mora12302_GR09-22.pdf

SR-123: Laughingwater Creek Bridge to Panther Creek Bridge June 2022

Table of Contents 1-i

Geotechnical Report No. 09-22

SR-123: Laughingwater Creek Bridge to Panther Creek Bridge

FINAL GEOTECHNICAL REPORT

WA NP MORA 123(2)

Mount Rainier National Park, Washington June 2022

Table of Contents 1-ii

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Table of Contents i

TABLE OF CONTENTS

1 INTRODUCTION

1.1 Project Description

1.2 Purpose and Scope

2 GEOLOGY

2.1 Geologic Hazards

2.1.1 Site Seismicity

3 SITE CONDITIONS

3.1 Climate Data Summary

3.2 Scour and Erosion Considerations

4 SUBSURFACE CONDITIONS

4.1 Subsurface Borings

4.1.1 Geotechnical Borings

4.1.2 Subgrade Borings

4.2 Groundwater

4.3 Laboratory Testing

5 ANALYSIS AND DESIGN RECOMMENDATIONS

5.1 Ditch Reconditioning

5.2 Subexcavations

5.2.1 Type 1 Subexcavations

5.2.2 Type 2 Subexcavations

5.2.3 Type 3 Subexcavations

5.3 STA 80+00 Culvert Design Considerations

5.4 STA 141+02 Culvert Design Considerations

6 CONSTRUCTION CONSIDERATIONS

6.1 Excavation

6.1.1 Potential Reuse of Excavated Material

6.1.2 Unsuitable Materials

6.2 Subgrade Preparation

7 LIMITATIONS

8 REFERENCES

List of Figures ii

LIST OF FIGURES

Figure 1-1 Project Location Map

Figure 1-2 Project Vicinity Map

Figure 2-1 Excerpt from Surficial Geology of Mount Rainier National Park (Crandell, 1969)

Figure 2-2 Five Percent Damped Design Response Spectrum

Figure 5-1 Type 1 Subexcavation Reinforcement Conceptual Illustration

Figure 5-2 Type 1 Subexcavation Subdrain Conceptual Illustration

Figure 5-3 Type 2 Subexcavation Reinforcement Conceptual Illustration

Figure 5-4 Type 2 Subexcavation Subdrain Conceptual Illustration

Figure 5-5 Type 3 Subexcavation Reinforcement Conceptual Illustration

Figure 5-6 Type 3 Subexcavation Subdrain Conceptual Illustration

List of Tables iii

LIST OF TABLES

Table 2-1 Summary of Seismic Parameters

Table 3-1 Climate Data Summary – Rainier Ohanapecosh, Washington (1926 to 2016)

Table 4-1 Geotechnical Exploration Locations, Exploration Depths, and Depths to Groundwater

Table 5-1 Type 1 Subexcavation Limits

Table 5-2 Type 2 Subexcavation Limits

Table 5-3 Type 3 Subexcavation Limits

List of Photos iv

LIST OF PHOTOS

Photo A-1. Test Boring BH21-01 Exploration with Culvert

Photo A-2. Test Boring BH21-02 Exploration Activity

Photo A-3. Organic Material Observed in SG21-07

Photo A-4. Asphalt Layer Observed Beneath Base in SG21-06

Photo A-5. Breccia Rock Observed in BH21-01, Sample R-4

Photo A-6. Andesite Rock Observed in BH21-02B, Sample R-5

Photo A-7. Subgrade Boring SG21-01 Downhole Stratigraphy

Photo A-8. Subgrade Boring SG21-02 Downhole Stratigraphy

Photo A-9. Subgrade Boring SG21-03 Downhole Stratigraphy

Photo A-10. Subgrade Boring SG21-04 Downhole Stratigraphy

Photo A-11. Subgrade Boring SG21-05 Downhole Stratigraphy

Photo A-12. Subgrade Boring SG21-06 Downhole Stratigraphy

Photo A-13. Subgrade Boring SG21-07 Downhole Stratigraphy

Photo A-14. Subgrade Boring SG21-08 Downhole Stratigraphy

Photo A-15. Subgrade Boring SG21-09 Downhole Stratigraphy

Photo A-16. Subgrade Boring SG21-11 Downhole Stratigraphy

Photo A-17. Subgrade Boring SG21-12 Downhole Stratigraphy

Photo A-18. Subgrade Boring SG21-13 Downhole Stratigraphy

Appendices v

APPENDICES

APPENDIX A – SITE PHOTOGRAPHS

See List of Photos

APPENDIX B – SITE MAPS

Figure B-1: Site Vicinity Map Figure B-2: Site Aerial Photograph Figure B-3-1 through Figure B-3-9: Boring Exploration Maps

APPENDIX C – SUBSURFACE EXPLORATION LOGGING

Descriptive Terminology for Boring Logs Boring Legend Test Borings BH21-01, BH21-02, and BH21-02B Subgrade Borings SG21-01 through SG21-13

APPENDIX D – LABORATORY TEST RESULTS

Introduction 6

1 INTRODUCTION

This report provides the geotechnical investigation results, analysis, and design and construction recommendations for the SR-123: Laughingwater Creek Bridge to Panther Creek Bridge project.

Washington State Route 123 (SR-123) is a state highway managed by Washington State Department of Transportation (WSDOT) and the US National Park Service (NPS) that provides access to Mount Rainier National Park in Washington, as shown below in Figure 1-1 and Figure 1-2. The coordinates and orthometric elevations referenced in this report are based on the Washington South SPCS NAD83 2011 coordinate system and the NAVD88 GEOID18 vertical datum unless stated otherwise. Project work contains an approximate 2.5-mile stretch in Lewis County, Washington before crossing into Pierce County, Washington for the remaining 0.2 miles.

As shown in the 70% Plan Set, the project limits extend from roadway stationing STA 7+18 to STA 154+43.88 (Milepost 5.0 to 7.7).

1.1 PROJECT DESCRIPTION

Proposed roadway improvements include a new roadway section, subexcavation improvements with underdrains, minor bridge repairs, two precast box culverts, and existing culvert maintenance, and parking area and turnout rehabilitation. Additional major drainage improvements may include rerouting of the stream at the second precast box culvert location.

Photos of the alignment and site investigation are listed in the List of Photos and shown in Appendix A.

1.2 PURPOSE AND SCOPE

The purpose of this report is to provide geotechnical recommendations for roadway grading and site preparation, precast box culvert foundation design, and construction considerations. The geotechnical scope of work included a visual reconnaissance along the existing roadway, a subsurface exploration program consisting of three geotechnical borings (BH21-01, BH21-02, and BH21-02B) and 13 subgrade borings (SG21-01 through SG21-13), laboratory soil index testing, preparation of an interim memorandum, and preparation of this report. Geotechnical and subgrade borings were completed by a drilling subcontractor under the direction of a Western Federal Lands Highway Division (WFLHD) geotechnical engineer. Laboratory tests were completed by WFLHD materials testing staff.

The following reports were previously prepared by WFLHD and are available by request:

• Subsurface Investigation Results and Preliminary Geotechnical Recommendations Memorandum, GM 01-22, dated February 1, 2022.

Introduction 7

Figure 1-1 Project Location Map

Introduction 8

Figure 1-2 Project Vicinity Map

Geology 9

2 GEOLOGY

The project alignment is located southeast of Mount Rainier, running generally parallel to and adjacent with the Ohanapecosh River. According to the Surficial Geology of Mount Rainier National Park (Crandell, 1969), the alignment is primarily mapped “Tbr”, with instances of “Ql” at the beginning of the project near Laughingwater Creek Bridge, “Qa” along the middle portion, and “Qe” near the end at Panther Creek Bridge.

The “Tbr” unit is defined as rock formations older than Mount Rainier (Eocene to Miocene or Pliocene). It is described as undifferentiated volcanic, sedimentary, and intrusive igneous rocks.

The “Ql” unit is defined as Landslide deposits (Holocene). Mapped geology indicates mapped landslide deposits were not observed to be moving in 1960 to 1966. The “Qa” unit is defined as Alluvium (Holocene). Alluvial deposits are generally loose deposits of clay, silt, sand, and gravel distributed by streams or rivers. The “Qe” unit is defined as Evans Creek Drift (Pleistocene). It is described as a Fraser Glaciation member of glacial deposits.

Figure 2-1 Excerpt from Surficial Geology of Mount Rainier National Park (Crandell, 1969)

Begin Project

Tbr

End Project

Geology 10

2.1 GEOLOGIC HAZARDS

Geologic hazards can include active faults, liquefaction and related phenomenon, soft or subsiding ground, strong ground shaking, and landsliding, among other natural hazards. Our search did not discover a published geologic hazard map for the vicinity. Based on the geologic mapping and the subsurface conditions encountered in our borings (discussed later in this report), it is our opinion that geologic hazards in the vicinity of the site may include: active faults, liquefaction and lateral spreading, and strong ground shaking. These hazards are discussed subsequently in Site Seismicity below.

2.1.1 SITE SEISMICITY

Information from the USGS Earthquake Hazards Quaternary Fault and Fold Database of the United States was used to locate nearby active faults. According to the website, the Ahtanum Ridge structures fault, unnamed faults of the Ahtanum Ridge uplift section (Citation ID 564b), runs northwest to southeast near the site vicinity. The normal fault is described as 59 kilometers (36.7 miles) in length with N88ºE strike and a vertical dip direction. The slip rate is reported to be in the less than 0.2 millimeters (0.008 inches) per year category, and the age is categorized as late Quaternary (130,000 years) (Lidke, et. al, 2016). The solid line of the mapping website indicates that the fault is well constrained.

The 2020 AASHTO LRFD Bridge Design Specifications (LRFD BDS) use earthquake design ground motion with a 7 percent probability of exceedance in 75 years, approximately equivalent to a return period of 1,000 years. The seismic hazard at the site and the importance of the proposed culverts dictate the level of seismic analysis that is required for the design. The seismic hazard principles within the current AASHTO Specifications are: 1) small to moderate earthquakes should be resisted without significant damage; 2) realistic seismic ground motion intensities and forces should be used in the design; and 3) exposure to shaking from large earthquakes may cause damage to the bridge, but the probability of collapse will be low and the damage will be limited to areas of the structure that are accessible for inspection and repair.

The LRFD BDS states that a site-specific probabilistic analysis to develop design response spectra shall be used if the site is located within 6 miles of an active fault and studies shall be considered to quantify near-fault effects on ground motions to determine if these could significantly influence the bridge response. The unnamed faults of the Ahtanum Ridge uplift section are no less than 32 miles east-southeast of the project, therefore, a site-specific probabilistic analysis is not needed.

The procedures outlined in Section 3.10 of the LRFD BDS were followed to characterize the seismic hazard. Based on Table C3.10.3.1-1—Steps for Site Classification of the LRFD BDS, the seismic Site Class is “D” for the proposed precast box culverts at approximate stationing STA 80+00 and 141+02 on SR-123.

