| |
FAQ
- What is Seaway?
- What are Seaway's technology goals?
- What is Seaway's Mobile Containment
(Control Zone) technology?
- What is a Mobile Containment Vessel?
- What are the different levels of
containment (i.e., Level 1, Level 2 or Level 3) provided by Seaway's
containment technology?
- How large is a Mobile Containment
Vessel?
- How are contaminated sediments removed
from the containment zone?
- How is the excavation monitored
to ensure the cleanup is effective?
- What are the micro-filters that
Seaway utilizes for water treatment?
- How does Seaway ensure that the
water in the containment zone is free of contamination during
Level 2 or 3 containment operations?
- How does Seaway maintain the stability
of the excavation during and after the vertical barrier wall is
removed?
- How does the production rate of
mobile containment operations compare with that of traditional
environmental dredging methods?
- How does the cost of mobile containment
operations compare with that of traditional environmental dredging
methods?
- What is a Contaminated Sediment
Excavator (CSE)?
- How does a CSE remove sediments?
- How does a CSE excavate sediments
with a reduced moisture content?
- How does a CSE excavate sediments
with reduced sediment migration?
- What is Seaway's Marine-Based Solids
Management system?
- What are the benefits of a Seaway
Marine-Based Solids Management approach over traditional solids
management methods?
- What is the purpose of Seaway's
Mobile Water Treatment Platform?
- How can Seaway's Mobile Water Treatment
Platform treat excess dredge waters?
- What is residual contamination
and how can Seaway's Mobile Water Treatment Platform reduce or
eliminate residual contamination?
What is Seaway?
Seaway Environmental Technologies,
Inc. is a marine engineering, construction, and operations firm
with offices and fabrication facilities located in Commack and Greenport,
New York, respectively. Over the past decade, Seaway has been involved
in the development of new technology to provide for the removal
and management of contaminated sediments from the marine environment
without the adverse ecological impacts that are associated with
traditional contaminated sediment dredging technology. Seaway business
goals include the implementation of site cleanups and the licensing
of its technologies to third parties.
Back to Top
What are Seaway's
technology goals?
Seaway’s goals are to provide for;
- Effective removal of contaminated sediments
that meet site specific cleanup standards,
- Containment of contaminants during the excavation
process,
- Treatment and discharge of a high quality water
collected in the process,
- Managed control of all excavated sediments,
- Secure transportation to the disposal site, with
- Minimal disruption to the local environment and
community,
- No land-based operations in the dredge vicinity
– all processes take place aboard specialized barges.
- Low moisture sediment extraction systems.
Back to Top
What
is Seaway's Mobile Containment (Control Zone) Technology?
Seaway’s Mobile Containment (control zone) technology is a
remediation strategy that provides the means to contain disturbed
sediments that result from dredging operations and which are susceptible
to migration from a dredge area into the surrounding water environment.
It establishes an area that can be effectively monitored to ensure
that remediation goals are met. To achieve these objectives Seaway
has introduced the concept of the “dredge control zone.”
The control zone is a secure dredging area that is maintained and
sealed off to prevent the release of contaminants generated inside
the zone. To establish such a zone in a practical dredging application,
Seaway has developed a Mobile Containment Vessel.
Back to Top
What
is a Mobile Containment Vessel?
A Mobile Containment Vessel is a multi-barge vessel with an inboard
rectangular opening, through which a vertical barrier wall is set
to surround the target dredge work zone. The barrier wall is formed
by interlocking steel sheet piles that are held in place and deployed
by a specially designed support system located on the inner hull
of the inner rectangular opening. Once deployed, the sheet pile
wall provides a semi-seal between the dredge area and the surrounding
water-body, preventing the free migration of particulate material
from the dredge area.
Back to Top
What
are the different levels of containment (i.e., Level 1, Level 2
or Level 3) provided by Seaway's containment technology?
Level 1 (Mobile Sheet Pile Containment)
- provides for containment of sediment disturbed during dredging
operations. This is accomplished by setting up one or more Mobile
Containment Vessels in which dredging can occur. The walled-in pen
prevents the free migration of sediment particulates during dredging
operations.
