2012-03-06_REPORT - M1974004 - Laserfiche WebLink

Home Browse Search

Martin Marietta Materials Spec -Agg Project 3.0 DATA COLLECTION 3.1 Discontinuity Measurements Structural geologic data collected for this evaluation included the observation and measurement of orientation (strike and dip) of the geologic discontinuities from the newly exposed rock faces in the quarry, descriptions of the character of the discontinuities and data point locations (taken relative to generally measured wall locations). Measurements were taken from the faces of advancing benches in both the southern expansion area, and in the main pit of the quarry. A handheld GPS was used to obtain wall location information and to identify where the structural data were collected from. Discontinuity measurements were obtained utilizing a Brunton compass both indirectly by sighting along the discontinuity surface; and where deemed safe, by direct measurement on the discontinuity surface. Field inspection and data collection occurred quarterly starting in August of 2011 and was completed in January of 2012. A total of 21 discontinuity measurements reflective of the prominent joint sets were collected and added to the measurements from previous years. When combined with data collected from previous annual reports (1997 -2002, 2004 -2011) and with borehole geophysical data collected during the 2003 geotechnical investigation, a total of 3108 strike and dip measurements of discontinuities in the quarry have been obtained over the past 15 years. Figure 4 is a stereographic contour plot of all of the data collected since 1997. Mining activity has occurred in the main pit since the last report and additional data points and observations during this study were collected from this area. The sump appears to look similar overall to the 2011 investigation. One exposure in the main pit was accessible during our site visits and this was a generally south facing temporary wall (Figure 2, Station 1). Access to the remainder of the main pit excavation for data collection was not possible due to continued mining activities during our visits. In the southern expansion area, an east facing temporary wall was exposed at the time of our data collections, with data points collected from this mining area included in this report (Figure 2, Station 2). Factors that contributed to limited exposures being available for data collection included: recent and multiple snowfall events, temporary walls covered by blasting debris that has not yet been removed, and efficient reclamation of exposed walls by the mine. One site visit was coordinated with Martin Marietta in order to evaluate and document an exposure in the southern expansion area during the exposure of the third fault mapped originally by Gable (1968). Data collected included structural data, rock samples and photos. 3.2 Slope Geometry An adequate evaluation of the structural geologic conditions of the quarry must also include accurate information regarding the Tong -term orientations of the pit walls. The wall orientations utilized in this report are based on the current mine plan developed by Martin Marietta (formerly Lafarge West, Inc.) in December, 2003 and match the current Colorado Division of Minerals and Geology mine plan (Figure 5). The wall orientations used for this analysis have been the same since the 2003 report. The dip direction and slope angle utilized to represent the final quarry walls are presented in Table 1 below. February 13, 2012 Page 4 Lachel & Associates, Inc. Project 11361017.00 ©2012 All Rights Reserved