Between 1971 and 1976, FECSA built the three generating units of the Sant Adrià power plant, known as San Adrián I, II and III, each with a capacity of 350 MW. Together, the complex reached a total output of 1,050 MW and operated as a reserve facility designed to cover peaks in the demand for electricity. At times, it supplied up to 30% of Catalonia’s energy during periods of high demand. In the original plans, the plant only had two chimneys but the subsequent expansion required the addition of a third. This explains why the chimneys are spaced unevenly. The plant created jobs and boosted the economy, but it also produced high levels of sulphur dioxide and other atmospheric pollutants.