"Soon after the Oil-Shale Demonstration Plant was established at Rifle, it was decided to construct two N-T-U type oil-shale retorts as the first large-scale units. A cost-plus-fixed-fee contract for the design, fabrication, and erection of the two 40-ton N-T-U retorts was awarded to the Southwestern Engineering Company of Los Angeles, California on September 25, 1945 , The contractor was furnished the basic flow diagrams, conditions of service, and Bureau engineers worked with the company's engineering staff to prepare the detailed design, fabrication and erection drawings. Excavation of the site was done by Bureau crews beginning on April 15, 1946 , and foundation work was completed July 17, 1946. The contractor's crews began construction of the equipment immediately following completion of the foundation work and the retorts were ready for operation in May 1947. Another cost-plus-fixed-fee contract was awarded to the same company for the design, fabrication, and erection of the crushing conveying-storage plant and it was erected concurrently with the retorts. The first retort was fired on May 8 , 1947, a few days before the dedication of the Oil-Shale Demonstration Plant. This report describes the N-T-U process, the related crushing- conveying-storage plant, and reviews the operations from May 8,1947, to May 11, 1948. During this period the retorts were operated to establish operating techniques , to train personnel., to determine the shortcomings of the equipment and make the necessary alterations to calibrate the equipment and instruments, and to establish the operating variables and thereby prepare a program of experimental work to evaluate each of the variables."