B08_Attach_13_Geotechnical_Investigation_Report_Alcatraz_Wharf.pdf

GEOTECHNICAL INVESTIGATION

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco, California

Prepared For:

Moffatt & Nichol 2185 N. California Blvd. Suite 500

Walnut Creek, California 94596

Prepared By:

Langan Engineering and Environmental Services, Inc.

135 Main Street, Suite 1500

San Francisco, California 94105

John Gouchon, PE, GE Principal/Vice President

11 March 2022 731713801

Geotechnical Investigation Alcatraz Wharf Seismic Retrofit San Francisco, California

11 March 2022 731713801

Page i

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 SCOPE OF SERVICES

3.0 DOCUMENT REVIEW

4.0 GEOLOGY

5.0 GEOLOGICAL RECONNAISSANCE

5.1 Site Reconnaissance and Geologic Mapping

5.2 Outcrop Analysis: Stereonet Plots and Rock Quality Designation (RQD)

6.0 SITE AND SUBSURFACE CONDITIONS

6.1 Site Conditions

6.2 Subsurface Conditions

7.0 CONCLUSIONS AND RECOMMENDATIONS

7.1 Site Specific Response Spectra and Time Series

7.1.1 Probabilistic Seismic Hazard Analysis

7.1.2 Probabilistic Model

7.1.3 Source Modeling and Characterization

7.1.4 Attenuation Relationships

7.1.5 PSHA Results

7.1.6 Deterministic Analysis

7.1.7 Recommended Spectra

7.1.8 Scaled Time Series

7.2 Foundations

7.2.1 Axial Capacity

7.2.2 Lateral Load Resistance

7.2.3 Construction Considerations

FIGURES

APPENDIX

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FIGURES

Figure 1 Site Location Map

Figure 2 Site Conditions and Previous Studies

Figure 3 Site Reconnaissance Map

Figure 4 Site Photos

Figure 5 Map of Geology, Major Faults and Earthquake Epicenters in the San Francisco Bay Area

Figure 6 PSHA Results with Directivity – 2 Percent Probability of Exceedance in 50 Years

Figure 7 2% Probability of Exceedance in 50 Years – Magnitude Distance Deaggregation Plots

Figure 8 Results of 84th Percentile Deterministic Analysis for a San Andreas Fault Event

Figure 9 Comparison of Deterministic, Probabilistic and Code Spectra

Figure 10 Recommended Spectra

Figure 11 Comparison of Initially Scaled SRSS and BSE – 2N Spectra

Figure 12 Comparison of Average Scaled SRSS and BSE – 2N Spectra

Figures 13 Comparison of MCER Response Spectra and Scaled Time Series through 23 for the 11 Ground Motions

APPENDIX

Appendix A NorCal Geophysical Report

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GEOTECHNICAL INVESTIGATION

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco, California

1.0 INTRODUCTION

Langan Engineering & Environmental Services, Inc. (Langan) is pleased to present the results of our recent field exploration and analyses for the proposed seismic upgrades to the wharf on

Alcatraz Island in San Francisco Bay, California, located as shown on Figure 1. Alcatraz is managed by the National Park Service (NPS). However, the wharf seismic retrofit is being funded by the

National Parks Conservancy, a non-profit organization that supports national parks. The wharf is the only access point for staff and visitors to the island. It was constructed in 1939 as a reinforced concrete beam and slab deck with steel shell concrete filled piles for support. It has undergone various repairs over the years, with the most recent and robust one occurring in 2001. Prior to

1934 Alcatraz was a military fort. In 1934 it was converted to a federal prison and operated as such until 1963. After being decommissioned it became a National Park.

The proposed improvements involve seismically strengthening the wharf to withstand earthquake forces. The strengthening includes installing three large-diameter steel pipe pile groups, known as Seismic Dolphins. We previously prepared several geotechnical reports for various structures and improvements on Alcatraz, including Building 64, the Barracks building just southwest of the wharf, and the prison hospital. The relative locations of the facilities are shown on Figure 2. We have received permission from the NPS to use the data collected during our studies of the Barracks and Hospital to provide geotechnical data for the wharf retrofit.

2.0 SCOPE OF SERVICES

Our scope of services was outlined in our contract with Moffatt & Nichol dated 1 March 2018.

Our scope consisted of:

reviewing available studies of the wharf and investigations completed for structures on the island where we observed similar bedrock conditions, our ongoing explorations for other island improvements, and readily available NPS historical documents;

a site reconnaissance to document rock outcrop conditions, strength characteristics (Schmidt hammer values), and measure bedding and discontinuity attitudes;

development of site-specific time series based on a previous investigation for the hospital;

development of design recommendations and parameters for analysis of the existing and proposed wharf foundation;

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11 March 2022 731713801 preparation of this report; and consultation with Moffatt & Nichol during final design, as needed.

3.0 DOCUMENT REVIEW

As part of our scope we reviewed previous studies and investigations that we performed near the wharf. In 2017, Langan performed a subsurface investigation for the seismic strengthening the Alcatraz Hospital Wing. Our investigation consisted of performing nine Dynamic

Penetrometer Tests (DPTs) and exploring three utility trenches (Langan, 2017). Our investigation concluded that the bedrock is shallow (between one and two feet below ground surface) on the eastern portion of the Hospital Wing, which is closest to the wharf.

Our study for the hospital included developing time series for use by the structural engineer

(Wiss, Janney, Elstner) in the seismic strengthening design for the hospital.

In May of 2018, Langan performed a geotechnical investigation for the Barracks, which is directly southwest of the wharf. We performed a site reconnaissance, geophysical surveys, and excavated a test pit. The investigation concluded that except for the southwest area of the building, which is likely underlain by fill, the Barracks is founded on bedrock (Langan, 2018b).

During the May 2018 investigation, we explored the area beneath the wharf and observed bedrock outcrops. The seismic refraction survey indicates the bedrock is moderately weathered.

The geophysical report prepared by Norcal Geophysical (Norcal) is included herein as Appendix A.

4.0 GEOLOGY

Our evaluation of the geology and seismicity of the area is based on our review of published reports and information in our files from other projects on Alcatraz Island and our current study.

The site is in San Francisco Bay, which lies within the Coast Ranges geomorphic province.

The San Francisco Bay depression resulted from interaction between the major faults of the

San Andreas fault zone, particularly the Hayward and San Andreas faults east and west of the bay, respectively (Atwater, 1979).

Bedrock consists of highly deformed and fractured sedimentary rocks of the Franciscan Complex.

