HomeMy WebLinkAbout609 S COLLEGE AVE MIXED USE - BDR200004 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTJanuary 31, 2020
Tree Line Builders
141 South College Avenue, Ste. 103
Fort Collins, CO 80524
Attn: Forest Glaser (forest@treelinebuilt.com)
Re: Geotechnical Subsurface Exploration
609 South College Avenue – Building Addition
Fort Collins, Colorado
EEC Project No. 20-01-015
Mr. Glaser:
Earth Engineering Company, Inc. (EEC) personnel have completed the geotechnical
subsurface exploration you requested for the proposed building addition to the single-
family residence at 609 South College Avenue in Fort Collins, Colorado. Results of that
subsurface exploration are provided with this report.
We understand the proposed addition to the single-family residence will be two story wood
frame addition supported over a full basement. We expect foundation loads for the
proposed addition will be light with continuous wall loads less than 3 kips per lineal foot
and individual column loads less than 50 kips. Small cuts and fills are expected in the
vicinity of the proposed building addition.
The purpose of this report is to describe the subsurface conditions encountered in the test
boring completed within the identified building envelope and provide geotechnical
recommendations for design and construction of foundations and support of floor slabs.
The residence site is located at 609 South College Avenue in Fort Collins, Colorado. The
property is presently developed with an existing residence located to the east of the
proposed addition envelope.
To develop information on existing subsurface conditions in the area of the proposed
building addition, one soil boring was advanced to a depth of approximately 25 feet below
site grades within the identified building envelope. A diagram indicating the approximate
boring location is included with this report. Site photographs were taken at the time of
drilling and are included with this report.
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 2
The boring was completed using a truck-mounted CME-55 drill rig equipped with a
hydraulic head employed in drilling and sampling operations. The borehole was advanced
using 4-inch nominal diameter continuous flight augers and samples of the subsurface
materials encountered were obtained using split-barrel and California barrel sampling
procedures in general accordance with ASTM Specification D-1586. In the split-barrel
and California barrel sampling procedures, standard sampling spoons are driven into the
ground using a 140-pound hammer falling a distance of 30 inches. The number of blows
required to advance the samplers is recorded and is used to estimate the in-situ relative
density of cohesionless materials and, to a lesser degree of accuracy, the consistency of
cohesive soils. All samples obtained in the field were sealed and returned to the laboratory
for further examination, classification and testing.
EEC field personnel were on-site during drilling to evaluate the subsurface conditions
encountered and direct the drilling activities. A field log was prepared based on observation
of disturbed samples and auger cuttings. Based on results of the field boring and laboratory
testing, subsurface conditions in the area of the residence can be summarized as follows.
Brown sandy lean clay soils were encountered at the surface at the boring location. The
sandy lean clay soils were very stiff in consistency and exhibited a low potential for
swelling with variation in moisture content at current moisture/density conditions. The
moderately plastic sandy lean clay soils were underlain by brown sand and gravel materials
at a depth of approximately 21 feet below present site grades. The sand and gravel materials
were medium dense in consistency and extended to the bottom of the boring at a depth of
approximately 25 feet below present site grades where the boring was terminated.
Observations were made at the time of drilling and approximately 24 hours after drilling
to evaluate the presence and depth to free water at the test boring location. At the time of
drilling, free water was observed in the completed site boring at a depth of approximately
23 feet below present site grades. Approximately 24 hours after drilling, free water was
observed at a depth of approximately 22 feet below present site grades. Longer term
observations in holes that are cased and sealed from the influence of surface water would
be required to more accurately determine fluctuations in groundwater levels over time.
Fluctuations in groundwater levels can occur based on hydrologic conditions and other
conditions not apparent at the time of this report. Zones of perched and/or trapped water
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 3
may also be encountered in more permeable zones within the subgrade soils at times
throughout the year.
The stratification boundaries indicated on the boring log represent the approximate
locations of changes in soil types; in-situ, the transition of materials may be gradual and
indistinct. In addition, the test boring provides an indication of subsurface conditions at the
test location; however, subsurface conditions may vary in relatively short distances away
from that location. Potential variations in subsurface conditions can best be evaluated by
close observation and testing of the subgrade materials during construction. If significant
variations from the conditions anticipated from the test boring appear evident at that time,
it may be necessary to re-evaluate the recommendations provided in this report.
ANALYSIS AND RECOMMENDATIONS
General
Some areas of backfill near the existing residence may be encountered during construction
of the building addition. We recommend removing those fill materials, if encountered, to
the natural in-situ sandy lean clay soils prior to construction of the new foundation to
reduce the potential for movement in the foundation and floor slabs subsequent to
construction.
Foundations
Based on the materials observed at the test boring location, it is our opinion the proposed
lightly loaded building addition could be supported on conventional footing foundations
bearing on undisturbed natural sandy lean clay soils. For design of footing foundations
bearing in the natural, very stiff sandy lean clay soils, we recommend using a 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. Total load should include full dead and live loads.
Exterior foundations and foundations in unheated areas should be located at least 30 inches
below adjacent exterior grade to provide frost cover protection. We recommend formed
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 4
continuous footings have a minimum width of 12 inches and isolated column foundations
have a minimum width of 24 inches.
We recommend the foundation footing design loads be balanced to promote relatively
uniform settlement, thereby reducing the potential for differential settlement. As an
alternative to balancing the design loads solely on settlement, designing the foundation
such that the dead-load pressure is balanced throughout the foundations could be
considered. Balancing the dead-load pressure would also reduce the potential for
differential settlement between adjacent footings. We estimate the long-term settlement of
footing foundations designed and constructed as recommended above would be less than
1 inch.
Groundwater was encountered at a depth of approximately 23 feet below present site grades
in the completed test boring. We recommend maintaining a minimum 3-feet separation
between the foundation bearing elevation and peak seasonal groundwater levels. Peak
seasonal groundwater levels are typically observed in mid to late summer.
No unusual problems are anticipated in the construction of the footing foundations. Care
should be taken to avoid disturbing the bearing soils. The natural site soils may be easily
disturbed by construction activities. Soils which are disturbed by the construction activities
or materials which have become dry and desiccated or wet and softened should be reworked
or removed from the foundation excavation prior to the placement of foundation concrete.
Differential settlement between the existing structure and the new additions could occur
and should be expected. The differential settlement may approach the total settlement
expected for the additions. Also, placement of the new addition foundation loads adjacent
to existing foundations could lead to some settlement of the existing foundation. The
potential for differential settlement should be addressed in the addition design.
Floor Slab and Exterior Slab-on-Grade Subgrades
In any slab-on-grade areas, those slabs may be supported on existing site soils or newly
placed and compacted fill. All existing vegetation and/or topsoil should be removed from
the floor or flatwork areas. After stripping and completing all cuts and prior to placement
of any fill, floor slabs or other flatwork, we recommend the in-place soils be scarified to a
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 5
minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95% of
the material's maximum dry density as determined in accordance with ASTM Specification
D-698, the standard Proctor procedure. The moisture content of the scarified soils should
be adjusted to be within the range of ±2% of standard Proctor optimum moisture at the
time of compaction. Scarification and compaction of subgrades in the basement addition
area of the structure would not be required.
Fill soils required to develop the floor slab subgrades should consist of approved, low-
volume change materials which are free from organic matter and debris. It is our opinion
the on-site sandy lean clay soils could be used as low-volume change fill in the floor areas.
Those fill materials should be placed in loose lifts not to exceed 9 inches thick, adjusted in
moisture content as recommended for the scarified soils and compacted to at least 95% of
standard Proctor maximum dry density.
After preparation of the subgrades, care should be taken to avoid disturbing the in-place
materials. Subgrade materials loosened or disturbed by the construction activities or
materials which become dry and desiccated or wet and softened should be removed and
replaced or reworked in place prior to placement of the floor slab concrete.
As a precaution, the floor slabs should be isolated from structural portions of the building
to prevent differential movement to those elements causing distress to the structure. That
isolation is typically developed through the use of a voided wall which is suspended from
the overhead first floor joist. Care should be taken in door framing, drywalling and
finishing to maintain a voided space which will allow for movement of the floor slab
without transmission of stresses to the overlying structure.
While laboratory testing completed for this report indicated the site soils sampled exhibited
relatively low swell potential, floor slab and exterior flatwork movement could occur and
should be expected. Slab movement is common in Colorado even in areas with relatively
low-swelling soils. Mitigation techniques to reduce the potential for post-construction
movement, such as overexcavation, moisture conditioning and replacement could be
considered; however, the risk for slab movement cannot be eliminated.
