Final_Geotechnical_Engineering_Report _Revision_1_-_Horse_Valley_Bridge.pdf

Final Geotechnical Engineering Report

Revision 1 Horse Valley Bridge

Highway 89 and Bullrush Road

Near Circleville, Utah

March 26, 2014

Terracon Project No.61145011

Prepared for:

Chamberlin Architects

437 Main Street

Grand Junction, Colorado

Prepared by:

Terracon Consultants, Inc.

14850 Pony Express Road, Suite 150N

Bluffdale, Utah

TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY ............................................................................................................. i

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 Project Description

2.2 Site Location and Description

3.0 SUBSURFACE CONDITIONS

3.1 Typical Subsurface Profile

3.2 Groundwater Conditions

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical Considerations

4.2 Earthwork

4.2.1 Site Preparation

4.2.2 Excavation

4.2.3 Subgrade Preparation

4.2.4 Fill Materials and Placement

4.2.5 Compaction Requirements

4.2.6 Grading and Drainage

4.2.7 Slopes

4.2.8 Construction Considerations

4.2.9 Dewatering

4.3 Shallow Foundations

4.3.1 Bearing Resistance

4.3.1 Shallow Spread Footing Settlement

4.4 Deep Foundations

4.5 Soil Corrosivity

4.6 Seismic Considerations

5.0 GENERAL COMMENTS

APPENDICES

APPENDIX A – FIELD EXPLORATION

Exhibit A-1 Project Vicinity Map

Exhibit A-2 Site Geology

Exhibit A-3 Exploration Plan

Exhibit A-4 Field Exploration Description

Exhibit A-5 to A-6 Boring Logs

Exhibit A-7 to A-9 Test Pit Logs

Exhibit A-10 Photo Log

APPENDIX B – SUPPORTING INFORMATION

Exhibit B-1 Laboratory Testing

Exhibit B-2 Grain Size Distribution

TABLE OF CONTENTS (continued)

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Exhibit B-3 Moisture Density Relationship (Proctor)

Exhibit B-4 to B-5 Direct Shear

Exhibit B-6 Atterberg Limits

Exhibit B-7 Analytical

APPENDIX C – SUPPORTING DOCUMENTS

Exhibit C-1 General Notes

Exhibit C-2 Unified Soil Classification System

Exhibit C-3 AASHTO Classification System

Final Geotechnical Engineering Report – Revision 1 Horse Valley Bridge ■ Near Circleville, Utah March 26, 2014 ■ Terracon Project No. 61140511

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EXECUTIVE SUMMARY

A geotechnical exploration has been performed for the Horse Valley Bridge project located approximately 12 miles south of Circleville, Utah. The investigation included drilling two soil borings and excavating three test pits to depths ranging from approximately 6 to 51½ feet below existing grade, collecting bulk samples from the existing embankments and proposed borrow sources, laboratory testing, engineering analysis and report preparation. This report summarizes the exploration and provides geotechnical recommendations regarding earthwork, embankment construction and design and construction of foundations for the proposed bridge structure.

Based on the information obtained from our subsurface exploration, the site is suitable for the proposed project. The following geotechnical considerations were identified:

Subsurface conditions encountered at the bridge abutments consisted of approximately

12 feet of undocumented fill comprised of silty sand with gravel and debris. The debris encountered consisted of plastic, wood and fabric. Native soils underlying the undocumented fill consisted of gravel with sand and varying amounts of silt, sand with gravel, well-graded sand, silty sand and silt. Cobbles and boulders as large as 36 inches were encountered at various depths as well. Heaving or flowing sands were also encountered at depth. Groundwater was encountered at depths of 13½ and 14 feet in borings B-1 and B-2, respectively.

The bridge may be supported on shallow foundations extending through the fill and bearing in dense native granular soils. Undocumented fill should be removed from beneath shallow foundations. Scour protection using channel armoring, concrete slabs or vertical cutoff walls will be necessary. Micropiles may also be considered to support the structure.

The AASHTO LRFD Bridge Design Site Class for this site is D. Liquefiable soils were not encountered in the samples taken in the borings.

The granular borrow area directly east of the proposed structure appears suitable for use as embankment and structural fill, provided it is processed to have oversized material removed. Material from the existing embankments may be reused as embankment material provided it is free of debris and has oversized material removed.

Close monitoring of the construction operations, including shallow fountain or micropile construction, discussed herein will be critical in verifying design resistances. We recommend that a qualified engineering and testing firm be retained to monitor this portion of the work.

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This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations.

FINAL GEOTECHNICAL ENGINEERING REPORT – REVISION 1

HORSE VALLEY BRIDGE

Highway 89 and Bullrush Road

Near Circleville, Utah

Terracon Project No. 61145011

March 26, 2014

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1.0 INTRODUCTION

A geotechnical exploration has been performed for the Horse Valley Bridge project located near

Circleville, Utah. The investigation included drilling two soil borings and excavating three test pits to depths ranging from approximately 6 to 51½ feet below existing grade, collecting bulk samples from the existing embankments and proposed borrow source, laboratory testing, engineering analysis and report preparation. Logs of the borings and test pits along with a

Project Vicinity Map, Site Geology and Exploration Location Plan (Exhibits A-1 through A-3) are included in Appendix A of this report. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included in Appendix B of this report. Descriptions of the field exploration and laboratory testing are included in their respective appendices.

