Wing Wall Geotech Report 31-1-20083-003 (Reference Material).pdf

SUBMITTED TO:

HDR, Inc.

2525 C Street, Suite 500 Anchorage, AK 99503

BY:

Shannon & Wilson, Inc.

2355 Hill Road Fairbanks, AK 99709

AECC 125

(907) 479-0600 www.shannonwilson.com

GEOTECHNICAL ENGINEERING REPORT

Wing Wall Baling Deck, Chena River Lakes Flood Control Project, Task 3

NORTH POLE, ALASKA

May 10, 2019

Shannon & Wilson No: 31-1-20083-003

Wing Wall Baling Deck, Chena River Lakes Flood Control Project, Task 3 Geotechnical Engineering Report

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CONTENTS

1 Introduction

1.1 Purpose and Scope

1.2 Project Understanding

2 Site and Geological Setting and Seismicity

2.1 Geological Setting

2.2 Seismicity

3 Site and Subsurface Conditions

4 Earthquake Hazards Analysis

5 Wing Wall Baling Deck

5.1 Foundation Recommendations

5.1.1 Axial Pile Capacity

5.1.2 Lateral Pile Resistance

5.1.3 Subgrade Modulus

5.2 Mechanically Stabilized Earth (MSE) Wall

5.2.1 Engineering Soil Parameters

5.2.2 Mechanically Stabilized Earth (MSE) Wall Embedment Depth and Reinforcement Length

5.2.3 Global Stability

5.2.3.1 Methodology and Software

5.2.3.2 Conditions Evaluated

5.2.3.3 Stability Analyses Results and Conclusions

6 Construction Considerations

6.1 Pile Installation

6.1.1 Pile Driving Equipment

6.1.2 Wave Equation Analysis

6.1.3 Monitoring Pile Driving

6.1.4 Pile Driving Acceptance Criteria

6.2 Mechanically Stabilized Earth (MSE) Wall Construction

6.2.1 Site Preparation

6.2.2 Wall Drainage

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6.2.3 Fill Placement and Compaction

6.3 Temporary Excavations

6.4 Construction Erosion Control

6.5 Snow and Weather Conditions

6.6 Plans Review and Construction Observation

7 Closure

8 References

Exhibits Exhibit 4-1: Peak Ground Accelerations (PGAs) Exhibit 5-1: Soil Parameters for use in LPILE Exhibit 5-2: P-multipliers and Pile Group Effects Exhibit 5-3: Recommended Soil Parameters for MSE Wall Design Exhibit 5-4: Global Stability Cases Considered Exhibit 5-5: Global Stability Analysis Results Exhibit 6-1: Gradation Requirements for Structural Fill

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Regional Geology Map Figure 4: Subsurface Profile A-A’ Figure 5: Subsurface Profile D-D’ Figure 6: Estimated Axial Pile Resistance; 24-inch Diameter Open-Ended Pipe Pile Figure 7: Profile D-D’ Stability Analysis, Existing Condition, Static Figure 8: Profile D-D’ Stability Analysis, Proposed Condition, Static Figure 9: Profile D-D’ Stability Analysis, Proposed Condition, Seismic Figure 10: Profile D-D’ Stability Analysis, Proposed Condition, Post-Seismic Figure 11: Profile D-D’ Stability Analysis, Existing Condition, Local GS, Static Figure 12: Profile D-D’ Stability Analysis, Proposed Condition, Local GS, Static Figure 13: Profile D-D’ Stability Analysis, Proposed Condition, Local GS, Seismic

Appendices Appendix A: Engineering Analyses Important Information iv

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ACRONYMS

ASCE American Society of Civil Engineers bgs below ground surface CAPWAP Case Pile Wave Analysis Program DSHA Deterministic Seismic Hazard Analysis FPGA site factor FS factor of safety g gravity H:V Horizontal to Vertical IBC International Building Code MS earthquake magnitude MCE maximum credible earthquake MCEIBC IBC maximum considered earthquake MDE maximum design earthquake MSE mechanically stabilized earth OBE operating basis earthquake PDA pile driving analyzer PGA peak ground acceleration PGAM mean peak ground acceleration SSZ Salcha seismic zone USACE U.S. Army Corps of Engineers USGS U.S. Geological Survey WEAP Wave Equation Analysis for Pile Driving

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1 INTRODUCTION

1.1 Purpose and Scope

This geotechnical engineering report presents the results of our geotechnical study for the Task 3 Wing Wall Baling Deck project at the Chena River Lakes Flood Control Project in North Pole, Alaska. Figure 1 presents a vicinity map showing the project location.

We conducted our services for the project in accordance with the HDR Geotechnical Subconsultant Agreement number 1000100026434, dated February 2018. Our scope of services, described in Attachment D of the above referenced Agreement, included:

Attending the kickoff meeting, Participating in bimonthly teleconferences, Collecting and reviewing existing subsurface data, Providing geotechnical engineering recommendations for the new wing wall deck, and

Preparing this Geotechnical Engineering Report.

We understand this report will be used for the development of construction drawings and specifications for the proposed wing wall baling deck. This report should not be used for other purposes without Shannon & Wilson’s review. The recommendations in this report supersede those provided in all previous versions of this report and those provided via email or other correspondence during the development of our report.

This report was prepared for the exclusive use of our client, HDR, and their representatives for this project.

1.2 Project Understanding

Based on our communications with the U.S. Army Corps of Engineers (USACE) and HDR and the project statement of work dated January 29, 2018, we understand the proposed project includes constructing a baling deck over the existing wing wall and adjacent to the proposed Closed Cell Sheet Pile Baling Deck that was designed under a previous phase of this project, as shown in Figure 2.

The USACE currently bails debris, including spruce, birch, and willow logs, with stumps that are trapped upstream of the bays of the control structure. Baling is currently performed from the top of the Control Works deck. The deck is narrow and has limited room to

31-1-20083-003 May 10, 2019 maneuver, and the line of sight from the crane operator to the debris is limited; in some areas, the crane operator is unable to see the debris that needs to be removed.

We provided geotechnical recommendations for the new baling deck in our report dated August 2018 (Shannon & Wilson, 2018a) as part of Task 6 of this project. Task 3 involves constructing a baling deck over the existing wing wall on the north side of the Chena River, as shown in Figure 2. The Wing Wall Baling Deck will connect to the proposed cellular sheet pile supported baling deck. The Wing Wall Baling Deck will be about 92 feet long and consist of precast concrete slabs supported by steel girders. A mechanically stabilized earth (MSE) wall will be constructed on the north side of the baling deck to connect the proposed deck to the existing grade.

