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Mr, Kenneth Olds November 15, 1988 202/799-5055 Page 4 static water level in the well was about 2.5 feet above the top of the screened interval . This situation is thought to have caused dissolved hydrocarbon levels in the water sample collected from MW-1 to be non-representative of hydrocarbon concentrations in the upper part of the aquifer. Dissolved TPH as diesel concentrations ranged from 72 ppb In MW-1 and 50 ppb in MW-4 to non-detectable in the remaining three wells. These levels indicate no significant contamination of groundwater by diesel in the existing monitoring wells, No EDB was detected in the analyzed water samples, and total lewd levels were either below or near the method detection limits. 'In summary, hydrogeologic and chemical data, obtained from the five existing wells in November 1987 and September/October 1988, indicated that the dissolved TPH as gasoline plume did not extend during this period to MW-3 and MW-4, which are located up gradient from the tank pit, nor did it extend northward to MW-5. However, down gradient from the tank pit and from the underground diesel tank, the impact on groundwater, if any, .is not defined. In order to define the downgradient extent of the dissolved hydrocarbon plume, GTI recommends drilling three additional boreholes and installing monitoring wells in then. Locations of the proposed monitoring wells are shown in Figure 1. Selected soil samples collected during drilling of the boreholes would be analyzed for TPH as gasoline and diesel, and BTEX concentrations. The three new wells would be surveyed for elevation control. A round of groundwater monitoring and sampling of all monitoring wells associated with the_pro.Ject__would__be._._performed -The-water samples would be analyzed .for BTEX and TPH as gasoline and diesel. The updated hydrogeologic and chemical data would