EPA 910/9-88-218
United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue
Seattle,WA 98101
October 1988
Alaska Operations Office - Anchorage
Causeways in the
Alaskan Beaufort Sea
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United States Environmental Protection Agency
Region 10
Causeways in the Alaskan Beaufort Sea
Prepared By:
Brian D. Ross
Fisheries Biologist
NEPA and Wetlands Review Section
Alaska Operations Office
Anchorage, Alaska
October, 1988
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
TABLE OF CONTENTS
Page
Abstract iii
Executive Summary iv
Introduction 1
Environmental Setting 2
Physical Environment 2
Biological Environment 5
Causeway Projects 9
Impacts of Causeways 11
Physical Impacts 12
Biological Impacts 17
Research Needs 22
Conclusion 23
References 24
Acknowledgements
Many people contributed their time, advice, and expertise to this document.
Helpful comments about technical content were made by several reviewers, too
numerous to list here. The efforts of each are greatly appreciated. Linda
Sewright 's technical editing skills were particularly helpful in making
complicated topics as understandable as possible. Finally, the graphics and
publishing abilities of Eric Meyerson and Christopher Moffett were nothing
short of heroic, especially considering the condition of the draft document and
the impossible schedule. Grateful acknowledgement is extended to all.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
ABSTRACT
Prior to the construction of major gravel
causeways in the central Beaufort Sea, the
shallow (< 2 m) nearshore environment of the
Prudhoe Bay area (including a nearby lagoon
system and two river deltas) was dominated in the
summer by a band of brackish, relatively warm
estuarine water. These estuarine conditions were
generally continuous along the nearshore during
both east and west winds. Conditions in this band
represent the most productive feeding and rearing
habitat for the Arctic anadromous fish of the
region. During prevailing easterly winds, the
West Dock causeway deflects the estuarine water
offshore. The deflected water mixes more directly
with offshore marine water and rapidly loses its
estuarine character. At the same time, the
deflected water is replaced by upwelled marine
water which then dominates the Stump Island
Lagoon-Gwydyr Bay complex. This upwelled
water causes a large area to be unsuitable as
feeding habitat for many anadromous fish, and
severs the nearshore band of estuarine habitat.
These alterations to the natural environment
cause fish migration to be delayed, and fish to be
isolated from unaffected habitat areas to the east
and west. Upon shifts to west winds, the marine
water upwelled into the lagoon system flows
around the causeway into Prudhoe Bay, forcing
anadromous fish rearing there to retreat toward
river delta fronts for refuge. TheEndicott
causeway also deflects the brackish coastal plume
offshore. Similar to the West Dock causeway, the
Endicott causeway induces upwelling of marine
water downwind from the structure. This
separates Sagavanirktok River water in the
nearshore from the diverted coastal water mass.
In this manner, the brackish coastal water mass
and the fresh river water each mix more directly
with marine water. These processes bring about
an overall degradation of nearshore estuarine
water quality, and hence habitat value.
Cumulatively, the West Dock and Endicott
causeways have fundamentally altered circulation
patterns and water quality across approximately
65 kilometers of the central Beaufort Sea coast.
These major changes in the physical environment
place populations of anadromous fish, and the
commercial and subsistence fisheries that rely
upon them, at substantial risk. Indicators from
causeway monitoring programs show that fish are
being affected by these habitat changes; and it is
possible that significant population declines have
already begun to occur.
ill
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
EXECUTIVE SUMMARY
Overview
The nearshore zone of the Prudhoe Bay area
functions biologically as a coastal estuary. The
warm, brackish water conditions found across the
area are more biologically productive than the
fresh or marine waters. Because of this
productivity, the area is critical for the
anadromous fish of the central Beaufort Sea which
are dependent upon estuarine conditions for
feeding and rearing. However, despite the
productivity of this estuarine habitat, the
harshness of the Arctic environment and the short
summer season cause these fish populations to be
slower growing and maturing than more southern
populations.
By disrupting circulation patterns and altering
the balance of fresh and marine water, the
existing causeways have significantly affected
water quality across approximately 65 kilometers
of the central Beaufort Sea. The water quality
alterations have reduced the quantity and quality
of estuarine habitat. These causeway-induced
changes decrease the ability of anadromous fish to
obtain sufficient energy for overwintering
survival, growth, and reproduction. Although the
risk of population-level impacts from these
changes cannot presently be quantified, several
indicators from environmental monitoring
programs suggest there is a substantial risk of
significant population-level impacts over the life
of the causeways. Eventually, existing causeways
could seriously disrupt the coastal fish community
and harm subsistence and commercial harvests in
Canada as well as in Alaska. Restoration of
circulation patterns similar to the pre-causeway
environment is necessary to reduce the impacts to
water quality and fish habitat. In contrast,
additional causeways proposed for the area would
significantly increase these impacts and risks.
Introduction
Prudhoe Bay is located on the central Beaufort Sea
coast approximately halfway between Point
Barrow and the Alaska-Canada border.
Considerable industrial activity has occurred in
the general Prudhoe Bay area, as it is the hub of
the largest producing oil field in the United States
and the origination point for the 1,300-kilometer
long Trans Alaska Pipeline System. This
industrial activity has spread into nearby offshore
waters as well, and three gravel causeways have
been constructed in the area. Two of these - the
West Dock causeway and the Endicott causeway -
extend four kilometers or more from shore and
have been the subject of considerable controversy
both prior to and since their construction.
The primary concerns about the gravel structures
are their impacts to nearshore water quality and
circulation patterns, and, consequently, the
quality of habitat for the anadromous fish
populations of the region. These fish are an
important resource for subsistence users in both
Alaska and Canada. During the brief summer
period when the Beaufort Sea is not frozen, the
fish are generally constrained to the immediate
nearshore zone where inhospitable marine
conditions are displaced by warmer, brackish
waters. It is across this same critical nearshore
zone that the causeways have been constructed,
disrupting nearshore circulation patterns and
causing the estuarine habitat to be replaced by
offshore marine water along many kilometers of
coastline.
The impacts and risks posed by Prudhoe Bay area
causeways are significant. The Alaska District,
U.S. Army Corps of Engineers, has declared the
impacts of the Endicott causeway unacceptable
and is considering mitigation measures. This
report has been prepared as a basis of support for
decisions about mitigation at both the Endicott
and West Dock causeways. The report
summarizes the current state of knowledge about
the nearshore environment and the impacts of
causeways in the central Beaufort Sea.
Environmental Setting
For 1 to 8 kilometers out from shore in the
Prudhoe Bay area, the Beaufort Sea is extremely
shallow - less than 2 meters deep. This includes
the broad Sagavanirktok River delta and the
coastal lagoon system to the west. During each
winter, these areas freeze completely to the bottom
and cannot serve as feeding and rearing habitat
for anadromous fish for about nine months. Open
surface water is found only during a few weeks in
the summer. Due to the extreme shallowness of
the nearshore, summer water currents are
determined by the wind. The direction of the
current, in turn, plays a large role in determining
water quality in the area.
During summer, warm, fresh water from rivers in
Canada and Alaska mixes with cold offshore
marine water to form a nearshore band of brackish
water, the "coastal water mass." This mass of
brackish water flows east or west along the
Beaufort Sea shoreline depending on the direction
of the prevailing winds. The Sagavanirktok River
is a major local source of fresh water input to the
coastal water mass, maintaining and enhancing
the estuarine habitat of the Prudhoe Bay area.
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Causeways in the Alaskan Beaufort Sea
Satellite images and hydrographic surveys
provide evidence that prior to the construction of
the causeways, the nearshore's estuarine
conditions were generally continuous across the
Prudhoe Bay area. Although the coastal water
mass behaved somewhat differently under
easterly versus westerly winds, the integrity of the
estuarine band could be maintained in either case.
Biologically, this nearshore estuarine zone is the
most critical feature of the summer coastal aquatic
environment. Here, the harsh conditions of the
Arctic Ocean - inhospitable for many organisms -
are moderated by a combination of increased solar
warming (due to shallowness), lower salinities,
and terrestrial as well as marine nutrient sources.
Productivity in this zone is higher for
phytoplankton, aquatic plants, invertebrates, and
fish than it is in adjacent marine or freshwater
environments. The anadromous fish of the region
are particularly dependent upon these more
moderate and productive estuarine conditions.
Numerically dominant anadromous fish species in
the Beaufort Sea include Arctic cisco, least cisco,
broad whitefish, and Arctic char. These fish
support subsistence fisheries in both the United
States and Canada, and play an ongoing role in
the native cultures of the American Arctic. Arctic
cisco in particular are an international resource,
with the individuals from the same population
being harvested in both the Alaskan Beaufort Sea
and throughout the Mackenzie River drainage in
Canada. All of the anadromous fish must obtain
the vast majority (90 percent or more) of their
energy intake for the entire year during the very
limited period of open water. The feeding and
rearing period is so limited (approximately 10
weeks) that these populations naturally grow and
mature more slowly than related populations and
species from more temperate areas. In addition,
the ability to acquire energy rapidly is so limited
that these fish are unable to spawn in consecutive
years. Even though food organisms may be
abundant, energy is clearly a limiting factor.
Temperature and salinity are extremely
important in determining the overall quality of
habitat for these fish. Typical marine conditions
in the Arctic are extreme - a combination of both
very cold temperatures and high salinities. These
conditions are energetically adverse and generally
represent unsuitable habitat conditions. The
amount of time that suitable temperature and
salinity conditions are available for rearing is of
paramount importance. A reduction in the
amount of foraging time will affect the scope for
growth for that year. "Mild" years, when
estuarine conditions persist in the nearshore zone
longer than average, can naturally result in
higher productivity and greater fish growth
overall. Conversely, "harsh" years reduce growth
potential because lowered temperatures slow
assimilation rates at the same time that higher
salinities invoke additional metabolic demands. If
conditions are severe, the fish will not be able to
accumulate sufficient energy reserves to survive
the overwintering period.
In the absence of causeways, estuarine conditions
were spread throughout the broad, shallow areas
of the central Beaufort Sea including Foggy Island
Bay, the Sagavanirktok River delta, Prudhoe Bay,
and the lagoon system to the west. In this habitat,
fish could presumably feed efficiently, with high
assimilation and growth rates, and with a
minimum of metabolic cost. This allowed net
energy gains to be maximized over the very short
summer, which in turn supported normal rates of
growth, reproduction, and overwintering survival.
Causeway Projects
Development of oil and gas reserves on Alaska's
North Slope has resulted in the construction of two
massive, solid-fill gravel causeways into the
Beaufort Sea. The West Dock causeway extends
approximztely 4 kilometers offshore from the
northwestern corner of Prudhoe Bay. A single, 15-
meter (50-foot) opening or "breach" was
constructed in the West Dock causeway in an
attempt to allow anadromous fish to pass the
structure. The nearly 8 kilometer long Endicott
causeway is located in the middle of the
Sagavanirktok River delta just east of Prudhoe
Bay. It includes a total of 215 meters (700 feet) of
breaching that was intended to allow fish passage
as well as to mitigate the water quality impacts
predicted by the Environmental Impact Statement
(EIS) for the project.
