Section 52.277 - Oxides of nitrogen, combustion gas concentration limitations(a) The following rules are being retained to the extent that the new rules are less stringent than the previously approved rules:(1) North Central Coast Intrastate Region:(i) Monterey Bay Unified APCD. (A) Rule 404(c) submitted on February 21, 1972 by the Monterey-Santa Cruz Unified APCD and previously approved as part of the SIP, is being retained for sources combusting gaseous fuels. Rule 404(c) will be in effect for Monterey and Santa Cruz Counties only. Rule 404(c), submitted on November 10, 1976 by the Monterey Bay Unified APCD, will only be in effect for sources combusting liquid or solid fuels with heat input rates greater than 11/2 billion BTU per hour in the Monterey and Santa Cruz portions of the Unified APCD.(B) Rule 408(b), submitted on February 21, 1972 by the San Benito County APCD and previously approved as part of the SIP, is being retained for sources combusting liquid, solid, or gaseous fuels with heat input rates less than 11/2 billion BTU per hour. Rule 408(b) will be in effect for San Benito County only. Rule 404(c), submitted on November 10, 1976 by the Monterey Bay unified APCD, will only be in effect for sources combusting liquid, solid, or gaseous fuels with heat input rates greater than 11/2 billion BTU per hour in the San Benito County portion of the Unified APCD.42 FR 56606, Oct. 27, 1977