EPA-R2-73-116
FEBRUARY 1973 Environmental Protection Technology Series
Removal of Oil
from under Piers
^eo sr^
Office of Research and Monitoring
U.S. Environmental Protection
Washington, DC 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-116
February 1973
REMOVAL OF OIL FROM UNDER PIERS
by
Bernard Katz
Project 15080 FVP
Project Officer:
Frank J. Freestone
Edison Water Quality Research Laboratories, NERC
Edison, New Jersey 08817
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office. Washington, D.C. 20J02
Price 65 cents domestic postpaid or 45 cents QPO Bookstore
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EPA Review Notice
This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessary reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
ii
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ABSTRACT
While this report deals primarily with methods of extracting oil
from under piers, it is recognized that simple extraction is not
enough, and that the oil should also be removed from the environ-
ment. Therefore, considerable attention has been paid to driving
the oil out in such a way that it can be picked up. The primary
means of extraction are by the establishment of artificial currents
under the contaminated pier, and a number of methods are suggested
to cope with various types of pier substructure.
Some other possible approaches, not involving flushing by artificial
currents, are also discussed. These include: uses of chemicals,
sinking, air entrainment and entombment.
A generalized description of pier structures is also included.
This report was submitted in partial fulfillment of Project 15080 FVP,
under the partial sponsorship of the Water Quality Office, Environmental
Protection Agency.
iii
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CONTENTS
Section Page
I Conclusions 1
II Introduction 3
III Piers 5
IV General Aspects of Oil Removal from Under Piers 7
V Methods Not Requiring Artificial Currents 9
VI Artificial Currents 11
VII Fire Streams 13
VIII Methods of Generating Under Pier Flow
Using Fire Streams 15
IX Methods of Applying Artificial Currents
Under Piers 17
X Acknowledgements 27
XI References 29
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FIGURES
Number Page
1 Use of Under Pier Boom 18
2 Clearing a Cul-de-Sac 22
3 Drawing Oil Out of an Embayment
by Entrainment 23
VI
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SECTION I
CONCLUSION
The methods described herein may be used to flush the area under almost
any structure built over water and supported by piling, provided there
is enough current generating capacity. Options other than flushing have
also been suggested. However, for any of these methods, adaptations to
particular situations will be required, and the on-scene coordinator
should thoroughly familiarize himself with the details of the structure
and the surrounding area. Also he should maintain a constant vigil to
be sure that his operation is having the desired effect.
No operation that extracts oil from under a pier can be considered
successful if most of the oil is not picked up, and all the suggested
methods have been devised with this in mind.
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SECTION II
INTRODUCTION
In any harbor there are likely to be numerous piling supported
structures beneath which spilled oil will collect. These will be
places where there is little or no flushing by the natural current,
and usually they will be inaccessible to pick-up devices. There are
several approaches to the problems posed by such oil; however, one
should realize that oil under a pier is less destructive to the
environment than the same oil would be if it were staining the shore-
line, coating the bottom, or dispersed in or floating on the surface
of open water. In short, unless the expelled oil can be contained
and subsequently picked up, it is better to leave it under the pier.
A quantity of oil seeped out over a long period of time will be less
noxious than the same quantity released all at once. This does not
mean that no attempt should be made to remove oil from under a pier;
rather it means that efforts at containment and pick-up should take
precedence over extraction. For this reason, although the main thrust
of this study has been towards getting oil out from under piers, con-
siderable attention has been paid to doing this in such a way that
control and pick-up is possible. However, the use of containment and
pick-up devices has not been treated in detail since these subjects
are amply described in other manuals, and such treatment is beyond the
scope of this one.
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SECTION III
PIERS
Although piling does affect the flow of water and oil, in most cases
this effect causes minor difficulties when compared with other
problems encountered in removal of oil from under piers. The effect
of piling becomes a relatively severe problem only: in the vicinity of
specialized structures, such as ferry slips, where the spaces (if any)
between piles are narrower than the piles themselves; when the oil is
extremely viscous, such as bunker C in cold weather; or where there is
a lot of floating debris that can clog the spaces between the piles.
The main problems presented by piling arise from the fact that piling
is almost always too dense to permit the maneuvering or manipulation of
any reasonable sized equipment in its midst.
The most common type of pier substructure in New York Harbor consists
of rows of piling which run transverse to the long axis of the pier,
whether this long axis is perpendicular or parallel to the shore. The
spacings between rows are from about 10 to 25 feet; between piles with-
in a row the spacings average from about 1 to 5 feet. These spacings,
of course, depend on the weight of the pier, the purpose for which it
was designed, the structural material (wood, steel, concrete), and the
thickness of supporting members. There are varying amounts of cross-
bracing and cribbing between piles, but most of the more common pier
types have some horizontal beams between piles that just clear the water
at low tide and are submerged at high tide. Most often they run along
a row of piles, but it is also common to find them stretched between
rows. Pier corners, especially of piers built for the mooring of
large ships and barges, are often very heavily constructed of thick
clusters of adjacent piles. Also the ends of piers and often the
sides too, are more heavily constructed than other parts. Many pier
ends are faced with solid wood or metal sheathing. Under some piers
the piles in a row tend to be grouped, with spaces between the piles
in a group being about one foot, and spaces between groups being
several feet. Many piers have fire walls underneath. Typically
these: take the place of one or more of the transverse rows, are
made of concrete, are supported by piles so that they extend down
almost to the low tide water level, and are placed 120 to 150 feet
apart.
