AZ_FTNP_PEFO_10(7)_Bridges_Final_Geotechnical_Report_2019-09-06.pdf

FINAL

Geotechnical Engineering Report

Bridge Nos. 8430 007P, 8430 008P and 8430 009P

AZ FTNP PEFO 10(7) – Main Park Road

Petrified Forest National Park

Apache County, Arizona

Yeh Project No.: 218-355

September 6, 2019

Prepared for:

Jacobs Engineering Group, Inc.

Attn: Mr. Jim Mills, P.E.

717 17th St, Suite 2750

Denver, CO 80202

Prepared by:

Yeh and Associates, Inc.

570 Turner Drive, Suite D Durango, Colorado 81303

Phone: 970-382-9590 Fax: 970-382-9583

MTalvitie Rectangle i

Table Of Contents

1. PURPOSE AND SCOPE OF STUDY

1.1 PURPOSE OF WORK

1.2 SCOPE OF WORK

2. PROPOSED CONSTRUCTION

3. GEOLOGIC SETTING AND SITE CONDITIONS

3.1 SURFICIAL DEPOSITS

3.2 BEDROCK

4. SUBSURFACE INVESTIGATION

4.1 FIELD EXPLORATION

4.2 LABORATORY TESTING

5. SUBSURFACE CONDITIONS

5.1 BRIDGE 7 – APPROXIMATE MILE POST 19.44

5.2 BRIDGE 8 – APPROXIMATE MILE POST 16.55

5.3 BRIDGE 9 – APPROXIMATE MILE POST 15.97

5.4 ALLUVIAL CHANNELS

5.5 GROUNDWATER

6. BOX CULVERT FOUNDATION RECOMMENDATIONS

7. BRIDGE FOUNDATION DESIGN RECOMMENDATIONS

7.1 DRIVEN H-PILE RECOMMENDATIONS

7.1.1 DRIVEN H-PILE AXIAL RESISTANCE

7.1.2 DRIVEN H-PILE AXIAL RESISTANCE FACTORS

7.1.3 DRIVEN H-PILE LATERAL RESISTANCE

7.1.4 GENERAL DRIVEN H-PILE RECOMMENDATIONS

7.2 DRILLED SHAFT RECOMMENDATIONS

7.2.1 DRILLED SHAFT NOMINAL AXIAL RESISTANCE

7.2.2 DRILLED SHAFT AXIAL RESISTANCE FACTORS

7.2.3 DRILLED SHAFT LATERAL RESISTANCE

7.2.4 GENERAL DRILLED SHAFT RECOMMENDATIONS

8. LATERAL EARTH PRESSURES

9. OTHER DESIGN CONSIDERATIONS

9.1 SOIL CORROSIVITY TEST RESULTS

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9.2 SEISMIC CONSIDERATIONS

10. LIMITATIONS

11. REFERENCES

APPENDICES

List Of Figures

FIGURE 1 - PROJECT LOCATION

FIGURE 2 - GEOLOGIC MAP, FROM MARTZ, ET AL., 2012

FIGURE 3 - GEOLOGIC UNITS, FROM MARTZ, ET AL., 2012

List Of Tables

TABLE 4-1. BORING SUMMARY

TABLE 6-1. LPILE PARAMETERS

TABLE 6-2. RECOMMENDED NOMINAL DRILLED SHAFT AXIAL RESISTANCE

TABLE 6-3. ESTIMATED TOP OF MEDIUM HARD BEDROCK ELEVATIONS

TABLE 8-1. CHEMICAL TEST RESULTS

TABLE 8-2. SEISMIC DESIGN PARAMETERS FOR SITE CLASS B (REFERENCE SITE CLASS)

TABLE 8-3. SEISMIC DESIGN PARAMETERS FOR SITE CLASS D

List Of Appendices

BRIDGE GEOLOGY AND EXPLORATORY BORING LOCATION MAPS .......................................... A

FIELD EXPLORATION LEGEND AND BORING LOGS ................................................................... B

LABORATORY TEST RESULTS .................................................................................................. C

USGS SEISMIC OUTPUT .......................................................................................................... D

DRILLING PHOTOS ................................................................................................................. E

Final Geotechnical Engineering Report, Bridge Nos. 8430 007P, 008P and 009P YA Project No. 218-355 AZ FTNP PEFO 10(7) Main Park Road September 6, 2019

1. PURPOSE AND SCOPE OF STUDY

This report presents the results of the Yeh and Associates, Inc. (Yeh) geotechnical engineering investigation for the proposed replacement of three bridges on the Main Park Road in Petrified

Forest National Park. Yeh has performed the work for the Federal Highway Administration, Central Federal Lands Highway Division; as a subconsultant to Jacobs Engineering Group, Inc.

(Jacobs). The study was performed in accordance with your notice to proceed authorized by your Subconsultant Agreement, executed October 16, 2018; and with Yeh’s Geotechnical

Investigation Plan, dated October 22, 2018.

1.1 Purpose of Work

The purpose of this report is to provide geotechnical investigation results and engineering recommendations for use by Jacobs and the project team for the design of three replacement bridges along the Main Park Road within Petrified Forest National Park. At the time of our field investigation the existing bridges, which are constructed as multi-cell box culverts, were proposed to be replaced with bridge structures having one or two spans. More recent plans provided by Jacobs show the proposed replacement structures will be multi-cell pre-cast concrete box culverts. This report provides foundation recommendations for the replacement box culverts as well as for the originally proposed replacement bridge structures and a discussion of the geotechnical engineering considerations for design and construction. The report includes locations and logs of the exploratory borings and results of the laboratory testing.

1.2 Scope of Work

Our scope of work included the following:

• Drilling six (6) Geotechnical borings to obtain subsurface information near the proposed bridge abutments. One boring was drilled at each abutment of the three bridges.

• Performing laboratory tests on select soil and bedrock samples collected during the subsurface investigation to determine the engineering characteristics of the on-site soils and bedrock.

• Preparing a report that:

o Summarizes field and laboratory data o Presents the results of geotechnical engineering analyses o Provides recommendations for earthwork, structure foundations, slopes, and material sources

2. PROPOSED CONSTRUCTION

The proposed project includes replacement of three existing roadway bridges (multi-cell box culverts) within Petrified Forest National Park. The project is located in Apache County in northeastern Arizona, approximately 23 miles east of the town of Holbrook along Interstate 40

(I-40) and between 15 and 20 miles south of I-40 on the Main Park Road. The project location is shown in Figure 1. The bridges are identified by number as 8430 007P, 8430 008P, and 8430

009P from south to north. Throughout this report, the structures will be referred to as Bridges 7, 8 and 9, respectively.

The existing two lane bridges were constructed in approximately 1933, as indicated by the

National Park Service, and consist of cast-in-place multi-cell concrete box culverts on shallow foundations. Bridges 7 and 9 are approximately 55 feet long, and have 5 cells; Bridge 8 is approximately 100 feet in length and consists of 9 cells. The existing box culverts will be replaced with pre-cast box culverts.

The proposed replacement box culverts at Bridges 8 and 9 will have 6 cells, each approximately

18.7 feet long for total lengths of approximately 112.5 feet. At Bridge 7 the new box culvert will have 5 cells of similar size for a total length of approximately 94 feet. The box culverts will have wingwalls at each corner and 5-foot deep cut-off walls along the upstream and downstream sides. The cut-off walls will extend beyond the ends of the box culverts under wingwall locations.

Preliminary plans showed proposed new bridges as single-span structures at Bridges 7 and 9, and a two-span structure at Bridge 8. The bridges would have approximately the same dimensions as the existing box culverts with lengths ranging from approximately 55 feet to 100 feet. Wingwalls were proposed at each corner of the bridges.

Figure 1 - Project Location

3. GEOLOGIC SETTING AND SITE CONDITIONS

The project is located within Petrified Forest National Park, in Apache County, Arizona. The three bridges lie within the U.S. Geological Survey (USGS) 7.5-minute quadrangle entitled

Adamana, AZ (USGS, 2018). Surficial geology of the area is described in the Geologic Map of

Petrified Forest National Park, Arizona and its associated report (Martz, et al., 2012). A portion of the map is presented in Figure 2, and Geologic Units are depicted in Figure 3. Average annual rainfall is approximately 10 inches, with occasional snow falling during the winter months. Ground elevations at the bridge sites range from approximately 5390 feet to 5485 feet above mean sea level.

3.1 Surficial Deposits

Surficial materials within the project vicinity consist of Quaternary dunes and sand sheets (Qd) and alluvium (Qsu). The bridge sites, including the channels they cross, are located on areas

N mapped as Qsu, Quaternary surficial deposits, undifferentiated. Martz, et al., 2012, partially describe the unit as follows:

Unconsolidated sand, silt, mud, and gravel; includes alluvial surfaces (slopewash and sheet-flow deposits), active stream channels (ephemeral and perennial), colluvium, floodplain deposits, and in-situ soil development.

The existing bridges span broad, low-angle ephemeral stream beds. The streams are generally dry, but during storm events, such as late summer “monsoons”, they can carry high flows of water capable of transporting larger sediments, and even cobble to boulder sized material.

The Main Park Road closely follows the natural terrain, and the roadbed appears to have been constructed by excavating native materials from the ditches to build up the roadway embankment. At bridge locations, short lengths of embankment appear to have been constructed into the channel in order to reduce the length of bridge required.

3.2 Bedrock

Mapped geologic units in the project vicinity include the Blue Mesa Member (Trcbm) and lower beds of the Sonsela Member of the Late Triassic Chinle Formation. Regionally, the sedimentary layers generally dip to the northeast at 1 to 2 degrees. The Blue Mesa Member is composed of mudstone with minor siltstone and sandstone with abundant wood and vertebrate fossils. The

Sonsela member, consisting of sandstone and mudstone with minor siltstone and conglomerate, is subdivided into beds based on age and visual and physical attributes. Three lower Sonsela beds are mapped within the project vicinity: the Camp Butte (Trcscb), Lot’s Wife (Trcslw) and

Rainbow Forest (Trcsrf) beds.

Figure 2 - Geologic Map, from Martz, et al., 2012

Bridge 7

Bridge 8

Bridge 9

Figure 3 - Geologic Units, from Martz, et al., 2012

4. SUBSURFACE INVESTIGATION

4.1 Field Exploration

Subsurface conditions within the project area were explored on November 5, 6 and 7, 2018.

Borings were drilled near the abutments of each of the three existing bridges. A truck-mounted

CME 75 drill rig was used to advance the borings using a hollow-stem auger. The drilling subcontractor was Enviro-Drill, Inc. of Albuquerque, New Mexico. Traffic control was provided by the Flagstaff Division of Quail Construction, LLC of Yuma, Arizona. Yeh’s contact with the

National Park Service was Kevin Dowell, Facility Manager for Petrified Forest National Park. Mr.

Dowell identified areas for which underground utilities needed to be located prior to commencement of drilling activities.

Locations of the borings were measured in the field from nearby site features; and approximate coordinates and elevations for the borings were recorded using a hand-held GPS unit. The locations of the exploratory borings are shown on the Log of Test Borings plan sheets in

Appendix A. A summary of the boring locations and depths is provided in Table 4-1. Boring

Logs are included in Appendix B; photographs of the drilling operations are included in

Appendix E.

