OK.ERFO.T500(1).Horton SloughFINAL_signed.pdf

HORTON SLOUGH TRAIL

SEQUOYAH NATIONAL

WILDLIFE REFUGE

SEQUOYAH COUNTY, OK

OK ERFO SEQU T500 (1)

FINAL Geotechnical Report Report No. OK-RE-T500-21-01

Prepared by:

Federal Highway Administration

Central Federal Lands Highway Division

Geotechnical Services Branch March 2021 ii

SIGNATURE SHEET

Report prepared by: ____________________________________________________________ Rebecca L. Borst, E.I., Geotechnical Engineer

Report reviewed by: ____________________________________________________________ James M. Arthurs, P.E., Ph.D., Geotechnical Engineer

Approved for distribution by: ____________________________________________________

Marilyn D. Dodson, P.E., Lead Geotechnical Engineer

Electronic Distribution N:\ OK\erfoT500(1)\Geotech\7_FINALDocs K:\TechServices\Geotech\1. Geotech Project Reports Project Management Project Development, Lead Designer Bridge i

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page i

Table of Contents

SECTION ONE --INTRODUCTION

1.1. BACKGROUND AND LOCATION

1.2. SCOPE AND PURPOSE

SECTION TWO --GEOLOGY AND SEISMICITY

2.1. REGIONAL GEOLOGY

2.2. SITE GEOLOGY

2.3. SITE SEISMICITY

2.3.1. Nearby Faults

2.3.2. Seismic Design Parameters

2.4. GEOLOGIC HAZARDS

SECTION THREE --FIELD EXPLORATION

3.1. FIELD EXPLORATION PROGRAM

3.1.1. Exploratory Borings

3.2. LABORATORY TESTING PROGRAM

SECTION FOUR --ANALYSIS AND RECOMMENDATIONS

4.1. STRUCTURE FOUNDATION DESIGN

4.1.1. Geotechnical Profiles

4.1.2. Groundwater and Soil Moisture Conditions

4.1.3. Bridge and Observation Deck Foundations

4.1.3.1. Helical Pile Axial Resistance

4.1.3.2. Helical Pile Lateral Resistance

4.1.4. Abutment Design

4.2. EMBANKMENTS

4.2.1. Temporary Cut Slopes and Shoring

4.3. CONSTRUCTION CONSIDERATIONS

SECTION FIVE --LIMITATIONS

SECTION SIX --REFERENCES

ii

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TABLES

Table 2.3: Summary of Seismic Parameters for Site Class D

Table 3.1: Summary of the Field Exploration Program

Table 3.2: Summary of Laboratory Index Test Results

Table 3.3: Summary of Laboratory Corrosivity Results

Table 4.1: Summary of Bridge Locations

Table 4.2: Summary of Structure Borings

Table 4.8: Equivalent Fluid Densities

FIGURES

Figure 1.1: Typical Trail Conditions Along Horton Slough

PLATES

Plate 1: Location Map Plate 2: Geology Map Plate 3: Boring Locations

APPENDICES

Appendix A: Field Exploration Appendix B: Laboratory Testing Appendix C: Field Exploration Photos

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 1

SECTION ONE--INTRODUCTION

1.1. BACKGROUND AND LOCATION

This report presents the results of the geotechnical engineering study and provides recommendations for the replacement of the Horton Slough pedestrian bridge and the Sandtown Woods observation decks for the Horton Slough OK ERFO T500 (1) project. Repairs are planned as part of the Emergency Relief for Federally Owned Roads (ERFO) program. The sites were damaged due to high flows in the Arkansas River and associated side channels during the spring and summer of 2019.

The project is within Sequoyah National Wildlife Refuge, Vian, Oklahoma. The project consists of two separate locations, the pedestrian bridge at Horton Slough and the observation decks along the Sandtown Woods Trail. The pedestrian bridge crossing Horton Slough is approximately 1,450 feet from the southern parking lot trailhead at an approximate elevation of 468 feet. Observation decks one and three along the Sandtown Woods Trail are respectively located at the parking lot trailhead and approximately 415 feet from the trailhead at an approximate elevation of 460 feet. Stationing in this report is based on preliminary 30% project plans dated June 2, 2020, and the bridge Type, Size and Location (TS&L) sheets dated July 2020 (RG No. 3185). The project is located in generally undeveloped, heavily vegetated terrain between the aforementioned elevations with heavy seasonal precipitation. A project location map is presented on Plate 1.

Figure 1.1: Typical Trail Conditions Along Horton Slough

The Horton Slough Nature Trail serves as access to Horton Slough as well as Sally Jones Lake for

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 2 recreational activities including hiking and fishing. The Sandtown Woods Trail serves as access to the Arkansas River and Upper Sandtown Bottom for hiking, nature observation, and fishing. The recreation sites are operated by the refuge staff. The overall goal of the Horton Slough Trail improvement project is to repair the damaged infrastructure, minimize lifecycle costs related to frequent flood damage, and improve access for the public. Sequoyah County experienced heavy rain, resulting in flooding in May of 2019. Within the Sequoyah National Wildlife refuge, much of the resulting damage was along waterways, including the Arkansas River and Horton Slough. High waters displaced the original suspension pedestrian bridge crossing Horton Slough from its timber pile foundations and deposited the structure in the slough. Flooding in the Arkansas River damaged erosion protection along the bank, washing away sections of the Sandtown Woods Trail, dislodging two observation decks and completely removing another.

This project proposes to replace the pedestrian bridge crossing Horton Slough along a new alignment, replace and rehabilitate the observation decks, as well as realign sections of the Sandtown Woods Trail. The proposed realignment at Sandtown Woods will depart the existing alignment and push further inland, avoiding previously damaged areas and possible future flooding damage. Observation deck one will be completely replaced and observation deck three will be placed on a new foundation.

Deeper foundations on helical piles will provide a cost-effective and more resilient structure to future flooding events.

