The Washington State Department of Transportation (WSDOT) reported at 8:15 a.m. this morning that a rollover collision is blocking the Union Avenue on-ramp to westbound SR 16 in Tacoma. Washington State Patrol, fire and aid are on scene. WSDOT Incident Response is en route. For updated information, visit http://www.wsdot.wa.gov/traffic or call 5-1-1.