Sewage Pump - Is Rainwater Seepage Normal?

Our house has a sump pump and a sewage pump. I replaced a failed sewage pump last fall with a Zoeller sewage pump and soon began noticing when it rains the pump runs. Perhaps our previous pump did the same thing and we only notice this pump because of its increased horsepower. Is it normal to receive rain seepage in a sewage pump basin?

Thanks, Dave