GR27-18 Final Geotech Report OR DOT 140(1) Klamath County Boat Marina to Lakeshore Dr.pdf

Klamath County Boat Marina to Lakeshore Drive February 2019

Table of Contents 1-i

Geotechnical Report No. 27-18

Klamath County Boat Marina to Lakeshore Drive

FINAL GEOTECHNICAL REPORT

OR DOT 140(1)

Oregon Department of Transportation Region 4

Klamath County, Oregon

February 2019

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Table of Contents i

TABLE OF CONTENTS

1 INTRODUCTION

1.1 Scope and Purpose

2 PROJECT DESCRIPTION

3 PREVIOUS ODOT PROJECTS

4 GEOLOGY

4.1 Geologic Hazards

4.2 Seismicity

5 SITE CONDITIONS

5.1 Average Temperatures and Precipitation

6 SUBSURFACE CONDITIONS

6.1 Laboratory Materials Testing

6.2 Soil and Rock Types

6.3 CPT Engineering Parameters

6.4 Groundwater

7 ANALYSIS AND DESIGN RECOMMENDATIONS

7.1 Option A: Cut Slope Option

7.2 Option B – Lake Embankment Option

7.3 Recommended Option

7.4 Special Rock Embankment

7.5 Soil Embankment Slopes

7.6 Cut Slopes

7.7 Infiltration

8 CONSTRUCTION CONSIDERATIONS

8.1 Excavation

8.2 Embankment

8.3 Aggregate Sources

9 LIMITATIONS

10 REFERENCES

List of Figures ii

LIST OF FIGURES

Figure 2-1 Project Location Map

Figure 2-2 Project Overview Map

Figure 4-1 Vicinity Topographic Map

Figure 4-2 Lake Section Topographic Map (USGS, 1985)

Figure 4-3 Project Area LiDAR Map (DOGAMI, 2018)

Figure 4-4 Geologic Map with Explorations

LIST OF TABLES

Table 4-1 Geologic Units Summary

Table 4-2 Geologic Hazard Mapping Summary

Table 5-1 Climate Data Summary

Table 6-1 Soil and Rock Types Encountered/Interpreted in Borings and Test Pits

Table 6-2 Data and Parameters from Pore Pressure Dissipation Tests

Table 7-1 Permanent Cut Slopes Design Summary

APPENDICES

APPENDIX A

Site Photographs

APPENDIX B

Exploration Location Plans

Introduction 1

1 INTRODUCTION

This report provides geotechnical investigation results, analysis, design and construction recommendations for Oregon Route 140 Klamath County Boat Marina to Lakeshore Drive project. This project was performed for Region 4 of the Oregon Department of Transportation (ODOT). The project involves widening and safety improvements to highway OR 140 from approximately milepost MP 57 to MP 63. This project will be designed and delivered by the Western Federal Lands Highway Division (WFLHD) of the Federal Highway Administration in collaboration with ODOT.

1.1 SCOPE AND PURPOSE

The geotechnical scope of work for this project included review of ODOT-provided data, a visual reconnaissance along the proposed alignment, and a subsurface exploration program consisting of three geotechnical test bore holes, 11 cone penetrometer tests (plus additional attempts), four test pits, and three infiltration tests. The geotechnical explorations were completed by Foundation Engineers, Inc. under contract to prime consultant WSP USA, Inc. as part of a task order from WFLHD.

This report was prepared to provide geotechnical design and construction recommendations for embankments, cut slopes, and other earthwork. The following memos and reports were previously prepared by WFLHD and our consultants:

• Preliminary Geotechnical Subsurface Characterization, OR DOT 140 (1), OR 140 - Klamath County Boat Marina to Lakeshore Drive, Klamath County, Oregon, WFL Geotechnical Report No. 10-17, dated October 19, 2017, by Foundation Engineering, Inc.

• OR 140 – Klamath County Boat Marina to Lakeshore Drive, OR DOT 140(1), Preliminary Geotechnical Design Memo, GM30-17, dated November 14, 2017, by Western Federal Lands Highway Division.

This report supersedes the previous memo. The Preliminary Geotechnical Subsurface Characterization report provides the explorations and test data for the project under separate cover. The project stationing referenced in this report is from the 70% Design Set, dated August 2018.

We understand that evaluation of a wetland mitigation site across the lake is underway.

Development of that site will involve excavation of waterways and construction of dikes. Test pits explorations are planned for both environmental and geotechnical purposes. Investigation results and geotechnical recommendations will be provided in a separate addendum report.

2 Project Description

2 PROJECT DESCRIPTION

According to the FLHD Project Charter, Oregon Route 140 is a state highway that traverses the southern portion of the state of Oregon. ODOT refers to this highway internally as route #270 and is called Lake of the Woods Highway. This project takes place on a segment of road that runs between the cities of Klamath Falls and Medford with a current seasonal average daily trips of 2,700. The highway is a designated Freight Route between Medford and Lakeview with 28 percent truck traffic. The project is located approximately 5 miles west of the city of Klamath Falls. This route is also designated as a part of the Volcanic Legacy Scenic Byway through the project. The approximate location of the project is shown in Figure 2-1 and Figure 2-2.

The route provides access to the Fremont-Winema National Forest, Rogue Siskiyou National Forest, BLM Lands, Klamath Lake and various recreational facilities. The route also provides access to public and private timber lands, residential property, and can be used as an alternate route to Crater Lake National Park. For a portion of the project corridor, the roadway runs adjacent to Klamath Lake.

The two-lane roadway (travel lanes, and shoulders) is too narrow to accommodate current and future traffic volumes and do not provide opportunities for bicycle use. This causes a severe safety concern for the public traveling along this roadway. Currently, there are not any protective measures to prevent vehicles from leaving the highway and going into the lake.

