Final_Geotech_report.pdf

GEOTECHNICAL EVALUATION

JUNCTION WASH BRIDGE

COCONINO NATIONAL FOREST, ARIZONA

CONTRACT NO. AG-8371-C-09-0004

PREPARED FOR:

USDA Forest Service

1824 South Thompson Street Flagstaff, Arizona 86001

PREPARED BY:

Ninyo & Moore

Geotechnical and Environmental Sciences Consultants 3202 East Harbour Drive Phoenix, Arizona 85034

February 22, 2011 Project No. 600587022

Geotechnical Evaluation February 22, 2011 Junction Wash Bridge, Coconino National Forest, Arizona Project No. 600587022

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TABLE OF CONTENTS

Page

1. INTRODUCTION

2. SCOPE OF SERVICES

3. SITE DESCRIPTION

4. PROJECT DESCRIPTION

5. FIELD EXPLORATION AND LABORATORY TESTING

6. GEOLOGY AND SUBSURFACE CONDITIONS

6.1. Geologic Setting

6.2. Subsurface Conditions

6.2.1. Asphalt Concrete and Aggregate Base

6.2.2. Fill

6.2.3. Colluvium

6.3. Groundwater Conditions

7. GEOLOGIC HAZARDS

7.1. Faulting and Seismicity

7.2. Land Subsidence and Earth Fissures

7.3. Landsliding

8. CONCLUSIONS

9. RECOMMENDATIONS

9.1. Site Preparation

9.2. Excavations

9.3. Grading, Fill Placement, and Compaction

9.4. Imported Fill

9.5. Seismic Design Considerations

9.6. Foundations

9.6.1. Drilled Shafts

9.6.2. Driven H-Pile Foundations

9.6.2.1. Construction Considerations for Driven Piles

9.6.3. Approach Slabs

9.6.4. Spread footing foundations

9.7. Retaining Walls

9.8. Corrosion

9.9. Concrete

9.10. Site Drainage

9.11. Pre-Construction Conference

9.12. Construction Observation and Testing

10. LIMITATIONS

11. REFERENCES

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Tables Table 1 – 2006 International Building Code Seismic Design Criteria Table 2 – Soil Parameters for Lateral Load Analysis of Drilled Shafts and Driven Piles Using

COM624P or LPILE Table 3 – Ultimate Driven H-Pile Axial Capacity, 14x89 Table 4 – ACI Requirements for Concrete Exposed to Sulfate-Containing Soil

Figures Figure 1 – Site Location Figure 2 – Boring Location Map Figure 3 – Retaining Wall Drainage Guidelines Figure 4 – Downward Axial Capacity Chart

Appendices Appendix A – Boring Logs Appendix B – Laboratory Testing

600587022R 1

1. INTRODUCTION

In accordance with our proposal dated September 7, 2010, and your authorization, we have performed a geotechnical evaluation for the proposed Junction Wash Bridge, situated approximately 0.1 miles east of the intersection of Interstate 17 (I-17) and Forest Road 618 in the

Coconino National Forest, Yavapai County, Arizona. The purpose of our evaluation was to assess the subsurface conditions at the project site in order to formulate geotechnical recommendations for design and construction of the proposed improvements. This report presents the results of our evaluation and our geotechnical conclusions and recommendations regarding the proposed construction.

2. SCOPE OF SERVICES

The scope of services for this study included the following:

• Reviewing readily available background data, including topographic maps, geologic maps and literature, in-house proprietary data, and aerial photographs.

• Marking out the boring locations and notifying Arizona Blue Stake of these locations prior to drilling.

• Drilling, logging and sampling two exploratory borings to depths of approximately 30 feet below ground surface (bgs). The boring logs are presented in Appendix A.

• Performing laboratory testing of selected samples to evaluate in-situ moisture and dry density, gradation analysis, Atterberg limits test, consolidation (response-to-wetting), and corrosivity characteristics (including pH, minimum electrical resistivity, soluble sulfates, and chlorides). The results of the laboratory testing are presented on the boring logs and/or in Appendix B.

• Preparing this report presenting our findings, conclusions, and recommendations regarding the geotechnical conditions of the project site.

Our scope of services did not include environmental consulting services, such as hazardous waste sampling or analytical testing at the site. A detailed scope of services and estimated fee for such services can be provided upon request.

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3. SITE DESCRIPTION

The project site is located in the southwest quarter of Section 17 in Township 15 North, Range 6

East, approximately 0.1 miles east of the intersection of I-17 and Forest Road 618 in the

Coconino National Forest, Yavapai County, Arizona. The general location of the site is depicted on Figure 1. At the time of our evaluation, the project site generally consisted of a two-way, asphalt paved forest road that traversed northwest-southeast and crossed Junction Wash via a box culvert structure. Scattered vegetation was observed around the site, and was more concentrated in areas of natural drainages. No areas of seepage, standing water, or flowing water was observed in the wash at the time of our evaluation.

According to the Casner Butte, Arizona 7.5 Minute, United States Geological Survey (USGS)

Topographic Quadrangle Map (1991), the site elevation is approximately 3,850 feet relative to mean sea level. The topography of the site generally has areas of relatively high topographic relief from nearby mountains. In general, the regional topography slopes from the northeast down to the southwest.

