HomeMy WebLinkAboutMONTAVA - PHASE D INFRASTRUCTURE - BDR240010 - SUBMITTAL DOCUMENTS - ROUND 1 - Geotechnical (Soils) Report SUBSURFACE EXPLORATION REPORT
MONTAVA DEVELOPMENT- PHASE D
GIDDINGS ROADWAY IMPROVEMENTS AND DETENTION POND
NORTHWEST CORNER OF GIDDINGS ROAD AND MOUNTAIN VISTA DRIVE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172058
Prepared for:
Montava Development, LLC
430 N College Avenue, Suite 410
Fort Collins, Colorado 80524
Attn: Mr. Max Moss (Maxghf2m.com), and
Mr. Forrest Hancock(forrest(cr�,montava.com)
Development Director
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
PM
1�
May 20, 2024 4iii
Montava Development, LLC EARTH ENGINEERING
430 N College Avenue, Suite 410 CONSULTANTS, LLC
Fort Collins, Colorado 80524
Attn: Mr. Max Moss (Max@hf2m.com), and
Mr. Forrest Hancock(forrest@montava.com)
Development Director
Re: Subsurface Exploration and Geotechnical Engineering Services
Giddings Road and Phase D Detention Area
Montava Development
Fort Collins, Larimer County, Colorado
EEC Project No. 1172058
Mr.Moss and Mr. Hancock:
Earth Engineering Consultants, LLC (EEC) personnel have completed field and laboratory
testing services in general accordance with the Larimer County Urban Area Street Standards
(LCUASS) Pavement Design criteria of in-place subgrades for the Giddings Road pavement
reconstruction adjacent to the Montava Subdivision — Phase D, in Fort Collins, Colorado. It
should be noted that EEC originally planned on drilling four (4) pavement related test borings
along Giddings Road and one (1)within the proposed detention pond; however with the presence
of existing utilities along edge of pavement as well as overhead power, we were only able to
complete a single test boring within Giddings Road,No. B-2 as further discussed herein. Results
of the subgrade evaluation and pavement thickness recommendations, based on the field and
laboratory test results and estimated 18-kip equivalent daily load application (EDLA) values for
this portion of the proposed roadway improvement, are provided with this report. This report
provides pavement thickness recommendations for Giddings Road assuming the classification as
an industrial collector roadway using an EDLA of 100 and discussion regarding the proposed
detention area in Phase D. The subsurface exploration was completed in general accordance
with the electronic /e-mail proposal dated April 10, 2024.
For this exploration, as previously stated, two (2) soil borings were completed on April 30, 2024,
to the depths of approximately 10 to 15 feet below the ground surface, one (1) within Giddings
Road, (labeled herein as B-2) and one (1) within the detention pond area, (labeled herein as 135)
on the enclosed "Test Boring Location Diagram. " The three (3) additional borings, (i.e. B-1, B-
4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 970-545-3908 FAX (970) 663-0282
www.earth-engineering.com
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
Page 2
3, and B-4) that were planned within the intersection of Giddings Road and Mountain Vista
Drive and along Giddings Road to the north, were not drilled due to conflict with existing
utilities. Site photographs of the proposed roadway improvement area at the time of our
exploration are also provided with this report. This subsurface exploration was carried out in
general accordance with our discussions with the client.
Laboratory testing on the recovered samples included moisture content tests of all samples, in-
situ dry density of appropriate samples, and an evaluation of the unconfined strength of selected
samples with a calibrated hand penetrometer. Atterberg limits and washed sieve analysis tests
were completed on select samples to evaluate the quantity and plasticity of the fines in the
subgrade soils. In addition, swell/consolidation tests were completed on select samples to
evaluate the soils' tendency to swell with increased moisture content at current moisture and
density conditions. These swell/consolidation tests were completed with the loading criteria as
recommended in the Larimer County Urban Area Street Standards (LCUASS) pavement design
criteria using an inundation/preloading criterion of 150 ps£ The quantity of water-soluble
sulfates was determined on select samples from previous investigations at the site, to evaluate the
risk of sulfate attack on site concrete. Results of the outlined tests are indicated on the attached
boring logs and summary sheets.
As a 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 soils' 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.
