GR_11-14_Geotech_Report_Segment_A-E.pdf

Geotechnical Report Historic Columbia River Highway

State Trail Hood River, Oregon

Report - June 2014

Columbia River Gorge Commission 1988

FEDERAL HIGHWAY

ADMINISTRATION

Report to:

CH2M Hill

2020 SW 4th Avenue

Portland, OR 97201

GEOTECHNICAL REPORT

HISTORIC COLUMBIA RIVER

HIGHWAY STATE TRAIL

SEGMENTS A TO E (WYETH TO MITCHELL CREEK)

June 2014

Submitted by:

Cornforth Consultants, Inc.

10250 SW Greenburg Road, Suite 111

Portland, OR 97223

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TABLE OF CONTENTS PAGE

1. INTRODUCTION

1.1 General

1.2 Scope of Work

1.2.1 Task 5.1.2 – Proposed Boring Locations for Exploration Report

1.2.2 Task 5.2 – Subsurface Exploration Work Report

1.2.3 Task 5.3 – Engineering Analysis and Geotechnical Report

1.2.4 Task 5.4 – Preliminary Retaining Wall Locations and Alternatives

2. SITE AND PROJECT DESCRIPTION

2.1 General

2.2 Trail Reaches

2.2.1 Harphan Creek Drainage – Segment A (13+00 to 26+50)

2.2.2 Existing Highway – Segment A (26+50 to 32+50)

2.2.3 Dog Hair Forest – Segment A (32+50 to 64+00)

2.2.4 Bin Walls 1 & 2 – Segment B (64+00 to 85+50)

2.2.5 Gap In Bin Walls – Segment B (85+50 to 86+90)

2.2.7 Bin Wall 3 – Segment B (86+90 to 91+50)

2.2.8 Shellrock Mountain – Segment B (91+50 to 97+50)

2.2.9 Existing Highway – Segment B (97+50 to 104+50)

2.2.10 Summit Creek Viaduct – Segments B & C (104+50 to 114+50)

2.2.11 Existing Highway – Segment C (114+50 to 136+50)

2.2.12 Bench Cut – Segment C (136+50 to 151+50)

2.2.14 Lindsey Creek Drainage – Segment D (151+50 to 155+00)

2.2.15 Dog Hair Forest – Segment D (155+00 to 172+00)

2.2.16 Warren Creek Drainage – Segment D (172+00 to 189+00)

2.2.17 Moderate Vegetated Talus – Segment D (189+00 to 195+00)

2.2.18 Steep Vegetated Talus – Segment D (195+00 to 219+00)

2.2.19 Viento Campground & Maintenance Yard – Segment E (300+36 to 313+50)

2.2.20 Existing Highway – Segment E (313+50 to 321+50)

2.2.21 I-84 Ditch/Existing Rock Cut Segment 1 – Segment E (321+50 to 326+00)

2.2.22 Existing Highway – Segment E (326+00 to 329+80)

2.2.23 I-84 Ditch/Existing Rock Cut Segment 2 – Segment E (329+80 to 334+75)

2.2.24 Existing Highway – Segment E (334+75 to 338+25)

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2.2.25 I-84 Ditch/Existing Rock Cut Segment 3 – Segment E (338+25 to 343+50)

2.2.26 Existing Highway – Segment E (343+50 to 348+25)

2.2.27 I-84 Ditch/Existing Rock Cut Segment 4 – Segment E (348+25 to 354+30)

2.2.28 Dog Hair Forest – Segment E (354+30 to 361+80)

2.2.29 Existing Highway – Segment E (361+80 to 366+00)

2.2.30 Rockfall Slopes/I-84 Ditch – Segment E (366+00 to 384+40)

2.2.31 Existing Highway – Segment E (384+40 to 388+00)

2.2.32 Perham Creek Drainage – Segment E (388+00 to 391+50)

2.2.33 Perham Meadow – Segment E (391+50 to 397+00)

2.2.34 I-84 Ditch/Existing Rock Cut Segment 5 – Segment E (397+00 to 405+80)

2.2.35 Existing Highway – Segment E (405+80 to 418+80)

2.2.36 Mitchell Creek Drainage – Segment E (418+80 to 426+08)

3. GEOLOGY

3.1 General

3.2 Geologic Setting

3.3 Regional Geology

3.4 Site Geology

3.4.1 Unconsolidated Geologic Units

3.4.2 Bedrock Geologic Units

3.4.3 Structural Geology

3.5 Geologic Hazards

3.5.1 Seismic Hazards

3.5.2 Volcanism

3.5.3 Landslide / Mass Movement

3.5.4 Debris Flows / Flooding

3.5.5 Talus

3.5.6 Rockfall

4. SURFACE RECONNAISSANCE

4.1 General

5. PRELIMINARY GEOTECHNICAL DESIGN RECOMMENDATIONS

5.1 General

5.2 Seismic Design Parameters

5.3 Harphan Creek Drainage – Segment A (13+00 to 26+50)

5.3.1 Anticipated Conditions

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5.3.2 Cut and Fill Slopes

5.3.3 Fill Materials

5.3.4 Wet Weather Construction

5.3.5 Subdrainage

5.3.6 Settlement

5.4 Dog Hair Forest – Segment A (32+50 to 64+00)

5.4.1 Anticipated Conditions

5.4.2 Cut and Fill Slopes

5.4.3 Fill Materials

5.4.4 Wet Weather Construction

5.4.5 Subdrainage

5.4.6 Settlement

5.4.7 Retaining Walls

5.5 Bin Walls 1 & 2 – Segment B (64+00 to 85+50)

5.5.1 Anticipated Conditions

5.5.2 Cut and Fill Slopes

5.5.3 Fill Materials

5.5.4 Wet Weather Construction

5.5.5 Subdrainage

5.5.6 Settlement

5.5.7 Retaining Walls

5.6 Gap in Bin Walls – Segment B (85+50 to 86+90)

5.6.1 Anticipated Conditions

5.6.2 Retaining Walls

5.6.3 Settlement

5.6.4 Fill Material

5.7 Bin Wall 3 – Segment B (86+90 to 91+50)

5.7.1 Anticipated Conditions

5.7.2 Cut and Fill Slopes

5.7.3 Fill Materials

5.7.4 Retaining Walls

5.7.5 Settlement

5.7.6 Wet Weather Construction

5.7.7 Subdrainage

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5.8 Shellrock Mountain – Segment B (91+50 to 97+50)

