2017-04-14_REPORT - M1974004 - Laserfiche WebLink

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Martin Marietta Materials Spec-Agg 2017 Annual Report 5.0 FIELD OBSERVATIONS Field observations for the 2017 Annual Report consisted of rock structure mapping and the collection of information regarding areas of visible, large-scale instability; seepage; and mining activity. Observations for the current annual report were made during two site visits, which took place in July and December 2016 respectively. During our visits, we performed rock structure mapping to collect representative discontinuity measurements from recently mined rock exposures in the Southern Expansion Areas (Figure 2; Photos 1 through 3). Orientation measurements (i.e., dip/dip direction) of joints, foliation, and faults were taken from the faces of advancing benches. A geological compass was used to obtain discontinuity measurements both indirectly by sighting along the discontinuity surfaces, and, where deemed safe, by direct measurement on the discontinuity surfaces. A handheld GPS was used to record the location of data collection points (Figure 2). A total of 76 discontinuity measurements were collected in 2016 at five data collection points, and were added to the measurements from previous years. When combined with data collected from previous annual reports (1997-2002, 2004-2016)and with borehole geophysical data collected during the 2003 geotechnical investigation, a total of 3,435 discontinuity orientation measurements have been obtained over the past 20 years. Figure 5 shows the 76 discontinuity orientation measurements collected for this annual report overlain on a contour stereonet plot of the entire Spec-Agg structural dataset. During our July and December 2016 site visits, we observed two new fault exposures (probably of the same fault)along the temporary excavation wall in the Southern Expansion Area at stations 17-02 and 17-05 (Figure 3 and Photo 3). The fault is oriented approximately east-west, with apparent dip/dip direction of 65-68/185-215 and was exposed in the north to north-east facing temporary wall of the expansion area. The fault zone consists of orange-reddish weathered, broken and blocky pegamatite rock, with parallel fracturing, and iron-stained slickenside surfaces with local clayey gouge. The location of this fault is, in general, a good match with the previously mapped trace. The apparent width of the fault zone varies from 10 to 15 feet. The fault orientation measurements for this annual report are presented with previous fault measurements and differentiated by the fault feature they represent in Figure 4. Minor raveling conditions resulting from rock fragmentation during blasting and subsequent freeze/thaw conditions exist along each wall in the quarry, but appear more prevalent along the south wall possibly due to the north facing exposure. The quarry walls observed during the 2016 site visits appeared to be relatively dry; with the exception of minor seepage visible in the southwest corner of the main pit, which has been documented in the past. Other than minor seepage observed along the temporary access road to the Southern Expansion Areas, no major seepage was observed. Additionally, we observed impounded water in the Main Pit floor(Photo 4). It is our understanding that there has been minimal or no pumping of the impounded water during the past year. Reportedly, during the September 12-13, 2013 historic rainfall event in Colorado, water flowing from highwalls caused some minor damage to temporary rock barriers along the temporary quarry access road. After planar failure along foliation planes in 1998 and 1999, the overall effective angle of the last three benches of the north walls of the Main Pit were reduced to an angle of 35°, which is consistent with the February 27,2017 Page 4 Lachel &Associates, Inc. Project 16C64003 00 ©2017 All Rights Reserved