GR04-15__Tiller_Trail_OR_Douglas_1(1)FINAL_29May2015.pdf

Tiller Trail Highway Reconstruction MP 40.2 – 40.41

OR DOUGLAS 1(1)

Geotechnical Report No. 04-15

Tiller Trail Highway Reconstruction MP 40.2 to 40.41

FINAL GEOTECHNIAL RECOMMENDATIONS

Douglas County, Oregon

May 2015

Geotechnical Report GR04-15 Page i April 2015

Contents

1. INTRODUCTION

1.1 Project Location

1.2 Scope of Project

2. SITE CHARACTERIZATION

2.1 Topography and Climate

2.2 Background Information

2.3 Site Geology

2.4 Surface Conditions and Site Observations

2.4.1 Site 1

2.4.2 Site 2

2.4.3 Site 3

3. SUBSURFACE CONDITIONS

3.1 Subsurface Investigation

3.2 Laboratory Testing

3.3 Findings

3.4 Groundwater

4. DISCUSSION AND RECOMMENDATIONS

4.1 Areas of Deformation

4.2 Deep Patch

4.3 Site 1 Mitigation

4.4 Site 2 and Site 3 Mitigation

4.5 Area between Sites

4.6 Earthwork

5. REFERENCES

Geotechnical Report GR04-15 Page ii April 2015

Appendices

APPENDIX A

Site Pictures

APPENDIX B

Plan and Profile View

APPENDIX C

Geologic Site

APPENDIX D

Boring Locations Map

APPENDIX E

Unified Soil Classification System Soil Descriptive Terminology Rock Descriptive Terminology Boring Logs and Core Pictures

APPENDIX F

Laboratory Test Reports

APPENDIX G

Historic Site Pictures

Geotechnical Report GR04-15 Page 1

1. INTRODUCTION

This report provides general geologic site conditions, the results of the geotechnical investigation, and final recommendations for the Tiller Trail Highway (Highway227) Rehabilitation MP 40.2 – 40.41, OR DOUGLAS 1(1) project.

These recommendations are based on the plan and profile set and cross-sections dated February 4, 2015. Figure B-1 shows the project plan and profile view and is contained in Appendix B.

1.1 Project Location

This project is located in Douglas County south of Drew, Oregon and about 10 miles north of Trail, Oregon. Forest Service Road 1616 intersects Highway 227 near the middle of the project. Figure 1 shows the project location map.

1.2 Scope of Project

The scope of this project is to reconstruct about 1100 feet of road between milepost 40.20 and milepost 40.41. The road is currently paved; however, severe cracking at three sites within the project limits require maintenance patching two to three times per year. Work will include excavation, improving roadway structural stability (subgrade stabilization and outboard lane stabilization/deep patch), drainage (cross sloping, ditches, and culverts), and asphaltic concrete paving. Due to project scope and budget constraints, geotechnical subsurface monitoring to measure ground movements was not included in the scope of the geotechnical investigation.

During project discussions with Douglas County Public Works Department engineer, Cody Smith, the scope of this project is to provide a short-term mitigation for the frequent road patching between MP40.2 and 40.41.

Figure 1: Project Location Map

Project Vicinity

Geotechnical Report GR04-15 Page 2

2. SITE CHARACTERIZATION

2.1 Topography and Climate

The project is located at an elevation of about 3000 feet in the south Cascade Mountains of Oregon at mid-elevation of Elk Creek Valley. The road traverses mountainous terrain with incised drainages. Based on historic topographic map and aerial photo, the alignment closely follows the 1940’s alignment. The area on both sides of the roadway was logged between 2003 and 2005.

The climate is moderate with occasional snow accumulation in typical winters. Table 1 shows the average maximum and minimum temperatures, and average monthly precipitation data for the period of 1996 to 2008 (Western Region Climate Center, 2014).

