carbonate ion

Hi, I have a question to carbonate ion (CO3--). The calculated pH value is 11, TIC = 8 mg/l, alkalinity = 146 mg/l. CE-QUAL calculates the following carbonat spezies: CO2 = 0 mg/l HCO3- = 0,7 mg/l CO3-- = 0 mg/l At a pH value of 11 TIC has to be existent as CO3--. Why is the carbonate ion 0? And whereto is the TIC of 7,3 mg/l (=8 - 0,7) lost? Can anybody help me? With many regards Michaela