B08_Attachment_2_BAND-266697_Final_GeotechnicalReport_Sept2024_0001.pdf

SUBMITTED TO:

Jacobs 3721 Rutledge Road NE, Ste B1 Albuquerque, NM 97109

BY:

Shannon & Wilson 5900 W. 38th Avenue Wheat Ridge, CO 80201

(303) 825-3800 www.shannonwilson.com

GEOTECHNICAL REPORT

NPS Bandelier National Monument Utility Rehabilitation

LOS ALAMOS & SANDOVAL COUNTIES, NEW MEXICO

September 26, 2024

Shannon & Wilson No: 107523-002

NPS Bandelier National Monument Utility Rehabilitation Geotechnical Report

107523-002 September 26, 2024 ii

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CONTENTS

1 Introduction

2 Site and Project Description

2.1 Below-Grade Water Tank and Maintenance Building

2.2 Utilities

2.3 Package Lift Station

2.4 Asphalt Pavement

3 Field Explorations and Laboratory Testing

3.1 Previous Investigation

3.2 Current Investigation

4 Geologic Setting and Subsurface Conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.2.1 Existing Pavement

4.2.2 Fill

4.2.3 Alluvium

4.2.4 Residual Soil

4.2.5 Bedrock

4.3 Groundwater

4.4 Anticipated Subsurface Conditions at Proposed Improvements

4.4.1 Below-Ground Water Tank and Mechanical Building

4.4.2 Utilities

4.4.3 Package Lift Station

4.4.4 Pavement Subgrade

4.4.5 Clay Subgrade

4.4.6 Sand Subgrade

5 Geologic Hazard Evaluation

5.1 Seismic Hazards

5.2 Corrosive Soil and Bedrock

5.3 Swelling and Collapsing Soil and Bedrock

6 Pavement Condition Assessment iii

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7 Geotechnical Engineering Recommendations

7.1 Pavement Design Recommendations

7.1.1 Design Criteria

7.1.2 Subgrade Design Strength

7.1.3 Swelling and Collapsing Soil and Bedrock Mitigation

7.1.4 Traffic Loading

7.1.5 Recommended HMA Pavement Section

7.1.6 Recommended PCC Parking Pads

7.1.7 Pavement Patches

7.2 Pavement Rehabilitation Alternatives

7.2.1 Full Depth Reclamation

7.2.2 Functional Mill and Overlay

7.2.3 Patching

7.2.4 Chip Seal

7.2.5 Crack Sealing and Crack Filling

7.2.6 Fog Seal

7.3 Seismic Design Considerations

7.4 Foundation Recommendations for Structures

7.4.1 Below-Grade Water Tank Foundation

7.4.2 Mechanical Building Foundation

7.4.3 Package Lift Station

7.4.4 Lateral Earth Pressures

7.4.5 Lateral Resistance

7.4.6 Uplift

7.5 Pipelines

7.5.1 Loads on Pipes

7.5.2 Thrust Restraint

7.5.3 Pipe Bedding and Backfill

8 Construction Considerations

8.1 Dewatering and Control of Water

8.2 Excavation and Support

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8.2.1 Excavation

8.2.2 Utility Considerations

8.2.3 Temporary Slopes and Shoring

8.2.3.1 Temporary Slopes

8.2.3.2 Shoring

8.3 Earthwork

8.3.1 Site Preparation

8.3.2 Structure Subgrades

8.3.3 Pavement Subgrades

8.4 Fill Placement and Compaction

8.4.1 Structural Backfill

8.4.2 Compaction of Bedrock-Derived Materials

8.5 Trenchless Crossing

8.6 Paving Materials

8.6.1 Hot Mix Asphalt

8.6.2 Portland Cement Concrete Pavement

8.6.3 Aggregate Base Course

8.7 Construction Observation

9 Closure

10 References

Exhibits Exhibit 4-1: Approximate Bedrock Depths Exhibit 5-1: Corrosion Testing Results Exhibit 5-2: Corrosivity Ratings Based on Soil Resistivity Exhibit 5-3: Corrosivity Ratings Based on Water Soluble Sulfate Exposure Exhibit 5-4: Swell Testing Results Exhibit 6-1: Pavement Condition Assessment Results Exhibit 7-1: R-value Testing Results Exhibit 7-2: Recommended Pavement Sections Exhibit 7-3: High Severity Fatigue Cracking (FHWA, 2014) Exhibit 7-4: Seismic Design Parameters Exhibit 7-5: Recommended Lateral Earth Pressures Exhibit 7-6: Recommended Pipe Bedding and Embedment Material Gradation v

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Tables Table 1: Summary of Borings

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Subsurface Investigations Appendix B: Laboratory Test Results Appendix C: Previous Geotechnical Logs and Laboratory Data Appendix D: Pavement Photographs Appendix E: Pavement Design Important Information

107523-002 September 26, 2024

1 INTRODUCTION

This report presents the results of our geotechnical explorations and provides our geotechnical engineering recommendations in support of the Design Development (DD) phase of work for the Bandelier National Monument Utility Rehabilitation Project (the project) in Los Alamos and Sandoval Counties, New Mexico. Our work was completed in accordance with our signed Professional Services Task Order Number 148045033 with Jacobs Government Services Company (Jacobs) dated September 14, 2023, and Revision Number 01 to this task order dated February 20, 2024. Under this agreement we:

Performed a subsurface investigation, including observation and logging of 37 borings, obtaining permits, completing utility locates, and coordinating traffic control;

Completed geotechnical laboratory tests on selected soil and bedrock samples;

Performed a visual condition assessment of asphalt pavement;

Evaluated potential geologic hazards;

Evaluated site subsurface conditions with respect to the proposed improvements;

Provided recommendations for geotechnical aspects of the project; and

Prepared this geotechnical report.