The project will involve widening the roadway to 12-foot wide travel lanes with 6-foot shoulders and realign the road where necessary. Widening will require the construction of stone embankments in Klamath Lake to prevent cuts into the very steep and unstable slopes on the southwest side of the project. Other improvements include development of wetland mitigation areas and installation of guardrail, high performance pavement markings, and shoulder and center-line rumble strips.

Representative site photographs of the current project area are included in Appendix A.

Project Description 3

Figure 2-1 Project Location Map

Figure 2-2 Project Overview Map

4 PREVIOUS ODOT PROJECTS

3 PREVIOUS ODOT PROJECTS

This project continues widening and safety improvements in the Lake of the Woods Highway corridor maintained by ODOT. The previous project was designed and constructed by ODOT in 2004 and ended at approximately MP 57. The following reports and documents were provided by ODOT for our use:

• Geotechnical Report, Lake of the Woods (Doak Mtn.) Section, Lake of the Woods Highway, (Hwy 270, M.P. 50.70 – 57.06), Klamath County, dated October 2003, by Oregon Department of Transportation, Geo/Hydro Section, Region 3 and Eastside Units

• Plans for Proposed Project, Grading, Drainage, Structures, Paving, Signing, Signals, & Roadside Development, Lake of the Woods (Doak Mtn.) Sec., Lake of the Woods Highway, Klamath County, dated April 2004, by State of Oregon Department of Transportation.

• Special Provisions for Grading, Drainage, Structures, Paving, Signing, Signals, and Roadside Development, Lake of the Woods (Doak Mtn.) Sec., Lake of the Woods Highway, Klamath County, dated 04-22-04, by State of Oregon Department of Transportation.

• Foundation Report, Geary Canal Bridge, Geary Canal Bridge Section, Lake of the Woods Highway, No. 270 (M.P. 58.83), Klamath County, Bridge 18142, Key 06265, dated March 1996, by Oregon Department of Transportation, Bridge Engineering Section, Foundation Design Unit

The 1996 Geary Canal Bridge report discussed large settlements of the bridge’s northwest approach embankment that was originally constructed in 1953. Approximately 45 feet of fill was reported to have been placed to achieve a 15-foot final fill height above the original mudline.

The report also mentions that moderate to heavy corrosion was observed in many of the steel piles due to the corrosive chemistry of the lake water. The report recommended replacement of the upper 6 feet of the northwest approach embankment with lightweight cinder stone to reduce the pervasive settlement issues with the NW embankment.

In 2003, ODOT prepared a report titled, “Lake of the Woods (Doak Mtn.) Section, Lake of the Woods Highway (Hwy. 270, M.P. 50.70 – 57.06), Klamath County,” dated October 2003 (Castro and others, 2003). This report discussed four main areas of the highway improvement project, of which Area 4 focused on the Klamath Lake Embankment. The following excerpts from the report summarizes their interpretation of the geology and sediment behavior of the lake shore area:

The normal faults generally control the spatial distribution of material types in the lake area. Along Howard Bay, on the up-thrown block of the fault, northwest of the highway, variably thick talus and basalt flows comprise the hillside. On the down-thrown block of the fault, along the roadway and the shores of the lake, PREVIOUS ODOT PROJECTS 5 roadway fill overlies a complex interfingering of materials including talus, shoreline lacustrine deposits, talus that has been reworked by waves along the lake shore, and lacustrine sands and silts. This interfingering of material is complex and highly variable due to the continued fault movement over time.

The 2003 ODOT geotechnical report also states that the diatomaceous silt was tested in the soil laboratory; this material showed significant variations and did not behave as typical sand or clay. Therefore, it was difficult to evaluate the strength and settlement parameters of these sediments. However, based on the previous studies on the Geary Canal Bridge, it appeared that the ratio of embankment that subsided below the original mudline to the embankment placed above the mudline was 1.5 subsided:1 above (i.e., 2.5 times the neat line volume).

In 2005 to 2006, ODOT constructed the widening of OR 140 from MP 50.70 to 57.06. The sections just west of the boat marina were widened into the lake by placing stone embankment material into the lake. Prior to placing the embankment, a geogrid reinforcement was anchored at the shoreline and rolled out over the very weak lake sediment to try to reduce the volume of material needed before the embankment stabilized. The resulting stone embankment volume was reported to be approximately 2.5 times the neat line volume of the embankment (i.e., theoretical volume above original mudline). This increase in volume was attributed to bearing capacity failure and settlement of the very weak diatomaceous silt and other lacustrine materials. Due to the very lightweight lake bed materials, the material simply shoved under and out in front of the embankment, eventually surfacing in the lake. We understand that this “mud wave” eventually dissipated due to re-settlement and wave action. Settlement monitoring measurements indicated that post-construction settlements of the embankment surcharge were only 0 to 3 inches over a 7- to 9-month settlement period.

ODOT informed us that this method of embankment construction was successful and suggested using this same approach for the remainder of the widening project to be delivered by WFLHD.

ODOT also expressed concern for the cutting into the steep slope areas on the southwest side of the roadway, due to the unstable conditions.

6 Geology

4 GEOLOGY

The project is in the Basin and Range geologic province of Oregon near the eastern edge of the Cascade Range geologic province. The terrain at the site transitions from the mountainous Cascade Range forming the high steep slopes on the southwestern side of the road alignment in the project area to the relatively flat lake and marsh areas of the Klamath Basin on the northeastern side of the road alignment. Figure 4-1 Vicinity Topographic Map, Figure 4-2 Lake Section Topographic Map, and Figure 4-3 Project Area LiDAR Map show the relative topographic relief of the project vicinity.

Map created with TOPO! © 2006 National Geographic & © 2005 Tele Atlas, North America, Inc., Rel., 07/2005

Figure 4-1 Vicinity Topographic Map

Geology 7

Figure 4-2 Lake Section Topographic Map (USGS, 1985)

According to the Geologic Map of the West Half of the Klamath Falls 1° by 2° Quadrangle, South-Central Oregon (Sherrod and Pickthorn, 1992) the site is mostly mapped as basalt of Basin and Range (Tb2), with scattered areas of vent deposits (Tv) mapped in the area, specifically around test pits TP17-01 and TP17-02. The road crosses the Caledonia Marsh southeast of the lake, which is mapped as surficial deposits (Qs), before rising up the hill. These sediments are also likely to be found in the lake itself, which is mapped as water in the geologic map. An excerpt of the geologic map with exploration locations is shown on Figure 4-4 Geologic Map with Explorations. Table 4-1 Geologic Units SummaryTable 4-1 below summarizes the unit information from the geologic map.

8 Geology

Figure 4-3 Project Area LiDAR Map (DOGAMI, 2018)

Geology 9

Figure 4-4 Geologic Map with Explorations

Qs

Tb2

Tb2

Qs

Tv

10 Geology

Table 4-1 Geologic Units Summary

Map Unit Symbol

Map Unit Name Map Unit Description

Tb2 Basalt of Basin and Range (Pliocene and Miocene) Unit 2

Aphyric to porphyritic lava flows and minor breccia; chiefly intergranular to subophitic and locally diktytaxitic basalt and lesser amount of intergranular basaltic andesite. Contains phenocrysts (1-2 mm long) of olivine and greater or lesser amounts of plagioclase and, locally, clinopyroxene. Locally includes interbedded, poorly exposed, poorly indurated sedimentary and pyroclastic volcanic rocks, which are commonly buried by basalt float. Unit Tb2 is further described as lava flows throughout southwestern, south-central, and northeastern part of map area. Lithologically indistinguishable from Unit Tb1 and is separated chiefly on geomorphic and structural criteria; overall, the unit probably contains a greater proportion of diktytaxitic lava compared to lava in unit Tb1, which dominantly intergranular in texture.

Tv Vent deposits (Pliocene and Miocene)

Cones and irregular piles of cinder, agglutinate, and minor lava flows and intrusions. Forms vents for the basalt of Basin and Range (Tb1, Tb2, and Tb3)

Qs Surficial deposits

Fine- to coarse-grained sediment deposited in channels, flood plains, marshes, and lakes.

According to the Atlas of Oregon Lakes, Upper Klamath Lake is a natural water body and is the largest freshwater lake in Oregon (Johnson, et al, 1985). The Atlas further describes the lake as being in a structural valley known as the Klamath Graben and is approximately 25 miles long and 2.5 to 12.5 miles wide. The surface water elevation is reported to fluctuate between a surface elevation of 4,137 feet to 4,147 feet, which is controlled by a low dam constructed in 1917 by the Bureau of Reclamation. The maximum depth of the lake is reported to be approximately 50 feet with most of the lake under 20 feet. The Atlas reports that the water has high concentrations of phosphorus derived from natural springs and surface runoff, as well other high concentrations of other nutrients derived from the Klamath Marsh through which the Williamson River passes as it feeds the lake. The lake is well-known to have large natural blooms of blue-green algae in the summer.

Based on the ODOT geotechnical reports, we understand that the primary sediment in the lake is a diatomaceous silt. We attempted to research the geologic history and properties of the diatomaceous silt and reviewed a paper titled, “Pluvial Lake Modoc, Klamath County, Oregon, and Modoc and Siskiyou County, California” (Dicken, 1980). This paper discussed the origins of Upper Klamath Lake, which was reported to be a shrunken remnant of much larger Lake Modoc that existed in the Pleistocene epoch. Lake Modoc reportedly had a maximum water elevation of

Geology 11

4,240 feet above sea level. For reference, Upper Klamath Lake levels over the period from January 2016 to February 2019 ranged from approximate elevations of 4,138 to 4,143 feet

(USGS, 2019).

The Dicken paper states that the lakes were formed by block faulting and igneous activity.

Basalt, andesite, and dacite flows and extrusions of cinders, ash, and pumice contributed to the filling of the depressions between the fault blocks to hundreds of meters in some cases. Some of the pumice came from the eruption of Mount Mazama 6,000 years ago during the formation of Crater Lake. Meltwater from the Cascade Range carried sediment including cinders, ash, and pumice to the lakes. Diatoms and peat accumulations also helped fill the lakes. Dicken reported that the lake sediment has a high water-holding capacity and are of such low density that when steamboats ran aground on Lower Klamath Lake at the turn of the century, the disturbed sediment sometimes floated to the surface of the lake.

4.1 GEOLOGIC HAZARDS

The Oregon HazVu: Statewide Geohazards Viewer website (DOGAMI, 2017a) was used to screen the project vicinity for geologic hazards, as well as the USGS Interactive Fault Map (USGS, 2017). Excerpts of these maps are shown in Figures A-7 through A-12 and indicate the following geologic hazards:

Table 4-2 Geologic Hazard Mapping Summary

Geologic Hazard Mapping Description

Earthquake Hazards:

Active Faults Nearest active faults are the Klamath graben fault system, South Klamath Lake section which underlie the road and site vicinity. The activity ages of the faults range from the < 1.6M years to <15,000 years categories.

Based on the distance to the site, the risk of surface rupture is considered high.

Liquefaction The existing roadway area along the edge of the lake is mapped as a moderate hazard and the lake and adjacent waterways are mapped as high hazard areas.

The risk is considered moderate to high based on the mapping and alluvial/lacustrine environments.

Expected earthquake shaking

“Very strong” mapping over the entire vicinity

Very strong ground motions expected.

12 Geology

Geologic Hazard Mapping Description

Earthquake epicenter Numerous earthquakes mapped over the vicinity, particularly over the Aspen Lake and mountainous area to the west of the project site.

Indicates a highly active earthquake region.

Landslide Hazard “High” mapping over the entire vicinity

Landsliding, rockfall, and associated hazard risks are high and are considered likely to occur.

Volcanic Hazard No areas mapped as high or moderate in the region.

Risk is considered low.

The SLIDO: Statewide Landslide Information Layer for Oregon website (DOGAMI, 2017b) does not map documented landslides within the project corridor.

The risks for earthquake-related geologic hazards are high, but no mitigations are currently recommended as discussed in the Seismicity section. Landslide hazards are also considered high and is a reason that significant excavation at the toe of the very high and steep slopes is not recommended.

4.2 SEISMICITY

The current project does not have any significant structures proposed, such as buildings, bridges, or retaining walls, or will improve areas that support such structures. The ODOT Geotechnical Design Manual (ODOT, 2014) Section 6.2.4 states:

Cut slopes, fill slopes, and embankments that are not bridge approach embankments are generally not evaluated for seismic instability unless they directly affect a bridge, highway retaining wall or other structure. Seismic instability associated with routine cuts and fills are typically not mitigated due to the high cost of applying such a design policy uniformly to all slopes statewide.

Therefore, the seismicity of the project area was not considered for in the design of the proposed cut slopes and embankments. If it is determined that seismic loads on slopes or embankments should be considered for this project, the WFL Geotechnical group should be contacted for additional recommendations.

Site Conditions 13

5 SITE CONDITIONS

Our reconnaissance of the project corridor was performed during site visits in July 2016 and August 2017. The project begins at mainline station 20+00 near the Klamath County Boat Marina and heads in the east corridor direction (south to southeastern compass direction) along the shore of Howard Bay. Steep slopes above the roadway are on the order of 400 to 900 feet in vertical relief with overall slope angles on the order of 32 to 35 degrees from horizontal (approximately 63 to 70 percent). Local slope angles are up to approximately 60 degrees (approximately 170 percent) at existing cuts near the toe of the slope.

The steep slopes are vegetated with a mixture of deciduous and evergreen trees and a moderately dense understory. Numerous talus fields are visible from the highway, and large boulders and smaller rockfall are scattered in the ditch along the south side of the highway.

Several areas show near vertical scarps in eroding, raveling, coarse colluvial material above the roadway; it is not immediately apparent whether these are from cut slopes for the original highway, landslide activity, or possible faulting offsets since the highway itself is parallel and adjacent to a fault line. Towards the end of the lake section near station 100+00, the cut slopes (or possible fault offset) become fairly high and steep in bedrock, on the order of 56 degrees from horizontal, which is the same angle as the rock bedding plane in some areas.

As the roadway continues eastward from the lake, it crosses over Geary Canal Bridge from approximately station 115+00 to 117+50 and onto embankments over the flat marshlands adjacent to the lake. The road then grades uphill with cuts on both sides of the roadway through scoriaceous to vesicular basalt slopes at overall angles of 1V:1.25H to 1V:1.5H (Vertical:Horizontal) up to approximately 40 feet high. The slopes angles in this section from approximate station 165+00 to 180+00 are roughly graded with pockets of less weathered boulders or rock outcrops amongst more highly weathered rock materials and overburden soils.

Numerous large boulders are visible in the field on the north side of the road at the beginning of this cut area, possibly from the previous cuts.

The road plateaus at approximate station 180+00 and is relatively level with relatively low cuts and fills several feet or less in height. The only significant slope in this end segment is on the left side of the roadway near station 240+00 where the existing cut slope is approximately 10 feet in height with basalt outcrops.

5.1 AVERAGE TEMPERATURES AND PRECIPITATION

The project site is in a moderately arid and snowy climate but with precipitation possible throughout the year.

14 Site Conditions

Table 5-1 shows the average maximum and minimum temperatures, average monthly precipitation, and average monthly snowfall data for the period from 1927 to 2016 for the Keno Oregon (354403) weather station (Western Region Climate Center, 2018).

Site Conditions 15

Table 5-1 Climate Data Summary

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

Avg. Max.

Temp. (F) 38.5 42.6 45.7 53.6 64.5 74.5 83.3 85.1 83.8 67.0 44.9 37.8 60.1

Avg. Min.

Temp. (F) 20.0 21.2 26.1 27.5 33.3 41.3 46.9 46.2 40.7 31.4 27.1 16.0 31.5

Avg. Total Precip. (in.) 2.84 1.99 1.92 1.28 1.21 0.88 0.34 0.45 0.63 1.50 2.59 3.21 18.84

Avg. Total Snow (in.) 16.0 9.9 6.5 2.1 0.2 0.0 0.0 0.0 0.0 0.5 6.4 13.5 55.0

Avg. Snow Depth (in.) 5 3 1 0 0 0 0 0 0 0 1 2 1

Note:

1) Period of Record : 07/01/1927 to 06/10/2016.

16 Subsurface Conditions

6 SUBSURFACE CONDITIONS

Previous work by ODOT on the adjacent Lake of the Woods (Doak Mountain) Section from MP

50.70 – 57.06 encountered very soft diatomaceous silt sediments in the lake (Castro and others, 2003). For that project geotechnical drilling was performed by ODOT drill crews, and many Standard Penetration Tests (SPT) recorded zero blowcounts with many samples being advanced by the weight of the drilling rods without use of the hammer. Many Shelby tube samples resulted in no recovery, even with the use of an Osterberg piston sampler. Cone penetration test (CPT) explorations were also performed by another ODOT study for the replacement of the Geary Canal Bridge (Six and Castro, 1996). Two CPTs were advanced to depths of approximately 100 and 209 feet.

In anticipation of encountering mostly very soft and very deep diatomaceous silts, WFLHD developed an exploration program that consisted of 13 CPT explorations with three widely-spaced SPT borings to collect soil samples. CPTs involve pushing a cone-tipped rod into the ground and electronically recording tip resistance, sleeve friction, and pore pressure.

