1996-02-02_HYDROLOGY - M1977493 - Laserfiche WebLink

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1111111111111111111 9 - ' —— Environmental Titan Environmental Corporation 7939 E.Arapahoe Rd., Suite 230 ^ Englewood,Colorado 80112 FEB 0 2 199b v Phone:(303)850-9852 Fax: (303)850-9910 January 30, 1996 Division 011,01"erais tx ueoioc�y Mr. Stuart Teuscher � G _ ' / �5101-004 Climax Mine " M 1 177 `� Q� Highway 91 Climax , Colorado 80429 Recommended Modifications Robinson Lake Cut-off Wall Dear Stuart: This letter provides a recommended modification to the concrete cut-off wall designed for the Robinson Lake Pump Back System. The original cut-off wall design called for a 24- inch deep minimum cut-off wall key to be excavated into the bedrock as a means to intercept any potential seepage within the bedrock. The cut-off wall would then be constructed as a single wall starting within the keyway. In the original design, no provisions were made to address conditions where the key could not be trenched. If, during excavation of the cut-off wall key, the bedrock strength precludes advancement of the keyway, a modification to the design is recommended to provide a watertight seal against the bedrock. It is recommended that a 24-inch concrete wall footing foundation be constructed on the surface of the bedrock prior to forming the cut-off wall. The purpose of the footing is to provide a large surface area seal onto the bedrock face, thus minimizing any potential seepage between the cut-off wall and bedrock. The footing will be constructed in the following steps: • The bedrock will be visually inspected to ensure the rock face is competent and free of any transmissive fractures or joints. The condition of the bedrock prior to footing construction will be documented; • The bedrock surface shall be cleaned to be free of soil, loose rock, or other foreign materials or substances to promote adhesion of the footing to the bedrock surface; A\MOD DOC