I don't know when this park actually closed, but I used to drive by the ACTION MOUNTAIN sign for years. I left the area in 1998, and I think the sign was still out (advertising season passes) at the entrance where an apartment complex now sits. As a teenager in high school in the early 90s, our cross country team ran in the woods up there one time, I believe we entered the woods from Blackwood/Clementon road (on the way to Camden County College in Blackwood). After getting lost (the woods were still very dense at that time), we ended up of what was Action Mountain. We could see the skyline of Philadelphia while looking down at the remnants of the park. There were old water slides, plenty of graffiti, and evidence of arson, but I don't remember anything from the "Ski Days". Although one could see large concrete blocks of cement that could have been for the ski lift or t-bar. Sadly, by this point, I think the park was a popular destination for partying and the growing of marijuana.
I meet a guy once who was a life guard at the park who told me a funny story about a fat guy making one of the slides impassable. A teacher I had also mentioned there used to be a lake back in that area where he took his son to swim?
I'd love to read more about the area/park, but I have found nothing except information on Pine Valley, the golf course which currently occupies the land. If anyone has a link to more info, I'd be very appreciative!