Just inside the entrance to Summerville's Wassamassaw Community Park are two fenced dog parks on either side of the road. The signs say that the one on the left (as you're entering) is for big dogs (> 20 lbs) and the one on the right (as you're entering) is for small dogs (< 20 lbs).
Both areas are roughly the same shape, long and rectangular, providing a good amount of room for long ball throws.
The park is pretty new (opened August 2008) so the grass is still largely intact, although there was a small muddy section near the middle that was probably started by a dog trying to dig something up. Looks like the park designers took drainage into account, as the ground slopes down toward a line along the middle of the park and towards a stormwater drain.
A few trees provide some shade, and several benches are available for people to sit on in both dog areas. There are also a couple of poop bag and disposal stations in each dog area.
One significant failing of the dog park is that there is only one water fountain, and it's located outside the large dog area. That means if you want to water your dog, you'll have to leash it, exit the park, get water and then go back in when you're finished. Or you can just wait until you're finished with the dog park and let your dog drink on your way out. Why the water was placed outside the dog area, I have no idea. I suspect the small dog area was put in as a bit of an afterthought, which would explain why there's no water fountain for the small dog area.
Not sure what the dog population is like in Summerville, but I'm sure once more people find out about this dog park, it'll be come very popular.
See the rest of the dog park photos here.
Here's a Google Map to the dog park
View Wassamassaw Park Dog Park in a larger map