GENERAL38956 - Laserfiche WebLink

Home Browse Search

-20- These long-term data records are useful to identify any pattern of water quality changes. As mining continues, the mine-related surface water quality and quantity impacts are expected to increase. By looking at water quality patterns we can attempt to identity a mine operation cause with a particular surface water effect. Dorchester Coal Company's hydrologic monitoring plan as stipulated should be adequate to plan for modification of surface or underground mining activities, if necessary, to minimize disturbances to the prevailing hydrologic balance (Rule 4.05.13(1)(b)). B. Surface Water The proposed permit area for the Dorchester No.l Mine, which lies within the pediment zone, is dissected by two major drainages; Newlin Creek, a perennial stream, and Magpie Creek, an ephemeral stream. The streams flow to the northwest and converge directly northeast of the permit area, as shown on the attached Operations Plan Map, Figure 2. At the time of the original submittal of this application, most of the flow of Newlin Creek was diverted upstream of the permit boundary and across the permit area via clay pipeline for the City of Florence water system. Currently, due to subsidence from historic mining in areas north of the permit area, the pipeline has ruptured and Newlin Creek has been flowing. Water quality of the flowing Newlin Creek is very good exceeding the drinking water standards only for iron. The second major drainage, Magpie Creek, has been diverted by the mining operation around the facilities area. (see Figure 5). This drainage and the diversion are also discussed in the Hydrologic Balance Section (Section V), the Backfilling and Grading Section (Section XVII), and Ponds, Impoundments and Division's Section (Section XVI). Pre-mining baseline data for this mine was not feasible, since previous mine disturbances occurred prior to any monitoring requirements. No water quality or quantity analyses were provided for Magpie Creek. No flows in Magpie Creek were observed by Dorchester Coal Company during the year preceding application for a permit, although flows measured by the Small Operator's Assistance Program for a nearby mine were included within the application. Because Magpie Creek is being diverted and reconstructed u on reclamation, any flows occurring within the channel should be monitored. Since Newlin Creek is now a perennial stream being undermined, it is important to ensure that subsidence will not induce stream depletions. However, current water measurement technology is not sufficient to detect minor stream depletions (+ or - 10 %). Furthermore, it is expected that Newlin Creek will be diverted in the near future when the pipeline is repaired. Under these circumstances the Division feels that effects to Newlin Creek can best be monitored through the mine inflow study stipulated earlier in this document: However, future results from the mine inflow study may show the need for surface monitoring if significant inflows ar~~ experienced below Newlin Creek. Dorchester's surface water monitoring plan provides for the monitoring of surface wager quality and quantity of Newlin Creek and Oak Creek. Magpie Creek monitoring will identify peak flows which will be useful at the time of stream channel reconstruction.