And we've made the choice by default. More often than not, it is subtle, gradual degradation. For example, nitrate levels, a water quality indicator, are creeping higher in our groundwater. Countywide, groundwater nitrate levels averaged 1 part per million in 1989. Ten years later it was 1.7 ppm, a 70 percent increase.
Nitrates derive from fertilizers, manure, septic systems and other human activity.
At levels 10 ppm or higher, they can cause blood disorders in babies. At 4 ppm, health officials start to take notice. Nitrates also are showing up in higher concentrations in urban streams, which are fed by groundwater. Chambers Creek, which runs through rapidly developing areas near Yelm Highway, shows nitrate levels doubling to roughly 3 ppm since the early 1990s. Many of the area lakes are overloaded with nutrients, in part from shoreline homes and stormwater runoff from nearby urban development, says county environmental health specialist Sue Davis.