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Matthew S. Hayes June 28, 1989 Page 4 An apparent trarunissiviry between 1.700 and 4,300 gpd/ft. was calculated on the basis of a pump test performed by WECC in well R-1 in 1976. Pumping at q4 gpm for 2 hours resulted in a drawdown of about 8 feet (data provided in Attachment 1). The appazent, relatively high transmissivity is not typical of the Rollins as described by Brooks and Ackerman (1986) in a regional aquifer evaluation: "Sandstone beds within the Mesaverde Formation in the study area generally have minimal primary permeability, although secondary permeability, such as fractures, can yield enough water for domestic well production. Transmissivities for the Mesaverde Formation in the North Fork of the Gunnison River valley are between 0.3 and 16.7 ft=/d for typically unfractured rocks (Brooks, 1983). Wells prod~.rcing from the Mesaverde Formation, which is exposed in the eastern part of the study area, yield between 0.7 and 24 gal/min~.~l.. The transmissivity range reported by Brooks and Ackerman for unfractured rock is approximately 10 to 1,000 times less than that measured in R-1. This data suAQests that the Rollins is typical of h r M cav rde except in localized fracture zones near outcrop areas. Review of data for the region indicates that none of the other mines in the ~rPa h^~e rnar~Fered-th~lion;nc nacto P Since the U.S. Steel mine as been active since 1906, any potential for severe water quality impact would probably be evident by this time. The water quality data for R-1 indicates total dissolved solids generally outside the range acceptable for drinking water, in the range of 580 - 1,480 mg/1 (data provided in Attachment 2). Total dissolved solids in R-1 is probably somewhat lower than Rollins wells located away from the North Fork. Data collected by Brooks and Ackerman (1986) show that Mesaverde ground water is generally not suitable for drinking water: