CO.FTNP.COLM.10(3).Rim_Rock_Drive_Spot_Repairs.2017.pdf

Rim Rock Drive Spot Repairs 2000+00 and 3000+00

Colorado National Monument Mesa County

CO FTNP COLM 10(3)

Final Geotechnical Design Report Report # CO-PX-COLM-17-01

Prepared by Federal Highway Administration

Central Federal Lands Highway Division

Geotechnical Services Branch

January 2017

Rim Rock Drive Spot Repairs 2000+00 and 3000+00 i January 2017

Table of Contents

SECTION ONE--INTRODUCTION AND BACKGROUND

1.1 INTRODUCTION

1.2 BACKGROUND

SECTION TWO--GEOLOGY AND SEISMICITY

2.1 GEOLOGY

2.2 SEISMICITY

SECTION THREE—FIELD EXPLORATION

FIELD EXPLORATION AND LABORATORY TESTING PROGRAM ............... 6 3.1

SECTION FOUR--ANALYSIS AND RECOMMENDATIONS

SITE 2000+00 ........................................................................................................... 7 4.1

4.1.1 Site 2000+00 Geotechnical Profile

4.1.2 Reinforced Soil Slope Design

SITE 3000+00 ......................................................................................................... 11 4.2

4.2.1 Site 3000+00 Geotechnical Profile

CONSTRUCTION CONSIDERATIONS ............................................................. 12 4.3 SPECIFICATIONS ............................................................................................... 12 4.4 LIMITATIONS ..................................................................................................... 12 4.5

SECTION FIVE -- REFERENCES

TABLES

TABLE 1:- Summary of Seismic Parameters Corrected for Class C Soil TABLE 2:- Minimum Acceptance Criteria for RSS Design TABLE 3:- Estimated Subsurface Material Properties for RSS Design TABLE 4:- Summary of Proposed RSS Stability Analyses

FIGURES

FIGURE 1 – Vicinity Map FIGURE 2 – Site Map and Boring Locations FIGURE 3 – Geology Map

APPENDICES

APPENDIX A - Field Exploration Program APPENDIX B - Laboratory Test Results APPENDIX C - Photographs APPENDIX D - RSS Analysis

Rim Rock Drive Spot Repairs 2000+00 and 3000+00 1 January 2017

SECTION ONE--INTRODUCTION and BACKGROUND

1.1 INTRODUCTION

This report presents the results of the geotechnical engineering study conducted for two potential spot repair locations associated with the Rim Rock Drive, CO FTNP COLM 10(3), project. The spot repairs are identified as having roadway settlement associated with embankment distress.

The spot repairs are designated as Sites 2000+00 and 3000+00 in the project plans, located on Rim Rock Drive approximately 9.0 and 9.2 miles, respectively, west of the intersection with East Glade Park Road. This intersection is near the beginning of the primary resurfacing portion of the project. The spot repair site locations are shown on Figure 1, Vicinity Map.

The objectives of this investigation are to evaluate and develop recommendations concerning potential repairs at these two sites. In accomplishing these objectives, the scope of work included field exploration, laboratory testing, correlation of available data, and engineering analysis. The field exploration included subsurface exploration and site reconnaissance.

The regional topography slopes to the northwest from an elevation of about 9,700 feet at the Pinon Mesa Highpoint to the Colorado River near Grand Junction, CO at an elevation of about 4,500 feet. The region contains gullies, canyons, cliffs, debris fans, and areas of relatively steep terrain. Rim Rock Drive consists of a winding two-lane roadway with sharp curves and variable widths climbing steeply though an undeveloped and sparsely vegetated arid desert environment.

The existing roadway at the project sites is approximately 20 feet wide and constructed utilizing steep cut and fill shoulder treatments with limited ditch width, consistent with side-cast construction techniques. Existing cut slopes extend to a height of approximately 20 feet and show evidence of continuous raveling and are typically not vegetated. Cut slopes in soil vary between 25 and 50 degrees and cut slopes in weathered bedrock range from 45 to 65 degrees while naturally occurring slopes are typically found between 25 and 35 degrees. Near vertical slopes exist where resistant sandstone bedrock is exposed. Fill slopes are typically less than 35 feet in height and embanked at angles of about 34 degrees (1V:1.5H).

1.2 BACKGROUND

Following rehabilitation of the roadway in the summer of 2007 (PRA COLM 10(1)), these two site locations have a long history of observed distress and repair attempts. A summary of documented events is as follows:

Past visual investigations in October 2007 and June 2008.

