United States
Environmental Protection
Agency
WH-553
Washington, DC 20460
Water
Assessment of
Environmental Fate and
Effects of Discharges from
Offshore Oil and Gas Operations
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ASSESSMENT OF ENVIRONMENTAL
FATE AND EFFECTS OF
DISCHARGES FROM OFFSHORE OIL
AND GAS OPERATIONS
Original By:
DALTON DALTON NEWPORT
3605 Warrensville Center Road
Shaker Heights, Ohio 44122
EPA Contract No. 68-01-6195
As Amended By:
Technical Resources. Inc.
3202 Monroe Street
Rockville. Maryland 20852
EPA Contract No. 68-01-6815
Work Assignment Manager: Eleanor Zimmerman
U. S. Environmental Protection Agency
Monitoring and Data Support Division
Office of Water Regulations and Standards
Washington. D. C. 20460
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ACKNOWLKDGKMKNTS
The original version of this report was produced in
November of 1982 by Dalton . Dalton . Newport (DDN) Inc. of
Cleveland. OH. During July. August, and September of 1984,
Technical Resources Inc. (TRI) of Rockville. MD incorporated
newly available data, amended, and edited the entire report.
The revisions to the original report have been substantial.
Significant contributions to the final report have been made by
all of the following individuals; thus, there is no principal
investigator:
Dr. Gary Petrazzuolo (TRI)
Dr. Allan D. Michael (TRI)
Dr. Charles A. Menzie (Consultant)
Hans Plugge (Consultant)
Eleanor J. Zimmerman (EPA)
The following individuals are acknowledged for their
contributions to the original report, as well as their new work
on catch per unit effort and species distribution which was
used in this report:
Robert H. Cole
Dr. Robert G. Rolan
Terry A. Mors
Lee Ann Smith
William K. Parland
Sharon E. Roth
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The following individuals reviewed drafts of the report
and/or supplied information that was used in this report.
Their help is greatly appreciated:
Thomas S. LaPointe (NOAA)
Timothy R. Goodspeed (NOAA)
Mark D. Schuldt (EPA)
Dr. Thomas W. Duke (EPA)
Alexander C. McBride (EPA)
Charles Robbins (EPA)
Raymond H. Johnson (EPA)
Marilyn E. Varela (EPA)
Justine V. Alchowiak (VERSAR. Inc.)
Judith R. English (VERSAR. Inc.)
Secretarial support and technical editing provided by
Debra A. Miles, and staff, from VERSAR. Inc. are also greatly
appreciated.
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TABLE OF CONTENTS
Page No.
LIST OF TABLES vi
LIST OF FIGURES xiii
EXECUTIVE SUMMARY ES-1
1.0 INTRODUCTION
1.1 REPORT OBJECTIVES AND METHODOLOGY 1-1
1.2 OVERVIEW OF OFFSHORE DRILLING 1-3
1. 3 WASTE DISCHARGES 1-13
2.0 SOURCES OF DISCHARGES TO THE MARINE ENVIRONMENT
2.1 SUMMARY 2-1
2.1.1 Drilling Fluids 2-1
2.1.2 Drill Cuttings 2-6
2.1.3 Produced Water 2-8
2 . 2 DRILLING FLUIDS 2-12
2.2.1 Types of Drilling Fluids 2-12
2.2.2 Functions of Drilling Fluids 2-18
2.2.3 Components of Drilling Fluids 2-19
2.2.3.1 Barite 2-19
2.2.3.2 Clays 2-24
2.2.3.3 Lignosulf onates : 2-24
2.2.3.4 Lignites 2-25
2.2.3.5 Biocides 2-25
2.2.3.6 Other Basic Additives 2-26
2.2.3.7 Specialty Additives 2-27
2.2.4 Chemical Characterization of Drilling
Fluid 2-30
2.2.4.1 Conventional Parameters 2-30
2.2.4.2 Metals 2-34
2.2.4.3 Organics 2-36
2.2.4.4 Oil-Based Additives for Water-based
Muds 2-36
2.2.4.5 Used Drilling Fluid Samples 2-38
2.2.5 Completion and Workover Fluids 2-40
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TABLE OF CONTENTS
(Continued)
Page No,
2. 3 DRILL CUTTINGS 2~44
2.3.1 Chemical Characteristics of Drill
Cuttings 2-45
2.4 DISCHARGE OF DRILLING FLUIDS AND DRILL CUTTINGS 2-50
2.4.1 Low Volume Bulk Discharges 2-50
2.4.2 High Volume Bulk Discharges 2-51
2.4.3 Quantities of Drilling Fluid
Discharged 2-51
2.4.4 Continuous Discharges 2-54
2.4.5 Oxygen Demand of Discharges 2-63
2 . 5 PRODUCED WATER 2-69
2.5.1 Chemical Characteristics of Produced Water ... 2-70
2.5.1.1 Organics 2-71
2.5.1.2 Inorganics 2-77
2.5.1.3 Radioactivity 2-78
2.5.1.4 Priority Pollutants 2-81
2.5.1.5 Conventional Parameters 2-82
2.5.2 Added Chemicals 2-84
2.5.2.1 Biocides 2-85
2.5.2.2 Coagulants 2-89
2.5.2.3 Corrosion Inhibitors 2-89
2.5.2.4 Cleaners 2-90
2.5.2.5 Emulsion Breakers and Dispersants 2-90
2.5.2.6 Paraffin Control Agents 2-90
2.5.2.7 Reverse Emulsion Breakers 2-90
2.5.2.8 Scale Inhibitors 2-90
2.5.3 Effects of Platform Age on Pollutant
Concentrations in Produced Water 2-90
2. 6 OTHER DISCHARGES 2-91
2.6.1 Composition and Discharge of Deck
Drainage 2-91
2.6.2 Discharge of Sanitary and Domestic Wastes 2-93
3.0 ENVIRONMENTAL FATE
3.1 SUMMARY 3-1
3.1.1 Drilling Fluids and Drill Cuttings 3_1
3.1.2 Produced Water 3-7
ii
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TABLE OF CONTENTS
(Continued)
Page No.
3.2 INTRODUCTION 3-8
3.3 PHYSICAL TRANSPORT PROCESSES 3-10
3.3.1 Drilling Fluids 3-10
3.3.1.1 Study Descriptions 3-11
3.3.1.2 Physical Transport Processes Affecting
the Upper Plume 3-13
3.3.1.3 Physical Transport Processes Affecting
the Lower Plume 3-22
3.3.1.4 Seafloor Sedimentation 3-25
3.3.1.5 Alterations in Sediment Barium Levels 3-30
3.3.1.6 Trace Metal and Physical Benthic
Alterations 3-39
3.3.2 Produced Water 3-47
3 .4 CHEMICAL TRANSPORT PROCESSES 3-56
3.4.1 Drilling Fluids 3-56
3.4.1.1 Inorganics 3-56
3.4.1.2 Organics 3-61
3.4.2 Produced Water 3-63
3 . 5 BIOLOGICAL TRANSPORT PROCESSES 3-63
3.5.1 Bioaccumulation 3-64
3.5.1.1 Drilling Fluids 3-64
3.5.1.2 Bioaccumulation of Hydrocarbons from
Produced Water 3-83
3.5.2 Biomagnif ication 3-85
3.5.3 Ingestion and Excretion 3-88
3.5.4 Sediment Reworking 3-89
4.0 TOXICITY TESTING
4.1 SUMMARY 4-1
4.1.1 Drilling Fluids 4-1
4.1.2 Produced Water 4-5
4.2 INTRODUCTION 4-7
4.2.1 Acute Toxicity Testing 4-8
4.2.2 Chronic Toxicity Testing 4-8
iii
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TABLE OF CONTENTS
(Continued)
Page No,
4. 3 TOXICITY OF DRILLING FLUIDS 4-9
4.3.1 Acute Toxicity of Drilling Fluids 4-11
4.3.2 Chronic Toxicity of Drilling Fluids 4-40
4.3.2.1 Stress Tests on Corals 4-40
4.3.2.2 Stress Tests on Other Organisms 4-45
4.3.3 Community Recruitment and Development 4-50
4.4 ACUTE TOXICITY OF PRODUCED WATER 4-52
4.4.1 Chronic and Sublethal Toxicity of
Produced Waters 4-57
4.4.2 Toxicity of Chemical Components of
Produced Water 4-61
5.0 FIELD STUDIES
5.1 SUMMARY 5-1
5.1.1 Studies Around Drilling Operations 5-1
5.1.1.1 Effects on Biota 5-2
5.1.1.2 Metals and Hydrocarbons in Sediments 5-3
5.1.1.3 Bioaccumulation of Metals and
Hydrocarbons 5-4
5.1.2 Studies Around Production Platforms 5-4
5.1.2.1 Hydrocarbons in Water 5-6
5.1.2.2 Hydrocarbons in Sediments 5-7
5.1.2.3 Hydrocarbons in Organisms 5-9
5.1.2.4 Trace Metals in Sediment and Fauna 5-10
5.1.2.5 Histopathology Studies 5-11
5.1.2.6 Benthic Studies 5-12
5.1.3 Catch and Effort Statistics 5-13
5.2 INTRODUCTION TO FIELD STUDIES 5-13
5.3 DISCHARGES OF DRILLING FLUIDS AND CUTTINGS 5-15
5.3.1 Mid-Atlantic Outer Continental Shelf 5-15
5.3.2 Georges Bank 5-20
5.3.3 Lower Cook Inlet 5-26
5.3.4 Beaufort Sea 5-27
5.3.5 Tanner Bank 5-28
5.4 DISCHARGES OF PRODUCED WATER 5-29
5.4.1 Buccaneer Gas and Oil Field 5-29
5.4.2 Central Gulf of Mexico 5-34
5.4.3 Timbalier Bay 5-37
5.4.4 Trinity Bay 5-40
5.4.5 Santa Barbara Channel. California 5-42
iv
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TABLE OF CONTENTS
(Continued)
Page No
5.5 CATCH AND EFFORT STATISTICS FOR THE
GULF OF MEXICO 5-42
6.0 ECOLOGICAL RESOURCE CHARACTERISTICS OF SHALLOWER MARINE
ENVIRONMENTS
6.1 SUMMARY 6-1
6.2 DEPTH DISTRIBUTION OF RESOURCE/NURSERY AREAS 6-2
6 . 3 ALASKAN RESOURCE AREAS 6-7
6.3.1 Beaufort Sea 6-7
6.3.2 Bering Sea 6-11
6.3.2.1 Norton Sound 6-12
6.3.3 Cook Inlet/Shelikof Strait 6-15
6.3.4 Bristol Bay/Aleutian Range 6-18
6.3.5 Gulf of Alaska 6-22
6.4 MARINE RESOURCE AREAS OFF CALIFORNIA 6-24
7.0 FINDINGS AND CONCLUSIONS
7.1 DRILLING FLUIDS AND CUTTINGS 7-1
7.1.1 Toxicity of Drilling Fluids 7-1
7.1.1.1 Toxicity- 7-1
7.1.1.2 Sources of Toxicity 7-2
7.1.1.3 Correlations to Toxicity 7-3
7.1.1.4 Bioaccumulation 7-4
7.1.2 Field Assessments of Impacts from Drilling
Activities 7-4
7.1.2.1 Studies of Impacts from Single Wells 7-4
7.1.2.2 Studies of Impacts from Multiple Wells 7-5
7.1.2.3 Factors Contributing to Potential
Impacts 7-6
7 . 2 PRODUCED WATER 7-9
7.2.1 Toxicity of Produced Water 7-9
7.2.2 Comparison with Other Assessments 7-12
REFERENCES
APPENDIX A - SUPPLEMENTARY INFORMATION ON FIELD STUDIES
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LIST OF TABLES
TABLE NO. TITLE PAGE NO.
1-1 Outer Continental Shelf Producing and
Non-producing Leases (Oil. Gas, Salt.
and^Sulfur) for Calendar Years 1954 and
1980 Only 1-5
1-2 Well Status, Outer Continental Shelf.
as of December 31, 1979. and December 31.
1980 1-6
1-3 Number and Average Depth of Offshore Wells
Completed in 1982 1-10
1-4 Depth of Exploratory and Development Wells
Reported Completed in 1982 1-12
2-1 EPA Generic Drilling Mud Types 2-15
2-2 Functions of Some Common Drilling Fluid
Chemical Additives 2-20
2-3 Metal Concentrations in Barite Samples 2-23
2-4 Situations Requiring Special Drilling
Fluid Additives or Formulations 2-28
2-5 Conventional Water Quality Parameters of
Generic Drilling Fluids 2-31
2-6 Metal Concentrations in Generic Drilling
Fluids 2-35
2-7 Results of Analysis of Organics in Drilling
Fluids 2-37
2-8 Hydrocarbon Concentrations of Drilling Fluid
Samples 2-39
2-9 Metals Content of Drilling Fluid Samples ... 2-41
2-10 Conventional Water Quality Parameters for
Drill Cuttings 2-46
2-11 Metal Concentrations in Drill Cuttings 2-47
VI
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
2-12 Results of GC/MS Analysis of Ocganics Drill
Cuttings 2-49
2-13 Average Mud Consumption (Ibs) for 72 Offshore
Oil and Gas Wells in the Gulf of Mexico .... 2-53
2-14 Discharges from Solids Control Equipment
from a Single Well in Lower Cook Inlet.
Alaska 2-55
2-15 Drill Cuttings from Typical Exploration
and Development Wells 2-56
2-16 summary of Drilling Fluid and Cuttings
Discharge Rates by Geographical Location ... 2-58
2-17 Profile of Proposed Drilling Fluid and
Cuttings Discharges from Two Offshore Wells 2-59
2-18 Solid Drilling Fluid Components Used in
Georges Bank Drilling 2-60
2-19 Liquid Drilling Fluid Components Used in
Georges Bank Drilling 2-61
2-20 Cuttings Analysis. Discharge 002 2-62
2-21 Supporting Calculations for Oxygen Demand
Values in the Presence of Oil 2-65
2-22 Comparison of Measured and Calculated Oxygen
Demand Values in the Presence of Oil 2-67
2-23 Platform Flotation Effluent Oil Content
Comparison for Gulf of Mexico Off
Louisiana 2-72
2-24 Low Molecular Weight Hydrocarbons in Produced
Water from the Buccaneer Gas and Oil Field.. 2-73
2-25 Volatile Liquid Aliphatic Hydrocarbons in
Produced Water Discharges from the Buccaneer
Field in the Gulf of Mexico 2-74
vii
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
2-26 Summary of Concentrations of Light Aromatic
Hydrocarbons Found in Produced Waters by
Recent Studies 2-76
2-27 Heavy Metal Concentrations in Produced
Water 2-79
2-28 Radium Content of Some Gulf Coast Oil Field
Produced Water 2-80
2-29 Produced Water Volumes and Possible Annual
Loadings of Priority Pollutants to the
Marine Environment 2-83
2-30 Chemicals Added to the Produced Water on
Platforms Surveyed by Jackson et al. (1981)
with Additional Information Provided by the
Manufacturers of the Chemicals 2-86
2-31 Other Offshore Drilling Rig Discharges 2-92
3-1 Lower Cook Inlet Current Velocities and
Direction 3-12
3-2 Upper Plume Dispersion Ratios of Whole
Drilling Fluids 3-16
3-3 Normalized Estimates of Distances to
Dispersion Ratios of 104. 105. and 106
at Current Speeds of 5. 10. and 15 cm/sec ... 3-19
3-4 Generalized Distances Required to Achieve
Specified Levels of Suspended Solids
Dispersion in the Upper Plume for Whole
Drilling Fluids at Fixed Current Speeds 3-20
3-5 Estimates of Distances Required to Achieve
Specified Levels of Dispersions of a
Soluble Drilling Fluid Tracer at Fixed
Current Speeds 3-23
3-6 Comparison of Radiotracer Dispersion Versus
Suspended Solids Dispersion and Rhodamine-WT
Dispersion 3-24
viii
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
3-7 Geometric Regression Coefficients and
Statistics for Total Sediment Barium
Concentrations Versus Distance from
Rig Site 3-31
3-8 Comparison of Actual and Predicted Levels of
Excess Sediment Barium 3-35
3-9 Comparison of Actual and Predicted Sediment
Barium Concentrations Around a Gulf of Mexico
Production Platform as a Function of Distance
from the Rig and Number of Wells 3-36
3-10 Summary of Sediment Trace Metal Alterations
from Drilling Activities 3-45
3-11 Maximum Discharge Flow (bbl/day) and
Number of Platforms in Water Less Than
Variable Depths 3-49
3-12 Average Daily Produced Water Volumes (bbl/day)
for the Model Platforms 3-50
3-13 Predicted Maximum Plume Depth and Plume
Centerline Dilution 3-51
3-14 Average Depth of State Waters 3-52
3-15 Plume Output with Currents 3-55
3-16 Buccaneer Temperature and Salinity
Profiles 3-57
3-17 Plume Model Computer Runs Using Actual
Water Column Density Profiles from the
Gulf of Mexico, Buccaneer Field Study 3-58
3-18 Concentration of Trace Metals in Barite .... 3-59
3-19 Summary of Metal Bioaccumulation
Study Results 3-73
3-20 Depuration of Metals Bioaccumulated
During Exposure to Drilling Fluids or
Components 3-79
ix
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
4-1 Summary Table of the Acute Lethal Toxicity
of Drilling Fluid ........................... 4-12
4-2 Comparison of Whole Fluid Toxicity and
Aqueous and Particulate Fraction Toxicity
for Some Organisms .......................... 4-13
4-3 Acute Lethal Toxicities of Used Drilling
Fluids and Drilling Fluid Components to
Marine Organisms ............................ 4-14
4-4 Toxicity of Layered Solid Phase (LSP) of
Used Drilling Fluids to Arctic Marine
Organisms ................................... 4-24
4-5 96-Hour LCso's for Several Species
Exposed to Four Drilling Fluids ............. 4-25
4-6 Toxicity of Used Drilling Fluids to
Mysids (Mysidopsis bahia) ................... 4-29
4-7 Drilling Fluid Toxicity to Grass
Shrimp (Palaemonetes intermedius) Larvae.... 4-30
4-8 Results of Continuous Exposure (48 h)
of 1-h Old Fertilized Eggs of Hard Clams
(Mercenaria mercenaria) to Liquid and
Suspended Particulate Phases of Various
Drilling Fluids. The Percentage of Each
Test Control (n=625±125 eggs) That Developed
into Normal Straight-hinge or "D" Stage
Larvae and the EC50 Is Given .............. 4-31
4-9 Summary of Bioassays ........................ 4-36
4-10 Toxicity of API #2 Fuel Oil. Mineral Oil.
and Oil-contaminated Drilling Fluids to
Grass Shrimp (Palaemonetes intermedius)
Larvae ...................................... 4-38
4-11 Spearman Rank Correlation Between LC50 ' s
and the Following Parameters ................ 4-39
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
4-12 Results of Acute Toxicity Tests with Eight
Laboratory-prepared Generic Drilling Fluids
and Mysids (Mysidopsis bahia) 4-41
4-13 Median Lethal Concentrations (LCso's) and
Associated 95% Confidence Intervals for
Organisms Acutely Exposed to Formation Water
Under Various Experimental Conditions 4-53
4-14 Acute Lethal Toxicity of Produced Waters
and Constituents of Produced Waters to
Marine Organisms 4-62
4-15 Acute Lethal Toxicity Values (LC50/EC50)
Which May Be Exceeded by Measured Discharge
Concentrations of Pollutants in Produced
Waters 4-66
4-16 Comparison of Concentrations of Constituents
of Produced Water with Available Water
Quality Criteria from Offshore Oil and Gas
Facilities 4-67
5-1 Characteristics of Selected Field Studies
Conducted Around Production Operations 5-5
5-2 Blue Crab Catch and Level of Effort for the
Gulf of Mexico. Louisiana, and the Gulf Less
Louisiana 5-53
6-1 Gulf of Mexico Cumulative Percent of
Nursery Area Cells Included in the
Analysis Area 6-5
6-2 East Coast Cumulative Percent of Nursery
Area Cells Included in the Analysis
Area 6-6
6-3 Spawning and Nursery Areas for Major
Commercial Fish and Invertebrate
Species in Norton Sound. Alaska 6-16
6-4 Vital Reproductive and Nursery Areas for
Important Commercial Fisheries in Cook
Inlet and Shelikof Strait 6-19
XI
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LIST OF TABLES
(Continued)
TABLE NO. TITLE PAGE NO.
6-5 Nursery Areas Located in Bristol Bay/
Aleutian Islands Area 6-21
6-6 Nursery Areas for Major Commercial Fish
and Invertebrate Species in the Gulf of
Alaska. Alaska 6-23
6-7 Spawning and Nursery Areas for Major
Commercial Fish and Invertebrate Species in
Central and Southern California 6-26
6-8 Areas of Special Biological Significance
(ASBS). Ecological Reserves/Refuges, and
Federal Estuarine Sanctuaries in Central
and Southern California 6-28
xii
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LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
1-1 Outer Continental Shelf Drilling Activity.
1954-1980 (USGS. 1981) 1-4
1-2 Discharges from the Drilling Operation 1-9
3-1 Dispersion Ratios of Whole Drilling
Fluids 3-17
3-2 Regression Plot of Whole Fluid Dispersion
Ratios and 90% Prediction Bands 3-18
3-3 Approximate Pattern of Initial Particle
Deposition 3-26
3-4 Spatial Distribution of Clay Content
in Sediments (Post-drilling) 3-28
3-5 Chromium Enrichment in the Kidneys of
Placopectin magellanicus Exposed to
0.10 g/1 Ferrochrome Lignosulfonate 3-66
5-1 Long-term Regional Stations 5-23
5-2 Site-specific Sampling Array Around Regional
Station 5. Stations 5-7. 5-13. 5-17. 5-21.
5-23. 5-24. 5-26. and 5-27 Are Secondary
Stations (of Lower Priority) and Are
Presently Archived 5-25
5-3 Shrimp Landing Productivity (Catch/Unit
Effort) in the Gulf of Mexico. 1950-1976 5-44
5-4 Shrimp CPUE (Ibs/trip) 5-45
5-5 Red Snapper Landing Productivity (Catch/Unit
Effort) in the Gulf of Mexico, 1950-1976... 5-46
5-6 Oyster Harvest Productivity (Catch/Unit
Effort) in the Gulf of Mexico. 1950-1976... 5-47
5-7 Blue Crab CPUE (Ibs/pot) (Pot Catch Only).. 5-48
5-8 Blue Crab Catch and Effort
Gulf of Mexico 5-49
XI11
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LIST OF FIGURES
(Continued)
FIGURE NO. TITLE PAGE NO.
5-9 Blue Crab Catch and Effort
Louisiana 5-50
5-10 Blue Crab Catch and Effort
Gulf - LA 5-51
6-1 Areas of Future Oil and Gas Development
in Alaska 6-8
6-2 Candidate Marine Sanctuaries and
Potential National Natural Landmarks in
or Adjacent to the Diapir Field 6-9
6-3 Bathymetry of the Norton Sound Region.
Depths are in Meters 6-13
6-4 The Northern Bering Sea Region. Norton
Sound Lease Areas to be Offered for Sale
are Contained Within the Block Diagram 6-14
6-5 OCS Lease Sale 60: Lower Cook Inlet -
Shelikof Strait 6-17
6-6 California Coastline 6-25
6-7 Areas of Special Biological Significance
Offshore Central and Northern
California 6-30
xiv
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EXECUTIVE SUMMARY
This report has reviewed and evaluated available
information on the composition, fate, and effects of the major
discharges (drilling fluids, cuttings, and produced water) from
offshore oil and gas platforms. Based on the review of a
substantial body of data, a large number of conclusions were
reached, as presented below. Notwithstanding the large data
base, datagaps and other factors contribute to a substantial
uncertainty in these conclusions. Thus, most conclusions here
are qualified.
DRILLING FLUIDS AND CUTTINGS
Drilling fluids are slurries with a high solids content
(25 to 75 percent w/w). largely due to their barite (BaSO )
and clay components. Drilling fluids also contain a large
variety of inorganic materials. To date, most attention has
focused on the effects of toxics. However, very few studies
have analyzed for toxics other than metals. Only one study has
reported a priority pollutant screen, in which pesticides were
not included. Fewer analyses have been conducted on cuttings.
The conclusions reached for drilling fluids and cuttings in
this report are as follows.
1. Acute lethal toxicity of drilling muds appears to be
correlated to added mineral or diesel oil, and
Biochemical Oxygen Demand (BOD). Diesel oil is a
particularly toxic component of drilling fluids. In
studies to date, mineral oil is less toxic (some 3- to
7-fold), but still is a substantial contributor to the
toxicity of drilling fluids. Adding diesel oil to any
ES-1
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mud produced a strong correlation with toxicity.
Toxicity also correlated well with diesel oil
equivalents (equivalent to API #2 fuel oil) in the
suspended particulate phase for nongeneric muds, but
somewhat less well with levels of aliphatics and
aromatics. Diesel oil equivalents, aliphatics. and
aromatics in whole muds generally correlated somewhat
less well with toxicity than did added oil in whole
muds. Toxicity of generic muds shows a very strong
correlation with BOD. Due to a lack of BOD data no
such correlation was possible for nongeneric muds.
Other factors, such as acidity and particle size, may
contribute to toxicity. Such contributions cannot be
assessed based on available data/methodology. Bulk
metals content appears to have a very low correlation
to acute lethal drilling mud toxicity. with the
possible exception of a weak correlation to chromium.
2. Based upon one Environmental Protection Agency (EPA)
study, in which a priority screen excluding pesticides
was conducted, only a single organic was detected in
generic drilling muds to which no oil had been added.
Toxic organics in drilling muds most probably would be
due to addition of mineral or diesel oils and/or
certain other additives, such as biocides. Many metal
priority pollutants, including antimony, arsenic.
cadmium, lead, and mercury were detected in both
generic and nongeneric muds. Metal levels in
nongeneric muds were, in general, at least one order
of magnitude higher than those in generic muds.
ES-2
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3. A major new finding in this assessment is that
drilling fluids contain high levels of 5-day
Biochemical Oxygen Demand (BOD ) as well as 20-day
Ultimate Oxygen Demand (UOD ), and Chemical Oxygen
Demand (COD). A median scenario estimate (average
mass load x average concentration) of the BOD measured
in muds and cuttings is 33 tons (kkg) per well
drilled. For the 1464 wells drilled in 1982. this
represents a total of 49.200 tons of BOD per year.
These BOD estimates are likely to be underestimates of
actual BOD because the toxicity of added oil reduces
measured BOD. Total Chemical Oxygen Demand (COD)
averaged 308 tons/well or 451.000 tons annually.
Total BOD from the muds and cuttings from the offshore
oil and gas industry is more than six times higher
than the total BOD of ocean dumped municipal sewage
sludge, although some 3.5-fold more sludge is disposed
on a mass basis. The total COD of discharged drilling
fluids and cuttings is more than 30 times higher than
the COD of all U.S. ocean dumped sewage sludge. Over
60 percent of this oxygen demand is estimated to be
discharged in Louisiana state waters.
4. Barite, the main component of most drilling fluids,
has a very high specific gravity (4.2 g/ml). As a
result, most barite settles out of the lower plume and
deposits in sediments. Such deposits may become
significant over time, particularly in low-energy
areas or in high energy areas with intensive drilling
activities. The small particle size of the barite can
cause physical effects, including substrate
alteration, suffocation, and/or abrasion of gills.
ES-3
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Heavy metals, such as cadmium, copper, antimony.
arsenic, lead, nickel, and mercury are associated with
barite. although they may also be associated with
other drilling fluid additives. Barite may represent
a significant contribution to heavy metal loadings of
sediments because it can comprise up to 70 percent of
drilling muds by weight.
Calcium, aluminum, and iron concentrations also can be
very high, i.e.. in the percentage range. Mercury
concentrations were uniformly low in generic muds (no
data were available for nongeneric muds), although
certain types of barite showed high excursions in
mercury and a variety of other associated trace metal
levels. Cadmium and chromium levels were low in
generic muds compared to nongeneric muds. Most of
these metals can be enriched in sediments around
drilling platforms and also show the potential for
bioaccumulation in laboratory studies and field
surveys.
Although, the significance of potential toxic
(including bioaccumulation) and physical effects of
particle deposition is not fully understood,
deposition represents a potential source of chronic.
sublethal impacts. At a workshop to model potential
impact, no "worst case" scenario could be developed.
based on available data and assessment methodologies.
While the risks from exploratory operations appear to
be limited, risks from intense drilling operations are
not yet quantifiable.
ES-4
-------
5. Several reviews of the literature on discharges from
offshore oil and gas activities have been completed.
There is general agreement among these with regard to
quantities of material discharged and toxicity. This
report has pointed out that there yet exists a lack of
understanding of the actual cause(s) of toxicity. that
one major factor. BOD. may have been overlooked, and
that toxicity test protocols and the unanticipated use
of lubricating/spotting oils may result in a
substantial underestimation of toxicity. Another
uncertainty arises from the extrapolation of single
species tests to assessments of overall effects.
6. Data on one-well operations are adequate to predict
with reasonable assurance that such activities result
in limited impacts within the limits of resolution of
existing studies. This review, however, does not
consider the current data base sufficient to evaluate
potential impacts from intensive exploration or
development activities. This concern is exacerbated
by the absence of any on-going or mandatory monitoring
program to address this concern. There have been only
two studies on fluid discharges from single
exploratory wells that are based on satisfactory
statistical and field sampling methods (i.e., that
were capable of detecting changes of less than
approximately 100 percent). There has been no
adequate study of an exploratory well in a shallow.
low-energy environment. More importantly, there have
been no benthic studies on the effects of discharges
from a development platform, involving a large number
of wells, in any type of environment. Thus, in the
ES-5
-------
absence of a satisfactory data gathering effort, the
potential risk of serious impacts may be high, for
intensive drilling activities, in vulnerable or valuable
areas. Such areas include shallow waters, poorly flushed
waters, waters subject to other sources of anthropogenic
or natural episodic stress, and hard bottom areas.
PRODUCED WATER
One of the issues related to regulating produced water
discharges is the uncertainty about the nature and extent of
effects. Some of this uncertainty (e.g., chronic effects of
produced water discharges) could be dealt with through focused
long-term studies. The following summarize the key
observations that have led to environmental concerns regarding
ocean discharge of produced waters:
1. Produced waters contain elevated concentrations of
certain petroleum hydrocarbons. In particular,
lighter aromatics (benzene through naphthalene) are
present. These are among the more acutely toxic
petroleum hydrocarbons. Toxicity tests on produced
waters (without biocides), and water soluble fractions
of crude oil. which contain similar concentrations of
light aromatic hydrocarbons, generally indicate that
the acute lethal toxicity of produced water is low.
However, some portion of the volatile toxic components
is lost upon collection and shipment of samples and
upon aeration of the test media (which was required to
maintain dissolved oxygen levels above 4 ppm).
ES-6
-------
2. Produced waters often contain various chemical
additives, although there is limited information on
the presence and quantities of these chemicals in the
discharge. These chemicals, which include biocides
used to control the growth of bacteria, can greatly
increase the toxicity of produced waters. This has
been revealed by laboratory toxicity tests and by cage
experiments in the field. Reports on divers working
near a produced water discharge that contained the
biocide acrolein also are informative: the divers
reported eye and skin irritations that were severe
enough to interrupt their activities.
3. There is clear evidence that hydrocarbons in produced
water discharges can exert chronic lethal effects on
benthic organisms around production platforms. This
was apparent for a relatively long-term, high volume
discharge at the shallow water (2.5 m) Trinity Bay
site and also for the relatively long-term, low volume
discharge in the deeper water (20 m) Buccaneer Field
site. The full spatial extent of chronic effects of
produced water discharges on benthos is difficult to
delineate from these studies because of the generally
elevated levels of hydrocarbons in sediments. This
creates a "signal to noise" problem with respect to
detecting effects of individual discharges.
ES-7
-------
Available information, in addition to the studies
noted above, suggests that shallow, coastal
environments are more vulnerable to effects of
produced water than deeper offshore areas. A recent
American Petroleum Institute (API) report notes that
transport of contaminants from the air/sea interface
to the sediments will be more efficient in shallower
coastal waters than offshore. In addition, the higher
turbidities characteristics of coastal waters would
also be conducive to sedimentation of contaminants.
The input of petroleum hydrocarbons (in particular
aromatics) could contribute to chronic pollution of
the water column. Although, the chemicals may be
rapidly mixed and dispersed upon entering the marine
environment, there is evidence that coastal waters of
Louisiana contain elevated levels of the volatile
liquid hydrocarbons characteristic of produced
waters. There are undoubtedly other sources of these
hydrocarbons as well, but concentrations are higher
around production platforms as evidenced by studies at
the Buccaneer Field. These concentrations are at
levels that could result in sublethal effects.
Transport to sediments is also a concern. The Trinity
Bay study, for example, noted that effluent
concentrations of naphthalenes (1.6 mg/liter) were
diluted rapidly (2000-fold at approximately 15 m).
Therefore, at the 15 m sampling site water column
concentrations would be calculated at 0.8 vg/liter.
while sediment concentrations of the site were
elevated to 20 mg/kg at the (sediment) surface and
over 40 mg/kg at some subsurface depths.
ES-8
-------
6. There have been several reviews that have attempted to
place various sources of petroleum hydrocarbons in
perspective through comparisons with other sources
(river discharge, tankers, oil seeps). Generally.
these show that produced water discharges contribute a
comparatively small percentage of the overall input on
an ocean-wide or world-wide basis. Two factors must
be considered with respect to this conclusion and with
regard to the regulation of this discharge. First.
although the relative contribution is small, the
discharge should not necessarily be ignored: there
are numerous instances where individual industrial
discharges are "small" but collectively contribute to
overall incremental pollution to the environment.
Second, discharges of produced water can exert
environmental effects at the local or regional level.
7. Produced waters contain other materials that are of
potential environmental concern. Radioactive
materials such as radium are found in some oil field
produced waters. The activity of these may be four
orders of magnitude greater than that of open ocean
waters. Other inorganics that may be present based on
limited data, include heavy metals, ammonia, hydrogen
sulfide. and various oxygen consuming substances.
Very high BOD levels were noted in one study of
produced water in southern California. Based on these
BOD levels, localized decreases in oxygen content were
predicted to occur. From the BOD levels observed in
ES-9
-------
this study and from industry estimates of produced
water volumes in the Gulf of Mexico, where a major
portion of offshore structures is located, the BOD
load from produced water in the Gulf of Mexico was
calculated to be 37.000 tons per year.
ES-10
-------
1.0 INTRODUCTION
The United States Environmental Protection Agency (EPA) has
prepared this study as part of the development of New Source
Performance Standards (NSPS) and Best Available Technology
(BAT) regulations for marine discharges from offshore oil and
gas drilling and production operations under the authority of
Sections 301. 304. and 306 of the Clean Water Act (CWA).
Excluded from consideration in the study are potential impacts
from oil spills, marine transportation, and pipelines, which
are covered under other sections of the CWA. Within EPA, the
proposed regulations are being developed by the Office of the
Water Regulations and Standards (OWRS). In support of this
effort this assessment will evaluate the discharges.
environmental fate, and potential environmental effects
associated with this industrial category.
1.1 REPORT OBJECTIVES AND METHODOLOGY
The overall objectives of this study are to characterize
and assess the fate and effects of discharges from offshore oil
and gas drilling and production activities. Four specific
objectives were outlined by EPA:
Present overall conclusions on the fate and effects of
drilling fluids and cuttings discharged to the marine
environment
Describe types and quantities of discharges from
offshore drilling and production operations
1-1
-------
Describe transport phenomena to which discharges will be
subjected, including physical, chemical, and biological
processes
Present information on the acute and chronic toxicity of
drilling fluids and produced waters on marine organisms
Some of the major references consulted for this report
were: "Environmental Assessment of Drilling Fluids and
Cuttings Released onto the Outer Continental Shelf for the Gulf
of Mexico" (Petrazzuolo. 1*981; 1983); "Fate and Effects of
Drilling Fluids and Cuttings Discharges in Lower Cook Inlet.
Alaska, and on Georges Bank" (Houghton et al.. 1981);
"Proceedings of the Symposium on Environmental Fate and Effects
of Drilling Fluids and Cuttings" (American Petroleum Institute.
1980); "Drilling Discharges in the Marine Environment"
(National Research Council, 1983); "A Study of Environmental
Effects of Exploratory Drilling on the Mid-Atlantic Outer
Continental Shelf" - (EG & G. 1982); "Effects of Oil Field
Brine Effluent on Benthic Organisms in Trinity Bay. Texas"
(Armstrong et al.. 1977); "Georges Bank Benthic Infauna
Monitoring Program" (Blake et al.. 1983); "Environmental
Assessment of Buccaneer Gas and Oil Field in the Northwestern
Gulf of Mexico. 1978-1979" (National Marine Fisheries Service.
1980). "Ecological Effects of Produced Water Discharges for
Offshore Oil and Gas Production Platforms" (Middleditch. 1984).
and "Results of the Drilling Fluids Research Program sponsored
by the Gulf Breeze Environmental Research Laboratory.
1976-1984. and Their Application to Hazard Assessment" (Duke
1-2
-------
and Parrish. 1984). Numerous other documents were also
reviewed as discussed in the sections and as listed in the
References section, and all information was integrated to
create a single comprehensive report.
Section 1 presents background information on offshore
drilling and production processes and associated discharges.
Section 2 details discharge characteristics and composition,
and quantifies discharge volumes; especially for drilling
fluids, cuttings and produced water. Section 3 describes the
environmental fate of discharges, including physical, chemical,
and biological pathways. Toxicity information on drilling muds
and produced waters is presented in Section 4. Section 5
presents summaries of field studies of particular interest
regarding drilling and production activity. Section 6 presents
information on the ecological resource characteristics of
shallower marine environments. Section 7 presents the findings
and conclusions.
1.2 OVERVIEW OF OFFSHORE DRILLING
Drilling activity on the outer continental shelf (OCS) has
been conducted with increasing frequency since the early
1950's. when drilling was confined primarily to the Louisiana
and Texas coasts. Since that time, drilling has expanded to
include the Atlantic. Pacific, and Alaskan coasts. This
increase in drilling activity can be seen in Figure 1-1.
Table 1-1 compares the number of producing and non-producing
OCS leases for the years 1954 and 1980. Most new wells today
are being drilled in the Gulf of Mexico, with other activity
off Alaska, California, and in the Atlantic (Table 1-2).
1-3
-------
I
*»
Figure 1-1
Outer Continental Shelt
Drilling Activity, 1954-1980 (USGS.1981)
N«w W«4I« Started
W«fa ComptoWI (Going Into Production)
Exploratory W«lhs Storied
Y«ar
-------
I
in
TABLE 1-1 OUTER CONTINENTAL SHELF
PRODUCING AND NON-PRODUCING LEASES (OIL, GAS, SALT AND SULFUR)
FOR CALENDAR YEARS 1954 AND 1980 ONLY
(USGS, 1981)
Activity during calendar year
Year ot activity
Adjacent state
1954
Louisiana
Louisiana-Sulfur
Texas
TOTAL ACTIVITY
DURING 1954
1980
Alabama
Alaska
California
Florida
Louisiana
Louisiana-Salt
Texas
Mid-Atlantic
South Atlantic
North Atlantic
Producing
Number
58
-
58
-
4
-
933
2
186
-
-
-
Acreage
240,028
-
-
240,028
-
18,915
-
4,029,519
4,995
970,805
-
-
-
Non-producing
Number
295
5
120
420
5
96
138
35
478
-
147
126
43
63
Acreage
1,066,739
25,000
196,926
1,288,665
28,495
495,680
741,770
201,600
2,127,361
-
794,841
737,304
224,813
358,659
Total
Number
353
5
120
478
5
96
142
35
1,411
2
333
126
43
63
Acreage
1,306,767
25,000
196,926
1,528,693
28,495
495,680
760,685
201,600
6,156,880
4,995
1,765,646
737,304
224,813
358,659
TOTAL ACTIVITY
DURING 1980 1,125
5,024,234
1,131
5,710,523
2,256 10,734,757
-------
en
TABLE 1-2 NELL STATUS, OUTER CONTINENTAL SHELF,
AS OF DECEMBER 31, 1979, AND DECEMBER 31, 1980
(USGS, 1981)
Producible .zone completions
Year
state
1979
Alaska
Atlantic
California
MAFLAa
Louisiana
Oregon
Texas
Washington
TOTAL
1980
Alaska
Atlantic
California
MAFLAa
Louisiana
Oregon
Texas
Washington
TOTAL
New wells
drilling
Active
2
4
4
5
114
-
46
175
v
2
10
2
130
-
47
-
191
Susp'd
_
-
11
10
382
-
187
-
590
_
-
37
36
479
-
187
-
739
Wells
completed
-
223
50
8,169 3,
-
522
8,964 3,
_
-
246
70
8,618 3,
-
704
9,638 3,
Active
Oil
_
-
205
47
175
-
41
-
468
-
-
213
54
045
-
81
393
Gas
-
4
2,653
-
308
2,965
-
-
-
2,596
-
399
2,995
Shut-in
Oil
_
-
6
7
1,018
-
15
1,046
-
-
14
9
1,194
-
27
1,244
Gas
_
-
1
638
-
68
707
-
-
-
3
806
-
112
921
Total
active f,
shut-in
M
-
211
59
7,484
-
432
8,186
-
-
227
66
7,641
-
619
8,553
Total
wells
27
32
441
183
14,970
4
1,651
8
.17,316
21
32
531
234
15,868
8
1,927
4
18,625
a MAFLA Mississippi, Alabama,, Florida.
-------
The Gulf of Mexico has been the location of the greatest
past and present offshore oil and gas activity. Through 1981.
84 percent of all U.S. offshore oil and gas wells were in the
Gulf of Mexico (NEC. 1983). Within the Gulf itself, the most
successful area has been the Louisiana outer continental
shelf. Offshore oil and gas wells in the Louisiana OCS area
numbered approximately 19.200 through 1981. and constituted
about 88 percent of all wells in the Gulf of Mexico (NEC. 1983)
Future domestic energy needs will continue to encourage
development of offshore fossil fuel resources. An extensive
effort to find and develop new reserves will be required, both
on land and in old and new offshore drilling areas. Some new
offshore fields currently considered for development are off
southern California. Alaska, and new areas in the Gulf of
Mexico (Mobile Bay), with some interest in the Atlantic.
Regulatory agencies, the industry, and many citizens have been
concerned about the potential environmental impact of
discharges from offshore drilling platforms and production
facilities.
Offshore oil and gas activities can be categorized into
exploratory, developmental, and production operations.
Exploratory drilling operations are conducted from drill
barges, jack-up rigs, drilling ships, or semi-submersible rigs
to identify the location of producing formations. Development
operations are conducted on platforms from which multiple wells
are drilled after a commercially exploitable reserve has been
identified. Production operations ensue during and after
developmental drilling. Oil and gas production may begin after
1-7
-------
drilling rigs have been removed; however, sometimes production
is started on early wells while drilling continues on
subsequent wells.
Modern drilling practices most commonly use a three-cone
roller cutter bit, which is rotated against the bottom of the
drill hole to grind through the rock. The bit is rotated by
means of a high-strength steel pipe called the drill string.
consisting of numerous 30-foot lengths of pipe threaded
together. Drilling fluids are suspensions of solids, in either
water or oil. circulated in the hole, which serve several
purposes in the drilling operation. The most important of
these are to maintain downhole pressure, lubricate and cool the
drill bit. and remove drill cuttings to the surface. Drilling
fluid passes down through the hollow drill string, out through
the bit. and back up the space (annulus) between the drill
string and the borehole wall. The basic drilling process and
associated discharges are discussed below and shown in
Figure 1-2.
During the first 50 m to 150 m (164 ft to 492 ft) of
drilling, seawater is generally used as the drilling fluid;
muds and cuttings (the drilled rock fragments) are discharged
directly to the seafloor. Then the surface conductor pipe and
blowout preventer are set and the marine riser is installed.
From this point on. a specially formulated drilling fluid is
added and continuously returned to the drilling rig. cleaned of
cuttings, and recirculated to the hole.
Well depth varies from area to area and by type of well
(Table 1-3. API 1983). In state waters, average well depths
ranged from 2,080 m (6.345 ft) in California to 3.586 m (10.929
1-8
-------
Figure 1-2 Discharges From The Drlllinfg Operation
/^SMUDHOBE^
KELLY
DRILL PIPE
PUMP
_-*-_r*_ I ifc_,ii>_ir*to
BLOWOUT
PREVENTER C
MUD RETURN LINE
CUTTINGS
REMOVAL
SYSTEM
TANK8
CUTTINGS
DISCHARGE
MUD DISCHARGE PIPE
'.' -bCEAN FLO.OR '."'' . .
t
DRILL COLLAR
VnibkWfehrvn' . f ^ f
BOREHOLE'. '..*., ' ".' ' ', ' ' > «
BIT
*
1-9
-------
NUMBER AND AVERAGE DEPTH OF OFFSHORE WELLS
COMPLETED IN 1982
Wells in State Waters
Alaska
California
Louisiana
Texas
Wells in Federal Waters
i
o Alaska
Atlantic
Gulf North
Pacific
OIL WELLS
' n ' Average '
1 Depth (ft.)
1 10,400
153 5,804
280 9,997
17 8,827
35 12,043
2 13,262
-
33 11,970
-
GAS WELLS
I i
n ' Average '
1 Depth (ft.) '
5 12,102
277 10,837
137 9,350
23 10,789
_ _
-
23 10,789
-
DRY WELLS
n ' Average '
' Depth (ft.) '
2 11,194
16 9,718
343 10,830
146 10,088
29 10,738
_ _
17,036
19 10,420
5 5,647
n
3
174
900
300
87
2
5
75
5
TOTAL
i
Average
1 Depth (ft.)
10,929
6,345
10,573
9,678
11,276
13,262
17,036
11,215
5,647
Total Offshore
486
8,784
442
10,388
536
10,390
1,464
9,930
From: API 1983,
-------
ft) in Alaska. Average well depth in Louisiana was 3,223 m
(10.573 ft). In Federal waters, average well depths ranged
from 1.853 m (5.647 ft) in the Pacific to 5.589 m (17.036 ft)
in the Atlantic.
Exploratory and development wells can have widely varying
depths and frequencies, depending on the general location
(Table 1-4). Although common statements* are that exploratory
wells are much deeper than development wells, this appears to
be true only in offshore California waters: 1.553 m (5.096 ft)
for development wells, and 2.918 m (9.574 ft) for exploratory
wells. For all other areas, such distinctions are much less
pronounced. In fact, for wells in federal waters in the Gulf
of Mexico, the exploratory wells are actually shallower (3.024
m or 9.922 ft) than development wells (3.400 m or 11.156 ft).
Exploratory wells average 3.155 m (10,351 ft) versus 2,749 m
(9,019 ft) for development wells; all wells (both exploratory
and development) have an average well depth of 2.865 m
(9.401 ft).
The results for total offshore wells are. however, much
determined by California well data. Eliminating California
wells nearly entirely eliminates the gap as well: exploratory
wells average 3.169 m (10,398 ft) versus 3.035 m (9.957 ft) for
development wells. All wells, without California wells
included, have an average depth of 3.078 m (10.097 ft). All
data reported here use weighted averages calculated from total
well footage data. The discrepancies in average number of
wells and well depths reported here results from reporting
discrepancies between two API sources; API (1983) and API
(1982a-l).
1-11
-------
TABLE 1-4 DEPTH OF EXPLORATORY AND DEVELOPMENT WELLS REPORTED
COMPLETED IN 1982
I
H
N)
DEVELOPMENT WELLS EXPLORATORY WELLS TOTAL
n
Wells in State Waters
Alaska 1
California 153
Louisiana 492
Texas 1 16
TOTAL 762
Wells in Federal Waters
Alaska
Atlantic
Gulf North 31
Pacific 0
TOTAL 31
Total Offshore 793
Average n Average n Average
Depth (ft.) Depth (ft.) Depth (ft.)
12,492 1 12,492
5,096 18 9,574 171 5,567
10,029 160 10,697 652 10,193
9,307 117 10,136 233 9.723
8,932 295 10,406 1,057 9,343
11,156 23 9,922 54 10,630
1 4,000 1 4.000
11,150 24 9,675 55 10,510
9.019 319 10.351 1,112 9,401
Based on API 1982 a-1.
-------
1.3 WASTE DISCHARGES
Discharges from offshore oil and gas activities include:
drilling fluid (or drilling mud)
drill cuttings and associated wash water
produced water (also referred to as brine, or
formation water)
deck drainage
sanitary waste
domestic wastes
test fluids
produced sand
ballast water
bilge water
desalinization unit discharges
cementing unit deck drainage and excess cement slurry
blow-out preventer (BOP) fluid
boiler blowdown
fire protection system test water
non-contact cooling water
Discharges from the first five categories have received the
most attention from regulators and researchers. The first
three categories are the primary contributors of potentially
toxic pollutants from offshore oil and gas operations, and will
be covered in greatest detail in this report. Drilling fluid
("mud"), drill cuttings, and produced water discharges also are
most significant by virtue of their constituents and volumes.
Drill cuttings are discharged continuously during drilling, and
a small amount of drilling fluid normally adheres to these
1-13
-------
cuttings. Drilling fluid discharges occur at intervals: when
water is added to control fluid viscosity, when well casing is
cemented, when the fluid system is changed, and at the end of
drilling.
Produced water, which is the brine brought up with the oil
or gas from the geologic formation during the production phase,
either can originate from the formation itself, or from water
injected to increase production. The unseparated crude oil is
brought to the surface and treated to remove this produced
water. Most produced oil or gas is transported to shore via
pipelines. Exceptions occur where oil is stored aboard the
platform or in tankers used for transport to shore.
Produced water contains trace metals, hydrocarbons, and
concentrated salts. The oil/water separation process may also
involve the addition of chemicals to improve process efficiency
and reduce equipment corrosion. These additives can include
biocides. deflocculants, emulsion breakers, and other chemicals
that may be found in the discharged produced water.
Deck drainage and sanitary waste discharges are less
significant than drilling fluid and produced water effluents.
Deck drainage consists of rain water or wash water that is
usually captured in gutters and transported to a sump tank for
oil separation prior to ocean discharge. Sanitary waste is
normally discharged after treatment by a U. S. Coast
Guard-approved marine sanitation device. These discharges are
greatest during the drilling phase, when manpower requirements
are highest. Cementing unit deck drainage discharges contain
compounds present in casing cement.
1-14
-------
The blow-out preventer (BOP) is a unit placed below the
drilling apparatus to stop the uncontrolled release of
formation fluids that can cause a blowout. The BOP unit must
be tested periodically according to Minerals Management Service
(MMS) operating orders. Hydraulic fluid in released to the
environment during testing. Produced sand is sand contained in
the produced fluids and occurs in some wells. The sand usually
settles out in the oil/water separator and is discharged
directly to the ocean. These and the other remaining
categories of discharges are discussed in greater detail in
Section 2.
1-15
-------
2.0 SOURCES OF DISCHARGES TO THE MARINE ENVIRONMENT
This section discusses the major discharges to the marine
environment from offshore oil and gas operations, including
drilling fluid, drill cuttings and produced waters.
2.1 SUMMARY
Various sources of discharges occur during offshore oil and
gas operations. Major sources include:
drilling fluid ("drilling mud")
drill cuttings
produced water ("formation water")
*
In addition, a number of less important sources exist. Such
sources include sanitary and domestic wastes, deck drainage.
fire protection system test water, blow-out preventer fluid.
cementing unit deck drainage and excess cement slurry,
non-contact cooling water, ballast water, and bilge water. The
discussion below focuses on the three major sources of
discharges.
2.1.1 Drilling Fluids
Drilling fluids are suspensions of solids, primarily barite
(BaSO ) and clay, with various additives in fresh water or
4
seawater. to which mineral or diesel oil are frequently added
as lubricants or to free stuck drill string. Drilling fluids
help to maintain downhole pressure, as well as to lubricate.
2-1
-------
cool, and clean the drill bit. Drilling fluid formulations are
highly dependent on the site, formation, and well depth at
which drilling occurs.
Some of the major components used in drilling fluids
include: barite. bentonite or attapulgite clays, (ferro)chrome
lignosulfonate. lignite, polyanionic cellulose, sodium
hydroxide, sodium bicarbonate, potassium chloride, and
diesel/mineral oil. Other additives that can be used include
hundreds of proprietary formulations broadly classified as
biocides. flocculants. deflocculants. surfactants, emulsifiers.
shale control agents, filtrate reducers, oxygen/sulfide/calcium
scavengers, and corrosion inhibitors.
Given the variability of drilling mud formulations. U.S.
EPA Region II and the Offshore Operators Committee (OOC)
developed the generic mud concept to avoid having to perform
chemical and toxicological characterization of each drilling
mud discharged. Eight distinct generic mud formulations were
identified as operationally necessary and sufficient for
drilling activities. Although discussed as a single mud. a
specific generic mud does not have a fixed formulation, but
rather a list of approved components and concentration ranges
for each approved component. No additives were allowed that
would significantly increase the toxicity of any generic mud.
The variability of these generic muds is also discussed in
the toxicity section, which presents the large toxicity
differences observed between different batches of the same
"generic" mud. Neither mineral oil nor diesel oil is an
approved component of any of the generic mud recipes.
Nonetheless, since the initial formulation of generic muds.
2-2
-------
diesel oil has been subsequently identified by the industry as
a necessary component in drilling fluids, at periodic usage
levels approximately equal to several other bulk components.
Although non-generic muds are comprised of much the same
basic components as generic muds, other additives may be used
without any restriction other than the BPT effluent limitation
of "no free oil." The use of numerous other additives in their
drilling fluids even further increases the variability in their
physiochemical characteristics, and thus their toxicity.
Due to the very nature of drilling fluids (i.e.. generally
a thick suspension), nonuniformity of samples imposes a large
inherent variability. Almost all investigations report a
variety of problems with material handling, mixing, sampling.
and extraction. Thus, results for most parameters display a
large statistical variability- In addition, a nonuniformity of
analytical methodologies in various studies further increases
the overall variability of the available data.
Recent chemical characterizations of generic muds with no
added oil show them generally to have a high 5-day Biochemical
Oxygen Demand. The high solids content muds have a very high
Biochemical Oxygen Demand (BOD : 1.373 to 2.743 mg/kg);
20-day Ultimate Oxygen Demand. (UOD : 1.733 to 4.223
^ w
mg/kg): Total Organic Carbon (TOG: 3.040 to 15.000 mg/kg). and
Chemical Oxygen Demand (COD: 8.000 to 41.200 mg/kg). The low
solids content generic muds (mud numbers 004. 005. and 006)
have far lower values for these characteristics, with BOD
levels from 9 to 216 mg/kg, UOD levels from 124 to 286
mg/kg. TOG levels from 100 to 1.220 mg/kg, and COD levels from
420 to 4.200 mg/kg.
2-3
-------
COD appears to reflect most accurately total organic
content, whereas TOG reflects free, i.e.. nonsequestered.
organic content. However, added mineral oil up to 10 percent
did not produce a positive sheen test or a commensurate
increase in TOC. BOD. or UOD. Added mineral oil did produce an
added oil concentration-related increase in COD.
Levels of added mineral oil. in excess of 1 percent.
decreased the BOD/UOD. compared to levels prior to oil
addition. Similar results were observed for high-sulfur diesel
oil. This indicates a toxic effect of the added oil on the
organisms that are responsible for generating the oxygen demand
measured in the BOD/UOD tests. Toxicity also is evident from
the abnormal time-versus-BOD curves, as well as BOD/UOD and
BOD/COD ratios. Thus, samples containing oil will have an
artificially low BOD because of the toxicity of the oil on the
organisms used to measure BOD or UOD. Nearly all generic muds,
including those to which no lubricant was added, contain some
oil and grease component (up to 1 percent, most probably
derived from the lignite component). Therefore, all BOD
values, including generic muds both with and without added oil.
could be underestimated. Following dispersion upon release in
the environment, however, this artificial depression of BOD
will be reduced. Thus, environmental dispersion will result in
a substantial increase in total expressed BOD. compared to that
measured.
Oil and grease data were highly variable for hot rolled
generic muds and did not correlate with either TOC, COD, or
total added mineral oil up to 10 percent. No equivalent data
2-4
-------
are available for nongeneric muds; thus, a large proportion of
oil in drilling mud appears sequestered on the barite and/or
bentonite (attapulgite) clay for the hot rolled generic muds.
Available metal analyses of drilling fluids are of a highly
variable nature due to nonuniformity of both sampling and
analytical techniques. Data for generic muds appear to
indicate fairly high levels of antimony (up to 4.0 ppm w/w dry
weight), arsenic (up to 17.2 ppm). and chromium (up to 908
ppm). Mercury and cadmium levels were always less than 0.75
ppm (w/w dry weight). Addition of oil did not significantly
alter the metal content of generic muds. Metal content of the
nongeneric muds was significantly higher than that of the
generic muds, especially for copper (23.4 to 3.448 ppm) and
iron (0.70 to 7.63 percent). No antimony, arsenic, or mercury
data were available for the nongeneric muds. Cadmium levels
(dry weight) ranged up to 11.8 ppm and exceeded 2.0 ppm in six
of 11 samples.
Except for n-dodecane (C-12 olefin) at levels less than 1
ppm (w/w wet weight), no organics were identified by a GC/MS
analysis of priority pollutants fractions of generic muds.
Addition of mineral oil resulted in added oil concentration-
dependent detection of phenanthrene. dibenzofuran, diphenylamine.
and biphenyl at total levels up to 30.2 mg/kg (wet weight).
Other studies report the presence of alkylated naphthalenes and
phenanthrenes at low levels and high levels of other
hydrocarbons, primarily cycloalkanes. following the addition of
five percent mineral oil. Addition of five percent high-sulfur
diesel oil resulted in detection of high levels of alkylated
benzenes, naphthalenes, and phenanthrenes. as well as large
quantities of n-alkanes. Of these chemicals only benzene.
naphthalene, and phenanthrene are priority pollutants.
2-5
-------
Data on levels of organics in nongeneric mud are limited to
levels of diesel oil (up to 0.94 percent or 9.400 mg/kg).
aliphatics (up to 7.200 mg/liter). and aromatics (up to 1.600
mg/liter). More detailed information was not available.
Given that 1.464 offshore wells were drilled in 1982 with
an average drilling time of generally less than 60 days, a
median estimate is that offshore drilling would result in an
average annual oxygen demand of 48.300 tons of BOD from
drilling fluid and cuttings. This number is six times higher
than the total BOD loading from all ocean dumped municipal
sewage sludge, and 30 times the COD. More importantly, this
oxygen demand is highly clustered: 900 of 1.464 offshore wells
drilled in 1982 were in Louisiana state waters.
Oxygen demand and oil content are important factors in the
toxicity of drilling fluids. However, the test phase and the
analytical determination of "oil" (or "diesel equivalents")
affect the correlation between oil content and toxicity. This
topic is discussed further in Section 4.
2.1.2 Drill Cuttings
Drill cuttings are the fragments of rock brought up in the
drilling fluid from the drilled formation. Cutting are removed
from the fluid by passing through a series of screens or
hydrocyclones that remove particulates. Generally, shale
shakers remove particles larger than 440 ym. (fine screen.
larger than 120 ym.); desanders remove particles in excess of
75 ym; and desilters remove particles in excess of 5 ym.
2-6
-------
Recovered cuttings are discharged from the platform. Some
amount of drilling fluid (approximately 5 percent, w/w) adheres
to these particles.
Extremely limited published data on the actual composition
of cuttings exist. In addition, composition will vary widely
from formation to formation. Based on the only available data.
for deep cuttings (>14.000 ft), cuttings appear much lighter
than most drilling fluids with densities from 1.0 to 1.6 g/ml.
Mater content of cuttings discharges appear to be about 20 to
30 percent. BOD and UOD average approximately 8,000 and 20.000
mg/kg. extremely high compared to sewage sludges (500 to 3.000
mg/kg). TOC ranges from 23.000 to 51.000 mg/kg. and COD ranges
from 90,000 to 270.000 mg/kg (or 9 to 27 percent). Cuttings
from oil-based mud systems can have free oil, as evidenced by
positive sheen tests at the 15 g level (i.e., one percent or
less free oil), although oil and grease levels varied from one
to 11 percent. Prior to washing. TOC, COD, sheen test results,
and oil and grease data generally indicated higher levels.
while lower BOD and UOD levels were observed prior to washing.
Metal levels, as expected, are highly variable. Mercury
levels were less than 0.5 ppm (dry weight), whereas cadmium
levels exceeded 2 ppm on two of three occasions. Levels of
organics in cuttings were extremely high compared to generic
drilling fluids with levels of polynuclear aromatics of up to
310 mg/kg. aromatic amines of up to 48 mg/kg. and with other
base-neutral organics of up to 255 mg/kg. These findings
probably are a result of contamination from the diesel oil mud
system, although crude oil contamination from the producing
zones of the formation cannot be eliminated as another source.
2-7
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2.1.3 Produced Water
When oil and gas are produced, water is often produced
along with them. This water is known as produced water,
formation water, or brine. Produced water may originate from
the reservoir or from waterflood treatment of the field, i.e..
from injecting water into the formation to increase oil
recovery. The quantity of produced water is dependent upon the
method of recovery and the nature of the formation. Generally.
the quantity increases with time for particular reservoirs.
However, it can vary greatly among formations. Produced water
discharges estimated for the EPA verification study ranged
between 134 bbl/day and 150.000 bbl/day (21-23.835 m3/day).
Produced water from offshore operations may be discharged
directly to the ocean from pipes either above or below the
water surface. In some cases, the water is piped to shore for
treatment and/or onshore injection; in other cases, the water
may be reinjected offshore either for disposal or pressure
maintenance purposes.
Produced water generally can be characterized as a brine
having salinities that may exceed those of ambient seawater.
Chloride levels of 37.000-110.000 ppm occurred in produced
water for ten platforms off Louisiana; normal values for
seawater are approximately 19.000 ppm. Produced water will
contain petroleum hydrocarbons (especially lower molecular
weight compounds) and metals, and may contain biocides and
other additives.
Lower, molecular weight hydrocarbons are more soluble in
produced water than the higher molecular weight compounds.
Among the lower molecular weight hydrocarbons are the volatile
2-8
-------
liquid hydrocarbons, which include the light aromatics (benzene
through naphthalene). These are among the most immediately
toxic components of petroleum. Concentrations on the order of
10-20 ppm have been measured in produced water for these
chemicals. In the EPA's 30-platform study, naphthalene was
found at concentrations on the order of 0.02-1.5 ppm. A number
of related compounds (e.g.. alkylated naphthalenes) are known
to be present in produced water, but were not specifically
analyzed in the platform verification study.
The concentrations of aromatics in produced water can be
used, together with information on the volumes of discharges,
to estimate discharge rates for specific chemicals. Discharge
quantities for several chemicals that have been examined
(benzene, toluene, and ethylbenzene) could exceed 10 kg/day for
larger facilities (including central facilities). Ranges for
average discharges (excluding central facilities), based on
EPA's 30 platform study, yield the following discharge rates:
benzene (<.01 to 7.7 kg/day), toluene (<.04 to 12.6 kg/day),
and ethylbenzene (<.01 to 3.8 kg/day). Produced water also
contains higher molecular weight alkanes and polynuclear
aromatic hydrocarbons.
Inorganic compounds present in produced waters include
heavy metals. Although various analyses have been carried out
on heavy metals, several authors have noted there has been
uncertainty about the quality of the data. Analyses conducted
during EPA's 30-platform verification study indicated that the
following metals were present in elevated concentrations
(ranges in concentrations are shown in parentheses with zero
identifying less than detection limits): Cd (0-98 ppb), Cu
(0-1.455 ppb). Pb (0-5.700 ppb). Ni (0-276 ppb). Ag (0-107
2-9
-------
ppb). and Zn (5-519 ppb). These ranges ace similar to those
reported in a previous EPA study. Other inorganic chemicals
that may be present, and add to oxygen demand, include ammonia
and hydrogen sulfide. For a project offshore southern
California, the estimated concentrations of these two compounds
could reach 800 mg/liter and 100 rag/liter, respectively.
Radioactive materials, such as radium, also have been found
in some oil field produced waters. Ra-226 activities in
filtered and unfiltered produced waters ranged from 16-395
pCi/liter. while Ra-228 activity ranged from 170 to 570
pCi/liter. These levels were significantly higher than
background (open ocean surface waters normally contain 0.05
pCi/liter of radium). EPA's Office of Radiation Programs
estimates resultant exposure at less than 1.0 mrem/yr, well
below international guidelines.
Many different chemicals may be added during production
operations and these may be present in the produced water
discharge. These include biocides. coagulants, corrosion
inhibitors, cleaners, dispersants, emulsion breakers, paraffin
control agents, reverse emulsion breakers, and scale
inhibitors. Detergents may also be found in produced water.
The use of these chemicals varies from one platform to another.
Biocides may be used to control sulfate reducing bacteria.
which may contribute in the corrosion of metal pipes and
tanks. Biocides that have been used include K-31
(glutaraldehyde). KC-14 (alkyldimethylbenzyl chloride).
acrolein. fatty amines, quaternary ammonium compounds,
2.2-dibromo-3-nitrilopropionamide, and chlorinated
2-10
-------
isothiazolines. A more complete list of biocides registered
for use in both secondary recovery operations and drilling muds
has been compiled by U.S. EPA.
One author has noted that most biocides are used in
concentrations no higher than 20 ppm. and the concentrations in
the effluents are usually a few ppm at most. Biocide
application rates are usually in direct proportion to their
efficacy. However, there is little quantitative data on
concentrations of these chemicals in produced water
discharges. This same author also noted that the biocide
acrolein (which is usually scavenged and thus not detected in
the effluent) may be reformed/released from its scavenged state
following discharge, and was thought to be the agent
responsible for eye and skin irritation of divers at the
platform, at one point sufficient to force them out of the
water.
Produced waters also may contain substances that exert an
oxygen demand. One report on produced water estimated COD
levels of 100-3,000 ppm (w/v) and BOD levels of 300-2.000
ppm. The presence of oxygen consuming substances also has been
evident in toxicity tests of produced water. For three- and
eight-platform scenarios off Santa Barbara, annual BOD loadings
were estimated at 6.740 and 18,000 metric tons. The authors
contrasted these estimates with the combined total of 264,000
metric tons per year associated with five major municipal
outfalls in southern California. They also also reported that
there could be localized depressions of dissolved oxygen at the
combined produced water discharge outfall. Using similar
numbers to calculate the total BOD mass in produced waters
released from Louisiana wells results in an estimated annual
BOD release of 37.000 tons from produced water discharges.
2-11
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2.2 DRILLING FLUIDS
Drilling fluid (or drilling "mud") is a suspension of
solids and dissolved materials in water or oil. which serves
several important functions in well drilling. Drilling mud
helps lubricate and cool the drill bit. clean the bit. maintain
sufficient hydrostatic pressure downhole. and remove drill
cuttings from the hole to the surface. In the early days of
oil drilling, water was used as the fluid. Today, wells are
much deeper, drilling conditions more demanding, and drilling
procedures far more sophisticated. Complex drilling fluids are
necessary for efficient, economical, and safe completion of the
well drilling operation. The types, functions, composition,
and discharge of drilling fluids are examined in this section.
2.2.1 Types of Drilling Fluids
Drilling fluids may be water-based or oil-based. In
water-based fluids, water forms the continuous phase of the
mixture and may constitute 27 to 90 percent of the mud by
volume. Either freshwater or seawater may be used.
Oil-based fluids are those in which oil. typically diesel
oil. serves as the continuous phase and water as the dispersed
phase. The most common kinds of oil-based muds in use today
are invert emulsions in which water may constitute as much as
50 percent of the mud by volume. Other types of oil-based muds
differ from invert emulsions in the amount of water used,
method of controlling viscosity and thixotropic properties.
wall-building materials, and fluid loss (Wright and Dudley.
1982). Oil-based muds are more expensive and more toxic than
2-12
-------
water-based muds, and would normally be used only foe
particularly demanding drilling conditions for which
water-based fluids would prove inadequate.
There is currently an increased interest in the use of
mineral oil-based muds as a substitute for diesel oil-based
muds. While both muds possess the same desirable properties.
mineral oil-based muds have a lower aromatic hydrocarbon
content and are less toxic. Moreover, the mineral oil-based
muds are not irritating to the skin and do not have a noxious
odor (Petrazzuolo. 1983). Air. gas. mist, or foam may also
serve as the drilling fluid in special situations, but these
are not used offshore.
Hater-based drilling fluids are the type most commonly used
offshore. The Best Practicable Technology (BPT) effluent
limitation stipulates no discharge of free oil for drilling
muds and cuttings, and this has prevented the discharge of
diesel oil- and mineral oil-based muds on the outer continental
shelf. The cuttings in both cases are usually discharged after
treatment. However, this varies depending on the requirements
in National Pollutant Discharge and Elimination System (NPDES)
permits issued by the regions or states. Mineral oil-based
muds are not widely used, but their use is becoming more
prevalent because they are less toxic than diesel oil-based
muds.
In 1978 the U.S. Environmental Protection Agency (EPA)
Region II granted offshore drilling NPDES permits to operators
drilling on leases in the Baltimore Canyon. As a permit
condition, the operators were required to perform a jointly
funded drilling mud bioassay program.
2-13
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The result was the development of the generic or standard
mud concept by the Offshore Operators Committee with EPA
Region II. in order to provide EPA with control over mud
components and discharges without requiring that each operator
perform bioassays and chemical test for each discharged mud.
Previously. EPA had not recognized differences in
water-based mud systems and had classified all muds as either
oil-based or water-based. However, for this joint industry
program, the Offshore Operators Committee Task Force on
Environmental Science and EPA Region II developed a spectrum of
eight generic mud types that included essentially all
water-based compositions and an acceptable drilling mud
bioassay procedure.
These eight generic muds were identified by reviewing
permit requests and selecting the minimum number of mud systems
that would include all those mud types named by prospective
permittees; these mud systems included virtually all
water-based muds used on the OCS. Concentration ranges were
specified for mud components to allow the operators sufficient
flexibility to drill safely. Table 2-1 shows the formulations
for each of the muds. Note that a high degree of variability
is allowed in the formulation of each mud. Thus, two samples
of the same generic mud will not necessarily have the same
physical or chemical characteristics, nor the same toxicity.
In the eight generic mud systems, only major components
were specified. Specialty additives (e.g.. lost circulation
materials, lubricity agents, etc.) needed for special drilling
situations were not included. If an unexpected need for a
2-14
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TABLE 2-1 EPA GENERIC DRILLING HUD TYPES
(Cole and Mitchell, 1984)
1. Seawater/Potassiurn/Polymer Hud
Components #/BBLa
KC1 5-50
Starch 2-12
Cellulose Polymer 0.25-5
XC Polymer 0.25-2
Drilled Solids 20-100
Caustic 0.5-3
Barite 0-450
Seawater As Needed
2. Seawater/Lignosulfonate Hud
Components #/BBL
Attapulgite or Bentonite 10-50
Lignosulfonate 2-15
Lignite 1-10
Caustic 1-5
Barite 25-450
Drilled Solids 20-100
Soda Ash/Sodium Bicarbonate 0-2
Cellulose Polymer 0.25-5
Seawater As Needed
3. Lime Hud
Components #/BBL
Lime 2-20
Bentonite 10-50
Lignosulfonate 2-15
Lignite 0-10
Barite 25-180
Caustic 1-5
Drilled Solids 20-100
Soda Ash/Sodium Bicarbonate 0-2
Freshwater As Needed
4. Nondispersed Hud
Components
Bentonite
Acrylic Polymer
Bari te
Drilled Solids
Freshwater
#/BBL
5-15
0.5-2
25-180
20-70
As Needed
2-15
-------
TABLE 2-1 EPA GENERIC DRILLING HUD TYPES
(Cole and Mitchell, 1984)
(Continued)
5. Spud Hud (slugged intermittently with seawater)
Components #/B8La
Attapulgite or Bentonite 10-50
Lime 0.5-1
Soda Ash/Sodium Bicarbonate 0-2
Caustic 0-2
Barite 0-50
Seawater As Needed
6. Seawater/Freshwater Gel Hud
Components #/BBL
Attapulgite or Bentonite Clay 10-50
Caustic 0.5-3
Cellulose Polymer 0-2
Drilled Solids 20-100
Barite 0-50
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Seawater/Freshwater As Needed
7- Lightly Treated Lignosulfonate Freshwater/Seawater Hud
Components #/BBL
Bentoni te 10-50
Barite 0-180
Caustic 1-3
Lignosulfonate 2-6
Lignite 0-4
Cellulose Polymer 0-2
Drilled Solids 20-100
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Seawater to Freshwater Ratio 1:1 approx.
2-16
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TABLE 2-1 EPA GENERIC DRILLING HUD TYPES
(Cole and Mitchell, 1984)
(Continued)
8. Lignosulfonate Freshwater Hud
Components #/BBLa
Bentonite 10-50
Barite 0-450
Caustic 2-5
Lignosulfonate 4-15
Lignite 2-10
Drilled Solids 20-100
Cellulose Polymer 0-2
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Freshwater As Needed
a (pounds per barrel)
2-17
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specialty additive arose, the operator was required to submit
the chemical composition, usage rates, and toxicity data on the
additive to EPA prior to its discharge.
Based on this information, the EPA Region would either
approve or disapprove the discharge of mud containing the
additive on a case-by-case basis. If there was a continuing
need for the additive, the operator could then submit bioassay
data on the mud containing the additive. The discharge would
only be allowed if the additive did not increase mud toxicity
unacceptably. Once an additive became "approved" in this way.
future discharges of muds containing the additive would be
allowed without conducting additional bioassays.
The approach has proved to be practical, and the generic
mud concept subsequently has been incorporated into individual
and general permits issued by EPA coastal Regions that have or
intend to issue NPDES permits to offshore facilities.
2.2.2 Functions of Drilling Fluids
Drilling fluids are specifically formulated to meet the
physical and chemical conditions of each particular well site.
Seawater alone is normally used to drill the first 50 to 100 m
(164 to 328 ft) of the well, and the drill cuttings produced
are discharged directly at the sea floor. After this point.
casing is set. and a specially formulated drilling mud will be
used. Mud composition is affected by geographic location, well
depth, and the rock type through which drilling will occur, and
will be altered as depth increases and rock formations and
other conditions change. The primary functions of drilling
fluids are:
2-18
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maintaining sufficient hydrostatic pressure to prevent
influx of formation fluids into the well-bore
cooling and lubricating the drill bit and drill string
removing cuttings and transporting them to the surface
maintaining cuttings in suspension during interruptions
in drilling
coating the bore wall with an impermeable filter cake to
prevent fluid loss to permeable formations
minimizing corrosion
maximizing the drilling rate
2.2.3 Components of Drilling Fluids
Four kinds of materials represent about 90 percent of the
total tonnage of all additives used in drilling mud--barite.
clays, lignosulfonates. and lignites. Other major components
include caustic soda, soda ash. lost circulation materials, and
other specialty additives as dictated by well requirements.
The functions of some common drilling fluid additives are
described below and in Table 2-2.
2.2.3.1 Barite
Barite is the mineral most commonly used as a weighting
material in drilling mud. Barite is mostly barium sulfate.
which is 59 percent barium by weight. Barite is a naturally
occurring mineral, is readily available and inexpensive, and is
characterized by high specific gravity (4.1 to 4.3 g/ml). low
water solubility (0.03 ppm in seawater). low Mohs' hardness
(2.5-3.5). and chemical inertness.
2-19
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TABLE 2-2 FUNCTIONS OF SOME COMMON DRILLING FLUID CHEMICAL ADDITIVES
1. Alkalinity and pH Control: Caustic soda, sodium carbonate, sodium bicarbonate, and lime are commonly used to
control the pH of drilling fluid and secondarily to control bacterial growth.
2. Biocides: Paraformaldehyde, alkylamines, caustic soda, lime, and starch preservatives are typically used as
bactericides to reduce the bacteria count in the mud system. Halogenated phenol bactericides are no longer
permitted for OCS use.
3. Calcium Removers: Caustic soda, soda ash, sodium bicarbonate, and certain polyphosphates are added to control the
calcium buildup which can prevent the proper functioning of drilling equipment.
4. Corrosion Inhibitors: Hydrated lime and amine salts are added to drilling fluids to reduce corrosion potential.
5. Defearners: Aluminum stearate and sodium aryl sulfonate are commonly used to reduce foaming action that occurs
particularly in brackish waters and saturated saltwater muds.
6. Emulsifiers: Ethyl hexanol, silicone compounds, modified lignosulfonates, and amionic and nomionic products are
used as emulsifiers to create a homogeneous mixture of two liquids.
N)
i
N> 7. Filtrate Loss Reducers: Bentonite clays, cellulose polymers such as sodium carboxymethyl cellulose (CMC) and
hydroxyethyl cellulose (HEC), and pregelated starch are added to drilling fluid to prevent the invasion of the
liquid phase into the formation.
8. Flocculants: Salt (or brine), hydrated lime, gypsum, and sodium tetraphosphate cause suspended colloids to group
into "floes" and settle out.
9. Foaming Agents: These products are designed to foam in the presence of water and allow air or gas drilling
through formations producing water.
10. Lost Circulation Materials: Wood chips or fibers, mica, sawdust, leather, nut shells, cellophane, shredded
rubber, fibrous mineral wool, and perlite are all used to plug pores in the well-bore wall to reduce or stop fluid
loss into the formation.
11. Lubricants: Certain hydrocarbons, mineral and vegetable oils, graphite powder, and soaps are used as lubricants
to reduce friction between the drill bit and the formation.
12. Shale Control Inhibitors: Gypsum, sodium silicate, polymers, limes, potassium chloride, and salt reduce wall
collapse caused by swelling or hydrous disintegration of shales.
13. Surface Active Agents (Surfactants): Emulsifiers, de-emulsifiers, and flocculants are used to alter a fluid's
viscosity, or wary its gel strength.
-------
N)
I
N)
TABLE 2-2 FUNCTIONS OF SOME COMMON DRILLING MUD CHEMICAL ADDITIVES
(Continued)
14. Thinners: Lignosulfonates, tannins, and various polyphosphates are used as thinners. These additives disperse
solids by deflocculating associated clay particles.
15. Weighting Materials: Products with high specific gravities, predominantly barite, calcium carbonate, siderite,
and iron oxides (hematite), are used to increase drilling mud weight.
16. Petroleum Hydrocarbons: These products (often diesel oil) may be added to mud systems for specialized purposes
such as freeing a stuck pipe. Hydraulic testing of blowout preventers also requires the use of hydrocarbons
-------
Trace impurities in barite include arsenic, cadmium,
chromium, copper, iron. lead, mercury, nickel, and zinc. These
impurities may occur as substitute metals in the barium sulfate
structure or as insoluble sulfides. The sulfides most often
associated with barite deposits are sphalerite (ZnS). galena
(PbS), and pyrite (FeS ) (Kramer et al.. 1980; Macdonald.
1982). Kramer et al.. (1980) showed that sphalerite in barite
deposits concentrates mercury and cadmium and pyrite
concentrates arsenic. Veined deposits of barite may show
concentrations of lead, zinc, mercury, and cadmium of one to
two orders of magnitude above background; bedded deposits may
show only minor enrichment relative to background.
Analyses of four separate samples of barite. (1) API
Standard. (2) North American, (3) European. (4) North American
revealed wide variations in trace metal content (CENTEC. 1984.
Table 2-3). The highest variability was observed for mercury,
arsenic, and iron. Whereas the European barite contained 1.78
ppm mercury, the API standard contained 0.035 ppm. and both
North American samples contained less than the detection level
of 0.030 ppm. Arsenic levels in the API standard were 8.40 and
9.30 ppm (see Table 2-3) as compared to less than detection
(0.200 ppm) or 0.357 ppm for the other three bacite samples.
This latter anomaly may be associated with the icon anomaly,
since arsenic is often found in association with sulfucous ores
such as FeS . Iron levels in the API standard barite were
4h
25,600 ppm as compared to 128 to 241 ppm for the other three
samples.
Similar but less pronounced anomalies in the API standard
were observed for copper and aluminum levels. Lead and
antimony levels appeared much higher in the API and European
2-22
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TABLE 2-3 METAL CONCENTRATIONS IN BARITE SAMPLES
M
I
CO
METHOD
Al
Ba
Be
Cd
Cr
Cu
Fe
Ni
Pb
Zn
Hg
Ag
As
Se
Sb
T1
FLAME
FLAME
FLAME
FLAME
FLAME
FLAME
FLAME
FLAME
FLAME
FLAME
NOS
FURNACE
FURNACE
FURNACE
FURNACE
FURNACE
API
API
API
API
API
API
API
API
API
API
NOS
EPA
API
EPA
API
EPA
API
EPA
API
EPA
API
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG
MG/KG3
MG/KG3
MG/KG3
NG/KG3
MG/KG3
MG/KG3
MG/KG3
MG/KG3
MG/KG3
MG/KG3
MG/KG3
API Standard
Bar-He
#lb
524
304
<1.20
<1.20
<3.00
68.4
25600
<3.00
45.4
164
0.035(1)
6.34
1.84(1)C
8.40
9.30
<0.500
c
1.40
1.06
<0.200
<0.200
N. American
Barite
#2B
72.6
1250
<1.20
<1.20
<3.00
5.72
128
<3.00
<6.00
7.69
<0.030
<0.200
<0.200
0.357
<0.500
c
<0.200
0.090(1)
<0.200
<0.200
European N.
Barite
#3b
926
642
<1.20
<1.20
<3.00
12.0
241
<3.00
23.8
202
1.78
1.40
2.39(1)C
<0.200
<0.200
<0.500
c
3.06
2.69
<0.200
<0.200
American
Barite u
#4b
55.0
834.0
<1.20
<1.20
<3.00
2.55
190
<3.00
<6.00
6.04
<0.030
0.6193
1.88
<0.200
<0.200
<0.500
c
<0.200
1.18
<0.200
0.286
FROM CENTEC, 1984
3 Wet weight basis.
b Mean of duplicate analysis.
c Furnace could not be run for Se or Hg using API method of sample digestion.
(1) Single analysis only.
NOS = Not otherwise specified.
-------
barite as compared to the two North American barites. It
should be noted here that the API barite standard is formulated
based on physical not chemical characteristics.
Barite and its associated contaminant metals are of low
solubility in seawater. and will remain primarily in
particulate form after discharge. The solubility of the metals
increases in sulfidic or reducing aquatic environments
(Macdonald. 1982).
2.2.3.2 Clays
Bentonite is the most widely used clay in drilling fluids.
Its crystal structure causes it to swell upon contact with
water, and this gelling property suspends solid material and
aids in the removal of drill cuttings from the borehole. The
sealing properties of bentonite also enable it to form an
impermeable filter cake on the well-bore wall to reduce loss of
drilling fluid to the formation. When concentrated brine is
encountered downhole. however, the swelling qualities of
bentonite clays are severely reduced, and attapulgite or
sepiolite clays are often substituted.
2.2.3.3 Lignosulfonates
Lignosulfonates are considered the best all-purpose
deflocculants for thinning water-based drilling fluids, and
serve to maintain the mud in a fluid state. Lignosulfonates
also serve secondary functions as shale control agents.
Deflocculants, rather than water, are usually used to thin
barite-containing muds, because adding water would increase the
2-24
-------
total fluid volume, reducing barite concentration, and thus
increasing the amount of barite necessary to achieve the proper
density.
Ferrochrome lignosulfonate is a widely used form of
lignosulfonate. It performs over a wide alkaline pH range, is
resistant to common mud contaminants, is temperature stable to
approximately 177° (350°). and will function in high soluble
salt concentrations. Chromium can represent up to three
percent of ferrochrome lignosulfonate by weight. Most of this
chromium is in the trivalent form (as opposed to the more toxic
hexavalent form), and is bound to clay particles, further
limiting its bioavailability and toxicity (McCulloch et al..
1980). Chrome lignosulfonate is also commonly used in drilling
muds.
2.2.3.4 Lignites
Lignites act as mud thinners and shale control agents, but
they are less soluble in seawater than lignosulfonates.
Lignite products are used to thin freshwater muds, reduce
drilling fluid loss to the formation, and aid in the control of
mud gelation at elevated temperatures. Lignites are
manufactured in a variety of forms, such as chrome lignite.
2.2.3.5 Biocides
Biocides are added for control of bacterial growth to the
following systems during drilling operations:
2-25
-------
water disposal systems (including wastewatec treatment)
watecflooding operations
cooling water circulation systems
drilling fluid/mud circulation systems
A recent EPA review (Zimmerman and deNagy. 1984) identified
27 chemicals as biocides used in both drilling muds and
secondary recovery operations. Only one of 27 is a priority
pollutant: pentachlorophenol. use of which is forbidden in any
operation activity (FR 7/3/79). Recommended dosages are very
situation-dependent and can vary from 1.0 to as high as 1200
ppm. Biocides with the lowest efficacy had the highest
recommended dosage and vice versa. It should be noted here
that not all wells will require use of biocides during
development.
Toxicity data is available for the most prevalent biocides
and is reviewed in Zimmerman and deNagy (1984). All of the
recommended treatment levels appear high in comparison to acute
and chronic effect levels for marine organisms.
2.2.3.6 Other Basic Additives
Other basic drilling fluid components include lime, caustic
soda, sodium carbonate (soda ash), and sodium bicarbonate,
which are used, among other functions, to control pH. The pH
of drilling fluid typically ranges from 9.0 to 10.5 and is
important because it affects the dispersibility of clays.
solubility of various chemicals, corrosion of steel materials.
and drilling fluid viscosity. Other such components function
as shale control inhibitors, corrosion inhibitors, lubricants.
and calcium removers. Usage of these additives varies widely
but is generally less than 50 tons per well.
2-26
-------
2.2.3.7 Specialty Additives
Specialty additives, in addition to biocides. include
defoamers (to aid accurate determination of mud pit levels).
surfactants and lubricants (to free a stuck drill string).
filtrate reducers and lost circulation materials (to render the
well-bore wall less permeable to fluid loss), and corrosion
inhibitors. Specialty additive usage in the Gulf of Mexico
typically constituted five to ten percent by weight of total
mud component use (Cole and Mitchell. 1984). However, the
specific geologic strata being drilled and well depth dictate
additive needs. Deeper wells generally present more demanding
drilling conditions, which in turn dictate the need for greater
quantities of specialty additives. Table 2-4 gives examples of
situations requiring special drilling fluid additives or
formulations.
Although specialty additives are used in relatively small
quantities, some of them may disproportionately contribute to
the toxic effects of whole drilling fluids because of their
high toxicity. The same holds true for process contaminants of
drilling fluid discharges. For example, drill pipe dope and
drill collar dope are applied to the threads of the drill pipe
and drill collar to lubricate and seal the connection. Drill
pipe dope is composed of 15 percent copper and 79 percent lead,
while drill collar dope is 35 percent zinc, 20 percent lead.
and 7 percent copper. These compounds may be the major source
of the lead and one source of the zinc and copper found in
drilling fluids (Shell Oil Co.. 1978a, as in Petrazzuolo. 1981;
and Ayers et al.. 1980a). Toxicity is discussed in greater
detail in Section 4 of this report.
2-27
-------
REQUIRING SPECIAL DRILLING FLUID ADDITIVES
OR FORMULATIONS (PES, 1980)
Situation
Problems encountered
Control measures and/or additives
Shale formations
Lost circulation
to
i
N)
00
Excessive filtration or
water loss
Water-based fluid may react with shale
to cause swelling, binding of the drill
string, fluid entry along fracture lines,
sloughing, hole enlargement, or hole
closure.
Loss of whole drilling fluid to forma-
tions resulting when total pressure
against formation exceeds total pressure
of the formation. Low pressure forma-
tions include those which are: cavern-
ous or open-fissure type; very coarse
or permeable (such as loose gravel);
easily fractured; and characterized by
natural or intrinsic fractures.
Excessive water loss to permeable forma-
tions may result in: thickening of the
filter cake causing tight places in the
hole and sticking of the drill string;
sloughing or caving-in of shales; diffi-
culties in interpreting electric logs
used to identify geologic strata. Corrmon
contaminants such as salt, cement and
anhydrite may cause flocculation of clays
to the extent that they are no longer
effective in controlling filtration or water
loss.
Shale control inhibitor additives such
as gypsum, limes, polymers, lignosul-
fonates, and sodium silicates (see
Table 2-2).
Reduction of mud weight; adoption of
special drilling methods such as "blind
drilling," drilling under pressure, or
drilling with air or aerated muds;
placement of soft plugs using lost cir-
culation materials (see Table 2-2); and
use of thickening or cementing materials.
Water loss may be reduced by adding
bentonites, starch, CHC, polymers, and
other filtrate loss reducers identified
in Table 2-2.
Formation pressure control
Formation fluid pressure may be classi-
fied as abnormally high, normal, and sub-
normal . Subnormal pressure zones are
subject to lost circulation problems.
Normal and abnormally high pressure
zones are subject to blow-out conditions.
Adjust drilling fluid to control forma-
tion pressure by increasing or decreas-
ing amount of weighting materials (Table
2-2) used; alter the gel strength or
viscosity of the mud by using surfactant
additives (Table 2-2); and install blow-
out prevention equipment.
-------
TABLE 2-4. SITUATIONS REQUIRING SPECIAL DRILLING FLUID AUUlUVti
OR FORMULATIONS (PES. 1980)
(Continued)
High bottom-hole temperatures
Elevated temperatures may cause mud com-
ponents to react with each other with
results such as accelerated thickening
of fluids. Sane additives and disper-
sants break down at high temperatures.
Temperature-induced changes in mud
properties may cause increased breakdown
of formation leading to lost circulation,
sloughing, etc.
Temperatures are a function of geologic
age and formation and cannot be con-
trolled. However, knowledge of borehole
temperature (from geothermal gradient
records or electric logs from adjacent
wells) will allow selection of heat tol-
erant additives (e.g.. chrome lignosul-
fonate muds are stable at temperatures up
to 177°C [350°F]).
N)
I
N)
ID
-------
2.2.4 Chemical Characterization of Drilling Fluid
A recent EPA sponsored study (CENTEC. 1984) described the
physicocheraical characteristics of eight generic drilling
fluids ("muds") as well as two muds (002/008) admixed with 1.
5. or 10 percent mineral oil. Table 2-1 shows the formulation
used for these eight generic muds. These muds were the same as
used in toxicity testing (see Section 4 and Duke and Parrish.
1984). Table 2-5 describes the physicochemical characteristics
of these muds.
2.2.4.1 Conventional Parameters
For all generic muds the pH was between 8 and 10 with only
the lime mud (003) having a pH of 12. [Admixing with oil
resulted in highly variable changes in pH. most of which appear
due to non-representative sampling/mixing.] Density varied
between 1.44 and 2.15 except for two very light (thin) muds.
005 and 006. which had a density of 1.09 and also had the
highest water content. Water content varied from 26.6 to 90.1
percent, with the heaviest mud having the least water content
and vice versa.
Two biochemical oxygen demand parameters were characterized
in several ways: Biochemical Oxygen Demand (5 day: BOD )
and Ultimate Oxygen Demand (20 day: UOD ). Both were
£ \)
performed with CENTEC activated seed and Polyseed in artificial
seawater. Average BOD varied from 9 to 2.743 mg/kg with
muds 004. 005, and 006 having very low BODs (9 to 216 mg/kg)
and the other muds having BOD 's ranging from 1.373 to 2.743
mg/kg. UODs showed a similar trend with values ranging from
124 to 4.223 rag/kg. Again, two disparate groups were
2-30
-------
TABLE 2-5
CONVENTIONAL MATER QUALITY PARAMETERS OF GENERIC DRILLING FLUIDS
Generic Type of Mud
Hud
001 KCL Polymer Mud
002 Seawater Lignosulfonate Mud
003 Lime Mud
004 Non-dispersed Mud
005 Spud Hud
006 Seawater/Freshwater Gel Mud
PH
8.05
10.10
11.92
8.60
8.10
7.95
007 Lightly treated Lignosulfonate 8.50
Mud
008 Lignosulfonate Freshwater Mud
002-00 Mud 002
002-01 Mud 002 + 1% Mineral Oil
002-05 Mud 002 + 5t Mineral Oil
002-10 Mud 002 + 101 Mineral Oil
008-00 Mud 008
008-01 Hud 008 + 11 Mineral Oil
008-05 Mud 008 + 51 Mineral Oil
008-10 Mud 008+101 Mineral Oil
8.60
10.10
10.95
9.75
8.55
8.60
8.00
9.22
8.50
Density
1.74
2.15
1.73
1.44
1.09
1.09
1.44
2.12
2.15
2.15
2.07
2.04
2.12
2.21
2.23
2.25
I
Weight
Loss
(103°C)
(a)
34.1
26.6
44.0
659.6
90.1
88.0
56.2
27.1
26.6
26.4
27.2
25.7
27.1
27.0
26.3
25.6
BOD-5
SOU
CENTEC
(ACT)
ma/kq(b)
1813
1483
1657
< 50
< 50
181
1470
1530
1483
1416
3416
1558
1530
1373
2207
1423
BOD-5
SOU
POLY-SEED
ma/kg
ma/kg (b)
2037
1373
2743
10
9
216
1386
1393
1373
2223
2157
1877
1393
2383
2023
1633
UOD-20
SOU
+
CAS
mg/ka(b)
4223
2717
3207
136
160
130
2187
2413
2717
4073
8340
9273
2413
4423
9773
7863
UOD-20
SOU
f
POLY
mg/kg (b)
3407
2330
3963
286
124
285
1733
1980
2330
5803
7473
6190
1980
4297
6940
6497
TOC
ma/kg(c)
3.040
15.000
15,000
1,220
100
686
5,650
14.200
15,000
15.900
26.300
36.500
14.200
13.400
20.800
24.200
COO
mo/kg (b)
8.000
39.900
41.200
4,200
420
1.800
15.300
34,900
39.900
46.100
98,300
144,000
34.900
53,800
75.300
99.600
SHEEN
TEST
(15g)(b)
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
Oil and
Grease
mg/kg
Sonifi-
cation(b)
532
1,270
796
520
597
661
1,710
1.400
1,270
2,730
11,700
14,800
1.400
1.990
7.080
12.300
Oil and
Grease
mg/kg
Soxhlet
Extraction(a)
4.860
2,750
1,240
1.820
140
672
572
7.380
2.750
2.400
23.400
40.400
7,380
2.560
7.670
2.800
to
I
U)
FROM: CENTEC, 1984
(a) Average of duplicates.
(b) Average of triplicate.
(c) Average of three triplicates.
ALL DATA WET WEIGHT
-------
apparent: Muds 004. 005. and 006 had UODs ranging from 124 to
286 mg/kg. whereas the remaining muds had UODs from 1.733 to
4,223 mg/kg. UOD s were approximately 1.5 to 2 times
higher than BODs with the exception of muds 004 and 005 where
UODs were from 3 to 28 times higher (which may be an artifact
as a result of the low values) and mud 006 where UOD was lower
than the BOD for the CENTEC activated seed, which appears to be
an aberration when compared to the results for 004 and 005.
Total organic carbon (TOC) content was lowest (100 to 1.220
mg/kg) in muds 004. 005. and 006. intermediate (3.040 to 5.650
mg/kg) in muds 001 and 007 and highest in muds 002. 003. and
008 (14,200 to 15.000 rag/kg). Chemical Oxygen Demand (COD) was
approximately 2.5 to 3 fold higher than TOC values but followed
the same trend. COD values were lowest for mud 004. 005. and
006 (420 to 4.000 mg/kg) intermediate for muds 001 and 007
(8.000 to 15,300 mg/kg). and highest in muds in 002. 003. and
008 (34.900 to 41.200 mg/kg).
None of the generic muds produced a sheen test at levels of
15 grams mud added, which should correspond to levels of free
oil of less than one percent. Oil and grease levels were
indeed low: between 520 and 1.710 mg/kg after Bonification and
between 140 and 7.300 mg/kg after Soxhlet extraction. The oil
and grease values did not show any logical correspondence to
TOC/COD values. Oil and grease (sonification) was highest in
002. 007. and 008 (1.270-1.710 mg/kg). and intermediate (520 to
796 mg/kg) in all other muds. Oil and grease (soxhlet) was
highest in 001. 002 and 008 (2.750 to 7.380 mg/kg) intermediate
in 003 and 004 (1.240 and 1.820 mg/kg) and lowest in 005. 006.
and 007 (140 to 672 mg/kg). Oil content data based on retort
method did not present reliable information.
2-32
-------
Admixture of mineral oil into muds 002 and 008 at levels of
1. 5, and 10 percent (samples 002-01. 002-05. 002-10. and
008-01. 008-05. 008-10. respectively) resulted in some rather
inconsistent results. Both muds are heavy and thus admixture
of lighter oil should result in lower density and lower water
content. Although density for the 002 series decreased.
density for the 008 series increased with oil addition.
Similarly. pH went down for the 002 series with inconsistent
results for the 008 series.
One would expect a continuous increase in oxygen demand
upon addition of oil. This, however, is not the case. Indeed.
addition of 1 percent oil results in an increase of biochemical
oxygen demand. Toxicity (as indicated by decreased BOD/UOD).
however, occurs at the 5 or 10 percent level. Note also that
addition of 1 to 10 percent oil (or 990 to 90.909 mg/kg) does
not result in commensurate increase in biochemical oxygen
demand nor (Table 2-5) in total organic carbon or oil and
grease levels. Chemical oxygen demand, on the other hand.
appears to reflect added oil levels well: very well for mud
002. not nearly as consistent for mud 008. Surprising are the
sheen test results: although designed to detect free oil
levels of 1 to 10 percent, not even the samples with at least
10 percent added mineral oil tested positive.
These results are not easily explainable: the added
mineral oil appears present based on COD data. However,
neither TOG. oil and grease (soxhlet or Bonification), the
sheen test, nor the BOD/UOD result is indicative of the known
amount of oil added. The BOD/UOD results are probably a result
of oil toxicity to the organisms. The other results reflect
two things: nonrepresentative sampling and a nonavailability
2-33
-------
of the oil. possibly as the result of the formation of gels.
Given the boiling point of mineral oil. it appears unlikely
that mineral oil evaporated from this solution during sample
preparation.
2.2.4.2 Metals
CENTEC (1984) reported metal analysis by atomic absorption
spectrometry for the following metals: aluminum, antimony,
arsenic, barium, beryllium, cadmium, copper, chromium, iron.
lead, mercury, nickel, selenium, silver, thallium, and zinc
(See Table 2-6). Beryllium, nickel, and selenium levels were
all below detection levels of 1. 6. and 3 ppm, respectively.
With few exceptions no remarkable excursions in metal levels
could be observed. Addition of mineral oil did not affect
metal levels. Barium data reported were highly variable and
unreliable due to incomplete (weak acid) sample digestion.
Chrome levels were highest (>. 300 ppm) in muds 002, 003.
007. and 008 and nondetectable (<3 ppm) in all other muds.
Arsenic levels were highest (11.7-17.2 ppm) in muds 003 and
008. intermediate (2.40-5.25 ppm) in muds 001. 002. and 004.
and lowest (<. 0.6 ppm) in muds 005. 006. and 007- Antimony
levels were highest (4 ppm) in mud 001. intermediate (0.26 to
1.06 ppm) in muds 002. 003. 004. and 008. and nondetectable
(<0.06 ppm) in muds 005. 006. and 007. Mercury levels were
highest in mud 003 (0.753 ppm). intermediate (0.261-0.437 ppm)
in muds 001. 002. 004. 006. and 008. and lowest (<0.1 ppm) in
muds 005 and 007. Cadmium levels were less than 0.75 ppm in
all muds.
2-34
-------
TABLE 2-6 METAL CONCENTRATIONS IN GENERIC DRILLING FLUIDS
Generic
Hud
001
002
003
004
005
006
007
008
002-00
002-01
002-05
002-10
008-00
008-01
008 OS
008-10
Zn
Type of Hud mg/kg
FLAHE(a)
KCl Polymer Hud
Seawater Lignosulfonate
Lime Hud
Non -dispersed Hud
Spud Hud
Scawatcr/Freshwatcr Gel Hud
Lightly treated
Lignosulfonate Hud
Lignosulfonate
Freshwater Hud
Hud 002
Hud 002 t 11 Mineral Oil
Hud 002 t 51 Mineral Oil
Hud 002 » 101 Mineral Oil
Hud 008
Hud 008 » 11 Mineral Oil
Mud 008 » 51 Mineral Oil
Mud 008 f 101 Mineral Oil
26.2
42.4
37.0
35.9
8.68
3.28
2.26
90.4
42.4
43.4
40.8
46.0
90.4
86.8
65.6
77.8
Be
mg/kg
FLAME (a)
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
Al
mg/kg
FLAHE(a)
190
1150
743
876
347
536
395
1150
1150
1200
1400
955
1150
998
862
857
Ba
mg/kg
FLAME
246
74.0
41.2
286
293
65.4
408
54.6
74.0
71.3
144.1
47.5
54.6
1240
27.0
39.5
Fe
mg/kg
FLAME (a)
1.890
2.860
2,170
1120
833
392
660
5.110
2,860
2,520
3.350
2.800
5.110
4,980
3,940
5,020
Cd
mg/kg
FLAME (a)
0.22
0.472(b)
0.378(b)
0.446 (b)
0.74(b)
0.42 (b)
0.142(b)
0.36
0.472(b)
0.395 (b)
0.7l7(b)
0.470(b)
0.36
0.18
0.28
0.36
Cr
mg/kg
FLAHE(a)
< 3.0
764
908
< 3.0
< 3.0
< 3.0
299
770
764
740
720
640
770
610
541
560
Cu
mg/kg
FLAME (a)
3.96
27.5
40.6
6.78
1.61
0.70
2.86
72.2
27.5
26.8
26.0
26.1
72.2
68.9
77.3
42.8
Ni
mg/kg
FLAHE(a)
< 6.0
< 6.0
< 6.0
< 6.0
< 6.0
< 6.0
< 6.0
< 6.0
< 6.0
7.76
9.80
6.98
< 6.0
< 6.0
< 6.0
< 6.0
Pb
mg/kg
FLAME (a)
7.74
1.82(b)
1.42(b)
41.2
52.5
3.51 (b)
1.53(b)
17.8
1.82(b)
6.83
6.20
1.17(b)
17.8
24.5
13.0
9.48
Hg Ag
g/kg mg/kg
NOS FURNACE (a)
0.261
0.264
0.753
0.437
< 0.010
0.297
0.0961
0.355
0.264
0.107
0.091
0.072
0.355
0.391
0.368
0.287
0.089
0.126
0.314
0.228
< 0.060
< 0.060
< 0.060
0.244
0.126
0.110
0.124
0.110
0.244
1.39
1.11
1.14
As
mg/kg
FURNACE (a)
4.64
2.40
17.2
S.25
0.258
0.621
0.497
11.7
2.40
1.47
1.70
1.97
11.7
12.2
9.61
9.24
Se Sb
mg/kg mg/kg
FURNACE (a) FURNACE (a)
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
< 3.0
4.00
0.260
1.06
0.473
< 0.060
< 0.60
< 0.060
0.794
0.260
0.239
0.522
0.160
0.794
2.65
2.70
2.02
Tl
mg/kg
FURNACE (a)
0.078
0.201
0.129
0.114
< 0.060
< 0.060
< 0.060
0.071
0.201
0.175
0.184
0.166
0.071
0.080(1)
0.074
0.062(1)
ts)
I
u>
Fran CENTtC. 1984.
(a) Dry weight basis, average of two samples.
(b) Samples run by HGA.
(1) Single analysis.
NOS = Not Otherwise Specified.
-------
2.2.4.3 Organics
The sole organic pollutant detected via GC/MS analysis for
volatile organics. base neutrals, and acid phenols of all the
muds was n-dodecane (C-12 alkane) at concentrations ranging
from 736 to 899 ppb (yg/kg) (CENTEC. 1984). Addition of
mineral oil resulted in dose-dependent detection of n-dodecane,
phenanthrene. dibenzothiophene. dibenzofuran. diphenylamine,
and biphenyl (Table 2-7).
2.2.4.4 Oil-based Additives for Water-based Muds
A recent industry-sponsored study described the
distribution of diesel oil hydrocarbons within base muds and
oil additives (Breteler et al.. 1984). Mineral, low sulfur.
and high sulfur diesel oils were each added to base (generic)
mud No. 8 at concentrations of 0.5, 2, and 5 percent. (No
solid phase determinations were performed at the 2 percent
level). Base mud hydrocarbon concentrations averaged 17.4 ppm
total hydrocarbons in the solid phase, compared to 17.1 ppm
after 10 days of exposure. Total hydrocarbon concentrations in
the mud solid phase following additions of oil did not reflect
the amount of oil added.
Total increase in hydrocarbons in solid phase at the 0.5
percent oil addition level were 191. 559. and 415 yg/g for
mineral, low. and high sulfur diesel oil. respectively -
Approximately 40 percent of these concentrations remained after
10 days of solid phase testing. At the 5 percent addition
level, total hydrocarbons in the solid phase increased to 2433.
2923. and 2513 yg/g. respectively. After 10 days of solid
phase testing 32 percent. 24 percent, and 36 percent remained.
2-36
-------
Table 2-7 RESULTS OF ANALYSIS OF ORGANICS IN DRILLING FLUIDS
RESULTS IN ug/kg (ALL BASE NEUTRAL FRACTION)
Control
EPA
ID
001
002
003
004
005
005
006
N)
I 006
u>
^ 007
008
002-01
002-05
002-10
008-01
008-05
008-10
Centec
ID
30854
30796
30934
30935
30855
30855
30856
30856
30797
30746
31055
31056
31057
31058
31059
31060
Center Phenan- Dibenzo-
ID threne thiophene
11487
11476
11479
11488
11480
11480 Dup.
11481
11481 Dup.
11477
11489
11486 1060
11482 8270
11484 19300
11490
11485 5580
11483 11100
Dibenzo- N-Dodecane Diphenyl-
furan C-12 amine
899
809
819
854
822
847
802
736
780
726
827 6540
1040 13300 4280
9380
933 8720 5200
Biphe
867
2290
1120
Fran: CENTEC. 1984
-------
respectively- Such losses were nearly complete at the end of
24 hours for mineral oil, whereas the relatively more soluble
diesel oils lost a significant portion between 24 and 48 hours.
As expected, the chemical composition of the three oil
additives varies drastically (Breteler et al.. 1984). Aromatic
hydrocarbons comprised 0.4 percent of total hydrocarbons in
mineral oil. 8 percent in low-sulfur diesel oil and 29 percent
in high sulfur diesel oil. Mineral oils consisted primarily of
cycloalkanes and only contained a small amount of n-alkanes.
The relative abundance of these alkylated benzenes decreased
once the oil was added to the mud. as a result of
volatilization during admixing.
If a mixture was stirred for 10 minutes and sampled after
one hour. 55 to 82 percent of the C thru C benzenes were
1 6
lost. If mixing time was increased to 4 hours. 70-100 percent
of total added benzenes were lost. Thus any studies looking at
drilling mud mixtures containing (added) oil should take into
account the amount of time spent mixing, settling, and aerating
as well as any "aging" effects.
2.2.4.5 Used Drilling Fluid Samples
The hydrocarbon and metal content of used drilling fluid
samples used for toxicity testing (see Section 4) was recently
reported by EPA (SAI. 1984 in Duke. 1984). Hydrocarbon content
reported as "diesel equivalents" (equivalent to API W2 fuel
oil) varied between 0.10 and 9.43 mg/g (Table 2-8). Whole mud
contained aliphatic hydrocarbons at levels of 22.4 to 7.230
mg/1. with aromatic hydrocarbons ranging from 11 to 1.600
mg/1. Levels of hydrocarbons in the suspended phase were at
2-38
-------
TABLE 2-8 HYDROCARBON CONCENTRATIONS OF DRILLING FLUID SAMPLES
IS)
1
u>
VO
Hyd
MIS
AN31
SV76
PI
P2
P3
P4
P5
P6
P7
P8
"Diesel"1
(mg/g)
0.19
1.18
3.59
9.43
2.14
3.98
0.67
1.41
0.10
0.50
0.56
Whole
Aliphatic
(mo/1)
34.5
604
1,430
6,900
1,052
7,230
680
930
22.4
101.3
474
Hud2
Suspended Par ticu late Phase
Aromatic Aliphatic
(mo/1) (mo/1)
22.13
292.5
496
1,600
275.6
675
209
390
11
40.0
250.9
0.046
0.325
3.52
14.2
0.694
15.8
0.462
3.74
0.039
0.063
1.37
Aromatic
(U9/1)
0.073
0.089
0.912
5.53
0.426
2.86
0.442
1.37
0.038
0.030
1.71
Polar Fraction
(ug/1)
25.0
497
1,630
950
1,380
1,120
147
165
13.6
478
836
Liouid Phase
Resolved Unresolved
(ma/1) (mo/1)
0.358
0.136
0.920
0.358
0.005
1.09
0.002
0.166
0.043
0.175
0.161
0.813
1.24
6.63
0.603
0.008
6.49
0.011
1.16
0
0
2.42
'values obtained by gas chromatographic/mass spectrometric analyses and external standards (NEA, 1984
as reported in Duke and Parrish, 1984).
2Total resolved and unresolved (SAI, 1984 as reported in Duke and Parrish, 1984).
3Total resolved and unresolved (SAI, 1984 as reported in Duke and Parrish, 1984).
4(SAI, 1984 as reported in Duke and Parrish, 1984).
-------
least two orders of magnitude lower. Levels of polar
hydrocarbons in the total suspended phase varied from 13.6 to
1.630 mg/1 and were generally the same or lower than the levels
of aromatic hydrocarbons. The liquid phase data are
uninterpretable as reported. The levels of hydrocarbons
observed in the suspended phase are very similar to those
observed by Breteler et al.. 1984 when up to 5 percent diesel
oil or mineral oil was added to generic mud No. 8.
An industry sponsored study (Breteler et al.. 1984) showed
that total hydrocarbon concentrations in the suspended phase
(on an equivalent solids level/oil addition) increase
dramatically (up to an order of magnitude) in the series
mineral oil < low sulfur diesel oil < high sulfur diesel oil.
Total levels of total hydrocarbons dropped drastically (up to
95 percent) during a standard 96-hour LC test, primarily as
a result of volatilization. Test solutions containing the
highest level of suspended total hydrocarbons showed the
highest relative decrease during the 96-hour test period.
Metal data (see Table 2-9) were highly variable. Whole mud
levels were invariably one order of magnitude, and often two
orders of magnitude, higher than those in the suspended
particulate phase, which in turn were at least one to two
orders of magnitude higher than those in the liquid phase.
Based upon a review of toxicity data, the only metal for which
a correlation may occur is chromium.
2.2.5 Completion and Workover Fluids
Completion and workover fluids are two special types of
well treatment fluids. Completion fluids are used during
completion of a well, and workover fluids are used when a well
is being reworked to increase hydrocarbon production.
2-40
-------
TABLE 2-9 METALS CONTENT OF DRILLING FLUID SAMPLES
1
Element
Al
Ba
Cd
Ca
Cr
Cu
Fe
Pb
Sr
Zn
MIB
MM SP LP
5.191 473 0.026
9.851 13.9 0.409
0.387 0.007 0.001
4.391
337.0 5.76 0.338
23.4 0.349 0.000
4.311 546 0.295
135 1.41 0.011
510
161 276 0.001
AN31
WM SP LP
3.741 1,206 0.079
21.81 15 0.469
2.38 0.076 0.005
1.57%
774 828 1.15
33.6 2.56 0.098
2.68% 1,565 1.09
142 1.20 0.040
538
247 14.5 0.526
DRILLING FLUID
SV76
WM SP LP
0.611 482 0.030
37.51 12.5 0.407
1.62 0.315 0.009
0.821
1,345 457 43.6
86.1 15.0 1.27
3.631 1,975 1.85
151 18.4 0.161
536
495 93.1 0.487
SAMPLES
PI
MM SP LP
1.011 555 0.047
36.91 10.7 0.460
1.85 0.26 0.004
0.861
814 221 3.34
62.3 15.9 0.119
3.441 1,566 1.49
129 13.3 0.093
303
410 52.5 0.075
P2
WM SP LP
0.761 793 0.009
37.21 8.05 3.32
11.8 2.38 0.007
0.651
483 237 0.896
39.7 11.8 0.019
0.701 1,784 1.27
291 40.6 0.046
226
2,064 338 0.007
P3
WM SP LP
1.301 661 0.132
35.11 22.9 0.813
2.10 0.053 0.002
0.741
459 138 2.60
90.4 11.1 0.243
5.671 1,810 1.84
100 10.2 0.104
383
439 41.8 0.140
N)
I
Vrcm SAI, 1984 as reported in Duke and Parrish, 1984.
WM = Whole Mud Concentrations expressed as ug/g dry weight, unless otherwise indicated.
SP = Suspended Particulate Concentrations expressed as pg/g wet weight, unless otherwise indicated.
LP = Liquid Phase Concentrations expressed as yg/1 wet weight, unless otherwise indicated.
-------
TABLE 2-9 METALS CONTENT OF DRILLING FLUID SAMPLES1 (Continued)
1
DRILLING FLUID SAMPLES
i
P4 | P5
j
Element WM SP LP ! UM SP LP
Al 1.56% 1,083 2.41
Ba 48.7% 11.7 10.7
Cd 8.27 3.06 0.004
Ca 0.18%
Cr 532 197 41.8
Cu 32.7 12.3 0.059
Fe 1.15% 2,896 32.4
Pb 221 28.2 1.56
Sr 207
Zn 1,384 476 0.804
0.71% 376 0.354
37.5% 15.9 1.04
2.34 0.075 0.003
0.57%
187 34.6 0.513
126 10.6 0.373
7.63% 1,996 1.60
104 9.07 0.054
346
175 27.5 0.007
P6
MH SP LP
5.10% 1,012 0.021
18.8% 15.8 0.134
10.5 0.556 0.017
0.19%
41.8 1.06 0.227
35.1 2.18 0.002
2.51% 1,243 0.108
210 10.2 0.003
120
1,755 80.4 0.007
P7
WM SP LP
4.47% 1,010 0.011
21.0% 19.4 0.328
0.21 0.018 0.001
0.46%
502 35.6 0.436
15.6 0.932 0.021
2.25% 1,001 0.288
92.1 1.45 0.004
258
144 6.30 0.007
P8
WM SP LP
0.68% 398 0.026
3.00% 15.9 0.302
0.410 0.024 0.002
1.54% __ __
480 133 11.0
3,448 16.0 0.268
1.25% 802.0 1.39
48.3 5.20 0.199
1,401
144 22.6 0.185
CO
I
*»
NJ
'From SAI, 1984 as reported in Duke and Parrish, 1984.
UH = Whole Mud Concentrations expressed as yg/g dry weight, unless otherwise indicated.
SP = Suspended Particulate Concentrations expressed as yg/g wet weight, unless otherwise indicated.
LP = Liquid Phase Concentrations expressed as yg/1 wet weight, unless otherwise indicated.
-------
Well completion occurs if a commercial-level hydrocarbon
reserve is discovered. The porous rock production zone can be
damaged by the mud solids and water contained in normal
drilling fluids. To avoid this damage and maximize the
production rate, a special low-solids completion fluid may be
used to drill through the production zone.
Salts are used in low-solids fluids to inhibit clay
swelling and gellation. and to obtain the necessary fluid
density without solid weighting materials (Eaton et al.,
1981). Sodium chloride, potassium chloride, calcium chloride.
calcium bromide, or zinc bromide may be used as weighting
materials, depending on the density required. The control of
viscosity and filtration rate also requires special
consideration in low-solids systems. Organic polymers such as
hydroxyethyl cellulose and xanthum gum are used for these
purposes. Ground calcium carbonate may also be used to
initiate filter cake formation in permeable sand. Corrosion
inhibitors, such as amine derivatives, are used in salt systems
to reduce damage to casing. At the concentrations used. 0.004
to 0.014 kg/1 (1.5 to 5 Ib/bbl). these corrosion inhibitors
also act as biostats to prevent microbial degradation of
polymers. Even so, additional biocides. buffers, defoamers.
and other specialty additives may be necessary to maintain
suitable drilling conditions.
Workover of a well involves "going back into" an already
producing well to increase the rate of hydrocarbon production
or reopening a "shut-in" well and reworking to increase
productivity to a commercially acceptable level. Workover
operations frequently use the fluid left in the well annulus
upon completion, which can be either a normal drilling fluid or
2-43
-------
a low-solids completion fluid (M. Jones. IMCO Services, to T.
Mors. Dalton'Dalton'Newport. personal communication,
1982). If the fluid left in the annulus is not appropriate for
the workover process, the fluid can be altered or removed and a
new drilling mud added.
High solids fluids are used in certain completion and
workover operations. They may contain the same materials as
typical drilling fluid except that they are freshly formulated
to avoid the fine drilled cuttings which accumulate in used
drilling fluid. Calcium carbonate or iron carbonate may be
used as the weighting material.
Little has been documented concerning the frequency or
quantity of completion or workover fluid use. Much of the
completion fluid would be left downhole, but the quantities
normally discharged are not documented. Similarly, data on
workover fluid volumes are lacking. Some data are available on
the toxicity of workover fluids to the white shrimp Penaeus
setiferus (see Section 4).
2.3 DRILL CUTTINGS
Drilling fluid circulates down the bore hole and back to
the surface, carrying drill cuttings with it. The cuttings are
removed from the fluid by one of several pieces of solids
control equipment. The shale shaker is a vibrating screen that
removes large particles from the fluid. Standard shaker
screens generally remove particles larger than 440vm (.017
in.), while fine screens can remove particles down to
approximately 120ym (.005 in.)(Houghton et al.. 1981). The
fluid then passes through the sand trap (if used), a
2-44
-------
gravitational settling tank which removes particles from
approximately 75 to 210nm (.003 to .008 in.). The next step,
the desilter is a hydrocyclone which uses centrifugal forces to
remove silt-sized particles (approximately 5 to 75ym or .0002
to .003 in.). The removed cuttings are discharged anywhere
from the platform itself to deep below the water surface
depending on the rig, but are typically discharged just above
the water surface. The processed drilling fluid is then
returned to the mud tanks for recirculation to the well.
Discharges from the solids removal system consist of drill
cuttings, wash water used to remove drilling fluid from the
cuttings, and drilling mud still adhering to the cuttings (Ray
and Meek. 1980). Another study by the same authors (Meek and
Ray. 1980) found that discharges from solids control equipment
(i.e.. cuttings) from a southern California OCS well were
composed of 96 percent cuttings solids and 4 percent adhering
drilling fluid. However, other data from a mid-Atlantic well
placed these values at 40 percent cuttings and 60 percent
adhering fluid (Ayers et al., 1980a).
2.3.1 Chemical Characteristics of Drill Cuttings
Only very limited data are available on the phvsico-
chemical characteristics of drilling cuttings, mostly from the
Georges Bank program and CENTEC (1984) analysis of three sets
of drilling cuttings from three different wells, all at depths
greater than 10.000 feet. In Tables 2-10 and 2-11 (A) denotes
a cuttings sampling taken prior to washing and (B) a sample
taken after washing. Density decreases and pH and water
content increase after washing as compared to before washing.
although with a considerable range between samples. Oxygen
2-45
-------
TABLE 2-10
CONVENTIONAL WATER QUALITY PARAMETERS FOR DRILL CUTTINGS
1A
IB
2A
28
3A
3B
South Timbal
Near Block
26 at 985 T
w mineral oil
South Marsh
Island Block
214 at 14,052'
w/Hilchetn
Carbotec
Vermill ion
Block 50 at
14,351' with
Mayobar Fare-
Kleen Mineral
pH Specific
Gravity
kq/1
Before 6.50 1.72
Washing
After 7.00 0.98
Washing
Before 8.42 2.07
Washing
After 9.82 1.41
Washing
Before 5.70 1.26
Washing
After 9.20 1.59
Washing
I SHEEN Oil and
Weight TEST Grease Oil and
Loss BOO-5 BOO-5 UOD-20 UOO-20 0.5 Sonifi- Grease
(103°C) SOW/CAS SOW/POLY SOW/CAS SOW/POLY TOC COO [1.5g] cation Soxhlet
(a) mq/kq(b) mg/kg(b) mg/kq(b) mq/kq(b) mg/kq(c) mq/kg(b) (15g)(b) mg/kq(b) mq/kq(a)
18.6 3,500 4,130 9.980 10,500 61,300 190,000 3/3
27.2 8,950 4,290 20,300 26,600 23,000 90,600 [0/3]
(3/3)
15.2 325 1,200 4,210 2,640 64,100 291.000 3/3
20.6 8,800 8,340 21,200 22,800 57,200 272,000 [0/3]
(3/3)
9.7 3,750 3,970 6,780 8,170 58,300 198,000 3/3
26.5 8,020 3.890 12,800 16,200 32,000 152,000 [0/3]
(3/3)
58,700 69,200
11,700 108.000
60,200 130,000
46,300 26,600
54,200 73.500
18.500 8.290
FRCtl CENTEC, 1984.
(a) Average of 2 measurements.
(b) Average of 3 measurements.
(c) Average of 3 triplicates.
-------
TABLE 2-11 METAL CONCENTRATIONS IN DRILL CUTTINGS
N)
I
1A
IB
2A
2B
3A
38
South limbal -
Block 26 at
985 T uith
mineral oil
South Harsh
Island Block
214 a 14.052'
M/Hilchon Carbotec
Vermill ion
Block 50 at
14.3S11 with
Hageobar
(ace-Kloan Mineral
Zn B* Al Ba ft Cd Cr Cu N» Pb Hg Ag As
ing/kg ing/kg ng/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg
FLAME (a) FlAHE(a) FLAME (a) FLAME FLAME (a) FLAME(a) FLAME (a) FLAME(a) FLAHE(a) FLAME (a) 7 (a) FURNACE (a) FURNACE (a)
Before 2710 < 1.0 7810 84.8 21800 16.4 10.8 55. 3 9.48 298 0.0933 0.510 10.3
Washing
After 356 < 1.0 10.500 235 19200 2.15 11.2 20.4 15.9 47.6 0.0920 0.227 7.00
Washing
Before 2030 < 1.0 6020 34.0 16600 10.3 9.48 40.7 12.1 115 0.4893 0.574 10.2
Washing
After 3200 < 1.0 5160 27.2 17400 15.8 12.0 42.6 6.20 264 0.3507 0.568 10.6
Wishing
Before 107 < 1.0 10900 54.0 30800 0.402(b) 11.7 20.6 < 6.00 21.4 0.1476 0.447 7.07
Washing
After 114 < 1.0 7160 84.2 20600 0.408(b) 10.7 26.6 10.4 52.1 0.944 0.222 8.36
Washing
Se Sb Tl
ng/kg mg/kg mg/kg
FURNACE (a) FURNACE (a) FURNACE
< 3.0 < 0.060 O.S70
< 3.0 < 0.350 0.228
< 3.0 < 0.350 0.339
< 3.0 < 0.060 0.866
< 3.0 < 0.300 0.235
< 3.0 < 0.300 0.134
(a) Average of duplicate sanplcs on a dry weight basis
(b) Ibidem HGA analysis.
From Contec, 1984.
-------
demand (as BOD_ and UOD-.) prior to washing is higher than
D & (J
those for drilling muds and increases substantially after
washing. In contrast, total organic carbon and chemical oxygen
demand either stay the same or drop substantially after
washing, as do sheen test results and oil and grease levels.
The increased BOD/UOD could indicate several things: the
additives used and admixed during washing (detergents) could
have high BOD demand, the decrease in "oil" levels allows a
better expression of BOD. or washing mechanically disturbs BOD
as a result of fine particulate aggregates, increasing surface
area and thus cuttings particulates. The latter explanation
appears favored, given the results observed by CENTEC (1984)
following the addition of oil to generic muds. Oxygen demand
increased slightly at low oil levels but decreased oxygen
demand (often to levels below those seen at zero percent oil
added) when higher levels of oil were admixed. This indicates
hydrocarbon toxicity on the organisms used to measure BOD.
Note that the sample with the highest TOG. COD. and oil and
grease level (2A) has a BOD an order of magnitude lower than
any other sample and that BOD/UOD increases dramatically after
washing.
Metal levels in cuttings were not of particular notice
(Table 2-11). Results mostly appear to indicate the high level
of inherent uncertainty of the analyses rather than any actual
trends. Metal levels before and after washing appear similar.
at least within the bounds of uncertainty. Mercury levels were
below 0.5 ppm (dry weight w/w) in all six samples, whereas
cadmium levels ranged as high as 16 ppm.
In contrast to drilling fluids, cuttings contained large
amounts of base neutral organics (See Table 2-12). which
probably derive from added/produced oil. Washing tended to
2-48
-------
NJ
I
t&
VD
TABLE 2-12
RESULTS OF GC/HS ANALYSIS OF ORGAN1CS DRILL CUTTINGS
(Results in ug/kg)
EPA
10
1A
IB
2A
2B
3A
3A
3B
3B
Blank
EPA
ID
1A
IB
2A
2B
3A
3A
3B
3B
Blank
EPA
ID
1A
IB
2A
2B
3A
3A
3B
3B
Blank
CENTEC
ID
30799
30802
30800
30803
30801
30801
30804
30804
CENTEC
ID
30799
30802
30800
30803
30801
30801
30804
30804
CENTEC
ID
30799
30802
30800
30803
30801
30801
30804
30804
CONTROL
CENTER
ID
12197
12199
12201
12203
12205
12205 Dup.
12207
12207 Dup.
12209
CONTROL
CENTER
ID
12197
12199
12201
12203
12205
12205 Dup.
12207
12207 Dup.
12209
CONTROL
CENTER
ID
12197
12199
12201
12203
12205
12205 Dup.
12207
12207 Dup.
12209
(B/N)
Acenaphthene
3020
38800
17300
1020
677
(B/N)
Phenanthrene
145000
65700
59900
71900
27500
25800
(B/N)
Diphenylamine
56500
23400
7180
5900
(B/N)
Naphthalene
149000
63500
3582
4080
10300
(B/N)
Pyrene
18900
7860
(B/N)
Alpha terpincol
6310
(A)
4-Nitrophenol
30400
(B/N)
Dibenzo-
thiopnene
37300
15000
(B/N)
Biphenyl
8940
1170
69400
33000
4230
4740
1840
2140
(B/N)
N-Nitrosodi-
phenylamine
56500
24300
2870
10200
3150
4110
(B/N)
Dibenzofuran
33700
21700
2150
2460
(B/N)
Bis (2-ethylhexyl)
Ph thaiate
17300
(B/N)
N-Dodecane
c-12
37300
6310
403000
185000
23000
29400
17500
18300
1620
FROM: CEN1EC.1984
-------
reduce organic levels by approximately 25 to 60 percent.
Polynuclear aromatics were present at high levels (up to over
90 rag/kg) (wet w/w) in cuttings after washing. Naphthalene was
detected in the control samples at levels exceeding those in
four out of six samples. Aromatic amines were present at
levels up to 48 mg/kg. Other chemicals detected included
dibenzothiophene. dibenzofuran, n-dodecane (C-12. which was
also present in controls), as well as alphaterpene.
2.4 DISCHARGE OF DRILLING FLUIDS AND DRILL CUTTINGS
Discharges from offshore oil and gas drilling operations
may be classified as either bulk or "semi-continuous." Bulk
discharges originate from the mud tanks and are associated with
drilling fluid, whereas so-called "semi-continuous" discharges
originate from the solids separation equipment and are
associated with drill cuttings. Bulk drilling fluid discharges
can be either low or high volume, and occur intermittently
during well drilling.
2.4.1 Low Volume Bulk Discharges
Low volume discharges are made to maintain the proper
solids levels in fluids, or for cementing operations or well
completion. At several points during drilling, the fine,
unfilterable particles in the mud will build up and cause
excessive viscosity. When this happens, low volume (16-32
m ) discharges are made and the mud is thinned with water
and/or additives (Ayers. 1982).
2-50
-------
2.4.2 High Volume Bulk Discharges
High volume discharges occur when:
drilling fluid must be removed to allow dilution with
water
drilling fluid is being changed from one type to another
drilling fluid tanks are being emptied at the end of
drilling (however, it is possible to save drilling fluid
for reuse)
High volume bulk drilling fluid discharges occur several
times while drilling a well, and can be at a rate of 250 to 700
bbl/hr or more and last from 20 minutes to three hours. The
total discharge per high volume event can be 2.000 barrels or
more. For example, bulk mud discharges were at a rate of 700
bbl/hr (maximum volume of 200 bbl) and occurred three times for
dilution purposes, and were 700 bbl/hr for up to three hr
(maximum volume 2.100 bbl) at the end of drilling for a well in
Lower Cook Inlet. Alaska (Houghton et al.. 1981). High and low
volume discharges of drilling fluids from the mud tanks usually
number 20 to 30 during the drilling of a well (G. Petrazzuolo.
TRI. to T. Mors, Dalton'Dalton'Newport, personal communication.
1982).
2.4.3 Quantities of Drilling Fluid Discharged
Table 2-13 shows quantities of the basic drilling fluid
components used as reported in a survey of 72 recently drilled
wells in the Gulf of Mexico (Cole and Mitchell. 1984). Various
study deficiencies have been noted since completion of this
study that appear to indicate significant underestimation of
2-51
-------
releases during this study. The average quantity of material
used was slightly in excess of 2.000.000 pounds per well, of
which more than 90 percent was devoted to basic components.
Barite and weighting materials alone accounted for 79 percent
of the total, or 1.6 million pounds. Mud usage was observed to
increase with depth, as expected, and usage of specialty
additive ("Other Components" in Table 2-13) increased sharply
in wells deeper than 13.000 feet. Total quantities of basic
and specialty components were found to be higher in exploratory
wells than developmental wells and higher in wells drilled in
Federal waters versus State waters. It should also be noted
that the usage of a given component varied considerably from
well to well, with standard deviations for all wells in excess
of mean values. Maximum values in particular can be seen to
exceed mean values by more than an order of magnitude, but
means also were exceeded by the standard deviation.
A distinction must be made between the amount of drilling
fluid used and the amount actually discharged. Some drilling
fluid is always lost to the geologic formation or left in the
well annulus at the completion of drilling. Ayers et al.,
(1982) prepared a materials balance for a Mid-Atlantic drilling
operation in which eighty-seven percent of the barite was
discharged, six percent was left downhole. and seven percent
could not be accounted for. For bentonite plus drilled solids.
eighty-nine percent was discharged, one percent was left
downhole. and ten percent was unaccounted for. For the
combined usage of lignite, chrome lignosulfonate. and cellulose
polymer, ninety-five percent of the material was discharged.
and five percent was listed as unaccounted for. The amounts
unaccounted for are presumed to be lost to the formation and/or
left downhole. Other estimates have been made indicating that
2-52
-------
TABLE 2-13 AVERAGE MUD CONSUMPTION (Ibs) FOR 72 OFFSHORE
OIL AND GAS WELLS IN THE GULF OF MEXICO
Mean Maximum
Basic Components
Barlte and weighting materials 1,645,613 19,012,499
Bentonlte and attapulgUe clays 182,517 1,039,699
Lignites and Hgnosulfonates 72,853 1,048,450
CaustU 33,266 360,000
Soda ash 700 9,999
L1me 5,508 88,750
Sodium bicarbonate 2,118 34,200
Subtotal. Basic Components 1,942,575
Other Components
Lost circulation and filtration control
materials
Lubricants
Thlnners
Calcium chloride
011 muds
Diesel oil
Other materials
Subtotal. Other Components
Total. All Components
26,412
1,097
117
14,473
56,583
8,802
31,561
139,045
2.081.620
688,900
38,870
8,100
345,450
999,999
304,421
630,153
Derived by Cole and Mitchell, based on Cole and Mitchell, 1984.
2-53
-------
a much lower proportion of drilling mud (25 to 59 percent) is
discharged (Continental Oil Company. 1979). The percentage
discharged will vary, of course, depending on the formation and
other well-specific characteristics.
2.4.4 Continuous Discharges
"Continuous" discharges are actually frequent, intermittent
discharges associated with the operation of the solids control
equipment. This equipment operates during drilling, typically
one-third to one-half of the time a drilling rig is on-site.
Discharges occur from less than an hour to 24 hours per day.
depending on the type of operations and the specific well.
Various types of continuous discharges are described in Table
2-14. Continuous discharge of drill cuttings has been reported
at an average of 10 to 50 bbl/day over the life of a drilling
operation (Petrazzuolo, 1981).
Data on drill cuttings production tend to be consistent
between wells. The bulk of discharged material (about 2.000
bbl) is generated within the first 1.500 m (5.000 ft) of
drilling. Another 2.000 bbl are produced between the 1.500 m
(5.000 ft) and 4.000 to 5,000 m (13.000 to 15.000 ft) depth.
and by the 6.100 m (20.000 ft) level, discharges have increased
by only another 1.000 bbl for a total of approximately
5.000 bbl (Petrazzuolo. 1981).
Approximate quantities of drilled solids for a typical well
as calculated by the Bureau of Land Management are presented in
Table 2-15. Because the diameter of the drill bit decreases
from over 30 inches initially to less than 10 inches at depths
of 6.100 m (20.000 ft), the volume of cuttings produced
2-54
-------
TABLE 2-14 DISCHARGES FROM SOLIDS CONTROL EQUIPMENT
FROM A SINGLE WELL IN LOWER COOK INLET. ALASKA
(Atlantic Richfield Company, 1978)
Source
Rate Cbbl/hrl
Frequency
Shale shaker
Desander
Desilter
Centrifuge
Sand trap
Sample trap
1-2
3
16-17
30
550-2650
1.5-3
Continuous during drilling
2-3 hr/day during drilling
2-3 hr/day during drilling
1-3 hr. every 2-3 days
2-10 min. every 2-3 days
5-10 min. every 2-3 days
2-55
-------
TABLE 2-15 DRILL CUTTINGS FROM TYPICAL EXPLORATION AND DEVELOPMENT WELLS3
(BLM, 1977)
N)
I
tn
Drill cuttings
Exploratory
Drilling
(m)
0-46
46-300
300-1,370
1,370-3,000
3.000-3,660
3,660-4,600
Total
interval
(ft)
0-150
150-1.000
1,000-4,500
4,500-10,000
10,000-12,000
12,000-15,000
Well
(cm)
90
80
50
38
38
25
diameter
(in)
36
32
20
15
15
10
Volume
bbl (m3)
187 (30)
846 (135)
1,361 (217)
1,206 (192)
439 (70)
291 (46)
4,330 (690)
Weight
t (mtons)
72 (66)
332 (302)
534 (486)
506 (460)
184 (167)
131 (119)
1.759 (1.600)
Development
Volume
bbl (m3)
187 (30)
846 (135)
1,361 (217)
1.206 (192)
3.413 (543)
Weight
t (mtons)
72 (66)
332 (302)
534 (486)
506 (460)
1,444 (1,310
a Hypothetical well depths: Exploratory - 4,600m (15,000 ft)
Development - 3.000m (10.000 ft)
-------
decreases as the well depth increases (Petrazzuolo. 1981). The
rate of discharge decreases since the speed of drilling slows
at greater depths. Petrazzuolo (1981) divides drill cutting
discharges into two periods:
the first 31 percent of the drilling period accounts for
81 percent of the cuttings discharge at an average rate
of 89 bbl/day
the remaining 69 percent of the program accounts for 19
percent of the cuttings discharge at an average rate of
10 bbl/day
Discharge rates for wells in different geographical locations
are summarized in Table 2-16. This table shows combined
discharges during drilling for both drilling fluid and drill
cuttings from four offshore wells.
Total quantities of discharged drilling fluid and drill
cuttings increase as well depth increases. The data in Table
2-16 for drill cuttings are illustrative, but hypothetical.
The best data for specific wells are from two proposed drilling
programs, one from the Shell Oil Company in the Gulf of Mexico.
and the other from the Exxon Corporation in the Mid-Atlantic.
both reported in Petrazzuolo (1981). Table 2-17 lists the
drilling time, mud type, and discharges from these wells
according to drilled depth.
Actual data for discharges from eight exploratory wells on
Georges Bank are shown in Tables 2-18 and 2-19. Analyses of
muds for metals and hydrocarbons at 1.000 foot intervals for a
single well on Georges Bank are shown in Table 2-20. The high
2-57
-------
TABLE 2-16 SUMMARY OP DRILLING FLUID AND CUTTINGS
DISCHARGE RATES BY GEOGRAPHICAL LOCATION
(bbl/day/well)
(adapted from Petrazzuolo. 1981)
DrillingDrillTotal
PCS location fluids cuttings discharges Source
Gulf Of Mexico 116 47 163 Shell Oil Co.. 1978
Mid-Atlantic 190-219 35-40 225-259 Ayers et al.. 1980a
Lower Cook Inlet.
Alaska 93-203 27-47 120-250 Houghton et al.. 1980
Tanner Bank.
California 26-28* 7-22* 33-50* Ecoaar. 1978
* Several inconsistencies vere noted in the reporting of these
quantities.
2-58
-------
TABLE 2-17. PROFILE OF PROPOSED DRILLING FLUID AND CUTTINGS DISCHARGES
FROM TWO OFFSHORE WELLS
(derived from Petrazzuolo, 1981)
Drilling Fluid Cuttings
Average Average
daily Total daily Total
Depth Time discharge discharge discharge discharge
interval (ft) (days) Hud type a (bbl/day) (bbl) b (bbl/dav) (bbl) b
Gulf of Mexico well (Shell Oil Company):
0-500
500-1,000
1,000-3,000
3,000-8,000
8,000-16,000
16,000-20,000
Mid-Atlantic well
0-300
300-1,000
1,000-4,500
4,500-12,000
12,000-15,000
1
2
6
27
61
38
SW
SW
SWG
LT FCLS-FW/SW
FCLS-FW
FCLS-FW
2,500
2,500
200
50
50
50
2,500
5,000
(1,000)
1,200
1,350
3,050
1,900
(800)
722
289
265
65
28
10
722
578
1,588
1,757
1,733
361
(Exxon Corporation):
1
2
3
85
35
SW
SWG
LT FCLS-FW/SW
FCLS-FW
FCLS-FW
850
24
180
171
20,000C
(600)
1,700
(700)
72
(2,228)
15,300
5,985
(1,000)
195
453
19
14
465C
390
1,359
1,615
490
a Drilling fluid abbreviations: SW = saltwater plus natural mud
SWG - saltwater plus bentonite or attapulgite
LT FCLS-FW/SW = lightly-treated ferrochrome lignosul-
fonate freshwater/saltwater system
FCLS-FW = freshwater ferrochrome lignosulfonate
system
b Numbers in parentheses represent bulk discharges.
c Discharged at seafloor, over a 10-hour period, plus 30 bbl excess cement.
2-59
-------
Table 2-18 SOLID DRILLING FLUID COMPONENTS USED IN GEORGES BANK DRILLING
Solids (pounds)
Barite
Bentonite
Caustic Soda
Lignite
Chrome Lignosulfonate
Sodium Bicarbonate
Lime
Sodium Acid
Pyrophosphate
N> Nut Plug
g Mica
Aluminum Stearate
Drispac
Soda Ash
Salt
SULF-XII
Poly RX
Spot
Super-Col
Chemtrol -X
Super Shale Trol 202
XC Polymer
WO 30
Calcium Chloride
L.C. 133
#1
1,117,900
496,600
44,150
39,400
46,950
1,750
3.950
550
550
1.500
850
350
200
-
-
-
-
-
-
-
-
-
-
C.C. 975
#1
774,700
510,600
57.500
37,450
70,400
8,150
200
900
2,250
2,000
-
3,450
15,000
141,600
-
-
-
-
-
-
-
-
-
L.C. 410
#1
1.124,100
1,284,300
87,100
-
60,750
-
2.650
300
49,450
225
14,150
2,300
-
6,500
-
-
-
-
-
-
-
-
L.C. 312
fl
2,387,800
706,400
105.600
54.400
36.000
-
2,350
-
950
500
34.400
7,400
-
-
19,450
4,550
-
-
-
-
-
-
L.C. 187
#1
2,651.000
1,103,700
166.750
113.200
144.350
9,200
2,450
300
6,250
50
39,350
29,600
9,760
-
-
-
69,800
99,750
21.950
150
100
-
L.C. 145 L.C. 2/3
fl fl
812.200 902,400
689,900 567,800
35.150 71,050
950
15,350 11,400
400
4,100 550
-
1,650
25
15.500 19.500
10. 100 12.200
-
-
4,500
-
-
-
-
-
-
- _
L.C. 35?
fl
2,834.000
1,285.400
122,950
-
86,350
-
7.550
-
41,600
18,000
425
17.150
6.300
-
2.350
52.800
-
-
-
-
-
-
5.400
-------
Table 2-19 LIQUID DRILLING FLUID COHPONENTS USED IN GEORGES BANK DRILLING
Liquids (gallons)
Foam Ban
Torque Trim
Lube 106
HO
Diesel Fuel
Free Pipe
to ^
i
£} Scale Ban
LD-8
WO Defoamer
Aqua Spot
Mentor 28
L.C. 133 C.C. 975 L.C. 410 L.C. 312 L.C. 187
fl #1 fl #1 fl
30 -
660
160
10 455
4.284
110
15
2,225
95
1.265
275
L.C. 145 L.C. 273 L.C. 357
fl fl fl
_
165
700
_
_
_
_
_
_
_
_. .
L.C. - Lydonia Canyon
C.C. - Corsair Canyon
-------
I
o\
Table 2-20 CUTTINGS ANALYSIS. DISCHARGE 002
BLOCK: MOBILE GB: 0027006
Mud Density. Ibs/gal
METALS ANALYSIS
1
13.55
1.2
14.51
2
13.55
2.3
8.07
3
14.88
DEPTH IN 1,000' INCREMENTS
4567
14.45
13.33
9.83
14.60
8
14.56
9
15.09
10
10.90
11
16.34
12
15.80
13
16.28
Arsenic. PPM
Barium. Per Cent
Cadmium. PPM
Chromium. PPM
Copper. PPM
Lead. PPM
Mercury. PPM
Nickel. PPM
Xanadium. PPM
Zinc. PPM
Iron. PPM
Aluminum. Per Cent
.34
.58
.23
4.40
.06
12.30
30.00
119.00
.23
.47
.23
4.51
.07
15.60
34.00
44.00
.20
.41
.20
3.99
.14
12.50
15.00
15.00
.01
.19
.01
4.89
.01
.86
3.10
.69
.23
3.86
.80
5.21
.04
15.23
34.00
282.00
.15
.15
50.00
13.40
31.00
.03
38.00
72.00
68.00
34.672.00
4.29
.74
.27
20.00
11.50
42.00
.02
10.00
29.00
59.00
18.553.00
2.61
.14
.03
29.00
2.90
94.00
.01
1.80
5.00
9.80
1554.00
.53
.13
.30
23.00
17.80
17.00
.04
41.00
67.00
80.00
31.000.00
4.54
.22
96.00
16.10
20.00
.03
31.00
67.00
21.652.00
.22
63.00
25.80
18.00
.03
37.00
75.00
33.162.00
.13
65.00
15.00
14.00
.02
22.00
38.00
16.775.00
.36
91.00
48.30
49.00
.02
71.00
121.00
52.363.00 26.
.27
36.00
20.50
20.00
.03
34.00
48.00
,727.00
.18
65.00
20.70
144.00
.03
33.00
50.00
27.856.00
HYDROCARBON ANALYSIS
Extract wt. mg/1
Aliphatics, F ,mg/l
Aromatics, F ,mq/l
Arcmatics. F^.mg/1
Sum F * F * F
% Recovery*
172.80
48.30
0.00
0.00
48.30
28.00
184.60
145.00
0.00
52.00
197.00
107.00
18.30
0.00
0.00
44.00
44.00
240.00
6.60
6.80
4.00
.40
11.20
170.00
129.40
0.00
0.00
0.00
0.00
0.00
316.00
62.00
161.00
7.40
230.40
73.00
797.00
183.00
264.00
49.00
496.00
62.00
166.00
0.00
18.00
10.00
28.00
17.00
914.00
0.00
33.00
15.00
48.00
5.00
187.00
98.00
89.00
6.00
193.00
103.00
136.00
113.00
11.00
5.00
129.00
95. .00
63.00
63.00
7.00
2.00
72.00
114.00
151.00
131.00
48.00
11.00
190.00
126.00
169.00
92.00
33.00
1.00
126.00
75.00
307.00
61.00
118.00
7.00
186.00
61.00
* (Sum/Ext, wt.)
-------
levels of icon that occur from 5.000 feet depth on down appear
mostly due to icon in the cuttings from the formation cathec
than added icon from the drilling fluid.
Thece ace two basic types of offshoce oil and gas wells.
Explocatocy wells can be defined as those drilled fcom movable
stcuctuces such as mobile drilling ships oc semi-submersible
cigs. Developmental (also cefecced to as "production") wells
ace those drilled fcom permanent platforms. Anywhere fcom a
dozen to as many as one hundred developmental wells may be
drilled fcom a single pcoduction platfocm. although 25 is
pcobably a ceasonable avecage foe a modern pcoduction
platfocm. While evecy well will be diffecent. exploratory
wells ace thought to be drilled somewhat deepec than
developmental wells. Howevec. cepocted data do not cleacly
suppoct this assumption (See Section 1.2, pp. 1-8 to 1-12).
Typical offshoce well depths (in the Gulf of Mexico) ace
approximately 10,000 ft (See Section 1.2).
2.4.5 Oxygen Demand of Discharges
The high oxygen demand of dischacged drilling fluids and
cuttings caises concecn cegacding its impact on dissolved
oxygen levels in offshoce watecs, especially in shallow aceas.
poocly mixed aceas. aceas subjected to episodic (oxygen)
depletion, and/oc heavily developed offshoce aceas. To assess
this concecn, an oxygen demand mass balance foe dischacged
drilling fluids and cuttings has been developed. Othec
dischacges fcom drilling rigs/platforms have an oxygen demand
(e.g.. sanitacy wastes, domestic wastes), but the oxygen demand
of these dischacges has not been assessed (the oxygen demand of
pcoduced watec is discussed below).
2-63
-------
The mass balance was developed from these scenarios: (1) a
low estimate scenario calculated from the lowest realistic
volume discharged mud at the lowest BOD/UOD levels; (2) a mean
estimate scenario, where volume and BOD/UOD data represent
average values; and (3) a high estimate scenario where the
upper estimates for these data were used.
Four separate sources of BOD/UOD were considered: Drilling
muds with a lubricant added (mineral oil); muds without added
oil; drill cuttings from muds with a mineral oil lubricant; and
cuttings from muds without oil. Assuming drilling mud volume
estimates contained in the NEC report (1983) represent the
range of discharge values (5.000 to 30.000 bbl/well). one can
estimate a low. median, and high value of 5,000 bbl/well.
15.000 bbl/well. and 30.000 bbl/well. A lubricant is assumed
to be used for about 50 percent of the well. Therefore. 50
percent of the drilling fluid contained 5 percent added mineral
oil; the remaining 50 percent contained no added oil.
For "clean" cuttings, an oxygen demand of zero was
assumed. Although, given the oxygen demand associated with
"clean" cuttings from nutrient content, these discharges will
have a BOD. At present, however, this oxygen demand has not
been quantified. Therefore, a BOD/UOD of zero for oil-free and
mud-free cuttings was assumed, while acknowledging that this
could substantially underestimate the total oxygen demand of
discharged cuttings.
For cuttings from mud systems, the assumption was made that
the adherent mud would be 5 percent of the cuttings, by
weight. This assumption produces a BOD/UOD equivalent to 5
percent of that for the cuttings-associated drilling mud.
2-64
-------
Therefore. BOD/UOD values were derived from muds that contained
no added mineral oil and mud that contained five percent
mineral oil. Cuttings discharges were assumed to be 1000 tons
(kkg) for all scenarios; it was assumed that lubricants would
be needed latter in the drilling program, thus 650 tons were
considered from non-oil-contaminated mud systems and 350 tons
from oil-contaminated muds.
Given the inhibition by oil of BOD/UOD measurements as
discussed above, a correction for oil inhibition was made on
the BOD/UOD data for oil-contaminated mud and cuttings (Table
2-21). BOD/UOD for 5 percent mineral oil mud was calculated as
equivalent to 5 X BOD/UOD for 1 percent mineral oil mud. Based
on these data, a correction factor for BOD 5 percent
[calculated]/BOD 5 percent [measured] was obtained that was
applied to the oily cuttings. Given that the oil and grease
levels in oily cuttings generally exceeded 5 percent, this
factor may be an undercorrection. The average BOD for oily and
non-oily mud discharges calculated in this fashion is 5,365
rag/kg. This value agrees very well with the average BOD for
mud discharges of 5,000 rag/kg derived by industry contractors
(see Breteler et al., 1984).
These results were used to calculate the oxygen demand mass
balance (See Table 2-22). and resulted in a median, one-well
scenario, total BOD estimate of 32.940 kg, with low estimate
and high estimate scenarios of 7,680 kg and 84,950 kg,
respectively. Total BOD contained in mud discharges averaged
23.500 kg per well, with a range of 3,050 kg to 73.930 kg BOD.
Total BOD in cuttings contributed 9.360 kg BOD to the median
scenario with a range of 4.630 kg to 11,020 kg BOD. The median
UOD estimate scenarios for one well is 76.270 kg. with a range
2-65
-------
TABLE 2-21 SUPPORTING CALCULATIONS FOR OXYGEN DEMAND VALUES IN THE PRESENCE OF OILa
N)
1
Hud BOD It
BOO 5t (calc)
BOD 51 (meas)
BOO calc/meas
UOD It
UOD 5t (calc)b
UOD 5t (meas)
UOD calc/meas
Cutting BOD (meas)
BOD (calc)
UOD (meas)
UOD (calc)
Low
1.373
6.860
2.023
3.39
4.073
20.365
6,942
2.93
3,890
13,190
12,800
37,500
Medium
1,850
9,240
2.450
3.77
4,650
23.240
8,132
2.86
7,050
26,580
19,980
57,140
High
2,383
11,920
3.416
3.49
5.803
29.015
9,773
2.97
8,950
31,240
26,600
79,000
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
HG/KG
Footnotes:
Based on Centec, 1984 data
bBOO 5t calculated as 5 x (BOD It)
-------
TABLE 2-22 COMPARISON OF MEASURED AND CALCULATED BOD VALUES IN THE PRESENCE OF OIL
Hud Nonoil
Discharges
Oil
(51 Oil)
Total
Cuttings Nonoil
(5% Hud)
Oil
Total
Total Total
Discharge
Low9
Hedianb
High
Lowc
Hedianc
Highc
Low
Median
High
Low"
Hediand
Method*1
Low6
Median6
High6
Low
Median
High
Low
Median
High
Density
Volume (g/l)
2,500 bbl 1.09
7,500 bbl 1.84
15.000 bbl 2.15
2.500 bbl 1.08f
7.500 bbl 1.79f
15.000 bbl 2.09f
5,000 bbl 1.06
15.000 bbl 1.82
30,000 bbl 2.12
650 tons
350 tons
1000 tons
BOD
mg/kg
Concentration
180
1,690
2,740
6,870
9,240
11,920
NA
NA
NA
9
85
137
13,190
26.530
31,240
NA
NA
NA
UOO
mg/kg COD
Concentration mg/kg
130
2.820
4.220
20.370
23.250
29.020
NA
NA
NA
6
141
211
37,500
57,140
79.000
NA
NA
NA
1.600
27.860
41.200
75.300
86.800
98.300
NA
NA
NA
36
1.393
2,060
90.600
171.530
272.000
NA
NA
NA
Total
BOO
Mass (kg)
80
3,730
14,140
2,970
19,850
59,790
3.050
23.580
73,930
6
55
89
4.620
9.300
10,930
4.630
9.360
11,020
7.680
32.940
84,950
Total
UOO
Mass (kg)
60
6,230
21,780
8.800
49,940
145,560
8,860
56.170
167,340
4
92
137
13,130
20.000
27.650
13,130
20,100
27.800
21.990
76.270
195.140
Total
COO
Mass (kg)
780
61.510
212,590
32,530
186.450
493,070
33,310
247,960
705,660
20
910
1.340
31,710
60,040
95.200
31,730
60,950
96.540
65,040
306.910
802,200
a Values represent average of available data for generic Hud 006.
b Values represent average of available data for generic Muds 001, 002, 003. 007 and 006.
c Data for 51 oil are calculated from It oil.
d Assumes no oxygen demand in cuttings and are 5% of oxygen demand data reported for Nonoil Muds shown above.
e Data are corrected for oil content based on ration of actual measured BOD values for 5% oil Muds - See also Table 2-22.
f Densities are the densities for nonoil muds corrected for oil density assuring d of 0.85 for oil
-------
of 21.990 kg to 195.140 kg. The range estimates ace narrow.
given the deliberate variabilities of the assumptions. Also.
both the corrected BOD and UOD estimates are much lower than
the theoretical maximum oxygen demand value, based on COD.
which is estimated at an average of 308.910 kg with a range of
65.040 kg to 802.200 kg.
Assuming an average drilling program of 60 days, the
average well will discharge approximately 550 kg BOD daily.
Using an annual activity of 1464 offshore wells (API 1983) at
33 tons (kkg) BOD per well, the total industry BOD discharge
from (offshore) oil and gas drilling activities results in a
mean annual estimated discharge of 48.300 tons, or an average
of 132 tons BOD per day. The low and high estimates, if
annualized industry-wide, are 11.300 tons BOD per year and
124.000 tons BOD per year, respectively. Average daily low and
high estimates, respectively, are 30 tons BOD per day and 340
tons BOD per day. Average total UOD and COD demand are,
expectedly. higher: 111.630 tons and 452,376 tons per year.
The BOD estimate for muds and cuttings can be compared to
that of sewage sludge. The estimated total input from ocean
disposal of domestic sewage in 1980 was 7.3 X 10 tons (NEC.
1983). The BOD of sewage sludge approximates 1.000 mg/kg; its
COD is approximately twice its BOD. Therefore, the BOD input
from ocean disposal of sewage sludge approximates 7,300 tons
per year (NRC. 1983). Thus. BOD from ocean discharge of
drilling muds and cuttings is more than six times that of ocean
disposed sewage sludge, while the COD is more than 30 times
higher.
2-68
-------
2.5 PRODUCED WATER
Water brought up from the hydrocarbon-bearing strata with
the produced oil and gas includes brines trapped with the oil
and gas in the formation and possibly water injected into the
reservoir to increase productivity. (Water injected to
increase hydrocarbon recovery is normally injected into wells
other than the producing wells). This trapped water is called
produced water, or formation water, process water, or brine.
and constitutes the major waste stream by volume from the
production phase of offshore oil and gas activity- Produced
waters are classified into three groups--meteoric. connate, and
mixed waters.
Meteoric water is water that has fallen as rain and has
filled up the porous and permeable shallow rocks or has
percolated through them along bedding planes, fractures, and
permeable layers. The presence of carbonates, bicarbonates,
and sulfates in oil field water suggests that part of this
water has come from the surface and is meteoric. Connate water
originally denoted the fossil seawater in which marine
sediments were originally deposited; presumably, originally
filling all pore spaces. Current usage uses the definition
connate water is that interstitial water existing in the
reservoir rock prior to the disturbance of that rock by
drilling. Most connate waters are brines, characterized by an
abundance of chlorides, particularly sodium chloride (NaCl).
and have concentrations of dissolved solids many times greater
than that of common seawater. Mixed waters are characterized
by both a high chloride and sulfate-carbonate-bicarbonate
content. This suggests a multiple originpresumably meteoric
water mixed with or partially displaced by the connate water of
the rock (DOI. 1982b).
2-69
-------
The amount of produced water that is generated is dependent
upon the method of recovery and the nature of the formation.
In some formations, water is generated with the oil and gas in
the early stages of production; in others, water is not
produced until the formation has been significantly depleted;
and in some, water is never produced. The quantities of
produced water that may be discharged vary considerably among
platforms, and can be comparatively large for central
processing facilities. At the Buccaneer Field, where one of
the major field studies on the effects of production operations
was conducted, produced water discharge was estimated to be 600
bbl/day (95.3 m3/day) (Middleditch. 1981). Produced water
discharges estimated for the EPA verification 30 platform study
ranged between 134 bbl/day-150.000 bbl/day (21-23.835 m3/day)
and averaged 4.011 bbl/day (637 m /day) excluding central
processing facilities and 9.577 bbl/day (1.522 m /day)
including these facilities. The discharge for the Trading Bay
Facility in Alaska was estimated to be 62.000 bbl/day (9.852
m /day) (Lysyj, 1981). The produced water may be discharged
either above or below the water surface. In some cases, the
water is piped to shore for onshore injection or treatment; in
other instances, the water may be reinjected offshore either
for disposal or pressure maintenance purposes.
2.5.1 Chemical Characteristics of Produced Water
Most produced waters are brines, characterized by an
abundance of sodium chloride, other chlorides, and dissolved
solids in concentrations several times greater than in
seawater. Approximately 61 percent of the mineral matter is
comprised of chlorides. Chlorides in produced water from ten
platforms in the Gulf of Mexico were in the range 37.000
2-70
-------
110.000 ppra (Jackson et al.. 1981): normal values foe seawater
are around 19.000 ppm. Other major mineral components include
34 percent sodium, three percent calcium, and two percent other
materials. Suspended and settleable solids are also present.
After passing through an oil-water separator, produced
water from oil and gas operations off the U.S. coast is usually
discharged into the sea or. in some cases, is reinjected for
disposal or pressure maintenance purposes. This produced water
contains hydrocarbons, metals, as well as other organic and
inorganic constituents. Data on the oil content of produced
water were obtained for ten platforms in the Gulf of Mexico off
Louisiana (Jackson et al.. 1981). For this study, the infrared
method of measuring oil content gave average values of 15-106
ppm and the gravimetric method. 7.6-77 ppm (Table 2-23). Note
the extremely high standard deviations of this measurement.
2.5.1.1 Organics
Lower molecular weight hydrocarbons are more soluble in
seawater than the higher molecular weight hydrocarbons and.
therefore, are preferentially partitioned from the produced oil
and gas into produced water. The lower molecular weight
hydrocarbons include the volatile liquid hydrocarbons (VLH) in
the C. to C_. range. These are important from an
environmental standpoint, since they include the light
aromatics (benzene through naphthalene) that are among the most
immediately toxic components of petroleum. Information on the
concentrations of these hydrocarbons in produced waters is
presented in Tables 2-24 and 2-25.
2-71
-------
TABLE 2-23 PLATFORM FLOTATION EFFLUENT OIL CONTENT
COMPARISON FOR GULF OF MEXICO OFF LOUISIANA
N>
I
Platform
SS107
SS198G
BDCCF5
ST131
BM2C
SM130B
EI18CF
UD45C
ST177
SP65B
GR-011. mq/1
Average (SO)
7.6
18
26
12
22
48
52
63
64
77
(5.2)
(9.2)
(6.9)
(13)
(6.7)
(16)
(24)
(95)
(74)
(73)
IR-Oil.
Average
15
36
36
37
39
48
76
81
95
106
mq/1
(SD)
(3.7)
(7.8)
(8.3)
(19)
(4.2)
(16)
(38)
(109)
(103)
(99)
"Dispersed" Oil. ma/1
Average
1.6
5.7
26
5.9
4.9
23
63
66
92
38
(SD)
(1.5)
(7.7)
(8.6)
(13)
(5.1)
(13)
(30)
(106)
(126)
(80)
"Soluble-
Oil. mo/1
Average (SD)
13
31
10
28
36
25
13
30
21
61
(2.7)
(2.7)
(2.3)
(3.1)
(4.1)
(4.7)
(13)
(32)
(13)
(15)
"Soluble" Oil,
fraction of
IR-Oil (t)
87
86
28
76
92
52
17
37
22
58
Note: Some numbers do not check because of rounding. Two significant figures have been retained in all
numbers below 100.
SD = Standard Deviation.
GR = Gravimetric method.
IR = Infrared method.
Source: Jackson et al., 1981.
-------
TABLE 2-24 LOW MOLECULAR WEIGHT HYDROCARBONS
IN PRODUCED WATER FROM THE BUCCANEER GAS AND OIL FIELD
Compound
Light hydrocarbons (ml /I)
Methane
Ethane
Propane
Iso-butane
Butane
Iso-pentane
Pentane
Total Light Hydrocarbons
Volatile hydrocarbons (yg/1)
n-Hexane
n -Heptane
n -Octane
n-Nonane
n-Decane
n-Undecane
n-Dodecane
n-Tridecane
n-Tetradecane
Benzene
Cyclohexane
Methyl cyclohexane
Toluene
Dimenthyl cyclohexane
Ethyl benzene
m, p-Xylene
o-Xylene
Total n-Cg-C]4
Total aromatic
Total Volatile Liquid
Hydrocarbons*
Mean
2,413
408
237
98
81
113
98
3,450
40
50
74
89
154
260
290
324
476
9,500
221
190
4,575
88
533
1,043
990
1,760
16,675
21,600*
Range
960
140
69
23
19
39
38
20
21
19
16
39
18
35
48
64
5,600
82
62
2,600
48
220
500
480
420
10,000
11,300
- 4,910
- 680
- 400
- 190
- 197
- 219
- 203
- 80
- 100
- 130
- 200
- 400
- 880
- 1,000
- 1,050
- 1,410
- 17,700
- 400
- 340
- 8,500
- 140
-1,100
- 1,900
- 1,800
- 5,100
-31,100
- 44,400
^Unresolved error in total addition.
Adapted from Brooks et al., 1980.
2-73
-------
TABLE 2-25 VOLATILE LIQUID ALIPHATIC HYDROCARBONS
IN PRODUCED WATER DISCHARGES FROM THE BUCCANEER FIELD
IN THE GULF OF MEXICO
Component
2-Methyl butane
n-Pentane
Hethylcyclopentane
2-Hethyl pentane
3-Hethylpentane
2 , 2-Oimethyl pentane
2,2,3-Trimethylpentane
1 ,3-Dimethylcyclopentane
l-Methyl-(1 or 3)-ethylcyclopentane
n-Hexane
3-Nethylhexane
2 , 2-Oimethy 1 -3-hexene
Cyclohexane
Methyl eye 1 ohexane
Dimethylcyclohexanes
Trimethyl cyclohexane
Ethyl eye lohexane
n-Propyl cyclohexane
Alkylcyclohexane
Heptanes
Octanes
Octene
Octadiene
n-Nonane
n-Decane
n-Undecane
n-Dodecane
n-Tridecane
n-Tetradecane
Branched alkane
Branched alkane
Methyl ethyl ketone
Methyl propyl ketone
Diethyl ketone
Methyl isobutyl ketone
2-Pentanone
Concentration
(DDb)
Middled itch (1980) Sauer (1981)
960
720
460
ND
80
ND
ND
240
ND
460
200
160
520
1,080
200
80
ND
ND
ND
580
120
380
40
ND
ND
ND
ND
ND
ND
ND
ND
300
ND
ND
ND
160
ND
ND
50
1,520
ND
SO9
170
ND
50
70
ND
ND
100
210
120
ND
230
230
70
68011
620^
ND
ND
520
410
310
140
110
50
10
20
70
570
300
190
ND
a The spectrum for 2,2-Dimethylpentane is similar to that of 2,2,3-
Trimethylbutane.
b The spectrum of 3-Hethylheptane (130 ppb) is similar to that of
2,5-Oimethylhexane; the spectrum of 2,6-Dimethylheptane (150 ppb) is
similar to that of 2-Methyloctane.
2-74
-------
Brooks et al.. (1980) obtained a mean VLH concentration of
21.6 ppm in produced waters from an oil and gas production
platform in the Buccaneer Field in the Gulf of Mexico off Texas
(Table 2-24); Sauer (1981) obtained a similar value for this
field. Over 80 percent of the VLHs in the produced water
consisted of light aromatic compounds, with benzene, toluene.
ethylbenzene. and m-. o-. and p-xylenes predominating.
Similar concentrations of light aromatic hydrocarbons have
been detected in produced waters from a number of other
platforms in the Gulf of Mexico and Alaska (Table 2-26).
Included among these is the EPA verification study for 30
platforms in the Gulf of Mexico (EPA. 1982). A companion study
was conducted for the Offshore Operators Committee by Radian
(1982) on duplicate samples taken from six of the 30 platforms
sampled during the EPA study; both sets of analyses were
subject to extensive quality control procedures. In addition.
EPA funded an earlier Rockwell International study of produced
water (Lysyj et al., 1982). The only one of these programs
involving analyses of samples from an area other than the Gulf
of Mexico was that of Lysyj et al. (1982). They found that the
average concentration of BTX compounds in treated effluents
discharged to Cook Inlet. Alaska, was 9.1 ppm. Benzene was the
predominant VLH compound in each of the studies.
Produced water from the Buccaneer Field was analyzed for
methylnaphthalenes. which are two-ring aromatic hydrocarbons.
The mean concentration of these compounds was 43 ppb with a
maximum of 170 ppb. Naphthalene concentrations measured during
the EPA verification 30 platform study in the Gulf of Mexico
ranged between 19 and 1454 ppb and averaged 187 ppb. For a set
of duplicate samples from six of these platforms. Radian (1982)
2-75
-------
TABLE 2-26 SUMMARY OF CONCENTRATIONS OF LIGHT AROMATIC HYDROCARBONS FOUND IN PRODUCED WATERS BY RECENT STUDIES
N>
!
-J
Concentration (pg/1)
Compound
a. Aromatic Hydrocarbons
Benzene
Toluene
Ethylbenzene
Naphthalene
m.p-Xylene
Xy 1 enes/Ethyl benzene
EPA Verification
Study for 30
Platforms
(Gulf of Mexico)
Mean Range
2,977 2-12.150
2,007 60-19,800
431 6-6.010
187 19-1,454
NS
NS
Radian Analysis for
Six of 30
in EPA
(Gulf of
Mean
3,500
2.400
230
150
NS
NS
Platforms
Study
Mexico)
Range
170-16.000
150-8,600
27-560
17-440
Buccaneer Field
Gulf
of Mexico
(Brooks et al . . 1980)
Mean
9,500
4.575
533
NS
1,043
NS
Range
5.600-17.700
2,600-8.500
220-1,100
500-1,900
Seven
Gulf
Facilities
of Mexico
(Lvsy.i et. al.. 1982)
Mean
1,100
800
NS
27a
NS
300
Range
400-2,400
400-2,100
ND-44
200-300
Three
Facilities
Alaskan Waters
Lysy.i et. al.. 1982)
Mean
5.500
2,700
NS
NS
NS
900
Range
3,700-6.500
1.900-3.400
500-1,300
aOetected in three wells; average includes only detected concentrations.
NS - Not sampled.
NO - Not detected.
-------
reported that average concentrations of naphthalene ranged
between 17-440 ppb. It should be noted that the EPA and Radian
analyses were limited to "priority pollutants" that include
naphthalene but not the alkylated derivatives. Thus, these
analyses do not reflect the total quantity of naphthalenes
present.
Produced water also contains higher molecular weight
aliphatic and aromatic hydrocarbons. Middleditch found that
the mean concentration of heavier saturated hydrocarbons (C.
12
Id was 3.4 i
with occasional observations as high as 12 ppm.
- C ) in produced water from the Buccaneer Field was 3.4 ppm
3 8
At present, there are little quantitative data on
concentrations of polynuclear aromatic hydrocarbons (PAHs) in
produced water. In the EPA 30 platform verification study.
benzo[a]pyrene was detected in three out of 73 samples.
Concentrations in these three samples were 4. 15. and 19 ppb.
Data from the Buccaneer Field study indicated that produced
water benzo[a]pyrene concentrations ranged up to 5 ppb with a
mean concentration of 1.2 ppb (Middleditch, 1981). This is
consistent with the EPA study and suggests that benzo[a]pyrene
is present in produced waters at low (ppb) levels.
2.5.1.2 Inorganics
Inorganic compounds present in produced waters include
heavy metals. However, as noted by Menzie (1982) and
Middleditch (1984). there has been uncertainty about the
quality of the data. This is in part due to the difficulty in
analyzing metals in heavy brine solutions. Work was conducted
at a single platform in the Buccaneer Field by Anderson et al..
2-77
-------
(1979) and by Tillery (1980), but results from this study have
shown wide discrepancies and do contain typographical errors
(Middleditch. 1984). Therefore, this report includes data from
three studies that sampled produced water from a number of
platforms in the Gulf of Mexico. These include the EPA 30
platform verification and the companion Radian (1982) studies.
and the Lysyj et al.. (1982) study (Table 2-27). These all
show generally similar ranges in concentrations of selected
metals in produced water.
An interesting component in produced water from the
Buccaneer Field that Middleditch (1981) observed was the
presence of elemental sulfur. He determined the concentration
of sulfur by a gravimetric procedure and found a maximum
concentration of 1200 ppm and a mean concentration of 460 ppm.
Other inorganic chemicals that may be present include ammonia
and hydrogen sulfide. For a project off Santa Barbara. ADL
(1984) reported that concentrations of these two compounds
could reach 800 mg/1 and 100 mg/1. respectively.
2.5.1.3 Radioactivity
Radioactive materials such as radium also are found in some
oil field produced waters, having leached from the shales and
sandstones of the geologic formation (EPA. 1978). Open ocean
surface waters normally contain 0.05 pCi/liter of radium.
Radionuclide data for filtered and unfiltered produced waters
from Gulf Coast drilling areas have shown Ra-226 concentrations
ranging from 16 to 393 pCi/liter. with a median of 254
pCi/liter. while Ra-228 content ranged from 170 to 570
pCi/liter (Table 2-28). The filtered produced waters were only
slightly lower in radium content (EPA. 1978). These levels of
2-78
-------
TABLE 2-27 HEAVY METAL CONCENTRATIONS IN PRODUCED WATER
Concentrations in
EPA Verification
Study Radian Study
30 Platforms for six of the
Metal
Antimony
Arsenic
Beryllium
Cadmium
Chromium
Copper
Iron
Lead
Mercury
Nickel
Selenium
Silver
Strontium
Thallium
Zinc
Gulf of
Mean
5.1
81.9
115.7
25.9
8.1
168
Mexico
Range
ND-98
NO- 1455
ND-57CO
ND-276
ND-107
5-519
Efib
Multi Platform Study
Gulf of Mexico
(Lysyj et al . , 1982)
Platforms
Meand
4
14
NO
300
90
NO
98
Range
ND-25
ND-15
NO- 140
ND-800
NO- 160
ND
28-320
Mean
ND
ND
2.7a
48.3s
260
124.7
597
0.4b
1,195C
NO
111*
ND
35 lc
Range
2-4
39-56
59-390
100-137
160-915
_J>
68-1674
72-108
190-640
ND - not detected
a Detected in three out of seven wells; average includes only detected
concentrations.
b Detected in one out of seven wells.
c Detected in four out of seven wells; average includes only detected
concentrations.
d Means are those calculated by Middleditch (1984).
2-79
-------
TABLE 2-28 RADIUM CONTENT OF SOME GULF COAST OIL
FIELD PRODUCED WATER
OU Field
Idanti/i cation
Bay de Chene, LA
Houma District, LA
Lafayette District, LA
Grand Island District, LA
Garden Island Bay, LA
Grand Bay, LA
Leeville, LA
Leeville, LA
Empire, LA
High Island, TX
Pelican Island, TX
Ra-226
(pCi/1)
327 + 5
131 ±3
298 + 5
144 * 4
393 + 7
183 + 4
321 t 20
254 ±12
199 + 6
313 + 4
16 + 5
Ra-228
(DCi/1)
426 + 26
170 + 11
328 + 20
202 + 13
570 + 34
385 + 30
318 + 22
407+29
Based on DOT 1982b.
2-80
-------
radioactivity ace significantly higher than background levels.
Research has suggested that there is a relationship between the
salinity of formation waters and their radium content.
Formation waters of increased salinity appear to have increased
Oadium content (Dr. David F. Reid to C. Mitchell.
Dalton'Dalton'Newport, personal communication. 1983).
The Office of Radiation Programs in EPA has performed some
preliminary health physics calculations to estimate the
potential for public health consequences from the radium
content in these discharges. These preliminary hypothetical
calculations indicate that a radiation dose to humans from the
consumption of seafood containing Ra-226 or Ra-228 from
produced water is approximately 1.0 mrem/yr or less, and this
is well below the allowable levels for humans based on
international guidelines of 500 mrem/yr.
The Office of Radiation Programs is initiating a one year
study at the University of Rhode Island MERL facility to assess
partitioning of Ra-226 in the marine ecosystem and its
biological uptake. EPA is also involved in the International
Atomic Energy Agency (IAEA) Advisory Group for defining
"de minimus" levels of naturally occurring and man-made
radionuclides for purposes of the London Dumping Convention.
2.5.1.4 Priority Pollutants
The EPA 30 platform verification study involved analyses of
priority pollutants. Data on the concentrations of aromatic
hydrocarbons and metals have already been presented. Two
2-81
-------
additional priority pollutants which were detected in the
produced water were 2.4-dimethylphenol and phenol.
Concentrations of these chemicals are given below.
Chemical
2 . 4-Dimethylphenol
Phenol
Mean
(ppb)
200a
2.343
Range
(DDb)
ND - 3.504
65 - 20.812
No. Samples
Where Not
Detected
5
0
Total
No.
Samples
63
63
aMean of 58 samples where chemical was detected.
Possible mass loadings of selected priority pollutants in
produced water to the marine environment were estimated based on
discharge volumes and pollutant concentrations (Table 2-29). The
estimates indicate that annual loadings of the chemical benzene
could exceed 25 metric tons (70 kg/day) for large discharges.
For average platforms (based on the verification study), loadings
could reach a few kg/day for several of the priority pollutants
examined.
2.5.1.5 Conventional Parameters
Produced water may also contain substances that exert oxygen
demand. ADL (1984) estimated that produced water discharges for
an operation off California could have COD levels of 100-3.000
mg/liter and BOD5 levels of 300-2.000 mg/liter. The minerals
Management Service (1983) presented information that indicated
BOD& ranged between 370-1.920 mg/1 and that COD ranged between
340 - 3,000 mg/1. The presence of oxygen consuming substances
was evident in bioassay tests on produced water (Rose and Ward.
1981). most of which had to be aerated to maintain oxygen levels
2-82
-------
TABLE 2-29 PRODUCED WATER VOLUMES AND POSSIBLE (ANNUAL) LOADINGS
OF PRIORITY POLLUTANTS TO THE MARINE ENVIRONMENT
Facility
Buccaneer c
Field,
Shell
Platform
30 Platforms d
in EPA
Verification
Study
Average
Excluding
Central
Facilities
Average includ-
ing Central
Facilities
Trading Bay e
Facility in
Volume3 >b
m^/day
(bbl/day)
95.3
(600)
21.3 - 23,835
(134 - 150,000)
637.4
(4,011)
1,521.8
(9,577)
9,851.8
(62,000)
Annual Loadings (kq)
Benzene
194 - 617
21.9 - 25,900
0.365 - 2,825
1.1 - 6,749
13,304 - 23,375
Toluene
91 - 296
14.6 - 17,462
14.6 - 4,606
32.9 - 10,997
6,833 - 12,228
Ethyl benzene
7.3 - 37
3.65 - 3,749
1.1 - 1,398
3.65 - 3,340
1,800 - 4,676f
Naphthalene
-
1.46 - 1,628
3.65 - 340
11 - 807
NA
M.P Xylene
18.3 - 65.7
NA
NA
NA
2.4 Dimethyl phenol
NA
1.46 - 1,741
NO - 814
NO - 1 ,909
NA
Phenol
NA
18.3 - 20,385
14.6 - 4,844
36.5 - 11,560
NA
to
I
o>
u>
NOTES
a. Volume of produced water at Buccaneer Field during the period of this field study is based on Middleditch (1981, pg. 10).
b. Volume of produced water-at Trading Bay..Facility, Alaska, is based on Lysyj (1981).
c. Loadings for the Buccaneer Field were estimated by multiplying the estimated discharge volume by the range in concentration reported for
produced water from the field.
d. Loadings for the 30 platform study discharges were estimated by multiplying the range in discharge volumes by the average concentrations, and
the average discharge volumes by the range in concentrations.
e. Loadings for the Trading Bay Facility were estimated by multiplying the estimated flow by the reported range in concentrations for discharges
in Alaskan waters.
f. Concentrations are for a combination of ethylbenzene and xylenes.
-------
above 4 mg/liter. In one series of tests where aeration was
not performed, oxygen levels decreased to 0.5-3.2 mg/liter and
1.2-4.0 mg/liter; controls remained above 4 mg/liter.
ADL (1984) also estimated that the BOD inputs associated
with projected three and eight platform scenarios in the Santa
Barbara Channel were 6.740 and 18.000 metric tons per year.
respectively. They compared this to the input from the five
major southern California municipal outfalls (264.000 metric
tons BOD/year). ADL estimated there could be localized
reductions in oxygen near the combined produced water outfall.
The presence of oxygen consuming substances in produced water
was also reported for North Sea operations.
Based on the BOD data for produced water provided by ADL
(1984). e.g., an average BOD of 400 mg/liter with a range of
300 to 2.000 rag/liter, an estimate of total input of BOD in
produced waters can be made. Total produced water values for
the Gulf of Mexico are available, based on industry sponsored
study performed by Walker. Haydel and Associates (1984). Using
an estimated total produced water value of 1.551.370 bbl/day
for the Gulf of Mexico in 1982. one can calculate an average
BOD loading in the Gulf of Mexico from produced water of 36,965
tons with a range of 27.180 to 781.200 metric tons per year.
2.5.2 Added Chemicals
Information on chemicals added to produced water is
provided in a report prepared for the American Petroleum
Institute by Middleditch (1984). Section 2.7 of that report is
2-84
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ceptinted in italics below. Where supplementary information
has been incorporated by EPA's technical writers, this is shown
in regular type.
Many different chemicals mat/ be used on production platforms as
biocides, coagulants, corrosion Inhibitors, cleaners, dlspersants,
emulsion breakers, paraffin control agents, reverse emulsion breakers,
and scale Inhibitors. Detergents used to clean the platforms Kill also
be found in produced water. The use of chemicals varies from one
platform to another, and it is unusual for more than a few of the many
available chemicals to be employed on any one platform. JACKSON et
al., (1981) has provided information on the chemicals used on ten
Louisiana production platforms: Table 2-30 lists the individual
chemicals mentioned in that report, along with information on their
compositions obtained from the suppliers. Most of the chemicals are
proprietary in nature and many are not composed of individual chemicals
with defined structures, so only an indication of their identification
or functions can be given.
Much of the information in this section of the review was provided by
interviews with chemical suppliers.
2.5.2.1 Biocides
Sulfate reducing bacteria (such as Pesulfovlbrlo^ can convert sulfate
ions to sulflde ions, which will corrode metal pipes and storage
vessels. Sulfate ions, in turn, are produced from elemental sulfur by
the action of sulfur oxidizing bacteria. One method of minimizing this
effect Is to reduce the bacterial populations by adding biocides to the
product stream. These substances, or their degradation products will,
therefore, be discharged In the produced water. Two biocides were used
in the Buccaneer Field during the first two years of the study
performed by MIDDLEDITCH (1981): K-31 fglutaraldehyde} and KC-14
2-85
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TABLE 2-30
CHEMICALS ADDED TO THE PRODUCED WATER
ON PLATFORMS SURVEYED BY JACKSON et al.. (1981).
WITH ADDITIONAL INFORMATION PROVIDED BY
THE MANUFACTURERS OF THE CHEMICALS (MIDDLEDITCH. 1984).
CHAMPION DQ61. Biocide
DOW CORNING 200. Foam inhibitor. Silicons polymer.
EXXON VARSOL. Hydrocarbon solvent.
GREAT SOUTHERN VALVE AND CHEMICAL GS1011. Heavy duty degreaser.
M-CHEM DW-9 RIG WASH. Soap.
METHANOL. Dewatering agent.
NALCO 8AF542. A blend of aluminum salt/polyamides-polyamines
in an aqueous solution.
NALCO VISCO 914. Paraffin control agent. Oxyalkylated
surfactants in terpene and aromatic solvent.
NALCO VISCO 970. Gas system corrosion inhibitor. A blend of
fatty acid amide salts in a hydrocarbon solvent.
NALCO KOAGULAN 3349. Flotation aid. Oxygenated polyamines and
inorganic salts.
NALCO VISCO 4400. Demulsifier. A blend of oxyalkylates.
TRETOLITE BR-4050 BROUSSARD. Demulsifier. A solution of
polyglycol. oxyalkylated phenol formaldehyde resins.
oxyalkylated phenols, and aryl sulfonates in aromatic
hydrocarbons and fatty alcohols (C6-C8).
TRETOLITE VEZ D-91. Antifoamer. A solution of silicon
compounds in aromatic hydrocarbons.
TETROLITE F-17. A solution of aryl sulfonates in aromatic
hydrocarbons.
TRETOLITE TOL-FLOTE FR-81. Flotation aid. A solution of
polyacrylamides in water and methol.
2-86
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TABLE 2-30
(Continued)
CHEMICALS ADDED TO THE PRODUCED WATER
ON PLATFORMS SURVEYED BY JACKSON et al.. (1981).
WITH ADDITIONAL INFORMATION PROVIDED BY
THE MANUFACTURERS OF THE CHEMICALS (MIDDLEDITCH. 1984)
TRETOLITE TOL-FLOTE FR-87. Flotation aid. A solution of slats
of quaternized amines, an acrylic polymer, a carboxylic acid.
and salt in water and methanol.
TRETOLITE TOL-FLOTE FR-88. Flotation aid.
quaternized amines in water.
A solution of
TRETOLITE TOL-FLOTE FR-98D. Flotation aid. A solution of an
acrylic-type polymer, salts of oxyalkylated amines, and salt in
water and methanol.
TRETOLITE JW 8206. Flotation aid. A solution of salts of
condensed alkanolamines, quaternized amines, and zinc chloride
in water and methanol.
TRETOLITE RN-3003. Demulsifier. A solution of oxyalkylated
phenol formaldehyde resins in aromatic hydrocarbons.
TRETOLITE RP-34. Demulsifier. A solution of oxyalkylated
phenol formaldehyde resins, polyglycols. and acylated
polyglycols in aromatic hydrocarbons and methanol.
TRETOLITE RP-79. Demulsifier. A solution of polyglycols in
aromatic hydrocarbons.
TRETOLITE RP-101. Demulsifier. A solution of polyglycols,
oxyalkylated phenol formaldehyde resins, and oxyalkylated
phenols in aromatic hydrocarbons and fatty alcohols.
TRETOLITE RP-2256. Demulsifier. A solution of oxyalkylated
phenol formaldehyde resins in aromatic hydrocarbons.
2-87
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TABLE 2-30
(Continued)
CHEMICALS ADDED TO THE PRODUCED WATER
ON PLATFORMS SURVEYED BY JACKSON et al.. (1981).
WITH ADDITIONAL INFORMATION PROVIDED BY
THE MANUFACTURERS OF THE CHEMICALS (MIDDLEDITCH. 1984).
TRETOLITE RP-2327. Demulsifier. A solution of oxyalkylated
phenol formaldehyde resins, aryl sulfonates. and osyalkylated
alkanolamines in aromatic hydrocarbons and isopropanol.
TRETOLITE SCALE PREVENTIVE SP-36. Scale inhibitor. A dry
powder of sulfamic acid coated with a quaternized amine and an
oxyalkylated phenol.
TRETOLITE SCALE PREVENTIVE SP-175. Scale inhibitor. A
solution of polyphosphate esters of oxyalkylated polyols and
alkanolamines in water and methanol.
TRETOLITE SCALE PREVENTIVE SP-246. Scale inhibitor. A
solution of an organic phosphonate in water.
TRETOLITE FLUDEX WF-123. Scale inhibitor. A solution of salts
of acylated amines and organic phosphonates in water and
methanol.
TRETOLITE FLUDEX WF-75S. Multi-purpose water treatment
additive. A solid stick containing polyglycols, quaternized
amines, fatty amines, and oxyalkylated phenol formaldehyde
resins.
TRETOLITE X-CIDE XC-102. Biocide. An aqueous solution of
glutaraldehyde.
TRETOLITE X-CIDE XC-370. Biocide. A solution of
oxydiethylenebis (alkyl dimethyl ammonium chloride) in water
and methanol.
TIDE. Detergent.
2-88
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(alkyIdlmethyIbenzyl chloride), both supplied by Champion Chemical
Company. A surfactant (Surfatron DQ44J was also employed. The weekly
alternation in application of the two biocides was only partially
successful in reducing the bacterial populations, so Shell Oil Co.
began using Magnacide B (acrolein) during the third year of the study.
Acrolein is a highly volatile, toxic, and reactive substance, and
residual acrolein in produced water was scavenged by treatment with
Hagnatreat OS-L (sodium biosulfite) prior to discharge. Acrolein was
never detected in produced water samples during this study
(HIDDLBDITCH, 1981: ROSE and HARD, 1981). However. Middleditch
(1984) notes that it may be released, i.e., the chemical
reaction reversed, following discharge.
Other traditional biocides Include fatty amines and quaternary ammonium
compounds. More modern biocides, which hydrolyze easily and have
relatively low fish toxic!ties, include
2,2~dibromo-3-nitriloproplonamide and chlorinated isothiazolines.
Most biocides are used in concentrations no higher than 20 ppm, and the
concentrations in the effluents are usually a few ppm at most.
There are. however, little or no quantitative data on
biocide concentrations in produced water discharges.
2.5.2.2 Coagulants
These include cationic and anionic substances and quaternary ammonium
compounds. Some coagulants contain zinc chloride in concentrations of
5-30 percent. Excessive concentrations of coagulants have an opposite
effect from that intended, so treatment with 1-5 ppm is attempted
initially, and the concentration may be raised later if the treatment
proves to be ineffective. Treatment at the rate of 20 ppm with a
formulation containing 30 percent zinc chloride will lead to discharge
of 7 ppm of zinc chloride in the effluent.
2.5.2.3 Corrosion Inhibitors
Corrosion inhibitors may contain fatty amines, fatty acid amides,
quaternary ammonium compounds, and fatty amine salts. Almost all are
cationic in nature. The amines are relatively toxic toward fish, and
the surface active agents tend to coat the gills of fish. However,
most of the residual corrosion inhibitor is contained in the oil., with
much less than 1 ppm remaining in the effluent. (Again, there is
little quantitative data on these concentrations.)
2-89
-------
2.5.2.4 Cleaners
Detergents used for washing the platforms collect In the separator
tanks (so that residual oil can be removed} and will be included in the
produced water. Concentrations of these detergents would usually be
low.
2.5.2.5 Emulsion Breakers and Dispersants
Emulsion breakers may be nonlonic or anlonlc polymers and Include
sulfonates and other esters as well as alkylene oxides. Most are
oil-soluble, but some are partially soluble In water. The alkylene
oxides are more soluble In oil at the elevated temperatures which
normally prevail. Low concentrations of ethoxylates and
low-molecular-weight acrylates might be employed as dispersants.
2.5.2.6 Paraffin Control Agents
The heavier paraffins can precipitate from the product stream at
ambient temperatures. Most control agents are fatty esters, which are
oil-soluble. Phenol adducts are also employed.
2.5.2.7 Reverse Emulsion Breakers
See coagulants.
2.5.2.8 Scale Inhibitors
Scale inhibitors Include phosphonates, phosphate esters. Inorganic
phosphates, and acrylic polymers. Typical concentrations in effluents
are 5-10 ppm. These substances are biodegradable and, accordingly,
will elevate the BOD of the produced water.
2.5.3 Effects of Platform Age on Pollutant Concentrations
in Produced Waters
It has been suggested that produced water pollutant
concentrations may change through time at a particular well.
For example, since water content (or water cut) of the produced
fluid generally increases as the well is depleted, the
concentration of organic pollutants might decrease with
2-90
-------
increasing well age. To test this possibility, data from the
30 platform EPA Verification Survey (EPA. 1982) were evaluated
to examine how pollutant concentrations in treated produced
water differed with the age of the production operation. Three
pollutantsbenzene, phenol, and zinc--were selected for this
analysis because they were among the most common pollutants in
the produced water discharges. Concentrations of these
chemicals in produced waters were compared among platforms that
differed in age as well as platforms with different water cuts
(sometimes an indicator of reservoir depletion). The results
of this analysis did not demonstrate any strong correlations of
chemical concentrations with indicators of platform/production
age.
2.6 OTHER DISCHARGES
Other discharges from offshore oil and gas operations
include deck drainage, sanitary, and domestic wastes, and other
minor waste sources such as food scraps, discharges from
compressor drains, cooling and heating circuits, desalinization
units, ballast from service/supply boats, cement unit deck
drains, BOP fluids, and produced sands. Most of these are not
well covered in the literature. Minimum and maximum discharge
rate estimates for some of these sources are shown in Table
2-31.
2.6.1 Composition and Discharge of Deck Drainage
Oil is the primary pollutant in deck drainage, although
detergent used in deck and equipment washing is also of
concern. During well completion, spillage of drilling fluids
may occur. Various acids are also used during workover
operations and contribute to deck drainage, but generally these
are neutralized prior to disposal.
2-91
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TABLE 2-31 OTHER OFFSHORE DRILLING RIG DISCHARGES
Average Flow Rate
Minimum
Maximum
Discharge name and parameters gpd m3/d
nrVd
Contaminated deck drainage
(work area drainage)
average flow rate
Sanitary waste discharge
average flow rate
(saltwater used)
Kitchen & shower discharge
(grey water)
average flow rate
Water distillation discharge
average flow rate
(saltwater brine)
Clean deck drainage
(rainwater and washwater)
average flow rate
BOP (blow out prevention)
systems) fluid average
flow rate
Boiler blowdowns
average flow rate
Fire water systems
average flow rate
Cooling water
(power generation system)
average flow rate
Delta temperature
(discharge °F - inlet °F)
Ballast water
average flow rate
(with no additives)
Cementing unit &
washdown drains
average flow rate
800 3.2 14,000 53.0
1,500 5.7 5,000 18.9
1,500 5.7 8,000 30.3
5,000 18.9 36,000 136.3
2,800 10.6 13,200 50.0
10 0.1 500 1.9
200 0.1
-SYSTEMS TEST ONLY-
400,000 1,515 5.2/MGD 19,690
5°F
3,000 11.4 26,000
B.4
20 0.1 500 1.9
Source
X)I, I982a.
2-92
-------
A typical platform-supported rig is equipped with pans to
collect deck and drilling floor drainage, which are gravity
separated into waste material and liquid effluent. Waste
materials are recovered in a sump tank, and either treated
prior to disposal, used in the drilling mud system, or
transported to shore. The liquid effluent consists primarily
of wash water and rain water, and is discharged overboard. A
typical rig discharges between 2.800 and 13,200 gallons of
clean deck drainage, and between 800 to 14,000 gallons of
contaminated deck drainage (from the work area) daily (DO1,
1982a).
2.6.2 Discharge of Sanitary and Domestic Wastes
The largest volumes of sanitary and domestic wastes are
generated during the drilling phase of oil and gas production
when manpower needs are highest. Domestic wastes, primarily
kitchen, laundry, and showering water ("grey water"), receive
little or no treatment before discharge. These waste flows can
range as high as 8,000 gallons and 5,000 gallons per platform
per day for domestic and sanitary waste, respectively (DO1,
1982a). Sanitary wastes are estimated to contribute
approximately 0.2 pounds per person per day of BOD loading
(Frazier et al.. 1977), and are treated prior to disposal. At
peak occupancy, a drilling rig might support between 12 and 80
persons.
2-93
-------
3.0 ENVIRONMENTAL FATE
3.1 SUMMARY
3.1.1 Drilling Fluids and Drill Cuttings
Field studies and models of the behavior of drilling
fluids and cuttings discharged to the marine environment have
focused on several aspects of their fate. Among these aspects
are: the transport of discharged materials in the water
column, both for particulate and soluble components; deposition
on the seafloor; and considerations of benthic short- and
long-term fate.
Discharged drilling fluids generally separate into two
plumes. Most of the discharged material (~90 percent by
weight) descends through the water column with the lower
plume. It is this plume that contributes most directly, and in
greatest guantity, to discharged materials deposited on the
seafloor. The upper plume, which is usually present in the
upper 10 to 20 m, contains the remaining material. Generally,
the lower plume, and its deposition of particulates on the
seafloor. has been considered most important to possible
impacts on the seafloor biota from discharge plumes. The upper
plume has received the most attention with regard to possible
water column impacts.
Field studies of suspended solids dispersion have sampled
I:he upper plume virtually exclusively. Results of four such
studies (two in the Gulf of Mexico, one off southern
California, one in the Atlantic) have been integrated and
3-1
-------
described by an empirically-derived multiple regression
analysis that estimates dispersion of solids, as a function of
time and discharge rate. This relationship was developed at an
EPA-sponsored Adaptive Environmental Assessment (AEA)
workshop. Predictions based on this relationship, for a
current speed of 15 cm/sec, indicate that dispersion in the
upper plume, as measured by suspended solids, will approximate
104 within 100 m. 105 within 500 m. and 10 within
2.000 m.
Because drilling fluids contain both particulate and
soluble components, and because particulates have an additional
mode of dispersion that does not apply to soluble components
(i.e.. gravitational settling, which takes solids out of the
water column and transfers them to the sediment), several
estimates of soluble component dilution also have been made.
Generally, it appears that dilution of soluble material in the
upper plume may proceed at one-half to one-tenth that of
dispersion particulates in the upper plume. Although these
estimates are reasonably consistent, this observation must be
somewhat tempered, however, because of the difficulties
involved in assessing interactions between soluble tracers and
drilling fluid components, such as fine particulates.
Dilution of drilling fluids in the water column beneath
ice has been examined in the Beaufort Sea. Results suggested
that nearfield dilution (100- to 1,000-fold) was 1-2 orders of
magnitude less than in open water situations. However, at
dilution ratios of 10 to 10 . the dilution under ice
appeared to approach that in open water. Sampling problems
encountered in this study may have resulted in an
overestimation of far-field dispersion. Therefore, these data
must be interpreted very cautiously.
3-2
-------
Drilling fluid components in a lower plume that reaches
the seafloor may be transported as a turbulent bottom plume.
Solids will continue to settle out while soluble components
will be diluted with distance. Such plumes have been observed
for dredged material disposal but no observations of such
plumes for drilling fluids have been attempted. Data on the
short-term fate of drilling discharges associated with the
lower plume appears largely to address the initial deposition
of the material on the seafloor. The lack of information on
the behavior of the lower plume generally should not be as
critical for exploratory operations. However, because of the
continued, long-term input associated with development
operations, this data gap represents a concern for potential
long-term impacts.
A model hat-, been developed by the Offshore Operators
Committee (OOC) for predicting the behavior of solid and
soluble components of the lower plume. This model appears to
provide a good physical representation of the fate of these
materials, within limits. The model has performed well when
compared to dynamic tank tests. However, field verification of
the model has not been completed. A verification study
currently is in progress. Thus, the present state of knowledge
of the behavior of drilling fluid plumes is that:
1. the upper plume, which comprises some 10 percent of
the material discharged and generally represents a
minor component for benthic impacts, has adequate
field data to develop empirical predictions of
dispersion but has not been physically modeled;
2. the lower plume, which comprises some 90 percent of
the material discharged and represents a major
component for benthic impacts, has a well-developed
physical model but has no sampling data to assess the
accuracy of model predictions.
3-3
-------
Much of the discharged drilling muds and cuttings will
initially reach the seafloor within a few hundred meters from
the drilling platform. In situations where a number of wells
are being drilled from a development platform, a pile of
cuttings (on the order of meters in thickness) could develop
around the platform and extend out to a few hundred meters.
The thickness of the cuttings pile would decrease with distance
from the platform. Finer materials, (e.g.. barite and clays)
associated with the cuttings, may extend further out from the
platform. For a single exploratory well drilled in the
mid-Atlantic, elevated clay levels, believed to be associated
with cuttings, extended out to approximately 800 m from the
well.
The subsequent fate of this deposited material will depend
primarily on the physical processes that resuspend and
transport particulates or entrain them into the sediments.
Biological or chemical factors could also be important in
stabilizing or mobilizing the material on the seafloor (e.g.,
through covalent binding of sediments or bioturbation).
Analyses of sediment barium and trace metal concentrations
have been used to examine nearfield fate of drilling fluids on
the seafloor, e.g.. the rate of dispersion of sedimented
material. If high concentrations of barium are persistently
found near a well site, this finding suggests it is in a lower
energy area, which favors deposition. If elevated levels
cannot be found, even soon after drilling, then this finding
suggests a higher energy environment, where resuspension and
sediment transport were promoted.
At present, the area-wide large-scale distribution of
drilling discharges is difficult to predict. However, it can
3-4
-------
be surmised that a number of drilling operations associated
with the development of a particular field could contribute to
a general regional increase of drilling-related materials on
the seafloor (many of these, perhaps not easily demonstrable.
because of natural, sampling, and analytical variability).
A power-law regression analysis was developed to relate
average barium levels to distance from the discharge source.
These equations described well the distance-dependent decrease
in sediment barium levels obtained in four field studies. A
multivariate analysis was used to estimate avnrago nedimwnt
barium levels with respect to distance and number of wells. At
locations of approximately 100 m to 30.000 m from a nine-well
platform, this analysis suggested that sediment barium data
collected early in the development phase of an operation may
provide accurate predictions of sediment barium levels later in
the operation.
Two attempts have been made to estimate spatial
distribution of discharged material from a two-well operation
in the Gulf of Mexico. One industry sponsored analysis
indicated that 49 percent of discharged barium had been
dispersed beyond a radius of 1.250 m from the platform.
Another analysis of these data indicated that 78 percent of the
barium was located within a 1.000 m radius, and essentially all
of the barium (calculated as 111 percent) was located within
1.250 m.
Data from exploratory drilling operations have been used
to examine deposition of metals resulting from drilling
operations. These indicate that several metals are deposited.
in a distance-dependent, manner, around platforms, including
cadmium, chromium, lead, mercury, nickel, vanadium, and zinc.
3-5
-------
Chemical and biological transport of drilling fluids is
poorly described. Much must be gleaned from general principles
and studies of other, related materials. Several broad
findings are suggested, but the data for a quantitative
assessment of their importance are lacking. Chemical transport
will most likely arise from oxidation/reduction reactions that
occur in sediments. Changes in redox potentials will effect
the speciation and physical distribution (i.e..
sorption-desorption reactions) of drilling mud constituents.
Bioaccumulation of a number of metals from exposure to
muds and mud components has been demonstrated in the laboratory
and in the field. Short-term laboratory experiments and field
exposures indicate that tissue enrichment factors were
generally less than an order of magnitude, with the exception
of barium and chromium. However, target organ analyses were
scant and improper test phases were often used. Also,
long-term exposures, which are particularly relevant to
assessing impacts of development operations, have been studied
just recently. Thus, a bionccumulation potential for those
discharges has been qual i t.at.i vely demonstrated, but cannot be
assesned quantitatively at this time.
Bioaccumulation of organics from drilling fluids, in
particular those associated with (diesel or mineral) oils added
as lubricants, has not been studied. However, such studies of
these oils themselves or their component substances indicate
that a variety of their to'xic constituents can be
bioaccumulated. Again, however, only a qualitative conclusion
may be reached.
3-6
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3.1.2 Produced Water
The major processes affecting the fate of discharged
producod water and associated chemicals include dispersion and
advect.ion. volatilization, and adsorption/nedimentation.
Concentrations of volatile liquid hydrocarbons discharged with
produced water at the Buccaneer Field were reduced on the order
4 5
of 10 -10 within 100 m from the platform, but generally
elevated levels were observed 3.5 km away. The Buccaneer Field
platform (600 bbl/day) is at the lower end of discharge volumes
reported for the EPA verification study (134 bbl/day-
150.000 bbl/day).
Hydrocarbons i.tiat become associated with sedimentary
parl.i.oles, either through water column interaction, settling to
the seafloor. or through bottom impact of the discharge plume.
can accumulate around production platforms. This was
particularly evident in the Trinity Bay Study. Concentrations
of naphthalenes in the sediment were enriched compared to
effluent lovels (21 mg/kg sediment versus 1.62 mg/liter in the
effluent). Also, levels of naphthalenes were elevated in the
immediate vicinity of the discharge with a subsurface
concentration maximum in the sediment. Subsequent fate of
petroleum hydrocarbons associated with sedimenis will depend on
the processes involved in resuwpendiny and l.rarisporting the
sediments, desorption processes and biological processes.
Because produced waters provide a continuing input of light
aromatic hydrocarbons over the life of a field (generally 10 to
30+ years), there is the potential for these chemicals to
accumulate in sediments. This diffurs from oil spill
situations wherein the chemicals are rapidly lost and the
sediments generally exhibit a decline of lighter aromatics with
time.
3-7
-------
To evaluate t.he impacts of produced water discharges in
shallow water. EPA employed a modified PLUME model. A series
of model runs were conducted to assess the pol.enl.ial for
benthic impacts from produced water discharges. Discharge
scenarios were developed for average discharge volumes for
various projected platform sizes, which were based on estimates
provided by the Eastern Research Group. Inc.
Because of the substantially increased possibility of
sediment accumulation of pollutants resulting from bottom
impact of the discharge plume, an analysis was conducted to
assess the potential for bottom impact. Results of this
analysis show that bottom impact is projected for water depths
approximately 20 meters or less. Thus, bottom impact is
projected for 12-well platforms or larger in the territorial
seas off of Texas and Louisiana. Bottom impact is projected
for larger platforms (40-58 wells) in Federal waters offshore
Texas and Louisiana.
3.2 INTRODUCTION
Drilling fluids contain quantities of coarse material.
fine material, dissolved solids, and free liquids. Upon
discharge, this mixture separates rapidly- An upper plume is
formed, probably from shear forces and local turbulent flow at
the discharge pipe. This plume will migrate to its level of
neutral buoyancy; particulates will slowly settle to the
bottom. This plume is advected with prevailing currents. The
fine solids settle at a rate depending on aggregate particle
size, which therefore, is very dependent on flocculation. The
upper plume contains about five to seven percent, by weight, of
the total drilling fluid discharge (Ayers et al.. 1980b).
3-8
-------
A lower plume contains the majority of discharged
materials. Coarser materials fall rapidly to the bottom out of
the lower plume, with a transit time so brief that the
influence of current is minimal. Ayers et al., (1980b) found
lower plume components deposited on the bottom within a few
meters of the discharge point. If water depths are great
enough to prevent bottom impact, the lower plume also will
reach its level of neutral buoyancy. Fine mud particulates
will be advected with ambient current flow, similar to their
behavior in the upper plume.
Both upper and lower plumes are affected by three kinds of
transport processes or pathways: physical, chemical, and
biological. Physical transport processes affect concentrations
of discharge components in the water column through dilution,
dispersion, and settling. Chemical and biological processes
are more significant for changes produced in the structure
and/or speciation of materials that affect their
bioavailability and toxicity.
Physical processes include currents, mixing, settling.
and diffusion. These processes include current
velocity and direction, tidal regime, kinetic energy
regime, and such receiving water characteristics as
density and stratification. Physical processes are
the best understood of the three transport pathways.
Chemical processes include the dissolution of
substances in seawater, particle flocculation.
complexing of compounds that may remove them from the
water column, redox/ionic changes, and adsorption of
dissolved pollutants on solids.
3-9
-------
Biological processes include bioaccumulation in soft
or hard tissues, fecal agglomeration and settling of
materials, and physical reworking to mix solids into
the sediment (bioturbation).
3.3 PHYSICAL TRANSPORT PROCESSES
3.3.1 Drilling Fluids
Environmental pollutant concentrations resulting from
offshore platform discharges are influenced by several factors
related to the discharge and the medium into which it is
released. Discharge related factors include the solids content
of the effluent, distribution of particle sizes and their
settling rates, effluent chemical composition, discharge rates
and duration, and density.
Environmental factors that affect dispersion and transport
of discharged material include velocity, direction, and
variability of currents, tidal influences, wave action, wind
regime, topography of the ocean bottom, bottom currents, and
turbulence caused by the platform wake. These factors
influence dispersion of effluents in the water column, and
resuspension and transport of solids settled on the seafloor.
Areas of high hydrodynamic energy will disperse discharges more
rapidly than less energetic areas.
The direction of the current determines the predominant
location of potential impacts, while current velocity
influences the extent of area affected. Velocity and boundary
conditions also affect mixing because turbulence increases with
current speed and proximity to the seafloor. Current velocity
3-10
-------
and turbulence can vary markedly with location/site
characteristics and affect the movement and concentration of
suspended matter, and entrainment/resuspension/advection of
sedimented matter.
3.3.1.1 Study Descriptions
Data from four offshore oil environmental studies (in
Georges Bank. Lower Cook Inlet. Tanner Bank, and the
Mid-Atlantic) illustrate variations in current regimes. At the
Georges Bank drilling location, flow varies seasonally
(Houghton et al.. 1981). Flow follows a partially closed.
clockwise gyre, averaging 10 cm/sec (0.33 ft/sec). A diffusion
model estimate that the residence time of a water parcel would
be two to three months during the summer and less than one
month during the winter (Butman et al., 1980 as in Houghton
et al.. 1981). Strong currents at the periphery of the gyre
would dilute a plume and transport it out of the area.
However, entrainment of a plume in the central water portion,
due to the gyre, could prolong exposures for organisms.
At Lower Cook Inlet, tidal currents dominate the net
circulation current (ARCO. 1978 as in Petrazzuolo. 1981).