The in-place pavement section along the existing Giddings Road consisted of approximately 7
inches of hot bituminous pavement (HBP) with no apparent aggregate base course (ABC)
material encountered. Subsurface soils encountered below the existing HBP pavement section
consisted of materials generally classified as lean sandy clay extending to the bottom of the
completed boring. The sandy clay soils were generally moist in-situ, very soft to stiff, exhibited
moderate plasticity, and no swell potential characteristics.
Observations were made while drilling and after completion of the borings to detect the presence
and depth to hydrostatic groundwater. Groundwater was not encountered in Boring B-2 below
the roadway. Groundwater was observed during drilling in boring B-5 at a depth of
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
Page 3
approximately 11 feet below the ground surface and at an approximate depth of 9 feet when
measured several days after drilling. 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 observations in cased holes sealed from the influence of surface water
would be required to evaluate long term water level fluctuations.
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 pavement design criteria. In this test, relatively intact samples obtained
directly from the California barrel 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 initial thickness.
Samples obtained at the 1 or 2-foot interval are generally pre-loaded and inundated with water at
an approximate 150 pounds per square foot (psf) increment to simulate the pavement loading
conditions in general accordance with LCUASS. After the inundation period, additional
incremental loads are applied to evaluate swell pressure and consolidation response as
appropriate.
For this assessment, we conducted a total of one (1) swell-consolidation test on subgrade
samples collected from an approximate depth of 2 feet below existing site grade during this
investigation. We have also considered data collected during previous investigations performed
nearby in Phase D of the Montava Subdivision. The swell index values for the soil samples
tested at the 150-psf inundation pressures revealed relatively nil to low potential swell
characteristics on the order of(-) 1.9 to (+) 0.3%.
The swell-index results were less than the LCUASS maximum allowable 2% criteria which is
used to determine if a swell-mitigation plan is necessary. Based on these results, a swell
mitigation plan would not be necessary. However, subgrade stabilization may be necessary if,
after preparing the subgrade to final elevation, the proof roll observation reveals soft, pumping or
rutting conditions. Chemical treatment with Portland cement provides stabilization for soft or
pumping subgrade soils, swell mitigation (if needed) and provides long term stabilization for the
entire subgrade.
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Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
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Subgrade preparation for the roadways within the subdivision should be completed in general
accordance with the recommendations presented in the Larimer County Urban Area Street
Standard Pavement Design Manual—Chapter 22.
Hveem Stabilometer(R-Value)
A composite sample of subgrade materials from the upper 4 feet below pavement grades was
obtained during the field exploration for laboratory Hveem Stabilometer/R-Value, (ASTM
Specification D2844) analyses to determine the subgrade strength characteristics of the in-place
subgrade materials. A summary of those test results is provided in the table below and graphical
results are presented with this report.
Table I-Summary of Laboratory(R-Value)Characteristics and Classification of Subgrade Soils
Boring Hveem Atterberg Limits and Classification
Depth,Ft. Stabilometer Liquid Plasticity %(-)No.
Nos. Soil Description
R-Value Limit Index 200 Sieve
B-2 1.0' -4.0' 15 30 16 57.5 Sandy Lean Clay(CL)
From these results, and as further discussed herein, we are using a conservative R-Value of 10 for
the AASSHTO pavement design along Giddings Road.
Pavement Subivade Preparation
The subgrade soils are generally low to moderate strength sandy lean clay exhibiting relatively
low swell potential characteristics. As previously mentioned, to enhance the subgrade strength
characteristics, a stabilization plan consisting of cement treatment, or an over excavation/ground
modification of the subgrades could be considered if needed. In addition to a subgrade strength
increase, cement treatment will accrue credit towards a reduction in the design thickness of the
pavement HMA and ABC sections. Water-soluble sulfate concentrations above the allowable
threshold for a single dose application were indicated in nearby soils. Additional sulfate testing
would be recommended during subgrade preparation if chemical treatment is planned.
