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4 Soil Vapor Extraction and Air Sparge Feasibility Evaluation Work Plan University Park September 15,2004 Page 2 r1 � ' establish the groundwater gradient and to monitor the concentrations of petroleum hydrocarbonsin site a , groundwater. In addition, Condor recommended the completion of a sensitive receptor survey within a radius of 2,000 feet of the site to investigate the potential for receptors that may be impacted by petroleum ` hydrocarbons in .the groundwater. Ms. Dot Lofstrom of the SJCEHD concurred with the recommendations. 1 An approved additional subsurface investigation was conducted in November and December, 2001. Results of the work indicated that soil contamination at the site was fully investigated. However, groundwater contamination was present down to the furthest extents of the investigation (approximately 81 feet below the ground surface) and at the lateral bounds of the investigated area, particularly,to the east. Based on the results of the investigation, Condor recommended quarterly groundwater monitoring, additional lateral and vertical groundwater characterization, and soil over-excavation as an aggressive I L remedial alternative that was most likely to result in rapid mitigation of site contamination, as requested E by the property owner. Ms. Rebecca Setliff of the SJCEHD agreed with the monitoring. and additional groundwater investigation portion of the recommendations, but requested the evaluation of the feasibility . of at least two remedial options for the site. Condor prepared a Problem Assessment Work Plan (PAWP) for the site dated January 23, 2003;'and a Work Plan for Soil and Groundwater Remediation dated March 3, 2003 to propose additional groundwater investigation at the site. As requested by the SJCEHD, the PAWP also included a remedial feasibility evaluation that compared and discussed remedial techniques for site remediation. In a letter F dated March 13, 2003 to Mr. Rosso, Ms. Margaret Lagorio and Mr. Nuel Henderson of the SJCEHD i approved the proposed CPT groundwater investigation described in the PAWP and concurred with Condor's recommendation that additional groundwater monitoring wells were needed to characterize and monitor the site. The SJCEHD also approved the proposed soil over-excavation as an interim remedial a measure but did not approve the proposed ozone sparging pending the results of additional groundwater characterization. Condor has conducted five quarterly monitoring events at the site (December 2001; June, September, December, 2002; and March 2003); field activities included measurement of water levels and collection of water samples from the-three site monitoring wells, MW-1, MW-2, and MW-3. Condor also recently re-initiated quarterly monitoring at the site in August, 2004. A report is currently being preparedi"under separate cover, for the monitoring event.Monitoring well MW-1 is located up gradient of the contaminant plume and, to date, no gasoline constituents have been detected in the groundwater samples collected from MWA. Samples from monitoring well MW-2, located southwest of the former UST location, have generally contained low concentrations of petroleum hydrocarbons constituents. Samples'; from monitoring well MW-3, located southeast and generally down gradient from the source area, have I contained low to moderate concentrations of several petroleum hydrocarbon constituents. The quarterly monitoring data generally indicate that groundwater conditions at the site have remained relatively static. The groundwater gradient direction has fluctuated from east-northeast to southeast and depth to groundwater has steadily declined from approximately 37.5 feet below ground surface to approximately 41.5 feet below ground surface. On April 14 through 17, 2003, Condor conducted additional groundwater investigation activities at the l site using CPT and direct push drilling methods to further characterize site geology, and to further evaluate the lateral and vertical extents of groundwater contamination. Results of the investigation are summarized in Condor's Additional Groundwater Investigation Report, dated August 19, 2003. The results indicated that while present to the maximum depths investigated, the gasoline constituents in groundwater generally attenuate rapidly with depth in the source area, and with the possible exception of i i1� CONDOR