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. .-.....'"l'... "'wL ~. - ( OPERATION AND MAINTf:NANCE 23 access for inspection and additional work. The maximum rate of discharge from the pioneer exceeded 40 cubic feet per second during the draining operations causing working conditions to be extremely difficult. At the east end of the pioneer tunnel a thick gunite lining was placed, extending from the main tunnel wall approximately 55 feet west in the pioneer_ A 7-foot thick solid gunite bulkhead, with a 24-inch diameter steel access pipe extending through it. was placed in the pioneer about 30 feet from the main tunnel wall. This pipe was fitted with a flange and an 8-inch valve to allow drainage of the Cabazon pioneer and access to it at any time inspection is found necessary in the future_ Pressure built up by storage of water in the pioneer will be held by the 7-foot thick bulkhead and the valve.. thereby relieving pressure on the wall of the main tunnel. The opening at the east end of the pioneer through the main tunnel wall was bulkheaded off with gunite after placing a 36-inch diameter steel pipe through the opening for permanent access_ The ruptured main tunnel lining near the east end of the pioneer was repaired by building up the lining to the original cross section by the appli- cation of gunite. The hole cut through the main tunnel wall to pro\'ide temporary access to the pioneer at Station 10360+60 was fitted with a 24-inch pipe for permanent access_ This pipe was closed off with a flange and 8-inch valve. The holes previously drilled to assist in draining the pioneer were permanently closed by filling with a dry pack. The work done on the pioneer tunnel resulted in cutting off practically all inflow into the main tunnel from the pioneer. Invert breaks were repaired near Stations 10270, 10454. 10485, and 10616- A total of 32 cubic yards of concrete was used in making these repairs. Pressure grouting was done at the east end of Cabazon pioneer tunnel. Station 10311+50. between Stations 10360 and 10365 and at Stations 10454. 10485, 10486, and 10615. A total of 2397 sacks of cement was used in 200 grout connections at pressures ranging from 50 to 350 pounds per square inch. The grouting and repair work was performed by District forces averag- ing 36 men. Work inside the tunnel was on a 3-shift basis. Operations were carried on from a headquarters camp at the east portal using the equipment and facilities assembled for the previous grouting operation_ The cost of grouting and repairs-for this second operation was $51,271.30, making a total cost to June 30, 1948 of $201,259_36.