These tidally driven currents switch directions every six
hours, and transport plots indicate little net movement.
Representative current velocities and directions at three
depths are shown for one site in Table 3-1 (Houghton et al.,
1981). Considerable cross-current turbulence is also produced
in Lower Cook Inlet throughout the water column during ebb and
flood tides, increasing the mixing action to which the
discharges are subjected.
3-11
-------
TABLE 3-1 LOWER COOK INLET CURRENT
VELOCITIES AND DIRECTION
(Houghton et al.. 1981)
Flood tide Ebb tide
Speed Avg. direction. Speed Avg. direction.
Current meter cm/sec degrees cm/sec degrees
depth (m) (knots) (true) (Knots) (true)
14 77.6
(1.5)
31 61.73
(1.2)
52 51.44
(1.0)
35
35
15
102.88
(2.0)
66.87
(1.3)
41.15
(0.8)
225
220
185
Tanner Bank is an example of a high energy regime affected
by numerous surges and shifting currents, but with a predomi-
nant surface and mid-depth flow to one direction, the southeast
(Ecomar, 1978 as in Petrazzuolo. 1981). Net surface water
movements were to the southeast and ranged from 0 to 67 cm/sec
(2.20 ft/sec), averaging 22.6 cm/sec (0.74 ft/sec). Net
mid-depth currents were to the east-southeast at an average
20.6 cm/sec (0.68 ft/sec). Near-bottom currents were measured
at 61 m in 63 m of water and averaged 24 cm/sec (0.79 ft/sec)
with a north-northwesterly flow. Wave-induced orbital current
patterns occurred intermittently at all depths at intervals of
about one day.
The Mid-Atlantic outer continental shelf near the
continental break east of Atlantic City. New Jersey, is an
example of a low-energy regime. The area is characterized by a
strong diurnal tide superimposed on a mean south or south-
westerly flow (EG&G. 1982). Bottom currents, which play an
important role in sediment resuspension and transport, flowed
3-12
-------
to the southwest 35 percent of the time, and to the southeast.
northwest, and northeast 28. 25. and 12 percent of the time,
respectively. Bottom currents were less than 10 cm/sec 62
percent of the time and less than 25 cm/sec for 95 percent of
the time.
In addition to current velocity. Houghton et al.. (1980 and
1981) indicate that turbulence, induced by submerged portions
of the drilling platform, may significantly contribute to
current effects on the dispersion of the muds. They attribute
increased dispersion of discharged materials, resulting from
transit through the submerged structure of a Cook Inlet
platform, to rig-induced turbulence. In their 1981 paper, they
concluded this turbulence will be significant if current speeds
are 5 to 10 cm/sec (0.16 to 0.32 ft/sec) or greater. However.
this wake-effect has not been systematically studied at other
locations. Ray and Meek (1980). for example, observed little
change in plume dilution with velocity variations between 2 and
45 cm/sec (0.076 and 1.48 ft/sec) at Tanner Bank.
3.3.1.2 Physical Transport Processes Affecting the Upper Plume
The materials contained in the upper plume may be subjected
to immediate wake-induced turbulence, and then are influenced
by oceanic turbulent dispersion processes. These materials are
transported at the speed and direction of prevailing currents.
Sinking rates of solids in the upper plume will largely depend
on four factors:
discharged material properties
receiving water characteristics
currents and turbulence
flocculation and agglomeration
3-13
-------
Physical properties of the discharged materials affect
mixing and sedimentation. For suspended clay participates.
particle size and both physical and biological flocculation
will determine settling rate. While oil exhibits little
tendency to sink, it has displayed the ability to flocculate
clay particles and to adsorb to particulates and sink with them
to the bottom (Middleditch. 1980).
One of the major receiving water characteristics
influencing plume behavior is density structure and
stratification. Density stratification can contribute to the
dissipation of dynamic forces in the dynamic collapse phase of
plume behavior, and represents the point at which passive
diffusion and settling of the individual particles become the
predominant dispersive mechanisms. Density stratification may
concentrate certain components along the pycnocline. If
flocculation produces particles large enough to overcome the
barrier, settling will continue. Also, if density
stratification is weak or the pycnocline is above the discharge
point, it may not affect plume behavior.
Ecomar (1978). as reported in Houghton et al.. (1981).
noted that upper plumes in the Gulf of Mexico followed major
pycnoclines in the receiving water. A similar finding has been
observed by Trefry et al. (1981) who traced barium levels along
pycnoclines. This type of transport is a potential concern
because sensitive life stages of planktonic. nektonic. and
benthic organisms may collect along the pycnocline. Ayers et
al. (1980b) observed that the bottom of the upper plume
followed a major pycnocline after drilling fluid discharges at
rates of 275 bbl/hr and 1.000 bbl/hr in the Gulf of Mexico.
3-14
-------
Flocculation and agglomeration affect plume behavior by
increasing sedimentation rates as larger particles are formed.
Flocculation is enhanced in salt or brackish waters due to
increased cohesion of clay particles (Meade. 1972).
Agglomeration also results in the formation of larger particles
from a number of smaller ones through the excretion of fecal
pellets by filter-feeding organisms.
The extent to which discharges are dispersed can be
estimated using dispersion ratios derived from measurements at
several drilling operations. These ratios are calculated as:
Dispersion _ suspended solids concentration of discharged fluid
Ratio ~ suspended solids concentration in samples
Dispersion ratios for drilling fluid discharges sampled in
upper plumes have been calculated, based on data from Tanner
Bank, the Gulf of Mexico, and the Mid-Atlantic (Petrazzuolo
1981; 1983a). Dispersion data from Lower Cook Inlet and the
Beaufort Sea were treated separately because the measured
tracer, the current structures, and bathymetry were
substantially different from these other OCS study sites.
Results are presented in Table 3-2. These data are graphically
displayed in Figure 3-1; in Figure 3-2 the aggregate regression
line has been drawn. Current-normalized estimates of
dispersion in each of these field studies and from a multiple
regression (dispersion vs. transport time and discharge rate)
of the combined data (Auble et al., 1982) are given in
Table 3-3.
Rearranged in Table 3-4 are the data from Table 3-2 and 3-3
to show the generalized distance plumes must travel to achieve
3-15
-------
TABLE 3-2 UPPER PLUME DISPERSION RATIOS OF WHOLE DRILLING FLUIDS* (Fran Petrazzuolo 1983a)
u>
I
Distance.
5
15
45
74
81
100
145
151
200
248
350
370
400
500
600
625
700
777
800
878
957
1000
1470
1550
1600
OCS Study Site (Discharge Rate, bbl/hr)
TB** GN GN NA NA
(12.8) (57) (275) (275) (500)
- 5.000 3.100
2,300 9.600
42.100
_____
96.699 - - 66.100
50.000
168,000
145.000 -
490.000 - 79.300 54.000
191,000 -
250.000
1,190.000
189,000 -
-----
694.000
_
214.000
-
2.250.000
-
-
-
_
3.600.000 ...
TB GN
(750) (1000)
-
1.675
9.900
-
-
_ _
-
_
-
-
59.400
-
61.900
_
227.000
_
349.000
52.900
1,190.000
1.723.000
444.000
650,000
1.300,000
* Dispersion ratios calculated as: (suspended solids in discharged fluid)
(suspended solids in the sanple)
** Abbreviations: TB (Tanner Bank); GN (Gulf of Mexico); NA (Mid-Atlantic)
Reference: Tanner Bank (Shell Oil Conpany 1978b)
Gulf of Mexico (Ayers et al.. 19806; Trefry et al.. 1961)
Mid-Atlantic (Ayers et al.. 198Oa)
-------
Figure 3-1
Dispersion Ratios of Whole Drilling Fluids
Discharge Rale (bbl/hr)
Bonk
X 275; Gulf of Moxteo
275; mld-Attonftc
500; mld-Attonilc
K 1000; Gulf of Mexico
10
Distance
1000
1000.000
100.000
10.000
3-17
-------
3-2
Regression Rot of Whole Fluid Dispersion Rotios
and 90% Prediction Bands
Y* 1.029X+416.87
r-0.86
Distance
tOM
3-18
-------
TABLE 3-3 NORMALIZED ESTIMATES OF DISTANCES TO DISPERSION RATIOS OF 104, 105, AND 106 AT CURRENT SPEEDS OF 5, 10, AND 15 on/sec*
CCS Study Site
(Discharge Rate)
TB (12.8)
GH (57)
GM (275)
HA (275)
HA (500)
TB (750)
GM (1000)
EPA/AEA (12.8)
(57)
(275)
(500)
(750)
(1000)
Dispersion Ratio
DR= 10*
tT 5 10 15
(min) (on/sec)
0.955 2.87 5.73 14.3
0.103 0.32 0.62 0.93
1.69 5.07 10.1 15.2
1.23 3.69 7.38 11.1
1.37 4.11 8.22 12.3
8.67 26.0 52.0 78.0
11.9 35.7 71.4 107
0.891 2.67 5.34 8.02
1.44 4.33 8.66 13.0
2.41 7.22 14.5 21.7
2.92 8.77 17.6 26.3
3.33 10.0 20.0 30.0
3.66 11.0 22.0 32.9
Dispersion Ratio
DR-105
tT 5 10 15
(min) (cm/sec)
9.45 28.4 56.7 85.1
1.52 4.56 9.13 13.7
7.33 22.0 44.0 66.0
11.9 35.7 71.4 107
16.5 49.5 99 149
44.8 134 269 403
38.9 117 233 350
7.22 21.7 43.3 65.0
11.7 35.1 70.2 105
19.5 58.6 117 176
23.7 71.1 142 213
27.0 81.1 162 243
29.7 89.0 178 267
Disperion Ratio
DR= 106
tT 5 10 15
(min) (on/sec)
93.6 281 562 842
22.5 67.4 135 202
31.8 95.4 191 286
112 336 672 1008
199 597 1194 1791
232 696 1392 2088
127 381 762 1143
58.6 176 351 527
94.9 285 569 854
158 475 948 1420
192 577 1155 1730
219 658 1315 1975
241 722 1445 2165
* References: From Petrazzuolo, 1983a, based on analyses presented in Auble et al., (1982).
-------
TABLE 3-4 GENERALIZED DISTANCES REQUIRED TO ACHIEVE SPECIFIED LEVELS
OF SUSPENDED SOLIDS DISPERSION IN THE UPPER PLUME FOR WHOLE
DRILLING FLUIDS AT FIXED CURRENT SPEEDS
Dispersion
Criterion
10*
10*
5 x 105
10*
Distance Required
(m)
(Current Speed, on/ sec)
5
35
150
300
700
10
75
300
700
1500
15
100
500
1000
2000
From Petrazzuolo (1983a).
3-20
-------
dispersion ratios of 10.000:1. 100,000:1. 500,000:1, and
1,000.000:1. respectively. From these data. Petrazzuolo
(1983a) estimated, for current speeds up to 15 cm/sec, that
10.000:1 dispersions are reached in 100 m (328 ft), 100,000:1
dispersions within 500 m (1,640 ft), 500,000:1 dispersions are
attained within 1,000 m (3,280 ft) and 1,000.000:1 dispersions
are attained within 2.000 m (6.380 ft).
Most studies of upper plume behavior have measured
particulate components and paid less attention to the liquid
and dissolved materials present. Presumably, these latter
components are subject to the same physical transport
processes, with the exclusion of settling, as particulate
matter. Studies suggest that suspended solids in the upper
plume may undergo a higher dispersion rate than dissolved
components.
Houghton et al.. (1980) measured upper plume transport
using a soluble, fluorescent dye (fluorescein). in Lower Cook
Inlet, where the currents are 41 to 103 cm/sec. They found
that the plume never sank below 23 m (75 ft), while water depth
at the site was 63 m (207 ft). Ayers et al., (1980b) estimated
upper plume volume from transmissometry data, in the Gulf of
Mexico, and found that a 275 bbl/hr drilling fluid discharge
exhibited a dilution ratio of 32.000:1 after 60 minutes and a
1.000 bbl/hr discharge showed a dilution ratio of 14.500:1
after 62 minutes. Dispersion ratios for suspended solids at
these distances would be approximately one to two orders of
magnitude greater than for soluble components.
3-21
-------
Petrazzuolo (1983a) analyzed estimates of "soluble" tracers
from the Cook Inlet data and from radiotracer data offshore of
southern California. The Cook Inlet data suggested that
dilution rates may be comparable to or at a rate approximately
half that of dispersion (based on generalized estimates of
distances to specified levels of dispersion; Table 3-5). These
correlations may be confounded by dye-clay interactions.
rendering this comparison more similar than would a true
"soluble11 component. The radiotracer data indicated that
dilution could be 4-10 times less than dispersion (Table 3-6).
based on dispersion/dilution estimates at specified distances.
However, these data were obtained only from samples taken in
the very near field (<100 m).
3.3.1.3 Physical Transport Processes Affecting the Lower Plume
The physical transport processes affecting the lower plume
differ somewhat from those influencing the upper plume. The
lower plume appears to have a component, comprised of coarser
material, that settles rapidly to the bottom regardless of
current velocity. This rapid settling is most pronounced
during high-rate bulk discharges, with their high downward
momentums. and in shallow water, because these conditions tend
to result in the plume reaching the bottom. At Tanner Bank,
the lower plume was relatively unaffected by average currents
of 21 cm/sec (0.69 ft/sec) and bottom surges up to 36 cm/sec
(1.18 ft/sec) (Ecomar. 1978).
The amount of fine solids settling to the bottom from the
lower plume depends on collision and cohesion of clay
particles, which in turn depends on suspended material
3-22
-------
TABLE 3-5 ESTIMATES OF DISTANCES REQUIRED TO ACHIEVE
SPECIFIED LEVELS OF DISPERSIONS OF A SOLUBLE DRILLING
FLUID TRACER AT FIXED CURRENT SPEEDS*
Dispersion
Criterion
10*
10*
5 x 105
106
Distance Required (m)
5
10-17
80-146
355-657
673-1,256
(Current Speed, cm/sec)
10 15
19-34 29-51
160-291 240-437
709-1,313 1,063-1,970
1,345-2,512 2,018-3,768
"Adapted from Atlantic Richfield (1978); Petrazzuolo (1983a).
Ranges in distances represent discharge rates of 21 to 1,200 bbl/hr.
3-23
-------
TABLE 3-6 COMPARISON OF RAOIOTRACER DISPERSION VERSUS SUSPENDED
SOLIDS DISPERSION AND RHODAMINE-WT DISPERSION3
Effluent
Dri 1 1 i ng
' Fluid
, (HTO)
f
Drill
Cuttings
(HTO)
l
Drilling
Fluid
(46Sc)
Distance
(m)
Transport
time
(min)
0.31 0.245
i
0.31
77
3.8
0.06
15.6
3.07
TB (10.0)
(3H; 46Sc)
TB (12.8)
(TSS)
3,130 i 2,570
I!
940 i 640
23,500 163,644
1 1 , 100
32,204
EPA/AEA
(TSS)
2,635
571
254,822
42,657
a. Adapted from Shell Oil Co. (1978b), Auble et al., (1982); in
Petrazzuolo (1983a).
Abbreviations:
TB - Tanner Bank; (values in parenthesis indicate discharge rate in bbl/hr);
(TSS) - total suspended solids;
(HTO) - tritiated water.
3 24
-------
concentration, salinity, and the cohesive quality of the
material. Fine particles tend to flocculate more readily than
larger particles. Houghton et al.. (1981) cites earlier work
by Drake (1976). which concluded that physical-chemical
flocculation can increase settling rates an order of magnitude
over rates for individual fine particles. Presently, there are
no water column sampling data from the lower plume. Its
dynamics must be inferred from limited sediment trap data and
from models of plume behavior (Brandsma et al.. 1980; Offshore
Operators Committee. 1984).
Biological processes have been shown to increase settling
rates for fine particles, which presumably could affect
drilling discharges. Filter feeding plankton ingest particles
ranging from 1 to 50 yiu in diameter, and excrete them in
Cecal pellets ranging from 30 to 3.000 pro in size (Haven and
Morales-Alamo. 1972. as in Houghton et al., 1981). Copepods
have been cited as playing an important role in biologically-
induced fine particle agglomeration by Manheim et al., (1970),
also as reported in Houghton et al., (1981).
3.3.1.4 Seafloor Sedimentation
Houghton et al.. (1981) produced an idealized pattern for
sedimentation around an offshore platform located in a tidal
regime (Figure 3-3). Zero net current was assumed. The area
of impact may have been overestimated from the true field case
because no initial downward motion was assumed, which provides
for a longer settling time and greater plume dispersion. The
result was an elliptical pattern, with the coarse fraction
3-25
-------
Cx)
I
ts)
' X' ~MOOm
/
/
1
/ -175m
/
__
1 *
\ \ 1
\ Xx 7
\ ^.
\
\,
^-^
E
~
7
""
E
?
-~
_
| -50m
^COARSE
\ \
\ *
-^ \
(MOmrn) * " 35cm/8ec '
) AXES OF TDAL ELUPSE \ \
\ \ J II
.
X>._ \S 1 1
\- D6CHAROE (-100 m ABOVE.' /
COARSE (10 mm - 2 mm) BOTTOM) ^ j
s f
^' /
. _ - "" ..
/
MTERMEDIATE (2 mm - 250/4) s'
MEDUMttSOjl - 74 tf
Rgure 3-3. Approximate pattern of initial particle deposition
(Houghton et al.,1981)
-------
(10 mm-2 mm) deposited within 125 to 175 m (410 to 574 ft) of
the discharge point, the intermediate fraction (2 mm-250 ym)
deposited at 1.000 to 1.400 m (3.280 to 4,592 ft), and the
medium fraction (250 ym-74 ym) deposited beyond that
distance. This is the greatest areal extent of bottom
sedimentation for continuous discharges under the assumed
conditions. Discontinuous discharges will be transported by
currents at the time of release, and will form a starburst
pattern over time (Zingula, 1975).
EG&G (1982) studied suspended sediment deposition near a
Mid-Atlantic outer continental shelf drilling operation in 120
m (400 ft) of water. Post-drilling clay accumulations are
displayed in Figure 3-4. The study showed grain size and clay
mineralogy distributions were affected by drilling discharges
in an area extending up to 800 m for a period of one year.
Sampling within a two-mile radius of the well site revealed
increases in sediment barium levels and changes in trace metal
sediment concentrations extending to at least this distance.
The extent of the area of accumulation is attributed to the
relatively low currents and greater water depth of the area as
compared to those of other outer continental shelf studies.
Houghton et al., (1981) studied deposition of drill
cuttings from a single exploratory well in Lower Cook Inlet by
comparing pre- and post-drilling core samples. Cores at 100 m
(330 ft) from the discharge showed an accumulation rate of 30
2
g/m per day. cores at 200 m (660 ft) showed an accumulation
o
rate of 10 g/m per day, and cores at 400 m (1.307 ft) showed
2
an accumulation rate of 1 g/m per day. Accumulations
occurred to a depth of at least 12 cm (4.7 in) with the
majority of cuttings accumulating to depths of 1 to 7 cm (0.4
to 2.7 in).
3-27
-------
Figure 3-4 Spatial distribution of clay content
In sediments (post-drilling)
(Ayers et al., 1982)
« (TYPICAL OF
PRE-DRILLING VALUES)
-------
Studies have shown the extent of drilling fluid
accumulation on the bottom to be inversely related to the
energy dynamics of the receiving water. Vertical mixing also
appears to be directly related to energy dynamics. Analysis of
sediments at Tanner Bank (Ray and Meek, 1980; Meek and Ray,
1980) ten days after the last discharge showed no visible
evidence of cuttings or mud accumulation even though over
800,000 kg (882 short tons) of solids had been discharged over
an 85 day period. Size analysis also indicated little change
in the grain size distribution.
Low energy environments, however, are not subject to
currents removing deposited material from the bottom or mixing
it into sediments. In the low-energy Mid-Atlantic environment,
for example. Menzie (1982) reported that cuttings piles were
visibly distinct one year after drilling had ceased. Zingula
(1975) also reported visible cuttings pile characteristics in
the Gulf of Mexico shortly after drilling had terminated.
One study in the Gulf of Mexico (Ayers et al.. 1980b) has
examined the short-term sedimentation of drilling fluids and
cuttings in 23 m of water. Sediment traps were deployed only
to a distance of 200 m. No distance-dependent quantitative
estimates were possible from the data. Ten- to 100-fold more
material was collected in traps after the 1,000 bbl/hr
discharge than after the 275 bbl/hr discharge. The relative
barium, chromium, and aluminum contents of collected matter was
more similar to that found in the initially discharged fluid
for the 1000 bbl/hr discharge than for the 275 bbl/hr
discharge. This suggests a reduced influence of differential
dispersion of these metals during the higher rate discharge.
3-29
-------
Vertical incorporation of plume components into sediments
is caused by physical resuspension processes and by biological
reworking of sediments. The relative contribution of these
processes to mixing has not been quantified. Vertical
entrainment occurs, but is not well-described. Petrazzuolo
(1981; 1983a) cites a Gulf of Mexico operation where barium
concentration was substantially enriched to a 4 cm (1.6 in)
depth at both 100 m (330 ft) and 500 m (1.600 ft) distances.
The upper 2 cm (0.8 in) of sediment was highly enriched with
barium. This study was conducted along one transect (not
aligned with major current flows) after four wells had been
drilled at the platform.
3.3.1.5 Alterations in Sediment Barium Levels
The long-term fate of discharge drilling fluids has been
followed in several studies using sediment barium levels as a
tracer. Four studies have been performed in the Gulf of Mexico
from which data have been analyzed to estimate the dispersion
of sediment barium.
Sediment levels of barium were determined for a shunted
discharge in Block 384 of the High Island area, approximately
5.300 m NNE of the West Flower Garden Bank (Union Oil
Company. 1977). The rig was located in 104-108 m of water and
shunted to a depth of 10 m from the bottom. The post-drilling
survey occurred 11-17 days after drilling operations ceased
(see Table 3-7).
Sediment barium levels have been determined for a Gulf of
Mexico drilling operation in Block A-389 of the High Island
3-30
-------
TABLE 3-7 GEONETRIC REGRESSION COEFFICIENTS AND STATISTICS FOR TOTAL
SEDIMENT BARIUM CONCENTRATIONS VERSUS DISTANCE FROM RIG SITE
OCS Study Site a b r2
West Flower 24,518 -0.480 0.854
Garden Bank
Mustang Island 37,142 -0.617 0.974
East Flower 24,501 -0.449 0.933
Garden Bank
Baker Bank, 140,185 -0.660 0.902
Cruise A
Baker Bank, 32,302 -0.446 0.876
Cruise D
Baker Bank, 50,848 -0.521 0.972
Cruise 0
Baker Bank 550,897 -0.828 0.869
Cruise M
SE of the
Estimate df
0.169 5
0.239 1
0.143 2
0.210 2
0.162 2
0.0858 2
0.310 2
P
0.0023
0.0536
0.0153
0.237
0.0302
0.0055
0.0330
Adapted from Petrazzuolo (1983a).
References - West Flower Garden Bank: Union Oil Company 1977
Mustang Island: Department of Interior 1976b
East Flower Garden Bank: Mobil Oil Corporation 1978
Baker Bank: Continental Oil Company 1979
3-31
-------
area, approximately 400 m from the "no activity" boundary of
the East Flower Bank, in 124 m of water (Mobil Oil Corporation
1978). Two wells were drilled. Discharges were shunted to
within 10 m of the bottom. Post-drilling sampling occurred
5-18 days after drilling-related discharges ceased (see
Table 3-7).
Sediments metal levels were determined for an exploratory
well located in about 36 m of water, near Mustang Island, on
the Texas OCS (Department of Interior 1976b). Post-drilling
sampling was reported to have occurred approximately three
months after drilling operations ceased. Among the metals that
were tested (barium, cadmium, chromium, copper, iron, lead,
nickel, and vanadium), only barium showed any obvious
difference between pre-drilling and post-drilling levels. Four
distances were sampled (0 m. 100 m. 500 m, and 1,000 m from the
rig) and sediment barium levels at the rig were lower than at
100 m. due to advection of the discharged material.
Sediment levels of barium were determined for a western
Gulf of Mexico drilling operation in 75 m of water on the Texas
OCS. near Baker Bank in the Mustang Island area (Continental
Oil Company. 1979). Sampling occurred during and after the
drilling of four wells. Sampling sites were oriented generally
to the NW on three closely-aligned radial transects. Replicate
values were obtained for four quarterly cruises at distances of
504 m. 1.004 m. 1.506 m. and 3.300 m.
Barium levels in the sediment within about 1.000 m of the
rig generally increased with time. However, interpretations of
3-32
-------
these data are confounded by the presence of other wells that
were drilled nearby. The most significant of these included
two exploratory wells located 100-150 m west of the study
platform.
The data from these four studies have been analyzed using
average sediment barium levels (with respect to direction) as a
function of radial distance (r) from the discharge source.
Regression analyses were performed on log-log transforms of
data sets for each study. The results and statistics for the
geometric regression analysis for total sediment Barium are
presented in Table 3-7. The form of the power law relationship
is:
BaEXCESS + B3BGND " BaTOTAL " a C
The resulting regression analyses for total sediment barium
are characterized by good to excellent statistics. All
regression coefficients are significantly different from zero.
with P-values ranging from 0.0037 to 0.0536. and most of the
2 2
regressions have a good r statistic (all r > 0.854).
Since data were available for sediment barium levels with
respect to both distance from the source and number of wells, a
multivariate geometric regression was performed. Sediment
barium levels were generated from the equations given in Table
3-7 for distances of 100 m. 500 m, and 500 m increments
thereafter until either a distance of 5,000 m or a level of
0 ppm excess barium was reached. These data were obtained for
an average of the two one-well operations, the two-well
operation, and the six-well operation described previously.
3-33
-------
The multivariate regression equation of sediment Ba as a
function of number of wells (N) and distance from the discharge
(r) was:
BaTOTAL - 7-423X105 (N1' 373)(r"1'283 ) + BaBGND
The value of r2 was 0.781 with 116 degrees of freedom. A
comparison of the multivariate equation estimates and the
bivariate source equation estimates is shown in Table 3-8.
The multivariate analysis for number of wells and distance
was used to estimate sediment barium levels at sampling
stations 102 m to 29.941 m from Platform "A" after nine wells
were drilled (Continental Oil Company 1982). These data
include discharge data from three additional wells taken after
the Platform "A" data were obtained. Platform "A" data formed
part of the multivariate analysis. Comparisons of the
estimates from the multivariate analysis and the actual
sampling data are presented in Table 3-9.
Only one multivariate estimate fell beyond the sampling
value ±1 standard deviation, and this exception was an
over-estimate of 18 percent (1.194 ppm versus an observed level
of 1.013 ±90 ppm). This analysis suggests that sediment barium
data collected early in the development phase of an operation
may provide accurate estimates of sediment barium levels later
in the operation. However, some qualifications apply.
3-34
-------
TABLE 3-8 COMPARISON OF ACTUAL AND PREDICTED LEVELS OF EXCESS SEDIMENT BARIUM
U>
1
Ul
W
Hunter of Wells 1
Multivariate
Distance (m) Estimate
100 2.000
(+9%)
500 337
(+llt)
1000 119
(+34%)
1500 104
(+18 11)
2000 62
(+1301)
2500 43
(+95%)
3000 32
(+78%)
3500 25
(+67%)
4000 21
(+62%)
4500 17
(+42%)
5000 15
(+36%)
Bivariate
Estimate
1.632
(1596-2122)**
303
(87-406)
89
(24-207)
37
(12-138)
27
(7-103)
22
(5-82)
18
(3-68)
15
(2-59)
13
(2-51)
12
(2-45)
11
(1-41)
2
Multivariate
Estimate
5.179
(+99%)
655
(-27%)
269
(-50%)
160
(-58%)
110
(-63%)
83
(-65%)
66
(-65%)
54
(+65%)
45
(-65%)
39
(-63%)
34
(-60%)
Bivariate
Estimate
2,602
(2582-2622)
902
(816-987)
540
(494-485)
385
(368-402)
295
(290-299)
234
(213-254)
190
(156-223)
155
(111-199)
128
(74-181)
105
(44-166)
86
(18-154)
6
Multivariate
Estimate
23,408
(+47%)
2,960
(+7%)
1,215
(-4%)
722
(-7%)
499
(-6%)
374
(-3%)
296
(+3%)
243
(+13%)
205
(+26%)
176
(+45%)
154
(+75%)
Bivariate
Estimate
1,591
(11,700-20,100)
2.777
(2,743-28,100)
1,272
(733-824)
779
(733-824)
533
(516-550)
386
(378-393)
287
(259-314)
216
(172-260)
163
(104-221)
121
(51-191)
88
(8-168)
Adapted from Petrazzuolo (1983a).
-------
TABLE 3-9 COMPARISON OF ACTUAL AND PREDICTED SEDIMENT BARIUM
CONCENTRATIONS AROUND A GULF OF MEXICO PRODUCTION PLATFORM
AS A FUNCTION OF DISTANCE FROM THE RIG AND NUMBER OF WELLS*
Number
of Wells
9
9
9
9
Distance
2385
102
12,073
29,941
Sediment Barium, ppm
Actual
1013±90***
46,692*3657***
(39,584-46,590)
637*88***
(552-728)
517*30***
(483-541)
Calculated**
1195
40,300
586
527
(mg/kg)
1% Difference
(+181)
(-81)
(81)
(v2t)
* Adapted from Continental Oil Company (1982), as in Petrazzuolo (1983a).
** Background level set at 500 ppm Ba; calculated value determined from:
BaTOT = 7.423xl05 (||1-373)^-1.285) tBaBGND
*** Mean f standard deviation (n = 3)
3-36
-------
This analysis represents the first preliminary effort at
predicting sediment barium levels from multiple well
operations. Although there are limitations in the available
data base, these limitations are not as important as the
establishment of a framework for the analysis of multiple well
effects. However, at least three identified limitations
exist: the lack of accurate barium discharge data, the effect
of differences in time scales for drilling multiple wells, and
geographic differences.
The first problem with the data base used in this approach
is that using "number" of wells is not as good a variable as an
accurate estimate of the amount of barium (as barite)
discharged. Lacking such data, however, the number of wells
must be considered a first-order approximation.
A second factor that needs further assessment is the effect
of time scale on the sediment barium dispersion equations. The
data base used in this analysis relies on sediment sampling
conducted shortly (two weeks to three months) after drilling
ceased, or during drilling for a multiple well operation.
These data reflect a discreet position of a dynamic equilibrium
between the accretion of drilling fluid solids in the sediment
and dispersive forces action on this sediment. The difference
in time scales, and therefore dispersive processes, involved in
drilling 6-10 wells is far different than drilling 60-100 wells.
The third consideration is that of the site-specific nature
of dispersion processes. A better understanding of more
fundamental processes is required before quantitative
comparison between different areas can be made confidently.
3-37
-------
One study has attempted to perform a quantitative
correlation of the amount of material discharged versus its
spatial distribution in the sediment (Mobil Oil Corporation
1978). In this study, an estimate of the quantity of barium
deposited in the sediment was performed by comparing the area
of a series of concentric rings about the platform to that of a
single core, and calculating average barium levels in this
"ring" based on (a) the observed barium levels in samples
obtained at discreet distances from the platform, and (b) the
dry weight of the sediment from a core. This analysis
indicated that about 40 percent of the discharge barium was
found outside a radius of 1,250 m from the platform.
These same data can be analyzed using a different
approach. Another method to estimate the total amount of
sediment barium within a given radius of the drillsite is to
obtain a function that describes the decrease in barium levels
with distance and integrate it with respect to both distance
and direction. From the studies cited above, it appears that a
fairly consistent function that describes the distance-
dependent relationship is: [BaJ = a r . The required
integration, with respect to both distance and direction, is
given by:
(a r dr)(r d6)
3-38
-------
Therefore, the cumulative concentration-area product of the
double integral is given by:
I
2ira r2+b (2 + b)
If the distance is set at 1.250 m and the site-specific value
of b is used (i.e.. b = 0.449), the estimates for this drilling
operation are 56,750 kg (78 percent) within 1.000 m of the
platform and 80.300 kg (111 percent) within 1,250 m of the
platform.
3.3.1.6 Trace Metal and Physical Benthic Alterations
An environmental study (Department of Interior, 1976a) was
conducted in approximately 33 m of water on the south Texas
outer continental shelf (Block 755, Mustang Island Lease
Area). The trace metal content of suspended sediments was not
thought to have been affected from drilling activities.
although seasonal variations and the effect of ship traffic
from the nearby Port Aransas shipping lanes confound the
interpretation of these results.
Lead has a 2.7-fold increase in the sediment at the
drillsite and a 1.9-fold increase at 1.000 m stations. At the
drillsite, zinc was elevated 2.5- to 3.5-fold and cadmium was
elevated 3- to 9-fold. These metals showed low levels, similar
to those taken before drilling, in the sediment 300 m from the
drill site.
3-39
-------
Comparisons of textural variability between the composite
pre-drilling and post-drilling sample suites showed significant
differences (95 percent confidence level) for skewness, silt
percentage, clay percentage, silt/clay ratio, and mean
diameter. The post-drilling site was significantly
coarser-grained, had a higher silt/clay ratio, and was less
coarsely skewed than the pre-drilling suite. No valid
conclusions were thought possible regarding the causes of the
textural differences.
A rig monitoring survey was conducted at an exploratory
site located near the north lease line of Mustang Island
(Texas). Block 792. in 36 m of water (Department of Interior.
1976b). Significant changes in the levels of sand, clay, silt,
and CaCO. occurred between before versus during drilling
phases. Sand, clay, and CaCO. levels increased
significantly, while silt levels showed a significant
decrease. Comparison of the during- and after-drilling levels
showed that the clay and CaCO. levels decreased significantly
and silt levels increased significantly. These authors
examined the metal/iron ratio for chromium, copper, lead,
nickel, and vanadium. The data indicated that no spatial
trends existed in the metal concentrations.
An environmental study in the central Gulf of Mexico has
examined chronic, low-level, heavy metal contamination from
active petroleum production platforms on the OCS (Tillery and
Thomas. 1980). Results from sediment chemistry data showed
concentration gradients that decreased with distance from the
platforms for barium, cadmium, chromium, copper, nickel, lead.
vanadium, and zinc at one or more platforms. These gradients
were not explained by the variability in sediment
characteristics.
3-40
-------
A study has investigated the environmental distribution of
metals from drilling fluids discharged into the Beaufort Sea.
near the Mackenzie River Delta (Crippen et al.. 1980). Mercury
contamination of sediments was obvious within 100 m of the
point of discharge, and mercury levels were somewhat elevated
above mean background levels (0.07 yg/g) at several other
stations. The highest mean value recorded was 6.4 vg/g
located less than 45 m from the shoreline of the island, just
north of the discharge.
The concentrations of arsenic, cadmium, chromium, lead, and
zinc in surface sediments exceeded background levels at one or
more stations in the vicinity of the discharge. Subsurface
concentrations of most metals, excluding chromium, were
substantially higher than surface sediment sample 45 m SW of
this discharge location. This sample was thought to be a
pocket of drilling fluid from operations prior to the use of
chrome lignosulfonate.
A study was conducted to monitor the environment fate
associated with above-ice disposal of drilling fluids and
cuttings in the Beaufort Sea (Sohio Alaska Petroleum Company
1982). Three wells were sampled, Sagavanirktok Delta Wells ft?
and #8 (Sag 7 and Sag 8). and Challenge Island Well ttl
(Challenge 1). Three sites (A, B. and C) were sampled at
Challenge 1.
P-test analyses indicated that there were no significant
differences (P < 0.05) among any pre- versus post-discharge
tests at disposal sites. For post-discharge tests of disposal
sites versus reference sites, a few significant differences
3-41
-------
were found. Median grain size decreased at Sag 8 and
Challenge 1 (Site C) for the >0.25 mm (percentage coarser)
fraction and at Sag 8 for the >0.150 mm fraction. Increased
median grain size occurred for the >0.250 mm fraction at
Challenge 1 (Sites A and B) and for the >0.150 mm fraction
(Site B).
Trace metal analyses were conducted on samples of drilling
fluids that were disposed. Comparison of pre- and
post-discharge bottom sediment samples from Sag 7 indicated
significant decreases in levels of barium, cadmium, and mercury
that were judged unrelated to drilling fluids. Analyses of
samples from Sag 8 indicated only that Ba levels decreased
significantly.
Analyses of Challenge 1 samples indicated significant
increases in levels of cadmium, chromium, lead, and zinc at
Sites A and B, and in copper, lead, and zinc at Site C.
Increases of chromium and zinc were considered related to
drilling fluids disposal. Cadmium data were not considered to
be explained by effluent discharges because cadmium levels in
the effluents and pre-discharge sediments were similar.
Elevations in lead were not judged to be drilling fluid-related
because of spatial patterns, other sediment characteristics.
and because Site C did not melt in place.
However, elevations of cadmium and lead levels could be
effluent-related. Although cadmium levels in early drilling
fluid samples (0.2 mg/kg) were similar to pre-discharge
sediment levels (0.19-0.35 rag/kg), an enrichment of cadmium in
drilling fluid effluents occurred at all disposal sites over
3-42
-------
time, to 0.8-1.1 mg/kg. Also, for cadmium, chromium, lead, and
zinc sediment levels were inversely related to distance from
disposal sites (A and B) for 0-60 m, 60-85 m, and 250 m data
sets.
Furthermore, for cadmium, lead, and zinc at Sag 7 and
chromium, copper, lead, and zinc at Sag 8. a consistent spatial
pattern of enrichment at the nearfield stations (approximately
85-200 m) occurred relative to pre-discharge levels and either
within-site or far-field (315-585 m) stations. These
enrichments were not statistically significant. However, trace
metal levels had 95 percent confidence levels that averaged
about 65 percent of the mean. This large variability
substantially reduces the ability to statistically resolve
differences among data sets.
Nonetheless, near-field enrichments were consistent. For
both lead and zinc, enrichment was 1.3-fold at Sag 7 and
1.2-fold at Sag 8, versus 2.3- to 2.6-fold for lead and
1.4-fold for zinc at Challenge 1. Chromium levels at Sag 7
increased 2-fold versus 1.4-fold at Challenge 1.
A study has assessed the impacts of above-ice drilling
effluent disposal techniques in the Beaufort Sea (Sohio Alaska
Petroleum Company, 1981), between the Midway Islands and
Prudhoe Bay. A simulated, above-ice disposal test was
conducted.
Grain size analyses of settling pan sediment indicated that
a rapid decrease in deposition rates occurred for most particle
sizes. At the center of the discharge hole, deposition was
3-43
-------
2
729 mg/cm for all grain size fractions. At 1.5 m and 3.0 m.
2 2
average deposition was 313 mg/cm and 168 rag/cm .
respectively. It was estimated that the average deposition of
2
all particle sizes was about 200 mg/cm over the test site.
The average deposition rate for particles less than 45 microns.
measured 3 m from the discharge point, was in the same general
range of deposition rates measured at two below-ice disposal
sites (166 mg/cm2 versus 66-368 mg/cm . respectively).
Bottom sediment trace metal levels indicated the presence of
drilling effluents three days after the discharge, but not
three months post-discharge.
Trace metal analyses of drilling fluid samples and
sediments were conducted both within and near the disposal
sites. At one site there were no notable differences as a
result of drilling activities. At the second site, however,
three metals showed possible enrichment: cobalt, copper, and
iron.
These sediment metal studies, when considered as a group
(Table 3-10), suggest the enrichment of certain metals in
surficial sediments may occur as a result of drilling
activities. While confounding factors occur in most of these
studies (i.e., seasonal variability and other natural and
anthropogenic sources of these metals) a distance-dependent
decrease in metal levels freguently is observed. However.
although drilling activities are implicated as a source of
metal enrichment, discharged drilling fluids and cuttings
probably are not the only drilling-related source.
3-44
-------
TABLE 3-10 SUMMARY OF SEDIMENT TRACE METAL ALTERATIONS FROM DRILLING ACTIVITIES3
u>
1
it*
in
Trace Metal
Location
Gulf of Mexico,
Mustang Island Area
suspended sediment
Surficial sediment
Gulf of Mexico,
Mustang Island Area
Central Gulf of Mexico
Hid Atlantic
'"'
Mackenzie River Delta
Beaufort Sea
As Cd Cr Cu Hg Ni Pb V Zn
NO- + ± ND - - ± -
(8-31x) (7-10x) (6-25x)
NO + _ _ ND - - - +
(3-9x) (2.5-3.5X)
NO ± + ± NO + - - NO
ND + + + ND + + +
- - - BLD + + +
(2.5x) (4-4x) (2-9. 5x) (4x)
+ + + NO + ND + ND +
(1.2-2.5) (2-6x) (4-7x) (1.2-15x) (1.5-2.2x) (11. 7x)
ND + + ± ND + ND +
(2-6x) (1.4-2X) (1.2-2.6X) (1.2-1.4x)
a. Adapted from Department of Interior (1976a, 1976b, 1977); Tillery and Thomas (1980);
Mariani et al., (1980); Crippen et al., (1980) after Petrazzuolo (1983a).
Abbreviations: ND (not determined)
+ (increased levels (magnitude change in parentheses) related to drilling)
(decreased levels related to drilling)
+ (isolated increases, not a clearly distance-related pattern)
BLD (below the level of detection)
-------
The only two metals that appear to be elevated around rigs
or platforms, and are clearly associated with drilling fluids.
are barium and chromium. A study in the Canadian Arctic found
that mercury would be the best trace metal tracer of discharged
fluids. Examination of mercury levels in fluids and sediments
for domestic operations is notably under-represented in the
studies that have been reviewed. The degree of similarity
between Canadian and domestic operations has not been
evaluated. However, the findings of the Netserk study and lack
of information on domestic operations indicate that the
relationship between drilling fluid discharges and sediment
mercury levels should be further clarified.
Metals that appear to be elevated as a result of drilling
activities, and not solely related to drilling fluids, include
cadmium, mercury, nickel, lead, vanadium, and zinc. Cadmium.
lead, and zinc may be associated with drilling fluids as
contaminants that occur from the use of pipe dope or pipe
thread compounds. Mercury, nickel, and zinc may originate from
sacrificial anodes. Cadmium, lead, and vanadium may also
originate from the release of fossil fuel in drilling
operations. This release can result from burning, incidental
discharges or spills from the rig or supply boat traffic, or
use as a lubricant in drilling fluids. Vanadium also may
derive from wearing of drill bits. In the Gulf of Mexico
platform study, brine (formation water) discharges were
identified as an additional potential source of metal
contamination.
3-46
-------
Although these metals were enriched in the sediment.
enrichment factors were generally low to moderate, seldom
exceeding a factor of 10. The spatial extent of this
enrichment also was limited. Either of two cases occurred:
enrichment was generally distributed but undetectable beyond
300-500 m or enrichment was directionally-based by bottom
current flows and extended further (to about 1,800 m) but
within a smaller angular component.
These considerations suggest that exploratory activities
will not result in environmentally significant levels of trace
metal contamination. However, other factors, such as the
intensity of exploratory activities, normal sediment loading,
and proximity either to commercial shell fisheries or to
subsistence populations, could alter this conclusion. Sediment
trace metal levels resulting from development drilling
operations need further clarification, especially relating to
the dynamics and extent of sediment contamination.
3.3.2 Produced Water
The Corvallis Environmental Research Laboratory, which is
part of the Ocean Discharge Division of EPA's Narragansett
Environmental Research Laboratory (ERL). has developed a PLUME
model that calculates height-of-rise and near-field initial
dilution from a discharge. These calculations are required by
regulations issued by the EPA to implement Section 301(h) and
403(c) of the Clean Water Act. Typical applications of this
3-47
-------
model, the PLUME model, have been for municipal ocean
discharges. The PLUME model is described in detail in two
reports (Baumgartner et al.. 1971; Teeter and Baumgartner.
1979).
The PLUME model was recently modified to predict dilution,
trap depth, and depth of maximum penetration of produced water
discharges from platforms. This model's predictions seem to
compare favorably with laboratory experiments for discharges of
drilling fluids and brine. Maximum discharge volumes for
platform sizes projected to be located in shallow water are
shown in Table 3-11. Average discharge volumes for various
platform sizes are shown in Table 3-12. Initial PLUME model
computer runs evaluated discharges of 3.000. 10,000. 25.000 and
50.000 bbl per day. Lower and upper specific gravity values of
actual brine discharges were used: 1.073 and 1.151 g/ml, which
corresponds to 80.500 mg/liter and 203.000 mg/liter total
dissolved solids (TDS), respectively.
PLUME model results are shown in Table 3-13. The table
presents the maximum depth of penetration of the discharge
plume, the center line dilution of the plume at the trap depth,
and the typical platform sizes modelled. The trap depth of the
plume is where the plume's density matches the density of the
receiving waters. However, because of the momentum of the jet,
the plume penetrates below the trap depth, to a maximum depth
of penetration. Table 3-13 assumes no current and an assumed
density profile for ocean environments. Table 3-14 presents
typical water depths in state waters for comparison to maximum
depths of penetration in Table 3-13.
3-48
-------
TABLE 3-11
MAXIMUM DISCHARGE FLOW (bbl/day) AND
NUMBER OF PLATFORMS IN WATER LESS THAN VARIABLE DEPTHS
Platform Size
Oil
Max. No.
Flow Platforms
Oil and Gas
Max. No.
Flow Platform*
Gulf 4
Gulf 2x6
Gulf 12
Gulf 24
Gulf 40
Gulf 58
2051
5129
5103
9287
16558
25880
6
12
3
0
0
_0
21
2122 28
5184 38
5213 14
9519 0
16847 0
26334 _0
80
Pac 16
Pac 40
Pac 34
5999
0
0
0
0
6081
14000
35000
0
0
_2
2
Beaufort1 48
Berin Platform 48
Beaufort2 48
66021
80294
94316
6
0
_0
6
1 Gravel Island
2 Platform
3-49
-------
TABLE 3-12
AVERAGE DAILY
PRODUCED MATER VOLUMES (bbl/day)
FOR THE MODEL PLATFORMS
Model Platforms
(Wells/Dlatform)
Gulf 12
24
40
58
Pacific 16
40
342
Atlantic 24
Cook Inlet, AK
Beaufort Sea, AK3
Bering Sea, AK
Beaufort. AK4
Oil
3,086
5,672
9,563
14,382
3,465
8,081
20,606
11,414
20,609
34,470
44,831
46.615
Type of Platform
Oil -Gas
3,259
5,819
10,104
15,237
3,694
8,345
21,250
11,823
20,608
34,470
46,391
49.242
Gas
410
2171
551
2,376
1,614
1 Assumed geopressured reservoir
2 Assumed very productive field for model
3 Gravel Island
Platform
3-50
-------
TABLE 3-13
PREDICTED MAXIMUM PLUME DEPTH AND PLUME CENTERLINE DILUTION1
Produced water Center line Center line Center line Center line
Depths (m) Discharge Dilution Dilution Dilution Dilution
of water Rate 3.000 at trap 10,000 at trap 25,000 at trap 50,000 at trap Assumed
Column On) bbl/dav death** depth depth death Condi tions3
u>
I
Ul
H
10
10
20
30
100
Model platforms
sizes
(wells/platform)
Bottom Bottom
7-9 28-56 Bottom
9-12 44-86 12-15
11-13 57-111 14-18
35-37 704-951 23-40
Gulf-12 Gulf-40
Pacific-16
Atlantic-24
Bottom Bottom
21* Bottom 17-31 Bottom
32* 16-Bottom 26-57 Bottom
42* 18-23 32-65 22-27
89* 40-44 186-265 43-49
Pacific-342 Bering Sea,
Pacific-40 Cook Inlet, AK
Unstratlfled
14* Stratified
Stratified
28* Stratified
121-182 Top 30 m mixed
layer,
stratified
below 30 m
AK
Beaufort. AK
1PLUME Model was used as developed by Environmental Research Laboratory-Corvallis
^Assumed very productive field for model
3Assumed no current in all cases and 1.073 g/ml and 1.151 g/ml density of discharge
*Di1ution at trap depth for discharge density of 1.073 g/ml only
**Average dilution equals 1.77 multiplied by centerline dilution.
-------
TABLE 3-14 AVERAGE DEPTH OF STATE WATERS
Texas* Louisiana Southern Northern Cook Bering Beaufort
(3 leagues) California California Inlet.AX Sea.AK AK
12 m 5m 150 m 150 m 24 m Norton 3 m
Sound-4 m
N. Aleutian
Basin-10 m
*A11 state waters in this table extend 3 miles offshore except Texas which has
three league designation (approximately nine miles)*
3-52
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For the platform sizes projected to be located within
territorial seas (Table 3-14), comparisons of their depths of
penetration from Table 3-13 to actual water depths reveal areas
where potential direct benthic impacts may occur due to bottom
impact of the plume and pollutant accumulation in the
sediment. The results shown in Table 3-13 are summarized below:
(1) Direct benthic impacts are possible in the territorial
seas of Texas and Louisiana. The average depth in the
territorial seas for these states is approximately
five meters. The average depth of state waters could
be higher than this because of Texas' state water
boundary of three leagues (nine miles from shore).
The discharge from a model 12-well platform is
projected to reach the bottom in water depths of less
than nine meters. For the majority of both oil and
oil-gas model platform sizes, plumes will impact the
bottom in state waters and the territorial seas
because water depth averages approximately five and
nine meters, respectively. Gas platforms were not
modelled because of their low discharge volumes.
(2) Larger platforms (40 to 58 wells) could cause impacts
in Federal waters because the discharge plume is
projected to descend to almost 20 meters. The water
depth in certain Federal waters off the Texas and
Louisiana coasts is considerably less than 20 meters.
(3) Plume model runs for other platform sizes, projected
to be located in the territorial seas in the Pacific
3-53
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(40 wells/platform) and in the Beaufort Sea. Alaska,
show that the plume could impact the bottom in water
depths of approximately 20 meters or less. The
average water depth in California's territorial seas
is 150 meters which should provide adequate protection
to the benthos. However, state waters in the Beaufort
Sea are an average of three meters deep, and impacts
may occur.
In an effort to evaluate the impact of currents on dilution
and depth of penetration of the plume, another model UMERGE
(Soldate et al.. unpublished) was used, which evaluated the
PLUME model, assuming a water column depth of 20 meters and
currents of 0. 2. 5. 10. 20. and 50 cm/sec. The results of
this analysis are shown in Table 3-15. These results show the
cross-sectional average dilution of the plume at any given
depth instead of center line dilution of the plume. The
average dilution is higher than the center line dilution
because more area is involved in the mixing calculation. From
Table 3-15. the maximum depth of penetration decreases, and the
average dilution increases as the current increases.
During the Buccaneer Field Study in the Gulf of Mexico, a
discharge plume was dye marked (discharge volumes of
approximately 600 bbl/day) and under calm conditions was
reported to penetrate to water depths of 10 meters from the
surface. Table 3-15 only shows a 3.000 bbl/day discharge,
which penetrates 8.9 to 11.3 meters, depending on the density
of the wastewater discharge and the ambient density
stratification. In order to better approximate a lower volume
discharge, such as in the Buccaneer Field, actual density
3-54
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TABLE 3-15
PLUME OUTPUT WITH CURRENTS
Produced Water 6" Pipe 12" Pipe
Volume Diameter Diameter
Currents BPD 3000 5000 10000 16000
0 cm/sec
2 cm/sec
5 cm/sec
10 cm/sec
20 on/sec
50 on/sec
1
2
1
2
1
2
1
2
1
2
1
2
8.
6.
8.
6.
7.
5.
5.
3.
3.
2.
2.
1.
,5'
7
5
7
8
8
7
9
4
3
1
6
* 135B
11. 3C
73
8.9
11.
8.
9.
7.
6.
4.
4.
2.
2.
2.
2
8
7
1
8
7
2
9
7
0
136
74
167
100
291
185
448
259
614
351
9.7
7.5
9
7
9
6
7
4
4
2
2
1
.6
.5
9
.1
.8
8
.0
.9
5
.2
.9
3
.6
.9
2
12.8
10.0
12.7
.9
11.4
.5
8.4
.8
5.1
.6
3.2
.4
119
64
119
65
139
81
225
146
374
218
518
297
11.5 100 12.8 89
15.1 17
11.4 100 12.8 89
15.1 17
11.1 110 12.6 95
14.1 16.1
5.6 290 6.9 241
6.8 8.3
3.9 411 3.8 352
4.1 4.7
Assumes stratified water column of 20 meter depth.
A trap depth (m)
B dilution at trap depth (ave.)
C max penetration (m)
1 discharge (gm/ml) 1.151
2 discharge (gm/ml) 1.073
NOTE - Max depth of penetration decreases as current increases.
Dilution increases as current increases.
3-55
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profiles for 1979 from the Buccaneer Field (Table 3-16). and
lower discharge volumes were used. The results of this
analysis are shown in Table 3-17.
The density profile of the water column is an important
factor in the estimates of plume penetration and dilution.
Seasonal stratification due to temperature or salinity
gradients can significantly influence the depth of
penetration. This was discussed in Section 3.3.1.2. The
results in Table 3-17 show that the plume penetrates to the
bottom (19 meters in this case) given winter and fall density
profiles for 1979. This was further than originally estimated
in Table 3-13 for a slightly higher value of 3000 bbl/day-
Under certain conditions i.e.. no currents or lower currents.
higher dissolved solids content, and certain density profiles,
the plume is projected to penetrate even further than was
projected earlier.
3.4 CHEMICAL TRANSPORT PROCESSES
3.4.1 Drilling Fluids
3.4.1.1 Inorganics
Most research on chemical transport processes affecting
offshore oil and gas discharges focuses on trace metal and
hydrocarbon components. The trace metals of interest in
drilling fluids include barium, chromium, lead, and zinc. The
source of barium in drilling fluids is barite; barite may be
contaminated with several metals of interest, including
arsenic, cadmium, lead, mercury, zinc, and other substances
(Table 3-18). These trace metals are discussed below as they
pertain to chemical transport processes.
3-56
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TABLE 3-16 BUCCANEER TEMPERATURE AM) SALINITY PROFILES
Sumner 1979
Depth Temp Salinity
On) C° toot)
A 1 29.3 32.5
6
j c
0
E
j F 6 29.4 32.8
G 9 29.4 33.0
H 11 29.3 33.2
I
J
K
L 16 29.3 34.2
H 19 29.0 34.6
Fall 1979
Depth Ta*> Salinity
fa) C° (not)
1-3 24.1 34.8
4 24.3 35.2
6 24.4 35.4
13 24.7 35.7
19 24.7 35.7
Winter 1979
Depth Temp Salinity
fa) C° toot)
2-8 14.0 34.6
11 12.5 34.4
12 12.5 34.8
14 12.0 34.6
19 12.0 34.6
Soring 1979
Depth Temp Salinity
fa) C° toot)
1 23.5 30.0
3 23.3 30.2
S 23.2 30.8
6 23.2 31.0
12 22.8 32.6
16 22.4 33.2
19 22.0 34.0
I
IP
-------
TABLE 3-17
PLUME MODEL COMPUTER RUNS USING ACTUAL WATER COLUMN DENSITY
PROFILES FROM THE GULF OF MEXICO, BUCCANEER FIELD STUDY
Maximum Depth of Penetration (meters) and Trap Depth (meters)
Discharge
Season Volumes 1.000 bbl/day 5.000 bbl/day
Sunnier 1979 13.9 (10) 18.0 (13)
Fall 1979 19.0 (bottom) 19.0 (bottom)
Winter 1979 18.2 (11) 19.0 (bottom)
Spring 1979 9.0 (6.8) 14.0 (10)
Assumes density of discharge 1.151 g/ml.
Assumes no current and a six inch diameter pipe.
3-58
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TABLE 3-18 CONCENTRATION OF TRACE METALS IN BARITE
Samples used in solubility
studies
Metal
Arsenic
Cadmium
Cobalt
Copper
Lead
Mercury
Nickel
Zinc
High trace
metal sample
67
12
5.4
91
1,370
8.1
33
2,750
Low trace
metal sample
1.8
0.65
2.2
7.6
0.95
0.13
5.7
9.8
Values from literature
review
Vein
deposits
7a
0.2-19
NO
2-97
4-1,220
0.06-14
19C
10-4,100
Bedded
deposits
500b
50b
<5-60
3-20
<10
0.06-0.19
<5-5
200*
(Adapted from Kramer, 1980)
NO = Not detected.
a One analysis.
b Semiquantitative emission spectrographic analysis.
c Mean of 83 analyses.
3-59
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Kramer et al.. (1980) found that seawater solubilities for
trace metals associated with powdered barite generally result
in concentrations below background levels. Exceptions were
lead and zinc sulfides. which may be released at levels
sufficient to raise concentrations in excess of ambient
seawater levels. MacDonald (1981) found that less than five
percent of metals in the sulfide phase is released to seawater.
Barite solubility in the ocean is controlled by the sulfate
solubility equilibrium, which becomes saturated at
concentrations of 30 to 40 v9/l (Houghton et al.. 1981).
Background sulfate concentrations in seawater are generally
high enough for discharged BaSO4 to remain a precipitate and
settle to sea bottom.
Chromium discharged in drilling fluids is primarily
adsorbed on clay a"nd silt particles, although some exists as a
free complex with soluble organic compounds. Chromium is added
to the mud system predominantly in the trivalent state as
chrome or ferrochrome lignosulfonate, or chrome-treated
lignite. It may be added in the hexavalent state as a
lignosulfonate extender, in the form of soluble chromates. The
hexavalent form is believed to be largely converted to the less
toxic trivalent form by reducing conditions downhole. The most
probable environmental fate of trivalent chromium is
precipitation as a hydroxide or oxide at pH > 5.
Transformation to hexavalent chromium in natural waters is
likely only when there is a large excess of manganese dioxide.
Simple oxidation by oxygen to the hexavalent state is very
slow, and not significant in comparison with other processes
(Schroeder and Lee. 1975).
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Dissolved metals tend to form insoluble complexes through
adsorption on fine-grained suspended solids and organic matter,
both of which are efficient scavengers of trace metals and
other contaminants. Laboratory studies indicate that a
majority of trace metals are associated with settleable solids
< 8 ym in size (Houghton et al.. 1981).
Trace metals, adsorbed to clay particles and settling to
the bottom, are subjected to different chemical conditions and
processes than when suspended in the water column. These
sorbed metals can be in a form available to bacteria and other
organisms if located at a clay lattice edge or at an adsorption
site (Houghton et al.. 1981). If the sediments become anoxic.
conversion of metals to insoluble sulfides is the most probable
reaction, and the metals are then removed from the water
column. Environments that experience episodic sediment
resuspension favor metal release if reducing conditions existed
previously in buried sediments; such current conditions also
allow further exposure of organic matter complexes for further
reduction and eventual release.
3.4.1.2 Orqanics
The only data generated to date on the partitioning of
organics in drilling muds were generated in a laboratory study
on admixtures of generic mud No. 8 with 5 percent high-sulfur
diesel oil (Breteler et al.. 1984). Admixture of the oil into
the drilling mud resulted in recovery from the mixture of 42
percent (4-hr mixture) or 45 percent (10 min mixture) of
hydrocarbons admixed. Longer mixing time (4 hours) resulted in
nearly complete evaporation of the lower alkylated benzenes and
other alkanes below C .
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After 10 minutes of mixing and a one hour settling time for
a one percent mud/seawater mixture. 30 percent of the
hydrocarbons were in the suspended particulate phase, with five
percent suspended and the remaining 25 percent in the aqueous
phase. The aqueous phase was relatively enriched in CIQ
alfcanes. Neither C^-Cg benzenes nor CIQ alkanes were
present in the suspended phase. The suspended phase was
enriched in alkylated naphthalenes and phenanthrenes, except
for C. phenanthrene. Suspended particulate phase (aqueous
suspended) was enriched in CQ-C4 (not C5and Cg) benzenes.
CQ-C- (not C4) naphthalene and CQ-C2 (not C3) phenanthrene.
Proportionately, naphthalenes, accounted for 84 percent of
aromatics and 51 percent of total organics in the suspended
phase as compared to 58 percent of aromatics and 17 percent of
total organics (recovered) in the whole mud (10 minute mixing;
1 hour settling). Mixing for 4 hours rather than 10 minutes
decreased hydrocarbons in settleable muds from 70 percent to 20
percent of total hydrocarbons recovered. Aqueous phase
hydrocarbon content increased from 25 to 62 percent of the
total. Particulate phase hydrocarbons increased from 5 to 18
percent of the total. After 4 hours, enrichment of the aqueous
phase was limited to C -C, benzenes and C naphthalene.
£t O \J
whereas the particulate phase was enriched in C -C
naphthalenes and CQ-C3 phenanthrenes. while alkylated
benzenes were again absent from the particulate phase.
When a 0.1 percent mud to seawater ratio was used. 10
minutes of mixing followed by one hour settling resulted in
recovery of 98 percent of alkylated hydrocarbons in the
suspended particulated phase, of which only 4 percent were in
the suspended phase. The suspended phase was enriched in C2-C4
naphthalene and CQ-C3 phenanthrenes. After 4 hours of
3-62
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mixing and one hour settling, 99.7 percent of hydrocarbons were
contained in the suspended particulate phase with 35 percent in
the suspended phase. The suspended phase was enriched in CIQ
n-alkanes but not in any other hydrocarbon. The aqueous phase
however, was enriched in CQ-C3 naphthalenes and CQ phenanthrene.
Overall recovery of aromatic hydrocarbons in this experiment,
however, was very low, thus hindering the interpretation of
these data.
3.4.2 Produced Water
Chemical processes important to the fate of produced water
constituents generally are those that affect metal and
petroleum hydrocarbon behavior in marine systems. Factors
affecting metals have been described above under drilling
fluids. Here, the processes affecting petroleum hydrocarbons
are briefly described.
Perhaps the most important factor affecting the fate of
hydrocarbons in produced water is volatilization. Produced
water contains a high fraction of volatile compounds (e.g.,
benzene), which will be lost from the system over time
depending upon their volatility. For higher molecular weight
compounds the major processes involve biodegradation of
compounds over time. Polynuclear aromatic hydrocarbons tend to
be more resistant to such degradation and, thus, can persist in
the environment (primarily sediment) for extended periods.
3.5 BIOLOGICAL TRANSPORT PROCESSES
Biological transport processes occur when an organism
performs an activity with one or more of the following results:
3-63
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an element or compound is removed from the water column;
a soluble element or compound is relocated within the
water column;
an insoluble form of an element or compound is made
available to the water column;
an insoluble form of an element or compound is relocated.
Biological transport processes include bioaccumulation in
soft and hard tissues, biomagnification. ingestion and
excretion in fecal pellets, and reworking of sediment to move
material to deeper layers (bioturbation).
3.5.1 Bioaccumulation
Bioaccumulation is the ability to concentrate substances.
including nutrients, naturally-occurring substances, and
xenobiotics. to levels above ambient concentrations.
Laboratory studies have shown that bioaccumulation of trace
metals can be reversed, at least in part. When an organism is
transferred from a contaminated environment to a clean one,
there generally occurs a decrease in pollutant concentration in
the organism.
3.5.1.1 Drilling Fluids
The majority of research on metal accumulation from
drilling fluids has focused on barite (barium) and ferrochrome
lignosulfonate (chromium). Liss et al., (1980) examined
chromium accumulation in sea scallops (Placopecten
maqellanicus) exposed to one part per thousand of used and
unused drilling muds and 0.03-1.0 parts per thousand
ferrochrome lignosulfonate. They found that chromium did not
3-64
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concentrate in the adductor muscle, but did concentrate in the
kidney. Scallops exposed to used and unused drilling fluids
accumulated chromium in the kidney at concentrations ranging
from two to four yg/g; for ferrochrome lignosulfonate.
concentrations ranged from 16 to 70 yg/g dry tissue.
Once exposure ceased, kidney chromium concentrations
decreased slowly; typically less than 10 percent after 24 hours
(Figure 3-5). These studies represent the results of exposures
of small sample sizes, ranging from three to six individuals.
McCulloch et al., (1980) noted accumulation of chromium in
clams and oysters after exposure to used drilling fluids, but
little net accumulation after depuration in clean seawater.
McCulloch et al.. (1980) exposed the marsh clam (Rangia
cuneata) to a layered solid phase of used ferrochrome
lignosulfonate drilling fluid, containing 485 mg chromium/kg.
The mean chromium concentration in soft tissue after a 24-hour
exposure was about five times the level found in control
animals. Two-thirds of this excess accumulation was lost after
24 hours depuration. When the same organism was exposed to the
mud aqueous fraction of this mud for 16 days, mean soft tissue
levels increased from 7 mg chromium/kg dry weight to 18 mg
chromium/kg. Nearly half of the excess accumulation was lost
in the first 24 hours of depuration, although no further loss
occurred during the following two weeks.
In a third experiment, test organisms were exposed to the
mud aqueous fraction of a used mid-weight lignosulfonate
drilling fluid (417 mg chromium/kg and 915 mg lead/kg dry
weight). Mean soft body concentrations of chromium and lead
increased by a factor of 1.5 after three days. Approximately
3-65
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24-
18-
v
a
tn
^»**
O
o>
12-
6-
3-
-depuration-
I-TEST
'CONTROL
* standard deviation
b numbar of organisms
Figure 3-5 Chromium enrichment in the kidneys of Placopectin magellanicus
exposed to 0.1O g/l ferrochrome lignosulfonate
(Liss et al.,1980)
-------
half of the excess for each metal was lost after four days of
depuration. When oyster spat (i.e.. juveniles) of the species
Crassostrea qiqas were exposed to this same used mid-weight
lignosulfonate drilling fluid, they exhibited soft tissue
increases in chromium concentration of two- to threefold in two
days, and fourfold after 14 days. Lead concentrations in soft
tissue increased twofold after 10 days, while no detectable
increase in soft tissue zinc concentrations was noted.
Tornberg et al.. (1980) exposed arctic amphipods to
mixtures of used, freshwater XC-polymer drilling fluids (5 to
20 percent by volume) and water. The greatest uptake in the
ten percent mixture occurred for cadmium, chromium, and lead.
and in the five percent mixture for zinc. Maximum uptake
relative to control organisms was fivefold for cadmium, and
twofold for chromium, lead, and zinc.
A field study of bioaccumulation in organisms around a
drilling operation on the mid-Atlantic OCS analyzed tissue data
from brittle stars, polychaetes. and molluscs. Based on
discharge and sediment analyses, the only metals exhibiting
elevated tissue concentrations that were attributed to drilling
discharges were barium and chromium (E6&G. 1982). Barium
concentrations increased significantly from pre-drilling levels
in polychaetes and brittle stars during the first post-drilling
survey (two weeks after the completion of drilling activity);
molluscs did not accumulate barium to an appreciable degree.
Barium tissue concentrations in polychaetes increased from
23.5 to 87.8 vg/g. Although, the highest tissue levels were
found in the immediate vicinity of the well, levels as high as
3-67
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206 yg/g were found at stations one mile away. Barium
concentrations in brittle stars increased from an average
tissue concentration of 15.2 ug/g to 217.8 yg/g. Tissue
levels were as high as 372 yg/g at one mile stations. Barium
tissue levels dropped to pre-drilling levels at all stations
after one year (second post-drilling survey).
Regarding chromium, the report (EG&G. 1982) noted that
"chromium concentrations in molluscs were generally within the
range observed during the pre-drilling cruise." However, this
range appears to utilize a single maximum value of 137.2 yg/g
(Station 14) which was six times higher than the next highest
observed value. This observation for chromium at Station 14
may have been influenced by a second well in the vicinity which
the authors point out had been drilled less than a year
earlier. Excluding this single outlier drops the pre-drilling
mean concentration from 12.9 yg/g to 6.7 yg/g. with the
result that chromium concentrations in molluscs during both
post-drilling cruises exceed the range observed during the
pre-drilling cruise.
Average chromium concentrations in mollusc tissues
increased from 6.71 yg/g to 18.5 yg/g to 31.7 yg/g over
the three cruises. Average chromium concentrations in
polychaete and brittle star tissues changed from 2.28 yg/g to
11.2 yg/g to 41.0 yg/g and 1.49 yg/g to 1.12 yg/g to
2.87 yg/g. respectively. The continued increase in tissue
chromium levels of all organisms over a year's time
(post-drilling I to post-drilling II) indicates possible
continued bioaccumulation of chromium from the low levels in
the sediments. EPA (1980) reports bioconcentration factors for
marine organisms of from 125 to 200 for hexavalent chromium and
from 86 to 153 for trivalent chromium.
3-68
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Carr et al.. (1982) exposed five marine species
representing three animal phyla (Arthropoda. Annelida, and
Hollusca) to three fractions of a used lignosulfonate drilling
fluid. The organisms showed an apparent ability to accumulate
chromium from the three mud fractions. In all but two cases,
chromium levels fell to pre-exposure levels during depuration.
However, marsh clams (Ranqia cuneata) and sandworms (Neanthes
virens) accumulated chromium to levels two times that of the
controls and retained a large fraction of the chromium for an
extended period of time.
Brannon and Rao (1979) exposed grass shrimp (Palaemonetes
puqio) to 5 mg/liter and 500 mg/liter mixtures of barite in a
flow-through seawater system. They analyzed for barium in the
carapace (hard tissue), hepatopancreas, and abdominal muscle
(soft tissues). Barite is highly insoluble in seawater and
some fraction of this particulate material settled to the
bottom of the test container. Water samples from the media
containing 5 and 50 mg barite per liter had barium
concentrations in the water column of 135 yg/liter and 267
vg/liter. respectively. The high barium concentrations were
apparently due to particulate matter that remained in
suspension rather than due to dissolved barium. Chow (1976)
reported a theoretical maximum of 46 yg/1 for barium in
seawater.
The researchers found that the shrimp exposed to barite
accumulated higher barium levels in their exoskeletal and soft
tissues than control shrimp in seawater. and that the level of
accumulation increased with increasing duration of exposure.
Cast off exuviae from the first through the fourth ecdysis, for
example, were found to contain 4.392; 13,240; 16.037; and
3-69
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19.987 mg/kg barium, respectively. Ingestion of settled barite
alone could not account for the increased body burdens
observed; elevated levels of soluble and/or suspended
particulate barite is the most likely cause (T. Duke. EPA, from
K. R. Rao. U. West Florida, to R. Cole. Dalton'Dalton'
Newport, personal communication, 1983).
Brannon and Rao also noted shrimp ingesting particulate
barite and eliminating it in fecal pellets. This could affect
fecal pellet nutritional value and sinking rate, which has
ecological significance because fecal pellets are important in
energy flow and nutrient cycling. Shrimp exposed to barite, in
the presence of adequate strontium and calcium in the test
water, were found to discriminate for barium and strontium
relative to calcium in the hepatopancreas and abdominal
muscle. This selective incorporation of barium into soft
tissues may provide a long-term opportunity for barium to enter
the food chain.
Shrimp were found to discriminate for barium and against
strontium relative to calcium in the exoskeleton. This changed
the relative mineral composition of cast exoskeletons of grass
shrimp from calcium > strontium > barium for control organisms
to calcium > barium > strontium for experimental organisms.
Incorporation of trace metals into hard tissue can result in
removal from the water column that is more long-term than soft
tissue incorporation. Although these removal processes may not
have toxic implications, they are pathways by which metals are
removed from the environment.
Chow and Snyder (1980) studied barium distribution in hard
tissues of marine invertebrates collected from the southern
California coast, and found that barium concentrations in
3-70
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calcareous exoskeletons were related to the type of organism.
Chitons (Nuttalina and Mopalia) averaged 7.4 ppm, mussel
(Mvtilus) averaged 1.2 ppm. and gastropods (Haliotis and
Tequla) averaged 0.8 and 0.5 ppm. respectively. The plates of
a barnacle (Balanus) had barium concentrations of 14 ppm, hard
tissue of a sea urchin (Stronqylocentrotus) had 22 ppm. and
corals (species unknown) displayed the highest concentration at
41 ppm.
Barium concentration was related to the mineralogical
structure of the skeleton. Calcite skeletons of gastropods are
composed of a crystal lattice that does not allow inclusion of
the larger barium ion, whereas aragonite skeletons of mussels
form a larger lattice structure which does allow for barium
incorporation. Skeletons that incorporate other chemical
compounds in carbonate form, such as those of the barnacle and
sea urchin, allow still higher barium concentrations in
skeletons.
For soft tissues. Chow and Snyder (1980) found the average
barium concentration in gills, muscles, and gonads was less
than one ppm with the exception of the Mvtilus specimens. The
barium concentration of their stomachs (with contents) showed a
wide range of from 0.57 ppm to 108 ppm. This indicates that
the digestive tract may be the route of barium entry for some
marine organisms. The standard deviation of barium content in
various organs of Mytilus exhibited the following trend;
stomach > gills > muscles > gonads > shells. This trend
supports the hypothesis that the digestive tract is the route
of barium entry. The trend also indicates that marine
organisms have some degree of regulation over the incorporation
of barium into their tissues.
3-71
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Conklin et al.. (1980) note that the mechanisms of barium
accumulation are poorly understood. There is some evidence
that barium transport is mediated by a divalent-cation-activated
adenosinetriphosphate (ATP) transport carrier as well as by
micropinocytotic activity of the digestive epithelium. The
latter hypothesis is supported by observations that grass
shrimp, juvenile lobsters, and meiobenthic nematodes ingest
particulate barite and accumulate it in their exoskeletons
(Brannon and Rao. 1979; Conklin et al.. 1980; Chow and Snyder.
1980).
Many crustaceans have long been known to incorporate
granular materials into their statocysts (organs of balance).
The granular materials are cemented together by glandular
secretions of the statocyst wall to form statoliths. The
ectodermal inner chitinous lining and contents of the
statocysts (fluid, sensory hairs, and statoliths) are cast off
during molting and renewed. Chow et al.. (1980) confirmed that
grass shrimp may incorporate sand grains, barite particles, or
drilling mud particles into their statocysts as they renew the
exoskeleton following a molt. The effects on the grass shrimp
of this barite incorporation remains to be investigated.
Laboratory data on metal accumulation have been summarized
by Petrazzuolo (1983a) in Table 3-19. Exposure to drilling
fluids or drilling fluid components has resulted in the
accumulation of barium, cadmium, chromium, lead, strontium, and
zinc. One metal for which laboratory bioaccumulation data were
conspicuous by their absence was mercury.
Maximal observed enrichment factors (tissue levels in
exposed animals compared to control animal tissue levels)
generally were low (1.6- to 3.4-fold), with the exception of
3-72
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TABLE 3-19 SUMMARY OF METAL BIOACCUNULATION STUDY RESULTS
Test
Organism
Dni sinus sp.,
Boekosimus sp.
Whole Animal
not gutted
Palaemonetes
pugio
Whole Animal
not gutted
Carapace
Heoatooan-
creas
Abdominal
muscle
Carapace
Hepatopan-
creas
Abdominal
Muscle
Test Substance
(Concentration,
PP»)
XC-polyser-Unical
fluid
(50.000)
(100,000)
(200.000)
Barite
5
50
5
50
Barite
500
500
500
Barite
500
500
500
Exposure
Period
(days)
20
static
7,
48-hour
replacement
«
8 days
post-ecdysis,
(48-hour
replacement)
106
Depura-
tion
Period
(days) Ba Ca
0
150
350
14 2.2
14 29
0 7.7
13
12
0
60-100 0.07
70-300 1
50-120 1
Metals. Enrichment Factor*. Ref.b
Cd Cr Cu Pb Sr Zn
1
3.2 1.2 2.0 1.6
6.4 1.8 2.2 1.3
6.0 1.4 1.5 1.5
2
1.3
1.9
1.8
2.2
1.2-2.5
1.9-2.8
1.5-2.8
1.6-7.4
0.03
0.71
«*)
I
-J
u>
Adapted from Petrazzuolo (1983a).
-------
TABLE 3-19 SUNNARY OF METAL BIOACCUNULATION STUDY RESULTS
(Continued)
Test
Organism
Nytilus edulis
(soft tissue)
Rangea cuneata
(soft tissue)
Test Substance Exposure
(Concentration, Period
ppm) (days)
12.7 Ib/gal 7
lignosulfonate
fluid, NAF
(Or . 1.4 ppm)
ferrochrome
lignosulfonate
(Cr » 0.7 ppm)
(Cr = 6.0 ppm)
CrC13
(Cr = 0.6 ppm)
12.7 Ib/gal 4,
lignosulfonate static
fluid, NAF
(50.000)
13.4 Ib/gal
lignosulfonate
fluid 16.
(100.000 NAF) static
(layered solid 4,
phase) daily
replacement
Depura-
tion Netals. Enrichment Factor* Ref.b
Period
(days) Ba Ca Cd Cr Cu Pb Sr Zn
6.6 3
13
64
50
1.4 1.7 4
4 1.1 1.2
2.5
1 1.7
14 1.6
4.3
1 2.0
U)
-------
TABLE 3-19 SUMMARY OF METAL ACCUMULATION STUDY RESULTS
(Continued)
U)
I
Test
Organist
Crassostrea-
gigas
[soft tissue)
Test Substance
(Concentration,
PP»)
9.2 Ib/gal
spud fluid
(40.000 HAF)
(10,000 SPP)
(20,000 SPP)
(40,000 SPP)
(60,000 SPP)
(80,000 SPP)
12.7 Ib/gal
lignosulfonate
fluid
(40,000 HAF)
(20.000 HAF)
(40.000 HAF)
(10,000 HAF)
(20,000 SPP)
(40,000 SPP)
(60,000 SPP)
(80,000 SPP)
Exposure
Period
(days)
10.
static
4,
24. hour
replacement
H
M
H
H
10,
static
14
14
4,
24-hour
replacement
N
*
H
N
Depura-
tion
Period
(days) Ba
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Metals. Enrichment Factor9 Ref .b
Ca Cd Cr Cu Pb Sr Zn
2.1 1.1
2.5
3.0
3.0
5.5
7.4
2.3 1.4
2.9
3.9
2.2
4.4
8.6
24
36
-------
TABLE 3-19 SUMMARY OF METAL BIOACCUHULATION STUDY RESULTS
(Continued)
u>
I
Test
Organism
Crassostrea
gigas
(soft tissue)
(Cont.)
Placopecten
magellanicus
Kidney
Adductor
Kidney
Adductor
Test Substance
(Concentration.
PP»)
17.4 Ib/gal
lignosulfonate
fluid
(40.000 MAF)
(20.000 NAF)
(40.000 MAF)
Uncirculated
lignosulfonate
fluid
(1.000)
(1.000)
Low density
lignosulfonate
fluid
(1.000)
(1.000)
FCLS
(30)
(100)
(1.000)
Exposure
Period
(days)
10.
static
14
14
28
28
14
27
14
27
14
14
14
Depura-
tion
Period
(days) Ba
0
0
0
0 8.8
0 10
15
15
14
14
14
Metals. Enrichment Factor4 Ref .b
Ca Cd Cr Cu Pb Sr Zn
0.56 1.0
2.1
2.2
2.6
1.2
1.6
2.1
2.3
2
2
2
5.7
3.2
6.0
5.2
7.2
6.0
-------
TABLE 3-19 SUMMARY OF METAL ACCUMULATION STUDY RESULTS
(Continued)
U)
1
Test Test Substance
Organism (Concentration,
ppm)
Myoxocephalus XC-polymer fluid
quadricornis
(gutted)
(5,000)
(10,000)
Depura-
Exposure tion Metals. Enrichment Factor3 Ref.b
Period Period
(days) (days) Ba Ca Cd Cr Cu Pb Sr Zn
36,
48-hour 6
replacement
3.3 1.1 1.25 1.2
2.9 3.1 1.7 1.2
a Enrichment Factor = Concentration in exposed group/concentration in controls.
b References: 1. Tornberg et al., (1980).
2. Brannon and Rao (1979).
3. Page et al., (1980).
4. McCulloch et al., (1980).
5. Liss et al., (1980).
6. Sohio Alaska Petroleum Company (1981).
Abbreviations: MAP - mud aqueous fraction
SPP - suspended particulate phase
FCLS - ferrochrome lignosulfonate
-------
barium (300-fold) and chromium (36-fold). Although functional
changes resulting from metal accumulation were not explicitly
addressed in these studies, no gross, overt functional changes
or potential alterations have been noted.
The ability of exposed animals to clear metals accumulated
during exposure to drilling fluids or components also have been
reported. These data are summarized (Petrazzuolo. 1983a) in
Table 3-20. Depuration studies suggest that a substantial
release of barium, chromium, lead, and strontium may occur.
For whole animal, soft tissue, and muscle tissue analyses,
40-90 percent of the excess metal (barium, lead, chromium, and
strontium) that was accumulated following 4- to 28-day
exposures was released during 1- to 14-day depuration periods.
Possibly, length of exposure and extent of depuration are
inversely related. Transient increases were observed in
chromium, lead, and strontium levels during the depuration
period. The only sustained increase (48 percent) during this
period occurred in chromium in scallop kidney. This finding is
somewhat confounded by a similar trend (+24 percent) in control
animals.
These data suggested that bioaccumulation of metals as a
result of drilling fluids discharges did not appear to be a
significant problem. Yet. three factors argued against this
conclusion. Instead. Petrazzuolo (1983a) assessed
bioaccumulation as a significant unknown. First, uptake
kinetics were not adequately described, largely attributable to
the rather short exposure periods. These exposures were most
often for 14 days or less.
3-78
-------
TABLE 3-20 DEPURATION OF METALS BIOACCUMULATED DURING
EXPOSURE TO DRILLING FLUIDS OR COMPONENTS3
Exposure
Test Test Period
Species Substance (days)
Palaemonetes
pugio
Rang i a cuneata
Placopectan
magellanicus
BaS04 7
ll ll
SLFC 1-4
(LSP)
MDLF 4
(MAF)
II
SLF 16
(HAF)
"
LDLF 27
(WN)
it n
FCLS 14
Depuration
Metal Tissue Depuration Period
Levelb (days)
Ba whole
animal.
not
gutted
Sr
Cr soft
tissue
Cr "
Pb
Cr
H
Cr kidney
Cr adductor
muscle
Cr kidney
-90%
-90%
-(40-65%)
-75%
-70%
-53%
-60%
+48%d
-63%
-(17-54%)
7
7
1
4
4
1
3-14
14
14
14
Adapted from Petrazzuolo U983a).
a Adapted from Brannon and Rao (1979); McCulloch et al. (1980),
Liss et al. (1980).
b Percentage of excess metal released.
c Abbreviations: SLF, MDLF, LDLF (seawater, medium density, and low
density lignosulfonate fluids), FCLS (ferrochrome lignosulfonate),
MAF, MM (mud aqueous fraction, whole fluid).
d Control animals exhibited a 24% increase during the depuration period.
3-79
-------
Occasionally 16- to 28-day exposures occurred; in one case, a
106-day exposure occurred but with only one intermediate value
reported.
The available data do not allow for any firm conclusions
about the extent of potential uptake. Simple saturation
kinetics occur for several metals and species. However.
complex saturation kinetics also occur frequently. The
long-term study with 106-day exposure did not report adequate
data to characterize uptake kinetics. Since metals are highly
persistent, long-term accumulation potential must be assessed.
Second, the focus of these studies was often diffuse.
Bioaccumulation studies should identify which of two
toxicologic problems is being addressed: (1) human health
impacts (edible tissue analyses) or (2) marine organism impacts
(target organ analyses). Functional studies must be undertaken
to link accumulation to adverse physiological/biochemical
responses.
Third, exposure levels were difficult to quantify in a
meaningful way for correlation to field exposure conditions.
The assessment of the bioaccumulation of drilling fluids-
related metals will be driven by the exposure of benthic
epifauna and infauna to drilling fluid particulates. Yet.
bioaccumulation studies routinely have tested whole fluids or
the aqueous phase of fluids. These exposures could have either
over-estimated or under-estimated potential accumulation.
Furthermore, in those studies that have tested solid phase
material, accumulation was only measured in response to a
deposit layer. Therefore, no concentration-effect relationship
can be constructed that could estimate uptake from anything but
a 100 percent exposure situation. This design does not lend
itself to a meaningful quantitative assessment.
3-80
-------
A more recent report by Neff et al., (1984) examined uptake
of barium and chromium from the liquid settleable phase of
drilling muds. Experiments included several species of
invertebrates; clams, worms, shrimp, scallops, lobsters, and
one fish (flounder). Lobsters and flounder were fed
contaminated and depurated worms to test for food chain
transfer or magnification. These experiments were performed
for longer periods of time (56 to 119 days) than previous
tests. Maximum bioenrichment factors for barium and chromium
were in the range of 2.6 to 16.8 for barium and 1.9 to 2.8 for
chromium. These results are consistent with previous tests.
The design of these experiments was intended to simulate
more realistic field conditions. However, the bioaccumulation
and bioenrichment values are compromised both by the
variability of the data and, more importantly, by the fact that
sediment barium and chromium levels decreased dramatically
during the course of each experiment (40-80 percent for barium,
25-60 percent for chromium). Thus, assessing exposure in these
experiments is very difficult and extrapolation to field
conditions, in which concentrations increase during drilling,
is confounded by this experimental design, not simplified.
In summary, Petrazzuolo (1983a) evaluated bioaccumulation
data for drilling fluids and components and concluded the
following:
(1) Several metals can be accumulated, including barium,
cadmium, chromium, lead, strontium, and zinc. Mercury is
conspicuous by the absence of any laboratory uptake data.
3-81
-------
(2) In terms of results, observations that militate against any
significant potential for adverse effects are: enrichment
factors are generally low (barium and chromium excluded).
depuration release levels are high, and no gross functional
alterations, resulting from metal accumulation following
high exposures to drilling fluids or components, have been
reported.
(3) Such a conclusion is largely compromised by several other
observations. Test results indicate that uptake kinetics
are not simple, with saturation plateaus beyond the scope
and predictive power of studies that have been conducted.
Test design problems also contribute to equivocal
interpretations and to poor utility in hazard assessment
analyses. These design problems include: the choice of
inappropriate drilling fluid fractions as test substances;
the use of only one effective exposure concentration for
fluid solids exposures; and the choice of tissues for
analyses that are inappropriate for the species.
(4) Because of (a) the extreme persistence of metals, (b) the
elevation of sediment metal levels resulting from drilling
discharges, (c) the notable toxicity of some of the metals
examined (cadmium and lead), (d) the absence of laboratory
data on a significantly toxic metals (mercury), and (e) the
inability to estimate potential effects from
environmentally realistic exposures, metal accumulation
should be considered an important area requiring further
study.
3-82
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3.5.1.2 Bioaccumulation of Hydrocarbons from Produced Water
There is evidence that hydrocarbons, discharged with
produced water, are bioaccumulated by various marine
organisms. In the Central Gulf of Mexico study (Nulton et al.,
1981) analyses revealed the presence of low levels of alkylated
benzenes, naphthalene, alkylated naphthalenes, phenanthrene.
alkylated three-ring aromatics. and pyrene in a variety of fish
and epifauna. Isomer distributions of alkylated benzenes and
naphthalenes were similar to those seen in crude oil.
Middleditch (1980) analyzed hydrocarbons in tissues of
organisms in the Buccaneer Field. During the first two years
of the study, tissue from barnacles from the platform fouling
community at depths ~ 3 m from the surface contained up to 4
ppm petroleum alkanes. Middleditch claims that biodegradation
of petroleum hydrocarbons in the barnacles was apparently
efficient. Analyses of the fouling mat on the platform
revealed that most samples contained petroleum hydrocarbons,
and concentrations were particularly high in those collected
just below the air/sea surface.
Middleditch (1980) found petroleum hydrocarbons in 15 of 31
fish species examined around the Buccaneer Field Platform.
They focused their analyses on four of the species--crested
blenny. sheepshead, spadefish, and red snapper. Virtually
every specimen of crested blenny examined contained petroleum
alkanes. In this species, the n-octadecane/phytane ratio was
similar to that of produced water but the n-heptadecane/
pristane ratio is distorted by the presence of endogenous
pristane of biogenic origin. The mean alkane concentration in
3-83
-------
this species was 6.8 ppm. This species feeds on the platform
fouling community, and it was suggested that this food was the
source of petroleum hydrocarbons to the fish.
Similar results were obtained with sheepshead. which also
partially feeds on the platform community. Petroleum alkanes
were found in about half of the muscle samples and in about one
quarter of the liver samples. The mean alkane concentrations
in these tissues were 4.6 and 6.1 ppm. respectively.
Spadefish exhibited lower concentrations of alkanes in
muscle and liver (0.6 and 2.0 ppm). and this species does not
utilize the platform fouling community as a food source to the
same extent as the two previously described species. Lower
levels of alkanes were also observed in red snapper (1.3 ppm in
muscle, and 1.1 ppm in livers).
With one exception, most shrimp analyzed by Middleditch did
not contain alkanes. This probably reflects the highly
migratory behavior of these animals. Similarly, the petroleum
hydrocarbons were not found in white squid.
Middleditch also examined nine benthic organisms for
petroleum hydrocarbons. Yellow corals (Alcvonarians) contained
alkanes but Middleditch suggested these could be of biogenic
origin. Various hydrocarbon profiles were observed in
species. Few of the specimens of winged oyster (Pteria
colymbus) contained petroleum alkanes while they did contain
methylnaphthalenes and benzo[a]pyrene.
3-84
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3.5.2 Biomagnification
Bioaccumulation relates to contaminant accumulation in a
single species. If the contaminant is passed from prey to
predator on to the next trophic level, a net increase in
pollutant body burden up the food chain can result, and is
known as biomagnification. Biomagnification is difficult to
test experimentally and is generally assessed by comparing body
burdens between organisms at different trophic levels.
Little information is available to allow an assessment of
biomagnification of the components of drilling fluid or
produced water discharges. Studies have been examined,
however, which assessed biomagnification of other inorganic and
organic pollutants in various food chains.
In an experiment to evaluate food chain transfer, sand
worms were fed to flounder and lobsters, including worms that
had been contaminated by living on barium-rich sediments and
those which had been subsequently depurated (Neff et al., 1984).
The mean barium level in contaminated worms was 22 yg/g,
whereas the controls contained 7.1 yg/g. Chromium levels were
1.02 yg/g in contaminated worms and 0.62 yg/g in controls. In
both cases depurated worms were not significantly different from
controls.
The mean enrichment in muscle barium concentration was
7.2-fold. Flounder fed contaminated food while living on
uncontaminated sediment did not accumulate barium in muscle
tissue. There was no significant uptake of chromium.
3-85
-------
Type of food had no effect on mean barium concentrations in
tail muscle of lobsters exposed to uncontaminated sediments.
Lobsters living on contaminated sediments accumulated barium in
muscle tissue when fed either uncontaminated or contaminated food.
The above data suggests that contact with sediments may be
more important in the bioaccumulation of barium than direct food
transfer. Throughout these experiments the metal content of food
was highly variable. Animals may have gone through periods of
uptake and depuration relative to this food and also the sediment
on which they were living. Because of the timing of analyses on
food (weekly) versus animals (at 56 days and 99 days), it is not
possible to develop any direct relationship between food source
and animal tissue concentrations.
Studies of DDT and PCB organochlorine compounds reveal that
accumulation of these compounds in the tissues of fish, mammals,
and birds from prey to predator occurs. Moreover, lipid
concentrations show an increase with trophic level which
indicates that dietary uptake and subsequent biomagnification is
taking place. Studies undertaken with fish provide clear
evidence that organochlorine uptake occurs more rapidly than does
elimination, leading to increasing pollutant burdens with time
and selective tissue accumulation at higher trophic levels
(Fowler, 1982). However, for species at lower trophic levels
such processes are less clear.
Fowler (1982) cites several studies analyzing specific food
chains for organochlorine biomagnification with mixed results.
It was suggested that these studies failed because they assumed
3-86
-------
the primary organochlorine input was through the food chain,
whereas recent studies indicate the water column may be the
primary source, at least for zooplankton. Fowler speculates
that plankton and small invertebrates accumulate substantial
amounts of material from the surrounding water, and will
reflect its composition more strongly than vertebrates, which
are generally larger and have less surface area for absorption
and therefore are more likely to accumulate most of their
organochlorines from prey consumed.
Data presented from California (Schafer et al.. 1982)
concern trace metal and organic compound contamination in the
marine environment. They examined three different food chains
in California and found increasing concentrations of DDT and
PCB with trophic level, but no evidence of increasing metal
concentrations except for organic mercury, which had a very
strong increase.
Most data on inorganic pollutant biomagnification show a
decrease in trace metal and radionuclide burden with higher
trophic level. However, there are exceptions found in specific
food chains. Dog whelks were found to have three times more
cadmium and four times more zinc than the limpets they consumed
(Pedan et al., 1973, as in Fowler, 1982), and subsequent
depuration experiments showed the whelks retained these
metals. However, other experimental results have shown that
whelks did not magnify zinc or iron in contaminated barnacles
upon which they were fed.
One qualification for much of the metal data, however, is
that muscle tissues were the most frequently sampled and
analyzed. These tissues are not known to be physiological
sinks for metal contaminants. No data have been identified
3-87
-------
that address target organ sites, such as hepatopancreas or
kidney tissues, which would be the functional analogs to
organic contaminants in fat and muscle tissue. Thus, the
apparent difference between organics and metals may be due to
the choice of tissue analyzed.
Cesium-137 has been shown by Fowler (1982) to accumulate in
higher trophic level fish in the food chain, and he concluded
that, "...the high degree of assimilation... from prey results
in an overall accumulation up the food chain." Studies
examining plutonium-237 also indicated biomagnification.
However, more recent work has shown that the implicated
organisms (starfish) rapidly absorb plutonium from the water
and eliminate it slowly. This further indicates the importance
of knowing the uptake pathways prior to making conclusions
regarding biomagnification.
Studies assessing biomagnification of petroleum
hydrocarbons are more limited than for other pollutants, but
the few data available suggest that these contaminants are not
subject to biomagnification. One reason for this observation
is that the primary source of these compounds for organisms may
be absorption from the water column rather than ingestion.
Also, biological half-times of some petroleum hydrocarbons may
be short, with many species purging themselves within a few
days. Middleditch (1980). in studying the fouling community
and associated pelagic fish, found that many species were
contaminated with hydrocarbons discharged in produced water.
3.5.3 Ingestion and Excretion
Organisms also remove material from suspension through
ingestion of suspended particulate matter and excretion of this
material in fecal pellets. These larger pellets exhibit
3-88
-------
different transport characteristics than the original smaller
particles. Houghton et al.. (1981) note that filter feeding
plankton and other organisms ingest fine suspended solids
(1 yin to 50 ym) and excrete large fecal pellets (30 ym to
3,000 ym) with a settling velocity typical of coarse silt or
fine sand grains. They also note that copepods are important
'in forming aggregate particles.
Zooplankton have been found to play a major role in
transporting metals and petroleum hydrocarbons from the upper
water levels to the sea bottom (Hall et al., 1978). The
largest fraction of ingested metals moves through the animal
with the unassimilated food and passes out with the fecal
pellets in a more concentrated state (Fowler, 1982).
Zooplankton fecal pellets have also been found to contain high
concentrations of petroleum oil. especially those of barnacle
larvae and copepods. Hall et al., (1978) calculate that a
population of calanoid copepods grazing on an oil slick could
transport three tons of oil per square kilometer per day to the
bottom.
3.5.4 Sediment Reworking
Another pathway of biological removal of pollutants
involves benthic organisms reworking sediment and mixing
surface material into deeper sediment layers. This process is
known as bioturbation, and moves barite and clays from drilling
mud to greater depths than they would otherwise achieve.
Bioturbation can also expose previously buried material, and
could be an important factor in potential long-term impacts.
No work was found to quantify bioturbation effects, although a
few studies have observed organisms living on a cuttings pile
3-89
-------
or in the vicinity of drilling discharges (Menzie et al.. 1980;
Ayers et al., 1980b). However, if the environment is one which
rapidly removes cuttings piles, or where physical forces
dominate resuspension and reworking processes, then biological
mixing activities may not prove significant.
3-90
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4.0 TOXICITY TESTING
4.1 SUMMARY
4.1.1 Drilling Fluids
The toxicity of drilling fluids and drilling fluid
components has been tested through laboratory tests using
single species and microcosm experiments. These were either
"acute" (short-term) tests in which the concentration that
produces 50 percent mortality in a given test species commonly
is determined or "chronic" (long-term) tests in which the
effect on survivability, growth, maturation, or reproduction is
assessed. Drilling mud toxicity tests have been performed
using whole muds or various component fractions, such as the
suspended particulate phase or mud aqueous fraction. Proposed
guidelines for suspended particulate phase toxicity testing
have been developed by EPA. The extrapolation of single
species tests to overall effects in the ecosystem still has a
large, inherent uncertainty.
Acute or short-term tests have generally indicated low
toxicity. In a summary of over 415 toxicity tests of 68 muds
using 70 species, 1-2 percent of the tests exhibited LC ' s
ranging from 100 to 999 ppm, 6 percent exhibited LC ' s
ranging from 1,000 to 10,000 ppm, 46 percent exhibited LC ' s
ranging from 10,000 to 100.000 ppm, and 44 percent exhibited
LC 's greater than 100,000 ppm. Two to three percent of the
data were not usable. A significant difference was noted
between the toxicity of generic muds, which appear to have
acute, lethal toxicity characteristics similar to the
distribution of the larger data set described above, and a
series of 11 nongeneric muds provided to EPA by the Petroleum
4-1
-------
Equipment Supplies Association. These latter muds, as a group,
appear to be substantially more toxic than would be anticipated
from the toxicity distribution of either the generic muds or
the larger data set. Whole muds appear to be more toxic than
aqueous or particulate fractions. The suspended particulate
phase appears to be more toxic than the other individual
phases. One author has ranked organisms according to their
sensitivity to drilling fluids in tests and found the following
order of decreasing sensitivity: copepods and other plankton,
shrimp, lobsters, mysids and finfish. bivalves, crabs,
amphipods. echinoderms. gastropods, and polychaetes and
isopods. Larval organisms are more sensitive than adult stages
(maximally 20-fold); animals are more susceptible during
molting.
Acute sublethal effects using a sensitive test species and
very toxic muds showed a low potential for sublethal effects.
with swimming behavior comroensurately affected at
concentrations approximately three-fold lower than mortality.
However, swimming behavior is not a particularly sensitive
sublethal indicator.
In another series of tests, the addition of mineral oil at
5 percent by volume produced burrowing impairment in two
species of invertebrates (softshell clam, sandworm). The same
sublethal responses were seen with the addition of 0.5 percent
low-sulfur or high-sulfur diesel fuel. Several species,
(shrimp, fish, scallops) have also been observed to exhibit
strong avoidance responses upon initial exposure to the
settleable fraction of water-based drilling muds.
Chronic or long-term toxicity tests performed on corals
include cleaning rates, polyp retraction, mucus secretion.
zooxanthellae expulsion, and growth rates. The effect of
4-2
-------
drilling muds on swimming rates in larval crabs, molting rates
and shelter construction time in lobster have also been
assessed.
The data base on chronic lethal effects is far smaller than
that on acute lethality; chronic lethal tests number only six.
compared to more than 400 acute lethal tests. The few chronic
data are consistent, however, and indicate that chronic lethal
toxicity is not likely to be more than some 20-fold greater
than acute lethal toxicity.
Chronic sublethal toxicity has been more extensively
studied than chronic lethal toxicity. Chronic sublethal
toxicity appears to range from three-fold to 75-fold greater
than acute lethal toxicity. and thus is within the same range
as chronic lethal effects. However, these sublethal data are
much more difficult to interpret. Toxicity end points are
difficult to interpret, physiologically and ecologically.
Sample sizes routinely are very small. Most importantly.
observations that sublethal effects occur "close" to lethal
effect levels miss the point; for most studies changes were
also noted at the lowest level tested. Thus, estimating
No-Observable-Effeet-Levels is not possible for much of the
reported data. /
Laboratory studies on recruitment and development of
benthic communities suggest that drilling mud and barite can
affect recruitmemt and alter benthic communities or depress
abundances. These data are corroborated by results from
artificial substrate experiments conducted in the Beaufort Sea;
these showed significantly different colonization rates at
drilling fluid test plots and control plots, especially for
amphipods and copepods.
4-3
-------
Muds are complex mixtures and there appears to be no single
explanation for toxicity. Some of the apparent (actual)
toxicity may be due to physical effects, such as particle size
coagulations, abrasions, etc. These are, however, a form of
toxicity. producing and contributing, in part or in combination
with chemical toxicity. to the end points (death) in acute
toxicity tests.
Oxygen demand appears strongly correlated with toxicity in
laboratory toxicity tests. Spearman Rank correlations of 96
hour LC data and BOD/UOD data showed a remarkably strong
correlation, especially with BOD data derived with
artificial seawater and activated seed. These data showed a
correlation of 0.97 with toxicity. All BOD/UOD values showed
correlations of 0.87 to 0.97 (BOD) and 0.91 to 0.95 (UOD). but
TOC/COD values gave correlations of 0.64 to 0.67. Given the
absence of oxygen demand data, no such correlation could be
developed for nongeneric muds. Another indicator of the large
inherent oxygen demand of drilling muds is that dissolved
oxygen levels in test environments dropped below normal.
notwithstanding the continuous aeration of test media that
followed pre-aeration of the test material. This was
especially noted during the first day of testing, during which
dissolved oxygen levels were depressed concentration--dependently
by the test muds.
Studies have found high correlations (diesel oil r=0.88;
mineral oil r=0.97) of toxicity with added (diesel/mineral) oil
to whole mud. Toxicity did not correlate quite as well with
the oil levels determined in a variety of mud samples
4-4
-------
(r=0.81). The available data indicate that this may be
partially due to various types of sequestrations within the
drilling fluid matrix as well as the variable presence of toxic
constituents in drilling fluids other than diesel or mineral
oil.
The variability and complexity in the composition of muds
is reflected in the results and interpretation of toxicity
tests. Test results of sample splits of the same mud performed
at two different laboratories have differed by an order of
magnitude. In such cases, laboratory procedure or sample
handling is a significant factor. Different batches of the
same generic mud have shown significantly different
toxicities. In this case different proportions of major
constituents (as allowed by mud type definition) may be a
factor. EPA has attempted to improve consistency in toxicity
test results by recommending standard procedures for sample
handling and testing. In recent interlaboratory tests on the
same batch of mud, consistent test results were obtained.
4.1.2 Produced Water
Available data on produced water acute lethal toxicity
indicates that these discharges are not particularly toxic.
However, several qualifications are required. Limited data on
96-hr LC values for produced waters that did not contain
measurable biocides were observed to range between 8,000 and
408.000 ppm for one series of tests. The LC values are
similar to those obtained for the water soluble fractions of
crude oils (140.000 - 430.000 ppm). While these waste streams
have some dissimilarities, both exhibit similar concentrations
of light aromatic hydrocarbons and these compounds may be
4-5
-------
contributing to the acute toxicity. These hydrocarbons may be
present partially as micelles, in addition to being dissolved.
However, it should be noted that an undetermined amount of
toxic compounds are lost from the produced water upon
collection, transport to the laboratory, and aeration.
Limited data for produced waters that contain biocides
indicate that these chemicals can increase the toxicity of the
effluent. LC values (48- and 96-hour) in the range of
1850-6500 ppm were observed for produced water containing an
undetermined amount of the biocides K-31 (glutaraldehyde) and
KC-14 (alkyldimethylbenzyl chloride) that were not scavenged.
Blennies kept in cages below the produced water discharge pipe
of a production platform in the Buccaneer Field suffered no
mortalities when the effluent had not been treated with
biocide. but approximately half of the blennies died (within 48
hrs) when biocides were present. (The type and concentration
of biocide in use was not documented.)
Another report noted that divers experienced eye and skin
irritation sufficient to interrupt their activities when
working near the produced water discharge from the Buccaneer
Field when acrolein was being used as a biocide. As already
noted, there are little data on the concentrations of biocides
in produced water although a variety of chemicals are used.
Over 500 products are currently registered with EPA's Office of
Pesticides as biocides in both drilling muds and waterflooding
operations.
Although the acute toxic effects of produced water appear
to be low (when biocides are absent), chronic lethal and
sublethal effects may occur inasmuch as these are generally
1-6
-------
exhibited at concentrations below those that are acutely
toxic. Chronic exposures could occur in the water column in
areas experiencing limited flushing and where the input of
produced water is continuous. However, hydrocarbons that have
become associated with the sediment are a more likely cause of
chronic exposure. Because of the continual input from produced
water, the sediment hydrocarbon load could include lighter
aromatic fractions as well as heavier molecular weight
hydrocarbons.
There is ample evidence to indicate that such hydrocarbon
accumulation can occur. Field studias at Trinity Bay and
Buccaneer Field also suggest that impacts have occurred on the
benthic fauna. Chronic sublethal toxicity of produced water
could occur at aromatic hydrocarbon levels on the order of
1 vg/1.
4.2 INTRODUCTION
This section presents information on the toxicity of drill-
ing mud and produced water discharges and the specific chemical
components of these discharges. The section also considers
potential ecological effects of effluents on community recruit-
ment. Toxicity tests are used to determine levels of pollutant
concentrations which can cause lethal or sublethal effects on
organisms, and are categorized as either acute or chronic.
Acute toxicity tests involve exposures of 96 hours or less.
while chronic toxicity tests involve long-term exposures.
usually entire or partial life cycles.
4-7
-------
4.2.1 Acute Toxicity Testing
Acute toxicity tests are used to determine the short-term
effects of a chemical or mixture on an organism. Results are
generally reported as the concentration at which 50 percent of
the organisms are killed (the LC or median lethal
concentration), or display a defined effect of toxicological
importance, such as loss of mobility (the EC or median
effects concentration). The higher the LC or EC for a
given exposure time, the lower the toxicity of the substance
being tested.
Acute toxicity tests can be conducted in static, renewal.
or flow-through systems. Static systems involve exposure to a
single batch of test solution for the full test period.
Renewal systems involve periodically replacing the test solu-
tion with new solution of the same concentration. In flow-
through systems, the test solution is continuously replaced and
excreted metabolites are removed. EPA's proposed protocol for
toxicity testing of drilling fluids specifies a static bioassay
system (Petrazzuolo. 1984).
4.2.2 Chronic Toxicity Testing
Chronic toxicity tests evaluate the long-term effects of
pollutant exposure on survivability. growth, maturation, and
reproduction. The results are generally expressed as a range.
with the smaller value the lowest concentration resulting in
the prescribed effect, and the larger value the highest
concentration not producing the effect. EPA (1980J) specifies
flow-through system testing protocols for chronic toxicity
tests.
4-8
-------
Chronic tests can be life cycle, partial life cycle, oc
early life stage. Life cycle testing exposes organisms from
embryo or newly-hatched larval stage through at least 24 hours
after the hatching of the next generation. Partial life cycle
tests expose organisms through part of the life cycle, and are
used in situations where the organism takes a long period
(e.g.. a year or more) to mature. Early life stage testing
focuses on the embryonic stage shortly after fertilization
through early juvenile development.
4.3 TOXICITY OF DRILLING FLUIDS
Toxicity testing data are used in impact assessments to
estimate the potential for environmental damage, even though
uncertainty arises from the extrapolation of single species
tests to assessments of overall effects. The scientific
interest in potential environmental effects of drilling has
prompted many researchers to conduct tests with various
drilling muds, drilling mud fractions, and a wide variety of
test organisms. The recently proposed EPA protocol for drill-
ing mud toxicity testing is based on EPA Region II bioassay
procedures, with certain modifications. This protocol speci-
fies testing of the suspended particulate phase (SPP) of drill-
ing mud. as follows:
Suspended Particulate Phase (SPP). One part by volume
of drilling fluid is added to nine parts seawater.
The drilling fluid-seawater slurry is well mixed and
the suspension is allowed to settle for one hour
before the supernatant SPP is siphoned off. The SPP
is mixed for five minutes and then used immediately in
bioassays.
4-9
-------
There are other drilling mud fractions which have been used
in bioassay testing, including:
Layered Solid Phase (LSP). A known volume of
drilling fluid is layered over the bottom of the test
vessel or added to seawater in the vessel. Although
little or no mixing of the slurry occurs during the
test, the water column contains a residual of very
fine particulates which do not settle out of solution.
Suspended Solids Phase (SSP). Known volumes of
drilling fluids are added to seawater and the mixture
is kept in suspension by aeration or mechanical means.
Mud Aqueous Fraction (MAP). One part by volume of
drilling fluid is added to either four or nine parts
seawater. The mixture is stirred thoroughly and then
allowed to settle for 20-24 hours. The resulting
supernatant MAP is siphoned off for immediate use in
bioassays. The MAF is similar to the SPP but has a
longer settling time, so the concentration of
particulates in the supernatant is lower.
Filtered Mud Aqueous Fraction (FMAF). The mud aqueous
fraction of whole drilling fluid is centrifuged and/or
passed through a 0.45ym filter and the resulting
solution is the filtered mud aqueous fraction.
Used muds appear to exhibit higher toxicity than new muds.
although this question remains controversial. Neff et al..
(1981) cite decomposition of organic materials during the
drilling process as the probable cause of increased toxicity of
4-10
-------
used drilling fluids. For example, the high temperature,
pressure, and alkalinity characteristic of downhole drilling
conditions can decompose chrome lignosulfonate to phenolic
compounds such as vanillin and isoeugenol (Carney and Harris,
1975, as cited in Neff et al.. 1981). The presence of diesel
oil in the used drilling mud has also been shown to contribute
to increased toxicity (Conklin et al., 1983; Duke and Parrish.
1984).
4.3.1 Acute Toxicity of Drilling Fluids
Acute toxicity tests of whole drilling fluids have
generally produced low toxicity. Petrazzuolo (1983a) sum-
marized the results of 415 such tests of 68 muds in 70 species
and found 1 to 2 percent had LC ' s ranging from 100 to 999
ppm. 6 percent had LC 's ranging from 1.000 to 9,999 ppm.
46 percent had LC 's ranging from 10.000 to 99.999 ppm. and
44 percent had LC 's of greater than 100.000 ppm (Table 4-1).
The toxicity level nomenclature is that of Hocutt and Stauffer
(1980). For purposes of comparison, almost all acute toxicities
to marine organisms for EPA's 129 priority pollutants fall into
the range from 0.007 ppm to 270 ppm (EPA. 1980a-i).
Test results also indicate that whole drilling fluid is more
toxic than the aqueous or particulate fractions (Table 4-2).
These data show whole fluid toxicity ranging from one to five
times that of the aqueous fraction, and 1.3 times the toxicity
of the particulate fraction. Acute toxicity tests for used
drilling fluids and drilling fluid components are shown in
Table 4-3. Criterion values for drilling fluid fractions in
the table are converted to whole fluid equivalents. For
example, the MAF is prepared by mixing one part drilling mud
4-11
-------
TABLE 4-1 SUHHARY TABLE Of THE ACUTE LETHAL TOXICITY OF DRILLING FLUID
Phy top lank ton
Invertebrates
Copepods
Isopods
Amphipods
Gastropods
Decapods
Shrimp
Crab
Lobster
Bivalves
Echinoderms
Nysids
Annelids
Finfish
TOTALS
Percentages as a fraction
of the total number of tests
Number of
species
tested
1
I
2
4
5
9
8
1
11
2
4
7
15
48
70
Number of
fluids
tested
9
9
4
11
5
23
18
2
22
2
17
14
24
40C
68
Number of
tests
12
11
6
22
10
66
32
7
59
4
64
34
80
303
415
392«
Nut
de terminable
5
1
0
0
0
0
1
0
19d
0
2(1)<*
3**
0
31(23)d
21
Number of 96-hour LC values (ppm)'
< 100
0
0
0
0
0
0
0
0
0
0
0
0
0
0
01
100-999
0
3
0
0
0
6(l)b
0
0
0
0
0
0
0
4-9
2.41
(|%)b
1000-9999
7
5
0
0
0
5
3
1
1
0
1
0
2
25
61
10.000-99.999
0
2
1
7
2
36
17
3
19
1
29
12
SO
179
461
> 100. 000
0
0
5
15
8
19
11
3
20
3
32
19
36
171
441
Average percentage in a category
for each group of animals
5.31
01
2.81
9.41
331
SOI
Adapted from Petrazzuolo (1983a).
a Placement in classes according to LC^g value.
Lowest boundary of range if L&JQ expressed as a range.
Cited values if given as >" "<". There were 199 such LC^n values; 95 were 100.000 ppm; 20 were <3,200 pom.
b These include tests conducted on drilling fluids obtained from Mobile Bay. Alabama, and which may not be representative of
drilling fluids used and discharged on the OCS. The value in parenthesis is the result of not including those drilling fluids.
c The fluids used in Gerber et al . . 1980. Neff et al.. 1980, and Carr et al. 1980 were all supplied by API. Their characteristics were very
similar and they may have been subsamples of the same fluids. If so. the total number of fluids tested would be 35.
d Data not available.
e iknfcer of tests with actual data.
-------
TABLE 4-2 COMPARISON OF WHOLE FLUID TOXICITY AND
AQUEOUS AND PARTICULATE FRACTION TOXICITY FOR
SOME ORGANISMS
(Petrazzuolo. 1981)
Whole fluid vs. Whole fluids vs.
Organism aqueous fraction particulate fraction
Gammarus (amphipod) > 1.4 to 3.6:1
Thais (gastropod) > 1.2:1
Cranaon (shrimp) > 1.1 to 1.4:1
Carcinus (crab) > 1.1 to 1.5:1
Homarus (lobster) > 3.5 to 5.3:1
Strongylocentrotus
(sea urchin) > 2:1
Coreqonus (whitefish) < 1.7:1
Neomvsis (shrimp) 1.3:1
4-13
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless otherwise noted; adapted from Petrazzuolo, 1981)
Test organism
Fluid description3
Criterion value (pan)
Toxicity
rating*1 Reference*:
USED DRILLING FLUIDS
ALGA
Skeletonema costatum
COPEPODS
Acartia tonsa
Imco LDLS/SW
Imco Lime/SW
Imco non-dispersed/SW
Lightly treated LS/SW-FW
Imco LDLS/SU
Imco Lime/SW
Imco non-dispersed/SW
Lightly treated LS/SW-FW
FCLS/FW
Saltwater Gel
1,325-4.700 (96-h EC50)
1,375 (%-h EC50)
5,700 (96-h EC50)
3,700 (96-h EC50)
5.300-9,300
5.600
66,500
10,000
100-230
100
ISOPODS
Gnori mosphaeroma oregonsis
Saduria entomon
AHPHIPODS
Anisoqamnarus confervicolus
Onisimus sp./Boekisina sp.
Gamnarus locusta
GASTROPODS
Nautica clausa. Neptuna sp.,
4 Buccinum sp.
Littorina littorea
Thais lapillis
FCLS/FW
XC-Polymer/Unical
CMC-Resinex Tannathin-Gel
FCLS/FW
FCLS/FW
XC-Polymer/Unical
Spud mud
HOLS
HOLS (NAF)
HOLS
HOLS (HAF)
CMC-Resinex Tannathin-Gel
LDLS (NAF)
LDLS
LDLS (NAF) ,
LOLS (suspended WN)
MOLS
MOLS (NAF)
HOLS
HOLS (MAF)
70,000 5-6 3
314,000-500,000 6 4
530,000-600,000 6 4
10,000-50,000 5 3
10,000-200,000 (48-h LC50) 5-6 3
200,000-436,000 6 4
100.000 6 5
74,000-90,000 5 5
100,000 6 5
28.000-88.000 5 5
100.000 6 5
600,000-700,000 6 4
100,000 6 5
83,000 5 5
100,000 6 5
15.000 5 5
100,000 6 5
100,000 6 5
100,000 6 5
100,000 6 5
4-14
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCso unless otherwise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
Fluid description*
Criterion value (pom)
Toxicity
rating5 Reference0
OECAPOOS-SHRINP
Artemia salina
Pandalus hypsinotus
Cranqon septemsoi nosa
Pandalus boreal is
Stage I larvae
Palaenonetes pugio
Stage I zoeae
Adults
Stage HI zoeae
Late premolt stage
02-04
Palaenonetes puqio
larvae
Penaeus aztecus
juvenile
FCLS/FW
FCLS/FW
Spud mud (NAF)
Seawater LS (NAF)
LOLS
LDLS (suspended UN)
LOLS (NAF)
HOLS
NOLS (suspended UN)
HOLS (NAF)
NOLS (FNAF)
HOLS
HOLS (suspended UN)
HOLS (NAF)
HOLS (FNAF)
HOLS (NAF)
HOLS (FNAF)
Spud mud (NAF)
Seawater-chrone LS (NAF)
NOLS (NAF)
HOLS (NAF)
HOLS (SPP)
Spud mud (NAF)
SeaiMter-chrame LS (NAF)
HOLS (NAF)
HOLS (NAF)
Lightly treated LS
HOLS (SPP)
Mobile Bay fluid
Mobile Bay fluid
Seawater LS
Lightly treated LS
Freshwater LS
Lime
FW/SW-LS
Non-dispersed
LTLS
Seawater -K-pol ymer
Seawater-chrome LS (NAF)
HOLS (NAF)
100,000 (48-h LCSO)
32,000-150,000
50,000-100,000 (48-h LCSO)
100,000
100,000
71,000
15,000
98,000-100,000
82,000
15,000
17,000
19,000
92,000
15,000
100,000
100,000
65,000
55,000
100,000
27,500
35,000
18,000
11,800
100,000
92,400
91,000
100,000
201
11,700-13,200
318-863
360-14,560
1,706-28,750
142
4,276-4,509
658
3,570
100,000
35,420
2,557
41,500
16,000
6
5-6
5
6
6
5
5
5
5
5
5
5
5
5
6
6
5
5
6
5
5
5
5
6
5
5
6
3
5
3
3-5
4-5
3
4
3
4
6
5
4
5
5
3
3
3
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
6
6
6
6
6
6
6
6
6
11
6
7
9
11
11
11
11
11
11
11
11
6
6
4-15
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCso unless other-vise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
Orchestia traskiana
DECAPODS-CRABS
Carcinus maenus
Clibanarius vittatus
Hanigrapsus nudus
DECAPODS-LOBSTER
Hororus arericanus
Stage V larvae
Adult
Larvae
BIVALVES
Nodiolus modiolus
Mytilus edilus
Fluid description9
Seawater-pol ymer
Pelly gel Chemical XC
KCI-XC-Polymer
Weighted shell polymer
Gel-SX-polymer
Imnak gel -XC-pol ymer
LDLS
LDLS (suspended MM)
LOLS (NAF)
HOLS
MOLS (suspended UN)
NOLS (NAF)
HOLS (NAF)
Seawater-chrcme LS (NAF)
MOLS (NAF)
HOLS (NAF)
Seawater polymer
Shell Kipnik-KCl polymer
Pelly gell chemical XC
KC1 -XC-pol ymer
Weighted shell polymer
Pelly weighted gel -XC-pol ymer
Imnak gel -XC-pol ymer
LDLS (NAF)
HOLS
NOLS (NAF)
LDLS
LDLS (NAF)
Mobile Bay/Jay fluids
FCLS/FW
Spud mud (NAF)
Seawater LS (NAF)
HOLS (NAF)
NOLS (suspended UN)
HOLS (NAF)
HOLS (suspended UN)
Criterion value (ppm)
230,000
80,000
14.000
34,000
420,000500,000
560.000
89,100
15,000
100.000
68,000-100,000
15,000
100.000
100,000
28.700
34,500
65.600
530,000
53,000
560,000
78,000
62,000
560,000
560.000
5,000
100,000
29,000
19,000-25,000
100,000
73.8-500 ppm
30,000
30.000 (14 day LCSO)
100,000
100,000
100,000
15,000
100,000
15,000
Toxicity
ratinob
6
5
5
5
6
6
5
5
6
5-6
5
6
6
5
5
5
6
5
6
5
5
6
6
5
6
5
5
6
2-3
5
5
6
6
6
5
6
5
Referents'
8
8
8
8
8
8
5
5
5
5
5
5
5
6
6
6
8
8
8
8
8
8
8
5
5
5
5
5
10
3
3
5
5
5
5
5
5
4-16
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless otherwise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
Hacama balthica
Placopecten magellanicus
Crassostrea gigas
Donax variabilis texasiana
Hya arenaria
Hercenaria mercenaria
Larvae
ECHINOOERNS
Strongy 1 ocentrotus
droebachiensis
Fluid description3
LDLS
LDLS (HAF)
LDLS (suspended UH)
HOLS
HOLS (MAP)
HOLS (FHAF)
LOLS
HOLS
Spud mud (SPP)
HOLS (SPP)
HOLS (SPP)
Spud mud (SPP)
Seawater-chrane LS (SPP)
HOLS (SPP)
HOLS (SPP)
Seawater polymer
Kipnik-KCl polymer
Polly gel chemical XC
KCl-XC-polymer
Weighted shell polymer
Weighted gel XC-polymer
Weighted KCl-XC-polymer
Imnak gel -XC-polymer
Seawater LS (LP)
Seawater LS (SPP)
LTLS (LP)
LTLS (SPP)
FWLS (LP)
FWLS (SPP)
FW/SW LS (LP)
FW/SW LS (SPP)
Lime (LP)
Lime (SPP)
Low solids non-dispersed (LP)
Low-solids non-dispersed (SPP)
Potassium polymer (LP)
Potassium polymer (SPP)
LDLS
LDLS (HAF)
HOLS
HOLS (MAP)
Criterion value (pom)
100,000
100,000
15,000
100,000
100,000
100,000
49,000
3,200
100,000
50,000-53,000
73,000-74,000
100,000
53,700
29,000
56,000
320,000
42,000
560,000
56,000
10,000
560,000
560,000
560,000
87-3,000
117-3,000
719-3,000
122-2,889
319-330
158-338
380
82
682
64
3,000
3,000
269
220
55,000
100,000
100,000
100,000
Toxicity
rating0
6
6
5
6
6
6
5
4
6
5
5
6
5
5
5
6
5
6
5
5
6
6
6
2-4
3-4
3-4
3-4
3
3
3
2
3
2
4
4
3
3
5
6
6
6
Reference0
5
5
5
5
5
5
5
5
6
6
6
6
6
6
6
8
8
8
8
8
8
8
8
11
11
11
11
11
11
11
11
11
11
11
11
11
11
5
5
5
5
4-17
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless other-vise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
HYSIOS
Neomysis integer
Mysis sp.
Mysidopsis almyra
Mysidopsis bahia
POLYCHAETES
Melaenis loveni
Fluid description3
FCLS/FW
CMC-Gel
CMC-Gel -Resinex
XC-polymer (supernatant)
XC-polyror
Spud mud (MAF)
Seawater-chrome LS (MAF)
MDLS (MAF)
HOLS (MAF)
MOLS (SPP)
HOLS (MAF)
MDLS (MAF) (static test)
Reference mud (MAF) (static test)
Seawater LS
Seawater LS (LP)
Seawater LS (SPP)
Seawater LS (SP)
LTLS
LTLS (LP)
LTLS (SPP)
LTLS (SP)
FWLS
FMLS (LP)
FWLS (SPP)
Lime
Lime (SPP)
Lime (SP)
FW/SW-LS
FW/SW-LS (LP)
FW/SW-LS (SPP)
FW/SW-LS (SP)
Low-solids non-dispersed
Low-solids non-dispersed (LP)
Low-solids non-dispersed (SPP)
Low-solids non-dispersed (SP)
Potassium polymer
Potassium polymer (LP)
Potassium polymer (SPP)
CMC-Resi nex-Tannathi n
CMC-Resi nex-Tannath i n-Ge 1
Criterion value (ppm)
10,000-200,000 (48-h LCSO)
10,000-125,000
142,000-349,000
58,000-93,000
250,000
50,000-170,000
100,000
27,000
12,800-13,000
16,000-32,500
32,000
26,800-66,300
72,100-113,000
100,000
429-1,557
150,000
15,123-19,825
50,000
14-1,958
150,000
1,641-50,000
1,246-2,437
301-1,500
97,238-121,476
14,068-29,265
87-98
650-791
8,213-1,369,393
115-379
150,000
11,380-38,362
50,000
1,500
150.000
50.000
50,000
1,500
150,000
26,025-28,070
600,000
700,000
Toxicity
rating**
5-6
5-6
6
5
6
5-6
6
5
5
5
5
5
5-6
6
3-4
6
5
5
2-4
6
3-5
3
3-4
5-6
5
2
3
4-6
3
6
5
5
4
6
5
5
4
6
5
6
6
Reference0
3
3
4
4
4
4
6
6
6
6
12
12
12
12
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
4
4
4-18
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless otherwise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
Nereis virens
Qphrvotrocha labronica
Neve is vexillosa
TELEOST FISH
Menidia menidia
Qncorhynchus gorbuscha
Leptocuttus armatus
Hyoxocephalus quadricornis
Coregonus nasus
Elegonus naraga
Boreogodus saida
Coregonus autumnal is
Fluid description3
Spud mud (MAP)
Seawater-LS (MAF)
LOLS
LDLS (MAF)
NDLS
MDLS (MAF)
HOLS
HOLS (MAF)
Spud mud (MAF)
Seawater-chrome LS (MAF)
MDLS (MAF)
HOLS (MAP)
Seawater polymer
Kipnik-KCl polymer
Gel chemical XC
KCl-XC-polymer
Weighted shell polymer
Weighted gel XC-polymer
Imnak gel -XC-polymer
Imco LDLS/SW
Imco Lime
Imco non-dispersed
Saltwater gel
LSLS-SW/FW
FCLS
FCLS/FW
FCLS/FW
CMC-Gel
CNC-Gel-Resinex
XC-Polymer
XC-Polymer (supernatant)
Lignosulfonate
CMC-Gel
XC-Polymer
XC-Polymer (supernatant)
Lignosulfonate
CMC-Gel
XC-Polymer
Lignosulfonate
Lignosulfonate
Criterion value (com)
100,000
100.000
100.000
100.000
100.000
100,000
100.000
100,000
100,000
100,000
60,000
100,000
220.000
37.000
560,000
41,000
23,000
320,000-560,000
200,000
56,500-175,000
43.000-53,000
345,000-385.000
100.000
48,500
100,000
3,000-29,000
100.000-200.000
120,000
50,000-70,000
50,000-215.000
250,000
350,000
200,000
57,000-370,000
100.000-250,000
0-100,000
170,000-300.000
250.000
200,000-250,000
85,000-1,000,000
Toxicity
rating15
6
6
6
6
6
6
6
6
6
6
5
5
6
5
6
5
5
6
6
5-6
5
6
6
5
6
4-5
6
6
5
5-6
6
6
6
5-6
6
6
6
6
6
6
Reference0
5
5
5
5
5
5
5
5
6
6
6
6
8
8
8
8
8
8
8
1
1
1
2
2
2
3
3
4
4
4
4
4
4
4
4
4
4
4
4
4
4-19
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless otherwise noted; adapted from Petrazzuolo, 1981)
(Continued)
Test organism
Fundulus heteroclitus
Salmo qairdneri (juvenile)
Oncorhynchus kisutch
(juvenile)
0^ keta (juvenile)
OK. gorbuscha (juvenile)
Fluid description*
Spud mud (MAF)
Seawater-LS (MAF)
MDLS (suspended whole mud)
MDLS (MAF)
HDLS (suspended whole mud)
HOLS (MAF)
Kipnik-KCl polymer
Seawater polymer
KC1-XC polymer
Weighted shell polymer
Pelly gel chemical -XC
Weighted gel XC-polymer
Imnak-Gel XC-polymer
Kipnik-KCl polymer
Seawater polymer
KC1-XC polymer
Weighted shell polymer
Pelly Gel chemical-XC
Weighted gel XC-polymer
Imnak-Gel XC-polymer
Kipnik-KCl polymer
Kipnik-KCl polymer
Criterion value (com)
100,000
100,000
15,000
100,000
15,000
100,000
24,000-42,000
130,000
34,000
16,000
42,000
18,000-48,000
42,000
29,000
130,000
20,000-23,000
4,000-15,000
28,000-130,000
24,000-190,000
23,000-30,000
24,000
41,000
Toxicity
rating
6
6
5
6
6
6
5
6
5
5
5
5
5
5
5
5
4^5
5-6
5-6
5
5
5
Reference1
5
5
5
5
5
5
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
DRILLING FLUID COMPONENTS
Skeletonema costatum
Arcartia tonsa
Panda 1 us hypsinotus
Molliensias latipinna
Penaeus setiferus
Barite
Aquagel
Barite
Aquagel
Barite
Aquagel
Barite
Calcite
Siderite
Chrome lignosulfonate
quebracho
Lignite
Sodium acid pyrophosphate
Hemlock bark extract
Pol yacry late
CaC03 workover additive
Chrome-treated lignosulfonate
Lead-treated lignosulfonate
385-1,650
9,600
590
22,000
100,000
100,000
100,000
100,000
100,000
7,800-12,200
135-158
15,500-24,500
1,200-7,100
265
3,500
1,925
465
2,100
3-4
4
3
5
6
6
6
6
6
4-5
3
5
4
3
4
4
3
4
2
3
2
2
3
3
13
13
13.
14
14
14
14
15
15
15
IS
15
4-20
-------
TABLE 4-3 ACUTE LETHAL TOXICITIES OF USED DRILLING FLUIDS AND DRILLING FLUID COMPONENTS TO MARINE ORGANISMS
(96-hour LCjQ unless otherwise noted; adapted from Petrazzuolo, 1981)
(Continued)
a Drilling fluids abbreviations (fluid fractions in parenthesis):
Fractions: WH = Whole Mud Descriptions: /SW = Saltwater dispersant
MAP . Mud aqueous fraction /FU = Freshwater dispersant
FMAF - Filtered mud aqueous fraction LS = Lignosulfonate
SPP - Suspended particulate phase LDLS = Low density lignosulfonate
SP = Solid phase MOLS = Medium density lignosulfonate
LP - Liquid phase HOLS = High density lignosulfonate
LTLS = Lightly treated lignosulfonate
FCLS = Ferrochrome lignosulfonate
b Toxicity ratings as per Hocutt & Stauffer. 1980.
1. Very toxic (1 ppm)
2. Toxic (1-100 ppm)
3. Moderately toxic (100-1,000 ppm)
4. Slightly toxic (1,000-10,000 ppm)
5. Practically non-toxic (10,000-100,000 ppm)
6. Non-toxic (100,000 ppm)
c References:
1. Imco, 1977.
2. Shell Oil Co., 1976 as cited in Petrazzuolo, 1981.
3. Atlantic Richfield, 1978, as cited in Petrazzuolo, 1981.
4. Tornberg et al., 1980.
5. Gerter et al., I960.
6. Neff et al., 1980.
7. ConkHn et al., 1980.
8. Environmental Protection Service, 1975, as cited in Petrazzuolo, 1981.
9. Conklln et al., 1983.
10. Capuzzo and Derby, 1982.
11. Duke et al., 1983 (or Rao, 1983).
12. Carr et al., 1980.
13. Qrantham and Sloan, 1975, as in Petrazzuolo, 1981.
14. Hollingsworth and Lockhart, 1975.
15. Chesser and McKenzie, 1975.
4-21
-------
with nine parts seawater, so an LC value derived from 100
percent MAF is actually the supernatant from a 10 percent
drilling fluid mixture and is therefore expressed as 100.000
ppm (10 percent whole fluid equivalent).
The calanoid copepod Acartia tonsa is one species that
exhibited sensitivity to drilling fluid and displayed a 96-hour
LC5Q of 100 ppm for both a used seawater gel and a
ferrochrome lignosulfonate freshwater drilling fluid (Shell Oil
Company. 1976. as in Petrazzuolo. 1981). A replicate test of
the ferrochrome lignosulfonate mud showed a 96-hour LC of
230 ppm. confirming the earlier results. IMCO Services (1977.
as in Petrazzuolo. 1981) conducted a study exposing Acartia
tonsa to four light-density lignosulfonate fluids, a lime
fluid, and a nondispersed fluid (primarily barite and
bentonite) with 96-hour LC results of 5.300 to 9.300 ppm
for the first five fluids, and 66.500 ppm for the nondispersed
fluid.
Pink salmon fry (Onchorhyncus qorbuscha) and several
species of Crustacea including a shrimp (Pandalus hypsinotus).
a mysid (Neomysis integer). an amphipod (Eoqammarus
confervicolus). and an isopod (Gnorimosphaeroma oregonensis)
were exposed to used high-density lignosulfonate drilling fluid
from Lower Cook Inlet. Alaska. Pink salmon fry were the most
sensitive, with 96-hour LC^'s ranging from 3.000 ppm for the
SSP to 24.000 ppm for LSP. The range for crustaceans was from
32,000 to more than 200.000 ppm (Houghton et al.. 1981).
In another experiment, stage 1 larvae of king crab, tanner
crab, dungeness crab, coonstripe shrimp, dock shrimp, and kelp
shrimp were exposed to LSP and FMAF of new and used drilling
4-22
-------
fluids. The 144-hr LC50's for the most toxic drilling fluid
ranged from 500 to 9.400 ppm for the LSP and 6.000 to 6.700 ppm
for the FMAF. indicating that the LSP fraction was more toxic
than the FMAF. The particulate fraction was estimated to
account for 80 percent of the observed toxicity. and the water-
soluble fraction the remaining 20 percent (Carls and Rice.
1981).
Tornberg et al. (1980) found used drilling fluids to be of
low toxicity to arctic marine organisms (Table 4-4). The
96-hour LC 's ranged from 40.000 to 700.000 ppm.
Seven arctic polymer drilling fluids were used for toxicity
testing of salmon (Houghton et al.. 1981). Five of the seven
fluids displayed a 96-hour LC__ of less than 40.000 ppm for
bU
the SSP fraction; the most toxic fluid had a 96-hour LC of
15.000 ppm. and the least toxic fluid a 96-hour LC of
190.000 ppm. Clam worms (polychaetes). soft-shelled clams.
purple shore crabs, and sand fleas had approximately the same
sensitivity to the fluids as did the salmon. These
invertebrate 96-hour LC 's ranged from 10.000 to more than
560.000 ppm.
In another cold-water test, Gerber et al. (1980) exposed
organisms to a seawater lignosulfonate mud and found 96-hour
LC 's ranging from 320.000 to greater than 1.000.000 ppm MAF
(corresponding to 32.000 to greater than 100.000 ppm whole
drilling fluid). When exposed to the LSP of a low-, medium-.
and high-density lignosulfonate drilling fluid and spud mud
(Table 4-5), adult sea scallops and adult lobsters were the
most sensitive of the cold-water organisms tested, with 96-hour
LC 'B of 3.200 ppm and 290,000 ppm. respectively.
4-23
-------
TABLE 4-4 TOXICITY OF LAYERED SOLID PHASE (LSP) OF
USED DRILLING FLUIDS TO ARCTIC MARINE ORGANISMS
(Totnberg et al.. 1980)
Organism
96-hr LC50 (ppm)
Isopods, snails, polychaetes
Mysids
Amphipods
Broad whitefish
Four horn sculpin
Arctic cod
Saffron cod
400.000 to
60,000 to
220.000 to
60.000 to
40.000 to
200.000 to
170.000 to
700,000
220,000
380,000
370.000
350.000
250.000
300.000
4-24
-------
TABLE 4-5 96-HOUR LC5o's FOR SEVERAL SPECIES EXPOSED
TO FOUR DRILLING FLUIDS
Whole mud LCso's (ppm)
Species
Crustaceans
Crangon septemsplnosa
Gammarus locusta
G. locusta
Pandalus borealls
(Stage I)
Cardnus maenas
Honnarus amerlcanus**
Bivalve Mollusks
Hvtnus edulls
Macoma balthlca
Placopecten magellanlcus
HDLSa
92,000
28,000
88,000
>100,000
>100,000
MDLSa
82,000
74,000
90,000
68,000
29,000
<3,200C
LDLSa
71,000
89,000
19,000
>100,000
49,000
SMa
>100,000
>100,000
Gastropod Mollusks
L1ttor1na llttorea >100,000 <100,000
Thais 1ap1111s 83,000
Polychaete Worms
Nereis vlrens >100,000 >100,000 >100,000
Echlnoderms
Strongvlocentrotus sp. >100,000 55,000
F1sh
Fundulus heteroclltus >100,000
Gerber et al., 1980
a HDLS = High density Hgnosulfonate drilling mud.
MDLS = Medium density llgnosulfonate drilling mud.
LDLS = Light density llgnosulfonate drilling mud.
SM = Spud mud.
b Mud Aqueous Fraction (MAF) changed dally.
c This value 1s 1n ml of mud/Hter of seawater and represents a 1mm
thick layer spread over natural mud 1n the aquarium.
4-25
-------
Neff et al. (1981) exposed several marine species to used
chrome lignosulfonate drilling fluids and attributed the solid
and liquid phase lethality to different mechanisms. They
hypothesized that the lethality of the liquid fraction (MAP)
stemmed from toxic effects of the water soluble compounds.
especially volatile organic compounds. The solid fraction
lethality was thought to be caused by both chemical toxicity of
soluble mud components, gill clogging from the suspended solids
phase, and smothering for the layered solid phase.
Petrazzuolo (1981) used a semi-quantitative procedure to
rank organisms in terms of sensitivity to drilling fluids,
based on laboratory tests. The results ranked groups of
organisms as follows, in order of decreasing sensitivity:
copepods and other plankton; shrimp; lobster; mysids and
finfish; bivalves; crab; amphipods; echinoderms; gastropods and
annelids; and isopods. This ranking is admittedly biased
because it is limited by the actual bioassay test results which
have been published, and not based on theoretical
considerations. For example, if more tests, more toxic
drilling fluids, and more sensitive life stages have been
tested on certain types of organisms, they would appear to be
more sensitive in the rankings. These shortcomings
notwithstanding, the ranking is a reasonable general indicator
of the relative sensitivity of organisms to drilling fluid.
Toxicity tests also highlight the toxicity variations which
occur during a given organism's life cycle. Larval stage
organisms are more sensitive than adult stages, and animals are
more sensitive while molting than during intermolt stages.
These variations affect the potential for impact associated
with, offshore operations. Drilling fluids discharged into an
4-26
-------
area occupied by an adult community will presumably cause less
impact than if the area were occupied by juvenile communities
or serves as a breeding ground. Many organisms, including
several commercially important species, have breeding or
nursery grounds in estuaries or salt marshes.
As drilling progresses on a given hole, increasing temper-
ature and pressures place increasing demands on the properties
of the drilling mud. This often necessitates the use of
greater quantities of both basic and specialized mud compo-
nents, which will presumably increase mud toxicity- Thus,
while every well is different, it is reasonable to expect a
general trend of increasing mud toxicity with increased well
depth. However, the addition of specialty additives is dic-
tated by well-specific needs which may be more severe at one
geologic stratum than another, and thus, mud taken from that
stage of drilling may contain more additives and be more toxic
than deeper stages.
Some drilling fluids have exhibited toxicities much higher
than average. One drilling fluid from Mobile Bay, Alabama,
exhibited a 96-hour LC_rt of approximately 100 ppm. Other
50
experiments by Rubenstein and Rigby (1980) found mortality to
lugworms, some toxicity to mysids. and inhibition of oyster
growth at concentrations less than 100 ppm. in 10-100 day
flow-through bioassay experiments. Analyses of these fluids
indicate hydrocarbon distributions characteristic of diesel
oil. which contribute significantly to the toxicity but are
probably not its sole source. However, the Mobile Bay fluid
was subject to Alabama's restrictions prohibiting oil and gas
activity discharges into territorial waters, and industry has
argued that the fluid was formulated with the intention that it
would not be discharged.
4-27
-------
Several recent studies have examined the relationship
between diesel oil content and the toxicity of drilling
fluids. An EPA project team has recently completed bioassays
on samples of eleven drilling fluids collected from operating
rigs in the Gulf of Mexico. The rigs were chosen at random and
represent different geographical areas and well depths.
The preliminary results of the many tests conducted are
presented in Table 4-6. Bioassays with Mysidopsis bahia
revealed that whole muds were more toxic than the various
fractions, and that the suspended solid phase was consistently
more toxic than the liquid phase. Whole mud 96-hour LC ' s
ranged from 14 to 1.958 ppm. Two of the mud samples had mean
LC 's in the range from 10 to 99 ppm. and four in the range
from 100 to 999 ppm. The 96-hour LC values for the
suspended particulate phase ranged from 650 to > 50.000 ppm.
Toxicity tests with larvae of the grass shrimp
(Palaemonetes puqio) (Table 4-7) indicated that they are not as
sensitive to whole muds as the raysids. Average 96-hour LC
values for whole muds ranged from 142 to 100.000 ppm.
Mercenaria mercenaria one-hour larvae showed a lack of
development (48-hour EC ) at relatively low concentrations
of the liquid and suspended solids phases of the muds
(Table 4-8). Concentrations as low as 87 and 64 ppm
(respectively) halted larval development. Similarly.
embryogenesis of Fundulus and echinoderms was affected by
drilling fluid exposure. "Safe" levels (defined as a
concentration of 10 percent of that having an adverse effect on
the most sensitive assay system) ranged from one to 100 ppm. A
study of sublethal effects of drilling mud on corals (Acrooora
4-28
-------
TABLE 4-6 TOXICITV OF USED DRILLING FLUIDS TO MYSIOS (HYSIDOPSIS BAHIA)
Duke and Parrish (I960)
EPA Hud
Code
NIB
ANSI
SV76
PI
P2
"F" P3
vo
P4
P5
P6
P7
P8
Hud Type
Seawater lignosulfonate
Seawater lignosulfonate
Seawater lignosulfonate
Lightly treated
lignosulfonate
Freshwater lignosulfonate
Lime
Freshwater lignosulfonate
Freshwater/seawater
lignosulfonate
Low solids nondispersed
Lightly treated
lignosulfonate
Seawater/potass i um/pol ymer
Wnole Hud
H.5003
1.008(541-1.557)
733 (429-888)
26(14-39)
459 (301-732)
92 (87-98)
>1.500
263(115-379)
>1,500
728(470-1,958)
>1.500
96-Hour LC5Q
Liquid Phase
NT4
>150,000
» 50, 000
>150,000
116,419
(111,572-121,476)
97,238
>150,000
>150,000
>150,000
>150,000
(pom: ul/1)
Suspended
Particulate
Phase2
NT
NT
17.633
(15,123-19.835)
1,936
(1,641-2.284)
18,830
(14,068-22,522)
726
(650-791)
27,233
(24,791-29,265)
24,770
(11,380-38,362)
>50,000
>50.000
27,137
(26,025-28,070)
Solid Phase
NT
NT
>50,000
1.456
(1,246-2,437)
NT
11,304
(8,213-1,369,393)
NT
>50.000
>50.000
NT
NT
Adapted from Duke and Parrish. 1984.
'Results of probit analyses; 951 confidence limits are in parentheses.
2lhe suspended particulate phase (SPP) was prepared by mixing 1 part drilling fluid with 4 parts seawater.
Therefore, these values should be multiplied by 0.20 in order to relate the 1:4 dilution tested to the SPP of
the whole drilling fluid.
3The toxicity concentrations for the "greater than" values (>1,500, >150,000, >50,000) were arbitrarily selected
for these specific tests.
4Not tested.
-------
TABLE 4-7 DRILLING FLUID TOXICITY TO GRASS SHRIHP
(PALAEHONETES INTERMEDIUS) LARVAE1
Hud
NIB
ANSI
SV76
PI
P2
P3
P4
P5
P6
P7
P8
NBS
Reference
lype
Seawater L i gnosu1fonate
Seawater L i gnosu1fonate
Seawater L i gnosu1fonate
Lightly Treated LignosuIfonate
Freshwater LignosuIfonate
Lime
Freshwater L i gnosu1fonate
Freshwater/Seawater L i gnosulfonate
Low Solids Nondispersed
Lightly Treated LignosuIfonate
Seawater/Potass i urn/Pol ymer
96-h LC50(95t CD
28,750 ppm (26,332-31,274)
2,390 ppm (1,896-2,862)
1,706 ppm (1,519-1,922)
142 ppm (133-153)
4,276 ppm (2,916-6,085)
658 ppm (588-742)
4,509 ppm (4,032-5,022)
3,570 ppm (3,272-3,854)
100,000 ppm
35,420 ppm (32,564-38,877)
2,577 ppm (2,231-2,794)
17,917 ppm (15,816-20,322)
'All tests conducted at 20 ppt salinity and 20+2°C with Day-1 larvae
(Conklin and Rao, in press).
Adapted from Duke and Parrish (1984).
4-30
-------
TABLE 4-8
RESULTS OF CONTINUOUS EXPOSURE (48 h) of 1-h OLD FERTILIZED EGGS
OF HARD CLAMS (Hercenaria tnercenaria) TO LIQUID AND SUSPENDED
PARTICULATE PHASES OF
EACH TEST CONTROL (n =
STRAIGHT-HINGE OR "D"
Drilling
Fluid
AN31
HIB
SV76
PI
P2
P3
P4
P5
P6
P7
P8
Liquid Phase
EC5o (ul/1)2
2,427(2,390-2,463)
>3,000
85(81-88)
712(690-734)
318(308-328)
683(665-702)
334(324-345)
385(371-399)
>3,000
>3,000
269(257-280).
VARIOUS DRILLING FLUIDS . THE PERCENTAGE OF
= 625+125 eggs) THAT DEVELOPED INTO NORMAL
STAGE LARVAE AND THE EC^ IS GIVEN1
Control 1
"0" Stage
88
95
88
97
97
98
98
98
97
97
93
Suspended
Particulate
EC50_M/U2
1,771 (1,710-1,831)
>3,000
117(115-119)
122(89-151)
156(149-162)
64(32-96)
347 (330-364)
382(370-395)
>3,000
2,799(2,667-2,899)
212(200-223)
Control t
"0" Stage
93
95
93
99
99
99
99
99
93
93
93
1 Fran NEA (1984) in Duke and Parrish (1984).
2 ECijg and 951 confidence limits.
4-31
-------
cervicornis) indicated a decrease in the calcification rate and
changes in amino acids at concentrations of 25 ppm.
All of the muds tested in this study were found to contain
some No. 2 fuel (diesel) oil. Surrogate "Diesel" oil content
ranged from 0.10 to 9.43 mg/g in the whole mud. Spearman Rank
Order Correlation of the relationship between toxicity and fuel
oil content showed a significant correlation between these
factors in all tests. In all cases, the drilling fluids with
higher diesel oil contents were more toxic to the organisms
tested. A higher correlation was found with "diesel"
(equivalent to API #2 fuel oil) content than with either
aromatic or aliphatic content. Toxicity also correlated better
with organics in the suspended particulate phase than with
organics in the whole mud. except for aromatics.
Chemical Content
Toxicity Aromatic Aliphatic "Diesel"
Whole Mud -0.79 -0.77 -0.81
Suspended Particulate Phase -0.77 -0.89 -0.96
Since all of the muds contained some diesel oil. and the oil is
clearly a factor in toxicity, then addition of diesel oil is a
likely contributor to the increased toxicity of used versus
unused drilling fluids.
Duke and Parrish (1984) found a significant negative
correlation (-0.976) between 96-hour LC and mineral oil
50
content of two generic muds. The mineral oil was added in
concentrations of 1 percent. 5 percent, and 10 percent to
generic muds #2 and #8. When 1 percent mineral oil was added.
4-32
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the 96-hour LC decreased from 51.6 percent to 13.4 percent
for generic mud #2 and from 29.3 percent to 7.1 percent for
generic mud #8. With 10 percent mineral oil. the LC
dropped to 0.49 percent for mud #2 and 0.76 percent for mud #8.
Conklin et al. (1983) also found a significant relationship
between the toxicity of drilling fluids and diesel oil
content. Their study was designed to assess the roles of
chromium and petroleum hydrocarbons in the total toxicity of
whole mud samples from Mobile Bay to adult grass shrimp
(Palaemonetes puqio). The range of 96-hour LC values was
from 360 to 14,560 ppm. The correlation between chromium
concentration of the mud and the LC value was not
50
significant; however, the correlation between diesel oil
concentration and the LC value was significant. As the
concentration of diesel oil in the muds increased, there was a
general increase in the toxicity values. Similar toxicity
tests using juvenile sheepshead minnows (Cyprinodon varieqatus)
showed higher LC levels but no significant correlation
between either chromium or diesel oil content and toxicity.
Capuzzo and Derby (1982) examined the effects of drilling
fluids on the developmental stages of the American lobster.
They tested a land-based "Jay" fluid and two fluids from Mobile
Bay. The lowest 96-hour LC observed was less than 100
ppm. Again, the toxicity of a particular fluid was apparently
related to the diesel oil content. The fluid exhibiting the
lowest toxicity contained no diesel oil. while the two fluids
with the highest toxicity contained two and four percent diesel
oil. respectively.
4-33
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Breteler et al. (1984) have examined the acute toxicity of
the suspended particulate and solid phases of a laboratory
formulated generic mud to which various amounts of mineral oil
and diesel fuel had been added. Animals tested included Mya
arenaria. the sandworm Nereis virens. and the grass shrimp
Palaemonetes puqio. The results generally agree with those of
previous studies. Mud to which diesel fuel had been added was
the most toxic, and the base mud was the least toxic. Hud to
which mineral oil had been added showed a toxicity between
these two extremes, and was approximately an order of magnitude
less toxic than diesel oil.
Addition of 0.5 percent to 5 percent mineral oil to the
base mud increased the toxicity of the suspended particulate
phase proportionally, resulting in a "moderate" toxicity at the
5 percent additive level. The suspended particulate phase of
mud containing 5 percent low or high sulfur diesel fuel
additive resulted in 50 percent mortality among mysid shrimp at
45 and 28 ppm mud added, respectively. Toxicity was directly
proportional to the concentration of added diesel fuel in the
mud. It is noted that substantial fractions of the toxic
aromatics in their mud were probably lost during handling and
preparation of the mud for testing, and. thus the results
likely underestimate the acute toxicity somewhat.
No mortality was observed in the marine animals following
exposure to the solid phase of the mud containing 0.5 to 5
percent mineral oil. However, the solid phase of muds
containing diesel fuel were toxic, with the high sulfur diesel
being more toxic than the low sulfur diesel.
There are still some unresolved issues with regard to
toxicity- One is the actual cause(s) of toxicity; another is
4-34
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consistency (a) foe the same muds and (b) between
laboratories. In 1981 EPA required a series of bioassays be
performed on generic muds that were to be used in Regions I and
II. The tests were duplicated at two laboratories
using sample splits of each mud type. Results (Table 4-9)
were, in some cases, comparable and at other times different by
an order of magnitude. There were general guidelines as to how
samples were handled and tests performed, but much of the
observed differences may be due to differences in the protocols
used by different laboratories. EPA has since published a more
detailed protocol for the handling and testing of samples
(Petrazzuolo. 1984).
A second source of discrepancy is in the types of drilling
muds. Generic muds are defined by a range for each component
and separate batches of a generic mud given the same name may
show differing toxicity. Tests on two sets of No. 2 and No. 8
muds provided to EPA and ERGO produced the following LC 's
whole mud equivalents (Duke et al.. 1984. ERGO 1984).
ERGO EPA
#2 7.100 ppm 62.000 ppm
#8 16.000 ppm 30.000 ppm
Unfortunately, chemical analyses were not reported for the
muds used in the ERGO tests and so the possible cause of
toxicity difference cannot be explained. EPA did. however, get
good correspondence when comparative tests were performed on
muds from the same batch at the Gulf Breeze and Narragansett
laboratories.
4-35
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TABU 4-9
SUMMARY OF BKMSSAYS(l)
Toxicitv Data(3)
Hud
No. Hud Type (4)
1 Potassium/Polymer/
Seawater
2 Lignosulfonate
3 Lime
4 Nondi spersed
5 Seawater Spud Hud
t*
1
w
o»
6 Seawater/Freshwater
Gel
7 Lightly Treated
Lignosulfonate
8 Lignosulfonate
Freshwater
Density
(I/gal) Laboratory
9.3 ERGO
NA(5)
12. 1 ERCO
KA(5)
10.4 ERCO
NA
9.2 ERCO
NA
8.2 ERCO
NA
9.3 ERCO
NA
9.6 ERCO
NA
9.3 ERCO
NA
Bysid Shriap (LC^-pom) 26 hr.
Liquid Suspended Parti oil ate
66.000
58.000
283.000
880.000
393.000
55% Survival
at 1.000.000 ppM
91.7% Survival
at 1.000.000 pm
96.7% Survival
at 1.000,000 ppm
98.3% Survival
80% Survival
at 1,000.000 ppm
88.4% Survival
at 1.000.000 ppm
517.000
51.7% Survival
at 1.000.000 ppm
70% Survival
at 1.000.000 ppm
95% Survival
at 1.000.000 ppm
90% Survival
at 1.000.000 ppm
25.000
70.900
53,200
870.000
66.000
860,000
86. 7% Survival
at 1.000.000 ppm
88.3% Survival
at 1.000,000 ppm
96.7% Survival
at 1,000.000 ppm
88.3% Survival
at 1.000.000 ppm
224.000
51.7% Survival
at 1,000.000 ppm
55% Survival
at 1.000,000 ppm
86% Survival
at 1.000.000
506.000
75% Survival
at 1.000.000 ppm
Hard Clans (2)
Solid
90% Survival
88% Survival
83.0% Survival
70% Survival
100% Survival
94% Survival
100% Survival
100% Survival
100% Survival
100% Survival
100% Survival
100% Survival
97% Survival
100% Survival
99% Survival
99% Survival
(1) Procedures described in Annex I of protocols developed by EPA Region II and OOC (1980).
(2) 10-day exposure*
(3) Complete reports filed with EPA Regions I and II.
(4) Composition, properties and metals analysis attached.
(5) Nornundcau Associates*
Adapted from Michaels, 1984.
-------
While we know that certain additives, such as diesel oil
and mineral oil. increase the toxicity of drilling muds (Table
4-10). there is no simple explanation and several factors may
be involved. In recent tests by ERGO and EPA. low dissolved
oxygen levels (DO) were reported. This occurred in spite of
the fact that samples were aerated to bring DO up to saturation
before animals were added and aeration continued through the
experiment. Drilling muds do exhibit significant oxygen demand
(see Section 2) and the possibility of this being a factor in
toxicity tests has not been fully evaluated.
To further investigate this factor. LC data for eight
generic muds were correlated with a variety of oxygen related
parameters. These included 5-day biological oxygen demand
(BOD ). 20-day ultimate oxygen demand (UOD ). chemical
oxygen demand (COD), and total organic carbon (TOC). The data
used were those reported by Duke and Parrish (1984) for
LC 's. Oxygen demand and total organic carbon data were
taken from the CENTEC (1984) analysis of the same muds.
Spearman Rank correlations are listed in Table 4-11.
Correlations between toxicity and both BOD and UOD were
3 £\J
very high (0.87-0.97) with the highest correlation for BOD
(CENTEC activated seed in artificial sea water), which was the
best indicator of BOD tested by CENTEC (1984). There was not
quite as good a correlation between toxicity and either TOC or
COD (0.67) .
As indicated earlier, the oxygen levels in test chambers
were enhanced by aeration, and thus the strong correlation
between toxicity and oxygen demand is all the more surprising.
4-37
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TABLE 4-10
TOXICITY OF API #2 FUEL OIL, MINERAL OIL, AND OIL-CONTAMINATED
DRILLING FLUIDS TO GRASS SHRIMP (PALAEHONETES INTERMEDIUS) LARVAE1
Oil Total oil
Materials Tested Added Content
(fl/1) (Q/l)
API #2 fuel oil3
Mineral Oil4
P7 mud None 0.68
P7 mud + API #2 fuel 17.52 18.20
P7 mud + API #2 fuel oil (hot-rolled) 17.52 18.20
P7 mud + mineral oil 17.52 18.20
P7 mud + mineral oil (hot-rolled) 17.52 18.20
NBS reference drilling mud None 0
NBS mud + API #2 fuel oil 18.20 18.20
NBS mud + API #2 fuel oil (hot-rolled) 18.20 18.20
NBS mud -i- mineral oil 18.20 18.20
NBS mud + mineral oil (hot-rolled) 18.20 18.20
PI drilling mud None 18.20
96-h LC & 95%
50 2
(DWTKLU1/1)
1.4
(1.3-1.6)
11.1
(9.8-12.5)
35,400
(32,564-38,877)
177
(165-190)
184
(108-218)
538
(446-638)
631
(580-674)
17,900
(15,816-20,332)
114
(82-132)
116
(89-133)
778
(713-845)
715
(638-788)
142
(133-153)
Vrom Conklin and Rao (In press).
^95% confidence limits computed by using a "t" value of 1.96.
Properties: Specific gravity at 20°C, 0.86; Pour point -23°C; Visocity, Saybolt, 38°C,
36; Saturates, wtl 62; Aromatics, wt% 38; Sulfur, wt%, 0.32.
Properties: Specific gravity at 15.5°C, 0.84-0.87; Flash point, 120-125°C;
Pour point, -12 to -15°C; Aniline point, 76-78°C; Visocity, CST 40°C, 4.1 to 4.3; Color
Saybolt, +28; Aromatics, wtl, 16-20; Sulfur, 400-600 ppm.
Adapted from Duke and Parrish, 1984.
4-38
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TABLE 4-11
SPEARMAN RANK
CORRELATION BETWEEN LC50's AND THE FOLLOWING PARAMETERS
Parameter
Spearman
Rank
Using Max. Cone.
Spearman Rank
Adjusted for Ties
Using Max. Cone.
Spearman Rank
Adjusted for Ties
Using Ave. Cone.
BOD
5
2
BOD,
5
3
BOD,
5
TOC
COD
A
UOD20
5
0.96
0.86
0.87
0.67
0.67
0.95
0.91
0.93
0.83
0.85
0.64
0.64
0.93
0.88
0.97
0.69
UOD
20
0.93
0.90
1. Artificial seawater with CENTEC activated seed (BOD5).
2. Regular dilution water with regular seed (6005).
3. Artificial seawater matrix with polyseed (6005).
4. SOW Matrix (synthetic seawater) using CENTEC Activated Seed.
5. Regular dilution water using regular sewage seed (UOD2Q.)-
6. SOW matrix using polyseed (U002o)-
4-39
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BOD may in fact reflect some other property of the muds.
such as clay or lignite content, which is then responsible for
toxicity in the tests.
It is quite clear that much more information is needed to
clarify the issue of the causative factors for the acute
toxicity of muds. It is quite probable that some of the
mortality seen in these tests is due to physical aspects such
as burial or gill-clogging. This may explain the wide range of
toxicity shown by the eight generic muds (2.700 ppm - 65.000
ppm: Table 4-12).
4.3.2 Chronic Toxicity of Drilling Fluids
Petrazzuolo (1981. 1983a) and Houghton et al. (1981)
reviewed a number of toxicity tests designed to measure chronic
toxicity of drilling fluids. Several of these studies had to
be discounted because of flawed methods. Only data from those
studies found accurate and reasonable by Petrazzuolo and
Houghton are included below.
4.3.2.1 Stress Tests on Corals
There has been considerable investigation regarding the
effects of whole drilling fluids on corals, due to their
sensitivity, ecological interest, and presence in the Texas
Flower Garden Banks area, which is currently under exploration
(see Section 5). Respiration, excretion, mucous production.
degree of polyp expansion, and clearing rates for materials
deposited on the surface are all useful parameters for
indicating stress.
4-40
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TABLE 4-12 RESULTS OF ACUTE TOXICIIV
GENERIC DRILLING FLUIDS AND
TESTS WITH EIGHT LABORATORY-PREPARED
MYSIDS (HYSIDOPSIS BAHIA)
Test
Location
Gulf Breeze
Drilling
Fluid
.,
#2
*3
*4
#5
Definitive Test'
(96-h LC50& 95% CL)
2.7% SPP3
(2.5-2.9)
51.6% SPP
(47.2-56.5)
16.3% SPP
(12.4-20.2)
12% mortality in
100% SPP
12% mortality in
100% SPP
Positive Control
(96-h LC5Q & 95% CL)
5.8 ppm4
(4.3-7.6)
7.5 ppm
(6.9-8.1)
7.3 ppm
(6.6-8.1)
3.4 ppm
(2.8-4.1)
Same as for It]
Definitive Test2
(96-h LC5Q & 95% CL)
3.3% SPP
(3.0-3.5)
62.1% SPP
(58.3-65.4)
20.3% SPP
(15.8-24.3)
*6
#7
20% mortality in
100% SPP
65.4% SPP
(54.4-80.4)
29.3% SPP
(27.2-31.5)
6.0 ppm
(5.4-6.6)
Same as for «6
Same as for #3
68.2% SPP
(55.0-87.4)
30.0% SPP
(27.7-32.3)
Narragansett
2.8%
(2.5-3.0)
No mortality in
100% SPP
6.2 ppm
(4.4-11)
3.3 ppm
(2.6-3.8)
Adapted from Duke and Parrish, 1984.
'calculations by moving average; no correction for control mortality unless stated.
^Calculations by SAS* probit; correction for all control mortality. Analyses performed R. Clifton
Bailey, U.S. EPA, Program Integration and Evaluation Staff (WH-586), Office of Water Regulations and
Standards, Washington, D.C. 20460.
3The suspended participate phase (SPP) was prepared by mixing 1 part drilling fluid with 9 parts sea-
water. Therefore, these values should be multiplied by 0.1 in order to relate the 1:9 dilution tested
to the SPP of the whole drilling fluid.
^Corrected for 13% control mortality.
-------
Laboratory experiments using the corals Montastrea and
Diplora showed essentially unchanged clearing rates after
applications of calcium carbonate, barite, and bentonite. How-
ever, exposure to a used drilling fluid significantly decreased
clearing rates, although dose quantification was not possible
(Thompson and Bright. 1977. as in Petrazzuolo. 1981). When
seven coral species were studied using in situ exposures to
used drilling fluid (Thompson and Bright. 1980). Montastrea and
Aqaricia displayed no mortality after a 96-hour exposure to 316
ppm concentrations, but 100 percent mortality at the 1.000 ppm
level. Stress reactions were displayed by six species at the
316 ppm exposure level, including partial or complete polyp
retraction and mucous secretion. A similar response was
observed after a 96-hour exposure to 100 ppm.
Thompson, in an undated report to the USGS. exposed
Montastrea and Porites to used drilling fluids from a well of
4,200 m (13.725 ft) drilling depth. The corals were buried for
eight hours under the fluid and then removed to a sand flat to
observe recovery. The exposure produced tissue atrophy and
decay, formation of loose strands of tissue, and expulsion of
zooxanthellae (zooxanthellae are algae living within coral
cells in a symbiotic relationship), all indicative of severe
stress. The Montastrea colonies were dead 15 hours after
removal, and the Porites colonies were dead after 10 days.
The effects of thin layer application to these species were
also observed. In situ exposures of drilling mud produced no
apparent effects on clearing rates; however, laboratory
applica- tions did demonstrate effects. Applications of 10 ml
thick carbonate sand or drilling fluid from a depth of either
4.200 m (13.800 ft) or 1,650 m (5.413 ft) were applied to the
corals, with the following results:
4-42
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colonies in the sand experiment cleared themselves in 4
hours
colonies in the 1.650 m fluid experiment cleared them-
selves in 2 hours
colonies in the 4,200 m fluid experiment were 20 per-
cent (Montastrea) and 40 percent (Porites) cleared after
4 hours. 20 percent (Montastrea) and 100 percent
(Porites) cleared after 26 hours
Additional testing with Porites indicated that the 4.200 m
fluid was more toxic than the 1.650 m fluid, probably because
the use of additives increases with well depth. No data are
available on actual drilling fluid composition, however.
Krone and Biggs (1980) exposed the coral (Madracis
decactis) to suspensions of 100 ppm drilling mud from Mobile
Bay. Alabama, which had been spiked with 0. 3. and 10 ppm
ferrochrome lignosulfonate (FCLS). The drilling mud was pre-
sumably one with a low (< 1 ppm) FCLS concentration. The
corals were exposed for 17 days, at which time they were placed
in uncontaminated seawater and allowed to recover for 48
hours. All the corals exposed to the FCLS-spiked mud exhibited
short-term increases in oxygen consumption and ammonia excre-
tion. Photographic documentation of the corals revealed a
progressive development of the following conditions: 1) a
reduction in the number of polyps expanded indicating little or
no active feeding; 2) extrusion of zooxanthellae; 3) bacterial
infections with subsequent algal overgrowth; and 4) large-scale
polyp mortality in two of the colonies. Coral behavior and
condition improved dramatically during the recovery period.
Polyps of surviving corals reexpanded and fed actively on day
two of the recovery period.
4-43
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Dodge (1982) evaluated the effects of drilling fluid expo-
sure on the skeletal extension of reef-building corals
CMontastrea annularis). Corals were exposed to 0. 1. 10. or
100 ppm drilling fluid ("Jay" fluid) for 48 days in a
flow-through bioassay procedure. The drilling mud composition
was changed approximately weekly as new mud taken from the well
was added. One significant change in mud composition was in
the diesel oil content, which was 0.4 percent by weight from
the fourth week to the end of the experiment. Corals exposed
to 100 ppm had significantly depressed linear growth rates and
increased mortality. Calcification rates of corals exposed to
100 ppm decreased by 53 percent after four weeks and by 84
percent after six weeks. There was no indication of lowered
growth rates for either the 1- or 10-ppm exposure.
Hudson and Robbin (1980) exposed corals (Montastrea
annularis) to unused drilling fluid in heavy doses of two to
four ram layers applied four times at 150-minute intervals.
Drilling mud particles were generally removed by a combination
of wave action, tentacle cleansing action, and mucus secre-
tions. At the end of the exposure period, corals were placed
in protected waters for six months. At the end of another six
months, the corals were removed and examined for growth char-
acteristics. Results of the growth analysis indicated that
heavy concentrations of drilling mud applied directly to the
coral surface over a period of only 7-1/2 hours reduced growth
rates and suppressed variability. Trace element analyses of
the corals indicated that neither barium nor chromium were
incorporated into the skeletal materials.
4-44
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Experiments with the coral Acropora cervicornis revealed
reduced calcification rates after exposure to concentrations as
low as 25 ppm of used Mobile Bay drilling mud (Kendall et al..
1983). Calcification rates in growing tips were reduced to 88,
83, and 62 percent of control values after 24-hour exposures to
25, 50, and 100 ppm (v/v) drilling mud. respectively. Effects
on soluble tissue protein and ninhydrin positive substance were
also noted at these or higher levels. Further experiments with
kaolin, designed to reproduce the turbidity levels of the
drilling mud without its chemical effects, revealed slight
metabolic changes to the corals that were much less pronounced
than those observed for the drilling mud treatments.
4.3.2.2 Stress Tests on Other Organisms
Other altered behavioral patterns in organisms have been
noted after chronic exposures to drilling mud. Dock shrimp and
dungeness crab larvae were exposed to 4,000 to 200.000 ppm
barite and 4.000 to 100,000 ppm bentonite. The EC
concentration inhibiting the swimming ability of half of the
crab larvae ranged from 77.600 to 85,600 ppm bentonite. and was
71.400 ppm for barite. EC 's for shrimp larvae ranged from
13,800 to 34,600 ppm bentonite, and 5,400 to 50,400 ppm
barite. Utilizing these results in conjunction with
concentrations of barite and bentonite in lignosulfonate
drilling fluids under the high energy Lower Cook Inlet mixing
conditions, the "zone of toxicity" would extend only a few
meters from the source (Houghton et al.. 1981).
Conklin et al. (1980) studied the effects of barite on the
grass shrimp (Palaemonetes puqio). They discovered that the
mucus in the midgut of the shrimp has a high affinity to barite
4-45
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particles. During long-term exposure to barite, considerable
quantities of mucus could be adsorbed to the barite and
excreted. This phenomenon exposes midgut epithelial cells to
the abrasive action of ingested barite particles and could lead
to both necrosis and erosion of the epithelial cells.
Carr et al. (1980) exposed opossum shrimp (Mvsidopsis) to
the MAP of used lignosulfonate drilling fluid and observed the
response of weight-specific respiration rates. Organisms in
different life stages were exposed to various concentrations.
Although respiration rates were nearly identical, average dry
weights were significantly lower in exposed shrimp.
Neff et al. (1984) utilized a number of biochemical and
physiological indices to detect pollutant stress in animals
exposed to the settleable fraction of a water-based drilling
fluid in situations including exposures of up to 119 days.
This is reflective of the time it generally takes to drill 1-3
wells at a particular location. The following biochemical or
physiological effects were noted: (1) there was a tendency for
coelomic fluid glucose concentration to be lower in the worm
Nereis virens exposed to the drilling mud settleable fraction
than in controls, though the difference was statistically
significant only at Day 14 of exposure; (2) after 14 days, net
shell growth in experimental clams was significantly less than
in controls (the authors note that it is uncertain whether the
difference in growth was due to the 14-day exposure or to
something during the pre-exposure period); (3) at 119 days the
oxygen consumed to nitrogen excreted (O:N ratio) was slightly.
but significantly, lower in experimental than in control clams;
(4) the O:N ratios of sand shrimp, C. septemspinosa were
slightly but not significantly lower in experimental than in
4-46
-------
control animals at both 4 and 14 days of exposure (the low O:N
ratios indicate that protein is being utilized as a catabolic
substrate, usually an indication of stress); (5) concentrations
of two free amino acids in N. virens and one free amino acid in
M. arenaria were significantly higher in experimental than in
control animals; (6) mean taurine/glycine molar ratio was
higher and the mean sum of threonine plus serine was lower in
experimental than in control clams, suggesting that some of
these animals were mildly stressed by exposure to the drilling
mud settleable fraction; (7) in a set of experiments at day 90.
liver glycogen concentrations in Class A and Class D flounder
were significantly lower than those in corresponding controls,
with a diet of drilling fluid- contaminated sandworms causing a
slight depletion of liver glycogen reserves in winter flounder;
the effect, was more pronounced in larger than smaller fish; (8)
lobsters that were exposed to sediments and food, which had
been contaminated with settleable fraction of drilling mud. had
the highest mean concentration of hepatopancreatic glucose plus
glycogen.
Neff et al. (1984) note that the settleable fraction of
water-based drilling mud resulted in "mild" stress as described
above. They note, however, that this stress was not sufficient
to affect growth of juvenile flounder and lobsters over the 99
to 119-day study period.
Ateraa et al. (1982) exposed lobster (Homarus americanus) to
three test mixtures: used drilling fluids from Mobile Bay.
Alabama; "Jay" fluids from a land-based drilling operation in
Florida; and natural mud sediment from Buzzards Bay,
Massachusetts. Water column and layered solid phase exposures
were conducted for five-day periods, and behavioral changes
4-47
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noted. In water column exposures, no significant difference in
mortality alone or organism damage alone was found, but when
the mortality and damage groups were added, the Jay fluid had
significantly greater effects than the Mobile Bay fluid or
Buzzards Bay mud. Two molts occurred during the exposure
period for most individuals. Time to first molt or number of
molting organisms was not significantly different for the three
substances. How- ever, for the second molt, the Jay fluid had
significantly fewer molts than the Mobile Bay fluid or the
Buzzards Bay mud.
Atema et al. (1982) also tested lobster preference to these
same three media as substrates. Spontaneous tail flipping (a
sign of stress) occurred in 29 drilling fluid exposures but
only three controls, and the time required to build a shelter
was twice as long for drilling fluid (59 minutes) than control
substrates. These behavioral changes would presumably have a
negative effect on lobster populations, causing the lobsters to
be more exposed to predators.
Finally, these same researchers tested the effect various
depths of drilling mud substrate had on lobster behavior, and
noted that increasing substrate depth both increased the time
before homesite construction would occur and decreased the
quality of the shelters. They also noted that a 4 mm layer of
a barite and bentonite mixture delayed shelter construction as
much as actual drilling fluids, suggesting that physical
effects alone can interfere with shelter building behavior.
Breteler et al. (1984) observed the behavior of three test
species (the clam Mya arenaria. sandworm Nereis virens. and the
grass shrimp Palaemonetes puqio) exposed to muds to which
various amounts of mineral oil and diesel fuel had been added.
4-48
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Effects of the muds on burrowing behavior were examined in
solid phase bioassays. Only one replicate containing base mud
(no oil additives) caused burrowing impairment among the worm.
Nereis. With the exception of some impairment of burrowing in
Mya during the second day of the bioassay. no visible
behavioral abnormalities were observed among bioassay organisms
during solid phase bioassays with drilling mud containing 0.5
percent mineral oil. However, low to moderate impairment of
burrowing occurred in both Mya and Nereis during solid phase
bioassays with drilling mud containing 5 percent mineral oil.
Sublethal effects were observed by Breteler et al. (1984)
among Nereis and Mva exposed to solid phases of drilling mud
containing either 0.5 percent or 5 percent low-sulfur diesel
fuel. Moderate numbers of Nereis failed to burrow during the
first stage of exposure at the 0.5 percent level, while most
worms were exposed on the surface at the 5 percent level.
However, within four days, all worms were burrowing. Still.
impaired burrowing behavior persisted throughout the bioassay
in moderate numbers of Mya at low and high levels of this
diesel fuel additive. More severe sublethal effects were
observed in the solid phase tests involving high-sulfur diesel
fuel. Moderate to high levels of impaired burrowing were
evident among Nereis and Mya as a result of exposure to the
solid phase prepared from drilling mud containing 0.5 percent
of this additive.
A sublethal response in shrimp also was observed by
Breteler et al. (1984) at the initiation of the solid phase
tests. Upon addition of test material to the tanks, the water
was very turbid and had a brownish appearance. Shrimp
exhibited avoidance responses by swimming against the glass
walls of the aquarium.
4-49
-------
In a companion study Neff et al. (1984) observed that
introduction of the settleable fraction into the treatment
aquarium provoked immediate and strong, but short-lived.
reactions in fish, scallops, and shrimp. Shrimp and fish first
tried to avoid the plume of settling drilling fluid and then
congregated near the water surface after they were enveloped by
the plume. This behavioral pattern persisted for 2-3 hours
after introduction of drilling fluid. Normal behavior resumed
after drilling fluid solids settled. Scallops exhibited
increased swimming activity with the introduction of drilling
fluid.
Individual components of drilling mud (e.g., chromium) may
also be toxic. For discussions of known toxicity information
on the 129 "priority pollutant" metals and organics pollutants,
see EPA (1980a). Consideration of individual toxicities may
not. however, be sufficient to predict the effects of exposure
in the field to mixtures as complex as drilling mud.
4.3.3 Community Recruitment and Development
A limited number of studies analyzed the effects of whole
drilling fluids or components on community recruitment and
development. One set of these studies introduced planktonic
larvae of several species into a flow-through system and
allowed them to settle on either a sand/drilling fluid mixture.
a sand bottom covered with a thin drilling fluid layer, or a
plain sand bottom for the control group. Organisms were
counted after 8 to 10 weeks.
Tagatz et al. (1982) used estuarine macrobenthic organisms
and found abundance significantly decreased by concentrations
of 50 ppm drilling mud. They also found rank correlation of
4-50
-------
species abundance and species diversity altered by a Mobile Bay
drilling mud treatment. Previous work by these same
researchers had shown whole used mud or barite to have a
detrimental effect on recruitment (Tagatz et al.. 1980).
Annelids, and to a lesser degree, coelenterates and moHusks,
were all significantly affected by the experimental treatment.
The authors concluded that drilling fluid could significantly
affect recruitment and possibly change the structure of the
food web.
Annelids were most affected by barite. and a 5 mm barite
layer over sand had more impact than the barite-sand mixture.
Mollusc abundance was significantly reduced only in the aquaria
with the barite layer over sand (Cantelmo et al., 1979). This
indicates that there is a physical as well as a chemical factor
inhibiting recruitment. Analysis of meiofaunal communities
under these same conditions showed significant increases in
total density (101 percent) and the density of nematodes (112
percent) for the 1:11 barite and sand mixture. The 1:4 barite
and sand mixture showed insignificant density increases, and
the barite cover reduced nematode and copepod densities below
the control and the 1:11 and 1:4 barite and sand mixtures.
These studies are difficult to interpret with regard to
actual field conditions, however. Only a few species contrib-
uted to the observed effects. However, they do suggest that
drilling fluid discharges can alter benthic communities within
the zone of heavy deposition by influencing larval recruitment.
4-51
-------
4.4 ACUTE TOXICITY OF PRODUCED WATER
A limited number of studies have examined the toxicity of
produced waters. A bioassay program was carried out by Rose
and Ward (1981) on produced water from the Buccaneer Field in
the Gulf of Mexico off Texas (Table 4-13). Results were
presented for four series of test conditions. Test series Nos.
1-3 were performed at a shore-based laboratory, while test
series No. 4 was conducted on the production platform. The
majority of tests were performed for series No. 1; these tests
were conducted at a shore-based laboratory and the media was
either aerated or naturally maintained above a dissolved oxygen
(DO) concentration of 4 mg/1. The 96-hour LC_rt value for
bU
this series ranged between 8.000 and 408.000 ppm. the lowest
(most toxic) value being obtained for larval brown shrimp.
In series No. 2 (conducted at a shore-based laboratory).
the test media were not maintained above 4 mg/1 DO and the
LC values were lower than those for the same species tested
in aerated media. For test series No. 3. flow-through
bioassays were conducted in the laboratory and again the media
were aerated, while in test series No. 4, flow-through tests
were performed on the platform with aerated media. All brine
samples during this phase had been treated with acrolein. a
highly reactive biocide that was scavenged with ammonium
bisulfite before discharge. The chemical was not detected in
any of the samples.
Rose and Ward (1981) also compared their results with a
previous study of toxicity of produced water from the Buccaneer
Field (Zein-Eldin and Keney. 1978). This earlier evaluation.
which also addressed the toxicity of produced water without
4-52
-------
Table 4-13 MEDIAN LETHAL CONCENTRATIONS (LC50's) AND ASSOCIATED 95%
CONFIDENCE INTERVALS FOR ORGANISMS ACUTELY EXPOSED TO FORMATION WATER
UNDER VARIOUS EXPERIMENTAL CONDITIONS, (ROSE & WARD, 1981).
Organism
Test Series No.
Brown shrimp
Larva
Subadult
Adult
White Shrimp
Subadult
Adult
Barnacle
Crested
blenny
Test Series No.
Barnacle
Cr. blenny
Test Series No.
White shrimp
Subadult
Test Series No.
Brown shrimp
Subadult
Barnacle
Season Formation
or test water used
1C
Spring 1979
Summer 1978
Fall 1978
Winter 1979
Spring 1979
Summer 1978
Fall 1978
Winter 1979
Spring 1979
Summer 1978
Fall 1978
Winter 1979
Summer 1978
Fall 1978
Winter 1979
Spring 1979
Summer 1978
Fall 1978
Winter 1979
Spring 1979
Summer 1978
Fall 1978
Spring, 1979
2d
Winter 1979
Spring 1979
3*
Fall 1978
4'
Spring 1979
Spring 1979
D
E
F
G
A
B
C
D
A
B
C
D
A
B
C
A
B
C
D
A
B
C
D
A
B
D
C
D
B
H
H
Testing
temp.
28
28
28
28
25+1
22+1
18+2
24+1
25+1
22+1
18+2
24+1
25+1
22+1
18+1
25+1
22+1
18+1
24+1
25+1
22+1
18+2
24+1
25+1
22+1
24+1
18+2
24+1
22+1
25-29
25-29
LCsoa'b
10,000
12,000
8,000
8,000
94,000
60,000
183,000
61,000
94,000
78,000
178,000
90,000
56,000
61,000
133,000
81,000
62,000
92.000
37,000
33,000
84,000
154,000
60.000
158,000
408,000
178.000
8.000
7,000
62,000
44,000
51,000
9«a?W
7,000-15,000
9,000-18,000
6,000-12,000
5,000-11,000
63,000-172,000
0-100,000
130,000-279,000
47,000-76,000
63,000-172,000
38,000-183,000
132,000-240,000
61,000-156.000
51,000-62,000
48,000-76,000
67,000-366,000
48,000-153,000
27,000-110,000
58,000-150,000
24,000-52,000
25,000-38,000
68,000-104.000
111,000-222,000
49,000-71,000
100,000-320,000
320,000-560,000
135,000-235,000
5,000-13,000
5,000-12,000
48,000-76,000
25,000-60,000
34,000-68,000
4-53
-------
Table 4-13 MEDIAN LETHAL CONCENTRATIONS (LC^'s) AND ASSOCIATED 951
CONFIDENCE INTERVALS FOR ORGANISMS ACUTELY EXPOSED TO FORMATION HATER
UNDER VARIOUS EXPERIMENTAL CONDITIONS, (ROSE & WARD, 1981).
(Continued)
and associated 95% confidence intervals are 96-hr values
except in the case of larval brown shrimp, for which 48-hr values are
reported. Units are ppm formation water.
In most cases, LC^g's and related confidence intervals were calculated by
the moving average method. However, the binomial method was employed in Test
Series No. 1 for subadult brown shrimp tested in the fall as well as for
crested blennies tested in the summer and fall. The p rob it method was used
for Test Series No. 4.
cStatic laboratory tests; oxygen demand of formation water not evaluated.
Except in the case of tests with larval brown shrimp, test and control media
were aerated to maintain dissolved oxygen concentration (DO) above 4 mg/1.
Aeration was not required to maintain a DO above 4 mg/1 in tests with larval
shrimp.
Static laboratory tests; oxygen demand of formation water evaluated. Test
and control media were not aerated. Although DO of control media remained
above 4 mg/1 during the tests, DO of test media decreased to 0.5-3.2 mg/1
(barnacle) and 1.2-4.0 mg/1 (crested blenny) by the end of the 96-hr testing
period.
^low-through laboratory tests; oxygen demand of formation water not
evaluated. Test and control media were aerated to maintain DO above 4 mg/1.
^Flow-through platfom tests; oxygen demand of formation water not
evaluated. Test and control media were aerated to maintain DO above 4 mg/1.
4-54
-------
considering oxygen demand, generated two sets of 96-hour LC5Q
values for juvenile white shrimp. In the first set. 96-hour
LC values of 1.850 - 6.500 ppm were obtained for produced
water treated with two biocides (K-31 and KG-14) that were not
scavenged. The second set of values was obtained for produced
water without the addition of biocides; these LC values
exceeded 100.000 ppm.
Rose and Ward (1981) suggested that the operator's current
practice of treating produced water with biocide (acrolein and
the scavenger, ammonium bisulfite) is more environmentally
protective than the previous practice (K-31 or KC-14 without
scavenger) and less environmentally protective than discharging
untreated produced water. The toxic effects of biocides in
produced waters were also observed by Workman and Jones
(1979). They found that blennies kept in cages below the
produced water discharge pipe of a production platform in the
Buccaneer Field suffered no mortalities when the effluent had
not been treated with biocide, but approximately half of the
blennies died (within 48 hours) when biocides were used. (The
type and concentration of biocide was not documented.)
Middleditch (1984) also noted that divers working near the
produced water discharge from Buccaneer Field experienced
occasional eye and skin irritation when the biocide acrolein
was being used. Middleditch noted that acrolein is routinely
"scavenged" by converting it to a bisulfite adduct, but that
this reaction is reversible; even though free acrolein may not
be detected in the effluent, it may be released after discharge.
4-55
-------
Because most of the laboratory bioassays cited above were
performed on media that were aerated and open to air. the
volatile hydrocarbons present in the produced waters may have
been lost as has been observed by Rice et al. (1979). As noted
in Section 2. the concentrations of volatile liquid
hydrocarbons in produced water from the Buccaneer Field were on
the order of 21 ppm, 80 percent of which were the more toxic
aromatics. In the above cited bioassays. an undetermined
amount of these hydrocarbons may have been lost during the
collection and transport of samples and as a result of
subsequent aeration.
Studies on the water-soluble fractions (WSF) of oil have
provided information that is helpful in evaluating the acute
lethal toxicity of produced water. WSFs contain fractions of
hydrocarbons similar to those found in produced water (i.e.,
the more soluble aromatic hydrocarbons). For example,
undiluted WSF of Cook Inlet crude oil contains about 7 ppro of
aromatic hydrocarbons. Rice et al. (1979) examined the
toxicity of WSF of Cook Inlet crude oil to 39 Alaskan marine
species. Pelagic fish and shrimp were the most sensitive to
the WSFs of crude oil with 96-hour LC values from 1-3 ppm
total aromatics (~140.000-430.000 ppm WSF). Rice et al.
estimated that concentrations of aromatic hydrocarbons in the
WSF declined over the 96-hour test period, by evaporation and
biodegradation. to about 20 percent of the initial
concentrations. Rice et al. (1981) found similar levels of
toxicity (100.000 - 400.000 ppm) for ballast-water treatment
effluent at Port Valdez. Alaska. They noted that the effluent
contained light aromatics in the 1-16 ppm range, similar to the
levels observed in produced waters (Section 2).
4-56
-------
The available information suggests that the acute toxicity
of produced water without the addition of biocides is low.
Toxicity that is present may be related to the light aromatic
hydrocarbons. However, a problem with assessing this toxicity
is the loss of the hydrocarbons during the course of the
exposure period. When biocides are present as in the tests
conducted by Zein-Eldin and Keney (1978), the toxicity of
produced water may be greatly increased. This toxicity may be
reduced if the biocide is scavenged prior to discharge as in
the tests conducted by Rose and Ward (1981). However, there is
also evidence that this process may be reversed subsequent to
discharge (Middleditch. 1984).
4.4.1 Chronic and Sublethal Toxicity of Produced Waters
Although the acute toxic effects of produced water appear
to be low (when biocides are absent), chronic lethal and
sublethal effects must be considered. Such effects are
expected to occur at concentrations below those that are
acutely toxic. Chronic exposures to organisms in the water
column could occur in areas where the hydrocarbons discharged
to the water column are not rapidly removed from the system and
where there is a continuous input. The potential for build-up
of hydrocarbons in the water column would be greater in
semi-enclosed coastal embayments with limited flushing than in
offshore regions. However, the rate of dilution, advection.
and other losses such as evaporation and sedimentation would
have to be considered before judging whether chronic effects on
water column organisms could occur.
4-57
-------
Hydrocarbons that have become associated with the sediments
are a more likely cause of chronic exposure. A number of
studies have indicated that petroleum hydrocarbons can become
incorporated into the sediments (NAS. 1975; Armstrong et al..
1977. API. 1977; Gearing et al., 1979). Studies have also
suggested that the lighter molecular weight hydrocarbons (the
major hydrocarbon fraction in produced water) are lost more
rapidly from sediments than the higher molecular weight
compounds. However, because produced water may be discharged
continuously, lighter as well as higher molecular weight
hydrocarbons have the potential for accumulating in the
sediment and exerting effects on benthic organisms.
Chronic lethal or sublethal effects of produced waters can
result from soluble petroleum hydrocarbon concentrations on the
order of a few parts-per-billion (yg/1) or less. For
example, although small amounts of oil (200 y/1 or less)
apparently stimulated growth of juveniles of the alga Fucus
endentatus. Steele (1972) found that even at the lowest
concentration of oil tested (0.2 vg/1) no fertilization of
this alga occurred, and the eggs lost viability and completely
disintegrated by the sixth day of the experiment. Other
experiments involving large enclosed water columns (4.8 m
diameter x 20 m deep) were used to examine the chronic effects
of low concentrations of oil to various planktonic organisms in
the field (Davies et al.. 1981). Copepods proved very
sensitive to an effluent water containing 5-15 wg/1 of oil.
Davies et al. (1981) reported that all components of the tested
zooplankton bottom invertebrates, Oithona. other copepods and
naupliar stages seem to be sensitive to effluent produced water
at dilution of 1:700.
4-58
-------
A general sublethal effect of hydrocarbons is narcosis.
For example. Sanborn and Maiins (1977) observed narcotization
of larval spot shrimp (Pandalus platyceros) and Dungeness crab
(Cancer maqister) zoeae exposed to 8 to 12 vg/1 naphthalene.
Animal behavior can also be affected at low
concentrations. For example. Atema and Stein (1974) found that
low levels of oil could affect the behavior of foraging
lobsters (Homarus americanus). At a measured hydrocarbon
concentration of 17.2 yg/1. there was a doubling of the time
period between noticing and pursuing food by lobsters.
Reproductive behavior of certain crabs may also be impaired at
soluble oil concentrations below 10 yg/1 (Takahashi and
Kittredge. 1973). The studies of Takahashi and Kittredge
(1973) and Jacobson and Boylan (1973) also indicate that low
concentrations of aromatic hydrocarbons - on the order of
1 yg/1 can disrupt the responses of crabs and snails to
chemical substances that normally initiate feeding behavior.
Burrowing activities of the clam Macoma balthica were affected
by water soluble fractions of Prudhoe Bay crude oil: at a
concentration of 36 vg/1 and an exposure period of 9 days,
many of the buried clams came to the sediment surface.
The above information indicates that chronic lethal and
sublethal effects can occur at concentrations on the order of a
few parts-per-billion of soluble hydrocarbons, particularly
aromatics. While numerous examples of threshold responses at
much higher concentrations can be found, it is clear that
concentrations on the order of 1 yg/1 (and perhaps even less)
will have effects on some marine biota.
4-59
-------
Some produced water also contains dissolved hydrogen
sulfide (H S). For example, produced water from fields in
the Santa Barbara Channel can contain a few hundred mg/1
H S. This chemical can be toxic to marine organisms.
£t
There are phylogenetic and habitat-related correlations to
H S tolerances (Theede et al.. 1969). In general, marine and
£
freshwater invertebrates have a much higher resistance than
freshwater fish. (No information on tolerance of marine fish
to H S was found during an initial search of the literature).
^
Polychaetes and many bivalves show the highest resistance among
invertebrates tested in experimental and field situations.
This phylogenetic pattern to H S tolerance appears related to
ft
a group's capabilities for facultative anaerobiosis (Caldwell
1975; Theede et al., 1969). Sedentary organisms appear more
tolerant than active species.
The acute toxicity levels of H S have been seen in the
range of 0.02 to 40 mg/1 in invertebrates and 0.04 to 1 mg/1 in
freshwater adult fish (Adelman and Smith, 1970; Caldwell, 1975;
Dimov et al.. 1970; Henriksson, 1969; Theede et al.. 1969;
Smith et al.. 1976).
Low concentrations of H S in water (as low as 0.01 mg/1)
c»
may adversely affect fish fry survival (Adelman and Smith.
1970; Smith et al.. 1976). These observations were made with
freshwater fish; as already noted, no data were found for
marine fish.
Invertebrate reproduction is also sensitive to H S. For
2
example, when fertilized oyster gametes were transiently
4-60
-------
exposed to H S. larval development was reduced (Caldwell
&
1975). A two-hour exposure to 0.3 mg/1 H S led to an
^
approximately 60 percent reduction in normal larval development
4.4.2 Toxicity of Chemical Components of Produced Water
Given the limited amount of toxicity data for produced
waters, it is useful to examine available toxicity data for
produced water constituents. Such an examination would not. of
course, account for possible synergistic effects among these
constituents in whole fluids. Nonetheless, this approach may
serve to expand an understanding of the major components of
produced water toxicity.
Table 4-14 presents available toxicity data for whole
produced waters and individual trace metal and hydrocarbon
constituents. Table 4-15 shows the measured range of
concentration of each pollutant in undiluted produced water.
and indicates which acute toxicity values may be exceeded by
the discharge concentrations for the species listed. Mean
discharge concentrations for zinc and phenol exceed at least
one of the LC values for Mercenaria mercenaria and
50
Stolephorus purperens. respectively.
Another way of using constituent data to assess produced
water toxicity is to compare the data with EPA's water quality
criteria for the protection of marine life and human health.
This is done in Table 4-16 and indicates that exceedances of
most of the criteria would occur for the highest reported
undiluted concentrations in produced water.
4-61
-------
TABLE 4-14 ACUTE LETHAL TOXICITY OF PRODUCED WATERS AND CONSTITUENTS OF
PRODUCED WATERS TO MARINE ORGANISMS
(96-hr LC50/EC50 unless otherwise noted)
Constituent/Species
a. Produced waters
Whole produced waters
Balanus tintinnabulum (Barnacle)3
Penaeus aztecus (Brown shrimp)3
Penaeus setiferus (White shrimp)3
Hypleurochilus geminatus (Crested blennie)3
Cyprinodon variegatas (Sheepshead minnow)
b. Trace metals
Zinc
Capitella capitata (Polychaete)
Neanthes arenaceodentata (Polychaete)
Nereis diversicolor (Polychaete)
Nereis virens (Sand worm)
Ophryotrocha labronica (Polychaete)
Crassostrea virginica (American oyster)3
Hercenaria mercenaria (Hard-shelled clam)
Life stage
Reference
Adult 83,000
N.H.F.S.. 1980
Adult 116,000 N.M.F.S., 1980
Adult 78,000-178,000 Rose & Ward, 1981
Subadult 60,000-183,000 Rose & Ward, 1981
Larvae 9,500 (48-hr LC50) N.M.F.S., 1980
Larvae 8.000-12,000 (48-hr
LC50) Rose & Ward, 1981
Adult 70,000
N.M.F.S., 1980
Adult 269,000 N.M.F.S., 1980
Adult 158,000-408,000 Rose & Ward, 1981
Adult 550.000-600,000 Andreason & Spears, 1983
Adult
Larvae
3.5
1.7
Adult 1.8
Juvenile 0.9
Adult
Adult
Adult
11-55
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
8.1 U.S. EPA, 1980
2.6 (168-hr LC50) U.S. EPA, 1980
Adult 1.0 (13-hr LC50) U.S. EPA, 1980
0.31 U.S. EPA, 1980
Larvae 0.75 (48-hr LCO) U.S. EPA, 1980
Larvae 0.50 (48-hr LC100) U.S. EPA, 1980
- 0.17 U.S. EPA, 1980
Larvae 0.20 (10-day LC50) U.S. EPA, 1980
Larvae 0.05-0.34 (12-day
LC5-LC95) U.S. EPA, 1980
Embryo 0.28 (48-hr LC100) U.S. EPA, 1980
4-62
-------
TABLE 4-14 ACUTE LETHAL TOXICITY OF PRODUCED WATERS AND CONSTITUENTS OF
PRODUCED WATERS TO MARINE ORGANISMS
(96-hr LC5Q/EC5Q unless otherwise noted)
(Continued)
Constituent/Soecies
Nya arenaria (Soft-shelled clam)
Hvtilus edulis (Mussel)
Hassarius obsoletus (Mud snai 1 )
Acartia clausi (Copepod)
Acartia tonsa (Copepod)
Eurvtemora af finis (Copepod)
Nitocra spinipes (Copepod)
Pseudodiaptanus coronatus (Copepod)
Tiqriopus japonicus (Copepod)
Hysidapsis bahia (Mysid shrimp)
Hvsidoosis bigelowi (Mysid shrimp)
Homarus americanus ( Lobster )b
Carcinus naenas (Crab)
Pagurus lonqj carpus (Hermit crab)
Alterias forbesi (Starfish)
ESffldylus heteroclitus (Mummichog)
Life stage
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Larvae
Larvae
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Larvae
LC50/EC50 (ppm)
5.2-7.2
1.5-3.1 (168-hr
LC50)
2.5-4.3
50.0
7.40 (168-hr LC50)
0.95
0.29
4.09
1.45
1.78
2.16
0.50
0.59
0.18-0.58
1.0
0.4
0.2 (168-hr LC50)
39.0
2.3 (168-hr LC50)
60
60 (96-hr LC28)
10.0-20.0 (168-hr
LC50)
157 (48-hr LC100)
43 (192-hr LCO)
66 (192-hr LC50)
83
Reference
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
menidia (Atlantic silverside)
Larvae 2.73-4.96
U.S. EPA, 1980
4-63
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TABLE 4-14 ACUTE LETHAL TOXICITY OF PRODUCED WATERS AND CONSTITUENTS OF
PRODUCED WATERS TO MARINE ORGANISMS
(96-hr LC50/EC5o unless otherwise noted)
(Continued)
Constituent/Species
Life stage LCs(i/EC5n(ppm)
Reference
Pseudop1euronectes americanus (Winter flounder)b Larvae 4.92-18.2
c. Hydrocarbons
Petroleum alkanes
Crassostrea virginica (American oyster)3 Adult
Penaeus aztecus (Brown shrimp)a Subadult
Penaeus duorarum (Pink shrimp)a Subadult
Penaeus setiferus (White shrimp)3 Adult
Benzene
Crassostrea qigas (Pacific oyster)
Tigriopus californicus (Copepod)
Nitocra spinipes (Copepod)
Crago franciscorum (Bay shrimp)
Palaemonetes pugio (Grass shrimp)
U.S. EPA, 1980
Cancer magister (Dungeness crab)
Morone saxtilis (Striped bass)
Toluene
Nitocra spinipes (Copepod)
Crassostrea gigas (Pacific oyster)
Mysidopsis bahia (Mysid shrimp)
Crago franciscorum (Bay shrimp)
(Continued)
33-154
56-133
56-133
37-92
Brook et al., 1980
Brooks et al.. 1980
Brooks et al., 1980
Brooks et al., 1980
924 U.S. EPA, 1980
450 U.S. EPA, 1980
82-111 (24-hr LC50) U.S. EPA, 1980
Adult
Larvae
Larvae
17.6
27
33.5-40.8 (24-hr
LC50)
74.4-90.8 (24-hr
LC50)
108
5.1-10.9
U.
U.
U.
U.
U.
U.
S.
S.
S.
S.
S.
S.
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
1980
1980
1980
1980
1980
1980
24.2-74.2 (24-hr
LC50)
1,050
56.3
3.7
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
U.S. EPA, 1980
4-64
-------
TABLE 4-14 ACUTE LETHAL TOXICITY OF PRODUCED WATERS AND CONSTITUENTS OF
PRODUCED WATERS TO MARINE ORGANISMS
(96-hr LC5Q/EC50 unless otherwise noted)
(Continued)
Const i tuent/Speci es
Palaanonetes pugio (Grass shrimp)
Oncorhvnchus kisutch (Coho salmon)
Cvprinodon variegatus (Sheepshead minnow)
Horone saxatilis (Striped bass)
Oncorhvnchus gorbuscha (Pink salmon)
Phenol
Palaanonetes pugio (Grass shrimp)
Crassostrea virginica (Eastern oyster)3
Hercenaria mercenaria (Hard clam)
Kuhlia sandvicensis (Mountain bass)
Salmo gairdneri (Rainbow trout)
Stolephorus purpureus (Nehu)
Naphthalene
Meanthes arenaceodentata (Polychaete)
Crassostrea gjgas (Pacific oyster)
Palaanonetes pugio (Grass shrimp)
Penaeus aztecus (Brown shrimp)3
Cvprinodon variegatus (Sheepshead minnow)
Qncorhvnchus gorbuscha (Pink salmon)
Life stage
LCCrt/ECCrt (POT)
9.5
Adult 17.2-38.1 (24-hr
LC50)
Larvae 25.8-30.6 (24-hr
LC50)
10-50
277-485
6.
fry 5.
5.
3
4
8
58.2
- 52.6
11
6.
0.
3.
19
2.
2.
2
fry 0.
9 (48-hr LC50)
51 (12-hr LC50)
8
19
6 (24-hr LC50)
4
5 (24-hr LC50)
4 (24-hr LC50)
9 (24-hr LC50)
Reference
U.
U.
U.
U.
U.
U.
S.
S.
S.
S.
S.
S.
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
Thomas &
U.
U.
U.
U.
U.
U.
U.
U.
U.
U.
S.
S.
S.
S.
S.
S.
S.
S.
S.
S.
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
U.S. EPA,
U.S. EPA,
Thomas &
1980
1980
1980
1980
1980
1980
Rice, 1979
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
Rice, 1979
'Species distribution data in NOAA data base for commercially important species in the Gulf of Mexico.
b
Species distribution data in NOAA data base for commercially important species in the Atlantic OCS.
4-65
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TABLE 4-15 ACUTE LETHAL TOXICITY VALUES (LCso/ECso) WHICH MAY BE EXCEEDED BY
MEASURED DISCHARGE CONCENTRATIONS OF POLLUTANTS IN PRODUCED WATERS
Discharge concentrations (ppm)a
Pollutant Range (mean)
Species
C5o (ppm)b
Zinc
0.005-0.519 (0.168)
e.
I
Benzene 0.002-12.2 (2.98)
Toluene 0.060-19.8 (2.07)
Phenol
0.065-20.8 (2.34)
Crassostrea virginica
Hercenaria mercenaria
Acartia tonsa
Hysidopsis bahia
Homarus americanus
Pagurus longicarpus
Horone saxatilis
Crago franciscorum
Palaemonetes pugio
Oncorhynchus kisutch
Oncorhynchus gorbuscha
Horone saxati1i s
Palaemonetes pugio
Kuhlia sandvicensis
Salmo gairdneri
Stolephorus purpurens
0.31
0.50 (48-hr LCTOO)
0.17
0.20 (10-day LC^)
0.05-0.34 (12-day
0.28 (48-hr LC100>
0.29
0.50
0.18-0.58
0.4
0.2 (168-hr
5.1-10.9
3.7
9.5
17.2-38.1 (24-hr
10-50
5.4
6.3
5.8
11
6.9 (48-hr
0.51 (12-hr
Naphthalene 0.019-1.45 (0.187)
Oncorhynchus gorbuscha 0.92 (24-hr
a Discharge concentrations from the 30-platform study (EPA, 1983).
b 96-hr LC (EC50) assumed unless otherwise noted.
-------
TABLE 4-16 COMPARISON OF CONCENTRATIONS OF CONSTITUENTS OF PRODUCED WATER
WITH AVAILABLE WATER QUALITY CRITERIA FROM OFFSHORE OIL AND GAS
FACILITIES
Range (mean) Criteria for protection of ug/1:
of discharge Saltwater aquatic life
Pollutant
Benzene
Ethyl benzene
Naphthalene
Phenol
Toluene
2, 4-Dimethyl phenol
Zinc
concentrations Chronic
2-12.150 (2,977) 700 C
6-6,010 (431)
19-1,454 (187) 100 C3
65-20,812 (2,343)
60-19,800 (2,007) 3,910 Cb
1-3,504 (200)
5-519 (168) 58
Acute
5,100 A
430 A
2,350 A
5800 A
6,300 A
,_
170
Human health
ingest ion of organisms
400 at 10-5
40 at 10-6
4 at 10~7
3,280
769,000
424,000
Abbreviations: C = Chronic effects noted; no proper criterion.
A = Acute effects noted; no proper criterion.
a Lowest reported chronic aquatic effects data from Anderson, 1979.
b Lowest reported chronic aquatic effects data from Thomas and Rice, 1979.
-------
5.0 FIELD STUDIES
5.1 SUMMARY
5.1.1 Studies around Drilling Operations
Field studies to determine the effects of drilling fluid
discharges on surrounding biota have been conducted in the
Mid-Atlantic. North Atlantic (Georges Bank), Lower Cook Inlet
and Beaufort Sea in Alaska, and Tanner Bank, California. The
sampling design of all but two of these studies limited the
assessment to detection of major changes. These studies have
only examined alterations resulting from exploratory (i.e., one
well) operations or limited bulk discharges. No such data on
biological effects exist for multiple well activities during
drilling operations.
The most effective way to monitor the biological effects of
drilling discharges is to take quantitative samples of the
benthic infauna - animals that live on the sea floor. Sample
variability is typically lower than that for planktonic or
pelagic communities and thus sampling precision is higher.
These animals do not move much, if at all, so they are much
more vulnerable to the particulate fraction of fluids that
accumulates on the bottom. The most common approach is to take
replicate quantitative samples and determine whether there have
been changes in species richness, species composition, or
abundance. With six replicate samples it is possible to detect
changes of 15-25 percent of the mean for numbers of species and
25-50 percent changes in the mean abundances of some individual
species.
5-1
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Only two of the field studies used such an approach: the
mid-Atlantic study and the Georges Bank study. The resolution
for detecting change in marine communities was considerably
lower in each of the remaining studies. These studies probably
were incapable of detecting statistically significant changes
of 100 percent or perhaps even greater.
5.1.1.1 Effects on Biota
Benthic studies in high energy environments (Lower Cook
Inlet. Georges Bank) have shown no substantial effects on
benthic biota. There was a significant general increase in the
number of species and densities during the four-month period of
the Cook Inlet study. Sites near the drilling operation.
however, showed decreases in several community parameters
relative to control sites. The authors concluded that no
drilling related effects were observed. However, spatial
temporal variability and a change in sampling design precludes
the detection of measurable changes. In the Georges Bank study
there were seasonal changes in some species abundances. In at
least one case, these changes were correlated with alterations
in sediment grain size. Accumulations of cuttings may have
contributed to these changes, but it is also known that the sea
floor on Georges Bank is scoured by winter storms.
The mid-Atlantic study was conducted in a lower energy
environment. The abundance of fish and decapods increased in
the vicinity of the well, possibly due to increased micro
relief provided by the cuttings pile or food availability.
Sessile megabenthos were subjected to burial. Densities of
major taxa decreased between the pre-drilling and first
post-drilling survey. There was some recovery after a one-year
5-2
-------
period. These changes were also reported at the one-mile and
two-mile stations, but because of annual variation, it was not
possible to determine whether or not those stations were within
or beyond the zone of influence.
5.1.1.2 Metals and Hydrocarbons in Sediments
Numerous studies have established sediment barium and trace
metal gradients around drilling sites. In the mid-Atlantic
study, all one-mile and one of the two-mile stations sampled in
both post-drilling surveys had elevated sediment barium
levels. On the southern flank at Georges Bank at 140 m depth,
there was an increase of barium from 30 to 107 ppm within a
200 m zone and a smaller increase was detected at 2.000 m. On
Georges Bank at 60 m depth, barium increased from 37 to 67 ppm
within a few hundred meters at the drilling site, and smaller
increases were detected up to six km distance. Elevated levels
of other metals such as arsenic, cadmium, chromium, lead.
mercury, nickel, vanadium, and zinc were found near the rig
site in one or more of the above studies.
There have been very few attempts to evaluate hydrocarbon
accumulation in sediments as a result of exploratory drilling
discharges. On Georges Bank aromatic hydrocarbon levels were
extremely low, and essentially constant over time. There are
reports of hydrocarbons in sediments around production
platforms (see Section 3), but it is impossible to determine
the relative contribution from drilling muds versus produced
waters.
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5.1.1.3 Bioaccumulation of Metals and Hydrocarbons
In the Beaufort Sea study there was some evidence of
accumulation of mercury but not of other metals. Barium levels
were not determined. In the mid-Atlantic study, increases in
tissue levels of barium were detected in the first
post-drilling study (conducted shortly after the termination of
drilling operations), but had returned to pre-drilling levels
after one year. Chromium concentrations were elevated during
the second post-drilling study. There was no evidence of
accumulation of metals in tissue in the higher energy
environments of Georges Bank and Cook Inlet.
5.1.2 Studies Around Production Platforms
A number of field studies have been conducted to examine
the environmental effects of production operations. The
characteristics of five major studies are presented in Table
5-1. These field studies are generally useful for evaluating
the chemical, biological, or physical parameters that are being
modified by operations related to production platforms.
It is more difficult to assess impacts over a greater
area. Such studies have been performed in regions that have
already experienced a number of years of production activity as
well as relatively large effects from other sources of
contamination such as the input of the Mississippi to the Gulf
of Mexico, tanker discharges, and atmospheric inputs. In
addition, because areas around production operations have
experienced discharges from drilling operations, there are
confounding factors related to sorting the effects of produced
water from those from drilling mud and cuttings.
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TABLE 5-1 CHARACTERISTICS OF SELECTED FIELD STUDIES CONDUCTED
AROUND PRODUCTION OPERATIONS
STUDY
GENERAL CHARACTERISTICS
en
I
01
Central Gulf of
Mexico Platform
Study (Southwest
Research Institute, 1981)
Buccaneer Field
Study, Gulf of
Mexico (Middleditch, 1981)
Trinity Bay Study,
Gulf of Mexico
(Armstrong et al. 1977)
Offshore Ecological Investi-
gation (Morgan et al. 1974;
Bender et al. 1979)
Santa Barbara
Channel, California
(Mearns & Moore, 1976)
Four primary and 16 secondary platforms were examined on Lousiana DCS west of
Mississippi delta. Platforms were located 5-120 km offshore in 6-75 m depths.
The influence of the Mississippi made it difficult to sort out the effects
attributable solely to platform operations.
The Buccaneer Field facilities, which consist of two production platforms had
been in operation for 15 years at the time of the study. The field is located
50.5 km south of Galveston, TX in a water depth of 20 m. Based on sediment and
physical oceanographic studies, the area appeared to be a relatively high-
energy environment.
Trinity Bay is an estuarine area along the coast of Texas and has a water depth
of approximately 2.5 m. Sediments are of a silt-clay nature and the water is
turbid. Produced water is discharged one meter from the bottom.
The study involved an examination of production and drilling operations in
Timbalier Bay. Data were reflected in the Bay and offshore to depths of 30 m.
Results of this study have been considered inconclusive.
The study involved the examination of two oil platforms located 3.5 km off-
shore in approximately 30 m depth. At the time of the study, the platforms
had been operating for about 15 years. Produced water was not discharged
at the platformsT
-------
This summary is largely based on three of the four Gulf of
Mexico studies as well as the Santa Barbara study. The
Offshore Ecological Investigation is described in the body of
the text, but because of the inconclusive nature and
controversial history of this project, it is not utilized in
this summary. The most comprehensive study of an individual
production operation has been for the Buccaneer Field, and data
from this study are cited extensively in the summary.
However, it should be noted that the discharge rate of
produced water from this platform (~600 bbl/day during the
study) was very much less than the average for the EPA 30
platform verification study, both including (9,577 bbl/day) and
excluding (4.011 bbl/day) central processing facilities, and is
nearer the lower range of discharges (134 bbl/day to 150,000
bbl/day) examined during the EPA 30-platform study. In
addition, the Buccaneer Field appears to be in a relatively
high energy area where discharges into the water column are
rapidly diluted and where sediments which contain contaminants
are resuspended and transported away from the area.
5.1.2.1 Hydrocarbons in Water
Volatile liquid hydrocarbons (VLH) were measured in
seawater at the Buccaneer Field but were not specifically
examined in the Central Gulf of Mexico or Trinity Bay studies.
However, one author has reported elevated levels (0.5 ppb) of
these compounds in waters of the Louisiana DCS as compared to
open ocean water, which suggests that there is a generalized
input of these chemicals to the DCS. Sources would include
rivers, tanker discharges, and oil/gas seeps, as well as
produced water. Aromatic VLHs accounted for 60-80 percent of
the total VLH in the surface waters.
5-6
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Elevated levels of VLH (~65 ppb) were observed
immediately below the discharge pipe in the Buccaneer Field,
but were rapidly diluted with distance. Reductions of VLH
concentrations at the Buccaneer Field platform were on the
order of 10 to 10 within about 50 m of the platform.
Concentrations of VLH around the platform were four times
higher than at platforms three km away which had no discharge.
However, values at this latter platform were still higher than
those which were considered anthropogenically affected.
The limited available information suggests that
hydrocarbons in the water column are rapidly diluted to low
levels, but that these levels persist for considerable
distances. The concentrations of hydrocarbons in water will
depend on such site specific characteristics as mixing and
dispersion and volume of discharge. As already noted, the
discharge from the Buccaneer Field is not especially high and
the marine environment is characterized by good mixing and
dispersion.
5.1.2.2 Hydrocarbons in Sediments
In the Central Gulf of Mexico studies, unresolved complex
mixtures of high molecular weight hydrocarbons and the presence
of multiple isomers of alkyl aromatic hydrocarbons and parent
compounds (e.g., naphthalene and phenanthrene) indicated the
presence of petrogenic hydrocarbons at six of the twenty
platforms. Only a few sediment samples in areawide studies in
the Buccaneer Field contained evidence of petroleum
hydrocarbons, based on analyses of high molecular weight
alkanes; aromatics were not analyzed.
5-7
-------
Elevated levels of naphthalenes (21 ppm) were observed in
sediments within 15 m of the outfall in the Trinity Bay study.
At 75 m from the platform, the concentrations of naphthalene in
the sediments were approximately 9 ppm. or 50 percent of the
values observed at the platform. Stations 450 m from the
discharge had naphthalene concentrations of approximately 6
ppm. Background levels were approximately 3 ppm (at a distance
of 3.963 to 5.793 m). Background levels of naphthalenes in
Trinity Bay sediments generally were high, indicating that an
areawide elevation in naphthalenes, and possibly other
contaminants, may have occurred.
A regression analysis of sediment naphthalene levels
indicated that background levels would be achieved at
approximately 1.769 m from the outfall. The vertical
distribution of sediment naphthalene levels at 15 m from the
outfall was examined. Surface levels (0-2 cm) were 21 ppm; a
subsurface maximum of 42 ppm occurred at a depth of 6-8 cm.
The effluent level of total naphthalenes was 1.6 ppm and
dilution was estimated to be 2.000-total at 15 m from the
outfall. The ambient water column concentration, therefore, is
estimated to be 0.8 ppb, which contrasts to a sediment level of
approximately 21 ppm.
The limited data suggest that hydrocarbons (including
moderately toxic compounds such as naphthalene) can accumulate
in sediments around production platforms. The likelihood of
this occurring is greater in shallower and/or low energy areas
than in deeper and/or higher energy regions. Because produced
water provides a continual source of hydrocarbons, it is
5-8
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possible to have a build-up of moderately toxic compounds which
otherwise would tend to be relatively rapidly removed from the
system.
5.1.2.3 Hydrocarbons in Organisms
In the Central Gulf of Mexico studies, analyses revealed
the presence of low levels of alkylated benzenes, naphthalene,
alkylated naphthalenes, phenanthrene, alkylated three-ring
aromatics, and pyrene in a variety of fish and epifauna.
Isoraer distributions of alkylated benzenes and naphthalenes
were similar to those seen in crude oil. The investigators
concluded that marine organisms in the study area were exposed
to a low level of petroleum hydrocarbons from oil and gas
development as well as other sources.
Analyses of hydrocarbons in biota in the Buccaneer Field
were generally limited to high molecular weight alkanes. These
were found in a variety of animals, and there was some
suggestion that the feeding habits of some fish could be
partially correlated with their content of petroleum
hydrocarbons. Fish'that are known to feed on the platform
fouling community contained higher concentrations of petroleum
hydrocarbons than those that feed in the water column.
Results suggest that some accumulation of petroleum
hydrocarbons in biota may occur. In the Central Gulf of Mexico
study (the only study where lighter aromatics were analyzed in
organisms), the presence of benzene and naphthalene compounds
suggests that produced water is a possible source of these
hydrocarbons.
5-9
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5.1.2.4 Trace Metals in Sediment and Fauna
Significant increases of trace metals concentrations were
observed at stations within 100 m of platforms, for the Central
Gulf of Mexico study. Beyond that area, metal levels could
usually be explained by natural geochemical processes.
Bioaccumulation of metals could not be specifically related to
production operations. The Mississippi River probably exerted
a dominant influence on trace metal concentrations in sediments
and organisms.
Based on a comparison of sediment metal data at the
Buccaneer Field with those from other areas of the Gulf of
Mexico, accumulations of mercury, manganese, strontium, and
zinc were apparent. The sediments around this platform tend to
be resuspended and dispersed due to wave and current action,
and no significant long-term accumulation occurs. In addition.
bioaccumulation of metals in organisms around the platform was
limited.
High zinc levels observed in sediments around platforms in
the Santa Barbara Channel could have been caused by metal
flakes from the platform or metal debris on the seafloor.
Rockfish tissues showed increased levels of vanadium.
The results suggest that trace metals accumulate in
sediments in the immediate vicinity of production platforms and
that there may be bioaccumulation. Sources could include
corrosion of metal structures, use of sacrificial electrodes,
various activities associated with operations on production
platforms, produced water discharges, engine exhaust, and
previous drilling discharges.
5-10
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5.1.2.5 Histopatholoqy Studies
Sites for the Central Gulf of Mexico study where relatively
higher incidences of histopathological conditions were observed
were generally located in the eastern part of the study area.
which was more contaminated with hydrocarbons and trace metals
either from production operations or other sources. Because
the spadefish had an inherently high incidence of
histopathological conditions, its distribution among platforms
and control areas (where it is absent) affects the frequency of
occurrence of these conditions.
Episodic disease epidemics in spadefish in the Buccaneer
Field were attributed to the actions of opportunistic pathogens
during periods of natural seasonal stress for the fish. Much
of this stress was believed to be due to combinations of
natural factors. However, the authors noted there was a
possibility that winter disease epidemics may have been related
to chronic, low-level discharges of contaminants, because
sheepshead residing at the platforms were characterized by a
higher degree of histopathological conditions than sheepshead
that migrated in and out of the study area. On the other hand.
red snapper at the production platforms did not exhibit
differences in the frequency of various anomalies as compared
to individuals at satellite platforms.
The results from histopathological studies provide little
evidence that discharges from production platforms induce
histopathological conditions by themselves. The contribution
of contaminants by the Mississippi River and the spatial
distribution pattern of species are confounding factors.
5-11
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5.1.2.6 Benthic studies
During the course of studies conducted as part of the
Central Gulf of Mexico program, the area experienced two
irregularly occurring phenomena - a tropical storm and anoxic
bottom conditions. The investigators noted that these caused
so much disruption of the benthic fauna that it was impossible
to clearly describe populations or discern the effects of
platform discharges.
Benthic assemblages around the production platform in the
Buccaneer Field were different from most of those in the study
area. Stations near the platform (< 100 m) had reduced faunal
abundance, relatively high species turnover, and the presence
of certain species that were rare in the remainder of the study
area. It appears that toxic effects, perhaps associated with
the presence of toxic chemicals (hydrocarbons and/or biocides),
appeared to contribute in part to these alterations.
Similar benthic impacts were observed in the Trinity Bay
study. Within -15 m of the discharge, the sediments were
almost devoid of benthic infauna. Numbers of individuals and
species increased with distance from the platform. (The
investigators considered stations more than 450 m from the
platform to be unaffected because organism densities exceeded a
number thought to be representative of control areas.) The low
abundance of benthic organisms was correlated with the elevated
concentrations of total naphthalenes in the sediments.
The results of these studies, in particular Buccaneer Field
and Trinity Bay which occurred in water depths of 20 and 2.5m,
respectively, suggest that production platforms can have an
5-12
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adverse effect on local benthic infaunal populations. Factors
that may affect the degree to which produced water discharges
affect the benthos include water depth, volume of discharge,
local dispersion characteristics, presence of suspended
sediments, and physical characteristics of the seafloor.
5.1.3 Catch and Effort Statistics
Trends in catch statistics for commercial fish landings
were examined for the Gulf of Mexico to determine if there are
any indications that offshore oil and gas operations could be a
factor affecting commercial fish and shellfish yields. It is
recognized that other factors such as adequate reporting.
overfishing, natural perturbations, fresh water inflow, and
other sources of pollution could all be factors affecting catch
statistics. However, the statistics do permit some gross
comparisons to be made.
Landings data for several important commercial fish and
shellfish - shrimp, red snapper, and blue crab - indicated
consistently lower catch-per-unit-effort from Louisiana waters
as compared to the rest of the Gulf of Mexico. Inasmuch as
over 88 percent of the offshore structures in the Gulf are
located in Louisiana, this raises an environmental concern with
respect to discharges from oil and gas platforms.
5.2 INTRODUCTION TO FIELD STUDIES
A number of field studies have been conducted to character-
ize material behavior and pollutant concentration, and to
monitor potential environmental effects of discharges from
offshore oil and gas operations. These field studies
5-13
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complement the laboratory studies discussed in Section 4, and
give a real-world perspective to the transport processes
identified in Section 3. This section focuses on the
environmental effects documented in the available literature
from the offshore drilling areas of the United States.
Information on areas of special interest. Flower Gardens,
Georges Bank, and Norton Sound, and administrative activities
for these areas is presented in Appendix A.
Major studies addressing exploratory drilling operations
have been conducted in the Mid-Atlantic DCS off the New Jersey
coast (EG & G. 1982), Georges Bank off the Massachusetts coast
(Payne et al., 1982; Bothner et al.. 1982; Blake et al.. 1983).
Lower Cook Inlet, Alaska (Lees and Houghton. 1980), the
Beaufort Sea (Crippen et al., 1980), and Tanner Bank off the
southern California coast (Ecomar. 1978; Meek and Ray, 1980;
Ray and Meek. 1980). Baker et al. (1981). in their
investigations in Louisiana OCS, found evidence of sublethal
chronic effects within 500 m of a petroleum production platform
due to hydrocarbons and trace metals, some of which appeared to
be derived from drilling fluids. Ayers et al. (1980b)
conducted a study of plume dispersion in the Gulf of Mexico.
but this project did not address the impacts to indigenous
marine biota.
The major studies analyzing environmental impacts from
produced water discharges have been conducted in the Gulf of
Mexico. Two of the most detailed field investigations are the
"Environmental Assessment of Buccaneer Gas and Oil Field in the
Northwestern Gulf of Mexico. 1975-1980" (Middleditch. 1984) and
the "Ecological Investigations of Petroleum Production
Platforms in the Central Gulf of Mexico" (Bedinger et al..
5-14
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1981). Some of the parameters examined by these studies were
previously scrutinized during the Offshore Ecology Investi-
gation which focused on Timbalier Bay. Louisiana (Bender
et al.. 1979). The most significant effects of produced waters
on biological communities have been documented when the
discharge is into shallow bays and estuaries. API sponsored a
study of the environmental effects of produced water discharges
into Trinity Bay. Texas (Armstrong et al.. 1977).
The summary for this section contains a synthesis of the
major studies as well as conclusions drawn from these studies.
The remainder of this section provides a synopsis of these
studies. It is organized into two major categories: discharge
of drilling fluids and production operations. Drilling-related
studies are limited to exploratory drilling. There have been
no comprehensive effects studies related to development
drilling.
5.3 DISCHARGES OF DRILLING FLUIDS AND CUTTINGS
5.3.1 Mid-Atlantic Outer Continental Shelf
An extensive study of a mid-Atlantic OCS well (EG & G.
1982) was funded by the Offshore Operators Committee and Exxon
at the request of EPA Region II. The overall objective of the
program was to evaluate the effects of drilling discharges on
ambient water quality, bottom sediments, and the benthic
community around an exploratory well. The study area was
located in Baltimore Canyon, which is approximately 156 km (97
miles) off the coast of New Jersey. This is a low energy area
with an average depth of 120 meters. Drilling of the
exploratory well took place from January 4. 1979 to July 15,
1979.
5-15
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The program consisted of four separate study elements:
(1) a pre-drilling survey to examine the physical, chemical,
and biological conditions in a 3.2-km diameter area around the
well site; (2) a discharge monitoring study to provide
quantity, composition, and fate information concerning the muds
and the solids control equipment (SCE) discharges; (3) a first
post-drilling survey performed two weeks after the completion
of the drilling activity examining the same parameters as the
pre-drilling survey in a 6.4-km diameter area around the well;
and (4) a second post-drilling survey conducted one year later
in the same 6.4-km diameter area.
During the drilling period, a total of 30.800 barrels of
bulk muds and 6.400 barrels of SCE discards were discharged
into the ocean. The upper plume formed from the discharges
contributed significantly to the suspended solids concentration
of the water column in the immediate vicinity of the well.
affecting light transmissivity. The suspended solids in the
A
upper plume dropped by a factor of 10 within 100 meters of
the discharge point and approached background levels within
350-600 meters.
Physical/chemical alterations to the surface sediments near
the well site were detectable up to two years after cessation
of discharge due to the low energy nature of the benthic envi-
ronment. These alterations included the presence of drill
cuttings (visible accumulations within 100 m of discharge).
mineralogical changes, and elevated barium concentrations in
the sediments. Normal sediments in the vicinity of the well
were comprised mostly of sand. silt. clay, and gravel.
Discharges of drilling wastes led to localized alterations of
the bottom materials. Increased clay content of the surface
5-16
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sediments for a distance of 800 m in a southwesterly direction
was detectable immediately after drilling was terminated but
not one year later. Barium levels in the sediments were also
elevated near the discharge in samples taken during post-
drilling surveys. Sediment barium concentrations were greatest
within the immediate vicinity of the well and decreased
exponentially with distance. There were significant changes in
the leachable fractions of barium, nickel, lead, vanadium, and
2inc in the top 15 cm of the sediments. No elevated levels of
oil and grease were observed.
During the course of this study, it was assumed that
one-mile and/or two-mile stations would be beyond the influence
of the discharges. However, all one-mile stations sampled in
both past drilling surveys had elevated sediment barium levels
and showed increased barium concentrations in polychaetes and
brittle star tissues. One of four two-mile stations also had
increased barium concentration in the sediments following
drilling. No sediment concentrations were available for this
station (or any two-mile station) prior to drilling discharges,
so it is not possible to ascertain whether this elevation was
due to drilling discharges or natural or historical phenomena.
No tissue data were available for trace metals in organisms at
any two-mile station either pre- or post-drilling. Due to
these data gaps one cannot be certain that discharge influences
did not extend out to the two-mile (3.2 km) stations.
Benthic organisms including molluscs, polychaetes. and
brittle stars were collected during both post-drilling surveys
for tissue analysis and held for a 24-hour depuration period
prior to analysis. This period is less than the conventional
48- to 72-hour period. Tissues were examined for arsenic.
5-17
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barium, copper, chromium, lead, mercury, nickel, vanadium, and
zinc. Only barium and chromium levels in tissues showed an
increase over background levels. Increased concentrations of
barium in tissues were detected in the first post-drilling
survey, but had decreased to pre-drilling levels after one
year. Chromium concentrations were elevated during the second
post-drilling survey- There was no correlation between either
barium or chromium concentrations in tissues and concentrations
in the sediments.
The abundance of fish and decapods (mobile megabenthos)
increased in the vicinity of the well. These organisms were
probably attracted to the area as a result of the increased
microrelief of the cuttings piles and food availability.
Sessile megabenthos were subject to the effects of burial.
Densities of the major taxa decreased between the pre-drilling
and the first post-drilling surveys. The densities showed
signs of a partial recovery after a one-year period (pre-
drilling = 8.011 ind./m2; post-drilling I = 1.729 ind./m2;
2
post-drilling II = 2.638 ind./m ). Possible impacts of
drilling discharges include burial, diminished larval recruit-
ment, and increased predator pressure. There was a significant
negative correlation between sediment barium concentrations and
the abundance of brittle stars following drilling. The lowered
abundance of brittle stars was still evident during the second
post-drilling survey.
EG & G (1982) reported that reductions in abundances may be
due to natural variability instead of drilling discharges since
they occur at the one- and two-mile stations. Unfortunately,
there are no pre-drilling abundance data available at the
5-18
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two-mile stations. Without this background data, it is not
possible to determine whether or not the one- and two-mile
stations are beyond the zone of influence. *
There was little change in the gross taxonomic structure of
the benthic community. Species richness paralleled decreases
in abundance, dropping from a mean areal richness of 70
2 ?
species/0.2 m to 38 species/0.2 m . There was little
change in the Shannon diversity or Pielou evenness indices.
For these analyses of community structure (diversity and
evenness), the benthic data set was reduced as follows:
"Singleton" species (taxa represented by a single
individual) were eliminated from the data set;
taxa were eliminated if they were represented by
lower-order taxa and accounted for less than 20
percent of the total individuals in the group: and
when a higher order taxon contained 20 percent or more
of the total number of individuals in that group, all
lower-order taxa were merged with the higher taxon.
The reason given for this reduction in the data set was to
allow greater confidence in the validity of the taxonomic
categories used in the structural analysis. However, these
reductions may mask important changes such as the elimination
of a sensitive species and/or a reduction in the total number
of species. This may bias the results of the diversity index.
since the most important component of Shannon's equation is the
evenness factor (number of individuals in species i). Accordingly.
5-19
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it seemed appropriate to recompute the Shannon-Weaver index on
the unreduced data set. The results of this test, however.
failed to indicate any major changes in community structure.
5.3.2 Georges Bank
The Georges Bank Monitoring Program was implemented by the
Minerals Management Service in cooperation with EPA. other
Federal agencies, and the affected coastal states in July 1981
to determine the potential impact of exploratory drilling
activities on benthic communities from Lease Sale No. 42 at
Georges Bank, off Massachusetts. One major goal of this
program has been to identify and document immediate and long-
term changes in hydrocarbons and trace metals in sediments and
epifauna as they relate to drilling activities and proximity to
exploratory platforms.
Georges Bank is located approximately 300 km (180 miles)
southeast of Cape Cod. Massachusetts. The monitoring program
consists of a series of seasonal cruises. The first four
cruises took place in July 1981. November 1981. February 1982.
and May 1982. These cruises spanned the period during which
the eight exploratory wells were drilled (December 1981 to June
1982). Cruises have since continued on a quarterly schedule.
Bothner et al. (1982) analyzed trace metals in the bottom
sediments. Their objectives were to determine whether dis-
charged drilling fluids accumulated on Georges Bank and the
extent to which trace metals increased in the sediments as a
result of accumulating muds. The sediments of Georges Bank are
typically 95 percent sand except for an area located south of
Nantucket Island. This area, appropriately referred to as the
5-20
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"Mud Patch." is thought to be a major depositional site and
contained from 38 to 97 percent fine materials (less than 62
tiro in diameter). Pre-drilling samples had metals concentra-
tions lower than crustal rocks, suggesting the area is
essentially uncontaminated with respect to the heavy metals
analyzed (aluminum, barium, cadmium, chromium, copper, iron.
lead, mercury, manganese, nickel, vanadium, and zinc). Barium
increases in the sediments were noted following the initiation
of drilling activities. The distribution of barium in the
sediments appeared to be biased to the west, which is
consistent with the expected transport based on mean current
flow. Block 410 in the lease area showed an average barium
increase from 30 to 107 ppm within a 200 m zone and a smaller
increase at distances up to 2,000 m. Block 312 showed average
barium increases from 37 to 67 ppm. Smaller increases were
measured at distances of up to six km from the drilling site.
There were no drilling-related changes in the concentrations of
chromium or other metals in the bulk sediments. Increases in
aluminum, chromium, copper, and mercury in the fine fractions
of the sediments were observed at the drill site in Block 410.
Payne et al. (1982) analyzed sediments for hydrocarbons and
epifaunal tissues for hydrocarbons and trace metals. Overall.
the aromatic hydrocarbon levels in the sediments were extremely
low and essentially constant over time. The highest and most
variable aliphatic and aromatic hydrocarbons were observed in
the "Mud Patch." Sediment analyses indicated that the majority
of the aliphatics were of biogenic origin and that drilling
fluid components accumulated in the "Mud Patch." There was
also little evidence of hydrocarbons accumulating in tissues.
One sample (Arctica islandica) had elevated concentrations.
compared to samples taken at other locations, of polynuclear
5-21
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aromatic hydrocarbons common to drilling fluids which may have
been present. However, it is not possible to categorically
state whether drilling fluids were the source of the
hydrocarbon accumulation. There was no evidence of metals
levels in epifaunal tissues changing over time. The total
number of tissue samples was limited, so a complete analysis
was not possible. Levels of cadmium, chromium, copper, iron.
lead, nickel, and zinc showed no significant change between the
1977 (ERGO) and 1982 (Payne et al.. 1982) sampling episodes.
The sampling plan for Georges Bank had two components. The
long-term or regional stations were established as three
transects: one through the lease tract area, one upcurrent
(eastward), and one downcurrent (net flow) (Figure 5-1).
Additional stations were established at the center of the Bank
and at depositional sites in the "Mud Patch" south at
Nantucket. in Lydonia and Oceanographic Canyons, and in the
Gulf of Maine on the north side of the Bank. A site-specific
set of 29 stations was sampled at 80 m depth in Block 312 near
the center of the lease site area (Figure 5-2). Stations were
established in a radial pattern at distances from 100 ro to six
km as well as at the rig site itself. A second small rig-site
study was conducted at Block 410 in 140 m on the southern flank
of the Bank. Three stations were located within 200 m of the
rig site and others approximately two km upcurrent and
downcurrent.
The long-term stations situated around the Bank were
established to examine trends over a large area and a long
period of time. Since only eight wells were drilled in a one-
year period, no drilling-related changes could be detected in
5-22
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43'
in
I
to
U)
^oyldencej
Bathymetry in Meters
72
71
68*
67
66
FIGURE 5-1 LONG-TERM REGIONAL STATIONS
(from Blake et. al., 1983)
-------
the benthic infauna. Differences between sampling data were
always smaller than differences between stations. There were
some seasonal changes in the fauna at Block 410 (stations
10.17.18) but none of the changes could be related to drilling
activity.
Drilling started in Block 312 in December 1981 and
continued until June 1982. Approximately 900 metric tons of
fluids and 1,000 metric tons of cuttings were discharged. Most
of the change in barium content at the sediment occurred
between the February and May cruises. Drill cuttings were
observed in the gravel fraction of sediments at Station 5-1.
The abundance of several species was compared over the four
seasons at those near-field stations showing the largest
increment in sediment barium concentration (5-8. 5-2. and 5-1);
those downcurrent stations showing moderate increments in
barium (5-10 and 5-25); and those upcurrent stations where
there was no evidence of drilling fluids at cuttings
accumulation (5-28 and Regional Station 2). At stations near
the rig site, there was a decrease in the number of individuals
per sample from July to November, with good recovery in
February, continuing through May. The downcurrent stations did
not experience a decline until February, and there was
substantial recovery by May. The upcurrent stations showed a
gradual increase in density through the four seasons.
Several species showed differing patterns of seasonal
abundance. The most dramatic population decline was shown by
the amphipod Ericthonius rubricornis. an epifaunal suspension
feeder.
5-24
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SAMPLING
LONGSHtLF
SITEXSPECIFIC
PLAN
FIGURE 5-2 Site-specific sampling array around regional station 5. Stations 5-7,
5-13, 5-17, 5-21, 5-23, 5-24, 5-26, and 5-27 are secondary stations
(of lower priority) and are presently archived.
(from Blake et. al., 1983)
5-25
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Most of the changes observed near the rig site can be
correlated with changes in sediment grain size characteristics.
These sediment changes could have been due to secondary action
of winter storms and/or accumulations of drill cuttings.
Evidence of drilling fluid accumulation did not occur until
May. by which time most species had shown substantial
recovery. Thus, it appears that the high energy environment of
the Bank prevented major accumulation of fluids or cuttings and
effects on the benthic infauna were therefore minimal or
non-existent. Bottom currents at Block 312 are approximately
50 cm/sec.
5.3.3 Lower Cook Inlet
Lees and Houghton (1980) studied the effects of drilling
fluids on the benthic communities at the Lower Cook Inlet.
Alaska. Continental Offshore Stratigraphic Test (COST) well.
The objective of this study was to determine species abundance
and composition and to evaluate the extent to which the drill-
ing activities may change these parameters. Changes which
might be detected are large alterations in species composition
or changes in the richness, diversity, or abundance of species.
The COST well was drilled from June 7 to September 26, 1977.
Benthic samples were taken before (June 6. 1977). during
(July 25. 1977). and after (September 19. 1977) the completion
of drilling, using a Ponar dredge. Underwater television pic-
tures of the seafloor showed no visible accumulation of cut-
tings. The maximum accumulation of cuttings in any benthic
sample was three percent by weight. Barium concentrations in
the benthic samples were within pre-drilling ranges.
5-26
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Benthic surveys showed a population typical of a shallow.
high energy, sandy substrate in a northern subarctic region.
There were some changes in benthic community composition over
the duration of the study, but none of the changes were
significant and none could be attributed to drilling
discharges. Individual and species abundances and Brillouin
diversity did not change significantly within 200 m of the well
site. Lees and Houghton did note that a comparison of pre- and
post-drilling data was complicated by an incomplete knowledge
of seasonal cycles for the arctic species and sampling
anomalies (i.e., inability to use same control sites for
pre- and post-drilling samples).
It was concluded that, due to the high energy nature of the
environment, drilling fluids and cuttings did not accumulate on
the seafloor at rates sufficient to alter the benthic communi-
ties.
5.3.4 Beaufort Sea
Crippen et al. (1980). under the sponsorship of ESSO
Petroleum Resources, Inc., examined metal levels in sediments
and benthos resulting from drilling fluid discharges into the
Beaufort Sea. Alaska. The primary objective of the program was
to investigate the environmental significance of metals in
drilling fluids discharged to the aquatic environment. The
study site was an artificial island constructed from local
borrow material in the Beaufort Sea near the Mackenzie River
delta. The average depth of the study area was approximately
seven meters.
5-27
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The exploratory well under study was drilled from
November 8, 1975, to May 19. 1976. and the sampling program was
carried out during August of 1977. The investigators sampled
47 stations for arsenic, cadmium, chromium, lead, mercury, and
zinc in the sediments and infaunal tissues. The barite used in
the drilling fluid which was discharged was a "dirty barite."
and contaminated with these same metals. Mercury concentra-
tions in the drilling fluid were 185 times higher than
background levels in the sediments.
When compared to background concentrations, elevated levels
of arsenic, cadmium, chromium, lead, and zinc in the sediments
were found at one or more stations near the discharge site.
Mercury levels were clearly elevated within a distance of
100 m. No correlation was found between metals levels in the
sediments and metals levels in tissues. There was some
evidence of bioaccumulation of mercury (up to an order of
magnitude) at two stations; other than this, evidence of
bioaccumulation of metals in infaunal tissues was absent.
Density and biomass of benthic organisms was reduced within
300 m of the artificial island. Crippen et al. (1980)
concluded that smothering and modification of the substrate by
borrow material during construction of the island had a greater
effect on benthic populations than drilling fluid disposal.
5.3.5 Tanner Bank
Tanner Bank is located approximately 160 km offshore from
Los Angeles. California. The area has been designated a
"unique biological area" by the Pacific Office of the Bureau of
Land Management for many reasons. The abundance and health of
5-28
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this unusual assemblage of organisms is exceptional. Baseline
studies funded by the BLM (Smith, 1976) have identified 94
completely new species. One discovery was of Neopilina sp.. an
extremely rare monoplacophoran mollusc thought to have long
been extinct.
Ecomar (as in Thomas et al.. 1983; Meek and Ray, 1980; Ray
and Meek. 1980) carried out a water quality investigation of
the area in conjunction with the drilling of an exploratory
well by the Shell Oil Company. Sampling during discharges of
drilling fluids (January to March, 1977) showed that the
discharges caused minor and transient modifications to the
receiving waters. The bulk of the discharged materials settled
to the bottom within 120 m of the discharge, while background
trace metal and suspended solids concentrations were reached
within 200 m. Ecomar (reported in Thomas et al.. 1983)
reported that "mud and cuttings dilution and dispersion was so
complete that residual materials were visually undetectable on
the rock reef or directly below the discharge site." An inves-
tigation of the reef-associated biota covering six linear km
from the discharge site concluded that drilling operations at
Tanner Bank had no significant observable adverse effect on the
associated reef community.
5.4 DISCHARGES OF PRODUCED WATER
5.4.1 Buccaneer Gas and Oil Field
The environmental assessment of the Buccaneer Gas and Oil
Field involved a five-year field and laboratory research
project funded by EPA through an interagency agreement with
NOAA. The Buccaneer Field study was initiated in 1975 and
completed in 1980.
5-29
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The study examined the effects of chronic, low-level expo-
sure of the ecosystem to contaminants generated by oil and gas
production activities. Specifically, the objectives of the
project were (1) to identify and document the types and extent
of biological, chemical, and physical alteration to the marine
ecosystem, (2) to identify the specific pollutants, their
quantities and effects, and (3) to develop the capability to
describe and predict fate and effects of environmental contami-
nants.
The Buccaneer Field is located approximately 49.6 km
southeast of Galveston. Texas, in 20 m water depth. There were
17 structures in the Field including two production platforms,
two living-quarters platforms, and 13 satellite structures.
The discharge of produced water was estimated at 600 bbl/day,
which is not a particularly high discharge. The area could be
characterized as a relatively high energy environment. The
work progressed in five stages:
Brief pilot study in the autumn and winter of 1975-1976
Extensive biological/chemical/physical survey in 1976-
1977 comparing Buccaneer Field to adjacent control areas
investigations within the Buccaneer Field (1977-1978)
comparing conditions around production platforms which
discharge produced water to those around satellite
structures which have no such discharges
Studies in 1978-1979 focusing on a) the concentration
and effects of pollutants in major components of the
marine ecosystem, b) the effect of circulation dynam-
ics and hydrography on the distribution of pollutants.
and c) mathematical models to describe and predict
sources, fate, and effects of pollutants
5-30
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Further focus on elements (a) and (b) above during
1979-1980 and the preparation of milestone reports.
Brooks et al. (1980) measured the concentrations of
volatile liquid hydrocarbons (VLH) in seawater at the Buccaneer
Field. Elevated levels (~65 ppb) were observed immediately
below the discharge pipe, but were rapidly diluted with
distance. Henzie (1982) estimated that reductions of VLH
concentrations at the Buccaneer Field platform were on the
4 5
order of 10 to 10 within about 50 m of the platform.
Concentrations of VLH around the platform were four times
higher than at platforms three km away which had no discharge.
However, values at this latter platform were still higher than
those Sauer (1980) considers anthropogenically affected.
Brooks et al. (1980) concluded that production platform
discharges in the Buccaneer Field do not measurably alter the
bulk composition of suspended particulates or biological
activity (as measured by the biochemical indicators chlorophyl
and ATP) in the water column in their immediate vicinity.
Surficial sediment data indicated that there was considerable
movement of fine grain material in the area, so contaminants
introduced to the sediments in Buccaneer Field may be rapidly
removed from the platform vicinity by resuspension and
transport. Only contaminants associated with coarse-grained
material would be expected to remain in the Field. These
observations were confirmed by the seasonal contamination
patterns of trace metals and hydrocarbons in the Field.
Gallaway (1980) selected the following indicators for the
study of biological impacts:
5-31
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standing crop biomass. community structure and compo-
sition, production and health or condition of the
biofouling community
relative abundance of demersal fishes and macro-
crustaceans
pelagic and reef fishes
He observed that there was a rich and diverse biofouling
community associated with the production platforms. These
artificial reefs aggregated nektonic species preferring these
habitats, as well as their predators. Produced waters were
toxic but the measurable effects on biota were generally
restricted to within a few meters of the outfall, as evidenced
by effects on the biofouling community. The biomass levels and
production rates of the biofouling community were depressed in
the vicinity of the outfall (generally to a vertical distance
of one meter and a horizontal distance of ten meters).
Middleditch (1980) examined 31 fish species for petroleum
hydrocarbon contamination, 15 of which contained measurable
quantities of petroleum hydrocarbons (alkanes. at 1.1-6.8
ppm). Tissue samples were not analyzed for lighter aromatic
hydrocarbons. A degree of correlation was found between the
feeding habits of some fish and their hydrocarbon content.
Those fish which fed on the biofouling community, which
contained elevated hydrocarbons, had higher concentrations than
those which fed in the water column. Hydrocarbon
concentrations were usually higher in the liver than in other
tissues. Additional detail on this part of the study is
provided in Section 3.
5-32
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The major pool of contaminants in the Buccaneer Field is
the surficial sediments (Middleditch. 1980). He determined
that the sediments contained concentrations of petroleum
alkanes as high as 50 ppm. Moreover, these concentrations were
dependent upon the total quantity of contaminants discharged
from the platform in the produced water. Middleditch1s
analysis was limited primarily to alkanes.
Petroleum hydrocarbons were detected at the air/sea inter-
face and in the mixing zone below the discharge pipes, but were
rarely found in above ambient concentrations in other seawater
samples (Middleditch, 1980). Based on data presented by Brooks
et al. (1980). concentrations of volatile liquid hydrocarbons
(VLB) at the production platform were approximately four times
higher than at a platform three km away which had no
discharge. Yet, values at this latter platform were still
higher than those given by Sauer (1980) for anthropogenically
influenced water. Tillery (1980) showed that brine discharges
have concentrations of barium, cadmium, chromium, iron,
mercury, manganese, thallium, and zinc significantly higher
than seawater. However, there has been a good deal of
uncertainty about the quality of the data on metal
concentrations in brines.
The currents and waves tend to dilute and disperse brine
discharges immediately upon discharge. There have been
short-term accumulations of barium, cadmium, chromium, copper,
and lead in the sediments, and more persistent accumulations of
mercury, manganese, strontium and zinc. There is no evidence
of bioaccumulation of trace metals in either the biofouling
community, spadefish, or sheepshead. Indications of
accumulation in the longspine porgy and sugar shrimp which were
observed cannot be confirmed statistically.
5-33
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Barium levels in the gill tissues of diseased fish were much
higher than in healthy fish gills. Those higher barium
concentrations could be caused by bioaccumulation or be
associated with fine particles trapped in the gills, either of
which may be responsible for the disease.
Alterations in the benthic fauna around the Buccaneer
production platform were observed by Harper et al. (1980).
Stations within 100 m of the platform had depressed faunal
abundance, a relatively high species turnover rate, and the
occurrence of a few species that were more frequently found at
these stations than in the remainder of the study area. The
authors offered several possible explanations for the altered
benthic conditions. However, it appeared that toxic effects,
perhaps associated with the presence of hydrocarbons and/or
biocides, were contributing at least in part to the altered
benthic community composition and abundance.
5.4.2 Central Gulf of Mexico
The ecological investigation of petroleum production plat-
forms in the Central Gulf of Mexico (Bedinger et al.. 1981) was
carried out by the Southwest Research Institute under the spon-
sorship of the Bureau of Land Management as part of their OCS
Environmental Studies Program. The study area for this inves-
tigation included 20 petroleum production platforms and four
control sites in the Louisiana OCS. The study was aimed at
defining the long-term cumulative effects of petroleum
production in this region. However, the Mississippi River
discharge exerted a major influence over the study area, and
this made it difficult if not impossible to discern effects
attributed solely to production operations.
5-34
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The specific objectives of this study were:
Determination of the distribution and concentration of
petroleum hydrocarbons, selected trace metals, and well
drilling related substances in surficial sediments and
tissues of commercially and/or ecologically important
benthic and demersal species.
Examination of microbial hydrocarbon degradation and
nutrient cycling processes and related nutrient
chemistry in surficial sediments.
Comparison of benthic communities in the immediate
vicinity of platforms with those at control sites.
Examination of the distribution of petroleum hydro-
carbons, selected trace metals, and well drilling
related substances in sediments according to depth.
Investigations of biofouling communities and the
"artificial reef" effect at a variety of platforms.
The program was designed to sample at various distances
from the platforms in order to determine long-term buildup of
contaminants in the sediments and foodweb. Sampling took place
during 1978 and 1979 at stations located 100. 500. 1.000. and
2.000 m from the platforms.
Nulton et al. (1981) analyzed for low molecular weight
hydrocarbons (LMW-HC) in the water column, total organic carbon
in the sediments, and high molecular weight hydrocarbons
5-35
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(HMW-HC) in the sediments and organisms. The LMW-HC analyses
of seawater indicate the entire area has a baseline level of
-------
which consistently showed the highest trace metals and hydro-
carbon contamination were the locations where histopathological
conditions in fish were common. Because the spadefish had a
high incidence of histopathological conditions, its
distribution among platforms (where it was common) and control
areas (where it was not common), affects the frequency of
occurrence of these conditions.
The results of the artificial reef studies (Gallaway
et al., 1981) indicate that the production platforms have
apparently expanded the available habitat for numerous fish and
invertebrate species. The produced water discharges had
localized detrimental effects on the fouling biota such as
lowered biomass and density, low survival rates of barnacles,
low production and recolonization rates, and a greatly altered
community structure.
Because of anoxic conditions and storm events, the benthic
community was greatly disturbed during the study period.
Therefore, it was not possible to examine the effects of
production operations on these organisms.
5.4.3 Timbalier Bay
The Gulf Universities Research Consortium conducted the
Offshore Ecology Investigation (OEI) of Timbalier Bay to help
determine the ecological impact of petroleum drilling and pro-
duction in coastal Louisiana. Morgan et al. (1974) summarized
eight synoptic field sampling and data collection exercises in
Timbalier Bay and offshore to a depth of 30 m (100 ft) covering
5-37
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a period from 1972 to 1974. The study encompassed the work of
23 principal investigators. An OEI Council of four scientists
evaluated and interpreted the results of the 23 individual
investigations.
Studies examined the physical setting (i.e.. water mass
movement, currents, geology), the chemical setting (i.e..
inorganic nutrients, hydrocarbons, trace elements), and the
biology (i.e.. phytoplanKton. primary productivity, benthic
plants, zooplankton. benthos, and ichthyofauna) of the area.
The final consensus report of the first OEI Council (Morgan
et al.. 1974) stated that "No harmful impact on the environment
from production or drilling is demonstrated" by the data col-
lected. They concluded that 79 percent of the individual
studies demonstrated either no impact or a beneficial impact.
while the remaining 21 percent of the investigations were
inconclusive for one reason or another. Their general conclu-
sions concerning the area were:
Natural phenomena have a much greater impact on the
ecosystem than petroleum activities.
Concentrations of compounds of OEI interest are suffi-
ciently low to present no known biological hazards.
Every indication of good ecological health is present.
Timbalier Bay has not undergone significant ecological
change attributable to petroleum activities.
5-38
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In 1979, Bender et al. undertook a reexamination of the
data and conclusions drawn from the OEI, in which they were
critical of the original OEI study design as a means of
responding to the program's objectives. Based on the original
data collected, which showed evidence of petroleum
contamination in the sediments at control and experimental
areas. Bender et al. (1979) surmised that "most of the OEI data
appear to be collected from the same 'population1 and should be
expected to be the same within statistical errors of
sampling." In addition, the temporal and spatial variability
of species and the "complete" mixing of the Gulf hydrocarbon
content suggest that the classical experimental versus control
design may be inappropriate. Bender et al. also noted that the
limited data-gathering effort of the OEI was probably
inadequate to definitively detect the low-level effects of oil
contamination.
The above qualifications notwithstanding. Perry (1974,
reported in Bender et al... 1979) found the production sites to
have the lowest fish biomass and species diversity, and
attributed this to encrusting of the bottom by drilling muds.
Other investigators produced data which indicated elevated
cadmium, lead, and zinc levels in the immediate vicinity of the
well. Overall, however, the results of the OEI are
inconclusive. These findings do not clearly indicate the
effect or the lack of an effect from oil drilling and
production in the Gulf of Mexico.
The re-evaluation also led to the conclusion that there
was no indication of environmental stress resulting from oil-
related activities. However, this conclusion was tempered with
5-39
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a few qualifications regarding the limitations of the original
experimental design and data base for defining the chronic
effects of oil. The researchers concluded that ". . .the
natural variability inherent in the biological, physical, and
chemical processes in the Gulf of Mexico precludes acquisition
of adequate, representative, or valid baseline data in a period
limited to two years."
5.4.4 Trinity Bay
Trinity Bay. Texas, is a shallow, turbid bay in the north-
eastern arm of the Galveston Bay complex. It contains several
oil fields and is an important area to recreational and com-
mercial fishermen. The separator platform chosen as the target
for this study is the largest in the Fishermen's Reef Field.
The oil and brine mixture is pumped from the ground into
separator tanks where it is allowed to separate. The oil is
transported to shore through pipelines and the brine is dis-
charged to the bay through a shunt whose mouth is three feet
(1 m) above the bottom. The mean depth at the platform is
eight feet (2.5 m) and the sediments are predominantly silty
clay.
The study sought to determine the concentrations of naph-
thalenes in the sediments and the abundance and distribution of
benthic organisms in relation to distance from the platform.
and whether these were correlated. Further, the researchers
compared concentrations of specific hydrocarbons in effluents,
bay water near the platform, and sediments, and determined
whether there was a zone of stimulation around the platform.
5-40
-------
Naphthalenes were chosen to indicate the presence of petroleum
hydrocarbons in the water and sediment because they are non-
biogenic in origin and are known to be some of the most toxic
components of petroleum.
The highest levels of naphthalene in the sediments (up to
110 ppm) were found within 15 m (50 ft) of the platform
outfall. Although the effluent was quickly diluted (2.000-fold
within 15 m). naphthalenes accumulated in the sediments to
concentrations 13 times the effluent concentrations. The high
and persistent naphthalene levels in the sediments were
probably due to turbid conditions and the slow degradation rate
of oil in sediments. Naphthalene concentrations decreased as
the distance from the outfall increased.
There was a significant inverse correlation between sedi-
ment naphthalene concentrations and the number of benthic
organisms. The bottom was essentially devoid of benthos within
15 m of the platform and the number of benthic species and
individuals was severely depressed for a radius of 152 m (500
feet). Apparently a low persistent concentration of naph-
thalenes was capable of restricting many species of benthic
organisms. The number of species increased with distance from
the platform. These results parallel those of an earlier
investigation (Mackin, 1971) in a shallow (2.4 m) Texas
estuary. Mackin reported that produced water discharges
totally eliminated the benthic community within 15 m of the
discharge and that some mortality of the benthos was evident at
a distance of 91 m. Causative factors in this study can be
reliably attributed to the platform discharges, since all other
factors were constant among stations.
5-41
-------
5.4.5 Santa Barbara Channel. California
This study was funded by API and involved an examination of
two oil platforms located 3.5 km offshore California in
approximately 30 m depth. At the time of the study, the
platforms had been operating for about 15 years. Results are
presented in Mearns and Moore (1976). Produced water from
these platforms is treated onshore at the Carpintria facility,
with an ocean discharge (E. Bromley, EPA Region IX; Personal
Communication to E. Zimmerman, EPA Headquarters).
Elevated levels of hydrocarbons in sediments were observed
around the platforms. Mearns and Moore (1976) concluded that
the composition of the hydrocarbons was characteristic of
weathered oil and was not indicative of present-day hydrocarbon
contamination. Elevated concentrations of zinc were also found
in the sediments around the platforms. However, the source of
this metal was unclear. Elevated concentrations of vanadium
were observed in rockfish.
The study also looked for impacts on benthic organisms.
There were no measurable detrimental impacts. However, there
was some indication of biostimulation. perhaps due to inputs of
organic material from the platform's biofouling community.
Again, there was no discharge of produced water at these
platforms.
5.5 CATCH AND EFFORT STATISTICS FOR THE GULF OF MEXICO
Trends in catch statistics for commercial fish landings may
reflect a number of factors including adequacy of reporting,
fishing pressure, natural perturbation, fresh water inflow, and
marine pollution effects. These trends are examined here in
5-42
-------
order to determine if there are any indications that offshore
oil and gas operations could be a factor affecting commercial
fish and shellfish yields. The National Marine Fisheries
Service (NMFS) offices have provided commercial fish landings
for the Gulf of Mexico from 1880-1982. The older statistics
prior to 1977. are not representative of the Fishery
Conservation Zone of 200 miles which came into existence in
1977.
Level-of-effort information which involves estimates of
operating units based on the number of fishermen, boats, and
gear involved in the catch was also obtained from NMFS. These
statistics are published for a number of species in the Gulf of
Mexico from 1950-1976. Statistics were compiled for shrimp.
red snapper, oyster, and blue crab, since these are some of the
most important commercial species.
Although catch-per-unit effort cannot be used as an
absolute index of fish abundance, productivity, or health, it
is a valuable index for monitoring annual fishery dynamics.
The results show that in comparison to the other Gulf states.
Louisiana waters have the lowest catch-per-unit effort for
shrimp and red snapper based on annual averages from 1950-1976
(Figures 5-3 through 5-5). Louisiana had a higher catch-per-unit
effort for oysters in comparison to the other Gulf states
(Figure 5-5).
For blue crabs, the catch-per-unit effort statistics are
calculated from 1963 when most of the trot lines were replaced
by pots. From 1963 to 1976. the catch-per-unit effort for blue
crabs is lower in Louisiana offshore waters when compared to
the average of the other Gulf states (Figure 5-6 through 5-10).
5-43
-------
FIGURE 5-3
SHRIMP LANDING PROUUCTMTY (CATCH/UNIT EFFORT)
IN THE GULF OF MEXICO, 1950-1976
\ s V\ M
V/ v \
1tSO
tWO IMS 1070
YEAR OF RECORD
1179
ttao
-------
in
I
*»
in
t>
1
I t>
100G
ft
\A
80C
Sb
CC
Q
Z
r>
o
o.
40C
eft
t
o
O
O
200
FIGURE 5-4
SHRIMP CPUE (Ibs/trlp)
o TOTAL GULF
GULF-LA
* LA ONLY
1955 6
8 9 60
5 6
YEAR
8 9 70
-------
FIGURE 5-5
in
i
a*
fc:
5
RED SNAPPER LANDING PRODUCTIVITY (CATCH/UNIT EFFORT)
IN THE GULF OF MEXICO, 1950-1976
fe =:
1*50
IttO »« WTO
YEAR OF RECORD
1f79
1*80
-------
FIGURE 5-6
OYSTER HARVEST PRODUCTIVITY (CATCH/UNIT EFFORI)
IN THE GULF OF MEXICO, 1950-1976
23-
20 H
13-
8-
ttSO 1t33 «M nn ItTO 1073 ttBO
YEAR OF RECORD
-------
500-
FIGURE 5-7
BLUE CRAB CPUE (ibs/pot)
(POT CATCH ONLY)
oJOTAL GULF
GULF-LA
TLA ONLY
400 J
3004
i
*
00
200{
100
1963
-i
8
9 7O 1
YEAR
-------
FIGURE 5-8
I
>
vo
18
16
(0
I
10
8
o 4
BLUE CRAB CATCH AND EFFORT
GULF OF MEXICO
1964 65 66 67 68 69 70 71 72 73 74 75 76
YEAR
50
45
40
35
o
30 g
O
25 g
Z
h20 2
10
-------
FIGURE 5-9
I
en
o
I
£
"
5
o
z
m
o
m
0
I
m
-4
g
-
c
m
o
H
0
3
5
0)
g
BLUE CRAB CATCH AND EFFORT
20
18
16
4
* 14
*~*
I
JL 12
i
j2 10
2*^
1
^*
3 6
g
-
0 4
T~
2
LOUISIANA
^
^^
^^*
--*
^^.^m"
^ f-..
T_ v / ^-^^
^^ / ^^ ~^~-M
V /
X" /
/" m
/ ^^^'^~~~^~~-.mi^~'^"
/ ^^
/<~m^*
V
50
45
40
r
35
O
30 Jj
O
25 W
Q
Z
f\
20 g
Z
O
!j
i
10
5
1^64 65 66 67 68 69 7O 7'l 72 73 74 75 76
YEAR
-------
FIGURE 5-10
IP
IT
s
S
Is
i ni
m
DC
O
UJ
(0
o
o.
2O
18
16
14
12
10
0 8
(A
8
o 4
BLUE CRAB CATCH AND EFFORT
GULF - LA
1964 55 t>667 68"
69 70
/EAR
Tl ~7275 74~
50
45
40
35
o
30
25
20 g
«
10
75 76
-------
Table 5-2 presents the calculations for blue crabs. Statistics
prior to 1964 could not be meaningfully interpreted because of
the gear changeover from trot lines to pots.
The National Marine Fisheries Service has suggested that
overfishing. loss of wetlands, and pollution from offshore oil
and gas platforms are possible factors for this trend in
catch-per-unit effort in Louisiana waters. Over 88 percent of
the offshore structures in the Gulf are located in Louisiana
offshore waters. Although not definitive, the evidence raises
an environmental concern with respect to discharges from oil
and gas platforms.
5-52
-------
TABLE 5-2 BLUE CRAB CATCH AND LEVEL OF EFFORT
FOR THE GULF OF MEXICO. LOUISIANA, AND THE GULF LESS LOUISIANA
Year
1964
1965
1966
1967
1968
in
i, 1969
u>
1970
1971
1972
1973
1974
1975
1976
Number of
Pots
70,145
90,085
115,010
125,611
125,611
129,026
138,700
151,240
151,220
158,480
170,345
194,330
219,919
Gulf of Mexico
Ibs x 1,000
19,383
31,760
25,896
26,106
24,401
26,083
33,004
33,568
34,305
42,9%
42,152
39,862
38,970
CPU£a
(Ibs/Pot)
276
352
225
207
190
202
236
223
227
271
247
205
177
Number of
Pots
3,250
11,465
40,200
58,785
65,600
67,900
75,800
84,100
87,600
93,600
108,100
122,800
144.000
Louisiana
Ibs x 1,000
2,483
4,813
4,606
5,422
6,927
8,581
7,771
10,579
12,268
20,569
19,903
16.165
15,169
Gulf Less Louisiana
CPUE
(Ibs/Pot)
115
92
106
126
103
126
140
220
184
132
105
131
105
Number of
Pots
66,895
78,620
74,810
66,826
60,011
61,126
63,900
67,140
63.620
64,880
62,245
71,530
75,919
Ibs x 1,000
16,900
26,947
21,290
20,684
17,474
17,502
25,233
22,989
22,037
22,427
22,249
23,697
23,801
CPUE
(Ibs/Pot)
252
343
285
310
291
286
395
342
346
346
357
331
314
Source: National Marine Fishery Service fishery statistics, 1964-1976.
= Catch-per-unit effort.
-------
6.0 ECOLOGICAL RESOURCE CHARACTERISTICS OF SHALLOWER
MARINE ENVIRONMENTS
6.1 SUMMARY
This section of the report examines ecological resource
characateristics of nearshore marine environments. These
generally include nursery areas since as larval and juvenile
forms are considered the life stages most sensitive to
discharges of wastes. The focus was primarily on shallower
areas because available information suggests that effects of
discharges are more likely to occur there. Information for
making these assessments was provided by NOAA as well as
reviews of environmental assessments, impact statements, and
contacts with state and federal agencies.
For each of the following areas, isobaths were identified
which enclosed most or much of the resource/nursery areas.
These are listed below:
AREA ISOBATH
Gulf of Mexico 20 m
Atlantic 20 m
Beaufort Sea 10 m
Bering Sea/Norton Sound 20 m
Cook Inlet/Shelikof Strait 50 m
Bristol Bay/Aleutian Range 50 m
Gulf of Alaska 50 m
California 50 m
6-1
-------
6.2 DEPTH DISTRIBUTION OF RESOURCE/NURSERY AREAS
Information presented in Sections 3-5 suggests that
shallower areas may be more susceptible to effects of oil and
gas discharges than deeper ocean areas. While review of Menzie
(1982) and Middleditch (1984) as well as information presented
in this report generally support this, it is more difficult to
identify a specific isobath beyond which effects would be
"substantially less significant." However, it is possible to
examine the ecological resource characteristics of shallower
ocean environments with a view toward identifying isobaths
within which key areas (e.g.. spawning, nursery grounds.
fishing banks) occur. These shallower areas constitute regions
that might be considered for an additional margin of
protection. An assessment was therefore made of the shallower
water ecological Resources of these areas.
Information on species distribution for the Gulf of Mexico
and the East Coast has been compiled for EPA by the Ocean
Assessments Division of the National Oceanic and Atmospheric
Administration (NOAA) based on computerized species
distribution data from the National Marine Fisheries Service
(NMFS). The list of species was selected from Tables 4-13 thru
4-16 of Section 4 on potential acute and chronic effects from
various pollutants found in produced waters. The following 15
species which were contaminated with petroleum hydrocarbons
during the Buccaneer Field study were also included in the
analyses:
6-2
-------
Archosarqus probatocephalus (sheepshead)
Centropristis philadelphica (rock sea bass)
Chaetodipterus faber (Atlantic spadefish)
Cynoscion arenarius (sand seatrout)
Lutianus campechanus (red snapper)
Micropoqon undulatus (Atlantic croaker)
Pomatomus saltatrix (bluefish)
Porichthys porosissimus (Atlantic midshipman)
Prionotus rubio (blackfin searobin)
Saurida brasiliensis (largescale lizardfish)
Stenotomus caprinus (longspine porgy)
Syacium papillosum (dusky flounder)
Symphurus plaqiusa (blackcheek tonguefish)
Synodus foetens (inshore lizardfish)
Urophycis floridanus (southern hake)
Nursery areas were chosen as key "resource areas" for this
analysis because they are where sensitive life stages
(pre-adult and post-larval) are expected to occur. NOAA did
not have some of the species listed above in their database or
many invertebrate species such as barnacles, polychaetes.
copepods, snails, etc. in their database for the Gulf of Mexico
or East Coast. Most of the available data is on commercially
important fish species and invertebrates, which vary by
region. Based on the information made available by NOAA a
significant portion of the nursery areas for the selected fish
and invertebrate species in the Atlantic and Gulf regions are
located within the 20 m (66 feet) isobath.
6-3
-------
Tables 6-1 and 6-2 show the percentage of the nursery areas
that would be protected by the designated areas (estuaries.
state waters. 10 m-2000 m water depths) for the Gulf of Mexico
and for the East Coast (estuaries, state waters, 20 m-2000 m
water depths).
Key resource (nursery) areas for the West Coast and Alaskan
analyses are more difficult to define because of the lack of a
computerized data base. NOAA only has preliminary data on
these areas and this could not be used at this time, except the
Bristol Bay analysis which is based on preliminary draft
information from NOAA. For the other analyses, information was
obtained from Environmental Impact Statements on offshore lease
sales. In addition. Ocean Discharge Criteria evaluations were
examined, and NMFS and state officials in Alaska and California
were contacted in order to provide information on these areas.
Section 6.3 discusses information for the Beaufort Sea, the
Bering Sea. Cook Inlet/Shelikof Strait. Gulf of Alaska, and
Bristol Bay which are all in Alaska. These regions were
selected because of new platform projections or potential
development in these areas. These areas constitute distinct
transition zones between subarctic and arctic environments.
Each supports distinct ecological communities. The vast
differences in physical and biological environments of these
five regions necessitated separate analyses of their marine
resources. These analyses indicate that a 10 meter isobath in
the Beaufort Sea. a 20 meter isobath in the Bering Sea (Norton
Sound), and a 50 meter isobath in Cook Inlet/Shelikof Strait.
Gulf of Alaska, and Bristol Bay would provide significant
protection of key vulnerable life stages for important
commercial and subsistence species.
6-4
-------
TABLE 6-1
GULF OF MEXICO
CUMULATIVE PERCENT OF NURSERY AREA CELLS INCLUDED IN THE ANALYSIS AREA
Soecies
Estuaries
State
Waters
10m
20m
60m
100m
200m
2000m
Fish
Atlantic Croaker
Sand Seatrout
Longspine Porgy
Bluefish
Red Snapper
Dusky Flounder
39
88
25
72
17
8
62
86
47
87
37
22
70
98
54
95
38
21
99
100
98
100
61
37
100
100
100
100
100
82
100
100
100
100
100
96
100
100
100
100
100
100
100
100
100
100
100
100
Invertebrates
Brown Shrimp
Pink Shrimp
White Shrimp
American Oyster
Blue Crab
Total Fish
Total Invertebrates
Total Fish and
Invertebrates
83
72
83
64
27
42
66
52
90
89
86
85
47
57
79
67
98
97
98
95
49
63
88
74
100
99
100
99
75
83
94
88
100
99
100
100
100
97
100
98
100
99
100
100
100
99
100
99
100
99
100
100
100
100
100
100
100
99
100
100
100
100
100
100
6-5
-------
TABLE 6-2
EAST COAST
CUMULATIVE PERCENT OF NURSERY AREA CELLS INCLUDED
IN THE ANALYSIS AREA
Species
Estuaries 20m
60m 100m 200m
2000m
Fish
Bluefish
Striped Bass
Atlantic Croaker
Winter Flounder
70
94
53
46
99
100
98
64
100
100
100
96
100
100
100
100
100
100
100
100
100
100
100
100
Invertebrates
Hard Clam
Soft Clam
American Oyster
American Lobster
Total Fish
Total Invertebrates
Total Fish and
Invertebrates
42
55
60
11
66
42
54
92
82
96
29
90
75
83
100
100
100
42
99
86
92
100
100
100
61
100
90
95
100
100
100
81
100
95
98
100
100
100
100
100
100
100
6-6
-------
Section 6-4 summarizes the available information for
California. Initial examination of the bathymetric maps
indicate that the 50 meter isobath will protect key areas of
ecological resource significance, including most of the known
nursery areas.
6.3 ALASKAN RESOURCE AREAS
Most future oil and gas exploration and production in
Alaska will be concentrated in several regions: the Beaufort
Sea, the Bering Sea (Norton Sound). Bristol Bay. Cook
Inlet/Shelikof Strait, and the Gulf of Alaska (Figure 6-1).
These five regions constitute distinct transition zones between
subarctic and arctic environments. Each supports a distinct
ecological community.
6.3.1 Beaufort Sea
The Beaufort Sea is located on the northern coast of Alaska
in the Arctic Ocean. The Diapir Field shown in Figure 6-2 is
the lease area under development. The area is characterized by
a low energy regime with little movement and mixing of
sediments. The biological resources of the area are
concentrated in three distinct zones. The nearshore zone, a
region of annual shorefast ice, includes waters less than two
meters deep and any enclosed or protected waters. The inshore
zone includes water from two to 20 meters deep and the offshore
zone includes all waters greater than 20 meters deep.
The Beaufort Sea/Arctic Ocean area is characterized by a
food web in which the zooplankton and epifauna (mysid shrimp.
6-7
-------
ARCTIC OCEAN
00
0 ml 200 4OO
I I I I I
I i i i i I i
Ohm 300 600
NORTON SOUND
BRISTOL BAY AND ALEUTIANS
W:K/N<; SI:A
BEAUFORT SEA
r^
* V .' ' I
"^
GULF OF ALASKA
GULF Ol-ALASKA
COOK INLET/SHELIKOF STRAIT
FIGURE 6-1 AREAS OF FUTURE OIL AND GAS DEVELOPMENT IN ALASKA
-------
IS**
!*«
ISO
144*
M4«
I
vO
!»*
10*
FIGURE 6-2 CANDIDATE MARINE SANCTUARIES AND POTENTIAL NATIONAL NATURAL
LANDMARKS IN OR ADJACENT TO THE DIAPIR FIELD
- LEGEND-
| [ Propond Moclnt SonctuorUt
I Huiruon Iluy/Simpicn Lagoon
2 Stilontton Sound Bouldir Patch
3 Oliihoi* Arctic WildliU Hong*
FT7] Potential Motional Natural Landmarki
(only water areai mapped)
4 Smith Day
5 Colville Diver Delta
J Cioti 111
souncrsi
I. NOAA (Villmliiorr Condidol* Marine Sancluarf
Sil* Lilting
2. IILM.I'JII2. Graphic IO.
-------
copepods. amphipods. euphasiids. etc.) comprise the major food
resource of birds, mammals, and fishes in the area. The bulk
of the fish feed in nearshore areas in enclosed or protected
waters less than two meters deep (i.e.. Simpson Lagoon).
Epifauna densities are greatest in the inshore areas (two to 20
meters). These areas serve as important feeding grounds for
nearshore populations. Available data suggest that fish
densitites are lower in the inshore zone (2-20 m) than the
nearshore zone (22 m). The paucity of sampling data from the
inshore and offshore zones makes any conclusions as to fish
distributions in these areas difficult.
Five biologically sensitive areas have been identified in
the Beaufort Sea. all of which are located shoreward of the
10 m isobath. These areas are the Salt Marshes; Harrison
Bay/Colville River Delta; Thetis Island; Simpson Lagoon; and
the Boulder Field. These areas are either important feeding
grounds for indigenous fish and bird species or like Boulder
Field, comprise unique biological communities.
The following are "key" fish (commercially and in terms of
ecosystem importance) in the Beaufort Sea ecosystem. They
comprise 91 to 98 percent of all fish in the Beaufort Sea and
their density is greatest within 100 meters of the mainland.
Arctic cisco - Coreqonus antunalis
Least cisco - Coreqonus sardinella
Arctic char - Salvelinus alpinus
Fourhorn sculpin - Myoxocephalus quadricornis
Arctic cod - Boreoqadus saida
6-10
-------
The Arctic cisco. Least cisco and Arctic char are
anadromous species which return to their natal streams for
spawning. The Fourhorn sculpin and Arctic cod are marine
fish. During the open-water season, anadromous and marine fish
appear to prefer and widely use nearshore habitats as feeding
and rearing areas, especially the enclosed or protected lagoons
and bays. Most fish retreat to the river drainage during the
winter months. The marine fish appear to move offshore during
the winter months. In late winter Arctic cod are up to thirty
times more abundant 100 miles offshore than nearshore.
The 10 m isobath, which generally falls within the state
waters (three mile geographical line) except in the Harrison
Bay/Colville River Delta region, includes the major feeding
grounds and nursery areas of the above key fish species and the
various "biologically sensitive areas" previously mentioned.
This isobath also includes the zone of maximum epifauna
density, and as such is an important source of raysids,
amphipods and copepods which migrate into shallower, nearshore
waters and provide a crucial base to the marine food web.
Thus, the 10 meter isobath will bound much of key resource
areas within the Beaufort Sea.
6.3.2 Bering Sea
The Bering Sea separates the western coast of Alaska from
Siberia. It is an important migratory channel for many species
of marine mammals and birds. There are several proposed lease
areas within the Bering Sea. The open water lease areas, such
as Navarin Basin, generally lie in deep waters (70 to 2,800 m)
and are not likely to support critical nursery habitats. There
6-11
-------
is some indication of spawning activity in these waters but
species life history distribution information is lacking for
these areas. The lease area proposed for Norton Sound lies in
shallower waters which are important nursery habitats for
several commercial species (see Figures 6-3 and 6-4).
6.3.2.1 Norton Sound
Norton Sound is an important transition zone between
subarctic and arctic marine communities. The area is
characterized by two separate energy regimes and water types.
The shallow coastal waters of Norton Sound ( 20 meters) are a
relatively warmer, low salinity, low energy environment
strongly influenced by the Yukon and Kuskokwim Rivers. The
western Bering Sea shelf waters are a colder, more saline, high
energy environment.
The Yukon-Kuskokwim River Delta is considered a vulnerable
coastal area which is a critical habitat for North America's
largest run of king salmon. Approximately one-third of this
delta region comprises the Clareance Rhode National Wildlife
Refuge. The delta is also critical to the natives' subsistence
harvest.
