Finally, review your application before submission to ensure all sections are complete. To assist Contra Costa County in its commitment to Equal Employment Opportunity, applicants are asked to voluntarily provide the following information.You may complete an on-line application at the Contra Costa Human Resources Department at 651 Pine St., 2nd Floor, Martinez, CA 94553. Customize in minutes. An incomplete application packet may disqualify an applicant. Do you work in Contra Costa County? Make adjustments to the sample. Utilize the upper and left panel tools to modify Contra costa credentialing application form. To complete the application, you will need to upload photos.