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~-- <br />` ZORICH - ERKER ENGINEERING, INC. Page 5 <br />hole log evaluation and on-site observation of the Salt Wash manber via <br />the underground workings that the mudstones and shales indeed isolate the <br />sandstone beds, thus causing rapid local changes in water occurrence. <br />I <br />7n many cases, a particular test hole could produce wet material and/or <br />a standing water level, while an adjacent hole would be dry, thus, <br />supporting this cronclusion. <br />Local faults in the area of the proposed open pit mine act . <br />I <br />as barriers to the flc~r of water. Observations made by the author in the <br />underground mine on the site revealed sealed faults and dry sandstone beds <br />above and below, as well as next to isolated beds of saturated sands. The <br />predominant occurrence of groundwater is, thus, in various isolated satur- <br />ated sandstone members. <br />The Sumcierville formation of the San Rafael Group which under- <br />lies the Nbrrison in this area varies fin shales to fine and medium <br />i <br />' grained sandstones. This and the underlying Estrada sandstone are <br />i <br />possibly the main aquifers in the area. Due to the mudstone and shales <br />of the Salt Wash member and the shaliness of the Sinmierville formation, <br />plus the fact that the proposed open pit mine will not penetrate a cortr <br />plete section of the Salt Wash member, these lower formations will remain <br />undisturbed. <br />Pit Wall Inflow Rate <br />In light of the above classification and characteristics of the <br />present geologic units, the groundwater inflow was estimated using the <br />. plan maps depicting the mine development versus time. The following was <br />