HomeMy WebLinkAboutFoothills Unitarian Church Expansion - MJA210002 - Geotechnical (Soils) Report SUBMITTAL DOCUMENTS - ROUND 1 - 06/23/2021 SUBSURFACE EXPLORATION REPORT
FOOTHILLS UNITARIAN CHURCH EXPANSION
1815 YORKTOWN AVENUE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1192097
Prepared for:
Foothills Unitarian Church
1815 Yorktown Avenue
Fort Collins, Colorado 80526
Attn: Mr. Chris Bettlach(buildingeMansionnfoothillsuu.org)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
December 20, 2019
EARTH ENGINEERING
CONSULTANTS, LLC
Foothills Unitarian Church
1815 Yorktown Avenue
Fort Collins, Colorado 80526
Attn: Mr. Chris Bettlach(buildingexpansion(a)foothillsuu.org)
Re: Subsurface Exploration Report
Foothills Unitarian Church Expansion
1815 Yorktown Avenue
Fort Collins, Colorado
EEC Project No. 1192097
Mr. Bettlach:
Enclosed, herewith, are the results of the subsurface exploration completed by Earth Engineering
Consultants, LLC (EEC) for the referenced project. For this exploration, three (3) soil borings
were extended to depths of approximately 15 to 25 feet below existing site grades within the
proposed development area as depicted on the test boring diagram. Four (4) borings were
originally planned; however, boring B-3 was not drilled due to utility conflicts in the general
vicinity. This subsurface exploration was carried out in general accordance with our proposal
dated July 19, 2019.
In summary, the subsurface conditions encountered beneath the surficial vegetation layer,
generally consisted of clayey/silty sand with varying amounts of gravel extending to sandy lean
clay in borings B-1 and B-2 at depths of approximately 14 to 29 feet below the ground surface
and to the depths explored at approximately 10 feet in boring B-4. The clayey/silty sand was
generally dry near surface, becoming moist nearing the groundwater table, loose to medium
dense, and exhibited low swell potential at current moisture-density conditions. Zones of more
granular soil and/or clayey soil were encountered at various depths within the sand soils. The
sandy lean clay was generally medium stiff to very stiff. Groundwater was observed in the
borings at depths of approximately 14 to 17 feet below the ground surface.
Based on the encountered subsurface conditions, in our opinion, the proposed building could be
supported on conventional spread footings bearing on approved undisturbed clayey/silty sand or
engineered fill soils. Care should be taken to ensure footings are placed on stable and uniform
4396 GREENFIELD DRIvE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX(970) 663-0282
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 2
soils to prevent differential movement. Floor slabs, flatwork, and pavements could also be
supported on the in-place clayey/silty sand and/or engineered fill soils provided the
recommendations as presented in the attached report are adhered to. Geotechnical
recommendations concerning design and construction of the proposed site improvements are
provided within the attached report.
We appreciate the opportunity to be of service to you on this project. If you have any questions
concerning the enclosed 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 Engineering Consultants,LLC Reviewed b
pDO LI ,y
. o
J 12 '
:e
FFSS/OIV A����
Erin Dunn, E.I.T. David A. Richer, P.E.
Project Engineer Senior Project Engineer
SUBSURFACE EXPLORATION REPORT
FOOTHILLS UNITARIAN CHURCH EXPANSION
1815 YORKTOWN AVENUE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1192097
December 20, 2019
INTRODUCTION
The geotechnical subsurface exploration for the proposed Foothills Unitarian Church expansion in
Windsor, Colorado has been completed. To develop subsurface information in the proposed
development area,three(3)soil borings were drilled to depths of approximately 10 to 30 feet below
existing site grades. Boring B-3 was omitted due to utility conflicts in the general vicinity. A
diagram indicating the approximate boring locations is included with this report.
We understand the proposed development consists of the construction of an administration addition
on the northeast side of the existing building and a sanctuary and classroom additions on the
southwest side of the building along with associated additional pavements.The administration and
classroom additions are expected to be constructed as slab-on-grade (no basement) while the
sanctuary portion is expected to be constructed with a potential below grade/basement level. We
anticipate maximum foundations loads will be relatively light to moderate with maximum wall and
column loads less than 4 klf and 150 kips, respectively. Floor loads are expected to be relatively
light.If actual loads exceed those assumed herein,we should be consulted to review and modify the
recommendations accordingly,if necessary. Small grade changes are expected to develop site grades
for the proposed improvements.
The purpose of this report is to describe the subsurface conditions encountered in the test borings,
analyze and evaluate the field and laboratory test data and provide geotechnical recommendations
concerning design and construction of foundations and floor slabs and support of flatwork and
pavements. Recommended pavement sections are also included.
