NM Cottonwood_FINAL Geotech Rpt_20210714.pdf

SUBMITTED TO:

HDR Engineering, Inc.

835 N Post Street Spokane, Washington 99201

BY:

Shannon & Wilson, Inc.

1321 Bannock St., Suite 200 Denver, Colorado 80204

(303) 825-3800 www.shannonwilson.com

GEOTECHNICAL REPORT

NM FLAP SJU 10(1)

Cottonwood Campground

SAN JUAN COUNTY, NEW MEXICO

July 2021

Shannon & Wilson No: 104000-001

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CONTENTS

1 Introduction

2 Project and Site Description

3 Subsurface Explorations and Laboratory Testing

3.1 Field Investigation

3.2 Geotechnical Laboratory Testing

4 Regional Geology and Subsurface Conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.3 Groundwater

4.4 Subsurface Variations

5 Geologic Hazard Evaluation

5.1 Seismic Hazards

5.2 Corrosion

6 Geotechnical Recommendations

6.1 Drilled Shafts

6.1.1 Axial Design

6.1.2 Lateral Resistance

6.2 Lateral Earth Pressures

7 Construction Considerations

7.1 Drilled Shaft Installation

7.1.1 Drilled Shaft Installation Methods and Equipment

7.1.2 Drilled Shaft Inspection and Observation

7.1.3 Concrete Placement

7.1.4 Non-Destructive Integrity Tests

7.2 Earthwork and Grading

7.2.1 Excavation

7.2.2 Fill Placement and Compaction

8 Closure

9 References iii

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Exhibits Exhibit 5-1: Seismic Design Ground Motion Parameters Exhibit 6-1: Recommended Lateral Earth Pressure Design Parameters

Table Table 1: Geotechnical Parameters for Deep Foundation Design

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Recommended P-Multipliers for Laterally Loaded Groups of Piles or Shafts Figure 4: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Suburface Explorations Appendix B: Laboratory Test Results Appendix C: Drilling Photographs Important Information

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1 INTRODUCTION

This report presents the results of our subsurface exploration program and geotechnical engineering recommendations for the proposed Cottonwood Campground Project (the Project) in San Juan County, New Mexico (Figure 1). The report summarizes our subsurface explorations, laboratory testing and geotechnical engineering studies, and presents conclusions and recommendations for design of bridge foundations. Our services were conducted in general accordance with our Task Order Agreement No. 020/1000100054367 with HDR Engineering, Inc. (HDR) dated August 31, 2020.

We understand this report will be used for design of the proposed Project. This report should not be used for other purposes without Shannon & Wilson’s review. Our scope of services included:

The limitations of our approved scope, schedule, and budget described in our contract;

Our understanding of the Project and information provided by HDR;

Subsurface conditions observed in the borings at the time our explorations were completed; and

The results of testing performed on samples collected from the explorations.

The objective of our geotechnical studies was to provide recommendations and construction considerations, as presented herein, for the proposed bridge. The authorized scope of services was based on this objective and this report should not be used for other purposes without Shannon & Wilson’s review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located in San Juan County, New Mexico within Navajo Lake State Park. The proposed project consists of a new bridge over a dry arroyo for a realigned section of Road 4280 west of the entrance to the Cottonwood Campground at Navajo State Park (Figure 2).

The proposed bridge will consist of an approximately 85-foot-long, single-span structure.

Based on discussions with HDR, we understand that the proposed bridge abutments will be founded on drilled shafts. Short abutment and wing walls may be required as part of the project. Roadway improvements will be completed for the project, however pavement design was not included in this scope of work.

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3 SUBSURFACE EXPLORATIONS AND LABORATORY

TESTING

3.1 Field Investigation

Shannon & Wilson conducted a field exploration program on October 22, 2020, to explore subsurface conditions near the proposed bridge location. The subsurface exploration program consisted of drilling and sampling two structure borings designated SW-01 and SW-02 and one pavement boring designated SW-03, as shown in Figure 2.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used. Photographs of the drilling locations are included in Appendix C.

3.2 Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index and engineering properties. Index tests included natural water content, grain size analysis, and Atterberg limits. Engineering properties tests included corrosion and uniaxial compressive strength. Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content, fines content, and Atterberg limits are also shown on the individual boring logs included in Appendix A.

4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

A review of the Geologic Map of the Aztec 1 degree x 2 degrees Quadrangle, Northwestern New Mexico and Southern Colorado (Manley and others, 1987) indicates that the surficial geology at the site consists of stream deposited Quaternary alluvium consisting of clay, silt, sand, and gravel. Bedrock near the site is mapped as the Nacimiento Formation consisting of sandstone within the project area.

4.2 Subsurface Conditions

Boring SW-01, the western bridge abutment boring, encountered medium dense to very dense, silty sand to an approximate depth of 6 feet below ground surface (bgs), followed by

Geotechnical Report

104000-001 July 2021 very dense gravel with silt and sand to a depth of 17 feet bgs. Cobbles were noted based on drill action and cutting returns. Sandstone was then encountered at (Elevation 5,670) to the termination depth of the boring at 34.3 feet. Within the sandstone, occasional thin, black coal seams with a petroleum odor were encountered.

