HomeMy WebLinkAboutCONFLUENCE - PDP - PDP170001 - SUBMITTAL DOCUMENTS - ROUND 2 - GEOTECHNICAL (SOILS) REPORTSUBSURFACE EXPLORATION REPORT
401, 405, AND 409 LINDEN STRRET – MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172004
Prepared for:
[au]workshop
405 Linden Street
Fort Collins, Colorado 80524
Attn: Mr. Jason Kersley (jkersley@auworkshop.co)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
February 21, 2017
[au]workshop
405 Linden Street
Fort Collins, Colorado 80524
Attn: Mr. Jason Kersley (jkersley@auworkshop.co)
Re: Subsurface Exploration Report
401, 405, and 409 Linden Street – Mixed Use Development
Fort Collins, Colorado
EEC Project No. 1172004
Mr. Kersley:
Enclosed, herewith, are the results of the geotechnical subsurface exploration completed by Earth
Engineering Consultants, LLC (EEC) for the referenced project. For this exploration, six (6) soil
borings were drilled on February 1, 2017 at preselect locations accessible to our drilling
equipment within the footprints of the proposed 4-story and 5-story buildings planned for
construction at 401, 405, and 409 Linden Street in Fort Collins, Colorado. The borings were
extended to approximate depths of 11 to 30 feet below present site grades. This study was
completed in general accordance with our updated/revised proposal dated January 16, 2017.
In summary, the subsurface soils encountered beneath the surficial landscape/open space areas,
generally consisted of fine to coarse granular materials. The sand and gravel with varying fines
and intermittent cobbles extended to the bedrock formation below. Siltstone/sandstone bedrock
was encountered in each of the borings at depths of approximately 10 to 12 feet below existing
site grades and extended to the depths explored, approximately 11 to 30 feet. Auger refusal was
encountered within the cemented sandstone layer in boring B-1 at a depth of approximately 11
feet. At the time of drilling free water was not encountered across the site to the depths explored.
Subsequent groundwater measurements were performed after drilling and free water was
observed in borings B-3 and B-6 at depths ranging from approximately depths of 17½ to 24 feet
below existing site grades.
Based on the subsurface conditions encountered in the test borings as well as the anticipated
maximum loading conditions, we recommend the proposed 4-story building with at grade
parking for the northern portion of the development site be supported on a drilled pier foundation
system extending into the underlying bedrock formation, while the proposed 5-story building
with full-depth basement for the southern portion of the site be supported on a conventional
SUBSURFACE EXPLORATION REPORT
401, 405, AND 409 LINDEN STREET – MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172004
February 21, 2017
INTRODUCTION
The subsurface exploration for the proposed 4-story and 5-story mixed use buildings planned for
construction at 401, 405, and 409 Linden Street in Fort Collins, Colorado, has been completed. For
this exploration, six (6) soil borings extending to depths of approximately 11 to 30 feet below
present site grades were drilled on February 1, 2017 at pre-selected locations within the proposed 4-
story and 5-story building footprints. This exploration was completed in general accordance with
our updated/revised proposal dated January 16, 2017.
We understand the proposed mixed use 4-story building would be constructed on the northern
portion of the development area and would include a level of parking at grade. The 5-story building
is planned on the southern portion of the site in an area partially occupied by an existing building.
The 5-story building footprint will also have a full-depth basement. The building footprints will
occupy a majority of the development area. The existing building on the southern portion of the site
will be demolished prior to construction of the new structures. Foundation loads for the new
structures are estimated to be moderate to high with continuous wall loads less than 10 klf and
maximum column loads up to 250 kips. Floor loads are expected to be light. Small grade changes
on the order of 1 to 2 feet are expected to develop final site grades.
The purpose of this report is to describe the subsurface conditions encountered in the test borings,
analyze and evaluate the test data and provide geotechnical recommendations concerning design and
construction of foundations and support of floor slabs for the new buildings.
EXPLORATION AND TESTING PROCEDURES
The boring locations were established in the field by representatives from Earth Engineering
Consultants, LLC (EEC) by pacing and estimating angles from identifiable site features. The
borings were positioned in locations accessible to our drilling equipment. Those approximate boring
locations are indicated on the attached boring location diagram. The locations of the borings should
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 2
be considered accurate only to the degree implied by the methods used to make the field
measurements. Photographs of the site taken at the time of drilling are included with this report.
The test borings were completed using a truck mounted, CME-75 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 with 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 and hardness of weathered bedrock. 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. Atterberg
Limits and washed sieve analysis tests were completed on selected samples to evaluate the quantity
and plasticity of fines in the subgrade samples. Swell/consolidation tests were completed on
selected samples to evaluate the potential for the subgrade materials to change volume with variation
in moisture and load. Soluble sulfate tests were completed on selected samples to evaluate potential
adverse reactions to site-cast concrete. Results of the outlined tests are indicated herein and/or on
the attached boring logs and summary sheets.
As part of the testing program, all samples were examined in the laboratory by an engineer 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. Classification of the bedrock was based on visual and tactual
observation of disturbed samples and auger cuttings. Coring and/or petrographic analysis may reveal
other rock types.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 3
SITE AND SUBSURFACE CONDITIONS
The area for the proposed 4-story building on the northern portion of the development area is
generally open space which includes two (2) existing sheds, several stockpiles of soil, trees and
fence lines. The area is relatively flat.