Mixed sandstone, shale, chert, greenstone, and sheared rock (mélange) with rare limestone, conglomerate, calc-silicate rock, schist, and other metamorphic rock characterize the assemblage. Regional geologic mapping indicates that Alcatraz is underlain by sandstone interbedded with thin shale layers (Schlocker, 1974).

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5.0 GEOLOGICAL RECONNAISSANCE

To provide site-specific information and evaluate the strength of the rock beneath the wharf, we performed a site reconnaissance that included mapping the area, and using a Schmidt hammer to determine approximate unconfined compressive strengths (UCS) of the exposed rock.

In addition to our site reconnaissance, we compared the bedrock conditions encountered beneath the wharf with our database on similar Franciscan bedrock to develop strength parameters for design of foundations.

We were able to observe conditions beneath the wharf via an access hatch on the concrete deck during a previous geotechnical investigation (Langan, 2018b). For this study, we accessed the area beneath the wharf during low tide from the area directly north of the start of the Agave Trail.

The details and findings of our field exploration are provided in the following sections.

5.1 Site Reconnaissance and Geologic Mapping

Our senior geologist performed reconnaissance geologic mapping to document rock characteristics, strength, and discontinuities exposed in the bedrock outcropping beneath the wharf during a site visit on 14 August 2018. During the site visit, we mapped two observation points below the wharf (Figure 3) and used a Schmidt hammer to determine the approximate unconfined compressive strength (UCS) of the exposed bedrock. The digital Schmidt hammer takes rebound readings (R) and converts these to UCS values. According to Katz et al. (2000), there are empirical relations with R values and measured UCS values. We took ten readings at each observation point, and noted the mean R values, as well as value ranges and standard deviations. The digital hammer provided us with UCS values in pounds per square inch (Table 1).

The Schmidt hammer values were utilized for pile design analysis. Discontinuity attitudes were measured where bedrock was exposed and accessible. Bedrock exposures and stereonet plots of discontinuity orientations are depicted on Figure 3, Site Reconnaissance Map.

We identified the rock in both observation points to be Franciscan sandstone.

Observation Point #1 contains one low angle bedding plane, one joint set, two separate joint planes, and random fractures which were frequently encountered in our transect. We collected ten Schmidt hammer values on the bedding surface for an average UCS value of 7,700 psi with a standard deviation of 1.5.

At Observation Point #2 we identified one bedding plane, three joint planes, and one random fracture. We collected ten Schmidt hammer values on the bedding surface for an average UCS

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11 March 2022 731713801 value of 9,050 psi with a standard deviation of 3.1. The Schmidt hammer test results taken in the field were used to supplement the data obtained in our document review for comparison with other data collected from the nearby sites.

TABLE 1

Schmidt Hammer Data

Deliverables Observation

Point #1 Observation

Point #2

Mean (R) 48.5 55.0

Range (R) 3.0 10.0

Standard Deviation (R) 1.5 3.1

Sample Size 10 10

Mean (PSI) 7,700 9,050

5.2 Outcrop Analysis: Stereonet Plots and Rock Quality Designation (RQD)

Bedding and discontinuity data was collected from the exposed bedrock outcrops beneath the wharf. This information, along with the general trend and dip of the slope, was used as an input in the Dips 7.0 software by RocScience Inc. to determine the predominant orientations of the discontinuities (joints and bedding). We determined four predominant families of discontinuities based on density of data. The joint sets, along with data from the Barracks (Langan, 2018b), were then analyzed using the stereonet plots shown on Figure 3.

Rock Quality Designation (RQD) is a qualitative description of a rock mass that measures the length of cumulative, intact rock core over four inches long and is divided by the total length of the core run (Deere, 1988). The percentage is then used for engineering analyses. Although RQD is commonly performed on rock core taken from a borehole, we performed this description on the outcrops below the wharf. Our geologist placed a ten-foot section of tape across the two observation points and took photographs of the four, five-foot sections. We applied the same procedures to determine RQD in photographs as are used to determine RQD of rock cores; we measured the cumulative length of intact rock over four inches in length and divided it by five feet. The calculated a range for each five-foot section is presented in Table 2. RQD values were utilized for pile design and analyses.

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TABLE 2

RQD Values (%)

Section (ft) Observation

Point #1 Observation

Point #2

0-5 59.6 ± 6.4 77.0 ± 3.9

5-10 74.0 ± 2.6 89.6 ± 1.0

6.0 SITE AND SUBSURFACE CONDITIONS

Information regarding the site and subsurface conditions are presented in the following subsections.

6.1 Site Conditions

The wharf is located along the northeast flank of Alcatraz Island; this portion of the island is characterized by moderately to steep, northeast-facing slope topography Figures 2 and 3.

The wharf is bound by the Barracks (Building 64) to the southwest and the San Francisco Bay to the west, north and east. The Dock Tower sits atop the northwest end of the wharf, and the

Sally Port and former Military Chapel sits atop the center of the wharf. A loading dock extends southeast of the wharf. We understand the existing wharf is supported by a reinforced concrete beam and slab deck with steel shell concrete-filled piles constructed in 1939 and has undergone numerous restoration efforts. A circa 1900 photograph (pre-prison) and a 2018 photograph of the wharf are shown in Figure 4.

6.2 Subsurface Conditions

Subsurface conditions on Alcatraz Island consist of Franciscan Complex sandstone bedrock (Schlocker, 1974). We have compiled the subsurface data from previous reports for nearby projects on Alcatraz. We used data from the Barracks geophysical report by Norcal

(Langan, 2018b) to characterize the rock.

The bearing materials under the Barracks were not well documented. To determine the interface between fill and bedrock around the Barracks, we retained the services of Norcal to perform three seismic refraction profiles, designated SR-1, SR-2, and SR-3, to obtain compressional-wave velocities of the underlying geologic materials to aid in determining the depth to bedrock on the northeastern and southwestern length of the building (Langan, 2018b). To supplement the seismic data, three ground penetrating radar (GPR) surveys were performed to locate underlying voids, bunker cells, utility corridors, and other underground conflicts that would interfere with the

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11 March 2022 731713801 seismic refraction profiles. The methodologies and results of the surveys are presented in a report issued by Norcal, which is included as Appendix A.

The results of previous studies and our geologic reconnaissance indicate the bedrock is occasionally to moderately fractured, moderately hard to hard, strong, moderately weathered, fine-grained and well-cemented. We observed iron staining on the surfaces, as well as surficial weathering and deposits related to salt water exposure, which changed the color of the rock.

