Contra Costa County - California has an employee rating of 3.7 out of 5 stars, based on 295 company reviews on Glassdoor which indicates that most employees have a good working experience there.
As a condition of employment, finalists for full-time, part-time, extra help, contingent workers (i.e. agency temporary employees), and temporary positions will be required to successfully pass pre-employment background investigation, medical examinations, drug screening, Department of Motor Vehicles (OMV) license ...
Typically, a drug screen failure will result in a lifetime ban -- unless you are a professional athlete. If it's a pre-employment drug screen failure, your application file will be flagged, preventing you from being considered for future positions.
California law allows an employer to require a "suspicionless" drug test as a condition of employment after a job offer is made but before the employee begins working.
Employers often conduct drug tests during the hiring process, but they may also reserve the right to drug test periodically. If an employer suspects that an employee is using drugs, they can schedule periodic drug screenings.