HomeMy WebLinkAboutPLANETSCALE LIVING - PDP200015 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTSoilogic, Inc.
3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144
March 17, 2020
Wayne D. Anderson, AIA, LLC
7825 West Ontario Place
Littleton, Colorado 80128
Re: Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street
Fort Collins, Colorado
Soilogic Project # 20-1045
Mr. Anderson:
Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface
exploration you requested for the proposed additions to the existing building located at
906 East Stuart Street in Fort Collins, Colorado. The results of our subsurface exploration
and pertinent geotechnical engineering recommendations are included with this report.
We understand the project involves construction of an addition on the north side of the
existing building and the possible construction of an addition on the east side of the
existing building. The additions will be one to two-story wood-frame structures
constructed as slab-on-grade. Foundation loads for the additions are expected to be
relatively light, with continuous wall loads less than 3 kips per lineal foot and individual
column loads (if any) less than 50 kips. Small grade changes are anticipated to develop
finish site grades in the areas of the proposed additions.
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 addition foundations and
support of floor slabs and exterior flatwork. 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.
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
2
SITE DESCRIPTION
The proposed/possible additions will be constructed on the north and east sides of the
existing building located at 906 East Stuart Street in Fort Collins, Colorado. We
understand the existing building is a single to two-story structure constructed as slab-on-
grade and is supported by some type of conventional spread footing foundation system.
We anticipate new footing foundations for the additions will bear at approximately the
same elevation the as existing foundations. At the time of our site exploration, the
proposed construction areas contained several small to medium-sized diameter deciduous
trees, wood chips, a thin mantle of vegetation and topsoil, exterior flatwork and other
landscaping improvements and were relatively level. The maximum difference in ground
surface elevation across the addition footprints was estimated to be less than two (2) feet.
EXPLORATION AND TESTING PROCEDURES
To develop subsurface information in the area of the proposed additions, two (2) soil
borings were extended to a depth of approximately 15 feet below present site grade as
near to the approximate addition footprints as site access would allow. The boring
locations were established in the field by Soilogic personnel based on discussion with the
client, the accessibility of the site and by pacing and estimating angles and distances from
identifiable site references. A diagram indicating the approximate boring locations is
included with this report. The boring locations indicated on this diagram should be
considered accurate only to the degree implied by the methods used to make the field
measurements. Graphic logs 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 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
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
3
obtained in the field were sealed and returned to the laboratory for further evaluation,
classification and testing.
The samples collected were tested in the laboratory to measure natural moisture content
and were visually and/or 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. A
thin layer of landscaping wood chips was encountered at the surface at the location of
boring B-2 and a thin mantle of vegetation and topsoil at the location of boring B-1. The
wood chip and vegetation layers were underlain by brown/reddish-brown lean clay with
varying amounts of sand and trace to minor amounts of gravel. The lean clay varied from
medium stiff to very stiff in terms of consistency, exhibited low swell potential at current
moisture and density conditions and extended to the bottom of both borings at a depth of
approximately 15 feet below present site grade.
The stratigraphy indicated on the included boring logs represents the approximate
location of changes in soil types. Actual changes may be more gradual than those
indicated.
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
4
Groundwater was not encountered in either of the completed site borings to the depth
explored (about 15 feet below ground surface) when checked immediately after 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 and/or
bedrock. Trapped water is typically encountered within more permeable zones of layered
soil and bedrock systems. The location and amount of perched/trapped water can also
vary over time.
ANALYSIS AND RECOMMENDATIONS
Demolition and Site Development
Within the proposed addition and new exterior flatwork areas, all existing foundations,
floor slabs and any other site improvements should be completely removed. Care will be
needed to ensure all in-place fill/backfill materials associated with the existing building
are also completely removed at this time. In addition, all trees, tree root systems and dry
and desiccated soils associated with the tree root systems should be completely removed
from within the areas of the proposed additions and beneath exterior flatwork. The depth
and extent of required removal can best be established at the time of excavation through
openhole observation. If/where required, the excavated/removed materials should be
replaced as controlled and compacted fill as outlined below.
After stripping and completing all cuts and removal procedures and prior to placement of
any fill, removal area backfill or exterior flatwork concrete, we recommend the exposed
subgrade soils be scarified to a depth of 9 inches, adjusted in moisture content and
compacted to at least 95% of the materials standard Proctor maximum dry density. The
moisture content of the scarified soils should be adjusted to be within the range of -1% to
+3% of standard Proctor optimum moisture content at the time of compaction.
