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EPA revises fugitive methane emission reporting rules

Hydrocarbon Engineering,

On December 23rd the EPA published a final rule revising fugitive methane reporting requirements for local gas distribution under the greenhouse gas reporting rule Subpart W. Subpart W requires natural gas distribution systems to annually report estimated gas leakage using equations and emission factors for mains, services and meter/regulator stations specified by EPA. APGA is pleased that EPA is not requiring utilities to conduct actual measurements of gas leaks, even though the estimation methods specified in Subpart W are quite complex and result in leakage estimated that bear no relationship to reality. APGA has created an Excel spreadsheet that allows members to enter main mileage, number of service lines and information on meter/regulator stations and let the spreadsheet perform the Subpart W calculations. Only systems that have estimated emissions over 25 000 t of CO2 equivalent must report. The first reports for calendar year 2011 are still due by March 30th 2012.

EPA made some significant changes from the rule it proposed on September 9th 2011. Emission factors for mains, services and meter/regulators have been lowered slightly because EPA used a different base pressure and temperature than used in gas industry standards. More significantly, EPA will allow utilities to use up to a 5 year cycle for conducting leakage surveys at gate stations where they receive gas from transmission pipelines. Under the original rule and the September 9th proposal annual leakage surveys were required to count the number of leaking components that is an input into EPA’s estimation calculations. The five year cycle is intended to match the existing leakage survey requirements of pipeline safety rules.

The downside of the five year cycle change is that EPA has also revisited its calculation equations. In attempting to update the APGA Subpart W calculator APGA discovered what we believe are errors and/or omissions in EPA’s calculation methods. APGA has contacted EPA about the concerns and is awaiting a reply. The good news is that it appears that the new calculation methods produce the same results as the prior methods, meaning that APGA members that used their Subpart W calculator and determined that they did not exceed the 25 000 t reporting limit will also be under the reporting threshold using the new calculation method. APGA has, however, removed their Subpart W calculator from the website until it can be updated with the new calculation methods.

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