PVMT Report_NM FTBL 2004(1) Wild Rivers BCB FINAL_ 2020.08.24.pdf

Final Pavement Report

NM FTBL 2004(1) Wild Rivers Back Country Byway

Rio Grande del Norte National Monument

Taos County, New Mexico

Yeh Project No.: 219-237

August 24, 2020

Prepared for:

Jacobs Engineering Group, Inc.

Attn: Aaron Swafford, P.E.

9191 South Jamaica Street

Englewood, Colorado 80112

Prepared by:

Yeh and Associates, Inc.

570 Turner Drive, Suite D Durango, Colorado 81303

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

Table Of Contents

1. PURPOSE AND SCOPE OF STUDY

1.1 PURPOSE OF WORK

1.2 SCOPE OF WORK

2. PROPOSED CONSTRUCTION

3. SITE CONDITIONS AND GEOLOGIC SETTING

3.1 CLIMATE AND TERRAIN

3.2 GEOLOGY

3.3 SOIL MAPS

4. PAVEMENT CONDITIONS

5. SUBSURFACE INVESTIGATION

5.1 FIELD EXPLORATION

5.2 LABORATORY TESTING

6. SUBSURFACE CONDITIONS

6.1 PAVEMENT AND BASE COURSE

6.2 SUBGRADE SOILS

6.2.1 PENETRATION RESISTANCE

6.2.2 CLASSIFICATION

6.2.3 CHEMICAL PROPERTIES

6.2.4 SWELL / CONSOLIDATION

6.2.5 RESISTANCE “R”-VALUES

7. PAVEMENT DESIGN RECOMMENDATIONS

7.1 PAVEMENT HISTORY

7.2 DESIGN TRAFFIC VOLUME

7.3 STRUCTURAL SECTION

7.3.1 SEGMENT 1 (ENTRANCE ROAD – PHASE II)

7.3.2 SEGMENT 1 (ENTRANCE ROAD – CURVE REALIGNMENTS – PHASE II)

7.3.3 SEGMENT 2A (LOOP ROAD, 2-WAY – PHASE I)

7.3.4 SEGMENT 2B

7.3.5 SEGMENT 3

7.4 HOT ASPHALT CONCRETE PAVEMENT MIX AND BINDER

i i

8. GEOTECHNICAL RECOMMENDATIONS

8.1 EARTHWORK DESIGN

8.1.1 GENERAL GRADING

8.1.2 REUSE OF ON-SITE SOIL

8.1.3 SUBGRADE PREPARATION

8.1.4 GRADED SLOPE DESIGN

8.2 CORROSION PROPERTIES OF ON-SITE SOILS

8.3 FOUNDATION RECOMMENDATIONS

9. LIMITATIONS

10. REFERENCES

APPENDICES

List Of Figures

FIGURE 2-1 PROJECT LOCATION - OVERVIEW

List Of Tables

TABLE 5-1 SUMMARY OF BORINGS

List Of Appendices

BORING LOCATION MAP ........................................................................................................ A

BORING LOGS ........................................................................................................................ B

LABORATORY TEST METHODS AND RESULTS .......................................................................... C

PAVEMENT DESIGN CALCULATIONS ....................................................................................... D

NRCS SOILS MAPS AND SOIL DESCRIPTIONS ........................................................................... E

PHOTOS OF DRILLING OPERATIONS ....................................................................................... F

PHOTOS OF PAVEMENT CONDITIONS .................................................................................... G

NM FTBL 2004(1) Wild Rivers BCB YA Project No. 219-237 Final Pavement Report August 24, 2020

1. PURPOSE AND SCOPE OF STUDY

Yeh and Associates, Inc. (Yeh), as a subconsultant to Jacobs Engineering Group, Inc. (Jacobs), has been retained by the Federal Highway Administration (FHWA), Central Federal Lands

Highway Division (CFLHD) to provide pavement design recommendations for the proposed rehabilitation of approximately 12.5 miles of roadway within the Bureau of Land Management’s

(BLM) Wild Rivers Back Country Byway (BCB) in Taos County, New Mexico. The study and recommendations were developed in accordance with our Scope of Work (SOW) dated October

25, 2019 and with our Geotechnical Investigation Plan, submitted to Jacobs on November 7, 2019.

1.1 Purpose of Work

This report presents the results of Yeh’s field investigation and pavement design analysis for use by Jacobs and the project team for proposed improvements to 12.5 miles of the Wild Rivers

BCB within the Wild Rivers Recreation Area, a portion of the Rio Grande del Norte National

Monument administered by the Bureau of Land Management (BLM). The project is generally described as a Resurfacing, Rehabilitation and Restoration (3R) project. Resurfacing and minor widening are planned, which will result in improved facilities for both automobile and bicycle traffic. The improvements will be designed and implemented in accordance with CFLHD and

American Association of State Highway and Transportation Officials (AASHTO) Highway Design

Standards, in cooperation with the BLM, New Mexico Department of Transportation (NMDOT) and the CFLHD Denver Service Center.

1.2 Scope of Work

Our SOW includes the following activities:

• Field investigation to include pavement condition survey and subgrade borings

(Completed Nov. 5, 2019)

• Laboratory testing of select samples from the borings (Completed Dec. 2019)

• Pavement cost analyses – relative cost assessments of viable options

• Preliminary Pavement Recommendations Technical Memo (Issued Dec. 18, 2019;

Updated Jan. 22, 2020)

• Draft Pavement Report

• Final Pavement Report

• Plan notes and Special Contract Requirements, as needed

2. PROPOSED CONSTRUCTION

This project consists of resurfacing and minor widening of 12.5 miles of the Wild Rivers BCB within the Wild Rivers Recreation Area of the Rio Grande del Norte National Monument. The project site is located in Taos County, New Mexico, and can be accessed by traveling 26.8 miles north of Taos on US Hwy 64 / NM 522 to the junction with NM 387, near the town of

Cerro, NM, as illustrated in Figure 2-1.

