HomeMy WebLinkAboutBachus and Schanker Law Office Building - FDP200031 - - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL SUBSURFACE EXPLORATION REPORT
WARREN FEDERAL CREDIT UNION – LOT 1 PAD “A” AND “B”
SOUTHEAST OF EAST DRAKE ROAD AND ILLINOIS DRIVE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1202069
Prepared for:
Aller Architects PC
c/o Julie (julie@ice3d.com)
2900 South College 3A
Fort Collins, Colorado 80525
Attn: Mr. Mick Aller (mick@aller-architects.com)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
4396 GREENFIELD DRIVE
W INDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
October 22, 2020
Aller Architects PC
c/o Julie (julie@ice3d.com)
2900 South College 3A
Fort Collins, Colorado 80525
Attn: Mr. Mick Aller (mick@aller-architects.com)
Re: Subsurface Exploration Report
Warren Federal Credit Union – Lot 1 Pad “A” and “B”
Southeast of East Drake Road and Illinois Drive
Fort Collins, Colorado
EEC Project No. 1202069
Mr. Aller:
Enclosed, herewith, are the results of the subsurface exploration completed by Earth Engineering
Consultants, LLC (EEC) for the referenced project. For this exploration, three (3) soil borings
were extended to depths of approximately 15 to 24 feet below existing site grades. This
subsurface exploration was carried out in general accordance with our proposal dated September
17, 2020.
In summary, the subsurface conditions encountered beneath the surficial vegetation/topsoil layer
in the test borings, generally consisted of lean clay with sand extending to the depths explored at
approximately 15 feet below the ground surface in boring B-2 and to the underlying sand and
gravel soils at depths of approximately 18 to 19 feet below the ground surface in the remaining
borings. The lean clay with sand subsoils were generally stiff to very stiff and exhibited low to
moderate swell potential at current moisture and density conditions. Sand/gravel soils were
encountered below the lean clay soils and extended to the depths explored, approximately 20 to
24 feet below the ground surface. The sand/gravel soils were dense to very dense and refusal was
encountered in boring B-3 at a depth of 24 feet due to a cobble zone encountered within the
boring. Groundwater was observed in borings B-1 and B-3 at depths of approximately 17 to 18
feet below the ground surface. Groundwater was not encountered in boring B-2 which extended
to a maximum depth of approximately 15 feet below the ground surface.
GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
WARREN FEDERAL CREDIT UNION – LOT 1 PADS “A” AND “B”
SOUTHEAST OF EAST DRAKE ROAD AND ILLINOIS DRIVE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1202069
October 22, 2020
INTRODUCTION
The geotechnical subsurface exploration for the proposed Warren Federal Credit Union Lot 1
buildings, planned for construction at the southeast corner of East Drake Road and Illinois Drive in
Fort Collins, Colorado has been completed. To develop subsurface information in the proposed
development area, three (3) soil borings were drilled to depths of approximately 15 to 24 feet below
existing site grades. A diagram indicating the approximate boring locations is included with this
report.
We understand the proposed development will include an approximate 3,700 square foot (SF)
building and 2,400 SF single-story slab-on-grade retail buildings. We anticipate maximum
foundations loads will be relatively light to moderate with maximum wall and column loads less than
4 klf and 150 kips, respectively. Floor loads are expected to be light. If the actual loads vary
significantly from the assumed loads, or if below grade construction is planned, we should be
consulted to verify our recommendations are consistent for the actual loads and proposed
foundation/floor slab elevations. Small grade changes are expected to develop site grades for the
proposed improvements.
The purpose of this report is to describe the subsurface conditions encountered in the test borings,
analyze and evaluate the field and laboratory test data and provide geotechnical recommendations
concerning design and construction of foundations and floor slabs and support of flatwork.
EXPLORATION AND TESTING PROCEDURES
The test boring locations were selected and established in the field by EEC personnel by pacing and
estimating angles from identifiable site features. The approximate locations of the borings are
shown on the attached boring location diagram. The boring locations should be considered accurate
only to the degree implied by the methods used to make the field measurements.
