SPOKANE, WA - The city of Spokane is taking a prehistoric approach to to homelessness. The city has purchased $150,000 in centuries-old basalt rocks, which will be strewn under I-90 overpasses to deter homeless people from setting up camp, according to the Spokesman Review .

It's not punishment, city officials told the newspaper. The rocks are being placed under I-90 overpasses as a form of encouragement, so homeless people head instead to homeless shelters. The Spokesman Review spoke to the City Council president, who noted that the homeless under I-90 are of concern to local business owners.

The rocks were dropped for a cost of $150,000, and city leaders say it's just one of many steps Spokane is taking to get people off the streets and into the shelter system, which is open 24 hours a day, seven days a week, due in part to city funding.

City Council President Ben Stuckart said he supports the boulder placement as part of a larger project to get homeless people to take advantage of homeless services. He added that the homeless people below I-90 have raised concerns among nearby business owners.

As the Spokesman Review reported, cities around the world have used environmental enhancements to rid public spaces of un-sheltered people. In July, for example, Tacoma made outdoor camping illegal in the city. If you violate Tacoma's ordinance, you could get a $1,000 fine or get sent to jail - although Tacoma police have been instructed to guide public campers to shelters.