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2.3 . 1 Physical The washpad consists of a concrete slab sloped for drainage to a central sump. Previously, a primary clarifier in the sump provided pre-treatment of the waste water prior to leaving the pad. Now the pad drain is plugged and a sump pump is used to transfer wastewater to a collection vehicle. Figure 3 illustrates the washpad sump configuration in cross section. The washpad drain pipe runs approximately 100 yards east to a secondary clarifier. The washpad discharge pipe is underground and has no cleanouts or other openings. Just before entering the clarifier a storm drain is plumbed into the washpad drain line. The secondary clarifier has three chambers and is of concrete construction. The top of the clarifier is at ground level . Figure 4 illustrates the secondary clarifier in plan and cross section. The secondary clarifier discharge runs 100 yards east discharging to an unlined collection pit. Discharge impounds here temporarily before exiting through another underground dram pipe. The pit discharge pipe conveys the flow north, under the flight line, into the airport storm dram system and eventually to discharge in Little John Creek. Catch basins 3-n the flight line collect most surface runoff north of the hanger and direct it into the dram line connecting with the Stockton Airport system. 2.3 .2 Chemical Stockton AASF personnel are mandated by military regulation to use approved solvents and cleaners for aircraft maintenance. Presently there are three products used at the washpad: 1 ) Airshow Gel - A petroleum based cleaning agent used on airframes 2 ) Unocal 140 Solvent - (Stoddard solvent) A kerosene like solvent used for degreasing 3 ) B&B 3100 - A petroleum based engine cleaning agent These three products are used at the washpad in quantity. Additionally, as aircraft are washed, minor amounts of fuel, oil and hydraulic fluid are rinsed onto the pad. Extensive laboratory analyses have been performed on untreated washpad wastewater samples . The following contaminants were detected in the effluent: • TPH • O&G • Chloroform • BTXE • Phenol • Cadmium • BOD • Barium • MBAS • COD • Mercury 7