Laserfiche WebLink
• INTRODUCTION <br />The U.S. Geological Survey's 2D, finite-difference, ground-water flow model, <br />MODFLOW (McDonald and Harbaugh, 1984), was used to simulate the effects of <br />long-term well pumpage from Peabody's Seneca IIW and Yoast mine properties on <br />local and regional surface flow. Two proposed water supply wells, one at each mine <br />site, will provide potable water for mine operation needs. Each well will pump water <br />from the Trout Creek Sandstone at an estimated constant rate of 35 gpm for a period <br />of approximately 15 yeazs for the Seneca IIW well (from year 1990 to 2004) and 9 <br />years for the Yoast well (from year 1996 to 2004). The model's focus was to <br />simulate ground-water flow in this sandstone and its interaction with surface flow. <br />Within aten-mile radius of both mine sites, the Trout Creek Sandstone crops out in <br />several major drainages: at the head of Hubberson Gulch, three places along Sage <br />• Creek, one place in Grassy Creek, two places in Fish Creek, four places along Trout <br />Creek, one place in Middle Creek, and in two places along the Yampa River <br />(Figure 1). It was necessary to determine the amount of stream loss that may occur <br />in these areas from long-term pumpage in order to evaluate potential impacts to <br />surrounding water-resource users and to accurately estimate stream replacement water <br />volumes. <br />The Trout Creek Sandstone is the uppermost member of the Illes formation and is <br />a prevalent marker bed in the region. The fine-grained sandstone forms massive <br />white cliffs and regionally averages 100 feet in thickness (Bass et al, 1955). The <br />sandstone was structurally deformed in the region by rising domes and tectonic <br />uplifting which created a series of northwest trending folds. In the area of the Seneca <br />IIW and Yoast properties, the sandstone dips 11-15° and is exposed along the eroded <br /> <br />