A look at the impacts of removing dams

By CHRIS FOWLER
HDR

The dedication of Lower Granite Dam in 1975 marked the completion of a system of four dams providing a navigable waterway on the Snake River from Lewiston, Idaho, to the confluence with the Columbia River, 140 miles downstream near Pasco.

This navigable waterway provided an efficient and low-cost transportation option to ship products to the export terminals in Portland and southwest Washington from production centers in Eastern Washington, Oregon and parts of Montana and Idaho.

Low-cost barge transportation has brought elevators and terminals to the Snake River, shifting local economies to take advantage of new opportunities. Photos courtesy of Army Corps of Engineers

Today, concerns over dwindling salmon populations are bringing the fate of the four dams under close scrutiny. Drawdown to natural river conditions is being considered as a way to reduce the mortality of migrating salmon.

Removal of the dams would end barging on the Snake, and have a significant impact on the region's transportation system which has taken full advantage of the barge network. In the upcoming months as the region is presented with a case for and a case against dam removal, the impacts to the transportation network, and the effect that these impacts will have on the people who depend upon it, must be given full consideration before a responsible decision can be made.

The debate over dam removal is extremely complex.

The endangered salmon species, identified as the beneficiaries of the proposed action, can travel thousands of miles in their lifetimes, making them susceptible to a wide range of environmental conditions and human actions. While it is generally agreed that the dams have at least some level of impact on these species, this impact is difficult to quantify to a degree that can be meaningfully compared to the costs of dam removal.

While the most critical aspect of the debate is almost certainly the determination of the dams' impact on fish, there are many other considerations being discussed. Losses in hydropower production, alterations to the irrigation system, losses and gains in recreational values and the need to meet Native American treaty rights, are just a few of the topics that need to be addressed. The transportation system is only one piece of a much broader debate.

Background

In 1992, the National Marine Fisheries Service listed four species of Snake River salmon as "endangered" under the Endangered Species Act. This listing triggered a series of events which have led the Army Corps of Engineers to consider the removal of four dams on the Lower Snake River.

Drawdown of dams such as Ice Harbor is being considered as a way to preserve more migrating salmon.

• the loss of the 140-mile navigable waterway extending from Lewiston, Idaho, to the Tri-Cities;

• an increase in the quantity of freight carried by truck and rail; and

• the structural destabilization of segments of important roads, bridges and rail lines adjacent to the river.

Loss of the Snake River as a navigable waterway is a particularly sensitive topic of discussion, as it would dramatically alter the system of production and shipment of goods throughout a broad area of Washington and Oregon as well as parts of Idaho and Montana. Temporary loss of service on major roads and rail segments could also have severe short-term impacts on the movement of goods in the region.

Moving commodities

Currently, over 4.4 million tons of commodities including wheat, barley, wood products, containers and petroleum are shipped on the Snake River each year. The removal of the dams would make the existing navigation channel impassable, and force shippers to find alternative routes to move their goods to market. Producers who currently truck their goods to Snake River ports for shipment by barge, would most likely truck their goods to the nearest downstream loading facility. This change from the current pattern would send the majority of the affected commodities to elevators and terminals in the Tri-Cities area.

A study commissioned by Washington's Legislative Transportation Committee estimated the increased costs to wheat producers for shipment via these alternative routes to be significant; as much as 23 cents per bushel of wheat for some producers located near Lewiston, Idaho. Cost increases across the area served by the Snake River ports would average approximately 11 cents per bushel, with producers nearest the Tri-Cities, (and thus nearer to the barge system that would continue to operate on the Columbia River) or remote from the Snake River ports showing the smallest increases.

Lower Granite Dam. The EIS on dam drawdown will be completed by the end of the year.

In addition to costs paid by producers, the state of Washington would experience cost increases as a result of heavy traffic on some of its major highways.

Specifically, the LTC study found that three corridors, Highway 395 from Ritzville to the Tri-Cities, State Road 26/Pasco-Kahlotus Highway from Colfax to the Tri-Cities, and State Road 124/US 12 from Clarkston to the Tri-Cities would all experience severe truck volume increases.

This increased traffic would accelerate the rate of deterioration of these roads, and create congestion and potential safety hazards on those state highways. In total, the effect on just these corridors could range from $87 million to $103 million in mobility and safety improvements. If a significant quantity of goods shifted from barge to rail, some improvements to the rail infrastructure would also be required. These improvements have been estimated to cost as much as $182 million to $214 million

Geotechnical impacts

Under a dam removal scenario, as the reservoirs are lowered, saturated soils adjacent to them will be drained of water, destabilizing slopes, and causing cracking, slumping and even landslides that could affect roads and rail lines that are an important part of the region's transportation network.

Prior to the drawdown of the dams, the at-risk infrastructure could be shored up to prevent any loss of service. This level of improvement is estimated to cost roughly $82 million to $162 million, a broad range that reflects the lack of a detailed study of the specific, geologic conditions present along each section of at-risk infrastructure.

Alternatively, failing infrastructure could be shored up on an as-needed basis at a potentially lower construction cost. However, the risk of long-term closure of some important rail and highway routes would generate costs that are not easily captured.

Next steps

Lower Monumental Dam. Congress would need to provide funding if drawdown is approved.

Congress will then decide whether or not to accept the Corps' recommendation, and if the recommendation favors a drawdown, Congress will need to decide whether or not to provide funding for the action. In the meantime, more and more species of salmon are being listed as endangered, and the quantity of goods being shipped on the river continues to grow.

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