GR07-15_Ketchum-Challis_FINAL.pdf

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Geotechnical Report No. 07-15

Final Geotechnical Report

KETCHUM-CHALLIS HIGHWAY

Pebble Beach Section

ID PFH 26(3)

May 14, 2015 Sawtooth National Recreation Area

Sawtooth National Forest Custer County, Idaho

Intentionally blank.

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Table of Contents

1. INTRODUCTION

1.1. PROJECT BACKGROUND

1.2. PROJECT LOCATION

1.3. PROJECT SCOPE

1.4. OTHER GEOTECHNICAL INFORMATION

1.5. GENERAL SITE CONDITIONS

1.6. SITE GEOLOGY

1.7. CLIMATE

2. SUBSURFACE INVESTIGATIONS

2.1. KETCHUM‐CHALLIS SUBSURFACE INVESTIGATIONS

2.2. GEOTECHNICAL INVESTIGATION LOCATIONS

2.3. GEOTECHNICAL BORING INVESTIGATION PROCEDURES

2.4. GROUNDWATER OBSERVATIONS

2.5. SLOPE INCLINOMETER CASING

2.6. LABORATORY TEST RESULTS ON GEOTECHNICAL BORING SAMPLES

2.6.a. Index Tests and Soil Classification 2.6.b. Direct Shear Tests

2.7. TEST PIT INVESTIGATIONS, GRAB SAMPLES AND LABORATORY TEST RESULTS

3. EARTHWORK RECOMMENDATIONS

3.1. DISCUSSION

3.1.a. Terrace Sections 3.1.b. Pebble Beach Section

3.2. FILL SLOPE AND SPECIAL ROCK EMBANKMENT RECOMMENDATIONS

3.3. CUT SLOPE RECOMMENDATIONS

3.4. POST‐CONSTRUCTION SLOPE VEGETATION

4. USE OF THIS REPORT

5. REFERENCES

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Appendices

APPENDIX A

Project Photos

APPENDIX B

2002 Surface Geology Maps Geotechnical Investigation Maps

APPENDIX C

AASHTO & Unified Soil Classification Systems Field Classifications for Soil and Rock Rock Descriptive Terms 2002 Boring Logs & Core Photographs 2002 Subgrade Boring Logs and Laboratory Test Reports

APPENDIX D

Unified Soil Classification System Soil Descriptive Terminology Rock Descriptive Terms 2010 Boring Logs & Core Photographs 2010 Laboratory Test Reports

APPENDIX E

Slope Inclinometer Data Reports

APPENDIX F

Test Pit Logs Laboratory Test Results – Test Pit Soil Samples Laboratory Test Results – Bulk Grab Samples

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Figure 1. Project Location Map

BEGIN PROJECT

126+75

MP 206.7

END PROJECT

192+10

MP 207.9

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1. INTRODUCTION

1.1. Project Background

Geotechnical investigations for this project began in the early 2000s. At that time, the project was

2.5 miles long (extending from about milepost 205.4 to 207.9) and the scope included a much wider typical section with high cut slopes, wide rockfall catchment ditches, and fill side retaining walls.

In order to reduce impacts and keep the road template more consistent with neighboring sections of the highway the typical section was narrowed and upslope rockfall mitigation measures were incorporated which eliminated the rockfall catchment ditches and reduced fill side wall heights.

The overall project was divided into the following phases:

Phase 1, ID PFH 26(2), was a scaling project between milepost 205.4 to 206.7 (project Stationing 61+00 to 127+50) that was constructed in fall 2012-spring 2013. [Note that the scaling project was 26(2) because this work was broken out to be constructed ahead of the main project 26-1(1).]

Phase 2, ID PFH 26-1(1), currently under construction, includes construction of MSE retaining walls for roadway widening, guardrail installation, and installation of rock bolts and dowels, steel mesh, and attenuator fencing for rockfall mitigation in the area locally known as “the narrows” from milepost 205.4 to 206.7 (project Stationing 61+00 to 127+50).

Phase 3, this project, ID PFH 26(3), includes reconstructing the section of road starting at the east end of the second phase and extending through the section known as “Pebble Beach” from milepost 206.7 to 207.9 (project Stationing 126+75 to 192+10).

This Geotechnical Report provides recommendations for cuts, fills, and special rock embankments for Phase 3 of the Ketchum-Challis project. Previous geotechnical reports contain subsurface information that may be repeated herein to provide additional information to the current project.

Refer to Section 1.4 for a summary of other geotechnical information available on this project.

Note that the stationing references in this report refer to the Plan-in-Hand (70%) Plan Set dated 2/24/2015.

1.2. Project Location

The project location is about 18 miles east of Stanley, ID, on State Highway 75 (Forest Highway 26), as shown on Figure 1 at the beginning of this report. The project is 1.238 miles long; extending from Station 126+75 to Station 192+10. This section of highway is within the Sawtooth National Recreation Area (NRA) which is part of the Sawtooth National Forest.

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1.3. Project Scope

The main objectives of this project are to mitigate the rockfall hazard (mostly the large round boulders that roll out of the slope at “Pebble Beach”, Station 170+00 to 186+00) and fill side slope erosion. The road will be reconstructed within the project limits listed above and will include grading, base, paving, drainage, culverts, and guardrail.

NOTE: The geotechnical investigations completed as part of this project extended beyond the current project limits; however, recommendations are not provided for areas outside of the project limits listed in Section 1.1. The sections that were removed from this project were completed and geotechnical reports were completed as part of the project development at that time.

1.4. Other Geotechnical Information

The following list is a summary of other geotechnical reports and memorandums completed that include information for this project and a brief summary of the information in the report.

Recommendations contained in this report (GR07-15) supersede all previous recommendations.

Geotechnical Report No. 05-12, Final Geotechnical Report, ID PFH 26-1(1), prepared by

Western Federal Lands Highway Division, June 20, 2012.

GR05-12 provides earthwork and retaining wall recommendations for Phase Two of the Ketchum Challis project through “the narrows”, located directly to the west of this project.

Material sources that were previously investigated by WFLHD are mapped.

Geotechnical Report No. 11-05, Wall Investigation, prepared by Western Federal Lands

Highway Division, March 2005.

GR11-05 provides recommendations for MSE retaining walls along the project. The retaining wall locations and heights have changed since publication of GR11-05, but the subsurface information is still relevant to the current design.

Geotechnical Report No. 2-04, Geotechnical Investigation, prepared by Western Federal

Lands Highway Division, April 2004.

GR2-04 provides recommendations and options for cut slope angles, cut slope stabilization considerations and options, ditch and rockfall catchment designs, roadway surfacing recommendations, and other cut and roadway design considerations. The cut slope design and rockfall mitigation approach have changed significantly since publication of GR2-04, but the subsurface information is still relevant to the current design. Note that the rockfall mitigation recommendations in this report (GR07-15) supersede all previous analysis and design in

GR2-04.

