Geotechnical Engineering Services Temporary Shoring Design

Geotechnical Engineering Services Temporary Shoring Design Evaluation

4732 Brooklyn Avenue NE Seattle, Washington

for Campus UW JV II, LLC

September 11, 2020

Geotechnical Engineering Services Temporary Shoring Design Evaluation

4732 Brooklyn Avenue NE Seattle, Washington

for Campus UW JV II, LLC

September 11, 2020

17425 NE Union Hill Road, Suite 250 Redmond, Washington 98052 425.861.6000

September 11, 2020 | Page i File No. 21060-002-00

Table of Contents 1.0 INTRODUCTION ............................................................................................................................................... 1 2.0 PROJECT DESCRIPTION .................................................................................................................................. 1 2.1. 4732 Brooklyn Avenue NE East Wall (North End) ..................................................................................... 1

3.0 SITE CONDITIONS ............................................................................................................................................ 2 3.1. Subsurface Conditions ............................................................................................................................... 2 3.2. Shear Wave Velocity ................................................................................................................................... 2 3.3. Groundwater Conditions ............................................................................................................................. 2 4.0 NUMERICAL ANALYSIS ................................................................................................................................... 2 4.1. PLAXIS Model .............................................................................................................................................. 2

4.1.1. PLAXIS Modeling Approach ............................................................................................................. 2 4.1.2. PLAXIS Mesh .................................................................................................................................... 3 4.1.3. Soil Constitutive Model ................................................................................................................... 3 4.1.4. Structural Elements ......................................................................................................................... 5 4.1.5. Surcharge Loads.............................................................................................................................. 6 4.1.6. Construction Sequence Simulation ................................................................................................ 6

5.0 RESULTS OF FINITE ELEMENT ANALYSIS ..................................................................................................... 7 5.1. Shoring Wall Deflections ............................................................................................................................ 7 5.2. Global Stability ............................................................................................................................................ 7 5.3. Conclusions ................................................................................................................................................. 7 6.0 LIMITATIONS ................................................................................................................................................... 8 7.0 REFERENCES .................................................................................................................................................. 8

FIGURES

Figure 1. Vicinity Map Figure 2. Site Plan Figure 3. Cross Section B-B’ Figure 4. PLAXIS Model – Soil Profile – Shear Wave Velocity Figure 5. PLAXIS 2D Soil Model Figure 6. PLAXIS 2D Model with Structure Elements Figure 7. Site-specific Friction Angle Correlation Figures 8 through 12. 4732 Brooklyn – Horizontal Displacements

APPENDICES

Appendix A. Report Limitations and Guidelines for Use

September 11, 2020 | Page 1 File No. 21060-002-00

1.0 INTRODUCTION

This report presents the results of GeoEngineers, Inc.’s (GeoEngineers) geotechnical analysis and evaluation of a portion of the temporary shoring design for the proposed 4732 Brooklyn Avenue NE project. The project site is located at the southeast corner of NE 50th Street and Brooklyn Avenue NE in Seattle’s University District neighborhood. The site is shown relative to surrounding physical features in Figure 1, Vicinity Map, and Figure 2, Site Plan.

GeoEngineers has completed numerical modeling of the planned temporary soil nail and full depth soldier pile shoring system for the north end of the east shoring wall to estimate anticipated deflections during construction. As part of the numerical modeling evaluation, we have reviewed the following documents:

■ Geotechnical report titled “Geotechnical Engineering Services, 4732 Brooklyn Avenue NE, Seattle, Washington” prepared by GeoEngineers, Inc., dated January 20, 2020.

■ Geotechnical report titled “Geotechnical Addendum Report 1, 4732 Brooklyn Avenue NE, Seattle, Washington” prepared by GeoEngineers, Inc., dated July 24, 2020.

■ Geophysical report titled “Downhole Shear Wave Survey at 4700 Brooklyn, Seattle, WA” prepared by Global Geophysics, October 3, 2017.

