Its presence in ground water above natural levels means that it is possible that other contaminants from the land surface may be reaching the water table. He added it was somewhat surprising that urban areas with these permeable deposits, such as parts of Tacoma and Olympia, are also at relatively high risk. Tesoriero is currently leading a USGS study in Whatcom County that will evaluate how quickly natural processes decrease nitrate concentrations in ground water. The maps produced using this model can help in targeting ground-water monitoring programs and in planning future land use, such as where to allow development using septic systems. They are also useful tools for educating the public about the potential of ground-water contamination from land use.
Copies are also available at some area libraries.
None of the concentrations exceeded drinking-water standards or guidelines, but concentrations of four pesticides exceeded maximum levels recommended for the protection of aquatic life. More pesticides were detected in urban than agricultural streams. This is because the total amount of pesticides used in urban areas in the populated Puget Sound region is about three times greater than the amount used in agricultural areas, say the investigators. Low levels of older-generation pesticides such as DDT were not found in water, but were found in streambed sediments. This is not surprising, according to the authors, because many studies nationwide report that older pesticides currently banned in the U.S. can still be found in sediments.