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The easiest way to do this is to set up a new fitbit account and add your Surge as though it were a brand new device.
This would require using a different email address though. If this is not an option then you'd first need to change the email address in your existing fitbit account to something random which will free up the address to be used in your new account.
If you'd rather reuse your existing account and email but just clear the data then you'd to contact customer support and ask them to do it for you: contact.fitbit.com