The area for the proposed 5-story building on the southern portion of the development area includes
an existing single-story building with several trees, fence lines, and small intermittent landscape
areas. The area is relatively flat.
Based on results of the field borings and laboratory testing, subsurface conditions can be generalized
as follows. At the surface of borings B-1 and B-2 was a thin layer of mulch and gravel, respectively.
At the surface of borings B-4 through B-6 was a thin layer of topsoil and vegetation. Underlying
the thin layer of gravel, and topsoil/vegetation for borings B-2, B-5 and B-6, and from the surface of
boring B-3, in general, was clayey/silty sand with trace gravels which extended to depths of
approximately 1 to 5 feet below existing site grades. The upper two (2) feet of clayey/silty sand
identified in borings B-2 and B-5 appeared to be fill material. Underlying the thin layer of mulch
and topsoil/vegetation in borings B-1 and B-4 and underlying the clayey/silty sand with trace gravels
in the remaining borings, in general, was sand and gravel with varying amounts of silt which
extended to underlying siltstone/sandstone bedrock. As presented on the enclosed boring logs,
interbedded cobbles were encountered at increased depths. The essentially granular materials, in
general, were medium dense to very dense in relative density, exhibited low to nil swell potential,
and moderate bearing capacity characteristics.
Siltstone/sandstone bedrock with occasional well cemented sandstone zones was encountered in
each of the borings at depths of approximately 10 to 12 feet below existing site grades and extended
to the depths explored, approximately 11 to 30 feet. The siltstone/sandstone bedrock, in general,
was poorly cemented to cemented at the overburden/bedrock interface, demonstrated moderate to
high bearing capacity characteristics, and low to nil swell potential. As presented on the enclosed
boring logs, boring B-1 was terminated at an approximate depth of 11 feet below site grades due to
auger refusal within a well cemented lens.
The stratification boundaries indicated on the boring logs represent the approximate locations of
changes in soil and rock types. In-situ, the transition of materials may be gradual and indistinct.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 4
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, free water was not encountered in any of
the borings to the depths explored, approximately 11 to 30 feet below existing site grades.
Temporary PVC casings were installed in the open boreholes B-3 and B-6 to maintain open borings
and allow for additional water level measurements while the remaining borings were backfilled.
Subsequent groundwater measurements were performed after drilling and free water was observed in
borings B-3 and B-6 at depths of approximately 17½ to 24 feet below ground surface. The
temporary pipes were removed and the bore holes were backfilled upon completion of the
subsequent water level measurements; subsequent groundwater measurements were not obtained.
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.
Zones of perched and/or trapped water can be encountered at times throughout the year in more
permeable zones in the subgrade soils and perched water is commonly observed in subgrade soils
immediately above lower permeability bedrock.
ANALYSIS AND RECOMMENDATIONS:
General Considerations
The site appears suitable for the proposed development based on the subsurface conditions observed at
the test boring locations; however, certain precautions will be required in the design and construction
addressing the near surface variable fill, the removal/excavation of cobbles at increased depths and
penetration of the underlying well cemented sandstone bedrock lenses.
Depending upon the depth of excavation for the southernmost building footprint to allow for basement
construction, consideration should be given to installing a perimeter drainage system to intercept
surface water infiltration from impacting the below grade level. Removal of large sized cobbles during
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 5
excavation procedures should be implemented to reduce the potential for point loading conditions
developing on the floor slabs.
It is anticipated that excavations for the proposed construction can be accomplished with
conventional earthmoving equipment. However, excavations penetrating the well-cemented
sandstone bedrock may require the use of specialized heavy-duty equipment such as a rock hammer
or core barrel to achieve final design elevations. Consideration should be given to obtaining a unit
price for difficult excavation in the contract documents for the project.
Depending upon the depth of any lower level construction, a shoring plan may be necessary to protect
the adjacent sidewall slopes. The project design team should use the subsurface information provided
herein to properly design a mechanism for shoring protection. EEC is available to provide
supplemental design criteria or details such as but not limited to secant piles or piers, soldier piers, or a
tie-back/bracing concept.
Although evidence of fill materials beyond the depths described herein, or underground facilities
were not observed during the site reconnaissance, such features could be encountered during
construction and/or demolition of the existing on-site buildings. If unexpected fills or underground
facilities are encountered, such features should be removed and the excavation thoroughly cleaned
prior to backfill placement and/or construction.
Swell/Consolidation Test Results
As a part of our laboratory testing, we conducted four (4) swell/consolidation tests on samples of the
overburden materials and underlying bedrock. The swell index values for the samples analyzed
revealed low to nil swell characteristics when inundated with water and pre-loaded at 500 psf and
1000 psf, as well as exhibiting a slight tendency to hydro-compact and consolidate with increased
loads. Results of the laboratory swell tests are indicated in the table below, on the attached boring
logs, and on the enclosed summary sheets.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 6
TABLE I - Swell Consolidation Test Results
Boring
No.
Depth,
ft.
Material Type
In-Situ Moisture
Content, %
Dry Density,
PCF
Inundation
Pressure, psf
Swell Index,
(+/-) %
B-1 2 Sand and Gravel with Silt 2.4 113.5 500 (-) 0.9
B-2 4 Silty/Clayey Sand with Gravel 15.8 105.2 500 (-) 0.4
B-3 14 Siltstone / Sandstone 15.0 98.0 1000 (-) 0.3
B-6 2 Silty/Clayey Sand with Gravel 2.6 113.3 500 (-) 0.7
The Colorado Association of Geotechnical Engineers (CAGE) uses the following information to
provide uniformity in terminology between geotechnical engineers to provide a relative correlation risk
performance 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.
TABLE II: Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Slab Performance Risk
Category
Representative Percent Swell
(500 psf Surcharge)
Representative Percent Swell
(1000 psf Surcharge)
Low 0 to < 3 0 < 2
Moderate 3 to < 5 2 to < 4
High 5 to < 8 4 to < 6
Very High > 8 > 6
Based on the laboratory test results, the in-situ samples of overburden material and underlying
bedrock were generally in the low risk range.
Site Preparation
We understand the existing building on the south portion of the proposed development area and the
sheds observed on the northern portion of the development area along with any associated site
improvements will be demolished/removed from the site prior to the construction of the new
buildings. In addition, all existing vegetation, tree root growth from the existing deciduous trees
within the site improvement areas, topsoil/vegetation, and any uncontrolled fill material that may be
encountered during the excavation phases, should be removed from improvement and/or fill areas on
the site. Demolition of the existing structures, concrete sidewalks, pavement and other
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 7
miscellaneous features should include complete removal of all concrete or debris within the
proposed construction area. Site preparation should include removal of any loose backfill found
adjacent to the existing site structures/improvements. All materials derived from the demolition of
the existing building, pavements, sidewalks or other site improvements should be removed from the
site and not be allowed for use in any on-site fills.
Although final site grades were not available at the time of this report, based on our understanding of
the proposed development, we expect cuts and fills up to 2 feet may be necessary to achieve design
grades in the improvement areas. After stripping, completing all cuts, and removing all
unacceptable materials/soils, and prior to placement of any fill or site improvements, we recommend
the exposed soils be scarified to a minimum depth of 9-inches, adjusted in moisture content to within
±2% of standard Proctor optimum moisture content for essentially cohesive materials or to a
workable moisture content for cohesionless materials and compacted to at least 95% of the material's
standard Proctor maximum dry density as determined in accordance with ASTM Specification
D698. If, after the various cuts as required extend into the undisturbed siltstone/sandstone bedrock
(i.e. the proposed 5-story building with full-depth basement), scarification, moisture conditioning
and compaction of the siltstone/sandstone bedrock would not be necessary.
Fill soils required for developing the buildings and site subgrades, after the initial zone has been
prepared or stabilized where necessary, should consist of approved, low-volume-change materials,
which are free from organic matter and debris. It is our opinion the on-site clayey/silty sand and
sand and gravel with varying silt material could be used as general site fill material, provided
adequate moisture treatment and compaction procedures are followed. We recommend all fill
materials and foundation wall backfill materials, be placed in loose lifts not to exceed 9 inches thick
and adjusted in moisture content and compacted as recommended for the scarified soils above.
Care should be exercised after preparation of the subgrades to avoid disturbing the subgrade
materials. Positive drainage should be developed away from the structure to avoid wetting of
subgrade materials.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 8
Foundation Systems – General Considerations
The site appears suitable for the proposed construction based on the results of our field exploration and
our understanding of the proposed development plans. With the proposed northern 4-story building with
at grade parking and the southern 5-story building with full depth basement, to reduce the potential for
differential settlement, straight shaft drilled piers and conventional spread footings for the proposed
buildings, bearing on and/or into the siltstone/sandstone bedrock should be considered. The following
foundation systems were evaluated for use on the site for the proposed buildings.
Straight shaft drilled piers bearing in the underlying bedrock formation for the proposed 4-story
building with at grade parking.
Conventional spread footings bearing on undisturbed siltstone/sandstone bedrock for the
proposed 5-story building with full-depth basement.
Drilled Piers/Caissons Foundations – Northern Building
Based on the subgrade conditions observed in the test borings and on the anticipated foundation loads,
we recommend supporting the proposed northern 4-story building on a grade beam and straight shaft
drilled pier/caisson foundation system extending into the underlying bedrock formation. Particular
attention will be required in the construction of drilled piers due to the presence of essentially
cohesionless materials, occasional cobbles, occasional zones of well cemented sandstone and presence
of perched groundwater. For removal of cobbles at increased depths, consideration should be given to
the use of 24-inch diameter drilled piers.
For axial compression loads, the drilled piers could be designed using a maximum end bearing pressure
of 40,000 pounds per square foot (psf), along with a skin-friction of 4,000 psf for the portion of the pier
extended into the underlying firm and/or harder bedrock formation. Straight shaft piers should be
drilled a minimum of 5 feet into competent or harder bedrock. Lower values may be appropriate for
pier “groupings” depending on the pier diameters and spacing. Pile groups should be evaluated
individually.
