ARCHIVED REPORTS_XR0012013 - Laserfiche WebLink

Home Browse Search

Mr Ron Rowe GROUNDWATER ACTIVITIES ' Groundwater Monitoring and Sampling Groundwater monitoring was conducted on August 3, 1999 The depth to groundwater was measured in each well and subtracted from the wellhead elevation to determine groundwater elevation Water levels fell an average of 0 38 feet since last monitored on May 4, 1999 Groundwater flow was generally easterly with a gradient averaging approximately 0 003 feet per foot A groundwater gradient map generated using the August 3, 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 August 3 through 5, 1999 Ground Zero collected groundwater samples from groundwater monitoring wells MW 1 through MW13 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 pnor 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 included in Attachment A Samples were placed on ice and transported under chain of custody to Argon Laboratories (DHS #2359) Samples were analyzed for TPHg using modified EPA method 8015 and BTEX using EPA method 8020 Additional sample matnx collected from monitoring wells MW1, MW3, ' MW4, MW7, MW 11, MW 12, and MW13 was 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 DTW in wells MW 1 through MW 12 were above the top of the screen interval Some have been ' for a year or more Petroleum hydrocarbons were detected in groundwater samples collected from all monitoring wells, except MW6, MW7, MW9, MW11, and MW12 Concentrations of petroleum hydrocarbons remained below laboratory detection limits in wells MW7 and MW9 for ' the third consecutive quarter Concentrations of TPHg and BTEX in the samples collected from wells MW5 and MW13 were within the middle historical range, although concentrations of benzene in MW 13 continue to decline and are an order or magnitude lower than detected in 1995 ' Hydrocarbon concentrations in MW 1, MW2 and MW8 continue to decrease The highest concentrations of TPHg and BTEX were detected in samples collected from wells MW4 and MW13 Hydrocarbon concentrations in MW4 surpassed those in MW5 during this event An ' overall increase in hydrocarbon concentrations in MW3 was also observed this quarter Wells MW3 and MW4 are located along the southern boundary of the subject property and are affected by offsite releases TPHg and BTEX concentrations ai a summanzed in Table 2 roWgffu 3qn 1999 I I