NM.FS.220 (1).Romero Creek Bridge.Geotech Rpt FINAL.March 2023_Shallow Foundation.pdf

ROMERO CREEK BRIDGE

GILA NATIONAL FOREST

CATRON COUNTY, NM

NM FS 220(1)

FINAL Geotechnical Report

Prepared by

Federal Highway Administration Central Federal Lands Highway Division

Geotechnical Services Branch

March 2023 ii

SIGNATURE SHEET

Report prepared by: ___________________________________________________________

Brendan L. McGarity, E.I., Geotechnical Engineer

Report reviewed by: ____________________________________________________________

Devin T. Dixon, P.E., Geotechnical Engineer

Approved for distribution by: ____________________________________________________

James M. Arthurs, P.E., Ph.D., Acting Lead Geotechnical Engineer

Distribution

Electronic:

N:\NM\220(1)\Geotech\7_FinalDocs

K:\TechServices\Geotech\1. Geotech Project Reports

Project Management (PDF only)

Project Development, Lead Designer (PDF only)

Bridge (PDF only)

Technical Services, Hydraulics (PDF only)

Page | i

TABLE OF CONTENTS

SECTION ONE - INTRODUCTION

1.1 BACKGROUND AND LOCATION

1.2 SCOPE AND PURPOSE

SECTION TWO - GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGY

2.2 SITE GEOLOGY

2.3 REGIONAL SEISMICITY

2.4 SEISMIC DESIGN PARAMETERS

2.5 GEOLOGIC HAZARDS

SECTION THREE - SUBSURFACE INVESTIGATION

3.1 SUBSURFACE EXPLORATION PROGRAM

3.2 LABORATORY TESTING PROGRAM

3.3 SUMMARY OF SITE CONDITIONS

3.3.1 General Topography

3.3.2 Surface Reconnaissance

3.3.3 Subsurface Conditions

3.3.4 Groundwater

SECTION FOUR - ANALYSIS & RECOMMENDATIONS

4.1 Bridge Foundation Design

4.1.1 Foundation Selection

4.1.2 Rock Characterization

4.1.3 Bearing Resistance

4.1.4 Sliding and Lateral Stability

4.1.5 Settlement

4.1.6 Scour Potential

4.1.7 Frost Potential

4.1.8 Corrosive Soil

4.2 ABUTMENT & WINGWALL DESIGN

4.3 Earthworks

4.3.1 Embankment and Fill Construction

4.3.2 Cut Slopes and Temporary Shoring

4.3.3 Shrink/Swell Recommendations

4.4 CONSTRUCTION CONSIDERATIONS

4.5 SPECIFICATIONS

4.6 DISCLAIMER/LIMITATIONS CLAUSE

SECTION FIVE - REFERENCES

Page | ii

TABLES

Table 2.1 – Summary of Nearby Seismic Source Faults Table 2.2 - Summary of Seismic Parameters Corrected for Site Class B Table 3.1 - Summary of Field Exploration Program

Table 3.2 - Summaries of Laboratory Index Test Results Table 3.3 - Summaries of Laboratory Corrosivity Results Table 3.4 - Summary of Uniaxial Compressive Strength Results Table 4.1 - Proposed Bridge Foundation Locations Table 4.2 – Summary of Spread Footing Design Information

Table 4.3 – Resistance Factors for Abutment Design Table 4.4 – Bearing Resistance Values Table 4.5 - Lateral Earth Pressures for Bridge Abutments and Wingwalls

FIGURES

Figure 4-1 – Allowable Bearing Pressure on Jointed Rock (Peck et. al., 1974)

PLATES

PLATE 1 Project Vicinity Map

PLATE 2 Geology Map

PLATE 3 Geology Map Legend

PLATE 4 Geotechnical Boring Locations

APPENDICES

APPENDIX A Field Exploration Program

APPENDIX B Laboratory Test Results

APPENDIX C Photographs

APPENDIX D Excavation Characteristics of Rock & Rippability Charts

Page | 1

Romero Creek Bridge, NM FS 220(1) March 2023

SECTION ONE - Introduction

1.1 BACKGROUND AND LOCATION

This report presents the results of the geotechnical engineering study and provides recommendations for the replacement of the Romero Creek Bridge in Catron County, New

Mexico. The project proposes to replace the existing Romero Creek Bridge, which is located approximately 9.6 miles northwest of Luna, NM within the Gila National Forest on Forest Route

220 (MP 7.325). A project vicinity map is presented on Plate 1 of this report.

The Romero Creek Bridge was originally constructed in 1954. The superstructure consists of a cast-in-place concrete deck. The substructure consists of vertical concrete cantilever abutment walls supported by spread footings extending to an unknown depth. Wingwalls are also present and supported by spread footings. The abutment foundation material is unknown but has been reported as stable according to the most recent inspection report dated August 2018. The seismic design detail vulnerability is unknown due to a lack of existing bridge plans.

The bridge deck has large areas, approximately 60 percent, of delamination that range from roughly 2 to 10 inches. The bridge inspection report, as noted before, indicates that the structural evaluation of the bridge is in poor to serious condition. Furthermore, the NFSR 220 route will soon be a main haul route for a future restoration project and the expected increase in logging truck traffic will contribute to additional bridge deterioration. Therefore, replacement of the Romero

Creek Bridge was determined to be the desired option, as opposed to maintenance, due to the limited remaining lifespan of the existing bridge.

The proposed replacement structure type is assumed to be a simple span prefabricated steel structure on vertical abutment walls on spread footings. Shallow foundations are proposed due to shallow bedrock in the subsurface. Considerations related to the abutments for the Romero Creek

Bridge are presented in Section 4 of this report.