To satisfy forces in the horizontal direction, piers may be designed for lateral loads using a modulus of
100 tons per cubic foot (tcf) for the portion of the pier in the fine to course granular subsoils, and 400
tcf in bedrock for a pier diameter of 12 inches. The coefficient of subgrade reaction for varying pier
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 9
diameters are as follows and generally conform to the formula of kh = 100/D, or 400/D, respectively,
for cohesionless soils and bedrock, in which D = pier diameter in feet:
Pier Diameter (inches) Coefficient of Subgrade Reaction (tons/ft3)
Cohesive Soils
Engineered Fill or
Granular Soils
Bedrock
18 33 50 267
24 25 38 200
30 20 30 160
36 17 25 133
When the lateral capacity of drilled piers is evaluated by the L-Pile (COM 624) computer program, we
recommend that internally generated load-deformation (P-Y) curves be used. The following
parameters may be used for the design of laterally loaded piers, using the L-Pile (COM 624) computer
program:
Parameters Native Granular Soils or Structural Fill Bedrock
Unit Weight of Soil (pcf) 130
(1) 125(1)
Average Undrained Shear Strength (psf) 0 5,000
Angle of Internal Friction () (degrees) 35 25
Coefficient of Subgrade Reaction, ks & kc (pci)
800-static
500 – cyclic
2,000 – static
800 - cyclic
Strain, 50 (%) (2) --- 0.004
*Notes: 1) Reduced by 62.4 PCF below the water table
2) The 50 values represent the strain corresponding to 50 percent of the maximum principal stress
difference. The modulus of subgrade reaction for static (ks) and cyclical (kc) are used by the L-Pile
computer programs to generate the slope of the initial portion of the “p-y curves.”
All piers should be reinforced full depth for the applied axial, lateral, and uplift stresses imposed.
The amount of reinforcing steel for expansion should be determined by the tensile force created by
the uplift force on each pier, with allowance for dead load.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 10
Drilling caissons to design depth should be possible with conventional heavy-duty single flight power
augers equipped with rock teeth on the majority of the site. However, areas of well-cemented
sandstone bedrock lenses may be encountered throughout the site at various depths where specialized
drilling equipment and/or rock excavating equipment may be required. Excavation penetrating the
well-cemented sandstone bedrock may require the use of specialized heavy-duty equipment, together
with rock augers and/or core barrels. Consideration should be given to obtaining a unit price for
difficult caisson excavation in the contract documents for the project.
With granular soils encountered on-site, as well as removal and/or drilling within large sized cobbles
zones, maintaining shafts may be difficult without stabilizing measures. We expect temporary casing
will be required to adequately/properly drill and clean piers prior to concrete placement.
Groundwater, if encountered, should be removed from each pier hole prior to concrete placement. Pier
concrete should be placed immediately after completion of drilling and cleaning.
A maximum 3-inch depth of groundwater is acceptable in each pier prior to concrete placement. If pier
concrete cannot be placed in dry conditions, a tremie should be used for concrete placement. Due to
potential sloughing and raveling, foundation concrete quantities may exceed calculated geometric
volumes. Pier concrete with slump in the range of 6 to 8 inches is recommended. Casing used for pier
construction should be withdrawn in a slow continuous manner maintaining a sufficient head of
concrete to prevent infiltration of water or the creation of voids in pier concrete.
Variable cobbles may be encountered in the granular materials overlying the siltstone/sandstone
bedrock. We suggest using larger diameter drilled piers, such as 24-inch or larger, to allow for
extraction of cobbles through the drilling process.
Foundation excavations should be observed by the geotechnical engineer. A representative of the
geotechnical engineer should inspect the bearing surface and pier configuration. If the soil conditions
encountered differ from those presented in this report, supplemental recommendations may be
required.
We estimate the long-term settlement of drilled pier foundations designed and constructed as
outlined above would be less than 1-inch.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 11
Conventional Spread Footing Foundations
Based on the subgrade conditions observed in the test borings and on the anticipated foundation
loads, we recommend supporting the proposed 5-story building with full-depth basement on
undisturbed siltstone/sandstone bedrock. For design of footing foundations bearing on the poorly
cemented to cemented siltstone/sandstone bedrock, we recommend using a net allowable total load
soil bearing pressure not to exceed 5,000 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.
In areas where the footing foundation bearing elevations would be above the competent
siltstone/sandstone bedrock or where the bedrock materials have been disturbed, we recommend
those footings be extended to bear on competent in-situ siltstone/sandstone bedrock.
Exterior foundations and foundations in unheated areas should be located at least 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 or grade beam foundations should not be used to allow for more thorough
evaluation of anticipated bearing soils at the time of construction.
Care should be taken to thoroughly evaluate anticipated bearing materials at the time of
construction. All footings for the structure should bear on uniform/similar materials to reduce the
potential for differential movement between soil types.
We estimate the long term-settlement of footing foundations designed and constructed as outlined
above would be less than 1-inch.
Seismic Site Classification
The site soil conditions consist of approximately 10-12 feet of medium dense to very dense
overburden soils overlying poorly cemented to cemented siltstone/sandstone bedrock. For those site
conditions, the 2015 International Building Code indicates a Seismic Site Classification of C.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 12
Lateral Earth Pressures
The proposed 5-story building for the southern portion of the development site will be constructed
over full-depth basement parking. In addition, any site retaining walls or similar structures would
also be subject to lateral soil forces. 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, including the below grade parking structure walls. 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 the table 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 essentially granular materials with a friction angle of 35
degrees. For the 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, it 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.
