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<br />^.I <br />1.1 'j ~ <br /> <br />24 <br /> <br />METROPOLITAN WATER DISTRICT <br /> <br />the concrete crews were within a few hundred feet of the point of <br />connection. The last concrete curb was placed by the west pOl'tal <br />crews just east of Lawrence adit December 31, 1938 and the last <br />invert three days latel'. On January 10, 1939 concreting of the <br />arch was started by them 582 feet east of Lawrence adit and com- <br />pleted at Potrero on May 29th. This work was dorle with a fixed <br />length of 121 feet of forms, which limited the speed of placing to <br />that distance as a daily maximum. The best monthly progress was <br />made in March with 3,423 feet of arch completed. <br /> <br />G,'outing Behind Concrete Lining <br />Grouting to fill voids back of the lining and to seal off infiltering <br />water was performed generally soon after the concrete had set. The <br />operation was carried on in stages. Test holes were drilled t.hrough <br />the lining systematically around the entire section, arch, side walls, <br />and invert. Where voids were found Or seepage was evident, grout <br />was injected through the test holes under pressures up to 100 <br />pounds per square inch and allowed to set. Later, further test drill- <br />ing was done, particularly' where rising water levels caused percola- <br />tion through joints in the lining, and high-pressure grouting was <br />resorted to. In this second operation, using mainly neat cement, <br />pressures up to 400 pounds pel' square inch were used. With the <br />. lining and grouting completed the water inflow in the thirteen miles <br />of tunnel was reduced from an average of 31,200 gallons per r1Iillllte <br />in June 1938. at which time 53 per cent of the lining had been <br />placed, to 710 g.p.m. in October 1939. <br /> <br />Clean-up <br />Following completion of the grouting operations, the tunnel track <br />and utilities were removed and the concrete lining was scraped and <br />scrubbed clean. The tunnel was ready to carry water before the end <br />of October and the first Colorado River water actually entered the <br />east portal about 11 :30 a.m. of November 1, 1989, when 10 cubic <br />feet per second of the aqueduct flow of 200 c.f.s. was admitted into ~ <br />the tunnel, the remainder being spilled into San Gorgonio Wash. <br />This small flow reached the west portal at 7 :08 p.m., compared <br />with the time of passage at theoretical velocity for full flow of <br />about 214 hours. <br />In the camps removal of plant and buildings was begun as soon <br />as possible after their use was discontinued. Heavy equipment, <br />hoists, and compressors, have been left on their foundations, with <br />necessary protective housing, pending sale. For the most part build- <br />