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<br />0022~~ <br /> <br />Durango Pumoing Plant - Stage 1 <br /> <br />b. Point Lookout Sandstone. - <br /> <br />1) The Point Lookout Sandstone consists of siltstone with interbedded <br />sandstone and minor shale. The siltstone is sandy, laminated to <br />thin bedded, and dark gray. Beds are often convoluted and <br />disturbed by bioturbation. Intense weathering is generally <br />confined to the top I to 3 feet where exposed near ground surface, <br />and the rock is generally slightly weathered to fresh below this <br />depth with iron staining primarily confined to bedding and fracture <br />surfaces. The siltstone is well indurated, moderately hard, and can <br />be scratched with light to moderate knife pressure. The core <br />generally breaks along bedding with a moderate hanuner blow. <br /> <br />2) The sandstone is interbedded throughout the siltstone with mostly <br />gradational contacts. It is fine to medium grained, laminated to <br />moderately bedded, and light gray. The sandstone is <br />predominantly slightly weathered to fresh and moderately hard. <br /> <br />3) Shale, encountered in drill holes DH-Il1 and DH-112, is dark <br />gray, laminated to very thinly bedded, and slakes after exposure to <br />air after several hours to days. It is moderately soft to soft and can <br />be grooved with slight to moderate knife pressure. <br /> <br />B. Structure <br /> <br />Bedding. - <br /> <br />a. Bedding at the pumping plant site is separated into two categories in <br />relationship to fault F-l. On the up-thrown block west of the fault, several <br />field observations indicate the Point Lookout Sandstone strikes from <br />N55E to N85E with an average of about N70E. These beds dip to the <br />southeast at 9 to 16 degrees with an average of 12 degrees. On the <br />downthrown block east of the fault, correlations between drill holes <br />indicate that the Menefee Formation strikes N48W and dips IO degrees to <br />the southwest. Sufficient outcrops for measuring bedding orientations in <br />the Menefee Formation are not present within the pumping plant site. The <br />regional strike and dip in this area is approximately N55E, 16 degrees SE <br />(Zapp,1949). <br /> <br />b. Most of the lithologies observed in the drill core were laminated to thinly <br />bedded (less than 3/8.inch to 1.0 foot), except for some of the sandstones <br />in the Point Lookout Sandstone and Menefee Formations. These <br />sandstones are predominantly thinly bedded (less than 1.0 foot) but range <br />occasionally to thickly bedded (up to 10.0 feet). <br /> <br />2. Jointing. - <br /> <br />a. Jointing at the pumping plant site has been observed primarily in drill core <br />with a prominent joint set in both the Menefee Formation and the Point <br />Lookout Sandstone which dips 65 to 85 degrees. A slightly less <br />prominent joint set dips 40 to 55 degrees. On Smelter Mountain <br />southwest of the pumping plant site, a prominent joint set strikes from <br /> <br />I. <br /> <br />Geology <br />00320 - 10 <br /> <br />( <br />