United States
           Environmental Protection
          Industrial Environmental Research
          Cincinnati OH 45268
EPA-600 7-80-1 14
May 1980
           Research and Development
Choosing  Offshore
Pipeline Routes

Problems and

R&D Program


Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology.  Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

      1.   Environmental  Health Effects Research
      2.   Environmental  Protection Technology
      3.   Ecological Research
      4.   Environmental  Monitoring
      5.   Socioeconomic Environmental Studies
      6.   Scientific and Technical Assessment Reports (STAR)
      7.   Interagency  Energy-Environment Research and Development
      8.   "Special" Reports
      9.   Miscellaneous Reports

This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded  under the 17-agency Federal  Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the  Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of  energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and  integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia  22161.

                                     May 1980

Ann M. Gowen, M. J. Goetz, and I. M. Waitsman
         Coastal Programs Division
    New England River Basins Commission
        Boston, Massachusetts 02109
   Interagency Agreement No. 78-D-X0063
              Project Officer

              John S. Farlow
 Oil and Hazardous Materials Spills Branch
Industrial Environmental Research Laboratory
         Edison, New Jersey 08817
          CINCINNATI, OHIO 45268

     This report has been reviewed by the Industrial Environ-
mental Research Laboratory-Cincinnati, U.S. Environmental Pro-
tection Agency and approved for publication.  Approval does
not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute
endorsement or recommendation for use, nor does the failure to
mention or test other commercial products indicate that other
commercial products are not available or cannot perform simi-
larly well as those mentioned.


     When energy and material resources are extracted, pro-
cessed, converted, and used, the related pollutional impacts on
our environment and even on our health often require that new
and increasingly more efficient pollution control methods be
used.  The Industrial Environmental Research Laboratory-Cincin-
nati (lERL-Ci) assists in developing and demonstrating new and
improved methodologies that will meet these needs both effi-
ciently and economically.

     This report provides concise information on the environ-
mental impacts associated with outer continental shelf pipe-
lines.  Topics discussed include general industry siting cri-
teria, geologic and environmental areas to avoid in pipeline
siting,and methods for minimizing unavoidable impacts.  This
information will be of interest to all those concerned with off-
shore petroleum pipeline planning, including pipeline corridors
and pipeline landfalls.  Further information may be obtained
through the Resource Extraction and Handling Division, Oil and
Hazardous Materials Spills Branch, Edison, New Jersey.
                       David G. Stephan

         Industrial Environmental Research Laboratory

     In 1977, the New England/New York Coastal Zone Task Force,
a group affiliated with the New England River Basins Commission
(NERBC), and made up of state coastal zone program managers,
recommended that the U.S. Environmental Protection Agency (EPA)
initiate a research project on the environmental impacts of oil
and gas pipeline construction and operation.  The Task Force
felt that should oil and/or gas be found on the region's outer
continental shelf  (OCS), they would need this type of informa-
tion to make sound decisions regarding OCS pipeline routing.
EPA, recognizing NERBC's continuing interest in OCS-related
activities, responded with a formal request that NERBC under-
take this project entitled "OCS Pipeline Construction and
Operation - Potential Environmental Problems and Recommenda-
tions for Mitigation of Impacts."  Work was begun in January

     The first report in this series, "The Environmental Ef-
fects of OCS Pipelines - Initial Findings," was finished in
June 1978, with two additional chapters added in September
1978.  This second report, "Choosing Offshore Pipeline Routes:
Problems and Solutions," incorporates comments on the first
draft and additional information on the potential problems as-
sociated with offshore pipeline routing.  Both reports were
prepared by the staff of the New England River Basins Commis-
sion under the sponsorship of the Industrial Environmental Re-
search Laboratory-Cincinnati, U.S. Environmental Protection

     This project was undertaken to provide detailed information
on the environmental impacts associated with outer continental
shelf (OCS) pipelines.  It is designed to be used by scientists
or engineers involved in offshore petroleum pipeline planning,
including pipeline corridors and pipeline landfalls.  The infor-
mation for the project comes primarily from written sources.

     The report discusses the environmental and fisheries prob-
lems associated with offshore pipelines.  There are two major
environmental concerns:  leaks or spills of hydrocarbons from
pipelines into ocean waters; and potential damage to sensitive
environmental areas on and near the pipeline route.  Fisheries
concerns center on potential losses of fishing area or gear due
to offshore pipelines, resulting in loss of fishing time, catch
and revenue.  The report focuses on how these problems can be
addressed during the pipeline planning and route selection pro-

     Geologic hazards  (such as sediment conditions, liquefac-
tion, scour, sand waves, erosion and seismic characteristics)
are highlighted as the major factors related to pipeline fail-
ure which can be addressed through the pipeline routing process.
Habitats and ecosystems (such as spawning grounds and salt
marshes) which are particularly susceptible to installation-re-
lated disturbances (which include organism losses, turbidity
effects, habitat alterations and changes in physical and chemi-
cal characteristics along the routes) are discussed.  These
areas as well as those where geologic hazards are most likely
to be encountered are described.

     Fishing problems highlighted include loss of access to
fishing areas due to pipelines both from platform to shore and
between platforms.  The effects of obstructions  (such as un-
buried or spanned pipelines, rocks, etc. exposed by trenching,
and debris from pipelaying activity and passing ships) on bot-
tom fishing gear are also considered.  The concept of pipeline
trenching for safety and stability is discussed.

     Finally, criteria to use in analyzing a proposed pipeline
route are presented.  Topics discussed include general industry
siting criteria, geologic and environmental areas to avoid in
pipeline siting and methods for minimizing unavoidable impacts.

     This report is submitted.in fulfillment of Interagency
Agreement No. EPA-78-X0063 by the New England River Basins Com-
mission under the sponsorship of the U.S. Environmental Protec-
tion Agency.  This report covers the period September 1, 1978
through March 1, 1979 and work was completed as of January 15,


Preface	iy
Abstract	  y
Figures	  x
Tables	xi
Acknowledgments	xii

     1.  Conclusions and Recommendations	  1
     2.  Defining the Problems — An Overview	  6
               Causes of Pipeline Failure	  7
                    Anchor Dragging	  8
                    Trawl Gear	  9
                    Corrosion and Other Structural Problems.. 12
                    Geological Hazards	 15
                    Preventing Failures - The Planning
                       Issues	 15
               Pipeline Installation-Related Disturbances.... 16
                    Offshore Installation Methods	 16
                        Pipelaying	 16
                        Pipeline Trenching	 20
                        Pipeline Burial	 20
                        Evaluating the Usefulness of
                           Trenching Offshore	 23
                    Nearshore/Landfall Installation Methods.. 24
                        Pull Technique	 24
                        Flotation Technique	 24
                    Environmental Disturbances from Pipeline
                       Installation	 26
                    The Extent of Environmental Disturbances. 27
                    Environmental Disturbances - The
                       Planning Issues	 28
     3.  Assessing the Environmental Problems	 30
               Geologic Hazards	 30
                    Sediment Conditions	 31
                    Liquefaction	 32
                    Pipeline Flotation	 33
                    Sediment Scour.,	 33
                    Sand Waves	 34
                    Shoreline Erosion	 36
                    Seismic Hazards...,	 37

                Environmental Disturbances	 39
                     Loss of Organisms	 39
                     Turbidity Effects	 41
                     Habitat Alteration	 43
                     Physical and Chemical Alterations	 44
      4.  Assessing the Fishing Problems	 46
                     Loss of Area	 46
                     Trawl Gear Damage	 48
                     Bottom Debris	 50
      5.  Solving the Problems - Choosing a Pipeline Route... 53
                Technical Siting Criteria	 53
                Preconstruction Planning	 58
                     Geoloqical Hazard Areas to Avoid	 58
                     Environmental Areas  to Avoid	 59
                     Preconstruction  Studies	 60
                     Pipeline/Fishing Interferences	 62
                         Trenching	 62
                         Consultation	 62
                Installation Techniques	 63
                     General Installation Methods	 63
                         Scheduling	 63
                         Construction Methods	 63
                         Restoration	 63
                         Debris	 63
                     Landfall Installation Methods	 64
                         Wetlands	 64
                         Beaches	 65
                Operational Procedures	 66
                     Recording Route  Location	 67
                     Pipeline Inspection	 67
                         Initial Inspection	 67
                         Start-up Inspection	 68
                         Annual Inspection	 68
                         Special Inspections	 68

References	 69

Bibliography	 74

I.  Calculating the Amount of Bottom Sediments Disturbed by
      Selected Offshore Activities	 79
          Amounts of Sediment Disturbed by Offshore
            Activities	 79
                Surf Clamming	 79
                Sea Scalloping	 80

                Otter Board Trawling	  81
          Amounts of Sediment Disturbed by Pipeline
             Trenching	  81
                Bureau of Land Management Estimates	  81
                FLAGS Study Trench Profiles	  82
                     Narrow Trench in Firm Soil	  82
                     Wide Trench in Soft Soil	  83
                Miles of Pipeline Laid	  84

II.  Industry's Procedures for OCS Pipeline Route Selection...  85
          Selecting A Route	  85
          Surveying A Route	  90


Number                                                     Page

  1   Anchor Penetration  	   9

  2   Concrete Anchor Protection System	   10

  3   Otter Trawl	   11

  4   Damage to Pipeline  Concrete After
        Five Impacts	   13

  5   Beam Trawl Gear	   14

  6   Center Ramp Pipeline Laybarge	   17

  7   Side Ramp Pipeline  Laybarge	   18

  8   Laybarge Method of  Pipelaying	   19

  9   Pipeline Trenching  Machines	21-22

 10   Pull Technique of Pipelaying	   25

 11   Threshold Velocities for Sediment Particle
         Movement	   35

 12   Trawl Gear Hooking  and Release	   49

 13   Deep Water Trenching Problems	   52


Number                                                   Page

  1   Sediment Disturbance by Selected Offshore
        Activities	27

  2   Susceptibility of Sediment Deposits to
        Liquefaction 	  32

  3   Pullover Loads on Trawl Doors	50

  4   Industrial Pipeline Siting Considerations	54

  5   Physical Constraints on Pipeline Landfalls
        Criteria for Evaluation	57

     My sincere appreciation goes to the report's principal
author, Ann W. Gowen, who researched and wrote the majority of
the document, and Michael J. Goetz, who prepared those sections
of the report which deal with geologic concerns.  Without their
thorough research and diligent efforts, this report could not
have been prepared.

     Of the many other persons and organizations who have as-
sisted in this project, we would like to thank those individuals
in the oil and gas industry who provided valuable information
and insight.  In particular, thanks go to the Pipeline Industry
Advisory Task Force  (set up in cooperation with the American
Petroleum Institute) and its Chairman, George G. Hughes, Jr., of
Exxon Pipeline Company, who provided invaluable technical input
to the project; and British Petroleum Company Limited  (London),
Shell U.K. Exploration and Production Limited (London), Brown-
aker Offshore  (Norway), and Seditech (Denmark) for providing
photos and information on their offshore activities.

     Special thanks also go to John S. Farlow, Project Officer
for the sponsor, the U.S. EPA's Industrial Environmental Re-
search Laboratory-Cincinnati, for his continued advice and sup-
port; and Larry Shanks, U.S. Fish and Wildlife Service and
Robert A. Matthews, U.S. Geological Survey for their insightful
review of earlier drafts.

                               Irvin M. Waitsman
                               Manager, Coastal Programs

                           SECTION 1

     A number of lease sales of outer continental shelf (OCS)
tracts for oil and gas development are now underway in areas
previously not involved in offshore petroleum activity.  Al-
though in light of the world petroleum situation this type of
development seems certain, apprehension is felt in these "fron-
tier" areas regarding potential problems associated with off-
shore development.

     One of the major sources of concern is the transportation
of oil and natural gas from offshore platforms to the shore.
Although pipelines are generally accepted as the safest method
of oil and gas transportation, uncertainty is still felt regard-
ing their possible effects on the locations chosen as pipeline
routes.  This project, sponsored by the U.S. Environmental Pro-
tection Agency (EPA), is designed to provide information on the
environmental effects of OCS oil and gas pipelines to officials
in frontier areas who may become involved in planning pipeline
routes from offshore development areas to land.  This document,
"Choosing Offshore Pipeline Routes:  Problems and Solutions,"
discusses environmental and fishing problems generally perceived
to be associated with offshore pipelines.  The report analyzes
these problems, considering their causes, potential extent of
impact, and where and/or when the impacts are likely to be the
most severe.  Industry's siting criteria, areas to be avoided in
routing, and methods to minimize unavoidable impacts are des-


     The major conclusion reached is that, in general, only
small-scale, localized impacts will result from pipeline instal-
lation and operation.  However, when choosing from among various
routes, certain' environmental and fisheries problems need to be
assessed and their solutions compared to assure that the safest,
most stable and most environmentally acceptable route will be
delineated.  There are two major environmental concerns associ-
ated with any pipeline siting decision:   (1) leaks or spills of
oil into ocean waters as a result of pipeline failures, and  (2)
potential damage to sensitive environmental areas on and near
the pipeline route.  Loss of access to fishing areas and damage

or loss of fishing gear due to pipelines are the two major areas
of potential impact on the offshore fishing industry.

     These issues and some recommendations for lessening their
potential effects are described below.  Because the emphasis in
this report is on minimizing the potential impacts through pre-
planning and the route selection process, these "routing solu-
tions" address primarily causes.  Therefore, methods for mini-
mizing the likelihood of a spill occurring rather than for mini-
mizing a spill's effects are highlighted; likewise, methods of
reducing potential fishing conflicts focus on lowering the chan-
ces of interference rather than on dealing with damages once

     In addition, this report is an overview of potential ef-
fects associated with pipeline installation and operation and
not a site-specific analysis of potential routes.  The various
geological, biological and fisheries issues described represent
the full range of possible problems which may be encountered
along a pipeline route.  The solutions described represent a
range of options available to minimize the potential effects of
pipeline installation and operation.  Area and site-specific
issues such as the probability of a particular problem occurring
or the severity of a particular problem have not been assessed.

     Therefore, the issues raised and solutions discussed
throughout the document can best be considered as a checklist
to use in assessing potential problems and considering alterna-
tive methods for lessening their impacts along a specific route,
rather than as an assessment itself.  In the final analysis, any
potential route will need to be evaluated individually, based on
technical, environmental and economic criteria and appropriate
mitigation measures chosen based on the characteristics of the
route under consideration.



     Of the four major causes of pipeline failures - corrosion,
anchor dragging, bottom trawling equipment and unstable geologic
conditions - geological conditions are the major concern which
can be addressed during the route selection process.  Because
unstable geologic conditions affect a pipeline's safety and sta-
bility, industry's pipeline siting criteria are also based, to
a large extent, on the geological conditions of proposed routes.


      Wherever feasible, geologically unstable areas should be
avoided during the route selection process.  Offshore these

areas include:  sand wave and scour areas, areas with unstable
sediment conditions, and submarine canyon heads.  Undesirable
nearshore and shoreline geologic conditions include:  high ero-
sion rates, steep slopes (greater than ten per cent), rocks and
very "spongy" wetlands.  In addition, because neither burial nor
artificial covering will protect a pipeline from large anchors,
shipping corridors and other areas where heavy vessels may drop
anchor should be avoided where possible.  However, pipelines can
and have been designed and routed through many of these undesir-
able areas, because other considerations, such as economics,
have outweighed the technical construction difficulties.



     Offshore trenching, and trenching and burial at the land-
fall are likely to cause the greatest amount of environmental
damage.  However, when quantitative comparisons are made to
other bottom disturbing activities, (bottom trawling, sea scal-
loping, etc.), it appears that pipeline trenching disturbs sig-
nificantly lesser quantities of bottom sediments.  Therefore,
when assessing the potential extent of disruption to the ecosys-
tems along a proposed route, the major consideration should be
the type and sensitivity of the system to damage, rather than
the quantity of disturbance.  Because the coastal zone contains
a greater array of diverse and frequently fragile habitats than
offshore areas, special attention should be given to potential
environmental effects nearshore and at the landfall.


     Key ecological areas and habitats should be avoided wher-
ever feasible.  These areas include:  small, unique, or rare
and endangered species habitats, spawning grounds, shellfish
beds, wetlands, grassbeds and coral reefs.  Once a route has
been chosen, good construction and restoration techniques can
further minimize the extent of damage.  Techniques include:
scheduling construction to avoid periods of highest biological
sensitivity (e.g., spawning periods), installing the line in the
shortest feasible period of time and restoring the disturbed
area as soon and as close to original conditions as possible.
Special techniques are also available to minimize installation
problems in particular ecosystems, such as wetlands and sand



     Both the gathering lines connecting platforms and the pipe-

line corridors from platforms to land may act as obstructions
which block access to fishing areas.  At the production area,
unburied connecting lines and the safety zones generally estab-
lished around platforms may eliminate as fishing areas both the
pipeline rights-of-way and the inner waters between platforms.
In addition, because of the risk of gear damage if hooked on
exposed lines, fishermen may choose to avoid passing over a
pipeline while trawling.  Thus, the pipeline itself may prevent
access by acting as a "dividing line" over which a vessel towing
gear will not pass.  Even in areas where the pipeline may ori-
ginally have been buried, trawling directly over lines may not
be advisable, based on past experience in which buried lines
have become re-exposed.  Therefore, when considering a potential
route, attention should be paid to the location of major fishing
areas, the trawling patterns of fishing vessels, and the extent
to which access may be blocked due to offshore pipeline place-


     Consultation with fishermen using offshore fishing grounds
to be traversed by a proposed pipeline is the best way to mini-
mize potential conflicts.  While crossing fishing grounds may be
unavoidable, consultations may reveal those areas most important
to the fishing interests.  Final routes can then be chosen based
on avoidance of those subareas delineated by the fishermen as
the most important portions of the larger fishing grounds.

     Where these delineated fishing subareas cannot be avoided,
technical choices regarding construction alternatives (e.g.,
premolded concrete coverings to provide additional protection)
may be considered to allow trawling to occur over the line.



     This issue has two components:  damage or loss of trawl
gear on exposed pipelines and gear damage or loss on bottom de-
bris present along a route.

     It has been suggested that the possibility of trawl gear
damage as a result of hooking on pipelines would be eliminated
if the pipelines were buried - the current practice in nearshore
and shallow areas  (less than 200 feet deep).  However, burial of
pipelines in deep offshore waters  (where bottom trawling takes
place) has often proved difficult to achieve.  Although a pipe-
line trench can be dug, many offshore areas have low bottom cur-
rents and little sediment movement, precluding natural backfil-
ling and burial.  Artificial backfill of pipeline trenches with
crushed stone has been tried in the North Sea, and has proved
expensive and inefficient.  When a pipeline is trenched but not>

buried, it has been demonstrated that the risk of damage both to
the trawl gear and the pipeline is significantly greater than
when a pipeline is lying directly on the ocean bottom.  However,
even when the pipeline is_ trenched but not buried, the chances
appear remote that trawl gear would hook, but not unhook—re-
sulting in loss of gear.

     On the other hand, damage is more likely to occur from bot-
tom debris, which can rip or tear fishing nets.  Bottom debris
encountered along a pipeline route may come from three pipeline-
related sources:  bottom materials dug up during trenching; ar-
tificial stone cover; and debris from pipelaying operations and
related vessels.


     The solutions to both these problems are, to a large ex-
tent, technological or engineering rather than routing-related.
Avoidance of bottom fishing areas will eliminate the risk of
trawl gear damage from pipelines.  In deep offshore areas where
this is not possible, an assessment of bottom current and sedi-
ment conditions may be necessary to determine the advisability
of trenching and burial.  Where natural burial is not expected
to occur, it may be more advisable to lay the pipeline directly
on the bottom  (rather than in a trench), and then cover it with
some type of additional protection  (e.g., premolded concrete

     The issue of damage to fishing gear as a result of debris
from pipelaying and other offshore activities is a difficult
one, and one which will not be resolved by changing a pipeline's
location.  Although the effectiveness of various methods for
lessening or limiting disposal of debris offshore are difficult
to assess, current laws and regulations prohibiting dumping at
sea may lessen the quantities of solid waste disposed in the
future.  In addition, when pipeline routing discussions are
underway, consideration may be given to the possibility of stip-
ulations in subcontracts to offshore service vessels prohibiting
offshore dumping and stipulating vessel liability for cleanup if
dumping does occur.

                            SECTION  2


     A number  of  lease  sales for  OCS  oil  and  gas development
tracts are  now underway in  U.S. offshore  areas previously not in-
volved in petroleum  activity.  Although in  light of  the world pet-
roleum situation  this type  of  development seems certain, much
concern  is  felt in these "frontier" areas regarding  potential
problems associated  with offshore development.

     One of the major sources  of  concern  is the transportation of
oil and  natural gas  from offshore platforms to the shore.  Cur-
rently,  there  are two methods  for transporting oil:  tanker/barge
or pipeline.   Due to the high  cost of liquefaction,  the only
practical method  of  natural gas transport is  via pipeline.  In
the U.S., pipelines  transport  all the natural gas and most  (95%)
of the oil  produced  offshore to land  (Shanks, 1978).

     Although  pipelines are generally accepted as the safest
method of oil  and gas transportation, there are still a number of
concerns regarding their possible effects on  the locations chosen
as pipeline routes.  There  are two major  sources of  concern:  the
environmental  risks  and the potential for interference with fish-
ing activity.   Environmental concerns focus on two areas:   (1)
leaks or spills of hydrocarbons from  pipelines into  coastal wa-
ters and (2) potential  installation-related damage to sensitive
environmental  areas  on  and  near the pipeline  route.  Fisheries-
related  issues  include  the  potential  loss of  fishing area or gear
due to pipeline placement and the resultant loss of  fishing time,
catch and revenue.

     The anticipated effects associated with  these problems are
many.  Oil  leaks  or  spills  , particularly those which come ashore
on sensitive coastal areas  such as marshes, may cause extensive
 The effects of natural gas on marine ecosystems are generally
 assumed to be negligible because it is thought that leaking gas
 would bubble up through the water column and dissipate into the
 atmosphere.  However, none of the literature examined to date
 has discussed this problem in detail, nor has mention been made
 of the effects of other constituents  (e.g., hydrogen sulfide)
 which might be produced in association with natural gas streams

damage to flora and fauna whose recovery rates may be low.  The
laying of the pipeline on the seafloor can cause loss of nonmo-
bile organisms directly beneath the line.  Digging pipeline
trenches in the seafloor can temporarily increase levels of sus-
pended solids in the water column near the construction site and
can result in altered habitat characteristics after the sediments
settle.  There may also be chemical and physical changes in the
water column and sediment structure in the construction area.
Depressions left in the seafloor due to the incomplete refilling
of pipeline trenches may alter bottom water circulation patterns.
Nearshore, pipeline installation may also cause short-term
changes in water column characteristics due to resuspension of
bottom sediments contaminated with toxic substances or with high*
concentrations of bacteria (which may lead to temporary localized
decreases in dissolved oxygen concentration).

     Fisheries problems center on two particular issues:   (1) the
loss of fishing area along the pipeline route and its associated
right-of-way, and (2) bottom obstructions which may cause fishing
gear damage or loss.  Even in areas where the pipeline may ori-
ginally be buried, these issues still concern fishermen because
past experience has shown that buried pipelines have become re-
exposed.  The "loss of fishing area" issue is magnified at the
production area itself, where gathering lines between platforms
may effectively eliminate both the pipeline rights-of-way and the
inner waters between the platforms as bottom trawling areas.

     Bottom obstructions to fishing may include rocks and mounds
of heavy clays exposed during the pipeline trenching operations
in addition to assorted debris from pipelaying operations and
passing ships.  Trawling equipment may become exposed or hooked
on unsupported segments of pipeline ("spans").  Even stone dumped
on pipelines for cover may get caught in fishing nets, causing
tears and possible loss.  (These issues are examined in greater
detail in Section 4—"Assessing the Fishing Problems.")

     Before making an assessment of the potential impacts associ-
ated with environmental problems adjacent to a pipeline, it is
necessary to understand what causes each problem and which of
these causes can be taken into account during the pipeline route
selection process.


     There are many suspected causes of pipeline breakage, in-
cluding:  anchor dragging; trawling; corrosion or other struc-
tural damage to the pipeline itself; and unstable geologic condi-
tions along the pipeline route.

Anchor Dragging

     Past experience   in  the Gulf of Mexico and the North Sea has
shown that dragging anchors can hook on exposed and buried pipe-
lines causing damage  to the pipeline.  In U.S. Geological Survey
(USGS) records of Gulf of Mexico pipeline leaks  (occurring from
1968-1978), of the 222 recorded incidents, 27 breaks were direct-
ly attributed to anchor dragging  (USGS, 1978).  In 1977, a
50,000 dead weight ton (DWT) tanker dragged its anchor across
the Norpipe Ekofisk to Teesside oil pipeline approximately four
miles offshore.  This caused a five-inch dent and necessitated
pipeline shutdown and repair  (New England River Basins Commission
[NERBC], 1979) .

     Protecting the pipeline from anchor dragging was one of many
subjects considered in a  comprehensive study undertaken prior to
construction of the Far North Liquids and Associated Gas System
(FLAGS) gasline.  Shell   Expro, the company which installed the
pipeline connecting the North Sea Brent Field to St. Fergus,
Scotland, commissioned a  series of studies to determine the saf-
est and most stable pipeline design and route.  Three separate
studies were undertaken  (Shell U.K. Exploration and Production
[Expro], 1977) to determine the risks of anchor hooking along the
FLAGS line and the usefulness of burial for pipeline protection.

     Study results indicated that the effectiveness of burial in
protecting pipelines  from anchors varies, depending on the type
of anchor involved and how deeply the anchor penetrates into the
sediments.  Most commercial vessel anchors bury 0.5-3 meters
(1.5-9.9 feet) into  the  sediment  (Broussard, D.L. et al., 1978).
Therefore, if a pipeline  is buried and remains buried to depths
of three meters or more,  it would be protected from these an-
chors.  However, in the case of oil-related vessels  (such as
pipelaying and derrick barge vessels) and large tankers, anchor
penetration may be significantly deeper - from five to seventeen
meters in good holding ground and even deeper in soft clays
(Shell Expro, 1977).   Figure 1 illustrates this point.  Det
Norske Veritas, a Norwegian company involved in safety and risk
analyses of offshore  structures, has also concluded that there is
currently no effective way of preventing pipeline damage by large
anchors, and, therefore,  recommends that pipelines be routed to
avoid areas of intense tanker or rig traffic  (NERBC, 1979).

     Besides pipeline burial, there are various structures avail-
able to protect pipelines laid directly on the seafloor from
dragging anchors.  For example, Seditech, a Danish firm, has
developed and model tested the Coral HC2 system for protection of
pipelines from objects dragging across the seafloor, in particu-
lar, ships' anchors.   The HC2 system is constructed of premolded
hinged concrete shields placed over a pipeline which detach when
caught by a dragging  anchor.  The pipeline would remain protec-
ted, however, due to  overlapping shield construction.  If re-


                Most vessels
                                          Rigs and tankers
             Source:   NERBC,  1979.

                    FIGURE 1,   ANCHOR PENETRATION,
moved, a shield would have to be repositioned by diver or  sub-
mersible.   (These structures would also promote sediment deposi-
tion over the pipeline.)  Figure 2 illustrates how  the system
works.  With the exception of very large anchors, it  is thought
that this system would protect pipelines from anchor  hooking.*

Trawl Gear

     Concern has frequently been expressed regarding  potential
interference between pipelines laid through bottom  fishing
grounds and the bottom trawling gear utilized by fishermen—in
particular, the large otter trawl doors used to keep  bottom fish-
ing nets spread apart.  Figure 3 shows a typical otter trawl as
it is approaching a pipeline.  In a four year petroleum industry-
sponsored program, VHL River and Harbor Laboratory  at the  Norwe-
gian Institute of Technology examined this problem  from both
sides--!.e., the extent of damage to the pipeline and the  extent
of damage to the trawl gear as a result of gear/pipeline impacts,
(Pipeline damage is considered here;  results of fishing gear
damage studies are presented in Section 4.)  The following are
the results of pipeline damage studies as presented in the Shell
Expro FLAGS Study.

     VHL determined that trawl doors could exert two  types of
force which could possibly damage a pipeline upon impact:   (1)
the impact force as the door hits the pipeline, and (2) the pull-
over force as the door is dragged over the pipeline.  Test
 0. Fjord Larsen,  (Director, Seditech,  Esbjerg,  Denmark)
 1978:  personal communication.


Immediately after installation
Typical pattern of natural sedimentation shortly after installation
Dragging anchor's removal of primary shield
1- Supporting cellular concrete module forming
  secondary shield in case (2) becomes removed
  by a ship's anchor.
  By pivoting around the axle (4) the modules
  adapt to the Irregularities of the seabed.

2- Triangular concrete plate forming primary shield
  against trawlboards and dragging anchors.
  The plate resting loosely on (1) • only prevented
  from sliding downwards - a dragging anchor
  hooking the edge of (3) will remove (2) and ride on
  this over the top of (1), cf. lowermost photo.

3 Concrete flaps hinged around (5). Within the
  Individual module the mutual pivotal motion of
  the flaps is limited, so that the flaps together
  always form a continuous surface.
  Due to their weight the flaps are In tight contact
  with the seabed, even If it is rugged- Crossing
  trawlboards therefore always pass over the cover
  without hooking the edge of (3).

4- Axle of several module lenghts

5- Axle of one module length.

6: Holes for neutralization of pressure differences.

7: Ship's anchor.

Source:    0.  Fjord   Lar-

sen,   (Director  Seditech,

Esbjerg,  Denmark)    1978:

personal  communication.

                   GROUND ROPE

                   HEADLINE WITH FLOATS
Source:   Carstens, 1977,  p.7.
                      FIGURE  3,   OTTER TRAWL

results indicated that the impact force from otter trawls of
various sizes and shapes was insufficient to cause significant
damage to the large diameter concrete-coated pipe used in the
experiments.  Damage is illustrated in Figure 4.  Impact tests
also showed no noticeable pipeline damage resulting from trawl
boards weighing less than 1000 kilograms (2205 pounds).  Pullover
force results indicated a net lateral movement of the pipeline
of less than 1.5 meters  (4.92 feet) after multiple crossings  (5)
with trawl gear.  However, pullover forces were significantly
higher in cases where the pipeline was trenched than when lying
on the ocean floor.  From these studies, Shell concluded that
concrete coating large diameter pipelines would provide more
than adequate protection from trawl door impacts  (Shell Expro,

     However, VHL test results did indicate that one type of bot-
tom trawling equipment—the beam trawl—severely damaged the
pipeline's concrete coating on practically every impact.  This
relatively new type of gear, used by Dutch fishermen, is designed
for flatfish bottom fishing and is significantly heavier than
otter trawl gear.  Figure 5 illustrates this type of gear.  VHL
suggests that design changes in the beam trawl may alleviate the
problem (Carstens, 1977).

Corrosion and Other Structural Problems^

     Corrosion is one of the major causes of leaks, particularly
in older pipelines.  Of the 91 recorded incidents of Gulf of
Mexico pipeline leaks from 1976-1978  (USGS, 1978), 50 were attri-
buted to corrosion.  Corrosion prevention is generally addressed
during the pipeline design process.  The outside of the steel
pipeline used offshore is first covered with a protective coat-
ing made of compounds such as asphalt, plastic or coal tar.
Glass fiber may be used to reinforce this corrosion prevention
coating.  The pipe is then coated with reinforced concrete which
is used to weight the pipeline and which offers additional exter-
nal mechanical protection to the corrosion wrap and the pipe.
In addition, chemical inhibitors may be injected into the sys-
tem, if the composition of the products being moved through the
pipe necessitates its use (for example, if the stream contains
hydrogen sulfide or carbon dioxide plus water.  )
 On the other hand, small diameter pipe  (as may be used in gath-
 ering lines), may not be as resistant to damage and may require
 additional protection beyond concrete coating.  (A.D. Pinson  [BP
 Trading Limited, London, England] 1979: personal  ccmmunication.)

 George Hughes,  (Exxon Pipeline Company, Houston, Texas) 1978:
 personal communication.


            Source:  Shell Expro,  1977,  p.35.

                           TOWING  DIRECTION
                CHAIN GROUNOROPE
                                                    6RI01 E
                    TRAWL SHOE
                    WEIGHT  430 kg
                     SIDE VIEW
Source:  Carstens,  1977,  p.3.
                     FIGURE 5,  BEAM  TRAWL GEAR,

     The potential for problems arising as a result of the use
of pipe having manufacturing imperfections is minimal due to rig-
id design standards for liquid petroleum and gas pipeline systems
set by the American Society of Mechanical Engineers and guide-
lines set by the American Petroleum Institute (API).   (For com-
plete specifications, see ANSI Publications B31.4 - 1974 Liquid
Petroleum Transportation Piping Systems, ANSI B31.8 - 1975
Gas Transmission and Distribution Piping Systems and API RP 1111
Recommended Practice for Design, Construction, Operation and
Maintenance of Offshore Hydrocarbon Pipelines - March, 1976.)

Geological Hazards

     Pipelines may also be damaged by unfavorable geological
conditions along an offshore pipeline route.  Adverse geological
conditions may result in exposure of previously buried pipeline,
possible pipeline bending, and under sufficient stress,  pipeline
breakage.  Numerous types of geological hazards are found off-
shore which may be grouped into two major hazard categories -
sediment instability and seismic activity.  Unstable sediments
offer poor foundation support for pipelines and may lose their
structural strength when shocked by an earthquake or intense
wave activity.  This loss of sediment strength may allow the
pipeline to settle into the sediments, placing bending stress on
the pipeline.  Sediments scouring away from beneath offshore
pipelines or eroding at landfall sites also cause additional
stress on spanned or exposed lengths of pipe.  Seismic activity
may cause violent sediment displacement and can trigger large
scale sediment mass movements which may cause spanning or break-
age of a pipeline.  While a pipeline may be structurally de-
signed to withstand these geologic hazards to some extent, where
possible these problem areas are avoided.  When industry surveys
each potential pipeline route, special emphasis is placed on the
geologic nature of the area considered.  This information is
then utilized to choose a route which is the most safe and sta-
ble from a geologic viewpoint.

Preventing Failures—The Planning Issues

     Of the potential causes of pipeline failure considered—an-
chor dragging, bottom fishing equipment, corrosion and geologic
conditions—the following conclusions may be drawn regarding how
each may be addressed during the process of choosing a pipeline

     The problem of anchors hooking on pipelines may be partial-
ly solved by pipeline burial.  However, this method is only ef-
fective for protecting against small ships' anchors and in areas
where the pipeline is buried and remains buried at a sufficient
depth.   (Generally, burial greater than three meters  [9.8 feet]
would be sufficient to protect against small anchors.)  Burial
will not protect pipelines from the anchors of large vessels


 (such as tankers and pipelaying barges) which can penetrate up
to 17 meters  (55.8 feet)  into  the ocean bottom.  Therefore, in
planning a pipeline route,  shipping corridors and other areas
where heavy vessels may drop anchor should be avoided where pos-

     Based on recent studies,  the potential for damage to pipe-
lines from bottom fishing gear is very small and may need to be
considered in pipeline route planning  (when considering pipeline
failure prevention) only  in areas where heavy beam trawls are

     The potential for pipeline failures due to corrosion and/or
structural imperfections  is generally minimized in the design
process in which pipeline specifications, coating and cathodic
protection methods are chosen  to accommodate those conditions
under which the pipeline  will  operate.

     Geologic hazards are the  major cause of pipeline failure
which can be addressed directly through the pipeline route selec-
tion process.  Therefore, these hazards, their potential effects
on a pipeline, and where  they  are the most likely to be encount-
ered in offshore and coastal areas are discussed in greater de-
tail in the Section 3—"Assessing the Environmental Problems."

     Environmental disturbances along a pipeline route are
caused by three separate phases of pipeline installation—laying
the pipeline on the bottom, and if the pipeline is to be buried,
digging the trench and burying the pipeline.  Each phase of in-
stallation can be accomplished by various methods, depending on
where the pipeline is being installed  (offshore or nearshore/
landfall) and the bottom conditions encountered.  The type and
extent of damage to the environment will also vary with the
method utilized and the type of environment disturbed.

Offshore Installation Methods

     Pipelaying;  Offshore pipelines are generally constructed
of lengths of steel pipe which are coated with compounds for cor-
rosion protection, and where necessary, concrete to provide suf-
ficient weight to prevent flotation.  Precoated pipe sections
are welded together and the welds covered by mastic on a pipeline
laybarge prior to lowering the pipeline to the seafloor.  Two
laybarge types currently used in the North Sea are shown in Fig-
ures 6 and 7.

     As the pipeline is lowered to the seafloor, two bending
stresses are exerted—one as the pipe leaves the laybarge (over-
bend) the other near the ocean floor  (sagbend).  To prevent over-
stressing, horizontal tension is applied to the pipeline and the


Photograph Courtesy of Brownaker Offshore A/S, 1978.

Photograph Courtesy of British Petroleum,  1978.
                    FIGURE 7,   SIDE RAMP  PIPELINE  BARGE,

pipeline is supported by a ramp  ("the stinger") as it leaves the
laybarge.  Figure 8 illustrates this laybarge method of pipelay-
Source:  after Allen et al.,  1976, p.64.
     Offshore pipelines may also be laid using the reel barge
technique.  Pipe joints are welded, covered with protective coat-
ing, and inspected at a shore base.  Pipe is wound onto a large
reel on a pipelaying barge.  The barge then moves to the pipelay-
ing site where the pipe is unreeled, straightened and lowered to
the ocean bottom.  While this method allows the quick installa-
tion of given lengths of pipe because onboard welding, inspect-
ing and coating operations are minimal, its use is currently
limited to pipelines without concrete coatings and which have
diameters of 16 inches or less.
 Pipeline Industry Advisory Task Force, 1979
personal communi-

     Pipeline Trenching;  If the pipeline is to be lowered into
the seafloor, a trench must be dug.  Three types of trenching
machines are currently available:  machines with rotating cutter-
heads which cut through the sediments; "jet sleds" which use
high pressure water jets to "blast away" sediments; and plow
type machines which push sediment aside as they are pulled across
the bottom.  The first two machines are lowered down and placed
over the pipeline, which, after sediment removal, settles into
the newly dug trench.  In the case of plowed trenches, the pipe-
line is welded and coated onshore, the trench dug, and the pipe-
line towed to the site and placed in the trench.  Suspended sedi-
ments from the first two trenching machines are sucked up into
attached pipes and discharged above and to the sides of the
trench; plow spoils remain on either side of the trench.

     The rate at which a trench can be dug varies with the
trenching machine used and the sediment types encountered.  Cut-
terhead trenchers can dig a trench up to 2.5 meters (8.2 feetf)
deep.  Reported trenching rates vary from 90-230 meters/hour
(296-755 feet) in sand to 130-500 meters/hour (427-1640 feet) in
clay (Norwegian Petroleum Directorate, 1978b).

     Along the Forties Field pipeline, jet sled rates averaged
approximately 1 kilometer/day  (0.62 miles) in clay materials.
While only one pass was necessary to dig the trench to the de-
sired depth of 1.8 meters  (6 feet) in clay, areas with sand and
silt sediments sometimes required two passes of the jet sled.
Rates in sand and silt averaged 3 kilometers/day  (1.86 miles)
with a peak rate of 5 kilometers/day  (3.1 miles)  (Walker, 1976).

     Because the plow technique is relatively new, its overall
capacity is not yet known.  However, one plow employed in the
North Sea dug a 1.1 meter  (3.6 feet) deep, 2.2 kilometer  (1.37
miles)  long trench through hard clay in 30 minutes (Underwater
Plow Prepares Trench for Statfjord Loading Pipeline, 1977).
Figure 9 illustrates these three trenching machines—a cutter-
head type, a jet sled, and a plow.

     The efficiency of any of these trenching machines and the
width of the trench dug is based on the characteristics of the
sediment being trenched and water depth.  Trenches through clay
sediments are generally narrow with vertical walls, while trench-
ing through sandy sediments results in wide shallow trenches.
In very muddy sediments, trenching may not be required as the
pipeline may settle into the sediments under its own weight
(Carstens, 1977).

     Pipeline burial;   Once pipelines have been laid, natural
processes of current and wave action are generally relied upon
to refill trenches.  However, in some cases, for example, the
North Sea Ekofisk to Emden, Germany gasline, artificial burial


                         POWER- PACKS
         -m _ ^. V -
       :CUHER  SUf.llON -'."^'•i-A-:
  Y  AIR
                                                 PULLING CABLE
                  / X  /  /
Source:   Carstens, T.,  1977, p.  4.

Source:  Brown, R.J., 1978, p. 69.
             FIGURE 9,  (CONTINUED)

has been required.  Crushed stone will be used in this case to
cover exposed pipeline lengths (NERBC, 1979).

     Evaluating the Usefulness of Trenching Offshore;  Trench-
ing and burial were originally prescribed for offshore pipe-
lines, based on onshore and nearshore pipeline experiences,
where burial provided the benefits of increased safety and sta-
bility.  For example, in the North Sea, all but one of the ma-
jor pipelines have been or are being trenched and buried.  How-
ever, extensive problems were experienced in attempting to bury
the Ekofisk to Emden pipeline, where numerous passes were often
required to dig the trench (averaging 3.2 passes to reach the
desired depth) and where subsequent inspection revealed that in
many places natural backfilling had not occurred.  Based on
these and other problems experienced in attempting to bury North
Sea pipelines, Shell Expro, as part of its comprehensive study
on the FLAGS gasline, initiated studies to test the validity of
the assumption that trenching would provide added safety and
stability to deep water offshore pipelines.  The following are
the major conclusions from that study  (NERBC, 1979) :

     •   bottom currents are insufficient in deep water
         areas to provide sediment transport and result-
         ing natural burial;

     •   trenches cut in the soft sediments which charac-
         terize deep water areas tend to have a wide pro-
         file rather than a narrow, well-defined profile;

     •   current technology in concrete coating and steel
         reinforcing is such that a trawl door will cause
         no more than a scratch  (16 millimeters  [0.6 inches]
         deep) on the pipeline coating and damage to the
         pipe will not occur;

     •   trawl doors sliding into a shallow or wide pro-
         file trench have more chance of being damaged
         than if the pipe had been laid directly on the
         sea bottom; and

     •   burial will not protect a pipeline from drag-
         ging rig or tanker anchors.

     Shell Expro concluded:  "Trenching in deepwater is not
necessary for stability; it provides no additional mechanical
protection, and furthermore, it caused an increase in the  risk
of damage to fishing gear."   (Shell Expro, 1977. p.i.)  Based
on their results, Shell Expro applied  to the United Kingdom (UK)
Department of Energy for approval of the FLAGS gasline, trench-
ing only where additional stability was needed,  such as near-
shore areas subject to strong bottom currents and  storm-induced
wave effects.  Approval was granted for the pipeline  (which was


 completed in June, 1978) with trenching required only in these
 unstable nearshore areas.

      Not all North Sea operators agree with the conclusions
 drawn from these experiments.  BP, for example, contends that
 pipelines which are trenched, but not buried, are marginally
 better from a risk viewpoint than those which are lying direct-
 ly on the ocean bottom.

      A final observation regarding offshore trenching is that
 the repeated passes by trenching machines required in many types
 of offshore sediments to dig trenches of sufficient depth, can
 cause physical damage to the concrete coating on the pipeline.
 This loss of coating may occur as the sled is raised or lowered
 over the pipeline or as a result of the high pressure water jets
 which may loosen already cracked concrete (Broussard et al.,
 1978) .

 Nearshore/Landfall Installation Methods

      Pipelines laid in nearshore waters and at the landfall site
 are always required to be buried.  As the water depths become
 too shallow for use of offshore equipment, modified techniques
 are used.

      Pull Technique;  This technique  (also known as the "push"
 or "push/pull" technique) requires a fairly firm shoreline,
 such as a sand or gravel beach, in which a small canal four to
 six feet deep and eight to ten feet wide is dredged.  Sheetpile
 retaining walls are often used to maintain the canal during
 construction.  Sections of pipe are welded onboard a laybarge
 which moves as close to the landfall site as possible.  Using
 onshore winches, the pipe is pulled into the canal and onto
 land.  The canal is then backfilled.  A right-of-way as large
 as 150 feet (Conner et al., 1976) to 250 feet (U.S. Coast Guard
 [USCG], 1976)  may be required.  This method was utilized suc-
 cessfully at the landfall for the 36" gasline from the Brent to
 St. Fergus, Scotland, and for the 48" lines coming ashore across
 a barrier beach from the Louisiana offshore port (LOOP) deep-
 water project.  Figure 10 illustrates this installation method.

      Flotation Technique;  The flotation technique is used at
 soft or unstable landfalls, such as marshes .^ Because this type
 of terrain cannot support the weight of pipe  and onshore lay-
 *H.D. Pinson,  (BP Trading Limited, London, England) 1979:  per-
  sonal communication.

**A 40 foot section of 36-inch uncoated pipe weighs approximate-
  ly 8,000 pounds; when coated with three to four inches of con-
  crete, a section may weigh up to 34,000 pounds.


Photograph Courtesy of British Petroleum, 1978.
                FIGURE  10,   "PULL"  TECHNIQUE  OF  PIPELAYING

ing equipment, a canal is dug so that conventional shallow water
pipelaying equipment may be used.  Canals which may be 40 to 50
feet wide and six to eight feet deep are dug inland from the
shoreline by barge-mounted dredges.  An additional trench for
the pipeline may be dug on the canal bottom.  Offshore flatbot-
tom barges can then move into the canal, laying the pipeline us-
ing the "stovepipe" or reel barge technique.  This method may
require a right-of-way from 300 feet  (Conner et al., 1976) to
450 feet  (USCG, 1976) wide.

Environmental Disturbances from Pipeline Installation

      There are four types of pipeline installation-related en-
vironmental disturbances which may occur along and adjacent to a
pipeline route.  These disturbances are:  loss of organisms; in-
creased turbidity; habitat alterations; and physical and chemi-
cal changes.

      Where pipelines are untrenched, as may occur in deep off-
shore waters, impacts will generally be minimal.  Small numbers
of organisms directly beneath the pipeline will be lost and
slight increases in turbidity may be experienced as the pipeline
touches bottom.  No changes in circulation patterns and the
overlying water's chemical composition would be expected from
unburied pipe.  In addition, unburied pipelines, like other off-
shore structures, may offer new habitat to colonizing species
attracted to this new "artificial reef."

      If trenching and burial occur, either offshore or in the
shoreline/landfall area, more extensive effects may be expected.
Trenching will displace those organisms living on the bottom and
in the sediments and will introduce suspended materials into the
water column as a result of jetting or dredging the trench or
canal.  For example, a short-term but tenfold increase in turbi-
dity was predicted as a result of trenching the LOOP project
pipelines    (USCG, 1976).  In some cases, this "mixing" may have
positive effects by creating a new temporary feeding ground for
water column and suspended benthic fauna.   If resuspended sedi-
ments are contaminated with toxic chemicals or bacteria, the
chemical composition of the water column immediately above the
pipeline may be temporarily affected.  Resettlement of sediments
may alter habitat characteristics and lead to changes in local
species composition at and near the pipeline.  Incomplete refil-
ling of offshore pipeline trenches may cause depressions in the
seafloor, possibly altering bottom circulation patterns.  Incom-
plete restoration of' landfall sites may result in "weak links"
(areas of low resistance to physical stress) along a shoreline
*H.E. DeGreenia,  (Tennessee Gas Pipeline, Houston, Texas) 1979:
personal communication.

which may  be  destroyed during  storms,  or may change hydrologic
patterns in a wetland.

The Extent of Environmental Disturbances

      Although it is possible  that  pipeline installation,  and in
particular, trenching, will cause some environmental damage,
there are  other offshore activities which may produce  comparable
disturbances.  For example, comparisons are possible between  the
amount  of  bottom sediment disturbed by pipelining and  other non-
oil and gas-related offshore activities.  These activities in-
clude offshore bottom fishing  using otter trawls, surf clamming
with hydraulic dredges or sea  scallop  harvesting, and  offshore
dredge  spoil  disposal.  Table  1  illustrates estimated  amounts
of sediment disturbed by these activities compared with projec-
ted amounts of sediment disturbed by  pipelaying activity.
                              OFFSHORE ACTIVITIES
                                    Equivalent miles of pipeline'
             Amount of Sediment   Lease sale
             Disturbed (millions  42 EIS for     FLAGS report
Activity      of cu yd/year)      Georges Bank   Narrow      Wide
Surf clamming
Sea scallops
Otter board trawling

 Calculations are based on  100 boats working 100 days per year.
 See Appendix I for additional assumptions and calculations.

DShanks, 1978, p.5.
Source:  NERBC,  1978

The final columns in Table 1, miles of pipeline, are based on
three different trench profiles: Georges Bank Lease Sale 42, En-
vironmental Impact Statement  (EIS) which estimated 8,000 cubic
yards (cu yd) of sediments disturbed per mile of pipeline;  and
two trench profiles diagrammed in the FLAGS report (p.21).  A
trench dug in clay with vertical walls was estimated to disturb
16,262 cu yd of sediment per mile of pipeline dug.  A shallow,
wide trench produced in sand was estimated to disturb 42,504 cu
yd of sediment per mile of pipeline.   (See Appendix A for calcu-
lations.)  These three trenches were chosen to represent a vari-
ety of sediment conditions and thus a variety of trench profiles
which might be encountered in laying an offshore pipeline.

     Even when considering the widest trench profile in which
the largest estimated quantities of sediment are disturbed, an-
nual disturbances by other offshore activities, such as dredging
and bottom fishing, are equivalent to 4,000 to 11,000 miles of
pipeline trenching.  By comparison, there are approximately
2,000 miles of oil and gas pipelines in the Barataria Bay region
of the Gulf of Mexico and approximately 1,750 miles of offshore
pipelines in the entire North Sea offshore development area.

Environmental Disturbances—The Planning Issues

     Of the various phases of pipeline installation, offshore
trenching, and landfall trenching and burial operations are
likely to cause the greatest amount of environmental disturb-
ance.  But when compared with other types of offshore bottom-
disturbing activities, the relative quantities of sediment dis-
turbed by trenching are significantly less.  In addition, the
surface area disturbed by trenching would be small and would
affect only a narrow corridor through a number of habitats.  In
comparison, fishing activities disturb large portions of speci-
fic areas  (fishing grounds).  While pipeline laying is a one-
time event, fishing in certain areas is a reoccurring one.  In
addition to man's activities, natural phenomena such as storm
and tidal action will also suspend and rework bottom sediments.
It appears, therefore, when considered quantitatively, that only
small-scale localized environmental alterations will occur as a
result of pipelaying activities.

     Therefore, the major conclusion regarding installation-re-
lated disturbances is that it is the character of the environ-
mental system disturbed  (rather than the degree of disturbance)
that will determine the impact.  For example, a pipeline laid
through a small or unique habitat will cause a significantly
greater impact than one passing through a large, environmentally
homogeneous  bottom area.

     These sensitive environmental areas can be identified and,
where possible, should be avoided during the pipeline route
selection process.  Therefore, further discussion will focus on


the types of systems which may be the most severely impacted by
pipeline installation-related disturbances, and where these sys-
tems are likely to be encountered offshore and at the shoreline

                           SECTION 3

     To minimize environmental damage from offshore pipelines,
the safest and most stable route from the production area to the
shore must be located.  To do this, it is first necessary to as-
sess each potential route, identifying those features which are
most likely to have an impact on or be impacted by the pipeline's
installation.  As concluded in the previous section, two major
factors should be considered in this assessment:

     •   the geological characteristics of the route.  Sedi-
         ment conditions and the seismic nature of the area
         will affect the stability of the pipeline, which
         will, in turn, determine its susceptibility to
         structural damage and possible leakage or failure;

     •   the characteristics of the ecosystems along the
         route.  Each system's sensitivity to various envi-
         ronmental disturbances will determine the extent of
         impact resulting from pipeline installation.

     This chapter will consider these factors, highlighting why
each is important and indicating where each is most likely to be
encountered along a pipeline route.


     The geologic nature of the OCS and coastal zone has a defi-
nite influence on the routing of pipelines in these offshore
areas.  The presence of thick layers of sediments, a high degree
of sediment variability and the constant modification of sedi-
ments by wave and current activity could result in sediment in-
stability that would be hazardous to pipeline installations.  The
major forms of sediment instability include:  variable sediment
conditions   (changes in the physical and engineering properties
of sediments), liquefaction  (a type of bearing strength loss),
pipeline flotation in fluid sediments, sediment scour, sand waves,
and shoreline erosion.

     The seismic characteristics of these regions may also influ-
ence pipeline routing.  The presence of active faults in an OCS


region would present several potential hazards to pipeline con-
struction and operation including:  fault movement, tectonic de-
formation; ground motion (shaking); earthquake-induced sediment
failures; and sediment mass movements.

Sediment Conditions

     The Problems;  The capability of the ocean floor to support
an offshore pipeline depends, in part, on the characteristics of
the sediments found along a proposed route.  Sediment strength
varies from extremely weak  (e.g., sediments made up of poorly
consolidated silts) to very strong in areas where dense sands
are present.

     Fine.- poorly consolidated silts (grain size 0.0625-0.004
millimeters), clays (less than 0.004 millimeters) and muds (mix-
tures of silt and clay) will generally provide poor structural
support.  These sediments are often deposited in a loose, "honey-
comb-like" framework,  which retains large quantities of water.
With slow settling and compaction, the pressure of the trapped
pore water increases,  resulting in an overall decrease in the
sediment strength.  Pore pressure may also be very high where
the deposition of fine sediments is rapid.  In either case, lit-
tle force is required to cause sediment failure  (a breakdown in
the sediment's structure and the resulting loss of strength)
(Blatt et al., 1972).

     Generally, as cohesion between sediment particles increas-
es, sediment strength and bearing capacity also increase.  In-
creased cohesion results when the clay content of fine sediments
is high.  Attractions between individual clay grains  (cohesive
forces) cause the sediments to "stick together."  Highly com-
pacted clays with numerous grain-to-grain contacts have in-
creased numbers of cohesive bonds, and greater sediment strength
(Wilun and Starzewski, 1972).  Compact, cohesive clays often have
good structure-bearing capacity because of this increased

     Dense, fine-to-medium sands should provide excellent sup-
port for structures placed on them.  Although slightly weaker,
sands interlayered with stiff, compact clays should also be ca-
pable of supporting a pipeline.

     Areas most likely to be affected;  Fine-grained, cohesion-
less sediments which have very low bearing strength may pose
problems in pipeline siting.  Areas where these sediment types
are most likely to be found include:

     •   lagoons, estuaries, wetlands and deltas.  Deltas
         are particularly hazardous because, in addition
         to unfavorable sediment type, deposition is rapid,
         forming a loose, very unstable sediment framework; and


     •    quiet,  deep sections of the continental  shelf
          and slope.

     In  addition,  where poorly consolidated  clays and  patches
of lagoonal  muds underlie surficial sands, the weight  of  a pipe-
line could cause the underlying fine sediments to compact or
fail, resulting  in local seafloor settling and subsequent pipe-
line damage  (Bureau of Land Management  [BLM], 1976).


     The Problems:  Liquefaction occurs when a sediment's grain-
to-grain structure is broken down, causing it to  more  closely
resemble a liquid  than a solid.  Sediment strength is  reduced
when "liquefied,"  and the capability of foundation sediments to
support  a pipeline is lessened.

     Rapid deposition of coarse silts and fine sands results in
the formation of a loosely packed, unstable  structure  in  which
the pore water bears a large amount of weight normally supported
by sediment  grains.  A wave or seismically induced shock  can
break down this  structure causing the pore water  to support al-
most all of  the  sediment grains; the sediment, in effect, be-
comes a  liquid with little or no strength.

     Areas most  likely to be affected;  Table 2 shows  the esti-
mated susceptibility to liquefaction of sedimentary deposits as-
sociated with the  continental shelf and coastal zone.  Generally,
locations with large quantities of recently  deposited  cohesion-
less sediments are most affected.

                 Susceptibility of Saturated, Cohesionless Sediments to Lique-
                 faction (by Age of Deposit)
Type of deposit
High wave
Low wave
Uncompacted fill
Compacted fill
<500 yr.
Very high
Very high
(500-10,000 yrs.)
(10,000-3 mil-
lion yrs.)
Very low
(Greater than
3 million yrs.)
Very low
Very low
Very low
Very low
Very low
Very low
    Source:  after Youd and Perkins,  1978. p.441.

Pipeline Flotation

     The Problems;  Fine sediments  (especially silts, muds and
clays) slowly backfilling a trench can mix with water to form a
dense, heavy fluid with little or no strength.  A pipeline hav-
ing a specific gravity lower than this fluid would float to the
sediment/water interface (mud line).  The backfill of the trench
may also be converted to a liquid state by liquefaction.  If
liquefaction occurs directly below the pipeline and the pipeline
has a higher specific gravity than the resulting fluid, the
pipeline will sink further into the liquefied sediments.

     Areas most likely to be affected:  Fine-grained sediments
are most likely to form a fluid trench backfill.  Areas where
these sediments types are likely to be found include:

     •   lagoons, estuaries, wetlands and deltas; and

     •   quiet, deep sections of the continental shelf
         and slope.

     Those areas that are susceptible to liquefaction may also
be subject to floating pipelines  (see Table 2).

Sediment Scour

     The Problems;  The removal of  sediments from around a bur-
ied pipeline by scour would expose  the line to stresses from
wave and current activity which could cause pipeline damage.
Where large quantities of sediments are removed from beneath the
pipeline, spans  (suspended lengths  of pipe) may result.  A
spanned pipeline would be subject to additional stresses from
sagging and from the flow of water  around the line.  With suf-
ficient current velocity, the pipeline may begin to vibrate,
resulting in damage to the pipeline or its concrete coating.
Pipeline vibration failures have occurred in Cook Inlet, Alaska,
in areas where pipelines are not buried and are exposed to high
velocity tidal currents  (Ralston and Herbich, 1968).  Pipeline
vibrations may have also been the cause of a line losing its
concrete coating and floating to the surface at Yell Sound in
the North Sea area  (Guerry, 1976).

     Water flowing over the seafloor exerts a force on the indi-
vidual sediment grains which tends  to cause movement.  The cur-
rent velocity necessary to initiate sediment movement is called
the threshold velocity and is primarily dependent on the grain
size of the sediments.  Fine-to-medium sand  (0.1-0.5 millime-
ters) generally requires a current  velocity on the  order of 15
to 50 centimeters  (0.5 to 1.5 feet) per second.  Coarser sands
 (0.5-2.0 millimeters) begin movement at current velocities of
20 to 100 centimeters  (0.6 to 3.3  feet) per second  while very


coarse sands and gravel require velocities in excess of 100 cen-
timeters  (3.3 feet) per second.

     Although fine grained sediments might be expected to have
lower threshold velocities than coarser sediments, experiments
have shown that as grain size decreases below 0.18 millimeters
(fine sand) threshold velocities begin to increase for some mix-
tures of  sediments.  Well-compacted, fine sediments produce a
smooth ocean bed, which reduces friction and increases cohesive
forces, which may, in turn, cause these increased threshold ve-
locities  (Inman, 1963).  Fine-grained clays  (0.001-0.002 milli-
meters) can have threshold velocities as high as 500 centimeters
(16.4 feet) per second  (as much as required for some sizes of
gravel).  Soft, loosely structured muds have lower threshold
velocities resulting from low cohesion, poor compaction and high
water content.  Figure 11 illustrates the range of threshold ve-
locities  for different sediment sizes.

     Areas most likely to be affected;  Shallow approaches to
the nearshore and shallow sections of the continental shelf
where wave and tidal current activity are high are most likely
to be subject to scour.  Tidal currents on Georges Bank in the
North Atlantic OCS may approach velocities of 90 to 200 centi-
meters (3 to 7 feet) per second—enough to move most sizes of
sand (BLM, 1977).  Shallow water storm waves may also produce
significant bottom velocities.  A storm wave 23 feet high in 30
feet of water could produce a bottom velocity of approximately
425 centimeters (14 feet) per second under the wave crest (BLM,

Sand Waves

     The  Problems;  There are two basic concerns associated with
the presence of sand waves:  the size of the features may pre-
sent a physical obstruction to pipeline construction activity;
and sand wave movement may uncover buried pipelines or subject
the pipeline to spanning.

     Sand waves (also called sand or tidal ridges), which cover
large sections of the North and mid-Atlantic OCS, average 7 ki-
lometers  (4 miles) in length and range as high as 30 meters  (98
ft.) in height.  Slopes of 17 degrees have been measured in pla-
ces on Georges Bank  (Offshore Navigation, Inc., 1976).

     Sand waves can be highly mobile features.  Their direction
of net migration appears to be associated with the direction of
ocean wave approach.  For example, on Georges Bank, ocean waves
approaching primarily from an easterly direction caused a gener-
al westward migration of approximately 300 meters (975 feet)
over a 25 to 28 year period  (BLM, 1977).  Various researchers
have reported yearly movements of 69 meters  (225 feet) off Vir-



                                                              100 g
      . Unconsolidated clay and silt

        CM  "3- (OOO^
        00 00°
        op poo
        o  6 do

•tf CO 00"-
o oo
O OO--
o oop
^ coood
                     Grain size, in millimeters
p ooo o  p opo
6 006 o  6 ooo
•q- cocoo o  o ooo
    •- CM  
ginia with single storms causing movements of as much as 82 me-
ters  (250 feet)  (BLM, 1976).

