Ordinarily the contractor will desire to place upon the street, along the line of the work, pipe, brick, sand, lumber, etc. This cannot be denied him, but he should be compelled to place and pile this material so as to interfere with travel as little as possible, and along only those stretches of street in which construction is to be begun within a week, or ten days at the outside. This material should be inspected as it is delivered, and that condemned removed at once.

Just before the work begins it is well to run levels carefully over all bench-marks to see that they have not been disturbed and to check previous levelling; also to establish new ones if necessary. It is desirable to so place these that one of them can be seen from the instrument when set up for giving grades to any part of the work. They should be accurate within at least .003 of a foot.

ART. 62. OTHER PRELIMINARIES.

Final arrangements should now be made for the oversight of the work, the proper instruments obtained, engineering and inspecting assistants engaged, an office or other headquarters arranged for, notebooks and blanks obtained for making and preserving records, final arrangements made as to right of way across private property and along county roads or others not controlled by the city or village.

Arrangements should be

made also for locating the branches for house-connections at
the points desired by the property-owners.
For this purpose
it is well to publish in the paper or otherwise make known to
the citizens that each is desired to drive, at his fence-line or
curb, a stake indicating the point at which he wishes his
house-connection to enter his property, and that in case no
such stake is driven the engineer or inspector will use his
judgment in locating such branches. Another method is that
of requesting that sketches of the property showing such

point be handed in on blanks to be furnished by the engineer; but the inability or hesitancy of many citizens to make the simplest drawing is an objection to this plan.

Counsel for the city should pass upon the sufficiency and correctness of the contracts signed, of the bonds given and of their signers, and all other legal matters in connection therewith, before the contractor is permitted to begin work.

CHAPTER XI.

LAYING OUT THE WORK.

ART. 63. LINING OUT TRENCHES.

SINCE the trench is seldom more than 6 inches wider on each side at the bottom than the sewer to be placed in it, it is necessary that the trench itself be carefully aligned, and this cannot be entrusted to the contractor except for short distances. For giving him the line the safest plan is to drive stakes or spikes along the centre of the proposed trench at intervals of about 50 feet. To assist in finding these, for checking, and to locate the centre of the sewer during construction, the distance should be taken from each of these to the curbing opposite, if there is any, or to a reference-stake, and a note made of this. The centre spikes or stakes should be some uniform distance apart to facilitate finding them. They should be set by a transit placed over the centre of a manhole on the line. The line should of course be straight between manholes, except in the case of large sewers, which may be curved, in which case the centre stakes should be set 10 or 15 feet apart. The location of manholes, flush-tanks, etc., should be fixed by two or more reference-stakes and pointed out to the contractor before he begins excavating, that he may make allowance for them in sheathing.

Some engineers in giving line rely entirely upon referencestakes placed a uniform distance from the centre of the trench,

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because the centre stakes will be removed in excavating. An experience with the unreliability of contractors' tapes and foremen's intelligence seems to argue in favor of the centre stakes, however.

It is well to do a large part of this lining out before construction gets well under way, since it is probable that the engineer corps will be kept busy with other work later. Each line should be located only after due consideration of the points referred to in Art. 34.

ART. 64. GIVING GRADE.

Several methods of giving grade are employed by different engineers, the principal being: By means of a cord stretched over the centre of the trench and parallel to the sewer grade; by stakes driven to grade along the centre line in the bottom of the trench; and by stakes driven at the ground-surface near the edge of the trench, their tops a uniform or stated distance above the sewer grade. (The grade used in both designing and construction is that of the inside bottom of the invert, which for convenience will be called the invert.) Each of these is used for both pipe and brick sewers, but only the first method is at all adapted to accurate laying of pipe sewers. For brick sewers either method may be used, but the first is most convenient in that the invert-templet can be set at any point along the trench, and that the bottom of the trench can be carried to the exact grade at every point, in advance of setting the templet, by measuring down from the cord. If stakes are driven in the bottom the templets can be accurately set only at points close to these, and the stakes can be driven only when the bottom is within a foot or less of grade, which necessitates the presence of the engineer upon the work almost constantly. If the stakes are driven along the edge of

the trench they can be set even before the excavation has been begun, enough for several days in advance being set at one time; but it is almost impossible to avoid errors in measuring down from these, since they are not directly above the sewer, and the stakes are apt to become loose or fall out with the cracking and caving of the edge of the trench.

The cord used in the first method may be fastened to a strip of wood nailed in a vertical position to a plank which stands upon edge with one end resting upon the ground on each side of the trench. This plank should extend at least 18 inches or 2 feet beyond the trench on each side and be firmly bedded into solid ground so that it cannot possibly settle, and should be held upright on edge by a stake driven on each side at each end, or by stones and earth solidly banked around the ends. These grade-planks should be not more than 33 feet

FIG. 5.-MEthod of Setting Grade-plank.

apart-25 feet would perhaps be better, since the cord will sag too much if the distance between supports be greater. On the top edge of these planks the centre of the trench is marked, and strips of wood about 1 inch X 2 inches X 24 inches are nailed so that one edge of each is in this centre line and truly vertical, as determined by a plumb-bob. On this edge is placed a mark exactly a whole number of feet above the sewer-invert immediately beneath, and a slight notch is cut to receive the cord. All notches in a given length of