I understand you weren't asking about minimums but I threw that in there to be thorough. If I'd been more thorough, I'd have also said that your takeoff alternate needs to be listed in C070. In any event, I will say again what I thought I was pretty clear about the first time. A takeoff alternate is listed for the sole purpose that should an aircraft have an emergency (engine failure) after departure, they have a legal alternate listed within the time/distance according to the regs.
121.197 says "In the case of an alternate airport for departure, as provided in §121.617, allowance may be made for fuel jettisoning in addition to normal consumption of fuel and oil when determining the weight anticipated at the time of arrival"
However, in the event of an emergency, which is what the takeoff alternate is intended for, 121.557 overrides all.
If you need further clarification on this, I'd suggest calling your local dispatch fed... good luck