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" Western •DO South l.orcna avenue Technologies Farmington. A'ew Mexico tf7401 ~no• (505) 327-9966 • (ax 327.5293 The ptullty People s~ r•ee March 17, 2000 Colorado Gravel Products 45247 Hwy 112 Center, Colorado 81125 Attn: Mr. Ken Smith Re: Gravel Pit North of Highway 112 Center, Colorado ~~~~~~ Qj~~~C~ ,~L~ M. 9~q~ CQp~ / e~wr ; ~ III IIIIIIIIIIIIIIII '~~eived MAR 2 3 2000 or„~ 0' n9o Fje ~~ of ly/ner~~6 Geolo9Y MAR 2 g 2000 Division o/hfirerab ~~~&o: 3120Vars As you requested on February 28, on March 7 and 15, 2000, we have completed our observations at the above referenced project. The purpose of our observations were to sample and visually determine gravel sand properties of the material and determine the slope stability of the proposed finished gravel. pit slope along the powerline. The proposed gravel pit will be located north across Highway 112 which is north of the existing concrete •batch plant and borrow pit. It is understood that the edge of the proposed borrow pit will be 40 feet from the powerline, with a slope of 3 to 1 (horizontal to vertical) extending down into the pit to a depth of about 26 feet. The gravel-sand mixture in the existing gravel pit consists of fine to coarse grained sand with gravel up to about 3 inches in diameter. It is understood that tho dopth of water in the pit varies depending on how much recharge water is being placed into the ground and if the canals are flowing. It is understood that the surrounding area water well data indicates that the gravel-sand material extends down to a depth of about 30 to 40 feet. At a depth of 30 to 40 feet a layer of clayey silt/clayey sand exists which is about 1-foot thick and is underlain by gravel-clayey sand material. Past experience and observation of the gravel-sand material indicates that this material probably has an angle of internal friction of at least 30 degrees. The clayey silt/clayey sand probably has an angle of internal friction of at least 20 degrees. The static stability of the existing slope was analyzed using strength parameters estimated from observations and past experience with similar materials. The analysis was conducted on the proposed slope configuration. A computer program (SB Slope) developed by Von Guten Engineerinfl Software using simplified Rishnp's Analyci¢ wac parfnrmeri fnr the proposed slope configuration. The results of the analysis indicates ttrat a slope stability of 2.0 was obtained.