EXPLORATION AND TESTING PROCEDURES
The test boring locations were selected and established in the field by EEC personnel by pacing and
estimating angles from identifiable site features. The approximate locations of the borings are
shown on the attached boring location diagram. The boring locations should be considered accurate
only to the degree implied by the methods used to make the field measurements.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 2
The test borings were advanced using a truck mounted,CME-55 drill rig equipped with a hydraulic
head employed in drilling and sampling operations. The boreholes were advanced using 4-inch
nominal diameter continuous flight augers. Samples of the subsurface materials encountered were
obtained using split-barrel and California barrel sampling procedures in general accordance with
ASTM Specifications D1586 and D3550, respectively.
In the split-barrel and California barrel sampling procedures,standard sampling spoons are advanced
into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of
blows required to advance the split-barrel and California barrel samplers is recorded and is used to
estimate the in-situ relative density of cohesionless soils and, to a lesser degree of accuracy, the
consistency of cohesive soils. In the California barrel sampling procedure,relatively intact samples
are obtained in removable brass liners.All samples obtained in the field were sealed and returned to
our laboratory for further examination, classification and testing.
Laboratory moisture content tests were completed on each of the recovered samples with unconfined
compressive strength of appropriate samples estimated using a calibrated hand penetrometer.
Atterberg limits and washed sieve analysis tests were completed on select samples to evaluate the
quantity and plasticity of fines in the subgrades. Swell/consolidation testing was completed on
select samples to evaluate the potential for the subgrade materials to change volume with variation in
moisture content and load. Soluble sulfate tests were completed on selected samples to estimate the
potential for sulfate attack on site cast concrete. Results of the outlined tests are indicated on the
attached boring logs and summary sheets.
As part of the testing program,all samples were examined in the laboratory and classified in general
accordance with the attached General Notes and the Unified Soil Classification System,based on the
soil's texture and plasticity. The estimated group symbol for the Unified Soil Classification System
is indicated on the boring logs and a brief description of that classification system is included with
this report.
SITE AND SUBSURFACE CONDITIONS
The proposed church building additions are planned for construction at the northeast and southwest
sides of the existing church building located at 1815 Yorktown Avenue in Fort Collins, Colorado.
The lot is currently vacant. Vegetation and topsoil consisting of sod was encountered at the surface
of the borings. Ground surface in this area is relatively flat.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 3
EEC field personnel were on site during drilling to evaluate the subsurface conditions encountered
and direct the drilling activities. Field logs prepared by EEC site personnel were based on visual and
tactual observation of disturbed samples and auger cuttings.The final boring logs included with this
report may contain modifications to the field logs based on results of laboratory testing and
evaluation. Based on results of the field borings and laboratory testing, subsurface conditions can be
generalized as follows.
From the ground surface, the subgrades underlying the existing vegetation described previously
consisted of clayey/silty sand with varying amounts of gravel extending to sandy lean clay in borings
B-1 and B-2 at depths of approximately 14 to 29 feet below the ground surface and to the depths
explored at approximately 10 feet in boring B-4. The clayey/silty sand was generally dry near
surface,becoming moist nearing the groundwater table,loose to medium dense, and exhibited low
swell potential at current moisture-density conditions.Zones of more granular soil and/or clayey soil
were encountered at various depths within the sand soils.The sandy lean clay was generally medium
stiff to very stiff.
The stratification boundaries indicated on the boring logs represent the approximate location of
changes in soil types; in-situ,the transition of materials may be gradual and indistinct.
GROUNDWATER CONDITIONS
Observations were made while drilling and after completion of the borings to detect the presence and
depth to hydrostatic groundwater. At the time of drilling,groundwater was observed in the borings
at a depth of approximately 14 to 17 feet below the ground surface. The borings were backfilled
upon completion of the drilling operations;therefore,subsequent groundwater measurements were
not performed.
Fluctuations in groundwater levels can occur over time depending on variations in hydrologic
conditions and other conditions not apparent at the time of this report. Longer term monitoring of
water levels in cased wells,which are sealed from the influence of surface water,would be required
to more accurately evaluate fluctuations in groundwater levels at the site. We have typically noted
deepest groundwater levels in late winter and shallowest groundwater levels in mid to late summer.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 4
ANALYSIS AND RECOMMENDATIONS
Swell—Consolidation Test Results
The swell-consolidation test is performed to evaluate the swell or collapse potential of soils to help
determine foundation, floor slab and pavement design criteria. In this test, relatively undisturbed
samples obtained directly from the California sampler are placed in a laboratory apparatus and
inundated with water under a predetermined load. The swell-index is the resulting amount of swell or
collapse after the inundation period expressed as a percent of the sample's preload/initial thickness.
