GR 02-20 Camas Road Geotechnical Report.pdf

Camas Road Slumps and Resurface Remaining 4 Miles Project March 2020

Table of Contents 1-i

Geotechnical Report No. 02-20

Camas Road Slumps and Resurface Remaining 4 Miles Project

GEOTECHNICAL REPORT

MT NPS GLAC 11(3)

Glacier National Park, Montana

March 2020

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Table of Contents i

TABLE OF CONTENTS

1 INTRODUCTION

1.1 Project Description

1.2 Purpose and Scope

2 GEOLOGY AND SITE CONDITIONS

2.1 Average Temperatures and Precipitation

2.2 Site Reconnaissance

3 SUBSURFACE CONDITIONS

3.1 Groundwater

4 RECOMMENDATIONS

4.1 Subexcavation

4.2 Station 195+00 Slump

4.3 Wolf Overlook Slump

4.4 Entry Kiosk

5 LIMITATIONS

6 REFERENCES

List of Figures ii

LIST OF FIGURES

Figure 1-1 Project Location Map

Figure 1-2 Vicinity Map

Figure 2-1 Excerpt from the Geologic Map of Glacier National Park, Montana (Whipple, 1992)

LIST OF TABLES

Table 2-1 Climate Data Summary

Table 4-1 Subexcavation Recommendations

APPENDICES

APPENDIX A

Site Photographs

APPENDIX B

Boring Log

APPENDIX C

Laboratory Test Results

APPENDIX D

Pavement Recommendations for PRA-GLAC 11(2), Camas Road, Geotechnical Report No.

3-95, Dated April 1995

Introduction 1

1 INTRODUCTION

This report provides the geotechnical investigation results, analysis, and final geotechnical recommendations for the Camas Road Slumps and Resurface Remaining 4 Miles Project. The project is located approximately 2 miles north of West Glacier, Montana in Glacier National Park.

The project begins at the intersection of Camas Road and Going-to-the-Sun Road (GTSR), as shown in Figure 1-1 Project Location Map, and Figure 1-2 Vicinity Map. The Camas Road was constructed in the mid 1960’s primarily to provide another link with outside park roads including the North Fork road that lies to the west of the North Fork of the Flathead River.

1.1 PROJECT DESCRIPTION

The project involves placing an asphalt overlay on top of the existing surface for approximately four miles. Subexcavation will be performed at locations of pavement distress and frost heave.

Several parking turnouts will be obliterated and a new entrance station near Fish Creek is expected to be constructed. A slump will be repaired along Camas Road and the Wolf Overlook Parking Area will be partially obliterated and regraded to mitigate a slump.

1.2 PURPOSE AND SCOPE

The purpose of this report is to provide geotechnical recommendations for project design and construction considerations. The geotechnical scope of work included a visual reconnaissance along the proposed alignment, a subsurface exploration program consisting of one geotechnical test boring, laboratory soil index testing, and preparation of this report. The geotechnical borings were completed by SK Geotechnical.

The following report provides the results of a 1993 subgrade investigation performed by WFLHD along Camas Road. The report is presented in Appendix D:

• Pavement Recommendations for PRA-GLAC 11(2), Camas Road, Geotechnical Report No. 3-95, Dated April 1995

All stationing referenced in the report is based on the project stationing as of March 2020, which is anticipated to be the final project stationing.

Figure 1-1 Project Location Map

Figure 1-2 Vicinity Map

Geology and Site Conditions 3

2 GEOLOGY AND SITE CONDITIONS

The project area is primarily underlain with deposits of glacial till (Qg) consisting of boulders and cobbles in a gravelly, sandy silt and clay matrix. Alluvium (Qal) consisting of sand and gravel deposits with lenses of silt is mapped from the intersection of Camas Road and GTSR to approximately 1,000 feet beyond McDonald Creek (Whipple, 1992). Figure 2-1 displays the mapped geology of the project area. WFL Geotechnical Report 3-95 provides the following description:

The topography is fairly flat with gently rolling hills. The roadways are constructed with relatively small cuts and fills. The till soils in the subgrade consist primarily of sandy, silty gravel to silty, sandy gravel.

Figure 2-1 Excerpt from the Geologic Map of Glacier National Park, Montana (Whipple, 1992)

Camas Road

4 Geology and Site Conditions

2.1 AVERAGE TEMPERATURES AND PRECIPITATION

Table 2-1 Climate Data Summary shows the average maximum and minimum temperatures, average monthly precipitation, and average monthly snowfall data for the period from 1948 to 2016 for the West Glacier, Montana (248806) weather station (Western Region Climate Center, 2017).

Table 2-1 Climate Data Summary

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

Avg. Max.

Temp. (F) 29.0 34.8 42.1 53.0 64.1 71.2 79.9 78.5 67.2 52.7 37.5 30.1 53.3

Avg. Min.