5.8.1 Anticipated Conditions

5.8.2 Cut and Fill Slopes

5.8.3 Fill Materials

5.8.4 Wet Weather Construction

5.9 Existing Highway – Segment B (97+50 to 104+50)

5.9.1 Anticipated Conditions

5.9.2 Cut and Fill Slopes

5.9.3 Fill Materials

5.9.4 Wet Weather Construction

5.10 Summit Creek Viaduct – Segments B & C (104+50 to 114+50)

5.10.1 Anticipated Conditions

5.10.2 Cut and Fill Slopes

5.10.3 Fill Materials

5.10.4 Wet Weather Construction

5.10.5 Retaining Walls

5.10.6 Settlement

5.10.7 Foundations

5.11 Bench Cut – Segment C (136+50 to 151+50)

5.11.1 Anticipated Conditions

5.11.2 Cut and Fill Slopes

5.12 Lindsey Creek Drainage – Segment D (151+50 to 155+00)

5.12.1 Anticipated Conditions

5.12.2 Cut and Fill Slopes

5.12.3 Fill Materials

5.12.4 Wet Weather Construction

5.12.5 Retaining Walls

5.12.6 Settlement

5.12.7 Dewatering & Excavation Shoring

5.13 Dog Hair Forest – Segment D (155+00 to 172+00)

5.13.1 Anticipated Conditions

5.13.2 Cut and Fill Slopes

5.13.3 Fill Materials

5.13.4 Wet Weather Construction

5.13.5 Retaining Walls

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5.13.6 Settlement

5.15 Warren Creek Drainage – Segment D (172+00 to 189+00)

5.15.1 Anticipated Conditions

5.15.2 Cut and Fill Slopes

5.15.3 Fill Materials

5.15.4 Settlement

5.15.5 Wet Weather Construction

5.15.6 Bridge at Warren Creek

5.15.7 Retaining Walls

5.15.8 Subdrainage

5.15.9 Dewatering & Excavation Shoring

5.16 Moderate to Steep Talus Slopes – Segment D (189+00 to 219+00)

5.16.1 Anticipated Conditions

5.16.2 Cut and Fill Slopes

5.16.3 Fill Materials

5.16.4 Settlement

5.16.5 Wet Weather Construction

5.16.6 Retaining Walls

5.17 Viento Campground & Maintenance Yard – Segment E (300+36 to 313+50)

5.17.1 Anticipated Conditions

5.17.2 Cut and Fill Slopes

5.17.3 Fill Materials

5.17.4 Wet Weather Construction

5.17.5 Retaining Walls

5.18 I-84 Ditch/Existing Rock Cut Segment 1 – Segment E (321+50 to 326+00)

5.18.1 Anticipated Conditions

5.18.2 Cut and Fill Slopes

5.18.3 Fill Materials

5.18.4 Retaining Walls

5.18.5 Wet Weather Construction

5.18.6 Subdrainage

5.19 I-84 Ditch/Existing Rock Cut Segment 2 – Segment E (329+80 to 334+75)

5.19.1 Anticipated Conditions

5.19.2 Cut and Fill Slopes

5.19.3 Fill Materials

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5.19.4 Wet Weather Construction

