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1 <br /> Ms Victoria McCartney <br /> May 11, 2006 <br /> Page 3 of 4 <br /> . Groundwater elevations at the site ranged from 1109 (MW-1) to 11 58 (MW-2) feet below mean sea <br />' level Groundwater elevations across the site have increased an average of 107 feet since the fourth <br /> quarter of 2005 The groundwater flow direction was generally to the east-northeast, as illustrated on the <br /> potentiometric map (Figure 1 of the G-R monitoring report, provided in Attachment 1) and the horizontal <br /> hydraulic gradient was approximately 0 006 feet per foot (fUft) The groundwater flow direction at the <br /> site has been predominately to the northeast since May of 2000 as depleted on the groundwater flow <br /> 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 4 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 /> above the MDL of the 3 Concentration in pglL Concentration In pglL Primary <br /> Constituents Samples (Well ID) (Well ID) (MCL) <br /> TPH-G 1 NA 6,400 (MW-3) i NA <br /> TPH-D 3 120 (MW-2) 1,900 (MW-3) �� NA <br /> TPH-MO 3 200 (MW-2) 450 (MW-3) NA <br /> Benzene 1 NA 710 (MW-3) ' 5 <br />�. MTBE 3 0 9 (MW-1) 2,600(MW- 13 <br /> TBA 2 34 (MW-3) 95(MW-2) NA <br />' ETBE 1 NA 10 (MW-2) NA <br /> TAME 1 NA 17 (MW-2) NA <br /> 1,2-DCA 1 NA 2(MW-2) 05 <br />' Notes <br /> MDL= Method Detection Limit / <br /> pg/L= Microgram per Liter,equivalent to parts per billion (ppb) <br />' NA= Not Applicable <br /> MCL= Maximum Contaminant Level <br /> Methanol, ethanol, DIPE and EDB were not detected at concentrations above the method detection limits ✓ <br /> (MDLs) Detections of TPH-D and TPH-MO in monitoring wells MW-1 through MW-3 listed above <br /> were noted by Lancaster as not typical of#2 fuel/diesel and motor oil, and are the result: of individual <br /> peaks of unknown chemicals eluting in the TPH-D and TPH-MO range <br /> Summary and Conclusions <br /> • During this quarter, groundwater flowed to the east-northeast at a horizontal hydraulic gradient of <br /> 0 006 ft/ft <br /> • Concentrations of petroleum hydrocarbon constituents for the first quarter of 2006 are generally <br /> consistent with the results of the fourth quarter of 2005 <br /> 3 1D000619-2033_00161022_First Qtr 2006 doe <br /> BLASLAND, BOLICK& LEE, INC <br /> engineers,scientists,economists <br />