PERMFILE111851 - Laserfiche WebLink

Home Browse Search

Baseline Cround Water Levels. • Alluvial Water Levels. Ten monitor wells (GW-52.W-6A1, -6A2, -6A3, -6A4, -7A1, -7A2, -BA1, -9A1, -19A, and -20A) have been in;.tal led to monitor water levels in the alluvial aquifer system along the Dry Creek side of Seneca II-W. Exhibits 7-1 and 7-2 show the alluvial monitor well locations and the potc~ntiometric surface, respectively. As can be seen from Exhibit 7-1, the alluvial wells have been located such that the alluvial aquifers associated with each major tributary to Dry Creek are monitored. Only the 005 and 006 tributary alluvial systems will be affected by the proposed mining plan. The other alluvial monitors will serve as ba<:kground control points. Since Well GW-52W-20A was not completed until the summer of 1990, no data from this well will be included in this discussion. Water level data for Wells GW-s2W-6A1, -6A2, -6A3, -6A4, -7A1, and -7A2 have been collected since August, 1980. Water level monitoring at Wells CW-52W-BA1, -9A1, and 19A began in January, 1981, April, 1982, and October, 1987, respectively. Monthly water level data for the alluvial wells, including hydrographs, are presented in Appendix 7-2. Appendix 7-1 contains the well completion information for the alluvial wells. • Cround water in the above-referenced alluvial aquifer system occurs under both unconfined and confined conditions. Well GW-52W-6A3 is a flowing artesian well with a mean water level of 0.42 feet above ground surface. The other eight alluvial wells have mean water levels below ground surface ranging from 1.9 feet at Well 7A1 to 10.4 feet at Well 19A. Mean saturated thicknesses in the portions of the alluvial aquifer system monitored, range from 41 feet to 46 feet along Watering Trough Cu lch and from 8 feet (nearer the alluvial boundary) to 58 feet along Hubberson Culch. The mean saturated thickness at Well 19A, located in the 006 tributary, is 20 feet. Measurable seasonal water level changes have been monitored in the alluvial aquifer. Excepting Well 8A1, all other alluvial wells show the shallowest mean water levels during the spring. In the case of Well BA1, the mean spring water level is 2.3 feet and the mean summer water level is 2.2 feet. Fall mean rva ter levels appear to be the deepest, excepting Well 8A1. At this site, mean winter water levels are the deepest. For the other alluvial wells, the mean fall water levels (the deepest mean water levels) range from +0.09 feet at Well 6A3 to It ,:S feet at Well 19A. No other consistent seasonal trends • can be discerned. The greatest wa*.er level fluctuations appear to occur in the summer, .~ 8