Figure 2-1 Project Location - Overview

The project area begins at the entrance to the Rio Grande del Norte National Monument, located 3.6 miles west of NM 522 at the western terminus of NM 387. The Wild Rivers BCB extends southwest and south, following the eastern rim of the Rio Grande River Gorge, and terminates in a loop at the southern end. The existing Wild Rivers BCB consists of two lanes surfaced with asphalt pavement, and is approximately 22 feet in width. The purpose of the project, as described in the SOW, is to enhance overall public access to the Wild Rivers area with surfacing improvements to rehabilitate, restore, and resurface (3R) the roads and parking areas.

The project is divided into three segments. Segment 1 includes the Entrance Road, 7.75 miles in length, extending from the Wild Rivers entrance, south to the top of the Loop Road. Segment

2 includes the 4.75-mile Loop Road in the southern part of the Wild Rivers area. Segment 2A is

1 mile in length and extends from the Entrance Road to the Visitor Center access; Segment 2B incorporates the remaining 3.75 miles of the Loop Road. Segment 1 is proposed to be widened from 22 feet to 30 feet, resulting in 11-foot lanes with 4-foot shoulders. Shoulder widths of 6 feet, with 11-foot lanes, are planned for Segment 2B. The project proposes to change the traffic pattern for Segment 2B from two-way to one-way in a clockwise direction, with a 2-foot left shoulder, 14-foot lane, and 6-foot right shoulder for bicycle traffic. Flattening of two horizontal curves in Segment 1 near the Guadalupe Trailhead has been proposed, and asphalt aprons for approach roads will be rebuilt.

Segment 3 includes rehabilitation of the paved parking areas at the Visitor Center and Fee

Area, and of the paved access roads to the Visitor Center and Host Site. Existing gravel-surfaced roads servicing the Host Site and accessing the La Junta Overlook will be reconditioned and paved. Gravel-surfaced roads at the overlooks and campgrounds will be reconditioned and receive new aggregate surfacing.

Project features and limits are shown in Appendix A.

Construction is proposed to be divided into two phases. Phase I, in 2020, will improve the Loop

Road, Segments 2A and 2B, and much of Segment 3. Segment 1 and the Fee Parking Area of

Segment 3 are tentatively scheduled for construction in 2023, as Phase II of the project.

3. SITE CONDITIONS AND GEOLOGIC SETTING

3.1 Climate and Terrain

Weather information posted by www.usclimatedata.com for the Cerro, NM weather station from

1981 through 2010 indicates monthly average high temperatures range from 37F in January to

82F in July. Monthly average lows range from 7F in January to 49F in July. The area receives an annual average of 14.56 inches of rainfall and 61 inches of snow. Summer monsoons favor the area from July into September. The greatest amount of monthly precipitation, an average of

2.4 inches, falls during the month of August.

The Wild Rivers BCB route runs generally south-southwest, crossing gently rolling terrain with elevations ranging from 7420 to 7580 feet above mean sea level. The roadway corridor is bounded by the 800 foot deep Rio Grande River Gorge on the west and is flanked by

Guadalupe Mountains North and South to the east. Runoff from the Guadalupe Mountains passes from east to west through the project area by way of a series of shallow, ephemeral drainages.

3.2 Geology

The project area lies to the east of and directly above the deep gorge of the Rio Grande River as it makes its way southward from Colorado’s San Luis Valley. At the project’s southern end lies the confluence of the Rio Grande with the Red River, which has its headwaters in the Gold

Hill mountains east of Questa, N.M. Surficial geology is delineated and described in the

Geologic Maps for the USGS Sunshine (Thompson, et al, 2014) and Guadalupe Mountain

(Kelson, et al, 2008) 7.5-minute Quadrangles. Portions of the maps, with the Yeh exploratory boring locations identified, are provided in Appendix A.

The regional terrain is dominated by late Tertiary (Pliocene) volcanic deposits. The northern portion of the Wild Rivers BCB skirts the western flank of the Guadalupe Mountains, composed of the Guadalupe Mountain dacite volcanic unit (Tag). A slightly younger unit, the Red River

Volcano (Tvr) deposit, straddles the Red River at the southern end of the project area, near the

Wild Rivers Visitor Center. The flat to gently sloping areas between the mountains and the gorge are underlain by the Servilleta Formation (Tsb/Tb), which consists of flows of dark-gray basalt.

The Red River Fault Zone slices through the project area along a NNW-SSE orientation, southwest of Guadalupe Mountain South. The fault zone consists of a series of normal fault strands with down-to-the-east senses of displacement. The faults displace late Pleistocene basalt exposed in the Rio Grande and Red River gorges and are marked by scarps in

Pleistocene alluvium that pre-dates incision of the gorges (Machette, et al, 2000). The fault zone crosses the Wild Rivers BCB just south of the Bear Crossing Trail pullout, where the roadway climbs steeply onto the upper, western block, which has been elevated relative to the terrain located east of the fault.

The Tsb/Tb basalt flows are capped with surficial units from a range of sources. The oldest of these, QtOrg, is identified as an early to middle Pleistocene stream terrace deposit near the confluence of the Rio Grande and Red River gorges. The Loop Road is largely situated on this unit. Somewhat younger middle Pleistocene alluvium deposits (Qao3) have been mapped adjacent to the Rio Grande River Gorge north of the Bear Crossing Trail. Alluvial fan deposits of middle to late Pleistocene (Qfu) and latest Pleistocene to Holocene (Qf and Qfyv) have formed where sediment has been eroded from the Guadalupe Mountains and deposited on the flatter surfaces below. Eolian deposits, Qe (Pleistocene to Holocene), have been mapped on top of the elevated basalt area located west of the Red River Fault Zone. The youngest deposits in the project area consist of Holocene stream channel and valley-floor alluvium, mapped as Qa/Qal.

3.3 Soil Maps

Natural Resources Conservation Service (NRCS) soil maps for the project area indicate that two main soil assemblages, or map units, are present along the length of the Wild Rivers BCB. The primary map unit is FHB, Fernando-Hernandez association, with slopes of 1 to 5 percent and depths of more than 80 inches to a restrictive feature. This unit is generally assigned to those areas mapped as geologic units QtOrg (in the center of that area), Qao3, Qfu, Qf, Qfyv and Qe.

Soil map unit OMD, Orejas-Montecito association, occupies areas near the edge of the gorge.

Slopes are generally 5 to 30 percent, with depths of 10 to 20 inches to lithic bedrock being typical. This unit is found at the outer fringe of geologic unit QtOrg and along portions mapped as geologic unit Tb/Tsb. Three minor soil map units are also identified within the project area:

HPC, Hernandez-Petaca association, in portions of the Qao3 alluvium; HKC, correlating with geologic units Qa/Qal; and MxE, Montecito-Rock outcrop complex, along the Red River Fault escarpment slope. Soil map unit descriptions are provided in Appendix E. Soil properties and chemical characteristics are discussed in Sections 6.2 and 8.2 of this report.

4. PAVEMENT CONDITIONS

Paved surfaces of the Wild Rivers BCB were examined in the field to determine the types and severities of pavement distresses that are present. The Federal Highway Administration’s

Distress Identification Manual for the Long-Term Pavement Performance Program (Miller, et al, 2003) was used as a reference for describing the distresses observed.

The asphalt paved surface exhibits transverse or “thermal” cracking throughout the length of the project. Spacing of the cracks is generally between 10 and 20 feet, with severity levels of low

(<¼ inch), medium (¼ inch > ¾ inch) and high (>¾ inch) being observed. A portion of the cracks have been sealed previously, primarily those in the northern ¾ mile of Segment 1. Newer, low severity transverse cracks have generally not been filled. Wider transverse cracks often have adjacent low to medium severity random cracking.

Block cracking is present within the project area. Discussion of this distress is addressed in sections of this report describing longitudinal and transverse cracking.

Longitudinal cracking was identified within the project area, both within and outside of the wheel path. These cracks have generally not been sealed. Cracking along the centerline joint, at low to medium severity, was nearly continuous throughout the length of the project. Intermittent occurrences of low to medium severity longitudinal cracking between the wheel paths were observed. Cracks within the wheel paths are discussed under fatigue cracking, below.

Fatigue or “alligator” cracking was found in isolated areas, primarily in Segment 2B where the outer lane is constructed in a fill condition. Other scattered incidences of low-severity fatigue cracking were noted in Segment 1.

Pavement edge cracking and shoulder drop-off conditions were observed at several locations throughout the project limits.

Rectangular patched areas are present at scattered locations. The patches were constructed using perimeter saw cuts, and are filled with asphalt mix that has not performed quite as well as the surrounding pavement. Minor raveling was present, and cracks have propagated away from the sawed edges of the patches, but the patching material does not appear to have settled.

Parking areas and approach road aprons exhibited fatigue cracking, severe oxidation, and raveling of the surface. None of these areas appear to have been improved with overlays or crack sealing since their original construction.

Representative photographs of pavement distresses from the Wild Rivers BCB are provided in

Appendix G.

5. SUBSURFACE INVESTIGATION

5.1 Field Exploration

Yeh conducted a geotechnical investigation for the Wild Rivers BCB project on November 14 and 15, 2019. Twenty-one (21) borings were drilled in or adjacent to the roadway prism and two

(2) borings were drilled in existing paved parking areas. A truck-mounted CME 75 drill rig advanced the borings using an 8-inch hollow-stem auger (HSA). Enviro-Drill, Inc. of

Albuquerque, NM, was the drilling services vendor. Due to the low traffic volumes at the site, traffic control for the drilling operations consisted of warning signs placed ahead of and behind the drilling operations.

Approximate coordinates and elevations for the borings were recorded using a hand-held GPS unit. Locations of the borings are shown in Appendix A, overlaid on images acquired from

Google Earth. Boring coordinates were also recorded by Jacobs’ survey crew, for projection onto the project alignment. Boring Logs are included in Appendix B, and photographs of the drilling operations are provided in Appendix F.

Along Segment 1, the Entrance Road, sixteen (16) borings were drilled into the existing roadway prism and one (1), boring WR-16, was drilled at the side of the road. A single boring, WR-18, was drilled within Segment 2A, and four (4) borings were drilled along Segment 2B.

Two (2) borings were drilled in existing paved parking areas in Segment 3: the Visitor Center and the Fee Pay area.

Borings were advanced to depths ranging from 5.0 to 10.5 feet with the exception of borings

WR-11, WR-13 and WR-16, where auger refusal was encountered. No groundwater was encountered in the borings. Results of the subsurface investigation are summarized in Table 5-

1.

Soil samples were collected from each of the borings during drilling. Samples were collected from auger cuttings and at intermittent depths from HSA borings utilizing either a standard 2 inch outside diameter (O.D.) split spoon sampler or a 2.5 inch O.D. “Modified California” sampler. The samplers were advanced by a 140 pound automatic (or “auto”) hammer with a 30 inch drop height. The number of blows required to drive the sampler 12 inches, or a fraction thereof, after an initial penetration of 6 inches for the standard sampler, constitutes the N-value as shown on the boring logs. N-values or penetration resistance can be correlated to the relative density of cohesionless soils and the consistency of cohesive soils.

Table 5-1 Summary of Borings

5.2 Laboratory Testing

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

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

Engineer and a program of laboratory testing was assigned. Specialized testing for chloride content was provided by Green Analytical Laboratories of Durango, Colorado. Hveem

Resistance “R” Value testing was performed at Yeh’s Denver laboratory.

The laboratory tests were performed on selected samples from the borings in accordance with the AASHTO and American Society of Testing and Materials (ASTM) procedures. Laboratory tests on samples included sieve analysis, Atterberg limits, natural moisture content, and R-

Value. In addition, selected samples were subjected to chemical analyses to evaluate soil

Boring Depth

Asphalt Thickness

Base Course

Thickness

Total Combined Thickness

Feet LT/RT (ft) (in) (in) (in)

WR-01 23+50 8 RT 5.0 6.0 10.0 16.0

WR-02 40+07 8 RT 6.0 6.0 4.0 10.0

WR-03 89+37 6 RT 5.0 5.0 4.0 9.0

WR-04 120+09 6 LT 6.5 6.0 3.0 9.0

WR-05 514+19 6 LT 5.0 6.0 4.0 10.0 Cemented Sand @ 2.5' WR-06 175+87 6 LT 5.0 5.5 6.0 11.5 Cemented Sand @ 2.5' WR-07 190+93 7 RT 6.5 6.0 5.0 11.0 Gravel & cobbles @ 3-4

