567—23.6(455B) Alternative emission limits (the “bubble concept”). Emission limits for individual emission points included in 567—23.3(455B) (except 23.3(2)“d,” 23.3(2)“b”(3), and 23.3(3)“a”(3)) and 567—23.4(455B) (except 23.4(12)“b” and 23.4(6)) may be replaced by alternative emission limits. The alternative emission limits must be consistent with 567—22.7(455B) and 567—subrule 25.1(12). Under this rule, less stringent control limits where costs of emission control are high may be allowed in exchange for more stringent control limits where costs of control are less expensive.