In 2008, the Texas Commission on Environmental Quality (TCEQ) set out to discover impediments to meeting the state's attainment status for National Ambient Air Quality Standards (NAAQS). They determined that planned maintenance activities contributed the lion's share of emissions events and a new set of rules aimed at controlling emissions during planned maintenance was created for Maintenance, Start-up and Shutdown (MSS) regulations. Enforcement began in 2010 and initially focused on Texas refiners.
MSS rules revolve around more effective control requirements for all “major” planned maintenance activities, where compounds have a vapor pressure greater than 0.50 psi and a volume greater than 10 cubic feet.Major MSS activities require a Best Available Control Technology (BACT) to capture attendant hazardous vapor streams. Other key elements focus on related monitoring and reporting requirements. MSS rules apply to both permanent and temporary facilities:
Emissions from temporary facilities are authorized provided they:
MSS provides general guidelines for air monitoring equipment and procedures; vacuum truck requirements; and control device requirements. Those general guidelines are often modified according to the specific plant permit.
MSS requires that VOCs be measured using instruments that meet all EPA Method 21 requirements - with a handful of exceptions. Beyond Method 21, MSS guidelines call for monitoring VOC concentrations for at least 5 minutes; for vac truck applications, readings must be taken every 15 minutes. Breakthrough occurs at 100 ppmv.
MSS also prescribes increased recordkeeping, which must be consistent and detailed:
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