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STATE OF COLORADO <br /> MINED LAND RECLAMATION DIVISION C <br /> Department of Natural Resources <br /> 1313 Sharman St..Room 215 <br /> Denver.CO 80203 + s <br /> 303 866-3567 <br /> FAX: 303 832-8106 <br /> Roy <br /> Governor <br /> MW&3W ti.lono, <br /> Division Director <br /> TO: Susan Morrison, Reclamation Specialist <br /> FROM: Jeff Martin <br /> DATE: August 5, 1992 <br /> SUBJECT: Seneca II potential AVF impacts, Peabody, C-80-005 <br /> THE ALLUVIAL VALLEY FLOOR ENVIRONMENTS ADJACENT TO SENECA II <br /> Five areas were designated as potential alluvial valley floors <br /> (AVF's) which may be impacted by mining activities at Peabody's <br /> Seneca II surface mine. <br /> In reference to 3.0 6.8(3) (ii) of the CSCMRA, both Cow Camp <br /> Creek and Bond Creek, the two relevant tributaries to Fish Creek, <br /> were found not to be AVF's due to ephemeral flows, deeply incised <br /> channels, and among other factors highly sinuous meanders - all of <br /> which render these stream valleys as negligibly arable. <br /> Both the 45 acre area near the confluence of Little Grassy <br /> Creek and Grassy Creek and a 40 acre area along Little Grassy Creek <br /> are designated AVF's. However, under 2.06.8 (5) (b) (i) (A) both of <br /> these AVF's remain exempted, because mining operations causing <br /> potential degradation were conducted prior to August 3, 1977. <br /> The only OMLR designated, non-exempted AVF adjacent to the <br /> Seneca II mine straddles Fish Creek between the confluence of Bond <br /> Creek and Fish Creek and extends to Fish Creek's confluence with <br /> Trout Creek several miles downstream. A 63 acre area in the SWI/4 <br /> of the NW1/2 of section 2, T5N, R86W is currently farmed via flood <br /> and sub-irrigation. Due to the short growing season, crop <br /> production is limited to species of hay; alfalfa, smooth brome, <br /> orchard grass, barley, wheat and oats. The Fish Creek AVF is the <br /> only arable AVF adjacent to the Seneca II mine and as such will be <br /> the sole topic of discussion. <br /> THE FISH CREEK AVF: MONITORING <br /> Mined land discharges to the Fish Creek drainage system may <br /> potentially impact the water quality via two processes: one, the <br /> migration of ground water downgradient of mining and two, <br /> streamflow contributions downstream by Bond and Cow Camp creeks. <br /> The significance of the first process is dismissed because of <br /> extremely slow ground water flow rates within the Bond and Cow Camp <br /> alluvium. Impacted groundwater should take over 100 years to reach <br />