• Summary of Site 2000+00 (Formerly Site 16+550) - Observations at this site included moderate pavement distress in the form of subgrade settlement and cracking of the

Rim Rock Drive Spot Repairs 2000+00 and 3000+00 2 January 2017 asphalt pavement. There were two noted dips and half-moon cracking with approximately 1 inch of roadway settlement. The cracking was observed in the gravel roadway shoulder and extends approximately 6 feet into the outboard lane, as measured from the left pavement edge. Observed cracks were hairline to approximately ½ inch in width. There were also noted areas of fill slope distress in the form of erosions rills and gullies from surface water. Surface water crosses the roadway at this location because of adverse drainage conditions along the inboard ditch. No changes in observations were reported between the October 2007 and June 2008 inspections.

• Summary of Site 3000+00 (Formerly Site 16+360) - Distress observed at this site included minor settlement of the subgrade and minor cracking directly above the fill slope. Observed cracks were hairline to approximately ½ inch in width. Surface runoff is crossing the roadway at this location because of adverse drainage conditions along the inboard ditch. Notable erosion rills and gullies along the fill slope from the presence of surface water were observed. The cracks were observed to have propagated between the October 2007 and June 2008 inspections.

The roadway distress was concluded to be attributed to inadequate compaction of subgrade materials during construction or the presence of low strength subgrade materials. The observed erosional features present along the fill slopes may have also contributed to roadway distress by decreasing slope stability and increasing the potential for rotational failure. It was anticipated that the observed distress would continue to deteriorate at a steady rate, given “normal” climatic influence with accelerated deterioration with increased precipitation rates.

Recommendations for Site 2000+00 consisted of a deep patch to 6 feet in the outboard lane and slope armoring. The deep patch was recommended to be constructed with properly compacted unclassified borrow and biaxial geogrid on a 1 foot vertical spacing. It is important to note that geogrid was not encountered during the current subsurface investigation.

Recommendations for Site 3000+00 consisted of ditch reconditioning and sub-excavation to 3 feet in the outboard lane and replacement with properly compacted unclassified borrow.

The sites were repaired in the summer of 2009 in association with the PRA COLM 10(2) project.

Soon after, the pavement preservation project, COLM-PRES-1(10), constructed sub-excavation patches in October and September of 2010 and applied a microsurface to the entire 24 miles of Rim Rock Drive in the spring of 2011. The exact locations of the patches are unknown, but the observed inboard lane patch at Site 2000+00 is suspected to be from this effort. Despite these repairs, a field inspection conducted July 2011 documented signs of further distress.

Recent visual investigations in July 2011.

• Summary of Site 2000+00 (Formerly Site C, Station 520+85 to 521+66) - Noticeable distress included settlement of about 1 to 1.5 inches and cracking in the outboard lane.

The armored slope was reported to show no signs of failure.

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• Summary of Site 3000+00 (Formerly Site B, Station 507+79 to 509+10) - Noted distress included minor settlement measuring less than one inch and few minor cracks in the pavement.

It was recommended that Site 2000+00 be monitored to document future movement until the spring of 2012 and a subsurface investigation be performed to gain a fundamental understanding of the subsurface/water conditions and develop a mitigation plan. In the meantime, installation of a Dip-warning sign was recommended.

It was recommended that Site 3000+00 be reconstructed by removing the existing pavement, recompacting subgrade materials and repaving the site. Drainage improvements were also recommended to direct surface water to nearby culverts.

No further repairs have been documented by CFLHD.

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SECTION TWO--GEOLOGY AND SEISMICITY

2.1 GEOLOGY

Colorado National Monument lies within the Colorado Plateau geologic province. The Colorado Plateau is primarily characterized by sedimentary rocks forming iron-stained plateaus, canyons and rivers and extends throughout most of the land between AZ, NM, CO, UT (four corners region). The province is named after the Colorado River and its main tributaries drain most of the region.

Colorado National Monument is an elongate area on the northeastern flank of the Uncompahgre Plateau, also known as the Uncompahgre Uplift. The landscape is Plateau Province landscape, with warm-hued rocks in horizontal layers and dry streambeds that convert into a raceway during high-intensity summer storms. The geologic section is comprised of mainly Mesozoic Era sedimentary rock overlying highly resistant Precambrian rock in the canyon bottoms. The Cretaceous rock consists of the Mancos Shale, Dakota Sandstone and the Burro Canyon Formation. The Jurassic rock consists of bands of rainbow-hued Morrison Formation, the varicolored mudstones and siltstones of the Summerville Formation, and the Entrada Sandstone.

The canyon rim in most areas of the Monument is the contact between the Summerville Formation and the Entrada Sandstone. The Triassic rock consists of sandstone and conglomerate of the Kayenta Formation, the bold, cliff-forming Wingate Sandstone that was once sand dunes, and the bright red shale of the Chinle Formation. The Precambrian rock consist of darker reddish gray to black gneiss and schist cut by light veins of granite similar to that of the Black Canyon National Monument. The upper surface of the Precambrian rock is an almost perfectly beveled plain that represents about a billion years of erosion. This event is referred to as the Great Unconformity.

