Two people who died in separate Contra Costa County crashes last week have been identified by authorities as Rachel Doron Arganek and Olga Yesenia Islas Plascencia. Arganek, 32, died in a solo vehicle crash in Walnut Creek early Thursday morning, according to police. The crash was reported at 5:06 a.m. near Rossmoor Parkway and Stanley Dollar Drive in the Rossmoor retirement community. Arganek was pronounced dead at the scene. No other details of the crash were provided by law enforcement. Islas Plascencia, 38, was driving a red Chevrolet Cruze Wednesday night when she collided with a blue Toyota Prius at the intersection of Willow Pass Road and Port Chicago Highway in Concord. Islas Plascencia was pronounced dead at the scene and the Prius driver was taken to the hospital but expected to survive. Both women were identified by the Contra Costa County Sheriff’s Office Coroner’s Division.