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EEC Project No. 1202069
October 22, 2020
Page 2
The test borings were advanced using a truck mounted, CME-55 drill rig equipped with a hydraulic
head employed in drilling and sampling operations. The boreholes were advanced using 4-inch
nominal diameter continuous flight augers. Samples of the subsurface materials encountered were
obtained using split-barrel and California barrel sampling procedures in general accordance with
ASTM Specifications D1586 and D3550, respectively.
In the split-barrel and California barrel sampling procedures, standard sampling spoons are advanced
into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of
blows required to advance the split-barrel and California barrel samplers is recorded and is used to
estimate the in-situ relative density of cohesionless soils and, to a lesser degree of accuracy, the
consistency of cohesive soils. In the California barrel sampling procedure, relatively intact samples
are obtained in removable brass liners. All samples obtained in the field were sealed and returned to
our laboratory for further examination, classification and testing.
Laboratory moisture content tests were completed on each of the recovered samples with unconfined
compressive strength of appropriate samples estimated using a calibrated hand penetrometer.
Atterberg limits and washed sieve analysis tests were completed on select samples to evaluate the
quantity and plasticity of fines in the subgrades. Swell/consolidation testing was completed on select
samples to evaluate the potential for the subgrade materials to change volume with variation in
moisture content and load. Soluble sulfate tests were completed on selected samples to estimate the
potential for sulfate attack on site cast concrete. Results of the outlined tests are indicated on the
attached boring logs and summary sheets.
As part of the testing program, all samples were examined in the laboratory and classified in general
accordance with the attached General Notes and the Unified Soil Classification System, based on the
soil’s texture and plasticity. The estimated group symbol for the Unified Soil Classification System
is indicated on the boring logs and a brief description of that classification system is included with
this report.
SITE AND SUBSURFACE CONDITIONS
The proposed buildings are planned for construction at the southeast corner of East Drake Road and
Illinois Drive in Fort Collins, Colorado. The lot is currently undeveloped. Vegetation, weeds, and
topsoil were observed at the surface of some borings. Ground surface in this area is relatively flat.
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EEC Project No. 1202069
October 22, 2020
Page 3
EEC field personnel were on site during drilling to evaluate the subsurface conditions encountered
and direct the drilling activities. Field logs prepared by EEC site personnel were based on visual and
tactual observation of disturbed samples and auger cuttings. The final boring logs included with this
report may contain modifications to the field logs based on results of laboratory testing and
evaluation. Based on results of the field borings and laboratory testing, subsurface conditions can be
generalized as follows.
From the ground surface, the subgrades underlying the surficial topsoil and vegetation described
previously consisted of lean clay with sand extending to the depths explored at approximately 15 feet
below the ground surface in boring B-2 and to the underlying sand and gravel soils at depths of
approximately 18 to 19 feet below the ground surface in the remaining borings. The lean clay with
sand subsoils were generally stiff to very stiff and exhibited low to moderate swell potential at
current moisture and density conditions. Sand/gravel soils were encountered below the lean clay
soils and extended to the depths explored, approximately 20 to 24 feet below the ground surface. The
sand/gravel soils were dense to very dense and refusal was encountered in boring B-3 at a depth of
24 feet due to a cobble zone encountered within the boring.
The stratification boundaries indicated on the boring logs represent the approximate location of
changes in soil types; in-situ, the transition of materials may be gradual and indistinct.
GROUNDWATER CONDITIONS
Observations were made while drilling and after completion of the borings to detect the presence and
depth to hydrostatic groundwater. At the time of drilling, perched groundwater was observed in a
borings B-1 and B-2 at depths of approximately 17 to 18 feet below the ground surface.
Groundwater was not encountered in boring B-2 which extended to a maximum depth of
approximately 15 feet below the ground surface. The borings were backfilled upon completion of the
drilling operations; therefore, subsequent groundwater measurements were not performed.
Fluctuations in groundwater levels can occur over time depending on variations in hydrologic
conditions and other conditions not apparent at the time of this report. Longer term monitoring of
water levels in cased wells, which are sealed from the influence of surface water, would be required
to more accurately evaluate fluctuations in groundwater levels at the site. We have typically noted
deepest groundwater levels in late winter and shallowest groundwater levels in mid to late summer.
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EEC Project No. 1202069
October 22, 2020
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ANALYSIS AND RECOMMENDATIONS
Swell – Consolidation Test Results
The swell-consolidation test is performed to evaluate the swell or collapse potential of soils to assist in
determining foundation, floor slab and pavement design criteria. In this test, relatively undisturbed
samples obtained directly from the California sampler are placed in a laboratory apparatus and
inundated with water under a predetermined load. The swell-index is the resulting amount of swell or
collapse after the inundation period expressed as a percent of the sample’s preload/initial thickness.
After the inundation period, additional incremental loads are applied to evaluate the swell pressure
and/or consolidation.
For this assessment, we conducted four (4) swell-consolidation tests on relatively undisturbed soil
samples obtained at various intervals/depths on the site. The swell index values for the in-situ soil
samples analyzed revealed low to moderate swell characteristics as indicated on the attached swell
test summaries. The (+) test results indicate the soil materials swell potential characteristics while
the (-) test results indicate the soils materials collapse/consolidation potential characteristics when
inundated with water. The following table summarizes the swell-consolidation laboratory test results
for samples obtained during our field explorations for the subject site.
Table I – Laboratory Swell-Consolidation Test Results
No of
Samples
Tested
Pre-Load /
Inundation
Pressure,
PSF
Description of Material
In-Situ Characteristics Range of Swell – Index
Test Results Range of Moisture
Contents, %
Range of Dry Densities,
PCF
Low End,
%
High
End, %
Low End,
PCF
High End,
PCF
Low End
(+/-) %
High
End, (+/-)
%
1 150 Lean Clay with Sand (CL) 6.6 94.2 (+) 2.7
2 500 Lean Clay with Sand (CL) 9.0 12.2 120.2 131.1 (+) 2.1 (+) 3.2
1 1000 Lean Clay with Sand (CL) 18.2 111.3 (-) 0.3
Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide
uniformity in terminology between geotechnical engineers to provide a relative correlation of slab
performance risk to measured swell. “The representative percent swell values are not necessarily
measured values; rather, they are a judgment of the swell of the soil and/or bedrock profile likely to
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EEC Project No. 1202069
October 22, 2020
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influence slab performance.” Geotechnical engineers use this information to also evaluate the swell
potential risks for foundation performance based on the risk categories.
Table II - Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Slab Performance Risk Category Representative Percent Swell
(500 psf Surcharge)
Representative Percent Swell
(1000 psf Surcharge)
Low 0 to < 3 0 < 2
Moderate 3 to < 5 2 to < 4
High 5 to < 8 4 to < 6
Very High > 8 > 6
Based on the laboratory test results, a majority of the in-situ samples analyzed for this project were
within the low to moderate range.
Site Preparation
Prior to placement of any fill and/or improvements, we recommend any existing topsoil, vegetation,
and any unsuitable materials be removed from the planned development areas. Due to the moderate
swell potential of the near surface lean clay soils, subgrades below interior floor slabs should be over
excavated a minimum of 4 feet below final floor slab elevations, and subgrades below spread
footings should be over excavated to a minimum depth of approximately 2 feet below footings. The
over excavation for each building should extend laterally in all directions beyond the edges of
foundations a minimum 8 inches for every 12 inches of excavation depth.
After removal of all topsoil, vegetation, overexcavation, and removal of unacceptable or unsuitable
subsoils and prior to placement of fill, the exposed soils should be scarified to a depth of 9 inches,
adjusted in moisture content to within ±2% of standard Proctor optimum moisture content and
compacted to at least 95% of the material's standard Proctor maximum dry density as determined in
accordance with ASTM Specification D698.
Fill materials used to replace the over-excavated zone and establish grades in the building areas,
after the initial zone has been prepared as recommended above, should consist of approved on-site
lean clay with sand subsoils or approved structural fill material which is free from organic matter
and debris. If on-site cohesive subsoils are used as engineered fill, they should be placed in
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EEC Project No. 1202069
October 22, 2020
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maximum 9-inch thick loose lifts, and be moisture conditioned and compacted as recommended for
the scarified soils. If structural fill materials are used, they should be graded similarly to a CDOT
Class 5, 6 or 7 aggregate base with sufficient fines to prevent ponding of water within the fill.