Additional causeways have been proposed by the
petroleum industry. The Lisburne causeway
would have extended over 4 kilometers into the
center of Prudhoe Bay to access a proposed drilling
island. This proposal was recently withdrawn in
favor of directional drilling from shore. The most
recent proposal with a causeway is the Niakuk
project. This proposal includes construction of a
2.2 kilometer long solid-fill causeway from Heald
Point, at the northeastern end of Prudhoe Bay, to a
man-made drilling island.
The primary concerns about these gravel
structures center on their impacts on nearshore
water circulation patterns, water quality, and,
consequently, the quality of estuarine habitat for
fish populations in the central Beaufort Sea.
During the brief summer period when the
Beaufort Sea is not frozen, anadromous fish are
generally restricted to the immediate nearshore
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Causeways in the Alaskan Beaufort Sea
zone which is warmer and less saline that the
inhospitable marine water offshore. It is across
this same critical nearshore zone that the
causeways have been constructed.
Impacts of Prudhoe Bay Area Causeways
The basic physical impacts of constructing
causeways within the estuarine nearshore zone
appear, with hindsight, to be easily predictable.
However, little knowledge of the nearshore
processes in the central Beaufort Sea existed
before construction of the first causeway began.
The evolution in knowledge during several years
of monitoring, however, has provided a clearer
picture of the processes affected by the causeways
and the ecological risks they represent.
Causeways have disrupted the nearshore
environment throughout the Prudhoe Bay area by:
1) deflecting both the estuarine coastal water mass
and river plumes offshore, concurrently degrading
their estuarine character through the loss of
thermal energy and freshwater to offshore areas;
2) causing enhanced upwelling and intrusion of
marine water directly into the nearshore zone,
thus regularly severing the band of estuarine
conditions along the coast; and 3) both delaying
breakup and accelerating freezeup in the
nearshore zone. Overall, fundamental alterations
in nearshore water quality and circulation
patterns have occurred along as much as 65
kilometers of the Prudhoe Bay area coastline.
The coastal water mass and the Sagavanirktok
River plume are deflected offshore by both the
West Dock and Endicott causeways despite the
breaching incorporated into each of them.
Offshore deflection causes enhanced mixing with
marine water and degradation of estuarine
conditions. Salinity of the deflected water has
been observed to increase at rates as high as 2
parts per thousand per kilometer (ppt/km) in
passing around the Endicott causeway and up to
another 9 ppt/km as a result of West Dock.
Offshore marine water up wells in place of the
deflected water. At the Endicott causeway,
salinity differences of 20 ppt have been observed
between the plume water on one side of the
causeway and upwelled water on the other side -
an impact three times greater than predicted in
the EIS for the project. West Dock causes an even
more dramatic intrusion of marine conditions into
the nearshore zone. During east winds, West Dock
can cause upwelled marine water to dominate the
Stump Island/Gwydyr Bay lagoon system for over
30 kilometers to the west. Upon shifts to westerly
winds, this same upwelled water flows east around
the causeway, quickly filling Prudhoe Bay.
The West Dock and Endicott causeways have also
affected ice dynamics in the Prudhoe Bay area.
Each causeway both deflects and restricts the
early season overflooding by river water, so that
breakup of sea ice in the vicinity of each causeway
has been delayed by up to two weeks. While
breakup is delayed, freezeup near the structures
has been noted to occur up to two weeks earlier
than elsewhere in the area since the causeways
tend to trap newly-forming ice.
The changes to circulation patterns, water quality,
and ice dynamics have dramatically affected fish
distribution and use of the Prudhoe Bay area.
Based on data from environmental monitoring
programs, it is known that when Prudhoe Bay is
filled with marine water (during shifts to west
winds) most anadromous fish that had been
feeding in the estuarine conditions of the bay are
forced to leave and take refuge in the
Sagavanirktok River delta. For these fish, all of
the time spent in refuge areas reduces the amount
of time they spend feeding in more productive
estuarine habitat. Even when such drastic water
quality changes do not occur and fish are not
forced to completely abandon the nearshore zone,
the quality of feeding habitat in the area is still
degraded as a result of offshore deflection of plume
waters. Degraded habitat quality either requires
a greater energy expenditure (due to higher
salinities) or reduces the assimilation rate (due to
lower temperatures) of food items taken.
Increased influence of marine conditions causes
both effects at once. Therefore, even when fish are
not forced to completely abandon the feeding
areas, the energetic costs of remaining in them are
increased and net energy gain is decreased.
The causeways have also altered ice dynamics
directly within the critical nearshore zone. Delays
in breakup and acceleration of freezeup local to the
causeways affect fish distribution between feeding
and overwintering areas. The highest catches of
anadromous fish during the early summer period
of initial dispersal to feeding areas have occurred
at the Niakuk Islands. Altered ice dynamics in
the vicinity of the proposed Niakuk causeway
would directly affect fish use of this important
migration corridor. In addition, to the extent that
causeway effects on ice dynamics reduce the
overall time available for feeding, the potential for
growth is also reduced. The limited breaching
proposed for this structure is not expected to
elimate these effects.
Causeway-induced effects on fish habitat carry
serious ramifications in terms of decreasing the
net energy intake of the anadromous fish. The
most immediate consequence is to anadromous
fish that do not acquire enough fat reserves to
survive the next overwintering period. These
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Causeways in the Alaskan Beaufort Sea
animals will die before the next spring. A year in
which increased overwintering mortality occurs
for some percentage of a population will result in a
direct and immediate decline in overall population
size by the same percentage. A population could
take several decades to recover in numbers even if
no similar overwintering mortality events were to
occur in subsequent years. Of course, if increased
overwinter mortality were to recur during
subsequent generations, recovery would not
proceed. If such conditions occurred more than
once to a single generation, the degree of the
resulting population decline would be multiplied.
Similar, but less immediate, impacts could also
occur if conditions become severe enough to reduce
growth without directly increasing overwinter
mortality. One such event per generation could
reduce fecundity or delay the age at which the fish
reach maturity and spawn. Reduced fecundity and
delayed maturity would also result in a direct
decline in population size.
Monitoring programs have provided evidence that
these impacts are already beginning to occur. The
indicators include: 1) basic changes in the
structure of the nearshore fish community to one
dominated by marine and relatively salt-tolerant
species, with freshwater species having all but
diasppeared in the area; 2) reduction in the
strength of young age-classes of Sagavanirktok
River broad whitefish since 1981; 3) smaller size-
at-age for a large cohort of Arctic cisco in the
Prudhoe Bay area in 1985, together with evidence
that they may not have survived overwintering;
and 4) evidence (including stomach sampling) that
food organisms are not effectively unlimited.
The proposed Niakuk causeway would exacerbate
the impacts and ecological risks posed by the
existing causeways. By deflecting the coastal
water mass and water from the west channel of the
Sagavanirktok River, the Niakuk causeway would
be expected to enhance the amount of marine
water upwelled in the vicinity of Prudhoe Bay.
The Niakuk causeway would further restrict river
overflooding into Prudhoe Bay, affecting the
formation of nearshore leads used by outmigrating
fish in the early summer. It would also accelerate
freeze-up processes within the single most
important pathway used by fish migrating to and
from the Sagavanirktok River overwintering sites
and refuge areas.
Taken together, causeway-induced alterations in,
circulation patterns, water quality, and ice
dynamics - occurring as they do directly within the
critical nearshore estuarine zone - now make
every year more similar to a naturally harsh year.
The indicators show that the anadromous fish of
the central Beaufort Sea are already being
affected by these conditions. This means that
long-term declines in their populations are likely.
Should truly harsh years be in store, catastrophic
impacts to these populations - and the fisheries
they support - can quickly occur. Given the lack of
reliable information on population sizes and the
fact that monitoring programs have not been
designed to measure population sizes directly, it is
possible that significant declines have already
begun to occur. Restoration of pre-causeway
circulation patterns, particularly restoration of
more continuous estuarine conditions in the
nearshore zone, is necessary in order to reduce
these impacts to fish habitat and water quality. In
contrast, construction of additional causeways in
the area would significantly increase these
impacts and risks.
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Causeways in the Alaskan Beaufort Sea
INTRODUCTION
Prudhoe Bay is located on the central Beaufort Sea
coast approximately halfway between Point
Barrow and the Alaska-Canada border (Figure 1).
Considerable industrial activity has occurred in
the general Prudhoe Bay area, as it is the hub of
the largest producing oil field in the United States
and the origination point for the 1,300-kilometer
long Trans Alaska Pipeline System. This
industrial activity has spread into nearby offshore
waters as well, and three gravel causeways have
been constructed in the area (Figure 2). Two of
these - the West Dock causeway and the Endicott
causeway - extend four kilometers or more from
shore and have been the subject of considerable
controversy both prior to and since their
construction. The primary concerns addressed in
this report are the impacts of the gravel structures
to water quality and circulation patterns, and,
consequently, to the quality of habitat for the
anadromous fish populations of the region. (Other
water quality issues, such as potential effects from
waste discharges associated with industrial
activities supported by the causeways, are
notdiscussed here.)
The region's anadromous fish are an important
resource for subsistence users in both Alaska and
Canada. During the brief summer feeding period
when the Beaufort Sea is not frozen, the fish are
generally constrained to the immediate nearshore
zone where inhospitable marine conditions are
displaced by warmer, brackish waters. It is across
this same critical nearshore zone that the
causeways have been constructed, disrupting
nearshore circulation patterns and causing the
warm, brackish habitat to be replaced by offshore
marine water across many miles of coastline. The
impacts and risks posed by Prudhoe Bay area
causeways are significant. The Alaska District,
U.S. Army Corps of Engineers, has declared the
impacts of the Endicott causeway unacceptable
and is considering mitigation measures. This
report has been prepared as a basis of support for
decisions about mitigation at both the Endicott
and West Dock causeways. The following pages
summarize the current state of knowledge about
the nearshore environment and the impacts of
causeways in the central Beaufort Sea.
Figure 1
The Beaufort Sea coast. The Colville and Mackenzie are the major rivers discharging into the Beaufort
Sea.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Beaufort Sea
\ Stump Island Lagoon
West Dock Causeway
N.^.- •
0123
Scale of Nautkal Milts
Figure 2
The Prudhoe Bay area, showing the locations of existing man-made gravel causeways.
ENVIRONMENTAL SETTING
The nearshore environment of the central
Beaufort Sea is very different, both physically and
biologically, from coastal zones elsewhere in the
United States. A basic understanding of this
special environment is necessary in order to place
the impacts and risks posed by nearshore
causeways into context. This section presents
information about the physical processes and
biological setting of the central Beaufort Sea coast
in the absence of the causeways. Because pre-
causeway baseline data are limited, this
discussion is based largely on data gathered since
construction of the West Dock causeway.
Emphasis is placed on the nearshore Prudhoe Bay
vicinity, defined here generally as extending from
Foggy Island Bay through Gwydyr Bay and from
shore to approximately the 6-meter depth (Figure 2).
PHYSICAL ENVIRONMENT
Much of the Prudhoe Bay area environment is
extremely shallow: the 2-meter isobath occurs
from 2 to 8 kilometers offshore in most locations
(Figure 2). A shoal, where water is only
approximately 1 meter deep, extends across the
mouth of Prudhoe Bay from near the base of the
West Dock causeway, past Gull Island, to the
Heald Point area. During the winter, approx-
imately 2 meters of ice forms along the Beaufort
Sea coast. This results in most of the nearshore
freezing completely to the bottom. This large area
cannot serve as feeding and rearing habitat for
fish until bottom-fast ice breaks up and open water
is available. Ice cover here lasts about nine
months, with open surface water found only
during about 8 to 12 weeks in the summer.
