Inspection and Compliance (Cont.)

A new technology for dredging inspection that is being implemented is

the Silent Inspector (SI). The SI uses state-of-the-art computer hardware

and software to measure multiple dredge state parameters and provide out-

put to automatically create USACE dredging reports. At this time, the SI

is most readily applied to hopper dredges. Future work involves develop-

ing similar automatic inspection systems for hydraulic pipeline and me-

chanical dredge types. Many types of information are recorded by the SI

including vessel speed, heading and position, hopper door status, vessel

draft, and water depth. For capping projects that use hopper dredges, the

SI can provide much of the needed information from dredging throughout

placement (Cox, Maresca, and Jarvela 1995).

SI technology has also been applied to dredged material placed from a

barge. A data logger on the barge records position and draft (from a pres-

sure sensor). When the barge doors or hull are opened, the change in draft

and location are recorded. The data can be downloaded to a computer at a

later time or broadcast via radio link to a shore station for real-time moni-

toring. Commercial systems are available, and the New England Division

has also provided some custom systems to the Districts. Both the Seattle

and San Francisco Districts have used this type of system to monitor place-

ment of dredged material.

During the placement of dredged material, periodic hydrographic sur-

veys may be desirable to track mound growth. These surveys can allow

the project manager to make midcourse adjustments in placement opera-

tions to effect changes in mound heights (either greater or less). Track

plots from dredge logs or placement positions provide good information

for long-term project placement locations.

Weather plays an important role in placement of dredged material not

only for barge positioning but also in exposing the dredged material mound

to unwanted erosion. As with most dredging projects, capping projects

should be conducted in the less energetic summer months. During this

time of year, storms are usually less frequent, thereby reducing the near-

bottom currents that tend to move bottom sediments. For capping projects,

this is particularly important to prevent the spread of contaminated mate-

rial. Therefore, capping projects should afford adequate time for contami-

nated material placement and cap material placement to be conducted

prior to the onset of fall/winter storms. Contingency plans that include

phased capping or staging cap material for easier postconstruction place-

ment should be considered for areas that are susceptible to hurricanes or

other summer storms.

Chapter 5 Equipment and Placement Techniques