5.19.5 Retaining Walls

5.19.6 Subdrainage

5.20 I-84 Ditch/Existing Rock Cut Segment 3 – Segment E (338+25 to 343+50)

5.20.1 Anticipated Conditions

5.20.2 Cut and Fill Slopes

5.20.3 Fill Materials

5.20.4 Retaining Walls

5.20.5 Settlement

5.20.6 Wet Weather Construction

5.20.7 Subdrainage

5.21 I-84 Ditch/Existing Rock Cut Segment 4 – Segment E (348+25 to 354+30)

5.21.1 Anticipated Conditions

5.21.2 Cut and Fill Slopes

5.21.3 Fill Materials

5.21.4 Wet Weather Construction

5.21.5 Subdrainage

5.22 Dog Hair Forest – Segment E (354+30 to 361+80)

5.22.1 Anticipated Conditions

5.22.2 Cut and Fill Slopes

5.22.3 Fill Materials

5.22.4 Retaining Walls

5.22.5 Settlement

5.22.6 Wet Weather Construction

5.22.7 Subdrainage

5.23 Rockfall Slopes/I-84 Ditch – Segment E (366+00 to 384+40)

5.23.1 Anticipated Conditions

5.23.2 Cut and Fill Slopes

5.23.3 Fill Materials

5.23.4 Retaining Walls

5.23.5 Wet Weather Construction

5.23.6 Subdrainage

5.24 Perham Creek Drainage to Perham Meadow– Segment E (388+00 to 397+00)

5.24.1 Anticipated Conditions

5.24.2 Cut and Fill Slopes

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5.24.3 Fill Materials

5.24.4 Perham Creek Bridge

5.24.5 Retaining Walls

5.24.6 Settlement

5.24.7 Wet Weather Construction

5.24.8 Subdrainage

5.25 I-84 Ditch/Existing Rock Cut Segment 5 – Segment E (397+00 to 405+80)

5.25.1 Anticipated Conditions

5.25.2 Cut and Fill Slopes

5.25.3 Fill Materials

5.25.4 Wet Weather Construction

5.25.5 Subdrainage

5.26 Mitchell Creek Drainage – Segment E (418+80 to 426+08)

5.26.1 Anticipated Conditions

5.26.2 Cut and Fill Slopes

5.26.3 Fill Materials

5.26.4 Wet Weather Construction

5.27 Bin Wall Condition Assessment

5.27.1 Bin Wall #1

5.27.2 Bin Wall #2

5.27.3 Bin Wall #3

5.27.4 Corrosion Testing

6. CONSTRUCTION CONSIDERATIONS

6.1 General

6.2 Existing HCRH Pavement

6.3 One Way Access

6.4 Drill Bench for Cut Wall

6.5 Temporary Cut for High-Side Walls

6.6 Material Source for Rockeries

6.7 Scaling and Rockfall Protection

6.8 Construction Surcharges

6.9 Groundwater Management

6.10 Obstructions

6.11 Historic Masonry Walls

6.12 Drilling and Grouting in Talus

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7. REFERENCES

LIST OF FIGURES

1. Geology Map

2. Geologic Hazards – Harphan Creek to Shellrock Mountain

3. Geologic Hazards – Shellrock Mountain to Starvation Creek

4. Geologic Hazards – Starvation Creek to Viento Creek

5. Geologic Hazards – Viento Creek to Mitchell Point

6. Typical Section Low Side MSE Wall

7. Typical Section High Side Soldier Pile Wall

8. Typical Section High Side Soil Nail Wall

9. Typical Section High Side Rockery

10. Typical Section High Side MSE Wall

11. Typical Section High Side Rockery

12. Typical Section Low Side Soldier Pile Wall

13. Typical Section Mass Concrete Fill

14. Typical Section MSE Wall At Bin Wall 3

15. Typical Section Viaduct Approach Fill

16. Typical Section MSE Walls At Lindsey Creek

17. Typical Section MSE Wall Sta. 155 to 165

18. Typical Section MSE Wall at Historic Ovens

19. Segment E High Side Soldier Pile Wall

20. Viento High Side Soil Nail Wall

21. Typical Section MSE Wall at Rock Cut

22. Segment E Low Side MSE Wall

23. Typical Section MSE Wall at Perham Creek

APPENDICES

Appendix A Geologic Narrative prepared by CH2M Hill

Appendix B Corrosion Testing Narrative prepared by CH2M Hill

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EXECUTIVE SUMMARY

Western Federal Lands Highway Division (WFLHD) is leading the design of a segment of the

Historic Columbia River Highway (HCRH) Trail between Wyeth and Hood River. This report presents concept-level geotechnical design recommendations for the portions of the trail between

Wyeth and Starvation Creek Trailhead (Segments A-D) and the portion between Viento Trailhead and Mitchell Creek (Segment E).

A geologic review and surface reconnaissance indicate the proposed alignment is underlain by primarily granular soils. It is anticipated that surface soils, excluding topsoil, would be suitable for reuse as embankment fill. Soils in the western reaches of the proposed alignment contain sufficient fines to be considered moisture sensitive. In general, soils in the eastern reaches are generally coarser with little fine fraction. Exceptions to this generalization occur near the Viento Trailhead, Perham

Creek and Mitchell Creek, where moisture-sensitive materials were encountered. Shallow groundwater is anticipated in western portions of the proposed alignment. It is anticipated that groundwater will impact design of cuts as well as grading operations.

New trail segments are located along Interstate 84 and on the slopes to the south. Embankments and retaining walls are proposed to maintain design grades and enhance user experience along the proposed alignment. Stability and construction impacts of retaining walls were evaluated using information available from a literature review and a surface reconnaissance of the site. In general, gravity retaining structures (rockeries and MSE walls) located on steep slopes have static and seismic factors-of-safety lower than AASHTO standards. Structural walls (soldier pile and soil nail) could be designed to achieve AASHTO standards for global stability. Stability of temporary cuts will dictate what type of retaining wall is feasible. Subsurface explorations and test cuts are planned to aid in the evaluation of temporary cut stability.

Structures are proposed at the Summit Creek Viaduct and the Warren Creek and Perham Creek crossings. Shallow foundations appear feasible at these locations. Shallow groundwater at Warren

Creek and Perham Creek will likely require dewatering and excavation shoring. Shallow bedrock at

Summit Creek will likely require tiedown anchors to resist uplift generated by overturning moments.

A bench cut up to 45 feet tall is proposed west of Lindsey Creek. Surface exposures suggest the cut is feasible and could generate a large volume of quality fill material. Uncertainties regarding the depth of overburden and structural discontinuities in the rock make it difficult to anticipate the footprint or visual impacts of the bench cut at this time. Temporary rockfall protection measures are likely to be needed during blasting to prevent rocks from impacting I-84.

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1. INTRODUCTION

1.1 General

The Federal Highway Administration Western Federal Lands Highway Division (WFLHD) has retained CH2M Hill to provide biological baseline reconnaissance and preliminary trail design for the

Historic Columbia River Highway State Trail Project. CH2M Hill retained Cornforth Consultants, Inc. to assist with geotechnical aspects of the preliminary trail design for Trail Segments A through E

(Wyeth to Mitchell Creek). This report presents the results of a surface reconnaissance of the proposed trail alignment and provides concept-level geotechnical design recommendations for retaining structures and stream crossing structures. Recommendations contained herein are intended to support conceptual civil and structural design efforts. Additional analyses will be necessary as civil, geotechnical, and structural designs are refined.

1.2 Scope of Work

Detailed descriptions of work tasks are outlined in the Statement of Work for Task Order T-13-001 of IDIQ Contract DTFH70-10-D-00020 dated February 26, 2013. The following paragraphs summarize geotechnical elements included in the Statement of Work.

1.2.1 Task 5.1.2 – Proposed Boring Locations for Exploration Report

This task involves performing a surface reconnaissance of the proposed alignment and developing a plan of proposed subsurface explorations. Objectives of the plan include locating explorations and access routes in a manner which provides data necessary for design and minimizing environmental impact.

1.2.2 Task 5.2 – Subsurface Exploration Work Report

The proposed exploration plan developed under Task 5.1.2 is summarized in a document suitable for review by regulators with jurisdiction over the area.

1.2.3 Task 5.3 – Engineering Analysis and Geotechnical Report

This task involves preparing a geotechnical report outlining concept-level design recommendation for retaining structures, bridges, cuts, and fills proposed for the project.

1.2.4 Task 5.4 – Preliminary Retaining Wall Locations and Alternatives

Based on the preliminary trail alignment and grade prepared by CH2M Hill, retaining wall options are to be identified for specific portions of the proposed alignment. Retaining wall options are intended to be consistent with aesthetic criteria established in the Historic Columbia River Highway

State Trail Guidelines. This task also includes a condition survey of three existing metal bin retaining walls adjacent to the proposed trail alignment.

