HomeMy WebLinkAboutReports - Soils - 10/10/2023 PRELIMINARY SUBSURFACE EXPLORATION REPORT
PROPOSED MULBERRY STREET MIXED-USE DEVELOPMENT
NORTH SIDE OF MULBERRY STREET AND WEST OF NORTH I-25 FRONTAGE ROAD
FORT COLLINS, COLORADO
EEC PROJECT NO. 1232071
Prepared for:
TDC-Development
Address:
Attn: Mr. Dean Barber(dbarberktdc-dev.com)
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
October 10, 2023
TDC-Development
Address: EARTH ENGINEERING
CONSULTANTS, LLC
Attn: Mr. Dean Barber(dbarbergtdc-dev.com)
Re: Preliminary Subsurface Exploration Report
Proposed Mulberry Street Mixed-Use Development
North side of Mulberry Street and West of North I-25 Frontage Road
Fort Collins, Colorado
EEC Project No. 1232071
Mr. Barber:
Enclosed, herewith, are the results of the preliminary subsurface exploration completed by Earth
Engineering Consultants, LLC (EEC) for the proposed Mulberry Street mixed-use development
planned for design and construction at the north side of Mulberry Street and west of North I-25
Frontage Road in Fort Collins, Colorado. For this exploration, EEC personnel advanced four (4)
preliminary soil borings to depths of approximately 20 to 25 feet below present site grades at pre-
selected locations within the various proposed building footprints and associated on-site pavement
improvements. This exploration was completed in general accordance with our proposal dated August
4,2023.
In summary, the subsurface conditions encountered beneath the surficial vegetation/topsoil generally
consisted of 8 to 12 feet of cohesive to slightly cohesive sandy lean clay to clayey-silty sand soils
extending to the underlying granular soils. The cohesive soils were generally moist, soft/ loose to very
stiff/ dense and exhibited nil to low swell potential with slight tendency to hydro-compact at current
moisture and density conditions. Sand/gravel with intermittent clay zones were encountered below the
cohesive to slightly cohesive soils and extended to the depths explored; approximately 20 to 25 feet
below the ground. Sand with clay and gravel soils were generally moist and were loose to dense.
Groundwater was observed in all of the borings at depths of approximately 8 to 12 feet below the
ground surface.
Based on the encountered subsurface conditions and anticipated maximum wall and column loads on
the order of 1 to 3 klf and 25 to 100 kips, respectively, in our opinion, the proposed retail /mixed-use
development structures could be supported on conventional spread footings bearing on approved
undisturbed overburden subsoils and/or approved engineered fill material. Pavements, interior floor
slabs, and exterior flatwork could be supported on a zone of scarified and moisture conditioned on-site
4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
Earth Engineering Consultants,LLC
EEC Project No. 1232071
October 10,2023
Page 2
subgrades and/or on a zone of engineered/controlled fill material provided the recommendations as
presented in the attached report are adhered to.
i
At the time of drilling, groundwater was encountered across the site within the preliminary borings at
depths of approximately 8 to 12 feet below existing site grades. If lower-level construction or full-
depth basements are being considered for the site, we would suggest that the lower-level subgrade(s)
be placed a minimum of 4 feet above the maximum anticipated rise in groundwater levels and a
combination exterior and interior perimeter drainage system(s) be installed. Foundations for slab-on-
grade buildings should also be placed at least 4 feet above maximum groundwater levels and have
proper drainage in areas with extremely shallow groundwater. Additional drainage system
recommendations are provided within the text portion of this report.
Preliminary geotechnical recommendations concerning design and construction of foundations and
support of floor slabs and pavements are provided within the text of the enclosed report. We appreciate
the opportunity to be of service to you on this project. If you have any questions concerning the
enclosed report, or if we can be of further service to you in any other way, please do not hesitate to
contact us.
Very truly yours,
Earth Engineering Consultants,LLC Reviewed b
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Ali Khorasani David A. Richer, P.E.
Project Engineer Senior Geotechnical Engineer
PRELIMINARY SUBSURFACE EXPLORATION REPORT
PROPOSED MULBERRY STREET MIXED-USE DEVELOPMENT
NORTH SIDE OF MULBERRY STREET AND WEST OF NORTH I-25 FRONTAGE ROAD
FORT COLLINS, COLORADO
EEC PROJECT NO. 1232071
October 10, 2023
INTRODUCTION
The preliminary subsurface exploration for the proposed mixed-use development planned for design
and construction at the north side of Mulberry Street and west of North Interstate 25 (I-25) in Fort
Collins, Colorado, has been completed. For this preliminary exploration, Earth Engineering
Consultants,LLC(EEC)advanced four(4)preliminary soil borings to depths of approximately 20 to
25 feet below present site grades at pre-selected locations within the various building footprints and
associated on-site pavement improvement areas, as presented on the enclosed site plan. Upon
completion of the drilling operations,the four(4)open bore holes were converted to temporary PVC
cased piezometers. Individual preliminary boring logs and the enclosed site plan indicating the
approximate boring locations are included with this report. This exploration was completed in
general accordance with our proposal dated August 4, 2023.
