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BULLETIN- 190, U. S. DEPARTMENT OF AGEICULTURE. 



BULKHEADS. 



A bulkhead should be constiTicted at the outlet of the underdrainage 

 system to avoid injury from frost and caving of the banks at that 

 point. This may be made of concrete, brick, or timber. Care should 

 be taken that it has a good foundation, in order that it may not be 



undermined. Figure 

 11 shows a concrete 

 bulkhead which may 

 be easily and cheaply 

 installed and which 

 will give satisfactory 

 service. A network of 

 wires or small rods of 

 copper or iron should 

 be placed across the 

 outlet to keep out 

 small animals. 



SOME TYPICAL 

 LEMS AND 

 TREATMENT. 



PROB- 

 THEIR 



INTERCEPTION OF LATERAL 

 SEEPAGE. 



Figure 12 is a map 

 and cross section of a 

 typical case of water- 

 logging due to seepage 

 from higher lands, to 

 which the interception 

 method of drainage 

 should be applied. 

 The damaging water 

 is conducted through 

 a pervious stratum 

 that lies at a moderate 

 depth, and owing to a 



Fig. 11.— Concrete bulkhead for protection of outlet of tile-drainage change in slopC f rom a 



^^^*^®°^' steep to a Hghter grade 



this water is forced to the surface.^ The drain should be located at 

 the change in slope, as shown, and should be run diagonally across 



1 The slopes of the land are indicated by lines drawn across the map, any one of which lines passes thi-ough 

 points of the same elevation, this elevation being that shown on the line. These are called contour lines. 

 The lines shown on the map are at 1-foot vertical intervals, and may be compared with the successive shore 

 lines of a pond of water which is rising or falling 1 foot at a time. It is plain that the degree of slope of 

 the land is indicated by the frequency of the contour Unes, the latter being close together on steep land 

 and spread apart on land of slight slope. 



