The engineer’s preliminary report should contain a section devoted to the feasibility of one or more plans which may be explained in more or less detail with a statement of the cost and advantages of each. A conclusion should be reached as to the most desirable plan and a recommendation made that this plan be installed. Other sections of the report may be devoted to a history of the growing demand, a description of the conditions necessitating sewerage, possible methods of financing, and such other subjects as may be pertinent. The making of the preliminary plan and the design of sewerage works are described in subsequent chapters. =9. Estimate of Cost.=—In making an estimate of cost the information should be presented in a readable and easily comprehended manner. It is necessary that the items be clearly defined and that all items be included. The method of determining the costs of doubtful items such as depreciation, interest charges, labor, etc., and the probability of the fluctuation of the costs of certain items should be explained. The engineer’s estimate may be divided somewhat as follows: Labor. Material. Overhead. This may include construction plant, office expense, supervision, bond, interest on borrowed capital, insurance, transportation, etc. The amount of the item is seldom less than 15 per cent and is usually over 20 per cent of the contract price. Contingencies. This allowance is usually 10 to 15 per cent of the contract price. Profit. This should be from 5 to 10 per cent of the sum of the four preceding items. The contract price is the sum of these items. To this may be added: Engineering. 2 to 5 per cent of the contract price. Extra Work. Zero to 15 per cent of the contract price; dependent on the character of the work, the completeness of the preliminary information, the completeness of the plans, etc. Legal expense. Purchase of land, rights of way, etc., etc. The cost of the sewer may be stated as so much per linear foot for different sizes of pipe, including all appurtenances such as manholes, catch-basins, etc., or the items may be separated in great detail somewhat as follows: Earth excavation, per cu. yd. Rock excavation, per cu. yd. Backfill, per cu. yd. Brick manholes, 3 feet by 4 feet, per foot of depth. Vitrified sewer pipe with cement joints, in place, ... inches in diameter, 0 to 6 feet deep 6 to 8 feet deep 8 to 10 feet deep Repaving, macadam per sq. yd. asphalt per sq. yd. Flush-tanks, ... gal. capacity, per tank. Service pipes to flush-tanks, per linear foot., etc., etc.