ARCHIVED REPORTS XR0008192 - Laserfiche WebLink

Home Browse Search

R604 •UPDATE 20 7-16-1993 Dissolved Petroleum Hydrocarbons in Ground Water (EPA method 5030 TPH as gasoline) : With the exception of MWS, MW2, and MW7 which contained 0 . 64, 0 .23 and 0 . 11 parts per million (mg/L) respectively, dissolved total fuel hydrocarbons, gasoline range (TPHg) , all other wells sampled were below detection limits on June 18, 1993 ( MW1, MW3 , MW4, and MW6) . MWS has tested below 1 ppm for gasoline range hydrocarbons since the June 24, 1991 sampling and the laboratory reported that MW2 does not match gasoline but contained a single peak This is the first time MW7 has tested above the detection limits . All other wells have tested below 1 ppm gasoline range hydrocarbons since the March 29, 1992 sampling This analysis substantiates the removal of hydrocarbons associated with the ground water and is evident in comparing the ground water samples obtained on December 16, 1991 to those obtained on March 5, 1992 and later, see Table 1 . Before vapor extraction, November 21, 1990, gasoline range hydrocarbons were detected in MW1 (2 mg/L) , and MWS (31 mg/L) BTEX in Ground Water (EPA method 602) . No wells contained any BTEXs in the samples of the monitoring wells from the March 5, and June 2, 1992 sampling During the December 16, 1991 sampling round only MW1, MW2 , and MW5, had BTEXs in very low concentrations During the September 11, 1992 sampling, sample results from MW1 detected only benzene (1 2 ug/L) and MW5 sample results indicated only the xylenes (4 1 ug/L) The December 7, 1992 sample results showed only MW5 to contain ethylbenzene (1 . 2 ug/L) and xylenes (35 ug/L) The most recent sampling (June 18, 1993) only MW5 and MW7 contained ethylbenzene at 5 4 and 0 4 ug/L and xylenes at 120 and 15 ug/L respectively MW5 is presently being utilized as a vapor extraction well This pulling of the contaminants to the well consequently increased concentrations Below are the maximum contaminant levels (MCL) s that are applied for drinking water in the California MAXIMUM CONTAMINANT LEVELS FOR PRIMARY DRINKING WATER, TITLE 22 or DHS. Primary MCL Secondary MCL (no adverse (aesthetic) heal th affects) BENZENE 1 ug/L TOLUENE 1000 ug/L 100 ug/L ETHYLBENZENE 700 ug/L 30 ug/L Total XYLENES 1750 ug/L 20 ug/L Vapor extraction has removed most BTEXs from the ground water as shown by sample results obtained from the monitoring wells The primary MCLS have been obtained since September 11, 1992, when MW1, tested 1 .2 ppb benzene. The secondary MCLs have also been . obtained, with the exception of MW5 which tested 120 ppb Xylenes on June 18 , 1993 . This well is used for vapor extraction and page 4