HomeMy WebLinkAboutMELDRUM OFFICE BUILDING - PDP - PDP130027 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED 6-STORY OFFICE BUILDING
111 SOUTH MELDRUM
FORT COLLINS, COLORADO
EEC PROJECT NO. 1132023
Prepared for:
Blue Ocean Enterprises, Inc.
416 West Oak
Fort Collins, Colorado 80521
Attn: Mr. Brandon Grebe (brandon.grebe@blueocean-inc.com)
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
EARTH ENGINEERING
CONSULTANTS, LLC
April 26, 2013
Blue Ocean Enterprises, Inc.
416 West Oak
Fort Collins, Colorado 80521
Attn: Mr. Brandon Grebe (brandon.grebe@blueocean-inc.com)
Re: Geotechnical Subsurface Exploration Report
Proposed 6-Story Office Building
111 South Meldrum
Fort Collins, Colorado
EEC Project No. 1132023
Mr. Grebe:
Enclosed, herewith, are the results of the geotechnical subsurface exploration completed by
Earth Engineering Consultants, LLC (EEC) for the referenced project. For this
exploration, three (3) soil borings were drilled on April 19, 2013 at select locations within
the footprint of the proposed office building to be located at 111 South Meldrum Street in
Fort Collins, Colorado. The area available to complete the borings was limited by an
existing building on the east portion of the site. The borings were extended to approximate
depths of 45 feet below present site grades. This study was completed in general
accordance with our proposal dated April 24, 2013.
In summary, the subsurface soils encountered beneath the surficial landscape/pavements,
generally consisted of cohesive sandy lean clay and lean clay with sand layers, which
extended to the fine to coarse granular strata below. Sand with gravel, varying fines and
intermittent cobbles was encountered beneath the upper cohesive soils at depths of
approximately 20 to 22 feet below existing site grades and extended to the bedrock below.
Claystone bedrock with intermittent sandstone lenses was encountered in each of the
borings beneath the overburden soils at depths of approximately 32 feet below existing site
grades and extended to the depths explored, approximately 45 feet. Groundwater was
encountered across the site during the field exploration at approximate depths of 20 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 6-story structure be
supported on a drilled pier foundation system extending into the underlying bedrock
GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED 6-STORY OFFICE BUILDING
111 SOUTH MELDRUM
FORT COLLINS, COLORADO
EEC PROJECT NO. 1132023
April 26, 2013
INTRODUCTION
The geotechnical subsurface exploration for the proposed 6-story office building to be
constructed at 111 South Meldrum Street in Fort Collins, Colorado, has been completed. For this
exploration, three (3) soil borings extending to depths of approximately 45 feet below present site
grades were drilled on April 19, 2013 at pre-selected locations within the new building footprint.
This exploration was completed in general accordance with our proposal dated April 24, 2013.
We understand the proposed office building will have a total floor area on the order of 45,000
square feet with a footprint of approximately 7,500 square feet. An existing building on the
eastern portion of the site will be demolished prior to construction of the new structure. The new
building is expected to include a full basement extending to a depth on the order of 13 feet below
the existing site grades. Foundation loads for the new structure are estimated to be moderate with
maximum column loads likely in the range of 500 kips. Floor loads are expected to be light.
Small grade changes are expected to develop final site grades outside of the basement area.
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 building.
EXPLORATION AND TESTING PROCEDURES
The boring locations were established in the field by representatives from Earth Engineering
Consultants, Inc. (EEC) by pacing and estimating angles from identifiable site features. Those
approximate boring locations are indicated on the attached boring location diagram. The
locations of the borings should 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.
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EEC Project No. 1132023
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The test borings were completed using a truck mounted, CME-55 drill rig equipped with a
hydraulic head employed in drilling and sampling operations. The boreholes were advanced
using 6-1/4-inch nominal inside diameter hollow stem augers. Samples of the subsurface
materials encountered were obtained using split barrel and California barrel sampling procedures
in general accordance with ASTM Specifications D1587 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 undisturbed 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 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 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.
