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i Figure 3 is a groundwater elevation contour map for June 28, 1994. The flow direction and �,- gradient are similar to the October 1993 monitoring: the overall gradient is southwesterly * and a mound is present near MW-l. The mounding creates a trough north of MW-4. The data confirms the gradient map for the October 1993 monitoring that appeared in the PAR. ' 4.2 Laboratory Analysis of Groundwater Samples No petroleum hydrocarbons were detected in samples from MW-6, MW-7 or MW-8. TPH ' as gasoline was detected in samples from MW-1 and MW-4 at concentrations of 88,000 µg/L (ppb) and 440 ppb, respectively. Benzene was detected in MW-1, MW-4 and MW-5 at 10,000 ppb, 17 ppb and 0.42 ppb, respectively. Ethylbenze, toluene and xylenes were also ' detected in MW-1 and MW-4. The analytical results are summarized in Table 2. The laboratory report and chain=of-custody are included in Appendix B. 1 5.0 CONCLUSIONS & RECOMMENDATIONS ' 5.1 Hydrocarbon Impacted Groundwater Petroleum hydrocarbons continue to fluctuate greatly in MW-1. Between October 1993 and ' March 1994, TPH concentrations in MW-1 decreased from 100,000 ppb to 69,000 ppb. However, in June 1994, the concentrations increased once again to 88,000 ppb. BTE&X concentrations have shown similar fluctuations. No apparent pattern can be seen from the existing data. ' Petroleum hydrocarbons in MW-4 have shown similar, but more subtle, fluctuations than those seen in MW-1. Petroleum hydrocarbons have only been detected intermittently in MW-5. It is likely that MW-5 continues to remain at the down-gradient edge of the ' hydrocarbon impacted groundwater plume. No petroleum hydrocarbons have ever been detected in MW-6, MW-7 or MW-8. In the ' "Quarterly Report - March 1994" GeoAudit recommended that the sampling frequency of MW-6, MW-7 and MW-8 be reduced to annually. In a letter dated May 10, 1994, the PHS/EHD did not concur with our recommendation and stated that "the gradient direction ' has been reported in at least three different directions within the last two years: north/northeast, northwest, and most recently south/southwest." ' However, groundwater flow direction has been consistently south/southwest for more than one year. GeoAudit believes that a reliable flow direction has been determined and once again recommends the sampling of MW-6, MW-7 and MW-8 only on an annual basis ' (March). Groundwater depth measurements should continue on a quarterly basis. GeoAudit recommends the next quarterly sampling be scheduled for September 1994. ne d,un.QRA/6-WL.4T 7