The whole cost of such alterations and improvements, or any part thereof, as may be agreed upon in the contract between the city and township, may be collected from the owners of property within the city, borough, and within the township, abutting along the line of the improvement, by an equal assessment on the foot front. Any portion of such cost not assessed against abutting property shall be paid one-half by each of the municipal divisions joining in the improvement.
53 P.S. § 1864