PORTLAND, Ore. (AP) — A monitoring well installed after last month's train derailment near Mosier, Oregon, has detected oil contamination in the ground water.

The state Department of Environmental Quality tells Portland station KATU that drinking water is not affected in the Columbia River Gorge town because those wells are uphill from where the oil train derailed June 3.

The agency said Wednesday that four monitoring wells were installed after the wreck, and one revealed significant oil contamination.

DEQ plans to install a treatment system that injects air into the underground water. The oxygen will stimulate the existing microbes that live in the water to break down the oil.

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