1.2 SCOPE AND PURPOSE

The scope of work included a geotechnical investigation, analysis, and recommendations for bridge foundations for use in design and construction. This involved several tasks including field reconnaissance, subsurface sampling, laboratory testing, interpretation and correlation of field measurements, and geotechnical engineering analysis. Specifically, this investigation was conducted to determine the subsurface profiles at the bridge location and develop recommendations concerning bridge foundations, retaining structures, geologic hazards, and construction considerations.

Page | 2

We understand that a hydraulics report has been prepared under separate cover by the CFLHD

Hydraulics Engineer. The hydraulics report includes discussion of flood impacts, such as bridge scour and water surface elevations.

Page | 3

SECTION TWO - Geology and Seismicity

2.1 REGIONAL GEOLOGY

The project is located within the Datil-Mogollon Section of the Colorado Plateau Province. This province is part of the Intermontane Plateaus physiographic region. The Colorado Plateau Province straddles the region known as The Four Corners, where the states of Arizona, Utah, Colorado, and

New Mexico meet. This province is characterized by ancient volcanic mountains, plateaus and buttes, deeply carved canyons, and amazing ranges in color. Elevations for the Colorado Plateau start near 2,000 feet above sea level, with plateau tops ranging from 5,000 to 7,000 feet and mountaintops reaching nearly 13,000 feet (NPS, 2020).

Quaternary and Tertiary rocks and deposits that exist within the region include siltstone, sandstone, shale, limestone, conglomerate, basalt, tuff, agglomerate, rhyolite, latite, andesite, volcanic sediments, dikes, plugs, sills, alluvium, gravel, sand, and silt. Cretaceous aged units include the

Mesa Verde group, Mancos shale, Dakota sandstone, diabase, and granite and related crystalline intrusive rocks. Jurassic, Triassic, and Permian units include the Morrison Formation, San Rafael

Group, Glen Canyon Group, Chinle Formation, Shinarump Conglomerate, Moenkopi Formation, Kaibab Limestone, Coconino Sandstone, and Supai Formation. Pennsylvanian deposits are also present. Older units, Carboniferous and Devonian to older Precambrian aged, include quartzite, Mescal Limestone, Apache Group, schist, and granite and granite gneiss. (Wilson & Moore, 1958;

Weber & Willard, 1959; Wilson et al., 1960).

2.2 SITE GEOLOGY

Although not mapped, the soil conditions at the site are assumed to be alluvium based on the stream bed deposits. The project site is mapped as underlain by basalt, volcanic conglomerate, andesite and basaltic andesite. This observation is consistent with the borings as will be discussed in Section

3 of this report. The deposits and landforms are volcanic in nature and the terrain can be described as mountainous and rugged. A geology map of the project area and corresponding map legends are presented in Plates 2 & 3.

2.3 REGIONAL SEISMICITY

No seismic hazard faults are located within 50 miles of the project. However, seven known

Quaternary faults are mapped within approximately 50 miles of the bridge site. These faults are considered inactive and are summarized in Table 2.1. The Vernon Fault Zone, Concho Fault, Coyote Wash Fault, Red Hills Faults and the Unnamed Fault East of Mangas are located north and northeast of the project site and the Alma Mesa Faults and Unnamed Faults East of Alma are located south and southeast of the project site. All fault systems are considered normal faults, with

Page | 4 the exception of Vernon Fault Zone, which is considered to be left lateral with slip rates less than

0.008 inches per year (USGS, 2022a).

Table 2.1 – Summary of Nearby Seismic Source Faults

FAULT OR

FAULT ZONE

DISTANCE

FROM

CENTER OF

PROJECT

SLIP-RATE

CATEGORY

DIP

DIRECTION

AVERAGE

STRIKE

FAULT

LENGTH

TIME OF MOST

RECENT

DEFORMATION

(miles) (inch/year) (miles) (years)

Red Hill Faults, (Class A)

No. 2138

13.7 <0.00787 SE; NW N25°E 9.3 <1,600,000

Coyote Wash Fault, (Class A)

No. 1015

18.4 <0.00787 SW N42°W 26.1 <750,000

Vernon Fault Zone, (Class A)

No. 1016

19.9 <0.00787 NE N46°W 35.4 <750,000

Concho Fault, (Class A)

No. 1014

27.1 <0.00787 NE N37°W 24.2 <750,000

Alma Mesa Faults, (Class A)

No. 941

28.3 <0.00787

E; SE; W;

NW

N23°E 9.32 <1,600,000

Unnamed Faults

East of Alma, (Class A)

No. 2011

30.9 <0.00787 W; E N12°W 7.5 <1,600,000

Unnamed Fault East of Mangas, (Class A)

No. 2137

46.2 <0.00787 SW N23°W 1.9 <1,600,000

2.4 SEISMIC DESIGN PARAMETERS

Recommended seismic response parameters for the Romero Creek Bridge project site design are based on the American Association of State Highway and Transportation Officials (AASHTO)

LRFD Bridge Design Specifications, 8th Edition, 2017, and represents horizontal peak ground acceleration (PGA) with 7 percent probability of exceedance in 75 years (approximate 1,000-year return period). The 1,000-year return period uniform hazard spectrum for the Romero Creek

Bridge project site, located at 33.91089°N latitude and 109.02387°W longitude, was obtained in accordance with the AASHTO ground motion maps.

Based on subsurface conditions encountered during drilling, in addition to the presence of shallow (< 10 feet deep) competent rock with moderate fracturing and weathering, the site is classified as Class B according to the site class definitions specified in Table 3.10.3.1-1 of

AASHTO. The recommended spectral acceleration coefficient values for probabilistic design are summarized in Table 2.2.

