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The water usage calculation above are based on measurements taken of the pumping chamber on June 29, 1992. The pumping chamber was measured to be 42 inches deep at the outlet and the pump observed lowering the liquid level in the tank by approximately 6 1/2 inches. Using these measurements and knowing the tank volume is 1000 gallons, the tank will hold approximately 23.8 gallons per inch and as drain back is prevented the entire volume of 155 gallons must enter the mound after each pumping. The pump counter readings, indicate that the amount of effluent being pumped into the mound is between 357 and 620 gallons per day. Some error is likely due to the fact that the pump may not turn on at the exact same point every time, however the dosage per pumping should be accurate assuming no significant sewage flow to the tanks during the time the pump is running. If the amount of liquid being pumped in to the mound system averages 385 gallons per day as calculated from the the pump counter readings, the usage is still well below the 600 gallon per day designed capacity of the system. For the past month this system appears to have received usage below its design capacity and the system was still observed to be surfacing on June 29. From this I would conclude that the mound drainfield is not operating to its full design capacity. Inspection of the mound in 1991 revealed that although effluent was ponding in the rock bed, the sand below was very dry indicating that the majority of the sewage was not passing through the sand to the soil surface for treatment. This condition would be most likely attributed to a problem with the materia 1 s or the way the mound was constructed rather than the design of the system as effluent is not reaching the soil treatment area but perching above the sand layer. The mound drainf ie ld must be reconstructed to remedy the problem. Repairs should include the removal of the existing mound, (including as much of the sand as possible without compacting the native soil below) and replacement of the mound. The septic tanks should also be inspected to verify that all joints are sealed to prevent leakage from surface and/or ground waters. Repairs should commence only after the mound is allowed to dry adequately by temporarily disconnecting the pump, and having a sewage hauler pump the tanks as often as neccessary to prevent overflow or backup into the house.