Bedrock underlying the spot repair locations belong to the “Upper Jurassic-age (~161.2 to 145.5 million years old) Morrison Formation” according to the “Geologic and Structure map of the Grand Junction quadrangle, Colorado and Utah” compiled by W.B. Cashion in 1973. The Morison Formation in the project area is comprised of the Tidwell Member. The Tidwell Member is approximately 40 meters thick and, as described by Cashion, 1973, primarily contains relatively thinly bedded mudstone with lesser amounts of sandstone and limestone. Quaternary age (11,500 years old to present) slumps and slides are mapped as overlying the Morrison Formation on the slopes above the roadway. Illustrated geologic units are displayed on Figure 3, Geology Map

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2.2 SEISMICITY

There are no known active or potentially active major faults that cross the project area. The closest mapped fault is the Redlands Fault Complex that extends along the northeast boundary of the Monument. The Upper Triassic Kayenta Formation is the youngest recognized offset across this fault complex; however, faults associated with the Uncompahgre Uplift are often considered to have experienced Quaternary movement. Despite the lack of evidence for Quaternary movement, the Redlands fault complex has been classified as a Quaternary fault.

Recommended seismic response parameters for the project site are based on the (AASHTO) LRFD Bridge Design Specifications, 7th Edition, 2014, and represents horizontal peak ground acceleration (PGA) with 7 percent probability of exceedance in 75 years (approximate 1000-year return period). The 1000-year return period uniform hazard spectrum, near the proposed repair site locations of 39.0648 N latitude and -108.7309 W longitude, was obtained in accordance with the AASHTO ground motion maps and corrected for the site class. Based on shallow bedrock and dense soils observed throughout the site, the site is classified as Class C according to 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 1.

TABLE 1:- Summary of Seismic Parameters Corrected for Class C Soil

Horizontal Peak Ground Acceleration, (As) 0.091g Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDs) 0.190g Horizontal Response Spectral Acceleration at Period of 1.0 sec, (SD1) 0.066g

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.20 Site Factor at Short-Period Range of Acceleration Spectrum, (Fa) 1.20 Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.70

Based on the long acceleration coefficient SD1 value of 0.066, the site is assigned to seismic hazard Zone 1 in accordance with Table 3.10.6-1 of AASHTO.

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SECTION THREE—FIELD EXPLORATION

FIELD EXPLORATION and LABORATORY TESTING PROGRAM 3.1

CFL geotechnical personnel conducted a subsurface investigation on December 2 and 3, 2015, to characterize subsurface materials. The subsurface exploration program consisted of drilling a total of 5 borings, 2 borings at Site 2000+00 and 3 borings at Site 3000+00. Boring locations are shown on Figure 2, Site Map and Boring Locations. Subsurface conditions were logged and representative samples were collected and transported to the CFLHD Materials Laboratory in Lakewood, CO, for physical property testing. More detailed descriptions of the work performed, borings logs, and laboratory test data are contained in Appendices A and B, respectively.

Subsurface exploration site photos are contained in Appendix C.

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SECTION FOUR--ANALYSIS AND RECOMMENDATIONS

This section provides observations, analysis, and recommendations of the proposed Sites 2000+00 and 3000+00 roadway rehabilitation. Subsurface characterization and geotechnical profiles were developed for use in the design of embankments. Alternatives for repair of the roadway distress sites include continued maintenance, pavement patching, and embankment replacement. Discussions with respect to construction considerations, specifications, and limitations are also included.

Site 2000+00 4.1

Observations from Site 2000+00 included noticeable distress of about 2 to 3.5 inches of settlement and half-moon cracking across the entire roadway. The armored slope appeared to be bulging near the toe. During the previous construction projects the site was rehabilitated by sub-excavating subsurface materials to a depth of 6 feet in the outboard lanes in the summer of 2009, and a smaller patch to a depth of 3 feet in the inboard lanes in late fall 2010. A microsurface was applied through the pavement preservation program in the spring of 2011. Observations from July 2011 reported noticeable distress included settlement of about 1 to 1.5 inches and cracking in the outboard lane. The evaluation concluded that a subsurface investigation should be performed to gain a fundamental understanding of the subsurface/water conditions and develop a mitigation plan. The current observations confirm continued embankment distress of increased settlement and propagation of half-moon cracking.

The observed settlement has resulted in a significant bump in the outboard lanes that may be a safety hazard to the traveling public and is recommended for repair. Repair alternatives for Site 2000+00 include a pavement patch or embankment replacement. The pavement patch consists of removal of the existing pavement, placing imported aggregate base course to relevel the roadway, and repaving. The embankment replacement consists of removal of the existing embankment to a stable stratum and reconstruction with imported select granular material.

Approximate depths of stable subgrade below the roadway are 25 feet at the embankment toe, 20 feet below the outboard lane, and 15 feet below the inboard lane.

Embankment replacement is recommended for repair of Site 2000+00. Without removal of fine grained moisture sensitive soils in the embankment and improved subsurface drainage, embankment distress is likely to continue. A pavement patch would only be a short term repair requiring recurring maintenance. In addition, a Reinforced Soil Slope (RSS) is recommended for embankment replacement to lessen environmental impacts and improve stability. A discussion of the geotechnical profile, analysis, and recommendations for RSS construction are presented in the following subsections.

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4.1.1 Site 2000+00 Geotechnical Profile

A geotechnical profile was developed for the design of the embankment replacement from the data collected during the subsurface investigation. Borings B-1 and B-2 were drilled in the inboard and outboard lanes, respectively, to determine subsurface conditions. The borings revealed a pavement section and imported granular subexcvations overlying unconsolidated Clayey SAND with gravel (SC) to Lean CLAY (CL) extending to Siltstone bedrock at depths of 13 feet in B-1 and 20 feet in B-2. Boring B-2 encountered harder drilling and auger refusal at a depth of 31 feet at an assumed sandstone layer.

The pavement sections consisted of about 0.4 feet of asphalt pavement and 0.6 feet of aggregate base course in both borings. The granular subexcavation material extended to a depth of 3 feet in B-1 and 6 feet in B-2 and classified as GRAVEL with Sand (GP-GM).

Uncorrected representative N-values from SPT’s ranged from 21 to 24 blows per 12 inches indicating medium dense apparent density. The course gravel had subrounded to rounded clasts and exhibited a dry moisture condition.

The Clayey SAND with gravel (SC) to Lean CLAY (CL) represents the embanked material from local sources and the natural overburden; however, no discernable contact was identified during the subsurface investigation. Fines content of tested samples ranged from 43 to 90 percent and exhibit a plasticity index range from 12 to 19 generally described as low to medium plastic. Uncorrected representative N-values from SPT’s ranged from 4 to 13 blows per 12 inches with an average of Navg = 8 indicating firm to stiff consistency. Soil moisture conditions were generally dry with an appearance generally described as gray to greenish mottled with brown. One dimensional swell potential tests indicate a collapse potential when subjected to wetting under anticipated loads.

Siltstone bedrock was encountered in borings B-1 at 13feet in depth and B-2 at 20 feet in depth. Exposed bedrock in the areas generally consists of thinly to very thinly interbedded green, gray, brown, reddish, and purple layers of siltstone, claystone, mudstone, and sandstones. The Siltstone is described as highly to moderately weathered with a relative hardness of very weak (R1) to medium strong (R3). Exposed sandstone observed in the vicinity of Site 2000+00 is described as moderately to slightly weathered with a relative hardness of medium strong (R3) to strong (R4).

Materials encountered were dry and groundwater was not detected in the borings at the time of drilling in December 2015; however, mottling and some staining indicate possible seasonal groundwater or after high precipitation events. Control of groundwater and surface water flows are imperative to stable embankments in these sensitive soils. The embankment should include a drainage system and groundwater should be anticipated and controlled during construction, especially during periods of high precipitation. Increased groundwater and soil moisture is expected during the wet winter and spring snow melt months.

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4.1.2 Reinforced Soil Slope Design

Reinforced Soil Slopes (RSS) were selected over conventional fill embankments constructed of flatter slope ratios to minimize environmental impacts. For geometric considerations, an embankment slope of 1(V):1.75(H) is recommended for this site. Analyses of the RSS were performed using ReSSA, Version 3.0, and GSTABLE7 with STEDwin Version 2.005.2 (GSTABLE), two dimensional, limit equilibrium computer programs from ADAMA Engineering and Gregory Geotechnical Software, respectively. The Simplified Bishop method of slices was used with isotropic soil parameters. The analysis conducted for RSS design consisted of external, compound, and internal stability in accordance with AASHTO “LRFD Bridge Design Specifications” (7th edition), and FHWA Publication NHI-10-024 and NHI-10-025, Volumes 1 and 2, respectively, entitled “Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes” dated November 2009.

Analysis incorporated rock armament and drainage recommendations contained herein.

Acceptance criteria used for design are shown in Table 2.

TABLE 2:- Minimum Acceptance Criteria for RSS

Stability Mode Minimum Acceptance Criteria

Global Stability

Static FS = 1.3 Seismic FS = 1.1

Sliding FS = 1.3 Internal/Compound

Stability Notes: FS = Factor of Safety

Material properties were estimated for foundation and embankment design based on observations during the field investigation, results of laboratory testing, and known empirical strength characteristics of like materials. In addition, slope stability was conducted to calibrate estimated material values of the overburden. The selected design values for soil unit weight (γ), internal friction angle (φ), and cohesion intercept (c) are shown in Table 3.

