DRAFT
Geotechnical Engineering Design Report Union Bay Place Development Seattle, Washington
Prepared for University Place, LLC
November 19, 2015 19174‐00
DRAFT Geotechnical Engineering Design Report Union Bay Place Development Seattle, Washington
Prepared for University Place, LLC
November 19, 2015 19174‐00
Prepared by Hart Crowser, Inc.
Benjamin M. Blanchette, PE Geotechnical Engineer [email protected]
Garry E. Horvitz, PE, LEG Madan Karkee, PhD, PE Sr. Principal Geotechnical Engineer Sr. Associate Geotechnical Engineer [email protected] [email protected]
1700 Westlake Avenue North, Suite 200 Seattle, Washington 98109-6212 Fax 206.328.5581 Tel 206.324.9530
Contents
INTRODUCTION 1
PURPOSE, SCOPE, AND THE USE OF THIS REPORT 1
PROJECT UNDERSTANDING 2
SUBSURFACE CONDITIONS 2 Soil Conditions 3 Groundwater 3 Hydraulic Conductivity (Slug Testing) 4
SEISMIC DESIGN RECOMMENDATIONS 5 Site Class 5 Liquefaction Assessment 6 Post‐Liquefaction Vertical Induced Settlement 7 Surface Rupture 7
GEOTECHNICAL ENGINEERING DESIGN RECOMMENDATIONS 7 General Considerations 7 Site Preparation 8 Pile Types 8 Augercast Pile Foundations 9 Vertical Pile Capacity 10 Lateral Pile Capacity 11 Passive Pressure on Pile Caps and Grade Beams 12 Augercast Pile Installation 12 Temporary Shoring 14 Lateral Earth Pressure 14 Soldier Pile Design 15 Soldier Pile Installation 15 Lagging 16 Tieback Anchor Design and Construction 17 Tieback Anchor Testing 18 Permanent Subgrade Walls 18 Lateral Earth Pressure Error! Bookmark not defined. Backfill Considerations Error! Bookmark not defined. Wall Drainage 19 Floor Slabs 19 Construction Dewatering 19
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Construction Dewatering Recommendations 19 Geotechnical Impacts of Dewatering 20 Permanent Drainage 21 Structural Fill 21 Use of On‐Site Soils as Structural Fill 22 Temporary Open Cuts 22 Utilities 23 Methane Venting 24
RECOMMENDATIONS FOR CONTINUING GEOTECHNICAL SERVICES 25 Design and Consulting Services 25 Construction Services 25
REFERENCES 26
TABLES 1 Groundwater Elevations 4 2 Seismic Design Parameters According to IBC 2012 6 3 Allowable Axial Capacity for Augercast Piles 10 4 Soil Parameters for LPILE Input (B‐3) 11 5 Pile P‐multipliers from AASHTO (2014) 11
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FIGURES 1 Vicinity Map 2 Site and Exploration Plan 3 Generalized Subsurface Cross Section A‐A’ 4 Generalized Subsurface Cross Section B‐B’ 5 Cascadia Earthquake Sources 6 Regional Fault Zones 7 Design of Temporary Cantilever or Single‐Support Soldier Pile Shoring 8 Lateral Soil Pressure for Permanent Condition 9 Surcharge Pressures Determination of Lateral Pressure Acting on Adjacent Shoring
ATTACHMENT 1 Tieback Anchor Testing Program
ATTACHMENT 2 Shoring Monitoring Program
APPENDIX A Field Exploration Methods and Analysis
APPENDIX B Laboratory Testing Program
APPENDIX C Historical Explorations
APPENDIX D Slug Testing
DRAFT 19174‐00 November 18, 2015
Geotechnical Engineering Design Report Union Bay Place Development Seattle, Washington
INTRODUCTION This report presents our geotechnical engineering design recommendations for the proposed Union Bay Place development in Seattle, Washington (Figure 1). The project is a new mid‐rise apartment building at 4603 and 4609 Union Bay Place NE.
This report presents our geotechnical engineering recommendations and is organized as follows:
Introduction; Purpose, Scope, and Use of This Report; Project Understanding; Subsurface Conditions; Seismic Design Recommendations; Geotechnical Engineering Design Recommendations; and Recommendations for Continuing Geotechnical Services.
Following the report text we include:
Figures illustrating site information and presenting our recommendations; Attachment 1, containing the tieback anchor testing program; Attachment 2, containing the shoring monitoring program; and Appendices containing the results of field exploration, laboratory testing, historical explorations, and slug testing.
PURPOSE, SCOPE, AND USE OF THIS REPORT The purpose of our work was to assess subsurface information and provide geotechnical engineering recommendations for design of the proposed Union Bay Place development. Our scope of work for this project included:
Corresponding and meeting with the design team; Reviewing historical geotechnical explorations; Drilling one soil borings and collecting soil samples; Installing two groundwater monitoring wells; Conducting field slug testing for soil permeability; Completing laboratory analysis on selected soil samples; Performing engineering analysis; and Providing engineering recommendations in this report.
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We prepared this report for the exclusive use of University Place LLC and its design consultants for specific application to the Union Bay Place development and site location. This report was prepared in accordance with our proposal dated August 28, 2015, and signed on September 8, 2015. Within the constraints of schedule and budget, we completed the work according to geotechnical practices generally accepted for work done in the same or similar localities, related to the nature of the work we accomplished, and done at the time our services were accomplished. We make no other warranty, express or implied.
PROJECT UNDERSTANDING The project consists of a wood‐frame mid‐rise (up to five above‐grade stories) residential building with one level of below‐grade parking. The project will occupy the entire footprint area of the site, which will require a temporary (or perhaps permanent) shoring and/or underpinning system to support the planned excavation for basement construction. At‐grade structures are adjacent to the site on the north and south sides.
Subsurface conditions at the site are generally similar to those encountered throughout the adjacent University Village area. The Burke Gilman Trail is an abandoned railroad grade in this area originally constructed along what was then the north shore of Lake Washington. When the Montlake Cut was constructed and the level of Lake Washington lowered by approximately nine feet, the area adjacent to the railroad grade was filled and reclaimed. This reclaimed area extends from University Village south to Husky Stadium. As a backwater slough, the area was occupied by deep peat deposits that thinned from south to north. Fill materials were placed on top of the old slough deposits and a landfill was developed to the south of and adjacent to NE 45th Street.
Groundwater in the area is high and generally close to the ground surface. In some areas artesian groundwater conditions exist in the lower dense bearing soils because the area is adjacent to and at the bottom of the surrounding hills. These conditions can be problematic for foundation construction. Also, the loose nature of the fills and underlying soft/loose natural soils, coupled with high groundwater, make the site susceptible to seismically induced liquefaction.
All the considerations above combine to make for complex foundation, shoring, and construction dewatering issues. The site is designated an Environmentally Critical Area by the City of Seattle Department of Planning and Development (DPD) in the categories of (1) proximity to an abandoned landfill (within 1,000 feet), (2) liquefaction, and (3) peat‐settlement‐prone areas.
SUBSURFACE CONDITIONS Our understanding of the subsurface conditions at the Union Bay Place development site is based on materials encountered in one soil boring advanced as part of this study, laboratory tests on selected soil samples, logs of existing explorations and a geotechnical pre‐design report completed by others at the site (Landau Associates 2015), available historical borings in the vicinity of the site, and our experience on other development projects for University Village. Details of the conditions found at our boring location are shown on the exploration logs in Appendix A. The results of geotechnical
19174‐00 November 18, 2015 DRAFT Union Bay Place Development | 3 laboratory testing are in Appendix B. Exploration borings performed by others at the site, and other historical borings in the vicinity, provided additional geotechnical data for this study and are in Appendix C. Results of our slug testing are in Appendix D.
The subsurface information used for this study represents conditions at discrete locations across the project site; actual conditions in other areas could vary. Furthermore, the nature and extent of any variations may not become evident until additional explorations are performed or until construction begins. If significant variations are observed at that time, we may need to modify our conclusions and recommendations accordingly to reflect actual site conditions.
Soil Conditions Our understanding of the subsurface conditions is based on our new boring (HC‐101) and monitoring wells (HC‐MW‐101 and HC‐MW‐102) completed as part of this study; existing explorations on or near the site (borings B‐1, B‐2, B‐3, TB‐1‐77, TB‐2‐77 and TB‐3‐77); and our previous experience at other nearby areas. Approximate locations of the soil explorations are illustrated on Figure 2, Site and Exploration Plan. Cross‐section profiles of generalized subsurface conditions estimated from these borings are presented on Figures 3 and 4.
The soil layers observed during the field explorations program were broadly categorized based on their engineering properties into Engineering Soil Units (ESUs). In general, the soils observed in the explorations consist of the following soil units, described in the order they were encountered from the ground surface down:
ESU 1 – SILT, SAND, and GRAVEL (FILL). A relatively thick (up to approximately 25‐foot‐thick) surficial layer of fill consisting of soft to stiff, sandy silt and very loose to medium dense gravelly, silty Sand and sandy Gravel was observed at the ground surface or beneath the existing 3‐ to 5‐ inch‐thick paved areas.
ESU 2 – Very soft to soft, organic SILT and PEAT. The peat was encountered directly under the fill in B‐1 from about 23 to 31 feet deep. The peat deposit is interbedded with occasional sand lenses. This unit poses the greatest potential for settlement at the site. Foundation elements should not bear in this soil unit.
ESU 3 – Medium dense to very dense, gravelly SAND. This unit was encountered directly below the fill or peat, and is interpreted to be glacially overridden. It consists of various amounts of slightly silty, gravelly to very gravelly SAND. This unit is suitable for foundation support. All the borings terminate in this soil unit.
Groundwater Groundwater was encountered during drilling in the borings completed for this study. Groundwater levels in the three on‐site monitoring wells were measured in February 2015 and October 2015. The location of the monitoring wells is shown on Figure 2. Groundwater elevation (NAVD 88 datum) data are presented in Table 1.
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Table 1 – Groundwater Elevations
Elevation at Monitoring Well Groundwater Location/Time HC-MW-101 HC-MW-102 B-2 B-3 Ground surface 45 43 45 45 ATD 32 n/a 33 32.5 February 2015 n/a n/a n/a 39.3 October 5, 2015 32.0 23.4 n/a 36.8 ATD = At time of drilling (an approximate value) All elevations in feet (NAVD 88 Datum) Monitoring well in B-3 is screened within the aquifer below about elevation 15 feet; the rise of groundwater above the ADT groundwater elevation indicates artesian conditions at depth, which is not representative of the near- surface groundwater elevation.
The groundwater table is within the Fill unit at an elevation that ranges from about 23 to 32 feet. Measured groundwater levels in HC‐MW‐101 and HC‐MW‐102 represent the groundwater within the fill. Measured groundwater levels in B‐3 are influenced by artesian pressure in the lower dense bearing soils. Groundwater elevations were highest at the east side of the site and lowest at the west side of the site. Because groundwater level at the east side (Union Bay Place NE side) of the site is approximately 8 to 9 feet higher than that at the west side, groundwater likely flows to the west. During a site reconnaissance no seeps were noted on the slope along the west property line that separates the subject site from the QFC site to the west.
Groundwater levels were obtained on the dates indicated on the logs, and are representative of the time the readings were taken. Groundwater elevations vary depending on location, season, precipitation, and other factors.
Hydraulic Conductivity (Slug Testing) Slug testing was conducted in wells HC‐MW‐101 and B‐3 on October 6, 2015, to determine the hydraulic conductivity of the fill. We could not perform a slug test in well HC‐MW‐102 because of insufficient water within the well. Slug tests are performed by rapidly inserting and removing a solid PVC rod into a well and measuring the recovery of the groundwater levels. When the PVC rod is inserted, it is a falling head test, and when the rod is removed, it is a rising head test. The water level data generated from the tests were analyzed using the Bouwer and Rice method.
Average hydraulic conductivities determined from slug tests range from 6.2 x 10‐4 to 1.9 x 10‐3 centimeters per second (cm/sec) (1.8 to 5.4 feet/day). This range of hydraulic conductivity is consistent with typical values for sand to silty sand. Slug test results are summarized in Appendix D.
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SEISMIC DESIGN RECOMMENDATIONS The site is in a seismically active area. In this section, we describe the seismic setting at the project site, identify the seismic basis of design, provide the code‐based response spectrum parameters, and discuss the seismic hazards at the site.
The seismicity of Western Washington is dominated by the Cascadia Subduction Zone, in which the offshore Juan de Fuca Plate subducts beneath the continental North American Plate. Including the subduction zone sources, three types of earthquakes are prevalent in Western Washington: interface subduction, intraslab subduction, and crustal earthquakes.
Subduction Zone Sources. Subduction of the offshore Juan de Fuca Plate below the North American Plate causes two distinct types of events. Large‐magnitude interface subduction earthquakes occur at shallow depths near the Washington coast at the interface between the two plates; an example is the 1700 earthquake, which had magnitude of approximately 9.0. A deeper zone of seismicity is associated with bending of the Juan de Fuca Plate below the Puget Sound Region; this bending produces intraslab subduction earthquakes at depths of 40 to 70 kilometers (e.g., the 1949, 1965, and 2001 earthquakes). Figure 5 depicts the Cascadia Subduction Zone and the various types of earthquakes it can produce.
Crustal Sources. Recent fault trenching and seismic records in the Puget Sound area indicate a distinct shallow zone of crustal seismicity (e.g., Seattle and Tacoma Faults), which may have surficial expressions and can extend 25 to 30 kilometers deep. Figure 6 shows the position of the Puget Sound crustal faults in relation to the project site.
