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Executive Summary
Draft Environmental
Impact Statement
September 1989
Evaluation of the Continued Use of the
Massachusetts Bay Dredged Material
Disposal Site
EPA
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United States Environmental Protection Agency Region I
John F. Kennedy Building
Boston, Massachusetts 02203-2211
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EXECUTIVE SUMMARY
DRAFT ENVIRONMENTAL IMPACT STATEMENT
FOR
THE MASSACHUSETTS BAY DREDGED MATERIAL
OCEAN DISPOSAL SITE DESIGNATION
Prepared by: . . •
U.S. Environmental Protection Agency, Region I
JFK Federal Building
Hater Quality Branch
Boston, MA 02203
Paul G. Keough, Acting
Regional Administrator
U.S. Environmental Protection Agency, Region I
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Date
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
w,ASM!MGTON, D.C. 20460
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40
71° 50' 40' 30' 20' 10' 70'
30'
20'
10'
42°
50'
40'
30'
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Figure ES-l Approximate location of the Massachusetts Bay
Disposal Site
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EXECUTIVE SUMMARY
The purpose of .this draft Environmental Impact Statement ("EIS")
is to evaluate.the continued use of the Massachusetts Bay Disposal
Site ("MBDS"), formerly the Foul Area Disposal Site, in accordance
with the criteria established in EPA's Ocean Dumping Regulations
at 40 CFR §§228.4 to 228.6 for disposal of dredged material. The
site is located in Massachusetts Bay in approximately 90 meters of
water and is two nautical miles in diameter. The center of the
site is at 42° 25.7', 70° 34.0', approximately 22 nautical miles
east of Boston (see Figure ES-1).
The MBDS is currently operating as an EPA approved interim dredged
material disposal site. The scope of this draft EIS has therefore
been restricted to determining its suitability for continued use.
Alternative ocean disposal sites are not evaluated. Only if this
draft EIS were to show that the existing site was unsuitable for
continued use would other sites in the area have been investigated.
The U.S. Army Corps of Engineers ("COE") has disposed or permitted
disposal of approximately 2.8 million cubic yards of dredged
material at the MBDS over the past twelve years. Designation of
the site as a permanent Ocean Dredged Material Disposal Site
("ODMDS") would provide a site of suitable size to accommodate the
regional disposal needs of areas ranging from Gloucester to
Plymouth, Massachusetts, with occasional use by interests from
greater distances. .
Final site designation does not constitute approval for actual
disposal of dredged material, it only serves to identify an ocean
disposal alternative for individual dredging project reviews. All
dredged material proposed for ocean disposal will continue to be
evaluated on an individual project basis .by .the COE, which has
responsibilities for issuing ocean disposal permits for dredged
material under Section 103 of the Marine Protection, Research, and
Sanctuaries Act.
EXISTING CONDITIONS AND ENVIRONMENTAL IMPACTS AT THE SITE
Temperature and Salinity
The physical environment at MBDS is influenced by the coastal New
England climate, low riverine inputs to the Massachusetts Bay
system and the general circulation pattern of the Gulf of Maine.
The water column at MBDS behaves in a manner typical of
northeastern continental shelf regions, usually with isothermal
conditions of approximately 5*C during the winter, and stratified
conditions with maximum surface temperatures near 18'C and a strong
thermocline at 20 meters in the summer. During the late fall, the
water column usually returns to isothermal conditions. Salinity
minima occur in late spring as a result of increased runoff, but
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vary only Minimally with most values ranging from 31 to 33.parts
per thousand.
Physical alterations of substrate owing to dredged material
disposal will be confined to the site. The center and western
areas of the site are currently covered with dredged material
deposits which are relatively thin, broad layers consisting
primarily of silts and some coarser sediments. There are regions
with cohesive clump deposits in the vicinity of the disposal buoy.
Side scan sonar and REMOTS6 surveys have documented dredged
material deposits and cohesive clumps in areas where disposal had
taken place several years earlier. Consequently, it appears that
neither physical disturbance from currents and waves, nor
bioturbation has significantly affected these deposits over the
past few years. It is expected .that dredged material deposited at
the site in the future will similarly remain in place.
currents
Previous studies and the results of recent investigations in the
vicinity of MBDS indicate that bottom currents are usually less
than 20 cm/s, while mid-depth and surface currents may be higher.
During strong northeast winter storms (i.e., approximately once
every four years), the bottom currents near MBDS may increase in
a southerly direction to maximum speeds of 30 cm/s. The tidal
currents at MBDS are characterized by mean velocities near the
surface of 15 to 20 cm/s in NNE-SSW orientation which decrease with
depth to lower velocity, less periodic currents near the bottom.