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1.5. General Site Conditions

This section of highway generally parallels the Salmon River which flows east within the project limits. The edge of the river ranges from 100 to 400 feet horizontal distance and 50 to 90 feet vertical distance below the outside edge of pavement. Photographs along the project alignment are contained in Appendix A.

Most of the existing road alignment within the project is supported on short fill embankments perched on level terrain on top of the terraces on the north side of the floodplain (see Photo 1 in Appendix A). The exception is the “Pebble Beach” section of the project from about Station 170+00 to 190+22 where the outside half of the road is supported on relatively steep fill slopes ranging between 1V:1.5H and 1:1 and the inside half of the road is cut slopes in rock and soil (see Photos 2 through 8 in Appendix A). The rock cut slopes are between 1:1 and 2V:1H and the soil cut slopes range between 1V:1.5H and 1:1. The unstable soil cut slope between about Station 176+00 and 179+00 is comprised of alluvial material with cobbles and boulders (further described in Section 1.6) and no vegetation which is why this area was given the name “Pebble Beach”.

1.6. Site Geology

The geologic setting of the project is well described in GR2-04. The paragraphs below were copied from GR2-04 with minor editorial changes to account for the changes to the project limits:

The project is located along a section of the Salmon River canyon that exhibits highly variable topography shaped by the geology and the effects of erosion.

The large flat terraces beyond each end of “The Narrows” were formed during ancient, high volume flows of the Salmon River. They are composed of silt, sand, gravel, and boulders called alluvium. Alluvium has usually been transported over substantial distances and consequently contains sub-rounded to well-rounded particles. Varying thicknesses of these deposits are visible in scattered locations along the walls of the River Canyon. Cut slopes in alluvium follow the angle of repose of sand (typically 32-34 degrees), though locally cemented strata and nested boulders result in steeper slopes in places (e.g. “Pebble Beach”).

The bedrock unit is 81 million year old granitic rock of the Idaho batholith, a huge, solidified intrusion of magma that is the primary rock unit in most of central Idaho. The rock is highly fractured and exhibits pronounced differential erosion due to the variations in weathering and decomposition of the rock mass. Joint systems are present but tend to be inconsistent, and they are masked in many areas along the project due to the dominance of the fracturing, deep weathering, and decomposition.

Observations along the bedrock cuts in the project area disclosed several joint sets. The joint sets are largely discontinuous and often curvilinear, and definable joint systems that control the stability of extensive sections of the rock slopes are generally absent. However, adverse joints that create slope instability and failures are observable in the form of wedge failures and locally adverse planar joints whose strike in places closely parallels the

GR07‐15 Page 4 alignment and whose dip in places directs rock failures toward the road. One favorable joint system visible primarily between stations 91+50 and 94+50 that dips downward into the rock mass left of the alignment was identified along some segments of the existing rock cuts. Although it is likely that this joint set continues back into the rock mass and will not adversely affect the new cut slopes, weathering and close fracturing in other segments may compromise surficial slope stability.

Weathering of the surfaces of the exposed rock cuts ranges from slightly weathered to highly weathered. Seams and pockets of decomposed rock are also present. Seams vary from an inch or less to several feet wide and are present in variable orientations. Pockets of decomposed rock may be large, including up to many tens of feet in width and breadth in existing cut faces. Lateral extent of decomposed seams and pockets into the slope (behind the slope face) has not been determined but can be presumed to vary substantially.

The Surface Geology Maps that were produced in GR02-04 are contained in Appendix B.

1.7. Climate

The project is located in the northern Rocky Mountains and it has warm dry summers and cold snowy winters typical of the region. The closest Western Regional Climate Center (WRCC) weather station is in Stanley, ID (Station ID 108676). Table 1 summarizes data obtained from the WRCC website.

Table 1. Period of Record Monthly Climate Summary for Stanley, ID (108676)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

Average Max.

Temp. (F)

26.5 33 41.7 49.6 59.6 68.1 78.5 77.8 68.5 56.3 38.7 26 52

Average Min.

Temp. (F) -0.9 0.3 8.8 19.5 27.6 33.1 35.6 32.9 27 21 12.2 -0.4 18.1

Average Total

Precip (in.)

1.6 1.31 1.13 1.07 1.24 1.18 0.59 0.61 0.75 0.99 1.52 1.59 13.58

Average Total

Snow Fall (in.)

17 14.1 11.2 3.9 1 0.1 0 0 0.3 1.8 10.2 15.2 74.9

Average Snow

Depth (in.)

17 20 16 7 0 0 0 0 0 0 2 8 6

NOTES:

Period of Record: 6/25/1916 to 2/24/2012.

Percent of possible observations for period of record: Max. Temp.: 83.1% Min. Temp.: 82.7% Precipitation: 79.5% Snowfall: 80.9% Snow Depth: 70%.

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2. SUBSURFACE INVESTIGATIONS

2.1. Ketchum-Challis Subsurface Investigations

Subsurface investigations were performed at two periods during development of this project. They can be generally summarized as the (year) 2002 investigation and the (year) 2010 investigation.

The initial investigation was completed in 2002. Within the current project limits it included geotechnical borings, test pits, and bulk grab samples. A slope inclinometer casing was installed in one of the geotechnical borings within the project limits. The results from the first phase of investigation were reported in GR02-04.

The second subsurface investigation was completed in 2010 and it consisted of additional borings within the project limits. At that time the previously installed slope inclinometer casings that were still accessible were read using the slope inclinometer probe.

As previously stated, some of the subsurface investigation locations discussed above are outside the current project limits so only the boring logs and laboratory test results that fall within the current project limits are included in this report.

2.2. Geotechnical Investigation Locations

During the first geotechnical investigation phase completed between October and December 2002, 12 of the geotechnical borings performed were within the current project limits. Four of the borings were intended to evaluate the road subgrade conditions, two of the borings were on the cut side of the road, and the other six were drilled on the fill side of the existing embankment. The 2002 investigation also included four test pits in exiting cuts and one grab sample within the project limits.

During the second geotechnical investigation phase completed in in September and October 2010, six additional subsurface investigation borings were completed within the project limits in the existing roadway.

The geotechnical investigation locations are summarized in Table 2. Geotechnical investigation location maps are contained in Appendix B.

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Table 2. Summary of Applicable Subsurface Investigation Locations

Boring # Station Offset from Centerline

2002 Subgrade Borings

KCSG-3 127+03 6’ RT

KCSG-4 145+40 5’ RT

KCSG-5 163+10 6’ RT

KCSG-6 184+80 14’RT

2002 Cut Side Test Pits

TP-5 172+20 5’ LT

TP-7 181+35 15’ LT

TP-8 183+00 15’ LT

TP-9 184+50 20’ LT

2002 Fill Side Borings

KC02-1 174+60 38’ RT

KC02-2 175+50 38’ RT

KC02-3 178+10 36’ RT

KC02-4 178+70 23’ RT

KC02-5 180+90 45’ RT

KC02-6* 182+20 32’ RT

2002 Cut Side Borings

KC02-7 178+65 130’ LT

KC02-8 177+30 140’ LT

2010 Fill Side Borings

KC10-25 173+25 20’ RT

KC10-26 174+50 20’ RT

KC10-27 175+40 20’ RT

KC10-28 178+00 20’ RT

KC10-29 179+50 20’ RT

KC10-30 182+15 15’ RT

NOTES:

*Slope inclinometer casing installed in KC02-6. See Slope Inclinometer Data Reports in Appendix E.

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2.3. Geotechnical Boring Investigation Procedures

Procedures used to complete the 2002 drilling investigations are described in GR11-05. The 2002 boring logs and core photographs are attached in Appendix C. The 2010 boring logs and core photographs are attached in Appendix D. The 2010 exploration is described below.

WFLHD contracted with Haztech Drilling, Inc. to complete the 2010 geotechnical borings. The borings were logged in the field by a geotechnical engineer from SK Geotechnical of Missoula, Montana. The samples retrieved from the borings were reviewed by WFLHD Geotechnical Engineer, Brian Collins, and selected samples were submitted to the WFLHD Material Laboratory for routine index testing and direct shear testing.

The 2010 borings were drilled through the existing road. A truck-mounted BK-81 drill was used to drill the geotechnical borings. Eight inch outside-diameter hollow-stem augers were used to advance the borings. Standard Penetration Tests (SPTs) were completed at 2.5 to 5 foot intervals.

The SPT consists of using a 140 pound hammer with a 30 inch drop to drive a 2 inch outside diameter split-barrel sampler 18 inches below the bottom of the bore hole and recording the number of blows for each 6 inch increment of penetration. The last two numbers (for the final 12 inch of penetration) are added together to determine the N-value, also known as the blow count, reported on the Boring Logs. A three inch diameter split-barrel sampler was alternated with the two inch (SPT) sampler in order to obtain a greater volume of material for laboratory testing. Despite this, due to the coarse materials encountered on the project, the split barrel samplers were too small to capture larger particles and therefore laboratory gradation test results of split barrel samples may not be representative of the actual material.

2.4. Groundwater Observations

Groundwater was encountered in only one of the borings (KC02-4) that was completed within the project limits. In KC02-4 groundwater was encountered at a depth of 18 feet (5.5 meters). Bedrock was encountered in KC02-4 at a depth of 20.3 feet (6.2 meters).

The groundwater table is expected to be coincident with the river elevation except where localized, perched water may be present in permeable soil layers overlying bedrock, similar to the observed water level in KC02-4.

The observed water levels and/or conditions indicated on the boring logs are as recorded at the time of the exploration. The water levels and/or conditions may vary considerably, with time, according to the climate, rainfall, and other factors and are otherwise dependent on the duration of and methods used in the exploration program. Groundwater levels fluctuate, and it is interpreted that the groundwater level in areas within the influence of the river will rise and fall with the level of the river or where local stratigraphic or geologic controls are present. Groundwater levels anywhere along the project corridor are likely to rise following periods of heavy precipitation and during spring thaw.

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2.5. Slope Inclinometer Casing

During the 2002 subsurface investigation, slope inclinometer casing was installed in Boring KC02-6. The borings with slope inclinometer casing are denoted with a “*” after the boring number in Table 2.

Slope inclinometer casing consists of either 1.9 or 2.75 inch diameter blue plastic pipe with two orthogonal sets of precision grooves on the inside of the casing. The casing extends down the bore hole well past the zone of expected movement. A slope inclinometer probe is a portable device used to measure ground movement. The probe is 30 inches long and it has two sets of wheels spaced at 24 inches that fit into the precision grooves on the inside of the casing. The probe contains two force-balanced servo-accelerometers that measure the tilt of the probe in two orthogonal planes. Readings are taken from the bottom of the casing up at two-foot intervals in each set of grooves. The initial survey establishes the shape of the casing. Subsequent surveys measure changes in the casing profile caused by ground movement. Displacement profiles are used to determine the magnitude, depth, direction, and rate of ground movement. The probe has an accuracy of ±0.01 inch per reading and ±0.3 inch per 50 readings (Slope Indicator Digital Inclinometer Probe datasheet, http://www.slopeindicator.com/pdf/digitilt-vertical-inclinometer-probe-datasheet.pdf, viewed 5/29/2012).

Two readings of the casings located within the current project limits were taken on 5/8/2003 and 4/23/2004. Two additional readings were completed on 5/11/2010. Data reports for the inclinometer in KC02-6 are contained in Appendix E. The data indicates minor slope movements up to about 0.1 inch between 13-15 feet below the ground surface and up to about 0.25 inch at the ground surface over the 7 year period.

2.6. Laboratory Test Results on Geotechnical Boring Samples

Laboratory testing consisted of routine index testing for classification of soil and direct shear strength testing. The laboratory test reports are attached following the boring logs in Appendix C (2002 subgrade investigation) and Appendix D (2010 investigation). Note that the boring logs and laboratory test reports for the 2002 investigation are in metric units, the standard at that time.

2.6.a. Index Tests and Soil Classification Split-barrel samples of the overburden material were submitted to the WFLHD Materials Laboratory for routine index testing. The following is a list of index test that were completed and the protocols that were followed:

Natural Moisture Content – AASHTO T265 (sample dried at 140° F) Particle Size Analysis to 0.02 mm – AASHTO T88 Liquid Limit, Plastic Limit, and Plasticity Index – AASHTO T89/T90 pH of Soil – AASHTO T289 Apparent Specific Gravity – AASHTO T100 Minimum Resistivity – AASHTO T288 Maximum Density – AASHTO T180

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The results of the index tests were used to classify the samples according the Unified Soil Classification System (USCS) and the American Association of State Highways and Transportation Officials (AASHTO) Classification System. The soil classifications are presented on the laboratory test reports.

It should be noted that due to the limited inside diameters of the 2 inch and 3 inch split barrel samplers used in the drilling investigations and the coarse nature of the on-site soils the laboratory materials classification may not be truly representative of the in situ conditions.

2.6.b. Direct Shear Tests Direct shear tests were performed on 9 split barrel and grab samples obtained from the geotechnical borings. Note that only two of those samples were from locations inside the current project limits;

however, the materials from the other locations are from the same parent geology and therefore the results were included to develop the envelope of shear strength parameters for the project.

Direct shear testing was completed in conformance with AASHTO T236 by the WFLHD Materials Laboratory. The direct shear test is performed on material passing the No. 10 Sieve. Direct Shear Test results are summarized in Table 3. Direct Shear Test Reports are contained in Appendix D.