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2. SITE AND PROJECT DESCRIPTION

2.1 General

The Historic Columbia River Highway (HCRH) was constructed between 1913 and 1922 and was

America’s first scenic highway. By the late 1940s and early 1950s, the initial construction of a water-level route that would become I-84 obliterated many sections of the HCRH, and left upland sections disconnected. The Columbia River Gorge National Scenic Area Act of 1986 directed the

State of Oregon to connect the abandoned sections of the HCRH as a pedestrian and cyclist trail.

Since 1987, the Oregon Department of Transportation has been working with stakeholders including the HCRH Advisory Committee, Oregon Parks and Recreation Department, the State Historic

Preservation Office, and Travel Oregon to restore the highway.

The HCRH State Trail Plan focuses on 11 miles of the trail between Exit 51 on I-84 (Wyeth) and

Ruthton Park. The proposed alignment is subdivided into the following segments:

Segment A – Wyeth to Shellrock Mountain

Segment B – Shellrock Mountain to Summit Creek

Segment C – Summit Creek to Lindsey Creek

Segment D – Lindsey Creek to Starvation Creek

Segment E – Viento to Mitchell Creek

Segment F – Mitchell Creek to Mitchell Point Tunnel

Segment G – Mitchell Point to Ruthton Point

Segment H – Ruthton Point to Ruthton Park

An overview of the proposed trail alignment is shown on the Geology Map in Figure 1. More detailed views of the proposed alignment are presented in Figures 2 through 5. Detailed plans of the trail showing limits of proposed cuts, fills, retaining walls, and stream crossing structures have been prepared by CH2M Hill’s roadway design team. The detailed plans are referenced in this report, but have been submitted to WFLHD under separate cover.

2.2 Trail Reaches

Segments A through E were subdivided into reaches with similar geologic conditions, topographic features, or proposed improvements. The following sections describe the existing conditions and the improvements proposed for the individual trail reaches.

2.2.1 Harphan Creek Drainage – Segment A (13+00 to 26+50)

Alignment Overview. The proposed trail would begin near 13+00 and meander east through the

Harphan Creek Drainage. The ground surface generally slopes down to the east and north between 5 and 10 degrees from horizontal. The area is densely vegetated with berry canes and medium-sized deciduous and evergreen trees. The proposed alignment encounters an existing embankment near

17+00 and runs east along its crest to approximately 19+50. The embankment varies between 10 and

15 feet tall and has side slopes near 2 Horizontal to 1 Vertical (2H:1V). Between 19+50 and 22+00, the proposed trail runs over a small ridge located at the top of the existing I-84 cut slope. Between

22+00 and 24+50, the proposed alignment traverses a low, flat area vegetated with grass. Near

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24+50, the proposed trail alignment climbs 15 vertical feet onto what appears to be a flood terrace and runs eastward through dense forest. The terrace has side slopes between 1H:1V and 1.5H:1V.

Near 26+50, the proposed alignment transitions to an existing section of HCRH.

Proposed Improvements. Embankment fills up to 5 feet with 3H:1V side slopes are proposed between the trailhead and the existing embankment. Between 17+00 and 19+50 the trail is located approximately at the top of the existing embankment. East of the existing embankment, cuts and fills up to 8 feet tall with 2H:1V side slopes are proposed until the alignment reaches the existing HCRH near 26+50.

2.2.2 Existing Highway – Segment A (26+50 to 32+50)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

The roadway bench varies between 15 and 20 feet wide. There is a 20-foot tall, 1.5H:1V slope below the bench and a long, 2H:1V slope above it. The area on either side of the bench is densely vegetated with medium-sized evergreen trees.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail.

Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface.

2.2.3 Dog Hair Forest – Segment A (32+50 to 64+00)

Alignment Overview. At 32+50, the existing HCRH section ends and the proposed alignment descends the slope toward I-84. There are existing horizontal drain pipes exiting the slope below the proposed trail alignment between 33+20 and 33+40. The trail reaches the shoulder of I-84 near

35+00 and runs along the toe of a slope that varies between 1.5H:1V and 1H:1V to approximately

40+00. This slope is densely vegetated with medium-sized evergreen trees, and appears to be a cut slope created during construction of I-84. At 40+00, the trail joins the alignment of an existing BPA service road. The trail veers south of the service road into the forest near 42+00. Between 42+00 and 44+50, the trail crosses ground that slopes down to the northwest at approximately 8H:1V. This portion of the proposed alignment is moderately vegetated with medium to large evergreen and deciduous trees. At 44+50 the trail begins traversing the face of a 2H:1V slope that is densely vegetated with small to medium evergreen trees. At 64+00 the trail encounters the first of three steel bin retaining walls.

Proposed Improvements. At the beginning of this reach a 1.5H:1V cut slope is proposed for the high side of the trail, although a retaining wall may be required to minimize the visual impact of the cut.

Embankment fills up to 7 feet with 3H:1V side slopes are proposed between 35+00 and 40+50. In general, these fills are along the alignment of the existing I-84 ditch. Cuts and fills less of than 3 feet are proposed between 40+50 and 44+50 where the trail follows the existing BPA service road and the slope below the service road. Embankments with 3H:1V side slopes are proposed for fill areas, and short retaining structures are proposed for cut areas. Between 44+50 and 64+00 the trail traverses across the face of an existing 2H:1V cut slope. A series of alternating high-side cut retaining walls and low-side fill retaining walls are proposed to support the trail through this reach. The exposed height of these walls is generally less than 10 feet. Near 61+50 the low-side retaining wall transitions to a 2H:1V embankment fill that reaches a maximum height of 10 feet near 64+00.

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2.2.4 Bin Walls 1 & 2 – Segment B (64+00 to 85+50)

Alignment Overview. At 64+00, the proposed trail begins running along the top of an existing steel bin retaining wall. Bin Wall 1 runs between 64+15 and 77+50 and varies between 3 and 13 feet tall.

