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Ralston Quarry Slope Stability <br /> Actual mining has been from the eastern side of the ridge. We understand that until <br /> approximately 20 years ago, tailings from the mining on the east side of the ridge were <br /> placed as fill on the west-facing side. The filled slope was graded at an approximately <br /> 2'/2 : 1 (horizontal : vertical) angle. In the early 20�00's, several retention ponds also <br /> were constructed along the toe of the fill slope. These features are indicated in the <br /> historical Google Earth® image (above right). <br /> SUBSURFACE EXPLORATION <br /> Subsurface exploration for the project was conducted in August and October, 2018. <br /> Twelve (12) test holes were drilled with a conventional, track-mounted drilling rig <br /> advancing 4-inch diameter auger to evaluate the subsurface conditions and retrieve <br /> samples for laboratory testing. The test holes were advanced at the approximate <br /> locations shown on the Google Earth® image in Figures 1 and 2 following the text, to <br /> depths of approximately 19 to 35 feet below existing grade. (Test Hole 5, however, met <br /> refusal on coarse materials at a depth of about 5 feet. Test Hole 9 met refusal at a <br /> depth of about 16 feet; and Test Hole 11 at a depth of about 6 feet.) A GROUND <br /> engineer directed the subsurface exploration, logged the test holes in the field, and <br /> prepared the samples for transport to our laboratory. <br /> Samples of the subsurface materials were retrieved with a 2-inch I.D. California liner <br /> sampler. The samplers were driven into the substrata with blows from a 140-pound <br /> hammer falling 30 inches, a procedure similar to that described by ASTM Method <br /> D1586. Penetration resistance values, when properly evaluated, indicate the relative <br /> density or consistency of soils. Depths at which the samples were obtained and <br /> associated penetration resistance values are shown on the test hole logs. <br /> In addition, in 2019, 16 test pits were excavated with a track-mounted excavator. The <br /> pits were advanced to depths of 8 to 22 feet at the approximate locations shown in <br /> Figures 1 and 2. Logs of the test holes are presented in Figures 3, 4 and 5. The logs of <br /> Test Holes 1 through 4 are re-drawn to elevation in Figure 6. Construction details of the <br /> groundwater monitoring and observation points installed at Test Holes 1 through 4 are <br /> provided in Figures 7 through 10. Logs of the test pits are provided in Figures 11 and 12 <br /> Explanatory notes and a legend are provided in Figures 13 and 14. <br /> Job No 19-1235 GROUND Engineering Consultants, Inc. Page 3 <br />