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SITE AND SUBSURFACE CONDITIONS
The area for the proposed building currently includes an existing 2-story building, a parking area,
and a small area currently landscaped with a deciduous tree. The site is relatively flat. A
“Google Earth” based diagram is attached depicting current site areas and approximate boring
locations.
Based on results of the field borings and laboratory testing, subsurface conditions can be
generalized as follows. The subsurface soils encountered beneath the existing pavement section,
generally consisted of cohesive sandy lean clay and lean clay with sand layers which extended to
a fine to coarse granular strata below. The cohesive soils were soft to firm to stiff, and exhibited
low expansive characteristics with slight compressible/consolidation characteristics with
increased depths. Intermittent sand and gravel lenses were encountered at increased depths
within the cohesive zone.
Poorly-graded sand with gravel and varying fines and intermittent cobbles was encountered
beneath the upper cohesive soils at depths of approximately 20 to 22 feet below existing site
grades and extended to the bedrock below. The granular materials were very dense.
Claystone bedrock with intermittent sandstone lenses was encountered in each of the borings
beneath the overburden soils at depths of approximately 32 feet below existing site grades and
extended to the depths explored, approximately 45 feet. The bedrock formation was weathered
nearer surface; however, became less weathered and more competent with depth. Boring B-3
was terminated at auger refusal or hard/cemented bedrock.
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.
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 observed across the
site at an approximate depth of 20 feet below existing site grades. The borings were backfilled
upon completion of our drilling operations with auger cuttings; subsequent groundwater
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EEC Project No. 1132023
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measurements were not obtained. The observed groundwater depths are consistent with
groundwater depths previously observed in other borings we have completed in the general area.
Fluctuations in groundwater levels can occur over time depending on variations in hydrologic
conditions, irrigation demands on and/or adjacent to the site 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
Swell/Consolidation Test Results
The swell/consolidation test is performed to evaluate the swell or collapse potential of soils or
bedrock and help establish foundation, floor slab and pavement design criteria. In this test,
relatively undisturbed samples obtained directly from the California barrel sampler are placed in a
laboratory apparatus and inundated with water under a predetermined load. All samples are
monitored for swell and consolidation. The swell-index is the resulting amount of swell or collapse
after the inundation period expressed as a percent of the sample’s initial thickness. After the
inundation period, additional incremental loads are applied to evaluate the swell pressure and/or
consolidation.
For this assessment, we conducted four (4) swell-consolidation tests at various intervals/depths
throughout the site. The three (3) swell tests completed on the cohesive overburden soils revealed
low expansive characteristics. The one (1) sample of the underlying bedrock formation also
revealed low swell potential characteristics. Results of the swell tests are indicated on the attached
boring logs and summary sheets.
Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide
uniformity in terminology between geotechnical engineers to provide a relative correlation of
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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.
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 overburden cohesive soils and the bedrock were within
the low range. Variations may exist across the site. The underlying Pierre Shale
Formation/claystone bedrock may exhibit higher swell potentials than those presented herein.
General Considerations and Discussion of Native Overburden Soils
The subject site is generally overlain by approximately 20 to 22 feet of cohesive clay soils which
extend to the fine to coarse granular soils below. Based on previous geotechnical subsurface
explorations performed in the vicinity, the cohesive subsoils have a tendency to consolidate when
inundated with water and subjected to increased loads. These soils would also show instability
and strength loss when wetted and/or subjected to construction traffic loads.
Final grading plans were not provided prior to the preparation of this subsurface exploration report.
Based on information provided, we estimate essentially none to possibly 2 feet of fill material may
be necessary within these areas to achieve final grades.
The recommendations contained in this report assume that small amounts of fill will be required,
and will be placed according to the recommendations provided herein. If there are any significant
deviations from the assumptions concerning fill depth and/or placement when the final site plan is
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developed, the conclusions and recommendations of this report should be reviewed and
confirmed/modified as necessary to reflect the final planned site configuration.
