911 services shall be designed to meet the individual circumstances of the Islands of St. Croix, St. John, St. Thomas, and Water Island and the public agencies participating in the 911 system. However, standardized processes between the two call centers, one on St. Croix and one on St. Thomas, will ensure optimal service and back-up capability in case of high call volumes, or the temporary incapacity of one center due to catastrophic weather or other circumstances. Every system shall be designed so that a 911 call is processed by means of one of the methods defined in section 1071 of this chapter, namely, direct dispatch, relay, or transfer; provided, however, at least two of the specified methods shall be available for use by the PSAP receiving the call.