We are volunteering for the Oregon State Parks and volunteer or work 20 hours/week for a full-hookup site plus laundry privileges. Depending on the Park and the vacant volunteer site one can be doing combo job of interpretive/maintenance, cabin cleaning, yurt hosts, or whatever the opening is .. their volunteer openings website has openings listed by month, year and the parks in need of volunteers.
Send an email indicating your interest and wait for a response or call to get more information. We sent an email to one day use area which we learned has no sewer hookups and instead has a honey-wagon once a week, well that wouldn't work for us, so we emailed a thank you, but not interested due to too small black/grey tanks for taking showers, etc. to depend on a honey wagon.
BTW We no longer do electric, plumbing, or clean restrooms. For us this works. Normally we work 20 hrs/week, but have done 30 hrs/week, depending on what needs to be done and what we are doing as to whether it is enjoyable or not.