Site Preparation
All existing vegetation, tree root growth from the existing deciduous trees within the site
improvement areas, topsoil, 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 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 up to 2 feet of fill material 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 and
compacted to at least 95% of the material's standard Proctor maximum dry density as determined
in accordance with ASTM Specification D-698.
Fill soils required for developing the building 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 cohesive
sandy clay soils 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, +/- 2% for cohesive soils and +/-
3% for cohesionless soils of optimum moisture content, and compacted to at least 95% of the
materials maximum dry density as determined in accordance with ASTM Specification D-698,
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the standard Proctor procedure. If the site’s cohesive sandy soils are used as fill material, care
will be needed to maintain the recommended moisture content prior to and during construction of
overlying improvements. Settlement of the backfill soils should be anticipated with total load
settlement estimated on the order of 1% of the backfill height.
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. Subgrade materials becoming wet subsequent to construction of the site
structure can result in unacceptable performance.
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. The following foundation system was
evaluated for use on the site for the proposed building.
Straight shaft drilled piers bearing into the underlying bedrock formation.
Alternative foundation systems could be considered and we would be pleased to provide additional
alternatives upon request.
Drilled Piers/Caissons Foundations
Based on the subgrade conditions observed in the test borings and on the anticipated foundation
loads, we recommend supporting the proposed 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 depth of bedrock and
presence of groundwater.
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 8 feet into competent or harder bedrock. Lower values
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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 50 tons per cubic foot (tcf) for the portion of the pier in native cohesive soils, 75 tcf for native
granular materials or engineered fill, and 400 tcf in bedrock for a pier diameter of 12 inches. The
coefficient of subgrade reaction for varying pier diameters is as follows:
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
On-Site Overburden
Cohesive Soils Bedrock
Unit Weight of Soil (pcf) 130
(1)
115
(1)
125
(1)
Cohesion (psf) 0 200 5000
Angle of Internal Friction (degrees) 35 25 20
Strain Corresponding to ½ Max. Principal
Stress Difference 50
--- 0.02 0.015
*Notes: 1) Reduce by 64 pcf below the water table
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. Varying zones
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of cobbles may also be encountered in the granular soils above the bedrock. 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.
Due to the presence of granular soils and groundwater at approximate depths of 20 feet below site
grades, 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 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.
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.
Seismic Site Classification
The site soil conditions consist of approximately 32 feet of overburden soils overlying
moderately hard to hard bedrock. For those site conditions, the 2009 International Building Code
indicates a Seismic Site Classification of C.
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Lateral Earth Pressures
The new office building will be constructed with a full basement. The basement walls will be
subjected to unbalanced lateral earth pressures. 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 basement 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 a 30 degrees or low volume change cohesive soils. 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 Low Plasticity Cohesive Medium Dense Granular
Wet Unit Weight 115 135
Saturated Unit Weight 135 145
Friction Angle () – (assumed) 25° 35°
Active Pressure Coefficient 0.40 0.27
At-rest Pressure Coefficient 0.58 0.42
Passive Pressure Coefficient 2.46 3.69
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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.
Basement Floor Slab
Based on the materials observed in the soil borings, it is our opinion the building basement floor
slab could be directly supported by the in-place stiff cohesive soils. A granular leveling course
could be used, if needed. Under slab vapor barrier should be used at the architect’s discretion.
The in-situ soils at basement level would likely show instability under construction traffic. Rutting,
potentially significant rutting, may occur under heavier loads associated with drilling equipment for
the caisson drilling. Construction of a stabilized mat may be needed to accommodate the
construction traffic. A crushed granular material may be considered for the stabilized mat zone.
After completion of the caissons, a finer granular zone could be placed over the stabilized material
to support the floor slab.
