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' Emergency Remediation - 2480 Tracy Blvd., Tracy, CA. • Page U excavation. The results of the analyses of sample WATER 3 and WATER 4 are listed in Table 1. Also listed in Table 1 are the results from analyses of two other samples of groundwater, WATER 2 and WATER 5, that were taken to confirm that no components of diesel fuel are present in the subsurface. None were detected in either sample. Treatment of Contaminated Water A process and instrumentation diagram for the groundwater pumping, treatment and discharge system is shown on Figure 4. Groundwater is pumped from the dewatering sump to a 20,000-gallon holding tank via a 2 in.-diameter hose. The flow rate is metered by a zero to 50 gpm rotameter. A gasoline-powered pump transfers the contaminated water through 2 in.-diameter hoses to a second 20,000-gallon holding tank via a pair of series-connected, 45-gallon hydraulic- capacity, granular activated carbon-adsorption units where components of fuel hydrocarbons are removed from the process stream. Treated water is held in the second holding tank until it is tested prior to discharge to the sanitary sewer via a 2 in. hose with an in-line flow totalizer. The 20,000-gallon tanks shown on the diagram represents any two of an array of tanks, that at one time during the emergency remediation program reached a total of eight, used to store the groundwater after it was pumped from the dewatering sump, and to hold the treated water before it was discharged to the sanitary sewer. Although groundwater was continuously pumped from the dewatering sump, the water-treatment system was operated as a batch process so that each tank of treated water could be sampled and analyzed, before it was discharge: To permit efficient re-direction of the process stream from one tank to another, as tanks were filled and emptied, the hoses connecting the dewatering sump, the activated-carbon units, and the flow totalizer in the discharge line were all equipped with quick-connection fittings at both ends. For the same reason, each process unit was isolated by shut-off valve assemblies designed to be rapidly transferred from one unit to another. Testing and Discharge of Treated Water to the Sanitary Sewer Before any treated water was released from the holding tanks, authorization to discharge the water to the sanitary sewer was obtained from the City of Tracy Public Works Department. By agreement with the City, the maximum rate of discharge was set at 10 gpm and the discharge was limited to water containing only low concentrations of total petroleum hydrocarbon and less than detectable concentrations of benzene, toluene, ethylbenzene and xylene isomers, except for cases where the water was affected only by very slightly elevated concentrations of the analytes of concern at concentrations very