Geo Rpt 03-12 Ketchum-Challis Rock Scaling.pdf

DE

PA

RT

MENT OF TRANSPORTATION

UNITED STATES OF AMERICA

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

WESTERN FEDERAL LANDS HIGHWAY DIVISION

VANCOUVER, WASHINGTON

Geotechnical Services

ROCK SCALING DESIGN

KETCHUM-CHALLIS HIGHWAY

ID PFH-26(2)

SAWTOOTH NATIONAL RECREATION AREA

CUSTER COUNTY, IDAHO

MAY 2012

Geotechnical Report No. 03-12

Report to:

Western Federal Lands Highway Division 610 East 5th Street

Vancouver, Washington 98661-3801

KETCHUM-CHALLIS HIGHWAY

ID PFH-26(2)

ROCK SCALING DESIGN

SAWTOOTH NATIONAL RECREATION AREA

CUSTER COUNTY, IDAHO

WFLHD GEOTECHNICAL REPORT NO. 03-12

May 2012

Submitted by:

David Evans & Associates 2100 SW River Parkway

Portland, OR 97201 and

Cornforth Consultants, Inc.

10250 Greenburg Road, Suite 111

Portland, OR 97223

Ketchum-Challis Highway, ID PFH 26(2), Rock Scaling Design 2199 WFLHD Geotechnical Report No. 03-12

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Table of Contents

1 Introduction

1.1 Background

1.2 Regional Climate

1.3 Geologic Setting and Site Description

1.4 Rockfall Hazard Rating System (RHRS) Results

2 Investigations and Analyses

2.1 Field and Office Studies

2.2 Rockfall Computer Simulations

3 Rockfall Mitigation Measures

3.1 Temporary Roadway Protection (Rock Protection Screen)

3.2 Rock Scaling (Hand/Blast/Mechanical)

3.3 Rockfall Protection Fence (Attenuator)

4 Rockfall Mitigation Designs

4.1 Section 1 – Station 78+05 to 82+00

4.2 Section 2 – Station 82+00 to 84+00

4.3 Section 3 – Station 84+00 to 86+10

4.4 Section 4 – Station 86+10 to 88+90

4.5 Section 5 – Station 88+90 to 91+00

4.6 Section 6 – Station 91+00 to 95+00

4.7 Section 7 – Station 95+00 to 97+70

4.8 Section 8 – Station 97+70 to 100+30

4.9 Section 9 – Station 100+30 to 102+10

4.10 Section 10 – Station 102+10 to 105+00

4.11 Section 11 – Station 105+00 to 107+60

4.12 Section 12 – Station 107+60 to 111+60

4.12.1 Rockfall Computer Simulation Summary

4.12.2 Rockfall Mitigation Measures

4.13 Section 13 – Station 111+60 to 115+35

4.14 Section 14 – Station 115+35 to 118+70

4.15 Section 15 – Station 118+70 to 120+80

5 Recommendations

5.1 Rockfall Mitigation Design Quantities

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5.2 Special Contract Requirements and Design Details

6 Closing

List of Tables

Table 1: Rockfall Section Slope Characteristics

Table 2: Section 1 Rockfall Mitigation Design Elements

Table 3: Section 2 Rockfall Mitigation Design Elements

Table 4: Section 3 Rockfall Mitigation Design Elements

Table 5: Section 4 Rockfall Mitigation Design Elements

Table 6: Section 5 Rockfall Mitigation Design Elements

Table 7: Section 6 Rockfall Mitigation Design Elements

Table 8: Section 7 Rockfall Mitigation Design Elements

Table 9: Section 8 Rockfall Mitigation Design Elements

Table 10: Section 9 Rockfall Mitigation Design Elements

Table 11: Section 10 Rockfall Mitigation Design Elements

Table 12: Section 11 Rockfall Mitigation Design Elements

Table 13: Section 12 Rockfall Mitigation Design Elements

Table 14: Section 13 Rockfall Mitigation Design Elements

Table 15: Section 14 Rockfall Mitigation Design Elements

Table 16: Section 15 Rockfall Mitigation Design Elements

Table 17: Rockfall Mitigation Design Quantities and Bid Item Nos

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List of Figures

Figure 1: Vicinity Map

Figure 2: Site Plan, Station 78+05 to 91+00

Figure 3: Site Plan, Station 91+00 to 102+10

Figure 4: Site Plan, Station 102+10 to 115+35

Figure 5: Site Plan, Station 115+35 to 120+80

List of Appendices

Appendix A: Rockfall Simulation Results

Appendix B: Annotated Design Photographs

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1 INTRODUCTION

1.1 Background

Western Federal Lands Highway Division (WFLHD) is planning to improve a roadway segment of Forest Highway 26 (Idaho State Route 75) in Custer County, Idaho. The roadway is located along the Salmon River and lies within the Sawtooth National Recreation Area (NRA).

Previous work by WFLHD focused on determining an appropriate approach to improve this highway section considering realignment or a major reconstruction option. After review, WFLHD and its partners, the Idaho Transportation Department (ITD) and the U.S. Forest Service (USFS), decided instead to move forward with a reduced reconstruction option. The planned improvements would include short retaining walls to address river erosion of the roadway embankments, and rockfall mitigation measures to reduce the significant rockfall hazards within the corridor.

