ERDC/CHL CHETN-IX-5
September 2001
The objective of the monitoring is to complement scheduled monitoring with supplementary
monitoring that will help evaluate the effectiveness of in-channel CAD cells at Boston Harbor.
Water quality monitoring of suspended solids is being conducted near the operation of two
environmentally sensitive clamshell buckets and a normal clamshell bucket to document the
benefits of the special buckets. The amount of water being added with each bucket type is also
being monitored since added water has an impact on the strength and density of the contaminated
material which influences its ability to support a cap. The contaminated dredged material
consolidation and strength prior to and after placement of the sand cap is being monitored.
Laboratory experiments are being conducted to measure consolidation, shear strengths, water
content, etc, of the contaminated sediments and the Boston blue clay to refine predictive
techniques for mound and cap performance. In addition, cap erosion predictions from both tidal
currents and ship prop wash are being measured and calculated to characterize the amount of cap
damage expected from either source. This information will be valuable to others considering
either in-channel CAD or conventional CAD sites.
Tom Bevill Lock and Dam, Alabama. After construction of the Tom Bevill Lock and Dam,
navigation problems were experienced with crosscurrents in the upper lock approach. As a result
of float studies, a rock deflector dike was constructed upstream on the east side of the channel. It
was successful in abating crosscurrents for low flows, however, the problem still existed when
significant spillway releases were made upstream. A physical model study was conducted to
determine improvements required for the alleviation of crosscurrents in the upper lock approach
that recommended an extension of the guide wall in the upper approach and removal of a portion
of the rock dike.
The objective of the monitoring effort is to determine if the guardrail extension and shortening of
the rock dike will result in a functionally effective lock approach as predicted. Monitoring will
evaluate flows in the upper lock approach and will include the collection of videography, current
data, bathymetric data, Global Positioning System (GPS) tow track measurements, pool
elevations, and gate openings at the project site. The head differential of the guard wall will also
be monitored. Information will be gathered for various discharges.
Aguadilla Harbor, Puerto Rico. The Aguadilla coastline is exposed to direct wave attack
from the northwest and indirectly from diffraction of waves from other directions. Prior to
construction of a breakwater, the local fishery was restricted to the use of small flat-bottomed
boats that could easily be hauled onto the limited beach front when not in use due to their
inability to pass through the breaker zone. Construction of a 304.8-m- (1,000-ft-) long rubble-
mound breakwater was completed in 1995, which afforded commercial fisherman the only
protected harbor along a 50-mile stretch of shoreline. During and following construction,
shoaling of a segment of the harbor was observed. Subsequent to completion, additional
shoaling was observed with limited wave activity.
The objective of the monitoring study is to study the harbor shoaling and effectiveness of the
breakwater on hydrodynamics in the harbor. Data is being obtained to determine the causes of
shoaling in the harbor and validate the effectiveness of the project design. Monitoring activities
include beach profiling north and south of the harbor and hydrographic surveys within the harbor
itself. Additionally, wave height and current data are being obtained nearshore and within the
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