A map showing the Howard County sulfur dioxide nonattainment area. The Big spring Carbon Black Plant (Tokai), the Big spring Refinery (Delek), and BHER Power Resources (BHER) are three sources of SO2 emissions within the Howard County nonattainment area and are outlined in yellow, blue, and black, respectively, in the figure. A Data Requirements Rule monitor, the Big Spring Midway monitor, or Continuous Ambient Monitoring Station 1072 (C1072), was sited across North Midway Road approximately 0.15 kilometer to the northeast of the Tokai Plant to monitor SO2 concentrations. This monitor is shown as a green triangle in the figure.