On and after July 1, 1990, if, prior to an arrest for an offense involving a controlled substance, marijuana, or a dangerous drug, a public employee notifies the employee's public employer that the employee illegally uses a controlled substance, marijuana, or a dangerous drug and is receiving or agrees to receive treatment under a drug abuse treatment and education program licensed under Chapter 5 of Title 26 and approved by (1) the State Personnel Board in the case of employees in the classified service of the state merit system or (2) the public employer having management and control of the employee in the case of other public employees, the public employee shall be entitled to maintain the employee's public employment for up to one year as long as the employee follows the treatment plan. During this period, the public employee shall not be separated from public employment solely on the basis of the employee's drug dependence, but the employee's work activities may be restructured if practicable to protect persons or property. No statement made by an employee to a supervisor of the public employee or other person in order to comply with this Code section shall be admissible in any civil, administrative, or criminal proceeding as evidence against the public employee. The rights granted by this Code section shall be available to a public employee only once during a five-year period and shall not apply to any public employee who has refused to be tested or who has tested positive for a controlled substance, marijuana, or a dangerous drug.