During the summer open-water period, the
direction of the current plays a large role in
determining regional water quality. Due to the
extreme shallowness of the nearshore area, water
movements are dominated by the wind, with
currents responding very rapidly to changes in
wind direction or intensity. Winds from the
easterly and westerly quadrants are by far the
most common during the open-water season, with
easterly winds generally prevailing. Therefore,
water movement within the broad, shallow
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
nearshore zone is primarily along-shore
throughout the summer and generally follows
bottom contours.
The two largest rivers that discharge into the
Beaufort Sea are the Mackenzie, approximately
160 kilometers east of the Alaska-Canada border,
and the Colville, about 70 kilometers west of
Prudhoe Bay (Figure 1). These two rivers provide
by far the greatest input of fresh water to the
Beaufort Sea. During the summer this water,
along with discharges from the Sagavanirktok
(Figure 2) and several smaller rivers, mixes with
cold offshore marine water to form a nearshore
brackish band called the "coastal water mass" (the
"coastal plume" of other authors). This band of
brackish water flows east or west along the
Beaufort Sea shoreline depending on the direction
of the prevailing winds, as described above.
Satellite images (Stringer, 1985; Envirosphere,
1987; Envirosphere, 1988c; NOAA, 1988) and
early hydrographic study (Barnes et al., 1977)
provide supporting evidence that prior to
construction of any causeways, the brackish
coastal water mass was a generally continuous
nearshore feature across the Prudhoe Bay area
under both easterly (Figure 3) and westerly winds
(Figure 4). Discharge from the Sagavanirktok
River helped to maintain the estuarine nature of
the coastal water mass as it flowed westward
(under easterly winds) past Prudhoe Bay and
through the Gwydyr Bay/Simpson Lagoon system.
The large Colville River discharge did the same for
these areas under westerly winds. Although
different physical processes influenced the coastal
plume under easterly versus westerly winds (as
described below), the plume's integrity as a
continuous mass of warm, brackish water was
generally aintained.
Villf III VlUtK'tll Mill-.
Figure 3
Generalized now of nearshore waters during sustained easterly winds, in the absence of the West
Dock and Endicott causeways. Heavy solid arrows denote flow of subsurface marine water. Cross-
hatched arrows denote surface flow of river and coastal water, with the density of cross-hatching
proportional to salinity. Adapted fom Envirosphere, 1988band NOAA, 1988.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Scale of N.iuinal Mil
Figure 4
Generalized flow of nearshore waters during sustained westerly winds, in the absence of the West
Dock and Endicott causeways. Heavy solid arrows denote flow of subsurface marine water Cross-
hatched arrows denote surface flow of river and coastal water, with the density of cross-hatching
proportional to salinity. Adapted from Envirosphere, 1988band NOAA, 1988.
East Wind, (Jewelling During easterly winds,
nearshore water levels are lowered due to an
offshore trend in the surface current (Britch et al.,
1983; NOAA, 1988). In a process called upwelling,
sea level is stabilized as the surface current is
replaced with deeper strata not affected by the
wind. In the absence of causeways, upwelling
could bring marine bottom water into nearshore
locations as shallow as 2-4 meters in the Prudhoe
Bay area (NOAA, 1988; Envirosphere, 1988d). A
typical upwelling event during strong easterly
winds, measured away from any causeway
influence, is depicted in Figure 5. Two aspects of
the phenomenon shown in the figure are
important. First, the high salinity water that
upwells to within the 3-meter depth remains
overlain with brackish coastal water - it does not
reach the surface. Second, because the area is
extremely shallow for several kilometers offshore,
the upwelled marine water does not invade very
far into the nearshore zone. Hence, under normal
circumstances, upwelling would not disrupt the
continuity of the coastal water mass or its
dominance across the broad, shallow Prudhoe Bay
area.
3 30
00 01 02 03 04 05 06 07 08 09 '0
Distance From Coast (Km)
Figure 5
Upwelling along the Sagavanirktok River delta
during easterly winds. In this 1982 example
measured at the present location of the
Endicott causeway, natural upwelling of high
salinity bottom water (shaded) can be seen
extending to approximately the 2.5 meter
depth.Adapted from Envirosphere, 1987b.
West Wind, Intrusions During westerly winds.the surface current has a small onshore component
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
that raises water levels. Initially, when the water
level begins to rise, the entire water mass moves
shoreward, generally preserving the cross-
sectional characteristics that were in existence at
the time the event began (Britch et al., 1983;
Envirosphere, 1988d). In other words, if the water
column is stratified to begin with, all of the strata
will move shoreward. This is called an intrusion.
For example, intrusion events can bring marine
bottom water over the Gull Island shoal (Figure 2)
and into Prudhoe Bay if marine water resides
shallow enough on the seaward slope of the shoal
before the intrusion begins. However, prior to
causeway construction, the water that would move
onshore during an intrusion event would be the
same brackish coastal plume water generally
dominant throughout the nearshore for much of
the open-water period. Intrusions, in that case,
would not result in any serious disruption of the
continuity of nearshore brackish conditions.
Overall, nearshore Prudhoe Bay area water levels
can vary by as much as 1 meter between strong
easterly and westerly winds. Since so much of the
area is less than two meters deep, it is not
surprising that changes in wind-driven current
and water levels significantly influence the
nearshore zone. The change in water level comes
about fairly rapidly upon shifts in wind direction
(or upon a relaxation in the strength of sustained
winds). Water levels generally stabilize within a
day or so after easterly or westerly winds have
established themeselves.
During sustained westerly winds "downwelling"
also occurs. Marine water that may have
upwelled into nearshore areas as shallow as 2-4
meters during east winds is forced further
offshore. However, this phenomenon generally
takes place farther offshore (outside the 2 or 3
meter depth contour) and after water levels have
equilibrated.
Ice Dynamics Ice cover persists for approximately
nine months along the Beaufort Sea coast (NOAA,
1988). During the winter, the nearshore Beaufort
Sea freezes to the bottom to depths of about 2
meters; this is the same general area occupied by
the coastal water mass during the summer. The
timing and dynamics of breakup and freeze-up can
influence the overall productivity of the nearshore
environment during the brief summer season. A
harsh year - one in which breakup is late and
freezeup early - could significantly limit overall
biological productivity. Conversely, an unusually
long open-water period during the summer would
allow for much higher productivity.
In the Arctic, rivers thaw and flow prior to the
breakup of sea ice. Fresh river water thus initially
flows over the top of the sea ice in the nearshore
zone. The presence of this over-ice flow of fresh,
warmer water speeds the breakup of nearshore sea
ice by flowing into and opening up cracks and
holes. The nearshore area thus usually has the
first open water, and leads in the sea ice form
there first. These leads are corridors for early
dispersal of anadromous fish from overwintering
sites to feeding and rearing areas. Prior to
construction of the West Dock and Endicott
causeways, overflooding from the Sagavanirktok,
Putuligayuk, and Kuparuk rivers was
unrestricted. Warm breakup flows covered the
entire Prudhoe Bay area coastline (Figure 6).
Figure 6
Estimated pre-causeway distribution of flood
waters from the Kuparuk and Sagavanirktok
rivers, based on LANDS AT image from May 30,
1985. Adapted from NOAA, 1988.
BIOLOGICAL ENVIRONMENT
During the summer in the central Beaufort Sea,
estuarine conditions dominated the broad, shallow
areas around Prudhoe Bay and the lagoon system
to the west in the absence of causeways (see
Physical Environment, above). These conditions
created a large expanse over which primary
productivity, and in turn the productivity of
invertebrates (predominantly mobile crustaceans -
principal prey for the anadromous fish), were
presumably high (Envirosphere, 1988b). This
nearshore estuarine habitat supported a fish food
resource much greater than exists in North Slope
rivers and streams. In this environment, fish
could feed fairly rapidly, with high assimilation
and growth rates and a minimum of metabolic
costs. This allowed net energy gain to be
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
maximized over the very short summer - critical
for overwintering survival, year-to-year growth,
and eventual reproduction (Smith, 1982).
Odum (1971) notes it to be "self-evident that
different (estuarine) circulation patterns and
gradients will greatly influence the distribution of
individual species" and describes natural arctic
ecosystems as a special class of physically stressed
estuarine ecosystems. This section describes the
biological setting of the Prudhoe Bay area and
what is known of ecological relationships in this
special estuarine environment.
Anadromous Fish Anadromous fish are those
that spawn in fresh water and migrate to rear in
marine or estuarine areas. Migration is
undertaken for the purposes of feeding, because
food is generally more available in marine and
estuarine areas than in fresh water (Congleton et
al., 1981 in Macdonald et al., 1988; Gross et al.,
1988). However, the energetic expenditures
associated with this migration in the extreme
conditions of the Arctic make the advantages of
this life history pattern marginal for most species
(Wohlschag, 1957). In contrast to anadromous fish
elsewhere that utilize estuaries for a relatively
short but critical period before moving into the
marine environment, Arctic marine waters are
inhospitable for anadromous fish (Macdonald et
al., 1988). Therefore, anadromous species in the
Beaufort Sea depend heavily on estuarine habitat
for feeding and rearing, because this habitat
represents the most productive, least severe of the
environmental conditions available to them.
The dominant anadromous fish species in the
Beaufort Sea include Arctic cisco (Coregonus
autumnalis). least cisco (Coregonus sardinella).
broad whitefish (Coregonus nasus). and Arctic
char (Salvelinus alpinus) (Figure 7). These fish
must obtain the vast majority of their entire year's
energy intake (90 percent or more) during the very
limited period of open water. The feeding and
rearing period, as well as the availability of
suitable habitat conditions during this period, is so
limited (approximately 10 weeks) that these
populations naturally grow and mature more
slowly than related populations and species from
more temperate areas (Craig and Haldorson, 1981;
Dutil, 1986). In addition, the ability to acquire
energy rapidly is so limited that these fish are
unable to spawn in consecutive years (Dutil, 1986;
NMFS, 1987).
A variety of other fish species are also found in
this area at times. In particular, Arctic cod
(Boreogadus saida) and fourhorn sculpin
(Mvoxoceohalus ouadricornis) are routinely
caught by post-causeway environmental
monitoring programs. Arctic cod, a marine
species, is often extremely abundant in association
with the higher salinity water.
The Arctic anadromous fish are an important
subsistence resource for native villages on the
Beaufort Sea coast (Jacobson and Wentworth,
1982) and throughout the Mackenzie River
drainage in Canada (NMFS, 1987). The only
commercial fishing operation in the Alaskan
Beaufort Sea is located in the Colville River delta.
This operation targets on these same anadromous
fish. Fish, and fishing, also play important roles
in the culture of the peoples native to the North
Slope (Jacobson and Wentworth, 1982). The
importance of anadromous fish increases when
other subsistence resources, such as caribou, are
less available.