We understand the master plan concept for this proposed development will include mixed-use
retail/commercial along with on-site pavement improvements as depicted on the enclosed site plan
provided to us by TDC on July 31,2023.Foundation loads are estimated to be light with maximum
continuous wall loads on the order of approximately 1 to 3 kips per linear foot(KLF)and maximum
column loads on the order of approximately 25 to 100 kips. Floor loads are expected to be light to
moderate. If actual loads exceed those assumed herein or if basement construction is being
considered for the site, we should be consulted to review and modify the recommendations
accordingly, if necessary. The pavements are expected to include areas for light duty automobile
traffic as well as areas for heavier duty traffic. Small grade changes, cuts and fills less than 4 feet
(+/-), are expected to develop site grades for the proposed development.
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, support of interior floor slabs, exterior flatwork, and design of
pavements for the proposed development.
Earth Engineering Consultants,LLC
EEC Project No. 1232071
October 10,2023
Page 2
EXPLORATION AND TESTING PROCEDURES
The boring locations were established in the field by representatives from EEC by pacing and
estimating angles from identifiable site features with the aid of a hand-held GPS unit using
appropriate Google Earth coordinates. 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.
The borings were performed using a truck-mounted CME-55 drill rig equipped with a hydraulic head
employed in drilling and sampling operations. The boreholes were advanced using 4-inch nominal
diameter continuous flight augers. After completion of the drilling operations, temporary
PVC/piezometer pipe was installed in the four(4)preliminary borings for supplemental groundwater
measurement purposes. These PVC casings were removed upon readings approximately 2 weeks
after drilling. Samples of the subsurface materials encountered were obtained using split-barrel and
California barrel sampling procedures in general accordance with ASTM Specifications D 1586 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 select 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. A water-soluble sulfate test was completed on a select sample 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 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
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EEC Project No. 1232071
October 10,2023
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Classification System is indicated on the boring logs and a brief description of that classification
system is included with this report.
SITE AND SUBSURFACE CONDITIONS
The proposed retail/mixed-use development planned for design and construction is located om the
north side of Mulberry Street and west of North I-25 Frontage Road. The project site is a vacant lot
that has previously been used for agricultural purposes. The cursory review of the historic Google
Earth imagery indicates minor stripping/earthwork/leveling operations after circa 2019. Sparse
vegetation and topsoil were encountered at the surface of each preliminary test boring. The relief
across is the site is approximately estimated to be on the order of 8 feet. Photographs of the site
taken at time of our drilling are provided with this report.
EEC field personnel were on site during drilling to evaluate the subsurface conditions encountered
and direct the drilling activities.Field logs prepared by EEC site personnel were based on visual and
tactual observation of disturbed samples and auger cuttings.The final boring logs included with this
report may contain modifications to the field logs based on results of laboratory testing and
evaluation.Based on results of the field borings and laboratory testing,subsurface conditions can be
generalized as follows.
The subsurface soils encountered beneath surficial vegetation/topsoil,generally consisted of 8 to 12
feet of cohesive to slightly cohesive sandy lean clay to clayey-silty sand soils extending to the
underlying granular soils. The cohesive soils were generally moist, soft/loose to very stiff/dense
and exhibited nil to low swell potential with slight tendency to hydro-compact at current moisture
and density conditions. Sand/gravel with intermittent clay zones were encountered below the
cohesive to slightly cohesive soils and were extended to the depths explored;approximately 20 to 25
feet below the ground. Sand with clay and gravel soils were generally moist and were loose to dense.
The stratification boundaries indicated on the boring logs represent the approximate locations of
changes in soil and bedrock types. In-situ,the transition of materials may be gradual and indistinct.
GROUNDWATER CONDITIONS
Observations were made while drilling and on October 2, 2023, within the installed temporary
piezometers,to detect the presence and level of groundwater.At the time of drilling and on October
2, 2023, groundwater was observed in the preliminary test borings at depths ranging from
Earth Engineering Consultants,LLC
EEC Project No. 1232071
October 10,2023
Page 4
approximately 8 to 12 feet below existing site grades. The measured depths to groundwater are
recorded near the upper right-hand corner of each boring log included with this report.The borings
were backfilled after drilling / upon the follow up measurements on October 2, 2023, therefore
subsequent groundwater measurements were not possible.The groundwater measurements provided
with this report are indicative of groundwater levels at the location and at the time the measurements
were completed.
Perched and/or trapped water may be encountered in more permeable zones in the subgrade soils at
times throughout the year. Perched water is commonly encountered in soils immediately overlying
less permeable bedrock materials.Fluctuations in ground water levels and in the location and amount
of perched water may occur over time depending on variations in hydrologic conditions,irrigation
activities on surrounding properties and other conditions not apparent at the time of this report.
ANALYSIS AND RECOMMENDATIONS
Swell—Consolidation Test Results
The swell-consolidation test is performed to evaluate the swell or collapse potential of soils or bedrock
to help determine foundation, floor slab, and pavement design criteria. In this test, relatively intact
samples obtained directly from the California barrel sampler are placed in a laboratory apparatus and
inundated with water under a predetermined load.All inundated samples are monitored for swell and
consolidation.The swell-index is the resulting amount of swell or collapse after inundation,expressed
as a percent of the sample's initial thickness.After the initial inundation period,additional incremental
loads are applied to evaluate the swell pressure and consolidation.
For this assessment, we conducted five (5) swell-consolidation tests on samples recovered from
various intervals/depths.The swell index values for the in-situ soil samples analyzed revealed low to
moderate swell characteristics as indicated on the attached swell test summaries.The(+)test results
indicate the soil materials swell potential characteristics while the (-) test results indicate the soils
materials collapse potential characteristics when inundated with water. The following table
summarizes the swell-consolidation laboratory test results for samples obtained during our field
explorations for the subject site.
