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Corrective Action Plan Page 32 is lit Under that condition the groundwater pumps remain de-energized until they are re- started by manual switching This prevents over-flow of the surge tank and permits the cause of the abnormally high water-level in the surge tank to be diagnosed and corrected before the system is reset for automatic operation Air pressure in the surge-tank is maintained at atmospheric pressure by a pressure/vacuum vent (PV-1) located on top of the tank The manway in the top of the tank (EV-1) also serves as an emergency venting device The manway cover is secured only by 314 in long bolts (without nuts) so that it will lift if an over-pressure condition develops inside the tank A check valve (VC-1) prevents reverse flow from the tank if the influent line is submerged and at a lugher hydraulic head than downstream parts of the system As may be required for maintenance, a valve (V-1) at the surge tank influent port allow it to be isolated from the rest of the system and a valve (V-4) on a drain-line at the bottom of the tank allows for it to be completely emptied Bag Filter, Water discharged from the surge tank by booster pump P-2 passes through the in-line, bag filter (F-1) which is constructed from stainless steel and equipped with a 10 micron polypropylene bag Pressure gauges (P-I) are located upstream and downstream of this filter so that the pressure drop across it can be monitored and the filter bag replaced when it becomes clogged Air Stripper Operation and Control. After exiting the bag filter (F-1), water discharged from the surge tank (ST-1) by the booster pump (P-2) passes through a rotameter-type flow meter (FI-1) and enters the top of the modular air-stripper unit (AS-1) that is housed in the noise-control enclosure (NCE-1) The 5 horse-power air stripper blower (BA-1), which is equipped with a silencer, is actuated by a signal transmitted to its motor controller from a radio frequency admittance type water level sensor probe (LS-1) installed in the surge tank (ST-1) This probe detects water rising in that vessel at least 5 min before it reaches the elevation required for the booster pump (P-2) that transfers water from the surge tank to the air stripper to be started This arrangement ensures that an adequate stream of high-pressure air is being forced through the stripper before contaminated water is infected into it In the event that the water level rises in the surge tank to a level sufficient for the air stripper blower to be actuated, but the inflow to that vessel stops under the action of the groundwater pump controls before the booster pump begins to transfer water to the air stripper, a time delay controller (TDC-I) de-energizes the blower motor 10 min after it has started The air supply for the stripper blower is drawn in through a duct that passes through the wall of the noise-control enclosure (NCE-1) The air stream exits the stripper through the i top and is carred out of the noise-control enclosure by a duct that connects to a 9 in diameter, 16 ft high, steel exhaust stack A sampling port (VSP-2) in the exhaust duct permits the discharged air to be sampled and analyzed for the concentrations of volatile hydrocarbons that it carries