     There are differing opinions on the effects of sediment
movement  (scour  and sand waves) on offshore structures.  It has
been suggested that the thick accumulation of sand around the
legs of the Texas Towers  (part of an offshore early warning ra-
dar system) on Georges Bank sufficiently weakened these struc-
tures to cause their abandonment and eventual removal  (Emery
and Uchupi, 1972) .  Other sources indicate that the Texas Towers
were removed only because they were obsolete and that proper
engineering and  maintenance can ensure the safe operation of
structures in areas of sand movement.*

     Areas most  likely to be affected;  Sand waves are generally
found in shallow areas of the continental shelf (less than 60
meters - approximately 200 feet deep) which are subject to swift
tidal currents and intense ocean wave activity.  While sand
waves found in deeper regions of the shelf are probably relict
features and nonmobile, some sand waves have been discovered
near the head of Wilmington Canyon on the mid-Atlantic OCS in 70
to 100 meters  (230 to 330 feet) of water that appear to respond
to storms and current flow in the canyon head (BLM, 1979).

Shoreline Erosion

     The Problems;  Shoreline erosion is a particular concern
when choosing a  landfall location for a pipeline.  To protect
the pipeline from exposure to the intense wave and current acti-
vity of the beach and nearshore, it is essential that the pipe-
line remain buried below the level of expected erosion.  Shore-
line erosion can be caused by one or more of the following fac-

     *   a reduction in longshore sediment supply.  Sedi-
         ments may be trapped by man-made obstructions
          (stabilized bluffs, jetties, groins, etc.) or
         natural obstructions  (tidal inlets, estuaries,
     •   storm wind and wave activity.  Permanent shore-
         line erosion appears to be associated with storms
         occurring every one and one-half years (Nordstrum
         et al., 1978);
     •   shoreline developments.  Modifying coastal areas
         through grading or drainage may cause disruptions
         and changes; and

     •   sea level rises.
 Pipeline Industry Advisory Task Force, 1979:  personal communi-


     Areas most likely to be affected;  Erosion is a major pro-
blem associated with most beaches and barrier beaches in the
United States; however, the following areas are generally most
susceptible to shoreline erosion:

     •   beaches and barrier beaches exposed directly to
         winds and ocean waves;

     •   beaches and barrier beaches downdrift from ob-
         structions to the natural longshore movement of
         sediments; and

     •   coastal cliffs or bluffs cut in unconsolidated

     Those coastal areas least susceptible to shoreline erosion

     •   protected bays and estuaries;

     •   rocky shorelines; and

     •   beaches not directly exposed to ocean waves.

Seismic Hazards

     The Problems;  Fault movement may be vertical, horizontal
or a combination of both.  Slight movement may place stresses on
a pipeline, but it has been estimated that a pipeline construc-
ted over a fault could withstand a vertical displacement of 15
to 25 feet before failing  (Arnold, 1967).

     The large scale horizontal or vertical movement of the
earth's crust is known as tectonic deformation.  During the 1964
Alaska earthquake, elevation changes averaged six feet over an
area of between 70,000 and 110,000 square miles of seafloor and
land in southern Alaska.  In some isolated areas vertical changes
amounted to nearly 50 feet (Nichols and Buchanan-Banks, 1974).

     The intensity of ground motion during an earthquake is de-
pendent on the composition and structure of the subsurface.
Thick, water-saturated sediments are subject to several times
more intensive motion than solid bedrock.  For example, ground
shaking measurements of San Francisco Bay muds are about ten
times greater than those for nearby bedrock  (Nichols and Buchan-
an-Banks, 1974).  Intense ground motion could damage a pipe-
line's coating or significantly weaken its structural integrity.
Ground motion can also induce sediment failures.  Liquefaction
of surface sediments can result in bearing capacity failures.
Where liquefaction occurs in subsurface sediments, stiff clays
on the surface can spread and move downslope.  These lateral
spreads can move as much as a mile  (usually tens of feet) on
slopes as low as one-half degree  (Hoose, 1978).  Subsurface

liquefaction  can  also  result  in  a  subsidence  of  surface  and sub-
surface  sediments.

     Where  sediments are  located on  sloping terrain and  sediment
failures occur  in surface or  subsurface  sediments, a mass move-
ment of  sediments downslope can  occur.   These large-scale move-
ments include slumping, landsliding,  debris flows and turbidity

     Slumping occurs principally in  areas where  there is signi-
ficant slope  and  thick, unconsolidated sediments (such as at the
edge of  the shelf)  and involves  a  simple downslope displacement
along a  plane of  failure  (a sediment  layer along which movement
occurs) with  no significant deformation  of the sediments' inter-
nal structure.  Sediment  slumps  observed by sub-bottom profiling
often resemble  down-dropped blocks or folds.   The failure planes
are also sometimes  visible on the  profiles and resemble  vertical
faults with offset  sediment layers on either  side.  There is a
potential for renewed  movement of  the slumped sediments  due to
their instability.

     Where  movement continues past the slumping  stage and the
sediment mass begins to move  along several failure planes, land-
sliding  is  the  result.  Compared to slumping,  there is increased
deformation of  the  internal sediment  structure during land-

     As water is  incorporated into a  landslide and the slide is
disturbed and remolded during movement,  motion begins to occur
along numerous  failure planes and  the slide begins to more
closely resemble  a  "liquid" flow.  The incorporation of water
into the sediment reduces its strength and the resuJ.ting mass is
very fluid.   When observed on land the downslope flow is called
a debris flow (e.g., mud  flows in  California).   Although subma-
rine debris flows have not been  observed directly, the water
available in  the  marine environment provides  one of the  condi-
tions necessary for the formation  of  submarine debris flows
(Hampton, 1972).

     Turbidity  currents are subaqueous suspensions of water and
sediments that  are  sufficiently  dense to flow downslope  under
the influence of  gravity.  It has  been suggested that large
turbidity currents  may be generated as a distinct phase  in the
downslope movement  of  submarine  debris flows  (Hampton, 1972).

     Areas  most likely to be  affected;   The coastal geologic
environments  most often affected by seismically-induced  ground
failures include  deltas,  wetlands  and lagoons.   Portions of
beach systems such  as  dunes,  or  the lee  side  of  sand spits may
also be susceptible when  saturated (Hoose, 1978).

     The slope of the terrain may also influence the type of
seismic hazard that may occur.  Steep terrain is subject to
slumps, landslides, debris flows, and turbidity currents.  Lat-
eral spreads and associated ground cracking and bearing strength
failures may occur on flat or gently sloping terrain (Hoose,
1978) .

     The edges of the continental shelf, the slope, and the
heads of submarine canyons are extremely susceptible to sediment
mass movements.  These areas contain large deposits of unstable,
unconsolidated sediments.  Slumping has been reported.in the vi-
cinity of Lydonia Canyon at the edge of the North Atlantic OCS
(Offshore Navigation, Inc., 1976) as well as along the mid-At-
lantic shelf edge (Bennet et al., 1978).  The existence of large,
destructive turbidity currents on the shelf slope has been sug-
gested.  It is believed that a large earthquake on the Grand
Banks in 1929 triggered a turbidity current that broke numerous
communication cables in the vicinity.  Velocities of this turbi-
dity current have been estimated to be at least 22.7 feet per
second (Emery et al., 1970).

     Mass movements are also known to occur closer to shore.  In
the Gulf of Mexico, a landslide of deltaic sediments overturned
one petroleum production platform and moved another three to
four feet (Glaeser and Smith, 1977) .  The failure of some pipe-
lines in the Gulf of Mexico has been attributed to slumping
movement of deltaic sediments (Demars et al., 1977).


     There are four major environmental disturbances caused by
offshore pipeline installation:  direct loss of bottom organisms
from construction activity; turbidity effects; habitat altera-
tions and alterations of physical and chemical characteristics
of the construction area.

Loss of Organisms

     The Problems;  Organism loss along the pipeline route can
be expected both where the pipeline is buried or unburied.
Where the pipeline is placed directly on the ocean bottom, only
those sessile and low mobility organisms on the sediment surface
directly beneath the pipeline will be lost.  Where the pipeline
is buried, both nonmobile organisms and those living in the sed-
iments will be removed.

     Because of the relatively small area disturbed by pipeline
installation, the number of organisms removed should not gener-
ally cause a large impact on the biological community.  There
are certain exceptions however,  such as the loss of organisms,
which are of special ecological or economic value.  Therefore,


during the route selection process, when considering the poten-
tial effects of organism loss along a prospective route, the
most important concern is the type of organisms present, in-
stead of the numbers or biomass of organisms lost.

     Areas most susceptible to damage:  Organism losses can re-
sult in ma]or impacts in a number of areas.  Although less ex-
tensive impacts can be expected in areas where offshore pipe-
lines are not buried, offshore areas with economic resources,
such as shellfish, lobsters or bottom fish  (e.g., flounder),
may be adversely impacted by pipeline installation.  In addition,
areas which contain small and/or unique habitats may be damaged
if a relatively large percentage of a given population is re-
moved.  "Live bottom'1 areas—offshore areas associated with rock
out-crops which have unusually high concentrations of inverte-
brates—and the "flower garden" coral reef areas off the Texas
coast, are examples of these unique habitat types.  Similarly,
damage to rare or endangered species or their habitats would
cause major impacts.

     Nearshore and at the landfall, where trenching is likely
and where more sensitive and vital habitats exist, the impacts
from organism loss may be more severe.  Impacts may be more ex-
tensive for a number of reasons.  First, these coastal systems
may be more fragile and, therefore, more susceptible to disrup-
tion and they may exhibit slower recovery rates.  In addition,
there is often a greater diversity of habitats in the coastal
zone than in offshore areas, making each individual habitat
smaller, and potentially more significant in coastal ecological

     Areas of particular concern when considering organism los-
ses along a pipeline route include:
     •   coral reefs—which are generally located in lati-
         tudes 28° north to 28° south, and in waters less
         than 120 feet deep, with temperatures greater than
         20° centigrade  (Stern and Stickle, 1978);
     •   wetlands (marshes)—particularly when the wetland
         is small and/or is one of few or the only marsh in
         the estuarine system.  The potential extent of marsh
         impacts is magnified because wetlands have slow re-
         covery rates  (up to 20 years may be required for
         complete restoration [Shanks, 1978]); and
     •   submerged grass beds—particularly in estuaries
         which have no shoreline marshes, because the grass
         beds then serve as primary nutrient sources and
         sediment stabilizing mechanisms (normally marsh
         functions)  for the estuaries.

     In addition, bottom areas used by fish for egglaying or
inhabited by bottom dwelling larvae or juvenile forms may be
adversely affected by bottom disturbances during those periods
when spawning or hatching has recently occurred.

Turbidity Effects

     The Problems:  Significant turbidity effects will occur
only when the pipeline is trenched.  When pipelines are unburied,
only very small localized elevations in turbidity will occur as
the pipeline touches the bottom (particularly when the pipe is
being laid in soft sediments).   Increased suspended sediments
from pipeline trenching may affect water column organisms and,
in very shallow water where light penetration is sufficient to
maintain them, bottom plants.   When sediments resettle, bottom
organisms may be smothered.  The extent of damage will vary de-
pending on the type of sediment disturbed (smaller sediment par-
ticles will remain suspended for longer periods of time), the
amounts of sediment suspended,  the flushing or mixing rate, and
the types of organisms present in the affected area.

     Water column organisms potentially affected by increased
turbidity include phytoplankton and zooplankton (microscopic
free-floating plants and animals)  and eggs, larvae and adult forms
of invertebrates and fish.

     There is currently some debate about the effects of in-
creased turbidity on phytoplankton photosynthetic rates.   While
laboratory studies have indicated a suppression in photosynthe-
sis with increasing turbidity (due to decreased light penetra-
tion) , field studies of dredging operations have generally shown
no long-term decrease in photosynthetic rates resulting from in-
creased turbidity levels.  Researchers have speculated that in-
terferences with photosynthesis resulting from increased suspen-
ded sediment concentrations and decreased light penetration, may
be offset by increased suspended nutrients which stimulate pho-
tosynthesis (Morton, 1977) .

     Possible effects on zooplankton vary according to species
sensitivity and suspended solids concentrations.  In laboratory
experiments, ingestion rates for two copepods  (microscopic crus-
taceans) were reduced by suspended solids concentrations of 50
milligrams per liter (mg/1)* (Stern and Stickle, 1978).  On the
 For comparison, average suspended solids concentrations in the
 Thames River, Connecticut estuary are as follows:  average
 river concentration: 5 mg/1; storm concentration: 10-20 mg/1;
 at dredge site  (while dredging with bucket dredge) : 200-400 mg/1
 (Bohlen F.,  1978: personal communication).  Louisiana coastal
 waters have natural suspended solids concentrations of 50-
 100 mg/1  (Degreenia,H.E.,1979: personal communication.)


 other hand, no obvious alterations in zooplankton species compo-
 sition or density were reported associated with increased turbi-
 dity due to dredging operations in Chesapeake Bay (Goodwyn,1970).
 It has been suggested that difficulties in sampling zooplankton
 may make accurate interpretation of field data difficult (Mor-
 ton, 1977).

     Eggs and larval forms of invertebrates and fish are pro-
bably the organisms most sensitive to increased turbidity levels.
It has been observed in laboratory experiments, however, that in
a well-mixed environment, concentrations of suspended fine
grained sediments up to 500 mg/1 did not affect hatching success
of four fish species—yellow perch, white perch, striped bass
and alewife.  Even though adult fish generally avoid areas of
high turbidity, in one dredging experiment done in Mobile Bay,
no damage to adult fish 25-50 yards from an active dredge was
observed.   (Stern and Stickle, 1978).

     Resettlement of suspended solids may affect those benthic
organisms which cannot move away from the area or which are in-
capable of reaching the surface after burial.  For example,
demersal  (bottom) fish eggs may be buried.  The symbiotic plant
life associated with coral reefs may also be smothered.  This is
a particular problem when the sediments are anaerobic, causing
suffocation  (Morton, 1977).  Most benthic organisms can, how-
ever, withstand high suspended solid concentrations for short
periods of time  (Saila et al., 1972).  Bivalves, for example,
generally exhibit no long-lasting effects from increased turbi-
dity.  While filtering rates decrease in turbid waters, when the
animals are placed in clearer water, original filtering levels
return  (Stern and Stickle, 1978).

     Areas most susceptible to damage;  While increased turbidi-
ty will result from pipeline trenching, effects will generally
be confined to a small area directly adjacent to the pipeline.
Based on dredging experiments, few long-term or severe impacts
are expected in most areas affected by high turbidities.  There
are, however, isolated situations and ecosystems which may be
severely affected by increased turbidity and which should be
considered during pipeline routing process.  These areas of par-
ticular concern include:
     •   coral reefs—which may be damaged by resettling
     •   areas with very slow circulation and/or flushing
         rates—where the sediments will not be quickly di-
         luted or removed (e.g., lagoons).  Impacts may be
         further magnified in these areas if bottom sedi-
         ments are made up of small grain size sediments
         which will remain suspended for longer periods of
         time; and


     •  spawning and nursery areas during season—eggs,
        larvae and juvenile forms are particularly sensi-
        tive to elevated suspended sediment levels.  During
        spawning season when large populations congregate
        in small areas, even adult fish become more vulner-
        able to any type of environmental disturbance.  Estu-
        aries are prime areas for spawning and are, therefore,
        areas of particular concern.

     In addition, pipeline-related turbidity increases may cause
adverse effects in areas with naturally clear waters which may
contain organisms less tolerant to turbidity increases than
those living in naturally turbid waters.

Habitat Alteration

     The Problems;  Habitat alterations may be associated with
both buried and unburied pipelines.  Unburied pipelines are ex-
pected to cause little long-term alteration, and may, in fact,
offer new habitat for colonizing species, similar to drilling
platforms and other submerged surfaces which act as "artificial
reefs."  In general, trenching for pipeline burial disturbs bot-
tom sediment structure which may alter the habitat characteris-
tics of the area trenched.

     In the marine environment, it appears that sediment struc-
ture and species composition and distribution are inter-related,
although direct relationships are not always clear.  Generally,
filterfeeding bottom organisms (e.g., bivalves) are found in
areas with sand and gravel bottoms, where strong currents keep
the small food particles  and organics in suspension.  Deposit
feeders (worms, etc.) are generally found in soft bottoms where
sediments are more easily foraged  (Morton, 1977).  If trenching
and resettlement results in temporary changes in sediment char-
acteristics of one of these habitats, short-term changes in spe-
cies composition may also occur.  For example, if the hard bot-
toms which generally characterize spawning grounds are changed
to soft bottoms during spawning season, spawning success may be
adversely affected.  In areas where extremely silty sediments
are resuspended, soft shifting bottoms may result.  Because this
bottom type does not offer sufficient strength to support most
types of bottom organism growth, the bottom is effectively
"sterilized" (LaRoe, 1977).

     At the landfall, pipeline installation may cause habitat
alteration, particularly in wetlands where the "spongy" sedi-
ments are compacted when dredged to form pipeline installation
canals.  Where the canal is not refilled, two new habitats re-
sult - the open water system in the canal itself and the com-
pacted sediment levees on either side.  Even where filling is
attempted, original sediment conditions may be impossible to du-
plicate (Conner, et al., 1976).


     Areas most susceptible to damage;  It is unlikely that sed-
iment disturbances sufficient to cause widespread habitat alter-
ation will result from most pipeline trenching operations in deep
water.  There are, however, certain areas which are particularly
vulnerable to alteration and which may sustain long-term damage
from changing habitat conditions.  These areas of particular
concern when considering potential pipeline routes include:

     •   wetlands—Habitat alteration is a frequent result
         of construction activity in wetlands.  Wetland
         sediment conditions are very difficult to restore
         to their original state after construction has
         occurred.  Frequently in place of original wetland
         sediment structure two new habitats are created -
         compacted sediment levees and open water canals;
     •   estuarine spawning areas—Particularly when the
         area is small or when it is the only area used
         by a particular species; and

     •   small or unique habitats.

Physical and Chemical Alterations

     The Problems;  There are three main concerns associated
with physical and chemical alterations to an area from pipeline
installation:  changing an area's physical structure; altering
circulation patterns; and changing chemical characteristics of
the water column.

     Changing the physical structure of an area is a particular
problem at the landfall site.  Altering dune structure by remo-
val and later reconstruction may lessen the dune's capacity to
protect upland areas behind it and may increase the rate of dune
erosion  (Rooney-Char and Ayres, 1978).  Likewise, pipelines
crossing barrier islands or beaches may affect their ability to
protect the areas landward.  In addition, the pipeline right-of-
way might present a  "weak link"  {area of low resistance to phys-
ical stress) which could be breached during a storm  (Rooney-Char
and Ayres, 1978).  Altering a wetland could change its hydrolo-
gical drainage patterns  (Longley, et al., 1978) and lessen its
filtering and buffering capacities.

     The potential for circulation changes from pipeline trench-
ing is greatest  in estuaries.  If the trench is not completely
refilled, a depression in the estuarine  floor may result, offer-
ing an easier avenue for salt water intrusion into the estuary.
Elevations in salinity further upstream  in the estuary may affect
spawning patterns and the distribution of estuarine organisms
 (LaRoe, 1977).

     The composition of sediments resuspended by pipeline  in-
stallation may affect the chemical constituents of the water


column.  Where sediments are severely contaminated with bacteria
and organic material, localized decreases in dissolved oxygen
levels may be expected (Morton, 1977).  Sediments with high or-
ganic and nutrient content  may also stimulate blue green algae
("nuisance") blooms  (Morton, 1977).  Whether or not toxic chem-
icals contained in sediments are released when resuspended is
currently a topic of controversy.  While some results seem to
indicate that toxic materials are released when contaminated
sediments are resuspended, other results contradict this conclu-
sion (see Stern and Stickle, 1978 and Grimwood, et al., 1978).

     Areas most susceptible to damage;  Areas of particular con-
cern when evaluating the potential for physical and chemical
alterations resulting from pipeline installation include:

     •   dunes, barrier beaches and barrier islands;

     •   wetlands; and

     •   areas having polluted bottom sediments.

