ARCHIVED REPORTS XR0006111 - Laserfiche WebLink

Home Browse Search

Figure 5A represents the hydrocarbon groundwater plume in the A zone and shows an elongated plume extending west of MW2 out to "Geoprobe" hole P9 were degradation has left only minor TPHg (470 ug/L), Toluene (0 65 ug/L) and tert-Butanol (Il ug/L), the degradation byproduct of MTBE Highest concentrations of TPHg are associated with the area that was over-excavated contained temporary piezometers PZIA and PZ2A and contained the highest concentration of hydrocarbons with 140,000 ug/L and 62,000 ug/L TPHg respectively on January 31, 2003 This area has since reduced to what is now excavation monitor well MW 10 (23,000 ug/L) Newly installed downgradient well MW9A is below laboratory lower detection limits Figure 5B represents the hydrocarbon groundwater plume in the B zone and shows a similar elongated plume extending west from MW2 out to "Geoprobe" hole P9 where degradation has left only minor amounts of Toluene (0 81 ug/L), Xylenes (0 83 ug/L) and MTBE (1 6 ug/L) Again the highest concentrations are associated with the area that was over-excavated contained temporary piezometers PZ1B and PZ213 with 40,000 ug/L and 16,000 ug/L TPHg respectively on January 31, 2003 Newly installed excavation well monitor well MWIO contains 23,000 ug/L Figure 6 illustrates the subsurface lithology and the extent of the A and B zones groundwater plumes within the A and B zones RECOMMENDATIONS The City of Stockton Department of Municipal Utilities in a letter addressed to Mary Sanchez, dated October 8 2004 Gave notice of intent to hold Mary Sanchez liable for costs of mitigating contamination that is encountered during the construction of a trunk sewer line along Country Club Blvd 1 Prior to and during the construction of the trunk sewer line perform interim remediation of the groundwater plume, in order to decrease the likelihood that contaminated groundwater from the Sanchez site will impact the sewer line construction 2 Develop an interim remediation plan/work plan to install a pump into excavation well MW 10 3 Obtain a sewer discharge permit to allow 10gpm discharge to the sanitary sewer at the clean-out located behind the building locate at 1876 Country Club Blvd 4 Construct the groundwater pump and treatment system immediately after receiving approval from San Joaquin County Health 5 Start pumping from MW 10 once the sewer discharge permit has been obtained TIDE FRAME January 15, 2004 First Quarter 2005 monitoring and sampling To be coordinated with AGE for same time DTW and sampling 6 Sanchez QM e 2004