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i� o � A S S O C I A T E S I N C The remaining oxygenates fuel additives were not detected above their respective laboratory method detection limits A review of the analytical data indicates that the MTBE concentration in groundwater exceeds the current California water quality goals for drinking water The California Department of ' Health Services (DHS) adopted a secondary drinking water standard (maximum contaminant level, MCL) of 5ppb for MTBE, effective January 7, 1999 The primary MCL established DHS for MTBE is currently under development, however Cal/EPA's Office of Environmental Health ' Hazard Assessment (OHHA) has adopted a 13 ppb Public Health Goal for MTBE which is being utilized by DHS as an action level Analytical results of groundwater samples are summarized in Table 3 5.0 ADDITIONAL SITE OBSERVATIONS During on-site well development activities, two existing 4-inch diameter-monitoring wells were detected approximately 100 feet southeast of the former on-site UST These wells appeared to have not been used for some time as evidenced by overgrown vegetation and appearance of the well head These wells appeared to have dedicated 4-inch submersible pumps installed in each casing and had markings identifying themselves as MW-208 and MW 320 Using a 100-foot probe, the depth to the bottom (DTB) of MW-208 was measured to be 80 feet bgs The DTB of well MW-320 exceeded 100 feet,the length of the probe These two wells appear to be a component of a separate subsurface investigation associated with P P an adjacent site located immediately east of the school grounds No well construction details or ' additional information was available for review by ATC Furthermore, SUSD staff has no immediate knowledge as to the purpose, age, or property access agreements associated with these ' wells Also, according to Mr Butch Schmidt of SUSD, additional monitoring wells are present at the site 6.0 DISCUSSION Based on the analytical results and field observations, soil and groundwater beneath the location of the former UST is currently impacted by petroleum hydrocarbon constituents The impacted soil appears to be generally limited to the upper 25 feet of the soil column with methyl tett-butyl ether (MTBE) detected at a low concentration at 35 feet bgs Laterally, impacted soil appears limited to an area within approximately eight feet from the former UST excavation (as exhibited by B-2 and B-3 data) Groundwater impaction is currently not defined although the initial ' groundwater analytical data suggest petroleum hydrocarbons does exceed current California water quality goals for drinking water w\172921reportslsumwel doc 5