Time-series plots of production

establish a production rate for the dredge just working on this side of the channel

with limited vessel traffic delays. From 0537 to 2101, in 10 advances the dredge

moved approximately 28,000 cu yd in 15.4 hr (working between Ranges 175 and

335 in bank heights estimated from 3 to 15 ft) for an average production rate of

1,800 cu yd/hr. The maximum production rate per advance of 4,000 cu yd/hr in

463 ft was also achieved during this interval.

To estimate the dredge's low production rate while working on the LDB side

of the channel, the time Beachbuilder worked on the negative range side of the

channel on 11 June (as described in detail above) to dredge the high spots was

used as a limiting factor. The Beachbuilder could not stay in the negative range

(LDB) side of the channel longer that 1.75 hr because it would have to move to

accommodate passing deep-draft vessels. Assuming that the dredge could stay on

that side of the channel for 1.75 hr and then would be forced to relocate to the

RDB side (assume 7 min), wait for vessel traffic (assume 5 min), then

re-establish location in the LBD side again (again 7 min), the total amount of

time just to move and wait for vessel traffic over a 24-hr period would be 3.41 hr.

Taking the average production rate of Beachbuilder in Reach 2 (1,600 cu yd/hr

or approximately 38,600 cu yd/day) as a first approximation of a "standard

production rate," the daily production of a dredge working in the LDB side

would be reduced by the time required to keep moving for passing vessels. So

instead of 38,600 cu yd/day, the dredge would move only 33,000 cu yd/day, or

have an hourly production rate of 1,400 cu yd/hr.

Time-series plots of production

Two examples of the Beachbuilder's time-series production data are given in

Figures 9 and 10. Figure 9 illustrates a 486-ft advance made on 11 June 2002,

with an average production rate of 2,411 cu yd/hr, which is fairly representative

of the average production rate from all the advances in Table 3 at 2,346 cu yd/hr.

The y-axis scale is in cubic yards per the dredge's advance every 10 sec.

Figure 10 shows the Beachbuilder's daily production on 13 June 2002, with the

y-axis scale in cubic yards per hour, that was calculated and reported in (the x-

axis) 10-sec increments.

Chapter 4

Dredging Operational Characteristics Analyses