Lessons learned about monitor performance from Acid Rain Program Emissions data

Affected utilities began collecting emissions data for allowance accounting under the Acid Rain Program in January 1995. The monitor quality assurance requirements and the missing data substitution procedures are major tenets of the program. This paper highlights some coarse statistics from a preliminary analysis of relative accuracy results and the amount of missing data substitution for SO2, NOx, and flow monitors. Relative accuracy test audit (RATA) results from 1/1/95 through 6/30/96 are examined. Of all RATAs performed, 98.1% were passed and 94.5% resulted in the monitor meeting the reduced frequency standard. The analysis of missing data considers only data from second quarter 1996 (4/1/96 - 6/30/96). 5.32 million hourly records were reported, with missing data substituted less than 3% of the time and an average availability for all monitors of 96%. The median percent monitor availability reported for all SO2, NOx, and flow monitors at the end of the quarter was an even higher 98%.