Soil Type Medium Dense Granular
Wet Unit Weight 135
Saturated Unit Weight 140
Friction Angle () – (assumed) 35°
Active Pressure Coefficient 0.27
At-rest Pressure Coefficient 0.43
Passive Pressure Coefficient 3.70
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 13
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.
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 Slab/Pavement/Flatwork Subgrades
After stripping and completing all cuts and prior to placement of any fill, floor slabs, pavements or
flatwork, we recommend the in-place materials be proof rolled with heavy construction equipment to
help locate any soft or loose materials in the exposed subgrades.
After stripping and completing all cuts including removal of existing fill, and prior to placement of
floor slabs or flatwork, we recommend the top 9 inches of the exposed subgrades be scarified and
recompacted as outlined the Site Preparation section of this report. We recommend fill materials
required to develop the subgrades consist of approved, low-volume change materials which are free
from organic matter and debris as recommended in the Site Preparation section of this report.
Although gravel bedding would not be required beneath the floor slabs to provide floor slab support,
a gravel leveling course could be considered.
Positive drainage should be developed away from the building and site improvements to reduce
potential for wetting of the bearing soils or subgrades and/or infiltration of water into the building
areas. Typically, a minimum slope away from the building of 1 inch per foot for the first 10 feet is
recommended. Flatter slopes may be used in flatwork areas.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 14
Perimeter Drainage System
We expect the below grade parking for the proposed 5-story southern building would extend to a
depth of approximately 12 to 16 feet below present surface grades. The subsurface soils
encountered in the test borings completed for this project included approximately 10 to 12 feet of
essentially granular material underlain by siltstone/sandstone bedrock. The test borings did not
encounter groundwater while drilling; however, groundwater was encountered at depths on the order
of 17½ to 24 feet below present site grades during subsequent measurements. As previously
discussed, fluctuations can occur in groundwater depths depending on variations in hydrologic
conditions and other conditions not apparent at the time of this report.
The structure is expected to be supported on conventional spread footing foundations bearing on the
siltstone/sandstone bedrock. With potential infiltration of surface water adjacent to the building and
potential perched water in subgrade soils immediately above the lower permeability bedrock, we
anticipate water could accumulate next to the below grade walls and result in hydrostatic loading on
those walls and, potentially, infiltration of water into the below grade areas. We suggest a perimeter
drain system be installed to remove surface infiltration water from the area adjacent to the below
grade walls and reduce the likelihood of development of hydrostatic loads on the walls and/or water
infiltration into the below grade area.
In general, a perimeter drain system would consist of properly sized perforated metal or plastic pipe
placed at the approximate bottom of the spread footing foundations and sloped to drain to a sump
area where accumulated water can be removed without reverse flow into the system. The drain line
should be surrounded by at least 6 inches of free draining granular fill with either the drain line or
granular fill wrapped in an appropriate filter fabric to prevent the intrusions of fines in the system.
Backfill above the drain line should consist of approved, low volume change material.
Installation of the drain system will reduce, not eliminate, the potential for infiltration of surface
and/or groundwater into the below grade areas and development of hydrostatic loads on structure
components. Pumps and other components require periodic inspections and maintenance to
maintain the system in functioning condition.
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 15
Water Soluble Sulfates (SO4)
The water soluble sulfate (SO4) testing of the on-site overburden and bedrock materials taken during
our subsurface exploration at varying depths are provided in the table below. Based on the reported
sulfate content test results, this report includes a recommendation for the CLASS or TYPE of cement
for use for contact in association with the on-site overburden and bedrock.
TABLE IV - Water Soluble Sulfate Test Results
Sample Location Description
Soluble Sulfate Content
(mg/kg)
Soluble Sulfate
Content (%)
B-2, S-5 @ 19’ Sandstone 440 0.04
B-5, S-3 @ 9’ Silty Sand and Gravel 180 0.02
Based on the results as presented in the table above, ACI 318, Section 4.2 indicates the site
overburden soils and bedrock generally have a low risk of sulfate attack on Portland cement
concrete. Therefore, Class 0 and Type I or Type I/II cement could be used for concrete on and
below site grades within the overburden soils and/or bedrock. Foundation concrete should be
designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
These results are being compared to the following table.
TABLE V - Requirements to Protect Against Damage to Concrete by Sulfate Attack from External Sources of
Sulfate
Severity of Sulfate exposure Water-soluble sulfate (SO4)
in dry soil, percent
Water-cement ratio,
maximum
Cementitious material
Requirements
Class 0 0.00 to 0.10% 0.45 Class 0
Class 1 0.11 to 0.20% 0.45 Class 1
Class 2 0.21 to 2.00% 0.45 Class 2
Class 3 2.01 of greater 0.45 Class 3
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 improvements in landscape areas. Flatter slopes could be
used in hardscapes areas although positive drainage should be maintained. Care should be taken in
planning of landscaping adjacent to the building and site improvement areas to avoid features which
would pond water adjacent to those elements. Placement of plants which require irrigation systems
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 16
or could result in fluctuations of the moisture content of the subgrade material should be avoided
adjacent to site improvements.
Excavations into the on-site soils may encounter a variety of conditions. If excavations extend into
the underlying cohesionless granular strata, caving soils may be encountered. 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.
