Whenever a developer proposes to drain the development's storm and surface waters in accord with Section 10.485, Storm Water and Sewage, to a watercourse by means of connection with and use of existing drains at his own cost and expense outside of said development and if such adjacent drains and facilities have been dedicated to the public, the developer shall be required to pay a reasonable charge to the City for the connection and use of such outside public drainage system. Such cost shall in no event exceed the estimated cost to the developer of constructing independent exterior drainage facilities to adequately carry such waters from the development to the nearest accessible natural watercourse.