■ 4732 Brooklyn Avenue NE Temporary Shoring Wall Plans, prepared by Ground Support PLLC, dated September 8, 2020.

2.0 PROJECT DESCRIPTION

GeoEngineers understands that Campus UW JV II, LLC is interested in developing a seven-story building with two levels of below-grade parking at the project site. The ground floor of the building will be occupied by Safeway, which occupies the building located at the current project site. Excavation depths for the planned development are anticipated to range up to 30 feet below existing site grades.

Temporary shoring will be required around the perimeter of the planned excavation and is planned to consist of soldier pile and tiebacks. We understand that an easement agreement was not obtained from the adjacent property owner located across the alley at the north end of the project site. Due to the limited right-of-way located within the alley, the project team has redesigned the shoring from soldier pile and tiebacks to soldier piles with soil nails, with the soil nails staying within the alley right-of-way.

GeoEngineers’ geotechnical engineering analysis summarized in this report was completed to provide an estimate of the deformation of the planned temporary shoring system for the northern portion of the east shoring wall.

2.1. 4732 Brooklyn Avenue NE East Wall (North End)

For the north end of the east wall, the ground surface elevation was modeled at Elevation 222 feet and the bottom of the excavation was modeled at Elevation 192 feet. The design section was cut near soldier pile E3.

September 11, 2020| Page 2 File No. 21060-002-00

3.0 SITE CONDITIONS

3.1. Subsurface Conditions

The soil encountered at the project site consist of relatively shallow fill and recent deposits overlying competent glacially consolidated soils. Interpreted cross section B-B’ (Figure 3), located along the alley, has been included to show the soil conditions closest to the design section.

3.2. Shear Wave Velocity

Downhole shear wave velocity testing (AB-101) was completed at 4700 Brooklyn Avenue NE, located directly south of the project site, by Global Geophysics on September 22, 2017. The results are summarized in the October 3, 2017 report which is included in the final geotechnical report for the 4732 Brooklyn Avenue NE project. The shear wave velocity profiles are summarized on Figure 4 and show the results of the Global Geophysics testing and the shear wave velocity profile used to develop soil stiffness parameters in the numerical modeling analysis.

3.3. Groundwater Conditions

Based on monitoring well and boring logs reviewed for the project and data from monitoring wells in the vicinity of the soldier pile and soil nail shoring system, the groundwater table near the north end of the project site is located at about Elevation 177 feet (45 feet below ground surface), which is below the bottom of excavation of the project site. Groundwater at the south end of the project site, which is located further away from the soldier pile and soil nail design condition, is located at higher elevations (between Elevation 197 and 199 feet).

4.0 NUMERICAL ANALYSIS

4.1. PLAXIS Model

The 4732 Brooklyn Avenue NE temporary shoring wall analysis for the soldier pile and soil nail condition was completed using the computer program PLAXIS V9 (PLAXIS). PLAXIS is a two-dimensional (2D), finite element application written for soil and rock mechanics analyses. Because PLAXIS is a 2D program, the temporary shoring system is modeled in a plane strain condition, where an equivalent 1-foot-wide section of the wall is analyzed with corresponding structural properties scaled by the horizontal spacing of the structural elements. As opposed to limit equilibrium analyses, which result in a factor of safety (FOS) of a shoring wall against failure, PLAXIS calculates forces and displacements of the shoring wall directly as the excavation is completed. The forces and displacements that are calculated by PLAXIS are dependent on the properties and constitutive models of the soil and structural elements. The following sections summarize the PLAXIS analysis completed and the estimated performance of the east shoring wall.

4.1.1. PLAXIS Modeling Approach

We used the computer program PLAXIS to evaluate the response of the east temporary shoring wall under the proposed excavation conditions. The loading conditions considered in our PLAXIS analysis is the short-term condition that occurs immediately after the excavation is completed. We modeled a staged construction sequence in detail for the 4732 Brooklyn Avenue NE as noted in the construction sequence simulation section below.