Page | 5

Table 2.2 - Summary of Seismic Parameters Corrected for Site Class B

Horizontal Peak Ground Acceleration, (PGA) 0.070 g

Horizontal Response Spectral Acceleration at Period of 0.2 sec, (Ss) 0.163 g

Horizontal Response Spectral Acceleration at Period of 1.0 sec, (S1) 0.049 g

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.0

Site Factor at Short-Period Range of Acceleration Spectrum, (Fa) 1.0

Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.0

Factored Horizontal Peak Ground Acceleration, (As) 0.070 g

Factored Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDs) 0.163 g

Factored Horizontal Response Spectral Acceleration at Period of 1.0 sec, (SD1) 0.049 g

Seismic Zone Zone 1

Based on the long acceleration coefficient SD1 value of 0.049, the project site is assigned to seismic hazard “Zone 1” in accordance with Table 3.10.6-1 of AASHTO. Based on this assignment, seismic loading is not likely to control design of structures for the project.

2.5 GEOLOGIC HAZARDS

Potential geologic hazards at the bridge site include those related to floods, earthquakes, and mass movement. Flooding, however, is the most common, widespread, and damaging of these geologic hazards and could pose a threat to the Romero Creek Bridge. Much of New Mexico is prone to flooding caused by thunderstorms that happen year-round. Severe thunderstorms are most common during the monsoon season, especially in July and August. Flooding can cause many effects due to contact with flood waters such as extensive erosion, debris flows, and slope instability (NOAA, 2020).

Earthquakes, as discussed in the previous section, are another potential geologic hazard. Western

New Mexico and the project site are located in an area of low potential for damaging earthquakes, although it is impossible to accurately predict the timing or location of future earthquakes. Another hazard related to earthquakes is liquefaction. Liquefaction is a phenomenon in which a cohesionless soil layer below the groundwater table loses a substantial amount of strength due to pore pressure generation resulting from ground shaking. Based on the subsurface conditions encountered at the project site and the low peak ground acceleration (PGA) indicated in Table 2.2, the risk of liquefaction is relatively low.

Mass movements are also common in New Mexico due to the steep mountainous and hilly terrain, heavy rains, and the fines content of the soil. These rock and soil movements include debris flows, landslides, and rockfalls. Although the bridge is located in terrain susceptible to mass movement, no indication of these events was observed during the site reconnaissance and are considered unlikely to impact this bridge site.

Page | 6

SECTION THREE - Subsurface Investigation

3.1 SUBSURFACE EXPLORATION PROGRAM

A subsurface investigation targeting the bridge site was performed by a Central Federal Lands

Highway Division (CFLHD) of the Federal Highway Administration (FHWA) geotechnical engineer on September 23, 2020. The geotechnical subsurface exploration program consisted of drilling a total of two borings to depths of 19 and 14 feet deep. One boring was drilled approximately 106 feet northwest of the northwest bridge abutment and another was drilled approximately 14 feet southeast of the southeast bridge abutment. Hollow-stem augers were used to drill through the overburden soils and bedrock samples were recovered using HQ3 diamond core drilling. Grab samples of the upper subsurface were collected. Subsurface conditions were logged, and representative samples were collected and transported to the CFLHD Materials

Laboratory in Lakewood, CO, for physical property testing. Logs of the explorations and boring locations are presented in Appendix A and Plate 4, respectively. Photographs related to this exploration can be found in Appendix C. A summary of the field exploration is provided in Table

3.1.

Table 3.1 - Summary of Field Exploration Program

EXPLORATION

DESIGNATION

LOCATION

APPROXIMATE

GROUND

ELEVATION (ft.)

TERMINATION

DEPTH (ft.)

DEPTH TO

GROUNDWATER

(ft.)

BH20-01

Northwest Abutment

STA 105+54

8.5 ft. RT

8,237 19 Not encountered.

BH20-02

Southeast Abutment

STA 103+37

14.5 ft. LT

8,235 14 Not encountered.

Note: The exploration locations were estimated relative to existing features. Ground elevations were estimated from survey data collected by CFL.

3.2 LABORATORY TESTING PROGRAM

Bulk soil samples of drill cuttings were recovered from the borings and tested in the laboratory to support the field classifications and to provide an estimate of the engineering characteristics and mechanical properties of the soil. Laboratory tests included moisture content (AASHTO T 255), sieve analysis (AASHTO T 11 and T 27), classification (AASHTO M145 and ASTM D 2487), Atterberg limits (AASHTO T89 and T90), resistivity (AASHTO T 288), soil pH (AASHTO T

289), sulfate content (AASHTO T 290), and chloride content (AASHTO T 291). When the necessary tests were completed, samples were classified using the Unified Soil Classification

System (USCS) and AASHTO soil classification system. Results of the testing are summarized below in Table 3.2 and are presented in Appendix B.

Page | 7

Table 3.2 - Summaries of Laboratory Index Test Results

BORING

NUMBER

SAMPLE

DEPTH

PERCENT

GRAVEL

PERCENT

SAND

PERCENT

PASSING

#200

LIQUID

LIMIT

PLASTIC

LIMIT

USCS

CLASS.

AASHTO

CLASS.

(feet)

BH20-01 0 – 1.5 30 58 12 NV NP SW-SM A-1-b (0)

BH20-02 0 – 2.5 43 46 11 27 15 SP-SC A-2-6 (0)

Soil test results indicated a limited range of material types including silty to clayey sands with gravel, classifying as A-1-b to A-2-6 by AASHTO and SW-SM and SP-SC by USCS.

Corrosivity and chemistry testing was conducted for the pavement investigation and is summarized in Table 3.3.

Table 3.3 - Summaries of Laboratory Corrosivity Results

BORING

NUMBER

SAMPLE

DEPTH

RESISTIVITY PH

SULFATE ION

CONTENT

CHLORIDE ION

CONTENT

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

BH20-02 0 – 2.5 4,770 8.7 30 4

Unconfined compressive strength (UCS) of rock materials was conducted on intact samples of rock core recovered from the borings. Results of the UCS testing are presented in Table 3.4.

Table 3.4 - Summary of Uniaxial Compressive Strength Results

BORING NUMBER SAMPLE DEPTH RQD1 LENGTH / DIAMETER2 UCS

(feet) (%) (psi)

BH20-01 11 - 16 35 1.9 13,410

BH20-01 16 - 19 11 2.2 11,000

BH20-02 6 - 11 30 1.9 8,320

BH20-02 11 - 14 58 1.8 4,750

1Rock Quality Designation for core run from which sample was taken.

2Values less than 2.0 do not meet the requirements of ASTM D 7012.

3.3 SUMMARY OF SITE CONDITIONS

The project site can be divided into two critical sections: the northwest bridge abutment and the southeast bridge abutment. This section presents the results of the surface reconnaissance and subsurface exploration.

Page | 8

3.3.1 General Topography

The general topography of the project site is characterized by steep mountains and lengthy deserts that encompass southeastern Arizona and southwestern New Mexico. Thick vegetation typical of both ponderosa pine and pinyon-juniper woodland forests is abundant at the project site. Romero

Creek flows under the Romero Creek Bridge from the west to the east and converges with Trout

Creek approximately 1.25 miles downstream of the project site.

3.3.2 Surface Reconnaissance

The terrain can be described as rolling and forested. Vegetation including junipers, small and large pines, and native grass species heavily cover much of the project site. Plate-shaped and blocky rock outcroppings protrude along the faces of the hilly slopes surrounding the creek channel.

Similar rock outcroppings were observed in the streambed as the creek was dry at the time of the investigation. The rock type is consistent with the geology discussed in Section 2. Much of the exposed rock faces are partially covered in moss, at least slightly weathered, and show signs of natural fracture patterns. The northwest abutment of the existing bridge is visibly founded on shallow bedrock. It is unclear whether or not the southeast abutment is founded on this same rock, however, by means of visual observation.

Boulders and broken bedrock fragments measured to be roughly 3 to 4 feet in diameter were observed in the river channel beneath and surrounding the bridge. Moderately dense forest vegetation, including three large pine trees near the northwest wingwall, lines both banks of the creek and alluvial soils and sediments encompass the bridge site. A previously installed water level gauge was also noted at the northwest wingwall. An unnamed, barely visible, dirt road intersects with Forest Route 220 roughly 90 feet northwest from the Romero Creek Bridge and continues to the southeast parallel to the river channel. The gravel surface of Forest Route 220 was measured to be roughly 6 to 8 inches thick near the bridge site. A wire fence with a steel gate, possibly indicating private property, exists roughly 120 to 130 feet southwest of the bridge site. Lastly, a large rock outcropping exposed in a hill face exists approximately 250 to 270 feet west of the bridge site. The exposed rock appears to be basalt, has mostly vertical fracture patterns along its face, is roughly 30 to 40 feet high, and is partially covered in moss.

3.3.3 Subsurface Conditions

The subsurface conditions at the northwest abutment of the Romero Creek Bridge were investigated by drilling boring BH20-01. The boring was advanced approximately 110 feet from the existing northwest abutment. The boring was advanced a large distance from the existing abutment due to the drill rig size and steep embankment slopes not providing enough space to allow the passage of traffic. Due to this, depth to bedrock is likely unrepresentative and variable for the northwest abutment, and a greater depth to bedrock could be expected. The boring encountered well graded sand with silt and gravel to a depth of approximately 7 feet. Gravel

Page | 9 content increased with depth and wood and other organic debris were noted at approximately 4 feet in depth. At 7 feet, basalt bedrock was encountered which then extended to the termination depth of 19 feet. The basalt was highly weathered to moderately weathered, with the degree of weathering lessening with depth. Core samples from approximately 7 to 10 feet had very poor to poor RQD (0 to 35%) with high gravel and cobble content. The basalt was medium strong to strong

(R3 to R4) with very closely spaced discontinuities ranging from 0 to 90 degrees in orientation

(from assumed horizontal). Some iron oxide and yellow staining was visible along with sand and clay infill (reduction in amount of infill with depth).

The subsurface conditions at the southeast bridge abutment were investigated by drilling boring

BH20-02. The boring encountered poorly graded sand with clay and gravel to a depth of approximately 2.5 feet. Basalt bedrock was then encountered which extended to the termination depth of 14 feet. Aside from the absence of a highly weathered and gravelly top section, the basalt displayed the same characteristics as described above for BH20-01.

3.3.4 Groundwater

Groundwater was not encountered during drilling in either borings BH20-01 or BH20-02 and

Romero Creek was dry during the time of the investigation. However, fluctuations in the groundwater level due to seasonal and climatic effects are expected.

Page | 10

SECTION FOUR - Analysis & Recommendations

This section presents analysis and recommendations for the bridge foundation, wingwalls, and construction considerations for the design and construction of the Romero Creek Bridge project.

Based on discussions with the project team, a replacement of the existing bridge is the preferred alternative. Generalized subsurface profiles were developed based on field reconnaissance, surficial visual evaluation, and subsurface investigations.

4.1 BRIDGE FOUNDATION DESIGN

A new prefabricated bridge structure is proposed to replace the existing Romero Creek Bridge.

The bridge is anticipated to be a roughly 50-foot long single-span structure. Based on the preliminary 95 percent design plans, the proposed abutment centerline stations and elevations are shown in Table 4.1.

Table 4.1 - Proposed Bridge Foundation Locations

FOUNDATION STATION CENTERLINE ELEVATION

Abutment 1 (Southeast) 103+68.00 8,235.07 FT

Abutment 2 (Northwest) 104+18.00 8,234.57 FT

4.1.1 Foundation Selection

Due to the presence of shallow bedrock in the subsurface, the bridge is anticipated to be supported on spread footings bearing on bedrock. The competent and hard nature of the basalt bedrock will be able to withstand the large bridge loads. In general, spread footings are more practical and less expensive compared to deep foundations at sites where sound bedrock can be reached by an excavation of 10 feet or less from the base of the substructure unit. Lastly, scour is not anticipated at the bridge site, further aiding the shallow foundation design decision (discussed further in subsection 4.1.6).