The wave conditions in the vicinity of MBDS result from both local
wind wave formation and propagation of long period waves generated
on the adjoining continental, shelf. The sheltering provided by the
coastline severely limits wave generation from the westerly
direction; waves from the westerly, quadrants larger than 1.8 m
occur rarely, and waves over 3.7 m are virtually nonexistent.
During disposal, some of the fine-grained sediments separate from
the dredged material plume during convective descent and usually
remain in suspension. The amount of material that is dispersed in
the disposal plume is dependent upon the physical characteristics
of the sediment, the volume of material disposed, and method of
disposal, and typically ranges from 3 to 5%.
Dredged material which settles on the bottom at MBDS can be
expected to remain in place for extended periods of time. Near-
bottom currents are low, averaging less than 7 cm/s. Occasional
higher velocities, near 20 cm/s in a westerly direction, have been
observed in near-bottom waters in response to easterly storm events
occurring in fall or winter. These near-bottom currents alone are
not predicted to be strong enough to resuspend sediments at MBDS.
However, surficial sediments may be re suspended by wave action on
rare occasions of severe easterly storm events. In order to
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generate waves of sufficient height and period to cause
resuspension, an easterly storm must have winds in excess of 40 mph
for a period of more than 12 hours, an event estimated to occur
approximately once every four years. However, based on data
obtained from the National Weather Service, such a storm only
occurred once during the period between 1978 and 1986. Such
resuspension events are rare and typically result in resuspension
of only 4% of the surficial material. Transport of the
resuspended dredged material in combination with resuspended
natural sediments would be to the west and southwest during these
events.
Bathymetry
The topography of the disposal site is characterized by a
relatively flat, featureless bottom throughout the site with the
notable exception of steep shoaling in the northeast and northwest
quadrants. The depths throughout the smooth, featureless area are
approximately 90 meters, with maximum depths occurring in a broad
depression in the south central portion of the site. The shoals
in the northeast quadrant represent glacially-formed features which
are associated with Stellwagen Bank to .the east of the site.
In the deeper portions of MBDS the bottom is a broad depression
with natural sediments composed of fine grained silt. Shoal areas
to the north and northeast are covered by coarser deposits.
Dredged material, previously deposited at the site, has not been
altered or transported significantly during the past several years.
Water Chemistry
The water column concentrations of all metals at MBDS are currently
below EPA's acute marine water quality criteria. The average
Polycyclic Aromatic Hydrocarbon ("PAH") and Polychlorinated
biphenyl ("PCS") water column concentrations at MBDS are considered
to be low.
Review of historical disposal data, water column chemistry,
sediment chemistry, and biotic tissue residue levels, indicates
that past disposals of dredged material at MBDS modified natural
ambient conditions. Water quality impacts are temporally limited
to immediately following the disposal event and spatially limited
to an area about the size of the site.
A numerical model was developed to determine temporal and spatial
variations of water column toxicant levels within a dump patch
during and subsequent to each historical barge disposal event at
the MBDS in 1982. The year 1982 was chosen as a worst case year
because the greatest volume of material disposed at the MBDS of all
recorded years occurred then. Exceedances of EPA's marine water
quality criteria were estimated to occur less than 1% of the time.
The water quality modeling conducted revealed that these
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exceedances occur occasionally but only for those constituents that
have relatively high ambient concentrations. EPA determined that
water quality impacts are temporary and limited to the period
immediately following the disposal event.
sediment Chemistry ;
The sediment metals concentrations on dredged material in MBDS are
generally in the moderate (Cr, Pb, and Zn) to low (As, Cu, Cd, Hg,
and Ni) contamination range based on the Massachusetts Division of
Water Pollution Control's sediment classification scheme. Areas
within the MBDS boundary but spatially remote from the dredged
material disposal point have metals levels that are comparable to
a reference area - outside the site. Therefore, significant
elevations of metal contaminants are restricted to the point of
disposal. . • . ;
Organic chemical data from MBDS indicates elevated concentrations
at the disposal area on dredged material. Carbon to nitrogen
ratios averaged 11.6 for the disposal site, and 8.6 for the
reference site, which is relatively equivalent to the unimpacted
site within MBDS at 8.7. Oil and grease levels were low (<0.5%)
but statistically elevated at the disposal area in comparison with
the reference sediment and unimpacted areas within the site.
Petroleum hydrocarbons were also quantitatively low but elevated
on the dredged material compared to reference levels areas within
the site but off dredged material. •
Polycyclic Aromatic Hydrocarbon ("PAH") compounds were not detected
throughout the study area except for 0.51 ppra- of flouranthene and
7.64 ppm of phthalate compounds, used as plasticizers, at a site
of recent disposal. Both of these values are typical of the urban
estuarine sediments which have been deposited at the site.
