SITE INFORMATION AND CORRESPONDENCE

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Mr. Mike Nakagawa - 2 - 17 February 2060- different 000different location than the other figures. Similarly, the text describes MW-9 adjacent to boring SB-3, but Figure 2 shows them 100 feet apart. Please submit a corrected Figure 2. The groundwater gradient for December 1997 is 0.01 feet/foot as noted in the text, but the gradient is 0.006 feet/foot as calculated from Figure 5, and was 0.001 feet/foot when calculated in April 1997. The groundwater contour map does not include the groundwater elevation at MW-6. When it is included, it appears that there is a groundwater mound offsite to the northwest, and MW-6 is downgradient of the facility. This finding invalidates the conclusion that the high nitrate concentration of 220 mg/1 found in MW-6 is upgradient of the formerly active portion of the site and invalidates the assessment that nitrate should not be included in a feasibility study. IT's argument that nitrate in groundwater at the Cal Farm site is attributed to an off-site upgradient source cannot be substantiated on this basis. Therefore;the feasibility study will need to address nitrate concentrations in groundwater. Second and Third Quarter 1998 Monitoring Report The figure presenting the June 1998 groundwater contour map identified the groundwater elevation as ND in MW-6 when the corresponding table identified it as—0.87 feet elevation. The figure also shows MW-4 elevation as—0.12 feet when the table shows it as +0.12 feet. The field log data agree with the table data. When the contours are redrawn, the groundwater mound observed in the northwest area of the facility in previous quarters once again is apparent. A localized groundwater mound appears at MW-8,which historically has been in the downgradient direction. The September 1998 groundwater contour incorrectly includes the data from the deep monitoring well (MW-7) with the data from the shallow monitoring wells. When the contours are redrawn, the groundwater mound in the northwest area is again apparent. The text notes that nitrate concentrations have increased considerably in both of these quarters relative to the previous one. The laboratory reported the nitrate as nitrate, and the tables presented the values as such. In previous quarters, the nitrate data was presented as nitrogen, which is 4.5 times lower than when nitrate is presented as nitrate. When the data are converted to nitrate as nitrogen, nitrate increased in MW-3, 4, 6, 7 and 9 and decreased in MW-2 and 8. The largest increases were approximately 100 mg/1 in MW-6 and MW-9 in June 1998, when the groundwater elevation was within three to five feet of the ground surface. This suggests that nitrate is present in the vadose zone at the shallow water table in these two locations, or that there was significant nitrate infiltration from surface ponding over the winter months. 1998 Annual Report and First Quarter 1999 Monitoring Report The groundwater contour map for September 1998 also incorrectly included MW-7 in the shallow groundwater contours. When the contours are redrawn, the groundwater mound is present in the northwest comer. This groundwater mound near the northwest corner of the facility disappeared in March 1999, and the gradient was in the southerly direction. A localized mound is present at MW-5, where it had appeared at the adjacent well in June 1998 (MW-8). In March 1999,nitrate concentrations in MW-6 and MW-9 decreased relative to June 1998, i.e. when groundwater elevations were similar to those found in June 1998.