The southern bridge abutment boring, SW-02, was drilled atop a sand embankment. The top of the sand embankment is approximately 10 feet higher than the ground surface at the bottom of the arroyo. In this boring, 21 feet of very loose to medium dense, silty sand was encountered. This was followed by 8 feet of very dense gravel with silt and sand before encountering sandstone at a depth of 29 feet bgs (Elevation 5,668). The sandstone extended to the termination depth of the boring at 45 feet. Thin, black coal seams with a petroleum odor were also encountered in this boring. Cobbles were noted throughout the alluvium based on drill action and cutting returns.

Boring SW-03 was drilled within the existing roadway and encountered a pavement section consisting of 2.5 inches of asphalt overlying 7.5 inches of aggregate base course overlying medium dense, clayey sand with gravel overlying loose silty sand to the bottom of the boring at 5.5 feet.

4.3 Groundwater

During drilling, groundwater was encountered at depths of approximately 11.5 and 23.4 feet bgs (elevation 5,676 feet and 5,673 feet) in borings SW-01 and SW-02, respectively. The groundwater level at the time of drilling is noted on each boring log included in Appendix A. No groundwater was encountered in boring SW-03. Groundwater fluctuations are likely and will depend on seasonal variations, local precipitation and runoff, and flood events.

4.4 Subsurface Variations

The explorations were performed to evaluate subsurface conditions at the Project site. Our observations are specific to the locations, depths, and times noted on the logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions.

Potential variation includes, but is not limited to:

The conditions between explorations may be different.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

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If conditions different from those described herein are encountered during construction, we should review our description of the subsurface conditions and reconsider our conclusions and recommendations.

5 GEOLOGIC HAZARD EVALUATION

5.1 Seismic Hazards

Based on a recent geologic map by the U.S. Geological Survey (USGS), the nearest fault to the Project is the Cannibal Fault, approximately 73.5 miles to the northeast (Widmann, 1999). Therefore, in our opinion, the potential for ground surface fault rupture is low.

Liquefaction may occur in loose, saturated, cohesionless soils when subjected to earthquake ground shaking. Based on the subsurface conditions encountered at the site and the relatively low peak ground acceleration (PGA) for this area, it is our opinion that the risk of liquefaction is low.

Using the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2020) criteria, and based on subsurface conditions encountered in our borings at the proposed bridge (assuming that similar conditions are present from the maximum depth of our boring to a depth of 100 feet), Site Class D is recommended for the proposed bridge.

Ground motion parameters were determined for the Project site using the USGS AASHTO 2009 Web Service Documentation Web Application (USGS, 2009) and procedures recommended by AASHTO (2020). Exhibit 5-1 presents recommended seismic design ground motion parameters.

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Exhibit 5-1: Seismic Design Ground Motion Parameters

Design Parameter Value

Peak Ground Acceleration 1 (PGAB) 0.049 g

Site Class D

Short-period Spectral Acceleration, SS 0.112 g

Long-period Spectral Acceleration, S1 0.039 g

Site Factor, FPGA 1.6

Site Factor, Fa 1.6

Site Factor, Fv 2.4

Peak Design Spectral Acceleration, AS 0.079 g

Short-period Design Spectral Acceleration, SDS 0.179 g

Long-period Design Spectral Acceleration, SD1 0.092 g

T0 0.10 sec.

TS 0.52 sec.

Seismic Zone 1

NOTES:

PGAB = peak ground acceleration for a site underlain by Site Class B soil (soft rock) Based on AASHTO 2020 Guide Specifications.

g = gravitational acceleration; sec. = seconds

5.2 Corrosion

The soil encountered at the project site can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, a select sample was tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Table B-1 in Appendix B.

Guidelines in AASHTO (2020) indicate that resistivity measured below 2,000 ohm-centimeters should be considered a corrosive. The resistivity measured in the sample was 5,397 ohm-centimeters. Based on correlations developed by Roberge (2012), these values suggest moderately corrosive subsurface conditions for metal in contact with subsurface materials across the site.

Soil or rock with sulfate concentrations more than 1,000 parts per million (0.1 percent) are indicative of potential degradation based on AASHTO (2020). The concentration of water-soluble sulfates measured in the sample was 0.002 percent by weight. Based on classifications as defined by ACI-318-19 (ACI, 2019), these test results suggest an exposure class S0 on concrete exposed to site soils.

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The test results and the above discussion are provided to assist the designer in the selection of project materials, concrete type, or other features with respect to corrosion. As appropriate, the designer should consider protective measures, such as coatings, upsizing for section loss, or using alternative materials to reduce the corrosion potential.

6 GEOTECHNICAL RECOMMENDATIONS

As discussed in Section 2, we understand the proposed bridge will consist of a single-span structure founded on drilled shafts. The borings indicate that bedrock was encountered at a depth of approximately 17 feet and 29 feet bgs in borings SW-01 and SW-02, respectively. In our opinion, drilled shafts are a cost-effective and appropriate foundation system for the bridge based on the subsurface conditions encountered at the site.

6.1 Drilled Shafts

Specifications and installation methods should be in general accordance with our recommendations and guidelines in the 2010 FHWA Manual, “Drilled Shafts: Construction Procedures and Design Methods” (Brown and others, 2018), LRFD criteria that were developed based on AASHTO LRFD Bridge Design Specifications (AASHTO, 2020) and the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (FHWA, 2014).

6.1.1 Axial Design

Drilled shafts can be designed for tip and side resistance in the bedrock. Axial resistance parameters are presented in Table 1. The nominal shaft resistance parameters provided in Table 1 are based on a single shaft and do not consider group action of closely spaced shafts closer than two diameters, center-to-center.

Due to disturbance from drilling tools and differences in strain compatibility between the soil and bedrock, side resistance from the overburden soils should be ignored. We recommend a minimum drilled shaft penetration of 1.5 shaft diameters into the bedrock.

The side resistance in the upper 2 feet of the bedrock should be ignored (due to weathering at the top of the layer and the potential disturbance from casing).

Assuming drilled shafts are constructed using good installation techniques and equipment based on criteria described in the 2010 FHWA Manual “Drilled Shafts: Construction Procedures and LRFD Design Methods” (Brown and others, 2018), we anticipate that total settlement for a single drilled shaft at the service limit state will be approximately ½ inch or less. This settlement value does not include elastic compression of the shaft under the

Geotechnical Report

104000-001 July 2021 allowable design load. We anticipate that differential settlement over the width of the bridge will be about 50% of this value. About 75% of the settlement is anticipated to occur as the load is applied with the remaining settlement occurring within the first year following construction.

6.1.2 Lateral Resistance

Lateral loads acting on the structure from wind, seismic, and other loadings are typically resisted by the deep foundation members. The lateral behavior of the shafts is highly dependent on the degree of fixity of the top of the shaft.

To determine the lateral resistance of an individual drilled shaft, and the deflection, shear and moment along the shaft, we have provided input parameters for the commercial software LPILE by Ensoft, Inc. (2019) in Table 1. LRFD design methods for lateral loading of shafts and piles utilize a resistance factor of 1.0 and are controlled by allowable movement criteria. If groups of drilled shafts are used, the effects of group interaction should be considered when evaluating the horizontal load-deflection behavior. When using the P-Y method of analysis, the values of P (load) should be factored appropriately to account for the group effects. Recommended values of P-multipliers for loading perpendicular and parallel to a line of shafts or piles are provided on Figure 3.

6.2 Lateral Earth Pressures

The lateral earth pressures on abutment and wing walls depend on many factors, including surcharge loads, the soil type, drainage provisions, and whether or not the top of the wall can yield or deflect laterally/rotate during and after excavation. Where walls are free to deflect, they can be designed for the active condition. Where a deflection greater than

0.001 times the height of the wall (0.001H) cannot occur, walls should be designed for at-rest conditions. Active and at-rest earth pressures provided in Exhibit 6-1 assume the walls are backfilled with properly compacted onsite silty sands or Structural Backfill in accordance with FP-14 Section 704.04 in a 1 horizontal to 1 vertical (1H:1V) zone extending upward from the base of the wall from a point 1.5 feet behind the wall.

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Exhibit 6-1: Recommended Lateral Earth Pressure Design Parameters

Design Parameter

Design Value

On-site Silty Sand Fill

Structural Backfill - FP-14 Section 704.04

Total Unit Weight (pcf) 130 135

Effective Friction Angle (degrees) 32 34

Cohesion (psf) 0 0

Active Earth Pressure Coefficient, KA 0.31 0.28

Equivalent Fluid Density for Active Conditions (pcf) 40 40

At-Rest Earth Pressure Coefficient, KO 0.47 0.44

Equivalent Fluid Density for At-Rest Conditions (pcf) 62 60

NOTES:

Does not include water pressure, see below.

pcf = pounds per cubic foot; psf = pounds per square foot

Surcharge loads from motor vehicles/traffic and construction equipment will induce additional lateral loads on walls. The pressures provided in Exhibit 6-1 do not account for surcharge loads. Lateral loads due to various types of surcharges may be calculated by multiplying the surcharge by the active or at-rest earth pressure coefficient (KA or KO). The earth pressure coefficients are also shown in Exhibit 6-1. Surcharge loads should be applied as recommended on Figure 4.

The parameters provided in Exhibit 6-1 assume a free-draining backfill condition. It will be important to control surface water and to provide drainage measures that reduce the potential for water to accumulate behind walls, particularly considering the proximity of walls to the arroyo.

Surface water behind the wall should not be allowed to discharge directly into the wall backfill materials. In addition, water should not be allowed to discharge or pond around retaining structures. We recommend sloping the ground surface in front of walls a minimum of 5 percent away from the wall face for a minimum horizontal distance of 10 feet measured from the face of the wall (or until a paved surface is encountered, whichever is less).

In general, materials with greater than about 3 percent fines content are not considered free draining. Assuming on-site silty sand fill or structural backfill is used, the backfill will not be free draining, and a rapid drawdown condition could occur following flood events, i.e., water could be trapped in the backfill after flood waters recede. This condition could be addressed by designing the wall for appropriate water pressures or by including internal

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104000-001 July 2021 drainage features to reduce the potential for water to accumulate in the backfill.

Appropriate drainage features could include:

Placement of a 12-inch thick drainage layer on the back face of the wall, with a discharge system (e.g., weep holes or a perforated collector pipe at the base of the drainage layer, daylighting to a suitable discharge point).

