OCS Study 

MMS 2003-061 

 

Refining and Revising the Gulf of Mexico 

Outer Continental Shelf Region 

High-Probability Model 

for Historic Shipwrecks 

Final Report 

Volume II: Technical Narrative 

U.S. Department of the Interior

Minerals Management Service 

Gulf of Mexico OCS Region 
U.S. Department of the Interior

Minerals Management Service 

Gulf of Mexico OCS Region 

OCS Study 

MMS 2003-061 

Refining and Revising the Gulf of Mexico 

Outer Continental Shelf Region 

High-Probability Model 

for Historic Shipwrecks 

Final Report 

Volume II: Technical Narrative 

Authors 

Charles E. Pearson 

Stephen R. James, Jr. 

Michael C. Krivor 

S. Dean El Darragi 

Lori Cunningham 

Prepared under MMS Contract 

1435-01-00-CT-31054 

by 

Panamerican Consultants, Inc. 

Memphis, Tennessee 

and 

Coastal Environments, Inc. 

Baton Rouge, Louisiana 

Published by 

New Orleans

December 2003 
iii

DISCLAIMER

This report was prepared under contract between the Minerals Management Service

(MMS), Panamerican Consultants, Inc., and Coastal Environments, Inc. This report has

been technically reviewed by the MMS and it has been approved for publication.

Approval does not signify that the contents necessarily reflect the views and policies of

the MMS, nor does mention of trade names or commercial products constitute

endorsement or recommendation for use. It is, however, exempt from review and

compliance with the MMS editorial standards.

REPORT AVAILIBILITY

Extra copies of this report may be obtained from the Public Information Unit (Mail Stop

5034) at the following address:

U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

Public Information Unit (MS 5034)

1201 Elmwood Park Boulevard

New Orleans, Louisiana 70123-2394

Telephone: (504) 736-2519 or

1-800-200-GULF

CITATION

Suggested citation:

Pearson, C.E., S.R. James, Jr., M.C. Krivor, S.D. El Darragi, and L. Cunningham.

2003. Refining and Revising the Gulf of Mexico Outer Continental Shelf Region

High-Probability Model for Historic Shipwrecks: Final Report. Volume II:

Technical Narrative. U.S. Dept. of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2003-061, 195

pp., 3 volumes.
v

ACKNOWLEDGMENTS

Many individuals, organizations and agencies have contributed to this study and

are acknowledged and thanked here. Dr. Rik Anuskiewicz, archaeologist with MMS,

New Orleans, served as Project Manager on this study for MMS. Dr. Jack Irion and

David Ball, archaeologists at MMS, New Orleans, freely provided information pertinent

to this study.

Several individuals were involved in the collection of shipwreck information from

various state agencies. Amy Mitchell examined Florida records, Andy Hall examined

records in Texas, and Sara Hahn visited depositories in Louisiana, Alabama and

Mississippi. Personnel at all of the state archaeological offices are thanked for the help

and information they provided. Particularly thanked are Dr. Thomas Eubanks, Louisiana

State Archaeologist; Steven Hoyt, Texas Marine Archaeologist; Dr. Thomas Maher,

Alabama State Archaeologist; Dr. Roger Smith, Florida Underwater Archaeology

Program, Bureau of Archaeological Research; and Doug Sims, formerly an archaeologist

with the Mississippi Department of Archives and History, now with the U.S. Army Corps

of Engineers. The various Corps of Engineers Districts that border the Gulf of Mexico,

also, were contacted for information on shipwrecks in their areas. Individuals from these

districts who provided information were Tommy Birchett, Dottie Gibbens, Joe Giliberti

and Brian Guevin.

Several individuals and agencies provided critical database information for this

study. These included Carl Clauson and Prasnee Wilschp of the National Imagery and

Mapping Agency; Steve Avery, National Oceanic and Atmospheric Administration; Roy

Lukins of the Gulf States Artificial Reef Committee; and David Ledet, Marine

Information Section, United States Coast Guard, 8th District. All of these individuals

provided electronic databases maintained by their agencies and willingly answered

questions concerning those databases. Amy Broussard and Eric Graham, Texas Sea

Grant Program, provided the database of snags and hangs maintained by Texas A&M

University; Bruce Ballard of the Louisiana Department of Natural Resources and Irvin

Jackson, Mississippi Department of Marine Resources, provided information on data

their agencies maintain on hangs and losses off of these two states. Avery Munson of

Broussard, Louisiana shared his extensive knowledge of wrecks off of coastal Louisiana

and Rob Floyd of Thales Geo Solutions, Prairieville, Louisiana, provided information

derived from his very extensive experience in conducting offshore remote sensing

surveys. Allen Saltus, Jr. of Prairieville, Louisiana provided additional information on

offshore survey and shipwrecks in the Gulf of Mexico. Dr. Erv Garrison, Department of

Anthropology, University of Georgia, provided information on some specific questions

concerning his earlier study, and Dr. Dan Mossler, Hampden-Sydney College, advised on

some of the statistical analyses used in this study. Staff at the Mariners Museum,

Newport News, Virginia, and the National Archives, Washington, D.C., are thanked for

the aid they provided researchers.
vi

Lori Cunningham of Coastal Environments, Inc., was responsible for all aspects

of the study involved with placing collected data into Microsoft Access and ArcView.

This included design of the database, manipulation of the collected data, and

development and design of all of the maps included with the ArcView database. Her

efforts were key to the success of this project. Dion O’Rielly, also of Coastal

Environments, Inc., aided Ms. Cunningham, and was responsible for finalizing the

Access database and converting much of the collected data into formats compatible for

use in Access and ArcView.

Panamerican would like to thank the many people involved with this project for

all their time and effort. First and foremost we would like to thank the Minerals

Management Service and more specifically Dr. Rik Anuskiewicz for allowing

Panamerican the opportunity to conduct this research. Dr. Anuskiewicz assisted us with

all phases of the project and his contributions are too numerous to mention.

Several people involved directly with the Task 3 survey must be thanked. We

would like to acknowledge Ross Johnson, Jon Bellino, and Misha Tchernychev of

Geometrics, Inc. as well as Melissa Marlowe and Doug Hrvoic with Marine Magnetics.

Each of these groups provided equipment, and more importantly, their time to make sure

the magnetometer data collected was suitable.

Panamerican acknowledges the help of Chris Appleyard, Mike Main, and Trace

Maurin of Vision Project Services, Inc. of Houston, Texas who were responsible for the

collection and processing of data. We appreciate the generosity of Loudes Ramos and

Coastal Oceanographics, Inc. for providing a copy of Hypack MAXTM for the survey. To

ensure the quality of data collected we would like to extend our appreciation to S. Dean

El Darragi with Telesis Geophysical Services of Lafayette, Louisiana. Larry Stephenson

of Harvey-Lynch, Inc. in Stafford, Texas has always provided much needed assistance

while in the field and was helpful in discussing the industry standards of magnetometers.

For logistical assistance and permitting for the State of Florida we must thank

James J. Miller and Della Scott-Ireton with the Bureau of Archaeological Research. We

also appreciate the help of Riley Hoggard with the National Park Service for assisting

with permits for the Gulf Islands National Seashore.

We must thank the boat captains who helped make this project a success: Jay

Venable and the crew with the M/V Enterprise and M/V Offshore Retriever, of Tampa,

Florida; Captain Kenny Barhanovich with the Miss Hospitality out of Biloxi, Mississippi;

and Captain Mac McLean with the Undertow III out of Pensacola, Florida. We would

also like to thank Sea Boat Rentals, Inc. for providing offshore support during Task 2.

A number of Panamerican personnel contributed to the success of the project.

The remote-sensing and dive crew consisted of Mike Tuttle, Jim Duff, Matt Elliott, Andy

Lydecker, Chris Rhodes, and Chuck Meide. John Rawls, Robin Moore, and Clay Gilpin

assisted as field technicians during Task 3 operations. Kate Gilow provided technical and

logistical support during all phases of the study. Kelly Blount compiled and edited the

report while Stephanie Gray provided computer graphics assistance.
vii

TABLE OF CONTENTS

PAGE

ACKNOWLEDGMENTS v

LIST OF FIGURES xi

LIST OF TABLES xvii

1.0: INTRODUCTION 1-1

1.1. Study Objectives 1-3

1.2. Study Area 1-4

1.3. Report Organization and Presentation of Data 1-5

2.0: RESEARCH APPROACH –TASK 1 2-1

2.1. Background Research 2-1

2.2. Sources of Data 2-2

2.2.1. Computerized Databases 2-2

2.2.2. Internet Resources 2-7

2.2.3. Published Secondary Literature 2-8

2.2.3.1. Cultural Resources Management Reports 2-10

2.2.4. MMS-Mandated Archaeological Survey Reports 2-13

2.2.5. Primary Documents 2-13

2.2.6. Directories 2-14

2.3. Compilation of Revised and Expanded Shipwreck Database 2-15

2.3.1. Shipwreck Information Form 2-16

3.0: SHIPWRECKS IN THE GULF OF MEXICO AND THE MMS

ARCHAEOLOGICAL PROGRAM: THE 1989 MODEL 3-1

3.1. Present Model of Shipwreck Occurrence in the Gulf of Mexico 3-1

3.1.1. 1989 MMS Gulf of Mexico Shipwreck Database 3-2

3.1.2. Characteristics of the 1989 Model of Shipwrecks in the GOMR 3-4

3.1.2.1. Historical Setting 3-4

3.1.2.2. Natural Setting 3-6

3.1.2.3. Factors of Shipwreck Preservation in the Gulf of Mexico 3-8

3.1.2.4. Analysis of the Spatial Distributions of Shipwrecks in the

1989 Study 3-8

3.1.2.5. Summary of Findings of the 1989 Study 3-9

3.2. Application of the 1989 Model of Shipwrecks in the Gulf of Mexico

to Cultural Resources Management by MMS 3-11

3.2.1. MMS Archaeological Survey Requirements 3-12

3.2.2. Results of MMS-Mandated Archaeological Surveys:

Testing the 1989 Model of Shipwreck Occurrences 3-15

3.2.2.1. Identification of High-Probability Lease Blocks 3-15
viii

3.2.2.2. Findings of the MMS Archaeological Survey GOMR

Program 3-18

3.2.3. Evaluating the 1989 GOMR Shipwreck Model 3-20

3.2.3.1. Precision and Accuracy in Shipwreck Locations in the 1989

Model 3-20

3.2.3.2. Testing the Predictability of the 1989 Shipwreck Model 3-24

4.0: 2001 MODEL OF SHIPWRECK OCCURRENCES IN THE

GULF OF MEXICO 4-1

4.1. Introduction 4-1

4.2. Compiling the 2001 Shipwreck Database 4-2

4.2.1. Nature of the Historic Record of Shipwrecks in the GOMR 4-2

4.2.2. Determining Geographic Coordinates for Shipwrecks in the

Database 4-7

4.3. Characteristics of the 2001 Shipwreck Database 4-8

4.3.1. Chronological Trends 4-11

4.3.1.1. Year of Loss 4-11

4.3.1.2. Age of Vessel at Loss 4-16

4.3.1.3. Season of Loss 4-18

4.3.2. Types of Vessels 4-22

4.3.3. Cause of Loss 4-30

4.4. Shipwreck Preservation Potentials in the Study Area 4-34

4.4.1. Sediment Characteristics and Preservation Potentials in the

Study Area 4-38

4.5. Patterns of Shipwreck Distributions 4-42

4.5.1. Introduction 4-42

4.5.2. Broad Spatial Patterns 4-44

4.5.3. Spatial Distributions in Shipwrecks Through Time 4-50

4.5.4. Distribution of Reported Shipwrecks by Reliability Categories 4-62

4.5.5. Spatial Analysis: 1.0- and 0.5-Degree Units of Latitude and

Longitude 4-69

4.5.6. Correlation of Reported Shipwrecks with Other Seafloor

Objects 4-73

4.5.6.1. Spatial Association of “Unknown Wrecks” to Named

Shipwrecks 4-73

4.5.6.2. Spatial Association of Shipwrecks with “Objects” 4-74

4.5.6.3. Spatial Association of Shipwrecks to “Objects” Identified

 During Offshore MMS-Mandated Remote-Sensing Surveys 4-78

4.5.6.4. Spatial Association of Shipwrecks to Reported Hang

 Sites 4-84

5.0: CORRELATION OF SEAFLOOR HANG SITES, LEASE-BLOCKS

SURVEY DATA, AND SHIPWRECK ARCHIVAL DATA: FIELD

INVESTIGATIONS – TASK 2 5-1

5.1. Ground-truthing of Selected Targets 5-1

5.1.1. Investigative Methods 5-6
ix

5.1.2. Remote-Sensing Survey: Methods and Equipment 5-6

5.1.3. Sidescan Sonar Survey: Results 5-11

5.1.4. Diver Investigations: Methods 5-32

5.1.5. Diver Investigations: Results 5-37

5.2. Discussion 5-49

6.0: COMPARISON OF MARINE MAGNETOMETER TECHNOLOGIES

AND SURVEY LINE SPACING – TASK 3 6-1

6.1. In-Field Magnetometer Comparison Survey 6-3

6.1.1. Survey Research Design 6-3

6.1.1.1. Investigated Shipwrecks 6-3

6.1.1.2. Survey Requirement Parameters 6-6

6.1.1.2.1. Survey Line Spacing 6-7

6.1.1.2.2. Base Stations 6-9

6.1.1.2.3. Navigation/Positioning 6-10

6.1.1.2.4. Post Survey Data Analysis and Presentation 6-11

6.1.2. Survey Methodology 6-12

6.1.3. Daily Survey Procedures 6-15

6.1.4. Post-Survey Data Processing 6-24

6.2. Survey Results 6-24

6.2.1. Magnetometer Amplitude Comparisons 6-25

6.2.2. Line Spacing 6-44

6.2.3. Effects of Vessel Speed on Amplitude or Durations 6-65

6.2.4. Base Stations 6-66

6.3. Shipwreck Types and Magnetic Signatures 6-72

7.0: SUMMARY AND CONCLUSIONS 7-1

7.1. Introduction 7-1

7.2. Model of Shipwreck Occurrences in the GOMR: The 2001 Shipwreck

Model 7-1

7.2.1. Characteristics of the Vessels in the 2001 Shipwreck Model 7-2

7.2.2. Spatial Patterning in the 2001 Shipwreck Model 7-3

7.3. Identification of High Probability Areas in the GOMR 7-5

7.4. Correlation of Hangs and Reported Shipwrecks 7-15

7.5. Comparison of Magnetometer Technologies and Survey Line Spacing 7-16

8.0: REFERENCES CITED 8-1
xi

LIST OF FIGURES

FIGURE PAGE

1-1. Study area. 1-5

2-1. Shipwreck Information Form used in data compilation. 2-17

2-2. MMS lease areas in the Gulf of Mexico Region. 2-21

2-3. Microsoft Access entry form. 2-27

3-1. Position of the Loop Current on January 2, 1982. 3-7

3-2. Numbers of MMS-required remote sensing surveys conducted per lease

area as indicated by archaeological reports received by MMS/GOMR.

Data as of September 2001. 3-19

3-3. Sidescan sonar image of a shipwreck in the Ship Shoal Area. 3-28

3-4. Numbers of vessels discovered by MMS-required surveys per lease

area. Data as of September 2001. 3-33

3-5. Numbers of reported shipwrecks per lease area indicated by the

1989 shipwreck database developed by Garrison et al. (1989). 3-34

4-1. Shipwreck frequencies in the GOMR by 25-year intervals, 1625-2001.

Data from 2001 shipwreck database. 4-12

4-2. Comparison of shipwreck frequencies in the GOMR by 25-year intervals

provided in the 1989 shipwreck database and the 2001 shipwreck

database. 4-14

4-3. Proportional frequencies of shipwrecks by 10-year intervals for three sets

of data: the 1989 data for the entire Gulf of Mexico region, data from the

Dry Tortugas and vicinity and the 2001 shipwreck data from Federal waters

of the Gulf of Mexico developed in this study. Data prior to 1800 is

consolidated. 4-15

4-4. Reported losses per month for vessels in the study area. Data from 2001

shipwreck database. 4-19

4-5. Reported losses per month for All Vessels and those identified as Shrimping

Vessels (Fishing Vessels, Trawlers, and Shrimp Trawlers). Data from 2001

shipwreck database. 4-21

4-6. Vessel types in the 2001 shipwreck database containing five or more

entries. 4-24

4-7. Relative frequencies of modes of propulsion recorded for vessels in the 2001

shipwreck database. 4-26

4-8. Relative frequencies of known causes of loss for vessels in the 2001

shipwreck database. 4-32

4-9. Numbers of “Founderings” per month for vessels in the 2001 shipwreck

database. 4-34

4-10. Sediment zones and preservation potential in the study area (adapted from

Rezak et al. 1985). 4-41

4-11. Positions of all entries classified as “Vessels” in the 2001 shipwreck

database. 4-45
xii

FIGURE PAGE

4-12. Historic shipping routes in the Gulf of Mexico. A. 1763-1821; B.

1821-1862 (adapted from Garrison et al. 1989:Figure II-4). 4-47

4-13. Modern shipping routes in the Gulf of Mexico (adapted from Garrison

et al. 1989:Figure II-5). 4-48

4-14. Number of reported shipwrecks per MMS lease area. Data from

2001 shipwreck database. 4-49

4-15. Number of reported shipwrecks per 1,000 square miles per MMS lease

area. Data from 2001 shipwreck database. 4-51

4-16. Position of reported shipwreck, 1600-1649. 4-52

4-17. Positions of reported shipwrecks, 1700-1749. 4-53

4-18. Positions of reported shipwrecks, 1750-1799. 4-54

4-19. Positions of reported shipwrecks, 1800-1849. 4-55

4-20. Positions of reported shipwrecks, 1850-1899. 4-56

4-21. Positions of reported shipwrecks, 1900-1949. 4-57

4-22. Positions of reported shipwrecks, 1950-2002. 4-58

4-23. Positions of reported shipwrecks of unknown date. 4-59

4-24. Frequency of reported shipwrecks by reliability categories. 4-64

4-25. Positions of reported shipwrecks assigned Reliability Factor 1. 4-65

4-26. Positions of reported shipwrecks assigned Reliability Factor 2. 4-66

4-27. Positions of reported shipwrecks assigned Reliability Factor 3. 4-67

4-28. Positions of reported shipwrecks assigned Reliability Factor 4, poor or

unknown reliability data. 4-68

4-29. One degree units containing 25 or more vessels with Location Reliability

of 1, 2, or 3. 4-71

4-30. One-half degree units containing 25 or more vessels with Location

Reliability of 1, 2, or 3. 4-72

5-1. Lease block map illustrating lease blocks selected for investigation. 5-3

5-2. Lease block map with Target 5 survey area. Located in South Timbalier 20,

the survey area encompassed the recorded locations of one unknown object,

one unknown vessel and four hangs. 5-4

5-3. The 110-foot Sea Ox used for remote-sensing refinement of 20 hang

sites within the GOMR. 5-7

5-4. Differential global positioning system (DGPS) used for the project. 5-7

5-5. Marine Sonic Technology sidescan sonar system. 5-8

5-6. Sea Scan PC plotter window showing overlapping coverage between

survey lines. 5-10

5-7. Geometrics Model G-866 marine magnetometer console and towfish. 5-10

5-8. Target 1, SM 17 survey area. 5-12

5-9. Sidescan sonar image of 1, Target SM 17. 5-12

5-10. Target 2, SM 19 survey area. 5-13

5-11. Target 3, SM 211 survey area 5-14

5-12. Target 4, SM 231 survey area. 5-15

5-13. Sidescan sonar image of drag scars from trawling activity near Target 4,

SM 231. 5-16
xiii

FIGURE PAGE

5-14. Target 5, ST 20 survey area. 5-17

5-15. Sidescan sonar image of Target 5a, ST 20. 5-17

5-16. Sidescan sonar image of Target 5b, ST 20. 5-18

5-17. Target 6, ST 77 survey area. 5-19

5-18. Target 7, SS 71 and Target 8, SS 71 survey area. 5-20

5-19. Target 9, SS 73 survey area. 5-21

5-20. Sidescan sonar image of Target 9, SS 73, tentatively identified as a trawl

net. 5-21

5-21. Target 10, SS 109 survey area. 5-22

5-22. Target 11, PL 2 survey area. 5-23

5-23. Target 12, PL 5 survey area. 5-24

5-24. Target 13, PL 14 survey area. 5-24

5-25. Target 14, VR 35 survey area. 5-25

5-26. Sidescan sonar image of Target 14, VR 35, identified as three small rises

off the seafloor. 5-26

5-27. Target 15, VR 118 survey area. 5-27

5-28. Sidescan sonar image of Target 15, VR 118. 5-27

5-29. Target 16, EI 23 survey area. 5-28

5-30. Target 17, EI 42 survey area. 5-29

5-31. Sidescan sonar image from Target 17, EI 42 showing numerous linear

features. 5-29

5-32. Target 18, EI 53 survey area. 5-30

5-33. Sidescan sonar image from Target 18, EI 53 showing what appears to be a

depression in the seafloor. 5-31

5-34. Target 19, EI 68 and Target 20, EI 68 survey areas. 5-32

5-35. Buoy deployment during target refinement. 5-34

5-36. Support vessel M/V Enterprise. 5-35

5-37. Survey and dive platform vessel M/V Offshore Retriever. 5-35

5-38. Diver, employing Surface Supplied Air, returning from a dive. 5-36

5-39. Magnetic contour map of Target 1, SM 17. 5-37

5-40. Diver sketch of the remains of Target 1, SM 17, identified as the base to

an offshore rig. 5-38

5-41. Example of an offshore rig. 5-39

5-42. Magnetic contour map of Target 2, SM 19. 5-40

5-43. Magnetic contour map of Target 5a, ST 20 showing an absence of magnetic

material within the survey area. 5-41

5-44. Magnetic contour map of Target 5b, ST 20. 5-42

5-45. Magnetic contour map of Target 9, SS 73. 5-44

5-46. Magnetic contour map of Target 14, VR 35. 5-45

5-47. Magnetic contour map of Target 15, VR 118. 5-47

5-48. Magnetic contour map of Target 17, EI 42. 5-48

5-49. Magnetic contour map of Target 18, EI 53. 5-50

6-1. While not completely obsolete, the G-866 is no longer being produced and

is being replaced with newer models by many companies. 6-2
xiv

FIGURE PAGE

6-2. G-877 proton precession marine magnetometer used in Task 3. 6-2

6-3. Marine Magnetics’ “SeaSPY” Overhauser effect marine magnetometer

used in Task 3. 6-2

6-4. G-881 cesium marine magnetometer used in Task 3. 6-2

6-5. Image of the Josephine, a metal-hulled sidewheeler (courtesy of the

Mariner’s Museum, Newport News, Virginia). 6-4

6-6. Acoustic image of the Josephine wreck site. 6-5

6-7. Site plan for the Rhoda shipwreck (courtesy of John Rawls). 6-6

6-8. 25-meter survey interval grid with 19 tracklines to be run in a north to

south direction at 4 knots. 6-7

6-9. 30-meter survey interval grid with 11 tracklines to be run in a north to

south direction at both 4 and 7 knots. 6-8

6-10. Gulf Islands National Seashore near Ocean Springs, Mississippi, provided

an excellent location for the land base stations. 6-13

6-11. Geometrics G-856 land base station ready to collect data at Perdido

Key, Florida. 6-13

6-12. Marine Magnetics Sentinel base station being readied to collect data

in Perdido Key, Florida. 6-14

6-13. 32-foot charter boat Undertow III, based out of Pensacola, Florida. 6-15

6-14. Stern of the vessel Quester being readied for daily survey. 6-16

6-15. Deploying the Marine Magnetics Sentinel base station near the wreck of

the Rhoda, Pensacola, Florida. 6-17

6-16. Marine Magnetics Sentinel underwater base station prior to daily

deployment. 6-18

6-17. EdgeTech Coastal Acoustic Release Transponder (CART). 6-18

6-18. EdgeTech AMD200 Deck Unit Command Transmitter used to transmit

a unique code to the CART. 6-19

6-19. AMD200 transponder ready to place in the water. 6-20

6-20. Recovery of the Marine Magnetics Sentinel underwater base station,

EdgeTech CART, and float after finishing a day of survey. 6-20

6-21. Geometrics G-877 being prepared for survey. 6-21

6-22. Marine Magnetics SeaSPY magnetometer being deployed. 6-22

6-23. Digital readout used to monitor the G-866 sensor depth during the Task 3

survey. 6-23

6-24. Sidescan sonar image of the barge located near the wreck of the Josephine

(courtesy of MMS/GOMR). 6-24

6-25. Josephine 25-meter survey interval grid total gamma deviation graph. 6-26

6-26. Josephine 30-meter survey interval 4-knot grid total gamma deviation

graph. 6-27

6-27. Josephine 30-meter survey interval 7-knot grid total gamma deviation

graph. 6-28

6-28. Rhoda 25-meter survey interval grid total gamma deviation graph. 6-29

6-29. Rhoda 30-meter survey interval 4-knot grid total gamma deviation graph. 6-30

6-30. Rhoda 30-meter survey interval 7-knot grid total gamma deviation graph. 6-31
xv

FIGURE PAGE

6-31. Top: Josephine 100-m transect interval, 100-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-48

6-32. Top: Josephine 100-m transect interval, 10-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-49

6-33. Top: Josephine 50-m odd transect interval, 100-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-50

6-34. Top: Josephine 50-m even transect interval, 100-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-51

6-35. Top: Josephine 50-m odd transect interval, 10-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-52

6-36. Top: Josephine 50-m even transect interval, 10-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-53

6-37. Top: Josephine 30-m (4-knot) transect interval, 100-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-54

6-38. Top: Josephine 30-m (4-knot) transect interval, 10-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-55

6-39. Top: Rhoda 100-m transect interval, 100-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-56

6-40. Top: Rhoda 100-m transect interval, 10-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-57

6-41. Top: Rhoda 50-m odd transect interval, 100-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-58

6-42. Top: Rhoda 50-m even transect interval, 100-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-59

6-43. Top: Rhoda 50-m odd transect interval, 10-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-60

6-44. Top: Rhoda 50-m even transect interval, 10-gamma contour map; middle:

two-dimensional view; bottom: three-dimensional view. 6-61

6-45. Top: Rhoda 30-m (4-knot) transect interval, 100-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-62

6-46. Top: Rhoda 30-m (4-knot) transect interval, 10-gamma contour map;

middle: two-dimensional view; bottom: three-dimensional view. 6-63

6-47. Strip charts for each of the three base station readings collected during the

survey of the Josephine with the G-881. 6-68

6-48. Josephine 30-meter survey interval 4-knot grid uncorrected data contoured

with 100-gamma interval. 6-70

6-49. Josephine 30-meter survey interval 4-knot grid G-856 corrected data

contoured with 100-gamma interval. 6-70

6-50. Josephine 30-meter survey interval 4-knot grid Sentinel corrected data

contoured with 100-gamma interval. 6-71

7-1. Historic shipwreck high probability lease blocks identified in the GOMR

in the 1989 study. 7-7

7-2. Overall shipwreck potentials by lease areas. 7-10

7-3. Historic shipwreck high probability lease blocks identified in the GOMR in

the present study. 7-13
xvii

LIST OF TABLES

TABLE PAGE

2-1. Codes Denoting Cause of Loss Categories in the Shipwreck Information

Form 2-20

2-2. MMS Lease Areas in the Gulf of Mexico Region 2-22

3-1. Distance Between Reported Location of Loss and Actual Location of

Identified Shipwrecks in the GOMR 3-23

3-2. High-Probability Lease Blocks that have been Surveyed for Historic

Shipwrecks as of September 2001 3-25

3-3. Vessels Identified by MMS Lease Area Surveys 3-28

3-4. “Objects” Identified by MMS Lease Area Surveys 3-31

3-5. Chi Square Analysis of GOMR Lease Block Survey Results 3-36

4-1. Differences Between Number of Shipwrecks Reported in 1989 Study and

This Study by Lease Area 4-8

4-2. Types of Vessels in the 2001 Shipwreck Database 4-22

4-3. Reported Causes of Loss 4-32

4-4. Unnamed Vessels that Lie within 500 m (1,640 feet) of Named

Vessels 4-75

4-5. Vessels that Lie within 500 m (1,640 feet) of Items Classified as

“Objects” 4-79

4-6. Vessels that Lie within 2.4 km (1.5 miles) of “Objects” Identified in

MMS-Mandated Surveys 4-83

4-7. Vessels that Lie within 200 m (650 feet) of Reported Hangs 4-85

5-1. Task 2 Targets Selected for Investigation 5-2

5-2. Targets Slated for Diver Investigation 5-33

6-1. Land Base Station Coordinates During the Task 3 Survey 6-12

6-2. Schedule of Task 3 Operations 6-16

6-3. Instrument Layback 6-21

6-4. Josephine Line Data for All Grids and Instruments 6-32

6-5. Rhoda Line Data for All Grids and Instruments 6-36

6-6. Survey Transect Interval Detection Rates by Instrument 6-45

6-7. Comparison of Duration and Amplitudes 6-66

6-8. Comparison of G-881 Data Values for Josephine 25-Meter Survey

Interval Grid 6-71

6-9. Compilation of Magnetic Data from Various Sources 6-75

7-1. Shipwreck Occurrence and Preservation Potentials for MMS Lease

Areas 7-8
1.0: INTRODUCTION

In 1973, the Federal government initiated a program to protect cultural resources

existing on the submerged lands of the Outer Continental Shelf (OCS) of the United

States from the effects of Federally funded and permitted activities. This program arose

out of a variety of legislation enacted to ensure the proper management and protection of

the nation’s cultural heritage. The most pertinent of these laws were the National

Historic Preservation Act of 1966, as amended, the National Environmental Policy Act

(1969), and the OCS Lands Act Amendments of 1978. The program was initially placed

under the authority of the Bureau of Land Management (BLM) and the United States

Geological Survey (USGS), and of particular concern was the impact that Federally

permitted mineral exploitation—principally oil and gas exploration and production—and

Federally funded projects might have on cultural properties on the OCS. Section

206(g)(3) of the OCS Lands Act Amendments of 1978 states specifically that “such

exploration (oil and gas) will not. . .disturb any site, structure, or object of historical or

archaeological significance.” In 1982 the Minerals Management Service (MMS), United

States Department of the Interior, gained the cultural resources management

responsibilities of OCS lands formerly held by the BLM and USGS and has administered

the program since that time.

When the Federal government initiated its management of cultural resources on

the OCS, it was recognized that a variety of types of cultural properties might exist there.

However, little was known about the nature, distribution or condition of these properties

that would be useful in developing strategies for their identification, assessment and

management. As a result, several regional baseline studies were initiated to collect the

information needed to develop and implement a reasonable cultural resources protection

plan for the OCS. The purpose of these studies has been to collect information on

archaeological resources on the OCS that can then be used to establish guidelines for the

proper identification and protection of these resources. The first of these baseline studies

was conducted for the Gulf of Mexico in 1977. Entitled Cultural Resources Evaluation

of the Northern Gulf of Mexico Continental Shelf (Coastal Environments, Inc. 1977), this

study considered historic resources, principally shipwrecks, as well as prehistoric

resources in the development of generalized statements about the nature, distribution and

preservation potential of these types of sites across the Gulf of Mexico OCS.

Subsequently similar baseline studies have been conducted for the remainder of the OCS

area of the United States. These have included the Atlantic coast from the Bay of Fundy

to Cape Hatteras by Harvard University (Bourque 1979); the Atlantic coast from Cape

Hatteras to Key West, Florida by Science Applications, Inc. (1981); the Alaskan area by

the University of Alaska, Fairbanks (Dixon et al. 1986); the Pacific coast south of Morro

Bay, California, by Science Applications, Inc. (1977) and PS Associates (Pierson et al.

1987); and the Pacific coast from Morro Bay north to the Canadian border (Espey,

Huston & Associates, Inc. 1990).

These studies have been used by MMS to develop strategies and guidelines for

addressing cultural resources relative to various types of permitted and funded activities
1-2

undertaken on the OCS. The Gulf of Mexico Region (GOMR) has certainly been most

critical in the entire management program, simply because of the nature of mineral

exploitation there. Thousands of oil and gas wells have been drilled, thousands of miles

of pipelines have been laid and other facilities and features comprising the infrastructure

of the mineral extraction industry have been developed. All of these activities are

ongoing and have a potential for impacting cultural remains that might exist on the vast

area of submerged lands of the Gulf of Mexico. As a result, MMS established

requirements for pre-development survey of specific “lease blocks” and pipeline rightsof-way in the Gulf of Mexico using remote-sensing technologies. These “lease blocks”

represent the 3-mile-square units into which the entire GOMR has been divided for

leasing purposes. The requirements for lease block and pipeline surveys and the resulting

reports have been codified and updated in a series of Notices to Lessees (NTL) that have

been issued since the mid-1970s. In addition, MMS has sponsored two studies in the

Gulf of Mexico region designed to enhance and update the information and

recommendations developed in the 1977 Coastal Environments, Inc. baseline study. One

of these studies was concerned specifically with prehistoric cultural resources on the Gulf

of Mexico OCS (Pearson et al. 1986). Using previously published geological

information, much of it derived from remote-sensing surveys conducted relative to the

MMS lease block survey requirements, as well as collected seismic and vibracore data,

this study developed a model of prehistoric site occurrence and preservation in the area of

the offshore Sabine River valley at the border of Texas and Louisiana. The other study,

conducted by the Texas A&M Research Foundation, was concerned with historic

shipwreck sites on the Gulf of Mexico OCS (Garrison et al. 1989). This study involved

two principal tasks: 1) the reevaluation of the high-probability zone for shipwreck

occurrences that had been identified as Cultural Resource Management Zone 1 in the

1977 Coastal Environments, Inc. baseline study, and 2) assess the use of the remotesensing equipment (magnetometer and sidescan sonar) in terms of the survey strategy

employed and the data interpretation then being used in MMS-mandated lease block

surveys. This study collected historical information on shipwrecks from numerous

sources, characterized the nature of this sample of shipwrecks, correlated the distribution

of shipwrecks against a variety of variables (e.g., historic shipping routes, current and

wind patterns, reef locations, etc.), and explored the preservation potential of wrecks in

various natural settings in the Gulf of Mexico. These data were used to develop

statements about shipwreck occurrences by identifying areas in the GOMR that had high,

moderate and low probabilities for the presence of historic shipwrecks. The second task

of the Garrison et al. (1989) study involved an in-field remote-sensing survey of areas

within three lease blocks offshore of Texas utilizing different line spacings. The

objective was to “establish an interpretive framework to characterize unidentified

magnetic anomalies and sidescan sonar contacts” (Garrison et al. 1989:1-4). Of specific

interest was the use of the magnetometer in detecting objects at various line spacings and

in trying to “characterize and differentiate, with a high degree of confidence,” differences

between metallic debris and potential shipwrecks (Garrison et al. 1989:II-226).

The MMS has used the results of the Coastal Environments, Inc. 1977 study and,

more specifically, the Garrison et al. 1989 effort to determine where remote-sensing

surveys for historic shipwrecks will be required in the Gulf of Mexico. Specifically, this
1-3

information has been used to identify individual 3-mile-square lease blocks and groups of

lease blocks that have a high-probability of containing historic shipwrecks and, further, to

develop remote-sensing survey strategies for these lease blocks. As of the summer of

2000, 2835 archaeological reports had been received by MMS of remote-sensing surveys

conducted within lease blocks and along pipeline rights-of-way in the GOMR. These

surveys had resulted in the discovery of a number of shipwrecks. However, over the

years deficiencies in the model of wreck distributions and occurrences have been noted,

plus new remote-sensing technologies have been developed that have application to the

MMS program of offshore surveys. In June of 2000, the Gulf of Mexico OCS Region of

MMS in New Orleans awarded a contract to Panamerican Consultants, of Memphis,

Tennessee to reevaluate and refine the work of the previous studies on historic

shipwrecks in the Gulf of Mexico, particularly the Garrison et al. (1989) study. The

results of this study are presented here and they represent an effort to enhance the

management of historic shipwrecks on the OCS in the Gulf of Mexico through a revision

of the model of shipwreck occurrences and a refinement of the survey strategies and

instrumentation used in their discovery.

1.1. Study Objectives

The objectives of this study were defined in the Request for Proposal issued by

MMS in April 2000. These objectives are:

1. To update and expand the existing MMS GOMR shipwreck database by

examining primary and secondary sources for shipwreck information. The

existing shipwreck database will be expanded to include specific identifying

characteristics of vessels potentially located on the OCS.

2. To determine the spatial correlation between: 1) shipwreck locations in the

updated shipwreck database; 2) recorded seafloor hang sites listed on the

MMS GOMR/NOAA sponsored “Fisherman’s Contingency Fund” or other

published or private fisherman hang books; and 3) sidescan sonar targets and

anomalies representing potential shipwrecks identified during previous OCS

lease block surveys. Then, to ground-truth selected locations where hang sites

and reported shipwreck locations appear to correlate to determine if hang sites

are shipwrecks.

3. To conduct a marine magnetometer survey over several verified shipwreck

sites using both the “industry-standard” proton precession magnetometer and

the new cesium magnetometer instrumentation to determine whether there is a

significant difference in their performance in detecting shipwrecks.

4. Based on the results from objectives (1), (2), and (3) prepare a revised

predictive model for shipwrecks in the GOMR, and recommend survey

instrumentation and strategies that would be the most effective in locating

these shipwrecks.
1-4

In order to achieve the established objectives of this study, the work effort was

divided into four principal tasks as noted in the MMS Request for Proposal. These were:

Task 1. Archival Data Collection

Task 2. Correlation of Seafloor Hang Sites, Lease Block Survey Data, and

Shipwreck Archival Data

Task 3. Comparison of Marine Magnetometer Technologies and Survey Line

Spacing

Task 4. Data Synthesis, Development of a Shipwreck Predictive Model, Analysis

of Magnetometer Technology, and Final Report of Findings

Details on the conduct of these tasks are presented in the following chapters.

1.2. Study Area

The geographic area considered in this study consists of those lands in the Gulf of

Mexico that fall under the authority of the MMS, generally referred to as the Gulf of

Mexico Region or GOMR. As shown in Figure 1-1, the study area coincides with the

extent of the United States Exclusive Economic Zone (EEZ). The EEZ consists of those

lands now incorporated into the “lease block” system used by MMS in its management of

mineral exploitation in the Gulf and incorporates most of the Gulf of Mexico north of

approximately 24o north latitude. For the purposes of historical and archival research,

data was collected on shipwrecks in the Gulf north of 24o and roughly between 81o and

98o west longitudes.

Analysis of shipwreck data and the data from MMS offshore surveys was

confined to the area of Federal lease blocks shown in Figure 1-1. The study area includes

only Federal waters and does not encompass the waters belonging to the five bordering

Gulf states. The position of these state boundaries varies. In Texas, the state boundary is

located three “leagues” from shore, equivalent to nine nautical miles or 10.36 statute

miles (16.67 km).1 For the states of Louisiana, Mississippi and Alabama, the boundary is

three statute miles (4.8 km) from shore, while the Florida state boundary in the Gulf of

Mexico is nine nautical miles or 10.36 statute miles (16.67 km) from shore. The

exclusion of state waters from consideration does have significant consequences when

dealing with historic shipwrecks in the region. It is generally recognized that wrecks tend

to concentrate along shorelines for very logical reasons. These are related to the obvious

hazards found in shallow, nearshore waters, the fact that vessels are often driven ashore

by weather conditions, plus the fact that the activities of vessels tend to be spatially

concentrated in nearshore areas around harbors and ports. The two previous studies of

historic shipwrecks in the Gulf of Mexico by Coastal Environments, Inc. (1977) and

Garrison et al. (1989) both demonstrated that the majority of recorded historic wrecks in

 

1 . English measurements are commonly used in this report because almost all activities conducted in the

GOMR rely on this system. This includes the basic leasing unit, the 3-mile-square lease block, around

which most remote sensing surveys are designed and the coordinate system (state plane or UTM in feet)

used in survey control and in reports of findings. Metric equivalents are provided where appropriate.
1-5

the Gulf of Mexico occurred in state waters. Thus, the elimination of state waters

removes a significant percentage of reported Gulf wrecks from the sample used in this

analysis.

20o

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW

ORLEANS GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

YUCATAN

98o 95o 90o 85o 81o

SOUTHERN BOUNDARY OF STUDY AREA FEDERAL LEASE BLOCKS

GULF OF MEXICO

Figure 1-1. Study area.

1.3. Report Organization and Presentation of Data

This report consists of two main sections. The first section deals principally with

the historical record of shipwrecks in the GOMR and the refinement and revision of the

list of shipwrecks currently being used by MMS. This section includes background

discussions on the present model of shipwreck occurrences in the GOMR and how that

model guides MMS offshore surveys. Also presented are discussions on the list of

wrecks developed in the present study. These discussions consider the rationale and

methods used for developing this list and present information on the characteristics of

this sample of known shipwrecks, including patterns of spatial distribution. This section

also provides discussions on the association of unidentified items and objects, such as

unidentified snags, objects, etc., with reported wrecks under the assumption that some of

these currently unidentified objects might, in fact, be historic wrecks.

A considerable amount of the information developed in this study is presented in

digital format, as stipulated in the MMS Scope of Work (SOW). Specifically, all of the

N
1-6

data on wrecks, unidentified objects, snags, and the like have been compiled into a

database using the program Microsoft Access and is presented in a Geographic

Information System (GIS) format using the program ArcView. These digitized data

constitute a significant segment of this report, and much of the data on wreck

distributions, occurrences and correlations are presented as maps, overlays, etc. only in a

digital format in ArcView. The objective is to provide MMS management personal with

data in an immediately useful GIS format to aid them in decision making. Textual

discussions do include maps, tables, etc., as needed to support discussions; however, in

some cases these consist only of portions of complete visuals presented in GIS format.

The second main section of this report deals with the field investigations

conducted in this study. This includes discussions on remote-sensing survey and diving

investigations undertaken to determine the identity of a series of hang sites selected as

potential wreck locations. These dive targets were selected from clusters of hangs that

could represent unreported vessel remains. In some cases these targets roughly

corresponded with reported vessel losses.

The majority of the second section presents the results of field trials in which old

and new magnetometer models were run on three survey grids of varying intervals and

speed over two shipwrecks in order to assess how each instrument recorded the same

wreck site, and if differences were present, determine if these findings predicated changes

to the current MMS GOMR survey methodology.
2.0: RESEARCH APPROACH – TASK 1

2.1. Background Research

The initial task of this study was to “update and expand the existing MMS GOMR

shipwreck database” through the examination of pertinent sources on shipwrecks. This

chapter provides information on the approach used to accomplish this task, principally,

by providing information on the various sources utilized, the rationale for selecting these

sources, and various shortcomings and biases that might exist in these sources.

The present “shipwreck database” used by MMS is the one developed by the

Garrison et al. (1989) study and it represented our point of departure. The objective was

not to go back and duplicate the work conducted by Garrison et al., but to expand upon

their findings where considered appropriate and productive. The Garrison et al. study

involved a fairly comprehensive examination of archival sources, publications and other

resources dealing with the history of navigation and with shipwrecks in the Gulf of

Mexico. Initially, no effort was made to reexamine all of the sources they used,

particularly the archival sources dealing with the early historic period. Rather, the first

effort of the background research was to examine pertinent publications, databases, etc.,

that have been produced since the 1989 study and to examine resources that they had not

utilized. For example, one resource that the Garrison et al. study did not examine in

detail is the large body of information found in the reports resulting from cultural

resources management (CRM) studies undertaken in the coastal regions of the various

states surrounding the Gulf. Examination of these reports involved visiting the state

offices holding these studies in the five states that border the Gulf of Mexico.

Some amount of archaeological research on historic shipwrecks in the Gulf of

Mexico has been conducted since 1989, although most of this is related to wrecks lying in

state waters. These studies were examined for the information they provided on

historical background and, particularly, on aspects of shipwreck preservation potentials

and processes of wreck site formation in various marine settings.

The Garrison et al. study relied on several computerized databases of shipwrecks

that were extant at the time. The present study has placed an even greater reliance on

these types of databases because they are becoming the principal medium for

documenting and archiving information on vessel losses in the Gulf of Mexico and

elsewhere. Some of the advantages, and perils, in this trend to collect and consolidate

shipwreck information into an increasingly smaller number of databases are discussed

below.

Since the Garrison et al. study, resources on shipwrecks and historic vessels have

proliferated on the Internet. A large number of Internet sites containing shipwreck as

well as general maritime history information were examined during this study. Most

duplicated information found elsewhere, but some proved to be useful.
2-2

Another valuable source of information used in this study, but not used by

Garrison et al., are the results of MMS-mandated remote-sensing surveys conducted in

the GOMR. As noted, over 2,800 survey reports have been received by the MMS since

the start of the archaeological survey program. From these reports MMS personnel

selected those that identified known or suspected wrecks or unidentified objects and

provided this information to the authors. This information expands considerably the

number of verified wrecks in the study area, although most are unidentified at present.

Also, the content of these reports sometimes includes valuable background historic

information. As is discussed more fully below, the data from these remote-sensing

surveys constitute the principal means by which the present model of shipwreck

distributions in the GOMR can be tested.

The information collected from these various sources was used to expand the

present MMS shipwreck database, plus their examination helped identify areas where

information in that database needed to be reassessed. This reassessment did involve

going back to some of the original sources used by Garrison et al. to clarify and/or to

collect additional information to incorporate in an expanded shipwreck database that

included information on vessel characteristics.

2.2. Sources of Data

Garrison et al. (1989 II-11) identified five major sources of shipwreck information

in their study. These were: 1) databanks; 2) documents; 3) directories; 4) descriptions;

and 5) secondary literary sources. Some of these same general categories of data sources

were examined in the present study, although the intensity and scope with which they

were used differed from the effort expended by Garrison et al. because of the factors

mentioned above. The following discussions consider the principal sources used in the

present study if they differed from those listed by Garrison et al. (1989) or, as in the case

of computerized databases, they contained significantly greater information than they did

in 1989.

2.2.1. Computerized Databases

Garrison et al. (1989:II-12) examined several computer-based data files or

databases in their study, which they identified as “data banks.” That study did note that

the availability of these computer databases was a great advantage over the earlier

Coastal Environments, Inc. 1977 study. Since 1989, most of the shipwreck databases

used by Garrison et al. have been expanded, plus several new databases with shipwreck

information have been developed. These databases represent efforts to systematically

arrange shipwreck information and offer significant advantages in information storage as

well as in its manipulation. However, these databases do have their shortcomings as is

pointed out in the following discussions. One advantage of some of these databases

(particularly those maintained by the U.S. Coast Guard and the National Oceanic and

Atmospheric Administration [NOAA]), at least for the present study area, is that they

include almost all vessels lost in the past couple of decades, somewhat lessening the need

to search widely for wreck information in other sources.
2-3

Minerals Management Service (MMS) Databases. The Minerals Management

Service office in New Orleans provided two electronic databases that were used in this

study. Of central importance is the list of wrecks in the GOMR developed during the

Garrison et al. (1989) study. This list, provided in Microsoft Excel format and containing

1,469 entries, represents the baseline of shipwreck information upon which the present

study built. This database includes the names of vessels (as well as several

“obstructions,” “fish havens,” etc.), their location in geographic coordinates, the offshore

lease block within which they fall, and the principal source from which the wreck

information was obtained. Miscellaneous information in the database includes a unique

identification number and an identification number assigned by the original source, if

applicable.

Another electronic database obtained from the MMS was the listing of snags and

hangs maintained as part of the Fisherman’s Gear Compensation Fund. These represent

hangs in the Gulf of Mexico identified by fishermen, principally shrimpers, as locations

where their nets were caught and damaged or lost. Although this list is not specifically

related to shipwrecks, it is known that wrecks, as well as other objects, exposed on the

seafloor in the Gulf of Mexico are often draped with shrimp nets that have been snagged

and lost on the wreck (James et al. 1991a; 1991b). Thus, snags and hangs might very

well mark the location of historic vessel remains. Addressing this question was one of

the objectives of this study and is discussed in more detail in later sections.

National Imagery and Mapping Agency (NIMA). NIMA is an agency of the

Department of Defense that maintains a variety of databases relating to mapped

resources, including shipwrecks, hangs, obstructions, well heads, platforms, etc. They

now serve as the central government agency for gathering these resources and providing

them to the public. NIMA collects information from a wide variety of public and private

sources, including the U.S. Coast Guard (USCG) and the Naval Oceanographic (formerly

Hydrographic) Office. Their principal database on shipwrecks is known as the NonSubmarine Contact (NSC) Database and it includes information provided to them from

various agencies and individuals. They do not collect field data or evaluate it. NIMA

now maintains the old Hangs and Obstructions file formerly kept by the Naval

Hydrographic Office (HO) and they receive all wreck and hang and obstruction data from

the USCG and the NOAA, although these last two agencies also maintain and provide to

the public their own databases. The NIMA database also includes incomplete

information from the old Merchant Vessels of the United States lists formerly maintained

by various government agencies, including the USCG. The NIMA Non-Submarine

Contact Database used in this study was obtained in October 2000 in Microsoft Excel

format and contained 1,234 entries for the Gulf of Mexico area. These included named

vessels as well as unknown vessels and objects, such as debris, wellheads and the like.

Variables for each entry are: classification (unclassified, confidential and secret), a

unique identification number, name, nationality, contact type (i.e., type of vessel or

object), flag of sinking agent, type of sinking agent, position evaluation, source of

information, location (latitude/longitude), source of depth information, depth in meters,

date of sinking, date of information and gross tonnage.
2-4

The NIMA database was not available when the Garrison et al. study was

conducted, but that study did utilize the Hangs and Obstructions (HO) file and the NOAA

databases that have been incorporated into the NIMA records.

United States Coast Guard (USCG). The United States Coast Guard maintains

a large database of shipwrecks, hangs, obstructions, etc., located in American waters

principally related to navigation procedures, hazards etc. The database used in this study

was obtained from the U.S. Coast Guard, Eighth Coast Guard District, New Orleans,

Chief of Aids to Navigation and consisted of all entries falling within the Gulf of Mexico

region. The database is in Microsoft Access (Access) format and contained 6,491 entries

as of the end of 2000. The USCG collects data itself as well as from a variety of other

sources. The USCG also does evaluation of some reported targets, particularly as they

might be related to navigation hazards that require removal or marking. The database is

of particular value because it includes information received from private sources relating

to lost vessels, discovered sunken or wrecked vessels, obstructions, etc. A very large

number of the losses contained in the USCG database fall within state waters and, thus,

were eliminated from the final list of wrecks and objects compiled for the study area.

Variables included for each entry in the USCG database are: a unique identification

number, a file number, name of vessel or object, length in feet, geographic position

(latitude/longitude), “status” (e.g., whether or not the entry was sunk, removed, salvaged,

a hazard, etc.), waterway where located (e.g., Gulf, GOM, Mississippi River, etc.), depth

in feet, remarks, state located in or near, and date of loss or report. This last entry on date

is of particular concern because while it may be the actual sinking date of a vessel, it also

might be the date the report of the loss was received by the USCG or the date the sunken

vessel or object was found and reported. In this last instance, the date given in the USCG

entry might be many years after the loss actually occurred. There is no way to

distinguish among these various dates in the USCG records, and clarification usually

requires comparisons with other sources of information.

The Coast Guard database does not include a variable indicating the known or

presumed “reliability” or accuracy of the positions provided. Thus, unless the entry can

be correlated with another source or database, it is often impossible to know how reliable

the locations of loss given in the USCG database are. As is discussed in more detail later,

the question of “reliability” of location is one of the most critical factors to be considered

when developing statements about a sample of wrecks within a given area, whether this

entails predictive statements about the spatial patterning of wrecks or the correlation of

reported wreck locations with spatially defined factors (e.g., hurricane tracks, natural

obstructions and hazards, etc.). Most researchers recognize that errors certainly exist in

the reliability of historically reported wreck locations, but the tendency has been to ignore

this problem when making final statements about wreck distributions or to rely on

assumptions about reliability that have very little basis in fact.

National Oceanic and Atmospheric Administration (NOAA). NOAA

maintains a database of wrecks and obstructions known as the Wrecks and Obstructions

File and in electronic form as the Automated Wrecks and Obstructions Information

System (AWOIS). The database consists principally of items that the National Ocean
2-5

Survey, a branch of NOAA, considers hazards to navigation. The full database is

available in digital form on CD and in a searchable form on the Internet. The online

version does not include all of the variables maintained by NOAA, but these are included

in the electronic version available on CD in Access format. The Access version of the

AWOIS database used in this study was obtained in July 2000 and contained 3,515

entries falling within the Gulf of Mexico area. This is probably the most widely used of

the computerized databases by the public and by the offshore oil and gas industry in

identifying targets or in assessing the probability of historic wreck occurrence in specific

areas. Individual files for each vessel include several categories of information, each

encompassing several variables. These include a category of general record information

that contains a unique record number, “vessel terms” (i.e., the name of the vessel or

identity of the object), the identity of the NOAA chart on which the object is plotted, and

the water depth at the object. A second category of data includes position information,

including the geographic coordinates, the datum used, and a three-level assessment of the

quality (i.e., reliability) of the position information (poor, low, and high). The third

category of data consists of “Project” information and includes a section on “History”

and one on “Field Notes.” This section provides available descriptive information on the

vessel or object and information on examinations undertaken by NOAA or other

agencies. For example, the “History” section might include the dimensions and cause of

loss of a vessel, or might provide information on an examination of the reported loss site.

A typical example of such an entry might read “Side Scan Sonar Negative. Evaluator

Recommends Deleting From Charts” and provide the date of the examination.

Additional entries on the AWOIS database include reference (i.e., the source of the

information used), year sunk, and a unique system number. This is one of the computerbased databases used by Garrison et al., but at the time it was provided only in an ASCII

format.

Texas Antiquities Shipwreck File (TAC). The Texas Antiquities Committee in

Austin, Texas, maintains this database. Presently this shipwreck file consists of a listing

of approximately 2,400 entries in Access format. However, this computerized database

includes only partial information on most entries. Complete entries are found only in the

paper version of the shipwreck file. Categories included in this file are: name of vessel,

year lost, position, Texas state lease block number and vessel type. The TAC also

maintains a series of maps on which all wrecks in the file are plotted. Many of the entries

in the database are derived from secondary sources and the vast majority of vessels in the

database fall in state waters.

The Florida Shipwreck File, Bureau of Archaeological Research (BAR). This

is the computerized shipwreck file maintained by the Bureau of Archaeological Research,

Florida Division of Historic Resources, Tallahassee. When this database was examined

in August 2000 it contained 282 entries of wrecks reported in the Gulf waters of the state.

The number encompasses only recorded wreck sites; historic accounts of vessel losses

maintained by BAR were not reviewed because these had already been examined by

Garrison et al. (1989:II-12). Information provided for each wreck entry includes site

number and name, location, age of vessel, and nationality when known. The vast

majority of the wreck sites in the BAR database fall in state waters, but the position
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information on many is questionable. This is because some of the wreck sites represent

unverified reports, plus, in the past some wreck positions were purposefully made overly

vague in an effort to deter looting.

Texas A&M University Hang File. The Texas A&M University Hang File

consists of a very large database of hang locations that have been collected by personnel

with the Texas A&M Sea Grant Program over many years. Most of the information has

been collected from shrimpers and consists of their reports on the location and,

sometimes, identity of hangs they have encountered. The listing includes approximately

13,000 records in state and Federal waters from about the mouth of the Mississippi River

westward to the Rio Grande. The Hang File is most commonly provided in a book form,

but in August 2000 a computerized version of the file was obtained for this study. The

database has not been updated in several years, plus almost all of the position information

was obtained with LORAN systems, which can incorporate inaccuracies on the order of a

quarter of a mile or more. Despite these problems, this database forms the largest

collection of hang information in the Gulf of Mexico, making it extremely useful for

correlating hang locations with shipwrecks. The hang database was compiled in a

Microsoft Word format, but a version converted to Excel was obtained for this study.

Artificial Reef Data File (Gulf States Artificial Reef Committee). A

computerized database containing information on artificial reefs in the Gulf of Mexico

was obtained in WordPerfect format from the Gulf States Artificial Reef Committee,

Gulf States Marine Fisheries Commission, Ocean Springs, Mississippi. When obtained

in November 2000 the database contained 143 entries but was still in the process of being

compiled and contains inaccuracies, duplications, and omissions (Ron Lukens, personal

communication 2000). Variables for each entry include the state and county in which the

artificial reef is permitted, the state permit number, the permit holder’s name and address,

whether the permit is active, the name of the reef, the offshore lease block in which the

reef is located, geographic coordinates of the reef, size of the reef in acres, minimum

depth, maximum depth, maximum relief of the reef, jurisdiction (state or Federal), the

date the reef was established and the material that forms the reef. Categories of material

include automobiles, boats, steel-hulled vessels, tires, oil and gas platforms, military

tanks, rock, concrete, etc. Those reefs reported to contain vessels of various types were

of interest to the present study.

Florida Division of Marine Fisheries Artificial Reef Database (FDMF). A

computerized database of artificial reefs off the Florida coast was obtained from the

Artificial Reef Program, Division of Marine Fisheries, Florida Fish and Wildlife

Conservation Commission (Florida Division of Marine Fisheries [FDMF] 2003). This

database has been recently made available in electronic format and was obtained in

February 2003. The database contains several thousand entries and includes artificial

reefs that fall in Florida state waters as well as those that fall in Federal waters. Variables

for each entry include the county in which the artificial reef is permitted, the name of the

reef, the date the reef was established, the material that forms the reef, the geographic

coordinates of the reef, and the water depth and relief of the reef. Categories of reef

materials include vessels of many types, automobiles, tires, oil and gas platforms,
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military tanks, bridge components, rock, concrete, etc. All vessels identified as

components of artificial reefs in Federal waters in this database were incorporated into

the shipwreck database developed in this study.

Miscellaneous Computer Databases. Several other computer-based databases

were examined for this study, but provided relatively little useful information. Among

these is a listing of shipwrecks occurring within the boundaries of the New Orleans

District, U.S. Army Corps of Engineers originally compiled in 1989 (Pearson et al. 1989).

Originally compiled in Dbase III format, this database contains approximately 1,800

reported and known vessel losses within the New Orleans District, which encompasses

most of southern Louisiana, including the inshore areas along the Gulf of Mexico. Most

of this file has been incorporated into the computerized state site file system at the

Division of Archaeology, Louisiana Department of Culture, Recreation and Tourism in

Baton Rouge. With only a few questionable exceptions, all of the vessels listed in this

database fall in state waters. The Galveston District, U.S. Army Corps of Engineers

maintains a listing of “Wrecks and Obstructions” containing over 600 entries. This list

has been developed mainly for navigation and dredging purposes and all of the vessels

and objects included appear to fall in state waters. The Mobile District and the

Jacksonville District, whose boundaries include Gulf of Mexico waters, were contacted,

but neither organization maintains any organized database of reported wrecks.

2.2.2. Internet Resources

Today there is a huge body of information on shipwrecks and maritime

archaeology and history available at sites on the world wide web, none of which was

available in 1989. For this study, searches were made on the Internet (normally using the

search engine Google) using a variety of keywords and keyword combinations, such as

shipwrecks, wrecks, Gulf of Mexico, marine disasters, underwater archaeology, maritime

history, etc. Many dozens of sites of interest were discovered, although the quality and

reliability of the information provided varied considerably. These include privately

maintained sites as well as sites for almost all of the public agencies and public and

private organizations, museums and educational institutions that collect or hold

information on shipwrecks. Many of these organizations have searchable databases

linked to their records or libraries. The Mariners Museum Research Library in Newport

News, Virginia, for example, enables online searches of its library and photograph

collections. Other agencies provide numerous links to other sites with pertinent

information. Florida State University, for example, provides links to a variety of sites

relating to underwater archaeology and shipwrecks. The number of shipwreck-related

Internet sites and the amount of information provided on Internet sites continues to grow.

While these Internet sources are extremely useful, it was found that most sites duplicated

information found elsewhere and many contain erroneous or non-verified information.

All must be used with caution. It is impossible to list all of the Internet sites that relate to

shipwrecks, but some of the non-agency and non-organization sites examined are

mentioned here.
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Several Internet sites strictly provide lists of wrecks and/or information on wreck

sites. These include sites such as “Lloyd’s Merchant Shipping Losses and Shipwrecks”

(www.lr.org/information/maritime/m-merchant.html) and “Wrecks.Net”

(www.wrecks.net), although the latter lists principally vessels lost in the Great Lakes.

Commonly these types of sites use secondary sources and databases, such as the AWOIS

records, for their information. There are also fee-based websites that sell information on

sunken vessels, such as “International Registry of Sunken Ships”

(http://users.accesscomm.ca/shipwreck/) and sites that provide more general information

on vessels, such as “Merchant Vessel Database” (www.boatman.com/mv) which, for a

fee, provides information on merchant and recreational vessels documented by the United

States Coast Guard. There are also a number of websites intended mainly for sport divers

and/or treasure hunters that provide information on wrecks considered to be interesting

dive sites. Most of these deal with Florida wrecks (e.g., MBT Divers webpage:

www.mbtdivers.com/NUMBERSH.htm); Association of Underwater Explorers webpage:

www.mikey.net/aue), but some, such as Texas Diver (www.texasdiver.com), provide

information for other areas. There are a few web pages that provide links to other sites

containing wreck information, such as “Shipwreck & Marine Disaster Links”

(www.home.gci.net/~alaskapi/success/shipwreck).

A large number of websites are designed principally to provide historical and

descriptive information on vessels, but commonly include information on losses. These

are among the most useful of the Internet sources because they often incorporate

descriptive information on vessels that is not included in the commonly available wreck

lists. Sites in this category include “Palmer List of Merchant Vessels”

(www.geocities.com/mppraetorius/intro-com) that contains an extensive listing of sail

and steam merchant vessels; “Haze Gray & Underway” (www.hazegray.org), a site

related to naval history and photography that includes fleet lists, vessel descriptions,

photographs, and the Dictionary of American Naval Fighting Ships containing the

histories of U.S. Navy vessels; “Schoonerman: Schooner and Tall Sailing Ships”

(www.schoonerman.com) that contains a large listing of sailing vessels with basic

descriptive information; “U.S. Merchant Marine” webpage (www.usmm.org) which

presents information on the U.S. merchant vessels and includes a listing of U.S. merchant

vessels lost in World War II; “Uboat.net” (www.uboat.net), a site that contains

comprehensive information on German submarines for the period 1938 to 1945 including

descriptions and specifications, crew lists, patrol summaries, etc.; and “Liberty Ships”

(www.andrew.cmu.edu/~pt/liberty/liberty1.html), which provides a complete listing of

liberty ships with descriptions and specifications and some photographs.

2.2.3. Published Secondary Literature

The Garrison et al. (1989:II-18) study formally addressed secondary literature, but

only in general statements about the availability of secondary sources for the Spanish and

French colonial period (Archives des Colonies n.d.; Chanu and Chanu 1955; Surrey

1916) and various sources on British and American wrecks such as Admiralty and

Foreign Office reports, Reports of the Steamboat Inspection Service, Reports of the U.S.

Life-Saving Service and the Official Records of the Union and Confederate Navies in the
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War of the Rebellion (ORN). However, some of these sources seem more appropriately

considered primary documents. Garrison et al. (1989:II-8) utilized several published

historical and archaeological studies available at the time, but note that the number

related specifically to wrecks in the Gulf of Mexico was relatively small. Several

publications have been produced since 1989 that provide useful information on maritime

history, archaeology and vessel losses in the Gulf of Mexico. Among the most valuable

of these historical syntheses are From Sail to Steam, a comprehensive study of the

maritime history of Texas by Richard Francaviglia (1998), and The French Thorn, an

examination of French activity in the Gulf region by Robert Weddle (1991) that

represents a sequel to his earlier work The Spanish Sea (Weddle 1985). Also useful are

the several volumes on the history of French Louisiana by Marcel Giraud (1974, 1987,

1993) published by Louisiana State University Press.

The results of a number of archaeological studies of shipwrecks in or near the

Gulf of Mexico have been published since 1989 that provide useful information on

broader questions of maritime history as well as more specific questions on vessel types,

cargoes, wreck condition and preservation in various settings, etc. All of the published

accounts discovered deal with wrecks lying in state waters, but they do have applicability

to the study area considered here. Among those not mentioned by Garrison et al. are

studies of the 1766 wreck of El Nuevo Constante of the Louisiana coast (Pearson and

Hoffman 1995); and the sixteenth century Emmanuel Point shipwreck in Pensacola Bay,

Florida (Smith et al. 1995; 1998). Although no full publication has appeared, numerous

papers have been presented on the history and archaeology of the seventeenth century

French vessel La Belle, whose remains have been excavated and recovered from

Matagorda Bay, Texas (see Weddle 2001 for a discussion of this vessel).

Another important category of secondary literature examined in this study that

was little used in the 1989 study was “diving guides,” which are publications produced

principally for the sport diving community. Three of these guides proved to be of great

value. These are Shipwrecks of Florida by Steven Singer (1992); Florida Shipwrecks by

Berg and Berg (1991); and The Captain’s Guide to Wrecks and Reefs by Laney Rinehart

(1998). The first two publications draw heavily from the secondary literature, although

Singer also used information from a variety of public documents such as Customs

Service, Coast Guard, and Life-Saving Station records, essentially many of the same

documents used by the Garrison et al. (1989) study. Rinehart’s publication relies heavily

on information derived from his own as well as other sport divers’ activities. As a result,

many of the wrecks recorded by Rinehart are unidentified, but many are found in no other

source. In addition, his listings include many types of objects in addition to vessels,

including such things as tires, miscellaneous metal scrap, pipes, army tanks, etc. Most of

Rinehart’s information is related to the Florida Gulf coast, but he does include a number

of vessels and objects off the coast of Alabama and Mississippi. Diving conditions

offshore of Louisiana and Texas are less desirable for sport diving than off of Florida,

such that there are many fewer recreational divers there. No comprehensive guides exist

for wrecks off of these two states, although Internet sites exist listing diving opportunities

for wrecks off of Texas.
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2.2.3.1. Cultural Resources Management Reports

 A critically important body of historical and archaeological data is contained in

the large number of reports resulting from cultural resources management (CRM) studies

of various sorts undertaken in the Gulf of Mexico region. Garrison et al. (1989) did not

specifically consider these sources, but they now probably represent our most extensive

source of information on the application of remote-sensing techniques in the search for

shipwrecks, on the archaeology of wrecks, and on the condition and preservation

potential of wrecks in various settings. Many of these studies have been conducted over

the past 30 years, particularly within the last 15 years, but they constitute a “gray

literature” that is either unknown or ignored by many researchers. Except for the surveys

in Federal waters mandated by MMS, almost all of these CRM studies have been

conducted in state waters and the reports are maintained by state offices, usually the

office of the State Archaeologist or a similar entity. Although mainly dealing with state

waters, many of these reports contain historical, archaeological and remote-sensing

information that has direct bearing on assessing shipwrecks in the study area. Because of

the importance of this class of sources the pertinent state offices in each of the five states

bordering the Gulf of Mexico (Florida, Mississippi, Alabama, Louisiana and Texas) were

visited to examine the cultural resources reports they hold.

In addition to literature related specifically to CRM projects, shipwreck-related

publications sponsored or produced by various state and Federal agencies and colleges

and universities were examined during the visits to state offices. Although not

specifically CRM in nature, several of these publications provided useful comparative

information and are noted in the following discussions.

A review of CRM and state- and university-sponsored reports reveals the

extensive amount of research on shipwrecks conducted along the coast in the past two

decades. Among these are numerous remote-sensing surveys, historical overviews and

archaeological projects conducted in many bays and waterways along the Gulf. A large

number of these studies were conducted for the U.S. Army Corps of Engineers, but some

were undertaken for other government entities, as well as private concerns. Examples in

Florida include several studies in the waters off Lee County (Hall 1998, 1999);

investigations in and near Pensacola Bay (Baumer 1990; Bense 1988; Franklin et al.

1991; James 1989; Hunter et al. 2000; Morris and Franklin 1995; Spirek et al. n.d.;

Tidewater Atlantic Research 1987); St. Andrew’s Bay (Pelletier et al. 2000); near

Longboat Key at Sarasota Bay (Sea Systems Corporation 1992); and an inventory of

wrecks at Dog Island in Franklin County (White et al. 1995). A number of studies have

been undertaken by the National Park Service on Park Service lands along the Florida

Gulf coast. These include a survey and assessment of underwater archaeological sites in

Biscayne National Park (Skowronek 1984; Wild and Brewer 1985); shipwreck studies of

the Dry Tortugas and the Fort Jefferson National Monument (Bearss 1971; Johnson 1982;

Murphy and Jonsson 1993); and the Florida portion of Gulf Islands National Seashore

(Tesar 1973). The study edited by Murphy and Jonsson (1993) proved to be of particular

use in providing a great deal of information on the reported and known wrecks in the Dry
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Tortugas National Park. This included information on causes of loss, dates of loss, etc.,

which formed a valuable body of comparative data for the present study.

A fairly large number of CRM studies have been undertaken along the central

Gulf coast, off the states of Alabama, Mississippi, and Louisiana. Mobile Bay, in

particular, has been subject to a considerable amount of study, principally in relation to

Corps of Engineers projects. Mistovich and Knight (1983) produced an overview of the

cultural resources of Mobile Bay that included a listing and discussion of 282 vessels

believed to have been lost in the area. Additionally, a series of remote-sensing surveys

and diving projects have been conducted in the bay (Irion 1983, 1985, 1986; Irion and

Bond 1984). Other CRM studies conducted along the Alabama and Mississippi coasts

include an historical overview of submerged cultural resources near Bayou La Batre,

Alabama (Mistovich 1987) and cultural resources studies of submerged resources of

Pascagoula Harbor (Mistovich et al. 1983), the waters around Biloxi (Mistovich et al.

1993) and the offshore barrier islands (Irion 1989).

A series of cultural resources studies has been undertaken in the coastal waters of

the state of Louisiana. These consist mainly of remote-sensing surveys and include work

in Breton Sound (Irion and Heinrich 1993; Irion et al. 1993; Pearson 2000), the

Terrebonne Bay area (Birchett and Pearson 1998; Pearson 2001) and Atchafalaya Bay

(Seidel et al. 1998). Some of these projects involved diving operations, although none

discovered any historic shipwrecks.

A small number of historic shipwrecks have been discovered along the Louisiana

coast, but relatively few have been studied to any extent. The only wreck to receive

extensive archaeological and historical study has been the Spanish merchantman El

Nuevo Constante, lost off the central Louisiana coast in a hurricane in 1766 (Pearson and

Hoffman 1995). This vessel lies in state waters at a depth of about seven-m (21 ft.) and

archaeological research indicated that the very lower portion of the approximately 38-mlong (125 ft.) hull, as well as numerous items of cargo, was well preserved and only

minimally scattered from the original position at the time of sinking. Although in state

waters, this wreck lies in an environmental setting that is commonly found in Federal

waters and, thus, provides a model of what might be expected at other wrecks in the

GOMR. A large pile of rock identified as ship’s ballast and some artifacts, including six

iron cannons, was found in shallow water off the Chandeleur Islands in southeastern

Louisiana (Garrison et al. 1989b). Founders marks on three of the iron cannons suggests

the guns were cast no earlier than 1771 and might have been made as late as 1784. The

authors speculate that the ballast and other materials were deposited during the third

quarter of the eighteenth century. No evidence of vessel remains was found and it is

speculated that the material was either dumped over the side to lighten a grounded vessel

or was lost when a vessel “turned turtle” prior to the vessel drifting off, possibly sinking

nearby (Garrison et al. 1989b:7–26—7–27).

The wreck of another eighteenth century Spanish vessel, El Cazador, was found

in approximately 100-m (300 ft) of water about 50 miles south of Grand Isle, Louisiana.

Lost in 1784, the wreck of El Cazador was discovered accidentally by a fishing boat in
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1984. Subsequently a group of salvers dove on the wreck and recovered a large number

of silver coins, a bronze cannon, cannon balls, an anchor, a bronze bell, fire brick,

pottery, and some other miscellaneous items (New York Times 1993; Summers 1996).

Unfortunately, little is known about the condition of the wreck, although reports indicate

that wood was present and that portions of the wreck were exposed above the bottom.

There is every reason to believe that other early wrecks will be exposed and similarly

well preserved throughout much of the lands of the GOMR. It is possible that deepwater

conditions, and/or possibly partial burial, have aided in the preservation of wood on El

Cazador. The recent discovery of what appears to be the well preserved, partial hull of a

wooden sailing vessel in over 2,000 feet of water off the mouth of the Mississippi River

provides additional support for the type of preservation, and exposure, that can be

expected for deepwater wrecks in the GOMR (Irion 2002).

A very large number of CRM studies has been conducted along the Texas coast,

many for the Corps of Engineers. Several of these have included archaeological

examinations of sunken wrecks in Gulf and near-Gulf waters that have particular

relevance to wrecks in the study area. Additionally, state agencies, particularly the Texas

Historical Commission, have undertaken a number of shipwreck-related studies along the

Texas coast. Among the more relevant studies are remote-sensing surveys in the lower

Sabine River area (Hoyt et al. 1994), in the Galveston Bay area (Arnold 1987; Arnold

and Oertling 1995; Espy, Huston & Associates, Inc. 1992, 1998; Hoyt 1993), in

Matagorda Bay (Arnold 1982; Pearson and Hudson 1990), in the Aransas Pass-Aransas

Bay-Corpus Christi Bay area (James and Pearson 1991; Pearson and Simmons 1994;

Pearson and Wells 1995) and along the lower Texas coast in the vicinity of Brownsville

and Padre Island (Espey, Huston & Associates 1981; 1990a; 1990b; Glander et al. 1990;

Hoyt 1991; Lenihan 1974; Nichols et al. 1981).

Although not a remote-sensing or shipwreck study per se, the work of Arnold et

al. (1998) on “Liberty Ships” of the Texas coast is a particularly useful source of

information. Brief examinations have been conducted of two shipwrecks off the Texas

coast, the Hatteras and the New York, both of which lie in Federal waters. The Hatteras

was an iron-hulled sidewheel steamer sunk in 1863 while employed as a U.S. Navy

blockading vessel. Examinations by Texas Historical Commission and MMS personnel

have provided basic information on the wreck site and a magnetic contour map

(Anuskiewicz and Arnold 1992; Arnold and Anuskiewicz 1995). The New York was a

sidewheel steamer lost in a storm in 1846. The wreck was found by a group of amateur

divers after a five-year search and was briefly examined by MMS personnel in 1997. The

MMS examination involved diver assessment and a remote-sensing survey of the wreck

site (Irion and Anuskiewicz 1999:20-23). Neither the Hatteras nor the New York have

been studied in any detail, but the small amount of information collected does expand on

our understanding of wreck conditions and preservation potential on the GOMR.

Most of the marine-related CRM work along the Gulf coast has involved remotesensing survey and some reconnaissance diving. However, as noted above, several

studies have resulted in the discovery and examination of shipwrecks, many of which

have been found and examined since the Garrison et al. study. Although the level of
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examination of these wrecks varies considerably, they do contribute to our understanding

of shipwrecks in the study area. Additionally, while most of these wrecks are located in

shallow inshore waters, some of these shallow-water environmental settings are

comparable to ones found in the offshore waters of the study area. Thus, these wrecks

can provide information on factors of critical importance in understanding wrecks in the

GOMR, such as site formation processes and preservation potentials in different settings,

and are used later to expand the discussions of shipwreck preservation presented in

Garrison et al. (1989:II-77–II-84).