WR-08 218+98 6 RT 5.0 4.0 6.0 10.0

WR-09 254+55 9 RT 5.0 5.5 5.0 10.5 Clayey Gravel @ 3.5' WR-10 260+86 9 LT 5.0 5.0 5.0 10.0 Cut section S of Bear Xing WR-11 269+06 8 RT 2.5 4.5 5.0 9.5 Auger Refusal @ 2.5'

WR-12 294+25 5 LT 6.5 4.5 5.0 9.5

WR-13 317+55 6 LT 3.0 4.0 8.0 12.0 Auger Refusal @ 3.0'

WR-15 348+69 7 RT 5.0 4.5 5.0 9.5

WR-16 384+73 32 LT 4.0 0.0 0.0 0.0 Auger refusal @ 4.0'

WR-17 405+43 7 LT 5.0 5.0 5.0 10.0

2A WR-18 450+11 6 LT 5.0 5.0 5.0 10.0

WR-20 480+59 6 LT 5.0 4.5 5.0 9.5

WR-21 547+43 5 LT 10.5 5.0 0.0 5.0 Fill Section

WR-22 605+69 6 LT 5.0 4.5 6.0 10.5

WR-23 668+43 0 LT 6.5 4.5 8.0 12.5

WR-14 340+35 42 RT 5.0 3.0 4.0 7.0 Fee Area Parking WR-19 468+88 247 LT 5.0 3.0 3.0 6.0 Visitor's Center Parking

Comments Project

Segment Boring No.

2B

Station Offset corrosivity: pH, water-soluble sulfate content, water-soluble chloride content, and resistivity. The laboratory test results and soil classifications are shown on the boring logs in Appendix B and are included in Appendix C, Laboratory Test Results.

Results from the Atterberg limits determination and sieve analysis were used to classify the soils according to AASHTO and the Unified Soil Classification System (USCS) standards. Atterberg limits were performed in accordance with AASHTO T89 and T90, and sieve analyses were performed in accordance with ASTM D421.

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

Four (4) swell/consolidation tests were performed to evaluate the swell or collapse potential of selected samples of the subsurface materials in accordance with ASTM D4546 Procedure B.

The swell or consolidation was measured by applying a surcharge of either 200 pounds per square foot (psf), 500 psf or 1,000 psf to the samples and adding water.

Hveem Resistance “R”-value tests were performed on four (4) bulk samples of subgrade soils.

The tests were performed in conformance with ASTM D 2844. Results of the R-value test are converted to resilient modulus, MR, the property which characterizes soil stiffness in flexible pavement design.

Four (4) samples were tested for chemical properties to evaluate the potential of the soil to be aggressive to concrete and to corrode buried metal. The tests included pH (ASTM D 4972 /

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

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

Laboratories, Inc.

6. SUBSURFACE CONDITIONS

6.1 Pavement and Base Course

The thickness of asphalt pavement encountered in the exploratory borings for Segments 1 and

2A ranged from 4 to 6 inches with an average of 5.2 inches. Aggregate base course (ABC), consisting of reclaimed pavement and imported aggregates, ranged from 3 to 10 inches in thickness, with an average of 5.3 inches. Asphalt thicknesses for Segment 2B were somewhat

1 0 less, ranging from 4.5 to 5 inches with an average of 4.6 inches, while the ABC ranged in thickness from 0 to 8 inches.

Samples of ABC collected from 4 borings (two from Segment 1 and one each from Segments

2A and 2B) were tested in the laboratory for purposes of classification. Gradation test results show the ABC to have 8 to 14 percent fines (passing the No. 200 sieve), with 41 to 49 percent sand and 41 to 47 percent gravel (retained on the #4 standard sieve). Atterberg limits testing determined the ABC samples had a Plasticity Index (PI) ranging from 4 to 13. Liquid Limits (LL) were between 24 and 31. Using the AASHTO method, the ABC was classified as A-1-a (0), A-2-

4 (0) or A-2-6 (0). Under the USCS, the ABC was categorized as GP-GC (poorly graded gravel with clay and sand); GM (silty gravel with sand); SP-SM-SC (poorly graded sand with silty clay and gravel); and SC (clayey sand with gravel). Due to the ABC’s consisting of pavement and base course processed together by full depth reclamation (FDR) in 2002, the ABC is darker in color than base course would generally be if it consisted of imported aggregate alone.

6.2 Subgrade Soils

Subsurface conditions to the depths of exploration generally consist of medium plasticity clays, with some proportion of sand; and clayey sand and gravel. No groundwater was encountered in the borings, but native soils were generally moist. In-situ moisture contents of fine-grained soils ranged from 13.8 to 28.6 percent. Fine-grained soils were encountered the full depth of Borings

WR-01 through WR-04, WR-08, WR-12, WR-14, WR-15, WR-17 through WR-20, WR-22 and

WR-23. Sand, weakly cemented with caliche, was encountered at a depth of 2.5 feet below the surface in Borings WR-05 and WR-06, north and south of the Guadalupe Trail pullout, respectively. No coring was performed, and the HSA was able to drill through the cemented material to a depth of 5.0 feet below the surface. Gravel or cemented material was encountered in Boring Nos. WR-07, WR-09 through WR-11, WR-13, WR-16 and WR-21.

6.2.1 Penetration Resistance

Penetration Resistance N-values for fine-grained native soils ranged from a low of 5 to a high of

24, with an average of 15 blows per foot (bpf). Coarser soils with a portion of gravel or weathered basalt had N-values ranging from 36 bpf to 38 blows per 4 inches. Auger refusal was encountered in boring WR-11, at the road cut south of Bear Crossing; in boring WR-13 in cemented soil or bedrock; and in boring WR-16 in clayey gravel.

1 1

6.2.2 Classification

Twelve (12) samples of subgrade soils collected from depths of less than 5 feet below the ground surface were tested for purposes of classification. Gradation test results show the soils to have between 24 and 78 percent fines. Sand portions ranged from 19 to 52 percent, while the gravel content ranged from 1 to 40 percent. Atterberg limits testing showed LL values of 26 to

46 percent and PI values ranging from 10 to 26. One sample, from boring WR-06, was non plastic. Under the AASHTO system, the soils were classified as follows: A-2-4 (0); A-2-6 (0); A-6 with group indices from (4) to (17); and A-7-6 (20). In the Unified Soil Classification System

(USCS), eight (8) of the samples were CL (low to medium plasticity clay with sand, sandy clay, or sandy clay with gravel). Two samples were SC (clayey sand with gravel); one sample was

GC (clayey gravel with sand); and one sample was SM (silty sand).

6.2.3 Chemical Properties

Chemical properties were measured for five (5) samples of subgrade soil. The pH was mildly alkaline and ranged from 7.4 to 7.5. Water-soluble sulfates were low, ranging from 0.001 to

0.021 percent. Water-soluble chlorides were present at detectable levels in only one sample, at

0.00140%. Resistivity values between 1600 and 3400 Ohm-cm were measured for four (4) samples.

6.2.4 Swell / Consolidation

Swell/consolidation testing, was performed on four (4) subgrade samples collected using the modified California sampler. One sample, from Boring WR-08, exhibited consolidation of 5.3 percent when wetted under an applied pressure of 500 psf. This sample had a natural moisture content of 13.8 percent and a natural dry density of 78.0 pounds per cubic foot (pcf). Two other samples exhibited minor consolidations of 0.2 and 0.4 percent under 500 psf. The natural moisture contents of these samples were 28.6 and 18.9 percent, respectively, and corresponding densities were 89.8 and 80.7 pcf. The fourth sample exhibited swell of 0.2 percent when wetted under an applied pressure of 500 psf. This sample had a natural moisture content of 15.5 percent and a natural dry density of 105.5 pcf.

6.2.5 Resistance “R”-Values

R-values were measured for four samples of subgrade soils. The lowest value, an R-value of 7, was obtained from Boring WR-03. The soil at this location was a medium plasticity sandy clay, classified as A-6 (13) under AASHTO and CL using the USCS. Low plasticity clay, AASHTO A-6

1 2

(4) and USCS CL, from Boring WR-08, produced an R-value of 10. Soils from Boring WR-18

(AASHTO A-6 (7) and USCS CL, sandy clay) produced an R-value of 11. Samples from four borings, WR-19; WR-20; WR-22 and WR-23, were similar in nature and were combined to test the R-value. A value of 9 was measured for the composite sample.

7. PAVEMENT DESIGN RECOMMENDATIONS

The geotechnical investigation was performed in pavement areas for the purpose of pavement design. The subsurface conditions encountered in the borings may not be representative of conditions outside the roadway prism. Additional investigations may be required to evaluate conditions in any areas where structures are proposed.

Pavement designs for the Wild Rivers BCB were performed in accordance with methods outlined in Chapter 11 of the FLH Project Development and Design Manual (PDDM) and the

1993 AASHTO Guide for the Design of Pavement Structures (AGDPS). The recommendations of this report assume that grading, fill materials, aggregate base course, full depth recycling and pavement will be placed and constructed in accordance with the FHWA’s Standard

Specifications for Construction of Roads and Bridges (FP-14). Compliance with these specifications is needed for the recommendations in this report to remain applicable.

7.1 Pavement History

A Draft Scoping Trip Report issued for this project in July 2014 reports that, per the BLM, the last rehabilitation occurred in 2002 and consisted of “rubblizing” the old pavement, mixing that with the previous base material to establish a new base, and paving with 6 inches of new asphalt. Subsequent to paving, spots where pavement failures had occurred were identified.

The Contractor dug out the failed areas to depths of 2 to 4 feet, and patched the repaired areas with select fill and asphalt. Saturated lenses of clay were encountered in many of the areas excavated for repairs. As noted in the “Pavement Conditions” section, above, cracks in some areas have been previously sealed.

7.2 Design Traffic Volume

The design traffic volume was estimated using the average annual daily traffic (AADT), determined from data provided to Jacobs by email on January 14, 2020. In the email, the BLM reported that the Fiscal Year (FY) 2019 continuous traffic count (2 directions) for the Wild Rivers

BCB was 33,938 vehicles. This data was used to estimate the number of 18-kip equivalent

1 3 single axle loads (ESALs) considering a design life of 20 years and an annual growth factor of

2%. In our analysis, we assumed that project completion would occur in 2020, and estimated a mix of 85% cars, 10% pickup trucks and vans, 3% trucks and RVs, and 2% Buses. The resulting

20-year Design ESAL value was 28,800. Subsection 11.2.1.2 of the PDDM directs, “If (the) design traffic ESALs is calculated to be less than 50,000, use 50,000 ESALs for design purposes when designing paved roads.” A design value of 50,000 ESALs was used for this project. ESALs calculations are included in Appendix D following the pavement design printouts.

7.3 Structural Section

As reported in Yeh’s January 22, 2020 Preliminary Pavement Recommendations memo

(Revised February 25, 2020), results of 20 borings show that the existing pavement thickness for the Wild Rivers BCB ranges from 4 to 6 inches. Base course was encountered beneath the pavement in all of the borings with the exception of WR-21, located at the southern tip of the

Loop Road. Natural subgrade materials generally consist of clayey sand and sandy clay.

Rehabilitation options for the Wild Rivers BCB were developed using PAVEXpress, an online software program based upon the AGDPS for flexible pavements. Parameters, set in accordance with the PDDM, are as follows:

• Serviceability: Initial = 4.2 (flexible pavement); Terminal = 2.0 (roadways with <500 ADT)

• Design Period: 20 years (3R project, rehabilitation)

• Design ESALs (W18) = 50,000

• R = 7; MR = 4900 psi, R = 11; MR = 7100 psi, and R = 9; MR = 6000 psi

• Reliability Level (R): 75 (roadways with <2500 ADT)

• Combined Standard Error (SO): 0.49

Measured Hveem Resistance “R” values for the subgrade were low, ranging between 7 and 11.

An R-value of 7 was used in Yeh’s pavement structural section design analysis for Segment 1.

An R-value of 11 was used for Segment 2A. For Segments 2B and 3, an R-value of 9 was assumed. Using Equation 1.5.3 from the AGDPS, the R-value of 7 was used to calculate a resilient modulus, MR = 4900 psi. For an R-value of 11, the resultant MR is 7100 psi, and for R =

9, the corresponding MR is 6000 psi.

MR = 1,000 + (555)(R-value) Equation 1.5.3

The resulting minimum required Structural Numbers (SN), given these input parameters, are

2.30 for R = 7, 2.00 for R = 11, and 2.10 for R = 9. Structural Coefficients for each surfacing material were assigned based on values provided in the FLH PDDM Exhibit 11.2-C, Layer

1 4

Types and Coefficients. A range of 0.10 to 012 is given for FDR. A conservative layer coefficient of 0.10 was used in our analysis. The same value was used for base course in-place beneath the parking area pavements and for the La Junta Overlook. Exhibit 11.2-C gives a range of 0.40 to 0.44 for HACP Item(s) 401 and 402. A coefficient of 0.44 was assigned to all new HACP. The resulting designs, presented in Appendix D, achieve the required SN’s. Multiple alternatives were provided in the Preliminary Pavement Recommendations memo. Additional discussion with CFLHD personnel occurred during an April 22 2020 teleconference. This report presents the alternates selected for final design. The preliminary memo is provided in Appendix D, for reference.

7.3.1 Segment 1 (Entrance Road – Phase II)

For Segment 1, widening the pavement from 22 to 30 feet.is planned. Full depth reclamation

(FDR), followed by a structural HACP overlay, is the preferred rehabilitation method. The equivalent of one inch of 302 aggregate should be placed on the pavement surface prior to reclamation. The FDR will process the aggregate, the existing pavement, and a portion of the existing base course to provide a total thickness of 9 inches. This material will be distributed across the full width of the new roadbed to a depth of 5.5 inches. The FDR layer will be surfaced with a 4 inch overlay of HACP, placed in two 2 inch lifts.

For Segment 1, all embankment material, whether derived from within the project limits or imported, should have a minimum R-value of 7.

7.3.2 Segment 1 (Entrance Road – Curve Realignments – Phase II)

Two areas are proposed for realignment along the Entrance Road. Phasing of the realignment may make the FDR process inappropriate at these locations. Embankment should be constructed of soil having a minimum R-value of 7. Five (5) inches of aggregate base course should be placed, followed by 4 inches (two 2 inch lifts) of HACP.

7.3.3 Segment 2A (Loop Road, 2-Way – Phase I)

This portion of the Loop Road, 1 mile in length, will be widened from 22 to 34 feet. FDR of the existing pavement and road base to a depth of 8 inches will be required. The reclaimed material should be distributed across the roadbed to a thickness of 5.0 inches. Supplemental widening of the roadbed with can be accomplished with the addition of aggregate to the outside margins, or by the addition of 302 aggregate to the surface in advance of the FDR process. The structural

1 5 section will be completed with an overlay of HACP 3.5 inches thick. We recommend lift thicknesses of 2.0 and 1.5 inches for the bottom and top lifts, respectively.

Embankment material for Segment 2A, whether derived from within the project limits or imported, should have a minimum R-value of 11.

7.3.4 Segment 2B

FDR is also recommended for the 3.75 miles of Segment 2B. Because no widening is proposed for this area, the addition of aggregate will not be necessary. Pulverizing, shaping and recompacting the existing asphalt and base course to a depth of 8 inches will provide an 8-inch base layer on which 3.0 inches of HACP can be placed. Two lifts of 1.5 inches each are recommended.

Because no widening is proposed for this segment, we do not anticipate there being a need for a significant volume of embankment material beneath the paved roadway. If embankment is required beneath the pavement structure, material having a minimum R-value of 9 should be used.

7.3.5 Segment 3

The existing pavement at the Visitor Center and Fee Area parking lots should be removed by milling. The existing aggregate base should be reworked and recompacted, with additional aggregate incorporated as needed to achieve a minimum thickness of 4 inches and to address localized soft spots. The parking lots should be paved with 3 inches of HACP.

Full Depth Reclamation should be used for the access to the Visitor Center and the paved access to the Host Site. The depth of FDR should be 4 inches, including 1 inch of 302 aggregate placed on the surface in advance of FDR, followed by paving with 3 inches of HACP.

The gravel surfaced potion of the Host Site access should be constructed in the same manner as the La Junta Overlook, described below.

The La Junta Overlook has low traffic volumes. A pavement section consisting of 3 inches of

HACP on 4 inches of aggregate base is recommended for this area. Pavement millings derived from the Visitor Center and Fee Area parking areas would be an acceptable alternative to imported aggregate at this location. A second alternative is to apply the equivalent of 1 inch of

302 aggregate to the existing surface, and recondition to a combined depth of 4 inches prior to placement of the HACP.

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The CFLHD’s 2010 CFLHD Supplement 11.4.2-1 to the PDDM was used to evaluate recommended thicknesses for gravel surfaced campground accesses and pullout areas.

Assuming a “Low” 18-kip ESAL range; a “Poor” relative quality of roadbed soil; and climatic region “VI”, the recommended aggregate thickness is 9 inches. As a comparison, Appendix A of the 2015 FHWA Gravel Roads Construction and Maintenance Guide recommends a minimum

6.5 inches of aggregate surfacing for these conditions. An aggregate surfacing thickness of 6.5 inches is recommended for the Wild Rivers BCB facilities. Assuming that the existing thickness is at least 2.5 inches, the addition of 4 inches of gravel surfacing is recommended.

7.4 Hot Asphalt Concrete Pavement Mix and Binder

We recommend a ½ inch (12.5 mm) Nominal Maximum Size Aggregate gyratory asphalt concrete mix design, conforming to FP-14 Table 401-1 for this project with a Design ESAL less than 0.3 million. We understand that the CFL prefers the Section 401 SCR, which requires a

Design ESAL level of 0.3 to <3 million. Aggregates should meet the requirements presented in subsection 703.07 and Table 703-4 of FP-14.

The preferred asphalt binder for all lifts is PG 58-28, as recommended by the NMDOT pavement design guidance for Taos County. The LTPPBind program indicates that PG 52-28 is acceptable for the project area. Printouts of the NMDOT reference and the LTPPBind data are presented in Appendix D following the ESAL calculation table.

8. GEOTECHNICAL RECOMMENDATIONS

8.1 Earthwork Design

8.1.1 General Grading

All site grading should conform to the applicable sections of FP-14. Fill materials should not contain organic matter or other deleterious material. Excess fill or cut material should be hauled offsite for proper disposal, unless an onsite location has been specifically identified for placement of excess fill on the project plans. Temporary excavations should conform to OSHA requirements.

