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EPA's Emissions Rule: Reliability at Stake?

SIP Call in a Nutshell
Fortnightly Magazine - August 2000

In Georgia and Missouri, it found that only a portion of NO x sources exerted any material effect on downwind states, and asked the EPA to rethink its budget calculations. Speaking in late June, Noonan said the EPA expected shortly to issue a proposal addressing those issues.

Kimber Scavo, environmental protection specialist at the EPA, says that if the EPA were using an eight-hour standard for assessing ozone levels rather than a one-hour standard, Wisconsin and several other states would be included in the NO x SIP Call.

As an EPA expert explains, "The one-hour standard is good at measuring peak concentrations of ozone in the air. The one-hour standard is very good at measuring the amount of smog over a one-hour period.

"But the health data that we collected showed that it is not only bad for your health to be exposed to ozone at the very highest levels. Instead, the health data shows that for children and the elderly, being exposed at a lower level over a longer period of time is very dangerous to your lungs and can cause damage.

The eight-hour standard measures the amount of ozone in the air over an eight-hour period. It is a rolling average. It is the highest eight hours of the day." The eight-hour standard is before the U.S. Supreme Court. The court will consider whether EPA overstepped its constitutional authority when ordering compliance under the eight-hour standard. (See sidebar, "Measuring Emissions.")

"We, as a company, are very sure that there will, in all likelihood, be an eight-hour standard," says Joe Maher, spokesman for Duke Power. "The question is what number do you use. What is the standard? The EPA had proposed 80 parts per billion. The lawsuit filed against the EPA found that there was no clear link between the science and the number that was picked as the standard."

Although Duke Power has no objection to the one-hour standard, the company would support a reasonable eight-hour standard, says Maher.

Most utilities already have begun deploying technology to reduce NO x emissions in anticipation of the ruling. Meanwhile, states have flexibility in choosing how to achieve the NO x reductions needed to meet the budget, notes Noonan at the EPA. Utilities will select from a combination of, among other options, a cap-and-trade allowance program, selective catalytic reduction (SCR), or selective non-catalytic reduction (SNCR) technologies.

Sampling techniques can make the difference.

In the appeal pending before the U.S. Supreme Court , a key issue concerns use of an eight-hour standard to measure attainment with ambient air quality targets for ozone. The Environmental Protection Agency in July 1997 chose the new eight-hour test to replace the old one-hour standard.

Under each standard, however, compliance or nonattainment can depend heavily on how and when the data is sampled.

In some areas, the seasonal pattern of ozone makes it unnecessary to measure for months at a time. Missing daily measurements can be inferred, based on actual measurements and averages of measurements taken on other days.

THE ONE-HOUR STANDARD. Compliance is attained if, over a three