Serious difficulties in the removal of oil from under piers can arise
from one or more of the following factors:
(a) Large size with respect to the means available for generating
water movement. One of the newer piers in New York Harbor covers 15
acres, and there are larger ones. Also there are many long stretches
of roadway supported by piling.
(b) Limited accessibility because of shallow water, adjacent structures,
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restricted channels, or moored vessels.
(c) Complex configuration; the plan views of many shore side installa-
tions exhibit varying degrees of complexity, from simple finger piers
to intricate juxtapositions of platforms and wharves. The shoreward
ends of many piers abut onto platforms or roadways which are themselves
on piling, rather than onto solid bulkheads or shoreline. This
provides additional places for oil to collect, as well as possible
escape routes for oil during cleanup operations. Some pile-supported
structures abut bulkheads on two or even three adjacent sides, thus
forming covered pockets or embayments. In most places where oil is
likely to collect, it will be impossible to establish a flow which
goes directly through without some diversion.
(c) Low clearance; the under sides of many structures are below the
water surface for part of the tidal cycle, and only a foot or so
above it at other times.
In practice, any possible combination of these obstacles can arise.
When coping with a particular set of problems, various types of
equipment will be required. In general, the larger the pier, the
larger will be the amount, size, and power of the equipment needed.
Some structures are big enough to exceed the capabilities of the
equipment presently available for driving the oil out. Thus, of the
above difficulties, large size is the one that will prove the most
intractable. While it will often be possible to clear a large area
by dividing it into sections and doing one section at a time, in many
cases it will not be possible.
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SECTION IV
GENERAL ASPECTS OF OIL REMOVAL FROM UNDER PIERS
Because the buildings along a shoreline can vary so widely in size,
substructure, accessibility and configuration, it is not possible
to develop a set of standard procedures for cleaning oil out from
under them. However, there are a number of general techniques that
can be applied to a wide variety of situations. These are described
below. Which to use will depend on the circumstance, and a proper
selection will require a detailed knowledge of the area to be cleared.
Therefore, the very first step should be to make a detailed examina-
tion of the pier's substructure from a small boat. Since the area
under many piers, especially those where oil is likely to become
trapped, is often very dark, powerful hand lanterns or flood lights
will often be necessary for an adequate inspection. The need for
such an inspection from a small boat cannot be stressed too strongly,
because the details of the substructure must be known if the operation
is to be effective, and these are often impossible to ascertain from
the deck of a fire boat or tug boat, from shore, or from a neighboring
pier. For example: For piers running parallel to and abutting with
a bulkhead it is necessary to know the distance between the bulkhead
and the outer edge. It is important to know if there is cross bracing
in the path of any proposed flow. Fire wall ends are often recessed
from the pier edge, and cannot be seen by an observer who is not at
the edge of the pier and well below the platform level. Conversely,
there are supports along some pier edges which, at a short distance,
appear to be the ends of fire walls; that they are not can only be
determined from closer inspection. Since we are concerned here with
trapped oil, that is, oil which is not rapidly escaping or spreading,
there is less need for haste, and we can take advantage of this fact
to plan a more effective operation from the start.
There are three phases to any successful removal operation: Extraction,
containment, and pick-up.
Pick-up involves the use of some sort of skimmer, and is relatively
straightforward. Except in rare cases where the piling is very open,
the only oil that can be picked up will be that which has been
extracted from under the pier and contained by boom. There are a
number of skimmers on the market. For all of them the efficiency of
their operation depends on the concentration of oil in their vicinity.
Hence the arrangement of boom and skimmer should be such that oil
will tend to concentrate around the pick-up point. In practice,
this means that the skimmer should be located as close as possible
to a corner or apex towards which the flow is established.
Boom performs a dual function. It not only prevents the escape of
oil driven from under a pier, but it also must channel this oil
towards the pick-up device. Sometimes boom can be used to keep a
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cleared area from becoming recontaminated. In general this requires
that the boom be deployed under the structure, and "will only be
possible where:
(a) There is enough overhead clearance and space between piles to
allow passage of a small boat. (A two-man rubber raft can be used.)
(b) There are no cross braces in the way.
(c) There is no current to force the boom hard up against a row of
piles.
For use in this way a boom having "internal" flotation is better than
one having detachable flotation, since it is less likely to snag.
Where the emergent flow is intercepted by the boom, its velocity
should be less than a half knot (it can be slightly higher where the
flow is not perpendicular to the boom), because larger velocities will
cause oil to be carried under the boom. In any case there is no need
for the emergent flow to have a large velocity. A slow, barely percep
tible drift into a gradually narrowing corner or pocket will deliver
all the oil that most skimmers can effectively handle. For example:
One small but effective vacuum type skimmer picks up fluid at a rate
of 1.5 ft^/min.The percentage of oil in this depends on the thickness
of the oil layer under the suction mouth. (The pickup rate is 15 ft^/m
if the mouth is completely immersed, but it cannot be used in this way
unless the oil layer is a few inches thick.) A 50 ft wide oil slick,
one tenth of an inch thick, being channelled towards a pocket where
this skimmer is operating need move at only 0.04 knots to keep this
skimmer well supplied.
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SECTION V
METHODS NOT REQUIRING ARTIFICIAL CURRENT
The main approach to the problem of oil trapped under piers is
flushing with artificial currents, but before discussing this,
there are several other options that deserve mention:
Strong air flow would be capable of dragging oil from under a pier.
It has an advantage over artificial water currents in that it would
produce very little turbulence and would thus cause very little
mechanical emulsification of the oil. In addition to a large wind
generator, heavy curtains might be required in most cases to channel
the air flow, and boom and skimmers would still be required to
channel and remove the oil. The necessary equipment is probably
unavailable in most harbors; therefore, this method is not one
suitable for general use.
Chemical solvents or dispersants would remove oil from under a pier,
and their application would be relatively easy. But the oil and
chemical would soon spread in substantial concentration through a
sizable volume of nearby water. The damage to the environment would
be increased rather than reduced. Even though some of the recently
developed dispersants are practically non-toxic, the oil would still
retain most of its harmful properties which are better restricted to
the area under the pier or they cannot be removed entirely. Therefore,
this method is the least acceptable of all, and would be illegal in
many cases.
It is also possible to sink the oil. This method is worthy of con-
sideration because the sediment under most piers, especially in
commercially active areas, is already badly contaminated, and further
damage to this relatively small and useless area might be preferable
to the damage wrought by the same oil elsewhere. A similar approach
is "entombment" of the oil by enclosing it with sheathing. Though
this may seem like doing it the hard way, the fact is that in many
cases it will be no harder or more time consuming than extraction
and pick-up of the oil. The sheathing need not extend from the
pier's deck down to the sediment; a. few feet above high water level
to a few feet below water level would be enough. There would be a
bonus in that the sheathing would protect the area from contamination
by subsequent spills in the vicinity. While it is true that "entombed"
oil may eventually seep out, and sunken oil will dissociate and dis-
perse, this will take a relatively long time, during which there
will be the opportunity for biodegradation of the oil; a process
which can be enhanced by seeding with the proper type of organisms
and aeration of the water under the pier.
Under certain conditions, a chemical surface collecting agent (SCA)
can be used to move oil from beneath a pier. Surface collecting
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agents are substances which reverse the tendency of most oil to
spread on water, and instead cause the patches to contract and
form "lenses". They do this by changing the surface tension balance.
To remove oil from under a pier, the SCA must displace the oil
rather than cause it to contract. This can be accomplished only
if the SCA is restricted to one side of the oil slick. Once the
SCA completely surrounds the oil patch, there is no longer a
difference in spreading force on either side, and it can no longer
produce any displacement. Since SCA spreads far more quickly than
most petroleum products that are likely to require removal, it is
important that there be no path through the oil slick or along its
edges by means of which the SCA can spread to the outer side. In
practice this means that SCA can only be used for flushing when
there is a continuous sheet of oil covering an embayment or cul-de-
sac from wall to wall. The SCA must be placed in the deepest corner
or against the farthest wall. Unless there is an access hole properly
located this will require that a small boat be taken under the pier
for placement of the SCA. It should not be poured directly onto the
oil. Rather a small patch of water must be cleared into which the
SCA is poured. This can best be done by vertically agitating a
plunger (a small plate attached to the end of a pole so that it is
perpendicular to the pole's axis) in the water near the surface.
This work with surface collecting agents has been limited to labora-
tory experiments and tests made on small spills of opportunity. These
have not enabled a determination of the quantitites of SCA needed to
achieve various displacements with different types of oil. However,
the amounts needed will be small because the SCA need only spread in
a very thin layer. For open water the prescribed dosage is two
gallons per linear mile of oil patch circumference. SCAs do not work
on thick, waxy oils such as Bunker C, or in waters having a high
concentration of detergent. Some of them are also ineffective in
cold weather. While wind and currents can interfere with the action
of an SCA, this is not likely to be a problem in the under-pier
areas where oil collects.
The use of surface collecting agents, dispersants, and sinkants is
now strictly regulated and they can only be used when so authorized
by the On Scene Coordinator (OSC). Entombment of the oil also requires
OSC approval since regulations now require that the oil be removed from
the water as quickly as possible.
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SECTION VI
ARTIFICIAL CURRENTS
The primary tools for extracting oil from beneath piers are artificial
water currents. There are two common means of generating these: Fire
streams and propwash. The different methods of generation produce
currents with slightly different characteristics: The first, of
course, is size. A boat's propellers are far more efficient genera-
tors of water movement than its pumps, even when they are powered by
the same engines. The second is shape. A fire stream's induced
current spreads about 80 degrees from the impact point of the stream.
The current pattern produced by propellers has a much smaller angle
of spread, only 5 to 10 degrees, though it is much wider to start
with. The third difference is in the nature of the turbulence.
Propellers produce larger eddies than streams of water even when
the energy outputs are comparable. And propeller turbulence has
a much stronger vertical component which extends much deeper. This
is important because turbulence causes mechanical emulsification of
the oil, and the large deep eddies can drag the oil droplets down
well below the skirt depth of even the largest boom. These droplets
have a natural tendency to rise, and will begin to do so as soon as
the turbulence subsides; however, the smaller droplets rise very
slowly. Thus, while it is possible to contain much of the oil set
in motion by propwash if the containment boom is located far enough
from the propellers, a substantial portion inevitably escapes. For
this reason, the use of propwash should be limited to these situa-
tions where fire streams are clearly inadequate, or where no fire
streams are available.
Despite these differences, the methods of applying artificial currents
are essentially the same whether they are generated by fire streams-
or propellers. However, fire streams are much easier to position
and control. In both cases, the boat must be moored, but the mooring
required for fire stream operation is much lighter and hence more
adaptable. Also monitors can be aimed, whereas to direct propwash
the entire boat must turn, and this will not always be possible.
While it is true in any clean-up operation that the coordinator should
constantly observe the effect of the various measures being employed,
it is even more important when using induced currents, because slight
changes in the parameters of the operation can change it from an
effective one to an unproductive, or even a counter productive one.
For example: A change in the wind can alter the impact point and/or
the strength of the fire stream; it can also affect the flow of oil
and the configuration of the boom array. Though we are concerned
with areas where the natural currents are virtually nil, they could
still be an important, though erratic and unpredictable, factor. It
takes time for an induced current pattern to stabilize, and a
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procedure that has been working well initially may become unsatis-
factory when fully developed. The rise and fall of the tide can
open or -close channels. In short the coordinator should repeatedly
assure himself that the effects of his operations are the ones he
desires.
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SECTION VII
FIRE STREAMS
In using fire streams at an oil spill, it is important to realize
that it is not the fire stream itself which controls or moves the
oil, but the current set up by it. In fact the fire stream should
not be allowed to impact on, or very close to the oil because, if
it does, the oil will be emulsified. To minimize this the impact
zone should be kept at least 50 feet from the oil slick when using
large caliber, high pressure streams. For under pier work, the
distance over which a fire stream generated current is effective
depends very much on how it is used as well as on its output. But
effective flow can generally be achieved a few hundred feet from
the impact zone. Though fire streams have produced useful oil
movement at distances of about a thousand feet, this was under ideal
conditions, and such ranges cannot be expected in general.
For purposes of controlling oil slicks, the useful output of a fire
stream is its continuous discharge of momentum. This momentum dis-
charge—the time rate of momentum output—is proportional to the
product of the nozzle tip area and tip pressure (velocity head).
It is, in fact, equal in magnitude, but opposite in direction, to the
reaction force on the nozzle. Unfortunately, the entire momentum
output of the tip is not usable. There are two reasons for this:
a) The fire stream usually enters the water at an angle. Therefore,
it has a horizontal and a vertical component. Only the horizontal
component is useful for the control of floating oil. The smaller
the angle of entry, the larger the horizontal component will be.
Decreasing the height of the tip, and increasing the pressure have
the effect of reducing the angle of entry. For any particular
height and pressure the angle will be the smallest when the tip is
aimed horizontally, and will increase as the angle between the nozzle
and the horizontal (whether elevation or depression) increases.
b) A portion of fire stream's momentum is lost to air resistance.
Although the process by which this happens is not fully understood,
it is known that, with the same pressure, air resistance increases
with increasing tip size and, with the same tip, air resistance in-
creases, at an even faster rate, with increasing pressure, d' Also
droplets are much more affected by air resistance than solid streams,
and the smaller the droplets the more they are affected. Thus nozzles
which tend to break up the fire stream into fog or fine spray are
generally ineffective. By the same token, solid streams should be
operated at pressures well below those at which coning occurs.
Of course, the longer the fire stream, the greater the effects of
air resistance. Thus, while the smallest angle of entry is achieved
when the nozzle is aimed horizontally, a slight downward angle of aim
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would shorten the fire stream, and the increase of momentum loss due
to increased angle of entry would tend to be offset by the decreased
loss due to the shorter fire stream. On the other hand, an upward
angle of aim increases the fire stream length and the air resistance
loss as well as increasing the angle of entry. Thus, depressing the
tip from horizontal by several degrees will have little effect, but
elevation from the horizontal produces rapid deterioration.
The fire stream establishes a fan-shaped current structure spreading
about 80 degrees from the impact zone. If this current structure
has components directed opposite to the natural current, a turbulent
rip zone will develop at its upstream edge. The distance from the
impact point and width of the "front" covered by the rip zone in-
crease as the horizontal momentum input to the water increases, and
as the natural current velocity decreases. In open water the net
flow in the rip zone is tangential to it and directed away from a
horizontal axis drawn parallel to the fire stream. But, when confined
in a channel so that the rip zone extends across the entire width of
the channel, there is no net flow in the rip and it becomes a null
current zone.
If the natural current is small, less than one half knot, the turbu-
lence of the rip zone is not intense, and it will be a barrier to
floating oil. Under these conditions the zone can be used to block
or direct the flow of oil. In general, this will be accomplished by
directing the fire stream in the direction of desired oil movement.
If the natural current is large, the turbulence of the rip zone will
be intense, and it will not be a barrier to floating oil. Under
these conditions, the fire stream may only be used to divert the oil,
usually by directing the stream at right angles to the direction of
the natural current. While these principles are generally applicable,
the majority of cases where it is necessary to apply artificial cur-
rents to remove oil from under a pier will require a diversion of the
current because a direct path between the source and the possible exits
for the oil will be impossible.
For a somewhat more detailed discussion of the use of fire streams in
oil spills see reference (2).
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SECTION VIII
METHODS OF GENERATING UNDER PIER FLOW USING FIRE STREAMS
Once .it has been determined to use artificial currents to flush an
under pier area, the two immediate problems are: How to establish
the flow, and where and in what direction to establish it. The
latter depends on the configuration of the area and will be discussed
subsequently.
The simplest way to establish a current is by mooring the boat to
an adjacent structure in a way that will permit its fire streams
(or propwash) to be directed as needed to set up the desired flow.
Unfortunately, it will often be impossible to find a suitable mooring.
The adjacent pier, if any, may be poorly oriented or too far away.
Though the impact zone does not have to be—and in most cases should
not be—at the edge of or under the pier being flushed, the fire
stream may not be able to span the distance with enough reserve
momentum to establish a sufficient flow. A fire stream's range depends
mainly on tip pressure and elevation. For any pressure the range can
be increased, up to a point, by elevating the tip from the horizontal.
But, if the angle of elevation exceeds several degrees, the effective-
ness of the stream as a current generator suffers. For a 3-inch tip
operating at 150 psi the maximum distance between the tip and the
impact zone, consistent with the generation of an effective flow, is
about 130 feet. In the absence of any natural current this will pro-
duce an effective flow extending about 300 feet from the impact zone.
Thus, under nearly ideal conditions we can expect to move oil at a
distance of about 430 feet from the monitor. The presence of even a
slight wind or a miniscule current from any direction except behind
the monitor will substantially reduce this distance.
Where it is not possible to operate effectively from an adjacent
pier, it may be possible to moor directly to the contaminated pier.
If the fire streams are to be directed perpendicular to, or at a large
angle to the pier edge, the boat must be held 50 to 100 feet away from
the edge with long mooring lines. The reaction force on the monitors
will be sufficient to hold the boat out, but it may be necessary to
use the engines and rudder to, compensate for yaw. If only the bow
monitor is used in conjunction with a single bow mooring line, the
thrust of the reaction force and the pull of the mooring line will
tend to assume the same line of action, and the mooring line may get
in the way of the fire stream. Two mooring lines to separate ballards
or cleats, with the fire stream directed between them, will avoid
this. Fore and aft mooring, with the boat parallel to the pier
edge, will permit the use of additional monitors and also of rail
pipes.
If under pier pipes are available, the fire boat can be moored
close to the pier. Since the nozzle is now at the edge of the pier
15
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it should, in general, be as close to the water surface as possible.
However, if the pier is large and the oil has receded from the edge
of the pier, the impact zone can be advanced by elevating the tip.
For some applications it would be better to have the tip at, or
slightly below the surface; these are described in a later section.
Use of hand held hose lines from small boats is the most versatile
method of generating flow under piers. It involves more effort, but
it can be used in many situations where other methods cannot, such as:
where there is no suitable mooring near enough; where the fire boat
cannot approach the pier because of obstructions or shallow water;
where (if the piling is not too dense) it is desirable to establish
the current deep under a large or complex pier. The only limitation
is the amount of hose available. If stand pipes or land pumpers are
available, it is not even necessary to have a fire boat present.
Because the effectiveness of the streams depends so much on the dis-
charge, the largest hose, tip, and pressure consistent with safe opera-
tion should be used. We have used a 2-1/2 inch hose with a 1-1/4
inch tip operating at 60 psi tip pressure without any difficulty.
However, when in operation both the tip and the small boat will have
to be secured. The boat should be secured sideways between piles by
fore and aft painters. The tip, operating between the piles, can
be secured by one or more hose straps or pieces of line. Reaction
force on the tip will be about 150 pounds (1-1/4 inch tip at 60 psi).
If the boats gunwale is fairly sturdy, the hose strap can be hooked
directly to it. The line or hose strap may also be attached to parts
of pier's substructure, but, if attached to piles, two lines to
separate piles will be needed. In all cases the attachment of the
line to the hose should be far enough behind the tip so that the tip
is just outboard of the gunwale.
The hose must be floated. If the hose is not to be taken under the .
pier, or if the pier's substructure is free of subsurface snags,
several large floats are adequate and quicker to attach. But in most
cases, it is better to use smaller floats more closely spaced. Quart
size floats with 3 to 4 foot spacings and an additional float at the
brass coupling supported the 2-1/2 inch hose very well. To further
reduce the possibility of snagging, the floats should be attached
with their long axis parallel to that of the hose. This can be done
with friction tape or with string; there appears to be no reason to
prefer one over the other. Because it is so much easier to handle
uncharged hose, it is better to affix the floats and play out the
hose before applying pressure. However, most fire hose is flat when
uncharged and round when charged, and the method of affixing the
floats must be able to accomodate the change in dimension. With
string this is done by first tying the string around the hose using
a square knot and leaving ends long enough to encircle the float and
tie another square knot. With tape, make a figure "8", lashing with
alternate clockwise turns around the hose and counter clockwise turns
around the float (or visa versa) and finish with a few turns around the
tape intersection between the hose and the float.
16
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SECTION IX
METHODS OF APPLYING ARTIFICIAL CURRENTS UNDER PIERS
Longitudinal Flushing
If it is possible to do so, the best way to flush the area under a
pier is to establish a flow perpendicular to the pier's long axis.
