Amend0005 PPI 116 FFG-62 MASW-Report.pdf

© 2022 ConeTec Group of Companies. All Rights Reserved.

PRESENTATION OF SITE INVESTIGATION RESULTS

Philadelphia Navy Yard FFG-62

Prepared for:

Whitman, Requardt & Associates

ConeTec Job No: 22-54-25022

Project Start Date: 9-Dec-2022 Project End Date: 9-Dec-2022

Report Date: 20-Jan-2023

Prepared by:

ConeTec Inc.

606-S Roxbury Industrial Center

Charles City, VA 23030

Tel: (804) 966-5696 Fax: (804) 966-5697

Toll Free: (800) 504-1116

ConeTecVA@conetec.com www.conetec.com www.conetecdataservices.com mailto:ConeTecVA@conetec.com http://www.conetec.com/ http://www.conetecdataservices.com/

Introduction

The enclosed report presents the results of a site investigation program conducted by ConeTec Inc. for Whitman, Requardt & Associates on the Philadelphia Navy Yard FFG-62 project. This program consisted of two (2) surface seismic lines located inside an existing building structure. Surface seismic data was processed using the Multichannel Analysis of Surface Wave (MASW) method to provide two-dimensional (2D) shear wave velocity profiles. Please note that this report, which also includes all accompanying data, are subject to the 3rd Party Disclaimer and Client Disclaimer that follow in the ‘Limitations’ section of this report.

Project Information

Project

Client Whitman, Requardt & Associates

Project Philadelphia Navy Yard FFG-62

ConeTec project number 22-54-25022

Coordinates and Mapping

Coordinates were collected with a consumer grade GPS at the start points of each seismic line and corrected using field photos and features identifiable in satellite imagery. Estimate for line end point coordinates were generated from the measured total line distance and using the building edge as a guide.

Coordinates for each station along the line were estimated by interpolating between end point coordinates using the measured geophone spacing and line orientation. Coordinates are referenced to WGS84 UTM Zone 18 North.

An overview map showing the MASW line locations is provided in the appendices of this report and in the digital release in PDF format. A summary table is also included in the appendices of this report and in Excel digital format. The summary table presents coordinates of the line start and end coordinates along with important survey parameters. All georeferenced products are presented in the Coordinate Reference System outlined in the table below.

Coordinates

Test Type Collection Method Horizontal Datum Vertical Reference

MASW Consumer grade GNSS WGS84 UTM Zone 18

North Existing Ground

Seismic Data Acquisition Procedures

The surface seismic dataset was acquired using the equipment outlined in the table below and acquired with the following parameters:

• 24 active channels with geophones spaced at 10 feet

• Seismic source offset from nearest geophone of 20 feet (2D data acquisition only)

• Sledge hammer seismic source

• Minimum of 4 impacts (stacks) per seismic recording

• A constant offset survey method was used where the source and geophone array are advanced

10 feet after each record

• Due to the limited space available only an additional 15 stations could be advanced for line MASW22-01 and MASW22-02

• Active shot seismic data recorded for 1 second at 0.25 ms sampling interval

• Passive seismic data recorded for 30 seconds at 2 ms sampling interval

• For line MASW22-02 a 1D sounding was performed with multiple offset records from both ends of the array with offsets of 10, 20, and 30 feet from the nearest geophone

Seismic Equipment Used for this Project

Seismograph Geophones Coupling Mechanism Trigger Style Seismic Sources

Geometrics Geode 24

24 x 2Hz vertical pucks piezoelectric 10 lb sledgehammer

MASW Data Quality and Analysis

The surface wave component of the raw seismic signal was analysed using the MASW method. Data quality was poor and suffered from low signal strength and poor surface wave energy coherency. Poor signal strength may be a result of thick concrete at surface overlying soft sediments, which can greatly impede energy transfer to the subsurface. All 24 channels were used in the analysis to maximize depth of investigation. Surface wave energy was interpreted in the 4 - 30 Hz band with phase velocities ranging from 400 – 700 ft/s. Line MASW22-01 had noticeably better data quality than MASW22-02, although neither line was particularly good. This poor data quality for MASW22-02 reduced the number of interpretable readings and shortened the 2D profile when compared with MASW22-01.