                            SECTION 4


     There are a number of concerns to fishermen regarding poten-
tial interferences between fishing and offshore petroleum activi-
ty.  There are two particular issues related to pipelines:

     •   loss of fishing area along a pipeline route and its
         associated rights-of-way; and

     •   bottom obstructions which may cause fishing gear
         damage or loss.  These obstructions include:  the
         pipeline itself when laid directly on the ocean
         floor, whether exposed or covered with stone, con-
         crete or some other protective coating; buried
         pipelines which become re-exposed by waves or cur-
         rents; rocks, clay, etc. exposed during pipeline
         trenching; and the bottom debris present along the
         pipeline route.

     This chapter discusses those pipeline/fishing interferences,
highlighting experiences and experimental results obtained in
the North Sea petroleum development area.


     Loss of fishing area to production platforms and pipelines
is a concern to fishermen both in U.S. frontier areas, (particu-
larly the Georges Bank and mid-Atlantic areas which support large
fishing industries) and in the North Sea.  A University of Aber-
deen report, commissioned by the British Fishing Federation and
the Scottish Fishermen's Federation, entitled "A Physical and
Economic Evaluation of Loss of Access to Fishing Grounds Due to
Oil and Gas Installations in the North Sea" examines this fish-
ing access problem as it pertains to North Sea development areas
(Department of Political Economy, 1978).   (In addition to area
lost to pipelines and rights-of-way, other oil and gas related
installations, including rigs and platforms, subsea completions
and suspended wellheads  [wells which have been drilled and capped
pending further development] are also discussed in the report.)

     This report estimated the range of area lost to fishing
activity due to pipeline installations based on two sets of as-
sumptions.  First, two pipeline corridor widths were assumed as


"safety zones" i.e., areas avoided by bottom trawling activity:
100 meters  (328 feet) and 500 meters  (1,640 feet).  Secondly,
assumptions were made regarding the proportion of the total pipe-
line corridor actually removed from bottom fishing activity.  Two
values were chosen:  20% and 100%.  Thus, four scenarios were
generated, from least area removed  (20% of a 100 meter wide pipe-
line corridor) to most area removed (100% of a 500 meter wide

     Estimates ranged from 30.86 square miles to 771.8 square
miles lost in the middle and North Sea  (above 55°N latitude) to
fishing activity as a result of the existing pipeline network
(consisting of approximately 1,235 miles of pipeline) (Depart-
ment of Political Economy, 1978).  Southern North Sea (south of
55°N latitude) loss estimates ranged from 9 square miles to 226
square miles  (Department of Political Economy, 1978).*

     Fish catch losses due to loss of fishing area access were
then estimated.  Two methods of estimating losses were employed
and yielded a range of 66 tons to 1,786 tons of demersal (bottom)
fish lost in the North and middle North Sea for the year 1976
(Department of Political Economy, 1978).

     The authors acknowledged, however, that numerous problems
were associated with this type of analysis, particularly the
catch loss estimates (Dept. of Political Economy, 1978).  This
was due in large part to the fact that, by nature, the amount
and accuracy of fish catch data is limited, making it difficult
to draw conclusions based strictly on statistical analysis of
the information.  In addition, it was difficult to determine ap-
propriate statistical methods for estimating catch loss.

     Nevertheless, the study points out even if quantitative loss
estimates are disregarded, qualitative analysis would seem to in-
fer that pipeline installation may result in loss of access along
the route.  For example, although pipeline burial at sufficient
depths should eliminate the risks of trawling interference, past
experience has shown that pipelines can and have become re-
exposed.  Because of the potential for gear damage or loss and
associated loss of fishing time and revenue should trawl equip-
ment become hooked, it would be understandable if the fishermen
chose to avoid both unburied and buried pipeline routes, and
 Similar estimates are presented in Olsen's  (1977) paper in Vol-
 ume II of the New England Regional Commission Report, "Fishing
 and Petroleum Interactions on Georges Bank."  Two "safety zones"
 are assumed - 1,650 feet  (500 m) and 300 feet (91.44m).  Esti-
 mated area lost to fishing ranged from 73 to 364 acres per mile.
 Applying these "loss per mile" figures to the 1,235 mile North-
 ern North Sea pipeline network results in estimated losses of
 135.85 square miles to 691.6 square miles.


large areas surrounding them  (Dept. of Political Economy, 1978).
There is also the inference of  "better safe than sorry" in the
reported request of oil companies, asking fishermen to "give
pipelines a wide berth in their operations" (Dept. of Political
Economy, 1978).

     An additional concern is the placement of gathering lines
to connect petroleum platforms.  These pipelines often form tri-
angular patterns which may result in total loss of fishing access
inside the boundaries inscribed by the platforms and the connect-
ing pipelines (NERBC, 1979).

     Regarding loss of fishing access due to pipeline installa-
tion in the North Sea, the Aberdeen Study concludes:  "Regardless
of the evaluation of the overall results we have presented for
the North Sea, there is no doubt that some fishermen have suf-
fered losses.  It is not really the Scottish or British fishing
industry as a whole which is affected, but rather particular
fishermen and fishing fleets in geographic areas."  (Dept. of
Political Economy, 1978).

     Recently, one of the authors of the University of Aberdeen
study, offered these additional observations on the numerical
estimates of area lost.  Overall, the estimated physical area
lost to fishermen due to structures related to offshore oil and
gas activity  (including pipelines, platforms, exploratory rigs
and suspended wellheads) ranged from 190 to 830 square nautical
miles (253 to 1104 square miles) for the whole North Sea.  This
area amounted to between 0.3% and 1.2% of the total fishing area
available (MacKay, 1979).  Pipelines, which account for 17% of
the lower case and 77% of the upper case estimates, would thus
be "responsible" for area losses of between 0.02% and 0.92% of
the total available fishing area in the North Sea.  The results
were summarized as follows:  "I think that it would be fair to
conclude that the statistical analysis is inconclusive.  In no
case is there firm evidence to  show a decline in catches follow-
ing the installation of exploration rigs, platforms, pipelines,
etc.  On the other hand, there  is no firm evidence to show the
opposite, and the statistical problems with the catch data are
such that it is unlikely that any conclusion will be reached."
(MacKay.- 1979).


     Although it is generally believed that bottom trawl gear
will not cause extensive damage to pipelines  (see FLAGS Study
results reported in Section 2), damage to trawl gear is also a
concern.  As part of the Shell-Expro FLAGS Study, VHL River and
Harbour Laboratory at the Norwegian Institute of Technology at
Trondheim, Norway ran a series of experiments to examine this
problem.  The following results were reported by Carstens  (1977).


     Three types of otter trawl boards were utilized in a series
of laboratory and field tests designed to examine how trawl
equipment responded to impact on pipelines.  Laboratory results
indicated hooking of gear on the pipeline did not occur when the
pipeline was struck by a board in a normal upright position.
Instead, the board passed over the pipeline and resumed its pre-
vious upright state.  This occurred regardless of whether the
pipeline rested on the bottom, was spanned, or was lying in a
trench.  However, when the trawl door was significantly tipped,
hooking lasted up to a few seconds, during which the tow warp
(rope) was stretched elastically.  Upon release, the tow warp
force was sufficient to accelerate the board to a high velocity;
at times the board even "took flight" for a few meters.  This is
illustrated in Figure 12.
^^^\ X?
yv .' / fo-^j1 > f> > > '.' .- •*. /*
^ .'*' --•
'' '! /
{' I /
\v '' X
' ''x'5'

M r'^''- ""
             VV   ^xx'            APPROXIMATE
             /' •*. xxxxx              DISTANCE 2m.
       Source:  Carstens, 1977, p.24.

     Field experiments showed similar results to those obtained
in the laboratory.  Hooking occurred three times when the otter
board struck the pipeline at an angle of less than  45°.  Tension
was sufficient to break the warp twice; the third time the  tow-
ing vessel was proceeding slowly and was brought to a complete

     Measured warp loads placed on the board tow lines increased
from three to five times the normal tension during board pull-
over.  This increased tension was observed with both untrenched
and spanned lines.  Trenched, but unburied, lines offered even
more resistance to trawl board pullover  (Broussard, et al.,1978).
Table 3 presents calculated pullover loads placed on the three
trawl door types.


Oval door
Rectangular door
Weight (kg)
Maximurrt Pullover Loads
(tonnes force)
          Source:  Shell Expro, 1977, p.43.

     The following conclusions were drawn  from these experiments.
First, if a trawl door hooks briefly on a  pipeline but then
quickly unhooks, no trawl door damage is likely.  On the other
hand, there is a remote chance that a trawl door will hook but
not unhook.  A number of unusual conditions are required to cause
this event.  To hook the pipeline, an otter trawl door must be
lying flat upon impact with the pipeline or must catch under a
spanned pipeline with a small bottom clearance.  The trawl door
may not unhook if conditions prohibit deflection of the door or
where the door becomes imbedded in very stiff bottom materials
(Carstens, 1977).  If the board hooks and  holds fast and the tow
warp breaks, besides losing the door, the  warp will snap, possi-
bly injuring crew on the ship's deck.


     There are three major types of bottom debris associated
with offshore pipeline routes:  bottom materials dug up in the
trenching process; stone which may be used to cover a pipeline;
and debris from pipelaying operations and  passing vessels.  Ob-
jects encountered by North Sea fishermen have ranged from oil
drums and scrap metal to steel cable, pipe turnings and heavy
machinery dumped overboard rather than repaired (NERBC, 1979).
Claims for gear losses caused by bottom debris in the North Sea

appear to have averaged approximately two per week in 1976 and
1977  (Dept. of Political Economy, 1978).

     Trenching operations often expose rocks and result in mounds
of sediment on either side of the trench which may catch the nets
of passing trawl gear.  Damage may also result when nets are
caught on damaged areas of a pipeline's concrete coating.  Fig-
ure 13 summarizes various fishing gear problems associated with
trenched offshore pipelines.

     Crushed stone has been considered for use in protecting
pipelines in North Sea areas where natural backfilling has not
or is not expected to occur.  For example, artificial burial of
portions of the Ekofisk to Emden pipeline was suggested after it
was discovered that much of the pipeline had not been buried
naturally  (NERBC, 1979).  However, North Sea fishermen have re-
ported that the crushed stone fill gathers in their nets, where
it wears holes, releasing both the fish and stone.  This results
in damaged gear and loss of catch (NERBC, 1979).

     Triggered in part by complaints received from fishermen,
Norwegian authorities requested that all license holders on the
Norwegian Continental Shelf perform debris surveys in all areas
affected by oil and gas activities including all pipeline routes,
abandoned well sites, and platform installations.  In response to
this request, the Norpipe pipeline routes from Ekofisk to Tees-
side  (oil) and Ekofisk  to Emden  (gas) were surveyed, and subse-
quent clean-up operations undertaken.

     Survey work began using side scan sonar  and submersible
vessels to locate and identify potential debris "targets" within
a 100 meter wide corridor along the pipeline route.  Targets
were then visually examined using a submersible and classified
as rubbish or debris.  Rubbish was defined as "minor or small ob-
jects considered to be unable to damage or hinder trawl nets or
endanger divers or the pipe itself"  (Kjolseth, 1978) and included
such objects as empty oil drums, boxes, tires, ropes, fishing
nets, etc.  These targets were not retrieved.  Debris was clas-
sified as  "any objects considered able to damage or hinder trawl
nets or endanger divers or the pipe itself"  (Kjolseth, 1978) and
included:  steel pulley blocks, plates or pipe, machinery parts,
etc.  Buoys and electronic "pingers" were attached to these deb-
ris targets, which were later retrieved.

     The Emden gasline survey lasted from July 26 to October 7,
1977, during which time over 50 debris articles along the approx-
imately 250 mile route were identified and retrieved.  The Eko-
fisk to Teesside oil pipeline survey took place from October 7
to December 11, 1977, when work was stopped due to bad weather.
Work was completed in 1978.  Estimated costs to Norpipe for the
1977 portion of the debris survey and retrieval were approxi-
mately $4 million  (NERBC, 1979) .


                                       Boulders exposed
                                       by trenching
                                                    " trenc--- '
            Increased   :
            pull over loads
                 No natural backfill
Concrete damage  extended
  by  jet sled
     Additional clay lumps
     caused by trenching
                                         field joint
                  Anchor mounds
Source:   Shell Expro, 1977, p.47

                           SECTION 5

     The process of selecting a final pipeline route from off-
shore platforms to the shoreline involves analysis of the tech-•
nological feasibility of installation and the geological and en-
vironmental characteristics of the route.  This chapter discus-
ses this final siting process, including:

     •   general industrial siting criteria to use in
         analyzing route feasibility;

     •   areas to avoid in pipeline siting, including
         geologically unstable and environmentally sen-
         sitive areas; and

     •   mitigation methods for minimizing unavoidable
         impacts, both to the environment and to the
         other users of the area.


     The technical feasibility of installing a proposed pipeline
can be determined by using criteria based on what the pipeline
industry considers the most and least desirable features of a
pipeline route.  (Appendix B contains a complete description of
industry's route selection procedures.)  Some of these consider-
ations are presented in Table 4.  Positive and negative aspects
of offshore and coastal areas and potential conflicts with
other coastal uses are shown.  Although this table describes
"least preferred" areas, it is possible for pipelines to be rn-
stalled in a number of these adverse situations, as illustrated
by North Sea experiences where, for example, cable crossings and
bedrock sea bottoms have not prevented pipeline installation
(NERBC, 1979).

     Table 5 presents technical criteria for screening potential
pipeline routes and landfalls developed by a consortium of gas
pipeline companies as part of a survey of sites along the British
coast.  This survey was undertaken in anticipation of discoveries
of additional offshore gas fields.  Similar to the U.S. industry
considerations in the previous table, these criteria, when taken
together, represent an ideal routing situation; "real world"
routes have often included many undesirable features, because

          Most Preferred Features
         Least Preferred Features

Submarine Topo-
Level or gradually sloping grade, rela-
tively stable contour
Submarine Sediment  Easily removed light sediments    (sand
                    or sandy loam), horizontal homogeneity
                    over line length, stable sediments over
                    full range of local current velocities
Continual, drastic up and down grade
changes, dynamic contour

Heavy sediments, not easily removed, which
require loosening before removal (mud, clay
gravel and rock), continual changes in
sediment composition over line length,
dynamic sediments within range of local
current velocities
Submarine Sand
No presence or historical presence
History of formation and presence

Barrier Islands
 Onshore  Sand
Homogeneous  (non-layered), stable high
bearing strength, low water table, non-
"runny" soils

Sandy ocean  front, relative historical
stability, little wetland or bay area
landward of  shore crossing
Accreting, sandy beach with historical
stability  (long-term and during storm

Small in size with historical erosion
levels small in magnitude
Diverse texture layers,  unstable low bear-
ing strength, high water table, ''runny" wet

Heavy sediment ocean front, significant
historical migration and tidal inlet for-
mation, large wetland or bay expanse be-
tween island and mainland

Eroding, heavy sediment ocean front with a
history of significant normal and storm-
induced erosion

Large in size  with historical erosion
levels large in magnitude

                                                    TABLE 4.
       Cons iderations
          Most Preferred Features
         Least Preferred Features
Firm soil conditions  (high traffic-
ability) with no obstructions such
as tree stumps

Small in size with a history of rela-
tive stability and no history as a run-
off area
Soft, muck soil conditions, (low traffic-
ability) with many obstructions which are
hard to remove

Large in size, with a history of erosion
and recession from the water's edge, and
a known run off point for upland storm,
flood and waste waters
    Commercial Fishing
Areas in which no bottom-disruptive
fishing techniques are employed or
foreseen to be, and areas which are
not controlled by private lease, license
or the like
Areas in which dredges, bottom trawling,
tongs, and the like are used in harvesting
fishery products, areas that are privately
leased or granted
Areas which contain no wreckage
Areas which have wrecks requiring circum-
    Ship Channels
    and Anchorages
No major or minor channels which require
periodic redredging of the route, no
anchorage area harboring large commer-
cial vessels in the route
Periodically dredged channels; commer-
cially utilized heavy anchorage areas
    Areas of Unex-
    ploded Ordnance
No designated explosives dumping
grounds or live ammunition practice
firing areas in the area, no record
of accidental ordnance release

Little or no recreational uses
Nearby areas of past unexploded ordnance
disposal or live ammunition practice firing
areas; records indicating possible presence
of accidentally released live ordnance

Frequent, highly used for recreation

                                        TABLE 4.  (Concluded)
         Most Preferred Features
         Least Preferred Features
Buoy Testing Areas  No buoy testing area to be traversed
Areas of Surface
and Bottom Activi-
ty Restrictions
No areas of activity restriction to
be traversed
Prohibited Areas    No prohibited areas to be traversed
Cable Areas

No cable areas to be traversed

Pre-existing ot easy to obtain, inex-
pensive and not likely to generate
public opposition
One or more buoy testing areas to be

One or more areas of activity restriction
to be traversed
One or more prohibited areas to be tra-

One or more cable areas to be traversed.

"Frontier" area, devoid of existing utility
rights-of-way, hard to obtain, expensive
and likely to generate public opposition
 Source:  after Rooney-Char and Ayres, 1978, p.104-106.

                              TABLE 5.


                    CRITERIA FOR EVALUATION
 Onshore (above limit of marine  activity)
         1.   500 acres land  with slope  under  five  percent;  well
             drained;  average  bearing capacity.
         2.   within one mile of  coast;  or
         3.   two sites with  similar  physical  characteristics:
             one 50 acres within one mile  of  coast,  one  500
             acres  within five-ten miles of the  coast.
 Coastal (from low  water mark  to upper  limit  of  marine activity)
         1.   less than ten percent slope.
         2.   sediment at least three meters.
         3.   absence of unstable/very mobile  sediments.
         4.   absence of hard untrenchable  rock outcrops.
         5.   absence of high velocity currents.
         6.   absence of rock cliffs  (ten meter high  soft  sediment
             cliffs permissable).
         7.   absence of unstable sand dunes.
         8.   space  for landing two pipelines  (100-200 meters).
 Offshore (low water mark to depth of 100  feet)
         1.   less than ten percent slope,  low to moderate undu-
         2.   sediments at least  two  meters deep.
         3.   absence of mobile seabed sediments, especially sand
         4.   absence of high velocity currents.
         5.   absence of untrenchable rock.
         6.   absence of deep trenches;  other major  seabed
         7.   absence of minor  seabed irregularities.

Source:  NERBC, 1979,  p.36.


other considerations  (such as economic factors) have outweighed
the technical difficulties in construction  (NERBC, 1979).


     In addition to studies examining the technical feasibility
of installing a pipeline along a proposed route, it is important
to identify those areas which should be avoided because of geo-
logic instability or  environmental sensitivity.  Preconstruction
planning should also  include consideration of potential inter-
ferences with fishing activity along the route.

Geological Hazard Areas to Avoid

     When industry considers a potential pipeline route, the
siting criteria are based to a large extent on a geologic analy-
sis of the area.  Generally, geologic hazard areas are those
containing the "least preferred features" (see Table 4) along
the route and include:
     •   areas with adverse sediment conditions—This includes
         soft, unconsolidated fine sediments that provide poor
         foundation characteristics or could form a fluid back-
         fill in a pipeline trench.  Sediments prone to lique-
         faction or other bearing strength failures should al-
         so be avoided;
     •   areas subject to scour—These are areas with swift
         bottom currents or intense wave activity with sedi-
         ments that are mobile under those current velocity
     •   sand waves—These large, mobile features may present
         a physical barrier to construction or expose a buried
         pipeline and subject it to possible spanning;

     •   eroding shorelines—Shorelines that have a past his-
         tory of significant erosion should be avoided;

     •   active faults—Active faults  (those that have dis-
         turbed recent sediments or have been the location of
         recent earthquakes) should be avoided in pipeline
     •   deltas—Deltas have large quantities of rapidly
         deposited, cohesionless sediments.  Their unstable
         sediment structure 'makes them susceptible to sedi-
         ment bearing strength failures.  The seaward edges
         of many deltas are the locations of sediment mass
         movements.   A high organic content within the sedi-
         ments allows the formation of gases that further
         weaken the sediment structure.

     •   heads of submarine canyons—These are sites of sedi-
         ment mass movements and have an irregular distribu-
         tion of erosional and depositional areas resulting
         in considerable bottom instability (Glaeser and
         Smith, 1977);

     •   slump areas—Areas with detachment of masses of sedi-
         ments near canyon heads and along the edges of contin-
         ental shelves or deltas should be avoided; and

     •   buried channels and valleys—Sediments filling buried
         valleys and channels are generally unconsolidated and
         in places have slump features that indicate instabil-
         ity (Glaeser and Smith, 1977).   The unconsolidated
         sediment fill has variable foundation characteris-
         tics and may be prone to bearing strength failures.

Environmental Areas to Avoid

     Because of the relatively small amount of disturbance and
the short time period involved, it appears that in general, only
small-scale, localized environmental damage will result from
pipeline installation activities.  However, there are particu-
larly sensitive environmental areas which may be easily disrup-
ted by pipeline installation (particularly trenching operations)
and which may take long periods of time to recover.  Where pos-
sible, these types of systems should be avoided in pipeline
routing.  These "avoidance areas" include:

     •   wetlands—Wetlands serve many vital coastal func-
         tions including:  acting as a transitional zone be-
         tween fresh and salt water; filtering out land-de-
         rived pollutants from runoff; providing food sup-
         plies (decomposed marsh vegetation) to adjacent
         coastal zone communities; and serving as spawning
         and nursery grounds for coastal fish and nesting
         and migratory resting areas for birds.  Because
         of their unique structure, wetlands, once altered,
         are very difficult to restore to their original
         nature.  Because of their ecological importance
         in coastal zone dynamics, and the difficulty in
         their restoration, wetlands should be avoided,
         whenever practicable, in pipeline routing;

     •   spawning and nursery areas—These areas include
         both offshore and nearshore  (particularly estuarine)
         areas.  Construction may be particularly damaging
         where trenching occurs and in areas used for demer-
         sal (bottom dwelling) spawning or larval growth.   If
         routing through these areas is unavoidable, construc-
         tion should be scheduled to avoid spawning and nur-
         sery seasons;

     •   barrier beaches and islands—Particularly those with
         a history of erosion;

     •   unique habitats—These include areas of particular
         ecological significance such as coral reefs, coastal
         ponds and "flower gardens;"

     •   rare or endangered species habitats; and

     •   small habitats—These include areas where the area
         disturbed by installation makes up a large percent-
         age of the total habitat, or where high concentra-
         tions of organisms exist in small areas.  These habi-
         tats include:  seagrass beds; kelp beds; and (where
         applicable)  shellfish beds.

     In addition, where possible, it may be advisable to avoid
areas with extremely polluted bottom sediment conditions.

Preconstruction Studies

     To locate "avoidance areas" and to determine geological and
ecological acceptability, preconstruction studies of a proposed
pipeline route may be necessary-*  Existing information may pro-
vide much of the necessary data for route assessment.  For ex-
ample, information on geological and ecological characteristics
of an offshore route may be obtained from:
     •   lease sale environmental impact statements—These
         assessments contain general geological and biolo-
         gical data and may include maps of surface sediments,
         currents, etc.;
     •   data records—From universities, research centers
         and oceanographic institutes which may have ongoing
         research projects in offshore areas under consider-
         ation for pipeline routing.   (National Oceanographic
         and Atmospheric Administration  [NOAA] - Sea Grant
         funded institutions may be prime information sources);

     •   federal agencies—Including NOAA and U.S. Geologi-
         cal Survey (USGS) for geological, physical and chem-
         ical oceanographic information; National Marine Fish-
         eries Service (NMFS) for fisheries data; and U.S.
         Fish and Wildlife Service for selected coastal eco-
         system characterizations; and
     •   state agencies—Including Coastal Zone Management
         and other natural resource planning agencies which
         may have detailed data and maps of state shoreline
 It ha-s-=been suggested that due to regulatory requirements  (e.g..
 Environmental Impact Statements) preconstruction studies would
 be necessary prior to pipeline installation.   Hock, J.  (Dept.
 of Energy) 1979:  personal communication.

         and nearshore systems and selected natural
         resource areas, e.g., wetlands.

     In addition, pipeline companies may have gathered much
site-specific information (particularly geological) on a pro-
posed pipeline route.

     In some cases, however, data may be insufficient and field
and/or laboratory studies may be necessary.  The following are
elements of a full-scale geological and ecological characteriza-
tion of a potential route.  (This complete baseline information-
gathering study would be modified to address the information
needs of a particular routing proposal.)  A complete geological
profile of an area would include the following types of data:

     •   bottom currents—Using continuous recording cur-
         rent meters;

     •   bottom and sub-bottom profiling—Using fathometers
         to determine water depth and seismic profiling (map-
         ping) to determine sediment configurations and iden-
         tify shallow subsurface hazards (faults, shallow
         deposits of natural gas, etc.);

     •   bottom obstacle detection—Using side scan sonar to
         detect bottom obstacles such as wrecks, rock out-
         crops and sand waves;

     •   sediment sampling—Using bottom coring devices to
         determine sediment type, strength and depth.  In
         addition, laboratory tests may be conducted on col-
         lected .samples to determine sediment strength and
         susceptibility to liquefaction; and

     •   seismicity-—Using ocean bottom seismometers along
         the proposed route(s).

     A complete ecological baseline data gathering study would
     •   ecosystems characterization—Identifying plant and
         animal species, number, and distribution, based on
         periodic samples taken at predetermined locations
         to ensure data comparability.  (Laboratory studies
         on construction effects [e.g., increased turbidity]
         on native species may be desirable); and

     •   literature reviews—Reviewing literature for results
         of previous experiments in which the same species,
         the same area or conditions similar to those expected
         from pipeline disturbance have been examined.
         Both field and laboratory results should be consid-

Pipeline/Fishing Interferences

     Potential pipeline/fishing interferences may be minimized
by frequent consultation with fishermen on routing alternatives
prior to final route selection.  In addition, prior to construc-
tion, an important technical consideration will be whether or
not to trench the pipeline in active bottom fishing areas.

     Trenching;  Originally, offshore pipelines were required to
be trenched because it was thought that the trenching (and ex-
pected natural burial) would protect the pipeline from damage
caused by hurricanes and other natural forces.  However, experi-
ments have shown that protection is not afforded in offshore
areas where natural burial does not occur, leaving the pipeline
trenched but exposed.  Experimental results indicated that con-
crete coating alone offered adequate protection from trawl gear
damage.  Raising and lowering trenching machines over a pipeline
may, in fact, cause damage to concrete coating, thus lessening
its protection ability.  In addition, trenched but unburied
pipelines actually posed a greater threat to bottom trawl equip-
ment than pipelines laying directly on the ocean floor.   (See
pages 26 through 30 and 60 through 62 for a detailed description
of these experiments and results.)  Therefore, it would appear
that in certain offshore segments of pipeline routes—in partic-
ular, where burial is not expected to occur (e.g., in areas of
low bottom current velocity) and where concrete coating alone is
thought to provide sufficient stability and protection—trench-
ing may not be necessary or advisable.

     Consultation;  Consultation with fishermen using offshore
fishing grounds which may be traversed by a pipeline is the best
way of minimizing potential fishing/pipeline conflicts.  In the
North Sea, various consultation methods are currently in use,
including both formal governmental channels of discussion and
informal coordinating efforts between fishermen and oil compan-
ies.  For example, final routing of the FLAGS gasline included
numerous consultations with fishermen's organizations because
the originally proposed route crossed several prime fishing
areas.  The fishermen suggested an alternate route, avoiding the
grounds.  A compromise route was chosen, which skirted the edges
of the grounds.  The fishermen, however, then requested that a
route very similar to the original be used because it was the
edges, rather than the center of the grounds which they pre-
ferred to fish (NERBC, 1979)'.

     Consultation with fishermen may also provide the benefit
of fishermen's knowledge of the pipeline routing area.  This was
shown to be the case in routing the Frigg gasline when local
fishermen provided information on an offshore rock formation
(Rattray Rocks) which was then avoided in pipeline siting (NERBC,


     Using appropriate construction and restoration techniques
can further minimize damage along a chosen pipeline route.
There are a number of general techniques which can be used in
various ecosystems, and others that are particularly applicable
to specific landfall types.

General Installation Methods

     The following techniques may be used along the entire length
of a pipeline route to minimize the disturbance related to pipe-
line construction.  Although it is recognized that it may not be
possible to use these methods in every case, they should be con-
sidered for use wherever possible.

     Scheduling;  Pipeline installation should be scheduled to
minimize adverse environmental impacts where practicable.  Con-
struction during fish and bird migration and during mating sea-
sons should be avoided wherever possible.  In addition, schedul-
ing during periods of lowest biological productivity may also be
considered to minimize impacts.  Lowest productivity, however,
generally occurs during the winter months - the most hazardous
time for pipelaying operations.  Construction time should be lim-
ited to the shortest time required and restoration of the dis-
turbed area (particularly at the landfall) should occur as soon
as possible.

     Construction Methods:  In areas with loose, cohesionless
sediments where high turbidity is expected, silt curtains  (poly-
ethylene sheets used to trap suspended sediments) may be used.
(These devices are only effective in areas with very slow water
movement.)  Where sediments are heavily polluted, hydraulic
dredges may be considered instead of conventional trench digging
machines.  If a dredge is used, polluted spoils from the trench
may be removed from the site and the trench refilled with clean
backfill material.  Two major difficulties are associated with
the dredging method:  appropriate disposal of the polluted
dredge spoils and acquisition of suitable clean backfill.  In
addition, this method could prove quite costly.

     Restoration;  The disturbed area  (particularly at landfall
area) should be restored as quickly and as close to original
conditions as possible.  Original substrates and native species
should be used wherever feasible.  Where pipelines traverse
fishing grounds, routes should be placed on appropriate naviga-
tion charts and fishermen notified of  the new pipeline installa-

     Debris;  Disposal of debris offshore in U.S. waters  is  cur-
rent ly~regulated by various acts including the Ocean Dumping Act
of 1972, and by OCS lease  stipulations and operating orders.


Recent passage of ocean dumping legislation may also help to re-
duce debris problems in the North Sea.  To ensure that no debris
is disposed of along future North Sea pipelines, Norpipe and
Phillips have drafted a clause pertaining to debris disposal at
sea which will be included in their contract stipulations with
pipeline installation contractors.  The clause states that:
     During the work, Contractor shall not dispose of
     any material into the sea or air, which can be of
     danger to or interfere with other marine activity
     or life.  The seafloor, sea, or air shall not be
     contaminated.  As soon as the work is completed,
     the seabed shall, if practical, be brought back to
     original condition and Contractor shall clear the
     premises of debris, waste material, and equipment
     remaining from the work.  Nothing shall be left
     which can interfere with fishing, marine, or other
     activity.  All material belonging to Company shall
     be loaded for storage or to a location as directed
     by the Company Representative.  Contractor shall
     be responsible for the recovery of any debris it
     dumps and shall bear the cost of such recovery
     operations.  (NERBC, 1979, p.57)

Landfall Installation Methods

     Wetlands;  Because of their unique coastal value and struc-
ture, wetlands disturbance should be minimized.  The following
construction and restoration techniques should be considered for
use whenever possible:
     •   crossings—Wetlands should be crossed at their nar-
         rowest point;
     •   pipeline installation—Pipelines should be trenched
         and buried.  Because it disturbs less area, the
         pull technique would be preferable to the flotation
         method.  In addition, wherever practicable, the
         "double ditching" construction technique should be
         used.  In this technique, topsoil and underlying
         soil are removed separately and stored on opposite
         sides of the trench.  When the trench is refilled,
         underlying soil, then topsoil are replaced in the
         trench.  Plugs may be placed at intersections of
         pipeline trenches and natural waterways to prevent
         interferences with natural drainage  (Longley et al.
         1978).  Refilling trenches should occur as soon as
         possible.  If additional clean fill is required to
         restore original topography  (in the event that ori-
         ginal sediments have settled and compacted), it
         should be placed in the trench first, followed by
         underlying sediments, then topsoil; and

     •   restoration—Affected areas should be restored as
         soon as possible with native vegetation.  Use of
         plants from adjoining wetlands may be considered
         to foster quicker regrowth.  If construction oc-
         curred in late summer or fall, another planting
         the following spring may be desirable to allow a
         full growing season prior to fall migratory bird

     The following methods may be used to control alterations in
marsh circulation patterns:

     •   subsurface waters—Impervious materials (such as
         clay) may be placed around the pipeline if ground
         water protection is necessary;

     •   surface circulation—Where pipeline installation
         canals cannot be refilled, plugs should be installed
         at intersections with natural streams to prevent
         mixing and drainage alterations.  Plugs should be
         designed to withstand any likely disturbance for
         the life of the pipeline.  Wherever possible, sur-
         face drainage patterns should be restored to pre-
         construction conditions when pipeline installation
         is completed; and

     •   pipeline elevation—In cases where no other alter-
         native will maintain original water circulation
         patterns, elevating the pipeline on pilings may
         be considered.  However, above ground elevation
         may expose the pipeline to much greater risk of
         damage than if the pipeline were buried.

     Beaches;  While accreting beaches are likely to suffer only
short-term and small-scale damage from pipeline installation,
severely eroding beaches and dune structures may suffer greater
damage from construction activity.  In naturally eroding shore-
line areas, pipelines should be buried below the projected depth
of sediment removal by erosion.  In some cases, artificial nour-
ishment (periodic placement of compatible sediments on the beach
landfall)  may also be considered to provide additional pipeline
protection.  In other cases, it may be necessary to use sediment
trapping structures such as groins, jetties, and breakwaters to
artificially build up a pipeline landfall.  While these accre-
tion structures will help stabilize the landfall, they may re-
sult in erosion downdrift of the accretion structure.  The fol-
lowing techniques may be considered to minimize these downdrift
     •   initial beach fill—Filling the landfall area with
         additional sand to supplement sediment provided by
         longshore drift; and

     •   sediment pumping—Pumping sediments updrift of the
         accretion structure into downdrift waters, thus re-
         introducing them into the longshore drift process.

     In areas where pipelines must be placed through dunes, the
following techniques may be considered to minimize installation

     •   construction—While trenches are open, they may
         be sprayed with substances such as crelawn bitumen,
         a tarlike material, to minimize slumping and dune
         erosion  (Walton and Ritchie, 1975).  Equipment move-
         ment should be limited to specific routes to protect
         areas adjacent to construction sites;

     •   sand storage—Trenching requires the removal of
         large quantxties of sand which need to be stored
         until replaced in the trench.  The upper layer of
         sand and vegetation and the remainder of the dune
         should be removed and stored separately in areas
         protected from wind erosion and disturbance by
         construction machinery.  While land directly be-
         hind the dune line would provide this protection,
         the vegetation in this area is fragile and would
         likely be destroyed by storage.  Therefore, other
         storage sites may be preferred.  Erosion of stored
         sand may be prevented by watering the storage area,
         covering it with protective material  (such as clay-
         rich soil), spraying it with erosion prevention sub-
         stances, and employing erosion control structures
         such as snow fences; and
     •   restoration—After pipelaying and artificial burial
         is complete, dunes should be restored to their origi-
         nal height and slope so that normal beach-dune sedi-
         ment exchange can resume.  The top layer of sand
         should be placed on the dune's surface and replanted
         with native vegetation.   (Annual spring plantings
         of mature vegetation may be necessary to ensure com-
         pletely successful restoration.)  Because dunes are
         particularly vulnerable to wind and wave erosion un-
         til they are restabilized, snowfences, brush, and
         where erosion may be particularly severe, stabili-
         zation structures, may be used to protect the dunes
         until the natural restabilizing process is completed.


     Various techniques may be used to ensure safe and efficient
operation of a pipeline system after installation.  These in-
clude:  notifying other users in the area of the pipeline's lo-
cation; and inspecting the pipeline at periodic intervals.


Recording Route Location

     Once installed, pipeline route locations should be ade-
quately identified to minimize the risks of interference with
other offshore activities.  Possible methods of notification in-
clude publishing the route's location in "Notice to Mariners"
and placement of the route on appropriate nautical charts.  If
necessary at the landfall, the pipeline's route may be delinea-
ted with appropriate markers.

Pipeline Inspection

     Pipeline inspection programs are designed to ensure the
proper installation and safe and efficient operation of a pipe-
line system.  In the U.S., pipeline inspection programs are ad-
ministered by the Office of Pipeline Safety - U.S. Department of
Transportation.  There is also a Memorandum of Understanding be-
tween the Department of Interior and the Department of Transpor-
tation which provides for coordination between the two depart-
ments in their OCS pipeline inspection activities.  Current reg-
ulations require only that surface waters over an underwater
pipeline be checked by the operator at least every two weeks to
observe any indications of leaks.  Additionally, those pipelines
utilizing cathodic protection require a yearly test of the pro-
tection system to determine if it meets federal requirements.
The pipeline construction industry also has self-imposed in-
spection programs which may involve a more careful check of the
pipeline system.  For example, pipeline companies make pressure
tests on the pipeline before the system is brought into service.
(For complete specifications on many U.S. inspection practices,
see American Petroleum Institute [API] Publication RP1111,
Recommended Practice for Designf Construction, Operation, and Main-
tenance of Offshore Hydrocarbon Pipelines - March 1976, and
R~iFrank Busby Associates, Underwater Inspection/Testing/Moni-
toring of Offshore Structures - February 1978.)

     Pipeline installations in the North Sea, particularly in
the United Kingdom and Norway, have more specific inspection re-
quirements.  For example, the Norwegian Petroleum Directorate
specifies three types of inspections:  initial inspection, start-
up inspection and annual inspection.  (Norwegian Petroleum Di-
rectorate , Guidelines for the Inspection of Primary and Second-
ary Structures of Production and Shipment Installations and
Underwater Pipeline Systems, 1978a, p.13-14).  In addition, Det
Norske Veritas(Rules for the Design, Construction and Inspec-
tion of Submarine Pipelines and Pipeline Risers, 1976) recom-
mends that special inspections be undertaken if the need arises
(e.g., in cases of known or suspected damage).

     Initial Inspection;  After installation, a pipeline system
is first visually inspected to determine the success of the pipe-
laying procedures.  Problems such as underwater spans  and me-


chanical damage  (e.g., damage to concrete coating) can be detec-
ted and documented by videotape or photographs.  Other aspects
of the inspections may include measurements of:

     •   burial depths at specific intervals along the

     •   bottom currents; and

     •   the interior of the pipeline to detect changes
         in diameter.  This is accomplished with mechani-
         cal measuring devices (such as "calibrating pigs")
         which are passed through the pipeline.

     Start-up Inspection;  Just prior to beginning operation, a
start-up safety inspection is made to determine the overall sta-
tus of the pipeline system.  Highly accurate determinations are
made of the location and condition of the pipeline in respect to
the seafloor.  Any problems, such as spanning, are documented
using videotapes or other acceptable recording methods.  Another
internal inspection of the pipeline is also performed.

     Annual Inspection:  The elements of annual inspection vary
from one pipeline system to another and generally depend on the
results and experiences of previous inspections.  Also given
consideration are the operating conditions for the particular
pipeline system.  The results of each inspection help determine
the status of the system and the likelihood of its safe opera-
tion until the next annual inspection.  Again, the basic ele-
ments of the inspection are similar to those of the initial in-

     Special Inspections;  Special inspections are generally re-
quired when events occur which might impair the safety, strength
or stability of the pipeline including:

     •   known or suspected pipeline damage;

     •   signs of pipeline deterioration;

     •   alteration, repair or replacement of the pipeline
         or sections of it; and
     •   where inspections  (initial, start-up, or annual)
         reveal  substantial changes in pipeline location,
         cover or "lying comfort."

     Any special inspection would be specifically designed to
provide the information necessary to ascertain the location and
extent of the problem.


Allen, D.W., R.B. Allen, R.E. Black, J.M. Friedman, L.G. Mallon,
     R.W. Morse, S.B. Peterson, and L.J. Smith.  1976.  Effects
     on Commercial Fishing of Petroleum Development Off the
     Northeastern United States.  Woods Hole Oceanographic In-
     stitution.80 pp.

American Petroleum Institute.  1976.  Recommended Practice for
     Design, Construction, Operation and Maintenance of Offshore
     Hydrocarbon Pipelines.  API Publication Number API RP 1111.
     22 pp.

American Society of Mechanical Engineers.  1974.  Liquid Petro-
     leum Transportation Piping Systems.  ANSI Publication Num-
     ber B31.4 - 1974, New York.  68 pp.

        1975.  Gas Transmission and Distribution Piping Systems.
     ANSI Publication Number B31.8 - 1975, New York.118 pp.

Arnold, K.E.  1967.  Soil Movements and Their Effects on Pipe-
     lines in the Mississippi Delta Region.  Unpublished M.S.
     Thesis, Tulane University-  74 pp.

Bennett, R.H., B.A. McGregor and J.W. Kofoed.  1978.  Marine
     Geotechnical Program of the Marine Geology and Geophysics
     Laboratory, Atlantic Oceanographic and Meterological Lab-
     oratories, National Oceanic and Atmospheric Administration.
     Miami, Florida.31 pp.

Blatt, H., G. Middleton and R. Murray.  1972.  Origin of Sedi-
     mentary Rocks.  New Jersey:  Prentice Hall, Inc.  634 pp.

Broussard, D.L., E.L. Killin, D.K. Kiltau and B.G.S. Taylor.
     1978.  "FLAGS Gasline - Design for Seabed Safety and Sta-
     bility."  European Offshore Petroleum Conference and Exhi-
     bition.  London, England.  14 pp.

Brown, R.J.  1978.  "Examining New Pipe Burial Methods."  Off-
     shore .  38(4):  68-75.

Bureau of Land Management.  1976.  Final Environmental State-
     ment - PCS Sale #40.  Prepared for U.S. Department of the
     Interior.  4 Volumes.

         1977.  Final Environmental Statement-OCS Sale #42.
     Prepared for U.S. Department of the Interior.  5 Volumes.

	•  1979.  Final Environmental Statement-OCS Sale #49.
     Prepared for U.S. Department of the Interior.  3 Volumes.

Busby, R. Frank, Associates.  1978.  Underwater Inspection/
     Testing/Monitoring of Offshore Structures.  Sponsored by
     U.S. Departments of Commerce, Energy and the Interior.
     Arlington, Virginia.  139 pp.

Carstens, Torkild.  1977.  Bottom Trawling Across North Sea
     Pipelines.  Prepared for International Conference for the
     Exploration of the Sea Statutory Meeting, Reykjavik, Ice-
     land.  29 pp.

Conner, W.H., J.H. Stone, L.M. Bahr, V.R. Bennett, J.R. Day, Jr.,
     and R.E. Turner.  1976.  Oil and Gas Characterization Im-
     pacts Guidelines.  Sea Grant Publication No. LSU-T-76-006.
     Louisiana State University, Center for Wetlands Resources,
     Baton Rouge, Louisiana.  148 pp.

Demars, K.R., V.A. Nacci and W.D. Wang.  1977.  "Pipeline Fail-
     ure:  A Need for Improved Analysis and Site Surveys."  Pro-
     ceedings :  Offshore Technology Conference.  OTC 2966:  63-

Dept. of Political Economy.  1978.  A Physical and Economic
     Evaluation of Loss of Access to Fishing Grounds Due to
     Oil and Gas Installations in the North Sea.Commissioned
     by the British Fishing Federation and the Scottish Fisher-
     men's Federation.  University of Aberdeen, Scotland.
     152 pp.

Det Norske Veritas.  1976.  Rules for the Design, Construction
     and Inspection of Submarine Pipelines and Pipeline Risers.
     H0vik, Norway:Det Norske Veritas.73 pp.

Emery, K.O., E. Uchupi, J.D. Phillips, C.O. Bowin and E.T.
     Bunce.  1970.  "Continental Rise Off Eastern North Ameri-
     ca."  American Association of Petroleum Geologists Bulle-
     tin.  54(1):  44-108.

Emery, K.O. and E. Uchupi.  1972.  "Western North Atlantic
     Ocean, Excerpted Section on Physiography of George's Bank
     and Hatteras-Cape Cod Shelf."  American Association of
     Petroleum Geologists Memoir 17.pp. 28-36.

Glaeser, J.D., and P.O. Smith.  1977.  Assessment of Geological
     Information of New York State's Coastal Zone and Outer
     Continental Shelf and Its Significance to Petroleum Ex-
     ploration and Development.  Prepared for New York State
     Science Service - Geological Survey.  2 Volumes.

Goodwyn, F.  1970.  "Zooplankton."  In Gross Physiological and
     Biological Effects of Overboard Spoil Disposal in Upper
     Chesapeake Bay.  Special Report No.  3.  University of Mary-
     land, Natural Resources Institute, College Park, Md.
     pp. 39-41.

Grimwood, C., J. Dufrene and J. McGhee.  1978.  "Chemical Re-
     lease from Coastal Louisiana Sediments."  In Coastal Zone
     '78.  New York:  American Society of Civil Engineers.
     Volume III:  2153-2157.

Guerry, T.L.  1976.  "Highlights of North Sea Pipeline Opera-
     tions."  Ocean Industry.  11(3):  23-28.

Hampton, M.A.  1972.  "The Role of Subaqueous Debris Flows in
     Generating Turbidity Currents."  Journal of Sedimentary
     Petrology.  42(1):  775-793.

Hoose,  S.N.  1978.  "Earthquake Induced Ground Failure."  In
     Coastal Zone '78.  New York:  American Society of Civil
     Engineers.  Volume III:  1508-1529.

Inman,  0.0.  1963.  "Sediments:  Physical Properties and
     Mechanics of Sedimentation."  In Submarine Geology.
     Edited by F.B. Shepard.  New York:  Harper and Row.
     pp.  101-151.

Kjolseth, 0.  1978.  Surveying Debris on the Shelf.

LaRoe,  E.T.  1977.  "Dredging."  In Coastal Ecosystem Manage-
     ment.  Edited by J. Clark.  New York:  John Wiley and
     Sons.  pp.  610-614.

Larson, D.W.  1978.  A Comparison of Environmental Aspects
     Between PCS Petroleum Activities and Other Selected Acti-
     vities.  Exxon Company, USA.  11 pp. plus Attachments.

Longley, W.L., R. Jackson and B. Snyder.  1978.  Managing Oil
     and Gas Activities in Coastal Environments.  U.S. Fish
     and Wildlife Service, Publication Number FWS/085 - 78/54.
     65 pp.

MacKay, G.A.  1979.  Statement before the U.S Department of the
     Interior, Bureau of Land Management, on Proposed OCS Oil
     and Gas Lease  Sale No.  42.  10 pp. plus Attachments.


Morton, J.W.  1977.  Ecological Effects of Dredging and Dredge
     Spoil Disposal.  U.S. Fish and Wildlife Service Publica-
     tion Number 94.  33 pp.

New England River Basins Commission  (NERBC).  1979.  North
     Sea Pipelines;  A Survey of Technology, Regulation and
     Use Conflicts in Oil and Gas Pipeline Operation (Draft).
     Boston, Massachusetts.67 pp.

Nichols, D.R., and J.M. Buchanan-Banks.  1974.  Seismic Hazards
     and Land Use Planning.  USGS Circular 690.  33 pp.

Nordstrum, D.F., S.F. Fisher, M.A. Burr, E.L. Frankel, T.C.
     Buckalew, and G.A. Kucma.  1978.  Coastal Geomorphology of
     New Jersey.  Volume 2.  Office of Coastal Zone Management,
     Division of Marine Sciences, State of New Jersey-  130
     pp.  plus Appendices.

Norwegian Petroleum Directorate.  1978a.  Guidelines for the
     Inspection of Primary and Secondary Structures of Produc-
     tion and Shipment Installations and Underwater Pipeline
     Systems.  Stavanger, Norway:  Norwegian Petroleum Director-
     ate.  17 pp.

        1978b.  Trenching and Burial of Pipelines on the Nor-
     wegian PCS.   (in Norwegian).  Stavanger,- Norway:  Norwe-
     gian Petroleum Directorate.  Tables 1 and 2.

Offshore Navigation, Inc.  1976.  High Resolution Marine Geo-
     physical Survey - Georges Bank, Atlantic PCS and Slope,
     Offshore Massachusetts, Proposed PCS Sale #42.  Prepared
     for U.S. Geological Survey.  69 pp.  plus Appendices.

Olsen, S.  1977.   "The Potential Impact on Commercial Fisher-
     ies of Ground Pre-empted by Petroleum-Related Structures
     on Georges Bank."  In Fishing and Petroleum Interactions
     on Georges Bank.  Energy Program Technical Report 77-1.
     Prepared for New England Regional Commission.  2:  219-245

Ralston, D.O., and J.B. Herbich.  1968.  The Effects of Waves
     and Currents on Submerged Pipelines.  Coastal and Ocean
     Engineering Division Report No. 101 - Army Corps of Engi-
     neers .  Texas A&M University.  118 pp.

Rooney-Char, A.H., and R.P. Ayres.  1978.  Offshore Pipeline
     Corridors and Landfalls in Coastal Virginia.  Special Re-
     port in Applied Marine Science and Ocean Engineering No.
     190.  Prepared for Office of the Secretary of Commerce
     and Resources, Richmond, Virginia.  139 pp.  plus Appen-

Saila, S.B.,S.D. Pratt, and T.T. Polgar.  1972.  Dredge Spoil
     Disposal in Long Island Sound.  Marine Technical Report 2.
     University of Rhode Island.  48 pp.

Shanks, L.R.  1978.  Coastal Systems and Management Options
     Related to PCS Development.  U.S. Fish and Wildlife Ser-
     vice Publication Number FWS/OBS-78/74.  13 pp.

Shell, U.K.  Exploration and Production (Expro).  1977.  FLAGS
     Gasline Seabed Safety and Stability-   London, England:
     Shell/Expro.55 pp.

Stern, E.M., andW.B. Stickle.  1978.  Effects of Turbidity and
     Suspended Materials.  Technical Report D-78-21.  Prepared
     for Army Corps of Engineers, Waterways Station, Vicksburg,
     Mississippi.  117 pp.

Sundborg, A,  1956.  "The River Klaralven, a Study of Fluvial
     Progresses."  Geografiska Annaler.  38:  127-316.

"Underwater Plow Prepares Trench for Statfjord Loading Pipe-
     line."  1977.  Ocean Industry.  12(8):  41-42.

U.S. Coast Guard.  1976.  Draft Environmental Impact/4(f)  State-
     ment.  LOOP Deepwater Port License Application.  Prepared
     for U.S. Department of Transportation.  2 Volumes plus

U.S. Geological Survey.  1978.  Pipeline Failure Data Open
     File Information.  Data for Oil and Gas Pipelines in Gulf
     of Mexico, 1967-1978.  Conservation Division, Metaire,
     Louisiana.  unnumbered.

Walker, D.B.L.  1976.  "A Technical Review of the Forties
     Field Submarine Pipeline."  Offshore Technology Confer-
     ence.  Preprint #2603:  819-826.

Walton, K., and W. Ritchie.  1975.  Environmental Appraisal of
     Pipeline Landfalls at St. Fergus  (Rattray Bay.)~  Shell
     U.K. Exploration and Production Limited.  24 pp.

Wilun, A., and K. Starzewski.  1972.  Soil Mechanics and Founda-
     tion Engineering.  New York:  John Wiley & Sons.  252 pp.

Youd, T.L., and D.M. Perkins.  1978.  "Mapping Liquefaction In-
     duced Ground Failure."  Journal of the Geotechnical Divi-
     sion.  American Society of Civil Engineers.  104 (GT 4):


Adkins, G. and P. Bowman.  1976.  A Study of the Fauna in
     Dredged Canals of Coastal Louisiana.Technical Bulletin
     No. 18~.  Prepared for Louisiana Wildlife and Fisheries
     Commission.  New Orleans, Louisiana.  71 pp.

Baker, J.M. ed. 1976.  Marine Ecology and Oil Pollution.  New
     York:  Halsted Press.  566 pp.

Baldwin, P.L. and M.F. Baldwin.  1976.  Onshore Planning for
     Offshore Oil Lessons from Scotland.The Conservation
     Foundation.183 pp.

British Gas.  November 1976.  Gas Plants and People.  Prepared
     for Symposium of the Institute of Gas Engineers.  25 pp.

Brown, R.J.  1971.  "Pipelines Can Be Designed to Resist Impact
     from Dragging Anchors and Fishing Boards."  Offshore Tech-
     nology Conference.  Preprint #1570:  579-584.

Bureau of Land Management.  1975.  Final Environmental State-
     ment.  Proposed Increase in Oil and Gas Leasing on the
     Outer Continental Shelf.  Prepared for U.S. Dept. of the

Chaisson, R.E., L. Smith and J. Fay-  1978.  "Oil Spills and
     Offshore Drilling."  Science.  199:  128-129.

Clark, J. and C. Terrell.  1978.  "Effects on Living Resources
     and Habitats."  Environmental Planning for Offshore Oil and
     Gas.  Volume IIiTPrepared for U.S. Fish and Wildlife
     Service.  Publication Number FWS/OBS-77/14.  220 pp.

Craig, N.J., J.W. Day, Jr., P- Kemp, A. Seaton,  W.G. Smith, and
     R.E. Turner.  1977.  Cumulative Impact Studies in the
     Louisiana Coastal Zone - Eutrophication - Land Loss.
     Edited by N.J. Craig and J\W. Day, Jr.Prepared for
     Louisiana State Planning Office.  Louisiana State Univer-
     sity, Center for Wetlands Resources, Baton Rouge, Louisi-
     ana.  157 pp.

Cronin, L.E., R.B. Biggs, D.A. Flemer, H.T. Pfitzenmeyer,
     F. Goodwyn, Jr., W.L. Dovel and D.E. Ritchie, Jr.  1970.
     Gross Physical and Biological Effects of Overboard Spoil
     Disposal in Upper Chesapeake Bay.  Special Report No. 3.
     University of Maryland, Natural Resources Institute,  Col-
     lege Park, Maryland.  66 pp.

Council on Environmental Quality. 1974.  PCS Oil and Gas,  An
     Environmental Assessment.  Volume I:  67-115.

Danenberger, E.P.  1976.  Oil Spills, 1971-75, Gulf of Mexico
     Outer Continental Shelf.  U.S. Geological Survey Circular
     741.  47 pp.

Daniels, M., and J.C. Swank.  1978.  "Northern North Sea Pipe-
     lines - The Brent System."  Offshore Technology Conference.
     Preprint #2601:  803-817.

Det Norske Veritas.  1978.  Method for Performing Risk Assess-
     ment of Submarine Pipelines.  Stavanger, Norway:  Det
     Norske Veritas.  7 pp.

Dickson, R.  1975.  "A Review of Current European Research into
     the Effects of Offshore Mining on the Fisheries."  Off-
     shore Technology Conference.  Preprint #2159:  103-110.

Ecology Analysts, Inc.  1976.  "Biological Impacts of the Three
     Offshore Energy Technologies".  In Working Papers;  Coastal
     Effects of Offshore Energy Systems.  Prepared for U.S.
     Congress,Office of Technology Assessment.  Volume II:
     V-I - V-29.

Gagliano, S.M.  1973.  "Canals, Dredging and Land Reclamation
     in the Louisiana Coastal Zone."  Report No. 14 of Hydrolo-
     gic and Geologic Studies of Coastal Louisiana.  Prepared
     for Dept. of the Army - Corps of Engineers.  Louisiana
     State University, Center for Wetlands Resources, Baton
     Rouge, Louisiana.  104 pp.

Godcharles, M.F.  1971.  A Study of the Effects of a Commercial
     Hydraulic Clam Dredge on Benthic Communities in Estuarine
     Areas.Technical Series No. 64.Florida Dept. of Natural
     Resources, St. Petersburg, Florida.  50 pp.

Herbich, J.B.  1975.  Coastal and Deep Ocean Dredging.  Houston,
     Texas:  Gulf Publishing Company,  p. 519-534.

Hollis, E.H., J.G. Boone, C.R. DeRose, and G.J. Murphy.  1964.
     A Literature Review of the Effects of Turbidity and Silta-
     tion on Aquatic Life - Staff Report.  Prepared for Dept.
     of Chesapeake Bay Affairs, Annapolis, Md.  26 pp.


Jagshitz, A. and R.C. Wakefield.  1971.  How to Build and Save
     Beaches and Dunes.  Marine Leaflet Series No. 4.  Agricul-
     tural Experiment Station Bulletin 408.  University of Rhode
     Island, Kingston, Rhode Island.  12 pp.

James, W.P., R.W. Hann, Jr. and F. Slowey.  1975.  "Effects of
     an Offshore Crude Oil Unloading Terminal on the Marine
     Environment."  Marine Technology Society Journal.  9(1):
     27-31.                 ——

Kaplan, E.H., J.R. Walker and M.G. Kraus.  1974.  "Some Effects
     of Dredging on Populations of Macrobenthic Organisms."
     Fishery Bulletin.  72(2):  445-480.

Kovach, R.  1975.  "Seismic Problems Related to OCS Develop-
     ment."  In Final Environmental Statement, Proposed Increase
     in Oil and Gas Leasing on the Outer Continental Shelf.
     Prepared for U.S. Dept. of Interior.  3:  865-872.

Kowalski, T. and S.B. Saila.  1976.  Working Paper;  Interfer-
     ence Problems Between the Oil Industry and Commercial Fish-
     eries in the North SeiuUniversity of Rhode Island, Coast-
     al Resource Center Working Paper, Kingston, R.I.  9 pp.

Library of Congress - Congressional Research Service.  1976.
     Effects of Offshore Oil and Natural Gas Development on the
     Coastal Zone"Prepared for Ad Hoc Select Committee on
     Outer Continental Shelf, House of Representatives.  pp.

Limoges, L.  1975.  "Environmental Impacts and Monitoring of
     Oil and Gas Pipelines."  Florida Coastal Policy Study.
     The Impact of Offshore Oil Development.  Florida State
     University and University of South Florida.  pp. 163-191.

Longley, W.L., R. Jackson, and B. Snyder.  1978.  The Develop-
     ment of Methods and Standards of Operation to Protect Fish
     and Wildlife Resources and Supporting Habitats of Coastal
     Wildlife Refuges During Oil and Gas Development - Draft.
     Prepared for U.S. Fish and Wildlife Service, Bay St. Louis,
     Mississippi.  Unnumbered.

May, E.B.  1973.  "Environmental Effects of Hydraulic Dredging
     in Estuaries."  Alabama Marine Resources Bulletin.  9:  1-

McGinnes, J.T., R.A. Ewing, C.A. Willingham, S.E. Rogers,
     D.H. Douglass, and D.L. Morrison.  1972.  Environmental
     Aspects of Gas Pipeline Operations in the Louisiana ColTstal
     Marshes"Prepared for Offshore Pipeline Committee.Bat-
     telle Columbus Laboratories, Columbus, Ohio.  88 pp. plus


Ministry of Industry - Norway.  1975.  Report No. 81 to Stort-
     ing.  Oslo, Norway:  Norwegian Ministry of Industry.
     pp. 9-15.

	.  1976.  Report No. 91 to Norwegian Storting (1975-76).
     Oslo, Norway:  Norwegian Ministry of Industry,  pp. 55-62.

New England River Basins Commission  (NERBC).  1976.  Factbook.
     Boston, Massachusetts.  422 pp.

O'Connor, J.M., D.A. Neumann, and J.A. Sherk, Jr.  1977.  Sub-
     lethal Effects of Suspended Sediments on Estuarine Fish.
     Technical Paper No. 77-3.  Prepared for U.S. Army Corps of
     Engineers.  Coastal Engineering Research Center, Fort Bel-
     voir, Virginia.  90 pp.

Offshore Oil Task Group - Massachusetts Institute of Technology.
     1973.  The Georges Bank Study; - Summary.  Report No. MITSG
     73-5.  Prepared for Sea Grant, the New England Regional
     Commission and New England River Basins Commission.  Mas-
     achusetts Institute of Technology, Cambridge, Massachu-
     setts.  84 pp.

Powers, F.T.  1978.  "Early Attention to Design Data can Lower
     Offshore Pipeline Cost."  Oil and Gas Journal.  76(19):

Ritchie, W.  1978.  "The Economic Viability of Some Coastal
     Dunes."  Shore and Beach.  24  (1) :  21-24.

St. Amant,  L.S.  1971.  "Impacts of Oil on the Gulf Coast."  In
     Transactions of the Thirty-Sixth North American Wildlife
     and Natural Resources Conference.  Wildlife Management
     Institute,  pp. 206-219.

	.  1972.  "The Petroleum Industry as It Affects Marine and
     Estuarine Ecology."  Journal of Petroleum Technology.
     pp. 385-392.

Sheldon, R.G.J.  1975.  "Effects on Fisheries."  In Petroleum
     and the Continental Shelf of North-West Europe.Edited
     by H.A. Cole.  New York:  John Wiley and Sons.  2:  75-81.

Sherk, J.A.  1972.  Current Status of the Knowledge of the Bio-
     logical Effects of Suspended and Deposited Sediments in
     Chesapeake Bay.  Taxa and Special Effects Summaries.  Con-
     tribution No. 515.  University of Maryland, Natural Resour-
     ces Institute.  College Park, Maryland,  pp. 5137-5144.

Sykes, J.E. and J.R. Hall.  1970.   "Comparative Distribution of
     Mollusks in Dredged and Undredged Portions of an Estuary
     with a Systematic List of Species."  Fishery Bulletin.
     68(2):  299-303.                     	

Tereco Corporation.  1976.  Impacts of Construction Activities
     in Wetlands of the United States.  Prepared for U.S. Envi-
     ronmental Protection Agency, Corvallis, Oregon.  EPA-600-

Thayer, G.W., D.A. Wolfe,and R.B. Williams.  1975.  "The Impact
     of Man on Seagrass Systems."  American Scientist.  69(3):

U.S. Dept. of the Interior.  1974.  Final Environmental Impact
     Statement - Deepwater Ports.   I:  IV-172 and IV-193.

U.S. Geological Survey.  1975a.  Sediments, Structural Frame-
     work, Petroleum Potential, Environmental Conditions and"
     Operational Considerations-of the U.S. Mid-Atlantic dcs".
     USGS Open File Report #75-61.  143 pp.

	.  1975b.  Sediments, Structural Framework, Petroleum
     Potential, Environmental Conditions and Operational Con-
     siderations of the U.S. South Atlantic PCS.  USGS Open
     File Report #75-353.  262 pp.

	.  1975c.  Sediments, Structural Framework, Petroleum
     Potential, Environmental Conditions and Operational Con-
     siderations of the U.S. North Atlantic PCS.  USGS Open
     File Report #75-411.179 pp.:

Willingham, C.A., B.W. Cornaby, and  D.G. Engstrom.  1975.  A
     Study of Selected Coastal Zone  Ecosystems in the Gulf of
     Mixico in Relation to Gas Pipelining Activities  (Technical
     Report).  Prepared for Offshore Pipeline Committee.  Bat-
     telle Columbus Laboratories, Columbus, Ohio.  175 pp.  plus

                          APPENDIX A


     This appendix presents the assumptions and calculations
made to generate the estimates of bottom sediments disturbed by
selected offshore activities as presented in Table 1 of the re-

     The first column ("Amount of Sediment Disturbed") contains
estimates derived from two sources.  Surf clam and sea scallop
values are based on similar calculations presented in a report
entitled, "A Comparison of Environmental Aspects between OCS Pe-
troleum Activities and Other Selected Activities"  by Dana W.
Larson (1978) , Exxon Company, USA.  Otter board trawling calcu-
lations are based on personal communications with R.R. Hickman
of Exxon Company, USA.

     The second column ("Miles of Pipeline") values are calcu-
lated based on information from OCS Lease Sale 42's Environ-
mental Impact Statement and from two trench profiles diagrammed
in Shell Expro's 1977 report, "FLAGS Gasline Seabed Safety and

     Assumptions and calculations for both columns are as fol-
lows :


     I. Surf Clamming


        1. An average boat dredges 8 hours per day/100 days
           per year.
        2. Working speed of a boat is 3 knots.

        3. Area of the bottom disturbed is 6 ft wide by
           1.5 ft deep.   (This equals 2,027 cu yd of bottom
           sediment disturbed per nautical mile.)

        4. One Hundred (100) boats are assumed.


     1. For 1 boat:

        3 nautical miles x  8 hours x   2,207 cu yd   _  48,648
              hour            day      nautical mile      cu yd
                                                of bottom sedi-
                                                ment disturbed

     2. For 100 boats working 100 days per year:

        48.6 x 103 cu yd   100 boats   100 days  _  486 x 106
              day        x    day    x   year         cu yd
                                                of bottom sedi-
                                                ment disturbed
II.  Sea Scalloping


     1. An average boat dredges 8 hours per day/100 days per yr,

     2. Working speed of a boat is 3.5 knots.

     3. Area of bottom disturbed is 10 ft wide by 0.25 ft deep.
        (This equals 563 cu yd of bottom sediment disturbed per
        nautical mile.)

     4. One Hundred (100) boats are assumed.


     1. For 1 boat:

        3.5 nautical miles   8 hours   563 cu yd  _   15,764
                hour          day       nautical       cu yd
                                        mile            day
                                                of bottom sedi-
                                                ment disturbed

     2. For 100 boats working 100 days per year:

        15.764 x 103 cu yd   100 boats    100 days = 158. x 10
                      day       day         year        cu yd
                                                of bottom sedi-
                                                ment disturbed

III. Otter Board Trawling


     1. An average boat trawls 6 hours per day/100 days per

     2. Working speed of a boat is 3 knots.

     3. Each boat pulls one trawl with two 10 foot trawl doors.

     4. Area of bottom disturbed is 17 ft wide by 0.25 ft deep.
        (This equals 957 cu yd of bottom sediment disturbed per
        nautical mile.)

     5. One Hundred  (100) boats are assumed.


     1. For 1 boat:

        3 nautical miles   6 hours   957 cu yd  _  17,226
              hour           day      nautical      cu yd
                                      mile           day
                                              of bottom sedi-
                                              ment disturbed

     2. For 100 boats working 100 days per year:

        17. x 10  cu yd   100 boats   100 days  _   _n   ,n6
                   day  x      day  x     y¥IF  ~  1/0 x t°
                     J           11          cu yd
                                              of bottom sedi-
                                              ment disturbed


     I. Bureau of Land Management 1977 Estimates - from Environ-
        mental Impact Statement - PCS Sale Number 42.

        "...if a trench is 5 feet deep and 6 to 12 feet wide,
        and if a parabolic cross section is assumed, the pipe-
        line would disturb approximately 4000 to 8000 cubic
        yards of sediment per mile, some of which would be re-
        suspended  (p.664)."

II. From:  Shell U.K. Expro. 1977.  FLAGS Gasline Seabed
    Safety and Stability - Figure 7', "FLAGS Gasline Typical
    Trench Profiles," (p.2.).
    a.  Narrow Trench in Firm Soil  (e.g., clay)

                    4 METRES MINIMUM-
    1. Trench is rectangular.
    2. Pipeline is 36 inches in diameter.
    1. Trench depth:
       3 ft pipeline + 3.3 ft  (1 meter  (m)) above
       pipeline = 6.3 ft deep
    2. Trench width = 13.2 ft  (4 m)
    3. Amount of sediment disturbed per mile of trenching
       6.3 ft x 13.2 ft x 5,280 ft/mile
                 27 cu ft/cu yd
 cu yd

b. Wide Trench in Soft Soil  (e.g., sand)
                     •UP TO 20 METRES^

1. Assume area of trench is sum of areas of 2 identical
   right triangles  (A) plus rectangle B
2. Pipeline is 36 inches in diameter.
1. To calculate areas:
   a = 3 f.t  (diameter of pipeline)
   b = 66 ft  (20m)  - 3 ft    31.5 ft
   c = 3 ft pipeline + 3.3 ft  (1m) above pipeline = 6.3 ft
2. area of 2 right  triangles =
       31.5 ft x 6.3 ft = 198.45 sq ft
3. area of middle rectangle
       6.3 ft x 3 ft = 18.9 ft
4. total area of trench =
       198.45 sq ft -I- 18.9 sq  ft = 217.35 sq ft
5. Amount of sediment disturbed per mile of pipeline
       217.35 sq ft x 5,280 ft/mile _ 42,504
              27 cu ft/cu ydcu yd

Ill.  Miles of Pipeline Laid

      Each of these three quantities of sediment disturbed per
      mile was then divided into estimated quantities of sedi-
      ment disturbed by offshore activities  (Table 1, Column 1)
      to derive three relative values "miles of pipeline laid."
      These values are presented in Column 2 of the Table.
      For example;

           1.58 x 108 cu yd of sediment
disturbed by sea
(Table 1, Column 1)
           8000 cu yd sediment disturbed
           mile of pipeline trenched  (EIS 42)
                   =  2000 miles of pipeline

                          APPENDIX B

                   INDUSTRY'S PROCEDURES FOR


             Pipeline Industry Advisory Task Force
                George G. Hughes, Jr., Chairman


     Before proceeding with a discussion of the selection of OCS
pipeline routes, it is appropriate to briefly describe the gen-
eral development process and timing for offshore fields.  The
typical offshore field goes through several developmental stages
before any hydrocarbons can be produced.  Industry first makes
exploratory geophysical studies in the area designated by the
Bureau of Land Management  (BLM) for the proposed sale to deter-
mine which tracts contain geologic structures that might be con-
ducive  to hydrocarbon accumulation.  One part of the tract
evaluation process is the estimation of the transportation costs
from the area of the lease sale.  Due to the highly proprietary
nature of the data associated with each tract, the transporta-
tion cost study is usually based on the assumption that produc-
tion will originate in the approximate center of the proposed
lease sale.  Because most lease sales include tracts that are
geographically separated by 50 or more miles, pipeline routes
are selected on a very general basis only.  By necessity, this
initial study is very general in nature due to the lack of spe-
cific data such as hydrocarbon type, production rate, location
of the production facilities, etc., and consequently the calcu-
lated transportation costs are strictly "order of magnitude"

     Based on the results of the geophysical studies, Industry
nominates tracts in the general area of interest and the BLM de-
cides which of the nominated tracts will be offered for lease
and begins to prepare an Environmental  Impact Statement.  After
completion of the Environmental  Impact  Statement and Public
Hearings concerning the impact of the proposed sale, the lease
sale is held.

     At the lease sale, various  companies  or individuals compe-
titively bid on individual tracts,  utilizing a sealed bid pro-
cess.  Once a tract is successfully leased, the leaseholder be-


gins exploratory  drilling  using  a mobile offshore drilling rig
to test  for  the existence  of  hydrocarbons.  These mobile rigs
may be the floating  variety,  such as  ship-shaped and semisubmer-
sible vessels or  they  may  be  of  the bottom-founded variety, such
as the jack-up or submersible barges  often used in shallow

     Exploratory  drilling  is  a two-phase process.  In the first
phase, a geologic structure is drilled to confirm or deny the
existence of a hydrocarbon accumulation.  In the second phase,
if promising discoveries are  made, further drilling is done to
establish the extent of the field and to determine whether the
field can be developed commercially.

     Initial planning  for  pipelines is done by selecting some
very generalized  routes for a pipeline to serve the lease area.
Based on the best information available  (although admittedly
speculative), a hypothetical  platform is selected and a pipeline
route is chosen from the platform to  what would seem to be the
most likely  onshore  destination-of the hydrocarbons.  At this
stage, planning does not usually include any "on-site" surveys
in the field, but is done  using  offshore naviagation charts,
city, county.- and state maps, National Oceanic and Atmospheric
Administration  (NOAA)  quadrangles, OCS official protraction dia-
grams (where available), and  data that are available from the
exploratory  geophysical studies.  The maps consulted are of var-
ious scales  and are  used primarily to identify topographic de-
tails that would  assist or hinder in  the general location of the
pipeline.  In addition, the mapping is used to determine line
lengths  and  other physical details to aid in further technical
and economic evaluation.

     To  minimize  exposure  to  offshore hazards, the route is usu-
ally selected to  follow a  fairly direct path from origin to des-
tination, to the  extent that  this is  permitted by the natural
topography and shore approach.   The minimum offshore line length
is desirable because of high  maintenance costs and required in-

     Offshore pipeline corridors, by  reducing the areal extent
of the pipeline network, reduce  the potential for future finds
to be transferred via  a portion  of an existing system.  Corri-
dors are also not considered  desirable from either a construc-
tion or  an operation standpoint.  The congestion created by mul-
tiple parallel pipelines promotes problems, even onshore, and
the anchoring requirements of offshore equipment (see Figure
B-l)  both during  construction and maintenance operations present
a recurring  hazard to  existing pipelines.  Several well-planned
lines to shore which may be many miles apart, instead of a sin-
gle corridor or line, offer a major advantage for transporting
discoveries  made  at  some later date,  by offering trunk lines to


                        NO. 8
NO. 10
NO. 11
                                                                                                  NO. 12
                                                                                                DIRECTION OF
                                                                                                VESSEL MOVEMENT
                        NO. 5
                                                  NO. 4
                                                                                       NO. 2

shore in closer proximity  to  the  new discovery.   It is not pos-
sible to predict where  the new  discoveries will be when the
initial line  is laid, as proven by  experience  in  the Gulf of
Mexico.  Discoveries currently  made in the Gulf of Mexico can
often be transported via trunk  lines laid many years ago, and
the fact that there are a  number  of lines to shore spaced
throughout the Gulf offers an opportunity to lay  shorter lateral
connections than if there  were  only one or two trunk lines to
shore.  There have been many  discoveries in the Gulf of Mexico
that were not large enough to justify the cost of a long lateral
line, but which could be developed  because of  their proximity to
an existing trunk line.

     Other considerations  in  the  route search  include:

     •   A friendly landfall—(that is, one which is compatible
         with pipeline  construction and maintenance and with
         the  restoration and  maintenance of the shoreline; and
         one  which minimizes  onshore pipeline  impact areas.)
         Some problem areas evaluated and avoided to the extent
         possible are congested coastal areas, wildlife pre-
         serves, wilderness areas and other known sensitive

     •   Bottom conditions—Canyons, boulder areas, rock out-
         croppings,ordinance dumps, unstable  areas (such as
         mud  slide, sand wave,  and  faulting areas) and other
         identified obstacles are also avoided to the extent pos-
     •   Ability to eliminate outside forces on the pipeline.
         Burial of pipelines  in shallow water  is  usually neces-
         sary to meet permit  requirements and  helps to minimize
         damage from external forces.  Ship anchorages and other
         areas with a high potential for damage to a pipeline are
         avoided; and
     •   Ability to minimize  effects of the pipeline on the en-
         vironment.  Environmentally sensitive areas such as
         oyster beds are considered.

     Once exploratory drilling  confirms the existence of hydro-
carbons in commercial quantities, platform and production faci-
lity construction in onshore  fabrication yards begins.  After
platforms are constructed,  they are transported to the desired
offshore location, erected, and attached to the ocean floor with
steel pilings.  After these stages  are complete,  development
drilling begins.  The total time  required from the confirmation
by exploratory drilling of a  commerical field  to  the initiation
of production usually ranges  from two to three years.  Of course,
these timing  figures are extremely  sensitive to the economic,
business, governmental  and social climates prevalent at the time
of development.  For example, material shortages  and regulatory


and legal delays can drastically increase the time required to
develop an offshore area.

     After the confirmation of a commercial discovery, one of
the^critical activities associated with field development is the
design and construction of a pipeline system on a timely basis.
Once exploratory drilling confirms that the field can be devel-
oped ^ commercially , the preliminary routes delineated for trans-
porting the oil and gas are evaluated in detail, considering all
engineering and construction factors as well as minimizing all
potential environmental disturbances.  At this time, suitable
high resolution topographic and geophysical route surveys are
made to aid in the selection of the final route and for permit
application.  All of the route selection factors described above
in the initial planning stage are now reconsidered based on "on-
site"  surveys  (described in detail below) and a re-evaluation of
all available data.

     The final planning of the optimum transportation system
will also include a survey of other companies who may be involved
in developing fields in the discovery area, to obtain production
estimates for their fields.  From this information, a forecast
of overall discovery area production over time—a throughput pro-
file—can be developed and estimates made of the pipeline capa-
city necessary to support the entire development area.  Common
pipeline facilities are desirable when feasible, because lower-
cost transportation can usually be provided if all producers in
an area use common lines (which take advantage of economies of

     This throughput profile  also determines the pipeline's
optimal economic size, an important parameter because of the
high cost of offshore construction.  Once operational, a line
that is too large will require a higher revenue to earn a rea-
sonable return on the investment; a line that is too small will
require prorating the available capacity or investing more money
to install new pipeline facilities.  Every effort, is made,
therefore, to optimize the line size.  This evaluation is also
tempered with consideration of future unforeseen needs.

     As it normally requires about a year to obtain large quan-
tities of steel line pipe, it is important that pipeline routes
and pipe sizes be established as early as possible in the de-
sign process so that line pipe and other critical materials can
be ordered.

     Once a route is selected, design criteria are developed as
a basis for the design of the pipeline.  Along with the infor-
mation gained from the surveys, these criteria are used to pre-
pare an application for a permit for construction.  These design

parameters are further expanded into a full set of Design and
Construction Specifications which satisfy applicable regulatory
authorities.  These specifications are also used to secure con-
tract bids for construction and are ultimately used by inspec-
tors during the construction of the pipeline.

     During the course of the construction, additional engineer-
ing, surveying and inspecting are required to see that the pipe-
line is constructed in the manner and location specified.  After
construction is completed, an "As-Built" Survey is made to docu-
ment the actual location of the finished pipeline.  "As-Built"
Survey results are mapped on a scale of 1" = 4,000' to conform
to the Official Protraction Diagram.


     When the need to construct a pipeline has been established,
suitable route surveys are made to determine the possible exis-
tence of hazards and archaeological remains and to aid in the
selection of the final route and* the preparation of permit appli-
cations.  These surveys are usually planned on OCS Official Pro-
traction Diagrams with a scale of 1" = 4,000' and are planned to
meet the BLM1s requirements for a geophysical hazard survey and
an archaeological survey.  Surveys performed are:

     •   Route Survey—Centerline and one offset line each side.
                       Offset lines for use in minor reroutes
                       during construction are generally about
                       1,000 feet distant from centerline.  Lo-
                       cation accuracy ranges from about 6.6
                       feet (2 meters) to 49.5 feet (15 meters).
                       General survey techniques employed are
                       Range/Range, Parabolic and Satellite

     • Bottom Profile—Usually conducted with a fathometer or
                       other similar type instrument on the cen-
                       ter line and both offset lines.

     • Sub-bottom
              Profile—Miniseismic record with penetration to
                       about 25 to 50 feet.
     •   Magnetometer—Determines magnetic anomalies such as
                       pipelines, cables, wrecks, junk, debris,
                       explosives, ammunition, etc.  Depending
                       on survey conditions and anomaly size,
                       detection may range from point location
                       to 200 feet laterally.

     •  Hazard and
               Surveys—The information gained from the above
                        surveys is correlated and studied to
                        develop a hazard survey.  These data
                        are also examined by an archeologist
                        to ascertain pertinent archeological
                        facts to a water depth of about 200

     The equipment to conduct these surveys can be housed in a
boat 75 feet to 85 feet in length so that all surveys are con-
ducted on a specific course simultaneously.  However, the wind/
wave/sea-state conditions usually dictate the vessel size.  In
the Gulf of Mexico, this would be generally in the 100-foot
long class where in the North Atlantic, a deep-draft vessel of
about 200-foot length might be required.

                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
                             3. RECIPIENT'S ACCESSION-NO.
         PROBLEMS  AND
   May 1980
                             6. PERFORMING ORGANIZATION CODE
  Ann M. Gowen, M.J.  Goetz & I.M. Waitsman
                             8. PERFORMING ORGANIZATION REPORT NO.
  Coastal Programs Division
  New England River  Basins Commission
  53 State Street, 1st floor
  Boston, MA  02109
                              10. PROGRAM ELEMENT NO.

                                  INE 826
                              11. CONTRACT/GRANT NO.
                                 IAG No. 78-D-X0063
  Industrial  Environmental Research Lab.
  Office of Research and Development
  U.S. Environmental Protection Agency
  Cincinnati, OH   45268
             - Cinn, OH
                              14. SPONSORING AGENCY CODE

       The report discusses the environmental  and  fisheries problems associated with
  offshore pipelines.   The report focuses on how these problems can be addressed
  during the pipeline  planning and route selection process.
       Geologic hazards are highlighted as the major factors related to pipeline fail-
  ure which can be addressed through the pipeline  routing process.  Habitats and
  ecosystems are particularly susceptible to installation-related disturbances.  These
  areas as well as those where geologic hazards  are most likely to be encountered are
       Fishing problems highlighted include loss of access to fishing areas due to
  pipelines both from  platform to shore and between platforms.  The effects of
  obstructions on bottom fishing gear are also considered.  The concept of pipeline
  trenching for safety and stability is discussed.
       Finally, criteria to use in analyzing a proposed pipeline route are presented.
  Topics discussed include general industry siting criteria, geologic and environ-
  mental areas to avoid in pipeline siting and methods for minimizing unavoidable
       The report is designed to be used by scientists or engineers involved in off-
  shore petroleum pipeline planning.
                                KEY WORDS AND DOCUMENT ANALYSIS
                                              b.lDENTIFIERS/OPEN ENDED TERMS
                                           c. COS AT I Field/Group
 Natural Gas
 Continental Shelves
                  Route Selection Criteria
                  Trenching & burial
                  Fishing Industry Conflic
                  Environmental Sensitivit
                  Geological Sensitivity

                 19. SECURITY CLASS (ThisReport)
              21. NO. OF PAGES
                                              20. SECURITY CLASS (This page)
                                                                         22. PRICE
EPA Form 2220-1 (9-73)
                                                                    US GOVERNMENT PRINTING OFFICE 1980-657-146/5690