Site Class We determined the soil site class using information about the supporting foundation soil in accordance with the 2012 International Building Code (IBC; International Code Council 2012). The soil site class is based on the soil characteristic and a weighted average of the blow counts observed to a depth of 100 feet below ground surface (bgs). For explorations advanced less than 100 feet bgs, we assumed the material density below the deepest sample remains constant to 100 feet. Based on these assumptions, seismic Site Class D would be assigned to the site. However, because the site contains potentially liquefiable soil as discussed below, it is classified as Site Class F. The IBC and ASCE 7‐10 require a site‐specific analysis to determine seismic parameters for Site Class F soils if the period of the structure is greater than 0.5 second. Based in the information provided by project structural engineer (KPFF), we understand the period of the proposed building will not exceed 0.5 second. Therefore, in accordance with ASCE 7‐10 (Section 21.3), the building can be designed to the code‐based Site Class D spectrum.
Seismic Design Parameters We understand that the seismic performance is being evaluated according to IBC 2012 and ASCE 7‐10.
The basis of design for IBC 2012 is the risk‐targeted maximum considered earthquake (MCER), which has a 2 percent probability of exceedance in 50 years, corresponding to a return period of 2,475 years.
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The basis of design for the 2012 IBC is two‐thirds of the hazard associated with the MCER. The IBC event is referred to as the design event (DE).
The parameters were obtained from the USGS Seismic Design Maps web application (http://earthquake.usgs.gov/designmaps/us/application.php; USGS 2008) and are shown in Table 2.
Table 2 – Seismic Design Parameters According to IBC 2012
Parameter Value Latitude 47.6626° N Longitude –122.2948° W Site class E Risk category III
Spectral response acceleration at short periods, SS 1.280 g
Spectral response acceleration at 1-second periods, S1 0.495 g
Site coefficient at short periods, Fa 1.0
Site coefficient at 1-second periods, Fv 1.505
MCER spectral acceleration at short periods, SMS 1.280 g
MCER spectral acceleration at 1-second periods, SM1 0.745 g
Design spectral acceleration at short periods, SDS 0.854 g
Design spectral acceleration at 1-second periods, SD1 0.497 g
Liquefaction Assessment Liquefaction is caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles, resulting in the sudden loss of shear strength in the soil. Granular soils that rely on inter‐particle friction for strength are susceptible to liquefaction until the excess pore pressures can dissipate. Sand boils and flows observed at the ground surface after an earthquake are the result of excess pore pressures dissipating upward, carrying soil particles with the draining water. In general, loose, saturated sandy soils with low silt and clay content are the most susceptible to liquefaction. Silty soils with low plasticity are also susceptible to liquefaction under relatively higher levels of ground shaking. For any soil type, the soil must be saturated for liquefaction to occur. Liquefaction can cause ground surface settlement and lateral spreading.
We used empirical methods to estimate liquefaction potential based on the standard penetration test (SPT) data obtained at the site. We used the SPT‐based liquefaction triggering procedure after Idriss and Boulanger (2008). For our analysis of the MCE hazard levels we used an earthquake magnitude of 7.0 and a peak ground acceleration (PGA) of 0.512 g, which we obtained from USGS for the site coordinates and Site Class D.
Our analysis shows that the loose fill soil below the groundwater table is susceptible to liquefaction.
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Post-Liquefaction Induced Vertical Settlement Post‐liquefaction settlement results from densification and redistribution of soils liquefied during earthquake shaking. The ground surface typically settles unevenly across the area, which can result in differential settlement of buildings.
We estimated liquefaction‐induced ground surface settlement using SPT corrections by Idriss and Boulanger (2008) and volumetric strain formulations by Yoshimine et al. (2006). We calculated free‐ field ground surface settlements from the volumetric strains in contractive soils. We estimate that approximately 2 to 4 inches of ground surface settlement could occur from an MCE event. Since this settlement estimate does not include possible effects of sand boils and blowout resulting in the loss of soil particles, actual liquefaction‐induced settlements may be even greater.
Surface Rupture The nearest mapped fault to the site is the North Trace of the Seattle Fault Zone, which lies approximately 5.9 miles to the south. Based on the distance to the fault and the relatively long return periods of earthquakes along the fault, we believe risk of surface fault rupture is low.
GEOTECHNICAL ENGINEERING DESIGN RECOMMENDATIONS This section of the report presents our conclusions and recommendations for the geotechnical aspects of design and construction on the project site. We developed our recommendations based on our current understanding of the project and the subsurface conditions encountered by our explorations. If the nature or location of the development is different than we have assumed, we should be notified so we can change or confirm our recommendations.
General Considerations Based on the current design plans and our discussions with the design team, the primary geotechnical considerations for this project are:
Foundations. The peat layer that underlies the site is very compressible. Any loads applied at the surface will consolidate the peat, which will result in surface settlement over time. In addition, the limited liquefaction‐induced subsidence will result in unacceptable levels of post‐construction settlement if shallow foundations are used. Wew recommend supporting the structure loads using augercast piles or drilled shafts.
Temporary Shoring. The project includes one level of below‐grade parking, which will require temporary (and possibly permanent) structural shoring of the planned excavation. The shoring will need to support existing at‐grade structures adjacent to the north and south sides of the site as well as the city right‐of‐way along Union. A cantilevered soldier pile wall, with the use of a soldier pile wall with one row of tieback where needed, is anticipated to provide a suitable option for temporary shoring. The temporary shoring along the north property line may consist of
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underpinning of the existing building or could be placed just to the south of the building such that the building will act as a surcharge on the shoring system. It is also possible that the shoring system could be used for vertical support of the new building.
Groundwater Control. Groundwater in the area is high and close to the anticipated basement slab level. To accommodate the proposed finish floor elevation, temporary dewatering will be needed and a permanent drainage layer will need to be installed. Alternatively, it may be appropriate to construct the lower portion of the lower level of the building to be “water tight”.
Site Preparation For site preparation, the asphalt pavements, concrete walkways, sidewalks, and landscape vegetation should be removed, and existing structures on the site should be demolished. Removed asphalt, brick, concrete, or topsoil should not be reused as structural fill.
It will likely be necessary to relocate or abandon some or all utilities. Excavation of these utility lines will occur through fill materials. Abandoned underground utilities should be removed or completely grouted. Ends of remaining abandoned utility lines should be sealed to prevent soil or water from entering the pipe. Soft or loose backfill materials should be removed, and excavations should be backfilled with structural fill.
Foundation Considerations Given the significant depth of compressible and liquefiable soils (25 to 40 feet, based on the existing borings at the site), some form of deep foundation system will be required to support the proposed structure. Typical pile types would be driven steel, augercast, drilled shafts, micropiles, or helical steel. All these have been used in the area and the choice depends on cost and the specific project conditions.
Driven piles are likely NOT a good choice for this site, as the vibrations associated with either impact or vibratory pile driving could affect the adjacent buildings.
Helical piles are literally screwed into the ground using high‐powered torque equipment. These piles were used successfully at the South Building at University Village, which is adjacent to the settlement‐ sensitive 45th Street Viaduct. Capacities of about 250 tons can be easily achieved. The downsides are that the equipment is not locally available and costs can be higher than would be practical.
Augercast piles are readily available locally and are low cost in terms of dollars per foot of length per ton of capacity, under normal circumstances. Their installation does not cause excessive vibrations. The risk with augercast piles is the potential for the foundation soils to heave due to artesian conditions at depth. The other cost factor for augercast piles at this site is the potential cost of disposing of the spoils from the pile holes. If the spoils are contaminated, the disposal cost can increase the effective unit cost of the piles.
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Small diameter drilled shafts may be an alternative for this site. Based on discussions with the design team it may be appropriate to use drilled shafts that are the same diameter as the proposed soldier piles for the shoring system. Micropiles may be an alternative to augercast piles or drilled shafts. The downside of micropiles is that they cannot develop substantial lateral capacity, so the structure would need to be designed to accommodate lateral force demands at the subgrade perimeter walls.
An alternative to pile foundations for this site is ground improvement that would prevent liquefaction and allow for support of the building on shallow foundations. Typical ground improvement methods include stone columns and rammed aggregate piers. Stone columns are constructed by vibrating a pipe into the ground and then placing rock through the bottom end of the pipe as the pipe is withdrawn. The vibration has the effect of partially densifying the ground and the column of stone adds strength to the ground such that shallow footings and slabs‐on‐grade can be used to support the building loads. Stone column ground improvement was successfully used for construction of the parking garage to the north of the existing QFC store
Rammed aggregate piers are somewhat similar to stone columns. They are constructed by driving a steel pipe to the desired depth and then placing rock through the pipe. A downhole rammer is then used to tamp the rock as the pipe is withdrawn. The process relies more on this ramming process to compact the rock than does the stone column process, which relies more heavily on vibration to densify the rock
The risk associated with both these methods of ground improvement is the potential for adverse impacts to the adjacent structures due to vibrations during installation. The risks and cost benefits associated with all these alternatives need to be evaluated by the entire project ream (especially including the contractor) to arrive at the best solution. At this point we are not addressing these ground improvement methods
Adjacent Structures Buildings are adjacent to the site on the northern and southern property lines. Available information indicates that the one‐story commercial building to the north bears on near‐grade shallow footings. The temporary shoring will need to support these shallow footings as well as supporting the new construction. The Safeway building to the south is pile‐supported. Available plans from the time the Safeway building was constructed indicate ground surface is about 6 to 8 feet beneath the building’s finished floor elevation; therefore, the bottom of the pile may be that far below floor elevation.
On the northeast side of the Safeway store (along the loading dock area) a short wall retains soil from the project site. This retaining wall appears to be pile‐supported and includes battered timber piles that may extend into the project site (depending on the depth of the piles).
Augercast Pile Foundations Because of the weak near‐surface soil at the site, we believe augercast piles may provide a cost‐ effective option to support the building loads. We anticipate that 16‐ to 24‐inch‐diameter piles may be used. This size and type of pile foundation can likely provide the necessary support for structural loads,
19174‐00 November 18, 2015 DRAFT 10 | Union Bay Place Development assuming proper design and installation. We will work with the project team to assess and provide design recommendations for other foundation support options if augercast piles are found to be problematic considering the artesian conditions at depth described above.
Vertical Pile Capacity Vertical compressive loads can be resisted by friction along the pile sides and by end‐bearing at the tip. Vertical uplift loads are resisted by friction alone. Column design loads are unknown at this time.
We recommend embedding the piles at least 15 feet into the medium dense to very dense, gravelly SAND (ESU 3) to develop the full allowable axial capacities recommended in Table 3. Capacities are generally based on the soil profile at B‐1 where peat was identified. Approximate bearing elevation contours are shown on Figure 2. With a base of structural slab at approximately elevation 32 feet, these piles are expected to be about 35 feet long, corresponding to a tip elevation of about –3 feet (i.e. tipped about 46 feet below existing ground surface).
Table 3 – Allowable Axial Capacity for Augercast Piles
Pile Diameter Allowable Allowable in inches Compression Tension Capacity in kips Capacity in kips 16 83 60 18 105 72 24 187 96 30 234 120
The allowable capacities provided incorporate the effects of downdrag loads resulting from compression of the soft peat and liquefaction‐induced settlement in the sand layers. We estimated the downdrag force using a depth to dense bearing soil of 31 feet, and a downdrag adhesion of 250 pounds per square foot (psf) around the perimeter of the pile. Based on this, the downdrag loads are estimated to be 32, 41, 49, and 61 kips for 16‐, 18‐, 24‐ and 30‐inch‐diameter piles, respectively. The allowable axial compressive capacities in Table 3 include a reduction equal to the downdrag loads expected from the peat and liquefiable soils.
The pile capacities are based on a factor of safety of 2.0 or greater for compressive and uplift loading. If piles are spaced greater than three pile diameters measured center‐to‐center, it will not be necessary to reduce the allowable compression capacities of individual piles in a pile group.
Higher capacities than those recommended above could be realized by conducting a full‐scale pile load test program to measure the load/deflection behavior of the augercast pile of the proposed size.
Estimated Pile Settlement. Assuming properly installed augercast piles, we estimate total settlement will range from 1/4 to 1 inch. Differential settlement between adjacent pile‐supported columns should
19174‐00 November 18, 2015 DRAFT Union Bay Place Development | 11 be less than about one‐half of the total settlement. The pile settlement associated with the design loads should occur within the first few days after loading. Any future additional settlement would likely result from downdrag forces caused by settlement of the peat layer or during and after liquefaction under earthquake shaking. This condition may result in some additional settlement of the pile foundation as additional end‐bearing capacity is mobilized by downdrag forces.
Lateral Pile Capacity Lateral loads, which may be imposed on the piles by wind or earthquake forces, can be resisted by horizontal bearing support of near‐surface soil adjacent to the piles. The lateral resistance of a drilled shaft depends on its length, stiffness in the direction of loading, proximity to other shafts, and degree of fixity at the head, as well as on the engineering properties of the soil. The computer program LPILE is often used to calculate lateral load capacity and deflection for the drilled shaft. LPILE uses lateral soil reaction (p) and lateral deflection (y) curves generalized from field load tests, along with soil input properties, to approximate lateral pile deflections and moments for piles subjected to an axial load.