The results of the Schmidt hammer tests indicates the compressive strength of the rock where tested varies from 7,700 to 9.050 psi as shown in Table 1. Our mapping indicates the RQD of the rock varies from about 60 to 90 as shown in Table 2 and generally increases with depth.

7.0 CONCLUSIONS AND RECOMMENDATIONS

We conclude the planned seismic strengthening can proceed as planned. The primary geotechnical concern is the presence of hard rock beneath the wharf, and the difficulty associated with constructing piles that penetrate sufficiently to achieve fixity in the rock. This and other geotechnical aspects of the project are discussed in the following sections of this report.

7.1 Site Specific Response Spectra and Time Series

The wharf will be seismically evaluated using ASCE/SEI 41-13, Seismic Evaluation and Retrofit of

Existing Buildings. Specifically, the wharf will be evaluated for the Basic Safety Earthquake 2N

(BSE-2N) and Basic Safety Earthquake 1N (BSE-1N). BSE-2N is defined in ASCE41-13 as the lesser of the Risk-Targeted probabilistic seismic hazard analysis (PSHA) for a 2 percent probability of exceedance in 50 years and the 84th percentile deterministic (with appropriate deterministic check) both in the maximum direction. BSE-1N is defined as two-thirds of BSE-2N. The BSE-2N and BSE-1N levels of shaking are equivalent to the Risk-Targeted Maximum Considered

Earthquake (MCER) and Design Earthquake (DE) as defined in the 2016 California Building Code

(CBC). We previously developed site-specific spectra for the MCER and DE levels of shaking for the Alcatraz Prison Hospital. Because the wharf is underlain by rock similar to the prison hospital and the levels of shaking are the same, we used the same spectra for the wharf.

The following subsections present the results of the Probabilistic Seismic Hazard Analysis (PSHA) and deterministic analysis.

7.1.1 Probabilistic Seismic Hazard Analysis

Because the location, recurrence interval, and magnitude of future earthquakes are uncertain, we performed a PSHA, which systematically accounts for these uncertainties. The results of a PSHA

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11 March 2022 731713801 define a uniform hazard for a site in terms of a probability that a particular level of shaking will be exceeded during the given life of the structure.

To perform a PSHA, information regarding the seismicity, location, and geometry of each source, along with empirical relationships that describe the rate of attenuation of strong ground motion with increasing distance from the source, are needed. The assumptions necessary to perform the PSHA are:

the geology and seismic tectonic history of the region are sufficiently known, such that the rate of occurrence of earthquakes can be modeled by historic or geologic data;

the level of ground motion at a particular site can be expressed by an attenuation relationship that is primarily dependent upon earthquake magnitude and distance from the source of the earthquake;

the earthquake occurrence can be modeled as a Poisson process with a constant mean occurrence rate.

As part of the development of the BSE-2N spectrum, we performed a PSHA to develop a site-specific response spectrum for a 2 percent probability of exceedance in 50 years.

The spectrum was developed using the computer code EZFRISK 8.00 (Fugro 2015).

The approach used in EZFRISK is based on the probabilistic seismic hazard model developed by

Cornell (1968) and McGuire (1976). Our analysis modeled the faults in the Bay Area as linear sources, and earthquake activities were assigned to the faults based on historical and geologic data. The levels of shaking were estimated using Next Generation Attenuation West-2 relationships that are primarily dependent upon the magnitude of the earthquake and the distance from the site to the fault.

7.1.2 Probabilistic Model

In probabilistic models, the occurrence of earthquake epicenters on a given fault is assumed to be uniformly distributed along the fault. This model considers ground motions arising from the portion of the fault rupture closest to the site rather than from the epicenter. Fault rupture lengths were modeled using fault rupture length-magnitude relationships given by Wells and

Coppersmith (1994).

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The probability of exceedance, Pe(Z), at a given ground-motion, Z, at the site within a specified time period, T, is given as:

Pe(Z) = 1 - e-V(z)T where V(z) is the mean annual rate of exceedance of ground motion level Z. V(z) can be calculated using the total-probability theorem.

i

MRMi drdmmrfmfrmzZPzV iii where:

i = the annual rate of earthquakes with magnitudes greater than a threshold Moi in source i

P [Z > z | m,r] = probability that an earthquake of magnitude m at distance r produces ground motion amplitude Z higher than z fMi(m) and fRi|Mi(r;m) = probability density functions for magnitude and distance

Z represents peak ground acceleration, or spectral acceleration values for a given frequency of vibration. The peak accelerations are assumed to be log-normally distributed about the mean with a standard error that is dependent upon the magnitude and attenuation relationship used.

7.1.3 Source Modeling and Characterization

The major active faults in the area are the San Andreas, San Gregorio, Hayward, and

Calaveras Faults. These and other faults of the region are shown on Figure 5. The segmentation of faults, mean characteristic magnitudes, and recurrence rates were modeled using the data presented in the WGCEP (2008) and Cao et al. (2003) reports. We also included the combination of fault segments and their associated magnitudes and recurrence rates as described in the

WGCEP (2008) in our seismic hazard model. Table 3 presents the distance and direction from the site to the fault, mean characteristic magnitude, mean slip rate, and fault length for individual fault segments within 100 km from the site. We used the California fault database identified as

“USGS 2014 Lower 48 v0.1” in EZFRISK 8.00. We understand EZFRISK obtained this database directly from USGS and models the faults with multiple segments. Each segment is characterized with multiple magnitudes, occurrence or slip rates and weights. This approach takes into account the epistemic uncertainty associated with the various seismic sources in our model.

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TABLE 3

Source Zone Parameters

Fault Segment

Approx.

Distance from fault (km)

Direction from Site

Mean Characteristic

Moment Magnitude

Mean Slip Rate

(mm/yr)

Fault Length

(km)

