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significant drilling mud was encountered (Nielsen, 1997). The process of inter- <br />aquiferwater-quality degradation by means of open-borehole completions is <br />described in Saulnier (1978), and Robson and Saulnier (1981). In addition, the <br />data in Weeks et al. (1974) and model results in Robson and Saulnier (1981) <br />indicate that in this part of Piceance Creek Basin, there is potential for <br />groundwater flow from the lower to the Upper Aquifer, especially along lower <br />Piceance Creek, permeability permitting. Therefore, it appears that the presence <br />of well 20-1 has locally altered the natural groundwater quality in the vicinity of <br />this well. <br />The laboratory analyses of upper-aquifer groundwater samples from the Yankee <br />Gulch Lease within +/-500 feet of well 20-1 indicate that this well may have <br />contributed to lowering the groundwater quality of the Upper Aquifer in the vicinity <br />of this well. In addition to higher dissolved-solids concentration, the laboratory <br />analyses of groundwater samples collected from welt 20-1 (Figure 1) show <br />concentrations of chromium, copper, lead, iron, nickel, and zinc (Agapito, 1999) <br />as compared to the trace-metal concentrations shown for the USGS and USBM <br />exploratory wells presented in Welder and Saulnier (1978), Dale and Weeks <br />(1978), and Saulnier (1978). However, it must be noted that in making this <br />comparison, the early reported analyses of the American Soda samples from well <br />20-1 report "total" concentrations of these trace metals from analyses of <br />unfiltered samples, whereas the USGS analyses report dissolved concentrations <br />from filtered samples. Thus, the samples from well 20-1 show higher <br />concentrations of suspended solids than found in other groundwater samples in <br />the Upper Aquifer. Operations in well 20-1 appear to have resulted in a large <br />amount of suspended metalliferous material in the well water. This material also <br />probably represents corrosion products of other debris left in 20-1 after the initial <br />1966 completion. The suspended-solids material appears to the source of the <br />elevated "total" concentrations of the trace metals. Therefore, the dissolved- <br />metals data reported by the USGS for other Upper Aquifer wells are difficult to <br />compare other than noting that during rewmptetion operations, drill pipe and <br />fishing tools were cut, ground, and otherwise damaged in the Lower Aquifer <br />interval. <br />The American Soda sample-analysis data indicate that well 20-1 may well have <br />created a local plume of groundwater with a higher salinity than found otherwise <br />in the area as described above and in Robson and Saulnier (1981). The extent <br />of this plume is not known at present. This mechanism for local groundwater <br />deterioration due to completion practices, or lack thereof, of exploratory <br />boreholes in Piceance Creek Basin is not an uncommon occurrence. The effect <br />of these boreholes on the water quality of both the upper and Lower Aquifers in <br />Piceance Creek Basin is part of the conceptual model of water quality in the <br />basin as described in Saulnier (1978). <br />An example of the extent of contamination due to well 20-1 may be seen in the <br />1997 to 1999 water quality data for American Soda wells 20-5 and 20-8 (Agapito, <br />Seotemher 7. 1999 5 <br />