Mercer, PA — (June 29, 2103) — Due to wet grounds and the threat of future storms, the races and fireworks set for June 29 have been cancelled. Mercer Raceway Park will be back in action on July 6 with the UNOH All Stars. The Approved Toilet Rentals 358 Modifieds and the Big Daddy’s Speed Center/Rock Concrete Modified Lites will have the night off.