2 SITE AND GEOLOGICAL SETTING AND SEISMICITY

2.1 Geological Setting

The project site is within the Tanana Lowlands physiographic province, which forms a large arcuate band of alluvial sediments between the Alaska Range and the Yukon-Tanana Uplands, as shown in Figure 3. The Lowlands consist of vegetated floodplains and low benches cut by the Tanana River and its tributaries. Soils in the Tanana Lowlands consist of interbedded alluvial sand and gravel covered by silty overbank deposits.

The thickness of alluvial sediments overlying bedrock is unknown at the project site;

however, it has been established to be as great as 600 feet below ground surface (bgs) near the control structure site. Former slough channels are commonly filled with organic silt and peat deposits. These deposits are laterally discontinuous and vary in thickness. The portion of the Tanana Lowlands in which the site is located has not been glaciated.

The project area is in a subarctic zone underlain by discontinuous permafrost. Permafrost is defined as ground that has remained at a temperature of 32 degrees Fahrenheit or less for two or more continuous years. The depth of permafrost measured in the project area is more than 200 feet. The thickness of the "active layer," the portion of the ground at or near the surface that undergoes an annual freeze-thaw cycle, is largely dependent on the type of ground cover and snow depth. Seasonal frost depths can exceed 12 feet bgs in areas kept clear of insulating snow cover such as roads, runways, taxiways, and parking areas. In natural, undisturbed, vegetated areas with thick organic surface cover, seasonal frost depths may be less than 2 feet bgs.

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2.2 Seismicity

The project site lies between right-lateral shear systems: the Denali Fault System approximately 90 miles south of the Moose Creek Dam and the Kaltag and Tintina Fault Systems approximately 80 miles north. The shear along these systems is believed to be the result of crustal adjustments in the North American Plate due to convergence with the Pacific Plate along the Gulf of Alaska.

Seismicity in the area has historically been concentrated in clusters or bands with a northeast-southwest trend that indicates active faulting, although no faults with Holocene displacement have been recognized in the Fairbanks area (Page and others, 1991). These seismic zones include the Salcha Seismic Zone (SSZ) just south of the Moose Creek Dam and the Fairbanks Seismic Zone and Minto Flats Seismic Zone about 35 miles northwest. Page and others (1995) hypothesized these bands delineate the edges of blocks rotating clockwise between two right-lateral shear systems. Outside these northeast-trending linear seismic zones, recorded seismicity appears diffuse. Earthquakes in the area typically occur at depths of less than 25 miles.

Within the past century, interior Alaska has been subjected to four large earthquakes. On July 22, 1937, a magnitude (MS) 7.0 event occurred in the SSZ about 19 miles east of the project site. This event, widely felt throughout central Alaska, produced extensive ground failures in the epicentral area (Page and others, 1995). Two other earthquakes, an October 16, 1947, MS 7.2 event about 65 miles southwest of the Moose Creek Dam and an August 27, 1904, MS 7.3 event suggest thrust-faulting, in contrast to the strike-slip faulting suggested in the area. The epicenter of the 1904 earthquake is uncertain. The November 3, 2002, MS 7.9 event on the Denali Fault, approximately 90 miles south of the project site, was felt widely throughout central and southern Alaska and resulted in minor liquefaction in the Fairbanks area. The peak horizontal ground acceleration of this event recorded on bedrock at the University of Alaska Fairbanks campus was 0.09 g (gravity).

3 SITE AND SUBSURFACE CONDITIONS

The project site is located northeast of the Moose Creek Dam (Figure 2). The proposed baling deck will be constructed on an existing fill embankment. This embankment has an approximately 2.5 Horizontal to 1 Vertical (2.5H:1V) to 3H:1V side slope facing the Chena River channel. An existing concrete cantilever wing wall extends from the Moose Creek Dam control structure to the north bank of the Chena River as shown in Figure 2.

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The existing embankment fill slope is covered in approximately 4 to 5 feet of riprap. During our site visits, we observed rock riprap approximately 8 to 24 inches in equivalent diameter. The material was open-graded and contained trace to few sand and gravel.

We developed our interpretation of the subsurface conditions at the site based on four borings we drilled in May 2018. Logs of these borings, results of geotechnical laboratory testing of soil samples retrieved from them, and descriptions of our exploration procedures and methods are presented in our Geotechnical Data Report (Shannon & Wilson, 2018a).

Our subsurface interpretations are presented in our Geotechnical Engineering Report (Shannon & Wilson, 2018b) and our generalized subsurface profiles (Figures 4 and 5).

In general, our borings encountered a pad of medium dense to dense sand and gravel fill material underlain by a deposit of loose to medium dense sand and gravel alluvium about 30 to 60 feet deep. We encountered medium dense sand and gravel alluvium deposits at the bottoms of our borings.

4 EARTHQUAKE HAZARDS ANALYSIS

The project is in a seismic area where major earthquakes can and have occurred. In accordance with USACE manual, Earthquake Design and Evaluation for Civil Works Projects, EM 1110-2-1806 (USACE, 2016), a seismic hazard analysis should be performed to evaluate the risk associated with those hazards. Earthquake-induced geologic hazards that may affect the site include ground-surface fault rupture and liquefaction and its associated effects (e.g., loss of shear strength, bearing-capacity failures, loss of lateral support, ground oscillation, lateral spreading, and ground settlement due to soil densification).

Our analyses of earthquake ground motions and earthquake-induced geologic hazards that may affect the site are described in the following sections. We describe our seismic hazard analysis in our Geotechnical Engineering Report dated August 2018 (Shannon & Wilson, 2018b).

We developed seismic ground motions for liquefaction and slope stability analyses in general accordance with the USACE manual, Earthquake Design and Evaluation for Civil Works Projects, EM 1110-2-1806 (USACE, 2016). This document provides three design earthquakes:

Maximum credible earthquake (MCE), Maximum design earthquake (MDE), and

Operating basis earthquake (OBE).

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USACE describes the MCE as the “largest earthquake that can reasonably be expected to be generated by a specific source on the basis of seismological and geologic evidence” (USACE, 2016). EM 1110-2-1806 recommends the MCE be determined using a site-specific Deterministic Seismic Hazard Analysis (DSHA). In lieu of a DSHA, we used the International Building Code (IBC) 2015 code to determine ground motions for the IBC maximum considered earthquake (MCEIBC) and assumed it to be equivalent to the MCE (International Code Council, Inc., 2014).

We estimated the MCEIBC using maps for bedrock ground motions published by the U.S.

Geological Survey (USGS) for ground motions with a 2% chance of occurrence in 50 years (USGS, 2018a and 2018b). We adjusted these values assuming Site Class D conditions at the site by applying a site factor (FPGA) of 1.11 (USGS, 2018a). We derived the mapped MCEIBC geometric mean peak ground acceleration (PGAM) using 2010 American Society of Civil Engineers (ASCE) 7 (with 2013 errata) (ASCE, 2013).

We used the USGS Unified Hazard Tool (USGS, 2018b) to estimate bedrock peak ground acceleration (PGA) values for the MDE and OBE earthquakes. We multiplied the same FPGA value of 1.11 used for the MCEIBC to the bedrock values from the MDE and OBE earthquake PGA values. These values are tabulated in Exhibit 4-1.

Exhibit 4-1: Peak Ground Accelerations (PGAs)

Earthquake Return Period Bedrock PGA (USGS, 2018b)

Site Modified

PGAM = FPGA×PGA

=1.11×PGA

Maximum Credible Earthquake (MCE) 2,500 years 0.39 g 0.44 g

Maximum Design Earthquake (MDE) 950 years 0.26 g 0.29 g

Operating Basis Earthquake (OBE) 144 years 0.10 g 0.11 g

We present our liquefaction analysis results in our Geotechnical Engineering Report dated August 2018 (Shannon & Wilson, 2018b). We used the MCE in our liquefaction and global stability analyses because it is the controlling earthquake.

5 WING WALL BALING DECK

We understand the proposed wing wall baling deck will be supported with steel pipe piles.

An MSE wall is proposed to support the soil adjacent to the bridge deck as shown in Figures 2 and 5. We understand the structure will be designed in accordance with the USACE manual, Design of Pile Foundations (USACE, 1991).

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A preliminary layout of the pile-supported wing wall deck is presented in Figure 2. The deck footprint is also indicated in Figure 4.

5.1 Foundation Recommendations

We understand that the proposed wing wall deck will be supported by 24-inch-diameter steel pipe piles. We understand that five piles will be seated on the heel of the existing wing wall foundation. The piles bearing on the existing wing wall foundation will be driven to the design depth, cleaned out, notched into the existing wing wall footing, and filled with concrete.

5.1.1 Axial Pile Capacity

We performed axial resistance analyses for driven 24-inch-diameter, open-end pipe piles.

We performed our analyses using our interpretation of the subsurface conditions, relative densities of the soil estimated from Standard Penetration Test N-values, and our experience with similar soil conditions.

We estimated the axial resistance using an in-house computer program. Figure 6 shows the plot of ultimate single-pile resistance versus depth for static compression and uplift. The factors of safety (FSs) shown in Figure 6 should be applied to the ultimate axial resistance to obtain the allowable axial resistance. Because the near-surface soil at the site is non-frost-susceptible, we did not consider uplift forces due to frost jacking. We understand that the USACE does not want to consider the effects of liquefaction on the proposed baling deck;

therefore, we did not provide downdrag loads due to liquefaction.

In our opinion, the axial capacity of the piles will not be affected if the piles are located a minimum of 2 feet from the edge of the sheet pile. However, to reduce the potential for interference between the sheet piles and pipe piles during construction, we recommend maintaining a 3-foot separation between the outside edge of steel pipe piles and inside face of the sheet piles.

5.1.2 Lateral Pile Resistance

The computer program LPILE may be used to generate p-y curves (load-deflection curves) for the lateral resistance analysis of the pipe piles and to calculate the magnitude of deflection, shear, and moment along the piles. The recommended soil parameters for input into LPILE under static soil conditions are summarized in Exhibit 5-1. We did not provide parameters to account for reduced strength due to liquefaction.

Based on our review of topographic maps around proposed pier locations, some of the piers are in or near the slope. The depth of the slope varies between about 8 and 35 feet, with side

31-1-20083-003 May 10, 2019 slopes ranging from 2H:1V to 10H:1V. The loss of lateral resistance as a result of sloping ground next to a shaft should be considered in the lateral analyses by entering the slope angle in LPILE.

To account for group effects, the recommended soil parameters in Exhibit 5-1 should be adjusted using the P-multipliers summarized in Exhibit 5-2. These efficiency factors should be used in lateral resistance analyses of pile groups.

Exhibit 5-1: Soil Parameters for use in LPILE

Soil Description Top Depth

(feet) Bottom Depth

(feet)

LPILE

Model

Effective Unit Weight

(pcf)

Friction Angle, ɸ (degrees)

Initial Modulus of Subgrade Reaction, k

(pci) Medium Dense to Dense

Gravel 0 15 Sand

(Reese) 130 36 125

Loose to Medium Dense Sand and Gravel

15 50 Sand (Reese)

62.6 34 60

Medium Dense Sand and Gravel

50 75 Sand (Reese)

67.6 36 75

NOTES:

pcf = pounds per cubic foot; pci = pounds per cubic inch

Exhibit 5-2: P-multipliers and Pile Group Effects

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5.1.3 Subgrade Modulus

We understand piles over the existing wing wall will bear on the existing wing wall foundation. The additional load from these piles on the existing wing wall foundation will result in increased bearing pressure on the subgrade. To evaluate the impact of the additional load on the response of the existing wing wall, we recommend that the structural engineer use a structural program that incorporates the stiffness of the existing wing wall footing and the subgrade reaction.

The modulus of subgrade reaction (kS) for the soil supporting the existing wing wall footing can be characterized using the following equations:

(1) 𝑘𝑘𝑠𝑠 = 𝑝𝑝/𝛿𝛿 (in units of force per length cubed) where:

p = applied stress δ = displacement under p

(2) 𝑘𝑘𝑠𝑠 = �0.65

𝐵𝐵

� ∙ �𝐸𝐸∙𝐵𝐵

𝐸𝐸𝑓𝑓𝐼𝐼𝑓𝑓

1/12

∙ � 𝐸𝐸

1−𝜈𝜈3 where:

B = width of footing E = subgrade material Young’s modulus Ef = footing Young’s modulus If = footing moment of inertia EfIf = footing stiffness υ = subgrade material Poisson’s Ratio

We recommend assuming υ = 0.3 and E = 500 kips per square foot.

