Laserfiche WebLink
1 <br /> wells MW-9 and MW-10} also suggest vertical (downward) groundwater <br /> gradient <br /> 10 . 0 CONCLUSIONS <br /> Only relatively low concentrations of PCE, TCE, 1,2-dichloropropane and <br /> chloroform were detected in groundwater samples collected from the site <br />' None of these concentrations detected exceeded California Department of <br /> Health Services (DHS) maximum contaminant levels (MCLs) for drinking <br /> t w ater <br /> Free-floating hydrocarbons are still present in monitoring well MW-5 <br /> This free-floating product appears to be of very limited extent since no <br />' more than a hydrocarbon sheen was present in any of the other <br /> surrounding monitoring wells or piezometers Monitoring well MW- 1 1 <br />' screened in the 55 to 70-foot zone at this location did not contain any <br /> significant hydrocarbon concentrations other than 910 ppb ethanol <br /> indicating that the vertical extent of contamination in this location is <br />' limited <br /> High hydrocarbon concentrations continue to be present in groundwater <br /> samples collected fiom monitoring well MW-6, with toluene, ethyl <br /> benzene and total xylene concentrations in this well exceeding DHS MCLs <br />' Benzene and MTBE, however, were not detected in groundwater samples <br /> collected from monitoring well MW-6 The hydrocarbon concentrations <br /> in monitoring well MW-6 have yet to show any obvious increasing or <br /> decreasing seasonal trends Groundwater samples collected from <br /> monitoring wells MW-7 and MW-8, which screen water-bearing zones <br /> below 55-feet bgs in this location, have much lower concentration of <br />' hydrocarbons showing the vertical extent of contamination in this <br /> location None of the samples collected from these deeper wells <br />' contained concentrations of any compound above DHS MCLs for drinking <br /> water, although minor concentrations of BTEX were detected in the <br /> groundwater sample collected from monitoring well MW-7, and minor <br />' concentrations of MTBE and ethanol were detected in groundwater <br /> samples collected from monitoring well MW-8 <br />' Groundwater samples collected from monitoring well MW-4 contained 3 8 <br /> ppb benzene and 43 ppb MTBE Both of these concentrations exceed DHS <br />' MCLs for drinking water <br /> Groundwater samples collected from monitoring well MW-3 contained 12 <br /> Mppb MTBE, which exceeds the secondary DHS MCL for MTBE of 5 ppb <br />' Franks One Stop Report — May 2000 <br /> -13- <br />