Structural fill material should be placed in loose lifts not to exceed 9 inches thick, adjusted to a
workable moisture content and compacted to at least 95% of standard Proctor maximum dry density
as determined by ASTM Specification D698.
Care should be exercised after preparation of the subgrades to avoid disturbing the subgrade
materials. The site lean clay with sand soils will be subject to instability/pumping with elevated
moisture contents. Positive drainage should be developed away from the structures and pavements
to avoid wetting of subgrade materials. Subgrade materials becoming wet subsequent to
construction of the site improvements can result in unacceptable performance.
Footing Foundations
Based on materials observed from the test boring locations, it is our opinion that the proposed
buildings could be supported on conventional footing foundations bearing on a minimum 2 feet of
properly placed fill materials, prepared as recommended in the section Site Preparation. For design
of footing foundations bearing on suitable strength subsoils or on properly placed fill, we
recommend using a maximum net allowable total load soil bearing pressure not to exceed 1,500 psf.
The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum
surrounding overburden pressure.
Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches
below adjacent exterior grade to provide frost protection. We recommend formed continuous
footings have a minimum width of 12 inches and isolated column foundations have a minimum
width of 24 inches. Trenched foundations should not be used.
No unusual problems are anticipated in completing the excavations required for construction of the
footing foundations. Care should be taken during construction to avoid disturbing the foundation
bearing materials. Materials which are loosened or disturbed by the construction activities or
materials which become dry and desiccated or wet and softened should be removed and replaced
prior to placement of foundation concrete. Care should be taken to ensure spread footings are placed
on similar materials in order to provide a uniform bearing stratum.
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EEC Project No. 1202069
October 22, 2020
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We estimate the long-term settlement of footing foundations designed and constructed as outlined
above would be 1 inch or less.
Floor Slabs and Exterior Flatwork
Subgrades for floor slabs and exterior flatwork should be prepared as outlined in the section Site
Preparation. For structural design of concrete slabs-on-grade, a modulus of subgrade reaction of
100 pounds per cubic inch (pci) could be used for floors supported on properly placed cohesive fill
materials or 200 pci if an imported structural fill material is selected.
Additional floor slab design and construction recommendations are as follows:
Interior partition walls should be separated/floated from floor slabs to allow for
independent movement.
Positive separations and/or isolation joints should be provided between slabs and all
foundations, columns, and utility lines to allow for independent movement.
Control joints should be provided in slabs to control the location and extent of
cracking.
Interior trench backfill placed beneath slabs should be compacted in a similar manner
as previously described for imported structural fill material.
Floor slabs should not be constructed on frozen subgrade.
Other design and construction considerations as outlined in the ACI Design Manual
should be followed.
For interior floor slabs, depending on the type of floor covering and adhesive used, those material
manufacturers may require that specific subgrade, capillary break, and/or vapor barrier requirements
be met. The project architect and/or material manufacturers should be consulted with for specific
under slab requirements.
Care should be exercised after development of the floor slab and exterior flatwork subgrades to
prevent disturbance of the in-place materials. Subgrade soils which are loosened or disturbed by
construction activities or soils which become wet and softened or dry and desiccated should be
removed and replaced or reworked in place prior to placement of the overlying slabs.
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EEC Project No. 1202069
October 22, 2020
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Lateral Earth Pressures
Portions of the new structure or site improvements which are constructed below grade may be
subject to lateral earth pressures. Passive lateral earth pressures may help resist the driving forces
for retaining wall or other similar site structures. Active lateral earth pressures could be used for
design of structures where some movement of the structure is anticipated, such as retaining walls.
The total deflection of structures for design with active earth pressure is estimated to be on the order
of one half of one percent of the height of the down slope side of the structure. We recommend at-
rest pressures be used for design of structures where rotation of the walls is restrained, such as below
grade walls for a building. Passive pressures and friction between the footing and bearing soils
could be used for design of resistance to movement of retaining walls.
