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PADEP Issues Draft Technical Guidance for the Determination of Significant Figures and Timeliness of Report Submittals

Posted: October 17th, 2012

Author: All4 Staff 

On September 8, 2012, Pennsylvania’s Department of Environmental Protection (PADEP) announced the availability of a draft technical guidance document entitled “Air Quality Program Guidance for Determination of Significant Figures and Timeliness of Report Submittal for Evaluation of Air Contaminant Emissions and Concentrations” (Document No. 273-4110-002).  The guidance document establishes conventions for rounding, truncation, and determination of significant figures for determining air contaminant emissions and ambient concentrations for potential to emit (PTE) calculations in air permit applications, source emissions testing, air quality modeling analyses, sampling, continuous source monitoring, periodic compliance reporting, and annual emissions inventories.  The guidance document also specifies the timeline for report submittals for source emissions testing and quarterly source monitoring reports.

Much of the guidance related to source emissions testing refers to other PADEP or U.S. EPA technical guidance, specifically the “Clean Air Act National Stack Testing Guidance” issued by U.S. EPA on September 30, 2005 for the determination of significant figures during source emissions testing.  The draft guidance also refers to PADEP’s Source Testing Manual Guidance Document for the timeline for the submittal of various reports and notifications.

Of particular importance to Facilities is the guidance related to continuous source monitoring and annual emissions inventories.  Relating to Continuous Source Monitoring, PADEP states that rounding and truncation conventions for reported data are established in the Continuous Source Monitoring Manual.  The draft guidance document states that PADEP will not round emissions data submitted by owners or operators in the quarterly source monitoring reports for the purposes of determining compliance with applicable emissions limits.  All emissions limits established to meet the requirements in 40 CFR Part 60 – Standards of Performance for New Stationary Sources may be reported to the same number of significant figures as the emission limits.  In the absence of any other conventions, PADEP identifies the number of significant figures that various averaging periods for gaseous emissions should be reported.  Hourly averages and daily, monthly, 365-day, 12-month, or annual sums or averages of reported hourly data should be evaluated to one (1) digit beyond the applicable emission limit contained in the Operating Permit or Plan Approval.  30-day averages of reported hourly data should be evaluated to two (2) digits beyond the applicable emission limit contained in the Operating Permit or Plan Approval.  Relating to annual emissions inventories, the historic standard conventions still apply.  PADEP states that emissions should be reported to the nearest hundredth ton for criteria pollutants.

Overall, the draft guidance document serves as a one-stop shop for all significant figure or rounding standards and conventions.  Upon finalization of this technical guidance document, facilities should adhere to these conventions to ensure consistency with PADEP expectations for all analyses and reports submitted.  Stay tuned to ALL4’s blog for any further updates on this technical guidance document.


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