Texas NSPS OOOO Storage Tanks in Parallel Compliance - Updated March 31, 2015
March 11, 2015

In an email dated March 10, 2015, the TCEQ discussed its enforcement discretion regarding NSPS OOOO storage tanks.  This was in response to the December 31, 2014, NSPS OOOO rule change that revised the definition of storage vessels (tanks). The new NSPS OOOO rule includes in the definition of a storage the following: “Two or more storage vessels connected in parallel are considered equivalent to a single storage vessel with throughput equal to the total throughput of the storage vessels connected in parallel.”  

 The new NSPS OOOO storage vessel definition clarifies the way crude oil, condensate and produced water storage tank(s) emissions are calculated to determine applicability. This impacts storage tanks already in service and TCEQ stated they must be reevaluated for applicability, emissions and controls. 

March 23, 2015 Proposed Changes to NSPS OOOO - Updated March 31, 2015

In a Federal Register Notice dated March 23, 2015, the EPA proposed changes to NSPS OOOO. One change proposed included amending NSPS OOOO to remove provisions in the rule regarding storage vessels connected or installed in parallel and to revise the definition of ‘‘storage vessel’’.

In the Federal Register Notice, EPA stated it was soliciting "comment on other approaches to help avoid or discourage installation or operation of storage vessels that would unnecessarily reduce the potential to emit (PTE) of a single storage vessel." and EPA stated, it seeks comments on, "other approaches to help avoid or discourage installations or operations of storage vessels that would unnecessarily reduce the PTE of a single storage vessel."

No guidance was given by EPA on compliance with the existing, promulgated storage tank definition in NSPS OOOO. 

 

Storage tank equipped with vapor reocvery tower (VRT) and vapor recovery unit (VRU).

HY-BON vapor recovery unit and vapor recovery tower for NSPS OOOO Quad O storage tank

 The new NSPS OOOO storage vessel definition clarifies the way crude oil, condensate and produced water storage tank(s) emissions are calculated to determine applicability. This impacts storage tanks already in service and TCEQ stated they must be reevaluated for applicability, emissions and controls.

Applicability Determination

Below shows a comparison of applicability calculations applying the clarified definition to storage tanks connected in serial manner and tanks connected in parallel. 

Storage Tank ID Serial Operation (tons VOC/year)            Parallel              (tons VOC/year)
1 5 25
2 5
3 5
4 5
5 5

 

The per tank emissions would be 5 tons VOC per year for the serial tanks and based on aggregating emissions in parallel connected tanks, the total would be 25 tons VOC/year. This means, based on the current definition, parallel tanks in this example would have to install emission controls since all 5 storage tanks would be considered one tank and total VOC emissions exceed 6 tons per year.   

 TCEQ Enforcement Discretion

TCEQ’s stated that it was granting enforcement discretion for Group 1 and 2 vessels in regards to applicability and compliance based on the new storage vessel definition. The discretion expires on April 15, 2016, and allows operators of parallel vessels additional time to reevaluate emissions and NSPS OOOO applicability. This applies to reporting, recordkeeping and control requirements. The scope of this enforcement discretion is limited to NSPS OOOO and applies only to vessels operated in parallel that were constructed, modified or reconstructed prior to December 31, 2014.

If a facility controls parallel storage tank emissions before April 15, 2016, and obtains enforceable limits below 6 tons VOC per year, then the storage tanks can avoid NSPS OOOO rule applicability for the tanks.

NOTE: This does not affect the compliance date of April 15, 2015, for Group 1 storage tanks that have been reported to the TCEQ prior to the rule change; or new tank batteries (after December 31, 2015). It only impacts those existing parallel storage tanks that are found now, based on the definition, to require emission controls for the storage tanks.

 

Action Items

Some action items for companies to consider:

  • Re-evaluate all storage tanks in parallel to determine rule applicability. This includes Group 1 and 2 storage tanks and can include direct measurement and calculation methods.
  • Document emissions and applicability determination.
  • Set up a timeline to comply. 
  • Install emission controls as required.
  • Get enforceable limits from TCEQ for storage tank VOC emissions prior to the April 15, 2016 date, as applicable. 

 

Let HY-BON help you stay in compliance with NSPS OOOO. We can assist by accurately quantifying emissions, “best in class” vapor recovery units (VRU), Vapor Recovery Towers (VRT) and enclosed combustors (ECU), and exceptional aftermarket support.