The Oregon Department of Environmental Quality says one of four monitoring wells on the north side of the railroad tracks in Mosier where June’s oil train derailment occurred has shown what is being described as “fairly significant” groundwater contamination.  Bob Schwarz of DEQ says Mosier’s drinking water comes from wells above the derailment site, so he’s confident drinking water has not been affected.  Schwarz says the biggest concern is for a wetland area between the derailment site and the Columbia River, and a treatment system will be installed at the location.  It will involve using pipes in the ground to inject air into the groundwater, and the oxygen in the air will stimulate naturally occurring microbes in the ground that will consume the oil.  Schwarz says the other three wells were fairly clean, with the contaminated well about 150 feet away from where the derailment occurred, and Schwarz says it could have been in a pathway where water flowed from firefighting efforts.