The rules for interpretation of district boundaries shall be as follows:

1.   Where a boundary line is shown as approximately following the centerline of a street or highway, a street line or highway right-of-way line, this centerline, street line, or right-of-way line shall be construed to be such boundary. The boundary line will be changed automatically whenever the centerline, street line, or highway right-of-line is changed, provided that the change does not exceed 20 feet.

2.   Where a boundary line is shown as following a lot line, such lot line shall be construed as the boundary.

3.   Where a boundary line follows a stream, such boundary shall be deemed to be the centerline of the stream. For any body of water, the regulations of the most restrictive adjacent district in which it is located shall apply.

4.   Where a boundary line is shown as approximately parallel to a street, highway, stream, or railroad line such boundary shall be construed as being parallel and at such distance from the centerline, as indicated on the zoning map.

5.   Where a district boundary line divides a lot which was held in single and separate ownership at the time the boundary line was established, the use regulations applicable to the least restrictive district shall extend over the portion of the line in the more restrictive district a distance of not more than 30 feet beyond the district boundary line.