After removal of unacceptable or unsuitable subsoils, and prior to placement of fill and/or site
improvements, the exposed soils should be scarified to a depth of 8 inches, adjusted in moisture
content to within ±3% of standard Proctor optimum moisture content for essentially cohesive
soils or to a workable moisture content for essentially granular materials, and compacted to at
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
Page 5
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
pavement/flatwork areas, after the initial zone has been prepared as recommended above, should
consist of approved on-site clayey soils or imported structural fill material which is free from
organic matter and debris. Approved structural fill materials should be graded similarly to a
CDOT Class 5, 6, or 7 aggregate base course (ABC) with sufficient fines to prevent ponding of
water within the fill. Fill materials should be placed in loose lifts not to exceed 8 inches thick,
adjusted in moisture content and compacted as recommended above for on-site cohesive soils
and adjusted in moisture content to ±3% of optimum and compacted to at least 95% of standard
Proctor maximum dry density as determined by ASTM Specification D698 for structural fill
materials.
If selected, a Portland cement treatment process would involve incorporating Type 1/II cement
within the upper 12 inches of the interior roadways' subgrade sections from back of curb to back
of curb, (in essence the full roadway width), prior to construction of the overlying pavement
structure. If cement is selected as the modification/stabilization plan, no over excavation would
be required. Stabilization should consist of blending 4 to 5% cement into the top 12 inches of the
subgrades. The blended materials should be adjusted in moisture content to slightly dry of
standard Proctor optimum moisture content and compacted to at least 95% of the materials
maximum dry density as determined in accordance with the standard Proctor procedure.
Compaction of the subgrade should be completed within two hours after initial blending of the
cement.
Proof rolling and recompacting the subgrade section is recommended immediately prior to
placement of the aggregate road base section. Soft or weak areas delineated by the proof rolling
operations should be undercut or stabilized in-place to achieve the appropriate subgrade support.
Moisture conditioning the site subgrade soils could result in pumping subgrade conditions with
elevated moisture contents in the subgrades. If pumping is observed, stabilization of the subgrades
with the addition of cement would be required. Additional recommendations can be provided at
time of the proof roll observation.
Pavement design methods are intended to provide structural sections with adequate thickness over
a particular subgrade such that wheel loads are reduced to a level the subgrade can support. The
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
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support characteristics of the subgrade for pavement design do not account for shrink/swell
movements of a slightly expansive essentially cohesive subgrade or consolidation of a wetted
subgrade. Thus, the pavement may be adequate from a structural standpoint, yet still experience
cracking and deformation due to shrink/swell related movement of the subgrade. It is therefore
important to minimize moisture changes in the subgrade to reduce shrink/swell movements.
Care will be needed after preparation of the subgrades to avoid disturbing the subgrade materials.
Positive drainage should be developed away from the pavements to avoid wetting of subgrade
materials. Subgrade materials becoming wet after construction of the site improvements can
result in unacceptable performance.
Long-term pavement performance will be dependent upon several factors, including maintaining
subgrade moisture levels and providing for preventive maintenance. The following
recommendations should be considered the minimum:
• The subgrade and the pavement surface should be adequately sloped to promote proper surface
drainage.
• Install pavement drainage surrounding areas anticipated for frequent wetting (e.g., landscaped
and irrigated islands, etc.),
• Install joint sealant and seal cracks immediately,
• Seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture
migration to subgrade soils;
• Placing compacted, low permeability backfill against the exterior side of curb and gutter;
• Placing curb, gutter, and/or sidewalk directly on approved proof rolled subgrade soils without
the use of base course materials.
Please note that if during or after placement of the stabilization or initial lift of pavement, the area
is observed to be yielding under vehicle traffic or construction equipment, it is recommended that
EEC be contacted for additional alternative methods of stabilization, or a change in the pavement
section.
Pavement—Design and Construction
We assumed that Giddings Road is an industrial collector roadway, therefore an assigned
equivalent daily load application (EDLA) value of 100 was used for the pavement design in
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
Page 7
general accordance with the LCUASS pavement design criteria. Pavement section
recommendations provided in this report are based on the traffic information outlined and the
subgrade field and laboratory test results as discussed herein.
Based on our site observations and test results, a conservative Hveem Stabilometer/R-value of 10
was used for the pavement design for the rough-graded pavement subgrades. Using the Colorado
Department of Transportation (CDOT) and the current Larimer County Pavement Design
Criteria (LCUASS), an R-value of 10 corresponds to a resilient modulus value of 3562 psi,
which was used in the pavement evaluation for the roadways included herein.
The American Association of State Highway and Transportation Officials (AASHTO) design
guidelines for pavement thicknesses were used to evaluate recommended pavement sections for
this project along with the current LCUASS Pavement Design Criteria. Recommended
pavement sections based on those evaluations are included below in Table I for Giddings Road.