We recommend using the LPILE soil input parameters in Table 4 for augercast piles. Our soil profile was primarily based on B‐1 on the west side of the site.
Table 4 – Soil Parameters for LPILE Input (B-1)
Effective Slope of Layer Layer Friction Soil Layer Unit Soil Soil Depth in Elevation Angle in Description Weight Model Modulus feet in feet degrees in pcf (k) in pci
API Fill 0 to 11 43 to 32 125 30 43 SAND Fill – API 11 to 23 32 to 20 62.6 30 32 submerged SAND API Peat 23 to 31 20 to 12 4.6 9 5 SAND Glacial soil API below 31 below 12 72.6 38 125 (till/outwash) SAND
For full lateral capacity, we recommend spacing piles at least 6D center‐to‐center. Shafts spaced closer than 6D should be adjusted for group effects according to Table 5. Interpolation should be used for spacing values other than 3D and 5D.
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Table 5 – Pile P-multipliers from AASHTO (2014)
AASHTO 2014 Reduction Factors (p-multipliers) Pile Spacing 1st Row 2nd Row 3rd and greater Rows
3D 0.8 0.4 0.3 5D 1.0 0.85 0.7
Liquefaction Effects. Likewise, p‐multipliers can be used in analysis to account for the reduced stiffness caused by liquefied soils. For the liquefied condition, LPILE analysis was performed using p‐ multipliers according to guidelines in the 2014 Washington State Department of Transportation (WSDOT) guidelines. P‐multipliers for liquefied soil and group effects are not applied simultaneously in accordance with those guidelines.
A p‐multiplier of 0.2 should be applied along the length of the liquefied zone only (Fill – submerged).
Passive Pressure on Pile Caps and Grade Beams Soil adjacent to pile caps and grade beams can passively resist structure movement. We recommend the following for calculating the passive soil resistance:
Neglect the upper 18 inches of soil below the structural slabs because of expected settlement of the subgrade soils.
Neglect passive resistance below elevation 21 feet, which corresponds to approximately the highest elevation of observed peat.
Use an allowable passive equivalent fluid weight of 115 pounds per cubic foot (pcf). This value assumes soil is below the groundwater table and includes a factor of safety of 1.5.
Augercast Pile Installation We recommend that a Hart Crowser representative observe the augercast pile installation to evaluate the contractor’s operation and collect and interpret the installation data. As the completed pile will be below the ground surface and cannot be observed during construction, judgment and experience must be used to determine whether it is acceptable. This also requires use of an augercast pile contractor who is familiar with such installations. We recommend close monitoring of installation procedures, such as installation sequence, auger withdrawal rate, grouting pressure, and quantity of grout used per pile. Variations from the established pattern, such as low grout pressure or excessive settlement of grout in a completed pile, would make the pile susceptible to rejection.
We recommend the following for augercast pile installation:
To prevent interconnection of grout between piles, do not install two piles within five pile diameters of each other in a single 24‐hour period. At the time of construction, evaluate whether this period may need to be increased because of the very soft peat layer.
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Require the contractor to provide a pressure gauge in the grout line.
Minimum pressures should be those required to maintain a steady flow of grout to the auger. A typical value of 100 pounds per square inch (psi) should be used for this purpose.
Rapid drops in the grout pressure of 50 psi or more occurring when otherwise accepted procedures are used should be specified as a possible cause for reconstructing the pile.
Grout injection and auger withdrawal from the soils should be done at rates that allow maintenance of a positive grout head of at least 10 feet above the bottom of the auger. A larger head may be required to counteract the high groundwater table and water pressure at the site.
Withdraw auger from hole at a slow rate so that pressure on the grout column is maintained.
Require contractor to provide a way to monitor quantity of grout used per pile. A stroke counter on the group pump is the most efficient means to determine grout quantity.
Require the contractor to rotate the auger after initial grout pumping (of about 2 cubic feet) before beginning to withdraw the auger.
Require the contractor to install a full length rebar (aka center bar) down the pile center when grouting is completed, to ensure a properly constructed pile.
Augercast piles will generate soil spoils that will likely need to be disposed of off site. Any environmental considerations that affect disposal of the spoils should be identified before construction.
Drilled Shaft Capacity For preliminary drilled shaft design we assumed that 2‐ or 3‐foot‐diameter drilled shafts will be sufficient for axial and lateral foundation support of the sterile corridor. The compressive capacity of drilled shaft foundations is achieved through a combination of end‐bearing support at the pile tip and side friction between the pile material and the soil along the embedded pile length.
We recommend using the allowable design capacity provided in Table 3 for drilled shafts.
Drilled Shaft Installation The contractor should review our recommendations and be prepared to address the construction considerations below. If significant variations are observed at any time, we may need to modify our conclusions and recommendations. For drilled shaft installation, we recommend:
Be aware that drilled shafts will produce a large volume of drill cuttings that may be contaminated and require chemical analysis; soil will likely require off‐site disposal.
Have the contractor review the boring logs thoroughly and choose appropriate drilling methods.
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Have the contractor clean slough and other loose material from the bottom of all drilled shafts before placing concrete.
Tremie the concrete from the bottom of the shaft if groundwater is encountered or if drilling mud is used to maintain an open hole.
Although cobbles and/or boulders were not encountered in explorations near the proposed drilled shaft locations, based on the local geology, the contractor should be prepared to deal with large obstructions that may be encountered during excavation.
Clean out the shaft toe no more than 6 hours before placing concrete so suspended solids do not have much time to settle to the toe and reduce its geotechnical stiffness.
Where multiple drilled shafts are planned within 5 diameters of each other, consider the timing of excavation and concrete placement of the adjacent shafts. Provide the adjacent drilled shaft with adequate cure time before starting to excavate the next drilled shaft. This will not only minimize the potential for communication between adjacent shafts but will also reduce the likelihood of disturbing the set and cure of the concrete in the recently poured shaft.
We recommend having a representative from Hart Crowser on site full time for special inspection of drilled shaft installation. The on‐site geotechnical representative should verify that soil conditions encountered during drilled shaft excavation match those assumed during design before concrete is placed. The geotechnical representative should also verify that the shaft is installed according to the project plans and specifications.
Temporary Shoring A shoring system will be required to provide temporary lateral support for safety and stability of the adjacent structures to the north and south of the proposed building, as well as for the right of way on the west side of the site. Based on the soil and groundwater conditions, it is our opinion that excavations could be supported using a combination of conventional soldier piles with tieback anchors and cantilevered soldier pile wall.
Shoring should be designed by a professional structural engineer registered in the State of Washington. We also recommend that we review the geotechnical aspects of the shoring design before construction. It is generally not the purpose of this report to provide specific criteria for the contractor’s construction means and methods. It should be the responsibility of the shoring contractor to verify actual ground conditions and determine the construction methods and procedures needed to install an appropriate shoring system.
Lateral Earth Pressure Lateral earth pressures for the design of the soldier pile wall depend on the type of wall and its ability to deform. The wall may be designed using active earth pressure if the top of the wall is allowed to
19174‐00 November 18, 2015 DRAFT Union Bay Place Development | 15 deform about 0.001 to 0.002 times the wall height and if no settlement‐sensitive structures or utilities are within the deformation zone.
At‐rest earth pressure should be used to design the wall if settlement‐sensitive structures or utilities exist within the potential deformation zone, or where the wall system is too stiff to allow sufficient lateral movement to develop an active condition. We recommend the following:
Use lateral earth pressures on Figure 7.
If construction or vehicular traffic will be present above the wall, within a distance from the wall face equal to the wall height, include a 2‐foot surcharge in the design, as shown on Figure 7.
Additional surcharge loads (e.g., adjacent footing loads, material stockpiles, or other large loads) should be computed using the methods shown on Figure 9. These additional loads should be added to those calculated for the shoring wall based on Figure 7.
The lateral earth pressures presented herein are based on dewatered conditions, with the understanding that hydrostatic pressure does not act on the walls.
Soldier Pile Design Soldier piles must be embedded deeply enough to provide kick‐out resistance for the portion of the wall below the lowest support. Soldier piles must be designed to carry the bending stresses from the lateral earth pressure against the pile and the lagging between soldier plies. We also recommend the following:
Design soldier piles to bear in the medium dense to very dense gravelly Sand layer (ESU 3).
Use end‐bearing and skin friction design values presented on Figure 7.
Embed piles at least 10 feet below the bottom of the excavation after allowing 2 feet for disturbance.
Design soldier piles for bending using a uniform loading equivalent to 80 percent of the design values and analyze for shear using total load.
For design against kickout, compute the lateral resistance on the basis of the passive pressure presented on Figure 7, acting over three times the diameter of the concreted soldier pile section or the pile spacing, whichever is less.
The above recommendations are based on proper installation of the soldier piles as described below.
Soldier Pile Installation Conditions such as caving soil and groundwater can loosen soils at the bottom of the soldier pile excavation and reduce bearing capacity of the zone of disturbed soils. We recommend that a Hart
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Crowser representative monitor soldier pile installations so that construction methods can be adjusted in a timely manner, if needed.
We recommend the following for soldier pile installation:
Require that the contractor to be prepared to case the soldier pile installations. The actual necessity of casing should be determined in the field at the time of installation.
Prohibit the use of drilling mud unless reviewed and approved by the geotechnical and structural engineer.
Place concrete in soldier pile holes with a tremie pipe. Hart Crowser must verify the integrity of the soil at the base of the hole before concrete is placed.
Lagging Loss of ground between the soldier piles is prevented using lagging. Lagging typically consists of timber planks or concrete panels. We recommend using the thickness (rough‐cut) of temporary lagging provided in Federal Highway Administration (FHWA) Geotechnical Engineering Circular No. 4, “Ground Anchors and Anchor Systems,” based on “Competent Soils” and the selected clear span of soldier piles. For clear spans of 5 feet or less, the recommended lagging thickness is 2 inches. For clear spans between 5 and 8 feet, the recommended lagging thickness is 3 inches.
Prompt and careful installation of lagging, particularly in areas of seepage and loose soils, is important for maintaining the integrity of the excavation. Proper installation should be the responsibility of the wall contractor so that soil failure, sloughing, and ground loss are prevented, and so that safe working conditions are provided.
Soldier pile wall construction may be difficult if cobbles, boulders, or loose sands and gravels are encountered in the excavation. If these conditions are encountered, substantial raveling of the soil could occur. The contractor should be prepared to place lagging in small vertical increments in areas of utility backfill or caving soil, and should be prepared to backfill voids behind the wall that may result from ground loss during construction.
We recommend the following for lagging:
Backfill voids greater than 1 inch using sand, pea gravel, or a porous slurry. Backfill the void spaces progressively as the excavation deepens. The backfill must not allow potential hydrostatic pressure buildup behind the wall. Drainage behind the wall must be maintained. If not, hydrostatic water pressure should be added to the recommended lateral earth pressures.
Install extra lagging above the shoring wall if there is a slope above the wall, to provide a partial barrier for material that could ravel down from the slope face and fall into the excavation.
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Tieback Anchor Design and Construction We expect that tieback anchors can be used for external lateral support of the soldier pile walls. We recommend the following for tieback anchor design:
Locate anchor portions of the tiebacks below the no‐load zone shown on Figure 7.
For planning, use allowable adhesion values presented on Figure 7, which are appropriate for pressure‐grouted anchors. The shoring contractor must choose appropriate means and methods to achieve the design adhesion based on their experience on similar sites.
Locate anchors at least three tieback diameters apart.
Pump structural grout into the anchor zone using a grout hose or tremie hose placed at the bottom of the anchor.
Install a bond breaker such as plastic sheathing or a PVC pipe around the tie rods within the no‐ load zone.
Grout and backfill tiebacks immediately after placing the anchor. To prevent collapse of the holes, ground loss, and surface subsidence, do not leave anchor holes open overnight.
Take care not to mine out large cavities in granular soil.
Maintain continuous cutting return if using pneumatic drilling techniques so that air pressure is not channeled to nearby utility vaults, corridors, or subgrade slabs, because air pressure may damage such structures.
Design anchor lengths so that they do not conflict with any underground utilities and/or support elements of the adjacent structures.
Identify existing facilities adjacent to the project site including buried utilities and foundations, as these may affect the location and length of the anchors.
Select the tieback anchor material and the installation technique. The selected installation method must be subject to field verification with performance and proof‐testing, as discussed in Attachment 1.
Install anchors to minimize ground loss and do not disturb previously installed anchors. During tieback drilling, wet or saturated zones will be encountered, and caving or blow‐in could occur. Drilling with a casing may reduce the potential for these conditions and ground loss.
Hart Crowser should review the design for anchor locations, capacities, and related criteria prior to implementation.
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The anchor design values recommended on Figure 7 include a factor of safety of at least 2.0. This factor of safety provides for a reasonable additional load capacity in case an unforeseen increase in unit soil load develops because of irregularities that can occur during installation of the anchor. The variable soil conditions and unit friction values mean that some field changes in anchor length may be necessary. For planning, we recommend designing anchors according to the above criteria.
Tieback Anchor Testing The tiebacks will be tested to confirm the appropriateness of the anchor design values and to verify that a suitable installation is achieved. The procedure for performance and proof‐testing is presented in Attachment 1 and summarized below. For testing of tieback anchors, we recommend:
Require the shoring contractor to complete two successful 200 percent performance tests on one tieback. Contract documents should be prepared such that additional verification tests could be performed on a unit price basis if different site conditions are encountered.