The U.S. Seismic Design Maps website (USGS, 2021) was used to determine the peak ground acceleration and spectral accelerations at the project site based on Site Class B rock. The spectral accelerations were then scaled to Site Class D using the site factors recommended by

Geology 11

AASHTO to represent the seismic accelerations based on actual ground conditions. The results of this analysis are presented below in Table 2-1.

Table 2-1 Summary of Seismic Parameters

Culvert #1

(STA 80+00)

Culvert #2

(STA 141+02)

Site Latitude 46.766072º 46.782166º

Site Longitude -121.548747º -121.553425º

Site Class at Project Site (by Soil Type and Penetration Resistance in Top 100 feet of Soil Profile)

D D

Horizontal Peak Ground Acceleration on Site Class B Rock (PGA) 0.279 0.282

Horizontal Response Spectral Acceleration at a Period of 0.2 sec on Site Class B Rock (Ss)

0.640 0.646

Horizontal Response Spectral Acceleration at a Period of 1.0 sec on Site Class B Rock (S1)

0.206 0.207

Mapped Peak Ground Acceleration Coefficient, FPGA 1.241 1.236

Mapped Short-Period Spectral Acceleration Coefficient, Fa 1.288 1.283

Mapped 1-sec Period Spectral Acceleration Coefficient, Fv 1.989 1.985

Scaled Peak Ground Acceleration for Project Site, Site Class D (As) 0.347 0.348 Scaled Horizontal Response Spectral Acceleration at a

Period of 0.2 sec for Project Site, Site Class D (SDS)

0.825 0.829

Scaled Horizontal Response Spectral Acceleration at a Period of 1.0 sec for Project Site, Site Class D (SD1)

0.409 0.412

AASHTO Seismic Zone 3 3

The values in Table 2-1 were used to develop the 5-percent-damped-design response spectrum shown in Figure 2-2 below for the project site.

Geology 12

Figure 2-2 Five Percent Damped Design Response Spectrum

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Sp ec tr al

A cc el er at io n R es po ns e, g

Period, T (seconds)

Site Conditions 13

3 SITE CONDITIONS

Initial site reconnaissance was conducted July 8, 2021 with a follow-up visit on August 18, 2021 to locate and mark proposed geotechnical and subgrade boring locations prior to commencement of subsurface exploration and to establish preliminary repair limits for subexcavation operations.

Please refer to Appendix A for photographs of site conditions.

The approximate 2.7-mile stretch of SR-123 between Laughingwater Creek Bridge and Panther Creek Bridge contained minimal observable pavement distress due to recent pavement preservation efforts. Pavement preservation efforts consisting of chip seal and/or micro-surfacing masked existing pavement cracking and any evidence of prior repair operations. For more information on pavement conditions, please refer to the Pavement Evaluation Report authored by Nassim Sabahfar of the WFLHD Materials Group in August, 2021.

3.1 CLIMATE DATA SUMMARY

Table 3-1 shows the average maximum and minimum temperatures, average monthly precipitation, and average monthly snowfall data for the period from 1926 to 2016 for the Rainier Ohanapecosh, Washington (456896) weather station (Western Region Climate Center, 2022).

Table 3-1 Climate Data Summary – Rainier Ohanapecosh, Washington (1926 to 2016)

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

Temp. (F) 36.0 39.3 43.3 49.2 64.0 68.5 77.2 78.6 69.3 59.7 41.8 36.8 55.3

Avg. Min.

Temp. (F) 25.9 27.4 29.5 32.0 38.6 44.5 48.9 49.2 45.1 35.8 30.9 27.1 36.2

Avg. Total Precip. (in.) 12.29 8.76 6.79 4.64 3.01 2.40 0.92 1.38 2.97 6.27 11.29 13.14 73.96

Avg. Total Snowfall (in.) 47.4 28.2 17.7 4.1 0.2 0.0 0.0 0.0 0.0 0.3 10.4 34.9 143.7

Avg. Snow Depth (in.) 20 25 21 10 1 0 0 0 0 0 1 9 7

Notes:

1 Period of Record : 10/13/1926 to 06/10/2016.

2 Percent of possible observations for period of record: Max. Temp.: 5.4% Min. Temp.: 5.4% Precipitation: 98.8 Snowfall:

95.5% Snow Depth: 94.4%.

3.2 SCOUR AND EROSION CONSIDERATIONS

Hydraulic impacts were evaluated by the WFLHD Hydraulic Group. General commentary and documentation was provided by Hydraulics Engineer Jenn Mora in the Line-and-Grade Hydraulics Report dated April 28, 2021. According to photos in the report, embankment scour was observed in the vicinity of the first proposed precast box culvert location (STA 80+00) at the 36-inch double-barrel concrete pipe culvert inlets. Local scour was observed on the left bank of an existing culvert (STA 139+84) inlet near the second proposed precast box culvert location (STA 141+02) caused by poor channel alignment.

Subsurface Conditions 14

4 SUBSURFACE CONDITIONS

The subsurface investigation for this project consisted of three geotechnical borings (BH21-01, BH21-02, and BH21-02B) and 13 subgrade borings (SG21-01 through SG21-13). Drilling methods for subgrade borings included asphalt coring and solid-stem auger. Sampling methods within subgrade borings included bulk grab samples utilizing hand tools and 2-inch diameter split-spoons driven during Standard Penetration Tests (SPT). Drilling methods for geotechnical borings included asphalt coring, hollow-stem auger, casing advancer, and HQ3 wireline coring. Sampling methods within geotechnical borings included 2-inch outside diameter split-spoons driven during SPTs and rock core samples obtained from HQ3 wireline coring apparatus. SPT samplers were driven with a 140-pound hammer dropped from 30 inches. The automatic hammer was rated with an average energy transfer efficiency of 76 percent per its hammer energy efficiency report produced in January 2021. The field blowcounts (raw data) were recorded for each 6-inch interval and are presented on the boring logs.

