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.