Laserfiche WebLink
4. 2018 Slide Area <br /> Ground Engineering conducted a thorough analysis of the slide area located on the west side of <br /> the main quarry. This analysis, and its recommendations, are attached to this exhibit. <br /> Justification of a 1.25 Slope Stability Factor for West Facing Slopes <br /> According to the DRMS Memorandum issued in May of 2018, if a critical structure could be <br /> affected by a slope failure, a 1.30 long term safety factor is required. If it is one which could not <br /> 4.11 affect a critical structure, a 1.25 safety factor is allowed. Both of these standards assume that <br /> actual data is available from test materials on site. As shown in the Ground Engineering Slope <br /> Stability Report of January 2018, sufficient data has been collected in the area of concern at this <br /> site, including 12 drill holes with logs, samples for strength parameters, moisture, density, etc. <br /> We are supplying the following documentation for classifying the structures below the west <br /> sloping areas of the Quarry as Non-Critical, resulting in a required factor of safety of 1.25 for <br /> areas where sufficient data has been collected: <br /> a) Zones 1 is the waste embankment area from the slide in 2018 and is graded to a slope of <br /> 3H:IV. This zone is addressed in the Ground Engineering Report. Zone 1 is not located <br /> within any reasonable distance to the Reservoir. <br /> b) Zone 2 has no critical structures within any distance that could be affected by a slide of <br /> this area. It is located south and east of the slide activity. See Figure GS-I. <br /> c) The slope failure that occurred in Zone 3 in 2018 was the largest that has ever been seen <br /> at the site since the quarry has been in operation. This slide only slightly encroached on <br /> the Denver Water Board Road and no material reached the Ralston Reservoir. It is highly <br /> unlikely that a new slide could result in any slide material entering the Reservoir, <br /> especially sufficient slide material entering the Reservoir that could result in"major <br /> environmental impact". <br /> d) There is a large relatively flat area below the toe of the slope in Zones 3 and 4, where <br /> slide activity has previously occurred. This relatively flat area will allow any potential <br /> new slide material to build up in the relatively flat area and prevent any large amount of <br /> Ralston Quarry 4rM 1.wkki and Anwrisim PHA' <br /> January 2019 GS-5 <br />