Specifically, a 4,300-foot-long section of Route 26 from approximately MP 205.72 to MP 206.53, referred to locally as “The Narrows,” was reviewed for rockfall mitigation. Our scope of work for this task order (IDIQ Contract DTFH70-10-D-00019, Task Order Number T-11-012) has been crafted to move forward with two separate construction contracts. The scope of work for Construction Contract #1 (ID PFH 26(2)) is to provide a portion of the rockfall mitigation including: rock scaling from Station 78+00 to Station 118+70, blast scaling at approximate project Station 100+36 and a rockfall protection fence (attenuator) that begins at Station 107+30. The remaining rockfall mitigation elements are included under Construction Contract #2 (ID PFH 26-1(1)). The combined design recommendations for the two construction contracts are a culmination of earlier conceptual design work that was detailed in WFLHD Geotechnical Report No. 11-10. The details for the recommended rockfall mitigation measures for Construction Contract #2 are provided in WFLHD Geotechnical Report No. 04-12. This report deals primarily with the scaling work covered by Construction Contract #1.

1.2 Regional Climate

The project site is located approximately 14 miles east-northeast of Stanley, Idaho. This area is in a cold semi-arid climate. According to data reviewed from the Western Regional Climate Center complied from 1963 to 2010 for Stanley, Idaho, the project site could experience a high monthly average temperature of around 58° F recorded for July, a low of approximately 12° F recorded for December and January, and an average annual temperature of around 35° F. Monthly average precipitation ranges from a low of 0.56 inches recorded for August, up to a high of 1.62 inches recorded for January, with an annual total precipitation of about 12.80 inches. This includes approximately 72 inches of annual average snowfall with extreme average annual snow depths ranging from 29 to 96 inches.

1.3 Geologic Setting and Site Description

The project site is within the Sawtooth Mountain Range, which is part of the Northern Rocky Mountain physiographic province. The overall geologic setting is dominated by the massive Idaho batholith consisting of intrusive volcanic rock units. The slope geology has been mapped by McIntyre and Johnson (1992) as Cretaceous aged biotite granodiorite. Historically, the area is seismically active, with the epicenter of the 1983, 6.9 Magnitude, Borah Peak earthquake located approximately 40 miles east of the project.

Generally, the exposed rock is granitic showing variable jointing and rock weathering. The joint spacing ranges from a few inches to 10 plus feet, and the joints are closed to open and in some cases filled with soil. The majority of rockfalls originate from this unit; however, the top of the cuts include a relatively

Cornforth Consultants Inc. 2 May 10, 2012 thin layer of talus, which contains rock pieces in a soil matrix. In addition, at both ends of the project, glacial till deposits are present. In these materials, weathering and erosion can remove the support provided by the soil matrix component of the till, which can produce up to boulder-sized rockfalls.

There are numerous outcrops positioned throughout the natural slope above the cut slopes and some of these extend over large areas. There is evidence that these produce rockfalls capable of reaching the highway. Design work to address these upslope areas and mitigate the rockfall potential is not part of our work scope. This project focuses on the existing highway cut slopes that produce the majority of rockfall and, thus, are difficult to maintain.

An example of the cut slope rockfall activity included one large block measuring roughly 15 x 8 x 6 feet and weighing about 60 tons that was pointed out as unstable during our initial project walk-through. By chance, the block fell onto the roadway overnight. Luckily no one was injured, but it took ITD maintenance personnel several hours to break the block into moveable-sized pieces in order to clear the roadway and reopen both lanes to traffic. Although it only fell about 35 feet, the impact energy was enough to laterally displace a large wedge of the pavement over 2 inches toward the Salmon River.

1.4 Rockfall Hazard Rating System (RHRS) Results

The project cut slopes have been separated into 15 sections based on their geological and slope characteristics. In many cases, the dividing line coincided with natural draws (chutes) that bisected the nearly continuous rock cuts. These chutes provide an avenue to deliver rockfalls from upslope onto the roadway. Where present, the rockfall potential provided by these chutes was evaluated as part of the Rockfall Hazard Rating System (RHRS) for the delineated slope sections.

The RHRS evaluations indicate that all 15 sections would be classified as ‘A’ rated slopes, demonstrating that each poses a medium to high rockfall hazard. Based on this, all 15 sections would warrant some form of rockfall mitigation. A detailed discussion of the RHRS results was provided in WFLHD Geotechnical Report No. 11-10. That information is not repeated in this report. A summary of slope characteristics for each section is provided in Table 1. The cut slope areas shown on the table are based on field observations of the slopes that are to be mitigated for this project.

