20 
BULLETIN" 190, U. S. DEPARTMENT OE AGRICULTURE. 
Ordinarily, a satisfactory relief well may be bored with an 8-inch 
post-hole auger. It should be cased with tile or pipe, or rilled with 
Ground Surface 
Dram 6 feet o^, 
at change ofs/ope 
' Per, /cos Sf'afum of great depth 
vmphHM 
■ill 
Hi llll 
^Wrelief well 
WStratisma/ict Connected, 
■■■1 
!!JI ; - 
wmm 
■h P r*m, 
mm. 
Fig. 13.— Section showing relief-well method, applied to the drainage of lands receiving water from a deep 
pervious stratum. 
coarse gravel. Relief wells in gravel, however, develop so much 
water that it is necessary to excavate a pit and build in a lumber or 
concrete box. 
Fig. 14. — Section showing method of draining soils underlain by hardpan at a shallow depth by the use of 
relief wells. Intercepting drain cuts off seepage carried on the top of the hardpan. 
DRAINAGE OF SOIL HAVING HARDPAN SUBSTRATUM. 
iinother case in which relief wells may contribute toward efficiency 
is shown in figure 14. In this case, which is frequently met with, a 
stratum of hardpan is found at a shallow depth, this being underlain 
