Complex sentence: Since it first opened the site allowed free access to the park to all the atttactions.In 2009 an admission fee was introduced for all members of the public entering the site that had not purchased a wristband.
Split into simpler sentences: Since it first opened the site had allowed free access to the park. However, in 2009 an admission fee was introduced for all members of the public entering the site who had not purchased a wristband.