Important commercial fisheries in Norton Sound include five
North American salmon (pink. chum. Chinook, cohoe. and king).
Pacific herring, and king crab. Other species in Norton Sound
which are important food resources for marine birds and mammals
found in the area include saffron cod. Arctic cod. starry
flounder, rainbow smelt, and tanner crab.
6-12
-------
tf-F V^Sr'^ *:' " **
fr-«fiy«j5»| fr i«
W^cSift.^-VN-
=5>TH-^ M^ir^^^-ti
FIGURE 6-3 BATHYMETRY OF THE NORTON SOUND REGION. DEPTHS ARE IN METERS.
6-13
-------
175
173
171
169
167
165
163
161
159
65
63
E2
61
CHUKOTSK
PENI
SEWARD PENINSULA
>
'.Port Cla/ence
Colovnin Day T B«sboro f^ .
Cape Darby >» \f t
y
SOUND UnaiakleetV
I '
siuart I. /
Cap* Romanzof
BERING SEA
Hall I.
\_ S»ricH«t Strait
St. Matthew
5
173
171
169
167
165
163
FIGURE 6-4 THE NORTHERN BERING SEA REGION. NORTON SOUND LEASE AREAS TO BE
OFFERED FOR SALE ARE CONTAINED WITHIN THE BLOCK DIAGRAM.
6-14
-------
The 20 m isobath (Table 6-3) incorporates most of the
Norton Sound area east of 165°W longitude (the area west of a
line which connects the mouth of the Yukon River on the
southern coast and Cape Nome on the northern coast). This
isobath encompasses most of the following important biological
habitats:
Critical Yukon-Kuskokwira Delta habitat (including
wildlife refuge)
Salmon nursery areas and initial smelt migration areas
Important king crab mating, molting and rearing areas
Pacific herring nursery areas
Arctic cod spawning grounds
Areas of concentration for saffron cod. starry flounder
and rainbow smelt (all collected primarily shoreward of
the 25 m isobath)
6.3.3 Cook Inlet/Shelikof Strait
Cook Inlet/Shelikof Strait is located on the southern coast
of Alaska and is an inlet of the Gulf of Alaska (Figure 6-5).
Cook Inlet is typically a very high energy environment with a
great deal of mixing and unstable bottom contours. Due to
shifting sand bars, the depth contours of Cook Inlet are not
always consistent. The environment is such that intertidal
communities have been documented at depths as great as 65
meters. Most oil and gas activity occurs in southern Cook
Inlet, south of Anchor Point.
The important habitats of Cook Inlet, i.e., areas utilized
by a disproportionate abundance of individuals and/or species.
6-15
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TABLE 6-3 SPAWNING AND NURSERY AREAS FOR MAJOR COMMERCIAL
FISH AND INVERTEBRATE SPECIES IN NORTON SOUND, ALASKA
Species
Reproductive/nursery area
Approximate % of nursery
area within the 20 m 1 sobath
Fish
P1nk salmon
Chum salmon
Chinook salmon
Coho salmon
Pacific
herring
Anadromous species associated
with Yukon River Delta which
spawn In freshwater streams;
young move along coast during
Initial two months of migration.
Spawns In subtldal region east
of 164°W longitude; eggs
adhere to Inshore vegetation.
100X
100%
Invertebrates
King crab
Tanner crab
Shallow, subtldal region
(0-20 m) extensively used for
spawning, molting, breeding,
feeding, and rearing of the
young. Entire coastal region
from Yukon Delta to Cape Rodney
may be Important nursery habitat.
Juvenile crabs found throughout
the area, Indicating this may be
an Important nursery area for
this crab.
100X
BOX
6-16
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FIGURE 6-5 OCS LEASE SALE 60:
LOWER COOK INLET - SHELIKOF STRAIT.
6-17
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include virtually all nearshore areas throughout Cook
Inlet/Shelikof Strait, including the coastal embayments and
islands. Kamishak and Kachemak Bays are particularly critical
nursery habitats for king crabs, dungeness crabs, and pandalid
shrimp. The king/tanner crab Bluff Point Sanctuary lies within
Kachemak Bay.
The offshore area between outer Kamishak Bay (Cape Douglas)
and the Barren Islands area contains a high density (up to
eleven times the number elsewhere in Cook Inlet) of adult and
juvenile tanner crab. The tanner crab may be considered the
benthic invertebrate most important to the functioning of the
Cook Inlet ecosystem. The average water depth in this tanner
crab nursery area is approximately 150 m.
Salmon, halibut. Pacific herring, king crab, tanner crab,
dungeness crab, and shrimp are the major commercial fisheries
in the Cook Inlet/Shelikof Strait area. The nursery areas for
most of these species have been described as being nearshore or
in intertidal areas (Table 6-4). The 50 m isobath, which
generally falls within state waters, will enclose most of the
nursery areas for these species (except tanner crab) in the
study area.
6.3.4 Bristol Bay/Aleutian Range
The southeast Bering Sea, particularly the estuarine
shallows of Bristol Bay is known for its high biological
activity. This area of Alaska is perhaps the most
controversial with regard to offshore oil and gas development
is due to its close proximity to salmon and crab fishing areas,
natural wildlife refugees and State of Alaska critical habitat
areas.
6-18
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TABLE 6-4 VITAL REPRODUCTIVE AND NURSERY AREAS FOR IMPORTANT
COMMERCIAL FISHERIES IN COOK INLET AND SHELIKOF STRAIT
Species
Reproductive/Nursery area
Approximate % of
nursery area within
the 50 m Isobath
Fish
Salmon
Pacific herring
Halibut
Freshwater streams and rivers; smelt
migrate along coastal area.
Spawn along shallow, 1ntert1dal zone
on nearshore vegetation.
Demersal larvae remain Inshore for one
to three years.
100%
10094
90%
Invertebrate
King crab
Dungeness crab
Tanner crab
Pandalld shrimp
Typically rear young 1n shallow
(0 to 20 m) water of Kamlshak and
Kachamak Bays and nearshore areas of
Kodlak Island and Shellkof Strait.
Nursery areas Include coastal waters
and embayments less than 60 m deep.
Juveniles collected 1n m1d-Kachemak
Bay and nearshore Kamlshak Bay and
Shellkof Strait.
Outer Kamlshak Bay and between Cape
Douglas and the Barren Islands.
Inner Kachemak Bay and nearshore
areas of Shellkof Strait near Cape
Gull.
80%
90%
50%
100%
6-19
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The eastern and southern margins of Bristol Bay are
bordered by the Alaska Peninsula. The Aleutian Range forms the
backdrop from which the elevation drops to a coastal plain.
This plain extends 16 to 30 km to a coast which is typified by
sandy beaches and brackish coastal lagoons. Bars, spits, and
barrier islands are numerous throughout the nearshore region.
To the north the shoreline includes several large estuaries and
lagoons, interspersed with sandy beaches and coastal bluffs.
The Pribilof Island group consists of two major islands,
St. George and St. Paul, and several small inlets. The
coastline of St. Paul Island consists generally of unstable
sandy beaches. The coastline of St. George Island is
characterized by steep bluffs and cliffs.
The coastal habitat along the Aleutians is noted for its
high infaunal standing stocks, especially clams. Crabs and
demersal fish, especially the juveniles of many species, are
abundant in coastal waters. The Bristol Bay habitat is
abundant with pacific herring, pink salmon, chum salmon, coho
salmon, sockeye salmon. Chinook salmon, saffron cod and other
species. These species and numerous other species have nursery
areas in this region.
The 50 m isobath, which generally falls inside of state
waters along the Aleutian Islands and Alaska Peninsula, will
enclose most of the nursery areas for salmon and other
important commercial fish as well as invertebrates like crabs
and shrimp (Table 6-5).
6-20
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TABLE 6-5
NURSERY AREAS LOCATED IN BRISTOL BAY/ALEUTIAN
ISLANDS AREA
Species
Approximate % of Nursery Area
within the 50 m Isobath
Crangonid Shrimp
Large Crangonid Shrimp
Other Pandalid Shrimp
Korean Hair Crab
Red King Crab
Tanner Crab
Chalky Macoma
Pacific Herring
Pink Salmon
Chum Salmon
Coho Salmon
Sockeye Salmon
Chinook Salmon
Capelin
Eulachon
Rainbow Smelt
Saffron Cod
Pacific Cod
Walleye Pollock
Yellowfin Sole
Alaska Plaice
Starry Flounder
Rock Sole
Pacific Halibut
90%
100%
50%
50%
100%
100%
50%
50-90%
100%
100%
100%
100%
100%
100%
100%
50%
100%
100%
100%
100%
50-90%
50%
50%
100%
50%
100%
70%
50%
50%
overall nurseries
major nursery areas
for juveniles less
than 40 mm carapace
for spawning &
small juveniles
for larger juveniles
for spawning &
small juveniles
for larger juveniles
for spawning & small
juveniles
for larger juveniles
for juveniles & spawn-
ing areas
of spawning & small
juveniles
of larger juveniles
of juveniles
6-21
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6.3.5 Gulf of Alaska
The Gulf of Alaska is bounded on the north by the coastline
of Alaska and on the south by the North Pacific Ocean. The
coastal topography is rugged. The Alaskan current is
continuous throughout the Gulf. However, in the Gulf of Alaska
the current intensifies and forms a concentrated stream along
the shelf break called the Alaska Stream.
Large populations of commercially valuable crabs, shrimp,
molluscs, salmon, herring, pollock, halibut, and other
groundfish use these waters as their principal spawning.
rearing, and foraging grounds. Coastal fiords and embayments
are the nursery areas for many key pelagic (e.g.. herring.
capeline. salmon) and benthic (e.g., halibut, pollock, cod)
fishes. Migratory routes of commercially important stock from
other Alaskan regions (e.g., Bristol Bay sockeye salmon. Unimak
Pacific Ocean perch, southeastern Alaskan Pacific halibut) lie
along the outer continental shelf of this area. Some of the
principal species inhabiting the coastal regions of the Gulf of
Alaska are shown in Table 6-6.
Juvenile shrimp are found in waters less than 40 m deep.
but live in greater depths in summer. The salmon and trout are
commonly found in oceanic waters and estuaries and in
freshwater watersheds draining into the Gulf. Pink, sockeye
and chum salmon are widely distributed in the Gulf of Alaska.
Their nursery areas are closer to the shoreline. A water depth
of 50 meters should enclose a substantial portion of the
nursery areas in this region.
6-22
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TABLE 6-6
NURSERY AREAS FOR MAJOR COMMERCIAL FISH AND INVERTEBRATE
SPECIES IN THE GULF OF ALASKA. ALASKA
Approximate Percent of
Nursery Area with the
Species 50 m Isobath
Pink Salmon 40 %
Chum <50 %
Sockeye 90 %
Coho 80 %
Chinook Salmon 100 %
Rainbow Trout 100 %
Cutthroat Trout 80 %
Pacific Herring 40 %
Pink Shrimp 80 %
Sidestripe Shrimp 80 %
Ocean Pink Shrimp 80 %
6-23
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6.4 MARINE RESOURCE AREAS OFF CALIFORNIA
The California offshore area (Figure 6-6) is a structurally
complex region typified by a highly irregular topography of
deep basins, islands, submarine canyons and rocky intertidal
regions. In comparison with the Gulf of Mexico region, the
continental shelf off California (200 m isobath) is fairly
narrow with a width of less than two miles in some areas.
The biological communities of the California Bight are also
extremely complex, consisting of many species and assemblages
which are difficult to summarize. For the purposes of this
analysis, the nursery areas of commercially important fish and
shellfish were considered. Table 6-7 summarizes the available
information concerning the distribution and depth of spawning
and nursery areas. The values in this table are based on a
limited database of distribution information and, at best,
represent approximations.
There are four types of areas of special biological concern
which are legally defined and controlled by the State of
California in an effort to protect intertidal and shallow
subtidal areas which contain unique or extraordinary biological
communities:
Ecological reserves
Marine life refuges
Reserves
Areas of special biological significance (ASBS).
6-24
-------
O\
I
NJ
cn
Lenne Areas
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4.
V
'*.
.«'
~ ^
«§./ £ }'''" V- \
7 # /"»» '«<
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^ilwul ^ l««|.l«. A ,§pi
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"«i"«V a)n,ifyv L.
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FIGURE 6-6 CALIFORNIA COASTLINE
-------
TABLE 6-7 SPAWNING AND NURSERY AREAS FOR MAJOR COMMERCIAL FISH
AND INVERTEBRATE SPECIES IN CENTRAL AND SOUTHERN CALIFORNIA
Species
Reproductive/Nursery area
Approximate % of
nursery area within
the 50 m isobath
Fish
Northern anchovy
Tuna
Rockfish
Jack mackerel
Pacific herring
Salmon
Sablefish
California halibut
Sole
Invertebrates
Rock crab
Dungeness crab
Abalone
Opalescant squid
Spawning occurs during winter and
spring nearshore; larvae associate
with mackerel and rockfish larvae in
shallow waters (<30m)
Nursery areas not within California
or U.S. waters
Nursery areas from tidepool level to
30 meters deep
Found in association with rockfish
larvae in shallow waters ( 30m)
Spawning and rearing nearshore and
estuaries and bays
Spawning in freshwater rivers; early
nursery areas nearshore
Juveniles found in less than 91 meters
of water in summer; migrates to
deeper water in the fall
Spawns in 5 to 18 meters
Known spawning areas offshore in
55-549 m water; pelagic larvae remain
many miles offshore
Inshore species, particularly in rocky
areas; inshore of 55 meters
Greatest concentrations in two to 35 m
water; bays and estuaries significant
nursery areas first two years
Reared and harvested in shallow water
areas of seven to 50 m depth
Schools move inshore to spawn; Monterey
Bay and Santa Barbara Channel Islands
important spawning areas
801
100%
100%
90%
100%
50%
100%
0%
90%
100%
100%
80%
6-26
-------
Table 6-8 lists these areas for southern and central
California. Figure 6-7 shows the location of most of these
areas in central California.
A zone enclosed by a 50 meter isobath will enclose the
nursery areas for most commercially important species, the
intertidal shorelines of offshore islands, and the areas of
biological concern. For the most part, the 50 meter isobath
falls within the state waters of California, occurring
approximately one to two miles off the coast. In some areas,
it extends beyond state waters.
6-27
-------
TABLE 6-8
AREAS OF SPECIAL BIOLOGICAL SIGNIFICANCE (ASBS). ECOLOGICAL
RESERVES/REFUGES. AND FEDERAL ESTUARINE SANCTUARIES IN
CENTRAL AND SOUTHERN CALIFORNIA
Central California
Areas of Special Biological Significance (ASBS):
1. Farallon Island
2. Pt. Reyes Headland Reserve
3. Bird Rock
4. Double Point
5. Duxbury Reef Reserve
6. James V. Fitzgerald Marine Reserve
7. Ano Nuevo P. and Island
8. Pacific Grove Marine Gardens Fish Refuge and Hopkins
Marine Life
9. Carmel Bay
10. Pt. Lobos Ecological Reserve
11. Julia Pfeiffer Burns Underwater Park
Ecological Reserves/Reserves:
1. Point Reyes Headland Reserve
2. Duxbury Reef Reserve
3. James V. Fitzgerald Marine Reserve
4. Point Lobos Ecological Reserve
5. Estero de Limantour Reserve
6. Morro Rock Ecological Reserve
7. Pismo Beach Ecological Reserve
Marine Life Refuges:
1. Pacific Grove Marine Gardens Fish Refuge
2. Hopkins Marine Life Refuge
3. California Sea Otter Refuge
Federal Estuarine Sanctuary:
1. Elkhorn Slough
6-28
-------
TABLE 6-8 (Continued)
AREAS OF SPECIAL BIOLOGICAL SIGNIFICANCE (ASBS). ECOLOGICAL
RESERVES/REFUGES. AND FEDERAL ESTUARINE SANCTUARIES IN
CENTRAL AND SOUTHERN CALIFORNIA
Southern California
Bolsa Chica Ecological Reserve
Heisler Park Ecological Reserve ASBS
Upper Newport Bay Ecological Reserve
Buena Vista Lagoon Ecological Reserve
San Diego - La Jolla Ecological Reserve ASBS
San Miguel Island Ecological Reserve ASBS
Anacapa Island Ecological Reserve ASBS
Santa Barbara Island Ecological Reserve ASBS
Abalone Cove Ecological Reserve -
Lover's Point Reserve (Catalina Island)
Farnsworth Bank Ecological Reserve ASBS
(Catalina Island)
Point Loma Reserve
Point Fermin Marine Refuge
Newport Beach Marine Life Refuge ASBS
Irvine Coast Marine Life Refuge ASBS
Laguna Beach Marine Life Refuge
South Laguna Beach Marine Life Refuge
Niguel Marine Life Refuge
Dana Point Marine Life Refuge
Doheny Beach Marine Life Refuge
San Diego Marine Life Refuge ASBS
Mugu Lagoon to Latigo Point ASBS
Santa Rosa Island ASBS
Santa Cruz Island ASBS
San Nicholas Island ASBS
Begg Rock ASBS
Santa Catalina Island including the following subareas: ASBS
Subarea 1 Isthmus
Subarea 2 North end of Little Harbor to Ben Weston Point
Subarea 3 Farnsworth Bank
Subarea 4 Binnacle Rock to Jewfish Point
San Clemente Island ASBS
Seal Beach National Wildlife Refuge U.S. Dept.
of Navy
Tijuana River National Estuary Sanctuary NOAA
Source: MMS. 1983.
6-29
-------
FIGURE 6-7 AREAS OF SPECIAL BIOLOGICAL SIGNIFICANCE OFFSHORE CENTRAL AND NORTHERN CALIFORNIA.
I
U>
o
AREAS OF SPECIAL CONCERN
AREAS OF SPECIAL BIOLOGICAL
SIGKF1CANCE (STATE)
NATIONAL WNJMJFE REFUGE
NATIONAL WLOERNESS AREA
(PT. REYES WJLDERttSS AREA)
NATIONAL MARME SANCTUARY
PROPOSED NATIONAL MARINE
SANCTUARY
NOMNATEO MARINE SANCTUARY
(CORDELL BANKS)
FEDERAL ESTUARME SANCTUARY
OFFSHORE NORTHIRNCM.FORNM
OFFSHORE CENTUM. CM.rORMA
SANTA BARBARA
-------
7.0 FINDINGS AND CONCLUSIONS
7.1 DRILLING FLUIDS AND CUTTINGS
The current status of assessments of the potential impacts
of drilling fluids and cuttings is that their conclusions are.
in general, marked by contradictions and/or are highly
qualified. The scope and utility of these general conclusions
are substantially reduced by these qualifications, which are
too frequently overlooked. The following sections present
those areas that are considered to be, by general consensus, of
low concern and those areas that possess a significant
potential for adverse environmental impacts.
7.1.1 Toxicity of Drilling Fluids
This review of the composition, chemistry, and toxicity of
drilling fluids covers four major topic areas: (1) the
toxicity of drilling muds; (2) the source of this toxicity;
(3) the correlation between mud components and/or
characteristics and toxicity; and (4) bioaccumulation. In
these discussions, a broad definition of "toxicity" is used
that includes not only chemically-mediated toxic effects, but
also any other potential source of an adverse environmental
effect caused by drilling muds (e.g., physical effects).
7.1.1.1 Toxicity
There is a general consensus that generic drilling muds
with no added diesel oil or mineral oil have low acute, lethal
7-1
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toxicity. However, the industry has acknowledged that the use
of diesel and/or mineral oils as lubricating and spotting
agents, at relatively high levels (two to four percent), is
necessary for efficient operations. The addition of even small
amounts (one percent) of diesel oil or mineral oil to generic
drilling muds cause them to become some 10- to 100-fold more
toxic.
Nongeneric muds (i.e., those which are not shown in Table
2-1) can be much more toxic than generic muds. One series of
industry-supplied nongeneric muds, contaminated with relatively
small amounts of oil (0.01-0.9 percent), were from 10 to 340
times more toxic than similar nongeneric muds, with the
exception of KCL polymer muds. The contribution of specialty
additives versus that of diesel oil to the observed toxicity of
these muds is not known. One of these nongeneric muds
exhibited a 96-hour LC5Q of 26 ppm. which is approximately of
the same order of toxicity as that of a biocide. formaldehyde
(25-31 ppm).
Also, drilling muds possess a high Biochemical Oxygen
Demand (BOD) that is highly correlated to their toxicity.
Because existing test protocols routinely require both
pre-aeration of drilling mud test materials and aeration of
test media, these test procedures may reduce substantially the
measured toxicity of drilling muds by masking potential BOD
effects.
7.1.1.2 Sources of Toxicity
There are three sources of potential adverse effects from
drilling muds: toxics, physical effects (grain-size
7-2
-------
alterations, smothering, abrasion, and/or clogging), and oxygen
demand. Existing studies have not been designed, and therefore
cannot be used, to discriminate between contributions of
physical and chemical components. This finding has been noted
in other reviews (Petrazzuolo. 1983a; NRC. 1983). The
correlation between BOD and toxicity is a recent finding of
this review. Test protocols, however, are not designed to
discriminate this effect from toxic or physical effects
(indeed, as indicated above, protocols are designed to minimize
this effect).
7.1.1.3 Correlations to Toxicity
Among drilling fluid components that have been examined,
only diesel oil and mineral oil possess a high, statistically
demonstrable correlation to observed toxicity. Biocides,
although existing data are insufficient for any statistical
analysis, are the only other group of components that can be
anticipated to substantially contribute to toxicity. However.
diesel and mineral oils, although correlated to toxicity. do
not explain all of the observed toxicity of muds, especially
for KCL polymer muds and lime muds.
Bulk metals content appears to have a low correlation to
observed toxicity of drilling muds, with the possible exception
of a weak correlation to chromium. The strong statistical
correlation between toxicity and BOD. which is all the more
surprising because of test designs that should have minimized
BOD effects, should be investigated further.
7-3
-------
7.1.1.4 Bioaccumulation
Laboratory studies have indicated that bioaccumulation has
been observed for nearly all metals that have been studied,
including barium, cadmium, chromium, lead, strontium, and
zinc. Barium and chromium show the most dramatic increases
(30- to 300-fold); others are much lower (2- to 25-fold). Data
on mercury are conspicuous by their absence. However.
bioaccumulation test procedures are characterized by design
factors that seriously reduce the ability to quantify the
bioaccumulation hazard of drilling muds.
Field data for either one-well operations or small drilling
fluid discharges show that sediment levels were elevated for a
variety of metals (barium, cadmium, chromium, lead, mercury,
nickel, vanadium, and zinc) in a distance-dependent manner.
Bioaccumulation was noted in field-collected organisms for
several of these metals, although at relatively low levels (2-
to 10-fold compared to organisms collected at reference
stations). There are no laboratory or field data that are
adequate to assess the bioaccumulation hazard of organic
components of drilling fluids.
7.1.2 Field Assessments of Impacts from Drilling Activities
7.1.2.1 Studies of Impacts from Single Wells
Although a number of studies have been conducted around
exploratory wells, the design of most of these studies was
sufficient only to detect gross changes in benthic communities
(i.e., changes of 100 percent or greater). Only two studies
7-4
-------
have been designed and performed that were capable of detecting
changes at low to moderate levels (i.e.. 25-50 percent).
One of these studies, conducted in a very high energy.
dispersive environment (Georges Bank), indicated that no
significant effects could be detected from single-well
discharges. The inability to detect effects does not
necessarily indicate a complete lack of impact, but that
effects are dispersed to relatively low levels (< 25-50
percent), over a larger area, in a high energy situation.
The second of these studies was conducted in an open shelf
area (Baltimore Canyon) of the mid-Atlantic. 160 km offshore.
in a water depth of 120 m. The mid-Atlantic study showed
effects to several hundred meters. These effects persisted at
least one year after the discharges ceased. The complete areal
extent of impact cannot be clearly delineated because of the
lack of adequate reference stations. Also, some uncertainty
exists as to whether the large overall change in benthic
densities in the area was due to natural variation.
There is no study of impacts from a single-well drilling
operation in a near-shore, shallow water situation that meets
reasonable statistical and sampling design criteria.
7-1.2.2 Studies of Impacts from Multiple Wells
Multiple-well discharges are associated with intensive,
local exploratory activities or development drilling. Several
attempts to assess the effects of development and production
7-5
-------
activities after the fact have been made in the Gulf of
Mexico. The studies are inconclusive because of problems in
finding adequate historical or spatial reference sites and in
determining the contribution of one factor (drilling mud
discharges) in a large, complex, multifactorial system.
Therefore, the studies of production facilities that have been
conducted to date do not allow an adequate assessment of
potential impacts that may result from multiple-well discharges
of muds and cuttings. In addition, no study has been conducted
to assess benthic impacts from a development operation.
7.1.2.3 Factors Contributing to Potential Impacts
Since existing studies only cover a very limited range of
drilling scenarios, this section will discuss some of the
factors that would contribute to situations of increased risk
from the discharge of muds and cuttings. Such increased risks
may be due to the nature or quantities of discharged materials.
the physical characteristics of the receiving water, or the
biological or usage characteristics of the receiving water.
Development Activities
The potential effects from development activities (as
opposed to exploratory activities) are due to the
quantities and nature of the materials discharged.
Greatly increased quantities of material are discharged
during development (typically. 24-60 wells per platform)
compared to a single-well operation. Also, the general
trend has been toward fewer platforms with more wells
per platform. This trend results in greater directional
7-6
-------
drilling, which is much more likely to require the use
of lubricating and spotting oils than straight-hole
exploratory drilling. Consequently, the muds used in
directional development drilling are likely to be among
the more toxic muds discharged.
Shallow and/or Poorly Flushed Coastal Waters
The areas where drilling fluids are most likely to cause
detectable problems associated with water column
toxicity are those with shallow water (i.e.. where
dispersion is limited) or poorly flushed/low energy
areas (i.e.. where the amount of muds discharged is
large compared to local water flux). Sediment toxicity
to benthic organisms, oxygen depletion effects, and
physical effects due to deposition also are most likely
to be observed in these areas.
Any effects due to oxygen depletion should be of short
duration, approximately six months to one year. The
persistence of physical effects and sediment toxicity is
not known, although in one low energy environment (the
Mid-Atlantic) partial recovery occurred within one
year. Barite. clays, and polynuclear aromatic
hydrocarbons are fairly persistent components of
drilling muds, and complete recovery may take a long
time in shallow and/or poorly flushed areas.
Areas Subjected to Other Sources of Pollution and/or
Episodic Stress
If an ecological system is already subjected to large
and varied contaminant inputs, adding further
7-7
-------
contaminants may cause significant problems, even if the
additional load is comparatively small. For example.
the BOD loadings described in Section 2 could contribute
significantly to water quality degradation in areas such
as Louisiana state waters, which are (1) shallow.
(2) subject to high levels of drilling activity.
(3) also subject to high levels of other contaminant
inputs (i.e.. via the Mississippi River), and (4) subject
to episodic anoxic events of unknown cause.
Areas that are subject to higher loadings from other
sources of pollution tend to be the nearshore coastal
areas, which are also often shallow, poorly flushed
areas. In addition, the usage of near-shore coastal
areas for recreation and commercial fishing is
characteristically high, which is yet another reason for
concern in assessing potential impacts from these
discharges.
Communities Ill-Adapted to Sedimentation Effects
Certain communities are not well-adapted to stresses
associated with sedimentation effects. These
communities generally are represented by clear-water.
hard-bottom communities. Examples would include coral
reefs, macrophyte beds, and "live-bottom" areas as
designated by the Minerals Management Service.
Shellfisheries
Because of several factors, shellfisheries represent
potentially high areas of environmental impact. In
7-8
-------
areas that may be subject to deposition or transport of
drilling muds from intensive drilling activities.
shellfisheries are a concern because: (1) there are
very limited data on sediment contaminant enrichment;
(2) several potential contaminants (metals and organics)
are highly persistent; (3) bioaccumulation data
qualitatively indicate a potential hazard, but are
insufficient to quantify the hazard from drilling muds;
and (4) the capacity of this group of animals to
accumulate such materials to exceptionally high levels
is well documented for both metals and organics. This
concern, therefore, is primarily based on the lack of
data adequate to quantify the potential effect.
7.2 PRODUCED WATER
7.2.1 Toxicity of Produced Water
Data presented in this review lead to the following
conclusions concerning the toxicity of produced water: (1) the
acute lethal toxicity of produced water that does not contain
biocides or other toxic chemical additives is low; (2) the
acute lethal toxicity of produced water is greatly increased
when biocides or other toxic chemical additives are present;
and (3) chronic toxicity of produced water is suggested by
existing data and must be investigated further.
There is very limited information on the toxicity of
produced water. Several acute lethal toxicity studies were
conducted at one platform in the Gulf of Mexico. Results from
these studies are consistent with the above conclusions. When
7-9
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biocides were present, and had not been scavenged, the acute
lethal toxicity of produced water was substantially greater
than when biocides either were not present, or had been
scavenged.
However, Middleditch (1984) noted that such scavenging
reactions are reversible. Thus, even though measurable
biocides may not be detected in the effluent, they could be
released after discharge. This possibility may explain why
divers working near the discharge of this particular platform.
at which acrolein was used as a biocide and was scavenged prior
to discharge, complained of eye and skin irritations, which at
times caused divers to discontinue their activities
temporarily. At present, there is very little information on
the extent of biocide or other chemical additive usage, the
concentrations of these chemicals in produced water discharges,
or the resultant toxic effects of these additives.
In the absence of biocides or other toxic additives, the
acute lethal toxicity of produced water appears to be reduced
and is probably related, in part, to the presence of lighter
aromatic hydrocarbons (benzene through naphthalene). The
toxicity tests conducted on produced water were performed in a
manner that would have resulted in loss of at least a portion
of these toxic volatile organics. Thus, these tests probably
underestimate acute lethal toxicity somewhat. Unfortunately.
no measurements were made of these compounds at any time during
the toxicity tests.
There is even less information on the chronic toxicity of
produced waters. Studies done in the North Sea have indicated
7-10
-------
that produced water can exert chronic effects on plankton at
diluted concentrations. The limited information suggests that
chronic effects from produced water discharges could be
important, at least in certain areas.
Because produced water discharges provide a continual input
of low levels of petroleum hydrocarbons and chemical additives.
there is the possibility of an accumulation in the water
column. Such an accumulation is most likely to occur in areas
of limited flushing. However, even at the high energy
Buccaneer Field site, elevated concentrations of volatile
liquid hydrocarbons were observed several kilometers from the
platform, despite a comparatively small produced water
discharge volume (600 bbl/day).
These elevated concentrations were above those that Sauer
(1980) identified as indicative of anthropogenically influenced
coastal waters of the Gulf of Mexico. Middleditch (1984) and
Sauer (1980) noted that while these low concentrations of
aromatic hydrocarbons (on the order of a few ppb) are well
below levels needed to cause mortalities, they are comparable
to levels reported as being responsible for behavioral changes
(i.e.. sublethal effects).
There is clear evidence that the hydrocarbons, and possibly
additives, that are present in produced water discharges can
exert chronic effects on benthic organisms around production
platforms. This was apparent both in the shallow water (2.5 m)
Trinity Bay study, where elevated concentrations of total
naphthalenes were observed in the sediments, but also in the
deeper water (20 m) Buccaneer Field site. The full areal
7-11
-------
extent of chronic effects of produced water discharges on the
benthos is difficult to delineate. This difficulty is due to
the generally elevated levels of hydrocarbons and other
chemicals in sediments over wide areas in the Gulf of Mexico.
This creates generalized contamination "signal to noise"
problems with respect to detecting effects of individual
discharges. Any field study probably would show, at best,
measurable localized effects. Beyond that, the influence of
discharges on the benthos could be integrated with other
influences (e.g.. other platforms, riverine inputs, etc.) and
could not be clearly delineated. Simply because measurable
effects are observed near individual platforms does not imply
that effects are locally restricted.
7.2.2 Comparison with Other Assessments
Two assessments of the environmental implications of
produced water discharges include a recent report by
Middleditch (1984) for the American Petroleum Institute (API)
and a review by Menzie (1982). These assessments used an
information base that was generally the same as that utilized
in this report. These two earlier assessments agree with this
report on most technical points. Disagreements occur mainly in
the significance attached to the observed effects. These
differences arise, in part, from the considerable uncertainty
that exists concerning environmental effects of produced water
discharges. For example, the API report prepared by
Middleditch (1984) concludes that "at the current time, we are
unable to claim that effects of produced water discharges have
been fully delineated."
7-12
-------
The Middleditch report also concludes that produced water
effects are probably minor and limited to a relatively small
area. Middleditch acknowledges that both the scientific and
local communities would find data more convincing if they were
adequate to define the maximum extent of specific effects.
However, as noted above, this effort is generally not possible
from field studies because effects from individual platforms
become integrated with other generalized influences beyond the
immediate vicinity of the platform (e.g.. beyond a few hundred
meters), and are extremely difficult to sort out.
Reviews, including that of Middleditch (1984). have
attempted to place various sources of petroleum hydrocarbons in
perspective through comparisons with other sources (river
discharge, tankers, oil seeps). Generally, such comparisons
show that produced water discharges contribute a comparatively
small percentage of the overall input on a Gulf-wide,
ocean-wide, or world-wide basis. This type of comparison is
often used to establish "significance." Thus, it is argued
that produced water discharges are not significant. However,
simply because the relative contribution is small, it does not
follow that produced water discharges are insignificant.
First, the collective sum of numerous small dischargers may not
represent a small contribution on a regional level. Second.
discharges of produced water can exert environmental effects
locally, as indicated by the data presented earlier.
Middleditch (1984) and Menzie (1982) both note Sauers
(1980) observation that the coastal Gulf of Mexico already
exhibits elevated levels of volatile liquid hydrocarbons and
that existing concentrations are in the range that could result
7-13
-------
in sublethal effects. Menzie (1982) suggests the possibility
that a build-up of hydrocarbons in the water column is possible
in areas of limited flushing (e.g.. coastal embayments). Both
reviewers acknowledge that effects of produced water discharges
are more likely to occur in shallow coastal areas than in
deeper offshore areas. However, neither report discusses this
effect in terms of a particular depth or area.
7-14
-------
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Proposed Water Discharges from Offshore Oil and Gas
Extraction Industry. Walk Haydel & Associates. Inc. New
Orleans. LA. Prepared for Offshore Operators Committee.
Workman. I.K. and C.E. Jones. 1979. Determine Effects of Oil
Field Discharges on Species Composition and Abundance of
Pelagic Fishes. Demersal Fishes and Macro-crustaceans in
the Oil Field. In; W.B. Jackson, ed. Environmental
Assessment of an Active Oil Field in the Northwestern Gulf
of Mexico. 1977-1978. Volume II: Data Management and
Biological Investigations. NTIS PB80-165970.
Wright. T.R. and R.D. Dudley, editors. 1982. World Oil's 1982
Guide to Drilling. Completion and Workover Fluids. World
Oil. Gulf Publishing Company. Houston. Texas.
Zein - Eldin, Z.P. and P.M. Keney. 1979. Bioassay of
Buccaneer Oil Field Effluents with Panaeid Dhrimp. In:
W.B. Jackson, ed.. Environmental Assessment of an Active
Oil Field in the Northwestern Gulf of Mexico. 1977-1978.
Vol. II: Data Management and Biological Investigations.
NTIS PB80165970.
Zimmerman. E.. and S. deNagy. 1984. Biocides in Use on Offshore
Oil and Gas Platforms and Rigs. U.S. Environmental
Protection Agency. 27 pp.
Zingula. R.P. 1975. Effects of Drilling Operations on the
Marine Environment. In; Conference of Proceedings on Envi-
ronmental Aspects of Chemical Use in Well-Drilling Opera-
tions. Houston. Texas. May 21-23. 1975. EPA-550/1-75-004.
443-450. Environmental Protection Agency. Washington. D.C.
R-36
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APPENDIX A
SUPPLEMENTARY INFORMATION ON
FIELD STUDIES
-------
A. SUPPLEMENTAL INFORMATION ON FIELD STUDIES
The exploration foe and production of offshore oil and gas
sometimes brings into conflict the demand for energy and the
need for environmental protection. In areas of particularly-
valuable ecologic resources, interest in these issues may run
high. Three locations of recent exploration in or near biolog-
ically sensitive areas are presented below: the Flower Garden
Banks (Gulf of Mexico), Georges Bank (North Atlantic), and
Norton Sound (Alaska). These brief case studies illustrate
the numerous issues involved in the controversy surrounding
offshore oil and gas development.
A.I THE FLOWER GARDEN BANKS
The Flower Garden Banks are the only true coral reefs in
the northwestern Gulf of Mexico and are located approximately
200 km (120 mi) off the coast of Galveston, Texas. There are
two major reefs, known as the East and West Banks, which occupy
approximately 28 and 40 hectares (69 and 99 acres), respec-
tively. The uniqueness of the reefs in this area affords them
special scientific and ecological interest. The area surround-
ing the banks is presently being explored for oil and gas
deposits, and there is concern that this and future drilling
may have adverse impacts on the health of the ecological
community in general and the corals in particular. The
material in this section draws heavily on the Draft Phase 3
Report, Effects of Drilling Muds on the Flower Garden Banks
Coral Reefs, prepared by Clement Associates, Inc., (1983) as
part of a settlement agreement regarding drilling in the area.
A-l
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A.1.1 Biota
The predominant coral species on the East and West Flower
Garden reefs are Montastrea annularis. Diploria striqosa.
Colpophyllia natans. Porites astreoides. Montastrea cavernosa.
and Millepora sp. (Gettleson. 1978). Smaller populations of
Madracis decatis. Mussa anulosa. and Aqaricia sp. have also
been noted. The major differences between biota of the two
banks are areas of Madracis mirabilis and leafy algae found
only at the East Bank (Bright 1977. reported in Clements 1983).
Corals are the organisms of greatest concern in the area,
although there are also other important biota present. The
corals generally extend to no more than 55 m (180 ft) in
depth. Below the coral, at depths of 50 to 80 m (164 to 263
ft), the predominant organisms are red coraline algae, which
secrete calcium carbonate and contribute to the structure of
the reef. Depths of 60 to 100 m (197 to 329 ft) constitute the
transition zone from shallow to deep water, and are inhabited
by antipatharian organisms. Antipatharians physically resemble
sea whips and can grow as long as 1.8 to 3 m (6 to 10 ft).
Various reef fish also inhabit this level. Significant impacts
on these deeper water organisms could affect the entire reef
ecosystem.
Corals are organisms which are sensitive to changes in
their environmental conditions. The Flower Gardens are thought
to be particularly vulnerable to stress for several reasons
(Clement, 1983):
(1) They are near the lower limit of the temperature range
tolerated by reef-building corals.
A-2
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(2) They contain a limited variety of species.
(3) They are physically isolated from other coral reefs
which could provide for recolonization if needed.
(4) There is empirical evidence that growth patterns for
one of the dominant species are correlated with water
temperatures and may also be affected by fluctuations
in discharge from the Mississippi and Atchafalaya
Rivers (Dodge and Lang. 1982).
(5) They are in a zone frequently affected by severe hur-
ricanes.
A.1.1.1 Impacts from Drilling Activity
Adverse effects on corals, if they occur, could be the
result of increased turbidity, decreased available sunlight, or
toxic effects from metals or organic compounds in drilling
fluids. The major potential threat is believed to be associ-
ated with turbidity and possible burial from drilling fluid
discharges.
There are few monitoring projects from the Banks. The most
extensive information available, collected under the direction
of the Minerals Management Service, includes topographic fea-
tures, geology, biological monitoring, water and sediment
dynamics, and hydrocarbon and carbon analyses. A final syn-
thesis report should be released in the near future. Other
biological monitoring and physical dispersion studies are also
in progress (Clements, 1983). Numerous controlled experiments
with corals have been conducted and are discussed in Section 4
of this report (Thompson and Bright, 1980; Hudson and Robin,
1980). These experiments verify the sensitivity of corals to
drilling muds.
A-3
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At French Frigate Shoals. Hawaii, coral reefs were able to
withstand a spill of 2.200 metric tons (2.426 tons) of kaolin
clay without extensive damage (Neff. 1980). Within 50 m of the
wreck some corals were smothered, and Pocillopora spp. were
bleached because of the lack of light, but survived. Beyond a
50 m (164 ft) radius, no effects to the corals were observed.
Exploratory drilling in a coral reef off Palawan Island in the
Philippines produced an estimated 70-90 percent reduction of
some coral species (Hudson et al.. 1982). The affected area
formed an ellipse 115 m by 85 m extending out from the well-
heads so coral mortalities were presumed to be caused by
smothering or toxic effects from discharged mud and cuttings.
A.1.1.2 Administrative Context
Several Federal agencies have responsibilities for various
aspects of the Flower Garden Banks. The Minerals Management
Service (formerly the Bureau of Land Management) administers
the leasing program. EPA, through the NPDES permitting
process, has responsibility for regulating discharges in the
area.
In order to resolve the conflicts regarding the environ-
mental acceptability of drilling in the area, in 1981 the EPA,
Natural Resources Defence Council, Sierra Club, and the inter-
ested oil companies entered into agreements regarding the
conduct of drilling. The agreements permitted the discharge of
water-based drilling fluids with certain restrictions and
required completion of monitoring studies and other research by
the oil companies. Monitoring will be conducted for: (1)
hydrocarbons, barium, and chromium in sediments. (2) barium
metals, and hydrocarbons in drilling fluids, and (3) possible
barium and chromium accumulation in a representative bivalue.
A-4
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Transect measurements, growth/regression measurements, and
larval recolonization will also be evaluated at the East Flower
Garden Bank. The monitoring of exploratory wells will continue
for six months after the end of drilling. Other oil companies
are funding a review of the existing scientific literature to
assess the potential adverse effects of drilling fluids on the
Flower Garden Banks (i.e.. the Clements. Inc. report).
The mutual agreements stipulate conditions that will apply
to all drilling in the area. Drilling is not allowed on the
banks themselves, and discharges must be a minimum of 1.000 m
(3.280 ft) from the 100 m (328 ft) isobath (depth) line. All
discharges within 5,500 m of the 100 m isobath line must be
diluted with seawater until discharge concentration is reduced
at lease one order of magnitude. Diesel oil is not permitted
in fluids discharged in the area. Finally, all discharges from
drilling platforms must be shunted to a point approximately
10 m (33 ft) from the bottom, releasing this material below the
thermocline. This practice should confine the discharged
material to an area near the sea bottom. Initial data indicate
that the shunting regulations are effective (Gettleson. 1978;
and McGrail et al.. 1982. reported in Clements. 1983). While
typical conditions in the area may keep these shunted discharges
near the bottom, such a conclusion must be accepted with cau-
tion. Many factors affecting ocean transport of pollutants are
poorly understood.
Monitoring of water quality, infaunal benthic, and nektonic
organisms is being conducted for the EPA by the National Marine
Fisheries Service. Underwater video systems are being used to
census fish populations at different sites and depths. Major
nektonic fish include creole fish, porgies. red snapper.
A-5
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grouper, and other reef fish. Monitoring efforts under this
program began with an initial cruise in October. 1980 and are
being focused in the vicinity of the Mobil production platform.
A.1.2 Recent Drilling Activity
Drilling began in the Flower Garden Banks area in 1973. At
least one production platform is in place in the Flower Garden
Banks area, installed by the Mobil Oil Corporation in the fall
of 1981. The platform is approximately 1.5 miles (2.500 m)
from the East Flower Garden Banks, and is projected to operate
eight production wells.
Approximately six exploratory wells have been drilled near
both the East and West Banks. Companies active in the area
include Mobil. Union Oil, American Natural Resources (formerly
American Natural Gas), Pennzoil, and Anadarko. Early results
from the work of Meyer (1981), Trefry et al., (1981), and
Trocine and Trefry (1982) of measured sediment accumulations of
barium, chromium, iron, and other trace metals contained in
drilling fluids, and found no evidence of trace metal pollution
from drilling activity in the area, except for barium. Cut-
tings piles in the area have been observed within 10 to 50 m of
the point of discharge. Elevated barium levels have been
observed out to 500 m from discharges, and drop to background
levels within 300 to 1,000 m (Clements, 1983). The Clements
report concludes that the two most likely causes of significant
environmental effects are (1) burial and other effects to
benthos in the near vicinity of the discharge, and (2) exposure
in the event of a blowout, should one occur. Both scenarios
are considered unlikely, as are other types of exposures,
leading to their conclusion that the overall risk to the reef
A-6
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ecosystem from drilling is minimal. There are, however, many
shortcomings in the current information base for assessing
potential impacts, which severely limits the ability to detect
impacts, should they be occurring. Thus, the initial indica-
tions of minimal adverse environmental effects should be
accepted with caution.
A.2 GEORGES BANK
The Georges Bank area is located approximately 300 km (180
mi) southeast of Cape Cod, Massachusetts. The area is situated
on the outer continental shelf, approximately 200 km (120 mi)
landward from the closest point of approach of the Gulf Stream.
Georges Bank has been described as one of the richest spawning
and fishing grounds in the world (Houghton et al.. 1981). The
controversy surrounding drilling here centers on whether the
search for oil and gas will have a damaging effect on the vital
fishing stocks of the area, and how these uses might be compat-
ibly maintained. Houghton et al., (1981) prepared a study of
the "Fate and Effects of Drilling Fluids and Cuttings at
Georges Bank" for the Bureau of Land Management, which provided
substantial data for this section.
A.2.1 Physical Setting
The hydrodynamic regime of Georges Bank is a high energy
one. Tracts already leased for drilling (Lease Sale No. 42)
are from 50 to 100 m (164 to 329 ft) deep; depths in tracts
scheduled for future leasing range from 100 to 2.000 m (328 to
6.562 ft). Summer thermal stratification is distinct, while in
winter the water temperatures are relatively uniform. Seasonal
salinity variations are less extreme than temperature
A-7
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variations; however, spring runoff from the continent does
result in some dilution of the upper water layers.
Flow patterns are complex. A mean clockwise gyre exists
over Georges Bank, while a counterclockwise flow pattern pre-
dominates just to the north in the Gulf of Maine. The gyre
over Georges Bank appears to be strongest in the spring and has
an intermittently closed circulation with potential for recir-
culating discharges, although considerable variability is
present in circulation patterns. Current meter readings near
the surface reveal a mean drift of approximately 25 to 30
cm/sec (0.82 to 0.98 ft/sec) in the northern part of the Bank,
and 5 to 10 cm/sec (0.164 to 0.33 ft/sec) in the southern
part. At greater depths, current speeds decrease.
Four potential surface and sub-surface exits from the over-
all circulatory system have been identified. One is to the
northwest and empties into the Gulf of Maine, which has been
identified as an area of potential accumulation of drilling
fluids. Other potential exits have been identified to the
northeast, south, and southwest. Recent research confirms that
the "Mud Patch" area (to the southwest of the Bank) is a sink
for fine-grained sediments and a potential sink for sediment
related pollutants (Bothner et al., 1981). While deposited
material may be subsequently removed from the Mud Patch to the
southwest, sediment inputs were found to exceed losses.
Georges Bank is located at the convergence of the southerly
flowing Labrador Current and the northerly flowing Gulf Stream,
which together drive the complex circulation and promote
upwelling. Vertical mixing of the water column is good, driven
A-8
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by the influence of winds and currents in this shallow area
(Houghton et al., 1981). Fine sediments do not accumulate much
because of high current speeds and frequent resuspension.
Storms passing through this area can be severe, particularly
during the winter months, contributing to the dispersal of
sediments.
The Georges Bank bottom sediment is composed primarily of
medium and fine sand, with patches of gravel, and small areas
of silt and clay. The presence of these four sediment types
promotes biological richness and diversity. Significant
quantities of mollusk shell fragments are present. More
detailed information on the Georges Bank physical environment
can be found in the Environmental Impact Statement for Lease
Sale NO. 52 (BLM, 1982) .
The ambient water column is contaminated with hydrocarbons,
presumably due to frequent marine discharges such as tanker
ballast discharge (BLM, 1977). The most severe oil spill to
occur in the area was the wreck of the oil tanker Argo Merchant
off Nantucket Island in 1976. which spilled nearly eight mil-
lion gallons of fuel oil.
A. 2.2 The Georges Bank Fishery
The richness of the Georges Bank fishery has been
attributed to a combination of several factors (Houghton
et al., 1981), namely:
The location of Georges Bank near the convergence of the
Labrador Current and the Gulf Stream, which results in
the upwelling of nutrient-laden bottom waters.
A-9
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Continuous vertical mixing of waters over the Bank due
to its shallowness and the influence of wind and
currents.
The high levels of mixing and nutrients which support a
rich pelagic food chain including phytoplankton.
zooplankton. and other nekton.
The high benthic diversity due to various types of
surficial sediments.
Productive benthic macroinvertebrate populations over
some parts of the bank which are correlated with high
bottom fish production.
Species which use Georges Bank extensively for spawning
include hake, herring, flounder, plaice, butterfish. cusk,
rockling. cunner. sculpin. and sand lance (Colten et al.. 1979,
as in Houghton et al.. 1981). Shellfish also comprise an
important economic resource on the bank, particularly sea
scallops and lobster. Shellfish of lesser importance include
surf clam, ocean quahog. and red crab.
A.2.3 Potential Impacts from Drilling Activity
Sea scallops (Placopecten maqellanicus) are among the
organisms of greatest concern with regard to drilling fluid and
cuttings impacts because of their commercial importance and
potential for accumulations of fine solids or trace metals.
Laboratory studies reveal accumulations of barium and chromium
in the kidneys of sea scallops after exposure to high concen-
trations of ferrochrome lignosulfonate drilling fluid (Liss et
A-10
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al.. 1980). However, the edible part of the scallop, the
adductor muscle, did not show similar accumulation. Sea
scallops are found primarily at depths of 40 to 100 m (131 to
328 ft) on firm sand or gravel bottoms. During the period
from 1961 to 1973. the scallop catch declined from a high of
10.900 kg (24.000 Ibs) to a low of only 1.800 kg (4.000) Ibs.
Houghton et al.. (1981) report that the stock has shown
recovery in recent years, as the Canadian fleet reported record
catches in 1977 through 1979, but the scallop fishery has since
shown a major decline.
The lobster fishery appears to have reached its peak
approximately 20 years ago. Declining catches have resulted in
fishing efforts moving out further from the coast. It is known
that lobsters are sensitive to environmental changes, and sen-
sitivity to drilling fluids has been shown in laboratory tests
(see Section 4).
Potential impacts of future drilling fluid accumulations on
the lobster community are unknown. Lobsters breed in shallow
coastal waters, and spend the rest of the year in the canyon
heads on the deeper areas of Georges Bank. Impacts could occur
either in the shallow breeding areas or in the canyon heads if
drilling materials are transported from platform proximities
to deeper waters by way of submarine canyons (Dr. Eng, EPA
Region I, to T. Mors, Dalton'Dalton'Newport, personal
communication. 1982).
Dispersion of the upper plume of drilling fluid discharges
in this area is expected to be rapid. Houghton et. al (1981)
estimate a dilution of 500 to 1,000:1 within a few meters of
the discharge, increasing to 10,000:1 within 100 or 200 m (328
or 656 ft). This might result in ambient concentrations in
A-ll
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the zone up to 100 m (328 ft) to be greater than the 96-hour
LC5 concentration level for the most sensitive species and
the most toxic muds (i.e.. LC5Q of 100 ppm). Serious effects
to nektonic organisms would be expected, however, only if they
maintain themselves within the plume near the platform for long
periods. Chronic impacts could be experienced by organisms
remaining very near the plume formed by the shale shaker
because of the semi-continuous nature of this discharge.
Planktonic organisms may be killed if entrained in the plume.
particularly during the sensitive molting period.
Benthic accumulations of fine solids are not expected to
persist in the Georges Bank area because wind and tidal tur-
bulence in the shallow waters removes deposited material
rapidly. Fine materials can eventually be transported out of
the Georges Bank area to depositional sinks such as the Gulf of
Maine. In such sinks, minimal impact is anticipated because of
dilution of drilling discharges with other accumulated solids.
and adaptation of organisms to the fine-grained sediments
(Houghton et al.. 1981). However, the initial cuttings pile
formation can impact the benthic community in highly localized
areas through burial.
Houghton et al.. (1981) conducted a worst case
environmental assessment for exploratory and development
scenarios in the Georges Bank area. They estimated the effect
of drilling mud discharges were spread evenly within a 3,218 m
(2 mi) radius of a well, and mixed to depths of 1 cm and 5 cm
(Table A-l). In the short-term scenarios (1 cm deep mixing),
drilling fluid discharges could be responsible for increases in
sediment concentrations of mud solids, barium (505 percent).
chromium (26 percent), nickel (3 percent), lead (1 percent) and
A-12
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TABLE A-l
INCREMENTAL CONCENTRATION OF HUD SOLIDS AND METALS
IN TOP 1 AND 5 CM OF BOTTOM SEDIMENTS WITHIN
2-MILE (3,218 m) RADIUS OF WELL
COMPARED TO AMBIENT METALS CONCENTRATIONS a
Mud
Component
Mud Solids
Ba
Cr
Cd
Pb
Hg
Ni
V
Zn
a Even spreading
b Data from ERCO
9, 12, 13, 18,
Total Amount
Discharged (kq)
627,500
305,175
964
< 4
23
< 4
39
41
332
Concentration (ma/kg)*5
1 cm 5 cm
1,205 241
586 117
1.9 0.4
0.008 0.002
0.044 0.009
0.008 0.002
0.08 0.02
0.08 0.02
Ambient
Concentration
(mg/kg)
116 (< 44 - 290)
7.2 (2.2 - 27)
1.3 (1.0 - 20)
4.2 (1.4 - 96)
-
2.4 (1.2 - 13)
11.5 (10 - 34)
0.6 0.1 5.2 (1.2 - 50)
within, and zero transport beyond, 3,218 m is assumed.
, 1980: median and range for totally digested samples from Stations
20, 21, 23, 25, 26, 28, and 29 in general vicinity of lease area.
Table reproduced without alteration from Houghton et al., (1981).
A-13
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zinc (11.5 percent) compared with background levels. In the
long-term scenario (5 cm deep mixing), the increase over
background concentration appears insignificant except for
barium (100 percent), chromium (5.5 percent), and zinc (2
percent).
The researchers also estimated bottom area affected by
drilling fluid and cuttings discharges from a high development
scenario (28 platforms, 420 wells). To estimate the extent of
effects caused by multiple wells, they assumed a radius of
accumulation 110 percent that of a single well for five or more
wells from a single platform. Given these assumptions, only
0.2 percent (127 km or 31.382 acres) of the Georges Bank
bottom area would be affected by drilling activity. This would
impact benthic organisms inhabiting the area near the dis-
charges, but should not seriously disrupt fish stocks which
depend on benthic organisms as a major source of food.
Finally, the researchers speculated on what might occur if
discharged drilling fluids became trapped in the Georges Bank
gyre. Assuming all fluids from one year were retained and
evenly distributed throughout the gyre, they found that
resultant pollutant levels would not be significantly greater
than baseline levels. Resultant concentrations would be 0.023
mg/1 of mud solids fluids, 0.01 vg/1 of barium, 0.04 yg/1
of Cr, and 0.15 yg/1 of Zn. In actuality, some of the dis-
charged material would be transported out of the gyre by the
circulatory patterns.
Bothner et al.. (1982) found post-drilling barium
concentrations in unfractionated sediments increased by 350
percent 200 m from one drill site and by 230 percent at a
A-14
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second. Elevated concentrations were observable at a distance
of 6 km from the rig. The authors estimated that, overall.
approxi- mately 18 percent of the barite discharged from the
second rig was contained in sediments within a 6 km radius.
based on samples taken one month before the end of drilling.
No changes in the concentrations of chromium or other metals in
sediments were observed which could be attributed to drilling
activity.
A.2.4 Administrative Context
To date only Lease Sale No. 42 in the Georges Bank area has
been completed. The sale was held in December 1979. and the
first drilling activity began in July 1981. Shell. Mobil.
Tenneco. and Conoco are involved; Exxon was involved, but has
since withdrawn from the area. Approximately eight exploratory
wells have been drilled with no hydrocarbon discovery, and no
further drilling is slated for the immediate future. A Final
Environmental Impact Statement for Lease Sale No. 52 was
published in April 1982 by the Bureau of Land Management (BLM.
1982). The area involved has since been modified and a new
sale is scheduled for the fall of 1984.
NPDES permits for drillers in the North Atlantic area
require shunting of all discharges to the "lowest point
achievable." which in practice would be 15 to 25 m (49 to 82
ft) below the surface. The intent of this requirement is to
limit adverse effects to pelagic eggs and larvae by confining
discharges to below the pycnocline. In Georges Bank, the
discharge pipes may not be below the pycnocline. No studies to
date have assessed the effectiveness of this technique in
achieving its intended objective.
A-15
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Permits further stipulate that only water-based drilling
fluids may be discharged. These fluids must be one of the
standard EPA generic formulations; if a non-standard mud or
constituent is used, it must be approved by EPA for ocean
discharge. Mud samples must be taken and analyzed for each
305 m (1,000 ft) of drilling which occurs.
In order to ensure the continued integrity of the Georges
Bank ecology, a Biological Task Force (BTF) including members
of MMS, FWS, USGS, EPA, and NOAA, and with the consultation of
the affected coastal states, was created to make recommenda-
tions on monitoring activities. Monitoring operations were
initiated in 1981 based on the recommendations of the BTF.
The monitoring program focused primarily on the chemistry and
quality of sediments and on effects to the benthic community.
Potential impacts to nectonic and planktonic organisms from
drilling fluid concentrations were judged by the BTF to be
unlikely. Thirteen "regional stations" were located to iden-
tify long-term sediment changes caused by oil and gas activi-
ties. The regional stations have monitored sediment pollution
and sample benthic epifauna and infauna. In addition, inten-
sive sampling using 29 site-specific stations took place within
close range (5 km or 3 mi) of an active exploratory drilling
rig. Sampling at these sites will continue for the duration of
the leasing period. The first research cruise of the program
took place in July of 1981 and four cruises have been completed
through 1982. Cruises were scheduled to provide a preliminary
evaluation of seasonal environmental variations. There was
some detrimental effect to the benthic community; however, it
was determined that severe winter storms in February 1982 were
responsible for resuspension of sediments which apparently
lessened the effects of drilling discharges (NEC, 1983).
A-16
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A.3 NORTON SOUND
Norton Sound, the site of proposed oil and gas Lease Sale
No. 57. is located in the northeastern Bering Sea off the
western coast of Alaska. The proposed lease area includes 429
blocks covering 2.4 million acres, or 29 percent of the total
Norton Sound area. Offshore distances range from 14.4 to«99.2
km (8.6 to 60 mi) and are closest to shore in the Yukon Delta
Region (BLM. 1982). Norton Sound can be divided into three
regions, each with its own unique flora, fauna, and ecological
vulnerabilities:
Yukon Delta region - a complex estuarine system which
includes the Clarence Rhodes National Wildlife Refuge.
Inner Norton Sound - the warmer, shallow Alaskan coastal
waters east of 163°W longitude.
Outer Norton Sound - the colder, deeper, more saline
waters ove
longitude.
waters overlying the Bering Sea shelf west of 163 W
Norton Sound lies along major migration routes for many
species of marine mammals and birds. The Yukon Delta region,
coastal bluffs, and rocky islands located in Norton Sound are
important nesting and foraging grounds for hundreds of species
of seabirds, shorebirds. and waterfowl. Marine animals found
in the Norton Sound area over the course of a year include five
endangered whale species and one endangered bird species.
The Norton Sound environment is currently in a pristine
state with no major industry and a local population of only
12.000 (OCSEAP. 1982). Disruption of the natural environment
may have sociological as well as environmental impacts; the
A-17
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natives of this area depend on the migrating mammals, native
fisheries, and seasonal bird populations for a subsistence
harvest. Some of the potential impacts from offshore oil and
gas activities include the risk of oil spills in the area's
harsh climate, adverse effects to the benthic biota from plat-
form discharges, possible disruption of migratory patterns of
marine mammals, and interference with the subsistence harvest
of the natives.
A. 3.1 Physical Setting
Norton Sound is a shallow region ranging in depth from 5 m
(16.4 ft) in Inner Norton Sound to 50 m (164 ft) north of St.
Lawrence Island and in the Bering Strait channel. The deepest
point in the proposed lease area is 27 m (88.6 ft) and the
average depth is about 17 m. The sea floor slopes gradually
westward from the Yukon Delta which results in a broad, heavily
vegetated, intertidal zone that is often miles wide.
The climate of the area is subarctic and semi-arid and four
distinct seasons control migration through the area and the
distribution of species native to the area. During the summer.
open water in the Inner Norton Sound area lasts from July
through October and exhibits distinct stratification. The
relatively warm freshwater from the Yukon River and surface
runoff is sufficient to overcome tidal mixing and flow into the
Sound. Cold, highly saline water of the bottom layers becomes
stagnant during the summer months, flushing only during storm
events. Strong surface to bottom currents in outer Norton
Sound result in more complete mixing of these waters than is
found in the eastern portion of Norton Sound.
A-18
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The autumn transition period begins in October with a
series of storms characterized by winds from variable
directions, and is the most likely time for storm surges to
occur. The entire Norton Sound area is vulnerable to these
storm surges which can cause a rise in sea level of 5 m
(16.4 ft) above tidal maximum (BLM. 1982). As the season
progresses the storm tracks begin to shift south as the winds
become northerly. Ice begins to form in the eastern Sound
during late October. Also beginning in October, the pack ice
edge in the Chukchi Sea reverses direction and is transported
through the Bering Strait to the western portion of Norton
Sound and the Bering Sea.
Winter lasts from January through April and is charac-
terized by a relatively complete ice cover over the Sound.
The various ice formations of Norton Sound include shorefast,
Norton Sound pack ice. and Bering Sea pack ice which move into
the area, each of which affects wildlife distribution and
migratory patterns, and could cause damage to offshore
structures.
Spring transition generally lasts from May to June and is a
period of rapid warming during which the ice quickly disap-
pears. Early weather systems parallel the Alaskan coast and
push the Bering Sea ice pack northward through the Bering
Strait and into the Chukchi Sea. These lead systems are major
migration corridors for marine birds and mammals.
A.3.2 Phytoplankton and Benthos
Primary productivity in Inner Norton Sound is low due to
turbidity from the sediment load carried by the Yukon River.
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The eastern sector of Inner Norton Sound is characterized by
large amounts of detrital organic carbon from the Yukon River.
The soft organic sediments in this area support deposit feeders
(polychaete worms, small clams, etc.) and associated predators
(snails, crabs, and benthic fishes). The western sector of
Inner Norton Sound is also a depositional environment but sedi-
ments are continuously resuspended and redistributed by the
current of the Yukon River. Species abundant in this area are
those characteristic of unstable depositional environments
(polychaete worms, clams, and echinoderms).
Primary productivity of Outer Norton Sound is high. There
are intense phytoplankton blooms each year associated with the
spring retreat of the ice sheet. Sedimentation rates are
lower, currents are more vigorous, and the benthic organisms
are dominated by suspension feeders.
Norton Sound supports a rich benthic community which plays
a key role in an extended food chain supporting a wide range of
marine mammals. Any disruption of this benthic base could
seriously affect the biota of the entire region. The inverte-
brate benthos are dominated by echinoderms (especially the
starfish Asterias amurensis) which represent 80 percent of the
invertebrate biomass and 60 percent of the combined inverte-
brate and demersal fish biomass. Gastropod mollusks are the
most abundant invertebrate of potential commercial importance.
Two species of king crabs are also present in sufficient num-
bers to support a commercial fishery. The red king crab
(Paralithodes platypus) and the blue king crab (Paralithodes
camtschatica) dominate the western and eastern basins, respec-
tively (OCSEAP. 1982).
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A.3.3 Fishes and Fisheries
Despite the large quantity of benthos, bottomfish are less
abundant in Norton Sound than in other Alaskan regions. Cod
and flatfish comprise over 75 percent of the demersal fish
biomass (OCSEAP. 1982). Saffron cod. Arctic cod. and starry
flounder are the most abundant demersal fish in the area;
other species present are the short-horned sculpin. yellowfin
sole, and Alaskan plaice. These six species are important
food sources for marine mammals and may be used by man as
subsistence species.
Five species of salmon (chum. pink. coho. Chinook, and
sockeye) are also found in the Norton Sound area. Commer-
cially, the most important pelagic species is the Pacific
herring. These fish spawn in the subtidal regions of Norton
Sound, where the pelagic larvae remain in the subtidal region
for up to two months (8LM, 1982). Other common pelagic fish
species are rainbow smelt, capelin. and the Pacific sandlance.
The sandlance is a major item in the diet of surface-feeding
seabirds.
A.3.4 Birds
The Norton Sound lease area is adjacent to the major
northern Bering seabird colonies and offshore bird concen-
tration areas. At least 5 million breeding seabirds. or 23
percent of Alaska's nesting population occur in this area (BLM.
1982). The lease area is adjacent to one of the most important
and productive waterfowl and shorebird habitats in North
America. During the summer season the seabirds are concen-
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trated in the large breeding colonies of St. Lawrence Island,
the Diomedes. and the Bluff Cliffs east of Nome. Most, but not
all. of these birds migrate south in October.
The birds of prey in the Norton Sound area include falcons
(e.g., gyrfalcon). owls (e.g.. snowy owl), hawks (e.g., marsh
hawk), and the golden eagle. Nesting areas for the birds of
prey are associated with major seabird colonies upon which they
depend as food sources. These birds, including the endangered
Peregrine falcon, also migrate south in September and October.
A. 3. 5 Marine Mammals
Marine mammal species that are strongly associated with
seasonal sea ice will be found in the Norton Sound area at some
time during the year. Most species follow the advance of the
Bering Sea ice pack in the fall and remain in the proposed
lease area until the spring retreat. This would include such
species as polar bear (Ursus maritimus). walrus (Odobenus
yosmarus). ringed seal (Phoca hispida). bearded seal
(Eriqnathus barbatus). spotted seal (Phoca vitulina larqha).
ribbon seal (Phoca fasciata). beluga whale (Delphinapterus
leucas). minke whale (Balaenoptera acutorostrata). and killer
whale (Orcinus orca).
Five endangered species of whales occur to a varying degree
in or near the proposed lease area. In general, they all
remain in western Norton Sound and the Bering Sea:
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Bowhead whale (Balaena mvsticetus)
Gray whale (Eschrichtius robustus)
Black whale (Megoptera novaeanqliae)
Fin whale (Balaenoptera physalus)
Sei whale (Balaenoptera borealis)
A.3.5.1 Administrative Context
OCS oil and gas Lease Sale No. 57 covers the Norton Sound
area. In addition to this Federal lease sale, the State of
Alaska 5-Year Oil and Gas Leasing Schedule also lists an
offshore sale in Norton Sound (Sale No. 38). USGS estimated
that for Lease Sale No. 57. at the peak of exploratory drill-
ing, an estimated 5 drilling rigs would complete 13 wells. If
exploratory drilling is successful, the developmental period
may include as many as 172 production wells operating from nine
production platforms (BLM. 1982).
The Atlantic-Richfield Company put in a Continental
Offshore Stratigraphic Test (COST) well on June 7. 1982. for
which it was issued a single discharge permit. The EPA has
issued a general NPDES permit to cover exploratory drilling
activity in this area.
A.3.6 Potential Impacts from Drilling Activity
The greatest danger from offshore oil and gas activity in
Norton Sound appears to be that of an oil spill. The chance of
such an accident occurring is magnified by the environmental
hazards unique to Norton Sound.
The Final EIS concluded that the large sediment load from
the Yukon would mask any deposition of drilling discharges
(BLM. 1982). which may also be the case foe lease blocks that
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lie in the deposition zone for the Yukon River. The Yukon
River deposits between 70 and 90 million metric tons of sedi-
ment into Norton Sound each year. However, insufficient
oceanographic information is available to determine the extent
of this zone or the deposition patterns for Yukon sediment
throughout the proposed lease areas.
Available information on water quality in Norton Sound
(BLM. 1982) indicates background levels of toxic metals to be
one and two orders of magnitude less than the applicable EPA
water quality criteria. Sediment analyses show hydrocarbons
present only in concentrations typical of biogenic origin.
There is no evidence of petroleum hydrocarbons in either the
water column or the sediments. Thus, the area is considered to
be in a pristine state.
Potential impacts to the benthos would be significant, but
it is not possible to evaluate this threat based on currently
available data. Another factor to be considered in assessing
the environmental impacts from drilling discharges is the
susceptibility of the area to periodic storm surges. These
events could, by redistributing localized platform discharges.
consequently redistribute the zone of impact.
6U.8. GOVERNMENT PRINTING OFFICE: 1985 1*63 530 32763
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