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needed to construct the several zones or segments of the embankment, in the case of <br />disposal of overburden materials in Streeter Canyon, there is little or no opportunity <br />to selectively excavate or place materials of widely different characteristics. The <br />most competent embankment will be obtained by achieving to the greatest degree possible <br />a vertical mixing of all the varied classes of material which derive from the open-pit <br />excavation. <br />there would be a further critical danger involved in compacting the material <br />to standards approaching those utilized in dam construction because of the non- <br />homogeneity of materials from the pit excavation. A high degree of structural integrity <br />achieved by compaction of one kind of material, for example, could in the long tens <br />lead to the formation of major voids or cracking of the completed embankment if <br />significant subsidence or consolidation of underlying fill materials were to take place. <br />In other words, the objective of attaining a relatively flexible fill mass could be <br />jeopardized by limiting the height of lifts and requiring a high degree of compaction <br />to the detriment of the integrity of the completed embankment. In brief, it is believed <br />while the Interim Regulations would be appropriate for fill construction under certain <br />conditions, they would if applied to the spoil fill in Streeter Canyon result in an <br />embankment of lesser integrity and safety than that obtainable under the operations <br />currently being followed. <br />A photo is appended hereto to illustrate some of the features of the embankment <br />described in this Memorandum. It shows the natural sorting of materials of various <br />sizes and competency achieved by end dumping with the larger and more competent <br />rock fragments eventually reaching the base of the fill and hence enhancing its <br />drainage characteristics and overall stability. <br />10 <br />