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Groundwater quality in the La Pine area of southern Deschutes County is at risk of nitrate contamination from onsite sewage treatment system discharge to groundwater. Nitrate concentrations detected in groundwater indicate that degradation of groundwater quality is in process in the densely developed areas. Most onsite systems in the region are conventional systems located in highly porous and permeable (rapidly draining) soils with no intervening layer protecting the underlying shallow aquifer.
Most water wells in the south county are 20 to 50 feet deep which is about 20 to 50 years old. However, since 1988, 750 tons of nitrates have filtered their way into the aquifer. He said tests in 1999 showed that half those nitrates are in a small strip beneath the land surface, and researchers estimated that they will work their way down to the level of wells in approximately 11 to 62 years depending on the depth of individual wells and their locations.
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