Testing the Testers: Accuracy in Environmental Compliance is Critical

(Cochise, AZ) In the world of environmental compliance, it’s not enough to get readings that say you’re following the latest regulations.

You also have to show that your testing equipment is accurate and producing valid results.  And the only way to show that is to test your testing equipment.

That seems like a lot of testing.

“Yes, it is,” said Chris Determan, AzGT senior environmental specialist.

Determan and his team at the Apache Generating Station spent the better part of an entire work week with a crew from American Environmental Testing(AET) recently, checking stack emissions data gathered by AzGT equipment versus data collected by AET’s calibrated equipment.

“It’s called ‘relative accuracy test audit,’ or RATA testing, and we have to do it to make sure our instruments are reading correctly. It’s required as part of our air operating permit from the Arizona Department of Environmental Quality (ADEQ),” Determan said.

Day one, Monday, June 20, involved setting up all the gear and calibrating it in preparation for the data runs. Days two and three were spent making multiple data runs and sampling the stack emissions with probes.  Arizona Department of Environmental Quality staff were on site during day two to observe the testing, which is routine.

The AET teams gathered multiple samples to test for nitrogen oxide emissions (NOx), sulphur dioxide (SO2), carbon dioxide (CO2), and particulate matter. They also test for the amount of moisture in the samples, which has to be factored out of the test results to get accurate emission readings. They also test for total air flow in cubic feet per minute.

“We do 12 different runs for one test. We take 15-second samples at each port (in the stacks), then rotate to the next port and do it again. Each run takes about five minutes,” Determan said.

The multiple samples are averaged out to arrive at the final emission level data.

“Once (the AET technicians) get their numbers, we enter them into our program to compare our numbers to theirs, and they can tell us pretty quickly if we’ve passed – which means our equipment is sampling and testing accurately,” Determan said.

If the difference between the two sets of samples is 7.5 percent or less, the sampling equipment and data results are considered accurate.

Less than 24 hours after testing was completed, Determan received the results: we passed, in all areas.

Michelle Freeark, director of safety and environmental services, said the results reflect the “dedication of the team to what we do.”

“We have great employees who work every day to ensure we’re doing everything we can to achieve environmental compliance, and it’s apparent whenever we undergo compliance testing like this,” Freeark said.

“This fulfills our obligations for the RATA testing required in our air operating permit for another year,” Freeark said.