Table 1: Rockfall Section Slope Characteristics

Slope Section

Stationing Length (ft)

Max. Cut Height (ft)

Cut Slope Area (sf)

RHRS

Score

RHRS

Rank Begin End

1 78+05 82+00 395 80 24,000 356 11 2 82+00 84+00 200 100 17,250 375 9 3 84+00 86+10 210 110 16,250 458 5 4 86+10 88+90 280 75 16,210 389 8 5 88+90 91+00 210 53 8,550 524 3 6 91+00 95+00 400 83 30,000 536 1 7 95+00 97+70 270 63 12,350 343 12 8 97+70 100+30 260 60 15,600 401 7 9 100+30 102+10 180 50 12,600 341 13 10 102+10 105+00 290 100 27,840 460 4 11 105+00 107+60 260 68 12,950 329 14 12 107+60 111+60 400 70 27,200 362 10 13 111+60 115+35 375 65 24,375 454 6 14 115+35 118+70 335 56 14,010 300 15 15 118+70 120+80 210 160 20,800 526 2

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2 INVESTIGATIONS AND ANALYSES

2.1 Field and Office Studies

The rockfall mitigation options for each of the 15 sections were developed in the field through observational and structural mapping techniques and then further refined by office analyses. Fieldwork was completed in June 2011 and involved four staff over several weeks. Field information was gathered using an 80-foot hi-lift to access each slope and provide a complete cut slope perspective. The slope areas above the cut slopes were accessed on foot. Traffic control was used to accommodate lane closures during the slope assessments.

Numerous aerial photographs of each slope were taken by helicopter during the project reconnaissance and these were used to document the recommended rock bolt and heavy scaling locations. Preliminary rockfall computer simulations were performed during the field program to evaluate mitigation concepts and confirm combinations of mitigation measures for each slope. Once the preliminary mitigation designs were defined, the access requirements and the constructability of the design concept were evaluated along with potential environmental implications. Office analyses have included a rigorous computer simulation program to refine the field designs.

2.2 Rockfall Computer Simulations

The computer program Rocfall (version 4.0) was used to model potential rockfall events to establish a range of likely rockfall trajectory and energy outcomes. Cross-sections used for modeling were extracted from topographic maps provided by WFLHD. The various material and slope parameters were recorded in the field. The modeled input values were based on the measured field parameters and adjusted during the analyses to calibrate the models to produce results consistent with observed rockfall conditions.

Based on direction from WFLHD, mitigation designs were developed considering a design goal that provides control for 90% of potential rockfall events, which is consistent with other transportation agencies.

The rockfall simulations provide guidance on the potential bounce heights, velocity, and kinetic energy of rockfalls as they pass various analysis points along a selected rockfall path. Typically, the selected rockfall paths are oriented perpendicular to the roadway; however, for this project some modeled cross-sections included non-perpendicular slope segments in order to recreate observed rockfall paths. The simulation results are used to evaluate the likelihood of rockfall reaching the roadway at untreated sites and to determine the best location, optimal height and capacity for planned rockfall mitigation measures to meet the WFLHD design criteria. For the rockfall models, the likely rockfall source areas are called initiation zones and these zones are based on observed slope materials and conditions. The modeled rockfall sizes are based on reported historical and/or observed rockfall information.

Rockfall Cross Section 19 was analyzed for the Rockfall Protection Fence (Attenuator) to be installed between Sections 11 and 12 at Station 107+88. Two rock masses were calculated using a unit weight of 160 pounds per cubic foot and diameters of 2 and 4 feet. Each analysis simulated 1000 rocks falling from the initiation zone. Modeling results provided in included in Appendix A include histograms for the simulated rockfall total kinetic energies and bounce heights at the proposed attenuator location along with tables showing the statistical analysis of the percentages of rocks retained in the roadside ditch.

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3 ROCKFALL MITIGATION MEASURES

Several mitigation measures were considered during field investigations and preliminary design phases for Construction Contract #1. As design progressed the following mitigation measures were selected for final design. In addition to the permanent mitigation measures, all slopes will require temporary road protection during various stages of construction, such as during the rock scaling operations.

• Temporary rockfall protection

• Rock scaling (hand/blast/mechanical)

• Rockfall protection fence (attenuator)

Special Contract Requirements (SCRs) have been developed for each identified mitigation element as discussed in Section 5 of this report. A brief description of each mitigation element including the temporary roadway protection is presented below.

3.1 Temporary Roadway Protection (Rock Protection Screen)

Scaling operations and other on-slope work will remove or dislodge a considerable amount of loose rocks and some will be large. Temporary roadway protection (TRP) would be used to contain scaling debris to facilitate cleanup, and provide roadway user protection during non-working hours for areas where the work is in progress. In addition, the TRP will limit the likelihood of material entering the river, and reduce the amount of material that could directly impact and possibly damage the existing road surface, guardrail, or roadway embankments.

TRP generally requires some form of barrier, such as precast concrete barriers or a moveable rockfall barrier system, typically located near the edge of pavement or as necessary to accommodate traffic flow.

For this project, a temporary concrete barrier with rock protection screen has been recommended. It will be installed through a portion of the project where on-slope work is being performed and then moved in segments as work progresses through the project. The barriers can be moved for reuse and then completely removed at the end of project. At the discretion of the Contractor, the recommended approach may be augmented or modified as necessary to control rockfall events based on the actual means and methods they employ and the resulting rockfall behavior.

