ARCHIVED REPORTS_XR0008046 CASE 1

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Station #11194 Quarterly Groundwater Monitoring Report (1 Q2006) April 28, 2006 Page 3 MONITORING AND SAMPLING PROCEDURES The current monitoring well network consists of 14 wells (AMW-1 through AMW-6 and MW-1 through MW-8) The portion of the well network that was sampled first quarter 2006 consisted of wells AMW-3, AMW-5, AMW-6, MW-4, MW-6, and MW-7 Groundwater samples were collected by Blaine Tech Services from each of the wells on January 26, 2006 The depth to water was measured to within 0 01 feet bgs in the monitoring wells from top of casing (TOC) using a water level indicator Well purging and sampling equipment was thoroughly cleaned prior to purging and sampling each well The sampling procedure for each well included measuring the water level and checking for the presence of LPH, using either an electronic indicator and a clear Teflon° bailer or an oil-water interface probe Wells not containing LPH were purged of approximately three casing volumes of water (or to dryness) using a submersible pump or bailer During purging, temperature, pH, and electrical conductivity were monitored After purging, water levels were allowed to recover to 80% of the original levels prior to collection of the water sample Groundwater samples were collected using a disposable Teflon® bailer, placed into appropriate Environmental Protection Agency (EPA) approved containers, labeled, logged onto chain-of- custody documents, and transported on ice to Sequoia Analytical laboratory, which is a • California state-certified laboratory Copies of the field notes are in Attachment B GROUNDWATER SAMPLE ANALYSES The groundwater samples were submitted to Sequoia Analytical laboratory for analysis of gasoline range organics (GRO), BTEX, and fuel oxygenate MtBE by EPA Method 8260B Results are discussed below The certified laboratory analytical report and chain-of-custody documentation are presented as Attachment C GROUNDWATER SAMPLE RESULTS AND DISTRIBUTION The depths to groundwater in site monitoring wells decreased in first quarter 2006 relative to the well depths of previous monitoring event The range of depths to groundwater in wells in fourth quarter 2005 was 4 85 to 7 35 feet below ground surface (bgs), while the range in first quarter 2006 was 4 47 (AMW-4, MW-3) to 6 96 (AMW-3) ft bgs The inferred direction of groundwater flow across the site was from the northwest at 0 006 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 Concentrations of GRO were detected above reporting limits in only two wells, MW-4 and MW- 6, at 240 pg/L and 920 pg/L, respectively Benzene was not detected above laboratory reporting limits in groundwater collected from any site monitoring wells Concentrations of • methyl tert-butyl ether (MtBE) were detected above reporting limits in five monitoring wells in first quarter 2006 (AMW-3, AMW-6, MW-4, MW-6, and MW-7) The highest concentration of 11BP-ARC0105 BP-COP Sites1111941Reports\QMRs111194 1Q06 QMR doc SECOR International Incorporated