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3. The assessment of the probable cumulative impacts of all anticipated coal <br />mining in the general area on the hydrologic balance, as described in <br />2.05.6(3), has been made by the Division. This assessment entitled "( <br />North Park Cumulative Hydrologic IMpact Assessment)" is available for <br />inspection at the offices of the Division. The Division finds that the <br />operations proposed under the application have been designed to prevent <br />damage to the hydrologic balance outside the proposed permit area. <br />(2.07.6(2)(c)>. <br />Probable Hydrologic Consequences <br />Description of the Environment <br />Groundwater <br />There are predominately three aquifers of interest in the Marr permit area: <br />the Sudduth coal aquifer, upland terrace deposits, and alluvial deposits. The <br />underburden at the site is the impermeable Pierre shale, with a permeability <br />of 0.15 gpd/f t2. The overburden sequence is composed of interbedded <br />siltstones and shales of the Coalmont formation with permeabilities ranging <br />from 0.37 gpd/f t2 to 7.5 gpd/f t2. Monitoring is focused on the coal <br />aquifer, alluvial deposits, and two wells which intersected water in the <br />overburden. <br />The physical characteristics of the coal aquifer suggest that it is a <br />moderately poor aquifer except where it is faulted, as reflected by <br />permeabilities of 3.8 gpd/ft in a well distant from a fault zone and 16.5 <br />gpd/f t2 in a well near a fault. These two wells suggested yields of less <br />than ten (10) gallons per minute and twenty (20> gallons per minute, <br />respectively. The aquifer quickly becomes confined east of the outcrop, which <br />results in artesian heads on wells completed in this zone. <br />Original recharge on undisturbed fifty (50> foot wide outcrop within the <br />permit area was calculated to be 4.75 acre-feet/year and storage capacity of a <br />3,200 acre area was 240 acre-feet. The only discharge of this aquifer in the <br />permit area appears to be a spring located at the Old Sudduth Mine, which <br />discharges an average of 1 gpm. The maximum mine pit inflow is projected to <br />occur during the mining of Pit 2 and would amount to 126 gpm. <br />The coal aquifer water quality is variable, with some wells showing a sodium <br />bicarbonate water and others reflecting a calcium bicarbonate/sulfate water. <br />It is slightly alkaline and total dissolved solids range from 183-1,166 mg/l, <br />averaging approximately 500 mg/l. Dissolved manganese concentrations exceed <br />the domestic standard regularly. This water is acceptable for stock and <br />limited domestic use. <br />The overburden physical characteristics were derived from two U.S.G.S. wells, <br />DH-38 and DH-4 within the general area. Permeabilities at these is <br />ranged from 0.37 gpd/f t2 to 7.5 gpd/f t2 resulting in yields of gpm` <br />The two overburden wells (wells 79-1 and 79-2) in the monitorin ro were <br />chosen simply because water was observed in the overburden during rilling. A <br />saline, sodic, sodium bicarbonate water is derived from this aquifer. TDS <br />ranges from 796 mg/1 to 1,708 mg/l, averaging 1,216 mg/1. Dissolved manganese <br />concentrations exceed the domestic standards regularly. <br />