Dredging Plan Raises Issuesby Natalie M. Henry
The Army Corps of Engineers is in a crunch to keep the Snake River shipping channel at a depth of 14-feet to accommodate regular barge traffic from Lewiston, Idaho, to Portland, Ore., a total of nearly 350 miles, and to keep Lewiston from flooding. The corps hopes to dredge the river this winter and use the material to create shallow water salmon habitat, while also raising levees three feet higher in Lewiston. According to the management plan, the corps will need to dredge a number of times over the next 20 years, which may affect endangered and threatened salmon in the river.
Numerous stakeholders commented on the plan during the comment period, which ended this week. Some of those comments -- including those from Idaho Department of Fish and Game (IDFG) , Washington Department of Fish and Wildlife (WDFW), Columbia River Inter-Tribal Fish Commission (CRITFC) and Save Our Wild Salmon (SOS) coalition -- criticized the corps for not considering a full range of alternatives, including a true "no action" decision, breaching the four lower Snake River dams and spilling water over the dams during the spring runoff to flush sediment through the river.
The corps maintains that it did consider not dredging and less dredging but was unable to identify any alternatives that would preclude the ultimate need for dredging.
Muddy river: what to do with all the sediment
The corps considered four alternatives: the first was a "no action" alternative that was categorized as "no change," meaning maintenance dredging with in-water disposal of sediment and dredged material; the second was maintenance dredging with in-water disposal to create fish habitat and a 3-foot levee raise; the third was maintenance dredging with disposal on land and a 3-foot levee raise; and the fourth was maintenance dredging with beneficial use of dredged material, both in water and out, and a 3-foot levee raise.
The corps chose the fourth alternative because the environmental impacts were equal to or less than the other alternatives considered, according to Jack Sands, project manager for the corps. Furthermore, Sands said, alternative four is the most cost effective way to maintain a 14-foot navigation channel in the reservoirs (see map). It also emphasizes beneficial uses for the dredged material, and it offers the most flexibility for implementing those beneficial uses. One example is a plan to take material retrieved during this winter's dredging and use it to create aquatic and terrestrial habitat in nearshore and shoreline habitat. But IDFG questions how beneficial that material will be and disagrees with the corps that placing the dredged material in shallow water will mitigate for the loss of shoreline and shallow water salmon habitat that occurred when the dams were built and the river impounded in the 1960s and 70s. Moreover, IDFG questioned how stable the artificially created habitat would be in light of fluctuating reservoir levels for power generation purposes, and waves created by barges and boats. Another question IDFG posed was how soon the habitat would be covered by silt, providing "the same poor quality habitat as most of the rest of the reservoir," IDFG's comments say.
IDFG also questioned what the corps would do with sediment the next time it dredges. The corps expects to have five to eight dredging contracts in the next 20 years, but IDFG maintains that dredging will only remove 5 percent of the annual build-up of sediment. The corps will make up the difference by raising the levees in Lewiston. IDFG suggested the corps flush the sediment through the dams, or at least consider the option.
A fifth alternative?
Flushing would occur in the spring when winter snowpack runs off through the river and deposits much of the year's sediment in the river. In a free-flowing river, sediment eventually flushes all the way to the Pacific Ocean, creating an estuary environment around Portland and Astoria, Ore. Flushing the sediment through would be cheaper for the corps, according to IDFG, although it could require seasonal modifications to reservoir operations, perhaps resulting in less power generation. Also, the sediment would accumulate at the three dams below McNary on the Columbia River and would need to either be dredged from those reservoirs or flushed again through those dams.
WDFW commented -- as did Idaho -- that the corps should consider flushing as an alternative to dredging. And CRITFC and SOS said flushing would benefit young out-migrating salmon through spill; spilling water creates more normal flow conditions, pushing salmon to sea at a normal rate and reducing predation, and spilling results in a high rate of dam passage survival and return rates, the tribes say. The tribes disagree with the corps' traditional method of taking fish out of the river and moving them past the dams in barges or trucks.
Responding to IDFG and SOS, the corps says flushing would require a drawdown in the reservoir. Without drawing down the reservoir, flushing would impact not only operations, but also project facilities and public infrastructure. "The impacts ... would exceed the benefits of sediment flushing," the corps says. In terms of fish passage, the corps said flushing would result in fish going through turbines, becoming trapped in the dam's "gatewells," or being delayed in eddies below the dams, subject to predation.
IDFG said if the corps continues to deal with sediment deposition simply through dredging, it will eventually run out of places to put the material. "The four alternatives analyzed do not cover a wide or creative range of solutions for the serious, long term problem of sediment accumulation," IDFG said.
Raising the levees
The corps plans to not only dredge but also raise Lewiston's levees by three feet. Raising the levees means some of the sediment and silt behind the last dam, Lower Granite, which is just downstream from Lewiston, can be left there and the corps can still maintain a 14-foot navigation channel. Due to delays in coming up with a dredging plan, the corps is currently keeping two of the five reservoir levels a bit higher than usual to maintain the 14-foot depth, Sands said.
In its formal comments, IDFG asks, "With almost three million cubic yards of sediment accumulating annually in the reservoir, how long will it be before the next levee raise is proposed?" The department worries a flooding event could overtop the levees near the end of the planning period, 75 years. And the corps' dredge plan says any future levee raises would require "extensive and expensive infrastructure changes, including raising or modifying several bridges in the Lewiston area," IDFG says.
A 14-foot channel vs. a 13-foot channel
The corps maintains that it is authorized to keep the navigation channel at a depth of 14 feet. But CRITFC challenges this assumption. "We believe that the corps, while authorized to maintain a navigation channel, is not required to keep it at 14 feet," CRITFC's comments say.
If the channel were not maintained at 14 feet, barges would need to be lighter, said Steve Frasher, president of Tidewater Barge. Tidewater is arguably the busiest of a handful of barge companies on the Snake. Frasher said a barge drafting 14 feet will carry 3,600 tons of wheat (the predominant commodity transported on the Snake River). Based on this assumption, a barge would have to relinquish 700 bushels of wheat per trip, which works out to $3,300 worth of wheat at current market prices.
"A loss of just one inch of draft capacity means well over $3,000 worth of someone's cargo must be left behind. And, looking at the whole Columbia-Snake system, over one-half of the wheat that comes to the Portland export market by barge originates in the Snake River portion of the system," Frasher said. "Shallow drafts on the Snake River would adversely impact fully 10 percent of all wheat our nation exports annually," he said.
(bluefish notes: most of the wheat on the Snake is loaded at grain terminals downstream of Lewiston. Most of the containers, predominately paper board from Potlatch, is loaded at Lewiston.)
A sixth alternative?
The corps could avoid the dredging controversy by breaching the four lower Snake River dams, according to SOS's comments. Breaching would not eliminate the dredging problem, but it would move it further down river, eventually becoming a more pressing problem at McNary dam around the Tri-Cities area. CRITFC agreed with SOS that breaching the dams should have at least been considered. The corps maintains that breaching the dams does not meet the congressionally authorized goals of the projects, one of which is to maintain a 14-foot channel for barge transportation.
Breaching would not entirely preclude barge traffic, CRITFC maintains: "The river without the channel and pools would continue to be navigable, just not at a depth of 14 feet." Even if the river were still navigable, most commodity transportation would have to move from barge to truck or rail.
Breaching the dams is an ongoing effort by conservationists and fish advocates to return the Snake River to natural flow conditions, which would benefit a number of species of salmon and steelhead that are listed under the Endangered Species Act. One species is already extinct, and another is nearly there with fewer than 10 fish returning annually in recent years. (see Count the Fish)
Chinook is one of the ESA-listed species on the Snake River. While dredging would occur between Dec. 15 and March 1, as dictated by the National Marine Fisheries Service to minimize the effects on fish, CRITFC maintains that the corps did not adequately analyze the effects of dredging on fall chinook that overwinter in lower Snake reservoirs and migrate seaward in the spring. The tribes say these young fall chinook that overwinter in the river are more likely to return to the river as adults, which is important for salmon recovery.
Commenters had further issues with how dredging would affect water quality on the river and charged the corps with not thoroughly addressing compliance with the Clean Water Act. The corps responded that it has worked closely with the U.S. EPA, the Washington Department of Ecology and the Idaho Department of Environmental Quality to comply with CWA. The corps is awaiting permits from Washington DOE, since all the disposal would occur in Washington.
The Washington DOE was concerned that dredged material might not be suitable for beneficial use, in which case it may cost more for the corps to dispose of it. The corps responded that if any material was deemed inappropriate for beneficial use, the corps would either deposit it in deep water areas or deposit it on land, and would cover any additional expenses.
CRITFC and SOS had further concerns that the dredging and disposal might affect water quality. Temperatures in Lower Snake and McNary reservoirs already exceed water quality standards, and increased water temperatures have been known to increase salmon predation, discourage returning adult salmon from spawning and harm salmon eggs, according to CRITFC.
The corps hopes to make a decision and get proper approval in time to dredge this winter. As the last reservoir continues to accumulate sediment, the flooding risk to Lewiston grows. And a large runoff next spring could significantly decrease channel depth and hinder barging.
Dredging and disposal will range from $2 million to $5 million for a typical dredging contract, Sands said. The corps anticipates five to eight dredging contracts for the next 20-year period and will need to request additional funding from Congress to cover most expenses; ports and marinas reimburse the corps for the cost of dredging the areas associated with the ports and marinas. The study on dredging has cost $3.6 million over four years, Sands said.
learn more on topics covered in the film
see the video
read the script
learn the songs