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WL D UFF RMR Aggregates, Inc. <br /> U N ❑ E R G R 0 U N 1 Rock Failure Analyses and Stabilization Report <br /> ENGIN E E R I N G,INC Mid Continent Limestone Quarry <br /> 2. SITE RECONNAISSACE <br /> 2.1. JANUARY 26, 2023 — SITE RECONNAISSANCE <br /> The aforementioned site reconnaissance performed eight days following the ground failure was <br /> primarily an overview of the event, documenting existing conditions and formulating a plan across <br /> represented disciplines to evaluate and stabilize the ground event. Photos with detailed captions <br /> from the reconnaissance are included in Appendix A. Photo 1 shows an overall view of the ground <br /> event on the west face that released along a northeast dipping joint with high to very high <br /> persistence. No other obvious cracking above the recent ground event release was observed on foot <br /> or by drone. Photos 2 and 3 highlight the upper two beds of limestone that sit on the more massive <br /> limestone below. The slide plane for the ground event occurred along bedding at these two upper <br /> beds. <br /> Two thin interbeds of laminar bedded, shaley mudstone bound the upper two limestone beds. The <br /> observed thin interbed of laminar bedded, shaley mudstone creates a potential failure plane of lesser <br /> cohesion and fiction angle than the limestone. In addition, significant icicles had formed primarily at <br /> the basal contact of the upper limestone to the mudstone interbed. However, it is somewhat unclear <br /> if the water was draining out along this basal contact, or if seepage down the face of the limestone <br /> was dripping and causing the icicles, or most likely both. <br /> 2.2. APRIL 14, 2023 —SITE RECONNAISSANCE <br /> A site mapping program was performed to collect structure data on the East Face, evaluate the <br /> strength parameters of the interbed and overall geologic/rock mass conditions and stability of the <br /> south-facing slope. Mapping on the East face was used as proxy for the currently unstable West face, <br /> which had been mapped previously to have a very similar stratigraphy and structure. During the field <br /> reconnaissance, the bedrock conditions were evaluated and classified by visual examination of <br /> surficial deposits and outcrops. Bedrockjoints, structure, fractures and weathering were assessed <br /> and classified, and the geometry of discontinuities (dip and dip direction) were measured with a <br /> Brunton compass. Structure measurements made during the April reconnaissance are provided in <br /> Appendix B and were supplemented with previous mapping for modeling. Measurements were made <br /> of rock mass discontinuities along the entirety of the slope to evaluate the range and variability of <br /> discontinuity geometry and character.The collected datasets are believed to be representative of the <br /> exposed rock mass. Exposed outcrops were characterized using the Hoek-Brown rock mass <br /> classification system to assess in-situ strength properties (Hoek, 20002).Joint surface conditions, such <br /> as continuity, spacing, aperture, infilling, roughness, seepage, and a rating of significance were <br /> characterized, and collated on data tables. The degree of roughness and larger-scale waviness of joint <br /> surfaces was evaluated using the Joint Roughness Coefficient (JRC) methodology of Barton (19773). <br /> z Hoek, E., 2000, Practical rock engineering: on-line document, rocscience.com <br /> 3 Barton, N.R. and Choubey, V., 1977, The shear strength of rock joints in theory and practice: Rock Mechanics, Vol. 10(1- <br /> 2), pp. 1-54. <br /> Page 3 <br /> 535 16th STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM <br />