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The general strategy in determining exploratory locations will be to start at the former UST excavation and move south in the downgradient groundwater flow direction as shown on Figure 2. The sample locations shown on Figure 2 may differ from actual locations if field conditions warrant. Presently, we anticipate advancing 14 borings; however the actual number may change as the field investigation proceeds. It is estimated that four or five boreholes to 40 feet bgs can be completed in one day, thus we estimate it will take three,possibly four days, to complete the field investigation. Each sample location will be identified using global positioning system (GPS) equipment. The sample locations will then be plotted on a site map and presented in the report. Data generated during the field investigation will also be used to prepare a figure showing the subsurface contaminant plume in three- dimensions. MIP Sample Methodology MIP is a semi-quantitative screening tool used for the detection of volatile compounds in subsurface soil and groundwater. The probe in itself has no sensory capability; it merely transfers vaporized samples of subsurface contaminants to gas-phase detectors (PID, FID, ECD) at the surface. MIPs are used in tandem with electrical conductivity (EC) sensors. The primary use of the EC sensor in the probe is to map stratigraphy. The two have been integrated into a single probe that is called an MIP. The essential comportents of the MIP characterization effort are: 1) a direct push rig; 2) an MIP; 3) an MIP carrier gas (nitrogen) supply controller; 4) a gaseous phase detector; and 5) a data display and logging system. MIP technology works by advancing the MIP through the strata to be explored. The MIP heats the matrix in contact with it and volatilizes contaminants, which enter the probe through a semi-permeable membrane-covered window and are transported to the surface by a continuous draft of inert nitrogen gas. The gas stream is conveyed to a measurement device, which then produces a quantitative result. The result is fed to a field computer, which provides a graphical display of real-time measurements as the probe advances through the soil. This tells the operator the depth of the contaminant, the relative concentration, and the type of soil in which the contaminant is located. After the probe equipment has been removed from the borehole, a temporary well PVC well casing and screen will be placed in the open borehole and grab groundwater sample will be collected to verify actual contaminant concentrations. Each sample will be analyzed for TPHg, BTEX, and MTBE following EPA Test Method 8260B. Decontamination of Equipment A response test will be performed at every new location prior to MIP advancement. This will be done to evaluate the condition of the semi-permeable membrane. The response will be compared to that of previous tests. A decline in response indicates the need for membrane replacement. To prevent cross-contamination of the MIP carrier gas trunk line, the line will be purged between vertical intervals. Purging is implemented by letting the system operate several minutes without advancing the probe. While the probe remains in place, cross-membrane contaminant transfer continues until the contaminants' gaseous phase near the membrane is depleted. Once the ingress of contaminants has stopped, the continuing flow of nitrogen gas flushes potentially remaining contaminants from the carrier gas trunk line. The carrier gas trunk line is considered purged of contaminants when the detectors read zero. Project No. E8323-06-01 -3- August 23,2007