3.2 Rock Scaling (Hand/Blast/Mechanical)

Scaling operations will require setting anchors above the cut slope to support the scalers working on ropes. Scaling is performed from the top down. To ensure safety, this operation is performed before any other slope treatments are initiated. At some locations, mechanical and/or blast scaling will be required where blocks and/or targeted excavation volumes are too large and/or impractical to scale by hand. Due to the variable nature of the bedrock, scaling would need to be closely managed by experienced rockfall mitigation specialists to prevent over-scaling in critical areas or unproductive efforts. Slope scaling will be conducted from the base of the ditch to an approximate line ten feet above the existing cut slope brow for the entire length of each slope section as described in the Plans.

The estimated quantity of scaling hours is based on general slope scaling of the entire slope area along with additional hours added to allow concentrated heavy scaling effort in complex, highly fractured or poorer quality rock areas. The estimate of general slope scaling was based on the total slope area with 300 square feet (sf) scaled per hour. For higher need areas, a value of 100 or 200 sf of slope scaling per hour was used based on how difficult or intense the required scaling was estimated to be. The areas

Cornforth Consultants Inc. 5 May 10, 2012 requiring heavy scaling have been illustrated on the annotated photographs in Appendix B. Some of the heavy scaling areas are located high up on the cut slopes and some include outcrops located above the general scaling limit.

3.3 Rockfall Protection Fence (Attenuator)

A rockfall attenuator is a protection measure that consists of wire rope net panels with a mesh backing that are elevated above the ground surface. The panels are attached to an upper support cable that runs between fence posts. These interconnected panels drape freely down slope to within a prescribed distance above the ditch line. The elevated section is used to intercept rockfall trajectories. Once captured, the rockfalls are channeled beneath the draped mesh, which dissipates the rockfall bounce height, velocity and energy so they can be retained in the roadside ditch. The main design requirement for this mitigation system to function properly is for the attenuator to be tall enough to intercept falling/bouncing rocks and capable of managing the anticipated rockfall energies.

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4 ROCKFALL MITIGATION DESIGNS

The recommendations for rockfall mitigation for Construction Contract #1 are primarily limited to slope scaling. The majority of the recommended rockfall mitigations will be included in Construction Contract #2. Once both contracts are completed, the installed measures will improve safety and reduce the amount of rockfall and required maintenance; however, the potential for rockfalls to occur and reach the roadway will still exist due primarily to the small fallout areas that will remain unchanged at the base of the cut slopes. Some of the anticipated rockfall activity will originate from upslope rockfall sources that are outside the scope of these mitigation efforts.

The Construction Contract #1 mitigation measures focus on slope scaling and minor blast scaling recommended at one location along with the installation of one rockfall protection fence (attenuator) to serve as a test installation to evaluate its serviceability in this climate that experiences heavy snowfall and occasional snow avalanches. Final mitigation design details and SCRs for these design elements and for the TRP have been prepared as discuss in Section 5.

All of the rockfall mitigation techniques that have been recommended are routinely constructed by rockfall mitigation contractors. Finding qualified companies to perform the planned work should not pose an unreasonable challenge to WFLHD.

The following discussion presents a summary of the proposed rockfall mitigation designs for each slope section. The quantity listed for each of individual design element is the design quantity. These have not been factored to produce the bid quantities that will appear in the final contract documents. A Vicinity Map and Site Plans are presented as Figures 1 through 5. The Site Plans show the limits of the 15 rockfall sections that have been defined for this project and the location where the single Rockfall Protection Fence (Attenuator) is to be installed between Sections 11 and 12. As introduced previously, annotated photographs illustrating the locations where heavy scaling is required, including the recommended blast scaling area, are provided in Appendix B.

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4.1 Section 1 – Station 78+05 to 82+00

Section 1 was ranked number 11 out of the 15 sites during the RHRS review. The cut slope is 395 feet long with a cut slope height that is roughly 80 feet tall. The cut slope area encompasses approximately 24,000 sf. A colluvial slope present at the west end of the section abuts a rock slope that comprises the majority of the cut slope. The geologic structure of the rock slope is comprised of a set of steeply dipping discontinuities that are oriented towards the roadway and a set of moderately dipping discontinuities that are dipping away from the roadway. These sets appear to combine to promote single block rockfall events on the order of 3 feet in maximum dimension.

For Construction Contract #1, 105 hours (hrs) of scaling are recommended. The locations identified for heavy scaling are illustrated on the annotated photographs in Appendix B.

Table 2: Section 1 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 78+05 82+00 105 hrs Additional scaling will be required for Contract #2

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4.2 Section 2 – Station 82+00 to 84+00

Section 2 ranked number 9 out of the 15 sites. The section is 200 feet long with a maximum cut slope height on the order of 100 feet and a slope area of roughly 17,250 sf. This section is comprised of a rock cut that has similar geologic structure to that of Section 1. Single rock block events on the order of 3- to 5-foot rocks can be anticipated with some larger events possible.

For Construction Contract #1, 95 hrs of scaling are recommended. The locations identified for heavy scaling are illustrated on the Annotated Photographs in Appendix B.