Depending upon the depth of any lower level construction, a shoring plan will be necessary to
protect the adjacent sidewall slopes. The project design team should use the subsurface information
provided herein to properly design a mechanism for shoring protection.
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 for [au]workshop 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
Earth Engineering Consultants, LLC
EEC Project No. 1172004
February 21, 2017
Page 17
reviewed and the conclusions of this report are modified or verified in writing by the geotechnical
engineer.
Earth Engineering Consultants, LLC
DRILLING AND EXPLORATION
DRILLING & SAMPLING SYMBOLS:
SS: Split Spoon ‐ 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample
ST: Thin‐Walled Tube ‐ 2" O.D., unless otherwise noted WS: Wash Sample
R: Ring Barrel Sampler ‐ 2.42" I.D., 3" O.D. unless otherwise noted
PA: Power Auger FT: Fish Tail Bit
HA: Hand Auger RB: Rock Bit
DB: Diamond Bit = 4", N, B BS: Bulk Sample
AS: Auger Sample PM: Pressure Meter
HS: Hollow Stem Auger WB: Wash Bore
Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2‐inch O.D. split spoon, except where noted.
WATER LEVEL MEASUREMENT SYMBOLS:
WL : Water Level WS : While Sampling
WCI: Wet Cave in WD : While Drilling
DCI: Dry Cave in BCR: Before Casing Removal
AB : After Boring ACR: After Casting Removal
Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated
levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D‐2488. Coarse Grained
Soils have move than 50% of their dry weight retained on a
#200 sieve; they are described as: boulders, cobbles, gravel or
sand. Fine Grained Soils have less than 50% of their dry weight
retained on a #200 sieve; they are described as : clays, if they
are plastic, and silts if they are slightly plastic or non‐plastic.
Major constituents may be added as modifiers and minor
constituents may be added according to the relative
proportions based on grain size. In addition to gradation,
coarse grained soils are defined on the basis of their relative in‐
place density and fine grained soils on the basis of their
consistency. Example: Lean clay with sand, trace gravel, stiff
(CL); silty sand, trace gravel, medium dense (SM).
CONSISTENCY OF FINE‐GRAINED SOILS
Unconfined Compressive
Strength, Qu, psf Consistency
< 500 Very Soft
500 ‐ 1,000 Soft
1,001 ‐ 2,000 Medium
2,001 ‐ 4,000 Stiff
4,001 ‐ 8,000 Very Stiff
8,001 ‐ 16,000 Very Hard
RELATIVE DENSITY OF COARSE‐GRAINED SOILS:
N‐Blows/ft Relative Density
0‐3 Very Loose
4‐9 Loose
10‐29 Medium Dense
30‐49 Dense
50‐80 Very Dense
80 + Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
joints. May be color change.
Moderate Some decomposition and color change
throughout.
High Rock highly decomposed, may be extremely
broken.
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
Earth Engineering Consultants, LLC
IIf soil contains >15% gravel, add "with gravel" to
group name
JIf Atterberg limits plots shaded area, soil is a CL-
ML, Silty clay
Unified Soil Classification System
1
2
B-3
B-2
B-1
B-4
B-6
B-5
Boring Location Diagram
401, 405, & 409 Linden Street - Mixed Use Development
Fort Collins, Colorado
EEC Project Number: 1172004 Date: February 2017
EARTH ENGINEERING CONSULTANTS, LLC
Approximate Boring
Locations
1
Legend
Site Photos
(Photos taken in approximate
location, in direction of arrow)
401, 405, 409 LINDEN STREET
MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172004
FEBRUARY 2017
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
MULCH _ _
1
SAND & GRAVEL with SILT (SP-SM/GP-GM) _ _
brown / tan 2
dense to very dense _ _
CS 3 37 -- 2.4 120.2 NL NP 9.2 <500 psf None
_ _
4
_ _
* intermittent cobbles with depth SS 5 50/11" -- 1.8 7.8
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 50/4" 500 14.7 98.5
SANDSTONE _ _
brown / grey / rust; poorly cemented to cemented with dept 11
*encountered auger refusal @ 11 feet _ _
BOTTOM OF BORING DEPTH 11.0' 12
_ _
13
_ _
14
_ _
15
_ _
16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
GRAVEL _ _
1
FILL MATERIAL: Clayey Sand with trace Gravel _ _
2
_ _ Cuttings -- 5.6
SILTY/CLAYEY SAND (SM/SC) 3
dark brown / brown _ _
with gravel & cobbles 4
_ _
CS 5 9 4000 15.8 99.3 28 8 42.1 <500 psf None
SAND & GRAVEL with SILT (SP-SM/GP-GM) _ _
brown / tan 6
loose _ _
with gravel & cobbles 7
_ _
8
_ _
9
_ _
SS 10 50/7" -- 2.2 10.8
_ _
11
_ _
12
_ _
SANDSTONE 13
grey _ _
poorly cemented to cemented 14
_ _
cave in at 3'; no recovery CS 15 --
_ _
16
_ _
17
_ _
18
_ _
19
_ _
SS 20 50/3" 9000+ 14.6
_ _
21
_ _
22
_ _
23
_ _
24
_ _
CS 25 50/0.5" -- 7.7
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
SANDSTONE 27
grey _ _
cemented 28
_ _
29
_ _
SS 30 50/3" 9000+ 13.3
_ _