2.2.4. MMS-Mandated Archaeological Survey Reports

One source of data not used in the Garrison et al. study is the results of some of

the 2,800 MMS mandated cultural resources studies that have been conducted in the Gulf

of Mexico since the 1970s. MMS personnel in New Orleans provided pertinent

information from survey reports where sunken vessels had been positively identified or

where objects that might be vessels had been identified. In the vast majority of cases, the

identification relied on sidescan sonar information; only a few instances relied on the

results of magnetometer data. The information provided by the MMS consisted of xerox

copies of selected portions of reports. This usually included a copy of the title page and

those pages describing the vessel or object discovered, a copy of the record of the vessel

or object, and, often, a portion of a map showing the identified vessel or object in relation

to survey track lines or other features. As is discussed in more detail later, these

archaeological survey reports and the surveys on which they are based are produced by

offshore survey or energy-related companies. In a few instances, MMS provided data

from the results of their own in-house remote-sensing surveys or diving operations.

Information from over 130 archaeological survey reports and MMS surveys or diver

inspections was received and reviewed. From these records, 90 sunken vessels have been

identified in addition to 43 targets classified as “objects” that may or may not represent

vessel remains. As is discussed in more detail later, this relatively small sample of

wrecks represents our best and most reliable set of data for testing the model of wreck

distributions in the GOMR developed by Garrison et al. (1989) and for assessing the

cultural resources remote-sensing survey program currently mandated by MMS.

2.2.5. Primary Documents 

Garrison et al. (1989:II-13) included “Documents” as a principal category of

source materials, noting that these consisted of “unpublished materials that provide

substantive data about shipwrecks.” Here, these are identified as “primary documents.”

Garrison et al. examined the most critical of these primary sources for their study, such

that the present effort mainly involved identifying and examining sources they had not

used and, when necessary, going back to some of the primary sources they used to collect

additional information. For example, U.S. Custom Service records for the Port of New

Orleans that were not examined by Garrison et al. were reviewed in this study. Among

the most pertinent of these records was the seven-volume set of ship enrollments and

registrations for New Orleans for the period 1804 to 1870 (Works Progress

Administration [hereinafter cited as WPA] 1942) and the records of casualties and wrecks
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occurring within the Port of New Orleans Custom District for the period 1873-1924

(WPA 1938). Both of these sets of records are considered primary documents, although

they constitute data abstracted from the original records.

Primary accounts of shipwrecks, particularly eyewitness accounts of participants,

while possibly the most reliable source of information, can require a considerable amount

of effort to find, particularly in an overview study of the kind undertaken here.

Numerous secondary sources, however, do contain first-hand accounts. For example,

contemporary accounts of the 1554 Spanish wrecks on Padre Island are provided in

Arnold and Weddle (1978), and eyewitness accounts of the 1766 sinking of El Nuevo

Constante as well as several other vessels involved in her salvage are recounted in

Pearson and Hoffman (1995). Similarly, many of the CRM studies examined include

first-hand accounts or extracts from contemporary newspapers of vessel sinkings.

Likewise, a few primary reports of Civil War vessel losses in the Gulf of Mexico were

gleaned from the Official Records of the Union and Confederate Navies in the War of the

Rebellion (ORN).

2.2.6. Directories

Garrison et al. (1989) included a category of research sources named

“Directories,” identified as “lists of the names of vessels [that] usually include dates and

locations of casualties.” Among the Directories examined in the 1989 study were the

Annual List of Merchant Vessels of the United States, which covers the years since 1867;

the American Bureau of Shipping Records; the various ship and shipping lists produced

by the Lloyds Company of London; and the Lytle-Holdcamper List (Mitchell 1975),

which is a directory of steam vessels constructed and lost in the United States for the

period 1790-1868. All of these directories were reexamined in the present study,

primarily to collect additional descriptive information on vessels and to clarify the

information provided on location of loss in order to develop assessments of reliability

(see below). In some instances, our review of these directories was undertaken to clarify

data presented in the list of wrecks developed in 1989. For example, a review was

undertaken of every issue of the Annual List of Merchant Vessels of the United States to

extract descriptive information on vessels lost in the Gulf of Mexico.

Several other listings of vessels and/or wrecks that may be classified as

“Directories” were examined in this study. Some of these are published, others are not.

Among these are the computerized listing of over 1,800 vessels lost within the boundary

of the New Orleans District of the U.S. Army Corps of Engineers mentioned earlier

(Pearson et al. 1989), and a listing of 213 abandoned and derelict vessels recorded along

the coast of Mississippi by the Mississippi Department of Marine Resources (Mississippi

Department of Marine Resources n.d.). The Louisiana Division of Archaeology has

developed a listing of shipwrecks from its site files, but like the two studies just noted,

almost all of the entries fall in state waters (Clune and Wheeler 1991). Similar agencies

in most other Gulf states have the capability of producing similar lists from the site file

records, if they are not already maintained or produced separately. The Office of

Conservation of the Louisiana Department of Natural Resources publishes a list of
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obstructions falling in state waters as part of their Underwater Obstruction Removal

Program (Louisiana Office of Conservation 2001). The information published in this

volume also is included online at the Department of Natural Resources website. This list

consists of obstructions identified in relation to the Fisherman’s Gear Compensation

Fund. Most of these obstructions are non-vessel objects such as pilings, dredge pipe, etc.,

but a few are vessels. Also, only a small number of these obstructions fall in Federal

waters and it appears that most of these are duplicated in the MMS database of offshore

snags and hangs mentioned earlier.

In addition, several of the CRM reports mentioned above contain lists of known

or reported vessel losses for specific areas. Again, most of these lists contain vessels lost

in state waters, but a few include losses within the present study area.

2.3. Compilation of Revised and Expanded Shipwreck Database

The principal objective of Task 1 of this study was to add to and expand the

shipwreck database developed out of the Garrison et al. (1989) study and currently used

by MMS in guiding cultural resources surveys on the GOMR. The development of this

database relied on the information collected from the various sources as discussed above.

The Garrison et al. shipwreck database included only a few categories of information.

The computerized version (Microsoft Excel format) of the database provided by the

MMS contains the following variables: “Number,” which is an arbitrary number

assigned to each entry; “Vessel Name;” “Date of Loss,” “Reference Number,” which is a

number assigned to or derived from the principal source of information on the vessel;

“Information Source,” which references the principal source from which information on

the loss was obtained; “Latitude;” “Longitude;” “MMS Lease Area;” and “MMS Lease

Block No.”

The full database of shipwrecks developed in the Garrison et al. study (1989:II10) included over 4,000 entries. However, the majority of these were in state waters.

The 1989 computerized database of wrecks received from the MMS in June 2000 lists

1,469 “shipwrecks” in Federal waters (see Volume III, Appendix A). However, this list

includes a number of duplicates, mostly consisting of the same vessels under slightly

different spellings, 244 items identified as “unknown” which are unidentified wrecks

derived from various sources, 23 “objects” and “obstructions” that may or may not be

shipwrecks, plus several “fish havens” which represent vessels scuttled as artificial reefs.

In addition, 240 of the wrecks included in the list are identified as falling within state

waters. These vessels are, apparently, included in the list because of questions about the

reliability of their reported location of loss and the presumption that they could, actually,

fall in Federal waters. Five of these wrecks are in Louisiana state waters; all of the rest

are in Texas waters. Two items in the Garrison et al. list are identified as “helicopters,”

but both have the same coordinates and may be the same object. The initial task of the

present study was to carefully reexamine this list to try to identify and rectify duplications

or errors, collect additional information on the listed vessels and to refine the locations of

loss, if possible. As is discussed below, this reexamination did result in the elimination

of a number of these vessels from the final shipwreck database.
2-16

Finally, it should be noted that information was collected on a variety of objects

other than identified shipwrecks. Many of the sources of data examined included items

identified only as “objects” or “obstructions” or items more specifically identified, such

as anchor, wire cable, pipe, rig, etc. Information on most of these items was collected

and is included in a master Access database, and was used in some of the analyses

conducted. In this master database, however, these types of items are classified as

“Objects” if there is no reason to believe they might represent shipwrecks, as opposed to

items classified as “Vessels” that are identified as shipwrecks on the basis of the best

available information. A few items identified as “objects” in other sets of data have been

reclassified as “vessels” for the purpose of this study. This principally includes objects

that might have been lost from vessels, such as anchors. Additionally included in the

category of “vessels” are a few objects that are not shipwrecks but that do represent

cultural items of interest to MMS in its management of cultural resources. Specifically,

these include airplanes and helicopters.

2.3.1. Shipwreck Information Form

In the present study, a particular effort was made to collect and add to the

database information about each reported loss that might aid in its identification should it

eventually be found. In consultation with MMS personnel, the authors developed a list of

variables to be recorded for each reported shipwreck that included information on

location of loss, physical characteristics, construction and ownership, and aspects of the

vessel’s function and use, particularly at the time of loss. In addition, notations on the

source(s) of information were recorded. Ultimately, all of these data were input into the

program Microsoft Access and, as noted, utilized in the GIS application ArcView. In

order to expedite the collection and incorporation of this information into the Access

database, a recording form was developed and used by the various researchers collecting

shipwreck information. An example of this form is provided as Figure 2-1. Many of the

entries in the form and in the Access database used codes, and Appendix B (in Volume

III) includes a complete key to those used for the various data fields used in the Access

database that was developed from this recording form.

As can be seen in the form, data on shipwrecks was collected on five principal

categories of information: General Information, Location, Vessel Description, Wreck

Site Information, and Documentation. As to be expected, the amount of information

collected on individual wrecks varied considerably. In most instances, information on a

relatively small number of variables, such as the name, type of vessel and date and

location of loss, could be found. In those situations where the wreck was identified only

on the basis of a remote-sensing survey even less information was available, possibly

consisting only of the location and general dimensions of the wreck. In the relatively

small number of cases where historical information on a particular vessel is abundant and

detailed, such as those lost during World War II, many variables could be entered.
2-17

MMS SHIPWRECK INFORMATION FORM

GENERAL INFORMATION

1. VESSEL NAME (55 characters)

______________________________________________________________________________________

2. ALTERNATE NAME (55 characters)

______________________________________________________________________________________

3. 1989 MMS NUMBER (5) ____________ 4. OFFICIAL NUMBER (10) ____________________

5. STATE SITE NUMBER (8) ____________________

6. DATE OF LOSS (mo-day-year) (8) ________________ 7. CAUSE OF LOSS (2) _____

LOCATION

8. MMS AREA (3) ______ 9. MMS LEASE BLOCK (3) _______

10. LATITUDE (8) ____________________ 11. LONGITUDE (8) ___________________________

12. LORAN COR. 1 (12) ______________________ 13. LORAN COR. 2 (12)

______________________

14. NEAREST LANDMARK (port, community, landform, etc.) (50)

______________________________________________________________________________________

______________________________________________________________________________________

15. NEAREST STATE (2) _____ 16. RELIABILITY OF LOCATION (2) _____

VESSEL DESCRIPTION

17. VESSEL TYPE (3) _____ 18. PROPULSION (2) _____ 19. DATE BUILT (year) (4) ___________

20. WHERE BUILT (3) ________ 21. MATERIAL (2) _____ 22. LENGTH (5) __________

23. BEAM (width) (4) _________ 24. DEPTH HOLD (4) _____________ 25. DRAFT (4) ___________

26. TONNAGE (gross) (4) ________ 27. TONNAGE (net) (4) _______ 28. NO. OF MASTS (1) _____

29. NO. OF DECKS (1) _____ 30. BOW SHAPE (3) __________ 31. STERN SHAPE (3) __________
2-18

32. BUILDER (35)

______________________________________________________________________________________

33. OWNER (35)

______________________________________________________________________________________

34. MAIN ENGINE TYPE (3) _________ 35. HORSEPOWER (4) ________

36. NO. OF CYLINDERS (4) __________ 37. CYLINDER SIZE (inches) (3) __________

38. STROKE (feet) (2) _____ 39. DATE ENGINE BUILT (year) (4) _________

40. ENGINE BUILDER (35)

_______________________________________________________________

41. NO. OF BOILERS (2) _____ 42. BOILER TYPE (3) __________

43. VESSEL USE (2) ________ 44. HOME PORT (3) __________

45. NATIONALITY (4) ________ 46. DESTINATION AT LOSS (3) ________

47. CARGO AT LOSS (25) _______________________________________________________________

48. ARMAMENT AT LOSS (no of guns) (3) ________ 49. VALUE AT LOSS (dollars) (8) ________

WRECK SITE INFORMATION

50. WATER DEPTH (feet) (4) _______ 51. SITE SIZE (square feet) (4) _______

52. BOTTOM TYPE (2) _______ 53. WRECK CONDITION (2) _______

54. WRECK EXPOSURE (2) ____ 55. MATERIAL COLLECTED (8) 1. ___ 2. ___ 3. ___ 4. ____

DOCUMENTATION

56. DATA DEPOSITORY (254)

______________________________________________________________ 

______________________________________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

_____________________________________________________________________________________
2-19

57. REFERENCES (254)

______________________________________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

58. LEASE BLOCK OR PIPELINE SURVEY OCS NO. (6) __________

59. VESSEL PHOTOGRAPHS (reference or attach) (35)

__________________________________________

60. MAGNETOMETER DATA (reference or attach) (35)

__________________________________________

61. SIDE SCAN SONAR RECORDS (reference or attach) (35)

_____________________________________

62. COMMENTS (254)

______________________________________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

63. RECORDER (12) ____________________________ 64. DATE RECORDED (8) ____________

65. SOURCE _________________

Figure 2-1. Shipwreck Information Form used in data compilation.

Most of the entries in the Shipwreck Information Form are self explanatory, but

some do require explanation. The General Information category includes variables for

vessel name, alternative name, 1989 MMS number, official number, state site number,

date of loss and cause of loss. An alternative name was entered if the vessel was known

by more than one name or if it appeared in different sources under different spellings.

The “1989 MMS number” entry simply records the arbitrary number assigned to this

vessel in the 1989 MMS shipwreck database, if it appeared in that list. Because all of the

vessels fall in Federal waters, only a very few had state site numbers assigned. The cause

of loss entry is that given in the source considered most reliable, although in many

instances, cause of loss is not given or it is only noted that the vessel was “sunk.” The

codes used and the corresponding causes of loss are listed below in Table 2-1.
2-20

Table 2-1. Codes Denoting Cause of Loss Categories

in the Shipwreck Information Form

CODE CAUSE

AB abandoned

BE beached

BU burned

CA capsized

CO collided

EX explosion

FO foundered

GF gunfire-battle

SC scuttled

ST stranded & swamped

SU sunk

UN unknown

The second category of information is related to the location of the wreck. “MMS

Area” refers to one of the 70 lease areas that the MMS presently identifies in the GOMR

and “MMS Lease Block” refers to the numbered lease block within that area. The 3-

mile-square lease block and the larger lease areas are used as principal units in some of

the analyses conducted in this study and are discussed more fully in the following

chapter. A map and list of the MMS Lease Areas are provided as Figure 2-2 (see Table

2-2 for key to abbreviations). “Latitude” and “Longitude” represent the coordinates of

the location of loss. For use in the Access database and in ArcView, this was converted

to decimal degrees.

Location, of course, is probably the most critical attribute assigned to any wreck

in this study because it is the basis upon which patterns of spatial distributions are

determined, high-probability areas are identified, and future decisions concerning remotesensing surveys in the GOMR will be made. Location information for the wrecks

identified in this study came from a wide variety of sources, in a variety of forms and

with varying degrees of reliability. Therefore, a full discussion on how wreck locations

were determined, the accuracy and precision of assigned locations and the problems

associated with such determinations is presented. Only converted Loran coordinates were

provided for a fairly large number of wrecks, such as those described in some of the sport

divers publications, so these coordinates were included in the form for the convenience of

those collecting the information. As has been mentioned, Loran coordinates can be quite

imprecise. Discussions with individuals who have attempted to relocate objects using

Loran coordinates indicate that relocation is easiest if the same Loran system is used with

the original Loran coordinates.

However, if, the Loran coordinates are converted into another coordinate system

(e.g., Latitude/Longitude) and/or different positioning equipment is used, relocation can

become difficult. It is apparent that converting Loran coordinates to other systems can

introduce imprecision; however, no studies seem to have been conducted to assess the

exact nature and extent of the error.
Figure 2-2. MMS lease areas in the Gulf of Mexico Region.
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Table 2-2. MMS Lease Areas in the Gulf of Mexico Region

LEASE AREAS CODE AREA IN ACRES AREA IN

SQUARE

MILES

% OF TOTAL

GOMR AREA

ALAMINOS CANYON AC 5,315,143.222 8,304.91 3.22

AMERY TERRACE AM 1,540,459.045 2,406.97 0.93

APALACHICOLA AP 3,529,460.676 5,514.78 2.14

ATWATER VALLEY AT 5,439,949.728 8,499.92 3.30

BRAZOS BA 973,068.225 1,520.42 0.59

BRAZOS A BAA 766,080.000 1,197.00 0.46

BAY MARCHAND BM 25,056.824 39.15 0.02

BRETON SOUND BS 280,154.703 437.74 0.17

CHANDELEUR CA 220,378.762 344.34 0.13

CORPUS CHRISTI CC 676,432.513 1,056.93 0.41

CAMPECHE ESCARPMENT CE 52,013.289 81.27 0.03

CHARLOTTE HARBOR CH 4,807,083.957 7,511.07 2.91

DESOTO CANYON DC 5,445,328.109 8,508.33 3.30

DESTIN DOME DD 5,045,878.773 7,884.19 3.06

DRY TORTUGAS DT 3,441,249.051 5,376.95 2.09

EAST BREAKS EB 4,677,830.500 7,309.11 2.83

EAST CAMERON EC 1,762,887.996 2,754.51 1.07

EUGENE ISLAND EI 1,996,141.212 3,118.97 1.21

THE ELBOW EL 5,156,726.396 8,057.38 3.13

EWING BANK EW 610,013.380 953.15 0.37

FLORIDA MIDDLE

GROUND

FM 5,006,232.622 7,822.24 3.03

FLORIDA PLAIN FP 3,380,023.567 5,281.29 2.05

GALVESTON GA 1,130,582.904 1,766.54 0.69

GALVESTON A GAA 1,457,280.000 2,277.00 0.88

GARDEN BANKS GB 5,001,323.317 7,814.57 3.03

GRAND ISLE GI 573,215.110 895.65 0.35

GREEN CANYON GC 5,393,813.446 8,427.83 3.27

GAINESVILLE GV 1,488,765.944 2,326.20 0.90

HENDERSON HE 5,446,970.742 8,510.89 3.30

HOWELL HOOK HH 5,444,400.620 8,506.88 3.30

HIGH ISLAND HI 845,749.744 1,321.48 0.51

HIGH ISLAND A HIA 3,432,960.000 5,364.00 2.08

KEATHLEY CANYON KC 5,448,699.086 8,513.59 3.30

KEY WEST KW 162,149.206 253.36 0.10

LLOYD LL 5,445,884.499 8,509.19 3.30

LUND SOUTH LS 1,437,055.635 2,245.40 0.87

LUND LU 5,441,032.921 8,501.61 3.30

MIAMI MA 1,187,064.377 1,854.79 0.72

MISSISSIPPI CANYON MC 4,748,859.409 7,420.09 2.88

MATAGORDA ISLAND MI 930,692.366 1,454.21 0.56

MATAGORDA ISLAND A MIA 51,840.000 81.00 0.03

MOBILE MO 650,576.541 1,016.53 0.39

MAIN PASS MP 1,547,390.992 2,417.80 0.94

MUSTANG ISLAND MU 910,277.487 1,422.31 0.55

MUSTANG ISLAND A MUA 1,008,000.000 1,575.00 0.61

ST. PETERSBURG PB 3,262,314.554 5,097.37 1.98

PENSACOLA PE 1,178,061.915 1,840.72 0.71

PORT ISABEL PI 1,372,583.425 2,144.66 0.83

SOUTH PELTO PL 125,176.539 195.59 0.08

NORTH PADRE ISLAND PN 829,812.601 1,296.58 0.50

NORTH PADRE ISLAND A PNA 599,040.000 936.00 0.36

PULLEY RIDGE PR 5,717,157.222 8,933.06 3.46

SOUTH PADRE ISLAND PS 829,382.009 1,295.91 0.50

N
2-23

Table 2-2 (continued). MMS Lease Areas in the Gulf of Mexico Region

LEASE AREAS CODE AREA IN ACRES AREA IN

SQUARE

MILES

% OF TOTAL

GOMR AREA

SOUTH PADRE ISLAND A PSA 518,400.000 810.00 0.31

RANKIN RK 3,437,509.027 5,371.11 2.08

SABINE PASS (LA) SA 60,265.459 94.16 0.04

SIGSBEE ESCARPMENT SE 1,173,025.015 1,832.85 0.71

SABINE PASS (TX) SX 24,060.688 37.59 0.01

SOUTH MARSH ISLAND SM 1,299,146.071 2,029.92 0.79

SOUTH PASS SP 435,274.387 680.12 0.26

SHIP SHOAL SS 1,816,440.123 2,838.19 1.10

SOUTH TIMBALIER ST 1,463,997.464 2,287.50 0.89

TARPON SPRINGS TP 3,036,509.304 4,744.55 1.84

TORTUGAS VALLEY TV 263,120.436 411.13 0.16

VIOSCA KNOLL VK 1,520,503.989 2,375.79 0.92

VERNON VN 5,302,784.044 8,285.60 3.21

VERMILION VR 1,982,747.472 3,098.04 1.20

WALKER RIDGE WR 5,564,793.647 8,694.99 3.37

WEST CAMERON WC 3,130,010.557 4,890.64 1.90

WEST DELTA WD 728,847.645 1,138.82 0.44

TOTALS 165,003,140.489 257,817.41 100.00

Individuals with practical experience in this matter indicate that errors of up to

one-quarter mile are not uncommonly encountered when using GPS and converted

coordinates in trying to locate objects originally discovered by Loran (Avery Munson,

personal communication 2001; Rob Floyd, personal communication 2001). In spite of

these known problems, it was necessary to convert all of those Loran coordinates

provided for losses into geographic coordinates (latitude and longitude) as required by the

MMS and as needed to input data into a GIS application.

When diving was conducted to relocate and evaluate targets as part of Task 2,

some of the targets selected (specifically, the reported hangs) to examine had originally

been positioned by Loran. As is noted in later discussions on Task 2, most of the targets

originally positioned by Loran were difficult or impossible to find.

Nearest landmark was included if provided in the original source of information

because it sometimes played a role in determining the location of the wreck. A typical

entry might be “Wine Island Pass, Louisiana,” “Cape St. George Lighthouse,” or “Port

Mansfield Jetties.”

The final variable in the Location category is “Reliability of Location.” This

reflects an assessment of how reliable the location of loss provided in the form actually is

using a numerical scale ranging from 1, very high reliability, to 4, very low reliability.

The use of this reliability factor represents an attempt to quantify how useful assigned

wreck positions might be in various types of analyses. However, the assignment of a

reliability value in most instances is in itself necessarily partially subjective because of

the nature of the original data on the shipwreck.
2-24

A specific effort was made to define the four reliability categories in terms of the

anticipated degree of difficulty there would be in relocating the wreck using the

technology presently used in MMS mandated surveys. It was felt that this approach

would be most useful to MMS in its cultural resources responsibilities as well as in trying

to relate specific wrecks or groups of wrecks to the concept of “high-probability”

locations. In essence, using wrecks assigned very low reliability factors (i.e., 3 or 4) in

the identification of tightly drawn “high-probability” areas is considered questionable.

The four reliability factors used are:

1. Wreck location is confirmed through physical verification and has been accurately

positioned (e.g., with GPS or on an accurate, modern map) or is identified on the

basis of accurately positioned remote-sensing survey. The location is considered

to be very reliable such that a wreck would be easy to relocate using standard

DGPS equipment.

2. A specific location is provided for a wreck or a vessel loss by an informant,

reported in the literature, or on a map. Included in this category are wrecks or

losses whose position is given to at least the nearest actual minute of latitude and

longitude, to a specific offshore lease block, and those that have been discovered

and positioned using Loran equipment. The location reliability of these wrecks or

losses is considered to be moderate to good. It is anticipated that these wrecks

could be discovered, but discovery would require a moderate amount of field

survey with remote-sensing equipment, plus it may require additional historical

research.

3. A general location for a wreck or a vessel loss is provided by an informant or in

the literature. Included in this category are vessels whose locations of loss are

given only in degrees of latitude and longitude. Also included in this category are

vessels whose general position of loss is provided in relation to a known

landmark, such as “10 miles south, southeast of Ship Island.” The location

reliability of these wrecks or losses is considered to be fair to poor. Discovery of

wrecks included in this category could be very difficult and commonly would

require a considerable amount of historical research and/or remote-sensing

survey.

4. Unreliable or vague location information is provided on a wreck or place of loss

of a vessel. Examples would include many early accounts of vessel losses such as

reports of vessels lost in hurricanes “near latitude such and such” or other general

indications of loss, such as “30 miles off Padre Island,” “off the coast of

Louisiana,” “south of Galveston,” or “between Galveston and New Orleans.”

Directed searches for these vessels are nearly impossible and their discovery will

mainly be by chance. Also included in this reliability category are items that were

reported to be “adrift,” when there is no evidence to indicate where, or if, they

sank as well as those cases where information is unavailable to make any

assessment of the reliability of the position given.
2-25

The third category of information included on the recording form is Vessel

Description. This category includes variables such as vessel type, length, width, beam,

draft, where built, year built, tonnage, material (material of the hull such as wood, iron,

steel, etc.) builder, propulsion, flag(s) sailed under, vessel destination when sunk, etc.

The variables and the codes used are given in the Key provided as Appendix B in

Volume III.

The descriptor used in the principal source of information on the loss was used

when available to describe the vessel. The rationale for using “historic” descriptors is of

concern for many of the variables, with Vessel Type probably being the most important.

Terms for vessel types are not always specific and individuals may use different terms

when referring to the same vessel or type of vessel. In some instances a ship or boat may

be designated by its rig, in others by its hull form, and in others by its use or function. A

single term might refer to a general class of vessels that could include various rigs, hull

forms and sizes. An example commonly encountered in the present study is the use of

the terms “Fishing Vessel” or “Motorized Vessel” that are used as vessel descriptors in

several of the larger computerized shipwreck databases, such as those maintained by the

U.S. Coast Guard and NIMA. In the Gulf of Mexico one can assume that “Fishing

Vessels” are most commonly shrimp trawlers simply because this is the most common

type of fishing vessel operating there. But, other types of vessels that can be generally

categorized as “Fishing Vessels” (e.g., snapper or menhaden boats) have been lost in the

Gulf. As a result, it is generally impossible to accurately ascertain when the U.S. Coast

Guard, for example, is referring to a shrimp trawler when it uses the term “Fishing

Vessel.” Cross-checking sources or going back to primary sources when possible has

allowed a refinement of some of these “Fishing Vessel” entries, but these are few in

number.

An added difficulty is that vessel terminology changes over time. For example, in

the seventeenth and into the eighteenth century the term “bilander” was applied to a twomasted vessel with square sails on the fore mast and square and lateen sails on the mizzen

or rear mast. Later the term “brig,” shortened from “brigantine,” came to be commonly

applied to this and similar types of rigs (MacGregor 1980:76-77). During part of the

eighteenth century both terms were in use. Adding to the confusion of vessel type

terminology is that it is often difficult to establish specific equivalencies among vessel

terms used in different languages.

There are no all-purpose classification schemes applicable to every situation in

anthropological or historical research. Classification has to be formulated with a specific

purpose in mind (Thomas 1974). Out of necessity, this study has had to rely mainly on

contemporary vessel terminology and descriptions in trying to establish a typology of

vessels lost in the study area. In effect, this is an “historical” typology forced upon us by

the nature of the data. This is not seen as a serious problem in the type of overview study

conducted here. In general, it is safe to state that the typology used is primarily

“morphological” in nature in that the types used “attempt to define broad generalities

(rather than focusing upon specific traits) simultaneously considering as many traits as

possible” (Thomas 1974:7). Because they are general in nature, morphological types are
2-26

primarily descriptive. As with any other morphological typology, vessel types are

abstract in that a type is “the composite description of many artifacts, each of which is

quite similar” (Thomas 1974:22) and every type encompasses some range of variability.

As noted, one reason for including this descriptive information in the database is

to enable identification of the vessel should it ever be found, particularly during the

course of a mandated MMS lease block survey. For example, information on bow and

stern shape might help identify a vessel on the basis of sonar images alone.

Information on only a few of these descriptive variables is available in the sources

examined for most of the vessels lost in the study area. For early vessels, this might

include only the historic term describing the type of vessel, such as frigate or brig. On

the other hand, for more recent vessels such as tankers sunk in World War II, or Liberty

Ships scuttled as artificial reefs, descriptive information is comprehensive.

The fourth category of information on the recording form is Wreck Site

Information. Data are included for the variables in this category only if the wreck has

been examined by divers or the wreck has been recorded on remote-sensing records.

Thus, a relatively small number of entries include information in this category.

The final category of information on the recording form is Documentation and

includes entries on the sources used for data as well as where data are located or housed.

For data derived from MMS archaeological survey reports, all of the information is

housed at their offices in New Orleans. Also, for MMS survey reports, the official

number assigned to the lease block or pipeline survey for which the report was produced

is provided when that information was available. In addition, a “Comment” section is

provided where miscellaneous information on the wreck or reported loss can be included.

A typical entry here might include the original statement about the location of the loss as

presented in the source of information for the entry (e.g., “lost about 25 miles southeast

of Galveston”) or statements about the various positions provided for a loss when it

appears in more than one source. Finally, the entry form includes spaces for the initials

of the researcher compiling the record, the date the record was compiled, and an

additional note on the principal source of the information.

As noted, this recording form was used by researchers when collecting

information from various sources. Ultimately, all of this information was entered into the

Access database developed for this study. The format of the Access database was altered

slightly from the recording form to make data entry more efficient. All of the categories

in the recording form were maintained, but a few were added, primarily to include

variables for manipulating the data. For example, the general categories of “Vessel” or

“Object” were assigned to each of the records, as was a variable for “Assigned Lease

Block.” This latter variable was used in the program ArcView to automatically assign

items to an MMS lease block on the basis of their geographic coordinates. This

assignment relied on lease block coordinate data provided by MMS. An example of the

four-page Access entry form is shown in Figure 2-3. Appendix B provides explanations

and keys to the data fields used in the Access database.
2-27

Figure 2-3. Microsoft Access entry form, page 1.
2-28

Figure 2-3. Microsoft Access entry form, page 2.
2-29

Figure 2-3. Microsoft Access entry form, page 3.
2-30

Figure 2-3. Microsoft Access entry form, page 4.

Ultimately, a list of 3,261 shipwrecks and objects was developed from the various

sources used. From this a list of 2,106 items classified as shipwrecks has been

developed. This list includes named vessels, unknown vessels, fish havens and artificial

reefs containing vessels, objects that might be associated with vessels (such as anchors or

anchor and cable), as well as helicopters and airplanes. Every effort has been made to

remove duplications from this list, but some might remain. This is particularly true in the

case of named vessels versus unknown vessels that have very similar or identical

locations of loss. Complete discussions on the final shipwreck database are presented in

Chapter 4.
3.0: SHIPWRECKS IN THE GULF OF MEXICO AND THE

MMS ARCHAEOLOGICAL PROGRAM: THE 1989 MODEL

3.1. Present Model of Shipwreck Occurrence in the Gulf of Mexico

The MMS program for identifying and protecting cultural resources on Federal

lands in the Gulf of Mexico began in 1973. As noted, implementation of the program

was related to a variety of Federal laws and regulations promulgated prior to that date.

Guidance of the program is provided in a series of Notices to Lessees and Letters to

Lessees that have been issued since the initiation of the program. These documents have

established the requirements and parameters for conducting surveys relative to mineral

leasing and operation in the Gulf. Additionally, MMS has funded the several studies

mentioned earlier on historic and prehistoric site potentials in the Gulf to aid them in

designing and implementing their cultural resources management program. The MMS

program of offshore archaeological surveys is the cornerstone of their overall

management of the cultural resources in the GOMR. The results of the MMS offshore

survey program, in terms of wreck discovery (or non-discovery), provide the principal

test of the existing model of shipwreck occurrences in the offshore area. Additionally,

the offshore surveys presently provide our best source of information for developing

future refinements to this model. Other sources of data, such as new or expanded

historical information, as well as specific archaeological programs as is represented by

one aspect of the present study, may certainly enhance our understanding of shipwreck

resources in the GOMR. But, it is unlikely that any other effort can be undertaken on the

scale and magnitude as the present offshore MMS survey program. Thus, an

understanding of the current status of that program, its design and implementation, and its

relative success in locating shipwreck properties in the Gulf is a critical component of the

present study.

The present MMS program of archaeological resources surveys for historic

shipwrecks relies largely on the findings and recommendations presented in the Coastal

Environments, Inc. (1977) study and, more specifically, in the Garrison et al. (1989)

study. Although commonly referred to as a “predictive model” of wreck occurrence in

the Gulf, Garrison et al. (1989) do not use this term and present their findings in the form

of general statements (Garrison et al. [1989:II-122] use the term extended hypotheses to

characterize some of their findings) concerning characteristics of the historic wrecks they

found information on and the spatial patterns of these wrecks relative to a variety of

historical/cultural and natural factors. In this chapter, a review of the Garrison et al.

findings is presented that includes evaluations and assessments of those findings that, in

part, have arisen from data collected in this study. Discussions on how the results of the

1989 study have been incorporated into the MMS offshore survey program are presented,

followed by an evaluation of the present MMS model of shipwreck occurrences, using

primarily data accumulated in MMS mandated cultural resources surveys. In the

following discussions the findings of the Garrison et al. study are considered equivalent

to the present MMS model of shipwreck occurrences and both are commonly referred to
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as the “1989 model” or, when referring specifically to the list of shipwrecks developed in

the Garrison et al. study, as the “1989 database” or “1989 wreck list.”

3.1.1. 1989 MMS Gulf of Mexico Shipwreck Database

As has been discussed earlier, an initial task of the Garrison et al. 1989 study was

to develop a listing of shipwrecks that had occurred in the Gulf of Mexico. In developing

this list they relied on a variety of sources of information, most of which have been

mentioned in previous chapters and many of which, also, were used in the present study.

The list of shipwrecks developed in 1989 contained “over 4,000” entries; however, this

included many losses in state waters (Garrison et al. 1989:Appendices G and H). That

study, as well as others (e.g., Bascom 1971; CEI 1977; Gearhart et al. 1990; Muckelroy

1977), clearly demonstrates that the majority of shipwrecks occur in “nearshore” waters

rather than in the open sea. For example, Marx (1971) estimated that almost 98 percent

of all vessel losses in the western hemisphere prior to 1825 occurred in less than 10-m of

water and within 1.5-km of a coast; others suggest only slightly lower percentages. The

data collected by Garrison et al. (1989:I-3) for the Gulf of Mexico indicated that “75

percent of shipwrecks occur in nearshore waters and the remainder in the open sea.”

What this means is that of the over 4,000 wrecks recorded in the Gulf by Garrison et al.

only a small percentage fall in Federal waters. In fact, the final list of “shipwrecks”

actually in the GOMR deriving from the 1989 study included a total of 1,469 entries. A

discussion of this list is important because it served as a basis for the identification of

high-probability areas in the GOMR and served as the starting point for developing a

revised listing of wrecks for the present study.

The list of shipwrecks identified in the GOMR in the 1989 study was provided by

MMS as a computerized database in Microsoft Excel format. For convenience and to

avoid confusion, this list is referred to as the “1989 shipwreck database” in the following

discussions. Nine variables are included in this database. These are: 1) Number-an

arbitrary number assigned to each entry; 2) Name-the name of the vessel or object (e.g.,

obstruction or unknown); 3) Date of Loss-year of loss of the vessel if known; 4)

Reference Number-a number assigned to or derived from the source of information for

the wreck; 5) Source-a code identifying the principal source of information for the wreck;

6) Ship Location-the reported location of the wreck in decimal latitude and longitude; 7)

Lease Area-the GOMR lease area in which the wreck falls; 8) Lease Block-the numbered

lease block in which the wreck falls; and 9) Centroid Location-the calculated center of

the lease block in which the wreck is located in decimal latitude and longitude. This

“centroid” concept was used in delineating some high-probability areas as is discussed

later.

The 1,469 entries in the 1989 shipwreck database include a number of items in

addition to named vessels. These include “obstructions,” “fish havens,” “liberty ships,”

and “unknown” vessels. The five “fish havens” in the database represent vessels sunk as

artificial reefs and are all derived from the AWOIS listings provided by NOAA, as are

the six “liberty ships” in the list. The 23 “obstructions” in the 1989 database represent

unidentified sunken objects that apparently have been identified as obstructions to
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navigation. One of these obstructions is identified as a helicopter, and the source of

information on all but one obstruction was the Naval Hydrographic Office (HO). The

single exception came from the AWOIS records of NOAA. The 244 items identified as

“unknown” represent unknown vessels. Information on these unknowns came from

several sources, but mainly AWOIS and HO.

A careful review of the 1989 shipwreck database reveals the presence of a number

of duplicate entries for the same vessel. It is apparent that in compiling this listing

Garrison et al. (1989) included duplicate information on the same vessel if it appeared in

different sources under different spellings or if the same vessel appeared at different

locations in these sources. For example, the vessel Breton Island appears three times in

the 1989 list at slightly different geographic coordinates falling in two different lease

blocks. Information on the Breton Island was obtained from three different sources.

Similarly, the vessel Capt. Carl appears twice in the list at slightly different coordinates,

although both place the vessel in the same lease block in the West Cameron area.

Examples of the same vessel appearing multiple times under slightly different spellings

include the Nona Gail and Nona Gale; the Cuahuhtemuc and Cuahutemac and the City S

Toledo and City of Toledo. Generally, information on the vessels listed more than once

under different spellings was derived from different sources, plus the locations of loss are

often slightly different. However, this is not always the case. The vessel listed as the

City S Toledo and City of Toledo is provided at the same position of loss, although the

information came from two sources, AWOIS and HO. It should be noted that this vessel

was actually named Cities Services Toledo, a tanker sunk by a German submarine in

World War II (Moore 1990).

The Garrison et al. (1989) inclusion of the same vessel several times because of

name or position differences represents a cautionary approach due to the inability in

many instances to determine which source of information was correct. In light of the

often poor quality and contradictory nature of these sources of information, this approach

is not seen as unreasonable if the objective is to be as inclusive as possible when

identifying high-probability locations and areas for wreck occurrences. However, these

multiple inclusions will skew to varying degrees most attempts to quantitatively

characterize the sample of wrecks in the database.

The 1989 shipwreck database also includes 240 vessels that fall in lease blocks

within state waters. Three of these vessels are in Louisiana waters; the remaining 237 are

in the state waters of Texas. Several of the Texas state lease blocks contain large

numbers of shipwrecks. For example, the 1989 database assigned 58 shipwrecks to the

same lease block in the South Padre Island Area and all, in fact, have been assigned the

same geographic coordinates. Information on almost all of these wrecks comes from

TAC files and they have been assigned the same coordinates because the historical

information on their place of loss is so vague. For example, many of these vessels are

simply reported as lost near or off Brazos Santiago Pass, the entrance into Brownsville at

the lower end of Padre Island.
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When identifiable duplicates are removed from the 1989 shipwreck database,

there appear to be 1,222 unique entries, although even here some duplications might still

exist. Of these entries, 986 are vessels falling in Federal waters, 214 are vessels falling in

state waters, and 22 items are “obstructions.”

The complete 1989 shipwreck database of 1,469 entries is important because it

was used as a principal source for identifying high-probability areas for shipwreck

occurrences in the GOMR. Ultimately, the 936 lease blocks in which these 1,469 wrecks

fall, plus adjacent blocks, were identified by MMS as high-probability locations and any

development of these blocks would require a survey strategy designed specifically to

locate historic shipwrecks. More complete discussions on these survey requirements are

presented below.

3.1.2. Characteristics of the 1989 Model of Shipwrecks in the GOMR

3.1.2.1. Historical Setting

The development of a listing of shipwrecks was only one aspect of the Garrison et

al. (1989) study. That study also presented a synthesis of the maritime history of the Gulf

of Mexico, extending from 1508 when Sebastian de Ocampo became the first European

to sail on Gulf waters (Weddle 1985), to the 1980s. This synthesis looked at the positions

of shipping routes and the development of ports in the Gulf of Mexico area over time as

precursors for understanding the distribution of shipwrecks in the region. The findings of

the present study did not indicate significant differences in the historical overview

presented in Garrison et al. Where divergences do exist, they are mainly differences in

emphasis on specific historic topics or trends. These differences are more fully

considered in the following chapter in discussions concerning the newly developed

shipwreck database. The historical overview developed by Garrison et al. (1989) is

briefly reviewed here.

The historical assessment by Garrison et al. (1989) showed that prior to 1700, the

trade routes in the Gulf were largely keyed to Spanish trade out of various ports along the

eastern coast of Mexico, of which Veracruz was the most important, and Central

America. Out of these ports the wealth of “New Spain” was carried back to Spain. Ports

in the Caribbean, such as Havana on Cuba and others on the island of Santa Domingo,

became important as stopping points for vessels traveling into and out of the Gulf

(Garrison et al. 1989:II-31–11-33). Havana, in particular, became significant as the

assembly point for the two principal Spanish convoys sailing annually between Spain and

the New World from the sixteenth to the end of the eighteenth century. These were the

New Spain flota, which sailed from Spain to Veracruz, and the Terra Firma flota that

sailed from Spain for Cartagena on the coast of Colombia. Both of these fleets were to

gather in Havana on their return to Spain (Pearson and Hoffman 1995:10).

The arrival of the French in the Gulf region in the late 1600s lead to the

development of several ports along the northern Gulf coast, such as Biloxi, Mobile, and

New Orleans. The growth of these and other ports and their increasing participation in
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maritime trade lead to a shift in Gulf trade routes in the eighteenth century. Shipping

activity was now concentrated along the central and eastern Gulf coast from about the

mouth of the Mississippi River eastward. The French also maintained trade connections

with their colonies in the Caribbean and, to a lesser extent, carried on trade with Spanish

ports in New Spain and Cuba.

The second half of the eighteenth century saw an increase in coastal trade along

the northern Gulf coast. In 1763, the French lost their holdings in Louisiana to Spain and

Britain but several of the old colonial ports remained important, particularly New

Orleans, Mobile and Pensacola. Trade continued to increase, particularly after the United

States’ acquisition of Louisiana in 1803 and Florida in 1819. The expansion of cotton

agriculture into the states of Alabama, Mississippi, and Louisiana in the 1820s and 1830s

had a great stimulus on maritime trade in the Gulf. Cotton became the principal cargo

shipped out of ports such as New Orleans and Mobile and was carried by sailing vessel,

and later steamship, to ports on the East coast, particularly New York, and Europe. At

about this same time, as Garrison et al. (1989:II-23) point out, there was an expansion in

the coastal trade west of the Mississippi River with the establishment of the Texas

Republic in 1836. Large numbers of sailing vessels of all sizes as well as steamers were

operating in the Gulf of Mexico during the period from 1830 to 1860. Numerous small

sloops and schooners as well as paddlewheel steamers were involved in the local

“coasting” trade carrying produce between coastal towns and communities from Florida

to Texas. Larger sailing vessels and steamships were carrying cotton in huge quantities

from New Orleans and Mobile out of the Gulf to distant American ports such as New

York or to Europe.

The advent of the Civil War, however, stopped all normal maritime commercial

activity in the Gulf. The establishment of the Federal blockade along the coast stopped

most vessels from entering and leaving ports after 1861; only a few blockade runners

remained active during the war.

Maritime commerce in the Gulf began to revive after the Civil War. Southern

ports soon established or reestablished direct trade connections with ports in South

America, Europe, the eastern United States and the Caribbean. Over time, fewer and

fewer United States vessels were used in this and other maritime trades, as a wide variety

of foreign vessels began to call at the old Gulf coast ports, as well as new ones, like

Tampa and Port Arthur. New commodities, such as oil, joined and began to replace some

of the traditional exports of the region. Garrison et al. (1989:II-23) note that the Gulf

trading patterns and routes established in the latter part of the nineteenth century

continued with relatively little change up to World War II. Established trading routes

were disrupted during the war, in part because of the operation of 24 German submarines

in the Gulf of Mexico that were successful in sinking over 50 vessels (Wiggins

1995:238). With the revival of commercial traffic after World War II, there was an

increase in traffic to secondary ports along the Gulf coast. The commodities carried by

vessels did change over time, with oil, grain and manufactured goods becoming

increasingly important exports. By the 1980s, the port of Galveston-Houston had become

the largest in the Gulf in terms of vessel traffic, followed by New Orleans-Mississippi
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River. The twentieth century did see a shift in the position of Gulf trade routes, as the

“principal axis of traffic shifted westward from the east-central Gulf to the west-central,”

a reversal of the trend seen in the late nineteenth century (Garrison et al. 1989:II-23). A

principal factor in this shift was the opening of the Panama Canal in 1914.

As noted, Garrison et al. (1989) provided this brief overview of the history of

maritime traffic in the Gulf of Mexico to set the stage for various analyses of the

shipwreck database they developed. Particularly important was the establishment and

locations of trade routes and ports over time, two variables that they used in analyses of

shipwreck distributions in the Gulf.

3.1.2.2. Natural Setting

Garrison et al. (1989) present discussions on the natural setting in the Gulf of

Mexico specifically as it related to its impact on the occurrence and distribution of

shipwrecks. They examined the occurrence of prominent natural hazards, such as reefs,

barrier islands, shoals and bars, and the impacts they have had on navigation and on

vessel loss. Garrison et al. (1989) also examined winds, currents and waves in the Gulf

as causal factors of vessel loss in the Gulf. Natural wind and current patterns were

particularly critical during the age of sail when vessels attempted to take advantage of

these natural forces whenever possible (Hoffman 1980). Thus, the positions of early

sailing routes were, to varying degrees, influenced by natural forces, particularly the

patterns of winds and currents.

Current circulation in the Gulf of Mexico is fairly complex and involves the

interaction of the dominant current, known as the Loop Current, and associated eddies.

The deeper waters of the Gulf are dominated by the Loop Current, which roughly

occupies the central Gulf. This current that enters the Gulf from the south makes a large

sweeping clockwise arc around the Gulf and exits to the east through the Straights of

Florida, to become the Gulf Stream in the Atlantic (Sturges 1993) (Figure 3-1). The path

of the Loop Current varies over time; portions might be only 10 to 20-km wide and

represent near-surface phenomena, while the full current might be 100-km wide and

penetrate to depths of 1,000 meters (Sturges 1993:28). The Loop Current often doubles

back on itself and strong “ring” currents often break off and continue to flow in a large

circle in the western Gulf.

The shallow waters of the Gulf of Mexico, as they exist on the Outer Continental

Shelf, are influenced by eddies produced by the Loop Current as well as by winds, tides

and freshwater inflow (Garrison et al. 1989:II-51). In the central and western Gulf, the

inshore flow is normally westward except during the summer months of June, July and

August, when it reverses and flows to the east. The westward flow is driven by the

prevailing winds, the easterly trades that blow generally in a westward direction for much

of the year. The inshore current flows in the eastern Gulf, along the coast of Florida, are

somewhat more variable because the prevailing easterlies blow across the shelf, limiting

the ability of longshore wind-driven currents to develop (Sturges 1993:38-39). During
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the summer months, the inshore current in the western Gulf reverses direction and flows

to the east (Garrison 1989:II-51).

Figure 3-1. Position of the Loop Current on January 2, 1982. The values represent sea surface

temperatures. The circular feature marked “WE” is a small anticyclonic, eddy or

detached ring (Sturges 1993:Figure 3.3).

The wind regime in the Gulf of Mexico is dominated by the prevailing trade

winds that blow generally from the east. In the western Gulf, wind direction varies from

a generally southwesterly flow in the summer to a northeasterly direction in the winter.

The wind direction in the eastern Gulf is less variable and most typically blows in a

generally westward direction (Garrison et al. 1989:II-51; Sturges 1993:42-44). This

prevailing wind regime is periodically interrupted by two other wind systems, “northers”

and hurricanes. During winter months, transient frontal systems, known as northers,

periodically move south from the continental United States into the Gulf of Mexico.

These frontal systems are often accompanied by strong winds that can create waves up to

seven meters high. These frontal systems often had deleterious impacts on vessels

traveling in the upper latitudes of the Gulf.

Hurricanes represent the strongest wind systems in the Gulf of Mexico and have

the greatest potential for damaging and sinking vessels. However, hurricanes are rare
3-8

events, with historical data indicating an average of only one hurricane a year entering

the Gulf of Mexico (Hayes 1967; Henry et al. 1975; Tannehill 1956). Garrison et al.

(1989:II-53-54) looked at hurricane paths and frequencies in the Gulf and their impacts

on vessel losses for the period from the earliest accounts of hurricane losses in the mid1500s up to the 1980s. They note that the paths of historic hurricanes in the Gulf are

difficult to plot accurately because they are so variable. As a result, it is difficult to

accurately correlate hurricanes with vessel losses unless there is a specific historical

account relating the loss to a specific hurricane. In their analysis of hurricane and vessel

loss data, Garrison et al. (1989:II-54) did not see a “strong correlation between hurricanes

and shipwrecks” and suggested that storms acted “only in concert with other variables

such as port location and shipping routes” in creating vessel losses.

3.1.2.3. Factors of Shipwreck Preservation in the Gulf of Mexico

The 1989 study also examined factors that might lead to the preservation of

historic shipwrecks in the GOMR by looking at pertinent environmental factors and their

known or presumed impacts on wrecks. In terms of wooden shipwrecks, Garrison et al.

(1989:II-69) note that the principal element in estimating preservation is “the

identification of the burial sediment, its depth, and the inherent biological communities

associated with such conditions.” Using a series of examples of historic wrecks from

various settings in the Gulf and elsewhere, they looked at the impacts of various natural

factors on wreck preservation. These factors included sediment characteristics, energy

zones, and biological and chemical factors. Comparing these factors against conditions

found at several specific shipwrecks, they drew several conclusions about the relationship

of preservation to site-specific environment. In general, the study concluded that

“preservation is enhanced in fine-grained sediment and low energy environments and

reduced in coarse grained sediment and dynamic environments” although rapid burial of

remains, even in coarser-grained sediments, can reduce deterioration. They also note that

preservation can be enhanced in oxygen-deprived deepwater settings, such as found in

parts of the northwestern Gulf of Mexico (Garrison et al. 1989:II-83; Rezak et al. 1985).

From this assessment of these various environmental factors on known

shipwrecks, the Garrison et al. study projected expected preservation potentials for

various areas of the Gulf of Mexico in terms of High, Moderate, or Low potential

(Garrison et al. 1989:Figure II-24).

3.1.2.4. Analysis of the Spatial Distributions of Shipwrecks in the

1989 Study

The 1989 study relied on a variety of statistical analyses to examine the shipwreck

database developed. Most of these analyses were directed at trying to assess the causal

factors behind observed spatial patterns seen in vessel losses. In addition, the study

looked at chronological trends in vessel losses and related these to several factors, such as

the development and distribution of ports around the Gulf and the shifting positions of

principal trade routes. Because that study collected only minimal information on vessel

characteristics, specifically the year of loss, characterization of the population of wrecks
3-9

in the database was limited to assessing the interrelationships of chronological factors and

spatial patterning.

In addition to looking at the simple spatial distribution of wrecks in the Gulf of

Mexico on the basis of reported position of loss, Garrison et al. (1989:II-86-II-114)

looked at vessel losses within quadrants of 0.5- and 1.0-degrees of latitude and longitude

in size and within the 3-mile-square standard MMS lease block. The 0.5-degree quadrant

analysis did show spatially discrete concentrations of wrecks that tended to be associated

with port locations and, to a lesser extent, with areas of marine hazards. Cluster analysis

was used to examine the association of 3-mile-square lease blocks on the basis of the

number of vessels they contained and the dates of losses of these vessels. Finally, factor

analysis was conducted on the wrecks in the database in an effort to discriminate some of

the causal factors behind the distribution of shipwrecks seen across the Gulf. One

analysis was concerned with chronological factors, and looked at the relationships

between the location of wrecks against seven variables: four time periods (seventeenth,

eighteenth, nineteenth, and twentieth centuries), age of ports, ports, and storms. The

location of wrecks was based on the recorded position of the loss in one of 26 areas that

consist of 1-degree-wide areas along the Gulf coastline from Brownsville to the Dry

Tortugas. Garrison et al. (1989:II-109) note that this analysis relates only to vessels lost

along “the Gulf coastline,” but it is impossible to tell from the discussions how far out in

the Gulf the 26 areas, and thus shipwrecks, used in the analysis extended. Interpretation

of the results of this factor analysis showed several things: 1) a spatial association of

sixteenth, seventeenth and eighteenth century wrecks versus eighteenth and nineteenth

century wrecks; 2) a moderate association of nineteenth century shipwrecks and port

development; and 3) the presence of a port seemed to be more strongly associated with

wreck frequency than with the number of years the port was in existence (Garrison et al.

1989:II-110).

The second factor analysis was concerned with areal factors and used six

variables (hurricanes, ports, routes, hazards, energy, and wrecks) and 10 cases (time

periods) per variable. Ten large areas encompassing the GOMR were compared using

these variables in relation to shipwreck frequencies in the areas. Although Garrison et al.

(1989:II-110) state that each of the six variables was considered within 10 time periods,

these periods are not defined and it is unknown if these represent even historical time

intervals since circa 1600 or are the uneven intervals used in the cluster analysis noted

above (i.e., 1600 to 1699, 1700 to 1749, 1750 to 1799, 1800 to 1849, 1850 to 1899, 1900

to 1919, 1920 to 1939, 1940 to 1959, 1960 to 1979, and 1980 to 1988 [see Garrison et al.

1989:Figure II-42]). The 10 areas were: 1. Rio Grande, 2. Western Area, 3. Central

Area, 4. Central Louisiana, 5. Miss./Alabama, 6. West Florida, 7. Big Bend, 8. Middle

Ground, 9. Southwest Florida, and 10. Dry Tortugas (Garrison et al. 1989:III–J-23). 

3.1.2.5. Summary of Findings of the 1989 Study

Garrison et al. (1989) note that the observed spatial distributions of shipwrecks in

the Gulf of Mexico do not always explain the causal factors behind these distributions.

That study’s efforts at factor and cluster analyses showed some relationships between
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positions of vessel loss and a variety of variables, but the causal link between the two is

not always evident. Among the general findings of the study was the fact that vessel

losses in the Gulf increased over time, which they attribute in part to improved

technology that leads modern mariners to expose their vessels to greater risks than earlier

navigators would have. The study also found a general association between hurricane

frequency and the occurrence of wrecks, but the “highest hurricane frequency areas” did

not always exhibit the highest occurrence of losses (Garrison et al. 1989:II-115).

Garrison et al. did note that it was very difficult to correlate individual vessel losses with

specific hurricanes or hurricane paths because of the often minimal information in the

historic records.

Another finding of the 1989 study was that wrecks did tend to concentrate at

natural hazards, as was expected. This was particularly evident in the over 300-km-long

complex of reefs and shoals forming the Florida Keys, the Marquesas and the Dry

Tortugas. Here, the “convergence of winds, current, reefs, and storms” all contributed to

making this probably the most dangerous portion of the Gulf, particularly for sailing

vessels (Garrison et al. 1989:II-115). Even after the advent of steam, this area remained

dangerous for shipping.

Garrison et al. (1989:II-116) observed several broad-scale patterns in the

distribution of shipwrecks in the Gulf. For one, there was an increase in losses in the

open waters of the eastern Gulf in the late nineteenth and twentieth century, related to

changes in shipping routes. For this same period, losses in the western Gulf tended to

occur in nearshore areas such that open water losses in the western Gulf were less than

half of those seen in the open waters of the eastern Gulf. The factors behind these

differences were not readily apparent, but they were thought to be linked to traffic

patterns (Garrison et al. 1989:II-116).

Garrison et al. (1989), in particular, show that shipwrecks in the Gulf are

concentrated in the nearshore areas, a point mentioned earlier and one observed by most

researchers. Further, the 1989 study showed a strong correlation between the locations of

wrecks and ports, a trend that is most evident beginning in the nineteenth century. It was

also found that the number of shipwrecks in the Gulf closely followed the number of

ports established (Garrison et al. 1989:II-120).

Relying on their findings concerning shipwreck distributions and preservation

potential, Garrison et al. (1989:II-122) assigned values of high, moderate or low to the 66

MMS-identified areas and subareas in the GOMR for the categories of “shipwreck

potential” and “preservation potential.” Shipwreck potential was based on density of

wrecks occurring in the area or subarea and were: low ≤ 175 wrecks per area; moderate

= 175 to 500 wrecks per area; and high ≥ 500 wrecks per area. Values for preservation

potential were derived from assumptions about the natural conditions found in the areas

relative to vessel preservation. These two values, shipwreck potential and preservation

potential, were merged to obtain an “overall potential” for each of the 66 areas.
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From this assignation of potentials to areas, Garrison et al. (1989:II-122) noted

several trends in the shipwreck data. These were: 1) an increased distribution of wrecks

in the eastern Gulf area away from the nearshore zone, but a lower preservation potential

relative to the central and western Gulf; 2) more early wrecks in the central and Eastern

Gulf than had been previously thought; and 3) an increased potential for unreported

wrecks in high density areas because of higher preservation potential.

Out of these findings, the 1989 study recommended several changes in Cultural

Resources Management Zone 1 (CRMZ1) (also called Archaeological Resource

Management Zone 1 [ARMZ1]), the identified shipwreck high-probability area then used

by MMS to guide offshore lease block surveys. Garrison et al. (1989:II-123)

recommended the following: 1) the CRMZ1 should be moved to within 10-km of the

coast; 2) delineation of several specific high-probability zones in the vicinity of several

ports and navigation hazards where high densities of wrecks were identified; and 3)

delineation of individual high-probability lease blocks outside of CRMZ1 and the highprobability zones related to the occurrence of specific historic shipwrecks. Because of

the often unreliability of the reported positions of vessel losses, the eight contiguous lease

blocks surrounding these individual blocks should, also, be considered high-probability

areas. Subsequently, this latter factor came to be called the “centroid concept.”

3.2. Application of the 1989 Model of Shipwrecks in the Gulf of Mexico to Cultural

Resources Management by MMS

Because of the findings in the Garrison et al. study, the MMS redefined the area

that had been designated as “high probability” in terms of historic shipwreck occurrence

and the remote-sensing survey techniques and strategies to be used. Prior to 1989 and

based on the 1977 Coastal Environments, Inc. study, all of the area shoreward of a line

roughly between the 40 and 60-m bathymetric contour line had been identified as

Cultural Resources Management Zone 1 (CRMZ1) or Archaeological Resource

Management Zone 1 (ARMZ1). This zone had been considered the high-probability area

in terms of historic shipwreck occurrence and was the area requiring the most stringent

remote-sensing survey strategies. As a result of the 1989 study, which showed that

approximately 80 percent of historic vessels were lost within 10 km of the shoreline,

MMS shifted the outer boundary of ARMZ1 to a point 10-km from the Gulf shoreline.

This placed most of the newly defined high-probability area in state waters and whereas

ARMZ1 originally contained an estimated 3,410 lease blocks, the redefinition of the

boundary reduced this number considerably (MMS 1990). MMS also accepted the

findings of the 0.5-degree quadrant analysis presented by Garrison et al. that identified

twenty-one 0.5-degree quadrants displaying reported shipwreck densities sufficient to

identify them as high-probability areas. These 21 quadrants were closely associated with

port locations or specific natural hazards; most of the lease blocks they contained fell in

state waters, outside of the boundaries of the GOMR. Finally, MMS adopted the centroid

concept proposed by Garrison et al. (1989) wherein a number of high-probability areas

consisting of units of nine contiguous lease blocks were identified (MMS 1990). These

units were defined because of the recognition that location data on so many shipwrecks

was so poor that it was deemed reasonable to encompass a larger area than the individual
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lease block in which the vessel was reported to have been lost. These units consisted of

that lease block, plus the eight contiguous blocks. These nine-block units fell outside of

the other identified high-probability areas and tend to be scattered widely across the

GOMR.

As a result of the 1989 study, in 1990 MMS estimated that it reduced the number

of high-probability lease blocks from approximately 3,410 to 710 (MMS 1990:3).

Included in these 710 lease blocks were those that contained wrecks previously

discovered by MMS-mandated surveys, a factor not considered in the Garrison et al.

recommendations. Essentially, these blocks were those that would be subjected to survey

strategies designed specifically to locate historic shipwrecks.

The Garrison et al. study also conducted a reevaluation of the remote-sensing

survey strategies then being employed in the GOMR, and the recommendations from

these findings were incorporated by MMS into their survey requirements. Complete

discussions on this aspect of the Garrison et al. study are provided in the second section

of this report, but they are briefly mentioned here to provide a background for the

following discussions on the results of offshore surveys as tests of the 1989 model.

Garrison et al. (1989) recommended, and MMS accepted, that the survey line spacing in

the newly identified high-probability lease blocks would be reduced from 150-m to 50-m

if the water depth in that lease block was less than 60-m. The other survey requirements

then in place, particularly the use of magnetometer and sidescan sonar, would be

maintained. Those high-probability lease blocks with water depths greater than 60-m

would require surveys with line spacing of 300-m, and no magnetometer would be

required because of the recognized difficulty of maintaining the position of a

magnetometer sensor at great depths (MMS 1990:2-3).

The redefinition of high-probability areas and change in survey strategies by

MMS established the parameters for offshore surveys as they have been conducted for

the past 12 years. Ultimately, the findings of these surveys provide the basis for testing

the model of shipwreck occurrence as developed by Garrison et al. (1989). Discussions

on the conduct of lease block surveys and their findings relative to the present MMS

shipwreck model are presented below.

3.2.1. MMS Archaeological Survey Requirements

The conduct of cultural resources remote-sensing surveys in the Gulf of Mexico

and the requirements for reporting on these surveys have been established in a series of

Notices to Lessees (NTLs) issued since 1974. These NTLs provide specific information

and guidelines for conducting cultural resources surveys on the OCS in the GOMR to all

lessees and operators of Federal oil, gas, sulfur and salt leases and pipeline rights-of-way

in the area. The NTLs provide information on required survey parameters and

instrumentation for use in designated lease blocks and establish the standards for the

archaeological resource reports required of every survey. In addition to the NTLs, MMS

has released a series of Letters to Lessees (LTLs) that mainly convey clarifications or

provide timely pertinent information.
3-13

Since 1975, changes in survey and report requirements have been incorporated

into these NTLs as knowledge of the potential cultural resources of the GOMR has been

refined, as technological advancements have occurred in the survey and geophysical

equipment used, and as pertinent regulatory authorities have changed. Presently (2002),

archaeological survey requirements in the GOMR are guided by Notice to Lessee No.

2002-G01, effective March 15, 2002. This new NTL (NTL No. 2002-G01) replaces NTL

No. 98-06, issued August 10, 1998. The Notices to Lessees provide guidelines relative to

drowned terrestrial prehistoric sites on the OCS as well as to historic period shipwrecks

and lighthouses. Only the historic period sites are of concern here. As noted, the present

requirements for survey for historic shipwreck sites are largely derived from the findings

of the Garrison et al. (1989) study.

To guide its mineral leasing activities, the Federal government has divided the

lands of the GOMR into 3-mile-square (23.3 km2) lease blocks. Groups of numbered

lease blocks are incorporated into larger areas. Presently there are 70 lease areas

designated in the GOMR (see Figure 2-2). The number of lease blocks within each lease

area varies considerably. For example, the South Pass Area, just off the mouth of the

Mississippi River, contains fewer than 100 lease blocks, while several of the larger areas

in the central Gulf (e.g., Atwater Valley Area, Lloyd Ridge Area, Henderson Area)

contain over 1,000 lease blocks. In those areas adjacent to the coast, many numbered

lease blocks fall completely or partially within state waters and thus outside of the

boundaries of the project area of the present study. Although the 3-mile-square is the

standard lease block size, numerous smaller blocks occur, specifically where boundaries

have been established between lease areas. The 3-mile-square lease block is extremely

important because it is the principal spatial unit that is used to incorporate the model of

shipwreck occurrences in the Gulf and it is the principal unit around which decisions are

made relative to the need for archaeological surveys. Additionally, other than pipeline

routes or specific well sites, the lease block represents the standard physical unit within

which most MMS-mandated archaeological surveys are conducted. Thus, it represents a

standard unit for making various sorts of quantitative comparisons across the vast area of

the GOMR.

MMS does not require cultural resources surveys in all offshore lease blocks, only

those known or considered highly likely to contain significant cultural resources, based

on the best available data. The survey requirements vary dependent upon whether the

lease block has been identified as having a high potential for containing shipwrecks or a

high potential for containing prehistoric sites. In regard to historic shipwrecks, MMS

requires two levels of archaeological resources surveys. In accordance with the

guidelines established by the latest NTL, effective March 15, 2002, for those lease blocks

identified as having a high probability of containing historic resources (i.e., principally

shipwrecks) and which exhibit water depths of 200-m (656 ft.) or less, the survey lines

must be no more than 50-m (164 ft.) apart. In those lease blocks with a high probability

of containing shipwrecks that fall in areas with water depths greater than 200-m, survey

line spacing must be no more than 300-m (984 ft.) apart. This latter spacing also is the

requirement for all lease blocks deemed to have a high probability of containing
3-14

prehistoric archaeological sites, regardless of water depth (MMS 2002). These same

standards are applied to pipeline rights-of-way and drilling platform sites.

The water depth parameters embodied in the new NTL represent a significant

difference over earlier requirements. The requirements in place between 1990 and 2002

used a water depth of 60-m as the separation between the 50-m survey line spacing and

the 300-m spacing relative to historic shipwrecks (MMS 1998). These were the

requirements in place over most of the period of the present study such that various

figures and analyses typically reference the 60-m contour as well as the 200-m contour.

Prior to 1990, the MMS mandated a survey line spacing of 150 m in all of the lease

blocks then assigned to the high-probability zone known as Archaeological Resources

Management Zone 1. It should be noted that all of the MMS survey data utilized in this

study was collected using the pre-2002 line spacing and water depth requirements.

Additionally, all of the lease blocks presently identified as high-probability locales

relative to prehistoric sites fall in water depths of less than 60-m and all of these require

the 300-m spacing survey. This is important to recognize because, as is noted below,

many of the shipwrecks identified by MMS-mandated surveys resulting from the 1989

study have been found in those lease blocks where survey was conducted because the

block was deemed to have a high potential for containing prehistoric sites, not historic

shipwrecks.

In those surveys requiring 50-m survey line spacing, the required remote-sensing

instruments are a proton precession or cesium total field magnetometer; a dual-channel,

dual-frequency sidescan sonar system; a high frequency sub-bottom acoustic profiler; and

a high frequency, narrow beam hydrographic echo sounder. The MMS also requires

specific operating parameters for these instruments. For instance, the magnetometer

sensor must be fitted with a depth sensor and it must be towed no more than 6-m (20 ft.)

above the seafloor, and the sidescan sonar system must be operated in the 300 to 500 kHz

range in water depths less than 200-m (MMS 2002). Navigation for surveys must utilize

“a state-of-the-art continuous positioning system correlated to annotated geophysical

records” (MMS 2002). In recent years, essentially all surveys have been conducted using

differentially corrected geographic positioning systems (DGPS).

The principal equipment difference between surveys requiring 50-m line spacing

and those requiring 300-m spacing is that the magnetometer is not required in the latter

when water depths are greater than 200 m. This is in part because of the difficulty in

controlling the position of the sensor at great depths, but also because the survey line

spacing is so great that even large ferrous objects, like a shipwreck, could easily go

undetected if they fell between two survey lines. The sidescan sonar is required in those

300-m blocks identified as having a high potential for containing prehistoric sites and, as

noted, its use in these circumstances has been instrumental in identifying the majority of

shipwrecks in the GOMR to date.

For historic shipwrecks, the two most critical instruments are the magnetometer

and sidescan sonar and, as is discussed below, the sidescan sonar has been most heavily

relied on in the identification of shipwrecks. The other instruments in the equipment
3-15

array, the subbottom profiler and depth sounder, are less commonly relied on in the

identification of wrecks, but sometimes they will provide information on the elevation of

a particular wreck, if the instrument passes directly over the target.

In addition to these equipment requirements, the NTLs also provide information

on the requirements of the archaeological survey report that is to be submitted to the

MMS upon completion of the remote-sensing survey.

3.2.2. Results of MMS-Mandated Archaeological Surveys: Testing the 1989

Model of Shipwreck Occurrences

3.2.2.1. Identification of High-Probability Lease Blocks

The results of the Garrison et al. (1989) study have guided the implementation of

the MMS archaeological survey program for the past 12 years. The results of that survey

program provide our best measure of the utility and reliability of the model of wreck

distributions derived from the 1989 study. Evaluation of the model requires information

on a variety of parameters. For example, it is important to know which high-probability

lease blocks were originally designated from the 1989 study, which of these highprobability lease blocks have been surveyed, and what are the results of those surveys.

Additionally, in order to obtain some quantitative measure of the reliability or

“predictability” of the 1989 model of shipwreck distributions, it is important to have the

same categories of information for those lease blocks identified as unlikely to contain

shipwrecks.

Exactly how many and which lease blocks have been identified as highprobability blocks for shipwrecks is of critical importance. The Garrison et al. (1989)

study does not provide a specific list of the high-probability lease blocks ultimately

identified, but their list of shipwrecks and their recommendations concerning the

identification of groups of lease blocks with high probabilities for containing wrecks

were used to develop the list. In their final shipwreck database Garrison et al. identified

1,469 “shipwrecks.” These shipwrecks fall into 851 offshore lease blocks. Seventy-two

of these lease blocks fall in state waters; the remaining 779 lease blocks fall in the

GOMR and are of principal interest here. As noted, however, this total number of wrecks

included many duplicates as well as some items classified as “obstructions” that may or

may not be actual vessels. Regardless, these 1,469 entries have served the MMS as one

basis for identifying high-probability areas in the GOMR. Working from this list of

wrecks, the MMS followed the recommendations of the 1989 study and designated

groups of high-probability lease blocks consisting of those falling within 10-km of the

coast line; those falling within the 0.5 degree quadrants which contain high densities of

reported wrecks; and the numerous nine-lease block units selected because of questions

about the reliability of a specific record of loss.

A comparison of the shipwreck database developed by Garrison et al. against the

lease blocks ultimately selected shows that the MMS utilized only reported vessel losses

greater than 50 years old to assign as center points for the nine-lease block units.
3-16

Younger wrecks and those for which no date of loss was known were not used in the

identification of the nine-lease block units. For example, Garrison et al. (1989) had

originally identified five vessel losses in the southern third of the Vermilion Area off the

western Louisiana coast. These losses all occur outside of the 60-meter depth zone.

These vessels were the Alaria, a vessel that sank in 1975; the Barger, date of loss

unknown; the Swiftfish, date of loss unknown, the Righard P., date of loss unknown; and

an unknown vessel, also with an unknown date of loss. Because the Alaria’s loss had

occurred less than 50 years earlier and because no information was available indicating

any of the other vessels were over 50 years old, the MMS has designated no highprobability areas in association with these reported wrecks.

Since 1989, additions and subtractions have been made to the original list of lease

blocks identified as high-probability locales for historic shipwrecks, and no compilation

of the originally identified blocks seems to exist (Rik Anuskiewicz, personal

communication 2002). Therefore, it has been necessary to reconstruct that original list

from data currently at hand. The MMS office in New Orleans provides specific

information to offshore lessees as to the survey requirements in the GOMR, including a

list of which offshore blocks require 50-m survey spacing (designated “50-m blocks” in

the following discussions) and which ones require 300-m spacing (designated “300-m

blocks”). This list is currently available online at the MMS, Gulf of Mexico Region,

New Orleans office webpage (www.gomr.mms.gov), and it was accessed in November

2001 to obtain a listing of high-probability lease blocks. This list includes 1,830 lease

blocks requiring 50-m survey line spacing, all of which are designated high-probability

lease blocks for historic shipwrecks. The list also includes over 6,000 lease blocks that

require surveys at 300-m line spacing. The vast majority of these 300-m blocks fall in

water less than 60-m deep and are identified as high-probability locales for prehistoric

site occurrence, not for historic shipwrecks. The selection of those 300-m blocks

identified as high-probability blocks for shipwrecks has relied on digital files of lease

blocks and their survey requirements developed by MMS and incorporated as a visual

entitled “Archaeological Resources in the Gulf of Mexico” (MMS 2000) depicting all

lease blocks in the GOMR. From these files and visual, 581 lease blocks requiring 300-

m survey spacing have been identified as high-probability blocks relative to historic

shipwrecks. This selection has relied primarily on identifying those lease blocks forming

the nine contiguous lease block units derived from the Garrison et al. (1989) list of

shipwrecks.

These 2,411 lease blocks comprise those that are now (November 2001) identified

by the MMS as high-probability blocks relative to historic shipwreck occurrence.

However, these blocks do not exactly represent those that were originally identified in the

Garrison et al. 1989 model of shipwreck occurrences in the GOMR. As noted, over time,

some deletions and additions to the originally compiled list have been made (Rik

Anuskiewicz, personal communication 2002). Most importantly has been the addition of

a number of lease blocks to the “high-probability” category when offshore surveys

identified shipwrecks or objects believed to be shipwrecks in them. Most of these lease

blocks containing identified shipwrecks, or possible shipwrecks, appear to have been

added in 1990 when the results of previously conducted MMS-mandated surveys were
3-17

incorporated into the results of the Garrison et al. study (MMS 1990). However, because

the lease blocks containing identified wrecks were not elements of the 1989 model of

shipwreck distributions as developed by Garrison et al., they must be removed from

consideration when testing that model. Apparently, no separate list of these additions has

been compiled by the MMS, but a careful review of the MMS digital files and visuals

noted earlier, plus the results of offshore remote-sensing surveys provided by the MMS,

indicates that 35 lease blocks containing identified wrecks are included as 50-m, highprobability blocks. Originally, these 35 lease blocks (all of which fall in water depths

less than 60 m) would have been designated 300-m high-probability blocks on the basis

of their prehistoric site potential; none were identified in the 1989 model as highprobability locales for historic shipwrecks. Additionally, 26 lease blocks (all in water

depths greater than 60-m) that were not identified as high-probability blocks in the 1989

model and, therefore, would have required no archaeological survey, were redesignated

300-m blocks because the remains of shipwrecks had or have been found in them. A

review of the present (November 2001) list of 2,411 blocks requiring survey for historic

shipwrecks provided on the MMS webpage reveals that these 61 lease blocks are now

included in that list. One lease block appears differently in this list of blocks requiring

survey and those provided in the digital files and visual supplied by the MMS. The

webpage list includes block Garden Banks 255, one of those changed from a no-survey

status to a 300-m survey requirement, but this block is not shown as a 300-m block on the

MMS visual (MMS 2000). However, the adjacent block, Garden Banks 254, is. A

review of extracts from archaeological survey reports obtained from the MMS reveals

that a pipeline survey passed through the area of Garden Banks 254 and 255 that

identified an “object” on the bottom. The MMS records for the survey place the object in

Garden Banks 254, but the coordinates from the survey place the object in Garden Banks

255. Regardless, the important point is that these 61 lease blocks have to be removed

from the present list of high-probability blocks in order to conduct any accurate

assessments of the shipwreck model as it was formulated in 1989.