The scope of our services did not include any environmental assessment or evaluation regarding the presence or absence of wetlands or toxic materials in the soil, surface water, or air, on or below the site. If a service is not specifically indicated in this report, do not assume it was performed.

The conclusions and recommendations in this report supersede those presented in our previous reports (Shannon & Wilson, 2022 and 2024). The purpose of this report is to provide Jacobs with updated recommendations based on the results of the current investigation. The boring logs and laboratory data presented in the 2022 report were utilized in our analyses, along with the data collected during the current investigation, and are included in Appendix C of this report.

2 SITE AND PROJECT DESCRIPTION

The project is located in Los Alamos and Sandoval Counties, approximately 6 miles south of Los Alamos, New Mexico (Figure 1). Based on discussions with Jacobs, proposed project improvements include a new 24,000-gallon below-grade water tank with an adjacent mechanical building, new utility lines (water, gas, and electrical) constructed by open

107523-002 September 26, 2024 trenching and trenchless methods, and a package lift station. In addition, sections of asphalt pavement are being evaluated for rehabilitation or replacement. Each of the proposed improvements is discussed below.

2.1 Below-Grade Water Tank and Maintenance Building

The below-grade cast-in-place (CIP) 24,000-gallon tank and adjacent mechanical building will be located near the intersection of the Entrance Road and the treatment pond access road (see Figure 2). The approximate plan dimensions of the tank are 20 feet by 29 feet with a foundation depth of approximately 15 feet below existing ground surface (bgs). The proposed mechanical building will be constructed at grade and will consist of precast/prefabricated concrete. The approximate plan dimensions of the mechanical building are 12 feet by 16 feet.

2.2 Utilities

New water and natural gas utilities will extend from the New Mexico Highway 4 (NM Hwy

4) blue water storage tank along the Entrance Road alignment to Bandelier Visitor Center.

At this time, the inside diameter of the water and gas lines is expected to range from 2- to 10-inches. The utilities are expected to be buried a maximum of about 5 feet below ground surface (bgs). Water transmission pipelines will consist of polyvinyl chloride (PVC), except where paralleling existing force main within 10 feet of the alignment. In this case, waterlines will consist of fused PVC. Natural gas lines will consist of medium density polyethylene (MPDE). Most of the new utilities will be constructed using open trench methods along previously disturbed corridors such as paved or gravel roads. However, one section of waterline along the Entrance Road is planned for construction using trenchless methods where it crosses under NM Hwy 4.

2.3 Package Lift Station

The package lift station will be located along the Overflow Parking Road on the south side of Rios de los Frijoles. It is planned as a 6-foot diameter precast concrete manhole and may extend as much as 20 feet bgs (Figure 2).

2.4 Asphalt Pavement

Hot mix asphalt (HMA) pavement rehabilitation and/or replacement may be performed throughout the site in the 13 areas as described below:

Entrance Road: A two lane, 3.2-mile-long road between NM Hwy 4 and the Visitors Center.

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Campground Road: Accessed approximately 0.2-mile from NM Hwy 4 along the Entrance Road and consists of a 0.4-mile, two-lane road that connects to Saltbrush Road, Paintbrush Road, Coopers Hawk Road and Field Operations Center, Juniper Campground Loops, Amphitheater parking, and bus stop parking.

Saltbrush Road, Paintbrush Road, and Parking: Accessed approximately 0.1-mile from Entrance Road along the Campground Road and consists of two loop roadways approximately 0.2-mile long that vary in width from one to two lanes. This road also includes several parking spaces.

Coopers Hawk Road and Field Operations Center Parking: Accessed at the turn off from Campground Road to Saltbrush and Paintbrush Roads and consists of a two-lane road approximately 0.2-mile long that ends at the Field Operations Center parking area.

Juniper Campground: Accessed using the Campground Road and consists of three one-way loops (Abert Squirrel Loop, Black Bear Loop, and Coyote Loop) each approximately 0.2- to 0.4-mile long.

Amphitheater Parking: Accessed using the Campground Road and consists of parking for approximately 20 cars.

Bus Stop Parking: Accessed using the Campground Road and is adjacent to the Amphitheater parking and consists of parking for approximately 20 cars and 4 busses.

(Some of the parking lot was under construction at the time of our 2023 exploration).

Fire Tower Lane and Parking: Accessed approximately 1.3-miles from NM Hwy 4 along the Entrance Road and consists of a vehicle turn around loop adjacent to the Entrance Road, a one-lane road to the Fire Tower Lane parking, and a parking area for several cars.

Agoyo Lane and Parking: Accessed approximately 2.9-miles from NM Hwy 4 along the Entrance Road and consists of a two-lane road approximately 0.1-mile long with parking at the end of the road for several vehicles.

Stonehouse Road and Parking: Accessed from the Visitor Center parking area and consists of a one lane road approximately 0.1- to 0.2- mile long with several small parking areas suitable for one or two cars each. One of the parking lots is surfaced with gravel and the others are asphalt pavement.

Frijoles Canyon Maintenance Parking: Accessed at the beginning of Stonehouse Road from the Visitor Center Main Parking and consists of parking for several maintenance vehicles.

Visitor Center Main Parking: Accessed at the end of the Entrance Road and consists of a loop with parking for approximately 80 cars and a few busses.

Overflow Parking Road: Accessed from the Entrance Road approximately 750 feet southeast of the Visitor Center Main Parking area and consists of a loop with parking for several vehicles.

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3 FIELD EXPLORATIONS AND LABORATORY TESTING

3.1 Previous Investigation

Shannon & Wilson performed a subsurface investigation in December 2021 during the preliminary design phase of the project (Shannon & Wilson, 2022). This investigation included 14 borings (designated SW-01 through SW-14). Boring logs and laboratory test results are included in Appendix C of this report for reference. A summary of the borings is included in Table 1, and approximate boring locations are shown in Figure 2.

3.2 Current Investigation

During the DD phase of the project, Shannon & Wilson’s field exploration program included 37 borings (designated SW-15 through SW-52) drilled during two mobilizations. The first mobilization was from November 2 to November 7, 2023, and consisted of drilling 28 borings. The second mobilization was from April 9 to April 11, 2024, and consisted of drilling nine borings. Boring SW-16 was not drilled due to utility clearing and permitting issues with the Los Alamos National Laboratory (LANL). Approximate boring locations are shown in Figure 2.

Appendix A describes the procedures used to complete the drilling and sampling of the geotechnical borings and presents the individual exploration logs along with an explanation of the symbols and terminology used on the logs.

We completed geotechnical laboratory testing to determine index and engineering properties of selected soil and rock samples retrieved from the borings. Laboratory tests included natural water content, Atterberg limits, grain-size distribution, corrosion testing, one-dimensional swell/collapse, R-Value, and proctor compaction. Laboratory test methods and results are provided in Appendix B. The natural water contents, Atterberg limits, and fines content are also indicated on the individual boring logs in Appendix A.

4 GEOLOGIC SETTING AND SUBSURFACE CONDITIONS

We based our understanding of the geology and subsurface conditions at the site on regional geologic maps, our field reconnaissance, and the results of our field exploration program.

107523-002 September 26, 2024

4.1 Regional Geology

We reviewed a geologic map of the Frijoles quadrangle (Goff and others, 2002), the southern half of which includes Bandelier National Monument. The regional geology of the project site is characterized by relatively recent (Eocene-age and later) volcanism and tectonic activity. Surficial units mapped within the project area consist primarily of pyroclastic fall deposits overlying ash-flow tuff from volcanic activity within the past fifty thousand to two million years. The pyroclastic deposits form part of the Pajarito Plateau, which has since been deeply incised by stream water erosion, resulting in the distinctive canyons and finger mesas within Bandelier National Monument.

Based on the mapping by Goff and others (2002), the project traverses multiple geologic units as described below:

Alluvium (Qal) – Holocene-age deposits of gravel, sand, and silt in canyon bottoms.

Terrace gravel (Qt) – Holocene-age, slightly older alluvium along the margins of streams and basins that is currently undergoing erosion.

El Cajete pyroclastic beds (Qvec) – Pleistocene-age (approximately 50- to 60-thousand-year-old) deposits of vesicular rhyolite rich in pumice.

Bandelier Tuff, Tshirege Member (Qbt) – Pleistocene-age (approximately 1.25 million years old) rhyolitic ash-flow tuff.

Mafic lava flows (Tcb) – Pliocene-age deposits of basalt exposed by erosion of overlying pyroclastic units.

Our observations of exposed rock slopes and subsurface samples from the borings along the project alignment are consistent with this mapping.

4.2 Subsurface Conditions

Subsurface conditions encountered in the explorations included asphalt pavement and aggregate base course, fill, alluvium, residual soil, and bedrock. A description of each of these units is provided in the sections below. Note that the boring logs included in Appendix C did not always identify the name of the geologic unit.

The explorations were completed to evaluate geotechnical soil and bedrock conditions at the site. Our observations are specific to the locations, depths, and times noted on the boring logs and may not be applicable to all areas of the project. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions. Section 9 describes the limitations of our geotechnical report as it relates to the project and subsurface conditions.

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4.2.1 Existing Pavement

The existing monument roadways and parking areas are paved with HMA pavement. The observed pavement thicknesses in the 31 borings ranged from 2-1/2 to 7 inches. Aggregate base course (ABC) was encountered in approximately 65% of our boring locations with thicknesses ranging from approximately 1 to 7 inches. A summary of observed pavement thicknesses is provided Table A-1 in Appendix A, along with photographs of pavement cores completed in our subsurface investigation.

4.2.2 Fill

Fill was observed in borings SW-05, SW-17, and SW-39 at the ground surface or below the asphalt pavement. The observed thickness of fill ranged from less than 1 foot to 8 feet.

However, some of these borings terminated in fill; therefore, the actual thickness of this unit is unknown. As observed in the borings, fill consisted of medium dense to very dense, silty sand (SM).

4.2.3 Alluvium

Alluvium was observed in borings SW-13, SW-14, SW-23, SW-41, SW-43, SW-45 to SW-50, and SW-52 at the ground surface or below the asphalt pavement. The alluvium was generally located at the bottom of the canyon near the Visitor Center. The observed thickness of alluvium ranged from less than 1 foot to 21.5 feet. However, most of these borings terminated in alluvium; therefore, the actual thickness of this unit is unknown. As observed in the borings, alluvium consisted of interbedded layers of very loose to very dense sand and gravel with varying amounts of silt and clay (SM, SP-SM, SC, and SP).

Boulders were observed in an adjacent slope at boring SW-14 and cobbles were inferred or observed in borings SW-43, S-46, SW-48, and SW-49. Very stiff to hard sandy silt (ML) was observed in a few locations.

4.2.4 Residual Soil

Most of the borings on top of the mesa above the Visitor Center encountered completely weathered rhyolite bedrock (including Cajete pyroclastic beds) or tuff bedrock at the ground surface (borings SW-01-SW-03, SW-06-SW-10, SW-15, SW-18-SW-22, SW-24-SW-33, SW-37, and SW-38). As described in Appendix A, the bedrock was logged as a soil in some areas with a dual rock description because the relatively weathered, low-strength bedrock (where encountered) may be considered more soil-like in engineering properties.

The completely weathered bedrock encountered at the surface was labeled as residual soil on the logs presented in Appendix A. The thickness of this material ranged from approximately 1 to 11 feet, varying by location. Locally, the residual soil layer may have

107523-002 September 26, 2024 been reworked or disturbed by surficial erosional and depositional processes. As encountered in the borings, residual soil consisted of very loose to dense sand with varying amounts of silt, clay, and gravel (SM, SP-SM, and SC). Medium stiff sandy silt (ML) and stiff to hard lean clay with varying amounts of silt and sand (CL, CL-ML) was also observed in some locations.