Fish Distribution in the Prudhoe Bay Area Prior
to construction of the West Dock causeway, least
cisco migrated into the Prudhoe Bay vicinity from
the Colville River and were the most numerous
anadromous fish species in Prudhoe Bay sampling
(Furniss, 1974; Doxey, 1977). Least cisco were
more abundant in the nearshore zone than Arctic
cod and fourhorn sculpin (marine species) and
much more abundant in the Prudhoe Bay vicinity
than the anadromous Arctic cisco. Arctic cisco
numbers were higher in the Colville River area,
and these fish apparently by-passed Prudhoe Bay
to a large extent during their migrations between
the Colville and Mackenzie rivers. Broad
whitefish, anadromous but less tolerant of marine
conditions than either least or Arctic cisco, were
nonetheless regularly present in river plumes
within the nearshore zone in the Prudhoe Bay
area. Freshwater species (including humpback
whitefish and round whitefish) also appear to have
been fairly regular members of this nearshore fish
community prior to the final extension of the West
Dock causeway.
Overall, the nearshore biological community of
the Prudhoe Bay area was characterized by the
presence of freshwater species and species
relatively intolerant of high salinity, low
temperature (marine) conditions; marine species
and Arctic cisco were only minor components of
the community.
The dominant anadromous fish species share some
similar habitat requirements and distribution, but
have important differences as well. Similarities
include distribution in the estuarine water of the
shallow nearshore zone, with feeding principally
on near-bottom (epibenthic) invertebrates
including mysids, amphipods, and copepods. In
addition, they all must return to suitable, non-
marine habitat to overwinter.
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U.S. Enu iron mental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Arctic char (Salvelinus alpinus)
Arctic cisco (Coregonus autumnalis}
Broad whitefish (Coregonus nasus]
Least cisco (Coregonus sardinella)
Figure 7
Anadromous fish species of primary concern in the central Beaufort Sea. Fish are shown in decreasing
order according to their relative importance. Shading indicates the relative tolerance of the fish to
high salinity and cold temperatures with tolerance increasing with the darkness of the shading. Fish
figures adapted from McPhail and Lindsey, 1970. Figure courtesy of C. Johnson, National Marine
Fisheries Service, Anchorage, Alaska.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Differences exist among the anadromous species
in terms of how they use specific salinity and
temperature ranges within the overall estuarine
zone. The fish may tolerate a broader range of
conditions than they normally use for feeding, but
they must optimize multiple environmental
variables in order to maximize their energy gains.
Broad whitefish utilize fresher-water areas, and
have a relatively localized distribution directly
associated with river deltas. For this reason, they
feed more exclusively on terrestrial- and riverine-
derived food sources such as insect larvae. Arctic
char often feed in and can tolerate higher
salinities (Roberts, 1971), but may move into
freshwater (if whitefish are not present) for
digestion (Johnson, 1981). Because of this and
physical differences that allow Arctic char to feed
more efficiently on other fish (Svardson, 1976),
they use different areas and have somewhat
different feeding habits.
Least cisco and Arctic cisco are intermediate in
their use of the nearshore habitat. Each of these
species can generally tolerate somewhat higher
salinities than broad whitefish, but they do not
range as far from the immediate nearshore areas
for feeding and rearing as Arctic char. Figure 8
shows a representation offish use within the
nearshore environment.
Another difference among species is their
distribution and dispersal from spawning and
overwintering areas. Least cisco in the Prudhoe
Bay area are near the eastern end of their summer
distribution; they spawn and overwinter in the
Colville River. This is in contrast to Arctic cisco,
that migrate as juveniles from spawning grounds
in the Mackenzie River to rear near the Colville
River. '' Arctic cisco also overwinter primarily in
the Colville. Arctic char are represented by
discrete spawning populations from several river
systems along the North Slope, although summer
feeding distributions intermingle.
Other differences in use of the nearshore
environment occur within species (for instance, by
size or age). For example, tolerance to higher
salinities and lower temperatures tends to
increase with age, especially for least and Arctic
cisco. Because of such differences, all shallow
brackish areas within the coastal zone cannot be
assumed to uniformly serve as "habitat" for all
species or size-classes of anadromous fish at all
times.
Habitat Requirements of Beaufort Sea
Anadromous Fish Temperature and salinity are
very important habitat parameters for Beaufort
Sea anadromous fish (Craig and Haldorsoh, 1981;
Low Food
Few Fish
Broad Whitefish
Amphipods
Chironomids
i Cistos
Amphipods /-h' I
My*&rilielaChlirCod
Amphipods
Cope pods
M. liturulis
Cold
>25 ppt
Few Fish
Low Food
1M
2M
Figure 8
General use of nearshore estuarine habitat by fish in the central Beaufort Sea. Adapted from
Envirosphere, 1987.
" It is often assumed that the Alaskan population of Arctic cisco merely represent* a passively distributing portion of the
overall Mackenzie River population, with the numbers in Alaskan waters being proportional to the percentage of Mackenzie
River water that is blown to the west in a given year (Fechhelm and Fissel, 1988). Other data suggest this may not be the
case (Envirosphere, 1988b; Envirosphere, 1988d). It is clear from the perspectives of management and risk that the Alaskan
Beaufort Sea Arctic cisco must be considered a discrete stock that undergoes an active, directed migration (although almost
certainly wind-aided). If this is true, effect* to these fish would not be quickly reversible if the causeways were removed.
These Arctic cisco may represent a genetically discrete stock originating in particular drainages of the Mackenzie, which
would imply a potential for long-term causeway effects to result in detrimental impacts to the gene pool, to community
structure, and to subsistence and commercial harvests in Canada as well as Alaska.
8
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Envirosphere, 1987; Envirosphere, 1988b;
Envirosphere, 1988d) and much is known about
their effects. Temperature and salinity conditions
have direct metabolic consequences; however,
each affects fish in different ways. Basically,
temperature affects the rate of energy utilization
while salinity affects its distribution within the
fish. For example, warm temperatures allow
faster assimilation of food, leading to a greater
amount of feeding and greater growth over time.
Very cold temperatures make these cold-blooded
organisms lethargic to the point that feeding and
growth rates slow dramatically, independent of
food availability (Brett, 1964; Brett, 1971; Brett,
1976). In contrast, very high or very low salinities
require that a large percentage of the fish's energy
be expended to regulate blood chemistry (Smith,
1982). The normal marine condition in the Arctic
is extreme - a combination of both very cold
temperatures and high salinity - and thus it
generally represents the least suitable habitat
conditions for anadromous fish.
Temperature in the Beaufort Sea is of particular
importance to anadromous fish. The period during
which relatively warm water dominates the
nearshore zone is even more limited than the
period of open water. As the summer progresses,
river discharges decline and solar warming
decreases (NOAA, 1988). Consequently, the
quality of feeding habitat for anadromous fish
often diminishes as the season progresses.
Although prey abundance remains high late in the
season (Bnvirosphere, 1987), cold marine
conditions reduce the energetic value of utilizing
this prey. Mild years - for example, when winds
tend to hold warm, fresh river water in the
nearshore zone longer than during harsher than
average years - can naturally result in higher
productivity and greater fish growth overall.
Conversely, harsh years reduce growth potential
because lowered temperatures slow assimilation
rates. (As described earlier, westerly winds tend to
hold fresh river water onshore, promoting more
efficient mixing with the coastal water mass.
These conditions result in both higher average
temperatures and lower salinities in the nearshore
zone.)
Although fish are affected by overall conditions, at
any given moment fish respond primarily to local
and immediate habitat quality. It is counter
productive for fish to remain in an energetically
negative environment. This is true at any time -
not just late in the season when the entire region
becomes more marine. Harsh years as described
above limit the overall amount and quality of
suitable feeding habitat available across the
region, but fish must still attempt to utilize the
most suitable habitat remaining available. At
some point the fish simply retreat from unsuitable
conditions (for example, when marine water
quickly invades the nearshore habitat).
Observations that cold marine water directly
inhibits the movement of anadromous fish in the
area have been made during the mid-summer
rearing period as well as late in the season
(Envirosphere, 1988b; Envirosphere, 1988d). It is
clear that site-specific conditions at a given time,
as opposed to average regional or seasonal
conditions, are of most immediate importance to
the fish.
Parameters other than temperature and salinity
surely have a role in determining habitat quality
for central Beaufort Sea anadromous fish, but
little is known about them. For example, little is
known about how to specifically define individual
niches, or what constitutes optimal feeding
habitat for the different anadromous fish species.
Such parameters as distance from spawning or
overwintering areas, water depth, wave height,
turbidity, wind direction or strength, predator-
prey interactions, and competition all probably
have some importance. Other important
ecological issues under speculation are how
"optimal" habitat for different sizes or species of
fish may be affected by interaction of the
parameters listed above and whether any of the
fish adopt behavioral strategies to maximize
growth and survival within a given set of
conditions. Overall, specific definition of niches
for individual species is lacking and without such
information the ability to make precise predictions
about the effects of nearshore industrial
developments on each species will continue to be
limited. Future study may provide useful
information. However, existing information is
sufficient for identifying the more obvious impacts
and risks of Beaufort Sea causeways.
CAUSEWAY PROJECTS
Two major causeways have been constructed in
the Prudhoe Bay area; each is a massive solid fill
gravel structure. The impacts of these causeways
on water quality and fish habitat have become a
major environmental concern. Studies to
document the impacts of the causeways have been
required by the permits authorizing causeway
construction. This section briefly describes the
causeways and the monitoring programs that have
been undertaken to determine their impacts.
The West Dock Causeway This was the first major
causeway to be built in the Prudhoe Bay area. The
13,000-foot (4,000+ meter) long causeway is
located at the northwestern corner of Prudhoe
Bay, on the eastern end of the Gwydyr Bay/Stump
Island lagoon complex (see Figure 2).
Construction occurred in three phases. The
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
original structure was built in 1975 as access to a
dockhead some 4,000 feet offshore. The second
4,000 + foot leg was completed the following year
under an emergency permit from the U.S. Army
Corps of Engineers because supply barges had
become frozen into the sea ice. An additional
dockhead that continues to support shipping
activities was built onto the end of the second leg.
The final 4,000-foot section of the causeway was
built in 1980 to provide access to a seawater intake
and treatment plant for waterflood of the Prudhoe
Bay oilfield (COB, 1980). (The West Dock
causeway is sometimes referred to as the
"Waterflood" causeway for this reason.) A 50-foot
(15-meter) bridged opening ("breach") was
constructed at the shoreward end of the final leg of
the causeway in an attempt to provide for fish
movement between Prudhoe Bay and the Gwydyr
Bay/Stump Island Lagoon system. Overall, the
construction of the West Dock causeway required
over 1,500,000 cubic yards of gravel. The West
Dock causeway is operated by ARCO Alaska, Inc.,
on behalf of the Prudhoe Bay Unit owner
companies.
The Endicott Causeway The Endicott causeway
was constructed in 1985 to provide access to two
man-made gravel oil production islands. This
causeway extends over 22,000 feet (7,000 meters)
into the Beaufort Sea from the middle of the
Sagavanirktok River delta just east of Prudhoe
Bay (see Figure 2). The Endicott causeway is
actually made up of two causeways: a 15,0004-
foot (4,700-meter) inter-island causeway, and a
10,000+ foot (3,150-meter) causeway to shore.
Two breaches, with a combined length of 700 feet
(220 meters), were built into this shoreward
causeway in an attempt to ameliorate impacts to
water quality and fish habitat predicted in the
Environmental Impact Statement (EIS) for the
project (COE, 1984). Over 2,700,000 cubic yards of
gravel were used to construct this causeway. The
Endicott causeway is operated by Standard Alaska
Production Company for the "Duck Island Unit"
owner companies.
Other Causeways In addition to the West Dock
and Endicott causeways, a small 1,100-foot (350-
meter) solid-fill gravel causeway known as East
Dock has been built on the eastern shore of
Prudhoe Bay (Figure 2, Figure 9). East Dock was
built in the early 1970s for shipping related to oil
exploration activities in the Prudhoe Bay area.
Other major causeways have been proposed in the
Prudhoe Bay area as well (Figure 9). The
Lisburne causeway, proposed by ARCO Alaska,
Inc. in 1984, would have extended over 13,000 feet
(4,200 meters) into the middle of Prudhoe Bay
from the western shore. It would have provided
access to an offshore drilling island for production
from a portion of the Lisburne oilfield. (Five
related drilling pads are all onshore and have been
permitted and constructed separately). This
Endicott Causeway
\
Sagavanirktok 'River Delta
Figure 9
Location of proposed causeways in relation to existing causeways in the Prudhoe Bay area. The Niakuk
causeway was proposed in 1988; the Lisburne causeway proposal has been withdrawn. Modified from
SAPC, 1988.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
proposal was withdrawn by the developers in 1987
in favor of directional drilling from the existing
onshore sites.
Another causeway was proposed by Standard
Alaska Production Company in 1987. If
constructed, the Niakuk causeway would be
nearly 7,000 feet (2,200 meters) long, extending
north from Heald Point (at the northeast corner of
Prudhoe Bay) to a man-made oil production island.
Additional solid-fill gravel causeways have been
contemplated by industry and may be proposed for
the Prudhoe Bay area in the future. EISs for
federal oil and gas lease sales have also discussed
causeways relating to nearer-shore outer
continental shelf development (DOI, 1982; DOI,
1984). In addition, the final legislative EIS for
management of the coastal plain of the Arctic
National Wildlife Refuge (ANWR), approximately
160 kilometers to the east of Prudhoe Bay,
assumes that causeways may be needed to support
port development there (DOI, 1987).
Causeway Monitoring Programs In 1972, Barnes
et al. (1977) conducted nearshore oceanographic
surveys across the central Beaufort Sea coast;
however, other environmental data predating
construction of the first portion of the West Dock
causeway are extremely limited. Just prior to and
following construction of its second leg in 1976, the
West Dock causeway was the subject of several
studies required by the Corps of Engineers
(Furniss, 1975; Bendock etal., 1979; WCC, 1979;
Moulton et al., 1980). In addition, after the
Waterflood extension was built in 1980, fisheries
and oceanographic monitoring continued for four
years (WCC, 1982; Envirosphere, 1983;
Envirosphere, 1984; Envirosphere, 1986). The
draft synthesis report for these four years of
monitoring was completed in 1988 (Envirosphere,
1988b).
The lack of pre-causeway baseline data is a serious
limitation to the West Dock causeway monitoring
programs. Also, environmental studies conducted
after that causeway's construction were poorly
coordinated. Monitoring objectives and methods
differed substantially among the different
investigators, such that comprehensive,
comparable data were not collected from year to
year. Each study differed as knowledge about how
to measure the effects of the causeways evolved.
As a result, only the final year's monitoring at the
West Dock causeway was reasonably
comprehensive and relatively comparable to the
approach later used at the Endicott causeway.
In contrast to West Dock causeway monitoring,
the Endicott causeway monitoring program was
intended to emphasize coordinated planning and
the collection of an internally consistent multi-
year data set. This monitoring program also
suffered from limited baseline data collection, this
time specific to the Sagavanirktok River delta
region. However, a complete monitoring program
was fielded during the first three years following
construction of the causeway in early 1985
(Envirosphere, 1987; Envirosphere, 1988a;
Envirosphere, 1988d;NOAA, 1988). The Corps of
Engineers decided to discontinue the major
fisheries and supporting oceanographic portions of
the Endicott causeway monitoring program after
results from the three years of study showed that
impacts substantially exceeded many of the
predictions made in the Endicott project EIS.
Other aspects of the monitoring program are
expected to continue, including a terrestrial
program and oceanographic monitoring not
directly related to the fisheries program.
As directed by the Corps of Engineers, the
Endicott causeway monitoring program was
habitat-based rather than population-based.
Habitat monitoring is more effective and
considerably less expensive than direct population
monitoring in the Arctic. Habitat monitoring has
its basis in accepted ecological principles. In
particular, it is recognized that populations in low
diversity physically stressed environments, or
those in environments that are subject to irregular
environmental perturbations, tend to be regulated
by physical components of the environment such
as weather, currents, temperature, etc. (Odum,
1971). Anadromous fish populations in the central
Beaufort Sea exist in an environment that fits
both the above descriptions well. Therefore,
attention for monitoring focused on habitat
changes and other indicators of potential
population-level impacts, as opposed to direct
measurement of population sizes through time.
This approach was intended to allow indicators of
environmental risk to be assessed before
irreversible adverse impacts were realized, rather
than after such impacts had already occurred.
IMPACTS OF CAUSEWAYS
The primary concerns about the West Dock and
Endicott causeways are their impacts to the water
quality and circulation patterns of the central
Beaufort Sea nearshore estuarine environment.
During their brief summer feeding period,
anadromous fish are generally constrained to this
immediate nearshore zone where inhospitable
marine conditions occurred less frequently in the
past. It is within this same critical nearshore zone
that causeways have disrupted circulation
patterns and caused estuarine habitat to be
replaced by offshore marine water across many
miles of coastline. The following sections discuss
the fundamental impacts of these massive
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
structures to the physical and biological
environments. (Other potential impacts - e.g.,
related to industrial discharges or spills - are not
addressed in this report.)
PHYSICAL IMPACTS
The basic physical impacts of constructing the
causeways within the estuarine nearshore zone
appear, with hindsight, to be easily predictable.
Unfortunately, little site-specific baseline
knowledge of nearshore processes in the central
Beaufort Sea was collected before construction of
either of the causeways had begun. The evolution
in knowledge during several years of monitoring,
however, has provided a clearer picture of the
processes affected by the causeways.
Overall, causeways have disrupted the nearshore
environment throughout the Prudhoe Bay area
because of their construction perpendicular to the
wind and nearshore current patterns. As will be
explained, this disruption occurs under both
easterly and westerly winds by: 1) deflecting both
the coastal water mass and river plumes offshore,
concurrently degrading their estuarine character
through the loss of thermal energy and freshwater
to offshore areas; 2) causing enhanced upwelling
and intrusion of marine water directly into the
nearshore environment, thus severing the band of
estuarine conditions along the coast; and 3) both
delaying breakup and accelerating freezeup in the
nearshore zone.
The coastal water mass and the river plumes are
deflected offshore by both the West Dock and
Endicott causeways despite the breaching
incorporated into each of them. Offshore
deflection causes enhanced mixing with marine
water and degradation of estuarine conditions.
Under easterly winds, marine water upwells to
replace the deflected water, and marine conditions
often extend and dominate for many kilometers
downstream. Today, the coastal water mass and
Sagavanirktok River plume no longer are
maintained in a generally continuous brackish
band across the Prudhoe Bay area. Instead,
nearshore water quality is more heterogenous,
and marine conditions have become much more
dominant. Overall, fundamental alterations in
nearshore water quality and circulation patterns
have occurred along as much as 65 kilometers of
the Prudhoe Bay area coastline.
Offshore Deflection of Estuarine Water Masses
During easterly winds, the coastal water mass
moves west along the coast until it encounters the
Kuparuk River Delta
( ^Prudhoe Ba\
Sagavanirktuk River Helta
Sole of Nautical Miles
Figure 10
Generalized flow of nearshore waters during sustained easterly winds since construction of the West
Dock and Endicott causeways, showing causeway-induced deflection of nearshore water masses.
Heavy solid arrows denote flow of subsurface marine water. Cross-hatched arrows denote surface
flow, with the density of cross-hatching proportional to salinity. Adapted from Envirosphere, 1988b
and NOAA, 1988.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Endicott causeway. The nearshore 500 feet of
breaching in the causeway generally does not
accomodate all of the flow from the east channel of
the Sagavanirktok River, and a portion of this flow
is deflected to the 200-foot breach farther offshore
(Envirosphere, 1988c; Envirosphere, 1988d). The
second breach is not always sufficient either, so at
times some of the river discharge is deflected
further - around the end of the causeway. Because
the existing causeway breaches are dominated by
fresh Sagavanirktok River plume water, almost
the entire coastal water mass is deflected offshore
and around the structure (Figure 10). Depending
on the precise direction of the wind, the deflected
water will be held offshore (southeasterly winds),
or will flow across the mouth of Prudhoe Bay,
primarily just outside the Gull Island shoal
(northeasterly winds). In general, a greater offshore
deflection causes greater contact with offshore
marine water and more rapid degradation of water
quality. Increasing salinities averaging over 2
parts per thousand per kilometer (ppt/km) have
been measured in the deflected water downwind
from the Endicott causeway (Envirosphere, 1988a).
In the vicinity of West Dock, the deflected coastal
water and the Sagavanirktok River plume often
merge, but do not pass directly into the lagoon
system as they did prior to construction of the
causeway. The 50-foot breach in the West Dock
causeway has been blocked almost continuously
since its construction by gravel eroded from the
causeway's sides. This breach allows virtually no
water to pass. Therefore, upon encountering the
causeway, coastal and Sagavanirktok River water
is deflected offshore (Figure 10) outside of Stump
Island Lagoon and Gwydyr Bay. Depending on the
precise direction of the wind (southeasterly or
northeasterly), all of the deflected water will be
held offshore, or a portion may re-enter the lagoon
system several kilometers to the west through
various entrances between the barrier islands.
After passing West Dock, the deflected water is
again placed into greater contact with marine
water and rapidly loses its estuarine character.
Salinity of the water deflected by the West Dock
causeway has been observed to increase at rates up
to an additional 9 ppt/km (NOAA, 1988).
Deflection of nearshore water masses also occurs
during westerly winds. However, the overall
physical impacts of the causeways differ during
east and west winds. Upwelling during easterly
winds and intrusions during the onset of westerly
winds, as described below, cause much of this
difference.
East Winds: UDwelling As water is deflected
offshore at each causeway during easterly winds,
the surface water in the lee of the structures is also
blown to the west. Under pre-causeway
y,M^|ff\tTi
VA>26 pptt feAO
^»trvfN\. »•;}.>*
Sagavanirktok River Delta
Figure 11
Salinity at 1 meter depth during sustained east winds, July 22,1986 survey. Note that upwelled high
salinity water (stippled) has been drawn into very shallow water between the Endicott causeway and
Heatd Point, and that even higher salinity water (shaded) has upwelled all the way in to the island-to-
shore leg of the causeway, despite existing breaches. Adapted from Envirosphere, 1988d.