4.1 SUBSURFACE BORINGS

Geotechnical borings BH21-01, BH21-02, and BH21-02B were advanced to depths of 50.4 feet,

30.8 feet, and 50.3 feet below ground surface (bgs), respectively. Boring BH21-02 terminated before reaching the contract-specified minimum depth of 50 feet bgs due to broken HQ3 coring apparatus, so boring BH21-02B was advanced approximately 5 feet north of the original location to satisfy the minimum depth criteria listed in the Statement of Work. Subgrade borings were advanced to depths between 1.8 and 7 feet bgs. Variable termination depths in subgrade borings were due to practical refusal of drill apparatus on boulders or rock. Explorations were conducted on SR-123 with the exception of SG21-11 through SG21-13, which were advanced on Stevens Canyon Road. Table 4-1 summarizes the subsurface exploration program performed for this project and Figures B-3-1 through B-3-12 display subsurface exploration locations. Boring logs and associated lab testing results may be found in Appendix C – Subsurface Exploration Logs and Appendix D – Laboratory Test Results.

Subsurface Conditions 15

Table 4-1 Geotechnical Exploration Locations, Exploration Depths, and Depths to Groundwater

Exploration

Location

Station (feet)

Approximate Offset (feet)

Elevation (feet)

Maximum Exploration

Depth (feet bgs)

Groundwater Depth5

(feet bgs) Latitude (°) Longitude (°)

BH21-01 46.7660292 -121.5487432 79+85 5.5 LT 2192.1 50.4 14.3

BH21-02 46.7818936 -121.5534204 139+96 7 LT 2273.4 30.8 22.0

BH21-02B* 46.781912 -121.553419 140+01 7 LT 2273.4 50.3 22.0

SG21-01 46.749348 -121.55723 11+62 7 LT 2134.4 6.0 NE

SG21-02 46.7514712 -121.557509 20+39 7 RT 2159.9 6.8 NE

SG21-03 46.752605 -121.556933 24+84 6 LT 2173.0 6.7 NE

SG21-04 46.758889 -121.5531992 50+40 5 LT 2216.7 7.0 NE

SG21-05 46.7622227 -121.5497612 65+51 6 RT 2204.6 6.7 NE

SG21-06 46.7650296 -121.5488467 76+19 5 LT 2191 6.8 NE

SG21-07 46.7710678 -121.5484446 98+29 7 LT 2211.9 6.5 NE

SG21-08 46.7765062 -121.5508377 119+04 7 RT 2236.5 3.5 NE

SG21-09 46.782542 -121.5534208 142+32 7.5 RT 2269 6.8 NE

SG21-10 46.7855198 -121.5542147 153+38 7.5 LT 2309.8 3.5 NE

SG21-11 46.754757 -121.5571067 1+77 11.5 LT 2184.2 7.0 NE

SG21-12 46.7555361 -121.5579091 - 6 LT 2178.21 1.8 NE

SG21-13 46.7561091 -121.5582411 - 4 RT 2178.31 3.5 NE

Notes:

1 Location not surveyed, approximate location based on site visit in October 2021.

2 Station unavailable.

3 LT = Left of Centerline, RT = Right of Centerline.

4 NE = Not Encountered.

5 Groundwater depth was measured at the time of drilling.

Subsurface Conditions 16

4.1.1 GEOTECHNICAL BORINGS

Geotechnical borings BH21-01, BH21-02, and BH21-02B were advanced adjacent to proposed culvert locations. Subsurface lithology in geotechnical borings was similar and may generally be grouped into three categories: roadway prism fill, alluvium, and bedrock.

Roadway prism fill consisted of medium dense, brownish gray, moist well-graded sand with silt and gravel underlain by very loose to dense, light brown to tan, moist silty sand with gravel.

Particle size in fill soils ranged from fine to coarse and angularity from subrounded to angular.

Alluvium soils consisted of very loose to very dense, grayish brown to orangish brown, moist silty SAND with gravel; dense to very dense, orangish brown, moist poorly-graded SAND with silt and gravel. Particle size for granular alluvium ranged from fine sands to gravel with cobbles and boulders, generally subrounded to rounded in angularity. Trace organics consisting of tree roots were observed at depths up to 15 feet bgs. Shallow native soils directly beneath fill sections had greater concentrations of organic material and were generally looser in relative density.

Depth to bedrock ranged from 24.8 feet bgs in BH21-02 and 25.2 in BH21-02B to 31.0 feet bgs in BH21-01. Bedrock consisted of breccia with strength and weathering characteristics ranging from extremely weak, residual soil to slightly weathered, strong rock, and andesite with strength and weathering characteristics ranging from slightly weathered, medium strong rock to fresh, very strong rock. Discontinuities ranged from very close to moderately spaced in poor to good condition in breccia and closely to very widely spaced in fair to good condition in andesite. RQD values ranged from 0 to 96 percent in breccia and 9 to 100 percent in andesite. Strength was observed to generally increase with depth.

4.1.2 SUBGRADE BORINGS

Subgrade borings SG21-01 through SG21-13 were advanced along the 2.8-mile long project alignment and the entrance to Stevens Canyon Road. Roadway sections along SR-123 and the entrance to Stevens Canyon Road were generally comprised of several layers of hot-mix asphalt concrete (HMAC) underlain by a screened aggregate product used as base and granular fill material as subgrade. The top layer of asphalt consisted of a thin layer of chipseal or microsurfacing that had been placed recently as part of the Park’s pavement preservation efforts.