Table 3. Summary of Laboratory Direct Shear Test Results

Boring No. & Location

Depth (feet)

Lab.

No.

Soil Classification

P10 2 P40 2 P200 2

Peak Angle of Internal

Friction (degrees)

Cohesion (psf) USCS1 AASHTO

KC10-06

66+90, 7.5’ Rt

10- 11.5

10-1743 SW-SM A-1-b 64.5 34.6 11.6 48 170

Grab sample, 76+30, 25’ Lt 0-2 10-1725 SW-SM A-1-a 43.8 20.1 6.1 38 790

KC10-11

82+00, 9.5’ Rt 2.5-6.5 10-1760 SP-SM A-1-a 46.3 27.7 8.6 38 650

Grab sample, 83+00, 15’ Rt 0-2 10-1727 SW-SM A-1-b 59.8 34.6 11.0 39 680

KC10-16

97+67, 4.25’ Rt 2.5-9 10-1774 SP-SM A-1-b 55.3 32.2 11.4 41 640

KC10-17

107+50, 9’ Rt 2.5-9 10-1778 SM A-1-b 56.6 33.4 13.7 39 490

KC10-24

122+50, 9.5’ Rt 2.5-6.5 10-1792 SM A-1-b 65.6 32.5 8.4 42 510

Grab sample, 176+50, 20’ Lt 3 0-2 10-1726 GP A-1-a 37.6 15.1 4.1 44 770

KC10-30

182+10, 4.5’ Rt 3 2.5-6.5 10-1812 SM A-1-b 69.3 40.1 15.7 36 740

Minimum 37.6 15.1 4.1 36 170

Average 55.4 30.0 10.7 41 600

Maximum 69.3 40.1 15.7 48 790

NOTES:

1All samples tested as ‘non-plastic’ according to AASHTO T89/90.

2P10 indicates the percent of material by weight passing the U.S. No. 10 Sieve, P40 indicates the percent of material by weight passing the U.S. No. 40 Sieve, P200 indicates the percent of material by weight passing the U.S. No. 200 Sieve.

3KC10-30 and the grab sample at Station 176+30 are inside the current project limits.

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2.7. Test Pit Investigations, Grab Samples and Laboratory Test Results

Nine backhoe test pits were completed as part of the 2002 investigation. Four of the 9 test pits, TP-5, TP-7, TP-8 and TP-9, are within the current project limits. In addition, two bulk samples were taken from “Pebble Beach”, one during the 2002 investigation and another during the 2010 investigation. The test pit and grab sample locations are shown on the Geotechnical Investigation Maps in Appendix B. A copy of the test pit logs is contained in Appendix F.

Selected samples from the test pits and bulk grab samples were submitted to the WFLHD Materials Laboratory for routine index tests.

The following is a list of index test that were completed and the protocols that were followed:

Natural Moisture Content – AASHTO T265 (sample dried at 140° F) Particle Size Analysis to 0.02 mm – AASHTO T88 Liquid Limit, Plastic Limit, and Plasticity Index – AASHTO T89/T90 pH of Soil – AASHTO T289 Apparent Specific Gravity – AASHTO T100 R-Value – AASHTO T190

Note that the test reports for the 2002 test pit and bulk samples are in metric units, the standard at that time.

The results of the index tests were used to classify the samples according to the Unified Soil Classification System (USCS) and the American Association of State Highways and Transportation Officials (AASHTO) Classification System. The soil classifications are presented on the laboratory test reports. The laboratory test reports are contained in Appendix F following the test pit logs.

It should be noted that laboratory particle size analyses were completed on the minus 3 inch (75 millimeters) or 4 inch (100 millimeters) material and due to the coarse nature of the on-site soils the laboratory materials classification may not be truly representative of the in situ conditions.

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3. EARTHWORK RECOMMENDATIONS

3.1. Discussion

The existing highway in the current project limits is between 22 to 23 feet wide (2 11 to 11.5 foot lanes without any paved shoulders). The new typical section will be 26 feet wide (two 11 foot lanes with 2 foot wide paved shoulders).

The project can be divided into two sections based on the proposed earthwork: 1) the Terrace sections, and 2) the Pebble Beach section.

3.1.a. Terrace Sections In the terrace sections (Station 126+75 to 170+00 and 186+00 to 192+10) the existing road is supported on short fill embankments perched on level terrain on the terraces on the north side of the floodplain. The proposed alignment across the terrace sections generally follows existing with a slight grade raise between 1 to 3 feet above existing.

Due to the generally level terrain across the terrace sections the earthwork will consist of cut and fill slopes with heights less than 10 feet vertical.

3.1.b. Pebble Beach Section In the Pebble Beach section (Station 170+00 to 186+00) the existing road is interpreted to be supported on partial bench construction, where material was excavated on the cut side of the road and cast onto the fill side. The proposed alignment through the Pebble Beach section shifts centerline about 15 feet further into the cut and raises grade 1 to 3 feet above existing.

One of the main objectives of this project is to improve the rockfall and erosion conditions through the Pebble Beach section. The soil cut slope at Pebble Beach contains subrounded to rounded cobbles and boulders in a matrix of sand and gravel. As the soil erodes around the cobbles and boulders they roll down the slope and into the Jersey barrier that was placed at the toe of the slope to keep the rolling rocks off the road. The existing road ditch widths are less than 5 feet on the cut side and they provide little rockfall catchment. Gravel shoulders less than 2 feet wide on the fill side before the steep slope drops to the river’s edge. Idaho DOT Maintenance has repaired several locations where erosion of the fill embankment threatens to undermine the road. Therefore the purpose of this project is to improve the conditions through the Pebble Beach section by mitigating the rockfall problem on the cut side of the road and addressing erosion on the fill side of the road.

The main issue with both the soil cut and fill slopes through the Pebble Beach section is that the slopes are marginally stable at inclinations between 1V:1.5H and 1:1 based on slope stability analysis and site observations. The slopes are interpreted to be inclined near the angle of repose of the material. At these inclinations the soils are highly susceptible to erosion by wind, rain, and runoff. Consequently, the slopes do not allow vegetation to become established and are susceptible to shallow slope creep when saturated. Throughout the project, non-bedrock slopes at inclinations of 1V:1.5 or flatter were relatively well vegetated and did not exhibit any signs of instability.

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Several options were considered to improve the conditions through Pebble Beach. The WFLHD Project Manager, Cross-Functional Design team, and partner agencies (Idaho DOT and Sawtooth NRA) selected to shift the road into the hillside, moving it away from the eroding fill slopes, and lay the cut slope back to a stable inclination that will be much less susceptible to erosion. This option was selected because it achieved the objectives of the project at the lowest cost and required the least amount of right-of-way acquisition.

This project will be a waste job due to the size of the cut proposed at Pebble Beach. Estimated quantities of excavation and embankment are shown in the project plans.