TABLE H: RECOMMENDED MINIMUM PAVEMENT SECTIONS
Giddings Road
18-kip EDLA—Industrial Collector Roadway as per LCUASS (2021) 100
18-kip ESAL 730,000
Reliability 85%
Resilient Modulus(R-value= 10) 3562
PSI Loss(Initial 4.5 Serviceability Index—Final 2.5=2.3) 2.2
Design Structure Number 4.02
Composite Section—Option A(assume Stable Subgrade)
Hot Mix Asphalt(HMA)Grading S(75)PG 64-28—Top Lift 3" @ 0.44= 1.32
Hot Mix Asphalt(HMA)—Grading S(75)PG 64-22—Bottom Lift 4" @ 0.44= 1.76
Aggregate Base Course—CDOT Class 5 or 6 9" g 0.11 =0.99
Structure Number (4.07)
Composite Section with Cement Treated Subgrade
Hot Mix Asphalt(HMA)Grading S(75)PG 64-28—Top Lift 3" @ 0.44= 1.32
Hot Mix Asphalt(HMA)—Grading S(75)PG 64-22—Bottom Lift 3" @ 0.44= 1.32
Aggregate Base Course—CDOT Class 5 or 6 8" @ 0.11 =0.88
Cement Treated Subgrade(12"treatment, 10"of Credit) 10" n,0.05=0.5
Structure Number (4.02)
The aggregate base should meet CDOT Class 5 or Class 6 specifications. Aggregate base should
be placed and compacted to achieve a minimum density of 95% of standard Proctor maximum
dry density(ASTM Specification D698).
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EEC Project No. 1172058
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The hot bituminous pavement (HBP) should be grading S (75) with PG 64-22 and PG 64-28
binder materials and should be designed in accordance with LCUASS pavement design criteria.
The HBP should be compacted to achieve 92-96% of the material's maximum specific gravity
(Rice Value).
The recommended pavement sections provided herein are minimums and periodic maintenance
should be expected. Since the slightly cohesive soils on the site have shrink/swell potential,
pavements could crack in the future primarily because of the volume change of the soils when
subjected to an increase in moisture content to the subgrade. The cracking, while not desirable,
does not necessarily constitute structural failure of the pavement. Stabilization of the subgrades
will reduce the potential for cracking of the pavements.
Preventive maintenance should be planned and provided through an on-going pavement
management program. Preventive maintenance activities are intended to slow the rate of pavement
deterioration, and to preserve the pavement investment. Preventive maintenance consists of both
localized maintenance (e.g., crack and joint sealing and patching) and global maintenance (e.g.,
surface sealing). Preventive maintenance is usually the first priority when implementing a planned
pavement maintenance program and provides the highest return on investment for pavements.
Prior to implementing any maintenance, additional engineering observation is recommended to
determine the type and extent of preventive maintenance.
Water Soluble Sulfates (SO4)
The water-soluble sulfate (SO4) content of the on-site overburden subsoils along Giddings Road
taken during our subsurface exploration 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 below.
Table III-Water Soluble Sulfate Test Results
Sample Location Description Soluble Sulfate Content(%)
B-2,S-1,at 2' Sandy Lean Clay(CL) 0.05
Based on the results of completed soluble sulfate tests of the overburden soils, ACI 318, Section
4.2 indicates a negligible to low risk of sulfate attack on Portland cement concrete; therefore,
ACI Class SO requirements should be followed for concrete placed in the overburden soils.
Roadway and foundation concrete should be designed in accordance with the provisions of the
Earth Engineering Consultants,LLC
Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
Page 9
ACI Design Manual, Section 318, Chapter 4.
It should be noted, that the water-soluble sulfate (SO4) content of the nearby overburden
subsoils, taken during multiple previous subsurface explorations at random locations and
intervals have ranged between 0.3 to 1.6 percent. Additionally, CDOT's threshold for water-
sulfate concentration in subgrade soil when considering chemical stabilization is 0.5 percent;
therefore, supplement testing along Giddings Road should be performed.
