Section R307-312-4 - Visible Emissions(1) Visible emissions from sources subject to R307-312 shall not exceed the opacity limits as specified in Table 1. TABLE 1 CATEGORY OPACITY LIMIT Crushers 12% Screens 7% Conveyor transfer points 7% Concrete batch plants 7% (2) Opacity Observation. (a) Opacity observations of emissions shall be conducted according to 40 CFR 60, Appendix A, Method 9.(b) The duration of the Method 9 observations shall be 30 minutes (five six-minute averages).(c) Compliance shall be based on the average of the five six-minute averages. The duration of Method 9 may be reduced to 6 minutes (one six-minute average) if the first six-minute average is below the limit specified in Table 1.Utah Admin. Code R307-312-4