ARCHIVED REPORTS_XR0002450 - Laserfiche WebLink

Home Browse Search

1 w CLEARWATER G R O U P Env vonmen ta[ Services presented as Figure 3 The estimated groundwater flow during this quarter is in southeast ' direction with a gradient of approximately from 0 0048 ft/ft to 0 0056 ft/ft The groundwater flow direction and gradient as determined by this sampling event is substantially similar to ' previous monitoring events ' Groundwater sampling results shown in Tables 1 and 2 for gasoline range hydrocarbons are summarized below Depth to groundwater range 8 63 ft (MW-8) to 9 61 ft (MW-1 and ' MW-3) feet below top-of-casing (TQC) Flow direction and gradient Easterly at approximately from 0 0048 to 0 0056 feet/foot ' Benzene concentration range From 0 8 gg/L (MW-7) to 160 gg/L (MW- 5B), below detection in MW-3 and MW-6 Toluene concentration range From 11 gg/L (MW-1) to 23 gg/L (MW- 5B), below detection in all other wells Ethylbenzene concentration range From 19 gg/L (MW-1) to 43 pg/L (MW- 5B), below detection in all other wells ' Xylenes concentration range From 0 84 gg/L (MW-7) to 82 gg/L (MW- 513), below detection in MW-3, MW-6, MW-8 ' TPH-g concentration range From 73 gg/L (MW-3) to 2,400 gg/L (MW- 5B), below detection in MW-6 MTBE concentration range Below laboratory method reporting limits ' I (<0 50 g ) ' Dissolved-phase hydrocarbon distribution maps including iso-concentration contours of benzene and TPHg in groundwater are presented as Figures 4 and 5, respectively Analytical reports for this groundwater-monitoring event are included as Attachment B Determination of Hydrocarbons First-Order Degradation Rates If natural attenuation or biodegradation is occurring within a plume, a reduction of hydrocarbons concentrations or mass is usually observed over time It usually occurs at a site, which has experienced source removal and/or some active remediation If natural attenuation or 4Q/04 Groundwater Monitormg Report 7