Table 3: Section 2 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 82+00 84+00 95 hrs Additional scaling will be

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4.3 Section 3 – Station 84+00 to 86+10

Section 3 ranked number 5 out of the 15 sites. The slope is 210 feet long with a maximum height on the order of 110 feet and a slope area of roughly 16,250 sf. Single block rockfall events typically 3 to 5 feet in size are possible. Two rockfall chutes are present that would serve to concentrate rockfall events from above the cut slope. The main rockfall paths for these two chutes are located at Station 84+16 and Station 86+05.

For Construction Contract #1, 100 hrs of scaling are recommended. The heavy scaling locations are illustrated on the Annotated Photographs in Appendix B.

Table 4: Section 3 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 84+00 82+00 100 hrs Additional scaling will be

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4.4 Section 4 – Station 86+10 to 88+90

Section 4 ranked number 8 out of the 15 sites. The slope is 280 feet long with a maximum height on the order of 75 feet and a slope area of roughly 16,210 sf. This slope section has two distinction rock outcrops separated by a rockfall chute. The chute located at approximately Station 87+06 would serve to concentrate rockfall events from above the cut slope. Single block rockfall events on the order of 3 to 5 feet in size are possible.

For Construction Contract #1, 90 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 5: Section 4 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 86+10 88+90 90 hrs Additional scaling will be conducted during Contract 2

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4.5 Section 5 – Station 88+90 to 91+00

Section 5 was rated number 3 out of the 15 sites. The slope is 210 feet long with a maximum height on the order of 53 feet and a slope area of roughly 8,550 sf. This slope is bounded by two chutes that produce higher frequency rockfalls. These chutes are located near Station 89+43 and Station 90+90.

Single block rockfall events of rocks 3 to 5 feet in size are possible at this slope.

Due to the higher rockfall activity within this section, traffic should not be allowed to queue within the Section 5 limits during construction.

For Construction Contract #1, 45 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 6: Section 5 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 88+90 91+00 45 hrs Additional scaling will be

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4.6 Section 6 – Station 91+00 to 95+00

The RHRS score for Section 6 placed it as number 1 out of the 15 sites. The slope is 400 feet long with a maximum height of about 83 feet and a slope area of roughly 30,000 sf. The geologic structure at this slope is very distinct with a set of steeply dipping discontinuities oriented toward the roadway that parallels the slope face and two conjugate joint sets that combine to form potential rockfall blocks. Some of these form large blocks, which was demonstrated by the 15-foot-long block that fell from the slope during the initial site visit. That event badly damaged the roadway and required repaving as shown in the photograph above.

Due to the higher rockfall activity within this section, traffic should not be allowed to queue within the Section 6 limits during construction.

For Construction Contract #1, 140 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 7: Section 6 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 91+00 95+00 140 hrs Additional scaling will be

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4.7 Section 7 – Station 95+00 to 97+70

Section 7 ranked number 12 out of the 15 sites. The slope is 270 feet long with a maximum height on the order of 63 feet and a slope area of roughly 12,350 sf. The majority of this section is comprised of slopes that produce higher frequency rockfall events with rock blocks typically on the order of 2 to 3 feet in maximum dimension.

For Construction Contract #1, 95 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 8: Section 7 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 95+00 97+70 95 hrs Additional scaling will be

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4.8 Section 8 – Station 97+70 to 100+30

Section 8 was rated number 7 out of the 15 sites. The slope is 260 feet long with a maximum height on the order of 60 feet. The slope area is approximately 15,600 sf. This section has several rock outcrops in the cut slope that could produce rock blocks typically up to 4 feet in maximum dimension. There are two chutes located at Stations 98+81 and 100+18 that concentrate rockfalls that originate upslope.

For Construction Contract #1, 110 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 9: Section 8 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 97+70 100+30 110 hrs Additional scaling will be

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4.9 Section 9 – Station 100+30 to 102+10

Section 9 was rated number 13 out of the 15 sites. The slope is 180 feet long and 50 feet tall with a slope area of roughly 12,600 sf. This section of slope has a chute at the western boundary (as described in the Section 8 discussion) and a chute centered at Station 102+08. These chutes serve to concentrate upslope rockfalls as evidenced by the rockfall craters in the roadway. The cut slope produces rock blocks ranging from 3 to 5 feet in maximum dimension. A tall near-vertical rock outcrop fin oriented roughly perpendicular to the roadway is located near Station 100+36. It appears that this fin of rock is too large to remove by hand scaling techniques and it is recommended that blasting methods be used.

For Construction Contract #1, 95 hrs of hand scaling and roughly 300 cubic yards (cy) of blast scaling are recommended. The blast scaling quantity is an in-place volume. A swell factor should be applied to estimate hauling requirements. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 10: Section 9 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 100+30 102+10 95 hrs Additional scaling will be

Slope Scaling (Blast Scaling) 100+26 100+46 300 cy

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4.10 Section 10 – Station 102+10 to 105+00

Section 10 rated number 4 out of the 15 sites. The slope is 290 feet long with a maximum height of 100 feet and a slope area of roughly 27,840 sf. The cut slope at this section has the potential to produce rock blocks on the order of 2 to 3 feet in maximum dimension.

