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range. Water quality concentrations are within the CDPHE agricultural use standard except <br /> for occasional annual manganese excursions. Receiving stream standards are met. TDS <br /> concentrations are with historical range and show a statistically significant increasing trend. <br /> A spoil spring survey of spring discharging of greater than 5 GPM(gallons per minute),is <br /> performed following snowmelt each year. One full suite of sample and field parameters <br /> samples are collected. <br /> For a more detailed discussion of both surface and ground water quality at the Seneca IIW Mine please <br /> reference the 2019 Annual Hydrology Report. <br /> F. Probable Hydrologic Consequences <br /> A determination of the probable hydrologic consequences of the mining and reclamation <br /> activities at the Seneca IIW Mine site constitute Tab 17 of the permit application. <br /> Includes in Tab 17 is an evaluation of quantity and quality effects on ground and surface <br /> water systems and mitigative measures to be taken both during and after mining. <br /> The Probable Hydrologic Consequences section of this document is divided into two <br /> subsections (Ground Water Effects and Surface Water Effects). <br /> Ground Water Effects (Original Permit Area) <br /> Probable hydrologic consequences to the ground water regime will be minimal. <br /> Localized effects to the hydrologic system include: <br /> 1) the drawdown of ground water, due to pit dewatering, for a few hundred to <br /> perhaps 1,000 feet from the pit; <br /> 2) possibly diminished quantity and quality of water in the Temple Well No. 1; <br /> 3) the probable dewatering and degradation of quality in some springs in the permit <br /> area, two of which are used for stock watering purposes; <br /> 4) the possible increase in water quantity and decrease in quality of alluvial water in <br /> Hubberson Gulch and its unnamed tributary along the access road, due to <br /> infiltration of spoils discharge; and <br /> 5) the establishment of a relatively unconfined aquifer of poor quality in the backfilled <br /> pits (spoils aquifers). <br /> During mining, inflows from perched aquifers within the Williams Fork overburden, <br /> from a limited Williams Fork overburden aquifer,and from the Wadge coal aquifer are <br /> expected. Inflows from units underlying the Wadge are not expected,as mining methods <br /> should not cause fracturing of the relatively impermeable underlying materials. Regional <br /> aquifers located in or near the permit area include the Tow Creek Sandstone, Trout <br /> Creek Sandstone and Twenty Mile Sandstone. <br /> The Twenty Mile Sandstone,which has been eroded over much of the Seneca IIW Mine <br /> area,will not be disturbed by mining operations, so its water quality and quantity will not <br /> be affected. <br /> The Tow Creek Sandstone lies more than 1300 feet below the Wadge coal. Due to the <br /> thickness of the interburden between the Tow Creek and Wadge, it is not likely that <br /> hydraulic pressures capable of affecting this aquifer will develop. Therefore,mining <br /> activities are not expected to disturb this regional aquifer. <br /> Page 23 of 37 <br />