TABLE 3:- Estimated Subsurface Material and Fill Properties for RSS Design

Description Total Unit

Weight, γ pcf.

Friction Angle, φ (deg)

Cohesion Intercept, c psf

SC-CL

Embankment Fill 100 22 100

SC-CL

Native Overburden 110 0 425

Siltstone 130 18 800 Select Granular

Backfill (704.08) 130 34 0

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The reinforced and retained portions of the embankment are recommended to be backfilled with select granular backfill in accordance with the requirements in Section 704.08 of the FP-

14. Based on laboratory testing results, on-site, existing fill and native soils will not meet the requirements for select granular backfill and should be imported.

The trial length and spacing were then modeled in RESSA and GSTABLE to determine final embedment length, spacing, and required tensile strength for the geosynthetic reinforcement to satisfy desired minimum factors of safety. Cross sections were evaluated at the maximum embankment height and/or where the slope in front of the fill embankment was the steepest.

A traffic surcharge of 250 psf was modeled in the analyses. The seismic coefficient used in design, representing the 7 percent in 75-year hazard level, was determined from equation C11.6.5-1 in AASHTO assuming 2.0 inches of tolerable lateral displacement. Groundwater was not detected in the borings; therefore, a water table was not included in the analyses. It is also recommended that embankments be benched into existing slopes and contain drainage systems on every bench.

In general, a minimum reinforcement embedment length of 0.6 times the height with two foot spacing satisfies acceptance criteria, for simplicity a minimum embedment length of 20 feet may be used for primary reinforcement. To aid in compaction at the face, a secondary reinforcement with an embedment length of 4 feet should be placed midway between primary reinforcement layers. Primary reinforcement should be Reinforcement Geogrid Type II and secondary reinforcement should be Reinforcement Geotextile Type I in accordance with Section 714.04 of the FP-14. RESSA output for the most critical cross section cases and the ten most critical global stability surfaces determined in GSTABLE are included in Appendix D. A summary of the proposed RSS is presented in Table 4.

Table 4: - Summary of Proposed RSS Stability Analyses

Station Description Reinforcement Stability

Length (ft)

Spacing (ft)

Strength (Tal)

Cross Section Case

Required F.S.

Calculated F.S.

2001+70

RSS Critical Surface for

H=30ft, 1:1.75 Slope

20 2 1500

Existing -- 1.0 Static 1.3 1.8

Seismic (7% in 75) 1.1 1.7

Sliding 1.3 1.8 Compound 1.3 1.6

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Site 3000+00 4.2

Observations from Site 3000+00 included minor distress of about 1 to 1.5 inches of settlement, various locations of half-moon cracking, and lateral and longitudinal cracking in both lanes of the roadway. During the previous construction projects the site was rehabilitated with various pavement and subexcavation patches of various depths in the summer of 2009 and fall of 2010 with a microsurface treatment in spring of 2011. Observations from July 2011 reported minor distress of settlement measuring less than one inch and few minor cracks in the pavement. The current observations confirm continued pavement distress of increased settlement and propagation of cracking.

The observed distress remains minor in agreement with the 2011 assessment; currently it is not considered a safety hazard to the traveling public using vehicles or bicycles. Repair alternatives for Site 3000+00 include continued maintenance though the pavement preservation program, pavement patch, or embankment replacement. Because the distress has remained minor for about 5 years, the maintenance approach is likely the most economical; therefore, the embankment replacement is not recommended even though this approach is the most resilient repair. It is recommended that the area be maintained through the pavement preservation program to achieve the longest lifecycle from previous repairs.

4.2.1 Site 3000+00 Geotechnical Profile

A geotechnical profile was developed from the data collected during the subsurface investigation. Borings B-3 and B-5 were drilled in the outboard lanes and B-4 was drilled in the inboard lane to determine subsurface conditions. The borings revealed a pavement section consisting of about 0.4 feet to 0.5 feet of asphalt pavement and 0.8 feet to 1.4 feet of aggregate base course overlying Lean Clay (CL) extending to Siltstone or Sandstone bedrock at depths of 4 to 13 feet.

The Lean Clay (CL) represents the embanked material from local sources in borings B-4 and B-5 and the natural overburden in Boring B-3. Fines content of tested samples ranged from 62 to 84 percent and exhibit a plasticity index of 15 generally described as medium plastic.

