ARCHIVED REPORTS XR0009904 - Laserfiche WebLink

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Corrective Action Plan Page 22 dispose a quantity of water equal to approximately three volumes of the submerged portion of the remedial excavation (i a some 300,000 gallons) This volume will be sufficient to evacuate all of the water that flows into the excavation and that will be affected by the contaminated soil that will be suspended in it during the excavation process and will flush an additional 200,000 gallons or thereabouts from adjacent areas of the subsurface which constitute the most severely affected, but inaccessible, zones of the subsurface 1 Contarninant Load in Water Pumped from Excavation To provide a basis for design of a groundwater treatment system, the results of analyses of ' samples recovered from monitoring NAV 1, NAV 3, NAV, 4 and ULT 9 in the period January 1993 to February 1995 were reviewed (see Table 3 for data base) These ' monitoring wells are located in, or very close to, the proposed remedial excavation The arithmetic mean of the concentrations of total petroleum hydrocarbons quantified as ' gasoline (TPHg), toluene, benzene, total xylenes and ethyl benzene detected in all samples recovered from each of the cited monitoring wells during the review period was computed These values have been designated as the Mean Maximum Concentrations and have been used for a scoping estimate of the likely contaminant load in the groundwater that will be pumped from the remedial excavation The results of the calculations described above are presented in the table below Analyte Mean Maximum Concentration mg/Liter (ppm) ' TPHg 362 ' Benzene 0 03 Toluene 0 16 Total Xylenes 0 83 ' Ethyl Benzene 006 ' The Mean Maximum Concentrations listed in the table were used to size the treatment system process units and estimate the rate of consumption of process materials under the expected maximum loading conditions The design and operation of the groundwater treatment system is described below 1