{TAIL ~ Controls} for the process allow for a wide variation in the amount of treatment chemicals used, dependent upon composition of contaminants in {HEAD ~ the groundwater} 
{ TAIL ~ Controls } for the process allow for a wide variation in the amount of treatment chemicals used , dependent upon composition of contaminants in { HEAD ~ the groundwater }
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD