HomeMy WebLinkAbout20221396.tiffS•
April 7, 2021.
Jay Basiliere
13813 County Road 74
Eaton, Colorado 80615
LOGIC
Re: Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption Al ►SE -1030
TBD County Road 74,
Weld County (Eaton), Colorado
Soilogic Project # 21-1092
Mr. Basiliere:
Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration
you requested for the proposed single-family residence to be constructed on proposed Lot
B, a part of amended subdivision exemption AM 1'SE-1030, near Eaton in unincorporated
Weld County, Colorado. The results of our subsurface exploration and pertinent
geotechnical engineering recommendations are included with this report.
We understand the proposed residence will be a single -story wood frame structure
constructed over a full basement and will include an attached garage with a slab -on -grade
floor. Foundation loads for the structure are expected to be relatively light, with continuous
wall loads less than 3.5 kips per lineal foot and individual column loads less than 75 kips.
Small grade changes are anticipated to develop finish site grades in the residence area.
The purpose of our exploration was to describe the subsurface conditions encountered in
the completed site borings and develop the test data necessary to provide recommendations
concerning design and construction of the residence foundation and support of floor slabs.
The conclusions and recommendations outlined in this report are based on results of the
completed field and laboratory testing and our experience with subsurface conditions in
this area.
Sollogic, Inc.
3522 Draft Horse Court • Loveland, Co 80538 • (970) 535-6144
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
2
SITE DESCRIPTION
The proposed residencewill be constructed on proposed Lot B, a part of Amended
Subdivision Exemption AMD E-1030, located at an as -yet -to -be -determined address on
the north side of County Road 74 near Eaton, in unincorporated Weld County, Colorado.
At the time of our site exploration, the proposed ground surface in the proposed
construction area contained a moderate growth of grass vegetation and was relatively level.
The maximum difference in ground surface elevation across the residence footprint was
estimated to be on the order of two (2) feet or less. Evidence of prior building construction
was not observed in the proposed construction area by Soilogic personnel at the time of
our site exploration.
EXPLORATION AND TESTING PROCEDURES
To develop subsurface information in the area of the proposed residence, two (2) soil
borings were extended to a depth of approximately 15 feet below present site grade within
the approximate residence footprint. The boring locations were established in the field by
Soilogic personnel by referencing approximate building corner stakes which had been
placed by the client. A diagram indicating the approximate boring locations is included
with this report. The boring locations should be considered accurate only to the degree
implied by the methods used by the client to establish the approximate building footprint
in the field. Graphic logs of each of the auger borings are also included.
The test holes were advanced using 4 -inch diameter continuous -flight auger, powered by a
truck -mounted CME-45 drill rig. Samples of the subsurface materials were obtained at
regular intervals using California barrel sampling procedures in general accordance with
ASTM i specification D-1586. Penetration resistance measurements were obtained by
driving the standard sampling barrel into the substrata using a 140 -pound hammer falling
a distance of 30 inches. The number of blows required to advance the sampler a distance
of 12 inches is recorded and helpful in estimating the consistency or relative density of the
soils encountered. In the California barrel sampling procedure, lesser disturbed samples are
obtained in removable brass liners. Samples of the subsurface materials obtained in the
field were sealed and returned to the laboratory for further evaluation, classification and
testing.
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
3
The samples collected were tested in the laboratory to measure natural moisture content
and were visually andlor manually classified in accordance with the Unified Soil
Classification System (USCS). The USCS group symbols are indicated on the attached
boring logs. An outline of the USCS classification system is included with this report.
As part of the laboratory testing, a calibrated hand penetrometer (CHP) was used to
estimate the unconfined compressive strength of essentially -cohesive specimens. The CHP
also provides a more reliable estimate of soil consistency than tactual observation alone.
Dry density, Atterberg limits, -200 wash and swell/consolidation tests were completed on
selected samples to help establish specific soil characteristics. Atterberg limits tests are
used to determine soil plasticity. The percent passing the #200 size sieve (-200 wash) test
is used to determine the percentage of fine-grained materials (clay and silt) in a sample.
Swell/consolidation tests are performed to evaluate soil volume change potential with
variation in moisture content. The results of the completed laboratory tests are outlined on
the attached boring logs and swell/consolidation test summaries.
SUBSURFACE CONDITIONS
The materials encountered in the completed site borings can be summarized as follows.
