existing south breakwater are also being obtained to determine if any negative impacts to the
structure have occurred as a result of the dredging improvements.
Marseilles Dam, Illinois. At Marseilles Dam navigation pools must be maintained within
narrow limits to prevent overtopping of fully closed tainter gates and to maintain adequate depths
in the shallow navigation channel. Prior to the 1989 installation of a remote operation system,
Marseilles Lock and Dam was attended 24 hours a day because the lock and dam are 3.86 km
(2.4 miles) apart. Also, prior to the installation of submersible tainter gates, ice often built up on
the structural members of the nonsubmersible gates and froze them in place. The old gates were
not designed to pass ice without being raised nearly wide open, which adversely affected the
pool and created scour downstream. Submersible gates in the past have had a tendency to
vibrate, possibly causing structural damage to dams and gates. Prior to installation of the
submersible tainter gates, a physical model investigation was conducted to determine vibrations
for various gate submergences.
The objective of the monitoring study is to determine if the remote operation system and
submersible tainter gates are performing as predicted and to determine any operational
limitations of these project features. Evaluation of hydrodynamic, scour, and ice flow conditions
as well as structural stesses on the submersible tainter gates are being performed. Pool
elevations, passage of ice through the submersible gates, downstream scour, and gate vibration
data are being obtained to determine design effectiveness.
Tedious Creek, Maryland. Prior to improvements, three docks, a boat ramp, and mooring
areas adjacent to the channel were exposed to severe wave energy that adversely affected
navigation and resulted in damages and delays to commercial vessels. The construction of two
shore-connected, rubble-mound breakwaters and revetments at the mouth of Tedious Creek was
completed in 1997 to protect the harbor from damaging waves. Gaps were incorporated into the
breakwaters to improve tidal circulation. Poor foundation material beneath the south breakwater
was dredged and backfilled with pea gravel, and the dredged material was beneficially used to
stabilize an adjacent eroding shoreline with geotextile tubes used to contain the material. This
area was planted with marsh vegetation.
The objective of the monitoring study is to evaluate the effectiveness of navigation
improvements in Tedious Creek Harbor from the standpoint of wave attenuation, tidal
circulation, sedimentation, and wetland impacts. The effectiveness of multidimensional
modeling tools used to design the project is also being evaluated relative to their accuracy and
productivity. Monitoring activities include the collection of wind, wave, current, tide, and
bathymetry data in the vicinity of the harbor to determine design effectiveness. The hydraulic
stability of the breakwater is also being evaluated.
Boston Harbor Confined Aquatic Disposal (CAD) Cells, Massachusetts. Navigation
improvements at Boston Harbor involve deepening tributaries of the Inner Harbor and associated
berthing areas. Lack of an upland disposal site and resource agency denial of permission to
place contaminated sediments in an open water site has resulted in the decision to use in-channel
CAD cells for placement of contaminated material dredged with an environmentally sensitive
clamshell bucket. This is the first application of in-channel CAD cells.