After the inundation period, additional incremental loads are applied to evaluate the swell pressure
and/or consolidation.
For this assessment,we conducted three(3)swell-consolidation tests on relatively undisturbed soil
samples obtained at various intervals/depths on the site. The swell index values for the in-situ soil
samples analyzed revealed low swell characteristics as indicated on the attached swell test
summaries. The(+)test results indicate the soil materials swell potential characteristics while the(-)
test results indicate the soils materials collapse/consolidation potential characteristics when
inundated with water. The following table summarizes the swell-consolidation laboratory test
results for samples obtained during our field explorations for the subject site.
TABLE I—Swell/Consolidation Test Results
Swell Consolidation Test Results
Boring Depth, Material Type In-Situ Dry Inundation Swell
No. ft. Moisture Density, Pressure, Index,%
Content,% PCF psf (+/-)
1 2 Clayey/Silty Sand(SM/SC) 9.1 126.4 500 (-)0.1
2 4 Clayey Sand(SC) 6.9 140.2 500 (+)0.0
4 2 Silty Sand(SM) 2.0 112.8 150 (+)0.3
Colorado Association of Geotechnical Engineers (CAGE)uses the following information to provide
uniformity in terminology between geotechnical engineers to provide a relative correlation of slab
performance risk to measured swell. "The representative percent swell values are not necessarily
measured values;rather,they are a judgment of the swell of the soil and/or bedrock profile likely to
influence slab performance." Geotechnical engineers use this information to also evaluate the swell
potential risks for foundation performance based on the risk categories.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 5
Table II-Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Slab Performance Risk Category Representative Percent Swell Representative Percent Swell
(500 psf Surcharge) (1000 psf Surcharge)
Low 0to<3 0<2
Moderate 3 to<5 2 to<4
High 5to<8 4to<6
Very High >8 >6
Based on the laboratory test results,the in-situ samples analyzed for this project were within the low
range.
Site Preparation
Prior to placement of any fill and/or improvements, we recommend any existing vegetation,
undocumented fill, flatwork,pavements and any unsuitable materials associated with the existing
building's backfill zone,be removed from the planned improvement areas. Care should be taken to
remove any previously placed, undocumented fill material with unknown origin or compaction
verification. Care should be taken to avoid disturbing existing foundation bearing materials. Over
excavations should be sloped away from the existing foundations to prevent undermining existing
foundations.
After removal of all topsoil,vegetation,and removal of unacceptable or unsuitable subsoils and prior
to placement of fill,the exposed soils should be scarified to a depth of 9 inches,adjusted in moisture
content to within±2%of standard Proctor optimum moisture content and compacted to at least 95%
of the material's standard Proctor maximum dry density as determined in accordance with ASTM
Specification D698.
Fill materials used to develop site grades,and for foundation backfill should consist of an approved
low volume change material, in our opinion, soils similar to the site clayey/silty sand materials or
imported granular structural fill material could be used. Imported granular materials should be
graded similarly to a CDOT Class 5, 6 or 7 aggregate base. Fill materials should be placed in loose
lifts not to exceed 9 inches thick, adjusted in moisture content to within f2% of standard Proctor
optimum moisture content and compacted to at least 95% of the material's standard Proctor
maximum dry density as determined in accordance with ASTM Specification D698.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 6
Care should be exercised after preparation of the subgrades to avoid disturbing the subgrade
materials. Materials which are loosened or disturbed should be reworked prior to placement of
foundations/flatwork.
Foundation System—General Considerations
It is our understanding that a portion of the sanctuary addition may be constructed below grade. If,
additional footings are constructed at elevations below immediately adjacent existing footings,
underpinning the existing footings will be required. We would be pleased to provide additional
foundation underpinning recommendations upon request.
Footing Foundations
Based on materials observed from the test boring locations, it is our opinion that the proposed
structures could be supported on conventional footing foundations bearing on approved native
undisturbed subsoils or properly placed and compacted fill materials,prepared as recommended in
the section Site Preparation. Care should be taken to construct the building additions on uniform
bearing to prevent differential movement. For design of footing foundations bearing on suitable
strength subsoils or on properly placed fill, we recommend using a net allowable total load soil
bearing pressure not to exceed 2,500 psf. The net bearing pressure refers to the pressure at
foundation bearing level in excess of the minimum surrounding overburden pressure. Total loads
should include full dead and live loads.
Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches
below adjacent exterior grade to provide frost protection. We recommend formed continuous
footings have a minimum width of 12 inches and isolated column foundations have a minimum
width of 24 inches. Trenched foundations should not be used.
No unusual problems are anticipated in completing the excavations required for construction of the
footing foundations. Care should be taken during construction to avoid disturbing the foundation
bearing materials. Materials which are loosened or disturbed by the construction activities or
materials which become dry and desiccated or wet and softened should be removed and replaced
prior to placement of foundation concrete.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 7
We estimate the long-term settlement of footing foundations designed and constructed as outlined
above would be 1 inch or less.
Lateral Earth Pressures
Portions of the new structure or site improvements which are constructed below grade may be
subject to lateral earth pressures. Passive lateral earth pressures may help resist the driving forces
for retaining wall or other similar site structures. Active lateral earth pressures could be used for
design of structures where some movement of the structure is anticipated, such as retaining walls.
The total deflection of structures for design with active earth pressure is estimated to be on the order
of one half of one percent of the height of the down slope side of the structure. We recommend at-
rest pressures be used for design of structures where rotation of the walls is restrained,such as below
grade walls for a building. Passive pressures and friction between the footing and bearing soils
could be used for design of resistance to movement of retaining walls.
Coefficient values for backfill with anticipated types of soils for calculation of active, at-rest and
passive earth pressures are provided in Table III below. Equivalent fluid pressure is equal to the
coefficient times the appropriate soil unit weight. Those coefficient values are based on horizontal
backfill with backfill soils consisting of on-site essentially cohesive subsoils. For at-rest and active
earth pressures,slopes down and away from the structure would result in reduced driving forces with
slopes up and away from the structures resulting in greater forces on the walls. The passive
resistance would be reduced with slopes away from the wall. The top 30 inches of soil on the
passive resistance side of walls could be used as a surcharge load;however, should not be used as a
part of the passive resistance value. Frictional resistance is equal to the tangent of the friction angle
times the normal force. Surcharge loads or point loads placed in the backfill can also create
additional loads on below grade walls. Those situations should be designed on an individual basis.
Table III-Lateral Earth Pressures
Soil Type On-Site Overburden Clayey/Silty Sand Imported Medium Dense Granular
Soils Material
Wet Unit Weight(ps£) 115 135
Saturated Unit Weight(psf) 135 140
Friction Angle(0)-(assumed) 30° 35°
Active Pressure Coefficient 0.33 0.27
At-rest Pressure Coefficient 0.50 0.43
Passive Pressure Coefficient 3.00 3.70
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 8
The outlined values do not include factors of safety nor allowances for hydrostatic loads and are
based on assumed friction angles, which should be verified after potential material sources have
been identified. Care should be taken to develop appropriate drainage systems behind below grade
walls to eliminate potential for hydrostatic loads developing on the walls. Those systems would
likely include perimeter drain systems extending to sump areas or free outfall where reverse flow
cannot occur into the system. Where necessary,appropriate hydrostatic load values should be used
for design.
Floor Slabs and Exterior Flatwork
Subgrades for floor slabs,flatwork and site pavements should be prepared as outlined in the section
Site Preparation. For structural design of concrete slabs-on-grade,a modulus of subgrade reaction
of 125 pounds per cubic inch(pci)could be used for floors supported on native undisturbed subsoils.
Additional floor slab design and construction recommendations are as follows:
• Interior partition walls should be separated/floated from floor slabs to allow for
independent movement.
• Positive separations and/or isolation joints should be provided between slabs and all
foundations, columns, and utility lines to allow for independent movement.
• Control joints should be provided in slabs to control the location and extent of
cracking.
• Interior trench backfill placed beneath slabs should be compacted in a similar manner
as previously described for imported structural fill material.
• Floor slabs should not be constructed on frozen subgrade.
• Other design and construction considerations as outlined in the ACI Design Manual
should be followed.
For interior floor slabs, depending on the type of floor covering and adhesive used,those material
manufacturers may require that specific subgrade,capillary break,and/or vapor barrier requirements
be met. The project architect and/or material manufacturers should be consulted with for specific
under slab requirements.
Care should be exercised after development of the floor slab and exterior flatwork subgrades to
prevent disturbance of the in-place materials. Subgrade soils which are loosened or disturbed by
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 9
construction activities or soils which become wet and softened or dry and desiccated should be
removed and replaced or reworked in place prior to placement of the overlying slabs.
