(a) Cluster systems are not authorized under this chapter after the effective date of these rules. Cluster systems may be authorized under other chapters of this title including Chapter 331 of this title (relating to Underground Injection Control).(b) Existing cluster systems may be repaired or altered under this chapter. However, the alteration may not result in an increase in the volume of the permitted flow or change the nature of the permitted flow. Existing cluster systems may be required to be authorized under other chapters of this title when the system has to be expanded or altered in a manner that increases the volume or changes the nature of the permitted flow.