Q310. For subpart AA in e-GGRT, on the screen to enter CO2 emissions from makeup chemicals, why are there two boxes to check?

A310. In accordance with the procedures for missing data for subpart AA (section 98.275), owners or operators are required to keep records of the procedures used to account for missing data and the boxes to check in e-GGRT are provided to indicate if a substitute value was used for the annual quantity of CaCO3 and Na2CO3 to calculate the CO2 emissions from makeup chemicals. Similarly, other subpart AA screens provide check boxes to indicate if substitute values were used for the mass of spent liquor solids used to calculate biogenic CO2, CH4 and N2O emissions using equations AA-1 and AA-2.