For Construction Contract #1, 155 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 11: Section 10 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 102+10 105+00 155 hrs Additional scaling will be

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4.11 Section 11 – Station 105+00 to 107+60

Section 11 ranked 14 out of the 15 sites. The slope is 260 feet long with a maximum height on the order of 68 feet and a slope area of roughly 12,950 sf. This section has one rockfall chute located at Station 105+60 that concentrates rockfalls that originate upslope. Single block events of rock blocks ranging from 2 to 3 feet are also common.

For Construction Contract #1, 85 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 12: Section 11 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 105+00 107+60 85 hrs Additional scaling will be

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4.12 Section 12 – Station 107+60 to 111+60

Section 12 was rated number 10 out of the 15 sites. The slope is 400 feet long and roughly 70 feet tall with a slope area of about 27,200 sf. This section contains colluvial material in the roadside ditch that reduces the effectiveness of the catchment area. The rock outcrops have the potential to produce rock blocks up to 4 feet in maximum dimension. A rockfall chute that begins near the end of Section 11, but is primarily within Section 12, is centered at approximately Station 107+75. A second chute is located near the end of Section 12 at Station 111+50.

4.12.1 Rockfall Computer Simulation Summary

Rockfall computer simulations were conducted on Cross Section 19 (Station 107+88). The simulation results indicate a 5-foot tall, 100 foot-ton capacity Rockfall Protection Fence (Attenuator) would be sufficient mitigation for this chute. The cross section location is illustrated on Figure 4 and rockfall computer simulation results are provided in Appendix A.

4.12.2 Rockfall Mitigation Measures

For Construction Contract #1, 130 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B. In addition, the installation of 930 square yards

(sy) of Rockfall Protection Fence (Attenuator) is recommended across the first rockfall chute during Construction Contract #1 to serve as a test of the durability and performance of these systems within this corridor. The station limits of the fence are listed below and its location is shown on Figure 4.

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Table 13: Section 12 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 107+60 111+60 130 hrs Additional scaling will be required for Contract #2

Rockfall Protection Fence (Attenuator) 107+30 108+19 930 sy

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4.13 Section 13 – Station 111+60 to 115+35

Section 13 ranked 6 out of the 15 sites. The slope is 375 feet long with a maximum height of about 65 feet and a slope area of roughly 24,375 sf. Rock outcrops in this section have the potential to produce rockfall blocks on the order of 3 feet in diameter. A rockfall chute is present at the start of the section as described in the Section 12 discussion. A second rockfall chute that concentrates rockfalls that originate upslope is located near Station 115+02.

For Construction Contract #1, 115 hrs of scaling are recommended. The heavy scaling locations are illustrated on the annotated photographs in Appendix B.

Table 14: Section 13 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 111+60 115+35 115 hrs Additional scaling will be

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4.14 Section 14 – Station 115+35 to 118+70

Section 14 was rated number 15 out of the 15 sites. The slope is 335 feet long with a maximum height on the order of 56 feet and a slope area of roughly 14,010 sf. Sets of steeply dipping discontinuities intersect sets of moderately dipping discontinuities forming rock blocks that are typically up to 3 feet in maximum dimension. The roadside ditch in this section tends to be wider than the other sections and ITD maintenance reported lower rockfall activity, which accounts for the lower rating of this section.

For Construction Contract #1, 125 hrs of scaling are recommended. The heavy scaling areas are illustrated on the annotated photographs in Appendix B.

Table 15: Section 14 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 115+35 118+70 125 hrs Additional scaling will be required for Contract #2

Cornforth Consultants Inc. 22 May 10, 2012

4.15 Section 15 – Station 118+70 to 120+80

Section 15 was rated number 2 out of the 15 sites. The slope is 210 feet long with a maximum height on the order of 160 feet and a slope area of roughly 20,800 sf. This section poses a different rockfall condition than the other 14 sections. The material is composed of glacial till that contains many larger boulders in a soil matrix. As the soil supporting the boulders is eroded away by rain, snowmelt and wind action, the boulders are released and the narrow ditch at the base of the slope is not adequate to restrict these blocks from entering the roadway.

Due to the higher rockfall activity and potential for rockfalls to enter the highway, traffic should not be allowed to queue within the Section 15 limits during construction.

For Construction Contract #1, 115 hrs of scaling are recommended. The heavy scaling areas are illustrated on the annotated photographs in Appendix B.

Table 16: Section 15 Rockfall Mitigation Design Elements

Design Element Stationing No. of

Units Units Notes Begin End

General Labor (Slope Scaling) 118+70 120+80 115 hrs Additional scaling will be required for Contract #2

Cornforth Consultants Inc. 23 May 10, 2012

5 RECOMMENDATIONS

5.1 Rockfall Mitigation Design Quantities

A summary of bid quantities for Construction Contract #1 is provided on Table 17. In addition to the listed bid quantities, we have estimated that scaling, including material from blasting and ditch cleaning, would yield approximately 10,000 to 15,000 cy of debris. Boulders that are 5 to 7 feet in diameter (nominal) are to be segregated from the scaling debris and stockpiled at the USFS Nip and Tuck Pit as shown on Figure 1.

Table 17: Rockfall Mitigation Design Quantities and Bid Item Nos.

