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.