There is a 15 to 20-foot wide bench on top of the bin wall that acts as rockfall catchment for the tall unvegetated talus slope to the south. There is a vertical, post-and-net rockfall catchment fence at the top of the bin wall. The bench at the top of the bin wall is sparsely vegetated with small evergreen trees and brush. The talus slope above the bin wall stands at approximately 36 degrees from horizontal and consists predominantly of 8- to 16-inch, angular rock fragments with little or no fine fraction. There is a section of historic masonry wall at the base of the talus slope between 69+30 and

73+20.

Between 77+50 and 80+00, the trail crosses a narrow, flat swale at the base of the talus slope. There is no bin wall in this section. The post-and-net rockfall catchment fence extends beyond the eastern end of Bin Wall 1. This portion of the proposed alignment is densely vegetated with medium-sized evergreen trees.

At 85+00, the trail encounters the second of three existing steel bin retaining walls. Bin Wall 2 extends from 80+00 to 85+50 and varies between 3 and 22 feet tall. There is a 20-foot wide bench on top of the bin wall that contains rockfall from the talus slope. Bin Wall 2 also has a rockfall catchment fence on the north side of the bench. The bench between the talus slope and the bin wall is sparsely vegetated with small evergreen trees and brush. The talus slope above Bin Wall 2 is similar to that above Bin Wall 1, but stands at approximately 38 degrees. At 85+50, Bin Wall 2 ends, but the rockfall catchment fence continues along the back of an existing concrete barrier.

Proposed Improvements. An embankment fill 9 feet high with 2H:1V side slopes is proposed at the beginning of this reach as the trail grade rises up onto Bin Wall 1. Fills less than 5 feet are proposed for the rest of the reach. In general, the fill thickness is zero on the north side of the trail next to the bin wall and increases to maximum thickness on the south side of the trail. Retaining walls or rockeries are proposed to retain the north side of the fill where there is a historic masonry wall.

Where no historic wall is present, conventional embankments would be used on the south side of the trail. A new rockfall catchment fence would be constructed between the trail and the talus slope. It has not been determined if the fence would be located upslope or downslope of the historic masonry wall.

2.2.5 Gap In Bin Walls – Segment B (85+50 to 86+90)

Alignment Overview. Between 85+50 and 86+90 the trail descends from the top of Bin Wall 2 along the base of a near-vertical rock cliff. There is an existing 10- to 12-foot wide rock bench approximately 10 to 15 vertical feet above the level of the ditch alongside I-84. This section is sparsely vegetated with small evergreen trees.

Proposed Improvements. A retaining wall is proposed to support the trail in this reach. The face of the retaining wall would be located approximately 5 feet behind the alignment of the existing bin walls to the east and west of this reach.

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2.2.7 Bin Wall 3 – Segment B (86+90 to 91+50)

Alignment Overview. Beginning at 86+90 the trail runs along the top of an existing metal bin retaining wall. Bin Wall 3 extends from 86+90 to 91+50 and varies between 6 and 17 feet tall.

There is a 20- to 25-foot wide bench behind the bin wall that serves as catchment for rockfall from the talus slope to the south. The bench is densely vegetated with medium-sized evergreen trees. The western half of Bin Wall 3 has a rockfall fence located along the north side of the catchment bench.

There is a section of historic masonry wall on the southern side of the rockfall catchment bench between 88+70 and 90+00.

Proposed Improvements. Bin Wall 3 is approximately 6 feet tall at the beginning of this reach. A retaining wall up to 12 feet tall is proposed to support the trail near 86+90. This wall would be located immediately behind the existing bins, but likely will impact the southern portion of the bins.

The height of the retaining wall quickly reduces to zero near 89+00 where the trail matches into the existing grade behind the taller portion of Bin Wall 3. From 89+00 to the end of the reach, embankment fills between 0 and 2 feet are proposed. In a couple locations, cuts up to 3 feet tall are proposed on the left side of the trail. These cuts may impact the existing bins of Bin Wall 3.

2.2.8 Shellrock Mountain – Segment B (91+50 to 97+50)

Alignment Overview. East of Bin Wall 3 the proposed trail alignment runs along the toe of a steep talus slope. This eastern flank of Shellrock Mountain is moderately to densely vegetated with medium-sized evergreen trees and stands approximately 36 degrees from horizontal.

Proposed Improvements. Embankment fills up to 2 feet high with 3H:1V side slopes are proposed in this reach.

2.2.9 Existing Highway – Segment B (97+50 to 104+50)

Alignment Overview. Near 97+50 the trail reaches a segment of existing HCRH that extends to approximately 104+50. The existing HCRH runs along the toe of the eastern flank of Shellrock

Mountain. The areas on either side of the HCRH section are densely vegetated with medium-sized evergreen trees and brush. There is evidence of recent rockfall at several locations along this reach of the trail.

Proposed Improvements. Embankment fills up to 2 feet high with 3H:1V side slopes are proposed in this reach.

2.2.10 Summit Creek Viaduct – Segments B & C (104+50 to 114+50)

Alignment Overview. At 104+50 the trail is located at the base of a rock outcrop that forms the western boundary of Summit Creek, a seasonal stream. Between 105+25 and 107+25 the trail crosses a flat, low-lying area at the bottom of the Summit Creek Drainage. Between 107+25 and

114+50 the trail is located at the base of the MP 53 rock cut. The MP 53 rock cut was modified by

ODOT in the 1980s to prevent rockfall from reaching I-84. Existing rockfall mitigation structures include a free-standing gabion barrier located on a bench approximately 60 feet above I-84 and a 12-foot high concrete bin wall located immediately north of the proposed trail alignment. The area between the toe of the rock cut and the concrete bin wall is sparsely vegetated with small trees and brush. Near 113+25 the proposed trail veers south and ascends a 1H:1V slope approximately 45

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vertical feet to a section of existing HCRH. The slope is densely vegetated with medium to large evergreen trees and low-lying brush.

Proposed Improvements. Fills up to 12 feet with 3H:1V side slopes are proposed at the west end of this reach as the trail grade is raised to transition to an elevated viaduct structure. Near 107+15 the trail reaches the existing free-standing concrete bin wall. This bin wall was used as a rockfall catchment barrier during construction of the MP 53 rock cut in the 1980s. ODOT elected to leave the bin wall in place following the construction effort to provide additional rockfall protection for I-84.

As part of the proposed trail construction, the existing bin wall would be removed, and a new wall would be constructed to retain the north side of the viaduct approach fill. Near 109+00 the trail transitions onto an elevated viaduct structure. A retaining wall would retain the east end of the viaduct abutment fill. The elevated viaduct would be supported on oversized footings or more modestly-sized footings with anchors to develop uplift resistance.

2.2.11 Existing Highway – Segment C (114+50 to 136+50)

Alignment Overview. Near 114+50 the trail transitions from viaduct structure onto a section of existing HCRH. The existing HCRH winds across a gently sloping ridge between the MP 53 rock cut and the Lindsey Creek drainage. There are several near-vertical to overhanging rock slopes on the south side of the HCRH. Some of these show signs of recent rockfall activity. The areas on either side of the HCRH are densely vegetated with medium-sized deciduous and evergreen trees.

Near 136+50 the existing HCRH grade ends at a steep rock outcrop.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail.

Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface.

2.2.12 Bench Cut – Segment C (136+50 to 151+50)

Alignment Overview. At approximately 136+50 the proposed alignment encounters a near-vertical rock cliff. The cliff forms the southwestern face of a ridge that trends northwest to southeast. There is approximately 60 feet of relief between the HCRH and the top of the ridge. The northeastern face of the ridge slopes down to the northeast between 2H:1V and 4H:1V. There is a steep slope in the middle of the northeastern face that separates two gently sloping benches that measure approximately

40 to 50 feet in width. The steep slope appears to be the eroded edge of an upper basalt flow. Both benches are vegetated primarily with grasses and low-lying brush. The proposed trail alignment roughly follows the upper bench. Near 143+50 the alignment enters the tree line on the south side of the upper bench. Between 143+50 and 151+50 the trail traverses a densely wooded slope that slopes down to the northeast between 1.5H:1V and 3H:1V. Between 146+00 and 151+00 the trail is located on or slightly downslope of an existing skid road. Near 151+00 the trail descends a 1H:1V slope that forms the western edge of the Lindsey Creek drainage.

Proposed Improvements. A bench cut with a base width between 20 and 40 feet is proposed in this reach. The height of the cut is variable, but reaches a maximum near 45 feet on the western end of the reach. The depth of the cut decreases moving from west to east.

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2.2.14 Lindsey Creek Drainage – Segment D (151+50 to 155+00)

Alignment Overview. This reach of the trail roughly follows the shoulder of I-84 across the relatively flat base of the Lindsey Creek drainage. There is an existing concrete box culvert at 152+15. The

Lindsey Creek drainage is moderately vegetated with medium to large deciduous trees and low-lying brush.

Proposed Improvements. Fills up to 3 feet with 3H:1V side slopes are proposed in this reach.

Retaining walls are proposed on the east and west sides of the existing concrete box culvert that carries Lindsey Creek under I-84. The trail is planned to be located on top of the box culvert.

2.2.15 Dog Hair Forest – Segment D (155+00 to 172+00)

Alignment Overview. At the eastern edge of the Lindsey Creek drainage the trail veers toward I-84 and runs along the base of a 1H:1V cut slope for approximately 450 feet. The cut slope is densely vegetated with small to medium evergreen trees. Between 159+50 and 161+00 the trail veers into a small drainage before returning to the shoulder of I-84. Between 161+00 and 170+00 the trail runs along the base of a densely wooded 1.5H:1V cut slope. At 170+00 the trail veers south and joins the alignment of an existing BPA service road and runs along the service road to the end of the reach near 172+00.

Proposed Improvements. Between 155+00 and 158+50, a low-side fill retaining wall up to 6 feet tall is proposed. At 158+50 the retaining wall transitions to an embankment fill with 3H:1V side slopes.

The embankment extends east to 161+70 where it transitions back to a low-side fill retaining wall.

The low-side retaining wall is up to 5 feet high and extends from 161+70 to 165+60. From 165+60 to the end of the reach, embankment fills less than 4 feet high with 3H:1V side slopes are proposed.

A high-side cut retaining wall up to 12 feet tall is proposed between 158+00 and 159+50 where the trail veers south into a narrow drainage. Between 160+50 and 161+50 high-side cut slopes of 2H:1V are proposed as the trail exits the narrow drainage and returns to the shoulder of I-84.

2.2.16 Warren Creek Drainage – Segment D (172+00 to 189+00)

Alignment Overview. Between 172+00 and 175+50 the trail follows what appears to be an old alluvial terrace deposit. The top of the terrace is approximately 15 feet above the bottom of the drainage. The slope between the top of the terrace and the bottom of the drainage is approximately

1.5H:1V. At 175+50 the trail descends off of the terrace deposit into the bottom of the drainage.

The bottom of the drainage slopes gently down to the west between 2 and 5 degrees from horizontal.

The basin is densely wooded with medium to large deciduous and evergreen trees. The proposed alignment crosses Warren Creek near 178+50. Warren Creek flows in a shallow, narrow channel 10 to 20 feet wide and 2 to 3 feet below the surrounding ground. Near 184+00 the trail ascends out of the bottom of the basin to follow the base of a vegetated talus slope. The proposed alignment follows an existing footpath to the end of the reach at 189+00. The areas on either side of the footpath are densely wooded with large evergreen trees.

Proposed Improvements. Between 172+50 and 173+50 a low-side fill retaining wall is proposed to be founded on the steep slope below the terrace bench. Once the trail descends off the terrace bench, fills up to 12 feet tall with side slopes varying between 2H:1V and 3H:1V are proposed. Retaining

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walls up to 5 feet high are proposed to retain abutment fills for the Warren Creek Bridge. The bridge is anticipated to be a single-span structure supported on shallow foundations.

2.2.17 Moderate Vegetated Talus – Segment D (189+00 to 195+00)

Alignment Overview. The proposed trail roughly follows an existing footpath between 189+00 and

192+00 as it approaches I-84. The footpath follows the base of a densely wooded slope that drops down to the northwest between 2H:1V and 4H:1V. Near 192+00 the trail begins to run along the shoulder of I-84 and the off ramp to the Starvation Creek Trailhead. There is a densely vegetated talus slope south of the trail that drops to the north at approximately 1.5H:1V.

