Wells have gone dry in the Yelm area and others have seen a significant drop. In Thurston County, all 1,200 public water supplies tap groundwater resources. Once contaminated, groundwater is difficult, expensive, or impossible to cleanse. Since large areas of the County are underlain with gravel, many aquifers contain no impervious layer, making them very susceptible to infiltration from contaminated stormwater and agricultural wastes, leaking septic systems and underground fuel tanks, illegal dumping or accidental spills. Existing regulations are inadequately enforced.
Insufficient information is available regarding a safe level of residential density.
Little is known about possible sea water intrusion into shoreline systems. Abandoned landfills and auto junk yards have not been examined for potential threat to groundwater. Accidents on rail and highway corridors can spill hazardous materials, contaminating groundwater before cleanup can occur. Gasoline and pesticide contamination caused 10-15 wells in North Thurston County to be abandoned. Nitrate levels are inching up at McAllister Springs.