8.1.2 Reuse of On-site Soil

On-site soil removed from excavations and free of topsoil, organics, clay lenses or clods, and oversized rock can be reused as borrow for general embankment fill and unclassified borrow.

1 7

Fill materials should not contain organic matter or other deleterious material. The soil samples tested were typically more than 10 percent below the optimum moisture content for compaction.

Moisture conditioning of the excavated soil will be necessary to make the material suitable for compaction.

8.1.3 Subgrade Preparation

The roadbed should be prepared for placement of aggregate base or embankment fill materials in accordance with FP-14. Prior to placing fill or base course materials, the subgrade should be scarified to a depth of 6 inches, conditioned to a moisture content suitable for compaction, and compacted in-place to at least 95 percent relative compaction. The subgrade should be observed following the initial excavation to evaluate whether or not additional unsuitable soft or compressible soil is present. If needed, subexcavation should be performed to remove soft or compressible soil prior to placing the embankment fill.

8.1.4 Graded Slope Design

The proposed project will involve embankment construction, excavation for cuts, and widening of existing cut and embankment slopes through undulating terrain with intervening drainages.

Fill slopes should be designed at grades of 1v:3h or flatter. Cut slopes should be designed to

1v:2h or flatter.

8.2 Corrosion Properties of On-site Soils

The chemical properties of on-site soils may make them unacceptable for use as Structural

Backfill in contact with unprotected steel structures. Water-soluble sulfate and chloride levels measured in the Yeh and Green Analytical laboratories were low. However, the low resistivity level (1600 Ohm-cm) measured in a sample from Boring WR-03 should be taken into consideration, as this is an indication of high soil corrosivity. NRCS Soils Maps and maps addressing Corrosion of Steel and Concrete are provided in Appendix E. The maps indicate that all of the soil map units are rated “Low” for risk of corrosion of concrete. For steel, however, corrosion risk is predicted to be “Moderate” and “High”.

When applicable, a layer of Structural Backfill or aggregate base course should be used as a separator between steel and native material. Other options for corrosion mitigation could include sacrificial metal (heavier gauge construction material) in design of structural elements and use of materials resistant to corrosion such as galvanized or epoxy coatings or cathodic protection systems. A qualified corrosion engineer should review this data to evaluate the appropriate level

1 8 of corrosion protection for subgrade utilities and buried metal and concrete structures proposed for the area.

8.3 Foundation Recommendations

If small structures are proposed, such as headwalls and wingwalls, we can provide design recommendations such as bearing resistance, lateral earth pressures and foundation soil preparation.

9. LIMITATIONS

This study was conducted in accordance with generally accepted geotechnical engineering practices in this area for use by the client for design of the proposed roadway reconstruction project. Recommendations herein are intended to be used for design by a qualified transportation engineer. The preliminary analyses and recommendations presented in this report are based upon our data obtained from limited field observations, widely spaced borings, laboratory testing, our understanding of the proposed construction and other information as discussed in this report. It is possible and likely that subsurface conditions may vary from those encountered in the borings. We should also review the design for conformance to the recommendations in the report when the scope of the proposed construction becomes established.

The scope of services for this project did not include, specifically or by implication, any environmental or biological (e.g. mold, fungi, and bacteria) assessment of the site or identification of prevention of pollutants, hazardous materials or conditions or biological conditions. If the owner is concerned about the potential for such contamination, conditions or pollution, other studies should be undertaken.

This report was prepared in substantial accordance with the generally accepted standards of practice for geotechnical engineering as exist in the site area at the time of our investigation. No warranties, express or implied, are intended or made. The recommendations in this report are based on the assumption that the Contracting Officer will conduct an adequate program of construction testing and observation to evaluate compliance with our recommendations.

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10. REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), AASHTO Guide for Design of Pavement Structures, Washington, D.C., 1993.

Kelson, K.I., Thompson, R. and Bauer, P.W., 2008, Preliminary Geologic map of the Guadalupe Mountain 7.5-minute quadrangle map, Taos County, New Mexico: New Mexico Bureau of Geology and Mineral Resources, Open-File Geologic Map OF-GM 168, scale 1:24,000.

Machette, M.N., Personius, S.F., Kelson, K.I., Dart, R.L. and Haller, K.M., 2000, Map and data for Quaternary faults and folds in New Mexico: U.S. Geological Survey Open File Report 98-521 (electronic version).

Miller, J.S. and Bellinger, W.Y., Distress Identification Manual for the Long-Term Pavement Performance Program (Fourth Revised Edition). Federal Highway Administration Publication No. FHWA-RD-03-031, June 2003.

PAVEXpress, https://pavexpress.com, © Pavia Systems, Inc., Delaware, U.S.

Thompson, R.A., Turner, K.J., Shroba, R.R., Cosca, M.A., Ruleman, C.A., Lee, J.P., and Brandt, T.R., 2014, Geologic map of the Sunshine 7.5’ quadrangle, Taos County, New Mexico: U.S. Geological Survey, Scientific Investigations Map SIM-3282, scale 1:24,000.

U.S. Department of Transportation, Federal Highway Administration, Federal Lands Highway, 2014. FP-14, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects., U.S. Department of Transportation, Federal Highway Administration, Federal Lands Highway Project Development and Design Manual (PDDM), Chapter 11 – Pavements, Government Printing Office, Washington, D.C., December 2014.

https://pavexpress.com/

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APPENDICES

BORING LOCATION MAP ........................................................................................................ A

BORING LOGS ........................................................................................................................ B

LABORATORY TEST METHODS AND RESULTS .......................................................................... C

PAVEMENT DESIGN CALCULATIONS ....................................................................................... D

NRCS SOILS MAPS AND SOIL DESCRIPTIONS ........................................................................... E

PHOTOS OF DRILLING OPERATIONS ....................................................................................... F

PHOTOS OF PAVEMENT CONDITIONS .................................................................................... G

Appendix A

BORING LOCATION MAP

Figure A-1 - Boring Locations – WR-01 through WR-11

Figure A-2 - Boring Locations WR-11 through WR-23

Figure A-3 – Borings WR-01 through WR-04 (Sunshine Quad)

Figure A-4 – Borings WR-05 through WR-12 (Guadalupe Mountain Quad)

Figure A-5 – Borings WR-13 through WR-23 (Guadalupe Mountain Quad)

Appendix B

BORING LOGS

Project Number: 219-237

NM FTBL 2004 (1) Wild Rivers BCB

Lithology Symbols (see Boring Logs for complete descriptions)

Asphalt USCS Low Plasticity Sandy Clay

Fill with Clay as major soil

Fill with Gravel as major soil

Fill with Sand as major soil USCS Clayey Gravel USCS Silty Gravel USCS Silt

USCS Clayey Sand USCS Silty Sand USCS Well-graded Sand

Lab Test Standards Other Lab Test Abbreviations pH Soil pH (AASHTO T289-91) S Water-Soluble Sulfate Content (AASHTO T290-91, ASTM D4327)

Chl Water-Soluble Chloride Content (AASHTO T291-91, ASTM D4327)

S/C Swell/Consolidation (ASTM D4546) UCCS Unconfined Compressive Strength (ASTM D2166) R-Value Resistance R-Value (ASTM D2844) DS (C) Direct Shear cohesion (ASTM D3080) DS (phi) Direct Shear friction angle (ASTM D3080) Re Electrical Resistivity (AASHTO T288-91) PtL Point Load Strength Index (ASTM D5731)

Notes

Moisture Content ASTM D2216 Dry Density ASTM D7263 Sand/Fines Content ASTM D421, ASTM C136, ASTM D1140

Atterberg Limits ASTM D4318 AASHTO Class. AASHTO M145, ASTM D3282

USCS Class. ASTM D2487 (Fines = % Passing #200 Sieve Sand = % Passing #4 Sieve, but not passing #200 Sieve)

Auger Cuttings Modified California Sampler (2.5 inch OD, 2.0 inch

ID)

Standard Penetration Test

(ASTM D1586)

Sample Types Legend for Symbols Used on Borehole Logs

Project:

Yeh and Associates, Inc.

C o n s u l t i n g E n g i n e e r s & S c i e n t i s t s

1. "Penetration Resistance" on the Boring Logs refers to the uncorrected N value for SPT samples only, as per ASTM D1586. For samples obtained with a Modified California sampler, drive depth is 12 inches, and "Penetration Resistance" refers to the sum of all blows. Where blow counts were > 50 for the 3rd increment (SPT) or 2nd increment (MC), "Penetration Resistance" combines the last and 2nd-to-last blows and lengths; for other increments with > 50 blows, the blows for the last increment are reported.

2. The Modified California sampler used to obtain samples is a 2.5-inch OD, 2.0-inch ID (1.95-inch ID with liners), split-barrel sampler with internal liners, as per ASTM D3550. Sampler is driven with a 140-pound hammer, dropped 30 inches per blow.

3. "ER" for the hammer is the Reported Calibrated Energy Transfer Ratio for that specific hammer, as provided by the drilling company.

3-3-2

0.0 - 0.5 ft. 6 inches asphalt.

0.5 - 1.3 ft. 10 inches Aggregate Base Course.

1.3 - 5.0 ft. sandy SILT, reddish brown, moist, medium stiff.

Bottom of Hole at 5.0 ft.

Total Depth: 5.0 ft Ground Elevation:

Coordinates: N: E:

Location: Sta. 23+50, 8' R

Groundwater Levels:

Logged By: B. Bunker

Final By: B. Bunker

Symbol Depth Date

Weather Notes:

Inclination from Horiz.: Vertical

Night Work:

Boring Began: 11/14/2019 Boring Completed: 11/14/2019 Drilling Method(s): Hollow-Stem Auger

Driller: Enviro-Drill, Inc.

Drill Rig: CME 75

Hammer: Automatic (hydraulic), ER: %

Project Name:

PAGE

AASHTO

& USCS

Classifi-cations

Fi ne s C on te nt

Pl as tic ity

In de x

Project Number: 219-237C o n s u l t i n g E n g i n e e r s & S c i e n t i s t s

Li qu id Li m it

Field Notes and

Other Lab Tests

NM FTBL 2004 (1) Wild Rivers BCB

Atterberg Limits

Boring No.: WR-01 Yeh and Associates, Inc.

El ev at io n (fe et

D ep th (fe et

Sa m pl e

Ty pe

Ad va nc em en t M et ho d

BO

R

IN

G

L O

G

- S

PT

C D

O T

ST

YL

E

-2

B

LM

W

IL

D

R

IV

ER

S.

G

PJ

YE

H A

SS

O

C

IA

TE

S

TE

M

PL

AT

E.

G

D T

LI

BR

AR

Y.

G

LB

/2 /2

M oi st ur e C on te nt

D ry D en si ty (p cf )Blows per 6 in Li th ol og y

Soil Samples

Material Description

Pe ne tra tio n R es is ta nc e

A-6 (13)

CL73 204025214.3

7-8

0.0 - 0.5 ft. 6 inches asphalt.

0.5 - 0.9 ft. 4 inches Aggregate base Course, blended with native clay.

0.9 - 6.0 ft. CLAY with sand, reddish brown, medium plasticity, moist, stiff.

Bottom of Hole at 6.0 ft.

Total Depth: 6.0 ft Ground Elevation:

Coordinates: N: E:

Location: Sta. 40+07, 8' R

Groundwater Levels:

Logged By: B. Bunker

Final By: B. Bunker

Symbol Depth Date

Weather Notes:

Inclination from Horiz.: Vertical

Night Work:

Boring Began: 11/14/2019 Boring Completed: 11/14/2019 Drilling Method(s): Hollow-Stem Auger

Driller: Enviro-Drill, Inc.

Drill Rig: CME 75

Hammer: Automatic (hydraulic), ER: %

Project Name:

PAGE

AASHTO

& USCS

Classifi-cations

Fi ne s C on te nt

Pl as tic ity

In de x

Project Number: 219-237C o n s u l t i n g E n g i n e e r s & S c i e n t i s t s

Li qu id Li m it

Field Notes and

Other Lab Tests

NM FTBL 2004 (1) Wild Rivers BCB

Atterberg Limits

Boring No.: WR-02 Yeh and Associates, Inc.

El ev at io n (fe et

D ep th (fe et

Sa m pl e

Ty pe

Ad va nc em en t M…