For anchors installed for the 200 percent verification test, the specifications should include components to prevent friction contribution between the grout column and the soil in the no‐load zone.
Proof‐load each production anchor to 133 percent of the design load to test for total movement and creep.
Permanent Subgrade Building Walls
Lateral Earth Pressures for Walls Constructed Against Temporary Shoring Permanent walls constructed flush with temporary shoring systems may be designed for the same active (or at‐rest) earth pressures used in the design of the shoring system (Figure 7).
Seismic Earth Pressure The lateral earth pressures for permanent walls must include a seismic earth pressure increment. This additional lateral earth pressure can be approximated as a rectangular uniform pressure of 7H for a yielding wall. Apply the seismic earth pressure from the top of the wall to the bottom of the excavation, a height that is defined as the height (H) of the wall as it is dimensioned and shown on Figure 8. This increment is calculated using the IBC hazard level for the site location.
Additional Surcharge Pressures We recommend applying a surcharge of 250 psf to the top of the proposed excavation for computations to provide some allowance for possible surface pressures near the excavation such as light vehicles or small material stockpiles. Surcharge pressures resulting from heavier loads such as buildings, footings, heavy equipment, or large material stockpiles should be calculated using Figure 9. These additional loads would be added to the soil pressure calculated for permanent foundation walls.
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Hydrostatic Groundwater Pressure
For walls that are not drained, add a triangular lateral hydrostatic pressure of 62.4HGW psf, where HGW is the depth of structure below the groundwater table. We recommend using a design groundwater table elevation of 32 feet.
This recommendation presumes that drainage will be installed above the groundwater table to prevent buildup of water pressure caused by perched water and precipitation. Walls without drainage must be designed for full horizontal hydrostatic pressure as well as hydrostatic uplift forces on the bottom of the slab‐on‐grade. Additionally, the waterproofing system would need to be designed and installed by others to facilitate a functioning, dry lowest level.
Wall Drainage To reduce the risk of potential hydrostatic pressure buildup, we recommend placing a dimpled geotextile drainage geocomposite (e.g., TenCate Mirafi G‐Series) between the soil and the building wall. Alternatively, free‐draining granular material (less than 3 percent passing the US No. 200 sieve) could be used as structural fill within an 18‐inch‐wide zone immediately behind the wall. This curtain drain should be continuous and hydraulically connected to a footing drain collection system at the base of the wall, as described in the Permanent Drainage section.
Floor Slabs We recommend using structural floor slabs supported on pile caps. Considering the poor soil conditions, the soil beneath the slab will settle over the life of the building, creating a void below the slab. The structural slab should be designed assuming no soil support. Permanent drainage below the slab should be installed as described in the Permanent Drainage section.
Construction Dewatering We anticipate an excavation to bottom of foundations of around 10 to 12 feet or more. This would place the bottom of excavation at or 1 to 2 feet below the static groundwater table. This is a significant depth below the groundwater table. Construction dewatering could likely be easily completed using construction dewatering wells or a well point system. If there are no contaminants or if their concentrations are low enough, the water could be disposed of in the sanitary system. Construction dewatering will need to be carefully assessed, as the groundwater table will be lowered not only at the Union Bay Place site but at the adjacent sites.
Construction Dewatering Recommendations The groundwater table is relatively shallow; therefore, we anticipate the groundwater table will be encountered during construction. Construction dewatering is required when excavating below the groundwater table to maintain dry and stable working conditions in the bottom of the excavation. Typically, contractors prefer to have the groundwater table lowered a foot or two below the bottom of excavations. At the project site, this equates to temporarily lowering the groundwater to about elevation 32 feet, which coincides with the design groundwater elevation. We recommend the following for dewatering during construction:
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Temporary construction dewatering will be required when excavations are below the groundwater table. The actual dewatering methods and schedule will be selected by the construction contractor, with our review. In our opinion, dewatering will require using a combination of sump and/or vacuum well point systems around the excavation. Dewatering will need to be continuous during construction below the groundwater table.
We recommend lowering the groundwater table by no more than 2 feet below the bottom of excavation to maintain stable working conditions in the bottom of the excavation while minimizing off‐site settlement. This could be reduced to 1 foot during construction, if necessary.
The contractor should use a qualified licensed hydrogeologist to design the dewatering system. The general contractor should retain an experienced dewatering contractor to install and operate the dewatering system. Hart Crowser should review the dewatering plan before it is implemented.
Steady‐state dewatering rates will vary depending on the excavation size and depth, dewatering method, schedule, and soil conditions. Generally, beginning dewatering one to two weeks before construction is recommended to allow sufficient time to reach design water levels. Initial dewatering rates can be much higher until a stabilized water level is achieved.
We recommend disposing of dewatering discharges by a local storm drain. Disposal of dewatering discharges by infiltration or recharge will likely be impractical because of the relatively shallow groundwater table.
Our services were provided to help assess temporary dewatering for the planned excavation, shoring, and construction of new utilities that will be, in part, beneath the groundwater table. Our estimate of dewatering discharge rates is based on our evaluation of how dewatering operations may be implemented at the site, considering conditions described in the geotechnical studies. The actual dewatering rates will depend on the dewatering methods and schedule selected by the contractor. Site‐specific information is limited to exploration borings and in situ hydraulic testing completed at widely spaced locations; therefore, conditions may differ from those assumed.
Geotechnical Impacts of Dewatering Geotechnical impacts of dewatering are primarily related to dewatering‐induced settlement. We estimated the settlement that could result from lowering the groundwater table at the site. Given the soft and compressible nature of the soils underlying the site, lowering the groundwater table will increase the overburden stress on these compressible soils, which could result in unwanted and excessive settlement of the adjacent buildings.
The Safeway building to the south is on pile foundations and would not be susceptible to settlement. The building to the north is on shallow footings and could be significantly affected by settlement from dewatering. The amount of settlement that occurs depends on the soil conditions, as well as on the amount and duration of dewatering. Once the dewatering plan is known, we should be notified so we can assess settlement that may occur during construction.
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Waterproofing If waterproofing is required below grade, a specialty waterproofing subconsultant should be retained to design it. We have seen waterproofing systems such as a heavy plastic membrane liners, bentonite clay panels (i.e., Volclay or equivalent), and other interior or exterior sealants used effectively on projects similar to this one.
Permanent Drainage We make the following comments and recommendations related to the permanent drainage system:
Use a drainage layer below the slab consisting of 4 inches of clean sandy 1‐inch‐minus gravel and containing less than 30 percent passing the US No. 4 Sieve and less than 3 percent fines (i.e., material passing the No. 200 US sieve) based on the minus 3/4‐inch fraction.
Place dimpled geotextile drainage geocomposite (e.g., TenCate Mirafi G‐Series) between the structural slab and the granular drainage layer. Cut holes in the membrane portion of this layer at vent locations to allow upward flow of methane gas.
Install perimeter cross drains in the granular drainage layer consisting of 4‐inch‐diameter perforated drain pipe spaced no more than 25 feet on center in 9‐inch‐thick drain trenches.
Locate the drain pipe a minimum of 3 inches below the base of the structural slab.
Slope pipe to drain at a minimum 0.5 percent. This slope requirement may require stacked drain pipes. The lower drain pipe should be a tight line (i.e., not perforated).
Locate pipe perforations on the top half of the pipe.
Use a separation geotextile fabric (e.g., TenCate Mirafi N‐Series) between the native soil and the drainage layer.
Dispose of drainage system water into a local storm drain. Site infiltration or recharge is impractical because of the shallow groundwater table.
Structural Fill We anticipate that structural fill will be required for backfilling behind walls, for backfilling of utility trenches and other miscellaneous excavations, and possibly for replacement of overexcavated, soft, or wet soils. We recommend the following regarding placement of structural fill:
Place structural fill in maximum 10‐inch‐thick loose lifts and compact it to a firm condition to support concrete placement as observed and verified by a Hart Crowser field representative.
The moisture content of the fill should be controlled within 2 percent of the optimum moisture. Optimum moisture is the moisture content corresponding to the maximum Proctor dry density.
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If a select soil will be imported for use as structural fill, we recommend using a clean, well‐graded sand or sand and gravel with less than 5 percent by weight passing the No. 200 mesh sieve (based on the minus 3/4‐inch fraction). If imported soil is used during wet weather periods, we recommend a gravel content (material coarser than a US No. 4 sieve) of at least 30 percent.
If small, hand‐operated compaction equipment is used to compact structural backfill, fill lifts should not exceed 8 inches of loose thickness.
Any import material to be used as structural fill should be sampled from the supplier’s pit before delivery or use on site, to determine the maximum dry density, gradation, and optimum moisture content.
Use of On‐Site Soils as Structural Fill The suitability of excavated site soils for structural fill will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the No. 200 sieve) increases, the soil becomes increasingly sensitive to small changes in moisture content, and adequate compaction becomes more difficult to achieve. Soil containing more than about 5 percent fines cannot be consistently compacted to a dense non‐yielding condition when the water content is greater than about 2 percent above or below optimum.
Drilling of augercast piles for structures in this area will generate cuttings of a variety of soil types. Peat cuttings are unsuitable for reuse as fill. We also recommend against using the underlying granular soil cuttings because of difficult segregation from unsuitable soils, and intermixed and wet conditions. In general the site soils are not well suited for reuse as structural fill.
Temporary Open Cuts The stability and safety of cut slopes depend on a number of factors, including:
The type and density of the soil; The presence and amount of any seepage; The depth of cut; The proximity of the cut to any surcharge loads near the top of the cut (such as stockpiled material, traffic, or structures) and the magnitude of these surcharges; The duration of the open excavation; and The care and methods used by the contractor.
Temporary soil cuts for site excavations that are more than 4 feet deep should be adequately sloped back to prevent sloughing and collapse in accordance with Washington Department of Occupational Safety and Health (DOSH) guidelines (WAC Chapter 296‐155 Part N). Based on these guidelines, the fill and native subsurface materials at the site would be classified as Type C. We recommend the following for open cuts:
Use a maximum allowable slope for excavations less than 20 feet deep of 1.5H:1V.
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Do not excavate below the bearing elevation of the existing footings or structural elements. Consult with the geotechnical engineer during construction to limit the size of these excavations and the amount of time they remain open. Protect the slope from erosion by using plastic sheeting, especially during wet weather excavation. Limit the maximum duration of the open excavation to the shortest time possible. Place no surcharge loads (equipment, materials) within 10 feet of the top of the slope, in general. However, more or less stringent requirements may apply depending on field conditions and actual surcharge loads. Use special care when excavating through the soft peat layer.
Because of the variables involved, actual slope angles required for stability in temporary cut areas can be only estimated (not determined precisely) before construction. We recommend that stability of the temporary slopes used for construction be the sole responsibility of the contractor, since the contractor is in control of the construction operation and is continuously at the site to observe the nature and condition of the subsurface. All excavations should be made in accordance with all local, state, and federal safety requirements.
Utilities Utility trench cut design should generally be the responsibility of the contractor. For shallow trench excavations (less than 4 feet in depth), open cutting may be used. Use of temporary shoring may be necessary if deeper excavations are required for placement of utilities. The contractor should verify the conditions of the side slopes during construction and layback trench cuts as necessary to conform to current standards of practice.
The minimum dry densities recommended below are a percentage of the modified Proctor maximum dry density as determined by the ASTM D1557 test procedure. Our recommendations for bedding and trench backfill materials are:
At least 4 inches of bedding is recommended for all pipe utilities. Bedding materials should consist of well‐graded sand and gravel with less than 3 percent material passing the No. 200 sieve (based on the minus 3/4‐inch fraction). Bedding material should be compacted to a firm non‐yielding condition.
The recommended bedding backfill materials can be used as backfill around the pipe utilities (pipe zone backfill). Pipe zone backfill should extend to at least the top of the pipe utility.
For bedding material beneath catch basins and manholes, we recommend 6 inches of imported structural fill (or acceptable on‐site material) that consists of well‐graded sand and gravel with less than 3 percent material passing the No. 200 sieve (based on the minus 3/4‐inch fraction). The bedding material should be compacted to 90 percent.
Utilities that extend below the groundwater table should be evaluated for the potential to float out of the ground at the high groundwater level.
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Deeper utilities may require dewatering well points to obtain a suitable working base. The contractor may elect to place a geotextile fabric at the base of the excavation to help create a suitable working surface.
Utilities should be designed for significant settlement between those pile‐supported and those supported on‐grade.
Utilities Below the Building. Settlement is expected to occur over time below the building. Utilities that gravity flow should be designed to hang from the structural slab so that the elevation remains unchanged under the building. The connection between these hanging utilities and those on grade must be designed for significant differential settlement. For pipe bedding and backfill around hanging utilities, we recommend using pea gravel. As subgrade settles over time, the pea gravel will have the ability to flow around the pipe and avoid a downdrag load that could possibly damage the pipe.
Utility Vaults. We recommend designing utility vaults to resist both the compressive load of the vault on the subgrade and the hydrostatic uplift force of the groundwater table acting on the base of the vault (i.e., design to preclude the vault from floating out of the ground when empty). Depending on space requirements, excavation for utility vaults may require temporary shoring.
Methane Venting The site is within a Critical Area as mapped by the City of Seattle because it is within 1,000 feet of a historical landfill (i.e., the Montlake Landfill that was across NE 45th Street). This landfill was closed in 1971. In addition to gases generated at the landfill, however, gases can be generated by organic decomposition of the peat. Based on the distance from the landfill and subsurface conditions, there is potential for migration of gas (primarily methane) to the site. Therefore, we recommend the following mitigation measures to protect against migration of methane or methane released from the peat soil underlying the site.