4.2.5 Bedrock

Bedrock was encountered in most of the borings below the residuum and extended to the bottom of the explorations. As encountered in the borings, bedrock consisted of extremely weak to weak, moderately weathered to fresh rhyolite (El Cajete pyroclastic beds) and Upper Bandelier Tuff. Basalt bedrock was also encountered in boring SW-13. The basalt was described as medium strong to very strong, slightly weathered rock. Approximate bedrock depths encountered during our subsurface investigations are shown in Exhibit 4-1.

Exhibit 4-1: Approximate Bedrock Depths

Boring Approx. Bedrock Depth

(ft) Bedrock Type

SW-03 2 Rhyolite

SW-02 0.2 Tuff

SW-13 0.2 Basalt

SW-17 9 Rhyolite

SW-23 7.3 Rhyolite

SW-25 6 Rhyolite

SW-29 7 Rhyolite

SW-30 3 Rhyolite

SW-31 2.5 Rhyolite

SW-32 4 Rhyolite

SW-33 10 Rhyolite

SW-34 0.2 Rhyolite

SW-35 0.2 Rhyolite

SW-36 0.6 Tuff

SW-37 4 Tuff

SW-38 1 Tuff

NOTE:

Approx. = Approximately; ft = feet

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4.3 Groundwater

Groundwater was encountered in borings SW-12, SW-48, and SW-49 at depths of 8.5, 9.0, and 9.8 feet bgs, respectively, at the time of drilling. Groundwater fluctuations are possible and will depend on many factors, including seasonal variations, local precipitation, runoff, and snow melt.

4.4 Anticipated Subsurface Conditions at Proposed Improvements

4.4.1 Below-Ground Water Tank and Mechanical Building

Subsurface conditions near the proposed 24,000-gallon below-ground water tank are based on borings SW-09, SW-37, and SW-38, which were drilled to depths ranging from 5.5 to 50.5 feet bgs. These borings encountered 4 to 11.5 feet of residual soil (medium dense to very dense, silty sand with varying amounts of gravel) underlain by completely weathered to extremely weak, slightly weathered to fresh Upper Bandelier Tuff. Bedrock was able to be augered to the maximum boring depth of 50.5 feet. No groundwater was encountered.

4.4.2 Utilities

Subsurface conditions encountered along the proposed utility lines are varied and will include both overburden soils, completely weathered bedrock, extremely weak to weak, rhyolite and tuff bedrock, along with medium strong to very strong basalt near boring SW- 13.

4.4.3 Package Lift Station

Subsurface conditions near the proposed package lift station are based on borings SW-14 and SW-52, which were drilled to depths ranging from 5 to 21.5 feet bgs. These borings encountered alluvium consisting of very loose to very dense sand with varying amounts of silt and gravel (SM, and SP-SM). Some of the silty sand graded to very stiff, sandy silt (ML).

No groundwater was encountered.

4.4.4 Pavement Subgrade

Subsurface conditions below the existing pavements varied throughout the site. However, in general, pavement subgrade conditions can be divided into two types: clay or sand.

4.4.5 Clay Subgrade

Clay subgrade materials were primarily observed in the Juniper Campground and surrounding areas (Campground Road west of Saltbrush Road, Juniper Campground loops, Amphitheater Parking, and Bus Stop Parking). The clayey subgrade consisted of lean clay

107523-002 September 26, 2024 with varying percentages of sand, silt with varying percentages of sand, and clayey sand [AASHTO soil classification A-4 and A-6]. The clay and silt varied from medium stiff to hard in consistency. Extremely weak to weak rhyolite bedrock was also encountered in the subgrade of some borings.

4.4.6 Sand Subgrade

Sand subgrade materials were observed throughout the rest of the site. The sandy subgrade consisted of sand with varying percentages of silt and clay [AASHTO soil classification A-1-a, A-1-b, A-2-4, A-3, A-4, and A-6]. Additionally, extremely weak to weak rhyolite or tuff bedrock was encountered in the subgrade of some borings.

5 GEOLOGIC HAZARD EVALUATION

5.1 Seismic Hazards

Based on geologic mapping, the nearest fault to the project site is the Pajarito Fault Zone, a late Quaternary-age normal fault that runs through Bandelier National Monument less than 5 miles west of the site (USGS, 2021 and McCalpin, 2005). The fault is not mapped as passing through the project site. The fault is primarily in Tertiary bedrock with a long-term average slip rate of 0.1 mm per year (McCalpin, 2005). National Park Service documents indicate that the most recent surface-rupturing earthquake within the fault zone occurred between 2,200 and 1,400 years ago, with no historic surface-rupturing earthquakes on record (KellerLynn, 2015). Most historic recorded earthquakes near the fault zone have been of magnitude 3.5 or lower (Gammans and others, 2017 and KellerLynn, 2015), with the most recent strong earthquake in the area recorded in 1918 in nearby Santa Fe County (estimated magnitude 6.0). The probability of an earthquake of magnitude 5.0 or greater occurring within the next 100 years affecting the area near the project site is estimated to be greater than 50 percent (KellerLynn, 2015).

Liquefaction can occur in loose, saturated, cohesionless soils when subjected to earthquake ground shaking. Based on the subsurface conditions at the site, it is our opinion that the risk of liquefaction is low.

Seismic compression may occur when loose, granular soils above the groundwater table are rearranged into a tighter packing configuration during seismic shaking, which can cause settlement. Based on subsurface conditions at the site, it is our opinion that the risk of settlement from seismic compression is generally low. However, looser alluvial soils as encountered in 11 borings (SW-11, SW-12, SW-14, SW-15, SW-19, SW-21, SW-22, SW-43, SW-

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45, SW-46, SW-47, SW-50, and SW-52) could be anticipated to compress and settle under the design seismic event (see Section 7.2).

