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This study evaluated the effect of wastewater strength and water table separation on failure due to clogging in columns (lysimeters) representing four common Florida drainfield configurations. 107 cm (42) long soil/fill profiles were packed into 20 cm (8") diameter vented columns and covered by 15 cm (6) of gravel. Testing conditions included three different wastewater strengths (average concentrations: low: CBOD5= 99 mg/L; TSS= 48 mg/L; Oil&Grease =13 mg/L; medium: CBOD5= 308 mg/L; TSS= 112 mg/L; Oil&Grease =31 mg/L; high: CBOD5= 640 mg/L; TSS= 164 mg/L; Oil&Grease =50 mg/L), with concentrations based on results of previous field sampling of restaurant wastewaters. Four different hydraulic loading rates, ranging from 2.6 to 4.9 cm/day (0.65 to 1.2 gpd/sqft), were employed, representing code requirements for each drainfield configuration. Two saturation conditions were included, 0.6 m (2ft) and 0.3 m (1 ft) separation from the water table. Each of these conditions was evaluated in triplicate to equal 72 individual columns. Columns were dosed twice daily with synthetic wastewater. Dosing was continued for 250 days or until failure, which was defined as ponding 15 cm (6) above the infiltrative surface at the time of the next morning dose.