Conn. Gen. Stat. § 47-52: When dividing line is a stream.

When the dividing line is a stream or pond, which does not take the place of a sufficient fence, and it is impracticable to make the fence in the line, if either party refuses to make a division fence on either side, two selectmen of the town shall, on application of either party, determine on which side of the stream or pond the fence shall be erected and maintained, or whether partly on one side and partly on the other, and what part each shall make and maintain, and deliver their determination in writing to the parties. If either refuses to make and maintain his part of the fence, the other may do so and recover the expense from the party so refusing.