We recommend installing a passive venting system beneath the building to protect against excessive methane gas buildup. This system works because methane gas is lighter than air and tends to migrate upward. The passive venting system consists of vertical vent risers and concrete treatment.
We recommend the following for vent risers:
Connect vent risers to allow upward air/gas flow from the granular drainage layer at the base of the structural slab.
Install six vent risers at locations around the building perimeter.
Locate and connect vent risers such that all areas below the structural slab can be vented.
Use cast iron vent risers that have a minimum inside diameter (ID) of 3 inches.
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Provide a rain guard at the top terminus of the vent riser that does not restrict the upward flow of air or methane from the pipe.
Install a bug screen near the base or top of the riser so the pipes cannot be used as a corridor for insects to the below‐slab area after expected ground settlement.
Terminate vent riser as follows: 5 feet above grade; 5 feet away from any window, door, roof hatch, opening, or air intake into the building; and 5 feet away from electrical devices.
RECOMMENDATIONS FOR CONTINUING GEOTECHNICAL SERVICES
Design and Consulting Services Throughout this report, we recommend that we provide additional geotechnical input during the design and construction process. These recommendations are generally summarized in this section.
We recommend that, before construction begins, we:
Continue to meet with the design team periodically as design concepts and design documents progress, Provide an update to this report as part of final design process, if necessary, and Review the final design plans to verify that the geotechnical engineering recommendations have been properly interpreted and implemented into the design.
Construction Services During the construction phase of the project, we recommend retaining us to observe the following activities:
Augercast pile installation; Installation and testing of shoring system elements; Placement and density testing of structural fill at the site (if any); Installation of sub‐slab, foundation, and wall drainage; Backfilling of utility trenches or around subgrade walls; and Other observations as required by DPD.
We recommend we review the following contractor submittals:
Pile installation logs, Shoring system displacement and monitoring results, and Construction dewatering systems and quantities of water produced.
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We should also:
Attend meetings as needed and Assist with other geotechnical engineering considerations that may arise during construction.
The purpose of our observations will be to verify compliance with design concepts and recommendations, and to allow design changes or evaluation of appropriate construction methods in case subsurface conditions differ from those anticipated before construction begins.
REFERENCES AASHTO 2014. AASHTO LRFD Bridge Design Specifications. American Association of State Highway and Transportation Officials. Washington, D.C.
ASCE 2010. Minimum Design Loads for Buildings and Other Structures, ASCE Standard ASCE/SEI 7‐10.
Idriss, I.M. and R.W. Boulanger 2008. Soil Liquefaction During Earthquakes. EERI Publication, MNO‐12.
International Code Council 2012. 2012 International Building Code.
Landau Associates 2015. Geotechnical Pre‐Design Report, 4603 and 4609 Union Bay Place NE Property. Seattle, Washington. February 10, 2015.
U.S. Navy 1982. Soil Mechanics, Design Manual 7.1, NAVFAC DM‐7.1/7.2.
WSDOT 2014. Geotechnical Design Manual M 46‐03.10. Washington State Department of Transportation. August 2014.
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19174‐00 November 18, 2015 DRAFT Project Site
Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), TomTom, Union Bay Place Development MapmyIndia, © OpenStreetMap contributors, and the GIS User Community Seattle, Washington
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Elevation Water level Standard penetration resistance in Screened interval (Offset distance) blows per foot Exploration number Exploration location 9 Legend (49')
HC-101
1917400-002 (XSec).dwg 1917400-002 11/18/15 EAL Note: Base map prepared from drawing provided by USGS and the University of 2001 Washington, 2001.
Maximum Not to Scale Source Magnitude
Cascadia Subduction Zone - Interface 9.0
Cascadia Subduction Zone - Intraslab 7.5
Crustal Faults 7.5
Union Bay Place Development Seattle, Washington
Cascadia Subduction Zone Earthquake Sources
1917400-AD (EQSouce).cdr 19174-00 11/15
Figure 1/18/15 1 5 EAL Project Site
Seattle
Union Bay Place Development Seattle, Washington
Regional Fault Zones N
1917400-003 (FaultZones).dwg 19174-00 11/15 0 10 20 Figure
11/18/15 Scale in Miles 6 EAL A. Lateral Soil Pressure Notes: 1. Determine depth of embedment (D) by B. Vertical Capacity of moment equilibrium of lateral soil pressures Soldier Pile around point A. Neglect moment resistance of soldier pile member at point A. D must also be S sufficient to provide necessary vertical capacity. B qs 2. Active pressure is assumed to act over pile spacing. Neglect Shaft Resistance in Upper 2 Feet 3. Passive pressure is assumed to act over twice the Ground Surface grouted soldier pile diameter or the pile spacing, Base of Excavation (Elevation Varies) whichever is smaller. Passive pressure includes factor of safety of about 1.5. 2' Zone of Deformation Not to Scale 4. It is assumed that the site is drained during construction so that hydrostatic pressure does not D act on the walls. (fs) A (Single Tieback Walls) 5. All dimensions in feet.
H 6. Do not use these design criteria for design of any (FT) other type of shoring wall. (fs) (qa) (qa) Allowable 2S 7. See Figure 9 to evaluate additional surcharge. Allowable Friction End Bearing X 8. Refer to Figure 2 for elevation of the bearing layer (ESU 3) 4D < 40KSF for tieback bond zone. Tieback no load zone above this line Native Sand 1.5 KSF and zone of deformation, whichever is longer. (ESU 3) B 1 9. Use a design groundwater elevation of 32 feet. 60O Base of Excavation Recommended Minimum Embedment Depth A (Cantilever Walls) 10 Feet into Native Dense Sands Neglect Passive Resistance in Upper 2 Feet 2' H/4 C. Allowable Tieback Anchor qs*0.5 (PSF) D Pullout Resistance (FT) Allowable Friction (Adhesion) Bearing Layer. Locate All Anchors Native Sand 2.0 KSF Behind this Line (ESU 3) Active Earth Pressure Submerged Allowable Passive Earth Pressure (See Note 8) Tieback Y(D+2)(PSF) Anchors 1. Allowable values include FS = 2. Active Conditions At Rest Conditions Passive Location 2. Verify with Load Test to 200% of Design Stress Level. (X) (X) (Y) See Text and Attachment 1. Fill (dry) 40 60 – Fill (submerged) 19 29 240 Union Bay Place Development Native (submerged) 16 26 320 Seattle, Washington
Design of Temporary Cantilevered or Single Support Soldier Pile Shoring 19174-00 11/15 qs = 250 psf (Traffic and Temporary Loads) + Additional Surcharge Loads Figure NOT TO SCALE 7 Drawing3.cdr 02/07/07 CAD (qa) Not to Scale Allowable End Bearing B 4D < 40KSF Neglect Shaft Resistance in Upper 2 Feet Base of Excavation (fs) 1.5 KSF Allowable Friction B (FT) 2' (fs) ertical Capacity of (qa) B. V Soldier Pile Recommended Minimum Embedment Depth 10 Feet into Native Dense Sands Native Sand D (FT) . A. D must also be A. D must also . Passive pressure includes A. Neglect moment resistance of A. Neglect moment ficient to provide necessary vertical capacity ficient to provide soldier pile member at point soldier pile member suf Determine depth of embedment (D) by Determine depth of lateral soil pressures moment equilibrium around point Active pressure is assumed to act over pile spacing. Active pressure is assumed to act over twice the Passive pressure is assumed or the pile spacing, grouted soldier pile diameter whichever is smaller factor of safety of about 1.5. is drained so that hydrostatic It is assumed that the site the walls. If wall is not drained, pressure does not act on shown in this figure use the hydrostatic pressure All dimensions in feet. criteria for design of Do not use these design wall. any other type of shoring See Figure 9 to evaluate additional surcharge pressures. Use a design groundwater elevation of 32 feet. Not to Scale 2. 3. 4. 5. 6. 7. 8. Notes: 1. H (FT) s q = 29 Y X = 60 )(PSF) aries) GW At Rest Conditions )+Y(H GW Additional Surcharge Loads S Active Earth Pressure X(D = 19 Y X = 40 Active Conditions Ground Surface (Elevation V Ground Surface (PSF)
emporary Loads) + T *0.5 s q + fic and raf 2S GW GW H D Location (PSF)
= 250 psf (T ) Native Sand (Dry) Native Sand (Submerged) s q GW Pressure Net Hydrostatic 62.4*(H + Union Bay Place Development Seattle, Washington 7H Design of Permanent Basement Walls Surcharge Seismic Lateral Seismic Lateral
1917400-AB (EPD).cdr 1917400-AB 19174-00 11/15
Figure A. Lateral Soil Pressures A. Lateral 1/12/15 1 8 EAL iew all Footing C. Continuous W C. Continuous to Excavation Parallel Section V Cross iew . Cross Section V Cross Small Isolated Footing Small Isolated
B(1). Approach B. all footings acting other than parallel to the excavation can be treated as series of discrete 1. Lateral pressures from adjacent structures should be added to lateral pressures on Figures 7 and 8. 2. W point loads, using 3. Contact Hart Crowser for surcharge recommendations, if necessary iew Notes:
Union Bay Place Development Seattle, Washington
Surcharge Pressures Determination of Lateral 1 Pressure Acting on Adjacent Shoring
1917400-AC (EPD).cdr 1917400-AC 17194-00 11/15 A. Strip Footing A. Strip Section V Cross Figure 1/18/15 1 9 EAL
ATTACHMENT 1 Tieback Anchor Testing Program
19174‐00 November 18, 2015 DRAFT
ATTACHMENT 1
Tieback Anchor Testing Program Conduct the performance and proof tests as follows:
Performance Test At least two performance tests should be completed before installation of production anchors. Each performance test should be conducted according to the following procedure:
1. The geotechnical engineer will select the testing locations with input from the shoring subcontractor. 2. The maximum stress in the prestressing steel should not exceed 80 percent of the ultimate tensile strength during performance testing [based on the Post Tensioning Institute manual]. The soldier pile and tieback may require extra reinforcement to permit stressing to 200 percent of design load as required for the performance test. 3. The performance test will measure anchor stress and displacement incrementally to values of unit skin friction equal to 200 percent of the design load. Load the anchor and measure deflections following the load sequence in Table 1‐1. Table 1-1 – Performance Test for Temporary Shoring
Load Level Hold Time Load Level Hold Time AL Until Stable 1.75DL Until Stable 0.25DL 10 min 1.50DL Until Stable 0.50DL 10 min 1.25DL Until Stable 0.75DL 10 min 1.00DL Until Stable 1.00DL 10 min 0.75DL Until Stable 1.25DL 10 min 0.50DL Until Stable 1.50DL 60 min (Creep) 0.25DL Until Stable 1.75DL 10 min AL Until Stable 2.00DL 10 min
4. For 10‐minute hold times, obtain and record deflection measurements during loading at intervals of 30 seconds, 1 minute, 2 minutes, 3 minutes, 5 minutes, 6 minutes, and 10 minutes. Measurements shall be made to an accuracy of 0.01 inch. 5. Perform a creep test at the 150 percent of design stress reading by holding the load constant to within 50 psi and recording readings at 30 seconds, 1 minute, 2 minutes, 3 minutes, 5 minutes, 6 minutes, and 10 minutes, 20 minutes, 30 minutes, 50 minutes, and 60 minutes. 6. A successful test does not experience pullout failure, holds the maximum test unit stress without considerable creep, and satisfies the apparent free length criteria. Pullout failure occurs when test measurements no longer exhibit a linear or near‐linear relationship between unit stress and movement over the entire 200 percent stress range.
19174‐00 November 18, 2015 DRAFT A-2 | Union Bay Place Development
Noticeable creep is defined as a rate of movement of not more than 0.04 inch between the 1‐ and 10‐minute readings, or not more than 0.08 inch between the 6‐ and 60‐minute readings. If the reading does not stabilize to 0.08 inch or less per log cycle of time, the test shall be considered to fail the creep criteria.
Minimum apparent free length, based on the measured elastic and residual movement, should be greater than 80 percent of the designed free length plus the jack length.
7. Perform tests without backfill ahead of the anchor, if the hole will remain open, to avoid any contributory resistance by the backfill. If the hole will not remain open during testing, provide a bond breaker on the tie rods and backfill the no load zone with a non‐cohesive non‐ structural mixture.
Proof Test For each production tieback anchor, follow the proof testing procedures outlined below:
1. Load each anchor to 133 percent of the design load in increments of approximately 25 percent of the design load (i.e., 0.25 DL, 0.50 DL, 0.75 DL, 1.00 DL, 1.25 DL, and 1.33 DL). The maximum stress in the prestressing steel should not exceed 80 percent of the ultimate tensile strength during proof testing. 2. Hold each incremental load for a period long enough to obtain a stable deflection measurement while recording deflections at each load increment. Hold the 133 percent load for a minimum of 10 minutes, recording the movement at times of 30 seconds, 1 minute, 2 minutes, and 5 minutes, 6 minutes, and 10 minutes. 3. A successful test is one that meets the same acceptance criteria as performance anchors, except that the creep portion of the test need not exceed 10 minutes if the 10‐minute creep criteria is meet. 4. Following proof loading, lock off each tieback anchor to 80 to 100 percent of the design load, except as specified.
