. Gravel with silt and sand appeared tan, medium dense, and
moist to saturated. We did encounter a 2-foot layer of silty sand between sandy lean
clay and poorly-graded gravel with sand in test pit TP-4.
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.
GEOTECHNICAL I ENVIRONMENTAL
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Ada County, Idaho
5.2 Subsurface Water
At the time of exploration, we encountered groundwater within test pits at depths
between 8 to 9'/2 feet below existing ground surface. Groundwater in the area is
typically influenced by local irrigation and nearby creeks and laterals. Groundwater
may also be influenced by precipitation, on-site construction, and development to
adjacent sites. Subsurface water will fluctuate throughout the different seasons of the
year but will most likely be affected during seasonal snow melt and irrigation seasons
(March to October).
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
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 planning, design and construction of the 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 and Over-Excavation Considerations
We did not review final grading plans for this development, but we anticipate site
grading will consist of cuts and fills of up to 2 feet. We should be notified if actual site
grading varies significantly from this stated information, as it may affect our
recommendations herein.
The site has three existing residences with associated outbuildings, infrastructure, and
mature trees. Removal and over-excavation of existing buildings, infrastructure, and
trees will be required as part of the development. The depths of over-excavation to
remove construction debris, underground utilities/infrastructure, and deep tree roots
will not be fully known until earthwork construction commences. Contingencies should
be made during earthwork construction to ensure that no construction debris remains,
and that tree roots (which could be as deep as 4 feet) are completely over-excavated
prior to site grading fill placement or construction of any kind.
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Ada County, Idaho
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 areas, and any
other development areas. We anticipate approximately 6 to 8 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.
Where encountered, existing foundations, infrastructure, unsuitable fill soils, and large
tree root areas must be over -excavated their entire depth below development areas.
Any over-excavated materials may only be reused within non-structural landscape
areas or must be disposed of off-site. In general, 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.
After site stripping and over-excavations of fill, debris, and tree roots, 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 backfills 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 to firm, non-yielding soil 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
GEOTECHNICAL I ENVIRONMENTAL
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Ada County, Idaho
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 directly over geosynthetic reinforcement should be
properly moisture conditioned prior to placement, and once placed, should be
statically rolled. This section is the "bridge" section over soft subgrades.
• 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 1.5HAV
(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.
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Ada County, Idaho
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 inches;
Crushed Base Course Retained on 3/4-inch Sieve < 10%;
Passing No. 200 Sieve < 10%; Non-plastic
Alternatively, meet ISPWC section 802 (Type I
Maximum size 5 2 inches;
Utility Trench Backfill Retained on 3/4-inch Sieve < 30%;
Passing No. 200 Sieve <_ 10° ; Non-plastic
Alternatively, meet ISPWC section 305 (Type I
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 T (0
Compaction
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 most likely consist of lean clay with sand,
sandy lean clay, or poorly-graded gravel with silt and sand. It is our opinion these soils
should provide adequate support for utilities, provided utility subgrades are compacted
utilizing vibratory methods, such as with a large vibrator hoe-pack. We recommend
backfilling trench excavations with fill soils which meet criteria in section 7.5 Materials,
as on-site fine-grained soils (clays) may be difficult to moisture-condition and compact
in utility trenches.
If utility pipe support soils are soft or yielding at the time of construction, excavation of
the support soils and replacement with a more competent structural fill may be
necessary. If utility pipe support soils are saturated at the time of construction (due to
shallow groundwater), dewatering practices may be required and/or over-excavating
GEOTECHNICAL I ENVIRONMENTAL
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Ada County, Idaho
and backfilling with suitable drain rock below utilities. If support soils yield and/or are
saturated at the time of construction, we should be notified in order to observe these
soils and provide additional recommendations, as necessary.
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 clayey_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 excavated to undisturbed
soil and backfilled with structural fill.
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 testing (within select test pits
throughout the site) within poorly-graded gravel with silt and sand where we obtained
field-measured seepage rates of 10 to 15 inches per hour (in/hr). We also performed
a seepage test within the silty sand layer observed in TP-4 where we obtained a field-
measured seepage rate of 5 in/hr.
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We recommend subsurface stormwater disposal occur within poorly-graded gravel
with silt and sand encountered at depths varying between 3 to 7 feet below existing
ground surfaces. Refer to exploration logs in Appendix B to verify contact depths of
these permeable soil layers throughout the site.
Based on our subsurface observations and our field testing, the following allowable
seepage rate should be utilized for on-site stormwater disposal. This allowable
seepage rate within poorly-graded gravel with silt and sand is based on the infiltration
rate of filter sands utilized at the base of seepage bed drain rock:
• Poorly-graded gravel and silt and sand ............................... 8 in/hr
Stormwater disposal facilities should be constructed a minimum of 1 foot into the
receiving soil. 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 the suitable receiving soil
is encountered (based on civil design), to confirm the recommended seepage rate, and
to ensure the separation/filter fabric has been properly installed.