Additionally, some other changes have been made to the original 1989 list of

high-probability blocks. A list provided by MMS in March 2002 indicates that 32 lease

blocks have had survey requirements changed from 50-m to 300-m and 27 blocks have

been released from all archaeological survey requirements (Rik Anuskiewicz, personal

communication 2002). A review of the recent list of blocks requiring survey on the

MMS webpage, however, reveals that a few of these changes have not been incorporated

into this list of blocks. For example, 18 lease blocks in the Mississippi Canyon Area

were reportedly released from any survey requirements in 1999, but one of these blocks

is still contained in the list of blocks requiring 300-m survey. This block has been

maintained as a high-probability area because the wreck of the freighter Alcoa Puritan,

sunk by a German submarine in 1942, is located on its boundary. Additionally, five lease

blocks in the South Timbalier Area and the two in the Galveston Area that are reported to

have been changed from 50-m to 300-m requirements in 1997 are still contained in the

MMS list of blocks requiring 50-m survey.

As a result of these various additions and subtractions, it is estimated that a total

of 2,384 high-probability lease blocks in Federal waters were identified in the original
3-18

1989 model of shipwreck occurrences (see Volume III, Appendix C). Of these, 1,804

lease blocks fall in water depths of less than 60-m and, prior to the new regulations issued

in March 2002, required 50-m survey, and 580 lie in deeper water and required 300-m

survey. These 2,384 lease blocks serve as the units for testing the 1989 model of

shipwreck occurrences in the GOMR. This testing requires knowledge of the results of

the MMS-mandated survey program.

3.2.2.2. Findings of the MMS Archaeological Survey GOMR

Program

Information provided by MMS/GOMR reveals that the first report of an offshore

archaeological resources survey was received by them on June 24, 1974. That study

reported on a remote-sensing survey conducted in block West Cameron 437 in offshore

Louisiana, an area where mineral activity has been intensive and where many additional

archaeological surveys subsequently have been conducted. In the intervening 27 years, to

September 2001, MMS/GOMR received 2,835 archaeological resources reports of

offshore surveys (Dave Ball, personal communication 2001). Most of these studies are

related to remote-sensing surveys conducted of entire 3-by-3-mile lease blocks. Some,

however, represent reports for remote-sensing surveys of portions of lease blocks or of

pipelines or well sites. Survey data received from MMS reveals that 2,220 offshore lease

blocks in Federal waters have been subjected to archaeological resources survey. These

include blocks where survey requirements were for the older 150-m as well as the 50-m

and 300-m survey line spacings required after 1990. Most of these lease blocks were

subjected to complete survey coverage. A number, however, appear to have been only

partially surveyed, or the portion surveyed consisted of a pipeline right-of-way passing

through the block. With the data supplied, it is impossible to determine how much area

was covered within these partially surveyed blocks. Also, many blocks have been

surveyed in part or in whole more than once. Several have been subject to survey as

many as four times. Resurvey of a lease block is often requested by the MMS when there

have been changes in the survey requirements for the block between the time of the initial

survey and the time of whatever activity is being conducted to stimulate another survey.

If each of the 2,220 lease blocks had been covered completely by remote-sensing

survey, it would represent a total of 19,980 square miles (51,748 km2

) of archaeological

survey coverage in the Gulf. The total area is certainly less than this, because of the

partial surveys noted. The almost twenty thousand square miles is a huge area, but it

represents only about 7.7 percent of the total area encompassed in the GOMR. Although

the results of these archaeological surveys do serve as our best test of the 1989 model of

wreck distributions, the surveys are not randomly distributed across the entire area of the

GOMR. Figure 3-2 presents information on the number of lease blocks surveyed per

lease area as revealed in archaeological survey reports on file at the MMS/GOMR.

Included in this figure are mainly those reports that are identified as lease block surveys

per se; some surveys of pipeline rights-of-way are not included.
Figure 3-2. Numbers of MMS-required remote-sensing surveys conducted per lease area as indicated by 

received by MMS/GOMR, New Orleans. Data as of September 2001.
3-20

As can be seen, the vast majority of required archaeological lease block surveys

have been conducted in the offshore areas of Texas, Louisiana, Alabama and Mississippi.

Several have been conducted off of the coast of Florida, where mineral exploitation has

been restricted, and few exist for the deeper waters of the central Gulf where

archaeological surveys are not commonly required. The fact that the vast majority of

archaeological surveys have been conducted in the inshore areas of the central and

western Gulf is important, because it represents a “bias” in testing the 1989 model of

wreck distributions. Presently, however, it is impossible to fully compensate for the

spatially restricted nature of the data at hand.

3.2.3. Evaluating the 1989 GOMR Shipwreck Model

3.2.3.1. Precision and Accuracy in Shipwreck Locations in the 1989

Model

The results of the MMS archaeological survey program are used to examine the

1989 shipwreck model in two ways. One is to compare the findings of the offshore

surveys against the specific location information (e.g., specific lease block) on

shipwrecks provided in the 1989 shipwreck database. The other is to examine the survey

findings against the less restrictive location information on wreck occurrences as

reflected in the 2,384 high-probability lease blocks identified in the 1989 model.

As noted, the 1989 shipwreck database contained 1,469 entries falling into 779

different GOMR lease blocks. Some of these entries represent items such as

“obstructions” that may or may not be shipwrecks, plus, as discussed previously, some

duplications exist, with the same vessel listed more than once. As of September 2001,

208 of these 779 high-probability lease blocks had been subjected entirely or in part to

archaeological survey. Survey reports from these lease blocks have been submitted and

reviewed by MMS personnel. As noted earlier, MMS survey requirements have changed

over time and it may be reasonable to presume that the identification of shipwrecks has

improved with these changes. This is probably most true relative to the use of the

magnetometer, where requirements for tighter line spacing and decreased sensor distance

from the seafloor have certainly improved detection. However, it is unknown how many

buried shipwrecks have been located during MMS-mandated surveys only with the

magnetometer because the policy of avoidance means that there are no requirements to

identify or verify the sources of magnetic signatures that might represent shipwrecks.

Essentially, all identifications of sunken vessels have relied on sidescan sonar or a

combination of sonar and magnetometer data. For the present analysis, it is assumed that

the collection of sidescan sonar data in the various surveys was generally adequate to

indicate whether exposed shipwrecks were present. Additionally, it has to be assumed

that the interpretation of the collected data was equivalent and reliable such that if wrecks

or objects were recorded on remote-sensing records, they were identified as such by the

person evaluating the data. Three of these 208 lease blocks contained objects whose

identity could not be confirmed; unidentified “vessels” were identified in four lease

blocks; nine lease blocks contained vessels whose identity was tentatively made, and 192

of these 208 blocks produced negative results; no shipwrecks or suspected shipwrecks
3-21

were found (see Volume III, Appendix D). Survey of one of the lease blocks identified in

the 1989 model as having a single “unknown vessel,” actually located three unidentified

vessels. Thus, 13 (6.25 percent) of the 208 lease blocks identified in the 1989 shipwreck

database that have been surveyed contained identified shipwrecks, while 192 (92.31

percent) of these lease blocks produced no evidence of wrecks.

As noted, this assessment considers only those lease blocks listed in the 1989

shipwreck database. These are those lease blocks within which the most reliably

determined geographic coordinates for shipwrecks fall; they do not represent all of the

high-probability blocks identified in the 1989 model of wreck occurrences. Therefore,

this examination is not a true test of that model, but it does bear on one of the significant

problems encountered in developing statements about historic vessel losses: the accuracy

of the information on location of loss. Garrison et al. (1989:II-11) discuss this problem,

noting that the accuracy of a shipwreck position as they used it was a function of “(1)

geographic coordinates given for the shipwreck and (2) level of precision in the particular

analysis.” The first factor is dependent upon the character of the report of the loss. For

most of the wrecks in the 1989 database, geographic coordinates have been assigned to a

shipwreck based on other types of information provided about the location of loss. For

many wrecks, particularly early ones, the information on loss is often simply a

description of the location in reference to a shore landmark. For example, the account of

loss might state that a vessel was lost “20 miles southeast of Grand Isle” or “west of

Tampa Bay,” or “four miles southwest of the Port Aransas jetties.” Generally, only the

most recent wreck reports provide geographic coordinates for the location of loss.

Regardless, all of these various modes of describing a location of loss had to be used to

obtain the geographic coordinates for the position of loss. As Garrison et al. (1989:II-10-

11) note, the various sources of information on wrecks were examined to determine the

most reliable one for developing the geographic coordinates of the location of loss.

The nature of the historical data on vessel losses means that the accuracy of

geographic coordinates obtained for many wrecks will be questionable. Garrison et al.

(1989) recognize this problem, but argue that the types of analyses they conducted did

not require high levels of precision in wreck locations. They typically considered spatial

distributions at the lease block or broader level. For example, they argue that correlating

shipwreck locations with hurricane paths or with travel routes, such as the routes of the

Spanish fleets in the sixteenth to eighteenth centuries, does not require a great deal of

precision because the hurricane paths and shipping routes themselves varied considerably

(Garrison et al. 1989:II-11).

The 1989 study did incorporate presumptions about the relative accuracy of

reported wreck locations into the delineation of high-probability areas. For instance,

Garrison et al. (1989:II-11) note that “the accuracy of the shipwreck positions is 0.16 for

an assigned lease block whose original report gave no quantitative position.” This

probability is based on the assumption that a reported shipwreck location will fall within

an area of six lease blocks, or 54 square miles, and is derived principally from

presumptions used by the Texas Antiquities Committee in their assessment of the margin

of error existing in wreck locations. This, also, is the same assumption about positioning
3-22

error used by Bourque (1979) in his baseline study for the Atlantic OCS. Although no

empirical evidence was provided to support this presumption about the relative accuracy

of reported shipwreck positions, the 1989 Garrison et al. study generally followed it in its

identification of the nine-lease-block high-probability units discussed earlier. In essence,

they assume that the margin of error for a reported wreck location is on the order of 4.5

miles. Thus, the actual wreck location would most likely be contained within the area

circumscribed by a 4.5-mile radius around its plotted location. In its application to the

GOMR, the high-probability area so defined includes the lease block in which the wreck

coordinates fall, plus the eight contiguous blocks. The use of this nine-lease-block

configuration implies that a shipwreck has a 0.11 probability of occurring in its assigned

lease block.

Garrison et al. (1989) had no reliable shipwreck data from the GOMR with which

to test this presumption about the precision of reported and derived wreck locations.

However, the results of the 208 offshore remote-sensing surveys used here permit a

preliminary effort in testing this presumption. Essentially, the results indicate that a

shipwreck has a 0.06 probability (i.e., 13 of 208) of falling in its specifically assigned

lease block, a much lower probability than presumed by the 1989 study or suggested by

other researchers (cf. Borque 1979). Even this low probability assumes that the wrecks

identified in the 13 lease blocks are actually the vessels listed in the 1989 shipwreck

database. The identity of one of these vessels, the Tulsa, has been verified by divers and

two others, the William H. Edwards and the Daniel Huger, are liberty ships sunk as

artificial reefs whose identity and location were well known when the 1989 database was

developed. A more rigorous assessment of the question of accuracy in reported wreck

locations will require verification of the identity of the other vessels and objects

discovered in these 13 lease blocks.

Another way to approach the question of accuracy in reported wreck locations is

to compare the actual coordinates of discovered wrecks against the coordinates derived

from historical sources. In the present instance, the positions of identified shipwrecks

that have been discovered by MMS-mandated archaeological surveys are compared

against the positions provided in the 1989 shipwreck database developed by Garrison et

al. (1989). Based on archaeological survey data supplied by MMS, ninety identified and

unidentified vessels have been discovered in the GOMR as a result of MMS-mandated

surveys. In addition, a number of items and objects have been found that may or may not

represent vessel remains. Of these, 13 vessels have been found whose identity has been

confirmed by diving or can be well established through sidescan sonar imagery and

which appeared in the 1989 shipwreck database (Table 3-1). This table provides the

distance in meters and miles between the location of a wreck as given in the 1989

database and the location where the vessel was actually found. The actual locations of

most of these vessels were recorded by state-of-the-art positioning during the course of

archaeological surveys and are believed to be extremely accurate. The location of the

wreck of the sidewheel steamer New York was obtained by MMS personnel during the

course of a remote-sensing survey and diving operations on the wreck (Irion and

Anuskiewicz 1999). Information on the actual position of the Virginia comes from Rob

Floyd (personal communication, 2001) and that of the R.W. Gallagher from Avery
3-23

Munson (personal communication, 2001). According to Munson, the R.W. Gallagher has

been located by an MMS-mandated survey, but has been misidentified as the Heredia.

The 1989 shipwreck database notes that reports of loss and the locations of loss for these

vessels came from a variety of historical sources. As Garrison et al. (1989) note, they

made use of what was considered the most reliable source in developing coordinates for

wreck locations. Excluded from this list of discovered vessels are several ships sunk as

artificial reefs since the 1970s that are included in the 1989 database, but whose exact

positions were essentially known at that time. Similarly, historic wrecks whose exact

locations were known in 1989, such as the Civil War steamer Hatteras, are excluded.

Table 3-1. Distance Between Reported Location of Loss and Actual Location of

Identified Shipwrecks in the GOMR

VESSEL DISTANCE

YEAR

OF

LOSS METERS MILES

ALCOA PURITAN 1942 15,025.86 9.34

BENJAMIN BREWSTER 1942 4,191.82 2.60

CITIES SERVICE

TOLEDO

1942 17,057.70 10.60

GULF TIDE 1947 84.98 0.05

GUNSMOKE 1977 162.49 0.10

JOSEPHINE 1881 2,803.00 1.74

NEW YORK 1846 151,488.64 94.14

R.E. LEE 1942 19,543.62 12.14

R.W. GALLAGHER 1942 2,889.63 1.80

SHEHERAZADE 1942 1,582.00 0.98

TULSA 1943 3,083.74 1.92

U-166 1942 221,196.61 137.45

VIRGINIA 1942 10,685.67 6.64

AVERAGE 34,599.67 21.50

As can be seen, the difference in reported location of loss and actual location

where the wreck was discovered ranges from 0.05 miles for the Gulf Tide to 137.5 miles

for the German submarine U-166, and averages 21.5 miles. One would expect that, in

general, the error in reported location of loss would be greater the farther back in time the

sinking occurred. This is probably true, and the U-166 represents a unique case. The

submarine was reportedly sunk by a bomb dropped from a United States Coast Guard

airplane off the central Louisiana coast in August 1942, but the pilot’s account of the

sinking could never be verified. The Coast Guard account placed the sinking in lease

block South Timbalier 75, and subsequent searches for the submarine have generally

considered this to be its general location of loss. However, in the summer of 2001, the

remains of the U-166 were discovered and positively identified in very deep water off the

mouth of the Mississippi River in the Mississippi Canyon Area. Subsequent to its

discovery, additional historical research of contemporary World War II records verified
3-24

that the submarine was, in fact, lost off the mouth of the Mississippi River, over 135

miles east of where it was previously believed to have been lost (Church 2002).

If the U-166 is eliminated from the list, the average error in location drops

considerably, to 11.9 miles. However, as can be seen, most of the wrecks on the list are

fairly modern, dating since World War II. The oldest wreck on the list, the steamer New

York, lost in 1846, was found almost 100 miles from the location provided in the 1989

shipwreck database. The case of the New York is believed to be more typical and it is

suspected that the geographic coordinates given for many early wrecks are in

considerable error. For example, the remains of the Spanish merchant vessel El Nuevo

Constante, sunk in 1766, were discovered in the late 1970s just off the coast of central

Louisiana (Pearson and Hoffman 1995). Various wreck lists compiled from secondary

historical accounts place the El Nuevo Constante as far west as Galveston, well over 100

miles from its actual location. The actual location of the sinking of El Nuevo Constante

could have been determined if primary documents relating to its loss had been discovered

and examined, as was the case for the U-166. However, overview studies, such as that of

Garrison et al. (1989) as well as the present work, generally are unable to examine

primary records in any detail.

Although the case of the U-166 demonstrates that significant errors in location

can exist even for relatively recent wrecks, it is obvious that the New York and El Nuevo

Constante are more typical of the situation for earlier wrecks. This assessment has used a

small sample of 13 positively identified wrecks and the results must be viewed with

caution. Seven of the wrecks do fall within 4.5 miles of their reported location of loss,

the distance that the 1989 study used as a generalized measure of potential error in

reported wreck locations to identify many high-probability zones. All but one of these

wrecks, however, post-date 1942, a period when reasonably accurate positions of

sinkings are to be expected. It appears that the 4.5-mile radius employed to identify

many high-probability areas in the GOMR underestimates the actual range of error that

exists, particularly for early wrecks. The data presented here reveal, as expected, that

considerable variability exists in the error associated with positions derived from historic

accounts of sinkings. These are unlikely to ever be fully reconciled, but it is not believed

that a single measure of this error should be assigned to all wrecks. As has been

discussed in earlier sections, during the collection and compilation of the shipwreck

database for this study an effort was made to quantify the “reliability” of the geographic

coordinates obtained for each vessel through an evaluation of the type of information

contained in the account of loss. In the following chapter, this concept of “reliability” is

more fully discussed in efforts to more carefully define the error anticipated to be

associated with particular wreck locations, and to more realistically define the size of

high-probability zones associated with these wrecks.

3.2.3.2. Testing the Predictability of the 1989 Shipwreck Model

The 1989 shipwreck model is further examined by comparing predicted wreck

locations against discovered wrecks across all of the 2,384 high-probability lease blocks

identified in the 1989 model (see Volume III, Appendix C). Data obtained from MMS in
3-25

September 2001 reveal that 2,220 lease blocks in the GOMR had been subjected to

archaeological survey as of that date (Dave Ball, personal communication 2001). (This

number actually refers to the number of archaeological survey reports received by the

MMS/GOMR. Sometimes lease blocks or pipeline rights-of-way are surveyed, but for

various reasons the archaeological reports are held for a considerable amount of time

before they are submitted to MMS.) Out of this number, 651 lease blocks were identified

in the 1989 model as high-probability blocks relative to shipwrecks (Table 3-2). The

remaining 1,569 blocks are identified as high-probability locales relative to prehistoric

sites. Of the 651 shipwreck high-probability blocks surveyed, 616 are what are now

(2001) identified as 50-m blocks and 35 are 300-m blocks. Some of the surveys of these

blocks were conducted prior to 1990 and were undertaken on 150-m line spacing. These

numbers suggest that approximately 27.3 percent of the total of 2,384 shipwreck highprobability lease blocks in the GOMR have been subjected to archaeological survey.

However, while most of these surveys consisted of complete lease block surveys, some

represent partial block surveys, pipeline rights-of-way, or well sites.

Table 3-2. High-Probability Lease Blocks

that have been Surveyed for Historic Shipwrecks as of September 2001

LEASE BLOCKS REQUIRING 50-M SURVEY INTERVAL

BA0342 EI0039 GA0255 GA0460 HI0106 HIA0509 MO0871

BA0364 EI0041 GA0256 GA0461 HI0107 MI0519 MO0873

BA0365 EI0042 GA0257 GA0462 HI0108 MI0528 MO0904

BA0376 EI0048 GA0268 EI0018 HI0109 MI0564 PN0948

BA0377 EI0049 GA0269 EI0019 HI0114 MI0565 PN0949

BA0378 EI0050 GA0270 EI0020 HI0135 MI0566 PN0954

BA0396 EI0056 GA0272 EI0022 HI0136 MI0567 PN0955

BA0397 EI0057 GA0273 EI0023 HI0137 MI0589 PN0957

BA0398 EI0058 GA0281 EI0024 HI0138 MI0591 PN0969

BA0399 EI0059 GA0282 EI0026 HI0140 MI0592 PN0970

BA0415 EI0060 GA0283 EI0027 HI0141 MI0599 PN0975

BA0416 EI0070 GA0286 EI0028 HI0142 MI0601 PN0976

BA0417 EI0071 GA0287 EI0029 HI0143 MI0602 PN0987

BA0430 EI0072 GA0288 EI0030 HI0154 MI0603 PN0989

BA0431 EI0079 GA0295 EI0031 HI0155 MI0622 PN0990

BA0432 EI0080 GA0296 EI0032 HI0156 MI0623 PN0993

BA0449 EI0138 GA0297 GI0017 HI0157 MI0631 PN0996

BA0477 EI0139 GA0298 GI0037 HI0160 MI0633 PN1010

BA0478 EI0140 GA0301 GI0045 HI0164 MI0635 PN1019

BA0490 EI0143 GA0302 GI0046 HI0175 MI0654 MO0908

BA0491 EI0149 GA0304 GI0054 HI0176 MI0663 MO0909

BA0509 EI0162 GA0312 GI0085 HI0177 MI0664 MO0910

BA0510 GA0104 GA0313 HI0019 HI0178 MI0666 MO0911

BA0514 GA0144 GA0315 HI0020 HI0194 MI0687 MO0912

BA0515 GA0151 GA0316 HI0021 HI0196 MI0688 MO0913

BA0516 GA0152 GA0319 HI0031 HI0197 MO0779 MO0944

BA0538 GA0181 GA0320 HI0034 HI0202 MO0819 MO0945

BS0041 GA0190 GA0324 HI0035 HI0204 MO0820 MO0946

BS0042 GA0191 GA0325 HI0036 HI0205 MO0821 MO0950

BS0053 GA0192 GA0330 HI0037 HI0206 MO0822 MO0951

BS0054 GA0209 GA0331 HI0038 HI0207 MO0823 MO0988

BS0055 GA0210 GA0332 HI0039 HI0208 MO0824 MO0989

CA0009 GA0222 GA0333 HI0047 HI0232 MO0826 MO0990
3-26

Table 3-2 (continued). High-Probability Lease Blocks

that have been Surveyed for Historic Shipwrecks as of September 2001

LEASE BLOCKS REQUIRING 50-M SURVEY INTERVAL

EC0002 GA0223 GA0334 HI0049 HI0236 MO0827 MO0992

EC0011 GA0226 GA0343 HI0051 HIA0007 MO0828 MO0993

EC0014 GA0227 GA0345 HI0053 HIA0018 MO0829 MO0997

EC0015 GA0237 GA0346 HI0054 HIA0019 MO0830 MO0998

EC0022 GA0238 GA0347 HI0065 HIA0020 MO0857 MO0999

EC0023 GA0239 GA0352 HI0066 HIA0021 MO0861 MO1002

EC0024 GA0240 GA0353 HI0067 HIA0022 MO0862 MP0007

EC0026 GA0241 GA0360 HI0089 HIA0023 MO0863 MP0018

EC0033 GA0242 GA0362 HI0090 HIA0024 MO0864 MP0019

EC0034 GA0250 GA0363 HI0092 HIA0107 MO0865 MP0020

EC0036 GA0251 GA0379 HI0093 HIA0122 MO0866 MP0029

EC0038 GA0252 GA0380 HI0095 HIA0123 MO0867 MP0043

EC0039 GA0253 GA0382 HI0098 HIA0133 MO0868 MP0057

EC0040 GA0254 GA0383 HI0105 HIA0506 MO0869 MP0061

MP0062 PE0934 SS0013 SS0144 VK0031 WC0039 WC0110

MP0063 PL0002 SS0026 SS0158 VK0033 WC0040 WC0111

MP0064 PL0004 SS0027 SS0159 VK0065 WC0041 WC0112

MP0069 PL0005 SS0028 SS0160 VK0066 WC0042 WC0113

MP0072 PL0006 SS0030 SS0167 VR0016 WC0043 WC0114

MP0090 PL0009 SS0031 SS0169 VR0017 WC0044 WC0115

MP0091 PL0010 SS0036 ST0011 VR0021 WC0045 WC0118

MP0092 PL0011 SS0037 ST0016 VR0022 WC0046 WC0134

MP0103 PL0016 SS0038 ST0024 VR0023 WC0047 WC0148

MP0114 PL0025 SS0050 ST0028 VR0025 WC0053 WC0166

MP0115 PN0894 SS0051 ST0029 VR0026 WC0054 WC0167

MP0116 PN0934 SS0062 ST0030 VR0027 WC0055 WC0186

MP0117 PN0935 SS0065 ST0031 VR0028 WC0056 WC0187

MU0745 PN0947 SS0067 ST0032 VR0034 WC0057 WC0188

MU0751 PS1073 SS0068 ST0033 VR0036 WC0059 WC0189

MU0759 PS1125 SS0069 ST0034 VR0037 WC0060 WC0291

MU0775 PS1166 SS0072 ST0035 VR0038 WC0061 WC0292

MU0776 SA0006 SS0073 ST0036 VR0039 WC0062 WD0016

MU0783 SA0007 SS0080 ST0046 VR0046 WC0063 WD0018

MU0792 SA0009 SS0085 ST0047 VR0047 WC0064 WD0020

MU0793 SA0011 SS0086 ST0048 VR0048 WC0065 WD0021

MU0811 SA0012 SS0087 ST0052 VR0054 WC0066 WD0022

MU0821 SA0014 SS0089 ST0062 VR0055 WC0067 WD0026

MU0822 SA0015 SS0090 ST0065 VR0056 WC0068 WD0027

MU0823 SA0016 SS0091 ST0066 VR0144 WC0069 WD0031

MU0827 SM0207 SS0092 ST0067 VR0145 WC0070 WD0032

MU0832 SM0208 SS0093 ST0068 VR0158 WC0071 WD0033

MU0833 SM0210 SS0094 ST0069 VR0159 WC0073 WD0034

MU0837 SM0212 SS0097 ST0070 VRO160 WC0079 WD0035

MU0842 SM0217 SS0098 ST0073 WC0018 WC0080 WD0036

MU0843 SM0218 SS0103 ST0074 WC0019 WC0090 WD0047

MU0848 SM0224 SS0104 ST0076 WC0021 WC0091 WD0048

MU0851 SM0228 SS0109 ST0080 WC0023 WC0092 WD0049

MU0853 SM0229 SS0110 ST0081 WC0024 WC0094 WD0057

MU0858 SM0237 SS0111 ST0082 WC0026 WC0095 WD0058

MU0859 SM0238 SS0113 ST0084 WC0027 WC0096 WD0059

PE0845 SM0239 SS0114 ST0102 WC0028 WC0097 WD0077
3-27

Table 3-2 (continued). High-Probability Lease Blocks

that have been Surveyed for Historic Shipwrecks as of September 2001

LEASE BLOCKS REQUIRING 300-M SURVEY INTERVAL

PE0846 SM0240 SS0127 ST0110 WC0033 WC0098 WD0078

PE0889 SM0241 SS0139 ST0111 WC0034 WC0099 WD0086

PE0890 SS0011 SS0140 SX0040 WC0035 WC0100 WD0098

PE0933 SS0012 SS0143 VK0022 WC0036 WC0109

EL0406 MC1007 SP0072 VK0870

EL0407 MC1008 VK0782 VK0871

EW0305 SP0032 VK0783 VK1000

EW0347 SP0034 VK0785 VK1001

GI0088 SP0036 VK0786 WD0109

MC0290 SP0037 VK0826

MC0291 SP0038 VK0827

MC0335 SP0044 VK0829

MC0963 SP0045 VK0830

MC0964 SP0060 VK0869

Data supplied by the MMS reveals, at this writing, that a total of 135 “vessels”

and “objects” have been identified in the GOMR as a result of MMS-mandated surveys.

Out of this number, 90 are deemed to be actual vessels, while the remaining 45 are

classified as unidentified objects. The identification of an item as a “vessel” or an

“object” relied on a review of the archaeological survey reports provided by MMS. As

noted, the information provided consisted of copied material extracted from the complete

reports and usually contained reproductions of sidescan sonar records and segments of

the text that reported on the findings and interpretations. Occasionally, portions of maps

and other remote-sensing records were provided, such as data from the magnetometer or

subbottom profiler. All of these data were reviewed and, in most instances, the

interpretations of the reviewer matched the identification provided in the report.

However, in a very few instances, careful examination of sidescan records

suggested that items identified in archaeological survey reports as “possible vessels” or

“possible shipwrecks” were more appropriately classified as “unidentified objects.”

Figure 3-3 provides an example of a sidescan sonar record from an MMS archaeological

survey report that shows a clear image of a vessel. Many images examined were of much

poorer quality than this one, making identification difficult. Information on these vessels

ultimately identified in the data is contained in Table 3-3. The table includes: 1) the ID

number of the vessel as contained in the database of shipwrecks developed for this study,

2) the name of the vessel if it is known or if there is some reasonable rationale for this

identification, 3) the lease area in which the wreck falls, and 4) a column indicating

whether or not the lease block in which it was found was identified as a high-probability

block in the 1989 shipwreck model and the survey line spacing assigned to that block.
3-28

Figure 3-3. Sidescan sonar image of a shipwreck in the Ship Shoal Area.

Table 3-3. Vessels Identified by MMS Lease Area Surveys

ID VESSEL* LEASE

AREA

HIGH-PROBABILITY

STATUS**

Identified Vessels

360 ALCOA PURITAN MC YES/300

354 ARKANSAS (?) MP NO

319 BENJAMIN BREWSTER BM YES/50

332 CAPTAIN BRANDON JOSEPH (?) GA YES/50

373 CITIES SERVICES TOLEDO SM NO

403 DALE & DAVID (?) VK NO

426 DANIEL HUGER (?) PE NO

417 GULF TIDE WC NO

362 GULFPENN (?) SP YES/300

372 GUNSMOKE (?) PB YES/50

386 HEREDIA (?) (R.W. GALLAGHER) SS NO

389 J.A. BISSO (?) ST NO

365 JOSEPHINE MO YES/50

329 MISS AGNES EI NO

379 MISS NATALIE (?) PL YES/50

344 NEW YORK HIA NO

350 PEGASUS (?) MP NO

411 RICHARD P. (?) VR NO

361 ROBERT E. LEE MC NO
3-29

Table 3-3. (continued). Vessels Identified by MMS Lease Area Surveys

ID VESSEL* LEASE

AREA

HIGH-PROBABILITY

STATUS**

Identified Vessels

334 SAINT MARY (?) GB NO

328 SHEHERAZADE EI NO

370 TULSA MO YES/50

751 U-166 MC NO

399 WILLIAM H. EDWARDS VK YES/50

Unidentified Vessels

366 ARTIFICIAL REEF MO YES/50

317 UNKNOWN VESSEL BA YES/50

316 UNKNOWN VESSEL BAA NO

318 UNKNOWN VESSEL BAA YES/300

321 UNKNOWN TUG EC NO

322 UNKNOWN VESSEL EC NO

323 UNKNOWN VESSEL (LAFOURCHE?) EC NO

15161 UNKNOWN VESSEL EC NO

15166 UNKNOWN BARGE EI NO

325 UNKNOWN VESSEL EI YES/50

326 UNKNOWN VESSEL EI NO

327 UNKNOWN VESSEL EI NO

1570 UNKNOWN WRECK (BECT 2?) EI NO

1571 UNKNOWN WRECK (BECK II) EI NO

15167 UNKNOWN VESSEL EI NO

330 UNKNOWN VESSEL EI NO

333 UNKNOWN VESSEL GA YES/50

335 UNKNOWN VESSEL GB NO

337 UNKNOWN VESSEL GC NO

15170 UNKNOWN VESSEL GI NO

339 UNKNOWN VESSEL GI YES/300

1616 UNKNOWN VESSEL (HAWKEYE?) HI NO

343 UNKNOWN VESSEL HI YES/50

15169 WOODEN WRECK MC NO

359 UNKNOWN VESSEL MC NO

15097 UNKNOWN VESSEL MC NO

363 UNKNOWN VESSEL MC NO

364 UNKNOWN VESSEL MC NO

369 UNKNOWN IRON VESSEL MO YES/50

368 UNKNOWN VESSEL MO YES/50

371 UNKNOWN VESSEL MO YES/50

346 UNKNOWN VESSEL MP YES/50

347 UNKNOWN VESSEL MP YES/50

349 UNKNOWN VESSEL MP NO

1615 UNKNOWN VESSEL MP NO

15096 UNKNOWN VESSEL MP NO

351 UNKNOWN VESSEL MP NO

352 UNKNOWN VESSEL MP NO

353 UNKNOWN VESSEL MP NO

356 UNKNOWN VESSEL MP NO

357 UNKNOWN VESSEL MP NO

378 UNKNOWN VESSEL PL YES/50

377 UNKNOWN VESSEL SM NO

391 UNKNOWN VESSEL SS YES/50

385 UNKNOWN VESSEL SS NO
3-30

Table 3-3. (continued). Vessels Identified by MMS Lease Area Surveys

ID VESSEL* LEASE

AREA

HIGH-PROBABILITY

STATUS**

Unidentified Vessels

384 UNKNOWN VESSEL SS NO

15168 UNKNOWN WRECK SS NO

387 UNKNOWN BARGE ST YES/50

394 UNKNOWN VESSEL ST YES/50

392 UNKNOWN VESSEL ST YES/50

15098 UNKNOWN VESSEL ST NO

396 UNKNOWN VESSEL SX YES/50

398 UNKNOWN VESSEL VK YES/50

1610 UNKNOWN VESSEL VK NO

400 UNKNOWN WRECK VK NO

402 UNKNOWN BARGE VK NO

405 UNKNOWN VESSEL VK NO

15095 UNKNOWN VESSEL VK YES/300

406 UNKNOWN VESSEL VK NO

407 UNKNOWN VESSEL VK YES/300

412 UNKNOWN OBJECT (AIRCRAFT?) VR NO

415 UNKNOWN VESSEL WC YES/50

418 UNKNOWN VESSEL WC NO

421 UNKNOWN VESSEL WC NO

1611 UNKNOWN VESSEL WD YES/50

1569 UNKNOWN VESSEL WD YES/50

*A “?” indicates tentative identification of vessel.

** Identifies whether or not the lease block was identified as having a high probability for

containing a shipwreck from data presented by Garrison et al. 1989 and the survey line

spacing required for the block. Data as of September 2001.

As shown in Table 3-3, twenty-four vessels have been assigned names, but the

identity of most has not been verified, so those that are tentatively identified are noted

with a question mark. The remaining 66 entries in the list represent unidentified vessels

of various sorts. In a few instances, the archaeological survey report provided a very

tentative identification of the vessel and these are noted, although their accuracy is

questionable. One of the items in the Unidentified Vessel category is identified as an

“Artificial Reef,” and this consisted of the remains of at least five medium-sized vessels

sunk as part of an artificial reef off the Alabama coast in the Mobile Area. One item in

the list is classified as an “Unidentified Object” and tentatively identified as an “aircraft.”

This item appeared as a rather amorphous object on sidescan records that were tentatively

identified as an aircraft in the archaeological survey report. A careful review of the

sidescan record did not enable an accurate identification of this object, but its

identification as an airplane must be considered tenuous. However, because aircraft are

included in the vessel category in the database developed in this study, this item is

included in this list of discovered vessels.

Table 3-4 provides similar information for items classified as “Objects” from

archaeological surveys. Most of these items appear on sidescan sonar records, but a few

consist of presently unidentified magnetic anomalies.
3-31

Table 3-4. “Objects” Identified by MMS Lease Area Surveys

ID OBJECT* LEASE

AREA

HIGHPROBABILITY

STATUS**

358 UNKNOWN OBJECT AP NO

320 UNKNOWN OBJECT EB NO

324 UNKNOWN OBJECT EC NO

15162 MAGNETIC ANOMALY 25 EC YES/50

15163 MAGNETIC ANOMALY 58 EC YES/50

15164 MAGNETIC ANOMALY 44 EC YES/50

15165 MAGNETIC ANOMALY 70 EC YES/50

331 UNKNOWN OBJECT EI NO

1614 UNKNOWN OBJECT GA YES/50

336 UNKNOWN OBJECT GB NO

338 UNKNOWN OBJECT GI NO

345 UNKNOWN OBJECT HIA NO

1573 ARMY TANKS MO YES/50

348 UNKNOWN OBJECT MP NO

355 UNKNOWN OBJECT MP NO

1572 UNKNOWN OBJECT MP NO

374 UNKNOWN OBJECT SM NO

375 UNKNOWN OBJECT SM NO

376 UNKNOWN OBJECT SM NO

382 UNKNOWN OBJECTS SP NO

1621 UNKNOWN OBJECT SP YES/300

1612 UNKNOWN OBJECT SS NO

1613 UNKNOWN OBJECT SS NO

1618 UNKNOWN OBJECT SS YES/50

388 UNKNOWN OBJECT ST NO

393 UNKNOWN OBJECT ST NO

395 UNKNOWN OBJECT ST NO

427 UNKNOWN OBJECT ST NO

397 UNKNOWN OBJECT VK YES/50

401 UNKNOWN OBJECT VK NO

408 UNKNOWN OBJECT VR NO

409 UNKNOWN OBJECT VR NO

410 UNKNOWN OBJECT VR NO

413 UNKNOWN OBJECT VR NO

1619 UNKNOWN OBJECT VR NO

1620 UNKNOWN OBJECT VR NO

404 UNKNOWN OBJECT WC YES/50

414 UNKNOWN OBJECT WC YES/50

416 UNKNOWN OBJECT WC NO

419 UNKNOWN OBJECT WC NO

420 UNKNOWN OBJECT WC NO

422 UNKNOWN OBJECTS WC NO

1622 UNKNOWN OBJECT WC NO

423 UNKNOWN OBJECT WD YES/50

425 UNKNOWN OBJECTS WD NO

* The identification is derived from the archaeological survey report.

** Indicates whether or not the lease block was identified as having a high

probability for containing a shipwreck from data presented by Garrison et al.

(1989) and the survey line spacing required for the block. Data as of

September 2001.
3-32

One of the items included in this list is the several “Army Tanks” identified in the

Mobile Area. These tanks are clearly distinguished on the sidescan records and represent

material placed on the seafloor to create an artificial reef. These tanks are classified as

“Objects” primarily because they have been purposefully placed at this location, unlike

airplanes and helicopters that have been classified as “Vessels” principally because they

represent cultural items accidentally lost at sea.

Specific information on the locations of all of these discovered vessels and objects

are readily available in the Access format shipwreck database provided with this report

and they can be viewed in the ArcView format provided. More generalized information

on the spatial distribution of wrecks discovered in the GOMR is provided in Figure 3-4.

This figure provides information on the numbers of vessels identified in various lease

areas. As can be seen, most of the vessels have been found in the waters off the central

Gulf, extending from near Mobile, Alabama, to the central Texas coast. Not surprisingly,

this area corresponds closely to the region where most of the offshore survey work has

been conducted, as shown in Figure 3-2 above. A very small number of vessels (N=4)

appear in areas where no lease block surveys are reported to have been conducted.

These vessels have been discovered during the course of pipeline right-of-way

surveys, rather than actual lease block surveys. Of some interest is a lack of discovery of

vessels on the lower Texas coast, an area that has been subjected to a considerable

amount of archaeological survey and an area where Garrison et al. (1989) project a fairly

large number of wrecks. For comparison, Figure 3-5 presents information on the

numbers of reported wrecks per lease area derived from the 1989 shipwreck database

developed by Garrison et al. (1989). As can be seen, the 1989 database lists over 150

wrecks in Federal waters along the lower Texas coast; why so few have been discovered

here is unknown. It is possible that wrecks in this area can be totally buried by the clay

and silty clay bottom sediments that characterize the region.

Excavations at one of the 1554 Spanish fleet wrecks (site 41KN10, believed to be

the vessel San Esteban) off Padre Island, Texas, revealed that all of the remains of the

vessel were buried by 0.6 to 1.3-m of sand, silt and shell. It was believed that wreckage

had migrated downward through loose sediments to an underlying dense and

impenetrable Pleistocene clay surface. Marine growth on artifacts indicated that

wreckage had been exposed in the water column for long periods of time prior to the

initiation of excavations in 1972 (Arnold and Weddle 1978:195-198). This site lies close

to shore where current and wave dynamics and sediments are somewhat different from

those in offshore areas; however, it is reasonable to assume that offshore wrecks in the

lower Texas area can become totally or partially buried. This is certainly true for two

nineteenth century wrecks known from the offshore area of the upper Texas coast, the

Hatteras and New York, both of which were partially buried when discovered (Arnold

and Anuskiewicz 1995; Irion and Anuskiewicz 1999).

One question to ask is whether the discovery of wrecks in the GOMR is a factor

of the number of remote-sensing surveys conducted in an area rather than the actual

density of wrecks in that area. If it is the latter, then one might argue that the

“predictability” of the 1989 model is supported.
Figure 3-4. Numbers of vessels discovered by MMS-required surveys per lease area. Data as of September 2
Figure 3-5. Numbers of reported shipwrecks per lease area indicated by the 1989 shipwreck database deve

 (1989).
3-35

To look at this relationship, correlation coefficients were computed on three sets

of survey data, using the 70 MMS lease areas as the spatial units of analysis. The

correlation analysis tool provided in the software program Microsoft Excel was used in

this analysis. Essentially, this analysis measures if two ranges of data move together; that

is, whether large numbers in one set are associated with large numbers in the other. The

analysis returns the covariance of two data sets divided by the product of their standard

deviations using the formula:

Px,y = cov (X,Y)/qx x qy where

qx

2

 = 1/n ∑ (Xi-ux)

2 and

qy

2

 = 1/n ∑ (Yi-uy)

2

The first correlation analysis looked at the relationship between the number of

surveys conducted in each lease area versus the number of vessels found. This analysis

indicated that there was a 0.6320 correlation between these two variables. This indicates

that there is a positive relationship between these two sets of data: i.e., the more surveys

conducted, the more vessels found, but that the correlation is not extremely high. The

second analysis looked at the relationship between the number of surveys conducted and

the number of vessels reported by lease area in the 1989 shipwreck model. This analysis

revealed a roughly similar correlation coefficient of 0.6409, again showing a moderate

correlation between the two variables. Finally, the relationship between the numbers of

vessels found by archaeological survey and losses reported by lease area in the 1989

model was examined. This relationship shows a weak correlation, producing a

correlation coefficient of 0.3786.

Another way to assess the reliability of the 1989 model of shipwrecks is to

determine if there is any significant difference between the number of shipwrecks found

in lease blocks designated high-probability blocks relative to the number found in

designated non-high-probability lease blocks. This analysis used all 2,220 lease blocks in

the GOMR for which there were archaeological survey reports, as of September 2001.

As noted earlier, 651 of these have been designated as high-probability lease blocks as a

result of the 1989 Garrison et al. study. Archaeological surveys have identified sunken

vessels in 33 of these lease blocks. A total of 57 sunken vessels have been identified in

the 1,569 non-high-probability lease blocks surveyed. Thus, the probability of finding a

shipwreck in a high-probability lease block is 0.05, only slightly higher than the

probability of finding a wreck in a non-high-probability block, which is 0.04.

A chi square test (x2

) was conducted to determine if there is any statistically

significant difference between the results of surveys conducted in high-probability blocks

and those conducted in non-high-probability blocks. The chi square test is a “goodnessof-fit” technique that can be used to determine the significance of differences between

independent groups using observed and expected occurrences (Siegel 1956:43, 104). In

the present case, the two independent groups are the surveys conducted in highprobability lease blocks (N=651) and those conducted in non-high-probability blocks

(N=1,569). Under the 1989 shipwreck model, the expectations are that there will be a
3-36

difference between the results of surveys in the two categories of lease blocks. Following

statistical hypothesis testing, this expectation would constitute what is known as the

“alternative hypothesis” (H1). Statistical tests are, normally, used to test what is called

the “null hypothesis” (Ho). In this instance, Ho states that there is no difference between

the two categories of lease blocks relative to the occurrence of shipwrecks. The

significance level selected for acceptance or rejection of the null hypothesis is .05, a

standard used in most social science research.

The formula used in analysis is one that is most applicable to 2 x 2 contingency

tables (Siegel 1956:107). The formula, contingency table and the computed value of x2

are presented in Table 3-5. The degree of freedom for a 2 x 2 chi square analysis = 1.

The computed value of x2 = 2.92. This value is less than the critical value of chi square

expected at a significant level of .05 (3.84) if there was a statistical difference between

the two categories of lease blocks (Siegel 1956:Table C). This means that the null

hypotheses cannot be rejected and we can assume that there is no statistical difference

between finding wrecks in high-probability lease blocks and finding wrecks in non-highprobability lease blocks.

Table 3-5. Chi Square Analysis of GOMR Lease Block Survey Results

x2 = N (|AD-BC| - N/2) 2

(A=B)(C=D)(A=C)(B=D)

where: N = number of cases

A, B, C, D = the cells in the contingency table

High-probability

blocks

Non-highprobability blocksTotal

With

shipwrecks

33 (A) 57 (B) 9 0

No shipwrecks 618 (C) 1512 (D) 2130

Total 651 1569 2220

x2 = 2.92

This analysis, of course, uses only the sample of surveys that have been

conducted and their results and the chi square analysis measures this sample. For the

present, we presume that this sample is representative of the population of highprobability and non-high-probability lease blocks in the GOMR, but there is currently no

way to evaluate this presumption. Additionally, we have used a level of significance of

.05, meaning that the finding has a 5 percent chance of not being true. As noted, the .05

level of significance is a standard accepted in social science research, but an examination

of critical values of chi square reveals that the null hypotheses could be rejected at a level

of significance of .10. If this level of significance were used, it would mean that the

finding has a 10 percent chance of not being true.
3-37

The various analyses presented here provide some quantitative evaluations of the

1989 model of shipwreck occurrences in the GOMR. These analyses have relied on

actual results of the MMS-mandated archaeological survey program, a program that has

been designed on the findings of the 1989 model. It is apparent from these analysis that

the “power of prediction” of the 1989 model in regard to shipwreck locations is

extremely weak. This weakness lies, principally, in the lack of precision found in the

geographic coordinates assigned to reported losses. This is certainly not surprising given

the nature of much of the available information on locations of loss, and is a problem that

was fully recognized in the 1989 Garrison et al. study. In light of the fact that a very

large number of historic accounts of vessel losses are extremely vague, rectifying this

problem would not be easy. If one wished to strengthen the location of loss information

on the entire population of reported shipwrecks in the GOMR, it would require an

extensive amount of historical research, principally in primary documents, and how

successful such an endeavor would be is unknown. Another way to strengthen the

predictability of the model is to weigh the available information on location of loss in

terms of its “reliability” and use this information to categorize the entire population of

reported wrecks in the GOMR in terms of their likelihood of discovery. Essentially, the

locations of some wrecks are predictable and the MMS archaeological survey program

can be designed in such a way to account for this. On the other hand, the locations of a

very large number of wrecks are not reliably predictable, a factor that, also, should be

incorporated into the MMS archaeological survey program. These questions are more

fully explored in the following chapter.
4-1

4.0: THE 2001 MODEL OF SHIPWRECK OCCURRENCES

IN THE GULF OF MEXICO

4.1. Introduction

The previous chapter discussed the model of shipwreck occurrences in the Gulf of

Mexico as derived from the 1989 study by Garrison et al. and how that model has been

used by MMS in its archaeological survey program in the GOMR. Several shortcomings

of the 1989 model have been pointed out. As noted, most of these shortcomings are

related to the nature of historic shipwreck data used in these types of overview studies.

The database of shipwrecks developed in the 1989 study represented one of its major

components and one of the principal tasks of the present study was to expand upon that

listing. As discussed in Chapter 1, Task 1 of the present study as described in the

Request for Proposal issued by MMS in April 2000 was to:

“. . . update and expand the existing MMS GOMR shipwreck database by

examining primary and secondary sources for shipwreck information. The

existing shipwreck database will be expanded to include specific

identifying characteristics of vessels potentially located on the OCS”

(MMS 2000).

The results of Task 1 are presented in this chapter. Included are discussions on

the procedures and rationale involved in acquiring data for the new shipwreck database

and some of the problems encountered in developing this listing. Characteristics of the

newly developed database are presented in terms of a variety of factors that relate to the

population of shipwrecks in the GOMR. These include a variety of quantitative and

qualitative measures of factors such as the types of vessels lost, period of loss, cause of

loss, etc. Discussions also include assessments of the preservation potential of

shipwrecks in the GOMR, drawing upon characteristics of the natural setting of the

region and the findings of recent archaeological research on shipwrecks in the area.

Finally, the spatial distributions of shipwrecks, as revealed in information contained in

the database, are discussed. The findings from these analyses and discussions constitute

a “model” of shipwreck occurrences in the GOMR. It is a model in that it represents a

simplified theoretical construct that depicts a set of complex phenomena. The variables

and attributes selected for consideration are those that are considered most meaningful to

the purposes of the model. The selection of some characteristics and the elimination of

others in analyses means that the model presented here, as with most other models, is

only a partial representation of reality (Clarke 1972:12). The effort has been made to

incorporate into the model those characteristics that will be most meaningful to the MMS

in its effort to protect historic shipwrecks in the GOMR and, specifically, to direct its

offshore archaeological resources remote-sensing survey program.

All of the following discussions build and draw upon the information presented in

Garrison et al. (1989) and numerous comparisons are made between the data obtained in

that study and this one. No extensive discussions on the maritime history of the Gulf of
4-2

Mexico are presented here. That history is amply discussed in the Garrison et al. (1989)

study and the earlier work by Coastal Environments, Inc. (1977). Additionally, a number

of published works provide excellent accounts on various aspects of the maritime history

of the Gulf of Mexico region (cf., Arnold and Weddle 1978; Francaviglia 1998; Pearson

and Hoffman 1995; Weddle 1985, 1991, 1995), plus the numerous cultural resources

management reports discussed earlier add to this. However, specific aspects of the

maritime history of the GOMR are briefly discussed when this is indicated by findings

made during the collection of information for this study and when that information might

not have been fully presented elsewhere.

Also discussed in this chapter are findings related to Task 2 of this study. As

described in the Request for Proposal, Task 2 was to:

“. . . determine the spatial correlation between: 1) shipwreck locations in

the updated shipwreck database; 2) recorded seafloor hang sites listed on

the MMS GOMR/NOAA sponsored “Fisherman’s Contingency Fund” or

other published or private fisherman hang books; and 3) sonar targets and

anomalies representing potential shipwrecks identified during previous

OCS lease block surveys. Then, to ground-truth selected locations where

hang sites and reported shipwreck locations appear to correlate to

determine if hang sites are shipwrecks” (MMS 2000).

The specific aspects of Task 2 included in this chapter are those related to the

spatial correlations seen between shipwreck locations and recorded seafloor hang sites

and previously located targets identified during previous MMS-mandated surveys. The

findings from this analysis were used to direct the ground-truthing of selected targets by

divers. The results of the diving operations are presented in the following chapter.

4.2. Compiling the 2001 Shipwreck Database

4.2.1. Nature of the Historic Record of Shipwrecks in the GOMR

The shipwreck database developed for this study ultimately contained 2,106

entries of items classified as “Vessels.” In addition, information on a total of 1,155 items

classified as “Objects” was collected. The 2,106 entries classified as “Vessels” comprise

the “2001 shipwreck database” as it is discussed here and it represents the list of critical

concern. The items identified as “Objects” are, however, utilized in some of the analyses

presented. The variables recorded for each entry have been noted in Chapter 1 and the

complete database with all “Vessels” and “Objects” is provided in Microsoft Access

format as a separate element of this technical report. Appendix E (see Volume III)

presents the 2001 shipwreck database containing what are considered the most critical

categories of information for the following discussions. These are: 1) Vessel ID

Number; 2) Vessel Name; 3) Vessel Type; 4) Cause of Loss; 5) Year Built; 6) Year of

Loss; 7 and 8) Latitude and Longitude determined for the position of loss in NAD27

decimal degrees; 9) MMS Lease Block in which the position of loss falls; 10) Location

Reliability; and 11) Source of information. Appendix E also includes an explanation of

each of these entries.
4-3

All of the various sources discussed in Chapter 2 were used in the compilation of

the shipwreck database presented as Appendix E. These sources varied considerably in

terms of the type and value of the information they provided. Some consideration of the

general nature of this information is in order. Everyone who works with the historical

record of shipwrecks recognizes the limitations inherent in much of this record. These

limitations are related to many factors, some of which can be overcome or partially

controlled, others which cannot. At the outset, it must be recognized that not all

shipwrecks have been incorporated into the historic record or the record of losses is so

vague as to be almost useless in a study of their distribution, as is attempted here. This is

particularly true during the earliest period of vessel activity in the Gulf of Mexico. The

first recorded shipwreck in the Gulf of Mexico seems to have occurred in early 1520,

when several ships of an expedition led by Panfiló de Narváez were sunk by a storm off

Tabasco on the eastern coast of present-day Mexico (Weddle 1985:117-118). However,

by this time, the Spanish had been sailing in or on the peripheries of the Gulf of Mexico

for almost two decades and it can be assumed that other ships were lost at earlier dates

and not recorded. Additionally, there are numerous early accounts of vessels lost that are

so vague as to have minimal value in distributional studies. Vessels were scattered by

storms and never seen again and ships sailed from ports, never to be heard from again.

Accounts of vessels lost out of sight of land may never appear, or will be vague and of

little use in trying to plot positions of loss.

While these problems in the data are more commonly found in the records of the

early historic period, they do continue into the present. Accounts and official records of

vessel losses in the Gulf of Mexico during the eighteenth and nineteenth century tend to

be associated with larger commercial or military ships. Losses of private vessels, or

small commercial vessels, are often never officially recorded or the record of loss is

extremely vague. Coastal Environments, Inc. (1977:16), for example, point out the

omission of small, coasting vessels in listings of wrecks in the Gulf of Mexico, despite

the fact that large numbers of small sloops and schooners were involved in this trade

during the nineteenth century and many were certainly lost. This continues into the

present, and an examination of the record of sinkings of craft such as those associated

with the offshore fishing and oil industry reveals that many have gone unreported or

under-reported or that information on their losses is vague.

The two previous studies of historic shipwrecks conducted by the MMS in the

Gulf of Mexico both recognized and commented on these inherent difficulties in historic

records of shipwrecks. Both of these studies drew heavily on secondary resources and

both noted the fragmentary and often contradictory nature of those resources. The

Coastal Environments, Inc. (1977:8-16) study discusses some of the significant problems

with using secondary resources. Many of the sources used in that study derived

information from “popular compendiums” that, in turn, drew from previous secondary

sources. Thus, “any errors or prejudices of earlier writers” become perpetuated in

subsequent publications (Coastal Environments, Inc. 1977:12). Additionally, secondary

sources commonly do not provide the criteria used to originally include or exclude

shipwrecks in their listings.
4-4

Changes in place names over time, or similarities in names, also can create

problems when dealing with secondary as well as primary sources. Coastal

Environments, Inc. (1977:13) commented on the Spanish use of the term La Florida to

refer to a huge area, encompassing parts of the Gulf of Mexico, Caribbean and Atlantic

Ocean. Some authors have placed sinkings in the Gulf of Mexico, when the only

reference to the loss was “in La Florida.” Numerous examples exist of changes in place

names or of confusion as to where an early place name actually meant. For example, the

Spanish originally used the name “Espîritu Santo” to refer to the Mississippi River; later

the French and the Spanish used the name to refer to present-day Matagorda Bay on the

central Texas coast, plus both also used the name “San Bernardo” to refer to Matagorda

Bay, while the French at times used the name “Saint Louis” (Weddle 1985:369;

1991:77). Additionally, over time Spanish and French accounts named a variety of

locations on the Gulf coast “Espiritu Santo” in part because of serious misunderstandings

of what was referred to in earlier accounts or errors in its true location (Weddle

1991:105).

Inevitably, these types of errors can find their way into even recent works. For

example, in the shipwreck database in the Gulf of Mexico developed in the Garrison et al.

(1989) study, two steamboats are recorded lost off the Chandeleur Islands (in lease block

Chandeleur Island 51) on the coast of southeastern Louisiana. These were the steamboats

Leopard and Rufus Putnam, both reportedly lost in 1825, making them among the earliest

steamboats lost in the Gulf of Mexico and thus of some historical interest. One facet of

the present study was to reevaluate, where possible, the wreck database created by

Garrison et al. in order to correct errors. In this particular instance, it was discovered that

Garrison et al. relied on information for these two vessels provided in the Coastal

Environments, Inc. (1977) study. Examination of the “Shipwreck Data Sheets” produced

by CEI indicated that they had obtained their information on the two wrecks from Bruce

Berman’s (1972) Encyclopedia of American Shipwrecks, one of the commonly used

popular compendiums of American shipwrecks. Berman and CEI each report that both of

these steamers were “snagged” and lost off “Pt. Chicot, LA” in 1825. CEI provides no

other specific locational information for the two vessels. Garrison et al., however, seem

to have identified Point Chicot as a place name associated with the Louisiana coast in or

near the Chandeleur Islands. An examination of maps of the region shows no landform

named Point Chicot, although there is a Chicot Island in Breton Sound inside of the

Chandeleurs.

It was apparent that there was a problem with the inclusion of these two vessels in

the 1989 MMS wreck list. Both vessels were unusually early for steamboats in the Gulf,

plus both had been reported “snagged,” which normally refers to a vessel running into a

log, a rather unlikely event off the Chandeleur Islands. Additionally, it was known that

Point Chicot was a place name found along the Mississippi River in northern Louisiana, a

location where snaggings of steamers was relatively common. This led to a review of

information on steamboat losses on the Mississippi River presented in what is known as

the Lytle-Holdcamper List, published as Merchant Steam Vessels of the United States,

1790-1868 (Mitchell 1975) and a recent cultural resources management study of the

navigation history and shipwrecks along this section of the Mississippi River (Wells et al.
4-5

1999). Both vessels are included in the Lytle-Holdcamper List, and both are reported to

have been snagged and lost at Point Chicot, Louisiana. Further, both of these steamboats

appear to have been typical western river steamers: the Leopard was a 73-ton sidewheeler

built at Silver Creek, Indiana, in 1822 while the Rufus Putnam was a 68-ton sidewheeler

constructed at Marietta, Ohio in 1822 (Mitchell 1975:126, 189). These two steamboats

were typical river steamers and it is unlikely that either would have ever ventured into the

Gulf of Mexico. Additionally, the reference to Point Chicot in the Lytle-Holdcamper List

seems clearly to refer to the location along the Mississippi River. It is apparent that

Berman (1972) indicated these vessels were lost in the Gulf of Mexico, a fact perpetuated

by the CEI and Garrison et al. studies, with Garrison et al. going on to identify Point

Chicot as a location near the Chandeleur Islands, possibly a confusion with Chicot Island.

The vessel Theresa F. is another example of the types of problems that are all too

often encountered when using various sources of data on even relatively recent

shipwrecks and the impact these problems can have on the MMS archaeological survey

program. In the list of wrecks derived from the Garrison et al. (1989) study two vessels

named Theresa F. are listed (see Appendix A). The coordinates given for both vessels

are the same and they fall within the West Delta Area, just off the mouth of the

Mississippi River. It appears that Garrison et al. listed this vessel twice because data

were derived from two different sources: the Hydrographic Office (HO) and the list of

losses provided in Merchant Vessels of the United States (MVUS). The information

derived from the MVUS records indicates the vessel was lost in 1960, while no date of

loss was provided in the HO records. A reexamination of the original MVUS records

(MVUS 1961) reveals that the vessel Theresa F. foundered in July 1960 “about 40 miles

ESE of Freeport, Texas.” The MVUS provides no additional information on the location

of the sinking of this Theresa F., but it is apparent that it did not sink anywhere near the

mouth of the Mississippi River. The coordinates used in the MMS wreck list by Garrison

et al. came from the records of the Hydrographic Office, but where that office got them is

unknown. The successor to the Hydrographic Office, the National Imagery and Mapping

Agency (NIMA), continued to use the coordinates, placing a vessel named Theresa F. in

the West Delta Area, off the mouth of the Mississippi (NIMA 2000).

In 1968, a vessel named Theresa F. did sink near the entrance to the Mississippi

River. The MVUS notes that the towboat Theresa F. “capsized and sank near SW Pass

Sea Buoy” while towing the barge Freeport 1 from Tampa, Florida to the Mississippi

River (MVUS 1969). No coordinates for the position of sinking are provided. It would

appear that this is the Theresa F. listed by Garrison et al. and that the Hydrographic

Office derived the coordinates for the location of loss from the verbal description given in

the MVUS (1969). However, Garrison et al. seem to have assigned the date of loss for

the Theresa F. sunk off Freeport, Texas, to the towboat sunk off Southwest Pass.

To add to the confusion, NIMA does report the loss of a vessel named Tricia F.

off the upper Texas coast in 1960 (NIMA 2000). The coordinates given by NIMA place

the sinking in the Galveston Area, about 40 miles south, southeast of Freeport, Texas.

This is almost certainly the vessel identified as the Theresa F. in MVUS records. It is

apparent that there has been considerable confusion about the vessels named Theresa F.
4-6

and Tricia F. The Theresa F. listed in the West Delta Area in the 1989 shipwreck

database, presumably, refers to the towboat that sank near the Southwest Pass Buoy in

1969, but the date of loss given is for the vessel of the same or similar name that sank

nine years earlier off Freeport, Texas.

As noted, the location of the Theresa F. off the mouth of the Mississippi River

was apparently derived from the original verbal description of its location of sinking near

the Sea Buoy. However, a more complete review of records relating to the loss of this

vessel has revealed that the coordinates provided by the HO and given in Garrison et al.

are incorrect. When the Theresa F. capsized, three of the men aboard were killed, an

event that resulted in an official inquiry and production of a Marine Casualty Report by

the United States Coast Guard (USCG 1971). The records of this inquiry provide very

specific coordinates for the position of loss, a position that is different from the one given

by the HO and used in the 1989 MMS wreck list. These USCG coordinates place the

location of the sinking of the Theresa F. in the South Pass Area, a short distance east of

the location given in the MMS wreck list. In light of the official nature of the Coast

Guard inquiry, it is believed that the coordinates they provide are the most accurate

location of the sinking of the Theresa F.

This kind of confusion is inevitably going to arise in certain cases because of the

nature of the available data on vessel losses. In this case, the confusion was greater than

normal because it seems to have been confounded by two vessels with the same or

similar names. Critically important is that the presumed location of the Theresa F. in the

West Delta Area is presented in all of the readily available and commonly used

shipwreck databases, including the list now used by the MMS, and remote-sensing

surveys in the area have relied on this presumption in the interpretation of their data.

The cases of the Theresa F., the Leopard and the Rufus Putnam serve to highlight

the kinds of errors likely to be incorporated in almost any listing of historic shipwrecks,

including the one presently used by the MMS to direct its offshore survey efforts.

Although the requirement of the present study was principally to build on and expand

upon the wreck list developed by Garrison et al., it became apparent with these vessels,

and other examples, that a reassessment of every one of the over 1,400 wrecks in the

1989 list would be necessary in order to clarify any errors that might exist. This

reassessment involved, where possible, a reexamination of the sources of data listed by

Garrison et al. (1989) for every entry in the 1989 shipwreck database. Some errors were

identified, resulting in some vessels being eliminated from the list while others were

assigned different locations of sinking. A particularly valuable aspect of this reevaluation

was that it collected information that could be used in assessing the “reliability” of the

location of loss for many individual vessels. As is discussed in more detail later, this

“reliability” assessment is considered an important element in modeling shipwreck

distributions within the study area. Some errors and contradictions in the data, however,

could not be resolved, a problem faced and recognized by the two earlier studies.
4-7

4.2.2. Determining Geographic Coordinates for Shipwrecks in the Database

The procedures described by Garrison et al. (1989:II-10-11) in assigning

geographic coordinates to reported shipwreck losses are essentially the same as those

used in this study. In the final database of shipwrecks developed, coordinates are

provided as decimal latitude and longitude, a format that allows the mapping of wreck

distributions in GIS formats. The 1989 shipwreck database represented the point of

departure for developing the present database and the geographic coordinates provided in

that study have been used except where additional data on wrecks suggested that that

information might be incorrect.

Most of the sources examined did not provide exact latitudes and longitudes for

losses; generally, the location of loss was provided in descriptive terms. These

descriptions have been included in the “Comment” section of the Access format

shipwreck database accompanying this report. The purpose of including these

descriptions is to provide researchers easy and direct access to the data from which the

coordinates were developed. Additionally, as has been discussed in an earlier chapter

and is more fully explained below, these descriptive statements often were the basis upon

which an assessment of a position’s “reliability” was obtained. When only descriptive

statements were available, these were followed to obtain the geographic coordinates by

plotting the position of the wreck in ArcView. For example, if the description of loss

stated that the vessel sank “about 12 miles southeast of Galveston” this position was

determined by scaling it off in ArcView. In those instances where the description stated

that a loss occurred “10 miles off Grand Isle” and no direction was provided, the position

was presumed to be perpendicular to that coastline, as did Garrison et al. (1989:II-11). In

the case of a large shore feature, such as Grand Isle, the center of the feature was used as

the reference point. A variety of maps and navigation charts were used to identify

various landforms and locations encountered in these descriptive statements.

It is apparent that some undetermined amount of error can be incorporated in the

coordinates obtained from these types of descriptions. Commonly, the distances and the

directions given are obviously “best guesses;” few contain language that would indicate

any great degree of precision in the estimate. Additionally, when no direction is given, it

is impossible to accurately assess the error incorporated in selecting a point perpendicular

to the named shore feature. This error is likely to be compounded when the onshore

position referenced is a large landform, such as “Grand Isle.”

If the source used provided geographic coordinates, these were used, even if they

were very general; for example, consisting of a position only to the nearest degree. A

large number of the wrecks included in the database had their positions originally

recorded in Loran coordinates that had been subsequently converted to geographic

coordinates. These geographic coordinates were used. Where multiple sources existed,

the source considered most reliable was used to determine the position of loss.

Generally, the most reliable source was a primary account of the loss, if one was found.

In those few instances where recent archaeological or remote-sensing survey work had

located historic vessels, the position of loss was obtained from this recent work.
4-8

4.3. Characteristics of the 2001 Shipwreck Database

The 2,106 entries in the shipwreck database compiled for this study represent

some presently unknown proportion of the total population of shipwrecks existing in the

GOMR. However, this listing is believed to incorporate much of the variability found in

that population of wrecks in terms of factors such as vessel types, causes of loss, periods

of loss, etc. In light of this presumption, the shipwreck database does provide a point of

departure for developing generalized statements about the population of wrecks in the

study area. As is discussed in more detail below, there are recognizable gaps in the

available shipwreck data that make it difficult to assess the reliability of some of the

generalizations presented. For example, there is an obvious underreporting of wrecks in

the study area for earlier historic periods. Because of this, it remains unknown as to how

accurately the shipwrecks that are known from early periods actually characterize the

population of wrecks from those periods. Similarly, there is a gap in our knowledge of

small pleasure and fishing craft that have been lost in the region in the twentieth century.

Many of these types of vessels operated outside of the purview of various government

agencies and thus their existence, as well as their loss, may have never been recorded. In

recent years, at least for the past 25 or so, the losses of many of these types of vessels

have been recorded (for example, in USCG records), but for much of the first half of the

twentieth century they may not have been. These types of vessels might be of lesser

concern in this study than in other similar ones because the study area includes only

Federal waters and excludes the nearshore, state waters where many of these types of

craft would have confined their activities.

Information in the shipwreck database is examined in a variety of ways. In most

of these efforts, comparisons are made with the 1989 shipwreck database developed by

Garrison et al. and, where appropriate, with other similar sets of data.

The 2001 shipwreck database represents an increase of 638 entries over the 1989

shipwreck database. However, as noted earlier, the 1989 database included a number of

obvious duplicate entries, some of which could be identified. If these duplicates were

removed, the increase in the number of entries in the new database would represent about

800 entries. Table 4-1 compares the number of wrecks reported in the 1989 database

against the numbers developed in this study by MMS lease area. The table also shows

the difference between the two data sets. As can be seen, in a few lease areas there are

fewer wrecks listed in the new database than had been included in the 1989 list. In most

instances, this was because it was determined that some vessels shown falling in Federal

waters in the 1989 list are now believed to be most reliably located in state waters.

Table 4-1. Differences Between Number of Shipwrecks Reported

in 1989 Study and This Study by Lease Area

LEASE AREA NUMBER OF

LOSSES-THIS

STUDY

NUMBER OF

LOSSES-1989

STUDY*

DIFFERENCE

ALAMINOS CANYON AC 1 1 0

AMERY TERRACE AM 0 0 0
4-9

Table 4-1. (continued). Differences Between Number of Shipwrecks Reported

in 1989 Study and This Study by Lease Area

LEASE AREA NUMBER OF

LOSSES-THIS

STUDY

NUMBER OF

LOSSES-1989

STUDY*

DIFFERENCE

APALACHICOLA AP 57 27 30

ATWATER VALLEY AT 5 0 5

BRAZOS BA 42 43 -1

BRAZOS A BAA 19 6 13

BAY MARCHAND BM 1 3 -2

BRETON SOUND BS 14 13 1

CHANDELEUR CA 8 1 7

CORPUS CHRISTI CC 3 1 2

CAMPECHE ESCARPMENT CE 0 0 0

CHARLOTTE HARBOR CH 45 21 24

DESOTO CANYON DC 10 11 -1

DESTIN DOME DD 37 17 20

DRY TORTUGAS DT 28 18 10

EAST BREAKS EB 7 5 2

EAST CAMERON EC 43 35 8

FLORIDA PLAIN FP 3 0 3

EUGENE ISLAND EI 97 51 46

THE ELBOW EL 6 7 -1

EWING BANK EW 2 1 1

FLORIDA MIDDLE GROUND FM 19 17 2

GALVESTON GA 93 73 20

GALVESTON A GAA 26 19 7

GARDEN BANKS GB 3 1 2

GRAND ISLE GI 29 18 11

GREEN CANYON GC 14 3 11

GAINESVILLE GV 8 8 0

HENDERSON HE 8 9 -1

HOWELL HOOK HH 10 10 0

HIGH ISLAND HI 50 33 17

HIGH ISLAND A HIA 60 24 36

KEATHLEY CANYON KC 1 3 -2

KEY WEST KW 5 1 4

LLOYD LL 10 6 4

LUND SOUTH LS 0 0 0

LUND LU 11 13 -2

MIAMI MA 10 6 4

MISSISSIPPI CANYON MC 36 20 16

MATAGORDA ISLAND MI 45 25 20

MATAGORDA ISLAND A MIA 0 1 -1

MOBILE MO 71 27 44

MAIN PASS MP 60 35 25

MUSTANG ISLAND MU 57 49 8

MUSTANG ISLAND A MUA 13 10 3

ST. PETERSBURG PB 57 24 33

PENSACOLA PE 93 21 72

PORT ISABEL PI 2 0 2

SOUTH PELTO PL 17 5 12

NORTH PADRE ISLAND PN 30 33 -3

NORTH PADRE ISLAND A PNA 8 5 3

PULLEY RIDGE PR 38 29 9

SOUTH PADRE ISLAND PS 44 38 6

SOUTH PADRE ISLAND A PSA 8 4 4

RANKIN RK 0 0 0

SABINE PASS (LA) SA 17 22 -5
4-10

Table 4-1. (continued). Differences Between Number of Shipwrecks Reported

in 1989 Study and This Study by Lease Area

LEASE AREA NUMBER OF

LOSSES-THIS

STUDY

NUMBER OF

LOSSES-1989

STUDY*

DIFFERENCE

SIGSBEE ESCARPMENT SE 0 0 0

SABINE PASS (TX) SX 2 6 -4

SOUTH MARSH ISLAND SM 32 19 13

SOUTH PASS SP 33 39 -6

SHIP SHOAL SS 95 51 44

SOUTH TIMBALIER ST 88 46 42

TARPON SPRINGS TP 55 57 -2

TORTUGAS VALLEY TV 0 0 0

VIOSCA KNOLL VK 21 10 11

VERNON VN 8 4 4

VERMILION VR 62 39 23

WALKER RIDGE WR 2 2 0

WEST CAMERON WC 124 72 52

WEST DELTA WD 55 30 25

OUTSIDE OF LEASE AREAS 148** 240 -92

TOTALS 2106 1468 638

*The 1989 shipwreck database does not include a lease area for one vessel, thus the total

number shown here is one less than the 1,469 entries in that database.

**Does not include vessels falling in numbered MMS lease blocks extending into or

lying entirely in state waters.

The 1989 shipwreck database, as noted earlier, did include 240 entries identified

as falling in state waters. The present database also includes a number of shipwrecks

whose reported positions fall in state waters, despite the fact that only shipwrecks within

MMS lease areas are of principal concern in this study. These particular vessels are

included in the database because of uncertainties about their location of loss. As shown

in Table 4-1, these include 148 entries with no lease block designations. These vessels

fall outside of numbered MMS lease blocks. A few of these vessels fall south of the

MMS lease areas, but most fall within the waters of the states bordering the Gulf. In

addition, there are 219 entries that fall in numbered MMS lease blocks that extend into or

lie entirely in state waters. Most of these entries lie in Louisiana and Texas state waters

and are identified in Appendix E. These vessels have been included in the shipwreck

database dependent upon the reliability value assigned to their reported position of loss.

Those vessels in state waters assigned a location reliability of 2 whose plotted position

falls closer to Federal waters than to the state shorelines have been included in the

database. Thus, if the vessel lies in Louisiana state waters, its reported position of loss

has been determined to be more than 1.5 miles from the shoreline. All of those vessels

with positions of loss in state waters or near the southern edge of the GOMR that are

assigned poor location reliabilities of 3 or 4 have been included in the database. In light

of the uncertainties about the reliability of the plotted position of these vessels, they may

actually lie within the MMS lease areas.

The 2,106 entries in the shipwreck database encompass a variety of items in

addition to historically reported shipwrecks. The entries include nine aircraft, nine
4-11

helicopters, 14 objects identified as anchors or anchors and chain, and structural remains

associated with an historic lighthouse, the Ship Shoal Lighthouse, an iron screw pile

structure erected off the Louisiana coast in 1859 (Cipra 1997:156-160). These items are

included because they represent, or have the potential for representing, historically

significant cultural remains. Within the list are an estimated 1,290 named shipwrecks,

that is, vessels whose official name has been determined. This number is an estimate,

because some shipwrecks are identified in various sources by descriptive statements or

nicknames that may or may not be the vessel’s official name. This is particularly true of

wreck names derived from sport diver accounts and records, such as “Lipscombe Tug,”

“O-Tower Barge,” or “Redfish Barge.” Sources were compared to try to sort out these

naming problems and identify the vessel’s actual name, but this was not always

successful.

The database also includes over 470 “Unknown Vessels” in addition to several

entries identified as “Unknown Wreck,” “Unknown Tug,” “Unknown Fishing Vessel”

and the like. Additional entries include 64 “Pleasure Craft” and other wrecks identified

only by their length, plus wrecks identified only as “Shrimp Boats,” “Wrecks,” “Sailing

Vessels,” and a number of “Barges” named in various ways. Sources were compared to

see if these unnamed entries could be associated with a named shipwreck and, where

possible, this was done. Otherwise, the nomenclature used in the original source was

maintained.

4.3.1. Chronological Trends

4.3.1.1. Year of Loss

Year of loss information was obtained for 1,419 vessels, or 67.4 percent of the

total items included in the 2001 shipwreck database. The earliest shipwreck included in

the database is the San Jorge, lost in 1625, and the latest losses are two vessels that were

sunk as elements of artificial reefs in the year 2001. Much of the information on recent

losses was obtained from computerized databases maintained by various government

agencies (e.g., NOAA, NIMA, and USCG) that are updated only periodically. Most of

these databases were obtained in the fall of 2000 and, therefore, they will contain only

some of the Gulf of Mexico losses for that year and it is possible that not all of the losses

for 1999 have been incorporated in all of these lists.