Advantages of CPT testing include providing a near continuous recording of data in very soft to moderately dense soil materials, as well as speed and lower expense of CPTs compared to traditional auger borings. The CPT data can be correlated to soil behavior types and numerous in-situ soil properties. Disadvantages of CPTs include refusal in dense sands/gravels, hard soils, boulders/bedrock, and no retrieval of soil samples. Other in-situ tests were also performed including shear wave velocity tests, pore pressure dissipation tests, and field vane shear tests, in attempts to gather additional data on the very soft materials.

WSP USA, Inc. was tasked by WFLHD with performing the subsurface characterization work.

Foundation Engineering, Inc. performed the work as WSP’s geotechnical subconsultant. Field work, which included barge drilling, barge CPTs, and test pits/infiltration testing was completed during August 2017. Haz-Tech Drilling of Meridian, Idaho was the drilling contractor. In Situ Engineering of Snohomish, Washington was the CPT contractor. Test pits were performed by McBride Excavating of Klamath Falls, Oregon. Foundation Engineering geologists logged the borings and test pits conditions. The CPT data were electronically recorded by In Situ during the testing. Eric Lim of WFLHD visited the site during the CPT and test pit explorations to observe the operations.

The approximate locations of the explorations are included on the exploration locations maps in Appendix B. The boring logs, CPT logs, and test pits logs are included in the Preliminary Geotechnical Subsurface Characterization report by WSP/Foundation Engineers, Inc., dated October 19, 2017, under separate cover. The explorations were performed from August 3 to 14, 2017.

6.1 LABORATORY MATERIALS TESTING

Selected split-barrel (SPT) soil samples and test pit samples were submitted to the WFLHD Materials Laboratory for soil index testing and rock strength testing. Laboratory test reports are

Subsurface Conditions 17 contained in the Preliminary Geotechnical Subsurface Characterization report (Foundation Engineering, Inc., 2017).

The following is a list of tests that were completed on the selected soil and rock samples and the standards that were followed:

• Particle Size Analysis – AASHTO T 88

• Liquid Limit, Plastic Limit, and Plasticity Index – AASHTO T 89/90

• Apparent Specific Gravity – AASHTO T 100

• Natural moisture – AASHTO T 265

• Organic Content – AASHTO T 267

• Rock Unconfined Compressive Strength – ASTM D 7012

The results of the soil index tests were used to classify the samples according the Unified Soil Classification System (USCS). The USCS classification of individual laboratory tested soil samples is reported on the boring and test pit logs.

6.2 SOIL AND ROCK TYPES

Subsurface materials encountered in the borings are summarized in Table 6-1 below.

Table 6-1 Soil and Rock Types Encountered/Interpreted in Borings and Test Pits

Soil / Rock Type Description

Explorations Encountered

Fill Man-placed soil and rock materials, including cobbles & boulders in silty sand matrix

BH17-01, BH17-

Colluvium Soil and rock/talus materials deposited near the base of a slope, including silty sand with gravel, cobbles & boulders in silty gravel with sand matrix, well-graded sand with silt, poorly-graded gravel with silt and sand, silt with sand and gravel, silty sand, poorly-graded sand with cobbles and boulders

BH17-01, BH17-

02, BH17-03,

TP17-01, TP17-

02, TP17-03,

TP17-04

Lacustrine Sediments settled within a lake, including diatomaceous/organic silt with sand with scattered cobbles

BH17-01, BH17-

02, BH17-03

Basalt Scoriaceous to moderately vesicular, reddish gray, fine-grained, moderately to slightly weathered, very weak to strong

BH17-01, BH17-

02, BH17-03

Direct descriptions of soils cannot be performed using CPT since samples are not retrieved.

However, the CPT data can be correlated to “soil behavior types” or SBT using correlations

18 Subsurface Conditions developed by Peter Robertson (Robertson and Cabal, 2015). It should be noted that the SBT descriptions may vary from soil samples classified from an adjacent boring in the same material, especially when the CPT data is normalized to take into account the in-situ vertical stresses.

In general, the very soft diatomaceous silts encountered in borings appear to correlate to “organic material”, “sensitive fine-grained”, “clay”, “clay-like - contractive”, “clay-like - contractive

- sensitive” soil behavior types. In some cases, it appears that the diatomaceous silt do not correlate to a soil behavior type at all, especially with normalized SBTs. Refer to the CPT logs and interpreted data plots in the Preliminary Geotechnical Subsurface Characterization (Foundation Engineering, Inc., 2017) for more detail and information.

6.3 CPT ENGINEERING PARAMETERS

The CPT data can also be correlated to certain engineering parameters, which is especially beneficial on this project since the very soft sediments are difficult to retrieve as intact specimens. Table 6-2 below summarizes data and calculated parameters from the pore pressure dissipation tests. Additional pore pressure dissipation data is provided in the Preliminary Geotechnical Subsurface Characterization report.

Table 6-2 Data and Parameters from Pore Pressure Dissipation Tests

CPT No. Depth (ft) SBT (normalized SBT, if diff.) t50 (s) ch

(ft2/year) kh (ft/s)

CPT17-01 6.89 Organic soil (n/a) 36 s 719 3.59 x 10-10

CPT17-05a 15.58 n/a1 50 516 2.93 x 10-10

CPT17-06a 19.91 Sand and silty sand 3 9,353 4.90 x 10-9

CPT17-07a 29.36 Clay and silty clay (sensitive fine-grained)

25 89,464 5.19 x 10-6

CPT17-07a 31.50 Clay (organic soil) 163 19,223 2.50 x 10-6

CPT17-08 25.43 Clay (organic soil) 182 17,307 2.79 x 10-6

CPT17-08a 24.93 Clay 247 9,401 3.88 x 10-7

CPT17-09 21.65 Clay 251 8,389 2.12 x 10-7

CPT17-09a 14.11 n/a1 78 331 1.98 x 10-10

CPT17-10 28.22 Clay 273 9,623 5.52 x 10-7

CPT17-10b 29.04 Clay 387 7,539 9.32 x 10-7

Notes: 1 test was at bottom of CPT at refusal

Seismic shear wave velocity tests were also performed in select CPTs at select depths, which are reported in Table 1D in the Preliminary Geotechnical Subsurface Characterization report.

