Books Online shows the permissions needed for CheckIdent

Permissions
DBCC CHECKIDENT permissions default to the table owner, members of the sysadmin fixed server role, and the db_owner and db_ddladmin fixed database role, and are not transferable.
Seems to be the same for TRUNCATE - interesting...

Permissions
TRUNCATE TABLE permissions default to the table owner, members of the sysadmin fixed server role, and the db_owner and db_ddladmin fixed database roles, and are not transferable.