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s ~ III IIIIIIIIIIIIIIII <br />~~ <br />CTL/THOMPSON, INC. <br />CONSULTING GEOTECHNICAL AND MATERIALS ENGINEERS <br />August 16, 1989 <br />Castle Concrete <br />P.O. Box 2379 <br />7250 Allegheny Drive <br />Colorado Springs, Colorado 80919 <br />Subject: Consultation <br />Slope Stability Analysis <br />Quarry Access Road <br />Snider (Queens Canyon) Quarry <br />Colorado Springs, Colorado <br />Job No. CS-1944 <br />Gentlemen: <br />We have prepared this letter to present our preliminary opinions regard- <br />ing stability of two fill areas adjacent to the quarry access road. The areas <br />are identified as Area 1 and Area 0. on mapping prepared by Obering, Wurth & <br />Associates. The major area involved was addressed by Obering, Wurth & As- <br />sociates in a report entitled "Snider Quarry Access Road Slope Stability <br />Report", dated July 1988, Project No. 88106. CTL/Thompson, Inc. w<<s retained <br />July 27, 1989 to evaluate stability. <br />We have recently been provided topographic cross-sections of ap- <br />proximately the maximum section of each area. That topography indicates the <br />slope in question at Area 1 is approximately 90 feet high and blocks a <br />drainage at the toe. Slopes on much of the face in Area 1 are betH~een 33 de- <br />grees (1.55:1) (horizontal to vertical) and 35 degrees (1.43:1). Area 2 is <br />about 60 feet high and at a slope of about 37 degrees (1.32:1). We understand <br />the slope at Area 1 has been comparatively stable for the last two years but <br />failed occasionally during the previous 20 years. The slope at 4rea 4 has <br />remained stable over its life. <br />Our experience indicates the steeper slopes at Area 1 and the slope at <br />Area 4 are at the materials dry, natural, angle of repose indicating a <br />stability factor safety of 1.0. If the materials become wetted, failure is <br />likely. Flattening will be necessary at both locations to increase stability. <br />We believe flattening can be accomplished by either filling or b,y removing <br />material. Filling may make the toe of the slope extend past the current per- <br />mit boundary. Removing material may necessitate moving the access road fur- <br />ther into the hillside. Moving the road into the hillside could cause some <br />uphill slope stability problems. <br />5240 MARK DA6LING BLVD. COLORADO SPRINGS.GOLORAD080918 (719)528-83X7 <br />