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i 1. INTRODUCTION At the request of ARCO Products Company (ARCO), EA Engineering, Science, and Technology (EA) oversaw routine closure of the oil-water separator/clarifiers at ARCO Facility No. 0548, located at 1612 Hammer Lane, Stockton, California (Figure 1). This report summarizes the field investigation and the analytical results for concrete and soil samples collected from beneath the sump of the oil-water separator/clarifier. Oil-water separator/clarifiers are used to separate and clarify industrial waste collected during the operation of the station's automobile repair bays. The industrial wastes may include petroleum hydrocarbons, degreasing compounds, solvents, and engine coolants. On 24 March 1992, Gettler-Ryan Inc. of Hayward, California, under contract to ARCO, closed the oil-water separator/clarifier. EA observed the closure and collected a concrete sample from the bottom ' of the sump and soil samples from native soils beneath the sump. The work was performed in accordance with ARCO's guidelines and local and state regulations. ' 2. FIELD INVESTIGATION ' Gettler-Ryan Inc., a general and environmental contracting company, closed the oil-water separator/clarifier located inside the building in the vicinity of the service bays (Figure 2). Prior to initiating the work, Gettler-Ryan obtained all necessary permits. The contents of the sump were pumped into 55-gallon drums, and the sludge that could not be removed by pumping was removed by field personnel using shovels and placed in a 55-gallon drum. The oil-water ' separator/clarifier sump outlet pipe was capped after the liquid and sludge were removed. The sump was cleaned using a high-pressure steam cleaner to remove residual materials. The water from the steam-cleaning that collected in the sump was pumped into drums. The drums were properly labeled and subsequently transported off the site by H&H Ship Service of San Francisco, a licensed waste hauler. The liquids in the drums were sampled by H&H Ship ' Service and were disposed of at the H&H Ship Service treatment, storage, and/or disposal (TSD) facility. ' After the sump was cleaned, a jackhammer was used to create a hole in the bottom of the sump. A sample of the fractured concrete was collected in brass tubes for laboratory analysis. The remaining concrete debris was removed and placed in drums. Samples of the soil beneath the sump were collected at various depths for possible chemical analysis: using a drive sampler, a soil sample was collected from native soil immediately beneath the concrete; a soil boring was ' advanced with a hand auger to five feet below the sump, and soil samples were collected. ' After the samples were collected, the borehole and the sump were backfilled with fill and soil to several inches below the surface. A concrete cap was placed on top of the backfill to complete the closure of the separator/clarifier. ' 548(1)/R01492/T%.2 1