Publication Summary

Twenty-three private water-supply wells were sampled bimonthly for one year to define nitrate concentrations in groundwater in a seven square mile area east of the city of Yelm. Twenty-two of the sampled wells tapped the principal aquifer, the Advance Outwash Aquifer that occurs at a depth of 70 to 100 feet below the ground surface. One sampled well tapped the uppermost aquifer that is little used for drinking water, because it is considered susceptible to contamination from surface activities.

Twenty-three private water-supply wells were sampled bimonthly for one year to define nitrate concentrations in groundwater in a seven square mile area east of the city of Yelm. Twenty-two of the sampled wells tapped the principal aquifer, the Advance Outwash Aquifer that occurs at a depth of 70 to 100 feet below the ground surface. One sampled well tapped the uppermost aquifer that is little used for drinking water, because it is considered susceptible to contamination from surface activities.

Well samples were tested for nitrate+nitrite-N, chloride, total dissolved solids, ammonium and fecal coliform. Nitrate has migrated to the Advance Outwash Aquifer. Areas where mean nitrate+nitrite-N concentrations exceed 3 mg/L and 5 mg/L are identified. Concentrations are not at alarming levels but are high enough that additional nitrogen loading should be prevented. Potential nitrate sources upgradient of the study area are identified. Wells should be resampled in a few years to ensure that conditions have not deteriorated. Long-term monitoring is recommended at Crystal Springs, a natural spring located one mile north of Yelm. Water quality samples at Crystal Springs could be a useful indicator for changes in groundwater quality for a portion of the area north of Yelm.

Link to EIM data for User Study ID YELMGW