haul unit delivers 120 tons of coal to navajo mine crushing and blending plant operatioi mining operations indicator lights glow as to cally monitors plant opera received laboratory technicia mining constitutes the principal business of utah construction & mining co the company engages directly in the mining of steam coal uranium and iron ore in the united states and in 1972 will begin the production of copper concentrates from a new mine and con centrator under development in british columbia canada in australia interests in iron ore and coking coal mines are held by a 90 owned subsidiary utah development company during 1970 pursuant to a policy decision of the parent corporation 10 of the stock of this subsidiary was issued to an australian holding company utah mining australia limited an indirect participation in the growth and earnings of utah development company was thereby made available to 13,000 australian investors this program was favorably received and has added a mutual feeling of partnership and good will to the already excellent relations prevailing between utah and the govern ment and people of australia with respect to our investment and operations in that country iron ore is also mined in peru by a subsidiary of our 46 owned affiliate marcona corporation which additionally engages in extensive ocean shipping operations through another subsidiary a 25%-owned affiliate pima mining company operates an open pit copper mine and concentrator near tucson arizona mining activities of utah and its subsidiaries and affiliates provided the bulk of the company's revenues and earnings in 1970 and contributed the greater part of the advance in profits over the previous year our share of com bined earnings from mining affiliates however was slightly lower than in 1969 utah and utah development company have in progress a major program of expansion of mining operations which began in 1968 and in its present scope will be completed in 1973 the total new capital investment required to carry out the program as presently authorized is in excess of 310 million and financing to supplement cash generated internally has been arranged to provide the nec essary additional funds the nature and extent of our expansions are described in the review of mining operations which follows coal in 1970 coal displaced iron ore as the principal contributor to the company's operating profits an increase in the production capacity of our navajo mine located on the navajo reservation in new mexico was com pleted during the year as the initial project in our mining expansion program navajo's higher output of steam coal is geared to the rate of fuel consumption of the four corners power plant coal sales in 1970 were 5.5 million tons more than 78 over 1969 sales of 3.1 million tons to meet the first full year's fuel requirements of generating unit no 4 and a short period of the requirements of generating unit no 5 which began com mercial service in the third quarter of our fiscal year the five units now in operation at the four corners plant have a combined capacity of 2,085 megawatts based on our experience to date the enlarged plant in normal operation will burn about 8 million tons of coal annually this tonnage will be supplied from our navajo mine under long-term requirements contracts con taining cost escalation provisions approximately 30 of the total