Dredge Production Characteristics

would agree that a dustpan dredge (like the Beachbuilder used in the demon-

stration) with propulsion and flexible discharge would present an acceptable risk

to navigation if the dredge worked on just one side, or half, of the channel at a

time (not have the flexible discharge extended across the entire channel width).

Two others who piloted vessels past the dredge during the demonstration agreed

and strongly agreed that a dredge like the Beachbuilder presented an acceptable

risk to navigation at the HOP without any operational modifications. The remain-

ing five pilots who responded to the survey had both stood a watch on the dredge

and had piloted a vessel past her during the demonstration. Of these five, one

strongly agreed and three agreed that the Beachbuilder presented an acceptable

risk to navigation at the HOP without any operational modifications. The remain-

ing pilot would strongly agree that the Beachbuilder presented an acceptable risk

to navigation at the HOP if it was restricted to dredging only the RDB side in the

reach from 1 mile Above Head of Passes to 1 mile Below Head of Passes. The

reason behind this restriction was that if a (especially outbound) vessel lost pro-

pulsion power, the current flowing into Pass A Loutre would cause the vessel to

move toward the LDB side and become a hazard to a dredge working there if it

could not move out of the way. Other pilots who stood a watch on the

Beachbuilder and were verbally interviewed also expressed this concern.

Dredge Production Characteristics

The dredge production characteristics were analyzed by reducing the data

from the contractors' daily dredge report and daily submittals on Engineer Form

4267, supplemental notes taken by USACE and contractor personnel, the time-

series data of the dustpan's x-, y-, z-positions, slurry density and velocity read-

ings, calculated production rate in cubic yards per hour, and bathymetry data

taken by daily hydrographic survey. Calculated production characteristics calcu-

lated include advance rates, approximate bank heights, and various types of

production rates.

Individual advance rates per cut and average rates for entire project

The individual advance rates were calculated using the start and stop times

and positions from dredge advances that did not experience significant delays.

The total time, linear distance traveled (calculated from start and stop coordi-

nates), and advance speed of each individual advance are listed in Table 5. These

advances were calculated for times of relatively uninterrupted dredging intervals

to determine advance rates without delays (i.e., adding shore line, cleaning pump,

etc.). Because of the experimental nature of this project, advance distances

ranged from 17 ft to 773 ft in length. A minimum advance rate of 0.9 ft/min and

maximum rate of 15.1 ft/min (the advance on 6 June at 1633 is deemed too short

and early in the demonstration to be counted) were logged during the demonstra-

tion with an average advance rate (based on 68 advances) for the entire demon-

stration of 5.8 ft/min. The average advance rate of the Beachbuilder while at

Reach 1 from start of dredging to stop including all delays (i.e., anchor handling,

Chapter 4

Dredging Operational Characteristics Analyses