Attempts to generate a current down the length of the pier will
generally be far more difficult and far less effective. There are
two reasons for this. The preferred direction of flow is parallel
to the rows of piles, and these run perpendicular to the long axis
for almost all piers. This is not so much because of piles them-
selves as it is because of the cross-bracing, which is much more
dense in a row than it is between rows. Many piers have fire walls
underneath; these almost always run perpendicular to the long axis
of the pier, and would permit longitudinal flushing only at dead
low water. Second, even with fairly open piling, most piers are
too long. Pier lengths well over 600 ft are common, while the effec-
tiveness of fire stream generated currents usually vanishes between
300 and 400 feet from the impact zone for the larger monitors. Prop-
wash may be capable of longitudinal flushing under long piers which
do not have transverse fire walls. In using propwash, the thrust of
the propellers should be at an absolute minimum initially, and
gradually increased as the edge of the oil recedes down the length
of the pier.
For longitudinal flushing, boom should be deployed along both
sides of the pier. The far end is assumed to be closed by a bulk-
head or shoreline (if not it will have to be boomed) and the skimmer
is located in one of the far corners. In the final stages of the
operation, smaller streams from hand lines will be useful in channel-
ing the remaining oil to the skimmer.
Transverse Flushing
Since currents generated artificially by boats have effective widths
from about twenty to about 200 feet (depending on how they are used
and how they are generated), while pier lengths often exceed 600 feet,
flushing under a pier with transverse currents will almost always be
a piecemeal task. The essentials of the operation are as follows:
The current is generated on one side of the pier, and the boom and
skimmer array is situated on the opposite side so as to intercept,
concentrate, and pick up the emerging oil. After a section has been
cleared, the current generator on one side, and the boom and skimmer
on the other side are moved down to the next section. When proceeding
in this way, it is necessary to prevent the section just cleared from
becoming recontaminated. If the artificial current is broad, this is
17
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MONITOR
• /
Co p o o/d
///// 1
/ / /
(o o o'cy d
/ / /
l>r-^~^~-^~-^l
o o o ovp c
O O O O Q C
000
ANCHOR
FLOAT
CONVENTIONAL
BOOM
FIGURE I
USE OF UNDER PIER BOOM
18
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accomplished by making each section about half the width of the
current. If the current is not wide, it will be necessary to
operate an auxiliary current in the section just cleared. The
rows of piles do inhibit broadening of the induced flow; therefore,
if the flow is being generated at the edge of the pier by under
pier pipes or hand lines, it will generally be possible to clear
only one aisle at a time. However, if a large monitor impacting
about 30 to 50 feet from the edge of the pier is used, the artificial
current will effectively span three or four aisles before it goes
under the pier. If it is possible for a small boat to pass under
the pier between rows of piling, boom may be deployed to protect
the cleared sections.
The collection boom will "belly" away from the pier, with the apex
of the belly near the strongest part of the emergent flow. If only
one current generator is used, the apex will be roughly opposite
the generator, if two are used, it will be opposite a point between
them. The array should be adjusted so that the skimmer is as close
as possible to the apex. If the emerging oil tends to collect
uniformly along the boom rather than being channelled towards the
apex, the belly should be deepened by slacking the boom. To deepen
the belly it may prove necessary to hold the boom and skimmer out
by means of a line to a nearby structure or to an anchored float.
If, for some reason, it is not possible to obtain a deep enough
belly, small hose lines can be used to establish a flow along the
inside of the boom towards the skimmer. In this case it will be
easier to locate the skimmer more to one side of the boom array,
establishing as much of a pocket there as possible, and operate
the hand line from the other side.
The procedures just described are suitable for a pier much longer
than it is wide, having bulkhead or shoreline on one or both ends,
and open water on both sides. Such piers are comparatively easy
to flush out because it is possible to establish a direct flow
entering on one side and emerging on the other. Since most such
piers extend into a channel where there is a natural current, oil
will not usually become trapped under them except near the shore-
ward end. In general, a pier under which an artificial flow can
be easily established will be subject to flushing by natural
currents. Conversely, piers not subject to natural flushing,
those under which oil is prone to collect, will be the most
difficult to clear. The following procedures have been developed
for such cases.
Under Pier Boom
Many piers and over-water roadways run parallel to and abut with
a shore line or bulkhead. The only possible exit for a flow
directed under such a structure is on the same side as the
entrance, but any flow so directed will tend to move along under
the structure, with most of the energy concentrated along the
19
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bulkhead, or inner edge and very little emerging. In the absence
of fire walls, it will be necessary to insert a barrier that will
deflect the flow outwards. If there is enough clearance for a
small boat, conventional boom can be used, but in many instances
the clearance, even at low tide, will be too small. To overcome
this problem we have constructed boom using boards with lead
weights for ballast and small floats for buoyancy. These are
bolted together, with wing nuts and preset bolts, and pushed under
the pier. The assembly and positioning is done with the boom in the
water by a man in a small boat, which must be moored to one of the
piles. As each section is added, the boom is extended further
under the pier. Up to 28 ft of this boom has been assembled with
relative ease, and greater lengths are evidently possible. To
accomplish its task, the boom should extend all the way across
the pier from the bulkhead on one side to the outermost piles on
the other. The outer end of this boom is matched with any type
of conventional boom which is then extended out towards mid-stream
and back toward the current generator, and secured to an anchored
float. The plank boom is braced against the applied current by a
row of piles, and it should be tied to the outermost of these piles
in such a way that it can rise or fall with the tide.