1.2. SCOPE AND PURPOSE

The scope of work includes a geotechnical investigation, analysis, and recommendations for bridges and observation deck foundations within the project limits for use in design and construction. This involves several tasks including field reconnaissance, subsurface investigations, and geotechnical engineering analysis. Specifically, this investigation is to determine the soil profiles at one bridge and two observation deck locations and develop recommendations concerning foundations, surface/subsurface drainage, geological hazards, material shrink/swell, and construction considerations. The stationing in this report is based on the preliminary 30 percent project plans, dated June 2, 2020.

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SECTION TWO--GEOLOGY AND SEISMICITY

2.1. REGIONAL GEOLOGY

The project site is located in the Arkoma Basin of the Ouachita Province. This area is located between the Ozark Mountains to the north and the Ouachita Mountains to the south (Foti, 2019). The Arkansas River is the major geographic feature of this Section. Dissected plateaus and folded ridges are common features, along with isolated steep sided mesas. Topographic relief in this area is generally low.

The site is mapped as primarily underlain by Quaternary Alluvium described as containing gravel, sand, silt, and clay (Marcher, 1969; Heran et al., 2003). Based on published maps, the bedrock is likely to belong to either McAlester and Hartshorne Formations (IPmh), or Atoka Formation (IPat).

Both units are of Pennsylvanian age and described as combinations of shale, siltstone, sandstone and limestone. A map of the regional geology is presented in Plate 2.

2.2. SITE GEOLOGY

The Horton Slough project area is located near the confluence of the Canadian River and the Arkansas River. The Arkansas River, historically a meandering river system, controls the local surficial geology. This report subsurface investigation was completed in September of 2020 that included the collection of soil samples to an approximate depth of 45 feet. In general, the borings encountered native alluvial deposits of silty sand with varying amounts of gravel overlying sedimentary bedrock, which are described in more detail in Section Three below. The investigation remains consistent with regionally published geology discussed above.

A geologic map of the project area is presented Plate 2 attached at the end of this report.

2.3. SITE SEISMICITY

2.3.1. Nearby Faults

No seismic source or Quaternary faults are mapped within 40 miles for the project (U.S. Geological Survey, 2020).

2.3.2. Seismic Design Parameters

One bridge and two observation decks are proposed for the project. The materials at the project site includes granular material of recent stream bed (alluvial) material, with sedimentary bedrock at depth. Seismic design parameters for analysis of these structures are presented in this section.

The American Association of State Highway and Transportation Officials (AASHTO) criteria for recommended seismic response parameters are based on the (AASHTO) LRFD Bridge Design Specifications, 7th Edition, 2014, and represents horizontal peak ground acceleration (PGA) with 7

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 4 percent probability of exceedance in 75 years (approximate 1000-year return period). The 1000-year return period uniform hazard spectrum for Horton Slough (35.4496204º N latitude and 94.977365º W longitudes) was obtained in accordance with the AASHTO ground motion maps. The site was classified as “Class D” per site class definitions specified in Table 3.10.3.1-1 of AASHTO based on the results of standard penetration test results. The recommended spectral acceleration coefficient values for probabilistic design are summarized in the following table.

Table 2.1: Summary of Seismic Parameters for Site Class D

Peak Seismic Ground Acceleration, (PGA) 0.053

Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SS) 0.120

Horizontal Response Spectral Acceleration at Period of 1.0 sec (S1) 0.047

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.6

Site Factor at Short-Period of Acceleration Spectrum, (Fa) 1.6

Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 2.4

Based on the long acceleration coefficient SD1 value of 0.113, the site is assigned to seismic hazard Zone 1 in accordance with Table 3.10.6-1 of AASHTO. Based on this designation, seismic conditions are assumed to not control design of structures at the project site.

2.4. GEOLOGIC HAZARDS

The project site is located within flood plains of the Arkansas River. The primary geologic hazard that may exist within the vicinity of the project area include flooding following periods of heavy precipitation. Some fine-grained soils and unconsolidated deposits in the project area are highly erodible, presenting concerns for performance of the trails. This hazard can generally be mitigated by relocation the trail alignments and supporting structures on a deeper foundation system.

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SECTION THREE--FIELD EXPLORATION

3.1. FIELD EXPLORATION PROGRAM

Central Federal Lands Highway Division (CFLHD) of the Federal Highway Administration (FHWA) geotechnical personnel conducted a subsurface investigation on September 2nd and 3rd, 2020, to characterize the subsurface materials at the bridge and observation deck sites. The geotechnical subsurface exploration plan consisted of drilling a total of four (4) borings. Due to drilling site access, only three (3) borings were completed. The purpose of the geotechnical borings was to investigate the proposed bridge and observation deck subsurface conditions. Boring locations are shown on Plate 3, Geotechnical Boring Locations. Subsurface conditions were logged and representative samples were collected and transported to the CFLHD Materials Laboratory in Lakewood, CO, for physical property testing. Logs of the explorations and laboratory test results are presented in Appendix A and B, respectively. A summary of the field exploration is provided in Table 3.1.

Table 3.1: Summary of the Field Exploration Program

EXPLORATION

DESIGNATION STATION OFFSET GROUND

ELEVATION

TERMINATION

ELEVATION

EXPLORATION

DEPTH

BH20-01* - - - - -

BH20-02 9+50 - ~ 468.5 ft. ~ 438.5 ft. 45 ft.

BH20-03 - - ~ 460 ft. ~ 415 ft. 47 ft.

BH20-04 - - ~ 460 ft. ~ 415 ft. 45 ft.

Notes: The exploration locations and elevations were estimated relative to features shown on the 30 percent project plans.

Elevations were estimated from Google Earth.

*Boring BH20-01 was not completed at the north side of the pedestrian bridge due to limited site access.

3.1.1. Exploratory Borings

Standard Testing and Engineering of Oklahoma City, Oklahoma, provided the drilling services using a CME 55 buggy-mounted drill rig. The geotechnical borings were advanced using 6-inch outside diameter hollow stem augers and mud rotary. Upon completion of drilling activities, field personnel backfilled the borings with cuttings generated during the drilling.

Drilling was completed in one mobilization. BH20-1 was not completed due to limited site access that would cause excessive trail damage due to wet, clayey conditions being unable to support the truck-mounted drill rig weight. Based on the site geology and consistent subsurface conditions between the investigated sites, as well as potential extension of the project delivery schedule and increase in budget, it was decided to abandon this proposed location and not remobilize to investigate it in the future. The potential benefits of the added costs and time would be limited.

Disturbed samples were obtained from soil materials encountered in the borings using the Standard

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Penetration Test (SPT), in accordance with AASHTO T-206. The SPT involves driving a 2-inch outside diameter, 1.375-inch inside diameter split spoon sampler 18 inches with a 140-pound hammer falling 30 inches and recording the blow counts per 6-inch of driving. An automatic-trip hammer was used to drive the samplers. The SPT N-value is the sum of the blow counts required to drive the sampler over the second and third 6-inch increments. The N-value provides a means for evaluating the relative density of cohesionless soils and consistency or stiffness of cohesive soils.

Where hard rock was encountered, an SPT samples was attempted, logged in the field, and brought to the CFLHD laboratory in Lakewood, Colorado, for further analysis.

In addition to the SPT and core samples mentioned above, grab samples were also collected when layer changes were noted that did not correspond with the SPT sampling frequency. Soil from the SPT split-spoon sampler and from grab samples were placed and sealed in plastic bags and were transported to the CFLHD Materials Laboratory for testing.

Photos of drilling equipment and field exploration activities are included in Appendix C.

3.2. LABORATORY TESTING PROGRAM

Soil samples recovered from the borings were tested in the laboratory to support the field classifications and to provide an estimate of the engineering characteristics and mechanical properties of the soil. Laboratory tests included gradation (AASHTO T88), classification (AASHTO M145) and Atterberg limits (AASHTO T89 and T90). When the necessary tests were completed, samples were classified using the Unified Soil Classification System (USCS) and AASHTO soil classification system. A summary of the soil test results is shown in Table 3.2.

Table 3.2: Summary of Laboratory Index Test Results

BORING

NUMBER

SAMPLE

DEPTH

(feet)

MOISTURE

CONTENT

PERCENT

SAND

PERCENT

PASSING

LL PI USCS AASHTO

BH20-02 5 – 6.5 - - - - - - -

BH20-02 10 – 11.5 21.8 62 38 NV NP SM A-4 (0)

BH20-02 20 – 21.5 19.7 89 11 NV NP SP-SM A-2-4 (0)

BH20-02 35 – 36.5 13.6 94.7 5.3 NV NP SP-SM A-1-b (0) BH20-02 40 – 41.5 16.4 97.3 1.7 NV NP SP A-1-b (0)

BH20-03 5 – 6.5 21.3 90.8 7.2 NV NP SP-SM A-3 (0)

BH20-03 10 – 11.5 21.8 95.1 4.9 NV NP SP A-3 (0)

BH20-03 20 – 21.5 19 82.2 2.8 NV NP SP A-1-b (0) BH20-03 40 – 41.5 11.9 55.5 3.5 NV NP SP A-1-a (0)

BH20-03* 45 – 46.5 12.4 20.8 3.2 - - GP -

BH20-04 15 – 16.5 25.3 98 2 NV NP SP A-3 (0)

BH20-04 30 – 31.5 15.8 78.5 1.5 NV NP SP A-1-b (0) BH20-04 40 – 41.5 15.9 61 4 NV NP SP A-1-a (0)

* Classifications based on field descriptions and incomplete lab testing.

- Tests not completed.

Soil test results indicated a range of material types including silty sand to poorly graded sand with

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 7 gravel materials, classifying as A-1-a to A-4 (0) by AASHTO and SP-SM, SM and SP by USCS.

The results of the laboratory tests are presented in Appendix B.

Corrosivity and chemistry testing of select samples were conducted as part of this investigation and are summarized in Table 3.3.

Table 3.3: Summary of Laboratory Corrosivity Results

BORING

NUMBER

SAMPLE

DEPTH RESISTIVITY PH

SULFATE

ION

CONTENT

CHLORIDE

ION

CONTENT

(feet) (ohm-cm) (ppm) (ppm)

BH20-2 5 – 6.5 6,430 8.4 40 12

Recommendations concerning corrosivity and sulfate attack will be presented in the FINAL Geotechnical Report.

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SECTION FOUR--ANALYSIS AND RECOMMENDATIONS

The Horton Slough project includes construction of one (1) new pedestrian bridge and two (2) overlook decks. This section provides analysis and recommendations for the bridge foundations, trail, and construction considerations.

For the analysis and foundation design of the proposed bridges and embankments, geotechnical profiles were developed from surface observation, geotechnical borings, and laboratory testing conducted during the geotechnical investigation. Bridge foundation and retaining wall design are in accordance with the American Associate of State Highway Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD), 8th Edition.

4.1. STRUCTURE FOUNDATION DESIGN

One (1) new bridge structure crossing the Horton Slough is proposed for this project. The structure is anticipated to be a single span structure. Bridge locations and dimensions from the Preliminary Layout drawings dated June 2, 2020 are summarized on Table 4.1. The bridge will be 6-feet wide to accommodate pedestrian traffic with hand rails, safety rails and a toe plate. Bridge location and elevations are based on the Type, Size, and Location plans dated July, 2020.

Table 4.1: Summary of Bridge Locations

BRIDGE START

STATION

CENTERLINE

DECK

ELEVATION AT

START

(feet)

END

STATION

CENTERLINE

DECK

ELEVATION AT

END

(feet)

Bridge 10+00 468.5 11+54 468.5

Two (2) observation deck structures are proposed along the Sandtown Woods trail. Observation deck one, located in proximity to the Sandtown Woods parking lot, will be completely replaced, and Observation Deck three will be reset on a new foundation. The decks will be 8 feet wide and 16 feet long.

