Mosier’s long history of water woes

As a result of the state report, the state stopped allowing irrigation wells to be drilled into two aquifers in a four-square mile area. It didn’t help.

Then the city of Mosier tried three times to repair a municipal well that was commingling, or allowing water to pass between two aquifers, without success. It was finally abandoned in 2013, said Lite, who is consulting on the Mosier Million project (see related story.)

When, due to commingling, a high-pressure aquifer leaks into a low-pressure aquifer, Lite said, it has the depleting effect of “pumping 24 hours a day, seven days a week, 365 days a year.” That particular city well had been leaking over 100 gallons a minute, around the clock, since 1973, he said.

Water levels continued a steady decline in the 2000s, and Lite found the water was discharging from the lower aquifers into the topmost aquifer and then into Mosier Creek.

What really sounded the alarm, Lite said, was an extensive 2012 study by the U.S. Geological Survey (USGS) that found as many as 150 wells may be commingling.

In one known commingling well it tested, it found that 70-135 gallons per minute were flowing up the borehole of the well into another aquifer.

It found 80-90 percent of the well water level decline was due to commingling, with the other 10-20 percent due to pumping out too much water.

The study found 80 percent of the well water was for agriculture use, 10 percent was for the city of Mosier, and the other 10 percent was the private wells of rural residents.

The wells sit in a swath of basalt covering large parts of Oregon, Washington and Idaho called the Columbia River Basalt Group. They are thin, very low storage aquifers, Lite said. “That’s why, if you depressurize them [through commingling] the water levels drop.”

But since they’re low storage, they’re also easy to recharge, he said.

“Our hope here is to plug up enough holes by replacing wells and we’re only going to get to 12 to 15 wells in this Mosier Million,” Lite said of a project underway to replace some commingling wells.

The 2012 USGS report prompted the creation of special standards for well construction, at the community’s request. They call for direct government oversight to ensure wells are built to standard.

Lite said government entities in the local community have spent some $1 million in local tax dollars over the years investigating the problem and trying to find a solution. He stressed it was a community-driven effort.