Aquifer Provides Drinking Water To 9 Out Of 10 People Underground Pockets Of Rock Trap Billions Of Gallons

Lost in the rhetoric surrounding federal protection of drinking water in Eastern Washington is a simple question: What is this aquifer anyway?

Imagine several underground pockets of loose rock in which billions of gallons of water are trapped by firmer rock above and below.

In Eastern Washington, there are several such pockets, and together they provide drinking water to nearly nine out of every 10 people living in seven counties bordered roughly by the Columbia, Snake and Spokane rivers.

Because water can flow in cracks leading from one pocket to another, all of them need to be protected as a single aquifer system, says Martha Sabol, a senior hydrogeologist for the U.S. Environmental Protection Agency.

Opponents question that conclusion, and say not enough is known yet to protect as large a region as the proposed Eastern Columbia Plateau Aquifer Systems.

They say the different water pockets could be separate aquifers that should be treated separately. A Wenatchee consultant hired by one group against the aquifer proposal concluded it is impossible for water to flow between the region’s two main pools, the Grand Ronde and the Wanapum.

The reason: a thick layer of underground clay that the consultant, Doug McFarland, said stretches from the Idaho border to Wenatchee.

The EPA and the U.S. Geological Survey contend this layer is made of clay, sand and gravel and lets water move from the Wanapum, the higher pool, to the Grand Ronde, the lower one.

Experts disagree over how much water could go between the two pools, but without some movement, said Sabol, it’s hard to explain how water gets to the Grande Ronde at all. USGS maps show water flowing from one pool to the other before rising under pressure to discharge into the Columbia River.

McFarland, hired by the antiaquifer Northwest Council of Governments and Associates, said his work breaks new ground.

“There is, to my knowledge, no other data out there like this,” he said.

McFarland said he used electromagnetic sensing techniques to detect the clay layer, placing his equipment every 10 miles or so from Wenatchee east to Airway Heights and from Grand Coulee south to Othello.

In both directions, he said, he detected the clay at least 20 to 30 meters thick between the Wanapum and Grande Ronde.

While his work did not span the entire proposed EPA aquifer area, McFarland said, “it’s very, very reasonable” to say the layer runs throughout the region.

Sabol said data from previous drillings show no evidence of the clay layer in many parts of the region.

USGS measurements show water flowing out of the Grande Ronde at the Columbia River, suggesting the only way it can be recharged is from the Wanapum, she said.

Jeff Brown, a former Washington State University hydrogeologist, bluntly characterized McFarland’s conclusion as “not correct.”

Referring to data collected by WSU, Brown does believe the EPA and USGS are incorrect in treating the Grande Ronde and Wanapum as a single aquifer system.

But Brown said there is a connection between the two and that it is increased by thousands of uncased wells punched between the two.