Laserfiche WebLink
IV - DESIGN ANALYSIS AND CRITERIA <br />The proposed mining slopes were analyzed using the XSTABL v5 computer program. XSTABL <br />was designed to analyze the slope stability of earth embankments subjected to several critical <br />situations that may occur during the life of the embankment. Static and pseudo-static conditions <br />were analyzed in each case. <br />Pseudo-static peak acceleration factors were taken from USGS information for the western <br />United States. The 2% probability of exceedance in 50 years (the most conservative) was used. <br />Surface loads equivalent to an HS 20 highway load were applied adjacent to each area, when <br />applicable, to simulate heavy equipment loading that could be present at that location. <br />For this project, seven cases were identified as critical during the mining operation: <br />Case 1 - Existing Weld County Road 51, existing overhead electric, gas, water, <br />and telephone lines to the east. The mining operation is adjacent to numerous man <br />made structures in this area. The proposed setback for mining is 55 feet from the <br />proposed permit boundary, and 25 feet from the existing County Road 51 right-of-way. <br />The mining depth was assumed to be 55 feet in this area based on bore log information <br />in the geotechnical reports. The mining side slopes in this location will be 3h:1v to 10 <br />feet below the expected water surface, and 2h:1 v from that point down to the pit bottom. <br />Case 2 - Existing fence, Weld County Road 58 to the south. The mining operation is <br />adjacent to an existing fence and Weld County Road 58 in this area. The proposed <br />setback for mining is 25 feet from the permit boundary/fence, and 60 feet from the Weld <br />County Road 58 right-of-way. The mining depth was assumed to be 79 feet in this area <br />based on bore log information in the geotechnical reports. The mining side slopes in this <br />location will be 3h:1 v to 10 feet below the expected water surface, and 2h:1 v from that <br />point down to the pit bottom. A horizontal bench will be located in the slope 3 feet above <br />the expected water surface to facilitate the construction of the slurry wall. <br />Case 3 - Existing oil/gas well to the southwest. The mining operation is adjacent to <br />an existing oil/gas well in this area. The proposed setback for mining is 150 feet from the <br />oil/gas well. The mining depth was assumed to be 64 feet in this area based on bore log <br />information in the geotechnical reports. The mining side slopes in this location will be <br />3h:1v to 10 feet below the expected water surface, and 2h:1v from that point down to the <br />pit bottom. <br />Case 4 - Existing oil/gas well to the southwest. The mining operation is adjacent to <br />an existing oil/gas well in this area. The proposed setback for mining is 150 feet from the <br />oil/gas well. The mining depth was assumed to be 78 feet in this area based on bore log <br />information in the geotechnical reports. The mining side slopes in this location will be <br />3h:1v to 10 feet below the expected water surface, and 2h:1v from that point down to the <br />pit bottom. <br />Case 5 - Existing access easement to the west. The mining operation is adjacent to <br />an existing access easement in this area. The proposed setback for mining is 25 feet <br />from the access easement, and 55 feet to the property/permit boundary. The mining <br />depth was assumed to be 76 feet in this area based on bore log information in the <br />Journey Ventures, LLC - Kersey Gravel Pit <br />Slope Stability Analysis <br />Page 2