36 



BULLETIN 502, U. S. DEPARTMENT OF AGRICULTURE. 



The land immediately northwest, north and northeast is irrigated. 

 It is higher than the tract under consideration and is underlain by 

 shale that outcrops in many places. As indicated on the map, a 

 shale ridge extends from these higher irrigated areas, and the trouble 

 first became e\ident over the backbone of this ridge and near the 

 point. In designing the drainage system one tile line was located 

 so as to follow up the backbone of this ridge and one along each 



s^\^\\er Irrigated Land 



Boundary of Affected Area.. 

 He/g/it abowe Datum... - — 90- 



SCALE or FEET 



100 500 



Fig. 10. — Twenty-aore tract near Grand Junction, Colo., showing plan of drainage. 



edge of the ridge. The system was installed in the spring of 1914. 

 The tile were put at an average depth of 6 feet and connected with 

 relief wells 2 inches in diameter that were bored into the shale to 

 depths of from 6 to 12 feet below the bottom of the trench, where 

 the water-bearing strata were encountered. One of these wells, of 

 which there are 35, was installed every 17 feet, and practically the 

 entire flow of water discharging at the outlet of the tile system comes 

 from them. 