3.2. Fill Slope and Special Rock Embankment Recommendations

It is anticipated that excavated material from the cuts will be used as embankment and will meet the requirements in Subsection 704.06 of the FP-14 for Unclassified Borrow. Fill slope embankments constructed of Unclassified Borrow can be sloped as steep as 1V:1.5H. However, flatter fill slopes will improve vegetation growth and excess material from the excavation will have to be hauled off the project; therefore, flatter fill slopes should be used wherever possible.

A mechanically placed special rock embankment is recommended on the right side from Station 135+00 to 140+50 where a sliver fill is proposed at slope inclinations up to 1V:1.5H in order to have the proposed fill slope catch the top of the existing 1V:1.5H fill slope. A mechanically placed special rock embankment is also recommended for the turnout on the right side from Station 155+25 to 156+50 where a fill slope as steep as 1V:1.25H is required in order to minimize impacts to the adjacent property owner.

Construct the mechanically placed special rock embankments (SRE) as follows:

Construct SRE according to Section 252 in FP-14 Maximum SRE slope face inclination is 1V:1.25H Embed the toe of the SRE 2 feet vertical distance below the toe of fill catch point and slope the excavation at 1:1 leaving a berm in front of the SRE Minimum horizontal width of the SRE is 8 feet Place a geotextile filter, class 1, type C, along the bottom, back, and top of the SRE

3.3. Cut Slope Recommendations

Cuts along this project will be made in soil and bedrock. A maximum cut slope inclination of 1V:1.5H is recommended in both soil and bedrock. Flatter soil slopes will improve vegetation growth and therefore 1V:2H cut slopes in soil are recommended where possible.

Bedrock will be encountered in some areas of the large cut proposed between Station 176+50 and 187+00. Bedrock is exposed in the lower portion of existing cut slopes from Station 173+00 to 176+00 and from Station 179+00 to 180+00 and it is interpreted that the contact elevation between overburden soil and bedrock will be variable through the entire cut. (See photos in Appendix A.)

Thus bedrock is likely to be encountered outside of these limits. If blasting is required to remove the bedrock pre-split is not needed since the cut slope is flatter than 1:1.

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3.4. Post-Construction Slope Vegetation

The newly exposed cut and fill slopes will be susceptible to erosion if left exposed for long periods.

An aggressive program to establish new vegetation is recommended.

A Type 5A turf reinforcement mat (TRM) meeting the requirements of Subsection 713.18 in the FP-14 is recommended for soil slopes steeper than 1V:2H and more than 10 feet vertical distance in height. A Type 4 temporary rolled erosion control product (RECP) meeting the requirements of Subsection 713.17(k) in the FP-14 can be considered in place of the TRM if the post-construction vegetation program will be aggressive enough to ensure that vegetation is established within the typical functional longevity period of 36 months for a Type 4 RECP.

GR07‐15 Page 14

4. USE OF THIS REPORT

This report was prepared to provide final geotechnical recommendations for the Pebble Beach section of the Ketchum-Challis project, ID PFH 26(3). Professional judgments and recommendations are presented in this report. They are based partly on evaluation of the technical information gathered, partly on historical reports, and partly on the Geotechnical Team’s general experience with subsurface conditions in the area. It should be noted the borings might not represent potentially unfavorable subsurface conditions between borings. The observed water levels and/or conditions indicated on the boring logs are as recorded at the time of the exploration.

The water levels and/or conditions may vary considerably, with time, according to the climate, rainfall, and other factors and are otherwise dependent on the duration of, and methods used in, and interpretations made from the exploration program.

If, during construction, soil conditions are encountered that vary from those discussed in this report or historical reports, or if design loads, project stationing, and/or configurations change, the Geotechnical Team should be notified immediately in order that it may evaluate effects, if any, on the recommendations contained in this report. The recommendations presented in this report are applicable only to this specific site. These data are not to be used for other purposes.

Questions regarding this report should be addressed to Brian Collins, WFLHD Geotechnical Engineer, at (360) 619-7657, or brian.collins@dot.gov.

GR07‐15 Page 15

5. REFERENCES

Geotechnical Report No. 2-04, Geotechnical Investigation, prepared by Western Federal Lands Highway Division, April 2004.

Geotechnical Report No. 11-05, Wall Investigation, prepared by Western Federal Lands Highway Division, March 2005.

Geotechnical Report No. 05-12, Final Geotechnical Report, prepared by Western Federal Lands Highway Division, June 20, 2012.

APPENDIX A

Project Photos

Photo 1. Station 156+00, looking ahead/east (Sep 2013).

Photo 2. Station 171+00, looking ahead/east (Sep 2013).

Appendix A

A-1

Photo 3. Station 172+00, looking ahead/east at slope below road (Sep 2013).

“Pebble Beach” is visible on the left behind the jersey barrier.

Photo 4. Station 175+00, looking back/west at rock cut (Sep 2013).

A-2

Photo 5. Station 176+00 looking left/north at “Pebble Beach” (Sep 2013).

Photo 6. Station 179+00 looking back/west at “Pebble Beach” (May 2010).

A-3

Photo 7. Station 183+00 looking back/west (May 2010).

Note blue slope inclinometer casings from KC02-6 projecting vertically out of the ground in center of photo just to the left of the pipe outlet.

Photo 8. Station 187+00 looking back/west (Sep 2013).

A-4

APPENDIX B

2002 Surface Geology Maps Geotechnical Investigation Maps

Appendix B

B-1

B-2

B-3

58505850

5855585558555855

586058605860

586558655865

587058705870

755875

5885 588

55890

578057805780

5780 5780

57855785

5790579

05790

57955795

5795579 55795

58005800

580558

580558055805

58105810

5830 5835

583558355835

58405840

58405840

58455845

5845584558455845

5850585058505850

58555855585558555855

586058605860586058605860

5865586558655865

58655865

5865586558655865 58655865

58705870

58755875

75587

5880 5880

58805880

126+75

KETCHUM-CHALLIS HIGHWAY

ID PFH 26(3)

El=5857.686

E=1466054.920

N=943805.902

BH

KCSG-3

KCSG-4

STATE PROJECT

NUMBER

SHEET

P

M

M a y

U

S S u r ft

D c m y fi le s p w p r o d u c ti o n d if ta .d g n

C h e c k e d b y

D e s ig n e d b y

PEBBLE BEACH SECTION

KETCHUM - CHALLIS

INVESTIGATION MAP

GEOTECHNICAL

LEGEND:

Test Pit

Grab Sample

Bore Hole

TP

GRAB

T

.0

0 P

C

.7

5 P

T

.7

5 P

T

.7

5 P

C

.6

BEGIN PROJECT

N

N

B-4

55765

57755775

57855785

58155815

58205820

655865

58705870

5875587

5890 58

5910 59

305830

58355835

58405840

58405840

585058

58505850

58555855

05860

58705870

58755875

5885 5

5885 5890

N

SHEET

M a y

U

S S u r ft m y fi le s p w p r o d u c ti o n d if tb .d g

C h e c k e d b y

D e s ig n e d b y

PEBBLE BEACH SECTION

KETCHUM - CHALLIS

INVESTIGATION MAP

GEOTECHNICAL

KCSG-5

BH

TP

TP-5

BH

KC10-25

BH

KC10-26

BH

KC10-27

BH

KC10-28

BH

KC10-29

BH

KC02-1

BH

KC02-2

BH

KC02-3

BH

KC02-4

KC02-8

BH

KC02-7

BH

GRAB

GRABG-1 G-2

P C

C

.8

P T

.3

P C

.1

C/E

C/E

C

E

0 P

C C

.1

B-5

58155815

58205820

58555855

58555855

58605860

5890 5890

5890 5890

5895 5895

0 5900

55910

5910N

END PROJECT

192+10.00

KETCHUM-CHALLIS HIGHWAY

ID PFH 26(3)

El= 5,820.052

E= 1,472,146.565

N= 943,403.572

BH BH

KC10-30KC02-5

TP

TP-7

BH

KC02-6

TP-8

TP

TP

TP-9

KCSG-6

SHEET

M a y

U

S S u r ft m y fi le s p w p r o d u c ti o n d if tc .d g

C h e c k e d b y

D e s ig n e d b y

PEBBLE BEACH SECTION

KETCHUM - CHALLIS

INVESTIGATION MAP

GEOTECHNICAL

P T

.3

P C

.5

P T

.2

C/E

C/E

C/E

C/E

B-6

APPENDIX C

AASHTO & Unified Soil Classification Systems Field Classifications for Soil and Rock

Rock Descriptive Terms 2002 Boring Logs & Core Photographs

2002 Subgrade Boring Logs and Laboratory Test Reports

Appendix C

C-1

C-2

C-3

C-4

C-5

C-6

C-7

C-8

C-9

C-10

C-11

C-12

C-13

C-14

C-15

C-16

C-17

C-18

C-19

C-20

C-21

C-22

C-23

C-24

C-25

C-26

C-27

APPENDIX D

Unified Soil Classification System Soil Descriptive Terminology

Rock Descriptive Terms 2010 Boring Logs & Core Photographs

2010 Laboratory Test Reports

Appendix D

D-1

S O

IL

D

E S

C R

IP

T

IV

E

T E

R M

IN

O

L O

G Y

C

N S

IS

T

E N

C Y

O F

C O

H E

S

IV

E S

O

IL

T N

-V al u e

(b lo w s/ ft

C on si st en cy

F ie ld

I d en ti fi ca ti on

V er y

S of t E as il y pe ne tr at ed s ev er al in ch es b y fi rs t

S of t

E as il y pe ne tr at ed s ev er al in ch es b y th um b

F ir m od er at e ef fo rt r eq ui re d to p en et ra te se ve ra l i nc he s by th um b ff

R ea di ly in de nt ed b y th um b bu t p en et ra te d on ly w it h gr ea t e ff or t

V er y S ff ea di ly in de nt ed b y th um bn ai l

H ar d

In de nt ed w it h di ff ic ul ty b y th um bn ai l

E

L A

T

IV

E D

E N

S

IT

Y

F

C

H E

S

IO

N L

E S

S S

O

IL

T N

-V al u e

(b lo w s/ ft

R el at iv e D en si ty

V er y

L oo

L oo

M ed iu m

D

D

V er y

D

A

R T

IC

L

E S

IZ

E

T er ie ve

S iz e

B ou ld

2”

0m m

C ob bl e

3”

2”

(7

5m m m m

G ra ve l – c oa rs e

¾

3”

(1 9m m

5m m

G ra ve l – f in e #4

¾

(4 .7

5m m

9m m

S an d co ar

#1

#4

(2 .0

0m m

.7 5m m

S an d m ed iu

#4

#1

(0 .4 m m

.0

0m m

S an d fi ne

#2

(0 .0 m m

.4 m m

S il t & C la y

0.

5m m

M O

IS

T

U R

E C

O N

T E

T ry us ty

, d ry to th e to uc h

M oi st am p, b ut n o vi si bl e fr ee w at

W et

V is ib le f re e w at er , s at ur at ed

, o ve r op ti um

D-2

ROCK DESCRIPTIVE TERMS

ROCK WEATHERING

Field Identification Term Crystals are bright. Discontinuities may show some minor surface staining.

No discoloration in rock fabric.

Fresh

Rock mass is generally fresh. Discontinuities are stained and may contain clay. Some discoloration in rock fabric.

Slightly Weathered

Significant portions of rock show discoloration and weathering effects.

Crystals are dull and show visible chemical alteration. Discontinuities are stained and may contain secondary mineral deposits.

Moderately Weathered

Rock can be excavated with geologist’s pick. All discontinuities exhibit secondary mineralization. Complete discoloration of rock fabric. Surface of core is friable and usually pitted due to washing out of highly altered minerals by drilling water.

Highly Weathered

Rock mass is completely decomposed. Original rock “fabric” may be evident. May be reduced to soil with hand pressure.

Decomposed

DISCONTINUITY SPACING ROCK QUALITY DESIGNATION (RQD)

Spacing (in) Spacing Term RQD % Designation < 2.5 Very Close 0 - 25 Very poor

2.5 – 8 Close 25 - 50 Poor 8 – 24 Moderately close 50 - 75 Fair 24 – 80 Wide 75 - 90 Good

> 80 Very Wide 90 - 100 Excellent

(RQD is the percent of a core run with intact lengths greater than 4 inches excluding breaks caused by drilling.)

INTACT ROCK HARDNESS

Field Identification UCS (psi) Hardness Term Indented by thumbnail. 40 - 150 Extremely Weak (R0) Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife.

150 - 730 Very Weak (R1)

Can be peeled by a pocket knife with difficulty, shallow indentations made by firm blow with geological hammer.

730 – 3,600 Weak (R2)

Cannot be scraped or peeled with a pocket knife, specimen can be fractured with a single blow of geological hammer.

3,600 – 7,300 Medium Strong (R3)

Specimen requires more than one blow of geological hammer to fracture it.

7,300 – 15,000 Strong (R4)

Specimen requires many blows of geological hammer to fracture it.

15,000 – 36,000 Very Strong (R5)

Specimen can only be chipped with geological hammer. > 36,000 Extremely Strong (R6)

(UCS – Unconfined Compressive Strength)

D-3

Rec. = 47%

RQD = 0%

Rec. = 50%

RQD = 0%

Rec. = 90%

RQD = 0%

Rec. = 100%

RQD = 13%

8-8-8 (10" = 56%)

4-6-11 (10" = 56%)

8-16-13 (5" = 28%)

5 1/4" ASPHALT CONCRETE

5 1/2" base, base/subgrade contact unclear brown, gravelly, silty SAND (SM), fine- to coarse-grained, moist, medium dense brown, bouldery, cobbly, sandy GRAVEL (GP), fine- to coarse-grained, nonplastic, moist, medium dense

Switch to HQ coring at 9 1/2'.

gray, moderately weathered, highly fractured, moderately open to open spacing, weak (R2), GRANITE, longitudinal fracturing

END OF BORING

Groundwater not observed.