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 6
Below Grade Areas
We recommend a perimeter drain system be constructed around all below grade areas to
reduce the potential for water seepage into below grade areas and/or development of
hydrostatic loads on below grade walls. In general, a perimeter drain system should consist
of perforated metal or plastic pipe placed around the exterior of the structure and sloped to
drain to a sump area where water can be removed without reverse flow occurring in the
system. The drain line should be surrounded by a minimum of 6 inches of appropriately
sized granular filter soil and either the granular filter soil or the drain line should be
surrounded in a filter fabric to prevent the accumulation of fines in the drain system.
Backfill placed adjacent to below grade walls above the drain system should consist of
approved, low-volume change materials which are free from organic matter and debris.
The on-site sandy lean clay soils could be used as backfill adjacent to the below grade
walls. If free draining granular soils are used as backfill adjacent to the below grade areas,
we recommend the top 2 feet of material be an essentially cohesive material to reduce
surface infiltration in the backfill. Those soils should be placed in loose lifts not to exceed
9 inches thick, adjusted in moisture content and compacted to at least 95% of the material's
standard Proctor maximum dry density. The moisture content of the fill soils should be
adjusted to be within the range of ±2% of standard Proctor optimum moisture at the time
of compaction.
Care should be taken in placing and compacting the wall backfill to avoid placing undue
lateral stress on the below grade walls. We recommend compaction using light mechanical
or hand compaction equipment.
For design of below grade walls where appropriate steps have been taken to eliminate the
buildup of hydrostatic loads, we recommend using an equivalent fluid pressure of 45
pounds per cubic foot. That recommended equivalent fluid pressure is based on an active
stress distribution analysis which includes an assumption of slight wall rotation. The
assumed wall rotation for an active case analysis may cause deflection on the order of 0.5%
of the wall height. The recommended equivalent fluid pressure does not include a factor
of safety nor an allowance for hydrostatic loads. Point loads placed in the backfill or
surcharge loads placed adjacent to the structure could add to the lateral forces on the below
grade walls.
Earth Engineering Company, Inc.
EEC Project No. 20-01-015
January 31, 2020
Page 7
Other Considerations
Positive drainage should be developed away from the structure with a minimum slope of 1
inch per foot for the first 10 feet away from the building. Care should be taken in planning
of landscaping adjacent to the residence to avoid features which would pond water adjacent
to the foundations or basement walls. Placement of plants which require irrigation systems
or could result in fluctuations of the moisture content of the subgrade materials should be
avoided adjacent to the structure. Lawn watering systems should not be placed within 5
feet of the perimeter of the building and spray heads should be designed not to spray water
on or immediately adjacent to the structure. Roof drains should be designed to discharge
at least 5 feet away from the structure and away from the pavement areas.
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data
obtained from the soil boring performed at the indicated location and from any other
information discussed in this report. This report does not reflect any variations which may
occur 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 that 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 and foundation construction phases to help determine that
the design requirements are fulfilled.
This report has been prepared for the exclusive use of Tree Line Builders 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
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:
Group
Symbol
Group Name
Cu≥4 and 1<Cc≤3
E GW Well-graded gravel
F
Cu<4 and/or 1>Cc>3
E 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≤3
E SW Well-graded sand
I
Cu<6 and/or 1>Cc>3
E 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
Silts and Clays
Liquid Limit 50 or
more
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
609 S. COLLEGE AVE.
BUILDING ADDITION
FORT COLLINS, CO
EEC PROJECT No. 20-01-015
JANUARY 2020
609 SOUTH COLLEGE AVENUE - BUILDING ADDITION
FORT COLLINS, COLORAOD
PROJECT NO: 20-01-015 DATE: JANUARY 2020
LOG OF BORING B-1
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: SM START DATE 1/28/2020 WHILE DRILLING 23'
AUGER TYPE: 4" CFA FINISH DATE 1/28/2020 AFTER DRILLING 23'
SPT HAMMER: AUTO SURFACE ELEV N/A 24 HOUR 22'
SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
_ _
SANDY LEAN CLAY (CL) 1
brown _ _
very stiff 2
silty _ _
CS 3 13 9000+ 9.2 102.9 < 500 psf None
_ _
4
_ _
CS 5 14 9000+ 9.0 99.0 30 12 81.3 1000 psf 0.7%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
light brown CS 10 17 9000+ 13.9 104.0 600 psf 0.1%
with gravel _ _
11
_ _
12
_ _
13
_ _
14
reddish brown _ _
CS 15 22 9000+ 12.6 122.2 < 1000 psf None@1000
_ _
16
_ _
17
_ _
18
_ _
19
_ _
CS 20 17 9000+ 12.2 122.7 < 1000 psf None@1000
_ _
21
_ _
SAND AND GRAVEL (SP-GP) 22
brown _ _
medium dense 23
_ _
24
_ _
25' BOTTOM OF BORING CS 25 20 -- 13.0 114.0
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: B-1, S-1 @ 2'
Liquid Limit: -- Plasticity Index: -- % Passing #200: --
Beginning Moisture: 11.0% Dry Density: 102.9 pcf Ending Moisture: 24.8%
Swell Pressure: < 500 psf % Swell @ 500 psf: None
Project: 609 South College Avenue - Addition
Fort Collins, Colorado
Project No.: 20-01-015
Date: January 2020
-10
-8
-6
-4
-2
0
2
4
6
8
10
0.01 0.1 1 10
Percent Movement
Load (TSF)
Water Added
Consolidation Swell
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: B-1, S-2 @ 4'
Liquid Limit: 30 Plasticity Index: 12 % Passing #200: 81.3
Beginning Moisture: 8.9% Dry Density: 99.6 pcf Ending Moisture: 24.3%
Swell Pressure: 1000 psf % Swell @ 500 psf: 0.7%
Project: 609 South College Avenue - Addition
Fort Collins, Colorado
Project No.: 20-01-015
Date: January 2020
-10
-8
-6
-4
-2
0
2
4
6
8
10
0.01 0.1 1 10
Percent Movement
Load (TSF)
Water Added
Consolidation Swell
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Light Brown Sandy Lean Clay with Gravel
Sample Location: B-1, S-3 @ 9'
Liquid Limit: -- Plasticity Index: -- % Passing #200: --
Beginning Moisture: 10.8% Dry Density: 104.0 pcf Ending Moisture: 22.2%
Swell Pressure: 600 psf % Swell @ 500 psf: 0.1%
Project: 609 South College Avenue - Addition
Fort Collins, Colorado
Project No.: 20-01-015
Date: January 2020
-10
-8
-6
-4
-2
0
2
4
6
8
10
0.01 0.1 1 10
Percent Movement
Load (TSF)
Water Added
Consolidation Swell
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Reddish Brown Sandy Lean Clay with Gravel
Sample Location: B-1, S-4 @ 14'
Liquid Limit: -- Plasticity Index: -- % Passing #200: --
Beginning Moisture: 13.3% Dry Density: 122.2 pcf Ending Moisture: 15.0%
Swell Pressure: < 1000 psf % Swell @ 1000 psf: None
Project: 609 South College Avenue - Addition
Fort Collins, Colorado
Project No.: 20-01-015
Date: January 2020
-10
-8
-6
-4
-2
0
2
4
6
8
10
0.01 0.1 1 10
Percent Movement
Load (TSF)
Water Added
Consolidation Swell
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Reddish Brown Sandy Lean Clay with Gravel
Sample Location: B-1, S-5 @ 19'
Liquid Limit: -- Plasticity Index: -- % Passing #200: --
Beginning Moisture: 13.4% Dry Density: 122.7 pcf Ending Moisture: 13.7%
Swell Pressure: < 1000 psf % Swell @ 1000 psf: None
Project: 609 South College Avenue - Addition
Fort Collins, Colorado
Project No.: 20-01-015
Date: January 2020
-10
-8
-6
-4
-2
0
2
4
6
8
10
0.01 0.1 1 10
Percent Movement
Load (TSF)
Water Added
Consolidation Swell
Earth Engineering Company
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
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
Silts and Clays
Liquid Limit less
than 50
IIf soil contains >15% gravel, add "with gravel" to
group name
JIf Atterberg limits plots shaded area, soil is a CL-
ML, Silty clay
GIf fines classify as CL-ML, use dual symbol GC-
CM, or SC-SM.
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
PLASTICITY 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
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
Earth Engineering Company