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<br />0922 <br /> <br />Calculated transmissivities range from 10.8 to 529 ft2/day. Aquifer <br />response to the drawdown/recovery tests are characteristic of limited <br />fractured reservoirs. Water samples from Wells 18, 21, and 24 show <br />mixed~cation-bicarbonate water, and the remaining samples are sodium- <br />bicarbonate water. The concentration of dissolved solids ranges from 290 <br />mg/l at Well 21 to 490 mg/l at Well 20. Fluoride concentration exceeds <br />1 mg/l for five of the samples, and ranges from 0.2 mg/l at Well 24 to <br />.,. <br />5 mg/l at Well 26. Zone 3 water quali~ has the least dissolved solids and <br />the most intermediate water ~pe in the central area of NOSR I, indicating <br />that recharge to this zone may occur in this region. Zone 3 water has a <br />medium salinity and low sodium hazard at the down-gradient wells. <br />Dissolved solids concentrations meet EPA drinking water standards at all <br />well s, but the fl uoride concentration exceeds the EPA Standards at Well s <br />15/16, 17, 20, and 26. <br /> <br />Zone 4 is found below the base of the R-6 zone. On NOSR 1, this zone <br />has an average thickness of 170 feet. Generally, the calculated values of <br />transmissivity and hydraulic conductivity are low and varia~le depending on <br />geographic location. Calculated transmissivity ranges from a low of 0.8 <br />ft2/day at Well 15/16, to a high of 48.5 ft2/day at Well 17. The response <br />of Zone 4 to the aquifer tests are typical of a fractured reservoir and <br />indicate a limited aquifer. All the groundwater in Zone 4 can be classed <br />as sodium-bicarbonate water. The lowest percentage of sodium and lowest <br />dissolved solids concentration are found at Well 21. All wells, except 20, <br />have elevated levels of fluoride with the maximum found at Well 15/16 <br />(7 mg/l). Most wells have low iron concentrations but 2 m9/l is reported <br />for Well 22. The chloride and sodium concentrations at Well 15/16 are the <br />hi9hest recorded on NOSR 1, indicating the possibility of some evaporite <br />mineral dissolution either on the northern rim of the reserve or in the <br />region immediately north towards Piceance Creek. The high concentration of <br />fluoride and dissolved solids at Well 15/16 also reflects the possibility <br />of increased mineral dissolution. A medium salinity hazard exists for <br />groundwater from all wells and a high salini~ hazard exists at Wells 15/16 <br />and 20. The sodium hazard is generally low, but a medium hazard is found <br />at Well 20 and a very high sodium hazard is indicated for Well 15/16. <br />Wells 15/16 and 20 exceed EPA drinking water standards for dissolved solids <br />and all wells, except 22, exceed the fluoride standard. <br /> <br />1-4 <br />