Attack by Drainage 137 



PERMANENT LINING OF DITCHES 



The method that is most economical and durable 

 for any special locality should be used.-'It is often 

 more economical in the long run to line ditches 

 with stone or concrete in permanent villages and 

 subtirbs of towns. A ditch may be properly 

 shaped and roughly lined with field stones, and the 

 bottom finished with cement mortar. If a fiat V- 

 shaped section is used, it is found best to round oflf 

 the bottom, so that obstructions will not remain in 

 the ditch and collect other debris. Elaborate 

 or very smooth finish for ditches is not essential. 



It may be thought more economical to maintain 

 open ditches than to line them, and in this case the 

 actual cost of maintenance, including cleaning, 

 regrading, and oiling treatment, should be accu- 

 rately kept. If one or more ditches are lined, a 

 true comparison of cost of the open ditch versus 

 the lined ditch can be made. 



Experience on the Isthmus has indicated that in 

 most cases it is better to line permanent small 

 ditches which would otherwise have to receive 

 treatment throughout the year. Before lining a 

 ditch an estimate of cost of lining was obtained, 

 and compared with the estimated cost of mainten- 

 ance and treatment necessary for the unlined ditch. 



