SITE INFORMATION AND CORRESPONDENCE

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1 Mr. William Moranda • - 2 - • 8 October 2003 Former Buffalo Tank Corporation, Stockton clays and silts. AGE could not collect a core sample between 42 and 50 feet bgs, but did collect a non- detect sample at 52 feet bgs. Groundwater was not encountered. Comments: 1) The Workplan does not adequately address how AGE will determine the need for monitoring wells in the field, what contaminant concentrations would determine a need for monitoring wells, or why two mobilizations are necessary to conduct a single investigation. A 24-hour laboratory turn-around time or an onsite mobile laboratory would be needed to keep the proposed Phase One borings open overnight while awaiting a decision to construct wells. Field screening with a Photo Ionizing Detector, while adequate for determining which soil samples require analysis, is not adequate to determine whether a monitoring well is necessary. Even if AGE were to revise the well determination criteria, the amount of contamination left in place and the proximity of groundwater to soil contamination would mandate installation of monitoring wells. 2) The Condor Report shows that high levels of soil contamination were left in place at both USTs. AGE investigated Tank 1 down to 52 feet bgs and found soil contamination down to at least 40 feet bgs (no sample core was recovered between 42 and 50 feet bgs). AGE also stated in a phone conversation on 26 September 2003 that, based on available regional data, groundwater probably occurs just below the 52 feet bgs depth of the deepest soil sample. Therefore, a minimum of three monitoring wells are necessary for this investigation. Additional wells may be required. Quarterly groundwater monitoring will continue for at least one hydrologic cycle (four consecutive quarters). 3) Sampling of groundwater from the two private wells is necessary to determine if contamination has impacted the wells. My letters of 6 August 2003 and 28 August 2003 requested sampling of both private wells, which are located between 80 and 200 feet of the USTs. Figure 2 of the Workplan shows the locations of both private wells. 4) Figure 3, Well Design, the blank casing length of 0-5 feet and slotted screen length of 5-15 feet does not make sense. The placement of the neat cement grout (0-40 feet), bentonite plug (40-43 feet) and filter pack (43-65 feet) makes sense if groundwater occurs at 55 feet bgs as drawn in Figure 3. The Workplan is approved with the following provisions: 1. Since constituents other than fuel hydrocarbons (paint thinner) were detected in soil previously, the full scan of EPA Method 8260B constituents should be reported during this investigation. If volatile organic compounds are detected in soil or groundwater, then those constituents will be added to the list of reported contaminants of concern. 2. All five borings are necessary for this phase of the investigation. My 28 August 2003 letter stated that a minimum of five borings are required for this investigation. 3. One mobilization will provide a more cost effective use of State Board UST Cleanup Funds. 4. A minimum of three monitoring wells shall be installed and sampled quarterly. Well constriction (screen placement) will be determined in the field based on depth(s) to groundwater.