Approximately 3 to 6 inches of vegetation and topsoil was encountered at the surface at
the boring locations. The vegetative soil layer was underlain by light brown to brown
clayey to silty sand with trace amounts of gravel. The clayey/silty sand varied from very
loose to medium dense in terms of relative density, exhibited no to low swell potential at
current moisture and density conditions and extended to the full depth explored in both
borings at a depth of approximately 15 feet below present site grade.
Groundwater was not encountered in either boring to the full depth explored at a depth of
about 15 feet below grade when checked immediately after completion of drilling.
Groundwater levels will vary seasonally and over time based on weather conditions, site
development, irrigation practices and other hydrologic conditions. Perched and/or trapped
groundwater conditions may also be encountered at times throughout the year. Perched
water is commonly encountered in soils overlying less permeable soil layers andlor
bedrock. Trapped water is typically encountered within more permeable zones of layered
Geotechnical Subsurface Exploration Report
Proposed. Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road. 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
4
soil and bedrock systems. The location and amount ofperched/trapped water can also vary
over time.
ANALYSIS AND RECOMMENDATIONS
General
Careful observation of the exposed foundation bearing materials should be completed at
the time of construction to ensure all footing foundations will be supported on like natural
materials with suitable strength. If extensive zones of very loose/disturbed, high moisture
content soils are encountered at that time, some o ere ..cavationibackfill or other approved
stabilization procedures may be required prior to foundation construction. We would be
happy to provide recommendations concerning subgrade stabilization at your request or
should they be deemed necessary.
Foundations
Based on the materials encountered in the completed site borings and results of laboratory
testing, it is our opinion the proposed lightly -loaded residence could be supported by
continuous spread footing and isolated pad foundations bearing on natural, undisturbed
clayey/silty sand with no to low swell potential. For design of footing foundations bearing
on natural, undisturbed, loose to medium dense clayey/silty sand, we recommend using a
maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, the residence
footings should be sized to maintain a minimum dead -load pressure of 500 psf, or as high
as practical on the foundation bearing materials.
Exterior footings should bear a minimum of 30 inches below finished adjacent exterior
grade to provide frost protection. We recommend formed strip footings have a minimum
width of 12 inches and isolated pad foundations have a minimum width of 24 inches in
order to facilitate construction and reduce the potential for development of eccentrically
loaded footings. Actual footing widths should be designed by a structural engineer.
For design of footing foundations and foundation walls to resist lateral movement, a
passive equivalent fluid pressure value of 275 pcf could be used. The top 30 inches of
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
5
subgrade could be considered a surcharge load but should not be used in the passive
resistance calculations. A coefficient of friction of 0.45 could be used between foundation
and floor slab concrete and the bearing soils to resist sliding. The recommended passive
equivalent fluid pressure value and coefficient of friction do not include a factor of safety.
We estimate settlement of footing foundations designed and constructed as outlined above
and resulting from the assumed structural loads would be on the order of 1 inch or less.
ifferential settlement could approach the amount of total settlement estimated above.
Floor Slabs
In the basement area of the residence, the floor slab could be supported directly on natural,
undisturbed clayey to silty sand. The garage and any other at -grade floor slabs could be
supported on reconditioned natural site sols and/or properly placed and compacted fill.
All existing vegetation and topsoil should be completely removed from at -grade floor slab
and any proposed fill areas. After stripping and completing all cuts and prior to placement
of any fill or flatwork concrete, we recommend the exposed subgrade soils be scarified to
a depth of 9 inches, adjusted to within the range of ±2% of standard Proctor optimum
moisture content and compacted to at least 95% of the material's standard Proctor
maximum dry density.
Fill soils required to develop at -grade floor slab and exterior flatwork subgrades should
consist of approved low -volume -change (LVC) soils free from organic matter, debris and
other objectionable materials. Based on results of the completed laboratory testing, it is our
opinion the native site clayey/silty sand could be used as fill in these areas provided care
is taken to develop the proper moisture content in those materials at the time of placement
and compaction. We recommend the site clayey/silty sand and/or similar soils be placed in
loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as
previously outlined. The garage and any other at -grade floor slabs could be supported
directly on the reconditioned subgrade soils and/or suitable fill soils placed and compacted
as outlined above.
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road. 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
6
Care should be taken to maintain the proper moisture content in all floor slab subgrade
soils prior to concrete placement. The developed at -grade floor slab subgrade soils should
not be left exposed for extended periods of time. In the event that the subgrade soils are
allowed to dry out or if rain, snowrnelt or water from any source is allowed to infiltrate
those materials, reworking of the subgrade soils or removal/replacement procedures may
be required.
