Passing vessel delays (cont.)

On 10 June the dredge was moved back to Sta 53+02 R 0 at 1136 and

dredged until 1322 (total dredging time 1 hr 46 min) when it was moved for

passing vessel traffic back to Sta 52+80 R 285. At 1622 the Beachbuilder moved

over to Sta 51+45 R -373 and dredged till 1656 (total dredging time of 34 min)

when it stopped on Sta 48+75 R -378, then relocated to Sta 51+89 R 125 and

continued dredging on the positive range side for the rest of the day.

After the most recent hydrographic survey was loaded into Beachbuilder's

dredge monitoring system on 11 June, it was decided that the priority dredging

locations in Reach 2 would be the "high (shoal) spots" located on the negative

range side during the day. This tactic was based on the experience from the

previous day that longer, continuous advances on the negative range side of the

channel were not possible with the volume of deep-draft vessels passing. The

screen shot of the dredge monitoring system with updated bathymetry is shown

in Figure 8. These high spots were dredged in the following sequence.

a. The dredge worked 39 min (Sta 58+50 R -130 to Sta 57+85 R -140)

(Figure 8 shows the dredge working on this high spot), then moved to

Sta 59+45 R 140 (with a 5-min transit time) due to two oncoming deep-

draft vessels for a vessel-delay-induced dredge transit time of 11 min.

The Beachbuilder was back dredging when the cross-channel wire was

dropped twice for the 39.3-ft and 23.4-ft draft vessels without inter-

ruption to dredging. It advanced to Sta 51+90 R 140 when it was relo-

cated to dredge another high spot (with a 5-min transit time).

b. The Beachbuilder was able to work/dredge 52 min (Sta 58+25 R -140 to

Sta 54+65 R -140) when oncoming vessel traffic once again required a

dredge repositioning to Sta 55+20 R 140 (10-min transit). There it

dredged for 40 min while three deep-draft vessels passed over the cross-

channel anchor lying on the bottom without interrupting dredging at the

repositioned location.

c. After the deep-draft vessels passed, the dredge was relocated to

Sta 58+25 R -140 (5-min transit time) and dredged to Sta 54+64 R -140

for 55 min before again being moved for oncoming vessel traffic. The

Beachbuilder set back to Sta 55+20 R 140 (for a 5-min transit time) and

dredged to Sta 51+90 R 140 for 35 min until the deep-draft ship passed.

d. The dredge was repositioned to Sta 60+00 R -95 with a 5-min transit

time, plus 5-min delay waiting on one of the hopper dredges to move.

There it dredged for 1 hr 25 min to Sta 52+00 R -125 until another

oncoming passing vessel required repositioning to Sta 60+00 R -55 (with

a 15-min transit time).

e. Once on station, it advanced to Sta 52+25 R -55, dredging for 1 hr

45 min when oncoming vessel traffic required repositioning again and

the cycle repeated.

This cycle was basically repeated on 12 June when the dredge worked on the

minus range side. On 13 June, the dredge stayed in the positive range channel

side to optimize dredge production in the thicker face on that side without the

numerous resetting delays. The dredging sequence for 11 June was listed in detail

to illustrate the following points:

Chapter 4

Dredging Operational Characteristics Analyses