The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

Subsurface soil conditions

Earthwork

Foundation support

Groundwater conditions

Lateral earth pressures

Seismic considerations

2.0 PROJECT INFORMATION

2.1 Project Description

Item Description

Site layout Refer to the Project Vicinity Map, Site Geology and Exploration Location

Plans (Exhibits A-1 to A-3)

Proposed scope Replace existing flatcar bridge crossing the Sevier River along Bullrush

Road with grade separation structures.

Proposed structure

■ Single-span bridge

■ 50 to 60 feet long, 16 feet wide

Bridge Foundation Layout Shallow foundations, bin wall foundations or micropile foundations.

Maximum Bridge Loads Service l: 200 to 300 kip per abutment (assumed)

Strength l: 300 to 400 kip per abutment (assumed)

Maximum allowable settlement Foundation: 1 inch total (assumed)

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Grading

Existing approach embankments contain metal scrap and various other forms of debris. All debris should be removed, resulting in fill placements on the order of 8 to 12 feet.

Cut and fill slopes Assumed to be no steeper than 2H:1V (Horizontal to Vertical)

Free-standing retaining walls Full height abutments 5 to 8 feet tall.

Design Guide AASHTO LRFD Bridge Design Specifications (2012)

1. BLM Request for Proposals Horse Valley Bridge Geotechnical Services PR 0040123061

2.2 Site Location and Description

Location

The project is located at Highway 89 and Bullrush road in Garfield

County, Utah. The coordinates for the proposed structure are

38.028391° N, -112.357345° W.

Existing improvements

Single span railroad flatcar bridge supported on concrete abutments that extends Bull Rush Road over the Sevier River. The bridge is approximately 54 feet long and 10 feet wide. Metal debris and scrap metal reported in concrete abutments and embankments. Cobbles and boulders line the river channel at the bridge crossing.

Bridge abutment and narrow channel backs up the Sevier River creating a pond on the upstream side. Two canal inlets are located upstream.

The river surface drops approximately 7 feet to the downstream side of the bridge. Some scour has been noted.

Current ground cover

Gravel and dirt roadway is present from Highway 89 to the end of

Bullrush Road. Sparse to moderate growth of native weeds and brush surround the site.

Existing topography

The existing bridge abutments create a moderate slope up to the bridge structure at both ends. Steep slopes and rock cliffs are located to the west of the site, while more moderate sloping hills are to the east, followed by mountain valleys and ridges.

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3.0 SUBSURFACE CONDITIONS

3.1 Site Geology

Mapped1 surface geologic units at the site are shown on the geologic map in Appendix A and summarized below.

Qal1: Alluvium in channels, flood plains and adjacent low river terraces consisting of sand, gravel, silt, and clay; subscript denotes relative age, with Qal1 younger and Qal2 older.

Qaf1: Alluvial-fan deposits consisting of poorly to moderately sorted silt, sand, and gravel deposited by streams, sheet wash, debris flows, and flash floods on alluvial fans and on coalesced alluvial fans and pediments (piedmont slopes); surface is modern and generally undissected.

Qaf3: Alluvial-fan deposits similar to Qaf1, with the surface moderately dissected by modern streams.

Ticc: Gray, monzonite (calc-alkaline) concordant intrusions of batholith size.

3.2 Typical Subsurface Profile

Based on the results of the borings, subsurface conditions on the project site can be generalized as follows:

Stratum

Approximate Depth to

Bottom of Stratum

(feet)

Material Description Consistency/

Density

1 12 to 13½ Fill- Silty sand with gravel with varying amounts of debris

2 49½ to 51½

Gravel with sand and varying amounts of silt, sand with gravel, well-graded sand, and layers of silty sand and silt with cobbles and boulders throughout the soil column up to 36 inches nominal diameter

Loose to very dense

1. Maximum depth explored in boring B-2.

2. Maximum depth explored in boring B-1.

Conditions encountered at each boring location are indicated on the individual boring logs.

Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Details for each of the borings can be found on the boring logs in Appendix A of this report.

Biek, R. F. 2003, Geologic Map of the Harrisburg Junction 7.5’ Quadrangle, Washington County, Utah, Utah Geological Survey Map 191, Reliable ■ Resourceful ■ Responsive 4

3.2 Groundwater Conditions

Groundwater was encountered at the following depths and locations.

Boring

Approximate

Groundwater Depth

Feet

B-1 13½

B-2 14

1. Groundwater depth encountered at the time of the field exploration, unless otherwise indicated.

These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times, or at other locations. Groundwater conditions can change with varying seasonal and weather conditions, and other factors. Evaluation of these factors is beyond the scope of this exploration. Therefore, subsurface water levels during construction, or at other times in the life of the structure, may be higher or lower than the levels indicated on the boring logs.

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical Considerations

Based on the results of the subsurface exploration, laboratory testing, and our analyses, it is our opinion that this site is suitable for the proposed construction provided the geotechnical engineering recommendations presented in this report are implemented in the design and construction of the project. Geotechnical considerations for this project include:

Bridge abutments may be supported on shallow spread footing foundations extended through the fill and bearing in dense native granular soils. Scour protection will be required. As an alternative, micropiles embedded a minimum of 35 feet below existing elevation may also be used for support of foundations. Micropiles should be permanently cased to a depth of 20 feet.

Scour potential should be evaluated at the structure location and potential impacts be considered in the design. Stream channel armament, concrete slabs or vertical cutoff walls should be used to protect the structure from scour.

Material sampled from the borrow area east of the bridge appears suitable for use as embankment and structural fill, though some screening to remove oversized material will be necessary to meet gradation requirements.

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The existing abutments are comprised of undocumented fill with a significant amount of debris present throughout. Additionally, the manner in which this fill was placed and compacted is unknown, and fill variability may range widely in both content and consistency/density. Shallow foundations should extend through the undocumented fill and bear in dense native gravel soil. Gravel roadway approaches to the bridge may settle and require regrading over time.

Geotechnical engineering recommendations for bridge foundations are outlined below. The recommendations contained in this report are based upon the results of field and laboratory testing (which are presented in Appendices A and B), engineering analyses, and our current understanding of the proposed project.

4.2 Earthwork

The following presents recommendations for site preparation, excavation, subgrade preparation and placement of structural and embankment fills on the project. The recommendations presented for design and construction of earth supported elements are contingent upon following the recommendations outlined in this section.

Earthwork on the project should be observed and evaluated by a qualified geotechnical firm.

The evaluation of earthwork should include observation and testing of structural and embankment fill, subgrade preparation, foundation bearing soils or micropile construction, and other geotechnical conditions exposed during the construction of the project.

4.2.1 Site Preparation

Strip and remove existing vegetation, debris, undocumented fill and other deleterious materials from proposed foundation areas. Debris and undocumented fill should be removed as well from below the approach embankments if future variable settlement of the gravel roadway is not acceptable.

Exposed surfaces should be free of mounds and depressions which could prevent uniform compaction. Following removal of unacceptable materials the exposed subgrade should be properly prepared prior to receiving fill or foundations. Exposed granular subgrade should be scarified to a minimum depth of 8 inches and compacted to the requirements of this report. If the percent of gravel prohibits establishing a proctor, visual observation and proof roll tests should be completed to document compaction. Soft or deflecting areas encountered during proof rolling should be removed and replaced with embankment or structural fill. Material placed below groundwater should consist of free draining granular backfill as specified in

Section 4.2.4.

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

Reliable ■ Resourceful ■ Responsive 6 operations. If it is necessary to dispose of organic materials on-site, they should be placed in non-structural areas.

Areas below approach fills should be initially graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill.

If fill is placed in areas of the site where existing slopes are steeper than 5:1 (horizontal:vertical), the area should be benched to reduce the potential for slippage between existing slopes and fills. Benches should be wide enough to accommodate compaction and earth moving equipment, and to allow placement of horizontal lifts of fill.

4.2.2 Excavation

It is anticipated that soil excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Where excavations penetrate down into cobbles and boulders, large equipment capable of removing this material or ripping or jack-hammering may be required to advance the excavation.

Groundwater seepage may be encountered in excavations approaching 10 to 15 feet in depth.

Pumping from sumps may be utilized to control water within the excavations.

4.2.3 Subgrade Preparation

If shallow foundations are implemented, the footing should extend through the fill material and bear in dense native granular soil. Loose soils encountered at foundation bearing depth after excavation should be surficially compacted prior to placement of the foundation system. If sufficient compaction cannot be achieved in-place, the loose soils should be removed and replaced with structural fill. For placement of structural fill below footings, the excavation should be widened laterally, at least eight inches for each foot of fill placed below footing base elevations. Free-draining granular backfill should be used for fill placement below groundwater.

Large cobble and boulder sized materials (> 12 inches in diameter) 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 such conditions are encountered in the footing excavations, the cobbles/boulders should be removed and replaced with structural fill, conditioned to near optimum moisture content and compacted; or the protruding cobble/boulder may be chiseled down a minimum 6 inches below bottom of footing and a layer of structural fill to be placed and compacted over top.

4.2.4 Fill Materials

All fill materials should be inorganic soils free of vegetation, debris, and fragments larger than four inches in size. Pea gravel or other similar non-cementitious, poorly-graded materials should not be used as fill or backfill without the prior approval of the geotechnical engineer. Fill material should meet the following requirements:

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Fill Type

Application

Requirements

Gradation

Plasticity Size

Percent finer by weight

Structural Fill

Required for all fill under foundations and behind bridge abutments

3 inch

No. 4 Sieve

No. 200 Sieve

35 – 70

15 max

Liquid Limit 30 max

Plasticity Index 6 max

Embankment Fill Bridge approach and backfill

4 inch

No. 200 Sieve

35 max

Liquid Limit 36 max

Plasticity Index 10 Max

Free Draining

Backfill Below groundwater

2 inch

1 inch

½ inch

No. 4

95 – 100

25 – 60

0 – 10

1. All fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

2. See section 4.5 Lateral Earth Pressures for limits behind walls/abutments.

The borrow area located approximately 200 feet east of existing bridge was sampled during the field exploration to evaluate suitability for use as fill on this project. Based on laboratory test results, the borrow material appear to meet the requirements of embankment and structural fill provided any oversize material is screened off. Existing embankment material sampled and tested appears to meet embankment fill material requirements provided oversize material is removed. The existing embankment will need to have fines content reduced to meet structural fill requirements. This can be accomplished by increasing the percent of gravel and sand to effectively reduce the percent fines. Mixing and processing of this material onsite will require additional sampling and laboratory testing to confirm the processed material meets report requirements.

4.2.5 Compaction and Placement Requirements

Recommended compaction and moisture content criteria for engineered fill materials are as follows:

Fill Lift Thickness 8-inches or less in loose thickness

Compaction

95% of the material’s maximum dry density. Use modified proctor – AASHTO T-180 for AASHTO A-1 soils and standard proctor AASHTO T-99 for all other soils.

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Moisture Content

Within 2% of optimum moisture content as determined by the appropriate Proctor test at the time of placement and compaction.

1. Fill should be tested frequently for moisture content and compaction during placement. Should the results of the in-place density tests indicate the specified moisture or compaction limits have not been met; the area represented by the test should be reworked and retested as required until the specified compaction is achieved. This may require adjustment of the moisture content.

If groundwater is encountered within the depth of the excavation, free draining granular backfill should be used. This material should be placed in lifts not exceeding 12 inches and should be tamped in place to seat the rock. A filter fabric, such as Mirafi 150N, should be placed over the free draining rock to minimize migration of fines into the rock.

If granular soils to be tested are too rocky to establish a proctor, full time visual observation should be completed. The material should be compacted until a firm and unyielding surface is reached. Proof roll tests may be completed to verify if the surface has been compacted.

4.2.6 Grading and Drainage

Positive drainage should be provided during construction and maintained throughout the life of the project. Infiltration of water below foundations should be prevented. We recommend that protective slopes be provided with a minimum grade of approximately five percent for at least 10 feet from foundations and bases of walls. Backfill against footings should be well compacted and free of all construction debris to reduce the possibility of moisture infiltration.

4.2.7 Slopes

Recommended maximum configurations for permanent cut and fill slopes are as follows:

Maximum Slope Configuration

Soil Type Horizontal:Vertical (H:V)

Granular Soil (Sand, Gravel) 2.5H:1V

1. Flatter slopes are required in areas of sloughing or seepage.

If steeper slopes are required for site development, stability analyses should be completed to design the grading plan.

The face of all fill slopes should be compacted to the minimum specification for fill embankments. Alternately, fill slopes can be over-built and trimmed to compacted material.

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4.2.8 Construction Considerations

Temporary cut slopes for shallow foundations will be required. Proposed cuts will be completed in granular soils ranging from gravel with sand, sand with gravel, and silty sand with gravel, with possible cobbles and boulders. Groundwater may be encountered in excavations.

Due to the nature of the soils observed in the borings and test pits, raveling or sloughing of the cut face may occur during construction. The excavation slope and exposed soils should be evaluated during the excavation process and the stability of the soils determined at that time by the Contractors’ Competent Person, as defined in the OSHA excavation guidelines. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of the cut slopes and bottom. Cut slopes may need to be sloped, shored or stabilized in the interest of safety following local, and federal regulations, including current OSHA excavation and trench safety standards. Temporary excavation slopes should be left exposed for as little time as practical.

4.2.9 Dewatering

Dewatering of shallow foundation excavations may be required. Pumping from sumps may be utilized to control groundwater within excavations, however well points may be required for significant groundwater flow, or where excavations penetrate groundwater to a significant depth.

The dewatering system should be designed to lower groundwater a minimum of 12 inches below excavation bottoms, and so that groundwater seeping from excavations walls does not occur.

We recommend that a qualified dewatering engineer be retained to evaluate appropriate dewatering parameters and the feasibility of dewatering at the site. The contractor should be responsible for the design and implementation of the dewatering system. We recommend that appropriate instrumentation (piezometers) be installed to monitor the piezometric surface during dewatering activities at the site. The Geotechnical Engineer should observe the de-watered piezometric surface prior to commencing facility excavations.

4.3 Shallow Foundations

The proposed bridge should be supported on conventional, strip foundations bearing in dense native granular soils. Consideration should be given to embedment of the foundations below scour depths or protecting the foundation from scour using bank armor or cutoff walls.

4.3.1 Bearing Resistance

Footing bearing resistance was determined in general accordance with AASHTO LRFD Bridge

Design Specifications, Section 10.6.3.1, Bearing Resistance of Soil. Bearing resistance was determined for a minimum embedment depth of 30 inches below the roadway surface

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(estimated frost depth) and an assumed minimum footing size of 5 feet by 20 feet. The following table provides input parameters and design recommendations for shallow foundations.

Description Value

Strength Limit Bearing Resistance

Factor

0.45

Factored Bearing Resistance 8.0 ksf

Nominal Bearing Resistance 17.8 ksf

Nominal Footing Lateral Friction

Coefficient

0.45

Service Limit Bearing Resistance

6.0 ksf

Bearing Material Native granular soils with a minimum effective internal friction angle of 34°.

1. AASHTO LRFD Bridge Design Specifications, Table 10.5.5.2.2-1, Resistance Factors for Geotechnical Resistance of Shallow Foundations at the Strength Limit State.

2. A resistance factor of 0.9 should be used for sliding, based on Table 10.5.5.5.4-1, Resistance Factors for Geotechnical Resistance of Shallow Foundations at the Strength Limit State.

3. Bearing resistance limits immediate settlement to 1 inch or less.

The following table summarizes input parameters for the bearing resistance.

Soil Unit Weight, (pcf)

Strength Parameters

Effective

Friction

Angle

Cohesion

(psf)

Native Gravel with Sand and

Silt 125 34 (native) 0

4.3.1 Shallow Spread Footing Settlement

Shallow spread footings designed for the service limit resistance are estimated to experience 1 inch or less of settlement.

4.4 Deep Foundations – Micropile

As an alternative, bridge abutments may be supported on Type B grouted (pressure grouted) micropile foundations provided the contractor is familiar with subsurface conditions at the site and provides the equipment and procedures capable of installing micropiles to design depths.

Micropiles should be designed based on the method described in the “Micropile Design and

Construction Guidelines – Implementation Manual FHWA-SA-97-070, June 2000” Load Factor

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Design (LFD) Method and the AASHTO LRFD Manual, and constructed in accordance with project plans and specifications.

For the purpose of this design, we have neglected side friction in the upper 18 feet of the profile, in order to take into account the undocumented fill and an assumed scour depth of 5 feet for both the design and extreme event flood scour depths. Based on this, micropiles should be embedded a minimum of 35 feet below existing elevation, or deeper as required by the scour analysis.

4.4.1 Micropile Axial Resistance

Micropile axial resistance was estimated based on soil borings, soil consistency and relative density and Reference Table 10.9.3.5.2-1 of AASHTO LRFD Manual. AASHTO LRFD resistance factors used in design are summarized below.

Micropile Resistance Factors

Foundation

Resistance Factors

Strength Limit Extreme

Limit Service

Limit Tip Shaft Uplift

Micropile -- 0.7

0.7

1.0 1.0

1. AASHTO LRFD Bridge Design Specifications, Table 10.5.5.2.5-1 and 10.5.5.2.3-1.

2. Tip resistance neglected.

3. Resistance factor assuming one load test and medium site variability.

Strength resistance factors provided assume that a minimum of one tension load (verification) test will be completed. One proof test at each abutment should also be completed.

Grout-to-ground bond strength for Type B (injecting grout under pressure) with the on-site soils

(Reference Table C10.9.3.5.2-1), α, values are as indicated in the following table:

Micropile Geotechnical Design Data

Stratum Description Depth

(feet)

Thickness

(feet) Consistency

Grout-to-Ground

Bond Nominal

Strength, α (ksf)

1 Fill: 0-12 12 -- ---

Gravel with Silt and Sand 12-24 12

Medium Dense to

Very Dense

3 Silt 24-30 5 -- 2.5

Gravel with Silt and Sand 30-38 9

Medium Dense to

Very Dense

5 Sand 38-43 5 --

1.7

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Gravel with Silt and Sand, some heaving layers

43-50 7 Medium Dense to

Very Dense

1. Heaving conditions encountered prior to sampling.

The following table summarizes resistance values for micropiles.

Micropile Resistance Summary

Diameter

(inches)

Estimated Embedment

Depth/Elevation

(feet)

Strength Limit

Resistance

=0.7

(kips/pile)

Uplift Resistance

=0.7 1, 2

(kips/pile)

Extreme Limit

Resistance

=1.0

(kips/pile)

Service Limit Resistance

Inch Settlement

=1.0

(kips/pile)

6 35 65 65 88 65

8 35 87 87 117 87

1. Resistance values presented are based on completing one tension load test at the site.

2. Micropiles subject to uplift should be checked for structural strength and connection strength.

3. Resistances neglect upper 18 feet of the soil profile.

Axial resistances are based on shaft friction only. End bearing capacity was neglected due to the relatively small contributing tip area relative to the area of shaft resistance and the pile movement required to mobilize frictional side resistance is significantly less than that needed to mobilize end bearing.

Permanent casing (such as API – American Petroleum Institute, 7.625 inch outside diameter) should be used extending a minimum of 5 feet past the scour zone, to aid in transferring structural loads to the pile and developing lateral resistance. Permanent casing should be plunged into the fresh grout or other methods used to ensure that grout surrounds the outside of the casing.

Micropile groups may experience a reduction in axial resistance depending upon configuration of the group. The reduction can be avoided by maintaining a minimum spacing between piles of

3 diameters center-to-center.

Micropiles should meet the following requirements:

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Each micropile should have a final minimum 6 or 8-inch diameter grout body. Exact length will depend on pile cap elevation and pile penetration into the pile cap.

Permanent casing (such as API, 7.625 inch outside diameter) will be required in the upper portion of the micropile depending on the scour depth.

A 2.5 inch outside diameter solid grade 150 bar installed at the center of the micropile.

All micropile grout mortars will have 28-day minimum compressive strength of

5000 psi.