Coefficient values for backfill with anticipated types of soils for calculation of active, at-rest and
passive earth pressures are provided in Table III below. Equivalent fluid pressure is equal to the
coefficient times the appropriate soil unit weight. Those coefficient values are based on horizontal
backfill with backfill soils consisting of on-site essentially cohesive subsoils. For at-rest and active
earth pressures, slopes down and away from the structure would result in reduced driving forces with
slopes up and away from the structures resulting in greater forces on the walls. The passive
resistance would be reduced with slopes away from the wall. The top 30 inches of soil on the
passive resistance side of walls could be used as a surcharge load; however, should not be used as a
part of the passive resistance value. Frictional resistance is equal to the tangent of the friction angle
times the normal force. Surcharge loads or point loads placed in the backfill can also create
additional loads on below grade walls. Those situations should be designed on an individual basis.
Table III - Lateral Earth Pressures
Soil Type On-Site Overburden Cohesive Soils Imported Medium Dense Granular
Material
Wet Unit Weight (psf) 115 135
Saturated Unit Weight (psf) 135 140
Friction Angle () – (assumed) 20° 35°
Active Pressure Coefficient 0..49 0.27
At-rest Pressure Coefficient 0.66 0.43
Passive Pressure Coefficient 2.04 3.70
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EEC Project No. 1202069
October 22, 2020
Page 9
The outlined values do not include factors of safety nor allowances for hydrostatic loads and are
based on assumed friction angles, which should be verified after potential material sources have been
identified. Care should be taken to develop appropriate drainage systems behind below grade walls
to eliminate potential for hydrostatic loads developing on the walls. Those systems would likely
include perimeter drain systems extending to sump areas or free outfall where reverse flow cannot
occur into the system. Where necessary, appropriate hydrostatic load values should be used for
design.
Seismic
The site soil conditions generally consist of lean clay soils which extend to the underlying granular
soils at depths of approximately 18 to 19 feet. For those site conditions, the International Building
Codes indicates a Seismic Site Classification of D. Drilling to a greater depth could reveal a
different site classification.
Water Soluble Sulfates (SO4)
The water-soluble sulfate (SO4) content of the on-site overburden subsoils, taken during our
subsurface exploration at random locations and intervals are provided below. Based on reported
sulfate content test results, the Class/severity of sulfate exposure for concrete in contact with the on-
site subsoils is provided in this report.
Table IV - Water Soluble Sulfate Test Results
Sample Location Description % of Soil by Weight
B-2, S-2, at 4’ Lean Clay with Sand (CL) 0.18
Based on the results as presented above, ACI 318, Section 4.2 indicates the site soils have a
moderate risk of sulfate attack on Portland cement concrete, therefore, ACI Class S1 requirements
should be followed for concrete placed in the lean clay soils and underlying bedrock. Foundation
concrete should be designed in accordance with the provisions of the ACI Design Manual, Section
318, Chapter 4.
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EEC Project No. 1202069
October 22, 2020
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Other Considerations
Positive drainage should be developed away from the structure and pavement areas with a minimum
slope of 1 inch per foot for the first 10 feet away from the improvements in landscape areas. Care
should be taken in planning of landscaping adjacent to the buildings to avoid features which would
pond water adjacent to the foundations or stemwalls. Placement of plants which require irrigation
systems or could result in fluctuations of the moisture content of the subgrade material should be
avoided adjacent to site improvements. Irrigation systems should not be placed within 5 feet of the
perimeter of the buildings and parking areas. Spray heads should be designed not to spray water on
or immediately adjacent to the structures or site pavements. Roof drains should be designed to
discharge at least 5 feet away from the structures and away from the pavement areas.
Excavations into the on-site lean clay can be expected to stand on relatively steep, temporary slopes
during construction. The individual contractor(s) should be made responsible for designing and
constructing stable, temporary excavations as required to maintain stability of both the excavation
sides and bottom. All excavations should be sloped or shored in the interest of safety following local
and federal regulations, including current OSHA excavation and trench safety standards.
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data obtained from the
soil borings performed at the indicated locations and from any other information discussed in this
report. This report does not reflect any variations, which may occur between borings or across the
site. The nature and extent of such variations may not become evident until construction. If
variations appear evident, it will be necessary to re-evaluate the recommendations of this report.
It is recommended that the geotechnical engineer be retained to review the plans and specifications,
so comments can be made regarding the interpretation and implementation of our geotechnical
recommendations in the design and specifications. It is further recommended that the geotechnical
engineer be retained for testing and observations during earthwork phases to help determine that the
design requirements are fulfilled.