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Polychlorinated biphenyl ("PCB") compounds were highly variable in
sediment concentration with disposal station values averaging 0.414
ppm and unimpacted areas within MBDS averaging 0.073 ppm.
Reference area PCB concentrations reflected the "settling basin"
nature of Stellwagen Basin averaging 0.061 ppm.
Chemical contaminant levels in sediments and biota on the site are
expected to be similar to existing conditions. These levels are
controlled primarily through the permitting process (rather than
site designation) and EPA's newly revised testing protocols should
help to prevent disposal of contaminated dredged material which
might impact biota at the site.
Tissue Residue
Tissue analyses of polychaetes, bivalves, and crustaceans at MBDS
revealed low levels of metal residues and no statistical elevations
over reference residues. Organic residue level data were generally
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highly variable and quantitatively low. One sample of Nephtys
incisa tissue from January 1986 on dredged material, exhibited an
elevated PCS concentration of 0.52 ppm wet .weight, however,
previous and subsequent sampling did not reveal concentrations as
high. PAH contamination was statistically higher on areas of
dredged material with respect to the reference sites.-
Quantitatively, PAH levels were less than 2.5 ppm dry weight and
predominately dominated by benzo(a)anthracene and chrysene.
Benthie community structure .
The benthic population studies indicate that the reference area and
areas within the site but off dredged material have similar benthic
community structures. The benthic community near the disposal buoy
is different than the reference area although the sediment types
are similar. The benthic population in areas where dredged
material has been historically deposited is clearly dominated by
oligochaetes. The assemblages are typical for populations
colonizing recently disturbed habitat exploiting the high organic
content of the substrate. The benthic community in areas within
HBDS not affected by dredged material is composed predominantly of
polychaetes, which occur normally in unimpacted areas of
Massachusetts Bay. Unimpacted areas within MBDS do have higher
densities of oligochaetes than the reference site. This may
indicate recruitment from stations on dredged material or another
type of perturbation, such as the foraging effects of organisms.
The sandy area within MBDS was similar to the sandy reference area.
The benthic community at the site will continue to impacted by
frequent disturbance and covering during disposal, but benthos
outside the site is not expected to be impacted.
Dredged material disposal at MBDS will not significantly affect the
plankton population of Massachusetts Bay. Localized impacts on
plankton may result from elevated suspended solids concentrations
for short periods of time following disposal. The .elution of
chemical contaminants in concentrations which could affect plankton
is not likely. EPA Marine Water Quality Criteria may be exceeded
for short periods of time for those constituents which have high
ambient concentrations. Potential interference with phytoplankton
and zooplankton productivity appear to be minimal.
Finfish
Finfish studies conducted at the MBDS suggest that notable finfish
resources exist near the site. The resident finfish community on
mud bottom at MBDS is dominated by American plaice and witch
flounder. Silver and red hake are abundant, commercially important
seasonal migrants at MBDS. Hard bottom communities at MBDS appear
to be dominated by redfish, ocean pout, cusk, and Atlantic
wolffish.
Benthic Resource Assessment Techniques studies suggest that fish
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community differences exist between dredged material and natural
bottom. Food resource availability and food utilization patterns
of dominant demersal fish may have been altered by previous dredged
material disposal. The, benthic community colonizing recently
disposed dredged material are typically dominated by polychaete
organisms of small body size and short life cycles, the preferred
prey of small finfish.
Continued disposal of dredged material at MBDS will not have a
significant impact on the marine resources of Massachusetts Bay.
Adverse impacts to individual organisms could occur during disposal
events, but are not predicted to be significant "outside of the
disposal site. Similarly, any changes in community structure
related to impacts on benthic food resources should be highly
localized and insignificant with' respect to fisheries resources on
a baywide basis.
Mammals, Reptiles, and Birds . . . •
The Gulf of Maine is within the range of several species of marine
mammals, turtles, and seabirds. Site specific studies conducted
in 1985-1986 identified non-endangered dominant marine mammals at
MBDS to include the Minke whale, the white sided dolphin, and the
harbor porpoise. Reptiles which may inhabit the MBDS include the
green turtle, the hawksbill turtle, and the leatherback turtle.
Dominant seabirds observed during these studies include the
northern fulmar, shearwaters, storm petrels, northern gannet,
Pomarine Jaeger, gulls, and alcids. •
Endangered Species
Several threatened and endangered species of marine mammals and
turtles occur in the vicinity of MBDS. The .Gulf of Maine waters
are high-use habitat for Fin, Humpback and Right whales between
spring and fall. Southwest Gulf of Maine is the subregion of
highest use per unit area by whales between Cape Hatteras, North
Carolina, and Nova Scotia. Several species of endangered whales
use this area throughout the year, with densest concentrations
occurring through fall. . . .
