Invalid Stack Test and Opacity Excursion at a Foundry
Ashford Foundry operates a cupola with a baghouse. Its Title V permit limits particulate matter to 0.05 gr/dscf and opacity to 20%. The permit requires annual stack testing at no less than 95% of the maximum process rate. In June, a contractor runs the test at 92% of maximum rate because a production line is down. The baghouse has a known torn bag; the contractor notes 'visible haze' but does not run Method 9. The laboratory reports PM at 0.058 gr/dscf and an isokinetic sampling rate of 85%. The opacity transmissometer during the test averages 18%, but the chart shows a 9-minute period at 26%. The plant manager wants to submit the test as 'substantially compliant' and delay any repair until the next scheduled shutdown in November. The permit requires deviation reports within two working days and a written report within 14 days.
1. Is the June stack test valid evidence of compliance? Discuss load, isokinetic rate, and bag condition.
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The June test is not valid evidence of compliance. The permit requires testing at no less than 95% of maximum process rate; 92% is below that, so the test did not represent the permitted operating condition. The isokinetic sampling rate of 85% is outside the normally acceptable 90–110% range for Method 5-type sampling, which means the PM result may be biased and is not a valid compliance determination. The torn bag means the baghouse was not operating as designed; that may be a worst-case condition, but it does not cure the other deficiencies.
The reported PM of 0.058 gr/dscf is above the 0.05 limit, but because the test is invalid, the facility should not treat it as a confirmed violation or as proof of compliance. It is an indication that the baghouse needs repair and that a valid retest is required. The contractor's 'visible haze' note is not a Method 9 observation. The plant manager's 'substantially compliant' label has no regulatory basis. The facility should repair the bag, then retest at ≥95% load with acceptable isokinetic rates, following the permit's test protocol and providing advance notice to the agency.
2. How should the opacity data and the 9-minute period at 26% be handled, given no Method 9 was run?
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Opacity is limited to 20%. The transmissometer average of 18% is below the limit, but the 9-minute period at 26% is more important. Many permits express opacity as a 6-minute average; a 9-minute period at 26% would likely produce at least one 6-minute average above 20%, which could be a violation. Whether the transmissometer data can be used for compliance depends on whether the monitor is certified and the permit specifies it as the compliance method. If it is not certified, Method 9 is the reference method, and the contractor did not run one.
The facility should review the continuous opacity data, the monitor's calibration and quality assurance, and the averaging period in the permit. It should not ignore the 26% period. If a certified observer can make a timely observation, do so; otherwise, document the data and investigate the cause (torn bag, startup, etc.). Report the possible opacity exceedance as a deviation if the permit's averaging method shows an exceedance. The 'visible haze' note supports the need for investigation but is not a substitute for Method 9.
3. What reporting and corrective actions are required, and what interim measures should be considered if repair waits until November?
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The permit requires a deviation report within two working days and a written report within 14 days. The two-day report should cover the invalid test, the torn bag, the PM result above the limit, and the possible opacity exceedance. The written report should include root cause, corrective action, and a retest plan. The facility should not wait until November to repair a known torn bag if it is causing exceedances or visible emissions. Interim measures could include reducing production, increasing baghouse inspections and bag-leak detection, monitoring pressure drop, and conducting daily visible-emission checks by a certified observer. If the repair truly cannot be done sooner, the facility should document why and propose interim controls.
The retest should be conducted at ≥95% of maximum rate, with acceptable isokinetic sampling, after repairs, and with proper notification. Records of the test, lab data, calibration, and corrective actions should be retained. If the agency asks for the June data, provide it with the explanation that it is not a valid compliance test. Do not submit it as a passing test.