; (B) modifying subsection (f) of that section to ensure that owners and operators use optical gas imaging monitoring pursuant to section 60.5397a of that title on a quarterly basis, unless the owner or operator receives approval from the Administrator, in writing, to use Method 21 of the Environmental Protection Agency (as described in appendix A–7 of part 60 of title 40, Code of Federal Regulations (as in effect on the date of enactment of this Act)) with a repair threshold of 500 parts per billion; (C) modifying 60.482–6a of title 40, Code of Federal Regulations, to ensure that the use of open-ended valves or lines is prohibited unless a showing is made that the use of an open-ended valve or line is necessary for safety reasons; and (D) modifying subpart VVa of part 60 of title 40, Code of Federal Regulations, to ensure that— (i) the term no detectable emissions is defined to mean an instrument reading of less than 50 parts per billion above background concentrations