13
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
Plum* tntwwly 0*cay
A \ OilUnc* Along Plum* (Kmi B
Scale of Nautical Miles
Figure 12
Detail of deflection and degradation of nearshore estuarine water at the Endicott causeway during
sustained easterly winds. The A-B transect follows the center-line of the deflected water. Inset shows
increasing salinity of the deflected water along the A-B transect. Adapted from Envirosphere, 1988b.
conditions, this water would be replaced by the
adjacent coastal and river water; however, the
causeways block this process. Subsurface marine
water is drawn instead from offshore and upwells
to replace the deflected water - even in very
shallow areas. While natural upwelling in the
region often brings marine water to the bottom in
areas that are as shallow as 2-4 meters, the
causeways result in upwelling to the surface in
downwind areas with depths of less than 1 meter
(Envirosphere, 1988d; NOAA, 1988). Given the
expanse of very shallow water in the vicinity,
significant additional areas now frequently
experience marine conditions due to this enhanced
upwelling.
The pattern of upwelling at the Endicott causeway
is influenced by the structure's location between
the two main channels of the Sagavanirktok
River. Replacement water is partially made up of
fresh discharge from the river. Some of this is
fresh water that has been deflected offshore
somewhat, flowing through the breaches in the
causeway. The fresh water flows across the delta,
past Heald Point and the Niakuk Islands at the
northeast corner of Prudhoe Bay. Some enters the
bay, and some crosses the bay along and outside
the Gull Island shoal. While the most immediate
nearshore area downwind of Endicott may thus
remain primarily fresh (Figure 10), marine bottom
water flowing in past the northwestern tip of the
causeway upwells in the shallows between the
causeway and shore (Figure 11).
The marine upwelling occurring at the Endicott
causeway extends in a band to the south and west
of the causeway's tip, occasionally to Heald Point.
Depending on the strength of the wind, marine
water also upwells to the east along the inside of
the inter-island causeway as far as the west side of
the island-to-shore leg of the structure (Figure 11).
Both the intensity and the overall extent of the
marine upwelling significantly exceeds the
Endicott project EIS predictions (COE, 1984).
Salinity differences of 20 ppt have been observed
between the plume water on one side of the
causeway and upwelled water on the other side -
an impact three times greater than predicted in
the EIS (Envirosphere, 1988c). The EIS also
predicted significant water quality changes would
occur within an area of about 11,000 acres; EPA
has calculated that the area affected has actually
exceeded 40,000 acres considering both east and
west wind conditions.
The offshore deflection of coastal water and the
marine upwelling along the delta front separate
the coastal water from much of the Sagavanirktok
River's fresh discharge for several kilometers.
Prior to the Endicott causeway, the river
discharge mixed directly with the coastal water
(see Figure 3), helping to maintain the estuarine
conditions across the Prudhoe Bay area (NOAA,
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
1988). Today these water masses are separated,
and each of them is in greater contact with marine
water (Envirosphere, 1988a; Envirosphere,
1988d). Thus, mixing causes each to become more
marine in character as it moves through the area
(Figure 12).
At the West Dock causeway, surface water
immediately downwind of the structure and
within the lagoon system is also blown west at the
same time that estuarine water is deflected
offshore. Unlike the Endicott causeway system,
however, there is no significant nearby source of
fresh water to partially replace the deflected
water. Instead, the deflected water is entirely
replaced by marine water from offshore that
upwells directly into Stump Island Lagoon.
Consequently, the West Dock causeway causes a
much more extensive invasion of marine
conditions into the nearshore zone. Marine water
upwelled as a result of the causeway can extend
throughout Gwydyr Bay (some 20 to 35
kilometers) and routinely dominates beyond the
Kuparuk River Delta (approximately 15
kilometers).
The overall impact of the West Dock and Endicott
causeways during easterly winds is that the zone
of estuarine water that had dominated the
nearshore area between the Colville and the
Sagavanirktok rivers in the pre-causeway
environment is no longer continuous under even
relatively low intensity east winds. In the absence
of the causeways, water would not be deflected
offshore and marine water would not frequently
dominate the lagoon system west of Prudhoe Bay
as it does today (NOAA, 1988).
West Winds: Intrusion During westerly winds,
the mass of upwelled marine water dominating
the lagoon system west of the West Dock causeway
begins to flow east around the causeway toward
Prudhoe Bay (Figure 13). As this occurs, water
level rises in an intrusion event (see Physical
Environment, above). The intrusion ends
relatively quickly as water level equilibrates, but
usually not before the more estuarine water that
had occupied Prudhoe Bay is displaced by the
marine water flowing in from the end of the West
Dock causeway (Envirosphere, 1988c; NOAA,
1988). Distinct boundaries between receding
estuarine water and incoming marine water are
observed at these times. In this manner, marine
conditions regularly occur in Prudhoe Bay as a
result of the West Dock causeway.
State ol Nnulical \lili-,
r
Figure 13
Generalized flow of nearshore waters during sustained westerly winds since construction of the West
Dock and Endicott causeways, showing causeway-induced deflection of nearshore water masses.
Heavy solid arrows denote flow of subsurface marine water. Cross-hatched arrows denote surface
flow, with the density of cross-hatching proportional to salinity. Adapted from Envirosphere, 1988b
and NOAA, 1988.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
If west winds persist, the Colville River plume will
eventually flow through the lagoon system,
reaching and passing around West Dock. This was
observed in 1984 and 1987. However,
meteorological records for the area indicate that
such conditions are unusual (Envirosphere,
1988d). Unfortunately, even when they do occur,
the Colville River plume is able to do little to flush
marine conditions from Prudhoe Bay, since most of
the plume's flow during westerly winds (after the
active intrusion ceases) occurs outside the Gull
Island shoal as a result of bathymetric steering
(NOAA, 1988). The first major marine intrusion
event of the season can thus adversely affect
Prudhoe Bay water quality for the remainder of
the open water period (Envirosphere, 1988b;
Envirosphere, 1988d; NOAA, 1988).
After passing Prudhoe Bay, coastal water (and at
times Colville River plume water) is also deflected
offshore by the Endicott causeway (Figure 13). As
also occurs during easterly winds, the 700 feet of
breaching in the structure is inadequate to
accommodate more than a small fraction of this
water. Some degradation of the estuarine
conditions of the deflected water occurs during
westerly winds as well. At these times, west
channel Sagavanirktok River water is forced to
mix both with marine water previously upwelled
by the Endicott causeway and with offshore
marine water as the plume is deflected around the
causeway. Water from the east channel of the
river also mixes with previously upwelled marine
water rather than with fresh water from the west
channel. In addition, being in the protected lee of
the causeway during westerly winds, east channel
water flows further from shore out over marine
waters, rather than flowing southeast into
southern Foggy Island Bay.
Fragmentation of Water Masses A net effect of the
causeways, considering both east wind and west
wind impacts, is that nearshore water masses
frequently become separated from like masses
along the coast. This water mass fragmentation
would not occur naturally under the same
meteorological conditions, except perhaps during
unusually harsh years (e.g., low river discharges,
cold temperatures). The large expanse of upwelled
marine water within the Simpson Lagoon system,
for instance, now routinely isolates the estuarine
conditions of the Prudhoe Bay area from similar
estuarine conditions maintained farther to the
west by the Colville River. As a result, each of
these areas is less accessible to feeding or
migrating anadromous fish (see Biological
Impacts, below). This east-west fragmentation of
conditions within the nearshore zone, while
dominant during easterly winds, also persists
during westerly winds. During the first days of
westerly winds, the upwelled marine water
continues to fragment the nearshore water
masses, but the location of the discontinuity is
simply moved to the other side of the West Dock
causeway (i.e., into Prudhoe Bay).
The Endicott causeway also fragments water
masses because of its location within the
Sagavanirktok River delta. Because this
structure causes marine water to upwell between
the fresh river discharge and the deflected
brackish coastal water, a north-south
fragmentation of nearshore water masses occurs.
This fragmentation results in enhanced mixing
between marine and coastal water, direct mixing
between fresh river water and upwelled marine
water in the nearshore zone, and a general
degradation of habitat quality for the area's
anadromous fish populations (see Biological
Impacts, below).
Each of the other causeways that have been
proposed for the Prudhoe Bay area would
exacerbate the water quality impacts described
above. The Lisburne causeway would have made
marine waters even more difficult to flush from
Prudhoe Bay. The Niakuk causeway would likely
enhance the amount of marine water upwelled
near Prudhoe Bay during easterly winds and
would add to the offshore deflection of coastal
plume water under westerly winds. The Niakuk
causeway could significantly increase the rate of
intrusion of marine water into Prudhoe Bay, as
well as make resulting marine conditions more
difficult to flush from the bay. Overall, the
Niakuk and Endicott causeways together would be
more problematic than either of them
individually.
Ice Dynamics The West Dock and Endicott
causeways have affected ice dynamics in the
Prudhoe Bay area by deflecting and restricting the
early season overflooding of river water, thereby
altering the natural patterns of sea ice breakup
(Figure 14). The breakup of sea ice in the vicinity
of each causeway has been delayed by up to two
weeks (Envirosphere, 1988b; Envirosphere, 1988d;
NOAA, 1988). Freeze up, however, is locally
accelerated by the structures. Depending on wind
direction, ice builds up behind the causeways and
can solidify more quickly there, causing freezeup
to occur up to two weeks earlier than elsewhere in
the area (Envirosphere, 1988d;NOAA, 1988).
These alterations in breakup and freezeup
patterns occur primarily within about 5 km of the
causeways (NOAA, 1988). However, this effect is
directly within the nearshore zone used by
anadromous fish. Alteration of ice dynamics
within this important ecological zone represents a
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
risk to these fish (see Biological Impacts, below).
The proposed Niakuk causeway would also alter
Figure 14
Distribution of flood waters from the Kuparuk
and Sagavanirktok rivers, from LANDS AT
image of May 30,1985. The West Dock
causeway can be seen to restrict overflooding
to western Prudhoe Bay. Adapted from NOAA,
1988.
ice dynamics. The proposed structure extending
from Heald Point would further restrict river
overflooding into Prudhoe Bay and breakup of sea
ice within the bay. It would also accelerate
freezeup in the nearshore zone and within the west
channel of the Sagavanirktok River. The limited
breaching proposed for this structure is not
expected to be capable of eliminating these effects.
BIOLOGICAL IMPACTS
Important feeding and rearing habitat for
anadromous fish in the Prudhoe Bay area has been
significantly altered due to the presence of the
West Dock and Endicott causeways. Marine water
dominates or modifies conditions across many
kilometers of the coast, and both the quality and
quantity of suitable feeding and rearing habitat
have been substantially reduced. In addition,
oceanographic changes associated with the
causeways have fragmented fish habitat both near
Prudhoe Bay and along the coast as a whole,
affecting fish migration and distributions.
Causeway-induced habitat impacts and
alterations in ice dynamics occur directly within
the critical nearshore zone, and are now making
every year more similar to a "harsh" year as
described earlier.
Serious risks to the fish populations are posed by
these habitat impacts. Habitat alterations can
lead to overutilization of accessible areas and
underutilization of inaccessible areas. This
change in utilization can translate into reductions
in feeding and therefore growth for these
populations that are already energetically limited.
Taken together, these changes can greatly impact
the populations and the overall coastal fish
community, even in the absence of catastrophic or
worst-case events or years.