Limiting the fines content of the wall backfill to 3 percent.

7 CONSTRUCTION CONSIDERATIONS

The applicability of the design parameters in Section 6 is contingent on good construction practice. Poor construction techniques may alter conditions from those upon which our recommendations are based, and therefore result in poor performance. Our analyses assume that this project will be constructed according to FP-14 U.S. Customary Units (FHWA, 2014) standards. The following sections provide additional construction considerations for this project.

7.1 Drilled Shaft Installation

7.1.1 Drilled Shaft Installation Methods and Equipment

Specifications and installation methods should be in general accordance with our recommendations and Section 565 of the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (FHWA, 2014).

Drilled shafts will obtain their capacity from within the bedrock. Our experience indicates heavy duty drill rigs using rock auger drill methods can penetrate sandstone bedrock similar to that encountered at the site. However, slower drilling rates should be expected in comparatively harder sandstone layers, which may necessitate alternate drilling methods, such as coring to achieve the minimum penetration. Laboratory test results completed on rock core samples indicated that the unconfined compressive strength (UCS) of the medium strong sandstone varied from about 4,800 to 5,860 pounds per square inch (psi). The UCS of the upper extremely weak to very weak sandstone is anticipated to be significantly lower (less than 700 psi). The means and methods of drilled shaft installation should be determined by the drilled shaft contractor. Further, as required by Section 565.04 of FP-14 (FHWA, 2014), the drilled shaft contractor should provide a construction plan that describes the proposed drilled shaft installation and construction methods.

Based on our subsurface explorations, approximately 17 to 29 feet of sand and gravel and cobbles with varying clay and silt content exists at the abutment locations. Based on our

Geotechnical Report

104000-001 July 2021 subsurface explorations, the drilled shafts will extend through gravel with cobbles. Based on drill action and considering that boulders were not observed during our geologic reconnaissance we do not anticipate encountering boulders during drilling. Cobbles can sometimes be excavated by conventional augers, but modified single-helix augers, designed with a taper and sometimes with a calyx bucket mounted on the top of the auger, a.k.a.

boulder rooters, are generally more successful at extracting larger cobble and smaller boulders if encountered (Brown and others, 2018). Groundwater was also encountered within the alluvium. We anticipate that temporary casing sealed into the bedrock will be required to prevent raveling, caving, and flowing conditions in the overburden. Where casing is used, it should be pushed, rotated, vibrated, or driven into the bedrock. The drilled shaft contractor will ultimately be responsible for selecting the means and methods of casing installation. The inside diameter of the casing should be equal to or larger than the specified drilled shaft dimensions. Where the casing is sealed into the bedrock bearing zone, bedrock penetration to achieve design capacity should begin at the bottom of the casing. If casing penetration of more than 2 feet into the bedrock occurs, we should be notified so that we may provide appropriate reduced side resistance parameters. Even with casing, groundwater can infiltrate into drilled shafts from perched water or within fractured or more permeable zones within the bedrock. Hence, the Contractor should be prepared for underwater concrete placement using a tremie pipe.

Installing temporary casing may be difficult if relatively clean, saturated sand and gravel are encountered during construction. If slurry methods are required to stabilize the excavation, we recommend the use of polymer or mineral slurry in accordance with Section 565.06 (b) of FP-14 (FHWA, 2014). The drilled shaft contractor should not be permitted to use natural or uncontrolled slurry methods during construction. Construction of drilled shafts using wet methods, i.e., slurry, is typically more difficult than constructing shafts using dry methods.

Because a wet excavation cannot be easily visually observed, good construction practices, particularly the recommendations discussed in Section 7.1.2, are critical to constructing shafts that perform adequately. Wet installation methods and specifications should be in accordance with Section 565 of FP-14 (FHWA, 2014).

7.1.2 Drilled Shaft Inspection and Observation

In accordance with Section 565.06 (a)(1) of FP-14 (FHWA, 2014), a geologist or engineer familiar with the subsurface conditions at the project site should observe drilled shaft installation to maintain a boring log of material excavated from the drilled shaft and to document other pertinent information during construction. The hole should be cleaned in accordance with Section 565.06 (a)(2) of FP-14 (FHWA, 2014) and observed by the geologist or engineer prior to pouring concrete. The drilling and concreting process should be

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104000-001 July 2021 relatively continuous with minimal stoppage of work between the completion of drilling, cleaning the hole, and the placement of concrete after setting the rebar cage. In addition, because concrete may need to be placed under water using a tremie pipe, quality construction techniques and observations by the geologist or engineer will be essential to drilled shaft installation and to confirm the shafts are installed in accordance with Section 565 of FP-14 (FHWA, 2014).

7.1.3 Concrete Placement

Groundwater inflow into drilled shafts from fractured or more permeable zones within the bedrock is possible. Pumping and/or tremie concrete placement may be required if significant water inflow develops in the bedrock or below the temporary casing, or shafts are constructed using wet methods. Tremie placement should be used if wet methods are used to construct the shafts, the excavation does not meet the criteria established in Section

565.06 (a)(2) of FP-14 (FHWA, 2014) for dry construction methods, or free-fall of the concrete (if the shaft meets the requirements for the dry construction method) measured from the bottom of the chute is more than 25 feet. The Contractor should be prepared to address these issues.

