Laserfiche WebLink
i <br /> Former Beacon Station 494 March 4, 1996 <br /> Stockton,California Quarterly Groundwater Monitoring <br /> Groundwater samples were collected from the monitoring wells on ,fanuary 16, 199_6 <br /> Collected samples were submitted under chain-of-custody to Western Environmental Science <br /> & Technology, a California Department of Health Services-certified analytical laboratory <br /> (ELAN No 1346) located in Davis, California Groundwater samples were analyzed for <br /> Total Petroleum Hydrocarbons as gasoline (TPHg) according to EPA Method 8015 and for <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX) according to EPA Method 602 <br /> Laboratory results are summarized on Table 1 Copies of the laboratory reports and chain- <br /> of-custody are included in Attachment D Laboratory result tables from sampling prior to <br /> April 1995 are shown in Attachment C <br /> Results <br /> Water-level data collected on February 21, 1996 were used to construct a Groundwater <br /> Contour Map (Figure 2) The groundwater elevation data indicates an overall groundwater <br /> flow direction toward the northeast and east with a adient of approximately 0 016 to 0 02 <br /> Data collected before the start-up of the treatment system had shown a groundwater flow <br /> generally toward the northeast The gradient appears to have resumed its natural northward <br /> trend since groundwater extraction has ceased Water-level data collected on January 16 was <br /> not used to construct a Groundwater Contour Map due to an error during the depth to water <br /> measurement procedures The groundwater has risen approximately 4 1 feet in the <br /> monitoring wells since the fourth quarter 1995 monitoring <br /> Concentrations of dissolved TPHg and BTEX have not been detected in any of the <br /> groundwater monitoring wells for two consecutive quarters Pnor to that the only benzene <br /> detected above 1 part per billion (ppb) was in MW -3 (the former groundwater extraction <br /> pumping well) at 13 ppb and 1 1 ppb in the second and third quarters, respectively <br /> Based the results of the groundwater monitoring, we recommend that this site be granted <br /> closure and the existing groundwater and vapor extraction wells at the site be properly <br /> destroyed <br /> . Report No 494gmr96 ql <br /> Job No 1494 31 2 HORIZON ENVIRONMENTAL INC <br />