4.1.1. Geotechnical Profiles

Borings labeled BH20-01 and BH20-02 were intended to be completed near the bridge abutments of the proposed bridge. Only BH20-02 was completed due to site access as discussed in Section 3.1.1 of this report. At the time of this report, it is not intended to mobilize a second time to complete BH20-01. Borings were advanced to appropriate depths for deep foundations using auger drilling techniques and mud rotary as described in Section 3 and Appendix A of this report. In general, three materials were encountered in the subsurface. These materials were generally characterized as topsoil

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 9 clayey sand (dark brown); clayey sand (light brown); and silty sand and gravel. Detailed descriptions of the boring logs are also included in Appendix A. A summary of the boring information is included in Table 4.2.

Table 4.2: Summary of Structure Borings

BORING

NO.

FOUNDATION

TYPE

BORING

DEPTH

STATION OFFSET

GROUND

ELEV.

WATER

ELEV.

STRONG

BEDROCK

ELEV.

(feet)

BH20-02 Bridge 1, South Abutment

45 ~9+50 - 468 455.5 NE

BH20-03 Observation Deck One

47 - - ~ 460 456 ~ 416.5

BH20-04 Observation Deck Three

45.2 - - ~ 460 456 ~ 417.5

Boring locations are based on handheld GPS and measuring from known features. Elevations are from Google Earth.

Station is per intermediate design filed dated June 2, 2020 NE = Not Encountered

Overburden materials generally classified as silty sand (SM) and poorly graded sand (SP) in accordance with the Unified Soil Classification System and as A-1-a and A-2-4 (0) in accordance with the AASHTO soil classification system. The SPT N-values within the overburden material range from N=2 to N=32 (very loose to dense). Values are generally assumed to be similar for the North abutment.

Alluvial materials were found from ground surface to the final depth of the boring. Flowing sands were encountered below the water table starting at approximately 20 feet in boring BH20-02 and at approximately 10 feet in borings BH20-03 & BH20-04. Flowing sands below the water table as well as rig failure impacted SPT testing for the interval from 20 feet to 40 feet at boring BH20-02. The N-value for this material was therefore assumed to be equal to the minimum N-value encountered during the subsurface exploration, or very loose. Bedrock was not encountered during drilling in BH20-02; however, bedrock is estimated to be located at approximately 50 to 55 feet based on other borehole information and regional geologic setting. Bedrock was encountered at approximately 43 feet for the Observation Deck borings.

Material properties were estimated for foundation design based on results of the field investigation, laboratory testing, published empirical relationships, and experience with similar materials. Design values are summarized in Table 4.3.

4.1.2. Groundwater and Soil Moisture Conditions

Groundwater was encountered in BH20-02 at the time of investigation at a depth of 12.5 feet below the ground surface (approximate elevation 455.5 feet). Groundwater is expected to be encountered at the same elevation at the Northern abutment based on the adjacent water elevation in the slough.

Ground water elevations can vary seasonally and in response to changes in surface water elevation.

Due to the fine to medium grain-size and low density of the deposits encountered on-site, flowing sands should be anticipated during construction.

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4.1.3. Bridge and Observation Deck Foundations

In general, spread footings were not considered due to potential for scour, undercutting, and loss of support for structural elements founded on the overburden soils. Site access with heavy equipment and depth to bedrock are likely to complicate installation of driven piles and drilled shafts. Micropiles are not recommended due to anticipated high lateral loading, scour, and higher relative cost and construction time. For ease of construction, to limit environmental impacts, and save costs, the design team prefers to use helical piles for the structure foundations.

Please reference the structural plans for bridge and observation deck loads factored for the strength limit state, provided by the bridge engineer.

Observation Decks Helical Pile Loading (Strength 1): 9.8 kips

Pedestrian Bridge Abutment Helical Pile Loading (Strength 1): 38 kips

4.1.3.1. Helical Pile Axial Resistance

Design analyses conducted using typical empirical methods based on an assumed SPT blowcount of 10 from boring BH-03 indicate that a nominal bearing pressure of approximately 41 kips per square foot (ksf) may be used for end bearing design in silty sand materials. Due to a scour depth of 1.6 feet, minimum embedment for the top of the helixes at the bridge abutment is 15 feet, and the minimum embedment for the top of the helixes at the observation decks is 10 feet. Minimum embedment at the observation decks begins at the bottom of the placed riprap, as shown on the structural plan sheets.

Although LRFD resistance factors for helical piles are not presented in the code, it is recommended that a resistance factor of 0.50 be used for design. This is based on the typical ASD factor of safety of 2.0 converted to a resistance factor of 0.50. Helix configurations (i.e., smaller diameter helixes with more flights) may result in more efficient installation. Installation torque measurements should be performed to verify pile capacity during construction in accordance with manufacturer recommendations. Note that installation torque may not correlate well to capacity where piles refuse on boulders or bedrock. These values and calculations were used for construction estimation purposes; the contractor is expected to determine the appropriate values and complete separate calculations for the design of the helical pile foundations based off the information provided.

The following procedure should be followed to meet the design requirements.

• All piles should be installed to the minimum depth required by the approved helical pile design and also to the minimum depth required for lateral resistance presented on the bridge plans.

• If refusal is encountered, the pile may be terminated at that depth provided it meets the minimum embedment depth required for lateral resistance presented on the plans and the helical pile designer approves of the early termination.

• Where piles meet refusal prior to the minimum embedment depth required for lateral resistance, the holes should be pre-drilled such that the minimum embedment is achieved while also meeting axial requirements.

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• Offsetting the helical pile and re-attempting to install may be considered with the approval of the bridge engineer.

• Shallow ground water and flowing sands may be encountered, which could extend the depth of required piles.

• Hard drilling was encountered in one boring due to dense sands with gravel.

These observations are for geotechnical axial resistance and lateral design calculations may control the final design (the greater depth of the two will control).

4.1.3.2. Helical Pile Lateral Resistance

Lateral load analysis has been performed, and is provided, by the Central Federal Lands bridge engineer using the software program Lpile developed by Ensoft, Inc. This program analyzes a single pile considering deflection as a function of design loads, foundation construction, and subsurface conditions. Table 4.4 provides preliminary Lpile input parameters for the foundation soils based on available subsurface information and generally accepted engineering correlations.

TABLE 4.3 - Lpile Input Parameters – Horton Slough Bridge

MATERIAL APPROXIMATE

DEPTH

APPROXIMATE

ELEVATION

LPILE

P-Y

MODEL

EFFECTIVE

UNIT

WEIGHT

(pcf)

FRICTION

(deg)

COHESION

(psf)

K

(lb/in3)

Dry Sand 0-5 460-455 Sand (Reese) 120 32 0 25

Wet loose Sand 5-30 455-430 Sand

(Reese) 63 32 0 20

Wet Medium

Dense Sand 30-43.5 430-416.5 Sand (Reese) 68 34 0 60

Bedrock (limestone) 43.5 416.5 *

*Bedrock penetration is not anticipated for helical piles.

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4.1.4. Abutment Design

Abutments and wing walls should be designed to resist lateral earth pressures and other applicable loads in accordance with AASHTO. Lateral earth pressure is influenced by the strength of the abutment backfill, the presence or absence of water, and the ability of the abutment or wall to move in response to lateral loads. Other loads, such as live loads, construction loads, and soil compaction loads should also be considered in the design.

Unbalanced water behind abutments and walls adds significant lateral pressure and should be avoided by using free draining gravity outlets for water. Contractor should be prepared to dewater during construction. Abutment and wing wall backfill should consist of structural backfill (SCR and FP-14, Subsection 704.04).

Where the abutment or wall is restrained such that it cannot deflect 0.002 times the wall height, the at-rest earth pressure coefficient should be used for design. If the wall is allowed to deflect, the active earth pressure coefficient should be used. The equivalent fluid densities for native materials, properly placed and compacted select granular backfill, and unclassified borrow above the water table are presented in Table 4.3. The values are unfactored loads and assume a horizontal backfill surface with no surcharge loading.

Table 4.3: Equivalent Fluid Densities

Backfill Type Assumed Backfill Properties Case

Unfactored Equivalent Fluid

Density (pcf)

Select Granular Backfill c’ = 0 psf φ’ = 34° γ’ = 125 pcf

Active 35

At-Rest 55

Unclassified Borrow c' = 0 psf φ’ = 30° γ’ = 120 pcf

Active 40

At-Rest 60

4.2. EMBANKMENTS

Temporary cut slopes and shoring may be required to construct permanent structures.

4.2.1. Temporary Cut Slopes and Shoring

Temporary cut slopes and shoring are not anticipated for construction of the bridge foundations and retaining walls. Ground water was encountered 12 feet below the surface (approximately 456 feet in elevation) at the time of drilling at the southern bridge abutment. Ground water levels can fluctuate seasonally and will change according to the elevation of the Arkansas River as well as Horton Slough.

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It should be assumed that the soils on site will be wet and may not be stable at the angles typically recommended by OSHA. Design and safety of this work is the responsibility of the contractor. The work shall be performed in a manner to minimize hazards and exposure to the public, construction personnel, and equipment. The contract should either include a temporary dewatering item or include the costs of temporary dewatering as subsidiary to the other pay items.

4.3. CONSTRUCTION CONSIDERATIONS

Specifications: All geotechnical recommendations stated above are incorporated into the SCRs to amend or are already incorporated within the FHWA Standard Specification for Construction of Roads and Bridges on Federal Highway Projects; known as FP-14.

Helical Piles: Construction of helical piles for the project will be complicated by several factors:

1) Site access,

2) Granular soils below the water table (flowing sands),

3) Shallow water table

4) Hard bedrock

Based on these factors, the Contractor should assume loose granular material will be encountered at both bridge abutments, as indicated in the boring logs. Ground water depth should be expected to fluctuate seasonally. The contractor should submit a helical pile design and construction plan in accordance with Section 582 of the SCR and FP-14. We anticipate that the following items will be included in the plan:

1) Helical pile materials

2) Subcontractor qualifications

3) Proposed construction sequence and schedule

4) Pile installation and verification equipment

5) Shop drawings and design calculations

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SECTION FIVE--LIMITATIONS

The recommendations in this report are based on the data obtained from exploratory borings, field review, and laboratory test results. The results of these explorations and tests represent conditions at the specific locations indicated. Subsurface variations across the site are likely and may not become evident until excavation is performed. The Analysis and Recommendations sections in this report include interpretations and recommendations developed by the Government in the process of preparing the design. These interpretations are not intended as a substitute for the personal investigation, independent interpretation, and judgment of the Contractor.

Horton Slough Trail, OK ERFO T500 (1) March 2021 Page 15

SECTION SIX--REFERENCES

American Association of State Highway and Transportation Officials (AASHTO). (2018).

“AASHTO LFRD Bridge Design Specifications”, 8th Edition.

Federal Highway Administration (FHWA), 2007, Geotechnical Technical Guidance Manual, dated May.

Federal Highway Administration (FHWA), 2008, Federal Lands Highway Project Development and Design Manual (PDDM), dated March.

Federal Highway Administration (FHWA), 2017, Soil Description and Identification Guidelines, dated December.

Helical Piles and Tiebacks Committee. (2019). Helical Pile Foundation Design Guide [PDF].

Hawthorne, New Jersey: Deep Foundations Institute.

Heran, W., Green, G., & Stoeser, D. (2003). A digital geologic map database for the State of Oklahoma [Map]. In Open-File Report OF-2003-247. U.S. Geological Survey.

