Korbin,
A cage around and over it sounds a good idea. I've recently been involved in some freshwater turtle research and found out that some turtles need the rain to soften the ground, so they lay their eggs. Apparently the soil in places, is just too hard for the turtles to dig into. It seems that the rain is the 'trigger' for the nesting to occur- they know its right to nest now.
It would be great if you could prevent the predation of these eggs by raccoons/skunks. We have trouble wih feral animals and non-native, introduced animals that dig up nests, as well as some native predators.
It probably would be a good idea to keep the grass clear of this nest. Do you know or have you been able to find out how long the incubation period is for these turtles?