The artificial flow should be directed at about a 45 degree angle
under the structure and towards the boom. (Figure 1) To achieve an
effective angularity along with an effective stream velocity, it
may be necessary to hold the fire boat away from the pier. This
can best be done by mooring a floating fender (a camel), 'or another
boat between the pier and the fire boat. The boom and the current
generator (or impact zone of the fire stream for deck monitors)
should be far enough apart so that the axis of the current is inter-
cepted by the bulkhead well before it reaches the boom. This means
that the wider the pier (i.e. the greater the distance between the
outer edge of the pier and the shoreline or bulkhead) the greater
must be the distance between the current generator and the under pier
boom. The objective is to create a flow under the pier along the
closed inner edge which is deflected outwards by the under pier
boom. The speed of the current when it reaches, and is diverted by
the boom, should be less than a half knot. The ultimate configura-
tion of the boom array will depend on the width and strength of the
current, the width of the structure, and the angle of entry of the
current. However, the flexible boom attached to the under pier boom
will form a belly in response to the flow, and the skimmer should be
located at its apex. Since each situation is likely to have its own
characteristics, on scene experimentation will probably be necessary
to achieve optimum results.
The under pier boom can be constructed of any material having enough
rigidity to enable it to be pushed under a pier. The prototype was
made of 10 ft x 1 ft x 1 inch pine boards, with 12 Ibs of ballast
along one edge, and two quart-size plastic bottles for flotation.
The boom had about 4 inches of freeboard and 8 inches of skirt. For
20
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strength there was one foot of overlap where the planks were joined
with four bolts and wing nuts backed by large washers. Because of
its rigidity, the under pier boom will not conform with the water
surface as waves pass; however, it is designed for use in places
where waves of more than a few inches height will only be an occa-
sional problem. If more freeboard or skirt is needed, broader
planks can be used.
Cul-de-Sacs
The substructures under many shoreside installations form basins
or cul-de-sacs having three sides closed and only one side open.
For example: A long pier or roadway running parallel to and abut-
ting with bulkhead, as described above, and also having transverse
fire walls, will form a series of such covered embayments. The
bulkheads are capable of diverting a flow outwards, so under pier
boom is not needed. But, because distance between the sides of the
basin is usually not much greater than the distance between the
mouth and the closed end, a different type of current structure
must be established. Instead of directing the current inwards, and
at an angle towards the bulkhead which is to deflect it outwards, we
try to establish a rotary flow entering along one side and emerging
along the other (Figure 2).
In establishing such a flow it is important that the current enter
only one side of the basin, leaving room on the other side for an
emergent flow. When using deck monitors, the fire streams should
be aimed as though the entering current were required to bounce off
one wall of the basin. If it is aimed too directly into the basin,
even though the impact zone is near one side of the basin's mouth,
the large angle of spread of the current could cause it to span the
entire width of the basin before it reaches the closed end; and the
only effect would be to drive the oil deeper into the basin. Aiming
the fire stream in this manner will cause a part of the induced
current to be wasted, since not all of it will be intercepted by the
wall and channelled into the basin. The further the impact zone from
the mouth of the basin the greater will be the proportion of the
momentum flux that is lost in this way, but it should never exceed
fifty percent, since the line of'aim should be into the basin's
mouth. Aiming the stream more towards the center will reduce this
loss, but, unless the basin is very wide or the impact point quite
close to the mouth, this loss cannot be eliminated completely with-
out destroying the rotary flow. However, the loss of momentum flux
does not appear to present a serious problem. We were able to achieve
the desired results in a 200 x 160 ft cul-de-sac, using a 5 inch tip,
operating at 75 psi, and impacting 60 ft from the mouth of the basin
with only about 60% of the flow entering it. If necessary the loss
could have been reduced by advancing the impact zone along the same
line of aim. Under pier pipes and hand lines from small boats can
also be used to establish a rotary flow. Since they are operated
21
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i
i
i
\ \
O OOOOOOyOOO
\
o o o o o o o^o
WALL
WASTED MOMENTUM
r
i \
FIRE STREAM
?f
o o o~o-"6~ o o
o~~o o o o o o c
WALL
o ooooooo
oooooooo cr^c
ooooooo o o (
WALL
OOOOOOOo
1
I
1
FIGURE 2
CLEARING A CUL-DE-SAC
22
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close to the edge of the pier and the lateral spread of their induced
flow is inhibited by the rows of piling, they can be aimed directly
into the basin along one wall. However, since their output is so
much smaller than that of monitors, it may be necessary to use two
or more streams, parallel and close to each other, to achieve the
desired flow. The boom must be deployed so as to intercept the emer-
gent flow without interfering with the entering flow. This will be
easier to accomplish when the current generators are close to the
pier edge. The ends of the boom can be secured to piles at the edge
of the pier, and the central portion, where the skimmer is to be
located, should be held away from the pier by an anchored float so
that the entire array forms a deep pocket.