N. San Andreas; SAN+SAP 13.6 West 7.73 22 274

N. San Andreas; SAN+SAP+SAS 13.6 West 7.87 21 336

N. San Andreas; SAO+SAN+SAP 13.6 West 7.95 22 410

N. San Andreas; SAO+SAN+SAP+SAS 13.6 West 8.05 22 472

N. San Andreas; SAP 13.6 West 7.23 17 85

N. San Andreas; SAP+SAS 13.6 West 7.48 17 147

N. San Andreas; SAN 14 West 7.51 24 189

N. San Andreas; SAO+SAN 14 West 8.00 24 326

Hayward-Rodgers Creek; HN 15 East 6.60 9 35

Hayward-Rodgers Creek; HN+HS 15 East 7.00 9 87

Hayward-Rodgers Creek; RC+HN 15 East 7.19 9 97

Hayward-Rodgers Creek; RC+HN+HS 15 East 7.33 9 150

San Gregorio Connected 18 West 7.50 5.5 176

Hayward-Rodgers Creek; HS 18 East 6.78 9 52

Hayward-Rodgers Creek; RC 29 North 7.07 9 62

Mount Diablo Thrust 34 East 6.70 2 25

Calaveras; CN 36 East 6.87 6 45

Calaveras; CN+CC 36 East 7.00 11 104

Calaveras; CN+CC+CS 36 East 7.03 12 123

Green Valley Connected 38 East 6.80 4.7 56

Point Reyes 38 West 6.90 0.3 47

West Napa 41 Northeast 6.70 1 30

Monte Vista-Shannon 46 Southeast 6.50 0.4 45

Greenville Connected 52 East 7.00 2 50

Great Valley 5, Pittsburg Kirby Hills 55 East 6.70 1 32

Great Valley 4b, Gordon Valley 66 Northeast 6.80 1.3 28

Calaveras; CC 69 Southeast 6.39 15 59

Calaveras; CC+CS 69 Southeast 6.50 15 78

Hunting Creek-Berryessa 72 Northeast 7.10 6 60

Great Valley 7 80 East 6.90 1.5 45

N. San Andreas; SAS 81 Southeast 7.12 17 62

Maacama-Garberville 87 North 7.40 9 221

Great Valley 4a, Trout Creek 87 Northeast 6.60 1.3 19

Zayante-Vergeles 91 Southeast 7.00 0.1 58

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7.1.4 Attenuation Relationships

Based on the subsurface conditions, the site is classified as a rock profile, Site Class B. Using the subsurface information, we estimated the average shear wave velocity of the 100 feet

(30 meters) below the foundations, VS30, of approximately 2,500 feet per second (760 meters per second).

Pacific Earthquake Engineering Research Center (PEER) embarked on the update of the

Next Generation Attenuation (NGA) ground motion prediction equations, which were published in 2008. We used the updated NGA West-2 ground motion prediction equations; specifically, Abrahamson et al. (2014), Boore et al. (2014), Campbell and Bozorgnia (2014) and Chiou and

Youngs (2014). These attenuation relationships include the average shear wave velocity in the upper 100 feet. Furthermore, these relationships were developed using the same database and each relationship is considered equally credible. Therefore, the average of the relationships was used to develop the recommended spectra.

The NGA relationships were developed for the orientation-independent geometric mean of the data. Geometric mean is defined as the square root of the product of the two recorded components.

7.1.5 PSHA Results

Figure 6 presents the results of the PSHA for two percent probability of exceedance in 50 years.

The average of the four attenuation relationships is also shown on these figures. The results presented on these figures are for the geometric mean as discussed in Section 7.1.4.

ASCE 41-13 specifies the development of BSE-2N site-specific response spectra in the maximum direction. Shahi and Baker (2014) provide scaling factors that modify the geometric mean spectra to provide spectral values for the maximum response (maximum direction). We used the scaling factors by Shahi and Baker (2014) to modify the average of the PSHA results for 2 percent probability of exceedance in 50 years. Figure 6 also presents the average of the PSHA results in the maximum direction.

Figure 7 presents the deaggregation plots of the PSHA results for the two percent probability of exceedance in 50 years hazard level. From the examination of these results, it can be seen that the San Andreas fault dominates the hazard at the project site at different periods of interest.

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7.1.6 Deterministic Analysis

We performed a deterministic analysis to develop the BSE-2N spectrum at the site. In a deterministic analysis, a given magnitude earthquake occurring at a certain distance from the source is considered as input into an appropriate ground motion attenuation relationship.

The governing earthquake scenario was defined as an earthquake on the San Andreas fault having a Moment Magnitude of about 8.0 occurring at a distance of about 13.6 km. This is consistent with the deaggregation results discussed in Section 7.1.5.

The same attenuation relationships as discussed in Section 7.1.4 were used in our deterministic analysis. The 84th percentile deterministic results for the four attenuation relationships as well as the average of the four relationships are presented on Figure 8 for the San Andreas fault. We also developed the 84th percentile deterministic spectrum in the maximum direction using the same scaling factors by Shahi and Baker (2014) as discussed in Section 4.5.

7.1.7 Recommended Spectra

The BSE-2N as defined in ASCE 41-13 is the lesser of the maximum direction PSHA spectrum having a two percent probability of exceedance in 50 years (2,475-year return period) or the maximum direction 84th percentile deterministic spectrum of the governing earthquake scenario.

Furthermore, the BSE-2N spectrum is defined as Risk-Targeted response spectrum, which corresponds to a targeted collapse probability of one percent in 50 years. According to USGS website the risk coefficients for the PSHA spectrum for short and long periods are, 1.070 and

1.013, respectively. We used these risk coefficients to develop the Risk-Targeted PSHA response spectrum.

We followed the procedures outlined in Chapter 21 of ASCE 7-10 to develop the site-specific spectra for BSE-2N. Chapter 21 of ASCE 7-10 requires the deterministic spectrum used to develop the BSE-2N not fall below the Deterministic Lower Limit spectrum as shown on

Figure 21.2-1 of ASCE 7-10. Furthermore we checked that the BSE-1N spectrum not fall below

80 percent of general design spectrum (Section 21.3 of Chapter 21 ASCE 7-10).

Figure 9 and Table 4 present a comparison of the site-specific spectra for the PSHA 2,475 year return period in the maximum direction, the 84th percentile deterministic in the maximum direction, and the Deterministic Lower Limit spectra for Site Class B per ASCE 7-10. For all periods the 84th percentile deterministic and Deterministic Lower Limit spectra are less than the

PSHA 2,475 year-return period and therefore the larger of the 84th percentile deterministic and

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11 March 2022 731713801 the Deterministic Lower Limit spectrum should be used to develop the BSE-2N spectrum.

The recommended BSE-2N spectrum is presented on Figure 9 and in Table 4.