“National Seismic Hazard Map”, United States Geological Survey (USGS), 2019, website:

http://earthquake.usgs.gov/research/hazmap

U.S. Geological Survey (2019). “Quaternary Fault and Fold Database of the United States.” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/hazards/qfaults/>.

http://earthquake.usgs.gov/research/hazmap

Horton Slough Trail, OK ERFO T500 (1) March 2021

PLATES

Legend

Lithology

Qal- Quaternary Alluvium

Gravel, sand, silt, and clay. Yields large amounts of water along the Arkansas River

■ Qt- Quaternary Terrace Deposits

Gravel. sand, silt, and clay. Yield moderate to large amounts of water along the Arkansas River; smaller amounts elsewhere

■ Pbo- Boggy Formation

Shale, sandstone, and coal; includes Bluejacket Sandstone Member.

■ Psa- Savanna Formation

Shale, limestone, and sandstone. Brown to greyish- brown and fine grained sand.

■ Pmh- McAlester & Hartshorne Formations

Shale, cherty sandstone beds, and coal. Shale is blue. grey or black with the grey color predominant

Pat- Atoka formation Shale, siltstone, sandstone, and limestone. Dark grey to white. Can contain chert conglomerates and iron concretions. NOTTO SCALE

STATE PROJECT

OK OK ERFO T�OO {1) Horton

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOLOGY MAP

STATE PROJECT

OK ERFO TS00 {l)

Boring Locations

Boring Location Latitude Longitude Elevation

BH20-01 North Abutment * - -

BH20-02 South Abutment 35.449332 -94.977589 468.5

BH20-03 North Obs Deck 35.440949 -95.021663 460

BH20-04 South Obs Deck 35.439795 -95.021729 460

Ground elevations, latitude, and longitude were estimated from Google Earth.

* Boring not drilled

NOTTO SCALE

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOTECHNICAL BORING

LOCATIONS

PLATE

APPENDIX A

Field Exploration

APPENDIX A

FIELD EXPLORATION PROGRAM

A.1 INTRODUCTION

The Central Federal Lands Highway Division (CFLHD) Geotechnical Section completed a field exploration program for OK ERFO T500 (1), Horton Slough, from September 2nd through September 3rd, 2020. The scope of work for the field exploration program included drilling a total of four borings each to a depth of 50-feet. Two borings were drilled for two observation decks near the Arkansas River. Two borings were planned for the Horton Slough pedestrian bridge; however, due to limited access for the North abutment, only one boring was drilled for the South abutment. The field exploration program was coordinated and observed by a Geotechnical Engineer from CFLHD. Field exploration locations are illustrated on the “Geotechnical Boring Locations” sheet in Plate 3. Individual boring logs are attached. These logs represent a compilation of field and laboratory data and description of the soil and rock by CFLHD Geotechnical personnel. The methods used to conduct the field exploration program are described below. Photos of drilling equipment and field exploration activities are included in Appendix C. All soil and rock samples collected during the field exploration program were transported to the CFLHD Materials Laboratory in Lakewood, Colorado for testing. A summary of the laboratory testing program is provided in Appendix B.

A.2 EXPLORATIONS

Borings

Standard Testing and Engineering Co. of Oklahoma City, OK provided the drilling services for the soil and rock borings. Borings were completed using a CME 550 drill rig. Borings were advanced through overburden using hollow stem augers and mud rotary with drive sampling until practical auger refusal was encountered or 50 feet was reached. Following drilling activities, field personnel backfilled the borings with cuttings generated during the drilling in accordance with applicable local, state, and federal regulations.

If water was encountered at the time of drilling, field personnel measured water levels in the borings. Fluctuations in the ground water level due to seasonal and climatic effects are expected.

A.3 SOIL AND ROCK SAMPLING

Borings

Disturbed samples were obtained from the borings in accordance with the Standard Penetration Test (SPT), the procedures of which are detailed in AASHTO T-206. The SPT involves driving a 2-inch outside diameter, 1.375-inch inside diameter split spoon sampler a depth of 18 inches with a 140-pound hammer falling a distance of 30 inches.

The number of blows required to advance the split-spoon sampler through each of the 6-inch increments was recorded. The SPT resistance, or N-value, is defined as the number of blows required to drive the sampler over the second and third 6-inch increments. The N-value provides a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils.

An energy corrected N-value, N60, is used to standardize the energy levels of the hammer system in the SPT to 60% efficiency. Representative portions of the split-spoon sample obtained in conjunction with the SPT were placed in plastic baggies and transported to the CFLHD Materials Laboratory for testing.

A.4 SOIL AND ROCK CLASSIFICATION SYSTEM

During the completion of borings and test pit excavations, CFLHD Geotechnical personnel collected soil/rock samples and prepared field logs of the borings. Soil identification and descriptions, as shown on the field logs, are based on ASTM D2488, a systematic process for identifying and describing individual soil samples by visual and manual means. When sufficient laboratory testing was completed, select samples from borings were classified using the Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) soil classification system. Both the visual soil identification system and the referenced soil classification systems are summarized in the attached Soil Classification Field Reference. Rock samples were classified based on the stratigraphic structure, rock strength, degree of weathering, and other properties. The rock classification system is summarized in the attached Rock Classification Field Reference.

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Unified Soil Classification System

SOIL CLASSIFICATION CHART & LEGEND

SILTY GRAVELS WITH OR WITHOUT SAND

HIGHLY ORGANIC SOILS

POORLY-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLEAN SANDS

WITH LESS THAN

15% FINES

GRAVELS WITH

15% OR MORE

FINES

GRAVELS

MORE THAN HALF

COARSE

FRACTION IS

LARGER THAN NO.