Because of the poor data observed on MASW22-02, a single sounding was collected where the geophone array was held static, centered at the 180 foot mark, and multiple records collected with shot locations offset from either end of the array at 10 foot spacing intervals. These six seismic time domain records were analysed and combined with a single passive record to create a combined overtone image which shows improved surface wave energy coherency. Example time domain traces and overtone images with picked dispersion curves are included in the appendices of this report.

MASW Results

For the MASW dataset interpreted dispersion curves were inverted to produce 2D shear wave velocity profiles. Due to the limited space available, and length of array use in the analysis, the resulting 2D shear wave velocity profile is 150 and 120 feet long for MASW22-01 and MASW22-02 respectively. Note that the shear wave velocity profile placement is referenced to the 0 foot mark along the line, which represents the first geophone location. The 2D shear wave velocity profiles are presented in the appendices of this report and in PDF format in the digital release. Shear wave velocity models are included in the digital release of this report as a CSV with columns of: FieldDist(ft), Easting(m), Northing(m), Depth(ft), and Vs(ft/s). It should be noted that the Depth column represent the layer bottom value for any given Vs. The FieldDist(ft) column is the distance measured in the field.

A 1D shear wave velocity sounding from line MASW22-02 is also presented in the appendices of this report and accompanied by a summary table. This sounding is also provided in the digital release in Excel spreadsheet format.

Shear wave velocity results collected on a previous visit, ConeTec job number 22-53-24685, were compared with the MASW derived shear wave velocity results. From job 22-53-24685 only a single SCPT sounding was available: SCPT22-01A. The results from SCPT22-01A compare well with the MASW results in the top 40 feet below grade, however below that the two MASW datasets deviate from the SCPT result.

MASW derived shear wave velocities transition above 500 ft/s below 40 feet, which is a consistent trend across both MASW datasets. It is important to note the following when comparing the results presented here to the shear wave velocity result from 22-53-24685:

• Surface based geophysical methods suffer from a decrease in vertical resolution with increasing depth

• The data quality observed in this dataset was of low quality resulting in higher (qualitative) uncertainty in the observed shear wave velocities

• The comparison only incorporates a single, localized comparison dataset (single SCPT sounding)

As with all surface based geophysical methods it is highly recommended to verify the results with insitu measurements before making design decisions.

Closure

Thank you for the opportunity to work on this project. The equipment used and the field procedures followed complied with current accepted practice standards.

ConeTec Inc.

Limitations

3rd Party Disclaimer

This report titled “Philadelphia Navy Yard FFG-62”, referred to as the (“Report”), was prepared by ConeTec for Whitman, Requardt & Associates. The Report is confidential and may not be distributed to or relied upon by any third parties without the express written consent of ConeTec.

Any third parties gaining access to the Report do not acquire any rights as a result of such access.

Any use which a third party makes of the Report, or any reliance on or decisions made based on it, are the responsibility of such third parties. ConeTec accepts no responsibility for loss, damage and/or expense, if any, suffered by any third parties as a result of decisions made, or actions taken or not taken, which are in any way based on, or related to, the Report or any portion(s) thereof.

Client Disclaimer

ConeTec was retained by Whitman, Requardt & Associates to collect shear wave velocity data using the MASW method and to provide 2D shear wave velocity models based on the surface wave measurements (“Data”) which is included in this report titled “Philadelphia Navy Yard FFG- 62”, which is referred to as the (“Report”). ConeTec has collected and reported the Data in accordance with current industry standards. No other warranty, express or implied, with respect to the Data is made by ConeTec. In order to properly understand the Data included in the Report, reference must be made to the documents accompanying and other sources referenced in the Report in their entirety. Any analysis, interpretation, judgment, calculations and/or geotechnical parameters (collectively “Interpretations”) included in the Report, including those based on the Data, are outside the scope of ConeTec’s retainer and are included in the Report as a courtesy only. Other than the Data, the contents of the Report (including any Interpretations) should not be relied upon in any fashion without independent verification and ConeTec is in no way responsible for any loss, damage or expense resulting from the use of, and/or reliance on, such material by any party.

