Section 49.124 - Rule for limiting visible emissions(a)What is the purpose of this section? This section limits the visible emissions of air pollutants from certain air pollution sources operating within the Indian reservation to control emissions of particulate matter to the atmosphere and ground-level concentrations of particulate matter, to detect the violation of other requirements in the "General Rules for Application to Indian Reservations in EPA Region 10", and to indicate whether a source is continuously maintained and properly operated.(b)Who is affected by this section? This section applies to any person who owns or operates an air pollution source that emits, or could emit, particulate matter or other visible air pollutants to the atmosphere, unless exempted in paragraph (c) of this section.(c)What is exempted from this section? This section does not apply to open burning, agricultural activities, forestry and silvicultural activities, non-commercial smoke houses, sweat houses or lodges, smudge pots, furnaces and boilers used exclusively to heat residential buildings with four or fewer dwelling units, fugitive dust from public roads owned or maintained by any Federal, Tribal, State, or local government, and emissions from fuel combustion in mobile sources.(d)What are the opacity limits for air pollution sources?(1) The visible emissions from an air pollution source must not exceed 20% opacity, averaged over any consecutive six-minute period, unless paragraph (d)(2) or (d)(3) of this section applies to the air pollution source.(2) The visible emissions from an air pollution source may exceed the 20% opacity limit if the owner or operator of the air pollution source demonstrates to the Regional Administrator's satisfaction that the presence of uncombined water, such as steam, is the only reason for the failure of an air pollution source to meet the 20% opacity limit.(3) The visible emissions from an oil-fired boiler or solid fuel-fired boiler that continuously measures opacity with a continuous opacity monitoring system (COMS) may exceed the 20% opacity limit during start-up, soot blowing, and grate cleaning for a single period of up to 15 consecutive minutes in any eight consecutive hours, but must not exceed 60% opacity at any time.(e)What is the reference method for determining compliance?(1) The reference method for determining compliance with the opacity limits is EPA Method 9. A complete description of this method is found in appendix A of 40 CFR part 60 .(2) An alternative reference method for determining compliance is a COMS that complies with Performance Specification 1 found in appendix B of 40 CFR part 60.(f)Definitions of terms used in this section. The following terms that are used in this section, are defined in § 49.123 General provisions: Act, agricultural activities, air pollutant, air pollution source, ambient air, coal, continuous opacity monitoring system (COMS), distillate fuel oil, emission, forestry or silvicultural activities, fuel, fuel oil, fugitive dust, gaseous fuel, grate cleaning, marine vessel, mobile sources, motor vehicle, nonroad engine, nonroad vehicle, oil-fired boiler, opacity, open burning, particulate matter, PM10, PM2.5, reference method, refuse, Regional Administrator, residual fuel oil, smudge pot, solid fuel, solid fuel-fired boiler, soot blowing, stack, standard conditions, start-up, stationary source, uncombined water, used oil, visible emissions, and wood.