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Groundwater Monitoring Plan <br />• Piezometers have been installed around the site to monitor water levels in the <br />alluvium, refuse fill material and the Roadside South Portals mine. Monitoring sites <br />include the Rapid and Cottonwood Creeks, the Cameo Refuse Disposal Areas No 1 <br />and 2, the Unit Train Loadout, the Rollins Sandstone wells, and the North Decline. <br />Monitoring data and analysis of ground water will be submitted annually as part of <br />the Annual Hydrologic Report and quarterly with the other results. Ground water <br />monitoring points are shown on Exhibit 56. <br />The Rapid Creek and Cottonwood Creek piezometers (GWMS-OlA, 016, 02A, <br />02B, 03A, and 03B) were installed, according to stipulation response SR06, to <br />determine if the alluvium along the creeks is being dewatered by mining activities. <br />--..Baseline monitoring of v:~2ter le„pIs in.these pieZOR!eterc ~,yae gonarallY done monthly <br />from September 1984 through September 1987 when accessible. Monitoring will be <br />continued on a biannual basis in May and September corresponding to the months of <br />high and low flow in the adjacent creeks. <br />• Piezometers have been installed in the Cameo Refuse Disposal Areas No. 1 and <br />No. 2 (CRDA-1 and CRDA-2) to monitor the actual piezometric water level in the piles <br />compared with the stability design assumptions. Three piezometers (CRDA-Ol <br />through 03) were installed on CRDA-1 in 1984 and a fourth (CRDA•Ola) was installed <br />in 1991. In 1991, 3 piezometers (CRDA-04 through 06) were installed on CRDA•2. <br />These piezometers were developed by installing a 2' perforated PVC pipe in an <br />approximate 4° diameter auger hole. The hole was left open the full length and <br />sealed near the surface. These piezometers have been monitored at least quarterly <br />since installation. Piezometer CRDA-O1 on CRDA-1 has consistently.shown higher -. -_ <br />water levels than assumed in the stability design calculations. To reevaluate stability <br />of the pile, an additional 16 temporary piezometers were installed in the same <br />manner as the original ones to define the extent of the high piezometric water level. <br />In December, 1993, Western Engineers of Grand Junction,. Colorado was retained to~ <br />• VOL5Tab18 18.4 7-7-99 <br />