Level 2 (Mobile Sheet Pile
Containment and Vacuuming) - provides for containment of
sediment disturbed during dredging operations as in Level 1 containment,
but adds a bottom vacuuming operation to remove dispersed sediment
(fluff) that is contained within the pen. This prevents the migration
of this sediment after the containment wall is removed and results
in a more effective cleanup of the waterway bottom and greater opportunity
to achieve target cleanup goals.
Level 3 (Low Pressure Control
Zone Containment) - provides the highest level of containment.
It establishes a low pressure zone inside the pen (or containment
area). This low pressure zone is established by pumping water from
the containment area to a water treatment facility located on the
control zone barge, which draws water outside-in, preventing the
loss of silt and soluble contamination from the dredge area. To
assist in establishing this low pressure control zone, the Mobile
Containment Vessel is equipped with a special joint-sealing system,
designed by Seaway.
Back to Top
How
large is a Mobile Containment Vessel?
Commercial-sized Containment Vessels can practically reach sizes
of approximately 140 feet long and 90 feet wide, with a 120-foot
by 70-foot rectangular control zones. Seaway’s sectional barge
design provides the means to deploy alternative size vessels, depending
on site-specific conditions.
Back to Top
How are
contaminated sediments removed from the containment zone?
Contaminated sediments are removed with a mechanical (clamshell
bucket), which provides the most favorable (low) liquids-to-solids
ratio for dredging. In Level 2 or 3 containment, operations, sediment
excavation is followed by settling and subsequent vacuuming of the
dispersed sediments (fluff) from the bottom of the containment zone.
This is accomplished using a cutterless vacuum dredge developed
by Seaway. This two-phased dredging approach (bucket dredging followed
by a cutterless vacuum polishing step) provides for a more effective
cleanup, which is more apt to meet target cleanup standards than
traditional sediment dredging approaches. In Level 3 operations,
all spillage or dispersion of particulates during excavation is
contained within the control zone. Bucket washing is unnecessary.
Buckets may be drained of free or excess water directly into the
control zone to reduce the quantity of water carried with the sediment.
Back to Top
How is
the excavation monitored to ensure the cleanup is effective?
The containment zone can be maintained in place until such time
that the zone can be certified as clean (i.e., the site has met
the cleanup goals). This is accomplished by sampling and monitoring
the sediment and the water column in the control zone. This method
of "controlled clean-up certification" is unavailable
when conventional dredging technology is utilized.
Back to Top
What are
the micro-filters that Seaway utilizes for water treatment?
When traditional technology is utilized during contaminated sediment
cleanup operations, all disturbed and re-suspended matter is released
to the ambient water environment. During the excavation of contaminated
sediments using Seaway Level 2 or 3 containment technology, most
if not alll re-suspended matter is contained within the containment
zone and is pumped to a water treatment facility for treatment.
When Mobile Water Treatment is required, Seaway has designed a treatment
facility that makes use of polymeric membrane filtration technology
to remove all sub micron-sized particles. Seaway’s system
is also capable of providing soluble contaminant treatment (activated
carbon adsorption) should soluble breakthrough occur.
Back to Top
How does Seaway ensure
that the water in the containment zone is free of contamination
during Level 3 containment operations?
By maintaining the containment zone, Seaway
has the capability of treating the water in the zone (several turnovers,
if necessary). This is accomplished by pumping water from the zone
through the treatment facility to achieve the desired water quality.
As Seaway pumps water out of the containment zone, more water is
permitted to flow into the zone to maintain a controlled differential
pressure gradient between the inner control zone and the ambient
water quality.
Back to Top
How does
Seaway maintain the stability of the excavation after the vertical
barrier wall is removed?
During the course of traditional contaminated sediment cleanup operations,
sediments are removed in layers to avoid deep cuts that could result
in wall instability and sediment collapse into the bottom trenches
produced during the excavation. This method of excavation results
in the exposure of sub-bottom layers of contaminated sediments to
the water column. The contaminated sediments in these sub-layers,
which in many instances may be more contaminated than upper sediment
layers, are free to migrate from the dredge site, until further
passes (digs) over the area can be made. The Seaway Mobile Containment
Vessel permits the excavation to proceed directly to the design
depth by using the vertical barrier wall (sheet piles) of the control
zone to provide the structural stability to maintain the excavation.