MULTICHANNEL ANALYSIS OF SURFACE WAVES

Multichannel analysis of surface waves (MASW) is a non-intrusive in-situ test that uses the principles of elasticity and surface wave dispersion to determine the variation of shear wave velocity with depth at a site. The observation that surface waves (Rayleigh waves) of different wavelengths propagate at different phase velocities in non-ideal media, is called dispersion. This is a direct result of the fact that surface waves of different wavelengths propagate along the surface to varying depths, and hence, if material stiffness changes with depth (as is the case with most non-ideal materials), then an appropriately selected wavelength band will reflect such changes in the velocity of propagation.

The field methods for surface wave testing are very similar to other surface seismic data collection methods. Surface geophones are placed in a linear array along a survey line at a known separation (typically one metre). A series of recordings (shots) are collected with a known in-line source offset from the array. Each shot gather is represented in the time-offset domain and shows the amplitude of wave propagation through the array (refer to Figure MASW-1). For detailed frequency analysis, multiple records with different shot offset distances are collected to help better define the broad spectrum frequency-phase velocity response of the medium. Two-dimensional cross sections can be collected by moving the geophone array a small distance (typically two meters) along the line and repeating the shots at set offsets.

Figure MASW-1. Typical MASW time domain record (shot gather)

Given that surface wave velocity is closely related to the shear wave velocity and the wavelength related to depth, the surface wave results can be used to develop a profile of shear wave velocity versus depth through a process referred to as inversion. The program used to perform the inversion is SurfSeis 6.6, developed by the Kansas Geological Survey. In SurfSeis, the raw time domain traces are transformed to the frequency domain to create what is referred to as an overtone image as shown in Figure MASW-2.

The overtone image displays the amplitude of the primary surface wave mode and any potential higher modes. A dispersion curve is fitted to the overtone image, and the inversion process is then used to determine the most appropriate shear wave velocity profile. The parameters used for the inversion of the dispersion data are provided in the data release folder in an Excel table.

Figure MASW-2. Overtone image and a picked dispersion curve

For each test location, a 1D shear wave velocity profile comprising of a number of velocity layers of variable thickness (refer to Figure MASW-3) is provided. For 2D testing a series of 1D tests are combined to produce a shear wave velocity cross section.

The depth of investigation is related to the ground conditions and the amount of energy delivered by the surface wave source. The surface wave method uses Rayleigh waves that travel horizontally along the ground surface to a depth of about one wavelength. The actual depth of sampling of the ground is considered to be one-half to one-third of the Rayleigh (surface) wave wavelength. The wavelengths measured by the equipment will be a function of the frequency of the source and the velocity of the surface waves through the ground. As the depth of investigation increases, there will be less certainty in terms of layer boundaries and velocity values.

Figure MASW-3. 1D inversion result with fitted dispersion curve

The equipment, field procedures, and analysis software used by ConeTec all conform to the currently accepted best practices for MASW testing. The results of geophysical testing are always interpretative to a certain extent and should be confirmed by drilling or other intrusive testing.

References

Miller, R.D., Xia, J., Park, C.B., and Ivanov, J.M., 1999, Multichannel analysis of surface waves to map bedrock, Kansas Geological Survey, The Leading Edge, December, p. 1392-1396.

Park, C.B., Miller, R.D., and Xia, J., 1998b, Ground roll as a tool to image near-surface anomaly: 68th Ann.

Internat. Mtg. Soc. Expl.Geophys., Expanded Abstracts, p. 874-877.

Park, C.B., Miller, R.D., and Xia, J., 1999, Multichannel analysis of surface waves: Geophysics, v. 64, n. 3,

pp. 800-808.

