4. Availability of C ontrol E quipment

**Comment:** Some commenters believe that there will be a shortage of control equipment available to meet the proposed storage vessel requirements , and recommend revisions to the compliance deadline for storage vessels based on a variety of considerations, including the availability of control devices, lead time needed for manufacturer testing of their c ombustors to be compliant with the NSPS and time ne eded to install the compliant devices. **Response:** We agree that it will likely take some time beyond the promulgation date of the NSPS for combustor manufacturers to have control devices constructed, tested, documented and available for operators to install in efforts to comply with the storage vessel requirements of the NSPS. Under the final rule, operators are not required to conduct individual performance test s on combustors installed in the field if the combustor manufacturer tests and documents for the owner or operator that the model achieves a control efficiency of 95.0 percent. The time required for te sting and documentation is often longer than for a single model when manufacturers provide multiple models for varying applications based on capa city. We believe this testing and documentation program would require an “adjustment period” for manufacturers to be ready to supply the operators with the correct equipment they need.We evaluated whether controls other than combustors would

be available during this adjustment period. Although vapor recovery units can provide 95.0 percent control for storage vessels and are one means of meeting the storage vessel standards in the NSPS, VRUs cannot be used in every situation. For example, storage vessels l ocated remotely where there is no available electrical service may not be able to be controlled using VRUs. In addition, storage vessels with low concentration emission streams or fluctuating emissions may not be amenable to control by VRUs. In light of the above, we conclude that there is no BSER for storage vessel affected sources during the first year after promulgation, which we believe is appropriate for the adjustment period mentioned above. At the end of this adjustment period, we believe owners and operators should have no problem securing control devices that are manufacturer

- tested and have appropriate documentation for determining control efficiency. Accordingly, the final rule provides for a one - year delay beginning [INSERT DATE OF PUBLICATION IN FEDERAL REGISTER] before the 95.0 percent control requirement is effective. With regard to providing time for operators to establish the need for controls and install them where called for, the EPA agrees tha t some lag time may be needed after initial start

- up for the owner or operator to determine the long

- term productionlevel of a well and to procure the appropriate control

equipment. EPA evaluated the approach taken in the Wyoming rules for new sources, wh ich allows from 30 to 90 days for a source to achieve compliance, depending on the area of the state. Wyoming allows only 30 days in ozone nonattainment areas, 60 days for concentrated development areas or 90 days elsewhere in the state. EPA believes that taking a similar approach in this NSPS is appropriate for new storage vessels at wells sites with no wells already in production. However, for replacement storage vessels or additional storage vessels at well sites with one or more wells already in product ion, we believe the operator already should have information on liquid composition and throughput. This information would allow estimation of VOC emissions to determine applicability of control requirements and for acquisition and installation of a control device concurrent with the replacement or additional storage vessel being installed. In the final rule, for storage vessels constructed, modified or reconstructed at well sites with no well already in production, we have provided for a 30

- day period for throughput to stabilize and for the operator to estimate VOC emissions to determine whether a control device will be required. If VOC emissions are estimated to be at least 6 tpy, the operator is provided an additional 30 days for the control device to become operational. We believethat the Wyoming experience illustrates that this will be

sufficient time to size and obtain suitable controls.