Earth Engineering Consultants,LLC
EEC Project No. 1232071
October 10,2023
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Table I—Laboratory Swell-Consolidation Test Results
In-Situ Characteristics
Pre-Load/ Range of Swell—Index
No of Range of Moisture Range of Dry Densities,
Inundation Test Results
Samples Pressure, Description of Material Contents,% PCF
Tested PSF Low High Low End, High Low End High End,
End,% End,% PCF End,PCF (+/-)% (+/-)%
Sandy Lean Clay CL) or
5 500 10.8 26.7 94.1 119.3 (-)0.5 0.0
Clayey-Silty Sand(SC-SM)
Colorado Association of Geotechnical Engineers (CAGE)uses the following information presented
below to provide uniformity in terminology between geotechnical engineers to provide a relative
correlation of 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.
Table U-Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Slab Performance Risk Category Representative Percent Swell Representative Percent Swell
(500 psf Surcharge) (1000 psf Surcharge)
Low 0to<3 0<2
Moderate 3 to<5 2 to<4
High 5 to<8 4 to<6
Very High >8 >6
Based on the laboratory test results, the swell/consolidation samples analyzed for this project at
current moisture contents and dry densities conditions were generally within nil to low swell range
and showed a slight tendency to hydro-compact when inundated with water.
General Considerations
General guidelines are provided below for the site subgrade preparation.However,it should be noted
that compaction and moisture requirements vary between builders and, consequently, between
geotechnical engineering companies. If the development lots will be marketed to a target group of
builders, fill placement criteria should be obtained from those builders and/or their geotechnical
engineering consultants prior to beginning earthwork activities on the site. Representatives from
those entities should verify that the fill is being placed consistent with the home builders'guidelines.
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EEC Project No. 1232071
October 10,2023
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Based on our field and laboratory testing information, the overburden soils on this lot include
approximately 8 to 12 feet of sandy lean clay to clayey-silty sand soils overlying gravel/sand soils.
Low swell potential was exhibited by the near surface clay samples; however, soft/compressible
soils were encountered at locations across the site at varying depths which requires special attention
depending on the final site grades and extension of the cut/fill operations.
Groundwater was observed at depths of 8 and 12 feet below the ground surface in the borings. We
suggest that floor slab subgrade(s)be placed a minimum of 4 feet above the maximum anticipated
rise in groundwater levels. If final site grading consists of cuts extending floor slabs to less than 4
feet above the maximum anticipated rise in groundwater,consideration could be given to designing
and installing a perimeter drainage system or to elevating/raising the site grades to establish the
minimum required 4-foot separation to the maximum anticipated rise in groundwater.
Site Preparation
All existing vegetation and/or topsoil should be removed from beneath site fills, roadways or
building subgrade areas. Stripping depths should be expected to vary,depending on current surface
elevations. In addition, any soft/loose native soils, or any existing fill materials without
documentation of controlled fill placement should be removed from improvement and/or new fill
areas.
After stripping and completing all cuts and prior to placement of any fill,floor slabs or pavements,
we recommend the exposed soils be scarified to a minimum depth of 9 inches,adjusted in moisture
content and compacted to at least 95% of the material's maximum dry density as determined in
accordance with ASTM Specification D698,the standard Proctor procedure.The moisture content of
the scarified materials should be adjusted to be within a range of±2%of standard Proctor optimum
moisture at the time of compaction.
In general, fill materials required to develop the building areas or site pavement subgrades should
consist of approved, low-volume change materials which are free from organic matter and debris.
The near surface sandy lean clay to clayey-silty sand soils could be used as fill in these areas. We
recommend the fill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture
content and compacted to at least 95% of the material's maximum dry density as determined in
accordance with the standard Proctor procedure. The moisture content of predominately clay soils
should be adjusted to be within the range of 12% of optimum moisture content at the time of
placement. Granular soil should be adjusted to a workable moisture content.
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EEC Project No. 1232071
October 10,2023
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Specific explorations should be completed for each building lot to develop recommendations
specific to the proposed structure and owner/builder and for specific pavement sections. The
preliminary recommendations provided in this report are,by necessity,general in nature and would
be superseded by site specific explorations/recommendations.
Foundation Systems—General Considerations
Based on the soils observed at the test boring locations,we believe the buildings could be supported
on conventional footing foundations bearing on approved in-situ site soils or on a zone of approved
placed and compacted fill material prepared as outlined above.Footings bearing on approved in-situ
native soils or on approved engineered fill material placed and compacted as described above could
be designed for a maximum net allowable total load soil bearing pressure ranging between 1,500 to
2,500 psf.A minimum dead load pressure would not be required. The net bearing pressure refers to
the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure.
Total load includes full dead load and live load conditions.
After completing a site-specific/lot-specific geotechnical exploration study, a thorough "open-
hole/foundation excavation" observation should be performed prior to foundation formwork
placement to verify the suitability of the in-place soils and determine the extent of any possible over
excavation and replacement procedures, if necessary.
After placement of the fill materials,for foundation support,care should be taken to avoid wetting or
drying of those materials. Bearing materials, which are loosened or disturbed by the construction
activities or materials,which become dry and desiccated or wet and softened,should be removed and
replaced or reworked in place prior to construction of the overlying improvements.