Causeway Effects on Population Sizes Little or no
reliable information exists about population sizes
for the nearshore fish species of the central
Beaufort Sea. Thus little direct evidence of
declines in population sizes can be cited. However,
some may question why this should remain the
situation after several years of causeway
monitoring. First, it is important to recall that
causeway monitoring, by design, has largely been
habitat-based (see Causeway Monitoring
Programs, above). It is therefore possible that
population declines have already begun to occur
that are simply going unmeasured. (It would take
a very large decline indeed to be obvious, given the
habitat focus of the monitoring to date. Once very
large population declines occur, it is usually too
late to easily reverse them.) Second, and perhaps
more important, is that reasonably comprehensive
monitoring has actually been conducted only for
four years, or about one-half the generation time
for the affected fish species. Since these fish take 8
to 12 years to mature, it would take at least that
long for the populations to decline obviously in the
absense of acute, catastrophic effects. While long-
term declines may be more probable than
catastrophic effects, the latter can also occur under
the appropriate set of conditions. This cannot be
discounted given the intended life of the
causeways.
Causeway Effects on Habitat Quality and Quantity
The alteration of coastal and Sagavanirktok River
plume water quality that results from offshore
deflection of these water masses at the West Dock
and Endicott causeways also represents a
degradation of habitat quality for anadromous
fish. These fish are highly dependent on estuarine
conditions in the nearshore waters (see Biological
Environment, above). As described earlier, the
causeways have displaced much of this habitat
offshore where its quality is rapidly degraded and
replaced it with unsuitable marine water.
In addition to the degradation offish habitat, the
West Dock and Endicott causeways have reduced
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
the total amount of suitable habitat available.
This is true in terms of both the area occupied by
suitable habitat under a given set of conditions
and in terms of the overall time during which
suitable habitat is available.
During both easterly and westerly winds,
unsuitable marine conditions dominate large
areas that once provided generally continuous
estuarine habitat. For example, it is estimated
that during prevailing easterly winds the Endicott
causeway results in the loss of at least 60 percent
of the shallow (< 2 meters) estuarine habitat that
would otherwise exist in the western
Sagavanirktok River delta (Envirosphere, 1988d).
Similarly, the West Dock and Endicott causeways
combined are estimated to cause the loss of
approximately 50 percent of the anadromous fish
habitat of the overall Endicott monitoring
program study area (from Foggy Island Bay west
through Gwydyr Bay (Envirosphere, 1988d). This
is consistent with EPA's calculations, based on
oceanographic survey data, that up to 365 square
kilometers of the nearshore zone that had provided
estuarine habitat prior to construction of the
causeways have been affected.
Marine conditions, together with altered ice
dynamics within the zone used by fish during
migrations between overwintering areas and
summer rearing areas, also reduce the total
amount of time during which suitable habitat is
available. These reductions in habitat quality and
quantity have resulted in altered fish use of the
Prudhoe Bay area, probable decreased feeding
efficiency, and decreased potential for overwinter
survival, growth, and reproduction.
Changes in Fish Use of the Prudhoe Bay Area The
increased fragmentation of water masses that
results from the Endicott and West Dock
causeways translates to increased fragmentation
of anadromous fish habitat. West Dock in
particular creates a discontinuity in the nearshore
fish habitat by enhancing upwelling of marine
water during east winds (the most common winds
during the summer). Eastward-moving fish from
the Colville River area have been observed to
retreat back to the west upon encountering marine
water upwelled in the lagoon system west of the
West Dock causeway (Moulton et al, 1986;
Envirosphere, 1987). Fish within Prudhoe Bay
are similarly blocked from moving west by this
expanse of inhospitable marine water. This
isolation offish on either side of the causeway can
affect return migrations to overwintering areas as
well as distributions to and between rearing areas
(Envirosphere, 1988b; Envirosphere, 1988d).
Overcrowding on one side of the causeway will
result in a reduction in feeding efficiency.
Similarly, if preferred overwintering sites are
made inaccessible at the critical time, the fish will
not reach a suitable site or may be forced to use
less suitable areas. As described earlier, the
Colville River delta is the primary overwintering
area for most of these fish. Delays in the return
migration to the Colville River have in fact been
observed at West Dock during east winds
(Envirosphere, 1988b). The extent to which such
delays have forced fish to attempt overwintering
in unsuitable areas is unknown. However, in the
winter of 1985/1986 a large number of Arctic cisco
attempted to overwinter in an apparently
unsuitable area of the Sagavanirktok River, and
died when oxygen levels dropped (Schmidt et al,
1987; Envirosphere, 1987).
Changes in fish distribution and use of Prudhoe
Bay occur during west winds, as well. The marine
water previously upweiled west of West Dock
flows back around the causeway when the wind
shifts to westerly, and marine water fills Prudhoe
Bay from the west to the east (see Physical
Impacts, above). This drives the anadromous fish
that had been feeding in the bay, especially Arctic
and least cisco, toward the fresh water of the
Sagavanirktok River delta where they can find
refuge from the marine conditions (Envirosphere,
1988b; Envirosphere, 1988d). However, all of the
time spent in refuge areas is time not spent
feeding in more productive estuarine habitat;
growth potential for these fish will therefore be
reduced in proportion to time spent in refuge.
At the same time, the fresher water nearest the
delta is the usual habitat of the broad whitefish. It
is unknown at this time whether the increased use
of the delta by other species results in
overcrowding or overutilization of the broad
whitefish habitat. However, sampling from 1982
through 1987 suggests a reduction in the strength
of younger age-classes corresponding to post-
causeway years of altered environmental
conditions (Envirosphere, 1988d).
Changes to Community Structure The composition
of the nearshore fish community of the Prudhoe
Bay area has changed dramatically since
construction of the West Dock and Endicott
causeways. Where least cisco once dominated and
freshwater species such as round and humpback
whitefish were regularly found (see Biological
Environment, above), these species now comprise
a relatively small portion of the fish sampled.
Instead, marine species - primarily Arctic cod -
have become dominant overall. At the same time,
Arctic cisco have become the dominant
anadromous fish in Prudhoe Bay. In general, the
nearshore fish community is now characterized
mainly by a combination of marine species and
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
anadromous species more tolerant of higher
salinities, while fresher-water species have all but
disappeared.
These changes are consistent with the dramatic
causeway-induced changes in the physical
conditions of the nearshore environment described
earlier. In particular, they are consistent with a
basic alteration in the balance of fresh and marine
waters that had previously defined the estuarine
character of the nearshore zone. Odum (1971), in a
discussion of estuarine ecology, states that it "is
self-evident that different circulation patterns and
gradients will greatly influence the distribution of
individual species, but so long as there are adapted
populations the overall productivity need not be
greatly affected by these differences." The
nearshore environment of the Prudhoe Bay area
now clearly experiences different circulation
patterns and gradients as a result of the West
Dock and Endicott causeways, and the
distribution of individual species has certainly
been affected. It is also possible that overall
productivity has not substantially changed.
However, that productivity has shifted from
anadromous and freshwater fish to dominance by
marine species - especially Arctic cod.
Bioenergeticg To the extent that fish use and
habitat of the Prudhoe Bay area have been altered
by the causeways, several biological impacts are
probable. All of these impacts are directly or
indirectly related to bioenergetics: the ability of
fish to aquire and store sufficient energy for
survival, growth, and reproduction. If sufficient
energy is not acquired and stored during each brief
summer feeding period, the populations will
decline.2' The West Dock and Endicott causeways
have seriously increased the probability that this
will occur. This discussion presents some of the
bioenergetic impacts and risks that anadromous
fish now face as a result of causeways in the
Prudhoe Bay area.
Implications of Temperature and Salinity Changes
Causeway-induced temperature and salinity
conditions are within the overall range that
naturally occurs across the region. This statement
would always be true - regardless of the degree of
causeway-induced impacts - because causeways
neither create nor destroy heat or salt. However,
not all water quality conditions within the range
found across the region are suitable for use by
anadromous fish. For example, nearshore
conditions range from liquid to solid but, of course,
solid ice does not serve as habitat for anadromous
fish. Even during the open water period, some
"natural" conditions in the region are often
outside the range of physiological tolerance for
some fish species. Exposure to conditions-within
but near limits of tolerance may allow fish to
survive, but will exact high metabolic costs (Brett,
1971; Smith, 1982). Even minor deviations
(e.g., 2-5°C) from "optimal" conditions can have
significant effects on growth and reproductive
potential (Magnusonetal., 1979). Whether in
Arctic or temperate regions, a fish's potential for
achieving an overall net energy gain that is
sufficient for overwintering, growth, and
reproduction will be directly reduced by both the
degree and persistence of extreme conditions
(Brett, 1976).
Arctic anadromous fish are not immune to these
consequences. Growth rates of broad whitefish in
the Prudhoe Bay area appear to be greater, on
average, during west wind years when warmer
temperatures and/or lower salinities have been
more predominant throughout the summer
feeding period (Envirosphere, 1988d). This
indicates that water quality conditions integrated
over the entire region and over the entire summer
can affect the overall health and condition of
Arctic anadromous fish populations. This is to be
expected because west winds keep warm, fresh
water nearshore, therefore resulting in generally
higher temperatures and lower salinities. In
contrast, east winds promote stratification,
upwelling, and increased marine influence on the
nearshore zone throughout the region.
However, as described earlier, fish do not respond
directly to average or regional conditions; they
must attempt to achieve the best compromise
2 / Some investigator? suggest that overwintering habitat is the only true limitation to the size of Arctic anadromous fish
populations. This would be due to physical limitations such as water quality (including dissolved oxygen I and space
(Schmidt et al., 1987). Physical factors would be expected to often become limiting in marginal overwintering areas (for
example, if higher numbers offish are forced to attempt overwintering in less dependable sites due to causeways blocking or
delaying migration to preferred Colville River sites). In fact, a water quality-related fish kill has been observed in a
marginal area of the Sagavanirktok River (Envirosphere, 1988d>. However, dependable, regularly used (e.g., Colville River
delta) overwintering areas, by definition, should be physically capable of supporting the populations in most years and
should not routinely limit the populations directly. (For example, it would be expected that severe dissolved oxygen
depletion would affect all the fish in a given overwintering pool - not just a few.) However, in especially harsh years,
overwintering may be directly limiting.
It is important to keep in mind that successful overwintering must occur not just in any one year, but in all years if survival
to reproduction is to occur for populations to be maintained. If energetic constraints significantly disrupt this continuum at
any point, the populations will decline and can even crash. Thus, even if causeways were to significantly impact fish
energetics only irregularly, these events would be capable of severely affecting the population over the long term.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
between several aspects of their immediate
surroundings. Salinity, temperature, and prey
availability are perhaps the most important of
these. Monitoring programs have observed that
many Arctic anadromous fish avoid marine
conditions in the Prudhoe Bay area (Envirosphere,
1987; Envirosphere, 1988d). This is a direct
indication that these fish, in fact, do not utilize all
the conditions that naturally occur within the
region.
The changes in fish distribution and use of the
Prudhoe Bay area are examples of immediate
behavioral responses to adverse conditions. Such
behavioral responses are not without cost,
however. As stated earlier, time spent in refuge
areas is time not spent feeding in more suitable
estuarine habitat. A reduction in the amount of
time foraging will affect the scope for growth for
that year. Just as east-wind-dominated years can
naturally limit growth by degrading conditions on
a regional scale, the more local effects of
causeways within the critical nearshore habitat
zone reduce the time spent feeding in high quality
habitat and also affect scope for growth.
