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La Plata Coal Draft Finings - 5 - May 18, 1987 <br />The La Plata No. 1 well, which has been reported to be in existence since <br />about 1905, is located at the facilities area of the mine. This well, for <br />which a water right has been filed, is probably completed in the Point Lookout <br />Sandstone. <br />In order to asses potential mining related impacts to the local hydrologic <br />system, La Plata Coal Corporation has committed to installing two monitoring <br />wells within the Hay Gulch alluvial valley. <br />One well will be completed within the Hay Gulch alluvium immediately down <br />gradient of the sediment pond. This well, which is to be completed within <br />thirty days of permit issuance, will be of adequate diameter and depth to <br />provide useful alluvial water quality and depth-to-water information. The <br />quarterly depth-to-water measurements and semi-annual water quality samples <br />for the parameters tabulated in attachment "A", will be sufficient to verify <br />that the sediment pond will not adversely impact the alluvial valley floor. <br />The second well will be completed in the Hay Gulch alluvium immediately down <br />gradient of the proposed leach field. This well, which is to be completed <br />within thirty day of permit issuance, will be of adequate diameter and depth <br />to provide useful alluvial depth-to-water information. Semi-annual water <br />level measurements will be adequate to provide useful information to ensure <br />that off-site damage does not occur. <br />The Hay Gulch alluvial aquifer, which is adjacent to the proposed operation, <br />has an estimated average depth of 20 feet, and an estimated cross-sectional <br />area of 25,200 square feet. The transmissivity of this aquifer has been <br />estimated to be 70,400 gallons per day per foot. The water table surface <br />varies from above ground surface to an estimated 8 foot below surface. The <br />water level is seasonally dependent, and varies between locations. The <br />direction of flow in this unconfined system is postulated to be parallel with <br />the strike of Hay Gulch. Recharge to the alluvium is principally from <br />snowmelt runoff and precipitation infiltration. Some contribution may be made <br />from the lower Menefee Formation, as well as from other tributary alluvial <br />bodies. <br />Historical observations from mines in the Hay Gulch area indicate that the <br />coal bearing strata are essentially dry. There have not been any documented <br />discharges from the La Plata No. 1 or from adjacent, abandoned mines. <br />Although it is expected that the workings will not encounter significant <br />quantities of water, overlying perched aquifers may dewater into the mine due <br />to mining activities. The inflow from these units should be small. This <br />water will be used in the course of mining operations. <br />The Point Lookout Sandstone aquifer is located about 275 feet below the mined <br />unit, and will not contribute water to, or be affected by, mining operations. <br />The operation is in compliance with requirements of this section. <br />