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- Y� ! �. 2 FINAL REMEDIAL PLAN " MANTECA BEAN FACILITY 229 MOFFAT BOULEVARD MANTECA, CALIFORNIA September 17, 1990 1.0 INTRODUCTION This report describes the plan to remediate petroiaum hydrocarbon impacted soil and groundwater at an inactive bean packaging warehouse facility located in Manteca,California (Figure 1). This facility,known as Manteca Bean,is owned by the Golden Grain Company of San Leandro,California. The source of petroleum hydrocarbons was a 700 gallon underground gasoline storage tank removed in ry November, 1986, The Preliminary Assessment Report(PAR)issued by Groundwater Technology in December,1989 determined the extent of hydrocarbon impacted soil and groundwater,and evaluated pote,itial treatment options. The distribution of petroleum hydrocarbons in the subsurface and the hydraulic properties of the soil matrix lead to the recommendation of a groundwater extraction and treatment system, and a soil vapor extraction and treatment system. Work completed since the PAR includes: o Monthly gauging and quarterly sa:ipling of the site monitoring welts and laboratory - analysis of groundwater samples. E. 1 o Performance of a soil vapor extraction pilot test to determine the radius of influence of i each vapor extraction well, initial vapor concentrations, and a dissipation curve of vapor concentrations with time. ` 2.0 BACKGROUND A Problem Assessment Report(PAR)for the Manteca Bean facility was submitted to San Joaquin County Public Health Services and to the Regional Water Quality Control Board - Central Valley in December,1989. A total of fourteen groundwater monitoring wells were installed during that investigation (Figure 2), and a soil gas survey was performed. _- 2.1 Site Geology Details of the subsurface geology are illustrated on geologic cross sections (Figures 3 and 4). From grade to approximately 25 feet below ground surface(BGS),the predominant material is well-graded --- L GROUNDWATER TECIINOLOC.Y,Nc.