Additional floor slab design and construction recommendations are as follows:
Positive separations and/or isolation joints should be provided between slabs and
all foundations, columns or utility lines to allow independent movement.
Control joints should be provided in slabs to control the location and extent of
cracking.
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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, Section 302.1R are recommended.
Perimeter Drain
We understand the referenced 6-story structure will include a full basement extending to a depth
of approximately 13 feet below present surface grades. The subsurface soils encountered in the
test borings completed for this project included approximately 20 to 22 feet of sandy lean clay
overlying sands and gravels which were underlain by weathered bedrock. The test borings
encountered groundwater at depths on the order of 20 feet below present site grades.
Depth to groundwater observed at this site was consistent with groundwater depths observed in
test borings completed on other projects in the general vicinity. However, some fluctuation can
occur in groundwater depths depending on variations in hydrologic conditions and other
conditions not apparent at the time of this report.
At a depth of approximately 13 feet below existing ground surface, the bottom of the basement
walls for the structure are expected to terminate in sandy lean clay subgrade soils. The structure
will be supported on drilled pier foundations extending to the underlying bedrock. With potential
infiltration of surface water adjacent to the building, we anticipate water could accumulate next to
the below grade walls and result in hydrostatic loading on those walls and, potentially, infiltration
of the surface 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 perforated metal or plastic pipe placed at
the approximate bottom of basement wall elevation 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.
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The basement floor will be on the order of 6 feet or greater above the groundwater measurements
recorded at the time of our exploration. Other explorations in this immediate area have indicated
groundwater at the approximate depth as measured on this project. However, some 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. With a high level of finish in the
basement area of this structure, we suggest consideration be given to installation of an underslab
drain system to reduce the potential for groundwater level rises to exert uplift pressures on the
floor slabs and/or infiltrate into below grade areas.
An underslab drain system would consist of an approximate 6-inch thick blanket of free draining
granular fill immediately beneath the basement floor slab with perforated drain line installed in
minimum 6-inch deep trenches at approximately 10-foot intervals across the width of the
building. An interior perimeter drain should be installed extending around the interior perimeter
of the building grade beam. Drain lines should allow for flow of water to a sump area without
reverse of flow into the system. The subgrade between the drain lines should be sloped to drain
towards each of the drain lines. The sandy lean clay subgrades should be separated from the
overlying free draining granular fill with a filter fabric to prevent infiltration of fines into the
system.
Installation of the drain systems 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.
Soil Corrosivity
The water soluble sulfate (SO4) testing of the on-site subgrade soils were approximately 0.08%.
Based on reported water soluble sulfate (SO4) testing of the on-site subgrade soils, this subsurface
exploration report includes a recommendation for the type of cement for use associated with the
on-site concrete in contact with the subgrade soils. The tests were performed by an
independent/outside laboratory, (Weld Lab of Greeley, Colorado) and the results of the laboratory
testing are shown in the table below.
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Water Soluble Sulfate Test Results
Sample Location Description Soluble Sulfate Content
(mg/kg)
Soluble Sulfate Content
(%)
B-1, S-9 at 39’ CLAYSTONE - BEDROCK 834 0.083
B-3, S-4 at 19’ Sandy LEAN CLAY (CL) <3 < 0.01
The results of the soluble sulfate tests indicate low potential for sulfate attack on Portland cement
concrete. ASTM Type I Portland cement may be suitable for concrete on and below site grade
within the overburden soils. However, if there is no, or minimal cost differential, use of ASTM
Type I/II Portland cement is recommended for additional sulfate resistance of construction concrete.
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 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 parking and drive areas to avoid
features which would pond water adjacent to the pavement, 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. Lawn watering
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 structure or
site pavements. Roof drains should be designed to discharge at least 5 feet away from the
structure and away from the pavement areas.
Excavations into the on-site soils may encounter a variety of conditions. Excavations into the on-
site clays can be expected to stand on relatively steep temporary slopes during construction.
However, if excavations extend into the underlying 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.
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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. Site-specific explorations should be
completed to develop site-specific recommendations for each of the site buildings.
This report has been prepared for the exclusive use for Blue Ocean Enterprises, Inc. 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 ground water. In low permeability soils, the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D-2488. Coarse Grained
Soils have move than 50% of their dry weight retained on a #200
sieve; they are described as: boulders, cobbles, gravel or sand.
Fine Grained Soils have less than 50% of their dry weight
retained on a #200 sieve; they are described as : clays, if they
are plastic, and silts if they are slightly plastic or non-plastic.
Major constituents may be added as modifiers and minor
constituents may be added according to the relative proportions
based on grain size. In addition to gradation, coarse grained
soils are defined on the basis of their relative in-place density
and fine grained soils on the basis of their consistency.
Example: Lean clay with sand, trace gravel, stiff (CL); silty
sand, trace gravel, medium dense (SM).
CONSISTENCY OF FINE-GRAINED SOILS
Unconfined Compressive
Strength, Qu, psf Consistency
< 500 Very Soft
500 - 1,000 Soft
1,001 - 2,000 Medium
2,001 - 4,000 Stiff
4,001 - 8,000 Very Stiff
8,001 - 16,000 Very Hard
RELATIVE DENSITY OF COARSE-GRAINED SOILS:
N-Blows/ft Relative Density
0-3 Very Loose
4-9 Loose
10-29 Medium Dense
30-49 Dense
50-80 Very Dense
80 + Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
joints. May be color change.
Moderate Some decomposition and color change
throughout.
High Rock highly decomposed, may be extremely
broken.
HARDNESS AND DEGREE OF CEMENTATION:
111 SOUTH MELDRUM
FORT COLLINS, COLORADO
EEC PROJECT NO. 1132023
APRIL 2013
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
ASPHALT (HMA) - Approximately 4-inches _ _
AGGR. BASE COURSE (ABC) - Approximately 6-inches 1
_ _
Sandy LEAN CLAY (CL) 2
firm, dark brown/brown, moist, fine to _ _
coarse sand, trace gravel and organics CS 3 7 4500 19.5 102.8
_ _
4
Sandy LEAN CLAY (CL) _ _
firm to stiff, brown, moist, fine-grained sand, SS 5 5 9000+ 11.4
calcareous deposits _ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 11 9000+ 14.4 101.7 35 16 82.8 1000 psf 0.7%
_ _
11
_ _
12
_ _
13
_ _
14
_ _
reddish brown, trace gravel, with brownish SS 15 8 7000 14.4
white clay seam _ _
16
_ _
17
_ _
18
_ _
19
fine to coarse-grained sand _ _
CS 20 23 5000 16.2 118.9
_ _
21
_ _
Poorly-graded SAND with silt and gravel (SP-SM) 22
very dense, brown/pink, wet, fine to coarse- _ _
grained sand 23
_ _
24
_ _
SS 25 50/9" -- 11.1 5.5
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
111 SOUTH MELDRUM
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 1000 PSF
Continued from Sheet 1 of 2 26
Poorly-graded SAND with silt and gravel (SP-SM) _ _
very dense, brown/pink, wet, fine to coarse- 27
grained sand _ _
28
_ _
29
_ _
SS 30 31 4000 29.9
_ _
CLAYSTONE 31
highly weathered, soft, brownish gray _ _
32
_ _
33
_ _
CLAYSTONE 34
slightly weathered, moderately hard to hard, CS _ _ 50/3" 9000+ 10.3 126.5 -- -- -- 2000 1.1%
dark gray, with cemented sandstone layers 35
_ _
36
_ _
37
_ _
38
_ _
39 Water soluble sulfate, SO4 = 834 mg/kg
SS _ _ 50/4.5" 9000+ 14.6
40
_ _
41
_ _
42
_ _
43
_ _