A summary of the spread footing design information is presented below in Table 4.2.

Page | 11

Table 4.2 – Summary of Spread Footing Design Information

FOUNDATION

ANTICIPATED BOTTOM OF

FOOTING ELEVATION

EMBEDMENT INTO COMPETENT

BEDROCK1

Abutment 1 (Southeast) 8226.0 FT 9.0 inches (minimum)

Abutment 2 (Northwest) 8222.0 FT 9.0 inches (minimum) 1Refer to the alternate footing embedment detail in the plan set if embedment into bedrock requirements cannot be met (i.e., bedrock is not encountered below specified footing depths).

4.1.2 Rock Characterization

A natural rock mass is rarely a continuous, isotropic, homogeneous material. It can be highly variable and may be difficult to characterize in a generalized manner. A rock mass is generally composed of intact or weathered blocks of rock separated by discontinuities such as joints or bedding planes. The discontinuity and weathering characteristics help establish the design recommendations for a footing on rock. These characteristics include, but are not limited to, the rock lithology, strength properties, deformation properties, frequency of discontinuities (RQD), spacing of discontinuities, orientation of discontinuities, aperture, filling, condition, degree of weathering, and the ground water condition. These properties were noted when applicable during the subsurface investigation and the rock layer was classified as basalt in the field. The following section discusses the strength properties used in design based on the subsurface investigation and lab test results.

Generalized Strength Criterion for Intact Rock

A generalized compressive strength value was determined for the rock mass based on engineering judgement, field observations, and lab test results on recovered rock specimens, summarized in

Table 3.4. The lowest values of unconfined compressive strength (UCS), 4,750 psi, was selected for design. A wide range of values, from 4,750 psi to 13,410 psi, were observed during testing.

Due to the weathered nature, low average RQD, and limited rock cores suitable for testing, the lowest UCS value was selected to be conservative given the variability of rock quality and limited test data.

Geologic Strength Index (GSI) Parameters and Intact Rock Properties

The Geologic Strength Index (GSI) was used to characterize the rock based on surface observations and boring data. The GSI is a modification to the Rock Mass Rating system (RMR) and assigns values to the following rock mass properties:

• Intact rock strength

• Rock Quality Designation (RQD)

• Discontinuities spacing

Page | 12

• Discontinuities condition

• Presence of groundwater

The rock composition was identified as basalt with fair to poor surface quality (moderately to highly weathered) and a blocky structure. Given these assignments, a GSI value of 40 was selected.

Other intact rock properties include the Hoek-Brown constant, mi; rock unit weight, γ; and the damage factor, D. Assigned values are 25 (average value for basalt), 180 pcf, and 0, respectively.

The damage factor of 0 assumes the rock will remain relatively undisturbed with traditional mechanical excavation. The following equations were then used to determine the appropriate curve fitting coefficients:

mb = mi ∗ exp (

GSI−100

) = 2.933 α = 0.5 +

∗ (exp (

−GSI

) − exp (−

)) = 0.511 s = exp (

GSI−100

9−3∗D ) = 0.001

4.1.3 Bearing Resistance

The proposed abutment footing locations are anticipated to bear on rock. Based on the subsurface materials encountered at the project site, the bearing resistance factors recommended for design were selected from the LRFD AASHTO Manual (2017), Table 10.5.5.2.2-1 and section 10.5.5.3.

A summary of resistance factors is presented in Table 4.3.

Table 4.3 – Resistance Factors for Abutment Design

LIMIT STATE

RESISTANCE FACTORS, φ

BEARING

RESISTANCE

SHEAR

RESISTANCE

TO SLIDING

PASSIVE

PRESSURE

RESISTANCE TO

SLIDING

Strength 0.45 0.80 0.50

Service and

Extreme Event

1.00 1.00 1.00

Strength Limit State

Bearing resistance at the strength limit state was evaluated using the Hoek-Brown Failure Criterion

Method and was then compared with allowable bearing pressures based on RQD values (Peck et al, 1974), upon which the lower value was selected for design.

Page | 13

The equation used to calculate the bearing resistance based on the Hoek Failure Criterion Method is shown below:

𝑞𝑢𝑙𝑡 = 𝜎𝑐𝑖 (√𝑠 + √(𝑚𝑏 √𝑠 + 𝑠)) where, qult = Nominal Bearing Resistance at the abutments mb and s = Criterion parameters σci = Uniaxial Compressive Strength of the intact rock

From this equation, the factored bearing resistance was calculated to be 771 psi (111 ksf). This value was then compared to allowable bearing pressures on jointed rock from Table 12.5 in Peck

et. al., 1974 (Figure 4-1 below).

Figure 4-1 – Allowable Bearing Pressure on Jointed Rock (Peck et. al., 1974)

From this table a value of 25 RQD was selected as representative of the rock mass, with a corresponding allowable bearing pressure of 60 ksf (30 Ton/ft2). A value of 60 ksf was then selected for design due to the high variability in degree of jointing and high degree of weathering in the rock mass. Additionally, the rock characteristics at Abutment 2 (Northwest) were largely unknown due to the boring location, and this lower bearing pressure was selected to account for this uncertainty.

Service Limit State

Presumptive values for the service limit state bearing resistance for various types of rock are presented in AASHTO Table C10.6.2.6.1-1. Based on this table, a service limit state bearing resistance of 160 ksf was selected for the basalt bedrock, assuming 1 inch of settlement.

Page | 14

Extreme Limit State

The bearing resistance for the extreme limit state was taken as the bearing resistance from Peck et.

al., with a resistance factor 1.0 applied (a resistance factor of 0.45 was assumed to have been applied to the 60 ksf value).