5.2 Corrosive Soil and Bedrock

The soil/rock encountered at the project site can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, selected samples were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are summarized below in Exhibit 5-1.

Exhibit 5-1: Corrosion Testing Results

Boring Depth (feet) Material pH

Resistivity (ohm-cm)

Sulfate Content

Chloride Content

SW-01 2.5 CL 7.6 2,600 0.01 0.008

SW-07 5.0 SM 8.9 4,600 0.02 0.005

SW-14 12.5 ML 6.9 3,400 0.01 0.007

SW-17 2.5 SM 10.1 5,500 0.01 0.023

SW-18 4.0 SM 8.3 6,700 <0.01 0.023

SW-27 4.0 CL 7.1 1,900 0.01 0.030

SW-32 2.5 SM 7.6 4,600 0.02 0.020

SW-34 2.0 SM 8.7 32,000 <0.01 0.020

SW-38 4.5 SM 8.9 10,000 <0.01 0.020

SW-48 0.0 SM 9.4 8,000 <0.1 0.025

NOTES:

Water-soluble sulfate and chloride content values are shown as percent weight in dry soil.

ohm-cm = ohm-centimeter

The resistivity measured in the samples ranged from 1,900 to 32,000 ohm-centimeters.

Based on correlations developed by Roberge (2012) as shown in Exhibit 5-2, these values suggest essentially noncorrosive to highly corrosive subsurface conditions for metallic pipe in contact with subsurface materials across the site. Only two of the 10 tests performed classified the soils as being essentially noncorrosive or mildly corrosive. The remaining tests classified the soils as being moderately to highly corrosive.

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Exhibit 5-2: Corrosivity Ratings Based on Soil Resistivity

Soil Resistivity (ohm-cm)

Corrosivity Rating

>20,000 Essentially Noncorrosive

10,000-20,000 Mildly Corrosive

5,000-10,000 Moderately Corrosive

3,000-5,000 Corrosive

1,000-3,000 Highly Corrosive

<1,000 Extremely Corrosive

The concentration of water-soluble sulfates measured in the samples was <0.01% to 0.02% by weight. Based on classifications as defined by ACI-318-19 (ACI, 2019) as shown in Exhibit 5-3, these test results classified as Negligible (S0) for concrete exposed to site soils.

Exhibit 5-3: Corrosivity Ratings Based on Water Soluble Sulfate Exposure

Water Soluble Sulfate in Soil (Percent by Weight)

Sulfate Severity (Class)

<0.10 Negligible (S0)

0.10-<0.20 Moderate (S1)

0.20-2.00 Severe (S2)

>2.00 Very Severe (S3)

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.

5.3 Swelling and Collapsing Soil and Bedrock

Many soil and rock formations are susceptible to volume change by swelling/collapsing.

This geologic phenomenon has the potential to cause substantial damage to lightly loaded structures, such as pavements. To provide an indication of the swell/collapse potential of near surface soil and bedrock materials at the site, we performed eight swell/consolidation tests on soil samples encountered in our explorations. All of the tests were run with an inundation pressure of 200 pounds per square foot (psf). The results are presented below in Exhibit 5-4 and are included in Appendix B.

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Exhibit 5-4: Swell Testing Results

Boring Depth (feet) Material % Swell/Collapse

SW-18 4.0 Residual Soil -0.4

SW-22 4.0 Residual Soil -4.2

SW-25 2.0 Residual Soil -0.8

SW-26 2.0 Residual Soil 1.1

SW-33 2.5 Residual Soil -0.4

SW-36 2.0 Upper Bandelier Tuff -0.2

SW-39 1.0 Fill -0.3

SW-41 4.0 Alluvium -0.7

The swell test result for boring SW-26 indicated a swell potential of 1.1%. The remaining tests indicted a collapse potential of less than 1%, except for the result from boring SW-22 which indicated a collapse potential of 4.2%. These results are indicative of a low swell and low to medium collapse potential. Swell/collapse mitigation recommendations for pavements are provided in Section 7.

6 PAVEMENT CONDITION ASSESSMENT

To evaluate the condition of the existing roadway pavement for potential rehabilitation options, Shannon & Wilson performed a visual pavement survey on October 25 and 26, 2023 to assess the general pavement condition and to identify areas of distress and typical crack patterns. We used the U.S. Fish and Wildlife Services (FWS) rating system to quantify levels of distress and to describe roadway conditions of asphalt pavements. Their five levels of pavement condition for asphalt are summarized below:

Excellent: Recently constructed or overlaid road where construction or overlay was performed correctly. No maintenance required.

Good: Low extent longitudinal and transverse cracks. All cracks are ¼ inch or less with little or no crack erosion. Patches are in good condition and applied correctly. Routine maintenance recommended.

Fair: Roads are in good structural condition with little or no fatigue cracking.

Longitudinal, transverse, and edge cracking is at medium extent and severity. Block cracking is extensive. Any patches are in good condition. Preventative maintenance recommended.

Poor: Road beginning to show signs of structural distress. Fatigue cracking is medium to high extent and medium severity. Cracking is severe. Surface may have severe block

107523-002 September 26, 2024 cracking and show. Patches are in fair to poor condition. There is moderate distortion or rutting and occasional potholes. Rehabilitation recommended.

Failed: Road is severely deteriorated. Signs of structural failure appear along with severe and extensive fatigue cracking, distortion, potholes, or extensive patches in poor condition. Reconstruction recommended.

Observations made by Shannon & Wilson along the 13 roadway segments and parking areas indicate asphalt pavement conditions of poor, fair, and good. Photographs of pavement conditions are presented in Appendix D. Our classification of pavement conditions by segment are summarized below in Exhibit 6-1, and presented graphically in Figure D-1 in Appendix D.