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
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
_ _
SILTY SAND (SM) 1
tan / grey _ _
medium dense to dense 2
_ _
3
_ _
4
_ _
SAND & GRAVEL with SILT (SP-SM/GP-GM) CS 5 50/7" -- 1.1 131.2
brown / tan _ _
very dense 6
with cobbles _ _
7
_ _
8
_ _
9
_ _
SS 10 50/11" -- 2.9
_ _
11
SILTSTONE / SANDSTONE _ _
olive / grey 12
poorly cemented to cemented _ _
13
_ _
14
_ _ % @ 1000 psf
CS 15 50/3" 9000 15.0 <1000 psf None
_ _
16
_ _
17
_ _
18
_ _
19
grey _ _
SS 20 50/2" 9000+ 15.3
_ _
21
_ _
22
_ _
23
_ _
24
_ _
CS 25 50/2" 9000 14.3
BOTTOM OF BORING DEPTH 25.0' _ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SAND & GRAVEL with SILT (SP-SM/GP-GM) _ _
brown / tan 2
very dense _ _
with cobbles CS 3 50/9" -- 2.6 127.9
_ _
4
_ _
SS 5 50/8" -- 1.4 12.3
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 50/8" -- 3.0 129.7
SILTSTONE / SANDSTONE _ _
grey / olive 11
poorly cemented to cemented _ _
12
_ _
13
_ _
14
_ _
SS 15 50/5" -- 16.1
_ _
16
_ _
17
_ _
18
_ _
19
_ _
grey CS 20 50/2.5" 9000 15.6 97.0
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 50/2" 4500 13.3
BOTTOM OF BORING DEPTH 25.5' _ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
FILL MATEIAL: Clayey Sand with trace Gravel _ _
2
_ _
SILTY SAND & GRAVEL (SM/GM) SS 3 50/11" -- 2.7
brown _ _
very dense to dense 4
_ _
brown / tan CS 5 44 -- 1.8 124.6 19 1 20.9
with cobbles _ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 50 -- 1.9
_ _
11
_ _
SILTSTONE / SANDSTONE 12
grey / olive _ _
poorly cemented to cemented 13
_ _
14
_ _
SS 15 50/4.5" -- 15.5
_ _
16
cemented from ~16-18' _ _
17
_ _
18
_ _
19
grey _ _
CS 20 50/2.5" 9000+ 13.3 109.0
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 50/1.5" -- 6.1
BOTTOM OF BORING DEPTH 25.5' _ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
SILTY / CLAYEY SAND (SM/SC); brown 1
_ _
SAND & GRAVEL (SP/GP) CS 2 34 8000 2.6 117.0 25 9 11.3 <500 psf None
brown / tan _ _
dense 3
_ _
4
_ _
* intermittent cobbles with depth SS 5 42 -- 1.7
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 29 -- 2.0 105.6 4.6
_ _
11
SANDSTONE _ _
grey / olive 12
poorly cemented to cemented _ _
13
_ _
14
with intermittent cemented zones _ _
SS 15 50/5" 9000+ 15.7
_ _
16
_ _
17
_ _
18
_ _
19
grey _ _
CS 20 50/2" 9000+ 14.1
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 50/2" 9000+ 14.1
BOTTOM OF BORING DEPTH 25.5' _ _
Earth Engineering Consultants, LLC
401, 405, & 409 LINDEN STREET - MIXED USE DEVELOPMENT
Project:
Location:
Project #:
Date:
401, 405, & 409 Linden St - Mixed Use Development
Fort Collins, Colorado
1172004
February 2017
Beginning Moisture: 2.4% Dry Density: 113.5 pcf Ending Moisture: 12.3%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Boring 1, Sample 1, Depth 2'
Liquid Limit: NL Plasticity Index: NP % Passing #200: 9.2%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sand & Gravel with Silt (SP-SM/GP-GM)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
401, 405, & 409 Linden St - Mixed Use Development
Fort Collins, Colorado
1172004
February 2017
Beginning Moisture: 15.8% Dry Density: 105.2 pcf Ending Moisture: 16.3%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Boring 2, Sample 2, Depth 4'
Liquid Limit: 28 Plasticity Index: 8 % Passing #200: 42.1%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Silty/Clayey Sand with Gravel (SM/SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown / Grey / Rust Sandstone
Sample Location: Boring 3, Sample 3, Depth 14'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
Beginning Moisture: 15.0% Dry Density: 98 pcf Ending Moisture: 24.6%
Swell Pressure: <1000 psf % Swell @ 1000: None
401, 405, & 409 Linden St - Mixed Use Development
Fort Collins, Colorado
1172004
February 2017
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
401, 405, & 409 Linden St - Mixed Use Development
Fort Collins, Colorado
1172004
February 2017
Beginning Moisture: 2.6% Dry Density: 113.3 pcf Ending Moisture: 16.4%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Boring 6, Sample 1, Depth 2'
Liquid Limit: 25 Plasticity Index: 9 % Passing #200: 11.3%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Silty/Clayey Sand & Gravel (SM/GM-SC/GC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: 401, 405, & 409 Linden Street - Mixed Use Development
Location: Fort Collins, Colorado
Project No: 1172004
Sample ID: B-1, S-2, 4'
Sample Desc.: Sand & Gravel with Silt (SP-SM/GP-GM)
Date: February 2017
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
100
100
100
94
79
72
58
47
45
38
28
23
18
12
7.8
0.74 0.12
Fine
46.61 0.86
D30 D
10 Cu
CC
February 2017
25.00 5.43 3.01
401, 405, & 409 Linden Street - Mixed Use Development
Fort Collins, Colorado
1172004
