1998-03-26_GENERAL DOCUMENTS - M1973021

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1996, all 26 post-repair survey points remained stable with maximum displacements of less than 0.1 ft. Based on these data, the existing reconfigured benches and toe buttress appeared to be stable during the latter half of 1996. Movement of the surface survey points since 1996 has been documented by surveys conducted in March and May 1997, and March 1998 to provide data to ' measure the performance of the slide repair during 1997. All the remaining points except for three exhibit less than 0.19 ft total movement to date demonstrating stable conditions for 1997. ' Three points, 2002, 2003 and 2004, exhibited movement during 1997. These points, however, are not in the active failure area, but rather were established at ' the top of the reconfigured slope along the cut line at natural ground surface at the top of the hill. Movement documented there represents local sloughing of the shallow soil and weathered rock near ground surface and not deep-seated movement. Point 2002 moved almost 3.5 ft in a local slump at the cut line before being lost. Points 2003 and 2004 have exhibited 0.23 ft and 0.67 ft of movement, respectively, since their installation. The area around Point 2002 has been regraded to a flatter slope angle. The area around Points 2003 and 2004 may ' also be regraded in the future if movement continues. There is still approximately 50 ft between these locations and the Limits of Mining 5.3 South End of Central Quarry A. The parent rock material is typically weak and is estimated to have an unconfined strength less than 15,000 psi. The rock here is estimated to correspond to the "poor" baseline rock mass conditions. B. The rock mass structure is highly fractured and contorted with little consistent jointing pattern. The primary joint set is along foliation of the gneiss and schist rock. Foliation joint dip orientation varies as does the strike, but is generally southerly and into (or less frequently westerly and parallel to) the slope ' orientation. Joint spacings typically range from several inches to approximately five ft. Joint surfaces vary greatly from fresh to highly-weathered. Weathered schist interbeds having a slick and weak character are frequent throughout the ' rock mass, and talc-like alteration is prevalent in this portion of the quarry. C. At least two secondary joint sets are present, generally orthogonal to the primary ' joint set. In some cases, they cut through primary jointing and in some cases they terminate at a primary joint. These secondary joints typically occur at intervals of one to five ft. In general, secondary joint surfaces are fresher and ' less-weathered than the primary joints along foliation and do not typically exhibit the smooth schist or mica surfaces. ' Based on the conditions observed with the present exposures, the rock mass at the south end of the Central Quarry is still classified as "poor" in terms of the ' 10 G:\PROJECTS\20200\002\97ANNRPT.W PF