We recommend concrete be designed and placed in accordance with Section 565.08 of FP-14 (FHWA, 2014). Drilled shaft defects in cased shafts are frequently the result of inadequate head of concrete, particularly when combined with marginal or low slump concrete. If a truck-mounted pump is used to tremie concrete, pull-out of the pipe can occur if a pressure surge causes upward boom movement. Adequate methods should be established to measure and confirm that minimum head requirements are met throughout the concrete placement process.

7.1.4 Non-Destructive Integrity Tests

As recommended in Sections 565.07 and 565.09 of FP-14 (FHWA, 2014), Crosshole Sonic Logging (CSL) should be used to evaluate the integrity of all production drilled shafts. CSL is a non-destructive testing method that requires steel tubes to be installed in the drilled shaft and tied to the rebar cage. The tubes are attached to the interior of the rebar cage and then the cage is lowered into the hole and the concrete is placed. After the concrete has cured, a sound source and receiver are lowered, maintaining a consistent elevation between source and sensor. A signal generator generates a sonic pulse from the emitter which is recorded by the sensor. Relative energy, waveform, and differential time are recorded and logged. This procedure is repeated at regular intervals throughout the shaft. By comparing the graphs from the various combinations of access tubes, a qualitative idea of the soundness of the concrete throughout the drilled shaft can be interpreted.

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7.2 Earthwork and Grading

Earthwork, including site preparation, placement of fill, and subgrade preparation, should conform to the requirements provided in Division 200 of the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14 (2014).

7.2.1 Excavation

The overburden soils can likely be excavated using conventional excavating equipment, such as a rubber-tired backhoe or tracked hydraulic excavator.

7.2.2 Fill Placement and Compaction

Wall backfill should consist of either onsite silty sand or Structural Backfill (FP-14 704.04) as discussed in Section 6.2. If a drainage layer at the face of the wall is not used, as discussed in Section 6.2, we recommend the backfill consist of FP-14 704.01 Foundation Fill or 704.07 Select Borrow. Based on our laboratory testing, the onsite subgrade materials encountered at the abutment locations may be suitable for use as wall backfill.

Fill should be placed in uniform, horizontal layers with the loose lift thickness not exceeding 8 inches for heavy, self-propelled compactors, or 4 inches for hand-operated mechanical compactors. The appropriate lift thickness will depend on the Contractor’s equipment and the moisture content and quality of the selected backfill material. Compaction of backfill adjacent to walls can result in higher lateral earth pressures against the walls. Therefore, small equipment that is hand-operated should be required within a line extending upward from the base of the structure at 0.5H:1V, to a maximum horizontal distance of 5 feet from the face of the wall to reduce this potential.

Wall backfill should be moisture conditioned within 2 percentage points of the optimum moisture content and to at least 95 percent of the maximum dry density as determined by AASHTO T99 (standard Proctor compaction effort) in accordance with FP-14 Section 208. It should be noted that as the amount of fines increases in the wall backfill (portion of soil particles passing a U.S. Standard No. 200 sieve), soil becomes more sensitive to small changes in moisture content, and adequate compaction becomes more difficult to achieve.

8 CLOSURE

This report has been prepared for the exclusive use of HDR and Central Federal Lands Highway Division for the purpose of providing geotechnical recommendations for the

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Cottonwood Campground project. This geotechnical design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analysis and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule and budget, the analyses, conclusions, and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

Shannon & Wilson, Inc. has prepared “Important Information about Your Geotechnical Report,” to assist you and others in understanding the use and limitations of our reports.

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9 REFERENCES

American Concrete Institute (ACI), 2019, Building code requirements for structural concrete and commentary, Farmington Hills, Mich., ACI 318-19.

American Association of State Highway and Transportation Officials (AASHTO), 2020, AASHTO LRFD bridge design specifications, Customary U.S. units, 9th edition:

Washington, D.C., American Association of State Highway and Transportation Officials.

Brown, D.A., Turner, J.P., Castelli, R.J., and Loehr, J.E., 2018, Drilled Shafts: Construction Procedures and LRFD Design Methods: NHI Course No. 132014, Geotechnical Engineering Circular No. 10, Washington, D.C., Report No. FHWA NHI-18-024.

Ensoft, Inc., 2019, LPILE 2019, A Program for Analyzing Stress and Deformation of Individual Piles or Drilled Shafts Under Lateral Load, Austin, Texas.

Manley, K., Scott, G.R., Wobus, R.A., 1987, Geologic Map of the Aztec 1 Degree x 2 Degrees Quadrangle, Northwestern New Mexico and Southern Colorado: U.S. Geological Survey, scale 1:250,000.

Roberge, P.R., 2012, Handbook of corrosion engineering, Second Edition: McGraw-Hill, New York, New York.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2014, Federal standard specifications for construction of roads and bridges on Federal Highway projects, FP-14 English Units: U.S. Department of Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/pse/specs/.

