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I :1 I I I l l .' l' ~ It ! ,., ~, l I , i;; '~Ij SAN J.^CINTO TUNNEL 23- adit, wOl'king toward the east. Placing of invert concrete was begun near the same station on November 1st and finished to the pre- viously lined section at the west end of the Cabazon pioneer on De- cember 3rd, a total of 10,369 feet being completed in this time. The 9,341 feet of invert between the east end of the Cabazon pioneer and Cabazon adit was placed in the four weeks from January 8 to February 4, 1939. In the meantime arch forms had been moved in and set against the arch concrete previously placed by the west portal crews, 582 feet east of Lawrence adit, in preparation for the final run in this eastern portion of the tunnel. Arch concreting was started Feb- ruar>' 8th and the remaining 20,232 feet was completed May 22, 1939, involving the hauling, mixing, and placing of 64,163 cubic yards of concrete. The best week's progress was 2,063 linear feet. The best month was March, when in 93 shifts 19,783 cubic yards of concrete were placed in 6,437 feet of arch, an average of 8.65 feet and 26.6 cubic yards per hour. West POl.t"l Pt"nt The concrete lining crew.. in the western portion of the tunnel continued placing operations concurrently with excavation until the connection was made, in November 1938, between the Potrero and Lawrence headings. In order more readily to handle the large volur11e of inflowing water, standard procedure was to prepare a section for lining, place concrete curbs along both sides with drain tile as needed, and follow at a short distance with the invert. In- flowing water was either diverted into the pioneer or piped over the area of operations to be dumped on the completed invert west of Potrero. shaft 01'_ pUj11P.ed to Jlle ",est p'ortal. .Temporar>> bridging for track was moved along on the curbs, being progressively re- placed by a bridge supported on posts resting on the newly finished invert. Then arch forms were set on tLe curbs and the arch concrete placed to complete the section. Prior to June 30,1938, in Potrero East, concrete curbs and invert had been completed to a point 6.112 feet east of Pob'era shaft, and arch concrete was being placed from that point toward the shaft. During July and August this arch work was finished to a connection with the existing lining just west of Potrero shaft, except for three short sections temporarily left unlined. The concrete placing crews then advanced curbs and invert as rapidly as possible behind the excavation forces. When the headings met, November 19, 1938,