5.2 Mechanically Stabilized Earth (MSE) Wall

An MSE wall is planned to connect the wing wall baling deck to existing grade on the landside of the structure. We understand that the type of MSE wall may be selected by the Contractor and wall supplier. We understand the USACE has specified the use of steel reinforcement and concrete wall fascia (e.g., concrete blocks or precast concrete facing panels).

5.2.1 Engineering Soil Parameters

We understand the internal and external MSE wall design will be performed by the wall supplier. We recommend using the following parameters for MSE wall internal and external design (Exhibit 5-3).

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Exhibit 5-3: Recommended Soil Parameters for MSE Wall Design

Parameter Retained Soil Reinforced Soil Foundation Soil

Unit weight (pcf) 125 135 125

Friction angle (degrees) 34 36 34

Cohesion (psf) 0 0 0

Allowable bearing capacity (psf) -- -- 4,000

Coefficient of sliding friction -- -- 0.42

NOTES:

pcf = pounds per cubic inch; psf = pounds per cubic foot

The MSE wall internal and external design should consider the design earthquake ground motions provided in Section 4.1.

5.2.2 Mechanically Stabilized Earth (MSE) Wall Embedment Depth and Reinforcement Length

The lowest layer of reinforcement should be located a minimum of 24 inches below the elevation at which there is a 4-foot horizontal distance from the wall face to the slope face in front of the wall, excluding the presence of riprap. The base of the excavation should be in non-frost-susceptible sand and gravel and should be compacted with several passes of a large vibratory compactor.

We recommend a minimum reinforcement length of 0.7H or 8 feet, whichever is greater, where H is the wall height. The reinforcement lengths may need to be increased to meet internal, external (bearing resistance, sliding, and overturning), or compound stability requirements. These failure modes should be evaluated by the MSE wall designer, as these failure modes depend on the reinforcement type and spacing selected by the wall designer.

5.2.3 Global Stability

We evaluated global stability of the proposed MSE wall structure in general accordance with the USACE manual, USACE Slope Stability Manual, EM 1110-2-1902 (USACE, 2003).

5.2.3.1 Methodology and Software

A global stability analysis is an evaluation of the overall stability of a structure. The result of this analysis is a FS defined as the ratio of resisting forces/moments to driving forces/moments.

We performed global slope stability analyses using the program SLOPE/W, Version 10 (Geo-Slope International, 2019). We used the Spencer method (1967), which satisfies both force and moment equilibrium, to compute the FS along possible failure surfaces. We

31-1-20083-003 May 10, 2019 defined a minimum failure surface depth of 5 feet. We used a two-step process to calculate critical failure surfaces for each analysis case. First, we specified circular slip surface entry and exit ranges on the ground surface behind the proposed cells and within the Chena River channel, respectively. Then we employed the SLOPE/W optimization technique, which systematically modifies the most critical circular failure surface, to find a non-circular failure surface with a lower FS.

5.2.3.2 Conditions Evaluated

We evaluated the global stability using the generalized geologic profile D-D' (Figure 5), because it represents the most critical condition along the proposed MSE wall.

We evaluated three primary loading cases for our global stability analyses. For each case we considered failure surfaces that extended from the top of the embankment down to the river channel and failure surfaces in the upper bench where the proposed retaining wall will be constructed. In this report, we refer to our analysis of the upper bench as local global stability. FS target and water level assumptions for these cases are summarized in Exhibit 5-4.

Exhibit 5-4: Global Stability Cases Considered

Case Target Factor of Safety

(FS)

Water Level Elevation in Chena River

(feet)

Static 1.5 493.5

Seismic (Pseudostatic) 1.3 493.5

Post-Seismic (Liquefied) -- 493.5

NOTE:

USACE does not wish to consider liquefaction in the design. We present liquefaction results for informational purposes only.

5.2.3.3 Stability Analyses Results and Conclusions

The results of our global stability analyses are presented in Figures 7 through 13 and tabulated in Exhibit 5-5.

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Exhibit 5-5: Global Stability Analysis Results

Figure Case Target FS FS Obtained from Analysis

7 Existing; Static 1.5 1.36

8 Proposed; Static 1.5 1.34

9 Proposed; Seismic (Pseudostatic) 1.3 0.83

10 Proposed; Post-Seismic (Liquefied) -- 0.35

11 Existing; Static – Local 1.5 1.79

12 Proposed; Static – Local 1.5 1.72

13 Proposed; Seismic (Pseudostatic) – Local 1.3 1.17

NOTE:

FS = factor of safety

Our analysis results suggest that the current conditions do not meet the target FS for failure surfaces that extend from the top of the embankment to the river channel and that MSE wall construction will not significantly impact the global stability for deep-seated failures.

Therefore, efforts to improve the stability of the overall embankment to achieve the target FS of 1.5 are not justified.

We did not evaluate the post-seismic condition for local global stability because it would not be significantly impacted by the presence of the proposed retaining wall. Our local global stability analysis results suggest that the proposed conditions meet the target FSs for failure surfaces of the upper bench that could impact the stability of the wall itself.

Appendix A includes our global stability calculations.

6 CONSTRUCTION CONSIDERATIONS

The applicability of the geotechnical design parameters we provide in the report is contingent upon good construction practice. Poor construction techniques and methods may alter conditions upon which our recommendations are based. The following sections discuss some construction considerations for this project.

6.1 Pile Installation

6.1.1 Pile Driving Equipment

We recommend using fixed-lead pile driving equipment to drive the steel pipe piles.

Hanging or swinging leads should not be used. Leads should be long enough so that the use of followers will not be necessary. An air-, steam-, or diesel-powered hammer may be

31-1-20083-003 May 10, 2019 used for driving the proposed piles. Contractors should not be allowed to use a vibratory hammer to install piles inside the cellular sheet pile structure.

Pile driving could be difficult if seasonally frozen ground is encountered. Therefore, we recommend that the Contractor have equipment available on site to predrill if needed. We recommend that predrilling, if needed, occur to a maximum depth of 20 feet.

We recommend that each pile be equipped with a high-strength steel tip to facilitate driving.

Driving steel pipe piles with an oversized high-strength steel tip could compromise the contact between the soil and the outside surface of the pile. To reduce the potential for compromising this contact and upward flow of groundwater around the outside of the casing, we recommend the driving tip and seam welds along the pile be flush with the outside surfaces of the piles.

6.1.2 Wave Equation Analysis

Efficient pile driving can be defined as driving the pile to the desired ultimate resistance at a reasonable blow count and with driving stresses not exceeding 80% of the yield strength of the pile. To establish driving criteria for pile installation, the Contractor should perform a Wave Equation Analyses for Pile Driving (WEAP) using data for the actual hammer/pile combination to be used to install the production piles. WEAP allows evaluation of driving stresses so an appropriate pile driving hammer size can be selected to obtain the desired pile resistance with reasonable blow counts and without damaging the piles. The Contractor should be required to provide a WEAP analysis for review and approval prior to pile driving.

6.1.3 Monitoring Pile Driving

Pile driving should be monitored by creating a continuous driving record of each pile. For this purpose, the Contractor should be required to mark the pile in 1-foot increments.

During redrive, additional 1-inch increments between the 1-foot marks would be required.

The pile driving record should be complete. The form should have spaces to record hammer stroke (diesel hammers), blows per foot, time, date, reasons for delays, and other pertinent information. The record should include tip elevation, driving criteria, and initials of inspectors making final acceptance of the pile. The pile driving records should be reviewed daily. For this purpose, we recommend that an experienced and qualified geotechnical engineer or their representative familiar with the subsurface conditions of the project site be retained to assist in construction monitoring.

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Driven piles should be checked for possible heave. The heave should be checked by surveying the elevation of each pile butt after a pile is driven. The heave data should be provided to the USACE and the Engineer to evaluate if redrive will be required. In general, if the heave is greater than 0.25 inch, the pile should be re-driven to original tip elevation.

It may be difficult to estimate the energy delivered by diesel hammers based on observation.

The Saximeter, developed by Pile Dynamic, Inc., can be used to record hammer strokes and provide an estimate of the driving energy of diesel hammers. If the Contractor selects a diesel hammer, we recommend that a Saximeter be used during pile driving.

6.1.4 Pile Driving Acceptance Criteria

To confirm that the required capacities are achieved, we recommend obtaining dynamic pile measurements using a pile driving analyzer (PDA) and signal matching with Case Pile Wave Analysis Program (CAPWAP) on a minimum of two piles. Piles to be tested should be selected by the USACE’s geotechnical representative. PDA measurements are typically obtained at the end of continuous driving and beginning of restrike. The results of the PDA measurements can be used in CAPWAP to estimate the total ultimate resistance of the piles, the distribution of soil resistance along the pile, and the load transmitted to the pile tip.

PDA results provide an indication whether desired resistances are achieved.

6.2 Mechanically Stabilized Earth (MSE) Wall Construction

6.2.1 Site Preparation

The area to be excavated for the MSE wall should be prepared by removing surficial silt, organics, riprap, and previously placed fill to the elevation required for the wall foundation.

Seasonal frost in the base of the excavation should be allowed to thaw a minimum of 2 feet below the base of the excavation prior to backfill. Seasonally frozen soils can be excavated and replaced with unfrozen non-frost-susceptible fill or allowed to thaw naturally.

6.2.2 Wall Drainage

We understand that the USACE does not want to have drainage pipes behind the wall because they frequently clog. To reduce the potential for water pressures developing behind the wall, we recommend constructing the wall using free-draining backfill as recommended in the following section.

6.2.3 Fill Placement and Compaction

Prior to wall construction, the Contractor should remove the existing riprap and bench the original ground where backfill will be placed on the existing slope. The face of each bench

31-1-20083-003 May 10, 2019 should be no more than 2 feet in height and should be vertical or near vertical as required to remain stable during material placement and compaction. The top of the bench should slope away from the cut face to drain and shall not be inclined steeper than 0.05 foot per foot. Benches damaged during work must be reestablished.

We recommend backfilling with non-frost-susceptible structural fill, meeting the following gradation limits (Exhibit 6-1):

Exhibit 6-1: Gradation Requirements for Structural Fill

Percent Passing

Soil Reinforced Soil – Steel

Reinforcement Retained Soil

4-inch 99-100 100

2-inch 75-100 100

1 ¼ inch

1-inch

No. 4 sieve 50-80 30-60

No. 40 0-30

No. 200 sieve 0-3 0-5

The reinforced soil will be placed and compacted within the proposed reinforced zone of the MSE wall to achieve the desired baling deck grade. Retained soil is placed and compacted behind the reinforced zone of the wall. For typical wall designs, structural backfill is required to be compacted to at least 95% of the modified proctor value (ASTM D1557).

Backfill should be placed in loose lifts no thicker than 12 inches for heavy equipment compactors. Small hand-operated compaction equipment should be used within 18 inches of the wall face. Loose lifts should be no thicker than 6 inches for hand-operated compaction equipment.

ASTM D6938 Procedure A should be used to measure in-place densities. The fill should consist of unfrozen material and be placed at above-freezing air temperatures. If previously placed fill freezes, for instance, overnight, the frozen material should be excavated and wasted or allowed to thaw and recompact prior to the placement of additional fill.

While preparing the MSE wall lifts, the Contractor should be sure that the machine direction of the reinforcement runs perpendicular to the wall face and that heave equipment not be allowed to run directly over the reinforcement.

31-1-20083-003 May 10, 2019

6.3 Temporary Excavations

For safe working conditions, prevention of ground loss, and protection of existing work, temporary shoring, and excavation slopes should be the responsibility of the Contractor, who will be at the job site to observe and control the work. All current and applicable safety regulations regarding shoring and excavation slopes should be followed.

6.4 Construction Erosion Control

The Contractor should employ proper erosion control measures during construction, especially if construction takes place during wet weather or in wet conditions. Covering work areas, soil stockpiles, and slopes with plastic; using sandbags to divert flow; using sumps to drain low areas; and other measures should be employed as necessary to permit proper completion of the work. Straw bales, geotextile silt fences, and drain inlet sediment screens/collection systems should be appropriately located to control soil movement and erosion. Erosion control methods and monitoring plans should be approved and in place before construction begins.