Bid Item No. Bid Item Title No. of Units Units Notes

20442-0000 Slope Scaling (Blast Scaling) 300 cy

20465-0000 Conserve and Place Boulder (5-7 feet)

15 each

62302-0100 Special Labor, Slope Scaling 1,600 hrs Additional scaling planned for Contract #2

65104-0000 Rockfall Protection Fence (Attenuator)

930 sy Additional attenuators planned for Contract #2

5.2 Special Contract Requirements and Design Details

Each of the bid items listed in Table 17 require a SCR since the mitigation elements have been customized for this project. The proposed SCRs are based on the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects FP-03. The SCRs and associated Design Details have been provided to David Evans and Associates for inclusion in the contract documents package.

Cornforth Consultants Inc. 24 May 10, 2012

6 CLOSING

We appreciate the opportunity to be of assistance to Western Federal Lands – Highway Division. If you have any questions or comments on this Final Design Report, please contact us at (503) 452- 1100.

Sincerely, CORNFORTH CONSULTANTS, INC.

Lawrence Pierson, C.E.G.

Senior Associate

Benjamin George, P.E., P.G.

Project Engineer

Cornforth Consultants, Inc.

Landslide Technology

Limitations in the Use and Interpretation of this Geotechnical Report

Our professional services were performed, our findings obtained, and our recommendations prepared in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties, either expressed or implied.

The geotechnical report was prepared for the use of the Owner in the design of the subject facility and should be made available to potential contractors and/or the Contractor for information on factual data only. This report should not be used for contractual purposes as a warranty of interpreted subsurface conditions such as those indicated by the interpretive boring and test pit logs, cross-sections, or discussion of subsurface conditions contained herein.

The analyses, conclusions and recommendations contained in the report are based on site conditions as they presently exist and assume that the exploratory borings, test pits, and/or probes are representative of the subsurface conditions of the site. If, during construction, subsurface conditions are found which are significantly different from those observed in the exploratory borings and test pits, or assumed to exist in the excavations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between the submission of this report and the start of work at the site, or if conditions have changed due to natural causes or construction operations at or adjacent to the site, this report should be reviewed to determine the applicability of the conclusions and recommendations considering the changed conditions and time lapse.

The Summary Boring Logs are our opinion of the subsurface conditions revealed by periodic sampling of the ground as the borings progressed. The soil descriptions and interfaces between strata are interpretive and actual changes may be gradual.

The boring logs and related information depict subsurface conditions only at these specific locations and at the particular time designated on the logs. Soil conditions at other locations may differ from conditions occurring at these boring locations. Also, the passage of time may result in a change in the soil conditions at these boring locations.

Groundwater levels often vary seasonally. Groundwater levels reported on the boring logs or in the body of the report are factual data only for the dates shown.

Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples, borings or test pits. Such unexpected conditions frequently require that additional expenditures be made to attain a properly constructed project. It is recommended that the Owner consider providing a contingency fund to accommodate such potential extra costs.

This firm cannot be responsible for any deviation from the intent of this report including, but not restricted to, any changes to the scheduled time of construction, the nature of the project or the specific construction methods or means indicated in this report; nor can our firm be responsible for any construction activity on sites other than the specific site referred to in this report.

Ketchum-Challis Highway, ID PFH-26(2), Rock Scaling Design 2199

Cornforth Consultants, Inc. May 10, 2012

APPENDIX A

Rockfall Simulation Results

Total K-E (ft-tons)

0 50 100 150 200

N o.

o f 2

-fo ot ro ck s

Height at Fence Location

0 2 4 6 8 10

N o.

o f 2

-fo ot ro ck s

Total K-E (ft-tons)

0 50 100 150 200

N o.

o f 4

-fo ot ro ck s

Height at Fence Location

0 2 4 6 8 10

N o.

o f 4

-fo ot ro ck s

2-foot diameter rocks 4-foot diameter rocks

CROSS SECTION 19

ATTENUATOR FENCE LOCATION STATISTICS

Percentile KE (ft‐tons) Impact Height (ft)

70% 6.4 0.6

80% 7.1 0.9

90% 8.2 1.5

95% 9.0 2.3

99% 10.7 3.6

Average 5.5 0.5

Maximum 13.2 5.2

2‐foot Rocks Percentile KE (ft‐tons) Impact Height (ft)

70% 38.9 0.1

80% 43.8 0.2

90% 52.4 0.5

95% 57.6 0.8

99% 72.9 1.6

Average 33.6 0.1

Maximum 87.7 3.5

4‐foot Rocks

Bottom of the Attenuator draped mesh

CROSS SECTION 19 - STATION 107+88

ROCKFALL SIMULATION TRAJECTORIES

2-FOOT DIAMETER ROCKS

Recommended location for the Rockfall Protection Fence (Attenuator)

Edge of Pavement

Recommended location for the Rockfall Protection Fence (Attenuator)

