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BIaeS Fnirronmental Management Inc U-Haul#709-50 002 70950 03 Groundwater Monitoring Report 1125/02 4 0 CONCLUSIONS Blaes Environmental conducted a groundwater monitoring event at U-Haul facility #709-50 on December 10, 11, and 12, 2001 In general, groundwater levels in December 2001 rose approximately five feet since September 2001 Based on the groundwater level measurements from the middle "B"well casings, the groundwater surface map for December 2001 indicated a slight flow gradient toward the north-northwest The highest groundwater elevation from the middle `B" well casings was measured in monitor well MW-4B Groundwater level measurements from the lower"C" well casings indicated a relative groundwater high at monitor wells MW-5C and MW-7C and a relative low at monitor well MW-8C Despite groundwater on the U-Haul property being relatively flat, the general flow gradient appears to be toward the west Analytical results of groundwater samples collected in December 2001 from the middle "B" and lower "C" well casings both indicated the presence of hydrocarbons in groundwater Results of samples collected from the middle `B" well casings revealed that the main portion of the hydrocarbon plume (with benzene concentrations greater than 1,000 pg/L) includes wells MW-3B, MW-413 and MW-613 Results of samples collected from the lower "C" well casings revealed that elevated concentrations of hydrocarbons exist near wells MW-4C and MW-6C These wells are located on the eastern and western property boundaries, respectively Despite the detection of hydrocarbons in well MW-4C and MW-6C, the central portion of the site near wells MW-2 and MW-3 did not contain detectable concentrations of TPHg or benzene in groundwater during this sampling event One noticeable difference between this sampling event compared with the September 2001 sampling event is the drop in hydrocarbon concentrations in groundwater from well MW-2C In general, the former fuel USTs and dispenser islands areas appear to be sources of the hydrocarbon plume near wells MW-2B and MW-3B The hydrocarbons detected in the lower "C" well casings do not appear to originate from the same source as the hydrocarbons detected in the middle "B" casings Due to the proximity of the former dispenser area,the detection of hydrocarbons in groundwater from well MW- 4 are likely associated with the former dispenser area The detection of hydrocarbons in groundwater i 10