In the present study, data on recent losses have been collected even though

historical significance as stipulated by the National Register of Historic Places normally

applies to resources over 50 years old. This follows the approach used by Garrison et al.

(1989), even though the ultimate selection of some high-probability lease blocks by the

MMS did eliminate vessels that have been lost in the past 50 years. Other studies (e.g.,

the Pacific coast MMS study by Gearhart et al. [1990]) have used a 50-year-ago date of

sinking as an end date for data collection. One of the hazards in using the 50-year-ago

loss date is that many vessels that have sunk within the past 50 years are greater than 50

years old and, thus, might represent significant historic resources under National Register

criteria. In this study, for example, year of build and year of loss were obtained for 689
4-12

vessels. Of these, 490 losses have occurred in the past 50 years (i.e., since 1950). Out of

this number, 242 vessels were 50 years old or greater in the year 2000, when the present

study was initiated. If the year of loss were the only criterion used for establishing

potential historical significance, these vessels, constituting 49.4 percent of the total in this

group, would be eliminated from consideration. It is impossible to know if this

proportion can be extended to those vessels of unknown date of build that have been lost

in the past 50 years, but it is presumed that a fairly large percentage of them are greater

than 50 years old.

Figure 4-1 provides data on vessel losses by 25-year intervals using the 1,419

entries in the database for which year of loss is known. These data show a pattern of an

overall increase in the frequency of vessel losses over time, with a very dramatic increase

in number of reported wrecks occurring after 1950. As seen in Figure 4-1, the 1951-1975

twenty-five-year interval has almost five times as many reported wrecks as the previous

interval. In fact, more losses are reported in the GOMR for the period 1951 to 1975 than

for the entire historic period before that date.

Figure 4-1. Shipwreck frequencies in the GOMR by 25-year intervals, 1625-

2001. Data from 2001 shipwreck database.

583

514

108

103

51

18

17

7

4

7

5

1

0

0

1

0 100 200 300 400 500 600 700

1976-2001

1951-1975

1926-1950

1901-1925

1876-1900

1851-1875

1826-1850

1801-1825

1776-1800

1751-1775

1726-1750

1701-1725

1676-1700

1651-1675

1625-1650

NUMBER

25 YEAR INTERVALS
4-13

This significant increase in the number of reported losses after 1950 is partially a

reflection of an actual increase in losses because of a significant increase in the number

of vessels operating on the Gulf of Mexico, but it is also a reflection of recent trends in

reporting losses. As has been noted, there is an obvious bias for underreporting losses

during earlier historic periods. Additionally, in the past several decades, reports of losses

have become more inclusive in terms of the types of vessels considered. For example,

the USCG and other agencies now record losses of pleasure craft and small fishing

vessels, classes of vessels that were typically ignored in earlier years as can be seen in

sources such as the Merchant Vessels of the United States.

One factor that has contributed to some of the increase in reported losses in the

past 25 years or so is the inclusion of a number of artificial reefs in the 2001 shipwreck

database. These represent vessels of various types deliberately scuttled in the past 25

years or so to form artificial reefs and fish havens. A number of these vessels are World

War II-era ships (particularly “Liberty Ships”) and their inclusion in the database tends to

disproportionately increase the representation of this class and age of vessels relative to

other types that have been lost to natural causes.

 The pattern of losses by 25-year-intervals seen in the 2001 shipwreck database is

very similar to that seen in the 1989 shipwreck database, as shown in Figure 4-2. The

two databases show a very similar pattern through the 1951-1975 interval. The

divergence after that date is because the 1989 database includes data only through 1987

and, as noted above, the present study has incorporated only a portion of the losses

occurring after the year 2000. It is not surprising that these two sets of data resemble one

another since they are dealing with the same subset of reported shipwrecks, e.g., those

occurring in Federal waters in the Gulf of Mexico, plus the present study drew

extensively on data contained in the 1989 database.

Garrison et al. (1989:Table II-15) also provide year of loss data in 10-year

intervals for the period 1500 to 1986, including 4,154 entries, and incorporate data on all

vessel losses in the Gulf of Mexico, including those occurring in state waters. In essence,

this dataset represents a regional compendium for frequency of losses over time. Murphy

and Jonsson (1993) have synthesized information on the vessel losses that occurred in the

Dry Tortugas and the immediate vicinity, southwest of the Florida Keys. In their data,

they include reports of actual losses as well as “casualties” which may or may not

actually result in a sinking. They have included casualties because they might produce

archaeological materials even if no sinking occurred, the same reason that these reports

are included in the present study. The Dry Tortugas data include information on the year

of loss or casualty for 215 vessels. These data can be viewed as a “local” set of

shipwreck information from the Gulf of Mexico, although the Dry Tortugas must be

considered somewhat atypical features relative to regional shipwreck occurrences.

Historically, the Dry Tortugas and the adjacent Marquesas Islands represented

one of the most dangerous hazards to shipping in the Gulf. These islands consist of a

series of low reefs and carbonate sandbanks extending westward from Key West and

lying at the edge of the main shipping channel between the Gulf of Mexico, the Western
4-14

Caribbean and the Atlantic Ocean. Over the years, these islands have been the site of

numerous shipwrecks; Bearss (1971) reported that they have been the site of the largest

number of wrecks in the Gulf of Mexico.

Figure 4-2. Comparison of shipwreck frequencies in the GOMR by 25-year intervals provided in the

 1989 shipwreck database and the 2001 shipwreck database.

The data on losses by decade provided by Murphy and Jonsson (1993) for the Dry

Tortugas and by Garrison et al. (1989) for the entire Gulf region are presented with the

data obtained in the present study in Figure 4-3. In this figure, the data have been

converted to percentages to permit valid comparisons and have been truncated at 1969,

the last year for which the Dry Tortugas data are available. The Garrison et al. “regional”

data generally follow the trend seen in the present shipwreck database up to the 1930-

1939 decade. After that, the present database exhibits proportionally more losses for the

next three decades. The Dry Tortugas loss data show considerable divergence from the

other two datasets.

All three sets of data show a peak of losses in the 1840-1849 decade, but the Dry

Tortugas data show a considerable increase in the proportional number of wrecks for the

three decades from 1830 to 1859. The Dry Tortugas data also show a peak in losses

during the two decades from 1880 to 1899 that is only slightly expressed in the other two

datasets. Interestingly, all three sets of data show a similar increase in losses for the

period 1900 to 1929. In general, as noted earlier, the trend seen in the 2001 shipwreck

database as well as the Garrison et al. “regional” 1989 database is an increase in reported

losses over time. Interestingly, this has not been the trend observed elsewhere.
4-15

Figure 4-3. Proportional frequencies of shipwrecks by 10-year intervals for three sets of data: the

1989 data for the entire Gulf of Mexico region, data from the Dry Tortugas and vicinity

and the 2001 shipwreck data from Federal waters of the Gulf of Mexico developed in

this study. Data prior to 1800 is consolidated. Gulf of Mexico regional data from

Garrison et al. (1989) and Dry Tortugas data from Murphy and Jonsson (1993).

The Dry Tortugas data shown in Figure 4-3 indicate a peak of losses in the 1850s,

two slight peaks in the 1880s and around 1910, and then a fairly rapid decline in losses

since then. Similarly, information on “casualties” and “strandings” for all of the United

States for the period 1906 to 1936 reported in the “Loss List” of the Merchant Vessels of

the United States shows a general decline in losses since the 1920s (Murphy and Jonsson

1993:150). Bourque (1979), in the study of shipwrecks on the Atlantic OCS, showed a

decline in losses after 1880 and the 1977 CEI study of shipwrecks in the Gulf of Mexico

reported a decline in losses after 1910. In contrast, the data in Figure 4-3 show a

significant increase in the number of losses in the GOMR beginning in the 1940s,

particularly after World War II. An examination of the types of vessels lost during this

period reveals that a significant number are identified as “Fishing Vessels” or more

specifically as “Shrimp Trawlers,” or as “Pleasure Vessels” or, on the basis of their

names or types, can be identified as vessels associated with the offshore oil and gas

industry.

This reflects the great expansion of the fishing, particularly shrimping, industry

across the entire Gulf of Mexico since the 1940s, and the development and expansion of

the offshore oil and gas industry in the central and western Gulf during the same period.

In addition, it reflects the rise of recreational boat use in the waters of the Gulf of

Mexico. For the past several decades the largest number of vessels operating in the Gulf
4-16

of Mexico have been associated with these three activities. Consequently, these types of

craft constitute the greatest number of losses.

These types of modern vessels appear to be underrepresented in the Dry Tortugas

shipwreck data presented by Murphy and Jonsson (1993). That study used 1969 as a

cutoff date, meaning that very recent losses are excluded. Additionally, it appears that

the historical sources used in the Dry Tortugas study were not those that typically include

information on recent losses, such as the U.S. Coast Guard records. Thus, some of the

divergence between the Dry Tortugas and the two Gulf of Mexico datasets for losses

occurring after the 1930-1939 decade is believed to be a factor of the sources of

information used, not a reflection of the actual losses that occurred.

Garrison et al. (1989) argue that the increase in losses during recent periods might

reflect the fact that modern sailors take greater risks because of their increased

confidence in and reliance on modern ship and navigation technology. This could be

true, but, as noted earlier, it is more likely that the increased number of losses in recent

years is principally a reflection of the tremendous increase in the number of vessels

operating on Gulf waters, particularly those associated with recreational boating, fishing,

and the oil and gas industry. Typically, these types of vessels are ignored in overview

studies of “historic shipwrecks” under a general presumption that they are of minimal

historical value. Some certainly are too young to meet the 50-year-old age criterion for

National Register significance, but many are over 50 years old and these and others can

provide valuable information on a variety of characteristics of these relatively recent

craft. The general neglect of these more recent classes of vessels by historians as well as

archaeologists means that, for some, we know less about their origins, construction and

technological development than we do about seventeenth century ships.

Less obvious temporal trends can be seen in the 2001 shipwreck database year-ofloss data. Only after 1725 do more than five wrecks per 25-year interval occur (see

Figure 4-1). This coincides with the establishment and expansion of settlements on the

northern Gulf of Mexico and an increase in cross-Gulf travel. Garrison et al. (1989:II-99)

show more wrecks for the whole Gulf of Mexico region prior to 1725, but the majority of

these represent vessels lost on shore or close to shore and not in offshore waters.

Additionally, there is no doubt a bias for underreporting wrecks during these very early

periods (Garrison et al. 1989:II-86). Only after 1875 do more than 50 losses occur for a

25-year interval (see Figure 4-1). This reflects the increase and expansion of maritime

trade in the Gulf during the last quarter of the nineteenth century with the establishment

of new Gulf ports such as Port Arthur and the growth of others, such as Tampa (Garrison

et al. 1989:II-23). Additionally, this increase reflects an expansion in reporting of wrecks

by various agencies and organizations. For example, in 1876 the United States Life

Saving Service began to publish its Annual Reports that included ship casualty data.

4.3.1.2. Age of Vessel at Loss

The 2001 shipwreck database contains 689 vessels for which date of build and

year of loss are reported. These constitute only 33 percent of the total entries in the
4-17

database, so the age at loss on this sample can only be extended to the entire database

with some caution. The average age for all of these vessels was 16.5 years at the time of

their reported loss or casualty. It was anticipated that the age of vessels lost would vary

over time, with earlier vessels tending to be older at the time of loss. Albion (1938:98),

for example, reports that the normal use-life of a nineteenth century merchant ship was

about 20 years while others suggest that the average age of vessels in 1900 was about 10

years (Murphy and Jonsson 1993). For the 38 vessels in the 2001 database lost before

1900, the average age was 11.6 years at the time of loss, while the average age of 654

vessels lost after 1900 was 16.7 years. This did not support the initial assumption that

earlier vessels would be older at the time of their loss and it is considerably at odds with

Albion’s (1938) estimate of the use-life of the typical nineteenth century merchant vessel.

To further examine the relationship of year of build and age at time of loss, correlation

coefficients were computed on two sets of age-related variables. One analysis compared

the year of build with the age of the vessel at the time of loss, while the other looked at

the correlation between the year of loss and the age of the vessel at loss. The correlation

analysis used in this analysis is provided in the software program Microsoft Excel and

has been described in Chapter 3. This analysis measures if two ranges of data move

together; that is, whether large numbers in one set are associated with large numbers in

the other. In the first analysis, which examined the relationship between the year of build

and the age at loss, the value of the correlation coefficient was a negative number, -

0.37244. This means that the farther back in time a vessel was constructed, the younger

it was at the time of its reported loss, although the correlation is weak. The correlation

coefficient obtained when comparing the year of loss with the age of the vessel at the

time of loss was a positive value, 0.07263, but is also indicative of a very weak

correlation. It is apparent that there is no strong correlation between period of loss and

the age of loss of vessels in the sample of 6989 vessels used here. As noted, it is

unknown how reflective this is of the entire population of vessels lost in the GOMR.

Vessel age at time of loss was also examined across vessel type. For the

nineteenth century it is generally assumed that sailing vessels had much longer life spans

than did steam vessels. This is certainly true when comparing sailing vessels, which had

life spans of 20 to 25 years, against western river steamers, which had notoriously short

life spans on the order of only five years (Hunter 1949; Pearson and Wells 1999).

However, relatively little information has been synthesized on the life span of steamers

operating in marine settings.

The 2001 shipwreck database contains 303 vessels with information on type, year

of build and year of loss. There are a total of 90 that can be identified as sailing vessels

in this number, most (N=82) of which are classified as “Schooners” in historical

accounts, while the remainder consist of vessels identified variously as “Ships,”

“Sloops,” “Brigs,” “Sailing Vessel,” etc. The average age at loss for these sailing vessels

was 21.9 years and 48 percent (N=43) of the vessels were over 20 years old at the time of

their loss. Many, but not all, of these vessels did operate during the nineteenth century,

so the data may not be directly comparable with other data sets dealing with nineteenth

century ships. The oldest vessel in the database is a sailing vessel, the schooner Henry

Mearn, which Singer (1992) reports was built in 1866 and sank in 1978 when 112 years
4-18

old. Murphy and Jonsson (1993:155) report that the average age for sailing ship

“casualties” in the Dry Tortugas was 13.5 years, while the average age for sailing ships

“lost” in the Dry Tortugas was 15.8 years. These figures are somewhat lower than seen

in the 2001 GOMR data, plus in the Dry Tortugas data, only 38 percent of the vessels lost

were older than 20 years. The lower average age of sailing vessels lost in the Dry

Tortugas relative to the open waters of the Gulf of Mexico as a whole cannot be fully

explained. However, it is likely that the increased hazard to shipping presented by the

Dry Tortugas played a part.

Only nine vessels classified as “steamers” are included in the 303 vessels with

information on type, year of build and year of loss (see Volume III, Appendix E). These

included vessels classified as “Sidewheelers,” “Sternwheelers,” and simply “Steamers.”

Seven of these vessels were constructed and operated in the nineteenth century, and two

were built and operated in the twentieth century. The average age for these vessels at the

time of loss was 8.7 years, considerably lower than that found for sailing vessels, as was

anticipated.

Further comparisons in differences in age of loss across types of vessels were

made by looking at other classes of vessels. For example, 54 vessels are identified

broadly as non-sailing merchant vessels. These include “Freighters” (n=18),

“Merchantman” (n=19) and “Tankers” (n=17). The average age for these vessels at time

of loss was 25.0 years. Sixty-five vessels can be classified generally as “fishing” craft.

These include 16 vessels identified as “Shrimp Trawlers” and 49 as “Fishing Vessels.”

The average age for these vessels at the time of loss was 14.6 years. Finally, the average

age at the time of loss of the 27 vessels classified as “Barges” was 13.2 years.

It is apparent from these numbers that vessels of various types have quite different

average life spans. This was generally expected and is related to factors such as size,

manner of construction, and function of the vessel. Those vessels classified as general

non-sailing “merchant vessels” had the longest average life spans of all types in the

sample, averaging 25.0 years old at the time of their loss. These tend to be large,

expensive vessels that are typically designed, constructed, and operated for long working

lives. Fishing vessels, on the other hand, tend to be smaller craft that are more

susceptible to natural and man-made hazards and thus tend to have shorter life spans.

Interestingly, the data suggest that there is no significant correlation between the age of a

vessel at the time of loss and the period of time when that vessel was built or operated.

4.3.1.3. Season of Loss

Information on the month of loss was obtained for 968 vessels and is presented as

a bar graph in Figure 4-4. The numbers of losses for each month are provided in the

graph. January and November have the highest recorded number of losses and March the

lowest, but overall there is a roughly equal distribution of losses across all months.

Seasonality of losses should provide some clues as to the impact that weather-related

events have had on shipwreck losses in the GOMR. As noted in the previous chapter, the

periods of poorest weather in the Gulf of Mexico tend to be during the winter months
4-19

when “northers” frequently cross the area, and the late summer and fall when hurricanes

can occur, mostly between August and October. A total of 354 vessels are reported to

have been lost during the four winter months of November, December, January and

February. This represents 36.6 percent of the total losses with a known month of loss,

again only slightly above the number that would be expected by chance. It appears that

poor winter weather (e.g., northers) has not had a significant impact on the overall

number of losses occurring over the course of the year in the GOMR.

Figure 4-4. Reported losses per month for vessels in the study area. Data from 2001 shipwreck

database.

Garrison et al. (1989:II-53 – II-68) present an extensive discussion on the impact

of hurricanes on shipwrecks in the Gulf of Mexico. In particular, they looked at the

spatial distributions of shipwrecks as they might relate to hurricane paths through time.

Their data did not show a strong correlation between hurricanes and shipwrecks over

time, either in frequency or spatial distribution (Garrison et al. 1989:II-54). They did

note that there was a correlation between numbers of losses and large hurricanes for

specific years, but in the majority of cases, the wrecks of interest occurred in state waters,

outside of the present study area. Relatively few hurricane-related vessel losses have

occurred in the study area since the 1989 study and these data would not substantially

alter the findings reported by Garrison et al. (1989). The shipwreck data collected in this

study do allow some generalizations about the relationships of hurricanes and vessel

losses in the Gulf that supplement the findings reported in the 1989 study.

Despite their danger, the frequency of hurricanes in the Gulf of Mexico is low.

Data for the late nineteenth and twentieth centuries indicate an average occurrence of

96

80

65

71 69

77

83

70

87

92 94

84

0

2 0

4 0

6 0

8 0

100

120

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

MONTH

NUMBER OF LOSSES

NUMBER OF LOSSES
4-20

only one hurricane per year in the Gulf of Mexico (Henry et al. 1975). In terms of the

present data shown in Figure 4-4, 25.7 percent of all reported losses occurred during the

principal hurricane season, August through October, essentially the number that would be

expected by chance. This suggests that, overall, hurricanes do not have a significant

impact on the numbers of vessels lost over the course of the year. While the data

presented here do not show a strong correlation between the hurricane season and

numbers of vessels lost, hurricanes and other weather-related phenomena did influence

shipping activity in the Gulf and had an impact on losses. The Spanish very quickly

learned of the dangers of hurricanes and scheduled their fleet sailings around the peak

hurricane season. Despite all efforts, however, they experienced severe losses because of

delays in fleet sailings or because of out-of-season hurricanes. Large numbers of Spanish

ships were lost in the Florida Keys and the Bahama Channels during hurricanes in 1633,

1715, and 1722. In 1766, delays in getting the annual fleet off from Veracruz until

September resulted in the loss of two ships run aground on the northern Gulf coast

(Pearson and Hoffman 1995).

In a study of historical hurricanes that considered their impact on shipwrecks,

Millas (1968) noted that the most important elements in the association of shipwrecks,

natural or historical factors and hurricanes are: 1) reported shipwreck frequency; 2)

seasonality; 3) historic period; and 4) development of ports and trade routes. As ports

increased, and shipping expanded along more diverse routes, the “interplay of a normal

storm frequency guaranteed a higher incidence of vessel losses” (Garrison et al. (1989:II53). If this is true, it is expected that the loss of vessels during the hurricane season

would show an increase in the GOMR over time corresponding to the known expansion

of shipping activity and sailing routes. By about 1875, the major ports on the northern

Gulf of Mexico had been established and shipping routes were fully expanded.

Presumably, then, vessel losses due to hurricanes would be proportionally greater after

1875 than before, meaning that losses during the peak hurricane season should also be

proportionally greater, unless non-weather factors are overriding the effects. The 2001

shipwreck database contains only 48 vessels with a known month of loss and a sinking

date prior to 1875. This sample is probably too small to be statistically meaningful, but

21, or 43.4 percent, of the losses occurred during the three-month peak hurricane season.

This number is somewhat greater than that obtained for the entire sample of 968 wrecks

and may suggest that hurricanes had a greater impact on vessel losses prior to 1875. This

finding seems to be at odds with the Garrison et al. presumption that losses to hurricanes

would increase after about 1875. However, it is possible that the high incidence of

hurricane-season losses during earlier years is mainly a factor of reporting, in that losses

due to hurricanes were more likely to elicit interest than were losses due to less dramatic

weather phenomena. 

Patterns in seasonality of vessel activity in the Gulf also will influence the number

of vessels lost during each month. For example, during the period from about 1830 to the

Civil War, large numbers of vessels traveling in the Gulf of Mexico were involved in the

cotton trade. Shipments of cotton peaked during the period from November to May and

it is possible that the increased numbers of vessels working in the region during this

period led to increased losses, which have contributed to the pattern of losses shown in
4-21

Figure 4-4. Also, since the late 1930s offshore shrimping has been important in the Gulf

of Mexico with very large numbers of vessels involved in it. Although Gulf shrimpers

often operate year-round, the peak seasons for nearshore shrimping have traditionally

been in the spring between May and July and in the fall and early winter from midAugust to mid-December. In light of the fact that a large number of the vessels included

in the 2001 shipwreck database are believed to be shrimp trawlers, it can be expected that

the seasonal activity of these vessels has influenced the monthly losses. This would be

particularly true when high numbers of these vessels coincided with adverse weather

conditions, such as during the winter months.

Figure 4-5 provides information on the relative frequency of losses by month for

all vessels with that information and for all “Shrimping Vessels” with month of loss

information. This category of Shrimping Vessels (N=131) includes those identified as

“Shrimp Trawlers,” “Trawlers,” and simply as “Fishing Vessels” in Appendix E. The

data indicate some significant divergences in the months of loss for Shrimping Vessels

relative to All Vessels, particularly for the months of June and July when proportionally

more Shrimping Vessels have been lost. These are the months when shrimping is at its

peak and when the largest number of trawlers are active. Shrimping Vessel losses also

occur in somewhat higher frequencies during November and January and February, but

they are lower during May and during the late summer and early fall. These data seem to

suggest that the shrimping season has a greater influence on the numbers of Shrimping

Vessels lost than does the weather. In essence, when more boats are operating in the

Gulf, more will be lost, regardless of seasonal weather patterns.

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

16,0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

MONTH

Shrimping

Vessels

All Vessels

Figure 4-5. Reported losses per month for All Vessels and those identified as

Shrimping Vessels (Fishing Vessels, Trawlers, and Shrimp Trawlers).

Data from 2001 shipwreck database.

PERCENTAGE
4-22

Murphy and Jonsson (1993) examined the month and season of loss for vessel

casualties and losses in the Dry Tortugas. Their data showed no strong association of

season with reported casualties or losses. For example, for both casualties and losses,

they found that between 51 and 53 percent occurred during the winter months of

September through January. In the GOMR sample, 453 wrecks are reported for this fivemonth period, representing 46.8 percent of the total for the year.

As Murphy and Jonsson (1993:148) found for the Dry Tortugas, it would appear

that weather, as a seasonal phenomena, has not been a strong primary determinant of

vessel losses in the GOMR. Many ships, of course, have been lost to bad weather in the

Gulf of Mexico, but factors other than the season of the year seem to be at play. For

example, Murphy and Jonsson (1993:148) suggest that “product seasonality and

concomitant shipping demands” have had an impact on the wreck population in the Dry

Tortugas. They note, for example, that vessels carrying cotton constituted a significant

number of those operating in the Gulf during much of the nineteenth century. The

transportation of cotton by ship peaked during November to May and in the Dry

Tortugas, the seasonal losses of vessels known to have carried cotton cargoes correlates

with this trend.

4.3.2. Types of Vessels

A large variety of vessel types have been used and lost in the waters of the Gulf of

Mexico. In the 2001 shipwreck database, “Vessel Type” was determined for 929 entries,

resulting in the identification of a total of 53 different types of vessels (Table 4-2).

Table 4-2. Types of Vessels in the 2001 Shipwreck Database

VESSEL TYPE CODE NUMBER

Barque BAR 2

Barge BGE 109

Barkentine BNK 1

Brig BRG 5

Brigantine BRI 2

Buoy Tender BYT 1

Cabin Cruiser CCR 2

Clipper CLP 1

Crane Barge CRB 2

Crewboat CRW 8

Cutter CUT 1

Destroyer Escort DES 2

Dive Tender DVT 2

Drilling Rig DIR 19

Dredge DRE 8

Exploration Vessel EXP 1

Fishing Vessel F/V 252

Ferryboat FER 3

Freighter FRT 25
4-23

Table 4-2. (continued). Types of Vessels in the 2001 Shipwreck Database

VESSEL TYPE CODE NUMBER

Gunboat GBT 1

Galleon GLN 2

Hopper Barge H/B 4

Jack-up Barge JUB 22

Landing Craft LDC 7

Landing Ship LNS 2

Landing Ship, Tanks LST 2

Lugger LUG 1

Motor Vessel M/V 65

Merchant MCH 36

Mine Sweeper MSW 1

Pleasure Craft P/C 64

Paddlewheel Boat PDL 1

Passenger Steamer PAS 3

Patrol Boat PAT 3

Sailboat SAI 11

Schooner/barge SB 1

Schooner SCH 104

Sidewheeler SDW 5

Shrimp Trawler SHM 36

Ship SHP 7

Skiff SKI 1

Sloop SLP 3

Steamer ST 4

Sternwheeler STW 1

Submarine SUB 6

Supply Vessel SPV 1

Tug or Tow boat T/B 3

Tanker TNK 23

Tow Boat TOW 3

Torpedo Boat TPB 1

Trawler TRA 5

Tugboat TUG 47

Yacht YCT 8

Total Known Vessel Types 930

Other

 Aircraft ACFT 9

 Anchor/Chain ANCH 14

 Helicopter HELO 9

Unknown/Unclassified 1145

TOTAL 2107

Figure 4-6 provides information on the numbers of vessels in each type for those

having five or more entries. As discussed in Chapter 2, the designation of a “Vessel

Type” was principally drawn from the historic sources used. In most instances this

resulted in a functional descriptor (e.g., Tanker, Fishing Vessel, Jack-up Barge), but often
4-24

in a more general statement about the rig or form of propulsion of the vessel (e.g.,

Schooner, Steamer, etc.). As noted earlier, there is no “correct” way to develop a

typology system. The one used here results in a large number of types, most but not all

of which are somewhat functional in nature. Like all typologies, it does have problems.

For example, “Schooners” comprise the second largest number of vessel types in the

database (N=104), but this is a category determined by type of rig and it might include a

variety of functional types of vessels, such as merchant vessels, fishing vessels, etc. The

historic sources examined do not permit an accurate functional classification of most of

the vessels included in the Schooner category.

252

109

104

65

64

36

36

25

23

22

19

11

8

8

8

7

7

6

5

5

5

46

0 50 100 150 200 250 300

Fishing Vessel

Barge

Schooner

Motor Vessel

Pleasure Craft

Tugboat

Merchant

Shrimp Trawler

Freighter

Tanker

Jack-up Barge

Drilling Rig

Sailboat

Crewboat

Dredge

Yacht

Landing Craft

Ship

Submarine

Brig 

Sidewheeler

Trawler

NUMBER

Figure 4-6. Vessel types in the 2001 shipwreck database containing five or more entries.
4-25

Other shipwreck studies have faced the same problem in developing vessel

typologies and have opted for differing strategies of classification. For example,

Gearhart et al. (1990), in their regional overview of shipwrecks along the Pacific coast,

used an approach similar to the one used in the present study, resulting in a fairly large

number of vessel types. They arrived at 38 types of vessels (plus an unknown category)

in their inventory of reported wrecks. Some categories are functional (e.g., Fishing, Tug)

while others are related to rig or propulsion (e.g., Schooner, Gas-powered, Oil-powered).

On the other hand, Murphy and Jonsson (1993) arrived at only nine vessel types,

plus an unknown category, in their typology of vessels lost or reported as casualties in the

Dry Tortugas. They used a few functional categories (e.g., Tanker, Barge), but most of

the 311 vessels in their sample were subsumed under rig or propulsion categories (e.g.,

Schooner, Brig, Engine Powered), resulting in a much smaller number of types of

vessels. Because of the various typologies used in different studies, quantitative

comparisons do become difficult, or must be made only across specific categories.

Figure 4-7 provides information on the mode of propulsion recorded for 683

vessels in the shipwreck database. Excluded are two entries identified as “towed” vessels

and one propelled by “oar.” Sailing craft as a whole comprise just over 22 percent of the

vessels of known type in the GOMR database. The vast majority of these are identified

as “Schooners” (N=104) and the others include miscellaneous craft such as “Brigs,”

“Sloops,” or just “Sailboats” (see Table 4-2, Figure 4-6). One vessel in the list is

identified as a sailing “lugger.” This was the small, seven-ton lugger Meteor, built in

1903 and lost in 1916 (Appendix E). The large number of schooners in the database is

not surprising, considering how important these sailing vessels became during the

nineteenth century. Schooners, with their fore-and-aft rigs, were first constructed in the

first quarter of the eighteenth century and began to gain popularity late in the century.

By the 1830s, the schooner and the single-masted sloop were the most common vessels

involved in maritime commercial activities along the coasts of the United States.

Schooners gained popularity because they were fast sailers and, with their fore-and-aft

rigs, they required fewer hands to man than did square rigged (“ship rigged”) vessels of

similar size. The two-masted schooner was the typical form into the 1830s, when threemasted versions began to be constructed. Later in the nineteenth and into the twentieth

century, schooners with four and more masts were built. These large schooners were

typically used in long-distance ocean trades. The smaller, two-masted schooner and the

sloop became the mainstay of the “coasting” or coastwise trade in the United States,

traveling between coastal ports carrying all manner of cargoes.

In the Gulf of Mexico, large numbers of schooners were used in the coasting trade

in the nineteenth century (Francaviglia 1998). An example of the numbers involved in

the trade can be seen by those enrolled and registered at the Port of New Orleans, the

largest port on the Gulf coast during this period. Between 1804 and 1820, 281 schooners

were enrolled at New Orleans; they represented the most popular “rig” of vessel enrolled

in the city. Of this number, only two had been constructed prior to 1790; the rest had

been constructed between 1791 and 1820, a period when the schooner was rapidly

growing in popularity and American coastwise trade was expanding (WPA 1942:1:x).
4-26

63,0

22,1

10,8

4,9

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

Oil/Diesel Powered Sail Powered Steam Powered Gasoline Powered

Propulsion

Percentage

 Figure 4-7. Relative frequencies of modes of propulsion recorded for vessels in the 2001

shipwreck database

Most of these schooners were involved in some aspect of the coasting trade.

Many were small, less than 50 or 60 feet long and under 100 tons of burden, and were

used to carry goods between small communities on the central Gulf coast and the larger

ports such as New Orleans, Mobile and Pensacola. By the period 1830 to 1840, a total of

498 schooners were enrolled in New Orleans and they still represent the most common Percentage
4-27

type of vessel enrolled in the city, followed by steamboats (N=334) (WPA 1942:3:xii).

As in earlier years, many of these vessels worked in the coasting trade; now, however,

some extended their trading activities westward to Texas, as well as eastward to ports

along the west Florida coast and panhandle. By this time cotton had become the South’s

principal export and New Orleans was a major cotton port. By 1840 many larger

schooners were sailing out of the Gulf to ports in the northeastern United States or

Europe with cotton and returning with a wide range of manufactured goods and

merchandise. Lumber also became an important commodity carried by schooners in the

coasting trade, as well as in long distance trade out of the Gulf region (Murphy and

Jonsson 1993). Schooners continued in use through the nineteenth century, but were

increasingly displaced by steam vessels after the 1840s.

Dates of build are known for 82 of the 104 schooners identified in the shipwreck

database. These range from 1831 to 1919, with about 70 percent (N=57) constructed

prior to 1900. The lengths of all but one of the schooners in the database range from 43

to 162 feet. The one exception was the 215-foot-long State, built in 1901. The burden

for 95 schooners is known and this ranged from just 11 tons to 2,052 tons. Most of the

39 schooners of less than 150 tons burden in the database are likely to have been involved

in the coastal trades. Many of those larger than 150 tons may have been principally

sailing in long-distance trades across the Gulf of Mexico, or to ports outside of the Gulf.

Other sailing vessels are only poorly represented in the shipwreck database.

These include 12 entries identified only as “Sailboats,” five as “Brigs,” three as “Sloops,”

two as “Brigantines,” three as “Barques” (Barks), seven as “Ships,” two as “Galleons,”

and one as a “Schooner Barge” (see Appendix E). Many of these represent early types of

vessels operating prior to the mid-nineteenth century; one of the reasons for their small

numbers might be due to the underreporting of losses during early periods, as has been

noted. This phenomenon also might be exaggerated when vessels lost onshore or in

nearshore waters have been eliminated from consideration, as in the present study.

In their Dry Tortugas data, Murphy and Jonsson (1993) found that sailing vessels

comprised the majority of vessel losses and vessel casualties. They represented 79.9

percent (N=201) of the 311 losses and casualties for which information on rig was

available. This is almost four times the representation of sailing vessels seen in the 2001

shipwreck database. It is believed that the principal reason for this lies in the sources

used for obtaining shipwreck information, as has been noted earlier, in that the Dry

Tortugas data do not incorporate shipwreck data from many of those sources that include

recent or non-commercial losses. The Dry Tortugas data do indicate that schooners were

the most common type of vessel lost there, comprising 36.7 percent of the losses.

However, many brigs (N=52), barks (N=52), and ships (N=43) are also included in the

loss and casualty data presented by Murphy and Jonsson (1993), classes of vessels poorly

represented in the 2001 GOMR database.

Vessels classed as “Fishing Vessels” comprise the largest category in the

shipwreck database. A total of 252 fishing vessels are identified in the database, forming

27.1 percent of the vessels assigned to type. A review of the available data on the age of
4-28

these vessels indicates that most, if not all, are twentieth century in date. Of the 49

Fishing Vessels for which date of build is known, the earliest is the Ida Q., built in 1924;

most of the others were constructed after 1950. The majority of these boats are believed

to be shrimp trawlers, although the sources providing data on their losses rarely identify

them as such. A small number might have been involved in other Gulf fisheries, such as

red snapper or menhaden. If the 41 vessels identified in the sources examined as “Shrimp

Trawlers” or “Trawlers” are added to the Fishing Vessel category, then it forms almost

one third (31.5 percent) of the total number of shipwrecks of known type in the database.

This large representation is seen primarily as a reflection of the importance of the Gulf

shrimping industry and a statement on the large number of shrimping vessels operating in

the region. The importance of the Gulf shrimping industry can be seen in the fact that in

the year 2000, Gulf of Mexico landings of the three principal shrimp species fished

(brown, white and pink shrimp) consisted of just over 125 metric tons valued at roughly

640 million dollars. Surprisingly, however, the importance of the types of vessels

involved in the industry and their potential large number as shipwrecks in the Gulf are

largely overlooked. Murphy and Jonsson (1993) make no mention of shrimp trawlers in

their study of wrecks in the Dry Tortugas, although shrimp boat wrecks are known to

exist there (Murphy 1993b:209). Garrison et al. did not include vessel type in their 1989

shipwreck database, but they do briefly describe the “Shrimper” in their Appendix E

listing vessel types used in the Gulf of Mexico (Garrison et al. 1989:Appendix E).

The shrimp trawler, and the offshore shrimping industry as it is known today,

developed as a result of the perfection of the otter trawl early in the twentieth century

(Robinson and Seidel 1995:22). Some have suggested that the Gulf of Mexico shrimp

trawler developed out of the sailing lugger with the replacement of the sail by gasoline

engines which had been perfected for use in boats during the latter years of the nineteenth

century (Custer 1994; Robinson and Seidel 1995). The sailing lugger was in common

use along the Louisiana, Mississippi, and Alabama coasts, particularly in the oyster

industry. There is debate as to how much the hull form changed with the adaptation of

the gasoline engine to the old sailing lugger form. Alterations known to have occurred

included the elimination of the centerboard trunk that was found on some sailing luggers

and the addition of an aft cabin to house the engine and controls. The earliest motorized

luggers were small, 20 to 30 feet long, but larger vessels were soon developed, apparently

originating in the Biloxi, Mississippi, area. These large vessels were more seaworthy and

most were adapted for use in oystering (Robinson and Seidel 1995:19). Wilson (1983)

suggests that the earliest vessel that can be defined as a shrimp trawler was the Eagle,

built in Bayou La Batre, Alabama in 1925. The early, lugger-form shrimper largely

confined its operation to inshore waters. Guevin (1991) reports that Florida fishermen

introduced the offshore shrimp trawler into the Gulf during the 1930s when the potential

for offshore shrimping in the Gulf was discovered. The vessel used came to be called the

“South Atlantic Trawler” and was a design derived from the Greek sponge boats used on

the west coast of Florida. If the Ida Q., built in 1924 and the earliest identified Fishing

Vessel in the 2001 shipwreck database, was in fact a shrimp trawler, it would represent

one of the earliest examples known and a vessel of obvious historic importance.
4-29

The shrimp trawler reached its present form and style in the very short period

between the end of World War II and about 1950. Possibly because of the need for

maximum rear deck working space, it was among the first powered fishing craft to have a

forward-located pilothouse. The hull, however, retained characteristics of the old Greek

sponge boats with its full body, sweeping sheer line and fine entrance. Originally built of

wood, most trawlers now have steel hulls (Guevin 1991).

Today, shrimp trawlers are typically powered by diesel engines, but some early

examples used gasoline engines. In fact, the Ida Q. mentioned above is reported to have

been powered by a gasoline engine (MVUS 1936). As shown in Figure 4-7, “Oil/Diesel

Powered” vessels constitute over 60 percent of those for which mode of propulsion was

recorded. Their high representation is largely because the publication Merchant Vessels

of the United States, which was one of the most important sources used in this study,

consistently provides this type of information on lost vessels. Many of the “Oil/Diesel

Powered” vessels are also identified as “Fishing Vessels.”

Another general class of vessels that is modestly represented in the 2001 database

incorporates those that are involved in the offshore oil and gas industry. These include

vessels identified as “Crewboats,” “Drilling Rigs,” “Supply Vessels,” and “Jack-up

Barges” (Table 4-2). Like the shrimp trawler discussed earlier, this class of vessels tends

to be ignored in historical shipwreck studies. In fact, some of the items, such as “Drilling

Rigs,” are generally not classified as vessels. As noted earlier, these are included because

they do represent cultural objects that might be discovered during the course of MMSmandated lease block surveys. Also, most of these types of vessels will be less than 50

years old, having been put into use after the late 1940s with the development of the

offshore oil industry. When considered as a whole, those vessels that can be identified as

related to the offshore oil and gas industry include 50 entries, representing only 5.4

percent of the vessels identified as to type. This is considered an under-representation of

the actual number of vessels in the database that were associated with the offshore

mineral industry. For example, some of the vessels identified only as “Barges” may have

been involved in some aspect of this industry, but the sources do not provide sufficient

information to determine this. Additionally, some of the vessels identified only as

“Motor Vessels” actually might be crewboats or offshore supply boats.

The first true offshore oil well was drilled off of Morgan City, Louisiana, in the

Ship Shoal Area in November 1947. Since that time a variety of watercraft have evolved

to supply the offshore oil industry. During the early years of the industry wooden shrimp

trawlers, luggers and the like were used and modified as necessary. By the mid-1950s,

however, vessels were being constructed specifically for offshore oil work. In 1955, the

Tidewater Marine Service Company of Louisiana launched the Ebb Tide, reportedly the

first vessel built expressly for service of the offshore oil industry (Tidewater Marine

Service Company 2002). Since then, huge numbers of vessels have been constructed

specifically for work in the offshore oil industry. These vessels are used to ferry workers

back and forth to offshore platforms and drilling rigs (crewboats), or carry cargo (supply

boats) or serve in specialized activities as anchor boats, dive boats, mud boats (to

transport drilling mud) or seismic survey boats. Typically these vessels are steel-hulled
4-30

and range from about 30 feet to as much as 400 feet long; many have a low, open deck aft

of a raised pilot house/crew’s quarter section. The low, open deck area serves as a work

or storage area and is typically over twice the length of the cabin/pilot house section

(Garrison et al. 1989:E-9). On some of the passenger carriers (crewboats), this aft work

area is decreased or eliminated and replaced by cabin space.

Early offshore drilling was conducted from barges modified for that purpose. The

first “submersible” drilling rig constructed specifically for offshore work was the Mr.

Charlie, built in 1953. This drilling rig consisted of a large barge measuring 220 feet

long, 75 feet wide and 14 feet deep with the drilling platform and machinery constructed

on it. During drilling, the barge was flooded to sink to the bottom where it provided a

stable platform for the work (The Rig Museum [www.rigmuseum.com]). The Mr.

Charlie was first used in East Bay, Louisiana, in 1954, but could operate only in water

less than 40 feet deep. Since that time large numbers of submersible and semisubmersible drilling rigs have been constructed and used in the Gulf of Mexico.

Twenty-two “Jack-up Barges” are included in the 2001 shipwreck database.

These also are a craft designed primarily for the offshore oil industry. They consist of a

barge on which tall legs (“spuds”) are mounted. Hydraulic engines are used to extend the

legs (usually three in number) to the bottom and, ultimately, to lift the barge above the

water. This turns the barge into a stable working platform; these vessels are used for all

kinds of construction and maintenance activities in the offshore oil industry.

4.3.3. Cause of Loss

One of the categories of information collected in this study was Cause of Loss.

Entries used in casualty tables provided in Merchant Vessels of the United States

provided a principal basis for developing the Cause of Loss categories. This publication

classifies vessel losses according to six principal types of casualty. These are:

1. Foundered - casualties due to leaking or capsizing of vessels, including vessels

lost at sea not due to collision or burning, and vessels not reported after

sailing.

2. Stranded - casualties due to vessels running aground, striking, rocks, reefs,

bars, etc.

3. Collided - collision between vessels only.

4. Burned - casualties due to fire.

5. Abandoned - casualties resulting from abandonment at sea not related to age.

6. Any other type of casualty.

Some modifications were made to these listings because of cause of loss entries

provided in other sources. The categories “Beached,” “Capsized,” “Explosion,”

“Gunfire-Battle,” “Scuttled,” and “Sunk” were added to the categories listed above on the

basis of specific information provided in other sources. The fact that various sources

categorize and report losses in different ways can create problems in analyses and

comparisons, but, as has been done for other categories of information, the effort here has
4-31

been fairly expansive in an effort to capture the variability expressed in the historical

records used. Among the problems that can be readily seen are that categories such as

“Capsized” given in one source might be classified as “Foundered” by the Merchant

Vessels of the United States. One of the most common listings for cause of loss in United

States Coast Guard records is simply “Sunk.” This category has been used in the

database, but it is often a statement of condition, not cause, because so many USCG

listings involve the remains of sunken vessels that have been discovered, not reports of

casualty events themselves.

In general, marine casualties can be classified as weather-related, equipmentrelated, or due to human error. In some but not all instances, the specific cause of loss

given for a vessel can be tied to one of these general causes. For example, many vessels

are reported to have “Foundered,” but only rarely are the events leading to the foundering

identified. It is generally believed to be weather-related, but this may not always be the

case (Gearhart et al. 1990:IV-68).

Not all of the marine casualties identified in the various sources and included as

losses in the 2001 shipwreck database actually represent sinkings. It is apparent from

some sources that vessels included in the database did not actually sink, but were

involved in marine accidents that did not result in the loss of a vessel, or that others were

salvaged after their sinking. In other instances cargo or ballast might have been

purposefully jettisoned and the event became reported as a casualty. It is not always

possible to identify these types of non-sinking accidents in the sources used. Despite this,

however, all events identified as marine casualties or accidents are included as losses

under the assumption that the accident or the subsequent salvage activity might have left

archaeological remains as evidence of the event. This follows the approach used in other,

similar studies (e.g., Gearhart et al. 1990; Murphy and Jonsson 1993; Pearson et al.

1989). When information is provided in the sources that might modify the cause of loss

entry, such as reports of salvage, these have been included in the Comments section in

the Access database.

Information on a cause of loss was collected for 1,300 entries in the database,

representing 61.7 percent of the total. This information is displayed in Table 4-3.

However, as can be seen, 486 of these fall under the category “Sunk.” An examination of

the database reveals that information on most of those vessels in this Sunk category

comes from USCG or from NIMA records. In most instances, the NIMA records

themselves were derived from USCG data. Additionally, 67 of the vessels in the Sunk

category are listed as Unknown Vessels, normally meaning that they represent

unidentified vessels that have been reported or discovered after their sinking. Thus, at

least for these 67 entries, the term Sunk is a statement on condition, not cause, and it is

likely that this observation can be extended to many of the named vessels for which sunk

is provided as a cause of loss. If the Sunk category is removed as a known cause of loss,

then 814 entries have what can be considered a known cause of loss. The relative

frequency of occurrences of these known causes of loss is provided in Figure 4-8.
4-32

Table 4-3. Reported Causes of Loss

CAUSE NUMBER OF

VESSELS

%

Abandoned AB 8 0.4

Beached BE 2 0.1

Burned BU 153 7.3

Capsized CA 14 0.7

Collided CO 82 3.9

Explosion EX 7 0.3

Foundered FO 374 17.8

Gunfire-Battle GF 44 2.1

Scuttled SC 101 4.8

Stranded/Swamped ST 29 1.4

Sunk SU 486 23.1

Unreported UN 806 38.3

TOTAL 2,106

Figure 4-8. Relative frequencies of known causes of loss for vessels in the 2001

shipwreck database.

46.0

18.8

12.4

10.1

5.4

3.6

1.7

1.0

0.9

0.2

0.0 10.0 20.0 30.0 40.0 50.0

Foundered

Burned

Scuttled

Collided

Gunfire-Battle

Stranded

Capsized

Abandoned

Explosion

Beached

CAUSE OF LOSS

PERCENTAGE

CAUSE OF LOSS
4-33

Vessels that “Foundered” constitute the majority of those with a known cause of

loss, representing almost one-half of the total. Other studies have shown that foundering

is generally a principal cause of reported losses, but this is in part because this category is

commonly used to encompass a variety of sinking events. For example, in Merchant

Vessels of the United States listings, foundering essentially encompasses any casualty that

cannot be explained in any other way. It is impossible to tell how many of the

founderings included in the database are weather-related, equipment-related or due to

human error. Summary statistics on vessel casualties for various portions of the United

States are available in the Annual Reports of the U.S. Life-Saving Service. These

statistics include information on whether losses are weather-related, related to navigation

or seamanship, related to equipment, or are due to other causes.

However, these data do not extend after 1914 and have minimal comparative

value in the present instance, because 311 (83 percent) of the founderings in the database

occurred after 1915. Garrison et al. (1989) do not provide cause of loss data in the 1989

shipwreck database, although they do discuss factors of loss in general terms, particularly

as related to hurricanes and natural features, such as shoals, bars and reefs.

If founderings are largely weather-related, one might expect more foundering

losses to occur during the late summer and winter months when Gulf weather conditions

tend to be at their worst, primarily because of hurricanes and northers. Figure 4-9

provides information on the frequency of occurrence of reported founderings by month

and the data do, in fact, show high occurrences during the worst weather months of

October through January. This seems to suggest that weather played some role in

founderings, but additional information would be needed to verify this assumption.

A substantial number (N=153) of vessels are reported to have burned. This

constitutes almost 20 percent of the total number of reported causes of losses. Vessels of

all types are included in this category so there does not appear to be any strong

correlation between vessel type and burning. However, the majority (N=126; 81.8

percent) of the burning cases occurred since 1950. Again, this high number is likely to be

a reflection of the underreporting of most specifics of vessel losses during early periods.

Forty-four vessels are reported to have been lost to “Gunfire-Battle” (Table 4-3).

The vast majority of these consist of vessels lost in the Gulf of Mexico during World War

II, mostly from actions by German U-boats (Appendix E). Twenty-nine vessels are

reported to have been lost due to “Stranding” or “Swamping” and two are reported to

have been “Beached.” Because the present study is considering only those vessels falling

in Federal waters, an initial assumption would be that few vessels would be lost in the

study area due to these causes. Relatively few hazards that could result in these causes of

loss exist in the study area. A review of the vessels included in these categories of losses

reveals that most have been assigned very low reliabilities for their positions of loss and a

few do fall in state waters. Thus, the possibility exists that some unknown number of

these losses resulting from stranding and beaching actually occurred in state waters.
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Figure 4-9. Numbers of “Founderings” per month for vessels in the 2001 shipwreck database.

Scuttlings account for 101 of the known reported causes of loss (Table 4-3). As

noted previously, this number is relatively high because of the inclusion in the database

of a number of vessels purposefully scuttled to create artificial fishing reefs.

4.4. Shipwreck Preservation Potentials in the Study Area

The 1989 study by Garrison et al. presents a detailed discussion on those factors

that affect the preservation of shipwrecks in the GOMR. Among the factors they

considered were energy zones, biological and chemical factors, water depth, and

sediment characteristics. In that discussion, they drew on previous archaeological work

that provided information on the survival of shipwreck material in various settings (e.g.

Clausen 1965; Mathewson 1975, 1977; Muckelroy 1978; Watts 1985; Keith et al. 1985;

Keith and Simmons 1986). They noted that the “key element in estimating preservation

of wooden shipwreck material is the identification of the burial sediment, its depth, and

the inherent biological communities associated with such conditions” (Garrison et al.

1989:II-69).

37

30

22 21

27

24 24

22

32

50

41

38

0

10

20

30

40

50

60

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

NUMBER
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In high-energy zones, such as those found in shallow water in the wave zone,

destruction of vessel fabric tends to be high, particularly in the case of wooden vessels.

A number of examples from the Gulf region have demonstrated the level of destruction of

wooden vessels grounded in shallow water where materials are either removed or

scattered around the wreck site. The general assumption is that waves and currents are

more damaging to a shipwreck than are biological or chemical factors (Muckelroy 1978).

However, even in high-energy settings such as in a wave zone, segments of vessels, in

particular the lower hull, as well as individual elements can be reasonably well preserved.

This is especially true if they become covered with sediment that can provide some

protection from the physical impacts of waves and currents as well as providing a lowoxygen environment that inhibits the activity of biological organisms. Garrison et al.

(1989) provide several examples from the Gulf region where the processes of sediment

transport lead to the rapid burial and ultimate preservation of ship remains in moderate to

high-energy environments. More recent studies from the region, such as those of the

wrecks of the Gen. C.B. Comstock in Texas (James et al. 1991a) and the Emanuel Point

Ship in Pensacola Bay (Smith et al. 1998), further substantiate these conclusions. Except

in a few locales, these high-energy zones do not occur in the study area, so these impacts

are of less concern than they are for shoreline settings.

The rapidity of burial and the nature of the sediments themselves are critical

factors in the degree of preservation of a shipwreck. Overall, the more rapidly elements

of a wreck are covered and the finer grained the sediments are, the greater the degree of

preservation. In general, fine-grained sediments, such as clays and silts, are more

conducive to preservation than are coarse-grained sediments, such as sand. Fine-grained

sediments tend to produce environments lower in oxygen content than do coarse

sediments, thus tending to restrict biological and chemical activity. The activities of

many organisms, such as the wood-damaging shipworm Teredo common to warm marine

waters, are eliminated or restricted by burial. However, some organisms, such as sulfidereducing bacteria, typically thrive in low dissolved oxygen environments, like those

found in muds (Richards 1957). These organisms tend to be destructive to metals,

particularly ferrous metals (Hamilton 1976). Thus, some settings that might be

conducive to the preservation of wood and other organics may be detrimental to certain

classes of metals.

In the Gulf of Mexico, the process of burial of shipwrecks is typically going to

occur more rapidly in shallow, nearshore waters where sediments are more mobile due to

currents and wave action. However, these nearshore sediments tend to be coarse grained

materials, thus the potential for preservation by rapidity of burial is, to some extent, offset

by the characteristics of the sediments. Additionally, it has been shown that wrecks in

nearshore settings do not necessarily remain buried after they are initially covered by

sediments. For example, examination of the 1913 wreck of the Army Engineers hopper

dredge Gen. C.B. Comstock, located at the outer edge of the wave zone off Freeport,

Texas, revealed that the burial and exposure of portions of the wreck varied over time

(James et al. 1991a). The degree of burial or exposure appeared to be seasonal,

presumably related to yearly current and wave patterns. Despite its location in a highenergy environment, excavation of the wreck revealed that the entire lower hull of the
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vessel was intact and wreckage was not scattered over a wide area. Additionally, the

wooden hull of the vessel was well preserved, as were numerous organic and some types

of metallic artifacts; although many of the ferrous items from the wreck did display

significant deterioration (James et al. 1991a). The rapid burial of the Comstock, even

though by coarse grained sands, contributed to its excellent preservation. Although, in

general, Garrison et al. argue that high energy environments are not conducive to

shipwreck preservation, they do note that in high energy settings with coarse grained

sediments, preservation can be enhanced if rapid burial of the remains occurs (Garrison et

al. 1989:II-83). This is exactly the situation found at the Comstock site.

The offshore sediments in the Gulf of Mexico tend to be fine-grained muds (clays

and silts) and their degrees of movement and rates of deposition are lower than is found

nearshore (McGowen et al. 1976). Overall, sediment rates in the open sea are only on the

order of 0.012 meters per year, but localized areas with more rapid rates do exist; for

example, just off the mouth of the Mississippi River and, to a lesser extent, in the

offshore areas of central and western Louisiana.

In recent years, particularly since the discovery of the RMS Titanic in 1985, our

knowledge of the preservation potential of shipwrecks in deep water has expanded

(Ballard 1989). Earlier assumptions were that vessels in deep water would, in general, be

well preserved because of the low energy settings found there and the low levels of

biological activity anticipated in deep, cold marine waters (Garrison et al. 1989:II-69).

However, it has been found that certain marine boring organisms can survive in very

deep water, as do marine bacteria that can result in the destruction of organic and metal

materials (Ryan 1987). The recent discovery of several wrecks in deep water in the Gulf

of Mexico adds to our information on deepwater wrecks, but does not clarify all of the

factors affecting preservation of wrecks in these settings. Information contained in

archaeological survey reports provided by the MMS indicate that as of September 2001,

16 vessels had been identified during offshore archaeological surveys in the GOMR in

water depths greater than 500 feet. Seven of these vessels were located in more than

3,000 feet of water. Sidescan sonar records represent the only information we have on

the conditions of most of these vessels. In general, these records depict complete or

largely complete hulls or major segments of vessels exposed above the seafloor. The

exposure indicates that these vessels have not been completely buried by sediments;

however, vessels that have been completely buried would not be detected by sidescan

sonar. The sidescan sonar records seem to indicate minimal dispersal of material around

these wrecks, but again, it is possible that the available records would not show small,

scattered objects. Also, other deepwater wrecks, particularly the Titanic, do show large

and obvious “debris trails” consisting of materials lost from the vessels as they sank

(Ballard 1989). It is likely that some deepwater wrecks in the Gulf, particularly some of

the large tankers and freighters sunk during World War II, will exhibit extensive and

obvious debris trails such as those seen with the Titanic.

Two of the deepwater wrecks found in the Gulf of Mexico have been more

carefully examined by ROV submersibles and video images provide additional insight

into their conditions. One of these vessels is the World War II German submarine U-166,
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discovered in approximately 5,000 feet of water off the mouth of the Mississippi River.

Images of the vessel indicate that the principal metallic structural elements are in

relatively good condition; however, the wooden grating that once covered the submarine

decks appears to have deteriorated completely (Church 2002). The hull segments of the

submarine are partially buried, but it is not known how much of this burial is due to

sedimentation since sinking or how much might be due to the impact of the vessel into

the soft bottom sediments at the actual sinking itself.

The remains of a wooden vessel have been recently discovered in 2,650 feet of

water in the same general vicinity as the U-166. These remains consist of an

approximately 60-foot-long segment of wooden hull resting upright on the bottom. It

appears as if all or most of the length of the hull is extant, and an estimated nine to 13

feet of its height. Metal sheathing was observed on the exterior of the hull and interior

features such as frames and the keelson could be seen. The exposure of these elements

suggests that there is very little sediment filling the interior of the hull. Overall, the wood

on the wreck appears to be in good condition and current presumptions are that it

represents a small sailing vessel (schooner?) lost during the first half of the nineteenth

century (Irion 2002). Like the U-166, this wooden wreck is only minimally covered by

sediment, supporting presumptions about the low rates of sedimentation in much of the

deep Gulf. However, the fact that the wood on this fairly early wreck appears to be well

preserved, while it is believed to be entirely gone on the recent submarine wreck,

suggests that the preservation of organics in deepwater settings in the GOMR are variable

and the result of complex phenomena that are not yet fully understood.

Another wreck discovered in relatively deep water in the Gulf of Mexico is that of

the eighteenth century Spanish vessel El Cazador. This wreck is located in

approximately 300 feet of water about 50 miles south of Grand Isle, Louisiana. Although

the wreck of El Cazador is in much shallower water than the two wrecks noted above, it

does provide some information on what to expect at wreck sites in the deeper waters of

the GOMR. El Cazador was lost in 1784 and discovered accidentally by a fishing boat in

1984. Subsequently a group of salvers dove on the wreck and recovered a large number

of silver coins, a bronze cannon, cannon balls, an anchor, a bronze bell, fire brick,

pottery, and some other miscellaneous items (New York Times 1993; Summers 1996).

Little is known about the condition of the wreck at the time of discovery, although reports

of the finders reveal that wood was present and that portions of the wreck were exposed

above the bottom. The minimal amount of information available on this eighteenth

century wreck does indicate that very little sediment covered it, reflective of the small

amount of sedimentation occurring in the deeper areas of the Gulf. A wide range of

metallic and other non-organic artifacts was preserved on the wreck site and it appears

that some wood was preserved, although the information on this is sketchy. The

condition of El Cazador seems to argue for reasonably good preservation of wrecks, even

wooden ones, in moderately deep waters of the study area.
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4.4.1. Sediment Characteristics and Preservation Potentials in the Study

Area

Garrison et al. (1989:II-77) note that, generally, the environments within which

shipwrecks can be found in the Gulf of Mexico can be classified as: 1) static and hypoxic

(e.g., low oxygen); and 2) dynamic and aerobic. The static and hypoxic environment is

considered most conducive to preservation, but as noted, variability in preservation

potentials does exist between these two very generalized settings.

Garrison et al. (1989) looked at 17 wreck sites from various shelf settings and

compared various physical characteristics of the wreck, such as distribution of wreckage

and the condition of organic and non organic remains, against environmental factors,

such as current velocity, biological activity, etc. Several conclusions were drawn from

these data (Garrison et al. 1989:II-78):

1. Structural remains tended to be poorly preserved where vessels were sunk in

dynamic, coarse sediment environments.

2. Organic remains tended to be poorly preserved in dynamic, coarse sediment

environments.

3. The preservation of other classes of artifacts varied widely with little observed

correlation with the specific environmental variables used in the analysis.

4. Discontinuous wreck sites occur only in dynamic, coarse sediment

environments.

5. Nineteenth century wrecks are better preserved than earlier wrecks.

Since the 1989 study, several historic wreck sites have been discovered in the

Gulf of Mexico. Those that are most relevant to the present study are those found in the

“open waters” of the Gulf; these are relatively few in number and most have been

discussed earlier. Among these are several off the Texas coast, including the “303 Hang

Wreck” consisting of the remains of a well-preserved, wooden two-masted schooner

approximately one mile off the upper Texas coast (James et al. 1991b); the latenineteenth century Army Engineers dredge Gen. C.B. Comstock, located just 600 meters

offshore of Surfside, Texas (James et al. 1991a); the wreck of the Civil War blockade

runner Denbigh, just offshore of Bolivar Peninsula near the entrance to Galveston Bay

(Arnold et al. 2002); and the wreck of the sidewheel steamer New York, lost in 1846 off

the upper Texas coast (Irion and Anuskiewicz 1999; Irion and Ball 2001).

 Wrecks that have been discovered off the central Gulf coast include the Spanish

vessel El Cazador, lost in 1794 and discovered in about 300 feet of water off the central

Louisiana coast; the recently discovered remains of the World War II German submarine

U-166 in about 5,000 feet of water off the mouth of the Mississippi River; the wellpreserved wooden hull of a circa 60-foot long vessel in roughly 2,600 feet of water off

the mouth of the Mississippi River; and the well-preserved remains of the iron hulled

sidewheel steamer Josephine that sank in 1881 south of Ship Island, Mississippi (Irion

and Anuskiewicz 1999). The available information on these wrecks is variable, because

few have been carefully studied. Where published information is available (e.g., the Gen.
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C.B. Comstock and the 303 Hang Wreck), that information typically supports the general

propositions about shipwreck preservation in the Gulf of Mexico presented by Garrison et

al. (1989). However, some slight alterations in Garrison’s expectations are suggested.

The most important of these seems to be that a greater chance of preservation

occurs in dynamic, high-energy environments than had been anticipated. It appears that

the processes that lead to burial and ultimately the protection of wrecks are not as

uncommon in these settings as had been thought as evidenced by numerous historic

wrecks discovered in moderate and high energy settings. In a number of cases, the

integrity of large portions of hull structure is maintained and often wood and other

organics are reasonably well preserved. It is possible that the conditions conducive to

wreck preservation in these high-energy environments are very localized. Examples of

these localized settings would be where topographic depressions exist into which

wreckage can settle and be covered by sediments or where sediment transport is

sufficiently rapid to quickly bury wreckage, creating a protective cover. It is likely that

the weight of wreckage combined with the scouring effects of currents can facilitate rapid

settling and burial in coarse-grained sediments. This may have been among the burial

processes occurring at one of the 1554 Padre Island wreck sites (41KN10) and at the

1913 wreck of the Gen. C.B. Comstock near the mouth of the Brazos River (Arnold and

Weddle 1978:198; James et al. 1991a). However, at both of these sites the presence of

marine growth and borer damage on buried remains indicated that they had been

uncovered and exposed for one or several periods of time in the past. In general,

however, these high-energy conditions are of only minimal concern in this study because

these settings are rare in the study area.

In some instances, the wreckage itself contributes to creating an environment

conducive to preservation. Structural pieces can serve as sediment traps, speeding up the

process of sediment accumulation. Ballast can cover structural elements and protect

them while in other settings, wreck structure attracts and encourages the growth of

marine organisms, such as oysters and barnacles, that can provide protection to wreck

elements. Both of these factors seem to have occurred at the sixteenth century Emanuel

Point Ship site. Located on a sand bar in Pensacola Bay, the wreck is capped by a large

pile of stone ballast plus a dense stratum of shell that has developed on the “artificial

reef” created by the ship remains (Smith et al. 1995:19). These have contributed to the

protection of the underlying vessel remains and to the preservation of a wide range of

organic and non-organic materials.

Despite the variability seen in shipwreck preservation, some generalizations about

the spatial distribution of environmental settings, and thus potentials for shipwreck

preservation, can be made. Ultimately, Garrison et al. (1989:II-77) determined that, in

general, the “main determining factor in the survival of archaeological remains is

sediment type and distribution.” Relying on the distribution of sediment types across the

outer continental shelf area of the Gulf of Mexico, that study identified regions of Low,

Moderate, and High shipwreck preservation potential (Garrison et al. 1989:Figure II-50).
4-40

Figure 4-10 presents information on general sediment distributions in the

continental shelf region of the Gulf derived from Rezak et al. (1985), overlain with MMS

lease areas. The expected preservation potentials of major sediment areas are classified

using the three categories of Low, Moderate, and High used in Garrison et al.

Information from recently discovered or examined shipwrecks, plus general information

on wreck conditions obtained during the development of the 2001 shipwreck database,

has suggested some changes in the preservation potentials of sediment areas originally

assigned by Garrison et al. (1989). Garrison had assigned a Low preservation potential

for almost all of the shelf area off the western coast of Florida. This is generally a karstic

shelf region overlain in areas by a veneer of sands that thickens shoreward (Berg 1986).

Archaeological wreck site descriptions from this region are available almost exclusively

for vessels lying in shallow, inshore waters and outside of the study area, such as around

the Dry Tortugas (e.g., Murphy 1993b).

However, the large number of sport diver accounts from this region indicate that

many of those wrecks lying in the shoreward portions of the GOMR along the Florida

coast are reasonably well preserved. Because of this, the inshore area characterized by

“quartz sand and shell” has been changed from the Low preservation potential assigned

by Garrison et al. to a Moderate preservation potential (Figure 4-10).

Garrison et al. assigned a Low preservation potential to all of the mostly karstic

shelf region off of Florida characterized by “Shell sand with quartz” sediments in Figure

4-10. This was because this is typically a sediment-starved area where the chances for

rapid burial of wreckage that might enhance preservation are relatively low (Garrison et

al. 1989:II-120). An overall lack of data on wrecks from this region makes it difficult to

confidently assign a preservation potential to this broad area. However, bottom

sediments do thicken shoreward in this area, plus, as noted above, numerous wellpreserved wrecks are known from the immediately adjacent “quartz sand and shell”

region (Figure 4-10). The availability of sufficient sediment for burial in parts of this

area, plus an overall low energy environment, suggests that the preservation potential of

portions of this broad region may be higher than estimated by Garrison et al. (1989). In

light of these factors, the entire region is assigned a Low to Moderate preservation

potential, recognizing that this assignment must remain tentative until such time as

additional wreck data are available.

The broad area of sand, silt and clay lying off the western Louisiana and upper

Texas coasts had been identified by Garrison et al. as having a Low-Moderate

preservation potential. The identification of several vessels in this area on MMS records,

plus the condition of the 303 Hang Wreck (James et al. 1991b) discovered in this

sedimentary setting, have been used to assign an overall Moderate preservation potential

to this region. The sand, silt and clay area off the extreme lower Texas coast is assigned a

Moderate preservation potential because its sedimentary character is similar to the region

of the upper Texas coast and Louisiana.
Figure 4-10. Sediment zones and preservation potential in the study area (adapted from Rezak et al. 1
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Garrison et al. (1989) classified the inshore region of “quartz sand” that borders

the shore of the Florida panhandle and extends westward to the Mississippi River delta as

having a Low-Moderate preservation potential. This sedimentary zone barely extends

into the study area, but several wrecks have been found in this zone and in the “shell sand

with quartz” zone lying farther offshore. Among these are the steamer Josephine and the

sailing vessel Tulsa, as well as several unidentified vessels discovered during the course

of MMS-mandated remote-sensing surveys. It is presumed that the preservation potential

of this zone will be variable, with inshore areas, where high energy conditions are more

likely to exist, having a lower potential than the deeper water sections. However, these

deeper water segments are those falling within the study area such that they have been

designated as Moderate in terms of preservation potential.

Assignment of preservation potentials to the entire deepwater section of the

GOMR is difficult because of a lack of wreck data. However, in the deep water area off

the mouth of the Mississippi River several wrecks have been discovered that show a

remarkable degree of preservation. Most of these have been identified only with sidescan

sonar but two, the World War II submarine U-166 and the unidentified wooden sailing

vessel believed to date to the nineteenth century, have been visually examined with video

cameras. Both are very well preserved and show minimal dispersion or burial by

sediment. We feel confident in assigning a Moderate-High preservation potential to this

area of the open Gulf (i.e., the Mississippi Canyon Area) and, based on findings from

deepwater areas around the world, it is likely that a similarly high potential can be

extended to almost all of the deepwater areas in the GOMR.

4.5. Patterns of Shipwreck Distributions

4.5.1. Introduction

The spatial distributions of historic shipwrecks in the GOMR is of ultimate

concern in this study. The foregoing discussions have considered a variety of

characteristics of the sample of shipwrecks included in the 2001 shipwreck database and

these characteristics constitute elements on the “model” of shipwreck occurrences in the

GOMR developed in this study. This section of the report presents discussions on the

spatial patterning observed in these shipwrecks, and examines this patterning relative to

chronological trends, vessel type, etc. Some data on distributions are presented as

illustrations in this section. However, the various files developed in ArcView from the

digital database in Microsoft Access that accompany this report represent the principal

visual expression of shipwreck data developed in this study. Additionally, the ArcView

files provide a GIS format that permits ease in manipulation of all of the shipwreck data

collected.

The present examination of shipwreck distributions builds upon that originally

presented in Garrison et al. (1989) and follows some approaches used in other similar

studies. The original Coastal Environments, Inc. (1977) study of shipwrecks in the Gulf

of Mexico compiled a list of shipwrecks and developed several generalizations about the

temporal and spatial distributions of wrecks across the Gulf. Other studies have
4-43

emphasized the relationship of various factors such as shipping routes, port locations,

natural hazards and the like with shipwreck locations and have argued that these factors

are “causal” in the observed distributions of shipwrecks (Pierson et al. 1987; Science

Applications, Inc. 1981).

Garrison et al. (1989) examined spatial distributions in a number of ways, some of

which are continued in the present study. As has been discussed in Chapter 3, they

looked at general trends in distributions over time, and examined the spatial patterning of

wrecks in light of a variety of spatial and temporal factors. One analysis looked at the

occurrence of shipwrecks across 1.0-degree and 0.5-degree quadrants of

latitude/longitude. Agglomerative cluster analysis was used to examine relationships

among shipwreck variables across 1.0-degree quadrants in the Gulf of Mexico. The

principal objective was to see if there were any spatial patterns observed in clusters of

quadrants produced across the number of shipwrecks within each quadrant and dates of

loss. Nine clusters were produced in the analysis, but the conclusions drawn about the

meaning of the clusters were very general (Garrison et al. 1989:II-101–109).

The 1989 study also used factor analysis to examine several variables affecting

shipwreck locations and patterns (Garrison et al. 1989:II-109). These factors were: 1),

historic shipping routes; 2) port location; 3) shoals, reefs, sandbars, and barrier islands; 4)

ocean currents and winds; and 5) historic hurricane routes. Their analysis used the

principal component factor analysis in the program STATVIEW. Two analyses were

undertaken. One factor analysis looked at chronological factors and examined seven

variables (four time periods, age of ports, ports, and storms) across 26 “observations.”

These observations were areal sectors developed by dividing the Gulf coastline into 26

units. Three factors resulted from this analysis. Factor 1 was “characterized as an

association of 16th, 17th, and 18th versus 19th and 20th century wreck locations” interpreted

as a demographic factor. An association of variables representing nineteenth century

shipwrecks and port development characterized factor 2. Factor 3 associated ports and

storms with wrecks, but the association was extremely weak. Generally, wreck

frequency seemed to be more closely associated with the number of years a port was in

existence, rather than the simple existence of the port.

The second factor analysis looked at areal phenomena. As noted previously, this

analysis used six variables (hurricanes, ports, routes, hazards, energy, and wrecks) and 10

cases (time periods) per variable, although the time periods are not defined. These

variables were examined across ten areas in the Gulf of Mexico. As described by

Garrison et al. (1989:II-110), the value of the variable “hurricane” was frequency per

time period as derived from Tannehill (1956); “ports” was number of ports; “routes” was

the number of periods with major inter- or intra-Gulf routes present; and “hazards”

represents major reef, shoal, or other hazards. “Energy” apparently represents major

energy zones in the Gulf, but this variable is not defined.

Two factors were identified in this analysis. Factor 1 was interpreted as depicting

a strong association of shipwrecks to routes and hazards and Factor 2 associated

shipwrecks with port locations.
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The present study places less reliance on statistical treatment of the shipwreck

data than did the Garrison et al. (1989) study. This has been done for a number of

reasons. For one, the greater amount of information collected on individual shipwrecks

has permitted a much more comprehensive discussion of the characteristics of the sample

of shipwrecks in the database than was possible for Garrison et al. (1989). These

characteristics have been presented in the earlier discussions and, in general, are believed

to be applicable to the population of shipwrecks in the GOMR as a whole. Additionally,

some of the analytical techniques undertaken by Garrison et al. (1989) directed at

characterizing the spatial distributions and associations of shipwrecks across the Gulf

may have less utility than thought. This is particularly evident in light of the

demonstrated unreliability of the position information available for a large number of

wrecks. If, as has been shown in the previous chapter, there is no statistically significant

difference between finding shipwrecks in identified high-probability areas and finding

them in designated non-high-probability areas, then using these same wreck positions in

statistical analyses that examine spatial parameters is certainly going to be questionable.

This does not mean, for example, that the associations of various factors (e.g., hurricane

occurrence, navigation routes, etc.) with shipwreck locations projected by Garrison et al.

(1989) may not have validity, but it does suggest that the strength of many of these

associations is likely to be weak. Until an increased degree of reliability can be obtained

for the positions of a very large number of reported shipwrecks, these factors will have

utility only in the very broadest sense. Principally because of this factor, no effort has

been made to expand upon the cluster and factor analyses approaches in Garrison et al.

(1989).

4.5.2. Broad Spatial Patterns

Figure 4-11 presents information on the locations of all reported wrecks in the

2001 shipwreck database. Overall, the spatial distribution of wrecks generally mirrors

that found by Garrison et al. (1989) and by CEI (1977). The majority of vessel losses are

in near coastal waters, even though wrecks known to fall in state waters have been

eliminated from the database. As seen in the figure, the majority (N=1,738 or 82.5

percent) of reported wrecks fall inshore of the 60-meter contour line, the line that has

until recently been used by MMS in the design of its historic shipwreck survey program.

Overall, this distribution tends to support the validity of the 60-meter contour as

meaningful in survey design. One area where a concentration of losses occurs outside of

the 60-meter contour is off the mouth of the Mississippi River. Here, deep water extends

close to shore and this fact, coupled with the importance and longevity of the Mississippi

River as an entrepot in maritime trade, has contributed to a concentration of losses. Other

areas of wreck concentrations are apparent. One is in the Dry Tortugas, Marquesas

Islands, and Florida Keys area off southwest Florida. As has been noted, this is an area

where the combined association of a major shipping route with the natural hazards of an

extensive reef and shoal complex has resulted in an increased potential for vessel losses.

It is also apparent that reported losses are more concentrated off the coast in the central

and western Gulf coast than in the eastern Gulf as a whole (Figure 4-11).
Figure 4-11. Positions of all entries classified as “Vessels” in the 2001 shipwreck database.
4-46

Within this general concentration, densities are higher near the mouth of the

Mississippi River and along the central Louisiana coast, in the area off of Galveston and

in the area off of Corpus Christi. Some of these concentrations are obviously reflective

of the locations of ports, as was noted by Garrison et al. (1989). A few vessel locations

fall south of 24o latitude and, thus, outside of the GOMR (Figure 4-11). These vessels

have been maintained in the 2001 database because of the unreliability of their reported

position of loss.

The density of wrecks in the open Gulf beyond the 60-meter contour line is

overall, relatively low, but more reported wrecks do occur in the eastern half of this area

than the western. Garrison et al. (1989:II-116) noted the same phenomena in their data

and it appears to be principally related to vessel traffic patterns. Historically, a principal

entrance and egress into the Gulf of Mexico has been through the Straits of Florida. As

seen in Figure 4-12, prior to the mid-nineteenth century the primary offshore routes of

vessels traveling into and out of the Gulf were concentrated in the area east of the

Mississippi River. Since the latter quarter of the nineteenth century, there has been an

expansion of routes into the western Gulf, as demonstrated by Figure 4-13 that shows

modern shipping routes in the Gulf of Mexico. Even in modern times, however, much of

the vessel traffic going to points outside of the Gulf passes through the Straits of Florida,

continuing to produce a concentration of traffic in the eastern Gulf. The 70 lease areas

designated in the GOMR by the MMS provide a convenient unit for examining broad

patterns of shipwreck distributions and complement the specific loss information

presented in Figure 4-11. Occurrences of reported shipwrecks across MMS-designated

lease areas are provided in Figure 4-14.

Although at a broader scale, Figure 4-14 also clearly portrays the pattern of

shipwrecks concentrated around the periphery of the Gulf, within the 60-meter contour,

with many fewer reported losses in the central Gulf area. In particular, reported losses

are concentrated in the lease areas along the Louisiana and upper Texas coast, and off the

western Florida panhandle. Also, there is a slight increase in losses in the nearshore lease

areas off of the central Florida Gulf coast, generally around Tampa.

This information is particularly useful when compared against the shipwreck

information in the 1989 shipwreck database presented earlier as Figure 3-5. The

categories of “Wrecks per Area” are equivalent in both figures. These figures

demonstrate increases in reported wrecks in the new database for all of the lease areas

along the central Gulf coast and much of the western coastal area. Particular increases

are indicated in lease areas off of Mobile and Pensacola and slight increases off the

central Florida coast in the vicinity of Tampa. Few obvious changes are seen in the

numbers of wrecks reported in lease areas in the open Gulf.

Several factors tend to account for the more obvious differences seen in the

occurrences of wrecks by lease area in the 1989 and the 2001 databases. Part of this is

simply the incorporation of an additional 12 years of wreck data. However, the nature of

the sources used and the types of entries accepted into the 2001 database are equally

important factors.
4-47

20o

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW ORLEANS GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

YUCATAN

98o 95o 90o 85o 81o

Route of the 

Spanish flota

Spanish, French, 

British trade route

Caribbean routeFrench, British 

Havana-FloridaLouisiana routes

1763-1821

20o

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW ORLEANS GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

YUCATAN

98o 95o 90o 85o 81o

Mexican trade

1821-1862

Coastwise trade

Coastwise trade

West Indies trade

New OrleansNew York packets

Havana trade

A

B

PENSACOLA

CEDAR KEY

PENSACOLA

Figure 4-12. Historic shipping routes in the Gulf of Mexico. A. 1763-1821; B. 1821-

1862 (adapted from Garrison et al. 1989:Figure II-4).

N

N
4-48

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW

ORLEANS HOUSTON/

GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

98o 95o 90o 85o 81o

PENSACOLA

FREEPORT

CORPUS CHRISTI

BROWNSVILLE

Shipping Routes

to Points Outside

of the Gulf

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW ORLEANS HOUSTON/

GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

98o 95o 90o 85o 81o

PENSACOLA

FREEPORT

CORPUS CHRISTI

BROWNSVILLE

Shipping Routes

to Points Within

the Gulf

Figure 4-13. Modern shipping routes in the Gulf of Mexico (adapted from Garrison et al.

1989:Figure II-5).

N

N
Figure 4-14. Number of reported shipwrecks per MMS lease area. Data from 2001 shipwreck databa
4-50

For example, the increase in numbers of wrecks along the Florida coast, and to a

lesser extent along the Alabama and Mississippi coasts, is partially related to the

inclusion of a considerable amount of wreck information derived from popular sport

diver publications and accounts. These sources were not utilized in the 1989 study, or

were only used sparingly. Two of these popular works, Rinehart (1998) and Singer

(1992), plus several sport diver webpages (e.g., MBT Divers), have been the principal

source for over 130 entries in the new database. Another factor contributing to the

increase in included wrecks has been a heavy reliance by the present study on several

electronic databases maintained by various government agencies on vessel casualties.

Some of these were used in the 1989 study, but not all. These databases contain large

numbers of unnamed and unidentified vessels, identified by entries such as “Unknown

Vessel,” “Obstruction,” “18-Foot-Pleasure Craft” and the like. These entries were

included in the present database when they could not be positively correlated with named

vessels or with other unknown vessels and objects. As noted earlier, there are close to

800 of these unnamed vessel entries in the database, representing about 38 percent of the

total. By contrast, in the 1989 database unnamed vessels and obstructions represent only

about 19 percent of the total entries.

Because the MMS GOMR lease areas are of varying sizes, the information on

frequency of reported wrecks shown in Figure 4-14 is somewhat misleading as an

expression of relative densities of vessels. Figure 4-15 presents the same data on vessel

losses by frequencies of reported wrecks per 1,000 square miles of lease area. The data

from four very small lease areas (Sabine [LA], Sabine [TX], South Pelto, and Bay

Marchand) have been combined with their immediately adjacent lease area so they will

not seriously skew the results. As can be seen, this considerably moderates some of the

large differences seen in the figure displaying simply the number of vessels per lease

area. Particularly evident is a reduction in the densities of wrecks off the central and

western Louisiana coast and a generally homogeneous distribution of wrecks along

almost the entire Florida coast.

4.5.3. Spatial Distributions in Shipwrecks Through Time

Chronological trends in GOMR vessel losses as they relate to frequency over

time, by season, and by other factors have been discussed previously. Figures 4-16

through 4-23 present information on the spatial distribution of vessels losses through time

in the study area. The information is provided in 50-year increments and serves to

portray broad trends in settlement and commerce around the northern Gulf of Mexico.

1600-1649. Only a single vessel dating earlier than 1700 is included in the

database. This is the galleon San Jorge, reportedly lost off the Texas coast in 1625

(Figure 4-16). However, the historical information on the loss of this vessel is very

vague and its true position is unknown (Berman 1972). As seen in Appendix E, the

geographic coordinates provided for this vessel have been assigned a Reliability Factor of

4, meaning that its reported position is very unreliable.
Figure 4-15. Number of reported shipwrecks per 1,000 square miles per MMS lease area. Data from  database.
Figure 4-16. Position of reported shipwreck, 1600-1649.
Figure 4-17. Positions of reported shipwrecks, 1700-1749.
Figure 4-18. Positions of reported shipwrecks, 1750-1799.
Figure 4-19. Positions of reported shipwrecks, 1800-1849.
Figure 4-20. Positions of reported shipwrecks, 1850-1899.
Figure 4-21. Positions of reported shipwrecks, 1900-1949.
Figure 4-22. Positions of reported shipwrecks, 1950-2002.
Figure 4-23. Positions of reported shipwrecks of unknown date.
4-60

The fact that there is only this single reported loss in the study area prior to 1700

is partially an expression of the small numbers of vessels actually sailing on the open

waters of the Gulf at that time. Those losses that are reported prior to 1700 tend to lie

close inshore, outside of the boundaries of the study area. As Garrison et al. (1989) note,

these earlier losses reflect the early period of Spanish exploration of the northern Gulf

and the establishment of the annual flota routes. The established route of the flota out of

Veracruz was north along the Mexican coast to about 25 degrees north and then northeast

until the Louisiana coast was sighted, and then south or southeast past the Florida Keys

and to Havana (Figure 4-12A).

If a hurricane struck the fleet while it was following this route, the general

tendency would be for ships to be driven in a roughly northerly or northeasterly direction

toward the shore. Most of the early known and reported flota losses consist of vessels

that were driven ashore under these circumstances, such as in 1554 and 1622. Little is

known about vessels that might have been lost far offshore in the open Gulf or, if known,

information on where they might have gone down is so inaccurate as to be of little use in

looking at spatial patterns of loss.

1650-1699. No vessels are reported lost in the study area for the period 1650 to

1699. Again, this is a reflection of both relatively light vessel traffic and the bias of

underreporting during these early periods, particularly of vessels lost far from land. A

number of losses are known to have occurred along the margins of the Gulf during this

period, but they lie outside of the study area (Garrison et al. 1989). Those that are known

or reported are mostly Spanish, but the recent discovery of the 1686 wreck of the French

vessel La Belle in Matagorda Bay, Texas, is reflective of the beginning of French activity

in the northern Gulf.

1700-1749. A small number of losses are reported in the study area during this

period. Most are located in the vicinity of the mouth of the Mississippi River and are

related to the establishment of French settlements in the Biloxi-New Orleans area early in

this period and, ultimately the establishment of the colony of Louisiana and the

development of New Orleans as a port (Figure 4-17). The lack of reported losses in the

western Gulf is seemingly due to the lack of cross-Gulf routes of trade and to the few

settlements then in that area.

1750-1799. There is both an increase in number and an expansion in the

distribution of losses reported in the study area during this period (Figure 4-18). This

reflects the expansion of settlements along the Gulf coast, plus an increase in maritime

commercial activity to serve the growing population. This expansion in commerce was

partially expressed in the establishment of additional trade routes across the open waters

of the Gulf (see Figure 4-12A). Several losses are reported west of the Mississippi River

and, for the first time, losses are reported in the deep waters of the Gulf, beyond the 60-

meter contour line.

1800-1849. During this period reported shipwrecks are thinly scattered across the

inshore waters of the entire study area (Figure 4-19). The first half of the nineteenth
4-61

century was a period of great expansion of shipping activity in the Gulf region. The

United States acquired the Louisiana Territory and New Orleans grew into an important

seaport, funneling goods into and out of the heartland of America via the Mississippi

River. Cotton agriculture expanded west from the eastern seaboard and the crop became

the most important export of the South. There was a tremendous expansion of the

coastwise trade as numerous small sailing vessels were used to transport cotton and other

products from small towns and landings into the major ports, such as New Orleans,

Mobile, and Pensacola. Larger sailing vessels were used to carry these products out of

the Gulf to northeastern centers, such as New York, or to European and Caribbean

destinations. The development of the steam engine represented a major technological

change that had great impact on water travel. The steam engine was quickly adapted to

use in ships and during this period steamers became involved in coastwise passenger and

cargo trade, as well as in the long distance trade to eastern and European ports. Maritime

trade to Texas became important during this period after its independence from Mexico

and particularly after it joined the Union (Francaviglia 1998; Pearson and Simmons

1995). In light of the large numbers of vessels known to have been sailing in Gulf waters

during the first half of the nineteenth century, it is believed that the small number of

losses reported for this period is a serious under-representation of actual losses.

1850-1899. Two obvious changes appear in the pattern of distribution of

shipwrecks in the study area during the latter half of the nineteenth century (Figure 4-20).

These are an increase in wrecks in the inshore waters of the western Gulf and an increase

in wrecks in the open waters of the eastern Gulf. This latter pattern reflects increasing

commercial vessel traffic along cross-Gulf routes, principally from New Orleans to the

Straits of Florida. The inshore, western Gulf losses express the establishment or

expansion of several important Texas ports, such as Galveston/Houston and Corpus

Christi. After the Civil War the expanding cattle industry in Texas came to prominence

in the state’s maritime commerce. Packeries, plants where cattle were butchered and

processed into meat, hides and tallow, sprang up along the Texas coast and these

products, as well as live cattle, became important exports. A large percentage of these

cargoes was carried aboard steamers that had been first put into service in the 1830s

(Guthrie 1988:80-93). The most important of the steamer lines operating along the Texas

coast was the Morgan Line, owned by transportation magnate Charles Morgan, who had

been attracted specifically to these Texas ports by the opportunities provided in shipping

cattle and cattle products (Baughman 1968).

Garrison et al. (1989:Table II-16) note that the “westward distribution [of wrecks]

is offset by the principal ports of New Orleans and Mobile in the North-central Gulf

area.” No similar concentration of wrecks is seen off either New Orleans or Mobile in

the present data and it is apparent that the pattern observed by Garrison et al. is because

of their inclusion of nearshore and onshore losses.

1900-1950. The pattern of wrecks in the study area for the first half of the

twentieth century reflects the full maturation of settlement and commercial patterns in the

Gulf that began in the late nineteenth century (Figure 4-21). Particularly important were

the continued growth of New Orleans and the rising importance of Tampa and several
4-62

Texas ports, such as Houston, Galveston, Freeport, Corpus Christi and Brownsville. This

period saw the birth and growth of the oil industry and the use of many vessels in the

transport of oil products. A number of wrecks occur in the open Gulf, but they are

concentrated in the eastern half of this area, reflecting a pattern that began prior to 1850.

This is believed to be indicative of the continued importance of traffic routes from New

Orleans and other central Gulf ports to the Straits of Florida, despite the expansion of

shipping routes into the western Gulf during this period.

Some of the increase in reported losses during this period is due to the expansion

of fisheries in the Gulf, as has been discussed earlier. The concentration of losses off of

the central Louisiana coast is partially related to the growth of the shrimping industry.

Garrison et al. (1989:Table II-100) report an increase in losses off the southwestern

Florida coast for 1940-1959, and suggest it is related to the expansion of fisheries and the

growth of the Tampa trade. The small cluster of wrecks shown in the vicinity of the

Florida Keys in Figure 4-21 appear to be an early expression of these phenomena.

1950-2002. As discussed earlier, there has been a tremendous increase in the

number of reported wrecks in the study area since 1950; this phenomenon is fully

expressed in Figure 4-22. There is a general concentration of losses off the coast from

the area of Pensacola west to southern Texas, with obvious clusters of wrecks off the

mouth of the Mississippi River and off Galveston, Freeport, and Corpus Christi. These

are in part reflective of the increasing growth of commerce into and out of these ports.

However, many of the losses during this period are of fishing vessels of various sorts, as

well as pleasure craft, and the concentrations seen are heavily influenced by the losses of

these types of vessels. Also, the expansion and growth of the offshore oil industry during

this period and the concomitant loss of vessels associated with it also contribute to the

concentration of vessels in the inshore areas of the central and western Gulf.

Overall, there are still a relatively small number of vessels lost in deeper waters of

the open Gulf, but the old pattern of a concentration in the eastern Gulf is no longer

obvious. The full maturation of the inter-Gulf shipping routes shown in Figure 4-13 is

expressed in the distribution of losses across the entire area of the central Gulf.

Shipwrecks of Unknown Date. Figure 4-23 presents the locations of all of the

vessels in the shipwreck database that have no date of loss. The concentration off the

Florida Keys is partially related to accounts from sport diver publications that report on

wrecks of unknown identity and age. Many of the other entries consist of items recorded

as Unknown Vessels, Obstructions, and the like. Some of the concentration seen off the

coast between Mobile and Galveston is due to Unknown Vessels identified during the

course of MMS-mandated surveys.

4.5.4. Distribution of Reported Shipwrecks by Reliability Categories

As has been discussed previously, it is believed that the principal reason for the

lack of predictability in the 1989 model of shipwreck distributions is the lack of precision

in the reported positions of a very large number of vessels. In an effort to gain a handle
4-63

on this rather significant problem, we attempted to quantify how reliable a position of

loss was by assigning a numerical value to reported positions of loss. These numerical

values (identified as Reliability Factors) ranged from 1, very high reliability, to 4, very

low reliability, and are defined in Chapter 2. The use of this reliability factor represents

an attempt to strengthen the reliability and predictability of the model of shipwreck

distributions developed. It was felt that this approach would be most useful to the MMS

in its management responsibilities as well as in trying to relate specific wrecks or groups

of wrecks to the concept of “high-probability” areas and locations. In essence, using

wrecks assigned very low reliability factors (i.e., 3 or 4) in the identification of tightly

drawn “high-probability” locales is considered questionable.

The assignment of a reliability factor relied on the available information in the

various sources used. As noted, the quality of this information varied widely. In some

instances, such as with data from MMS-mandated offshore surveys that used state-of-theart-positioning systems, we are confident of the recorded positions. In other instances,

we have relied on the information provided in the source as to the reliability of the

position of loss. For example, NOAA (AWOIS) provides a three-level assessment of the

“quality” of the coordinates on many losses, with specific definitions as to what each

level means in terms of the likely error in the position. These levels of quality were

generally used in assigning reliability to entries in the database. However, in numerous

instances, a cross check of the original source of data for the AWOIS entry indicated that

the information on the location of loss was not always as precise as suggested by the level

of quality assigned. Where these discrepancies were found, the presumed reliability of

the original source was used. Other sources used for shipwreck data provide no

assessment on the potential error that might be contained in a given position, and

reliability had to be determined on the basis of a reading of the available records of loss.

Specifics on how this selection was made have been presented in Chapter 2.

Ultimately, a Reliability Factor of 1 was assigned to 214 entries in the shipwreck

database, a Factor of 2 was assigned to 807 entries, a Factor of 3 to 566 entries, and a

Factor of 4 to 519 entries (Figure 4-24). Figures 4-25 through 4-28 provide information

on the spatial distributions of losses by Reliability Factor. The losses assigned a Factor

of 1 tend to be concentrated off the central and western Gulf coast, with another

concentration in the Florida Keys. The vessels in the Florida Keys tend to represent

losses reported as shipwreck sites to the state of Florida while those along the central and

western Gulf coast are mainly discoveries from offshore remote-sensing surveys. Losses

assigned a Factor of 2 are widely spread around the perimeter of the Gulf, with

concentrations extending from near Pensacola westward.

Vessels assigned Reliability Factors of 1 and 2 represent 48.5 percent (N=1021)

of the total entries in the 2001 shipwreck database. These losses are those with the most

accurately reported positions and are those that are considered most useful in accurately

modeling spatial distributions of shipwrecks in the GOMR and in the delineation of

specific, spatially defined high-probability locales.
4-64

 Figure 4-24. Frequency of reported shipwrecks by reliability categories.

Figure 4-27 provides information on entries assigned a Reliability Factor of 3.

The accuracy of the recorded positions of these vessels is considered poor to moderate.

These 566 losses, comprising 26.9 percent of the entries in the database, are widely

scattered around the periphery of the study area. However, several noticeable

concentrations are seen off the Texas coast. Information on the vessels in this category is

derived from a variety of sources, but large numbers were originally recorded in the lists

of losses published in Merchant Vessels of the United States. A typical position of loss

provided for these vessels would be “about 25 miles NE of Port Isabel.” The imprecision

in these types of descriptions of loss is the reason that these have been assigned

Reliability Factors of 3. Vessels placed in this category have only questionable utility in

accurately modeling wreck distributions in the study area.

214

807

566

519

0

100

200

300

400

500

600

700

800

900

1234

RELIABILITY FACTORS

NUMBER OF SHIPWRECKS
Figure 4-25. Positions of reported shipwrecks assigned Reliability Factor 1.
Figure 4-26. Positions of reported shipwrecks assigned Reliability Factor 2.
Figure 4-27. Positions of reported shipwrecks assigned Reliability Factor 3.
Figure 4-28. Positions of reported shipwrecks assigned Reliability Factor 4, poor or unknown reliability data.
4-69

Because of this, it is not believed that they can be realistically used to identify

specific high-probability locations, such as an individual offshore lease block or a small

cluster of lease blocks. It seems most reasonable to use vessels assigned a Reliability

Factor of 3 only in the identification of spatially large high-probability zones. The

reported positions of loss for vessels assigned a Reliability Factor of 4 are shown in

Figure 4-28. The poor precision of reported locations or the lack of information on the

potential error in the positions of these vessels means that they have little utility in

realistically modeling shipwreck distribution in the study area.

4.5.5. Spatial Analysis: 1.0- and 0.5-Degree Units of Latitude and

Longitude

In their treatment of the 1989 shipwreck data, Garrison et al. (1989) examined the

distribution of wrecks across the Gulf in 1.0- and 0.5-degree quadrants of latitude and

longitude. In that analysis, they established the arithmetic mean centers of aggregations

of shipwrecks in quadrants of this size, primarily to examine concentrations of wrecks at

a scale fine enough to be useful in identifying potential high-probability areas.

Ultimately, the results of the 1.0-degree quadrant analysis were found not to be useful in

revealing patterns in the distribution of wrecks. The large size of the area prohibited the

expression of meaningful distributions. However, the 0.5-degree analysis did show

meaningful patterns in wreck distributions and the results became one basis for

identifying lease blocks with high probabilities of containing shipwrecks.

A similar approach was used to examine wreck distributions in the present study.

The purpose was to portray wreck distributions in an objective manner and, if

concentrations were seen in these distributions that appeared to be meaningful, use them,

as did Garrison et al. in the identification of high-probability areas. As was done in the

1989 study, the distributions of wrecks were examined by looking at their concentration

or aggregation within 1.0- and 0.5-degree units of area. The result of the analysis is

essentially a reflection of wreck densities across the study area. The analysis was

conducted using the analytical tools available in ArcView. This was considered

important because one objective of this study was to incorporate all of the collected data

into a GIS format that could be used by MMS personnel in the management of offshore

cultural resources. ArcView is extremely flexible and it is anticipated that the MMS will

use the data submitted in a variety of analytical procedures beyond those considered or

undertaken in this study.

The procedures in this analysis involved first establishing 1.0- and 0.5-degreediameter circles (e.g., 0.5-degree [49.568 km/30.8 miles] and 0.25-degree [24.784

km/15.40 miles] radii or “buffers”) around every vessel entry in the 2001 shipwreck

database that had been assigned a Reliability Factor of 1, 2, or 3. It was felt that those

vessels with very poor reliability (Reliability Factor 4) or an unknown reliability should

be eliminated from the analysis because of the serious questions about their actual

location. The elimination of these very poorly positioned losses should strengthen any

arguments developed from the distribution patterns seen, including the identification of

high-probability areas. The inclusion of these poorly positioned entries would only serve

to reduce the reliability in predicting which wrecks would actually fall in these areas.
4-70

Once the 0.5- and 0.25-degree buffers were established around every entry,

ArcView was queried to display all of the buffered zones that contained 50 or more and

25 or more reported wrecks. These numbers were selected as a reasonable starting point

in the analysis after viewing overall numbers and densities of wrecks in the study area

and after viewing several different densities per buffered area. This procedure resulted in

the identification of clusters of wrecks with densities of 25 or more and 50 or more per

1.0- and 0.5-degree-diameter areas. The results indicated that the use of 50 or more

wrecks per unit was not useful in assessing wreck distributions; very few 1.0-degree units

and no 0.5-degree units were identified containing this number of vessels.

Figures 4-29 and 4-30 show the locations of those 1.0-degree and 0.5-degree units

containing 25 or more reported shipwrecks. In presenting this information, these 1.0- and

0.5-degree diameter areas have been converted into the standard 3-by-3-mile lease block

units used by MMS by showing every offshore lease block that is contained within or that

intersects the 1.0- and 0.5-degree circles. As seen in Figure 4-29, the use of the larger

1.0-degree units is not particularly useful in discerning interpretable patterns; it simply

shows the distribution of wrecks at a very gross level along almost the entire Gulf coast.

The pattern of wreck distribution shown in the 0.5-degree analysis, however, does

show some meaningful distributions. As shown in Figure 4-30, concentrations of

reported losses occur in the central and western Gulf, principally within the 60-m

contour. To some extent, these concentrations correlate with the locations of principal

ports, a phenomenon also seen by Garrison et al. in their use of 0.5-degree quadrants.

What is reflected is not so much the use of (and ultimate loss near) these ports by large,

commercial vessels such as tankers or other merchant vessels, but the use of these major

ports, as well as adjacent smaller docking facilities, by large numbers of fishing vessels,

particularly shrimpers, as well as pleasure craft and offshore oil service vessels. This

increased usage has resulted in increased losses.

In particular, the extension of areas of high reported wreck densities west of the

Mississippi River along the central Louisiana coast is an indication of the high number of

fishing and oil industry-related vessels that have been lost there. This part of the coast of

Louisiana contains numerous small ports (e.g., Cocodrie, Morgan City, Houma) out of

which these types of craft have operated in the past, and continue to operate today. Only

off the mouth of the Mississippi River do concentrations of losses extend much beyond

the 60-m contour line. This is accounted for by a combination of high vessel traffic

associated with the Mississippi River and by the extension of deep water close to shore.

In contrast to the western and central nearshore Gulf region, the eastern Gulf off

the coast of Florida shows no concentrations of reported losses in the analysis using 0.5-

degree-diameter units (Figure 4-30). However, when the size of the unit of analysis is

increased to 1.0 degree, as shown in Figure 4-29, an extensive area off the central Florida

coast and in the area just north of the Florida Keys is displayed. These generalized

clusters appear to be reflective of shipping activity associated with the Tampa region and

with the increase in numbers of vessels reported lost in and near the region of the Keys.
Figure 4-29. One-degree units containing 25 or more vessels with Location Reliability of 1, 2, or 3.
Figure 4-30. One-half degree units containing 25 or more vessels with Location Reliability of 1, 2, or 3.
4-73

The results of these analyses are similar in many ways to those arrived at by

Garrison et al. (1989). They also found that the use of areas 1.0-degree in size was too

gross to see meaningful patterns. Their analysis using 0.5-degree quadrants with 50 or

more vessels was quite similar to the results presented here (Garrison et al. 1989:Figure

II-40). That analysis relied on losses in state waters as well as in Federal waters, and

used the number of 50 or more vessels rather than 25, but it did show concentrations of

losses near port areas along the central and western Gulf coast. The only high

concentration quadrants shown east of Pensacola by Garrison et al. were in the Florida

Keys themselves.

4.5.6. Correlation of Reported Shipwrecks with Other Seafloor Objects

Task 2 of this study involved the correlation of reported shipwreck locations in

the updated database with seafloor hang sites and with targets identified during MMSmandated remote-sensing surveys and to ground truth approximately 20 selected

locations where hang sites or objects and reported shipwreck locations were spatially

correlated. The reason for looking at the spatial relationship between reported hangs and

reported shipwrecks is because of the common observation that shrimp nets are often

caught on exposed portions of wrecks in the Gulf of Mexico. Particularly expressive of

this phenomenon is the 303 Hang Wreck, a wooden, two-master schooner located

approximately one mile off the upper Texas coast (James et al. 1991b). This wreck had

originally been identified as a shrimp net hang, designated “Hang 303.” Numerous other

similar examples are known. The proposition was that clusters of reported shrimp net

hangs would correlate with reported shipwreck locations. The relationship between

reported shipwrecks and other seafloor objects was examined in several ways.

Shipwreck locations were compared against items classified as “Objects” in the database,

the positions of named shipwrecks were compared against the positions of “Unknown

Shipwrecks” and, finally, reported shipwreck locations were compared against reported

net hang locations.

4.5.6.1. Spatial Association of “Unknown Wrecks” to Named

Shipwrecks

It is suspected that some number of the entries in the 2001 shipwreck database

classified as unknown vessels or wrecks are, in fact, the same as some of the named

vessels in the database. During the compilation of the database, if the information

examined permitted a clear indication that a named vessel in one source was, in fact,

equivalent to an unnamed vessel in another source, only the named vessel was

maintained. However, in many instances these associations were unclear or not possible

and both entries were kept. To more fully examine the possibility that unknown wrecks

in the database might be the same entities as some identified or named vessels, the spatial

relationship between the two categories was looked at. Initially, ArcView was queried to

identify all vessels in the database identified as “Unknown” in any form that lay within

2.4 km, or 1.5 miles, of any named or identified vessel. This distance was used because it

represents one-half the distance across the standard 3-x-3-mile offshore lease block,

meaning that the analysis looked at roughly lease block-sized units. This resulted in the
4-74

selection of 219 unknown vessel entries, many of which are multiple, in that the same

unknown vessel might fall within 2.4 km of more than one named vessel. The large

number of multiple entries suggested that meaningful spatial relationships were not going

to be seen in such a large area. Therefore, this list was shortened to encompass only

those unknown vessel entries lying within 500 m (1,640 feet) of named or identified

vessels. These data are shown in Table 4-4.

Seventy-one entries are included in Table 4-4. Confining the area of the search

eliminated most duplicates, but a few remain. For example, the Unknown Vessel ID No.

12456 lies almost exactly at the same location given for the vessel Antonio Ensen (or

Antonio Ensenat) and about 186 m from a vessel identified only as a “Wreck” in the sport

diver publication by Rinehart (1998). Both Unknown Vessel listings are derived from

AWOIS, as is the entry for the Antonio Ensen, a merchant vessel lost in 1943. There

seems to be no doubt that one of the Unknown Vessel entries is equivalent to the listing

for the Antonio Ensen, even though both are derived from AWOIS. This simply shows

the types of duplications that commonly can be found in the same source.

It is also possible that the Wreck identified by Rinehart is also the Antonio Ensen,

and that the 186-m difference between the two locations is simply related to errors in the

positioning systems used in the two sources.

It is apparent from the entries in Table 4-4 that some unknown vessels can be

reasonably associated with named vessels whose identity and position are known or

considered very reliable. An example would be the case of the Unknown Vessel assigned

Vessel ID Number 12423 that lies about 9-m from the wreck of the Breton Island.

Presumably, these entries refer to the same vessel. In other instances, the close spatial

association of entries might serve to strengthen the reliability of the positions provided

for named vessels. For example, the Unknown Vessel identified by Vessel ID Number

11691 has been assigned a location reliability of 1 on the basis of information provided in

the NIMA records, and it lies only 25 meters from the reported location of the barge

identified as R.O. 6, that has been assigned a location reliability of 2. If these represent

the same vessel, then it would be possible to assign the R.O. 2 a Reliability Factor of 1

for its position.

For the present, it is impossible to positively equate most of the unknown vessels

with the named vessels in Table 4-4, although it does appear that many exist. Physical

identification/diver verification is likely to be the only way to make positive associations.

4.5.6.2. Spatial Association of Shipwrecks with “Objects”

As noted earlier 1,155 entries in the database were classified as “Objects.” Some of these

have been identified on the basis of information provided in the sources used, and include

items such as Obstructions, Well Heads, Cylinder Tanks, Pipes, etc. However, how

reliable these identifications are is unknown. In addition, a number of entries consist of

items that are unidentified and are classified only as Objects
Table 4-4. Unnamed Vessels that Lie within 500 m (1,640 feet) of Named Vessels

LOCATION

RELIABILITY

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

UNNAMED

VESSEL

DISTANCE

TO NAMED

VESSEL

(meters)

NAMED

VESSEL ID

NUMBER

VESSEL NAME LOCATIONAL

RELIABILITY

OF NAMED

VESSEL

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

NAMED VESSEL

EL 2 GA TAC 18.9 236 HATTERAS 1 GA CEI; TACEL 2 GA TAC 32.9 238 CLEO SUE 3 GA AWOIS; TACEL 3 GA NIMA 8.3 1468 TX-2981-ZV 3 GA USCGEL 1 BAA MMS 382.8 1463 MY LADY 2 BAA USCGEL 1 EI MMS 379.1 1283 WAGON TRAIN 2 EI USCGEL 1 SS MMS 451.0 1117 RIG 2 SS USCG

CK 2 PE AWOIS 62.5 1838 LIPSCOMB TUG 1 PE RINEHARTCK 2 PE USCG 123.1 452 OFFSHORE 1/2 BARGE 2 PE RINEHARTOR

2 P

E USCG 169.1 447 TUG NORTH OF

SPARKMAN

2 P

E RINEHART

CK 2 MO USCG 454.8 921 LIBERTY SHIP 2 MO AWOIS

EL 4 SA USCG 1.1 918 QUE 5 2 SA MVUSEL 4 MO USCG 53.6 596 VACA DEL MAR 2 MO AWOIS; MVUSEL 4 PE USCG 104.0 1673 CANDY SHIP 2 PE RINEHART

EL 1 MC NIMA 25.1 1205 R.O. 6 2 MC MVUSEL 2 PB NIMA 1.2 1278 THAT’S-A-MY-BOAT 2 PB NIMAEL 1 CH NIMA 176.4 1658 HMS BAY RONTO 2 CH BERGEL 2 PR NIMA 75.1 1831 SHERRI F 2 PR RINEHARTEL 4 GA NIMA 20.9 207 ATHENA 2 3 GA AWOIS; TACEL 4 MI NIMA 14.7 142 LYCO I 2 MI AWOIS; TACEL 4 EC NIMA 1.0 926 SP 2 2 EC MVUSEL 1 MI NIMA 120.0 130 OCEAN EXPRESS 2 MI AWOISEL 1 EI NIMA 0.0 1312 PHILADELPHIA 2 EI USCGEL 1 SM NIMA 60.1 373 CITIES SERVICES

TOLEDO

1 SM MMS

EL 1 MU NIMA 43.2 101 MADALINE GOFORTH 3 MU MVUS; AWOISEL 2 GA NIMA 32.4 243 CAPT. DOC 3 GA AWOIS; TACEL 1 PS NIMA 45.3 53 BEULAH 3 PS AWOISEL 2 MI NIMA 41.0 1295 AIRCRAFT/CESSNA 210 2 MI USCGEL 2 PSA NIMA 0.0 1451 MEXICAN BOAT 3 PSA USCGEL 2 MI NIMA 40.9 1484 RIO NUECES 3 MI USCGEL 2 ST NIMA 67.6 1952 25 FT DERELICT F/V 2 ST USCGEL 2 EI NIMA 102.6 1395 JESSIE CURRIEL 2 EI USCGEL 1 BAA NIMA 41.1 1958 26 FT FIBERGLASS P/C 2 BAA USCGEL 1 WC NIMA 101.6 1555 WRECKS AND

OBSTRUCTIONS

2 W

C USCG

4-75
le 4-4. (continued). Unnamed Vessels that Lie within 500 m (1,640 feet) of Named Vessels

LOCATION

RELIABILITY

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

UNNAMED

VESSEL

DISTANCE

TO NAMED

VESSEL

(meters)

NAMED

VESSEL ID

NUMBER

VESSEL NAME LOCATIONAL

RELIABILITY

OF NAMED

VESSEL

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

NAMED VESSEL

EL 1 HI NIMA 41.3 1029 VICTORY 2 HI AWOISEL 1 HIA NIMA 41.3 1275 SEA PILOT 2 HIA USCGEL 1 BAA NIMA 0.4 1274 SEA LIONESS 2 BAA USCGEL 1 ST NIMA 31.4 1238 GEMINI 2 ST USCGEL 2 EI NIMA 0.8 1100 BELL 206 HELICOPTER 2 EI USCGEL 2 SS NIMA 9.2 882 BRETON ISLAND 1 SS AWOISEL 4 DT AWOIS 52.7 1754 LANDING CRAFT 3 DT SINGEREL 4 CH AWOIS 215.8 1658 HMS BAY RONTO 2 CH BERGEL 4 CH AWOIS 223.6 1658 HMS BAY RONTO 2 CH BERGEL 4 PB AWOIS 1.1 993 ANTONIO ENSEN 2 PB AWOISEL 4 PB AWOIS 186.3 1784 WRECK 2 PB RINEHARTEL 4 MU AWOIS 53.9 94 HELICOPTER 2 MU AWOISEL 4 PB AWOIS 38.1 1983 41 FOOT P/C 2 PB USCGEL 4 TP AWOIS 34.5 1788 YSD-71 3 TP LEGACYEL 4 HIA AWOIS 32.5 1436 SAN ANTONIO 3 HIA USCGEL 4 HI AWOIS 41.6 298 MR. B. 3 HI AWOIS, TACEL 4 PE AWOIS 147.2 1673 CANDY SHIP 2 PE RINEHARTEL 4 PE AWOIS 101.7 1673 CANDY SHIP 2 PE RINEHARTEL 4 PE AWOIS 22.9 1968 WOODEN HULL BOATS 2 PE USCGEL 4 WD AWOIS 27.3 1314 DRILLING RIG 2 WD USCGEL 4 PB AWOIS 38.5 1960 26FT P/C 2 PB USCGEL 4 SS AWOIS 72.8 386 HEREDIA 1 SS MMSEL 4 PE AWOIS 178.2 449 BARGE NORTH OF

SPARKMAN

2 P

E RINEHART

EL 4 PE AWOIS 263.5 450 SHRIMP BOAT OFF

MOBILE BAY

2 P

E RINEHART

EL 4 MO AWOIS 271.7 442 DRYDOCK 2 MO RINEHARTEL 4 KW AWOIS 49.4 1823 SAILING VESSEL 3 KW SINGEREL 4 WC AWOIS 29.5 608 CAPT. JACK 3 WC GARRISONEL 4 PE AWOIS 56.8 451 WALLACE 1 PE RINEHARTEL 4 PB AWOIS 407.4 1626 10 FATHOM WRECK 2 PB RINEHARTEL 4 PE AWOIS 48.8 1510 STEEL TUG BOAT 2 PE USCGEL 4 DD AWOIS 24.5 1400 LARGE BARGE 2 DD USCGEL 4 PE AWOIS 91.1 1838 LIPSCOMB TUG 1 PE RINEHART

4-76
le 4-4. (continued). Unnamed Vessels that Lie within 500 m (1,640 feet) of Named Vessels

LOCATION

RELIABILITY

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

UNNAMED

VESSEL

DISTANCE

TO NAMED

VESSEL

(meters)

NAMED

VESSEL ID

NUMBER

VESSEL NAME LOCATIONAL

RELIABILITY

OF NAMED

VESSEL

MMS

LEASE

AREA

INFORMATION

SOURCE FOR

NAMED VESSEL

EL 4 PL AWOIS 27.4 1393 JACK-UP RIG 2 PL USCGEL 4 PL AWOIS 28.0 530 CRANE 3 PL HOEL 4 WC AWOIS 19.0 1555 WRECKS AND

OBSTRUCTIONS

2 W

C USCG

EL 4 MU AWOIS 96.9 1464 NOAA WRECK 2 MU USCGEL 4 HI AWOIS 19.2 1945 22 FT BAYLINER 2 HI USCGEL 4 HIA AWOIS 23.1 1551 WRECK 2 HIA USCG

4-77
4-78

To see if named vessels could be associated with these objects, the spatial

relationship of all items classified as Vessels in the database was compared against all

items as Objects. As with the assessment of unknown vessels to named vessels, ArcView

was queried to identify all Vessels that lay within 500-m (1,640 feet) of an entry

identified as an Object. The results are shown in Table 4-5.

As can be seen, a number of vessels lie close to items classified as objects. For

example, the vessel Allen is reported to be less than one meter away from an unidentified

“obstruction.” Both entries come from AWOIS data, but could very well represent the

same item in light of the numerous duplications contained in the AWOIS records. In

other instances, Vessels with known and very reliable locations, such as the liberty ships

Edward W. Scripps and George L. Farley, sunk as artificial reefs, are closely associated

with unidentified objects whose positions are not reliably known. In instances where

items classified as Unknown Vessels are spatially close to identified Objects, this could

mean that the vessels have been misidentified and mis-classified. For example, the

Unknown Vessel assigned Vessel ID Number 12659 is less than 30 m from an object

identified as a “collapsed oil well structure” by the USCG. It is possible that the AWOIS

records identifying this entry as a Vessel are incorrect. The lack of information provided

in many of the sources prohibits positive associations between the two classes of entries,

and in most instances diving to verify these associations will be necessary.

4.5.6.3. Spatial Association of Shipwrecks to “Objects” Identified

During Offshore MMS-Mandated Remote-Sensing Surveys

One of the specific requirements of Task 2 was to correlate reported shipwreck

locations with objects identified during MMS lease block surveys. Table 4-6 presents

information on all entries classified as Vessels in the 2001 database that fall within 2.4-

km (1.5 miles) of items identified as unknown objects during offshore remote-sensing

surveys as listed in Table 3-5. This distance was selected to provide some relationship to

the standard 3-x-3-mile lease block within which most surveys are undertaken. Only 17

associations are shown and in only four of these are the distances between the vessel and

the unidentified object less than 500-m. In two instances entries classified as “Unknown

Vessel” are within 60 meters of “Unknown Objects” identified during MMS surveys. It

is believed that these unknown objects are very accurately positioned and could very well

represent the nearby vessels. In fact, one of the Unknown Vessels was also identified

during an MMS survey.

The great distances between the other Unknown Vessels and the Objects from

MMS surveys make it difficult to ascertain if, in fact, the two are the same object. The

named vessels in Table 4-6 all have been assigned Reliability Factors of 2, 3 or 4,

meaning that there are varying amounts of error in their plotted position. Thus, any one

of these vessels could be the object identified during the remote-sensing survey, but the

only way to verify this would be through physical examination of the Unknown Object.
Table 4-5. Vessels that Lie within 500 m (1,640 feet) of Items Classified as “Objects”

AME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFO.

SOURCE

DISTANCE

TO

OBJECT

(meters)

OBJECT

ID

NUMBER

OBJECT NAME LOCATIONAL

RELIABILITY

OF OBJECT

OBJECT

INFO.

SOURCE

ass P/C 2 BAA USCG 279.6 7299 BLOWN OUT PIPELINE 4 USCG

C 2 PB USCG 319.2 14084 OBSTRUCTION 4 AWOIS

V 2 SS USCG 305.4 7219 DESTROYED OIL PLATFORM 4 USCG

N 2 P

E AWOIS 0.7 13127 OBSTRUCTION 4 AWOIS

P. 2 W

C USCG 361.6 7027 SUBMERGED OBSTRUCTION 4 USCG

P. 2 W

C USCG 416.5 14459 OBSTRUCTION 4 AWOIS

OT 3 M

P MVUS 498.4 1572 UNKNOWN OBJECT 1 MMS

E 2 W

C AWOIS 28.1 7060 SUB OBSTN 4 USCG

M 2 M

O USCG 9.6 14087 OBSTRUCTION 4 AWOIS

GE 2 M

O RINEHART 310.6 12603 OBSTRUCTION 4 AWOIS

EISER 1 M

U TAC 43.3 13150 OBSTRUCTION 4 AWOIS

E 3 PL HO 0.8 11978 OBJECT 1 NIMAE 3 PL HO 343.4 14717 OBSTRUCTION 4 AWOISE 3 PL HO 346.7 1890 CYLINDER TANK 2 USCGE 3 PL HO 346.7 7141 CYLINDER TANK 3 USCG

8 2 WD MVUS 485.6 11645 OBJECT 1 NIMA

SCRIPPS 1 PS TAC 10.1 46 OBSTRUCTION 2 HOSCRIPPS 1 PS TAC 92.9 12120 OBJECT 2 NIMASCRIPPS 1 PS TAC 96.8 47 OBSTRUCTION 2 HO

ig 1 AP RINEHART 207.7 12717 OBSTRUCTION 4 AWOIS

FARLEY 1 PS TAC 10.1 46 OBSTRUCTION 2 HOFARLEY 1 PS TAC 92.9 12120 OBJECT 2 NIMAFARLEY 1 PS TAC 96.8 47 OBSTRUCTION 2 HO

ND VI 2 MI USCG 41.6 14183 OBSTRUCTION 4 AWOIS

AS 1 G

A CEI; TAC 13.2 12649 OBSTRUCTION 4 AWOIS

AS 1 G

A CEI; TAC 20.4 7577 OIL WELL CHRISTMAS TREE 4 USCG

TER 2 MU AWOIS 11.7 12109 OBJECT 4 NIMA

M II 2 S

P MVUS 368.6 12943 OBSTRUCTION 4 AWOIS

M II 2 S

P MVUS 373.4 11671 OBJECT 1 NIMA

M II 2 S

P MVUS 373.4 7450 WELL HEAD 4 USCG

E 2 W

C AWOIS 92.4 14938 OBSTRUCTION 4 AWOIS

E 2 W

C AWOIS 434.0 14940 OBSTRUCTION 4 AWOIS

OMAS 1 PS TAC 10.1 46 OBSTRUCTION 2 HOOMAS 1 PS TAC 92.9 12120 OBJECT 2 NIMAOMAS 1 PS TAC 96.8 47 OBSTRUCTION 2 HO

THERS 3 M

O USCG 304.8 12574 OBSTRUCTION 4 AWOIS

4-79
4-5. (continued). Vessels that Lie within 500 m (1,640 feet) of Items Classified as “Objects”

AME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFO.

SOURCE

DISTANCE

TO OBJECT

(meters)

OBJECT

ID

NUMBER

OBJECT NAME LOCATIONAL

RELIABILITY

OF OBJECT

OBJECT

INFO.

SOURCE

SHIP 2 MO AWOIS 0.7 13101 OBSTRUCTION 4 AWOIS

HIE 3 M

O USCG 78.9 7102 BUOY HI 4 USCG

TION 4 SS USCG 0.2 652 OBSTRUCTION 2 HO

D 3 MI H

O 50.9 13179 OBSTRUCTION 4 AWOIS

 52 2 EI USCG 28.9 12685 OBSTRUCTION 4 AWOIS

CKSON 1 M

U TAC 43.3 13150 OBSTRUCTION 4 AWOIS

HORSE 2 S

P USCG 328.5 6874 PILING 4 USCG

RGE "E" 2 MO RINEHART 97.4 12603 OBSTRUCTION 4 AWOIS

ER 2 A

P RINEHART 203.1 12717 OBSTRUCTION 4 AWOIS

OD

ON

2 M

O RINEHART 56.2 14139 OBSTRUCTION 4 AWOIS

ILLING

4 S

T USCG 0.8 653 OBSTRUCTION 2 HO

ILLING

4 S

T USCG 241.7 14190 OBSTRUCTION 4 AWOIS

1 M

O MMS 24.5 13097 OBSTRUCTION 4 AWOIS

1 M

O MMS 32.8 14112 OBSTRUCTION 4 AWOIS

 IRON

L

1 M

O MMS 18.4 14120 OBSTRUCTION 4 AWOIS

VESSEL 1 VK MMS 26.4 14125 OBSTRUCTION 4 AWOISVESSEL 2 GA TAC 27.5 7577 OIL WELL CHRISTMAS TREE 4 USCG

VESSEL 4 WD AWOIS 27.6 7572 COLLAPSED OIL WELL

STRUCTURE

4 USCG

VESSEL 4 PL AWOIS 27.8 11978 OBJECT 1 NIMAVESSEL 4 PL AWOIS 27.8 7461 CRANE 4 USCG

VESSEL 2 GA TAC 30.6 12649 OBSTRUCTION 4 AWOISVESSEL 2 GA TAC 32.1 12524 OBSTRUCTION 4 AWOISVESSEL 2 GA TAC 32.7 12519 OBSTRUCTION 4 AWOIS

VESSEL 1 HIA NIMA 33.4 12489 OBSTRUCTION 4 AWOISVESSEL 1 MP MMS 35.9 1572 UNKNOWN OBJECT 1 MMSVESSEL 2 ST NIMA 41.0 11680 OBJECT 1 NIMAVESSEL 4 MU AWOIS 42.7 12109 OBJECT 4 NIMA

VESSEL 2 GA TAC 44.4 12522 OBSTRUCTION 4 AWOISVESSEL 2 GA TAC 54.1 7585 CONCRETE BLOCK 4 USCG

VESSEL 2 WC NIMA 56.0 416 UNKNOWN OBJECT 1 MMS

4-80
4-5. (continued). Vessels that Lie within 500 m (1,640 feet) of Items Classified as “Objects”

AME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFO.

SOURCE

DISTANCE

TO

OBJECT

(meters)

OBJECT

ID

NUMBER

OBJECT NAME LOCATIONAL

RELIABILITY

OF OBJECT

OBJECT

INFO.

SOURCE

VESSEL 4 PE AWOIS 57.3 13107 OBSTRUCTION 4 AWOISVESSEL 2 MP NIMA 61.7 7227 TELEDYNE 16 4 USCGVESSEL 2 MP NIMA 62.3 7227 TELEDYNE 16 4 USCGVESSEL 1 ST MMS 64.8 395 UNKNOWN OBJECT 1 MMSVESSEL 4 SA AWOIS 65.0 7537 OBSTRUCTION 4 USCGVESSEL 4 SA AWOIS 65.7 650 OBSTRUCTION 2 HOVESSEL 4 AWOIS 84.0 12638 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 96.9 15037 OBSTRUCTION 4 AWOIS

VESSEL 2 GA TAC 101.7 7592 STEEL SKELETON TOWER 4 USCGVESSEL 2 GA TAC 107.9 12539 OBSTRUCTION 4 AWOIS

VESSEL 4 AWOIS 111.7 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 140.9 12729 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 151.4 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 158.5 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 162.9 12731 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 176.0 15037 OBSTRUCTION 4 AWOISVESSEL 1 NIMA 185.8 15031 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 187.9 12431 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 199.9 15031 OBSTRUCTION 4 AWOISVESSEL 4 SS AWOIS 203.9 12941 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 235.4 12731 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 243.7 15017 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 245.6 15034 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 255.2 12971 OBSTRUCTION 4 AWOIS

VESSEL 1 MP MMS 255.4 12664 OBSTRUCTION 4 AWOIS

VESSEL 4 AWOIS 255.8 15017 OBSTRUCTION 4 AWOISVESSEL 1 BAA NIMA 262.7 7299 BLOWN OUT PIPELINE 4 USCG

VESSEL 1 MP MMS 262.8 7597 OBSTRUCTION 4 USCG

VESSEL 4 AWOIS 270.6 15039 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 272.1 15040 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 295.6 15040 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 298.1 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 299.8 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 308.5 12638 OBSTRUCTION 4 AWOISVESSEL 4 PB AWOIS 315.0 14084 OBSTRUCTION 4 AWOIS

4-81
4-5. (continued). Vessels that Lie within 500 m (1,640 feet) of Items Classified as “Objects”

AME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFO.

SOURCE

DISTANCE

TO

OBJECT

(meters)

OBJECT

ID

NUMBER

OBJECT NAME LOCATIONAL

RELIABILITY

OF OBJECT

OBJECT

INFO.

SOURCE

VESSEL 4 AWOIS 328.0 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 334.2 12633 OBSTRUCTION 4 AWOISVESSEL 4 PL AWOIS 342.4 14717 OBSTRUCTION 4 AWOISVESSEL 4 PL AWOIS 347.5 1890 Cylinder Tank 2 USCGVESSEL 4 PL AWOIS 347.5 7141 CYLINDER TANK 3 USCGVESSEL 4 AWOIS 373.3 15015 OBSTRUCTION 4 AWOISVESSEL 4 ST NIMA 373.9 11828 OBJECT 4 NIMAVESSEL 1 NIMA 377.0 15015 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 380.3 12731 OBSTRUCTION 4 AWOISVESSEL 4 ST NIMA 384.0 11828 OBJECT 4 NIMAVESSEL 4 AWOIS 385.6 12642 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 387.1 12632 OBSTRUCTION 4 AWOIS

VESSEL 4 EI USCG 398.2 12033 OBJECT 1 NIMA

VESSEL 4 AWOIS 403.9 12641 OBSTRUCTION 4 AWOISVESSEL 1 HIA NIMA 405.6 7567 OBSTRUCTION 4 USCGVESSEL 4 AWOIS 406.4 15034 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 413.9 12643 OBSTRUCTION 4 AWOISVESSEL 4 HIA NIMA 414.9 15140 HIGH ISLAND A-281 REEF 2 GSMFCVESSEL 1 HIA NIMA 426.4 12490 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 441.1 12734 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 445.5 12731 OBSTRUCTION 4 AWOIS

VESSEL 1 SS MMS 451.0 7110 CAPSIZED RIG 4 USCG

VESSEL 4 MO AWOIS 453.1 13116 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 458.7 12632 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 461.1 15037 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 461.8 15037 OBSTRUCTION 4 AWOISVESSEL 4 ST NIMA 470.0 11828 OBJECT 4 NIMAVESSEL 4 AWOIS 479.8 12633 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 492.5 11742 OBJECT 1 NIMAVESSEL 1 NIMA 494.8 12731 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 495.7 12434 OBSTRUCTION 4 AWOISVESSEL 4 AWOIS 496.8 12642 OBSTRUCTION 4 AWOIS

WRECK 2 MO USCG 454.8 13101 OBSTRUCTION 4 AWOIS

CE 1 P

E RINEHART 0.7 13107 OBSTRUCTION 4 AWOIS

DWARDS 1 V

K RINEHART

1998

22.5 13109 OBSTRUCTION 4 AWOIS

4-82
. Vessels that Lie within 2.4 km (1.5 miles) of “Objects” Identified in MMS-Mandated Surveys

AME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO

OBJECT

(meters)

OBJECT

ID

NUMBER

OBJECT NAME LOCATIONAL

RELIABILITY

OF OBJECT

OBJECT

INFORMATION

SOURCE

S 3 SS LLOYDS 1685.9 1618 UNKNOWN OBJECT 1 MMS

OT 3 M

P MVUS 498.4 1572 UNKNOWN OBJECT 1 MMS

AVE 3 SS AWOIS 1685.9 1618 UNKNOWN OBJECT 1 MMS

ER 2 S

T USCG 2002.3 393 UNKNOWN OBJECT 1 MMS

AY 2 V

R USCG 1843.8 408 UNKNOWN OBJECT 1 MMS

UNT 2 S

P USCG 2236.4 382 UNKNOWN

OBJECTS

1 MMS

RIG 2 MP USCG 1959.3 1572 UNKNOWN OBJECT 1 MMS

E 2 S

T USCG 1038.4 395 UNKNOWN OBJECT 1 MMS

N 2 W

C USCG 798.2 414 UNKNOWN OBJECT 1 MMS

 II 4 W

C MVUS 1722.8 1622 UNKNOWN OBJECT 1 MMS

AND 2 V

R MVUS 1126.9 410 UNKNOWN OBJECT 1 MMS

VESSEL 1 MP MMS 35.9 1572 UNKNOWN OBJECT 1 MMSVESSEL 2 WC NIMA 56.0 416 UNKNOWN OBJECT 1 MMSVESSEL 2 SS NIMA 661.7 1618 UNKNOWN OBJECT 1 MMSVESSEL 4 SS AWOIS 675.3 1618 UNKNOWN OBJECT 1 MMSVESSEL 2 ST NIMA 2167.5 388 UNKNOWN OBJECT 1 MMSVESSEL 4 GI NIMA 2178.8 338 UNKNOWN OBJECT 1 MMS

4-83
4-84

4.5.6.4. Spatial Association of Shipwrecks to Reported Hang Sites

For many years, shrimpers in the Gulf of Mexico have collected information on

the positions of “hang” sites, locations where their nets have been caught or damaged by

objects on the bottom. The principal reason for doing this has been to permit avoidance

of these objects because the damage or loss of fishing gear can represent a considerable

expense to the fisherman. The identities of the objects producing the hangs are rarely

known, but range from pilings to pipe to historic shipwrecks. Net hangs and snags are

particularly common in areas where the offshore oil industry has been active and where,

over time, numerous large objects have been lost or abandoned on the seafloor. Over the

years a number of private listings of hangs have been compiled by individual shrimpers

or shrimper organizations, plus several official listings of hangs have been developed. In

the present analysis, two sets of hang data were used: one maintained by Texas A&M

University and one maintained by the MMS.

The largest of the official listings of offshore hangs is the Texas A&M Hang File,

developed by the Texas A&M University Sea Grant Program. This file contains over

13,000 entries covering an area generally west of the mouth of the Mississippi River.

The information included in the Texas A&M Hang File has been collected from many

shrimpers over many years and the positions of hangs have been recorded using a variety

of techniques. The vast majority of the positions were obtained with Loran systems that

can, as noted earlier, incorporate inaccuracies of up to a quarter mile. Despite the

potential for positioning error, the Texas A&M Hang File represents the largest compiled

source of hang data and is invaluable in the type of analysis undertaken here. The Hang

File data used were a computerized version of the file obtained from the Texas Sea Grant

Program in which all hang positions had been converted to latitudes/longitudes.

The listings of hangs and snags obtained from the MMS represents data

maintained as part of the Fisherman’s Gear Compensation Fund. These represent hangs

in the Gulf of Mexico identified by fishermen, principally shrimpers, as locations where

their nets were caught and damaged or lost. Many of the hangs in the Gulf are objects

derived from the offshore oil industry and include items such as pipes, abandoned well

sites, discarded equipment, etc. The Fisherman’s Gear Compensation Fund draws on

monies pooled by the oil industry to compensate fishermen for damaged or lost gear.

One way to assess the association of shipwrecks and hang sites is to examine the

spatial relationships of the two. Presumably, some shipwrecks that have been snagged by

nets over the years will be represented by reported hangs. Table 4-7 presents a listing of

all “Vessels” in the 2001 shipwreck database that lie within 200-m (650 feet) of a

reported hang included in the MMS or Texas A&M hang listings. A fairly small number

of vessels are represented in this sample, although increasing the distance in the analysis

significantly expands the number of vessels included. However, one aspect of this

analysis was to help direct a field program that involved diving on hangs that might be

associated with wrecks, and it was felt that a 200-m search radius encompassed the

largest area that reasonably could be examined.
Table 4-7. Vessels that Lie within 200 m (650 feet) of Reported Hangs

 NAME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO HANG

(meters)

INFORMATION

SOURCE FOR

HANG

MMS FISH FUND NO.

OR TEXAS A&M ID

NUMBER

REMARKS OR

DATE OF HANG

 P/C 4 USCG 48.3 A&M 314

 QUEEN 2 PS USCG 93.3 A&M 8502

NO. 2 2 EI MVUS 122.8 MMS 19910001 1/1/90

L VESSEL 3 EI USCG 163.5 MMS 1988008 DESTROYED A

NET AND 2

DOORS

ERNATIONAL

P LEGS

2 SS USCG 155.4 MMS 1993150 8/20/93

ERNATIONAL

P LEGS

2 SS USCG 168.5 MMS 1994131 9/7/94

DOC 3 G

A AWOIS; TAC 180.1 A&M 1231

WEISER 1 M

U TAC 0.6 MMS 19913954

BARGE 2 MU USCG 184.7 A&M 7463

RILLER 2 ST NIMA 146.8 A&M 5187RILLER 2 ST NIMA 146.8 A&M 3889

SO (?) 1 S

T MMS 33.5 A&M 5535

SO (?) 1 S

T MMS 33.5 A&M 3648

P RIG 2 MP USCG 93.8 MMS 1991140 8/29/91

URRIEL 2 EI USCG 175.0 MMS 1990138 LOST TWO 50'

NETS

HOUEST 2 V

R NIMA 196.8 A&M 3136

ISE 3 E

C MVUS 107.0 A&M 1957

NTHA 3 PS AWOIS 101.5 A&M 4770NTHA 3 PS AWOIS 101.0 A&M 8350

JOHN 4 S

T MVUS 141.1 A&M 4192

JOHN 4 S

T MVUS 141.1 A&M 5381

Y M. 3 W

C AWOIS 100.0 A&M 2050

RICK 2 M

P NIMA 86.7 MMS 1994127 8/30/94

RICK 2 M

P NIMA 128.7 MMS 1991016 10/22/90

GNES 1 EI MMS 73.5 MMS 1989073 LOST 2-54' NETS,

1 LAZY LINE

4-85
Table 4-7. (continued). Vessels that Lie within 200 m (650 feet) of Reported Hangs

 NAME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO HANG

(meters)

INFORMATION

SOURCE FOR

HANG

MMS FISH FUND NO.

OR TEXAS A&M ID

NUMBER

REMARKS OR

DATE OF HANG

ON/VESSEL 4 VR USCG 172.3 A&M 10439

OUISE 3 G

A MVUS 45.0 A&M 1038

OUISE 3 G

A MVUS 45.0 A&M 5970

ACKSON 1 M

U TAC 0.6 MMS 19913954

TA 3 P

N MVUS 143.2 A&M 8644

ENT 3 P

L USCG 28.0 A&M 5081

ENT 3 P

L USCG 28.0 A&M 3805

PION 2 M

U AWOIS 137.1 A&M 6590

PION 2 M

U AWOIS 137.1 A&M 214

ZADE (?) 1 EI MMS 165.9 A&M 10891

DEZ 3 PS USCG 190.5 A&M 8496

N SHIP 2 WC USCG 189.2 MMS 1984182 LOST ENTIRE

SIDE RIG

BANA 2 M

U TAC, AWOIS 65.4 A&M 6962

SHARK 2 W

C USCG 0.0 MMS 1996003 10/16/95

 BRAD 2 EI MVUS 85.3 A&M 9881

WIND 3 EC H

O 178.8 A&M 2607

OWN 4 SS AWOIS 47.6 A&M 3511

WN TUG 1 EC MMS 190.8 A&M 2305

N VESSEL 1 GI MMS 110.1 A&M 4227N VESSEL 1 GI MMS 110.1 A&M 5414N VESSEL 1 GI MMS 144.8 MMS 1990233 9/10/90; LOST

3 BRIDLES

CABLES, 2

DUMMY DOORS,

2 NETS

N VESSEL 1 GI MMS 112.4 MMS 1991126 8/8/91N VESSEL 1 SS MMS 150.7 MMS 1997046 LOST A 90 FISH

TRAWL

COMPLETE

EXCEPT THE

FLOAT LINE

4-86
Table 4-7. (continued). Vessels that Lie within 200 m (650 feet) of Reported Hangs

 NAME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO HANG

(meters)

INFORMATION

SOURCE FOR

HANG

MMS FISH FUND NO.

OR TEXAS A&M ID

NUMBER

REMARKS OR

DATE OF HANG

N VESSEL 1 WC MMS 43.4 MMS 1984182 LOST ENTIRE

SIDE RIG

N VESSEL 2 ST NIMA 134.6 MMS 1988098N VESSEL 4 ST NIMA 164.7 MMS 1993069B 1/7/93N VESSEL 4 WD NIMA 158.7 MMS 1993075 1/19/93N VESSEL 4 ST NIMA 193.1 MMS 1990149 5/7/90N VESSEL 4 GI NIMA 139.2 A&M 4627 5/7/90N VESSEL 4 GI NIMA 139.2 A&M 5119N VESSEL 4 ST NIMA 147.0 MMS 1993039 11/20/92N VESSEL 4 ST NIMA 195.0 MMS 1993069 1/7/93N VESSEL 4 ST NIMA 195.9 MMS 1993069B 1/7/93N VESSEL 4 ST NIMA 153.9 MMS 1993077B 1/21/93N VESSEL 4 ST NIMA 13.7 MMS 1993069B 1/7/93N VESSEL 4 SP NIMA 109.5 MMS 1993094 3/3/93N VESSEL 4 GI NIMA 96.9 MMS 1993099 3/17/93N VESSEL 2 ST NIMA 54.6 MMS 1993121 6/4/93N VESSEL 2 GI NIMA 194.2 MMS 1993124 6/15/93N VESSEL 2 ST NIMA 61.2 A&M 3824N VESSEL 2 ST NIMA 61.2 A&M 5108N VESSEL 1 EI NIMA 149.2 MMS 1990066B DAMAGE NOT

LISTED.

N VESSEL 2 SM NIMA 49.8 A&M 11326N VESSEL 1 VR NIMA 125.3 A&M 3060N VESSEL 1 VR NIMA 109.9 A&M 10807N VESSEL 4 SM NIMA 56.2 MMS 992011 92/11/16; LOST 2

45' NETS

W/TEDS,10X40

DOORS, CABLE

N VESSEL 4 SM NIMA 56.2 MMS 1993033 92/11/16 LOST 2

45' NETS W/TEDS,

10 X40 DOORS,

CAB

4-87
Table 4-7. (continued). Vessels That Lie within 200 m (650 feet) of Reported Hangs.

 NAME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO HANG

(meters)

INFORMATION

SOURCE FOR

HANG

MMS FISH FUND NO.

OR TEXAS A&M ID

NUMBER

REMARKS OR

DATE OF HANG

N VESSEL 4 MU NIMA 0.0 MMS 1993036 92-11-18 LOST 2

58'NETS, CHAIN,

AND ROPE

N VESSEL 4 EI NIMA 113.7 MMS 1993078 1/22/93N VESSEL 4 SS NIMA 117.7 A&M 9459N VESSEL 4 EI NIMA 117.6 MMS 1994014 1/11/93N VESSEL 4 VR NIMA 140.8 MMS 1986001 BROKE 2 NETSN VESSEL 4 EI NIMA 61.0 MMS 1993097 3/16/1993;

DAMAGED 2-40'

NETS, 2 TEDS

N VESSEL 4 PL NIMA 195.6 MMS 1993101 3/25/93N VESSEL 4 SS NIMA 107.1 MMS 1993104 4/8/93N VESSEL 4 SS NIMA 159.0 MMS 1993105 4/13/93N VESSEL 1 GI MMS 120.3 A&M 4443N VESSEL 1 GI MMS 110.1 MMS 1985128 DAMAGED NET,

BOARD, CHAIN

N VESSEL 4 ST NIMA 196.9 MMS 1993090 2/24/93N VESSEL 2 ST NIMA 165.6 MMS 1993123 6/15/93N VESSEL 2 MP NIMA 95.0 MMS 1993130B 6/29/93N VESSEL 1 VR NIMA 125.3 A&M 11578N VESSEL 2 GA NIMA 182.2 A&M 1231N VESSEL 2 SS NIMA 96.9 A&M 10566N VESSEL 4 SM NIMA 56.2 MMS 1992011 92/11/16; LOST 2

45' NETS

W/TEDS,10X40

DOORS, CABLE

N VESSEL 4 SS NIMA 158.6 MMS 1993083 1/29/93N VESSEL 4 SS NIMA 144.8 MMS 1993083 1/29/93N VESSEL 1 GI MMS 120.3 A&M 5644N VESSEL 4 GI NIMA 165.1 MMS 1993065 12/29/93

4-88
Table 4-7. (continued). Vessels That Lie within 200 m (650 feet) of Reported Hangs.

 NAME LOCATION

RELIABILITY

MMS

LEASE

AREA

VESSEL

INFORMATION

SOURCE

DISTANCE

TO HANG

(meters)

INFORMATION

SOURCE FOR

HANG

MMS FISH FUND NO.

OR TEXAS A&M ID

NUMBER

REMARKS OR

DATE OF HANG

N VESSEL 4 ST NIMA 165.3 MMS 1993077 1/21/93N VESSEL 1 SS NIMA 55.7 A&M 3511N VESSEL 4 SM NIMA 98.3 A&M 3201N VESSEL 4 VR NIMA 197.0 A&M 3225

N VESSEL

RCHE?)

1 E

C MMS 197.1 A&M 2194

N VESSEL

RCHE?)

1 E

C MMS 197.1 A&M 11594

N WRECK

T 2?)

1 EI MMS 114.3 A&M 11144

 TRAIN 2 EI USCG 54.1 MMS 1985152 LOST 1 NET,

DAMAGED 1 NET

MA 3 W

D AWOIS 172.9 A&M 3777

MA 3 W

D AWOIS 172.9 A&M 5041

4-89
4-90

Most of the vessels in Table 4-7 are spatially associated only with a single

reported hang. A few, however, are within 200 meters of multiple hangs. For example,

the vessel identified as “Cal Dive International Jack Up Legs” and presumably

representing the legs from a jack-up barge, is within 200 meters of two hangs included in

the MMS data. The two hangs are both approximately 160 meters away from the named

vessel. There is no way of knowing if these hangs are associated with the reported jackup legs, but if they are, it would seem to suggest that the recorded position of the vessel is

160 meters or so off.

Several vessels are associated with multiple Texas A&M hangs, but the data on

most of these are somewhat confusing. For example, the vessel Pearl Louise is near two

Texas A&M hang locations recorded by different ID numbers, but the distance to both is

exactly the same. This appears to be related to the conversion of hang positions from

Loran to geographic coordinates that resulted in a rounding off of the latter.

Despite the large number of hangs reported in the GOMR, only a few can be

spatially correlated with reported shipwreck locations. This finding was not particularly

surprising and at the beginning of this study it was proposed that relatively few spatial

associations between these two categories would be found (Panamerican Consultants,

Inc. 2000). This was because of the known lack of precision in most of the coordinates

available for hang sites, plus the unreliability anticipated in the position information for a

great many shipwrecks in the GOMR.

In addition to this assessment of the spatial relationships of vessels and reported

hangs, ArcView was used to identify individual clusters or groups of hangs that existed

by themselves. The assumption was that clusters of hangs derived from multiple reports

would correlate with some relatively substantial object on the bottom, possibly an

unreported historic object. A large number of clusters of two or more hangs falling

within a 200-m circle were identified across the nearshore waters of the central and

western Gulf. Of ultimate concern, however, were clusters that were located in a

spatially confined area and in less than 100 feet of water, because this information was

going to be used to direct diving operations that were restricted to this water depth.
5.0: CORRELATION OF SEAFLOOR HANG SITES,

LEASE BLOCK SURVEY DATA, AND SHIPWRECK ARCHIVAL

DATA: FIELD INVESTIGATIONS - TASK 2

5.1. Ground-truthing of Selected Targets

As discussed in Chapter 4, a component of Task 2 of this study involved an

assessment of the relationship between reported shipwreck locations and reported hang

and snag sites under the presumption that some reported hang sites represent shipwrecks.

The rationale for conducting this assessment is the demonstrated fact that shipwrecks in

the Gulf of Mexico are often festooned with nets, ropes, cables, etc., that have been

caught on exposed elements. The first phase of this task involved correlating the

positions of reported shipwrecks, unknown shipwrecks, objects and hang sites as has

been discussed in Chapter 4. The second phase of Task 2 involved ground-truthing a

sample of selected hang sites and reported shipwreck and object locations in an effort to

determine if hang sites represented actual shipwrecks. As specified in the Scope of

Work, approximately 20 targets were to be selected and then subjected to remote-sensing

survey to determine if obvious seafloor features existed. If any targets represented

seafloor features of interest, then diving would be conducted to determine their identity

and, if any were vessels, to make assessments of significance to the extent possible.

The selection of the 20 targets relied on vessel and object data in the 2001

shipwreck database and reported hang data from the Texas A&M and MMS hang files

discussed previously. Target selection drew on the information on the spatial correlation

of reported shipwrecks, unknown shipwrecks, objects and hangs as presented in Tables 4-

4, 4-5 and 4-6 and on visual examination of these data presented in ArcView format.

Target selection was based on a variety of factors, the most critical relating to a target’s

ability to address questions concerning hang/shipwreck correlations. Targets chosen for

examination had the following characteristics:

• Groups of hangs that correlate spatially (cluster around or near) with unidentified

objects that had been discovered during remote-sensing surveys.

• Groups of hangs that correlate spatially (cluster around or near) with a reported wreck

location.

• Groups of hangs that correlate spatially (cluster around or near) with only themselves,

the cluster suggesting the presence of an object exposed above the seafloor.

• Precisely located unidentified objects discovered during remote-sensing surveys,

regardless of association with hangs under the presumption that these might represent

unidentified shipwrecks.
5-2

Additional factors involved in the target selection process related to practical

considerations of conducting the field investigations, and included the depth of water at

targets, as well as their location relative to access. The SOW provided by MMS

stipulated that all targets to be investigated had to be situated in less than 100 feet of

water, thus allowing for relatively safe diving conditions. Furthermore, during the

selection process consideration was given to how far potential targets were from a port,

as well as the distances between targets, distance being a critical element relative to

budget constraints and how much time was available for target examination. While the

entire GOMR area inshore of the 100-foot depth line was reviewed during target

selection, the area that had the highest concentration of targets meeting the above-stated

characteristics and which, also, complied with the concerns about water depth and

distance, was located offshore of central Louisiana. After consultation with MMS

GOMR personnel on the selection process, 20 targets in this area were chosen and

approved for investigation (Table 5-1). Figure 5-1 illustrates the location of these targets

in the area offshore of Louisiana.

Table 5-1. Task 2 Targets Selected for Investigation

Target No Lease

Block

Target Type Survey Area

(feet)

Comments

1 SM 17 1 unknown object (374)* 600 x 600 Amorphous sidescan target, LR 1**

2 SM 19 1 unknown object (375) 600 x 600 Rectangular sidescan target, LR 1

3 SM 211 4 hangs, 1 unknown vessel (12424) 1600 x 1650 LR 2 for unknown vessel

4 SM 231 1 hang, 1 unknown vessel (12373) 1000 x 1000 LR 4 for unknown vessel

5a

5b

ST 20

ST 20

4 hangs,

1 unknown object (11840),

1 unknown vessel (11836)

900 x 1500

600 x 600 LR 4 for object and vessel

6 ST 77 1 hang, 1 unknown vessel (389) 1100 x 1700 Sidescan target, possible J.A. Bisso?,

LR 1 for unknown vessel

7 SS 71 2 hangs 1350 x 700 Possible association with # 8

8 SS 71 1 hang, 1 unknown object (12379) 650 x 1450 Possible association with # 7, LR 4 for

object

9 SS 73 2 hangs, 2 unknown objects (12376

and 12380)

1000 x 1700 LR 4 for objects

10 SS 109 1 hang, 2 unknown vessels (12502

and 12166)

1300 x 1000 LR 2 for unknown vessel 12166, LR 4

for unknown vessel 12502

11 PL 2 1 hang, 1 unknown object (12382) 800 x 1800 LR 4 for unknown object

12 PL 5 1 hang, 1 unknown vessel (12415) 750 x 1400 LR 4 for unknown vessel

13 PL 14 3 hangs 1400 x 2600 Possible association with # 15

14 VR 35 1 hang, 1 unknown vessel (12409) 1000 x 1000 LR 4 for unknown vessel

15 VR 118 1 unknown object (408) 600 x 600 Amorphous sidescan target, LR 1

16 EI 23 3 hangs, 1 unknow vessel (12405) 1600 x 2000 LR 4 for unknown vessel

17 EI 42 2 hangs, 1 unknown vessel (12363) 1700 x 1500 Possible association with # 18, LR 4

for unknown vessel

18 EI 53 1 hang, 2 unknown vessels (12402

and 12359)

1500 x 1400 Possible association with # 17, LR 4

for unknown vessels

19 EI 68 3 hangs 1300 x 1300 Possible association with # 20

20 EI 68 1 unknown object (obstruction,

7076)

600 x 600 Possible association with # 19, LR 4

for unknown object

* Numbers refer to CEI ID Number of vessel and object entries in 2001 Shipwreck Database; **LR = Location Reliability
Figure 5-1. Lease block map illustrating lease blocks containing targets selected for investigation
5-4

These “targets” do not represent single point locations, but consist of areas

surrounding an individual item or a cluster of items, as indicated in Table 5-1 and

illustrated in Figure 5-2. With the exception of those targets deemed to be very precisely

located (e.g., Targets from Table 5-1 with a Location Reliability of 1), we elected to

examine a fairly large block around multiple hangs, objects, or unknown vessels. Each

block was designated a single “target,” rather than each item within the block. This was

implemented on the belief that closely clustered items could represent the same object

that had been given slightly different coordinates in various sources. This was believed

to be particularly pertinent for the hangs, because their coordinates typically represented

converted Loran positions, positions known to often contain some amount of error.

Furthermore, designating each item in a cluster as a separate target would have

minimized the ability to correlate discrete, but spatially clustered objects.

Figure 5-2. Lease block map with Target 5 survey area. Located in

South Timbalier 20, the survey area encompassed the

recorded locations of one unknown object, one

unknown vessel and four hangs.

This is particularly relevant in light of the above-stated presumption that closely

clustered hangs or obstructions could represent the same object with slightly different

coordinates. As opposed to 20 separate, individual targets, the use of these survey areas

as “targets” offered a much larger sample of 52 recorded “items” to investigate that

included 31 hangs, 12 unknown vessels, and nine unknown objects. Even this number of

52 items, however, represents an extremely small sample of the total number of vessels,
5-5

objects and hangs known to exist in the Gulf of Mexico. The results of these target

investigations must be viewed in this light and any effort to extrapolate these results to

the GOMR as a whole has to be considered tentative at best.

