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• 9tstbac Work Plan, MWAS Rehabilitation, and Bulk Extraction Former ARCO Service Station No.443 September 20, 2011 Rehabilitation of Monitoring Well MW-1S A blockage has been reported in monitoring well MW-1S since the May 2010 groundwater sampling event which has prevented the collection of groundwater samples. On June 28, 2011 Stantec mobilized to the site to investigate the presence of the blockage using a downhole video camera. The object is a round, thin-wall hollow cylinder in the well at a depth of approximately 50 feet. The object resembles a disposable groundwater bailer with the end removed. Stantec proposes to mobilize to the site with a subcontracted vacuum truck to attempt to remove the blockage from the well. Following successful removal of the blockage the downhole video camera will again be used to verify the integrity of the well. Bulk Extraction Monthly groundwater extraction events were previously conducted at the site from October 21, 2008 through March 25, 2009, as described in the Addendum to Interim Remediation Action Plan dated September 10, 2008. During the events, groundwater was extracted from wells MW- 1 S, MW-2S, and MW-1 D. A total of 8,812 gallons was extracted from the three wells during the six extraction events. During the last extraction event on March 25, 2009, depth to water(DTW) and vacuum measurements were additionally collected from wells MW-3S, MW-4S, MW-5, and deep well MW-8. Initially the six extraction events appeared to have reduced concentrations of GRO and benzene in well MW-1D, the impact on the shallow wells was inconclusive; however, after reviewing additional sampling events since this time the extraction events appear to have had an effect. Stantec proposes to reinitiate bulk extraction at the site. 3,000 to 5,000-gallon capacity vacuum truck will extract water from well MW-1S monthly for six months. An initial goal of 1,000 gallons of water per event well will be attempted. Dependent upon the yield, extraction goals may be changed in future events. During each event radius of influence will be monitored in the surrounding monitoring wells. Monthly status reports will be submitted to the regulator prior to the next scheduled event. The monitoring and sampling schedule will be adjusted to evaluate the effectiveness of GWE. Schedule Stantec is prepared to initiate field activities upon approval of this work plan by the SJCEHD. Stantec anticipates that the well rehabilitation will occur during the first monthly bulk extraction event. 443 WorkPlan MW1S Bulk Extraction 2011.doc 2