Uncorrected representative N-values from SPT’s in B-3 ranged from 40 to 53 blows per 12 inches indicating very stiff to hard consistency. Uncorrected representative N-values from SPT’s in the embanked material in B-4 and B-5 ranged from 5 to 35 blows per 12 inches with an average of Navg = 15 indicating stiff soil consistency. Soil moisture conditions were generally dry with an appearance generally described as gray to greenish mottled with brown.

One dimensional swell potential tests indicate a collapse potential when subjected to wetting under anticipated loads.

Siltstone bedrock was encountered in boring B-3 at 4 feet in depth. Exposed bedrock in the areas generally consists of thinly to very thinly interbedded green, gray, brown, reddish, and purple layers of siltstone, claystone, mudstone, and sandstone. The siltstone is described as highly to moderately weathered with a relative hardness of very weak (R1) to medium strong

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(R3). Exposed sandstone observed in the vicinity of Site 3000+00 is described as moderately to slightly weathered with a relative hardness of medium strong (R3) to strong (R4).

CONSTRUCTION CONSIDERATIONS 4.3

Roadway excavations are proposed at steep slopes and are anticipated to encounter moisture sensitive fine-grained cohesive soils and weak to strong bedrock with large boulders (3-feet in diameter or larger) requiring carefully planned and uniquely adapted excavation approaches. The contractor will be required to make the final determination on the rippability characteristics of encountered material based on review of site conditions and equipment capabilities.

Depending on the time of year, surface water and groundwater seeps might be present during excavation and construction of cut slopes and embankments. Control of groundwater and surface water flows are imperative to maintaining stable working conditions. Temporary diversion, dewatering and stabilization methods for foundation construction will depend on conditions encountered.

SPECIFICATIONS 4.4

Special provisions were developed to be consistent with geotechnical recommendations stated above and should be 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. SCR sections provided are Section 204 – Excavation and Embankment, Section 207- Earthwork Geosynthetics, Section 261- Reinforced Soil Slopes, Section 704- Soil, Section 705- Rock, and Section 714 – Geosynthetic Material.

LIMITATIONS 4.5

The recommendations in this report are based on the data obtained from exploratory borings, field review, and the 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.

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SECTION FIVE -- REFERENCES

ADAMA Engineering, Inc, Computer Program, ReSSA, Version 3.0, Copyright 2001-2013.

American Association of State Highway and Transportation Officials (AASHTO), 2014, LFRD

BRIDGE DESIGN SPECIFICATIONS, 7th Edition

Cashion, W.B., Geologic and structure map of the Grand Junction quadrangle, Colorado and

Utah: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-735, scale 1:250,000 dated 1973.

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

March.

FHWA, 2009, Design of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, Publication FHWA-NHI-10-024, dated November.

Federal Lands Highway (FLH), 2006, “Technical Guidance Manual (TGM)”, A geotechnical supplement to the FLH Project Development and Design Manual.

Federal Lands Highway (FLH), 2014, “Standard Specifications for Construction of roads and

Bridges on Federal Highway Projects, FP-14.”

GDI Digital Geologic Map of the Colorado National Monument and Adjacent Areas, Colorado

(GRI MapCode CNMO).

Gregory Geotechnical Software & Herald Van Aller, Computer Program, GSTABLE7 with

STEDwin, Version 2.005.2, Copyright 2006.

Oregon Department of Transportation Highway Division. 1987. “Soil and Rock Classification

Manual.”

Pearthree, P.A., compiler, 1995, Quaternary fault and fold database of the United States: U.S.

Geological Survey website, http://earthquakes.usgs.gov/regional/qfaults.

United States Geological Survey (USGS), 2008, “National Seismic Hazard Map”, website:

http://earthquake.usgs.gov/research/hazmap http://earthquakes.usgs.gov/regional/qfaults http://earthquake.usgs.gov/research/hazmap

FIGURES

FIGURE 1 – Vicinity Map FIGURE 2 – Site Map and Boring Locations FIGURE 3 – 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 CO FTNP COLM Rim Rock Drive, on December 2 and 3, 2015. The scope of work for the field exploration program included drilling a total of five borings. Each component of the field exploration program was coordinated and observed by a Geotechnical Engineer from CFLHD. Field exploration location plans, as well as individual boring logs are attached. These logs represent a compilation of field and laboratory data and description of the soil samples 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 the attachments. Representative 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

D.A. Smith Drilling Company, Inc. of Grand Junction, Colorado provided the drilling services for the soil borings. Borings were completed using a SIMCO 9100 truck mounted drill rig.

Borings B-1 and B-2 were drilled near Site 2000+00 to depths ranging from approximately 18 to

31.5 feet below ground surface and borings B-3 through B-5 were drilled near site 3000+00 to depths ranging from approximately 8 to 13 feet below ground surface. Borings were drilled and sampled using 4-inch inside diameter hollow stem augers and were terminated at auger refusal except for in borings B-1 and B-3.