6.5 Snow and Weather Conditions

We recommend performing excavation operations, pile driving, and MSE wall construction during warmer months when it is less likely that snow will fall or be present on the ground (e.g., May to September).

6.6 Plans Review and Construction Observation

We recommend that Shannon & Wilson be retained to review those portions of the plans and specifications that pertain to the pile-supported baling deck, MSE wall, and associated earthwork to determine if they are consistent with our recommendations. We recommend that we be retained to visit the site during the geotechnical aspects of construction to observe that the work is accomplished in accordance with our recommendations.

7 CLOSURE

Our interpretations, analyses, conclusions, and recommendations are based on the following:

The limitations of our approved scope, schedule, and budget.

Our understanding of the project and information provided by the Owner and our client.

Our previous experience near the project site and on similar projects in the area.

31-1-20083-003 May 10, 2019

This report was prepared for the exclusive use of HDR for specific application to the design and construction of the baling improvements at Chena River Lakes Flood Control Project.

The analyses and recommendations presented in this report apply to the proposed design developed by the design team. This report is not intended to be used or relied upon for any other purpose. Shannon & Wilson has prepared a document titled, “Important Information About Your Geotechnical/Environmental Report,” which is enclosed. Please read this document to learn how you can lower your risks for this project.

8 REFERENCES

American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures (3rd printing): Reston, Va., American Society of Civil Engineers, ASCE Standard ASCE/SEI 7-10.

Geo-Slope International, 2019, SLOPE/W v 10: Calgary, Alberta, Geo-Slope International.

International Code Council, Inc., 2014, International building code 2015: Country Club Hills, Ill., International Code Council, Inc., 700 p.

Page, R.A.; Biswas, N.N.; Lahr, J.C.; and Pulpan, H., 1991, Seismicity of continental Alaska, in Slemmons, D.B.; Engdahl, E.R.; Zoback, M.D.; and Blackwell, D.D., eds., Neotectonics of North America: Boulder, Colo., Geological Society of America, Decade of North American Geology, p. 47-68.

Page, R.A.; Plafker, George; and Pulpan, Hans, 1995, Block rotation in east-central Alaska: A framework for evaluating earthquake potential: Geology v. 23, no. 7, p. 629-632.

Spencer, E., 1967, A method of analysis of the stability of embankments assuming parallel inter-slice forces: Geotechnique, v. 17, no. 1, p. 11-26.

Shannon & Wilson, Inc., 2018a, Baling improvements, Chena River Lakes Flood Control Project, geotechnical data report, North Pole, Alaska : Report prepared by Shannon & Wilson, Inc., Fairbanks, Alaska, project no. 31-1-20083-006, for HDR, Inc., Anchorage, Alaska, June.

Shannon & Wilson, Inc., 2018b, Baling improvements, Chena River Lakes Flood Control Project, geotechnical engineering report, North Pole, Alaska : Report prepared by Shannon & Wilson, Inc., Fairbanks, Alaska, project no. 31-1-20083-006, for HDR, Inc., Anchorage, Alaska, August.

31-1-20083-003 May 10, 2019

U.S. Army Corps of Engineers (USACE), Engineering and Design, 1991, Design of Pile Foundations, Engineering Manual 1110-2-1902: Washington, D.C., January, available:

https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManual s/EM_1110-2-2906.pdf?ver=2013-09-04-070827-700

U.S. Army Corps of Engineers (USACE), Engineering and Design, 2003, Slope Stability, Engineering Manual 1110-2-1902: Washington, D.C., October, available:

https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManual s/EM_1110-2-1902.pdf.

U.S. Army Corps of Engineers, 2016, Engineering and design - earthquake design and evaluation for civil works projects: U.S. Army Corps of Engineers, Engineer Manual EM 1110-2-1806, 1 v, May 31, available:

https://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulat ions/ER_1110-2-1806.pdf

U.S. Geological Survey (USGS), 2018a, U.S. Seismic Design Maps Applications: Available:

https://earthquake.usgs.gov/designmaps/us/application.php, accessed May 2018.

U.S. Geological Survey, 2018b, Unified hazard tool: Available:

https://earthquake.usgs.gov/hazards/interactive/, accessed May, 2018.

https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-2906.pdf?ver=2013-09-04-070827-700 https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-2906.pdf?ver=2013-09-04-070827-700 https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-1902.pdf https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-1902.pdf https://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1110-2-1806.pdf https://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1110-2-1806.pdf https://earthquake.usgs.gov/designmaps/us/application.php https://earthquake.usgs.gov/hazards/interactive/

© 2018 Microsoft Corporation © 2018 DigitalGlobe ©CNES (2018) Distribution Airbus DS

PROJECT

LOCATION

L a u r a n c e

R o a d

R i c h a r d s n

H i g h w a y

North Pole

Moose Creek

C h e n a R i v e r

M o o s e C r e e k

VICINITY MAP

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

May 2019 31-1-20083-003

Fairbanks

Alaska

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

F i l e n a m e

J

V c i n i t y

M a p d w g

D a t e

L g i n a w p

5000 10000

Approximate Scale in Feet

Project

Location

MT

FIG. 1

AP-3016

AP-3017

AP-3015

AP-3018

F i l e n a m e

D

P r o j e c t s S

W

M o o s e

C r e e k

C

H L

P l a n d y o u t s e p l a n t e g i n c a b r y

SITE AND EXPLORATION PLAN

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

31-1-20083-003May 2019

AP-3015

A

Boring Designation and

Approximate Location

Generalized

Subsurface Profile

LEGEND

NOTE

Figure adapted from client file, "CHENA

EXHIBIT SK-001.dwg", received 6-6-2018 and

"CHL020-S-101.dwg", received 3-7-2019.