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EEC Project No. 1202069
October 22, 2020
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This report has been prepared for the exclusive use of Aller Architects PC for specific application to
the project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranty, express or implied, is made. In the event that any changes in
the nature, design, or location of the project as outlined in this report are planned, the conclusions
and recommendations contained in this report shall not be considered valid unless the changes are
reviewed, and the conclusions of this report are modified or verified in writing by the geotechnical
engineer.
Earth Engineering Consultants, LLC
DRILLING AND EXPLORATION
DRILLING & SAMPLING SYMBOLS:
SS: Split Spoon ‐ 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample
ST: Thin‐Walled Tube ‐ 2" O.D., unless otherwise noted WS: Wash Sample
R: Ring Barrel Sampler ‐ 2.42" I.D., 3" O.D. unless otherwise noted
PA: Power Auger FT: Fish Tail Bit
HA: Hand Auger RB: Rock Bit
DB: Diamond Bit = 4", N, B BS: Bulk Sample
AS: Auger Sample PM: Pressure Meter
HS: Hollow Stem Auger WB: Wash Bore
Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2‐inch O.D. split spoon, except where noted.
WATER LEVEL MEASUREMENT SYMBOLS:
WL : Water Level WS : While Sampling
WCI: Wet Cave in WD : While Drilling
DCI: Dry Cave in BCR: Before Casing Removal
AB : After Boring ACR: After Casting Removal
Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated
levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D‐2488. Coarse Grained
Soils have move than 50% of their dry weight retained on a
#200 sieve; they are described as: boulders, cobbles, gravel or
sand. Fine Grained Soils have less than 50% of their dry weight
retained on a #200 sieve; they are 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 relative in‐
place density and fine grained soils on the basis of their
consistency. Example: Lean clay with sand, trace gravel, stiff
(CL); silty sand, trace gravel, medium dense (SM).
CONSISTENCY OF FINE‐GRAINED SOILS
Unconfined Compressive
Strength, Qu, psf Consistency
< 500 Very Soft
500 ‐ 1,000 Soft
1,001 ‐ 2,000 Medium
2,001 ‐ 4,000 Stiff
4,001 ‐ 8,000 Very Stiff
8,001 ‐ 16,000 Very Hard
RELATIVE DENSITY OF COARSE‐GRAINED SOILS:
N‐Blows/ft Relative Density
0‐3 Very Loose
4‐9 Loose
10‐29 Medium Dense
30‐49 Dense
50‐80 Very Dense
80 + Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
joints. May be color change.
Moderate Some decomposition and color change
throughout.
High Rock highly decomposed, may be extremely
broken.
HARDNESS AND DEGREE OF CEMENTATION:
Limestone and Dolomite:
Hard Difficult to scratch with knife.
Moderately Can be scratched easily with knife.
Hard Cannot be scratched with fingernail.
Soft Can be scratched with fingernail.
Shale, Siltstone and Claystone:
Hard Can be scratched easily with knife, cannot be
scratched with fingernail.
Moderately Can be scratched with fingernail.
Hard
Soft Can be easily dented but not molded with
fingers.
Sandstone and Conglomerate:
Well Capable of scratching a knife blade.
Cemented
Cemented Can be scratched with knife.
Poorly Can be broken apart easily with fingers.
Cemented
Group
Symbol
Group Name
Cu≥4 and 1<Cc≤3E GW Well-graded gravel F
Cu<4 and/or 1>Cc>3E GP Poorly-graded gravel F
Fines classify as ML or MH GM Silty gravel G,H
Fines Classify as CL or CH GC Clayey Gravel F,G,H
Cu≥6 and 1<Cc≤3E SW Well-graded sand I
Cu<6 and/or 1>Cc>3E SP Poorly-graded sand I
Fines classify as ML or MH SM Silty sand G,H,I
Fines classify as CL or CH SC Clayey sand G,H,I
inorganic PI>7 and plots on or above "A" Line CL Lean clay K,L,M
PI<4 or plots below "A" Line ML Silt K,L,M
organic Liquid Limit - oven dried Organic clay K,L,M,N
Liquid Limit - not dried Organic silt K,L,M,O
inorganic PI plots on or above "A" Line CH Fat clay K,L,M
PI plots below "A" Line MH Elastic Silt K,L,M
organic Liquid Limit - oven dried Organic clay K,L,M,P
Liquid Limit - not dried Organic silt K,L,M,O
Highly organic soils PT Peat
(D30)2
D10 x D60
GW-GM well graded gravel with silt NPI≥4 and plots on or above "A" line.
GW-GC well-graded gravel with clay OPI≤4 or plots below "A" line.
GP-GM poorly-graded gravel with silt PPI plots on or above "A" line.
GP-GC poorly-graded gravel with clay QPI plots below "A" line.
SW-SM well-graded sand with silt
SW-SC well-graded sand with clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
Earth Engineering Consultants, LLC
IIf soil contains >15% gravel, add "with gravel" to
group name
JIf Atterberg limits plots shaded area, soil is a CL-
ML, Silty clay
Unified Soil Classification System
Soil Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests
Sands 50% or more
coarse fraction
passes No. 4 sieve
Fine-Grained Soils
50% or more passes
the No. 200 sieve
<0.75 OL
Gravels with Fines
more than 12%
fines
Clean Sands Less
than 5% fines
Sands with Fines
more than 12%
fines
Clean Gravels Less
than 5% fines
Gravels more than
50% of coarse
fraction retained on
No. 4 sieve
Coarse - Grained Soils
more than 50%
retained on No. 200
sieve
CGravels with 5 to 12% fines required dual symbols:
Kif soil contains 15 to 29% plus No. 200, add "with sand"
or "with gravel", whichever is predominant.
<0.75 OH
Primarily organic matter, dark in color, and organic odor
ABased on the material passing the 3-in. (75-mm)
sieve
ECu=D60/D10 Cc=
HIf fines are organic, add "with organic fines" to
group name
LIf soil contains ≥ 30% plus No. 200 predominantly sand,
add "sandy" to group name.
MIf soil contains ≥30% plus No. 200 predominantly gravel,
add "gravelly" to group name.
DSands with 5 to 12% fines require dual symbols:
BIf field sample contained cobbles or boulders, or
both, add "with cobbles or boulders, or both" to
group name.FIf soil contains ≥15% sand, add "with sand" to
GIf fines classify as CL-ML, use dual symbol GC-
CM, or SC-SM.
Silts and Clays
Liquid Limit less
than 50
Silts and Clays
Liquid Limit 50 or
more
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110PLASTICITY INDEX (PI) LIQUID LIMIT (LL)
ML OR OL
MH OR OH
For Classification of fine-grained soils and
fine-grained fraction of coarse-grained
soils.
Equation of "A"-line
Horizontal at PI=4 to LL=25.5
then PI-0.73 (LL-20)
Equation of "U"-line
Vertical at LL=16 to PI-7,
then PI=0.9 (LL-8)
CL-ML
B-3B-2B-112Boring Location DiagramWarren Federal Credit Union- Fort Collins, ColoradoEEC Project #: 1202069October 2020EARTH ENGINEERING CONSULTANTS, LLCASSro[imate BoringLocations1LegendSite PKotos PKotos taNen in aSSro[imatelocation, in direction oI arroZ
WARREN FEDERAL CREDIT UNION
FORT COLLINS, COLORADO
EEC PROJECT NO. 1202069
OCTOBER 2020
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
SPARSE VEGETATION & TOPSOIL _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
very stiff to stiff _ _
3
_ _
4
_ _
CS 5 27 9000+ 9.0 118.8 35 18 82.8 4500 psf 3.2%
_ _
6
_ _
7
_ _
8
_ _
9
brown / reddish _ _
SS 10 4 8500 15.6
_ _
11
_ _
12
_ _
13
_ _
14
_ _
CS 15 18 9000+ 15.7 114.0
_ _
16
_ _
17
_ _
18
_ _
SAND / GRAVEL (SP / GP) 19
brown / gray / rust _ _
very dense SS 20 50/11" 1000 12.7
_ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
WARREN FEDERAL CREDIT UNION
FORT COLLINS, COLORADO
LOG OF BORING B-1PROJECT NO: 1202069 OCTOBER 2020
SHEET 1 OF 1 WATER DEPTH
START DATE 10/7/2020 WHILE DRILLING 17.0'
FINISH DATE 10/7/2020
A-LIMITS SWELL