Table 1: Average maximum and minimum temperatures and average monthly precipitation

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. Max. Temp. °F 47.7 53.8 58.9 64.0 73.4 81.5 92.0 90.8 83.7 69.2 53.8 46.0 Avg. Min. Temp. °F 32.3 33.5 36.5 39.9 46.6 51.9 59.0 57.4 49.7 41.2 36.6 32.6 Avg. Temp. °F 40.0 43.6 47.7 52.0 60.0 66.7 75.5 74.1 66.7 55.2 45.2 39.3 Avg. Monthly Precipitation (in.) 3.00 2.11 1.64 1.70 1.31 0.41 0.15 0.41 0.37 1.23 3.35 3.53

2.2 Background Information

The project site is the location of Shangri-La Log Mill that operated in the 1940’s.

Michael Schurke, WFLHD Archaeologist, provided in an email dated April 1, 2014 a document showing historic map and photos of Shangri-La log mill (see Appendix G).

2.3 Site Geology

The geology of the area includes Oligocene-aged volcanic rocks overlying older layers of Tuff and other volcanic rocks. These layers dip about 10 degrees easterly towards Elk Creek. Threehorn Mountain lies west of the project about 3 miles and is mapped as Oligocene-aged basalt and basaltic andesite flows. The lower north and northeast flank of Threehorn Mountain contains Pleistocene and Holocene-aged landslide deposits shown mapped as Qls by Murray, 2001 (See Appendix C). Oregon Department of Geology and Mineral Industries, Statewide Landslide Information for Oregon SLIDO, is an interactive landslide mapping site. Landslide deposits are mapped at the project location (Figure C-3).

Overburden materials are primarily residual soils, alluvium, and landslide deposits. The materials underlying and surrounding the roadway have been disturbed by human activity.

2.4 Surface Conditions and Site Observations

Through this section of roadway, the vertical alignment undulates significantly and three sites exhibit substantial blade patching. Figure 2 shows a satellite view of the project and

Geotechnical Report GR04-15 Page 3 specific site locations discussed within this document. Figure 2 shows a relatively new continuous patch between Site 1 and Site 2; however, during site visits only recent patching was present at the three sites discussed below.

No significant springs or seeps were seen in the cut slopes; the right ditch near stations 202+00 and 207+50 are highly vegetated compared to the surrounding area and may indicate seepage from the cut slopes.

2.4.1 Site 1

Picture A-1 is Google Earth street view dated 2012 that shows a discontinuous arcuate crack within the outboard lane. Cracks in the pavement were not present during November 2013, September 2014, and March 2015 field visits; however, on both sides of the roadway patching the shoulder exhibits vertical displacement of about 2 feet (Pictures A-2 and A-3). Based on the roadway patching and the interpreted scarp in the shoulder the length of pavement affected is about 40 feet.

2.4.2 Site 2

Site 2 is located about 110 feet north of intersection with FS Road 1616 (Pictures A-4, 5, 6, and 7). This site exhibits cracking, lateral displacement, and differential settlement of about 1-inch occurring across the roadway at about 45 to 55 degrees from parallel to the road with lateral movement of the north side of the crack. Interruptions of the pavement striping illustrate the lateral displacement of this site.

A sag pond is located west (right) side of the roadway, (Figure 2) and encompasses an area about 10 feet by 15 feet and located about 30 feet from the edge of the pavement. Water may be migrating into the subgrade reducing the strength and stability of the soil.

Dewatering might help to improve subgrade conditions; however, the scope of the project does not include drainage other than ditching and cross drains.

2.4.3 Site 3

This site consists of an embankment across a poorly defined drainage area. There is 24-inch CMP culvert about 12 feet below the roadway surface. Asphalt patching is about 50 feet long.

This site has the greatest magnitude of movement of the three sites and requires the most maintenance. Differential settlement of the pavement up to 2 inches is present and a probe extends into a pavement crack about 4 feet. Interruptions of the pavement striping illustrate the lateral displacement of this site.

