could then be fed into K-25 or the calutrons at the Y-12. Kellex estimated that using the enriched feed from K-27 could lift the output from K-25 from 35 to 60 percent uranium-235. Construction started at K-27 on 3April 1945, and was completed in December 1945. The construction work was expedited by making it "virtually a Chinese copy" of a section of K-25. By 31 December 1946, when the Manhattan Project ended, 110,048,961 man-hours of construction work had been performed at the K-25 site. The total cost, including that of K-27, was $479,589,999 (equivalent to $ in ). The water tower (K-1206-F) was a structure that held of water. It was built in 1958 by the Chicago Bridge and Iron Company and served as reservoir for the fire suppression system. Over of steel was used in its construction. It operated until 3 June 2013, when the valves were turned off. It was then drained and disconnected, and was taken out of service on 15 July. On 3 August 2013, it was demolished with explosives. Operations The preliminary specification for the K-25 plant in March 1943 called for it to produce a day of product that was 90 percent uranium-235. As the practical difficulties were realized, this target was reduced to 36 percent. On the other hand, the cascade design meant construction did not need to be complete before the plant started operating. In August 1943, Kellex submitted a schedule that called for a capability to produce material enriched to 5percent uranium-235 by 1June 1945, 15 percent by 1July 1945, and 36 percent by 23 August 1945. This schedule was revised in August 1944 to 0.9 percent by 1January 1945, 5percent by 10 June 1945, 15 percent by 1August 1945, 23 percent by 13 September 1945, and 36 percent as soon as possible after that. A meeting between the Manhattan District and Kellogg on 12 December 1942 recommended the K-25 plant be operated by Union Carbide. This would be through a wholly owned subsidiary, Carbon and Carbide Chemicals. A cost-plus-fixed-fee contract was signed on 18 January 1943, setting the fee at $75,000 per month. This was later increased to $96,000 a month to operate both K-25 and K-27. Union Carbide did not wish to be the sole operator of the facility. Union Carbide suggested the conditioning plant be built and operated by Ford, Bacon & Davis. The Manhattan District found this