ROCKFALL TRAJECTORIES WITHOUT ATTENUATOR INSTALLATION

ROCKFALL TRAJECTORIES WITH ATTENUATOR INSTALLATION

Bottom of the Attenuator draped mesh

ROCKFALL TRAJECTORIES WITHOUT ATTENUATOR INSTALLATION

CROSS SECTION 19 - STATION 107+88

ROCKFALL SIMULATION TRAJECTORIES

4-FOOT DIAMETER ROCKS

Recommended location for the Rockfall Protection Fence (Attenuator)

Edge of Pavement

Recommended location for the Rockfall Protection Fence (Attenuator)

ROCKFALL TRAJECTORIES WITH ATTENUATOR INSTALLATION

Ketchum-Challis Highway, ID PFH-26(2), Rock Scaling Design 2199

Cornforth Consultants, Inc. May 10, 2012

APPENDIX B

Annotated Design Photographs

NOTES:

1. CONDUCT GENERAL SCALING ON

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

2199/Photos/D01-1.ai NAU

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 1 - ANNOTATED PHOTOGRAPH 1 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 1 - ANNOTATED PHOTOGRAPH 1 OF 2

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 1 - ANNOTATED PHOTOGRAPH 2 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 1 - ANNOTATED PHOTOGRAPH 2 OF 2

2199/Photos/D01-2.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

2/3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26-(2)

SECTION 2 - ANNOTATED PHOTOGRAPH 1 OF 1

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 2 - ANNOTATED PHOTOGRAPH 1 OF 1

2199/Photos/D02.ai Nau

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26-(2)

SECTION 3 - ANNOTATED PHOTOGRAPH 1 OF 1

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 3 - ANNOTATED PHOTOGRAPH 1 OF 1

2199/Photos/D03.ai NAU

3/4

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26-(2)

SECTION 4 - ANNOTATED PHOTOGRAPH 1 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 4 - ANNOTATED PHOTOGRAPH 1 OF 3

2199/Photos/D04-1.ai NAU

3/4

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 4 - ANNOTATED PHOTOGRAPH 2 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 4 - ANNOTATED PHOTOGRAPH 2 OF 3

2199/Photos/D04-2.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 4 - ANNOTATED PHOTOGRAPH 3 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 4 - ANNOTATED PHOTOGRAPH 3 OF 3

2199/Photos/D04-3.ai NAU

4/5

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 5 - ANNOTATED PHOTOGRAPH 1 OF 1

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 5 - ANNOTATED PHOTOGRAPH 1 OF 1

2199/photos/D05.ai NAU

5/6

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 6 - ANNOTATED PHOTOGRAPH 1 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 6 - ANNOTATED PHOTOGRAPH 1 OF 2

2199/Photos/D06-1.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 6 - ANNOTATED PHOTOGRAPH 2 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 6 - ANNOTATED PHOTOGRAPH 2 OF 2

2199/Photos/D06-2.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 7 - ANNOTATED PHOTOGRAPH 1 OF 1

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 7 - ANNOTATED PHOTOGRAPH 1 OF 1

2199/Photos/D07.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 1 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 1 OF 3

2199/Photos/D08-1.ai NAU

7/8

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 2 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 2 OF 3

2199/Photos/D08-2.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 3 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 8 - ANNOTATED PHOTOGRAPH 3 OF 3

2199/Photos/D08-3.ai NAU

8/9

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

ANTICIPATED BLAST

SCALING AREA

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 1 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 1 OF 3

2199/Photos/D09-1.ai NAU

8/9

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 2 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 2 OF 3

2199/Photos/D09-2.ai NAU

9/10

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 3 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 9 - ANNOTATED PHOTOGRAPH 3 OF 3

2199/Photos/D09-3.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 10 - ANNOTATED PHOTOGRAPH 1 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 10 - ANNOTATED PHOTOGRAPH 1 OF 2

2199/Photos/D10-1.ai NAU

9/10

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 10 - ANNOTATED PHOTOGRAPH 2 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 10 - ANNOTATED PHOTOGRAPH 2 OF 2

2199/Photos/D10-2.ai NAU

10/11

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 11 - ANNOTATED PHOTOGRAPH 1 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 11 - ANNOTATED PHOTOGRAPH 1 OF 2

2199/Photos/D11-1.ai NAU

10/11

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 11 - ANNOTATED PHOTOGRAPH 2 OF 2

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 11 - ANNOTATED PHOTOGRAPH 2 OF 2

2199/Photos/D11-2.ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 1 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 1 OF 3

2199/Photos/D12-1.ai NAU

11/12

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 2 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 2 OF 3

2199/Photos/D12-2ai NAU

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 3 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 12 - ANNOTATED PHOTOGRAPH 3 OF 3

2199/Photos/D12-3.ai NAU

12/13

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 13 - ANNOTATED PHOTOGRAPH 1 OF 3

KETCHUM-CHALLIS HIGHWAY, ID PFH 26 (2)

SECTION 13 - ANNOTATED PHOTOGRAPH 1 OF 3

2199/Photos/D13-1.ai NAU

12/13

ENTIRE SLOPE. CONCENTRATED

EFFORTS REQUIRED IN HEAVY

SCALING AREA.

LEGEND

HEAVY SCALING AREA

NOT TO SCALE

KETCHUM-CHALLIS HIGHWAY, ID PFH…