; and (ii) the general conditions of that miner’s assigned working section or other area where the miner is expected to work or travel. (B) Not later than 180 days after the date of enactment of the Robert C. Byrd Mine Safety Protection Act of 2017 , the Secretary shall promulgate interim final rules implementing the requirements of subparagraph (A). The Secretary shall issue a final rule not later than 2 years after such date. . 502. Rock dust standards (a) Standards Section 304(d) ( 30 U.S.C. 864(d) ) is amended— (1) by striking Where rock and inserting the following: Rock dust .— (1) In general Where rock ; (2) by striking 65 per centum and all that follows and inserting 80 percent. Where methane is present in any ventilating current, the percentage of incombustible content of such combined dusts shall be increased 0.4 percent for each 0.1 percent of methane.