Two aerial photographs of the site were available to review for this project. Aerial photographs from the USGS dated 2003 and 2007 depicted the project site as being similar to its current condition, with an asphalt-paved roadway crossing Junction Wash via a box culvert.

4. PROJECT DESCRIPTION

This project includes the design and construction of a new bridge to replace the existing structure, to cross over Junction Wash along Forest Road 618. The new bridge is planned to be approximately 50 feet long and 35 feet wide, and be a single-span structure. Approach slabs will be constructed on both sides of the bridge. At the time of this report, we understand that the bridge is anticipated to be supported on deep foundations (e.g. drilled shafts or driven piles).

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5. FIELD EXPLORATION AND LABORATORY TESTING

On October 18, 2010, Ninyo & Moore conducted a subsurface evaluation at the site in order to assess the existing subsurface conditions and to collect soil samples for laboratory testing. Our evaluation consisted of the drilling, logging, and sampling of two exploratory borings to depths of approximately 30 feet bgs. The borings, denoted as B-1 and B-2, were drilled adjacent to the sides of the existing culvert on top of the existing embankment. The borings were drilled using a

CME-75 drill rig equipped with a ODEX percussion drilling equipment. Bulk and relatively undisturbed soil samples were collected at selected intervals. Detailed descriptions of the soils encountered are presented in the test pit logs in Appendix A. The general locations of the borings are denoted on the Boring Location Map (Figure 2).

The soil samples collected from our field activities were transported to the Ninyo & Moore laboratory in Phoenix, Arizona for geotechnical laboratory testing. The testing included in-situ moisture content and dry density, particle-size gradation, Atterberg limits, consolidation

(response-to-wetting), and corrosivity characteristics (including pH, minimum electrical resistivity, soluble sulfates, and chlorides). The results of the in-situ moisture content and dry density testing are presented on the boring logs in Appendix A. A description of each laboratory test method and the remainder of the test results are presented in Appendix B.

6. GEOLOGY AND SUBSURFACE CONDITIONS

The geology and subsurface conditions at the site are described in the following sections.

6.1. Geologic Setting

The project site is located in what is known as the Transition Zone physiographic province, an approximately 50-mile wide mountain belt that traverses northwest-southeast through central Arizona. This province is the physiographic transition between the Colorado Plateau province and Basin and Range province in Arizona. The province is characterized by the presence of Proterozoic (1.7 billion years) granitic and metamorphic rocks that were exposed as the sedimentary Paleozoic (510 million years) and Mesozoic (245 million years)

600587022R 4 rocks were eroded away. High-angle normal faults and block faulting occurred during the

Mid-Tertiary which also coincided with an increase in volcanic activity during this time

(Kamilli and Richard, 1998).

The surficial geology of the site is described as Tertiary-age colluvial deposits. These deposits generally consist of a cemented layer of sand, gravel, and boulders (Weir, et. al, 1986).

6.2. Subsurface Conditions

Our knowledge of the subsurface conditions at the project site is based on our field exploration and laboratory testing, and our understanding of the general geology of the area.

The following sections provide a generalized description of the materials encountered. More detailed descriptions are presented on the boring logs in Appendix A.

6.2.1. Asphalt Concrete and Aggregate Base

Asphalt concrete (AC) was encountered at the surface of our borings and was approximately 2 inches thick in our borings. Aggregate base (AB) was encountered underlying the AC, and was approximately 2 inches thick in our borings.

6.2.2. Fill

Embankment fill was encountered at the surface of our borings and extended to approximately 10 feet below ground surface. The fill generally consisted of clayey and silty sand with varying amounts of gravel in our borings.

6.2.3. Colluvium

Colluvium was encountered underlying the fill material, and extended to the total explored depths. The colluvium generally consisted of clayey sand with gravel. Cobbles and possible boulders were also observed in our borings in the colluvial material.

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6.3. Groundwater Conditions

Groundwater was not encountered in our borings. Based on information presented by the

Arizona Department of Water Resources (ADWR), groundwater historically has been measured in nearby wells to be on the order of approximately 170 feet bgs. Groundwater levels may fluctuate depending on seasonal variations, precipitation, and close proximity of

Junction Wash. Perched groundwater conditions may be anticipated during and after periods of precipitation and water flow in the wash.

7. GEOLOGIC HAZARDS

The following sections describe potential geologic hazards at the site, including faulting and seismicity, land subsidence and earth fissures, and landsliding.

7.1. Faulting and Seismicity

Based on our field observations, review of pertinent geologic data, and analysis of aerial photographs, faults are not located within or immediately adjacent to the study area. The closest known Quaternary-age fault to the site is the Mormon Lake Fault Zone, located approximately 28 miles to the northeast of the site (Pearthree, 1998). The Mormon Lake

Fault Zone is situated along the eastern side of Mormon Lake. The fault zone is a series of north-northwest striking normal faults that dip to the east-southeast. The recent movement along this fault was approximately 1.6 million years ago during the early Pleistocene epoch.

The slip-rate category of this fault is less than 0.2 millimeters per year (Pearthree, 1998).

7.2. Land Subsidence and Earth Fissures

Active areas of ground surface subsidence have not been documented near the study area

(Schumann and Genualdi, 1986). Based upon our field reconnaissance and review of the referenced material, there are no known earth fissures underlying or near the subject area.

