ARCHIVED REPORTS_XR0012015 - Laserfiche WebLink

Home Browse Search

' Mr Ron Rowe Page 2 GROUNDWATER ACTIVITIES ' Groundwater Monitoringand Sampling P g Groundwater monitoring was conducted on February 10, 1999 The depth to groundwater was ' measured in each well and subtracted from the wellhead elevation to determine groundwater elevation Water levels rose an average of 147 feet since last monitored on November 10, 1998 ' Groundwater flow was generally easterly with a gradient ranging from approximately 0 002 to 0 005 feet per foot A groundwater gradient map generated using the February 10, 1999 monitoring data is shown on Figure 2 Recent groundwater monitoring data are summarized in ' Table 1 Monitoring logs and well construction information are included in Attachment A On February 10 through 12, 1999 Ground Zero collected groundwater samples from groundwater ' monitoring wells MWI. through MW 13 At least three well casing volumes were purged from each groundwater monitoring well prior to sampling Physical parameters (pH, conductivity, temperature) were monitored during purging and allowed to stabilize prior to sampling Samples ' were collected after groundwater recharged to 100% of the original level Purged water was contained in 55-gallon drums approved by the Department of Transportation and stored onsite in a locked enclosure Purge logs are presented in Attachment A Samples were placed on ice and transported under chain of custody to Argon Laboratories (DHS #1873) Samples were analyzed for TPHg using modified EPA method 8015 and BTEX using ' EPA method 8020 Additional sample matrix collected from monitoring wells MWl, MW3, MW4, MW l 1, MW 12, and MW 13 was delivered by Argon under chain of custody to ' McCampbell Analytical in Pacheco, California (DHS #1644) and analyzed for oxygenates using modified EPA method 8260 Analytical results for TPHg, BTEX and MTBE are summarized in Table 2, oxygenate results are summarized in Table 3 Attachment B contains laboratory reports ' and chain of custody documentation Groundwater Analytical Results ' Petroleum hydrocarbons were detected in groundwater samples collected from all monitoring wells, except MW6, MW 10, MW i I, and MW 12. Concentrations of petroleum hydrocarbons decreased to below laboratory detection limits in wells MW7 and MW9 (except for benzene and toluene which were reported at concentrations near the laboratory detection limit) Concentrations of TPHg and BTEX in the samples collected from MW 1, MW2, MW4, MW8, and MW 13 were within the middle to low historical range The highest concentrations of TPHg and BTEX were detected in ' samples collected from wells MW5, and MW 13 TPHg and BTEX concentrations are summarized in Table 2 ratMgmrll qmi 999