Abstract
The discovery of the widespread contamination of the Californian alluvial-basin aquifers by plumes of dissolved-phase chlorinated solvents (TCE, CFCs, TCA, PCE) in the period 1979–1981 was partly the result of recommended industrial waste-disposal practices during the preceding decades. In order for the present contamination to have been anticipated and minimized, several conditions would all have to have been met by about 1950. First, chlorinated solvents would have to have been identified as potential drinking-water contaminants such that the disposal of chlorinated solvents on dry soil would have been prohibited (or strictly regulated) and accidental spills rapidly cleaned up. Second, monitor-well networks would have to have been operational up-gradient of water-supply wells and near solvent-using facilities, and gas-chromatographic methods capable of detecting aqueous contamination well below 1 ppm would have to have been in widespread use. Third, a paradigm explaining the subsurface migration and fate of dense nonaqueous phase liquids would have to have been published and widely accepted at approximately the same time as the identification of chlorinated solvents as potential drinking-water contaminants. Unfortunately, the first two of these conditions were not met until the 1970s and the third not until the 1980s. Furthermore, all three conditions were not only necessary, but also were complementary requirements for the anticipation of ground-water contamination in the Californian basins.