Therefore, land subsidence and earth fissures are not expected to be a constraint to the project.

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7.3. Landsliding

No landslides or indications of deep-seated landsliding were noted at the site during our field exploration or our review of available geologic literature, topographic maps, and aerial photographs.

8. CONCLUSIONS

Based on the results of our subsurface evaluation, laboratory testing, and data analysis, it is our opinion that the proposed construction is feasible from a geotechnical standpoint, provided that the recommendations of this report are incorporated into the design and construction of the proposed project, as appropriate. Geotechnical considerations include the following:

• Excavation of the on-site soils may be difficult and/or slow due to the presence of coarse material (i.e. cobbles and possible boulders).

• Imported soils and soils generated from on-site excavation activities that exhibit a low plasticity and very low to low swell potential can generally be used for engineered fill.

• Groundwater was not encountered during our field exploration. Based on data collected in nearby wells, the regional groundwater table has historically been estimated to be at approximately 170 feet bgs. Perched groundwater conditions may be anticipated during and after periods of precipitation and water flow in the wash.

• No known or reported geologic hazards are reported underlying, or immediately adjacent to, the site.

• Corrosivity test results indicate that subgrade soils generally exhibit a corrosive potential to ferrous metals. The sulfate content of the tested soils presents a negligible indication of sulfate attack to concrete.

9. RECOMMENDATIONS

The following sections present our geotechnical recommendations for the proposed construction.

If the proposed construction is changed from that discussed in this report, Ninyo & Moore should be contacted for additional recommendations.

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9.1. Site Preparation

Construction areas should be cleared and grubbed of deleterious materials, including grass, weeds, construction debris, and any other material that might interfere with the performance or progress of the work. These materials, if found anywhere along the areas of the proposed improvements, should be disposed at a legal dumpsite.

It may be desirable to recognize utilities, underground and above-ground structures or other features that are near the planned construction and to survey or document (e.g., photographs, video, official documentation, etc.) their pre-construction condition. The findings of the survey could be used to document any damage to the existing utilities or structures that might result from this construction.

9.2. Excavations

As previously mentioned, the fill and colluvial material encountered in our borings generally consisted of clayey and silty sand with varying amounts of gravel. In addition, scattered caliche filaments and nodules, as well as cobbles and possible boulders were encountered in our borings, which could be more difficult to excavate depending on the actual degree of cementation and/or particle size encountered during construction. Heavy-duty excavation equipment in good operating condition will be needed to reach the anticipated foundation depths for the proposed bridge.

The contractor is also responsible to provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with Occupational Safety and Health

Administration (OSHA) requirements, for employees working in an excavation that may expose them to the danger of moving ground. Depending on space limitations or other constraints, sloped excavations may be unfeasible. The contractor may utilize a temporary shoring system to stabilize deep excavations. If construction or earth material is stored or equipment is operated near an excavation, flatter slope geometry or stronger shoring should be used during construction. Additionally, existing structures, if any, adjacent to excavations

600587022R 8 may need to be underpinned. The information contained in this report may not be sufficient to design shoring or underpinning.

9.3. Grading, Fill Placement, and Compaction

Imported soils and soils generated from on-site excavation activities that exhibit relatively low plasticity indices and very low expansion potential are generally suitable for use as engineered fill. Relatively low plasticity indices are defined as having a Plasticity Index

([PI] by American Society for Testing and Materials [ASTM] 4318) value of 20 or less. Very low to low expansion potential soils are defined as having an Expansion Index (evaluated in accordance with ASTM D 4829) of 50 or less. Atterberg limits tests performed on soil samples obtained from our bridge borings indicated that the soils tested were non-plastic

(PI=0). Based on these results, many of the on-site soils should be suitable for re-use as engineered fill. An earthwork (shrinkage) factor of 10 to 20 percent is estimated for the on-site soils.

In addition, suitable fill should not include deleterious or organic material (more than 4 percent); clay lumps, construction debris, rock particles, and other non-soil fill materials larger than 4 inches in dimension. This material should be disposed of off-site or in non-structural areas.

We recommend that engineered fill associated with this project be moisture-conditioned

(slightly above optimum) and compacted to 95 percent relative compaction at a moisture content generally near its optimum. The fill should be placed in lifts no more than 8 inches in loose thickness. An earthwork shrinkage factor is estimated to range from approximately

10 to 25 percent.

We recommend that any proposed retaining wall or wing-wall foundations be supported on a zone of adequately moisture-conditioned and compacted engineered fill, extending 2 feet below the foundation bearing elevation. This new fill should be placed in horizontal lifts no more than approximately 8 inches in loose thickness and compacted by appropriate mechanical methods, to 95 percent relative compaction, in accordance with ASTM D 698, at

600587022R 9 a moisture content generally above optimum moisture. The overexcavation should extend laterally 2 feet or more horizontally beyond the foundation footprint.

9.4. Imported Fill

Imported fill, if utilized, should consist of granular material with a very low or low expansion potential. Import material in contact with ferrous metals should have low corrosion potential (minimum resistivity more than 2,000 ohm-cm, chloride content less than 25 parts per million [ppm]). In lieu of this, corrosion protection techniques (e.g. pipe wrapping, cathodic protection, etc.) may be utilized. Material in contact with concrete should have a soluble sulfate content of less than 0.1 percent. The geotechnical consultant should evaluate such materials and details of their placement prior to importation.

9.5. Seismic Design Considerations

Based on a Probabilistic Seismic Hazard Assessment for the conterminous United States, issued by the USGS (2002 data), the site is located in a zone where the peak ground accelerations having 10, 5, and 2 percent probability of being exceeded in 50 years are

0.05g, 0.08g, and 0.13g, respectively. These ground motion values are calculated for "firm rock" sites, which correspond to a shear-wave velocity of approximately 2,500 feet per second in approximately the top 100 feet bgs. Different soil or rock types may amplify or de-amplify these values. The proposed improvements should be designed in accordance with the requirements of governing jurisdictions and applicable building codes. Table 1 presents the seismic design parameters for the site in accordance with International Building Code

(IBC, 2006) guidelines and mapped spectral acceleration parameters (USGS, 2009).

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Table 1 – 2006 International Building Code Seismic Design Criteria

Seismic Design Factors Value Site Class C Site Coefficient, Fa 1.2 Site Coefficient, Fv 1.7 Mapped Spectral Acceleration at 0.2-second Period, Ss 0.306 g Mapped Spectral Acceleration at 1.0-second Period, S1 0.093 g Spectral Acceleration at 0.2-second Period Adjusted for Site Class, SMS 0.367 g Spectral Acceleration at 1.0-second Period Adjusted for Site Class, SM1 0.157 g Design Spectral Response Acceleration at 0.2-second Period, SDS 0.245 g Design Spectral Response Acceleration at 1.0-second Period, SD1 0.105 g

9.6. Foundations

We understand that drilled shafts will be utilized in the design of the bridge foundation. The following sections provide considerations for the deep foundation system.

9.6.1. Drilled Shafts

Based on the soil information and the anticipated loads, it is our opinion that cast-in-place, reinforced concrete drilled shafts are feasible to support the new bridge structure.

We recommend that the drilled shafts be installed according to the Arizona Department of Transportation (ADOT) Standard Specification 609 and the recommendations outlined in this report.

An axial capacity design chart for the bridge is presented on Figure 4. This figure summarizes our axial loading recommendations for a single drilled shaft. The recommendations were generally formulated using side friction resistance, end bearing, and an assumed factor of safety of 2.5. We recommend a shaft diameter of 3 feet or more to assisted in removing possible cobble (or larger)-sized fragments.

These recommendations are based on the results of the exploratory borings, laboratory tests, and appropriate analytical methods for estimating the axial capacity of drilled

600587022R 11 shaft foundations (American Association of State Highway Transportation Officials -

Beta Method).

In addition, the design charts reflect the shallowest allowable drilled shaft embedment depth to be 10 feet below existing grade based on the structural loads and the subsurface soil conditions observed in our exploratory borings. We are assuming that the finished grade will be close to the existing grade at the boring locations. Larger diameter shafts or deeper shaft embedment could be considered if that proves to be more convenient or better satisfies the lateral load demands; however, deeper geotechnical borings may be needed if the drilled shaft embedment depths exceed the depths of the current borings.

Reductions to capacity resulting from scour erosion were not incorporated in our evaluation.

The allowable drilled shaft capacities presented in Figure 4 are for single shafts, with no group reduction factor applied. For a drilled shaft center-to-center spacing of 3B (where

B is the diameter of the shaft in question), the above capacities should be multiplied by a reduction factor of 0.67. This reduction factor should linearly increase until a spacing of 4B is achieved, at which point the reduction factor is not applied (reduction factor =

1.0). For intermediate spacing, the reduction factor may be estimated by linear interpolation.

We estimate that total settlement of a single shaft, with the assumed loading condition, should be less than approximately ½-inch provided that the shaft is founded in dense, colluvial materials and the end bearing surface is not significantly disturbed during drilling and bottom cleaning operation. This estimate is based on the soil conditions observed and recorded in our exploratory borings, assumed loading conditions, and our experience with similar soils.

The soil parameters recommended for lateral load analyses of drilled shafts are presented in Table 2 below. We understand that lateral load analyses of drilled shafts will be performed by others.

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Table 2 – Soil Parameters for Lateral Load Analysis of Drilled Shafts and Driven Piles Using COM624P or LPILE

Approx.

Depth Below

Existing Ground

Surface(ft)

Soil Type to be used in Lateral Analysis

Effective Unit

Weight, (pcf)

Cohesion (psf)

Angle of Internal Friction (degrees) p-y modulus, K (lb/in3)

Strain Factor

E50

0'-30’ Sand

(Reese Criteria)

110 0 32 50 –

15-30’ Sand

(Reese Criteria)

115 0 38 225 –

The drilled shaft construction should be observed and evaluated by the project geotechnical consultant to check that competent bearing material has been reached and that the bearing surface has been adequately cleaned.

Where possible, the drilled shafts should be constructed in the “dry” (i.e. no more than 3 inches of water covering the base of the drilled shaft excavation). Also, the bottom of the hole should be cleaned such that no more than 3 inches of loose material remains.

