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5~ <br />'Ldnm.vtt4 .awuaaxq !^~n Ax sa 'sw?Lmam :Jinn. <br />aon-irrigation season and 11.3 .`,'s :o ... cfs during [he Irrigation saasun. The maioriry of flow <br />observed at [hest ;wn stations is a resuit of irrigation return during ;hat season. Flows a[ <br />stations SW V1U1 and $W Y105 locared on the Wes: [aceral Diceh varied from U.U during <br />the non-irrigation season to '_?.9 during,~ugust 19&4. Hydroemphs For the period of record <br />far each of these four stations are contained with [he dam in Appendix A. <br />Surface water quality data collected from smtions SW-ti 101, SW-Y103. SW-Y 104, and SW- <br />NI05 are contained in Appendix B for the period of record of July 1986 through February <br />1990. Minimum and maximum values For conductivity, Ph, temperature, and [oral dissolved <br />solids aze contained in Table 3. This information a presented for the irrigation season <br />(April through September) and the non-irrigation season (October through March). <br />Tnlinear and stiff diagrams of water quality data are contained in Appendix C As indicated <br />from these dam summaries, there is a signi5wne difference in water quality from the <br />irrigation season to the aon-irrigatioo season Water quality during the irrgadoa season ac <br />smdons SW-N103. SW-X1104, and SW-;1105 is a m&ed calcium-sulfate bicarbonate type <br />water with lower toml dissolved solids. On Calamity Draw at s[arion SW-101, tite water <br />quality shifts shghcly to a [nixed magnesiutn/talcium ,-ulfase type water. Generally, water <br />quality in Calamity Draw is of a better quality during the irrigation season due ro irrigation <br />return. This can be noted by the hightr !lows and lower total dissolved solids. There were <br />• no surface water violations of water quality standards (Table 3) during [he period of record. <br />Groundwater Monitoring <br />Topography is the principal element governing shallow aquifers (<400 feet) in the Carron <br />Land Section of the Colorado Pla[eau Phvsiograohic Provide. Groundwater Oow is <br />andcipa[ed to move in the direction of surface relief. <br />-There are 24 groundwater wells located in the vicinity of the Yew Horizon Mine ?site. <br />Table ~ provides [he completion information for [here wells. Of these. oNy 12 wells are <br />deemed agproptiate to analyze for dte new thine plan (see Map L04.7-1). Appendix D <br />rnnmins the groundwater level dam with a hydrograoh of each of the 12 weds for the period <br />of record [tom Jury 1986 [hrough February 1990. Ware: in the Calamity Dmw alluvium was <br />monitored at GW-Y22. Water levels varied seasonally with a mndnuous tilt in levels during <br />the irrigation season. The peak was observed during the fall (SeptemberiOc[oher). Water <br />levels in the overburden at wells GW-?V15. GW=Y13P2, and GW-V21 also-varied wish the <br />irrigation, reaching a peak in the hydrograph during the period of May through September. <br />Variation in wave: level was as much as .5 fee[ betwten the irrigation and non-irrigation <br />seasons. The Dakota Coal seams was manitortd a[ we?h GW-~ l4. GW-v1iP1, GW-Y20, <br />and GW-Y;0. Wazer levels in these wells follow the same seasonal variation with irrigation, <br />however. are no[ as variable as the overburden. Ware: levels varied i ro 15 tee[ between <br />the irriga[ion and non-irrigation stawtu, with wtU G W-V;0 being artesian during the peak <br />:I.~ir <br /> <br />Attachment 2.04.7-5-7 <br />