ARCHIVED REPORTS XR0001043 - Laserfiche WebLink

Home Browse Search

Geolo Out rec/utles Etc Page 5 g g 2nd Quarter 2004 Groundwater Monitoring Report Project No 507 2 August 30,2004 ' 0 Figure 4 illustrates the relationship between groundwater elevation and TPH-G concentrations in well MW-9 (located in the core of the plume) An inverse trend was consistent for the first four monitoring events, and then it was parallel between March 2001 and December 2002, but since has had a variable relationship The effects of the infection pilot test can be seen as the concentrations have dropped precipitously since the ' first infection on March 19, 2004 • Trend lines added to the data in Figure 4 show that as the groundwater elevation has ' lowered since 1999 that the concentration of TPH-G has increased This suggests that concentration is directly related to groundwater level at the site O Figure 5 illustrates the relationship between groundwater elevation and TPH-G ' concentrations in well MW-5 (located up/cross gradient of the core of the plume) An inverse trend was consistent for the first four monitoring events, and then it was parallel between March 2001 and December 2002, but has since returned to an inverse ' relationship ® Figure 6 indicates an inconsistent relationship between groundwater elevation and contaminant concentrations in well MW-6 The slope increases for this event and it is ' probable that the chemical infections in March have not influenced this well No data is included for the December 2002 event due to the well's inaccessibility m Figures 4, 5, & 6 illustrate that the concentrations of TPH-G increase as the water table decreases, suggesting that the plume is stable and not being degraded by natural biodegradation causes It also suggests that the vadose zone soils contain abundant ' mobile phase petroleum product o The groundwater gradient is relatively flat and the direction of groundwater flow has varied during the course of the investigation ' a Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) were measured (Table 4) and the results suggest that all eleven wells sampled are either in the core of the contamination plume or are immediately down gradient from the plume and within the ' halo of reaction depleted water caused by biodegradation of the contaminants Well MW-9 has an anomalously high ORP & DO values for being in the center of the plume, probably due to the effects of the infection pilot test ' • Figure 7 is a contour map indicating the TPH-G concentrations on June 4, 2004 The groundwater plume is localized in the vicinity of the former UST excavation The bulls- eye pattern to the TPH-G contour map in Figure 7 shows that the center of the plume has ' not moved from its source and suggests that contaminant migration may be occurring primarily by diffusion with a slight influence by advection