"Water quality data collected from monitoring wells in the Piceance Creek Basin oil shale area can be significantly influenced by well design and sampling techniques. Many of these influences can be attributed to hydro geologic complexities, which can have notable variations on a fairly local scale. To adequately address these complexities, a site-specific characterization of the hydrogeology is necessary. This is particularly important for specifying well construction details of monitoring wells for a ground-water quality monitoring program. Data collected during the bailing of deep aquifer wells on Federal Prototype Oil Shale Lease Tract C-a indicates the need for consistent and representative sample collection depths. Appreciable changes in water quality can be induced by variations in sample collection depths. In addition, unrepresentative data can be obtained due to the incorrect selection of intervals to be sampled in the well. Care must be taken to sample consistently from the same depth and aquifer interval during each and every sampling effort. Studies such as these provide necessary background information for developing ground-water monitoring guidelines in the oil shale region. Sampling procedures must be consistent to assure representative data collection. In addition, wells should be designed and completed according to the local hydrogeology and the specific goals of the monitoring program."