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BLA&lEnveronmental Management Inc U-haul#709-50 002-70950-02 Semi-,Annual Report 12/14/00 northern portion of the property and that groundwater from the deep casings contained hydrocarbons y across the site Analytical results of groundwater samples collected from the well casings screened across the groundwater interface (casings `B" and MW-8A) reveal the highest concentrations of hydrocarbons in groundwater from wells MW-313 and MW-4B The concentrations of hydrocarbons in groundwater from ' MW-313 (97,000 µg2 TPHg and 37,000 µg2 benzene) were similar to those reported for the June 2000 sampling event Again, these results suggest that monitor well MW-3B is near the source area of ihydrocarbons The extent of hydrocarbons at the groundwater surface is defined by analytical results of groundwater samples collected from monitor wells MW-8A to the northwest, and MW-5B and MW-1B to the north These groundwater samples did not contain detectable concentrations of TPHg or benzene The detection of 9 9 gg/L benzene in groundwater from monitor well MW-9B suggests that the southern extent of hydrocarbons in groundwater is near MW-913 The eastern extent of hydrocarbons in groundwater remains undefined The hydrocarbon concentration map for wells screened across the groundwater interface in the middle casings(Figure 8) shows a pattern centered at the former dispenser islands, similar to the pattern shown in Figure 4 Analysis ofoundwater samples from the �' p original wells (lower casings) screened at depths of approximately 60 and 100 feet bgs indicated that detectable hydrocarbons were present in groundwater across the site Analytical results of groundwater samples revealed the highest con p g centrations of hydrocarbons in groundwater from wells MW-4 and MW-6 The concentration of hydrocarbons in groundwater from MW-4 (14,000 p.g/L TPHg and 3,600 µg2 benzene) were similar to the results from MW-4B However, near non-detectable levels of hydrocarbons in groundwater from monitor well MW-3 (<500 pg/L TPHg and 2 4 gg/L benzene) suggests that the western dispenser island was not a source area for deep-water impact Hydrocarbons detected in groundwater from MW-6 (19,000 µg2 TPHg and E15,000 gg/L benzene) contrast with the lower hydrocarbon concentrations detected in groundwater from MW-6B With exception to the samples from MW-4 and MW-6, analysis of groundwater from the other Ion-site wells indicated low level concentrations of hydrocarbons The hydrocarbon concentration map for the lower casing wells (Figure 9) shows the extent of hydrocarbons in groundwater extending off site to the west and east in a similar manner as the June 2000 results for the deep casing samples The extent of hydrocarbons in groundwater from the lower well casings remains undefined across the site ILaboratoryanalysis ysis of groundwater samples for MTBE, TBA, DIPE, ETBE, TAME indicated a single detection of TBA Groundwater from monitor well MW-9B contained TBA at a concentration of 24 13