LOGGING IN THE DOUGLAS FIR REGION. 191 



Case 3. — One camp in 1913 used crib bridges exclusively, the cost 

 ranging from $2 to $6 per linear foot, exclusive of the gtumpage, and 

 varying for the most part with the height. Cribbings 20 feet in 

 height cost about $6 per linear foot. 



(2) Trestles. — Trestles are used in crossing streams and depres- 

 sions when the cost of fillg would be excessive, also on swampy or 

 moving ground where no other method would be practical. The ad- 

 vantage of this form, of road on swampy ground is that a firm 

 foundation is secured, stamps need not be removed, and the cost of 

 maintenance for the first few years is low. The main disadvantage 

 is the fire danger. This, however, can be minimized by clearing 

 away the brush on each side. 



Two types of trestle are used in the construction of logging rail- 

 roads in the region ; namely, pile-bent and frame-bent trestles. 



{a) Pile-bent trestles are used largely in stream beds and swampy 

 spots where good foundations for frame trestles can not be secured. 

 They are used extensively, however, in locations adapted for the 

 frame-bent type. Low pile trestle bents, up to a height of 25 feet, 

 consist of 3 or 4 piles from 12 to 15 inches in diameter. On medium 

 height trestles, from 25 to 60 feet, four piles are used. They are 

 driven in a row across the roadbed with a pile driver to bedrock or 

 solid bottom, being sawed off at the required height above ground. 

 Hewn caps, 14 feet long, 12 inches and up in thickness, with not less 

 than a 12-inch face, are drift-bolted on top of them. The bents, 

 which are spaced 16 feet apart, are connected by two hewn or sawed 

 stringers 16 or 32 feet in length and 17 inches and up in thickness, 

 with 12 to 16 inch faces, a stringer being placed under each rail on 

 top of the caps and at right angles to them to support the crossties. 

 In many cases hewn stringers prove the cheapest in the long run. 



Guard rails are placed on top of the ends of the ties parallel to the 

 stringers and spiked to every other tie to keep the ties from bunch- 

 ing. Trestles over 25 feet in height, as a rule, are braced by standard 

 methods. If a trestle curves heavily it is braced, even though it is no 

 more than 15 feet high. 



The labor cost of constructing pile-bent trestles of the above de- 

 scription is about as follows : 



Average height : li JJar Foot.i 



5 to 10 feet (no bracing) $2.00 



10 to 15 feet (no bracing) 2.20 



15 to 20 feet (no bracing) 2. 50 



20 to 25 feet (with bracing) 3. 00 



25 to 40 feet (with bracing) 4. 00 



40 to 60 feet (with bracing) 5. 00 



1 Includes the cost of yarding the material to the site. 