TABLE 4

Comparison of Site-specific and Code Spectra for Development of BSE-2N Spectrum per ASCE 7-10

Sa (g) for 5 percent damping

Period (seconds)

Risk-Targeted PSHA

– 2,475 Year Return Period – Maximum

Direction

Deterministic 84th Percentile –

Maximum Direction

ASCE 7-10

Deterministic Lower

Limit Site Class B Recommended

BSE-2N

0.01 0.926 0.628 0.600 0.628

0.10 2.108 1.304 1.350 1.350

0.12 2.146 1.337 1.500 1.500

0.20 2.258 1.434 1.500 1.500

0.30 1.918 1.251 1.500 1.500

0.40 1.648 1.096 1.500 1.500

0.50 1.451 0.974 1.200 1.200

0.60 1.263 0.850 1.000 1.000

0.75 1.067 0.720 0.811 0.811

1.00 0.783 0.566 0.600 0.600

1.50 0.517 0.391 0.414 0.414

2.00 0.385 0.300 0.300 0.300

3.00 0.256 0.211 0.200 0.211

4.00 0.194 0.168 0.150 0.168

Table 5 presents the development of recommended BSE-1N spectrum following the procedures outlined in Chapter 21 of ASCE 7-10. The BSE-1N is defined as 2/3 of the BSE-2N per ASCE 7-10;

however, the recommended BSE-1N may not be below 80 percent of the general spectrum at any period (ASCE 41-3 Section 2.4.2.1.2). Figure 10 and Table 3 presents a comparison of 2/3 of the BSE-2N spectrum and 80 percent of the general spectrum for Site Class B. As shown in

Table 5 and Figure 10, 80 percent of the general spectrum is lower than 2/3 of the BSE-2N spectrum for all periods. Therefore, we recommend that 2/3 of the BSE-2N spectrum be used to develop the BSE-1N spectrum. The recommended BSE-1N spectrum is shown on Figure 9.

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TABLE 5

Comparison of Site-specific and Code Spectra for Development of BSE-1N Spectrum per ASCE 7-10

Sa (g) for 5 percent damping

Period (seconds)

Recommended

BSE-2N

2/3 times

BSE-2N

80% of General Design Spectrum

Recommended

BSE-1N

0.01 0.628 0.418 0.320 0.418

0.10 1.350 0.900 0.720 0.900

0.12 1.500 1.000 0.800 1.000

0.20 1.500 1.000 0.800 1.000

0.30 1.500 1.000 0.800 1.000

0.40 1.500 1.000 0.800 1.000

0.50 1.200 0.800 0.640 0.800

0.60 1.000 0.667 0.533 0.667

0.75 0.811 0.541 0.427 0.541

1.00 0.600 0.400 0.320 0.400

1.50 0.414 0.276 0.213 0.276

2.00 0.300 0.200 0.160 0.200

3.00 0.211 0.141 0.107 0.141

4.00 0.168 0.112 0.080 0.112

The recommended BSE-2N and BSE-1N spectra are presented on Figure 10 along with a comparison of the ASCE 7-10 mapped based spectra. Digitized values of the recommended spectra are presented in Table 6.

TABLE 6

Recommended BSE-2N and BSE-1N Spectra Spectral Acceleration (g’s)

Period (seconds)

BSE-2N

Damping Ratio 5%

BSE-1N

Damping Ratio 5%

0.01 0.628 0.418

0.10 1.350 0.900

0.12 1.500 1.000

0.20 1.500 1.000

0.30 1.500 1.000

0.40 1.500 1.000

0.50 1.200 0.800

0.60 1.000 0.667

0.75 0.811 0.541

1.00 0.600 0.400

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Period (seconds)

BSE-2N

Damping Ratio 5%

BSE-1N

Damping Ratio 5%

1.50 0.414 0.276

2.00 0.300 0.200

3.00 0.211 0.141

4.00 0.168 0.112

Because site-specific procedure was used to determine the recommended BSE-2N and BSE-1N response spectra, the corresponding values of SMS, SM1, SDS and SD1 per Section 21.4 of

ASCE 7-10 should be used as shown in Table 7.

TABLE 7

Design Spectral Acceleration Value

Parameter Spectral Acceleration

Value (g’s)

SMS 1.5

SM1 0.600

SDS 1.0

SD1 0.400

7.1.8 Scaled Time Series

The selection of recorded time series is an important step in developing the site-specific ground motions. The intent in this selection process is to choose time series that have a similar magnitude, and distance as that of the recommended BSE-2N. We searched for records with the following attributes:

Moment Magnitude greater than or equal to 6.5 to 8

Rupture distance less 15 km

VS30 less than 900 m/s

ASCE 41-13 requires the average the sum of the squares (SRSS) from eleven ground motions generally matches or exceeds the target response spectrum over the period range of interest;

for this study we used 0.2T to 1.5T. We developed the sum of the squares (SRSS) for each pair of horizontal time series. The time series was scaled such that the average of the SRSS would not fall below the recommended spectrum in the period range from 0.2T to 1.5T.

San Francisco, California

11 March 2022 731713801

We used the computer program QuakeManager version 1.10 (Earthquake Solutions 2016) to select the proposed time series. The algorithm used in QuakeManager calculates the sum of the squared error (SSE) between the target spectrum (BSE-2N) and initially scaled SRSS for each pair of time series in the database. These scaling factors were based on the algorithm used in

QuakeManager to reduce the SSE of the suite. The proposed time series were selected generally based on the least SSE; however, we also used our judgment to include time series from a larger earthquake that may not have had the lowest SSE. Table 8 presents the eleven time series used for scaling to BSE-2N.

Figure 11 presents a comparison of the initially scaled SRSS spectra for the suite of time series along with average of the eleven spectra and the target BSE-2N.

San Francisco, California

11 March 2022 731713801

TABLE 8

Time Series Used for Scaling1

NGA

Seq.

No. EQ Name

Fault Mech. Year Station Name Mag.

Rrup (km)

Vs30 (m/sec) Comp.

PGA

(g)

PGV

(cm/ sec)

PGD

(cm)

Lowest Useable

Freq.

(Hz)

Tp Pulse Period2

(sec)

DurationD 5-75%

Estimated Range 4 to 30 (sec)

Duration D5-95%

Estimated Range 6 to 49 (sec)

Arias Intensity

Estimated Range

0.4 to 3.0 (m/sec)

139 Tabas Reverse 1978 Dayhook 7.35 14 472 L T

0.32 0.41

22.3 27.1

15.2 7.4

0.25 6.7 6.6

11.3 11.0

1.4 1.4

Irpinia, Italy-01

Normal 1980 Sturno 6.90 11 382

0.23 0.32

37.0 71.9

13.1 29.3

0.125 3.3 7.0 6.1

15.0 15.2

1.2 1.4

Loma Prieta

Reverse -oblique

Gilroy Array

No. 3

6.93 12 349 0, 90

0.56 0.37

36.3 45.4

10.8 24.1

0.125 2.6 2.7 3.1

6.4 11.4

2.1 1.4

Loma Prieta

Reverse Oblique

Saratoga – Aloha Ave.