19174‐00 November 18, 2015 DRAFT
ATTACHMENT 2 Shoring Monitoring Program
19174‐00 November 18, 2015 DRAFT
ATTACHMENT 2
Shoring Monitoring Program A shoring monitoring program provides early warning if the shoring does not perform as anticipated. We recommend that the following components be included in the shoring monitoring program during construction:
Adjacent building surveys; Optical surveying; and Geotechnical instrumentation (Inclinometer).
All monitoring data should be submitted to Hart Crowser for weekly review. The data will be included in our field transmittals to the project team and DPD during construction. Details of our expectations for shoring monitoring are included below.
Adjacent Building Surveys We recommend that adjacent buildings be surveyed before, during, and after construction. The pre‐ construction survey will establish the baseline of existing conditions (e.g., identifying the size and locations of any cracks). The surveys should consist of a videotape and/or photographs of the interior and exterior of adjacent buildings and detailed mapping of all cracks. Any existing cracks could be monitored with a crack gauge.
Optical Surveying We recommend optical surveys of horizontal and vertical movements of: (1) the surface of the adjacent streets, (2) buildings on and adjacent to the site, and (3) the shoring system itself. The contractor, in coordination with the geotechnical engineer, should establish two reference lines adjacent to the excavation at horizontal distances back from the excavation face of about 1/3 H and H, where H is the final excavation height. Typically, these lines will be established near the curb line and across the street from the excavation face. The points on the adjacent buildings can be set either at the base or on the roof of the buildings.
Shoring system monitoring should include measuring vertical and horizontal movement at the top of every other soldier pile, and any geotechnical instrumentation (e.g., inclinometers) used for the project.
The measuring system for the shoring monitoring should have an accuracy of at least 0.005 foot. All reference points on the ground surface should be installed and read before excavation begins. The frequency of readings will depend on the results of previous readings and the rate of construction. At a minimum, readings on the external points should be taken once a week through construction until below‐grade structural elements (floors, decks, columns, etc.) are completed, or as specified by the structural and geotechnical engineers. Readings on the top of soldier piles and the face of existing buildings on or adjacent to the property should be taken at least twice a week during this time. We
19174‐00 November 18, 2015 DRAFT A-2 | Union Bay Place Development recommend that an independent surveyor hired by the owner to record the data at least once per week with the other reading taken by the surveyor or contractor.
Geotechnical Instrumentation (Inclinometer) We recommend installing inclinometer casings behind the shoring along the building to the north. The casings should extend at least 10 feet below the bottom of the soldier piles. The number and location of the casings should be coordinated with Hart Crowser and the contractor. Hart Crowser can be hired to install the casings behind the shoring using a subcontracted driller; or, the shoring contractor may install the inclinometer casings. We recommend inclinometer surveys at least once per week during shoring construction. After the perimeter footing has been placed and cured, Hart Crowser may elect to reduce the inclinometer survey frequency.
19174‐00 November 18, 2015 DRAFT
APPENDIX A Field Exploration Methods and Analysis
19174‐00 November 18, 2015 DRAFT
APPENDIX A
Field Exploration Methods and Analysis This appendix documents the processes Hart Crowser used to determine the nature of the site soil and groundwater. This appendix includes information on the following subjects:
Explorations and Their Location; Hollow‐Stem Auger Borings; Standard Penetration Test Procedures; Monitoring Well Installation; and Water Level Measurement.
Explorations and Their Location Subsurface explorations for this project included one hollow‐stem auger (HSA) boring. The exploration log in this appendix shows our interpretation of the drilling, excavation, sampling, and testing data. The log indicates the depth where soils change. Note that the actual change may be gradual. In the field, we classified the samples taken from the exploration according to the methods presented on Figure A‐1 ‐ Key to Exploration Logs. This figure also provides a legend explaining the symbols and abbreviations used in the logs.
Figure 2 illustrates the horizontal locations of explorations, which are based on field measurements from existing physical features. The elevations on the logs are taken from the elevation contours shown on Figure 2 that were provided to us. The vertical datum is NAVD88.
Hollow-Stem Auger Borings One HSA boring, designated HC‐101, was drilled on September 28, 2015 to a final depth of 36.3 feet below the ground surface. The boring was completed using a Mobile B‐60 track‐mounted drill rig with a 4.25‐inch inside diameter HSA. The boring was advanced by Holt Services, Inc., and continuously observed by a geologist from Hart Crowser. A detailed field log was prepared. Samples were obtained at 2.5‐ to 5‐foot‐depth intervals using standard penetration test procedures. Drilling fluid was continually added to the augers and maintained at a level to control heaving conditions at the bottom of the auger.
The boring logs is presented on Figure A‐2.
Standard Penetration Test Procedures The standard penetration test (SPT) method (as described in ASTM D 1586) was used to obtain disturbed samples. This test is an approximate measure of soil density and consistency. To be useful, the results must be used with engineering judgment in conjunction with other tests. The SPT test employs a standard 2‐inch‐outside‐diameter split‐spoon sampler. Using a 140‐pound hammer, free‐ falling 30 inches, the sampler is driven into the soil for 18 inches. The number of blows required to
19174‐00 November 18, 2015 DRAFT A-2 | Union Bay Place Development drive the sampler the last 12 inches only is the Standard Penetration Resistance. This resistance, or blow count, measures the relative density of granular soils and the consistency of cohesive soils. If a total of 50 blows are struck within any 6‐inch interval, the driving is stopped and the blow count is recorded as 50 blows for the actual penetration distance. The blow counts are plotted on the boring logs at their respective sample depths.
Monitoring Well Installation Monitoring wells were installed in borings HC‐MW‐101 and HC‐MW‐102 to allow for long‐term groundwater level monitoring at the site. The monitoring wells were installed on September 28, 2015. We used 2‐inch‐diameter Schedule 40 PVC riser pipe and 2‐inch‐diameter 0.020‐inch machine‐slotted screen for the well casings and screens. The well screen and casing riser were lowered down through the hollow‐stem auger. As the auger was withdrawn, No. 10/20 silica sand was placed in the annular (ring‐shaped) space from the base of the boring to approximately 2 to 3 feet above the top of the well screen. Well seals were constructed by placing bentonite chips in the annular space on top of the filter sand to within 3 feet of the ground surface. The remaining annular space was backfilled with concrete to complete the surface seal. For security, the monitoring wells were completed with a flush‐mounted steel monument set in concrete. The monitoring wells were installed in accordance with Washington State Department of Ecology regulations.
The monitoring well construction details are illustrated on the boring logs on Figures A‐3 and A‐4.
Water Level Measurement Water levels in the monitoring wells were measured using a water level probe, graduated in 0.01‐foot increments.
19174‐00 November 18, 2015 DRAFT Key to Exploration Logs Sample Description Classification of soils in this report is based on visual field and laboratory observations which include density/consistency, moisture condition, grain size, and Moisture plasticity estimates and should not be construed to imply field nor laboratory testing Dry Little perceptible moisture unless presented herein. Visual-manual classification methods of ASTM D 2488 Damp Some perceptible moisture, likely below optimum were used as an identification guide. Moist Likely near optimum moisture content Soil descriptions consist of the following: Wet Much perceptible moisture, likely above optimum Density/consistency, moisture, color, minor constituents, MAJOR CONSTITUENT, additional remarks. Minor Constituents Estimated Percentage Density/Consistency Trace <5 Soil density/consistency in borings is related primarily to the Standard Slightly (clayey, silty, etc.) 5 - 12 Penetration Resistance. Soil density/consistency in test pits and probes is estimated based on visual observation and is presented parenthetically on the Clayey, silty, sandy, gravelly 12 - 30 Very (clayey, silty, etc.) 30 - 50 logs. Standard Standard Approximate SAND or GRAVEL Penetration SILT or CLAY Penetration Shear Strength Density Resistance (N) Consistency Resistance (N) in TSF in Blows/Foot in Blows/Foot Laboratory Test Symbols Very loose 0 to 4 Very soft 0 to 2 <0.125 Loose 4 to 10 Soft 2 to 4 0.125 to 0.25 GS Grain Size Classification Medium dense 10 to 30 Medium stiff 4 to 8 0.25 to 0.5 CN Consolidation Dense 30 to 50 Stiff 8 to 15 0.5 to 1.0 UU Unconsolidated Undrained Triaxial Very dense >50 Very stiff 15 to 30 1.0 to 2.0 CU Consolidated Undrained Triaxial Hard >30 >2.0 CD Consolidated Drained Triaxial QU Unconfined Compression Sampling Test Symbols DS Direct Shear K Permeability 1.5" I.D. Split Spoon Grab (Jar) 3.0" I.D. Split Spoon PP Pocket Penetrometer Approximate Compressive Strength in TSF Shelby Tube (Pushed) Bag TV Torvane Cuttings Core Run Approximate Shear Strength in TSF CBR California Bearing Ratio SOIL CLASSIFICATION CHART MD Moisture Density Relationship AL Atterberg Limits SYMBOLS TYPICAL MAJOR DIVISIONS GRAPH LETTER DESCRIPTIONS Water Content in Percent
CLEAN WELL-GRADED GRAVELS, GRAVEL - Liquid Limit GW SAND MIXTURES, LITTLE OR NO GRAVEL GRAVELS FINES Natural AND Plastic Limit GRAVELLY POORLY-GRADED GRAVELS, SOILS (LITTLE OR NO FINES) GP GRAVEL - SAND MIXTURES, LITTLE PID Photoionization Detector Reading OR NO FINES COARSE CA Chemical Analysis GRAINED GRAVELS WITH SILTY GRAVELS, GRAVEL - SAND - DT In Situ Density in PCF SOILS MORE THAN 50% FINES GM SILT MIXTURES OF COARSE FRACTION OT Tests by Others RETAINED ON NO. 4 SIEVE (APPRECIABLE CLAYEY GRAVELS, GRAVEL - SAND - AMOUNT OF FINES) GC CLAY MIXTURES Groundwater Indicators CLEAN SANDS SW WELL-GRADED SANDS, GRAVELLY MORE THAN 50% SAND SANDS, LITTLE OR NO FINES OF MATERIAL IS AND Groundwater Level on Date LARGER THAN SANDY or (ATD) At Time of Drilling NO. 200 SIEVE SOILS POORLY-GRADED SANDS, SIZE (LITTLE OR NO FINES) SP GRAVELLY SAND, LITTLE OR NO FINES Groundwater Seepage (Test Pits) SANDS WITH SILTY SANDS, SAND - SILT MORE THAN 50% FINES SM MIXTURES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE CLAYEY SANDS, SAND - CLAY AMOUNT OF FINES) SC MIXTURES Sample Key
INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR ML CLAYEY FINE SANDS OR CLAYEY Sample Type Sample Recovery SILTS WITH SLIGHT PLASTICITY SILTS INORGANIC CLAYS OF LOW TO FINE LIQUID LIMIT MEDIUM PLASTICITY, GRAVELLY AND LESS THAN 50 CL CLAYS, SANDY CLAYS, SILTY CLAYS, 12 GRAINED CLAYS LEAN CLAYS S-1 23 SOILS 50/3" OL ORGANIC SILTS AND ORGANIC SILTY Sample CLAYS OF LOW PLASTICITY Number Blows per 6 inches MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO. 200 SIEVE SIZE SILTS LIQUID LIMIT INORGANIC CLAYS OF HIGH AND GREATER THAN 50 CH PLASTICITY CLAYS
ORGANIC CLAYS OF MEDIUM TO OH HIGH PLASTICITY, ORGANIC SILTS 19174-00 9/15 PEAT, HUMUS, SWAMP SOILS WITH HIGHLY ORGANIC SOILS PT HIGH ORGANIC CONTENTS Figure A-1
KEY SHEET 1917400-BL.GPJ SHEET HC_CORP.GDT 11/3/15 KEY NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS Boring Log HC-101 Location: Lat: 47.662840 Long: -122.294780 Drill Equipment: Mobile B-60 w/HSA Approximate Ground Surface Elevation: 45 Feet Hammer Type: SPT w/ 140 lb. Automatic hammer Horizontal Datum: WGS84 Hole Diameter: 8 inches Vertical Datum: NAVD88 Logged By: B. McDonald Reviewed By: J. Bruce
STANDARD LAB PENETRATION RESISTANCE TESTS USCS Graphic Depth Class Log Soil Descriptions in Feet Sample Blows per Foot 0 10 2030 40 50+ 0 SM 8 inches of Asphalt over loose, moist, brown to dark brown, silty SAND with scattered dark S-1 brown organics. (FILL) Gravelly. 2 S-2 1 1
5 1 S-3 1 2
Occasional wood fragments. 1 GS S-4 1 2
10 4 S-5 1 3
SP-SM Loose to medium dense, grayish brown, 4 slightly silty, fine to medium SAND. S-6 4 GS ATD 5
15 3 S-7 11 16
SP-SM Very dense, wet, gray, slightly silty to silty, 15 fine to medium SAND with occasional gravel. S-8 33 39 GS Slightly sandy SILT layers. 20 13 S-9 50/6''
25 SM Very dense, wet, gray, silty, fine SAND with 5 S-10 23 occasional gravel. 42
30 5 Moist. 37 S-11 40 50/5'' GS
35 36 S-12 65/4'' Bottom of Boring at 36.3 Feet. Started 09/28/15. Completed 09/28/15.