Fill and removal area backfill soils required to develop the site 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
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
5
opinion the natural site lean clay could be used as fill and backfill provided the proper
moisture content is developed in those materials at the time of placement and
compaction. If required, imported soils should consist of approved LVC and relatively
impervious soils free from organic matter and debris. Site fill and backfill should contain
a minimum of 25% fines in order to reduce the ability of those materials to pond and
transmit water. Suitable fill and backfill soils should be placed in loose lifts not to exceed
9 inches thick, adjusted in moisture content and compacted as recommended for the
scarified soils above.
Care should be taken to avoid disturbing all subgrade soils prior to placement of any
overlying improvements. Soils which are allowed to dry out or become wet and softened
or disturbed by the construction activities should be removed and replaced or reworked in
place prior to concrete placement.
Foundations
Based on the materials encountered in the completed site borings and results of
laboratory testing, it is our opinion the proposed lightly-loaded building additions could
be supported by continuous spread footing and isolated pad foundations bearing on
natural, undisturbed lean clay with low volume change potential and/or properly placed
and compacted overexcavation/backfill (if/where required). For design of new footing
foundations bearing on natural, undisturbed medium stiff to very stiff lean clay and/or
properly placed and compacted overexcavation/backfill, we recommend using a
maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, we
recommend continuous spread footing and isolated pad foundations be designed to
maintain a minimum dead-load pressure of 500 psf (or as high as practical) on the
supporting soils.
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.
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
6
For design of footing foundations and foundation walls to resist lateral movement, a
passive equivalent fluid pressure value of 250 pcf could be used. The top 30 inches of
subgrade could be considered a surcharge load but should not be used in the passive
resistance calculations. A coefficient of friction of 0.35 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.
Backfill placed adjacent to foundation walls should consist of LVC potential and
relatively impervious soils free from organic matter, debris and other objectionable
materials. The natural site lean clay 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 lean clay or similar backfill soils be placed in loose lifts
not to exceed 9 inches thick, adjusted in moisture and compacted as recommended for the
scarified soils in the “Demolition and Site Development” section of this report.
Excessive lateral stresses can be 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.
We estimate settlement of footing foundations designed and constructed as outlined
above and resulting from the assumed structural loads would be less than 1 inch.
Differential settlement could approach the amount of total settlement estimated above. If
water from any source is allowed to infiltrate the foundation bearing soils, additional
movement of the foundations could occur. Some differential settlement should be
anticipated between the existing structure and proposed additions. An allowance for some
differential movement should be included in design.
Floor Slabs & Exterior Flatwork
The addition floor slabs and exterior flatwork could be supported directly on
reconditioned lean clay with low swell potential and/or properly moisture conditioned
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
7
and compacted fill or overexcavation/backfill soils (if/where required) developed as
outlined in the “Demolition and Site Development” section of this report.
Care should be taken to maintain the proper moisture content and avoid disturbing all
floor slab/flatwork subgrade soils prior to concrete placement. The exposed floor slab/
flatwork 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, snowmelt 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 addition 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 section of
the building and/or additions. A minimum 1½-inch void space is recommended beneath
all floating walls. Special attention to door framing, drywall installation, stair systems
and trim carpentry should be taken to isolate those elements from the floor slab, 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, 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 (ACI) section 302.
Geotechnical Subsurface Exploration Report
Proposed Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
8
Exterior flatwork will experience some movement subsequent to construction as the
subgrade soils increase in moisture content. Based on results of the completed field and
laboratory testing, we expect the amount of movement of exterior flatwork supported on
reconditioned natural site soils and/or properly placed and compacted fill and/or removal
area backfill would be limited. If undocumented fill is encountered in exterior flatwork
areas, overexcavation/backfill procedures could be considered to reduce the potential for
total and differential movement in these areas. Care should be taken to ensure exterior
flatwork is designed to provide positive drainage away from the building and addition
and that positive drainage is maintained throughout the life of the proposed
improvements.
Drainage
Positive drainage is imperative for satisfactory long-term performance of the proposed
addition and associated site improvements. We recommend positive drainage be
developed away from the additions 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 building and building additions. Shallower slopes could be considered in hardscape
areas. In the event that poor or negative drainage develops adjacent to the building and/
or building additions 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 structure additions 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 and building additions
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 Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
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 reflect 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 Renovation/Additions to Existing Building
906 East Stuart Street, Fort Collins, Colorado
Soilogic Project # 20-1045
10
3/17/2020
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. Reviewed by:
Alec Kaljian, E.I. Darrel DiCarlo, P.E.