The general steps in our PLAXIS modeling were as follows:

1. Develop a PLAXIS 2D mesh that represents the critical section along the east shoring wall. This includes the soil, groundwater levels, soldier piles, and the traffic/construction surcharge anticipated behind the shoring wall during construction.

2. Develop appropriate soil properties that represent anticipated subsurface conditions under the short-term condition that occurs immediately after the excavations are completed. For this project, a more advanced soil model (Hardening-Soil [HS] Model; Schanz et al. 1999) that can capture the nonlinear stress-strain behavior of the soils was used in the simulation of the construction stages identified for this project.

3. Simulate the construction sequence developed by the project design and construction team in various stages to evaluate the response of the temporary shoring wall at the completion of the excavation.

4.1.2. PLAXIS Mesh

Figure 5 shows the 2D soil model developed in PLAXIS for the critical section along the east shoring wall. The section was cut near the location of soldier piles E3. The static groundwater was modeled at Elevation 177 feet. Figure 6 shows the structural elements modeled in PLAXIS at the end of the 4732 Brooklyn Avenue NE construction, which includes soldier pile and soil nails. The traffic/construction surcharge loads along the alley and parking lot were also incorporated in the analysis.

4.1.3. Soil Constitutive Model

The soil was modeled using the HS model in PLAXIS. The HS model is formulated using the classical theory of plasticity in an elasto-plastic framework. The HS model calculates soil strain using a stress dependent soil stiffness relationship. Schanz et al. (1999) provides a detailed description of the HS model.

The HS model is a shear and volumetric hardening constitutive model for the simulation of soil behavior. The selection of strength-based parameters (friction angle and cohesion) and stiffness-based parameters is important to give reasonable soil response under complex loading conditions. The strength-related parameters (friction angle and cohesion) are determined from SPT-based correlations. The small-strain shear modulus, G0, is calculated as:

𝐺𝐺0 = 𝜌𝜌𝑣𝑣𝑠𝑠2

where ρ is the soil density and vs is the shear wave velocity at the site.

The small strain Young’s modulus, E0, is calculated as:

𝐸𝐸0 = 2(1 + ν)𝐺𝐺0

where ν is the Poisson ratio.


The unloading-reloading modulus, Eur, is calculated based on E0 as:

𝐸𝐸𝑢𝑢𝑢𝑢 = 𝐸𝐸0/𝑘𝑘1

where k1 is the model parameter, which represents the relationship between small-strain modulus and unloading-reloading modulus. The typical range for k1 is 1.0 to 3.0.

The secant modulus, E50, is calculated based on Eur, as:

𝐸𝐸50 = 𝐸𝐸𝑢𝑢𝑢𝑢/𝑘𝑘2

where k2 is the model parameter, which represents the relationship between secant modulus and unloading-reloading modulus. The typical range for k2 is 2.0 to 5.0. The default value recommended in PLAXIS is 3.0.

The stress dependent unloading-reloading modulus is calculated as:

𝐸𝐸𝑢𝑢𝑢𝑢 = 𝐸𝐸𝑢𝑢𝑢𝑢𝑢𝑢𝑟𝑟𝑟𝑟𝑍𝑍𝑚𝑚

𝑍𝑍 = (𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 − 𝜎𝜎3) �𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 + 𝑝𝑝𝑢𝑢𝑟𝑟𝑟𝑟�⁄

where m is the model parameter; c is the soil cohesion, pref is the reference pressure as 1 atm. For clays, m is usually close to 1.0. For sands, m is usually between 0.4 and 0.9.

The friction angle of each soil layer was evaluated considering a variety of correlations as shown in Figure 7, includes: National Highway Institute (NHI) (2001), which is from Hatanaka and Uchida (1996) via Mayne et al. (2001), Schmertmann (1975), Peck et al. (1974), Terzaghi et al.(1996) (for both coarse and fine grains) and Washington State Department of Transportation (WSDOT) Geotechnical Design Manual (GDM), which is from AASHTO 2012 correlations derived from Bowles (1977). The selected friction angles are presented in Table 1, which considers the mean minus 1 standard deviation to account for potential soil variability. The small strain shear modulus G0 is estimated based on shear wave velocity measurements from geophysical testing completed near the site.

