In answer to your question…..there’s a tent campground in Taylors Island which is about 35-45 minutes away. It’s attached to a mobile home park. It’s a bit sketchy, imho.
Now you didn’t ask but… RU really ready to camp in possibly rain/cold after spending $750 for the race and countless hours in training? I stayed about five minutes from the starting line in a really great AirBNB room for $100. There are still options for substantially less than that available now.
Whatever you do — good luck and have fun!