Depending on the type of auger used and the depth of the pier excavation, alternative cleaning techniques, including hand cleaning or vacuuming, may be needed. For drilled shafts constructed in the “dry”, the concrete may be placed by the free-fall method. This method consists of using a vertical section of concrete chute to direct the concrete flow out of the truck in a vertical stream of concrete with a relatively small diameter. The stream should be aimed to avoid hitting the sides of the drilled shaft or the reinforcing cage, which could cause concrete segregation. Adequate compaction will be achieved by free-fall of the concrete up to the top 10 feet. The top 10 feet of concrete should be vibrated in order to achieve proper compaction. The concrete should be designed so that the slump during placement is in the range of 4 to 6 inches for dry, uncased conditions.

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Where the drilled shaft are constructed in the “wet”, a tremie pipe connected either to a hopper or concrete pump should be used to displace the water in the drilled shaft excavation upwards as the concrete is placed. If this method is used, detailed procedures should be submitted by the contractor for review and approval by the geotechnical engineer. The top 10 feet of concrete should be vibrated in order to achieve proper compaction. The concrete should be designed so that the slump during placement is in the range of 7 to 9 inches for conditions other than a dry, uncased hole.

Due to the presence of granular soils, some sloughing or caving may occur. For this reason, it may be appropriate to use a temporary casing or the slurry method while installing the shafts at some locations. The contractor should be prepared to use a full length casing, if needed.

We recommend that the drilled shafts installation and the foundation concrete mix design be in accordance with ADOT Standard Specification 609 (2008). A requirement of this specification includes submission of a detailed installation plan to the Engineer by the drilled shaft contractor. The Geotechnical Engineer should be given the opportunity to review the plans, specifications, and the contractor’s installation plan prior to construction.

9.6.2. Driven H-Pile Foundations

Per your request, we are also providing recommendations for driven pile foundations.

For this foundation alternative, a steel H 14x89 was selected for analysis. The allowable loads and recommended lengths for the driven piles were analyzed using the computer program Driven 1.0 (Federal Highway Administration [FHWA], 2001). Vertical support provided by a pile cap, grade beam or structural slab was neglected in our analyses. The results of our axial pile capacity evaluation are summarized in Table 3.

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Table 3 – Ultimate Driven H-Pile Axial Capacity, 14x89

Tip Depth

(ft) *Ultimate Downward Capacity (kips)

5 10 10 41 15 71 20 104 25 141 30 183

*Allowable axial driven pile capacities for use in design may be calculated based on dividing the ultimate capacity by the appropriate factor of safety (FS) as discussed below.

The tabulated capacities do not include the weight of the pile. The following recommended factors of safety should be used to estimate allowable driven pile axial capacities:

• FS = 3.5 if a pile driving formula (we recommend the Gates dynamic formula) is used for construction verification

• FS = 2.75 if a wave equation analysis is done (as we recommend in the following section)

• FS = 2.5 if, prior to production, an indicator pile testing program, using equipment recommended by the drivability analysis, be performed to further evaluate pile driving conditions, termination criteria, and design assumptions.

We recommend that piles be spaced no closer than three times the pile greatest diameter dimension. The axial pile capacities may be increased by one-third when considering loads of short duration such as wind or seismic forces. No axial load group reduction factors are recommended. However, the recommendations for lateral load group reduction factors for driven piles are the same as those for drilled shafts, as discussed in the previous section.

Allowable steel pile design stresses should be kept below 0.25fy for the design loads and below 0.9fy for driving stresses, where fy is the yield strength.

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9.6.2.1. Construction Considerations for Driven Piles

Due to the presence of cobbles and possible boulders in the very dense colluvium material underlying the site, driving piles to the needed depths will be difficult. In addition, driven piles should be installed as closely as possible to specified limits of vertical and horizontal alignment. This will be difficult to achieve with the subsurface conditions at the site. Pulling piles into position, post driving, is not recommended. Contractors with substantial experience in driving piles in Arizona should be used for the construction. It should be noted that there are few contractors in Arizona with this level of experience in driving piles.

Driving piles creates ground vibrations and noise that can be disturbing to occupants of nearby buildings during installation and wildlife. An evaluation of the current conditions of any existing adjacent structures or utilities should be performed to assess pre-pile driving conditions to compare with post-pile driving conditions. During construction, additional measures can be taken to reduce the potential for vibration-related damage to any existing adjacent structures. The effect of the pile-driving operations on structures within approximately 50 feet of the site should be evaluated, if applicable. Further, it is prudent to perform pre-construction surveys of any structures within approximately 100 feet or more of the site to reduce the potential for damage claims pertaining to the pile driving.

For this foundation alternative, the contractor should perform a wave equation driveability analysis to select the appropriate hammer and related equipment to drive the piles to the design embedment depths without overstressing or damaging the piles. The results of the analysis should be submitted to the geotechnical engineer for review prior to the installation of the production plies.

Open-ended pipe piles may tend to “plug” during driving in granular soils at a depth of about 30 diameters or less, but varies according to hammer energy. This may result in a sudden increase in driving resistance, further increasing the driving conditions during construction.

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Jetting and spudding to facilitate pile driving is not recommended. When driving in grouped or closely spaced conditions, driving should be properly sequenced to reduce lateral or vertical displacement of previously driven piles. The geotechnical consultant should observe the pile driving operations for indicator and production piles.