TABLE 1. HARDENING SOIL MODEL PROPERTIES

Parameter Fill Recent Deposits Glacially Consolidated Soils

Depth (feet) 0-5 5-10 10-22 22-40 40-50 50-120

Shear Wave Velocity (feet/second) 600 600 1,000 1,000 1,266 1,820

Soil Unit Weight (pcf) 120 125 135

Friction Angle (degree) 30 34 40

Cohesion (psf) 50 100 200

Soil Deviatoric Stiffness, E50,ref (ksf) 1,168 1,072 1,948 4,411 6,465 11,030

Soil Compression Stiffness, EOED,ref (ksf) 1,168 1,072 1,948 4,411 6,465 11,030

Unload/Reload Stiffness, Eur,ref (ksf) 3,505 3,217 5,845 13,233 19,396 33,090


Parameter Fill Recent Deposits Glacially Consolidated Soils

PH Model Parameter, m 0.5 0.7 0.7 0.5 0.5 0.5

Interface Friction Coefficient, Rinter 0.67 0.67 0.67 0.67 0.67 0.67

Notes: pcf – pounds per cubic foot ksf – kips per square foot

4.1.4. Structural Elements

The structural elements modeled for the 4732 Brooklyn Avenue NE east shoring wall include soldier piles, timber lagging and soil nails. The soldier piles were modeled as elasto-plastic plates with a bending stiffness and a normal stiffness to simulate the behavior of the wall. The effect of the timber lagging was accounted for by increasing the bending and normal stiffness of the soldier piles after the excavation was complete and the soil nails were installed. The soil nails were modeled as fixed-end elastoplastic springs that have a normal stiffness component. The soil nails installed for the 4732 Brooklyn Avenue NE project include an ultimate pullout capacity of 3 (Rows 1 through 3) or 6 kips per foot (Rows 4 and 5). The interaction between the shoring wall and surrounding soil is modeled using interface elements, modeled by choosing a suitable value for the strength factor of the interface (Rinter). This factor relates the interface shear strength (wall friction and adhesion) to the soil shear strength (friction angle and cohesion). The value of Rinter was selected as 0.67 for soldier piles (Fleming et al. 2009).

4.1.4.1. Soldier pile Plate Input Parameters The bending and normal stiffness of the structural elements depend on the modulus of elasticity of the material, E, the moment of inertia of the structural elements, I, and the cross sectional area of the structural elements, A. Bending and normal stiffness of an individual element are first calculated and are then scaled using the horizontal spacing of the structural element to produce an equivalent stiffness to be used in a 2D plane strain condition.

For the 4732 Brooklyn Avenue NE east shoring wall, the soldier piles consist of Grade 50 steel wide-flange beams set in 30-inch-diameter (minimum) drilled shafts that are backfilled with controlled density fill (CDF). Per the temporary shoring plans, a W18x35 steel section was modeled for the design cross section. The horizontal spacing of the soldier piles were set to be 4 feet on center. The toe elevation of soldier piles was at 182 feet, which include 10 feet of embedment at the end of excavation. The timber lagging was modeled as 4-inch-thick wood. The equivalent bending and normal stiffness of the soldier pile, CDF and timber lagging was estimated by combining the stiffness of the three elements. The equivalent bending and normal stiffness of the soldier piles modeled in PLAXIS are summarized in Table 2.