44 (No recovery)
SS _ _ 50/0"
BOTTOM OF BORING DEPTH 44.0' 45
_ _
46
_ _
47
_ _
48
_ _
49
_ _
50
_ _
Earth Engineering Consultants
111 SOUTH MELDRUM
FORT COLLINS, CO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
ASPHALT (HMA) - Approximately 3.5-inches _ _
AGGR. BASE COURSE (ABC) - Approximately 6-inches 1
_ _
Sandy LEAN CLAY (CL) 2
firm to stiff, light brown, dry, fine-grained sand, _ _
trace organics 3
_ _
4
_ _
CS 5 10 9000 13.9 99.4 31 15 66.9 1250 psf 0.5%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
moist SS 10 6 6500 19.6
_ _
11
_ _
12
_ _
13
_ _
14
_ _
reddish brown, fine to coarse-grained sand SS 15 8 5000 18.3
_ _
16
_ _
17
_ _
18
_ _
19
_ _
CS 20 50/10" 8000 6.2 127.6
_ _
Poorly-graded SAND with gravel (SP) 21
very dense, brown/pink, wet, fine to coarse- _ _
grained sand, trace silt 22
_ _
23
_ _
24
_ _
SS 25 50/9" -- 12.6
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
111 SOUTH MELDRUM
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
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
Poorly-graded SAND with gravel (SP) _ _
very dense, brown/pink, wet, fine to coarse- 27
grained sand, trace silt _ _
28
_ _
29
_ _
SS 30 50/9" -- 14.3
_ _
31
_ _
32
_ _
33
_ _
CLAYSTONE 34
slightly weathered, moderately hard to hard, CS _ _ 50/3.5" 9000+ 14.0 121.3
dark gray, with cemented sandstone layers 35
_ _
36
_ _
37
_ _
38
_ _
39
SS _ _ 50/2" 9000+ 16.1
40
_ _
41
_ _
42
_ _
43
_ _
44
SS _ _ 50/5" 9000+ 15.8 -- 39 17 54.4
45
_ _
46
_ _
47
_ _
48 (No recovery)
SS _ _ 50/1"
BOTTOM OF BORING DEPTH 48.0' 49
_ _
50
_ _
Earth Engineering Consultants
111 SOUTH MELDRUM
FORT COLLINS, CO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
ASPHALT (HMA) - Approximately 4-inches _ _
AGGR. BASE COURSE (ABC) - Approximately 5-inches 1
_ _
Sandy LEAN CLAY (CL) 2
soft, brown, moist, fine-grained sand, trace organics, _ _
calcareous deposits 3
_ _
4
_ _
SS 5 4 7000 11.8
_ _
6
_ _
7
_ _
8
LEAN CLAY with sand (CL) _ _
firm to stiff, brown, moist, fine-grained sand 9
calcareous deposits _ _
CS 10 8 9000 16.4 104.9 32 13 76.5 <500 psf 0.1%
_ _
11
_ _
12
_ _
13
_ _
14
_ _
reddish brown SS 15 5 2000 9.9
_ _
16
_ _
17
_ _
18
_ _
19
trace gravel, with brownish white clay seam _ _ Water soluble sulfate, SO4 < 1 mg/kg
SS 20 16 9000+ 18.7
_ _
21
_ _
22
_ _
Well-graded SAND with silt and gravel (SW-SM) 23
very dense, brown/pink, wet, fine to coarse- _ _
grained sand 24
_ _
SS 25 50/11" -- 12.0
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
111 SOUTH MELDRUM
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 6" HS
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
Well-graded SAND with silt and gravel (SW-SM) _ _
very dense, brown/pink, wet, fine to coarse- 27
grained sand _ _
28
_ _
29
_ _
SS 30 50/9" -- 11.7 5.9
_ _
31
_ _
32
_ _
CLAYSTONE 33
slightly weathered, moderately hard to hard, _ _
dark gray, with cemented sandstone layers 34
SS _ _ 50/5" 9000+ 20.2
35
_ _
36
_ _
37
_ _
38
_ _
39
CS _ _ 50/3" 9000+ 12.8 114.6
40
_ _
41
_ _
42
_ _
43
_ _
44
SS _ _ 50/2" 6000 13.0
45
AUGER REFUSAL, BOTTOM OF BORING DEPTH 45.0' _ _
46
_ _
47
_ _
48
_ _
49
_ _
50
_ _
Earth Engineering Consultants
111 SOUTH MELDRUM
FORT COLLINS, CO
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: LEAN CLAY with sand (CL), light brown, moist, fine-grained sand
Sample Location: Boring 1, Sample 3, Depth 9'
Liquid Limit: 35 Plasticity Index: 16 % Passing #200: 82.8%
Beginning Moisture: 14.4% Dry Density: 104.5 pcf Ending Moisture: 21.1%
Swell Pressure: 1000 psf % Swell @ 500: 0.7%
111 South Meldrum
Fort Collins, Colorado
1132023
April 2013
-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: CLAYSTONE, dark gray, moist, soft
Sample Location: Boring 1, Sample 8, Depth 34'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
Beginning Moisture: 10.3% Dry Density: 126.5 pcf Ending Moisture: 13.4%
Swell Pressure: 2000 psf % Swell @ 1000: 1.1%
111 South Meldrum
Fort Collins, Colorado
1132023
April 2013
-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: Sandy LEAN CLAY (CL), light brown, dry, fine-grained sand
Sample Location: Boring 2, Sample 1, Depth 4'
Liquid Limit: 31 Plasticity Index: 15 % Passing #200: 66.9%
Beginning Moisture: 13.9% Dry Density: 111.4 pcf Ending Moisture: 17.6%
Swell Pressure: 1250 psf % Swell @ 500: 0.5%
111 South Meldrum
Fort Collins, Colorado
1132023
April 2013
-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: LEAN CLAY with sand (CL), brown, moist, fine-grained sand
Sample Location: Boring 3, Sample 2, Depth 9'
Liquid Limit: 32 Plasticity Index: 13 % Passing #200: 76.5%
Beginning Moisture: 16.4% Dry Density: 105.4 pcf Ending Moisture: 19.3%
Swell Pressure: <500 psf % Swell @ 500: 0.1%
111 South Meldrum
Fort Collins, Colorado
1132023
April 2013
-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
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
111 South Meldrum
Fort Collins, CO
1132023
Boring 1, Sample 6, Depth 24'
Poorly-graded SAND with silt and gravel (SP-SM), brown/pink, wet
4/22/2013
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium Fine
6"
5"
4"
3"
2.5"
2"
1 1/2"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16 No. 30
No. 40
No. 50
No. 100
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
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
111 South Meldrum
Fort Collins, CO
1132023
Boring 3, Sample 6, Depth 29'
Well-graded SAND with silt and gravel (SW-SM), brown/pink, wet
4/22/2013
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium Fine
6"
5"
4"
3"
2.5"
2"
1 1/2"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16 No. 30
No. 40
No. 50
No. 100
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
PROJECT NO: 1132023 LOG OF BORING B-3 APRIL 2013
SHEET 2 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
4/19/2013 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, CO
PROJECT NO: 1132023 LOG OF BORING B-3 APRIL 2013
SHEET 1 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 4/19/2013 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1132023 LOG OF BORING B-2 APRIL 2013
SHEET 2 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
4/19/2013 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, CO
PROJECT NO: 1132023 LOG OF BORING B-2 APRIL 2013
SHEET 1 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 4/19/2013 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1132023 LOG OF BORING B-1 APRIL 2013
SHEET 2 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
4/19/2013 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, CO
PROJECT NO: 1132023 LOG OF BORING B-1 APRIL 2013
SHEET 1 OF 2 WATER DEPTH
START DATE 4/19/2013 WHILE DRILLING 20'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 4/19/2013 AFTER DRILLING N/A
A-LIMITS SWELL
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