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Pitch Reclamation Project -Sediment Control Embankment November, 2002 The embankment is about 80 ft high at the maximum section and has a crest elevation at Elev. 9905 ft . It creates a pond area of about 5.4 acres at Elev. 9900 ft with a corresponding capacity f about 88.3 ac-fr. An emergency overflow spillway exists through the right abutment (looking downstream) with a crest elevation of Elev.9900 ft. A low level discharge pipe is in place with the inlet invert at Elev. 9878 ft. The pond bottom is at about Elev. 9859 f[ based on survey records. Therefore, the pond cannot be completely drained by gravity flow. The pond capacity at the invert of the outlet pipe is about 13 ac-ft. A plan view of the embankment is shown in Figure 2. Based on the embankment geometry and site observations, it appears that the right abutment of the embankment was excavated to create a small bench at the downstream toe of the embankment at about Elev. 9865 ft for construction of the sand filter plant. As a result the embankment height is relatively uniform at about 35 ft for approximately 150 ft in this azea. The left abutment rises up from Indian Creek at about a 3.SH:1 V slope. 2.2 Embankment Description The following embankment description is based on available design and construction records, and a current survey of the downstream face of the embankment. It is intended to be a general description of the embankment section for reference used in the initial embankment evaluation. Specific findings from the field exploration and construction activities that were included in the embankment evaluation and final remedial design are presented in following sections of this report. Figure 3 shows a cross section of the embankment based on the original design drawings. The sediment control embankment was designed and constructed as an earthen embankment using locally available materials. The embankment section consists of a core constructed of relatively impermeable material and [he upstream and downstream shells constructed of a sandy, gravelly material with fines and up to 6-in cobbles distributed throughout the soil mixture. The source of the core material was primarily highly weathered and altered volcanic bedrock that outcropped upstream of the embankment alignment. The shell material was mostly generated from the bedrock excavation of the spillway through the right abutment and adjacent borrow pits in the same material. As shown in Figure 3, there is no chimney drain between the core and downstream shell of the embankment, nor a blanket . drain under the downstream shell. A foundation drain pipe is located along contour under the The Nomestake Mining Company -3- The Glasgow Engineering Group. Mc.