TABLE 2. PLAXIS SOLDIER PILE STRUCTURAL PROPERTIES

Structural Element Bending Stiffness, (EI)

(kip-ft2/ft) Normal Stiffness, (EA)

(kips/ft)

Soldier Pile (W18x86) and CDF 8.13E+04 2.17E+05

Soldier Pile (W18x86), CDF and Timber Lagging 8.19E+04 2.80E+05


4.1.4.2. Soil Nail Fixed-End Anchor Element Input Parameters The soil nails were modeled as fixed-end anchors. A fixed-end anchor is a one-node elastic/elasto-plastic spring element with a constant normal stiffness. The other end of the spring, defined by the equivalent length, is fixed. The normal stiffness was computed for each soil nail using the anticipated axial deflection under the design loads. The calculated normal stiffness of the soil nails was calibrated with load test data from GeoEngineers’ observed shoring projects in similar soil conditions in the downtown Seattle area. The horizontal spacing of the soil nails is 4 feet. The structural properties of the soil nails in PLAXIS are summarized in Table 3.

TABLE 3. PLAXIS SOIL NAIL STRUCTURAL PROPERTIES

Structural Element

Elevation (feet)

Total Length (feet)

Declination (deg)

Normal Stiffness, EA (kips)

Prestress Load (kips)

Row 1 Soil Nail 216 14 15 7.06E+03 N/A

Row 2 Soil Nail 211 14 15 7.06E+03 N/A

Row 3 Soil Nail 206 14 15 7.06E+03 N/A

Row 4 Soil Nail 200 14 15 1.41E+04 N/A

Row 5 Soil Nail 195 14 15 1.41E+04 N/A

The soil nails will not be secured using shotcrete facing. Instead, the soil nails will be secured to the soldier piles with a nut and plate; however, the soil nails will not be pre-stressed (soil nails will remain passive). Additionally, the soil nails were considered to be 14 feet long which is the alley width present for the bumpout between soldier piles E6 and E15.

4.1.5. Surcharge Loads

External loads considered in our PLAXIS model include a 12-foot-wide, 500 pounds per square foot (psf) traffic/construction surcharge applied at grade and offset 2 feet from the face of east shoring wall and a 250 psf parking lot surcharge starting from 14 feet away off the east shoring wall to the modeling boundary. As noted above, although the design section was cut at E3, the soil nail lengths and surcharges are consistent with the section present between soldier piles E6 through E15 that have 3 feet less of alley width due to the alley dedication.

4.1.6. Construction Sequence Simulation

The construction of the proposed shoring walls in PLAXIS is modeled in stages. The modeling sequence used in our numerical simulation is as follows:

1. Set up model geometry and calculate initial stress conditions.

2. Apply surcharge loads.

3. Install soldier piles.

4. Excavate to Elevation 214 feet and install timber lagging.

5. Install row 1 soil nails.










5.0 RESULTS OF FINITE ELEMENT ANALYSIS

Using the approach described above, GeoEngineers evaluated the effect of the excavation on the lateral deflection of the temporary shoring wall.

5.1. Shoring Wall Deflections

Figures 8 through 12 present the horizontal displacement contours for the 4732 Brooklyn Avenue NE project at various stages of construction. At the end of excavation (Figure 12), the predicted horizontal displacement is approximately 0.66 inches. The maximum horizontal deflection occurs at the top of shoring wall, which indicates the cantilever-type behavior of the shoring wall with short soil nail lengths. The estimated deformations represent the best estimate deformation of the temporary shoring system. Factors that affect performance of shoring walls include soil variability, workmanship, soldier pile installation, and soil nail drilling and grouting techniques which will influence the actual deformations. This predicted deformation is less than the Seattle Department of Construction and Inspections (SDCI)/Seattle Department of Transportation (SDOT) deformation tolerance of 1 inch.

5.2. Global Stability

We also completed a global stability analysis for the east wall design section using a phi-c reduction calculation within the PLAXIS program. The phi-c reduction calculation computes a global FOS for the system by reducing the strength parameters of the soil. The results show that the critical failure surface for global stability of the system has a FOS of 1.65.

