Field Study of an Unconfined Spoil Disposal Area of the Gulf Intracoastal Waterway in Galveston Bay, Texas

Dredge spoil obtained from maintenance dredging of the Gulf Intracoastal Waterway is presently disposed in unconfined, submerged spoil areas alongside the channel. Grain size analysis of bottom sediment samples, depth soundings and wooden stakes were employed in field investigations to determine the approximate location of material from one such spoil area over a five month period after disposal. Immediately following deposition, over 40 percent of the spoil (based on original in-channel volume) had left the designated spoil area and spread out over the bay floor primarily as a mud-density flow. Eventually spoil covered an area about three times larger than the original spoil area. Return of the spoil to the newly dredged channel did not appear significant during the study period primarily because of the predominant direction of tidal currents and due to the presence of a submerged dike along the channel. A brief summary of dredging and spoil disposal practices is also included. (Modified author abstract)