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' Mr. Nuel Henderson Page 3 of 5 contains laboratory reports and chain of custody documentation. Attachment C contains graphs of contaminant concentrations over time. ' MTBE was below laboratory method detection limits ( DLs) in wells MW5, MW8, MW13B, MW 15A, MW 15C and MW 16B. MTBE was detected in wells MW 1 (6.4 parts per billion - ' ppb) and MW2 (26 ppb) for the first time. MTBE was also detected in MW3 (24,000 ppb), MW4 (8,100 ppb), MW7 (32 ppb), MW9 (1.5 ppb), MW12 (71 ppb), MW14 (38,000 ppb), ' MW15B (600 ppb) and MW16A (4,700 ppb). These wells are affected by MTBE releases originating at 101 S. Wilson Way and/or 130 S. Wilson Way. ' EDB was not detected in any of the wells sampled. 1,2-DCA was detected in wells MW 1, MW8, MW 12, MW13B, MW 15A, MW 15B and MW 15C. Detected concentrations of 1,2-- DCA ranged from 0.8 ppb in MW15A to 1,200 ppb in MW13B. Analytical results for ' gasoline oxygenates, EDB and 1,2-DCA are summarized in Table 3. Attachment B contains laboratory reports and chain of custody documentation. ' Vapor Extraction Wells TPHg and BTEX concentrations in the water sample collected from VW1 were within ' historical ranges. Benzene and toluene concentrations in the water sample collected from VW3 were the highest recorded since monitoring began. MTBE was not detected in well ' • VW1, but was detected in VW3 at a concentration of 51 ppb. The water sample collected from vapor well VW1 contained 1,2-DCA at a concentration of 1,100 ppb. This additive was not detected in the sample collected from VW3. TPHg and BTEX concentrations are summarized in Table 2. 1,2-DCA, EDB and gasoline oxygenate additive concentrations are summarized in Table 3. Attachment B contains laboratory reports and chain of custody documentation. 1 GROUNDWATER SAMPLING SUMMARY AND DISCUSSION ' • Water levels rose during this quarter. Groundwater elevation data continue to show a predominantly easterly-northeasterly groundwater flow direction. An upward vertical 1 gradient component was observed across the site. • Petroleum hydrocarbon concentrations in the wells affected by the onsite release were ' within historical ranges. The extent of groundwater contamination associated with the onsite release is stable and contaminant concentrations are stable to decreasing. ' • The plume of contamination originating from offsite source(s) is continuing to spread. High levels of MTBE persist in wells along the southern portion of the property. MTBE ' has also affected downgradient wells MW 12 and MW 15B where concentrations have risen over time. ' G.\GR0VN0ZEIR0EKIQMR000511q,n2005.doc