Exhibit 6-1: Pavement Condition Assessment Results

Roadway Poor

Condition Fair

Condition Good

Condition Comments

Entrance Road X

Low to high extent and severity transverse cracking. Low extent and low to medium severity longitudinal cracking. Parking areas had low to high extent and severity block cracking. Juniper Campground loop roads had occasional areas with low to medium severity edge cracking.

Campground Road X

Saltbrush & Paintbrush Roads and Parking

X

Coopers Hawk Road and Field Operations Center Parking

X

Juniper Campground X

Amphitheater Parking X

Bus Stop Parking X

Fire Tower Lane and Parking X X

Medium to high extent and severity transverse and longitudinal cracking. Medium to high extent and severity block cracking.

Agoyo Lane and Parking X X

Stonehouse Road and Parking

X X

Frijoles Canyon Maintenance Parking

X X

Visitor Center Main Parking X Low to high extent and severity transverse cracking. Low extent and low to medium severity longitudinal cracking. Parking areas had low to high extent and severity block cracking.

Overflow Parking Road X No to low extent and severity cracking observed.

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7 GEOTECHNICAL ENGINEERING

RECOMMENDATIONS

The recommendations presented in the following sections are based on our understanding of the project based on conversations with Jacobs and our subsurface exploration and laboratory testing program.

7.1 Pavement Design Recommendations

At the time of this report preparation, the scope of the monument's pavement rehabilitation and/or reconstruction has not been finalized including the specific roadways to be replaced, or rehabilitated. The following sections provide reconstruction design recommendations and provide a general discussion of rehabilitation alternatives.

7.1.1 Design Criteria

We understand that pavement rehabilitation and reconstruction areas are currently unknown. Our pavement design and results are based on the design procedures presented in the 1993 AASHTO Guide for the Design of Pavement Structures (AGDPS) with guidance from the New Mexico Department of Transportation (NMDOT) Design Manual (NMDOT, 2020). The following sections summarize our pavement analysis and design assumptions (pavement design inputs and calculations are presented in Appendix E).

7.1.2 Subgrade Design Strength

As discussed in Section 4.4, soils below the proposed pavement vary in the project area. The subgrade strength for the project was evaluated by R-value testing on samples of the subgrade material. R-value testing results are shown Exhibit 7-1.

Exhibit 7-1: R-value Testing Results

Boring

AASHTO

Classification R-value

SW-26 A-4 45

SW-36 A-2-4 68

SW-50 A-1-b 72

To estimate the design subgrade strength, a correlation from R-value to resilient modulus was utilized. Correlations from the AGDPS (AASHTO, 1993) are limited to R-values of 20 or less. No local NMDOT R-value correlations are available, but a City of Albuquerque

107523-002 September 26, 2024 correlation is available from their Development Process Manual (2020). For our analysis, we assumed a design R-value of 45 and correlated this value to a design resilient modulus of 10,322 psi.

7.1.3 Swelling and Collapsing Soil and Bedrock Mitigation

As discussed in Section 5.3, all but one of the swell/consolidation test results indicated low collapse potential; the remaining sample from SW-22 indicated moderate swell potential.

Considering the test results and that site development is not anticipated to significantly change the moisture regime at the site, we recommend moisture treating the upper 8 inches of subgrade material below the pavement section. See Section 8.3.3 for moisture treatment and compaction requirements for the pavement subgrade.

Our recommendation assumes surface drainage patterns don't change and wet utilities don't leak. At new structures, it is also important that proper surface drainage be designed and maintained to prevent ponding and reduce infiltration near pavements. Irrigation near pavements should not be performed.

7.1.4 Traffic Loading

Traffic loading was estimated using shuttle bus schedule information provided on the National Park Service website for Bandelier National Monument (US Department of the Interior, 2022), traffic counts provided by Jacobs, and guidance from the AGDPS (AASHTO, 1993). We assumed three types of vehicles contribute to traffic loading within the park:

shuttle buses, garbage trucks, and passenger vehicles. We estimated the total annual one-way vehicle passes for each vehicle type. We projected the annual one-way vehicle passes for a pavement design life of 20 years using a growth rate of 2%, which was provided by Jacobs.

To estimate the passenger vehicle passes, we used average annual daily traffic (AADT) volumes from 2022 that were provided by Jacobs. The data showed AADT of 770 vehicles per day for the Entrance Road and less than 200 vehicles per day for the other roads. We assumed the traffic was one way and was for passenger vehicles. This traffic was projected forward using the 2% growth rate and assuming a paving year of 2025 and a design life of 20 years.

We assumed one garbage truck per week visits the park with an average weight of 54 kips.

The National Park Service website provided a shuttle bus schedule for Bandelier National Monument (US Department of the Interior, 2022). The website stated that buses run seven days a week from June to the middle of October (we assumed five total months). The

107523-002 September 26, 2024 website also stated that buses start at 9:00AM each day and run every half hour on weekdays and every 20 minutes on weekends. We assumed buses stop running at 5:00PM.

We assumed the average weight of a shuttle bus was 32 kips.

After determining the number of passes for each vehicle type, we then used axle load equivalency factors for flexible pavement provided in Appendix D of the AASHTO GDPS (AASHTO, 1993) to estimate the 18-kip equivalent single axle loading (ESAL) along the Entrance Road. We calculated a 20-year design value of approximately 81,000 ESALs for roadways where shuttle bus traffic is anticipated. See Appendix E for the traffic loading calculation.

The shuttle busses contribute the majority of the vehicular traffic loading. For our analysis, we provided pavement sections for the project shuttle bus routes as well as low volume roads (access roads without routine shuttle bus traffic). For the low volume road design, we used the AGDPS (AASHTO, 1993) minimum traffic loading of 50,000 ESALs.

7.1.5 Recommended HMA Pavement Section

Exhibit 7-2 summarizes our recommended pavement sections.

Exhibit 7-2: Recommended Pavement Sections

Roadway

Design Traffic Loading (ESALs) Alt. 1 Alt. 2 Alt. 3

Shuttle Bus Routes 80,000 4-1/2 in. HMA 3-1/2 in. HMA 4 in. ABC

3 in. HMA 6 in. FDR

Low Volume Roads (3) 50,000 4 in. HMA 3 in. HMA 4 in. ABC

3 in. HMA 6 in. FDR

NOTE:

A Class 1 geotextile separator should be provided below ABC.

A 6-inch minimum existing pavement section is required for FDR. Where existing pavement is not thick enough, the underlying ABC

(if present) or new ABC may be added to achieve the required thickness.

Low volume roads are all roads with average annual daily traffic less than 200 vehicles per day and that do not have routine shuttle bus traffic.

Refer to Appendix E for the pavement design analysis worksheets.

ABC = Aggregate Base Course; Alt. = Alternative; ABC = Aggregate Base Course; ESALs = 18-kip equivalent single axle loading; FDR = Full Depth Reclamation; HMA = Hot Mix Asphalt; in. = inches.

7.1.6 Recommended PCC Parking Pads

We understand that reinforced Portland Cement Concrete (PCC) pavement parking pads will be constructed at the visitor center parking lot. We recommend following standard plan sheet 501-1 from Federal Lands Highway (U.S. Department of Transportation, 2024) for the continuously reinforced PCC pavement parking pad. The details from sheet 501-1 call

107523-002 September 26, 2024 for W6 x W6 welded wire mesh or no. 4 bars spaced 12 in. by 24 in. For the PCC pavement thickness, we recommend 6 inches.

7.1.7 Pavement Patches

When patching pavement, the patch should match the existing pavement section or follow the recommended pavement thicknesses in Section 7.1.5 if the existing pavement section is thinner than the recommended pavement sections.

In narrow pavement patches (e.g., adjacent to curb and gutter or for utility cuts), compaction of the HMA will be difficult and may require the use of narrow handheld equipment to compact the individual HMA lifts. The size of handheld equipment available may require enlarging the size of the pavement repair patch to utilize larger equipment.

Pavement patches to repair damaged pavements should be saw cut into rectangular areas.

The longitudinal saw cuts (relative to the direction of traffic) should be located along the edge of the proposed lane or in the center of the lane. If necessary, we recommend widening the patch to relocate the saw cut from wheel paths for improved long-term performance of the patch.

7.2 Pavement Rehabilitation Alternatives

As described in Section 6, the majority of roadway and parking areas are considered to be in fair to good condition. Only four roadway segments were considered to be in fair to poor condition: Fire Tower Lane and Parking, Agoyo Lane and Parking, Frijoles Canyon Maintenance Parking, and Stonehouse Road and Parking. At this time, it is not known where and to what extent pavement rehabilitation may occur. At a minimum, we understand that in the areas where utility trenches are excavated in the roadway, half of the roadway will require replacement or repair. See Section 7.1.7 for pavement patching recommendations, Section 7.5 for recommendations for backfill of utility trenches, and Section 8.3 for pavement subgrade compaction recommendations.

High-severity fatigue or alligator cracking indicates the pavement section can no longer support traffic loading and rehabilitation is generally not possible. Refer to 2014 FHWA Distress Identification Manual for the definitions of crack pattern distress levels (FHWA, 2014). High-severity fatigue cracking typically looks like moderately or severely spalled interconnected cracks forming a complete pattern (see Exhibit 7-3). For pavement areas with high-severity fatigue cracking, we recommend replacing the pavement section before performing a rehabilitation on the adjacent pavement area.

Exhibit 7-3: High Severity Fatigue Cracking (FHWA, 2014)

When selecting pavement rehabilitation options, the project team should consider cost, size of rehabilitation area, length of traffic control lane closures and durations, effect on expected ride quality of pavement, and expected extension of pavement service life. Based on pavement subgrade conditions, our visual pavement condition assessment, and the existing pavement section thicknesses, we recommend the following six feasible pavement rehabilitation/reconstruction methods for consideration of the project team.

7.2.1 Full Depth Reclamation

Full Depth Reclamation (FDR) consists of pulverizing the existing pavement section in-place so that becomes the base of a new HMA pavement section. A new HMA surface layer is then paved over the FDR prepared roadway, typically resulting in an overall raise to the roadway grade. Utilizing FDR effectively provides a new pavement section and eliminates the potential for reflective cracking from the underlying pavement. Another benefit is that the existing pavement does not need to be hauled away as it is incorporated into the new pavement section.

One issue with completing FDR at the site is that shallow bedrock was observed underlying the pavement in many of the roadway segments. In these locations, there may be an

107523-002 September 26, 2024 increased risk of damaging the machinery used to pulverize the existing pavement section.

In our opinion, we anticipate this risk to be low due to the extremely weak rhyolite and tuff units encountered in the borings. However, boring SW-13 encountered medium strong to strong basalt bedrock at a depth of approximately 0.2 feet below the ground surface. In this area, there is a higher risk of the bedrock impacting the FDR machinery if encountered below the pavement section.

Also, due to the variability in pavement thicknesses observed, the contractor should verify the existing pavement section thickness prior to performing FDR to confirm that the required FDR thickness can be achieved from the existing pavement section. If the combined existing HMA and ABC thicknesses are insufficient, the contractor should be prepared to place additional ABC material to achieve the FDR thickness provided in Exhibit 7-2. The additional ABC should be placed prior to completing the FDR pulverization process. Table A-1 in Appendix A presents a summary of pavement section thicknesses observed during our subsurface investigations.

7.2.2 Functional Mill and Overlay

The functional mill and overlay approach is typically adequate for preventative maintenance and will increase ride quality. However, it will not provide a significant extension of the pavement service life. Furthermore, reflective cracking from wide cracks in the milled pavement is likely.

As previously described, the measured asphalt thickness varied from 2 1/2 to 7 inches thick but was typically on the order of 4 inches. The milling process removes the surface lift of HMA that typically oxidizes over time and can become brittle (resulting in a lower durability pavement). A minimum thickness of 3 inches of asphalt pavement should remain in place after milling to support construction equipment and reduce the risk of the un-milled pavement being cracked or completely removed. Based on the observed thicknesses of the existing pavement, there is a risk for the locations with thin HMA to be completely removed during the milling process. Further, if the entire HMA section is removed, the contractor will be responsible for reconditioning the underlying base course or subgrade and paving a thicker HMA section resulting in additional costs.

Typical mill and overlay thickness are 2 inches of mill with 2 inches of overlay. Therefore, this type of maintenance might not be appropriate for areas of the project where the asphalt pavement is thinner than 5 inches thick. As an alternative, the milling of the HMA thickness can either be reduced or omitted, resulting in a grade raise of the roadway profile.

However, leaving the surface lift of HMA in place (typically removed by milling) could result in reduced durability, and could require a thicker overlay.

107523-002 September 26, 2024

7.2.3 Patching

Saw cutting around wide transverse cracks and fatigue cracked areas and replacing the pavement section will extend pavement service life. This procedure will also reduce ride quality if differential settlement occurs between the patched area and the existing asphalt.

We do not recommend this approach for the Entrance Road because based on the observed transverse crack spacing, patching would result in a network of closely spaced patches and poor ride quality.

7.2.4 Chip Seal

Chip seal provides a new wearing course and waterproofs low severity cracking with no pavement structure improvement. Installing a chip seal on existing asphalt pavement can extend the service life of the existing pavement section, but existing cacks will propagate through the chip seal. During our visual pavement assessment, we observed the Entrance Road pavement had been previously surfaced with a chip seal. Transverse cracks and occasional longitudinal cracks had propagated upwards through the chip seal in some areas. Other than these propagating cracks, the roadway was considered to be in good condition using the FWS rating system.

7.2.5 Crack Sealing and Crack Filling

Crack sealing and crack filling is generally a short-term treatment (typically less than 1-year) and is typically performed between pavement rehabilitations and will generally not improve ride quality. The FHWA manual of practice titled Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements (Smith and Romine, 1999) has the following definitions.

Crack Sealing – The placement of specialized treatment materials above or into working cracks using unique configurations to prevent the intrusion of water and incompressibles into the crack.

Crack Filling – The placement of ordinary treatment materials into non-working cracks to substantially reduce infiltration of water and to reinforce the adjacent pavement.

The difference between working and non-working cracks can be identified by measuring their horizontal movement over the duration of a year.

Working Crack - 1/8 inch or greater

Non-working Crack - less than 1/8 inch

Typically, high severity cracks, such as the ones observed throughout the project area, are caused by thermal expansion and contraction of the HMA pavement between day/night and

107523-002 September 26, 2024 between the seasons. These are considered working cracks because they continue moving after the crack has formed and typically keep increasing in aperture with time. Therefore, it is generally difficult to achieve a lasting repair, and we recommend crack sealing or replacing the pavement section if cracks have an aperture of 1/8 inch or greater. Crack filling can be utilized for smaller cracks (less than 1/8 inch).

Available products for crack sealing are asphalt rubber, rubberized asphalt, low-modulus rubberized asphalt, and self-leveling silicone. Available products for crack filling are polymer-modified emulsion, fiberized asphalt, asphalt cement, and asphalt emulsion.

Regardless of how a crack is filled or sealed, annually maintenance should be expected between scheduled pavement rehabilitation. In accordance with Smith and Romine (1999), we recommend performing crack sealing during moderately cool temperatures (spring or fall) so the aperture of the cracks are in the middle of their working range.

7.2.6 Fog Seal

Fog seal is another short-term treatment between scheduled pavement rehabilitations. Fog seal typically involves applying a thin layer of asphalt emulsion to the existing HMA pavement to seal non-working cracks and slow the oxidization of the existing pavement surface. This short-term treatment method will generally extend pavement service life by one to two years, but will not seal working cracks or fatigue cracked pavement areas, nor will it improve ride quality.

7.3 Seismic Design Considerations

We understand that design ground motion parameters will be based on the requirements of the 2021 International Building Code (International Code Council, 2021), which has adopted the ASCE 7-16 design code for minimum design loads on buildings (ASCE, 2017). These design loads are in turn based on the USGS National Seismic Hazard Maps that were updated in 2008 (Petersen and others, 2008). The design ground motions are based on the risk-targeted maximum considered earthquake (MCER) as defined in ASCE 7-16. Based on encountered soil and rock conditions, the site can best be described as Site Class C at the proposed 24,000-gallon water tank locations and Site Class D at the proposed lift station location. The following exhibit provides seismic design parameters for the project.

107523-002 September 26, 2024

Exhibit 7-4: Seismic Design Parameters

Design Parameter Value

Peak Ground Acceleration (PGAB)¹ 0.218 g

Short-period Spectral Acceleration, SS 0.507 g

Long-period Spectral Acceleration, S1 0.166 g

Site Class C D

Site Factor, FPGA 1.2 1.38

Site Factor, Fa 1.3 1.39

Site Factor, Fv 1.5 2.27

Site Modified Peak Ground Acceleration, PGAm 0.262 g 0.301 g

Site Modified Spectral Acceleration (0.2 s), SMS 0.659 g 0.705 g

Site Modified Spectral Acceleration (1.0 s), SM1 0.249 g 0.377 g

Seismic Design Value (0.2 s), SDS 0.439 g 0.470 g

Seismic Design Value (1.0 s), SD1 0.166 g 0.251 g

NOTES:

PGAB refers to peak ground acceleration for a site underlain by Site Class B soil (rock).

g = gravity; sec. = seconds

7.4 Foundation Recommendations for Structures

We understand that the structures will be supported on shallow foundations (conventional spread footings or a mat).