1981-11-13_PERMIT FILE - C1981013 (47)

Home Browse Search

material was collected from a hole about 10" in diameter and 18" deep. (Volume was measured to be 25.06 liters. ) In-place density for the sample was computed to be 110#/ft3. The entire sample was submitted for laboratory determination of physical parameters necessary for the theoretical stability analysis presented in this Exhibit. On November 3, 1981 , test pits located on Figure 1 were dug to determine the hydrology and character of foundation material on which the structure would rest after topsoil was removed. A graphical presen- tation of foundation material is displayed on Figure 2. The remaining ponded water observed by Mined Land Reclamation staff on October 8, 1981 , was pumped, beginning November 3 intermittently over the next four days to dewater the area proposed for the coal processing waste pile so top- soil could be removed. Since the pumps were pulled in early November, no additional water has collected. Any seepage from the diversion is traveling in the underlying alluvium. Ponding is confirmed to be the result of the fine clastics overlving the alluvium serving as a semi- permeable barrier. The pit excavation shown on Figures 1 and 2 confirms an open gravel 3-4' thick will remain as foundation material providing an underdrain for any seepage from the Ciruela Canyon diversion. Because that seepage will remain in contact with the alluvium only and because the deep percolation per unit area will be no greater than that computed for the Allen facility p. 50 ff, Exhibit 6, no significant impact on water quality is anticipated. Although the hydrology is now understood, the theoretical slope stability analysis imposes a phreatic surface at elev. 7109, some 8-10' above the alluvium bedrock interface (see Figure 3). Results of the theoretical stability analysis are contained in the accompanying Water Waste & Land, Inc. report. -2-