Park, C.B., Miller, R.D., Xia, J., and Ivanov, J., 2007, Multichannel analysis of surface waves (MASW)-active and passive methods: The Leading Edge, January.

SurfSeis website: http://www.kgs.ku.edu/software/surfseis/index.html

Xia, J., R.D. Miller, and C.B. Park, 2000a, Advantages of calculating shear-wave velocity from surface waves with higher modes: [Exp. Abs.]: Soc. Expl. Geophys., p. 1295-1298.

Xia, J., Miller, R.D., Park, C.B., and Ivanov, J., 2000b, Construction of 2-D vertical shear-wave velocity field by the Multichannel Analysis of Surface Wave technique, Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP 2000), Washington D.C, February 20-24, p. 1197-1206.

APPENDICES

The appendices listed below are included in the report:

• Overview Map

• 2D MASW Summary and Results

• 1D MASW Summary and Results

• MASW Time Domain Traces and Overtone Images

OVERVIEW MAP

485620

485620

485640

485640

485660

485660

485680

485680

485700

485700

485720

485720

485740

485740

Seismic Line

Legend

Philadelphia Navy Yard FFG-62 - Seismic Lines

ConeTec Job Number:

Survey Date(s):

Coordinate Reference System:

Map Scale:

Units:

Imagery Source:

22-54-25022 9-Dec-2022 WGS84 UTM Zone 18 North 1:750 meters Google Earth

2D MASW SUMMARY AND RESULTS

Job No: 22-54-25022 Client: Whitman, Requardt & Associates Project: Philadelphia Navy Yard FFG-62 Start Date: 09-Dec-2022 End Date: 09-Dec-2022

2D MASW TEST SUMMARY

Section ID Date Source Type Geophone

Spacing (ft)

Shot Spacing

(ft)

Section Length

(ft)

Array Length

(ft)

Start of Section Easting1

(m)

Start of Section

Northing1

(m)

End of Section Easting1

(m)

End of Section Northing1

(m)

Refer to Notation Number

MASW22-01 09-Dec-2022 sledge hammer 10 10 370 230 485676 4415282 485664 4415394

MASW22-02 09-Dec-2022 sledge hammer 10 10 370 230 485700 4415288 485691 4415400

1. Coordinates are referenced to WGS84 UTM Zone 18 North

Sheet 1 of 1

1D MASW SUMMARY AND RESULTS

Project: Philadelphia Navy Yard FFG-62 Start Date: 09-Dec-2022 End Date: 09-Dec-2022

1D MASW TEST SUMMARY

Sounding ID Date Location Geophone

Spacing (ft)

Array Length

(ft)

Center Point Easting1

(m)

Center Point Northing1

(m)

Refer to Notation Number

MASW22-02-1D 09-Dec-2022 MASW22-02 at 180 ft 10 230 485696 4415342

1. Coordinates referenced to WGS84 UTM Zone 18 North

Project: Philadelphia Navy Yard FFG-62 Sounding ID: MASW22-02-1D Date: 09-Dec-2022

1D MASW SHEAR WAVE VELOCITY TEST RESULTS

Layer Number

Layer Thickness (ft)

Depth of Bottom of Layer

(ft)

Vs (ft/s)

1 2.8 2.8 437

2 3.4 6.2 439

3 4.3 10.5 455

4 5.4 15.9 427

5 6.8 22.7 396

6 8.4 31.1 396

7 10.5 41.6 523

8 13.2 54.8 779

9 16.5 71.3 838

10 17.8 89.1 768

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

100.0

0 200 400 600 800 1000 1200

De pt h (ft

Vs (ft/s)

MASW TIME DOMAIN TRACES AND OVERTONE IMAGES

MASW22-01: Example time domain trace (top) and overtone image with picked dispersion curve (bottom).

MASW22-02: Example time domain trace (top) and overtone image with picked dispersion curve (bottom).

MASW22-02-1D(180ft): Example time domain trace (top) and combined active and passive overtone image with picked dispersion curve (bottom).