Addicts would bring their own drugs to the injection site.  I’m pretty sure these drugs had no manufacturing and distribution oversight by the FDA … more likely a Mexican or Columbian drug cartel.  Who knows the purity and potency of the drugs?  The addict could very well be injecting poison.
Secondly, a legal issue could be raised about Bellevue hosting an illegal and dangerous “Attractive Nuisance”.  Same legal argument when swimming pool owners do not adequately protect children from drowning via a fence etc.   A drug addict suffers brain injury or dies then sues the city. Does anyone not believe lawyers would take the cases of the addicts?