GENERAL31745 - Laserfiche WebLink

Home Browse Search

_P 7_ 1) Surface flow from disturbed areas would carry higher sediment concentrations than natural runoff. However, Rule 4.05.2 requires that all disturbed flow pass through a properly designed sediment control pond. Effluent from the pond is required to meet NPDES limitations prior to discharge. During operation, monitoring and inspection by the Division ensures that the sediment control system is maintained to function as designed. At the close of operations, surface disturbances would be reclaimed and the sediment control system would not be removed until after the establishment of revegetation. As a result, the increased sediment load carried by disturbed flows would not be expected to reach receiving streams. Furthermore, discharge points for each of the four mines are into ephemeral drainages which are characterized by very high sediment loads in their natural states. 2) Only one mine, the Dorchester No. 1, has proposed to discharge mine water into a receiving stream. The mine water will pass through a treatment facility prior to discharge. The quality of the discharge is required to meet NPDES effluent limitations. 3) Eeachate from surface water seepage through waste piles may degrade the quality of both surface and ground water as a result of the proposed mining operations. All three of the underground mines (Dorchester, Newlin Creek and Twin Pines) will have to dispose of mine waste rock. When this material comes in contact with water, a leachate water is produced which is usual]y of poorer quality than the natural waters. If the leachate were to come in contact with natural surface or ground water, degraded water quality may result. The reclaimed spoils left by the one surface mine (G.E.C.) could also produce a leachate water. The waste piles and reclaimed spoil configurations (rave been designed to minimize potential hydrologic impacts. The impacts to the hydrologic balance due to the leachate water from the waste piles and spoils from the proposed mining operations will be minimized in the following ways. The waste piles and spoils will be located above the piezometric surface, limiting the leachate to dissolution from transient flow. The post-mining topography will be contoured to the approximate original contour, thus preventing the formation of impoundments and the resultant contamination of ground water recharge. Also, the fills will be compacted which will significantly reduce the infiltration of water. The proposed waste piles will be covered with non-toxic, non-acid-forming materials which will also decrease contact between the waste and water. Water quality impacts wil] also be minimized by revegetation. Revegetation will result in higher evapotranspiration rates, reducing the amount of infiltration, thereby reducing the amount of leachate produced. Therefore, no significant additional water quality impacts to leachate generation are anticipated.