1996-11-08_HYDROLOGY - M1984049 - Laserfiche WebLink

Home Browse Search

DURANG�* Received OFFICE HOWARDSVILLE MILL OCT 0 71996 SURFACE AND GROUNDWATER MONITORING PLAN Dur:.ngo Field Office 0ivislon c!Mnera!s &Geology Surface water and groundwater monitoring at the site is necessary to characterize the ambient conditions and to deduce the impacts to surface and groundwater attributable to operations at the mill site. In developing this monitoring plan, the W.T. Cohan report (1985) and the CDMG memorandum (1995) were consulted. Hydrologic conditions at the site are complicated by the historic pre-law mining and milling operations both at the Howardsville site and upstream along and above the Animas River. Cohan (1985) and CDMG (1995) both concluded that surface and groundwater impacts attributable to pre-law mining and milling were occurring above, adjacent to, and below the Howardsville Mill site. The assignment of hydrologic impacts attributable to the Howardsville Mill is therefore complex. The monitoring of both surface and ground water to establish conditions above, within, adjacent to, and below the mill is the goal of the proposed monitoring program Monitoring locations are identified on Figure 1. Surface Water Monitoring Monitoring Sites A total of six surface water monitoring sites are proposed for the Howardsville Mill. Three of the sites will provide information on water quality above the mill, two will assess mill contributions within the permit and disturbed area, and one will provide data from downstream of the mill. In order to characterize the "baseline" inflows, three surface water monitoring sites are proposed. The first site is located upstream of the surface water diversion ditch, within the base flow of the Animas River. The second site is located at the origin of the surface water diversion ditch on the north side of the road and the south side of the tailings embankment. A third site is proposed for inflows above the ore stockpile area (above the French drain). These sites will be sampled at the same time as other surface water sites throughout the year. A surface water site which will reveal any surface water contributions attributable to the adjacent tailings or surface water from the mill site will be located at the terminus of the surface water diversion ditch. The actual sampling site may be above the junction with the Animas River, as the low gradient of the surface water diversion ditch allows backwater mixing with the Animas River adjacent to the terminus of the diversion ditch. A mid-site surface water monitoring station is proposed within the Animas River immediately north of the flood protection dike and the new tailings pond. This site should collect any surface water issuing from the area below the new tailings pond, but