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Organic vapor(OV) concentrations at the site are somewhat lower than expected However, ithe effect of the blower system of the OV readings is uncertain, the blower could be "masking"actual OV measurements. However,a definite correlation between oxygen,carbon dioxide and OV readings can be seen at the site In each well, when OV readings are greatest, the oxygen concentrations are low and carbon dioxide concentrations are high, the converse is also true The relationship between OV, oxygen and carbon dioxide is predictable The OV represent a presence of hydrocarbons, the primary source of"food" for the degrading bacteria,when-the bacteria are active, carbon dioxide is created and oxygen is depleted The OV•COZ-01 relationship may provide the most convincing evidence of the success of bioremediation at the site The initial post-inoculation groundwater samples indicate that hydrocarbon degrading bacteria are present in moderate numbers Between four and eight species of hydrocarbon degraders (HC degraders) are present in each well Samples collected on September 19, 1994 indicated that the largest number of total bacteria are present in MW-11, however, only four species of HC degraders were present in MW-11 Well EW-1 had the greatest number of species of HC degraders but had the Io% est overall total number of bacteria Additional samples collected over the next months will provide more data for comparison purposes 42 Groundwater Gradient and Direction The depth to first groundwater ranges from 61 feet at the north end of the site to 63 feet southwest of the site The data indicates a drop in elevation of approximately 2 feet since June 1994 The drop in elevation is uniform throughout the site area and is consistent with seasonal decreases in groundwater elevations Figure 4 is a groundwater gradient map, based upon the data collected on September 19, 1994 Groundwater flow in the vicinity of the site is south-southwest, as in previous monitoring events, the gradient steepens towards the south end of the site 4.3 Petroleum Hydrocarbon Impacted Groundwater Petroleum hydrocarbons were detected in groundwater from eight of the ten wells sampled TPH ranged from 86 ppb (MW-10) to 1,800 ppb (MW-14) Detectable BTE&X concentrations ranged from 14 ppb (toluene, MW-8) to 280 ppb (xTIenes, MW-14) As in previous samples, no TPH or BTE&X were detected in samples from MW-12 and MW-13 The analytical results are summarized in Table 4 The laboratory results and chain-of- custody are included in Appendix E For the fourth consecutive quarter, EDB was detected only in the sample from MW-14 (1 2 ppb Lead was detected in very low concentrations in samples from MW-11 and MW-12 The analytical results are summarized in Table 5 The laboratory report and chain-of-custody o.-Mdy R p my 94n3s GEWQMs