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i 4.0 Hydrogeologic Conditions • 5 Groundwater is present beneath the site at a depth of 35 28, 35 27, 35 13 and 34 73 feet below top of casing (btc), as measured on 11/11/03 in the four groundwater monitoring wells (MW-1, MW-2, MW-3 and MW-4 respectively) installed on site The elevation of groundwater in MW- 1, MW-2, MW-3 and MW-4 was calculated by EI to be at 22 26, 21 85, 22 29 and 22 38 feet I below mean sea level respectively, based upon casing elevation data from Kier & Wright Civil Engineers and Surveyors ' ' 5.0 Findings ' 51 Groundwater Level Measurements The elevation of groundwater in MW-1, MW-2, MW-3 and MW4 was calculated by El to be at 22 26, 21 85, 22 29 and 22 38 feet below mean sea level respectively on 11/11/03 ' EI utilized the groundwater measurements to determine the direction of groundwater flow and the groundwater gradient present beneath the surface The groundwater flows southeasterly at a gradient of 0 00323 ft/ft The groundwater elevations have decreased approximately one-third of a foot since last quarter and over 5 feet since monitoring began in 1999 Groundwater elevations are listed in Table 1, and shown graphically in Figure 4 10 5.2 Groundwater Sample Analysis Results TPH-gasoline reappeared this quarter in MW-I, however, THP-diesel is no longer evident Benzene and toluene disappeared, but ethyl benzene and total xylenes remain MW-1 remains free of motor oil contamination ' MW-2 continued to show motor oil contamination as well as contamination from TPH-diesel and TPH-gasoline The contamination levels increased slightly this quarter though motor oilbU contamination has still showed a significant drop overall, from 110,000 ppm in December 2001 �r`'Yr, to 6 7 ppm in the latest sampling Minor contamination from BTEX and MTBE, however, 1, a DIPE is no longer present TBA has reappeared,the first time since March &n��l 2061 t G 5 �,S� n I � Mm4eJ, MW-3 continues to remain free from contamination since June 2002 MW-4 showed an increase in TPH-gasoline contamination BTEX contamination has decreased and DIPE is no longer present, however, TBA contamination has appeared for the Ifirst time MW-4 remains free of diesel or motor oil contamination All groundwater samples secured by EI were logged in a chain-of-custody form, placed in an on-site refrigerator and picked up by a California Department of Health Services (DHS) certified laboratory for analysis for • Total petroleum hydrocarbons as diesel, oil and gasoline (TPHg, TPHd and TPHo) b, ' EPA Method 8015 ND+ 14b me M ffv- t A�aa `►� �3x1<d4 d.�u;( PAA "jv�%- • Volatile aromatic compounds — benzene, toluene, ethyl benzene and total xylenes I 5 I