50 100

Scale in Feet

FIG. 2

A

A'

D

D'

Chena River

Wing Wall Footing Outline

Existing Top Wing Wall

Edge of Crane Track

PS31 Sheet Piles

155'

Moose Creek Dam

Control Structure

PROPOSED CLOSED CELL

BALING DECK STRUCTURE

PER TASKS 1 AND 2A OF

THIS DESIGN PROJECT

PROPOSED WING

WALL BALING DECK

PROPOSED MECHANICALLY

STABILIZED EARTH WALL

PARKS HIGHWAY

ST

EE

SE

EX

PR

ES

SW

AY

/H

IG

HW

AY

RICHARDSON HIGHWAY

EL

LIO

TT

HI

GH

WA

Y

|<yqm

|kp

|kp

|<yqs

|<yqsTKg

TKg

|kp |kp

|<yqs

|kp

|kp

Dmi

|kp

|kp

|<yqs

|<yqs

|kp

|<yqs

MDts

|<yqs

|kp |kp

|<yqs

|kp

|<yqm

Kmgr|<yqs|<yqs

TKg

|<yqs |<yqs

Kmgr |<yqs

|kp

|<yqs

|kp

|kp

|<yqs

|<yqm

|<yqm

|kp |kp

|<yqs

|<yqs

|<yqs |<yqs|<yqs TKg|<yqm

|<yqs

Moose Creek Dam Control Structure

0 1 2 3 4 5 6 7 80.5

Miles Wing Wall Baling Deck

Chena River Lakes Flood Control Project North Pole, Alaska

May 2019

REGIONAL GEOLOGY MAP

FIG. 3

31-1-20083-003p

LEGEND

Project_location

Qs Unconsolidated surficial deposits, undivided

Water

QTs Poorly consolidated surficial deposits

Tvu Volcanic rocks of southern Alaska

TKg Felsic granitic rocks

Kmgr Granitic rocks of central and southeast Alaska

Kmqm Quartz monzonite, monzonite, and syenite

Pze Eclogite and associated rocks

MDts Totatlanika Schist

Dmi Metamorphosed mafic igneous rocks

Pzkp Keevy Peak Formation and similar rocks

PzPxygs Gneiss, schist, and quartzite

MzPzyo Peridotite of dismembered ophiolite of the Yukon-Tanana region

MDag Augen gneiss and orthogneiss

CPxwn Wickersham and Neruokpuk units

PzPxyqs Quartzite and pelitic schist

PzPxyqm Pelitic schist, including Chena River sequence

Pzyms Mafic schist and amphibolite

Map source: Wilson and others, 2015, USGS

A p p r o x i m a t

E l e v a t i o n

F e t

A p p r o x i m a e v a t i o n e t

Distance in Feet

0 30 60 90 120 150 180 210 240 270 300 330 360 390 420

Loose to Medium Dense Sand and Gravel (Alluvium)

Medium Dense to Dense Sand and Gravel (Fill)

Medium Dense to Dense Sand and Gravel (Fill)

Loose to Medium Dense Sand and Gravel (Alluvium)

Medium Dense Sand and Gravel (Alluvium)

Medium Dense Sand and Gravel (Alluvium)

05-13-18

AP-3017

05-10-18

AP-3018

6"

05-11-18

AP-3016

(Proj. 8' NE) (Proj. 24' SW) (Proj. 35.5' SW)

West Cell Center Cell East Cell

GRAB

05-12-18

AP-3015

(Proj. 88' SW)

D

F i l e n a m e

D

P r o j e c t s S

W

M o o s e

C r e e k

C

H L

P l a n d y o u t p r o f i l t e g i n c a b r y

FIG. 4

GENERALIZED SUBSURFACE

PROFILE A-A'

30 60

Scale in Feet

1. Existing and proposed grades, proposed features, and design elevations are adapted from client file, "CHENA EXHIBIT SK-001.dwg", received 6-6-2018 and "CHL020-S-101.dwg", received 3-7-2019.

2. This subsurface profile is generalized from materials observed in soil borings. Variations may exist between profile and actual conditions.

NOTES

Northwest

A

Southeast

A'

Vertical = Horizontal

Existing Ground Surface

PROPOSED SHEET

PILE COFFERDAMS

SHEET PILE EMBEDMENT

TO BE DETERMINED

DESIGN MUDLINE

EL 480 FT

74/10"

AP-3015

05-10-18

(Proj. 50' E) Designation of Boring

Projected Distance and Direction

Sample and Penetration

Resistance in Blows/Foot or Blows per Inches Driven

USCS Symbol

Approximate Geologic Contact

Bottom of Boring

Date of Completion

LEGEND

Water Level

During Drilling

Frozen at

Time of Drilling

Wing Wall Baling Deck

Chena River Lakes Flood Control Project North Pole, Alaska

31-1-20083-003May 2019

PROPOSED WING

WALL BALING DECK

p r o x i m a e v a t i o n e t

A p p r o x i m a e v a t i o n e t

Distance in Feet

0 30 60 90 120 150 180 210 240 270 300 330 360 390 420

162430

05-13-18

AP-3017

413927

05-10-18

AP-3018

GRAB

233841

05-12-18

AP-3015

Loose to Medium Dense Sand and Gravel (Alluvium)

Medium Dense to Dense Sand and Gravel (Fill)

Medium Dense Sand and Gravel (Alluvium)

(Proj. 36' NW)(Proj. 53' SE) (Proj. 16' NW)

A

F i l e n a m e

D

P r o j e c t s S

W

M o o s e

C r e e k

C

H L

P l a n d y o u t p r o f i l d t e g i n c a b r y

FIG. 5

GENERALIZED SUBSURFACE

PROFILE D-D'

30 60

Scale in Feet

D D'

Vertical = Horizontal

Existing Ground Surface

74/10"

AP-3015

05-10-18

(Proj. 50' E) Designation of Boring

Projected Distance and Direction

Sample and Penetration

Resistance in Blows/Foot or Blows per Inches Driven

USCS Symbol

Approximate Geologic Contact

Bottom of Boring

Date of Completion

LEGEND

Water Level

During Drilling

Frozen at

Time of Drilling

Wing Wall Baling Deck

Chena River Lakes Flood Control Project North Pole, Alaska

31-1-20083-003May 2019

Southwest Northeast

PROPOSED WING

WALL BALING DECK

DESIGN MUDLINE EL 480 FT

1. Existing and proposed grades, proposed features, and design elevations are adapted from client files, "CHENA EXHIBIT

SK-001.dwg", received 6-6-2018 and "CHL020-S-101.dwg", received 3-7-2019.

2. This subsurface profile is generalized from materials observed in soil borings. Variations may exist between profile and actual conditions.

3. Bathymetric data is unavailable. Dashed line shown in this figure was developed by extrapolating the ground surface slope at the existing shorelines down to the proposed mudline elevation.