U.S. Geological Survey (USGS) AASHTO 2009 Web Service Documentation Web Application (USGS, 2009). Available from:

https://earthquake.usgs.gov/ws/designmaps/

Widmann, B.L., compiler, 1999, Fault number 2337, Cannibal fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 11/03/2020 09:05 AM.

http://flh.fhwa.dot.gov/resources/pse/specs/ https://earthquake.usgs.gov/ws/designmaps/

Cottonwood Camground

Geotechnical Report

Table 1 - Geotechnical Parameters for Deep Foundation Design

Top Bottom Top Bottom Nominal Unit

Side Resistance

Strength Limit State Resistance

Factor Nominal Unit

Base Resistance

Strength Limit State Resistance

Factor p-y Curve

Total Unit Weight, γ

Peak Friction Angle, ϕ'

Strain Factor

Uniaxial Compressive

Strength, qu

Initial Modulus of Rock Mass RQD

(Boring ID) (ft) (ft) (ft) (ft) (ft) (ksf) (ksf) (pcf) (deg) εrm (psi) (psi) (%)

0 6 5,687 5,681 Medium Dense to Very Dense, Silty Sand - - - - Sand 125 34 - - - -

6 17 5,681 5,670 Very Dense, Poorly-Graded Gravel with Silt, Sand, and Cobbles - - - - Sand 130 38 - - - -

17 34 5,670 5,653 Sandstone 12 0.55 180 0.50 Strong Rock 130 - 0.0005 500 100,000 50

0 21 5,697 5,676 Very Loose to Medium Dense, Silty Sand - - - - Sand 115 30 - - - -

21 29 5,676 5,668 Very Dense, Poorly-Graded Gravel with Silt, Sand, and Cobbles - - - - Sand 130 38 - - - -

29 45 5,668 5,652 Sandstone 12 0.55 180 0.50 Strong Rock 130 - 0.0005 500 100,000 50

NOTES:

1 Ground surface elevation were based on the surveyed boring locations provided by HDR.

2 Design groundwater elevations should correspond to the arroyo flood elevation. Groundwater depth indicated is based on the value measured during drilling.

3 Factored shaft end bearing should be calculated by multipling the nominal unit end bearing by the area of the shaft and the given resistance factor. Factored side resistance should be calculated by multiplying the nominal unit side friction by the surface area of the sides of the shaft and the given resistance factor. Total factored axial compressive capacity for the shaft is determined by summing the factored end bearing resistance and factored side friction resistance.

4 Resistance factors should be reduced by 0.1 when considering uplift and by 0.2 for non-redundant shafts.

5 Side resistance is neglected in overburden.

6 Side resistance should be ignored in the top 2 feet of sandstone due to weathering at the top of the layer and the potential for disturbance from casing during installation.

7 The nominal shaft resistance parameters above are based on a single shaft and do not consider group action of closely spaced shafts (closer than 2 diameters, center to center).

8 The LPILE parameters are for a horizontal ground surface on the side of the foundation resisting lateral loading. Sloping ground surface modifications should be included as per Ensoft, Inc.'s recommendations for the LPILE program as necessary.

9 The LPILE parameters do not consider group effects. See Figure 3 for recommended p-multipliers.

10 Adjustments to the design parameters may be required to account for elevation changes due to final grading or for the inclusion of additional materials at the abutments.

11 Lateral loading analysis should consider the potential for soil loss due to scour and flooding.

12 For design below the water table, the effective unit weight of soil (γ' = γ - γw , γw = 62.4 pcf) should be used.

deg = degrees; ft = feet; ksf = kips per square foot; NA = Not applicable; pcf = pounds per cubic foot; psf = pounds per square foot

LPILE PARAMETERS 8, 9, 10, 11, 12

Abutment 2 (based on

SW-02)

Abutment 1 (based on

SW-01)

Drilled Shaft Axial Resistance Parameters 3, 4, 5, 6, 7

Depth Below Existing Ground Surface Elevation 1

5,676

5,674

Side Resistance Base ResistanceLocation Groundwater

Elevation 2 Generalized Soil/Rock

Description

104000-001 Page 1 of 1 T1 foundation parameters.xlsx - 2/5/2021

VICINITY MAP

FIG. 1

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Approximate Scale in Miles

1.5 3

July 2021

F i l e n a m e

I E

F D

E N s

C

F L

N

M

C o t t o n w o D r a f t i n g F d w g

D a t e

L o g i n m l w

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

MT

104000-001

NM FLAP SJU 10(1)

Cottonwood Campground

San Juan County, New Mexico

PROJECT

LOCATION

Project

Location

New Mexico

Las Cruces

Tucumcari

Socorro

Albuquerque

Santa Fe

Raton

Gallup

Najavo City

Turley

Najavo Dam

104000-001

SITE AND EXPLORATION PLAN

July 2021

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

F i l e

I E

F D

E N s

C

F L

N

M

C o t t o n w o D r a f t i n g F d t e

A u t h o r

A

E G

NM FLAP SJU 10(1)

Cottonwood Campground

San Juan County, New Mexico

MT

SW-01

LEGEND

Boring Designation and Approximate Location

NOTES

1. Map adapted from aerial imagery provided by Google Earth

Pro, reproduced by permission granted by Google Earth ™

Mapping Service.