40
45
NEW BORING LOG BORING 1917400-BL.GPJNEW HC_CORP.GDT 11/6/1 020 40 60 80 100+ Water Content in Percent
1. Refer to Figure A-1 for explanation of descriptions and symbols. 2. Soil descriptions and stratum lines are interpretive and actual changes may be gradual. 3. USCS designations are based on visual manual classification (ASTM D 2488) unless otherwise 19174-00 9/15 supported by laboratory testing (ASTM D 2487). 4. Groundwater level, if indicated, is at time of drilling (ATD) or for date specified. Level may vary Figure A-2 with time. Monitoring Well Log HC-MW-101 Location: Drill Equipment: Approximate Ground Surface Elevation: 45 Feet Hammer Type: Horizontal Datum: WGS84 Hole Diameter: inches Vertical Datum: NAVD88 Logged By: B. McDonald Reviewed By: J. Bruce
STANDARD LAB PENETRATION RESISTANCE TESTS USCS Graphic Depth Well Class Log Soil Descriptions in Feet Construction Sample Blows per Foot 0 10 2030 40 50+ 0 - Flush mount monument Concrete Bentonite chips
5
10-20 Silica sand 10 Screened 2" PVC
ATD
15
20 Bottom of Boring at 20.0 Feet. Started 09/28/15. Completed 09/28/15.
Ecology Well Tag #BJE-898 25
30 5
35
40
45
NEW BORING LOG BORING 1917400-BL.GPJNEW HC_CORP.GDT 11/6/1 020 40 60 80 100+ Water Content in Percent
1. Refer to Figure A-1 for explanation of descriptions and symbols. 2. Soil descriptions and stratum lines are interpretive and actual changes may be gradual. 3. USCS designations are based on visual manual classification (ASTM D 2488) unless otherwise 19174-00 9/15 supported by laboratory testing (ASTM D 2487). 4. Groundwater level, if indicated, is at time of drilling (ATD) or for date specified. Level may vary Figure A-3 with time. Monitoring Well Log HC-MW-102 Location: Lat: 47.662400 Long: -122.295470 Drill Equipment: Approximate Ground Surface Elevation: 42 Feet Hammer Type: Horizontal Datum: WGS84 Hole Diameter: inches Vertical Datum: NAVD88 Logged By: B. McDonald Reviewed By: J. Bruce
STANDARD LAB PENETRATION RESISTANCE TESTS USCS Graphic Depth Well Class Log Soil Descriptions in Feet Construction Sample Blows per Foot 0 10 2030 40 50+ 0 - Flush mount monument Concrete Bentonite chips
5
10-20 Silica sand 10 Screened 2" PVC
15
20
Bottom of Boring at 20.0 Feet. Started 09/28/15. Completed 09/28/15.
25 Ecology Well Tag #BJE-899
30 5
35
40
45
NEW BORING LOG BORING 1917400-BL.GPJNEW HC_CORP.GDT 11/6/1 020 40 60 80 100+ Water Content in Percent
1. Refer to Figure A-1 for explanation of descriptions and symbols. 2. Soil descriptions and stratum lines are interpretive and actual changes may be gradual. 3. USCS designations are based on visual manual classification (ASTM D 2488) unless otherwise 19174-00 9/15 supported by laboratory testing (ASTM D 2487). 4. Groundwater level, if indicated, is at time of drilling (ATD) or for date specified. Level may vary Figure A-4 with time.
APPENDIX B Laboratory Testing Program
19174‐00 November 18, 2015 DRAFT
APPENDIX B
Laboratory Testing Program A laboratory testing program was performed for this study to evaluate the basic index and geotechnical engineering properties of the site soils. The tests performed and the procedures followed are outlined below.
Soil Classification Soil samples from the explorations were visually classified in the field and then taken to our laboratory where the classifications were verified in a relatively controlled laboratory environment. Field and laboratory observations include relative density/consistency, moisture condition, and grain size estimates.
The classifications of selected samples were checked by laboratory tests such as grain size analyses. Classifications were made in general accordance with the Unified Soil Classification (USC) System, ASTM D 2487, as presented on Figure B‐1.
Water Content Determinations Water content was determined for most samples recovered in the explorations in general accordance with ASTM D 2216, as soon as possible following their arrival in our laboratory. Water contents were not determined for very small samples or samples where large gravel contents would result in unrepresentative values. The results of these tests are plotted or presented at the respective sample depth on the exploration logs. In addition, water contents are routinely determined for samples subjected to other testing. These are also presented on the exploration logs.
Grain Size Analysis Grain size distribution was analyzed on representative samples in general accordance with ASTM D 422. Wet sieve analysis was used to determine the size distribution greater than the U.S. No. 200 mesh sieve. The results of the tests are presented as curves on Figures B‐2 and B‐3 plotting percent finer by weight versus grain size.
19174‐00 November 18, 2015 DRAFT Unified Soil Classification (USC) System Soil Grain Size
Size of Opening In Inches Number of Mesh per Inch Grain Size in Millimetres (US Standard)
2
/
1
6
20 40
2 200
3
4
60
4
1 1/4
3/4
.006 5/8
.003
.02 .008
1 3/8
.06 .03 .01 1/2 .001
100 .004
.04 .002
12 10
1 1
8 6 4 3 2
.8 .4 .2
.3
.6
10
60 40
80 30 20
.01
.08 .02
.06 .04 .03
300 200 100
.001
.002
.008 .004 .003
.006 Grain Size in Millimetres
COBBLES GRAVEL SAND SILT and CLAY
Coarse-Grained Soils Fine-Grained Soils
Coarse-Grained Soils G W G P G M G C S W S P S M S C * * Clean GRAVEL <5% fines GRAVEL with >12% fines Clean SAND <5% fines SAND with >12% fines GRAVEL >50% coarse fraction larger than No. 4 SAND >50% coarse fraction smaller than No. 4 Coarse-Grained Soils >50% larger than No. 200 sieve
2 D60 >4 for G W (D30 ) G W and S W & 1<_ <_ 3 G P and S P Clean GRAVEL or SAND not meeting D >6 for S W 10 D10 X D 60 requirements for G W and S W
G M and S M Atterberg limits below A line with PI <4 G C and S C Atterberg limits above A Line with PI >7
* Coarse-grained soils with percentage of fines between 5 and 12 are considered borderline cases requiring use of dual symbols.
D10 , D 30 , and D 60 are the particles diameter of which 10, 30, and 60 percent, respectively, of the soil weight are finer. Fine-Grained Soils M L C L O L M H C H O H Pt
SILT CLAY Organic SILT CLAY Organic Highly Organic Soils with Liquid Limit <50% Soils with Liquid Limit >50% Soils
Fine-Grained Soils >50% smaller than No. 200 sieve
60 60
50 C H 50
40 40 C L 30 A Line 30
Plasticity Index 20 M H or O H 20
10 C L - M L M L 10 or O L 0 0 0 10 20 30 40 50 60 70 80 90 100 Liquid Limit
SRF Grain Size (B-1).cdr 3/06 19174-00 9/15 Figure B-1 Particle Size Distribution Test Report 6 in. 6 in. 3 in. 2 in. 1 in. 3/4 in. 1/2 in. 3/8 #4 #10 #20 #30 #40 #60 #100 #140 #200 1-1/2 in. 1-1/2 100
90
80
70
60
50
40 PERCENTFINER
30
20
10
0 100 10 1 0.1 0.01 0.001 GRAIN SIZE - mm % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 17.7 69.5 12.8 0.0 13.7 79.8 6.5 0.0 4.7 65.2 30.1
LL PI D85 D60 D50 D30 D15 D10 Cc Cu 5.636 0.591 0.404 0.22 0.091 3.983 0.574 0.419 0.284 0.18 0.1391.02 4.14 0.982 0.322 0.233 MATERIAL DESCRIPTION USCS NAT. MOIST. silty gravelly SAND SM 26.1% slightly silty, gravelly SAND SP-SM 16.9% very silty SAND, trace gravel SM 18.5% Remarks: Project: Union Bay Place
Client: Source: HC-101 Sample No.: S-4 Depth: 7.5 to 9.0 Source: HC-101 Sample No.: S-6 Depth: 12.5 to 14.0 Source: HC-101 Sample No.: S-8 Depth: 17.5 to 19.0
19174-00 9/15 Figure B-2 GRAIN SIZE 1917400-BL.GPJSIZE GRAIN HC_CORP.GDT 11/3/15 Particle Size Distribution Test Report 6 in. 6 in. 3 in. 2 in. 1 in. 3/4 in. 1/2 in. 3/8 #4 #10 #20 #30 #40 #60 #100 #140 #200 1-1/2 in. 1-1/2 100
90
80
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40 PERCENTFINER
30
20
10
0 100 10 1 0.1 0.01 0.001 GRAIN SIZE - mm % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 2.2 74.0 23.8
LL PI D85 D60 D50 D30 D15 D10 Cc Cu 0.37 0.206 0.177 0.099
MATERIAL DESCRIPTION USCS NAT. MOIST. silty SAND, trace gravel SM 15.2%
Remarks: Project: Union Bay Place
Client: Source: HC-101 Sample No.: S-11 Depth: 30.0 to 31.5
19174-00 9/15 Figure B-3 GRAIN SIZE 1917400-BL.GPJSIZE GRAIN HC_CORP.GDT 11/3/15
APPENDIX C Historical Explorations
19174‐00 November 18, 2015 DRAFT
APPENDIX C
Historical Explorations In addition to the explorations and laboratory test results presented in Appendices A and B, we reviewed previous explorations and lab test results by others to gain an understanding of the subsurface conditions within unexplored portions of the site. Logs by others are included as they were produced by others for reference only and Hart Crowser is not responsible for the accuracy or completeness of the information presented in the logs. Approximate locations of the previous explorations by others are shown on Figure 2; actual locations may differ from those shown.
19174‐00 November 18, 2015 DRAFT B-1 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 43 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) Logged By: Date:
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol Groundwater 20 40 60 80 0 AC Asphalt Pavement (~0.4 feet thickness) GM Gray, sandy GRAVEL with silt (crushed, 1 1/4 inch minus); no odors, sheen, or ML staining observed PID=0 40 (FILL) S-1 b2 6 W = 20 AL Mottled gray and brown, very sandy SILT/CLAY with gravel and organics; no ML 5 PID=0 odors, sheen, or staining observed (medium stiff, wet) S-2 b2 5 W = 22 Mottled gray and brown, gravelly, sandy SILT; no odors, sheen, or staining PID=0.3 observed (medium stiff, wet) 35 S-3 b2 17 W = 12 AC Asphalt pavement or debris SM 10 Gray, very gravelly, fine to medium SAND PID=0.1 with silt and trace organics; no odors, S-4 b2 14 sheen, or staining observed (medium dense, moist)
SM Mottled gray and brown, gravelly, silty to 30 PID=0.4 very silty, fine to medium SAND; no odors, S-5 b2 11 W = 12 sheen, or staining observed (loose to medium dense, wet)
15
S-6 b2 5 PID=0 16.5 ft ATD
SM Brown, gravelly, silty, fine to medium 25 PID=0 SAND to trace gravel and fine organics; no S-7 b2 8 W = 22 odors, sheen, or staining observed (loose, moist to wet)
20 S-8 b2 5 PID=0 - concrete debris
20 PT Brown, PEAT (massive with some fiberous); no odors, sheen, or staining observed (stiff, moist to wet) 25 (ALLUVIUM) PID=0.2 S-9 b2 14 278 W = 278
15
30 S-10A b2 17 PID=0.3 ML/ Gray brown, clayey SILT with sand; no S-10B b CL odors, sheen, or staining observed (stiff, SM moist to wet)
10 Mottled light brown and reddish brown, very silty, fine to medium SAND with trace SM gravel; no odors, sheen, or staining observed (medium dense, wet) 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-1 A-2 Seattle, Washington (1 of 2) B-1 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 43 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) Logged By: Date:
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol Groundwater 20 40 60 80 35 PID=0.1 SM (ADVANCE OUTWASH) S-11 b2 39 W = 16 Light brown, gravelly, fine to medium GS SAND with silt to silty, fine to medium SAND with gravel; no odors, sheen, or staining observed (dense, wet) 5 SP Light brown, fine to medium SAND; no odors, sheen, or staining observed (very dense, wet) 50/ 40 50/ S-12 b2 PID=0 4" 4"
Boring Completed Total Depth of Boring = 40.8 ft.
