Proposed reservoir could taint Columbia River

YAKIMA — A massive reservoir intended to provide a more reliable water supply for Washington farmers could seep so much it would significantly raise the water table at the nation's most contaminated nuclear site, increasing the risk of those contaminants reaching the Columbia River, a new report concludes.

The analysis released this week by the U.S. Bureau of Reclamation is a setback for plans to improve irrigation in Central Washington's drought-prone Yakima Valley, which is home to hops, wine grapes, tree fruit and other crops. At the same time, it raises concerns about contamination at the nearby Hanford nuclear reservation flowing more easily to the Pacific Northwest's largest river.

The Black Rock reservoir, which would be about five miles west of Hanford, is one of six proposals for increasing water storage and easing chronic shortages in Eastern Washington. Water would be pumped from the Columbia from the pool behind Priest Rapids Dam to the reservoir about 30 miles east of Yakima to provide water for Yakima Valley irrigators and improve streamflows for fish in the Yakima River.

The reservoir would hold an estimated 1.6 million acre-feet of water. An acre-foot is the amount of water needed to cover an acre 1 foot deep.

In the first 13 months, the annual rate of seepage from the reservoir could be as low as 72,900 acre-feet or as high as 121,000 acre-feet, or about 39 billion gallons, according to the report. After five years, when the ground beneath the river is likely saturated and an equilibrium is reached, the seepage rate would fall to between 32,100 and 54,300 acre-feet and continue to gradually decline.

Generally, off-channel reservoirs that are not located directly on rivers have a seepage rate of between 1 percent and 3 percent, said Gerald Kelso, manager of the Upper Columbia area for the Bureau of Reclamation. Black Rock falls into that range, and the seepage findings were not a surprise, Kelso said.

Seepage flow

But the flow direction of that seepage is east toward the Hanford site, where the federal government has been working to clean up radioactive contamination in the soil and groundwater from Cold War-era nuclear-weapons production.

"Our major concerns with the information we have received is that it would raise the water table and rewet, remobilize contaminants," said Jane Hedges, Hanford program manager for the state Department of Ecology.

The U.S. Department of Energy, which manages the Hanford cleanup, also expressed concern about the findings and asked to participate in future studies to provide technical expertise.

"It's clear to us that the proposed reservoir could significantly affect the movement of contaminants through the vadose zone [above the permanent groundwater level] and in the groundwater beneath the Hanford site," spokeswoman Colleen French said in a statement. Already, groundwater from an estimated 80 square miles of the 586-square-mile site is contaminated above drinking-water standards.

According to the study, the water table could be raised between 20 to 40 feet at Hanford's 200 East and 200 West areas, where some 53 million gallons of radioactive waste are stored in 177 underground tanks, some of which are known to have leaked.

A previous study released in March examined the impact of raising the water table 60 feet, the historical high in that part of the Hanford Site, on four known radioactive contaminants: tritium, iodine-129, technetium-99 and uranium-238.

That study found that transport of these contaminants was slightly accelerated, but the increased amount of water also diluted them.

However, the earlier study reviewed only the impact on contaminants already in groundwater, not on contaminants in the soil that could be captured by raising the water table. It also did not look at any cumulative impacts over time and the impact on aquatic life, said Vicky Freedman, senior research scientist at Pacific Northwest National Laboratory, which conducted the study.

"It's not to say we wouldn't come to the same conclusion, but that's not what we studied. That study was done with the intent of revisiting it once more data had been gathered," she said.

Impact statement

An environmental-impact statement on the project is expected to be completed in January.

Sid Morrison, chairman of the board of the Yakima Basin Storage Alliance, also wasn't surprised by the results. But he said water that does leak from the dam could be captured or pumped out of the ground before it reaches Hanford.

"Every dam that's ever been built leaks," he said. "We could look at that water in a different location as an asset. If you pump in the right places, you can mitigate the negative impacts and create some very positive ones."

The latest study results aren't the first stumbling blocks for Black Rock.

Estimates to build and operate Black Rock have been as high as $6.3 billion. An earlier analysis of the proposed reservoir showed a national benefit of 28 cents for every dollar spent to build and operate it. That analysis did not review local benefits, such as recreation.

In addition, federal officials have said the reservoir likely would serve only Yakima Valley needs and would not address other water needs in the larger Columbia Basin, where several other storage options are under review.

Rachael Paschal Osborn, director of the Center for Environmental Law and Policy, called the findings "alarming."

"I'm not sure this is the total death knell, but it should be," she said.