Opinion ID: 314135
Heading Depth: 4
Heading Rank: 4

Heading: Opacity Standard

Text: Apart from the standard directly regulating particulate concentration, EPA has adopted an opacity standard which provides that there shall be no discharge of particulate matter from the kiln which is: [96] Greater than 10 percent opacity, except that where the presence of uncombined water is the only reason for failure to meet the requirements for this subparagraph, such failure shall not be a violation of this section. Opacity is defined by the regulation as the degree to which emissions reduce the transmission of light and obscure the view of an object in the background. [97] It may be, as EPA argues, that the opacity test is an important enforcement tool, [98] and that the results of an opacity test, which is normally performed at some distance from the plant by trained observers, offers a cheaper and faster method of determining compliance than enforcement of the particulate concentration standard. [99] However, it is one thing to use a method of testing to observe possible violations of a standard; it is another to constitute that method as the standard itself. If the opacity test is to be a standard, and if violations can result in enforcement actions without further testing, the standard musta be consistent with the statute and congressional intent. The thrust of the manufacturers' comments to EPA, and repeated here, is that the opacity test is arbitrarythat inspectors will be unable within any reasonable degree of accuracy to determine whether permitted opacity is 10%. The critical question is how accurate can opacity observations be. On this point we essentially have before us only the contentions of the parties. The manufacturers do point to a test conducted for the National Center for Air Pollution Control (U.S.Dept.H.E.W.), where six trained smoke inspectors evaluated a white training plume known to have 0% opacity. [100] All six inspectors rated the plume at more than 0% opacity and 3 evaluated it at more than 20%. A plume known to be at 20% opacity was rated higher than 20% by 5 of the 6 inspectors (one rated it lower) and 2 of them rated it at almost 40%. Problems may also be posed for deciding when opacity is due to water content and when it is not. [101] The difficulty is that this test has the thrust of indicating that opacity measurements are inherently inadequate, and does not seem to be probative of the manufacturer's quite different claim, namely, that it is at the low ranges that opacity tests become less reliable, and too unreliable to be a legal standard. On the other hand, EPA's brief does nothing more than point to the fact that many states have required that the plumes from stack emissions conform to a specified percentage of opacity. We note, however, that the opacity standard is at least 20% in the states cited, which corresponds to No. 1 on the Ringelman Smoke Chart. [102] We think the HEW test adduced by petitioners, though not decisive, suffices to require further consideration and explanation by EPA on remand, and a showing on the record that 10% opacity measurements can be made within reasonable accuracy. [103]