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July 15, 1977 Interpretative Ruling: Allowable Emissions Baseline 25.3The emission offsets should generally be made on a pounds per hour basis when all facilities involved in the emission offset are operating at the maximum expected production rate. Use of pounds-per-hour should help negate false emission offset credits that would result from the use of annual emissions and low annual capacity factors. Since the use of annual emissions may also be appropriate, it would be advisable to use the historical annual capacity factor for the source providing the offsets.
The secondary emissions from the electric power generation needed to supply a new source is not required to get offsets. Since the additional electricity could presumably be generated anywhere on the power supply grid, the amount and location of the secondary emissions might vary significantly and do not meet the test of footnote 3 of the interpretive ruling.