B-1, S-2, 4'
Sand & Gravel with Silt (SP-SM/GP-GM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: 401, 405, & 409 Linden Street - Mixed Use Development
Location: Fort Collins, Colorado
Project No: 1172004
Sample ID: B-2, S-3, 9'
Sample Desc.: Sand & Gravel with Silt (SP-SM/GP-GM)
Date: February 2017
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
100
100
91
87
85
79
70
59
57
49
36
29
24
16
10.8
0.44 ‐‐‐
Fine
‐‐‐ ‐‐‐
D30 D
10 Cu
CC
February 2017
37.50 2.49 1.31
401, 405, & 409 Linden Street - Mixed Use Development
Fort Collins, Colorado
1172004
B-2, S-3, 9'
Sand & Gravel with Silt (SP-SM/GP-GM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: 401, 405, & 409 Linden Street - Mixed Use Development
Location: Fort Collins, Colorado
Project No: 1172004
Sample ID: B-4, S-2, 4'
Sample Desc.: Silty Sand & Gravel (SM/GM)
Date: February 2017
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
100
100
92
87
75
67
57
47
45
39
30
26
23
19
12.3
0.59 ‐‐‐
Fine
‐‐‐ ‐‐‐
D30 D
10 Cu
CC
February 2017
37.50 6.07 3.04
401, 405, & 409 Linden Street - Mixed Use Development
Fort Collins, Colorado
1172004
B-4, S-2, 4'
Silty Sand & Gravel (SM/GM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: 401, 405, & 409 Linden Street - Mixed Use Development
Location: Fort Collins, Colorado
Project No: 1172004
Sample ID: B-6, S-3, 9'
Sample Desc.: Sand & Gravel (SP/GP)
Date: February 2017
22
18
13
7
4.6
100
91
70
63
39
100
100
100
100
100
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
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
February 2017
9.50 1.91 1.55
401, 405, & 409 Linden Street - Mixed Use Development
Fort Collins, Colorado
1172004
B-6, S-3, 9'
Sand & Gravel (SP/GP)
D100 D
60 D50
0.86 0.22
Fine
8.63 1.74
D30 D
10 Cu
CC
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-6 FEBRUARY 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 2/20/2017 17.5'
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-5 FEBRUARY 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-4 FEBRUARY 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-3 FEBRUARY 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 2/8/2017 24'
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1172004 LOG OF BORING B-2 FEBRUARY 2017
SHEET 2 OF 2 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
2/1/2017 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-2 FEBRUARY 2017
SHEET 1 OF 2 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1172004 LOG OF BORING B-1 FEBRUARY 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 2/1/2017 WHILE DRILLING None
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 2/1/2017 AFTER DRILLING N/A
A-LIMITS SWELL
Soil Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests
Sands 50% or more
coarse fraction
passes No. 4 sieve
Fine-Grained Soils
50% or more passes
the No. 200 sieve
<0.75 OL
Gravels with Fines
more than 12%
fines
Clean Sands Less
than 5% fines
Sands with Fines
more than 12%
fines
Clean Gravels Less
than 5% fines
Gravels more than
50% of coarse
fraction retained on
No. 4 sieve
Coarse - Grained Soils
more than 50%
retained on No. 200
sieve
CGravels with 5 to 12% fines required dual symbols:
Kif soil contains 15 to 29% plus No. 200, add "with sand"
or "with gravel", whichever is predominant.
<0.75 OH
Primarily organic matter, dark in color, and organic odor
ABased on the material passing the 3-in. (75-mm)
sieve
ECu=D60/D10 Cc=
HIf fines are organic, add "with organic fines" to
group name
LIf soil contains ≥ 30% plus No. 200 predominantly sand,
add "sandy" to group name.
MIf soil contains ≥30% plus No. 200 predominantly gravel,
add "gravelly" to group name.
DSands with 5 to 12% fines require dual symbols:
BIf field sample contained cobbles or boulders, or
both, add "with cobbles or boulders, or both" to
group name. FIf soil contains ≥15% sand, add "with sand" to
GIf fines classify as CL-ML, use dual symbol GC-
CM, or SC-SM.
Silts and Clays
Liquid Limit less
than 50
Silts and Clays
Liquid Limit 50 or
more
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
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
HARDNESS AND DEGREE OF CEMENTATION:
Limestone and Dolomite:
Hard Difficult to scratch with knife.
Moderately Can be scratched easily with knife.
Hard Cannot be scratched with fingernail.
Soft Can be scratched with fingernail.
Shale, Siltstone and Claystone:
Hard Can be scratched easily with knife, cannot be
scratched with fingernail.
Moderately Can be scratched with fingernail.
Hard
Soft Can be easily dented but not molded with
fingers.
Sandstone and Conglomerate:
Well Capable of scratching a knife blade.
Cemented
Cemented Can be scratched with knife.
Poorly Can be broken apart easily with fingers.
Cemented