In lieu of assessing the total cost of a particular project as herein provided, the Council annually between the first days of January and July of each year, may determine the average cost of installing water and sewer mains or lines and on the basis of such determination may make assessments of such average cost of any portion thereof during the following fiscal year beginning July 1. The average cost of such installation shall include the cost of the particular size and material of lines completed during the preceding calendar year. It also may include the anticipated increase in labor and materials costs based upon the average of such increases during the preceding five calendar years. The assessment of the average cost of such line shall not be made until after the particular assessment project has been completed. The purpose of this is to distribute before equitably the cost of the installation of water and sewer lines throughout the Town; to permit a property owner to know in advance what the cost of installation of water and sewer lines benefitting his property will be; and to permit the most expeditious assessment of cost against property after completion of the installation of such lines. The actual cost of acquisition of rights-of-way also may be assessed as a part of the cost of an individual project. If the right-of-way costs have not been determined and assessed with the assessment of the average installation costs at the time of the completion of the project, such costs may be assessed separately when they are determined.