Table 5-1 presents the number (Target No.) assigned to the target, the MMS lease

block within which the target is located, the Target Types as identified in the sources of

information used, the size of the survey area examined by remote-sensing survey at the

target location, and Comments that provide basic information on the targets. Under

Target Type, the CEI ID Number from the 2001 shipwreck database is provided for

vessels and objects. Included in the Comments are the location reliability factors for

objects and vessels derived from the 2001 shipwreck database. During target selection,

an effort was made to incorporate the concept of location reliability into the process. For

example, as shown in Table 5-1, three of the targets with location reliability factors of 1

(i.e., with what are believed to be very precise positions) are associated with unknown

objects, while one (Target 6) is associated with an unknown vessel tentatively identified

as the J.A. Bisso. Thus, these targets offered the opportunity to determine if these

precisely located “objects” might, in fact, represent the remains of vessels, while in the

case of Target 6, it would provide a verification of a tentative identification, as well as

determine if the reported hang at Target 6 was associated with the vessel.

Target 3 consists of a cluster of four reported hangs, plus an unknown vessel

assigned a location reliability of 2, indicating a moderately high reliability in its reported

position. In this instance, investigation would enable an assessment of this reliability

assignment, plus it would examine the relationship of hang sites with wreck sites, should

the unknown vessel be located here. The same reasoning was used in the selection of

other targets containing reported hangs and unknown vessels. As seen in Table 5-1, most

of the “unknown vessels” at these targets have reliability factors of 4, indicating a low

reliability for the reported location, or that no information was available to make such an

assessment. It would have been desirable to examine targets that expressed a range of

location reliabilities, but relatively few unknown vessels with nearby hangs were

identified within the offshore area selected for diving and most of these had location

reliabilities of 4.

Target 5 consists of a cluster of four hangs, plus an unknown object and an

unknown vessel, both of which have a location reliability of 4. Additionally, these latter

two items have the same coordinates and both are derived from the same source, the

electronic database produced by the National Imagery and Mapping Agency (NIMA). It

is likely that these represent the same item that has been entered twice in the NIMA

database. However, one is clearly identified as a vessel, while the other isn’t. As seen in

Table 5-1, Target 5 has been separated into 5a and 5b because the area of the hangs

(Target 5a) was examined separately from the area of the unknown vessel and object

(Target 5b). The rationale for this division is presented in the discussion of Target 5.

There are several other instances of “unknown vessels” and “unknown objects”

with the same coordinates in the 2001 shipwreck database. Sometimes these are derived

from the same source of information, and sometimes they are from different sources. In
5-6

the cases where both items were identified as the same thing, either a vessel or an object,

only one was retained in the database. However, in instances where one is identified as a

vessel and one as an object, both have been retained unless other information was found

to substantiate the presumption that they represented the same item. This was done

because it is presently impossible to accurately classify either entry as a vessel or an

object.

In the case of Target 10, in lease block Ship Shoal 109, one hang and two

unknown vessels are identified in proximity to one another. One of these vessels has

been assigned a location reliability of 2 and the other a reliability of 4. The reported

locations of the two vessels are very close to one another, and it is possible that the two

actually represent the same vessel that has been provided slightly different coordinates in

different sources. Target 20 is an unidentified object, identified as an “obstruction” in

USCG records. In fact, the USCG record for this entry notes that there was a report of a

cable snagging on the obstruction (see 2001 shipwreck database).

5.1.1. Investigative Methods

The investigation of the 20 selected targets was conducted in two phases, a survey

phase that served to locate the target (if present), and a diving phase to verify, identify

and, to the extent possible, assess the historical significance of objects or vessels found.

As stated above, 20 previously selected targets were to be surveyed using a

magnetometer, sidescan sonar and DGPS positioning; the area of survey coverage at each

target is provided above in Table 5-1. For targets precisely located during previous

remote-sensing surveys and those consisting of single items, a close-interval remotesensing survey was conducted of only a small block (600 feet x 600 feet) with the target

coordinates at the center of the block (e.g., see Targets 1, 2, 15 and 20 in Table 5-1). The

areas surveyed at other targets were sufficiently large to encompass the items of interest.

If an above-seafloor feature was identified during remote-sensing survey, its position

would be refined with a close-interval sidescan sonar and magnetometer survey to obtain

sufficiently precise information to direct subsequent diver investigation. A five-person

archaeological dive team would then examine targets that represented above-seafloor

features in order to determine their identity and, to the extent possible, assess their

historical significance. The instruments and methods used in target survey and

examination are discussed below, along with their respective findings.

5.1.2. Remote-Sensing Survey: Methods and Equipment

Positioning for all of the survey work utilized a Motorola LGT-1000 Global

Positioning System (GPS) linked to a Starlink MRB-2A MSK Radiobeacon receiver for

differential (DGPS) capabilities. The remote-sensing instruments used were a Marine

Sonic sidescan sonar and an EG&G Model 866 marine magnetometer. The vessel Sea

Ox, out of the ASCO fuel dock in Intracoastal City, Louisiana, was used for the initial

remote-sensing survey phase of the 20 targets. The Sea Ox is a 110-foot utility boat

provided by Sea Boat Rentals, Inc. of Galliano, Louisiana (Figure 5-3).
5-7

Figure 5-3. The 110-foot Sea Ox used for remote-sensing refinement of 20 hang sites within the

GOMR.

Differential Global Positioning System. Accurate positioning was essential to

permit returns to locations for supplemental remote-sensing operations and diver

investigation of targets. These positioning functions were accomplished using a

Motorola LGT-1000 GPS (Figure 5-4). The Motorola LGT-1000 is a global positioning

system that, when linked to the Starlink MRB-2A, MSK Radiobeacon receiver, attains

differential capabilities. These electronic devices interpret transmissions from satellites

in the Earth’s orbit and from a shore-based station to provide accurate coordinate

positioning data for offshore surveys.

Figure 5-4. Differential global positioning system (DGPS) used for the project.
5-8

The Motorola system processes both satellite data and differential data transmitted

from a shore-based GPS station utilizing RTCM 104 corrections. The shore-based

differential station monitors the difference between the position that the shore-based

receiver derives from satellite transmissions and that station’s known position.

Transmitting the differential that corrected the difference between received and known

positions, the DGPS constantly monitored the navigation beacon radio transmissions in

order to provide a real-time correction to any variation between the satellite-derived and

actual position.

Both the satellite transmissions and the differential transmissions received from

the shore-based navigation beacon were displayed directly onto the screen of the LGT1000 and were updated continuously every second. The level of accuracy for the system

was considered at ±1 meter throughout the survey. For this survey, Louisiana South State

Plane Coordinates, based on the 1927 North American Datum (NAD 27), were used.

Sidescan Sonar. The sidescan sonar system used was a Marine Sonic

Technology Sea Scan (Figure 5-5). The software included with the Sea Scan Personal

Computer (PC) system controls the collection of sonar imagery as well as navigational

input and displays the data to the operator utilizing a 13-inch color monitor. The Sea

Scan PC allows the operator to view wide tracts of the seafloor by isonifying along a

predetermined swath width and recording the strength of the echoes from the seafloor.

This is performed by a towfish towed just above the seafloor. The towfish emits a

continuous, narrowly focused beam of sound perpendicular to the path of forward

motion. The sound pulses pass through the water and are reflected by the seafloor and

from various objects resting on it, such as shipwrecks, debris, and topographic features

(sand ripples, rocks, etc.). The strength of the signal returned to the towfish is recorded

and the entire sonar record line is drawn onto the screen for viewing. An image of the

seafloor is constructed line by line as the sonar record line from each pulse of the sonar is

returned to the PC and then displayed onto the color monitor.

Figure 5-5. Marine Sonic Technology sidescan sonar system.
5-9

The Sea Scan PC utilizes an Intel-based computer with the Windows v3.1

operating system for system control and data display. The Sea Scan program allows the

operator to control the sonar data collection process, zoom in on various sonar images for

increased axial resolution, and to save sonar images with the related navigational data.

The Sea Scan PC can read navigational information from external navigational

devices such as GPS and Loran C units. External navigational units must support the

NMEA 0183 Standard for Interfacing Marine Electronics Navigational Devices 1.5,

which was adopted in December 1987 by the National Marine Electronics Association

(NMEA). The NMEA proprieties allow marine instruments to send and receive

information based on a block serial transmission. NMEA sentences (each uniquely

identified by a header that identifies the transmitter) are transmitted over a serial cable.

Any external navigational system that supports these sentences then sends the

information to a serial port on the Sea Scan PC. When an incoming sentence arrives, the

Sea Scan PC accounts for the current latitude and longitude, course-over-ground, and

speed-over-ground.

The function of the Sea Scan PC software is to display the relevant sonar image

on the screen. Every time the sonar towfish emits an acoustic pulse, the reflection data is

recorded and displayed along a horizontal line on the display screen. As the towfish

passes over the seafloor, it continually emits an acoustic pulse. The image of the seafloor

is then drawn by the reflection data, line by line. The reflection data is recorded in a

1,000-line image file. Therefore, only the latest 1,000 lines of the sonar record are stored

in the computer’s memory. Unless every 1,000-line file is saved automatically, when a

new sonar line is recorded it writes over the old sonar line.

For every acoustic return from the seafloor, an intensity value (from zero to 255)

is recorded. A value of zero indicates that no return was detected in that particular

sample and an intensity level of 255 indicates that the maximum intensity was detected.

It is these 256 levels of acoustic intensity that are drawn onto the color monitor utilizing a

64-element color scale. Therefore, the intensity values between zero and 255 are

converted to an intensity value of zero to 63, which are then drawn on the screen by the

color scale elements of zero to 63, respectively.

The Sea Scan PC also features an integrated plotter with a current and survey

mode plot display function. The plotter allows the operator to set search patterns and

monitor swath coverage while collecting sonar records (Figure 5-6). Once a feature (such

as a shipwreck) is located, it may be marked on the Sea Scan plotter for future reference.

Magnetometer. The magnetometer used was a Geometrics 866 marine

magnetometer (Figure 5-7). The G-866 is comprised of a hydrocarbon-filled sensor, a

tow cable, and a topside console where signal processing and amplification is achieved.

An external printer is utilized to print the collected data. The G-866 is probably the most

well known and was once the most widely used magnetometer. The “industry-standard”

for many years, while not completely obsolete, it is no longer being produced and is

being replaced with newer models by many companies.
5-10

Figure 5-6. Sea Scan PC plotter window showing overlapping coverage between survey

lines.

Figure 5-7. Geometrics Model G-866 marine magnetometer console and towfish.
5-11

5.1.3. Sidescan Sonar Survey: Results

The initial plan for the first phase of target evaluations was to undertake a remotesensing survey of each target location using both the sidescan sonar and the

magnetometer. However, during the mobilization of the survey vessel Sea Ox, it was

determined that the magnetometer cable brought for the survey was not long enough to

distance itself from the magnetic interference of the vessel. Rather than expend time

waiting for a new cable, it was decided to proceed with the survey of targets using the

sidescan sonar alone. This did not seriously affect the overall results of Task 2, because

the intent was to dive only at targets where obvious bottom features (potential hangs)

were seen, information that would come only from the results of the sidescan sonar

survey. Essentially, this first survey effort with the sidescan sonar resulted in the

elimination of several targets from further evaluation. Subsequently, prior to diving,

magnetometer surveys were conducted at those targets that did exhibit identifiable

bottom features. The sidescan sonar survey of targets was conducted between August 21

and 24, 2001. The results of the sidescan sonar survey of all 20 targets are presented

below. This is followed by discussions of the magnetometer surveys and diver

investigations at those targets where they were warranted.

Each of the targets was subjected to a sidescan sonar survey of various grid sizes

(see various plot maps). To establish the number of survey lines (or “track lines”) needed

to achieve adequate coverage, the location of the target item, or the center of the group of

target items, was entered into a computer and the appropriate number of offsets

calculated along the shortest side of the pre-determined grid square. The space between

track lines depended upon the size of the grid. While only seven track lines were

necessary to adequately survey any grid, every track line had overlapping swath coverage

providing complete coverage of each area.

Target 1, SM 17. The sidescan sonar survey of Target 1, located in lease block

South Marsh 17, was conducted on August 22, 2001. Target 1 consisted of a single

unknown object identified during an MMS-mandated remote-sensing survey (Lease

block survey G12886, see Table 5-1 and 2001 shipwreck database). The reported

position for the target was at Louisiana South State Plane Coordinates (NAD 27) N =

91370, E = 1769105. A survey block measuring 600 feet square and centered on this

position was fully covered with seven parallel track lines (Figure 5-8). Survey lines were

spaced 100 feet apart and oriented in a north-south direction. Water depth at the target

was approximately 80 feet.

A review of the sidescan sonar records in the field identified an object on the sea

bottom near the center of the surveyed area, very close to the position identified in the

original survey records (Figure 5-9). This object was observed on at least three survey

lines and consisted of several thin, linear elements lying parallel to one another combined

with at least three shorter, crossing diagonal members. The maximum length of the target

was approximately 47 feet. The regular geometry of this object suggested that it was

manmade, thus Target 1 was slated for additional magnetometer and diver investigations.
5-12

Figure 5-8. Target 1, SM 17 survey area.

Figure 5-9. Sidescan sonar image of Target 1, SM 17; note the diagonal

cross features of the target.
5-13

Target 2, SM 19. Target 2, located in the southwestern quarter of lease block

South Marsh 19, like Target 1, consisted of a single unknown object identified during a

previous MMS-mandated sidescan sonar survey (Lease block survey G16319, see Table

5-1 and 2001 shipwreck database). The sidescan sonar records of the previous survey

indicated that the object was rectangular and measured about 13 by 26 feet in size. An

object tentatively identified as a piece of shrimp net was trailing from one side of the

object. The sidescan sonar survey of Target 2 was undertaken on August 22, 2001

(Figure 5-10). A survey block measuring 600 feet square was centered over the object’s

location (Louisiana South State Plane Coordinates [NAD 27] N = 85755 E = 1797839)

and this area was fully covered with seven parallel track lines. Survey lines were spaced

100 feet apart, oriented in a north-south direction. Water depth at the target was 80 feet.

Figure 5-10. Target 2, SM 19 survey area.

The review of the collected sidescan sonar data indicated no above-seafloor

objects. Despite these findings, however, a magnetometer survey was subsequently

conducted over this target location because of the precise nature of the information on its

existence presented in the MMS-mandated survey. The results of the magnetometer

survey are discussed later, but it is noted that they, also, were negative.

Target 3, SM 211. Target 3 is located near the western boundary of lease block

South Marsh Island 211 (Figure 5-11). As listed in Table 5-1, this target contained four

hang sites and one unknown vessel assigned a position reliability of 2 (CEI ID Number

12424 in the 2001 shipwreck database). This target was selected, principally, to see if the

cluster of snags might represent the unknown vessel. An initial effort to conduct a

sidescan sonar survey of this target was undertaken on August 21, 2001, but water depths

at the target were on the order of only 10 feet, too shallow to collect useable data because
5-14

of the deep draft of the Sea Ox. The sidescan sonar survey was subsequently conducted

with another vessel on September 13, 2001. The water depth was approximately 10 feet

at the time of the sidescan sonar refinement.

Figure 5-11. Target 3, SM 211 survey area.

The survey area at Target 3 measured 1650 feet by 1600 feet in size, with the long

axis of the survey block oriented in a north-south direction. The survey block was

centered on the five items reportedly located here (at Louisiana South State Plane

Coordinates (NAD27) N = 29599; E = 1751134). Survey coverage of the area was

accomplished with seven survey lines consisting of a centerline and three offsets to the

east and west. The line spacing was 233 feet between survey track lines. The sidescan

sonar was set to 50-meters-per-channel, thus giving a 100-meter-per-transect swath (328

feet). This allowed for an approximately 30 percent overlap on adjacent transects, giving

full coverage of the target area. Analysis of the sidescan sonar data in the field and more

detailed examination in the lab identified no obvious seafloor features of interest. Natural

features in the record indicated only the presence of dolphins and a school of fish or

shrimp during the running of the survey lines.

Several reasons may lie behind the fact that no seafloor objects were identified at

Target 3. First, the positions of all of the items identified at this target must be

considered somewhat imprecise. The unknown vessel has been assigned a location

reliability of 2, suggesting the potential for some error in its reported position, and all of

the hangs apparently were originally reported in Loran coordinates. Secondly, evidence

of recent shrimp trawling activity through the target area was obvious in net drag scars on

sonar records, suggesting that the reported hangs might have been displaced or

completely removed through this activity at some time in the past. Thirdly, it is possible

that the hangs reported at this location were buried at the time of the sidescan sonar
5-15

survey. The shallow water at Target 3, plus its inshore position, places it at a location

where bottom sediments can be moved around by wave action as well as by nearshore

currents. As discussed previously, marine growth and wood damage to the remains of

vessels such as El Nuevo Constante, which is located off the western Louisiana coast in

about 20 feet of water, suggest periodic burial and exposure of remains. Similarly, the

hangs at Target 3 might be periodically exposed or buried, dependent upon wave, storm

and current conditions and their impacts on sediment transport. Because there were no

indications of any above-seabed features in the target area, no further work was

recommended for this location.

Target 4, SM 231. Target 4, located in lease block South Marsh Island 231,

consisted of one reported hang and one unknown vessel (Figure 5-12). The unknown

vessel (CEI ID Number 12373 in the 2001 shipwreck database) was assigned a very low

location reliability of 4, indicating a vague and possibly unreliable position. Target 4 was

surveyed by sidescan sonar on August 23, 2001, when water depths over the area ranged

from 9 to 12 feet. The survey area measured 1,000 feet by 1,000 feet and was centered

on a point midway between the reported positions of the two items at the target

(Louisiana South State Plane Coordinates [NAD 27] N = 258031; E = 1756892).

Figure 5-12. Target 4, SM 231 survey area.

Seven track lines were run over the target area in an alternating north-south

direction. Line spacing was 150 feet with the sidescan sonar swath coverage set at 50-

meters per channel. During the survey, numerous drag scars from trawling activities

were visible on the sonar records (Figure 5-13). No other cultural objects or features

were noted and, therefore, Target 4 was eliminated from additional examination.
5-16

Figure 5-13. Sidescan sonar image of drag scars from trawling activity near Target

4, SM 231.

Target 5, ST 20. Target 5, located in the southern portion of lease block South

Timbalier 20, encompassed a cluster of four hangs, one unknown object and one

unknown vessel (see Table 5-1). The water depth at Target 5 was 38 to 42 feet. As noted

earlier, the unknown object and vessel both had been assigned very poor location

reliability (reliability of 4), but both had the same reported position and might represent

the same item identified in two different ways. Because of the great distance between the

cluster of hangs and the unknown vessel and object, the entire target area was surveyed in

two parts. In subsequent discussions, the cluster of hangs is identified as Target 5a, while

the unknown vessel and object are identified as Target 5b.

The sidescan sonar survey of Target 5a, the cluster of hangs located in the

southern part of the target area, was conducted on August 22, 2001. The survey area over

the hangs measured 900 feet by 1,500 feet and was centered at Louisiana South State

Plane Coordinates (NAD 27) N = 121405; E = 2326904. Complete coverage of this area

was obtained with seven survey track lines spaced 140 feet apart. Swath coverage was set

at 50-meters per channel during the survey of this area.

Review of the sidescan sonar data during the survey identified a slight rise on the

seafloor in the area of the reported hang sites (Figures 5-14 and 5-15). The anomalous

rise covers an area approximately 34.5 feet square. Because of the presence of this

object, this area of Target 5 was slated for subsequent magnetometer survey and diver

examination.
5-17

Figure 5-14. Target 5, ST 20 survey area.

Figure 5-15. Sidescan sonar image of Target 5a, ST 20.
5-18

The second part of the survey of Target 5 considered the reported unknown vessel

and unknown object in the northern portion of the target area. Survey coverage of these

items, designated Target 5b, was accomplished with seven survey lines spaced 100 feet

apart with swath coverage set at 50-meters per channel. The survey block over these

items measured 600 feet by 600 feet and was centered at their reported location

(Louisiana South State Plane Coordinates [NAD27] ).

Sidescan sonar records at the Target 5b location revealed the presence of a large

number of linear objects covering a substantial area. The total area of the target could not

be determined due to the large amount of sea life (i.e., fish, shrimp) over the target

obscuring the sonar return. The linear objects appear to be strewn across the seafloor in

roughly a northwest to southeast orientation (Figure 5-16). Because of the presence of

these objects, this portion of the Target 5 area was also selected for later magnetometer

survey and diver examination.

Figure 5-16. Sidescan sonar image of Target 5b, ST 20; note the large

number of linear features on the seafloor. A school of

fish or shrimp swimming over the target account for the

heavy masking effect.

Target 6, ST 77. Target 6, located in lease block South Timbalier 77, consisted

of a reported hang site and an unknown vessel (see Table 5-1; Figure 5-17). The

unknown vessel had been located during a previous MMS-mandated remote-sensing

survey and had been tentatively identified as a vessel named J.A. Bisso in a cultural

resources survey report by Northland Research, Inc., in the year 2000 (see CEI ID

Number 389 in the 2001 shipwreck database).

The sidescan sonar survey of Target 6 was conducted on August 22, 2001. The

area surveyed measured 1,000 feet by 1,700 feet and was centered on Louisiana South
5-19

State Plane Coordinates (NAD 27) N = 33503; E = 2219914. Seven track lines (oriented

north/south) were run over the area, completely covering the selected target area. Track

lines were spaced 150 feet apart, covering an area 1,050 feet total. Water depth on site

was approximately 56 feet. No obvious seafloor features were observed on the collected

sidescan records. Due to these negative findings, no additional investigations were slated

for this area.

Figure 5-17. Target 6, ST 77 survey area.

Target 7, SS 71. Target 7, located in lease block Ship Shoal 71, consisted of two

reported hang locations positioned approximately 700 feet apart (see Table 5-1; Figure 5-

18). One hang location came from Texas A&M records and was a converted Loran

position. The other hang location came from MMS Fisherman Contingency Fund records

and may be a converted Loran coordinate, although this is not specified in the available

records. The fact that the hang was reported in 1986, before GPS was in common use,

suggests it was originally recorded in Loran.

The survey area at Target 7 consisted of a 1,350-foot-by-700-foot block centered

at Louisiana South State Plane Coordinates (NAD 27) N = 103952; E = 2133989, a point

midway between the two hang locations. Sidescan sonar coverage of this block was

achieved with seven survey lines spaced 110 feet apart and run in a north-south direction.

Sidescan sonar swath coverage was set at 50 meters per channel. No seafloor features

were observed on the sonar records and no additional work was undertaken at Target 7.
5-20

Figure 5-18. Target 7, SS 71 and Target 8, SS 71 survey area.

Target 8, SS 71. Target 8 is located in lease block Ship Shoal 71, a short distance

northeast of Target 7. The items in Target 8 consisted of one reported hang and one

unknown object (CEI ID Number 12379 in the 2001 shipwreck database) (Figure 5-18).

The unknown object had been assigned a poor location reliability factor of 4. A 650-

foot-by-1450-foot survey block was established over the target area, centered at

Louisiana South State Plane Coordinates (NAD27) N = 105495; E = 2135365, a point

midway between the hang and object locations. Sidescan sonar coverage of this block

was achieved with seven survey lines spaced 110 feet apart and run in a east-west

direction. The sidescan sonar swath coverage was set at 50 meters per channel. A

careful review of the collected sonar records revealed no objects of interest on the bottom

and Target 8 was eliminated from additional consideration.

Target 9, SS 73. Target 9, located in lease block Ship Shoal 73, consisted of two

reported hang locations and two unknown objects (see Table 5-1; Figure 5-19). Both

objects are assigned a poor location reliability of 4. A survey grid measuring 1,700 feet

by 1,000 feet was centered over a point representing the midpoint of this cluster of

objects (at Louisiana South State Plane Coordinates [NAD27] N = 108065; E =

2097455). This target was surveyed on August 23, 2001, and coverage was achieved

with seven track lines run in a east-west orientation. Survey lines were spaced at 150 feet

with swath coverage set at 50 meters per channel.
5-21

Figure 5-19. Target 9, SS 73 survey area.

The sidescan sonar records revealed the presence of one feature of interest in the

target area. This was an elongated object, narrower at one end than the other, that

somewhat resembled a stretched-out trawl net (Figure 5-20). The anomaly covers an area

approximately 66.42 feet square. The existence of this object resulted in the selection of

Target 9 for later magnetometer survey and diver investigation.

Figure 5-20. Sidescan sonar image of Target 9, SS 73, tentatively

identified as a trawl net.
5-22

Target 10, SS 109. Target 10 is located in lease block Ship Shoal 109 in

approximately 40 feet of water. The target contained a single reported hang and two

unknown vessels (see Table 5-1). One vessel had been assigned a moderate location

reliability of 2 and the other a poor location reliability of 4. A survey block measuring

1,300 feet by 1,000 feet that encompassed these objects was surveyed with the sidescan

sonar on August 22, 2001 (Figure 5-21). This block was centered at Louisiana South

State Plane Coordinates (NAD27) N = 60816; E = 2080221. Complete coverage of this

block was attained with seven survey track lines oriented in an east-west direction and

spaced 170 feet apart. Sidescan sonar swath coverage was set at 50 meters per channel.

No objects of interest were identified on the sonar records and no additional

investigations were conducted at Target 10.

Figure 5-21. Target 10, SS 109 survey area.

Target 11, PL 2. Target 11 is located in lease block South Pelto 2 in

approximately 30 to 35 feet of water. The items identified at this target were a single

reported hang and single unknown object that had been assigned a poor location

reliability of 4 (see Table 5-1). The survey grid at Target 11 measured 800 feet by 1,800

feet in size and was centered at Louisiana South State Plane Coordinates (NAD27) N =

122525; E = 2210109, a point midway between the reported positions of the two items of

interest (Figure 5-22). Full survey coverage of the Target 11 area was obtained with

seven survey track lines oriented in a north-south direction and spaced 100 feet apart.

Sidescan sonar swath coverage was set at 50 meters per channel. A review of sonar

records during and after the survey revealed no objects of interest within the area and it

was eliminated from additional investigations.
5-23

Figure 5-22. Target 11, PL 2 survey area.

Target 12, PL 5. Target 12, located in lease block South Pelto 5, consisted of

one reported hang and one unknown vessel that had been assigned a poor location

reliability of 4 (see Table 5-1). Water depths over the target area ranged from 30 to 35

feet. The sidescan sonar survey of Target 12 was conducted on August 22, 2001 (Figure

5-23) and involved examination of an area measuring 1,000 feet by 1,600 feet. This

survey block was centered at a point midway between the reported positions of the hang

and the unknown vessel (at Louisiana South State Plane Coordinates [NAD27] N =

123641; E = 2260010), and complete coverage was achieved with seven survey lines run

in a north-south direction and spaced 100 feet apart. Swath coverage was set at 50 meters

per channel. A review of all sidescan sonar records failed to identify any seafloor objects

of interest within the survey area. Therefore, Target 12 was eliminated from further

investigation.

Target 13, PL 14. Target 13, located in lease block South Pelto 14, consisted of

three reported hang locations, all derived from Texas A&M records. The water depth at

Target 13 is approximately 42 feet. A survey grid measuring 1,400 feet by 2,600 feet

was positioned over a spot representing the center point of this group of hangs (Louisiana

South State Plane Coordinates [NAD27] N = 98381; E = 2236364) (Figure 5-24). Full

sidescan sonar coverage was achieved with seven survey lines spaced 220 feet apart and

run in a north-south direction. Careful review of the sidescan sonar records identified no

objects of interest within the area and Target 13 was eliminated from further

investigations.
5-24

Figure 5-23. Target 12, PL 5 survey area.

Figure 5-24. Target 13, PL 14 survey area.
5-25

Target 14, VR 35. Target 14 was located in lease block Vermilion 35 and

consisted of one reported hang and one unknown vessel that was assigned a poor position

reliability of 4 (see Table 5-1). The hang position is derived from MMS Fisherman

Contingency Fund data and the record notes that the hang “broke 2 nets,” seemingly

indicating a substantial object on the bottom. A 1,000-by-1,000-foot survey block was

established over a point midway between the two objects (at Louisiana South State Plane

Coordinates [NAD27] N = 279330; E = 1676149), and sidescan sonar coverage was

obtained with seven survey lines run in a north-south direction (Figure 5-25). Swath

coverage was set at 50 meters per channel. Water depth on site was about 30 feet.

Figure 5-25. Target 14, VR 35 survey area.

The sidescan sonar records revealed a group of three low rises or humps on the

seafloor in the target area (Figure 5-26). These rises cover a small area measuring 29.3

feet square. Because of the presence of these objects, Target 14 was slated for additional

investigation in the form of a magnetometer survey and diver examination.
5-26

Figure 5-26. Sidescan sonar image of Target 14, VR 35, identified as three small rises off the

seafloor.

Target 15, VR 118. Target 15, located in lease block Vermilion 118, contained a

single unidentified object recorded during an MMS-mandated survey and assigned a

position reliability of 1 (see Table 5-1). A survey grid measuring 600-feet-square was

positioned over the object location (at Louisiana South State Plane Coordinates [NAD27]

N =164262; E= 1633365), and the sidescan sonar survey of the target was conducted on

August 21, 2001 (Figure 5-27). Coverage of the area was achieved with seven survey

lines spaced 100 feet apart, oriented in a north-south direction. Sidescan sonar swath

coverage was set at 50 meters per channel and water depth on site was 65 feet.

Sonar records revealed the presence of an object on the seafloor near the center of

the surveyed area. The object was recorded on three alternate track lines and appeared to

consist of a linear feature measuring approximately 45 feet long, off of which extended a

number of shorter, diagonal and intersecting pieces (Figure 5-28). The identity of this

somewhat amorphous-shaped object could not be determined, but its regular and

geometric form suggested it was a cultural item and, thus, it was slated for additional

magnetometer survey and diver investigation.
5-27

Figure 5-27. Target 15, VR 118 survey area.

Figure 5-28. Sidescan sonar image of Target 15, VR 118. Note the interesting

linear features of the target.
5-28

Target 16, EI 23. Target 16, located in lease block Eugene Island 23, consisted

of three reported hangs and one unknown vessel. All of the hangs were derived from

MMS Fisherman Contingency Fund records and the unknown vessel had been assigned a

location reliability of 4, indicating poor reliability (see Table 5-1). A 1,600-foot-by2,000-foot survey grid, centered on the midpoint of the cluster of items (at Louisiana

South State Plane Coordinates [NAD27] N = 246163; E = 1870024), was established and

the sidescan sonar survey was conducted on August 23, 2001 (Figure 5-29). Coverage

was achieved with seven survey lines oriented in an east-west direction and spaced 195

feet apart. Sidescan sonar swath coverage was set at 50 meters per channel. Water depth

at Target 16 ranged from 15 to 18 feet.

Figure 5-29. Target 16, EI 23 survey area.

A careful review of sonar records identified no objects of interest and no

additional work was slated for Target 16.

Target 17, EI 42. Target 17, located in lease block Eugene Island 42, consisted

of two reported hangs and one unknown vessel (see Table 5-1; Figure 5-30). The vessel

had been assigned a poor location reliability of 4. A 1,700-foot-by-1,500-foot survey

grid was established over the center point of the three items (at Louisiana South State

Plane Coordinates [NAD27] N = 212656; E = 1919534); the sidescan sonar survey was

conducted along seven track lines spaced 235 feet apart and oriented in an east-west

direction. Sidescan sonar coverage was set at 50 meters per channel. Water depths over

the survey area ranged from 20 to 25 feet. A review of the sidescan sonar records

identified a large area of unidentified objects consisting of parallel, linear and somewhat

sinuous features (Figure 5-31).
5-29

Figure 5-30. Target 17, EI 42 survey area.

Figure 5-31. Sidescan sonar image from Target 17, EI 42 showing numerous

linear features.
5-30

These features resembled the drag scars from trawling activity that were

commonly observed in this and other areas surveyed, but these were more obvious and

much more clearly delineated than any others observed. Although these features might

simply reflect very recent trawling activity at this location, it was decided to conduct a

magnetometer survey and diver investigations at Target 17 to try to verify their identity.

Target 18, EI 53. Target 18, located in the northeastern corner of lease block

Eugene Island 53, consisted of one reported hang site and two unknown vessels, both of

which had been assigned a poor location reliability of 4 (see Table 5-1). A survey block

measuring 1,500 feet by 1,400 feet was established over the midpoint of this cluster of

items (at Louisiana South State Plane Coordinates [NAD27] N = 210472; E =1919780),

and the sidescan sonar survey was conducted on August 23, 2001 (Figure 5-32). Full

coverage of the target area was achieved with seven survey track lines spaced 220 feet

apart. The water depth at the target was 21 feet.

Figure 5-32. Target 18, EI 53 survey area.

As was typical of many of the areas surveyed, a number of drag marks from

shrimp trawling activity were observed in the Target 18 area. No other obvious cultural

features were observed on sonar records; however, what appeared to be a depression in

the seafloor was noted (Figure 5-33). The depression appears to be associated with a
5-31

shrimp trawler scar extending across the seafloor. Because this target represented an

anomalous feature on the seafloor, it was slated for additional investigations by

magnetometer and divers.

Figure 5-33. Sidescan sonar image from Target 18, EI 53 showing what appears to be a

depression in the seafloor.

Target 19, EI 68. Target 19, located near the northern boundary of lease block

Eugene Island 68, consisted of three reported hang locations (see Table 5-1). Two of

these hangs come from Texas A&M records and one comes from MMS Fisherman

Contingency Fund records. A survey block measuring 1,300 feet by 1,300 feet was

established over the midpoint of the cluster of hangs (at Louisiana South State Plane

Coordinates [NAD27] N = 196479 E = 1854345), and it was surveyed along a series of

seven track lines spaced 200 feet apart and oriented in a north-south direction (Figure 5-

34). The water depth at Target 19 was 30 to 35 feet.

Monitoring of the sonar records during the survey, as well as a complete review

of all records at a later date, identified no seafloor features of interest in the Target 19

area. Therefore, no additional work was slated for this target.
5-32

Figure 5-34. Target 19, EI 68 and Target 20, EI 68 survey areas.

Target 20, EI 68. Target 20 consisted of a single unknown object located in the

northwestern quarter of lease block Eugene Island 68 that was assigned a poor location

reliability of 4 (see Table 5-1). This object is derived from USCG records that identify it

as an “obstruction” and note that there was a report of a cable snagging on it (see CEI ID

Number 7076 in the 2001 shipwreck database). A 600-foot-by-600-foot survey grid was

centered over the reported position of the object (Louisiana South State Plane

Coordinates [NAD27] N = 194237; E = 1854821) (Figure 5-34). Full coverage of the

target area was achieved along a series of seven track lines, spaced at 100-foot intervals.

The sidescan sonar records revealed no features of interest and Target 20 was

eliminated from additional examination.

5.1.4. Diver Investigations: Methods

The sidescan sonar surveys identified objects of interest at nine of the 20 targets

examined. Information on those targets containing objects of interest is listed in Table 5-

2. Each of these targets was subjected to a systematic magnetometer survey and then

diving was conducted.
5-33

Table 5-2. Targets Slated for Diver Investigation

Target

Number

MMS Lease

Block

Northing Easting Area Length Comments

1 SM17 91412.389 1769078.602 na 6.16m Linear features, likely

manmade.

5a ST20 120988.557 2326372.413 77.6 m. sq. 9.28m Sizeable rise off seafloor.

5b ST20 121970.913 2327104.371 na na Unidentified linear feature(s)

with lg. amounts of sea life.

9 SS73 107659.226 2097948.188 na 20.13m Linear feature, possibly

trawling net.

14 VR35 279351.382 1675945.699 10 m. sq. 4.45m Three small rises off

seafloor.

15 VR118 164324.464 1633326.653 na 14.21m Criss-crossed linear features,

likely manmade.

17 EI42 212565.767 1918883.951 na na Unidentified linear feature(s)

with lg. amounts of sea life.

18 EI53 210344.367 1920340.807 na 26.05m Sizeable depression in the

seafloor.

(Note: All coordinates are presented in Louisiana South State Plane, NAD 27).

The magnetometer survey utilized a Geometrics G-866 magnetometer and similar

survey procedures were conducted at each of the nine targets. Initially, a survey block

measuring 600 feet by 600 feet was established over each target location using the

coordinates obtained from the sidescan sonar survey as the center point of the block. The

survey of each target was conducted along a series of parallel track lines spaced at 100-

foot intervals. The magnetometer sensor was towed behind and beyond the magnetic

influence of the vessel and at a depth of not more than 20 feet above the bottom. All

magnetometer data were integrated concurrently with the DGPS and onboard navigation

system. A review of the collected magnetic data was undertaken in the field to determine

the absence/presence of ferrous metal within the survey area. If magnetic anomalies were

recorded within the area, their location was noted and procedures to refine their positions

were conducted. This refinement involved conducting additional passes over the

anomaly with the magnetometer and dropping buoys at the point of maximum magnetic

change, the presumed center of the magnetic anomaly. Buoys were continually dropped

and recovered until this point was precisely located (Figure 5-35). Once the magnetic

target was relocated and buoyed, remote-sensing operations ceased and diving began.

Initial diver investigation of targets took place between September 12 and 15,

2001. Vessels employed included the 53-foot M/V Mañana and the M/V Carrier, a 100-

foot utility boat out of Morgan City, Louisiana (leased from Seaboat Rentals, Inc.). Both

vessels were mobilized out of Intracoastal City, Louisiana. The Mañana was to serve as

the dive and survey boat and the Carrier as crew accommodations. This was necessary

due to the distance offshore of some targets and scarcity of shore facilities along the

Louisiana coastline.
5-34

Figure 5-35. Buoy deployment during target refinement.

Vessel problems forced an end to the diving activity after just two targets were

examined. Target examination was recommenced on October 5, with the vessels M/V

Enterprise and the M/V Offshore Retriever. The M/V Enterprise, a 60-foot long-range

cruiser/trawler, served as a support vessel and living quarters for the crew (Figure 5-36).

The 44-foot M/V Offshore Retriever served as the primary survey vessel and dive

platform (Figure 5-37). Dive operations were completed on October 18, 2001.

A standard set of procedures was used during the diver investigation of each

target. Once the target was relocated and buoyed, the dive vessel was securely anchored

over the target location. A diver was then placed in the water at the buoy location to

begin a bottom search.

The first objective was to obtain an accurate depth reading using a pneumo gauge,

then relay the environmental conditions on the seafloor (i.e., current, bottom type,

visibility). Currents tended to be minimal during the investigation and bottom types

tended to be soft sediments. Visibility, affected by depth and excessive swell, typically

ranged from zero to five feet.
5-35

Figure 5-36. Support vessel M/V Enterprise.

Figure 5-37. Survey and dive platform vessel M/V Offshore Retriever.
5-36

If the source of the anomaly was not discovered near the buoyed location, the

diver was then guided (by means of surface communications) to a pre-determined

distance from the buoy. The diver’s location, in relationship to the buoy, was then

recorded by the surface crew and further examination involved the diver searching the

bottom while swinging in arcs across the target area, controlled by the dive hose. At the

end of each arc, the dive hose was let out 10 feet and the diver swung another arc in the

opposite direction. While moving along the bottom the diver would extend his body and

feel for objects. Diver arcs continued around the buoyed location until the area was

systematically and completely covered or until the target was located. Arcs around the

target area extended the full length of the diver’s rig, typically 200 feet in all directions

from the target location. Divers relayed information on bottom conditions (e.g., sediment

characteristics, topography) and discoveries to the surface where notes were made.

Surface Supplied Air (SSA) was used during all diving operations. Divers

employed a Superlight 17-B helmet connected to a surface-supplied air source, radio

communications cable, safety tether, and pneumo hose (Figure 5-38). On the surface

various individuals and pieces of equipment ensured safe dive operations. A dive tender

was required to aid the diver in donning and doffing equipment and to tend the diver

while submerged and moving about the seabed. The radio operator kept in constant

contact with the diver and relayed messages between the diver and the surface support

team. A standby diver was on site during all diving in case of an emergency. A dive

supervisor was present to coordinate the activity of the diver and surface support team.

Figure 5-38. Diver, employing Surface Supplied Air, returning from a dive.
5-37

5.1.5. Diver Investigations: Results

Target 1, SM 17. The magnetometer survey of Target 1 was conducted on

September 15, 2001. The findings of the sidescan sonar (discussed above) had indicated

the presence of several thin, linear elements lying parallel to one another combined with

at least three shorter, crossing diagonal members. The maximum length of the object was

approximately 47 feet and its position was recorded at state plane coordinates N = 91328;

E = 1769119. This position was buoyed and served as the center point for the

magnetometer survey. A magnetic contour map showing the results of the survey is

presented as Figure 5-39. As can be seen, a relatively complex set of magnetic signatures

was recorded, principally in the southeastern quarter of the survey grid. The complex

magnetic anomaly located closest to the target observed on sidescan sonar records, at

state plane coordinates N = 91330 E = 1769290, had a total magnetic deviation of 114

gammas and covered an area approximately 192 feet across. The intent was to

immediately dive on Target 1, but high seas (five to eight feet) and 20-knot winds

delayed diving operations until conditions were more favorable.

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Figure 5-39. Magnetic contour map of Target 1, SM 17.
5-38

Diving was conducted at Target 1 on October 18, 2001. Water depth at the target

was 81 feet and visibility on the bottom ranged from zero to one foot with no current.

Within 11 minutes of searching the target area, the diver located the target, which

appeared to be the base of an offshore oil or gas platform. The exposed remains consist

of a 12-inch-diameter vertical post; one large iron diagonal reinforcement (extending into

the sediment); two smaller diagonal reinforcements (also extending into the sediment);

one broken horizontal iron beam (extending off the vertical piling); and two disarticulated

iron supports (Figure 5-40). Similarities in this structure can be seen in existing offshore

oil and gas platforms that employ larger cylindrical pilings as well as diagonal cross

braces (Figure 5-41). A depth reading with a pneumo-gauge taken at the top of the large,

vertical post registered 72 feet, meaning that this element rises approximately nine feet

above the bottom. The magnetic signatures to the east and southeast of these materials

suggest that other remains of the structure exist in that direction.

Figure 5-40. Diver sketch of the remains of Target 1, SM 17, identified as the

base to an offshore rig (Note: Figure not to scale).

The relief and substantial construction of these objects suggest that they would

represent a dangerous hang to shrimp nets. However, neither the Texas A&M nor the

MMS data list any hangs in close proximity to Target 1. The diver reported no shrimp

trawling nets hung on the obstruction during the investigation.
5-39

Figure 5-41. Example of an offshore rig.

Target 2, SM 19. As noted in the previous discussions, the sidescan sonar

survey of Target 2 revealed no features of interest. However, the failure to find anything

at this location was somewhat unexpected, because the object reported to be here had

been discovered during an MMS-mandated remote-sensing survey and, thus, is presumed

to have been precisely located. Therefore, despite the negative findings of the sidescan

sonar survey, it was decided to undertake a magnetometer survey at Target 2 as an

additional check of this area. This survey was conducted on October 18, 2001. The area

surveyed consisted of a 600-foot-square block centered on the reported state plane

coordinates of the object (N= 85755; E = 1797839). The survey was conducted along

nine survey track lines, spaced at 100-foot intervals and oriented in a north-south

direction (Figure 5-42). Weather conditions during the survey were relatively calm with

two-foot seas and east winds blowing five to 10 knots.

As shown in Figure 5-42, no magnetic anomalies were recorded over the reported

target location. There are several possibilities as to why Target 2 was not discovered. It

is conceivable that the target location was incorrectly reported in the original survey

report. While this is possible, it is unlikely considering the typical accuracy involved in

offshore cultural resources and hazard remote-sensing surveys. Another, and probably

more reasonable explanation, is that the object has been displaced from its original

position by trawling activity. As noted earlier, the original survey report did note that a

piece of shrimp net appeared to be attached to the object, suggesting that it was acting as

a hang. The size of the object, about 13 by 26 feet, indicates that it might have been a

large box or tank of some sort. Although such an object might be heavy, it appears to be

of a size that could be dragged at least short distances when caught by a shrimp net.
5-40

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Figure 5-42. Magnetic contour map of Target 2, SM 19.

Target 5a, ST 20. The sidescan sonar survey of the target designated Target 5a

identified a hump or rise off the seafloor. It was impossible to determine if this was a

natural or a manmade feature. A magnetometer survey of this target location was

undertaken on October 8, 2001. The survey was conducted along seven track lines run in

a north-south direction over an area measuring 600-feet square (Figure 5-43). This

survey block was centered over the position of the identified seafloor feature and the

survey lines were spaced 100 feet apart.

The contour map of the recorded magnetics, shown as Figure 5-43, revealed only

a small, localized magnetic anomaly in the southeastern portion of the survey block. The

magnetic deflection of this anomaly was only 49 gammas and the fact that it was
5-41

recorded only on a single track line is suggestive of a small, isolated ferrous object. 

Despite its small size, a diver examined this anomaly. Examination involved the diver

searching the bottom while swinging in arcs across the target area, controlled by the dive

hose. The water depth at this target was 42 feet. Ultimately, a systematic search of an

area measuring 200 feet by 200 feet was covered around the small magnetic anomaly.

No objects were discovered.

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Figure 5-43. Magnetic contour map of Target 5a, ST 20 showing an absence of magnetic material

within the survey area.
5-42

Target 5b, ST 20. The magnetometer survey of Target 5b, the reported unknown

vessel and unknown object located in the northern portion of the Target 5 area, was

conducted on October 8, 2001. The sidescan sonar survey of this target revealed the

presence of a large number of linear objects on the seafloor. The position of these objects

was buoyed and a 600-foot-by-600-foot survey block was established around this point.

This block was surveyed with the magnetometer along seven track lines oriented in a

north-south direction and spaced 100 feet apart. The survey recorded a large magnetic

anomaly very close to the buoyed position at the center of the survey block (Figure 5-44).

The total magnetic deviation of this signature was 4,079 gammas and it covered an area

approximately 380 feet across. After completion of the basic magnetic survey, the target

area was refined with additional survey and a buoy was placed at the identified center of

the magnetic signature. During the refinement survey, fathometer records revealed an

object rising five or six feet above the seafloor at the magnetic anomaly. The water depth

at the target was 38 feet.

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Figure 5-44. Magnetic contour map of Target 5b, ST 20.
5-43

Once the target was buoyed, diving operations commenced. Within a few

minutes of reaching the bottom, the diver located a large number of iron or steel pipes

stacked on the seafloor. The pipes appeared to have diameters ranging from 10 to 12

inches. It was determined that the pipes were oriented in a north-south direction, but

their overall length was not ascertained. In some areas the pipes rose five to six feet into

the water column. A few pieces of one-inch-diameter rope, apparently entangled in the

pipes, were noted. The center of the pile of pipes was determined to be at state plane

coordinates N = 121990; E = 2327100.

All of the pipes had a layer of marine growth on their surface and it is presumed

that they represent pipeline or platform construction material or dredge pipe. How these

pipes got to this location is unknown. It is possible that they accidentally fell off an

offshore supply vessel or they may have been purposefully dumped to avoid appropriate

disposal procedures. Of some interest is the location of these pipes relative to the various

objects identified in the Target 5 area. The pipes are located at almost the exact position

of the reported unknown vessel and unknown object designated Target 5b. As noted

earlier, both of these items had been assigned a poor location reliability of 4 and it was

believed that both likely represented the same item, even though they appear as separate

entries in the computerized database of Non-Submarine Contacts maintained by the

National Imagery and Mapping Agency (see Table 5-1). The poor location reliability

was assigned to these items because the NIMA records provide no information regarding

the reliability of the coordinates for them. It is believed, however, that the “unknown

vessel” and the “unknown object” in NIMA records both refer to this pile of pipes and

that the coordinates given by NIMA are accurate. Exactly why the NIMA database lists

two different items at this location is unknown, but it is presumably because they had two

sources of information for the same position, one source calling it an unknown object and

the other an unknown vessel.

Also of interest relative to this pile of pipes are the several hang locations

designated as Target 5a. These hangs are clustered approximately 1300 feet south,

southwest of the pile of pipes, yet neither the sidescan sonar, magnetometer survey nor

the diving operations discovered anything at the Target 5a location. Hang records for the

Fisherman Contingency Fund obtained from MMS reveal that these hangs date from as

early as 1992, and it appears that all of the hang locations were originally recorded as

Loran coordinates. It is further believed that the slight variations in the reported positions

of the hangs is related both to the inherent inaccuracies in Loran and to how close to the

actual hang location the original Loran readings were obtained. Thus, it is believed that

the cluster of hangs identified as Target 5a likely represents a single object. Finally, it is

also believed that this single object producing the hangs is actually the pile of pipes

identified as Target 5b. The approximately 1300-foot difference between the positions of

the cluster of hangs and the pile of pipes is probably principally related to error in the

algorithm used to convert the Loran coordinates to latitude/longitude coordinates.

Target 9, SS 73. The magnetometer survey of Target 9, located in lease block

Ship Shoal 73, was conducted on October 7, 2001. The sidescan sonar survey of this

target had revealed the presence of a linear object tentatively identified as a trawl net (see
5-44

Table 5-2). As at the other target locations, a 600-foot-square survey block was

established over the identified target position and the magnetometer survey was

conducted along seven track lines spaced 100 feet apart and oriented in a north-south

direction. No discernable magnetic anomalies were recorded during the survey (Figure

5-45); however, it was decided to have a diver examine the target area to try to locate and

ascertain the identity of the feature identified by sidescan sonar. The water depth at the

target was 30 feet and the search procedures used were the same as described above. The

diver reported several apparent trawl net scars crossing the ocean floor, but no evidence

of the feature identified during the earlier sidescan sonar survey. If this object was, in

fact, a trawl net, it is likely to have drifted away from its original position or been

dragged away by shrimping activity.

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Figure 5-45. Magnetic contour map of Target 9, SS 73.
5-45

Target 14, VR 35. The magnetometer survey of Target 14, in lease block

Vermilion 35, was attempted on September 14, 2001, but equipment malfunctions

delayed the survey until October 12, 2001 (Figure 5-46). One reported hang and one

unknown vessel had been identified at this location and the sidescan sonar survey had

recorded three small rises on the seafloor whose identity could not be determined (see

Tables 5-1 and 5-2). A 600-foot-by-600-foot block was established around the center

point of the identified sidescan sonar target (state plane coordinates N = 279,269 E =

1,675,988) and the magnetometer survey was conducted along seven track lines spaced

100 feet apart and oriented in an east-west direction. Water depth at the target site was

approximately 30 feet.

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Figure 5-46. Magnetic contour map of Target 14, VR 35.
5-46

No magnetic anomalies of interest were recorded at this target; however, diver

examination of the bottom was undertaken in order to try to locate and identify the three

low mounds identified during the sidescan sonar survey. The previously described

bottom search techniques were employed that encompassed an area extending

approximately 100 feet on all sides of the identified target position. The diver reported a

smooth and flat bottom consisting of soft mud in the entire area searched. Neither the

three low rises nor any other cultural features or objects were discovered. It is suspected

that the three slight rises observed on the sidescan sonar are natural features that were too

low and indistinct for the diver to identify.

Target 15, VR 118. The magnetometer survey of Target 15, located in the

northwestern quarter of lease block Vermilion 118, was conducted on October 12, 2001.

The sidescan sonar survey of this target had identified a series of linear features at this

location, consisting of an approximately 45-foot long piece with several shorter linear

pieces crossing or extending off of it at various angles. The object could not be

identified, but its regular and geometric form suggested it was manmade. A 600-footsquare survey block was established over the target location and the magnetometer

survey was conducted along seven track lines spaced at 100-foot intervals and oriented in

a north-south direction. A single, large magnetic anomaly was recorded near the middle

of the survey block, centered very close to the position recorded for the target (Figure 5-

47). The magnetic signature consisted of a dipole measuring approximately 300 feet

across with a total magnetic deviation of 1,755 gammas.

Upon completion of the magnetometer survey the center of the magnetic anomaly

was determined through additional refinement survey and buoyed. The water depth at the

buoyed location was 65 feet. Diving operations were undertaken using the standard

procedures described earlier. On the bottom, very close to the buoy location, the diver

discovered a large amount of metal (steel?) cable, much of which was heavily encrusted

with marine growth. Just south of the cable, the diver identified a long piece of partially

buried pipe lying on the seafloor with an identifiable lip on the exposed end as well as a

three-inch-diameter eyelet and associated bolt. The pipe was tentatively identified as an

“outrigger” from a shrimp boat. Additional investigation of the possible outrigger

identified a substantial amount of shrimp net snagged along the object. The diver

proceeded down the presumed outrigger and discovered the side of a metal boat hull

located at state plane coordinates N = 164350 E = 1633370. The vessel appeared to be

lying on its side and it is believed to be the wreck of a modern shrimp trawler, probably

with a steel hull. A depth reading taken on the side of the hull revealed a depth of 57

feet, meaning that the hull rises about eight feet above the bottom.

Only a limited amount of time was available for diver examination of this target,

and dimensional information on the wreck was not obtained. However, there is no doubt

that it represents the remains of a shrimp trawler, probably a modern one. Target 15 had

originally been identified as an “unknown object” with a location reliability of 1, on the

basis of a previously conducted remote-sensing survey (see Table 5-1 and CEI ID

Number 408 in the 2001 shipwreck database). The identity of this vessel at Target 15 is

unknown; however, as shown above in Table 4-6, only one vessel in the 2001 shipwreck
5-47

database is reported to have been lost within 1.5 miles of its location. This is the fishing

vessel Castaway, which, according to USCG records, was lost in lease block Vermilion

119 about 6,050 feet (1844 m) away. The Castaway has been assigned a location

reliability of 2, meaning that its reported position is only moderately reliable (see CEI ID

Number 1325 in the 2001 shipwreck database). Little is known about the Castaway, but

its identification as a “fishing vessel” almost certainly means that it was a shrimp trawler,

like the vessel found at Target 15. The fact that the Castaway was likely a shrimp trawler

and that its reported position of loss is not precisely known means that it might be the

vessel at Target 15, but this cannot be confirmed with the data presently at hand.

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Figure 5-47. Magnetic contour map of Target 15, VR 118.
5-48

Target 17, EI 42. The magnetometer survey and diver investigation of Target 17

was conducted on October 14, 2001. This target originally had been identified as the

location of two hangs and one unknown vessel, the latter assigned a poor location

reliability of 4. The sidescan sonar survey of this target had revealed the presence of

numerous linear and sinuous parallel features that could not be identified. A buoy was

placed at the target coordinates and a 600-foot-square survey block was centered on this

location. The magnetometer survey of this block was accomplished along seven survey

lines spaced 100 feet apart and oriented in a north-south direction. As shown in the

magnetic contour map presented as Figure 5-48, a linear magnetic anomaly with a

magnetic deviation of 55 gammas was recorded near the survey block’s northwest corner.

The center of this magnetic signature was determined through additional survey and was

buoyed, and diving operations were conducted.

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Figure 5-48. Magnetic contour map of Target 17, EI 42.
5-49

The water depth at the buoy was 14.5 feet and visibility was minimal because the

water was heavily laden with silt due to high winds during the previous night. The diver

search of the target area followed the standard procedures described earlier and covered

an area extending just over 200 feet in all directions from the buoyed target center. No

cultural objects or features of any type were found during the search. The source for the

magnetic anomaly appears to be buried, but it may represent a single piece of metal pipe

or some other linear debris. This assumption is based on the anomaly’s linear appearance

and its relatively small magnetic intensity. The feature(s) recorded during the sidescan

sonar survey (see Figure 5-31) may not have been bottom features at all, but a large

school of fish or shrimp.

Target 17 is located in relatively shallow water where sediment transport can be

fairly high due to wave action and nearshore currents. Thus, the source of the magnetic

anomaly, which was buried at the time of the present examination, may be exposed at

other times. If so, it could represent the source object for the two hangs reported near its

location. Further, the now-buried object might represent the source of the report for the

“unknown vessel” located nearby. However, verification of either of these presumptions

would require excavation and exposure of the buried object.

Target 18, EI 53. The magnetometer and diver investigation of Target 18,

located in lease block Eugene Island 53, was undertaken on October 14, 2001. The

objects originally identified at this location had been a single hang and two unknown

vessels that had been assigned poor location reliabilities of 4 (see Table 5-1). The

sidescan sonar survey of this target revealed only what appeared to be a depression in the

seafloor (see Table 5-2). The position of this depression was buoyed and a 600-by-600-

foot survey block was established around it. The magnetometer survey of this block was

accomplished along seven track lines spaced at 100-foot intervals, oriented in a northsouth direction. No significant magnetic anomalies were recorded (Figure 5-49).

Diving was undertaken to try to locate and identify the “depression” seen on

sidescan records (see Figure 5-33). The water depth at the target location was 14.5 feet.

Diver examination involved the standard procedures discussed previously. The area

around the identified “depression” was completely examined, but no evidence of the

depression was found, nor were any cultural features or objects. The diver did note that

there were numerous areas of very “soft” sediment. It is possible that the depression

originally seen on sidescan sonar records was one of these area of soft sediments where

the sediments had been removed by current or wave action or had been dug out by the

board of a shrimp net.

5.2. Discussion

This chapter has presented the results of the final portion of Task 2 of this study,

the field investigation of a series of selected targets in the GOMR to determine their

identity. The overall objective of Task 2 was to determine if there were correlations

between a variety of objects identified in the GOMR, specifically hang sites, reported

shipwreck and targets identified during previous lease block remote-sensing surveys.
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Information on the spatial relationships of some of these classes of objects is presented in

Chapter 4. This information, plus published hang data and data from the 2001 shipwreck

database presented in ArcView format, was used in the selection of the 20 target areas

examined by remote-sensing survey and diving. One particular interest of this phase of

the study was the relationship between reported net hang locations and objects or

shipwrecks. As noted previously, several of the historic shipwrecks discovered in the

region are entangled with pieces of nets and ropes lost by fishermen, principally

shrimpers. Additionally, several thousand hang locations have been reported in the

GOMR. Thus, it is presumed that some unknown number of individual or, possibly more

likely, clusters of reported hangs represent historic shipwreck locations.

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Figure 5-49. Magnetic contour map of Target 18, EI 53.
5-51

The 20 target areas selected actually contained or represented 52 recorded “items”

that included 31 hangs, 12 unknown vessels, and nine unknown objects. The initial

sidescan sonar survey of the selected target areas revealed that only eight target areas

contained bottom features indicative of submerged cultural objects (see Table 5-2).

Because one target area, Target 5, was divided into two areas, 5a and 5b, this represented

nine target locations ultimately examined. Target inspection indicated that of the nine

potential targets, only one, Target 15, represented a shipwreck. Located in Lease Block

VR 118, Target 15 is identified as a modern, steel-hulled shrimp trawler unassociated

with any hangs listed in the MMS or Texas A&M databases. The only identified vessel

reported to have been lost in the near vicinity of Target 15 is the fishing vessel

(presumably shrimp trawler) Castaway, lost in 1983 at a reported position over a mile

away. However, the reported position of loss of the Castaway has been assigned only a

moderate level of reliability, meaning that the vessel found at Target 15 could be the

Castaway. The available information suggests that this vessel does not meet the criteria

for eligibility to the National Register of Historic Places (NRHP). Interestingly, this one

shipwreck was not associated with any of the hang locations maintained by MMS or

Texas A&M.

Of the remaining eight targets, one represented what is believed to be the remains

of a destroyed oil or gas platform, one consists of a large pile of metal pipe, while

nothing was found exposed on the bottom at the remaining six. However, magnetics at

one of these six targets, Target 17 in lease block Eugene Island 42, suggest the presence

of a buried object, possibly a piece of pipe.

Two of the items discovered during diving, the vessel at Target 15 and the

presumed platform remains at Target 1, represent objects identified during OCS lease

block surveys. As anticipated, both of these objects were very accurately positioned and

were discovered within a few feet of the position reported in the original survey.

Additionally, both of these objects rise several feet above the seafloor and could easily

hang shrimp nets; in fact, the vessel was entangled with a considerable quantity of net

and rope. However, neither of these targets represents reported hang locations. In fact,

nothing was found in the near vicinity of any of the reported hang locations examined.

These results raise several questions about the spatial relationship of reported hang

locations and objects on the bottom in the GOMR.

Probably most important is the accuracy of the reported hang locations. As has

been discussed, inaccuracies in reported hang locations can arise from a variety of

factors. These include the use of Loran for recording many of them and the fact that the

position of the snag on the bottom may not be the exact location where the person

actually recorded the position because of factors such as net length and boat movement as

the hang position was recorded. Additionally, the conversion of Loran coordinates into

other coordinate systems appears to embody inaccuracies. All of these factors may be in

play at the Target 5 location. As noted above, a large pile of iron pipe was found about

1,300 feet from a cluster of reported hangs. Diver examination of the area of the hangs

found nothing on the bottom, and it is believed that the pipes actually represent the source

of all of these hangs. The relatively slight differences in the locations of the individual
5-52

hangs may be due to inherent inaccuracies in the Loran system and to factors (e.g., boat

movement, net and net line length, etc.) preventing the fishermen from recording

coordinates directly over the hang location. This has resulted in a tightly grouped cluster

of reported hangs. However, this entire cluster is about 1,300 feet from the pipes that are

believed to represent the actual hang. This error appears to be related to the conversion

of Loran coordinates into the geographic coordinates (i.e., latitude and longitude) in the

MMS hang records and then into the state plane coordinates used during the survey and

diving operations reported here. It is presumed that if a Loran system had been used to

relocate Target 5, it in fact would have identified a point very close to the pile of pipes.

The error undoubtedly arises in the conversion from Loran to other coordinate

systems because no error is typically found in converting back and forth between

latitude/longitude and state plane systems. For example, during a recent attempt to

relocate an historic wreck originally positioned by Loran, Krivor (2002) reports several

hundred feet of error when converting from Loran to state plane coordinates, but very

little error when converting from state plane to latitude/longitude. It would appear that the

algorithms used to convert Loran coordinates need more study.

Another explanation that may account for the failure to discover some objects at

their reported coordinates is because they have been moved from their original locations.

This phenomena has been well documented in areas where shrimp trawling is common.

In a study in Mobile Bay, Irion (1986) found that 24 percent of anomaly positions

originally recorded could not be relocated. He attributed this to shrimpers catching and

moving the objects from their originally surveyed positions. Garrison et al. (1989:II-222)

reported a similar phenomenon in their study in the GOMR where 25 percent of

anomalies selected for ground truthing could not be relocated. Similar findings are

reported by Pearson and Hudson (1990:34) in Matagorda Bay, Texas; by Tuttle (1999) in

the Gulf of Mexico off Quintana, Texas; by Krivor (2000) off Rockaway, New York; and

by Tuttle and Krivor (2000) in Charleston Harbor, South Carolina.

In the present study, Target 2 in lease block South Marsh Island 19 might be a

case where the target object has been moved from its original location. As noted, the

unknown object at Target 2 consisted of a rectangular box identified during a previous

lease block remote-sensing survey (see Table 5-1). It is presumed that the object was

very precisely located; however, no evidence of this object was found during the sidescan

sonar survey of Target 2. The most reasonable explanation for not finding the box seems

to be that it has been moved from its original position. Interestingly, the original survey

report notes that an object tentatively identified as a piece of shrimp net was caught on

one side of the box. This suggests that the box did act as a snag for nets, although no

recorded hang sites are located in the near vicinity of Target 2 (see Figure 5-10). The

lack of reported hangs at this location might support the idea that the box was moveable,

and that when caught it shifted and nets came loose before they or the vessel’s rigging

were seriously damaged.

In the case of Target 5b, the pile of large-diameter pipes, we have been able to

clarify the identity and assigned position reliability factor. As noted, two items were
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reported at this position, an unknown vessel and an unknown object, both of which had

been assigned a poor position reliability factor of 4. The unknown vessel at this location

can be eliminated from the 2001 shipwreck database and the unknown object can be

assigned a location reliability of 1.

As noted, the relationship of reported hangs to shipwrecks is of particular interest

because it is believed that individual or clusters of reported hang sites might be useful as

indicators of unreported shipwrecks. Only one target, Target 15, was identified as a

wreck, albeit a modern trawler. The vessel has been very tentatively identified as the

Castaway, reportedly lost in 1983. However, while shrimp net was entangled on Target

15, it is not recorded as a hang location in the two sources of hang data used. In spite of

these findings, we know that hangs can and do represent historic shipwrecks. Two

examples include the 303 Hang site off the Texas coast and the remains of the El Nuevo

Constante off the Louisiana coast. The latter site represents the remains of an eighteenth

century Spanish merchantman located by a shrimper in 1980. Pearson and Hoffman

(1995:4) note that the shrimper, Curtis Blume, caught his nets on the wreck when he

“was dragging in the shallow, muddy waters about a mile offshore of the Rockefeller

Wildlife Refuge in southwestern Louisiana. This was only the second time Blume had

fished this particular spot; the local Louisiana shrimpers avoided the area because it was

known to contain a snag that damaged nets.” Subsequent excavation of the wreck

discovered numerous pieces of netting and rope entangled in the remains.

The second example is the 303 Hang wreck site. The site represents the intact

hull of a two-masted schooner that local Texas shrimpers know as the “303 Hang” in

reference to the Loran coordinates that identify the location as a net snag. Discovered

when a pipeline was built atop the wreck, the 100-foot wooden-hulled vessel sits upright

in 30 feet of water, but completely buried in the bottom. Designated state site 41BO173,

archaeological investigations revealed that shrimp netting was entangled on both the bow

stem and stern post (James et al. 1991b). One phenomenon observed at this site was that

it might have acted as a hang only seasonally. During the initial inspection of the site in

January, three feet of fine, silty sand covered the vessel, but when investigated in July,

the sand had disappeared, leaving the top edge of the hull visible. James et al. (1991b:31)

hypothesized that the sand had migrated over the wreck with the “summer being a period

of little or no sand coverage [and] with winter seeing a remigration and accumulation of

sands to the offshore areas. Snagged shrimp nets on both the stem and stern posts, along

with other modern debris in the hull, were noted during the January investigation,

suggesting that the wreck had undergone and was most likely still undergoing alternating

periods of exposure and coverage.” It is presumed that other wrecks and objects lying on

the bottom in other areas of the GOMR act as similar, seasonally exposed hangs.
6.0: COMPARISON OF MARINE MAGNETOMETER

TECHNOLOGIES AND SURVEY LINE SPACING - TASK 3

As stated in the SOW, the goals of Task 3 were: 1) a comparison of the “industrystandard” proton magnetometer (i.e., Geometrics 866) that is currently employed in

marine archaeological surveys to the current state-of-the-art cesium magnetometer to

determine if a change in the Minerals Management Service Gulf of Mexico Region

(GOMR) survey methodology is warranted; and 2) to evaluate both magnetometers at

various survey line spacings to determine the minimally acceptable survey line spacing

for detecting historic shipwrecks. To accomplish this task, magnetometer surveys would

be conducted over two known shipwrecks.

Ultimately, four magnetometer models were employed for this task, a Geometrics

866 (G-866), a Geometrics 877 (G-877), a Geometrics 881 (G-881), and a Marine

Magnetics SeaSpy (SeaSpy). While only two magnetometers were initially identified for

the study, discussions with the project geophysicist, S. Dean El Darragi, and MMS

personnel indicated that it would be beneficial to the project to field-assess other

magnetometer models in addition to the two currently identified in the contract for the

survey trials of Task 3. Two additional magnetometer types were identified that were

believed should be added to the Phase 3 survey. These included an Overhauser effect

proton magnetometer and the new G-877 proton precession magnetometer. The G-877 is

the replacement for the proton precession industry standards currently employed in the

Gulf, i.e., the Geometrics 801 and the 866 precession proton magnetometers. These latter

models, while still employed by many of the survey companies involved in the oil and

gas industry, are no longer being produced (as well as their respective parts), and are

being phased out by many firms. It was believed that employment of the G-877 would

contribute significantly to the project in that the assessment of magnetometer types in a

shipwreck survey mode would be a much more “up-to-date” study given the fact that the

current G-866 slated to be assessed against the cesium model is no longer being

produced. Relative to employment of the Overhauser type magnetometers, produced by

Marine Magnetics and others (i.e., GEM Systems), Overhauser magnetometers offer

similar sensitivity as the cesium magnetometers, particularly at moderate speeds (both the

cesium and Overhauser are more sensitive to magnetic deviations than their free

precession counterparts). Perhaps more germane to our study is the fact that these

magnetometers are and will be employed by Gulf survey companies on projects that will

have MMS purview. In conversations with FUGRO (John Chance and Associates), they

have stated that they will be replacing their aging proton precession units (the G-801 and

G-866) with newer Overhauser proton magnetometers. Therefore, the addition of these

two models offered to keep the study “up-to-date” and more reflective of systems

employed now and that will be employed in the future by oil and gas industry-related

companies.

Figures 6-1 through 6-4 illustrate the four magnetometers employed in this aspect

of the investigation. For a detailed discussion on magnetometer technologies and their

employment in the Gulf’s oil and gas industry, please refer to Appendix F.
Figure 6.2 The G-87

precessiomagnetomin Task 3.

Figure 6-3. Marine Magnetics’ “SeaSPY” Overhauser effect marine magnetometer used in Task 3.

Figure 6-1. While not completely obselete, the G-866 is no longer

being produced and is being replaced with newermodels by many companies.

Figure 6.4 G-881 cesi

magnetomin Task 3.
6-3

Besides the two additional magnetometers, it was also decided that a submersible

base station be tested to determine its applicability to offshore surveys as it might apply

to post-mission processing of magnetic data, especially with regard to surveys with line

spacing of 50-m. Mirroring the NTL 98-06, the new NTL 2002-01 requirements do not

stipulate the employment of base stations or contouring of magnetometer data. This is a

reflection of the fact that, apart from oil rigs or platforms which cannot be employed as a

suitable location because of their inherent magnetism, there is nowhere to place a base

station in offshore Gulf waters. Currently, the locations of encountered magnetic

anomalies are simply marked with a symbol (▲) and an identifying number, and

presented in tabular format with anomaly information including line number, shot point,

and coordinates. With regard to the latter, exact coordinates for the object creating a

magnetic anomaly are next to impossible to acquire when data is not contoured.

Contouring would in many cases locate the source of the anomaly exactly. Therefore, a

Sentinel® submersible base station was included in this task in an effort to assess its

functionality in the field, and answer questions concerning employment in offshore

surveys relative to issues of diurnal variation and the functionality of contouring.

6.1. In-Field Magnetometer Comparison Survey

6.1.1. Survey Research Design

The second aspect of Task 3 was to evaluate the four magnetometers at various

line spacings to determine the minimally acceptable survey line spacing for detecting

historic shipwrecks, as well as to determine if there are differences between the various

magnetometers in detecting a wreck site. To accomplish this task, the marine survey was

to be conducted with each magnetometer over two known shipwrecks at varying transect

intervals. The wrecks employed in the survey were the Josephine, an iron-hulled

sidewheeler, and the Rhoda, a wooden-hulled sailing ship. Both nineteenth century

wrecks, it was thought that surveying a wooden- and an iron-hulled vessel would

generate more comparative data relative to the detection of different types of wrecks, than

if two wrecks of the same hull composition had been selected.

6.1.1.1. Investigated Shipwrecks

The Josephine. The first vessel chosen for the assessment survey of

magnetometers and line spacing was the Josephine, a metal-hulled sidewheeler (Figure 6-

5). Investigated in 1997 and 1999 by divers from the MMS and designated state site

22Hr843, the shipwreck was identified as the remains of the nineteenth century merchant

steamship (Ball et al. 2001).

Built in 1868 for Charles Morgan at the Harlan and Hallingsworth shipyard in

Wilmington, Delaware, the Josephine was 235 feet long and 34 feet in breadth, with an

18.5 ft. depth of hold. Employed for over twelve years between Louisiana and Texas as a

passenger, mail, and cargo carrier, the vessel was reassigned to the New Orleans to

Havana route in January 1881. In February of that year, on its return to New Orleans the
6-4

vessel ran into severe weather and began to take on water. It eventually foundered south

of Biloxi, between Horn and Ship Islands, Mississippi. As stated by Ball et al.:

...the wreck lies in 38 feet of water, about six miles off the Mississippi Barrier

Islands. Though most of the lower hull of the wreck remains buried in sediment,

the upper hull, above the waterline, is no longer present. The most prominent

features of the vessel are the remains of the paddlewheels and the walking beam

engine, which has collapsed to the starboard side of the wreck. The walking

beam, a diamond-shaped feature mounted on an A-frame, connected the engine

piston to the eccentric of the paddlewheels. Several spokes are still present on the

paddlewheels, and both paddlewheel shafts are still mounted in their pillow

blocks. The remains of the smokestack and the boilers also lie nearby (Ball et al.

2001:134).

Figure 6-5. Image of the Josephine, a metal-hulled sidewheeler (courtesy of the Mariner’s Museum,

Newport News, Virginia).

As indicated by the acoustic image presented in Figure 6-6, the remains appear to

represent an extremely intact wreck site. Ball et al. state that:

...during the sinking process the Josephine’s iron hull remained intact. Soon after

the vessel sank the below-deck portion of the wreck filled with sand and mud,

preserving artifacts below the mudline. This shipwreck has remained undisturbed

for 120 years and represents a virtual time capsule from the year 1881. Even

though most of the ship’s exposed wooden features such as the wheel-house and

above-deck cabins have disappeared, the passengers’ and crew’s personal items,

the ship’s cargo below the main deck, and all of the mechanical components of

the ship’s steam engine would be well preserved (Ball et al. 2001:136).
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Figure 6-6. Acoustic image of the Josephine wreck site. Note the outline of

the hull, the paddlewheels, collapsed smoke stack and boilers

(as presented in Ball et al. 2001:136).

The Rhoda . The second vessel chosen for the assessment survey of

magnetometers and line spacing was the Rhoda, a Canadian-built wooden-hulled bark.

First recorded in 1991 by the Florida Bureau of Archaeological Research (BAR) and

designated state site 8ES1899 (Franklin et al. 1991), the site underwent preliminary

investigations in 2000 by the University of West Florida (UWF). Currently the Master

thesis topic for university student John Rawls, the majority of information for the Rhoda

comes from his research, including a recent paper presented at the Society for Historical

Archaeology Conference in Mobile, Alabama.

Built for Edmiston and Co. timber importers by William Russell in 1864 in

Quebec City, Quebec, Canada, she was 186 feet long, 33 feet in breadth, and 22 feet in

depth. Copper-clad and originally ship-rigged, she was re-rigged in 1873 as a bark. She

arrived in Pensacola in August of 1882, and while in port was driven across the bay

during a violent storm and capsized near Santa Rosa Island. Condemned and offered for

public salvage, it is uncertain to what extent if any salvage operations were conducted,

and the vessel disappeared from public record after being sold for $725 (Rawls 2001).

Recently investigated by UWF (Figure 6-7), as stated by Rawls:

The site encompasses an area of ca. 1170 square meters on the seabed. Many of

the ship’s architectural features are exposed above the bottom surface and exhibit

moderate preservation. These architectural features include timbers, two ballast

piles, a row of standing iron features, many iron ‘knees,’ and many unidentified

concretions. A possible galley stove which might be associated with the vessel is

located on the north end of the site (Rawls 2001).
6-6

Figure 6-7. Site plan for the Rhoda shipwreck (courtesy of John Rawls).

With the site containing numerous in situ artifacts such as ceramics, glass, and a

set of parallel rules for navigation, he goes on to state that “the site appears to be

moderately disturbed from years of commercial fishing activities (i.e., dragging of shrimp

nets). Also a popular fishing location, fishermen have deposited modern debris on the

site in efforts to artificially enhance its reef-like environment” (Rawls 2001).