Detention Pond
Based on our review of the site plan, a proposed detention pond is planned near the northwest
corner of Giddings Road and Mountain Vista Drive, in the general vicinity of Boring B-5. A
water detention pond, by definition, detains water. A detention pond is a low-lying area that is
designed to temporarily hold a set amount of water while slowly draining to another location
and/or infiltrating into the below grade subsoils. When an area is paved, or covered with a
building, water runs off the property much faster than when it is in a natural state. Normally it is
a grassy field with elevated earthen lined berms/embankments, with a couple of concrete culverts
running towards a drainage pipe. A hydrologist will design a water detention pond to
temporarily detain the water and keep the runoff to the desired rate. When the rain ends, though,
the water detention pond will be empty shortly afterwards. To assist in the detention pond
design, we completed boring B-5 which, indicated the subsurface conditions, in general
consisted of approximately 13 feet of cohesive lean clay with sand soils underlain a stratum of
granular sand/gravel material which extended to the depth explored, approximately 15%2 feet
below existing site grades. Soils percolation was not performed; however, based on our
experience with the subsurface conditions, and the texture, etc. of the subsoils, in our opinion
these subsoils would typically have a soil percolation rate on the or 40 to 60 minutes. Infiltration
designs for the detention pond should be designed in accordance with State of Colorado and
local municipality guidelines and include an appropriate factor of safety.
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
i
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Giddings Road and Phase D Detention Pond—Montava Subdivision
EEC Project No. 1172058
May 20,2024
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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 construction phases
to help determine that the design requirements are fulfilled.
This report has been prepared for the exclusive use of Montava Development, LLC 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 modified or verified in
writing by the geotechnical engineer.
We appreciate the opportunity to be of service to you on this project. If you have any questions
concerning this report, or if we can be of further service to you in any other way, please do not
hesitate to contact us.
Very truly yours,
Earth En ineering Consultants,LLC
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David A. Richer,P.E.
Senior Geotechnical Engineer
Cc: TST,Inc. Consulting Engineers Jonathan Sweet(jsweetktstinc.com)
Derek Patterson(dpaerson ,tstinc.com)
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
PHYSICAL PROPERTIES OF BEDROCK
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D-2488. Coarse Grained DEGREE OF WEATHERING:
Soils have move than 50% of their dry weight retained on a Slight Slight decomposition of parent material on
#200 sieve;they are described as: boulders,cobbles,gravel or joints. May be color change.
sand. Fine Grained Soils have less than 50%of their dry weight Moderate Some decomposition and color change
retained on a#200 sieve;they are described as : clays, if they throughout.
are plastic, and silts if they are slightly plastic or non-plastic. High Rock highly decomposed, may be extremely
Major constituents may be added as modifiers and minor broken.
constituents may be added according to the relative
proportions based on grain size. In addition to gradation, HARDNESS AND DEGREE OF CEMENTATION:
coarse grained soils are defined on the basis of their relative in- Limestone and Dolomite:
place density and fine grained soils on the basis of their Hard Difficult to scratch with knife.
consistency. Example: Lean clay with sand,trace gravel, stiff
(CL);silty sand,trace gravel, medium dense(SM). Moderately Can be scratched easily with knife.
CONSISTENCY OF FINE-GRAINED SOILS Hard Cannot be scratched with fingernail.
Unconfined Compressive Soft Can be scratched with fingernail.
Strength,Qu, psf Consistency
Shale,Siltstone and Claystone:
< 500 Very Soft Hard Can be scratched easily with knife,cannot be
500- 1,000 Soft scratched with fingernail.
1,001- 2,000 Medium Moderately Can be scratched with fingernail.
2,001- 4,000 Stiff Hard
4,001- 8,000 Very Stiff Soft Can be easily dented but not molded with
8,001-16,000 Very Hard fingers.
Sandstone and Conglomerate:
RELATIVE DENSITY OF COARSE-GRAINED SOILS: Well Capable of scratching a knife blade.
N-Blows/ft Relative Density Cemented
0-3 Very Loose Cemented Can be scratched with knife.
4-9 Loose
10-29 Medium Dense Poorly Can be broken apart easily with fingers.