The proper separation from bottom of stormwater disposal facilities and seasonal high
groundwater should be maintained. As stated above, we observed groundwater at the
time of exploration varying between 8 to 9'/2 feet below ground; we anticipate these
groundwater levels to rise. We installed slotted PVC pipes within every test pit on-site
for future groundwater monitoring. At a minimum, these pipes should be monitored
during seasonal snow melt and irrigation seasons (March to October), or as required
by governing jurisdictions, to confirm seasonal high groundwater elevations at the site.
7.11 Asphalt Pavements
Prior to pavement section construction, the pavement subgrade should be proof-rolled
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. Majority of roadway subgrade soils throughout
the site will consist of lean clay with sand or sandy lean clay. Based on laboratory
testing we obtained a CBR of 9.7 for lean clay with sand, which is equivalent to an R-
value of 24. Based on the variability of on-site clayey-type soils and our experience
with clayey-type soils, we recommend an R-value of 17 be utilized for asphalt roadway
pavement section design.
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 subgrade preparation requirements,
design assumptions, and considering minimum frost depth requirements in the area,
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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 10
Collector Roadway 3 6 13
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.
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 removal of any other unsuitable construction debris
and soils, and deep tree roots (where encountered).
• Observe subgrade proof-rolling and approve subgrades prior to fill construction
materials placement, or roadway section construction.
• Observe removal of disturbed soil and subgrade stabilization, if required.
• Observe seepage bed subgrades, confirm subsurface seepage rates by
performing seepage testing within stormwater disposal facility locations, and
observe overall construction.
• 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.
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Ada County, Idaho
• 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 planning, design, and construction of the
proposed Daphne Properties Development in Ada County, 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
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Figure A-1 Site Vicinity Map
■ _• _ IEvaluation
Daphne Properties ••
A •a County, • •
Linder255 N. •. • Suite 100 Client: Criterion Land Management,
Meridian, • • 83642 Project •
• �i i� i�i KIT.-N.-T.T.-STOW R "INSWO
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Legend , N
0 Approximate location of test pit observed by ALLWEST. w .j'" E
t? Slotted PVC pipe installed in test pit.
Figure A-2 - Exploration Location Plan
Geotechnical Evaluation
ALLWEST
Daphne Properties Development
Ada County, Idaho
255 N. Linder Road, Suite 100 Client: Criterion Land Management, LLC
Meridian, Idaho 83642 Project No.: 519-522G
Phone: (208) 895-7898 Fax: (208) 898-3959 Date: March 2020
Appendix B
Test Pit Logs
Unified Soil Classification System (USCS)
ALLWEST
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 1
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°39'6.1524"(43.651709°)
= LONGITUDE(DEGREES):W-116°27'10.2528" (-116.452848°) W
F U U �
o j TOTAL DEPTH:9.5'
0CL
DESCRIPTION W U) NOTES
Poorly-graded GRAVEL with silt and sand(Fill);tan, medium
FILL dense,moist
Lean CLAY with sand(Native);brown,very stiff to hard, moist
1
BG
2
CL
3 ...weak to moderate cementation observed from 3 to 5 feet
4
5 Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated
0
6 °
0
0
7 o
GP-GM
0
O
o
— O —
9 °
0
Test pit terminated at 9-1/2 feet due to caving.
Slotted PVC pipe installed to 9-1/2 feet.
1
1
1
1
1
WATER LEVELS
8.5' a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 2
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°39'6.2928"(43.651748°)
= LONGITUDE(DEGREES):W-116°27'6.03" (-116.451675°) W
F U U �
o j TOTAL DEPTH:9'
0CL
DESCRIPTION W U) NOTES
Lean CLAY with sand(Native);brown,very stiff to hard, moist Significant roots and vegetation observed to 6
inches.
1 BG Passing No.200 sieve=74%
Moisture content=25%
2
CL
3 ...weak to moderate cementation observed from 3 to 5-1/2 feet
4
5
Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated °
6 0
0
o BG
7 Field seepage test performed at 7 feet.
GP-GM ° Field seepage rate= 15 in/hr.
O
8 - o
O
0
9 Test pit terminated at 9 feet due to caving.
Slotted PVC pipe installed to 9 feet.
1
1
1
1
1
WATER LEVELS
8' a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 3
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°39'3.384"(43.65094°)
= LONGITUDE(DEGREES):W-116°27'5.9832" (-116.451662°) W
F U U �
o j TOTAL DEPTH: 10'
0CL
DESCRIPTION W U) NOTES
FILL Lean CLAY with sand(Fill); brown,stiff, moist BG Significant roots and vegetation observed to 6
inches.
Sandy CLAY(Native); brown,very stiff to hard, moist
1
2 ...weak to moderate cementation observed from 2 to 5 feet
CL
3
4
5 Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated
0
6 °
0
0
7 o
GP-GM
0
O
0
O
9 - ° _V_
0
0
10— Test pit terminated at 10 feet due to caving.
Slotted PVC pipe installed to 10 feet.