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 16 inches and isolated column foundations have a minimum width of 30 inches.
We estimate the total long-term settlement of footings designed as outlined above would be about f-
inch.
Earth Engineering Consultants,LLC
EEC Project No. 1232071
October 10,2023
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Preliminary Floor Slab/Exterior Flatwork Subuades
We recommend all existing vegetation/topsoil be removed from beneath the floor slab and exterior
flatwork areas as previously outlined.After stripping and completing all cuts and prior to placement
of any flatwork concrete or fill, the exposed subgrades should be scarified, adjusted in moisture
content and compacted.If the subgrades become dry and desiccated prior to floor slab construction,
it may be necessary to rework the subgrades prior to floor slab placement.
Fill soils required to develop the floor slab subgrades should consist of approved, low-volume
change materials which are free from organic matter and debris. Those fill materials should be
placed as previously outlined and surcharged/preloaded and/or monitored as necessary to limit total
and differential movement after construction of overlying improvements.
Preliminary Basement Design and Construction
Groundwater was encountered across the site within the preliminary soil borings at approximate
depths of 8 to 12 feet below existing site grades.If lower-level construction for either garden-level or
full-depth basements is being considered for the site, we would suggest that the lower-level
subgrade(s)be placed a minimum of 4 feet above maximum anticipated rise in groundwater levels,
or a combination exterior and interior perimeter drainage system(s)be installed.
Consideration could be given to 1)either designing and installing an area underdrain system to lower
the groundwater levels provided a gravity discharge point can be established. If a gravity
outlet/system cannot be designed another consideration would be to design and install a mechanical
sump pump system to discharge the collected groundwater within the underdrain system, or 2)
elevate/raise the site grades to establish the minimum required four (4) foot separation to the
maximum anticipated rise in groundwater. EEC is available to assist in the underdrain design if
requested.
The following information should also be considered, as previously mentioned,would be to install
an interior and exterior perimeter drainage system for each individual residence. To reduce the
potential for groundwater to enter the lower level/basement area of the structure(s),installation of a
dewatering system is recommended. The dewatering system should, at a minimum, include an
under-slab gravel drainage layer sloped to an interior perimeter drainage system. The following
provides preliminary design recommendations for interior and exterior perimeter drainage systems.
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EEC Project No. 1232071
October 10,2023
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The under-slab drainage system should consist of a properly sized perforated pipe,embedded in free-
draining gravel,placed in a trench at least 12 inches in width. The trench should be inset from the
interior edge of the nearest foundation a minimum of 12 inches. In addition, the trench should be
located such that an imaginary line extending downward at a 45-degree angle from the foundation
does not intersect the nearest edge of the trench. Gravel should extend a minimum of 3 inches
beneath the bottom of the pipe.The under-slab drainage system should be sloped at a minimum 1/8
inch per foot to a suitable outlet, such as a sump and pump system.
The under-slab drainage layer should consist of a minimum 6-inch thickness of free-draining gravel
meeting the specifications of ASTM C33, Size No. 57 or 67 or equivalent. Cross-connecting
drainage pipes should be provided beneath the slab at minimum 15-foot intervals and should
discharge to the perimeter drainage system.
Sizing of drainage pipe will be dependent upon groundwater flow into the dewatering system.
Groundwater flow rates will fluctuate with permeability of the soils to be dewatered and the depth to
which groundwater may rise in the future. Pump tests to determine groundwater flow rates are
recommended in order to properly design the system.For preliminary design purposes,the drainage
pipe,sump,and pump system should be sized for a projected flow of 0.5 x 10-3 cubic feet per second
(cfs)per lineal foot of drainage pipe.Additional recommendations can be provided upon request and
should be presented in final subsurface exploration reports for each residential lot.
Preliminary Pavement Subl4rades
Fill materials required to develop the pavement subgrades should consist of approved,low-volume
change materials, free from organic matter and debris. Imported structural fill materials similar to
CDOT Class 5, 6 or 7 base course material could be used in these areas. We recommend those fill
soils be placed as recommended in the Site Preparation section of this report.
The essentially cohesive soils may show strength loss and instability when wetted. Stabilization of
those subgrades could be necessary at the time of construction to develop a stable platform for
subsequent paving. Stabilization could be predesigned into the subgrades to mitigate swell, and the
stabilized subgrades would be considered a part of the pavement section. Consideration could be
given to a fly ash treatment concept for swell mitigation and/or stabilization, should pumping
conditions develop.
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EEC Project No. 1232071
October 10,2023
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If a subgrade stabilization concept is chosen/required,consideration could be given to incorporating
Class C fly ash within the upper 12-inches of the site pavements prior to construction of the
overlying pavement structure. Stabilization should consist of blending 13%by dry weight of Class C
fly ash in the top 12 inches of the subgrades. The blended materials should be adjusted in moisture
content to slightly dry of standard Proctor optimum moisture content and compacted to at least 95%
of the material's maximum dry density as determined in accordance with the standard Proctor
procedure.Compaction of the subgrade should be completed within two hours after initial blending
of the Class C fly ash.
Pavement sections are based on assumed traffic volumes and subgrade strength characteristics.
Based on the materials encountered,we believe an estimated R-value of 10 would be appropriate for
design of the pavements supported on the subgrade soils. Suggested preliminary pavement sections
for the light duty and heavy-duty on-site pavement improvement sections are provided below in
Table III.A final pavement design thickness evaluation will be determined when a pavement design
exploration is completed (after subgrades are developed to ± 6 inches of design and wet utilities
installed).
Hot mix asphalt(HMA)underlain by aggregate base course,or a non-reinforced concrete pavement
may be feasible options for the proposed on-site paved sections.HMA pavements may show rutting
and distress in areas of heavy truck traffic or in truck loading and turning areas. Concrete pavements
should be considered in those areas.
Table III—Recommended Minimum Pavement Sections
Automobile Parking Heavy Duty Areas
18-kip EDLA 7 15
18-kip ESAL's 51,100 109,500
Reliability 75% 85%
Resilient Modulus(R=10) 3562 psi 3562 psi
PSI Loss 2.5 2.2
Design Structure Number 2.47 2.96
(A)Composite
Hot Bituminous Pavement 4" 5"
Aggregate Base 7" 7"
(Design Structural Number) (2.53) (2.97)
(B)Composite with Fly Ash Treated Subgrade
Hot Bituminous Pavement 3'/z" 4"
Aggregate Base 6" 7"
Fly Ash Treated Subgrade 12" 12"
(Design Structure Number 2.70 3.03
(C)PCC(Non-reinforced) 5" 6"
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EEC Project No. 1232071
October 10,2023
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Asphalt surfacing should consist of grading 5-75 or SX-75 hot bituminous pavement with PG 64-22
or PG 58-28 binder in accordance with LCUASS.Aggregate base should be consistent with CDOT
requirements for Class 5 or Class 6 aggregate base.
As previously mentioned,a final subgrade investigation and pavement design should be performed
in general accordance with LCUASS standards prior to placement of any pavement sections, to
determine the required pavement section after design configurations, roadway utilities have been
installed and roadway have been prepared to "rough" subgrade elevations have been completed.
Underground Utility Systems
All piping should be adequately bedded for proper load distribution.It is suggested that clean,graded
gravel compacted to 70 percent of Relative Density ASTM D4253 be used as bedding.Where utilities
are excavated below groundwater, temporary dewatering will be required during excavation, pipe
placement and backfilling operations for proper construction.Utility trenches should be excavated on
safe and stable slopes in accordance with OSHA regulations as further discussed herein. Backfill
should consist of on-site soils or approved imported materials.The pipe backfill should be compacted
to a minimum of 95 percent of Standard Proctor Density ASTM D698.
Water Soluble Sulfates (SO4)
The water-soluble sulfate (SO4) content of the on-site overburden subsoils, taken during our
subsurface exploration at random locations and intervals are provided below. Based on reported
sulfate content test results,the Class/severity of sulfate exposure for concrete in contact with the on-
site subsoils is provided in this report.
Table IV-Water Soluble Sulfate Test Results
Sample Location Description %of Soil by Weight
B-8 S-2 4' Sandy Lean Clay(CL) 0.06
Based on the results as presented above,ACI 318, Section 4.2 indicates the site soils have a low risk
of sulfate attack on Portland cement concrete, therefore, ACI Class SO requirements should be
followed for concrete placed in the overburden soils. Foundation concrete should be designed in
accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
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EEC Project No. 1232071
October 10,2023
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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,parking, and drive areas to avoid features which
would pond water adjacent to the pavements,foundations,or stem walls.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.
Excavations into the on-site soils may encounter a variety of conditions.Excavations into the on-site
clay soils can be expected to stand on relatively steep temporary slopes during construction while
excavations extending to the gravel/sand soils may experience caving/sloughing. The individual
contractor(s) should be made responsible for designing and constructing stable, temporary
excavations as required to maintain stability of both the excavation sides and bottom. All
excavations should be sloped or shored in the interest of safety following local and federal
regulations, including current OSHA excavation and trench safety standards.
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data obtained from the
soil borings performed at the indicated locations and from any other information discussed in this
report. This report does not reflect any variations which may occur between borings or across the
site. The nature and extent of such variations may not become evident until construction. If
variations appear evident, it will be necessary to re-evaluate the recommendations of this report.
It is recommended that the geotechnical engineer be retained to review the plans and specifications,
so comments can be made regarding the interpretation and implementation of our geotechnical
recommendations in the design and specifications. It is further recommended that the geotechnical
engineer be retained for testing and observations during earthwork phases to help determine that the
design requirements are fulfilled.
This report has been prepared for the exclusive use for TDC-Development 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
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EEC Project No. 1232071
October 10,2023
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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
PHYSICAL PROPERTIES OF BEDROCK
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D-2488. Coarse Grained DEGREE OF WEATHERING:
Soils have move than 50% of their dry weight retained on a Slight Slight decomposition of parent material on
#200 sieve;they are described as: boulders,cobbles,gravel or joints. May be color change.
sand. Fine Grained Soils have less than 50%of their dry weight Moderate Some decomposition and color change
retained on a#200 sieve;they are described as : clays, if they throughout.
are plastic, and silts if they are slightly plastic or non-plastic. High Rock highly decomposed, may be extremely
Major constituents may be added as modifiers and minor broken.
constituents may be added according to the relative
proportions based on grain size. In addition to gradation, HARDNESS AND DEGREE OF CEMENTATION:
coarse grained soils are defined on the basis of their relative in- Limestone and Dolomite:
place density and fine grained soils on the basis of their Hard Difficult to scratch with knife.
consistency. Example: Lean clay with sand,trace gravel, stiff
(CL);silty sand,trace gravel, medium dense(SM). Moderately Can be scratched easily with knife.
CONSISTENCY OF FINE-GRAINED SOILS Hard Cannot be scratched with fingernail.
Unconfined Compressive Soft Can be scratched with fingernail.
Strength,Qu, psf Consistency
Shale,Siltstone and Claystone:
< 500 Very Soft Hard Can be scratched easily with knife,cannot be
500- 1,000 Soft scratched with fingernail.
1,001- 2,000 Medium Moderately Can be scratched with fingernail.
2,001- 4,000 Stiff Hard
4,001- 8,000 Very Stiff Soft Can be easily dented but not molded with
8,001-16,000 Very Hard fingers.
Sandstone and Conglomerate:
RELATIVE DENSITY OF COARSE-GRAINED SOILS: Well Capable of scratching a knife blade.
N-Blows/ft Relative Density Cemented
0-3 Very Loose Cemented Can be scratched with knife.
4-9 Loose
10-29 Medium Dense Poorly Can be broken apart easily with fingers.
30-49 Dense Cemented
50-80 Very Dense
80+ Extremely Dense
Earth Engineering Consultants, LLC
UNIFIED SOIL CLASSIFICATION SYSTEM
Soil Classification
Group Group Name
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Symbol
Coarse-Grained Soils Gravels more than Clean Gravels Less Cu24 and 1<Cc<3E GW Well-graded gravel F
more than 50% 50%of coarse than 5%fines
retained on No.200 fraction retained on Cu<4 and/or 1>Cc>3E GP Poorly-graded gravel F
sieve No.4 sieve Gravels with Fines Fines classify as ML or MH GM Silty gravel G'"
more than 12%
fines Fines Classify as CL or CH GC Clayey Gravel F'G'"
Sands 50%or more Clean Sands Less Cu>_6 and 1<Cc53E SW Well-graded sand
coarse fraction than 5%fines
passes No.4 sieve Cu<6 and/or 1>Cc>3E SP Poorly-graded sand
Sands with Fines Fines classify as ML or MH SM Silty sand G'"'l
more than 12%
fines Fines classify as CL or CH SC Clayey sand G'"'l
Fine-Grained Soils Silts and Clays inorganic PI>7 and plots on or above"A"Line CL Lean clay K,L,M
50%or more passes Liquid Limit less
the No.200 sieve than 50 PI<4 or plots below"A"Line ML Silt K,L,M
organic Liquid Limit-oven dried Organic clay K,L,M,N
<0.75 OL
Liquid Limit-not dried Organic silt K,L,M,o
Silts and Clays inorganic PI plots on or above"A"Line CH Fat clay K,L,M
Liquid Limit 50 or
more PI plots below"A"Line MH Elastic Silt K,L,M
organic Liquid Limit-oven dried Organic clay K,L,M,P
<0.75 OH
Liquid Limit-not dried Organic silt K,L,M,o
Highly organic soils Primarily organic matter,dark in color,and organic odor PT Peat
ABased on the material passing the 3-in.(75-mm) Cu=D60/Dlo Cc= (DBO)z Kif soil contains 15 to 29%plus No.200,add"with sand"
sieve D10 x D60 or"with gravel",whichever is predominant.
BIf field sample contained cobbles or boulders,or Llf soil contains 2 30%plus No.200 predominantly sand,
both,add"with cobbles or boulders,or both"to add"sandy"to group name.
group name. IF Ifsoil contains>_15%sand,add"with sand"to MY soil contains>_30%plus No.200 predominantly gravel,
cGravels with 5 to 12%fines required dual symbols: GIf fines classify as CL-ML,use dual symbol GC- add"gravelly"to group name.
GW-GM well graded gravel with silt CM,or SC-SM. NP124 and plots on or above"A"line.
GW-GC well-graded gravel with clay "If fines are organic,add"with organic fines"to 0PI54 or plots below"A"line.
GP-GM poorly-graded gravel with silt group name PPI plots on or above"A"line.
GP-GC poorly-graded gravel with clay If soil contains>15%gravel,add"with gravel"to °PI plots below"A"line.
OSands with 5 to 12%fines require dual symbols: group name
SW-SM well-graded sand with silt 'If Atterberg limits plots shaded area,soil is a CL-
SW-SC well-graded sand with clay ML,Silty clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
60
For Classification of fine-grained soils and
fine-grained fraction of coarse-grained
50 soils.
