ARCHIVED REPORTS XR0010022 - Laserfiche WebLink

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Date: April 28,2005 Quarter: V Quarter,2005 • Sample MSAB was not preserved to pH<2 for the EPA Method 8260B analysis.The reported results for benzene, toluene, ethylbenzene, and total xylenes (BTEX) in sample MS-113 may be biased low since the analyses for these analytes were performed 2 days beyond the U.S. EPA recommended holding time of 7 days for unpreserved samples. • The reported result for GRO in sample VW-I may be biased high as demonstrated by a high surrogate recovery due to matrix interference. • The elevated reporting limits were the result of dilutions performed by the laboratory in order to quantitate a target analyte. DISCUSSION: GRO, BTEX, methyl tert-butyl ether (MtBE), tert-butyl alcohol (TBA), 1,2-dichlorothane (1,2-DCA), and ethanol were detected above laboratory reporting limits in groundwater samples collected from site wells this quarter. GRO, benzene, and MtBE concentrations in the monitoring wells (MW) were generally consistent with historical data. MtBE in MW-3, benzene in MW-4, and GRO in MW-5 were not detected above laboratory reporting limits this quarter. Additionally in MW-4,MtBE decreased from 18 micrograms per liter(µg11..),reported during fourth quarter 2004, to 1.7 µg/L this quarter. GRO, benzene, and MtBE concentrations in the vapor extraction wells (VW) were generally consistent with historical data with a few exceptions. GRO concentrations in VW-I increased however,per The previous section, this result may be biased high and is considerably less than the historic high concentration reported during and since May 1997. GRO concentrations in VW-8 and VW-10 decreased from 15,000 µg/L and 34,000µg/L,reported during fourth quarter 2004,to 4,I00µg/1,and 12,000µg/L,respectively,this quarter.In VW- 11,GRO and MtBE were not detected and benzene concentrations decreased from 48µg/L to 0.75µg/L this quarter. In VW-12, benzene concentrations increased to 23 µg/L.; the first detection and the highest concentration reported since December 2002. GRO, benzene, and MtBE concentrations in the microsparge (MS) wells were generally consistent with historical data with one exception. In MS-313, MtBE was detected (33 µg/L) at the highest concentration since sampling began in December 2002. The average depth to water at the site was approximately 41.75 feet bgs during this quarter. Groundwater elevations increased approximately three feet relative to the previous sampling event. The inferred direction of groundwater flow across the site ranged from the northwest to southeast with an average hydraulic gradient of 0.003 ft/ft. This report is based on data, site conditions, and other information that are generally applicable as of the date of the report,and the conclusions and recommendations herein are therefore applicable only to that time frame. TABLES Table I Groundwater Monitoring and Analytical Data Table 2 Fuel Oxygenates Analytical Data Table 3 Groundwater Gradient Data FIGURES Figure 1 Groundwater Elevation Contours Figure 2 Groundwater Analytical Summary APPENDICES Appendix A Field and Laboratory Procedures Appendix B Laboratory Analytical Reports,Chain-of-Custody Documentation,and Field Data Sheets Appendix C GeoTracker Upload Confirmation KAWprocessVS RP ARCM02130\Q�anerly1200MI QTR 05\2130 GWMR EQ05 Joc Page 2