Seismic
The site soil conditions generally consist of clayey/silty sand with varying amounts of gravel
underlain by sandy lean clay. For those site conditions,the International Building Codes indicates a
Seismic Site Classification of D. Drilling to a greater depth could reveal a different site
classification.
Pavements
Pavement subgrades should be prepared as outlined in the section Site Preparation. We anticipate
the site pavements will include areas designated for light-duty automobile traffic as well as some
areas for heavier automobile and heavy-duty truck traffic. For design purposes, an assumed
equivalent daily load axle(EDLA)rating of 7 is used in the light-duty pavement areas and an EDLA
of 15 is used in the heavy-duty pavement areas.
Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the
aggregate road base section. Soft or weak areas delineated by the proofrolling operations should be
undercut or stabilized in-place to achieve the appropriate subgrade support. Based on the subsurface
conditions encountered at the site, an assumed R-value of 10 was used in design of the pavement
sections.
If additional stabilization is required, consideration could be given to a fly ash treatment of the
subgrades. The fly ash treatment process would involve incorporating Class C fly ash 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.
Stabilization would consist of blending 13%by dry weight of Class C fly ash in 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 Class C fly ash.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 10
Recommended minimum pavement sections are provided below in Table IV. HBP sections may
show rutting/distress in truck loading and drive areas; therefore, concrete pavements should be
considered in these areas. The recommended pavement sections are considered minimum; thus,
periodic maintenance should be expected.
Table IV-Recommended Pavement Sections
Light Duty Areas Heavy Duty Areas
18-kip EDLA 7 15
18-kip ESAL 51,100 109,500
Reliability 75% 80%
Resilient Modulus(Based on R-Value=10) 3562 3562
PSI Loss 2.5 2.2
Design Structure Number 2.47 2.88
Composite Section—Option A(assume Stable Subgrade)
Hot Mix Asphalt 4" 5"
Aggregate Base Course 7" 7"
Structure Number (2.53) (2.97)
Composite Section with Fly Ash Treated Subgrade
Hot Mix Asphalt 3-1/2" 4"
Aggregate Base Course 6" 6"
Fly Ash Treated Subgrade(assume half-credit) 12" 12"
Structure Number (2.80) (3.02)
PCC(Non-reinforced)—placed on a stable subgrade 5%" 6"
We recommend aggregate base meet a CDOT Class 5 or Class 6 aggregate base. Aggregate base
should be adjusted in moisture content and compacted to achieve a minimum of 95% of standard
Proctor maximum dry density.
HBP should be graded as SX or S and be prepared with 75 gyrations using a Superpave gyratory
compactor in accordance with CDOT standards. The HBP should consist of PG 58-28 or PG 64-22
asphalt binder. HBP should be compacted to achieve 92 to 96%of the mix's theoretical maximum
specific gravity(Rice Value).
Portland cement concrete should be an approved exterior pavement mix with a minimum 28-day
compressive strength of 4,500 psi and should be air entrained. Wire mesh or fiber could be considered
to reduce shrinkage cracking.
Longitudinal and transverse joints should be provided as needed in concrete pavements for
expansion/contraction and isolation. The location and extent of joints should be based upon the final
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 11
pavement geometry. Sawed joints should be cut in general accordance with ACI recommendations.
All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load
transfer.
Water Soluble Sulfates (SO4)
The water-soluble sulfate (SO4) content of the on-site overburden subsoils, taken during our
subsurface exploration at random locations and intervals are provided below. Based on reported
sulfate content test results,the Class/severity of sulfate exposure for concrete in contact with the on-
site subsoils is provided in this report.
Table V-Water Soluble Sulfate Test Results
Sample Location Description %of Soil by Weight
B-1,S-2,at 4' Well Graded Sand with Silt(SW—SM) 0.02
B-2,S-2,at 9' Clayey Sand(SC) 0.01
Based on the results as presented above,ACI 318, Section 4.2 indicates the site soils have a low risk
of sulfate attack on Portland cement concrete, therefore, ACI Class SO requirements should be
followed for concrete placed in the silty/clayey sand soils. Foundation concrete should be designed
in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
Other Considerations
Positive drainage should be developed away from the structures and pavement areas with a
minimum slope of 1 inch per foot for the first 10 feet away from the improvements in landscape
areas. Care should betaken in planning of landscaping(if required)adjacent to the building to avoid
features which would pond water adjacent to the foundations or stemwalls. Placement of plants
which require irrigation systems or could result in fluctuations of the moisture content of the
subgrade material should be avoided adjacent to site improvements. Irrigation systems should not be
placed within 5 feet of the perimeter of the building and parking areas. Spray heads should be
designed not to spray water on or immediately adjacent to the structures or site pavements. Roof
drains should be designed to discharge at least 5 feet away from the structures and away from the
pavement areas.
