OK, its roughly 200 acres of legal riding. You do need an offroad plate and insurance. The cops do a blitz a few times in the spring and give out tickets with no exceptions.
Its sandy loam and all sand in some areas. Perfect riding always and no mud, even if it rained the night before. Lots of woops, a couple of short, but steep hill climbs, straightaways and tight woods trails. A bit of everything.
I have no idea how many miles of trails but you can ride flat out for a full day and probably not see the same trail twice. Lots of intersections in the trails where you have to be very careful of other riders.
There's also another riding area about six miles away called St. Williams Forest. It run by the same park department, but its mainly tight woods trails; not as much fun.