Temp. (F) 15.7 18.8 23.3 29.9 37.2 43.7 47.6 46.4 39.1 31.9 25.0 18.5 31.4

Avg. Total Precip. (in.) 3.5 2.3 2.0 1.9 2.6 3.5 1.7 1.6 2.1 2.4 3.1 3.3 29.8

Avg. Total Snowfall

(in.)

37.8 21.4 14.8 3.5 0.5 0.2 0.0 0.0 0.1 1.9 16.5 35.6 132.1

Avg. Snow Depth (in.) 18 21 18 5 0 0 0 0 0 0 2 9 6

Note:

1) Period of Record: 07/01/1948 to 06/08/2016.

2) Percent of possible observations for period of record: Max. Temp.: 99.1% Min. Temp.: 99.3%

Precipitation: 99.3% Snowfall: 98.4% Snow Depth: 98.1%.

2.2 SITE RECONNAISSANCE

A site visit was performed on 9/28/2016. The purpose of the visit was to walk the project alignment to evaluate pavement and subgrade conditions for the development of subexcavation recommendations. WFL geotechnical and materials engineers performed the alignment walk.

Subexcavation recommendations are provided in Section 4.1.

The slump failures at Wolf Overlook and along Camas Road (approximate STA 195+00) were also preliminarily evaluated at this time. The slumps at both locations have been present for several years; concrete jersey barriers have been placed at the head scarps of the slumps. The STA 195+00 slump scarp measured approximately 100 feet along the road and 20 to 25 feet in height. Exposed soils at the slump consisted of sandy silt with gravel, cobbles, and boulders.

Boulders up to 36” were observed at the slump. Two grab samples were obtained during the site visit.

Geology and Site Conditions 5

The failure at the Wolf Overlook has damaged the sidewalk adjacent to the parking area. The failure appears to be caused by surface runoff draining to and over the slope face. The existing drainage ditch along Camas Road directs runoff toward the slope.

A second site visit was performed on 5/15/2017 to view the slump sites with National Park Service representatives. Site photos taken during the visits are provided in Appendix A.

6 Subsurface Conditions

3 SUBSURFACE CONDITIONS

One subsurface boring was completed at the STA 195+00 slump site on December 4, 2016. The boring was drilled in the NB travel lane adjacent to the existing slump. Boring BH16-01 was advanced to a depth of 18 feet when auger refusal was met on a boulder. The augers were extracted and the boring moved 5 feet north and drilled to a depth of 34.3 feet when auger refusal was met again. Soils encountered generally consisted of dense to very dense clayey Gravel with sand, cobbles, and boulders. The driller noted very hard drilling conditions. The boring logs are provided in Appendix B.

Soil samples were shipped to WFLHD and laboratory index testing consisting of moisture content, sieve analysis, and Atterberg Limits determination were performed on selected representative samples. Laboratory test results are presented in Appendix C. Subgrade boring logs and laboratory results from the 1993 WFL investigation are presented in Appendix D.

3.1 GROUNDWATER

Groundwater was not directly measured in boring BH16-01 prior to the introduction of drilling fluids at a depth of 8 feet to help auger advancement. Seeps along Camas Road have been observed throughout the year and the cut side ditch at the STA 195+00 slump has been observed to contain water. The season groundwater table is likely near the subgrade level near STA 195+00.

During the September 2016 site visit water was observed within two longitudinal pavement cracks at ~STA 178+00. Weather records at West Glacier, MT indicate 0.11 inches of rain fell in the week prior to the site visit with no rain in the previous three days. Based on the weather records it is believed the water in the cracks was not from rain. Runoff and seeps from the ditch and cut slope upstation of the observed cracks has likely saturated the subgrade in this location. A horizontal cutoff drain is recommended at this location.

Recommendations 7

4 RECOMMENDATIONS

4.1 SUBEXCAVATION

Recommended locations of subexcavation are provided in Table 4-1. The recommendations were developed based on observed pavement distress and settlement during the September 2016 site visit. Subexcavation should extend to a depth at least 24-inches below the subgrade elevation, unless otherwise noted, and be backfilled with select borrow. It is recommended to place type 1, class C separation and stabilization geotextile at the base of subexcavations. Subexcavations should daylight on the side of the embankment or include a piped drainage system with outlets to prevent a “bath tub” section that will retain water below the pavement.

Table 4-1 Subexcavation Recommendations

Approximate Station Width Notes

32+10 to 41+55 Half, Right

61+42 to 62+20 Half, Left

62+62 to 63+35 Half, Right

156+05 to 157+65 Full

174+70 to 175+70 Full 12-inch depth of subexcavation

176+45 to 178+05 Full

188+40 to 189+55 Half, Right Place reinforcement geogrid at base of subexcavation

199+35 to 202+75 Full

205+45 to 206+30 Full

231+00 to 234+15 Full

4.2 STATION 195+00 SLUMP

The STA 195+00 slump scarp measured approximately 100 feet along the road and 20 to 25 feet in height. Exposed soils at the slump consisted of sandy silt with gravel, cobbles, and boulders.

Boulders up to 36” were observed at the slump. The observed failure surface was relatively shallow (less than 5 feet) and likely caused by surface runoff and saturated slope conditions.

Based on Google Earth imagery, the failure has been present since at least 2011. The failure was modeled using the program Slide version 7. It is recommended to excavate the disturbed soil at the site and replace and with clean, angular rock fill.

8 Recommendations

4.3 WOLF OVERLOOK SLUMP

The failure at the Wolf Overlook has damaged the sidewalk adjacent to the parking area. Based on Google Earth imagery, the failure occurred between 2007 and 2009. The circular failure appears to be caused by surface runoff draining to and over the slope face and saturating the ground. The slump appears to have been stable since the initial failure. The existing drainage ditch along Camas Road directs runoff toward the slope. It is understood that it is acceptable to the Park to reduce the pullout width near the failure. It is recommended to direct all surface runoff away from the slope. Regrading operations should not place any additional material near the scarp of the failure. If the edge of the reduced width pullout is approximately 10 feet from the failure scarp and the surface runoff is directed away from the slope, it is expected the failure will not impact the new pullout geometry.

4.4 ENTRY KIOSK

A new entry kiosk is planned to be installed following the completion of this project. Below are foundation recommendations for the planned entry kiosk.

Recommended allowable/service limit state bearing pressure: 4 ksf Recommended allowable/factored coefficient of friction: 0.45 Recommended allowable/factored passive earth pressure: *220 psf/ft *Passive earth pressure should be neglected within 2 feet of the final ground surface.

Limitations 9

5 LIMITATIONS

This report was prepared to provide subsurface investigation results and geotechnical recommendations for the proposed Camas Road Slumps and Resurface Remaining 4 Miles project. 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 borings might not represent potentially unfavorable subsurface conditions away from the borings. The observed conditions indicated on the logs are as recorded at the time of the exploration. The water levels and/or conditions may vary considerably, with season/time, changes in 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 soil conditions are encountered during construction that vary from those discussed in this report, 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 Evan Garich, WFLHD Geotechnical Engineer, at (360) 619-7824, or evan.garich@dot.gov.

mailto:evan.garich@dot.gov

10 Limitations

GEOTECHNICAL REPORT NO. 02-20

FINAL GEOTECHNICAL REPORT

Camas Road Slumps and Resurfacing Remaining 4 Miles Project

MT NPS GLAC 11(3)

Glacier National Park, Montana

March 2020

References 11

6 REFERENCES

Western Federal Lands (1995) Pavement Recommendations for PRA-GLAC 11(2), Camas Road, Geotechnical Report No. 3-95, Dated April 1995

Western Regional Climate Center (2017), Cooperative Climatological Data Summaries, West Glacier, Montana (248809): http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?mt8809, accessed September 8, 2017.

Whipple, J. W. (1992) Geologic Map of Glacier National Park, Montana

AASHTO LRFD Bridge Design Specifications, Eighth Edition American Association of State Highway and Transportation Officials, Washington, D.C.

http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?mt8809

APPENDIX A – SITE PHOTOGRAPHS

Photo A-2, Face of STA 195+00 slump.

Photo A-1, STA 195+00 slump.

Photo A-4, Boring operations (BH16-01 Camas), 12/4/2016.

Photo A-3, Grab sample location at STA 195+00 slump.

Photo A-6, Wolf Overlook failure.

Photo A-5, Boring operations (BH16-01 Camas), 12/4/2016.

Photo A-8, Looking toward Wolf Overlook and failure from Camas Road ditch.

Photo A-7, Wolf Overlook failure.

Photo A-10, Patch over distress, approx. STA 62+00.

Photo A-9, Pavement cracking, approx. STA 35+00.

Photo A-12, Rutting and cracking, approx. STA 157+00.

Photo A-11, Rutting and cracking, approx. STA 63+00.

Photo A-13, Settlement and cracking, approx. STA 178+00.

Photo A-14, Settlement and cracking, approx. STA 189+00.

Photo A-15, Rutting and cracking, approx. STA 200+00.

Photo A-16, Rutting and cracking, approx. STA 232+00.

APPENDIX B – BORING LOGS

B-1

FIGCAMAS ROAD BORING LOCATION PLAN

Camas Road Investigation Glacier National Park, Montana

Project No.

Scale:

File Name:

Date:

N.T.S

Oct. 5, 2016

Western Federal Lands Highway Division 610 East Fifth Street Vancouver, WA 98661

SOIL DESCRIPTIVE TERMINOLOGY

CONSISTENCY OF COHESIVE SOILS

SPT N-Value (blows/ft) Consistency Field Identification

0 - 1 Very Soft Easily penetrated several inches by first

2 - 4 Soft Easily penetrated several inches by thumb

5 - 8 Firm Moderate effort required to penetrate several inches by thumb

9 - 15 Stiff Readily indented by thumb but penetrated only with great effort

16 - 30 Very Stiff Readily indented by thumbnail

> 30 Hard Indented with difficulty by thumbnail

RELATIVE DENSITY OF

COHESIONLESS SOILS

SPT N-Value (blows/ft) Relative Density

0 - 4 Very Loose

5 - 10 Loose

11 - 30 Medium Dense

31 - 50 Dense

> 50 Very Dense

PARTICLE SIZE

Term Sieve Size Boulder > 12” (>300mm)

Cobble 3” - 12” (75mm - 300mm)

Gravel – coarse ¾” - 3” (19mm - 75mm)

Gravel – fine #4 - ¾” (4.75mm - 19mm)

Sand – coarse #10 - #4 (2.00mm - 4.75mm)

Sand – medium #40 - #10 (0.425mm - 2.00mm)

Sand – fine #200 - #40 (0.075mm - 0.425mm)

Silt & Clay < #200 (<0.075mm)

MOISTURE CONTENT

Dry Dusty, dry to the touch

Moist Damp, but no visible free water

Wet Visible free water, saturated, over optimum

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 STRENGTH

Field Identification UCS (psi) Hardness Term Indented by thumbnail. 35 - 150 Extremely Weak (R0) Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife. 150 - 725 Very Weak (R1)

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

725 – 3,500 Weak (R2)

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

3,500 – 7,000 Medium Strong (R3)

Specimen requires more than one blow of geological hammer to fracture it. 7,000 – 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)

16-21-22 (18" = 100%)

9-14-16 (18" = 100%)

16-50-32 (16" = 89%)

11-16-22 (17" = 94%)

8-11-16 (7" = 39%)

30-42-50/3" (9" = 58%)

9-39-50/5" (11" = 65%)

20-50/4" (7" = 73%)

50-5"

15/50-5" (4" = 37%)

2/8/12 (7" = 39%)

3/13/9 (9" = 50%)

9/16/15 (0" = 0%)

50/1½" (1" = 83%)

50-3" (3" = 83%)

Asphalt Concrete (2¾" thick) Clayey GRAVEL with sand, dense, brown, moist, fine to coarse, angular, homogeneous. Fill.

Silty clayey GRAVEL with sand, cobbles, and boulders, dense to very dense, brown, moist, fine to coarse clasts, subrounded clasts, low plasticity, no dilatancy, homogeneous. Glacial till.

Added about 5 gallons of water at 8' to help drill rig advance.

Seams of gravel during drilling.

Silty GRAVEL with sand, cobbles, and boulders, very dense, brown, moist, fine to coarse, subrounded to subangular, low plasticity, homogeneous. Glacial till.

Very hard drilling below 15'.

Met auger refusal at 18' at staked location. Extracted auger and moved boring 5' north and redrilled to 18' and resumed sampling.

Becomes medium dense to dense

Becomes very dense

END OF BORING

0.3

1.8

11.0

34.3

FIELD "N" VALUE

FIELD

BLOW

COUNT

(Recovery)

LATITUDE (DEGREES): N 48° 33' 45.29" (48.56258°)

LONGITUDE (DEGREES): W -114° 0' 42.30" (-114.01175°)

D E

P T

H ft

Sheet 1 of 1

BORING LOG (US Customary Units)

S A

M P

LE

DRILLING METHODS:

DATE FINISHED:

TOTAL DEPTH: 34.3'

LIQUID LIMIT

AFTER DRILLING

2.5" OD Mod CA Sampler (MC)

Split Spoon

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

8" hollow stem auger to 35'

0.0

4.0

8.0

12.0

16.0

20.0

24.0

28.0

32.0

36.0

40.0

Auger refusal and broke bit at 34.3'. Road closed during fieldwork due to weather conditions, not plowed.

NOTES:

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SK Geotech LOGGER: Dustin Hutzenbiler

Cloudy, 32°-34°, windy, heavy snow.

DATE STARTED:

0.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Chad Binstock

WEATHER:

PROJECT: MT NPS GLAC 11(3)

Automatic

WATER CONTENT (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

DRILL: CME-75

D E

P T

H ft

12/4/2016

S A

M P

LE

R

12/4/2016

STATION, OFFSET:

PLASTIC LIMIT

APPENDIX C – LABORATORY TEST RESULTS

APPENDIX D – GEOTECHNICAL REPORT NO. 3-95