The following uses shall be exempt from charge:
(a) Non-consumptive uses of less than 1,000 gallons during any day, and less than 100,000 gallons during any quarter.
(b) Ballast water used for shipping purposes.
(c) Water taken, withdrawn or diverted from streams tributary to the river master's gauging station at Montague.
(d) Water taken, withdrawn or diverted below R.M. 38 (the mouth of the Cohansey River) and such proportion of waters taken, diverted or withdrawn above R.M. 38 and below R.M. 92.4 (the mouth of the Schuylkill River) as the Executive Director may determine, on the basis of hydrologic studies, would have no discernible effect upon the maintenance of the salt front below the mouth of the Schuylkill River.