NOTES

Minimum Operational (Bailing)

Water El. 493.5 Ft

Lowest Water El. 487.2 Ft

See Note 3

PROPOSED MECHANICALLY

STABILIZED EARTH WALL

4/2/2019-GDM_DP_Axial_24-inch_Open End.xlsm

1. This analysis is based on a single pile and does not consider group action of closely spaced piles (closer than 2.5 diameters, center to center)

2. Allowable capacity should be determined by applying the following minimum factor-of safety values according to ACE EM 1110-2-2096:

Loading Condition Compression Tension

Usual 3.0 3.0 Unusual 2.25 2.25 Extreme 1.7 1.7

Note: These values are based on theoretical or emipircal prediction not verified by load test. If a pile driving analyzer or load test is completed the minimum factor of safety may be reduced.

FIG. 6

ASSUMED SUBSURFACE

PROFILE

Based on Nearby Explorations:

AP-3018

May 2019

BORING AP-3018

ESTIMATED AXIAL PILE RESISTANCE

24-INCH DIAMETER OPEN-ENDED PIPE PILE

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

31-1-20083-003

0 50 100 150 200 250 300 350 400

PI

LE

T

IP

D

EP

TH

B

EL

O

W T

O P

O F

PI

LE

C

AP

(f ee t)

ULTIMATE AXIAL PILE RESISTANCE (tons)

Ultimate Compressive Capacity

Ultimate Uplift Capacity

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

Loose to Medium Dense Gravels and Sands (above GWT)

0'

Loose to Medium Dense Gravels and Sands (below GWT)

14'

Medium dense - Sands and Gravels

32.5'

Medium Dense - Gravels and Sands

52.5'

Bottom of Boring at

75.0 feet

1.36

Distance (feet) -30 20 70 120 170 220 270 320 370 420

El ev at io n (fe et

El ev at io n (fe et

Elev. 514 ft

Water EL. 493.5 FT

May 2019 31-1-20083-003

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Notes:

1. SLOPE/W Analysis Name:

1 Existing Conditions_Static_Global

2. Factor of Safety Calculation Method:

Spencer

3. Analysis includes a horizontal acceleration coefficient of 0 g.

Di re ct or y:

C

:\U se rs \k w s\

Do cu m en ts \P as t P ro je ct s\

M oo se C re ek

D am

\G C-

S ta bi lit y\

D D' Southwest Northeast

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

Color Name Model Unit Weight (pcf)

Cohesion' (psf)

Phi'

Loose Sand & Gravel

Mohr-Coulomb 125 0 34

MD Sand & Gravel

Mohr-Coulomb 130 0 36

Riprap Mohr-Coulomb 110 0 45

FIG. 7

PROFILE D-D' STABILITY ANALYSIS

EXISTING CONDITIONS

STATIC

1.34

-30 20 70 120 170 220 270 320 370 420

El ev at io n (fe et

El ev at io n (fe et

Elev. 514 ft

Water EL. 493.5 FT

Surcharge (Unit Weight): 570 pcf

May 2019 31-1-20083-003

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Notes:

1. SLOPE/W Analysis Name:

2 Proposed Conditions_Static_Global

2. Factor of Safety Calculation Method:

Spencer

3. Analysis includes a horizontal acceleration coefficient of 0 g.

Di re ct or y:

C

:\U se rs \k w s\

Do cu m en ts \P as t P ro je ct s\

M oo se C re ek

D am

\G C-

S ta bi lit y\

D D' Southwest Northeast

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

Color Name Model Unit Weight (pcf)

Cohesion' (psf)

Phi'

Loose Sand & Gravel

Mohr-Coulomb 125 0 34

MD Sand & Gravel

Mohr-Coulomb 130 0 36

MSE Wall High Strength 135

Riprap Mohr-Coulomb 110 0 45

FIG. 8

PROFILE D-D' STABILITY ANALYSIS

PROPOSED CONDITIONS

STATIC

0.83

-30 20 70 120 170 220 270 320 370 420

El ev at io n (fe et

El ev at io n (fe et

Elev. 514 ft

Water EL. 493.5 FT

Horz Seismic Coef.: 0.22

May 2019 31-1-20083-003

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Notes:

1. SLOPE/W Analysis Name:

3 Proposed Conditions_Seismic_Global

2. Factor of Safety Calculation Method:

Spencer

3. Analysis includes a horizontal acceleration coefficient of 0.22 g.

Di re ct or y:

C

:\U se rs \k w s\

Do cu m en ts \P as t P ro je ct s\

M oo se C re ek

D am

\G C-

S ta bi lit y\

D D' Southwest Northeast

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

Color Name Model Unit Weight (pcf)

Cohesion' (psf)

Phi'

Loose Sand & Gravel

Mohr-Coulomb 125 0 34

MD Sand & Gravel

Mohr-Coulomb 130 0 36

MSE Wall High Strength 135

Riprap Mohr-Coulomb 110 0 45

FIG. 9

PROFILE D-D' STABILITY ANALYSIS

SESIMIC

0.35

-30 20 70 120 170 220 270 320 370 420

El ev at io n (fe et

El ev at io n (fe et

Elev. 514 ft

Water EL. 493.5 FT

Surcharge (Unit Weight): 570 pcf

May 2019 31-1-20083-003

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Notes:

1. SLOPE/W Analysis Name:

4 Proposed Conditions_Post-Seismic_Global

2. Factor of Safety Calculation Method:

Spencer

3. Analysis includes a horizontal acceleration coefficient of 0 g.

Di re ct or y:

C

:\U se rs \k w s\

Do cu m en ts \P as t P ro je ct s\

M oo se C re ek

D am

\G C-

S ta bi lit y\

D D' Southwest Northeast

Wing Wall Baling Deck Chena River Lakes Flood Control Project

North Pole, Alaska

Color Name Model Unit Weight (pcf)

Cohesion' (psf)

Phi'

Loose Sand & Gravel (Liquefied - Above Elev.

460')

Mohr-Coulomb 125 0 8

Loose Sand & Gravel (Liquefied - Below Elev.

460')

Mohr-Coulomb 125 0 12

MD Sand & Gravel Mohr-Coulomb 130 0 36

MSE Wall High Strength 135

Riprap Mohr-Coulomb 110 0 45

FIG. 10

PROFILE D-D' STABILITY ANALYSIS

POST-SEISMIC

1.79

-30 20 70 120 170 220 270 320 370 420

El ev at io n (fe…