4 SIEVE

MAJOR DIVISIONS TYPICAL NAMES

WELL-GRADED GRAVELS WITH OR WITHOUT

SAND

POORLY-GRADED GRAVELS WITH OR

WITHOUT SAND

ORGANIC SILTS OR CLAYS OF HIGH

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

PEAT AND OTHER HIGHLY ORGANIC SOILS

CLAYEY SANDS WITH OR WITHOUT GRAVEL

C O

A R

S E

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A

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S O

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T H

A N

H A

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NOTE: Coarse-grained soils with between 5% and 12% passing the No.200 sieve and fine-grained soils with limits plotting in the gray zone on the plasticity chart have dual classifications.

SILTS AND CLAYS

LIQUID LIMIT 50% OR LESS

Unconfined Compression No Recovery

SILTS AND CLAYS

LIQUID LIMIT GREATER THAN 50%

UC

NR

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N

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SANDS WITH 15%

OR MORE FINES

SANDS

MORE THAN HALF

COARSE

FRACTION IS

FINER THAN NO. 4

SIEVE SIZE

INORGANIC CLAYS OF HIGH PLASTICITY

WITH OR WITHOUT SAND OR GRAVEL

Liquid Limit Plastic Index Moisture Content Dry Density Non Plastic No Valve

Water Level at Time of Drilling

Stabilized Water Level

CLEAN GRAVELS

WITH LESS THAN

15% FINES

Abbreviations

WELL-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLAYEY GRAVELS WITH OR WITHOUT SAND

INORGANIC SILTS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

INORGANIC CLAYS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

LL

PI

W

DD

NP

NV

SILTY SANDS WITH OR WITHOUT GRAVEL

ORGANIC SILTS OR CLAYS OF LOW TO

MEDIUM PLASTICITY WITH OR WITHOUT

SAND OR GRAVEL

INORGANIC SILTS OF HIGH PLASTICITY WITH

OR WITHOUT SAND OR GRAVEL

Use primary colors or hyphenated compound primary colors. Use "mottled" or "streaked" if necessary.

4. Color Dry Dry to touch, dusty Moist Damp but no visible water Wet Visible free water

5. Moisture Content

Flat Width/Thickness >3 Elongated Length/Width >3

Flat & Elongated Meets both of the above

Applies to sand, gravel, cobbles and boulders.

Length, width and thickness refer to the greatest, intermediate and least dimensions, respectively.

6c. Particle Shape

N Density N Consistency

Unconfined Compressive Strength qu

(tsf)

Undrained Compressive Strength su

(tsf)

Behavior

0-4 Very Loose 0-1 Very Soft <0.25 <0.125 Extrudes between fingers when squeezed

5-10 Loose 2-4 Soft 0.25-0.50 0.125-0.25 Remolded by light finger pressure

11-30 Medium Dense 5-8 Firm 0.50-1.00 0.25-0.50

Imprinted easily with fingers, remolded by strong finger pressure

31-50 Dense 9-15 Stiff 1.00-2.00 0.50-1.00 Imprinted with considerable finger pressure, indented by finger nail

>50 Very Dense 16-30 Very Stiff 2.00-4.00 1.00-2.00 Barely imprinted by fingers or indented by finger nail

>30 Hard >4.00 >2.00 Not imprinted by fingers or difficult to indent with finger nail

SAND & GRAVEL SILT AND CLAY

3. Consistency and Density:

Angular Sharp edges and relatively plane sides.

Subangular Same as angular with rounded edges.

Subrounded Nearly plane sides but well-rounded corners and edges.

Rounded Smooth curved sides and no edges.

Well-

Rounded Very Smooth surfaces, spherical or ovular, no edges.

6b. Particle Angularity Applies to coarse sand, gravel, cobbles and boulders.

Sieve < #200 Flour or smaller

Fine > #200 to #40 Flour to sugar Medium #40 to #10 Sugar to rock salt Course #10 to #4 Rock salt to pea-sized

Fine #4 to 3/4 in. Pea-sized to thumb Coarse 3/4 in. to 3 in. Tumb to fist Cobble 3 in. to 12 in. Fist to basketball

Boulders > 12 in. Larger than Basketball

Material

Gravel

6a. Particle Size

Silt or Clay

Sand

Particle Size Approximate Scale

Example, fine-grained soil: Lean CLAY with Sand (CL)- stiff, brown, moist, medium plasticity, laminated Example, coarse-grained soil: Silty SAND with Gravel (SM)-medium dense, gray, wet, fine to coarse grained, angular to subangular gravel, weakly cemented Example, fine-grained soil (Long Form):

Clayey GRAVEL with SAND (CL-ML)- loose to soft, dark brownish green to pale brownish gray, wet; fine to medium grained, angular, flat sand; coarse grained, rounded elongated gravel, some chert, trace coarse gravel, and cobbles, medium plasticity, dessicated, weak cementation, low dry strength, rapid dilatancy, moderate HCL reaction, hydrocarbon odor, iron oxide staining, alluvium fill, (Quaternary Alluvium), Additional Description.

1. Group Name (Pg. 3) 9.

2. Group Symbol (Pg. 3) 10.

3. Consistency / Relative Density (Pg. 1) 11.

4. Color (Pg. 1) 12.

5. Moisture (Pg. 1) 13.

6. Particle Size / Shape / Angularity (Pg. 1) 14.

7. Plasticity (Pg. 2) 15.

8. Structure (Pg. 2)

Odor (Pg. 2)

Staining (Pg. 2)

Cementation (Pg. 2) Organics Dry Strength (Pg. 2) Dilatancy (Pg. 2) HCL Rxn (Pg. 2)

Weak Crumbles with little finger pressure Moderate Crumbles with considerable finger pressure Strong Will not crumble with finger pressure

Intact coarse-grained soil

9. Cementation

Nonplastic Thread cannot be rolled at any water content.

Low The thread can barely be rolled and the lump cannot be formed when drier than the plastic limit.

Medium The thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. The lump crumbles when drier than the plastic limit.

High It takes considerable time kneading and rolling to reach the plastic limit. The thread can be rerolled several times after reaching the plastic limit. The lump can be formed without crumbling when drier than the plastic limit.

Toughness test: Shape the specimen into an elongated pat and rolled on a smooth surface or between the palms into a thread ~1/8”. If the sample is too wet to roll, it should be allowed to dry. Fold the thread and reroll repeatedly until the thread crumbles at a diameter of ~1/8”. This will be near the plastic limit. Note the pressure required to roll the thread near the plastic limit and the strength of the thread. After the thread crumbles, the pieces should be lumped together and kneaded until the lump crumbles. Note the toughness during kneading.

On the basis of observations made during the toughness test, describe plasticity.

7. Plasticity

None No visible reaction Weak Some reaction, bubbles forming slowly Strong Violent reaction, with bubbles forming immediately

13. HCL Reaction 14. Odor 15. Staining None None

Chemical Hyrodcarbon Hyrodcarbon Iron Oxide

Organic

None No visible change Slow Water appears slowly during shaking and does not disappear or disappears slowly during squeezing.

Rapid Water appears quickly during shaking and disappears quickly during squeezing.

12. Dilatancy

1. Mold soil, adding water if necessary, into ~1/2” diameter ball with soft but not sticky consistency.

2. Smooth in palm of one hand with knife blade. Shake horizontally, striking the side of the hand vigorously against the other hand several times. Note the reaction of water appearing on the surface.

4. After Dilatancy has been determined perform the Toughness test (see explanation in #7).

3. Squeeze by closing the hand or pinching the soil between fingers. The reaction is the speed with which water appears while shaking and disappears while squeezing.

None Crumbles into powder with mere pressure of handling.

Low Crumbles into powder with some finger pressure.

Medium Breaks into pieces with considerable finger pressure.

High Cannot be broken with finger pressure, will break between hard surface and thumb.

Very High Cannot be broken between hard surface and thumb.

1. Mold a ball ~1” diameter until it has the consistency of putty, adding water if necessary.

2. From the ball, make at least 3 ½” diameter balls. Allow to air dry.

3. If the specimen contains natural dry lumps, those that are ~1/2” diameter may be used in place of molded balls.

4. Test the strength of the dry balls or lumps by crushing between the fingers.

11. Dry Strength

Stratified Alternating layers > 1/4 inch, note thickness.

Laminated Alternating layers < 1/4 inch, note thickness.

Fissured Contains shears or separations along planes of weakness.

Slickensided Shear planes appear polished or glossy, sometimes striated.

Blocky Cohesive soil can be broken down into harder, angular lumps.

Lensed Inclusion of small pockets of different soils, note thickenss.

Homogeneous Same color and appearance throughout.

Mottled Spots or patches possessing no apparent pattern Varved Distinct laminations of lacustrine sediments predominantly clayey

Desiccated Shrinkage cracks due to dehydration of fine-clayey soil

8. Structure Terms

2. Color For consistency, describe when wet.

Use primary or hyphenated compound primary colors.

1. Rock Type Common classifications; gneiss, granite, shale, etc. A modifier may be necessary to describe a sedimentary rock formed from a combination of soil types, i.e., Silty

SANDSTONE.

V. Coarse Grained > 1/4 in.

Coarse Grained 3/16-1/4 in. Easily distinguished by naked eye Medium Grained 1/16-3/16 in. Can be distinguished by naked eye

Fine Grained Up to 1/16 in. Barley distinguished by naked eye V. Fine Grained Cannot distinguished by naked eye

3a. Grain Size

V. thickly bedded > 3ft Thickly bedded 18 in. - 3 ft Thinly bedded 2-18 in.

V. thinly bedded 3/8- 2 in.

Laminated 3/16- 3/8 in.

Thinly laminated < 3/16 in.

3c. Bedding For Sedimentary Rock

Fresh No visible sign of rock material weathering; perhaps slight discoloration on major discontinuity surfaces.

Slightly weathered Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be discolored by weathering and may be somewhat weaker externally than in its fresh condition.

Moderately weathered Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework as corestones.

Highly weathered More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework as corestones.

Completely weathered (Decomposed)

All rock material is decomposed and/or disintegrated to a soil. The original mass structure is still largely intact.

Residual Soil All rock mass is converted to a soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the volume has not been significantly transported.

4. Weathering

EXAMPLES

GNEISS- Dark gray, moderately weathered, strong. Biotite foliation, low angle, close. Quartz veins, close, low angle, stepped. Primary joint set, close, low angle, tight, moderately weathered, very narrow with rust surface staining and spotty clay infilling, rough planar. (SLIVER PLUME GRANITE) GRANODIORITE- Grey to white, medium grained, slightly weathered, strong, joints are moderate to high angle, very close, rough, open to closed, FE stained joints. Poor Circulation.

SANDSTONE- Tan to reddish brown, fine to medium grained, sub rounded, thinly bedded, moderately weathered, strong, joints are low angle, very close, closed, rough. FE surface staining throughout sample, some organics seen in joint sets.

1 Rock Type (CAPITAL LETTERS) (Pg.1) 6

2 Color (Pg.1) a. Type e. Separation 3 Grain Size or Bedding (Pg.1) b. Stratification f. Infilling & Weathering

4 Weathering (Pg.1) c. Spacing g. Roughness 5 Strength (Pg.1) d. Orientation

Discontinuities (Pg.2)

Miscellaneous (Pg.2) Formation or Unit Name (CAPITAL LETTERS)

Core should be placed in core boxes from left to right, top to bottom. The rock description for each core run should include, in this order:

Angular Show very little wear, grain edges are sharp Subangular Show definite effects of wear, grain edges slightly rounded Subrounded Shows considerable wear , grain edges rounded smooth Rounded Shows extreme wear, grain edges smoothed to broad curves Well-Rounded Very Smooth surfaces, spherical or ovular, no edges.

For Sedimentary Rock 3b. Grain Shape

3d. Structure For Sedimentary Rock

Banded Bedded

Cross Bedded Flow Banded

Foliated Interbedded Laminated Massive

R5 Very strong rock Spec…