30-49 Dense Cemented
50-80 Very Dense
80+ Extremely Dense
Earth Engineering Consultants, LLC
UNIFIED SOIL CLASSIFICATION SYSTEM
Soil Classification
Group Group Name
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Symbol
Coarse-Grained Soils Gravels more than Clean Gravels Less Cu24 and 1<Cc<3E GW Well-graded gravel F
more than 50% 50%of coarse than 5%fines
retained on No.200 fraction retained on Cu<4 and/or 1>Cc>3E GP Poorly-graded gravel F
sieve No.4 sieve Gravels with Fines Fines classify as ML or MH GM Silty gravel G'"
more than 12%
fines Fines Classify as CL or CH GC Clayey Gravel F'G'"
Sands 50%or more Clean Sands Less Cu>_6 and 1<Cc53E SW Well-graded sand
coarse fraction than 5%fines
passes No.4 sieve Cu<6 and/or 1>Cc>3E SP Poorly-graded sand
Sands with Fines Fines classify as ML or MH SM Silty sand G'"'l
more than 12%
fines Fines classify as CL or CH SC Clayey sand G'"'l
Fine-Grained Soils Silts and Clays inorganic PI>7 and plots on or above"A"Line CL Lean clay K,L,M
50%or more passes Liquid Limit less
the No.200 sieve than 50 PI<4 or plots below"A"Line ML Silt K,L,M
organic Liquid Limit-oven dried Organic clay K,L,M,N
<0.75 OL
Liquid Limit-not dried Organic silt K,L,M,o
Silts and Clays inorganic PI plots on or above"A"Line CH Fat clay K,L,M
Liquid Limit 50 or
more PI plots below"A"Line MH Elastic Silt K,L,M
organic Liquid Limit-oven dried Organic clay K,L,M,P
<0.75 OH
Liquid Limit-not dried Organic silt K,L,M,o
Highly organic soils Primarily organic matter,dark in color,and organic odor PT Peat
ABased on the material passing the 3-in.(75-mm) Cu=D60/Dlo Cc= (DBO)z Kif soil contains 15 to 29%plus No.200,add"with sand"
sieve D10 x D60 or"with gravel",whichever is predominant.
BIf field sample contained cobbles or boulders,or Llf soil contains 2 30%plus No.200 predominantly sand,
both,add"with cobbles or boulders,or both"to add"sandy"to group name.
group name. IF Ifsoil contains>_15%sand,add"with sand"to MY soil contains>_30%plus No.200 predominantly gravel,
cGravels with 5 to 12%fines required dual symbols: GIf fines classify as CL-ML,use dual symbol GC- add"gravelly"to group name.
GW-GM well graded gravel with silt CM,or SC-SM. NP124 and plots on or above"A"line.
GW-GC well-graded gravel with clay "If fines are organic,add"with organic fines"to 0PI54 or plots below"A"line.
GP-GM poorly-graded gravel with silt group name PPI plots on or above"A"line.
GP-GC poorly-graded gravel with clay If soil contains>15%gravel,add"with gravel"to °PI plots below"A"line.
OSands with 5 to 12%fines require dual symbols: group name
SW-SM well-graded sand with silt 'If Atterberg limits plots shaded area,soil is a CL-
SW-SC well-graded sand with clay ML,Silty clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
60
For Classification of fine-grained soils and
fine-grained fraction of coarse-grained
50 soils.