9.6.3. Approach Slabs

The design of the approach slabs is the responsibility of the structural engineer. We recommend that the slab be reinforced with steel. The placement of reinforcement in the slab is vital for satisfactory performance. We also recommend that the slab be underlain by 4 inches or more of compacted AB material that is compacted to 100 percent relative compaction at a moisture content slightly above optimum. The AB material should further be underlain by 2 feet of fill compacted to 95 percent relative compaction or more in accordance with ASTM D 698.

Soils underlying the slabs should be moisture conditioned and compacted in horizontal lifts approximately 8 inches in loose thickness and compacted by appropriate mechanical methods to a relative compaction of 95 percent or more in accordance with

ASTM D 698 at a moisture content generally above its laboratory optimum. As previously mentioned, an earthwork (shrinkage) factor of approximately 10 to 25 percent is estimated for the on-site soils.

Control joints should be constructed at intervals designed by the structural engineer to help reduce random cracking of the slab. Positive drainage should be established and maintained adjacent to the approach slabs.

9.6.4. Spread footing foundations

Spread footings may be used for wing-walls or miscellaneous retaining walls for this project. Spread footings should be supported at a depth of 24 or more inches below finished grade, on 2 or more feet of engineered fill, as described in Section 9.3.

Continuous retaining wall footings should have a width of 3 or more feet. Footings may

600587022R 17 be designed using an allowable bearing pressure of up to 2,500 pounds per square foot

(psf) for static conditions. Spread footings should be reinforced in accordance with the recommendations of the structural engineer. The allowable soil bearing pressure may be increased by one-third when considering total loads including loads of short duration such as wind or seismic forces.

Total and differential settlement of up to about 1 inch and 1/2 inch, respectively, may occur. Distortions of about 1 inch (vertical) over 20 feet (horizontal) are possible.

Foundations bearing on moisture-conditioned recompacted material and subject to lateral loadings may be designed using an ultimate coefficient of friction of 0.35 (total frictional resistance equals the coefficient of friction multiplied by the dead load). A passive resistance value of 300 psf of depth can be used. The passive resistance may be increased by one-third when considering loads of short duration such as wind or seismic forces. The foundations should preferably be proportioned such that the resultant force from total loads, including lateral loading, falls within the kern (i.e., middle one-third of the footing base).

9.7. Retaining Walls

Retaining wall foundations, including wing walls, should be founded in the manner described in the previous sections.

Retaining walls that are not restrained from movement at the top and have a level backfill behind the wall may be designed using an “active” equivalent fluid unit weight of 35 pounds per cubic foot (pcf). This value assumes compaction within about 5 feet of the wall will be accomplished with relatively light compaction equipment, that very low to low expansive backfill will be placed behind the wall, and that drainage will be provided to minimize the possibility of unbalanced hydrostatic pressures. Unrestrained retaining walls should also be designed to resist a horizontal earth pressure of 0.30q. The value for “q” represents the vertical surcharge pressure induced by adjacent light loads, slab, or traffic loads plus any adjacent footing loads.

600587022R 18

For passive resistance to lateral loads, we recommend that an equivalent fluid weight of

300 pcf be used. This value assumes that the ground is horizontal for a distance of 10 feet or more in front of the wall or three times the height generating the passive pressure, whichever is more. We recommend that the upper 12 inches of soil not protected by pavement or a concrete slab be neglected when calculating passive resistance. For frictional resistance to lateral loads, we recommend that a coefficient of friction of 0.35 be used between soil and concrete. The ultimate lateral resistance can be taken as the sum of the frictional resistance and passive resistance. The passive resistance values may be increased by one-third when considering loads of short duration, such as wind or seismic forces.

The “at-rest” earth pressure against walls that are restrained at the top or braced so that they cannot yield, and with level backfill, may be taken as equivalent to the pressure exerted by a fluid weighing 55 pcf. Restrained retaining walls should also be designed to resist a horizontal earth pressure of 0.5q. The value for “q” represents the vertical surcharge pressure induced by adjacent light loads, slab, or traffic loads plus any adjacent footing loads.

Measures should be taken so that moisture does not build up behind retaining walls.

Retaining walls should be provided with a drain, as shown on Figure 3. Back drainage measures should include free draining backfill material, filter fabric to hinder particle migration, and perforated drainpipes or weepholes. In lieu of the wrapped open-graded gravel, a geocomposite drainage mat attached to the wall and discharging into the drain pipe or weep holes may be considered. Drainpipes should outlet away from structures, and retaining walls should be waterproofed in accordance with the recommendations of the project civil engineer or architect. To reduce the potential for water- and sulfate/salt-related damage to the retaining walls, particular care should be taken in the selection of the appropriate type of waterproofing material to be utilized and in the application of this material.

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9.8. Corrosion

The corrosion potential of the on-site materials was analyzed to evaluate its potential effect on any buried pipelines. Corrosion potential was evaluated using the results of our laboratory testing on a selected soil sample obtained from our borings that was considered representative of the subsurface soils at the project site.

Laboratory testing consisted of pH, minimum electrical resistivity, and chloride and soluble sulfate contents. The pH and minimum electrical resistivity tests were performed in general accordance with Arizona Test 236b, while sulfate and chloride tests were performed in accordance with Arizona Tests 733 and 736 respectively. The results of the corrosivity tests are presented in Appendix B.

