ARCHIVED REPORTS_XR0004584 - Laserfiche WebLink

Home Browse Search

4.0 RESULTS • 4.1 Depth to Groundwater and Hydraulic Gradient P Y The depth to groundwater on January 20 was between 36 and 37 feet, which is a nearly identical to the depth in October 2003 (Table 1) The calculated elevation of the water table is approximately 21 feet below sea level Figure 3 illustrates the hydraulic gradient and general direction of groundwater flow As in previous quarters, the contours form an arcuate pattern and indicate that the piezometric surface slopes eastward In the First Quarter 2003 Report we observed that the hydraulic gradient between VM-7 and VM-1 appeared to be steeper than east of VM-1 Whether this was a temporary anomaly, a problem with the elevation survey, or due to groundwater recharge from a leaking sewer line near VM-7 wad undetermined This anomaly has persisted, and survey errors or temporary anomalies can now be ruled out Apparently, the anomalously high water table in VM-7 is real and is responsible for the higher gradient between that well and VM-1 4 2 Analytical Results Hydrocarbon concentrations in January 2004 were quite similar to those measured in September 2003 in all wells Total Petroleum Hydrocarbon concentrations decreased slightly in VM-1 and VM-2 and moderately in VM-3, were unchanged in VM-6 and VM-7, and increased slightly in . VM-8 and moderately in VM-4 (Table 2) Total BTEX concentrations increased slightly in VM- 1, VM-4, VM-6, VM-7, and VM-8 but declined in VM-2 These changes do not appear to be particulaily significant at this time Hence, the isocontour map of TPH-g in Figure 4 closely resembles the map presented in the October 2003 Problem Assessment Report and So 11 Remedration Plan 5.0 CONCLUSIONS Groundwater monitoring in the first quarter of 2004 supports the data collected in 2003 regarding the direction of groundwater flow and the extent of groundwater contamination The data also confirm that the depth to groundwater is greater than at any time since December 1997 (seven years ago), which again reiterates the fact that now is the opportune time to install and operate a soil vapor extraction (SVE) system to remove petroleum hydrocarbons from the unsaturated zone Upgradient Environmental submitted a cost estimate to the State Underground Tank Cleanup Fund in late January 2004 and was informed that the pre-approval process is no longer being utilized We are therefore moving forward with implementation of the recommendations in the 2004 Problem Assessment Report and Soil Remediation Plan The San Joaquin Valley Air Pollution Control District has been contacted regarding permit requirements for the construction and operation of an SVE system, and the permit application was submitted in early February A vapor extraction/destruction unit has been located and will be available for mobilization to the site as soon as a permit to operate has been issued 3