1986-12-31_REPORT - C1981008 (3)

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level . Shallowing of the water level coincides with the operation of the irrigation ditches, usually between April and October. The water levels decline between November and April . If water levels respond due to precipitation events, they are masked by the effect of recharge from the irrigation network. There is no evidence that mining has lowered the piezometric surface in the vicinity of these wells. 2. Well GW-N3 -- Underburden Water level measurements have been taken at this well on a monthly basis since August, 1979. The water level hydrograph for this well shows a maximum seasonal water level fluctuation of about seven feet during the period between 1980 and 1983. The fluctuation in static water level in 1984, 1985, and 1986 is only about two feet. Shallowing of the static water level generally occurs between May and September, coinciding with the operation of the irrigation ditches. 3. Well GW-N4 -- Dakota Coal Water level measurements have been made at this well on a monthly basis since August, 1979. The water level hydrograph for this well shows a maximum seasonal water level fluctuation of about 2.5 feet. The water levels generally increase between June and October and decline between November and May. It appears that there is about a one-month lag between when the irrigation system starts up in April and when the static water levels in the coal seam respond. There are no discernable water level responses to precipitation, nor can any effect from mining be observed. 4. Shop Well GW-N5 -- Underburden Well GW-N5 was intended to be used as the mine supply well but, because of its extremely poor quality, it was never used for anything except a monitor well . The water level hydrograph for this well shows seasonal water level fluctuations of a few feet during the past two years. The reason for this trend is not 74