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.

The location and elevation of individual borings were estimated relative to features shown on the plan set. Boring locations are listed on individual boring logs and are show below in Table A-1.

Following drilling activities, field personnel backfilled the borings with cuttings generated during the drilling in accordance with applicable local, state, and federal regulations.

TABLE A-1

FIELD EXPLORATION LOCATIONS

Approx.

Station(1)

Offset From Centerline(1)

Approx.

Elevation (ft)

Exploration Designation

Approx.

Depth (ft) Location

2001+95 5’ LT 6,435 B-1 18 Site 2000+00 2002+23 5’ RT 6,433.5 B-2 31.5

3001+00 5’ RT 6,381 B-3 8

Site 3000+00 3003+25 5’ LT 6,369 B-4 13

3004+10 5’ RT 6,364.5 B-5 12.5

(1)Station and offset estimated from 30% drawings dated April, 2016

A.3 SOIL SAMPLING

Disturbed samples were obtained from the borings in accordance with the Standard Penetration Test (SPT), the procedures of which are detailed in AASHTO T-206. The SPT involves driving a 2-inch outside diameter, 1.375-inch inside diameter split spoon sampler a depth of 18 inches with a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the split-spoon sampler through each of the 6-inch increments was recorded. The SPT resistance, or N-value, is defined as the number of blows required to drive the sampler over the second and third 6-inch increments. The N-value provides a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils. An automatic-trip hammer was used to drive the samplers for this project.

Representative portions of the split-spoon sample obtained in conjunction with the SPT were placed in plastic baggies and transported to the CFLHD Materials Laboratory for testing.

Samples were also obtained using a modified California (MC) barrel sampler. The MC test procedure is similar to the SPT, except a large diameter barrel sampler (2.5-inch O.D., lined with 2-inch-diamter brass sleeves) is used. As a result of the larger diameter, the MC sampler yields slightly higher raw blow counts when compared to SPT N-values for similar soils. However, because the blow counts differ slightly, and because the difference in blow count does not significantly impact our results, the raw MC blow counts over the 6-inch increment were used to define the relative density and consistency of the subsurface materials. MC samples were sealed with plastic end caps and transported to the CFLHD Materials Laboratory for testing.

Relatively undisturbed samples were obtained using a Shelby tube in accordance with the test method procedures of AASHTO T 207. The Shelby tube is a thin wall tube commonly used to obtain samples of cohesive soils for strength and consolidation testing. Commonly used Shelby tubes have a 3.0-inch outside diameter and a 2.875-inch inside diameter, with a length of 36 inches. The Shelby tube sampler is not driven, but slowly pushed with a single, continuous motion using the drill rig’s hydraulic system. Following sampling, Shelby tubes were sealed and carefully transported to the CFLHD Materials Laboratory for extrusion and testing.

A.4 SOIL 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

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C

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A

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H A

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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

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S M

O R

E T

H A

N H

A

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IS

F

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E

R T

H A

N N

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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

Boulders > 12 in. Larger than Basketball

Material

Gravel

6a. Particle Size

Silt or Clay

Sand

Particle Size Approximate Scale

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

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

1. Group Name (Pg. 3) 9.

2. Group Symbol (Pg. 3) 10.

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

4. Color (Pg. 1) 12.

5. Moisture (Pg. 1) 13.

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

7. Plasticity (Pg. 2) 15.

8. Structure (Pg. 2)

Odor (Pg. 2)

Staining (Pg. 2)

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

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

Intact coarse-grained soil

9. Cementation

Nonplastic Thread cannot be rolled at any water content.

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

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

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

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

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

7. Plasticity

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

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

Chemical Hyrodcarbon Hyrodcarbon Iron Oxide

Organic

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

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

12. Dilatancy

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

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

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

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

None Crumbles into powder with mere pressure of handling.

Low Crumbles into powder with some finger pressure.

Medium Breaks into pieces with considerable finger pressure.

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

Very High Cannot be broken between hard surface and thumb.

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

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

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

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

11. Dry Strength

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

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

Fissured Contains shears or separations along planes of weakness.

Slickensided Shear planes appear polished or glossy, sometimes striated.

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

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

Homogeneous Same color and appearance throughout.

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

Desiccated Shrinkage cracks due to dehydration of fine-clayey soil

8. Structure Terms

0.0 - 0.4 ft ASPHALT PAVEMENT

0.4 - 1.0 ft BASE COURSE

1.0 - 3.0 ft GRAVEL WITH SAND : medium dense, brown, dry, coarse gravel to 2.5 feet, subrounded to rounded clasts from 2.5 to 3.0 feet (FILL)

3.0 - 13.0 ft CLAYEY SAND WITH GRAVEL TO LEAN CLAY:

loose to medium dense, firm to stiff, gray to greenish gray mottled with brown, dry, low to medium plasticity, blocky

13.0 - 18.0 ft SILTSTONE: gray, laminated, highly to moderately weathered, dry (MORRISON FORMATION)

18.0 ft Thin sandstone lenses. No auger refusal. No groundwater detected.