FIG. 2

300 600

Approximate Scale in Feet

R d

Cottonwood Campground

Cottonwood Day Use Area

S n

J n

R i v e r

Access Road

Realignment Bridge

Parking Area

SW-02

SW-01

SW-03

104000-001_F3 - P-Multipliers.xlsx

NOTE:

Reference: AASHTO LRFD Bridge Design Specifications (2012) - Table 10.7.2.4-1 (from Hannigan et al., 2006)

The P-multipliers provided above were developed for vertical piles/shafts only. Batter piles provide a much stiffer response than vertical piles/shafts when loaded in the direction of the batter.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1.20

2 3 4 5 6 p- M ul tip lie r

S/B

1st Row 2nd Row 3rd Row or Higher

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

RECOMMENDED P-MULTIPLIERS

FOR LATERALLY LOADED

GROUPS OF PILES OR SHAFTS

2nd Row

3rd Row

1st Row

4th Row

Load Direction

Trailing Rows

Leading Row For Load acting in this direction, use p-Multiplier of the 1st Row

S

B

July 2021 104000-001

FIG. 3

NM FLAP SJU 10(1)

San Juan County, New Mexico

For m ≤ 0.4: s H

= 0.28 (psf) (see Note 3)

F i l e

I E

F D

E N s

C

F L

N

M

J o h n

D u n D r a f t i n g F

T y p

S u r c h a r g e d t e

A t h o r j c g

W a l l

PLAN VIEW

2.0 q

1.5

D e p t h

F a c t o r

Z

B

1.0

0.0

0.5

W a l l

Z

Wall Line

UNIFORM SURCHARGE

a b

EARTH BERM

(see Note 4)

Note:

H z=nH

Bottom of

Excavation x = mH

Point Load in Pounds s H

(psf)

ELEVATION VIEW

x = mH

H

Bottom of

Excavation

W a l l z=nH s H

(psf)

Line Load in

Pounds/Foot

B) LATERAL PRESSURE DUE TO LINE LOAD

i.e. NARROW CONTINUOUS FOOTING

PARALLEL TO WALL

C) LATERAL PRESSURE DUE TO STRIP LOAD

W a l l

W a l l

W a l l

A) LATERAL PRESSURE DUE TO POINT LOAD

i.e. SMALL ISOLATED FOOTING OR WHEEL LOAD y

D) LATERAL PRESSURE DUE TO EARTH BERM

OR UNIFORM SURCHARGE

Bottom of

Excavation

Bottom of

Excavation

E) LATERAL PRESSURE DUE

TO ADJACENT FOOTING

(see Notes 5 and 6)

0 0.5 1.0

L

B

NOTES

Figures are not drawn to scale.

Applicable surcharge pressures should be added to appropriate temporary and permanent wall lateral earth and water pressure.

If point or line loads are close to the back of the wall such that m £ 0.4, it may be more appropriate to model the actual load distribution (i.e., Detail E) or use more rigorous analysis methods.

See text for recommended K values.

The stress is estimated on the back of the wall at the center of the length, L, of loading.

The estimated stress is based on a Poisson's ratio of 0.5.

W a l l

Bearing

Pressure q (psf)

1.

2.

3.

4.

5.

6.

I p

, Influence Factor s H

= 2(I p

) q s

Lateral Footing

Pressure on Wall

(derived from NAVFAC DM 7.02, 1986; and Sandhu, Earth Pressure on Walls Due to Surcharge, 1974)

(derived from Poulos and Davis, Elastic Solutions for

Soil and Rock Mechanics, 1974; and Terzaghi and

Peck, Soil Mechanics in Engineering Practice, 1967)

(NAVFAC DM 7.02, 1986)

(derived from Fang, Foundation

Engineering Handbook, 1991)

(NAVFAC DM 7.2, 1986)

Point Load in Pounds g = Unit Weight of Earth Berm

Bearing

Pressure

Earth

Berm s H

= Lateral Pressure in radians

ELEVATION VIEW

(see Note 3)

(see Note 3) q s

L

2B

Q p

H n

(0.16 + n

For m > 0.4: s H

= 1.77 (psf)

Q p

H m n

(m

+ n

Q p s H s'

H

= s H cos

(1.1q) (psf) s'

H s'

H

For m ≤ 0.4: s H

= 0.20 (psf) (see Note 3)

Q l

H n

(0.16 + n

For m > 0.4: s H

= 1.28 (psf)

Q l

H m n

(m

+ n

Q l

Q p y ≤ 33°

H s

≤ 15 Feet

(K)(g)(H s s H

H s s H

= (K)q s

(see Note 4) q s

(psf) s H

= (b - sin b cos2a) (psf)

2q p

L

= 0.25

= 0.5

= 1 s H

L

2B

L

2B

L

2B

RECOMMENDED SURCHARGE

LOADING FOR TEMPORARY AND

PERMANENT WALLS

FIG. 4

104000-001July 2021

NM FLAP SJU 10(1)

7/14/2021-104000-001_AA.docx A-i

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Appendix A: Subsurface Ex plorations

Appendix A

Subsurface Explorations

CONTENTS

A.1 Introduction ........................................................................................................................... A-1

A.2 Explorations ........................................................................................................................... A-1

A.2.1 Soil and Rock Classification System ...................................................................... A-1

A.2.2 Standard Penetration Test (SPT) ............................................................................ A-2

A.2.3 Modified California (MC) Test and Sampling ..................................................... A-2

A.2.4 Bulk Sampling .......................................................................................................... A-2

