I am confused by the voices used in these two sentences:
While there's a conceptual proposal on the table for a new Appleton Public Library in a mixed-use development, there are still plenty of details to be worked out and questions to be answered, Mayor Tim Hanna cautioned Monday. Source
As Sophie opened her garden gate, she looked in the mailbox. There was usually a lot of junk mail and a few big envelopes for her mother, a pile to dump on the kitchen table before she went up to her room to start her homework. - Jostein Gaarder, "Sophie's World"
I think both details and pile are objects of their respective verbs, work out and dump. But I don't understand why different voices are used in these two infinitive phrases?
Could anyone please kindly help me to understand this difference?