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70 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-1 A-2 Seattle, Washington (2 of 2) B-2 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 45 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) Logged By: Date:
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol Groundwater 20 40 60 80 0 45 AC Asphalt Pavement (~0.4 feet thickness) SM Mottled gray and brown, gravelly, silty, fine to medium SAND and silty, fine to medium SAND with gravel; no odors, sheen, or PID=0 staining observed (loose to medium dense, S-1 b2 10 W = 19 moist to wet) (FILL) 5 40 - burnt wood debris PID=0.1 S-2 b2 4
PID=0 S-3 b2 5 W = 23 - painted wood debris and fine organics
10 35 SM Brown, silty, gravelly, fine to medium PID=0.2 SAND with asphalt pavement/debris; no S-4 b2 13 odors, sheen, or staining observed (medium dense, moist) 12.0 ft ATD
SM/ Mottled brown and gray, very sandy SILT PID=0.2 ML W = 17 with gravel and fine organics and S-5 b2 2 interbedded silty, fine SAND; no odors, sheen, or staining observed (very loose to loose/soft, wet) 15 30 PID=0.1 S-6 b2 3 W = 17 AL
SM Brown, silty, very gravelly, fine to medium PID=0 SAND; no odors, sheen, or staining S-7 b2 2 observed (very loose to loose, wet)
20 25 PID=0 W = 27 S-8 b2 11
25 20 PID=0 S-9 b2 27 ML/ Light brown to yellow brown, fine sandy, CL clayey SILT with gravel; no odors, sheen, SM or staining observed (medium dense/very stiff, wet) (ADVANCE OUTWASH) SP Light brown, silty to very silty, fine to medium SAND with fine gravel; no odors, 30 15 sheen, or staining observed (medium PID=0.1 dense/very stiff, wet) S-10 b2 31 W = 22 Light brown, fine SAND; no odors, sheen, or staining observed (dense, wet)
SP/ SM 50/ 35 10 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-2 A-3 Seattle, Washington (1 of 2) B-2 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 45 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) Logged By: Date:
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol Groundwater 20 40 60 80 35 10 S-11 b2 50/ PID=0.1 SP/ Light brown, gravelly, fine to medium 4" 4" W = 14 SM SAND and interbedded fine to medium SAND with silt and trace gravel; no odors, sheen, or staining observed (very dense, wet)
SP Light brown, fine to medium SAND; no odors, sheen, or staining observed (very dense, wet) 50/ 40 5 50/ S-12 b2 PID=0 4" 4"
Boring Completed Total Depth of Boring = 40.8 ft.
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70 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-2 A-3 Seattle, Washington (2 of 2) B-3 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 45 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) (DOE#: BJA-544) Logged By: Date: DETAIL WELL
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol 20 40 60 80 0 45 SM Crushed Rock(0.5 foot thickness) SM Mottled gray and brown, silty, gravelly, fine to medium SAND; no odors, sheen, or staining observed (medium dense, moist) PID=0 (FILL) S-1 b2 18 W = 12
5 40 ML Gray Brown, CLAY with fine sand and thin 5.7 ft PID=0.1 interbedded silty, clayey, fine SAND; no S-2 b2 8 odors, sheen, or staining observed (medium stiff to stiff, moist)
PID=0 S-3 b2 4 W = 31 AL
10 35 PID=0 S-4 b2 4 W = 27 12.5 ft SM Brown, very silty, fine to medium SAND PID=0 with gravel; no odors, sheen, or staining S-5 b2 2 observed (very loose, wet)
15 30 PID=0 W = 18 S-6 b2 4
SP Light brown, gravelly, fine to medium PID=0 SAND; no odors, sheen, or staining S-7 b2 34 observed (dense, wet) (ADVANCE OUTWASH) SP Reddish brown, fine to medium SAND with 20 25 PID=0 interbedded gravelly, fine to medium W = 20 S-8A b2 87 SAND; no odors, sheen, or staining PID=0 S-8B b2 SM observed (very dense, wet)
Light brown, very silty, fine to medium SP SAND with gravel and interbedded fine sandy SILT; no odors, sheen, or staining observed (very dense, wet) 50/ 25 20 50/ PID=0 Light brown, silty, fine SAND and fine S-9 b2 6" 6" W = 21 SAND with silt; no odors, sheen, or staining observed (very dense, wet)
SP- Gray, gravel to very gravelly, fine to 50/ 30 15 50/ SM medium SAND with silt; no odors, sheen, S-10 b2 PID=0 6" 6" or staining observed (very dense, wet)
50/ 35 10 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-3 A-4 Seattle, Washington (1 of 2) B-3 LAI Project No: 1379002.020.021 Moisture Content (%) SAMPLE DATA SOIL PROFILE Plastic Liquid Limit Limit 20 40 60 80 Drilling Method: Hollow-Stem Auger SPT N-Value Non-Standard N-Value Ground Elevation (ft): 45 20 40 60 80 Cascade Drilling Inc. Drilled By: Fines Content (%) (DOE#: BJA-544) Logged By: Date: DETAIL WELL
Depth (ft) Elevation (ft) Sample Number & Interval Sampler Type Blows/Foot Test Data Graphic Symbol USCS Symbol 20 40 60 80 35 10 S-11 b2 50/ PID=0 SP- Gray, gravel to very gravelly, fine to 4" 4" W = 14 SM medium SAND with silt; no odors, sheen, or staining observed (very dense, wet)
SP Gray, gravel to very gravelly, fine to medium SAND with trace silt; no odors, sheen, or staining observed (very dense, wet) 50/ 40 5 50/ S-12 b2 PID=0 5" 5"
Boring Completed Total Depth of Boring = 40.9 ft.
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70 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ SOIL BORING LOG WITH GRAPH WITH LOG BORING SOIL N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Log of Boring B-3 A-4 Seattle, Washington (2 of 2) 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ GRAIN SIZE FIGURE
U.S. Sieve Opening in Inches U.S. Sieve Numbers Hydrometer
6 4 3 2 1.5 1 3/4 1/2 3/8 3 4 6 8 10 14 16 20 30 40 50 60 100 140 200 100
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0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters Gravel Sand Cobbles Silt or Clay Coarse Fine Coarse Medium Fine
Exploration Sample Depth Natural Unified Soil Symbol Soil Description Number Number (ft) Moisture (%) Classification B-1 S-11 35.0 16 Gravelly, fine to medium SAND with silt SP-SM B-2 S-10 30.0 22 Fine SAND with medium sand and trace silt SP B-3 S-9 25.0 21 Silty, fine SAND SM
4603 and 4609 Union Bay Figure Place NE Grain Size Distribution Seattle, Washington A-5 60
CL CH
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0 0 10 20 30 40 50 60 70 80 90 100 110 Liquid Limit (LL)
ATTERBERG LIMIT TEST RESULTS
Exploration Sample Liquid Plastic Plasticity Natural Unified Soil Symbol Number Number Depth Limit Limit Index Moisture Soil Description Classification (ft) (%) (%) (%) (%) B-1 S-1 2.5 24 18 6 20 Very sandy, SILT/CLAY with gravel ML/CL B-2 S-6 15.0 21 18 3 17 Very sandy SILT with gravel ML B-3 S-3 7.5 44 23 21 31 CLAY CL
ASTM D 4318 Test Method 1379002.020.021 2/10/15 N:\PROJECTS\1379002.020.021.GPJ ATTERBERG LIMITS FIGURE LIMITS ATTERBERG N:\PROJECTS\1379002.020.021.GPJ 2/10/15 1379002.020.021
4603 and 4609 Union Bay Figure Place NE Plasticity Chart Seattle, Washington A-6
APPENDIX D Slug Testing
19174‐00 November 18, 2015 DRAFT
APPENDIX D
Slug Testing This appendix presents the results of slug testing that was conducted for the Union Bay Place Development in Seattle, Washington. Slug tests were performed to determine hydraulic conductivity of formation for use in estimating flow rates during dewatering.
Slug tests are performed by suddenly inserting or removing a solid PVC rod in a well and measuring the recovery of the water levels during the test. A test conducted by the insertion of the PVC rod into the well is referred to as a falling head test and the following removal of the rod is called a rising head test. The water level data generated from the tests were analyzed using the commercial software AquiferWin32 Version 3 (Environmental Simulations, Inc., 2003). The slug test analysis is based on the Bouwer and Rice method (Bouwer and Rice 1976; Bouwer 1989) to obtain an estimated value of hydraulic conductivity of the aquifer.
SLUG TESTING RESULTS Slug testing was conducted in wells HC‐MW‐101 and B‐3 on October 6, 2015. Slug tests were not performed in well HC‐MW‐102 due to insufficient water within the well. A summary of monitoring well construction details is provided in Table 1. Shallow soils at the project site consist of poorly graded Sand, silty Sand, and poorly graded Sand with silt and gravel units. Stratigraphic units at HC‐ MW‐102 were inferred from log borings from Landau Associates boring B‐1 that was drilled in the vicinity of HC‐MW‐102. The wells were screened in three stratigraphic units and are summarized below:
HC‐MW‐101 was screened in the silty Sand and poorly graded Sand units; HC‐MW‐102 was screened in the silty Sand unit; and B‐3 was screened in poorly graded Sand with silt and gravel, and poorly graded Sand units.
A summary of slug testing results is provided in Table 2. Hydrographs of HC‐MW‐1‐1 and B‐3 are provided as Figure 1. The slug test plots are provided as Figure 2 and Figure 3. Multiple sets of falling and rising head tests were performed on each well. The results of the falling and rising head tests compare favorably. Average hydraulic conductivities determined from slug tests range from 6.2 x 10‐4 to 1.9 x 10‐3 cm/sec (1.8 to 5.4 feet/day). This hydraulic conductivity range is typical for silt and silty sand (Freeze and Cherry 1979).
REFERENCES Bouwer H. 1989. The Bouwer and Rice Slug Test – An Update. Ground Water 27(3): 304‐309.
Bouwer H. and R.C. Rice 1976. A Slug Test for Determining Hydraulic Conductivity of Unconfined Aquifers with Completely or Partially Penetrating Wells. Water Resources Research 12(3): 423‐428.
Environmental Simulations, Inc. 2003. Guide to Using AquiferWin32 Version 3.
19174‐00 November 18, 2015 DRAFT A-2 | Union Bay Place Development
Freeze, R.A. and J.A. Cherry 1979. Groundwater. Prentice‐Hall, Englewood Cliffs, New Jersey.
Attachments: Table D‐1 – Monitoring Well Construction Summary Table D‐2 – Summary of Slug Test Results Figure D‐1 – HC‐MW‐101 and B‐3 Hydrographs Figure D‐2 – HC‐MW‐101 Representative Slug Tests Results Figure D‐3 – B‐3 Representative Slug Tests Results
19174‐00 November 18, 2015 DRAFT Table D-1 - Monitoring Well Construction Summary
Well ID HC-MW-101 HC-MW-102 B-3 Boring Depth in Feet 20.0 21.4 42.0 Well Depth in Feet 20.0 21.4 40.0 Screen Interval Depth in Feet 9.6 to 19.6 10.8 to 20.8 30.0 to 40.0 Depth to Sediment in Feet (1) 19.7 20.2 39.8 Depth to Water in Feet (1) 13.0 18.6 8.2 Saturated Thickness in Feet 6.8 1.6 31.5 Screened Interval Soil Description SM, SP SM* SP-SM**, SP**
Notes: (1) Depth to sediment and depth to water was measured on October 5, 2015. SM = Silty SAND. SP = Poorly graded SAND. NA = Data not available. * According to Landau Associates Log Boring of B-1. **According to Landau Associates Log Boring of B-3.
Hart Crowser 1798401\Slug Test Tables and Figures - Table 1 Table D-2 - Summary of Slug Test Results
Bouwer and Rice Well ID Test Type Test Number K in ft/day K in cm/sec Falling Head Test 1 5.4 1.9E-03 Rising Head Test 2 6.0 2.1E-03 Falling Head Test 3 4.5 1.6E-03 HC-MW-101 Rising Head Test 4 6.0 2.1E-03 Falling Head Test 5 4.3 1.5E-03 Rising Head Test 6 6.0 2.1E-03 Average 5.3 1.9E-03 NA NA NA NA HC-MW-102 Average NA NA Falling Head Test 1 1.6 5.7E-04 Rising Head Test 2 1.5 5.3E-04 Falling Head Test 3 1.9 6.7E-04 B-3 Rising Head Test 4 1.5 5.2E-04 Falling Head Test 5 2.3 8.0E-04 Average 1.8 6.2E-04
Notes: NA = Data not available.
Hart Crowser 1798401\Slug Test Tables and Figures - Table 2 s and Figures.xls
Union Bay Place Seattle, Washington
HC-MW-101 and B-3 Hydrographs
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0 10 Displacement in Feet Displacement
-1 10 0.0 8.6 17.2 25.8 34.4 43.0 Time in Seconds Hydraulic Conductivity 1.6e-003 cm/sec
HC-MW-101 Test 2 - Rising Head 1 10 s and Figures.xls
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-2 10 0.0 8.0 16.0 24.0 32.0 40.0
Time in Seconds Hydraulic Conductivity 2.1e-003 cm/sec
Union Bay Place Seattle, Washington
HC-MW-101 Representative Slug Tests Results Note: Bouwer and Rice method was used for the slug test analysis. 19174-00 10/15 Figure
BLB 10/8/15 \\seafs\projects\Notebooks\1917400_Union Bay Place Development Design\Analysis and Calcs\Slug Test\Slug Test TableTest Test\Slug Calcs\Slug and Design\Analysis Development Place Bay \\seafs\projects\Notebooks\1917400_Union 10/8/15 BLB D-2 B-3 Test 3 - Falling Head 1 10
0 10 Displacement in Feet
-1 10 0.0 24.2 48.4 72.6 96.8 121.0 Time in Seconds Hydraulic Conductivity 6.7e-004 cm/sec
B-3 Test 4 - Rising Head 2 10 s and
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-1 10 0.0 34.2 68.4 102.6 136.8 171.0
Time in Seconds Hydraulic Conductivity 5.2e-004 cm/sec
Union Bay Place Seattle, Washington
B-3 Representative Slug Tests Results Note: Bouwer and Rice method was used for the slug test analysis. 19174-00 10/15 Figure
BLB 10/8/15 \\seafs\projects\Notebooks\1917400_Union Bay Place Development Design\Analysis and Calcs\Slug Test\Slug Test TableTest Test\Slug Calcs\Slug and Design\Analysis Development Place Bay \\seafs\projects\Notebooks\1917400_Union 10/8/15 BLB D-3