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Portland, OR—A new study released by the Oregon Department of Environmental Quality shows elevated levels of nitrate above background levels and arsenic in some wells in the Mid-Rogue Basin and encourages private well owners to routinely test their wells.

The study was conducted by DEQ's Statewide Groundwater Monitoring Program in parts of Jackson and Josephine counties and included Grants Pass, Shady Cove, Central Point, Medford and Ashland. In February and October 2015, DEQ employees sampled 107 private wells for nitrate, arsenic, bacteria, pesticides, metals and common ions. The domestic wells provide drinking water for homes and farm animals and are also used to irrigate gardens and lawns. While DEQ doesn't regulate drinking wells, the testing can help DEQ understand the condition of aquifers and the information gathered can help owners learn more about their well water.

Among the findings:

-Elevated nitrate levels above natural groundwater conditions were detected around Central Point and north and west of Medford.

-Only four percent of the 107 wells tested had nitrate concentrations above the maximum contaminant level (10 milligrams per liter) set by the U.S. Environmental Protection Agency for public water systems.

-Six percent of wells showed arsenic levels above the maximum contaminant level of 10 micrograms per liter.

-At least one pesticide or chemical resulting from the breakdown of a pesticide was detected in 38 percent of the wells –though all of the readings were well below the level considered a threat to human health.

-Coliform bacteria were detected in 43 percent of wells tested, which may indicate contamination of the aquifer or problems with individual well construction or sealing.

DEQ encourages private well owners to routinely test wells for nitrate, bacteria and arsenic. More information on how homeowners can better protect their wells can be found at:

The Statewide Groundwater Monitoring Program began collecting samples in 2015 to study groundwater conditions throughout Oregon, to detect emerging groundwater quality problems and inform groundwater users of potential risks. It conducts two regional groundwater studies a year. The study areas are selected based on a variety of data including nitrate data collected during real estate transactions.

Additional analysis of the groundwater data collected by DEQ in the Mid-Rogue will be conducted by the Jackson County Soil and Water Conservation District in 2017.

View the study at:

Katherine Benenati, Public Affairs Specialist, Eugene, 541-686-7997,


Environment & Energy