Publication Summary

Thirteen wells in the central Ahtanum Valley of Yakima County were monitored quarterly from March 2001 to December 2002 for traditional field parameters and a small suite of laboratory analyzed constituents, to determine if groundwater quality has changed appreciable since area wells were first broadly sampled in June 1973. Apparent increases in nitrate+nitrite-N concentrations were noted between 1973 and 1992 and between 1973 and 2002. There was an apparent decrease in nitrate+nitrite-N concentrations between 1992 and 2002.

Thirteen wells in the central Ahtanum Valley of Yakima County were monitored quarterly from March 2001 through December 2002 for traditional field parameters and a small suite of laboratory analyzed constituents, to determine if groundwater quality has changed appreciably since area wells were first broadly sampled in June 1973.

Nitrate+nitrite-N concentrations ranged from 0.04 to 7.1 mg/L. Concentrations of total persulfate nitrogen were similar, ranging from 0.1 to 8.0 mg/L. Fecal coliform bacteria were detected in samples from two wells at concentrations ranging from 4 to 35 CFU/100 ml, while total coliform bacteria were detected in samples from eight wells at concentrations ranging from 1 to 73 CFU/100 ml. Chloride concentrations ranged from 0.57 to 34.3 mg/L, while total iron and manganese concentrations ranged from less than 10 to 3030 µg/L, and less than 1 to 29.6 µg/L, respectively.

Trends in nitrate+nitrite-N concentration were evaluated using data from sampling events conducted in June 1973 (99 wells), September 1992 (16 wells), and September 2002 (13 wells). Apparent increases in nitrate+nitrite-N concentrations were noted between 1973 and 1992, and between 1973 and 2002. There was an apparent decrease in nitrate+nitrite-N concentrations between 1992 and 2002.

Link to EIM data for User Study ID KSIN0006