Laserfiche WebLink
alluvium, overburden, Dakota coal, underburden, the overburden and coal, and <br /> overburden/coal/underburden. The monitor well network consists of 35 monitor wells <br /> drilled and installed by Peabody. Fifteen of the wells are located at Nucla Mine and 19 <br /> are at the Nucla East mining area. Table 15-5 summarizes pertinent information for each <br /> of the monitoring wells. Exhibit 7-1 (Tab 7) shows the location of each monitor well . <br /> Well completion summaries and lithologic logs for the monitor wells are contained in <br /> Appendix 15-2. <br /> Well Completion and Development <br /> There are ten monitor wells (GW-N1, GW-N1P1, GW-N3, GW-N4, GW-N5, GW-N6, GW-N8, GW-N9, <br /> GW-N10, and GW-Nll) within and adjacent to the Nucla Mine that were installed in 1977 and <br /> 1979. The completion information on the ten original Nucla wells lacks specific <br /> completion details. Monitor Well GW-N5 was mined out in 1987. In the summer of 1986, 13 <br /> new monitor wells (GW-N13 through GW-N22) were completed in the Nucla East mining area to <br /> help define the baseline conditions of that area. Also, three multiple completion <br /> (overburden, coal, and underburden) monitor wells (GW-N23, GW-N24, and GW-N25) were <br /> installed at what is called the scraper pit area of the Nucla Mine. All three of the <br /> scraper pit area monitor wells have been dry since they were installed. In August and <br /> September 1987, four additional monitor wells were completed at the Nucla Mine; three in <br /> the spoil material (GW-N26, GW-N27, and GW-N28) and one in the Dakota coal (GW-N4R). <br /> Monitor Well GW-N4R was installed as a replacement monitor well for Well GW-N4. In <br /> addition to the four monitor wells installed at Nucla Mine, six exploration bore holes <br /> (GW-N29 through GW-34) were completed as monitor wells in the vicinity of the Nucla East <br /> mining area. Peabody installed the six additional monitor wells to provide better <br /> definition of water levels and water chemistry. <br /> For quality control, each monitor well is developed and evaluated before it is <br /> incorporated into the long term monitoring program. The first stage of development <br /> entails air lifting immediately after the well is drilled and completed. Drill pipe is <br /> lowered inside the casing of a four-inch well (1 1/4-inch steel pipe in a 2-inch well) and <br /> then air is injected into the well forcing water, sediment, and contaminants out the top <br /> of the casing. The air supply is periodically shut off, allowing the aerated water column <br /> to fall back down the well bore which effectively back surges the well. At this stage of <br /> development, the approximate well yield can be estimated. If a constant flow of water can <br /> be air lifted from the well and measured, the volume is generally about 60 percent of the <br /> 15-10 Revised 04/11/88 <br />