Project Engineer Senior Project Engineer
LOG OF BORING B-1
1/1 CME 45
4" CFA
Automatic
JL / BM
Estimated Swell % Passing
SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve
(ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%)
4-6" VEGETATION & TOPSOIL -
1
-
2
-
3 CS 8 17.8 102.4 9000+ 0.4% - - - -
-
4
-
5 CS 8 18.5 103.7 7000 - - 36 22 72.2%
-
6
-
CL LEAN CLAY with varying 7
amounts of SAND -
brown, reddish-brown 8
medium stiff to very stiff -
trace to minor GRAVEL 9
-
10 CS 10 9.3 101.0 9000+ 0.4% 800 - - -
-
11
-
12
-
13
-
14
-
15 CS 20 12.2 117.1 9000+ - - - - -
BOTTOM OF BORING @ 15.0' -
16
-
17
-
18
-
19
-
20
-
21
-
22
-
23
-
24
-
25
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
LOG OF BORING B-2
1/1 CME 45
4" CFA
Automatic
JL / BM
Estimated Swell % Passing
SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve
(ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%)
2-4" MULCH -
1
-
2
-
3 CS 8 17.7 101.3 9000+ 0.3% - - - -
-
4
-
5 CS 11 12.6 103.3 9000+ 1.2% 1800 - - -
-
6
-
CL LEAN CLAY with varying 7
amounts of SAND -
brown, reddish-brown 8
medium stiff to stiff -
trace to minor GRAVEL 9
-
10 CS 10 11.8 105.6 8500 - - - - -
-
11
-
12
-
13
-
14
-
15 CS 11 16.9 110.0 6500 - - - - -
BOTTOM OF BORING @ 15.0' -
16
-
17
-
18
-
19
-
20
-
21
-
22
-
23
-
24
-
25
- -
USCS
Liquid Limit -
Plasticity Index -
% Passing #200 -
Dry Density (pcf) 102.4
500
Final Moisture 19.0%
% Swell @ 500 psf 0.4%
Swell Pressure (psf) -
Sample ID: B-1 @ 2
Sample Description: Brown Lean Clay with Sand (CL)
(Swell Only)
Initial Moisture 17.8%
SWELL/CONSOLIDATION TEST SUMMARY
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
Project # 20-1045
March 2020
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
10 100 1000 10000 100000
---------
Applied Load (psf)
Liquid Limit -
Plasticity Index -
% Passing #200 -
Dry Density (pcf) 101.0
SWELL/CONSOLIDATION TEST SUMMARY
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
Project # 20-1045
March 2020
Initial Moisture 9.3%
Sample ID: B-1 @ 9
Sample Description: Brown Sandy Lean Clay (CL) with trace Gravel
500
Final Moisture 21.6%
% Swell @ 500 psf 0.4%
Swell Pressure (psf) 800
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
10 100 1000 10000 100000
---------
Applied Load (psf)
Liquid Limit -
Plasticity Index -
% Passing #200 -
Dry Density (pcf) 101.3
SWELL/CONSOLIDATION TEST SUMMARY
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
Project # 20-1045
March 2020
Initial Moisture 17.7%
Sample ID: B-2 @ 2
Sample Description: Brown Lean Clay with Sand (CL)
(Swell Only)
500
Final Moisture 19.6%
% Swell @ 500 psf 0.3%
Swell Pressure (psf) -
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
10 100 1000 10000 100000
---------
Applied Load (psf)
Liquid Limit -
Plasticity Index -
% Passing #200 -
Dry Density (pcf) 103.3
SWELL/CONSOLIDATION TEST SUMMARY
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
Project # 20-1045
March 2020
Initial Moisture 12.6%
Sample ID: B-2 @ 4
Sample Description: Brown Sandy Lean Clay (CL) with trace Gravel
500
Final Moisture 22.1%
% Swell @ 500 psf 1.2%
Swell Pressure (psf) 1,800
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
10 100 1000 10000 100000
---------
Applied Load (psf)
UNIFIED SOIL CLASSIFICATION SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification
Group
Symbol
Group NameB
Clean Gravels Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF
Less than 5% finesC Cu
< 4 and/or 1 > Cc > 3E GP Poorly graded gravelF
Fines classify as ML or MH GM Silty gravelF,G, H
Coarse Grained Soils
More than 50% retained
on No. 200 sieve
Gravels
More than 50% of coarse
fraction retained on
No. 4 sieve Gravels with Fines More
than 12% finesC Fines classify as CL or CH GC Clayey gravelF,G,H
Clean Sands Cu ! 6 and 1 " Cc " 3E SW Well graded sandI
Less than 5% finesD Cu
< 6 and/or 1 > Cc > 3E SP Poorly graded sandI
Fines classify as ML or MH SM Silty sandG,H,I
Sands
50% or more of coarse
fraction passes
No. 4 sieve Sands with Fines
More than 12% finesD Fines classify as CL or CH SC Clayey sandG,H,I
Silts and Clays PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M
Liquid limit less than 50
Inorganic
PI < 4 or plots below “A” lineJ ML SiltK,L,M
Liquid limit - oven
dried
Organic clayK,L,M,N
Fine-Grained Soils
50% or more passes the
No. 200 sieve
Organic
Liquid limit - not
dried
< 0.75 OL
Organic siltK,L,M,O
Inorganic PI plots on or above “A” line CH Fat clayK,L,M
Silts and Clays
Liquid limit 50 or more
PI plots below “A” line MH Elastic siltK,L,M
Organic Liquid limit - oven dried Organic clayK,L,M,P
Liquid limit - not dried
< 0.75 OH
Organic siltK,L,M,Q
Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-in. (75-mm) sieve
B If field sample contained cobbles or boulders, or both, add “with cobbles
or boulders, or both” to group name.
C Gravels with 5 to 12% fines require dual symbols: GW-GM well graded
gravel with silt, GW-GC well graded gravel with clay, GP-GM poorly
graded gravel with silt, GP-GC poorly graded gravel with clay.
D Sands with 5 to 12% fines require dual symbols: 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
E Cu = D60/D10 Cc =
GENERAL NOTES
DRILLING & SAMPLING SYMBOLS:
SS: Split Spoon - 1⅜" I.D., 2" O.D., unless otherwise noted HS: Hollow Stem Auger
ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA: Power Auger
RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA: Hand Auger
CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB: Rock Bit
BS: Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary
The number of blows required to advance a standard 2-inch O.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” O.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: 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 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 COARSE-GRAINED SOILS BEDROCK
(CB)
Blows/Ft.
(SS)
Blows/Ft.
Consistency
(CB)
Blows/Ft.
(SS)
Blows/Ft.
Relative
Density
(CB)
Blows/Ft.
(SS)
Blows/Ft.
Consistency
< 3 0-2 Very Soft 0-5 < 3 Very Loose < 24 < 20 Weathered
3-5 3-4 Soft 6-14 4-9 Loose 24-35 20-29 Firm
6-10 5-8 Medium Stiff 15-46 10-29 Medium Dense 36-60 30-49 Medium Hard
11-18 9-15 Stiff 47-79 30-50 Dense 61-96 50-79 Hard
19-36 16-30 Very Stiff > 79 > 50 Very Dense > 96 > 79 Very Hard
> 36 > 30 Hard
RELATIVE PROPORTIONS OF SAND AND
GRAVEL
GRAIN SIZE TERMINOLOGY
Descriptive Terms of
Other Constituents
Percent of
Dry Weight
Major Component
of Sample
Particle Size
Trace < 15 Boulders Over 12 in. (300mm)
With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm)
Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm)
Sand
Silt or Clay
#4 to #200 sieve (4.75mm to 0.075mm)
Passing #200 Sieve (0.075mm)
RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION
Descriptive Terms of
Other Constituents
Percent of
Dry Weight
Term Plasticity Index
Trace
With
Modifiers
< 5
5 – 12
> 12
Non-plastic
Low
Medium
High
0
1-10
11-30
30+
F If soil contains ! 15% sand, add “with sand” to group name.
G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
HIf fines are organic, add “with organic fines” to group name.
I If soil contains ! 15% gravel, add “with gravel” to group name.
J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.
K If soil contains 15 to 29% plus No. 200, add “with sand” or “with
gravel,” whichever is predominant.
L If soil contains ! 30% plus No. 200 predominantly sand, add
“sandy” to group name.
M If soil contains ! 30% plus No. 200, predominantly gravel, add
“gravelly” to group name.
N PI ! 4 and plots on or above “A” line.
O PI < 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.
Sampler
Atterberg Limits
- - Field Personnel:
Start Date 2/27/2020 Auger Type: During Drilling None
Finish Date 2/27/2020 Hammer Type: After Drilling None
Sheet Drilling Rig: Water Depth Information
PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING
906 EAST STUART STREET, FORT COLLINS, COLORADO
Project # 20-1045
March 2020
Project # 20-1045
March 2020
Sheet Drilling Rig: Water Depth Information
Start Date 2/27/2020 Auger Type: During Drilling None
Finish Date 2/27/2020 Hammer Type: After Drilling None
USCS
Sampler
Atterberg Limits
- - Field Personnel: - -