Floor slabs should be designed and constructed as floating slabs, separated from foundation
walls, columns and plumbing and mechanical penetrations by the use of block outs or
appropriate isolation material. Additionally, we recommend all partition walls supported
above slabs -on -grade be constructed as floating walls to help reduce the potential for
differential slab -to -foundation movement causing distress in upper sections of the
structure. A minimum one and one-half (11/2) inch void space is recommended beneath all
floating walls. Special attention to door and stair framing, drywall installation and trim
carpentry should be taken to isolate those elements from the floor slabs, allowing for some
differential floor slab -to -foundation movement to occur without transmitting stresses to the
overlying structure.
Depending on the type of floor covering and floor covering adhesive used in finished slab -
on -grade areas (if any), a vapor barrier may be required immediately beneath the floor slabs
in order to maintain flooring product manufacturer warranties. A vapor barrier would help
reduce the transmission of moisture through the floor slab. However, the unilateral
moisture release caused by placing concrete on an impermeable surface can increase slab
curl. The amount of slab curl can be reduced by careful selection of an appropriate concrete
mix; however, slab curl cannot be eliminated. We recommend the owner, architect and
flooring contractor consider the performance of the slab, in conjunction with the proposed
flooring products to help determine if a vapor barrier will be required and where best to
position the vapor barrier in relation to the floor slab. Additional guidance and
recommendations concerning slab -on -grade design can be found in American Concrete
Institute (ACT) section 302.
Geotechnical Subsurface Exploration Report
Proposed. Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road. 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
7
Basement Construction
We recommend a perimeter drain system be installed around all below -grade areas to help
reduce the potential for water infiltration into the basement area and/or the development of
hydrostatic pressures behind the below -grade walls. . perimeter drain system should
consist of a 4 -inch diameter perforated drain pipe surrounded by a minimum of six (6.)
inches of free -draining gravel. A filter fabric should be installed around the free -draining
gravel or perforated pipe to reduce the potential for an influx of fine-grained soils into the
system. The invert of the drain pipe, at its high point, should be placed at approximate
foundation bearing level, run around the exterior perimeter of the below -grade area with a
minimum slope of 14 -inch per foot to facilitate efficient water removal and should
discharge to a sump pump and pit system. Care should be taken at the time of perimeter
drain installation to avoid disturbing those soils providing support to the residence footing
foundations (extending down at a 1:1 slope from the bottom edges of the footings).
Backfill placed adjacent to below -grade walls should consist of LVC potential and
relatively impervious soils free from organic matter, debris and other objectionable
materials. The natural site clayey/silty sand soils could be used as backfill in this area,
provided the proper moisture content in those materials at the time of placement and
compaction. We recommend the natural site clayey/silty sand and/or similar backfill soils
be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture and compacted as
outlined in the "Floor Slabs" section of this report.
Excessive lateral stresses canbe imposed on foundation walls when using heavier
mechanical compaction equipment. We recommend compaction of unbalanced foundation
wall backfill soils be completed using light mechanical or hand compaction equipment.
Lateral Earth Pressures
For design of below -grade walls where preventative measures have been taken to reduce
the potential for development of hydrostatic loads on the walls, we recommend using an
at -rest equivalent fluid pressure value of 65 pounds per cubic foot. A modified active
equivalent fluid pressure of 55 pounds per cubic foot could be used for partially restrained
conditioned where some rotation of the below -grade walls must occur to develop the active
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
8
earth pressure state. That rotation can result in cracking of the below -grade walls typically
in between corners and other restrained points. The amount of deflection of the top of the
wall can be estimated at 0.5% times the height of the wall.
Variables that affect lateral earth pressures include but are not limited to the shrink/swell
potential of the backfill soils, backfill compaction and geometry, wetting of the backfill
soils, surcharge loads and point loads developed in the backfill materials. The
recommended equivalent fluid pressure values do not include a factor of safety or an
allowance for hydrostatic loads. Use of expansive soil backfill, excessive compaction of
the wall backfill or surcharge loads placed adjacent to the below -grade walls can add to the
lateral earth pressures causing the equivalent fluid pressure values used in design to be
exceeded.
