"LETC continually monitors the process waters at and near their experimental sites, in compliance with federal standards. Samples are periodically taken and submitted to independent 1.bs for chemical analysis. Usually about 20 tests are performed for each sample, though there have been as many as 45 or as few as 2. There are three major sources for our data: Rock springs } in situ oil shale, Hanna } underground coal gasification, TS-1S } tar sands. We have various other data from earlier experiments and retort runs, but these do not really fit into any well defined group. Or each of the 3 major data sets, there are divisions into sites and subdivisions by wells. The geographical layout of the wells is different for every site, but the wells tend to form a grid around the given site. Some of the wells can therefore be quite isolated from others at the same site. Our task has been to try to set up some coherent scheme for analyzing the data, for trying to assess its environmental impact and to determine which parameters are most important in determining this impact."