A.2.5 Rock Core Sampling ................................................................................................ A-3

Figures Figure A-1: Soil Description and Log Key Figure A-2: Rock Classification and Log Key Figure A-3 through A-5: Log of Borings SW-01 through SW-03 Figure A-6 and A-7: Rock Core Photographs, Boring SW-01 and SW-02

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A.1 INTRODUCTION

Shannon & Wilson’s field exploration program was conducted on October 22, 2020, and consisted of drilling three borings, designated SW-01 through SW-03 at the locations shown on Figure 2. Photographs of boring locations are provided in Appendix C. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The borings were coordinated (including subcontractor coordination and utility locates) and observed by Shannon & Wilson. Individual boring logs are presented in Figures A-3 through A-5. These exploration logs represent our interpretation of the contents of the field logs and select results of laboratory testing. The borings were drilled by Vine Laboratories, Inc. of Commerce City, Colorado (under subcontract to Shannon & Wilson) using an ATV mounted CME-750X drill rig. The borings were advanced to depths ranging from approximately 34.3 to 45.0 feet for the two structure borings and 5.5 feet for the pavement boring. The structure borings utilized 6-inch outer diameter hollow-stem-auger drilling techniques and NQ2 rock coring methods. The pavement boring used 4-inch solid-stem-auger drilling methods. Where groundwater was encountered, our field representative measured the approximate depth to groundwater using an electronic water level indicator.

On completion of drilling, the borings were backfilled with cuttings and spread to approximately match the existing grade. Additionally, the offset location and direction of the borings was measured from the staked location. The offset locations were later used to obtain elevations of the borings from the "NM FLAP SJU 10(1)_Mapping.dgn" file provided by HDR, Inc.

A.2.1 Soil and Rock Classification System

During exploration, our representative collected samples and prepared field logs of the explorations. Soil classification for this project was based on ASTM International (ASTM) Designation: D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), and ASTM Designation: D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). The Unified Soil Classification System is summarized in Figure A-1. The Shannon & Wilson representative classified rock samples in general accordance with the International Society of Rock Mechanics (ISRM) classification method. According to this system, rocks are classified based on the stratigraphic structure, rock strength, degree of weathering, and other properties. The rock classification system is summarized in Figure A-2.

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A.2.2 Standard Penetration Test (SPT)

Disturbed samples were obtained in the borings in general accordance with the Standard Penetration Test (SPT) (ASTM Designation: D1586). The SPT consists of driving a 2-inch outside diameter, 1.375-inch inside diameter split-spoon sampler a distance of 18 inches with a 140-pound hammer free-falling a distance of 30 inches. An automatic hammer system was used to advance the samplers. The energy transfer ratio (ETR) for the hammer on the CME-750X ATV mounted drill rig was 97% based on a July 2019 report provided by Vine Laboratories. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6-inch increment of penetration and summed the blow counts for the last two 6-inch increments. This sum is recorded as the penetration resistance number, or N-value. If high penetration resistance prevented driving the total length of the sampler, the Shannon & Wilson field representative recorded the partial penetration depth and blow count. The N-values provide a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils (see Figure A-1). The raw N-values are shown on the individual boring logs.

Representative portions of the split-spoon sample obtained in conjunction with the SPT were placed in a screw-top plastic jar and transported to our laboratory.

A.2.3 Modified California (MC) Test and Sampling

Samples were also obtained using a modified California (MC) barrel sampler. The MC test procedure is similar to the SPT, except a larger diameter barrel sampler (2½-inch O.D., lined with 2-inch-diameter brass tubing) is used and only driven 12 inches. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6-inch increment of penetration. As a result of the larger diameter, the MC sampler yields slightly higher raw blow count numbers when compared to SPT N-values for similar soils. Because the difference in blow counts does not significantly impact our evaluation, we used the field MC blow counts over the 12-inch increment to define the relative density and consistency/stiffness of the subsurface materials following SPT terminology. Representative samples were sealed in the brass liner tubes with plastic caps and transported to our laboratory.

A.2.4 Bulk Sampling

A bulk soil sample was obtained by collecting the drill cuttings from the upper 4 feet of boring SW-03. Approximately 5 pounds of cuttings were placed in a plastic bag and transported to our laboratory for further analysis and testing.

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A.2.5 Rock Core Sampling

Rock samples were collected using NQ2 double tube wireline coring methods (1.875-inch-nominal-diameter rock core). During coring, cuttings were removed from the borehole by circulating water down through the drill rods and back up the annulus of the boring. Core runs were 5 feet in length, except for the first core run, which reamed out disturbed material at the bottom of the borehole.

Percent recovery and rock quality designation (RQD) values are shown on the boring log where coring was completed. Percent recovery is the ratio of the length of recovered core to the total length of the core run. RQD is the ratio, expressed as a percent, of the sum of the length of intact core pieces greater than 4 inches long in a run to the total length of the core run. Following drilling, the core was logged by the Shannon & Wilson field representative, then stored in cardboard core boxes and transported to the Shannon & Wilson laboratory.

Photographs of cores are presented in Figures A-6 and A-7.

July 2021 104000-001

Cottonwood Campground

San Juan County, New Mexico

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

CONSTITUENT2

SOIL DESCRIPTION

AND LOG KEY

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. A-1

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All…