Figure 5. Location of preplacement sediment samples

ERDC TN-DOER-N6

March 2000

through the May 1999 survey. Less than a foot of change can be detected over most of the study

area, which is within the accuracy of the surveys. The cohesiveness of the material appears to be

sufficient to maintain the irregular mound morphology. That is, even though the material is

fine-grained, it has not formed a mild-sloped mound.

Sediment Samples. Sediment samples were collected from the placement area in October before

the dredging operation began. These preplacement sediment samples provide a description of the

native sediments of the ebb shoal. Fifty-four samples were collected in a square grid pattern within

and surrounding the placement area as indicated in Figure 5. Forty samples were collected on

20 October 1998. A single sample identified as "Probe" was taken on 21 October 1998. Thirteen

additional samples were collected on 26 October 1998 to the west to provide better coverage around

the placement site. The samples were collected with a 1,000-g bucket dredge, though only 20 g of

sediments per sample was needed for analysis.

T r ench

Figure 5. Location of preplacement sediment samples

Three sediment samples were collected at different times during the dredging operation at the dredge

site in the Mobile River to characterize the in situ dredged material. These samples were collected

from the clamshell bucket just prior to disposing into the barge. After the dredged material was