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BLAFJEnvironmentat Management Inc U-Haul#709-50 002-70950-02 Semi-Mnuai Report 12{14100 Hydrocarbons detected in groundwater from MW-6B (5,100 p,g/L TPHg and 1,700 leg/L benzene) differ considerably with non-detectable results from MW-6A The hydrocarbon concentration map for the `B" casing wells (Figure 5) shows the extent of hydrocarbons in groundwater extending off site to the west and east Hydrocarbons were detected in groundwater from wells surrounding the on-site building (MW-1B, MW-2B, MW-3B, MW-6B, and MW-9B) Non-detectable results from MW-5B define the extent to the north However, detectable results from MW-9B suggest the hydrocarbon plume extents tfurther south Analytical results of groundwater samples collected from the original wells (lower wells, casing "C") screened between approximately 60 and 100 feet bgs reveal the highest concentrations of hydrocarbons in groundwater from wells MW-6 and MW-4 The concentrations of hydrocarbons in groundwater from MW-6 (41,000 pg/L TPHg and 12,000 µg/L benzene) indicate a shift in the hydrocarbon concentration pattern from the former dispenser islands to the western portion of the site Although hydrocarbon concentrations in groundwater from MW-4 (13,000 }ig/L TPHg and 2,000 ptg/L benzene) are comparable to those in groundwater from MW-4B, the low level detections in groundwater from MW-3 (59 µg/L TPHG and <0 5 µg2 benzene) suggest that hydrocarbons in groundwater from MW-4 may be isolated from those in groundwater from MW-6 The hydrocarbon concentration map for lower wells (Figure 6) shows the extent of hydrocarbons in groundwater extending off site to the west and east in a similar manner as the middle wells However, the concentrations in groundwater from monitor wells MW-1 and MW-2 are much lower and the overall extent and degree of hydrocarbons in groundwater is more confined to the western half of the site Laboratory analysis of groundwater samples for MTBE, TBA, DIPS, ETBE, TAME, and napthalene indicated detections of MTBE, TBA and napthalene Results indicated detectable concentrations of MTBE ranging from 0 6 gg/L (MW-1B) to 830 µg/L (MW-3A) TSA was detected in groundwater samples MW-3A and MW-3B at concentrations of 330 gg/L and 120 jig/L,respectively Napthalene was detected in eight of the 22 groundwater samples at concentrations ranging from 10 jig/l, (MW-IA)to 570 1 µg/L (MW-4B) Analysis also indicated that the 22 groundwater samples did not contain detectable concentrations of DIPS, ETBE, or TAME 4 10