The soil pH value of the sample tested was 7.7, which is considered to be alkaline. The minimum electrical resistivity value from the sample tested was 1,710 ohm-cm, which may be corrosive to ferrous materials. The chloride content of the sample tested was 44 ppm, which may also be considered corrosive to ferrous materials. The soluble sulfate content of the samples was 0.003 percent by weight, which is considered to be a negligible amount for sulfate attack on concrete.

The results of the corrosion testing indicate that the on-site materials could be corrosive to ferrous metals. Therefore, we recommend that special consideration be given to the use of heavy-gauge, corrosion-protected, underground steel pipe. As an alternative, plastic pipe could be considered. A corrosion specialist should be consulted for further recommendations.

9.9. Concrete

Laboratory chemical tests performed on a select soil sample from borings indicated a soluble sulfate content of 0.003 percent by weight. Based on the following tabulated American

Concrete Institute (ACI) guidelines, the on-site soils have a negligible sulfate exposure for concrete.

600587022R 20

Table 4 – ACI Requirements for Concrete Exposed to Sulfate-Containing Soil f’c, Normal-Weight and Lightweight

Aggregate Concrete, psi

Sulfate Exposure

Water- Soluble Sulfate

(SO4) in Soil, Percentage by Weight

Cement Type

Water- Cementitious

Materials Ratio, by Weight, Normal-Weight

Aggregate Concrete1 x 0.00689 for MPa

Negligible 0.00 - 0.10 -- -- -- Moderate2 0.10 - 0.20 II, IP(MS), IS

(MS)

0.50 or less 4,000 or more

Severe 0.20 - 2.00 V 0.45 or less 4,500 or more Very severe Over 2.00 V plus pozzolan3 0.45 or less 4,500 or more 1 A lower water-cementitious materials ratio or higher strength may be needed for low permeability or for protection against corrosion of embedded items or freezing and thawing (Table 4.2.2).

2 Seawater.

3 Pozzolan that has been evaluated by test or service record to improve sulfate resistance when used in concrete containing Type V cement.

Notwithstanding the sulfate test results and due to the limited number of chemical tests performed, as well as our experience with similar soil conditions and regional practice, we recommend that “Type II” cement be used for the construction of concrete structures at this site. Due to potential uncertainties as to the use of reclaimed irrigation water, or topsoil that may contain higher sulfate contents, pozzolan, or admixtures designed to increase sulfate resistance may be considered.

The concrete should have a water-cementitious materials ratio no more than 0.50 by weight for normal weight aggregate concrete. The structural engineer should select the concrete design strength based on the project specific loading conditions. However, higher strength concrete may be selected for increased durability, resistance to slab curling and shrinkage cracking. Concrete mix design for drilled shaft foundations should follow ADOT Standard

Specifications Section 609.

600587022R 21

9.10. Site Drainage

Positive surface drainage should be provided to divert water away from the roadway.

Surface water should not be permitted to drain toward the road. Erosion protection (e.g.

vegetation, etc.) should be utilized on the sides of the roadway embankment to protect the roadway from water damage.

9.11. Pre-Construction Conference

We recommend that a pre-construction conference be held. Representatives of the owner, civil engineer, the geotechnical consultant, and the contractor should be in attendance to discuss the project plans and schedule. Our office should be notified if the project description included herein is incorrect, or if the project characteristics are significantly changed.

9.12. Construction Observation and Testing

During construction operations, we recommend that a qualified geotechnical consultant perform observation and testing services for the project. These services should be performed to evaluate exposed subgrade conditions, including the extent and depth of overexcavation, to evaluate the suitability of proposed borrow materials for use as fill and to observe placement and test compaction of fill soils. If another geotechnical consultant is selected to perform observation and testing services for the project, we request that the selected consultant provide a letter to the owner, with a copy to Ninyo & Moore, indicating that they fully understand our recommendations and that they are in full agreement with the recommendations contained in this report. Qualified subcontractors utilizing appropriate techniques and construction materials should perform construction of the proposed improvements.

10. LIMITATIONS

The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care

600587022R 22 exercised by geotechnical consultants performing similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document.

This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant perform an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing.

Our conclusions, recommendations, and opinions are based on an analysis of the observed site conditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified and additional recommendations, if warranted, will be provided upon request. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control.

600587022R 23

This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

11. REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 2002, Standard Specifications for Highway Bridges, 17th Edition.

American Concrete Institute, 1991a, Guidelines for Concrete Floor and Slab Construction (ACI 302.1R).

American Concrete Institute, 1991b, Guidelines for Residential Cast-in-Place Concrete Construction (ACI 332R).

American Society for Testing and Materials (ASTM), 2010 Annual Book of ASTM Standards.

Arizona Department of Transportation 2008 Standard Specifications for Road and Bridge Construction.

Arizona Department of Water Resources (ADWR). Drillers logs in file.

Euge, K.M., Schell, B.A., and Lam, I.P., 1992, Development of Seismic Acceleration Contour Maps for Arizona: Arizona Department of Transportation Report No. AZ 92-344: dated September.

International Code Council, 2006, International Building Code.

Kamilli, R.J., Richards, S.M., editors, 1998 Geologic Highway Map of Arizona: Tucson, Arizona Geological Society and Arizona Geological Survey, 1 sheet containing text and figures.

Scale 1:1,000,000.

Ninyo & Moore, In-house proprietary information.

