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• TABLE 17-29 (Continued) Probable Hvdrologic Consequences Analysis Results Significance 6. (Continued) aquifer is projected to increase TDS levels 29 percent immediately below the 005 tributary. The extent of the overburden and coal aquifer TDS increases will be limited to the immediate down- gradient vicinity of the pits. The extent of the Dry Creek alluvial aquifer TDS increase should be limited to within 1 mile downg ra dient of the 005 tributary confluence. The duration of the changes will be long term (in excess of 20 years). Spoil discharge to the Sage Creek alluvial aquifer is projected to cause a negligible TDS increase. to be disturbed anywhere in the vicinity of the mine, thus the TDS increases are of no significance as they have not changed the potential use of the water, nor injured any existing uses. The extent of the bed- rock aquifer impacts will be very limited because of the extremely low hydraulic conductivity values. The premi ning water use potential for the Dry Creek alluvial aquifer is marginal to unsuitable for stock and irrigation use. The conductivity increase will not reduce the hay grass productivity levels in the two subirri gated fields in Section 9 and the TDS increase will not preclude the use of Olson Spring (alluvial well) 5-45 as stock water. The °m extent of TDS increases are limited to above the SG-5 site because of dilution and additional recharge. The TDS impacts are of no significance to the potential or existing alluvial water uses in the above- referenced reaches of Dry Creek. There is no significance from spoil discharge to the Sage Creek alluvial aquifer as the percent change will be unmeasurable. 7. Impact of spoil water on surface water quality. Spoil discharge to Dry Creek st reamflow will result in a 114 percent increase in TDS at the SC-5 site, a 44 percent increase in TDS in the stream reach between the northwest corner of Section 34 and the southwest corner of Section 22. From this point on in the stream- flow, the spoil blended TDS level is at least 59 percent lower than back- ground levels. The extent of the spoil increased TDS is approximately 5 miles in length from the 006 tributary/ Hubberson Gulch confluence. The The premi ning use potential for Dry Creek is marginal to unsuitable for irrigation use and stock use. There are no flood irrigated hay fields along the 5 mile reach of Dry Creek (affected zone) that divert water from Dry Creek because the adjacent alluvial land is either unsuit- able for flood irrigating or the flows in Dry Creek are insufficient to rely on for irrigation practices. A71 the flood irrigated fields in this reach are irrigated from reservoir water. Beyond this 5-mile reach, dryland farm saline