Table 4-1. Boring Summary

Bridge Boring Number

Elevation (feet)

Depth (feet)

Approximate Mile Post Location

BR7-1 5483 41.7 19.439 NB Lane N of Existing Bridge 8430 007P BR7-2 5482 37.0 19.452 SB Lane S of Existing Bridge 8430 007P

BR8-1 5401 40.0 16.539 NB Lane N of Existing Bridge 8430 008P BR8-2 5401 38.4 16.558 SB Lane S of Existing Bridge 8430 008P

BR9-1 5391 51.3 15.964 NB Lane N of Existing Bridge 8430 009P BR9-2 5391 47.0 15.975 SB Lane S of Existing Bridge 8430 009P

Bulk samples of material from the stream channels were collected by hand excavation. Soil and bedrock samples were recovered from the borings during drilling. Samples were collected from auger cuttings and at intermittent depths utilizing either a standard 2 inch O.D. split spoon sampler, or a 2.5 inch O.D. “Modified California” sampler. The samplers were advanced by a

140 pound automatic hammer with a 30 inch drop height. The number of blows required to drive the sampler 12 inches, or a fraction thereof, after an initial penetration of 6 inches for the standard sampler, constitutes the N-value as shown on the boring logs. N-values can be correlated to the relative density of cohesionless soils and consistency of cohesive soils.

Soft bedrock conditions within the Chinle Formation prevented the use of wireline coring. A typical wireline coring operation consists of a two part system. A casing with a cutting head is advanced into the rock, and the lead cutting section contains an inner sample barrel that incases the rock core. The inner barrel can be retrieved with a unique cable line and a spring loaded assembly that is lowered through the casing and attaches to the inner sample barrel. In all coring operations the cutting head must be cooled, and the cuttings need to be flushed out of the boring. This can be achieved with the circulation of water through the casing, or by injecting air. In either case, the drilling fluid, or air, that is injected needs to be able to pass completely through the system.

The composition of the rock in the Chinle Formation is fine grained mudstone and claystone.

When this type of rock is cored with water or air as the drilling fluid, the cuttings are very fine clay sized partials that can easily clog the coring system, blocking off the air or water circulation to the cutting head, especially if any ground water or wet soil conditions are encountered. Moist to wet soils were present at the bridge locations. During our attempt to core using air as a coolant, the barrel circulation was almost immediately blocked off and the core barrel could not be advanced. Due to the soft composition of the rock, it was decided that the use of water to cool and flush the system would substantially degrade the core samples. Therefore, wire-line core samples of the bedrock were not obtained from the borings.

4.2 Laboratory Testing

Samples recovered during the subsurface investigation were transported to Yeh’s laboratory in

Durango, Colorado. The samples and field logs of the borings were reviewed by the Project

Engineer and a program of laboratory testing was assigned. Specialized testing for soil corrosivity was performed by Green Analytical Laboratories of Durango, Colorado. Unconfined

Compressive Strength tests on bedrock were performed at Yeh’s Denver, Colorado laboratory.

The laboratory tests were performed on selected samples from the borings in general accordance with the American Association of State Highway and Transportation Officials

(AASHTO) and American Society of Testing and Materials (ASTM) procedures. Laboratory tests on samples included sieve analysis, Atterberg limits, natural moisture content, dry density, swell/consolidation, and unconfined compressive strength. In addition, selected samples were subjected to chemical analyses to evaluate soil corrosivity: pH, water-soluble sulfate content, water-soluble chloride content and resistivity. The laboratory test results are included in

Appendix C and are shown on the boring logs in Appendix B.

Results from the Atterberg limits determination and sieve analysis were used to classify the soils according to AASHTO and the Unified Soil Classification System (USCS) standards. Atterberg limits were performed in general accordance with AASHTO T89 and T90, and sieve analyses were performed in general accordance with ASTM D421. Soil classifications are shown on the boring logs in Appendix B and on the summaries in Appendix C.

The moisture content and density of a soil can be useful for characterizing a soil’s consistency, compressibility, and strength. High moisture contents can also be an indicator of the recent depth to groundwater. Dry density tests and moisture content tests were performed in general accordance with ASTM D2937 and ASTM D2216, respectively.

Three (3) swell/consolidation tests were performed to determine the swell or collapse potential of selected samples of the subsurface materials in general accordance with ASTM D4546

Procedure B. The swell was measured by applying a surcharge of either 200 pounds per square foot (psf), 500 psf or 1,000 psf to the samples and adding water. Appendix C presents a summary and graphical results of the swell/consolidation test results. The test results also appear on the applicable boring logs in Appendix B.

Unconfined compressive strength tests were conducted on three (3) samples obtained using a

Modified California sampler. The tests were performed in general conformance with ASTM D

2166. Unconfined compressive strength test results are provided in Appendix C.

Five (5) samples were tested for chemical properties to evaluate the potential of the soil to be aggressive to concrete and to corrode buried metal. The tests included pH (ASTM D 4972 /

AASHTO T 289), soluble sulfate content (AASHTO T 290), and soil resistivity (AASHTO T 288).

Water-soluble chloride measurements (EPA 300.0) were performed by Green Analytical

Laboratories, Inc. The test results are summarized in Appendix C and presented on applicable boring logs in Appendix B.

5. SUBSURFACE CONDITIONS

Exploratory borings were drilled through the existing roadway surface. Beneath the pavement the borings encountered a layer of embankment fill or surficial deposit consisting of clayey sand

1 0 to depths ranging from 7 to 26 feet. Sedimentary strata of the Chinle Formation were encountered beneath the sand. This formation consists of interbedded mudstone and sandstone, and should be considered an Intermediate Geomaterial (IGM), as defined in the

AASHTO Load Resistance Factor Design Bridge Design Specifications, 8th Edition, 2017

(AASHTO LRFD).

Moisture content in the unconsolidated surficial deposits tended to increase with depth, transitioning from “dry” or “damp” near the surface to “wet” near the contact with the Chinle

Formation. Free moisture, indicating saturated conditions, was not observed in the borings. Wet soil conditions are likely due to groundwater previously perched at or above the bedrock surface.