Pearthree, P.A., 1998, Quaternary Fault Data and Map for Arizona: Arizona Geological Survey, Open-File Report OFR 98-24.

United States Geological Survey, 1991, Casner Butte, Coconino County, 7.5 Minute Series (Topographic): Scale 1" = 2,000'.

United States Geological Survey, 2008, National Seismic Hazard Mapping Project, World Wide Web, http://earthquake.usgs.gov/research/hazmaps/.

Weir, G.W. et. al, 1986, Preliminary Geologic Map of the Sedona 30’ x 60’ Quadrangle, Yavapai and Coconino Counties, Arizona United States Geological Survey, Open-File Report OF- 86-164, scale 1:100000.

AERIAL PHOTOGRAPHS

Source Date

USGS 2003, 2007

SITE LOCATION

FIGURE

1DATE:

2/11 file no: 0587vmap1110

PROJECT NO:

600587022 COCONINO NATIONAL FOREST, ARIZONA

JUNCTION WASH BRIDGE

Ap p ro x i ma te Sca l e :

1 i n ch = 20 0 0 f e e t

Note: All dimensions, directions and locations are approximate.

N

Source: US Geological Survey, 7.5-minute topographic map, Casner Butte, Arizona, map rev. 1965.

APPROXIMATE

SITE LOCATION

Ap p ro x i ma te Sca l e :

1 i n ch = 40 f e e t fil e n o b lm

BORING LOCATION MAP

FIGURE

2DATE:

2/11

N

PROJECT NO:

600587022 COCONINO NATIONAL FOREST, ARIZONA

JUNCTION WASH BRIDGE

Source: Basemap modified after Great West Engineering, 8/9/10.

Note: All dimensions, directions, and locations are approximate.

LEGEND

Boring LocationB-2

B-2

B-1 B-2 file no: 0587dtl1110

RETAINING WALL

DRAINAGE GUIDELINES

FIGURE

SOIL BACKFILL COMPACTED

PER REPORT

NOT TO SCALE

OUTLET

4-INCH-DIAMETER PERFORATED

SCHEDULE 40 PVC PIPE OR EQUIVALENT

INSTALLED WITH PERFORATIONS DOWN;

1% GRADIENT OR MORE TO A SUITABLE

3/4-INCH OPEN-GRADED GRAVEL WRAPPED

IN AN APPROVED GEOFABRIC.

3 INCHES

WALL FOOTING

FINISHED GRADE

RETAINING WALL

12 INCHES

V A

R

IE

S

12 INCHES

6 INCHES OR MORE

GEOFABRIC

NOTE:

IN LIEU OF THE WRAPPED OPEN-GRADED GRAVEL, A GEOCOMPOSITE

DRAINAGE MAT ATTACHED TO THE WALL AND DISCHARGING INTO THE

DRAIN PIPE OR WEEP HOLES MAY BE CONSIDERED.

PROJECT NO:

600587022

JUNCTION WASH BRIDGE

COCONINO NATIONAL FOREST, ARIZONA

DATE:

2/11 fil e n o d tl1 b

DOWNWARD AXIAL CAPACITY CHART

FIGURE

4DATE:

2/11

PROJECT NO:

600587022 COCONINO NATIONAL FOREST, ARIZONA

JUNCTION WASH BRIDGE

ALLOWABLE DOWNWARD CAPACITY FOR SINGLE DRILLED SHAFT

JUNCTION WASH BRIDGE

YAVAPAI COUNTY, ARIZONA

0 500 1000

Allowable Downard Axial Capacity for Single Isolated Drilled Shaft (kips)

D e p th B e lo w E x is ti n g G ro u n d

S u rf a c e

(F e e t)

3' Shaft

4' Shaft

5' Shaft

Note: Axial group reduction factor must be applied to the results of this chart as discussed in our report.

APPENDIX A

BORING LOGS

Field Procedure for the Collection of Disturbed Samples Disturbed soil samples were obtained in the field using the following methods.

Bulk Samples Bulk samples of representative earth materials were obtained from the exploratory borings.

The samples were bagged and transported to the laboratory for testing.

The Standard Penetration Test Spoon Disturbed drive samples of earth materials were obtained by means of a Standard Penetration Test spoon sampler. The sampler is composed of a split barrel with an external diameter of 2 inches and an unlined internal diameter of 1-3/8 inches. The spoon was driven up to 18 inches into the ground with a 140-pound hammer free-falling from a height of 30 inches in general accordance with ASTM D 1586. The blow counts were recorded for every 6 inches of penetration; the blow counts reported on the logs are those for the last 12 inches of penetration. Soil samples were observed and removed from the spoon, bagged, sealed, and transported to the laboratory for testing.

Field Procedure for the Collection of Relatively Undisturbed Samples Relatively undisturbed soil samples were obtained in the field using the following method.

The Modified Split-Barrel Drive Sampler The sampler, with an external diameter of 3.0 inches, was lined with 1-inch long, thin brass rings with inside diameters of approximately 2.4 inches. The sample barrel was driven into the ground with a 140-pound hammer free-falling from a height of 30 inches in general accordance with ASTM D 1586. The samples were removed from the sample barrel in the brass rings, sealed, and transported to the laboratory for testing.

M AJOR DIVISIONS TYPICAL NAM ES

GW W ell graded gravels or gravel-sand mixtures, little…