Subsurface Conditions 19

Velocities ranged widely from 143 to 2,444 feet per second, showing no discernible pattern or correlation to tip resistance or soil behavior type. It should be noted that the CPT operator reported difficulty and potentially unreliable results in many tests due to the very soft and fluid-like behavior of the lake sediments. Test results with low confidence were not report in Table 1D, although the plots are included in the Preliminary Geotechnical Subsurface Characterization report. Foundation Engineers reported that most of the velocities were unreasonably high and may represent the velocity of boulders and cobbles, steel rods, P-waves, or some combination thereof. They also reported that the shear wave velocity of 143 feet per second may be the more accurate estimate of the shear wave velocity of the very soft diatomaceous/organic silt sediments.

6.4 GROUNDWATER

All the borings and CPTs were performed in the lake; therefore, groundwater levels are at the ground surface or mudline. Water depths above mudline were measured and presented in Table 1A: Boring and CPT Locations in the Preliminary Geotechnical Subsurface Characterization report.

Groundwater was not encountered in the test pits at the time of the exploration. However, it should be noted that the test pits were excavated in mid to late summer, when groundwater levels are typically at their lowest. Groundwater levels should be expected to fluctuate with precipitation, seasonal variations, irrigation, changes in grade/adjacent land use, and other on-and off-site factors.

20 Analysis and Design Recommendations

7 ANALYSIS AND DESIGN RECOMMENDATIONS

The above information was analyzed to determine geotechnical design recommendations for the proposed road widening project. The two primary geotechnical challenges to the project are the 400- to 900-foot-high steep slope area with active rockfall on one side of the road, and the very soft and very weak diatomaceous silt sediments on the other side of the road. Two road widening alignment options are discussed below with regard to geotechnical issues: Option A – Cut Slopes; and, Option B – Lake Embankment.

7.1 OPTION A: CUT SLOPE OPTION

One option for the proposed road widening would be to stay out of the lake and cut into the hillside on the southwest side of the road. The advantages of this option would be no in-water work and less fill or import material needed for embankment.

The disadvantages of this option are that the slopes are very steep, very high, and potentially unstable. Additional or significant cuts into the steep slope areas would bring the roadway closer to the rockfall hazards, and could result in slope instability by removing the supporting buttress of the toe materials. Due to the overall height and steepness, it is not feasible to flatten out the slopes for stability. Therefore, cuts would require retaining walls, rockfall fences/netting, or other expensive mitigation for unstable slopes.

7.2 OPTION B – LAKE EMBANKMENT OPTION

Another option of road widening is to fill a portion of the lake shoreline with rock embankment.

The advantage of this option is that the existing steep slopes would remain largely untouched, thus not increasing the rockfall and slope instability hazards. During meetings with ODOT, we were informed that the existing steep slopes’ performance and rockfall hazards are acceptable, since only an occasional rock makes it to the road. ODOT also expressed satisfaction with the construction and performance of the previous lake embankment at the end of the Doak Mountain project. Other than one relatively minor crack soon after construction, the lake embankment has been performing well and is deemed a success.

The disadvantage of the lake embankment option is that the volume of fill required will be substantial. Based on the information from the past projects at Geary Bridge Canal and the adjacent section of the OR-140 Doak Mountain section widening project, filling in the lake would require approximately 2.5 times the neat line volume above the mudline. The embankment material would need to the durable and relatively clean rock, since it will be placed underwater.

Since no significant cuts would be performed with this option, a borrow source would have to be identified and rock imported to the site at a substantial cost.

7.3 RECOMMENDED OPTION

Based on the above advantages and disadvantages, we recommend that the Option B – Lake Embankment option be selected for the proposed alignment. Steep slopes, rockfall mitigation, and retaining walls all require maintenance and still involve moderate levels of risk at a high

Analysis and Design Recommendations 21 cost. Based on the documentation of the previously constructed lake embankment, the risks for lake embankment are better known and the performance appears to be adequate with relatively low maintenance. We understand that some minor cuts on the southwest side of the roadway will still be necessary to optimize the design and limit the extent of the fill in the lake.

The following sections provide design recommendations for construction of the recommended lake embankment option.

7.4 SPECIAL ROCK EMBANKMENT

The embankment into the lake will require the use of durable, clean, and angular rock materials that requires little compactive effort, is free-draining, and maintains its strength under water.

These types of embankments were termed “stone embankment” by ODOT on the Doak Mountain project, but are typically called Special Rock Embankments (SRE) on Federal Lands Highway projects. The previous Doak Mountain project by ODOT used a stone embankment slope angle of 1V:3H with good success. Our preliminary designs used the 1V:3H slope angle, but due to the significant volumes and high cost we were asked to evaluate steeper slope angles. Based on slope stability modeling and lower overall height of the SRE on the current project compared to the Doak Mountain section, we recommend a final face of slope angle of 1V:2.5H for SREs. The SRE specifications were based on the stone embankment material specifications used on the previous Doak Mountain project.

Prior to placement of the SRE, a reinforcement geosynthetic should be placed over the existing shoreline. The landward edge of the geosynthetic should be anchored to the shore. Significant displacement of the lake sediments and SRE material is expected through a combination of bearing capacity failure and static settlement. Therefore, the embankment construction should be staged to provide sufficient time between fill layers to allow for excess pore pressures to dissipate from the weak subgrade materials. Based on the previous ODOT plans, no more than a 3-foot thickness of fill was allowed within a 24-hour period.

