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Figure 5A represents the hydrocarbon groundwater plume in the A zone and shows an <br /> elongated plume extending west of MW2 out to "Geoprobe" hole P9 were degradation <br /> has left only minor TPHg(470 ug/L), Toluene (0 65 ug/L) and tert-Butanol (11 ug/L), the <br /> degradation byproduct of MTBE Highest concentrations of TPHg are associated with <br /> the area that was over-excavated contained temporary piezometers PZ1A and PZ2A and <br /> contained the highest concentration of hydrocarbons with 140,000 ug/L and 62,000 ug/L <br /> TPHg respectively on January 31, 2003 This area has since reduced to what is now <br /> excavation monitor well MW10 (18000 ug/L) Newly installed downgradient well <br /> MW9A is below laboratory lower detection limits <br /> Figure 5B represents the hydrocarbon groundwater plume in the B zone and shows a <br /> similar elongated plume extending west from MW2 out to "Geoprobe" hole P9 where <br /> degradation has left only minor amounts of Toluene (0 81 ug/L), Xylenes (0 83 ug/L) <br /> and MTBE (1 6 ug/L) Again the highest concentrations are associated with the area that <br /> was over-excavated contained temporary piezometers PZIB and PZ213 with 40,000 ug/L <br /> and 16,000 ug/L TPHg respectively on January 31, 2003 Newly installed excavation <br /> well monitor well MW 10 contains 18000 ug/L <br /> Figure 6 illustrates the subsurface lithology and the extent of the A and B zones <br /> groundwater plumes within the A and B zones <br /> RECOMMENDATIONS <br /> The City of Stockton Department of Municipal Utilities in a letter addressed to Mary <br /> Sanchez, dated October 8 2004 Gave notice of intent to hold Mary Sanchez liable for <br /> costs of mitigating contamination that is encountered during the construction of a trunk <br /> sewer line along Country Club Blvd <br /> 1 Prior to and during the construction of the trunk sewer line in order to decrease <br /> the likelihood that contaminated groundwater from the Sanchez site will impact <br /> the sewer line construction, perforin interim remediation of the groundwater <br /> plume <br /> 2 Develop an interim remediation plan/work plan to install a pump into excavation <br /> well.MW10 <br /> 3 Obtain a sewer discharge permit to allow 10gpm discharge to the sanitary sewer <br /> at the clean-out located behind the building locate at 1876 Country Club Blvd <br /> 4 Construct the groundwater pump and treatment system immediately after <br /> receiving approval from San Joaquin County Health <br /> 5 Start pumping from MW 10 once the sewer discharge permit has been obtained <br /> TIME FRAME <br /> October 15, 2004 Fourth Quarter 2004 monitoring and sampling To be coordinated <br /> with AGE for same time DTW and sampling <br /> November 2004 Install groundwater pump and treatment system <br /> 9 Sanchez QM 3rd 2004 <br />