Yeh and Associates, Inc.
Consulting Engineers & Scientists
FINAL GEOTECHNICAL ENGINEERING REPORT
EVERGREEN GOLF COURSE BRIDGES
EVERGREEN, CO
July 30, 2012
YEH Project Nos. 211-200 & 211-201
Prepared For:
Felsburg Holt & Ullevig
6300 S. Syracuse Way, Suite 600
Centennial, CO 80111
Attn: Brian D. Wiltshire, P.E.
City and County of Denver
Parks and Recreation
201 West Colfax Ave., Dept. 605
Denver, CO 80202
Attn: Greg Cieciek
Prepared By:
Yeh and Associates, Inc.
5700 E. Evans Ave.
Denver, CO 80222
Phone (303) 781-9590
Fax (303) 781-9583
Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
TABLE OF CONTENTS
PAGE
1.0 PURPOSE AND SCOPE ....................................................................................................... 1 2.0 PROPOSED CONSTRUCTION............................................................................................. 1 3.0 SUBSURFACE INVESTIGATION ......................................................................................... 3 4.0 LABORATORY TESTING ..................................................................................................... 4 5.0 SITE CONDITIONS ............................................................................................................... 4 6.0 REGIONAL GEOLOGY ......................................................................................................... 6 7.0 SUBSURFACE CONDITIONS .............................................................................................. 6 8.0 GEOLOGIC RELATED ENGINEERING CONSTRAINTS .................................................... 7 8.1 Seismicity ........................................................................................................................ 7 8.2 Groundwater ................................................................................................................... 8 8.3 Water-Soluble Sulfates ................................................................................................... 8 8.4 Corrosion ........................................................................................................................ 8 9.0 BRIDGE FOUNDATION RECOMMENDATIONS ................................................................. 9 9.1 Shallow GRS Footing Foundations ................................................................................. 9 9.2 Spread Footing Foundations ........................................................................................ 10 9.3 Driven Pile Foundations ................................................................................................ 11 10.0 DRILLED SHAFT FOUNDATIONS ..................................................................................... 13 11.0 Earthwork ........................................................................................................................... 14 11.1 General Considerations ................................................................................................ 14 11.2 Site Preparation ............................................................................................................ 15 12.0 LIMITATIONS ...................................................................................................................... 16 13.0 references ........................................................................................................................... 17 LIST OF FIGURES
PAGE
Figure 1 – Project location map. ................................................................................................... 2 Figure 2 – Approximate boring location map. ............................................................................... 3 Figure 3 – The existing south abutment at the upstream (vehicle) bridge is overturned. ............. 5 Figure 4 – The existing concrete shaft at the north abutment of the downstream (golf cart)
bridge has deteriorated and is slightly overturned. ....................................................... 5 Figure 5 – Schematic drawing of a GRS-Integrated Bridge System foundation. ........................ 10 LIST OF TABLES
PAGE
Table 1 – Approximate Bedrock Elevations at the Proposed Bridge Abutments .......................... 7 Table 2 – Estimated Pile Tip Elevations ..................................................................................... 12 Table 3 – LPILE Parameters ....................................................................................................... 13 APPENDICES
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
APPENDIX
Boring Logs ................................................................................................................................ A Laboratory Test Results ............................................................................................................ B Boring Location/Engineering Geology Sheets ....................................................................... C iii
Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
1.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
PURPOSE AND SCOPE
This report presents the results of our geotechnical study for two proposed bridges at the
Evergreen Golf Course in Evergreen, Colorado. The project location is shown in Figure 1. The
purpose of our study includes:


Evaluating the general geotechnical characteristics of the subsurface soils and
bedrock at the bridge locations, and
Providing geotechnical recommendations and parameters for the design and
construction of the proposed bridges.
A field exploration program consisting of geologic reconnaissance and exploratory drilling was
conducted to obtain information on subsurface conditions. Yeh and Associates, Inc., through
the use of a private drilling subcontractor, drilled and logged exploratory borings. Soil samples
were obtained during the field explorations and examined by the project personnel.
Representative samples were tested to determine the classification and engineering
characteristics of the on-site soil and rock materials.
Based on the information obtained, Yeh and Associates has completed an evaluation of
subsurface conditions. This report summarizes the data gathered, the results of our analysis,
and our recommendations based on the proposed construction, site reconnaissance,
geotechnical subsurface investigation, and results of laboratory testing in accordance with our
scope of work. General bridge foundation recommendations and a discussion of geotechnical
engineering considerations are included in this report.
2.0
PROPOSED CONSTRUCTION
The Evergreen Golf Course is part of the Golf division within the City of Denver Parks and
Recreation department. This project involves entirely replacing the upstream bridge, and
completing major improvements to the downstream existing bridge; both bridges are near the
golf clubhouse and restaurant. At present, the upstream bridge carries vehicle traffic over Bear
Creek to an overflow parking area, and is also used for golf cart and pedestrian traffic between
the clubhouse and Tee 1. The downstream bridge currently carries golf cart and pedestrian
traffic over Bear Creek, between Tee 9 and Tee 10.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
Location of bridges
Evergreen Golf Course
Figure 1 – Project location map.
Proposed construction includes replacement of the entire upstream bridge, including new
foundations, and replacement of the abutment foundations at the downstream bridge (the
girders and bridge deck of the downstream bridge will be removed during construction and reset on the new foundations). The proposed bridge locations are the same as the existing bridge
locations at both sites. Based on information provided to Yeh by FHU, the proposed upstream
bridge will have a single span of approximately 30 feet, and a total deck width of 15.5 feet. The
proposed downstream bridge will have a single span of approximately 42 feet, and a total deck
width of approximately 10 feet. The structure types have not yet been determined; both bridges
may be constructed using steel girders with a concrete deck, a pre-fabricated bridge structure,
or possibly a box culvert structure. Both bridges will be used for the same purposes as at
present.
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Evergreen Golf Course Bridges, Evergreen, Colorado
3.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
SUBSURFACE INVESTIGATION
The subsurface conditions were explored between October 31 and November 3, 2011. The
subsurface investigation utilized a Central Mine Equipment (CME) 55 truck-mounted drill rig
owned and operated by a private subcontractor. A total of 4 borings were drilled to depths
ranging from 17 to 35 feet below existing grade (One boring at each of the four proposed bridge
foundation locations). The borings were vertically advanced using 4-inch diameter solid-stem
continuous flight augers and NQ-sized wireline coring methods. Figure 2 shows the
approximate boring locations.
YA-PG-1
YA-V-1
YA-PG-2
YA-V-2
Figure 2 – Approximate boring location map.
Soil samples were collected typically at five-foot intervals in the overburden soils in each boring,
utilizing standard split spoon and modified California samplers (sampler type was chosen based
on material type), driven by a 140-pound hammer with a 30-inch stroke. This procedure is
similar to the Standard Penetration Test (ASTM D1586). The number of blows required to drive
the sampler 12 inches, or a fraction thereof, constituted the N-value as shown on the boring logs
(Appendix A).
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Evergreen Golf Course Bridges, Evergreen, Colorado
4.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
LABORATORY TESTING
Selected soil samples collected during the site investigation were tested to determine the
classification and engineering characteristics. Laboratory tests performed included natural
density, natural moisture content, gradation analysis, Atterberg limits, swell/consolidation, pH,
water-soluble sulfate content, and resistivity. The soil samples were classified according to both
AASHTO and USCS classification systems. The laboratory test results are presented in
Appendix B.
5.0
SITE CONDITIONS
The two existing bridges are located across Bear Creek at the Evergreen Golf Course, near the
clubhouse and parking lot. The existing upstream bridge is a steel girder structure with a wood
and asphalt deck and steel handrails, supported on shallow concrete abutments. The bridge
was constructed approximately 1965, and its foundations have both experienced significant
overturning and erosion (Figure 3). Small plants have taken root in the deteriorated wooden
decking material on the east side of the bridge. Asphalt paving extends from the bridge
abutments into the parking areas on both sides.
The existing downstream bridge is a pre-fabricated steel structure with a wood deck and wood
handrails, with abutments supported on shallow 18-inch diameter concrete shafts. The existing
span is approximately 42 feet. The date of construction for this bridge is unknown, and the
foundations have experienced significant overturning and erosion damage to the concrete
shafts and the soils around them (Figure 4). We did not determine how deep the concrete
shafts extend, which could be shallow or deep. Asphalt paving extends for a few feet behind
the abutments, where the golf cart path on both sides becomes a dirt path.
The banks of the creek around both bridges are covered in cobbles and boulders in some
places, with other places simply soil covered with grasses and shrubs. These banks are sloping
at approximately 1:1, and are about 5 feet high. The surrounding terrain is fairly flat around the
creek for a few hundred feet, and then steeper slopes begin on both sides of Bear Creek.
Surrounding vegetation consists of cultivated vegetation on the golf course fairways and natural
trees and grasses in other areas. The City of Evergreen is generally located in a narrow river
valley and the surrounding mountainous terrain of the Front Range.
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Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
Figure 3 – The existing south abutment at the upstream (vehicle) bridge is overturned.
Figure 4 – The existing concrete shaft at the north abutment of the downstream (golf
cart) bridge has deteriorated and is slightly overturned.
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Evergreen Golf Course Bridges, Evergreen, Colorado
6.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
REGIONAL GEOLOGY
The United States Geological Survey (USGS) has mapped the bedrock at the subject site as
being fine- to medium-grained Precambrian (older than 590 million years) biotite gneiss with
areas of small intrusive (e.g. granite) bodies scattered throughout (Sheridan et al, 1972). The
gneiss bedrock is described as generally strongly foliated, with 10-50 percent or more of biotite
and muscovite, which are soft minerals. Other bedrock types consisting of the intrusive Silver
Plume quartz monzonite may also exist at depth at this location; quartz monzonite is generally a
harder rock than biotite gneiss.
More recent deposits of alluvial material overlie the bedrock. These deposits are mapped as
Upper Holocene (within the last 10,000 years) Post-Piney Creek Alluvium and Piney Creek
Alluvium, consisting of unconsolidated sediments of silt, sand, and gravel, commonly reworked
every few years by floods. This material generally makes up the stream deposits in the vicinity
of Bear Lake, including at the proposed bridge locations.
7.0
SUBSURFACE CONDITIONS
Based on our subsurface investigation and published geologic maps, the subsurface materials
at the subject site are relatively consistent, with naturally occurring unconsolidated sediments
overlying medium hard metamorphic and igneous bedrock. At the upstream bridge, the
thickness of the overburden soils at the boring locations ranged from 15.5 to 16 feet below
existing grade. At the downstream bridge, the thickness of overburden soils at the boring
locations ranged from 11 to 12 feet below existing grade.
Overburden materials encountered in borings at both bridge sites generally consist of gravelly
sand, with some cobbles and silt. These soils are generally medium dense to very dense, with
blow counts ranging from 20 to 71 blows per foot. The bedrock encountered in the borings
consists of extremely weathered to moderately weathered, extremely soft to hard gneiss, with
intrusive layers of fresh to moderately weathered, very hard granite. Bedrock was encountered
in all four borings. Groundwater was encountered in all four borings, at depths between 4.5 and
5.6 feet below existing grade.
Boring logs are provided in Appendix A. An engineering geology sheet at the proposed bridge
location is presented in Appendix C. The boring locations have not been surveyed at this time.
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Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
The approximate existing ground surface elevation, the approximate depth (below existing
grade) to bedrock, and the approximate elevation of the top of bedrock at each boring location is
presented in Table 1.
Table 1 – Approximate Bedrock Elevations at the Proposed Bridge Abutments
Boring
No.
YA-V-1
YA-V-2
YA-PG-1
YA-PG-2
8.0
Location
Upstream (vehicle)
bridge, north
abutment
Upstream (vehicle)
bridge, south
abutment
Downstream
(ped/golf) bridge,
north abutment
Downstream
(ped/golf) bridge,
south abutment
Approx. Existing
Ground Surface
Elev. (ft.)
Approximate
Depth to Bedrock
(ft.)
Approximate
Bedrock Elevation
(ft.)
7087.5
16.0
7071.5
7087.5
15.5
7072
7085
12.0
7073
7085
11.0
7074
GEOLOGIC RELATED ENGINEERING CONSTRAINTS
Based on our review of the project site, it appears that the geologic-related engineering
constraints for the design and construction of the proposed bridge crossings include:
8.1
Seismicity
This area, like most of central Colorado, is subject to a low degree of seismic activity. No active
faults are known to exist in the immediate site area, and fault rupture is not a plausible hazard at
the site. Based on the AASHTO LRFD Bridge Design Specifications (2009 Interims), the site
classifies as Site Class D for seismic loading (Table 3.10.3.1-1). According to the USGS
Seismic Design Parameters software (Version 2.10), using 2007 AASHTO guidelines, a
factored peak ground acceleration (Fpga*PGA) of 0.105g (g = gravity) may be used for this site,
with a 7% probability of exceedance in 75 years (equal to an approximate 1000-year return
period, as outlined by AASHTO). The horizontal response spectral acceleration coefficients at a
0.2-sec period (SS) and 1.0-sec period (S1) are 0.138g and 0.036g, respectively, for the same
return period. These values may be used to construct the Design Response Spectrum for use
in seismic design of the bridge structures.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
8.2
YA Project Nos. 211-200 & 211-201
July 30, 2012
Groundwater
Water levels were recorded during drilling at depths between 4.5 and 5.6 feet below current
grade. This roughly corresponds with the water level in the creek immediately adjacent.
Groundwater conditions in the area will likely vary considerably throughout the year. Variations
can occur during different seasons, following precipitation events, irrigation, after construction
and site grading, and due to changes in surface and subsurface drainage characteristics of the
surrounding area. Depending upon the depth of excavation, location of the bedrock surface and
seasonal conditions, groundwater is likely to be encountered in excavations on the site deeper
than 4 feet.
8.3
Water-Soluble Sulfates
The concentrations of water-soluble sulfates measured in two samples obtained from the
exploratory borings were 0.001 percent in both samples. This concentration of water-soluble
sulfates represents a Class 0 degree of sulfate attack on concrete exposed to these geologic
materials. The degree of attack is based on a range of Class 0 (negligible) to Class 3 (very
severe) as described in the American Concrete Institute (ACI) Standard 201.2R, “Guide to
Durable Concrete” and a Class 0 as presented in the CDOT Section 601, Structural Concrete,
of the Standard Specifications for Road and Bridge Construction, 2011 edition.
Based on these sulfate tests, the soils along both the bridge alignments present a very low
potential for sulfate attack on concrete. Therefore, sulfate resistant concrete mix designs are
not required, per ACI and AASHTO.
8.4
Corrosion
pH and electrical resistivity tests were performed to evaluate the potential attack on concrete
and buried metal at the site. The chemical analyses results for two samples indicated pH
values of 7.5 and 7.7. These values are slightly basic and should represent a negligible degree
of pH attack on concrete and metal exposed to these materials. Electrical resistivity
measurements conducted on two samples indicated resistivity values of 6878 and 12610 ohmcm. The laboratory soil resistivity value indicates the soils have a mild to moderate degree of
corrosiveness to uncoated steel when subjected to ambient stray currents.
These corrosion potential measurements can be used to determine the type or thickness of
metallic materials to be specified on this project in accordance with the CDOT Specifications.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
9.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
BRIDGE FOUNDATION RECOMMENDATIONS
Our subsurface investigation involved advancing borings at each of the proposed bridge
abutment locations. Based on the information provided by FHU and our site investigation, both
deep and shallow foundations are geotechnically viable options. However, with shallow
foundations there is a possibility of undermining due to scour. The depth of scour should be
determined for a major flooding event and the elevation of the base of foundation should be set
a minimum of 24 inches below this depth. Additional slope armoring such as rip-rap or sheetpiles should be placed along the channel to protect the bridge foundations. At this time, scour
analysis (by others) has not been performed, and FHU has informed us that shallow foundations
are not preferred for this project; however, we have included preliminary recommendations for
this option. Design parameters for the foundation systems are presented below.
9.1
Shallow GRS Footing Foundations
Depending on the scour potential (yet to be determined by others), the site may be suitable for
the use of a Geosynthetic Reinforced Soil (GRS) Integrated Bridge System foundation. This is
a fairly new technology currently being promoted by the Federal Highways Administration for
accelerated bridge construction. The method uses closely-spaced layers of geosynthetic
reinforcement and compacted granular fill material to build up a reinforced soil foundation, a
GRS abutment, and a GRS- integrated approach (Figure 5). Bridge girders are placed directly
onto the GRS abutment.
This type of foundation is ideal for single-span structures over small creeks with low scour
potential. The advantages over a traditional shallow foundation usually include speed of
construction, cost effectiveness, and alleviating the frequent problem of the “bump at the bridge”
due to the integrated approach. Based on the scour analysis, we can provide more detailed
recommendations for this option as requested.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
Figure 5 – Schematic drawing of a GRS-Integrated Bridge System foundation.
9.2
Spread Footing Foundations
The following design and construction details should be observed for shallow conventional
spread foundations placed on the medium dense to very dense gravelly sand encountered at
the site. Generally, the soil and bedrock properties are estimated from uncorrected blow count
data and material descriptions contained in the Yeh boring logs presented in Appendix A.
1. For foundations constructed on the native alluvial sand materials, we recommend a
nominal bearing resistance of 6 ksf for shallow foundations 3 feet wide or larger, with
a resistance factor of 0.45. We estimate total settlement of less than 1 inch if the
above bearing resistance is used.
2. Footings should be placed a minimum of 3 feet below the lowest adjacent grade to
provide adequate cover for frost protection.
3. Resistance to sliding at the bottom of the footing can be calculated based on a
coefficient of friction of 0.47 for the silty sand soils. For LRFD design a resistance
factor of 0.85 should be applied to the nominal sliding resistance value for cast-inplace (CIP) concrete.
4. All footing excavations should be observed by an experienced engineering geologist
or geotechnical engineer prior to placement of concrete.
5. Areas of loose soils may be encountered at foundation bearing depth after
excavation is completed for footings. When such conditions exist beneath planned
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
footing areas, the subgrade soils should be compacted prior to placement of the
foundation system.
6. In addition, large cobble material may be encountered beneath footing areas. Such
conditions could create point loads on the bottom of footings, increasing the potential
for differential foundation movement. If cobbles are encountered in the footing
excavations, they should be removed and replaced with engineered fill, placed and
compacted as discussed in the Earthwork section
7. Backfill adjacent to the abutments should be compacted with moisture density
control.
9.3
Driven Pile Foundations
Driven H-piles should be installed per Section 502 of the CDOT Standard Specifications
for Road and Bridge Construction, 2011 edition.
1. For LRFD axial compression design and Grade 50 steel, a maximum combined end
bearing and skin friction nominal bearing capacity equal to 30 kips per square inch (ksi)
multiplied by the cross sectional area of the pile can be used for H-piles driven to virtual
refusal into bedrock. The “factored” bearing resistance is the product of the nominal
bearing capacity and a resistance factor. Per AASHTO, a resistance factor of 0.65 may
be used provided that a minimum number of piles are dynamically monitored with
subsequent signal matching analyses as described in CDOT Standard Specification
Section Section 502.05. If dynamic monitoring is not performed, a resistance factor of
0.30 should be used.
2. After selection of the pile size and type, a wave equation analysis should be performed
for the anticipated subsurface conditions using a computer program for the analysis of
pile driving (WEAP). The WEAP analysis will indicate the minimum size of hammer in
terms of energy rating that the contractor should provide to successfully install the
foundation piles to the required penetration into bedrock. The Special Provisions to the
construction contract should define the minimum hammer size as well as the
Contractor’s quality control monitoring requirements. The WEAP analysis will also
estimate both compressive and tensile driving stresses and the pile penetration
resistance at the end-of-driving. The piles should be installed to a driving resistance
determined by the wave equation analysis.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
H-piles should be driven to virtual refusal (10 blows per inch) into the underlying bedrock unless
indicated otherwise by the WEAP analyses. The estimated pile tip elevations are presented in
3. Table 2. Actual depth of driving refusal may vary from the estimated tip elevations.
4. The pile-driving hammer shall be configured to deliver maximum energy at the end-ofdriving unless directed otherwise by the engineer.
