Debris Mapping and Characterization Strategies for Pre-Remedy Assessment
at
Contaminated Sediment Sites
Characterization and remediation of contaminated sediment sites is often
hampered by the presence of both natural and anthropogenic debris fields.
Debris can interfere with or damage sampling devices such as sediment grabs
and particularly coring devices. Dredging operations can be susceptible
to interference from debris, often reducing the efficiency of the dredging
process, excluding debris areas from cleanup, requiring specialized dredge
equipment, increasing the potential for residuals, or leading to delays
for removal of the debris. Debris can also interfere with capping systems,
reducing cap integrity, requiring over-capping, or leading to delays during
placement. Some forms of debris can also represent potential long-term
sources for contamination to the surrounding sediment, water and biota.
Typical source debris can include drums of hazardous materials, unexploded
ordinance, treated lumber and pier pilings, wood pulp, batteries, slag,
mining waste, and sunken vessels.
Traditionally, debris identification
and mapping at contaminated sediment sites has been carried
out by sediment sampling devices, diver inspections and/or simple geophysical
techniques
such as bathymetric or side-scan sonar surveys coupled with
GPS navigation. Diver inspection is generally the most reliable method
for identification
of debris, but can be very time consuming and expensive,
particularly over large-scale sites. Diver inspections are also limited
by water visibility
and safety considerations such as boat and ship navigation.
Traditional geophysical methods are more amenable for wide-area mapping,
but are generally
limited in their ability to identify the nature of the debris,
and may have difficulty in identifying buried debris, or smaller items
that may
still hamper sampling and remediation efforts.
This project will review existing and emerging technologies for
debris mapping and identification. This
review will include (but not be limited to)
non-intrusive geophysical mapping techniques such as interferometric
side-scan and sector-scanning sonars, underwater ground-penetrating
radar, towed
magnetometer/electromagnetic detectors, multi-frequency sub-bottom
profiling, ROV/AUV video systems, and laser-scanning imagers.
Target detection and
identification algorithms for individual and integrated platforms
will also be reviewed. Based on this review, candidate technologies
will be selected
for field-scale testing.
Selected technologies will be tested individually at field scale. Integrated
approaches will be designed and tested in the field to evaluate
the combine effectiveness of multiple approaches.
For example, mapping and target identification using geophysical
methods followed by AUV video to classify specific targets.
Field testing will
be validated on the basis of known (placed) targets and/or
traditional diver inspections.
Capabilities (direct support):
Applications:
-
Pre-remedial investigations at Navy IR sites
- Improve Navy’s ability to effectively assess and
manage contaminated sediment sites
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