1
1
1
1
WATER LEVELS
9' EZ WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 4
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°39'3.168"(43.65088°)
= LONGITUDE(DEGREES):W-116°27'10.3356" (-116.452871°) W
F U U �
o j TOTAL DEPTH: 10'
0CL
DESCRIPTION W U) NOTES
Sandy lean CLAY(Native); brown,very stiff to hard,moist Significant roots and vegetation observed to 8
inches.
1
BG
2
cL BG Passing No.200 sieve=56%
Moisture content= 16%
3 ...weak to moderate cementation observed from 3 to 5 feet
4
5 Silty SAND;tan,medium dense, moist
Field seepage test performed at 5-1/2 feet.
BG Field seepage rate=5 in/hr.
6 sM Passing No.200 sieve= 15%
Moisture content= 11%
Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated
0
8 0
GP-GM
0
9 0
— o
O
1 Test pit terminated at 10 feet due to caving.
Slotted PVC pipe installed to 10 feet.
1
1
1
1
WATER LEVELS
9.5' a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 5
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°39'0.2304"(43.650064°)
= LONGITUDE(DEGREES):W-116°27'10.1232" (-116.452812°) W
F U U �
o j TOTAL DEPTH:9.5'
0CL
DESCRIPTION W U) NOTES
Lean CLAY with sand(Native);brown,very stiff to hard, moist Significant roots and vegetation observed to 6
inches.
BG
1 Passing No.200 sieve=74%
c� BK Moisture content=22%
ILL=34, PL= 18,PI= 16
CBR=9.7
2
BG
3 Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated
DU
4 0
0
0
5 O
DU
0
BG
g Field seepage test performed at 6 feet.
GP-GM o Field seepage rate= 10 in/hr.
DU
7 0
O
DU
DU
0
O
0
9 0 _V_
0
Test pit terminated at 9-1/2 feet due to caving.
Slotted PVC pipe installed to 9-1/2 feet.
1
1
1
1
1
WATER LEVELS
9' EZ WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST TESTING&ENGINEERING DATE STARTED: 1/29/2020 TP - 6
DATE FINISHED: 1/29/2020 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:519-522G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Daphne Property Development
LATITUDE(DEGREES):N 43°38'59.4384"(43.649844°)
= LONGITUDE(DEGREES):W-116°27'6.0984" (-116.451694°) W
F U U �
o j TOTAL DEPTH: 10'
0CL
DESCRIPTION W U) NOTES
Lean CLAY with sand(Native);brown,very stiff to hard, moist Significant roots and vegetation observed to 6
inches.
1
BG
...weak to moderate cementation observed from 1-1/2 to 5 feet
2
CL
3
4
5 Poorly-graded GRAVEL with silt and sand;tan, medium dense,
moist to saturated
0
6 °
0
0
7 o
GP-GM
0
O
0
O
9 - ° _V_
0
0
10— Test pit terminated at 10 feet due to caving.
Slotted PVC pipe installed to 10 feet.
1
1
1
1
WATER LEVELS
9' EZ 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 Grave l-Sand-Cla Mixtures.
Well-Graded Sand,
CLEAN SW Gravelly Sand.
SANDS SP Poorly-Graded Sand,
SANDS Gravelly Sand.
Silty Sand,
SANDS 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)
2 1 - 1.5 25 26 74 Lean CLAY with SAND CL
4 2.5- 3 16 44 56 Sandy lean CLAY CL
4 5.5- 6 11 85 15 Silty SAND SM
5 1 - 2 22 26 74 34 16 9.7 Lean CLAY with SAND 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 Testing and Engineering, Inc.
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 30
c F-
LU C/) '
Q i
J /
a� 20
H
U
LU
J /
J
Q 10
0 ;
c
L-MIL ML or OL MH or OH
0
0 10 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT
0 MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
• Lean Clay with sand 34 18 16 74% CL
w
c
CD
U
X
U
U
U
7
O
` Project No. 519-522G Client: Criterion Land Management Remarks:
aD Project: Daphne Property Development
c *Location:TP-5 Depth: 1-2'
co
V-
0
a ALLWEST TESTING & ENGINEERING
d!E
Meridian Idaho Figure C-1
Tested By: C. Downes Checked By:J.Varozza
California Bearing Ratio
ASTM D 1883
Project: Daphne Properties Development Project No.: 519-522G
Client: Criterion Land Management Location: TP-5 @ 1 - 2'
Date Tested: 2/18/2020 Compaction Method: ASTM D1557
Tested By: C. Downes / I Varozza Class.: Lean CLAY with sand (CL)
200
175
150
a
125
c
0
'a 100
0 PSI @ 0.1 inch penetration=97
v
N 75
50
25
0
0 0.1 0.2 0.3 0.4 0.5
Penetration(inches)
CBR @ 0.1 Inch Penetration: 9.7 Maximum Dry Unit Weight (pcf): 113.7
Swell (%): 1.0 Optimum Water Content (%): 14.9
Dry Unit Weight Before Soak(pcf): 102.6 Remold of Max. Dry Unt Wgt(%): 90
Water Content Before Soak (%): 14.7
Water Content After Soak, Top 1 Inch (%): 22.2
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 ALLWEST Testing Engineering, Inc.