Monitoring Dredged Material Disposal at Mouth of Columbia River, Washington/Oregon, USA

The entrance channel at the Mouth of the Columbia River requires annual dredging of 3 to 5 million cu m (3.9 to 6.5 million cu yd) of fine-to-medium sand to maintain the navigation channel at the authorized depth. The sandy dredged material is placed in EPA- approved Ocean Dredged Material Disposal Sites (ODMDS). Exceedance of ODMDS capacity at the Mouth of the Columbia River creates two, operational problems for the Portland District: (a) The overall footprint of disposed dredged material extends beyond the existing ODMDS formally permitted boundaries by as much as 915 m (3,000 ft) in some cases, and (b) dredged material within the ODMDS has accumulated to such an aerial and vertical extent that adverse sea conditions are created. In some cases, mounds rise 18.3 to 21.4 m (60 to 70 ft) above surrounding bathymetry. Mariners report that the ODMDS mounds cause waves to steepen and/or break in the vicinity of the sites, and that these waves conditions are hazardous to navigation. The original document contains color images. All DTIC reproductions will be in black and white.