Equation of"A"-line
40 Horizontal at PI=4 to LL=25.5
x then PI-0.73(LL-20)
o Equation of"U"-fine
z
� 30 Vertical at LL=16 to PI-7,
then PI=0.9(LI-8)
a 20
p� MH o OH
10 ML OL
CL- L'
i
0
0 10 20 30 40 50 60 70 80 90 100 110
410 LIQUID LIMIT(LL)
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Legend
$Approximate Boring
Locations
1. Site Photos
(Photos taken in approximate
location,in direction of arrow)
Boring Location Diagram
Mulberry Street Mixed-Use-Development
Fort Collins, Colorado
North EEC Project #.- 1232071 Date.- October 2023
Not to Scale
EARTH ENGINEERING CONSULTANTS, LLC
MULBERRY ST MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
PROJECT NO: 1232071 LOG OF BORING B-1 DATE: SEPTEMBER 2023
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 9/14/2023 WHILE DRILLING 10.5'
AUGER TYPE: 4"CFA FINISH DATE 9/14/2023 9/20/2023 8'
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A
SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWSIFT (PSF) (%) (PCF) LL PI (%) PRESSURE %@ 500 PSF
SPARSE VEGETATION
1
SANDY LEAN CLAY(CL)
brown 2
medium stiff
CS 3 4 5500 12.1 111.2
4
Water-Soluble Sulfate Content=0.06%
[C—S 5 5 1000 12.9 107.7 26 7 51.4 <500 PSF None
6
7
8
9
CS 10 8 2500 20.9 1 100.9
11
SILTY SAND WITH GRAVEL(SM) 12
brown/red/white
medium dense to loose 13
with intermittent clay seams
14
FC—S 15 24 4.6 120.9
16
17
18
19
*clay seams CS 20 6 11.0 1 113.7 1 18.7
21
22
23
24
CS 25 4 1 22.2
BOTTOM OF BORING DEPTH 25'
Earth Engineering Consultants, LLC
MULBERRY ST MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
PROJECT NO: 1232071 LOG OF BORING B-2 DATE: SEPTEMBER 2023
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 9/14/2023 WHILE DRILLING 10,
AUGER TYPE: 4"CFA FINISH DATE 9/14/2023 9/20/2023 8.7'
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A
SOIL DESCRIPTION D IN QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWSIFT (PSF) (%) (PCF) ILLPI (%) PRESSURE %@ 500 PSF
VEGETATION AND TOPSOIL
1
SANDY LEAN CLAY(CL)
brown 2
very stiff
3
4
[CS
5 16 9000+ 11.4 123.4
6
7
8
WELL GRADED SAND WITH GRAVEL(SW) 9
brown/red/white
dense Fc s 10 34 7.9 127.6 1 4.6
with intermittent clay seams
11
12
13
14
FC—S 15 39 11.6 130.1
16
17
18
19
CS 20 40 9.2 133.0
BOTTOM OF BORING DEPTH 20'
21
22
23
24
25
Earth Engineering Consultants, LLC
MULBERRY ST MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
PROJECT NO: 1232071 LOG OF BORING B-3 DATE: SEPTEMBER 2023
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 9/14/2023 WHILE DRILLING 12'
AUGER TYPE: 4"CFA FINISH DATE 9/14/2023 9/20/2023 11'
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A
SOIL DESCRIPTION D IN QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWSIFT (PSF) (%) (PCF) IL
LPI (%) PRESSURE %@ 500 PSF
VEGETATION AND TOPSOIL
1
CLAYEY-SILTY SAND(SC-SM)
brown 2
medium dense
with calcareous deposits 3
4
[CS
5 16 4500 26.7 100.6 24 5 39.6 <500 PSF None
6
7
SANDY LEAN CLAY(CL) 8
brown
medium stiff 9
Fc_s 10 4 1500 25.4 96.5 31 1 8 56.0 <500 PSF None
11
SAND/GRAVEL(SP/GP) 12
brown/red/white
medium dense 13
14
FC—S 15 22 14.7 103.6
16
17
18
19
CS 20 16 12.4
BOTTOM OF BORING DEPTH 20'
21
22
23
24
25
Earth Engineering Consultants, LLC
MULBERRY ST MIXED USE DEVELOPMENT
FORT COLLINS, COLORADO
PROJECT NO: 1232071 LOG OF BORING B-4 DATE: SEPTEMBER 2023
RIG TYPE: CME55 SHEET 1 OF 1 WATER DEPTH
FOREMAN: DG START DATE 9/14/2023 WHILE DRILLING 12'
AUGER TYPE: 4"CFA FINISH DATE 9/14/2023 9/20/2023 10.5'
SPT HAMMER: AUTOMATIC SURFACE ELEV N/A
SOIL DESCRIPTION D IN QU MC DD A-LIMITS -200 SWELL
TYPE (FEET) BLOWSIFT (PSF) (%) (PCF) ILLPI (%) PRESSURE %@ 500 PSF
VEGETATION AND TOPSOIL
1
SANDY LEAN CLAY(CL)
brown 2
very stiff to soft _ _
CS 3 22 9000+ 10.8 112.2 <500 PSF None
4
[C-S 5 21 9000+ 11.6 122.0
6
7
8
9
Fc—S 10 3 500 13.1 117.4
11
12
SAND/GRAVEL(SP/GP) 13
brown/red/white
dense to medium dense 14
Fc—
S 15 42 10.6 132.9
16
17
18
19
CS 20 26 9.9 1 132.2
BOTTOM OF BORING DEPTH 20'
21
22
23
24
25
Earth Engineering Consultants, LLC
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: Boring 1, Sample 2, Depth 4'
Liquid Limit: 26 JPlasticity Index: 7 % Passing#200: 51.4%
Beginning Moisture: 12.9% Dry Density: 106.3 pcf JEnding Moisture: 17.4%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
a�
3
4.0
_ 2.0
m
E
m
0
0.0
Y
_
U
U
L
a Water Added
-2.0
0 -4.0
0
M
0
U)
o -6.0
U
-8.0 -
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins, Colorado
Project#: 1232071
Date: September 2023
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: Boring 2, Sample 1, Depth 4'
Liquid Limit: -- I Plasticity Index: -- % Passing#200: --
Beginning Moisture: 11.4% 1 Dry Density: 119.3 pcf JEnding Moisture: 10.6%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
aD
3
4.0
_ 2.0
m
E
m
0
0.0
Y
_
U
L
Water Added
a
-2.0
0 -4.0
0
M
0
C
o -6.0
U
-8.0 -
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins, Colorado
Project#: 1232071
Date: September 2023
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Clayey-Silty Sand (SC-SM)
Sample Location: Boring 3, Sample 1, Depth 4'
Liquid Limit: 24 JPlasticity Index: 5 % Passing#200: 39.6%
Beginning Moisture: 26.7% Dry Density: 97.6 pcf JEnding Moisture: 16.7%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
aD
3
4.0
_ 2.0
m
E
m
0
0.0
Y
_
U
U
L
a
-2.0
d
C -4.0
Water Adde
0
M
0
C
o -6.0
U
-8.0 -
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins, Colorado
Project#: 1232071
Date: September 2023
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: Boring 3, Sample 2, Depth 9'
Liquid Limit: 31 JPlasticity Index: 8 % Passing#200: 56.0%
Beginning Moisture: 25.4% Dry Density: 94.1 pcf JEnding Moisture: 27.9%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
a�
3
4.0
_ 2.0
m
E
m
0
0.0
Y
_
U
U
L
a -2.0 Water Added
C -4.0
0
M
0
C
o -6.0
U
-8.0
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins, Colorado
Project#: 1232071
Date: September 2023
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay
Sample Location: Boring 4, Sample 1, Depth 2'
Liquid Limit: -- I Plasticity Index: -- % Passing#200: --
Beginning Moisture: 10.8% 1 Dry Density: 102.6 pcf JEnding Moisture: 16.4%
Swell Pressure: <500 psf %Swell @ 500: None
10.0
8.0
6.0
aD
3
4.0
_ 2.0
m
E
m
0
0.0
Y
_
U
U
L
Water Added
a
-2.0
0 -4.0
0
M
0
C
o -6.0
U
-8.0 -
-10.0
0.01 0.1 1 10
Load (TSF)
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins, Colorado
Project#: 1232071
Date: September 2023
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis(AASHTO T 11&T 27/ASTM C 117&C 136)
Sieve Size Percent Passing
2 1/2" (63 mm) 100
2" (50 mm) 100
1 1/2" (37.5 mm) 100
1" (25 mm) 100
3/4" (19 mm) 98
1/2" (12.5 mm) 85
3/8" (9.5 mm) 80
No.4 (4.75 mm) 70
No.8 (2.36 mm) 59
No.10 (2 mm) 56
No. 16 (1.18 mm) 50
No.30 (0.6 mm) 43
No.40 (0.425 mm) 38
No.50 (0.3 mm) 34
No.100 (0.15 mm) 26
No.200 (0.075 mm) 18.7
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins,Colorado
Project No: 1232071
Sample ID: 61 S4 19
Sample Desc.: Silty Sand with Gravel(SM)
Date: October 2023
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Standard Sieve Size
5" Y 2" 1" 1/2" No.4 No.10 No.30 No.50 No.200
6" 4" 2.5 1.51, 3/4" 3/8" No.8 No.16 No.40 No.100
100
90 \%\
80
70
60 �\""N
0
50
LM
Q)
40
L
I_L
30
20
10
0 LL
1000 100 10 1 0.1 0.01
Grain Size (mm)
Gravel Sand
Cobble Silt or Clay
Coarse Fine Coarse Medium Fine
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins,Colorado �100 �60 �50 �30 �10 Cu CC
Project No: 1232071
25.00 2.66 1.19 0.23 --- --- ---
Sample ID: B1 S4 19 -
Sample Desc.: Silty Sand with Gravel(SM)
Date: October 2023
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis(AASHTO T 11&T 27/ASTM C 117&C 136)
Sieve Size Percent Passing
2 1/2" (63 mm) 100
2" (50 mm) 100
1 1/2" (37.5 mm) 100
1" (25 mm) 100
3/4" (19 mm) 100
1/2" (12.5 mm) 100
3/8" (9.5 mm) 97
No.4 (4.75 mm) 81
No.8 (2.36 mm) 56
No.10 (2 mm) 52
No. 16 (1.18 mm) 40
No.30 (0.6 mm) 27
No.40 (0.425 mm) 21
No.50 (0.3 mm) 15
No.100 (0.15 mm) 8
No.200 (0.075 mm) 4.6
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins,Colorado
Project No: 1232071
Sample ID: B2 S2 9
Sample Desc.: well Graded Sand with Gravel(SW)
Date: October 2023
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Standard Sieve Size
5" 3" 2" 1" 1/2" No.4 No.10 No.30 No.50 No.200
6" 4" 2.5" 1.5" 3/4" 3/8" No.8 No.16 No.40 No.100
100
90
80
70
60
0
50
Q)
40
ILL
30
20
10
0
1000 100 10 1 0.1 0.01
Grain Size (mm)
Gravel Sand
Cobble Silt or Clay
Coarse Fine Coarse Medium Fine
Project: Mulberry Street Mixed-Use-Development
Location: Fort Collins,Colorado �100 �60 �50 �30 �10 Cu CC
Project No: 1232071
Sample ID: B2 S2 9 12.50 2.70 1.87 0.73 0.19 14.02 1.03
Sample Desc.: well Graded Sand with Gravel(SW)
Date: October 2023