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Ms. Victoria McCartney <br /> May 16, 2006 <br /> Page 3 of 4 <br /> • <br />' hydraulic gradient ranged from approximately 0.002 to 0.004 feet per foot (ft/ft). The groundwater flow <br /> direction at the site has been predominately to the southeast since the second quarter of 2000 as depicted <br /> on the groundwater flow direction rose diagram presented in Attachment 2. <br /> Sample Analytical Results <br />' A concentration map for TPH-G, TPH-D, benzene and MTBE is presented as Figure 2 of the G-R <br /> monitoring report (Attachment 1). Analytical results for the quarterly groundwater monitoring event are <br /> presented in Tables 1 through 3 of the G-R monitoring report (Attachment 1). Maximum and minimum <br />' concentrations of the petroleum hydrocarbon constituents detected in the groundwater samples are <br /> presented in the table below: <br /> Number of Detections Minimum Maximum California <br /> Constituents above the MDL of the Concentration in Ng/L Concentration in Ng/L Primary <br /> 10 Samples (Well ID) (Well ID) (MCL) <br />' TPH-G 3 ND 2,000 (MW-15) NA <br /> TPH-D 8 ND 1,400 (MW-15) NA <br /> TPH-MO 8 ND 360 (MW-15D) NA <br />' Benzene 3 ND 290 (MW-15) 5 <br /> MTBE 1 ND 3 (MW-14) 13 <br /> _TBA 1 ND 19 (MW-15) NA <br />' • <br /> Notes: <br /> MDL = Method Detection Limit. <br /> Ng/L = Microgram per Liter, equivalent to parts per billion (ppb). <br /> NA = Not applicable. <br /> ND = Non-detect at or above laboratory detection limits. <br />' MCL = Maximum Contaminant Level. <br /> Methanol, ethanol, DIPE, ETBE, TAME, 1,2-DCA, and EDB were not detected at concentrations above <br /> the method detection limits (MDLs). Concentrations of petroleum hydrocarbon constituents for the first <br /> quarter of 2006 are generally consistent or slightly lower than the results of the fourth quarter of 2005. <br /> ' Summary and Conclusions <br /> • During this quarter, groundwater flowed to the southeast at a horizontal hydraulic gradient <br /> ranging from 0.002 to 0.004 ft/ft. <br /> ' • Concentrations of petroleum hydrocarbon constituents for the first quarter of 2006 are generally <br /> consistent or slightly lower than the results of the fourth quarter of 2005. <br /> ' • Concentrations of benzene exceeded the California Primary MCL in the groundwater sample <br /> collected from monitoring wells MW-15 and MW-15D. -at MW-7 <br /> ' 11362822.doc <br /> BLASLAND, BOUCK& LEE, INC. <br /> ' engineers,scientists, economists <br />