5.1 Bridge 7 – Approximate Mile Post 19.44

Borings BR7-1 and BR7-2 were drilled behind the existing north and south abutments of this structure to depths of 41.7 and 37.0 feet, respectively. The measured asphalt pavement thickness was 6 inches at both locations.

At Boring BR7-1, the pavement was underlain by clayey sand with a trace of gravel to a depth of

11 feet. The upper 6 feet of this zone appears to be embankment fill, constructed from the on-site materials which comprise the lower portion of the layer. Because of the similar properties of the fill and native soils, it was difficult to determine the depth of fill. Penetration resistance N values in this layer ranged from 27 to 36 blows per foot (bpf) using the split-spoon sampler. At

Boring BR7-2, a layer of road base approximately 6 inches thick was encountered directly beneath the pavement. This was underlain by a layer of silty sand with some gravel and scattered cobbles to a depth of 7 feet. The sand layers encountered in both borings were damp and medium dense to dense. One bulk sample of the sand was tested for purposes of classification. Gradation test results show the soil has 37 percent fines (passing the No. 200 standard sieve) with the remaining percentage as sand and a trace amount of gravel. The

Plasticity Index was 22. The AASHTO classification was A-7-6 (3); using the Unified Soil

Classification System (USCS), the soil is a clayey sand (SC).

The sand was underlain in Borings BR7-1 and BR7-2 by sedimentary strata of the Chinle

Formation, encountered at depths of 11 feet in Boring BR7-1 and 7 feet in Boring BR7-2. N values in this deposit ranged from 29 bpf to 50 blows for 4 inches penetration. Natural moisture contents were between 14.0 and 23.3 percent, and the dry density ranged from 90.4 to 101.4

1 1 pounds per cubic foot (pcf). One bulk sample of the bedrock obtained from auger cuttings was tested for index properties. The sample had 53% sand and 47% fines, with a Plasticity Index of

39. The results of swell/consolidation for a Modified California sample of bedrock from Boring

BR7-1 at a depth of 20 feet indicate +2.7% (swell). Unconfined compressive strength of the bedrock was measured at 6,285 pounds per square foot (psf) for one Modified California sample from Boring BR7-1 from a depth of 25 feet.

Corrosivity properties were evaluated for one sample of the clayey sand fill. The pH was 9.6, water-soluble sulfate was 0.155%, chlorides were measured at 0.0336%, and the resistivity was

500 ohm-cm. One sample of the Chinle Formation bedrock was tested for corrosive potential;

the pH was 9.2, water-soluble sulfate was 0.340%, the chloride content was 0.00158%, and the resistivity was 700 ohm-cm.

5.2 Bridge 8 – Approximate Mile Post 16.55

Borings BR8-1 and BR8-2 were drilled behind the existing north and south abutments of Bridge

8 to depths of 40.0 and 38.4 feet, respectively. The recorded asphalt pavement thickness was between 5 and 6 inches; beneath the pavement was 12 inches of aggregate base course.

At Boring BR8-1, the base course was underlain by clayey sand fill and dense native clayey sand with a trace of gravel to a depth of 10.5 feet. The N value for this dense layer was 50 blows per 2 inches using the split-spoon sampler. The high N value may be due to cobbles or boulders encountered by the sampler. At Boring BR8-2, the base course was underlain by a layer of dry, dense, silty sand embankment fill to a depth of approximately 7.0 feet. Two feet of wet, loose to medium dense silty sand was encountered beneath the fill. One bulk sample from

Boring BR8-1 was tested for purposes of classification. Gradation test results show the material has 36 percent clayey fines (passing the No. 200 standard sieve) with the remaining percentage as sand and a trace amount of gravel. The Plasticity Index was 12, and the AASHTO classification was A-6 (0). Using the USCS, the material is classified as a clayey sand (SC).

The sand was underlain in Borings BR8-1 and BR8-2 by the Chinle Formation bedrock. N values in this deposit ranged from 42 bpf to 50 blows for 4 inches. Two split spoon samples of bedrock from Boring BR8-2 were crushed in the laboratory and tested for purposes of classification. At a depth of 10 feet below the surface, the material had 58% fines and 42% sand, with a Plasticity Index of 26. At 31 feet, the fines content was 73 percent and the Plasticity

Index was 49. Natural moisture contents in the Chinle Formation bedrock were between 20.1

1 2 and 27.5 percent at Boring BR8-1 and from 16.0 to 16.2 percent at Boring BR8-2. The dry density ranged from 88.8 to 96.3 pcf. One sample of the bedrock was tested for swell/consolidation, and the result was +0.6% (swell). Unconfined compressive strength was measured for one sample of bedrock from Boring BR8-1. The result of 2,516 psf was significantly lower than anticipated and the shape of the stress-strain curve generated from the test indicates that the sample may have been disturbed during the sampling process.

Potential soil corrosivity was evaluated for one clayey sand sample. The pH was 9.5, water-soluble sulfate was 0.115%, chlorides were measured at 0.0156%, and the resistivity was 560 ohm-cm. One sample of auger cuttings from the Chinle Formation was tested to evaluate corrosive potential; the pH was 9.6, water-soluble sulfate was 0.235%, the chloride content was

0.00197%, and the resistivity was 360 ohm-cm.

5.3 Bridge 9 – Approximate Mile Post 15.97

Borings BR9-1 and BR9-2 were drilled behind the existing north and south abutments of Bridge

9 to depths of 51.3 and 47.0 feet, respectively. The measured asphalt pavement thickness was

5 inches. Beneath the pavement was a layer of aggregate base course ranging from 8 to 10 inches in thickness.

At Boring BR9-1, the base course was underlain by damp silty sand embankment fill, with a trace of gravel, to a depth of 4.0 feet. Beneath the fill the boring encountered approximately 22 feet of native wet silty sand with a layer of sandy silt at 14 to 16 feet. The N value for this material using the split-spoon sampler ranged from 35 bpf at 5 feet to 5 bpf at a depth of 20 feet.