Drainage
Positive drainage is imperative for satisfactory long-term performance of the proposed
residence and associated site improvements. We recommend positive drainage be
developed away from the structure during construction and maintained throughout the life
of the site improvements, with twelve (12) inches of fall in the first 10 feet away from the
residence. Shallower slopes could be considered in hardscape a areas. In the event that poor
or negative drainage develops adjacent to the residence over time, the original grade and
associated positive drainage outlined above should be immediately restored.
Care should be taken in the planning of landscaping to avoid features which could result in
the fluctuation of the moisture content of the foundation bearing and/or flatwork subgrade
soils. We recommend watering systems be placed a minimum of 5 feet away from the
perimeter of the site structure and be designed to discharge away from all site
improvements. Gutter systems should be considered to help reduce the potential for water
ponding adjacent to the building, with the gutter downspouts, roof drains or scuppers
extended to discharge a minimum of 5 feet away from structural, flatwork and pavement
elements. Water which is allowed to pond adjacent to site improvements can result in
unsatisfactory performance of those improvements over time.
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road. 74, Weld County (Eaton), Colorado
Soilogic Project # 21-1092
9
GENERAL COMMENTS
This report was prepared based upon the data obtained from the completed site exploration,
laboratory testing, engineering analysis and any other information discussed. The
completed borings provide an indication of subsurface conditions at the boring locations
only. Variations in subsurface conditions can occur in relatively short distances away from
the borings. This report does not refect any variations which may occur across the site or
away from the borings. If variations in the subsurface conditions anticipated become
evident, the geotechnical engineer should be notified immediately so that further evaluation
can be completed and when warranted, alternative recommendations provided.
The scope of services for this project does not include either specifically or by implication
any biological or environmental assessment of the site or identification or prevention of
pollutants or hazardous materials or conditions. Other studies should be completed if
concerns over the potential of such contamination or pollution exist.
The geotechnical engineer should be retained to review the plans and specifications so that
comments can be made regarding the interpretation and implementation of our
geotechnical recommendations in the design and specifications. The geotechnical engineer
should also be retained to provide testing and observation services during construction to
help determine that the design requirements are fulfilled.
This report has been prepared for the exclusive use of our client for specific application to
the project discussed and has been prepared in accordance with the generally accepted
standard of care for the profession. No warranties express or implied, are made. The
conclusions and recommendations contained in this report should not be considered valid
in the event that any changes in the nature, design or location of the project as outlined in
this report are planned, unless those changes are reviewed and the conclusions of this report
modified and verified in writing by the geotechnical engineer.
Geotechnical Subsurface Exploration Report
Proposed Lot B, A Part of Amended Subdivision Exemption AMDSE-1030
TBD County Road 74, Weld County (Eaton), Colorado
Soilogic Project # 214092
10
We appreciate the opportunity to be of service to you on this project. If you have any
questions concerning the enclosed information or if we can be of further service to you in
any way, please do not hesitate to contact us.
Very Truly Yours,
Soilogic, Inc.
Alec Kaljian, P.E.
Project Engineer
Reviewed by:
Darrel DiCarlo, F.E.
Senior Project Engineer
APRIL 2021
PROJECT #21-1092
BORING LOCATION DIAGRAM
ScL_sic7
APPROXIMATE
LOCATION OF
PROPOSEB
RESIDENCE -
B-2
PROPOSED LOT B
PROPOSED LOT B, PART OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, 'GELD COUNTY (EATON), COLORADO
PROPOSED
LOG
OF BORING
LOT
B-1
B, A
TBD
PART
COUNTY
OF
AMENDED
ROAD
74,
Project
WELD
April
SUBDIVISION
COUNTY
# 21-1092
2021SDI'_
(EATON), COLORADO
EXEMPTION
AMDSE-'1030
LOGIC
Sheet 1/1
Drilling Rig: CME 45
Water Depth
Information
Start Date 3/23/2021
Auger
Type: 4"
CFA
During Drilling
None
Finish
Date 3/23/2021
Hammer
Type:
Automatic
After
Drilling
None
Surface Elev.
