|Document Type:||Contract Report|
|Title:||Impact of flow-lane disposal at Dobelbower Bar|
|Author/Editor:||Theodore H. Blahm, Robert J. McConnell|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||U.S. Army Corps of Engineers. Portland, Oregon|
Various methods of dredging are used by the U.S. Army Corps of Engineers to accomplish channel maintenance. Hopper dredges are utilized at locations where the dredged material can be placed in deep areas of the river or taken out to sea. Pipeline dredges are used in locations where material can be pumped to a site on land or to an in water site away from the channel. Clamshell dredging is sometimes required; with the dredged material being placed on a barge for subsequent removal to a location for disposal or commercial use.
By whatever means, dredging involves the movement of a significant amount of dredged material even in low-volume flow years. In the past, dredged material was used for the construction of islands and for beach nourishment along eroded areas. During recent years, however, there has been a reduced need for this material along the Columbia River, and it has become increasingly difficult to find suitable disposal sites.
The concept of placing the material in water near the channel (flow-lane disposal) was developed with the idea that there would be less adverse impact on uplands and wetlands and on aquatic life forms and associated fisheries. To test this concept, the Dobelbower Dredge Study was developed. This study was designed to examine the extent of the turbidity plume, distribution of the dredged material, and the impact on the aquatic life forms resulting from inwater pipeline disposal. Initial conclusions were: