2023-08-31_ENFORCEMENT - M1982121

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K1L D UFF RMR Aggregates, Inc. U N ❑ E R G R 0 U N ❑ Rock Failure Analyses and Stabilization Report E NGIN E E R I N G,INC. Mid Continent Limestone Ouarry Chaffee Group. Near the southeast flank of the White River Uplift, the Gilman Sandstone, the upper unit of the Chaffee Group, is predominantly a 16-foot thick calcareous sandstone (Kirkham et al., 2008), pinching out towards Glenwood Springs. The site area is bound to the north by a mapped bedrock graben,just south of the Glenwood monocline axis, exposing the younger fossiliferous limestone unit of the Lower Pennsylvanian-age Belden formation. Outcrops of the Belden appear below the existing quarry as well, unconformably overlying the Leadville Limestone. Mid Continent Limestone Quarry Geology Leadville Limestone in the location of active quarry operations is mapped by Kirkham et al. as dipping between 24 and 38 degrees to the south-southwest, which forms dip slopes and tends to control hillside slope topography. A series of roughly east-west trending normal faults crosscut the area but are not mapped as continuous across the proposed expansion area. These structures are likely a westward extension of the normal-oblique Grizzly Creek Shear Zone, and the secondary influence on the site's rock mass, outside bedding. Previous analyses of the Leadville Limestone performed for RMRA indicates the coarse crystalline rock is composed of 90%to 98% calcium carbonate and low in both magnesium chloride and silica. Boreholes completed by Colorado Fuel & Iron Corporation (CF&I) in the 1950's and 1960s were provided by RMRA to KUE as scanned hardcopy with approximate locations. Borehole Lynx 05-001 in the area of the ground event describes the upper 36 feet of the rock as follows: Upper Leadville Limestone, med to dark gray, hard,fine grained, some recrystallized, numerous fractures in all directions re-cemented with w/white, yellow, brown, & pink calcite. Some limonite stain, Good acid reaction. Porous zones at 28-0 to 28-5 and 29-9 to 30-6. Lower in section, thin mud seams are identified at 51-9 and 58-3, but no description of soft interbeds are included. Also of significant note to the modeling of the recent ground event, 1966 borehole Lynx 05-099 drilled vertically in the area of the event identifies dip in the upper 40 feet of the section as 40 degrees. Site Topography RMR Aggregates, Inc. has developed a very detailed site topographic map, which shows a moderately-steep, south-facing slope. Slope topography decreases upslope, from south to north, along the top of the fold.The topography lays back from 1.4:1 at the southern extent at the existing quarry highwall to roughly 2.5:1 moving uphill 220 yards towards the potential area of proposed long- term stabilization. Page 2 535 16th STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM