DRAINAGE METHODS FOR COUNTY ROADS. 81 
free from honeycombed spots, and no point in the surface shall deviate from the 
elevation indicated on the plan by more than one-quarter inch. 
Joints shall be made in the gutter at intervals of approximately 20 feet. The 
joints shall be one-quarter inch in thickness and shall be made by means of 
bituminous felt boards, which shall be perpendicular to the center line of the 
gutter and shall extend entirely through the concrete throughout the width of 
the gutter. 
PBOTECTION. 
After the gutter is completed as above described the concrete shall be pro- 
tected from too rapid drying by means of a suitable covering. In drying weather 
the gutter shall be covered with canvas as soon as it is finished. The canvas 
shall be spread in such a manner as not to mar the surface of the gutter and 
shall be left in place for about 24 hours, until the concrete has hardened suffi- 
ciently not to be damaged by the spreading of an earth covering. It shall then 
be removed and the entire surface of the gutter covered with a layer of earth 
or sand about 2 inches thick. The earth covering shall remain on the concrete 
and be kept thoroughly moist for a period of two weeks, and during this period 
the concrete shall not be subjected to loads of any kind. 
TILE DRAINS. 
Tile drains shall be constructed where indicated on the plans and when com- 
pleted shall conform accurately to the lines and grades established by the en- 
gineer. The work of constructing tile drains shall, in all cases, begin at the 
outlet end of the drain and proceed uphill. 
TRENCH. 
Trenches for tile drains shall be excavated to a uniform grade such that when 
the tile is laid it will rest on the bottom of the trench and have the required 
elevation at all points, and this shall be assured by means of a taut wire or 
cord stretched between standards established from the engineer's stakes. The 
width of the trench shall be such that the tile may be readily laid according to 
the required alignment without the necessity of gouging into the banks of the 
trench. The bottom width shall in no case be less than 10 inches. Where stone 
occurs in the trench it shall be excavated to a depth of at least 6 inches below 
the bottom of the tile, and the space thus made shall be refilled with earth of 
suitable character and thoroughly tamped before the tile is laid. Where the 
bottom of the trench is not sufficiently stable, in the judgment of the engineer, 
to support the tile without clanger of unequal settlement 1 by 6 inch wooden 
boards shall be placed flat in the trench for the tile to rest upon. Where boards 
are required, the contractor will be paid for the actual cost of the boards de- 
livered on the work and for the work of placing them, plus 10 per cent. 
LAYING THE TILE. 
In laying the tile the successive sections shall each be turned until the abut- 
ting ends fit closely together, and such small openings as may be unavoidable 
at the joints shall be made to come at the bottom. Any opening more than one- 
quarter inch wide shall be covered with either broken tile or cement mortar. 
Wherever two drains come together the junction shall be made by means of T 
or Y branches and not by cutting two straight sections of tile to fit at an angle. 
66998°— 18— Bull. 724 6 
