Table No. LIST OF TABLES, Page. 55 ..... 56 70 72 Urban Population of the United States VI. Illustrating Monthly Variation in the Con- VIII. Hourly Variations in Water Consumption... 73 74 VII. Illustrating Extreme Daily Variations in X. Water Consumption at Louisville, Ky.. 79 81 XII. Comparison of Sewer Gaugings.. 84 XIII. Gaugings of Water Street Main Sewer, Kal- 89 XIV. Illustrating Effect of Increased Section, the 95 Volume of Discharge Remaining the Same 99 XVI. Minimum Velocities and Grades in Circular Sewers... 105 XVII. Showing Maximum Rate of Sewage Flow... 109 112 XIX. Comparing the Discharge in Various Cases as Given by Different Standard Formulæ 125 XX. Showing Increased Frictional Head Re- Bids on Sewer Construction, West Troy, N. Y. Bids on Sewer Construction, Dayton, Ohio.. Cost of Thirty-Five Sewerage Systems. Actual Cost of Labor and Material.. XXXII. Actual Cost of Labor and Material... XXXIII. Actual Cost of Labor and Material. XXXIV. Actual Cost of Labor and Material. The Separate System of Sewerage. CHAPTER I. INTRODUCTION. "Sanitary Engineering" has been defined as that branch of engineering which has for its object the improvement of the health of towns and districts, by bringing to them a supply of those things which promote health, and carrying from them those things which are injurious to it. The three principal requirements for the promotion of health are wholesome food, pure water, and pure air. An abundant and cheap supply of food is best secured by perfecting the means of transportation by land and water. Pure water may be supplied by suitable water works. The air is kept pure by removing from the districts those things which pollute it: that is, by removing all garbage, and by carrying out a proper system of drainage and sewerage. Although all of these works contribute to the health of a district, yet the subdivision of labor in these times has increased the number of specialties in the engineering profession and has limited the field of the Sanitary Engineer. By common consent the engineer who plans and executes works for improving the means for transportation is called a Civil Engineer; the engineer of a system of water works is called a Hydraulic Engineer; leaving the Sanitary Engineer the task of removing from any locality whatever may be detrimental to health; thus assigning to him the roll of scientific scavenger. Man himself is the principal cause of the defilement of his surroundings. His presence brings pollution to earth, air and water. Nature provides a remedy which is efficient only to a limited extent. Refuse from the animal kingdom is food for the vegetable kingdom. But when human beings congregate in masses nature can no longer meet the demands. In country districts, where the population is sparse, the disposal of excrementitious and refuse matter is easily managed by each householder in his own way. And even if that way be unadvisable the only sufferers are himself and those of his own household, and no one else will care to interfere. The methods usually there adopted, however, become very objectionable wherever the people congregate in large numbers. The conditions of living become changed. The sanitary condition of the immediate surroundings of each individual concerns not only himself, but the whole community in which he lives; and what was before a personal matter now becomes a question of public policy. In all densely populated areas, as in large villages and cities, the disposal of the solid and liquid refuse becomes a serious problem. The Mosaic regulations (Deut. xxiii, 1213) can not be enforced, and to store the filth of a city within the city is simply to invite disease and death. The use of the pits, dug in the earth, as receptacles for refuse, is in every way objectionable. The soil becomes polluted with sewage, and the air is filled with the noxious gases arising from the sewage soaked earth, and from the putrefying masses in vaults and cess-pools. The decomposition of so much refuse in such close proximity to the dwellings is detrimental to health in two ways. It uses up the oxygen from the air, and loads it with pestilential gases. If cesspools are used at all, they should be water tight. This necessitates the constantly recurring trouble of carrying |