Don't do it! I work for a remediation company and removal of contaminated soils is something we do (as well as dispose at our own facilities and other things). The soil you receive may have things that you can identify (roots/compost, asphalt, brick, concrete, debris, etc) and you can usually smell petroleum impacted soils. But there are many contaminates (PCBs, lead, arsenic, etc) that you cannot readily detect by sight or smell. And most urban fill has something nasty in it.
At the end of the day, the contractor that dumps something nasty on your property may not have any responsibility and you will be held responsible. Get some nice clean sand delivered from a material yard. Most big commercial quarries or yards have to be able to submit clean certifications to the state and big clients.