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1 11010gica17-eckiucsfirc Page 4 GW Momtormg Report Ted Peters-AST Project No 701 2 July 31,2002 1 A chain of custody document, listing all samples collected, accompanied the samples from ' field to laboratory, thereby providing a means to track their movement and ensure their integrity All water purged from each monitoring well was placed in a 55 gallon DOT approved ' container, properly labeled and stored on site 2.3 Groundwater Sample Analyses ' Groundwater samples from the wells were submitted to K1FF Analytical (State Certified Laboratory#2236) and analyzed for ' • BTEX by EPA method 8260B • TPH-G by EPA method 8260B • TEPH-D by EPA method 8015M ' • Volatile Organic Compounds by EPA method 8260B (except MW-8) Dissolved lead, gasoline oxygenates (MTBE, DIPE, ETBE, TAME, TBA), methanol & ethanol were not analyzed They were all non-detect for the March 2002 event and omitted in accordance with the MRP A Chain of Custody was completed for all samples collected and tracked to ensure sample integrity The results and the detection limits for these analyses are listed in Table 2 of Appendix A, while the lab analytical results are presented in Appendix B ' 3.0 FINDINGS AND DISCUSSION ' The results of the groundwater sample analyses show the following • Groundwater samples from four of the five AST monitoring wells (MW-4, MW-5, MW- 6 and MW-7) reveal the presence of TPH-G or gasoline constituents • Wells MW-5 contained TPH-D at 130,000 µg/l • Free diesel product was not detected in MW-5 for the event but it has been detected in the well during previous events ' • Well MW-8 did not contain contaminant concentrations above the laboratory reporting limits for the fourth consecutive event This well is cross gradient to the former AST location and down gradient from the former UST location • Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) measurements � (Table 3) suggest that all of the AST wells are in the core of the contamination plume or are immediately down gradient of the plume Negative ORP values and low DO values ' indicate that the wells are within the halo of reaction depleted water caused by biodegradation of the contaminants For the June 19, 2002, event, all five wells had negative ORP values MW-6 is upgradient of the primary contamination sources (diesel ' ASTs) and MW-8 is perpendicular to gradient • Figure 4 illustrates TPH-G concentrations in groundwater in the vicinity of the former ASTs The highest level of TPH-G detected is in well MW-5, which is different from past events, which showed that MW-7 on the northwest side of the parcel had the 1