ARCHIVED REPORTS_XR0003772 - Laserfiche WebLink

Home Browse Search

' 04 June 1999 AGE-NC Project No 98-0448 ' Page 4of5 ground water could greatly modify the inferred ground water flow direction 1 • Ground water was approximately 26 feet above the screened intervals in monitoring well MW4-B Therefore this well is "drowned", and yields a sample representative of deeper ' screened ground water Due to the deeper screen interval at MW-4B, ground water elevation data for MW-4B was not utilized to contour ground water elevations ' • Between December 1998 and March 1999, ground water elevation increased an average 1 36 feet at the site • TPH-g was detected in water samples collected from MW-1, MW-2, MW-4A, MW-4B and ' MW-6 at concentrations ranging as high as 95,000 ug/1, however, the laboratory reported either unmodified or weakly modified gasoline was significant (MW-1, MW-2, MW-4A, ' MW-4B and MW-6) or heavier gasoline range compounds was significant (MW-6) • Various BTEX compounds were detected in water samples collected from wells MW-1, MW-2,MW-4A and MW-413 at concentrations ranging as high as 18,000 ug/l The greatest benzene concentration was detected from MW-4A at a concentration of 3,600 ug/l • MTBE was detected in a water sample collected from MW-413 utilizing EPA Method 8260 ' at a concentration of 1 2 ug/l o Concentrations of benzene detected in samples collected from wells MW-1, MW-2, MW-4A and MW-413 were above the State of California Maximum Contaminant Level (MCL) for drinking water of 1 0 ppb I • DIPE was detected from MW-1 and MW-413 at concentrations of 20 ,ug/l and 1 4 ug/l, respectively No other fuel oxygenating compounds were detected from analyzed water samples ' • In September 1998, concentrations of MTBE were detected at MW-2 at a concentration of 690 ug/1 (by EPA Method 8020), however, in December 1998, MTBE was not detected above a laboratory reporting limit of 200 ug/l and in March 1999, MTBE was not detected above 100 ug/l • From December 1998 to March 1999, a slight decrease in dissolved petroleum hydrocarbon concentrations was observed from well MW-1, MW-413 and MW-6 (Table 2) Conversely, a slight increase was observed from well MW-4A None of the increases or decreases appears to be related to a significant trend I * The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-2 and MW-4 indicate that these wells are within or near the dissolved petroleum hydrocarbon"core area" of the plume (Figure 4) • • The horizontal extent of impacted ground water has not been delineated to the west, Advanced GeoEnvlronmental,Inc I