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Geological reclutics Inc. Page 4 Additional Pilot Test Work Plan Project No. 770.2 January 23, 2009 Vertical gradients have been calculated for the MW-5/105 & MW-6/106 well pairs during the ` investigation. Similar to the historical lateral directions, the direction of groundwater in the vertical plane also fluctuates at the site. Both positive and negative vertical gradients have been calculated for the site. The magnitude of vertical groundwater flow direction ranged from—0.02 to 0.01 for the site investigation. Groundwater elevation in shallow and deep aquifers has increased as much as 15.06 and 15.09 feet since September 2005 respectively. The increasing trend is observed in groundwater elevation since then, so that a daily increase in groundwater elevation is ,., estimated as 0.016 feet/day. Tables 1 & 2 in Appendix A contain the groundw er elevations and gradients recorded for +� the water table and deep wells, respectively. TableJ includes the well construction details. ��/v 2.3 Contamin7in t Distribution Iv 1�4tI4 { u Tables 4 through Appendix A contain the site's historical ,,-S�groundwater data. _— Figures 7 and 8 illustrate the soil and groundwater contaminant distribution as su ep rimp9sed on the two cross-sections A - A' and B — B', respectively."The data from th 'Jue, July�int groundwater monitoring event and the October 2005 CPT boreholes are presentale diagrams adjacent to the respective well's screened interval. 2.3.1 Soil In Figure 7, a column of soil contamination is present under the former UST excavation/dispenser area. In the vicinity of MW-6/MW-106, no soil contamination w �f detected and Wm. Hunter & Associates stated no contamination was present in MW-3. ;previously I suggested that the contamination migrated downward to impact the groundwater /Not � without less permeable soil layers causing lat ral dis ersion higher in the column. With the t addition of the CPT data, there is a smallZmoui f TPH-D at 50 feet bgs in CPT-2, but clean soils are above and below at 40 and 65 feet bgs, respectively. This contradicts our p y" earlier interpretation. In Figure 8, a similar situation is present. A "stringer" of laterally ""s �r p displaced TPH-D is evident in MW-104 at 55 feet bgs. However, it is noted that this depth is 5Y within the historical range of groundwater fluctuations and could be caused by water transport. The field geologist noted a strong HC odor at 40 feet bgs as d a free product interface at 45.5 feet bgs in boring MW-7. The soil concentration of 9,720 mg/kg TPH-D @ 45 feet bgs corroborates with the free product noted at this depth. It is likely that the geologist had two encountered non-aqueous phase liquids (NAPLs) entrained in the silty soil. TPH-D was detected in soil at 55 feet at a concentration of 12,200 mg/kg, then attenuating to 331 mg/kg at 70 feet bgs. Once reaching the groundwater table the diesel contamination spread laterally 4.0 with the rise and fall of the groundwater table. 4W V