Table 2 – Estimated Pile Tip Elevations
Boring
No.
YA-V-1
YA-V-2
YA-PG-1
YA-PG-2
Location
Upstream (vehicle)
bridge, north
abutment
Upstream (vehicle)
bridge, south
abutment
Downstream
(ped/golf) bridge,
north abutment
Downstream
(ped/golf) bridge,
south abutment
Approximate
Elevation Top of
Bedrock (ft.)
Estimated Pile Tip
Elevation (ft.)
7071.5
7069.5
7072
7070.5
7073
7069
7074
7070
5. A nominal uplift capacity of single H-piles of 12 psi may be used, with a resistance factor
of 0.25. If the H-piles penetrate at least 5 feet into bedrock, uplift capacity may be
assumed to be 20 percent of the downward pile capacity.
6. Based on the results of our field exploration, laboratory testing and our experience with
similar properly constructed pile foundations, we estimate individual pile settlement will
be less than ½ inch when designed according to the criteria presented in this report.
7. Piles may be designed to resist lateral loads using the recommendations in Table 3
below. The upper 3 feet of the pile should be neglected in lateral load resistance
calculations.
8. It is anticipated that negative skin friction on H-piles will be minimal.
9. To eliminate axial and lateral reduction factors, a minimum spacing requirement for the
piles should be three diameters (equivalent) center to center.
10. A qualified representative of a registered Professional Engineer should observe piledriving activities on a full-time basis. Piles should be observed and checked for
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Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
crimping, buckling and alignment. Also, a record should be kept of embedment depths
and penetration resistances for each pile.
For lateral resistance of deep foundations, the input parameters provided in Table 3 are
recommended. These input parameters are for use with the computer program LPILE 6.0 and
the associated LPILE technical manual to develop the soil models used to determine the Hpiles’ and drilled shafts’ response to lateral loading. The table describes the values associated
with the soil types encountered in the borings. Individual soil layers and their extent can be
averaged or distinguished by referring to the boring logs. The soils and/or bedrock materials
prone to future disturbance, such as from scour, utility excavations or frost heave, should be
neglected in the lateral pile analyses.
Material
Type
Soil Type
Code
Number*
Unit
Weight,
 (pci)
Table 3 – LPILE Parameters
Horizontal
Friction
Cohesion, Subgrade
Angle,
Reaction,
c (psi)

Ks (pci)
Uniaxial
Comp.
Strength
(psi)
Modulus
of
RQD
Elasticit (%)
y (psi)
krm
4
Granular Soil
0.0781
34°
0
90
----
----
----
----
0.081
----
----
----
500
5.8x105
0
5x10-5
0.081
----
----
----
750
5.8x105
15
5x10-5
Sand
9
Bedrock
(Upper 3 ft)
Weak
Rock
9
Bedrock
(Below 3 ft)
10.0
Weak
Rock
DRILLED SHAFT FOUNDATIONS
The following preliminary design and construction details should be considered for drilled shafts
extended into bedrock for preliminary design estimate purposes.
1. Using Load Resistance Factor Design (LRFD) criteria, assuming the drilled shaft is
drilled and embedded into competent igneous or metamorphic bedrock, a nominal
(unfactored) tip resistance of 120 ksf and a nominal (unfactored) side resistance of
12 ksf may be used. Due to the brittle nature of the rock, the design of the shaft
should be either end bearing or side shear but not both, per AASHTO.
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Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
2. We recommend a tip resistance factor of 0.50 and a side resistance factor of 0.55.
Settlement of the structure using the LRFD method should be checked against
loadings obtained based on service limit state.
3. Shafts should penetrate a minimum length of 10 feet below the crystalline bedrock
surface, which includes weathered or unweathered bedrock surfaces.
4. For lateral loading analysis using LPILE, the parameters in Table 3 above may be
used.
5. The minimum spacing requirements between shafts should be three diameters from
center to center. For lateral loading, recommended P multipliers are 0.5 for tangent
shafts, increasing linearly to 1.0 for shafts placed at 3 diameters or greater.
Additional capacity reduction factors can be provided if required for conditions other
than those anticipated.
6. The presence of cobbles and boulders may make drilling and setting casing difficult,
and penetration into bedrock, particularly the hard granite bedrock, may require the
use of a rock bucket. The granite bedrock is typically harder and less fractured.
Bedrock may be very hard at various elevations. The contractor should mobilize
equipment of sufficient size and operating condition to achieve the required design
bedrock penetration.
7. The presence of water in all of the exploratory borings, and potentially caving soil in
some borings, indicates casing and/or dewatering equipment may be required. In no
case should concrete be placed in more than 3 inches of water unless the tremie
method is used. If water cannot be removed or prevented with the use of casing
and/or dewatering equipment prior to placement of concrete, the tremie method, as
described in the CDOT Standard Specifications for Road and Bridge Construction,
should be used after the hole has been cleaned. Casing and/or slurry may also be
needed where caving soils are encountered to maintain the hole for construction.