5.3. Conclusions

Based on the results of the numerical analysis using the estimated soil parameters, the soil nail and full depth soldier pile temporary shoring system planned for the east wall is estimated to have temporary shoring deformations that meet the SDCI/SDOT wall deflection criteria of less than 1 inch. Sensitivity analyses were completed to investigate the potential response of a reduction in shear strength of the glacially consolidated soils.

A monitoring program consisting of optical survey of the top of the shoring wall will be implemented to monitor the temporary shoring system during construction. One of the advantages with completing numerical modeling of a temporary shoring system is that the measured deformations can be compared to the predicted deformations for various stages of construction. If shoring wall deformations are trending higher than predicted, mitigation measures can be implemented. For the soldier pile and soil nail system planned for this project, mitigation measures can be easily implemented by adding additional soil nails,


changing facing, or pre-stressing selected rows of soil nails in specified areas to address deflection (horizontal movement).

6.0 LIMITATIONS

We have prepared this report for use by Campus UW JV II, LLC, and other members of the design team for shoring design of the 4732 Brooklyn Avenue NE project.

Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions express or implied, should be understood.

Please refer to Appendix A, Report Limitations and Guidelines for Use, for additional information pertaining to use of this report.

7.0 REFERENCES

Bentley Systems, Inc. (2017). “Plaxis 2D Version 2017.01”.

Bowles, J.E. 1977. Foundation Analysis and Design, Second Edition. McGraw–Hill Book Company, New York, NY.

Fleming, K., Weltman, A., Randolph, M. and Elson, K. (2009). “Piling Engineering.” Taylor & Francis Group, London and New York, pp. 407.

Hatanaka, M. and Uchida, A., 1996. Empirical correlation between penetration resistance and internal friction angle of sandy soils. Soils and foundations, 36(4), pp.1-9.

Mayne, P.W., Christopher, B.R. and DeJong, J., 2001. Manual on Subsurface Investigations. National Highway Institute Publication No. FHWA NHI-01-031. Federal Highway Administration, Washington, DC.

National Highway Institute. (2001) “Manual on Subsurface Investigations.” Publication No. FHWA NHI-01-031, Federal Highway Administration, Washington, DC.

Peck, R.B., Hanson, W.E. and Thornburn, T.H., 1974. Foundation engineering, 2nd ed,. New York: Wiley.

Schanz T., P.A. Vermeer and P.G. Bonnier (1999). “The hardening soil model: formulation and verification.” Beyond 2000 in Computation Geotechnics – 10 Years of PLAXIS, Balkema, Rotterdam, pp 1-16.

Schmertmann, 1975, Measurement of In-Situ Shear Strength. Proceedings of ASCE Specialty Conference on In-Situ Measurements of Soil Properties. Raleigh, NC, Vol. 2: 57-138.

Terzaghi, K., Peck, R.B. and Mesri, G., 1996. Soil mechanics in engineering practice. John Wiley & Sons, AASHTO 2012

Washington State Department of Transportation, 2019, “WSDOT Geotechnical Design Manual, M 46-03.12.”

FIGU

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Vicinity Map

Figure 1

4732 Brooklyn Avenue NESeattle, Washington

2,000 2,0000

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Data Source: Mapbox Open Street Map, 2018

Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

Projection: NAD 1983 UTM Zone 10N

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Brooklyn Ave NE

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Site Boundary

GEI-1 Boring by GeoEngineers, 2018 (Current Study)

Seismic Boring by Aspect, 2017

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Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing

features discussed in an attached document. GeoEngineers, Inc. cannotguarantee the accuracy and content of electronic files. The master file isstored by GeoEngineers, Inc. and will serve as the official record of thiscommunication.

Data Source: Base Survey from Bush, Roed & Hitchings, Inc., dated 12/04/18.

