(a) General rule.--If a municipal corporation is bounded by the nearest margin of a navigable stream and the opposite municipal corporation is also bounded by the nearest margin of the same stream, the middle of the stream shall be the boundary between the municipal corporations. (b) Prior actions unaffected.--Nothing in this section shall be construed to affect any boundary established prior to the effective date of this section between municipal corporations or repeal any local or special law contrary to this section.
Pennsylvania Legal Code