0.4 0.9

7.0

20.0

29.5

RECOVERY (%)

0 50

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 44° 15' 2.34" (44.25065043°)

LONGITUDE (DEGREES): W 114° 39' 1.36" (114.6503789°)

ELEVATION: 5815.812'

D E

P T

H ft

E

LE

V ft)

Sheet 1 of 1

BORING LOG (US Customary Units)

S A

M P

LE

DRILLING METHODS:

DATE FINISHED:

TOTAL DEPTH: 29.5' (BOTTOM ELEV: 5786.312')

RQD (%)

AFTER DRILLING

Solid Stem Auger

Rock / Soil Core

3" OD Split Spoon (D&M)

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

4.25" ID auger to 9.5' then HQ coring to 29.5'

173+25, 20' RT

0.0

4.0

8.0

12.0

16.0

20.0

24.0

28.0

32.0

36.0

40.0

5815.8

5811.8

5807.8

5803.8

5799.8

5795.8

5791.8

5787.8

5783.8

5779.8

5775.8

Boring locations determined using recreational grade GPS unit.NOTES:

BORING KC10-25

COMPANY:

F ile

: I :\T

E C

H

S E

R V

IC

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S \G

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C H

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IN

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\P R

O

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C T

S \K

E T

C H

U M

-C H

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LL

IS

.G

J

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I:

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E C

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E S

\G E

O T

E C

H N

IC

A

L S

E R

V

IC

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\G

IN

T \L

IB

R

A R

Y \F

H W

A L

IB

R

A R

Y .G

LB

ri nt ed

: 5 /1

3/

2" OD Split Spoon (SPT)

Haztech LOGGER: SK Geotechnical

DATE STARTED:

0.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

Automatic

WATER CONTENT (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

DRILL: BK 81

D E

P T

H ft

9/30/2010

S A

M P

LE

R

9/30/2010

STATION, OFFSET:

D-4

BORING KC10-25

PHOTOGRAPH LOG

F ile

I:

\T E

C H

_S E

R V

IC

E

S \G

E O

T E

C H

N

IC

A L

S E

R V

IC

E

S \G

IN

T

\P R

O

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C T

S \K

E T

C H

U M

-C H

A

LL

IS

0.

G ib

I:

\T E

C H

_S E

R V

IC

E

S \G

E O

T E

C H

N

IC

A L

S E

R V

IC

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S \G

IN

T

\L

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R A

R Y

\F H

W A

LI

B

R A

R Y rin te d:

/1 3/

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

STATION, OFFSET: 173+25 , 20' RT

SURFACE ELEVATION: 5815.812ft

Sheet 1 of 1

Figure KC10-25.2 Depth: 24ft [Elev 5791.812ft] to 29.5ft [Elev 5786.312ft]

Figure KC10-25.1 Depth: 9.5ft [Elev 5806.312ft] to 24ft [Elev 5791.812ft]

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

D-5

Rec. = 100%

RQD = 83%

Rec. = 100%

RQD = 63%

Rec. = 98%

RQD = 67%

50/1" (0" = 0%)

7-10-8 (6" = 33%)

10-30-40/2½" (12" = 83%)

5" ASPHALT CONCRETE

3" base, base/subgrade contact unclear brownish-gray, bouldery, cobbly, silty, sandy GRAVEL (SP-SM), fine- to coarse-grained, nonplastic, medium dense to very dense

Switch to HQ coring at 9 1/2'.

gray, slightly weathered, moderately fractured, moderately open spacing, moderately strong (R3), GRANITE gray, moderately weathered, highly fractured to moderately fractured, moderately open spacing, weak to moderately strong (R2-R3), GRANITE, iron staining in fractures

END OF BORING

Groundwater not observed.

0.4 0.7

9.5

14.5

24.5

RECOVERY (%)

0 50

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 44° 15' 3.19" (44.25088591°)

LONGITUDE (DEGREES): W 114° 39' 0.12" (114.6500333°)

ELEVATION: 5813.713'

D E

P T

H ft

E

LE

V ft)

Sheet 1 of 1

BORING LOG (US Customary Units)

S A

M P

LE

DRILLING METHODS:

DATE FINISHED:

TOTAL DEPTH: 24.5' (BOTTOM ELEV: 5789.213')

LIQUID LIMIT

RQD (%)

AFTER DRILLING

Solid Stem Auger

Rock / Soil Core

3" OD Split Spoon (D&M)

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

4.25" ID auger to 9.5' then HQ coring to 2431.5'

174+50, 20' RT

0.0

4.0

8.0

12.0

16.0

20.0

24.0

28.0

32.0

36.0

40.0

5813.7

5809.7

5805.7

5801.7

5797.7

5793.7

5789.7

5785.7

5781.7

5777.7

5773.7

Boring locations determined using recreational grade GPS unit.NOTES:

BORING KC10-26

COMPANY:

F ile

: I :\T

E C

H

S E

R V

IC

E

S \G

E O

T E

C H

N

IC

A L

S E

R V

IC

E

S \G

IN

T

\P R

O

JE

C T

S \K

E T

C H

U M

-C H

A

LL

IS

.G

I:

\T

E C

H _S

E R

V

IC

E S

\G E

O T

E C

H N

IC

A

L S

E R

V

IC

E S

\G

IN

T \L

IB

R

A R

Y \F

H W

A L

IB

R

A R

Y nt ed

: 5 /1

3/

2" OD Split Spoon (SPT)

Haztech LOGGER: SK Geotechnical

DATE STARTED:

0.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

Automatic

WATER CONTENT (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

DRILL: BK 81

D E

P T

H ft

9/28/2010

S A

M P

LE

R

9/28/2010

STATION, OFFSET:

PLASTIC LIMIT

D-6

BORING KC10-26

F ile

I:

\T E

C H

_S E

R V

IC

E

S \G

E O

T E

C H

N

IC

A L

S E

R V

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\P R

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-C H

A

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IS

0.

