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December 1986 4 863-2060 <br /> <br />Boreholes drilled in Area 9j10 were located based on the follow- <br />ing criteria: <br />1) Location near drainages to allow evaluation of worst- <br />case floor conditions, since weathering is expected to <br />be more severe near these drainages; <br />2) Location on the down-thrown side of faults, which should <br />represent worst-case piezometric conditions; <br />3) Reasonable spatial distribution; and <br />4) Location on or near existing roads where topsoil has not <br />been placed. <br />2.2 Piezometer Installation <br />Upon completion of each boring, nominal 1-inch diameter Schedule <br />80 PVC pipe was placed in each borehole to facilitate subsequent <br />• piezometric monitoring. Machine-slotted PVC casing (0.020-inch <br />wide slots) and similar flush-joint riser pipe were placed as <br />shown on Figure 8 and on the boring logs. Colorado Silica sand <br />(10-20 size) was then placed in the annular space to above the <br />slotted PVC. A minimum 2-foot thick bentonite pellet plug was <br />used to seal the annular space above each sand pack, and the <br />remaining annular space was backfilLed with mine spoil materials. <br /> <br />Golder Associates <br />