If folks are in Williston having arrived looking for a job and don't have one, they need to move on. Idle hands -- illicit drugs, fights, etc.
If folks are in Williston with a (high-paying) job, they need work with their employer for a place to stay, and/or hotel, motel, or man-camp.
It sounds very, very hard-hearted, but life is not fair, and the city is inviting additional problems, not the least of which is removing a recreational facility.
Helping folks move on can be done humanely with the help of a social worker and/or the clergy, with the funds that would be used for a homeless shelter to pay for transportation back home.