G

I:

\T E

C H

_S E

R V

IC

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S \G

E O

T E

C H

N

IC

A L

S E

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IC

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S \G

IN

T

\L

IB

R A

R Y

\F H

W A

LI

B

R A

R Y te d:

/1 3/

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

STATION, OFFSET: 174+50 , 20' RT

SURFACE ELEVATION: 5813.713ft

Sheet 1 of 1

Figure KC10-26.2 Depth: 17.5ft [Elev 5796.213ft] to 24.5ft [Elev 5789.213ft]

Figure KC10-26.1 Depth: 9.5ft [Elev 5804.213ft] to 17.5ft [Elev 5796.213ft]

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

D-7

Rec. = 86%

RQD = 19%

Rec. = 70%

RQD = 70%

Rec. = 100%

RQD = 16%

Rec. = 94%

RQD = 42%

6-4-4 (7" = 39%)

4-4-4 (10" = 56%)

4-7-4 (4" = 22%)

9-40-44 (5" = 28%)

55/6" (4" = 67%)

7 1/2" ASPHALT CONCRETE

8" base, base/subgrade contact unclear grayish brown, silty, sandy GRAVEL (SW-SM), fine- to medium-grained, nonplastic, damp, loose gray, bouldery, cobbly, silty, gravelly SAND (SP), medium-to coarse-grained, nonplastic, damp, very dense

Switch to HQ coring at 14 1/2'.

gray, moderately weathered, highly fractured, open spacing, weak to moderately strong (R2-R3), GRANITE, some iron staining in fractures

-becoming moderately fractured, moderately strong (R3)

END OF BORING

Groundwater not observed.

0.6 1.3

9.0

14.5

29.5

RECOVERY (%)

0 50

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 44° 15' 3.73" (44.25103473°)

LONGITUDE (DEGREES): W 114° 38' 59.17" (114.6497703°)

ELEVATION: 5813.124'

D E

P T

H ft

E

LE

V ft)

Sheet 1 of 1

BORING LOG (US Customary Units)

S A

M P

LE

DRILLING METHODS:

DATE FINISHED:

TOTAL DEPTH: 29.5' (BOTTOM ELEV: 5783.624')

LIQUID LIMIT

RQD (%)

AFTER DRILLING

Solid Stem Auger

Rock / Soil Core

3" OD Split Spoon (D&M)

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

4.25" ID auger to 14.5' then HQ coring to 29.5'

175+40, 20' RT

0.0

4.0

8.0

12.0

16.0

20.0

24.0

28.0

32.0

36.0

40.0

5813.1

5809.1

5805.1

5801.1

5797.1

5793.1

5789.1

5785.1

5781.1

5777.1

5773.1

Boring locations determined using recreational grade GPS unit.NOTES:

BORING KC10-27

COMPANY:

F ile

: I :\T

E C

H

S E

R V

IC

E

S \G

E O

T E

C H

N

IC

A L

S E

R V

IC

E

S \G

IN

T

\P R

O

JE

C T

S \K

E T

C H

U M

-C H

A

LL

IS

.G

I:

\T

E C

H _S

E R

V

IC

E S

\G E

O T

E C

H N

IC

A

L S

E R

V

IC

E S

\G

IN

T \L

IB

R

A R

Y \F

H W

A L

IB

R

A R

Y nt ed

: 5 /1

3/

2" OD Split Spoon (SPT)

Haztech LOGGER: SK Geotechnical

DATE STARTED:

0.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

Automatic

WATER CONTENT (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

DRILL: BK 81

D E

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H ft

9/29/2010

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9/29/2010

STATION, OFFSET:

PLASTIC LIMIT

D-8

BORING KC10-27

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PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

STATION, OFFSET: 175+40 , 20' RT

SURFACE ELEVATION: 5813.124ft

Sheet 1 of 1

Figure KC10-27.2 Depth: 22.5ft [Elev 5790.624ft] to 29.5ft [Elev 5783.624ft]

Figure KC10-27.1 Depth: 14.5ft [Elev 5798.624ft] to 22.5ft [Elev 5790.624ft]

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

D-9

2-1-2 (2" = 11%)

1-2-1 (2" = 11%)

1-2-1 (5" = 28%)

11-11-16 (6" = 33%)

7-6-4

23-31-33 (12" = 67%)

9-22-23 (8" = 44%)

50/4" (5" = 139%)

50/4" (4" = 111%)

7 1/4" ASPHALT CONCRETE

3" base, base/subgrade contact unclear brown, gravelly, silty SAND (SM), fine- to medium-grained, nonplastic, damp, very loose

-color change to dark brown, trace roots grayish brown, bouldery, cobbly, gravelly, silty SAND (SP-SM), coarse-grained, nonplastic, wet, loose

-dense to very dense below 15'

END OF BORING

Water down 12' with 12 1/2' of hollow-stem auger in the ground.

Water not observed to dry cave-in depth of 8 1/2' immediately after withdrawal of auger.

0.6 0.9

11.0

30.3

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 44° 15' 5.03" (44.2513966°)

LONGITUDE (DEGREES): W 114° 38' 56.08" (114.6489121°)

ELEVATION: 5814.022'

D E

P T

H ft

E

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V ft)

Sheet 1 of 1

BORING LOG (US Customary Units)

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DRILLING METHODS:

DATE FINISHED:

TOTAL DEPTH: 30.3' (BOTTOM ELEV: 5783.722')

AFTER DRILLING

Solid Stem Auger

3" OD Split Spoon (D&M)

2" OD Split Spoon (SPT)

AT COMPLETION

G R

A P

H

IC

L O

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DESCRIPTION

4.25" ID auger to 30'

178+00, 20' RT

0.0

4.0

8.0

12.0

16.0

20.0

24.0

28.0

32.0

36.0

40.0

5814.0

5810.0

5806.0

5802.0

5798.0

5794.0

5790.0

5786.0

5782.0

5778.0

5774.0

Boring locations determined using recreational grade GPS unit.NOTES:

BORING KC10-28

COMPANY:

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3/

Haztech LOGGER: SK Geotechnical

DATE STARTED:

0.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

PROJECT: ID PFH 26-1(1), Ketchum-Challis Highway

Automatic

WATER CONTENT (%)

12'

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

DRILL: BK 81

D E

P T

H ft

9/29/2010

S A

M P

LE

R

9/29/2010

STATION, OFFSET:

D-10

Rec. = 89%

RQD = 45%

Rec. = 94%

RQD = 39%

Rec. = 100%

RQD = 58%

Rec. = 67%

RQD = 0%

Rec. = 100%

RQD = 50%

Rec. = 86%

RQD = 33%

Rec. = 88%

RQD = 88%

10-41-50 (12" = 67%)

7 1/2" ASPHALT CONCRETE

3" base, base/subgrade contact unclear light brown, cobbly, gravelly, silty SAND (SM), fine- to medium-grained, nonplastic, damp, very dense

Switch to HQ coring at 4'.

grayish brown, moderately weathered, highly to moderately fractured, open to moderately open spacing, weak to moderately strong (R2-R3), GRANITE, some iron staining in fractures

-bedrock very blocky, difficult to core full 5' run

END OF BORING

Groundwater not observed.

0.6 0.9

4.0

25.5

RECOVERY (%)

0 50

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 44° 15' 5.50" (44.25152786°)

LONGITUDE…