Equation of"A"-line
40 Horizontal at PI=4 to LL=25.5
x then PI-0.73(LL-20)
o Equation of"U"-fine
z
� 30 Vertical at LL=16 to PI-7,
then PI=0.9(LI-8)
a 20
p� MH o OH
10 MLciiOL
0
0 10 20 30 40 50 60 70 80 90 100 110
420 LIQUID LIMIT(LL)
Earth Engineering Consultants,LLC
B-4
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3 BORES ALONG GIDDING
B-3
\ \ \ ONE BORE FOR
DETENTION AREA 1
1 sue, B-5
Legend \\\ 1`? \ I
$Approximate Boring _ \_ \ i+ B-2
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Locations _Mountain Vista Dr
Y�\ ONE BORE ALONG MOUNTAIN
Site Photos \ `VISTA FOR INTERIM LEFT \
\ SS I TURN LANE EXPANSION
/Photos taken in approximate _
location,in direction ofarrow)
*13-1,B-3,and B-4 Not Drilled
Due to Utility Conflicts
Boring Location Diagram
Montava Development- Giddings Rd Pavements
Fort Collins, Colorado
North EEC Project #: 1172058 Date: May 2024
Not to Scale
EARTH ENGINEERING CONSULTANTS, LLC
MONTAVA DEVELOPMENT -GIDDINGS RD PAVEMENTS
FORT COLLINS, COLORADO
PROJECT NO: 1172058 LOG OF BORING B-2 DATE: MAY 2024
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 4/30/2024 WHILE DRILLING None
AUGER TYPE: 4"CFA FINISH DATE 4/30/2024 AFTER DRILLING N/A
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A 24 HOUR N/A
SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWS/FT (PSF) (%) (PCF) LL PI (%) PRESSURE %@ 500 PSF
ASPHALT-7"
1
SANDY LEAN CLAY(CL)
brown/gray/rust 2
%@ 150 PSF
Fc_s 3 13 7000 20.3 106.2 31 16 57.5 <150 PSF None
4
SS 5 15 4000 13.0
LEAN CLAY(CL)
brown 6
with gyspum crystals 7
8
9
SS 10 2 1000 18.1
BOTTOM OF BORING DEPTH 10.5' 11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Earth Engineering Consultants, LLC
MONTAVA DEVELOPMENT -GIDDINGS RD PAVEMENTS
FORT COLLINS, COLORADO
PROJECT NO: 1172058 LOG OF BORING B-5 DATE: MAY 2024
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 4/30/2024 WHILE DRILLING 11'
AUGER TYPE: 4"CFA FINISH DATE 4/30/2024 5/1/2024 9.2"
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A
SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWS/FT (PSF) (%) (PCF) LL PI (%) PRESSURE %@ 500 PSF
SPARSE VEGETATION
1
SANDY LEAN CLAY(CL)
brown 2
with gpysum crystals 3
4 FC_
S 5 15 7000 17.6 109.5
6
7
8
9
LSS 10 12 3000 19.0 1 31 1 19 50.9
11
12
13
SAND(SP) 14
SS 15 17 12.9
BOTTOM OF BORING DEPTH 15.5' 16
17
18
19
20
21
22
23
24
25
Earth Engineering Consultants, LLC
SWELL / CONSOLIDATION TEST RESULTS
Material Description: brown Sandy Lean Clay(CL)
Sample Location: Boring 2, Sample 1, Depth 2'
Liquid Limit: 30 Plasticity Index: 16 % Passing#200: 57.5%
Beginning Moisture: 20.3% Dry Density: 104.7 pcf JEnding Moisture: 18.8%
Swell Pressure: <150 psf %Swell @ 150: None
10.0
8.0
6.0
am
3
4.0
2.0
c
E
0
0.0
c
m
U
L
Water Added
a
-2.0
-4.0
0
a
0
w
o -6.0
U
-8.0
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Montava Development-Giddings Rd Pavements
Location: Fort Collins, Colorado
Project#: 1172058
Date: May 2024
RESISTANCE R-VALUE & EXPANSION PRESSURE OFf " a '
COMPACTED SOIL -ASTM D2844
PROJECT: Montava Development- Giddings Road Improvements PROJECT NO. 1172058
LOCATION: Fort Collins, Colorado DATE May-24
MATERIAL DESCRIPTION: Sandy Lean Clay(CL)
SAMPLE LOCATION: Composite Subgrade Sample -Test Boring B-2 @ 1 -5-feet
LIQUID LIMIT: 30 PLASTICITY INDEX: 16 1 %PASSING #200: 57.5
R-VALUE LABORATORY TEST RESULTS
TEST SPECIMEN NO. 1 2 3
COMPACTION PRESSURE (PSI) 100 125 150
DENSITY (PCF) 109.8 111.7 113.6
MOISTURE CONTENT (%) 18.5 18.1 16.9
EXPANSION PRESSURE (PSI) 0.00 0.00 0.00
HORIZONTAL PRESSURE @ 160 PSI 137 128 115
SAMPLE HEIGHT (INCHES) 2.53 2.50 2.50
EXUDATION PRESSURE (PSI) 171.6 257.5 411.3
UNCORRECTED R-VALUE 9.0 13.1 19.3
CORRECTED R-VALUE 9.0 13.1 19.3
R-VALUE @ 300 PSI EXUDATION PRESSURE = 15 RESILIENT MODULUS, PSI = 4,195
100
90
80
70
60
m
50
40
30
20
10
0
0 50 100 150 200 250 300 350 400 450 500 550 600
Exudation Pressure, PSI