Earth Engineering Consultants,LLC
EEC Project No. 1192097
December 20,2019
Page 12
Excavations into the zones of essentially granular silty sand soils have the potential for
caving/sloughing side walls. The individual contractor(s)should be made responsible for designing
and constructing stable, temporary excavations as required to maintain stability of both the
excavation sides and bottom. All excavations should be sloped or shored in the interest of safety
following local and federal regulations, including current OSHA excavation and trench safety
standards.
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data obtained from
the soil borings performed at the indicated locations and from any other information discussed in this
report. This report does not reflect any variations,which may occur between borings or across the
site. The nature and extent of such variations may not become evident until construction. If
variations appear evident, it will be necessary to re-evaluate the recommendations of this report.
It is recommended that the geotechnical engineer be retained to review the plans and specifications
so comments can be made regarding the interpretation and implementation of our geotechnical
recommendations in the design and specifications. It is further recommended that the geotechnical
engineer be retained for testing and observations during earthwork phases to help determine that the
design requirements are fulfilled.
This report has been prepared for the exclusive use of Foothills Unitarian Church for specific
application to the project discussed and has been prepared in accordance with generally accepted
geotechnical engineering practices. No warranty,express or implied,is made. In the event that any
changes in the nature, design, or location of the project as outlined in this report are planned, the
conclusions and recommendations contained in this report shall not be considered valid unless the
changes are reviewed and the conclusions of this report are modified or verified in writing by the
geotechnical engineer.
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 groundwater. In low permeability soils,the accurate determination of groundwater 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 SO%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 48
Earth Engineering Consultants, LLC
UNIRED SOIL CLASSIFICATION ION 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<Cc53F GW Well-graded gravel`
more than 50% 50%of coarse than 5%fines
retained on No.200 fraction retained on Cu<4 and/or 1>Cc>3F 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<Cc<3t SW Well-graded sand'
coarse fraction than 5%fines
passes No.4 sieve Cu<6 and/or 1>Cc>3F SP Poorly-graded sand
Sands with Fines Fines classify as ML or MH SM Silty sand o'"'l
more than 12%
fines Fines classify as CL or CH SC Clayey sand o'"'l
Fine-Grained Soils Silts and Clays inorganic PI>7 and plots on or above"A"Line CL Lean clay
50%or more passes Liquid Limit less
the No.200 sieve than 50 PI<4 or plots below"A"Line ML Silt
organic Liquid Limit-oven dried Organic clay K,L,M,N
<0.75 OIL
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,LM,F
<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
"Based on the material passing the 3-in.(75-mm) rCu=Dw/DLo Cc= (DBo) Kif soil contains 15 to 29%plus No.200,add"with sand"
sieve DLo x Dw or"with gravel",whichever is predominant.
BIf field sample contained cobbles or boulders,or `If soil contains>_30%plus No.200 predominantly sand,
both,add"with cobbles or boulders,or both"to add"sandy"to group name.
group name. Flf soil contains 215%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. "PI>_4 and plots on or above"A"line.
GW-GC well-graded gravel with clay "If fines are organic,add"with organic fines"to 0P154 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 IIf soil contains>15%gravel,add"with gravel"to °PI plots below"A"line.
°Sands with 5 to 12%fines require dual symbols: group name
SW-SM well-graded sand with silt iIf 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.
Jc,' Jce
Equation of"A"-line .•J,' 0\ .•p
a,40 Horizontal at PI=4 to LL=25.5
x then PI-0.73(LL-20) L�
o Equation of"U"-line
z
30 Vertical at LL=16 to PI-7,
then PI=0.9(LL-8)
N
3 zo
p� MH o OH
oP
10 /1z ,,
cL ML OL
0
0 10 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT(ILL)
Earth Engineering Consultants,LLC
YORKTOWN AVENUE
X
k Q
A INISTRATIO B- � o
MEMO �� ti D
MEMO
GARDEJM
� I J
o
o
/ mil
/ 'S JAGGEG _
ENTRANCE COURT �.�q g i O
SOCIAL HALL
i w
868TALL5 O
4 EAST LOT TOTAL O
—
� SOCIAL COURT LI'L KIDS �
- _' "-PLAYGROUND
FOYER \ / �,4-1
t3kr
E CATION
B-2 B-4
SANCTUARY +ATL
ti
/ OLDERODS\_.