Even when drastic water quality changes do not
occur and fish are not forced to take refuge, the
quality of feeding habitat in the Prudhoe Bay area
is often degraded by the presence of the causeways.
This occurs because the brackish coastal water is
deflected at each causeway, resulting in increased
mixing with marine water and an overall decrease
in temperature and increase in salinity.
Therefore, even though fish are not always forced
to completely abandon the feeding area, the
energetic costs of remaining there are greater and
less net energy gain is possible.
The frequency of such episodes will vary from year
to year, as will the degree of degradation of feeding
habitat quality. However, since energy is already
a direct limitation, fish will be affected to some
extent each year. Reduced health and condition
(fat reserves) of individuals translates into
population impacts if overwintering mortality
increases, age of maturity is delayed, or fecundity
is reduced.
Food A uailability It has been estimated that the
abundance of food organisms used by the
anadromous fish greatly overshadows what the
fish could possibly consume (Craig and Haldorson,
1981; Moulton et al., 1986). However, abundance
is not the same as availability. Only those
organisms that are available to the fish can
possibly become food; and abundant food in one
area is not available if surrounding water quality
conditions deny the fish access to it. Beyond this,
not all food organisms within a given patch of
accessible habitat are necessarily available to all
species and size-classes offish. An abundance of
food types preferred by one fish does not mean that
other fish in the area can use them. The fact that
Arctic populations of anadromous fish grow and
mature more slowly and cannot spawn in
consecutive years clearly indicates that energy is a
limiting factor for them (abundance of food
notwithstanding). Important supporting evidence
has come from fish stomach sampling. Each year
of monitoring has found a significant percentage of
empty stomachs (Envirosphere, 1987;
Envirosphere, 1988d; Envirosphere, 1988e).
Given that food organisms, overall, are highly
abundant, empty stomachs are a strong indication
that food intake is not always high and that food is
not effectively unlimited.
In addition to such natural energetic limitations,
evidence has been collected through causeway
monitoring programs indicating that the
causeways have further limited the energy
available to anadromous fish. For example, 1985
sampling found that for an abundant year-class of
Arctic cisco, the size of individual fish in the
Prudhoe Bay area was significantly smaller than
that of individuals of the same year class captured
outside the area. A smaller size-at-age can result
from differential feeding success. The size
difference did not reappear in the 1986 sampling,
and it is unknown whether these smaller fish were
too weak to survive the winter and thus
disappeared from the population. However, a
large mortality did occur during the winter of
1985-1986 in the Sagavanirktok River
(Envirosphere, 1987c). The apparent downward
trend to the Sagavanirktok River broad whitefish
population may also be a result of a reduction in
food availability, either due to a reduction in
available habitat or due to competition from other
displaced anadromous fish. The dramatic shift in
the make-up of the overall nearshore fish
community also indicates that feeding
opportunities for fresher-water species have been
reduced. However, lack of monitoring emphasis
on these species limits the ability to determine
whether they have suffered population declines.
Consequences of Reduced Energy Intake There
are serious ramifications to causeways further
limiting the net energy intake potential for the
anadromous fish populations. In the immediate
sense, fish are at risk of not acquiring enough fat
reserves to survive the subsequent overwintering
period. A year in which this occurs for some
percentage of any population will result in a direct
and immediate decline in overall population size
by the same percentage. If such a decline is
sufficient to overshadow any compensatory
mechanisms that may exist, the affected
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
population could take several decades to recover
even if no further increase in overwintering
mortality were to occur in subsequent years (EPA,
1985).
Significant but less immediate impacts could also
occur if conditions in a given year are not so severe
that overwintering mortality occurs, but are still
severe enough to reduce growth. Only one such
year per generation might be necessary to delay
the age at which the affected fish reach maturity
and spawn. Delayed maturity for a substantial
proportion of any of the fish populations also can
result in a direct decline in population size;
however, it would not become evident until several
years later when the affected age-class matures.
Again, the population could require several
decades to recover even if there were no further
effects to other age-classes. Of course, if such
conditions were to recur during subsequent
generations, recovery would not proceed at all;
and if such conditions occurred more than once to a
single generation, the intensity of the impact
would be multiplied. The same types of effects
could result from a reduction in fecundity as well
(which also can result from reduced net energy
intake and reduced size) even if maturation is not
delayed.
Taken together, causeway-induced alterations in
circulation patterns, water quality, and ice
dynamics - occurring as they do directly within the
critical nearshore zone - now make every year
more similar to a naturally harsh year. This
means that long-term declines in the populations
of central Beaufort Sea anadromous fish are
likely. Should truly harsh years be in store,
catastrophic impacts to these populations - and the
fisheries they support - may quickly occur. Given
the lack of reliable information on population sizes
and the fact that monitoring programs have not
been designed to measure population sizes
directly, it is possible that significant declines
have already begun to occur.
RESEARCH NEEDS
After several years of fairly intensive field
investigation, much remains to be learned about
the nearshore environment of the Prudhoe Bay
area. Research opportunities exist in terms of
both oceanographic and fisheries issues.
Now that a reasonable basic understanding exists
of the physical processes that dominate in the
nearshore zone, it should be possible to accurately
model them mathematically. Three-dimensional
computer-based circulation modeling has been
recommended for adequately describing and
predicting impacts of existing and proposed
nearshore structures (NOAA, 1988). To be useful,
such modeling should be capable of sufficient
resolution to simulate local oceanographic
processes and interactions, and should possess a
sufficient number of internal test points to allow
evaluation of a variety of scenarios. In addition,
an appropriate model would need extensive
calibration and verification using field-collected
data prior to implementation. Computer modeling
has been applied to Prudhoe Bay area causeway
issues in the past; however, it has been highly
controversial. True state-of-the-art modeling,
thoroughly reviewed and approved by appropriate
governmental agencies, should be capable of
accurately simulating Prudhoe Bay area
conditions. Such a model would prove an
important tool for decision-making, but could take
several years to fully develop.
In addition to modeling, oceanographic field
surveys of the nearshore zone outside the
boundaries of the Endicott monitoring program
study area are needed. Some study related to
offshore oil and gas leasing programs is ongoing,
but the level of intensity is far short of what is
desirable for site-specific decision-making. In
general, much more information about nearshore
oceanographic processes and hydrographic
conditions across the entire Beaufort Sea coast is
needed.
A substantial amount of research remains to be
conducted on Beaufort Sea fish and fish
populations - much of it basic in nature. Some
stock identification work is ongoing, but further
work would be important. In particular, an
enhanced international effort to identify
spawning areas for Arctic cisco in the Mackenzie
River basin, and to determine whether discrete
spawning populations exist, is needed.
Distribution and abundance information for the
fresher-water species that appear to have basically
disappeared from Prudhoe Bay sampling is
important to acquire, and reliable population-level
data for all nearshore species would certainly be
useful. The latter may continue to be difficult to
effectively gather, given the importance of tagging
to the effort and the extreme sensitivity of some
species to the tagging methods so far employed.
Laboratory study of basic physiological responses
of the different fish species (and life history stages)
is basic information that is particularly lacking.
Some studies have been performed and others are
ongoing, but investigation into these areas is in its
infancy for Beaufort Sea anadromous fish. Too
often, such studies are directed at specific, narrow
questions and at the same time the data they
generate are interpreted too broadly. It is
important that basic physiological and behavioral
studies continue, but extreme caution should be
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
exercised in any attempts to directly interpret
field observations with limited laboratory data.
The single most important type of data needed,
however, is adequate site-specific environmental
baseline data concerning any new projects
proposed for the Beaufort Sea's nearshore zone.
This cannot be over-emphasized. The lack of
adequate baseline data has been the most serious
limitation to decision-making for Prudhoe Bay
area causeways to date, affecting initial
permitting decisions, the design of the monitoring
programs, the effectiveness of the monitoring, and
ultimately decisions about mitigation. Effective
and timely decisions can only be made where a
basic understanding of the affected environment
exists. By conducting several years of intensive
monitoring, a basic site-specific understanding of
the nearshore Prudhoe Bay environment is now
available. Ensuring that it also exists for future
construction proposals throughout the nearshore
zone of the Beaufort Sea is the best way to ensure
that unnecessary and irreparable impacts to the
aquatic environment can be avoided.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
CONCLUSION
The nearshore estuarine conditions of the Prudhoe
Bay area are critical feeding and rearing habitat
for many central Beaufort Sea anadromous fish.
The West Dock and Endicott causeways have
significantly altered the balance of fresh and
marine waters throughout this area,
fundamentally altering water quality and
circulation patterns along as much as 65 kilo-
meters of coastline. The Arctic fish populations
affected by these oceanographic changes are
already naturally limited by their environment to
the extent that they are slower growing and
maturing than more southern populations.
Causeway-induced habitat changes further limit
the ability of these fish to obtain sufficient energy
for overwintering survival, growth, and
reproduction.
The causeway monitoring programs have been
designed around the premise - basic to ecological
study worldwide - that suitable habitat is a
necessary prerequisite to healthy populations. In
addition, such an approach allows mitigation
decisions to be made before population-level
impacts have already become irreversible,
whereas simple monitoring of population sizes
generally does not. As a result, post-causeway
monitoring programs have not directly measured
population sizes for the anadromous fish species of
the Prudhoe Bay area and little or no reliable
information about population sizes exists.
Therefore, claims about there being a lack of
evidence for population-level impacts are
misleading. It is possible that significant declines
are already occurring for some species, and that
this is simply going unmeasured. In fact,
monitoring programs have identified a variety of
indicators showing that this may be the case.
These indicators include: 1) basic changes in the
structure of the nearshore fish community to one
dominated by marine and relatively salt-tolerant
species, with freshwater species having all but
diasppeared; 2) reduction in the strength of young
age-classes of Sagavanirktok River broad
whitefish since 1981; 3) smaller size-at-age for a
large cohort of Arctic cisco in the Prudhoe Bay
area in 1985, together with evidence that they
may not have survived overwintering; and 4)
evidence (including stomach sampling) that food
organisms are not effectively unlimited.
In effect, the West Dock and Endicott causeways
make each year similar to a naturally harsh year,
wherein disruption offish habitat decreases the
potential for survival, growth, and eventual
reproduction. The probability of population-level
impacts is not presently quantifiable, but is
believed to be substantial given the variability in
weather and oceanographic conditions that can be
expected over the life of the causeways.
Ultimately, the individual anadromous fish, their
central Beaufort Sea populations, and the overall
nearshore fish community are at risk.
Eventually, the causeways could seriously harm
subsistence and commercial harvests in the Arctic.
These fish are also an international resource,
supporting subsistence users in both the United
States and Canada, and playing an ongoing role in
the native cultures of the American Arctic.
Restoration of natural nearshore circulation and
water quality would be required in order to reduce
the risks faced by central Beaufort Sea
anadromous fish. In contrast, construction of
additional causeways in the area would
significantly increase the existing impacts and
risks.
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U.S. Environmental Protection Agency, Region 10
Causeways in the Alaskan Beaufort Sea
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