BHT at 18.0 ft

GP-GM

SC

CL

11/11/10

4/5/5

2/3/3

11/19/27

50-2"

SPT

MC

MC

SPT

SPT

6434.6

0.50 33%

1.50 100%

1.50 100%

0.15 10%

0.15 75%

U .S

.C .S

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

BORING LOG

Driller: D.A. Smith G ra ph ic L og

Description: (Density, Color, Type, Moisture, Other)

R un

/S am p N

o. Length Recov.

feet

% Rec.

Sheet 1 of 1Date: December 2015Project Name: CO FTNP COLM 10 (3) Rim Rock Drive

Boring Location: STA 2001+95, 5 ft LT

Coordinates:

Drill: SIMCO 9100

Field Logged By: B. Peters

Revisions/Final By: Z. Erdogan

Depth Elevation

(feet)

RQD

SPT

Blows per 6 in

Boring No. B-1

Type of Boring: Auger

Casing Used: HSA

Boring Began: 12/3/15

Ground Elev: 6435.0 ft

Water Depth:

Date:

Time:

Size: 4" I.D.

Completed: 12/3/15

Weather: 18oF Sunny

B O

R

IN

G L

O G

C O

F T

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C O

LM

(3

G

P J

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/2 7/

0.4 - 1.0 ft BASE COURSE

1.0 - 6.0 ft GRAVEL WITH SAND : medium dense, brown, dry, coarse gravel to 2.5 feet, subrounded to rounded clasts from 2.5 to 3.0 feet (FILL)

6.0 - 20.0 ft CLAYEY SAND WITH GRAVEL TO LEAN CLAY:

loose to medium dense, firm to stiff, gray to greenish gray mottled with brown, dry, low to medium plasticity, blocky. Harder drilling at

8.0 feet.

8.0 ft Harder drilling.

15.5 ft Cobbles present.

16.0 ft UCS from pocket penetrometer = 1.5-2.0 tsf and Su from torvane = 400-900 psf. Gradual bedrock contact at 18 to 20 feet.

Sandstone lenses, 4-inch thick at 20.0 feet.

20.0 - 31.5 ft SILTSTONE: gray, laminated, interbedded with some thin sandstone layers, highly to moderately weathered, dry

(MORRISON FORMATION).

24.5 ft Harder drilling.

31.0 ft Harder drilling. Auger refusal. No groundwater detected.

BHT at 31.5 ft

GP-GM

SC

CL

CL

11/12/12

2/2/2

2/5/8

50-2"

50-2"

SPT

SPT

ST

MC

MC

SPT

6433.1 6432.5

6427.5

6413.5

1.50 100%

1.10 73%

3.00 100%

1.28 85%

1.50 100%

0.00 0%

U .S

.C .S

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS HIGHWAY DIVISION

BORING LOG

Driller: D.A. Smith G ra ph ic L og

Description: (Density, Color, Type, Moisture, Other)

R un

/S am p N

o. Length Recov.

feet

% Rec.

Sheet 1 of 1Date: December 2015Project Name: CO FTNP COLM 10 (3) Rim Rock Drive

Boring Location: STA 2002+23, 5 ft RT

Coordinates:

Drill: SIMCO 9100

Field Logged By: B. Peters

Revisions/Final By: Z. Erdogan

Depth Elevation

(feet)

RQD

SPT

Blows per 6 in

Boring No. B-2

Type of Boring: Auger

Casing Used: HSA

Boring Began: 12/2/15

Ground Elev: 6433.5 ft

Water Depth:

Date:

Time:

Size: 4" I.D.

Completed: 12/2/15

Weather: 30oF Sunny

B O

R

IN

G L

O G

C O

F T

N P

C O

LM

(3

G

P J

S W

IF

T

T R

A

IL

.G P

J

/2

0.4 - 1.5 ft BASE COURSE

1.5 - 4.0 ft LEAN CLAY: stiff to very stiff, red brown with gray lenses, dry to moist, medium to high plasticity

4.0 - 8.4 ft SILTSTONE: gray, laminated, moderately to slightly weathered, dry (MORRISON FORMATION)

8.0 ft No auger refusal. No groundwater detected.

BHT at 8.0 ft

CL 15/20/20

11/21/32

45/50-5"

MC

SPT

SPT

6380.6

6379.5

6372.6

1.50 100%

1.50 100%

0.40 100%

U .S

.C .S

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

CENTRAL FEDERAL LANDS…