PLAYGROUND
WEST LOT TOTAL
aFOiC> _ _B-3
Legend - ati- - - - - - - - - - - - - -- - ---- -- ------ -�
- 15'RFAR SEIBAGK
Ory
Approximate lvY1 ate Boring _ _ — _ _ _ _ _ _ _ _ _ _ PROPERiYLINE '!•
Locations _ - -
x
Note: B-3 Not Drilled DRAKE ROAD
ass io m n a
Due to Utility Conflict
Site Photos
(Photos taken in approximate
location,in direction ofarrowl
Boring Location Diagram
Foothills Unitarian Church Expansion - Fort Collins, Colorado
EEC Project #: 1192097
North December 2019
Not to Scale
EARTH ENGINEERING CONSULTANTS, LLC
� � ��T' .1� .fir,-' � �` fit \ �g -�L•, - � - '
• n �
PHOTO # 2
EEC
FOOTHILLS UNITARIAN CHURCH EXPANSION
FORT COLLINS,COLORADO
PROJECT NO:1192097 LOG OF BORING B-1 DATE: DECEMBER 2019
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 1219/2019 WHILE DRILLING 17.0'
AUGER TYPE: 4"CFA FINISH DATE 1 2/912 01 9 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 I%) PRESSURE %(d S00 PSF
VEGETATION&TOPSOIL-SOD
1
CLAYEY/SILTY SAND(SC/SM)
brown/red 2
medium dense
F.I. 3 23 8000 9.1 124.5 21 5 27.5 <500 psf NQne
4
SS 5 30 4.9
WELL GRADED SAND with SILT(SW-SM)
brown/red 6
medium dense
7
8
9
CS 10 26 5.1 97.2 11
11
12
13
14
SANDY LEAN CLAY(CL) FS.
15 20 3000 8.0
brown/red
very stiff 16
17
18
19
CS 20 25 17.8 113.6
BOTTOM OF BORING DEPTH 2O.0'
21
22
23
24
25
Earth Engineering Consultants, LLC
FOOTHILLS UNITARIAN CHURCH EXPANSION
FORT COLLINS,COLORADO
PROJECT NO:1192097 LOG OF BORING B-2 DATE: DECEMBER 2019
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 1112512019 WHILE DRILLING 14.0'
AUGER TYPE: 4"CFA FINISH DATE 1112 5/2 01 9 AFTER DRILLING N/A
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A 24 HOUR N/A
SOIL DESCRIPTION D N QU Me DD A.LIMITS -210 SWELL
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI I%) PRESSURE %(d S00 PSF
VEGETATION&TOPSOIL-SOD
1
CLAYEY SAND(SC)
red 2
medium dense to loose
with gravel 3
4
CS 5 18 2500 6.9 123.8 30 15 17.9 <500 psf None
6
7
8
9
red I brown
gravel seam FS.
__10 21 6.5
11
12
13
14
more clayey from approx 14.5'to 24' CS 15 6 17.2 115.6
16
17
18
19
__
FS.
20 8 20.8
21
22
23
24
SAND&GRAVEL(SP&GP)
brown/gray/rust,medium dense CS 25 26 13.1 120.7
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
FOOTHILLS UNITARIAN CHURCH EXPANSION
FORT COLLINS,COLORADO
PROJECT NO:1192097 LOG OF BORING B-2 DATE: DECEMBER 2019
RIG TYPE: CME55 SHEET 2 OF WATER DEPTH
FOREMAN: DG START DATE 1112512019 WHILE DRILLING 14.0'
AUGER TYPE: 4"CFA FINISH DATE 1112 5/2 01 9 AFTER DRILLING N/A
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A 24 HOUR N/A
SOIL DESCRIPTION D N OU MC DD A-LIMITS -200 SWELL
TYPE (FEET) (BLOWS/FT) (PSF) I%) (PCF) LL PI (%) PRESSURE ,@ 500 PSF
Continued from Sheet 1 of 2 26
SAND&GRAVEL(SP&GP) 27
brown/gray/rust
medium dense 28
29
LEAN CLAY(CL)
red SS 30 7 500 26.8
medium stiff
BOTTOM OF BORING DEPTH 30.5' 31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Earth Engineering Consultants, LLC
FOOTHILLS UNITARIAN CHURCH EXPANSION
FORT COLLINS,COLORADO
PROJECT NO:1192097 LOG OF BORING B4 DATE: DECEMBER 2019
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 1112512019 WHILE DRILLING None
AUGER TYPE: 4"CFA FINISH DATE 1112 5/2 01 9 AFTER DRILLING N/A
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A 24 HOUR N/A
SOIL DESCRIPTION D N QU MC DD A.LIMITS -210 SWELL
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI I%) PRESSURE %(d S00 PSF
VEGETATION&TOPSOIL-SOD
1
SILTY SAND(SM)
brown/red 2
medium dense to loose %e ISO pat
CS 3 17 2.0 104.8 NIL NP 9.0 350 psf 0.3%
4
FS.
