I remeber considering that one last season. I don't think it has hook-ups. Certainly it didn't have electricity, which I thought was a bit comical as the park is run for the State Park system by Tacoma City Light.
You might want to look at the State Parks website, www.parks.wa.gov
. If you fill in approx dates and specify electricity water and sewer, you'll find the sites all flag as "Restricted" and when you look at specific site features, power isn't available.
I think I e-mailed the park system Q&A last year and they confirmed no electric.