CORRESPONDENCE_1994-1998 - Laserfiche WebLink

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2 BACKGROUND The results of the first quarter 1994 sampling program at the Harney Lane Sanitary Landfill showed that a volatile organic compound, PCE, was detected in the groundwater sample from well MW-2 at a concentration of 0.8 pg/l. This exceeds the method detection limit (MDL) of 0.5 pg/l. However, the maximum contaminant level (MCL) for PCE, 5.0 pg/l, was not exceeded. The RWQCB was notified(letter dated April 20, 1994) of this release as required in Section 2550.8] of Article 5. Section 2550.8j also requires that the well be resampled to verify that there is a statistical evidence of a release from the waste management unit. During the second quarter's sampling event, which occurred April 28, 1994, an additional sample was collected from MW-2 (i.e., two samples were collected on the same date). The results of the quarterly sample and retest sample verified the occurrence of PCE in well MW-2. Analytical results of the samples were 0.5 and 0.7 µg/1, respectively. On a separate issue, EMCON submitted a workplan on May 5, 1994, for conducting an investigation to evaluate source of impacts to water quality in groundwater monitoring well MW-4 at Harney Lane Sanitary Landfill. This was in response to the RWQCB request (letter to the San Joaquin County dated March 14, 1994) that an investigation be conducted to determine if impacts to groundwater detected into monitoring well MW-4 represent leakage from the landfill or the evaporation/infiltration ponds located adjacent to the landfill. The San Joaquin County Housing Authority operates a migrant farm worker housing facility on land immediately adjacent to the Harney Lane Sanitary Landfill. Waste water from the housing facility is treated in an aerated oxidation pond and discharged into two evaporation/infiltration ponds. These evaporation/infiltration ponds are located adjacent to well MW-4 which monitors groundwater quality along the perimeter of the Harney Lane Sanitary Landfill. It is possible that the adjacent evaporation/infiltration ponds are the source of the impacts detected in groundwater samples from monitoring well MW-4 at the landfill. The RWQCB has not approved the implementation of this workplan as of this date. The workplan is included as Appendix B. In summary, the San Joaquin County (County) believes that it has taken a prudent approach in the evaluation of the release at the Harney Lane Sanitary Landfill. The SAC/pjM3M390011.8a1-94/1Fc:9 Rev.0, 10/17/94 0939-001.18 3