6.1.1.2. Survey Requirement Parameters

The magnetometer comparative survey adhered to methodology currently

required by the MMS/GOMR Notice to Lessees (NTL) No. 98-06, Enclosure 1, Section

II, Data Acquisition Instrumentation, and Section III, Survey Parameters. Data

Acquisition Instrumentation and Survey Parameters employed are as follows:

• The sensor of the magnetometer must be towed as near as possible to the seafloor; a

distance of six meters (20 feet) or less is required.

• A mechanical or digital depth sensor must be attached to the magnetometer sensor,

and each survey line must be annotated with tow sensor depth and the start of the line

(SOL) and end of the line (EOL) times.

• Magnetometer sensitivity must be one gamma or less, with the data sampling rate not

to exceed one-second intervals. The use of the “zero-mode” setting is prohibited.

• Background noise level must not exceed three gammas peak to peak.

• The magnetometer sensor must be towed at a distance far enough astern that

precludes magnetic influence from the survey vessel.
6-7

• Navigation for the survey must be accomplished by using a state-of-the-art

continuous positioning system correlated to annotated geophysical records. The

navigation system must have an accuracy of five meters or less.

6.1.1.2.1. Survey Line Spacing

As stated, the survey would be conducted with each of the four magnetometers

over two known shipwrecks at varying transect intervals. Illustrated below in Figure 6-8

and Figure 6-9, two transect grids would be run with each instrument, one based on a 30-

meter parallel survey interval and a larger one based on a 25-meter parallel survey

interval, with the wreck coordinates at or near the center of the grid.

Figure 6-8. 25-meter survey interval grid with 19 tracklines to be run in a north to south

direction at four knots.
6-8

Presented in Figure 6-8, the large 25-meter survey interval grid was 600 meters

square and, employing the wreck coordinates as the center of the grid (Line 9), was

initially composed of 17 transects or lines spaced at 25 meters out to 150 meters and then

intervals were spaced at 200 and 300 meters. However, during field trials it was elected

to add two additional lines spaced at 25 meters to either side of Line 17 (i.e., 16 and 18)

to allow for complete coverage of a wooden barge located southeast of and in close

proximity to the Josephine. Illustrated in Figure 6-9, the 30-meter survey interval grid

was 150 meters square and was composed of transects spaced at 30 meters. Line 6

crossed the center of the wreck coordinates in this grid.

Figure 6-9. 30-meter survey interval grid with 11 tracklines to be run in a north to south

direction at both four and seven knots.
6-9

All surveys were to be run in a north/south direction beginning on either the west

or east side of the established grid. If a west to east direction was chosen for a starting

point on the grid, then all instruments were to employ this direction of grid survey. Both

grids were to be surveyed with each instrument at a constant four-knot vessel speed.

However, the 30-meter survey interval grid was again to be surveyed at seven knots with

all instruments. With respect to the survey, a total of three grids were to be run with each

instrument, both a 25- and a 30-meter survey interval grid, each at four knots, and a 30-

meter survey interval grid at seven knots.

It should be understood that the employment of a 25-meter survey interval in the

25-meter survey interval grid was not intended to address issues of a 25-meter survey

interval increment (i.e., 25-meter versus 30-meter versus 50-meter). Rather, during post

processing and analysis the employment of a 25-meter interval allowed the 50-meter

survey interval grid to be shifted to the right or left by 25 meters in an effort to determine

if the wreck site would fall outside of or go undetected by the 50-meter interval.

6.1.1.2.2. Base Stations

Mirroring both the NTL 98-06 and the new NTL 2002-G01 requirements, the

SOW did not stipulate the employment of base stations or contouring of magnetometer

data. As stated above, this is a reflection of the fact that, apart from oil rigs or platforms

which cannot be employed as a suitable location because of their inherent magnetism,

there is nowhere to place a base station in offshore Gulf waters. However, besides testing

two additional magnetometers, it was also decided that a submersible base station be

tested to determine its applicability to offshore surveys as it might apply to post-mission

processing of magnetic data, especially with regard to surveys with line spacing of 50-m.

Because a Sentinel® submersible base station was included in this task in an effort to

assess its functionality in the field, and answer questions concerning employment in

offshore surveys relative to issues of diurnal variation and the applicability of contouring,

land base stations were also included to provide comparative base station data. Listed

below, two land-based base stations and one submersible base station were to be

employed. They included:

• Marine Magnetics’ “Sentinel Sub-Sea” submersible base station

• Marine Magnetics’ “Land Sentinel” land-based base station

• Geometrics land-based base station

Each company’s land station was to be employed during the survey with their

respective magnetometer. Marine Magnetics’ “Sentinel Sub-Sea” submersible Base

Station would be employed for the duration of the survey. For the Pensacola survey, the

land base station was placed at Fort Pickens. For the Biloxi survey, the base station was

placed on Ship Island. Both administered by the National Park Service, permits were

acquired from the Gulf Shores National Seashore for land base station placement.
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6.1.1.2.3. Navigation/Positioning

It was proposed that navigation during the grid survey would be accomplished

with a Trimble AG132 DGPS linked to a navigation and data logging computer running

Hypack MAX software for navigation and data archiving. An SG Brown Gyro would

also be used to accurately determine sensor lay-back. State Plane coordinates, based on

the 1983 North American Datum (NAD 83) coordinate system, were used for this project.

6.1.1.2.4. Post Survey Data Analysis and Presentation

The Research Design proposed that analysis and presentation of data was to

initially consist of:

• Strip chart examples for each instrument on each shipwreck will be produced for each

survey grid of varying line space.

• Production of tables of recorded data (gamma strength, duration, line spacing, sensor

depth, vessel speed, etc.).

• Contour maps from data generated by each magnetometer for each survey grid of

varying line space.

Furthermore, analysis and presentation of data would be directly related to

addressing questions concerning instrumentation and survey parameters. Questions to be

addressed included but were not limited to the following:

• Magnetometer Type – While we realize that certain magnetometers are more

sensitive than others (i.e., cesium versus proton), we need to determine how each

magnetometer type detects the same wreck site with regard to signal strength and

duration. Employing strip charts and magnetic contour maps for each instrument,

maximum gamma deviation and duration will be analyzed and compared with one

another.

• Line Spacing – What is the maximum/minimum line spacing or interval that allows

detection of the wreck by each instrument? With the two grids we will be able to

assess how each instrument detects each wreck site employing a 30-meter survey

interval, a 25-meter survey interval, a 50-meter survey interval, a 100-meter survey

interval, a 150-meter survey interval, and a 300-meter survey interval. Employing

strip charts and magnetic contour maps for each instrument, maximum gamma

deviation and duration will be analyzed and compared with one another for each grid

interval.

• Vessel Speed – Do increased speeds affect ability of instruments to detect a wreck,

and/or how are increased speeds reflected in the recorded maximum gamma deviation

and duration of a known wreck site? As stated, both grids will be surveyed with each

instrument at a constant four knot vessel speed. However, the 30-meter survey
6-11

interval grid will again be run at seven knots. Employing strip charts and magnetic

contour maps for each instrument, signal strength and duration will be analyzed and

compared with one another to address questions regarding increased survey speeds,

including speed relative to increased noise.

• Diurnal Variation – Is diurnal variation sufficient to affect the interpretation of

magnetic data, especially in the evaluation of a magnetic signature relative to the

possibility of it representing a shipwreck? And does adjusting for diurnal variation

affect, enhance, or alter magnetic signatures and their subsequent interpretation in

these settings? Additionally, is there a difference between employment of data from

the land-based and submersible base station readings? These questions will be

addressed by comparing strip charts, magnetic contour maps, and tabular signal

strength and duration data that:

• Is in its original and unsmoothed format.

• Has been “smoothed” with base station readings, both from the land-based and

submersible stations.

• Has been “smoothed” with an averaging program without the use of base station

readings.

• Shipwreck Signatures – It is possible that the magnetic signatures of relatively intact

wrecks, as might be expected in much of the GOMR, will not produce the complex

signatures commonly found at dispersed wreck sites in high energy environments,

like surf zone settings. Wreck sites in the offshore GOMR may more typically

produce relatively simple magnetic signatures. Therefore, will recorded magnetic

signatures match those previously described by Garrison et al. (1989) and derived

from earlier work? Employing strip charts, tabular data, and magnetic contour maps,

signatures will be analyzed and compared with earlier findings/hypotheses to address

this question, as well as to more specifically characterize the magnetic signature/s of

historic vessels in the GOMR.

6.1.2. Survey Methodology

The methods employed during the Task 3 survey were the same during the entire

project. Regardless of the vessel utilized, all survey equipment was set up first, including

the Trimble AG132 GPS unit, the SG Brown Meridian gyrocompass and all associated

navigation computers. In an effort to provide accurate navigation, the current edition of

Hypack MAX (Version 5b) was used to create the 25-m survey interval grids and the 30-

m survey interval grids over each respective wreck site. Refer to Appendix G for a

detailed discussion of the survey equipment employed during this aspect of the

investigation.

Coordinates for the Josephine were provided by the MMS while the coordinates

for the Rhoda were provided courtesy of the University of West Florida’s Program in

Underwater Archaeology. Wreck locations were forwarded onto VPSI at which time the

survey grids were established.
6-12

Base Stations. Base stations, two land-based and one underwater unit, were

employed for the duration of the survey to address diurnal variation. The two land-based

stations were the Geometrics 856 and the Marine Magnetics Sentinel Base Station. The

underwater base station was the Marine Magnetics Sentinel Sub-Sea Base Station.

Suitable locations for the land base stations were found prior to the survey. The

initial location for the land base stations in Pensacola, Florida was located on the barrier

islands near Fort Pickens. While this location was suitable for the base stations and was

approximately one mile from the Rhoda, personnel from Geometrics were concerned

about the location’s close proximity to the seashore. It has been speculated that

placement of a base station in close proximity to an active surf zone may affect localized

changes in the Earth’s magnetic field due to tides, the conductive property of sea water,

and the possibility of electrical currents in the sea water. These factors may cause

inaccurate readings that do not reflect the general time variations in the magnetic field

(George Tait, personal communication September 2002). To alleviate any potential data

problems, the land base station location was moved on June 23, 2001 to Perdido Key,

located west of Fort Pickens. This area, situated further from the seashore, allowed for

easy access for base station deployment. The following table indicates the location of

both the land base stations for both Pensacola and Biloxi (Table 6-1).

Table 6-1. Land Base Station Coordinates During the Task 3 Survey

Location Northing Easting

Pensacola, FL. – Fort Pickens 3354141 477676

Pensacola, Fl. – Perdido Key 3350811 454637

Ocean Springs, MS. – Gulf Islands National Seashore 3363291 327954

(All coordinates provided in UTM 16, NAD27)

The land base station location for the Josephine was originally going to be set up

on Ship Island, one of the barrier islands located offshore the Mississippi coastline.

While this location would have been suitable, time constraints getting to Ship Island (via

the survey vessel) and setting up the equipment were not feasible. An additional location

was decided upon at the Gulf Islands National Seashore, located immediately east of

Ocean Springs, Mississippi (Figure 6-10). This location was easy to reach prior to survey

each morning and was relatively free of magnetic interference.

Each base station was set up prior to each day’s remote-sensing survey.

Technicians from Geometrics as well as Marine Magnetics were responsible for setting

up each base station prior to survey work each day (Figures 6-11 and 6-12). A field

technician from Panamerican watched the instruments each day to discourage any

tampering with the equipment. At the end of each day each base station was shut off and

the data downloaded to computer. Data collected every day was then provided to

Panamerican at the end of the survey.
6-13

Figure 6-10. Gulf Islands National Seashore near Oceans Springs,

Mississippi provided an excellent location for the land

base stations.

 Figure 6-11. Geometrics’ G-856 land base station ready to

 collect data at Perdido Key, Florida.
6-14

Figure 6-12. Marine Magnetics Sentinel base station being readied to collect data in Perdido Key,

Florida.

Research Permits. To comply with Federal and state research requirements,

non-intrusive permits were obtained from both the United States Department of the

Interior (National Park Service) and the Florida Department of State (Division of

Historical Resources, Bureau of Archaeological Research). A Scientific Research and

Collecting Permit (Study #GUIS-00012, Permit #GUIS-2001-SCI-0011) was issued for

the survey, allowing for the placement of land base stations within the Gulf Islands

National Seashore.

Additionally, a non-intrusive research permit was granted for survey work over

the Rhoda (1A-32 Archaeological Research Permit Number 0001.38 Comparison of

Marine Magnetometer Technologies, 8ES2994) by the Florida Department of State,

Division of Historical Resources, Bureau of Archaeological Research. Each permit was

provided to the appropriate land-managing agency prior to survey and was carried at all

times by Panamerican personnel during field work.

Survey Vessels. Due to vessel availability, weather conditions, and

environmental constraints, it was necessary to use a number of vessels during Task 3

remote-sensing operations. Beginning in Pensacola, Florida on June 21, 2001, the first

vessel used during the task was provided by AAA Fishing Charters, based out of Perdido

Key, Florida. The vessel was the Quester, a 40-foot charter boat with a 13-foot 6-inch

beam. Although the vessel was suitable for remote-sensing operations, its draught and

the presence of a shoal at the south end of the Rhoda’s 25-meter survey interval grid

prompted a change in survey vessels when operations reconvened later in the year.
6-15

Moving to the Josephine site on June 25, 2001, all equipment was again set up

and calibrated aboard the Miss Hospitality, a 51-foot long, 16-foot wide charter boat

equipped with twin V8 diesel engines (608 horsepower). Since the wreck of the

Josephine was approximately 12 miles off Biloxi, Mississippi, this boat was ideally

suited for offshore survey work. An air-conditioned cab helped keep all electronics dry

and cool during the running of the survey.

Returning to the Rhoda site on October 1, 2001 to finish the Task 3 survey, a

more suitable survey vessel was located, considering the presence of a notable shoal at

the south end of the 25-meter survey interval grid. Provided by Undertow Marine

Towing of Pensacola, the Undertow III was a 32-foot long crew boat with a 12-foot beam

and a 4.7 foot depth of hold (Figure 6-13). The vessel, powered by an 871 Detroit diesel,

had ample rear deck space and an enclosed cabin to protect all electronics. This vessel

was also employed when the survey reconvened at the Josephine site.

Figure 6-13. 32-foot charter boat Undertow III, based out of Pensacola, Florida.

6.1.3. Daily Survey Procedures

After setting up the navigational equipment and land base stations, the appropriate

magnetometers were brought onboard the respective survey vessel, depending on which

was to be used that day (Figure 6-14). Once established which instrument(s) would be

run, the survey vessel proceeded to the appropriate wreck site to begin running tracklines.

The following table represents the schedule during Task 3 operations (Table 6-2).
6-16

Figure 6-14. Stern of the vessel Quester being readied for daily survey. All instruments were

typically brought onboard each day.

Table 6-2. Schedule of Task 3 Operations

Date Wreck Site Instrument Survey Interval Grid

completed

Comments

6/21/01 Mobilization

6/22/01 Rhoda G-881 25-m., 30-m. 4knt.

6/23/01 Rhoda G-881

SeaSPY

30-m. 7 knt.

25-m.

6/24/01 Rhoda SeaSPY

G-877

30-m. 4knt.,

30-m. 7 knt.

 25-m.

6/25/01 Josephine G-881 25-m., 30-m. 4knt.,

30-m. 7 knt.

6/26/01 Josephine G-877 25-m., 30-m. 4knt.,

30-m. 7 knt.

6/27/01 Josephine SeaSPY None Adverse weather

6/28/01 Demobilization

9/26/01 Josephine Mobilization

9/27/01 Josephine SeaSPY 25-m., 30-m. 4knt.,

30-m. 7 knt.

9/28/01 Josephine G-866 None Blown G-866 bulkheads

9/29/01 Josephine G-866 25-m., 30-m. 4knt.,

30-m. 7 knt.
6-17

Table 6-2. (continued). Schedule of Task 3 Operations

Date Wreck Site Instrument Survey Interval Grid

completed

Comments

9/30/01 Travel

10/01/01 Rhoda G-866

G-877

25-m., 30-m. 4knt.,

30-m. 7 knt.,

30-m. 4knt.,

30-m. 7 knt.

10/02/01 Travel

Underwater Base Station. Upon reaching the survey area, the first objective was

to deploy the Marine Magnetics Underwater Sentinel Base Station. Placed within a half

mile of the 25-meter grid, the Sentinel base station was deployed each morning prior to

running track lines and then retrieved at the end of the day before returning to the dock

(Figure 6-15).

Figure 6-15. Deploying the Marine Magnetics Sentinel base station near the wreck of the Rhoda,

Pensacola, Florida.

The Sentinel base station was rigged with a concrete block that acted as a weight,

keeping the instrument on the seafloor. A buoy rigged to the top of the Sentinel base

station kept the instrument vertical in the water column and provided positive flotation to

the unit(s) when released to the surface (Figure 6-16).
6-18

Figure 6-16. The Marine Magnetics Sentinel underwater base station prior to daily deployment.

Attached to the concrete block was a release mechanism produced by EdgeTech

Communication and Control Products Group (EdgeTech). Referred to as a Coastal

Acoustic Release Transponder (CART), this mechanism allows for equipment to be

placed on the seafloor and retrieved (at the surface) when an acoustic signal is sent to the

unit (Figure 6-17).

Figure 6-17. The EdgeTech Coastal Acoustic Release

Transponder (CART).

This unit is designed for applications from the surf zone through the continental

shelf (to a depth rating of 1,000 meters) and can release up to 500 kg. EdgeTech utilizes

alkaline batteries (with a long life option for extended deployments), providing 1 1/2

years of operation. To release the CART, in effect sending the Sentinel base station to
6-19

the surface (where it was recovered after each day of survey), an EdgeTech AMD200

Deck Unit Command Transmitter was used (Figure 6-18). Lightweight and durable, the

AMD200 is capable of transmitting all EdgeTech commands using a Binary Acoustic

Coding System (BACS). Small, reliable, and self-contained, this system utilizes a Binary

FSK-1 6,11 block cyclic code with 12,000 unique command codes.

Figure 6-18. EdgeTech AMD200 Deck Unit Command Transmitter used to transmit a unique

code to the CART.

At the end of each day of survey, a unique code was typed into the AMD200 after

placing a transponder over the side of the survey vessel into the water (Figure 6-19). The

acoustic release on the CART would then be triggered, sending the CART, Sentinel Base

Station and float to the surface (Figure 6-20). One exception to the Sentinel being

recovered at the end of each day occurred on September 27, 2001. After using the

AMD200 transmitter to recover the Sentinel base station, the unit did not return to the

surface. The unit remained on the seafloor until the afternoon of September 29, 2001

when it was recovered by a Panamerican diver. After manually recovering the base

station, it was observed that the release mechanism failed to disengage after the AMD200

signal was sent to the unit from the survey vessel, apparently due to a damaged internal

component.

It was speculated that the unit was damaged when the elasticity in the release

assembly bounced the concrete anchor up, in effect rendering the release useless.

EdgeTech indicated that the unit’s internal structure was not as strong as usual since the

unit used during the Task 3 operations was a prototype. The current release mechanisms

produced by EdgeTech are apparently much stronger than the prototype (Doug Hrvoic,

personal communication May 2002).
6-20

Figure 6-19. AMD200 transponder ready to place in the water.

Figure 6-20. Recovery of the Marine Magnetics Sentinel underwater base station, EdgeTech CART,

and float after finishing a day of survey.
6-21

Survey Track lines. Once the position of each wreck was determined, a series of

track lines was then created with Hypack MAX. The appropriate interval offsets (25-

meter interval, 30-meter interval) were applied to the respective grids, providing the

necessary coverage for the survey.

The appropriate magnetometer was readied for operations after deploying the

Sentinel underwater base station. Each towfish was set up prior to deployment on the

stern of the survey vessel and readied for survey (Figure 6-21). After water depth over

the wreck site was determined, the appropriate amount of cable was let out and the survey

vessel was brought up to speed (four or seven knots). After enough cable was let out to

satisfy MMS requirements, the running of survey lines began (Table 6-3), starting west of

each grid and proceeding to the east over both vessels.

Figure 6-21. Geometrics 877 being prepared for survey.

Table 6-3. Instrument Layback

Instrument Rhoda Josephine

G-866

25-meter SI* grid 80’ (24.4m) 132’ (40.2m)

30-meter SI grid, 4 knot 80’ (24.4m) 132’ (40.2m)

30-meter SI grid, 7 knot 110’(33.5m) 180’ (54.8m)

G-877

25-meter SI grid 120’ (36.6m) 240’ (73m)

30-meter SI grid, 4 knot 120’ (36.6m) 240’ (73m)

30-meter SI grid, 7 knot 135’ (41m) 300’ (91.5m)
6-22

Table 6-3. (continued). Instrument Layback

Instrument Rhoda Josephine

G-881

25-meter SI grid 75’ (22.8m) 170’ (51.8m)

30-meter SI grid, 4 knot 75’ (22.8m) 170’ (51.8m)

30-meter SI grid, 7 knot 100’ (30.5m) 220’ (67m)

SeaSPY

25-meter SI grid 150’ (46m) 125’ (38m)

30-meter SI grid, 4 knot 150’ (46m) 125’ (38m)

30-meter SI grid, 7 knot 150’ (46m) 222’ (68m)

*SI = Survey Interval

All magnetometers used during the Task 3 survey were equipped with depth

sensors, allowing all to be towed at the required depth of 20 feet or less (from the

seafloor) as stipulated by MMS survey parameters. During the survey the depth of each

towfish was constantly monitored to comply with these survey standards.

The Geometrics 881, the Geometrics 877, and Marine Magnetics SeaSPY were

equipped with internal sensors, allowing the depth to be monitored digitally during each

track line. The Marine Magnetics SeaSPY unit also employed an altimeter, allowing for

the operator to view the distance of the towfish from the ocean floor (Figure 6-22).

Figure 6-22. The Marine Magnetics SeaSPY magnetometer being deployed. Note the cylindrical

altimeter sensor near the nose of the towfish.
6-23

Combined use of the depth sensor and altimeter data can provide users with a

bathymetric image of any given survey area. The depth sensor input from each of these

instruments was recorded as a separate stream of data, allowing for the vertical position

of the towfish within the water column to be determined at any location within a grid.

The Geometrics G-866 was not equipped with an internal depth sensor; rather, an

attached unit was mounted approximately three feet up the cable from the sensor (0.5%

100 psig sensor for 150’ max. water depth). This sensor is equipped with an HSP LCD

digital readout (with RS-232 output and zero/span adjust) that is easily viewed during the

running of track lines (Figure 6-23). Depth readings were then recorded on the G-866

stripchart for review later during data processing.

Figure 6-23. Digital readout used to monitor the G-866 sensor depth during the Task 3 survey.

Prior to any Task 3 field work the original survey research design (prepared by

Panamerican) outlined the survey parameters to be followed during operations. These

parameters included vessel speed, line spacing, survey grid size, and towfish depth.

While this research design was strictly adhered to during the survey, one addition was

made while in the field. While underway to the Josephine, Rik Anuskiewicz and Captain

Kenny Barhanovich recalled the presence of an additional wreck within the 25-meter

survey interval grid. This wreck consists of a barge identified during the preliminary

remote-sensing survey conducted by the MMS of the Josephine (Figure 6-24).

Since the wreck represents another example of a vessel type found within the

GOMR, it was decided to obtain the coordinates of the wreck from the MMS. The wreck

was then plotted within the existing 25-meter survey interval grid. Plotting the

coordinates of the barge placed it very near the 200-meter offset on the southeast corner

of the 25-meter survey interval grid. To collect additional magnetometer data from the

barge, two track lines were added to the existing 25-meter survey interval grid. These

lines, spaced 175-meters and another placed at 225-meters from the zero line, in effect
6-24

boxed in the extent of the barge and increased the total number of lines run over the

Josephine from seventeen to nineteen.

Figure 6-24. Sidescan sonar image of the barge located near

the wreck of the Josephine (courtesy of

MMS/GOMR).

6.1.4. Post-Survey Data Processing

The system for post-survey data processing for the Rhoda and the Josephine

wrecks was the Coastal Oceanographics’ Hypack Max Version 5b program. The data for

each magnetometer was viewed in the raw format. All spikes and extra tails on the end

of the grid lines were edited out and the remainder then saved into an edited format.

Once in the edited format a graph was prepared, as well as a graph for the base stations

(Marine Magnetics, Sentinel land base station, Marine Magnetics underwater Sentinel

base station, and the Geometrics G-856 base station). All grids were then separated into

separate line files in an Excel format for further line comparison and data quality. Each

line file was then processed by line and graphed for a visualization of data, allowing for a

complete and thorough review of each track line of data as well as the inspection of any

anomaly signatures. Maximum and minimum gamma signatures were closely examined

as well as magnetic signature duration, and positioning data (i.e., northings and eastings).

6.2. Survey Results

As described above, all four magnetometers were run on three grids over two

shipwrecks in an effort to determine how each instrument detected that same wreck site

with regard to maximum gamma deviation and duration. It should be stated that this

aspect of the investigation was not a contest to determine which instrument recorded the

highest gamma amplitude or deviation at the greatest spaced interval, nor was it a

controlled laboratory experiment where a sensor could be pulled past a piece of iron of a

known mass along an unwavering track spaced at an exactly known distance unaffected

by wind or current. Rather, it was a field trial conducted to simulate an actual survey
6-25

environment, with the Josephine situated in a high-current, open-ocean location and the

Rhoda in a somewhat protected bay environment, and to assess how each instrument

recorded the same wreck site, and if differences were present, determine if these findings

predicated changes to the current MMS/GOMR survey methodology.

6.2.1. Magnetometer Amplitude Comparisons

Basic magnetometer data for each instrument is presented in a number of graphic

and tabular formats that illustrate differences in gamma amplitude or deviation and

duration. Figures 6-25 through 6-27 are line graphs for the 25-meter survey interval grid,

the 30-meter survey interval grid, and the 30-meter survey interval 7-knot grid

respectively, that represent the total gamma deviation or amplitude for each instrument

over the Josephine wreck site by track line. Table 6-4 lists maximum, minimum, and

total gamma deviation for each of the various instruments, again by numbered track line

for each of the survey grids over the Josephine. Similarly, Figures 6-28 through 6-30 are

line graphs for the 25-meter survey interval grid, the 30-meter survey interval grid, and

the 30-meter survey interval 7-knot grid respectively, that represent the total gamma

deviation for each instrument over the Rhoda wreck site by track line. Table 6-5 lists

maximum, minimum and total gamma deviation for each of the various instruments,

again by numbered track line, for each of the survey grids over the Rhoda.

Accompanying comparative strip charts for each instrument by line for the various grids

for each wreck are presented in Appendices I-N.

Beginning with the Josephine grids, two wrecks are actually represented in the

Josephine 25-meter survey interval grid: the Josephine, which is the much larger

anomaly, and a smaller anomaly produced by the wreck of a (suspected?) wooden barge

located several hundred feet away to the east, southeast. Both the graph in Figure 6-25

and Table 6-4 reveal that over the center of the wreck (Line 9), the G-877 magnetometer

had the largest gamma deviation (13,442), with the SeaSPY having a similar but slightly

lower reading (12,371), followed by the G-881 (9,068) and then the G-866 at 6,639

gamma. The same order occurred over the barge, with the highest deviation recorded by

the G-877 at 4,682 gamma, followed by the SeaSPY at 4,088 gamma, the G-881 at 3,379

gamma, and then the G-866 at 1,879 gamma.

In gross gamma deviation, all four instruments detected the wreck site with large

readings beginning with Line 7 through 11, with the highest readings at Lines 9 and 10

respectively. As indicated by Line 8, the G-877 had a much larger initial gamma

perturbation/detection rise. However, this reading, as well as a similar occurrence for the

G-881 on Line 18 on the barge wreck, may be a result of a minor track line variation

between sensors that is discussed below. While the readings from all instruments

represent large magnetic anomalies for both wrecks in this grid, it is interesting to note

that the G-877 appears at first glance to be the most sensitive with respect to gamma

deviation, a surprising finding given that its sensitivity is theoretically below that of the

Overhauser and cesium sensors (see above discussion). However, as the following

illustrations and tables indicate, there is some variation in which instrument records the

highest deviation.
Figure 6-25. Josephine 25-meter survey interval grid total gamma deviation graph.
Figure 6-26. Josephine 30-meter survey interval 4-knot grid total gamma deviation graph.
Figure 6-27. Josephine 30-meter survey interval 7-knot grid total gamma deviation graph.
Figure 6-28. Rhoda 25-meter survey interval grid total gamma deviation graph.
Figure 6-29. Rhoda 30-meter survey interval 4-knot grid total gamma deviation graph.
Figure 6-30. Rhoda 30-meter survey interval 7-knot grid total gamma deviation graph.
6-32

Table 6-4. Josephine Line Data for All Grids and Instruments

JOSEPHINE 25-METER SURVEY INTERVAL GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)*

1 49136 49130 49150 20 N/A

2 49136 49131 49139 8 N/A

3 49134 49120 49160 40 N/A

4 49131 49110 49139 29 N/A

5 49131 49113 49138 25 347’

6 49131 49106 49142 36 387’

7 49131 48993 49142 149 364’

8 49133 48030 50641 2611 537’

9 49132 47367 53237 5870 534’

10 49135 45986 52625 6639 587’

11 49135 48925 49148 223 439’

12 49137 49056 49142 86 449’

13 49138 49116 49141 25 347’

14 49140 49124 49142 18 72’

15 49140 49099 49144 45 186’

16 49141 48991 49159 168 321’

17 49142 48356 50235 1879 511’

18 49143 48946 49197 251 288’

19 49143 49135 49161 26 N/A

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49268 49265 49270 5 N/A

2 49263 49260 49262 2 N/A

3 49263 49259 49261 2 N/A

4 49256 49209 49412 203 95’

5 49246 49200 49246 46 272’

6 49240 49198 49247 49 442’

7 49244 49121 49245 124 419’

8 49245 44039 50609 6570 537’

9 49249 37186 50628 13442 564’

10 49256 40336 50433 10097 570’

11 49264 48803 49269 466 288’

12 49248 49174 49250 76 390’

13 49250 49231 49261 30 678’

14 49241 49213 49327 114 249’

15 49242 49204 49254 50 268’

16 49246 48938 49266 328 302’

17 49247 45581 50263 4682 367’

18 49253 48967 49289 322 275’

19 49257 49256 49258 2 N/A

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49252 49251 49253 2 N/A

2 49251 49258 49260 2 N/A

3 49263 49259 49264 5 N/A

4 49267 49172 49277 105 114’

5 49269 49257 49270 13 223’

6 49271 49242 49271 29 311’
6-33

Table 6-4. (continued). Josephine Line Data for All Grids and Instruments

JOSEPHINE 25-METER SURVEY INTERVAL GRID

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)*

7 49273 49163 49274 111 334’

8 49272 48199 50728 2529 577’

9 49268 47107 56137 9030 547’

10 49266 46212 52701 6489 505’

11 49262 48808 49311 503 265’

12 49257 49179 49259 80 259’

13 49267 49243 49269 26 350’

14 49270 49252 49336 84 124’

15 49273 49243 49273 30 62’

16 49276 49169 49286 117 160’

17 49271 47677 51056 3379 350’

18 49275 48623 50131 1508 318’

19 49274 49271 49277 6 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49256 49255 49257 2 N/A

2 49218 49216 49219 3 N/A

3 49218 49211 49220 9 285’

4 49219 49184 49221 37 482’

5 49219 49207 49220 13 485’

6 49222 49193 49221 28 528’

7 49222 49111 49223 112 613’

8 49224 48369 49805 1436 541’

9 49220 46708 59079 12371 810’

10 49220 45680 53863 8183 695’

11 49219 48803 49251 448 557’

12 49221 49159 49222 63 721’

13 49219 49192 49221 29 695’

14 49219 49200 49252 52 780’

15 49217 49182 49218 36 649’

16 49217 49013 49259 246 373’

17 49218 47345 51433 4088 387’

18 49216 48834 49350 516 426’

19 49216 49213 49218 5 N/A

JOSEPHINE 30-METER SURVEY INTERVAL 4 KNOT GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49143 49134 49175 41 N/A

2 49143 49125 49150 25 N/A

3 49146 49126 49162 36 226’

4 49147 49066 49154 88 360’

5 49145 48375 50847 2472 413’

6 49151 47648 53276 5628 442’

7 49153 48340 50363 2023 311’

8 49155 49005 49158 153 305’

9 49156 49128 49157 29 209’

10 49156 49136 49175 39 193’

11 49154 49116 49166 50 229’
6-34

Table 6-4. (continued). Josephine Line Data for All Grids and Instruments

JOSEPHINE 30-METER SURVEY INTERVAL 4 KNOT GRID

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49253 49258 49260 2 n/a

2 49261 49247 49261 14 68’

3 49264 49240 49264 24 141’

4 49265 49161 49266 105 288’

5 49266 47382 51285 3903 396’

6 49267 39352 50724 11372 472’

7 49269 43579 50304 6725 324’

8 49268 49055 49261 206 301’

9 49269 49234 49269 35 213’

10 49279 49252 49285 33 85’

11 49268 49227 49269 42 226’

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49269 49264 49270 6 N/A

2 49270 49254 49270 16 N/A

3 49272 49251 49272 21 N/A

4 49276 49188 49276 88 288’

5 49278 48043 50873 2830 350’

6 49268 47119 55993 8874 476’

7 49271 47719 52191 4472 488’

8 49274 49083 49274 191 231’

9 49277 49253 49277 24 226’

10 49279 49261 49322 61 N/A

11 49281 49247 49285 38 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49193 49185 49199 14 N/A

2 49197 49185 49195 10 N/A

3 49196 49169 49194 25 396’

4 49197 49098 49199 101 367’

5 49200 46547 54475 7928 534’

6 49207 46629 58232 11603 557’

7 49212 46729 55366 8637 629’

8 49222 49024 49222 198 478’

9 49220 49180 49221 41 554’

10 49220 49197 49245 48 500’

11 49210 49210 49213 3 N/A

JOSEPHINE 30-METER SURVEY INTERVAL 7 KNOT GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49155 49157 49175 18 N/A

2 49156 49145 49163 18 229’

3 49155 49134 49159 25 164’

4 49155 48840 49162 322 301’

5 49157 48173 50768 2595 541’

6 49156 47131 52598 5467 501’

7 49158 48227 49667 1440 364’
6-35

Table 6-4. (continued). Josephine Line Data for All Grids and Instruments

JOSEPHINE 30-METER SURVEY INTERVAL 7 KNOT GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)

8 49158 49026 49158 132 367’

9 49159 49142 49168 26 137’

10 49160 49135 49162 27 91’

11 49161 49110 49169 59 160’

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49275 49271 49276 5 N/A

2 49263 49250 49263 13 N/A

3 49267 49240 49267 27 118’

4 49274 49230 49274 44 279’

5 49275 48637 49352 715 370’

6 49276 38677 50859 12182 534’

7 49265 47325 51871 4546 380’

8 49263 49155 49265 110 357’

9 49272 49249 49272 23 219’

10 49275 49255 49322 67 52’

11 49277 49230 49285 55 N/A

G-881

Line Background Minimum Maximum Amplitude Duration

1 49282 49277 49282 5 N/A

2 49283 49269 49283 14 N/A

3 49283 49261 49283 22 354’

4 49282 49193 49282 89 469’

5 49282 48182 50724 2542 400’

6 49282 47146 55820 8674 544’

7 49283 48049 51108 3059 472’

8 49283 49183 49285 102 150’

9 49283 49264 49284 20 172’

10 49280 49256 49281 25 N/A

11 49281 49248 49281 33 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49215 49211 49217 6 N/A

2 49216 49197 49217 20 101’

3 49216 49183 49217 34 508’

4 49219 49136 49222 86 537’

5 49219 47649 51210 3561 423’

6 49221 45692 49280 3588 639’

7 49222 46773 53486 6713 724’

8 49223 49006 49224 218 148’

9 49224 49153 49225 72 449’

10 49226 49204 49320 116 541’

11 49226 49197 49238 41 567’

*Duration of an anomaly is the distance necessary for the wavelength to reach a

maximum and/or minimum and return to ambient background.
6-36

Table 6-5. Rhoda Line Data for All Grids and Instruments

RHODA 25-METER SURVEY INTERVAL GRID

G-866

Line Background Minimum Maximum Amplitude Duration(ft.)*

1 49263 49255 49272 17 N/A

2 49264 49246 49273 27 N/A

3 49262 49253 49270 17 N/A

4 49260 49243 49274 31 N/A

5 49257 49251 49267 16 N/A

6 49254 49243 49263 20 N/A

7 49253 49248 49260 12 N/A

8 49249 49211 49268 57 65’

9 49250 48907 49941 1034 341’

10 49245 49142 49633 491 403’

11 49246 49240 49256 16 154’

12 49240 49231 49259 28 N/A

13 49246 49234 49260 26 N/A

14 49245 49227 49266 39 N/A

15 49247 49239 49259 20 N/A

16 49245 49225 49264 39 N/A

17 49245 49229 49263 34 N/A

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49358 49352 49359 7 N/A

2 49363 49361 49363 2 N/A

3 49367 49366 49367 1 N/A

4 49363 49362 49365 3 N/A

5 49366 49364 49368 4 N/A

6 49366 49345 49404 59 124’

7 49366 49314 49558 244 95’

8 49366 49323 49387 64 154’

9 49358 46737 50664 3927 298’

10 49363 48766 50256 1490 383’

11 49365 49354 49369 15 239’

12 49370 49368 49371 3 108’

13 49370 49359 49373 14 N/A

14 49370 49363 49371 8 N/A

15 49365 49355 49374 19 N/A

16 49362 49358 49364 6 N/A

17 49362 49320 49428 108 N/A

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49331 49328 49332 4 N/A

2 49330 49328 49356 28 N/A

3 49331 49328 49331 3 N/A

4 49331 49327 49331 4 N/A

5 49331 49326 49331 5 N/A

6 49330 49316 49381 65 127’

7 49329 49279 49450 171 85’

8 49330 49213 49410 197 413’
6-37

Table 6-5. (continued). Rhoda Line Data for All Grids and Instruments

G-881

Line Background Minimum Maximum Amplitude Duration(ft.)*

9 49330 48801 50336 1535 249'

10 49333 49207 49684 477 314'

11 49331 49326 49337 11 400'

12 49337 49323 49344 21 337'

13 49336 49331 49336 5 N/A

14 49341 49333 49340 7 N/A

15 49340 49337 49343 6 N/A

16 49344 49345 49347 2 N/A

17 49347 49337 49371 34 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49341 49339 49341 2 N/A

2 49340 49338 49342 4 N/A

3 49343 49342 49344 2 N/A

4 49344 49342 49345 3 N/A

5 49344 49343 49345 2 N/A

6 49343 49301 49556 255 75'

7 49341 49323 49349 26 59'

8 49343 49289 49392 103 131'

9 49355 48570 50975 2405 423'

10 49345 49193 49770 577 334'

11 49345 49339 49347 8 216'

12 49345 49340 49351 11 85'

13 49347 49345 49348 3 N/A

14 49350 49348 49351 3 N/A

15 49353 49337 49370 33 N/A

16 49355 49352 49355 3 N/A

17 49358 49357 49360 3 N/A

RHODA 30-METER SURVEY INTERVAL 4 KNOT GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49243 49227 49248 21 N/A

2 49241 49234 49249 15 N/A

3 49240 49225 49254 29 N/A

4 49240 49231 49247 16 186'

5 49238 49217 49257 40 200'

6 49240 48809 49980 1171 534'

7 49240 49181 49322 141 485'

8 49244 49232 49252 20 344'

9 49244 49229 49254 25 N/A

10 49244 49237 49252 15 N/A

11 49245 49231 49257 26 N/A

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49274 49273 49275 2 N/A

2 49274 49273 49276 3 N/A

3 49275 49267 49279 12 23'
6-38

Table 6-5. (continued). Rhoda Line Data for All Grids and Instruments

RHODA 30-METER SURVEY INTERVAL 4 KNOT GRID

G-877

Line Background Minimum Maximum Amplitude Duration (ft.)

4 49276 49274 49278 4 N/A

5 49280 49273 49284 11 265'

6 49277 48239 50378 2139 380'

7 49279 49165 49616 451 314'

8 49280 49275 49281 6 137'

9 49281 49275 49287 12 141'

10 49280 49278 49281 3 N/A

11 49284 49282 49286 4 N/A

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49349 49162 49353 191 N/A

2 49350 49350 49351 1 N/A

3 49351 49345 49354 9 124'

4 49352 49350 49363 13 45'

5 49355 49328 49383 55 291'

6 49356 48849 50422 1573 383'

7 49350 49208 49639 431 220'

8 49352 49350 49353 3 98'

9 49352 49327 49370 43 95'

10 49355 49353 49356 3 N/A

11 49356 49353 49358 5 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49353 49351 49352 1 N/A

2 49348 49346 49348 2 N/A

3 49345 49344 49346 2 N/A

4 49340 49339 49348 9 85'

5 49337 49330 49340 10 49'

6 49335 48517 50629 2112 357'

7 49347 49348 49370 22 331'

8 49352 49335 49359 24 203'

9 49344 49277 49401 124 82'

10 49339 49338 49342 4 N/A

11 49335 49334 49336 2 N/A

RHODA 30-METER SURVEY INTERVAL 7 KNOT GRID

G-866

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49258 49249 49266 17 N/A

2 49253 49251 49266 15 N/A

3 49259 49248 49271 23 N/A

4 49259 49253 49262 9 N/A

5 49258 49254 49262 8 N/A

6 49260 48996 49823 827 472'

7 49260 49224 49357 133 432'

8 49255 49256 49266 10 N/A

9 49262 49246 49269 23 196'

10 49262 49256 49276 20 N/A

11 49265 49261 49268 7 N/A
6-39

Table 6-5. (continued). Rhoda Line Data for All Grids and Instruments

RHODA 30-METER SURVEY INTERVAL 7 KNOT GRID

G-877

Line Background Minimum Maximum Amplitude Duration(ft.)*

1 49286 49285 49287 2 N/A

2 49286 49285 49287 2 N/A

3 49288 49280 49291 11 52'

4 49288 49285 49289 4 N/A

5 49289 49272 49291 19 85'

6 49289 48925 49775 850 360'

7 49289 49232 49410 178 485'

8 49288 49283 49291 8 232'

9 49289 49278 49295 17 180'

10 49288 49283 49290 7 N/A

11 49288 49285 49291 6 N/A

G-881

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49342 49340 49345 5 N/A

2 49338 49337 49339 2 N/A

3 49335 49329 49338 9 124'

4 49334 49330 49336 6 180'

5 49334 49310 49350 40 423'

6 49335 48946 50034 1088 331'

7 49335 49276 49408 132 252'

8 49331 49327 49338 11 108'

9 49331 49319 49338 19 95'

10 49332 49330 49332 2 N/A

11 49332 49327 49333 6 N/A

SeaSPY

Line Background Minimum Maximum Amplitude Duration (ft.)

1 49334 49333 49334 1 N/A

2 49329 49329 49330 1 N/A

3 49333 49331 49336 5 N/A

4 49329 49326 49330 4 N/A

5 49327 49322 49331 9 N/A

6 49324 48529 50397 1868 338'

7 49323 49216 49419 203 337'

8 49323 49319 49323 4 147'

9 49324 49296 49340 44 98'

10 49324 49323 49325 2 N/A

11 49325 49317 49327 10 N/A

*Duration of an anomaly is the distance necessary for the wavelength to reach a

maximum and/or minimum and return to ambient background.

Figure 6-28 illustrates the Rhoda 25-meter survey interval grid total gamma

deviation graph; Table 6-5 lists maximum, minimum and total gamma deviation for each

of the instruments over the wooden-hulled wreck site. Apart from minor differences due

to track line variation between sensors on Lines 6 and 7, the G-877 had the largest

gamma deviation over the Rhoda with 3,927 gamma. The SeaSPY again had a slightly
6-40

lower reading of 2,405 gamma, followed by the G-881 at 1,535 gamma, and the G-866 at

1,034 gamma.

Figures 6-26 and 6-29 illustrate the Josephine and the Rhoda 30-meter survey

interval grid total gamma deviation graphs, followed by Figures 6-27 and 6-30 which are

the 30-meter survey interval 7-knot graphs for each wreck. Tables 6-4 and 6-5

accompany their respective graphs. Unlike both the 25-meter survey interval grids, the

SeaSPY has the highest reading in the 30-m grid over the Josephine at 11,603 gamma on

the central line, Line 6 (Figure 6-26). The G-877 has a similar but slightly lower reading

with 11,372 gamma followed by the G-881 at 8,874 gamma, and the G-866 at 5,628

gamma. This order is reflected for Lines 5 and 7 but with the added characteristic that

the SeaSPY has much higher amplitudes than all three other instruments. Possibly a

result of minor track line offset (see easting positions), these findings appear to be

reflected in the 30-meter survey interval 7-knot grid discussed below.

The Rhoda 30-meter survey interval grid total gamma deviation graph (Figure 6-

29) reflects readings similar for both the Josephine and Rhoda 25-meter survey interval

grids as well (Table 6-5), with the order of intensity being the G-877 at 2,139 gamma, the

SeaSPY (2,112), the G-881 (1,573), and then the G-866 at 1,171 total gamma deviation

for Line 6, the line with the highest readings. It is interesting to note that the SeaSPY

falls below all the instruments on Line 7.

The Josephine 30-meter survey interval 7-knot grid total gamma deviation graph

(Figure 6-27, Table 6-4) seemingly reflects readings similar to the 30-meter survey

interval 4-knot grid but with one caveat. At face value the 30-meter survey interval 7-

knot grid looks dissimilar to the other grids in that the SeaSPY has the lowest reading on

the centerline, even well below both the G-881 and the G-866. However, it has the

highest reading of all instruments for both Lines 5 and 7, reflective of readings for the 30-

meter survey interval 4-knot grid. Unable to characterize this occurrence, a review of the

raw data indicated that when the sensor started to detect the highest reading it went into

an “initialized tuning” mode and unknowingly ceased recording accurate magnetic data

for some 13 seconds. Discussions with the manufacturer stated that:

...the wreck’s magnetic effect was so huge that at this speed, the magnetic field at

the sensor was changing faster than the maximum spec of the instrument.

Looking at the data, it was changing at about 3000nT [nanoTeslas = gammas] per

second. The SeaSPY firmware [that was on] monitors the quality of the data, and

when it falls below a certain value it is designed to automatically reset the

operating parameters to ensure that everything is set correctly. Note that in the 4

knot survey, the anomaly appears perfectly. This is because the field changes

slower - around 1800nT per second....The firmware’s automatic monitoring

features can be switched off, and in this case, I am sure that the mag would have

read the full anomaly at 7 knots as well (Doug Hrovic, personal communication

2002).
6-41

Given this information, it is suspected that if the firmware’s automatic monitoring

feature had been switched off, the SeaSPY would have recorded a similar reading on the

30-meter survey interval 4-knot grid, equal to or above the G-877, as well as the other

two instruments.

The Rhoda 30-meter survey interval 7-knot grid total gamma deviation graph

(Figure 6-30, Table 6-5) is somewhat similar to the Josephine’s 30-meter survey interval

7-knot grid if we take into account the “firmware” issue discussed above in that the

SeaSPY has the highest reading on Line 6, the centerline, with 1,868 gamma, followed by

the G-881 with 1,088 gamma, the G-877 surprisingly lower than the G-881 with 850

gamma, and then the G-866 with 827 gamma. Possibly a reflection of increased speed, a

review of positioning coordinates indicates that all sensor positions are comparable to

within one or two meters of the track line center. When compared to recorded readings

on Line 9 of the 25-meter survey interval grid, which has the same easting coordinates,

the readings are much lower at the greater speed even though sensor positions are

comparable to within one or two meters of the track line center. However, these findings

are not reflected in the Josephine grids. When recorded readings for all instruments on

Line 9 of the Josephine 25-meter survey interval grid are compared with Line 6 of the

wreck’s 30-meter survey interval 7 knot grid, the readings are only slightly lower.

While the order of which instrument records the highest deviation appears

generally to remain relatively constant, with the SeaSPY and G-877 exchanging places

followed by the G-881 and then the G-866, the variation in that order seems to be due to

minor differences associated with track line position (i.e., the location of the sensor).

Lending credence to this statement is the fact that different readings were recorded for

many of the same instruments along the same line of the same grid, additional lines being

run for one reason or another (i.e., aborted due to vessel traffic, offline, etc.).

Furthermore, gamma deviation for the same instrument varied widely for the same line

but on different grids, like that mentioned in the paragraph above. For instance, the Line

9 reading for the G-877 Josephine 25-meter survey interval grid is 13,442 total gamma

deviation, while the total gamma deviation for Line 6 of the 30-meter survey interval grid

(both lines having the exact same easting) is 11,372, over two thousand gammas

different. The reading was similar in the northing but some four meters different in the

easting. This variation in readings is common as indicated in Table 6-4.

If we look at the graphic presentation of the grid lines in Appendices I through N,

as well as data in Tables 6-4 and 6-5, we are able to compare shape and duration of the

recorded readings by line. As stated by Garrison et al., “the shape of a magnetic anomaly

along a survey line is a result of the same factors that influence the amplitude,”

orientation of the anomaly source within the Earth’s external field. He goes on to state

that “most authors refer to shape as dipolar or monopolar. The fall-off of the strength of

the anomaly is expressed in the slope of the profile. Typically, the steeper slope values

are associated with dipolar anomalies while monopolar anomalies have broader, less

steep profiles” (1989:II-173). The report lists rules (after Tite 1972) that anomalies

ideally follow in the GOMR:
6-42

1. The maximum of the anomaly lies to the south of the feature, the displacement

being approximately equal to one-third of the depth to the center of the feature;

2. The separation between two points, in a straight line traverse, at which the

anomaly has half its maximum value is approximately equal to the depth or width

of the feature, whichever is greater; and

3. A reverse anomaly (i.e., decrease in magnetic field intensity) may occur to the

north of the feature at a distance equal to the depth; the reverse anomaly does not

exceed 10 percent of the maximum normal value of the anomaly except in the

case of metallic iron (Garrison et al. 1989:II-173).

Another quantitative descriptive parameter of magnetic data is duration. More

properly defined as wavelength or the total observed magnetic perturbation, duration can

be measured in temporal units as well as the spatial unit of distance along a track line.

By comparing both duration and shape (see Appendices I through N and Tables 6-4 and

6-5), we are able to make several statements for each instrument.

Tables 6-4 and 6-5 present duration of the recorded amplitude by line for each

wreck grid. Many lines are marked as N/A or non applicable if there was no perturbation

or if it was thought that a recorded anomaly did not relate to the wreck site. This was

especially true for the Rhoda, as anomalies that appeared on lines hundreds of meters

away from the wreck site were thought to be non-related debris. Additionally, it was

impossible to determine the eastern terminus of magnetic influence of the Josephine and

the western terminus of influence for the barge, as the influence seems to run together

(see Lines 11 through 15 of Appendix I), making characterizations of these lines

problematic at best.

A review of the duration (Tables 6-4 and 6-5) and strip charts for the 25-meter

survey interval grid track lines immediately atop and to the east of the Josephine shows

that, beginning from the east, the wreck site’s magnetism begins to first affect Line 5.

We see a small amplitude anomaly but with several hundred feet duration for all

instruments for this line. Generally and as expected, both the amplitude and duration

steadily intensify and increase for each track line closer to the center of the wreck. For

the center lines over the wreck with the highest amplitude, Lines 8, 9 and 10, the duration

is highest as well. Interestingly, the SeaSPY records the highest duration for these and

other lines, appreciably higher in many instances, although the G-877 had the highest

amplitudes for the lines. The G-866 and G-881 had durations similar to one another, with

the G-866 slightly higher. Interestingly, the G-866 had the highest duration of all

instruments on Line 17, the centerline over the barge, although its amplitude was the

lowest.

Similar to the 25-meter survey interval grid, the SeaSPY had the highest duration

for the 30-meter survey interval grid as well, with the other instruments generally equal

in duration for all lines. The 30-meter survey interval 7-knot grid again shows the

SeaSPY with the highest durations. In a comparison between the 30-meter survey
6-43

interval grids, the durations for the respective lines for each instrument vary to the point

that no real comparisons can be made. For instance, the durations for the SeaSPY are

higher for Lines 3, 4, 6, and 7 of the 30-meter survey interval 7-knot grid but higher on

Lines 5, 8 and 9 of the 30-meter survey interval 4-knot grid.

With the wreck centered at Lines 8, 9 and 10, duration readings for the Rhoda 25-

meter survey interval grid find the G-877 and the G-881 with generally the higher

readings. However, similar to the above 30-meter survey interval grid comparisons, the

durations for the respective lines for each instrument vary to the point that no real

comparisons can be made. With respect to the Rhoda 30-meter survey interval 4-knot

grid, the G-866 has the highest durations for any instrument, although it had the lowest

amplitude readings (similar to Josephine Line 17). The other three instruments generally

had similar durations. Reflecting findings of the 25-meter survey interval grid, the 30-

meter survey interval 7-knot grid durations for the respective lines for each instrument

again vary to the point that no real comparisons can be made. This holds true as well in

comparison between the 30-meter survey interval 4 knot grids.

A qualitative review of the magnetic strip charts allows for a comparison of the

anomalies recorded by each instrument by line and grid and raises several aspects of

anomaly shape as well as characteristics of each instrument (Appendix I through N).

Beginning with the Josephine 25-meter survey interval grid, we see the G-866 is

somewhat noisy for the first four lines, which are presented in a 10 gamma scale, while

the other instruments are extremely quiet. Two anomalies not associated with the main

part of the wreck site (possibly an anchor?) appear on Line 4. Recorded as two small

anomalies by the G-866, it is recorded as a small and relatively large anomaly

respectively by the other three instruments; however, each instrument records both

anomalies somewhat differently. While the G-877 and G-881 record the smaller anomaly

to the north (left), it is just the opposite for the SeaSPY. Both the SeaSPY and G-881

show the southern anomaly in a broad negative field. This same broad or long duration

negative is seen on all instruments for Line 5, although the SeaSPY has a brief positive at

the maximum negative and the G-877 has an abrupt negative. Line 6 again sees a broad

or long duration negative for all instruments but of greater amplitude. Line 7 is again a

long duration negative but of increasing amplitude. Line 8 is a dipole but with varying

maximum negative and positive amplitudes and illustrates the rule listed above that the

maximum of the anomaly lies to the south of the feature. With the exception of the G877, Line 9 shows similar dipoles for the other three instruments with some complexity

in the negative. The G-877 signature differs because the line was inadvertently run in the

opposite direction to the others. While admittedly straying from the research design, it

serves to illustrate the effect that direction of survey has on shape characteristics of an

anomaly, given that lease block survey lines are not all run in the same direction.

Line 10 shows similar dipoles with the exception again of the G-877, which has a

much smaller positive and a much larger negative than the other three. Line 11 shows

similar dipoles but with varying complexity to the signal in its initial positive amplitude.

Lines 12 and 13 are generally broad negatives with lowering amplitude, suggesting that

these lines are no longer over the main wreckage but to the side. However, the G-877 has
6-44

a small positive, indicating some material still in the vicinity. Line 14 is a broad negative

with a brief but sharp positive, with the exception of the G-866, which lacks the latter

characteristic. Line 15 is a complex series of mainly negatives for all instruments, while

Line 16 shows a dipole with a large negative (again, the G-877 was run in the opposite

direction). Lines 17 (centered over the barge) and 18 again show similar large dipoles

for the instruments while Line 19 is void of any anomaly. At this point it should be

mentioned that the high amplitude of the barge suggests that it may be composed of iron

and not wood as initially indicated.

With only slight differences, the 30-meter survey interval 4-knot grid varies in

anomaly shape, similar to the 25-meter survey interval grid, with each instrument mostly

reflecting the same shape. When compared to the 30-meter survey interval 7-knot grid,

only minor variations are observed, most of which may be explained to likely differences

in exact sensor position.

Findings for the Rhoda grid lines are similar to those seen for the Josephine, a

much larger wreck whose magnetic effect was recorded over many more lines than the

wooden bark. Examining the main lines over the wreck site—Lines 8, 9 and

10—variation is seen for the instruments in Line 8 while Lines 9 and 10 appear to be

mostly mirror images. Examination of the 30-meter survey interval 4-knot grid generally

shows the same minor variation. Differences in Line 5 for the G-881, however, are

attributable to the instrument recording a higher amplitude, while the exact opposite

occurs on Line 8 where the instrument records a low perturbation. Similar to the

Josephine, when compared to the 30-meter survey interval 7-knot grid, only minor

variations are observed, most of which may be explained to likely differences in exact

sensor position.

Aside from duration or shape issues, the strip chart records presented in

Appendices I through N beg mention of the NTL’s instrumentation guidelines as they

pertain to magnetometer strip chart recorders. Reflecting abilities of the for-years

industry standard but now antiquated G-801 and G-866 systems, the NTL requires dual

scale readings, strip chart speeds, and annotation of the strip charts with shot points and

recorder speed. However, given the computer-driven, digital-nature of all instruments

today, these requirements appear now to be outmoded and in need of revision, at least for

those magnetometers that are totally digital (i.e., G-877, G-881, SeaSPY, etc.). Magnetic

data from these digital models is collected simultaneously in the same file along with

positioning, depth, time, layback, gyro, etc., making annotation unnecessary.

Additionally, the strip chart is presented digitally on the screen in navigation programs

such as HYPACK® and may be set at any gamma scale. Furthermore, when postprocessing data, track lines and any attendant anomalies can also be viewed and

presented in any gamma scale to allow for optimum characterization of that anomaly.

6.2.2. Line Spacing

As stated above, magnetometers were to be evaluated “at various line spacing to

determine the minimally acceptable survey line spacing for detecting historic

shipwrecks.” The current 2002 NTL stipulates that for “OCS blocks that have a high
6-45

probability for containing historic resources in water depths 200 meters or less, the

survey line spacing is no more than 50 meters. For OCS blocks that have a high

probability for containing prehistoric archaeological resources or historic resources in

water depths greater than 200 meters (656 feet), the survey line spacing is no more than

300 meters” (MMS 2002).

Leaving aside for now discussions on the size of shipwrecks as archaeomagnetic

features or previously posited shipwreck signal characteristics (see Garrison et al.

1989:II-211-226), Table 6-6 below represents detection of our three known shipwrecks at

varying line spacing or transect interval.

Table 6-6. Survey Transect Interval Detection Rates by Instrument

G-866

Transect Interval Josephine Rhoda Barge

300-m No No No

150-m Yes No No

2 lines low amplitude

100-m Yes No Yes

1 line high, 1 line low 1 line low amplitude

50-m Yes Yes Yes

2 lines high, 2 lines low 1 line high, 1 line low 1 line high, 1 line low

30-m (4-knot) Yes Yes NA

3 lines high, 4 lines low 1 line high, 3 lines low

G-881

Transect Interval Josephine Rhoda Barge

300-m No No No

150-m Yes No No

2 lines low amplitude

100-m Yes Yes Yes

1 line high, 1 line low 1 line low amplitude 1 line low amplitude

50-m Yes Yes Yes

2 lines high, 2 lines low 1 line high, 1 line low 1 line high, 1 line low

Transect Interval Josephine Rhoda Barge

30-m (4-knot) Yes Yes NA

3 lines high, 3 lines low 2 lines high, 2 lines low

G-877

Transect Interval Josephine Rhoda Barge

300-m No No No

150-m Yes No No

2 lines low amplitude

100-m Yes Yes Yes

1 line high, 1 line low 1 line low amplitude 1 line high deviation

50-m Yes Yes Yes

2 lines high, 2 lines low 1 line high, 2 lines low 2 lines high deviation

30-m (4-knot) Yes Yes NA

3 lines high, 4 lines low 3 lines high, 2 lines low
6-46

Table 6-6. (continued). Survey Transect Interval Detection Rates by Instrument

SeaSPY

Transect Interval Josephine Rhoda Barge

300-m No No No

150-m Yes No No

2 lines low amplitude

100-m Yes Yes Yes

1 line high, 1 line low 1 line low amplitude 1 line high amplitude

50-m Yes Yes Yes

2 lines high, 2 lines low 1 line high, 1 line low 2 lines high deviation

30-m (4-knot) Yes Yes NA

3 lines high, 4 lines low 1 line high, 4 lines low

Based on Table 6-4 above, each instrument’s grid was reviewed as it related to the

detection of each known site location at varying transect intervals. It was attempted to

treat each wreck site as if it were the only wreck in that grid. Treating all three wreck

sites as separate entities would allow not only an assessment of minimal acceptable

transect spacing, but might indicate minimal transect spacing based on vessel type (i.e.,

metal-hulled, wooden-sailing, wooden barge). As discussed above, however, it was

difficult if not impossible, at least with respect to a review of the strip charts, to

determine the eastern terminus of magnetic influence for the Josephine and the western

terminus of influence for the barge, the influence seeming to run together (see Lines 11

through 15 of Appendix I).

The data from the various transects in the table were projected atop the wreck site

and then shifted over one or more lines in an effort to determine if the wreck site would

fall outside of or go undetected by the chosen transect interval. For example, if we look at

the G-881 data in Table 6-4, the Josephine wreck site on the 25-meter survey interval

grid falls mainly between Transect Lines 7 and 12 with the highest gamma deviation on

Lines 9 and 10 (the 105 gamma reading on Line 4 is not part of the main wreck site, but

may be an anchor or some other related component). If we had started the survey on Line

3, the G-881 would not have detected the vessel at a 300-meter survey interval because

the wreck site basically covers 175-meter or eight 25-meter survey lines, and of these

eight Lines 6 and 13 are relatively minor perturbations (because the eastern terminus is

somewhat problematic given the presence of the barge, Line 13 is thought to be the

terminus for the Josephine given its similarity to Line 6). If a 150-meter transect survey

interval began a line at Line 6 (minor amplitude), this line would have produced a minor

negative amplitude anomaly of 29 gamma, and 150 meters away Line 12 would have

produced another relatively minor amplitude anomaly of 80 gamma (200 gamma was

chosen as the demarcation between High and Low amplitude in Table 6-6). If a 100-

meter transect survey interval began at Line 6, the survey would have detected a high

deviation of 6,488 gamma but only on one line, Line 10, and a low amplitude anomaly on

Line 12 (see Table 6-6). Starting at Line 12 and going the other direction also would

have detected the wreck at a very high gamma deviation but again on only one line, Line

9. Employing a 50-meter transect survey interval and beginning at Line 6, the G-881
6-47

would have detected the wreck on Line 8 at 2,490 gamma, Line 10 at 6,488 gamma, and

Line 12 at 80 gamma. In Table 6-6, the Josephine is shown as being detected on a 50-

meter transect survey interval on two lines with high gamma deviation (Lines 8 and 10)

and on one line (Line 12) with a low gamma deviation. In the 30-meter survey interval

four-knot transect, the Josephine would be detected across five survey lines, three of

which have extremely high deviation (Lines 5, 6 and 7), and two with low gamma

deviation (Lines 4 and 8), low deviation being under 200 gamma. Lines 3 through 9 are

employed on the 30-meter survey interval grid as the extent of the wreck and reflect the

same extent as the 25-meter survey interval grid.

This same method was applied to the barge and all grids for the Rhoda. Recorded

mainly on Lines 16, 17 and 18 of the 25-meter survey interval grid, the barge site was

considered to cover Lines 15 through 18. Based on Table 6-5 and strip chart print-outs

(Appendices I-N), the Rhoda on the 25-meter survey interval grid falls between Lines 6

through 10.

In an effort to help visualize and quantify the detection rates at the various

transect intervals, contour maps were generated in Surfer 7.0® with G-881 data for both

the Josephine and the Rhoda 25-meter survey interval and 30-meter survey interval 4-

knot grids (Figures 6-31 through 6-46). In addition to precisely locating the wreck site, a

contour map presents a visual signature of the site that can then be analyzed relative to its

complexity and spatial attributes. For our purposes the contour maps also allow us to

comparatively visualize the differences in the magnetic signatures recorded at the varying

survey transect intervals.

Created by employing the Inverse Distance to Power and Spline Smoothing

functions of Surfer®, the maps represent 100-meter survey interval transect data presented

at both a 100 and 10 gamma contour; two 50-meter survey interval transects, one with

even lines and one with odd lines, each presented at both a 100 and 10 gamma contour;

and finally the 30-meter survey interval 4-knot grid, presented at both a 100 and 10

gamma contour. Each transect interval and its attendant gamma contour is presented in

three contour maps of varied two and three-dimensional views for better visualization of

the anomaly’s signature as it relates to complexity, spatial attributes, and minimum and

maximum gamma deviation.

Notice the Josephine is visible at the 100-meter survey interval transect even

when presented at a 100 gamma two-dimensional contour, while the Rhoda is

problematic at best when presented at a two-dimensional 10 gamma contour and basically

nonexistent as a 100 gamma contour map. All three wrecks are present on the 50-meter

odd-even survey interval transect 100 gamma contour maps; however, the Rhoda

becomes a much more complex signature when presented at a 10 gamma contour

interval. Note that while there are differences between the 50-meter survey interval odd

and even transects, all three wreck sites were detected. Also note the increasing

complexity of the wreck sites as the transect interval becomes narrower (i.e., 100-meter,

50-meter, 30-meter).
6-48

feet

Contour interval 100 gamma

0 50 100 150

N 0 50 100 150

feet

Contour interval 100 gamma

48850

48950

49050

49150

49250

N 0 50 100 150

feet

Contour interval 100 gamma

Figure 6-31. Top: Josephine 100-m transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-49

0 50 100 150

feet

Contour interval 10 gamma

N 0 50 100 150

feet

Contour interval 10 gamma

48850

48950

49050

49150

49250

N 0 50 100 150

feet

Contour interval 10 gamma

Figure 6-32. Top: Josephine 100-m transect interval, 10-gamma contour map; middle: twodimensional view, bottom: three-dimensional view.
6-50

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

48000

49000

50000

51000

52000

53000

54000

0 50 100 150

Figure 6-33. Top: Josephine 50-m odd transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-51

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

47000

48000

49000

50000

51000

N

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-34. Top: Josephine 50-m even transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-52

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 10 gamma

48000

49000

50000

51000

52000

53000

54000

0 50 100 150

Figure 6-35. Top: Josephine 50-m odd transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-53

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

47000

48000

49000

50000

51000

N

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-36. Top: Josephine 50-m even transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-54

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

47500

48500

49500

50500

51500

52500

53500

54500

55500

N

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-37. Top: Josephine 30-m (4-knot) transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-55

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 10 gamma

0 50 100 150

47500

48500

49500

50500

51500

52500

53500

54500

55500

N

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-38. Top: Josephine 30-m (4-knot) transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-56

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

49270

49320

49370

N feet

Contour interval 100 gamma

0 50 100 150

Figure 6-39. Top: Rhoda 100-m transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-57

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

49270

49320

49370

N feet

Contour interval 10 gamma

0 50 100 150

Figure 6-40. Top: Rhoda 100-m transect interval, 10-gamma contour map; middle: two-dimensional

view; bottom: three-dimensional view.
6-58

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

48877

49377

49877

N

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-41. Top: Rhoda 50-m odd transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-59

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

49270

49320

49370

N feet

Contour interval 10 gamma

0 50 100 150

Figure 6-42. Top: Rhoda 50-m even transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-60

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 10 gamma

0 50 100 150

48877

49377

49877

N

feet

Contour interval 10 gamma

0 50 100 150

Figure 6-43. Top: Rhoda 50-m odd transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-61

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 10 gamma

0 50 100 150

49206

49306

49406

49506

49606

N

feet

Contour interval 10 gamma

0 50 100 150

Figure 6-44. Top: Rhoda 50-m even transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-62

feet

Contour interval 100 gamma

0 50 100 150

N

feet

Contour interval 100 gamma

0 50 100 150

48804

49004

49204

49404

49604

49804

50004

50204

50404

N feet

Contour interval 100 gamma

0 50 100 150

Figure 6-45. Top: Rhoda 30-m (4-knot) transect interval, 100-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-63

feet

Contour interval 10 gamma

0 50 100 150

N

feet

Contour interval 10 gamma

0 50 100 150

48804

49004

49204

49404

49604

49804

50004

50204

50404

N

feet

Contour interval 10 gamma

0 50 100 150

Figure 6-46. Top: Rhoda 30-m (4-knot) transect interval, 10-gamma contour map; middle: twodimensional view; bottom: three-dimensional view.
6-64

Allowing a visual comparison between transect intervals specific to our study, it

can be stated that contour maps employed in any survey provide critical analytic aspects

of an anomaly such as location, amplitude, size and complexity. As illustrated by the

50-meter and 30-meter survey interval transect maps, even without the use of a base

station, offshore survey data can be effectively contoured in situations where a survey is

conducted as a single unit (i.e., not split over multiple days).

Findings in Table 6-6 indicate that none of the three vessels would be located with

a 300-m survey interval transect, even with a wreck site with such high magnetic

influence as the Josephine. While the vessel is detected as a low amplitude anomaly on

two transect lines by all instruments on the 150-meter survey interval transect, however,

the other two vessels go undetected. With the exception of the G-866, the Rhoda is

detected by all instruments on the 100-meter survey interval transect as a single line of

low amplitude. The Josephine is detected at this interval on two transect lines, one with a

high and one with a low amplitude. The barge is detected by all instruments on the 100-

meter survey interval transect but varies by instrument as either a single transect line of

either high or low amplitude. The 50-meter survey interval transect, the interval or line

spacing stipulated by the NTL for water depths of 200 meters or less, detects all wrecks

by all instruments on multiple transect lines of varying amplitude. The metal-hulled

Josephine, obviously larger in magnetic influence than the Rhoda or the barge, is

detected on two transect lines of high and two lines of low amplitude for all instruments.

Both the Rhoda and the barge are detected by all instruments at a minimum of one high

and one low amplitude line, although the barge is detected at high amplitude on two

transect lines by the G-877 and the SeaSPY. However, as illustrated in Table 6-6, the 30-

meter survey interval transect, because of its narrower spacing, detects both the Josephine

and Rhoda on more lines and at higher amplitude by all instruments than with the 50-

meter survey interval transect. Although the 30-meter survey interval transect is not a

requirement of MMS surveys, it has been adopted by several state agencies with purview

over submerged cultural resources. Relative to the states that border the GOMR,

Louisiana defers to the MMS NTL and typically requires a 50-meter survey interval

transect, Mississippi employs a 30-meter survey interval, and both Texas and Florida

require surveys to be conducted with 30-meter line spacing in areas of high probability

within their state waters.

The ability of the current 50-meter survey interval transect to effectively record

the wrecks examined in this study has been amply demonstrated and argues for its

effectiveness in locating many of the classes of vessels known to have been lost in the

GOMR. However, it should be emphasized that the vessels examined in the present

study are large and contain considerable quantities of ferrous metal. The 50-meter survey

interval is unlikely to be effective in identifying all wreck types in the GOMR, especially

earlier wrecks containing less iron or small wooden vessels or parts of wooden vessels

that produce smaller magnetic signatures.

Discussions with the Florida State Underwater Archaeologist indicated that

several early and extremely significant shipwrecks, such as the Emanuel Point Wreck and

the Nuestra Señora del Rosario (which date to 1559 and 1705 respectively), would have
6-65

gone undetected with a 50-meter survey interval transect because of their lack of

detectable magnetic materials (Roger Smith, personal communication 2002). In the case

of the Emanuel Point Wreck, the second oldest shipwreck discovered in the United

States, a single anchor was the main anomaly source. Therefore, it is recommended that

in order to provide better detection capability for all types of shipwrecks, especially

earlier wrecks which might be the most historically significant types within the GOMR, a

closer spaced transect interval, such as the 30-meter survey interval, should be considered

by the MMS for employment in high probability areas.

6.2.3. Effects of Vessel Speed on Amplitude or Durations

Two questions were identified with respect to vessel speed and its

effect on magnetic data:

• Do increased speeds affect the ability of instruments to detect a wreck?

• How are increased speeds reflected in the recorded signal strength and duration of the

magnetics of a known wreck site?

As stated above, the Rhoda 30-meter survey interval 7-knot grid total gamma

deviation was different than readings from all previous graphs, with the SeaSPY having

the highest reading on Line 6, the centerline, with 1,868 gamma, followed by the G-881

with 1,088 gamma, the G-877 with 850 gamma, and the G-866 with 827 gamma.

Thought to possibly be a reflection of increased speed, a review of positioning

coordinates indicated that all sensor positions were comparable to within one or two

meters of the track line center for Line 6. When compared to recorded readings on Line 6

of the 30-meter survey interval 4-knot grid, the readings are only slightly lower.

However, Line 7 has a higher reading for the 30-meter survey interval 7-knot grid. When

compared to Line 9 of the 25-meter survey interval grid which has the same easting

coordinates, the readings are much lower at the greater speed, even though sensor

positions are comparable to within one or two meters of the track line center. A review

of all instruments for the Rhoda grids shows that the 30-meter survey interval 7-knot grid

generally has lower readings but not always. However, these findings are not reflected in

the Josephine grids. When recorded readings for all instruments for all grids are

compared, the readings are generally the same with little variation in readings.

Furthermore, between the 30-meter survey interval 4-knot and the 30-meter survey

interval 7-knot grids, the highest readings recorded over the wreck are from the 30-meter

survey interval 7-knot grid.

With regard to the question of whether increased speeds are reflected in the

duration of the magnetics of a known wreck, Garrison et al. state that “a survey of eight

knots will produce a shorter duration signature than one done at four knots” (1989:II223). A comparison of durations obtained on Line 9 of the 25-meter survey interval grid

for both wrecks and those obtained on Line 6 of both the 30-meter survey interval 4-knot

and the 30-meter survey interval 7-knot is presented in Table 6-7 to address this issue

(these lines for each wreck have the same easting and all lines are the central line over
6-66

each wreck site). The table illustrates that the high speed survey over the Josephine

actually had higher numbers than its 30-meter survey interval counterpart, and, with the

exception of the SeaSPY reading, the 30-meter survey interval 7-knot numbers are only

slightly lower than the 25-meter survey interval grid. Almost converse to the Josephine,

the Rhoda 25-meter survey interval grid is generally lower than the 30-meter survey

interval 7-knot grid, while the 30-meter survey interval 4-knot grid has higher readings

than both other grids, but again with the exception of the SeaSPY reading. These

findings seem to argue against the Garrison et al. statement and indicate that durations are

not affected by speed, and, based on the data presented in Table 6-7, neither is amplitude.

Table 6-7. Comparison of Duration and Amplitude

Josephine

Survey Duration (ft) Amplitude

Interval Grid G-866 G-881 G-877 SeaSpy G-866 G-881 G-877 SeaSpy

25-M 534' 547' 564' 810' 5,870 9,030 13,442 12,371

30-M 4-Knot 442' 476' 472' 557' 5,628 8,847 11,372 11,603

30-M 7-Knot 501' 544' 534' 639' 5,467 8,674 12,182 3,588

Rhoda

Survey Duration (ft) Amplitude

Interval Grid G-866 G-881 G-877 SeaSpy G-866 G-881 G-877 SeaSpy

25-M 341' 249' 298' 423' 1,034 1,535 3,927 2,405

30-M 4-Knot 534' 383' 380' 357' 1,171 1,573 2,139 2,112

30-M 7-Knot 472' 331' 360' 338' 827 1,088 850 1,868

It should be stated that different tow bodies (i.e., sensors) will behave differently

with respect to speed changes. Sensor depth is affected by cable layback, weight of cable

(i.e., steel, kevlar) and sensor, tow speed, cable diameter, hydrodynamics of the tow

body, and the effects of cable or tow body depressors. For an interactive display of the

differences produced by varying speed, and cable and sensor type, please visit

<http://www.geometrics.com/TowDepth.htm>. With regard to our survey, uniform

sensor depths reflecting NTL requirements were maintained at the higher speed by

increasing layback and/or adding additional cable weights depending on the requirements

of each instrument to maintain the proper depth.