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
SPARSE VEGETATION & WEEDS _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
very stiff to stiff _ _% @ 150 psf
CS 3 28 6500 6.6 104.9 36 18 83.7 550 psf 2.7%
_ _
4
_ _
SS 5 10 9000+ 13.8
_ _
6
_ _
7
_ _
8
_ _
9
red / brown _ _% @ 1000 psf
CS 10 12 8000 18.2 105.1 < 1000 psf None
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 15 9000+ 16.0
_ _
BOTTOM OF BORING DEPTH 15.5' 16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
WARREN FEDERAL CREDIT UNION
FORT COLLINS, COLORADO
PROJECT NO: 1202069 LOG OF BORING B-2 OCTOBER 2020
SHEET 1 OF 1 WATER DEPTH
START DATE 10/7/2020 WHILE DRILLING None
FINISH DATE 10/7/2020
A-LIMITS SWELL
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
SPARSE VEGETATION & WEEDS _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits 3
_ _
4
_ _
CS 5 18 9000+ 12.2 116.7 35 20 78.7 4500 psf 2.1%
_ _
6
_ _
7
_ _
8
_ _
9
brown / red _ _
SS 10 7 9000+ 13.6
_ _
11
_ _
12
_ _
13
_ _
14
_ _
CS 15 15 9000+ 20.8 105.1
_ _
16
_ _
17
_ _
18
_ _
19
_ _
SAND / GRAVEL (SP / GP) SS 20 50 500 14.5
brown / gray / rust _ _
dense 21
_ _
22
_ _
23
_ _
24
* hit rock, no sample recovery SS _ _
BOTTOM OF BORING DEPTH 24.5'25
_ _
Earth Engineering Consultants, LLC
WARREN FEDERAL CREDIT UNION
FORT COLLINS, COLORADO
PROJECT NO: 1202069 LOG OF BORING B-3 OCTOBER 2020
SHEET 1 OF 1 WATER DEPTH
START DATE 10/7/2020 WHILE DRILLING 18.0'
FINISH DATE 10/7/2020
A-LIMITS SWELL
Project:
Location:
Project #:
Date:
Warren Federal Credit Union
Fort Collins, Colorado
1202069
October 2020
Beginning Moisture: 9.0% Dry Density: 131.1 pcf Ending Moisture: 13.7%
Swell Pressure: 4500 psf % Swell @ 500: 3.2%
Sample Location: Boring 1, Sample 1, Depth 4'
Liquid Limit: 35 Plasticity Index: 18 % Passing #200: 82.8%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10Percent MovementLoad (TSF)SwellConsolidatioWater Added
Project:
Location:
Project #:
Date:
Warren Federal Credit Union
Fort Collins, Colorado
1202069
October 2020
Beginning Moisture: 6.6% Dry Density: 94.2 pcf Ending Moisture: 25.5%
Swell Pressure: 550 psf % Swell @ 150: 2.7%
Sample Location: Boring 2, Sample 1, Depth 2'
Liquid Limit: 36 Plasticity Index: 18 % Passing #200: 83.7%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10Percent MovementLoad (TSF)SwellConsolidatioWater Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Red / Brown Lean Clay with Sand (CL)
Sample Location: Boring 2, Sample 3, Depth 9'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
Beginning Moisture: 18.2% Dry Density: 111.3 pcf Ending Moisture: 18.3%
Swell Pressure: < 1000 psf % Swell @ 1000: None
Warren Federal Credit Union
Fort Collins, Colorado
1202069
October 2020
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10Percent MovementLoad (TSF)SwellConsolidatioWater Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
Sample Location: Boring 3, Sample 1, Depth 4'
Liquid Limit: 35 Plasticity Index: 20 % Passing #200: 78.7%
Beginning Moisture: 12.2% Dry Density: 120.2 pcf Ending Moisture: 15.5%
Swell Pressure: 4500 psf % Swell @ 500: 2.1%
Warren Federal Credit Union
Fort Collins, Colorado
1202069
October 2020
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10Percent MovementLoad (TSF)SwellConsolidatioWater Added