Projection: Washington State Plane, North Zone, NAD83, US Foot

WE

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Boring by Geotech Consultants, 2013

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GEI-2 Boring with Monitoring Well by GeoEngineers, 2018 (Current Study)

Sonic Boring by Aspect, 2016 Boring by Dames and Moore, 1977

MW-01 Boring with Monitoring Well by GeoEngineers, 1990

MW-15

Boring by The Riley Group, 2013

AB-101

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Soil ConditionsBased on Observations

During Construction

Lowest Finished FloorLocated at ApproximatelyElevation 197 Feet

Fill

Recent Deposits

Glacially Consolidated Soils

NE 50thStreet

Bottom of Footing LocatedBetween Approximately

Elevation 198 and 199.5 Feet

Figure 3


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Notes:1. The subsurface conditions shown are based on interpolation between

widely spaced explorations and should be considered approximate; actualsubsurface conditions may vary from those shown.

2. This figure is for informational purposes only. It is intended to assist in theidentification of features discussed in a related document. Data werecompiled from sources as listed in this figure. The data sources do notguarantee these data are accurate or complete. There may have beenupdates to the data since the publication of this figure. This figure is acopy of a master document. The hard copy is stored by GeoEngineers, Inc.and will serve as the official document of record.

Datum: NAVD 88, unless otherwise noted.

Horizontal Scale in Feet

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Vertical Scale in Feet

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Vertical Exaggeration: 4X

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Soil Classification

Groundwater Measured in Piezometer

Blow Count

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Glacially Consolidated Soils

21060-002-00 Date Exported: 09/09/2020

Figure 4

4732 Brooklyn Avenue NE

Seattle, WashingtonNotes:1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document.

GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will

serve as the official record of this communication.

PLAXIS Model – Soil Profile

Shear Wave Velocity

21060-002-00 Date Exported: 09/09/2020

Figure 5






PLAXIS 2D Soil Model

Ground Surface

El. 222 ft

Glacially Consolidated Soils 22–40 ft

GWT El. 177 ft

Recent Deposits 10-22 ft

Recent Deposits 5-10 ft

Fill 0-5 ft

Glacially Consolidated Soils 40–50 ft

Glacially Consolidated Soils >50 ft

Proposed 4732 Brooklyn Avenue NE DevelopmentAlley4749 University Way NE

21060-002-00 Date Exported: 09/09/2020

Figure 6






PLAXIS 2D Model With Structural Elements

(End of 4732 Brooklyn Excavation)

Alley Traffic

Surcharge/Construction

500 psf

Row 5 Soil Nail

Row 4 Soil Nail

Row 3 Soil Nail

Row 2 Soil Nail

Row 1 Soil Nail

4732 Brooklyn East Shoring Wall

H Pile W18x35

4-ft Spacing

4-in Timber Lagging

30-in Drilled Shaft backfilled with CDF

Bottom of

Excavation El. 192 ft

Parking Lot Traffic Surcharge

250 psf

21060-002-00 Date Exported: 09/09/2020

Figure 7






Site-specific Friction Angle Correlation

Fill Recent Deposits Glacially Consolidated Soils

21060-002-00 Date Exported: 09/09/2020

Figure 8






4732 Brooklyn – Horizontal Displacements

Excavate to El. 214 ft and Install Row 1 Soil Nail

Alley Traffic


500 psf Parking Lot Traffic Surcharge

250 psf

Δx max = 0.14 inches

21060-002-00 Date Exported: 09/09/2020

Figure 9








Alley Traffic



250 psf


21060-002-00 Date Exported: 09/09/2020

Figure 10








Alley Traffic



250 psf


21060-002-00 Date Exported: 09/09/2020

Figure 11








Alley Traffic



250 psf


21060-002-00 Date Exported: 09/09/2020

Figure 12









Global Stability

Factor of Safety = 1.65

Alley Traffic



250 psf

AP

PE

ND

ICE

S

APPENDIX A Report Limitations and Guidelines for Use

September 11, 2020| Page A-1 File No. 22832-001-00

APPENDIX A REPORT LIMITATIONS AND GUIDELINES FOR USE1

This appendix provides information to help you manage your risks with respect to the use of this report.

Geotechnical Services Are Performed for Specific Purposes, Persons and Projects

This report has been prepared for the exclusive use of Campus UW JV II, LLC and other project team members for the 4732 Brooklyn Avenue NE project. This report is not intended for use by others, and the information contained herein is not applicable to other sites.

GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted geotechnical practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated.

A Geotechnical Engineering or Geologic Report Is Based on a Unique Set of Project-specific Factors

This report has been prepared for the 4732 Brooklyn Avenue NE project in Seattle, Washington. GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates otherwise, do not rely on this report if it was:

■ Not prepared for you,

■ Not prepared for your project,

■ Not prepared for the specific site explored, or

■ Completed before important project changes were made.

For example, changes that can affect the applicability of this report include those that affect:

■ The function of the proposed structure;

■ Elevation, configuration, location, orientation or weight of the proposed structure;

■ Composition of the design team; or

■ Project ownership.

1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org .

September 11, 2020 | Page A-2 File No. 22832-001-00

If important changes are made after the date of this report, GeoEngineers should be given the opportunity to review our interpretations and recommendations and provide written modifications or confirmation, as appropriate.

Subsurface Conditions Can Change This geotechnical or geologic report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by manmade events such as construction on or adjacent to the site, or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. Always contact GeoEngineers before applying a report to determine if it remains applicable.

Most Geotechnical and Geologic Findings Are Professional Opinions Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then applied our professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions.

Geotechnical Engineering Report Recommendations Are Not Final Do not over-rely on the preliminary construction recommendations included in this report. These recommendations are not final, because they were developed principally from GeoEngineers’ professional judgment and opinion. GeoEngineers’ recommendations can be finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability for this report's recommendations if we do not perform construction observation.

Sufficient monitoring, testing and consultation by GeoEngineers should be provided during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork activities are completed in accordance with our recommendations. Retaining GeoEngineers for construction observation for this project is the most effective method of managing the risks associated with unanticipated conditions.

A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation Misinterpretation of this report by other design team members can result in costly problems. You could lower that risk by having GeoEngineers confer with appropriate members of the design team after submitting the report. Also retain GeoEngineers to review pertinent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering or geologic report. Reduce that risk by having GeoEngineers participate in pre-bid and preconstruction conferences, and by providing construction observation.

Do Not Redraw the Exploration Logs Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering or geologic report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk.

September 11, 2020| Page A-3 File No. 22832-001-00

Give Contractors a Complete Report and Guidance Some owners and design professionals believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering or geologic report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only then might an owner be in a position to give contractors the best information available, while requiring them to at least share the financial responsibilities stemming from unanticipated conditions. Further, a contingency for unanticipated conditions should be included in your project budget and schedule.

Contractors Are Responsible for Site Safety on Their Own Construction Projects Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to on-site personnel and to adjacent properties.

Read These Provisions Closely Some clients, design professionals and contractors may not recognize that the geoscience practices (geotechnical engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. GeoEngineers includes these explanatory “limitations” provisions in our reports to help reduce such risks. Please confer with GeoEngineers if you are unclear how these “Report Limitations and Guidelines for Use” apply to your project or site.

Geotechnical, Geologic and Environmental Reports Should Not Be Interchanged The equipment, techniques and personnel used to perform an environmental study differ significantly from those used to perform a geotechnical or geologic study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually relate any environmental findings, conclusions or recommendations, e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding a specific project.

Biological Pollutants GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention or assessment of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations, recommendations, findings, or conclusions regarding the detecting, assessing, preventing or abating of Biological Pollutants and no conclusions or inferences should be drawn regarding Biological Pollutants, as they may relate to this project. The term “Biological Pollutants” includes, but is not limited to, molds, fungi, spores, bacteria, and viruses, and/or any of their byproducts.

If Client desires these specialized services, they should be obtained from a consultant who offers services in this specialized field.

Documents

Geotechnical Engineering Services Temporary Shoring Design