U.S. Water News Online
YAKIMA, Wash. -- 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 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
radioactive 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
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
one 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 continues to gradually
decline over time.
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.
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
The U.S. Department of Energy, which manages 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 and in
the groundwater beneath the Hanford site," spokeswoman Colleen French
said in a statement.
Already, groundwater at 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 only reviewed 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.
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
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
In addition, federal officials have said the reservoir likely
would only serve 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. "We're spending an awful lot of money to try to clean up
the mess at Hanford, and to even consider building a reservoir that
cold have an adverse effect on that cleanup is unthinkable."
So far, about $14 million has been spent to study the two Yakima
Valley proposals. The other proposal is Wymer Dam, which would hold
an estimated 175,000 acre feet of water about 15 miles north of
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