8. A representative of the geotechnical engineer should observe shaft drilling
operations on a full-time basis.
11.0
EARTHWORK
11.1
General Considerations
Based on the proposed construction, it is anticipated only limited site grading will be needed for
the proposed bridges. The following presents recommendations for site preparation,
excavation, subgrade preparation and placement of engineered fills on the project.
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YA Project Nos. 211-200 & 211-201
July 30, 2012
Earthwork on the project should be observed and evaluated by the geotechnical engineer. The
evaluation of earthwork should include observation and testing of engineered fills, subgrade
preparation, foundation bearing soils and other geotechnical conditions exposed during the
construction of the project.
11.2
Site Preparation
Strip and remove existing vegetation and other deleterious materials from proposed building
areas. All exposed surfaces should be free of mounds and depressions, which could prevent
uniform compaction.
Stripped materials consisting of vegetation and organic materials should be wasted from the site
or used to revegetate landscaped areas or exposed slopes after completion of grading
operations.
Demolition of the existing upstream bridge structure should include complete removal of all
foundation systems within the proposed construction area. This includes removal of any loose
backfill found adjacent to existing foundations. Demolition of the existing downstream bridge
structure will only include removal (without dismantling) of the existing pre-fabricated bridge
structure, and removal of existing foundations and abutments down to existing grade. If the
existing foundations and abutments are shallow (as has been assumed based on field
reconnaissance), then they should be entirely removed. Materials derived from the demolition
of existing structures and pavements should be removed from the site and should not be
allowed for use in any on-site engineered fills.
It is anticipated that excavations for the proposed construction can be accomplished with
conventional heavy-duty earthmoving equipment. Depending upon the depth of excavation,
location of the bedrock surface and seasonal conditions, groundwater may likely be
encountered in excavations on the site. Pumping from sumps may be utilized to control water
within excavations. Well points may be required if significant groundwater flow is encountered
or where excavations penetrate groundwater to a significant depth.
15
Final Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
13.0
YA Project Nos. 211-200 & 211-201
July 30, 2012
REFERENCES
Sheridan, D.M., Reed, J.C. Jr., and Bryant, B., 1972, Geologic Map of the Evergreen
Quadrangle, Jefferson County, Colorado, USGS Map I-786-A, U.S. Dept. of the Interior,
Washington, D.C.
Adams, M., et al, 2011, Geosynthetic Reinforced Soil Integrated Bridge System, Interim
Implementation Guide, FHWA Report No. FHWA-HRT-11-026, U.S. Dept. of
Transportation, Washington, D.C.
17
DRAFT Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
APPENDIX A
Boring Logs
YEH AND ASSOCIATES, INC.
GEOTECHNICAL ENGINEERING CONSULTANTS
Boring Began: 11/1/2011
Drilling Method: Solid-Stem Auger/Wireline Coring
Drill: CME 55
Project: Evergreen Golf Course Bridges
Boring: YA-PG-1
Project Number: 211-200/201Date: 11/7/11
Sheet 1 of 1
Completed: 11/1/2011
Drill Bit:
Casing:
Weather: M Cloudy / 33 F
Total Depth: 30.0 ft
Ground Elevation: 7085.0 ft
Location: At NW Abut.
Coordinates: N: E:
Driller: Dakota Drilling
Ground Water Notes:
Rock
RQD
Recovery (%)
Run / Sample Type
Depth
(feet)
Inclination: Vertical
Elevation
(feet)
4.5 ft
11/1/11
-
Depth
Date
Time
Final By: S. Hansen
-
-
-
Soil Samples
Blows
per
6 in
N
Lithology
Logged By: J. El-Hehiawy
Material
Description
Field Notes
and
Lab Tests
0.0 - 0.3 ft. ASPHALT 4 inches.
0.3 - 12.0 ft. gravelly SAND with cobbles and silt,
brown, no plasticity, wet, medium dense to dense,
fine to coarse grained.
7080
7075
5
17/20/32
52
12/8/12
20
MC= 11.7 %
#200= 7 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-a (0)
USCS: SP-SM
10
12.0 - 17.8 ft. GNEISS, gray, decomposed,
extremely soft, fine grained, foliation is very close at
a moderate angle.
BORING LOG 211-201_BORING LOGS.GPJ YEH ASSOCIATES.GDT 12/05/11
7070
7065
7060
7055
15
50:4"
92
0
34
0
40
0
50:4"
17.8 - 21.3 ft. GRANITE, pink with gray,
moderately weathered, very hard, medium grained.
20
21.3 - 30.0 ft. GNEISS, dark gray, moderately
weathered, hard, fine grained, foliation is very close
at a moderate angle. With small intrusions (2-3
inches wide) of hard pink granite, similar to above..
25
30
Bottom of Hole at 30.0 ft.
