News Release
| Release Number: | 01-119 |
| Dated: | 8/15/2001 |
| Contact: | Heidi Y. Helwig, 503-808-4510 |
Portland, Ore. -- To keep the mouth of the Columbia River (MCR) as safe as possible for water traffic, and to maintain the intent of a court-approved settlement agreement, the U.S. Army Corps of Engineers will remove some dredged material from one of the designated ocean disposal sites for dredge material.
The Corps' management objective at this site is to place material in such a way that it does not mound to the extent that would create a 10 percent increase in wave heights over the site.
Hydrographic surveys taken in July of this year indicate that dredged material in a portion of the ocean disposal Site E at the MCR has mounded beyond the agreed upon level. Beginning today the Corps will remove at least 130,000 cubic yards of material from that area to eliminate the mound. When the work is completed, which is expected to take about two days, the Corps will perform additional surveys to confirm the mound was removed.
While the Corps has observed mounding at Site E during the past two years, experience shows mounds generally erode during winter storms. The present mound, however, is higher and wider than in previous years. Therefore, the Corps is taking preventative actions to reduce the level of the mound now rather than wait for winter storms. The dredge Essayons will do the work.
The Corps also has stopped disposing of additional dredge material in Site E at least until next dredging season and will conduct engineering analyses to determine how to ensure future placement in this site is maintained within designated limits.
While the Corps and the state of Washington prefer to place material in Site E because it keeps sand in the littoral system (near the shore zone), "navigation safety is of paramount importance," said Doris McKillip who oversees the Corps' Waterways Maintenance Section.
A contract dredge using Site E this year-the Padre Island-has been directed to place additional dredged material in Site F, which is an offshore deep water site and is in the transiting area for Columbia River Bar pilots. The pilots were notified of the decision.
These actions have been coordinated with the Environmental Protection Agency (EPA), the Washington Department of Ecology and the Columbia River Crab Fishermen's Association. EPA concurs that the work is consistent with site management agreements.
To keep channels deep enough to allow for safe shipping, the Corps removes about 4 million to 5 million cubic yards of sand each year from the MCR and the Columbia River federal navigation channel. This material must be placed at one of the pre-approved ocean disposal sites.
The volumes of infill in the federal navigation channel in the vicinity of Site E are 40 percent higher than those observed in 1991, McKillip said. This may be due to low water conditions in the Columbia River system, which creates less erosional flow in this area. It also may be due to a mild 2000-2001 winter storm season at the mouth of the Columbia River, which reduced the volume of material entering the littoral flow from the current ocean disposal sites.