The air inside the wetwell shall be continuously monitored to detect the presence of hydrogen sulfide and combustible gases and for oxygen deficiency.

The air analyzer system shall consist of MSA (Mine Safety Appliance Company) Model 5300 microprocessor based control unit with Trigas sample flow system.

If hydrogen sulfide or combustible gas levels are greater than their set points or if oxygen level is below the setpoint in the wetwell, signals are to be transmitted to the SCADA system (via interface relays). A strobe light in the wetwell is also to be activated under such conditions.

The air analyzer control unit shall be located in a weatherproof control cabinet near the wetwell and the sample flow enclosure shall be mounted below or near the control unit. A one-quarter-inch nylon tubing in one-inch Schedule 80 PVC conduit shall be run from the pump enclosure to the wetwell for air sampling.

The strobe light in the wetwell shall be suitable for use in hazardous locations (Class I, Division 2, Group D): Killark catalog number SHBG-2-23R, incandescent type, bracket mount with zenon lamp, red lens and guard.

Air analyzer system schematic is shown on Drawing DG-08-06. (Design Guideline DG-08 § 17.0, dated August 2006)