4.4.2 Micropile Lateral Resistance

Lateral resistance of micropiles was estimated using Table 5-3 of the FHWA-SA-97-070 manual for dense granular soil and pile diameters between 5½ to 7 inches and wall thickness of 0.36 to

0.50 inches. It is anticipated that a lateral load of 3.4 to 5 kips would produce approximately ¼ inch of deflection at the top of a vertical micropile under pinned head condition. In areas where additional lateral resistance is required, additional battered micropiles may be installed. This information can be provided upon request.

It should be noted that undocumented fill was encountered in both borings. Though the fill appears to be dense to very dense at the majority of the sample locations, it could vary, affecting lateral resistance of the piles. Also, lateral resistance will depend on scour depth and if the foundations will be exposed after the scour event. Additional lateral analysis should be completed once scour depth and micropile setback from the river channel is determined.

4.4.3 Construction Considerations

The borings indicated a dense to very dense granular profile with some cobbles and boulders, water at a depth of approximately 13 to 14 feet, as well as layers of soils that may heave during micropile installation. The contractor should be aware of these conditions and bring the necessary equipment and use the appropriate methods to complete the pile excavations to the design depth.

Micropile excavations should be completed using temporary or permanent casing to maintain integrity of the excavation walls within the soil profile. Drilling fluid or grout may be used to wash soil cuttings to the surface while drilling through the soil. Temporary casing should be pulled as the grout is placed to provide final contact between the soil and the grout. Once grouting is completed and temporary casing extracted, the permanent casing should be plunged to design depth into the fresh grout.

Type B grouting requires grout to be placed under pressure.

The geotechnical load resistance of a micropile is highly sensitive to the processes used during pile construction, specifically the technique used to drill, flush the drill cuttings, and grout the pile. Therefore, verification of the design parameters such as grout-to-ground bond strength

Reliable ■ Resourceful ■ Responsive 14 used in design should be performed using field load testing. Select piles should be tested for resistance in accordance with FWHA document "Micropile Design and Construction Guidelines -

Implementation Manual FHWA-SA-97-070, June 2000.”. Testing should include verification tests and proof tests. Verification tests should be loaded incrementally up to 2.5 times the factored controlling design load (DL). The verification tests will be used to verify the design grout-to-rock bond strength and should be performed on sacrificial, non-production piles. Proof tests should be loaded incrementally up to DL and may be performed on production piles. A minimum of one verification test for the project and one proof test at each abutment or 5 percent of the production piles, whichever is greater should be completed.

Test loading should be applied incrementally in accordance with ASTM D3689 and FHWA-SA-

97-070. Installation and testing of the micropiles should be completed by an experienced specialty contractor familiar with soil conditions at this site.

Micropiles are planned to extend into medium dense to very dense, poorly-graded sand gravel.

The contractor should be made aware of the soil and groundwater conditions at the site and provide appropriate equipment to extend piles to the design depths and maintain stable excavations during pile installation.

4.5 Soil Corrosivity

Chemical testing was performed on select soil samples collected in the soil borings and results are summarized below.

CHEMICAL TEST RESULTS

Sample Location

Test Results pH Resistivity

(ohm-cm)

Sulfate

(mg/kg)

Sodium

(mg/kg)

TP-1 @ 0-6 feet 8.29 1,610 189 1,050

Borrow @ 0-5 feet 8.25 1,640 90.7 1,200

An aggressive subsurface environment where corrosion can deteriorate steel members over their design life can generally be identified by soil resistivity and pH tests. The following criteria are specified in AASHTO LRFD Section 10.7.5.

Electrical resistivity less than 2,000 ohm-cm pH less than 5.5 pH between 5.5 and 8.5 in soils with high organic content

On site soils are considered highly corrosive to buried steel based on laboratory test results.

Reliable ■ Resourceful ■ Responsive 15

Based ACI 318 Table 4.3.1, the potential for sulfate attack on concrete is estimated to be negligible. Results of soluble sulfate testing indicate that ASTM Type I or II Portland cement is suitable for concrete on and below grade.

4.6 Seismic Considerations

Seismic design parameters including peak ground acceleration (PGA) and spectral accelerations for 0.2 second (Ss) and 1.0 second (S1) periods for an event with 7 percent probability of exceedance (PE) in 75 years at the project site was determined from the following database:

2009 AASHTO LRFD Seismic Bridge Design with 2010 Interim

AASHTO Guide Specifications for LRFD Seismic Bridge Design, Version 2.10

PGA and spectral values are provided in the following table. These values are for site class B, and should be adjusted for site effects using appropriate site factors from AASHTO LRFD

Bridge Design manual.

SEISMIC DESIGN PARAMETERS

Description Value

7% PE in 75 year

2010 Interim AASHTO LRFD Bridge

Design Site Class Definition (AASHTO) D

Site Latitude N 38.028417°

Site Longitude W -112.35728°

So PGA – Site Class B 0.29g

Ss Spectral Acceleration for a Short Period

(0.2sec) – Site Class B 0.73g

S1 Spectral Acceleration for a 1-Second

Period – Site Class B 0.23g

Fpga Site Factor at Zero-Period 1.22

Fa Site Factor for Short Period (0.2 sec) 1.21

Fv Site Coefficient for a 1-Second Period 1.94

Strong ground shaking is anticipated at the site during a design seismic event. Liquefiable soils were not encountered at the sample depths in the borings. Ground surface settlement from a seismic event is estimated to be 1 inch or less during a design seismic event.

Reliable ■ Resourceful ■ Responsive 16

5.0 GENERAL COMMENTS

Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical engineering recommendations in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, slope construction and other earth-related construction phases of the project.

The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided.

The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing.

APPENDIX A

FIELD EXPLORATION

PROJECT VICINITY MAP

Horse Valley Bridge Highway 89 and Bullrush Road

Circleville, UT

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY

QUADRANGLES INCLUDE: FREMONT PASS, UT (1/1/1966) and BULL RUSH PEAK, UT (1/1/2002).

14850 Pony Express Rd, Ste 150N

Bluffdale, UT

61145011 Project Manager:

Drawn by:

Checked by:

Approved by:

kdm jwg rlc

1:24,000

3/7/2014

Project No.

Scale:

File Name:

Date:

A-1

Exhibit jwg

Project No.

Task No.

Scale:

Date:

61145011

Not to Scale

3/7/2014

Project Mngr:

Drawn By:

Checked By:

Approved By:

kdm rlc

SITE GEOLOGY

Horse Valley Bridge Highway 89 and Bullrush Road

Near Circleville, Utah 14850 S Pony Express Rd., Ste. 150N

Bluffdale, Utah 84065

EXHIBIT

A-2 DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES.

Rowley P.D., et al, 2005, Interim Geologic Map of the

Beaver 30’x60’ Quadrangle, Beaver, Piute, Iron, and

Garfield Counties, Utah, Utah Geological Survey Open-

File Report 454

Bridge Location

EXPLORATION PLAN

Chamberlin - Horse Valley Bridge Highway 89 and Bullrush Road

Circleville, UT

14850 Pony Express Rd, Ste 150N

Bluffdale, UT

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

61145011

AERIAL PHOTOGRAPHY PROVIDED

BY MICROSOFT BING MAPS

jwg rlc rlc

AS SHOWN

3-25-14

Scale:

A-3

Exhibit Project Manager:

Drawn by:

Checked by:

Approved by:

Project No.

File Name:

Date:

Reliable ■ Resourceful ■ Responsive Exhibit A-4

Field Exploration Description

The proposed boring locations were laid out in the field by a Terracon and Bureau of Land

Management (BLM) personnel using site plans provided by the client. Latitude and longitude indicated on the boring logs were obtained by a hand-held GPS unit. The locations and elevations of the borings should be considered accurate only to the degree implied by the means and methods used to define them.

The subsurface exploration was completed using a Fraste track mounted drill rig using odex drilling procedures. Samples of the soil encountered in the borings were obtained using the split-barrel sampling procedures using SPT samplers.

In the split-barrel sampling procedure, the number of blows required to advance a standard 2-inch O.D. split-barrel sampler the last 12 inches of the typical total 18-inch penetration by means of a 140-pound hammer with a free fall of 30 inches, is the standard penetration resistance value (SPT-N). This value is used to estimate the in situ relative density of cohesionless soils and consistency of cohesive soils.

An automatic SPT hammer was used to advance the split-barrel sampler in the borings performed on this site. A significantly greater efficiency is achieved with the automatic hammer compared to the conventional safety hammer operated with a cathead and rope. This higher efficiency has an appreciable effect on the SPT-N value. The effect of the automatic hammer's efficiency has been considered in the interpretation and analysis of the subsurface information for this report.

The samples were tagged for identification, sealed to reduce moisture loss, and taken to our laboratory for further examination, testing, and classification. Information provided on the boring logs attached to this report includes soil descriptions, consistency evaluations, boring depths, sampling intervals, and groundwater conditions. The borings were backfilled with odex cuttings prior to the drill crew leaving the site.

A field log of each boring was prepared by Terracon’s engineer during drilling. These logs included visual classifications of the materials encountered during drilling as well as the engineer’s and driller’s interpretation of the subsurface conditions between samples. Final boring logs included with this report represent the engineer's interpretation of the field logs and include modifications based on laboratory observation and tests of the samples.

12.0

- Direct shear test at 25 feet.

FILL - SILTY SAND WITH GRAVEL , brown, debris present throughout

-Wood debris observed

POORLY GRADED GRAVEL WITH SAND (GP), with cobbles and boulders, gray, medium dense to very dense

-Drilled through boulder from 12 feet to 15 feet

9-8-10 N=18

11-12-13 N=25

10-13-50/6" N=50/6"

6-13-17 N=30

50/1" N=50/1"

20-25-18 N=43

8-8-10 N=18

NP8

50/6"

50/1"

See Exhibit A-2

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 38.028472° Longitude: -112.35747°

G R

A P

H

IC

L O

G

SITE:

13.5 feet while drilling

WATER LEVEL OBSERVATIONS

Advancement Method:

Odex

Abandonment Method:

Borings backfilled with soil cuttings upon completion.

