I'm curious what is involved in connecting a 6" gravity sewer service to a 12" force main. The 6" service is for a restroom (2 sinks, 3 water closets, 1 urinal total) and a splash pad for a children's play area.
Also, be sure to check with whoever owns the 12 forcemain as you are designing your pump station. Some municipalities may not allow the connection of a forcemain into a forcemain.