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Doc Date:12/11/ 02 01 III I II I II I II IIII III <br />sss <br />• Rule 2' Permits <br />Surface Water <br />Surface water flow within the permit azea is limited and occurs in conjunction with storm events or <br />snowmelt. Flow within Lorenci[o and Cow is discontinuous along the channel length due to communication <br />between the colluvial materials and the stream (see discussion in Exhibit 8). The watersheds are small in <br />lateral extent, with the exception of Lorencito Canyon, which receives over half of its flow from watersheds <br />upstream ofthe azea. The baseline reconnaissance suggests that springs contribute an insignificant flow to <br />the annual yields from the watersheds. Consequently, there is little surface water flow to be impacted <br />during mining. <br />The probable hydrologic consequences of mining on surface water in the Lorencito Canyon permit azea <br />will vary depending upon the type ofdisturbance, and the period oftime under discussion. There will be <br />two types of potential disturbance atthe site: facilities area disturbance and disturbance associated with <br />surface mining. Disturbances will vary from the operational phase tothepost-mining or reclamation phase. <br />Impacts are typically classified into changes in flow or changes in water quality. <br />Quantitative impacts to surface waters which are derived from disturbances during operations will consist <br />ofincreases in peak discharges and runoffvolumes associated with the reduction ofvegetative cover. Most <br />of the runoff from disturbances associated with the operation will be treated by sediment ponds, which will <br />• discharge storm waters for several days following a storm event. This will modify the stream's original <br />runoffhydrograph byextending the period of flow. Elevated peak discharges from the disturbed areas wil I <br />occur across limited azeas, as ponds will be located as close to disturbances as possible. <br />LCC is intending to use surface water from the operation's sediment ponds for dust suppression. In <br />addition, water will be required for potable water, bath house use, and water within the mine. Water <br />consumption requirements will range from 6 acre-feet in 1997 to 87 acre-feet in 2001. Water consumption <br />is not expected to increase for the duration of the life-of--mine (Table 2.05.2-1). <br />It is anticipated that long-term, there will be low flow springs dischazging from the surface mine on the north <br />facing slopes ofJeffCanyonand Cow Canyon following snowmelt and precipitation events. The springs <br />will exhibit flows from March through June, as a consequence ofsnowmelt, and may flow again in August <br />andSeptemberifprecipitationfromlatesummerthunderstormsisconsiderable. Typicallytherewillbea <br />two-to-four week delay between the period ofhigh infiltration and the subsequent discharge from the <br />aquifer. Spoil spring discharges mayconlributetotheI'urgatoireltiverduringthespring,ifwaterisn,nning <br />in the streams. It is unlikely that the fall discharges will travel to the Purgatoire, due to their limited flow <br />rates and the high infiltration which will occur in the dry canyon bottoms. <br />Qualitative changes to surface waters which are derived from disturbances during operations will consist <br />ofincreases in total suspended solids (TSS) and total dissolved solids (TDS). The increases in suspended <br />solids will be restricted to the disturbance azeas, as sediment ponds and other sediment control measures <br />. will be utilized to decrease sediment to levels below eftluent limitations, incompliance with applicable State <br />and Federal Laws and current interpretations oftheregulations. This will result in an increase of scouring <br />PR-ol <br />2.05-100 (revised 07/25/01) <br />