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Subsurface fhdrocarbon Assessmenr • The waters exceed water quality criteria and standards of salinity for irrigation and domestic uses (Table 3 and Appendix ~. Three of the four sites, (N-Decline, RSN and UTL} exceed the agricultural-based state ground water standazd for fluoride. In addition, RSS and the N-Decline sites also exceed domestic standards for iron. RSN exceeds the domestic water quality criteria and standazd for bazium, and the UTL site exceeds the water quality criteria for irrigation of boron- sensitive crops. Water from the N-Decline site could present some limitations for domestic and agricultural use due to its elevated pH of 8.7. In summary, water from the Rollins Sandstone in this area would pose considerable limitations for domestic, agricultural or stockwatering uses. Water from the Rollins Sandstone sites were compazed with other water quality information collected by Powderhorn. The USGS collected monthly water quality data from October 1992 through September 1995. The Colorado River water is a calcium sulfate water of widely varying salinity, TDS ranging from 290 - 1230 mg/L, depending on flows, and moderate hazdness, ranging from 110 - 260 mg/L. There is little similarity between the two populations of data. The alluvial wells in the unit train loadout area are sodium bicazbonate waters with total dissolved solids concentrations ranging from 568 - 2410 mg/L, hardness ranging from 45 - 217 mg/L, and SARs ranging from 4.54 - 31 mg/L based on samples taken during the 1993 water yeaz. The Rollins sites exhibit a similar type of water, with elevated salinities, but the hardness and SAR levels are not similaz. Powderhorn has been performing annual mine water inflow studies since 1987. The weighted average conductivity from the Roadside South Mine inflows in 1995 was 2288 umhos/cm, while the weighted average inflows from the Roadside North Portal site was 849 • umhos/cm. Site RS-5, monitored on 9/28/95, is a sodium carbonate water with a.pH of 8.8, a •TDS of 506 mg/I, a hardness of 37 mg/I, and art SAR of 13.4. This site is dissimilar from the Rollins due to its low salinity and low SAR. Site CA-1, the underdrain at the Roadside North Portal, was sampled in December, 1992, and the sodium bicarbonate water had a TDS of 349 mg/1, a pH of 8.4, a hardness of 92 mg/L and an SAR of 15.8. This site is also unlike the Rollins sites due to its low salinity and low SAR, as well as its higher hardness. Discharges from NPDES sites 001 and 002 at the Roadside South Mine and from site 004 at the Roadside North Portal show sodium bicarbonate waters with elevated TDS levels ranging from 960 - 3137 mg/I.,, high hardnesses ranging from 98 - 159 mg/L, and widely varying SARs ranging from 6.95 - 73.18 (samples were acquired from January 1, 1979 through September 30, 1995). The pHs of the NPDES sites range from 7.53 - 8.36. The Rollins sites also have saline, sodium bicarbonate waters with elevated SARs, but the hardness ranges from 13.9 - 37.3 mg/L, and the pHs are more alkaline, ranging from 8.2 - 8.7. This analysis has been based on a single set of analyses from the four Rollins Sandstone sites, and average concentrations observed from multiple analyses in Powderhorn's historic sampling program. Hardness and SAR appeaz to be sensitive parameters for differentiating one water from another, and it appears that there is little similarity between the Rollins sites and the Colorado River, its alluvium, the mine inflows, or the corresponding mitre water discharge sites. These results may be refined with further future analyses, but the data does not suggest that the Rollins is commingling with mine waters, nor that the Rollins is a water bearing zone of beneficial use due to limitations to domestic, irrigation, and stock watering uses. • r2.59J\I\Scptember 9. 1941 ]_0