Ohio EPA Seeks Additional Information When Permitting Gas Dehydration Facilities
Ohio EPA’s Division of Air Pollution Control has issued a new guidance document directed at applicants for air permits associated with dehydration facilities (primarily midstream companies and natural gas compressors). The guidance notes that Ohio EPA has recently received applications for dehydration facilities that did not contain sufficient information for the agency to process the applications. To avoid problems in processing permit applications for such facilities in the future, Ohio EPA has detailed additional information it seeks about their emissions, above and beyond the information that is required by the application form itself. Specifically, Ohio EPA seeks the following:
More detailed information about the basis for emissions calculations
The application must include calculations of expected air pollutant emissions, including emissions associated with startup, shutdown, and maintenance operations. Supporting information must describe the basis for the data and any assumptions or safety factors used. For example, if expected maximum incoming gas flow rate is a parameter in the calculations, the application should explain how the maximum flow rate was determined. If controls are used, the application should provide a basis for the level of control assumed. The calculation methodology (e.g. AP-42, mass balance, E&P Tanks, etc.) should also be provided, as well as the actual emissions estimates resulting from the calculations.
Emissions associated with uncontrolled vent releases
Ohio EPA asks that applications for dehydration facilities describe each exhaust point (e.g., dehydrator flash tank vent, pressure relief valve, manual release valve, etc.) that is expected to experience periodic releases as part of the normal operation of the facility and whose operation is not already accounted for as part of an emissions source elsewhere in the permit application. Pressure safety valves that are only used to prevent catastrophic failures are not required to be included. For each exhaust point, the applicant must provide a company ID number, the equipment served by the vent or valve, the expected frequency and duration of venting, and the emissions expected as a result.
Process flow diagram
As part of the guidance, Ohio EPA clarifies that process flow diagrams submitted as part of a permit application should not be overly simplified and need to provide all of the information requested within Question 6 of the application. In addition, Ohio EPA asks that applicants provide a written explanation of the inlet and outlet materials, the chemical and physical processes that occur along the way, and the emissions that result from each item on the diagram.
The application must include an accurately scaled and detailed plot plan depicting the location of all process equipment, emissions units, and vent points that vent periodically during normal operation, as well as air pollution control equipment and property lines. If plans are not final at the time of the application, an initial plan should be submitted, followed by a revised plot plan once final designs are complete. In addition, the applicant should provide a scaled map, satellite image, or other depiction of the location of the closest occupied structure within one-half mile of the property line in each of the four compass quadrants (northeast, southeast, southwest, northwest).
Support for de minimis determinations
If the applicant determines that emissions from certain equipment will be de minimis and thus exempt from permitting, Ohio EPA seeks information about the method by which the applicant reached such a conclusion. This would include calculations or regulatory analysis undertaken in support of a de minimis determination. Ohio EPA notes that de minimis determinations for activities identified as “trivial” in Ohio EPA’s Engineering Guide #62 need no justification.
Uncontrolled emissions during startup or shutdown
Applicants should explain what uncontrolled emissions are expected to occur during startup and shutdown, the emission rate, and the expected duration of emissions.
Finally, Ohio EPA encourages permit applicants to work with their permit writer when seeking any new application.