All exposed sub-layers are contained within the control zone until
the cleanup is completed. Where excavation depths are such that
wall stability is in question, prior to the removal of the vertical
barrier wall, Seaway introduces capping material (clean fill) into
the control zone to provide the necessary supporting material to
maintain the stability of the excavated area after the vessel is
deployed to another location.
Back to Top
How does
the production rate of Mobile Containment Vessel operations compare
with that of traditional environmental dredging methods?
The production rate of mobile containment operations will be comparable,
to that of traditional environmental dredging methods. This is because
mobile containment operations can include provisions for deploying
multiple containment vessels along the contaminated waterway. Multiple
vessel deployment permits the crane or excavation barge to shift
from vessel to vessel, thereby maintaining a consistent dredging
rate (which will dependent on the bucket dredging rate). In addition
during mobile containment operations, the primary concern of the
dredge operator will be the production rate, and not sediment re-suspension
and contaminant migration. When these latter factors are the primary
the focus of the operator , the production rate will invariably
suffer. The absence of bucket washing requirements between each
immersion cycle (in Level 3 containment operations) canl further
enhance the production rate over that of traditional approaches.
Finally, the use of a two-phased cleanup operation in the control
zone (as described above) will provide for a more effective cleanup,
reducing the need for multiple passes at the contaminated dredge
site. Multiple passes, in an attempt to meet target cleanup goals,
are typical occurrences at contaminated sediment cleanup sites.
Back to Top
How
does the cost of Mobile Containment operations compare with that
of traditional environmental dredging methods?
Traditional environmental dredging operations
are plagued by cost overruns, due in great part to the inability
of the operation to achieve target goals without the use of multiple
site passes, project stoppages due to contaminant release events,
and extraordinarily high sampling and analytical budgets to monitor
the impact of the operation and the effectiveness of the cleanup.
While Seaway deploys additional equipment and manpower to effect
a control zone cleanup, overall costs can be expected to be comparable
and even less than than traditional approaches due to greater assurances
that the site will be effectively cleaned without the need for multiple
passes, the elimination of work stoppages associated with contaminated
release events and a reduction in the need for extensive downstream
sampling and analytical efforts to monitor the excavation. Finally,
the Seaway Control Zone technology prevents the migration of contaminants
to other locations, thereby reducing the possibility of further
remediation action resulting from the dispersion of contaminants
from the original dredging location.
Back to Top
What is
a CSE?
When traditional dredging equipment is utilized, much of the excess
water removed with the sediments is free water. This free water,
which is typically removed (in dewatering processes) contains contaminants
and must be treated prior to discharge. All water that is or cannot
be removed from the excavated mud, must be disposed of with the
contaminated sediments. As a result, the recovery of sediments with
minimal moisture has significant economic advantages. A Contaminated
Sediment Excavator (CSE) is a specialized sediment removal bucket
that is designed to recover low moisture content sediments with
a reduction in turbidity generated doing the excavation process.
Back to Top
How does
a CSE remove sediments?
The CSE consists of two basic components. They include a mechanical
dredge (bucket) and a housing or enclosure. The mechanical dredge
(bucket) is contained within the rectangular-shaped housing that
is open on the bottom, where a single-hinged door is used to open
or close the housing bottom. During the excavation process, the
CSE is lowered to the bottom of the waterway where the bucket extracts
from the open bottom to collect sediment, similar to that a conventional
dredging operation. After the sediment is collected, the bucket
retracts into the housing and the single-hinged door closes as the
CSE with its sediment load is raised to the surface.
Back to Top
How
does a CSE excavate sediments with a reduced moisture content?
The CSE is a mechanical dredge bucket that is contained
within an enclosure or housing. As the CSE descends underwater,
compressed air is introduced into the housing at a pneumatic pressure
that is balanced against the hydrostatic pressure outside of the
housing. As long as the pressure inside of the housing is equivalent
to that of the external hydrostatic pressure the internal housing
is maintained water-free. As a result, the CSE can be lowered to
the bottom of the waterway and an excavation can be made in a dry
environment. Excavating in a dry environment prevents the water
column from mixing with the excavated muds during the dredge removal
process resulting in the removal of sediment with a moisture content
at or near the in-situ moisture content of the sediment (no free-water).
Back to Top
How does
a CSE excavate sediments with reduced sediment migration?
By establishing a dry environment in which to dredge (as described
above), the layer of sediment excavated from the bottom with the
bucket is prevented from mixing with the water column. As a result,
less turbulence is produced during the excavation, resulting in
less sediment migration. In addition, after the bucket completes
a dig and is retracted into the housing (as described above), as
the CSE is being raised a reduction in pneumatic pressure inside
the housing, can further be used to induce a "low pressure"
zone that draws water and dispersed particulates, in the vicinity
of the bucket, into the housing. As the CSE clears the bottom, the
single-hinged door is closed and excess water collected is pumped
to the surface for treatment.
Back to Top
What is
Seaway's Marine-Based Solids Management system?
Marine-Based Solids Management is a system designed to collect and
containerize the excavated sediments on a marine platform and to
transport the sediments to an existing port facility or facilities,
where the sediment can offloaded for transport to a disposal site.
The Seaway system makes use of two primary platforms: 1) a solids
processing vessel and 2) a container vessel. The solids processing
vessel, which operates in conjunction with the crane or excavator
barge, is designed to receive the dredge material from a mechanical
dredge operation, remove oversize debris and physically stabilize
the dredged sediment (reduce its moisture content) by mixing the
sediment with hydrating reagents. Once the sediment is blended with
the hydrating reagant, the stabilized sediment is conveyed to an
independent container vessel, where the stabilized sediment is discharged
into containers that are subsequently sealed and transported (on
the container vessel) to an existing port capable of offloading
and transporting the sediment containers to a disposal site. The
Seaway solids processing vessel contains a slip in which the container
vessel can be docked to receive the stabilized sediments. Multiple
container vessels are used to move the physically stabilized sediments
to maintain a continuous operation.
Back to Top
What are
the benefits of Seaway's Marine-Based Solids Management approach
over traditional solids management methods?
Marine-Based Solids Management provides the means to collect, transport
and dispose of contaminated sediments without the need for on-shore
offloading, storage, dewatering , and solids transfer and land-based
transportation facilities at the cleanup site. There is "minimal"
disruption to the local community when a Seaway Marine-Based strategy
is employed. The containerization of dredged sediment eliminates
the transport of contaminated muds in open barges or the pumping
of muds to large open shoreside storage lagoons. In addition, when
compared to solids management requirements and the respective costs
associated with hydraulic dredging operations, which include pumping,
settling, dewatering, water treatment, and solids storage and transport
operations, Seaway believes that Marine-Based Solids Management
provides significant economic incentives.
Back to Top
What
is the purpose of Seaway's Mobile Water Treatment Platform?
Seaway's patented mobile water treatment platform (MWTP) provides
the means to treat excess dredge water. Excess dredge water is the
fluid that drains from the contaminated dredged sediments during
the dredging and material handling process. The MWTP provides a
new operational approach to manage the waters that are generated
during dredging operations, without the need for land-based water
treatment facilities. In addition Seaway's MWTP provides a new operational
method to remove residual contamination that is left behind during
dredging operations and can migrate to downstream locations after
the completion of the dredging operation.
Back to Top
How can
Seaway's Mobile Water Treatment Platform treat excess dredge waters?
When contaminated dredged muds are deposited into barges for transport,
free or excess dredge water, which is brought up with the contaminated
sediments, can occupy a large volume of the barge. This water must
be contained and brought to shore where it is treated prior to its
return to the receiving water. Seaway's mobile water treatment platform
(MWTP) provides the means to treat excess dredge water at the source
thereby increasing the transport capacity of the barge and eliminating
the need for onshore water treatment of this contaminated water.
Back to Top
What is
residual contamination and how can Seaway's Mobile Water Treatment
Platform remove this contamination?
Due to the nature of the dredging process, a residual fluffy layer
of low density highly contaminated sediment will resettle to the
bottom of the waterway. This layer is source of contamination that
can readily migrate to downstream areas, is highly available to
enter the food chain and prevents cleanups from achieving low residual
concentrations in the remaining sediments. Multiple dredging passes
using conventional technologies have shown to be ineffective in
removing this residual contamination. Seaway’s patented mobile
water treatment plant, coupled with its cutter-less vacuum head
technology, provides the means to Vacuum Sweep this residual fluff
layer. Used in tandem with a dredging operation, Seaway’s
Vacuum Sweep Operation provides the most effective means to remove
sediment inventory and residual contamination.
Back to Top
|
|