Geotechnical Report GR04-15 Page 4

Figure 2: Satellite View of the Project

3. SUBSURFACE CONDITIONS

3.1 Subsurface Investigation

Western Federal Lands Highway Division (WFLHD) conducted a subsurface investigation in September 2014. Haz-Tech Drilling, Inc. of Meridian, Idaho performed the subsurface drilling operations using a truck-mounted BK-81 drill. Seven borings were advanced with 8-inch hollow-stem auger. Depths ranged from 21.0 to 46.5 feet Standard Penetration Test (SPT) samples were obtained at select intervals. A 2-inch outside diameter (O.D.) Standard Penetration Test (SPT) sampler and a 3-inch O.D.

sampler were used to acquire disturbed soil samples and determine apparent density and consistency of the soils. Undisturbed Shelby tube samples were also collected in six borings. In boring B14-02, HQ3 wireline coring system was used in the last 10 feet of the borehole to verify bedrock.

Three subgrade borings were drilled using a solid-stem auger with a 14-inch bit to depths ranging between 3 feet and 3.5 feet. In all three holes the auger met refusal from cobble(s). After the removal of the auger a SPT was performed at the bottom of the boring. In two of the borings the SPT was performed off center in the boring to avoid cobbles. Bulk samples were also collected from the auger cuttings and sidewalls

Inferred direction of landslide

Geotechnical Report GR04-15 Page 5

The WFL project geotechnical engineer field classified and logged soil strata and thicknesses (see Appendix D).

3.2 Laboratory Testing

Selected soil samples representative of the project subsurface conditions were submitted to the WFLHD Materials Testing Laboratory in Vancouver, Washington. Laboratory soil tests included grain size analysis (AASHTO T 88), Atterberg Limits (AASHTO T 89 and T 90), Specific Gravity (AASHTO T 100), Natural Moisture Content (AASHTO T 265), and organic content (AASHTO T 267).

3.3 Findings

Table 2 shows a summary of boring locations, averaged asphalt and base thicknesses, and pertinent laboratory information. The laboratory test reports are contained in Appendix F.

Table 2: Boring locations, average asphalt and base thickness and pertinent laboratory information.

Geotechnical Report GR04-15 Page 6

The three subgrade borings, drilled outside of Sites 1, 2, and 3, encountered 11 to 14.5 inches of asphalt. Base material consisted of 2.5 to 3.5 inches of 1-inch minus angular silty gravel and clayey gravel and sub-base material consisted of 10 to 22 inches of 2-inch minus sub-angular clayey gravel.

Asphalt thickness measured in the borings within the limits of Sites 1, 2, and 3 ranges between 24 and 65 inches. The corresponding base material consists of 12 to 30 inches of 2-inch minus angular silty gravel. Generally, the soils underlying the pavement structure include sandy fat clay, silty sand, and clayey sand.

Boring 14-01 at Site 1 encountered wet silty sand underlying the clay layer at a depth of

18.5 feet. The boring remained open after removing the auger. One half hour later, free water was measured 15 feet below the road surface.

Boring 14-02 at Site 1 encountered a piece of metal CMP, measuring 4 inches by 2 inches, in the auger spoils between 15 and 18 feet below the road surface. However, this depth may not represent the actual depth at which it originated.

Boring 14-09 and Boring 14-11 at Site 3 encountered a zone of very loose to loose soil between 13 and 38 feet below pavement surface. The soil encountered at Site 3, 13 to 38 feet below the road surface, exhibited very loose to loose apparent density. Soils in these two borings became wet at 17 feet in boring in B14-09 and 24 feet in boring B14-11;

however no free water was measured 30 minutes after pulling the auger in B14-09. Free water was not measured in B14-11 due to traffic conditions.

3.4 Groundwater

Groundwater and wet soil conditions were observed in some borings during September 2014. The water levels and/or conditions may vary considerably, with time, according to the climate, rainfall, and other factors. Groundwater levels are anticipated to be even closer to the ground surface during the wet winter months.

4. DISCUSSION AND RECOMMENDATIONS

4.1 Areas of Deformation

Groundwater levels fluctuate during the year and from year to year. Based on the last ten-year measured precipitation average at Canyonville, Oregon, the 2014-2015 measured precipitation was near or below average (Weather Data, 2015). Based on visual assessments in September 2014 and March 2015, it appears that no maintenance patching occurred at these three sites during that period, and it is inferred that the reduced precipitation resulted in lower ground water levels and lower magnitude of movement. However, in years of average or greater precipitation, it is interpreted that changes in the groundwater level will result in greater magnitude of movement at those sites.

Geotechnical Report GR04-15 Page 7

The following recommendations assume shallow failure planes at each site rather than the distress being caused by weak soils and consolidation. Site 1 is assumed to be a localized landslide caused by seasonal rise of ground water. The head of the slide appears to be within the shoulder and the outboard lane. Sites 2 and 3 are inferred lateral extents of one larger landslide. The recommendations in this report are designed to provide a reduction of maintenance at the three sites; however, they are not designed to provide permanent stabilization. The deep patch mitigations are extended beyond the limits of the localized blade patching to reduce the propagation of pavement cracks outside of the reinforced limits.

4.2 Deep Patch

The recommended deep patch reinforcement consists of layers of biaxial geogrid with 9-inch vertical spacing and backfilled with angular durable crushed rock. The deep patches should be constructed to subexcavation depths of 3.75 and 4.5 feet measured vertically below subgrade elevation. Geogrid should be placed in continuous strips transverse to road centerline in order to provide the intended roadway stability. A non-woven earthwork geotextile should be placed between base rock and underlying deep patch backfill and between the underlying embankment and the first layer of geogrid. The biaxial geogrid should be lapped back 4 feet at the slope face. A thin layer of gravel (approximately 1-inch) should be placed between the lap and the overlying layer to prevent direct contact between adjacent geogrid layers.

An underdrain system should be installed at the heel of all deep patch locations. The underdrain system should consist of a 4-inch diameter perforated collector pipe in a 12-inch wide by 12-inch deep trench backfilled with granular backfill and lined with a non-woven type 1-B earthwork geotextile running the length of the deep patch. Non-perforated outlet pipes should be installed that drain across the road and daylight on the slope outside of the limits of the sites. Details for the deep patch construction are contained in the project plan set.

4.3 Site 1 Mitigation

A deep patch is recommended at this site where the road is interpreted to cross over the head of a landslide. The purpose of the deep patch is to minimize the future development and propagation of surface cracking within the roadway surface. Construct a full width 3.75-foot deep patch between stations 201+10 and 202+10.

A 14-foot deep intercept trench drain within the right ditch line was considered for this site to reduce the pore water pressure at the crown of the slide. However, without geotechnical instrumentation monitoring of depth of slide plane and water level changes, the effectiveness of construction an intercept trench drain is not clear. Therefore an intercept trench drain is not recommended.

4.4 Site 2 and Site 3 Mitigation

The recommended mitigation is to construct full width deep patch to minimize the development and propagation of surface distress related to landslide displacements.

Construct a 4.5-foot deep patch between stations 204+63 and 205+48 (Site 2) and

Geotechnical Report GR04-15 Page 9

5. REFERENCES

Federal Highway Administration Lands Highway, 2006, Technical Guidance Manual (TGM), A Geotechnical Supplement to the FLH Project Development and Design Manual.

Oregon Department of Geology and Mineral Industries, Statewide Landslide Information for Oregon SLIDO, http://www.oregongeology.org/slido/index.html

Weather Warehouse, Historical Weather Data, Canyonville, Oregon. http://weather-warehouse.com/WeatherHistory/PastWeatherData_Canyonville2S_Canyonville_OR_Jan uary.html, accessed 2March2015.

Western Regional Climate Center, Medford Airport, Oregon, Climatological Summary July 1996 to December 2008, www.wrcc.dri.edu/summary/mfr.or.html, accessed Nov 11, 2014.

http://www.oregongeology.org/slido/index.html http://weather-warehouse.com/WeatherHistory/PastWeatherData_Canyonville2S_Canyonville_OR_January.html http://weather-warehouse.com/WeatherHistory/PastWeatherData_Canyonville2S_Canyonville_OR_January.html http://weather-warehouse.com/WeatherHistory/PastWeatherData_Canyonville2S_Canyonville_OR_January.html http://www.wrcc.dri.edu/summary/mfr.or.html

Geotechnical Report GR04-15

APPENDIX A

Site Pictures

Geotechnical Memorandum GR04-15 A-1 Tiller Trail, OR Highway 227, MP 40.2 to 40.4

Picture A-1: Site 1, looking north, 2012, Google Earth

Picture A-2: Site 1, looking south, November 2013

Interpreted head scarp

Cracks in pavement

Geotechnical Memorandum GR04-15 A-2

Figure A-3: Site 1, looking north

Interpreted head scarp

Geotechnical Memorandum GR04-15 A-3

Picture A-4: Site 2, looking south, 2012, Google Earth

Picture A-5: Site 2 looking north, March 2015

Reflective crack through recent patch

Geotechnical Memorandum GR04-15 A-4

Picture A-6: Site 2, looking north, March 2015

Picture A-7: Site 2, looking east, March 2015

Geotechnical Memorandum GR04-15 A-5

Picture A-8: Site 3, looking north, 2012, Google Earth

Picture A-9: Site 3, looking south, November 2013

Shoulder offset and crack

Pavement crack

5 feet of BST and shoulder offset

Geotechnical Memorandum GR04-15 A-6

Picture A-10: Site 3, west side of roadway, November 2013

Picture A-11: Site 3, looking east across road, March 2015

Geotechnical Memorandum GR04-15 A-7

Picture A-12: Site 3, looking west across road, March 2015

Picture A-13: Site 3, hole in ditch, March 2015

Hole in right ditch

APPENDIX B

Plan and Profile View

3145 314

0 3

CUYD

EXC.

CUYD

EMB.

3195 3230

3200 3235

3205 3240

3210 3245

3215 3250

3220 3255

3225 3260

3230 3265

3235 3270

D.2

STATE PROJECT

NUMBER

SHEET

OR

DOUGLAS 1(1)

P

M

D e c e m b e r

B .B a s e .U

S c m y fi le s p w p r o d u c ti o n d

W o r k d d .c e l

C h e c k e d b y

D e s ig n e d b y

200+00 202+50 205+00 207+50 210+00 212+50 214+00

D

R= 250.00'

T= 46.36'

L= 91.67'

D

R= 600.00'

T= 20.67'

L= 41.31'

D

R= 250.00'

T= 27.60'

L= 54.98'

D

R= 250.00'

T= 31.92'

L= 63.50' D

R= 500.00'

T= 89.17'

L= 176.48'

CP

CP

CP

CP

CP

CP

CP

CP

CP

CP

500 CP

Line to be constructed

Slope stake limits

Slope stake limits

Profile grade

Profile grade

Existing ground

Existing ground

BEGIN PROJECT END PROJECT

200+00.00

OR DOUGLAS 1(1)

213+17.62

OR DOUGLAS 1(1)

El=3197.84

E=20284.5583

N=11068.9242

El=3263.85

E=19939.7858

N=9820.0219

P O

T

.0

P C

.7

P T

.0

P C

.9

P T

.6

P C

.6

P T

.5

P C

.6

P C

C

.1

P T

.6

U P

+5.

,1

.8

+5.

,2

.8

APPENDIX C

Geologic Site Map

Figure C-1: Geologic map in the vicinity of the project.

Figure C-2: Cross section view south of the project.

General project location

Figure C-3: An image from Oregon Interactive Landslide map SLIDO

Project Location

APPENDIX D

Boring Locations Map

Geotechnical Subsurface Boring Locations Tiller Trail, OR Highway 227, MP 40.2 to 40.41

Site 2 42°47’09.5” -122° 52’06.2”

Site 1 42°47’12.8” -122° 52’05.9”

Site 3 42°47’04.4” -122° 52’08.3”

Culvert

FS Road 1616

2 Concrete Lined Culverts, Side-by-Side

Sag Pond

N

B14-01 B14-02

SG14-06

B14-05

B14-04

SG14-03

B14-11

B14-08

SG14-07

B14-09

APPENDIX E

Unified Soil Classification System Soil Descriptive Terminology

Rock Descriptive Terminology Boring Logs and Core Pictures

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lnot~n·c ltl u. mteK.eovs Ot diatomJCtous tint s.andv or s.ifty toiiJ, tfi1UC: SIIU .

lnor91nic cl•vs of h~ pl1sticity. fat efiVJ.

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on frxtion Sm•IIH than No •o Sitw Siu

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ROCK DESCRIPTIVE TERMS

ROCK WEATHERING

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

No discoloration in rock fabric. Fresh

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

Slightly Weathered

Significant portions of rock show discoloration and weathering effects.

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

Moderately Weathered

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

Highly Weathered

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

DISCONTINUITY SPACING ROCK QUALITY DESIGNATION (RQD)

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

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

> 80 Very Wide 90 - 100 Excellent (RQD is the percent of a core run with intact lengths greater than 4 inches excluding breaks caused by drilling.)

INTACT ROCK HARDNESS

Field Identification UCS (psi) Hardness Term Indented by thumbnail. 40 - 150 Extremely Weak (R0) Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife. 150 - 730 Very Weak (R1)

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

730 – 3,600 Weak (R2)

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

3,600 – 7,300 Medium Strong (R3)

Specimen requires more than one blow of geological hammer to fracture it. 7,300 – 15,000 Strong (R4)

Specimen requires many blows of geological hammer to fracture it. 15,000 – 36,000 Very Strong (R5)

Specimen can only be chipped with geological hammer. > 36,000 Extremely Strong (R6) (UCS – Unconfined Compressive Strength)

Geotechnical Memorandum GR04-15 Appendix E

Figure E-1: Rock Core - B14-02 - 20.2' to 28.9'

Figure E-2: Rock Core - B14-02 - 28.9' to 30.2'

APPENDIX F

Laboratory Test Reports

APPENDIX G

Historic Site Pictures

Figure G-1. Detail of the 1944 USGS Tiller Quad, 15’ Series, showing the location of the “Shangri-La Mill” at the intersection of the Tiller-Trail Highway and Forest Road 1616—within the current project area.

Figure G-2. Detail of a 1943 aerial photograph showing the Shangri-La Mill

Figure G-3. “Tiller Mill and Lumber Company sawmills on Rogue-Umpqua Divide in winter probably 1943. Frozen mill pond with logs cove red with snow in foreground. The site was dubbed ‘Shangrila’ by James Hilton, from his book Lost Horizon, who saw it on a spring day from a commercial airliner. The name stuck.” (Photo from “Swivel-Chair Logger: The Life and Work of Anton A. ‘Tony’ Lausmann” by Bert Webber, 1976, Ye Galleon Press, Fairfield, WA.)

Figure G-4. “Loggers’ cabins at Shangrila community were vacant during winter mill shut down. (Photo from “Swivel-Chair Logger: The Life and Work of Anton A. ‘Tony’

Lausmann” by Bert Webber, 1976, Ye Galleon Press, Fairfield, WA.)

Figure G-5. Distribution of historic debris observed during pedestrian survey of the Tiller-Trail Highway Reconstruction Project APE. The APE encompasses the former “Shangri-La Mill” site, a ca WWII-era lumber mill.