5 21 3.3
6
7
8
9
SS 10 9 8.6
with occasional clay zones
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
SWELL/CONSOLIDATION TEST RESULTS
Material Description: Brown/Red Clayey/Silty Sand(SM/SC)
Sample Location: Boring 1,Sample 1, Depth 2'
Liquid Limit: 21 IPlasticity Index: 5 % Passing#200: 27.5%
Beginning Moisture: 9.1% JDry Density: 126.4 pcf JEnding Moisture: 12.3%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
co 3
4.0
2.0
c
m
E
d
0
2 0.0
.r
c
d
d Water Added
a
-2.0
-4.0
0
0
y
o -6.0
U
-8.0
-10.0
0.01 0.1 1 10
Load(TSF)
Project: Foothills Unitarian Church Expansion
Location: Fort Collins,Colorado
Project#: 1192097
Date: December 2019
SWELL/CONSOLIDATION TEST RESULTS
Material Description: Red Clayey Sand(SC)
Sample Location: Boring 2,Sample 1, Depth 4'
Liquid Limit: 30 IPlasticity Index: 15 % Passing#200: 17.9%
Beginning Moisture: 6.9% JDry Density: 140.2 pcf JEnding Moisture: 11.7%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
co 3
4.0
2.0
c
m
E
d
0
2 0.0
.r
c
d
L
d Water Added
-2.0
-4.0
0
0
y
o -6.0
U
-8.0
-10.0
0.01 0.1 1 10
Load(TSF)
Project: Foothills Unitarian Church Expansion
Location: Fort Collins,Colorado
Project#: 1192097
Date: December 2019
SWELL/CONSOLIDATION TEST RESULTS
Material Description: Brown/Red Silty Sand (SM)
Sample Location: Boring 4,Sample 1, Depth 2'
Liquid Limit: NL IPlasticity Index: NP %a Passing#200: 9.0%
Beginning Moisture: 2.0% JDry Density: 112.8 pcf JEnding Moisture: 17.5%
Swell Pressure: 350 psf %Swell @ 150: 0.3%
10.0
8.0
6.0
co 3
4.0
2.0
c
m
E
d
0
2 0.0
.r
c
d
L
d Water Added
-2.0
-4.0
0
0
y
o -6.0
U
-8.0
-10.0
0.01 0.1 1 10
Load(TSF)
Project: Foothills Unitarian Church Expansion
Location: Fort Collins,Colorado
Project#: 1192097
Date: December 2019
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis(AASHTO T 11&T 27/ASTM C 117&C 136)
Sieve Size Percent Passing
2 1/2" (63 mm) 100
2" (50 mm) 100
1 1/2" (37.5 mm) 100
1" (25 mm) 100
3/4" (19 mm) 100
1/2" (12.5 mm) 93
3/8" (9.5 mm) 91
No.4 (4.75 mm) 84
No.8 (2.36 mm) 72
No.10 (2 mm) 68
No.16 (1.18 mm) 57
No.30 (0.6 mm) 40
No.40 (0.425 mm) 32
No.50 (0.3 mm) 24
No.100 (0.15 mm) 15
No.200 (0.075 mm) 11.0
Project: Foothills Unitarian Church Expansion
Location: Fort Collins,Colorado
Project No: 1192097
Sample ID: B-1,S-3,at 9'
Sample Desc.: Well Graded Sand with Silt and Gravel(SW-SM)
Date: December 2019
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests(ASTM C117&C136)
Standard Sieve Size
5" 3" 2" 1" 1/2" No.4 No.10 No.30 No.50 No.200
6" 4" 2.5" 1.5" 3/4" 3/8" No.8 No.16 No.40 No.100
100
90
80
70
60
0
t 50
rn
40
L
N
c
IL
30
20
10
0 'T -2H I
1000 100 10 1 0.1 0.01
Grain Size (mm)
Cobble Gravel Sand Silt or Clay
Coarse Fine Coarse Medium Fine
Project: Foothills Unitarian Church Expansion
Location: Fort Collins,Colorado �100 �60 �50 �30 Rio Cu Cc
Project No: 1192097
Sample ID: B-1,S-3,at 9' 19.00 1.37 0.93 0.39 0.08 18.33 1.47
Sample Desc.: Well Graded Sand with Silt and Gravel(SW-SM)
Date: December 2019