what church owns and maintains the park?

This, like all public parks, is run by the local Parks & Recreation Department. Part of your tax Hazeldale Park happens to be part of Tualatin Hills Park & Recreation District. Here's the link: http://www.thprd.org/parks-and-trails/detail/hazeldale-park Hope this is helpful! :)

City park

Hazeldale park is owned and maintained by Tualatin Hills Parks and Recreation Department.