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