Laserfiche WebLink
C <br />Aprt128, 2004 <br />Mr. Brad Janes <br />Varra Companies <br />8120 Gage Street <br />Frederick, CO 80516 <br />Subject: Slope Stability <br />Durham Pit <br />Greeley, Colorado <br />CGRS Project No.1-136-9640aa <br />Dear Mr. Janes: <br />I have reviewed the slope stability analysis generated by Division of Minerals and Geology. The <br />method used was the modified Bishop method. CGRS utilized a method commonly known as the <br />Friction Circle method as a comparison analysis. Based on available information our slope stability <br />analysis closely approximates the results presented in DMG's analysis. Our analysis did indicate that <br />excavation slopes of 0.577:1 (80 degree angle from horizontaq may be stable wRhin the limits of <br />various setbacks. The generally accepted safety factor for temporary excavations is on the orJer of <br />1.2. It is our understanding that Varra Companies has mine slopes whhin the Durham faality <br />approaching 0.5:1 and that these slopes have been stable for over a year. <br />It should be noted that our slope stsbilhy calculations assume that soil properties are consistent. Our <br />calculations were generated using an F~ccel spreadsheet and should be used for comparison <br />purposes only. <br />Sincerely, <br />CGRS, INC <br />Joby L. Adams, P.G. <br />PrtnapaVtiydrogeologist <br />C:\WINDOWS\Temporery Internet Files\Content.lESWL23GX2FWope.doe <br />