6.93 9 381

0.51 0.33

41.6, 46.0

16.3 33.3

0.125 4.6 3.7 4.1

9.4 8.2

1.5 1.1

Cape

Mendocino Reverse 1992

Cape Mendocino

7.01 7 567

1.49 1.03

122.3 42.4

32.6 13.1

0.07 - 2.5 2.9

6.2 9.7

6.0 2.4

1119 Kobe Strike-

Slip 1995 Takarazuka 6.90 0.3 312

0.69 0.61

68.4 86.2

26.7 20.8

0.1625 1.8 2.9 2.0

4.6 3.6

3.0 3.9

Chi-Chi Taiwan

Reverse Oblique

1999 TCU075 7.65 0.9 513

E N

0.33 0.26

109.6 36.1

96.6 31.6

0.05 5.0 18.0 20.8

26.9 31.3

3.0 1.2

Chi-Chi Taiwan

Reverse Oblique

1999 TCU079 7.65 11 363

E N

0.59 0.42

70.5 33.7

7.54 15.6

0.25 - 18.7 19.8

24.2 26.9

7.7 3.8

Manjil, Strike- Slip

1990 Abbar 7.37 13 724 L T

0.51 0.50

42.5 50.6

14.9 23.8

0.13 7.4

10.8 28.7 29.1

4.6 7.5

5813 Iwate Reverse 2009 Mizusawaku

Interior O Ganecho

6.90 7.9 413

EW

NS

0.26 0.36

19.8 33.9

8.7 15.0

.1 11.5 12.1

40.6 33.1

1.4 2.1

5818 Iwate Reverse 2009 Kurhara City 6.90 13 512

EW

NS

0.70 0.42

48.7 43.1

21.6 15.9

0.1 - 6.8 6.6

13.4 15.2

7.3 4.6

1 These records and metadata were obtained from the NGA-West2 On-Line Ground-Motion Database Tool

2 From the NGA-West2 On-Line Ground-Motion Database Tool; (-) denotes none pulse record

San Francisco, California

11 March 2022 731713801

ASCE 41-13 requires that the average of the SRSS from the ground motions generally matches or exceeds the target response spectrum over the period range of interest. Based on discussions with Moffatt & Nichol, the period range of interest was 0.0 to 1.5 seconds. We modified the initial scalars developed by QuakeManager version 1.10 to meet this requirement. The scaling factors are presented in Table 9 for the BSE-2N; because the BSE-1N spectrum is 2/3 of the

BSE-2N spectrum the scaling factors may be multiplied by 2/3 to obtain the appropriate BSE-1N scaling factors, if needed.

TABLE 9

Scaling Factors for BSE-2N Time Series

Time Series Scaling Factor

Tabas Dayook 1.61

Irpinia, Sturno 1.74

Loma Prieta, Gilroy No. 3 1.16

Loma Prieta, Saratoga Aloha Ave 1.74

Cape Mendocino Cape Mendocino 0.63

Kobe Takarazuka 0.58

Chi-Chi Taiwan TCU075 1.74

Chi-Chi Taiwan TCU079 0.81

Manjil Abbar 1.04

Iwate, Mizusawaku Interior O Ganecho 1.74

Iwate, Kurihara City 0.81

Figure 12 presents a comparison of the final scaled SRSS spectra for the BSE-2N as well as the recommended BSE-2N, where the period range of scaling is from 0.0 to 1.5 seconds. Figures 13 through 23 present the acceleration, velocity, and displacement of the scaled orthogonal components of time series and comparison between the scaled spectra for each component, SRSS and the recommended spectra for the BSE-2N (target) ground motion level.

7.2 Foundations

The existing wharf is supported on cast in place concrete piles. They were constructed by drilling or blasting a 16-inch diameter hole, assumed to be about 3 feet deep in sandstone bedrock.

A 16-inch diameter pipe with 3/8-inch wall was set vertically into the hole. Steel reinforcing bars were then placed in the full length of the pipe, which was then filled with concrete.

San Francisco, California

11 March 2022 731713801

The proposed strengthening includes installing three large-diameter steel pipe pile groups.

We understand Moffat & Nichol is considering 30-inch diameter pipe piles. The following sections present our conclusions and recommendations for the existing and proposed foundations.

7.2.1 Axial Capacity

Piles should gain support mainly in end bearing in the sandstone bedrock. Allowable compression capacities are presented in Table 10.

TABLE 10

Allowable Compression Pile Capacities

Pile Type

Qallowable

Dead Plus Live Load2

(kips)

Existing 16-inch-diameter concrete filled pipe

Proposed 30-inch diameter pipe

The allowable dead plus live load axial capacities include a factor of safety (FS) of at least 3.

The allowable loads may be increased by one-third for total loads including wind or seismic.

Uplift loads may be resisted by skin friction. An allowable skin friction value of 2,500 pounds per square foot may be used for piles embedded in rock.

7.2.2 Lateral Load Resistance

Existing and new piles will develop lateral resistance from the passive pressure acting on the bottom portion of the piles and their structural rigidity. The allowable lateral capacity of the piles depends on:

the pile stiffness the strength of the surrounding rock axial load on the pile the allowable deflection at the top and bottom of pile the allowable moment capacity of the pile the free length of the pile pile head fixity.

San Francisco, California

11 March 2022 731713801

TABLE 12

Lateral Load Capacities of Proposed Piles

Pile Diameter (inches)

Pile Free Length3

(feet)

Minimum Embedment in Rock4

(feet)

Lateral Load (kips)

Maximum Moment at Pile

Head (kip-inches)

Maximum Moment below

Pile Head (kip-inches)

Depth to Maximum Moment

(feet)

Deflection at Top/Toe (inches)

Proposed

7.5 306 17.0*103 15.3*103 9.6 1.40 / 0.25

10 420 17.0*103 28.7*103 10.2 1.82 / 0.25

12.5 566 17.0*103 46.9*103 10.7 2.80 / 0.25

15 679 17.0*103 60.4*103 11.0 3.40 / 0.12

7.5 192 17.0*103 18.8*103 16.1 2.37 / 0.25

10 278 17.0*103 35.3*103 16.3 3.50 / 0.25

12.5 391 17.0*103 57.7*103 16.8 5.70 / 0.25

15 406 17.0*103 60.4*103 16.8 5.46 / 0.06

The lateral capacities are for single piles only. To account for group effects, the lateral load capacity of a single pile should be multiplied by the appropriate reduction factors shown in

Table 13. However, the maximum moment for a single pile with an unfactored load should be used to check the design of individual piles in a group. The reduction factors are based on a minimum center-to-center spacing of three pile diameters. Where piles are spaced at least eight pile diameters in all directions, no group reduction factors need to be applied. Reduction for other pile group spacing can be provided once the number and arrangement of piles are known.

TABLE 13

Lateral Group Reduction Factors

Number of Piles within Pile Cap

Lateral Group Reduction Factor

2 0.9

3 to 5 0.8

>6 0.7

7.2.3 Construction Considerations

For the piles to develop fixity at the toe the minimum depth presented in Table 12 should be achieved. However, depending on the local weathering, fracturing and hardness of the rock, it could be difficult to achieve the required embedment. The type of equipment used and the

Pile free length is measured from top of pile to top of rock.

Minimum embedment in rock to provide pile fixity.

San Francisco, California

11 March 2022 731713801 amount of effort the contractor is willing to use will also affect the depth that the contractor can achieve. We recommend that the contractor observe the rock exposed beneath the wharf and review the seismic refraction data presented in Appendix A to evaluate the equipment needed to achieve the required embedment depth. If the required embedment depth cannot be achieved we should perform additional lateral pile analysis to model the embedment achieved in the field and evaluate the results with Moffatt & Nichol.

San Francisco, California

11 March 2022 731713801

REFERENCES

2014 Working Group on California Earthquake Probabilities (2015). “UCERF3: A New Earthquake Forecast for California’s Complex Fault System”, U.S. Geological Survey 2015-3009, 6 p., http://pubs.usgs.gov/fs/2015/3009

Atwater, B.F., (1979). “Ancient Processes at the Site of Southern San Francisco Bay: Movement of the Crust and Changes in Sea Level, published in San Francisco Bay: The Urbanized Estuary;

Investigations into the Natural History of San Francisco Bay and Delta with Reference to the Influence of Man,” Pacific Division, American Association for the Advancement of Science, San Francisco, California, Conomos, T.J, ed., pp. 31-45.

Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C. J. (2003). “The Revised 2002 California Probabilistic Seismic Hazard Maps.”

Katz, O., Reches, Z., and Roegiers, J.-C. (2000). “Evaluation of mechanical rock properties using a Schmidt Hammer,” International Journal of Rock Mechanics and Minin Sciences, 37, 723-728.

Langan Engineering & Environmental Services, Inc. (2018a). Geotechnical Investigation, Alcatraz Prison Hospital, San Francisco, California. 1 March.

Langan Engineering & Environmental Services, Inc. (2018b). Geotechnical Investigation, Alcatraz Barracks Building, San Francisco, California. 31 May.

Langan Engineering & Environmental Services, Inc. (2017). Subsurface Investigation, Alcatraz Hospital Wing, Alcatraz Island, San Francisco, California. 31 March.

Schlocker, J. (1974). “Geology of the San Francisco North Quadrangle, California.”

Sloan, D. (1992). “The Yerba Buena Mud – Record of the Last Interglacial Predecessor of San Francisco Bay, California,” Geological Society of America Bulletin, v. 104, pp. 716-727.

Toppozada, T. R. and Borchardt G. (1998). “Re-Evaluation of the 1836 ‘Hayward Fault’ and the 1838 San Andreas Fault Earthquakes.” Bulletin of Seismological Society of America, 88(1), 140-159.

FIGURES

Wharf

SITE

Date 10/3/2018

SITE LOCATION MAP

Project No. 731713801 Figure 1

\\la ng an .co m\ da ta\

SF

O\ da ta8 \73

1\P roj ec t D ata

\A rcG

IS

\M

XD

\G eo log ic_ Fig ure s\S ite Lo ca tio n M ap

.m xd

U se r: b sa ylo r

0 4,0002,000

Feet

Legend Site Location Wharf

Notes:

1. Aerial imagery provided by Near Map, aerial flown on 7/13/2018.

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco, California

0 10050

Feet

"J

"J&(

"J

WharfBarracks (Building 164)

Hospital Wing

GP

R-3

GP

R-2

GP

R-1

SR-1

SR-2

SR-3

14100

6 2

10 0

6 4

102102

74 72

DPT-11

B

C

A

DPT-6DPT-8

DPT-7

TP-2

TP-1

DPT-9

DPT-13

DPT-12 DPT-1

DPT-14 DPT-2

DPT-15 DTP-5DPT-4

DPT-3

DPT-16

TP-1

DPT-10

Date 10/3/2018

SITE CONDITIONS AND PREVIOUS STUDIES

Project No. 731713801 Figure 2

\\la ng an .co m\ da ta\

SF

O\ da ta8 \73

1\P roj ec t D ata

\A rcG

IS

\M

XD

\G eo log ic_ Fig ure s\S ite C on dit ion s a nd P rev iou s S tud ies .m xd U se r: b sa ylo r

Notes:

1. Aerial imagery provided by Near Map, aerial flown on 7/13/2018.

2. Lidar data obtained from the Northern California Fault System Lidar Survey dated April 17, 2007. Elevations presented above the ellipsoid (WGS84), elevations not converted to orthometric heights.

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco, California

0 12060

Feet

Legend

Approximate location of utility trench exposing subsurface conditions by Langan, February 2017

Approximate location of dynamic penetration test by Langan, September 2017

Approximate location of dynamic penetration test by Langan, February 2017

"J Approximate location of test pit by Langan, February 2018 "J Approximate location of test pit by Langan, September 2017

Approximate location of GPR traverse by Norcal Geophysical, February 2018 Approximate location of seismic refraction by Norcal Geophysical, February 2018

Barracks (Building 164) Hospital Wing Wharf Approximate location of bulkhead wall Lidar Surface Elevation Contour - 2ft. Interval

GPR-1

SR-1

TP-1

TP-1

DPT-1

DPT-10

A

OBSERVATION POINT #1

OBSERVATION POINT #2

WHARF

WOOD DOCK

Mean Strike/ Dip

Mean Strike/ Dip

Pile location

Existing tide height at time of observation

Extent observed in place rock outcrop

5 foot contour (as provided by Moffatt & Nichol, August 2018)

1 foot contour (as provided by Moffatt & Nichol, August 2018)

Extent of study area

Scale

0 30 Feet 09/14/18 731713801 3

SITE RECONNAISSANCE MAP

Date Project No. Figure

San Francisco, California

ALCATRAZ WHARF SEISMIC RETROFIT

EXPLANATION

Lower Hemisphere Density Plot of

Discontinuities at Observation Point #2

Lower Hemisphere Density Plot of

Discontinuities at Observation Point #1

Date Project No. Figure09/07/18 731713801 4

San Francisco, California SITE PHOTOS

Site Photo, dated 1900.

Site Photo, dated 2018.

SITE

PAC IF ICPAC IF IC

OCEANOCEAN

Rodgers

Creek

Point Reyes

Monte

Vista-Shannon

G reen

Valley

San Andreas

San G regorio

C onnected

Hayward

Mount DiabloThrust

SITE

Alameda

Contra Costa

San Mateo

Santa Clara

Solano

San Francisco

Marin

Date 9/14/2018

MAP OF GEOLOGY, MAJOR FAULTS,

AND EARTHQUAKE EPICENTERS IN

THE SAN FRANCISCO BAY AREA

Project No. 731713801 Figure 5

\\l an ga n.

co m \d at a\ S F O \ d at a8 \7 0 1 \P ro je ct D at a\ A rc G

IS

\M X D \G eo lo gi c_ Fi gu r e s\ Fa ul ts ,E ar th qu ak es ,G eo l o gy .m xd

U se r:

bs ay lo r

0 2010

Miles

Legend Earthquake Epicenter 2

Magnitude 5 to 5.9

Magnitude 6 to 6.9

Magnitude 7 to 7.4

Magnitude 7.5 to 8

Fault 1

County Boundary 3 Notes:

1. Quaternary fault data displayed are based on a generalized version of U.S Geological Survey (USGS) Quaternary Fault and fold database, 2010. For cartographic purposes only.

2. The Earthquake Epicenter (Magnitude) data is provided by the USGS and is current through 08/26/2014.

3. Fault map basemap hillshade and County boundaries provided by USGS and California Department of Transportation.

4. Geology mapped in 1948 -61 by Julius Schlocker, M.G. Bonilla, D.H. Radbruch, C.A. Kaye, and W.I. Konkoff. USGS Geologic Map of t he San Francisco North Quadrangle published in 1968.

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco, California

0 4,0002,000

Feet

Geologic Unit 4

KJss Clastic sedimentary rocks; sandstone; thick-bedded and massive graywacke sandstone interbedded with thin layers of shale and fine-grained sandstone; some thick conglomerate lenses.

Artificial fill; Predominantly dune sand but includes silt, clay, rock waste from excavations, manmade debris, and organice waste. Probable fill material indicated in parentheses.

Maximum thickness approximately 60 feet

Landslide deposits; Generally unstratified mixtures of bedrock, sand, silt, and clay in varying proportions. Qly, younger landslide deposit. Qlo, older landslide deposits

Slope debris and ravine fill; Angular rock fragments in sand, silt, and clay matrix;

generally light yellow to reddish brown. Maximum thickness approximately 80 feet

Qaf

Ql

Qsr

Damping Ratio = 5%

Notes:

1. Estimated VS30 760 meters per second

2. Maximum direction factors from Shahi and Baker (2014)

Project No. 731713801 Figure 6

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

PSHA RESULTS WITH DIRECTIVITY - 2 PERCENT

PROBABILITY OF EXCEEDANCE IN 50 YEARS

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Abrahamson et al. (2014)

Boore et al. (2014)

Campbell and Bozorgnia (2014)

Chiou and Youngs (2014)

Average

Average - Maximum Direction

(a) PGA

(b) Sa, T = 1.0 seconds

(c) Sa, T = 4.0 seconds

Project No. 731568704 Figure 7

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

2% PROBABILITY OF EXCEEDANCE IN 50 YEARS -

MAGNITUDE DISTANCE DEAGGREGATION PLOTS

Date 08/17/18

1. Estimated VS30 760 meters per second

2. Mw = 8.05, Dist. = 13.6 km from the San Andreas fault

3. Maximum direction factors from Shahi and Baker (2014)

Project No. 731713801 Figure 8

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

RESULTS OF 84

th

PERCENTILE DETERMINISTIC

ANALYSIS FOR A SAN ANDREAS FAULT EVENT

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Abrahamson et al. (2014)

Boore et al. (2014)

Campbell and Bozorgnia (2014)

Chiou and Youngs (2014)

Average

Average - Maximum Direction

1. Estimated VS30 760 meters per second

2. Maximum direction factors from Shahi and Baker (2014)

Project No. 731713801 Figure 9

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

COMPARISON OF DETERMINISTIC, PROBABILISTIC AND

CODE SPECTRA

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Risk-Targeted PSHA - 2,475 year return period - Maximum Direction

84th Percentile Determinstic - Maximum Direction

ASCE 7-10 Deterministic Lower Limit, Site Class D

ASCE 7-16 - 80% MCER Site Class B

Recommended MCER

2/3 times MCER

ASCE 7-16- 80% General Design Site Class B

Recommended DE

1. Estimated VS30 760 meters per second

Project No. 731713801 Figure 10

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

RECOMMENDED SPECTRA

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Recommended MCER

ASCE 7-16 - MCER Site Class B

Recommended DE

ASCE 7-16 - DE Site Class B

Note: Period range of interest is 0.02 seconds to 1.50 seconds

Project No. 731713801 Figure 11

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

COMPARISON OF AVERAGE INITIALLY SCALED SRSS

AND BSE - 2N SPECTRA

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Tabas Dayook

Irpinia, Sturno

Loma Prieta, Gilroy No. 3

Loma Prieta, Saratoga Aloha Ave

Cape Mendocino Cape Mendocino

Kobe Takarazuka

Chi-Chi Taiwan TCU075

Chi-Chi Taiwan TCU079

Manjil Abbar

Iwate, Mizusawaku Interior O Ganecho

Iwate, Kurihara City

BSE - 2N

Average SRSS

Recommended BSE - 2N

Note: Period range of interest is 0.02 seconds to 1.50 seconds

Project No. 731713801 Figure 12

ALCATRAZ WHARF SEISMIC RETROFIT

San Francisco California

COMPARISON OF AVERAGE SCALED SRSS AND BSE -

2N SPECTRA

Date 10/18/18

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

S P

E C

T R

A L

A C

C E

L E

R A

T

IO

N g 's

PERIOD (seconds)

Tabas Dayook

Irpinia, Sturno

Loma Prieta, Gilroy No. 3

Loma Prieta, Saratoga Aloha Ave

Cape Mendocino Cape Mendocino

Kobe Takarazuka

Chi-Chi Taiwan TCU075

Chi-Chi Taiwan TCU079

Manjil Abbar

Iwate, Mizusawaku Interior O Ganecho

Iwate, Kurihara City

Average Scaled

BSE - 2N

Date 10/18/18 Project No. 731713801 Figure 13

San Francisco California

COMPARISON OF MCER…