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4,000 mg/l. Between 1980 and 2009, TDS in Pond 002 discharges have increased from the 2,500- <br />mg/1 level to around 4,000 mg/l. <br />Grassy Creek drains most of the Fish Creek anticline and the western flank of the Tow Creek <br />anticline. Upstream from the confluence with Little Grassy Creek, flows, in Grassy Creek are fed by <br />snowmelt in the springtime which causes flow to peak in May or June between 2 and 3 cfs, and then <br />by late summer flow diminishes to zero or near zero. Alluvial water may contribute to baseflow in <br />late summer. Water in Grassy Creek is primarily a calcium-sodium bicarbonate type with high <br />magnesium. TDS concentration in Grassy Creek above the Little Grassy Creek confluence varies <br />inversely with flow rate, ranging from approximately 700 mg/l during; high springtime flows to <br />approximately 900 mg/l during late summer or fall low flow. Grassy Creek water has a naturally <br />high iron and magnesium content. TDS in Grassy Creek is significantly increased by inflows of coal <br />spoil leachate from Seneca II reclaimed pits that reaches Grassy Creek via Pond 002 discharging to <br />Little Grassy Creek, which then flows into Grassy Creek. Pond 002 frequently discharges around 0.5 <br />cfs of water that has TDS between 3,000 and 4,000 mg/1. These discharges have significantly <br />contributed to a rise in TDS in Grassy Creek. Late summer samples from Grassy Creek taken <br />downstream from the Seneca II Mine at site SW-S2-2, has shown a gradual increase in TDS from the <br />1,900-mg/1 level in the early 1980s to above 3,400 mg/l in 2009. There have been no users of <br />Grassy Creek surface water since abandonment of an irrigation diversion. on Grassy Creek, one mile <br />upstream from Little Grassy Creek. <br />Grassy Creek is joined by Scotchman's Gulch 500 feet north of the permit boundary, approximately <br />one-fourth mile downstream from the area proposed for disturbance by PSCM underground mining <br />activities. Grassy Creek receives intermittent flows from Scotchmans Gulch that originate in Annand <br />Draw. Springtime flows in Annand Draw are predominately from the melting of snowpack. Late <br />spring to early summer flows are a combination of bank storage, runof3F from precipitation events <br />over saturated or frozen ground, or flows from springs that are recharged. by snowmelt. During the <br />remainder of the year, the Armand Draw channel flows only in response; to rainfall. <br />Fish Creek has its headwaters in the Dunckley Flattops five miles south of the PSCM permit area, <br />and drains most of Twentymile Park, the synclinal structural and topographic basin where the Foidel <br />Creek underground mine and the reclaimed Eckman Park surface mine are located. Fish Creek <br />receives flows from Cow Camp Creek which originates on the eastern flank of the Tow Creek <br />anticline, from the Pond 004 watershed in the PSCM permit area. Flow in. Cow Camp Creek peaks in <br />springtime at about 1 cfs, then commonly diminishes to zero or near zero by late summer. Total <br />dissolved solids in Fish Creek water usually are usually between 3,000 and 4,500 mg/l. <br />Climate <br />The climate of the region has the characteristics of a continental highland. region: low precipitation, <br />large fluctuations in diurnal temperatures, low humidity, moderate wind, and high levels of <br />insolation (exposure to sunlight). Annual precipitation in the vicinity of the permit area is between <br />16 and 19 inches, based on records from the Seneca II-W Mine (about 7 miles west of the PSCM) <br />and the town of Hayden (about 9 miles northwest of the PSCM). The average annual minimum <br />temperature is 27 degrees and the average annual maximum temperature is 58 degrees for the time <br />period 1909 to 2007 as reported by the Western Regional Climate Center. Precipitation is distributed <br />Peabody Sage Creek Mine 8 May 7, 2010