MC= 8.9 %
#200= 5 %
LL= NV
PL= NP
PI= NP
pH= 7.5
S= 0.001 %
Re= 12610 ohms-cm
AASHTO: A-1-b (0)
USCS: SP-SM
MC= 4.7 %
#200= 17 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-b (0)
USCS: SM
YEH AND ASSOCIATES, INC.
GEOTECHNICAL ENGINEERING CONSULTANTS
Boring Began: 10/31/2011
Drilling Method: Solid-Stem Auger/Wireline Coring
Drill: CME 55
Project: Evergreen Golf Course Bridges
Boring: YA-PG-2
Project Number: 211-200/201Date: 11/7/11
Sheet 1 of 1
Completed: 10/31/2011
Drill Bit:
Casing:
Weather: Clear / 41 F
Total Depth: 35.0 ft
Ground Elevation: 7085.0 ft
Location: At SE Abut.
Coordinates: N: E:
Driller: Dakota Drilling
Ground Water Notes:
Rock
RQD
Recovery (%)
Run / Sample Type
Depth
(feet)
Inclination: Vertical
Elevation
(feet)
5.0 ft
10/31/11
-
Depth
Date
Time
Final By: S. Hansen
-
-
-
Soil Samples
Blows
per
6 in
N
Lithology
Logged By: J. El-Hehiawy
Material
Description
Field Notes
and
Lab Tests
0.0 - 0.4 ft. ASPHALT 5 inches.
0.4 - 11.0 ft. gravelly SAND with cobbles, brown,
no plasticity, wet, medium dense to very dense, fine
to coarse grained.
7080
10
42/29
71
MC= 7.9 %
#200= 4 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-a (0)
USCS: GW
12/14
26
MC= 7 %
#200= 4 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-a (0)
USCS: GP-GM
11.0 - 35.0 ft. GNEISS, gray, decomposed to
moderately weathered, extremely soft to hard,
fine-grained, foliation is very close at a moderate
angle.
BORING LOG 211-201_BORING LOGS.GPJ YEH ASSOCIATES.GDT 12/05/11
7070
20
7060
30
7050
46
50:1"
50:1"
50:0"
50:0"
50:0"
50:0"
8
Bottom of Hole at 35.0 ft.
YEH AND ASSOCIATES, INC.
GEOTECHNICAL ENGINEERING CONSULTANTS
Boring Began: 11/3/2011
Drilling Method: Solid-Stem Auger/Wireline Coring
Drill: CME 55
Project: Evergreen Golf Course Bridges
Boring: YA-V-1
Project Number: 211-200/201Date: 11/7/11
Sheet 1 of 1
Completed: 11/3/2011
Drill Bit:
Casing:
Weather: Clear / 25 F
Total Depth: 29.5 ft
Ground Elevation: 7087.5 ft
Location: Approx 15' NW of N Abut.
Coordinates: N: E:
Driller: Dakota Drilling
Ground Water Notes:
Rock
RQD
Recovery (%)
Run / Sample Type
Depth
(feet)
Inclination: Vertical
Elevation
(feet)
5.0 ft
11/3/11
-
Depth
Date
Time
Final By: S. Hansen
-
-
-
Soil Samples
Blows
per
6 in
N
Lithology
Logged By: J. El-Hehiawy
Material
Description
Field Notes
and
Lab Tests
0.0 - 0.4 ft. ASPHALT 5 inches.
0.4 - 16.0 ft. gravelly SAND with cobbles and silt,
brown, no plasticity, wet, medium dense to dense,
fine to coarse grained.
7085
5
12/15/29
44
13/12/12
24
MC= 10.7 %
#200= 7 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-a (0)
USCS: SP-SM
7080
10
MC= 12.7 %
#200= 11 %
LL= NV
PL= NP
PI= NP
pH= 7.7
S= 0.001 %
Re= 6878 ohms-cm
AASHTO: A-1-b (0)
USCS: SW-SM
7075
BORING LOG 211-201_BORING LOGS.GPJ YEH ASSOCIATES.GDT 12/05/11
15
7070
76
18
100
46
76
30
16.0 - 17.5 ft. GNEISS, dark gray, moderately
weathered, hard, fine-grained, foliation is very close
at a moderate angle.
17.5 - 28.2 ft. GRANITE, pink, slightly weathered,
very hard, medium-grained.
20
7065
25
7060
30
28.2 - 29.5 ft. GNEISS, dark gray, moderately
weathered, medium hard to very hard, fine-grained,
foliation is very close at a moderate angle.
Bottom of Hole at 29.5 ft.
YEH AND ASSOCIATES, INC.
GEOTECHNICAL ENGINEERING CONSULTANTS
Boring Began: 10/31/2011
Drilling Method: Solid-Stem Auger/Wireline Coring
Drill: CME 55
Project: Evergreen Golf Course Bridges
Boring: YA-V-2
Project Number: 211-200/201Date: 11/7/11
Sheet 1 of 1
Completed: 10/31/2011
Drill Bit:
Casing:
Weather: Clear / 50 F
Total Depth: 17.0 ft
Ground Elevation: 7087.5 ft
Location: Approx 8' W of S Abut.
Coordinates: N: E:
Driller: Dakota Drilling
Ground Water Notes:
Rock
RQD
Recovery (%)
Run / Sample Type
Depth
(feet)
Inclination: Vertical
Elevation
(feet)
5.6 ft
10/31/11
-
Depth
Date
Time
Final By: S. Hansen
-
-
-
Soil Samples
Blows
per
6 in
N
Lithology
Logged By: J. El-Hehiawy
Material
Description
Field Notes
and
Lab Tests
0.0 - 15.5 ft. gravelly SAND with cobbles and silt,
brown and gray, no plasticity, wet, medium dense,
fine to coarse grained.
7085
5
13/21
34
15/14
29
MC= 9.3 %
DD= 125.6 pcf
#200= 5 %
LL= NV
PL= NP
PI= NP
AASHTO: A-1-a (0)
USCS: SW-SM
7080
10
MC= 8.3 %
DD= 129.5 pcf
#200= 7 %
LL= NV
PL= NP
PI= NP
S/C= -0.2 %
AASHTO: A-1-a (0)
USCS: SP-SM
7075
15
BORING LOG 211-201_BORING LOGS.GPJ YEH ASSOCIATES.GDT 12/05/11
88
15.5 - 17.0 ft. GRANITE, pink and gray, fresh, very
hard, fine to medium grained.
Bottom of Hole at 17.0 ft.
7070
20
7065
25
7060
44
Difficulty drilling this very
hard granite material.
DRAFT Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
APPENDIX B
Laboratory Test Results
YEH & ASSOCIATES, INC
Summary of Laboratory Test Results
211 - 200
Project No:
Sample Location
Boring
NO.
Sample
Depth (ft)
Type
Natural
Moisture
M
i t
Content
(%)
Project Name:
Natural Dry
Gravell
G
Density
> #4
(pcf)
(%)
_
CCD Evergreen Vehicle Bridge
Gradation
Atterberg
Sand
(%)
Fines
<
Fi
#200
(%)
LL
PL
PI
39
54
7
NV
NP
NP
29
60
11
NV
NP
NP
V-1
5-6.5
Baggie
10.7
V-1
V1
10-11
5
10
11.5
Baggie
12 7
12.7
V-2
5-6
CA
9.3
125.6
40
55
5
NV
NP
NP
V-2
10-11
CA
8.3
129.5
35
58
7
NV
NP
NP
Scour
0-2
0
Bulk
u
3.3
3
3
74
26
6
0.4
0
NV
NP
NP
Rev 2 - 8/02
_
_
Page 1 of 1
pH
_
Unconf.
Comp.
C
Strength
(psf)
_
_
_
_
_
Water
( )/
% Swell (+)
Soluble
S
l bl Resistivity
R i ti it
ConsoliSulfate ohm.cm
dation (-)
%
_
_
_
77
7.7
0 001
0.001
6878
_
_
_
_
_
_
_
_
_
11/16/2011
Date:
-0.2
_
_
_
CLASSIFICATION
AASHTO
USCS
A-1-a
(
0
)
SP - SM
A-1-b
A
1b
(
0
)
SW - SM
A-1-a
(
0
)
SW - SM
A-1-a
(
0
)
SP - SM
A-1-a
a
(
0
)
GW
G
YEH & ASSOCIATES, INC
Summary of Laboratory Test Results
211 - 201
Project No:
Sample Location
Boring
NO.
Sample
Depth (ft)
Type
Natural
Moisture
M
i t
Content
(%)
PG-1
5-6.5
Baggie
11.7
PG-1
PG 1
10-11
5
10
11.5
Baggie
89
8.9
PG-1
15-16
Baggie
4.7
PG-2
5-6
CA
7.9
PG-2
PG
2
10-11
0
CA
C
7.0
0
Rev 2 - 8/02
Project Name:
Natural Dry
Gravell
G
Density
> #4
(pcf)
(%)
_
_
_
_
_
CCD Evergreen Ped Bridge
Gradation
Atterberg
Sand
(%)
Fines
<
Fi
#200
(%)
LL
PL
PI
39
54
7
NV
NP
NP
30
65
5
NV
NP
NP
13
71
17
NV
NP
NP
62
34
4
NV
NP
NP
57
5
38
4
NV
NP
NP
Page 1 of 1
pH
_
Unconf.
Comp.
C
Strength
(psf)
_
_
_
_
_
_
_
_
_
_
_
_
_
_
Water
( )
% Swell (+)
Soluble
S
l bl Resistivity
R i ti it
/ ConsoliSulfate ohm.cm
dation (-)
%
_
_
_
75
7.5
0 001
0.001
12610
_
_
_
_
11/16/2011
Date:
CLASSIFICATION
AASHTO
USCS
A-1-a
(
0
)
SP - SM
A-1-b
A
1b
(
0
)
SP - SM
A-1-b
(
0
)
SM
A-1-a
(
0
)
GW
A-1-a
a
(
0
)
GP - GM
G
G
DRAFT Geotechnical Report
Evergreen Golf Course Bridges, Evergreen, Colorado
YA Project Nos. 211-200 & 211-201
July 30, 2012
APPENDIX C
Boring Location/Engineering Geology Sheets