The final grade should also be surcharged with an approximately 2-foot thick layer of material resulting in a 250 psf load. The surcharge should start at the existing road edge and taper down at a 1V:2H slope to zero thickness at the ordinary high water level of the lake. The surcharge material should match the underlying embankment material so that settled areas will not require correction with sliver fills. Removal of excess surcharge material will be required after a minimum waiting period of 4 months or when it appears that 90 percent of consolidation has occurred based on settlement monitoring.

It should be noted that from station 112+00 to 114+95.17 at Geary Canal Bridge, the soils were documented in previous ODOT reports to be highly sensitive to long-term settlement. Therefore, any additional fill will likely cause long-term settlement of the embankment relative to the pile-supported bridge. Furthermore, the external loading may create downdrag or settlement issues with the bridge piling. We understand that embankment fill will be required from station 112+00 to 114+95.17 on the north side of the highway for water quality treatment of roadway runoff adjacent to the lake, although this embankment thickness was reduced in the 70 percent plan set. Some long-term settlement may be encountered here post-construction, if significant amounts of fill are placed in this location.

22 Analysis and Design Recommendations

7.5 SOIL EMBANKMENT SLOPES

All other non-lake fill areas are considered soil embankment areas and should be generally limited to maximum slopes of 1V:2H. These slopes should be designed for both temporary and permanent erosion control, such as the use of a hydromulch with tackifier or rolled erosion control products.

7.6 CUT SLOPES

Significant cut slope areas were evaluated with test pits for both stability and excavatability. Cut slope analyses are based on a combination of acceptable performance of existing cut slopes and the rock/soil materials observed. The following table provides our cut slope recommendations.

Table 7-1 Permanent Cut Slopes Design Summary

Design Stations Recommended Max. Cut Slope

Anticipated Soil/Rock Conditions Comments

20+00 to 110+00 1V:2H Colluvial soil and rock

Limit cut slopes and use flattest slope possible.

Limited sections of 1:1.5 cuts up to ~10 feet in vertical height OK.

162+00 to ~185+00 1V:1.5H

Basalt varies from scoriaceous to slightly vesicular, moderately weathered to slightly weathered, very weak to strong rock. Highly weathered residual soil / colluvium in between rock outcrops and at base of slopes

Rock ranges from relatively exacavatable scoria to very difficult to excavate basalt.

Breakers and/or selective blasting to break up massive rock areas will be needed.

~185+00 to 320+00 1V:1.5H

Basalt, slightly to moderately vesicular, moderately weathered to slightly weathered, weak to strong to strong rock. Silt with gravel/cobbles/boulders colluvium in between rock outcrops and at base of slopes

Rock ranges from exacavatable along existing fractures to very difficult to excavate basalt. Breakers and/or selective blasting to break up massive rock areas will be needed.

Construction Considerations 23

In general, the cut slopes in the scoriaceous and weathered rock will perform better at slope angles of 1V:1.5H. Rockfall boulders encountered in the existing ditches should also be cleaned out during construction.

7.7 INFILTRATION

Infiltration testing was performed as part of the geotechnical investigation. Infiltration tests were either performed in the bottom of the test pits or adjacent to them. A target depth of approximately 2 feet below the existing ditch grade was intended to determine the infiltration rates for stormwater design of proposed ditches.

The excavations were limited by the bedrock encountered in test pit TP17-04. It should be noted that a significant portion of the water was observed to be infiltrating into the sidewalls, of the pits. Descriptions of the test procedures and results are provided in the Preliminary Geotechnical Subsurface Characterization report. Results of the infiltration tests are shown in Table 1F in Preliminary Geotechnical Subsurface Characterization report.

8 CONSTRUCTION CONSIDERATIONS

8.1 EXCAVATION

The slightly to moderately weathered cuts from the original road construction may be able to be excavated a few feet with heavy equipment, although hydraulic breakers or other rock splitting methods will likely be needed for higher and deeper cuts and in fresher/stronger rock areas. The contractor should be responsible for walking the site and determining the best means and methods for performing the soil and rock cuts based on the constraints of the project. Some rock cuts will likely be too narrow to use a bulldozer with a ripping shank, and time intensive hydraulic hammering will likely be necessary. Some boulders may be embedded within soil-like areas, and may require reduction with breakers/splitters to excavate and haul off the materials.

8.2 EMBANKMENT

Non-lake roadway embankment can be constructed with roadway excavation materials consisting of rock and a mixture of sand, silt, and gravel. Embankments constructed with silty sand matrix material excavated on site should be constructed no steeper than 1V:2H. Care should be taken when mixing rock with soil, since open-graded rock placed against soil can allow the finer material to migrate into the voids of the rock resulting in settling or loss of ground in extreme cases. Geotextile filter fabrics or well-graded materials should be used to filter the finer materials and keep them separated.

For lake embankment areas, subgrade preparation should include removal of boulders and large obstructions from shoreline and lake bottom area as needed to place separation-stabilization geotextile in a smooth layer without wrinkles or folds. Lake embankment will consist of special rock embankment material and should be placed in a controlled manner that minimizes wrinkling or damage of the reinforcement geotextile and works from the shoreline outward. Turbidity curtains must be used to contain sediment stirred up by construction

24 Construction Considerations activities. The SRE material should be consolidated using static (non-vibratory) methods, such as track walking or bucket tamping. No more than 3 feet of SRE material should be placed within a 24-hour period to allow excess pore pressures to dissipate from the lake sediments. To reduce impacts to fish and reduce turbidity, end dumping will not be allowed. Material must be placed at the water level or below with a bucket, clamshell, or dozer blade.

8.3 AGGREGATE SOURCES

No aggregate sources will be provided by the Government. The contractor will need to identify their own aggregate sources, such as commercial pits or development of a new pit. Aggregate source materials will be required to meet Specification section 705 of FP-14 and any Special Contract Requirements (SCRs).

Limitations 25

9 LIMITATIONS

This report was prepared to provide subsurface investigation results and geotechnical recommendations for road widening for the OR 140 Klamath County Boat Marina to Lakeshore Drive project in Klamath County, Oregon. Professional judgments and recommendations are presented in this report. They are based partly on evaluation of the technical information gathered and partly on the Geotechnical Team’s general experience with subsurface conditions in the area. It should be noted the explorations might not represent potentially unfavorable subsurface conditions between the exploration locations. The observed water levels and/or conditions indicated on the exploration logs are as recorded at the time of the exploration. The water levels and/or conditions may vary considerably, with time, according to the climate, rainfall, and other factors and are otherwise dependent on the duration of, and methods used in, and interpretations made from the exploration program.

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

Questions regarding this report should be addressed to Eric Lim, WFLHD Geotechnical Engineer, at (360) 619-7826, or eric.lim@dot.gov.

mailto:eric.lim@dot.gov

References 27

10 REFERENCES

Dicken, S.N., 1980, “Pluvial Lake Modoc, Klamath County, Oregon, and Modoc and Siskiyou, Counties, California,” Oregon Geology, vol. 42, no. 11, November 1980, pp. 179-187.

DOGAMI, 2017a, Oregon HazVu: Statewide Geohazards Viewer website, http://www.oregongeology.org/hazvu/, Department of Geology and Mineral Industries, accessed 10/18/2017.

DOGAMI, 2017b, SLIDO: Statewide Landslide Information Layer website, http://www.oregongeology.org/sub/slido/, Department of Geology and Mineral Industries, accessed 10/18/2017.

DOGAMI, 2018, DOGAMI Lidar Viewer website, https://gis.dogami.oregon.gov/maps/lidarviewer/, Department of Geology and Mineral Industries, accessed 10/30/2018.

FHWA, 2014, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects FP-14, United States Department of Transportation, Federal Highway Administration

Foundation Engineering, Inc., 2017, Preliminary Geotechnical Subsurface Characterization, OR DOT 140 (1), OR 140 - Klamath County Boat Marina to Lakeshore Drive, Klamath County, Oregon, WFL Geotechnical Report No. 10-17, dated October 19, 2017

Johnson et al., 1985, Atlas of Oregon Lakes, accessed from https://aol.research.pdx.edu/lakes/18010203003572, accessed on October 31, 2017.

Castro, P., Pfeiffer, A., Renteria, R., (2003), Geotechnical Report, Lake of the Woods (Doak Mtn.) Section, Lake of the Woods Highway (Hwy. 270, M.P. 50.70 – 57.06), Klamath County, Oregon Department of Transportation, October 2003.

ODOT, (2014), Geotechnical Design Manual, Oregon Department of Transportation, Technical Services Branch, Geo-Environmental Section.

Robertson, P.K., and Cabal, K.L., 2015, Guide to Cone Penetration Testing for Geotechnical Engineering, 6th Edition, Greg Drilling & Testing.

Sherrod, D.R. and Pickthorn, L.B., 1992, Geologic Map of the West Half of the Klamath Falls 1° by 2° Quadrangle, South-Central Oregon: U.S. Geological Survey, Misc. Investigations Series MAP I-2182, scale 1:250,000.

http://www.oregongeology.org/hazvu/ http://www.oregongeology.org/sub/slido/ https://gis.dogami.oregon.gov/maps/lidarviewer/ https://aol.research.pdx.edu/lakes/18010203003572

28 References

Six, J. and Castro, P., 1996, Foundation Report, Geary Canal Bridge, Geary Canal Bridge Section, Lake of the Woods Highway, No. 270 (M.P. 58.83) Klamath County, Bridge 18142 Key 06265, Oregon Department of Transportation, March 1996.

Western Federal Lands Highway Division, 2017, OR 140 – Klamath County Boat Marina to Lakeshore Drive, OR DOT 140(1), Preliminary Geotechnical Design Memo, GM30-17, dated November 14, 2017.

Western Regional Climate Center, 2018, Cooperative Climatological Data Summaries, Keno, OR (354403): www.wrcc.dri.edu, accessed December 11, 2018

USGS, 1985, Howard Bay Quadrangle Oregon - Klamath 7.5 minute series (Topogrpahic), U.S.

Geological Survey, scale 1:24,000.

USGS, 1991, Klamath Fall Oregon-California 30 x 60 minute quadrangle, U.S. Geological Survey, scale 1:100,000.

USGS, 2017, Quaternary Fault and Fold Database of the United States, Interactive Fault Map website, http://earthquake.usgs.gov/hazards/qfaults/map/, United States Geologic Survey, accessed 10/18/2017.

USGS, 2019, National Water Information System, Web Interface website, https://waterdata.usgs.gov/nwis/uv?site_no=11507000, United States Geologic Survey, accessed 2/1/2019.

http://www.wrcc.dri.edu/ http://earthquake.usgs.gov/hazards/qfaults/map/ https://waterdata.usgs.gov/nwis/uv?site_no=11507000

APPENDIX A

Site Photographs

Photo A-2, Shoreline and upslope area beyond facing southwest from boat ramp area near STA 30+00. Note the numerous talus slopes above the roadway.

Photo A-1, Upslope area facing southwest near STA 17+00. Note poor vegetation establishment on cut slopes.

Photo A-4, Upslope area facing northwest near STA 34+00

Photo A-3, OR-140 roadway facing north near STA 34+00.

Photo A-6, Shoreline of Upper Klamath Lake facing north near STA 35+00.

Photo A-5, Shoreline of Upper Klamath Lake facing south near STA 35+00.

Photo A-8, Rockfall ditch area…