6.2.4. Base Stations

Mirroring both the NTL 98-06 and the new NTL 2002-G01 requirements, the

SOW did not stipulate the employment of base stations or contouring of magnetometer

data. As stated above, this is a reflection of the fact that, apart from oil rigs or platforms

which cannot be employed as a suitable location because of their inherent magnetism,

there is nowhere to place a base station in offshore Gulf waters. It was recommended,

however, that a submersible base station be tested to determine its applicability to

offshore surveys as it might apply to post-mission processing of magnetic data, especially

with regard to surveys with line spacing of 50-meters. Because a Sentinel submersible
6-67

base station was included in this task in an effort to assess its functionality in the field,

and answer questions concerning employment in offshore surveys relative to issues of

diurnal variation and the applicability of contouring, land base stations were also

included to provide comparative base station data. As indicated above, three base

stations were employed during the survey of each vessel, the Sentinel submersible, a

Marine Magnetics land, and a G-856 land base station. The Sentinel collected readings at

one-second intervals while the other two took readings every twenty seconds. Presented

in Figure 6-47 are strip charts for each of the three base station readings collected during

the survey of the Josephine with the G-881. Representative of all other survey days, the

graphs show almost identical readings for the three instruments over an eight-hour

period. Both land base stations show several small perturbations that are not seen on the

Sentinel, the latter’s readings being exceptionally smooth, most likely a reflection of its

location underwater away from land activity. These small perturbations and what

appears as low-level noise are observed on some of the other land base station days as

well, but the overall readings for all three instruments are similar.

While not stipulated as a requirement by the NTL 2002-G01, employment of the

Sentinel during our investigation highlighted its potential as an offshore tool in the

collection of data for post-processing of magnetic survey data. As discussed above,

however, the acoustic release failed on one occasion and had to be retrieved manually by

divers, a scenario impossible in most GOMR survey situations. A prototype, the release

is said to have undergone corrective redesign.

In addition to assessing differences in land versus submersible base stations, data

from the base stations was employed to determine its applicability to offshore surveys as

it might apply to post-mission processing of magnetic data, especially with regard to

surveys with line spacing of 50-m. Additionally, data was employed to determine if

correcting for diurnal variation affects, enhances, or alters magnetic signatures.

In simplified terms, because the Earth’s magnetic field varies over time, these

variations can cause inaccuracies in survey data, particularly if the data is collected over

multiple days. The effects of this variation can be corrected by collecting parallel

magnetic data at a fixed sensor location over the period of the survey. This base station

data is time-correlated to the survey data, and can be employed to remove the effects the

short term and diurnal variations present in the Earth’s magnetic field. Corrections are

achieved by subtracting corresponding time readings of the base station data from the

survey data using the following formula:

Diurnal Reading(t) = Roving Mag(t) – Base Station(t), where (t) = identical time

Ideally, base station readings are taken at the same time interval as the survey

data. In the event of fewer base station readings, the processing software discussed

below will interpolate the missing readings.
6-68

Figure 6-47. Strip charts for each of the three base station readings collected

during the survey of the Josephine with the G-881.

Geometrics G-856 Base Station

49000

49050

49100

49150

49200

49250

49300

49350

49400

49450

49500

1 115 229 343 457 571 685 799 913 1027 1141 1255

No. of Readings

Magnetic Field

Marine Magnetics Land Base Station

49000

49050

49100

49150

49200

49250

49300

49350

49400

49450

49500

1 118 235 352 469 586 703 820 937 1054 1171

No. of Readings

Magnetic Field Magnetic Field Magnetic Field

Sentinel U/W Base Station

49000

49050

49100

49150

49200

49250

49300

49350

49400

49450

49500

1 2482 4963 7444 9925 12406 14887 17368 19849 22330 24811

No. of Readings

Magnetic Field Magnetic Field
6-69

Processing of magnetometer base station and survey data to remove short term

and diurnal variations in magnetic data is called “correcting.” Correction was achieved

for our purposes using software from Geometrics called MagMap2000. This software

can read and process magnetic data from a variety of sources, and functions included line

by line analysis, graphical editing and processing of data, analysis of anomalies, and

contouring of data. Corrections are achieved through a simple operation in

MagMap2000. The result is a text file in Surfer (.DAT) format which contains, in

addition to the original magnetic data, an additional column containing the corrected

readings. The resulting file is then opened in Surfer 7.0, gridded using Inverse Distance

to Power and Spline Smoothing, and a contour map created.

Corrections were performed on Geometrics G-881 magnetometer data collected at

the Josephine site on June 25, 2001 over three different grids. Two different base

stations were used, including a Geometrics G-856 land-based and a Sentinel sea-based.

The results are displayed in Figures 6-48 through 6-50. The data was contoured in 100

gamma intervals.

As previously discussed, several hypotheses were posed regarding the evaluation

of the effects of diurnal variation on magnetic data:

• Does adjusting for diurnal variation affect, enhance, or alter magnetic signatures and

their subsequent interpretation?

• Is there a difference between employment of data from the land-based and

submersible base stations readings?

In addressing these questions, the data compared had the following

characteristics:

• Is in its original, uncorrected format.

• Has been corrected with base station readings from both land-based and submersible

base stations.

Does adjusting for diurnal variation affect, enhance, or alter magnetic signatures

and their subsequent interpretation? A simple comparison of the data for each correction

illustrates the extent to which the corrections affect the original data (Table 6-8). When

examining the Geometrics 881 data for the 30-meter survey interval 4-knot grid, one can

see that the difference between the uncorrected data, data corrected with the G-856 land

base, and data corrected with the Sentinel marine base is negligible. Consequently, the

contour maps are very similar (Figures 6-48 through 6-50). Similar results were obtained

with other combinations of grids and speeds.
Figure 6-48. Josephine 30-meter survey interval 4-knot grid G-856

 uncorrected data contoured with 100 gamma interval.

Figure 6-49. Josephine 30-meter survey inte

 corrected data contoured with 
6-71

feet

Contour interval 100 gamma

0 50 100 150

Figure 6-50. Josephine 30-meter survey interval 4-knot grid Sentinel

corrected data contoured with 100 gamma interval..

Table 6-8. Comparison of G-881 Data Values

for Josephine 25-Meter Survey Interval Grid.

Data Low Mag Reading High Mag Reading Range

uncorrected 46211.89 62526.56 16314.67

856 corrected -3007.96 13296.1 16304.06

Sentinel corrected -3055.98 13255.61 16311.59

As stated above, during current surveys the locations of encountered magnetic

anomalies are simply marked with a symbol (▲) and an identifying number, and

presented in tabular format with anomaly information including line number, shot point,

and coordinates. With regard to the latter, exact coordinates for a magnetic anomaly are

next to impossible to acquire when data is not contoured. While one can tell where along

the survey line it was encountered, one cannot tell if the anomaly originated from a

source to the right, to the left, or directly on the survey line. Contouring would in many

cases precisely locate the position of the anomaly. Furthermore, and perhaps more

importantly, a contour presents a visual signature of the anomaly that can then be

analyzed relative to its complexity and spatial attributes, signature characteristics that
6-72

help differentiate between anomalies that potentially represent an historic shipwreck and

those that represent modern ferromagnetic debris.

Because the difference between corrected data and uncorrected data is negligible,

and the fact that contouring presents critical analytic data, it should be concluded that,

even without base station data, offshore survey data should be contoured in situations

where a survey is conducted as a single unit (i.e., not split over multiple days).

6.3. Shipwreck Types and Magnetic Signatures

A number of studies have attempted to systematically classify the physical

expressions of shipwrecks in terms of spatial distributions of materials and anticipations

about the preservation of various structural elements. For example, Muckelroy (1978)

has presented the idea of classifying wreck sites along a simple dichotomy. In his

scheme, wreck sites can be classified as “discontinuous” or “continuous,” which are

expressions of the spatial distribution of wreck materials and are reflective of site

formation processes, particularly the initial processes. The “continuous” site is one in

which wreck materials are localized and elements and objects are not separated by

extensive sterile areas. The “discontinuous” site is one where wreckage is widely

scattered as a result of the wrecking process. Although the discontinuous wreck pattern

is generally considered to occur in high energy settings, such as along beaches and

shallow coastal areas (e.g., Clausen and Arnold 1975), they can exist in deepwater

settings if the initial wrecking event included processes that tore apart or scattered vessel

elements at and during sinking. In the GOMR, one can envision a discontinuous wreck

site in the case of an explosion and fire aboard a wooden-hulled steamer. However, the

general lack of high-energy settings in the GOMR indicates that the typical historic

shipwreck site in the study area will display a “continuous” pattern in terms of

distribution, a presumption generally supported by the available sidescan sonar imagery

from the area as noted previously.

Others have attempted to correlate shipwreck patterns with particular types of

magnetic signatures. For example, Delgado et al. (1984) and Gearhart (1988) have

classified shipwreck patterns in terms of the spatial distribution of wreck materials and

the anticipated characteristics of correlative magnetic signatures. Their work has dealt

exclusively with high-energy settings, such that their findings are not totally applicable to

the GOMR, but they are mentioned briefly. Reflecting mid-range theory building, they

identify three types of sites based on the spatial distribution of wreckage. These are the

buoyant hull pattern, buoyant hull fracture pattern, and the buoyant structure pattern.

The buoyant hull site is one which is “continuous” under Muckelroy’s definition

and reflects a situation where a vessel came ashore relatively intact. Gearhart (1988:40-

43) argues that the magnetic signature associated with these types of wrecks will,

typically, consist of a linear distribution of multiple anomaly peaks embedded in a larger,

principal magnetic signature. Additionally, the long axis of the overall anomaly pattern

will be oriented along the axis of the hull. Gearhart also notes that the long axis of the

anomaly, and the vessel’s hull, will be parallel to the water line because of the tendency
6-73

of a buoyant hull to turn broadside to waves when aground. Note that the signatures for

our three vessels, both in tabular and contour map format, fall within the confines of the

buoyant hull site definition.

The buoyant hull fracture site is reflective of a vessel’s hull that breaks up soon

after coming ashore. Therefore, wave action tends to scatter vessel elements away from

the main body of the wreck. If waves are sufficiently large, vessel components can be

scattered high up the beach while buoyant objects might drift away. The magnetic

signature associated with this type of wreck will consist of the pattern seen with the

buoyant hull site, plus a pattern of lower intensity, spatially discrete (single source)

anomalies radiating inland (upslope) and downcurrent from the principal signature

(Gearhart 1988:41).

The buoyant structure wreck site develops when a vessel breaks up offshore and

only buoyant objects float ashore. This wreck type might leave a trail of wreckage

scattered for some distance along a beach. Gearhart (1988:43) suggests that the magnetic

signature associated with this wreck type will consist of numerous, spatially separated

anomalies of varying intensities generally scattered in uneven patterns along a beach.

While these studies are of some interest in correlating wreck characteristics and

processes to magnetic signatures, they specifically relate to near-shore, high-energy

settings. These settings are rare in the study area (GOMR), such that these models have

only minimal direct applicability. In identifying anomaly patterns that are characteristic

for shipwrecks within the GOMR, Garrison et al. summarize characteristics that

differentiate between shipwrecks and modern ferromagnetic debris.

Anomaly and Sidescan Sonar Patterns Characteristic of Historic Shipwrecks

1. multiple peak anomalies or spatial frequency;

2. differential amplitude anomalies;

3. areal distribution >10,000 square m;

4. long gradients and duration;

5. axial or linear orientation of anomalies;

6. scour areas associated with anomalies;

7. exposed structure is geometrically complex and associated with anomalies; and

8. relative locational permanence.

Anomaly and Sidescan Sonar Patterns Characteristic of Modern Ferromagnetic

Debris

6. single peak anomalies or no spatial frequency;

7. few if any differential amplitude anomalies;

8. localized areal distribution <10,000 square m;

9. sharp gradients and short duration;

10. random, non-axial orientation of anomalies;

11. scour areas with no associated anomalies;
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12. exposed debris geometrically simple; and

13. relative locational permanence.

14. (Garrison et al. 1989:II-223)

All three wrecks investigated in our study certainly meet the majority of

characteristics for historic shipwrecks listed above. And while not a part of the study,

obtained sidescan images of at least the Josephine and the barge indicate that, at least for

these two wrecks, the last three characteristics apply as well.

Related to the characteristics of amplitude and duration, in an effort to assess

potential significance of anomalies, Pearson et al. developed general characteristics of

magnetometer signatures most likely to represent shipwrecks. The report states that “the

amplitude of magnetic anomalies associated with shipwrecks vary [sic] considerably, but,

in general, the signature of large watercraft, or portions of watercraft, range from

moderate to high intensity (>50 gammas) when the sensor is at distances of 20 ft. or so”

(1991:70). Employing a table of magnetic data from various sources as baseline data, the

report goes on to state that “data suggest that at a distance of 20 ft. or less watercraft of

moderate size are likely to produce a magnetic anomaly (this would be a complex

signature, i.e., a cluster of dipoles and/or monopoles) greater than 80 or 90 ft. across the

smallest dimension...” (Pearson et al. 1991:70).

While establishing baseline amounts of amplitude and duration reflective of the

magnetic characteristics for a shipwreck site, the authors recognize “that a considerable

amount of variability does occur” (Pearson et al. 1991:70). Generated in an effort to test

the 50-gamma/80-foot criteria and determine amount of variability, Table 6-9 lists

numerous shipwrecks as well as single- and multiple-source objects located by magnetic

survey and verified by divers. Although not an exhaustive compilation of known

shipwreck signatures, all shipwrecks meet and surpass the 50-gamma/80-foot criteria,

while all single-object readings, with the exception of the pipeline, fall below the criteria.

However, the signature of the pipeline should show up as a linear feature on a magnetic

contour map and not be confused with a single-source object. While the shipwrecks and

single objects adhere to the 50-gamma/80-foot criteria, the multiple objects do not. If all

targets listed in the table had to be prioritized as to the potential for representing a

shipwreck site based on the 50-gamma/80-foot criteria, three multiple-object targets

would have to be classified as potentially significant.

Appreciably lower in amplitude than the 200 gamma high/low demarcation

employed in the interval detection rates above, it is interesting to note that the Rhoda (the

wreck with the lowest recorded amplitude in our study) would not meet the 50-

gamma/80-foot criteria of a potentially significant anomaly employing a 100-meter

interval with the SeaSPY, the G-877, or the G-866 (see Table 6-5 above). Rather, it

would only begin to meet this criteria for all four instruments once the 50-meter transect

interval was employed.
6-75

Table 6-9. Compilation of Magnetic Data from Various Sources

Vessel/Object Type & Size Amplitude Duration Reference

Shipwrecks

J.D. Hinde 129-ft sternwheeler 573 110 Gearhart and Hoyt 1990

Mary Somers iron-hulled sidewheeler 5,000 400 Pearson et al. 1993

Gen. C.B. Comstock 177-ft. wooden hopper dredge 200 200 James et al. 1991a

Mary 234-ft. iron-hulled sidewheeler 1,180 400 Hoyt 1990

El Nuevo Constante 126-ft. wooden collier 65 250 Pearson et al. 1991

Virginius sidewheel blockade runner 12,000 400 Tuttle 2002

Tug wooden with machinery 30,357 176 Tuttle and Mitchell 1998

Mexico 288-ton wooden bark 1,260 454 Tuttle and Mitchell 1998

Star of the West 172-ton ocean-going wooden- 8,300 400 Krivor et al. 2002

James Stockton 55-ft. wooden schooner 80 130 Pearson et al. 1991

Homer 148-ft. wooden sidewheeler 810 200 Pearson and Saltus 1993

modern shrimp boat segment 27 x 5 ft. 350 90 Pearson et al. 1991

Confederate numerous vessels with 110 Long Irion and Bond 1984

Single Objects

pipeline 18-in. diameter 1570 200 Duff 1996

anchor 6-ft. shaft 30 270 Pearson et al. 1991

iron anvil 150 lbs. 598 26 Pearson et al. 1991

engine block modern gasoline 357 60 Rogers et al. 1990

steel drum 55 gallon 191 35 Rogers et al. 1990

pipe 8 ft. long x 3 in. diameter 121 40 Rogers et al. 1990

railroad rail segment 4-ft. section 216 40 Rogers et al. 1990

Multiple Objects

anchor/wire rope 8-ft. modern stockless/large 910 140 Rogers et al. 1990

Anomaly F stiff arm crane from a dredge 986 40 secs. Irion and Bond 1984

cable and chain 5 ft 30 50 Pearson et al. 1991

scattered ferrous 14 x 3 ft 100 110 Pearson et al. 1991

Although Garrison et al. modern debris-type anomalies “do not mimic patterns

expected for historic shipwrecks” (1989:II-223), in a later study Pearson et al. state that

“even though a considerable body of magnetic signature data for shipwrecks is now

available, it is impossible to positively associate a specific signature with a shipwreck or

any other feature” (1991:69). However, the general lack of high-energy settings in the

GOMR indicates that the typical historic shipwreck site in the study area will display a

“continuous” pattern in terms of distribution, a presumption generally supported by both

the magnetic signatures of our three investigated sites and the available sidescan sonar

imagery from the area as noted previously.
7.0: SUMMARY AND CONCLUSIONS

7.1. Introduction

The overall objective of this study has been to provide the Minerals Management

Service with information that will enhance its ability to protect historic shipwreck

resources in the Gulf of Mexico Region (GOMR) from the effects of its permitted

actions. Data have been collected on reported shipwreck occurrences and these have

been used to characterize particular aspects of the shipwreck population believed to exist

in the Gulf of Mexico. Particularly important has been an assessment of the spatial

distributions of reported shipwrecks and their utility in defining areas of high probability

that can be used to direct future offshore remote-sensing surveys. Additionally, field

work was undertaken to evaluate several offshore targets that represent reported hang

sites and unidentified objects in order to clarify the relationship between these types of

items and historic shipwrecks. Finally, controlled surveys were conducted over two

identified wreck sites using several marine magnetometers in various survey parameters.

The results were used to identify optimum survey parameters and instrumentation in

offshore remote-sensing surveys. The results of all of these aspects of the study are

summarized in this chapter and recommendations arising from these findings are

presented.

7.2. Model of Shipwreck Occurrences in the GOMR: The 2001 Shipwreck Model

The Scope of Work for this study requested the preparation of “a revised

predictive model for shipwrecks in the GOMR.” The model in question was that

developed in the 1989 study by Garrison et al. That study collected and synthesized a

considerable amount of information on shipwrecks in the Gulf of Mexico and developed

statements about the patterns of occurrences and distributions of those wrecks. Like any

model, the 1989 study attempted to synthesize complex observations and isolate the

“essential factors and interrelationships” which accounted for the variability seen in the

objects of interest, i.e., shipwrecks (Clarke 1972:12). That model relied principally on

the spatial distribution of reported shipwreck losses to develop generalizations about

those factors influencing the observed distributions. From the MMS perspective of

cultural resources protection, the critical expression of the 1989 model is found in the

high-probability areas (e.g., lease blocks) identified in the GOMR that are being used to

direct offshore remote-sensing surveys.

Like most models, the 1989 model of shipwreck occurrences in the GOMR must

be considered hypothetical in nature. It was based on particular sets of collected data and

seemed reasonable in light of that data. However, as is also the case in most models,

changes and alterations in the model are conceivable and, in fact, expected with the

collection of greater amounts of data. The Scope of Work for the present study required

that the 1989 model be revised and expanded and we considered that testing that model

was prerequisite to undertaking these tasks. As has been demonstrated in previous

sections, shortcomings in the 1989 model exist. These shortcomings can be related
7-2

mainly to the lack of precision that exists in the positions assigned to a very large number

of shipwrecks in the GOMR. An effort has been made to ameliorate this problem,

principally by weighing the reliability of the coordinates provided for shipwrecks and

recognizing that some will be useful in some sorts of spatial analyses, but not in others.

7.2.1. Characteristics of the Vessels in the 2001 Shipwreck Model

Data were collected that relate to various physical, chronological and spatial

characteristics of the 2,106 reported shipwrecks in the compiled database. Many of the

conclusions and inferences drawn from analyses of this sample of reported wrecks are

very similar to those proposed by Garrison et al. (1989); others add to and expand on the

information contained in that study.

Garrison et al. collected no information on vessel characteristics other than the

year of loss and reported position of loss. Some of the conclusions of that study

concerning the chronology of losses are mirrored in the findings presented here. Both

have revealed that the frequencies of reported wrecks in the GOMR increase through

time, with a quantitative increase occurring after about 1950. The present database, in

fact, shows that more vessels have been reported lost in the Gulf of Mexico in the past 50

years than in the previous four hundred. This can be related to several factors, but it is

not believed that the increase in losses through time is due to improved technologies that

influence modern mariners to take more risks, as suggested by Garrison et al. (1989:II115). Rather, it is expressive of the sheer number of vessels operating in the Gulf,

numbers that have increased dramatically in the past several decades. These vessels are

exposed to the same weather conditions and similar natural and man-induced hazards

faced by earlier ships, and even modern technologies cannot overcome all of these

dangers, resulting in losses. Additionally, these high numbers reflect the enhanced level

of reporting of marine casualties by various agencies that has occurred in the past 50

years. Interestingly, other studies, including the CEI (1977) study of losses in the Gulf of

Mexico, have not shown similar increases in casualties and losses in recent years. This

discrepancy appears to lie principally in the types of sources used to collect shipwreck

information and the definition of what constitutes an historic shipwreck. Other studies

have tended to rely on sources that provide information only on named vessels and/or on

vessels that can generally be categorized as “commercial” in nature. This has resulted in

the exclusion of large numbers of unnamed and unidentified wrecks and many smaller

vessels, such as those involved in fishing and recreational activities, all of which were

included in the present study.

The age of vessels included in the 2001 shipwreck database at the time of loss

does not show a strong correlation with the historical period of use, but appears to be

most closely associated with the type of vessel and how it was used. Large, twentiethcentury merchant ships lost in the GOMR are the oldest vessels as a class, with an

average use life of about 25 years, while the average use life of modern fishing vessels is

only about 15 years. The average age of the small sample of pre-modern steam-powered

vessels lost in the study area was only about nine years.
7-3

The age of vessels at loss in the database is presumed to provide some

information about the attributes of the entire population of wrecks in the study area. In

addition, age at loss is an important MMS cultural resources consideration in that it

relates to the identification of significant historic shipwrecks in the GOMR under the

guidelines established by the National Register of Historic Places. These guidelines,

generally, impart significance only on vessels that are over 50 years old. Analyses

presented here have demonstrated that using the year of loss as the date from which the

50-year interval for potential significance is computed eliminates almost 50 percent of

vessels that should be included because of their age when lost. Thus, when the year of

build is known, it rather than the year of loss must be used in identifying potentially

historic shipwrecks and, by extension, in identifying high-probability areas.

Information collected on vessel types lost in the GOMR shows that fishing vessels

of various sorts, but principally shrimp trawlers, are the most numerous class of losses

reported and likely represent the most numerous type of vessel in the entire population of

wrecks. Most of these fishing vessels are twentieth century in date and generally have

been overlooked by historians and archaeologists. Early vessels that attract the most

historical and archaeological interest are relatively few in numbers and widely scattered

in distribution.

Causes of loss were examined using information derived from various historical

sources. Garrison et al. (1989) discussed effects of hurricanes in detail and concluded

that they account for about 16 percent of losses during the period 1945-1976, while

others (Chanu and Chanu 1955) have suggested that storms accounted for a similar

percentage of losses in the Spanish flota vessels. Losses since the 1989 study provide

little additional information on the effects of hurricanes, but seasonal patterns of loss

were examined for all reported shipwrecks. Overall, there is no strong correlation with

season of the year and frequency of losses, suggesting that neither hurricanes nor winter

storms are overriding factors in the losses of vessels throughout the course of a year.

However, an examination of the losses of vessels associated with shrimping shows a

strong seasonal pattern in losses. Significantly, more shrimping vessels were lost during

the peaks of the shrimping season in the spring and in the fall than during the rest of the

year. In this instance, as it has been noted relative to the increased frequency of losses

through time, it is argued that the number of vessels in the Gulf at any one month or

season of the year is a stronger predictor of the frequency of losses that will occur than is

the weather. Similar findings have been made for vessels operating in the nineteenth

century cotton trade that were lost in the Dry Tortugas (Murphy and Jonsson 1993).

7.2.2. Spatial Patterning in the 2001 Shipwreck Model

Although there are questions about the reliability of the specific positions

provided for many reported losses, the general distribution of known shipwrecks in the

GOMR is considered meaningful. The overall patterns of wreck distributions seen in the

2001 database are in many ways similar to those shown in Garrison et al. (1989), even

though many of the discussions in that study did consider nearshore and onshore wrecks

not utilized in this one. The concentration of reported losses in waters closer to shore
7-4

shown by most researchers is reflected in the 2001 GOMR shipwreck data. Because

losses occurring inshore of Federal waters are not included in the present study, the data

on reported wreck locations relative to the shoreline is not directly comparable to other

studies. However, as noted earlier, over 80 percent of all reported losses in the database

fall inside of the 60-m contour line (see Figure 4-11).

The elimination of inshore losses (i.e., in state waters) in this study does exclude

the concentrations of wrecks at natural hazard locations such as the Dry Tortugas, Cape

San Blas, and the Chandeleur Islands that were apparent in the Garrison et al. (1989)

data. Natural hazards such as these are uncommon in the deeper waters of the GOMR

and, thus, have had less influence on shipwrecks there. A concentration of reported

losses in the shallow waters of the Ship Shoal area off of the Louisiana coast represents

one of the few areas where these types of natural features seem to have influenced losses

in the study area.

The overall distributions of wrecks in the study area reflect broad settlement and

economic trends and their influence on maritime traffic and routes. Very few losses

occurred in the study area prior to 1750, and significant increases in numbers do not

appear until after 1850. In light of the known history of vessel use in the 1800 to 1840

period, and the small number of losses reported for that period, we must assume that

losses for this period are seriously underreported. This is possibly true for earlier periods,

but seems to be most apparent for the first half of the nineteenth century.

Few early vessel losses are seen in the western Gulf and the early losses after

1700 are generally indicative of settlement and trading activities along the central and

eastern Gulf relating to the expansion of French settlement and control along the northern

Gulf coast. Garrison et al. (1989) attempted to correlate trading routes with shipwreck

losses, but found difficulty in quantitatively defining the spatial relationships between the

two. In light of these results, this study has not attempted a similar approach. However,

the patterns of wreck distributions over time presented above clearly show that, at a broad

level, the locations of loss correlate with the development of historic shipping routes.

The increased numbers and concentrations of losses in nearshore areas of the

central and western Gulf beginning in 1900, and particularly after 1950, appear to be

closely related to the growth of the shrimping industry as well as recreational boating and

the offshore oil and gas industry. Beginning in the nineteenth century, concentrations of

vessels do occur off of major ports of the central and western Gulf, but these are not so

apparent along the Florida coast. Garrison et al. (1989) noted a similar concentration of

vessels in areas of ports beginning in the nineteenth century, although it appears that

many of the losses they used to examine this association lay in state waters.

Garrison et al. (1989:II-116) also noted that the western Gulf had high

concentrations of losses both along and near shore, while the eastern Gulf had an

incidence of shipwrecks in the open sea that was more than double that of the west.

Garrison et al. (1989) do not define the specific area meant by the “open sea,” but the

present study does not show such a large difference between those vessels in nearshore
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areas and offshore areas in the eastern Gulf (see Figures 4-11 and 4-15). The apparent

reason for this divergence from the Garrison et al. data is the use in this study of different

sources for wreck information, particularly sport diving guides, that contain a great deal

of information on losses off the west coast of Florida. It is still apparent, however, that

the differences in overall reported wreck frequencies for inshore and offshore waters of

the study area are greater for the central and western Gulf than for the eastern Gulf.

The potentials for shipwreck preservation in the study area have been reviewed,

supplementing information provided in Garrison et al. (1989) with more recent

information on losses from the open waters of the Gulf. The new data suggest that

conditions for preservation in high-energy settings in the Gulf region appear to be

somewhat better and more widespread than previously had been thought. In general,

however, these types of high-energy settings are relatively rare in the GOMR such that

sediment transport and deposition is moderate to low over much of the study area. Some

amount of burial by sediment certainly does occur in some areas, but even at the few

early vessels examined in the study area, such as the Civil War steamer Hatteras, lost in

1863 (Anuskiewicz and Arnold 1992), the sidewheel steamers New York, lost in 1846,

and the Josephine, lost in 1881 (Irion and Ball 2001; Irion and Anuskiewicz 1999), vessel

remains are still exposed above the seafloor. A review of sidescan sonar records from

MMS-mandated surveys reveals that a large number of the vessels identified appear to be

relatively intact, show minimal scatter of wreckage, and commonly are only partially

buried by sediment. These conditions appear to exist throughout much of the GOMR

where water depths are over 10-m or so. However, many of the vessels seen in these

sidescan sonar records appear to be relatively modern and might represent steel-hulled

ships whose preservation will differ from wooden-hulled examples. Few of these vessels

have been examined by divers and specifics on their identities and conditions remain

unknown.

Only in recent years has any information been collected on the condition of

wrecks in deepwater portions of the GOMR. Although only a small number of deepwater

wrecks have been found, the available evidence suggests that preservation is good,

generally supporting findings from other parts of the world.

7.3. Identification of High-Probability Areas in the GOMR

The two previous studies of shipwrecks in the GOMR have each identified “highprobability areas” for shipwrecks in the Gulf of Mexico that have been used to direct

offshore remote-sensing surveys. The CEI (1977) study noted that shipwrecks tended to

be concentrated in a zone within about 10-km of the shoreline and were concentrated in

areas of seaports, natural hazards and navigation routes. This zone was designated as

Cultural Resource Management Zone 1 (CRMZ1), but as Garrison et al. (1989) noted, its

outer boundary was often well beyond 10-km from the coast as finally drawn. The

Garrison et al. (1989) study relied more heavily on finer scale assessments of the

densities of reported shipwreck locations in their identification of high-probability areas

in the Gulf. They suggested maintaining the high-probability zone lying within 10 km of

the coast, plus they identified specific areas of high wreck densities resulting from their
7-6

analysis using the quadrant approach discussed earlier. The high-probability zones they

delineated generally fell in the vicinity of several ports and navigation hazards where

high densities of wrecks were identified. Ultimately, the MMS used the results of the

0.5-degree quadrant analysis in the identification of high-probability zones. Additionally,

Garrison et al. (1989) recognized that individual lease blocks outside of the highprobability quadrants and CRMZ1 should be considered high-probability locations

because of their potential for containing shipwrecks. Because of the often unreliability of

the reported positions of loss of vessels, Garrison et al. (1989) suggested that the eight

contiguous lease blocks surrounding the individual block with a reported wreck location

also should be considered high-probability areas. Figure 7-1 provides information on the

location of historic shipwreck high-probability areas (i.e., by lease block) in the GOMR

presently identified by the MMS as derived from the Garrison et al. (1989) study.

Various analyses presented in this study have demonstrated that the predictability

of the 1989 model as it has been used to identify high-probability areas in the GOMR is

weak. Relying on GOMR remote-sensing survey data, it has been shown that there is no

statistically significant difference between discovering a shipwreck in an identified highprobability lease block or in finding one in a lease block not assigned a high probability

of containing historic wrecks. The principal reason behind this is the unreliability in the

reported positions of loss for so many vessels. Because of the nature of the reports of

loss on these vessels, it is impossible to entirely overcome this built-in error in the data.

However, an effort has been made to account for the potential error inherent in reports of

loss by assigning measures of reliability to the determined geographic coordinates of loss.

The assignment of geographic positions to a vessel ultimately derives from a complex set

of variables related to the initial account of loss. The use of a measure of reliability, as is

done here, cannot take into account all of those variables, nor in many if not most cases,

can it entirely ameliorate all of the error incorporated in many wreck positions finally

obtained.

However, this represents an initial step in trying to measure the utility of the

principal variable used in spatial analyses, the position of loss. As long as no efforts are

made to account for this error, the strength of statements about shipwreck distributions in

the GOMR will remain weak and the predictability of any models of these distributions

will be uncertain.

Other techniques for increasing reliability of positions are possible, but the most

obvious ones are difficult to accomplish. For example, a careful search for, review and

analysis of every primary account of loss for every vessel assigned a questionable

position might serve to accomplish some of this. This would be a tremendous

undertaking and would not clear up the questions about many losses. In a large number

of cases, the original accounts of loss simply do not contain sufficient information to

strengthen the accuracy of the assigned position of loss. For the present, we believe that

the use of reliability assessments, as is done here, is the most expedient and efficient way

of enhancing the strength and predictability of statements about the spatial distributions

of shipwrecks in the study area.
Figure 7-1. Historic shipwreck high-probability lease blocks identified in the GOMR in the 1989 study.
7-8

A general assessment of the probability of occurrence of shipwrecks in the study

area can be achieved by comparing wreck densities with preservation potentials across

the GOMR. This follows an approach presented in Garrison et al. (1989) for the GOMR

and by Pearson et al. (1989) for historic vessel losses within the boundaries of the New

Orleans District of the U.S. Army Corps of Engineers. Data on shipwreck densities,

preservation potential and overall potential are provided in Table 7-1 for the 70 MMS

lease areas in the GOMR. The overall potential represents the merged value of

shipwreck densities and preservation potential. The preservation potentials are derived

from information on sedimentary characteristics and on known shipwreck preservation

for areas of the GOMR as displayed in Figure 4-10. Shipwreck densities are derived

from the distributions of shipwrecks across lease areas per 1,000 square miles of area as

shown in Figure 4-15. The values used in Table 7-1 are: Low ≤ 25 reported wrecks per

1,000 mi2; Moderate = 26 to 50 reported wrecks and High ≥51 reported wrecks.

Table 7-1. Shipwreck Occurrence and Preservation Potentials

for MMS Lease Areas

LEASE AREA SHIPWRECK

POTENTIAL

PRESERVATION

POTENTIAL

OVERALL

POTENTIAL

SOUTH TEXAS

PORT ISABEL LOW HIGH-MODERATE MODERATE

SOUTH PADRE ISLAND MODERATE HIGH MODERATE TO HIGH

SOUTH PADRE ISLAND A LOW HIGH MODERATE

CORPUS CHRISTI LOW HIGH MODERATE

NORTH PADRE ISLAND MODERATE HIGH MODERATE TO HIGH

NORTH PADRE ISLAND A LOW HIGH MODERATE

MUSTANG ISLAND MODERATE HIGH MODERATE TO HIGH

MUSTANG ISLAND A LOW HIGH MODERATE

CENTRAL/EAST TEXAS

MATAGORDA ISLAND MODERATE HIGH MODERATE TO HIGH

MATAGORDA ISLAND A LOW HIGH MODERATE

BRAZOS MODERATE MODERATE TO HIGH MODERATE TO HIGH

BRAZOS A LOW MODERATE TO HIGH MODERATE

GALVESTON AREA HIGH MODERATE TO HIGH HIGH

GALVESTON AREA A LOW MODERATE LOW TO MODERATE

HIGH ISLAND MODERATE MODERATE MODERATE

HIGH ISLAND A LOW MODERATE LOW TO MODERATE

SABINE PASS (TX) HIGH MODERATE MODERATE TO HIGH

WESTERN LOUISIANA

SABINE PASS (LA) HIGH MODERATE MODERATE TO HIGH

WEST CAMERON LOW MODERATE LOW TO MODERATE

EAST CAMERON LOW MODERATE TO HIGH MODERATE

VERMILION LOW MODERATE TO HIGH MODERATE

SOUTH MARSH ISLAND LOW MODERATE TO HIGH MODERATE

EUGENE ISLAND MODERATE MODERATE TO HIGH MODERATE TO HIGH

CENTRAL/EASTERN LOUISIANA

SHIP SHOAL MODERATE MODERATE TO HIGH MODERATE TO HIGH

SOUTH PELTO HIGH MODERATE TO HIGH HIGH

SOUTH TIMBALIER MODERATE MODERATE TO HIGH MODERATE TO HIGH

EWING BANK LOW MODERATE TO HIGH MODERATE
7-9

Table 7-1. (continued). Shipwreck Occurrence and Preservation Potentials

for MMS Lease Areas

LEASE AREA SHIPWRECK

POTENTIAL

PRESERVATION

POTENTIAL

OVERALL

POTENTIAL

GRAND ISLE AREA MODERATE MODERATE TO HIGH MODERATE TO HIGH

BAY MARCHAND HIGH MODERATE TO HIGH HIGH

WEST DELTA MODERATE MODERATE TO HIGH MODERATE TO HIGH

MISSISSIPPI CANYON LOW MODERATE TO HIGH MODERATE

SOUTH PASS MODERATE MODERATE TO HIGH MODERATE TO HIGH

MAIN PASS LOW MODERATE TO HIGH MODERATE

BRETON SOUND MODERATE MODERATE MODERATE

MISSISSIPPI/ALABAMA

CHANDELEUR LOW MODERATE TO HIGH MODERATE

MOBILE HIGH MODERATE TO HIGH HIGH

VIOSCA KNOLL LOW MODERATE TO HIGH MODERATE

FLORIDA PANHANDLE

PENSACOLA MODERATE MODERATE MODERATE

DESTIN DOME LOW LOW TO MODERATE LOW TO MODERATE

APALACHICOLA LOW LOW TO MODERATE LOW TO MODERATE

CENTRAL FLORIDA

GAINESVILLE LOW MODERATE LOW TO MODERATE

TARPON SPRINGS LOW LOW TO MODERATE LOW TO MODERATE

ST. PETERSBURG LOW LOW TO MODERATE LOW TO MODERATE

CHARLOTTE HARBOR LOW LOW TO MODERATE LOW TO MODERATE

SOUTHWEST FLORIDA

PULLEY RIDGE LOW LOW TO MODERATE LOW TO MODERATE

MIAMI LOW LOW TO MODERATE LOW TO MODERATE

KEY WEST LOW MODERATE LOW TO MODERATE

DRY TORTUGAS LOW LOW TO MODERATE LOW TO MODERATE

WESTERN OPEN GULF LOW UNKNOWN UNKNOWN

EASTERN OPEN GULF LOW UNKNOWN UNKNOWN

As seen in Figure 7-2, the distribution of overall shipwreck potentials across the

GOMR shows moderate to high potentials along the western and central Gulf in the

nearshore lease areas, decreasing to a low to moderate potential in the nearshore areas in

the eastern part of the Gulf. This is generally the trend observed by Garrison et al.

(1989). However, it is suspected that the overall shipwreck potentials obtained for some

lease areas are underestimates of their true potential. This seems to be particularly true

for some of the lease areas off the central and western Louisiana coast, such as those

from the Eugene Island to West Cameron areas, and those south of Mobile, Alabama. As

shown in Figure 3-4, offshore remote-sensing surveys have located a number of sunken

vessels in these areas. Sidescan sonar records suggest that many of these wrecks are well

preserved and in reasonably good condition. However, few of these wrecks have been

physically examined by divers and their identity, age, and true condition are not known.

Additionally, these are lease areas where numerous remote-sensing surveys have been

conducted and the densities of known wrecks here is certainly partially reflective of this.
Figure 7-2. Overall shipwreck potentials by lease areas.
7-11

Table 7-1 and Figure 7-2 provide general information on shipwreck potentials

across the GOMR. The identification of specific and spatially more restricted highprobability zones in this study generally follows the technique presented by Garrison et

al. (1989), tempered with the concept of reliability discussed above. We have used

ArcView to objectively identify areas of shipwreck densities using the data from the 2001

shipwreck database. Ultimately, we suggest that those areas containing densities of 25 or

more reported shipwrecks per 0.5-degree unit of area should be classified as highprobability areas.

We have attempted to strengthen the reliability of the true shipwreck potential of

these selected areas by eliminating from consideration all of those reported wrecks that

have a very low reliability in their reported position of loss or for which insufficient

information is available to make such an assessment (i.e., Reliability Factor 4). ArcView

uses circular areas in its density analysis and these have been converted into standard

MMS offshore lease blocks by including in each high-probability area all of the lease

blocks within or that intersect the circular areas.

These high-probability 0.5-degree units exist as overlapping and adjacent entities

extending along the central and western Gulf coast (see Figure 4-30). Although Garrison

et al. (1989) used many losses from inshore state waters, and the present study uses only

those in state waters assigned location Reliability Factors 2 and 3, the general distribution

of the 0.5-degree high-probability units in the 1989 study resembles the ones obtained

here. To an extent, these areas reflect “port’ activity, as was indicated by Garrison et al.

(1989), but not necessarily losses occurring in and around port entrances, where the

combination of high vessel densities and natural hazards produced increased losses. In

the present instance, the concentration of losses in the general vicinity of ports is seen

primarily as a reflection of higher vessel densities with only minimal influences from

natural hazards like shoals, bars, etc.

These 0.5-degree units encompass only a segment of the reported shipwreck

population in the GOMR and, as in the Garrison et al. (1989) study, we suggest that the

identification of high-probability areas outside of these high density zones must be

considered to take into account other reported wrecks. In the identification of other areas,

we have relied heavily on the Reliability Factors discussed above. First, we suggest that

all lease blocks containing reported or discovered shipwrecks assigned a Reliability

Factor of 1 should be classified as high-probability lease blocks. Secondly, we suggest

that all lease blocks containing the positions of reported shipwrecks assigned a Reliability

Factor 2 be considered as high-probability lease blocks. Further, following the lead of

Garrison et al. (1989), because of the potential for some error in the positions of vessels

assigned a Reliability Factor 2, we suggest that the eight contiguous lease blocks around

the one containing the vessel position be included as high-probability blocks.

No effort has been made to further refine the identification of these lease blocks

on other vessel attributes, of which age is probably the most important. Specifically,

vessels generally have to be over 50 years old to be considered historically significant

and thus of greatest concern to MMS cultural resources protection endeavors. However,

age is a “moving target” and it seems more appropriate for the MMS to use ArcView and
7-12

the information contained in the 2001 shipwreck database to identify those vessels (and

associated individual lease blocks or nine-lease block clusters) which should be

maintained in this high-probability class through time. As discussed earlier, date of build

is available for many vessels in the database and should be used over the date of loss in

computing age for an assessment of potential significance.

Vessels assigned a Reliability Factor of 3 have been eliminated from

consideration in the selection of individual high-probability lease blocks because of

concerns about the potential for error in their reported position. They have, however,

been used in the identification of the more general 0.5-degree areas of high probability.

As noted, vessels assigned a Reliability Factor of 4, because of serious questions about

their position accuracy, have not been used in identifying high-probability areas.

Garrison et al. (1989) also identified as high-probability areas all of the lease

blocks in Federal waters falling within 10 km of the shoreline, essentially maintaining the

principal recommendation from the earlier 1977 CEI study (see Figure 7-1). Ultimately,

all of these high-probability lease blocks as identified by the MMS for its survey program

fall off of the states of Louisiana, Mississippi and Alabama, where state boundaries

extend only 4.8-km (three miles) offshore. The data collected in the present study do not

support the specific delineation of those Federal lease blocks within 10-km of the

coastline as high-probability blocks. However, as seen in Figure 4-30, most of these

lease blocks are encompassed within the 0.5-degree units containing 25 or more reported

losses and thus are delineated as high-probability lease blocks on this criterion.

Figure 7-3 provides information on the distribution of all of the various classes of

high-probability areas identified in this study. A full listing of the lease blocks included

in all of these areas is provided as an ArcView file. As can be seen, high-probability

areas are concentrated off the central and western Gulf coasts, principally within the 60-

m contour line. The most significant concentration of identified high-probability lease

blocks beyond the 60-m contour is off the mouth of the Mississippi River. Under the

most recent NTL regarding MMS archaeological survey requirements, those highprobability lease blocks falling in water depths of less than 200-m would be subjected to

remote-sensing surveys using line spacing of 50-m, while those in deeper waters would

utilize 300-m line spacing.

As seen in Figure 7-3, only a relatively small number of high-probability lease

blocks fall in water deeper than 200-m. This means that the vast majority of the lease

blocks identified as high-probability areas in this study will be subjected to remotesensing surveys using 50-m line spacing.

The total number of lease blocks identified as high-probability locales in this

study is 5,198, considerably more than the 2,469 currently identified by MMS. As can be

seen in Figures 7-1 and 7-3, much of the increase is in our identification of many more

high-probability lease blocks along the central and western Gulf coast. There is a slight

increase in the number of high-probability lease blocks identified in the eastern Gulf off

the Florida coast, while little difference is seen in the number of high-probability lease

blocks identified in the deeper waters of the Gulf by the two studies.
Figure 7-3. Historic shipwreck high-probability lease blocks identified in the GOMR in the present study
7-14

The identification of a greater number of high-probability lease blocks in this

study results from several factors. The demonstrated poor predictability of the 1989

model lies principally in the unreliability of reported positions of loss. In the

identification of 0.5-degree high-probability units we have utilized a wreck density that

results in the selection of areas that are fairly large under the presumption that this will

“capture” some of the positioning errors known to exist. As a result, these 0.5-degree

areas encompass more lease blocks than did those in the 1989 study.

Another reason for the increased number of high-probability lease blocks is

because no effort has been made to eliminate vessels that are less than 50 years old in the

identification of the high-probability lease blocks outside of the 0.5-degree units. As

noted above, the age of vessels reported lost in the GOMR is a “moving target” that will

require periodic assessments and updates by the MMS in its identification of potentially

significant wrecks and the selection of high-probability areas. The data necessary to do

this are provided in the ArcView files and shipwreck database submitted as part of this

study. Although we recommend that the MMS undertake the process of eliminating

vessels and their associated high-probability areas on the basis of age, the database has

been examined along these lines to provide some idea of how many lease blocks might be

eliminated assuming the age criterion is based on the year 2001. The findings are

presented below.

In the selection of high-probability lease blocks outside of the 0.5-degree units,

502 entries in the shipwreck database were used, all of which have been assigned

Reliability Factors 1 or 2 for their position reliability. Date of build information reveals

that 44 of these vessels have been constructed since 1951 and, because they are less than

50 years old, they do not meet the age criterion for significance. All 44 of these vessels

have been assigned a Reliability Factor of 2, therefore each has been incorporated into a

nine-lease-block high-probability unit. Together, these 44 vessels incorporate 396 highprobability lease blocks that, as of the year 2001, could be subtracted from the 5,198

high-probability lease blocks identified in our model. The date of build is unknown for

396 of the 502 entries used to identify high-probability lease blocks outside of the 0.5-

degree units. Two hundred four of these have been lost since 1951 and, under the

parameters of the 1989 model, would be eliminated in the identification of highprobability blocks because they sank less than 50 years ago. One hundred seventy-two of

these are assigned a Reliability Factor of 2 and 32 a Reliability Factor of 1, meaning that

these losses together incorporate 1,580 lease blocks that could be eliminated as highprobability blocks if date of sinking is used in assessing age and potential significance.

Finally, no date of loss is available for 185 of the vessels used in the selection of highprobability lease blocks outside of the 0-5-degree units. Of these, 130 are assigned a

Reliability Factor of 2 and 55 a Reliability Factor of 1, and together they contribute to the

identification of 1,225 high-probability lease blocks. In sum, these vessels that are either

known to be less than 50 years old, or sank in the past 50 years, or whose date of sinking

is unknown, contribute to the identification of a total of 3,201 high-probability lease

blocks in our model. However, many of these represent overlapping lease blocks and the

actual number of individual lease blocks involved is 2,155. Therefore, if these criteria

are used for eliminating vessels that are or might be non-significant because they are less
7-15

than 50 years old, it would reduce the total number of identified high-probability lease

blocks in our model to 3,043. In essence, the 5,198 identified high-probability blocks

must be considered a maximum number that will be reduced dependent upon the criteria

selected by the MMS for eliminating any vessels deemed non-significant on the basis of

age. As noted in Chapter 4, almost 50 percent of all vessels lost in the GOMR in the past

50 years with a known date of build are over 50 years old. Thus, the MMS must be

cognizant of the fact that using the date of loss in identifying vessels that might meet the

National Register age criterion for significance is going to eliminate from consideration a

large number of vessels whose true age does meet that 50-year-old requirement.

The high-probability areas identified in this study constitute the most important

expression of the “model” of shipwreck occurrence in the Gulf of Mexico relative to

MMS management of historic shipwrecks in the GOMR. It is a model, and thus is a

simplified expression of sets of complex phenomena. An effort has been made to make

the shipwreck data more useful in identifying high-probability locations through the

collection of more information on more attributes than had been done in the 1989 study.

In addition, the concept of “Reliability” in terms of reported position of loss has been

incorporated in an attempt to strengthen the identification of high-probability areas. We

believe that the predictability of the 2001 shipwreck model has been enhanced by the

addition of these various elements, but ultimately, the model will require testing to

ascertain its viability.

7.4. Correlation of Hangs and Reported Shipwrecks

In an effort to correlate hangs with reported shipwreck positions, ground-truthing

was conducted of selected hang sites, unknown objects, unknown vessels and reported

shipwreck locations.

The initial sidescan sonar survey of each of the 20 target areas revealed that only

nine target areas contained bottom features indicative of submerged cultural resources

(see Table 5-1). Target inspection indicated that of the nine potential targets, only one

represented a shipwreck. Located in the Vermillion Area, Target 15 was a modern steelhulled shrimp trawler unassociated with any reported hangs. This vessel is not considered

significant based on National Register of Historic Places (NRHP) eligibility criteria. Of

the remaining targets, two represented modern debris such as pipe or platform debris

associated with the oil industry, and six represented natural bottom features or had

negative findings.

The 20 target areas investigated actually encompassed 52 reported or recorded

objects, 31 of which were reported hang locations. These 31 reported hang locations fall

in 16 of the targets (actually target areas) examined. These hangs represent locations

where fishermen, principally shrimpers, have caught their nets on objects on the bottom.

The examination of these reported hangs was of particular interest because of the

demonstrated fact that historic wrecks in the GOMR are commonly entangled in shrimp

netting and rope, meaning that some hang locations should represent unreported wrecks.

At only one of the 16 targets containing reported hangs, Target 5, was an object found
7-16

that might constitute the hang site. Even in this instance, however, the object believed to

have produced the hangs (a pile of pipes designated Target 5a) was over 1,000 feet away

from the reported hang locations. One other target, Target 17, is believed to contain a

buried object that could constitute a hang when exposed, although this is only a tentative

assumption. If we assume that both Target 5 and Target 17 do contain the objects

producing the reported nearby hangs, then the correlation of reported hang locations with

an object on the bottom has been verified in only 12.5 percent (2 of 16 targets) of the

cases examined. If only Target 5 is considered to be reliably identified as a hang source,

then in only 1 in 16 (6.3 percent) instances were reported hang locations associated with a

verified object.

In no instance did reported hang locations correlate with a shipwreck. The

remains of the modern trawler found at Target 15, the only vessel found during the

diving, are not spatially associated with any reported hang locations provided in the

Texas A&M or MMS hang records used. However, a large quantity of netting was

entangled on the trawler, indicating that it has snagged nets. Why it is not listed as a

hang in the sources examined is unknown. The one other object discovered that would

constitute an obvious hang is Target 1, the probable remains of an oil or gas platform

found in lease block South Marsh Island 17. However, like the wreck at Target 15, there

is no indication that this object has been reported as a hang location.

As noted previously, the 20 targets examined represent an extremely small sample

of the total population of hangs, objects and shipwrecks reported in the GOMR. At only

one of 16 target locations could reported hangs be associated with an object on the

bottom and in this instance, the object and the hangs are approximately 1,300 feet apart.

As has been discussed, this discrepancy in positions is almost certainly due to the

conversion of Loran coordinates, in which most hang positions were originally recorded,

into latitude/longitude or state plane coordinates. No information was collected that

could be used to evaluate how consistent this 1,300-foot difference is across the GOMR.

However, it is suspected to vary dependent upon location. In the case of Target 5, it is

very likely that if a Loran system had been used to relocate the cluster of hangs, the

actual position obtained in the GOMR would have been very close to the pile of pipes.

Target 15, the modern shrimp trawler, is identified in the 2001 shipwreck

database as an unknown object. This object had been located during a lease block

remote-sensing survey and appears as an amorphous object.

7.5. Comparison of Magnetometer Technologies and Survey Line Spacing

As stated in the SOW, the goals of Task 3 were: 1) a comparison of the

“industry-standard” proton magnetometer (i.e., Geometrics 866) that is currently

employed in marine archaeological surveys to the current state-of-the-art cesium

magnetometer to determine if a change in the MMS/GOMR survey methodology is

warranted; and 2) to evaluate both magnetometers at various survey line spacings to

determine the minimally acceptable survey line spacing for detecting historic shipwrecks.

To accomplish this task, the marine survey was to be conducted with each magnetometer
7-17

over two known shipwrecks at varying transect intervals. The wrecks employed in the

survey initially included the Josephine, an iron-hulled sidewheeler and the Rhoda, a

wooden-hulled sailing ship, but subsequently included a barge suspected of being ironhulled.

While only two magnetometers were initially identified for the study, it was

decided that it would be beneficial to the investigation to field-assess other magnetometer

models in addition to the two currently identified in the contract for the survey trials of

Task 3. These included an Overhauser effect proton magnetometer and the new

Geometrics G-877 proton precession magnetometer. The G-877 is the replacement for

the proton precession industry standards currently employed in the Gulf, i.e., the G-801

and the G-866 precession proton magnetometers. These latter models, while still

employed by many of the survey companies involved in the oil and gas industry, are no

longer being produced (as well as their respective parts), and are being phased out by

many firms. Relative to employment of the Overhauser type magnetometers, produced

by Marine Magnetics and others (i.e., GEM Systems), Overhauser magnetometers offer

nearly the same sensitivity as the cesium magnetometers, particularly at moderate speeds.

Perhaps more germane to our study is the fact that these magnetometers are and will be

employed by Gulf survey companies on projects that will have MMS purview. Therefore,

the addition of these two models offered to keep the study “up-to-date” and more

reflective of systems employed now and that will be employed in the future by oil and

gas industry-related companies. The four models employed in our survey included the

Geometrics G-866, Geometrics G-877, Geometrics G-881, and Marine Magnetics’

SeaSPY.

Besides the two additional magnetometers, it was also decided that a submersible

base station be tested to determine its applicability to offshore surveys as it might apply

to post-mission processing of magnetic data, especially with regard to surveys with line

spacing of 50-m. Mirroring the NTL 98-06, the new NTL 2002-01 requirements do not

stipulate the employment of base stations or contouring of magnetometer data. This is a

reflection of the fact that, apart from oil rigs or platforms that cannot be employed as a

suitable location because of their inherent magnetism, there is nowhere to place a base

station in offshore Gulf waters. Currently, the locations of encountered magnetic

anomalies are simply marked with a symbol (_) and an identifying number, and presented

in tabular format with anomaly information including line number, shot point, and

coordinates. With regard to the latter, exact coordinates for a magnetic anomaly are next

to impossible to acquire when data is not contoured. Contouring would in many cases

locate the anomaly exactly. However, surveys are often conducted over many days with

interruptions by weather common. Without a base station to correct for this effect, the

diurnal variation that would be recorded during surveys that extended over a long period

of time makes contouring problematic at best. Therefore, a Sentinel® submersible base

station was included in this task in an effort to assess its functionality in the field, and

answer questions concerning employment in offshore surveys relative to issues of diurnal

variation and the applicability of contouring.
7-18

During Task 3 of the investigation, all four magnetometers were run on three

grids over two shipwrecks in an effort to determine how each instrument detected that

same wreck site with regard to maximum amplitude and duration. It should be stated that

this aspect of the investigation was not a contest to determine which instrument recorded

the highest gamma amplitude or deviation at the greatest spaced interval; nor was it a

controlled laboratory experiment where a sensor could be pulled past a piece of iron of a

known mass along an unwavering track spaced at an exactly known distance unaffected

by wind or current. Rather, it was a field trial conducted to simulate an actual survey

environment, with the Josephine situated in a high-current, open-ocean location and the

Rhoda in a somewhat protected bay environment, and to assess how each instrument

recorded the same wreck site, and if differences were present, determine if these findings

predicated changes to the current MMS GOMR survey methodology. Our investigation

revealed that all magnetometers performed well in the field trials, including the G-866, a

system that is antiquated although functional in most respects. Specific findings of this

aspect of the investigations are as follows:

• While the order of which instrument records the highest amplitude appears generally

to remain relatively constant, with the SeaSPY and G-877 exchanging places

followed by the G-881 and then the G-866, the variation in that order seems to be due

to minor differences associated with track line position (i.e., the location of the

sensor).

• The ability of the current 50-m transect interval to effectively record the wrecks

examined in this study has been amply demonstrated and argues for its effectiveness

in locating many of the classes of vessels known to have been lost in the GOMR.

However, it should be emphasized that the vessels examined in the present study are

large and contain considerable quantities of ferrous metal. The 50-m interval is

unlikely to be effective in identifying all wreck types in the GOMR, especially earlier

wrecks containing less iron or small wooden vessels or parts of wooden vessels that

produce smaller magnetic signatures. Therefore, it is recommended that in order to

provide better detection capability for all types of shipwrecks, especially earlier

wrecks which might be the most historically significant types within the GOMR, a

closer spaced transect interval, such as the 30-m interval, should be considered by the

MMS for employment in high-probability areas.

• Reflecting abilities of the for-years industry standard but now antiquated G-801 and

G-866 systems, the NTL requires dual scale readings, strip chart speeds, and

annotation of the strip charts with shot points and recorder speed. However, given the

computer-driven, digital-nature of all instruments today, these requirements appear

now to be outmoded and in need of revision, at least for those magnetometers that are

totally digital (i.e., G-877, G-881, SeaSpy, etc.). Magnetic data from these digital

models is collected simultaneously in the same file along with positioning, depth,

time, layback, gyro, etc., making annotation unnecessary. Additionally, the strip

chart is presented digitally on the screen in HYPACK (and other navigation

programs) and may be set at any gamma scale. Furthermore, when post-processing
7-19

data, track lines and any attendant anomalies can also be viewed and presented in any

gamma scale to allow for optimum characterization of that anomaly.

• Relative to the increased depth of 200 meters or less for survey of high-probability

OCS blocks, early magnetometer sensor types such as the G-866 have significant

limitations in that they physically will not sink below 225 feet regardless of how

much tow cable is deployed. This does not allow the sensor to be towed within the

MMS specification of six meters of the seafloor in deeper waters. Therefore, the

magnetometer chosen for survey at the deeper depths should be required to meet

depth parameters.

• Durations for each instrument vary to the point that no real comparisons can be made.

And, durations and amplitude do not appear to be affected by speeds up to 7 knots.

• While not stipulated as a requirement by the NTL, employment of the Sentinel during

our investigation highlighted its potential as an offshore tool in the collection of data

for post-processing of magnetic survey data. Although the actual magnetometer

operated excellently, collecting extremely smooth data, as discussed above the

acoustic release failed on one occasion and had to be retrieved manually by divers, a

scenario impossible in most GOMR survey situations. A prototype, the release is said

to have undergone corrective redesign. We suggest additional field trials of the

release mechanism before recommending this recovery system.

• Because contouring presents critical analytic data, it is recommended that even

without the use of a base station, offshore survey data should be contoured in

situations where a survey is conducted as a single unit (i.e., not split over multiple

days).

• For all magnetometers, the manufacturer’s firmware automatic monitoring feature

should be switched off if it will impede the collection of data such as occurred with

the SeaSPY.
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White, N.M., K.D. Ryder, S.M. Grammer, and K.L. Mayo. 1995. Archaeological Survey

of Dog Island, Franklin County, Florida. Department of Anthropology,

University of South Florida. Submitted to the Barrier Island Trust, Tallahassee,

Florida.

Wiggins, M. 1995. Torpedoes in the Gulf: Galveston and the U-boats, 1942-1943.

College Station, Texas: Texas A&M University Press.

Wild, K.S., Jr., and D.M. Brewer. 1985. Underwater Archeological Survey and Site

Assessment of Biscayne National Park. Tallahassee, Florida: Southeast

Archeological Center, National Park Service.
8-18

Wilson, E.M. 1983. A Typology of Vessels Known to have Been Used in the Mobile

Bay Region From the 16th Through the Twentieth Century. T.S. Mistovich and

V.J. Knight, Jr., eds. Cultural Resources Survey of Mobile Harbor, Alabama.

OSM Archaeological Consultants, Inc., Moundville, Ala. Prepared for the U.S.

Army Corps of Engineers, Mobile District.

Works Progress Administration [WPA]. 1938. Wreck Reports - A Record of Casualties

to Persons and Vessels on the Mississippi River, Its Tributaries, on Lakes and

Other Waterways of the U.S. Customs District, Port of New Orleans, 1873-1924.

Survey of Federal Archives in Louisiana, Service Division, Works Projects

Administration. On file at Hill Memorial Library, Louisiana State University,

Baton Rouge.

Works Progress Administration [WPA]. 1942. Ship Registers and Enrollments of New

Orleans, Louisiana. Vols. 1-6. Survey of Federal Archives in Louisiana, Service

Division, Works Projects Administration. On file at Hill Memorial Library,

Louisiana State University, Baton Rouge.

INTERNET WEBSITES REFERENCED

Association of Underwater Explorers. (www.mikey.net/aue).

Haze Gray & Underway. www.hazegray.org.

International Registry of Sunken Ships. http://users.accesscomm.ca/shipwreck/.

Liberty Ships. www.andrew.cmu.edu/~pt/liberty/liberty1.html.

Lloyd’s Merchant Shipping Losses and Shipwrecks.

www.lr.org/information/maritime/m-merchant.html

MBT Divers. www.mbtdivers.com/NUMBERSH.htm.

Merchant Vessel Database. www.boatman.com/mv.

Minerals Management Service, Gulf of Mexico Region, New Orleans.

www.gomr.mms.gov.

Palmer List of Merchant Vessels. www.geocities.com/mppraetorius/intro-com.

The Rig Museum. 2002. www.rigmuseum.com.

Schoonerman: Schooner and Tall Sailing Ships. www.schoonerman.com.

Shipwreck & Marine Disaster Links. www.home.gci.net/~alaskapi/success/shipwreck.
8-19

Texas Diver. www.texasdiver.com.

Tidewater Marine Service Company. 2002. www.tdw.com.

Uboat.net. www.uboat.net.

U.S. Merchant Marine. www.usmm.org.

Wrecks.Net. www.wrecks.net.
8-20

2001 SHIPWRECK DATABASE REFERENCES

(Principal references used in compiling the 2001 Shipwreck Database)

Arnold, J.B. III and R.J. Anuskiewicz. 1995. USS Hatteras: Site Monitoring and

Mapping, pp. 82-87. In Paul F. Johnston (editor). Underwater Archaeology

Proceedings From the Society for Historical Archaeology Conference.

Arnold, J.B. III, J.L. Goloboy, A.W. Hall, R.A. Hall, and J.D. Shively. 1998. Texas'

Liberty Ships: From World War II Working-Class Heroes to Artificial Reefs.

Bulletin No. 99-1. Texas Parks and Wildlife, Austin.

Bauer, J.K. 1970. Ships of the Navy 1775-1969. New York: Rensselaer Polytechnic

Institute.

Berg, D. and D. Berg. 1991. Florida Shipwrecks: The Diver's Guide to Shipwrecks

Around the State of Florida & the Florida Keys. East Rockaway, New Jersey:

Aqua Explorers, Inc.

Berman, B.D. 1972. Encyclopedia of American Shipwrecks. Boston, Massachusetts:

The Mariners Press.

Birchett, T.C.C. and C.E. Pearson. 1998. Underwater Cultural Resources Survey of the

Houma Navigation Canal, Cat Island Pass Channel Realignment, Terrebonne

Parish, Louisiana. Coastal Environments, Inc., Baton Rouge. Prepared for the

U.S. Army Corps of Engineers, New Orleans District.

Browning, R.M., Jr. 1996. U.S. Merchant Vessel War Casualties of World War II.

Annapolis, Maryland: Naval Institute Press,

Church, R.A. 2002. Unraveling the Mystery: The Discovery of the German Submarine

U-166. Paper presented at The Minerals Management Service 2002 Information

Transfer Meeting, January 8-10, Kenner, Louisiana.

Cipra, D.C. 1997. Lighthouses, Lightships, and the Gulf of Mexico. Alexandria,

Virginia: Cypress Communications.

Coastal Environments, Inc. 1977. Cultural Resources Evaluation of the Northern Gulf of

Mexico Continental Shelf. 3 volumes. Prepared by Coastal Environments, Inc.,

for the Bureau of Land Management, U.S. Department of the Interior, New

Orleans Outer Continental Shelf Office. Springfield, Virginia: National

Technical Information Service.

Cowles, D.D. (compiler) 1983. The Official Military Atlas of the Civil War. Reprint.

New York, New York: The Fairfax Press.
8-21

Evans, J. n.d. State and Federally Funded Artificial Reefs of Florida, 1985-1995.

Designed and produced by the author. On file at Florida Bureau of

Archaeological Research, Division of Historical Resources, Florida Department

of State, Tallahassee.

Fairfield Industries. 1979. Mouth of Colorado River, Texas Project. Cultural Resources

Assessment Aug.-Oct. 1979. Fairfield Industries. Prepared for U.S. Army Corps

of Engineers, Galveston District.

Garrison, E.G., C.P. Giammona, F.J. Kelly, A.R. Tripp, and G.A. Wolff. 1989. Historic

Shipwrecks and Magnetic Anomalies of the Northern Gulf of Mexico:

Reevaluation of Archaeological Resource Management Zone 1. 3 volumes. The

Texas A&M Research Foundation, College Station, Texas. OCS Study/MMS 89-

0024. U.S. Department of the Interior, Minerals Management Service, Gulf of

Mexico OCS Region, New Orleans, Louisiana.

Hall, H. 1884. Report on the Ship-Building Industry of the United States.

Miscellaneous Documents of the House of Representatives, Second Session, 47th

Congress. Washington, D.C.: Government Printing Office.

Hoyt, S.D. 1993. Offshore Underwater Investigations, Houston-Galveston Navigation

Channels, Texas Project. Galveston, Harris, Liberty and Chambers Counties,

Texas. Espey, Huston & Associates, Inc., Austin, Texas. Prepared for the U.S.

Army Corps of Engineers, Galveston District.

Irion, J.B. and R.J. Anuskiewicz. 1999. MMS Seafloor Monitoring Project: First Annual

Technical Report, 1997 Field Season. OCS Report, MMS 99-0014. U.S.

Department of the Interior, Minerals Management Service, Gulf of Mexico OCS

Region, New Orleans, Louisiana.

Irion, J.B. and D.A. Ball. 2001. The New York and the Josephine, Two Steamships of

the Charles Morgan Line. International Journal of Nautical Archaeology

30(1):6-11.

Irion, J.B. and P.V. Heinrich. 1993. Phase II Cultural Resource Investigation of

Submerged Anomalies, Breton Sound Disposal Area, Plaquemines Parish,

Louisiana. R. Christopher Goodwin & Associates, New Orleans. Prepared for

the U.S. Army Corps of Engineers, New Orleans District.

James, S.R., Jr. 1991. Magnetometer Survey and Ground Truthing Anomalies Corpus

Christi Ship Channel, Aransas and Nueces Counties, Texas. Panamerican

Consultants, Inc., Tuscaloosa, Alabama, and Coastal Environments, Inc., Baton

Rouge. Prepared for the U.S. Army Corps of Engineers, Galveston District.
8-22

Lochhead, J.L. 1954. Disasters to American Vessels, Sail and Steam, 1841-1846.

Compiled from the New York Shipping and Commercial List. Mariners Museum,

Newport News, Virginia.

Lonsdale, A.L. and H.R. Kaplan. 1972. A Guide to Sunken Ships in American Waters.

Arlington, Virginia: Compass Publications Inc.

Lloyd’s of London. 1987. Lloyd's Weekly Casualty Reports. London: Lloyds of

London Press, LTD, London.

MacMillan, B., R.C. Smith, and J. Miller. 1996. U.S. Navy and Confederate Shipwrecks

in Florida: The Florida Navy Legacy Project Phase One: Historical & Archival

Compilation, Volume Two: Florida Shipwreck Database. Submitted to Naval

Historical Center, Washington, D.C. Bureau of Archaeological Research, Florida

Division of Historical Resources, Tallahassee.

Marx, R.F. 1971. Shipwrecks of the Western Hemisphere, 1492-1825. New York, New

York: David McKay Company, Inc.

Marx, R.F. 1985. Shipwrecks in Florida Waters. Chuluota, Florida: The Mickler

House.

Mitchell, C.B. 1975. Merchant Steam Vessels of the United States 1790-1868: "The

Lytle-Holdcamper List." With Supplements. Staten Island, New York:

Steamship Historical Society of America.

Moore, A.R. 1990. A Careless Word...a Needles Sinking: A History of the Staggering

Losses Suffered by the U.S. Merchant Marine, Both in Ships and Personnel,

During world War II. 5th edition. Kings Point, New York: American Merchant

Marine Museum.

National Park Service. 1994. Inventory of Historic Light Stations. Washington, D.C.:

National Park Service, History Division.

Naval History Division. 1971. Civil War Naval Chronology 1861-1865. Navy

Department. Washington, D.C.: U.S. Government Printing Office.

Panamerican Maritime, L.L.C. 1999. Diver Evaluation of Eighteen Unidentified Remote

Sensing Targets Offshore Quintana, Texas. Panamerican Maritime, L.L.C.,

Memphis. Prepared for Exxon Pipeline Company, Houston, Texas, and MPC

International, Inc., Houston, Texas.

Pearson, C.E. and P.E. Hoffman. 1995. The Last Voyage of El Nuevo Constante: The

Wreck and Recovery of an Eighteenth-Century Spanish Ship off the Louisiana

Coast. Baton Rouge, Louisiana: Louisiana State University Press.
8-23

Pybas, D. 1991. Atlas of Artificial Reefs in Florida, 4th edition. Gainesville, Florida:

Florida Sea Grant Program. University of Florida.

Rinehart, Captain L.T. 1998. The Captain's Guide to Wrecks and Reefs. Privately

printed by the author.

Rohwer, J. (translated by J.A. Broadwin). 1983. Axis Submarine Successes 1939-1949.

Annapolis: Naval Institute Press.

Silverstone, P.H. 1989. Warships of the Civil War Navies. Annapolis: Naval Institute

Press.

Singer, S.D. 1992. Shipwrecks of Florida. Sarasota, Fla.: Pineapple Press. Inc.

Summer, J. 1996. Ten Days on the Cazador. Diver Magazine, June 1996.

Townsend, T. 1980. Texas Treasure Coast. Austin, Texas: Eakin Press.

Way, F., Jr. (compiler). 1994. Way's Packet Directory, 1848-1994. Athens, Ohio: Ohio

University Press.

Wiggins, M. 1995. Torpedoes in the Gulf: Galveston and the U-boats, 1942-1943.

College Station, Texas: Texas A&M University Press.

Works Progress Administration [WPA]. 1938. Wreck Reports - A Record of Casualties

to Persons and Vessels on the Mississippi River, Its Tributaries, on Lakes and

Other Waterways of the U.S. Customs District, Port of New Orleans, 1873-1924.

Survey of Federal Archives in Louisiana, Service Division, Works Projects

Administration. On file at Hill Memorial Library, Louisiana State University,

Baton Rouge.

Works Progress Administration [WPA]. 1942. Ship Registers and Enrollments of New

Orleans, Louisiana. Vols. 1-6. Survey of Federal Archives in Louisiana, Service

Division, Works Projects Administration. On file at Hill Memorial Library,

Louisiana State University, Baton Rouge.

Electronic Databases, Unpublished Documents and other Government Publications

ANC. Archives des Colonies. n.d. Archives des Colonies, Series C13A, C13B, and

C13C. Microfilm Copies, Special Collections, Howard-Tilton Library, Tulane

University, New Orleans.

ASSOCIATION OF UNDERWATER EXPLORERS. Web page of the Association of

Underwater Explorers. (www.mikey.net/aue).
8-24

AWOIS. Automated Wrecks and Obstructions Information Service files maintained by

the National Oceanic and Atmospheric Administration (NOAA).

FAC. Shipwreck records maintained by the Florida Bureau of Archaeological Research,

Tallahassee.

FDMF. Database of artificial reefs off the coast of Florida maintained by the Artificial

Reef Program, Florida Division of Marine Fisheries, Florida Fish and Wildlife

Conservation Commission, Tallahassee.

GSMFC. Database of artificial reefs in the Gulf of Mexico maintained by the Gulf States

Marine Fisheries Commission, Ocean Springs, Mississippi.

MBT Divers. Web page of MBT Divers, Pensacola, Florida.

(www.mbtdivers.com/NUMBERSH.htm).

MVUS. Merchant Vessels of the United States. United States Government Printing

Office, Washington, D.C. Published by various agencies (United States Bureau

of Customs, 1868-1880; United States Department of the Treasury, 1881-1935;

United States Bureau of Marine Inspection and Navigation; 1936-1941; and

United States Coast Guard; 1941-) .

NIMA. Non-submarine Contact Database maintained by the National Imagery and

Mapping Agency (NIMA), Washington DC. Included in this database are the

Hangs and Obstructions files formerly maintained by the U.S. Navy,

Hydrographic Office.

TAC. Data obtained from the Texas Antiquities committee Shipwreck Files, Austin,

Texas.

USCG. Data obtained from electronic database of wrecks, hazards and obstructions

maintained by the United States Guard.

USCGCR. Data obtained from United States Coast Guard Marine Board Casualty

Reports (www.uscg.mil/hq/g-m/moa)

USLS. U.S. Life-Saving Service, various years. Annual Reports of the Operations of

the U.S. Life-Saving Service.

WADES. Data obtained from wadespages Web page (www.wadespages.com).

WWW.UBOATNET.WEB. Web page devoted to German U-boats.
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility 

for most of our nationally owned public lands and natural resources. This includes fostering 

sound use of our land and water resources; protecting our fish, wildlife, and biological diversity; 

preserving the environmental and cultural values of our national parks and historical places; 

and providing for the enjoyment of life through outdoor recreation. The Department assesses 

our energy and mineral resources and works to ensure that their development is in the best 

interests of all our people by encouraging stewardship and citizen participation in their care. 

The Department also has a major responsibility for American Indian reservation communities 

and for people who live in island territories under U.S. administration. 

The Minerals Management Service Mission 

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) 

primary responsibilities are to manage the mineral resources located on the Nation's Outer 

Continental Shelf (OCS), collect revenue from the Federal OCS and onshore Federal and Indian 

lands, and distribute those revenues. 

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program 

administers the OCS competitive leasing program and oversees the safe and environmentally 

sound exploration and production of our Nation's offshore natural gas, oil and other mineral 

resources. The MMS Minerals Revenue Management meets its responsibilities by ensuring the 

efficient, timely and accurate collection and disbursement of revenue from mineral leasing and 

production due to Indian tribes and allottees, States and the U.S. Treasury. 

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being 

responsive to the public's concerns and interests by maintaining a dialogue with all potentially 

affected parties and (2) carrying out its programs with an emphasis on working to enhance the 

quality of life for all Americans by lending MMS assistance and expertise to economic 

development and environmental protection.