A summary of these values at each limit state is presented in Table 4.4.

Table 4.4 – Bearing Resistance Values

STRENGTH LIMIT STATE SERVICE LIMIT STATE EXTREME EVENT LIMIT STATE

60 ksf 160 ksf 133 ksf

4.1.4 Sliding and Lateral Stability

Sliding is not anticipated to control foundation design if the footings are constructed with the recommended 9-inch embedment into bedrock (Table 4.2). However, for cast-in-place concrete on clean, sound rock a coefficient of friction, tan δ, of 0.70 with a friction angle, δ, of 35° should be used.

Lateral loads imposed on the abutments due to lateral earth pressure and horizontal seismic forces may be resisted by the friction developed between the cast-in-place concrete footings and the supporting rock with a resistance factor of 0.80. For the passive earth pressure component, a resistance factor of 0.50 is recommended.

4.1.5 Settlement

When rock has a relative rating greater than 10 for RQD and joint spacing, and is classified as fair to very good according to the Geomechanics Classification system, elastic settlements may generally be assumed to be less than 0.5 inches (AASHTO 10.6.2.4.4). The basalt bedrock displayed RQD values ranging from 11% to 58% during the subsurface investigation, and rock surface quality was rated as fair to poor, thus elastic settlement is estimated to be less than 0.5 inches at the abutments.

4.1.6 Scour Potential

By extending the footings to embedment on underlying bedrock, along with the presence of bedrock material at the proposed abutments and within the channel bed, contraction scour and local abutment scour are not anticipated. Further discussion on scour potential is discussed in detail in the Final Hydraulics Report under Section 4.7.

4.1.7 Frost Potential

The spread footings should be designed to bear below the depth of frost potential. For New Mexico, the average frost depth is 18 inches.

Page | 15

4.1.8 Corrosive Soil

Soil corrosivity testing was performed on a select sample at BH20-02. Results indicate the on-site soils to have low corrosion potential as presented in AASHTO 5.14.2.4.

4.2 ABUTMENT & WINGWALL DESIGN

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

Unbalanced water behind an abutment or wall adds significant lateral pressure and should be avoided by using free draining gravity outlets for water. Abutment and wingwall backfill should consist of structural backfill as specified in Section 704.04 of FP-14.

The coefficient of at-rest earth pressure should be used for design if the abutment is so restrained that it cannot be expected to rotate (deflect at the top) 0.002 times the wall height. Where deflection of the abutment can be expected, a coefficient of active earth pressure should be used for wall design. Active and at-rest lateral earth pressures of native materials and properly placed and compacted structural backfill are presented in Table 4.5. The values are unfactored loads and assume that the surface of the soil slope behind the wall is horizontal with no surcharge loading.

Page | 16

Table 4.5 - Lateral Earth Pressures for Bridge Abutments and Wingwalls

Backfill Type Assumed Backfill

Properties Case

Unfactored

Equivalent Fluid

Density (pcf)

Nominal Friction

Factor

Structural Backfill c = 0 psf

= 34 deg.

γ = 125 pcf

Active 35 0.67

At-Rest 55 0.67

Native Soil c = 0 psf

= 30 deg γ = 118 pcf

Active 39 0.58

At-Rest 59 0.58

Bearing resistance and settlement for abutment wingwalls was not considered as they are proposed to share a foundation with the bridge abutments.

4.3 EARTHWORKS

4.3.1 Embankment and Fill Construction

Embankment construction is anticipated in relation to the construction of the proposed bridge structure, wingwalls, and approach road reconstruction. Soils in the project area, including existing embankment fills, are typically sand with silt and gravel or sand with clay and gravel. The existing embankment fills have been constructed at approximately 1V:1.5H to 1V:2H and appear to be performing adequately. The embankment areas should be constructed with traditional embankment construction methods. Construct permanent long-term embankments with a maximum slope ratio of 1V:2H to maintain slope stability and reduce potential for erosion.

4.3.2 Cut Slopes and Temporary Shoring

Cut slopes are anticipated for construction of the bridge foundations and wingwalls. Shoring may be desirable depending on preferences to limit areas of disturbance. Groundwater is not anticipated to be encountered during construction, but levels may fluctuate seasonally, and dewatering could be necessary. Design and safety of this work is the responsibility of the contractor. The work shall be performed in a manner to minimize hazards and exposure to the public, construction personnel, and equipment.

4.3.3 Shrink/Swell Recommendations

On-site soils expected to be encountered within the project limits generally consist of sand with gravel and varying amounts of silt and clay. It is estimated that these soils will have a 10 percent shrink percentage, corresponding to a shrink/swell factor of 0.90. The recommended shrink/swell factor is based on a combination of standard tabled values for common materials in the FLH

Page | 17

Technical Guidance Manual (2006) and experience with other CFLHD projects in similar materials.

4.4 CONSTRUCTION CONSIDERATIONS

Excavation: Excavate using equipment capable of removing the material while preventing material from escaping outside the construction limits. The contractor is responsible for safety of excavations and shoring design.

Based on the subsurface investigation and surface reconnaissance, the rock encountered, primarily basalt, is expected to be very difficult to excavate in the area surrounding the abutments of the

Romero Creek Bridge due to its high unconfined compressive strength; though, natural fracture patterns, jointing, and relatively low RQD values (approximately 30% in upper 5 feet) may help ease the process of ripping. However, final determination of bedrock rippability is the responsibility of the contractor. Shear wave velocity of the geologic layers was not evaluated by geophysical methods.

Based on Table D.1 in Appendix D, the rock encountered can be presumed to be between the very hard and extremely hard rock descriptions. Blasting is not anticipated due to the degree of weathering and nature of the jointing patterns. If deemed necessary, blasting is the responsibility of the contractor and standard specifications in FP-14 Section 205 should be adhered to. Additional information regarding the excavation characteristics of rock and rippability charts can also be found in Appendix D.

Foundation Preparation: For the bridge structure, prepare the foundation subgrade in accordance with FP-14 Section 208 and the special contract requirements (SCR). It is required that the foundation excavations be inspected by a CFLHD geotechnical engineer prior to the construction and installation of the footing.

Depth to bedrock at the northwest abutment, and corresponding bottom of footing elevation, is approximate and variance from this value may be expected due to the boring being advanced over

100 feet from the proposed abutment location. In the instance where embedment requirements into existing rock cannot be met (i.e., depth to bedrock is deeper than specified or an irregular bedrock surface exists), the alternate embedment detail found in the project plan set should be followed. If the depth to bedrock is larger than 3 feet below the anticipated depths, then the CO must be notified prior to construction. Additionally, low to moderate RQD values, approximately 30%, were encountered during the subsurface investigation. It is likely during foundation preparation that the use of non-shrink grout or lean concrete backfill to fill existing fractures and joints will be necessary.

Page | 18

Dewatering: Groundwater was not encountered at the time of the investigation nor was the stream active. Though, seasonal fluctuations of groundwater levels should be expected, and dewatering may be needed depending on time of construction.

4.5 SPECIFICATIONS

Special provisions were developed to be consistent with geotechnical recommendations stated above and were incorporated into the special contract requirements (SCR) to amend the FHWA

Standard Specification for Construction of Roads and Bridges on Federal Highway Projects;

known as FP-14.

4.6 DISCLAIMER/LIMITATIONS CLAUSE

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

Page | 19

SECTION FIVE - References

American Association of State Highway and Transportation Officials (AASHTO), 2017, LFRD

Bridge Design Specifications, 8th Edition.

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

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

Federal Highway Administration (FHWA), 2014, Standard Specifications for Construction of

Roads and Bridges on Federal Highway Projects FP-14.

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

Federal Highway Administration (FHWA), 2017, Rock Characterization Guidelines, dated

December.

Federal Highway Administration (FHWA), 2021, “NM FS 220(1) Final Hydraulics Report,” dated January 14.

“Frost Line Penetration Map in the U.S.” Hammerpedia, < https://www.hammerpedia.com/frost-line-map/>

Haneberg, William C., 1992, “Geologic hazards in New Mexico - part 1,” New Mexico Bureau of Mines and Mineral Resources, New Mexico Geology (NWG): Volume 14, Number 2, Page 34, dated May.

Jochems, Andy & Love, Dave, 2019, “Earthquakes in New Mexico,” New Mexico Bureau of

Geology & Mineral Resources- New Mexico Institute of Mining & Technology, revised

October 18.

National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Accessed: November 2020, “NWS ABQ Monsoon Awareness - Flash Floods,”

<https://www.weather.gov/abq/prepawaremonsoonflashfloods#:~:text=Flash%20floods%2

0in%20New%20Mexico,the%20graph%20to%20the%20right).>

National Park Service (NPS), 2020, “Series: Physiographic Provinces, Colorado Plateau

Province,” updated April 30, 2018, <https://www.nps.gov/articles/basinrange.htm>.

Peck, R.B., Hanson, W.E., & Thornburn, T.H. (1974). “Foundation Engineering.” New York, NY: Wiley and Sons Inc.

U.S. Geological Survey (USGS), 2022(a), “Quaternary Fault and Fold Database of the United

States,” Interactive fault map & database search, USGS Earthquake Hazards Program, <https://earthquake.usgs.gov/hazards/qfaults/>.

U.S. Geological Survey (USGS), 2022(b), “Vs30 Map Viewer,” online map, USGS Earthquake

Hazards Program, <https://earthquake.usgs.gov/data/vs30/>.

Page | 20

U.S. Geologic Survey (USGS), 2022(c), “U.S. Seismic Design Maps,” USGS Earthquake Hazards

Program, <http://earthquake.usgs.gov/designmaps/us/application.php> &

<https://earthquake.usgs.gov/ws/designmaps/aashto-2009.json?latitude=34&longitude=-

118&siteClass=C&title=Example>.

Weber, R.H., and Willard, M.E., 1959, “Reconnaissance geologic map of Reserve thirty-minute quadrangle”: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 12, scale 1:126,720.

Wilson, E.D., and Moore, R.T., 1958, “Geologic Map of Graham and Greenlee Counties, Arizona”: Arizona Bureau of Mines, County Geologic Map Series M-3-4, scale

1:375,000.

Wilson, E.D., Moore, R.T., and O’Haire, R.T., 1960, “Geologic Map of Navajo and Apache

Counties, Arizona”: Arizona Bureau of Mines - Univ. of Arizona, Arizona County Map

Series 03-07, scale 1:375,000.

Page | 21

PLATES

PROJECT VICINITY MAP, GEOLOGY MAP,

GEOLOGY MAP LEGEND, GEOTECHNICAL

BORING LOCATIONS

N

NOTTO SCALE

MAP 1

(Arizona)

MAP2

(Arizona)

MAP 1: [Wilson, E.D., Moore, R. T. and O'Haire, R. T., 1960, -Geologic Map of Navajo and Apache Counties, Arizona•:

Arizona Bureau of Mines - Univ. of Arizona, Arizona County Map Serles 03-07, scale 1 :375,000.J

MAP 2: [WIison, E.D., and Moore, R. T,, 1958, -Geologic Map of Graham and Greenlee Counties, Arizona-:

Arizona Bureau of Mines, County Geologic Map Serles M-3·4, scale 1: 375,000.J

MAP 3: [Weber, R.H., and WIiiard, M.E., 1959, •Reconnaissance geologic map of Reserve thirty-minute quadrangle-:

New Mexico Bureau of Mines and Mineral Resources, Geologic Map 12, scale l: 126,720,)