At Boring BR9-2, the base course was underlain by damp to wet, medium dense to loose, silty sand to a depth of approximately 25.5 feet. Two bulk samples from the silty sand layer were tested for purposes of classification. Gradation test results show the material has 12 to 19 percent fines, with the remaining percentage as sand and a trace amount of gravel. The

Plasticity Index ranged from 6 to 12, and the AASHTO classification was A-2-4 (0) and A-2-6

(0). Using the USCS, the samples were classified as SM-SC and SP-SC.

The borings at Bridge 9 encountered bedrock of the Chinle Formation at depths of 25.5 to 26.0 feet below the ground surface. N values in this deposit increased with depth from 16 bpf to 50 blows for 5 inches. One bulk sample of auger cuttings from Boring BR9-2 was tested for index properties. At a depth of 30 feet below the surface, the bedrock material had 45% fines and

50% sand, with a trace of gravel. The Plasticity Index was 12. Natural moisture contents in the

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Chinle Formation were between 17.0 and 22.0 percent, and dry densities ranged from 103.3 to

108.3 pcf. One sample, from Boring BR9-2 at 45 feet, was tested for swell/consolidation, and the result was +4.8% (swell). An unconfined compressive strength of 6,533 psf was measured for one sample from Boring BR9-1 at 30 feet depth.

Soil corrosivity potential was evaluated for one sample of the Chinle Formation at Bridge 9; from

Boring BR9-2 at a depth of 30 to 35 feet. The pH of the sample was 9.4, water-soluble sulfate content was 0.180%, chloride content was 0.0382%, and resistivity was 460 ohm-cm.

5.4 Alluvial Channels

Bulk samples of streambed materials were collected by hand from the alluvial channels upstream and downstream of Bridges 7, 8 and 9. Natural moisture contents were between 11 and 20 percent, with the exception of downstream of Bridge 9, which measured 4 percent.

Gradations for the samples were similar. Gravel content was between 1 and 11 percent, and the percentage of fines ranged from 1 to 10 percent. Results of Atterberg Limits testing indicate that all of the samples were non plastic. AASHTO classifications were A-1-b (0) and A-3 (0). The soils were classified as poorly sorted sands or silty sands, SP or SP-SM, using the USCS method.

5.5 Groundwater

Groundwater was not encountered in the borings at the time of drilling. Groundwater conditions in the study area may vary throughout the year. Precipitation events of sufficient magnitude to cause flow to occur in the ephemeral streams at the bridge sites are expected to saturate the alluvium on the channel floor. Due to the granular nature of the alluvium, flows will continue to move downgradient beneath the surface after the storm event passes.

The fine-grained, flat-lying mudstones and clayey sandstones of the Chinle Formation are expected to have relatively low permeability. Moisture contents in surficial deposits overlying the bedrock may be elevated after seasonal precipitation events.

6. BOX CULVERT FOUNDATION RECOMMENDATIONS

Concrete box culverts (CBCs) are proposed to replace the existing CBCs that serve as bridges on the Main Park Road. We understand that each of the existing structures is likely to be replaced with a series of pre-cast concrete box culvert cells spanning the channel. We expect

1 4 that the individual box culvert cells will be rigidly interconnected so that the structures are similar to a large, single raft-type spread footing supported at shallow depth. The CBCs will have relatively light foundation loads. The potential total and differential settlements will control the foundation design for the CBCs (Service Limit State Design). The loose to medium dense clayey to silty sand soils encountered in the borings will settle under the relatively light loads due to the replacement CBCs and the anticipated traffic loads. Analysis shows the bearing soils can provide relatively high nominal bearing resistance for footings with dimensions of the proposed CBCs. The nominal resistance is much less when potential movements at the service limit state are considered. Recommendations for box culvert foundations are presented below.

1. Box culverts should be constructed on properly placed native soil or Structural Backfill that is in compliance with Section 704 of the current Standard Specifications for Road and Bridge Construction on Federal Highway Projects (FP-14). The upper 6 inches of native soils under the CBCs should be moisture conditioned and compacted prior to placing the pre-cast cells. Unsuitable materials, such as wet soils or soft clay soils, encountered at foundation level should be removed and replaced with compacted on-site soils or Structural Backfill in accordance with Section 208 of FP-14.

2. Where the bottoms of the CBCs will be within 2 feet of the bedrock, the upper portion of the bedrock should be removed and replaced with Structural Backfill so that the entire

CBC bears on at least 2 feet of native soil or Structural Backfill.

3. Using design criteria from AASHTO LRFD, a nominal bearing resistance of qn = 1.5 ksf should be used for the shallow spread footing foundations supporting the CBCs. This assumes a minimum effective CBC width of 33 feet. A resistance factor of 1.0, per

Section 10.5.5.1 in AASHTO LRFD should be applied to the nominal bearing resistance.

4. The factored bearing resistance is expected to result in less than 1 inch of total and differential settlements. The settlement is expected to occur immediately after placement of the CBCs due to the granular nature of the native soils and structural backfill.

5. Using design criteria from AASHTO LRFD, a coefficient of friction of 0.50 between native soil or Structural Backfill and pre-cast CBC cells should be used to calculate nominal sliding resistance. A resistance factor of ϕτ = 0.90 per Section 10.5.5.2.2 in AASHTO

LRFD should be applied to the nominal sliding resistance.

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6. Shallow spread footing foundations for the CBC wing walls should be protected from frost action. Footings should be placed a minimum of 2.0 feet below final grade to provide adequate frost protection.

7. Spread footings for wingwalls should be placed on a minimum thickness of 2 feet of

Structural Backfill that extends 2 feet beyond the outside edges the spread footings.

Wingwall footings placed on compacted Structural Backfill can be designed for a nominal bearing resistance of 5.0 ksf. A resistance factor of 0.45 should be used per Table

10.5.5.2.2-1 of AASHTO LRFD.

8. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures resulting from flow in the washes; adjacent roadways;

construction materials; and equipment.

7. BRIDGE FOUNDATION DESIGN RECOMMENDATIONS

Subsurface conditions at the sites of Bridges 7 and 8 consist of approximately 7 to 10.5 feet of loose to dense clayey and silty sand overburden soils over hard claystone/sandstone bedrock.

At Bridge 9, the loose clayey sand layer extends to a depth of 25.5 to 26 beneath the existing roadway surface.

Bearing resistance in the overburden soils will be relatively low and shallow foundations, such as spread footings, designed to support bridge loads will need to be relatively large and could experience unacceptable total and differential settlements. Deep foundations bearing in the bedrock will have high load carrying capacity and low potential for settlement. We recommend deep foundations for support of bridges.

The bridge abutments may be supported on driven H-piles or drilled shafts. Recommendations for driven piles are presented in Section 6.1 and drilled shaft recommendations are provided in

Section 6.2.

Soil and bedrock properties were estimated from penetration resistance, material descriptions, and laboratory data. The design and construction of the foundation elements should comply with all applicable requirements and guidelines listed in AASHTO LRFD.

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7.1 Driven H-Pile Recommendations

7.1.1 Driven H-Pile Axial Resistance

Steel H-piles driven into bedrock may be designed for a nominal axial resistance equal to 30 kips per square inch (ksi) multiplied by the cross sectional area of the pile for piles composed of

Grade 50 ksi steel. Piles should be driven into the underlying bedrock to the limit of compressive driving stress as defined in FP-14. A wave equation analysis using the Contractor’s pile driving equipment is necessary to estimate pile drivability.

7.1.2 Driven H-Pile Axial Resistance Factors

Assuming a pile driving analyzer (PDA) is used to monitor pile driving, a resistance factor of

0.65 may be used per AASHTO LRFD Table 10.5.5.2.3-1. Per AASHTO LRFD recommendations, a resistance factor of 0.50 can be used for wave equation analysis only, without pile dynamic measurements such as PDA monitoring, but with field confirmation of hammer performance.

7.1.3 Driven H-Pile Lateral Resistance

The input parameters provided in Table 6-1 are recommended for use with the computer program LPILE to develop the soil models used to evaluate the driven H-pile response to lateral loading. Table 6-1 provides the estimated values associated with the soil types encountered in the borings. The parameters can also be used for drilled shafts, which will be described in

Section 6.2. The nature and type of loading should be considered carefully. The values in Table

6-1 may need to be revised for foundation elements that are relatively close to a retaining wall.

Individual soil layers and their extent can be averaged or distinguished by referring to the boring logs at the locations of the proposed foundations. The soils and/or bedrock materials prone to future disturbance, such as from utility excavations or frost heave, should be neglected in the lateral load analyses to the depth of disturbance, which may require more than but should not be less than 3 feet.

Recommendations for p-y multiplier values (Pm values) to account for the reduction in lateral capacity due to group effects are provided in Section 10.7.3.12 of AASHTO (2017). The Pm value will depend on the direction of the applied load, center-to-center spacing, and location of the foundation element within the group.

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Table 7-1. LPILE Parameters

Soil Type LPILE Soil Criteria

Effective Unit

Weight (pcf) Friction Angle, φ

(deg.)

Cohesion, c (psf)

Strain Factor, ε50 p-y modulus kstatic (pci)

AGT 1 BGT AGT BGT

Fill

Clayey, Silty and Gravelly Sands

Sand (Reese) 120 57.5 30 - - 25 20

Native Silty and Clayey

Sands and Gravels

Sand (Reese) 120 57.5 30 - - 25 20

Decomposed and Weathered

Claystone/Sandstone

Stiff Clay (Welch & Reese) 120 57.5 - 1000 0.008 - 100

Hard to Very hard Claystone/Sandstone

Bedrock

Stiff Clay w/o Free Water

(Welch & Reese) 125 125 - 8000 0.004 - -

Notes

(1) AGT is an abbreviation for above groundwater table, BGT is an abbreviation for below groundwater table.

7.1.4 General Driven H-Pile Recommendations

The following recommendations are for the design and construction of driven H-piles.

1. Based on the results of the field investigation and experience with similar properly constructed driven pile foundations, it is estimated that settlement will be less than approximately ½ inch when designed according to the criteria presented in this report.

2. A minimum spacing requirement for the piles should be three diameters (equivalent) center to center.

3. Driven piles should be driven with protective cast steel pile points or equivalent to provide better pile tip seating and to prevent potential damage from large size soil particles and hard bedrock layers which may be present at the site.

4. A qualified representative of a geotechnical engineer should observe pile-driving activities on a full-time basis. Piles should be observed and checked for crimping, buckling, and alignment. A record should be kept of embedment depths and penetration resistances for each pile.

5. It is estimated that the piles will penetrate approximately 10 to 15 feet into medium hard bedrock. The final tip elevations will depend on bedrock conditions encountered during driving.

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6. If the pile penetration extends below the estimated pile penetration into bedrock by 10 feet or more, the pile driving operations should be temporarily suspended for dynamic monitoring with PDA. We recommend that the subject pile be allowed to rest overnight or longer before restriking and monitoring the beginning-of-restrike with a PDA. The data collected with the PDA shall then be reduced using the software CAPWAP to determine the final nominal pile resistance. The pile driving criteria may be modified by the engineer based on the PDA/CAPWAP results.

7.2 Drilled Shaft Recommendations

7.2.1 Drilled Shaft Nominal Axial Resistance

The bearing resistance for drilled shafts should be developed from the side and tip resistance in the underlying bedrock, below the anticipated depth of scour. The side resistance from the overburden and embankment soil should be neglected due to the potential for scour. As described in Brown, et. al., Appendix B, the design approach in Abu-Hejleh et al. (2003) provides recommendations for the use of an updated Colorado SPT-based (UCSB) design method. In this design method, the nominal side and tip resistance of a drilled shaft in the sedimentary bedrock is proportional to the driven sampler penetration resistance. This approach was used to estimate the axial resistance in the bedrock. Based on practice in similar bedrock formations in Colorado, the modified California penetration resistance is considered to be equivalent to a standard penetration test (SPT) penetration resistance, i.e. N value, in bedrock.

