Within 30 days after service of a request for production or such longer time as the department may permit, the recipient of the request shall serve on the department a written response with respect to each item requested, either stating that inspection and copying will be permitted as requested or objecting to the request and stating the grounds of the objection. Unless a request for production is objected to, the recipient of the request shall thereafter permit the inspection and copying requested by the department. (GC 12963.2)