Publication Summary

This work was undertaken to assess current groundwater quality conditions and trends for the high-growth communities of Agnew and Carlsborg which lie north and west of the city of Sequim. Eight previously sampled wells were monitored quarterly from December 2000 to September 2002 for field parameters, total persulfate nitrogen, nitrate+nitrite-N, total and fecal coliform bacteria, chloride, total iron, and total manganese. Trend analysis of the nitrate data for each well suggests that, of the eight wells evaluated, three showed a statistically significant increase in nitrate-N concentration, four showed no trend, and one showed a decreasing trend.

Eight wells in the Agnew and Carlsborg area of Clallam County were monitored quarterly from December 2000 through September 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 systematically sampled in 1980.

Based on this evaluation, nitrate+nitrite-N concentrations ranged from <0.01 to 4.58 mg/L. Concentrations of total persulfate nitrogen were similar, ranging from <0.01 to 4.31 mg/L. Fecal coliform bacteria were not detected in any samples; however, total coliform bacteria were detected in approximately 16 percent of total samples at concentrations ranging from 1 to 45 CFU/100 ml. Chloride concentrations ranged from 2.97 to 14.3 mg/L, while total iron and manganese concentrations ranged from <10 to 2540 µg/L and <1.0 to 795 µg/L, respectively.

Trend analysis of the nitrate data for each well suggests that, of the eight wells evaluated, three showed a statistically significant increase in nitrate concentration, four showed no trend, and one showed a decreasing trend.

Comparative evaluation of split samples processed at the Clallam County Environmental Laboratory and Ecology′s Manchester Environmental Laboratory indicated good agreement in fecal coliform analyses and generally poor agreement in paired nitrate-N analyses.

Link to EIM data for User Study ID KSIN0005