ARCHIVED REPORTS_THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT

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Stantec L & M OPERABLE UNIT-THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling October 28, 2011 nature of the SPH, and the presence of emulsified SPH and groundwater in some of these wells, the depth to groundwater/SPH interface and corresponding SPH thickness have historically been difficult to accurately measure. This is evident by the inability to obtain SPH thickness measurements from wells 2AMW-14 and DPE-4 in December 2002, from well DPE-8 in February 2004, and from wells DPE-8 and DPE-10 in May 2005. Variations in measured depth to water/SPH and SPH thickness are apparent in several of these wells from quarter to quarter. This may also be attributed to seasonal fluctuations in groundwater levels. SPH or sheen has historically been reported in well 2AMW-14 since May 2002 (Table 3, Figure 9). Historical thickness of SPH in well 2AMW-14 has ranged from 0.02 ft reported during the first quarter 2005 to a maximum thickness of 2.99 ft reported during the fourth quarter 2003. Well 2AMW-14 was not assessed during the third through fourth quarters of 2004 due to its connection to a free product removal system. However, well 2AMW-14 has been accessible in recent quarters and has contained sheen only. SPH or sheen has historically been reported in well MW-10 since February 2004 and has ranged in thickness from 0.01 to 3.09 ft (February 2007; Table 3). Well MW-10 was abandoned in November 2008 due to the city of Stockton's excavation activities. Historical measurable thickness of SPH in wells DPE-1 through DPE-13 and MW-40 has ranged from 0.01 ft (DPE-12, February 2005) to a shallow zone maximum thickness of 11.72 ft (DPE-1, November 2003). Well MW-40 was abandoned in November 2008 due to the city of Stockton's excavation activities. All DPE wells contained only sheen during 3Q11. A summary of 3Q11 SPH thickness and SPH sheen in comparison to the 2Q11 is provided in the following table. SPH removal activities are scheduled to be conducted quarterly (at a minimum) for on and off Site wells which repeatedly contain measurable thickness of SPH and are not connected to a free product removal system. It should be noted that these SPH removal activities are typically performed between quarterly monitoring events (as noted on the table), and are likely to influence reported SPH thickness. I:\Tidewater\TW Stockton(P2A)\QMRs\2011\3Q11\3011 QSSR QRSR QMR Stockton_FINAL.doc 2.19