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Mr Chuck Carmel • March 10, 1994 Page 2 i Quarterly Sampling Field and Analytical Methods Emcon personnel measured depth-to-water, supervised purging of each well, and collected groundwater samples at the site A copy of Emcon's field notes is included in Exhibit A The purge water generated during tlus sampling event was temporarily stored on site in 55-gallon barrels then transported off site by Balch Petroleum Company All groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G) and benzene, toluene, ethylbenzene, and xylenes (BTEX) by U S Environmental Protection Agency Methods 5030/8020/DHS LUFT Quarterly Sampling Results and Discussion Emcon's field notes and the analytical report from the quarterly groundwater sampling are contained in Exhibit A Table 1 in Exhibit B presents the water-level data for this site Table 2 in Exhibit B summarizes historical groundwater flow direction and gradient data • for this site Figure 1 shows the water-level elevations for each well and the contours of equal water-level elevation for November 9, 1993 Figure 2 shows BTEX and TPH-G concentrations for each well sampled, and the approximate extent of benzene in the groundwater Table 3 in Exhibit B presents the groundwater analytical data The general groundwater flow direction is to the northeast under a hydraulic gradient of 0 003 Water-level elevations have decreased an average of 0 29 feet since the last quarterly monitoring (August 1993) The TPH-G and BTEX concentrations detected in the samples collected this quarter are generally consistent with previously reported results in wells E-3, E-b, E-S, E-9, E-10, E- 11, and BHD-1 The hydrocarbon concentrations detected in BHD-1 are thought to be attributed to the Chevron station across the street from the ARCO site Chevron's well MW-1 is located approximately 30 feet to the north of well BHD-1 and near Chevron's former underground storage tank location Samples from Chevron's MW-1 generally contain similar TPH-G and BTEX concentrations to those in BHD-1 Concentrations of BTEX and TPH-G in the samples from wells E-4 and E-5 are lower than detected in the past five sampling events The BTEX concentrations were consistent with previous results in samples collected from wells E-7 and E-12, but the TPH-G concentrations were slightly lower The samples from off-site wells PR-1, PR-2, and BHD-2 did not contain detectable concentrations of hydrocarbons, indicating that off-site migration is being contained by the . Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 03110/9A7453NRF.PORTS4THQTR RPr