OTA - Seneca Energy Plant - Questionable Numbers

The air pollutant numbers predicted for the Seneca Power Plant are estimates. Some are more likely to be accurate than others. Some are probably not accurate at all. First let's look at some of the numbers.

Air Pollution

The following are some of the predicted pollutants for the Seneca Cogeneration Plant. For a more detailed list and their impacts, click here.

Continuous Monitoring

Continuous monitoring is exactly what it sounds like - monitoring that takes place on a continuous basis. Most pollution monitoring that takes place is sample based. The facility being monitored is warned days in advance - giving them plenty of time to switch to the cleanest fuel possible. Then the monitoring agency shows-up and takes several samples over a small peroid of time. That sample is supposed to reflect the emissions for the facility until the next sample is taken months or years later. Full of flaws? You bet.

Air Monitoring

Currently only NOx, CO, and PM are proposed for continuous monitoring. To ensure the health of EWEB’s customers, continuous testing should be performed for SO2 and as many Hazardous Air Pollutants (HAPs) as possible - especially Benzene, Dioxins, HCl, and Formaldahyde. Furthermore, that data should be monitored by LRAPA – not Seneca. Technology exists to directly transfer data from the sensors to LRAPA to ease the burden on Seneca.

EWEB could include continuous monitoring for pollutants in their “terms of agreement” negotiations. LRAPA could make it a requirement for their permit.

Why Should They?

Because predicted emissions are inexact and continuous monitoring is the most accurate method available.

In Seneca's "Air Pollutant Discharge" permit, they use a variety of sources to predict their emissions. The EPA-42 emission factor is what most agencies use, and Seneca's permit uses them too. But it also uses other sources that range from a study done by the Dept of Ecology in WA, to a study done by the National Council of Paper Industry for Air and Stream Improvement (which apparently isn’t even public information), to hiring a lab to come-up with an estimate based on one fuel sample that Seneca themselves provided. In all but one of these instances the resulting emissions are lower than if they continued to use the EPA’s numbers. In fact, in the case of benzene, the resulting number was 40 times lower than what the EPA number would’ve produced.

In some cases, this may be justified. But it is important, because it reflects that the amount of predicted emissions vary depending on who you talk to. In other words, predicting emissions in wood boilers is not an exact science. The problem of estimating emissions is made worse by the fact that emissions vary greatly according to the fuel source - some wood burns cleaner than others.

Predicted emission levels are important, because they are used to determine the level of pollution control technology Seneca must use. If they exceed certain levels, they are required by law to use better technology, which means less air pollution. NOTE: Levels of various pollutants will be measured immediately after the plant is built and running. But that is only one sample and Seneca is likely to use it's cleanest wood sources. It's not an accurate means of monitoring pollutants.

Finally, unreliable predicted emission levels are important because even by using the lowest prediction numbers, several of Senca's pollutants are just slightly below the levels that would require stronger pollution control.

In other words, continuous monitoring could lead to less emissions. At the very least, it will provide an accurate picture of the emissions being produced by the proposed power plant.