You are here

Southern Willamette Valley Groundwater Management Area

Southern Willamette Valley Groundwater Management Area (GWMA)

The Southern Willamette Valley Groundwater Management Area (GWMA) was declared in 2004 because of high nitrate contamination in a 230 square mile area of the Willamette Valley. A multi-year, multi-stakeholder process is addressing the nitrate contamination issue.   The GWMA encompasses portions of Lane, Linn, and Benton counties and includes five cities (Corvallis, Harrisburg, Monroe, Junction City, and Coburg).   Scientific studies have found nitrate to be associated with methemoglobinemia (blue baby syndrome), diabetes, negative reproductive outcomes, and various forms of cancer.  Public water suppliers must test their water regularly but rural home owners are not required to do so and are often unaware of contamination issues.

Extensive testing in 2000-02 by the Department of Environmental Quality concluded that nitrate was a contaminant of concern in groundwater in the Southern Willamette Valley.  Nitrate was found at greater than 7 mg/L in more than 20% of samples analyzed in 2000 and 2001.  Those with high levels were re-sampled in 2002 and more than 90% of those samples were still above 7mg/L. Nitrate was found at many locations at concentrations greater than the public drinking water standard (10 mg/L) and at more than three times the standard in several locations. DEQ now monitors the GWMA groundwater quality quarterly by sampling at 41 well locations. Our pollutant load reduction target is to reduce all nitrate levels in the groundwater to less than 7mg/L.