-
Field
Personnel:
JL
/ BM
- -
0
0,
D
SOIL
DESCRIPTION
Depth
(ft)
et
"N"
MC
CM
(pcf)
DD
Estimated
(psi)
q ,
% Swell
500
psf
@
Swell
Pressure
(psf)
Atterberg
Limits
%
#
Passing
200 Sieve
(%)
E
LL
PI
3-6" VEGETATION
& TOPSOIL
-
SC-SM
CLAYEY to SILTY SAND
brown to light brown
loose to medium dense
1
2
3
CS
28
4.7
110.5
900O+
0.5%
800
-
-
-
4
5
CS
23
6.9
108.9
900O+
1.1%
1700
16
8
26.5%
6
7
-
8
-
9
10
CS
8
17.2
104.9
900O+
None
<500
-
-
-
11
12
13
14
15
CS
5
21.1
100.1
<500
-
-
-
-
-
OF BORING @ 15.0'
-
16
17
18
19
20
21
22
23
24
25
BOTTOM
PROPOSED
LOG OF BORING
LOT El, A PART
TBD COUNTY
B-2
•
AMENDED
74,
WELD
April
SUBDIVISION
COUNTY (EATON),
/I 21-1092
2021
E
COLORADO
EMP'TI
*IN AMDSE-1030
SOr LOGIC
F
ROAD
Project
Sheet 1/1
Drilling Rig: CME 45
Water Depth
Information
Start Date 3/23/2021
Auger Type:
4" CFA
During Drilling
None
Finish Date 3/2312021
Hammer Type:
Automatic
After Drilling
None
Surface Elev. -
Field Personnel:
JL / BM
-
0
ampler
Estimated
Swell
% Passing
O
SOIL
DESCRIPTION
Depth
"N"
MC
DD
qu
% Swell
@
Pressure
Atterberg Limits
# 200 Sieve
D
(ft)
(%)
(pc
(psf)
500
psf
(psf)
LL
PI
(%)
3-6" VEGETATION
& TOPSOIL
-
1
2
3
4
5
CS
21
7.6
110.6
9000+
1.7%
1800
-
-
-
6
7
SC-SM
CLAYEY to SILTY SAN D
-
brown to light brown
8
loose to medium dense
-
9
10
CS
9
20.1
100.6
9000+
None
<500
-
-
-
11
12
13
14
15
CS
6
19.3
104.0
<500
-
-
-
-
-
OF BORING @ 15.0'
-
BOTTOM
16
17
18
19
20
21
22
23
24
25
PROPOSED LOT B, A PAT OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, WELD COUNTY (EATON), COLORADO
Project # 21-1092
April 2021
SWELL/CONSOLIDATION TEST SUMMARY
12
10
8
6
can
4
2
0
ca
0
c
0
0
0
-2
-4
-6
-8
- 10
- 12
10
dded
Voter
100
1000
Applied Load (psf)
10000
100000
Sample ID: B-'1 @ 2
Sample Description: Light Brown Clayey to Silty Sand (S -SM)
Initial
Moisture
4.7%
Liquid Limit -
Final Moisture 20.3%
Plasticity
Index -
% Swell @ 500 psf 0.5%
% Passing #200 -
Swell Pressure (psf) 800
Dry
Density
(pcf) 110.5
SCfjLOGIC
PROPOSED LOT B, A PAT OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, WELD COUNTY (EATON), COLORADO
Project # 21-1092
April 2021
SWELL/CONSOLIDATION TEST SUMMARY
Sample ID: B-1 @ 4
Sample Description: Light Brown Clayey to Silty Sand (SC -SPA)
Initial
Moisture
6.9%
Liquid Limit 16
Final Moisture 22.5%
Plasticity
Index
% Swell @ 500 psf 1.1%
% Passing #200 26.5%
Swell Pressure (psf) 1,700
Dry
Density
(pcf) 108.9
SOf..OSIC
PROPOSED LOT B, A PAT OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, WELD COUNTY (EATON), COLORADO
Project # 21-1092
April 2021
SWELL/CONSOLIDATION TEST SUMMARY
Sample ID: B-1 @ 9
Sample Description: Brown Clayey to Silty Sand (SC-SM)
Initial
Moisture
17.2%
Liquid Limit
-
Final Moisture 16.1%
Plasticity
Index -
% Swell @ 500 psf None
% Passing #200
Swell Pressure (psf) <500
Dry
Density
(pcf)
104.9
SCfjLOGIC
PROPOSED LOT B, A PAT OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, WELD COUNTY (EATON), COLORADO
Project # 21-1092
April 2021
SWELL/CONSOLIDATION TEST SUMMARY
Sample ID: B-2 a"r 4
Sample Description: Light Brown Clayey to Silty Sand (SC-SM)
Initial
Moisture
7.6%
Liquid Limit -
Final Moisture 26.2%
Plasticity
Index -
% Swell @ 500 psf 1.7%
% Passing #200 -
Swell Pressure (psf) 1,800
Dry
Density
(pcf) 110.6
SCfjLOGIC
PROPOSED LOT B, A PAT OF AMENDED SUBDIVISION EXEMPTION AMDSE-1030