If the basin is very narrow and fairly deep, with walls extending to
the bottom (in effect a closed channel) it may be possible to set up a
vertical rotary flow. To do this an under pier pipe with the tip sub-
merged is used, and it is aimed into the basin at a downward angle, so
that the current flows inward along the bottom and outwards near the
surface. This is likely to stir up and flush out quite a bit of silt as
well as oil. Since the mouth of the channel is narrow, the boom and cur-
rent generator must be placed in tandem; therefore the tip should be well
below the skirt depth of the boom. There are two possibilities; if there
is a convenient hose hole or a means of securing the under pier pipe to
the pier edge, the boom and skimmer can be placed outboard of the tip. If
this is not possible, the ends of the boom will have to be fastened to the
walls of the basin far enough under the pier so that the boom forms a deep
pocket with its apex under the edge of the pier. (It may be necessary to
drive studs for securing the boom ends.) The under pier pipe can then be
operated from the rail of a boat moored across the mouth of the channel
so that its stream passes under the boom. So far this method has only
been attempted on a laboratory scale, and the limits of its effectiveness
are not known.
Entrainment
A current moving through a body of water will drag some of the
surrounding water with it. This process, entrainment, can be used
to set up a flow of surface water out of a small basin by establish-
ing a surface flow across the mouth of the basin. (Figure 3) On the
whole this method is far less effective than the methods described
above, but it might be useful in some situations. Since the out-
flowing surface water must be replaced, and in the case of a basin
it is replaced by in-flowing bottom water, propwash, because of its
depth, is not suitable unless the basin is very deep. Because of
the large angle of spread of currents generated by deck monitors,
it may be difficult to prevent a portion of the entraining current
from entering the basin and setting up a rotary surface flow.
But it will not be an efficient rotary flow, since much of the
entrained, emerging water will be recirculated back into the basin.
This difficulty can be reduced by keeping the tip as close as possible
23
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SKIMMER
BOOM
FLOAT
ANCHOR
FIGURE 3
DRAWING OIL OUT OF AN EMBAYMENT BY ENTRAPMENT
24
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to the surface. To create a significant flow out of the basin the
entraining current must be quite strong. For this reason the
size of the area that can be cleared by entrainment is limited;
the maximum being about 100 ft on a side. Finally since the
emerging flow becomes a part of the much higher velocity and more
turbulent entraining current, the oil is subject to severe emulsi-
fication. For successful containment and pick-up the boom must not
intercept the entraining current until it has become very Weak, i.e.
less than 1/2 knot.
25
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SECTION X
ACKNOWLEDGMENTS
The practical use of fire boats and other apparatus at actual spills
at numerous test exercises provided the basic information for this
report. The Officers and Members of the Marine Division of the NYFD
and the personnel of Alpine Geophysical Associates were the principal
project participants.
The guidance of Mr. Frank Freestone, EPA Project Officer, and the
cooperation of the City of New York and the U. S. Navy in providing
the test basin at Wallabout Creek, Brooklyn, New York, is gratefully
acknowledged.
27
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SECTION XI
REFERENCES
(1) Casey, James F. (1970) Fire Service Hydraulics
Reuben H. Donnelly Corp., N.Y.C., 427 pp.
(2) Katz, B. and Cross, R. (unpublished report) "Use of Fire
Streams to Control Floating Oil" submitted to the
Water Quality Office, EPA, by NYFD, December, 1971.
U. S. GOVERNMENT PRINTING OFFICE : 1973—514-153/218
29
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
2.
3. Accession No.
w
4. Title
REMOVAL OF OIL FROM UNDER PIERS
7. Authot(s)
5. Report Date
6.
8. Fvrformiitg Organization
Report No.
Katz, Bernard
9. Organization
Alpine Geophysical Associates, Inc.
under contract to
New Tork City Fire Department
10. Project No.
15080 FVP
11. Contract/Grant No.
lj Type . f Repo ^ and
Period Covered
12. Sponsorin; Organisation Environmental Protection Agency, W.Q.O.
IS. Supplementary Notes
Environmental Protection Agency report
number, EPA-R2-73-116, February 1973.
w. Abstract while this report deals primarily with methods of extracting oil
from under piers, it is recognized that simple extraction is not
enough, and that the oil should also be removed from the environ-
ment. Therefore, considerable attention has been paid to driving
the oil out in such a way that it can be. picked up. The primary
means of extraction are by the establishment of artificial currents
under the contaminated pier, and a number of methods are suggested
to cope with various types of pier substructure.
Some other possible approaches, not involving flushing by artificial
currents, are also discussed. These include: uses of chemicals,
sinking, air entralnment and entombment.
A generalized description of pier structures is also included
This report was submitted in partial fulfillment of Project 15080 FVP
under the partial sponsorship of the Water Quality Office, Environ-
mental Protection Agency.
Spills> *011 poiiution *Hydrulics, *Jets, *Piers, *Docks,
*Boats, *Nozzles, ^Emulsions, Entralnment
J7b. identifiers 'e Departments, *Surface Currents, *Monltor Streams,
*Hose Streams, Surface Collecting Agent
17c. COWRR Field & Group 05D
18. ' Availability
19. Security Class.
'Repor )
'7. Se rityC: is.
(Page)
21. No. of
Pages £9
2. Pr., n
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 2O24O
Abstractor
Bernard Katz
I institution Alpine Geophysical Assoc. Inc. for N.Y.F.D
WfcSIC 1O2 (REV. JUNE 1971)
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