¢MAP3

(New Mexico)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

GEOLOGY MAP

APPENDIX A

FIELD EXPLORATION PROGRAM

APPENDIX A

FIELD EXPLORATION PROGRAM

A.1 INTRODUCTION

The Central Federal Lands Highway Division (CFLHD) Geotechnical Section completed a field exploration program for NM FS 220(1), Romero Creek Bridge, on September 23rd, 2020. The scope of work for the field exploration program included drilling a total of two borings to depths of 19 feet & 14 feet. One boring was drilled near the northwest bridge abutment and another was drilled near the southeast bridge abutment. The field exploration program was coordinated and observed by a Geotechnical Engineer from CFLHD. Field exploration locations are illustrated on the “Geotechnical Boring Locations” sheet in Plate 4. Individual boring logs are attached. These logs represent a compilation of field and laboratory data and description of the soil and rock by

CFLHD Geotechnical personnel. The methods used to conduct the field exploration program are described below. Photos of drilling equipment and field exploration activities are included in

Appendix D. All soil and rock samples collected during the field exploration program were transported to the CFLHD Materials Laboratory in Lakewood, Colorado for testing. A summary of the laboratory testing program is provided in Appendix B.

A.2 EXPLORATIONS

Borings

Geomechanics Southwest, Inc. of Phoenix, AZ provided the drilling services for the soil and rock borings. Borings were completed using a CME 75 drill rig. Borings were advanced through overburden using hollow stem augers with drive sampling until practical auger refusal was encountered. After refusal, the borings were advanced using a rock coring and continuous sampling system. Following drilling activities, field personnel backfilled the borings with cuttings generated during the drilling in accordance with applicable local, state, and federal regulations.

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

A.3 SOIL AND ROCK SAMPLING

Borings

Disturbed soil grab samples were obtained from drill cuttings during augering in the shallow subsurface. Representative portions of grab samples were placed in plastic baggies and transported to the CFLHD Materials Laboratory for testing.

Rock samples were collected from borings using triple-tube HQ wireline coring methods.

During coring, cuttings were removed from the borehole by circulating water down the drill rods and back up the annulus of the boring. Core runs ranged between approximately two and five feet in length. Percent recovery and rock quality designation (RQD) values are shown on the boring logs. Percent recovery is the ratio of the length of recovered core to the total length of the core run. RQD is the ratio 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 CFLHD Geotechnical personnel, then stored in cardboard core boxes and transported to the CFLHD Materials Laboratory.

A.4 SOIL AND ROCK CLASSIFICATION SYSTEM

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

Classification Field Reference.

G rfc

Te xt

!S O

IL

C

A

LS

S

IF

IC

A

TI

O

N C

H A

R T

L

E G

E N

D

3/

/2

3:

:5

P

M

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

Unified Soil Classification System

SOIL CLASSIFICATION CHART & LEGEND

SILTY GRAVELS WITH OR WITHOUT SAND

HIGHLY ORGANIC SOILS

POORLY-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLEAN SANDS

WITH LESS THAN

15% FINES

GRAVELS WITH

15% OR MORE

FINES

GRAVELS

MORE THAN HALF

COARSE

FRACTION IS

LARGER THAN NO.

4 SIEVE

MAJOR DIVISIONS TYPICAL NAMES

WELL-GRADED GRAVELS WITH OR WITHOUT

SAND

POORLY-GRADED GRAVELS WITH OR

WITHOUT SAND

ORGANIC SILTS OR CLAYS OF HIGH

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

PEAT AND OTHER HIGHLY ORGANIC SOILS

CLAYEY SANDS WITH OR WITHOUT GRAVEL

C O

A R

S E

-G R

A

IN

E D

S O

IL

S

M O

R E

T H

A N

H A

LF

IS

C O

A R

S E

R T

H A

N N

O . 2

S

IE

V

E

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

SILTS AND CLAYS

LIQUID LIMIT 50% OR LESS

Unconfined Compression No Recovery

SILTS AND CLAYS

LIQUID LIMIT GREATER THAN 50%

UC

NR

FI

N

E -G

R A

IN

E

D S

O

IL

S M

O R

E T

H A

N H

A

LF

IS

F

IN

E

R T

H A

N N

O . 2

S

IE

V

E

SANDS WITH 15%

OR MORE FINES

SANDS

MORE THAN HALF

COARSE

FRACTION IS

FINER THAN NO. 4

SIEVE SIZE

INORGANIC CLAYS OF HIGH PLASTICITY

WITH OR WITHOUT SAND OR GRAVEL

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

Water Level at Time of Drilling

Stabilized Water Level

CLEAN GRAVELS

WITH LESS THAN

15% FINES

Abbreviations

WELL-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLAYEY GRAVELS WITH OR WITHOUT SAND

INORGANIC SILTS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

INORGANIC CLAYS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

LL

PI

W

DD

NP

NV

SILTY SANDS WITH OR WITHOUT GRAVEL

ORGANIC SILTS OR CLAYS OF LOW TO

MEDIUM PLASTICITY WITH OR WITHOUT

SAND OR GRAVEL

INORGANIC SILTS OF HIGH PLASTICITY WITH

OR WITHOUT SAND OR GRAVEL

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

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

5. Moisture Content

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

Flat & Elongated Meets both of the above

Applies to sand, gravel, cobbles and boulders.

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

6c. Particle Shape

N Density N Consistency

Unconfined Compressive Strength qu

(tsf)

Undrained Compressive Strength su

(tsf)

Behavior

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

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

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

Imprinted easily with fingers, remolded by strong finger pressure

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

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

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

SAND & GRAVEL SILT AND CLAY

3. Consistency and Density:

Angular Sharp edges and relatively plane sides.

Subangular Same as angular with rounded edges.

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

Rounded Smooth curved sides and no edges.

Well-

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

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

Sieve < #200 Flour or smaller

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

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

Boulder…