You are describing a fairly common application. A lot of homeowners will install 2 sump pumps in their sump basin for this type of situation. The main pump will be set to activate at about 12 inches of water and the secondary pump will be set to activate at about 14-16 inches of water in the event the main pump cannot handle the amount of water coming in. Please note however, that you will also need protection in the event of a power outage. In that case, your best defense is a higher output BATTERY BACKUP SYSTEM or a small STANDBY GENERATOR.