Proposed Improvements. Fills up to 10 feet high are proposed in this reach of the trail. Embankment slopes of 3H:1V are proposed for most fills. Near 190+50 there are historic ovens approximately 60 feet left of trail centerline. A low-side fill retaining wall up to 8 feet tall is proposed in the vicinity of the ovens to confine trail users to the trail.

2.2.18 Steep Vegetated Talus – Segment D (195+00 to 219+00)

Alignment Overview. Between 195+00 and 219+00 the trail follows the base of a steep, vegetated talus slope that varies between 2H:1V and 1H:1V. The existing trail is supported on a rubble rockery approximately 4 feet high between 198+00 and 200+50. Near 210+50 there is a 10-foot-tall berm between the trail and the toe of the talus slope. The berm has side slopes slightly less than 1H:1V and appears to have been constructed to contain rockfall originating from the cliffs at the top of the talus slope. The rockfall berm extends to approximately 216+00. From 216+00 to 219+00 the proposed trail traverses the base of a near-vertical, 80-foot-tall rock cliff.

Proposed Improvements. This reach of the trail would roughly follow the existing line and grade of the Starvation Ridge Trail #414. In general, proposed cuts and fills are less than 2 feet high. There is a short section near 217+00 where a fill of 5 feet is proposed. Where additional width is required, embankment slopes of 3H:1V are proposed. Between 208+00 and 215+00 high-side cut walls are proposed. In general these cut walls are less than 2 feet high and are located at the toe of the talus slope or rockfall catchment berm.

2.2.19 Viento Campground & Maintenance Yard – Segment E (300+36 to 313+50)

Alignment Overview. Segment E of the proposed trail would begin at 300+36 and run east along the edge of the existing parking lot and maintenance road at Viento Campground. The trail crosses the existing maintenance road and follows the northern boundary of the maintenance yard near 308+00.

East of the maintenance yard the proposed trail merges with an existing 4-wheel drive access road and runs over a small ridge, near 310+00. The trail matches into the existing HCRH segment at

313+50.

Proposed Improvements. Rockeries up to 6.5 feet tall are proposed along the south side of the Viento parking lot. A 7-foot cut with 1.5H:1V side slopes is proposed at the east end of the parking lot where the trail curves north along Viento Creek. A through cut up to 20 feet tall is proposed along the 4-wheel drive road with side slopes of 1.5H:1V on the left and rockery or soldier pile wall on the right. Embankment fills up to 3 feet with 3H:1V side slopes are proposed from the end of the through cut to 313+50 where the trail merges into existing HCRH.

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2.2.20 Existing Highway – Segment E (313+50 to 321+50)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

There is a 15-foot tall rock outcrop near Station 314+00 LT, and a tall vegetated talus slope near

314+00 RT. Debris flow deposits up to 2 feet thick were observed covering the existing highway from 317+75 to 318+75.

Proposed Improvements. No new structures are proposed for this reach of the trail. Regrading will be required near 318+00 where debris flow deposits have covered the existing highway. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.21 I-84 Ditch/Existing Rock Cut Segment 1 – Segment E (321+50 to 326+00)

Alignment Overview. The proposed trail descends an existing 1.5H:1V cut slope at 321+80 to reach the shoulder of I-84 at 323+50. The trail then runs along the shoulder of the Interstate at the toe of a

300-foot-tall rock slope. At 325+00 the trail veers south around the edge of the rock slope to match into a segment of existing HCRH at 326+00.

Proposed Improvements. A high-side rockery or soldier pile wall is proposed from 321+80 to

322+80 with a maximum height of 10 feet. Embankment fills up to 5 feet with side slopes between

3H:1V and 2H:1V are proposed from 322+80 to 324+40. A second high-side rockery with a maximum height of 4 feet is proposed from 325+20 to 325+50.

2.2.22 Existing Highway – Segment E (326+00 to 329+80)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail.

Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.23 I-84 Ditch/Existing Rock Cut Segment 2 – Segment E (329+80 to 334+75)

Alignment Overview. The proposed trail runs along the shoulder of I-84 near the toe of an existing

200-foot-tall rock slope that varies between 1.5H:1V and 0.5H:1V. The trail begins to veer off the shoulder at 333+60 and matches a segment of existing HCRH at 334+75.

Proposed Improvements. High-side rockeries with a maximum height of 3 feet are proposed from

330+20 to 330+50 and from 334+10 to 334+50, where the trail clips the toe of the existing rock slope. Between the two short rockeries, the trail is supported on embankments fills up to 5 feet high.

Embankment side slopes vary between 4H:1V and 3H:1V.

2.2.24 Existing Highway – Segment E (334+75 to 338+25)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

There is approximately 300 cubic yards of stripped pavement and rock rubble stockpiled on the existing highway at 337+75.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail, except for removal of the waste stockpile at 337+75. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

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2.2.25 I-84 Ditch/Existing Rock Cut Segment 3 – Segment E (338+25 to 343+50)

Alignment Overview. The proposed trail descends along a 2H:1V vegetated talus slope that transitions to rock outcrop at 339+00 before reaching the Interstate shoulder at 339+80. The trail runs along the shoulder at the toe of a tall rock slope from 339+80 to 341+50. The trail curves to the south around the edge of the rock slope at 341+50 and climbs to reach an existing HCRH rock cut at

342+40. The trail matches into a segment of existing HCRH near 343+50.

Proposed Improvements. A through cut with a maximum height of 10 feet is proposed where the trail descends an existing 2H:1V vegetated talus slope from 338+30 to 338+80. The through cut would include a 2H:1V cut slope on the left and a high-side rockery or soldier pile wall on the right.

A 13-foot-tall, 1.5H:1V cut slope is proposed on the high side of the trail from 338+80 to 339+40 where the vegetated talus transitions to rock. A low-side MSE wall with a maximum height of 13 feet and 3H:1V inboard fill slopes is proposed from 339+10 to 341+50 along the Interstate shoulder. A high-side 1.5H:1V cut with a maximum height of 11 feet is proposed near 342+00 where the trail veers away from the Interstate. A through cut is proposed from 342+40 to 343+10 where the trail ascends to match into a section of existing HCRH. The through cut would include a high-side rockery or soldier pile wall with a maximum height of 11 feet and a low-side 1.5H:1V cut slope 7 feet high. The trail matches into a segment of existing highway at 343+50.

2.2.26 Existing Highway – Segment E (343+50 to 348+25)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail, except for removal of stockpiled soil debris near 344+00. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.27 I-84 Ditch/Existing Rock Cut Segment 4 – Segment E (348+25 to 354+30)

Alignment Overview. The proposed trail is located in the Interstate ditch and follows the toe of an existing 100-foot-tall rock slope.

Proposed Improvements. The proposed trail in this area is to be raised up to 5 feet above grade with side slopes that vary from 4H:1V to 3H:1V.

2.2.28 Dog Hair Forest – Segment E (354+30 to 361+80)

Alignment Overview. The proposed trail begins to ascend across an existing 1H:1V vegetated talus cut slope at 354+30. The trail runs parallel to the Interstate along the existing cut slope to 359+50, where it descends again to the Interstate shoulder at 361+00. The trail curves to the south at 361+00 and matches into a segment of existing HCRH at 361+80.

Proposed Improvements. At the end of the existing rock cut at 354+30 the proposed trail cuts across the existing 1H:1V cut slope with the centerline approximately at grade. The cut on the high-side of the trail would be retained by a rockery or soldier pile wall with a maximum height of 8 feet. Low-side MSE walls founded on the existing cut slope with a maximum height of 10 feet are proposed from 354+20 to 359+80. Cuts up to 10 feet high with slopes ranging from 1.5H:1V to 2H:1V are proposed on the left and right side of the trail from 360+30 to 361+80 where the alignment curves south to meet with an existing segment of HCRH.

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2.2.29 Existing Highway – Segment E (361+80 to 366+00)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.30 Rockfall Slopes/I-84 Ditch – Segment E (366+00 to 384+40)

Alignment Overview. After leaving the existing highway at 366+00, the proposed trail traverses an existing vegetated talus slope, ranging from 4H:1V to 1H:1V, before descending to the Interstate shoulder at 370+50. From 370+50, the proposed trail follows the toe of an existing rock cut in the highway shoulder to 383+50 where it veers south to meet a section of existing HCRH at 384+00.

Proposed Improvements. The proposed trail in this section starts with a slight fill condition less than

2 feet high at 366+00. The trail transitions into a cut with 2H:1V high-side cut slopes up to 8 feet as it traverses the vegetated talus slope from 366+50 to 369+40. A high-side rockery is proposed as the trail descends again toward the Interstate shoulder from 369+40 to 370+20. Small cuts and fills of less than 5 feet with 3H:1V side slopes are proposed along the Interstate ditch from 370+00 to

383+50. A high-side rockery with a maximum height of 3 feet is proposed from 383+50 to 383+90.

Low-side fills up to 3 feet with 3H:1V side slopes are proposed from 383+00 to 384+50. A 7-foot-tall 1.5H:1V cut slope is proposed to extend from the east end of the high-side rockery at 383+90 to approximately 384+40.

2.2.31 Existing Highway – Segment E (384+40 to 388+00)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.32 Perham Creek Drainage – Segment E (388+00 to 391+50)

Alignment Overview. After leaving the existing highway at 388+00, the proposed trail intersects

Perham Creek at 389+20. After crossing Perham Creek, the trail emerges from a wooded area near

391+50 and runs parallel to the Interstate.

Proposed Improvements. An abutment fill up to 5 feet high is proposed for the west side of Perham

Creek bridge with an MSE wall on the left and a 3H:1V fill slope on the right. Abutment fills up to 6 feet high with 3H:1V side slopes are proposed for the east approach to Perham Creek Bridge. The

Perham Creek Bridge is planned to be a single-span structure founded on shallow footings.

2.2.33 Perham Meadow – Segment E (391+50 to 397+00)

Alignment Overview. The proposed trail runs through a flat meadow roughly parallel with the

Interstate until returning to the Interstate ditch at 397+00.

Proposed Improvements. The proposed trail would traverse the meadow near existing grade, with slight cuts and fills having side slopes ranging from 3H:1V to 4H:1V.

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2.2.34 I-84 Ditch/Existing Rock Cut Segment 5 – Segment E (397+00 to 405+80)

Alignment Overview. The trail runs along the Interstate ditch at the toe of an existing 0.25H:1V rock cut from 397+00 to 404+00. At the end of the rock slope, the trail veers south and ascends an existing cut slope to meet with a segment of HCRH at 405+80.

Proposed Improvements. Embankment fills up to 8 feet high with side slopes ranging from 2H:1V to

3H:1V are proposed along the existing Interstate ditch. The existing ditch is a rockfall catchment/storage area. A 17-foot-tall, 0.25H:1V sliver cut is proposed on the right side of the trail between 400+20 and 404+00.

2.2.35 Existing Highway – Segment E (405+80 to 418+80)

Alignment Overview. This portion of the trail would be located along a section of existing HCRH.

Proposed Improvements. No new structures or grading are proposed for this reach of the trail. Where possible, the existing asphalt surfacing will be cleared off and used for the trail surface or potentially overlaid with new asphalt.

2.2.36 Mitchell Creek Drainage – Segment E (418+80 to 426+08)

Alignment Overview. The reach of existing HCRH ends near 418+80, and the trail immediately veers north to cross over Mitchell Creek. After crossing Mitchell Creek, the trail continues east along the crest of an existing 1.5H:1V cut slope. The proposed trail descends from the crest of the existing cut slope at 423+00 and merges into existing HCRH at 426+08.

Proposed Improvements. A new culvert is proposed near 419+80 where Mitchell Creek has incised a channel across the alignment. Once north of Mitchell Creek, the proposed trail follows the crest of an existing cut slope crest from 420+00 to 423+00. High-side cuts up to 18 feet high with 1.5H:1V to

2H:1V slopes are proposed to create the bench for the trail. Low-side cut slopes daylight from the outboard edge of the proposed trail in this section.