2010-05-07_GENERAL DOCUMENTS - C2009087

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