Old roadway surfacing material was observed beneath base layers in some instances. Organic material was encountered in several subgrade borings at the fill and native soil interface, and was generally accompanied by very loose sands.

HMAC sections were generally comprised of two to four lifts with total thicknesses ranging from 4 to 10 inches. Roadway base material consisted of medium dense, well-graded, screened aggregate products with maximum nominal particle size ranging from 0.625-inch to 1.5-inch. Old roadway surfacing layers were observed in subgrade borings SG21-05 through SG21-09 at thicknesses ranging from 0.5 to 1 inch. Subsurface roadway surfacing material encountered consisted of an oily gravel product and degraded asphalt concrete. For more information on pavement conditions and recommendations, please refer to the Pavement Evaluation Report dated August 2021, and the Final Pavement Structure Recommendations Memo dated February 2022 authored by Nassim Sabahfar of the WFLHD Materials Group. Subgrade material consisted

Subsurface Conditions 17 of clayey and silty gravel with sand, cobbles and boulders, and silty to well-graded sands with relative densities ranging from very loose to very dense. Practical refusal of drill apparatus was encountered in subgrade borings SG21-08, SG21-10, SG21-12, and SG21-13 at depths between

1.8 and 3.5 feet bgs.

Organics were encountered in subgrade borings SG21-06 through SG21-09. In subgrade borings SG21-06 and SG21-07, organic material was accompanied by very loose sand. The SPT sampler was observed to sink 2 to 4 inches immediately upon placement in both subgrade borings between depths of 2 and 5 feet bgs.

4.2 GROUNDWATER

Groundwater was observed at the time of drilling at 14.3 feet bgs in geotechnical boring BH21-01 and 22.0 feet bgs in BH22-02 and BH22-02B. Depths to groundwater generally correlated well with adjacent surface water elevations. Table 4-1 summarizes groundwater depths encountered at the time of drilling. Groundwater was not observed in any subgrade borings and no monitoring instrumentation was installed. It should be noted these groundwater measurements were taken during fall (October 2021) and groundwater and soil moisture conditions should be expected to fluctuate with water level, precipitation, seasonal snow melt, and other seasonal factors.

4.3 LABORATORY TESTING

Selected soil samples were submitted to the WFL Materials Laboratory for routine soil index testing and R value analysis. Laboratory test reports are presented in Appendix D for select samples from subgrade and geotechnical borings SG21-02, SG21-03, SG21-05, SG21-09, SG21-13, BH21-01, and BH21-02.

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

● Particle Size Analysis - AASHTO T 88

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

● Natural Moisture – AASHTO T 265

● Apparent Specific Gravity – AASHTO T100

● Soil Classification – AASHTO DL145

● R Value – AASHTO WL190

The results of the soil index tests were used to classify the samples according to the Unified Soil Classification System (USCS). USCS classifications are reported on the boring logs where samples were selected for testing.

Analysis and Design Recommendations 18

5 ANALYSIS AND DESIGN RECOMMENDATIONS

This section presents geotechnical recommendations for roadway subexcavations to address areas where pavement distress and drainage issues were observed, and for precast box culvert foundation design considerations. The recommendations provided herein are intended to mitigate mechanisms causing pavement distress and reduce risk of similar pavement damage in the future.

5.1 DITCH RECONDITIONING

As mentioned in the Pavement Evaluation Report by the WFLHD Materials Group, roadside ditches along SR-123 were observed to be clogged with overgrown vegetation and debris from nearby trees. Excess material in ditches may obstruct ditch water flow and promote subsequent seepage into base and subgrade materials adjacent to these ditches. By reconditioning roadside ditches, runoff will flow away from the roadway section and reduce infiltration into base and subgrade materials. Continued maintenance of roadside ditches is an integral part of subexcavation repair efforts.

5.2 SUBEXCAVATIONS

Geotechnical mitigations for the project include full-width roadway repairs of 1- to 3-foot thick subexcavation sections. Given the expectation of maintaining existing grade with a new proposed pavement section of 4 inches of HMAC over 6 inches of recycled aggregate base, vertical subexcavation limits will extend to a maximum depth of 46 inches below finished grade.

Subexcavations will be backfilled with well-compacted, free-draining select borrow as discussed below. The proposed repairs will be lined with separation/stabilization geotextile and reinforced with up to three layers of geogrid spaced vertically 12 inches apart. The total length of proposed subexcavation repairs is approximately 4,210 feet, which represents about 29% of the total length of the project. Conceptual illustrations of subexcavation types are shown below in Figures 5-1 through 5-6.

Analysis and Design Recommendations 19

5.2.1 TYPE 1 SUBEXCAVATIONS

Type 1 subexcavations are proposed as listed under Table 5-1. Conceptual illustrations of Type 1 subexcavation reinforcement layouts and subdrain configurations are shown in Figure 5-1 and Figure 5-2 below. Note that the 12-inch thick excavation is lined with a separation/stabilization geotextile and that a single layer of stabilization geogrid is used in this type of subexcavation.

Backfill should consist of material meeting the Select Borrow material specification of the FHWA Standard Specifications FP-14. The geogrid is placed so that it runs up the front and back sides of the excavation and is “wrapped” back (wrapped lap) a minimum of 6 feet into the excavation at the aggregate base-select borrow interface.

