In most cases such a location would be chosen in any event, because of the necessity for obtaining cheap land, since considerable areas are required.

The cost of filtration plants cannot be estimated very closely without definite knowledge of the amount of grading necessary, and of the local cost of sand, gravel, broken stone, coke and similar materials. Each acre of filter five feet deep contains 8067 cubic yards of filter material, and this has in most plants cost from $1 to $2 in place. In a considerable number of plants fine sand filters are made by stripping the top soil from natural

sand beds and placing under-drains by trenching. In coarsegrain filters, however, this is not possible; unless a bed of coarse and perfectly clean gravel be available for a sprinkling filtera formation which is very rare. The distributing pipes and nozzles for 10 acres of sprinkling filter at Columbus, O., cost $27,700, and the filtering material in place (80,120 cubic yards) cost $125,800. Six septic tanks in the same plant having a combined capacity of 8,020,000 gallons cost $66,730, of which $48,070 was for reinforced concrete, $12,530 for sluice gates, and the balance for earth work, scum boards and miscellaneous. The total cost of septic tanks, sprinkling filters and settling

basins, with gate house, piping and all appurtenances, for purifying 20,000,000 gallons in 24 hours cost $456,350 or $22,820 per million gallons per day. The following table, compiled from data collected by the Ohio State Board of Health, gives the cost and other data of the plants in that State:

TABLE NO. 26

DESCRIPTION AND COST OF MUNICIPAL PURIFICATION PLANTS IN OHIO

(From Report of Ohio State Board of Health, 1908)

ART. 86. SEWAGE TREATMENT PLANTS IN THE UNITED STATES

The table given herewith, prepared by the Author, is believed to be the only one ever compiled which gives anything like a complete list of the sewage disposal plants in the United States. The information was obtained from State boards of health when possible. Where obtained from other sources, this is indicated by an asterisk.