14850 S. Pony Express Rd, Suite 150N Bluffdale, Utah

Notes:

Project No.: 61145011

Drill Rig: Fraste

Boring Started: 2/13/2014

BORING LOG NO. B-1

Chamberlin ArchitectsCLIENT:

Grand Junction, Colorado

Driller: Conetec

Boring Completed: 2/13/2014

PROJECT: Horse Valley Bridge

Highway 89 and Bullrush Road Near Circleville, Utah

Exhibit:

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

A-5T H

IS

B

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IN

G

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IS

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/2

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LIMITS

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D E

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38.0

43.0

51.5

POORLY GRADED GRAVEL WITH SAND (GP), with cobbles and boulders, gray, medium dense to very dense (continued)

WELL GRADED SAND (SW), some gravel, gray

-6" heaving sands at 40 feet before sampling

POORLY GRADED GRAVEL WITH SAND (GP), brown to reddish-brown, dense to very dense, possible cobbles

-6" heaving sands at 50 feet before sampling

Boring Terminated at 52 Feet

21-27-15 N=42

16-20-16 N=36

1-2-6-14 N=8

24-24-26 N=50

3-9-13-28 N=22

1222 NP

See Exhibit A-2

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 38.028472° Longitude: -112.35747°

G R

A P

H

IC

L O

G

SITE:

13.5 feet while drilling

WATER LEVEL OBSERVATIONS

Advancement Method:

Odex

Abandonment Method:

Borings backfilled with soil cuttings upon completion.

14850 S. Pony Express Rd, Suite 150N Bluffdale, Utah

Notes:

Project No.: 61145011

Drill Rig: Fraste

Boring Started: 2/13/2014

BORING LOG NO. B-1

Chamberlin ArchitectsCLIENT:

Grand Junction, Colorado

Driller: Conetec

Boring Completed: 2/13/2014

PROJECT: Horse Valley Bridge

Highway 89 and Bullrush Road Near Circleville, Utah

Exhibit:

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

A-5T H

IS

B

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IN

G

L O

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IS

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13.5

25.0

FILL - SILTY SAND WITH GRAVEL (SM), brown, debris present throughout

-More gravel

-Debris consisting of plastic and fabric, sample bouncing on elastic debris

POORLY GRADED GRAVEL WITH SILT AND SAND

(GP-GM), gray, medium dense to very dense

SILT (ML), brown

-Heaving sands encountered at 25 feet before sampling

14-10-7 N=17

5-5-4 N=9

6-5-25 N=30

25-50/4" N=50/4"

37-20-31 N=51

2-9-14 N=23

3-4-14 N=18

A-1-a

NP

NP

50/4"

See Exhibit A-2

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 38.028417° Longitude: -112.35728°

G R

A P

H

IC

L O

G

SITE:

14 feet while drilling

WATER LEVEL OBSERVATIONS

Advancement Method:

Odex

Abandonment Method:

Borings backfilled with soil cuttings upon completion.

14850 S. Pony Express Rd, Suite 150N Bluffdale, Utah

Notes:

Project No.: 61145011

Drill Rig: Fraste

Boring Started: 2/12/2014

BORING LOG NO. B-2

Chamberlin ArchitectsCLIENT:

Grand Junction, Colorado

Driller: Conetec

Boring Completed: 2/12/2014

PROJECT: Horse Valley Bridge

Highway 89 and Bullrush Road Near Circleville, Utah

Exhibit:

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

A-6T H

IS

B

O R

IN

G

L O

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IS

N O

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A

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D

IF

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P A

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D F

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A

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30.0

43.0

48.0

49.5

SILT (ML), brown (continued) -Drilling casing plugged with material at 28 feet

POORLY GRADED SAND WITH GRAVEL (SP), gray to brown, medium dense to dense, possible cobbles

-Drilling casing plugged with material after sampling

POORLY GRADED GRAVEL WITH SAND (GP), gray, medium dense, possible cobbles

SILTY SAND (SM), assumed

-Heaving sand while drilling at 48 feet Boring Terminated at 49.5 Feet

14-16-9 N=25

10-20-21 N=41

19-19-22 N=41

37-12-12 N=24

10-6-8 N=14

See Exhibit A-2

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 38.028417° Longitude: -112.35728°

G R

A P

H

IC

L O

G

SITE:

14 feet while drilling

WATER LEVEL OBSERVATIONS

Advancement Method:

Odex

Abandonment Method:

Borings backfilled with soil cuttings upon completion.

14850 S. Pony Express Rd, Suite 150N Bluffdale, Utah

Notes:

Project No.: 61145011

Drill Rig: Fraste

Boring Started: 2/12/2014

BORING LOG NO. B-2

Chamberlin ArchitectsCLIENT:

Grand Junction, Colorado

Driller: Conetec

Boring Completed: 2/12/2014

PROJECT: Horse Valley Bridge

Highway 89 and Bullrush Road Near Circleville, Utah

Exhibit:

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

A-6T H

IS

B

O R

IN

G

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LIMITS

LL-PL-PI

D E

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W A

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R L

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8.0

0-6 ft - Direct Shear and Analytical

SILTY SAND WITH GRAVEL (SM), brown to dark brown, fine to coarse sand, fine to coarse gravel

-Organics present to 3 feet below existing grade

Boring Terminated at 8 Feet

203 NP

See Exhibit A-2

Hammer Type: Not ApplicableStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 38.028414° Longitude: -112.35746°

G R

A P

H

IC

L O

G

SITE:

Not encountered during excavation

WATER LEVEL OBSERVATIONS

Advancement Method:

Bucket

Abandonment Method:

Test pit backfilled with…