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Threatened or endangered species of marine turtles which may.
inhabit the study area include the loggerhead turtle and the
Atlantic Ridleys turtle, albeit Massachusetts Bay is considered
marginal habitat for both these species. Although other species
of turtles have been sited, the leatherback turtle is typically the
only., species found in the study area.
Continued disposal of dredged material at MBDS is not likely to
have any significant impact on endangered species, their prey, or
the habitat essential to their, survival. Contaminant levels in
prey species, such as sand lances are comparable to Massachusetts
Bay-wide background contamination. .No evidence of significant
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contaminant"remobilization exists with respect to dredged material
disposal at MBDS. 'Prey items of turtles are not anticipated to be
impacted owing to the limited persistence of spatial and temporal
disposal impacts. Tug and barge activity is riot anticipated to
interfere significantly with endangered species, since the
organisms can avoid traffic. -'
Management Strategies
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Site management integrates permitting, enforcement, monitoring, and
data interpretation to continually evaluate the appropriateness of
ocean disposal in relation to the Marine Protection, Research, and
Sanctuaries Act ("MPRSA") and the Ocean Dumping Criteria. The COE
is the permitting authority for ocean disposal of dredged material.
Enforcement is a joint responsibility of EPA and the COE. EPA has
the primary responsibility for management of ocean disposal sites.
The COE permitting process consists basically of three parts:
alternative analysis; sampling and analysis; and decision-making.
The need for ocean disposal, and potential land-based alternatives,
is identified in light of potential impacts of the proposed dumping
on environmental, aesthetic, recreational, or economic values.
Actual disposal may be permitted only after the applicant has shown
that no practicable alternatives to ocean disposal exist. The
permittee is required to develop a sampling plan which is
representative of the most contaminated areas so that a "worst
case" scenario is presented. Permits are issued only after the
tests have shown biological acceptability. Ultimately the decision
to deny, approve, or place restrictions on a permit is subjective
because the regulations do not prohibit environmental change' but
rather "unacceptable adverse impact." The COE coordinates all
projects closely with the EPA, the National Marine Fisheries
Service, and the U.S. Fish and Wildlife Service, all of which
cooperatively decide whether the dumping will unreasonably degrade
or endanger human health, welfare, or amenities, or the marine
environment* ecological systems, or economic potentialities.
EPA and the COE currently implement the methods set forth in their
regional testing protocol to determine whether dredged material
will cause a significant adverse impact to the marine environment
if disposed. The protocol consists of a tiered .approach. The
first tier involves a historical data review which is conducted so
that a determination can be made regarding whether certain types
and concentrations of contaminants are likely to be present in the
sediments to be dredged. Several exclusionary criteria are set
forth, which, if met would negate the need for further testing.
The second tier is the prebioassay stage, where bulk sediment
chemistry and grain size evaluations are performed to detect the
types and levels of chemicals which are present. The third tier
consists of bioassay and bioaccumulation testing, direct indicators
of. potential ecological effects. The results of these tests are
compared to identical tests performed on: (i) a reference sediment
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which Should represent ecological conditions at a site similar to
the disposal site but not affected by dredged material and (ii) a
control sediment to ensure that any observed effects are caused
only by differences in "sediment quality and not differing
laboratory conditions. A decision is made depending upon how
closely the impacts on organisms exposed to dredged.material and
the reference sediment compare.
A "clean11 reference site is essential to any ocean disposal program
as it may govern what material is suitable for ocean disposal. EPA
is continuing to investigate the acceptability, of the, existing
reference site'and exploring alternatives to it.
Another important part of dredged material management at MBDS is
navigation control during disposal operations. Recent surveys at
MBDS have shown that dredged material was restricted to an area
with a radius of approximately 500 meters for a deposit of about
250,000 m3 placed in the vicinity of a taut moored buoy. Tighter
control of the scows could potentially reduce this areal coverage
further. EPA and the COE jointly develop specific monitoring plans
each year as part of the disposal site management.
CONCLUSION
The designation of MBDS as a disposal site for dredged material
appears to be appropriate. Intensive oceanographic evaluations
performed at MBDS indicate that continued use of the site for
dredged material disposal will not have any significant adverse
environmental impacts. It is apparent that material deposited at
the site remains in place, and since the area has previously been
used for disposal of dredged material such a designation would not
degrade additional areas of the ocean. As scientific understanding
of oceanographic processes evolves the management of MBDS will be
continually reassessed.
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