RATES OF CHARGE FOR SEWERAGE SERVICE. By Samuel A. Greeley, of Pearse, Greeley & Hansen, Consulting Engineers, Chicago, Illinois. 1. Statement of the Problem. At the present time, the cost of building sewerage works is commonly met by one of the three following methods: (a) By a direct charge or assessment against the property to be served. This method is termed a "local or district assessment," or a "local assessment based on benefits," and occasionally a "frontage. assessment." Individual property owners may pay their assessment or contribution in one initial lump sum, or in 10 or 20 serial payments. Generally, the municipality issues assessment bonds which are retired from the proceeds of the assessment. In any event, an annual payment for the sewerage works results. (b) By the issuance of bonds secured by the general credit of the community. An interest and sinking fund is set up for carrying and retiring the issue, frequently in 20 years. (c) By allotment from the general fund. This comprises an annual sum raised by general taxation. Operating and maintenance expenses are commonly defrayed by levying a tax therefore; but often no special levy is made and the annual expense is covered by an allotment from the general fund. Except by the method of an assessment based on benefits, the cost of sewerage service is thus distributed amongst the property owners in accordance with the assessed valuation of their property without direct regard to the use individual owners make of the works. In some cases this results in an unbalanced payment for the service. One user of the sewerage system may discharge relatively small quantities of weak or dilute sewage. Another user, paying the same annual tax, may discharge large quantities of strong sewage difficult and costly to handle. Attorneys have advised that such a situation constitutes discrimination in favor of the large user, although general community policy may justify the inequality. The question then arises as to how the cost of sewerage service should be equitably divided among the producers of the sewage for the use of the sewerage service. Two points are obvious. The cost should be spread over the population in a fair manner, and in such a way as to best foster the well-being and growth of the community. A charge or levy should be made (or a rate fixed) commensurate to the service rendered and this rate of charge should be fair, it should have no elements of discrimination and it should be sufficient to raise an annual revenue to meet the total annual costs. The fundamental aspects of this problem with citations of present day practice and experience are briefly stated in the following paragraphs. 2. Sewerage Works. Sewerage works in general comprise the following parts: Collecting Sewers Sewage Treatment Works Collecting sewers are designed to carry off domestic sewage, surface sewage, and industrial sewage. Such sewers are built either as combined sewers to carry off all the sewage in one system of pipes, or as separate sewers in which the surface sewage and other innocuous wastes are collected in one system and the domestic, industrial and other strong sewages in another system of sewers. Surface sewage and sufficiently diluted sewage from combined sewers can often be discharged directly into the nearest and most convenient drainage. course. Domestic and other strong sewages generally require some degree of treatment before they are discharged into a stream, lake or ocean. Where the land is flat, pumping is often required. Both pumping stations and sewage treatment works add to the annual cost and are increasingly important parts of the sewerage works. 3. Financing Methods. When the construction of sewerage works is paid for by an assessment based largely on benefits, the procedure constitutes a charge for the service rendered, in so far as benefits are a measure of the use made of the sewers, or of the service rendered. But the assessment covers only the fixed or capital charges and not maintenance and operation. Such a service, use, or benefit charge may have been in the minds of the framers of the various local assessment acts. These acts are, many of them, a quarter of a century or more old in point of origin and their framers could not have embraced the entire cost of sewerage works maintenance and operation with the then meagre experience with sewage disposal. When the cost of sewerage works is met by a tax levy based on assessed valuation to cover bond interest, sinking fund and operating expenses, the sewerage service becomes a community enterprise in contrast with the individual charge for use characteristic of water, gas and electric service. 4. Approximate Cost Data. The problem can be better visualized with some general approximate cost data in mind. Local conditions vary so much, that only general figures can be given. Collecting sewers for all kinds of sewage cost in the neighborhood of $4.00 to $5.00 per front foot of assessable property, which amounts to around 200 feet per gross acre in the sewerage district. If the density of population is 10 per acre at the time of construction, the collecting sewers on a combined basis will cost about $90.00 per capita. Estimated costs of several sewer systems proposed for the North District of Decatur, Ill., are shown in Table 1. Intercepting sewers have a much wider variation in cost. In the Illinois Sanitary Districts, intercepting sewers, exclusive of pumping stations, have cost from about $3.00 up to $25.00 per capita of the population at the time of construction. For purposes of illustration, I have used $12.00 per capita. Costs of sewage treatment works for average domestic sewage including pumping stations are more comparable for different communities. A few round figures are given in Table 2. These figures indicate that $15.00 per capita may be used for illustration. The total investment per capita of population at the time of construction is thus about as follows: Collecting Sewers Intercepting Sewers Sewage Treatment Works $ 90.00 12.00 15.00 $117.00 Present-day financing permits raising money through local bonds on a twenty-year sinking fund basis for an equal annual payment of about 7.5%. The construction of sewerage works thus costs about $8.78 per capita per year. For intercepting sewers and sewage treatment works only, the annual cost is $2.03 per capita for the fixed charge. Thus the cost of sewage disposal comprising intercepting sewers, pumping stations and treatment works is commonly only a small portion of the total cost of the sewerage works. TABLE 1-RATES OF CHARGE FOR SEWERAGE SERVICE Cost of Sewers Per Front Foot as Estimated for the North Side Sewer District, Decatur, Illinois Cost of Sewers Fer Foot Approximate Capacity of Sewers Cubic Feet Per Second Per Acre |