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Site SW-N3 is located on Tuttle Draw downstream of mining as shown on Exhibit 7-1. <br />• Discharge measurements have routinely been collected from this site since April, 1980. <br />Flow at SW-N3 is artifically controlled for the most part of the year_from.irrigation <br />return-f-low ,f rom_the lower Second Park lateral irrigation ditch. During the irrigation <br />season, a significant portion of the flow at SW-N3 is contributed by NPDES 001 pond <br />,located just upstream of SW-N3 on the West Return Ditch (see Exhibit 7-1). Measured <br />discharge at Site SW -N3 range from ,019 cfs up to 9.35 cfs (see Table 7-40}. During the <br />irrigation season, the means of measured discharge range between about .5 cfs and 4.67 <br />cfs. Measured high flows for this period range between .665 (April) and 9.35 cfs <br />(September). During the non-irrigation season, discharge measurements ranged between .019 <br />and 2.09 cfs. It should be stressed that discharge measurements at surface water <br />monitoring sites at both the Nucla Mine and Nucla East mining area were not necessarily <br />collected on the same day. Measured high and low flows previously and subsequently <br />discussed for up- and downstream sites established in one drainage may not reflect <br />"same-day" measurements. <br />West Return Ditch. The West Return Ditch is a tributary to Tuttle Draw and is commonly <br />used for conveying irrigation tail water to Tuttle Draw (see Exhibit 7-1). Flow in this <br />• ditch generally recedes to zero in the lower reaches after the end of the irrigation <br />season. Site SW-N7 is located above Site SW-N6, just above the northern permit boundary <br />for the Nucla Mine. SW-N6 is established about k mile below SW-N7 on the West Return <br />Ditch. <br />Measured discharge at SW-N6 has been routinely collected since August of 1980. Table 7-41 <br />presents means and ranges of discharge measurements collected at surface water monitoring <br />Sites SW-N6 and SW-N7. Flow generally recedes to zero during the non-irrigation season. <br />Of the 44 monitoring visits made at SW-N6 for the period of record during the <br />non-irrigation period (November through April), flow larger than one-hundreth of a cfs <br />have been measured only six times. For the irrigation season, flows at SW-N6 has been <br />commonly observed, ranging from zero up to a high of 1.34 cfs. <br />SW-N7 was established as a surface water monitoring site in March of 1987. This site was <br /> established by Peabody for obtaining baseline data in the case that mining in the <br /> "triangle area" might begin in early 1987. The triangle area is a small strip of land <br /> located below existing Site SW-N7, bordered by the County Road 2650 on the west and the <br />• county landfill on the east (see Exhibit 12-1, Tab 12). Although plans for mining the <br />7-116 Revised 04/11!88 <br />