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