Table 6-2 contains the recommended values for the nominal side and tip resistance for drilled shafts founded in the underlying medium hard bedrock. The upper three feet of bedrock penetration shall not be used for drilled shaft resistance due to the likelihood of construction disturbance and possible additional weathering. Bedrock above the depth of scour should also be neglected when calculating side resistance. The minimum spacing requirements between drilled shafts should be three diameters from center-to-center to account for axial group effects.

Table 7-2. Recommended Nominal Drilled Shaft Axial Resistance

Bridge 7 Bridge 8 Bridge 9

North South North South North South

Estimated Drilled Shaft Nominal Tip Resistance

Medium Hard Bedrock (ksf)

46.0 46.0 36.0 36.0 27.0 27.0

Estimated Drilled Shaft Nominal Side Resistance

Medium Hard Bedrock (ksf)

3.8 3.8 3.0 3.0 2.3 2.3

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Estimated elevations of medium hard bedrock at each proposed abutment are shown in Table

6-3.

Table 7-3. Estimated Top of Medium Hard Bedrock Elevations

Bridge 7 Bridge 8 Bridge 9

North South North South North South

Estimated Top of Medium Hard Bedrock (ft) 5468 5466 5386 5386 5356 5360

7.2.2 Drilled Shaft Axial Resistance Factors

Based on Section 10.5.5.2.4-1 in AASHTO LRFD, a resistance factor of 0.60 should be used for the side resistance and resistance factor of 0.55 should be used for the tip resistance.

Additionally, based on the recommendations in Section 10.5.5.2.4 in AASHTO LRFD, for the locations where there is a single drilled shaft, the side and tip resistance factors should be decreased by 20% because the foundation is considered non-redundant. Therefore, in locations where there is a single drilled shaft, a side resistance factor of 0.48 and a tip resistance factor of

0.44 should be used in design.

7.2.3 Drilled Shaft Lateral Resistance

The information provided previously in Section 6.1.3 can be used to evaluate the lateral resistance of drilled shafts.

7.2.4 General Drilled Shaft Recommendations

The following recommendations can be used in the design and construction of the drilled shafts.

1. Groundwater and potentially caving soils may be encountered during drilling depending on the time of year and location. Laboratory test results show elevated moisture contents in the overburden soils. This is an indication of fluctuating groundwater levels. The presence of groundwater may cause caving in the sand soils during drilled shaft construction. The Contractor shall construct the drilled shafts using means and methods that maintain a stable hole. Temporary casing seated in the bedrock mat be required to prevent caving and groundwater intrusion into drilled shafts prior to concrete placement.

2. Scattered cobbles and boulders were encountered in the borings at Bridges 7 and 8 and may be encountered in the overburden soils at all abutment and pier locations.

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3. Bedrock may contain very hard layers. The contractor should mobilize equipment of sufficient size and operating condition to achieve the required design bedrock penetration.

4. Drilled shaft construction shall not disturb previously installed drilled shafts. The drilled shaft concrete should have sufficient time to cure before construction on a drilled shaft within three shaft diameters (center to center spacing) begins to prevent interaction between shafts during excavation and concrete placement.

5. Based on the results of the field investigation and experience with similar properly constructed drilled shaft foundations, it is estimated that foundation settlement will be less than approximately ½ inch when designed according to the criteria presented in this report.

6. A representative of the geotechnical engineer should observe drilled shaft installation operations on a full-time basis.

8. LATERAL EARTH PRESSURES

External loads to be used in the analyses and design of CBCs, retaining walls, bridge abutments and wing walls should consist of earth pressure loads, traffic loads, and any other potential surcharge loads. Typical drainage details to create positive surface drainage away from retaining structures and prevent hydrostatic pressure buildup behind walls shall be included in the design. The drainage should be designed and constructed to properly contain and transfer surface and subsurface water without saturating the soil around the abutments, wing walls and other retaining structures.

All abutment and wall backfill material should meet the requirements for Structural Backfill in accordance with Section 704 of FP-14. All backfill adjacent to the abutments and retaining walls shall be placed and compacted in accordance with Section 208 of FP-14. It is recommended that compaction of backfill materials be observed and evaluated by an experienced geotechnical engineer or engineer’s representative.

A lateral abutment wall and retaining wall movement or rotation of approximately 0.1 to 0.2 percent of the wall height may be required to mobilize active earth pressure for the recommended backfill materials. If the estimated wall movement is less than this amount, an at-rest soil pressure should be used in design. In order to mobilize passive earth pressure, lateral

2 1 wall movement or rotation of approximately 1.0 to 2.0 percent of the wall height may be required for the recommended backfill materials. It should be carefully considered if this amount of movement can be accepted before passive earth pressure is used in the design.

Earth pressure loading within and along the backs of the CBC cells, bridge abutments, wing walls and other retaining structures will be controlled by the Structural Backfill. We recommend that active, at-rest, and passive lateral earth pressures used for the design of the structures be based on an effective angle of internal friction of 34 degrees, and a unit weight of 135 pounds per cubic foot (pcf) for Structural Backfill. The following coefficients can be used for design assuming a horizontal backslope:

• Active earth pressure coefficient (ka) of 0.28

• Passive earth pressure coefficient (kp) of 3.53

• At-rest earth pressure coefficient (k0) of 0.44

Lateral earth pressures for a non-horizontal backslope can be estimated using section 3.11 in

AASHTO LRFD. A resistance factor of 0.50 should be used when considering passive earth pressure from Structural Backfill to resist sliding or overturning.