Table 5-1 Type 1 Subexcavation Limits

Subex Start (feet) Subex End (feet) Length (feet) Width

Type 1 STA 19+80 STA 21+05 125 Full Width

STA 48+25 STA 54+40 615 Full Width

Figure 5-1 Type 1 Subexcavation Reinforcement Conceptual Illustration

Figure 5-2 Type 1 Subexcavation Subdrain Conceptual Illustration

Analysis and Design Recommendations 20

5.2.2 TYPE 2 SUBEXCAVATIONS

Type 2 subexcavations are proposed as listed under Table 5-2. Conceptual illustrations of Type 2 subexcavation reinforcement layouts and subdrain configurations are shown in Figure 5-3 and Figure 5-4 below. Note that the 24-inch thick excavation is lined with a separation/stabilization geotextile and that two layers of stabilization geogrid spaced 12 inches apart are used in this type of subexcavation. Backfill should consist of material meeting the Select Borrow material specification of the FP-14. The geogrid is placed so that it runs up the front and back sides of the excavation and is “wrapped” back (wrapped lap) a minimum of 6 feet into the excavation at the aggregate base-select borrow interface.

Table 5-2 Type 2 Subexcavation Limits

Subex Start (feet) Subex End (feet) Length (feet) Width

Type 2

STA 24+75 STA 26+00 125 Full Width

STA 85+50 STA 93+00 750 Full Width

STA 108+00 STA 111+00 300 Full Width

STA 113+20 STA 121+30 810 Full Width

Figure 5-3 Type 2 Subexcavation Reinforcement Conceptual Illustration

Figure 5-4 Type 2 Subexcavation Subdrain Conceptual Illustration

Analysis and Design Recommendations 21

5.2.3 TYPE 3 SUBEXCAVATIONS

Type 3 subexcavations are proposed as listed under Table 5-3. Conceptual illustrations of Type 3 subexcavation reinforcement layouts and subdrain configurations are shown in Figure 5-5 and Figure 5-6 below. Note that the 36-inch thick excavation is lined with a separation/stabilization geotextile and that three layers of stabilization geogrid are used in this type of subexcavation.

Backfill should consist of material meeting the Select Borrow material specification of the FP-14.

The geogrid is placed so that it runs up the front and back sides of the excavation and is “wrapped” back (wrapped lap) a minimum of 6 feet into the excavation at the aggregate base-select borrow interface.

Table 5-3 Type 3 Subexcavation Limits

Subex Start (feet) Subex End (feet) Length (feet) Width

Type 3

STA 72+10 STA 77+20 510 Full Width

STA 79+40 STA 80+15 75 Full Width

STA 93+00 STA 102+00 900 Full Width

STA 141+30 STA 144+00 270 Full Width

Figure 5-5 Type 3 Subexcavation Reinforcement Conceptual Illustration

Figure 5-6 Type 3 Subexcavation Subdrain Conceptual Illustration

Analysis and Design Recommendations 22

5.3 STA 80+00 CULVERT DESIGN CONSIDERATIONS

Based on correspondence with WFLHD Hydraulics Engineer Jenn Mora and the 70% Design Plan Set, the existing double-barrel 36-inch diameter concrete pipe culverts at this location will be replaced by a 9-foot by 9-foot precast concrete box culvert with precast wingwalls and footings.

Excavation of up to approximately 15 feet below the existing roadway grade will be required to install the new culvert. As indicated in Geotechnical Borings, very loose to medium dense silty sands and poorly-graded sand with silt and gravel were observed in boring BH21-01, which was advanced in direct proximity to this culvert. Rock is not anticipated at depths shallower than 30 feet bgs.

The recommended bearing capacity at the Service Limit State is 2000 psf on native granular materials. If soft fine-grained or organic materials are encountered, the project geotechnical engineer should be notified to evaluate the subgrade and provide additional recommendations.

5.4 STA 141+02 CULVERT DESIGN CONSIDERATIONS

Based on correspondence with WFLHD Hydraulics Engineer Jenn Mora and the 70% Design Plan Set, the existing 30-inch diameter concrete pipe culvert at STA 139+84 will be cleaned and protected in-place, and a new 4-foot by 4-foot precast concrete box culvert with precast wingwalls and footings will be installed at STA 141+02. Excavation of up to approximately 12 feet below the existing roadway grade will be required to install the new culvert. As indicated in Geotechnical Borings, very loose to very dense silty sands with gravel were observed in borings BH21-02 and BH21-02B at depths between 6 and 25 feet bgs, which were advanced in direct proximity to the proposed culvert. Cobbles and boulders were encountered at depths between 11 and 13 feet bgs, and trace organics were observed in very loose silty sand layers. Rock is not anticipated at depths shallower than 24.5 feet bgs.

The recommended bearing capacity at the Service Limit State is 2000 psf on native granular materials. If soft fine-grained or organic materials are encountered, the project geotechnical engineer should be notified to evaluate the subgrade and provide additional recommendations.

Construction Considerations 23

6 CONSTRUCTION CONSIDERATIONS

6.1 EXCAVATION

Excavation of subsurface material is expected to be feasible with conventional equipment and should be performed in accordance with the FP-14. Temporary excavation slopes should be performed according to OSHA safety requirements and in general accordance with the Plan Set.

Based on review of subsurface exploration logs, bedrock excavation is not anticipated on this project, however, cobbles and boulders may be encountered at some locations. If boulders or cobbles are encountered with protrusions in excess of four inches at the bottom of excavations, the surface should be smoothed and leveled using rock breaking equipment and techniques.

Alternatively, protruding boulders or cobbles may be removed and their voids should be backfilled with material meeting Section 704.06 Unclassified Borrow of the FP-14. If organics are encountered, they should be removed and backfilled with material meeting Section 704.06 Unclassified Borrow.

6.1.1 POTENTIAL REUSE OF EXCAVATED MATERIAL

It is anticipated that most of the material excavated from the subexcavations will not meet Section

704.07 Select Borrow based on laboratory test results of base and subgrade material acquired during the geotechnical exploration. However, tested materials do appear to meet Section 704.06 Unclassified Borrow. Percent passing the No. 200 sieve on tested samples ranged from approximately 7 to 14 percent. Non-organic roadway excavated material could be reused as embankment.

Processing of excavated material would require added space for material storage and processing on site with water during construction. Furthermore, no subgrade samples were tested for durability, abrasion, weathering, and other tests for aggregate production suitability and mineral aggregate quality, so it is recommended aggregate testing be completed if uses other than Unclassified Borrow are considered.

6.1.2 UNSUITABLE MATERIALS

Unsuitable material are defined as materials not capable of creating stable foundations, embankments, or roadbeds. Unsuitable material includes muck, sod, or soils with high organic contents, such as those generated during clearing and grubbing operations for the project.

Unsuitable materials should be transported offsite to a legal disposal site or stockpiled locally for later use in landscaping and/or non-structural fill applications.

6.2 SUBGRADE PREPARATION

For all excavations within the roadbed and wherever subgrade is exposed, prepare the subgrade in accordance with Section 2014.06(b) by scarifying 6 inches below the subgrade and compacting according to Section 204.11.

Limitations 24

7 LIMITATIONS

This report was prepared to provide subsurface investigation results and geotechnical recommendations for the proposed SR-123: Laughingwater Creek Bridge to Panther Creek Bridge 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 water levels and/or 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 Hayden Gluck, WFLHD Geotechnical Engineer, at (360) 619-7591 or hayden.gluck@dot.gov and Eric Lim, WFLHD Geotechnical Engineer, at (360) 619-7826 or eric.lim@dot.gov.

mailto:hayden.gluck@dot.gov mailto:eric.lim@dot.gov

Limitations 25

GEOTECHNICAL REPORT NO. 09-22

FINAL GEOTECHNICAL REPORT

SR-123: Laughingwater Creek Bridge to Panther Creek Bridge Project

WA NP MORA 123(2)

Mount Rainier National Park, Washington

June 2022

Prepared by: _________________________________________ Hayden Gluck, Geotechnical Engineer

Reviewed by: _________________________________________ Eric Lim, Senior Geotechnical Engineer

Approved by: _________________________________________ Douglas A. Anderson, Geotechnical Functional Manager

References 26

8 REFERENCES

American Association of State Highway and Transportation Officials (2020), AASHTO LRFD Bridge Design Specifications, 9th Edition, Washington, D.C.

Crandell, D.R. (1969), Surficial Geology of Mount Rainier National Park, Washington, Geological Survey Bulletin 1288, U.S. Geological Survey

FLH (2017), Federal Lands Highway Soil and Rock Characterization Guidelines, Federal Highway Administration, December 2017.

Lidke, D.J., and Haller, K.M., compilers (2016), Fault number 564b, Ahtanum Ridge structures, unnamed faults of the Ahtanum Ridge uplift, in Quaternary fault and fold database of the United States, U.S. Geological Survey, website, https://earthquakes.usgs.gov/hazards/qfaults, accessed January 2022.

Mora, J. (2021), Line and Grade Hydraulics Report, U.S. Department of Transportation, Federal Highway Administration, Western Federal Lands Highway Division.

Sabahfar, N. (2021), Rehabilitation of SR 123 - Pavement Evaluation Report, U.S. Department of Transportation, Federal Highway Administration, Western Federal Lands Highway Division.

Sabahfar, N. (2022), Final Pavement Structure Recommendations, U.S. Department of Transportation, Federal Highway Administration, Western Federal Lands Highway Division.

U.S. Geologic Survey (2022a), U.S. Seismic Design Maps, website, https://earthquake.usgs.gov/ws/designmaps/aashto-2009, USGS Geologic Hazards Science Center Golden, CO, accessed June, 2022.

United States Geologic Survey, (2022), Quaternary Fault and Fold Database of the United States, Interactive Fault Map: https://www.usgs.gov/programs/earthquake-hazards/faults, USGS Geologic Hazards Science Center Golden, CO, accessed June, 2022.

Western Regional Climate Center (2016), Cooperative Climatological Data Summaries, Rainier Ohanapecosh, Washington (456896): https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa6896, accessed June, 2022 https://earthquakes.usgs.gov/hazards/qfaults https://earthquake.usgs.gov/ws/designmaps/aashto-2009 https://www.usgs.gov/programs/earthquake-hazards/faults https://www.usgs.gov/programs/earthquake-hazards/faults https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa6896

Appendix 27

APPENDIX A – SITE PHOTOGRAPHS

Photo A-1. Test Boring BH21-01 Exploration with Culvert Photo A-2. Test Boring BH21-02 Exploration Activity Photo A-3. Organic Material Observed in SG21-07 Photo A-4. Asphalt Layer Observed Beneath Base in SG21-06 Photo A-5. Breccia Rock Observed in BH21-01, Sample R-4 Photo A-6. Andesite Rock Observed in BH21-02B, Sample R-5 Photo A-7. Subgrade Boring SG21-01 Downhole Stratigraphy Photo A-8. Subgrade Boring SG21-02 Downhole Stratigraphy Photo A-9. Subgrade Boring SG21-03 Downhole Stratigraphy Photo A-10. Subgrade Boring SG21-04 Downhole Stratigraphy Photo A-11. Subgrade Boring SG21-05 Downhole Stratigraphy Photo A-12. Subgrade Boring SG21-06 Downhole Stratigraphy Photo A-13. Subgrade Boring SG21-07 Downhole Stratigraphy Photo A-14. Subgrade Boring SG21-08 Downhole Stratigraphy Photo A-15. Subgrade Boring SG21-09 Downhole Stratigraphy Photo A-16. Subgrade Boring SG21-11 Downhole Stratigraphy Photo A-17. Subgrade Boring SG21-12 Downhole Stratigraphy Photo A-18. Subgrade Boring SG21-13 Downhole Stratigraphy

Appendix 28

Photo A-1. Test Boring BH21-01 Exploration with Culvert

Appendix 29

Photo A-2. Test Boring BH21-02 Exploration Activity

Appendix 30

Photo A-3. Organic Material Observed in SG21-07

Appendix 31

Photo A-4. Asphalt Layer Observed Beneath Base in SG21-06

Appendix 32

Photo A-5. Breccia Rock Observed in BH21-01, Sample R-4

Appendix 33

Photo A-6. Andesite Rock Observed in BH21-02B, Sample R-5

Appendix 34

Photo A-7. Subgrade Boring SG21-01 Downhole Stratigraphy

Appendix 35

Photo A-8. Subgrade Boring SG21-02 Downhole Stratigraphy

Appendix 36

Photo A-9. Subgrade Boring SG21-03 Downhole Stratigraphy

Appendix 37

Photo A-10. Subgrade Boring SG21-04 Downhole Stratigraphy

Appendix 38

Photo A-11. Subgrade Boring SG21-05 Downhole Stratigraphy

Appendix 39

Photo A-12. Subgrade Boring SG21-06 Downhole Stratigraphy

Appendix 40

Photo A-13. Subgrade Boring SG21-07 Downhole Stratigraphy

Appendix 41

Photo A-14. Subgrade Boring SG21-08 Downhole Stratigraphy

Appendix 42

Photo A-15. Subgrade Boring SG21-09 Downhole Stratigraphy

Appendix 43

Photo A-16. Subgrade Boring SG21-11 Downhole Stratigraphy

Appendix 44

Photo A-17. Subgrade Boring SG21-12 Downhole Stratigraphy

Appendix 45

Photo A-18. Subgrade Boring SG21-13 Downhole Stratigraphy

Appendix 46

APPENDIX B – SITE MAPS

Figure B-1: Site Vicinity Map Figure B-2: Site Aerial Photograph Figure B-3-1 through Figure B-3-9: Boring Exploration Maps

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

Project No.

PROJECT LOCATION MAP Figure

WA NPS MORA 123(2)

Scale

SR-123: LAUGHINGWATER CREEK BRIDGE TO

PANTHER CREEK BRIDGE

MOUNT RAINIER NATIONAL PARK, WA

B-1

See Scale File Name:

MORA 123(2) 1.PPT

Date:

JANUARY 2022

ProjectPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooojjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt

Project Location

Vancouver, WA 98661

Project No.

VICINITY MAP Figure

WA NPS MORA 123(2)

Scale

SR-123: LAUGHINGWATER CREEK BRIDGE TO

PANTHER CREEK BRIDGE

MOUNT RAINIER NATIONAL PARK, WA

B-2

See Scale File Name:

MORA 123(2) 1.PPT

Date:

JANUARY 2022

Project

Bridge Location Bridge Location

PPPPPPPPPPPPPPPPPPPPPPPPPPPPPrrrrrrrrrrrrrrrrrrooooooooooooooooojjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeecccccccccccccccccctttttttttttt

BBBBBBBBBBBBBBBBBBBBBBBBBBBBrrrrrrrrrrriiiiiiiiiiiiddddddddddddddgggggggggggggeeeeeeeeeeeeee LLLLLLLLLLLoooooooooooooocccccccccccccaaaaaaaaaaaaaaattttttttttttiiiiiiiiiiiooooooooooooooooooonnnnnnnnnnn BBBBBBBBBBBBBBBBBBBBBBBBBrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrriiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee LLLLLLLLLLLLLLLLLLLLooooooooooooocccccccccccaaaaaaaaaaaaaattttttttttttttiiiiiiiiiiiiiiiooooooooooooonnnnnnnnnnBBBBBBBBBBBBBBBrrr

End Project

Begin Project

Vancouver, WA 98661

Project No. BORING LOCATION MAP FigureWA NPS MORA 123(2) Scale

SR-123: Laughingwater Creek Bridge to Panther Creek Bridge B-3-9

See Base Image File Name:

FIGURE 3-9.PPTX

Date:

1/21/2022

SG21-13

SG21-12

Appendix 58

APPENDIX C – SUBSURFACE EXPLORATION LOGS

Descriptive Terminology for Boring Logs Boring Legend Test Borings BH21-01, BH21-02, and BH21-02B Subgrade Borings SG21-01 through SG21-13

10/04/2018

A B

E

C D

C D

E

D,F

D,F

I

C H

C H

I

F,H

F,H

J K,L,M

J K,L,M

K,L,M,N

K,L,M,O

K,L,M

K,L,M

K,L,M,P

K,L,M,Q

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

Descriptive Terminology for Boring Logs

10/04/2018 cannot can

If rock is considered to be completely weathered, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

If rock is considered to be completely weathered, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

Appendix 83

APPENDIX D – LABORATORY TEST RESULTS

6.2 Subgrade Preparation