REV06564 - Laserfiche WebLink

Home Browse Search

basin. NPDES 004 and Sites 6 and 10 are located on Cow Camp Creek. NPDES 008 and site 12 are located on Bond Creek. Sites 11 and 13 exist on Fish Creek. Stream site 6 was originally established to determine the premining characteristics of Cow Camp Creek. Monitoring site 6 was discontinued to eliminate redundancy with stream site 10 further downstream at its confluence with Fish Creek. Instantaneous flow measurements are collected at ali three creeks. Like the Grassy Creek drainage, streamflows in the Fish Creek basin aze seasonally vaziable with peak flows occurring in the spring in response to snowmelt runoff. F. Probable Hydrologic Consequences A determination of the probable hydrologic consequences of the mining and reclamation activities at the Seneca II Mine site has been made by the applicant and is found in Volume 4, Tab 7, Section VILB of the permit application. This section includes an evaluation of quantity and quality effects on ground and surface water systems and mitigative measures to be taken both during and after mining. The Probable Hydrologic Consequences section of this document is divided into two main subsections; Surface Water Effects and Ground Water Effects. Surface Water Effects The Seneca II Mine is located in the upper Yampa River basin on the north flank of the Williams Fork Mountains. The mine is located on a watershed divide between the Fish Creek drainage basin to the east and the Grassy Creek drainage basin to the west. Most of the previous mining at the site has occun•ed in the Little Grassy Creek basin which is tributary to Grassy Creek, a perennial tributary to the Yampa River. Mining in the Fish Creek basin began in 1982, in the Cow Camp Creek tributary basin. As mining in this drainage was completed, an area in another tributary basin of Fish Creek, Bond Creek, was disturbed. Mining activity occurred throughout the life-of--mine in this basin. All mining activities have ceased and reclamation is neazly complete. The effects ofmining on the water quality and quantity in each of these surface water basins are discussed below. Grassy Creek Drainage Basin Grassy Creek is a northerly flowing minor tributary of the Yampa River east of Hayden, Colorado. The Seneca II Mine is located about three miles upstream of the confluence with the Yampa River, and includes about 860 acres of disturbed lands within this drainage basin. Surface water monitoring sites are located above and below the mine to quantify mine-related impacts. Two ponds, NPDES 002 and 003, discharge between these two stations to Grassy Creek. The operator has conducted monitoring of dischazge and water quality at the two surface sites in the Grassy Creek drainage since 1981. At the station above the mine 21