TBD COUNTY ROAD 74, WELD COUNTY (EATON), COLORADO
Project # 21-1092
April 2021
SWELL/CONSOLIDATION TEST SUMMARY
Sample ID: B-2 @ 9
Sample Description: Brown Clayey to Silty Sand (SC-SM)
Initial
Moisture
20.1%
Liquid Limit
-
Final Moisture 19.1%
Plasticity
Index -
% Swell @ 500 psf None
% Passing #200 -
Swell Pressure (psf) <500
Dry
Density
(pcf)
100.6
SCfjLOGIC
UNIFIED
Criteria for Assigning Group
SOIL CLASSIFICATION
and Group Names Using Laboratory
SYSTEM
Tests'
Soil Classification
Symbols
Group
Symbol Group Name'
Coarse Grained Soils
More than �, retained
on No. 200 sieve
Gravels
More than 50% of coarse
fraction retained on
No. 4 sieve
Clean Gravels
Less than 5% fines
Cu ≥ 4 and 1 s Cc s 3E GW Well graded gravel
Cu < 4 and/or 1 › Cc > 3E GP Poorly graded gravelF
Gravels with Fines More
than 12% fines'
Fines classify as ML or MH GM Silty graver.'"
Fines classify as CL or CH GC Clayey graver"
Sands
50% or more of coarse
fraction passes
No. 4 sieve
Clean Sands
Less than 5% fines°
Cu ≥ 6 and 1 ≤ Cc s 35 SW Well graded
sand'
sand"
Cu < 6 and/or 1 c. 3E SP Poorly graded
Sands with Fines
More than 12% fines°
Fines classify as ML or MH SM Silty sandaH°"
Fines classify as CL or CH SC Clayey sand""
Fine -Grained Soils
50% or more passes the
No. 200 sieve
Silts and Clays
Liquid limit less than 50
Inorganic
PI > 7 and plots on or above "A" line' CL Lean clay"` -M
PI < 4 or plots below "A" line ML Si It'{ L':,
Organic
Liquid limit - oven
dried
< 0.75 OL
Organic clay'
Liquid limit - not
dried
Organic siltK -M'°
Sifts and Clays
Liquid limit 50 or more
Inorganic
PI plots on or above "A" line CH Fat claf`-T
PI plots below "A" line MH Elastic sit"
Organic
Liquid limit - oven dried
0.75 OH
Organic c ay"`.1-."
Liquid limit - not dried
organic satin"
Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material
Bit field sample contained
or boulders, or both" to
CGravels with 5 to 12%
gravel with silt, GW-GC
graded gravel with silt,
°Sands with 5 to 12% fines
sand with silt, SW -SC
sand with silt, SP -SC poorly
Cu = a
E'sa ago Gc
passing the 3 -in. (75
cobbles or boulders,
group name.
fines require dual
well graded gravel
GP -GC poorly graded
require dual symbols:
well graded sand
graded sand
(D_;,}:
-mm) sieve
or both,
symbols:
with clay,
gravel
SW-SM
with clay, SP-SM
with clay
to group
GC -GM,
add
OW -GM
GP -GM
with clay.
name.
or SC-SM.
"with
well
well
poorly
"If fines
cobbles ' If soil
J If Atterberg
graded K If soil
poorly gravel,
If soil
graded "sand
graded M
If soil
"gravelly"
N PI
° PI
P PI
0 PI
are
contains
contains
�}
whichever
contains
y " to
contains
≥ 4 and
< 4 or
plots on
plots below
plots
organic,
limits
rou
group
to group
plots
below
or above
"A"
≥
15
a
≥
on
add
15%
plot
to 29%
is predominant.
30%
name.
a
30 to
name.
or
"A"
"A"
line.
"with
gravel,
in shaded
plus
plus
above
line.
line.
organic
add "with
area,
plus No. 200,
No. 200
No. 200,
"A„ line.
fines"
predominantly
predominantly
to group
gravel" to group
soil is a CL -ML,
add "with sand"
sand,
name.
name.
silty clay.
or "with
add
gravel, add
D10
F If soil contains a 15% sand,
Olt fines classify as CL -ML,
X Dso
add "with sand"
use dual symbol
60 I
For classification
soils
of coarse
I
and fine-grained
-grained
of "A"
at P1=4
1=0.73
of "U"
at LL=1
1=0.9 (LL
- line
(LL
- line
e to
-8)
I
of
soils
to LL=25.5.
-20)
P l=7,
fine-grained
fraction
I
e/
}
,f`
f
/r
50 —
Equation
�,•
,,
%
# ,r
}`
r
' CiS
.
-
s
Horizontal
X 40 ther
W
o Equation
z Vertical
> 30 ther
H
r
f
f r
/
C
.'
O
o
CD
Co 20
r
,
l
MH
or
OH
10
j,
,
ML
or
OL
CL
,ML
7
0
a 13 16 20 30 40
LIQUID
50
LIMIT
80
(LLB
70 80 90 100 110
GENERAL NOTES
DRILLING & SAMPLING SYMBOLS:
SS:
ST:
RS:
CS:
BS:
Split Spoon -1 %" I.D., 2" O.O.1 unless otherwise noted
Thin -Walled Tube — 2.5" O.D., unless otherwise noted
Ring Sampler - 2.47 I.D., 3" O.D., unless otherwise noted
California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted
Bulk Sample or Auger Sample
HS:
.
PA:
HA:
RB:
WB:
Hollow Stem Auger
Power Auger
Hand Auger
Rock Bit
Wash Boring or Mud Rotary
The number of blows required to advance a standard 2 -inch G.D. split -spoon sampler (SS) the last 12 inches of the total 18 -inch
penetration with a 140 -pound hammer falling 30 inches is considered the Standard Penetration" or"N-value". For 2.5" 0.D.
California Barrel samplers (CB) the penetration value is reported as the number of blows required to advance the sampler 12
inches using a 140 -pound hammer falling 30 inches, reported as "blows per inch," and is not considered equivalent to the
"Standard Penetration" or "N -value".
WATER LEVEL MEASUREMENT SYMBOLS:
WL:
WCI:
DCI:
AB:
Water Level
Wet Cave in
Dry Cave in
After Boring
WS:
WO:
BCR:
ACR:
While Samplling
While Drilling
Before Casing Removal
After Casing Removal
Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other
times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater.
In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations.
DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils
have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand.
Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they
are plastic, and silts if they are slightly plastic or non -plastic. Major constituents may be added as modifiers and minor constituents
may be added according to the relative proportions based on grain size. In addition to gradation, coarse -grained soils are defined
on the basis of their in -place relative density and fine-grained soils on the basis of their consistency.
FINE-GRAINED SOILS
Blows/Ft.
<3
3-5
6-10
11-18
19-36
36
Blows/Ft.
0-2
3-4
5-8
9-15
16-30
>30
Consistenc
Very Soft
Soft
Medium Stiff
Stiff
Very Stiff
Hard
COARSE -GRAINED SOILS
Blows/Ft.
0-5
6-14
15-46
47-79
>79
RELATIVE PROPORTIONS OF SAND AND
GRAVEL
Descriptive Terms of
Other Constituents
Trace
With
Modifier
Percent of
Dry Weight
<15
15-29
>30
RELATIVE PROPORTIONS OF FINES
Descriptive Terms of
Other Constituents
Trace
With
Modifiers
Percent of
Dry Weight
<5
5-12
>12
SS
Blows/Ft.
<3
4-9
10-29
30-50
>50
Relative
Densit
Very Loose
Loose
Medium Dense
Dense
Very Dense
(CB)
Blows/Ft.
<24
24-35
36-60
61-96
>96
BEDROCK
(SS)
Blows/Ft.
<20
20-29
30-49
50-79
>79
GRAIN SIZE TERMINOLOGY
Major Component
of Sample
Boulders
Cobbles
Gravel
Sand
Silt or Clay
Consistency
Weathered
Firm
Medium Hard
Hard
Very Hard
Particle Size
Over 12 in. (300mm)
12 in. to 3 in. (300mm to 75 mm)
3 in. to #4 sieve (75mm to 4.75 mm)
#4 to #200 sieve (4.75mm to 0.075mm)
Passing #200 Sieve (0.075 mm)
PLASTICITY DESCRIPTION
Term
Non -plastic
Low
Medium
High
Plasticity Index
0
1-10
11-30
30+
SC LCSIC
Hello