Figure 1. Location of drift transects in Cook Inlet, Alaska

ERDC TN-DOER-E14

August 2001

material disposal event from the Viking operation. Sessions 16 and 17 monitored the Crystal Gayle

dredging operations. Sessions 18 and 19 attempted to record ambient conditions in the vicinity of

the Viking. After an initial assessment of the data, it was determined that more ambient data were

required to complete the analysis. Ambient recording sessions 20-24 were completed the following

year (August 2000).

Bucket dredges, exemplified by the Viking, are relatively stationary (Figure 2). While operating,

the dredge swings slowly in an arc across the channel cut as material is excavated. This is

accomplished by pivoting the dredge on vertical pilings called spuds that are alternately raised and

lowered from the stern corners of the dredge. Cables to anchors set roughly perpendicular to the

forward section of the dredge are used to shift the lateral position of the digging area. Periodically,

as the cut advances, the anchors are reset. Sounds produced by this type of dredging can best be

described as repetitive rather than continuous. Bucket dredging entails lowering the open bucket

through the water column, closing the bucket after impact on the bottom, lifting the bucket up

through the water column, and emptying the bucket into a barge. For the purpose of sound

characterization six distinct "events" composing a single cycle of bucket deployment and retrieval

were identified: