profile, on which are plotted the surface grade and the sewer. Since for the original profile elevations were in general taken at 100-foot intervals only, and as a check on these, the elevation of the surface should be taken and noted at each gradeplank when grade is being given for sewer construction.

The depth of each manhole, lamp-hole, and other appurtenance should be obtainable from the profile, but as a check each should be measured with a levelling-rod or tape. Each manhole, lamp-hole, flush-tank, and inlet should be designated by a number, by which it is referred to. It is almost impossible otherwise to correctly count and keep track of these, especially the manholes, so many of which are each common to two lines of sewer.

Inlet-connections may be measured from their upper end Whatever the limits to be taken they should be carefully set forth in the specifications.

to the shoulder of the branch or slant.

If

Rock should be measured before excavation in most instances, although its original surface can often be judged afterward by that showing along the sides of the trench. the rock-surface is fairly even and uniform readings may be taken at intervals of 10 feet; but if it be uneven and jagged these should be, not at regular intervals, but wherever necessary to give accurate results. All measurements, whether of earth, rock, sewer, or manhole, should be taken to tenths of a foot. It is customary to allow the contractor a certain cross-section of trench, and pay him nothing for excess excavation nor deduct for a less area of section. But the trench at the bottom should be kept the full width called for.

A final-estimate book should be kept, in which is entered an exact statement of each piece of work as it is completed, but not before then. The measurements should be classified under the items for which bids were received, and the location of each given; thus:

A pocket field-book should be constantly at hand, in which are entered all measurements taken, the points of the beginning and ending of "sheathing left in trench," of sub-drains, of foundations, the location of all Y's, the details and quantities of "extras," the location of underground structures for future reference, and the date of beginning and ending of construction on each stretch of sewer. These notes should be copied every evening into an office-book, since a loss of these data would be serious and irreparable. The general appearance of such notes is shown on page 259.

It is well also to have a pocket copy of the profile of each street, showing the sewer as designed, with size, grade, elevation, location of manholes, flush-tanks, and other appurtenances. This method of taking these data to the field for use seems to be more complete and convenient than copying them down into a notebook.

According to most contracts the contractor must be paid monthly, and for this purpose monthly estimates must be made by the engineer. He should estimate each month the total amount of each item completed to date, from which is deducted the total estimated the month previous, the difference being the amount performed during the month. This method prevents the carrying ahead or accumulation of any errors which may be made in any one monthly estimate, which errors are liable to occur owing to the fact that such estimate

must often be made hastily and simultaneously with the oversight of construction-work. Uncompleted work must be estimated according to the judgment of the engineer as equivalent to so much completed work of the same class.

For the final estimate all measurements as given in the final-estimate book should be checked with the field-book and in every other way possible, and every precaution taken to secure absolute absence of error in measurements or calculations. As a check upon the estimate it would be well to obtain from the contractor the bill of pipe, brick, and iron used by him upon the work, allowance of course being made for material condemned or unused.

ART. 68. FINAL INSPECTION.

He

The final inspection of the work before its acceptance from the contractor should be thorough, and made by the engineer in person or by an experienced, trustworthy assistant. should enter every flush-tank, manhole, inlet, or other appurtenance sufficiently large for this, taking its dimensions, noticing whether the head or grating is at the proper level and substantially set, the brick-work smooth, the form regular, the steps properly set at the prescribed intervals, that no ground-water leaks through the brick-work, that pipes passing through the walls are properly built in with surrounding "bull's-eyes;" that the bottoms of manholes are formed according to instructions, the invert-channel being straight or with a uniform curve, of the proper width, and its grade uniform through the manhole and of the proper elevation, and that the benches have the specified slope; also, if there are subdrains, the hand-holes should be inspected, and these as well as the manholes should be free from dirt. Lamp-holes should be inspected by lowering a lamp into each and noting whether it is straight and vertical, and by seeing that the heads are

If

set according to specifications and at the proper grade. Flush-tanks should be filled with water and tested for tightness for at least 24 hours, during which time the water-level in them should not lower more than one or two inches. automatic flushing apparatus is set it should be tested with a stream sufficiently small to fill it in not less than 24 hours. To expedite the test it can be rapidly filled and discharged once to test its proper working, then rapidly filled three quarters way to the discharging-point and the inflowing stream cut down to the rate above mentioned, to see that the siphon does not "trickle," but holds the water until the height is reached calculated to cause a complete siphoning of the water in the tank.

Every foot of sewer and inlet-connection should be inspected. Sewers 24 inches or over in diameter should be entered and each joint inspected, if they are pipe sewers, to see that no jute or cement protrudes into the sewer and that there is no leakage. In case of the former the protruding cement or jute should be removed; and if there is leakage this should be stopped, for which purpose there may be calked into the joint from the inside dry cement immediately followed by jute, cloth, or similar material to hold it in place until set; or wooden wedges, or tea-lead may be used. If these or similar methods fail it may be necessary to uncover the pipe and apply additional cement on the outside, backed and supported by concrete if necessary. Any cracked or broken pipe should be dug up and replaced. The branches should be examined also to see that a water-tight cover is in each one which is not already connected with a house-drain.

If the sewer is of brick the brick-work should be smooth, with struck or pointed joints and without any cracks. To determine whether the form and dimensions are as specified a skeleton templet may be used. If the sewer is circular this may consist of two light rods, each of a length equal to the