Based on the plans provided, it appears that excavations for the cutoff walls at Bridges 7 and 8 will encounter clayey sandstone bedrock. If the cutoff walls are cast-in-place against the bedrock, the bedrock will provide passive earth pressure to resist sliding provided it is not subject to scour. The passive resistance can be calculated using a uniformly distributed passive earth pressure of 250 psf for the portion of the cutoff wall in bedrock.

9. OTHER DESIGN CONSIDERATIONS

9.1 Soil Corrosivity Test Results

Yeh performed chemical tests on samples obtained during the field investigation that are considered representative of soils encounter in the borings. The tests were performed to evaluate the potential for corrosion of buried metal and degradation of buried concrete. The test results can be found in Appendix C. Test results are summarized in Table 8-1.

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Table 9-1. Chemical Test Results

Water Soluble Sulfates

Water Soluble Chlorides pH Resistivity

0.115% to 0.340% 0.002% to 0.038% 9.2 to 9.6 360 to 700 ohm*cm

Based on the test results, and the rating system provided in FHWA Publication No. FHWA NHI-

16-072, Geotechnical Engineering Circular No. 5, Geotechnical Site Characterization (GEC 5) the soils and bedrock encountered at the site are expected to be severely corrosive to buried metal and concrete. A qualified corrosion engineer should review the laboratory data and boring logs to determine the appropriate level of corrosion protection for materials in contact with these soils. Sulfate resistant cement is recommended for concrete in contact with the on-site soils.

9.2 Seismic Considerations

No current active faults are known to exist in the immediate vicinity of the proposed bridges.

Based on the site class definitions provided in Table 3.10.3.1-1 of AASHTO (2017), the site can be categorized as a Site Class D. Based on the recommendations in Table 3.10.6-1 of AASHTO

(2017) the bridge site can be classified as a Seismic Zone 1.

The peak ground acceleration (PGA) and the short- and long- period spectral acceleration coefficients (Ss and S1, respectively) for a Site Class B (reference site class) were determined using the seismic design maps from the USGS website; the output is included in Appendix D.

The seismic design parameters for a Site Class B and Site Class D are shown in Tables 8-2 and

8-3, respectively.

Table 9-2. Seismic Design Parameters for Site Class B (Reference Site Class)

PGA (0.0 sec) SS (0.2 sec) S1 (1.0 sec)

0.048 g 0.105 g 0.034 g

Table 9-3. Seismic Design Parameters for Site Class D

As (0.0 sec) SDS (0.2 sec) SD1 (1.0 sec)

0.076 g 0.169 g 0.081 g

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10. LIMITATIONS

This report was prepared for the exclusive use of our client for use in design of the proposed construction. Within the limitations of the scope, schedule, and budget, the work presented in this report was performed in accordance with generally accepted principles and practices in this area at the time this report was prepared. We make no other warranty, either express or implied.

The classifications, conclusions, and recommendations submitted in this report are based on the data obtained from published and unpublished maps, reports, geotechnical analyses, and our exploratory borings. Our conclusions and recommendations are based on our understanding of the project as described in this report and the site conditions as interpreted from the explorations. This data may not necessarily reflect variations in the subsurface conditions and water levels occurring at other locations.

The nature and extent of subsurface variations may not become evident until excavation is performed. Variations in the data may also occur with the passage of time. If during construction, fill, soil, rock, or groundwater conditions appear to be different from those described in this report, this office should be advised immediately so we could review these conditions and reconsider our recommendations. If there is a substantial lapse of time between the submission of this report and the start of work at the site, or if conditions have changed because of natural forces or construction operations at or adjacent to the site, we recommend that this report be reviewed to determine the applicability of the conclusions and recommendations concerning the changed conditions or time lapse. We recommend on-site observation of foundation excavations and foundation subgrade conditions by an experienced geotechnical engineer or engineer’s representative.

The scope of work of this investigation did not include hazardous materials sampling or environmental sampling, investigation, or analyses. In addition, we did not evaluate the site for potential impacts to natural resources, including wetlands, endangered species, or environmentally critical areas.

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11. REFERENCES

AASHTO LRFD. AASHTO Load Resistance Factor Design (LRFD) Bridge Design Specifications, Eighth Edition. Washington, D.C.: American Association of State Highway and Transportation Officials, 2017.

Abu-Hejleh, N., O-Neill, M.W., Hanneman, D., Atwooll, W.J., 2003. Improvement of the Geotechnical Axial Design Methodology for Colorado’s Drilled Shafts Socketed in Weak Rocks, Final Report. Colorado Department of Transportation Research Branch, July 2003, Report No. CDOT-DTD-R-2003-6.

Brown, D.A., Turner, J.P. and Castelli, R.J., 2010. Geotechnical Engineering Circular No. 10 Drilled Shafts: Construction Procedures and LRFD Design Methods. Washington, D.C.:

Federal Highway Administration Report No. FHWA NHI-10-016, May 2010.

FP-14, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects. U.S. Department of Transportation, Federal Highway Administration, Federal Lands Highway, 2014.

Martz, J.W., Parker, W.G., Skinner, L. and Raucci, J.J., Umhoefer, P. and Blakey, R.C., 2012, Geologic Map of Petrified Forest National Park, Arizona. Arizona Geological Survey Contributed Map CM-12-A, 1 map sheet, 1:50,000 map scale, 18 p.

U.S. Geological Survey (USGS), 2018, Adamana Quadrangle, Arizona, 7.5-Minute Series, 1:24,000.

Federal Highway Administration, 2016, Publication No. FHWA NHI-16-072, Geotechnical Site Characterization Geotechnical Engineering Circular No. 5, 2 5

APPENDICES

BRIDGE GEOLOGY AND EXPLORATORY BORING LOCATION MAPS .......................................... A

FIELD EXPLORATION LEGEND AND BORING LOGS .........................................