1995-02-06_REVISION - M1977378 - Laserfiche WebLink

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Terry Tunnel Bulkhead Construction Certification Report Page 5 The bulkhead rock-concrete contact has been grouted to specifications and all indications are that the low pressure grouting was successful and complete. 9) Diversion Pipe Flow Data The Division in its list of concerns dated April 15, 1993 requested that flow data be provided prior to the concrete pour for the American Tunnel bulkhead , and again after the curing period , prior to closing the valve. SGC committed to submit flow measurements (taken during construction of the forms (working days only) ) with the notification of pour date for evaluation by the Division and measure flows daily for 3 days following the pour for submittal with the construction performance certification. Since this commitment was made in relation to the water diversion through the bulkhead, SGC feels that it was also applicable to the Terry Tunnel bulkhead and thereby submitted flow data to the Division during the 8/31/94 inspection visit and submits additional data with this certification submittal (Table 1) . This data shows that the design flow was not exceeded . The data in Table 1 was generated by measuring the H flume on the Terry Tunnel discharge to Eureka Creek. This is representative of the flow through the diversion pipe because no other source of water exists between tnese points. Flows were not taken on 8/26/94 , 8/27/94 and 9/l/94 because the ponds were filling or water was being used during the settling pond cleaning operation that was in progress. The setup within the mine to keep water away from the bulkhead site during construction and curing of the bulkhead consisted of a sump catchment where a pump picked up the water and pumped it through the diversion pipe. This pump was in operation throughout the monitoring period . A safety coffer dam was built across the drift in front of the bulkhead to catch the flow and divert it through the diversion pipe by gravity in case the pump failed. Either system was adequate to handle the flows measured without allowing water to reach the bulkhead although the pump system was favored because it kept the working area (drift in front of the safety dam) dry.