DEAINAGE 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. ' . 



PKOTECTION. 



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. 



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 danger 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 sti'aight sections of tile to fit at an angle. 

 66998°— 18— Bull. 724 6 



