Just in case you weren't aware don't disregard anything as "not possible in this area". Hampton Park has seen many activities through it's loooong history. At one time there was a city zoo there!
As a side note, if you didn't know already be VERY cautious about detecting on Charleston City property. They have some very strict and specific laws about detecting. They can't say anything about private property detecting (as long as you have owner permission of course!), but they have a pretty stiff penalty; $500, 30 days in jail or both as well as the ability to seize and destroy your equipment upon conviction. The specific verbiage reads: "Treasure hunting. Metal detecting and/or digging in public parks, public rights-of-way, and playgrounds is prohibited. " They have some HIGHLY anal ordinances in general there, and they're not hesitant about enforcing them.